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Biomedical subjects

M Gans

Publications and source records attributed to M Gans.

8 recordsLinked to original sources
PubMed1992

Developmental anomalies derived from exposure of zygotes and first-cleavage embryos to mutagens.

Results of continuing studies indicate that the mouse zygote and two-cell embryo stages are a window of susceptibility in the experimental induction of congenital anomalies with certain mutagenic agents. The mechanisms by which the mutagens initiate the pathogenesis of these developmental defects are not known. However, in certain cases there is evidence that a nonconventional, perhaps epigenetic, mechanism is involved. Detailed characterization of the spectrum of anomalies induced and comparison of responses at the various stages exposed allowed classification of the mutagens generally into two groups. One group is characterized by being effective only in the early stages of zygote development and capable of producing a relatively high incidence of fetal death and hydrops. The other group affects all of the zygote stages studied as well as the two cell-embryo, but does not increase the incidence of fetal death and hydrops. Except for hydrops, chemicals in the two groups do not differ in terms of the types of anomalies present among malformed live fetuses, which bear a resemblance to a subset of common, sporadic human developmental anomalies that are of unknown etiology. This similarity raises the possibility that certain human developmental defects may have their origins in events that happen in the zygote and early pre-implantation stages.

Abnormalities, Drug-Induced↗
PubMed1991

Visual function after optic neuritis: a preliminary study.

We assessed visual function after recovery from optic neuritis in 15 consecutive patients using five objective tests: colour vision testing with Ishihara colour plates and with D15 colour desaturated spots, Humphrey automated perimetry, contrast acuity testing with Regan letter charts and testing of visual evoked response (VER). Recovery of visual function was not found to be dependent on presenting Snellen visual acuity or treatment with oral steroids. The most sensitive measures of residual visual deficit were mean defect on automated perimetry, low-contrast acuity and VER.

Adult↗
PubMed1990

Reversal of progressive nyctalopia in a patient with Crohn's disease.

A 51-year-old man who had undergone several partial bowel resections for Crohn's disease presented with progressively decreased night vision. Electroretinography showed a flat scotopic response and a diminished, delayed photopic response. Measurement of stool fat showed marked fat malabsorption. Treatment with parenteral nutrition, including administration of vitamin A, resulted in marked improvement in the scotopic and photopic response and subjective improvement in his night vision. Patients with malabsorption states should be followed to avoid irreversible visual loss.

Color Perception↗
PubMed1990

Discriminative properties of morphine that modulate associations between tastes and lithium chloride.

Wistar rats learned to withhold consumption of a target solution when morphine preceded presentation of the target solution and lithium chloride (LiCl) and to consume the same target solution when saline preceded the presentation of the solution. After this serial feature discrimination training, morphine did not block the formation of a Pavlovian association between saccharin and LiCl but did suppress consumption of familiar tap water. After Pavlovian conditioning, morphine blocked the formation of an association between saccharin and LiCl but did not suppress consumption of a familiar tap water solution. The roles of morphine and saline can be interchanged. It appears that the morphine discriminative stimulus is calling up a representation of neither the conditioned stimulus nor the unconditional stimulus alone, but rather a modified representation of some aspect of their association.

Animals↗
PubMed1986

Homonymous hemianopia following electrical injury.

The clinical spectrum of electrical injuries is complex and diverse. Despite the high annual incidence of electrical accidents, little has been reported recently regarding the neurological deficits associated with this form of trauma. The most frequently cited reviews are those of Critchley, Langworthy, Naville and De Morsier, and Silversides. These authors have divided the neurological complications into three groups based on the temporal relationship between the shock and the manifestation of clinical signs: immediate, secondary, and delayed. The present case developed a dense homonymous hemianopia 4 days following an electrical accident. The details of the above mentioned classification, as well as a review of the pathophysiology, will be presented.

Accidents, Occupational↗
PubMed1975

Isolation and characterization of sex-linked female-sterile mutants in Drosophila melanogaster.

The purpose of the experiments described was to identify X chromosome genes functioning mainly or exclusively during oogenesis. Two mutagenesis experiments were carried out with ethyl methane sulfonate. Following treatment inducing 60% lethals, 9% of the treated X chromosomes carried a female sterility mutation which did not otherwise seriously affect viability. Among--95 isolated mutants, 19 were heat-sensitive and 5 cold-sensitive. The mutants have been classified as follows: I (16 mutants; 12 complementation groups): the females laid few or no eggs; the defect concerned either ovulation or oogenesis. II (37 mutants; 18 complementation groups): the female laid morphologically abnormal eggs, often with increased membrane permeability. III A (13 mutants; at least 8 complementation groups): the homozygous females were sterile if mated to mutant males; their progeny (homo- and hemizygous) died at a late embryonic stage (11 mutants), at the larval stage (1 mutant) or at the pupal stage (1 mutant). However fertility was partly restored by breeding to wild-type males as shown by survival of some heterozygous descendants. III B (29 mutants; 22 complementation groups): the fertility of the females was not restored by breeding to a wild-type male. Most of the eggs of 13 of the mutants died at a late stage of embryogenesis. The eggs of the others ceased development earlier or, perhaps, remained unfertilized. The distribution of the number of mutants per complementation group led to an estimation of a total of about 150 X-linked genes involved in female fertility. The females of three mutants, heat-sensitive and totally sterile at 29 degrees, produced at a lower temperature descendants morphologically abnormal or deprived of germ cells. Three other mutants not described in detail showed a reduction in female fertility with many descendants lacking germ cells. A desirable mutant which was not recovered was one with normal fertile females producing descendants which, regardless of their genotype, bore specific morphological abnormalities. The value of the mutants isolated for analysis of the complex processes leading to egg formation and initiation of development is discussed.

Animals↗
PubMedDate not supplied

Contrast sensitivity letter charts as a test of visual function in amblyopia.

Anisometropic and strabismic amblyopes were studied using the Regan Contrast Sensitivity Charts. At all levels of contrast, the amblyopic eyes of both the strabismic and anisometropic patients scored significantly lower than did their fellow normal eyes, which were used as controls. In comparing the differences between the normal and amblyopic eyes of both groups, we noted a normalization of the visual function of strabismic amblyopes at low contrast. This feature was not observed in the anisometropic amblyopes who consistently scored poorly when viewing either the high or low contrast chart.

Adolescent↗