Chloris gayana (Rhodes grass), a better host for the mas production ofGlomus fasciculatum inoculum

Seven different hosts,Panicum maximum, Chrysopogon fulvis, Themeda triandra, Chloris gayana, Brachiaria brizantha, Paspalum scrobiculatum andEleusine coracana were screened in order to select a better host for mass multiplication ofGlomus fasciculatum inoculum. Of these,Chloris gayana (Rhodes grass) was found to be the best host on the basis of root colonization and spore production and of the infective propagules of the potball.     

Ecology and community dynamics of Kubo people in the tropical lowlands of Papua New Guinea

Kubo producer-units (families and independent bachelors) could have been self-sufficient in the production of bananas but chose not to be. Nor did they seek self-sufficiency in the production of any combination of staple carbohydrate foods (bananas, tubers, sago flour) or, in the long term, strive for balance in the exchange of food with other producer-units. Despite the fact that bananas, which provided 50% of people's energy needs, were a delayed-return crop Kubo communities were very unstable. This instability and the failure to choose the option of self-sufficiency were connected and were mediated through intense intracommunity sharing that, ultimately, served to negotiate a concern with sorcery. The people grew bananas in the way they did, not out of environmental necessity, but to accommodate the crop to the needs of sharing and, thereby, facilitate community living.     

Simulation of field scale denitrification losses from soils under grass ley and barley

Denitrification losses from soils under barley and grass ley crops were simulated. The model, which includes the major processes determining inputs, transformations and outputs of nitrogen in arable soils, represents a scale compatible with information generally available in agricultural field research. The denitrification part of the model includes a field potential denitrification rate and functions for the effect of soil aeration status, soil temperature and soil nitrate content. Easily metabolizable organic matter is assumed not to limit denitrification. Simulated values were compared with denitrification measurements made during two growing seasons in the barley and grass ley treatments of a field experiment in central Sweden.Calibration revealed that the optimal parameter values describing the effect of soil aeration on denitrification rates were similar for both treatments. The response function derived agreed well with two data sets found in the literature. The potential denitrification rate constant, derived in the simulations, was higher for grass ley than for barley, which was consistent with the differences in overall rates of carbon and nitrogen turnover found between treatments.The simulated mean denitrification rates for the two seasons were within 20% of the mean of the measured values. However, simulated denitrification showed less temporal variability and a less skewed frequency distribution than measured denitrification. Some of the measured denitrification events not explained by the model could have been due to the stimulating effects of soil drying/wetting and freezing/thawing on microbial activity.     

Sodium-pump activity and its inhibition by extracellular calcium in cardiac myocytes of guinea pigs

Myocardial sodium-pump activity was examined from ouabain-sensitive ⁸⁶Rb⁺ uptake using myocytes isolated from guinea-pig heart. Either sodium loading or the sodium ionophore, monensin, increased ⁸⁶Rb⁺ uptake by over 400%, indicating that the amount of Na⁺ available to the pump is the primary determinant of its activity, and that the sodium pump has a substantial reserve capacity in quiescent myocytes. Moreover, the degree of the above stimulation is markedly higher than corresponding values reported with multicellular preparations, suggesting that diffusion barriers make it impossible to observe the capacity of the sodium pump in the latter preparations. Removal of extracellular Ca²⁺ increased ouabain-sensitive ⁸⁶Rb⁺ uptake, probably by enhancing turnover of the sodium pump rather than increasing availability of Na⁺ to the pump.     

Convergence of genetic distances in a migration matrix model

A recurring problem with the use of migration matrix models of genetic differentiation has to do with their convergence properties. In practice, predictions can be drawn from these models only at equilibrium; but in the case of the standard predictors (most of which are modifications of Wright's FST), it can take an unrealistically large number of generations to approach equilibrium. An alternative set of predictors, the set of all pairwise genetic distances among the populations that define the rows and columns of the migration matrix, is investigated here. These distances are shown analytically to converge much more rapidly than the more commonly used predictors. In an application of the model to migration data on a human population from Papua New Guinea, it takes only about three to four generations for the pairwise distances to converge, in contrast to more than 100 generations for one of the standard predictors. In this case, moreover, the distances predicted by the model at equilibrium are similar to those calculated from the available genetic data.     

k-Binding and Degradation of [3H]Dynorphin A (1–8) and [3H]Dynorphin A (1–9) in Suspensions of Guinea Pig Brain Membranes

Following incubation of [3H]dynorphin A (1-8) and [3H]dynorphin A (1-9) with suspensions of guinea pig brain membranes, analysis of the supernatants by HPLC has shown that both peptides are degraded at 25 degrees C and at 0 degrees C. Bestatin and captopril reduce degradation at 0 degrees C but for a similar degree of protection at 25 degrees C arginine-containing dipeptides are also required. The effects of these peptidase inhibitors on the degradation profiles indicate that [3H]dynorphin A (1-8) has three main sites of cleavage: the Tyr1-Gly2, Arg6-Arg7, and Leu5-Arg6 bonds. With [3H]dynorphin A (1-9) as substrate the Arg7-Ile8 and Ile8-Arg9 bonds are also liable to cleavage. In binding assays, in contrast to the effects of peptidase inhibitors on the degradation of unbound [3H]dynorphin A (1-8) and [3H]dynorphin A (1-9), bestatin and captopril have little effect on the binding characteristics of the tritiated dynorphin A fragments at the kappa-site at 0 degrees C. However, at 25 degrees C binding is low in the absence of peptidase inhibitors. When binding at mu- and delta-sites is prevented, the maximal binding capacities of [3H]dynorphin A (1-8), [3H]dynorphin A (1-9), and [3H](-)-bremazocine at the kappa-site are similar; [3H]dynorphin A (1-9) has 5-10 times higher affinity for the kappa-site than [3H]dynorphin A (1-8). Comparison of the effects of peptidase inhibitors on unbound dynorphin A fragments with their effects in binding assays suggests that the bound peptides are protected from the action of peptidases.     

Heterogeneity of hepatic microsomal UDP-glucuronosyltransferase(s) activities: comparison between human and mammalian species activities

The first comparative profiles of UDP-glucuronosyltransferase(s) (UDPGT) activities obtained under standard conditions in vitro in mammals (man, rat [Wistar and Gunn], mouse, monkey [Papio papio and Cynomolgus], pig, guinea pig, rabbit, dog) are presented for 16 aglycones. A decreasing scale of these activities was obtained from planar to bulky molecules. The scale was identical for each of the mammals studied, including man. Statistical analysis of the results revealed a division of the aglycones into three groups, one being correlated with the molecular form called GT1 the two others with the GT2 form. The profile of activities in the Gunn rat revealed very weak activity towards planar molecules (GT1). These results provide evidence that under standard conditions, human UDPGT activities are comparable to those from other animals.     

Dye coupling in the organ of Corti

Summary Dye-coupling in an in vitro preparation of the supporting cells of the guinea-pig organ of Corti was evaluated by use of the fluorescent dyes, Lucifer Yellow, fluorescein and 6 carboxyfluorescein. Despite the presence of good electrical coupling in Hensen cells (coupling ratios >0.6) the spread of Lucifer yellow was inconsistent. Hensen cells are very susceptible to photoinactivation, i.e., cell injury upon illumination of intracellular dye; and this in conjunction with Lucifer Yellow's charge and K+-induced precipitability may account for its variability of spread. Fluorescein and 6 carboxyfluorescein, on the other hand, spread more readily and to a greater extent than Lucifer Yellow, often spreading to cell types other than those of Hensen. Dye spread is rapid, occurring within a few minutes. These results suggest that molecules of metabolic importance also may be shared by the supporting cells of the organ of Corti.     

Correlation of neuronal size and peptide immunoreactivity in the guinea-pig trigeminal ganglion

Summary Frequency and size of guinea-pig trigeminal neurones immunoreactive with antisera to -neo-endorphin(-neo-END), dynorphin A-(DYN), vasoactive intestinal polypeptide-(VIP), somatostatin-(SOM), and substance P-(SP) are reported. Co-localisation of the various peptides to the same ganglion cells was investigated immunocytochemically in consecutive 7-m thick paraffin sections. According to their size, all peptide-immunoreactive neurones belong to the class of small ganglion cells. Within this cell group, SP-immunoreactive neurones appear to be the largest, followed by SOM-, VIP-, -neo-END- and DYN-immunoreactive ganglion cells. The observed differences in size are statistically significant with the exception of that between -neo-END and DYN. This finding correlates well with the observed co-occurrence of the two immunoreactive peptides. All -neo-END-immunoreactive perikarya are also reactive to VIP antisera. These neurones are significantly smaller than those containing VIP-immunoreactivity exclusively. Ganglion cells displaying co-existence of -neoEND- and SP-immunoreactivity or VIP- and SP-immunoreactivity are found too infrequently to allow morphometric analysis. Some non-immunoreactive ganglion cells are shown to be approached by dense baskets of VIP-, -neo-END- or SP-immunoreactive varicose fibres, indicating the presence of intraganglionic modulation sites. The combination of immunohistochemistry and morphometry presented in this study allows the differentiation of diverse populations of primary afferent neurones exhibiting peptide immunoreactivity, most likely reflecting their involvement in different central and peripheral reflex arcs and sensory modalities.