Transmitter release at the hair cell ribbon synapse.

Neurotransmitters are released continuously at ribbon synapses in the retina and cochlea. Notably, a single ribbon synapse of inner hair cells provides the entire input to each cochlear afferent fiber. We investigated hair cell transmitter release in the postnatal rat cochlea by recording excitatory postsynaptic currents (EPSCs) from afferent boutons directly abutting the ribbon synapse. EPSCs were carried by rapidly gating AMPA receptors. EPSCs were clustered in time, indicating the possibility of coordinate release. Amplitude distributions of spontaneous EPSCs were highly skewed, peaking at 0.4 nS and ranging up to 20 times larger. Hair cell depolarization increased EPSC frequency up to 150 Hz without altering the amplitude distribution. We propose that the ribbon synapse operates by multivesicular release, possibly to achieve high-frequency transmission.     

5-HT1A dysfunction in borderline personality disorder

BACKGROUND: A number of challenge studies have reported abnormalities of serotonergic function in borderline personality disorder (BPD). There are, however, problems with the pharmacological probes used in these studies since fenfluramine and m-CPP are not only serotonergic agents but also induce release of catecholamines, particularly dopamine. Therefore, we tested whether subjects with BPD showed a blunted prolactin (PRL) response to flesinoxan, a highly potent and selective 5-HT1A agonist. METHODS: Flesinoxan challenge test was carried out in 20 BPD in-patients and 20 healthy controls matched for gender but not for age. Since 16 BPD in-patients exhibited major depressive co-morbidity, a group of 20 depressed in-patients matched for gender but not for age was also included. RESULTS: BPD in-patients exhibited blunted PRL responses as compared to controls, whereas depressed in-patients did not differ from controls. Moreover, PRL responses were lower among BPD in-patients than among depressed in-patients. Among the BPD in-patients, PRL responses to flesinoxan were lower in patients with past history of suicide attempts (N = 8) than in those with a negative history. CONCLUSIONS: The results show major involvement of serotonergic function in BPD and are consistent with previous studies linking lower serotonergic activity with impulsivity. More particularly, our data suggest that BPD is characterized by lower 5-HT1A receptor sensitivity. Moreover, the data support the involvement of 5-HT1A activity in suicidal behaviour. However, this conclusion is limited because other hormonal responses such as ACTH and cortisol were not assessed, and because BPD was assessed by a self-report questionnaire and not a structured clinical interview.     

Modulation of anti-acetylcholine receptor antibody specificities and of experimental autoimmune myasthenia gravis by synthetic peptides.

Synthetic peptides corresponding to selected sequences from the nicotinic acetylcholine receptor (AChR) were employed to identify possible antigenic determinants within the receptor which can modulate the anti-AChR response and experimental autoimmune myasthenia gravis (EAMG). Immunization of rabbits with peptides T alpha 73-89, T alpha 351-368, T delta 354-367 and H alpha 351-368, prior to AChR inoculation, affected the course of EAMG in six out of eight rabbits. These six protected rabbits survived three inoculations of AChR and survived for at least five months after the third injection with AChR, whereas control rabbits died following one or two injections of AChR. The survival of peptide-preimmunized rabbits injected with AChR seemed to correlate with the antibody specificities in immunoblots. Following AChR inoculation there was a shift in reactivity, from a subunit-restricted response, to reactivity with all subunits of the receptor. This shift was delayed in protected rabbits. This may indicate that the reactivity with the entire Torpedo receptor molecule represents a loss of tolerance to AChR which culminates in the autoimmune disease, EAMG.     

Weight loss in patients with hematological neoplasias is associated with immune system stimulation

Summary Weight loss is the main symptom of so-called tumor cachexia. The pathogenetic mechanisms underlying cachexia are poorly understood; however, it appears that enhanced formation of cytokines such as interferon- and tumor necrosis factor- are involved. In 94 patients suffering from hematological neoplasias we compared body weight changes with serum neopterin, tryptophan, and kynurenine. Biochemical changes, the formation of neopterin, the degradation of tryptophan are closely related to interferon- activity. The majority of our patients had increased neopterin and decreased tryptophan concentrations. Weight loss was seen particularly in patients with higher neopterin and lower tryptophan values. An association between higher neopterin levels and greater weight loss was apparent at study entry and during the follow-up of patients. Our data support the concept that weight loss is closely linked to endogenous interferon- activity.Abbreviations NHL non-Hodgkin's lymphoma - HD Hodgkin's disease - MM multiple myeloma - MGUS monoclonal gammopathy of unknown significance - IFN- interferon- - TNF- tumor necrosis factor-     

Evaluation of in vitro methods for testing susceptibility of anaerobes to ampicillin-sulbactam and amoxicillin-clavulanic acid.

A total of 97 anaerobic bacteria were tested for susceptibility to ampicillin, ampicillin-sulbactam, and amoxicillin-clavulanic acid by broth microdilution and disk elution methods, the results of which were compared with those of the reference agar dilution method. With the broth microdilution method, approximately 95% of MICs were within 1 dilution of those of the reference agar method, with a definite (0.6 to 0.7 dilution) trend toward lower MICs. The disk elution test performed satisfactorily, but additional anaerobic isolates resistant to ampicillin-sulbactam and/or amoxicillin-clavulanic acid (currently rare) are needed to assure the predictability of resistance by the disk elution test.     

Pathogenesis of Shigella diarrhea: rabbit intestinal cell microvillus membrane binding site for Shigella toxin

This study examined the binding of purified 125I-labeled shigella toxin to rabbit jejunal microvillus membranes (MVMs). Toxin binding was concentration dependent, saturable, reversible, and specifically inhibited by unlabeled toxin. The calculated number of toxin molecules bound at 4 degrees C was 7.9 X 10(10) (3 X 10(10) to 2 X 10(11))/micrograms of MVM protein or 1.2 X 10(6) per enterocyte. Scatchard analysis showed the binding site to be of a single class with an equilibrium association constant, K, of 4.7 X 10(9) M-1 at 4 degrees C. Binding was inversely related to the temperature of incubation. A total of 80% of the labeled toxin binding at 4 degrees C dissociated from MVM when the temperature was raised to 37 degrees C, but reassociated when the temperature was again brought to 4 degrees C. There was no structural or functional change of MVM due to toxin as monitored by electron microscopy or assay of MVM sucrase activity. These studies demonstrate a specific binding site for shigella toxin on rabbit MVMs. The physiological relevance of this receptor remains to be determined.     

Neopterin as a new biochemical marker in the clinical assessment of ulcerative colitis

In previous publications we showed that neopterin, a pyrazino-pyrimidin compound, represents a biochemical marker for the assessment of cellular immune responses. We thought that the evaluation of this marker molecule might enable insight into the activity of cellular immune responses underlying ulcerative colitis (UC). Evaluation of urinary neopterin excretion in 25 consecutive untreated UC patients revealed striking correlations between neopterin levels and the severity of disease: elevated levels were observed in 9 out of 9 patients with moderately severe to severe, in 3 of 4 with mild and in none of 12 patients with quiescent disease. Further evidence for a correlation between disease activity and neopterin excretion was obtained on the basis of long-term follow-up studies performed in 4 cases. These studies indicated normalization of neopterin levels when clinical remission was achieved. Thereafter, the relative significance of neopterin excretion for determination of clinical stage was assessed by linear correlation analyses and was compared with conventional clinical parameters such as anemia, number of motions per day, raised temperature, ESR and extent of bowel involvement. The logarithm of neopterin excretion and the extent of bowel involvement were the two single parameters most closely related to the clinical stage of ulcerative colitis. We, therefore, conclude that evaluation of neopterin excretion in ulcerative colitis patients represents a new and useful tool for the clinical monitoring of disease activity.     

Use of non-neutralizing monoclonal antibodies in an ELISA for intratypic differentiation of 28 echovirus type 25 clinical isolates.

Three non-neutralizing monoclonal antibodies were produced and selected against echovirus type 25 JV-4 prototype strain. They were used in an ELISA to investigate the intratypic differentiation of 28 wild isolates. Clinical isolates fell into seven different groups according to their reactivity patterns in ELISA. Two of the non-neutralizing monoclonal antibodies, 9E4 and 6D3, were highly specific, while the third, 6C9, may recognize an epitope common to other types of echoviruses. In contrast, mouse polyclonal antiserum exhibited large cross-reactivities among echovirus serotypes. The reactivity patterns and the geographical origin of the isolates were generally not correlated and, in the same area, four major antigenic variants sometimes coexisted, especially in the south of France. Moreover, reactivity patterns found with ELISA were hardly ever correlated with those observed in a previous study when neutralization tests were used. These results again underline the non-correlation between structure and biological function in the Picornavirus family.