Photoperiod effects on circadian rhythms and puberty onset in African catfish Clarias gariepinus

ABSTRACT Photoperiod manipulation is routinely used in the aquaculture industry with the aim to enhance growth by manipulating the timing of reproduction in several commercially important temperate fish species. However, there are clear gaps in our understanding of how photoperiod is perceived by the circadian axis and transmitted to the brain to alter reproduction. Furthermore, due to the wide range of environments inhabited by fish, it is unlikely that one single organization exists. It is therefore believed that comparative studies of temperate species “models” with tropical species such as the African catfish (Clarias gariepinus) that adapted to different environments characterized by weaker light signals can help in such an aim. A number of studies were therefore performed in this PhD project to expand our knowledge on circadian biology and environmental physiological effects in African catfish. The first aim was to characterize the circadian melatonin system in this species (chapter 3). Results clearly showed that the control of melatonin production by the pineal gland was very different in the African catfish as compared to temperate species such as salmon and trout. Indeed, melatonin production appeared to mainly depend on light stimuli perceived by the eyes as opposed to salmonids where light directly perceived by the pineal gland regulates its own melatonin production within photoreceptors. The main evidence was obtained in ophthalmectomised fish that were unable to synthesize and release melatonin into the blood circulation during the dark period. This was the first time that such a decentralized organisation, similar in a way to the mammalian system, was found in any teleost species. In vitro results also supported such findings as African catfish pineal glands in isolation were not able to normally produce melatonin at night as usually seen in all other fish species studied so far. This indirectly suggested that pineal gland photo-sensitivity might be different in this tropical species. Further studies were performed to better determine the amount of light that can be perceived by the African catfish pineal gland depending on light transmittance though the skull (where the pineal gland is located). Surprisingly, it appeared that catfish cranium act as a stronger light filter than in other species resulting in lower light irradiance of the pineal gland. This could explain, although it still needs to be further confirmed, why African catfish photic control of melatonin produced by the pineal would have evolved differently than in temperate species. The work then focused on better characterizing diel melatonin production and endogenous entrainment through exposure to continuous photic regimes (continuous light, LL or darkness, DD) (chapter 4). Daily melatonin profiles of fish exposed to 12L:12D photoperiod (routinely used in indoor systems) confirmed low melatonin production at day (<10 pg/ml) and increase at night (50 pg/ml) as reported in most vertebrate species studied to date. Interestingly, results also showed that melatonin production or suppression can anticipate the change from night to day with basal melatonin levels observed 45 mins prior to the switch on of the light. These observations clearly suggest the involvement of a clock-controlled system of melatonin secretion that is capable of anticipating the next photophase period. Furthermore, when constant light (LL) was applied, day/night melatonin rhythms were abolished as expected due to the constant photic inhibition of AANAT activity (e.g. one of the enzyme responsible for the conversion of serotonin into melatonin). However when fish were exposed to constant darkness (DD), a strong endogenous melatonin rhythm (maintained for at least 4 days and 18 days in catfish and Nile tilapia respectively) was found, demonstrating once again the presence of robust circadian oscillators in this species. The next aim of the doctoral project was then to investigate circadian behaviour of catfish through locomotor activity studies (Chapter 5). African catfish is again a very interesting “model” due to its reported nocturnal activity rhythmicity as compared to most other teleosts species. Locomotor activity is considered as a very useful tool to elucidate the mechanisms of circadian organization in both invertebrates and vertebrates circadian. Results first confirmed the nocturnal activity rhythms in the species. Furthermore, clear circadian endogenous rhythms were observed under constant light (LL) or darkness (DD) during several days before losing rhythmicity. Interestingly, the activity levels varied depending on the stocking density. Finally, the last aim of this project was to test the effects of a range of photoperiodic manipulations on growth performances, sexual development and reproductive performances in African catfish reared from eggs to puberty. Results did not show any differences at the early sages (up to 90 days post hatching) in growth performances nor mortality (high) between control 12L:12D and LL treatments. In contrast, during the juvenile-adult period (from 120 to 360 DPH), significant growth effects were observed, as previously reported in other catfish species, with fish under LL displaying lower growth rate, food consumption and feed conversion efficiency in comparison to most other treatments (12:12, LL, 6:6, 6:18, 12-LL and LL-12) especially 12l:12D. However, no major effects of the photoperiodic treatments were observed with all fish recruited into puberty and developing gonads although differences in the timing of gametogenesis could be observed, especially a delay (circa 2 months) in females exposed to short daylength (6L:18D and 6L:6D). As for egg quality, egg diameter was the only parameter to differ between treatments (slightly larger in egg batch from LL treated females). Overall, none of the photoperiodic regime suppressed maturation in African catfish as opposed to some temperate species. The work carried out during this PhD project clearly advanced our understanding of circadian rhythmicity, light perception and effects of photoperiod on physiology in a tropical species. Future studies are now required to further characterise the circadian system and link it to evolutionary trends within vertebrates

The petrology and geochemistry of ophiolites from the Khawr Fakkan region. Northern Oman range, United Arab Emirates

The field relationships, petrography, geochemistry and phase chemistry of the peridotite-gabbro-basalt sequence of the Khawr Fakkan - Wadi Shi - Wadi Madha area suggest that the various components are genetically related. They result from partial melting of the upper mantle, followed by fractional crystallisation of the basic magma generated by this process. The rocks comprise a typical ophiolite sequence and are similar to assemblages from other Alpine-type ultramafic complexes. The area studied may be broadly subdivided into two major zones. In the west the rocks are principally tectonised ultramafics, while to the east of these a series of cumulate gabbros, with dolerite dykes particularly prevelant in the east, passes upwards into basaltic lavas. The tectonised ultramafics are separated from the gabbroic and basaltic rocks by an easterly-dipping thrust- fault zone, which strikes approximately north-south. The rock types exposed in the area to the west of the major thrust fault are harzburgites, dunites and wehrlites. They are all, to some extent, serpentinised. The harzburgites have an intensely tectonised fabric, and consist of an assemblage of highly refractory chemistry. The dunites also show a strong tectonic fabric and total absence of cumulus textures. Textural evidence shows that most of the wehrlites are strongly deformed. A set of criteria to distinguish the refractory residua of partial melting from the cumulates are developed from analytical data and textural evidence. The rock types exposed to the east of the major thrust fault are gabbyo cumulates. The cumulus types recognised include olivine pyroxenites, olivine gabbros, norites and hypersthene gabbros, gabbros and anorthosites and leucocratic gabbros. Where transected by faults gabbro mylonites are developed. Cumulus textures include heteradcumulates, adcumulates and mesocumulates. The basaltic rocks occur both as intrusive dolerite dykes and as lava flows. The basalts are invariably altered, with ferroraagnesian minerals being represented by amphibole in the most part. They are also silicified. variation in major and trace elements reveal that the crustal members of the ophiolite suite (gabbros and basaltic rocks) are tholeiitic. The parent magma being a low-Ti and low-K tholeiitic type. Whole-rock analyses and mineral chemistry are used in an attempt to estimate the nature and composition of the partial-melt magma from which both the cumulate gabbros and basaltic rocks have evolved. A variety of methods have been used, and compared, in an attempt to estimate the equilibration temperatures and pressures of the ultramafic rocks and cumulate gabbros. The application of several geothermometers gave values for dunite of 872 to 1075ºC, for harzburgites of 1099 to 1167ºC, for a wehrlite of 1104ºC, and for the rare rock- type plagioclase peridotite, a somewhat higher value of 1263ºC. Temperatures recorded for olivine pyroxenite cumulates range from 879 to 974ºC, and for gabbros and norites from 839 to 999ºC. Lower temperatures of 909 to 989ºC using an orthopyroxene-clinopyroxene geothermometer, as compared to 1099 to 1167ºC, for the harzburgites may reflect the late, lower temperature, crystallisation of clinopyroxene from trapped liquid. In all cases pressures were less than 7 Kb and correspond to a maximum depth of about 22 Km in the oceanic setting

Should We Do Bilateral Internal Mammary Artery Grafting in Diabetic Patients?

Nowadays, potential advantages of BIMA grafting are recognized overall in terms of long-term survival1 and by not increasing operative morbidity. One of the major restrictions for extending the use of BIMA grafting is the current impossibility of generalizing the procedure to higher risk patients. These results tend to confirm recent results that promote the use of BIMA grafting in every kind of patients and consequently to confirm the generalization of the procedure, without being afraid of sternal complications. The absence of deep sternal wound infection in our study shows that there is no contraindication of BITA grafting among diabetic patients

Studies on the cell autonomous role for notch in definitive haematopoiesis and Tet genes' requirements in early organogenesis

In vertebrates, haematopoiesis is maintained by self-renewing multipotent haematopoietic stem cells (HSCs) in the adult bone marrow. HSCs are specified and generated during early embryonic development from arterial endothelial cells in the ventral wall of the dorsal aorta (vDA) that become haemogenic. Examination of mib mutants and rbpja/b morphants zebrafish embryos, that have defects in Notch signalling show that both arterial specification and HSCs development require an intact Notch signalling pathway. Utilizing in-house generated zebrafish Notch reporter lines, we show that Notch signalling initiates in the migrating hEC progenitors before their arrival to the midline to form the DA. Following arterial specification, Notch activity rapidly increases in the DA cells and persists at high levels until the time point of HSC emergence from the vDA, then sharply falls to hardly detectable levels. Embryos treated with the γ-secretase inhibitor DAPT or DAPM lose HSC development but retain arterial specification. Quantification of the residual Notch activity in our reporter lines by RT-PCR, revealed that low levels of Notch signalling retained in treated embryos are sufficient for arterial gene expression, while high levels of Notch signalling are required for hECs induction. Additional to these loss of function experiments, our endothelial specific gain of function studies suggested that continuous expression of nicd in the ECs in stable transgenic lines prevent cells from differentiation into mature HSCs that can leave the vDA to seed the CHT. By contrast, transient expression of nicd in ECs appeared to expand HSC fate and allow cells to seed the CHT, suggesting that down-regulation of Notch signalling is essential to enable cells committed to the blood lineage to leave the vDA and seed the CHT. These data represent the first demonstration, to our knowledge, that cell autonomous Notch induction in ECs in vivo is sufficient to expand HSC formation in vertebrates. Ten-Eleven-Translocation (Tet) proteins are a family of enzymes known to be actively involved in DNA de-methylation by 5-mC oxidation. This process is essential for proper development and cell lineage specification. Here, we used zebrafish tet1/2/3 morpholinos to study the role of Tet enzymes in zebrafish development and organogenesis. Our results showed that individual depletion of Tet1 or Tet3 enzymes is sufficient to arrest zebrafish development at the onset of somitogenesis, whereas tet2 morphants appear normal. Moreover, analysis of mildly affected morphants shows that Tet1 knockdown leads to atypical neurogenesis in zebrafish embryos. Global 5hmC levels are dramatically reduced in both tet1 and tet3 morphants, indicating the importance of Tet proteins in vertebrate organogenesis

Analysis of Clients' Needs and Satisfaction in the Construction Industry in Gaza Strip

The construction industry is backwarded compared to other fields of industry all over the world regarding the customer satisfaction issues. This research discussed the clients' and consultants' needs or expectations, based on the levels of implied importance and performance provided by local contractors. A structured questionnaire was adopted in this study. The obtained data were statistically analyzed to find out the relationship between the obtained results for clients and consultants regarding the importance and the satisfaction with the provided performance by local contractors regarding the identified satisfaction factors based on the relative importance indices of the different factors. The results revealed that both clients and consultants agreed with each other on the importance of the identified satisfaction factors. They also agreed that they are not satisfied with the provided levels of performance by local contractors, and the contractors need to improve their practices and procedures. These factors were ranked according to the implied importance by both clients and consultants. The most important factors to achieve clients' and consultants' satisfaction were also identified. The most important factors within the adopted groups were: understanding the contract documents and specifications, managing the site through top management levels, finishing the project within time, budget and quality, providing personal protection equipment, availability of maximum resources, availability of highly qualified personnel, completion of defects and handing over, and finally honesty and integrity in dealing with clients and consultants. Finally, a conceptual framework was developed showing a methodology for meeting the needs and expectations of clients and consultants in the local construction industry. It was found that the different parties must carry out better communication with each other. Common understanding and cooperation must prevail to achieve better working environment, leading to improved levels of satisfaction for both clients and consultants

Studies on the cell autonomous role for notch in definitive haematopoiesis and Tet genes' requirements in early organogenesis

In vertebrates, haematopoiesis is maintained by self-renewing multipotent haematopoietic stem cells (HSCs) in the adult bone marrow. HSCs are specified and generated during early embryonic development from arterial endothelial cells in the ventral wall of the dorsal aorta (vDA) that become haemogenic. Examination of mib mutants and rbpja/b morphants zebrafish embryos, that have defects in Notch signalling show that both arterial specification and HSCs development require an intact Notch signalling pathway. Utilizing in-house generated zebrafish Notch reporter lines, we show that Notch signalling initiates in the migrating hEC progenitors before their arrival to the midline to form the DA. Following arterial specification, Notch activity rapidly increases in the DA cells and persists at high levels until the time point of HSC emergence from the vDA, then sharply falls to hardly detectable levels. Embryos treated with the γ-secretase inhibitor DAPT or DAPM lose HSC development but retain arterial specification. Quantification of the residual Notch activity in our reporter lines by RT-PCR, revealed that low levels of Notch signalling retained in treated embryos are sufficient for arterial gene expression, while high levels of Notch signalling are required for hECs induction. Additional to these loss of function experiments, our endothelial specific gain of function studies suggested that continuous expression of nicd in the ECs in stable transgenic lines prevent cells from differentiation into mature HSCs that can leave the vDA to seed the CHT. By contrast, transient expression of nicd in ECs appeared to expand HSC fate and allow cells to seed the CHT, suggesting that down-regulation of Notch signalling is essential to enable cells committed to the blood lineage to leave the vDA and seed the CHT. These data represent the first demonstration, to our knowledge, that cell autonomous Notch induction in ECs in vivo is sufficient to expand HSC formation in vertebrates. Ten-Eleven-Translocation (Tet) proteins are a family of enzymes known to be actively involved in DNA de-methylation by 5-mC oxidation. This process is essential for proper development and cell lineage specification. Here, we used zebrafish tet1/2/3 morpholinos to study the role of Tet enzymes in zebrafish development and organogenesis. Our results showed that individual depletion of Tet1 or Tet3 enzymes is sufficient to arrest zebrafish development at the onset of somitogenesis, whereas tet2 morphants appear normal. Moreover, analysis of mildly affected morphants shows that Tet1 knockdown leads to atypical neurogenesis in zebrafish embryos. Global 5hmC levels are dramatically reduced in both tet1 and tet3 morphants, indicating the importance of Tet proteins in vertebrate organogenesis

The Structure of the Quaternary Words in Arabic: A Study in the Origin and the Structural Form

This research tackles the theoretical vision of the issue of forming the quaternary words in Arabic. The research embraces the hypothesis highlighting that the quaternary is not improvised etymologically speaking, taking in consideration its commonness at the form of four connected consonants. The research is a part of a progressive study The Quaternary and The Quinary Structures of Word Roots in Arabic: A morphological Semantical Applied Study about the existence of the quaternary words in the ancient, medieval and modern scripts represented by the Holy Quran, al-Mufaddalyyat, al-Hadeeth in Saheeh Muslim, al-Muqabasat, the Thesaurus of Arab Proverbs by abd al-Rahman Afif, and al-Shawqyyat to reveal its semantic and pragmatic values. It also reveals its Arabic and foreign etymological forms, syllabification and morphology in roots and derivatives. In order to prove the hypothesis, the research focuses on three points; the linguistic value of the quaternary among the old and contemporary scholars, the ways of forming the quaternary, and the location of the fourth consonant in the root. The research concludes that the quaternary is etymologically a derived structure comes out of a smaller structure; almost tripartite and binary sometimes. In addition, the location of the fourth letter is not determined in the initial, the middle or the rear and its forming is not restricted by the standardized derivative suffixes, prefixes or infixes, but it can be formed of all Arabic alphabet

Development Of Efficient Multi-Level Discrete Wavelet Transform Hardware Architecture For Image Compression

Berfokuskan pengkomputeran intensif dalam gelombang kecil diskret (DWT), reka bentuk seni bina perkakasan efisen bagi pengkomputeran laju menjadi imperatif terutamanya dalam aplikasi masa nyata. Focusing on the intensive computations involved in the discrete wavelet transform (DWT), the design of efficient hardware architectures for a fast computation of the transform has become imperative, especially for real-time applications

HFAQM: A hybrid fair active queue management mechanism to improve fairness and stability for wireless local area network

Active Queue Management (AQM) is a proactive scheme that controls network congestion by avoiding it before it happens. When implementing AQM in wireless networks, several contemporary issues must be considered, such as interference, collisions, multipath-fading, propagation distance and shadowing effects, which affect the transmission rate of the links. These issues in WLAN networks with the existence of different types of flow have a direct effect on fairness. The main idea behind the wireless network is using the flexibility of radio waves to transfer data from point to point that is giving WLAN the flexibility and mobility: wireless nodes can connect, disconnect or even move from one access point to another rapidly. However, this affects the stability of the WLAN network. This research aims to reduce unfairness and instability by proposing a Hybrid-Fair AQM (HFAQM) scheme. HFAQM comprises two mechanisms: Congestion Indicator Mechanism (CIM), and Control Function Mechanism (CFM). CIM was designed to improve fairness in WLANs by hybridizing queue delay with arrival rate as parameters to calculate the congestion level. Whereas, CFM was developed to improve network stability by using an adaptive control function with the ability to drop and mark packets to overcome the rapidly changing characteristics of WLAN network. A series of experimental studies were conducted to validate the proposed mechanisms and four variants of AQM schemes, RED, REM, AVQ and CoDel, were chosen to evaluate the performance of HFAQM through simulation. The findings show that HFAQM’s main achievement is 99% fairness and improved stability by 10% from the closest scheme, with better throughput, queue length, queue loss, and outgoing link utilization as secondary achievements. The proposed scheme provides significantly better fairness and stability in WLAN environment, with the existence of different types of flow

Specification of downlink-fixed reference channel DL-FRC for 5G new radio technology

The next generation for mobile communication is new radio (NR) that supporting air interface which referred to the fifth generation or 5G. Long term evolution (LTE), universal mobile telecommunications system (UMTS), and global system for mobile communication (GSM) are 5G NR predecessors, also referred to as fourth generation (4G), third generation (3G) and second generation (2G) technologies. Pseudo-noise (PN) code length and modulation technique used in the 5G technology affect the output spectrum and the payload of DL-FRC specification, in this paper quadrature phase shift keying (QPSK), 16 QAM modulation approaches tested under additive white Gaussian noise (AWGN) in term of bit error rate (BER) which used with 5G technology system implemented with MATLAB-Simulink and programing and, resulting of 1672, 12296 bit/slot payload at frequency range FR1 from 450 MHz-6 GHz and 4424, 20496 bit/slot payload at frequency range FR2 from 24.25 GHz-52.6 GHz, also determining subcarrier spacing, allocated source block, duplex mode, payload bit/slot, RBW (KHz), sampling rate (MHz), the gain and the bandwidth of main, side loop where illustrated