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Biomedical subjects

C Gonzalez

Publications and source records attributed to C Gonzalez.

At least 271 records · Page 15Linked to original sources
PubMed1985

Effect of streptozotocin diabetes and insulin replacement on growth hormone in rats.

The effects of insulin deprivation on the growth rate, plasma and pituitary growth hormone (GH) and GH synthesis were investigated in male Wistar rats. Diabetes was induced by administration of streptozotocin (STZ), 7 mg/100 g bw, and plasma and pituitary GH levels were measured by means of a specific radioimmunoassay. GH synthesis was determined in pituitaries by the in vitro incorporation of [3H] leucine into specific immunoprecipitates. The body weight and the pituitary GH content of normally developing rats showed an almost linear increase throughout the observation period, whereas diabetic rats stopped growing immediately after receiving STZ, and remained smaller than age-paired controls. Pituitary GH content remained within the control range through the 5 days following STZ administration and thereafter decreased reaching 10% of control values by the 30th day. Furthermore, pituitaries from diabetic rats incorporated [3H] leucine into r-GH at a greatly reduced rate, which could explain the diminished r-GH storage in pituitaries of diabetic rats. Plasma GH concentrations remained within the normal range for 10 days after STZ, thereafter plasma GH were markedly reduced. Insulin treatment prevented the metabolic changes, and restored normal levels of plasma and pituitary GH in diabetic rats. These findings indicate that diabetes, in rat, is characterized by an inhibitory effect on GH secretion, probably via a diminished GH synthesis by the pituitary gland.

Animals↗
PubMed1984

Effects of low pH on synthesis and release of catecholamines in the cat carotid body in vitro.

The rates of dopamine and noradrenaline synthesis in the cat carotid body (c.b.) are 5.9 +/- 0.58 pmol/c.b./2 h and 0.3 +/- 0.02 pmol/c.b./2 h, respectively. The synthesis is doubled when the organs are incubated at pH 7. Similarly, low pH induces a release of dopamine from the c.b. which is proportional to increased activity in the carotid sinus nerve.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1984

Resistance of Aeromonas hydrophila to beta-lactam antibiotics.

The activity of some beta-lactam antibiotics upon 20 strains of Aeromonas hydrophila and some properties of their beta-lactamases have been studied. High degree of resistance to benzylpenicillin and lower resistance to ampicillin and cephaloridine was observed. Clavulanic acid showed the highest activity. When clavulanic acid was assayed at subinhibitory concentrations in association with ampicillin. MICs of the latter decreased to two- to eight-fold. All strains produced inducible beta-lactamases with high activity upon ampicillin. A group of cephalosporinase-like enzymes was also found. Some beta-lactamases were inhibited by cloxacillin, and most of them were completely inhibited by 5 mg/l of clavulanic acid. Low impermeability of Aerom. hydrophila cells to beta-lactams was observed.

Aeromonas↗
PubMed1983

Effects of verapamil and manganese on the vasoconstrictor responses to noradrenaline, serotonin and potassium in human and goat cerebral arteries.

The effects of verapamil and manganese (Mn2+) on the noradrenaline (NA), serotonin (5-HT) and potassium (K+)-induced contractions were studied in human and goat cerebral arteries. Verapamil and Mn2+ relaxed both kinds of cerebral vessels previously contracted with 10(-5) M NA, 10(-5) M 5-HT and 75 mM K+. The ID50 (50% inhibition of maximum contraction) was around 10(-7) M for the organic antagonist and 10(-3) M for the inorganic one. The ID50 for the Ca2+ antagonists in K+-induced contractions was smaller than that for NA and 5-HT-evoked contractions. Preincubation of segments with verapamil (10(-6) M) or Mn2+ (2 X 10(-3) or 5 X 10(-3) M) caused inhibition of the contractions evoked by the three agents that was greater in the case of K+. The inhibitory effects of verapamil were reversed by adding Ca2+ to the bath. The removal of Ca2+ from the extracellular medium reduced the contractions elicited by the three vasoconstrictor agents in both cerebral blood vessels. This reduction was greater for K+ than for the other two. These results indicate that both cerebral vessels are very susceptible to Ca2+ omission and to Ca2+ entry blockers such as verapamil and Mn2+, which could be of interest to treat cerebral vasospasm.

Animals↗
PubMed1983

Differential susceptibility of Aeromonas hydrophila and Enterobacteriaceae to nalidixic acid.

The susceptibility of 49 strains of Aeromonas hydrophila and 77 strains of Enterobacteriaceae towards nalidixic acid was compared by tube dilution and agar diffusion methods. A higher susceptibility was exhibited by Aerom. hydrophila and no overlap in MICs was found for strains of the two groups of microorganisms. Discs containing 0.25 microgram of nalidixic acid produced measurable zones of growth inhibition with Aerom. hydrophila and no zones with the Enterobacteriaceae. The use of a disc with 0.25 microgram of nalidixic acid for the primary differentiation of strains of Aerom. hydrophila from those of the Enterobacteriaceae with similar biochemical properties is suggested.

Aeromonas↗
PubMed1983

Severe renovascular hypertension in a recipient of renal transplant: an indication for nephrectomy?

A 28-year-old patient receiving a kidney transplant from a 2-year-old cadaver kidney donor is described. The patient developed hypertension in the posttransplant period due to renal arterial stenosis. The hypertension was unresponsive to oral therapy after several unsuccessful attempts to correct the stenosis, nephrectomy of the transplanted kidney was performed resulting in the control of the hypertension.

Adult↗
PubMed1983

Leucopenia, hypoxia and complement activation in haemodialysis. Three unrelated phenomena.

Acute, transient leucopenia occurs in uraemic patients during the first minutes of haemodialysis, haemofiltration and ultrafiltration, and this leucopenia depends on the membrane used: maximal with cuprophan, less marked using cellulose acetate in haemofiltration and minimal with polyacrylonitrile. Complement activation was noted in all dialysis procedures except ultrafiltration. However, no correlation was found between the intensity of the complement activation and the degree of leucopenia. Significant hypoxia only appeared in haemodialysis using an acetate bath even with the polyacrylonitrile membrane. Sequential ultrafiltration-dialysis studies clearly demonstrate that leucopenia and hypoxia are unrelated effects of haemodialysis. Leucopenia depends on the membrane used and hypoxia may be related to the use of an acetate dialysate. In addition, the presence of dialysis fluid was necessary for membrane-induced complement activation suggesting an important influence of the dialysate on membrane biocompatibility.

Acetates↗
PubMed1982

Catecholamine synthesis in rabbit carotid body in vitro.

1. Catecholamine synthesis in rabbit carotid body was studied in vitro using [(3)H]DOPA and [(3)H]tyrosine as precursors. The effects of sympathectomy and transection of the carotid sinus nerve on [(3)H]dopamine ([(3)H]DA) and [(3)H]noradrenaline ([(3)H]NA) synthesis were investigated in chronically denervated carotid bodies.2. When [(3)H]DOPA was used as precursor, the synthesis of [(3)H]DA was linear for more than 6 hr. The carotid body synthesized larger amounts of [(3)H]catecholamines than when [(3)H]tyrosine was used as precursor, but most of this excess was liberated into the incubation media. Using 10 muM-[(3)H]DOPA as precursor, the synthesis rates were 6.76 and 1.51 n-mole/g per hr for [(3)H]DA and [(3)H]NA, respectively; with 40 muM-[(3)H]DOPA, these values increased to 19.22 and 3.23 n-mole/g per hr, respectively.3. The relationship between [(3)H]DOPA concentration and [(3)H]DA synthesis was linear throughout the range 5-40 muM-[(3)H]DOPA.4. Sympathectomy reduced the synthesis of [(3)H]NA by 90% and [(3)H]DA by 37% when [(3)H]DOPA was used as precursor.5. When [(3)H]tyrosine (40 muM) was used as precursor, synthesis of [(3)H]catecholamines was linear for at least 4 hr, with rates of 12.10 and 0.85 n-mole/g per hr for [(3)H]DA and [(3)H]NA, respectively.6. [(3)H]DA and [(3)H]NA synthesis from [(3)H]tyrosine exhibited the characteristics of saturable processes, with K(m) values of 16.8 and 17.6 muM, respectively.7. 6-methyltetrahydropterine (6-MPH(4), 100 muM), a synthetic analogue of the natural co-factor for tyrosine hydroxylase, increased [(3)H]DA and [(3)H]NA synthesis from [(3) H]tyrosine in both the carotid body and superior cervical ganglion, with the greatest effect seen in the carotid body.8. When [(3)H]tyrosine was used as precursor, sympathectomy of the carotid body reduced [(3)H]NA synthesis by 80%, but did not alter [(3)H]DA or [(3)H]tyrosine levels in the tissue. Transection of the carotid sinus nerve had no effect on [(3)H]catecholamine synthesis in the carotid body.

Animals↗
PubMed1982

Effects of hypoxia on catecholamine synthesis in rabbit carotid body in vitro.

1. Unanaesthetized, unrestrained rabbits were exposed for 3 hr in a chamber to either air, hypoxic gas mixtures (10% or 14% O(2) in N(2)) or a hyperoxic gas mixture (50% O(2) in N(2)). The carotid bodies were then removed and incubated for 3 hr in modified Tyrode media equilibrated with 100% O(2) and containing either [(3)H]tyrosine or [(3)H]DOPA. The contents of [(3)H]DA and [(3)H]NA in the tissue were determined as described in the preceding paper.2. When [(3)H]DOPA was used as precursor, neither labelled dopamine (DA) or noradrenaline (NA) synthesis was increased in carotid bodies from rabbits exposed to 10% O(2) in N(2). Following exposure to 10% O(2) in N(2) and incubation with [(3)H]tyrosine, however, [(3)H]DA synthesis was increased by 72% above control (air) values while [(3)H]NA synthesis was unchanged. Less severe hypoxia, 14% O(2) in N(2), resulted in a smaller increase in [(3)H]DA synthesis, i.e. 53% above control value. Again, [(3)H]NA synthesis was unchanged. Similar experiments with the superior cervical ganglion involving exposure of the animals to either 10% or 14% O(2) in N(2) did not produce any change in the amounts of [(3)H]DA or [(3)H]NA synthesized from [(3)H]tyrosine when compared to control animals breathing air.3. Sympathectomy of the carotid body or transection of the carotid sinus nerve 12-15 days prior to hypoxic exposure (10% O(2) in N(2)) did not alter the increase in [(3)H]DA synthesis compared to normally innervated carotid bodies.4. Carotid bodies incubated with [(3)H]tyrosine for 2 hr in an alternating O(2)/N(2) sequence (5 min in media equilibrated with 100% O(2) followed by 3 min in media equilibrated with 100% N(2)) synthesized 37% more [(3)H]DA than control carotid bodies similarly exposed to an alternating O(2)/O(2) sequence. [(3)H]NA synthesis was unchanged. However, tissue levels of non-metabolized [(3)H]tyrosine were reduced by 19% in the carotid bodies exposed to the O(2)/N(2) sequence.5. Exposure of rabbits for 3 hr to 50% O(2) in N(2), followed by incubation of their carotid bodies in [(3)H]tyrosine, resulted in a 19% decrease in the absolute value for [(3)H]DA synthesis compared to control carotid bodies, but this difference was not significant (P > 0.05). However, [(3)H]NA synthesis was significantly reduced (51%; P < 0.05) in the hyperoxic carotid bodies. Similar experiments with the superior cervical ganglion showed that [(3)H]DA and [(3)H]NA synthesis were unchanged under control vs. hyperoxic conditions.6. Carotid bodies incubated with [(3)H]tyrosine for 3 hr, then transferred for 1 hr to unlabelled media equilibrated with 10% O(2) in N(2), released 81% more [(3)H]DA, and contained 38% less [(3)H]DA, than similarly treated carotid bodies exposed to 100% O(2). [(3)H]NA was not detectable in the media, and tissue levels of [(3)H]NA were the same in both hypoxic and control carotid bodies.

Animals↗
PubMed1982

Effects of low oxygen on the release of dopamine from the rabbit carotid body in vitro.

1. Rabbit carotid bodies were pre-loaded with [(3)H]dopamine (DA) synthesized from [(3)H]tyrosine and then mounted in a vertical drop-type superfusion chamber which permitted simultaneous collection of released [(3)H]DA and recording of chemoreceptor discharge from the carotid sinus nerve.2. The time course of the spontaneous release of [(3)H]DA (superfusion with media equilibrated with 100% O(2)) in the presence of monoamine oxidase inhibitors exhibited two linear components, an initial steep phase followed after 3-4 hr by a later slower phase of release.3. When a 5 min low O(2) stimulus was delivered during the initial steep linear component of resting [(3)H]DA release, there was an abrupt increase in release, the magnitude of which was stimulus-dependent.4. The efflux of total radioactivity from the preparation declined exponentially with time; under resting conditions it was principally non-metabolized [(3)H]tyrosine. During stimulation, however the efflux increased, and 60-80% of the radioactivity could be attributed to [(3)H]DA.5. For a given low O(2) stimulus, the ratio of [(3)H]DA release during the stimulus period over that in the preceding control period remained approximately the same throughout a single experiment. Ratios for different low O(2) stimuli (50, 40, 30, 20, 10 and 0% O(2) in N(2)) yielded a parabolic relationship when plotted against stimulus intensity.6. Transection of the carotid sinus nerve or removal of the superior cervical ganglion 12-15 days prior to the experiment did not affect the release of [(3)H]DA at moderate stimulus intensities (superfusion with media equilibrated with 30% or 10% O(2) in N(2)) but both procedures significantly depressed release at the highest stimulus intensity (100% N(2)).7. Chemoreceptor discharge and [(3)H]DA release were simultaneously monitored in experiments using superfusion media free of monoamine oxidase inhibitors. In these experiments, the efflux of [(3)H]dihydroxyphenyl acetic acid (DOPAC) was also measured. The increase in peak chemosensory discharge was closely correlated with the increase in total release ([(3)H]DA + [(3)H]DOPAC) during stimulation with a series of low O(2) stimuli.8. Release of [(3)H]DA was almost completely abolished during superfusion with Ca(2+)-free, high Mg(2+) (2.1 mM) media, and the stimulus-related efflux of [(3)H]DOPAC was significantly reduced. However, chemoreceptor discharge was diminished by only 55%. These data are discussed with respect to their implications for DA as a chemosensory transmitter in rabbit carotid body.

Action Potentials↗
PubMed1981

Peptides isolated from the venom of Conus geographus block neuromuscular transmission.

The effects of a mixture of two peptides (GI and GII), purified from the venom of the marine gastropod, Conus geographus, were studied on neuromuscular transmission in the isolated mouse phrenic nerve--diaphragm and frog sciatic nerve--sartorius muscles. The GI--GII mixture rapidly blocked nerve-evoked contractions of the mouse diaphragm at bath concentrations greater than or equal to 0.2 microM but had no effect on contractions elicited by direct muscle stimulation. Paralytic concentrations of GI--GII had no significant effect on the compound nerve action potential of the bullfrog sciatic nerve. Similar concentrations of GI--GII produced a rapid reduction of endplate potential (epp) and miniature endplate potential amplitudes, apparently by a postsynaptic effect because the decrease in epp amplitude produced by subparalytic doses was not accompanied by significant alteration in the epp quantal content. The GI--GII mixture also inhibited [125I]alpha-bungarotoxin binding to endplate regions of the mouse diaphragm in a dose-dependent manner and was at least 10 times more potent than d-tubocurarine. We conclude that the blockage of vertebrate neuromuscular transmission by GI--GII is in part due to antagonism of acetylcholine binding to its receptor at motor endplates.

Animals↗
PubMed1981

[3H]Spiroperidol binding in normal and denervated carotid bodies.

Specific dopamine receptors were studied in freshly dissected, unhomogenized rabbit carotid bodies incubated in [3H]spiroperidol. Total binding and non-specific binding were determined in the absence and presence of 0.2 microM (+)-butaclamol, respectively. Specific binding in normal carotid bodies incubated at near saturating concentrations (0.38 nM) was 1.63 +/- 0.58 pmol/g of tissue. Chronic section of the carotid sinus nerve (14 days) resulted in a 64% reduction (P less than 0.05) in specific binding. We conclude that the majority of specific dopaminergic receptors are located on carotid sinus nerve afferent terminals.

Animals↗