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Biomedical subjects

R Garcia

Publications and source records attributed to R Garcia.

At least 253 records · Page 14Linked to original sources
PubMed1991

C-erbB-2 oncogene protein in in situ and invasive lobular breast neoplasia.

Lobular carcinoma in situ (LCIS) has uncertain malignant potential; biologic markers that will identify patients at risk for a poor clinical outcome have been sought actively. Amplification of the c-erbB-2 protooncogene has been correlated with poor prognosis in invasive mammary carcinoma, and immunohistochemical evaluation for expression of the oncogene protein has been correlated with gene amplification. The authors retrospectively evaluated 62 cases of lobular neoplasia for expression of the c-erbB-2 gene product on formalin-fixed, deparaffinized sections, using two monoclonal anti-erbB-2 (p185) antibodies (c-neu Ab3 and m-erb) and one polyclonal anti-erbB-2 antibody (pAb 1) by the avidin-biotin-peroxidase method. All 62 cases were negative with the pAb 1 antibody; one of 62 cases was weakly positive with the c-neu Ab3 in a membranous pattern. Expression of c-erbB-2 gene product was identified on adjacent invasive ductal carcinoma in one case and in adjacent ductal carcinoma in situ in another. None of 15 cases if infiltrating lobular carcinoma was positive with either of the two anti-c-erbB-2 antibodies. Strong positivity was found on benign epithelium in one case, demonstrating epitheliosis. In summary, evidence of expression of the c-erbB-2 gene product was found in one of 57 cases of LCIS and none of 15 cases of invasive lobular carcinoma. This suggests that, in contrast to reported data concerning intraductal and invasive ductal carcinoma, c-erbB-2 oncogene amplification and/or overexpression does not play a significant role in the progression of lobular breast neoplasia.

Antibodies, Monoclonal↗
PubMed1991

Identification of enhancer sequences 3' of the rabbit Ig kappa L chain loci.

The rabbit is useful for studies of Ig L chain gene expression because of a great disparity in expression of two isotypic forms of the kappa L chain. Normally, K1 is expressed at high levels and K2 is almost silent; expression of K2 increases in mutant or experimentally allotype-suppressed animals. The reasons for the preferential utilization of the K1 isotype have not been fully elucidated. We were interested in looking for second enhancers 3' of the C kappa genes because the absence of a 3' enhancer in the K2 locus could explain the preferential utilization of the K1 isotype. However, we found a strong region of enhancer activity about 7 kb downstream of the C kappa 2 gene. Sequences in this region are highly conserved between rabbit, man, and mouse. There also appears to be a homologous 3' enhancer region in the rabbit K1 locus. We also confirmed earlier reports that the rabbit K1 intron enhancer is inactive in transient transfections into mouse B cells but find that the same construct has low but significant activity in a human B cell line. In a comparable construct the K2 intron enhancer is without activity suggesting possible differential activity of the intronic enhancers.

Animals↗
PubMed1991

Synergism of atrial pressure and adrenergic stimulation for ANF release in the rat.

The effect of adrenergic stimulation on atrial natriuretic factor (ANF) release was studied in conscious rats. 60 min i.v. infusion of 15 micrograms/kg/min phenylephrine produced an elevation in mean arterial pressure of about 50 mmHg that was associated with an immediate, transitory increase in both central venous (CVP) and left ventricular end-diastolic (LVEDP) pressures. Heart rate was not changed. The elevation in CVP, but not LVEDP, persisted until 5 min, together with a 50-fold increase in plasma C-terminal ANF concentrations (from 19 +/- 5 to 1010 +/- 339 fmol/ml); at 30 min, in the absence of any increases in CVP or LVEDP, plasma ANF was still elevated by 5-fold (114 +/- 35 fmol/ml). It is suggested that adrenergic stimulation 'per se' can induce ANF release, independently of atrial pressure. Furthermore, combined adrenergic stimulation and increased atrial wall tension could result in a potentiation of the ANF secretory response 'in vivo', in the case where both stimuli are present concomitantly.

Animals↗
PubMed1991

Atrial natriuretic factor release during acute infusion of isoproterenol in the conscious rat.

The effect of beta-adrenergic stimulation on atrial natriuretic factor (ANF) release was studied in conscious rats. 20-min infusion of 85 or 850 ng kg-1 min-1 isoproterenol (ISO) resulted in positive inotropic and chronotropic responses and no elevation of atrial pressures. A slight increase in plasma ANF, together with a drop in blood pressure, were observed only in the group infused with the higher dose. During the infusion of 850 ng kg-1 min-1 ISO, there was no relationship between plasma ANF and any of the haemodynamic parameters, with the exception of mean arterial pressure (r = 0.72, P less than 0.05, n = 9). Larger doses (greater than 3 micrograms kg-1 min-1) were toxic. We conclude that beta-adrenergic stimulation is not an important stimulus for ANF release when diastolic resting tension is low.

Animals↗
PubMed1991

Cellular growth response to epidermal growth factor in colon carcinoma cells with an amplified epidermal growth factor receptor derived from a familial adenomatous polyposis patient.

The receptor binding and cellular growth responses to exogenous epidermal growth factor (EGF) were studied using the DiFi cell line established from a familial adenomatous polyposis patient. The number of cell membrane EGF receptors on DiFi cells, as measured by competitive radioligand binding assays and Scatchard analysis of 125I-EGF binding isotherms, was calculated to be 4.8 x 10(6) receptors/cell. An acid prewash step performed prior to ligand binding assays did not reveal additional receptor numbers. A single, low-affinity receptor population was identified by Scatchard analysis, with an apparent Kd of 4.6 nM. This result was confirmed by radioligand binding studies performed in the presence and absence of the receptor-antagonist monoclonal antibody 528 IgG that binds predominantly to the low-affinity form of the EGF receptor. DiFi cells at 50-60% confluence, when exposed to 50 nM exogenous EGF, exhibited a rapid but partial (30%) reduction in their cell membrane-associated receptor, characteristic of sequestration. Exposure of DiFi cells to 50 nM EGF for longer periods of time (4 h) did not result in any further reduction in EGF-receptor number. The cellular growth response of DiFi cells to exogenous EGF was studied in monolayer cultures as well as in a soft agarose assay. Inhibition of soft agar colony formation was observed at exogenous EGF concentrations greater than 1.7 nM, and inhibition of monolayer growth occurred at EGF concentrations greater than 1 nM. In immune complex kinase assays, the DiFi receptor showed similar specific activity to that from the well-characterized A431 cell line. Additionally, phosphorylation of the receptor on tyrosine was qualitatively similar to that of A431 cells, further suggesting that the DiFi receptors identified by EGF-binding studies were biologically functional.

Adenomatous Polyposis Coli↗
PubMed1991

Atrial natriuretic factor and volume expansion-induced natriuresis in the spontaneously hypertensive rat.

The implication of atrial natriuretic factor (ANF) during acute volume expansion in the spontaneously hypertensive rat (SHR) was evaluated. The effect of short-term afterload relief was also investigated. Fourteen- to 15-week-old SHR and Wistar-Kyoto (WKY) rats were treated with hydralazine for 5 days. The systolic blood pressure (BP) of SHR decreased to normotensive levels but cardiac hypertrophy was not reduced. Isotonic, iso-oncotic volume expansion (equivalent to 10% of total blood volume) was performed 3 times at 15-min intervals on conscious animals. The effect of volume expansion on central venous pressure was identical among the groups. Changes in left ventricular end-diastolic pressure (LVEDP) induced by volume expansion were greater in SHR than in WKY rats and were not affected by treatment. The increases in plasma N-terminal ANF (ANF-(1-98)) concentrations were larger in both treated and untreated SHR verses WKY rats. Despite enhanced ANF release in SHR, the overall magnitude of the diuretic and natriuretic responses to volume expansion was similar in all groups. The natriuretic response was strongly correlated with plasma ANF in WKY rats, this relationship was weak in control SHR, and restored by treatment. It is suggested that ANF release is not impaired in SHR at a 10% volume load; however, there seems to be a lower renal responsiveness to ANF in SHR.

Animals↗
PubMed1991

Occupational asthma caused by Brazil ginseng dust.

The inhalation of different substances of plant origin can cause immediate and late onset asthma. The list of these agents responsible for such reactions is continuously increasing. We discuss a patient who developed symptoms of asthma after exposure to Pfaffia paniculata root powder used in the manufacturing of Brazil ginseng capsules. Airway hyperreactivity was confirmed by a positive bronchial challenge to methacholine. Sensitivity to this dust was confirmed by immediate skin test reactivity, a positive bronchial challenge (immediate response), and the presence of specific IgE detected by ELISA technique to an aqueous extract. The bronchial response was inhibited by sodium cromoglycate. Unexposed subjects did not exhibit reactivity to this ginseng extract with any of the tests referred to above. The same study performed with Korean ginseng (Panax ginseng) elicited negative results. This study is the first, to our knowledge, that links ginseng-root dust to occupational asthma.

Adult↗
PubMed1991

Neither ventricles nor afterload relief influence the raised plasma atrial natriuretic factor induced by volume expansion in the spontaneously hypertensive rat.

STUDY OBJECTIVE: The aims were (1) to study the influence of afterload relief on the rise in atrial natriuretic factor (ANF) which occurs during acute volume expansion in the spontaneously hypertensive rat (SHR); (2) to assess the contribution of the atria and the ventricles to ANF release under these circumstances. DESIGN: In the first series of experiments, SHR were treated with captopril (150 mg.kg-1.d-1) orally for 10 d. Untreated SHR and Wistar-Kyoto (WKY) rats served as controls. Volume expansion, equivalent to 10% of the total blood volume, was performed three times with human plasma protein fraction at 15 min intervals on conscious animals. Some haemodynamic variables and plasma ANF were measured. Tissue ANF measurements were conducted on another series of treated and control SHR not submitted to volume expansion. In another series of experiments, conscious SHR and WKY rats were submitted to repetitive 30% volume expansion (three times at 15 min intervals). Non-expanded animals served as controls. At the end of the experiments, tissue ANF measurements were performed. EXPERIMENTAL MATERIAL: All experiments were conducted on 15 week old SHR and WKY rats. MEASUREMENTS AND MAIN RESULTS: Captopril treatment reduced systolic blood pressure and cardiac hypertrophy in SHR. During volume expansion, changes in left ventricular end diastolic pressure were greater in control SHR than in treated SHR or WKY rats. Central venous pressure was affected similarly by volume expansion in both SHR groups. Plasma ANF rises induced by volume expansion were equal in all groups. Captopril treatment had no effect on right or left auricular ANF content prior to volume expansion. Repetitive 30% expansion reduced both right and left auricular ANF concentrations to the same extent (approximately 300-1500 ng.mg-1 protein) in SHR and WKY groups. Ventricular ANF was not affected by volume expansion in SHR, whereas volume expanded WKY rats had higher right and left ventricular ANF concentrations than their non-expanded controls. CONCLUSIONS: (1) The increase in plasma ANF during volume expansion is not impaired in SHR with newly established hypertension; (2) captopril treatment decreases afterload and the changes in left ventricular end diastolic pressure during volume expansion in SHR, without affecting plasma ANF increases; (3) both the auricles, but not the ventricles, contribute to enhanced ANF secretion caused by acute volume expansion in SHR and WKY rats.

Animals↗
PubMed1991

Gelled diet for screwworm (Diptera: Calliphoridae) mass production.

A rearing system based on a diet gelled with Water-Lock G-400, a synthetic superabsorbent (poly(2-propenamide-co-2-propenoic acid, sodium salt)) (WL), was compared with the standard rearing system (liquid diet suspended in acetate fibers) for the mass production of screwworms, Cochliomyia hominivorax (Coquerel). The WL rearing system yielded 2% heavier pupae, 32% higher egg to pupa survival, and required 54% less diet and 88% less labor than the standard rearing system. Other advantages of the WL system include reduced susceptibility to suboptimal environmental conditions and labor practices and characteristics conducive to centralization and mechanization of rearing procedures.

Animals↗
PubMed1991

Insulin-sparing effects of pancreatic polypeptide in congenitally obese rodents.

Chronic treatment with bovine pancreatic polypeptide (bPP) is reported to decrease body weight and reduce fasting glucose and insulin concentrations in congenitally obese mice. The present study examines the effects of acute and chronic bPP treatment on insulin release and glucose clearance in lean and obese rodents. After single injections of 0, 5, 50, or 500 micrograms of bPP/kg of body weight, the insulin response to an intragastric glucose meal (5 g/kg of body weight) was substantially inhibited by the two higher doses of bPP. The change in glucose concentration over time was similar among all animals except those receiving the highest dose of bPP (500 micrograms/kg of body weight); in this group, glucose rose to higher levels and was slower to return to basal levels. Chronic treatment of rats with 200 micrograms of bPP/day/kg of body weight for 5 days did not modify glucose or insulin responses to the glucose meal, but did increase the activity of hepatic glycogen synthetase. In contrast, basal glucose levels were lower in obese mice (ob/ob) treated with bPP and glucose clearance was improved in the treated group after injection of exogenous insulin. Islet hormone concentrations in pancreatic extracts were compared in lean and obese mice treated with and without 200 micrograms of bPP/day/kg of body weight for 5 days. The pancreases of obese mice had higher concentrations of insulin and PP, and treatment with exogenous bPP increased endogenous PP in the pancreases of both phenotypes. Treatment with exogenous bPP also increased the insulin content of obese pancreases, but was without effect in pancreases of lean mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Regulation of glomerular atrial natriuretic factor receptor subtypes by renal sympathetic nerves.

The modulation of glomerular atrial natriuretic factor (ANF) receptors (ANF-R1 and ANF-R2) was examined in rats after unilateral (Uni-DNx), bilateral (Bil-DNx), and sham renal denervation (Sham-DNx). Glomerular ANF receptor density was higher in both left and right kidneys (1,138 +/- 73 and 952 +/- 100 fmol/mg protein, respectively) of Bil-DNx rats than in Sham-DNx animals (302 +/- 9 and 328 +/- 13 fmol/mg protein, respectively). The denervated (left) kidney from Uni-DNx rats also showed higher ANF receptor density (1,146 +/- 68 fmol/mg protein) than the contralateral untouched kidney (602 +/- 34 fmol/mg protein). Plasma ANF-(99-126) and ANF-(1-98) levels were significantly lower in the Bil-DNx group than in either Uni-DNx or Sham-DNx animals. Affinity cross-linking studies followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography demonstrated that both ANF-R1 and ANF-R2 receptors were upregulated in the same proportion in denervated kidneys. Guanosine 3',5'-cyclic monophosphate production by isolated glomeruli from denervated kidneys of either Bil-DNx or Uni-DNx rats was significantly higher than that of Sham-DNx controls. We conclude that renal sympathetic nerves regulate both glomerular ANF-R1 and ANF-R2-receptor subtypes.

Animals↗
PubMed1991

Ventricular tachycardia as a first manifestation of right ventricular myxoma--a case presentation.

The authors present a case of a thirty-nine-year-old white man in good health who developed episodes of ventricular tachycardia as a first manifestation of a right ventricular myxoma, which was diagnosed by two-dimensional echocardiogram and then resected with no complications and total disappearance of the cardiac arrhythmia. After reviewing the literature they consider the present case as a rare manifestation of an infrequent location of an uncommon disease.

Adult↗
PubMed1991

Atrial natriuretic factor release during volume expansion in the spontaneously hypertensive rat--effect of long-term hydralazine treatment.

We tested the ability of spontaneously hypertensive rats (SHR) to release atrial natriuretic factor (ANF) during acute volume loading and its relationship to right and left atrial pressures. The effect of decreasing cardiac afterload by hypotensive treatment was also investigated. Fourteen to 15-week-old SHR and Wistar-Kyoto (WKY) rats were treated with hydralazine (12 mg/kg.day p.o.) for a period of 4 weeks. Untreated rats served as controls. The systolic blood pressure (BP) of SHR decreased to normotensive levels and cardiac hypertrophy was also reduced. Isotonic, iso-oncotic volume expansion (VE) was performed 3 times as 10% increments and at 15-min intervals. Despite greater changes in left-ventricular end-diastolic pressures (LVEDP) and to a lesser extent in central venous pressure (CVP) in SHR controls, the increases in plasma ANF (N-terminal concentrations) induced by VE were of a similar magnitude in both SHR and WKY control rats. The LVEDP and ANF C-terminal elevations were of a lower magnitude in treated SHR. Auricular ANF concentrations, measured at the end of VE, were lower in the left and higher in the right atrium in SHR versus WKY. It is concluded that despite a lower distensibility of their left atrium, ANF release is not impaired in SHR upon a VE. This adequate ANF release is obtained through higher increases in atrial pressures.

Animals↗
PubMed1991

Supplemental use of liquid amprolium in skip-a-day feeding of replacement pullets.

The addition of liquid amprolium to the drinking water on days when medicated (amprolium) ration was not fed in a restricted feeding (skip-a-day) program improved protection against a primary exposure to Eimeria acervulina and Eimeria tenella, yet still allowed for the development of protective immunity to subsequent challenge. With E. tenella, the best protection, as measured by reduction of lesion score, was provided by amprolium given in the drinking water on alternate days to feed medication when compared with the use of amprolium only in the feed or liquid amprolium at less frequent intervals (every second or third nonfeeding day). With Eimeria maxima, amprolium in the feed did not significantly lower lesion score compared with the score in unmedicated pullets; however, the further addition of amprolium to the drinking water did. When pullets were reared in floor pens previously seeded with coccidia, amprolium medication in the feed alone reduced the E. tenella-induced mortality rate from 28 to 8%. The addition of amprolium in the drinking water on nonfeeding days eliminated all deaths. Floor-reared pullets were caged after 3 wk and challenged 1 wk later with the same species of coccidial oocysts used to immunize on the floor. Coccidial lesion scores following challenge were eliminated or markedly lower than in pen-reared (unimmunized) pullets similarly challenged. This indicated that protective immunity developed despite the use of amprolium in the drinking water.

Amprolium↗
PubMed1991

Downregulation of glomerular and vascular atrial natriuretic factor receptor subtypes by angiotensin II.

We have previously reported that pressor doses of angiotensin II induce atrial natriuretic factor (ANF) release. Since the number of glomerular and vascular ANF receptors may vary inversely with plasma ANF levels, we investigated whether they are modified by angiotensin II. Male rats were infused intraperitoneally for 7 days with either a non-pressor (200 ng/kg per min) or a pressor (800 ng/kg per min) dose of angiotensin II. Sham-infused animals served as controls. Blood pressure and plasma C- and N-terminal ANF were higher, and atrial ANF concentrations lower, in pressor than in either non-pressor or sham-infused groups. Glomerular ANF receptor density was lower in pressor than in either non-pressor or sham-infused animals. The production of cyclic guanosine monophosphate by isolated glomeruli was significantly lower in pressor than in either non-pressor or sham-infused groups. Vascular ANF receptor density was lower in pressor than in either sham-infused or non-pressor rats. No difference in affinity was observed in any group for either glomerular or vascular ANF receptors. Neither the density nor the affinity of glomerular and vascular ANF receptors were affected by prior washing of the membranes with an acid solution (pH 5.0). Irreversible cross-linking of 125I-ANF followed by sodium dodecylsulfate-polyacrylamide gel electrophoresis in reducing conditions and autoradiography demonstrated that both high- and low-molecular weight receptors were downregulated in glomerular membranes, but only the low-molecular weight receptor was reduced in vascular membranes after a high-dose infusion of angiotensin II. We conclude that angiotensin II induces a true downregulation of its glomerular and vascular receptor subtypes, probably by increasing plasma ANF levels. A direct or indirect effect of angiotensin II on ANF receptor regulation cannot be eliminated, however.

Angiotensin II↗
PubMed1991

Effect of herbimycin A on growth and pp60c-src activity in human colon tumor cell lines.

The effect of herbimycin A, an ansamycin antibiotic which inhibits cellular transformation by retroviral tyrosine kinases, on the monolayer growth of seven colon tumor cell lines and one cell line established from normal colonic mucosa, CCL239, was examined. Each colon tumor cell line tested showed dose-dependent growth inhibition in response to herbimycin A. A 125ng ml-1 dose of the antibiotic caused greater than 40% growth inhibition in all colon tumor cell lines after two cell doublings. In contrast, at similar herbimycin A concentrations only 12% inhibition was observed in 'normal' CCL239 cells. No major morphologic changes were observed at the light microscopic level in any of the tumor cell lines or CCL239 cells in response to treatment with herbimycin A. Studies using the HT29 colon adenocarcinoma cell line showed dose-dependent inactivation of pp60c-src by herbimycin A, resulting in decreased autophosphorylation, enolase phosphorylation and steady-state levels, which correlated with cellular growth inhibition. Herbimycin A-induced reductions in pp60c-src kinase activity preceded changes in pp60c-src steady-state levels. Growth and pp60c-src inhibition were reversible following removal of herbimycin A from cell culture media. Our results suggest that regulation of pp60c-src tyrosine kinase activity may be important in growth control of colon tumor cells.

Adenocarcinoma↗