In vitro formation of chromium complex from higher plants

Chromium as either chromate or chromic ion reacts with expressed alfalfa liquid to form two complexes. The larger complex may be assembled from the smaller complex and the formation of the larger complex requires a heat labile factor.     

Postmating Reproductive isolation between strains of Drosophila willistoni

Speciation can occur through the presence of reproductive isolation barriers that impede mating, restrict cross-fertilization, or render inviable/sterile hybrid progeny. The D. willistoni subgroup is ideally suited for studies of speciation, with examples of both allopatry and sympatry, a range of isolation barriers, and the availability of one species complete genome sequence to facilitate genetic studies of divergence. D. w. willistoni has the largest geographic distribution among members of the Drosophila willistoni subgroup, spanning from Argentina to the southern United States, including the Caribbean islands. A subspecies of D. w. willistoni, D. w. quechua, is geographically separated by the Andes mountain range and has evolved unidirectional sterility, in that only male offspring of D. w. quechua females × D. w. willistoni males are sterile. Whether D. w. willistoni flies residing east of the Andes belong to one or more D. willistoni subspecies remains unresolved. Here we perform fecundity assays and show that F1 hybrid males produced from crosses between different strains found in Central America, North America, and northern Caribbean islands are reproductively isolated from South American and southern Caribbean island strains as a result of unidirectional hybrid male sterility. Our results show the existence of a reproductive isolation barrier between the northern and southern strains and suggest a subdivision of the previously identified D. willistoni willistoni species into 2 new subspecies.     

A comparison of the effects of testosterone on aggressive responses by the domestic chick to the human hand and to a large sphere

In young male chicks a single injection of testosterone oenanthate leads to a long-lasting facilitation of behaviour patterns related to adult attack, courtship and copulation. The same responses, in particular facilitated pecking, may be evoked, with a similar time course of facilitation and subsequent waning, by a human hand or a white featureless sphere. The dose-response curve to the androgen is also similar for these two objects. A very simple stimulus thus appears to be capable of evoking at least one major component of aggressive behaviour, as well as other responses normally directed to conspecifics. Pecking of the sphere increases within 4–7 h of a second injection of the androgen, given after facilitation due to the first has disappeared, whereas the first requires 48–72 h to become effective. This rapid effect is not dependent on the age of the animal, nor on prior experience of pecking the sphere—indeed this causes marked habituation of all response to the sphere, whether or not response is facilitated by testosterone during the initial experience. It appears to result from central ‘priming’, perhaps by a process similar to the reversal of refractoriness to central androgen implants by prior systemic priming with testosterone, which has been previously reported for adult castrates.     

Cerebral ventricular transport and uptake: Importance for CCK-mediated satiety

Brain cholecystokinin (CCK) peptides have been proposed to be involved in the control of feed intake. We have examined the importance of the cerebral ventricular system in CCK-mediated satiety in sheep. Continuous injection of 0.64 pmol/min CCK-8 into the lateral ventricles (LV) decreased feeding, whereas injection of neither 0.64 nor 2.55 pmol/min CCK-8 into the cisterna magna (CM) significantly affected feeding. Thus, it is likely that the rostral, but not caudal, ventricular compartments and/or adjacent brain areas are involved in CCK-8 mediated satiety. The rate of injection of carrier solution (synthetic cerebrospinal fluid [sCSF]) was found to affect feed intake during a continuous 75 min injection: feed intakes were greater during injection of sCSF at 0.10 ml/min than during either 0.03 ml/min sCSF or no injection (sham). Injection of 0.64 pmol/min CCK-8 in either 0.03 or 0.10 ml/min decreased feeding. The increased feeding during 0.10 ml/min sCSF injection may have been due to dilution of endogenous CCK released into CSF during the meal. To determine the percent recovery from CSF of exogenous CCK-8, CSF samples from CM were collected during 3 hr continuous LV injections of CCK-8 and inulin (for measurement of bulk absorption). Only 20 to 40 percent of administered CCK-8 was recovered in CM CSF. The loss of CCK-8 was probably not due to degradation in the CSF by proteolytic enzymes, since CCK-8 concentrations did not decrease during in vitro incubation at 37°C for up to 24 hr. We propose that CCK-8 is released during feeding into the ventricular system, and subsequently taken up from CSF by specialized ependymal cells for transport to sites of action.