Testosterone alters duodenal calcium transport and longitudinal bone growth rate in parallel in the male rat.

Duodenal active calcium transport and longitudinal bone growth rate have been shown previously to be regulated in parallel by alteration of gonadal hormone status in sexually maturing female rats. The present study was designed to extend these observations to the sexually maturing male rat. Male rats were orchidectomized (ORX) and given Silastic implants containing either testosterone or estradiol at 6 weeks of age. At 9 weeks of age, duodenal active calcium transport was measured by the everted gut sac method and longitudinal bone growth rate was determined by tetracycline labeling. Decreases in body weight, longitudinal bone growth rate, duodenal calcium transport, and serum Ca and P were exhibited by ORX animals as compared with age-matched control animals. Testosterone administration to ORX animals resulted in an increase in body weight, longitudinal bone growth rate, duodenal calcium transport, and serum Ca and P as compared with ORX animals to a level not significantly different from that of age-matched control animals. Estradiol administration to ORX animals resulted in an additional decrease in body weight, although no significant effect on duodenal calcium transport, serum Ca, or P was noted as compared with ORX animals. There were no statistically significant alterations in the circulating levels of 1,25-dihydroxyvitamin D, parathyroid hormone, or osteocalcin in response to any of the experimental manipulations of gonadal status. These results indicate that, as in the female, gonadal hormone status affects intestinal calcium transport in sexually maturing male rats in parallel with changes in bone growth rate by mechanisms that are independent of circulating levels of 1,25-dihydroxyvitamin D.     

Alpine vascular plant species richness: the importance of daily maximum temperature and pH

Species richness in the alpine zone varies dramatically when communities are compared. We explored (i) which stress and disturbance factors were highly correlated with species richness, (ii) whether the intermediate stress hypothesis (ISH) and the intermediate disturbance hypothesis (IDH) can be applied to alpine ecosystems, and (iii) whether standing crop can be used as an easily measurable surrogate for causal factors determining species richness in the alpine zone. Species numbers and standing crop were determined in 14 alpine plant communities in the Swiss Alps. To quantify the stress and disturbance factors in each community, air temperature, relative air humidity, wind speed, global radiation, UV-B radiation, length of the growing season, soil suction, pH, main soil nutrients, waterlogging, soil movement, number of avalanches, level of denudation, winter dieback, herbivory, wind damage, and days with frost were measured or observed. The present study revealed that 82% of the variance in␣vascular species richness among sites could be explained by just two abiotic factors, daily maximum temperature and soil pH. Daily maximum temperature and pH affect species richness both directly and via their effects on other environmental variables. Some stress and disturbance factors were related to species richness in a monotonic way, others in an unimodal way. Monotonic relationships suggest that the harsher the environment is, the fewer species can survive in such habitats. In cases of unimodal relationships (ISH and IDH) species richness decreases at both ends of the gradients due to the harsh environment and/or the interaction of other environmental factors. Competition and disturbance seemed only to play a secondary role in the form of fine-tuning species richness in specific communities. Thus, we concluded that neither the ISH nor the IDH can be considered useful conceptual models for the alpine zone. Furthermore, we found that standing crop can be used as an easily measurable surrogate for causal factors determining species richness in the alpine zone, even though there is no direct causality.     

Simple reversed-phase high-performance liquid chromatography quantitation of ganciclovir in human serum and urine

A fast, simple, and cost-effective HPLC method for the quantitation of the antiviral drug ganciclovir is described. The serum samples are extracted with perchloric acid and neutralized with potassium phosphate buffer, and urine samples are diluted with distilled water. A reversed-phase column with isocratic elution by 15 mM potassium phosphate buffer (pH 2.5) containing 0.25% acetonitrile is used to separate ganciclovir; quantitation is by UV absorbance at 254 nm. Total turnaround time is 22 min; more than 3000 samples can be run on a single column without loss of peak quality. The limit of quantitation is 0.05 μg/ml. Recoveries varied from 91 to 10% with coefficients of variation ranging from 0.387 to 7.95%.     

Pleiotropic action of the murine quaking locus: Structure of the qk v allele

The spontaneous allele quaking^viable (qk ^v ) exerts effects on myelination and spermiogenesis. The defects generated by qk ^v were not separated in a multilocus mapping cross that provided a mapping resolution of 0.1 centiMorgans (cM). Furthermore, no distortions suggestive of a large chromosomal anomaly associated with qk ^v were apparent. One plausible interpretation is that the quaking locus contains more than one functional domain, either organized into overlapping genes or expressed by alternative splicing mechanisms. The cloning needed to analyze this locus will be enhanced by the very high resolution of the meiotic mapping cross reported here. The recombinational distances on this qk ^v map were compressed compared with those previously reported in a high-resolution map for qk ^1–1, an embryonic lethal allele of quaking induced by ethylnitrosourea. Additional crosses confirmed prior reports that the sex and the genetic background of the heterozygous parent can affect recombinational distances. These joint effects on recombination are strong enough to account for the discrepancy between the two maps. This variability of two-factor map values leads to the preferred multilocus map-building protocol discussed in the accompanying paper.     

Synthesis of N-carboxyalkyl and N-aminoalkyl functionalized dipeptide building units for the assembly of backbone cyclic peptides.

To improve the assembly of backbone cyclic peptides, N-functionalized dipeptide building units were synthesized. The corresponding N-aminoalkyl or N-carboxyalkyl amino acids were formed by alkylation or reductive alkylation of amino acid benzyl or tert-butyl esters. In the case of N-aminoalkyl amino acid derivatives the aldehydes for reductive alkylation were obtained from N,O-dimethyl hydroxamates of N-protected amino acids by reduction with LiAlH4. N-carboxymethyl amino acids were synthesized by alkylation using bromoacetic acid ester and the N-carboxyethyl amino acids via reductive alkylation using aldehydes derived from formyl Meldrums acid. Removal of the carboxy protecting group leads to free N-alkyl amino acids of very low solubility in organic solvents, allowing efficient purification by extraction of the crude product. These N-alkyl amino acids were converted to their tetramethylsilane-esters by silylation with N,O-bis-(trimethylsilyl)acetamide and could thus be used for the coupling with Fmoc-protected amino acid chlorides or fluorides. To avoid racemization the tert-butyl esters of N-alkyl amino acids were coupled with the Fmoc-amino acid halides in the presence of the weak base collidine. Both the N-aminoalkyl and N-carboxyalkyl functionalized dipeptide building units could be obtained in good yield and purity. For peptide assembly on the solid support, the allyl type protection of the branching moiety turned out to be most suitable. The Fmoc-protected N-functionalized dipeptide units can be used like any amino acid derivative under the standard conditions for Fmoc-solid phase synthesis.     

Dynamic features of cells expressing macrophage properties in tissue cultures of dissociated cerebral cortex from the rat

Summary Two previously identified forms of macrophage were investigated in primary cultures of cerebral cortical cells. Dynamic features were revealed through time-lapse video recording and aspects of macrophage function were assessed. The two cell forms were shown to be different pre-mitotic stages of a single cell type. The cell cycle for these cells involved an initial large, flat, quiescent cell which retracted to yield a slightly rounded form with numerous processes. This latter form lost processes and developed profuse filopodia as it became very rounded just prior to division; both resulting daughter cells then regained the initial large flat appearance. These cells possessed several properties of macrophages, including phagocytosis, nucleoside diphosphatase enzyme, and CR3 receptors. These properties were transient, expressed just before and after mitosis, but subsequently down-regulated in the flat daughter cells. Because of this feature, it was difficult to determine the exact size of this cell population; however, the observed rate of proliferation suggests it may be substantial. It is suggested that these cells correspond to non-microglial macrophages of brain tissue and, because of their significant down-regulation, they may be difficult to detect. This may be important in studies of brain accessory immune cells in tissue culture.