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M Levitan

Publications and source records attributed to M Levitan.

14 recordsLinked to original sources
PubMed1993

Studies of linkage in populations. X. Altitude and autosomal gene arrangements in Drosophila robusta.

Data are presented concerning the gene arrangements in the second and third chromosomes of Drosophila robusta in eight altitudinal transects. A consistent change is the increase in the arrangement 2L-3, particularly in the linkage combination 2L-3.2R, with increasing altitude. The reciprocal decrease with increasing altitude affects several different 2-left arrangements, most consistently 2L-1. The arrangements of 2-right show no significant variation with altitude, and those of 3-right do so only in a few samples of the two northern transects studied, none in any of the southern ones. These results confirm previous evidence for the significant role of the arrangements of the left arm of the second chromosome in the adaptations of this species to altitude and suggest further that interactions of linked arrangements are involved in these adaptations. The data also indicate that the factors responsible for the altitudinal adaptations of this species are in many cases not the same ones that are responsible for variations in its gene arrangements with latitude.

Altitude↗
PubMed1993

Mutability, sterility and suppression in P-M hybrid dysgenesis: the influence of P subline, cross, chromosome, sex and P-element structure.

Three Harwich P sublines with different P-element activity potential were used to investigate the influence of P-derived chromosomes on snw mutability and vg suppression and to relate the induction of these dysgenic traits to the number and structure of P elements. Destabilization of the snw allele, a measure of P transposase activity, was differentially influenced by the major autosomes. Chromosome 2 of the standard Harwich subline, Hw, induced only 60% of the level of mutability relative to chromosome 3, whereas chromosome 3 of the weakest Harwich subline, Hf, induced only 50% of the mutability relative to chromosome 2. In somatic suppression of the vg21-3 allele, chromosome 3 of the Hf subline produced a lower level of complete suppression as compared to chromosome 3 of the Hw or the Hs subline (the high hybrid-dysgenesis-inducing subline). The level of these dysgenic traits and GD sterility, was not correlated with the number of P elements per individual (67-68) or per chromosome arm which was very similar among the sublines. The number of complete P elements per genome, based on Southern blot analysis of the X and major autosomes, ranged from 15 to 19. Destabilization of the snw allele and vg suppression by chromosome 3 was correlated with a greater number of complete P elements. Two novel unexpected observations emerged from these studies: both snw mutability and vg suppression data demonstrated high P-element activity in hybrids derived from non-dysgenic crosses irrespective of Harwich subline, indicating a lack of P-cytotype regulation. Mutability in non-dysgenic males ranged from 40 to 60% of the level found in dysgenic males. The high snw mutability and low GD sterility in non-dysgenic hybrids suggests that these traits may arise by a different mechanism.

Alleles↗
PubMed1986

Repetitive pseudoseizures incorrectly managed as status epilepticus.

Pseudoseizures should be considered in the differential diagnosis of intractable seizures. Incorrect diagnosis may result in incorrect management, with the patient unnecessarily exposed to side effects of drugs. The authors report on three patients who presented with uncontrolled seizures originally diagnosed and managed as status epilepticus. Electroencephalography performed during provoked attacks led to a diagnosis of pseudoseizures. Psychiatric assessment revealed psychologic disorders. The patients received supportive therapy, and the pseudoseizures stopped.

Adult↗
PubMed1986

25 years of a unique chromosome-breakage system. I. Principal features and comparison to other systems.

The principal features of the D. robusta chromosome-breakage system are reviewed and compared to intrinsic chromosome-breakage systems in other Drosophila species, particularly the 'hybrid dysgenesis' systems of D. melanogaster. The data indicate that the D. robusta system is unique in many respects, especially in its combination of a reciprocal cross effect, traceable to its maternal or cytoplasmic inheritance, exclusive susceptibility of the paternal chromosomes, and the randomness of the breaks on the chromosomes.

Animals↗
PubMed1985

Serologic survey for markers of hepatitis B infection in dermatologists.

A serologic survey for markers of hepatitis B virus (HBV) infection was conducted in 593 dermatologists. Serologic evidence for previous infection was found in 15.4%, indicating that dermatologists are an at-risk population comparable to many other specialties of medicine. Dermatologists with a history of blood transfusion, tattoo, and homosexuality had an increased prevalence of serologic markers for HBV. The type of practice, extent of surgery, and glove-wearing practices did not correlate with HBV serologic markers.

Adult↗
PubMed1984

Leishmaniasis.

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Adolescent↗
PubMed1980

The chief financial officer's qualifications for the chief executive officer's job.

The changing character of the role of the CFO raises the question of whether the terminal role for someone starting in the financial track is the CFO position or whether the training received in financial management prepares an individual to accept the responsibility of the CEO position. An examination of the responsibilities of both roles comparing their similarities and differences is helpful in answering this question. Job descriptions will vary from institution to institution, depending upon the special needs and circumstances that exist. However, certain characteristics are common to both the CEO and the CFO. Table 2-1 presents a brief comparison of these two roles.

Administrative Personnel↗
PubMed1973

Associations of alleles of the esterase-1 locus with gene arrangements of the left arm of the second chromosome in Drosophila robusta.

Evidence of strong associations of Est-1 alleles with the 2L, 2L1 and 2L3 gene arrangements of the left arm of the second chromosome in D. robusta is presented. Each gene arrangement is polymorphic for three to four Est-1 alleles. The allele frequencies differ in the 2L3 and 2L arrangements; the allele Est-1(.92) is 8% in the 2L3 arrangement (n=203)-this allele is 82% in the 2L arrangement (n=203); the allele Est-1(1.0) is 66% and 14.8% in the 2L3 and 2L arrangements, respectively. There are no differences in allele frequencies in 2L3 arrangements from any of the widely separated seven different populations; similarly the allele frequencies in the 2L arrangement are alike in all five widely separated populations studied. The allele frequencies in the 2L1 arrangement are intermediate to those observed in the 2L3 and the 2L arrangements and show north-south clinal change. These associations between Est-1 alleles and gene arrangements of the left arm of the second chromosome are due to natural selection favoring different allele frequencies in different gene arrangements, as a result of epistatic interactions between the Est-1 locus and the loci on the gene arrangements. As expected, we observe that the proportion of heterozygotes is greater in the inversion heterokaryotypes than in the homokaryotypes.

Animals↗