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At least 1,711 records · Page 95Linked to original sources
PubMedDate not supplied

[The size of small mammals and the number of fleas parasitizing them].

Correlation analysis of many-year's data on the distribution and number of fleas parasitizing on 281,627 mammals of 21 species in the pest natural foci of the Aral Sea coastal area has demonstrated that the number of mammalian ectoparasites was determined by ecological features as well as by the size of animals: higher numbers of bloodsucking insects could parasitize on animals of a larger size. Values of correlation coefficients of Spearman ranks between body size and number of fleas are high and significant. This fact has remained unnoticed, probably, due to extreme variability in the fleas number indicators obtained in epizootiological studies. This makes their suitability to important studies requiring high precision of the initial data rather doubtful.

Animals↗
PubMed1989

[The dual-nature of the retina of mammals].

Using the literary review and author's data the morphologic criterion in the distinction of cones and rods is being discussed. It is based on a distinction of the chromatin structure in the photoreceptor kernels. The rod chromatin is organized by one or a few large blocks which disguise a nucleolus. The cone chromatin is a crumbly grain. One or two nucleoli can be seen clearly. Obviously, the manner of the chromatin condensation reflects the physiological and biochemical distinctions of cones and rods. Even nocturnal or diurnal mammals have mixed double retina. These facts contradict to the Walls' theory of evolution in photoreceptors (transmutation theory) and agree to the Dollo's low. Double-natured retina is a significant condition for its plastic and private adaptation in changing of ecological conditions.

Animals↗
PubMed1989

[Vasopressin, oxytocin and angiotensin receptors in mammals].

The synthesis of new radiolabelled compounds and the evolution of the techniques designed to study the hormonal receptors allow a better understanding of their properties. Three types of vasopressin receptors have been described: the V1a receptor of liver and blood vessels, the V1b receptor of hypophysis and the V2 receptor of kidney. Such a classification was based on two criteria: The structure of the binding site and the nature of the second messenger produced. The V2 receptor coupled positively to adenylate cyclase regulates the water reabsorption via the increase of intracellular cyclic AMP. The V1a and V1b receptors involved in glycogenolysis, contraction and probably neurotransmission mobilize intracellular calcium via a positive coupling to phospholipase C. These two receptors exhibit different recognition patterns for vasopressin analogues. In mammals, the oxytocin receptors are mainly involved in myometrial contraction and lactation. Their characterization are generally difficult since they also interact with vasopressin and are sometimes colocated with vasopressin receptors. As for V1 receptor, they are coupled to phospholipase C and mobilized intracellular calcium. The receptors of angiotensin II regulate the blood pressure by different mechanisms. They are coupled to at least two transduction mechanisms (positive coupling to phospholipase C and negative coupling to adenylate cyclase). Electrophysiological data seems to indicate that such receptor may also control a calcium channel. Yet different molecules (cAMP, calcium, inositol phosphates, diacyl-glycerol) trigger the hormonal effect of angiotensin II inside the cell.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Aluminum toxicity in mammals: a minireview.

The element aluminum is ubiquitous in nature. Although its role in the metabolism of living systems remains to be elucidated, under certain circumstances aluminum is known to be toxic. The following topics concerning the toxicologic aspects of aluminum in mammals are covered in this brief review: major sources of the metal in humans, clinical toxicology, and experimental toxicology. Diagnosis, prevention and treatment of aluminum overload are also discussed in the clinical toxicology section. Moreover, acute and chronic toxicity studies, behavioral and neurofibrillary changes, mutagenicity, carcinogenicity, and reproductive and developmental effects of the metal are reviewed in the experimental toxicology section. Aluminum, under ordinary circumstances, can accumulate in patients receiving long-term hemodialysis, which has been associated with various severe disorders.

Aluminum↗
PubMedDate not supplied

[Quantitative estimation of the modification of mutagenic effect in experiments on mammals using a regression modification index].

A regressive modification index (RMI = beta M - beta/beta.100) is suggested to quantitatively evaluate modification of the mutagenic effect in experiments on mammals. It is based on the correlation of regressive equation "dose mutagen--effects" coefficients beta M and beta in variants with and without modifier, respectively. Regressive modification indices of various doses of phenobarbital are calculated in experiments on rats with cyclophosphamide and fotrin.

Animals↗
PubMed1987

Occurrence and distribution of Hantavirus in wild living mammals in Belgium.

Small mammals were screened for the presence of antibodies to Hantaan virus (HTN) and Hantavirus (HV) antigen in Belgium. Antibody and antigen-positive animals were found in different parts of the country. One insectivore and five rodent species were found positive. The highest prevalence of infection was found in the bank vole (Clethrionomys glareolus). A relation between infected animals and wet habitats was observed. It was obvious that in bank vole the likelihood of infection increased with age.

Age Factors↗
PubMedDate not supplied

[Faunistic analysis of the fleas on small mammals in the trans-Aral Sea area].

Materials on occurrence and abundance of 36 species of fleas on 17 species of small mammals are systematized. A great similarity between the faunas of ectoparasites of rodents and predators has been shown by means of special indices. The conception of parasitic field is formulated which implies the phenomenon of community of the fauna of plague vectors parasitic on its potential carriers. Some aspects of the formation of parasitic field and its possible effect the epizootic process are considered. It is established that the similarity between the faunas of fleas from different animals is ensured in this region first of all by a wide distribution of specific parasites of gerbils.

Animals↗
PubMed1988

[Macromutation and evolution: the fixation of Goldschmidt's macromutations as species and genus traits. Hairlessness mutations in mammals].

A brief survey of the development of concepts on the role of macromutations in evolution is given. Contrary to Iu. A. Filipchenko (1926, 1927), who introduced the "micro- and macromutation" terms and believed that regularities of macroevolution could not be reduced to microevolutionary processes, the majority of "synthetists" explained any form of evolution by changes in allele frequencies. From the studies of Drosophila homoeotic mutants R. Goldschmidt (1940) developed the concept of "hopeful monsters" and their role in macroevolution. However, the homoeotic mutants are of drastically reduced viability, which allows the gradualists to reject Goldschmidt's ideas. The distribution of hairlessness mutations (hairless, nude etc.) with the monogenic pattern of inheritance in mammals was studied. Hairless mutants are known in Peromyscus, Mus musculus, Rattus rattus, R. norvegicus, Canis familiaris, Ovis aries. Hairlessness as norm is found in 53 among contemporaneous 1037 mammalian genera. Part of these cases (hairlessness in all Cetacea and Sirenia) may be explained in terms of both macromutations and obligatory gradualism. There is no doubt as to the macromutational origin of hairlessness in the bat Cheiromeles and the rodent Heterocephalus (Bathyergidae); the genera systematically and ecologically close to these have normal pelage. It is quite possible that hairlessness of walrus (Odobenus) has the same origin. The appearance and fixation of single Goldschmidt's macromutation cannot yet be considered as a macroevolutionary process, though the possibility of fixation of a macromutation in nature as a species and genus character contradicts strongly the concept of obligatory gradualism of evolution.

Animals↗
PubMedDate not supplied

[Fleas of small mammals and birds in the forest-park area of the city of Novosibirsk].

The distribution of fleas of small mammals and birds in the nidi of tick-borne encephalitis was analysed. 23 species were recorded from the forest-park zone. Palaeopsylla soricis starki, Amalaraeus penicilliger penicilliger, Megabothris rectangulatus, Ctenophthalmus assimilis, Hystrichopsylla talpae were dominant. They amounted to 90% of the total number of fleas. The greatest species variety of fleas was noted in afforested low-lying parts with rich species composition of hosts.

Animals↗
PubMed1977

Mesostigmatid mites of small mammals from the Hindu Kush (Afghanistan).

During the First Czechoslovak mountaineering expedition to the Hindu Kush (1965) a material of mesostigmatid mites was collected from small mammals, yielding 16 species. Due to the fact that it is the first collection of these parasites studied in Afghanistan, a zoogeographic analysis, altitudinal stratification and epidemiological estimation are appended.

Afghanistan↗
PubMed1987

Dispersal in patchy environments: effect on the prevalence of small mammal ectoparasites.

Part-time ectoparasites on small mammals disperse via the habitat, while full-time parasites spread throughout the host population by direct contacts between host animals. It is therefore supposed that the effect of the natural environment is different for the two groups. This was studied as differences between observed and expected prevalence, the percentage of the infested host population, during different environmental conditions. Two possible mechanisms of such an effect were analysed, i.e. a) host selection and its change with host frequency and b) parasite migration and reproduction rates as reflected by the frequency distribution patterns on the hosts. As expected the prevalence of full-time ectoparasites (Anoplura and subfamily Laelapinae) could be predicted on the basis of host species frequencies during different environmental conditions, with the exception of one louse species (Hoplopleura acanthopus), because of its restricted distribution. Prediction was not possible for part-time ectoparasites (subfamily Hameogamasinae). Species of the subfamily Haemogamasinae were more catholic in host selection than species of Anoplura and subfamily Laelapinae. The haemogamasin mites changed host species to a greater extent than did Anoplura and Laelapinae. All haemogamasin mites had short-tailed frequency distribution patterns and all Anoplura and Laelapinae, except Hyperlaelaps microti, had long-tailed frequency distributions.

Animals↗
PubMed1987

[Comparative anatomy of the velopharyngeal complex in mammals--excluding primates (1)].

From the anatomic element known with the man by the name of soft palatal-pharyngeal sphincter and which takes a major part in the phonation, the swallowing, the breathing, we have studied the evolutive morphology of the soft palatal-pharyngeal unity in several mammals. This unity which includes the levator palati and palatopharyngeus muscles is confirmed by the phylogenic and embryologic investigations. The comparative anatomy of the rat, rabbit, sheep and lion, allows to make obvious a evolutive line characterized by the gradual divergence of the axis of the two muscles common to the soft palatal and pharyngeal musculature, which could correspond with a phylogenic evolution.

Anatomy, Comparative↗
PubMedDate not supplied

[Parthenogenesis in mammals].

A review of studies dealing with spontaneous and induced parthenogenesis in mammals. The main methods of artificial egg activation, ways of their development and causes of mortality of the parthenogenetic mouse embryos are considered. The possibilities of using parthenogenesis for solving urgent problems of mammalian developmental biology are estimated and prospects of further studies in this field are outlined.

Animals↗
PubMed1986

Comparison of ear tissue regeneration in mammals.

These studies, on a variety of laboratory, zoo and agricultural animals, show that the phenomenon of replacement of tissues lost in an ear punch is common to some other mammals as well as the rabbit, although the rabbit appears to be the most proficient in this process. It is suggested that the cartilage may be replaced in two ways, namely through the formation of a blastema as originally hypothesised by Markelova (Vorontsova & Liosner, 1960), and also from the perichondrium. The finding of bone tissue is supportive evidence enabling the suggestion that dedifferentiation, followed by deviant redifferentiation, does occur in the process of regeneration.

Animals↗
PubMed1978

Neural control of pineal function in mammals and birds.

Pineal function in mammals is regulated by a system with four major neural components. The first is a retinohypothalamic projection from the ganglion cells of the retina to the suprachiasmatic nucleus of the hypthalamus. The suprachiasmatic nucleus appears to function as a circadian oscillating system projecting into the hypothalamus and this represents the second component. The third component is constituted of a brainstem pathway from the lateral hypothalamus to the intermediolateral cell column of the upper thoracic spinal cord. The fourth component is the preganglionic and postganglionic sympathetic system arising from the upper thoracic cord to innervate the superior cervical ganglion which, in turn, innervates the pineal gland. No direct neural control of the pineal gland has been demonstrated in birds.

Animals↗
PubMed1985

Spermiogenesis and spermatozoa in mammals.

This is a summarizing review about some aspects of the morphogenesis and characteristics of mammalian spermatozoon. The morphology, biogenesis and function of the different spermatozoon structures are analysed, as well as different aspects, like immunology and endocrine control. Comparative morphology, fate and function of the male gamete during its passage through the epididymis and female tract are commented. The fact, that the phenomenon of spermiogenesis continues with the maturative changes in the epididymis, and that modifications occur in the female genital tract is put forward; this idea seems to be basic for understanding the role of many spermatozoon structures, as well as many biochemical and molecular changes that take place in the gamete. On the other hand, all these changes (spermiogenesis, maturation, capacitation and acrosomal reaction in the female tract), as well as the interaction sperm/egg are sequentially dependent, and are focussed on the sperming capacity of reaching and fertilizing the egg. Many gaps exist in regard to the functional role of different spermatozoon structures, and three important questions are emphasized with a view to solving these problems: a) The importance of the comparative analysis of spermatozoon and egg structures in different mammalian species. b) The necessity to develop ample studies using in vivo situations, particularly in reference to the changes occurred in the female tract. In this regard, the majority of studies have been developed in the in vitro situation, which is very different from the natural environment. c) The importance of using and compiling the different data (morphological, biochemical, molecular, etc.) about spermiogenesis, spermatozoon and fertilization. In the future, the use of new technologies appears as a promising idea to clarify doubts about spermatozoa biogenesis and function in mammals.

Animals↗
PubMed1986

Congenital malformations of the flipper in three West Indian manatees, Trichechus manatus, and a proposed mechanism for development of ectrodactyly and cleft hand in mammals.

Three cases of congenital ectrodactyly of the flipper in the manatee are described, including one case of bilaterally-symmetrical cleft hand. A hypothesis assumes that a defect in the apical ectodermal ridge (AER) in the developing hand plate of the early embryo is the initiating factor in the development of ectrodactylous and cleft hand malformations in man and other mammals. Variations in the site, extent, and time of the AER defect will account for many of the morphologic variations observed in these congenital malformations.

Animals↗
PubMed1986

A glass drinking tube for small birds and mammals.

A drinking tube was fabricated with a piece of 8 or 10 mm O.D. glass tubing. It gives accurate measurement of the volume of liquid consumed by small birds and mammals. The tube can be readily cleaned and autoclaved.

Animal Husbandry↗