Effects of H2-receptor antagonists on 3H-cimetidine binding and histamine-stimulation of cellular cAMP in isolated guinea pig gastric glands

3H-Cimetidine binding to plasma membranes of isolated guinea pig gastric glands was investigated, and the effects of five H2-receptor antagonists on 3H-cimetidine binding and histamine stimulation of cellular cAMP were compared. Of the five cations tested, Cu++ markedly increased specific 3H-cimetidine binding. 3H-Cimetidine had high affinity (Kd = 0.41 x 10(-6) M) and low affinity (Kd = 12.8 x 10(-6) M) binding sites. Cimetidine and etintidine were potent inhibitors of 3H-cimetidine binding, while famotidine, ranitidine and TZU-0460 were not. Histamine stimulation of cellular cAMP was competitively inhibited by H2-receptor antagonists yielding pA2 values of 6.41 for cimetidine, 6.82 for etintidine, 6.87 for ranitidine, 6.94 for TZU-0460 and 7.60 for famotidine. Because the KB value (log KB = -pA2) of 0.39 x 10(-6) M for cimetidine is close to the Kd value for the high affinity 3H-cimetidine binding site, it is presumed to represent a part of the H2-receptor, and the relative potency of etintidine against cimetidine in inhibiting 3H-cimetidine binding is similar to that in inhibiting histamine stimulation of cellular cAMP. These results suggest that imidazole-derived H2-receptor antagonists (cimetidine and etintidine) and non-imidazole H2-receptor antagonists (famotidine, ranitidine and TZU-0460) compete with histamine at different sites on the H2-receptor of the gastric glands.     

Clinical evaluation of lumbar disc hernia in the teenagers

Lumbar disc herniation is a rare occurrence in teenagers. There are several questions as to its pathogenesis, relationship to trauma, and clinical manifestations compared with those in adults. In the present paper, we described nine cases of teen-age lumbar disc herniation, which accounts for about 3.3% of all the operated lumbar disc herniations in our clinic. In the discussion, 687 cases of teen-age lumbar disc herniation were analyzed from the world literature. The clinical signs and symptoms in teenagers showed no distinct difference from those in adults. Laségue's sign was found in nearly all the patients. Although direct or indirect trauma to the lumbar region may play an important role in causing disc herniation in teenagers, a more important factor seems to be the degeneration of the disc material, which begins in children earlier than usually suspected. Although surgical therapy has been advocated by many authors, it must be followed up for a long term before the efficacy of such treatment for teenagers can be confidently ascertained.     

Fungal flora in rainwater

We analyzed rainwater samples collected throughout a year for fungal flora and compared the results to those from atmospheric samples. Differences between the seasonal variation in number of fungi in rainwater and that in number of fungi in the atmosphere were found; that is, there was less of a difference among rainfall samples from different sampling points than among atmospheric samples. In the rainwater samples 29 fungal genera were detected, whereas only 17 were detected in the atmospheric samples. The variations in Cladosporium and Penicillium were the determinants of the total number of fungi in rainwater, whereas in air the variation in Cladosporium alone was the determinant. Sampling of rainwater therefore can be expected to provide information on fungal flora in the troposphere that cannot be obtained by means of air sampling.     

Effect of lafutidine on CGRP release from cultured rat dorsal root ganglion cells

Lafutidine increased capsaicin-stimulated CGRP release from isolated rat stomach without changing basal CGRP levels. In order to clarify the mechanism of this effect, we used cultured rat DRG cells and measured CGRP release. (1) DRG cells were treated with each drug, and the CGRP content of the supernatant was determined by EIA. (2) RGM-1 cells were co-cultured with DRG cells through a cell culture insert, and capsaicin-evoked CGRP release from the DRG cells was determined when lafutidine or PGE₂ was added to the RGM-1 cells. (3) The supernatant of isolated rat stomach incubated with lafutidine was added to cultured DRG cells, and capsaicin-evoked CGRP release was determined. PGE2, but not lafutidine, augmented capsaicin-evoked CGRP release from DRG cells. Lafutidine did not modulate CGRP release from DRG cells, even though it sensitized CGRP-containing afferent nerves in the rat stomach. Lafutidne and PGE₂ may have different mechanisms of sensitization.     

Mitogenic activity of lipopolysaccharide from Bacteroides intermedius against C3H/HeJ mice spleen cells

Bacteroides intermedius is one of the periodontal disease generative bacteria. Lipopolysaccharide preparation obtained from B. intermedius ATCC 25611 and ATCC 33563 strains was investigated as to Limulus activity observed with Pyrodic (endotoxin specific) reagent, and mitogenic activity in both normal and tolerant mice induced by Escherichia coli. Limulus activities of all LPS's were nearly similar to that of E. coli. LPS's preparation from B. intermedius were found to be strongly mitogenic for C3H/HeN mice spleen cells, whereas no LPS preparations were mitogenic for thymocytes of BALB/c mice. LPS-nonresponsive C3H/HeJ mice spleen cells were found to good mitogenic responses to LPS's from B. intermedius, as well as LPS from B. gingivalis 381 strain. Polymyxin B had remarkable inhibitory effect on the mitogenicity of LPS's from B. intermedius for C3H/HeN and C3H/HeJ mice spleen cells, also that activity of B. gingivalis LPS was inhibited by polymyxin B. The mitogenicity of the LPS from B. intermedius, as measured in C3H/HeJ mice spleen cells, was considerably resistant to the proteolytic effects of proteinase K.     

Identification of the sites of asparagine-linked glycosylation on the human thyrotropin receptor and studies on their role in receptor function and expression

The amino-terminal ectodomain of human thyrotropin receptor (TSHR) contains six potential N-linked glycosylation sites (N-Xaa-S/T). This study was designed to evaluate the functional role of TSHR carbohydrates in detail. Because our previous mutagenesis study by Asn to Gln substitutions suggested the critical role of the first and third glycosylation sites (amino acids 77 and 113) for expression of the functional TSHR, we first constructed TSHR mutants having these two glycosylation sites to elucidate whether these two sites are sufficient for TSHR function and expression; this mutant however proved to be nonfunctional. Also the expression levels and function of TSHR mutants with a Ser/Thr to Ala substitution at the first or third glycosylation site were found to be intact. These data indicate that our previous data appear to result from amino acid substitution itself, not from disruption of glycosylation. The next series of the mutants was therefore constructed to identify at least how many glycosylation sites are necessary. Neither TSH binding nor cAMP response was detected in TSHR mutants with three glycosylation sites. However, the mutants with four glycosylation sites were fully functional in terms of TSH binding and cAMP production, although the expression levels were 30 to 40% of that in wild-type TSHR. Finally, Western blot revealed that all six glycosylation sites are actually glycosylated. These data indicate that 1) TSHR ectodomain contains six N-linked carbohydrates, and 2) glycosylation of at least four sites appears necessary for expression of the functional TSHR.