Asoka Srinivasan

Hemolymph juvenile hormone titers in pupal and adult stages of southwestern corn borer [Diatraea grandiosella (pyralidae)] and relationship with egg development.

Juvenile hormones I, II and III were monitored in hemolymph of pupal and adult stages of various ages of Diatraea grandiosella females. JH III was the predominant homologue followed by JH II, and JH I was rarely detectable. At day 5 after pupation, no JH was detectable. JH titers increased from 7.5days after pupation to a peak of 24.8ngml(-1) JH II and 26ngml(-1) JH III at adult emergence and then declined to low levels by 24h after emergence. Ovarian development in D. grandiosella parallels changes in hemolymph JH titers, but the role of JH in vitellogenesis is unclear since the time of vitellogenesis initiation has yet to be determined. No apparent vitellogenin deposition was observed in eggs 5days after pupation. Some oocytes were partially vitellogenic by 7.5days after pupation and oocytes continued to grow afterwards, but no oocytes were chorionated during the pupal stage. Chorionated oocytes were observed in 24-h-old female moths. Juvenile hormone is essential for chorion formation in this species, because decapitated pupae treated with 10&mgr;g JH III in corn oil developed chorionated oocytes while decapitated pupae treated with corn oil did not.

Mating in Heliothis virescens: transfer of juvenile hormone during copulation by male to female and stimulation of biosynthesis of endogenous juvenile hormone.

Studies were undertaken to determine whether adult males of Heliothis virescens transfer juvenile hormone (JH) to females during copulation, and an in vitro radiochemical assay was used to determine whether mating causes an allatotropic effect, i.e., stimulation of JH biosynthesis by corpora allata (CA). In vitro, CA from 3-day-old mated females synthesized and released approximately 2.5 times total JH as that of CA from comparably aged virgin females. Of the homologues, JH II exhibited significant increase in mated females; JH I also increased but not significantly. JH III remained similar to that of virgin females. This is the first demonstration of an allatotropic effect of mating in moths. In contrast to the female, CA of virgin males did not produce any JH, but accessory sex glands (ASG) in 3-day-old males synthesized small amounts of JH. Immediately after adult emergence, male ASG contained approximately 1.5 ng JH I and II, which increased by 12 h after emergence and remained at this high level up to 54 h after emergence. JH III was barely detected in ASG. JH in ASG of mated male immediately after uncoupling was depleted almost completely, and 24 h later recovered to levels comparable to that of 54-h-old virgin male. Virgin female bursa copulatrix did not contain any JH, but mated female bursa, immediately after uncoupling, had JH at levels comparable to that observed in virgin male ASG. By 6 h after uncoupling, JH levels decreased dramatically in mated female bursa. These data suggest the transfer of JH to females by the male.

Temporal profiles of juvenile hormone titers and egg production in virgin and mated females of Heliothis virescens (Noctuidae)

Juvenile hormones (JH) I, II, and III were monitored in hemolymph of virgin and mated females of various ages in Heliothis virescens. JH I was the predominant homologue followed by JH II, but JH II was present at a higher level in young virgin females. JH III was detectable only at a low level. In virgin females, hemolymph JH titers were low at emergence (2.2ng/ml-total amount of JH I and JH II), but increased thereafter and reached a maximum at 24h of age (53.5ng/ml). At 30h and 36h of age, JH titers dropped to a low level, but increased again in older virgin females. After mating, JH titers increased significantly. JH titers at 0h after uncoupling (137.4ng/ml) were nearly 3 times as high as those in 24-h-old virgin females. Within 6h after uncoupling, JH titers decreased slightly, but titers increased with age of mated females and reached a level of 320.2ng/ml hemolymph at 72h after uncoupling. The titer of JH I and JH II was correlated highly with total number of eggs produced (r(2)=0.70, P<0.001). Mating stimulated JH production, resulting in an increase in egg production.

Parasitoid-host endocrine relations: self-reliance or co-optation?

High titers of juvenile hormone (JH) maintain developmental arrest in Manduca sexta larvae parasitized by Cotesia congregata. Parasitized hosts exhibit up to 9.5 times greater amounts of total hemolymph JH (from 0.6+/-0.09 to 2.51+/-0.43ng/ml) compared to non-parasitized controls. Elevated titers are observed throughout the fifth instar, even beyond egression of the parasitoids on day 5. GC-MS analysis revealed that in hemolymph of unparasitized control larvae, JH I is the major homolog and levels of JH III are negligible; in parasitized individuals the amounts of JH I, II, and III rise, and JH III predominates. Neck ligation ensured separation of M. sextas corpora allata from the posterior section, which contained most of the parasitoids in the infected insects. When the posterior region was sampled, JHs were not detected in the non-parasitzed larvae, but in those parasitized, JH III was found (1.98+/-0.29ng/ml, 24 h post-ligation). JH III was the only homolog produced and secreted by the parasitoid in in vitro culture. This is the first report stating that a parasitoid secretes JH III and may contribute, at least in part, to the circulating titer in the host hemocoel, concurrently promoting host production of JH I and II.

Spermatophore formation and regulation of egg maturation and oviposition in female Heliothis virescens by the male

This study was undertaken, using various surgical manipulations, to examine the role and functions of accessory sex glands and testes in Heliothis virescens in spermatophore formation and stimulation of egg maturation in mated females. Normal females mated to accessory sex glandectomized (-ASG) males produced fewer eggs and retained most of their eggs in ovarioles compared with females mated to sham-operated (+ASG) or normal males. The ASG are the source of the components for spermatophore formation in H. virescens. Females mated to castrated (-Testes) males showed similar pattern of egg production as did females mated to -ASG males. Females mated to -Testes males and those mated to sham-operated (+Testes) or normal males were found to have spermatophore in the bursa after uncoupling. Normal females mated to allatectomized (-CA) males developed similar numbers of total eggs as did females mated to sham-operated (+CA) males and normal males.

Vitellogenin in Pupal Hemolymph of Diatraea grandiosella (Lepidoptera: Pyralidae)

Abstract Vitellogenin (Vg) concentration was determined in pupal hemolymph of female southwestern corn borer, Diatraea grandiosella (Dyar). Vitellogenin concentration increased significantly with pupal age. Vitellogenin level reached 7 mg/ml on day 7 after pupation. The vitellogenin was separable into 2 apoproteins on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), with molecular weights of 145,000 for apoVg-I and 38,000 for apoVg-II. SDS-PAGE analysis revealed that vitellogenin polypetides in female pupal hemolymph appeared to be identical to those from eggs, but were absent in male and early female pupal hemolymph. A method to quantify vitellogenin by indirect ELISA is described. Results from this study and those of a previous study suggest that juvenile hormone does not have a role in vitellogenesis but does so in choriogenesis.

Capacity-Building for Career Paths in Public Health and Biomedical Research for Undergraduate Minority Students: A Jackson Heart Study Success Model

OBJECTIVE This article chronicles the building of individual student capacity as well as faculty and institutional capacity, within the context of a population-based, longitudinal study of African Americans and cardiovascular disease. The purpose of this article is to present preliminary data documenting the results of this approach. DESIGN The JHS Scholars program is designed, under the organizational structure of the Natural Sciences Division at Tougaloo College, to provide solid preparation in quantitative skills through: good preparation in mathematics and the sciences; a high level of reading comprehension; hands-on learning experiences; and mentoring and counseling to sustain the motivation of the students to pursue further studies. SETTING This program is on the campus of a private Historically Black College in Mississippi. PARTICIPANTS The participants in the program are undergraduate students. MAIN OUTCOME MEASURES Data, which included information on major area of study, institution attended, degrees earned and position in the workforce, were analyzed using STATA 14. RESULTS Of 167 scholars, 46 are currently enrolled, while 118 have graduated. One half have completed graduate or professional programs, including; medicine, public health, pharmacy, nursing, and biomedical science; approximately one-fourth (25.4 %) are enrolled in graduate or professional programs; and nearly one tenth (9.3%) completed graduate degrees in law, education, business or English. CONCLUSIONS These data could assist other institutions in understanding the career development process that helps underrepresented minority students in higher education to make career choices on a path toward public health, health professions, biomedical research, and related careers.