PubMed Health⌕ Search

Biomedical subjects

M S Deol

Publications and source records attributed to M S Deol.

At least 19 recordsLinked to original sources
PubMed1986

Genetic activity at the albino locus in Cattanach's insertion in the mouse.

Cattanach's insertion (Is(In7;X)1Ct or XCt) includes the normal allele at the albino locus (c+), which is subject to inactivation of the X chromosome carrying it, so that XCtX; cc mice have albino and pigmented patches. The X-autosome translocation T(X;16)16H or XT16H leads to preferential inactivation of the other X chromosome in female cells, so that XCtXT16H; cc mice are almost entirely white. However, they grow darker with age, as if reversal of inactivation of the c+ allele were taking place in increasing numbers of melanocytes. To test whether this is dependent only on age or whether it is related to the number of times the animal has moulted, hair was repeatedly plucked from selected areas at the early telogen stage when the follicles are also removed, assuming that the melanocytes or melanoblasts in that region of the skin would be forced to undergo further divisions to colonize the new follicles. The plucked areas grew darker at the same rate as the rest of the coat, suggesting that the progressive reversal of inactivation is dependent only on age. As direct examination of melanocytes in the follicles is difficult, they were examined in the choroid and the retinal pigment epithelium (RPE) of the eye. The frequency of the pigmented cells was lower in the choroid than in the RPE. Since the melanocytes in these structures are different in origin as well as in physical characteristics, it appears that cell type influences either reversal of inactivation, or the frequency with which the influence of the X chromosome extends to the albino locus.

Albinism↗
PubMed1983

Early degeneration of sensory and ganglion cells in the inner ear of mice with uncomplicated genetic deafness (dn): preliminary observations.

Deafness (dn/dn) mouse cochlea was investigated by electron microscopy in order to detect the first postnatal signs of histopathology. At birth, the inner hair cells (IHCs) showed abnormal vacuolization, afferent dendrites at IHC level appeared swollen and devoid of cytoplasmic content, and most of the neurons of the spiral ganglion contained an abnormal smooth endoplasmic. At day 7, these abnormalities had greatly increased, especially in the spiral ganglion neurons where large patches of filamentous material were found. These observations can account for the permanent electrophysiological deafness of dn/dn mice. Moreover, these data, showing early cytological abnormalities in both the IHCs and the spiral ganglion neurons, indicate that it is difficult to simply classify the deafness mutation as being 'degenerative'; some 'morphogenetic' processes are likely also involved.

Animals↗
PubMed1983

The effects of the pink-eyed unstable gene on the retinal pigment epithelium of the mouse.

Pink-eyed unstable (pun), an autosomal gene in the mouse, causes variegation of the coat. In some melanocytes it functions as the normal allele p+, producing dark pigment, and in others as the mutant p, producing light pigment. As a study of another unstable gene at a different locus had shown that the instability was strongly influenced by the tissue environment, it seemed desirable to find out whether this also applied to pun. An examination of the retinal pigment epithelium, the only structure in mammals in which it is practicable to determine the position of individual melanocytes, showed that the distribution of dark and light cells in pun pun animals was not random. The dark cells increased in frequency with the distance from the optic nerve, suggesting that the tissue environment was a factor in the instability of the gene (i.e. in its rate of mutation), although the increase was less striking than in the other mutant. It is generally assumed that when pun behaves as p+ it is a case of reversion, and that reversion can also occur in germ cells, the revertant p+ allele subsequently behaving as a stable gene. It is here argued that it is unlikely to be a case of reversion, and that the evidence for the involvement of the germ line is inconclusive. Further, it is suggested that the phenotype of pun pun animals is probably an instance of Position Effect variegation, the instability resulting from some chromosomal alteration, which is too small to be cytologically detectable.

Alleles↗
PubMed1982

Cochlear potentials in the Bronx waltzer mutant mouse.

The Bronx waltzer mutant mouse has a unique cochlear abnormality in which the outer hair cells appear normal but the inner hair cells are absent. Potentials recorded from the round window indicate that the gross cochlear nerve action potential is very small or absent and cochlear microphonics are present but of small amplitude. Positive and negative summating potentials can both be recorded, indicating that mammalian outer hair cells are capable of producing both positive and negative DC potentials.

Animals↗
PubMed1982

Patterns of matrix vesicle calcification in osteomalacia of Gyro mice.

Homozygous Gyro mice manifest widespread abnormalities in the inner ear and other parts of the skeleton. These disorders were attributed to a sex linked dominant gene. In the present study, tissue specimens were obtained from the inner ear and maxillary and tibial bones, and undecalcified samples were processed for light and transmission electron microscopy. Light microscopy revealed osseous changes consistent with osteomalacia. These alterations comprised broad bands of osteoid with partial or complete failure of calcification. Electron micrographs showed longitudinal calcifying fronts composed of hydroxyapatite crystals. Abundance of matrix vesicles could be demonstrated in the extracellular matrix. Many of the vesicles contained crystaline mineral. In addition, calcification alongside collagen fibers was recorded. Occasionally, apatite crystals were attached to plasma membranes. Female and hemizygous male mice showed normal patterns of calcification. The findings in the affected Gyro mice appear to be similar to previously reported changes in human osteomalacia. Further definition of the pathological process in this animal model may be valuable in defining mechanisms operative in the development of osteomalacia in man.

Animals↗
PubMed1975

Racial differences in pigmentation and natural selection.

The inheritance of skin colour in man is not well understood. A clearer understanding could be obtained by taking into account the biological basis and genetical control of pigmentation in other mammals, particularly the experimental species. In these, most of the loci governing pigmentation are pleiotropic, colour being only one of the traits affected by them. Their products are evidently concerned with other metabolic pathways as well. There is strong evidence for inter-specific homology of pigmentation loci in mammals, and the situation in man may not be radically different. It is therefore possible that racial differences in skin colour may have resulted from the action of natural selection on these other functions of pigmentation genes.

Alleles↗
PubMed1973

Genetic mechanisms determining the central visual pathways of mice.

Albino mammals have abnormal visual pathways. "Flecked" mice have a variegated pigment distribution, with roughly half the cells normally pigmented and half albino. They do not show the albino abnormality in the visual pathways. The gene at the albino locus, which determines the course of the visual pathways must, thus, have an extracellular action.

Albinism↗