Vasopressin-induced taurine efflux from rat pituicytes: a potential negative feedback for hormone secretion

Previous work on the whole neurohypophysis has shown that hypotonic conditions increase release of taurine from neurohypophysial astrocytes (pituicytes). The present work confirms that taurine is present in cultured pituicytes, and that its specific release increases in response to a hypotonic shock. We next show that vasopressin (VP) and oxytocin (OT) also specifically release taurine from pituicytes. With an EC₅₀ of ∼2 n m , VP is much more potent than OT, and the effects of both hormones are blocked by SR 49059, a V_1a receptor antagonist. This pharmacological profile matches the one for VP- and OT-evoked calcium signals in pituicytes, consistent with the fact that VP-induced taurine efflux is blocked by BAPTA-AM. However, BAPTA-AM also blocks the taurine efflux induced by a 270 mosmol l⁻¹ challenge, which per se does not evoke any calcium signal, suggesting a permissive role for calcium in this case. Nevertheless, the fact that structurally unrelated calcium-mobilizing agents and ionomycin are able to induce taurine efflux suggests that calcium may also play a signalling role in this event. It is widely accepted that in hypotonic conditions taurine exits cells through anionic channels. Antagonism by the chloride channel inhibitors 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) suggests the same pathway for VP-induced taurine efflux, which is also blocked in hypertonic conditions (330 mosmol l⁻¹). Moreover, it is likely that the osmosensitivity of the taurine channel is up-regulated by calcium. These results, together with our in situ experiments showing stimulation of taurine release by endogenous VP, strengthen the concept of a glial control of neurohormone output.     

Presence of autoantibodies to apolipoprotein A-1 in patients with acute coronary syndrome further links autoimmunity to cardiovascular disease

Anti-apolipoprotein A-1 (Apo A-1) autoantibodies were described in autoimmune disorders such as systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS) and might be involved in the genesis of arterial and venous thrombotic events. To investigate the presence of these autoantibodies in patients with acute coronary syndrome (ACS) without other features of autoimmunity, we set up an enzyme-linked immunosorbent assay (ELISA) for anti-Apo A-1 antibodies. We used it to investigate their prevalence in ACS as compared to SLE and APS and correlated them to plasma Apo A-1 and serum amyloid A protein (SAA) concentrations. The prevalence of anti-Apo A-1 autoantibodies in the healthy control group was 1% (1/92), but was significantly higher in other groups: 21% (11/53) in ACS group (P=0.001), 13% (12/92) in SLE and/or APS group (P=0.005). Multiple linear regression revealed a significant correlation between plasma Apo A-1 (r=-0.72, P=0.013), plasma SAA concentration (r=0.76, P=0.0066) and anti-Apo A-1 IgG titre in ACS patients. The presence of anti-Apo A-1 autoantibodies in patients with ACS highlights an additional link between autoimmunity, inflammation and atherosclerosis.     

Various protocols for determining estrogens by the enzymatic method using estradiol dehydrogenase. Respective procedures and advantages

Up to now, more than 40.000 determinations of urinary estrogens (E1 + E2) have been carried out in routine clinical analysis by the enzymatic method using estradiol dehydrogenase. This method makes use of the transhydrogenating activity of the placental enzyme: this enzyme transfers hydrogen from NADP to NAD with recycling of the specific substrate (E1 + E2). For several years the necessary reagents have been commercially available in the form of a kit. Nonetheless, various improvements have been made to the measurement of reduced NAD, which accumulates in the reaction medium and is directly proportional to the concentration of the two estrogens. Three protocols are available at present: Spectrophotometric measurement at 340 nm (initial technique); Colorimetric measurement at 492 nm. The pink colour measured arises from the reduction of a tetrazolium salt (INT) by reduced NAD in a coupled system using diaphorase; Measurement by bioluminescence of the light energy liberated on the reduction of flavin derivatives by NADH. The reaction is mediated by various enzymes isolated from marine bacteria (FMN oxidoreductase and luciferase) in the presence of an aliphatic aldehyde (decanal). The procedure for each of these protocols is described as well as the means for controlling the linearity of the reaction. The choice of protocol is determined by the biological fluid available, the speed of response desired and the cost of the analysis.     

Family and Illness Predictors of Outcome in Pediatric Brain Tumors

Investigated the prediction of cognitive and behavioral outcomesin 63 children with heterogenous brain tumors. Hierarchicalmultiple regression analyses were used to determine how family-relatedvariables added to the prediction of children's outcome overand above illness measures. The best predictors of children'sbehavior problems and adaptive behavior were family and demographicvariables, whereas the best predictors of achievement were illnessand demographic variables. A combination of family and illnessvariables, however, was the best predictor of intellectual functioning.In addition to identifying specific predictors of cognitiveand behavioral outcome in children with brain tumors, theseresults lend initial support for the inclusion of contextualfactors such as family stress, maternal coping, number of parentsin the home, and family SES measures in studies of how diseasefactors affect outcomes in pediatric brain tumor patients.     

Epithelial cell heterogeneity in the guinea pig thymus: immunohistochemical characterization of four thymic epithelial subsets defined by monoclonal anti-keratin antibodies

Keratins are a family of related polypeptides constitutive of the cytoskeleton of epithelial cells and are never found in nonepithelial tissues. Thymic epithelial cells (TEC), known to induce T cell differentiation, are the keratin-containing cells within the thymus. Using four monoclonal anti-keratin antibodies (KL1, KL4, AE2, AE3) directed against keratins of different molecular weight, we have investigated the guinea pig thymic epithelium. The immunohistochemical analysis of thymic cryostatic sections revealed that the keratin expression of TEC varied according to their location in the thymic lobula; the thymic cortex was specifically stained by AE3 whereas the thymic medulla and the subcapsular cortex were recognized by KL4. In addition, KL1 and AE2 exclusively labeled Hassall's corpuscles. The biochemical analysis of keratins extracted from the thymus showed that each TEC subset was characterized by an unique pattern of keratin polypeptides. This study extends the concept of thymic epithelium heterogeneity and suggests that anti-keratin antibodies which allow the typing of TEC subsets may be valuable tools for studying the differentiation of thymic epithelium and its in vitro function on T lymphocytes.     

Long-term reduction of vasopressin excretion induced by the central injection of an immunoconjugate (antibody to vasopressin linked to ricin a chain)

We have previously demonstrated that vasopressin-producing neurons are the target of monoclonal antibodies to vasopressin microinjected into the brain tissue. At the same time, this central microinjection of vasopressin-monoclonal antibody into the supraoptic nuclei produced hydro-osmotic disorders mimicking the effects of a central diabetes insipidus. In order to investigate the increase in both duration and amplitude of the biological effects seen after the injection of vasopressin-monoclonal antibody, an immunoconjugate was constructed with the vasopressin-monoclonal antibody IgG1k isotype and the cytotoxic part of the ricin molecule, the ricin A chain. The biological parameters, such as diuresis and urine osmolality which are directly regulated by vasopressin, and vasopressin excretion, were measured after the central injection of this immunotoxin/immunoconjugate. The consequences of immunotoxin injection were also studied when immunotoxin was co-injected with monensin (50 nM) which has been shown to decrease the intracellular degradation of immunotoxin, and plasma complement, which has been shown to increase the neuronal uptake of immunotoxin. Single injection of immunotoxin near the hypothalamic supraoptic nuclei significantly increased diuresis and decreased vasopressin excretion. However, these effects were only transient and disappeared 24 h later. Four successive injections of immunotoxin (one per day) with monensin induced a decrease of vasopressin excretion which was still observed after a resting period of four days after the fourth injection. The long-term reduction of vasopressin excretion was induced in rats receiving four successive injections of a mixture consisting of immunotoxin with monensin and plasma complement. In such experiments, the vasopressin content of urine remained low (55% under the baseline value), two weeks after the fourth injection of immunotoxin. At the same time, the diuresis was increased (80% above the baseline value) and urine osmolality lowered (45% under the baseline value). When non-specific IgG replaced specific antibody, vasopressin excretion, diuresis as well as urine osmolality were unchanged.

The results of this study demonstrated that the use of a specific immunotoxin results in a local interference with the vasopressinergic neurons and induces a long-term reduction of vasopressin secretion.     

Comparative toxicity,protective, histamine sensitizing and leucocytosis promoting activities in mice ofBordetella pertussis culture fluid,bacterial cells and cell extracts

Bordetella pertussis bacterial cells, bacterial extracts, and concentrated culture supernatant fluid were comparatively examined for histamine sensitizing and leucocytosis promoting activities, toxicity (mouse weight gain test), immunoprotective potency and lipopolysaccharide bioassay. The activity of histamine sensitizing factor always paralleled that of leucocytosis promoting factor. In contrast, important differences were demonstrated regarding the toxicity and protective activity of the three preparations. Culture supernatant was more toxic and less protective than either bacterial cells or cell extract. Although the latter had lower protective potency than whole cells, its lower toxicity might lead to its consideration as a possible potential vaccine.