Campylobacter enteritis in Johannesburg

In order to establish a reasonable protocol for a diagnostic laboratory we conducted a survey during which we confined the routine culture of stool samples for Campylobacter fetus to two groups--all infants under 2 years of age, and older children and adults with obviously diarrhoeic stools. Camp. fetus was isolated from 100 of 2323 stool specimens (4,3%). This is within the 3 - 8% isolation rates previously reported from surveys in which all specimens were cultured. Camp. fetus isolates represented 16,9% of all bacterial pathogens isolated, and Black infants showed a significantly greater isolation rate than White infants. We feel that culture for Camp. fetus is an essential part of any routine bacteriological investigation of diarrhoea. A partially selective culture policy for Camp. fetus will result in a recovery rate at least equal to that of Salmonella and enteropathogenic Escherichia coli.     

Specific changes in the in vitro production of prostanoids by the ovine cervix at parturition

A method of tissue superfusion has been used to measure in vitro prostanoid production by the ovine cervix during late pregnancy and at parturition. In late pregnancy (105-135 days of gestation) cervical tissue produced relatively large amounts of prostaglandin E (PGE); in comparison, the production rates of prostaglandin F (PGF), 13, 14-dihydro-15-oxo-prostaglandin F (PGFM) and 6-oxo-prostaglandin F1 alpha were generally low. Thromboxane B2 (TXB2) production was minimal and often unmeasurable. There were significant increases in the production rates of PGE and 6-oxo-PGF1 alpha by cervical tissue taken immediately after delivery, when compared to late pregnancy. Mean production rates of PGE increased from 19.8 +/- 4.1 to 43.8 +/- 7.4 ng/g. dry wt./min; 6-oxo-PGF1 alpha production rates increased more than three-fold from 10.0 +/- 2.7 to 34.6 +/- 9.8 ng/g. dry wt./min (means +/- S.E.M.). There were no significant differences in the rates of production of PGF, PGFM and TXB2 by the two groups.     

Effects of 2,2'-dipyridyl and related compounds on platelet prostaglandin synthesis and platelet function

2,2'-dipyridyl, a chelator of ferrous iron and inhibitor of platelet aggregation, was studied together with several similar compounds to determine the mechanism of their effects on platelets. All of these compounds were more potent inhibitors of arachidonic-acid-mediated aggregation (IC50, 0.17-1.8 mM) than of ADP-mediated aggregation (IC50, 7.6-19.7 mM). At low concentrations required to inhibit arachidonic-acid-mediated aggregation, 2,2'-dipyridyl, 4,4'-dipyridyl and 2-chloropyridine specifically inhibited the platelet cyclo-oxygenase. The mechanism of inhibition of ADP-induced aggregation was investigated, but was not explained. At concentrations needed to inhibit ADP-induced aggregation, 2,2'-dipyridyl did not alter cell ultrastructure, serotonin or nucleotide content or interfere with release of [14C]arachidonic acid or calcium movements. Therefore, our results indicate that 2,2'-dipyridyl and related compounds have two effects on platelets, both due to the unprotonated form. The inhibition of cyclo-oxygenase by low concentrations of these compounds is not due to bidentate iron chelation, since 4,4'-dipyridyl was almost as effective as 2,2'-dipyridyl, but is compatible with binding of these inhibitors to the iron in the heme of the cyclo-oxygenase.     

Reduced growth factor requirements and accelerated cell-cycle kinetics in adult human melanocytes transformed with SV40 large T antigen

Melanomas develop with high frequency in transgenic mice in which oncogenic sequences of the SV40 DNA tumor virus have been specifically targeted to melanocytes. To investigate the role of SV40 in melanomagenesis, cultured human melanocytes were transformed with a retroviral shuttle vector encoding the SV40 large T antigen and examined for changes in cell-cycle kinetics and growth-factor dependence. Colonies expressing the viral oncogene were morphologically indistinguishable from their non-T-antigen-transformed counterparts. Also like normal melanocytes, the infected cells remained anchorage dependent and non-tumorigenic in nude mice. However, T-antigen-positive cultures exhibited significantly accelerated population doubling times, increased saturation densities with highly confluent monolayers and a three- to fourfold extended life span. Most interestingly, cell-cycle analysis revealed a measurable shift from quiescent to cycling cells in T-antigen-expressing cultures and an acquired ability to progress more rapidly through G1. Moreover, T-antigen-positive melanocytes proliferated in the absence of PMA and required markedly reduced levels of exogenous bFGF. These studies indicate that the viral oncogen of simian virus 40 provides melanocytes with distinct growth advantages that may render these cells unusually susceptible to additional environmental challenges necessary for full expression of the malignant phenotype.     

Residues Val254, His256, and Phe259 of the angiotensin II AT1 receptor are not involved in ligand binding but participate in signal transduction

The role of the external third of helix VI of the angiotensin II (AII) AT1 receptor for the interaction with its ligand and for the subsequent signal transduction was investigated by individually replacing residues 252-256 by Ala, and residues 259 or 261 by Tyr, and permanently transfecting the resulting mutants to Chinese hamster ovary (CHO) cells. Binding experiments showed no great changes in affinity of any of the mutants for AII, [Sar1]-AII, or [Sar1, Leu8]-AII, but the affinity for the nonpeptide antagonist DuP753 was significantly decreased. The inositol phosphate response to AII was remarkably decreased in mutants V254A, H256A, and F259Y. These results indicate that AT1 residues Val254, His256, and Phe259 are not involved in ligand binding but participate in signal transduction. Based in these results and in others from the literature, it is suggested that, in addition to the His256 imidazole ring, the Phe259 aromatic ring interacts with the AII's Phe8, thus contributing to the signal-triggering mechanism.     

IL-1 in gingival crevicular fluid following closed root planing and papillary flap debridement

Interleukin (IL)-1 alpha and beta are cytokines which can mediate inflammatory, bone resorbing, and reparative effects in the periodontium, but few longitudinal data exist exploring their role following periodontal therapy. This study examined gingival crevicular fluid (GCF) concentrations of IL-1 alpha and IL-1 beta at sites with shallow sulci (SS) or inflamed moderate/advanced pockets (M/AP) before and 6 months after treatment with closed scaling/root planing (SC/RP) or papillary flap debridement (PFD), all in the same subject (n = 14 patients). No significant differences were noted in IL-1 alpha or beta concentrations (determined with two-site enzyme-linked immunosorbent assays) between SS and M/AP sites at baseline. While both therapies improved clinical parameters of periodontal disease, IL-1 alpha concentration increased significantly (p < 0.05) in M/AP-PFD sites 6 months after treatment, but were unchanged in other groups. IL-1 beta concentrations were numerically lower after therapy, except for a significant increase (p < 0.05) in M/AP-PFD sites. These data suggest that surgical wound healing in an inflamed, plaque-infected site (M/AP-PFD) results in prolonged production of IL-1, which may be a reflection of the extent of tissue trauma and delayed wound healing. In spite of increased IL-1 levels, these sites demonstrated significant short-term improvement in clinical attachment level (+ 1.8 mm, p < or = 0.001) postoperatively.