Travelling waves in a tissue interaction model for skin pattern formation

Tissue interaction plays a major role in many morphogenetic processes, particularly those associated with skin organ primordia. We examine travelling wave solutions in a tissue interaction model for skin pattern formation which is firmly based on the known biology. From a phase space analysis we conjecture the existence of travelling waves with specific wave speeds. Subsequently, analytical approximations to the wave profiles are derived using perturbation methods. We then show numerically that such travelling wave solutions do exist and that they are in good agreement with our analytical results. Finally, the biological implications of our analysis are discussed

Sequential pattern formation in a model for skin morphogenesis

During morphogenesis regular patterns often develop behind a frontier of pattern formation which travels across the prospective tissue. Here the authors consider the propagating patterns exhibited in a two-dimensional domain by a tissue interaction mechanochemical model for skin pattern formation. It is shown that the model can exhibit travelling waves of complex spatial pattern formation. Two alternative mechanisms that can produce such sequential patterning are presented. In particular, it is demonstrated that the specification of a simple quasi-one-dimensional pattern is all that is required to determine a complex two-dimensional pattern. Finally, the model solutions are related to actual pattern propagation during chick feather primordia initiation

Effect of curd suppression of a calf milk replacer fed at increasing levels on nutrient digestibility and body mass-gain

Two groups of eight Friesland bull calves each were used in the trial. Calves received a commercial, coagulable milk replacer in which casein coagulation either was normal (CM treatment), or was prevented by the precipitation of Ca++ with an oxalic acid-sodium hydroxide buffer (NCM treatment). In both treatments, the daily milk replacer feeding level (percentage of birth mass) was increased from 9% (week 1), to 12% (week 2), 15% (week 3) and 18% (week 4). Calves were weighed at weekly intervals and occurrence of diarrhoea was monitored. At four weeks of age, five calves from each treatment were randomly selected for a digestibility trial of seven days. Body mass-gain and efficiency of feed conversion (kg dry matter/kg gain) were 10,4 kg and 1,7; and 10,7 kg and 1,6 for the CM and NCM treatments, respectively. Digestibility coefficients were 90,2 and 91,1 % (dry matter), 91,9 and 93,6% (organic matter), and 81,0 and 85,6% (crude protein), for CM and NCM respectively. It was concluded that prevention of abomasal curd formation had no effect on body mass-gain, occurrence of diarrhoea, or digestibility of dry matter, organic matter and crude protein. Digestibility coefficients remained high, even at a daily feeding level of 18% of birth mass.Twee groepe van agt Friesbulkalwers elk is in die proef gebruik. Kalwers het 'n kommersiele, koaguleerbare melksurrogaat ontvang waarin koagulering of normaal was (CM-behandeling), of voorkom is deur die presipitering van Ca++ met 'n oksaalsuur-natriumhidroksiedbuffer (NCM-behandeling). Daaglikse melksurrogaatvoedingspeil (persentasie van geboortemassa) het in albei behandelings toegeneem vanaf 9% (week 1), tot 12% (week 2), 15% (week 3) en 18% (week 4). Kalwers is weekliks geweeg en die voorkoms van diarree is gemonitor. Vyf kalwers uit elke groep is op vier-weke-ouderdom ewekansig geselekteer vir 'n verteringsproef van sewe dae. Massatoename en doeltreffendheid van voeromsetting (kg droemateriaal/kg toename) was 10,4 kg en 1,7; en 10,7 kg en 1,6 vir die CM- en NCMbehandelings onderskeidelik. Verteerbaarheidskoeffisiente was 90,2 en 91,1% (droemateriaal), 91,9 en 93,6% (organiese materiaal) en 81,0 en 85,6% (ruprotei'en) vir CM en NCM, onderskeidelik. Die gevolgtrekking is gemaak dat voorkoming van abomasale stolselvorming geen invloed op massatoename, voorkoms van diarree, of die verteerbaarheid van droemateriaal, organiese materiaal en ruprotei'en gehad het nie. Verteerbaarheidskoeffisiente het hoog gebly, selfs teen 'n daaglikse voedingspeil van 18% van geboortemassa.Keywords: calves, milk replacers, casein, curd formation, digestibility, body mass-gai

On a model mechanism for the spatial patterning of teeth primordia in the Alligator

We propose a model mechanism for the initiation and spatial positioning of teeth primordia in the alligator,Alligator mississippiensis. Detailed embryological studies by Westergaard & Ferguson (1986, 1987, 1990) show that jaw growth plays a crucial role in the developmental patterning of the tooth initiation process. Based on biological data we develop a reaction-diffusion mechanism, which crucially includes domain growth. The model can reproduce the spatial pattern development of the first seven teeth primordia in the lower half jaw ofA. mississippiensis. The results for the precise spatio-temporal sequence compare well with detailed developmental experiments

Partial differential equations for self-organization in cellular and developmental biology

Understanding the mechanisms governing and regulating the emergence of structure and heterogeneity within cellular systems, such as the developing embryo, represents a multiscale challenge typifying current integrative biology research, namely, explaining the macroscale behaviour of a system from microscale dynamics. This review will focus upon modelling how cell-based dynamics orchestrate the emergence of higher level structure. After surveying representative biological examples and the models used to describe them, we will assess how developments at the scale of molecular biology have impacted on current theoretical frameworks, and the new modelling opportunities that are emerging as a result. We shall restrict our survey of mathematical approaches to partial differential equations and the tools required for their analysis. We will discuss the gap between the modelling abstraction and biological reality, the challenges this presents and highlight some open problems in the field

Modelling the spatial patterning of the primordia in the lower jaw of alligator mississippiensis

We propose a model mechanism for the initiation and spatial positioning of teeth primordia in the alligator, Alligator mississippiensis. Detailed embryological studies12–14 have shown that jaw growth plays a crucial role in the developmental patterning of the tooth initiation process. The development of the spatial pattern occurs on a timescale comparable to jaw growth. Based on biological data we develop a dynamic patterning mechanism, which crucially includes domain growth. The mechanism can reproduce the spatial pattern development of the first seven teeth primordia in the lower jaw of A. mississippiensis. The results for the precise spatio-temporal sequence compare well with experiment

Parascedosporium and its relatives: phylogeny and ecological trends

The genus Scedosporium and its relatives comprising microascalean anamorphs with slimy conidia were studied. Graphium and Parascedosporium also belong to this complex, while teleomorphs are found in Pseudallescheria, Petriella, Petriellopsis, and Lophotrichus. Species complexes were clearly resolved by rDNA ITS sequencing. Significantly different ecological trends were observed between resolved species aggregates. The Pseudallescheria and Scedosporium prolificans clades were the only lineages with a marked opportunistic potential to mammals, while Petriella species were associated primarily with soil enriched by, e.g. dung. A consistent association with bark beetles was observed in the Graphium clade. The ex-type strain of Rhinocladium lesnei, CBS 108.10 was incorrectly implicated by Vuillemin (1910) in a case of human mycetoma; its sequence was identical to that of the ex-type strain of Parascedosporium tectonae, CBS 127.84

Fungal Planet description sheets: 154–213

Novel species of microfungi described in the present study include the following from South Africa: Camarosporium aloes, Phaeococcomyces aloes and Phoma aloes from Aloe, C. psoraleae, Diaporthe psoraleae and D. psoraleae-pinnatae from Psoralea, Colletotrichum euphorbiae from Euphorbia, Coniothyrium prosopidis and Peyronellaea prosopidis from Prosopis, Diaporthe cassines from Cassine, D. diospyricola from Diospyros, Diaporthe maytenicola from Maytenus, Harknessia proteae from Protea, Neofusicoccum ursorum and N. cryptoaustrale from Eucalyptus, Ochrocladosporium adansoniae from Adansonia, Pilidium pseudoconcavum from Greyia radlkoferi, Stagonospora pseudopaludosa from Phragmites and Toxicocladosporium ficiniae from Ficinia. Several species were also described from Thailand, namely: Chaetopsina pini and C. pinicola from Pinus spp., Myrmecridium thailandicum from reed litter, Passalora pseudotithoniae from Tithonia, Pallidocercospora ventilago from Ventilago, Pyricularia bothriochloae from Bothriochloa and Sphaerulina rhododendricola from Rhododendron. Novelties from Spain include Cladophialophora multiseptata, Knufia tsunedae and Pleuroascus rectipilus from soil and Cyphellophora catalaunica from river sediments. Species from the USA include Bipolaris drechsleri from Microstegium, Calonectria blephiliae from Blephilia, Kellermania macrospora (epitype) and K. pseudoyuccigena from Yucca. Three new species are described from Mexico, namely Neophaeosphaeria agaves and K. agaves from Agave and Phytophthora ipomoeae from Ipomoea. Other African species include Calonectria mossambicensis from Eucalyptus (Mozambique), Harzia cameroonensis from an unknown creeper (Cameroon), Mastigosporella anisophylleae from Anisophyllea (Zambia) and Teratosphaeria terminaliae from Terminalia (Zimbabwe). Species from Europe include Auxarthron longisporum from forest soil (Portugal), Discosia pseudoartocreas from Tilia (Austria), Paraconiothyrium polonense and P. lycopodinum from Lycopodium (Poland) and Stachybotrys oleronensis from Iris (France). Two species of Chrysosporium are described from Antarctica, namely C. magnasporum and C. oceanitesii. Finally, Licea xanthospora is described from Australia, Hypochnicium huinayensis from Chile and Custingophora blanchettei from Uruguay. Novel genera of Ascomycetes include Neomycosphaerella from Pseudopentameris macrantha (South Africa), and Paramycosphaerella from Brachystegia sp. (Zimbabwe). Novel hyphomycete genera include Pseudocatenomycopsis from Rothmannia (Zambia), Neopseudocercospora from Terminalia (Zambia) and Neodeightoniella from Phragmites (South Africa), while Dimorphiopsis from Brachystegia (Zambia) represents a novel coelomycetous genus. Furthermore, Alanphillipsia is introduced as a new genus in the Botryosphaeriaceae with four species, A. aloes, A. aloeigena and A. aloetica from Aloe spp. and A. euphorbiae from Euphorbia sp. (South Africa). A new combination is also proposed for Brachysporium torulosum (Deightoniella black tip of banana) as Corynespora torulosa. Morphological and culture characteristics along with ITS DNA barcodes are provided for all taxa

The effect of the addition of a lactic acid bacterial inoculant to maize at ensiling on silage composition, silage intake, milk production and milk composition

CITATION: Meeske, R., et al. 2002. The effect of the addition of a lactic acid bacterial inoculant to maize at ensiling on silage composition, silage intake, milk production and milk composition. South African Journal of Animal Science, 32(4):263-270.The original publication is available at https://www.sasas.co.za/The aim of the study was to determine the effect of the addition of a lactic acid bacterial inoculant to maize at ensiling on the fermentation dynamics during ensiling, aerobic stability of the silage as well as the intake, milk production and milk composition of Jersey cows fed maize silage diets. The inoculant contained Lactobacillus plantarum and Pediococcus acidilactici as well as amylase. Maize was ensiled in laboratory and bunker silos. The inoculant did not result in a more rapid lowering of the pH or a more rapid lactic acid production compared to untreated maize silage made in laboratory silos. Both the control and inoculated maize silages were well preserved with a pH of 3.57 and 3.62, a lactic acid concentration of 66 and 63 g/kg DM and an ammonia nitrogen concentration of 5.88 and 5.10 g/100 g of total nitrogen respectively. No butyric acid was found in either untreated or inoculated maize silage. The maize silages made in the bunker silos were well preserved with a DM of 283 and 307 g/kg silage, pH of 3.50 and 3.51, lactic acid of 37.0 and 35.3 g/kg DM for the control and inoculated maize silage, respectively. The addition of the inoculant to maize at ensiling improved the palatability, intake and the aerobic stability of maize silage compared to the untreated control maize silage. The intake of untreated and inoculated maize silage by Jersey cows was 7.6 and 8.4 kg DM/day for the control and inoculant treatment, respectively. Milk production, milk composition, live weight and condition score of Jersey cows was not significantly affected by the addition of the inoculant to maize silage.https://www.sasas.co.za/journals/the-effect-of-the-addition-of-a-lactic-acid-bacterial-inoculant-to-maize-at-ensiling-on-silage-composition-silage-intake-milk/Publisher's versio