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Biomedical subjects

L Ehrman

Publications and source records attributed to L Ehrman.

At least 19 recordsLinked to original sources
PubMed2004

Effects of culture, sex, and age on the distribution of handedness: an evaluation of the sensitivity of three measures of handedness.

The present study examined the effects of culture, age, and sex on three measures of handedness: writing hand, Annett's primary handedness items, and a measure based on hand preference for 11 activities. Using data from a large international study, the relationship between the culture in which participants learned to write (as defined by Hofstede's cultural dimensions) and adult handedness was examined. Participants who learned to write in formal cultures were less likely to be classified as left-handed than those who learned in less formal cultures. Older participants and those who learned to write in formal cultures were more likely to be classified as left-handed by the Annett and 11 item measures than by the writing hand classification. Across measures females were less likely to be classified as left-handed than males. Handedness for writing was found to be more sensitive to cultural influences than the other measures. These results suggest that some measures of handedness may be more sensitive to specific handedness aetiologies than others.

Adolescent↗
PubMed1999

Developmental isolation and subsequent adult behavior of Drosophila paulistorum. V. Survey of six sibling species.

In an investigation into the effects of developmental isolation from all conspecifics, the Drosophila willistoni group of six sibling species responded to differing degrees: all six are reproductively isolated from D. paulistorum, the tester species. Drosophila pavlovskiana, a narrow endemic, proved the most vulnerable, responding by reducing its adult sexual isolation, if eggs, any instar, and sometimes even pupae were socially isolated. To lesser degrees, D. tropicalis and D. willistoni both produced similar results only when their eggs were isolated, i.e., when from the moment of egg deposition on, there was absolutely no contact with other flies until testing for mating behavior. The remaining siblings, D. equinoxialis and D. insularis, were immovable.

Animals↗
PubMed1998

Developmental isolation and subsequent adult behavior of Drosophila paulistorum. IV. Courtship.

Early social experiences play important roles in adult Drosophila paulistorum mate selection. Differences in courtship between control males and wholly socially isolated males were observed in chambers. Socially isolated males displayed more courtship toward virgin females than did controls. Socially isolated males were more successful in competing for mates. Yet socially isolated males from all six semispecies also displayed notable frequencies of homosexual behavior.

Analysis of Variance↗
PubMed1996

Developmental isolation and subsequent adult behavior of Drosophila paulistorum. II. prior experience.

Preadult seclusion imposed upon members of the Drosophila paulistorum complex of intersterile semispecies significantly decreased sexual isolation between adults of the semispecies. While seclusion at any developmental stage had this effect, there were quantitative variations correlated with the stage at which seclusion had been initiated: the earlier the stage at which seclusion began, the more frequent were the heterogamic matings. All the stages of development seemed to contribute to final adult sexual behavior, with no single stage emerging as the most important experiential phase. Seclusion also significantly affected intrasemispecific matings, in that flies were more likely to mate with partners having similar experiences.

Animals↗
PubMed1996

Developmental isolation and subsequent adult behavior of Drosophila paulistorum. III. Alternative rearing.

We have been utilizing members of the Drosophila paulistorum complex of semispecies to study the development of adult discriminatory behavior. In this study, three rearing methods were used to examine the effects of previous exposure to heterosemispecifics on reproductive isolation among the various semispecies. Experimental flies were exposed to heterosemispecifics by one of three methods: exposure to airborne heterosemispecific stimuli from egg through sexual maturity, physical contact with heterosemispecifics only during the postimaginal period, and mixed culturing (total physical contact with heterosemispecific individuals during each of five preimaginal stages). Effects of the first treatment varied with semispecies. The second treatment had no significant effect on mating behavior. The third treatment of mixed culturing reinforced sexual isolation.

Animals↗
PubMed1995

Bacterial entomopathogens from the Drosophila paulistorum semispecies complex.

Bacteria which are infectious by inoculation in lepidoptera have been isolated and characterized from semispecies comprising the Drosophila paulistorum complex. These microorganisms are pathogenic toward lepidopteran hosts such as Heliothis virescens when introduced by injection of Drosophila tissue extracts and have been given the trivial name DpLE (D. paulistorum lepidopteran entomopathogen). The DpLE from two of the semispecies, Transitional and Andean, were determined to be related to Proteus vulgaris based upon nucleotide sequence comparisons of 16S rDNA genes. Infectivity and 16S rDNA-based PCR assays showed the bacterium to be localized in a number of drosophilid tissues except adult heads and thoraces. Based upon similar experiments, the DpLE in transinfected Heliothis larvae were found in all tissues assayed prior to the onset of mortality. Stocks of Drosophila which had spontaneously lost DpLE continued to produce sterile sons when crossed with incompatible semispecies' females, confirming that the bacilliform DpLE is not the causative agent of the Drosophila paulistorum intersemispecific hybrid male sterility. Acquisition of the sequences of the 16S rDNA molecules of DpLE from all six semispecies permitted the construction of a phylogenetic tree in which the groupings were found not to be congruent with the phylogenies of their insect hosts.

Animals↗
PubMed1994

An international study of human handedness: the data.

Human handedness has been the subject of systematic study since 1646, but there is no agreement among researchers as to who can be considered a left-hander, what is the etiology of left-handedness, or what the proportion of left-handedness is in the world's population. This article reports the results of a handedness survey administered to 12,000 subjects in 17 countries, the largest handedness survey attempted. The paper discusses methods for determining handedness, the probability of a genetic component for handedness, and the relationship of sex, birth order, multiple birth, and first-degree relative's handedness on subject's handedness. A hypothesis for the etiology of left-handedness is presented.

Adult↗
PubMed1992

Developmental isolation and subsequent adult behavior of Drosophila paulistorum. I. Survey of the six semispecies.

We present results deriving from the inception of an investigation (involving 4,000 scored matings) into the development of discriminatory behavior in Drosophila paulistorum. We examined two complementary situations for their effects on mating behavior: physical isolation (seclusion) beginning at each of six developmental stages and exposure to heterosemispecifics during all preadult stages (mixed culturing). Preadult seclusion at certain stages decreased sexual isolation between three of four semispecific pairs. Seclusion effect, or lack thereof, varied with semispecies and with the stage at which seclusion was imposed: the earlier the stage at which seclusion was initiated, the more drastic the effect. In contrast, mixed culturing increased sexual isolation between the one pair of semispecies that was tested.

Animals↗
PubMed1990

Developmental isolation and subsequent adult behavior of Drosophila pseudoobscura.

When isolated from all contact with other flies until the opportunity to exercise mating choices, Drosophila pseudoobscura displays genetically-mediated compensatory behavior: heterokaryotypic females are more vulnerable than homokaryotes to wholly restricted contact with conspecifics. They are less able to demonstrate normal frequency-dependent sexual selection after isolation than their own homokaryotypes. However, the later the isolation in this holometabolous insect--eggs, first instars, second instars, third instars, pupae, imagoes--the fewer the behavioral effects of this isolation.

Animals↗
PubMed1984

Streptococcal L-forms isolated from Drosophila paulistorum semispecies cause sterility in male progeny.

The Drosophila paulistorum complex contains six semispecies that do not normally interbreed. In the laboratory, crosses between semispecies produce fertile daughters and sterile sons. Microbial endosymbionts have been observed in all D. paulistorum flies that display this male sterility. Streptococcal L-forms have been isolated from the Andean-Brazilian (Mesitas) and Transitional (Santa Marta) semispecies and cultured in artificial medium. Transfer of these L-forms from their native hosts into reciprocal semispecies resulted in sterile male progeny. When L-forms were inoculated into the semispecies from which they had been isolated, most of the male progeny were fertile. Control streptococcal L-forms did not show this sterility pattern.

Crosses, Genetic↗
PubMed1984

Sequences homologous to P elements occur in Drosophila paulistorum.

P elements, a class of mobile genetic elements that cause hybrid dysgenesis in Drosophila melanogaster, have thus far been shown to occur only in this species. Using whole genome blot analysis, we present evidence which indicates that sequences homologous to D. melanogaster P elements also occur in Drosophila paulistorum, a distant relative. D. paulistorum is considered a species complex, consisting of six known incipient species or semispecies. All six semispecies possess P element homologous sequences. We further show that there is conservation of restriction enzyme recognition sites between the D. melanogaster and D. paulistorum P element sequences. The presence of P elements in these two species may clarify the roles of recent invasion and rapid loss in the temporal distribution of P elements in Drosophila.

Animals↗
PubMed1984

Induction by streptococcal L-forms of two reproductive isolating mechanisms in Drosophila paulistorum.

The six semispecies of the Drosophila paulistorum complex do not normally interbreed, but when hybrids are produced in the laboratory, the males are sterile. In earlier work, cytoplasmic components responsible for this sterility had been transferred by injection of streptococcal L-forms isolated from the Mesitas and Santa Marta flies. To extend these findings, and L-form from the Centro-American flies was injected into three semispecies. Transfer of L-form from one semispecies to another resulted in sterile male progeny. The L-form isolated from Mesitas was injected into all six semispecies. Results simulated "hybrid inviability," i.e., only the Mesitas semispecies produced the expected number of offspring, and the total number of progeny from the other five semispecies was considerably reduced. Despite the small numbers of males, reflecting induced inviability, there was evidence that the transfer of L-forms from one semispecies to another simultaneously caused sterility in male progeny.

Animals↗
PubMed1983

The development of laterality.

Experimental data, primarily from experiments with Drosophila, and observational data, primarily from human beings, are presented to show if their is a genetic basis for laterality. The evidence was found to be inconclusive. It is proposed that there for three etiologies of lefthandedness in human beings: pathological, natural, and learned.

Animals↗
PubMed1981

Sexual isolation among isofemale strains within a population of Drosophila immigrans.

Eight isofemale strains of the cosmopolitan species Drosophila immigrans derived from single location in Melbourne, Australia, were crossed in all combinations to test for sexual isolation. Statistically significant sexual isolation occurred in 12 of 28 crosses, with one strain showing significant isolation from the other seven. There were significantly unequal male mating propensities (relative rates of mating) in 7 of the 28 crosses.

Animals↗
PubMed1980

Sexual isolation among widely distributed populations of Drosophila immigrans.

Six strains of the cosmopolitan species D. immigrans from the Australian life zone plus one from the USA, show weak sexual isolation and more rarely sexual selection. Levels of sexual isolation cannot be related to geographic distances. Assortative mating may have evolved as a byproduct of ecological divergence.

Animals↗