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Biomedical subjects

M F Cheng

Publications and source records attributed to M F Cheng.

At least 55 records · Page 3Linked to original sources
PubMed1989

Camptothecin hypersensitivity in poly(adenosine diphosphate-ribose) polymerase-deficient cell lines.

Mutant cell lines, derived from the Chinese hamster V79 cell line, deficient in poly(adenosine diphosphate-ribose) polymerase activity, and previously shown to be resistant to topoisomerase II inhibitors, were found to be hypersensitive to camptothecin, a topoisomerase I inhibitor. In all the cell lines, camptothecin induced dose-dependent protein-associated DNA single-strand breaks and sister chromatid exchanges. The increased sensitivity to camptothecin-induced cytotoxicity was not associated with an increase in DNA single strand breaks or sister chromatid exchanges. These results suggest the absence of any direct causal relation between (1) camptothecin induced sister chromatid exchanges and cytotoxicity or (2) camptothecin induced DNA strand breaks and cytotoxicity. The hypersensitivity of these mutant cell lines to camptothecin suggests that poly(adenosine diphosphate-ribose) polymerase is involved with topoisomerase I in modulating camptothecin induced cytotoxicity.

Animals↗
PubMed1988

Behavioral stimulation of ovarian growth.

The present study was conducted to test the following hypothesis: male courtship induced egg-laying behavior in the female ring dove is mediated by the female's nest-coo display which feeds back to stimulate her ovarian system through the mechanisms of audio- and proprioceptive feedback. In Experiment I, females were exposed to 24 hr male courtship and then received playback of different nest-coos in the absence of their mates. All playback was effective in inducing the females to perform nest-coo displays, but none as effective as presence of the courting males. A specified level of the female's nest-coo display determined whether there would be changes in follicular diameter. The females which received no playback after 24 hr pairing with the male (control) did not show any change in the follicular diameter. In Experiment II, females were deafened by removal of cochleae and upon recovery paired with males. Half of those deafened females performed nest-coo displays and subsequently laid clutches. The others failed to perform the display and did not lay. We conclude that both proprioceptive feedback and audio-feedback must be involved to yield maximal stimulation of follicular growth by the female's nest-coo display.

Animals↗
PubMed1987

Ascending vocalization pathways in the female ring dove: projections of the nucleus intercollicularis.

Nest-coo (courtship) vocalization is an estrogen-dependent component of a sequence of behaviors leading to egg-laying in the ring dove (Streptopelia risoria). Implantation of estrogen in the nucleus intercollicularis of ovariectomized females restores the ability to produce nest-coos. Lesion of n. intercollicularis specifically disrupts nest-cooing and inhibits follicular development. We used anterograde transport of tritiated leucine to identify regions that receive input from n. intercollicularis. As a control, isotope was injected in an auditory nucleus (nucleus mesencephalicus lateralis, pars dorsalis) neighboring the n. intercollicularis. A strong projection to the nucleus was observed, demonstrating a potential interaction between auditory and vocalization systems at the level of the midbrain. Local projections of n. intercollicularis were observed in midbrain and hind brain nuclei including the nucleus tegmenti pedunculo-pontinus, pars compacta and nucleus papillioformis. A conspicuous projection ascended centrally via the mesencephalic central gray. Proceeding rostrally, this pathway was traced to the nucleus periventricularis magnocellularis and tissue surrounding it. At its rostral extent, the pathway was found to project to the nucleus preopticus medialis, the anterior medial hypothalamus, and the lateral hypothalamus. These results are consistent with the possibility of a nucleus intercollicularis projection to regions that regulate reproductive function.

Animals↗
PubMed1987

Retrograde HRP demonstration of afferent projections to the midbrain and nest calls in the ring dove.

Midbrain control of vocalization was evaluated in the ring dove by determining the major afferent inputs with retrograde tract tracing technique. Horseradish peroxidase was infused into various portions of the nucleus intercollicularis, an estrogen concentrating area, which disrupts nest calls when lesioned and induces the vocalization when stimulated by estrogen. Most labelled cell bodies were found in the archistriatum, including a region homologous to the mammalian amygdala.

Afferent Pathways↗
PubMed1986

Female cooing promotes ovarian development in ring doves.

In female ring doves (Streptopelia risoria), hearing their own coos promoted greater follicular growth than hearing males coo, as demonstrated by the playback of various coos to experimentally muted females, under normal conditions. This difference in follicular growth suggests that the females' own cooing, not the males' cooing, stimulates the ovarian response.

Animals↗
PubMed1986

Breeding experience modulating androgen dependent courtship behavior in male ring doves (Streptopelia risoria).

Courtship behavior of reproductively experienced males was compared with that of age-matched inexperienced males before and after castration and during treatments with hormones (testosterone propionate and estradiol benzoate). Inexperienced males displayed significantly lower levels of nest-oriented courtship, the nest-cooing (nest-soliciting) and wingflippings; however, agonistic courtship, the bow-cooing, was not affected by breeding experience. The lower level of nest-cooing display in the inexperienced males persisted even when their circulating level of androgen as measured by RIA was no different from that of experienced males. Estrogen treatments, however, produced no group difference in levels of nest-coo display. These results were discussed in the context of hormone-behavior relationships.

Animals↗
PubMed1985

Thyroid development in altricial ring doves, Streptopelia risoria.

The development of thyroid function in altricial ring doves was assessed by measuring thyroid hormone concentrations in the serum, hormone content of the thyroid glands and hepatic 5'-monodeiodinase activity. Thyroid function is low at hatching and increases during the first eight days while the nestlings are ectothermic and completely dependent on parental care. The rate of increase of serum hormone concentrations slows after Day 8; hormone concentrations are stable by Day 15 and for the remainder of the nestling and early fledgling periods while locomotor ability, feeding self-sufficiency and thermoregulatory ability are maturing. Increases in serum hormone concentrations precede increases in thyroidal hormone content. T3/T4 ratios in serum are much higher than those of stored hormones in the thyroid. Deiodination of T4 to T3 is important in T3 production throughout development but most so in the early nestling stages.

Animals↗
PubMed1984

Hormonal mediation of reproductive behavior.

Reproductive capability requires synchronization of both endocrine and behavioral components of reproduction. The classic view of reproductive behavior was that there was simply direct stimulation of a behavioral response by the appropriate gonadal steroid. However, it has become clear with recent developments in the field of behavioral endocrinology that the relationship of hormonal and behavioral processes is complex. In addition to the complexity of the mechanisms involved, other factors, both social and environmental, influence both the endocrine and behavioral responses. This paper provides an overview of selected issues within the field of behavioral endocrinology which deal with mechanisms of hormonal induction of behavior at various stages of the life cycle and with factors that interact with these processes.

Aging↗
PubMed1984

Factors in the dose-response effect of testosterone in the male ring dove.

The dose-response effect of testosterone propionate on six behavioral patterns was examined in the castrated male ring dove. There was no dose-response effect when all behaviors were compared on the 13th day, the last day of systemic injection. However, a discernible dose-response effect in two behavioral patterns (Bow-coos and Nest-coos) was found on the day when maximal response was manifested. The latency (days) of maximal response differs from one behavioral pattern to the next, but is generally constant for each behavioral pattern at all dose levels.

Animals↗
PubMed1983

Serum prolactin levels and crop-sac development in ring doves during a breeding cycle.

Using a turkey prolactin radioimmunoassay, the serum prolactin levels of male and female ring doves (Streptopelia risoria) during the breeding cycle were measured and their circulating prolactin levels were compared to crop-sac weight on a within-bird basis. During the early phase of the incubation period, crop weight showed a delayed response to prolactin stimulation and there was no correlation; during the midincubation period when prolactin and crop-sac weight were increasing, there was a strong positive correlation; around hatching, when prolactin was at its peak, there was no correlation. There were again strong positive correlations at later samples, when squabs were developing and both prolactin and crop-sac weight were declining. Thus, it appears that the correlation between the circulating prolactin level and crop-sac development depends on the stage of the breeding cycle. While males and females showed similar pattern of circulating prolactin during the period of incubation and parental care, only females consistently showed a postovulatory rise of prolactin. These results were discussed in the context of the role of prolactin in the breeding cycle.

Animals↗
PubMed1982

The role of nest-building activity of gonadotrophin secretions and the reproductive success of ring doves (Streptopelia risoria).

This study was undertaken to investigate the intricate relations between prelaying nest-building activity and preovulatory hormonal changes, and the effects of these events on breeding success. Pairs of ring doves were allowed to go through a complete breeding cycle under four conditions of nest-building opportunity. Nest were self-made, pre-made, pre-made and covered, or removed daily to generate various levels of building activity. Behavioral and hormonal changes were observed throughout the cycle. Blood levels of gonadotrophins were monitored by daily measurements with the method or radioimmunoassay. A depression of follicle-stimulating hormone (FSH) typically was associated with every preovulatory surge of luteinizing hormone (LH); an LH surge not accompanied by a FSH dip was not followed by ovulation. Moreover, the FSH depression was significantly correlated with the level of nest-building activity. These findings led to the proposal that nest-building activity stimulated preovulatory FSH change and, hence, ovulation. The constructed nest in turn appeared to promote incubation behavior. These results are discussed in the context of breeding success.

Animals↗
PubMed1982

Effects of testosterone metabolites and estrogen in the midbrain control of courtship behavior in the male ring dove (Streptopelia risoria).

Relative effectiveness of testosterone (T) and its metabolites in the midbrain to induce courtship behavior was investigated in male ring doves. T, 5 alpha-dihydrotestosterone (5 alpha-DHT), 5 beta-dihydrotestosterone, estradiol-17 beta (E), or cholesterol was implanted in or around the nucleus intercollicularis region (ICo) of the castrated male. Resulting courtship behavior was observed by pairing the treated males with stimulus females. T, 5 alpha-DHT and E activated nest-cooling behavior pattern when placed in the ICo region only. Other male courtship behaviors were not induced, induced in each brain region tested or induced by all the hormones. Hormone diffusions from the implant did not appear to be responsible for these results since many implants within 1 mm of the ICo region failed to activate nest-cooling. These data support the idea that the midbrain along with the hypothalamic region mediate male courtship behavior.

Androgens↗
PubMed1981

The role of the midbrain in courtship behavior of the female ring dove (Streptopelia risoria): evidence from radiofrequency lesion and hormone implant studies.

The involvement of the nucleus intercollicularis (ICo) region of the midbrain, an estrogen-sensitive area, in the expression of estrogen-dependent female courtship behavior was examined with radiofrequency lesion and intracranial hormone implant techniques. Bilateral lesions in the ICo region caused a reduction in the female's nest coos, and no reduction in other behaviors in response to male courtship. In addition, the follicles of the ICo lesioned females failed to grow in response to male courtship. A second experiment showed that the difference in follicular size between ICo-lesioned and sham-ICo-lesioned females was not observed if females were visually isolated from males, suggesting that tonic ovarian activity was not affected by ICo lesions. In the third experiment, unilateral 30-gauge implant containing estrogen (E) or estradiol benzoate (EB) in the ICo region of bilaterally ovariectomized females restored the nest-coo, though not to the level obtained with systemic EB injections. Other behaviors were not selectively affected by E or EB implants in the ICo region. Diffusion from the implant was probably not responsible for the elicitation of the nest-coo, since the oviduct weights of females implanted with E or EB and cholesterol did not differ. These data are consistent with the hypothesis that the ICo region is involved in the expression of vocal (cooing) courtship behavior in the female ring dove.

Animals↗