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PubMed2001

Outer submucous plexus: an intrinsic nerve network involved in both secretory and motility processes in the intestine of large mammals and humans.

The architecture of the enteric nerve networks in the gastrointestinal tract appears to be more complex in large mammals, including humans, than in small laboratory animals. At least two distinct ganglionic nerve plexuses could be identified in the submucous layer in the digestive tract of large mammals. While functionally and morphologically similar neuron populations are found in the intestinal wall of both small and large mammals, significant differences in their topographical organization and neurochemical features may be present. This short review clearly illustrates that the close and exclusive association, which has been assumed so far between the efferent pathways of the submucous plexus and regulation of intestinal secretion/absorption on the one hand and between the myenteric plexus and regulation of intestinal motility on the other hand, cannot be interpreted that strictly. An attempt has been made to give a briefoverview of the current status of the identification of distinct functional enteric neuronal classes in the gastrointestinal tract of large mammals using the pig and human intestine as references, and to compare these data with the more extensive information gathered from the guinea-pig intestine.

Animals↗
PubMed1976

Neonatal Escherichia coli infections in domestic mammals: transmissibility of pathogenic characteristics.

Apart from the fact that different serotypes are involved, natural and experimental Escherichia coli infection in domestic mammals closely resembles natural E. coli infection in human beings. Some of the important characteristics of E. coli strains that cause disease in domestic mammals are determined by transmissible plasmids. These include enterotoxin, haemolysin and K88 antigen in piglet enteropathogenic strains and enterotoxin and K99 antigen production in calf and lamb enteropathogenic strains; most strains that cause generalized infections in young domestic mammals, i.e. invasive strains, also produce plasmid-determined colicine V. These are all good reasons for employing young domestic mammals as the animal model for studying certain aspects of E. coli infection in human beings. Exploiting the fact that plasmids can be introduced into bacterial cells by conjugation and can be removed from them by "curing", bacterial strains were created that differed from each other, as far as could be determined, only by the presence or absence of one or more of these plasmid-determined properties. These strains, or cell-free preparations of them, were then given by mouth to piglets, calves, lambs and baby rabbits. The results showed that the K88 antigen, probably on account of its adhesive properties, permitted pig enteropathogenic strains of E. coli to proliferate in the small intestine of piglets; the K99 antigen performed a similar function in calf and lamb enteropathogenic strains. The enterotoxin produced by the proliferating organisms was then chiefly responsible for the subsequent movement of fluid from the body into the small intestine and the consequent diarrhoea. Possession of the Col V plasmid contributed significantly to the virulence of invasive strains of E. coli by enabling them to resist more successfully the defence mechanisms of the host.

Animals↗
PubMed1991

Neurotoxic esterase activity in brain, spinal cord and platelets of certain birds and mammals.

The level of neurotoxic esterase in brain, spinal cord and platelets of certain birds and mammals has been determined. The enzyme activity for the birds was maximal in hens and for the mammals was maximal in rats. The activity decreased progressively in the cerebral cortex, corpus striatum, spinal cord and blood platelets of the birds as well as the mammals. The difference in the susceptibility of birds and mammals to organophosphate-induced delayed neurotoxicity may be related to differences in the relative concentrations of the enzyme in the different species.

Animals↗
PubMed2002

Comparative observations on corneas, with special reference to Bowman's layer and Descemet's membrane in mammals and amphibians.

Corneas of tadpole, mouse, rat, guinea pig, rabbit, cat, cattle, and human were examined by TEM and SEM in a comparative study. The differences between species were noted mainly by using TEM. Bowman's layer showed a tendency to be well developed in higher mammals. Tadpoles lack a Bowman's layer, lower mammals have a thin Bowman's layer, and higher mammals have a thick Bowman's layer. The boundary between the substantia propria and Descemet's membrane was distinct in higher mammals. On the other hand, there are no differences in thickness of the collagen fibrils that constitute Bowman's layer and those of the substantia propria. NaOH digestion was utilized for SEM preparation. SEM imaging revealed a textured appearance of the epithelial side of Bowman's layer. In Descemet's membrane, fibrous long spacing (FLS) fiber-like structures, which are arranged in parallel to the endothelium, were observed by both TEM and SEM. To our knowledge, this is the first report of SEM observations of FLS fiber-like structures on the endothelial surface of Descemet's membrane. SEM at a plane normal to the plane of the cornea showed that Descemet's membrane has a piled laminar structure. Descemet's membrane is closely associated with the collagen layer of the substantia propria. Collagen fibrils invading from the substantia propria into Descemet's membrane were observed with both TEM and SEM.

Animals↗
PubMed1997

Considerations on genetic and environmental factors that contribute to resistance or sensitivity of mammals including humans to toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and related compounds. Part 1: Genetic factors affecting the toxicity of TCDD.

The marked species differences in short-term toxicity (30-day LD50) of ca. 10,000 (LD50: guinea pigs ca. 1 microgram/kg body wt and Han/Wistar Kuopio rats more than 9600 micrograms/kg body wt) of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is one of the central issues of the controversies that have developed on the validity of risk assessment strategies for TCDD and related compounds. One of the most challenging issues that toxicologists face today is the identification of genes that contribute to or are responsible for increased resistance or sensitivity to TCDD and related compounds. It is assumed that most, if not all, toxic effects of TCDD are mediated more or less through the binding affinity to the Ah receptor. This hypothesis was extended and tries to explain the differences in sensitivity/resistance of animals including humans to TCDD by their total fat (lipid) content. In this respect the gene or genes which is or are responsible for obesity of mammals including humans are of great interest. An obvious linear positive logarithmic relationship between the oral 30-day LD50 (microgram/kg) of TCDD in different species and strains of mammals and their total body fat content (TBF%) was found: log LD50 = 5.30 x log (TBF)-3.22, or LD50 = 0.000603 x (TBF)5.30. By means of this regression the toxicity of TCDD in mammals including humans of different age and/or body weight can be predicted if their total body fat content is known. Examples of single-gene and polygenic disease models in different mammals, such as nonobese diabetic, diabetic, viable yellow, obese, and fat mice, as well as transgenic mice, and other suitable animal models, such as fatty Zucker rats, Han/Wistar (Kuopio) rats, and minipigs, are discussed, and predicted LD50 values of TCDD in these animals and humans are presented.

Animals↗
PubMed1996

Characterization of two new preproGnRH mRNAs in the tree shrew: first direct evidence for mesencephalic GnRH gene expression in a placental mammal.

Reproductive maturation and regulation is centrally orchestrated by gonadotropin-releasing hormone (GnRH). GnRH produced in the vertebrate hypothalamus acts on the pituitary to regulate gonadotropins. In nonplacental mammalian species, it has recently been shown that a second GnRH gene is expressed in mesencephalic cells. Here, we report the cDNA sequences and expression patterns for two distinct genes encoding the hypothalamic and mesencephalic GnRH forms in the brain of a placental mammal, the tree shrew (Tupaia glis belangeri). The novel mammalian GnRH form, designated here as [His5Trp7Tyr8]GnRH (often called chicken GnRH II), is expressed in neurons of the mesencephalon and is the first nonhypothalamic form to be isolated from a mammal. Its peptide sequence is identical to the form previously reported in fish, amphibians, reptiles, and birds, revealing that it has remained unchanged for 500 million years. In contrast, the sequences of the hypothalamic GnRH decapeptides vary by as much as 50% across vertebrate species. The remarkable sequence conservation of mesencephalic GnRH suggests that it has been highly constrained throughout evolution, perhaps indicating an important, conserved nongonadotropic role. The discovery and localization of two mRNAs encoding distinct GnRH forms in an advanced mammal suggest that other mammals, including primates, may also have a second GnRH gene with expression localized in the midbrain.

Amino Acid Sequence↗
PubMed2002

Lack of a distinct gradient in biomarker responses in small mammals collected at different distances from a highway.

This study describes biomarker effects in small mammals exposed to traffic emissions. Animals were collected at 10-50 m (site 1), 150-200 m (site 2), and 5 km (site 3) from a very busy highway (A2). To distinguish between routes of exposure, strictly carnivorous common shrews ( Sorex araneus) and predominantly herbivorous bank voles ( Clethrionomys glareolus) were collected. As a measure of exposure to polycyclic aromatic hydrocarbons (PAHs), aromatic DNA adduct levels were determined by (32)P-postlabeling techniques in tissue from heart, lung, and liver. Lead (Pb), cadmium (Cd), and copper (Cu) levels were analyzed in kidney as a measure of exposure to heavy metals. EROD and PROD activity and retinoid levels were determined in liver as effect biomarkers for exposure to PAHs and polyhalogenated aromatic hydrocarbons (PHAHs). Relatively high Cd levels in S. araneus and in particular elevated DNA adduct levels in C. glareolus indicated that small mammals at site 3 were exposed to more compounds than at sites 1 and 2 (3 > or = 1 > 2). The latter effect is probably due to an incidental and actual input of airborne pollutants that is deposited on plant surfaces. By consumption of above-ground vegetation, voles are chronically exposed to this pollution. Relatively high background input of PAHs probably hinders that the traffic-related gradient of airborne PAH concentrations found in an earlier study is reflected in DNA adduct levels in small mammals in the present study. Moreover, historical biomarkers for exposure to traffic emissions, such as increased kidney Pb levels, increased hepatic EROD activity, and disturbed hepatic vitamin A homeostasis are no longer applicable to indicate differences in exposure. This is a result of the ban on addition of Pb and chlorinated scavengers to gasoline and of cleaner combustion techniques, which were enforced by law over the past decade. Finally, it is advisable to use only juvenile small mammals for in situ monitoring of diffuse pollution because DNA adduct levels increased with age.

Age Factors↗
PubMed2003

AP1 genes in Fugu indicate a divergent transcriptional control to that of mammals.

The draft genomic sequence of the Japanese puffer fish, Fugu rubripes, has now been announced. This is the first complete sequence of a teleost fish and the second available vertebrate sequence, the first being that of human. For the first time, whole-genome comparisons between two vertebrates can be undertaken. Early analysis has suggested that there may be surprising differences in gene regulation between human and fish. In mammals, a gene commonly has several functions, and this may not always be the case in fish. Many gene families comprise more members in fish than they do in mammals, possibly because each fish gene has evolved an individual function. Complexities of gene regulation in mammals has hampered studies of all biological processes from cell proliferation to cell death. Determining the activities of the AP1 transcription factor proteins has been non-trivial. The AP1 complex typically comprises two proteins, a Jun (c-Jun, JunB, and JunD) and a Fos (c-Fos, FosB, Fra1, and Fra2). These proteins can form both homodimers and heterodimers among-themselves and can interact with additional proteins; thus, dissecting their individual roles has been difficult. We have determined that Fugu has more Jun and Fos genes than mammals, and if each proves to have a separate function, then addressing the roles of the individual AP1 proteins in Fugu may be simpler than in human.

Amino Acid Sequence↗
PubMed2003

Functional capacities of marsupial hearts: size and mitochondrial parameters indicate higher aerobic capabilities than generally seen in placental mammals.

This study of marsupial hearts explored the aerobic capacities of this group of mammals; recent information suggests that marsupials possess higher aerobic abilities than previously accepted. Characteristics such as heart mass, mitochondrial features and capillary parameters were examined. A comprehensive study of the heart of red kangaroos was included because of the high maximum oxygen consumption of this species. Goats were also included as a reference placental mammal. Marsupials have a heart that is generally larger than that of placentals. The allometric equation for the relationship between heart mass and body mass for marsupials was M(h)=7.5M(b)(0.944) (M(h) in g and M(b) in kg); the equivalent equation for placental mammals was M(h)=6.0M(b)(0.97). Mitochondrial volume density and inner mitochondrial surface density do not differ between the two mammal groups; although capillary parameters indicated a lower capillary volume in marsupials. Heart size appears to be the major difference between the two groups. The overall pattern seen in marsupials is similar to that of "athletic" placentals and indicates a relatively high aerobic potential.

Analysis of Variance↗
PubMed1999

Mycophagy by small mammals in the coniferous forests of North America: nutritional value of sporocarps of Rhizopogon vinicolor, a common hypogeous fungus.

We evaluated the nutritional value of sporocarps of Rhizopogon vinicolor, a common hypogeous fungus in the coniferous forests of North America, for two small mammal species: the Californian red-backed vole (Clethrionomys californicus) and the northern flying squirrel (Glaucomys sabrinus). Although the nitrogen concentration of sporocarps was high, much of it was in non-protein form or associated with cell walls, suggesting that it may be of low nutritional value or protected from mammalian digestive enzymes. Sporocarps also had high concentrations of cell wall constituents, indicating low availability of digestible energy. When fed a diet of this fungus alone in a controlled feeding experiment both mammal species lost a small amount of body mass. Digestibilities of dry matter, nitrogen, cell wall constituents and energy from sporocarps by both species were lower than the digestibilities of other food types by other similarly sized small mammals. Red-backed voles digested the various components of sporocarps at least as well as the flying squirrels, even though they were almost six-fold smaller in body mass. This observation supports the notion that red-backed voles, like other microtine rodents, have morphological and physiological adaptations of the digestive system that are postulated to permit greater digestion of fibrous diets than predicted on the basis of body size. Despite this, our results re-affirm previous conclusions that hypogeous fungi are only of moderate nutritional value for most small, hindgut-fermenting mammals. Future studies should focus on the importance of mixed-species of fungi in the diet of small mammalian mycophagists.

Adaptation, Physiological↗
PubMed1998

Cortical perineuronal nets in the gray short-tailed opossum (Monodelphis domestica): a distribution pattern contrasting with that shown in placental mammals.

Extracellular matrix proteoglycans accumulated in perineuronal nets and in certain neuropil zones have been shown to influence the immediate neuronal microenvironment, and to contribute to the chemoarchitectonic characteristics of neuronal networks. Studies in different placental mammals, including the human, have suggested that the major principles of extracellular matrix distribution remained constant during phylogenesis of the different mammalian strains. However, the comparison of matrix distribution between various species also indicates that striking deviations from the basic pattern may occur, although their functional significance appears unknown as yet. This study examines the extracellular matrix in the forebrain of a basic American marsupial, which has evolved independently of placental mammals for more than 100 million years. Brain sections obtained from adult gray short-tailed opossums (Monodelphis domestica) were stained for extracellular matrix components using the N-acetylgalactosamine-binding lectin Wisteria floribunda agglutinin (WFA), a polyclonal antibody against chondroitin sulfate proteoglycans (CSPG), and biotinylated hyaluronectin for the detection of hyaluronan. In subcortical regions, the distribution patterns of WFA-stained and CSPG-immunoreactive perineuronal nets were similar to those reported previously in placental mammals. In contrast, a unique distribution was found in the neocortex. This distribution was characterized by the presence of perineuronal nets around pyramidal cells and matrix components within the adjacent neuropil that together form a continuously labeled zone in layer V. Weakly stained nets ensheathed less numerous pyramidal cells in the upper layers II/III and a few multipolar cortical neurons. Dual staining experiments showed that cortical net-associated neurons were rarely immunopositive for parvalbumin. This fact, in addition to the predominant association of extracellular matrix components with layer V pyramidal cells, differentiates the neocortex in Monodelphis from that of all placental mammals studied to date. Regarding the basic phylogenetic position of this marsupial species it remains to be shown if these distribution characteristics of extracellular matrix may represent also a basic feature of cortical organization.

Acetylgalactosamine↗
PubMed1981

Scaling of oxidative and glycolytic enzymes in mammals.

The catalytic activities of several oxidative and glycolytic enzymes were determined in the gastrocnemius muscle of 10 mammalian species differing in body weight by nearly 6 orders of magnitude. When expressed in terms of units gm-1, the activities of enzymes functioning in oxidative metabolism (citrate synthase, beta-hydroxybutyrylCoA dehydrogenase, and malate dehydrogenase) decrease as body weight increases. Log-log plots (activity gm-1 vs body mass) yield straight lines with negative slopes that are less than the allometric exponent (-0.25) typically observed for basal metabolic rates. Since the amount of power a muscle can generate depends upon the catalytic potential of its enzyme machinery (the higher the catalytic potential the higher the maximum rate of energy generation), these data predict that the scope for aerobic activity in large mammals should be greater than in small mammals if nothing else becomes limiting, a result in fact recently obtained by Taylor et al. (Respir. Physiol., 1981). In contrast to the scaling of oxidative enzymes, the activities of enzymes functioning in anaerobic glycogenolysis (glycogen phosphorylase, pyruvate kinase, and lactate dehydrogenase) increase as body size increases. Log-log plots (activity gm-1 vs body mass) display a positive slope indicating that the larger the animal the higher the glycolytic potential of its skeletal muscles. This unexpected result may indicate higher relative power costs for burst type locomotion in larger mammals, which is in fact observed in within-species studies of man. However, the scaling of anaerobic muscle power has not been closely assessed in between-species comparisons of mammals varying greatly in body size.

Animals↗
PubMed1990

Derivation of the nucleoproteins (NP) of influenza A viruses isolated from marine mammals.

The nucleoprotein (NP) genes of influenza viruses were sequenced from a variety of virus isolates derived from marine mammals: whales from the Pacific and Atlantic oceans, seal and gull from the Western Atlantic, and a tern from the Caspian Sea. In comparison to published NP sequences, we found pairs of NPs derived from avian and marine mammal isolates to be closely related, e.g., the gull-whale and mallard-seal pairs from the Atlantic Coast of the USA and the tern-Pacific Ocean whale pair of the Eastern Hemisphere. Our analysis suggests that influenza viruses have been independently introduced into marine mammals from avian sources for each of our three examples. Furthermore, the closeness of the relationship in these avian-mammalian NP pairs indicates that the introductions are relatively recent. The sequences of these marine mammal NPs are avian-like and can be clearly distinguished from human NPs. Our results provide further support of interspecies transmission of influenza A viruses from the avian host reservoir directly to mammalian hosts.

Amino Acid Sequence↗
PubMed1990

Accumulation of cardiac lipofuscin in mammals: correlation between sexual maturation and the first appearance of lipofuscin.

Accumulation of lipofuscin is an important phenomenon of the cellular aging process. The first appearance of cardiac lipofuscin showed a good correlation with sexual maturation, which was correlated with maximum life-span of mammals. Large metabolic changes occurred at sexual maturation. From these results, it is suggested that sexual maturation of mammals is the initiation period of the aging process. Correlation between sexual maturation and longevity was re-evaluated using many mammals. Domestic and laboratory animals showed an earlier sexual maturation than other mammals, including rodents.

Aging↗
PubMed1993

Determination of inorganic constituents in marine mammal tissues.

Analyses of selected tissues from the Alaska Marine Mammal Tissue Archival Project (AMMTAP) have provided comprehensive information related to levels of 36 trace elements and methyl-mercury in marine mammal tissues. Liver, kidney and muscle tissues from two northern fur seals, four ringed seals and six belukha whales were analyzed. The bulk of the investigated tissues and additional tissues from a total of 65 marine mammals are banked in the AMMTAP. The results are compared to literature values for trace element concentrations in marine mammal tissues and their relevance to environmental studies is discussed.

Alaska↗
PubMed1995

Predicting cadmium, lead and fluoride levels in small mammals from soil residues and by species-species extrapolation.

The effects of heavy metals on wild mammals are often assessed by analysing residues in body organs. This paper reviews published studies to determine whether cadmium (Cd), lead (Pb) and fluoride (F) residues in small mammals can be predicted directly from residues in soil or, when this is not possible, from residues in other species. It was found that residues in soil could be used to predict Cd and Pb concentrations in small mammals. There were significant (P < 0.05) relationships between Cd residues in soil and in the liver and kidneys of wood mice Apodemus sylvaticus and common shrews Sorex araneus; similar relationships occurred in field voles Microtus agrestis (0.05 < P < 0.10). There were also significant relationships between Pb residues in soil and body organs for wood mice and field voles. Insufficient data were available to relate either Pb levels in soil to those in shrews or F levels in soil to residues in any species. However, both Cd and F residues in any one of the three small mammal species examined could be predicted from the corresponding residues in the other species, there being significant relationships between species for residues in the liver and kidneys (Cd) or bone (F). Too few data were available to determine species-species relationships for Pb.

Journal Article↗
PubMed2003

The monotreme genome: a patchwork of reptile, mammal and unique features?

The first specimen of platypus (Ornithorhynchus anatinus) that reached Britain in the late 18th century was regarded a scientific hoax. Over decades the anatomical characteristics of these unique mammals, such as egg laying and the existence of mammary glands, were hotly debated before they were accepted. Within the last 40 years, more and more details of monotreme physiology, histology, reproduction and genetics have been revealed. Some show similarities with birds or reptiles, some with therian mammals, but many are very specific to monotremes. The genome is no exception to monotreme uniqueness. An early opinion was that the karyotype, composed of a few large chromosomes and many small ones, resembled bird and reptile macro- and micro-chromosomes. However, the platypus genome also features characteristics that are not present in other mammals, such as a complex translocation system. The sex chromosome system is still not resolved. Nothing is known about dosage compensation and, unlike in therian mammals, there seems to be no genomic imprinting. In this article we will recount the mysteries of the monotreme genome and describe how we are using recently developed technology to identify chromosomes in mitosis, meiosis and sperm, to map genes to chromosomes, to unravel the sex chromosome system and the translocation chain and investigate X inactivation and genomic imprinting in monotremes.

Animals↗
PubMed2006

Bovine tuberculosis infection in wild mammals in the South-West region of England: a survey of prevalence and a semi-quantitative assessment of the relative risks to cattle.

In the United Kingdom, badgers are implicated in the transmission of Mycobacterium bovis to cattle, but little information is available on the potential role of other wild mammals. This paper presents the results of the largest systematic UK survey of M. bovis infection in other wild mammals. Mammal carcasses (4715) from throughout the South-West region of England were subjected to a systematic post mortem examination, microbiological culture of tissues and spoligotyping of isolates. Infection was confirmed in fox, stoat, polecat, common shrew, yellow-necked mouse, wood mouse, field vole, grey squirrel, roe deer, red deer, fallow deer and muntjac. Prevalence in deer may have been underestimated because the majority were incomplete carcasses, which reduced the likelihood of detecting infection. Infected cases were found in Wiltshire, Somerset, Devon and Cornwall, Gloucestershire and Herefordshire. Lesions were found in a high proportion of spoligotype-positive fallow, red and roe deer, and a single fox, stoat and muntjac. M. bovis spoligotypes occurred in a similar frequency of occurrence to that in cattle and badgers. Data on prevalence, pathology, abundance and ecology of wild mammals was integrated in a semi-quantitative risk assessment of the likelihood of transmission to cattle relative to badgers. Although most species presented a relatively low risk, higher values and uncertainty associated with muntjac, roe, red and in particular fallow deer, suggest they require further investigation. The results suggest that deer should be considered as potential, although probably localised, sources of infection for cattle.

Animals↗