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Biomedical subjects

G Torres

Publications and source records attributed to G Torres.

At least 91 records · Page 5Linked to original sources
PubMed1993

Polyclonal 111In-IgG, 125I-LDL and 125I-endothelin-1 accumulation in experimental arterial wall injury.

To test iodine-125 labelled low-density lipoprotein (125I-LDL), polyclonal indium-111 labelled immunoglobulin G (111In-IgG) and iodine-125 labelled endothelin-1 uptake in metabolically active atheromatous plaques after arterial wall injury, we performed balloon de-endothelialization of carotid arteries or abdominal aortas in 24 New Zealand male rabbits which were fed with a normal diet (n = 14) or a hypercholesterolaemic diet (n = 10) after surgery. Six weeks later the animals were injected with 200 microCi of 125I-LDL and/or with 100 microCi of 111In-IgG or with 9 microCi of 125I-endothelin-1. Forty-eight hours later the animals were sacrificed. Carotid arteries and aortas were removed, counted and fixed for autoradiography and light microscopy examination. Contralateral carotid arteries and thoracic aortas served as controls. Significant 111In-IgG uptake was observed in the injured arteries at autoradiography, with localization mainly in the healing edges, and at well counting. The percentage of the injected dose per gram (%D.inj/g) was 0.0188 +/- 0.06 versus 0.0059 +/- 0.003 in controls (P < 0.05). There was no difference in 111In-IgG uptake between arteries with injury alone and those with active atheroma formation at the site of the injury. Significant 125I-LDL uptake was observed only when lipid deposition was present at light microscopy (%D.inj/g of 0.0024 +/- 0.0005 vs. 0.0010 +/- 0.0003 in controls, P < 0.05). 125I-endothelin-1 accumulation was observed in four of five injured aortas both at autoradiography, with diffuse localization, and at well counting (%D.inj/g of 0.0012 +/- 0.0004 in the abdominal aortas vs 0.0008 +/- 0.0003 in the thoracic aortas).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Cocaine-induced expression of striatal c-fos in the rat is inhibited by NMDA receptor antagonists.

To assess the possible involvement of NMDA receptors in mediating the expression of striatal c-fos by cocaine injection, we investigated the effects of the noncompetitive NMDA receptor antagonists, ketamine and (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801), as well as the competitive NMDA receptor antagonist, 3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), in the perikarya of cocaine-treated rat brains. As previously shown by our group, administration of 20 mg/kg cocaine (IP) resulted in the immunocytochemical expression of the protooncogene in numerous cells of the caudate putamen (dorsal/sensorimotor striatum). A ketamine mixture anesthetic (2 mg/kg), however, administered 30 min prior to cocaine exposure completely blocked such genomic expression. Pretreatment with MK-801 (1 mg/kg) or CPP (5 mg/kg) also interfered, albeit to a lesser extent, with the expression of c-fos by cocaine in awake animals. These results indicate that cocaine induction of cellular c-fos in the caudate putamen is mediated at least in part by NMDA-sensitive receptors.

Animals↗
PubMed1993

Preexisting human anti-murine antibodies and the effect of immune complexes on the outcome of immunoscintigraphy.

Radiolabeled monoclonal antibodies (MoAb) are useful in radionuclide imaging. Human anti-murine antibodies (HAMA), however, could produce immunologic effects or alter the outcome of immunoscintigraphy. Three patients are reported who had been exposed previously to radiolabeled MoAbs and in whom subsequent immunoscintigraphy was performed. All patients showed abnormal biodistribution of the antibody and increased hepatic uptake. Human anti-murine antibody was demonstrated in all patients. These results indicate that immune complexes are formed after HAMA-MoAb reaction and are then phagocytosed by cells of the reticuloendothelial system.

Aged↗
PubMed1993

Salivary alpha-amylase: role in dental plaque and caries formation.

Salivary alpha-amylase, one of the most plentiful components in human saliva, has at least three distinct biological functions. The enzymatic activity of alpha-amylase undoubtedly plays a role in carbohydrate digestion. Amylase in solution binds with high affinity to a selected group of oral streptococci, a function that may contribute to bacterial clearance and nutrition. The fact that alpha-amylase is also found in acquired enamel pellicle suggests a role in the adhesion of alpha-amylase-binding bacteria. All of these biological activities seem to depend on an intact enzyme conformation. Binding of alpha-amylase to bacteria and teeth may have important implications for dental plaque and caries formation. alpha-Amylase bound to bacteria in plaque may facilitate dietary starch hydrolysis to provide additional glucose for metabolism by plaque microorganisms in close proximity to the tooth surface. The resulting lactic acid produced may be added to the pool of acid in plaque to contribute to tooth demineralization.

Animals↗
PubMed1993

Myocyte cell damage after administration of doxorubicin or mitoxantrone in breast cancer patients assessed by indium 111 antimyosin monoclonal antibody studies.

PURPOSE: To compare myocyte cell damage induced by doxorubicin or mitoxantrone, we performed left ventricular ejection fraction (LVEF) measurements and indium 111 antimyosin antibody studies in a group of patients with advanced breast cancer who had been treated with these anthracycline derivatives. PATIENTS AND METHODS: We studied 35 patients eligible to receive chemotherapy including the anthracyclines: doxorubicin or mitoxantrone (cumulative dose of doxorubicin, 500 mg/m2; or mitoxantrone, 120 mg/m2). LVEF was measured before and after 10 cycles of chemotherapy. Antimyosin uptake in the myocardium was quantified by means of a heart-to-lung ratio (HLR). RESULTS: Patients treated with doxorubicin presented with a significant decrease in LVEF after chemotherapy (before, 60.4% +/- 8.92%; after, 49.8% +/- 9.71%; P = .001). Antimyosin uptake was observed in all patients with a HLR of 2.03 +/- 0.25. Seven of eight patients with a HLR greater than 2.03 had a greater than 10% decrease in LVEF. Patients treated with mitoxantrone did not present with a decrease in LVEF after chemotherapy (before, 55.4% +/- 6.25%; after, 55.8% +/- 7.25%; not significant). Antimyosin uptake was observed in 14 of 17 patients with a HLR of 1.77 +/- 0.18 (P < .05). CONCLUSION: 111In antimyosin monoclonal antibodies defect myocardial cell damage produced by doxorubicin and mitoxantrone. In patients with advanced breast cancer, cumulative doses of 120 mg/m2 of mitoxantrone produce less myocardial cell damage than cumulative doses of 500 mg/m2 of doxorubicin. 111In antimyosin uptake without decrease in LVEF after treatment with mitoxantrone indicates the presence of myocyte cell damage, but not to the extent necessary to deteriorate function. These results indicate that 111In antimyosin antibody studies are useful in the noninvasive comparative assessment of cardiotoxicity produced by different anthracycline derivatives.

Adult↗
PubMed1993

A new approach to combatting iodine deficiency in developing countries: the controlled release of iodine in water by a silicone elastomer.

OBJECTIVES: Four hundred million people or more may be exposed to iodine deficiency worldwide, in developing countries in particular. Because of the practical problems with existing methods for the large-scale prevention of iodine deficiency, the authors developed a new approach to collective prophylaxis. METHODS: This approach relies on the controlled diffusion of iodine into water from a silicone elastomer. Silicone matrices installed in a bore well released iodine at a rate sufficient to permit the daily per capita intake of at least 100 micrograms of iodine, the amount recommended by the World Health Organization. The matrices were tested over 1 year in a village in Mali, West Africa, an area in which goiter was highly endemic. The effects on the well water and population were compared with those of a placebo system in a control village. RESULTS: An increase in urinary iodine levels was observed in the treated population, and after 12 months the incidence of goiter had fallen from 53.2% to 29.2%. CONCLUSIONS: This new concept, adaptable to all sources of water supply, may contribute to the eradication of iodine deficiency.

Adult↗
PubMed1993

Detection of doxorubicin cardiotoxicity in patients with sarcomas by indium-111-antimyosin monoclonal antibody studies.

To assess myocardial cell damage due to doxorubicin cardiotoxicity, we prospectively studied 30 patients with sarcomas who were receiving chemotherapy, including doxorubicin. Sixteen patients were treated by continuous infusion over 72 hr and 14 patients were treated by bolus injection. Antimyosin studies and left ventricular ejection fraction (LVEF) measurements were performed before chemotherapy and at intermediate and maximal cumulative doses. Myocardial antimyosin uptake was quantified by a heart-to-lung ratio (HLR). Myocardial antimyosin uptake was observed in all patients at 240-300 mg/m2 when ejection fraction was still maintained. Seven patients presented with a decrease of > or = 10% in absolute ejection fraction units at 420-600 mg/m2. Five of these patients had mild congestive heart failure. All patients who presented with a decrease in LVEF > or = 10% at 420-600 mg/m2 had increased antimyosin uptake with HLR > or = 1.90 at a cumulative dose of 240-300 mg/m2. Patients who were treated with continuous infusion had less antimyosin uptake than those who were treated with bolus administration (mean HLR of 1.70 +/- 0.09 versus HLR of 2.01 +/- 0.16 at a cumulative dose of 240-300 mg/m2, p < 0.01; HLR of 1.86 +/- 0.12 versus HLR of 2.32 +/- 0.34 at a cumulative dose of 420-600 mg/m2, p < 0.01). Two of 16 patients treated by continuous infusion and 5 of 14 patients treated by bolus injection presented with a decrease in ejection fraction > or = 10%. LVEF after chemotherapy in the infusion group was 56% +/- 5% and 48% +/- 8% (p < 0.05) in the bolus group. Antimyosin studies are helpful in the assessment of doxorubicin cardiotoxicity. Intense antimyosin uptake at intermediate cumulative doses identifies patients at risk of cardiotoxicity before ejection fraction deteriorates. Patients with sarcomas treated by continuous infusion present with less antimyosin uptake than those treated with bolus injection, indicating less severe cardiotoxicity.

Antibodies, Monoclonal↗
PubMed1992

Co-release of neuropeptide Y (NPY) and noradrenaline from the sympathetic nerve terminals supplying the rat vas deferens; influence of calcium and the stimulation intensity.

Epididymal (E) and prostatic (P) segments of the rat vas deferens were incubated with tritium-labeled noradrenaline (NA); upon transmural electrical stimulation for 20 or 60 s (70 V, 1 ms, 3-35 Hz), the outflow of immunoreactive neuropeptide Y (ir-NPY) and NA was detected in the superfusion media. Ir-NPY was detected only following trains of 35 Hz for 60 s in both E and P. In contrast, tritium was released in a graded fashion following trains of 3, 15 or 35 Hz stimulation for 60 s in E, whereas in P it reached a plateau at frequencies larger than 15 Hz. The outflow of tritium, under present conditions, was dependent on the duration of the stimuli, while the release of ir-NPY was only evoked with stimuli of 60 s duration. In the absence of external Ca2+, neurotransmission was blocked and co-release of ir-NPY and NA was prevented.

Animals↗
PubMed1992

Immunocytochemical and in situ hybridization detection of hypothalamic neuropeptides from postmortem unfixed rat brains.

The effects of postmortem delay on neuropeptide-containing perikarya was studied in the paraventricular nucleus (PVN) of the rat hypothalamus. Serial sections from brains kept in the skull after death for 6 h and immunocytochemically processed for oxytocin (OT), vasopressin (AVP) and corticotropin releasing factor (CRF) or hybridized in situ for CRF resulted in the well preserved phenotypic expression and stability of mRNA of the aforementioned neuropeptides. Furthermore in most cases, AVP and CRF expression was discernibly enhanced relative to prefixed immunopositive tissue. Results of this study suggest that postmortem variables do not significantly alter the neurochemical coding of magnocellular or parvocellular neurosecretory systems, and support the view that rat and human brain topography can be investigated from tissue left in situ after death for a relatively long period of time.

Adrenalectomy↗
PubMed1992

Differential effects of central and peripheral injection of interleukin-1 beta on brain c-fos expression and neuroendocrine functions.

Cytokines such as interleukin-1 beta (IL-1 beta) alter the activity of the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes in the rat. However, the brain sites at which IL-1 beta exerts these effects have not been well identified. The present study sought to identify some of these sites, using c-fos protein expression as an index of cellular activation. We also attempted to determine possible differences between the effects of peripheral and central injection of IL-1 beta on the activation of specific brain areas. Castrated male rats received intravenous (i.v.) or intracerebroventricular (i.c.v.) injections of IL-1 beta through a jugular catheter or a permanent cannula implanted in the right lateral ventricle, respectively. Blood samples were taken before, as well as 30 and 120 min after i.v. or i.c.v. IL-1 beta infusion in order to measure plasma ACTH and LH levels. Immediately thereafter, the rats were anesthetized with pentobarbital, then perfused. Their brains were removed and postfixed for one hour. Thirty-microns frozen sections were cut and approximately every fourth tissue section was processed for c-fos expression by an avidin-biotin-peroxidase method. Both i.v. (1 microgram) and i.c.v. (100 ng) injection of IL-1 beta significantly increased plasma ACTH levels, but only i.c.v. treatment measurably inhibited LH secretion. I.c.v. infusion of the cytokine markedly augmented c-fos expression in the paraventricular nucleus (PVN) and the arcuate nucleus (ARC) of the hypothalamus. A large amount of CRF cells in the PVN contained labelled c-fos protein (as measured by a double labelling technique), which indicates that CRF perikarya in this hypothalamic region are activated by the central administration of IL-1 beta. In contrast, i.v. injection of IL-1 beta did not significantly alter c-fos expression in the PVN or the ARC of the hypothalamus. These results suggest that the increased HPA axis activity which follows the peripheral IL-1 beta administration, a phenomenon previously shown to depend on endogenous CRF, does not require immediate activation of hypothalamic CRF perikarya. Thus our results indicate that the stimulatory effect of blood-born cytokine may be exerted at the level of nerve terminals in the median eminence. In contrast, i.c.v.-injected IL-1 beta appears to activate the HPA axis through a stimulation of CRF neurons within the parvocellular part of PVN.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenocorticotropic Hormone↗
PubMed1992

[Cerebral single-photon emission-computed tomography. A semiquantitative analysis of vascular areas in patients with cerebrovascular pathology].

BACKGROUND: Brain SPECT perfusion studies in patients with cerebral stroke may be useful to evaluate distant perfusion abnormalities. METHODS: 99mTc-HMPAO brain SPECT studies were performed in 17 patients with ischemic lesions in the basal ganglia and/or internal capsule demonstrated by NMR. Regions of interest were adjusted in representative transverse slices to the vascular territories of the anterior, middle, posterior and communicating cerebral arteries. RESULTS: Patients with ischemic lesions in the right basal ganglia showed increased cerebral perfusion in the left middle artery territory (0.95 +/- 0.13 versus 0.80 +/- 0.06; p = 0.0365). Patients with ischemic lesions in the left basal ganglia showed increased perfusion in the right anterior artery territory (0.93 +/- 0.09 versus 0.82 +/- 0.09; p = 0.0464), in the left anterior artery territory (0.93 +/- 0.09 versus 0.83 +/- 0.14; p = 0.0464), in the left middle artery territory (0.92 +/- 0.09 versus 0.78 +/- 0.05; p = 0.0079) and in the left posterior artery territory (1.05 +/- 0.14 versus 0.90 +/- 0.09; p = 0.036). Patients with ischemic lesions in the right internal capsule showed increased perfusion in the right posterior artery territory (0.95 +/- 0.11 versus 1.10 +/- 0.18; p = 0.0431). CONCLUSIONS: These results show the presence of delayed luxury perfusion phenomena in regions distant from the ischemic site.

Aged↗
PubMed1992

Differential effects of intermittent or continuous exposure to cocaine on the hypothalamic-pituitary-adrenal axis and c-fos expression.

Accumulating evidence indicates that acute administration of cocaine alters neuroendocrine functions. In order to ascertain the long-term effects of cocaine on the male rat's hypothalamic-pituitary-adrenal (HPA) axis, a series of experiments were performed utilizing two different paradigms of cocaine administration for 6 days. In the first paradigm, rats received daily intravenous injections of cocaine (5 mg/kg), while in the second, they were continuously exposed to the drug (5 or 100 mg/kg/day) via osmotic pumps. We measured plasma adrenocorticotropin hormone (ACTH) and corticosterone levels, as well as the brain pattern of the proto-oncogene c-fos expression in response to either mode of drug administration. Repeated, intermittent injections of cocaine caused consistent increases in ACTH and corticosterone secretion over a 30-min sampling period on days 2, 4 and 6. This paradigm of drug administration also induced considerable, short-lasting and reversible c-fos expression in the caudate putamen but not in hypothalamic regions associated with endocrine function. In contrast, we consistently failed to observe any measurable increases in ACTH or corticosterone secretion at any time during continuous exposure to the drug. Administration of cocaine by osmotic pumps also had no effect on c-fos expression in the caudate putamen, indicating that c-fos expression as well as activation of the HPA axis are dependent upon the mode and frequency in which cocaine is administered. We conclude that continuous exposure to cocaine does not appear to activate the HPA axis, while intermittent injections of the drug induce repeated increases in plasma ACTH and corticosterone levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1992

Technetium-99m human polyclonal immunoglobulin G studies and conventional bone scans to detect active joint inflammation in chronic rheumatoid arthritis.

Rheumatoid arthritis is a chronic polyarthritis in which active inflamed joints coexist with joints in remission. We performed bone scans (99mTc-DPD) and 99mTc human polyclonal immunoglobulin G scans (99mTc-IgG) in 18 patients with rheumatoid arthritis to assess the uptake in actively inflamed joints and in joints in which remission after inflammation had occurred. A quantitative analysis of tracer uptake in each joint was performed on both scans. In 123 joints without current active inflammation, an increased 99mTc-DPD uptake was observed (2.31 +/- 1.27), whereas no 99mTc-IgG uptake was noted (1.18 +/- 0.32). Some 78 joints with mild pain or swelling exhibited increased 99mTc-DPD uptake (2.48 +/- 1.14) and increased 99mTc-IgG uptake (1.76 +/- 0.50; P less than 0.001), while 21 joints with moderate to severe pain or swelling exhibited increased 99mTc-DPD uptake (2.39 +/- 0.93) and increased 99mTc-IgG uptake (1.79 +/- 0.51; P less than 0.001). In conclusion, 99mTc-IgG scans distinguish between joints with and without active inflammation in chronic rheumatoid arthritis, whereas bone scans do not. Thus, 99mTc-IgG scans may be useful in identifying joints with current active inflammation in rheumatoid arthritis.

Aged↗
PubMed1992

Cocaine-induced stimulation of the rat hypothalamic-pituitary-adrenal axis is progressively attenuated following hourly-interval regimens of the drug.

The role of multiple (iv) injections of cocaine on the rat hypothalamic-pituitary-adrenal (HPA) axis was examined using four different temporal regimens of drug exposure. In intact rats, cocaine (5 mg/kg) consistently stimulated the secretion of adrenocorticotropin hormone (ACTH) and corticosterone over a 6 hr interval regimen. In all experimental groups, administration of the vehicle alone failed to measurably alter the secretion of the aforementioned hormones. When rats where exposed to the drug over a 4 hr interval regimen, a modest attenuation of ACTH, but not corticosterone, secretion was observed following the third and last cocaine injection. To test whether the attenuation of ACTH secretion to cocaine administration was caused by corticosterone-mediated negative feedback, the response of intact and adrenalectomized (ADX) rats over 2 hr and 1 hr interval regimens was compared. In intact rats, both drug interval regimens resulted in a significant attenuation of ACTH secretion following, the second and third injections of the drug. ADX rats, on the other hand, exhibited significant increases in ACTH levels following either interval regimens, though we observed a modest blunting of pituitary responsiveness to the 1 hr regimen. From these results we conclude that in intact rats the activity of the HPA axis is significantly attenuated in response to multiple, acute cocaine injections, and that this decreased response may be at least in part caused by a negative corticoid feedback mechanism.

Adrenalectomy↗
PubMed1992

Cocaine-induced ACTH secretion: dependence of plasma levels of the drug and mode of exposure.

To determine whether changes in pituitary responsiveness might account for the lack of corticotropin (ACTH) stimulation following 6 consecutive days of continuous cocaine administration (5 or 25 mg/kg/day, via osmotic minipumps), the hormonal response of vehicle- or cocaine-pretreated male rats was compared. Intravenous injections of synthetic corticotropin-releasing factor (CRF) (0.2, 1, or 5 micrograms/kg) elicited dose-dependent increases in ACTH secretion irrespective of whether rats had been previously exposed to cocaine or not. Similarly, in both vehicle- and cocaine-pretreated rats ACTH response to acute injections of the drug was identical, indicating that pituitary corticotrophs remained responsive following continuous administration of cocaine. To determine and compare plasma concentrations of cocaine and its metabolites after continuous or acute administration of the drug, pharmacokinetics analysis of concentration vs. time was ascertained. Circulating concentrations of cocaine from rats continuously exposed to the drug were relatively low throughout the 6 days of exposure. In contrast, intravenous injections of cocaine produced peak concentrations of the drug that were significantly higher than those measured during continuous cocaine infusion. Such peak concentrations in cocaine correlated with marked increases in plasma ACTH levels. Plasma concentrations of the metabolites benzoylecgonine and methyl ester ecgonine followed a pharmacokinetic clearance similar to that of the parent compound, with low concentrations detected during continuous exposure whereas high concentrations were observed following intravenous injections of the drug. Our results suggest two nonmutually exclusive conclusions. First, there may be a critical threshold of cocaine plasma concentrations (as indicated by our results as being over 800 ng/ml) that are necessary for activation of the hypothalamic-pituitary-adrenal axis to occur.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1992

Nursing research in the VA system. A consortium approach.

Five Veterans' Administration Medical Centers formed a consortium to promote nursing research. Consortium arrangements focusing on research are reviewed based on the literature, the consortium's experience, and a survey of 171 VA facilities. Consortiums are suggested for multisite facilities, such as city, state, proprietary, and religious hospital systems, to increase the quality and quantity of nursing research where institutional mechanisms for overcoming the difficulties of meeting and sharing information are already in place.

Hospitals, Veterans↗
PubMed1992

[Detection of respiratory syncytial and adenovirus in nasopharyngeal aspirates: comparison of cellular cultures and immunofluorescence].

Respiratory syncytial and adenovirus are 2 of the most important pathogens for respiratory infection in infancy. We compared the results of cellular cultures and immunofluorescence in the detection of these agents in nasopharyngeal exudates from hospitalized infants. Evidence for respiratory syncytial virus was searched in 776 samples. Immunofluorescence was much more sensitive, detecting 303 positive results, compared to only 142 for cell culture. Compared to immunofluorescence, the sensitivity and specificity of cell culture was 44% and 98%, respectively. Adenoviruses were investigated in 498 samples by both techniques. 88 positive results were identified by cell culture and only 30 by immunofluorescence. The sensitivity of immunofluorescence, compared to cell culture, was 31%, with a specificity of 99%. Thus, immunofluorescence is the technique of choice for detection of respiratory syncytial virus, while cell culture is preferable for adenovirus.

Adenoviridae Infections↗