Prostaglandin biosynthesis by human decidual cells: effects of inflammatory mediators

There is substantial evidence that decidual activation, in association with infection, is linked with the onset of both preterm and term labor. We therefore undertook the present study to evaluate prostaglandin production and its potential regulation by inflammatory mediators in human decidual cells in primary monolayer culture. Upon attaining confluence, the cells were incubated with endotoxin, interleukin 1 alpha (IL1 alpha), interleukin 1 beta (IL1 beta); or tumor necrosis factor (TNF). Production of prostaglandin (PG) E2 and PGF2 alpha was determined using specific radioimmunoassays. Endotoxin and these cytokines all induced significant concentration-dependent increases in PGE2 and PGF2 alpha production. Our results suggest that term human decidual cells are responsive to endotoxin and cytokines and that generation of these substances in the decidua or nearby (eg. in response to infection) will lead to increased prostaglandin production and uterine contractions.     

Voltammetric studies on the electrochemical behaviour of membrane-entrapped hemes

Summary The electrochemical behaviour of Fe(III)-protoporphyrin IX entrapped into a cellulose triacetate membrane has been investigated by cyclic voltammetry. The physical entrapment into a solid matrix does not modify the redox properties of the entrapped berries, which also act as efficient promoters in the electrochemistry of cytochromec. Such a system represents a promising example of a simple solid-state promoter, and stimulates further investigations in order to obtain more complex systems that may be of significance for basic and applied bioelectrochemistry.     

DR antigen expression on ovarian carcinoma cells does not correlate with their capacity to elicit an autologous proliferative response

Summary Expression of HLA-DR antigens by purified preparations of human ovarian carcinoma cells freshly isolated from surgical specimens was examined in parallel with the capacity of tumor cells to elicit a blastogenic response from autologous lymphocytes in mixed lymphocyte-tumor culture (MLTC) assay. Of 21 tumor preparations, 11 (52%) reacted with monoclonal antibodies 279 and/or 949 specific for a monomorphic determinant of HLA-DR antigens, with heterogeneous positivity, ranging between 30% and 95%. In this series of patients positive MLTC occurred in 8/21 individual experiments. The HLA-DR expression was proportionally similar in tumors giving positive MLTC (4/8=50%) and negative MLTC (7/13=53%). The lack of correlation between DR expression on tumor cells and stimulatory activity in autologous MLTC and the fact that DR-negative tumors could induce lymphocyte stimulation, support the hypothesis that blastogenesis occurs upon recognition of tumor-associated antigens, different from DR molecules, possibly tumor-specific antigens.     

Serological recognition of HLA-DR allodeterminant corresponding to DNA sequence involved in gene conversion

HLA class 11 molecules were isolated from mouse L cells transfected with a DR gene and an allele, 52a, of locus DR III from an HLA-homozygous cell line, AVL, of the DR3 haplotype. The isolated molecules were found to possess a new allospecificity, named TR81. This specificity behaved allelic to the previously described DR III locus. The TR81 specificity was also present on the DR I gene product of the DR3 haplotype. The nucleotide sequence of the gene encoding TR81 differs from TR81-negative DR genes of the DRw52 family in only two codons, both located in the regions known to be involved in a gene conversion event. Consequently, the following conclusions can be formulated. (a) TR81 is a bi-locus specificity and allelic to TR22 only in its DR III locus localization. (b) The TR81 specificity is the phenotypic counterpart of the gene conversion event which led to the generation of the DR I gene of the DR3 haplotype. (c) One or both individual amino acid substitutions in the first domain of the DR chain are responsible for the TR81 allospecificity. (d) Since TR81 is expressed on the DR I chain of the DR3 haplotype, it is possible that TR81 and DR3 represent the same serological specificity.     

Isolation and biochemical characterization of Streptomyces clavuligerus mutants in the biosynthesis of clavulanic acid and cephamycin C

Summary Seven mutants of Streptomyces clavuligerus blocked in the biosynthesis of clavulanic acid, cephamycin C, or both antibiotics, have been isolated and characterized. Mutants nca1 and nca2 were unable to synthesize clavulanic acid but produced cephamycin C. Mutants nce1 and nce2 were completely blocked in cephamycin C production but formed clavulanic acid. A third group (mutants ncc1, ncc4 and ncc5) failed to produce both antibiotics. Arginase activity (forming ornithine) was very low in mutants ncc1 and ncc5. All the mutants blocked in clavulanic acid biosynthesis showed a normal ornithine--aminotransferase activity. Mutant ncc1, blocked in cephamycin biosynthesis, lacked completely lysine--aminotransferase (forming -aminoadipic acid) and isopenicillin N synthase. Two other mutants (nce2 and nce5) lacked isopenicillin N synthase. There was a good correlation between the isopenicillin N synthase and the lysine--aminotransferase activities of the nca mutants and the ability of those strains to produce cephamycin C. The condensing enzyme involved in the formation of the clavulanic acid nucleus appears to be different from the isopenicillin N synthase.Dedicated to Professor H.-J. Rehm on the occasion of his 60th birthday     

Intrinsic and extrinsic innervation of the amphibians esophagic myenteric plexuses

The innervation of Rana ridibunda esophagus myenteric plexuses has been studied by the following methods: demonstration of cholinesterase activity; FIF method for catecholamines; immunohistochemistry for VIP, SP and SOM, and conventional electron microscopy. The cholinergic innervation is important in the esophagus wall where, in addition to the well known extrinsic component, there is a rich intrinsic plexus with cells and fibres widely distributed. The esophagus, together with the intestine, are the Rana gut portions where the adrenergic component is more broadly expressed. The adrenergic innervation seems to be almost entirely of extrinsic origin. We have shown that, for the tested peptides, there is an intrinsic innervation represented by VIP, SP and SOM like plexuses. We do not discard nonetheless an extrinsic component. The ultrastructure reveals the morphological characteristics of the enteric neurons as well as the fine inter-relationships between the nervous elements and the functional components of the esophagic wall.     

Electrogenic behavior of the human red cell Ca2+ pump revealed by disulfonic stilbenes

Summary A systematic study was made of the action of 4-acetamido-4-isothiocyanostilbene-2,2-disulfonic acid (SITS) and 4,4-diisothiocyanostilbene-2,2-disulfonic acid (DIDS) on active Ca²⁺ transport of human erythrocytes. Pumping activity was estimated in inside-out vesicles (IOV's) by means of Ca²⁺-selective electrodes or use of tracer⁴⁵Ca²⁺. The stilbenes exhibited an approximately equal inhibitory potency and their action could be overcome by carbonyl cyanidep-trifluoromethoxyphenylhydrazone (FCCP) at low but not at high stilbene concentrations. In the absence of DIDS. Ca²⁺ transport was not affected upon addition of valinomycin, but it was appreciably reduced when vesicles were preincubated with low DIDS concentrations. Such an effect was strictly dependent on the external K⁺ concentration and it was abolished when valinomycin was added together with FCCP. Similar results were obtained using IOV's prepared from intact cells which had been previously exposed to the stilbene. The findings clearly demonstrate the presence in human red cells of a partially electrogenic Ca²⁺ pump, exchanging one Ca²⁺ ion for one proton.     

A novel class of ammonium assimilation mutants of the photosynthetic bacterium Rhodobacter capsulatus

Nitrogen assimilation in Rhodobacter capsulatus has been shown to proceed via the coupled action of glutamine synthetase (GS) and glutamate synthase (GOGAT) with no measurable glutamate dehydrogenase (GDH) present. We have recently isolated a novel class of mutants of R. capsulatus strain B100 that lacks a detectable GOGAT activity but is able to grow at wild type rates under nitrogen-fixing conditions. While NH ₄ ⁺ -supported growth in the mutants was normal under anaerobic/photosynthetic conditions, the growth rate was decreased under aerobic conditions. Ammonium and methylammonium uptake experiments indicated that there was a clear difference in the ammonium assimilatory capabilities in these mutants under aerobic versus anaerobic growth. Regulation of expression of a nifH : : lacZ fusion in these mutants was not impaired. The possible existence of alternative ammonium assimilatory pathways is discussed.     

Social stimuli fail to act as entraining agents of circadian rhythms in the golden hamster

Summary The ability of social stimuli to act as entraining agents of circadian rhythms was investigated in golden hamsters (Mesocricetus auratus). In a first experiment, pairs of male hamsters (one of them enucleated and the other intact) were maintained under a light-dark (LD) cycle with a period of 23.3 h. Running-wheel activity was recorded to determine the effect of social interaction on the free-running circadian rhythm of activity. In several pairs, general activity and body temperature were also recorded. In all pairs the intact animals entrained to the LD cycle, whereas the activity rhythms of the enucleated animals free-ran with periods of approximately 24 h and showed no apparent sign of synchronization or relative coordination with the other member of the pair. In a second experiment, male hamsters maintained in constant darkness received pulses of social interaction, which have been reported to induce phase shifts of the activity rhythm. Consistent phase shifts in the running-wheel activity rhythm were not induced by the social pulses in our experiment. These results suggest strongly that social stimuli are not effective entraining agents of circadian rhythms in the golden hamster.Abbreviations CT circadian time - LD light-dark