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PubMed2006

Proprioception in the extraocular muscles of mammals and man.

This article summarizes the authors' previous studies on proprioceptors in extraocular muscles (EOMs) of mammals and man. They report on muscle spindles in the EOMs of man, Golgi tendon organs in the EOMs of even-toed ungulates, and palisade endings in the EOMs of the cat. Muscle spindles: Muscle spindles are present in the EOMs of some mammals and in the EOMs of man. Compared with muscle spindles in other skeletal muscles, those in human EOMs exhibit structural differences. These structural differences may indicate a special function. Golgi tendon organs: Golgi tendon organs are absent in human EOMs. Golgi tendon organs exhibiting a specific morphology are present in the EOMs of even-toed ungulates. Their high number and rich innervation indicate functional importance. Palisade endings: Palisade endings are nervous end organs confined to the EOMs of mammals and man. It is assumed that these organs have a proprioceptive function. The authors show that palisade endings are immunoreactive for antibodies against choline acetyltransferase. Neuromuscular contacts, if present in palisade endings, are alpha -bungarotoxin positive as well. Taken together, these results show that palisade endings exhibit molecular characteristics of effector organs.

Aged↗
PubMed1990

cDNA cloning reveals the molecular structure of a sperm surface protein, PH-20, involved in sperm-egg adhesion and the wide distribution of its gene among mammals.

Sperm binding to the egg zona pellucida in mammals is a cell-cell adhesion process that is generally species specific. The guinea pig sperm protein PH-20 has a required function in sperm adhesion to the zona pellucida of guinea pig eggs. PH-20 is located on both the sperm plasma membrane and acrosomal membrane. We report here the isolation and sequence of a full-length cDNA for PH-20 (available from EMBL/GenBank/DDBJ under accession number X56332). The derived amino acid sequence shows a mature protein of 468 amino acids containing six N-linked glycosylation sites and twelve cysteines, eight of which are tightly clustered near the COOH terminus. The sequence indicates PH-20 is a novel protein with no relationship to the mouse sperm adhesion protein galactosyl transferase and no significant homology with other known proteins. The two PH-20 populations, plasma membrane and acrosomal membrane, could arise because one form of PH-20 is encoded and differentially targeted at different spermatogenic stages. Alternatively, two different forms of PH-20 could be encoded. Our evidence thus far reveals only one sequence coding for PH-20: Southern blots of guinea pig genomic DNA indicated there is a single PH-20 gene, Northern blots showed a single size PH-20 message (approximately 2.2 kb), and no sequence variants were found among the sequenced cDNA clones. Cross-species Southern blots reveal the presence of a homologue of the PH-20 gene in mouse, rat, hamster, rabbit, bovine, monkey, and human genomic DNA, showing the PH-20 gene is conserved among mammals. Since genes for zona glycoproteins are also conserved among mammals, the general features of sperm and zona proteins involved in mammalian sperm-egg adhesion may have been evolutionarily maintained. Species specificity may result from limited changes in these molecules, either in their binding domains or in other regions that affect the ability of the binding domains to interact.

Amino Acid Sequence↗
PubMed2000

Parental Care: The Key to Understanding Endothermy and Other Convergent Features in Birds and Mammals.

Birds and mammals share a number of features that are remarkably similar but that have evolved independently. One of these characters, endothermy, has been suggested to have played a cardinal role in avian and mammalian evolution. I hypothesize that it is parental care, rather than endothermy, that is the key to understanding the amazing convergence between mammals and birds. Endothermy may have arisen as a consequence of selection for parental care because endothermy enables a parent to control incubation temperature. The remarkable ability of many birds and mammals to sustain vigorous exercise may also have arisen as a consequence of selection for parental care because provisioning of offspring often requires sustained vigorous exercise. Because extensive parental care encompasses a wide range of behaviors, morphology, and physiology, it may be a key innovation that accounts for the majority of convergent avian and mammalian characters.

Journal Article↗
PubMed2001

Lassa fever in Guinea: II. Distribution and prevalence of Lassa virus infection in small mammals.

Rodents of the genus Mastomys form the reservoir for Lassa virus (LV), an arenavirus that causes a potentially severe hemorrhagic illness, Lassa fever (LF). Although Mastomys rodents exist throughout sub-Saharan Africa, areas of human LF appear to be quite focal. The distribution of small mammals and LV-infected Mastomys has been assessed in only a few countries. We conducted a survey of small mammals in selected regions of Guinea to assess the degree to which LV poses a public health risk in that country. A total of 1,616 small mammals, including 956 (59%) Mastomys, were captured from 444 households and seven bush sites. Mastomys made up > 90% of the captured animals in the savannah, savannah-forest transition, and forest regions of Guinea, while Mus musculus dominated in coastal and urban sites. Animals were analyzed via enzyme-linked immunosorbent assay (ELISA) for LV-specific antigen (blood and spleen homogenate) and IgG antibody (blood only). Virus isolation from spleen homogenates was also performed on a subset of animals. Lassa antibody and antigen were found in 96 (11%) and 46 (5%), respectively, of 884 tested Mastomys. Antibody and antigen were essentially mutually exclusive and showed profiles consistent with vertical transmission of both LV and antibody. LV was isolated only from Mastomys. ELISA antigen constituted an acceptable surrogate for virus isolation, with a sensitivity and specificity when performed on blood of 78% (95% confidence interval: 68-83%) and 98% (95-99%), respectively. The proportion of LV-infected Mastomys per region ranged from 0 to 9% and was highest in the savannah and forest zones. The proportion of infected animals per village varied considerably, even between villages in close proximity. Infected animals tended to cluster in relatively few houses, suggesting the existence of focal "hot spots" of LV-infected Mastomys that may account for the observed heterogeneous distribution of LF.

Animals↗
PubMed2006

Natural tick-borne encephalitis virus infection among wild small mammals in the southeastern part of western Siberia, Russia.

Infestation of small mammals, including common shrews Sorex araneus L., field mice Apodemus agrarius Pallas, and red voles Clethrionomus rutilus Schreber, with immature Ixodes persulcatus ticks and their infection with tickborne encephalitis virus (TBEV) were studied in the forest-steppe habitat in the vicinity of Novosibirsk, Russia. Larval ticks parasitize all three host species, but virtually all nymphs were found only on field mice and red voles. Detection of the viral RNA using reverse transcription (RT) with subsequent nested polymerase chain reaction (nPCR) and of viral antigen using enzyme-linked immunosorbent assay (ELISA) revealed a high prevalence of TBEV-positive animals in both the summer and winter. The proportion of small mammals with hemagglutination inhibition (HI) antibodies was significantly lower than with ELISA-detected antibodies. Taken together, the data suggest that small mammals may maintain TBEV as a persistent infection throughout the year.

Animals↗
PubMed1990

Evolutionary relationships of class II major-histocompatibility-complex genes in mammals.

The major histocompatibility complex (MHC) class II molecule consists of noncovalently associated alpha and beta chains. In mammals studied so far, the class II MHC can be divided into a number of regions, each containing one or more alpha-chain genes (A genes) and beta-chain genes (B genes), and it has been known for some time that orthologous relationships exist between genes in corresponding regions from different mammalian species. A phylogenetic analysis of DNA sequences of class II A and B genes confirmed these relationships; but no such orthologous relationship was observed between the B genes of mammals and those of birds. Thus, the class II regions have diverged since the separation of birds and mammals (approximately 300 Mya) but before the radiation of the placental mammalian orders (60-80 Mya). Comparison of the phylogenetic trees for A and B genes revealed an unexpected characteristic of DP-region genes: DPB genes are most closely related to DQB genes, whereas DPA chain genes are most closely related to DRA-chain genes. Thus, the DP region seems to have originated through a recombinational event which brought together a DQB gene and a DRA gene (perhaps approximately 120 Mya). The 5' untranslated region of all class II genes includes sequences which are believed to be important in regulating class II gene expression but which are not conserved in known pseudogenes. These sequences are conserved to an extraordinary degree in the human DQB1 gene and its mouse homologue A beta 1, suggesting that regulation of expression of this locus may play a key role in expression of the entire class II MHC.

Amino Acids↗
PubMed1998

Mediterranean Europe as an area of endemism for small mammals rather than a source for northwards postglacial colonization.

There is a general perception that central and northern Europe were colonized by range expansion from Mediterranean refugia at the end of the last glaciation. Data from various species support this scenario, but we question its universality. Our mitochondrial DNA studies on three widespread species of small mammal suggest that colonization may have occurred from glacial refugia in central Europe-western Asia. The haplotypes on the Mediterranean peninsulae are distinctive from those found elsewhere. Rather than contributing to the postglacial colonization of Europe, Mediterranean populations of widespread small mammals may represent long-term isolates undergoing allopatric speciation. This could explain the high endemism of small mammals associated with the Mediterranean peninsulae.

Animals↗
PubMed2002

Testosterone promotes paternal behaviour in a monogamous mammal via conversion to oestrogen.

Although high testosterone (T) levels inhibit paternal behaviour in birds breeding in temperate zones many paternal mammals have a very different breeding biology, characterized by a post-partum oestrus. In species with post-partum oestrus, males may engage in T-dependent behaviours such as aggression and copulation simultaneously with paternal behaviour. We previously found that T promotes paternal behaviour in the California mouse, Peromyscus californicus. We examine whether this effect is mediated by the conversion of T to oestradiol (E(2)) by aromatase. In the first experiment, gonadectomized males treated with T or E(2) implants showed higher levels of huddling and pup grooming behaviour than gonadectomized males treated with dihydrotestosterone or empty implants. In the second experiment, we used an aromatase inhibitor (fadrozole) (FAD) to confirm these results. Gonadectomized males treated with T + vehicle or E(2) + FAD showed higher levels of huddling and pup grooming behaviour than gonadectomized males treated with T + FAD or empty implants. Although E(2) is known to promote the onset of maternal behaviour to our knowledge our results are the first to demonstrate that E(2) can promote paternal behaviour in a paternal mammal. These results may explain how mammals express paternal behaviour while T levels are elevated.

Animals↗
PubMed1997

Location and ultrastructure of Borrelia japonica in naturally infected Ixodes ovatus and small mammals.

The internal organs of Ixodes ovatus and the ears of wild rodents (Apodemus speciosus, Eothenomys smithii) and an insectivore (Crocidura dsinezumi) were cultured to isolate borreliae; positive samples were examined for the distribution and dissemination of spirochetes in the host tissues using electron microscopy. Seven isolates were derived from the unfed ticks and the three species of mammals. These isolates were identified as Borrelia japonica judging from the outer surface protein profile using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and reactivity to a B. japonica-specific monoclonal antibody. Borreliae were found only in the midgut lumen of the tick in close contact with the microvilli on the midgut epithelium; on the other hand, borreliae found in the ears of mammals existed freely in the collagenous intercellular substances of connective tissues or in close contact with fibrocytes. The ultrastructural disparities between the borreliae in ticks and mammals appeared to correspond to differences in motility. Interestingly, the borrelia which invaded through the perineurium appeared to contact the basement membrane of a Schwann cell that enclosed several nonmyelinated nerve fibers. This may offer important information regarding the involvement of the nervous system in Lyme disease.

Animals↗
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↗
PubMed1968

Vagal control of thermal panting in mammals and birds.

1. The role of the vagus nerves during normal respiration and thermal polypnoea was examined in four species of mammals and four species of birds by lung/air sac inflation and cervical vagotomy.2. The Hering-Breuer inflation reflex could be elicited in all of the mammals during both normal respiration and panting; it was present in the fowl and pigeon at normal body temperature only.3. Section of one vagus during hyperthermia reduced respiratory frequency in most animals and increased depth. Bilateral vagotomy had little further effect in the panting rabbit, lamb and pigeon, but abolished rapid respiration in the rat, guinea-pig, fowl, duck and quail.4. Vagotomized lambs and pigeons started panting in response to increasing body temperature, although the rate attained was slower than in intact animals. Guinea-pig, rat, fowl and quail did not pant under these conditions.5. Appropriate afferent vagal stimulation in the vagotomized fowl maintained normal respiration or thermal panting.6. It is concluded that panting can, in some mammals and birds, be controlled by central mechanisms alone, while in others it depends on extrinsic stimuli mediated by way of the vagus nerves.

Animals↗
PubMed1996

Fossil Evidence for a Late Cretaceous Origin of "Hoofed" Mammals

Seventeen of eighteen orders of living placental mammals are not known before 65 million years ago. The monophyly of each order is well established, but interrelations have been less certain. A superordinal grouping of up to seven extant orders plus a variety of extinct orders, all included within Ungulata ("hoofed" mammals), can be linked to Late Cretaceous mammals from the 85-million-year-old Bissekty Formation, Uzbekistan (and, less certainly, North America and Europe), thus pushing the origin of this major clade back by 20 million years. Ungulatomorphs are not closely related to primates, rodents, or rabbits.

Journal Article↗
PubMed1987

Conservation of brain amyloid proteins in aged mammals and humans with Alzheimer's disease.

The formation of clusters of altered axons and dendrites surrounding extracellular deposits of amyloid filaments (neuritic plaques) is a major feature of the human brain in both aging and Alzheimer's disease. A panel of antibodies against amyloid filaments and their constituent proteins from humans with Alzheimer's disease cross-reacted with neuritic plaque and cerebrovascular amyloid deposits in five other species of aged mammals, including monkey, orangutan, polar bear, and dog. Antibodies to a 28-amino acid peptide representing the partial protein sequence of the human amyloid filaments recognized the cortical and microvascular amyloid of all of the aged mammals examined. Plaque amyloid, plaque neurites, and neuronal cell bodies in the aged animals showed no reaction with antibodies to human paired helical filaments. Thus, with age, the amyloid proteins associated with progressive cortical degeneration in Alzheimer's disease are also deposited in the brains of other mammals. Aged primates can provide biochemically relevant models for principal features of Alzheimer's disease: cerebrovascular amyloidosis and neuritic plaque formation.

Aging↗
PubMed1985

Geometrical differences among homologous neurons in mammals.

The dendritic arbors of sympathetic neurons in different species of mammals vary systematically: the superior cervical ganglion cells of smaller mammals have fewer and less extensive dendrites than the homologous neurons in larger animals. This difference in dendritic complexity according to body size is reflected in the convergence of ganglionic innervation; the ganglion cells of progressively larger mammals are innervated by progressively more axons. These relations have implications both for the function of homologous neural systems in animals of different sizes and for the regulation of neuronal geometry during development.

Animals↗
PubMed2001

Evidence that the Campylobacter fetus sap locus is an ancient genomic constituent with origins before mammals and reptiles diverged.

Campylobacter fetus bacteria, isolated from both mammals and reptiles, may be either subsp. fetus or subsp. venerealis and either serotype A or serotype B. Surface layer proteins, expressed and secreted by genes in the sap locus, play an important role in C. fetus virulence. To assess whether the sap locus represents a pathogenicity island and to gain further insights into C. fetus evolution, we examined several C. fetus genes in 18 isolates. All of the isolates had 5 to 9 sapA or sapB homologs. One strain (85-387) possessed both sapA and sapB homologs, suggesting a recombinational event in the sap locus between sapA and sapB strains. When we amplified and analyzed nucleotide sequences from portions of housekeeping gene recA (501 bp) and sapD (450 bp), a part of the 6-kb sap invertible element, the phylogenies of the genes were highly parallel. Among the 15 isolates from mammals, serotype A and serotype B strains generally had consistent positions. The fact that the serotype A C. fetus subsp. fetus and subsp. venerealis strains were on the same branch suggests that their differentiation occurred after the type A-type B split. Isolates from mammals and reptiles formed two distinct tight phylogenetic clusters that were well separated. Sequence analysis of 16S rRNA showed that the reptile strains form a distinct phylotype between mammalian C. fetus and Campylobacter hyointestinalis. The phylogenies and sequence results showing that sapD and recA have similar G + C contents and substitution rates suggest that the sap locus is not a pathogenicity island but rather is an ancient constituent of the C. fetus genome, integral to its biology.

Amino Acid Sequence↗
PubMed2000

Molecular characterization of Brucella strains isolated from marine mammals.

Recently, gram-negative bacteria isolated from a variety of marine mammals have been identified as Brucella species by conventional phenotypic analysis. This study found the 16S rRNA gene from one representative isolate was identical to the homologous sequences of Brucella abortus, B. melitensis, B. canis, and B. suis. IS711-based DNA fingerprinting of 23 isolates from marine mammals showed all the isolates differed from the classical Brucella species. In general, fingerprint patterns grouped by host species. The data suggest that the marine mammal isolates are distinct types of Brucella and not one of the classical species or biovars invading new host species. In keeping with historical precedent, the designation of several new Brucella species may be appropriate.

Animals↗
PubMed1989

Influence of hematocrit on whole blood glucose levels: new evidence from marine mammals.

The water content and glucose concentration in the whole blood of marine mammals were found to be correlated to red blood cell concentration. Because hematocrit (Hct) undergoes significant periodic shifts in these mammals during periods of apnea and/or diving, the measured values of whole blood glucose change due to alterations in Hct, independent of shifts in metabolite regulatory pathways. In contrast to humans, where red blood cell and plasma glucose concentrations are equivalent, in most other mammalian species red blood cell glucose concentration is much lower than that in plasma. Therefore, as Hct increases, the whole blood concentration of glucose must decrease in a linear manner, depending on the magnitude of the Hct change and the concentration of glucose in the blood cells. This study demonstrates that water and metabolite distribution must be considered when interpreting whole blood metabolite data. The results suggest that plasma or serum analysis of metabolites would avoid distribution problems. This is especially critical in species where Hct varies during the course of the experiment, as in exercising or diving mammals.

Animals↗
PubMed2003

Surfactant from diving aquatic mammals.

Diving mammals that descend to depths of 50-70 m or greater fully collapse the gas exchanging portions of their lungs and then reexpand these areas with ascent. To investigate whether these animals may have evolved a uniquely developed surfactant system to facilitate repetitive alveolar collapse and expansion, we have analyzed surfactant in bronchoalveolar lavage fluid (BAL) obtained from nine pinnipeds and from pigs and humans. In contrast to BAL from terrestrial mammals, BAL from pinnipeds has a higher concentration of phospholipid and relatively more fluidic phosphatidylcholine molecular species, perhaps to facilitate rapid spreading during alveolar reexpansion. Normalized concentrations of hydrophobic surfactant proteins B and C were not significantly different among pinnipeds and terrestrial mammals by immunologic assay, but separation of proteins by gel electrophoresis indicated a greater content of surfactant protein B in elephant seal surfactant than in human surfactant. Remarkably, surfactant from the deepest diving pinnipeds produced moderately elevated in vitro minimum surface tension measurements, a finding not explained by the presence of protein or neutral lipid inhibitors. Further study of the composition and function of pinniped surfactants may contribute to the design of optimized therapeutic surfactants.

Animals↗