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Biomedical subjects

R Garcia

Publications and source records attributed to R Garcia.

At least 19 recordsLinked to original sources
PubMed1995

Pharmacological and biochemical profiles of unique neurotensin 8-13 analogs exhibiting species selectivity, stereoselectivity, and superagonism.

Recently, the rat neurotensin receptor and the two human neurotensin receptor clones (differing by one amino acid residue) have been isolated. We present results with 33 newly synthesized neurotensin analogs. We have evaluated their binding potency at the three neurotensin receptor clones by determining equilibrium dissociation constants and coupling to phosphatidylinositol turnover. Our work focused on position 8 and 9 substitutions as well as position 11 of the neurotensin hexamer NT8-13. The results presented include: 1) the development of a compound that is species selective, with a binding potency at the rat receptor that is 20-fold more potent than at the human receptor; 2) the development of a pair of stereoselective compounds with the L-isomer exhibiting 190-700-fold more potency than the D-isomer; and 3) the development of an agonist that has a Kd of 0.3 and 0.2 nM at the human and rat neurotensin receptor, respectively, ranking it as among the most potent tested. Also, we present the first evidence that 1) the effect of pi electrons at position 11 (L-Tyr) are important for binding to the neurotensin receptor, and 2) the length of the side chain on position 9 (L-Arg) changes binding potency.

Amino Acid Sequence↗
PubMed1995

Phase I/II study of intravitreal cidofovir for the treatment of cytomegalovirus retinitis in patients with the acquired immunodeficiency syndrome.

PURPOSE: In this study we evaluated the safety and efficacy of the nucleoside phosphonate analogue intravitreal cidofovir to treat cytomegalovirus retinitis in humans. METHODS: We conducted a phase I/II unmasked consecutive case series in a single-center institutional referral practice. Eligible patients with the acquired immunodeficiency syndrome had active cytomegalovirus retinitis in at least one eye, despite adequate intravenous therapy with ganciclovir or foscarnet, were intolerant to intravenous therapy, were noncompliant with intravenous therapy, or refused intravenous therapy. In a preliminary safety study (Group 1), ten eyes of nine patients received 14 injections of cidofovir while being treated concurrently with intravenous ganciclovir. In a dose-escalating efficacy study (Group 2), eight eyes of seven patients received 11 injections of cidofovir as sole treatment for cytomegalovirus retinitis. The primary outcome was time to retinitis progression. RESULTS: In the Group 1 eyes receiving 20 micrograms of cidofovir, the median time to retinitis progression was between 49 and 92 days (mean, 78 days). In Group 2 eyes treated with 20 micrograms cidofovir, the median time to retinitis progression was 64 days (mean, 63 days). Hypotony occurred in the two eyes treated with a 100-micrograms dose of cidofovir and in one of three eyes receiving a 40-micrograms dose. No adverse effects resulted from the remaining 20 cidofovir injections. CONCLUSIONS: Cidofovir (also known as HPMPC) appears to be safe and effective for the local treatment of cytomegalovirus retinitis, providing a long duration of antiviral effect. These preliminary results indicate that additional studies should be performed to investigate more fully this promising medication.

AIDS-Related Opportunistic Infections↗
PubMed1995

Localization of atrial natriuretic factor receptors in the mesenteric arterial bed. Comparison with angiotensin II and endothelin receptors.

Although receptors for atrial natriuretic factor (ANF) and angiotensin II (Ang II) have been reported in rat mesenteric arteries, both peptides induce weak biological responses. Endothelin-1 (ET-1) evokes a potent vasoconstriction in the mesenteric artery. To identify the tissue localization of ANF, Ang II, and ET-1 receptors, radioligand binding experiments with 125I-ANF, 125I-[Sar1,Ile8]Ang II, and 125I-ET-1 were performed in defatted mesenteric arteries and in the surrounding adipose tissue. 125I-ANF binding assays in adipose tissue showed a single class of high-affinity binding sites (Bmax, 420 +/- 16 fmol/mg protein; Kd, 343 +/- 16 pmol/L). In vascular membranes, most 125I-ANF binding was nonspecific. The majority of receptors present in adipose tissue recognized ANF, C-type natriuretic peptide (CNP), and des-[Gln18,Ser19,Gly20,Leu21,Gly22]ANF-(4- 23) (C-ANF) with close affinities, with C-ANF competing for > 98% of the binding sites. In adipocytes, ANF and CNP stimulated cGMP generation. cGMP production by mesenteric arteries was stimulated by sodium nitroprusside but not by ANF or CNP. Autoradiographic localization of 125I-ANF and 125I-ET-1 showed that in the case of ANF, most specific binding occurred in adipocytes, whereas for ET-1, specific binding was present in both adipose tissue and mesenteric arteries. Cross-linking of 125I-ANF followed by SDS-PAGE revealed two receptor species of 130 and 70 kD in adipose membranes and none in vascular tissue. Both were completely displaced by ANF, CNP, and C-ANF. 125I-[Sar1,Ile8]Ang II binding assays in adipose tissue exhibited a single class of binding sites (Bmax, 211 +/- 4 fmol/mg protein; Kd, 520 +/- 10 pmol/L.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1995

Effect of component fixation method on osteolysis in total knee arthroplasty.

Eighty-three total knee arthroplasties done at a single university hospital were reviewed specifically to examine the presence of lysis. Components that were radiographically loose were excluded. The incidence of lysis varied significantly with the method of component fixation. The highest incidence of lysis (30%) was seen when the tibial component was fixed with cement and screws and the femoral component was implanted without cement. When the tibial component was fixed with cement and screws and the femoral components was cemented, the incidence of lysis was 13% (2 of 13). When the femoral component was press fit and the tibia was cemented without screws, the incidence of lysis was 10% (1 of 10). When the femoral and tibial components were cemented and no screws were used, the incidence of lysis was 0 (0 of 12). Using screws with cement to fix the tibial component was associated with a high incidence of lysis and cannot be recommended. A press fit femoral component also may contribute to the incidence of lysis.

Aged↗
PubMed1995

Transient downregulation of glomerular atrial natriuretic factor receptors in high output heart failure in the rat.

OBJECTIVE: The renal response to exogenous atrial natriuretic factor (ANF) is blunted in chronic heart failure. The aim of the present studies was to investigate whether renal ANF receptor regulation in chronic heart failure is a time related event. METHODS: Glomerular ANF receptors were analysed in radioligand binding experiments at 0, 1, 2, 6, 12, 24, and 48 h, as well as at 1, 2, 4, and 8 weeks after the induction of an aortocaval shunt. RESULTS: Rats with aortocaval shunts had lower packed cell volume and body weight and higher relative heart weight than sham operated controls. Plasma ANF C and N terminal levels were increased in shunt rats as early as 5 min after establishment of the shunt. Right and left atrial ANF concentrations were decreased and ventricular ANF concentration was increased in shunt rats at 6 and 12 h respectively. Competitive inhibition of 125I-ANF binding showed that at 6 h the density (Bmax) of glomerular ANF receptors was significantly lower than in the controls [518(SEM 10) v 759(12) fmol.mg-1 protein] without differences in their affinity (Kd). The low Bmax in shunt animals persisted at 12, 24, and 48 h, even at 1 week [Bmax: 400(29) and 713(28) fmol.mg-1 protein; Kd: 80(2) and 70(4) pM, for AC rats and controls, respectively]. Bmax values were not significantly different at 2, 4, and 8 weeks. In 24 h animals, C-ANF displaced 65% of total binding, with both total and C ANF binding sites being 38% lower in shunt animals. CONCLUSION: Downregulation of glomerular ANF receptors is a transient event during the development of high output heart failure in the rat. Thus the blunted renal response to ANF during chronic heart failure is not likely to be due to a decrease in renal ANF receptor density or affinity.

Animals↗
PubMed1994

Clinical and histopathologic study of varicella zoster virus retinitis in patients with the acquired immunodeficiency syndrome.

Varicella zoster virus retinitis in patients with the acquired immunodeficiency syndrome is known to be a devastating disease. We studied a series of six consecutive patients that sheds new light on the clinical manifestations and treatment options of this disorder. All patients had episodes of cutaneous zoster, long-term exposure to oral acyclovir, and CD4+ T lymphocyte counts less than 50 cells/mm3. Two of the six patients had simultaneous radiographically demonstrable and histologically proven varicella zoster virus encephalitis; this is an important association. Histologic examination of autopsy specimens disclosed that the retinal infection by varicella zoster virus involves the retinal pigment epithelium more heavily than the inner retina, which is consistent with the characteristic clinical impression of an outer retinal necrosis.

AIDS-Related Opportunistic Infections↗
PubMed1994

Allopurinol dose is important for attenuation of liver dysfunction after normothermic ischemia: correlation between bile flow and liver enzymes in circulation.

We have investigated the effect of two doses of allopurinol (ALL) (100 and 50 mg/kg) administered i.v. on liver function after 1 h of normothermic ischemia. ALL given in a concentration of 100 mg/kg significantly improved bile output after 1 and 24 h of reperfusion. Hepatocyte injury reflected by alanine aminotransferase (ALT) and lactic dehydrogenase (LDH) in plasma was also significantly reduced at 24 h, but not at 1 h of reperfusion compared with controls. ALL administered at a concentration of 50 mg/kg had some protective effect. Significant correlation between circulating liver enzymes and bile output at 24 h after reperfusion indicates an important pathophysiologic link between hepatocyte function and injury in this time window.

Alanine Transaminase↗
PubMed1994

Captopril treatment does not restore either the renal or the ANF release response during volume expansion in moderate to severe high output heart failure.

OBJECTIVE: Atrial natriuretic factor (ANF) release and the renal response to moderate volume expansion have been shown to be conserved in rats with a mild to moderate degree of high output heart failure (aortocaval shunt). The aim of this study was to investigate whether these variables are also conserved in animals with moderate to severe heart failure induced by an aortocaval shunt. The effect of angiotensin converting enzyme (ACE) inhibition by captopril on these responses was also investigated. METHODS: An aortocaval shunt was developed in Sprague-Dawley rats weighing 180-200 g; sham operated rats served as controls. Three weeks after surgery, three experimental groups were established: aortocaval shunt and sham operated controls, and aortocaval shunt rats treated with captopril during the last week before the experiments were started. Four weeks after surgery, haemodynamic variables, ANF release, diuresis, and natriuresis were evaluated following a moderate volume expansion. RESULTS: Mean arterial blood pressure was lower in shunt animals and still lower in the ACE inhibited group than in the sham operated controls. Central venous pressure and left ventricular end diastolic pressure (LVEDP) were significantly higher in untreated shunt rats than in their controls. ACE inhibition returned the raised central venous pressure, but not LVEDP, to control values. Shunt rats had lower baseline urinary sodium excretion (UNaV), urinary volume, and packed cell volume than their sham operated controls. ACE inhibition reversed baseline urinary volume to control values. Baseline COOH terminal and HN2 terminal ANF were greatly increased in both treated and untreated shunt rats. Volume expansion was performed three times in conscious animals at 15 min intervals with human plasma protein fraction. Its effect on LVEDP was similar in all three groups, but the increase in central venous pressure was much higher in untreated shunt animals. UNaV, urinary volume, and the release of COOH terminal and NH2 terminal ANF in response to volume expansion were blunted in both treated and untreated shunt rats when compared with their sham operated counterparts. Both absolute and relative heart weights were significantly lower in captopril treated shunt animals than in the untreated shunt group, the latter presenting very significant cardiac hypertrophy. CONCLUSIONS: Aortocaval shunt animals with moderate to severe heart failure show a blunted ANF release and renal response to volume expansion, which, despite significant haemodynamic improvement, are not restored by ACE inhibition.

Animals↗
PubMed1994

Clinical and immunological changes in AIDS patients following adoptive therapy with activated autologous CD8 T cells and interleukin-2 infusion.

OBJECTIVES: (1) To determine the safety and feasibility of repetitive reinfusions of activated autologous CD8 cells followed by low-dose continuous interleukin (IL)-2 infusion in patients with AIDS. (2) To study the relationships between clinical responses, surface marker phenotypic distributions and cytokine expression patterns of both cultured CD8 cells and lymphocytes in the peripheral blood compartment. DESIGN: Six adult patients with Centers for Disease Control and Prevention group IV HIV-1 disease ranging from mild to severe, were studied. All patients were receiving zidovudine prior to and during the study period, and had initial CD4 and CD8 cell counts > 50 and 200 x 10(6)/l, respectively. METHODS: Autologous CD8 T cells (10(8)-10(10)) were reinfused five times after ex vivo culture and stimulation with phytohemagglutinin and recombinant (r) IL-2. The fifth such infusion was followed by 5 days of rIL-2 infusion. Phenotypes and cytokine expression patterns of the expanded cells were determined as well as serum levels of immune mediators throughout the study. RESULTS: Patients showed stable CD4 and CD8 cell counts, p24 antigenemia, and minimal toxicity over the 24-week protocol study. Clinical improvement was observed in lymphadenopathy (six out of six), oral hairy leukoplakia (three out of four), and Kaposi's sarcoma (KS; two out of two) in the patients studied. In vivo induction of detectable levels of bioactive acid-stable interferon (IFN)-alpha, but not of other cytokines studied, upon activated CD8 cell reinfusion was associated consistently with improvement of oral hairy leukoplakia. However, partial regression of KS was observed after the CD8 cell infusion cycles and without IFN-alpha induction. In one of the two patients studied, KS regression was associated with decreased IL-1 alpha serum levels. In the other patient, who had failed previous IFN-alpha therapy, KS regression was observed after a decline in reinfused CD8 cell-associated gene expression of tumor necrosis factor (TNF)-beta. Both IL-1 alpha and TNF-beta are growth factors for KS cells. CONCLUSIONS: These observations demonstrate the feasibility and safety of ex vivo CD8 cell activation, expansion, and reinfusion, and rIL-2 infusion in AIDS patients. The findings in this Phase I trial suggest potential clinical efficacy and encourage Phase II trials. The correlations obtained between clinical and immunological states could contribute to an understanding of the relationship between CD8 T-cell function and HIV-1-associated disease progression.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Systemic strongyloidiasis in patients infected with the human immunodeficiency virus. A report of 3 cases and review of the literature.

We report 3 cases of systemic strongyloidiasis in HIV-infected individuals and review 11 additional cases reported in the English-language literature. Systemic strongloidiasis is a rare and potentially fatal complication of late-stage HIV disease. A combination of gastrointestinal and respiratory symptoms in an HIV-infected patient who has been to an endemic area should prompt the clinician to search for S. stercoralis in stool and sputum specimens. Treatment failures occur commonly, and careful follow-up is warranted. New antihelminthic drugs (such as ivermectin) seem promising and need to be evaluated in controlled studies.

AIDS-Related Opportunistic Infections↗
PubMed1994

Prevalence of antibodies to different Leptospira interrogans serovars in pigs on large farms.

A seroepidemiological survey was carried out in the province of Badajoz (south-western Spain) in order to determine the presence and spread of Leptospira interrogans. The 521 sera tested were drawn from breeding sows on 28 large farms (15 with fewer than 60 and 13 with over 60 breeders). Immunological testing was performed using the Martin-Pettit micro-agglutination technique. Pigs with titres equal to or greater than 1:100 were considered positive. Haemolysed and/or contaminated test sera were reprocessed following filter-paper treatment. A total of 10.56% of pigs tested proved positive, 39.28% of farms being affected. The following L. interrogans serovars were detected: pomona (6.53%), castellonis (1.15%), sejroe (1.15%), grippotyphosa (0.96%), australis (0.38%), hebdomadis (0.19%) and icterohaemorrhagiae (0.19%).

Animals↗
PubMed1994

Pathophysiology of HIV related thrombocytopenia: an analysis of 41 patients.

AIM: To analyse the pathogenic mechanism of HIV related thrombocytopenia. METHODS: Forty one patients with thrombocytopenia and HIV-1 infection were investigated over two years. Anticardiolipin antibodies were measured using an enzyme linked immunosorbent assay and antiplatelet antibodies were measured using an immunocapture technique. Tests for VDRL, C3 and C4, antinuclear antibodies and rheumatoid factor were also carried out in all patients and 80 control subjects (HIV-1 positive but non-thrombocytopenic). Indiumoxine labelled platelets were transfused in 13 patients. P24 antigen were also measured in 12 bone marrow aspirates. RESULTS: Antiplatelet antibodies and circulating immune complexes were found exclusively in the thrombocytopenic group; values for antiplatelet antibodies and circulating immune complexes were both higher in homosexual and bisexual patients. Three kinds of pattern were observed using 111 In-labelled platelets: splenic (n = 10); hepatic (n = 2); and destruction of bone marrow in just one case. The two most influential factors in the sequestration pattern were antiplatelet antibodies in the splenic uptake and circulating immune complexes in the hepatic and marrow sequestration. All patients, except three, had decreased platelet recovery. In those patients with a CD4 lymphocyte count of less than 200 x 10(6) cells/l the recovery was clearly greater (53%) than in patients who had more than 200 x 10(6) /l (28%). Finally, in seven of the 12 patients who were chosen for immunohistochemical study, p24 antigen was detected in the megakaryocytes, verifying that HIV-1 infects such cells. CONCLUSIONS: The pathogenic mechanism of HIV related thrombocytopenia is probably multifaceted. Antiplatelet antibodies and circulating immune complexes would cause peripheral destruction in the spleen, liver, and bone marrow, in that order; and, on the other hand, there would be an ineffective immune thrombopoiesis and direct infection of the megakaryocytes which could cause a change in the function and maturity of these cells.

Antigen-Antibody Complex↗
PubMed1994

Human nasal mucosal changes after exposure to urban pollution.

Millions of people worldwide are living in areas where ozone (O3) concentrations exceed health standards (an hourly average of 235 micrograms/m3/0.12 ppm, not to be exceeded more than once per year). Ozone induces acute nasal inflammatory responses and significant epithelial lesions in experimental animals and humans. To determine the nasal effects of a 15-day exposure to an urban polluted atmosphere with O3 as the main pollutant, we studied a population of healthy, young males newly arrived to southwest metropolitan Mexico City (SWMMC). The study included 49 non-smoking residents in an unpolluted port, Veracruz City; 14 subjects stayed in the port and served as controls, while 35 subjects traveled to SWMMC and had serial nasal lavages at different times after arriving in SWMMC. Subjects had exposures to ambient O3 an average of 10.2 hr/day, with a total cumulative O3 exposure of 10.644 ppm.hr. Nasal inflammatory responses, polymorphonuclear leukocyte PMN-CD11b surface expression, rhinoscopic changes, and respiratory symptoms were evaluated. Exposed subjects had massive nasal epithelial shedding and significant responses in PMN nasal influx (p < 0.00001) and in PMN-CD11b expression (p < 0.05). Cumulative O3 exposure correlated with respiratory symptoms, PMNs (rs = 0.2374, p < 0.01), and CD11b (rs = 0.3094, p < 0.01); 94% of exposed subjects experienced respiratory symptoms, and 97% left the city with an abnormal nasal mucosa by rhinoscopy. Nasal epithelial changes persisted 2 weeks after the exposed subjects returned to their nonpolluted environment. Exposure to an urban polluted atmosphere induces significant and persistent nasal epithelial alterations in healthy subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Purification and characterization of a human neutrophil lipocalin (HNL) from the secondary granules of human neutrophils.

A 45 kDa-protein was purified from the granules of human neutrophils. The protein consists of two apparently identical subunits. The isoelectric point was pH 8.40, and the molecular weight 45 kDa (unreduced) or 24 kDa (reduced). Treatment of the protein with Endoglucosidase F resulted in a reduction in the molecular weight to 20 kDa, indicating the presence of N-linked carbohydrate. The extinction coeffient was E1%,1cm = 13.76 at 280 nm. The 60 amino acid sequence revealed up to 65% sequence homology with rat alpha 2-microglobulin-related protein, which belongs to the lipocalin family. The protein co-sedimented with secondary (specific) granule marker proteins and correlated to the neutrophil content of Lactoferrin (r = 0.81, p < 0.001) and was estimated to be 0.59 microgram 10(-6) cells. Release studies showed that the neutrophils released 51.4 +/- 9.0% of the total cellular content of the protein when they were exposed to serum-opsonized particles, which was much higher than the release of Myeloperoxidase (12.7 +/- 3.5%) and Lactoferrin (22.9 +/- 4.7%). The N-terminal and four tryptic fragment amino acid sequence of the protein was identical with an N-formyl peptide binding 24 kDa protein and gelatinase associated protein of human neutrophils. In conclusion, we have purified and characterized a protein, human neutrophil lipocalin (HNL), from the secondary granules of human neutrophils and shown that it is readily mobilized from the neutrophils upon stimulation.

Acute-Phase Proteins↗
PubMed1994

Rat renal preglomerular vessels, glomeruli and papillae do not express detectable quantities of B-type natriuretic peptide receptor.

DESIGN: Atrial natriuretic factor (ANF) receptor subtypes were quantitated by radioligand studies in three different rat renal isolated tissues: preglomerular vessels, glomeruli and papillae. RESULTS: In preglomerular vessels 100% of [125I]-ANF binding was displaced with high affinity by ANF. C-ANF (des-[Gln18,Ser19,Gly20,Leu21,Gly22]ANP(4- 23)) a specific ligand for ANP-C receptors, displaced 30% of total binding with a lower affinity than ANF. C-type natriuretic peptide (CNP) displaced [125I]-ANF binding in a biphasic manner, indicating that it binds to two sites with affinities three orders of magnitude apart. When CNP was incubated in the presence of 0.1 mumol/l C-ANF to saturate ANP-C receptors, the high-affinity binding site vanished and maximum binding decreased to 70%, suggesting that CNP binds with high affinity to ANP-C receptors. Since the ANP-A receptor has little or no avidity for CNP, it is probably the low-affinity binding site. CNP and C-ANF displaced most [125I]-[Tyr]CNP(1-22) binding with very close affinities, indicating that CNP binds primarily preglomerular vascular ANP-C receptors. In glomeruli CNP behaved similarly to C-ANF in its ability to displace approximately 85% of [125I]-ANF binding; the remaining 15% was completely displaced by ANF. C-ANF and CNP inhibited 100% of [125I]-[Tyr]CNP(1-22) binding. Both findings suggest that [125I]-[Tyr]CNP(1-22) binds ANP-C receptors exclusively. In renal papillae no displacement of [125I]-ANF by C-ANF was observed, and CNP was bound to ANP-A receptors with the same very low affinity as in preglomerular vessels. The absence of [125I]-[Tyr]CNP(1-22) binding to papillary membranes indicates that ANP-B receptors are not expressed in that tissue. Unlike ANF, CNP stimulated cGMP production in glomeruli and papillae only at extremely high, supraphysiological concentrations. CONCLUSION: The present results suggest that ANP-B receptors either are absent or are present in undetectable amounts in rat renal preglomerular vessels, glomeruli and papillae.

Animals↗
PubMed1993

Cationic liposome-mediated incorporation of prostatic acid phosphatase protein into human prostate carcinoma cells.

Lipofectin, the commercially available cationic liposome, was used to introduce the purified prostatic acid phosphatase protein into the established human prostate carcinoma cells. The incorporated phosphatase protein which retained its enzymatic activity as demonstrated by the tartrate-sensitive acid phosphatase assay was localized in the cytoplasm by immunofluorescence staining. Further, cells that were treated with phosphatase/Lipofectin complexes expressed a decreased phosphotyrosine level, presumably due to the endogenous protein tyrosine phosphatase activity of the acid phosphatase protein. A cationic liposome such as lipofectin may thus be employed to mediate transport of other acidic proteins into cells, providing a way to examine their biological functions in vivo.

Acid Phosphatase↗