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Biomedical subjects

M Leong

Publications and source records attributed to M Leong.

9 recordsLinked to original sources
PubMed1987

Hormone-induced and maturational changes in electric organ discharges and electroreceptor tuning in the weakly electric fish Apteronotus.

Plasticity in the frequency of the electric organ discharge (EOD) and electroreceptor tuning of weakly electric fish was studied in the genus Apteronotus. Both hormone-induced and maturational changes in EOD frequency and electroreceptor tuning were examined. Apteronotus is different from all other steroid-responsive weakly electric fish in that estradiol-17 beta, rather than androgens, induces discharge frequency decreases. This result can account for the 'reversed' discharge frequency dimorphism found in Apteronotus in which, counter to all other known sexually dimorphic electric fish, females have lower discharge frequencies than males. Studies of electroreceptor tuning in Apteronotus indicate that electroreceptors are closely tuned to the frequency of the EOD. This finding was noted not only in adult animals, but also in juvenile animals shortly after the onset of their EODs. Tuning plasticity in Apteronotus, as in other species studied, is associated with altered EOD frequencies and was noted in both maturational EOD changes and in estrogen-induced changes. Thus, tuning plasticity appears to be a general phenomenon which occurs concurrent with a variety of EOD changes.

Androgens↗
PubMed1979

Fetal-maternal transfusion following early abortion.

Therapeutic abortion has been a major potential source of Rh isoimmunization. Popularization of early termination necessitates reconfirmation of established policies. This study involved 75 patients, selected at random, in whom pre- and post-abortion blood smears were studied for fetal-maternal hemorrhage. Results showed that this may occur even in early suction termination. The significance of these findings was discussed in relation to the cost-effectiveness and the dosage of anti-Rho (D) globulin administered to patients.

Abortion, Therapeutic↗
PubMed1977

Temperature regulation in a hypometabolic primate, the slow loris (Nycticebus coucang).

Six slow loris were exposed to air temperatures between 10 degrees C and 40 degrees C. Rectal temperature was stable (mean, 34.8 degrees C) at air temperatures between 17 degrees C and 31 degrees C; at higher air temperatures, the animals became hyperthermic. Oxygen consumption was minimal at air temperatures of 31.4-36.6 degrees C; the mean value (0.250 ml O2 g-1 h-1) was only 36% of the expected level for a eutherian Mammal. The slow loris increased its heat production at lower air temperatures. Thermal polypnea occurred in response to heat, and some of the animals were able to dissipate their entire metabolic heat production at lower air temperatures. Thermal polypnea occurred in response to heat, and some of the animals were able the combined thermal conductance of the tissues and haircoat was 73% of the predicted values. It was concluded that, in spite of its low metabolic rate, the slow loris had effective responses to moderate cold, and that, in addition, it was well adapted to a hot climate.

Animals↗
PubMedDate not supplied

Osmotic load from glucose polymers.

Glucose polymer is a carbohydrate source with variable chain lengths of glucose units which may result in variable osmolality. The osmolality of two commercial glucose polymers was measured in reconstituted powder infant formulas, and the change in osmolality of infant milk formulas at the same increases in energy density (67 kcal/dL to 81 and 97 kcal/dL) from the use of additional milk powder or glucose polymers was compared. All samples were prepared from powders (to nearest 0.1 mg), and osmolality was measured by freezing point depression. For both glucose polymers the within-batch variability of the measured osmolality was less than 3.5%, and between-batch variability of the measured osmolality was less than 9.6%. The measured osmolality varies linearly with energy density (p less than 0.001) and was highest in infant formula reconstituted from milk powder alone. However, there exist significant differences in the measured osmolality between different glucose polymer preparations. At high energy densities (greater than or equal to 97 kcal/dL), infant milk formulas prepared with milk powder alone or with the addition of certain glucose polymer preparation may have high osmolality (greater than or equal to 450 mosm/kg) and theoretically predispose the infant to complications of hyperosmotic feeds.

Glucose↗