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Biomedical subjects

I Garcia

Publications and source records attributed to I Garcia.

At least 91 records · Page 5Linked to original sources
PubMed1997

Prevention of autoimmune diabetes mellitus in NOD mice by transgenic expression of soluble tumor necrosis factor receptor p55.

The non-obese diabetic (NOD) mouse represents a relevant animal model of autoimmunity for insulin-dependent diabetes mellitus. The pathogenic role of tumor necrosis factor (TNF) in insulitis and beta cell destruction observed in these mice remains controversial, since injections of TNF or of anti-TNF antibodies have been reported to exert protection or acceleration of diabetes, depending on the timing of administration. In this study, we demonstrate that, in contrast to the non-transgenic littermates, NOD mice with permanent neutralization of TNF by high blood levels of soluble TNF receptor p55-human FcIgG3-fusion molecules resulting from the expression of a transgene are protected from spontaneous diabetes. They are also protected from accelerated forms of disease caused by transfer of NOD spleen cells or cyclophosphamide injections. This protection is associated with a marked decrease in the severity and incidence of insulitis and in the expression of the adhesion molecules MAdCAM-1 and ICAM-1 on the venules of pancreatic islets. These data suggest a central role for TNF-alpha in the mediation of insulitis and of the subsequent destruction of insulin-secreting beta-cells observed in NOD mice. They may be relevant to cell-mediated autoimmune diseases in general, in which treatment with soluble TNF receptors might be beneficial.

Animals↗
PubMed1997

High sensitivity of transgenic mice expressing soluble TNFR1 fusion protein to mycobacterial infections: synergistic action of TNF and IFN-gamma in the differentiation of protective granulomas.

To investigate the role of tumor necrosis factor (TNF) in protective immune responses to Mycobacterium tuberculosis and M. bovis Bacillus Calmette Guérin (BCG), we have used transgenic mice unable to use TNF because of the expression of high amounts of a soluble TNF receptor (R) type I (sTNFR1) fusion protein, and studied resistance of these mice to infection by lethality assays, evaluation of bacterial recovery and histologic examination. These mice showed a strongly increased sensitivity to M. tuberculosis and BCG infections, with bacterial overgrowth and marked inhibition of macrophage differentiation within granulomas; after M. tuberculosis infection, this resulted in extensive lesions of caseous necrosis in the lung. To explore the respective roles of TNF and interferon (IFN)-gamma in resistance to BCG and granuloma differentiation, controls and sTNFR1-transgenic mice were compared to IFN-gammaR mutant mice and mice double defective in TNF and IFN-gamma activity (obtained by crossing transgenic and mutant mice). The three groups of deficient mice showed a strongly enhanced susceptibility to BCG infection, with the following decreasing order of sensitivity between groups: TNF + IFN-gamma --> TNF --> IFN-gamma-deficient mice. The hepatic granulomas of IFN-gammaR mutant mice were small and contained eosinophils but few differentiated macrophages; compared to those of sTNFR1-transgenic mice, acid-fast bacilli were less numerous within the macrophages. Granulomas of double-deficient mice were strikingly different by their very large size and cellular content, made up large numbers of polymorphonuclears, eosinophils, and cells undergoing apoptosis, but without detectable differentiated macrophages; acid-fast bacilli were spread in the lesions. These studies show the essential role of both TNF and IFN-gamma in the development, during mycobacterial infections, of protective granulomas containing highly differentiated macrophages capable of destroying ingested bacteria, and emphasize that these two cytokines act synergistically in granuloma formation.

Animals↗
PubMed1997

Effects of an immune-enhancing diet in critically injured patients.

OBJECTIVE: To determine the effects of an immune-enhancing experimental diet (XD = supplemental arginine, trace elements, and increased omega-3 fatty acids) versus standard diet (SD), on immune cell function and clinical outcome of critically injured patients. DESIGN: Prospective randomized clinical trial of patients admitted to the surgical intensive care unit after trauma (Injury Severity Score > 13). MATERIALS AND METHODS: Patients received early enteral nutrition with either XD or SD for a minimum of 5 days. MEASUREMENTS: Mortality, intensive care unit, ventilator, and hospital days, as well as incidence of adult respiratory distress syndrome (ARDS) and infectious complications were recorded. Nutritional parameters were also studied. Peripheral blood leukocytes were isolated from normal volunteers and from patients on days 1, 6, and 10 of feeding. MAIN RESULTS: Demographics and injury severity were similar in both groups. Both SD (n = 21) and XD (n = 22) groups revealed depressed monocyte function (tumor necrosis factor, prostaglandin E2, and procoagulant activity) on day 1 compared with a reference group (p < 0.05). However, monocytes from XD patients began to "normalize" their response (tumor necrosis factor, prostaglandin E2, and procoagulant activity) by day 6. Although ARDS occurred more frequently in the XD group (45 vs. 19%), the majority of ARDS in both groups occurred very early, with only three patients in the XD (13.6%) and one patient in the SD (4.7%) groups developing ARDS after study entry. XD patients remained on the ventilator longer (16.4 vs. 9.7 days) and in the hospital longer (32.9 vs. 22 days) compared with the SD group, but overall mortality was nearly identical (4.5 vs. 5%). CONCLUSION: The exact role and timing for diets with immune-enhancing effects has yet to be defined.

Adjuvants, Immunologic↗
PubMed1997

Evidence for a protective role of tumor necrosis factor in the acute phase of Trypanosoma cruzi infection in mice.

A possible role for tumor necrosis factor (TNF) alpha during Trypanosoma cruzi infection was explored by using transgenic mice expressing in blood high levels of a soluble TNFR1-FcIgG3 fusion protein, which neutralizes the effects of TNF in vivo. Nontransgenic littermates were used as controls. The transgenic mice showed high susceptibility to T. cruzi infection. Inocula sublethal for control mice resulted in over 80% mortality associated with higher levels of parasites in the blood. In histological sections of the hearts of transgenic mice, large parasitic clusters without inflammatory cell infiltrates around the parasites were seen, while smaller parasitic clusters associated with leukocytes were seen in control mice. No difference in specific antibody response or lymphocyte composition of the spleen was found between transgenic and control mice, although the unresponsiveness of spleen cells to concanavalin A stimulation in vitro, typical of the acute phase of T. cruzi infection, was less pronounced in transgenic mice. Infected transgenic mice produced higher levels of gamma interferon than did control mice. These results confirm that TNF is involved in mechanisms leading to parasite clearance and protection from death in the acute phase of T. cruzi infection. More importantly, the data reveal that TNF is necessary for the establishment of effective tissue inflammation and parasite load control in acute experimental Chagas' disease myocarditis.

Acute-Phase Reaction↗
PubMed1997

Central epithelial odontogenic ghost cell tumour. A case report.

Central epithelial odontogenic ghost cell tumour, a neoplastic variant of calcifying odontogenic cyst, is a rare lesion with a very few cases published in the English literature. Histologically, the tumour consists of clusters of infiltrating odontogenic epithelium and ghost cells in varying numbers. We describe the first case of central epithelial odontogenic ghost cell tumour occurring in a pregnant woman and in which determination of bone densitometry in the preoperative panoramic radiographs has been performed. We have reviewed the literature available in English and compared it with our case.

Adult↗
PubMed1996

Inhibition of submandibular and lacrimal gland infiltration in nonobese diabetic mice by transgenic expression of soluble TNF-receptor p55.

Besides a prominent mononuclear cell infiltration of the islets of Langerhans, nonobese diabetic (NOD) mice also show massive cellular infiltrates of the submandibular and lacrimal glands concomitant with histological signs of tissue damage. To obtain insights into the mechanisms operative during the initiation and progression of tissue damage, we followed by in situ hybridization the appearance of cells containing mRNA of the gene encoding the proinflammatory cytokine TNF-alpha in the cellular infiltrates. Cells expressing TNF-alpha are mainly located in infiltrates, are absent in nonaffected glands, and are preferentially found among CD4 T cells. Secretion of TNF-alpha by gland-infiltrating cells was confirmed by an ELISPOT procedure. Direct evidence for an instrumental role of TNF-alpha in initiation and progression of submandibular and lacrimal gland infiltration is provided by the observed significant reduction in the extent of infiltration in nonobese diabetic mice transgenic for a soluble TNF receptor p55 fused to the Fc part of human IgG3. This protection from infiltration is paralleled by decreased expression of the adhesion molecules ICAM-1 and VCAM-1 in submandibular and lacrimal glands. These data suggest a central role of TNF-alpha in the initiation and progression of autoimmune tissue destruction of salivary glands and indicate beneficial effects of soluble TNF receptors in the treatment of organ-specific autoimmune diseases.

Animals↗
PubMed1996

Calcium and calmodulin regulate lipopolysaccharide-induced alveolar macrophage production of tumor necrosis factor and procoagulant activity.

BACKGROUND: Alterations in macrophage (M phi) function are responsible, in part, for adult respiratory distress syndrome and multiple organ failure developing in patients with sepsis. Elucidation and control of these M phi mechanisms during sepsis are crucial to our understanding of this disease and, ultimately, to improving survival of these patients. OBJECTIVE: To investigate the involvement of calcium flux in endotoxin-induced alveolar M phi production of tumor necrosis factor (TNF) and procoagulant (PC) activity. DESIGN: Rabbit alveolar M phi obtained by bronchoalveolar lavage were exposed to endotoxin in the form of lipopolysaccharide (LPS) extracted from Escherichia coli 0111:B4 in the presence of different specific calcium agonists and antagonists. The TNF expression was measured in the supernatant by L929 bioassays. The PC activity was determined in cell lysates by a one-step coagulation assay. RESULTS: Macrophages activated by LPS produce enormous levels of TNF and PC. Either W7 (20 mumol/L), a calmodulin antagonist, or TMB-8 (50 mumol/L), which prevents calcium release from the endoplasmic reticulum, inhibited production of both TNF and PC activity. Verapamil (50 mumol/L) alone or combined with TMB-8 significantly inhibited both TNF and PC production by LPS-stimulated M phi. Elevating intracellular calcium ([Ca2+]i), using the calcium ionophore, A23187, or thapsigargin alone, did not induce M phi production of TNF but significantly augmented LPS-stimulated TNF production. CONCLUSION: Our results indicate that increased intracellular calcium causing signal transduction activation through the calmodulin pathway is a necessary, but insufficient, component of the LPS signaling in M phi.

Animals↗
PubMed1996

Effects of supplemental dietary arginine, canola oil, and trace elements on cellular immune function in critically injured patients.

Dietary nutrients may have pharmacological value in modulating the immune system. We studied the effects of two enteral diets, which differed in their content of arginine, fat source, and select trace elements, on immune function in critically injured patients. Leukocytes were isolated from healthy volunteers and severely injured (ISS > 13) patients on the first, sixth, and tenth day of receiving either a standard diet or experimental diet. Monocytes were assayed for tumor necrosis factor, procoagulant activity, and prostaglandin E2 following endotoxin exposure. Neutrophil oxidant production and lymphocyte blastogenesis was assessed. Leukocyte function was uniformly depressed compared to normal patients on day 1. The response of leukocytes from patients receiving experimental diet improved or "normalized" by day 6, while remaining depressed in patients receiving standard diet. Dietary nutrient modification can effect cellular immune responses to inflammatory stimuli in severely injured patients.

Adolescent↗
PubMed1996

[Multicenter evaluation of thr Abbott glycosylated hemoglobin assay on IMx].

The Abbott IMx glycated hemoglobin assay was evaluated in a multicentre study. This method utilizes boronate affinity chromatography, and ion-capture technology. This assay determines both total glycohemoglobin (% GHb) and percentage of hemoglobin Alc (% HbAlc). The precision of the assay was evaluated: the intra-assay and interassay coefficients of variation were judged to be satisfactory (< 6.5%). We determined the accuracy of the assay by comparison with a reference HPLC assay for 603 specimens; coefficients of correlation were between 0.88 and 0.96. We studied the interference of bilirubin and glucose and found no interference at usual concentrations. The presence of abnormal hemoglobins (HbF and some Hb structural variants HbS, HbC) was not detected with the Abbott IMx assay; however, this assay showed no significant interference from the hemoglobin variants tested for heterozygous hemoglobinopathies (percentage of abnormal hemoglobin < 60%). We also determined normal values for HbAlc with this technology (164 specimens): 4.1 to 6.1%.

Chromatography, Affinity↗
PubMed1996

Oxidants augment endotoxin-induced activation of alveolar macrophages.

Endotoxin (lipopolysaccharide) stimulation of macrophages (M phi) induces the generation of toxic reactive oxygen intermediates (ROI); however, recent studies implicate intracellular redox changes in signal transduction pathways for cytokines. To test whether oxidant stress modulates M phi activation, rabbit alveolar M phi were exposed to the following: diamide (oxidizes intracellular glutathione); glucose oxidase (generates hydrogen peroxide); or xanthine oxidase (generates superoxide), before lipopolysaccharide. Supernatants were assayed for tumor necrosis factor (TNF) and cell lysates were assayed for procoagulant activity (PCA). TNF mRNA was analyzed by Northern blot. M phi exposure to diamide and glucose oxidase augmented TNF production, PCA expression, and TNF mRNA accumulation; however, xanthine oxidase exposure inhibited TNF production while augmenting PCA expression. M phi signal transduction can be enhanced by increasing cellular oxidant stress. The differential response of TNF versus PCA suggests the existence of distinct redox-sensitive signal transduction pathways. These data define a mechanism by which oxidants generated during inflammation may modulate M phi function.

Animals↗
PubMed1996

Recovery of unused operating room supplies for overseas orthopedic surgery.

Recovery of surplus operating room (OR) materials may contribute needed supplies to volunteer overseas surgical efforts. However, recovery often generates supplies that are highly heterogeneous in nature. In order to evaluate the nature and quantity of supplies useful to orthopedic surgical missions, the present investigation evaluated the material generated from 381 consecutive orthopedic cases performed during three 3-month assessment periods over 3 years. The amount of recovered material varied markedly within and among procedure types as well as surgeons. Nevertheless, the long-term, OR-wide recovery program at Yale-New Haven Hospital has provided a highly reliable source of usable materials over the 4-year life of the program.

Equipment and Supplies↗
PubMed1995

Transgenic mice expressing high levels of soluble TNF-R1 fusion protein are protected from lethal septic shock and cerebral malaria, and are highly sensitive to Listeria monocytogenes and Leishmania major infections.

Mice bearing a transgene coding for a soluble tumor necrosis factor receptor type 1 (TNFR1)-FcIgG3 fusion protein and placed under the control of the alpha-1-antitrypsin gene promoter were generated. Depending on the mouse line, blood levels of the protein ranged from 25 ng/ml to over 100 micrograms/ml; this level of expression was most often transmitted to the transgene-bearing progeny as a relatively stable feature. High-expressor mice were completely resistant to lipopolysaccharide-induced shock and lethality, including after D-galactosamine sensitization, and mice expressing about 1 microgram of the fusion protein/ml were partially (60%) protected. In contrast, mice expressing less than 0.1 microgram of the protein/ml were more sensitive than controls with respect to incidence and time of death, even though the biological activity of serum tumor necrosis factor (TNF) was partially neutralized. High-expressor mice of the adequate genetic background were markedly, although not completely, protected from death by cerebral malaria after injection with Plasmodium berghei. They were highly susceptible to Listeria monocytogenes, dying from bacterial dissemination after sublethal infection, and to Leishmania major, displaying severe, non-healing lesions after local infection. Under the same conditions, mice expressing about 1 microgram protein/ml were only partially sensitive to these last agents, compared to non-transgenic littermate mice which were fully resistant. These transgenic mice represent a model of permanent, complete or partial, impairment of TNF use, which compares favorably, for ease of breeding and for the range of effects, to mice bearing gene disruptions.

Animals↗
PubMed1995

Liver transplantation in patients with Budd-Chiari syndrome.

Patients with Budd-Chiari syndrome (obstruction of the hepatic veins) and associated hepatic insufficiency may be candidates for orthotopic liver transplantation (OLT). In our series of 405 OLT patients, 3 were transplanted due to Budd-Chiari syndrome (0.7%). The indication for liver transplantation in these patients was severe hepatic insufficiency (chronic in two and acute in the third one). Morphologic study of the obstructions revealed apparently different causes, including thrombi, membranous webs in hepatic veins, and hydatid cyst compression. The surgical technique employed in these transplantations was similar to that for other etiologies. Due to its implications for the future course of OLT, it is important to determine the exact etiology of Budd-Chiari syndrome in the pretransplant period and to treat the patients with early and long-term anticoagulant therapy to avoid syndrome recurrence.

Adolescent↗
PubMed1995

Antioxidants attenuate endotoxin-induced activation of alveolar macrophages.

BACKGROUND: Endotoxin (lipopolysaccharide [LPS]) stimulation of tissue-fixed macrophages induces the generation of toxic oxidants. However, recent studies also implicate redox changes in both the signal transduction pathways for cytokine genes and the generation of physiologically active arachidonic acid metabolites. Because cytokines and arachidonic acid metabolites initiate and perpetuate deleterious systemic inflammatory responses, we tested whether macrophage activation could be modulated by antioxidants. METHODS: Rabbit alveolar macrophages were obtained by bronchoalveolar lavage, isolated, treated with the antioxidants vitamin E or N-acetylcysteine (NAC), and stimulated with an optimal dose of LPS (10 ng/ml). Assays were performed for tumor necrosis factor (TNF), procoagulant activity, and prostaglandin E2. Total cellular RNA was extracted for Northern blot analysis of TNF messenger RNA. RESULTS: Exposure of the macrophage to the antioxidants vitamin E and NAC inhibited TNF production, accumulation of TNF messenger RNA, procoagulant activity expression, and prostaglandin E2 production. CONCLUSIONS: Macrophage signal transduction of LPS is dependent on the generation of reactive oxygen intermediates that can be blocked both at the level of the lipid membrane (vitamin E) and at the intracellular level (NAC). This suggests a potential therapeutic role for antioxidants is disease states such as adult respiratory distress syndrome and multiple organ failure syndrome, which are characterized by excessive macrophage activation.

Acetylcysteine↗
PubMed1995

Expression of a tumor necrosis factor-alpha transgene in murine lung causes lymphocytic and fibrosing alveolitis. A mouse model of progressive pulmonary fibrosis.

The murine TNF-alpha gene was expressed under the control of the human surfactant protein SP-C promoter in transgenic mice. A number of the SP-C TNF-alpha mice died at birth or after a few weeks with very severe lung lesions. Surviving mice transmitted a pulmonary disease to their offspring, the severity and evolution of which was related to the level of TNF-alpha mRNA in the lung; TNF-alpha RNA was detected in alveolar epithelium, presumably in type II epithelial cells. In a longitudinal study of two independent mouse lines, pulmonary pathology, at 1-2 mo of age, consisted of a leukocytic alveolitis with a predominance of T lymphocytes. Leukocyte infiltration was associated with endothelial changes and increased levels of mRNA for the endothelial adhesion molecule VCAM-1. In the following months, alveolar spaces enlarged in association with thickening of the alveolar walls due to an accumulation of desmin-containing fibroblasts, collagen fibers, and lymphocytes. Alveolar surfaces were lined by regenerating type II epithelial cells, and alveolar spaces contained desquamating epithelial cells in places. Platelet trapping in the damaged alveolar capillaries was observed. Pulmonary pathology in the SP-C TNF-alpha mice bears a striking resemblance to human idiopathic pulmonary fibrosis, in which increased expression of TNF-alpha in type II epithelial cells has also been noted. These mice provide a valuable animal model for understanding the pathogenesis of pulmonary fibrosis and exploring possible therapeutic approaches.

Animals↗
PubMed1995

A clinopathologic review of 8 liver graft primary nonfunctions.

In a group of 276 consecutive liver transplants 8 primary graft nonfunctions were identified (2.9%). Recipients showed a progressive elevation of transferases (mean maximum value ALT: 5000 +/- 1892 U/l) and bilirubin (mean maximum value: 20 +/- 11.8 mg/dl) and a decrease in the percent prothrombin time (mean minimum value 26 +/- 13 min.) in the post-implantation survival time of the 8 grafts (range 1-5 days). No statistically significant differences were observed between mean cold and warm-ischemia times for these 8 donor organs and those of a control group of 92 consecutive grafts. All organs except one were ABO isogroup and all except another one displayed negative lymphocytotoxic crossmatch. Predominantly small-droplet hepatocytic vacuolization with no nuclear displacement was observed in plastic-embedded semithin sections of all post-primary nonfunction liver tissues (severe in 4 grafts, centri-mediozonal in 2, and centrolobular in 2). In 3 cases where fresh liver tissue was available the lipidic nature of the vacuoles was confirmed with electron microscopy and with frozen sections stained with Sudan III. Other microscopic lesions were also observed: spotty monocellular coagulative necroses, variable extension of zonal coagulative necroses and hemorrhages, cholestasis and minor mixed inflammatory infiltrate. Comparative microscopic study of these tissues with the protocol biopsy specimens obtained 2-4 hours after reperfusion demonstrated previous liver cell-vacuolization in only 3 cases. In conclusion, an acute progressive microvascular steatosis developed in this primary nonfunction series. No specific etiopathogenic factors were identified.

Adolescent↗