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Biomedical subjects

R Garcia

Publications and source records attributed to R Garcia.

At least 19 recordsLinked to original sources
PubMed1992

Migration of grafted rat astrocytes: dependence on source/target organ.

Neonatal rat cortical astrocytes migrate extensively after transplantation into the brains of adult hosts. However, the effects of cues provided by different sources of donor astrocytes and by different target sites of implantation on this migration is unknown. In order to investigate the significance of regional influences on glial migration, we established primary cultures of astrocytes derived from 1-3 day old rat cerebral cortex, hippocampus, and hypothalamus. After in vitro labelling with either Fast Blue or fluorescein-labelled latex beads, these astrocytes were inoculated into different target regions of the adult rat brain by stereotaxic injection with a Hamilton syringe. Astrocytes implanted into the cerebral cortex migrated extensively throughout the adult brain regardless of their donor source. These implanted cells were intimately associated with the ventricular wall, glial limitans, vasculature, and fiber bundles. Astrocytes homografted into the hippocampus and the hypothalamus migrated primarily within and around the respective homotopic target organs. Migration of astrocytes derived from cerebral cortex was also limited when injections were made into these two regions. In these latter cases, migration appeared to be less guided by other cellular or regional cues than was migration after implantation into the cerebral cortex. These results suggest that the migration patterns of astrocytes grafted after tissue culture are more dependent on the target implantation site than on the donor organ.

Animals↗
PubMed1992

Family pesticide use in the home, garden, orchard, and yard.

This study examined family use of pesticides in the home, garden, orchard, and yard. Data were collected from 238 families in Missouri during telephone interviews from June 1989 to March 1990. Nearly all families (97.8%) used pesticides at least one time per year and two thirds used pesticides more than five times per year. More than 80% used pesticides during pregnancy and 70% used pesticides during the first 6 months of a child's life. The most common setting for family pesticide use was in the home, where 80% of families used pesticides at least once per year. This was followed by herbicide use to control yard weeds (57% of families) and insecticide use to control fleas and ticks on pets (50% of families). A substantial number of families also used pesticides in the garden or orchard (33%). Flea collars were the most popular pest control product (50% of families). Carbaryl or Sevin was also popular, with 28.2% of families reporting use. No-pest-strips (dichlorvos) and Kwell shampoo (lindane) were used by almost 10% of participating families. Examination of study data revealed that families limited exposure to pesticides for the mother during pregnancy and for children during the first 6 months of life. Families failed to recognize and reduce pervasive exposures associated with no-pest-strips and flea collars.

Animals↗
PubMed1992

Vascular atrial natriuretic factor receptors in spontaneously hypertensive rats.

OBJECTIVE: The aim was to investigate vascular receptors for atrial natriuretic factor (ANF) in spontaneously hypertensive (SHR), Wistar-Kyoto (WKY), and Wistar rats (WR) at different ages. METHODS: Relaxation and guanylate cyclase responses of blood vessels to atrial natriuretic factor were investigated, as was the binding of 125I-ANF to vascular membranes and ANF receptor subtypes, using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) in reducing conditions, after solubilisation and irreversible binding of 125I-ANF. RESULTS: Vascular relaxation responses of aorta showed an increased sensitivity to ANF in four week old SHR [pD2 = 8.9 (SEM 0.1) v 8.5(0.1) in WKY rats, p < 0.05] while sensitivity was similar for the three strains at older ages. Production of cyclic GMP in mesenteric arteries in response to 100 nmol.litre-1 ANF was greater (p < 0.05) in SHR than in WKY rats at four weeks of age, but was similar in older rats. The density of binding sites for ANF in mesenteric arteries, however, was lower in SHR at four weeks (p < 0.01), and increased in older rats, becoming similar to that of normotensive rats at 12 weeks of age. Affinity of ANF sites was similar in all strains. The proportion of high and low molecular weight ANF binding peptides in solubilised blood vessel membranes on SDS-PAGE was similar in all strains except in four week old SHR, in which binding to the high molecular weight band (presumably the guanylate cyclase containing receptor) was increased relative to the low molecular weight band (non-cyclase-coupled receptor) in comparison to other strains and ages. CONCLUSIONS: Activity of guanylate cyclase in response to occupancy of ANF receptors may be increased in young SHR. Normal relaxation of blood vessels in response to ANF in older SHR could result in failure to counteract the increased vasoconstrictor activity present in these rats, which could play a role in the increase in blood pressure.

Animals↗
PubMed1992

Accelographic train-of-four at near-threshold currents.

The authors evaluated train-of-four (TOF) fade, as quantified by accelography, in response to neurostimulation at currents ranging from 10 to 60 mA. This was done to determine the range of currents over which measurements of fade remain consistent. In 31 patients (ASA Physical Status 1,2, and 3), anesthesia was induced with fentanyl, midazolam, and thiopental and was maintained with isoflurane and 66% nitrous oxide in oxygen. Surface stimulating electrodes were placed over the ulnar nerve, and an acceleration transducer was placed on the thumb. Succinylcholine was administered to facilitate tracheal intubation; after neuromuscular recovery, a bolus of vecuronium (0.01-0.05 mg.kg-1) and an infusion (0.25-1.5 micrograms.kg-1.min-1) were administered. After documentation of a stable TOF ratio, accelographic TOF responses were quantified in response to 200-microseconds stimulation at 10, 15, 20, 30, 40, 50, and 60 mA, in random order. A total of 95 data sets were collected at different depths of blockade. The TOF ratios maintained intercurrent consistency (P = not significant by nonparametric repeated measures analysis of variance), except at currents near the fourth-twitch (T4) threshold current. This inconsistency was eliminated by testing at greater than or equal to 10 mA above threshold. TOF ratios obtained at 10 mA above T4 threshold correlated highly with those at 60 mA (Spearman r value = 0.94). The authors conclude that the TOF ratio is consistent over a wide range of stimulating currents and that testing with submaximal currents can be performed reliably at greater than or equal to 10 mA above the T4 threshold.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

The hippocampo-septal projection in mice: long-term potentiation in the lateral septum.

In anaesthetized young mice, the fimbria was stimulated and field potentials were recorded ipsilaterally in the lateral septum (LS). Evoked responses were typically characterized by a two-component negative wave (N2 and N3) followed by a low amplitude positive wave. The amplitudes and latencies were highest and shortest respectively in the dorsal LS for the N3 component and in the ventral LS for the N2 component. Tetanic stimulation of the fimbria induced long-term potentiation (LTP) only in the case of the N3 component. The differential changes in N2 and N3 following tetanic fimbrial stimulation are discussed in the context that the dorsal LS appears to exhibit a higher density of LTP-mediating receptors.

Animals↗
PubMed1992

Identification of the defective NADPH-oxidase component in chronic granulomatous disease: a study of 57 European families.

Chronic Granulomatous Disease (CGD) manifests as a predisposition to infection as a result of defective function of the NADPH oxidase of phagocytic cells. Proteins identified as part of this system include two subunits of a cytochrome b (cytochrome b-245) and two cytosolic factors. The affected oxidase component was determined in 63 CGD patients from 57 families, by Western blotting of extracts of their neutrophils with antibodies to those proteins. 38 (67%) of the families were X-linked with a defect of the beta subunit of the cytochrome. 13 (23%) lacked p47-phox, 3 (5%) p67-phox, and 3 (5%) the alpha subunit of the cytochrome.

Amino Acid Sequence↗
PubMed1992

Production of heterohybridomas secreting autoreactive and polyreactive human monoclonal antibodies.

Peripheral blood lymphocytes from two polytransfused renal dialysis patients were transformed by Epstein-Barr virus, fused to a heteromyeloma and cloned. Eight human monoclonal antibodies from the resulting clones were tested for their binding to a variety of antigens by ELISA, indirect immunofluorescence and immunoblotting. Antigens tested included B-cell lines, T and B lymphocytes, red blood cells, chronic lymphocytic leukaemic B cells, IgG, ssDNA, dsDNA, histones, nucleoprotamine, sperm nuclei, thymus and spleen extracts, MOLT4 cell lysates, affinity purified autoantigens, tetanus toxoid, bacterial lipopolysaccharide, insulin, and a tissue section screen. These human monoclonal antibodies reacted with more than one antigen to varying degrees and were autoreactive and polyreactive. One of these heterohybridoma cell lines exhibited cytoplasmic staining with an anti-CD5 monoclonal. Our findings support the concept that in adult individuals a subset of B cells produce heterogeneous IgM antibodies which can bind to a variety of different autoantigens and also to foreign antigens. These monoclonals were different from the autoantibodies usually seen in renal dialysis patients in the sense that they were not lymphocytotoxic.

Antibodies↗
PubMed1992

Chronic captopril and losartan (DuP 753) administration in rats with high-output heart failure.

We investigated the role of atrial natriuretic factor (ANF) and the renin-angiotensin system as well as the effects of losartan in rats with aortocaval (AC) shunts. Right atrial and left ventricular end-diastolic pressures (LVEDP) were higher and mean arterial blood pressure (MAP) was lower in AC shunt animals than in their controls. AC shunt rats presented marked cardiac hypertrophy, decreased right atrial ANF concentration, and increased ventricular ANF content and concentration. Plasma ANF levels were elevated, and hematocrit was lower in AC shunt animals than in controls. Captopril or losartan treatment decreased MAP and returned LVEDP to sham-operated control values. A clear regression of cardiac hypertrophy was evident in both treated AC shunt groups, with plasma ANF levels tending to follow those in sham-operated rats. Plasma COOH-terminal ANF levels were decreased and urinary volume and hematocrit were increased in losartan-treated AC shunt animals. We conclude that chronic angiotensin converting enzyme inhibition and angiotension II receptor antagonism improved hemodynamic conditions, diminished water retention, reversed cardiac hypertrophy, and restored plasma and tissue ANF to more "normal" levels in rats with moderate high-output heart failure.

Angiotensin Receptor Antagonists↗
PubMed1992

Divergent regulation of atrial natriuretic factor receptors in high-output heart failure.

We have investigated whether binding parameters and subtypes of glomerular, papillary, and vascular atrial natriuretic factor (ANF) receptors differ in rats with moderate high-output heart failure [aortocaval (AC) shunt] from their sham-operated controls. Body weight was lower and relative heart weight was higher in the AC shunt group than in the control group. Plasma renin activity (PRA) was also greater in AC shunt rats. Plasma COOH- and NH2-terminal ANF levels were higher in AC shunt animals than in their control counterparts. Total atrial ANF content was elevated in both the right and left atria of the AC shunt group. Glomerular and papillary ANF receptor density (Bmax) and ANF receptor affinity (Kd) were similar in both AC shunt and control rats. Vascular ANF receptor density and affinity were lower in AC shunt (Bmax = 65 +/- 13 fmol.mg protein; Kd = 467 +/- 52 pM) than in control rats (Bmax = 188 +/- 34 fmol.mg protein; Kd = 278 +/- 11 pM). Irreversible cross-linking of 125I-labeled ANF followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions and radioautography demonstrated that both high- and low-molecular weight receptors were unchanged in glomerular membranes and downregulated in vascular membranes from AC shunt animals. However, guanosine 3',5'-cyclic monophosphate (cGMP) production by the isolated glomeruli of AC shunt rats was lower than that of controls. We conclude that in the presence of elevated plasma ANF levels, glomerular, papillary, and vascular ANF receptors may be regulated differently.

Animals↗
PubMed1992

Rat brain natriuretic peptide is localized in atrial granules and released into the circulation.

Rat brain natriuretic peptide (BNP) was detected by radioimmunoassay in heart atria and ventricles and in plasma. We have investigated its localization in atria and the possibility of cosecretion of atrial natriuretic factor (ANF) and BNP into the circulation. BNP was detected by chromatographic analysis and immunoblotting in the isolated atrial granules together with ANF: It consisted of two immunoreactive proteins of 14,000 and 2,500 apparent molecular weight. By immunohistochemical methods, BNP was particularly found in the perinuclear region of atrial cardiocytes. Double-labeling immunocytochemical methods colocalized BNP and ANF in the same atrial secretory granules. Basal plasma BNP levels ranged from 2.6 to 4.4 fmol/ml. After stimuli by morphine injection or an aortocaval shunt, BNP levels increased by 4- and 7-fold, respectively, whereas ANF levels rose by 50- and 6-fold, respectively. Depending on the stimulus, BNP release into the circulation is not necessarily proportional to ANF, indicating that BNP may originate not only from the atrial granules but also from other tissues such as the ventricles. These results suggest that BNP may participate with ANF in blood pressure control and salt and water homeostasis.

Animals↗
PubMed1992

Angiotensin II receptor subtypes in rat renal preglomerular vessels.

A simple technique to isolate rat renal preglomerular vessels is described. Kidneys were pressed against a 0.3 mm stainless steel grid. The whole vascular tree, including the interlobar, arcuate, and interlobular arteries, as well as the afferent arterioles, remained on the grid surface from where they were recovered. Extensive washing yielded a highly pure preparation of renal microvessels. Radioligand binding experiments were performed to characterize 125I-[Sar1,Ile8]-ANG II binding sites in preglomerular microvessel membranes. Equilibrium saturation binding experiments revealed the presence of one group of high affinity receptors (Kd = 1.22 +/- 0.171 nM; Bmax = 209 +/- 14 fmol/mg protein). Competitive inhibition experiments with two highly specific nonpeptide ANG II antagonists, losartan (DuP 753), which is specific for the AT1 receptor subtype, and PD123319, which is specific for the AT2 subtype, demonstrated that the large majority of, if not all, ANG II receptors in rat renal preglomerular vessels correspond to the AT1 subtype.

Angiotensin II↗
PubMed1992

Characterization of glomerular angiotensin II receptor subtypes.

Radioligand-receptor binding techniques identified two angiotensin II (ANG II) receptor subtypes in rat renal glomerular membranes. This characterization was made possible by employing two highly-specific nonpeptide ANG II antagonists: Losartan (DuP 753), which is specific to the AT1 subtype, and PD 123319, which is specific to the AT2 subtype. The majority of ANG II receptors in glomerular membranes corresponded to the AT1 subtype.

Angiotensin II↗