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At least 613 records · Page 34Linked to original sources
PubMed1980

Comparative studies of alpha-lactalbumin and lysozyme: the proteins of kangaroo (Megaleia rufa and Macropus giganteus) and horse (Equus caballus).

As part of a study of the 'whey' proteins of various mammals, a comparison is made of the alpha-lactalbumins and lysozymes of the kangaroo and horse. In the milk of the red kangaroo (Megaleia rufa) there is only one alpha-lactalbumin and it occurs throughout lactation, but no lysozyme has been detected. There are two alpha-lactalbumins in the milk of the grey kangaroo (Macropus giganteus), one, designated alpha-lactalbumin Zone B, is present throughout lactation; the second, designated alpha-lactalbumin Zone A, is present only in late lactation. One lysozyme is also present. The milk of the horse (Equus caballus) contains one alpha-lactalbumin and at least one lysozyme. Partial amino acid sequences are proposed from sequence determination and from analyses of tryptic peptides compared with the known sequences of other alpha-lactalbumins and lysozymes.

Amino Acid Sequence↗
PubMed1979

Observations of the pineal region of non-eutherian mammals.

A survey has been made of the pineal region of the brain of 11 species of marsupials belonging to 5 families and a species from both families of monotremes. The results show that the pineal body of non-eutherian mammals, although well-defined in all species, has a very varied morphology. Three types of pineal recess occur: (i) a pineal recess in sensu stricto, (ii) an intercommissural pineal recess, and (iii) an infrapineal recess. The existence of nerve fibres which pass through the pineal body and form a spatial link between the habenular and posterior commissures, has been demonstrated in marsupials and monotremes. It is also likely that these animals as well as eutherian mammals possess a nervus conarii. Nerve cells are not a constant feature of the non-eutherian pineal body. The subcommissural organ (SCO) is present in all species. It does not exhibit the same degree of morphological variation as the pineal body. Horizontal sections available for 4 species within 3 families of marsupials show it to be composed of a median portion jointed to bilateral protuberances. Large nerve cells occur within the SCO in all marsupial species; they are absent from the monotreme SCO. Tentatively, the relationship of these neurons to the SCO is considered to be merely one of association. The importance of an extended comparative study of this region in non-eutherian mammals in order to add insight into its phylogeny and function is emphasized.

Animals↗
PubMed1986

Bistratified amacrine cells in the retina of the tammar wallaby--Macropus eugenii.

Cajal (1911) noted that bistratified amacrine cells were common in non mammalian species and extremely rare in the mammalian retina. An examination of the marsupial retina of the tammar wallaby, stained with a modified Golgi procedure, revealed that a particular type of bistratified amacrine was frequently impregnated with the silver stain. Flat mount and transverse sections showed that the morphology of this cell did not correspond with any of the species-dependent bistratified amacrines reproduced in Cajal's drawings. Instead, the cell appeared to be almost identical to the AII or rod amacrine that has been observed in a number of mammalian retinas. The relative frequency with which the cell appears in our material, and its confirmed rod input in other species, are both consistent with the grazing habits of the tammar wallaby which is a crepuscular animal that does most of its feeding at dusk and after dark.

Animals↗
PubMed1991

Role of transferrin in iron uptake by the brain: a comparative study.

The role of specific transferrin (Tf) and Tf receptor interaction on brain capillary endothelial cells in iron transport from the plasma to the brain was investigated by using Tf from several species of animals labeled with 59Fe and 125I, and 15-day and adult rats. The rate of iron transfer was much greater in the 15-day rats. It was greatest with Tf from the mammals, rat, rabbit and human, but much lower with chicken ovotransferrin and quokka (a marsupial), toad, lizard, crocodile, and fish Tf. The uptake of Tf by the brain showed a similar pattern, except for a very high uptake of ovotransferrin (ovoTf). Iron uptake by the femurs (a source of bone marrow) was also high with Tf from the mammalian species and low with the other types of Tf, but showed little change with aging of the animals. It is concluded that iron transport into the brain is dependent on the function of Tf receptors, probably on capillary endothelial cells, and that these receptors show the same type of species specificity as the receptors on immature erythroid cells. Also, the decrease in iron uptake by the brain as rats age from 15 days to adulthood is specific for the brain and is not a general effect of the aging process.

Alligators and Crocodiles↗
PubMed1992

Energy metabolism in potoroine marsupials.

Fasting and fed metabolic rates were measured in three species of potoroine marsupials, the rufous rat-kangaroo (Aepyprymnus rufescens), the long-nosed potoroo (Potorous tridactylus) and the brush-tailed bettong (Bettongia penicillata). There were no significant differences among potoroine species in fasting metabolic rate. The lowest fasting heat production for each species was 11-20% less than the interspecific value of 295 kJ.kg-0.75.day-1 for basal metabolism of mature, non-reproductive eutherian homeotherms. The respiratory quotient of all species was reduced significantly as starvation proceeded, but only for B. penicillata was there a significant effect of starvation duration on fasting heat production. The night-time activity of P. tridactylus and B. penicillata doubled their daytime fasting heat production; the corresponding increase for A. rufescens was only 25%. The calorimetric measurement of fed animals showed no differences in digestible energy or metabolisable energy between species. Nevertheless, P. tridactylus and B. penicillata produced more heat per unit metabolic body mass. The maintenance energy requirements (kJ.kg-0.75.day-1) were 479, 494 and 345 for P. tridactylus, B. penicillata and A. rufescens, respectively. The net availability of metabolisable energy was about 0.70 in the three species. The combined heat production of fed female A. rufescens and their pouch young stayed relatively constant for the first two-thirds of pouch life, after which it rose sharply (20%) in response to the rapid growth of the young. Only during the last week of pouch life did the female enter negative energy balance. There was no indication that the metabolism of the female increased in response to the presence of a pouch young. The presence of pouch young did not alter the efficiency of utilisation of metabolisable energy. The daily energy requirement for maintenance was 0.83 MJ.day-1 or 0.36 MJ.kg-0.75.day-1.

Animals↗
PubMed1995

Digestive performance and selective digesta retention in the long-nosed bandicoot, Perameles nasuta, a small omnivorous marsupial.

Bandicoots are opportunistic omnivores that feed on invertebrates, fungi and both epigeal and hypogeal plant parts. We examined the performance of the digestive tract of the long-nosed bandicoot (Perameles nasuta) in terms of intake and total digestibility, patterns of excretion of inert digesta markers, and likely sites of digesta retention, on two diets designed to mimic part of their natural plant and insect diets. On the insect diet (mealworm larvae), bandicoots virtually maintained body mass at a digestible energy intake of 511 kJ.kg-0.75.day-1 and were in strongly positive nitrogen balance. In contrast, on the plant diet (shredded sweet potato), bandicoots ate only one-third as much digestible energy, lost 7% body mass, and were in negative nitrogen balance. Mean retention times of two particle markers on the plant diet (27.5 and 27.0 h) were more than double those on the insect diet (12.4 and 11.2 h), and on both diets the mean retention time of the fluid digesta marker was greater than those of the particle markers, indicating consistent selective retention of fluid digesta in the gut. It was seen radiographically than in mealworm-fed bandicoots major sites of digesta retention were the distal colon and rectum, whereas in the sweet potato-fed animals the caecum and proximal colon were principal sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effects of water restriction on digestive function in two macropodid marsupials from divergent habitats and the feral goat.

The effects of water restriction on digestive function in the euro (Macropus robustus erubescens) found in the arid zone of inland Australia, the eastern wallaroo (M.r.robustus) from more mesic regions of eastern Australia, and the feral goat (Capra hircus) found throughout the range of M. robustus, were compared in order to examine some physiological adaptations required by herbivores for the exploitation of arid environments. Eight animals of each species were held in individual metabolism cages in temperature-moderated rooms and given a chopped hay diet ad libitum. Half the animals were restricted to 40 ml water.kg-0.80.day-1. This was 40%, 32% and 57% of voluntary drinking water intake in the euro, wallaroo and goat, respectively. All species responded to water restriction by reducing faecal, urinary and evaporative water losses in association with reductions in feed intake. All animals increased urine osmolality and electrolyte concentrations but not to maximal levels, while packed-cell volume and plasma osmolality and electrolyte concentrations were unaffected by water restriction. The euro displayed a suite of characteristics that separated it from the wallaroo in terms of physiological adaptation, including lower voluntary water intake, an increase in fibre digestibility and maintenance of nitrogen balance during water restriction, and lower faecal water efflux associated with a consistently lower faecal water content (54% versus 59% water in the wallaroo during water restriction, P < 0.05). The euro's colon was 37% longer (P < 0.01) than that of the wallaroo. The goat had the lowest faecal water efflux (P < 0.05) and the longest colon (P < 0.001). Water restriction did not affect water content in digesta, nor short-chain fatty acid concentrations or production rates in vitro. Total body water, as a proportion of body mass, was depressed (P < 0.05) in the macropodids, but not in the goat. The reduction in dietary nitrogen intake, which accompanied water restriction, was partially compensated by an increase in urea degradation in the gut from 68% to 76% of urea synthesis water-restricted macropodids. These responses to water restriction are discussed in relation to those reported in other macropodid and ruminant species.

Animals↗
PubMed1992

Hindgut fermentation in the wombats: two marsupial grazers.

The wombats Vombatus ursinus and Lasiorhinus latifrons have a capacious proximal colon with only a vestigial caecum. The pattern of microbial fermentation in the hindgut of both species was studied in captive animals fed a pelleted straw diet and in wild wombats feeding on their natural winter diets. Digesta pH was low in the stomach but near neutrality along the hindgut, indicating effective absorption and/or buffering of the colonic contents. Initial proportions and production rates of short chain fatty acids in vitro reflected the fermentation of plant cell walls. Proportions of isobutyrate, isovalerate and n-valerate increased towards the distal colon indicating proteolysis and subsequent fermentation of amino acids. The low ammonia content of digesta fluid suggested that ammonia released from these amino acids was absorbed and utilized by the wombats and their gut microbes. Wild wombats had higher concentrations and production rates of short chain fatty acids than captive animals, which was consistent with the higher apparent digestibility of their natural diet. The energy from short chain fatty acids in captive animals was 30-33% of digestible intake. Energy intakes were low and similar to resting metabolic rates estimated for marsupials. Actual resting metabolic rates of the wombats are probably lower than these estimates, and the proportion of energy derived from fermentation substantially higher than the 53-61% estimated in wild wombats. The energy from fermentation clearly enables wombats to utilize diets high in fibre.

Animals↗
PubMed1981

Sister chromatid exchanges and heterochromatin.

The inter- and intrachromosomal distribution patterns of SCEs obtained with or without mutagen treatment are reviewed and compared, with each other as to their relation to heterochromatin and with the distribution patterns of chromatid aberrations that occurred either "spontaneously" in chromosomes of repair-defective human syndromes or after treatment with the mutagens (BrdU, ethylalcohol, DMBA, TMBA, maleic hydrazide, MMS, MMC). The conclusions are: No general rule is detectable for nonrandom involvement of heterochromatin in spontaneous SCEs. Mutagen-induced SCEs show the same or very similar distribution patterns as the spontaneous ones and are in no case as preferentially located as chromatid aberrations (which involve mainly the junctions between eu- and heterochromatin or other special regions). Therefore, a specific mutagen sensitivity of heterochromatin-aberrations does not exist (or is less pronounced) for SCEs. This supports the inference that different mechanisms underlie the origins of the two phenomena.

Animals↗
PubMed1978

Mitotic asynchrony of multinucleate cells in tissue culture.

A high degree of mitotic asynchrony is reported for spontaneously arising multinucleate cells of HeLa and Pt-K1, tissue culture cell lines. Neither nuclear number, nor nuclear size nor the presence or absence of nucleoli, could be directly related to the asynchronous behaviour of the cells. Suboptimal levels of nutrients led to a higher frequency of asynchrony. A partial compartmentation of the cytoplasm could be detected in some of the multinucleate cells. The compartmentation of the cytoplasm may lead to an uneven distribution of inducer and non-inducer metabolites. All these factors together may be responsible for the high degree of mitotic asynchrony.

Animals↗
PubMed1979

Effects of griseofulvin on mitosis in PtK1 cells.

The concentration dependent effects of griseofulvin (GF) on mitosis in PtK1 cells were studied using a combination of time lapse cinematography and polarization and electron microscopy. Low concentrations of GF (4 X 10(-5) M) allowed a substantial number of cells to enter and complete an apparently normal mitosis. At higher concentrations of GF (1 X 10(-4) M and 2.5 X 10(-4) M) all cells entering mitosis were arrested. Typical c-mitotic chromosome arrays were observed at 1 X 10(-4) M GF with microtubules present but no spindle formed. At 2.5 X 10(-4) M GF chromosomes did not orient toward a common center to form a c-mitotic figure, but instead remained in a loosely clustered grouping at the center of the cell. Electron microscopy showed microtubles to be absent but revealed in irregularly shaped electron dense cloud around the centrioles. Quantitative polarization microscopy of metaphase cells perfused with GF showed rapid loss of spindle birefringence after exposure to the drug. Coinciding with loss of birefringence the spindle shrank rapidly with a pronounced shortening of pole to pole distance.

Animals↗