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PubMedDate not supplied

[The mammals of Guinea as reservoirs and carriers of arboviruses].

A great body of data on the fauna and ecology of wild mammals and their participation in the circulation of arboviruses were collected when the ecology of the latter of the Republic of Guinea was studied in 1978 to 1989. A hundred and eighteen species belonging to 10 orders were identified. Over 2,000 biological specimens were virologically and serologically examined. Six arboviruses were isolated. These included Dugbe virus (from the hussar monkey Cercopithecus (Erythrocebus patas) and 5 viruses from chiropters: Rift valley fever, from Micropteropus pusillus, Miniopterus schreibersi, and Hipposideros caffer, Saboya, Fomede, and Ank 6909 from Nycteris gambiensis and Kolenter from Hipposideros sp. Fomede, Kolente, and Ank 6909 viruses turned out to be new species for science. Rodents were found to have viral antigens of Lass fever (Mastomys natalensis, Tatera valida kempi and Rattus rattus), Dugbe and Chikungunya fevers (M. natalensis) and West Nile fever (Mus sp.). A serological survey of mammals revealed that the latter had antibodies to 12 arboviruses. Thus, the mammals of Guinea participate in the circulation of 18 arboviruses, 13 of them are pathogenic for man.

Animals↗
PubMedDate not supplied

[Organs of hearing and equilibrium during ontogenesis of mammals].

The peripheral part of acoustic analyzer was studied during pre- and postnatal development of mammals. The main trends of structural evolution of the outer, middle, and inner ear were followed in representatives of different ecological groups during postnatal development. The use of ecologomorphological approach made it possible to establish that specific structural features of the hearing organ in different mammals are determined by adaptation to specific acoustic properties of the environment. It was shown that morphofunctional adaptations directed at optimization of acoustic sensitivity in different environmental conditions were leading in the hearing organ evolution. Comparative-embryological studies of the peripheral part of acoustic system made it possible to determine the stages of formation of individual structures and establish general patterns of prenatal development of the organs of hearing and equilibrium in different mammals.

Animals↗
PubMed1983

The natural history of salmonellae in mammals of the tropical Kimberley region, Western Australia.

Screening for salmonellae was conducted on five occasions within a year on mammals from many different habitats in the Mitchell Plateau area of the tropical Kimberley Division of Western Australia. Some data were obtained from reptiles. Forty-two Salmonella serotypes, two Edwardsiella and one Arizona strain were isolated. Marsupials harbour significantly more (1.6 times) Salmonella serotypes than eutherians. Eleven Salmonella serotypes and one Arizona strain were isolated from reptiles. All Salmonella strains were common to the mammalian species. Varanid lizards showed higher prevalence of salmonellae than other reptilian families. Top carnivores (reptile and marsupial) show relatively high numbers of Salmonella serotypes and prevalence levels. Four mammalian species showed marked seasonal variation in the prevalence of salmonellae and three species in the number of serotypes isolated. Pooled mammalian community data for individual survey sites showed similar seasonal variation which reflected the pattern seen in the predominant host species on the site. Significant seasonal variation in the prevalence of salmonella was concurrent in three of the host species showing maximum prevalence in the wet season (January-summer) followed by a declining prevalence to the end of the dry season (October). Prevalence in the fourth species was also high in January, but continued to increase after the wet season (April) before decreasing as the dry season progressed (July and October). Dendrograms of association showed that the salmonella 'community' does not associate according to any systematic category of the hosts and no evidence of such communities was found using other criteria, such as site or coastal vs inland locations. No evidence was found for host or site specificity of given serotypes. Multiple serotype infections by salmonella were common, with up to three present in mammals and reptiles, and they occurred at random. When hosts in coastal habitats were compared with those in inland sites higher, lower or no difference was found in the prevalence of salmonella, depending upon which host was considered. Sites with similar mammals and vegetation sometimes showed marked differences in salmonella prevalence at a given time. Generally a given Salmonella serotype was lost from the host within congruent to 3 months. Surveys for salmonellae should be designed to include a range of species, replicated vegetation types and, especially, be repeated in several seasons. Edwardsiella tarda was isolated twice from a carnivorous marsupial.

Animal Population Groups↗
PubMed1995

Differences in ligamenta flava among some mammals.

The ligamenta flava of the thoracolumbar spine of mammals with great spinal mobility have a larger content of elastin than in animals with little spinal motion. The elastin content is also higher in the ligamenta flava of mammals with arched backs and prolonged sitting posture than in nonsitting mammals with the vertebral column in the shape of a flat bow. The ligamentum flavum appears to be important; a) in the control of intervertebra movements, b) in providing intrinsic stability to the spine in the sitting and standing postures and c) in maintaining a smooth surface in the posterior wall of the spinal canal and neural foraminae.

Animals↗
PubMedDate not supplied

[Different types of gametocytes in mammal's Haemosporidia. Correlations with the morphology of the tissue schizonts. Hypothesis on the evolution of the group (author's transl)].

The Haemosporidia of Mammals are classified in 3 groups according to the morphology of the gametocytes: 1) group "vivax" with Hepatocystis and several species of Plasmodium; 2) group "malariae" with Nycteria and a second group of Plasmodium; 3) group "falciparum" with only Plasmodium. In each group there is a correlation between the morphology of the gametocytes and that of the exo-erythrocytic schizonts. Through discussing the host-range and comparing the life cycles of Haemosporidia in Birds, Reptiles and Mammals, we suggest a hypothesis of the polyphyletism of Plasmodium of Mammals.

Animals↗
PubMed1998

An automated system, based on microchips, for monitoring individual activity in wild small mammals.

A new battery-operated system based on microchips has been developed for detecting free-moving, wild small mammals. An electronic identification unit connected to a portable data-logger can simultaneously accommodate up to eight detector antennae, which are positioned in the habitat of the species under study. The system can operate even in extreme weather conditions and has the capacity to distinguish and record individual mammals entering burrows or visiting artificial feeding stations. Detection events are stored in a data-logger and subsequently can be edited and analysed by many common software packages. A pilot study tested the system by monitoring the visits of three species of small mammals to artificial feeding stations. Further possible applications are discussed.

Animal Identification Systems↗
PubMed1998

Phenotypic manifestations during the development of the dominant and default gonads in mammals and birds.

The dominant embryonic gonad--testis in mammals and ovary in birds--secretes one or more morphogenetic substances that exert a major effect on the phenotype of the embryo. When deprived of their gonads, mammalian embryos develop into females, and avian embryos assume predominantly male characteristics, although retaining both oviducts. In order to fulfill their task of masculinizing the reproductive tract, mammalian testes grow and differentiate faster than ovaries. In birds the pattern is less straightforward. In 5-day-old embryos of White Leghorn chickens, sexual differentiation manifests itself in two different ways: (1) the gonads of ZZ embryos are larger, and on day 6 contain more protein and DNA than those of ZW embryos; (2) in both sexes, left gonads are larger than right gonads and contain a thick "germinal epithelium" capable of giving rise to an ovarian cortex under the influence of oestrogen. The pattern changes in embryos aged between 7 and 8 days, when the left gonad of ZW embryos outgrows all others, developing into an ovary, and when the bilateral asymmetry between left and right gonads increases in female embryos. A remnant of gonadal bilateral asymmetry is seen in the distribution of gonads in cases of true hermaphroditism in humans and other mammals. Whereas the initial fast growth of the mammalian testis is assumed to be due to one or more Y-chromosomal genes, that of the early avian testis is mostly simply explained as the effect in the disomic state of one or more genes on the Z chromosome. However, the later growth of the avian ovary is more likely to be due to oestrogen than to a direct gene effect. It is postulated that oestrogen has lost its power to determine ovarian development in mammals, in which both sexes are exposed to the oestrogen-rich environment of the uterus. Hence, the task of sex determination devolves on the fetal testis, whose early development and hormonal function are required to induce the male phenotype, the female phenotype arising in default mode.

Animals↗
PubMed1998

[Calcitonin and stanniocalcin. Particular aspects of the endocrine regulation of phospho-calcium metabolism in mammals and fish].

The hypocalcemic and hypophosphatemic peptide calcitonin (CT) is secreted by mammalain thyroid parafollicular cells and fish ultimobranchial body. Over a dozen species of CTs have been cloned and/or sequenced. They can be separated into three classes based on structural and biological similarities: teleost/avian, artiodactyl, and human/rat. In mammals, CT exerts its anti-hypercalcemic and hypophosphatemic effects by inhibiting osteoclastic bone resorption and renal tubular phosphate reabsorption, respectively. CT receptors (CTRs) are members of a subfamily of seven-transmembrane domain, G protein-coupled receptors that include those for several other peptide hormones. Basic amino acid substitutions within the CT molecule enhance potency, probably by conferring a helical structure to the peptide. This might explain the enhanced potency of fish CTs for mammalian CTRs. The presence and secretion of salmon CT-like immunoreactive material have been described in both the murine and human central nervous systems, which possess CTRs. These findings are consistent with a role for this peptide acting as a neurotransmitter in mammals. Stanniocalcin (STC) is another hypocalcemic hormone originally identified in fish. In fish STC exerts its anti-hypercalcemic effect by regulating calcium and phosphate transports by the gills, intestine and kidney. Although fish ultimobranchial cells are much less responsive to the secretagogic effects of Ca2+ than mammalian parafollicular cells, the secretion of both CT and STC are positively regulated by extracellular calcium. STC has also been recently identified in humans and rats. It is released by some renal tubular cells and might play a role in the regulation of phosphate metabolism. Nevertheless, the true physiologic roles for CT in fish and STC in mammals, respectively, remain unknown.

Animals↗
PubMed1997

Refined solution structure of the anti-mammal and anti-insect LqqIII scorpion toxin: comparison with other scorpion toxins.

The solution structure of the anti-mammal and anti-insect LqqIII toxin from the scorpion Leiurus quinquestriatus quinquestriatus was refined and compared with other long-chain scorpion toxins. This structure, determined by 1H-NMR and molecular modeling, involves an alpha-helix (18-29) linked to a three-stranded beta-sheet (2-6, 33-39, and 43-51) by two disulfide bridges. The average RMSD between the 15 best structures and the mean structure is 0.71 A for C alpha atoms. Comparison between LqqIII, the potent anti-mammal AaHII, and the weakly active variant-3 toxins revealed that the LqqIII three-dimensional structure is closer to that of AaHII than to the variant-3 structure. Moreover, striking analogies were observed between the electrostatic and hydrophobic potentials of LqqIII and AaHII. Several residues are well conserved in long-chain scorpion toxin sequences and seem to be important in protein structure stability and function. Some of them are involved in the CS alpha beta (Cysteine Stabilized alpha-helix beta-sheet) motif. A comparison between the sequences of the RII rat brain and the Drosophila extracellular loops forming scorpion toxin binding-sites of Na+ channels displays differences in the subsites interacting with anti-mammal or anti-insect toxins. This suggests that hydrophobic as well as electrostatic interactions are essential for the binding and specificity of long-chain scorpion toxins.

Amino Acid Sequence↗
PubMed2000

BmK AS: new scorpion neurotoxin binds to distinct receptor sites of mammal and insect voltage-gated sodium channels.

This study was undertaken to assess the binding properties of BmK AS on both mammal and insect excitable cell membranes. It was found that BmK AS bound specifically to a single class of non-interacting binding sites on both rat brain and cockroach nerve cord synaptosomes with high affinity (K(d) = 1.49 +/- 0.14 and 0.79 +/- 0.29 nM) and low capacity (B(max) = 1.39 +/- 0.09 and 6.60 +/- 1.25 pmol/mg protein), respectively. Binding kinetics showed that BmK AS could bind and reach equilibrium quickly, and dissociate partially from its binding sites on both kinds of synaptosomes. The binding of BmK AS was independent of membrane potential. Veratridine could not modify the binding of BmK AS. The competitive binding assay showed that specific binding of (125)I-BmK AS could be significantly inhibited by native BmK AS, BmK AS-1, BmK IT2 and BmK IT on both synaptosomes. Unexpectedly, only about 20-30% binding of BmK AS on mammal synaptosomes was inhibited by BmK I at 10(-5)-10(-9) M, but not on insect synaptosomes. It thus suggests that BmK AS type neurotoxins might bind to a distinct receptor site of sodium channels on mammal and insect excitable cell membranes with a manner similar to beta-scorpion toxins.

Animals↗
PubMed1979

An evolutionary view of the male reproductive tract and sperm maturation in a monotreme mammal--the echidna, Tachyglossus aculeatus.

In exploring the evolution and adaptive significance of epididymal function, we have studied the male excurrent duct and spermatozoa of a monotreme mammal--the echidna. Sperm maturation in the echidna excurrent duct appears simpler than that in most therians examined. Furthermore, neither the duct nor the spermatozoa of the echidna display specific therian characteristics; they bear a much closer resemblance to those of non-passerine birds. The echidna spermatozoon is filiform, the sperm tail has no distinctive features, and the anterior seventh of the undulating nucleus is covered by a modest acrosome. Immediately behind this a restricted apposition between plasma membrane and nuclear envelope constitutes a post-acrosomal ring. This is evident also in some reptiles and marsupials, whereas in Eutheria such a membrane association appears as the posterior ring at the base of the sperm nucleus. Maturation of spermatozoa in the Wolffian duct of the echidna appears to be expressed only in a changing capacity for motility and in loss of the cytoplasmic droplet. Neither surface, structural nor acrosomal changes that characterize sperm maturation in therian mammals have been detected in maturing echidna spermatozoa. The echidna duct displays little of the regional complexity of the epithelium that typifies this duct in the Theria. Of five regions distinguishable on the basis of epithelial morphology, the first two appear to be counterparts of efferent ducts by virtue of a low columnar, partially ciliated epithelium. The tall pseudo-stratified Golgi-rich epithelium of the major portion of the duct broadly resembles that of the therian epididymis, but it displays only two structurally distinguishable regions, the more distal being the site of a dense luminal secretion. The foamy epithelial cells of the fifth and terminal region, characterized by a mass of supra-nuclear vesicles and rough ER, suggest a secretory function that may in some way contribute significantly to the ejaculate, for accessory glands are poorly developed in monotremes. The possibility is considered that the relative complexity of epididymal function and sperm structure in therian mammals could have been determined by evolutionary change in the milieu of the female tract, and/or in the character of the egg vestments that the fertilizing spermatozoon must penetrate.

Animals↗
PubMed1987

Brain sizes, surfaces, and neuronal sizes of the cortex cerebri: a stereological investigation of man and his variability and a comparison with some mammals (primates, whales, marsupials, insectivores, and one elephant).

This study deals with the stereological estimation of macroscopic sizes of brain and cortex, i.e., volume, surface, and folding, and of microscopic neuronal sizes, i.e., density, mean size, size distribution, and number of neurons. The results show that the degree of variability in man amounts to about 15%. A decrease in volume of the different gray structures can be observed in man after the age of 65 years. The surface, folding index, and length of convolution do not alter with aging. The comparison with mammals of various sizes allows the conclusion that there is a high correlation to brain size for nearly all macroscopic values. Man and elephant, however, have a cortical surface which is, in comparison with whales, relatively small. In contrast, whales have very small cortices compared with man. At the cytoarchitectonic level, the neuronal density has a correlation to brain size. Contrary to other mammals, the primates and man have a high fraction of small granular neurons, especially in layer 4. The assumption that the number of cortical neurons beneath a given surface area of cortex is the same in all mammals cannot be verified, especially in those with large brains. The allometric connection between brain size and parameters is not valid for all measurements (e.g., thickness of cortex, mean size of neurons, perikaryal size distribution, and glial density). Yet some other measurements are well correlated.

Animals↗
PubMed1998

Small mammal populations and community under conditions of extremely high thallium contamination in the environment.

Studies were carried out in the vicinity of a zinc smelter in southern Poland, 50 km northwest of Krakow, where the previous measurements with another bioindication method revealed huge thallium levels in the environment. The mammals (106 individuals in total) were captured in four wooded areas situated 1.5 to 2.5 km in various directions from the plant and in two reference sites, located far from industrial emission sources. Very high Tl levels were found in livers and kidneys of all mammals examined from the two areas nearest the smelter. Bank voles were the most loaded (maximum Tl in kidneys, 34.27 microgram/g dry mass; in livers, 14.53 microgram/g; values from unpolluted areas were below the detection limit, 0.07 microgram/g). A distinct decrease in the amount of hair-a characteristic of thallium poisoning-was observed in several individuals. The extreme case was a wood mouse with the rear half of its body almost entirely hairless (!). Densities of single populations and the whole community were very low, up to 4.8 individuals/ha, including insectivores. Numerical proportions between species were changed in comparison to unpolluted areas. The age structure was deformed, with a disproportionate small participation by young generations. Among the males studied, only sexually inactive individuals were found. The condition of populations and the community of small mammals living here was much worse compared with data from the surroundings of other zinc smelters.

Alopecia↗
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

Location of the X inactivation center in primates and other mammals.

In humans, the X chromosome inactivation center and an X inactivation-associated metaphase fold are at the same location (bands Xq13----21) or are very closely associated. In other mammals, the location of the X inactivation center is unknown, but it has been suggested that the relationship between the inactivation center and the inactivation-associated fold may make it a useful marker for both identifying the inactivated X and locating the inactivation center in other mammalian species. If a similar metaphase fold is present in other mammals, the inactivation center would be located at the same site or very nearby. All of nine primate species did express an inactivation-associated fold. In most, the fold was located at the band homologous to human Xq13----q21. In one of two chimpanzees, band Xq23----q24 was implicated. In five other mammals an inactivation-associated fold was observed, but in two species, no fold was observed.

Animals↗
PubMed1977

Comparative psychoacoustics: perspectives of peripheral sound analysis in mammals.

Psychophysical data on hearing in mammals are summarized. The data are then correlated to the anatomy and physiology of the ear. Common mechanisms of sound transfer and analysis in the acoustic system, with stress on the auditory periphery, are discussed. In this paper an attempt is made to bring basic psychoacoustic data from man and mammals in a logical line with the anatomy, physiology, and biophysics of the ear. This comparative approach is based on man and those five mammals, including bat and dolphin, for which sufficient data are available.

Animals↗
PubMed1989

Functional similarities in the mechanical design of the aorta in lower vertebrates and mammals.

The mechanical properties of the aorta from the toad Bufo marinus, the lizard Gekko gecko and the garter snake Thamnophis radix were compared to those of the rat, by inflation of vessel segments in vitro. The arteries of the lower vertebrates, like those of mammals, were compliant, highly resilient, and non-linearly elastic. The elastic modulus of the artery wall was similar in the lower vertebrates and mammals, at their respective mean physiological pressures. We conclude that the aorta in each of these animals is suitably designed to function effectively as an elastic pulse smoothing component in the circulation; differences in the pressure wave transmission characteristics of lower vertebrates and mammals do not result from dissimilarities in arterial elastic properties, but from substantial differences in heart rate of these two groups.

Animals↗