Industrial contributions to desertification in South America

Degradation of tropical lands has a grim inevitability. This is true of semi-arid and seasonal ecosystems as it is of the rainforests, whose plight has been the principal focus of attention in recent years. The broad belt of savanna-like vegetation in central South America has suffered an accelerating decline in productivity due to overclearing and overgrazing, a process that can be traced directly to the industrialization of Europe in the 19th century. The remorseless slide towards unproductivity need not be slow: a mere 50-100 years seems more than adequate, even for the more robust landscapes. With careful management however, some of these lands are slowly recovering.     

Clinical Trial of Lincomycin Hydrochloride in Reiter's Disease

A double-blind trial comparing lincomycin hydrochloride (Mycivin) and placebo in 22 patients with Reiter''s disease showed no significant difference in clinical or laboratory findings between the two groups. It is concluded that lincomycin hydrochloride is no more effective than placebo in the treatment of Reiter''s disease.     

Expression of enzymatically active enkephalinase (neutral endopeptidase) in mammalian cells

A cDNA encoding the rat enkephalinase protein (neutral endopeptidase; EC 3.4.24.11) has been constructed from overlapping lambda gt10 cDNA clones. This cDNA was inserted into an expression plasmid containing the cytomegalovirus enhancer and promoter. When transfected with this plasmid, Cos 7 cells transiently expressed the enkephalinase protein in a membrane-bound state. Recombinant enkephalinase recovered in solubilized extracts from transfected Cos 7 cells was enzymatically active and displayed properties similar to those of the native enzyme with respect to sensitivity to classical enkephalinase inhibitors.     

Alpha subunit variants of the human glycine receptor: primary structures, functional expression and chromosomal localization of the corresponding genes.

Two cDNAs encoding variants (alpha 1 and alpha 2) of the strychnine binding subunit of the inhibitory glycine receptor (GlyR) were isolated from a human fetal brain cDNA library. The predicted amino acid sequences exhibit approximately 99% and approximately 76% identity to the previously characterized rat 48 kd polypeptide. Heterologous expression of the human alpha 1 and alpha 2 subunits in Xenopus oocytes resulted in the formation of glycine-gated strychnine-sensitive chloride channels, indicating that both polypeptides can form functional GlyRs. Using a panel of rodent-human hybrid cell lines, the gene encoding alpha 2 was mapped to the short arm (Xp21.2-p22.1) of the human X chromosome. In contrast, the alpha 1 subunit gene is autosomally located. These data indicate molecular heterogeneity of the human GlyR at the level of alpha subunit genes.     

Structural and functional characterization of the gamma 1 subunit of GABAA/benzodiazepine receptors.

The GABAA receptor gamma 1 subunit of human, rat and bovine origin was molecularly cloned and compared with the gamma 2 subunit in structure and function. Both gamma subunit variants share 74% sequence similarity and are prominently synthesized in often distinct areas of the central nervous system as documented by in situ hybridization. When co-expressed with alpha and beta subunits in Xenopus oocytes and mammalian cells, the gamma variants mediate the potentiation of GABA evoked currents by benzodiazepines and help generate high-affinity binding sites for these drugs. However, these sites show disparate pharmacological properties which, for receptors assembled from alpha 1, beta 1 and gamma 1 subunits, are characterized by the conspicuous loss in affinity for neutral antagonists (e.g. flumazenil) and negative modulators (e.g. DMCM). These findings reveal a pronounced effect of gamma subunit variants on GABAA/benzodiazepine receptor pharmacology.     

Biological activity and metabolic clearance of recombinant human follicle stimulating hormone produced in Sp2/0 myeloma cells

Human follicle stimulating hormone is a pituitary glycoprotein that is essential for the maintenance of ovarian follicle development and testicular spermatogenesis. Like other members of the glycoprotein hormone family, it contains a common a subunit and a hormone specific subunit. Each subunit contains two glycosylation sites. The specific structures of the oligosaccharides of human follicle stimulating hormone have been shown to influence both thein vitro andin vivo bioactivity. Since the carbohydrate structure of a protein reflects the glycosylation apparatus of the host cells in which the protein is expressed, we examined the isoform profiles,in vitro bioactivity and metabolic clearance of a preparation of purified recombinant human follicle stimulating hormone derived from a stable, transfected Sp2/0 myeloma cell line, and pituitary human follicle stimulating hormone. Isoelectric focussing and chromatofocussing studies of human follicle stimulating hormone preparations both showed a more basic isoform profile for the recombinant human follicle stimulating hormone compared to that of pituitary human follicle stimulating hormone. The recombinant human follicle stimulating hormone had a significantly higher radioreceptor activity compared to that of pituitary human follicle stimulating hormone, consistent with a greaterin vitro potency. Pharmacokinetic studies in rats indicated a similar terminal half life (124 min) to that of the pituitary human follicle stimulating hormone (119 min). Preliminary carbohydrate analysis showed recombinant human follicle stimulating hormone to contain high mannose and/or hybrid type, in addition to complex type carbohydrate chains, terminating with both2,3 and2,6 linked sialic acids. These results demonstrate that recombinant human follicle stimulating hormone made in the Sp2/0 myeloma cells is sialylated, has a more basic isoform profile, and has a greaterin vitro biological potency compared to those of the pituitary human follicle stimulating hormone.     

Use of a fluorescent dye to measure secretion from intact bovine anterior pituitary cells

The fluorescent dye FM1-43 has been used to indicate membrane changes in individual bovine anterior pituitary cells exposed to secretory stimuli. After ten minutes incubation with FM1-43 (2 M), cells showed three patterns of dye fluorescence: annular, partly filled and uniformly filled. FM1-43 fluorescence was increased in 61% of the cells by TRH (40 nM), a physiological stimulus for prolactin secretion, and in 89% of the cells by 60 mM external K⁺. The fluorescence also increased when cells incubated in the presence of quinpirole, a dopamine D2-receptor agonist which inhibits prolactin secretion, were exposed to raclopride, a D-2 antagonist. The increases in FM1-43 fluorescence caused by these treatments suggests that the dye acts as an indicator of secretion, possibly through incorporation into secretory vesicle membranes exposed on the cell surface during exocytosis. If the dye was washed away after loading, the fluorescence of partly and uniformly filled cells was retained and a rise in fluorescence could still be seen on stimulation by TRH. This suggests that some dye had been taken up by endocytosis and trapped in an intracellular compartment, which expanded through membrane recapture after TRH stimulation. FM1-43 could therefore be a useful probe for membrane cycling associated with secretory responses.