Protective autoimmunity: interferon-gamma enables microglia to remove glutamate without evoking inflammatory mediators.

Glutamate in excessive amounts is a major contributor to neuronal degeneration, and its removal is attributed mainly to astrocytes. Traumatic injury to the central nervous system (CNS) is often accompanied by disappearance of astrocytes from the lesion site and failure of the remaining cells to withstand the ensuing toxicity. Microglia that repopulate the lesion site are the usual suspects for causing redox imbalance and inflammation and thus further exacerbating the neurotoxicity. However, our group recently demonstrated that early post-injury activation of microglia as antigen-presenting cells correlates with an ability to withstand injurious conditions. Moreover, we found that T cells reactive to CNS-specific self-antigens protected neurons against glutamate toxicity. Here, we show that antigen-specific autoimmune T cells, by tailoring the microglial phenotype, can increase the ability of microglia-enriched cultures to remove glutamate. This T-cell-mediated effect could not be achieved by the potent microglia-activating agent lipopolysaccharide (LPS), but was dose-dependently reproduced by the Th1 cytokine interferon (IFN)-gamma and significantly reduced by neutralizing anti-IFN-gamma antibodies. Under the same conditions, IFN-gamma had no effect on cultured astrocytes. Up-regulation of glutamate uptake induced by IFN-gamma activation was not accompanied by the acute inflammatory response seen in LPS-activated cultures. These findings suggest that T cells or their cytokines can cause microglia to adopt a phenotype that facilitates rather than impairs glutamate clearance, possibly contributing to restoration of homeostasis.

Neuronal survival after CNS insult is determined by a genetically encoded autoimmune response.

Injury to the CNS is often followed by a spread of damage (secondary degeneration), resulting in neuronal losses that are substantially greater than might have been predicted from the severity of the primary insult. Studies in our laboratory have shown that injured CNS neurons can benefit from active or passive immunization with CNS myelin-associated antigens. The fact that autoimmune T-cells can be both beneficial and destructive, taken together with the established phenomenon of genetic predisposition to autoimmune diseases, raises the question: will genetic predisposition to autoimmune diseases affect the outcome of traumatic insult to the CNS? Here we show that the survival rate of retinal ganglion cells in adult mice or rats after crush injury of the optic nerve or intravitreal injection of a toxic dosage of glutamate is up to twofold higher in strains that are resistant to the CNS autoimmune disease experimental autoimmune encephalomyelitis (EAE) than in susceptible strains. The difference was found to be attributed, at least in part, to a beneficial T-cell response that was spontaneously evoked after CNS insult in the resistant but not in the susceptible strains. In animals of EAE-resistant but not of EAE-susceptible strains devoid of mature T-cells (as a result of having undergone thymectomy at birth), the numbers of surviving neurons after optic nerve injury were significantly lower (by 60%) than in the corresponding normal animals. Moreover, the rate of retinal ganglion cell survival was higher when the optic nerve injury was preceded by an unrelated CNS (spinal cord) injury in the resistant strains but not in the susceptible strains. It thus seems that, in normal animals of EAE-resistant strains (but not of susceptible strains), the injury evokes an endogenous protective response that is T-cell dependent. These findings imply that a protective T-cell-dependent response and resistance to autoimmune disease are regulated by a common mechanism. The results of this study compel us to modify our understanding of autoimmunity and autoimmune diseases, as well as the role of autoimmunity in non-autoimmune CNS disorders. They also obviously have far-reaching clinical implications in terms of prognosis and individual therapy.

A role for a novel luminal endoplasmic reticulum aminopeptidase in final trimming of 26 S proteasome-generated major histocompatability complex class I antigenic peptides.

Peptides presented to cytotoxic T lymphocytes by the class I major histocompatability complex are 8-11 residues long. Although proteasomal activity generates the precise C termini of antigenic epitopes, the mechanism(s) involved in generation of the precise N termini is largely unknown. To investigate the mechanism of N-terminal peptide processing, we used a cell-free system in which two recombinant ornithine decarboxylase (ODC) constructs, one expressing the native H2-K(b)-restricted ovalbumin (ova)-derived epitope SIINFEKL (ODC-ova) and the other expressing the extended epitope LESIINFEKL (ODC-LEova), were targeted to degradation by 26 S proteasomes followed by import into microsomes. We found that the cleavage specificity of the 26 S proteasome was influenced by the N-terminal flanking amino acids leading to significantly different yields of the final epitope SIINFEKL. Following incubation in the presence of purified 26 S proteasome, ODC-LEova generated largely ESIINFEKL that was efficiently converted to the final epitope SIINFEKL following translocation into microsomes. The conversion of ESIINFEKL to SIINFEKL was strictly dependent on the presence of H2-K(b) and was completely inhibited by the metalloaminopeptidase inhibitor 1,10-phenanthroline. Importantly, the converting activity was resistant to a stringent salt/EDTA wash of the microsomes and was only apparent when transport of TAP, the transporter associated with antigen processing, was facilitated. These results strongly suggest a crucial role for a luminal endoplasmic reticulum-resident metalloaminopeptidase in the N-terminal trimming of major histocompatability complex class I-associated peptides.

26 S proteasome-mediated production of an authentic major histocompatibility class I-restricted epitope from an intact protein substrate.

Peptides displayed on the cell surface by major histocompatibility class I molecules (MHC class I) are generated by proteolytic processing of protein-antigens in the cytoplasm. Initially, antigens are degraded by the 26 S proteasome, most probably following ubiquitination. However, it is unclear whether this proteolysis results in the generation of MHC class I ligands or if further processing is required. To investigate the role of the 26 S proteasome in antigen presentation, we analyzed the processing of an intact antigen by purified 26 S proteasome. A recombinant ornithine decarboxylase was produced harboring the H-2K(b)-restricted peptide epitope, derived from ovalbumin SIINFEKL (termed ODC-ova). Utilizing recombinant antizyme to target the antigen to the 26 S proteasome, we found that proteolysis of ODC-ova by the 26 S proteasome resulted in the generation of the K(b)-ligand. Mass spectrometry analysis indicated that in addition to SIINFEKL, the N-terminally extended ligand, HSIINFEKL, was also generated. Production of SIINFEKL was linear with time and directly proportional to the rate of ODC-ova degradation. The overall yield of SIINFEKL was approximately 5% of the amount of ODC-ova degraded. The addition of PA28, the 20 S, or the 20 S-PA28 complex to the 26 S proteasome did not significantly affect the yield of the antigenic peptide. These findings demonstrate that the 26 S proteasome can efficiently digest an intact physiological substrate and generate an authentic MHC class I-restricted epitope.

Glutamine synthetase protects against neuronal degeneration in injured retinal tissue.

The neurotransmitter glutamate is neurotoxic when it is accumulated in a massive amount in the extracellular fluid. Excessive release of glutamate has been shown to be a major cause of neuronal degeneration after central nervous system injury. Under normal conditions, accumulation of synaptically released glutamate is prevented, at least in part, by a glial uptake system in which the glia-specific enzyme glutamine synthetase (GS) plays a key role. We postulated that glial cells cannot cope with glutamate neurotoxicity because the level of GS is not high enough to catalyze the excessive amounts of glutamate released by damaged neurons. We examined whether elevation of GS expression in glial cells protects against neuronal degeneration in injured retinal tissue. Analysis of lactate dehydrogenase efflux, DNA fragmentation, and histological sections revealed that hormonal induction of the endogenous GS gene in retinal glial cells correlates with a decline in neuronal degeneration, whereas inhibition of GS activity by methionine sulfoximine leads to increased cell death. A supply of purified GS enzyme to the culture medium of retinal explants or directly to the embryo in ovo causes a dose-dependent decline in the extent of cell death. These results show that GS is a potent neuroprotectant and that elevation of GS expression in glial cells activates an endogenous mechanism whereby neurons are protected from the deleterious effects of excess glutamate in extracellular fluid after trauma or ischemia. Our results suggest new approaches to the clinical handling of neuronal degeneration.

Cross-linking of porin with glutardialdehyde: a test for the adequacy of premises of cross-linking theory.

Exposure of porin from Escherichia coli to glutardialdehyde followed by SDS-gel electrophoresis in 3% polyacrylamide yielded three bands that were identified in order of decreasing mobility as monomers and two and three cross-linked polypeptide chains. The distribution of protein among the three species for different extents of reaction showed a remarkably good agreement with corresponding values predicted from cross linking theory for an oligomer composed of three identical subunits arranged according to a 3-fold rotation axis. Electrophoresis performed in 7.5% polyacrylamide yielded four bands that were assigned to polypeptide chain monomers, dimers, and two types of trimers carrying two and three intersubunit cross-links. Our findings provide evidence that the central premise of cross-linking theory, viz. that the intersubunit cross-links formed upon exposure of a protein to a bifunctional reagent be governed by the symmetry of the molecule, is valid. Careful interpretation of cross-linking experiments thus proves an effective method to assess the oligomeric structure of a protein and reveal the symmetry underlying the spatial arrangement of the subunits within the molecule.

Perioperative prophylactic cephazolin in spinal surgery. A double-blind placebo-controlled trial.

We investigated the efficacy of a single dose of 1 g of cephazolin in reducing postoperative infections in patients undergoing 'clean' operations on the lumbar spine. In a double-blind, randomised, trial there were 21 wound or urinary infections in the 71 patients who received placebo and nine in the 70 who received cephazolin (p < 0.05). Nine of the placebo patients (12.7%) developed wound infections (complicated by bacteraemia in two) compared with three (4.3%) in the cephazolin group (p = 0.07). Hospital stay was longer for infected patients than for non-infected patients (p < 0.05). Cephazolin-resistant pathogens were isolated more frequently from patients who received cephazolin than from those who received placebo.

Molecular symmetry and arrangement of subunits in extracellular hemoglobin from Caenestheria inopinata.

The subunit structure of extracellular hemoglobin from the clam shrimp Caenestheria inopinata was studied using the method of cross-linking by bifunctional reagents followed by SDS/PAGE. Two phases were distinguished in the cross-linking by glutardialdehyde: a fast phase characterized by the appearance of two bands in electrophoresis corresponding to single polypeptide chains and cross-linked chain pairs, and a slow phase where five bands corresponding to even numbers, 2-10, of cross-linked polypeptide chains are observed. Theoretical curves for the distribution of protein among the various cross-linked species were calculated assuming allowed arrangements of ten identical subunits. Equally good descriptions of the cross-linking were provided by two models with dihedral symmetry: a ring arrangement with two types of alternating interactions and a two-layered eclipsed arrangement with one type of interaction between subunits from different layers and another between subunits within the same layer. A way out of the ambiguity was found by carrying out the fast phase of the cross-linking reaction with dimethyl-3,3'-dithiobispropionimidate.2HCl, a bifunctional reagent containing an S-S bond that can be cleaved by 2-mercaptoethanol, following up with glutardialdehyde in the slow phase. The observation in the presence of 2-mercaptoethanol of electrophoretic bands corresponding to trimeric and higher cross-linked polypeptide chain species rules out the alternating ring and confirms the two-layered eclipsed model. The arrangement of subunits found in this work from consecutive cross-linking can account satisfactorily for molecular profiles previously obtained from electron microscopy of Caenestheria hemoglobin.

The effect of dibromochloropropane (DBCP) on in vitro cyclic AMP levels and testosterone production in rat testes.

Adult male rats were injected s.c. once a week for 3 weeks with DBCP, 20 mg/kg BW. Animals were sacrified 20 weeks after last injection. Body and testes weights were recorded and testes were taken for standard histological preparation and for in vitro experiments. The in vitro experiments were carried out on testes slices (90-110 mg) incubated for 3 h with or without the addition of hCG to the incubation medium. Cyclic AMP content of the tissue as well as testosterone released into the incubation medium were determined. Testes weights of DBCP treated animals were 68% lower than that of controls. All semiferous tubules were damaged and shrunken, thus, their number per microscope field was 2.6 times that of controls. Cyclic AMP levels in testes slices were similar in both DBCP treated and controls. The addition of hCG stimulated cyclic AMP accumulation to a much higher level in the DBCP treated than in controls. When calculated per one pair of testes the content in unstimulated pair was more than twice that of DBCP treated. Stimulation of hCG increased both DBCP treated and controls to similar levels. Testosterone release into the medium by slices was higher in DBCP treated than in controls and so was also the increment due to hCG stimulation. Similar results were obtained when testosterone release was calculated per one pair of testes. It is suggested that since the major testicular compartment damaged by DBCP is the tubular one, the proportion of the interstitium per testicular unit weight is larger than in controls, thus, cyclic AMP content increment due to hCG stimulation is much higher.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproductive performance of dibromochloropropane-treated female rats.

Dibromochloropropane (DBCP) is an effective nematocide which has been shown to suppress spermatogenesis and cause infertility in both men and male rats. There are no similar reports concerning the effects of DBCP on female reproduction. The purpose of the present study was to attempt to interfere with the various phases of oogenesis. Proestral or pregnant rats were injected subcutaneously once with 40 mg/kg DBCP on one of each days of L12-L20 of gestation; a double dose (80 mg/kg) was injected in eight consecutive days (L11-L18). In addition, L13 fetuses were injected--directly into the amniotic sac--with 0.1 mg DBCP. Pooled data from the various days of gestation revealed that postimplantation losses were three times as high in the DBCP-treated animals as in DMSO-treated controls. Perinatal deaths were 58% higher and mean pup weights were 30% lower in the DBCP-treated rats than in controls. The reproductive performance of females exposed to DBCP while in utero was affected only to a limited degree (reduced number of ovulations and implantations) as compared with their DMSO counterparts. Doubling the dose (80 mg/kg) seriously reduced the birth weight of pups (50% of controls), all of which died within several hours post-partum. Direct injection of DBCP into embryos or to proestral rats did not have any adverse effects on their future reproductive performance. In contrast to the effect on spermatogenesis, it appears that oogenesis and ova are unaffected by DBCP.

Spinal cord involvement as the presenting symptom of acute monocytic leukemia.

Spinal cord involvement in leukemia is rare and has been described only once in association with acute monocytic leukemia. A patient whose presenting symptom of acute monocytic leukemia was the syndrome of cauda equina compression due to an epidural and retroperitoneal leukemic mass is reported. Peripheral blood smears were normal throughout the evolution of the disease. The radiological, surgical, and pathological findings are presented, and the therapeutic, along with the prognostic implications of spinal cord involvement by leukemia are discussed.

Long term effects of dibromochloropropane (DBCP) on male rats' reproductive system.

Adult male rats were injected s.c. once a week for 3 weeks with DBCP, 20 mg/kg B.W. Animals were sacrificed 5, 9, 13, 17, 25 and 50 weeks after last injection. Body weight was recorded once a week. Prior to sacrifice each male was presented with proestral females in order to determine the male's mating behaviour and fertility. Testes were removed, weighed and taken for standard histological examination. DBCP treatment caused a reduction of body weight which reverted back to control levels some 17 weeks post injection. Testes weights were reduced and remained low despite the recovery of body weight. Generally, all males showed normal mating behaviour but most of them were infertile. Testicular histology showed a correlation between decreasing testicular weight and increasing percentage of degenerated seminiferous tubules, which was on the other hand correlated with decreasing tubular diameter. Serum levels of FSH and LH were significantly increased in the infertile DBCP treated males while values for the fertile ones were similar to those of controls. There were no differences in serum testosterone levels between DBCP treated and control animals. It is concluded that in DBCP treated rats testicular degenerative damages are associated with increased circulating gonadotrophin levels and with normal testosterone levels. Although mating behaviour is unaffected fertility is depressed and does not recover for at least 50 weeks post injection. It is suggested that DBCP treatment affects mainly the activity of the Sertoli cells while the Leydig cells are affected to a much lesser degree.

Spinal intradural ependymal cyst: a case report and review of the literature.

Spinal intradural ependymal cysts are extremely rare. The case presented is the sixth reported in the literature. The symptoms are consistent clinically and radiologically with a spinal intradural space-occupying lesion. The cyst wall is lined with both ciliated and nonciliated cells, resting directly on connective tissue. The exact embryonal origin of these cysts is obscure.

Unusual delayed onset of diabetes insipidus following closed head trauma. Case report.

A case of delayed onset of diabetes insipidus (DI), which developed 27 days after a closed head injury, is reported. The patient sustained only a minor neurological deficit and, except for antidiuretic hormone (ADH) insufficiency, hypothalamic function was intact. This selective damage of posterior pituitary function was total and permanent. Ischemia due to vascular injury may be the most likely etiology. Once the diagnosis of delayed posttraumatic DI is confirmed, the treatment of choice is DDAVP (desmopressin acetate). In contradistinction to DI immediately following minor head injury, most patients with a delayed onset of DI after trauma have permanent ADH deficiency.

The proprietary hospital industry: a financial analysis 1972-1982.

This paper evaluates the performance of both specific firms within the American for-profit hospital industry and the industry as a whole. First, traditional financial analysis is used to evaluate individual publicly traded for-profit chains. Then, industry performance from 1973 to 1982 is evaluated using a set of measures based on Modern Portfolio Theory. The traditional financial analysis indicates that the industry seems increasingly profitable as well as increasingly healthy from the perspective of utilizing its assets and reducing its collection period. However, the industry's rapid growth rate has strained its ability to use additional debt funding and has created a potentially dangerous liquidity position. Measures based on Modern Portfolio Theory indicate that the average return of the industry has improved over the past 5 years. However, its risk has also increased. Nevertheless, the increase in risk is more than offset by the increased average return. In addition, recent legislation designed 'to reward the efficient' has introduced a significant degree of uncertainty into the industry's performance for the coming years. Thus, hospitals' ability to maintain the substantial profitability and rate of growth they have experienced over the past decade will depend on how well they will adapt to the changing environment.

Thoracic disc herniation associated with papilledema. Case report.

The occurrence of papilledema in a patient with progressive spastic paraparesis due to herniation of the T11-12 intervertebral disc is reported. The papilledema resolved following discectomy. The association and possible pathogenetic mechanisms between spinal cord lesions and signs of raised intracranial pressure are reviewed.

Computerized tomography in combat-related craniocerebral penetrating missile injuries.

Our experience in the use of computerized tomography (CT) in the evaluation and treatment of combat-related penetrating missile injuries of the head in 12 cases is summarized. Advantages observed in the use of CT include accurate delineation of in-driven bony and metallic fragments, the relation of hematomas to the missile tract and detection of brain abscesses. The availability of a CT scanner for use in military medicine may further reduce the mortality and morbidity due to combat-related cranial missile injuries.

Brown-Séquard syndrome associated with brachial plexus injury in neck trauma.

A case of adult cervical trauma that resulted in a clinical picture of Brown-Séquard syndrome and unilateral brachial plexus injury is presented. Rotational hyperflexion of the cervical spine is thought to have resulted in subluxation of C5-6 with root avulsions, leading to this unusual combination of findings.