Digitally Signed Records – Friend or Foe?

Long-term preservation of digitally signed records may be a challenging task. Digital signatures expire and digital certificates may be revoked, thus influencing the trustworthiness of archived digital records. The authors firstly explain the problems and then proceed to a description of the planned research. The research will be conducted on a sample of digitally signed and archived electronic forms stored in the PDF file format, originating from the period from 2006 to 2009

Long-term Preservation of Validity of Electronically Signed Records

The authors explain the context in which electronic records are being preserved. They explain the concept of authentic electronic records and proceed with the analysis of the technologies supporting trust in electronic records. They start by explaining the Public Key Infrastructure as the requirement for electronic signatures, digital certificates, the concept of non-repudiation, trusted archive service, timestamps and trusted digital timestamping. Further, they analyse formats of electronic signatures – XMLDSig, XAdES, CAdES, PAdES – and their possible influence on the long-term preservation of validity of electronically signed records. The authors conclude that although strict requirements of certain types of electronic signatures can ensure authenticity, integrity and non-repudiation of preserved records, they will still require preservation action on the level of medium and files

The concept of establishment of electronic archive in public administration

Cilj ove doktorske disertacije je izrada modela informacijskog sustava za dugotrajnu pohranu elektroniĉki potpisanih dokumenata u podruĉju javne uprave. Za potrebe izrade modela obraĊen je referentni teorijski model za dugotrajnu pohranu elektroniĉkih informacijskih objekata – OAIS. Opisane su odgovornosti i sastavnice te funkcionalni entiteti navedenog modela. ObraĊena su teorijska saznanja s podruĉju infrastrukture javnog kljuĉa (PKI) zbog tehnologija i koncepata koji podrţavaju povjerenje u elektroniĉke zapise: digitalni certifikat, elektroniĉki potpis, napredni elektroniĉki potpis, certifikacijski (CA) i registracijski autoritet (RA), elektroniĉki vremenski ţig i dr. Uredbom eIDAS (Uredba (EU) br. 910/2014) je za podruĉje Europske Unije stavljena van snage do tada vaţeća EU Direktiva 1999/93/EC o okviru Zajednice za elektroniĉke potpise. Utjecaj Uredbe eIDAS je vrlo dalekoseţan za pravno reguliranje elemenata za dugotrajno oĉuvanje elektroniĉki potpisanih zapisa. Navedena uredba je propisala i koncept kvalificiranog pruţatelj usluga povjerenja (za izdavanje certifikata, vremenskih ţigova i dr.). Posebno su detaljno obraĊeni formati naprednog elektroniĉkog potpisa: XAdES, CAdES i PADES. Takvi formati potpisa omogućavaju oĉuvanje u dugom roku pa su iz tog razloga posebno zanimljivi. Detaljno su obraĊeni procesi izraĊivanja i validacije naprednog elektroniĉkog potpisa. Prepoznat je pojam dokaza postojanja, tj. PoE (engl. Proof of Existence) elektroniĉkog potpisa kao kljuĉan za ovaj rad. U prouĉavanju podruĉja dugoroĉnog oĉuvanja integriteta i autentiĉnosti elektroniĉkih zapisa s elektroniĉkim potpisima obraĊene su ĉetiri strategije oĉuvanja: uklanjanje elektroniĉkih potpisa, biljeţenje traga o elektroniĉkim potpisima u metapodacima, biljeţenje valjanosti o elektroniĉkim potpisima u blokchainu te oĉuvanje elektroniĉkih potpisa. Oĉuvanje elektroniĉkih potpisa je ĉesto implicitno definirano u zakonskim propisima te je stoga bilo i izazov za ovaj istraţivaĉki rad. Detaljno je obraĊena tematika elektroniĉke javne uprave (pojam, faze, mobilna javna uprava i sektori). Da bi se bolje shvatila vaţnost arhiva u elektroniĉkoj javnoj upravi obraĊen je kontekst elektroniĉke javne uprave u Europskoj Uniji i Republici Hrvatskoj. Sudjelovao sam na InterPARES Trust istraţivaĉkom projektu na temu analize elektroniĉkih javnih usluga. Analizirani su razliĉiti aspekti javnih e-usluga, a sa stanovišta ovog rada su posebno zanimljivi rezultati s podruĉja dugoroĉnog oĉuvanja elektroniĉkih zapisa te su i izneseni u ovom radu. Osim toga, istraţena je dostupnost servisa i komponenata temeljenih na infrastrukturi javnog kljuĉa u RH koji se mogu uĉinkovito iskoristiti za izgradnju infrastrukture za potpisivanje i dugotrajnu pohranu elektroniĉki potpisanih dokumenata. Konaĉno je dana i analiza uspješnosti elektroniĉkih javnih uprava po više metodologija. Napravljena je detaljna analiza razliĉitih aspekata elektroniĉki potpisanih dokumenata (interoperabilnost, pravna ureĊenost, rokovi ĉuvanja, norme za dugotrajnu pohranu). ObraĊen je i pojam elektroniĉke isprave u smislu zamjene za papirnate sluţbene dokumente izdane od javne uprave. Analizirani su hrvatski i strani zakoni s tog podruĉja. Kao priprema za izradu modela dugotrajne pohrane elektroniĉki potpisanih dokumenata obavljena je analiza uspješnih implementacija e-arhiva iz Hrvatske, Njemaĉke, Italije, Austrije, Litve i Estonije. ObraĊeni je i jedan referentni model za dugotrajnu pohranu te su analizirani rezultati istraţivaĉkog EARK projekta. S obzirom na saznanja iz analize uspješnih praksi i referentnih modela izradio sam model informacijskog sustava za pohranu elektroniĉki potpisanih dokumenta. RazraĊeni model se temelji na OAIS referentnom modelu. Vrlo bitan dio u izradi navedenog modela je razrada pojma oĉuvanja dokaza postojanja. Predlaţe se korištenje standarda RFC 6283 (XMLERS) za zapis oĉuvanja dokaza postojanja. Osim toga, kljuĉno u izradi modela je korištenje usluga kvalificiranih pruţatelja usluga povjerenja za certifikate i za vremenske ţigove. Kvalificirani vremenski ţig poprima i znaĉenje arhivskog vremenskog ţiga. IzraĊeni model podrazumijeva produţenje potpisa prije isteka prikladnosti korištenih algoritama. Osnovna namjera produţenja potpisa jest osigurati provjerljivost cjelovitosti i autentiĉnosti već potpisanih dokumenata. Osim toga i vremenski ţigovi s vremenom mogu izgubiti svoju prikladnost pa se pravovremeno treba dohvaćati novi vremenski ţig. Predloţeno je rješenje i za dugotrajno oĉuvanje elektroniĉke isprave na naĉin da tehnološka implementacija podrţi pravni okvir. Predloţeni su i formati dokumenata za ovaj model te korištenje formata naprednog elektroniĉkog potpisa. Predloţeni su formati iz AdES obitelji potpisa: XAdES, CAdES i PAdES. Na kraju rada je dan prijedlog uspostave infrastrukture za dugotrajno oĉuvanje potpisanih elektroniĉkih dokumenata u Republici Hrvatskoj.The aim of this PhD thesis is to develop a model of the information system for the long term storage of electronically signed documents within public administration domain. For the purpose of building the model, the referent theoretical model for the long term storage of electronic information objects - OAIS is elaborated. The responsibilities, components and the functional entities of the mentioned model are described. Theoretical findings in connection with public key infrastructure (PKI) are covered because of the technologies and concepts that support the confidence in electronic records: digital certificate, electronic signature, advanced electronic signature, certificate authority (CA), registration authority (RA), electronic timestamp etc. The EU Directive 1999/93/EC on a Community framework for electronic signatures was derrogated in the EU area by eIDAS regulation (EU Regulation no. 910/2014). The influence of the eIDAS regulation is far-reaching for the legal regulation of the elements for the longterm preservation of electronically signed records. The regulation laid out the concept of the qualified trust server provider (for the certificate issuance, timestamps, etc.). Certain formats of advanced electronic signature are thoroughly covered. Such signature formats enable longterm preservation what makes these formats particularly interesting. The processes of development and validation of advanced electronic signature are described in detail. The term Proof of Existence (PoE) of electronic signature is recognized as key for this thesis. Studying the area of the long-term integrity and authenticity preservation of electronic records with electronic signatures four strategies of preservation are covered: the removal of electronic signatures, keeping track of electronic signatures within the metadata, recording electronic signature validity within the blokchain and the preservation of electronic signatures. The preservation of electronic signatures was a challenge for this thesis because it is often implicitly defined within legal regulations. The concept of electronic public administration is thoroughly covered (the term, phases, mobile public administration, sectors). To have a better understanding of the importance of archives in the electronic public administration the context of electronic public administration in the European Union and in the Republic of Croatia is described. The author took part at InterPARES Trust research project that was based on the analysis of electronic public services. Different aspects of public e-services are analyzed, form the point of this work the results from the area of electronic records long-term preservation are especially interesting and as such are elaborated in this thesis. Furthermore, the availability of services and components based on the public key infrastructure in the Republic of Croatia that can be efficiently used for signing and long term-storage of electronically signed document infrastructure development is investigated. Finally the analysis of efficacy of electronic public administrations according to numerous methodologies is presented. A detailed analysis of different aspects of electronically signed documents (interoperability, legal regulation, preservation time period, long-term storage standards) is made. The term electronic document as a substitute for official paper documents issued by public administration is elaborated. Croatian and foreign legal regulations are analyzed. As a preparation for the long-term storage of electronically signed documents model an analysis of successful e-archive implementations from Croatia, Germany, Italy, Austria, Lithuania and Estonia is made. One referent model for the long-term storage is elaborated and the results of the E-ARK research project are analyzed. Based on the findings from the analysis of successful practices and referent models the author built a model of the information system for storage of electronically signed documents. The developed model is based on OAIS reference model. An important part of the above mentioned model development is the elaboration of preservation of the proof of existence term. The use of RFC 6283 (XMLERS) standard for the Evidence Record Syntax is recommended. On top of that the use of qualified trust service providers for certificates and for timestamps is key for this model development. Qualified timestamp also takes the meaning of an archive timestamp. The developed model implies signature renewal before an expiration of the validity of the algorithms used. The main purpose of the signature renewal is to insure the verification of completeness of already signed documents. Additionally, timestamps can lose their validity as time passes so new timestamps must be acquired in time. The solution for the electronic document long-term preservation is suggested so that technological implementation supports legal regulation. Document formats for this model are suggested as well as the usage of the advanced electronic signature format. The formats from the AdES family of signatures are proposed: XAdES, CAdES, PAdES. At the end of this thesis the suggestion to set up an infrastructure for the long-term storage of electronically signed documents in the Republic of Croatia is given

Analysis of Influence of Croatian Legislation on e-Business and Long-Term Preservation of Digitally Signed Documents

U radu autori istražuju hrvatski zakonodavni okvir koji se odnosi na elektroničko poslovanje te ga stavljaju u kontekst sličnog zakonodavnoga okvira u zemljama Europske unije. Zbog boljeg razumijevanja problema koji se pojavljuju u rješenjima hrvatskoga zakonodavca autori identificiraju ključne elemente infrastrukture javnoga ključa (PKI) koji su značajni za elektroničko poslovanje. Autori tumače pojmove infrastruktura javnog ključa, digitalni certifikat, kvalificirani certifikat, certifikacijska služba, registracijski autoritet, neporecivost, pouzdana arhivska služba, vremenski žig, pouzdani vremenski žig, elektronički potpis, napredni elektronički potpis, te PDF/A. Potom analiziraju postojeća zakonodavna ograničenja u Hrvatskoj koja sprječavaju širu primjenu elektroničkoga poslovanja u praksi. Pritom provode komparativnu analizu s Direktivom 1999/93/EC, identificiraju problematične segmente postojećih zakona te predlažu njihova konkretna poboljšanja. Konačno, autori se osvrću ulogu arhivista u dugoročnom očuvanju elektronički potpisanih dokumenata.The authors analyse Croatian legal framework covering e-business and compare it to the legal framework in the EU countries. Firstly, in order to better explain the problems that they detect in the Croatian legislation, the authors identify and explain the key elements in the public key infrastructure (PKI) concept which are relevant for e-Business. Therefore, the concepts of public key infrastructure,digital certificates, qualified certificates, certification authority, registration authority, non-repudiation, trusted archival service (TAS), time stamp, trusted digital time stamp, electronic signature, advanced electronic signature, and PDF/A are explained. Further, the authors analyse the existing constraints in Croatian legislation that make wider application and usage of e-Business rather complicate. By comparatively analysing the Croatian legislation and the “Directive 1999/93/EC of the European Parliament and of the Council of 13 December 1999 on a Community framework for electronic signatures” they identify the problematic segments of the existing legislation and suggest how they could be improved. Finally, considering the results of the research, the authors reflect on the role of archivists in the long-term preservation of digitally signed documents

Novi pogledi na anatomiju grkljana dobrog dupina (Tursiops truncatus).

The mammalian larynx is an organ which serves as a barrier to prevent food from entering the respiratory system, and in most mammals it is used to produce sound. Although the general morphology of the cetacean larynx has been known for a long time, its detailed anatomy has been poorly studied, which has resulted in many inconsistencies in the available literature, particularly regarding the nature of the dorsal paired cartilages of the arytenoepiglottic tube, and the mucosal folds found in laryngeal cavity. The aim of this paper is to give a comprehensive description of the structures associated with the larynx of the bottlenose dolphin (Tursiops truncatus, Montagu, 1821), using the well-known laryngeal morphology of humans and various domestic mammals as guidelines. The structure of the larynx was studied in 7 bottlenose dolphins of both sexes, using the classical dissection method on fresh specimens and some conserved with 4 % water diluted formaldehyde. Although careful dissection showed distinct morphological differences between the laryngeal cartilages of the bottlenose dolphin and terrestrial mammals, most of the muscles attached to them were consistent with that of terrestrial mammals. We present structures characteristic to the larynx of the bottlenose dolphin, such as two ligaments which are not present in domestic mammals and humans. Furthermore, based on the comparison with human and animal laryngeal anatomy, we conclude that the dorsal paired cartilages of the arytenoepiglottic tube in the bottlenose dolphin most likely correspond to the cuneiform process of terrestrial mammals, and that the median and lateral folds found in the laryngeal cavity should not be identified as vocal and ventricular folds.Grkljan sisavaca je organ koji predstavlja zaštitu od ulaska hrane u dišni sustav, a većini sisavaca služi i za proizvodnju zvuka. Iako je općenita anatomija grkljana kitova odavno poznata, detalji su slabo proučavani što je za posljedicu imalo razne nedosljednosti u dostupnoj literaturi, pogotovo na temu prirode dorzalnih parnih hrskavica aritenoepiglotične cijevi i nabora sluznice u grkljanskoj šupljini. Cilj ovog rada je iznijeti potanki opis struktura grkljana dobrog dupina (Tursiops truncatus, Montagu, 1821), pri čemu se kao smjernice rabe dobro upoznata anatomija grkljana domaćih sisavaca i čovjeka. Građa grkljana se proučavala na 7 dobrih dupina oba spola služeći se klasičnim metodama sekcije na svježim uzorcima i arhivskim uzorcima uščuvanim u 4 % -tnom formaldehidu razrijeđenim u vodi. Iako je pažljiva sekcija pokazala očigledne morfološke razlike u hrskavicama između dobrog dupina i kopnenih sisavaca, većina mišića koji se prihvaćaju za njih su odgovarajući kopnenim sisavcima. Iznosimo strukture koje su karakteristične za grkljan dobrog dupina kao što su: dva ligamenta koji nisu prisutni u čovjeka i domaćih sisavaca. Također, na temelju usporedbe s ljudskim i životinjskim grkljanima, zaključujemo da dorzalne, parne hrskavice aritenoepiglotične cijevi najvjerojatnije odgovaraju kuneiformnom izdanku domaćih sisavaca, a da se medijani i lateralni nabori sluznice grkljanske šupljine ne bi trebali poistovjećivati s glasnicama

Are mice, rats, and rabbits good models for physiological, pharmacological and toxicological studies in humans?

In the mammalian kidneys, handling of various organic compounds is mediated by multispecific organic anion and cation transporters localized in the luminal and contraluminal cell membrane domains of specific nephron segments, largely in proximal tubules. These transporters are responsible for cellular uptake and/or elimination of endogenous and xenobiotic organic compounds, including various anionic and cationic drugs, thus contributing to their reabsorption and/or secretion along the nephron. Recent studies have indicated a pivotal role of these transporters in drug resistance, drug-drug interactions, and drug-induced nephrotoxicity, whereas the presence of disfunctional transporters due to truncated isoforms or point mutations can cause genetic diseases. In rat, mouse and rabbit nephrons, a number of these transporters exhibit sex differences in their protein and/or mRNA expression. In comparison with the expression in rodents and rabbits, in the human nephrons some transporters are absent, some exhibit different localization in the cell membrane domains, and none exhibit the sex-dependent expression. Species differences in some transporters have been further demonstrated concerning substrate selectivity, distribution in cells along the nephron, levels of mRNA and/or protein expression, sensitivity to inhibitors, and regulation. Overall these differences in the mammalian kidneys indicate that: a) data on the membrane transporters-related functions in one species can not simply be regarded as relevant for other species, and b) many physiological, pharmacological, and toxicological findings related to organic anion and cation transport and transporters in rodents and rabbits do not reflect the situation in humans

Metaboličke osobitosti četveroglavog bedrenog mišića (m. quadriceps femoris) u ovaca pasmine Lička pramenka hranjenih uz dodatak plemenite pečurke (Agaricus bisporus).

The objective of this study was to verify the presence of oxidative enzymes in the quadriceps femoris muscle of Lika Pramenka sheep and to evaluate the effect of supplement from button mushrooms, Agaricus bisporus (A. bisporus), on the histochemical and morphological characteristics of the muscles. Fourteen oneyear-old Lika Pramenka sheep were randomly divided into two groups (control and experimental groups) comprising 7 animals each. The experiment was conducted over a period of 6 weeks of the winter feeding period. The control group of sheep was fed with a standard feed without antimicrobials or growth promoters. The experimental group was given the same feed but with an additional 1.5% of dry A. bisporus. During the experiment access to water and feed was ad libitum. Samples were tested for the size and type of muscle fibers, as well as for the presence of oxidative enzymes. The diameter of muscle fibers and histochemical reactions profiles were significantly greater in animals fed with the A. bisporus supplement. On the basis of the increased activity of oxidative enzymes, which resulted in pronounced cell metabolism and increased muscle mass, we conclude that A. bisporus displays growth promoter effects.Cilj ovog istraživanja bio je provjeriti prisutnost oksidativnih enzima u četveroglavom bedrenom mišiću (m. quadriceps femoris) ovaca pasmine Lička pramenka te procijeniti učinak u hranu dodanog pripravka plemenite pečurke Agaricus bisporus (A. bisporus) na histokemijske i morfološke karakteristike mišića. Četrnaest jednogodišnjih ovaca bilo je nasumično odabrano i podijeljeno u dvije skupine (kontrolna i pokusna skupina) s po sedam životinja. Pokus je bio proveden tijekom 6 tjedana hranjenja. Kontrolna skupina bila je hranjena standardnom hranom, dok je pokusnoj skupini u standardnu hranu umješano 1,5% suhog pripravka A. bisporus. Tijekom cijelog pokusnog razdoblja hrana i voda bile su životinjama dostupne ad libitum. Uzorci m. quadriceps femoris ovaca u pokusu bili su analizirani s obzirom na veličinu i tip mišićnog vlakna, te na prisutnost oksidativnih enzima. Mišićna vlakna većih promjera i snažnije histokemijske reakcije zabilježena su u ovaca hranjenih s dodatkom A. bisporus. Temeljem povećane aktivnosti oksidativnih enzima, što je rezultiralo pojačanim staničnim metabolizmom i povećanom mišićnom masom ovaca hranjenih uz dodatak pripravka plemenite pečurke, možemo zaključiti da A. bisporus ima učinak promotora rasta

Oksalat – od okoliša do bubrežnih kamenaca

Oxalate urolithiasis (nephrolithiasis) is the most frequent type of kidney stone disease. Epidemiological research has shown that urolithiasis is approximately twice as common in men as in women, but the underlying mechanism of this sex-related prevalence is unclear. Oxalate in the organism partially originate from food (exogenous oxalate) and largely as a metabolic end-product from numerous precursors generated mainly in the liver (endogenous oxalate). Oxalate concentrations in plasma and urine can be modified by various foodstuffs, which can interact in positively or negatively by affecting oxalate absorption, excretion, and/or its metabolic pathways. Oxalate is mostly removed from blood by kidneys and partially via bile and intestinal excretion. In the kidneys, after reaching certain conditions, such as high tubular concentration and damaged integrity of the tubule epithelium, oxalate can precipitate and initiate the formation of stones. Recent studies have indicated the importance of the SoLute Carrier 26 (SLC26) family of membrane transporters for handling oxalate. Two members of this family [Sulfate Anion Transporter 1 (SAT-1; SLC26A1) and Chloride/Formate EXchanger (CFEX; SLC26A6)] may contribute to oxalate transport in the intestine, liver, and kidneys. Malfunction or absence of SAT-1 or CFEX has been associated with hyperoxaluria and urolithiasis. However, numerous questions regarding their roles in oxalate transport in the respective organs and male-prevalent urolithiasis, as well as the role of sex hormones in the expression of these transporters at the level of mRNA and protein, still remain to be answered.Oksalatna urolitijaza (nefrolitijaza) najučestaliji je tip bolesti bubrežnih kamenaca. Rezultati epidemioloških istraživanja pokazali su da je urolitijaza približno dvostruko učestalija u muškaraca nego u žena, ali osnovni mehanizam nastanka ove spolno-ovisne prevalencije nije razjašnjen. Oksalat u organizmu dijelom potječe iz hrane (egzogeni oksalat), a glavninom nastaje kao konačni produkt metabolizma raznih preteča u jetrima (endogeni oksalat). Na koncentraciju oksalata u plazmi i urinu utječu razne tvari iz hrane, koje mogu pozitivno ili negativno djelovati na apsorpciju, metaboličke puteve i/ili izlučivanje oksalata. Oksalat se iz organizma izlučuje u manjem obimu putem žuči u crijevo, a glavninom bubrezima. U bubrezima, pri odgovarajućim uvjetima kao što su visoka koncentracija oksalata i oštećenje epitela bubrežnih kanalića, oksalat može precipitirati i time potaknuti stvaranje kamenaca. Rezultati novih istraživanja upućuju na važnost membranskih prijenosnika otopljenih tvari (SoLute Carriers) iz obitelji 26 (SLC26) za prijenos oksalata u specifičnim organima. Smatra se da dva člana ove obitelji: prijenosnik sulfatnog aniona (Sulfate Anion Transporter 1; SAT-1; SLC26A1) i izmjenjivač klora i mravlje kiseline (Chloride/Formate EXchanger; CFEX; SLC26A6), imaju značajnu ulogu u prijenosu oksalata u crijevima, jetrima i bubrezima; hiperoksalurija i nefrolitijaza utvrđeni su pri slaboj aktivnosti ili nedostatku SAT-1 i CFEX proteina. Međutim, još uvijek postoje brojne nejasnoće glede prijenosa oksalata u navedenim organima, mehanizma nastanka spolnih razlika u nefrolitijazi i utjecaja spolnih hormona na ekspresiju proteina i mRNA za navedene prijenosnike

Prijenos glukoze kroz epitel tankoga crijeva

The duodenum, jejunum and ileum are parts of the small intestine and the sites of the terminal stages of enzymatic digestion, and the majority of nutrient, electrolyte and water absorption. The apical, luminal membrane of the enterocyte is built of numerous microvilli that increase the absorptive surface of the cell. Carbohydrates, in the form of monosaccharides, oligosaccharides and especially polysaccharides, make up the largest quantitative and energetic part of the diet of most animals, including humans. Galactose, fructose and glucose, the final degradation products of polysaccharide and oligosaccharide enzymatic digestion, can be absorbed by enterocytes either by active transport or by facilitated diffusion. In the small intestine, the transepithelial transport of glucose, the most abundant monosaccharide after carbohydrate digestion and the main source of energy, is performed by a specific membrane transporter located in the brush border membrane of the enterocyte, the sodiumglucose cotransporter 1 (SGLT1). While SGLT1 transports glucose across the brush border membrane, a specific basolateral membrane glucose transporter, the sodium-independent glucose transporter 2 (GLUT2), transfers glucose out of the enterocyte down the concentration gradient. The sodium-potassium pump (Na/KATPase), as a sodium and potassium ion transporter, is functionally closely related to the sodium-dependent SGLT1. Na/KATPase is responsible for maintaining the electrochemical gradient of sodium ions, as the driving force for glucose transport via SGLT1. Transepithelial transport of glucose in the small intestine and the differentiation of enterocytes occurs relatively early during the foetal period, allowing glucose to be absorbed from ingested amniotic fluid. Nutrient transport is possible along the whole villus-crypt axis during intrauterine development, while transport shifts toward the villus tip in the mature small intestine. With maturation, glucose transport rates change not only across the villus-crypt axis, but also along the proximodistal axis in the small intestine. The glucose absorption rate shows differences between subunits of the small intestine depending on the age and type of ingested carbohydrates, where complex carbohydrates replace less complex carbohydrates or disaccharides.Duodenum, jejunum i ileum dijelovi su tankog crijeva gdje se dovršava enzimatska razgradnja i najveći opseg apsorpcije hranjivih tvari, elektrolita i vode. Apikalna, luminalna stanična membrana enterocita građena je od brojnih mikrovila koji povećavaju apsorpcijsku površinu stanice. Ugljikohidrati, u obliku monosaharida, oligosaharida i posebno polisaharida, čine najveći kvantitativni i energetski dio prehrane većine životinja, ali i ljudi. Galaktozu, fruktozu i glukozu, krajnje produkte enzimatske razgradnje polisaharida i oligosaharida, enterociti mogu apsorbirati aktivnim prijenosom ili olakšanom difuzijom. Transepitelni prijenos glukoze, najzastupljenijeg monosaharida nakon razgradnje ugljikohidrata i glavni izvor energija u tankom se crijevu odvija pomoću specifičnog transmembranskog prijenosnika smještenog u četkastom porubu membrane enterocita, prijenosnika glukoze ovisnog o natriju 1 (engl. sodiumglucose cotransporter 1, SGLT1). Dok SGLT1 prenosi glukozu preko četkastog poruba membrane, specifični prijenosnik smješten na bazolateralnoj membrani, prijenosnik glukoze neovisan o natriju 2 (engl. glucose transporter 2, GLUT2), prenosi glukozu iz enterocita niz koncentracijski gradijent. Natrij-kalijeva pumpa (Na/K-ATPaza), kao prijenosnik iona natrija i kalija, funkcionalno je usko povezana sa SGLT1. Na/K-ATPaza odgovorna je za održavanje elektrokemijskog gradijenta natrijevih iona, koji je pokretačka sila prijenosa glukoze putem SGLT1 prijenosnika. Transepitelni prijenos glukoze u tankom crijevu pojavljuje se relativno rano tijekom fetalnog razdoblja, zajedno s diferencijacijom enterocita, što omogućava apsorpciju glukoze iz progutane amnionske tekućine. Prijenos hranjivih tvari moguć je tijekom intrauterinog razvoja duž cijele dužine crijevne resice, dok se u zrelom tankom crijevu prijenos hranjivih tvari pomiče prema vrhu crijevne resice. Sazrijevanjem tankog crijeva aktivnost prijenosnika ne mijenja se samo duž crijevne resice, nego i duž proksimo-distalne osi u tankom crijevu. Apsorpcija glukoze u pojedinim dijelovima tankog crijeva mijenja se ovisno o dobi i vrsti konzumiranih ugljikohidrata, pogotovo kada složeni ugljikohidrati zamjenjuju manje složene ugljikohidrate ili disaharide u prehrani

Ontogenetske promjene morfometrijskih vrijednosti prsne peraje u dobrih dupina (Tursiops truncatus).

The aim of the present study was to investigate and compare the morphometric characteristics of the flippers in male and female bottlenose dolphins (Tursiops truncatus) of various ages. We investigated the right flippers of 64 bottlenose dolphinc specimens - 36 males and 28 females, in an age span of from 6 months to 28 years. Two numeric indices were suggested in order to establish the numerical relationship between the external measures of the flipper and the total body length of each animal. The index of the flipper measurements (IxF) directly showed the differences in flipper sizes in the investigated dolphins, whereas the index of the flipper measurements and the total body length (IxBL) displayed the differences in the flipper size in relation to the body length of the studied dolphins. By comparing these indices in dolphins of different ages, noticeable variations in flipper dimensions during total body growth were observed. In bottlenose dolphins, both flipper indices were highly correlated with the animal’s body length. The mean value of the index of the flipper measurements and the total body length (IxBL) was somewhat higher in female bottlenose dolphins. Both the flipper indices were highly correlated with the animal’s age, and our results suggest that the flipper grows until the tenth year of age, after which it does not change substantially until the 25th year of age. After that age the flipper size starts to decrease.Cilj ovog istraživanja bio je usporedba morfometrijskih obilježja prsne peraje u mužjaka i ženki dobrih dupina različite dobi. Istražene su desne prsne peraje od 64 dobra dupina (Tursiops truncatus) - 36 mužjaka i 28 ženki u dobnom rasponu od 6 mjeseci do 28 godina. Predložena su dva numerička indeksa kojima bi se utvrdila numerička povezanost između vanjskih mjera prsne peraje i ukupne dužine tijela svake životinje. Indeks mjera prsne peraje (IxF) izravno pokazuje razlike u veličini prsne peraje istraženih dupina, dok indeks mjera prsne peraje i ukupne dužine tijela (IxBL) pokazuje razlike u veličini prsne peraje u odnosu na ukupnu dužinu tijela istraženih dupina. Usporedbom tih indeksa u dupina različite dobi utvrđene su varijacije u dimenzijama prsne peraje tijekom ukupnog rasta tijela životinje. U dobrih dupina, oba indeksa bila su u visokoj korelaciji s ukupnom dužinom tijela. Srednja vrijednost indeksa mjera prsne peraje i ukupne dužine tijela bila je nešto veća u skupini ženki istraženih dupina. Oba indeksa bila su u visokoj korelaciji s dobi životinje te naše istraživanje pokazuje da prsna peraja u dupina raste do dobi od 10 godina, nakon čega se značajno ne mijenja do dobi od 25 godina. Nakon te dobi, veličina prsne peraje počinje se smanjivati