Karyotypes of bats of the subfamily carolliinae (mammalia; phyllostomatidae) and their evolutionary implications

Zusammenfassung Es werden die Kennzeichen der Chromosomen vonRhinophylla fischeri, R. pumilio undCarollia castanea beschrieben. Für die GattungCarollia ist bei niedriger Diploidzahl (21 , 20 ) eine niedrige « nombre fondamental » (34–36) charakteristisch. Für die GattungRhinophylla wird eine grössere Diploidzahl (34–36) und eine grössere « nombre fondamental » (56–62) gefunden.

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We thank Dr.C. J. Marinkelle andA. Cadena of the Universidad de Los Andes for assistance and facilities.Pvt. Genaro Lopez assisted with the field work. Dr.R. Strandtmann translated the summary. Supported by National Science Foundation Grant No. GB-8120.     

Ecological and evolutionary implications of digestive processes: Bird preferences and the sugar constituents of floral nectar and fruit pulp

Plants pollinated and dispersed by different groups of birds offer different kinds of sugars in nectar and fruit pulp. The preferences and physiological traits of avian pollinators and seed dispersers are broadly correlated with the sugar composition of the nectar and fruit that they feed on and appear to have influenced the evolution of the sugar composition of the rewards that plants offer. Hummingbirds prefer sucrose whereas many nectar- and fruit-eating passerines prefer glucose and fructose. Preference for hexoses in passerines seems to be associated with poor sucrose assimilation resulting from two physiological mechanisms: lack of intestinal sucrase activity and fast passage rates. Sucrase activity absence appears to be restricted to a single phylogenetic group (the sturnid-muscicapid lineage). Fast passage rates seem to be characteristic of many small frugivores and to hinder the assimilation of complex nutrients that require hydrolysis before absorption. Hummingbirds have extremely specialized digestive traits that allow them to assimilate sucrose at high rates and with extremely high efficiency. These specialized digestive traits appear not to be present in many nectar-feeding passerines.     

Nuclear protrusions in malignant tumours with large abnormal chromosomes: Observations on C-banded preparations

Summary The appearances are described in 4 human tumours having nuclear protrusions associated with large abnormal chromosomes. In C-banded preparations, chromocentres were seen in the protrusions only where interstitial C-bands were present on the long arm of the abnormal chromosome, providing evidence that the protrusions are indeed formed by the long arms.This work was supported by a grant from the Cancer Research Campaign.     

Inhibition of exocytosis in bovine adrenal medullary cells by botulinum toxin type D

Botulinum toxins are known to block transmitter release at peripheral cholinergic synapses, producing muscular weakness and paralysis. The toxins may also block adrenergic transmission, although this effect is less well understood. The mechanisms by which toxins act are unclear. They are proteins of relative molecular mass approximately 150,000 and are structurally similar to tetanus toxin. It is generally accepted that a rise in intracellular calcium concentration is sufficient to trigger secretion by exocytosis, but it is not known whether the toxins block secretion by preventing this Ca transient or whether they act downstream from Ca entry by interfering with the process of exocytosis itself. We have attempted to resolve these questions in the case of the adrenergic system by studying the effects of botulinum toxins (types A, B, D and E) on the secretory response of isolated bovine adrenal medullary cells maintained in culture. The cells were either challenged with various secretagogues or rendered leaky and challenged directly with Ca buffers. We report here that botulinum toxin type D inhibits secretion in a time- and dose-dependent manner, the results being entirely consistent with the idea that the toxin acts at or near the site of exocytosis rather than at the sites controlling the rise in free Ca.     

Spina bifida and maternal Rh phenotype

Summary Based on the sample in this study (members of the Spina Bifida Association of America), there are approximately 2.15 times as many mothers with Rh-blood type than would be expected in a similar sized sample of the general population.     

Exogenous melatonin and melanophore development inXenopus

Summary Xenopus larvae raised from stage 21 in melatonin solution and upon a dark background had fewer head melanophores at stage 48 than control animals not exposed to melatonin. Rearing larvae in melatonin solution seems to mimic rearing larvae on a light background.