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PubMed1988

A review of dental microwear and diet in modern mammals.

Recent work has shown that microscopic wear patterns on teeth may yield insights into variations in diet and tooth use in modern and prehistoric mammals. This paper presents a review of dental microwear and diet in modern mammals, plus a discussion of topics for further research. To date, incisor and molar microwear have been examined, although there are far fewer studies of the former. Facilitated by the use of high-resolution casts and scanning electron microscopy, analyses have ranged from: qualitative to quantitative, low magnification to high magnification, and experimental studies to comparative studies of museum collections. Results are encouraging and may lead to further insights into a variety of topics including food processing and dental microstructure.

Animals↗
PubMed1988

Characteristics and regulation of active transport in lungs from young and aged mammals.

From the data presented here, it appears that the ability to stimulate solute (and water) clearance from the alveolar spaces may decrease with aging. This implies that the management of elderly patients with respiratory diseases or complications may necessitate a different approach than that useful in younger patients. Many of the active transport mechanisms well-characterized in other epithelia now seem to be important for maintaining the alveolar air spaces in their normally "dry" condition in the lungs of fetal and young, sexually mature mammals. In situations in which excess fluid is present in the air spaces of the lung, it is likely that the normal regulation of these active transport processes may play a major processes may play a major role in alveolar fluid clearance. Various exogenous agents may be helpful in stimulating the active solute and water reabsorption from air space to vascular space in both fetal and young sexually mature mammals. Further studies on the effects of aging on the characteristics and regulation of lung fluid balance are still needed.

Aging↗
PubMed1987

Neurotoxic effect of capsaicin in mammals.

Capsaicin is now widely used to explore and/or prove the role of peptide-containing primary afferent neurones in different somato- and viscerosensory functions. The present paper deals with the morphological effects of capsaicin administered according to currently used experimental paradigms. As it has been repeatedly confirmed in the recent literature, administration of capsaicin to newborn mammals results in a highly selective degeneration of a particular population of small sized, B-type primary afferent neurones located in spinal and cranial sensory ganglia. Chemosensitive i.e. capsaicin sensitive primary sensory neurones (CPSNs) correspond to primary sensory ganglion cells which contain neuropeptides. The permanent functional impairments and the decrease in the peptide contents of the sensory neurones observed after neonatal capsaicin treatment may be accounted for an irreversible loss of CPSNs. Direct application of capsaicin to peripheral nerves results in an apparently irreversible functional impairment of unmyelinated afferent fibres implicated in nociceptive, viscerosensory and neurogenic inflammatory mechanisms. Morphological observations indicate that perineural treatment with capsaicin initiates a selective but delayed degeneration process of unmyelinated afferent nerve fibres presumably due to an inhibition of intraneuronal transport mechanisms. In contrast with perineural capsaicin treatment affecting the chemistry and function of the whole sensory neurone, injection of capsaicin into the subarachnoid space results in an irreversible abolition of the "afferent" but not the "efferent" function of CPSNs. Accordingly, noxious thermal or chemical stimuli applied to the peripheral innervation areas of the trigeminal nucleus caudalis or the affected segments of the spinal cord fail to induce nociceptive reflexes because of the degeneration of the central terminals of CPSNs. However, in these same skin areas, application of chemical irritants invariably evoked the neurogenic inflammatory response, indicating that CPSNs deprived of their central terminals maintain their capacity to synthesize and release the peptide(s) responsible for the initiation of that response. In contrast with previous findings, our recent studies furnished evidence for a selective neurodegenerative action of systemically injected capsaicin in adult mammals, as well. Therefore, some of the irreversible functional impairments produced by capsaicin in adult animals may result from the degeneration of a particular subpopulation of CPSNs.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1985

Generation of troponin T isoforms by alternative RNA splicing in avian skeletal muscle. Conserved and divergent features in birds and mammals.

We describe the isolation and sequence analysis of quail muscle cDNA clones encoding two closely related isoforms of the striated muscle contractile protein, troponin T. The cDNAs represent two troponin T mRNAs that exhibit an unusual sequence relationship. The two mRNAs have identical sequences over hundreds of nucleotides including 3' untranslated regions, but they differ dramatically in a discrete, internally located block of 38 nucleotides. The two alternative sequences of this 38-nucleotide block encode two different but related versions of amino acid residues 230-242, near the C terminus of the protein. These results are consistent with a novel mechanism of troponin T isoform generation by alternative mRNA splicing pathways from a single gene containing two different exons corresponding to amino acids 229-242, as recently proposed by Medford et al. (Medford, R. M., Nguyen, H. T., Destree, A. T., Summers, E., and Nadal-Ginard, B. (1984) Cell 38, 409-421). This proposal was based on analysis of a rat troponin T genomic DNA clone and a cDNA clone corresponding to one of the two alternatively spliced mRNAs. Our analysis of quail troponin T cDNA clones, apparently corresponding to two alternatively spliced mRNA species, provides important new evidence for this novel mechanism of troponin T isoform generation and reveals the differential splicing mechanism to be of great antiquity, antedating the bird-mammal divergence. One of the quail alternative isoform sequences clearly corresponds to one of the rat sequences, but the other quail alternative sequence does not correspond to either of the rat sequences. This result suggests a greater complexity of troponin T gene structure or a greater diversity of troponin T isoform genes than is currently known, and also has implications for the functional significance of the troponin T protein isoform heterogeneity. Comparison of quail and mammal alternative isoform sequences also reveals strongly conserved features which suggest that all the isoform alternative amino acid sequences are variations on a common structural theme.

Amino Acid Sequence↗
PubMed1985

[Tooth homology in mammals].

The development of the chewing, lacerative and omnivorous dentition type was confirmed on the base of the author's studies on the dentition of placentalia representatives. The use of vegetable food by the rodents and herbivorous mammals induces an efficient development of molars, absence or reduced number of incisors and canines of the upper jaw and increased number of incisors and absence of canines of the lower jaw, resulting into the proposal of an alteration of the dentition formula for rabbits and for the rest of the rodents (Simplicidentata), for herbivorous and for horses. In beasts of prey, besides the efficient development of the canines, a transition of the premolars and certain molars into laceratives is found. In omnivorous mammals, together with the efficient development of canines, an efficient development of molars and premolars as chewing teeth is also established.

Animals↗
PubMed1979

Mutagenicity studies with nitrofurans. I. Mutagenicity of nitrofurylacrylic acid for mammals.

Cytogenetic analysis of mouse bone-marrow cells, the dominant lethal test in mice and the cytogenetic analysis of human peripheral lymphocytes in vitro were used to study the mutagenicity of 3-(5-nitro-2-furyl)acrylic acid (5-NFA) for mammals. The bone-marrow cytogenetic analysis was performed in female mice exposed to 5-NFA administered intraperitoneally in single doses of 15--120 mg/kg and in 5 repeated doses of 15 and 30 mg/kg, intragastrically in single doses of 30--240 mg/kg and 5 repeated doses of 30 and 60 mg/kg, and perorally for 12 weeks to 5-NFA concentration of 10, 100 and 1000 mg 5-FNA/1 in drinking water. The bone-marrow analysis was performed in this case after 12 days, 3, 4, 6, 8, 10 and 12 weeks exposure. No increase in chromosome damage attributable to dosing with 5-NFA occurred in any of these experiments. Experiments in which mice were exposed to 5-NFA in drinking water for 12 weeks and then treated with a single i.p. dose of 2 mg of the mutagen TEPA [trix-(1-aziridinyl)phosphine oxide] per kg revealed that, at a concentration of 1000 mg 5-NFA/1, the clastogenic activity of TEPA was reduced to that in untreated animals. The dominant lethal test was performed in male mice exposed to 5-NFA applied intraperitoneally in single doses of 40--120 mg/kg and in 5 repeated doses of 10--30 mg/kg, intragastrically in 5 repeated doses of 20--60 mg/kg, and perorally for 4 weeks in drinking water containing 5-NFA at concentrations of 10, 100, 316 and 1000 mg/l. No significant differences were detected between the exposed and control groups of animals. Experiments in which male mice were exposed to 5-NFA in drinking water and treated after the 4-week exposure to 5-NFA with 1 mg TEPA/kg revealed that a concentration of 1000 mg 5-NFA/1 reduced TEPA-induced dominant lethality to within control values. A reduction in male fertility was observed after the single or repeated 5-NFA doses, but no changes when 5-NFA was applied in drinking water. The cytogenetic analysis of human peripheral lymphocytes exposed in vitro for the last 24 h of culture to concentrations of 1--100 micrograms 5-NFA/Ml did not show any compound-related chromosomal changes. The results of dominant-lethal and bone-marrow cytogenetic studies in mice after consumption of drinking water containing 1000 mg of 5-NFA/1 for 12 weeks and dosed subsequently with TEPA suggests that 5-NFA has some antimutagenic activity. Because none of the studies reported revealed any compound-related genetic activity, the results suggest that 5-NFA is not a chromosome-breaking agent in mammals.

Acrylates↗
PubMed1980

Prolactin as a regulator of fluid and electrolyte metabolism in mammals.

The evidence that prolactin is a fluid and electrolyte regulator in mammals is reviewed, with particular emphasis on the renal actions of prolactin. Prolactin receptors are found in mammalian kidneys. Prolactin modulates renal formation of cyclic AMP and polyamines and it leads to demonstrable histological changes in the proximal tubules. The renal actions of prolactin primarily involve modulation of the effects of other hormones and are therefore critically dependent on the background physiological situation. Prolactin seems able to cause a prolonged reduction in water, sodium, and potassium excretion, a pattern that is imitated by no other hormone with the possible exception of growth hormone. Prolactin preparations can cause an acute antidiuresis, which may in part be related to contamination of prolactin preparations with vasopressin. However, most of the described effects cannot be explained by vasopressin contamination. This is particularly so with the effects of prolactin on water movements across fetal skin, the amniotic membrane, and in the eye where prolactin and vasopressin have diametrically opposite effects. It is concluded that prolactin is a regulator of fluid and electrolyte metabolism in mammals but that it is a modulator rather than a primary controlling factor.

Aldosterone↗
PubMed1983

X-chromosome inactivation and evolution in marsupials and other mammals.

Sex chromosome dosage compensation in Australian marsupials exhibits several characteristics not ordinarily manifested in eutherian mammals. They are: 1) preferential inactivation of the paternally derived X-chromosome in somatic tissues; 2) a state of partial inactivity at some paternally derived X-linked gene loci in some cells; 3) absence of dosage compensation in some cell types; 4) absence of nuclear sex dimorphism at interphase; 5) discordance between late DNA replication and gene inactivation in some cell types; 6) failure of the X-chromosome to behave as a single unit. Despite these seemingly major differences between the dosage compensation systems of Australian marsupials and eutherians, there are also many underlying similarities. We propose that the two systems arose from a common ancestral mechanism in which the X-chromosome was regulated in a piecemeal fashion, rather than as a whole. To determine more precisely the sequence and timing of evolutionary events, we have initiated an investigation of dosage compensation in American marsupials, which diverged from Australian marsupials soon after the divergence of marsupials from eutherian mammals.

Animals↗
PubMedDate not supplied

[Cerebrosides and sulfocerebrosides in the brain of insectivorous mammals].

Brain cerebrosides (C) and sulfocerebrosides (S) of Insectivora, which represent the most ancient and primitive order of placentary mammals, were first studied. The content of C and S is higher in hedgehogs (Erinaceus europaeus, E. auritus) and mole (Talpa europaea) brains as compared to shrew (Sorex araneus) brain. Hydroxy fatty acids predominate over normal fatty acids in C of all studied insectivora brains. The fatty acid content of C and S of the Insectivora brains is similar in being rich in palmitic, stearic and behenic normal acids and hydroxybehenic and hydroxylignocerinic acids. Hydroxy fatty acids of C and S are more saturated and they have a longer chain (sum C24-26 acids) than the normal acids. C and S of insectivora and primate brains are compared. The data may be of importance for the understanding of the biochemical evolution of the nervous system of mammals.

Animals↗
PubMed1982

Sites and regulation of carnitine biosynthesis in mammals.

Although the pathway of carnitine biosynthesis in mammals is known, the location of active synthesis of carnitine and regulation of the pathway have not been clearly defined. Studies in several laboratories have shown that the enzymes that collectively convert epsilon-N-trimethyllysine (epsilon-N-TML) to gamma-butyrobetaine are found in all tissues studied in rats and humans, but distribution of the final enzyme of the pathway, gamma-butyrobetaine, 2-oxoglutarate dioxygenase (gamma-butyrobetaine hydroxylase) is variable from one species to another. Evidence from studies in rats and humans indicates that uptake and metabolism of epsilon-N-TML by the kidney is necessary for carnitine biosynthesis from circulating epsilon-N-TML. Limited data now available suggest that some of the intracellularly derived epsilon-N-TML is metabolized to gamma-butyrobetaine and carnitine in the tissue of origin, and some is released into the circulation. epsilon-N-TML in mammals is apparently derived from lysine residues in proteins, which are methylated and later released by protein hydrolysis. This source probably provides sufficient substrate for carnitine biosynthesis. Carnitine biosynthesis from epsilon-N-TML is not regulated by end-product feedback mechanisms. Hepatic gamma-butyrobetaine hydroxylase activity in rats and humans is developmentally regulated, and is increased by dietary L-thyroxine in adult rats. No other mechanisms for regulation of carnitine biosynthesis have been identified.

Adult↗
PubMedDate not supplied

[Arbovirus infections in Tunisia: new serological survey of small wild mammals].

Sera of 103 small wild mammals (rodents, insectivora, cheiroptera) trapped at the beginning of 1980 in different areas of Tunisia were studied for antibody against 15 arboviruses. In inhibition haemagglutination tests, positive reactions were found against Dengue type 2 (2.2%), Tahyna (18.4%), Arumowot (42.7%) and Sicilian sandfly fever (31%) viruses. No antibody was found for 8 tick-borne viruses. In comparison with previous sero-surveys, our results indicated a fall of West Nile virus activity and the emergence of Tahyna virus. The possibility that wild cycles involving small mammals and the two phleboviruses may exist in Tunisia is discussed.

Animal Population Groups↗
PubMed1983

The circadian timing system in mammals: two pacemakers preside over many secondary oscillators.

There is considerable evidence to indicate that circadian timekeeping in mammals is accomplished by a multioscillator system. Circadian rhythms in physiological variables may under certain circumstances adopt different periodicities within the same animal, and many mammalian tissues have been shown capable of generating persisting circadian rhythms in vitro. However, as yet only one circadian pacemaker has been identified unequivocally: the suprachiasmatic nuclei (SCN) in the anterior hypothalamus. This paper presents evidence that mammals possess another major circadian pacemaking system that is normally coupled to the SCN but that can function independently. Each of these major pacemakers presides over a considerable number of secondary oscillators located in diverse tissues.

Animals↗
PubMed1980

Survey of dermatophytes in the hair of small mammals from Austria.

Apparently healthy hair of insectivores and rodents originating from two regions situated at different altitudes in Austria was examined on the presence of dermatophytes. Dermatophytes Microsporum persicolor, Trichophyton georgiae, T. mentagrophytes var. erinacei, T. mentagrophytes var. mentagrophytes and T. terrestre were recovered from the hair of 27 animals (32.9%), belonging to 10 species. The results revealed evident specificity of dermatophytes to host mammals irrespective of the effect of different altitude of localities. The existence of dermatophytes in the healthy hair of mammals is due either to mere contamination from environment (findings of geophilic species) or to inapparent infection (findings of zoophilic species).

Animals↗
PubMed1981

Embryonic hemoglobins in man and other mammals.

This report attempts to review the present state of research on embryonic hemoglobins in humans and other mammals from a cytologic, molecular, and clinical point of view. In all mammals, the yolk sac is the site responsible for the "primitive" erythropoiesis, which produces an erythroid population characterized by peculiar cytologic features and globin gene expression. Morphological and molecular events that underlie prenatal erythropoiesis are described herein giving rise to questions regarding biology at large (i.e., the differential activity of genes capable of similar functions); molecular biology of eukaryotic genes (i.e., globin gene organization and structural subtleties); and clinical hematology (i.e., syndromes associated with the appearance of embryonic hemoglobins.

Aneuploidy↗
PubMed1982

[The position of seals in the system of mammals (author's transl)].

The common seal Phoca vitulina belongs to the order Pinnipedia, a group of marine mammals, the majority of which live in the colder seas. Two main groups are differentiated within this order: Otarioidea and Phocoidea. The Otarioidea are divided into two families: Otariidae (sea lions and fur seals) and Odobenidae (walruses): the Phocoidea consist of the family Phocidae (seals) only. The Pinnipedia are closely related to the order Carnivora: they probably originated about 50 million years ago from a group of mammals related to bears. Otarioidea and Phocoidea are now usually regarded as close relatives, n view of among others, biochemical and parasitological characters.

Animals↗
PubMedDate not supplied

[Relative content of cholesterol and microviscosity of serum apo-B-containing lipoproteins of mammals].

Microviscosity of serum lipoproteins of different classes of mammals was estimated by eximerization of pyrene fluorescent probe. It has been shown that protein-lipid particles of high density have the highest microviscosity, while lipoproteins of low density--the lowest. For apoB-containing lipoproteins of different mammals a high positive correlation was found between pyrene fluorescence parameter, reflecting microviscosity and cholesterin-phospholipid ratio in the particles.

Animals↗