SEARCH · PubMed Health

Results for “Mammals”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources

PubMed1977

Lead levels in small mammals and selected invertebrates associated with highways of different traffic densities.

Lead levels in small mammals were studied in 6 areas -- 3 associated with highways of different traffic densities, and 3 control sites in forested areas. Lead levels were also studied in insects from 2 traffic areas and in earthworms from different distances from 2 traffic areas. Lead levels were low in insects ranging from 3.84 microng/g to 3.35 microng/g. Lead levels in earthworms were highest in those recovered closest to highways and from the area with the higher traffic volume. Lead levels in mammals generally was highest in mammals from areas of higher traffic densities. Higher levels of lead were found in shrews than in Peromyscus and Microtus.

Animals↗

PubMed1978

The scaling of maximal oxygen consumption and pulmonary dimensions in small mammals.

This report has reexamined the relationship between standard and maximal rates of oxygen consumption (VO2std and VO2max) and pulmonary surface area in mammals whose weights extend over the lower half of the total log weight range in mammals. For combined groups of wild and laboratory animals with body weights of 2--3700 g, the following equations pertain: VO2std (ml . min-1) = 0.0602 . W0.727; VO2std, or the factorial aerobic scope, is nearly constant over this weight range at approximately 6.6 (range 5.8--7.1). In view of this finding, earlier studies relating SA or pulmonary diffusion capacity to VO2std are still appropriate models for pulmonary constraints on metabolic rate. The data summarized here suggest that, at least for wild species of mammals, pulmonary diffusion capacity may limit VO2max.

Animals↗

PubMed1975

Blood oxygen affinity and alveolar ventilation in relation in body weight in mammals.

The validity of the concept relating blood oxygen affinity and alveolar ventilation to body weight in homeothermic mammals was reexamined with blood pH used as the fixed variable. Blood Po2 at 50% saturation at pH 7.4 (P50(7.4)) and PCO2 of oxygenated blood at pH 7.4 (PCO2(7.4)) from a variety of homeothermic mammals were determined at 37 degrees C by in vitro equilibration techniques. In some species, arterial PCO2, PO2, and pH were also measured. PCO2(7.4), which was similar to arterial PCO2, showed a correlation coefficient of +0.33 with body weight over the range of 28-100,000 g and +0.90 among the species under 200 g. P50(7.4) values, which ranged from 26.0 to 38.7 mmHg for all the species, were not well correlated (r = -0.43) with body weight. For the small mammals (less than 200 g) the correlation coefficient was -0.91. In vivo P50 at the body temperature and arterial pH, although different from P50(7.4), showed a similar correlation with body weight. The lack of valid generalization suggests that body weight is only one of the composite factors that influence O2 transport systems.

Animals↗

PubMed1976

A simple method of tracking mammals and locating triatomine vectors of Trypanosoma cruzi in Amazonian forest.

A simple method of tracking mammals from capture points to their refuges was developed to study Trypanosoma cruzi reservoir-vector associations in Belém forest. A device containing a spool of fine line was carried by released mammals so that the line unwound under minimum tension as the animal proceeded and could be followed the day after release. Twenty-three triatomine bugs of five species were found with 3 of 15 mammals retrieved.

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↗

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↗

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↗

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↗

PubMedDate not supplied

On the evolution of X-chromosome inactivation in mammals and the clinical consequences to man--a hypothesis.

A clinical analysis of abnormal sex chromosome states in man suggests that Lyon's recent X-Y translocation hypothesis for the evolution of X-chromosome inactivation in mammals most likely would have lead to an evolutionary dead-end. Therefore, as an alternate I have hypothesized that: X-chromosome inactivation in somatic cells of mammals could have evolved by a complementary process of one by one heterozygous physical deletion in males and heterozygous inactivation in females of genes for "somatic" traits scattered throughout the genome whose effective output had become 50% excessive during prior evolution. However, this complementary process could occur safely only if the genes so deleted or inactivated first segregated by chance onto the evolving sex-chromosomes via a one by one reciprocal exchange for non-sex related genes already there. The complementary process thereby would allow slow evolution of the Y-chromosome in the male and X-chromosome inactivation in the female. Evolution of X-chromosome inactivation in this manner is compatible with Ohno's observation of "conservation" of the X-chromosome in mammals; and the occurrance of clinical "somatic" abnormalities in the abnormal X or Y chromosome states of man despite X-chromosome inactivation.

Aneuploidy↗

PubMed1978

The long search for the causes of congenital malformations in mammals.

The history of teratology is reviewed. Methods available for causing malformations in mammals by subtle changes in the environment during pregnancy are discussed. A table is provided in which the commoner teratogens are listed. Methods are described by means of which the activity of some common teratogens may be opposed. The occurrence at Battle Creek, Michigan, USA, of a chemical agent dangerous to health, life and development of all mammals is described. This gives an indication that injury and death to all mammals, as in the Sevaso disaster, including teratogenesis may be expected to be a fairly frequent occurrence in the years to come.

Abnormalities, Drug-Induced↗

PubMed1977

The occurrence of babesiasis affecting small terrestrial mammals and the importance of this zoonosis in Europe.

A short survey is given of the occurrence of babesiasis affecting small terrestrial mammals in some parts of Europe. Results obtained in studies of 7,038 small terrestrial mammals (42 species) from Czechoslovakia, Austria, Hungary, Yugoslavia and Bulgaria, show the distribution of Babesia microti in these countries. The authors found babesias in the following host species: Neomys anomalus, Clethrionomys glareolus. Microtus arvalis, M. agrestis, Apodemus agratius, A. flavicollis, A. sylvaticus and Mus musculus. The average incidence was very low-0.2% and varied in individual countries from negative to 0.7%. Problems of the natural foci of B. microti in Central Europe and discussed and hitherto recorded cases of Babesia infections in man are summarised. The epidemiological importance of the unspecific mammal hosts of B. microti is emphasised and the necessity of surveillance of this zoonosis in Europe is pointed out.

Animals↗

PubMed2024

Genetic linkage disequilibrium of deleterious mutations in threatened mammals.

The impact of negative selection against deleterious mutations in endangered species remains underexplored. Recent studies have measured mutation load by comparing the accumulation of deleterious mutations, however, this method is most effective when comparing within and between populations of phylogenetically closely related species. Here, we introduced new statistics, LDcor, and its standardized form nLDcor, which allows us to detect and compare global linkage disequilibrium of deleterious mutations across species using unphased genotypes. These statistics measure averaged pairwise standardized covariance and standardize mutation differences based on the standard deviation of alleles to reflect selection intensity. We then examined selection strength in the genomes of seven mammals. Tigers exhibited an over-dispersion of deleterious mutations, while gorillas, giant pandas, and golden snub-nosed monkeys displayed negative linkage disequilibrium. Furthermore, the distribution of deleterious mutations in threatened mammals did not reveal consistent trends. Our results indicate that these newly developed statistics could help us understand the genetic burden of threatened species.

Animals↗

PubMed1978

Ultrastructure of capillaries in the conduction system of the heart in various mammals.

The capillaries in the atrioventricular node and atriventricular bundle of the heart (mammals) were investigated by thin sections and freeze-etch replicas. Fenestrated endothelial cells were found to occur in all mammals examined in this study. These fenestrations (500 +/- 50 A diameter) are bridged by a diaphragm and occur in relatively small sieve areas. In contrast to the AV-node and AV-bundle, the non-specialized myocardium is supplied by continuous capillaries. The presence of the fenestrated capillary in the conduction system of the heart may serve to increase both permeability and passive transport capacity.

Animals↗

PubMed1979

Enamel structure in some therapsids and mesozoic mammals.

The distribution of enamel tubules, the shapes and arrangements of prisms, and the orientation of crystals in ground sections from several therapsids and mesozoic mammals have been investigated by conventional and polarizing microscopy. Along each of three separate phylogenetic lines which evolved occluding teeth, there was a progressive increase in the numbers of enamel tubules. In the investigation, the arcade-shaped prisms typical of recent mammals were first seen in material from the Cretaceous period. All the enamels investigated from the Triassic contained columns of crystals, which were deduced as hexagonal. The inner ends of the crystals within each column deviated towards the center of the column. It is concluded that the existence of an interprismatic region provides the most important distinction between prismatic enamels and the hexagonal columns of crystals in the Triassic material.

Animals↗

PubMed1979

Yersinia enterocolitica among small wild mammals in France.

A survey of Yersinia enterocolitica was made in two French areas (Indre and Alsace) in several components of the terrestrial ecosystem. Y. enterocolitica has been isolated from several habitats and from numerous species of small mammals. The trap line method enabled us to estimate the density of the two abundant small mammal species, Microtus arvalis and Apodemus sylvaticus, and the densities of Y. enterocolitica carriers. The frequency of isolation was high when temperatures were low, but did not seem to be in direct relationship with animal densities. Infectious lesions were never found in spleens or intestines of 1893 captured animals. Samples of fresh water, fresh-water fish, soil and earthworms were occasionally collected. A total of 163 strains were isolated. Of these, 99 were of biochemical type 1; 20 different 0 serogroups were found.

Animals↗

PubMed2026

The emergence and diversification of the DUX gene family across placental mammals.

The DUX gene family encodes transcription factors with paired homeodomains. It has critical roles in embryogenesis and disease, including facioscapulohumeral muscular dystrophy (FSHD) and cancer. This study conducts a comparative analysis of the DUX gene family-DUXA, DUXB (including DUXBL), and DUXC (including DUX4 and Dux)-across placental mammals, highlighting their structural diversity within macrosatellite repeat contexts. Using long-read genomes, we explore gene distribution, array patterns, and phylogenetic relationships in various vertebrate species. Our analysis reveals that DUXA and DUXB are highly conserved, with intriguing variations such as intronless forms likely arising from ancestral retrotransposition events. While DUXBL is inconsistently retained across clades, its locus-which in non-placental mammals harbors the ancestral single-homeodomain sDUX gene-served as an evolutionary hub for diversification, giving rise to DUXA, DUXB and DUXC, as well as macrosatellite tandem array structures. Sequence conservation and syntenic analyses demonstrate array adaptability, exemplified by higher-order repeats in orangutans and disrupted patterns of concerted evolution in elephants. Furthermore, analysis of human pseudo-DUX4 arrays indicates their potential role in disease mechanisms, including as possible contributors to rare cases of FSHD, warranting further investigation. This study thus provides insights into DUX-family gene evolution, offering a foundation for future research into developmental roles and disease implications.

Animals↗

PubMed1977

Monogamy in mammals.

This review considers the behavioral, ecological, and reproductive characteristics of mammals exhibiting monogamy, i.e., mating exclusivity. From a discussion of the life histories of selected species of monogamous primates, carnivores, rodents and ungulates, several trends emerge. Two forms of monogamy occur, Type I, facultative, and Type II, obligate. The selective pressures leading to these two forms of monogamy may have been different. Facultative monogamy may result when a species exists at very low densities, with males and females being so spaced that only a single member of the opposite sex is available for mating. Obligate monogamy appears to occur when a solitary female cannot rear a litter without aid from conspecifics, but the carrying capacity of the habitat is insufficient to allow more than one female to breed simultaneously within the same home range. Within both types of monogamy, the following traits are typically seen: (1) adults show little sexual dimorphism either physically or behaviorally: (2) the adult male and female exhibit infrequent socio-sexual interactions except during the early stages of pair bond formation. Additional trends specific to mammals exhibiting obligate monogamy are: (1) the young exhibit delayed sexual maturation in the presence of the parents, and thus only the adult pair breeds; (2) the older juveniles aid in rearing young siblings; and (3) the adult male (father) aids in the rearing of young by any or all of the following: carrying, feeding, defending, and socializing offspring.

Animals↗

PubMed1977

Nature and rate of neoplasia found in captive wild mammals, birds, and reptiles at necropsy.

The nature and rate of neoplasia found at necropsy of captive wild animals of the Zoological Society of San Diego collection were studied. Neoplasia was present at necropsy in 2.75% of 3,127 mammals, 1.89% of 5,957 birds, and 2.19% of 1,233 reptiles. Neoplasms were not detected during 198 necropsies of amphibians. Gross and histologic examinations were performed on the 92 mammalian, 111 avian, and 28 reptilian neoplasms. The lesions were diagnosed. The findings findings included a high frequency of lymphosarcomas in birds and reptiles, multiple lung adenomas in mammals, multiple endocrine tumors in 2 European mouflons (Ovis musimon), and proliferative lesions of the biliary and pancreatic ductal systems in several species.

Animals↗