Basal metabolic rate and energetics of reproduction in therian mammals

Traditionally, the fact that reproduction in eutherian (= placental) mammals tends towards prolonged intrauterine development and short lactation has been interpreted as an evolutionary advance over the metatherian (= marsupial) short gestation and prolonged lactation. However, it has recently been postulated that marsupial reproduction involves low initial energy investment and may be advantageous by minimizing energy loss if conditions necessitate early termination. Moreover, because marsupials have basal metabolic rates (BMRs) 30% lower than those of most eutherians, it has been suggested that daily and total energy expenditures during reproduction may also be lower. We have now tested the predictions that low BMR is maintained during reproduction and that initial investment is lower in marsupials. Using indirect calorimetry, we have made the first longitudinal measurements of energy expenditure during reproduction for a marsupial and for two eutherian species with low BMRs. We find that initial investment is lowest in a eutherian and total energetic expenditures were greatest for the marsupial. We also find that, relative to BMR, all three species have increased mean maternal resting metabolic rates (RMRs) during both gestation and lactation; this is the first evidence that mammals with low BMRs can substantially elevate metabolism for prolonged periods during gestation and lactation.     

The c-erb-A gene encodes a thyroid hormone receptor

The cDNA sequence of human c-erb-A, the cellular counterpart of the viral oncogene v-erb-A, indicates that the protein encoded by the gene is related to the steroid hormone receptors. Binding studies with the protein show it to be a receptor for thyroid hormones.     

Starvation-induced changes in the autoradiographic localisation of valine uptake by rat small intestine

We report here the effects of a 72-h fast on the localisation of Na-dependent [3H]-valine uptake by rat small intestine. Starvation results in the earlier appearance of valine transport during cell migration and an enhanced accumulation of the amino acid at the villus tip.     

Mammalian arylsulfatases A and B: relative rates of hydrolysis of artificial substrates

Summary Rodent and bovine arylsulfatase B hydrolyze 4-methylumbelliferyl sulfate (4MUS) 10- to 30-fold more efficiently than arylsulfatase A. Therefore, 4MUS grossly underestimates arylsulfatase A activity in the presence of excess arylsulfatase B.     

Colour mixing and colour preferences in neonate gulls

Zusammenfassung Junggeschlüpfte Silber- und Heringsmöven zeigen beim Picken von kleinflächigen, beweglichen Reizen Spektralfarbbevorzugungen. Drei theoretische Modelle sind vorgeschlagen worden, die diese Bevorzugungen erklären sollen. Die Voraussagen dieser Modelle bezüglich der Bevorzugung von Mischfarben wurden experimentell geprüft und als nicht zutreffend befunden. Vielmehr legen die Ergebnisse die Vermutung nahe, dass die Bevorzugung nicht, wie bisher angenommen, auf einem afferenten sensorischen Filtermechanismus beruht, sondern auf einen mehr zentralen, postperzeptualen Prozess zurückzuführen ist.     

The effect of reserpine upon gastrointestinal serotonin in the sprague-dawley rat

Zusammenfassung Der Serotoningehalt der Schleimhaut von 14 gastrointestinalen Geweben von Sprague-Dawley Rattenmännchen und -weibchen wurde nach i.p. Injektion von Reserpin spektrophotofluorimetrisch gemessen. Die Verteilung von Serotonin im Magendarmkanal 4 und 16 h nach der Reserpininjektion zeigte, dass Magengewebe und Kolongewebe nach 16 h mehr entleert waren als nach 4 h, während Dünndarm und Appendix nach 4 h mehr entleert waren als nach 16 h.

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This research was supported by U.S.P.H.S. grant No. AM 07909, toJ. H. Thompson.     

Starvation-induced changes in the autoradiographic localisation of valine uptake by rat small intestine

Summary We report here the effects of a 72-h fast on the localisation of Na-dependent [³H]-valine uptake by rat small intestine. Starvation results in the earlier appearance of valine transport during cell migration and an enhanced accumulation of the amino acid at the villus tip.Acknowledgments. We wish to thank MW Smith, PS James and IS King (AFRC Institute of Animal Physiology, Babraham, Cambridge) for facilities and advice regarding autoradiography. Financial support from the British Digestive Foundation and Eli Lilly and Company is appreciated.     

Karyotypes of six species of African Cichlidae (Pisces: Perciformes)

Summary Diploid numbers of 40–46 were found among the 6 species of African Cichlidae included in this karyotypic study. More species must be studies before any generalized conclusions regarding correlations between karyotypic morphology and phylogeny can be made.This study was supported by a grant from the Smithsonian Institution's TFH Fund.