Biomedical subjects

M Rodriguez

Publications and source records attributed to M Rodriguez.

At least 217 records · Page 12Linked to original sources

PubMed1998

Perforin-dependent neurologic injury in a viral model of multiple sclerosis.

In this study we demonstrate perforin-mediated cytotoxic effector function is necessary for viral clearance and may directly contribute to the development of neurologic deficits after demyelination in the Theiler's murine encephalomyelitis virus (TMEV) model of multiple sclerosis. We previously demonstrated major histocompatability complex (MHC) class I-deficient (beta2m-deficient) mice with an otherwise resistant genotype develop severe demyelination with minimal neurologic disease when chronically infected with TMEV. These studies implicate CD8(+) T cells as the pathogenic cell in the induction of neurologic disease after demyelination. To determine which effector mechanisms of CD8(+) T cells, granule exocytosis or Fas ligand expression, play a role in the development of demyelination and clinical disease, we infected perforin-deficient, lpr (Fas mutation), and gld (Fas ligand mutation) mice with TMEV. Perforin-deficient mice showed viral persistence in the CNS, chronic brain pathology, and demyelination in the spinal cord white matter. Perforin-deficient mice demonstrated severely impaired MHC class I-restricted cytotoxicity against viral epitopes, but normal MHC class II-restricted delayed-type hypersensitivity responses to virus antigen. Despite demyelination, virus-infected perforin-deficient mice showed only minimal neurologic deficits as indicated by clinical disease score, activity monitoring, and footprint analysis. Perforin- and MHC class II-deficient mice (with functional CD8(+) T cells and perforin molecules and an H-2(b) haplotype) had comparable demyelination and genotype, however, only the latter showed severe clinical disease. Gld and lpr mice demonstrated normal TMEV-specific cytotoxicity and maintained resistance to TMEV-induced demyelinating disease. These studies implicate perforin release by CD8(+) T cells as a potential mechanism by which neurologic deficits are induced after demyelination.

Animals↗

PubMed1998

Failure of treatment with Linomide or oral myelin tolerization to ameliorate demyelination in a viral model of multiple sclerosis.

Both Linomide (quinoline-3-carboxamide) and tolerization with self-antigens have been demonstrated to successfully ameliorate demyelinating disease in experimental autoimmune encephalomyelitis (EAE). Based on the autoimmune hypothesis of multiple sclerosis (MS), both agents have been tested in clinical trials but have been found to be toxic or not efficacious. We investigated the efficacy of these immunomodulators in an alternative experimental model of MS, a virus-induced demyelinating disease. Oral administration of Linomide to Theiler's virus-infected mice beginning either at time of infection or at day 15 post-infection (p.i.) resulted in an increased percentage of spinal cord quadrants with demyelination. Administration of Linomide beginning at day 15 p.i. increased lesion size as compared to infected control-treated mice. Treatment with 80 mg kg(-1) day(-1) of Linomide beginning at the time of infection significantly increased the number of Theiler's murine encephalomyelitis virus (TMEV)-positive cells mm(-2) of spinal cord white matter. There were no differences in the amount of remyelination between mice treated with Linomide or water. However, chronically infected mice treated with Linomide had severely reduced spontaneous vertical activity as measured using a activity wheel. Oral tolerization of mice with mouse or bovine myelin had no effect on virus-induced demyelination or virus antigen expression. The contrasting results obtained between the TMEV model and the autoimmune model of demyelination do not support recent reports suggesting that the underlying mechanism of demyelination in the Theiler's model is autoimmune.

Adjuvants, Immunologic↗

PubMed1998

Confirmation and quantitation of selected sulfonylurea, imidazolinone, and sulfonamide herbicides in surface water using electrospray LC/MS.

A multianalyte method has been developed for the confirmation and quantitation of 16 selected sulfonylurea, imidazolinone, and sulfonamide herbicides in surface water. Samples are acidified, the analytes are extracted using RP-102 extraction cartridges, and the extracts are cleaned-up using an anion-exchange cartridge (SAX) stacked on top of an alumina cartridge. The final extracts are evaporated to dryness, redissolved in 10:90 or 20:80 acetonitrile/water, and analyzed using electrospray LC/MS. Confirmation criteria were defined so that identification of the analytes could be made with a reasonable degree of scientific certainty. Confirmation required that (1) LC/MS retention times of the analytes be within 1% of the retention times of the standards, (2) the molecular ion and two characteristic fragment ions per analyte be present, and (3) ion abundance ratios of the fragment ions relative to the molecular ion be within 20% of the ion ratios obtained for the standards. Each of the analytes in all of the samples used to validate this method met these confirmation criteria. Quantitation of the analytes at 0.1 and 1.0 ppb was demonstrated, with average recoveries between 70% and 114% and relative standard deviations that were less than 13%. The limit of quantitation (LOQ) for this method is 0.1 ppb (ng/mL) for all analytes. Six water types were used for the validation of this method.

Acetolactate Synthase↗

PubMed1998

Efficacy of lamivudine in controlling hepatitis B virus recurrence after liver transplantation.

BACKGROUND: Indication of liver transplantation for patients infected with hepatitis B virus (HBV) remains controversial because of the high incidence of posttransplant HBV recurrence and aggressive involvement of the allograft. In this article, we provide evidence that the introduction of lamivudine may favorably alter the prognosis of these patients. METHODS: Lamivudine was used in 40 HBV-infected adult patients suffering from chronic end-stage liver disease who underwent liver transplantation. The drug was used in the following settings: failure of prolonged passive immunoprophylaxis, elective conversion from immunoprophylaxis, de novo posttransplant HBV infection, and primary treatment with lamivudine which started before and continued after transplantation. Twenty patients (50%) had viral replication at the time lamivudine was started. Posttransplant and antiviral treatment follow-ups were 8-64 months (median follow-up: 27.5 months) and 9-39 months (median follow-up: 19 months), respectively. RESULTS: The patient and graft survival rates were 97.5% (39/40). Thirty-three patients (82.5%) have remained free of viral recurrence. In the seven re-infected patients, the manifestations of HBV involvement of the allograft have been mild. There have been no side effects related to lamivudine, and the treatment is substantially less costly than with other anti-HBV agents. CONCLUSIONS: Compared with historic series utilizing other modalities of treatment, the use of lamivudine has, so far, yielded superior results. This drug may be an important acquisition for antiviral prophylaxis in HBV-infected liver recipients. Because of the risk of viral mutations, however, efforts should proceed to achieve more efficacious methods for prevention and control of HBV recurrence.

Adult↗

PubMed1998

Theiler's virus infection of genetically susceptible mice induces central nervous system-infiltrating CTLs with no apparent viral or major myelin antigenic specificity.

Intracranial infection of susceptible mice with Theiler's virus results in persistent infection and spinal cord demyelination similar to human multiple sclerosis. While central nervous system infiltrating lymphocytes (CNS-ILs) in these mice display no virus-specific CTL activity, the cells were found to be activated killers using a specificity-independent assay. We previously demonstrated that the depletion of T cells in persistently infected mice significantly decreases demyelinating disease. Consequently, we have investigated the killing pathways employed by CNS-ILs that are isolated from persistently infected animals, the relative contribution of CD4 and CD8 cells in the generation of these CTLs, and the reactivity of this cell population to two putative autoantigens in the CNS. In vitro or in vivo manipulation of T cell populations using Abs or genetic knockout strategies demonstrate that the cytotoxic activity is primarily mediated by CD8+ T cells, and that perforin is an important molecule in the effector pathway. Since effector functions in infected mice were not inhibited by the depletion of CD4 cells with mAb but was blocked genetically in CD4 knockout mice, CD4+ T cells appear to play a helper role in the generation of CD8+ CTLs. We found no evidence of autoimmune-mediated demyelination, as the CD8+ CTLs were not reactive to two major myelin autoantigens, myelin basic protein and proteolipid protein. Our finding that CNS-ILs that are isolated from mice susceptible to persistent virus infection are neither specific for virus or myelin autoantigens is consistent with the possibility that CD8+ CTLs mediate CNS damage as a result of nonspecific activation by virus.

Animals↗

PubMed1998

Potent dipeptide inhibitors of the pp60c-src SH2 domain.

The design, synthesis, and evaluation of dipeptide analogues as ligands for the pp60c-src SH2 domain are described. The critical binding interactions between Ac-Tyr-Glu-N(n-C5H11)2 (2) and the protein are established and form the basis for our structure-based drug design efforts. The effects of changes in both the C-terminal (11-27) and N-terminal (51-69) portions of the dipeptide are explored. Analogues with reduced overall charge (92-95) are also investigated. We demonstrate the feasibility of pairing structurally diverse subunits in a modest dipeptide framework with the goal of increasing the druglike attributes without sacrificing binding affinity.

Crystallography, X-Ray↗

PubMed1998

The formation of a covalent complex between a dipeptide ligand and the src SH2 domain.

The X-ray crystal structure of the src SH2 domain revealed the presence of a thiol residue (Cys 188) located proximal to the phosphotyrosine portion of a dipeptide ligand. An aldehyde bearing ligand (1) was designed to position an electrophilic carbonyl group in the vicinity of the thiol. X-ray crystallographic and NMR examination of the complex formed between (1) and the src SH2 domain revealed a hemithioacetal formed by addition of the thiol to the aldehyde group with an additional stabilizing hydrogen bond between the acetal hydroxyl and a backbone carbonyl.

Aldehydes↗

PubMed1998

Expression of the human histocompatibility leukocyte antigen DR3 transgene reduces the severity of demyelination in a murine model of multiple sclerosis.

The role of various MHC genes in determining the progression of multiple sclerosis (MS) remains controversial. The HLA-DR3 gene has been associated with benign relapsing MS in some genetic epidemiologic studies, but with disease progression in others. We induced demyelination in highly susceptible B10.M and B10.Q mice expressing the DR3 (HLA-DRB1*0301) transgene to determine directly the effects of a human transgene by infecting them with Theiler's murine encephalomyelitis virus (TMEV). DR3+ mice experienced a dramatic reduction in the extent and severity of demyelination compared with DR3- littermate controls, whereas anti-TMEV antibody titers, delayed-type hypersensitivity responses, and levels of infectious virus, virus antigen, and virus RNA were similar in both groups. To address a possible mechanism of how the human transgene is reducing virus-induced demyelination, we analyzed cytokine expression in the lesions and also determined whether B10.M mice can respond to peptides derived from the DR3 molecule. Intense staining for IFN-gamma and IL-4, T helper (TH) 1 and TH2 cytokines, respectively, was found in the lesions of TMEV-infected DR3- mice but not in the DR3+ transgenic mice at day 21 after infection. DR3 peptides elicited strong proliferative responses in B10.M mice but not in B10.M (DR3+) mice. These experiments are the first to demonstrate that a human class II DR gene can alter the severity of demyelination in an animal model of MS without influencing viral load. These experiments are consistent with a mechanism by which DR3 reduces demyelination by altering the cytokine expression in the lesions, possibly by deleting T cells involved in virus-induced pathology.

Animals↗

PubMed1998

Acceleration in the rate of CNS remyelination in lysolecithin-induced demyelination.

One important therapeutic goal during CNS injury from trauma or demyelinating diseases such as multiple sclerosis is to develop methods to promote remyelination. We tested the hypothesis that spontaneous remyelination in the toxic nonimmune model of lysolecithin-induced demyelination can be enhanced by manipulating the inflammatory response. In PBS-treated SJL/J mice, the number of remyelinating axons per square millimeter of lesion area increased significantly 3 and 5 weeks after lysolecithin injection in the spinal cord. However, methylprednisolone or a monoclonal antibody (mAb), SCH94.03, developed for its ability to promote remyelination in the Theiler's virus murine model of demyelination, further increased the number of remyelinating axons per lesion area at 3 weeks by a factor of 2.6 and 1.9, respectively, but did not increase the ratio of myelin sheath thickness to axon diameter or the number of cells incorporating tritiated thymidine in the lesion. After 3 weeks, the number of remyelinating axons in the methylprednisolone or mAb SCH94.03 treatment groups was similar to the spontaneous remyelination in the 5 week PBS control-treated group, indicating that these treatments promoted remyelination by increasing its rate rather than its extent. To address a mechanism for promoting remyelination, through an effect on scavenger function, we assessed morphometrically the number of macrophages in lesions after methylprednisolone and mAb SCH94.03 treatment. Methylprednisolone reduced the number of macrophages, but SCH94.03 did not, although both enhanced remyelination. This study supports the hypothesis that even in toxic nonprimary immune demyelination, manipulating the inflammatory response is a benefit in myelin repair.

Animals↗

PubMed1998

Inflammatory potential of C-reactive protein complexes compared to immune complexes.

C-reactive protein (CRP) is an acute phase serum protein that binds to phosphocholine (PC) and to components of damaged tissue. CRP resembles antibody in that it binds to ligands and activates the classical complement pathway. To compare the processing of CRP complexes to that of IgG complexes, we have prepared complexes containing the same ligand, PC-conjugated BSA, and IgG antibody to either BSA or CRP. We previously demonstrated similar complement-mediated binding of these complexes to erythrocyte complement receptors. CRP and IgG also bind to receptors on neutrophils (PMN), providing another possible pathway for clearance of ligands. PMN binding of IgG complexes can lead to activation with damaging inflammatory consequences. In the present report we have used CRP and IgG complexes containing PC-BSA to compare binding to PMN and activation of PMN adherence to endothelial cells. The results indicate that CRP complexes do not activate PMN whereas IgG complexes do. Binding assays indicate that there is substantially greater binding of IgG than CRP complexes to PMN.

Animals↗

PubMed1998

Interferon-gamma in progression to chronic demyelination and neurological deficit following acute EAE.

The cytokine interferon-gamma (IFNgamma) is implicated in the induction of acute CNS inflammation, but it is less clear what role if any IFNgamma plays in progression to chronic demyelination and neurological deficit. To address this issue, we have expressed IFNgamma in myelinating oligodendrocytes of transgenic mice. MHC I immunostaining and iNOS mRNA were upregulated in their CNS, but such transgenic mice showed no spontaneous CNS inflammation or demyelination, and the incidence, severity, and histopathology of experimental autoimmune encephalomyelitis (EAE) were similar to nontransgenic controls. In contrast to control mice, which remit from EAE with resolution of glial reactivity and leukocytic infiltration, transgenics showed chronic neurological deficits. While activated microglia/macrophages persisted in demyelinating lesions for over 100 days, CD4(+) T lymphocytes were no longer present in CNS. IFNgamma therefore may play a role in chronic demyelination and long-term disability following the induction of demyelinating disease. Because IFNgamma may have neural as well as immune-infiltrating origins, these findings generate a new perspective on its role in the CNS.

Animals↗

PubMed1998

The PTH-calcium relationship during a range of infused PTH doses in the parathyroidectomized rat.

To establish the PTH dosage that maintains normal mineral homeostasis in the PTX rat, a series of doses of rat 1-34 PTH were infused via a subcutaneously implanted miniosmotic pump. The doses were 0, 0.011, 0.022, 0.044, and 0.11 microg/100 g/hour. After 48 hours, serum calcium ranged from 5.56 +/- 0.02 to 16.29 +/- 0.25 mg/dl, ANOVA P < 0.001, and serum phosphorus from 12.49 +/- 0.03 to 5.33 +/- 0.34 mg/dl, ANOVA P < 0.001. By post hoc test, the serum calcium level was different (P < 0.05) at every PTH dose; the serum phosphorus level was different (P < 0.05) at every PTH dose except between the two highest doses. The PTH dosage that produced a normal serum calcium (10.09 +/- 0.10 mg/dl) and phosphorus (6.90 +/- 0.18 mg/dl) was 0.022 microg/100 g/hour. The relationship between increasing doses of PTH and both serum calcium and phosphorus was curvilinear and the calcium-phosphorus product was remarkably constant from a serum calcium of 7-13 mg/dl. The increase in serum calcium and the decrease in serum phosphorus were more rapid at lower than at higher PTH doses so that for both, an asymptote was reached. At the highest serum calcium values, the calcium-phosphorus product increased and in individual rats, an increase in serum phosphorus was associated with a decrease in serum calcium. In summary, this study shows that (1) for rat 1-34 PTH, the normal replacement dose in the PTX rat with normal renal function on a normal diet is 0.022 microg/100 g/hour; (2) the relationship between PTH and both serum calcium and phosphorus is curvilinear, and an asymptote is reached for both; and (3) the calcium-phosphorus product is remarkably constant as the serum calcium increases from 7 to 13 mg/dl and only increased during marked hypercalcemia when serum phosphorus did not decrease further or even tended to increase.

Analysis of Variance↗

PubMed1998

[Single ventricle (cor trilocular biatriatum). A case report].

Univentricular hearts represent rare complex cardial malformations. We report a case of a 34-year old male with single ventricle, two atria, tricuspid atresia, large atrial septal defect, complete transposition and pulmonary valvar stenosis. There were no signs of chronic pulmonary hypertension. Intensive clinical analysis of the cardiac malformation was first performed at the age of five years. Conclusion was that the patient would have no benefit from operation. The patient had nearly normal live conditions with a profession, family and some sportive activities like squash. He died of sudden cardiac death. The malformation was examined by sequential segmental analysis and in comparison with the embryonic development. Special features are emphasized. Clinical picture, prognosis and therapy are reported from literature. During the last years development of cardiac surgery achieved good results. Special morphologic constellations, as in our case, may be the reason that conservative therapy can be sufficient for prolonged survival with good quality of life.

Adult↗

PubMed1998

Quantal processing of visual information in the brain.

In order to test if vision is a continuous processing system that analyses information immediately after it arrives at the retina or a discontinuous system that accumulates information and periodically analyses a data quantum, the time required by 38 healthy adults to solve simple visual tasks was accurately quantified. The main finding of the present study was that the processing time for visual tasks is always a multiple of a basic unit whose duration was 30-40 ms. Present data support the hypothesis that visual information is processed in the brain with a discontinuous flow of discrete-time quanta. Data suggest two processing ways for the visual system, one that with a high time-resolution (30-40 ms) operates under high-illumination conditions, and the other that with a low time-resolution (100-120 ms) is put into operation in low-illumination conditions.

Adult↗

PubMed1998

Safety and tolerance of medical nutritional products as sole sources of nutrition in people on hemodialysis.

OBJECTIVE: Establish and compare the safety and tolerance of three medical nutritional products when used as sole sources of nutrition in stable hemodialysis patients. DESIGN: Prospectively randomized, controlled, single blind, parallel design. SETTING: Three outpatient hemodialysis clinics. PARTICIPANTS: Seventy-nine normally nourished, stable, anuric, adequately dialyzed, adult outpatients with end-stage renal disease (ESRD) and requiring thrice weekly hemodialysis. INTERVENTION: A 3-week trial was conducted. During the first week, baseline medical history and physical examination, gastrointestinal symptom, urea kinetic, bowel habit, and biochemical data were collected while participants ingested their usual diet. During the last 2 weeks, the same data were collected while participants orally ingested 35 kcal/kg actual weight/d of one of three medical nutritional products as a sole source of nutrition. Products were a standard medical nutritional (EN-9527) and two renal nutritionals (EN-9528 and EN-9529). The latter product was a reformulation of EN-9528 and contained added beta-carotene and fructooligosaccharides. MAIN OUTCOME MEASURES: Gastrointestinal symptoms, bowel habits (stool frequency and consistency), routine blood chemistries, urea kinetics, and normalized protein catabolic rate (nPCR) RESULTS: All three groups achieved a mean energy and protein intake of approximately 35 kcal/kg/d and 1.25 g protein/kg/d during the last 10 days of the sole source feeding period. Adherence with the formula ingestion targets was assessed using both a patient-completed product consumption log and nPCR. By intent to treat analysis, there were no changes in number or severity of gastrointestinal symptoms, stool frequency or stool consistency, or urea kinetics between the baseline week and during product consumption. In comparison to the standard formulation, the disease-specific formulations resulted in improved serum phosphorus and calcium-phosphorus product. Patients receiving the fructooligosaccharide-containing product (EN-9529), by Chi-squared analysis, had less constipation than for the comparable product without oligosaccharides (EN-9528) or the standard medical nutritional (EN-9527). CONCLUSION: Use of enteral nutritionals as a sole source of nutrition is both possible and well tolerated in hemodialyzed patients. Selection of a disease-specific formulation offered advantages over a standard formulation in the management of biochemical complications of renal disease when the products were used as a sole source of nutrition.

Blood Urea Nitrogen↗

PubMed1998

Effect of serum phosphate on parathyroid hormone secretion during hemodialysis.

BACKGROUND: Recent studies have demonstrated that a high concentration of phosphate directly stimulates parathyroid hormone (PTH) secretion. High serum levels of phosphate are usually observed in patients with end-stage renal disease. The aim of the present study was to evaluate whether serum phosphate concentration had an acute effect on PTH secretion in hemodialysis patients. The levels of serum phosphate were manipulated during the hemodialysis session by using a phosphate free dialysate or a dialysate with a high content of phosphate. METHODS: Ten stable hemodialysis patients with PTH values above 300 pg/ml were included in the study. A PTH-calcium curve was obtained during both high phosphate and phosphate free hemodialysis. RESULTS: The serum phosphate concentration remained high (2.17 +/- 0.18 mM) throughout the high phosphate hemodialysis and decreased progressively to normal levels (1.02 +/- 0.06 mM) during the phosphate free hemodialysis. The serum PTH levels at maximal inhibition by hypercalcemia (minimal PTH) were greater during the high phosphate than the phosphate free hemodialysis (413 +/- 79 vs. 318 +/- 76 pg/ml, P < 0.003). In all patients the values of minimum PTH were greater during the high phosphorus than the phosphorus free hemodialysis. The values of maximally stimulated PTH during hypocalcemia and the set point of the PTH-calcium curve were similar during the high phosphate and the phosphate free hemodialysis. CONCLUSION: The maintenance of high serum phosphorus levels during hemodialysis prevented, in part, the inhibition of PTH secretion by calcium, which strongly suggests that in hemodialysis patients high serum phosphate contributes directly to the elevation of PTH levels despite normal or high serum calcium concentration.

Adult↗

PubMed1998

Protective role of the Mycobacterium smegmatis IdeR against reactive oxygen species and isoniazid toxicity.

OBJECTIVE: To understand the mechanism by which IdeR is necessary for maintaining wild type levels of KatG and SodA enzyme activity and normal isoniazid (INH) resistance. DESIGN: To identify the step(s) of SodA and KatG function that were affected by the ideR mutation, quantitative western immunoassays and ribonucleic acid (RNA) hybridizations were performed. To see if the increased INH sensitivity of the ideR mutant was caused by lower SodA activity, the Mycobacterium smegmatis sod gene was inactivated. RESULTS: The levels of KatG and SodA mRNA and protein in the M. smegmatis IdeR mutant are decreased to approximately 20-40% of those observed in the wild type parent strain. This is quantitatively similar to the decrease in KatG and SodA enzyme activities originally observed in the ideR strain. The M. smegmatis sodA mutant was slightly more sensitive to INH, compared to the wild type strain and was more resistant than the ideR mutant. CONCLUSION: IdeR is necessary for full expression of the M. smegmatis katG and sodA genes. It is not yet known whether this protein acts directly at the gene level. The lower levels of SodA contribute slightly to the increased susceptibility to INH of the ideR mutant, but cannot explain the magnitude of the INH sensitivity observed when IdeR is not present. These data suggest that IdeR is a regulator of the cellular stress response, as it has a protective role in cells facing environmental stresses, such as increased levels of reactive oxygen species and INH toxic intermediates. These conclusions do not necessarily apply to IdeR's role in M. tuberculosis physiology, since we have not inactivated its gene in this pathogen.

Antitubercular Agents↗

PubMed1998

Multiple sclerosis: lessons from neuropathology.

The focus of multiple sclerosis (MS) research has been on attempts to identify the specific pathogenic mechanism responsible for producing the multifocal central nervous system inflammatory demyelinating lesions. However, extensive in vitro and in vivo evidence suggests that multiple different immunological mechanisms may produce the typical demyelinated plaque. A detailed examination of actively demyelinating MS lesions reveals a profound heterogeneity in the structural and immunopathological patterns of demyelination and oligodendrocyte pathology between different MS patients, suggesting multiple pathogenic mechanisms may contribute to oligodendrocyte and myelin injury in MS. These observations raise the question whether MS may be a neurological syndrome with different immunopathological mechanisms triggering a common pathway rather than a single disease with a uniform mechanism of myelin destruction. With the advent of new tools for neurobiological and immunological research applied to actively demyelinated MS lesions, an opportunity exists to reevaluate MS neuropathology. This review highlights the spectrum of the inflammatory demyelinating diseases, the multitude of effector mechanisms that may produce myelin destruction, and the pathologic heterogeneity observed in MS lesions. A careful evaluation of MS neuropathology should provide important clues regarding the induction, target, evolution, and pathogenesis of this complex disease.

Autoantibodies↗