Interaction of phytotropins with the NPA receptor

The chemical and stereochemical properties of phytotropins are described in terms of a receptor model, based on their ability to bind to a receptor isolated from maize coleoptiles. Their root gravitropic properties are correlated with their ability to bind to the receptor. It is suggested that their ability to inhibit auxin transport, without more, may not be enough to explain their physiological effects.     

Aggression persists after ovariectomy in female rats

Aggression occurs not only in males but also in females, however, under different sex-specific stimulus and endocrine conditions. After being housed with males, female rats exhibit frequent and intense aggressive behavior toward unfamiliar rats. However, the female residents primarily attack female intruder rats, while the male residents attack males and not females. Altering the hormonal condition of the intruders can modify the behavior that they provoke from the residents. Castration of the male intruders reduces aggression from male residents, but ovariectomy of the female intruders does not alter the behavior of the female residents. Treatment of the gonadectomized intruders with gonadal steroids significantly alters the response of the male residents. Resident-intruder aggressive behavior depends on the presence of the testes in the male residents but not on the ovaries or on lactation in the female residents. Even 7 weeks after ovariectomy the female residents continue to show aggressive behavior toward female intruders. In the same time period the castrated male residents show a marked decrease in aggressive and sexual behavior.     

An improved purification method for cytosolic malate dehydrogenase from several sources

A new purification method for cytosolic malate dehydrogenases from several sources has been developed. The procedure, employing chromatographies on 5'AMP-Sepharose, DEAE-Sephacel and Blue-Sepharose, allows for a rapid isolation of the enzyme (approximately 40 hours), in large quantities, with good yields (45-54%). The specific activity of final preparations were around 1300 I.U./mg and were judged homogeneous by polyacrylamide gradient gel and sodium dodecyl sulfate polyacrylamide gel electrophoresis, high performance size exclusion chromatography and isoelectric focusing.     

Direct microsensor measurement of nitric oxide production by the osteoclast.

Nitric oxide (NO) triggers marked osteoclast retraction which closely resembles that due to Ca2+. The effect of Ca2+ has been attributed to a stimulated release of NO. Here, we show for the first time, by direct measurement with a microsensor, that osteoclasts do indeed produce NO and that this production is enhanced by a high Ca2+. We also show that the Ca2+ ionophore, A23187, mimics the latter. Furthermore, osteoclasts on dentine produce more NO than osteoclasts on glass and NO release from dentine-plated osteoclasts is much less sensitive to stimulation by Ca2+. Finally, the microsomal Ca2+ store-depleting agent, thapsigargin, attenuates NO release only from osteoclasts on glass, suggesting that stored Ca2+ has the dominant effect in modulating NO release from non-resorbing cells. NO is a powerful inhibitor of bone resorption: a direct demonstration of its production is therefore strong evidence for a role in modulating osteoclast function.     

The unpredictability of favourability: condition assessment and protected areas in England

The probability that protected areas will deliver their potential for maintaining or enhancing biodiversity is likely to be maximised if they are appropriately and effectively managed. As a result, governments and conservation agencies are devoting much attention to the management of protected areas. In the U.K., the demand for performance accountability has resulted in Public Service Agreements (PSA) that set out targets for government departments to deliver results in return for investments being made. One such target for England is to ensure that all nationally important wildlife sites are in favourable condition by 2010. Here, we tested the hypothesis, of potential strategic importance, that the ecological condition of these sites is predictable from relationships with a range of physical, environmental and demographic variables. We used binary logistic regression to investigate these relationships, using the results of English Nature’s 1997–2003 condition assessment exercise. Generally, sites in unfavourable condition tend to be larger in area, located at higher elevations, but with higher human population density and are more spatially isolated from units of the same habitat. However, despite the range of different parameters included in our models, the extent to which the condition of any given site could be predicted was low. Our results have implications for the delivery of PSA targets, funding allocation, and the location of new protected areas.     

Phenotypic characterization of ouabain-resistant Aedes albopictus cells.

The phenotype of a ouabain-resistant Aedes albopictus cell line has been partially characterized. Treatment of ouabain-sensitive cells with 0.005-1.0 mM ouabain resulted in an 80% reduction in the uptake of 86rubidium (86Rb+), an ion with an affinity for the K+ pump binding site; ouabain-resistant cells showed only a 40% reduction with 1.0 mM ouabain. When ouabain-sensitive cells were incubated in the presence of ouabain (0.1 mM) for one and one-half to three hours, the molar ratio of intracellular Na+/K+ rose from 0.2 to 4.2. In ouabain-resistant cells, a similar treatment had very little effect. Based on [3H] ouabain-binding studies, ouabain-resistant cells were estimated to have 60% fewer binding sites per cell than ouabain-sensitive cells. The spontaneous mutation rate from ouabain sensitivity to ouabain resistance was calculated to be 1-6 x 10(-8) mutations/cell/generation, a value similar to that reported for mammalian cells at the analogous locus.     

Effect of a low-frequency magnetic field on systemic arterial pressure in spontaneously hypertensive rats

The effect of low-frequency magnetic field (MF) on systemic blood pressure has been studied in chronic experiments on 21 spontaneously hypertensive rats. The animals' kidney area was exposed to MF (induction value 30T). Direct blood pressure measurements have revealed an antihypertensive effect.