Immunodeficiency in RFM/(T6xRFM)F1 mouse chimaeras with lethal host-versus-graft syndrome.

Rather than central tolerance, the perinatal inoculation of related F1 hybrid spleen cells into inbred mice may result in host-versus-graft (HVG) reactions manifested as transient autoimmunity, or as a lethal immunodeficiency syndrome. RFM/(T6xRFM)F1 chimaeras with lethal disease die in 30 days with lymphosplenomegaly, immune complexes and impaired immune responses. The present studies used in vitro proliferation assays to show that the HVG reaction caused hyperplasia sufficient to account for the lymphosplenomegaly, while also causing severe impairment of splenic and nodal cell responses to concanavalin A (Con A) and to bacterial lipopolysaccharide (LPS). By 25 days, HVG mice could not distinguish between self and non-self as judged by mixed lymphocyte reactions (MLR) to RFM, (T6xRFM)F1 and third party A/J cells. There were no indications that host cells reactive to F1 donor cells had undergone clonal deletion, anergy or expansion. Flow cytometry revealed that donor T lymphocytes achieved stable engraftment, mostly in the nodes, despite the HVG reaction. Taken together with previous observations, these studies showed that HVG reactions in young parent F1/chimaeras can result in an immunodeficiency state which is characterized by an early appearing, profound and persistent impairment of both host and donor T and B cell functions. The results suggest that HVG reactions can contribute directly to immune deficits seen after clinical allogeneic bone marrow transplantation.     

Beta 2-microglobulin amyloidosis (AB2M) in patients undergoing long-term hemodialysis. A new type of amyloid

Amyloidosis has been increasingly recognized in association with renal failure and chronic hemodialysis. This report describes three patients who had long-term hemodialysis (between 7-18 years), in whom deposits developed of a new type of amyloid of beta 2-microglobulin origin. Beta 2-microglobulin amyloid (AB2M) was found in multiple organs, i.e., bone, subendocardium, gastrointestinal blood vessels, tongue, and carpal tunnel connective tissue. AB2M displayed characteristic amyloid features on conventional light and polarized microscopic examination after congo red staining. However immunostaining with anti-amyloid A protein, kappa, and lambda antisera were negative. The studied material reacted positively with beta 2-microglobulin antisera, identifying AB2M in all three cases. Ultrastructural study revealed an unusual curvi-linear fibrillar configuration. AB2M appears to be a new subtype of systemic amyloidosis secondary to renal failure and long-term hemodialysis.     

Comparison of fixed concentration and fixed ratio options for dilution susceptibility testing of gram-negative bacilli to ampicillin and ampicillin/sulbactam

Ampicillin combined with sulbactam was tested at both fixed ratio (2:1 and 1:1) and fixed sulbactam concentrations (4 µg/ml, 8 µg/ml and 16 µg/ml) against 2440 consecutively isolated gram-negative bacilli. Sulbactam significantly enhanced the spectrum of ampicillin activity. Overall, at 8 µg/ml ampicillin inhibited 50 % of theEnterobacteriaceae isolates, whereas 69 % to 84 % of the isolates were inhibited by the various sulbactam combinations. The widest spectrum of activity for ampicillin/sulbactam was achieved by testing at a fixed sulbactam concentration of 16 µg/ml, followed by the 1:1 ratio and the fixed 8 µg/ml (84 %, 76 % and 74 % inhibited, respectively). The amount of sulbactam at the susceptible breakpoint concentrations of ampicillin markedly affected the percentage of susceptible strains. Combinations that include 8 µg/ml of sulbactam are suggested for consideration.     

T-cell antigenic sites involved in myasthenia gravis: correlations with antibody titre and disease severity

We have evaluated the ability of eight synthetic peptides corresponding to selected regions of the alpha-subunit from human (H) or Torpedo (T) acetylcholine receptor (AChR) to stimulate proliferative responses of peripheral blood lymphocytes (PBL) and thymic cells from patients with Myasthenia Gravis (MG) in comparison to healthy controls. Using PBL, two of the peptides were most reactive: in the 40 myasthenic patients tested, peptide 169-181 (H) induced significant proliferative responses in 10 patients and peptide 351-368 (H) in five, while there was no response in any of the 34 healthy controls tested. Interestingly, clear associations between proliferation to peptides and clinical data were observed. Indeed, among responding patients, all presented thymic hyperplasia and most showed a high anti-AChR Ab titre and/or a severe form of the disease. In addition, responses to AChR cytoplasmic sequences were observed only in severely affected patients. Correlation with HLA-DR haplotype, sought in a subgroup of patients, indicated that response to 169-181 (H) is associated with HLA-DR5 in the patients presenting a high anti-AChR antibody titre. Using thymic lymphocytes, few responses were obtained with the human peptides, suggesting that the frequency of autoreactive cells is lower than in the blood. Similar to PBL, responses to peptides were observed only with lymphocytes isolated from hyperplastic thymuses. The correlations observed between responses to peptides and clinical parameters underline the pathophysiological relevance of our data and indicate that pathogenic and nonpathogenic T-cell antigenic sites involved in the anti-AChR response could be identified by this approach.     

In vivo release of neurotransmitters in the medial basal hypothalamus of the monkey

Summary In vivo release rates of norepinephrine (NE), epinephrine (E), dopamine (DA), gammaaminobutyric acid (GABA), glutamate (GLU) and beta-endorphin (E) in the medial basal hypothalamus (MBH) of unanaesthetized female macaca fascicularis monkey, and the effects thereon of estrogen (E2) treatment, have been estimated using pushpull perfusion methodology. DA, NE, E, GABA, GLU and E were all detectable in 30 min perfusate fractions. No direct correlation between their release rates and those of LH and PRL could be observed. E2 induced an initial decrease, then an increase, in LH and PRL secretion, and concomitant changes in the release patterns of DA, NE, E. GABA and GLU were apparent. This study demonstrates that in vivo push-pull perfusion methodology may be applied to the unanaesthetized monkey, and when combined with venous catheterization for serial blood sampling may prove to be a powerful tool in the investigation of the central molecular events governing neuroendocrine functions.     

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.