Surface components of HeLa cells that inhibit cytadherence of Chlamydia trachomatis

Isolated HeLa plasma membrane (PM) preparations and extracts containing either cell-surface proteins or lipids were examined for inhibition of adherence of radiolabeled Chlamydia trachomatis serovar E elementary bodies to glutaraldehyde-fixed HeLa monolayers. A dose-dependent adherence-inhibitory activity could be demonstrated with the PM. A urea extract as well as lipids from HeLa cells also inhibited chlamydial cytadherence. The inhibitory activity of the PM was trypsin-sensitive. It was absent when the urea extract was prepared from trypsin-treated HeLa cells. The urea extract was subjected to electrophoresis and protein blotting using a native gel system. Probing with radiolabeled chlamydial cytadhesin showed a single protein present in the urea extract that could represent a HeLa cell protein receptor for the chlamydiae.

Further characterization of an outer membrane protein of Chlamydia trachomatis with cytadherence properties

To further characterize the chlamydial cytadhesin (CCA), we have examined it for saturability of binding to HeLa cells that were grown as monolayers and in suspension. The CCA exhibited specific cytadherence properties of binding to HeLa cells that appeared to be saturable. The CCA showed a substantial decrease in binding to trypsin-treated HeLa cells in suspension. This finding, together with the fact that the CCA itself is known to be trypsin-sensitive, suggested a protein-protein type of interaction between CCA and HeLa cells. Periodate treatment of the CCA did not result in significant reduction in cytadherence, which implies that sugar moieties were probably not involved in CCA binding to HeLa cells. Whilst attempts to produce antibodies to the CCA in rabbits was unsuccessful, the CCA reacted with antibodies in a human serum known to contain high titer antibodies to Chlamydia trachomatis, suggesting it can be immunogenic, and is possibly expressed during human infection.

Catabolite repression vs derepression, an approach to differentiation during sporulation in Bacillus subtilis

Glutamine, like glucose, repressed sporulation and the synthesis of mycobacillin and dipicolinic acid by Bacillus subtilis, and these syntheses were depressed by dibutyryl cyclic GMP but not by dibutyryl cyclic AMP. Neither of these dibutyryl cyclic nucleotides affected sporulation or a number of spore-associated parameters in the strain under normal physiological conditions. Mutants insensitive to glutamine repression were indifferent to the addition of either of the dibutyryl cyclic nucleotides both in the presence and in the absence of glutamine. Sporulation resulted from the remission of repression obtained under the catabolically active state.

Host passage-dependent wheat germ agglutinin-binding proteins of Chlamydia trachomatis

Wheat germ agglutinin (WGA)-binding proteins in the highly purified elementary bodies (EB) of Chlamydia trachomatis were detected by an ELISA-like assay of immobilized EB. Trypsin-sensitivity of the WGA-binding moieties was detected only in the chlamydiae grown in HeLa cells. A nonionic detergent, beta-octyl-D-glucopyranoside (OG), was used to extract proteins from the purified EB. Proteins in the extract were resolved by SDS-PAGE and probed with 125I-labelled WGA. Several proteins reacted with WGA in a specific manner. Some of these WGA-binding proteins in the EB of serovars L1 and E exhibited altered molecular mass after adaptation in the two alternate hosts, HeLa and McCoy cells. These results suggest that WGA-binding proteins exist in chlamydiae.

A heat-labile protein of Chlamydia trachomatis binds to HeLa cells and inhibits the adherence of chlamydiae

From highly purified elementary bodies (EBs) of Chlamydia trachomatis, we have identified a protein of 38 kDa that selectively binds to monolayer cultures of HeLa cells. This protein, which we have named the chlamydial cytadhesin (CCA), is present on the surface of the EBs of three C. trachomatis serovars (B, E, and L1) that were examined. Localization of the CCA at the surface was confirmed by its ability to be labeled when viable EBs were iodinated and by its absence in preparations from trypsin-treated EBs. Viable EBs, but not heated or trypsin-treated EBs, inhibited the binding of the CCA to HeLa cells, indicating competition for a common receptor on the host cell membrane. A dose-dependent inhibition of adherence of radioactive EBs to HeLa cells was effected by extracts containing the CCA. This inhibition occurred even with extracts prepared from the EB of heterologous serovars. However, no inhibition could be demonstrated with extracts prepared from heat-treated EBs. Heat treatment of the extract resulted in the loss of ability of the CCA to bind to the host cells. HeLa cells preincubated with CCA-containing chlamydial extract showed reduced ability to bind labeled EBs and to develop cytoplasmic inclusions after infection. This protective activity was lost after exposure of the extract to heat. These findings indicate that the CCA is a thermolabile surface-exposed chlamydial adhesin; it may be useful in the development of vaccines for diseases caused by the pathogenic bacterium.

Ischemic preconditioning is not mediated by free radicals in the isolated rabbit heart

Preconditioning has been implicated to involve a free radical mechanism in the in vivo infarct size model. We have demonstrated preconditioning in the isolated rabbit heart and studied the effect of Mn-superoxide dismutase (SOD) on preconditioning. Buffer perfused control hearts (C) were subjected to 1-h global ischemia followed by 1-h reperfusion, and the percent recovery of developed tension (%DT; relative to preischemic) was measured via a left ventricular balloon connected to a polygraph recorder. The coronary effluent was assayed for lactate dehydrogenase release (LDH; IU/kg BW). Preconditioned hearts (P) received a single episode of 5-min ischemia and 5-min reperfusion before 1 h of ischemia and reperfusion. SOD treated hearts received SOD at 5 mg/L in the buffers at all times. The results show that while SOD attenuated enzyme release and functional loss in control hearts, it had no effect on preconditioned hearts. Therefore, preconditioning is unlikely to be mediated by superoxide anion in the isolated rabbit heart.

Extensive heterogeneity of the protein composition of Chlamydia trachomatis following serial passage in two different cell lines

To determine if the host-modulated adherence characteristics of the intracellular bacterial pathogen Chlamydia trachomatis were due to the acquisition of altered surface-exposed proteins, highly purified chlamydiae grown in two different host cells were analysed. Two serovars, L1 and E, were grown for multiple passages in both HeLa and McCoy host cells. Numerous protein differences in the chlamydial elementary bodies (EB) of each serovar grown in the two different hosts were detected by two-dimensional (2-D) gel electrophoresis and fluorography of radioactively labelled proteins. At least four to six serial passages in the alternative host were necessary before the changes were apparent. Iodination of suspensions of purified chlamydiae and 2-D electrophoresis revealed several surface proteins that were determined by the host cells in which the bacteria had replicated. These iodinated chlamydial proteins were removed by treatment of the iodinated EB with trypsin, indicating their location at the bacterial surface. Two of the major constituents of the outer-membrane complex, the cysteine- and methionine-rich 60 kDa and 40 kDa proteins, remained unchanged in both molecular mass and charge during the host adaptation. Several chlamydial proteins capable of binding iodinated host membrane preparations also exhibited host-dependent alterations. Immunoblotting experiments with a rabbit and a human polyclonal sera indicated that distinct host-specified chlamydial proteins were reactive with the two sera.

Adherence of multiple serovars of Chlamydia trachomatis to a common receptor on HeLa and McCoy cells is mediated by thermolabile protein(s)

Several aspects of the adherence of purified elementary bodies (EB) of Chlamydia trachomatis to HeLa and to McCoy cells were examined using different techniques, including an ELISA. Serovar-specific, biotinylated monoclonal antibodies were used to detect cell-bound chlamydiae. In addition, purified chlamydiae were biotinylated and their adherence properties were studied. The assays were done at 4 degrees C to exclude the energy-dependent internalization of the cell-bound EB and host-cell membrane recycling that occur at 37 degrees C. Saturation kinetics were routinely observed at 4 degrees C, and the rate of adherence remained linear for approximately 60 min. Lineweaver-Burk analysis of the kinetics data showed that adherence of any one serovar was competitively inhibited by other serovars of C. trachomatis. This competition for the same receptor on the two alternative hosts, HeLa and McCoy, was also seen when the adherence assays were done at 37 degrees C in the presence of sodium azide, an energy poison that inhibits endocytosis of cell-bound chlamydiae. Chlamydiae exposed to 56 degrees C for 5 min, or treated with low doses of trypsin, failed to exhibit competitive inhibition, having suffered considerable loss of the ability to adhere to host-cells. These data suggest that heat- and trypsin-labile chlamydial moieties participate in the adherence reaction, and that oculo-genital serovars of C. trachomatis, including that of lymphogranuloma venereum, attach to the same receptor on the host-cell membrane.

Repression of sporulation: isolation and characterization of repression-resistant mutants of Bacillus subtilis

The sporulation of Bacillus subtilis B34 was repressed by 24 h if glutamine or ammonium chloride but not glutamate was added at late log phase (70 h) when glucose and glutamate were nearly exhausted. Glutamine-resistant mutants were isolated by selective heat treatment during the delay period induced by glutamine. Glutamine-resistant mutants showed cross resistance not only against ammonium chloride but also against glucose just as glucose-resistant mutants showed resistance against nitrogenous catabolites.

Effects of aspirin and paracetamol on ATPases of human fetal brain: an in vitro study

In vitro effects of aspirin and paracetamol at the doses 200, 400, 600, 800 nmole/mg protein on ATPases activity were studied in the cerebrum and cerebellum of human fetus covering the age range from 10 weeks to 32 weeks of gestation. Both aspirin and paracetamol inhibit Na+K+ ATPase and Mg2+ ATPase in a dose dependent manner. The inhibition of Na+K+ ATPase and Mg2+ ATPase activity which may affect the release and uptake of biogenic amines in CNS, hinders the maturation of human fetal brain.

Characterization of versilin-sensitive sites in self-sensitive producer and sensitive non-producer or unrelated organism

Studies on self-sensitivity of producer mutant vs. sensitivity of non-producer parent and unrelated organism showed that versilin inhibited spore germination and sporulation in the self-sensitive producer mutant, non-producer parent Aspergillus versicolor N5 and the unrelated sensitive Trichophyton rubrum. Sporulation appeared to be more sensitive than spore germination. The inhibition of in vivo synthesis of protein was very marked, but inhibition of RNA and DNA was slight and moderate, respectively. Thus versilin was not specific in its action, but the principal sensitive site was protein synthesis, as further suggested by inhibition of polyU-directed in vitro synthesis of polyphenylalanine. The activation of leucine was unaffected, but the formation of leucyl-tRNA was severely inhibited in all three strains. The differences in sensitivities between the strains were the same, whether as whole cells or as cell-free extracts. Thus the nature of the sensitive site appeared to be identical in the self-sensitive producer and sensitive non-producer or unrelated organism.