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Biomedical subjects

J Jaramillo

Publications and source records attributed to J Jaramillo.

At least 37 records · Page 2Linked to original sources
PubMed1994

Hip isometric strength following knee surgery.

Hip exercises are frequently prescribed following knee injury and subsequent surgery based on the assumption that hip weakness exists. No data, however, are available that support hip weakness following knee trauma or surgery. Therefore, the purpose of this study was to compare hip strength in patients after knee surgery. Twenty-seven patients who had undergone unilateral knee surgery were tested for hip flexor, extensor, abductor, and adductor isometric strength prior to initiation of rehabilitation. Multivariate analysis of variance revealed significant hip weakness in all four hip muscle groups of the surgical extremities (11.9-25.3%, p < or = 0.05) when compared with nonsurgical extremities. Both peak and endurance force were affected. The greatest percent difference between the surgical and nonsurgical extremity occurred for hip extension peak (25.3%) and endurance (22.6%) force development. We recommend assessment of hip strength following knee surgery and appropriate resistive exercises if weakness exists.

Adolescent↗
PubMed1992

Regional and subcellular distribution of [125I]endothelin binding sites in rat brain.

The binding of [125I]endothelin-1 (125I-ET-1) to membranes from whole rat brain, from individual brain regions, and derived from subcellular fractionation of whole rat brain was investigated. 125I-ET-1 binding to whole rat brain membranes was rapid, concentration-dependent, saturable, and characterized as irreversible because it was not displaced by unlabeled endothelin-1 (ET-1) and different concentrations of ligand produced, with time, a similar magnitude of binding. The maximum binding site capacity and second-order forward rate association constant of binding were 1,946 +/- 147 fm/mg protein and 5.53 +/- 1.72 x 10(6) M-1 s-1. Removal of either extramembranal calcium or membrane-bound calcium and calcium binding proteins did not affect the binding of 125I-ET-1 to whole rat brain membranes. The brain stem and cerebellum contained the highest levels of 125I-ET-1 binding sites, whereas the cerebral cortex, striatum, and hippocampus contained binding site levels three- to fourfold less. Subcellular fractionation of whole rat brain and subsequent analyses of the distribution of 125I-ET-1 binding demonstrated a twofold enrichment of binding sites in the synaptosomal fraction compared to the homogenate. The myelin fraction contained a similar density of binding sites compared to the homogenate, while the mitochondrial and microsomal fractions contained considerably less binding sites. The ribosomal fraction did not contain any 125I-ET-1 binding sites. The subcellular distribution of 125I-ET-1 binding sites did not correlate with the distribution of 5'-nucleotidase, cytochrome-C oxidase, phosphodiesterase, and alkaline phosphatase. Depletion of extracellular calcium increased 125I-ET-1 binding in the synaptosomal fraction but not in the myelin and mitochondrial fractions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Characterization of intestinal smooth muscle responses and binding sites for endothelin.

The contractile activity of and binding sites for endothelin-1 (ET-1) were investigated in isolated guinea-pig ileal longitudinal smooth muscle (GPILM). ET-1 produced concentration-dependent contractions of GPILM that either slowly subsided in the continued presence of ET-1 or rapidly subsided following washing of the tissue. The ED50 value for ET-1 contractions was 4.2 +/- 1.3 x 10(-9) M. The removal of extracellular calcium or pretreatment with nifedipine produced a complete inhibition of the contractions to ET-1. The IC50 value of nifedipine for inhibition of ET-1 mediated contractions was 3.0 +/- 0.8 x 10(-8) M. ET-1 produced a marked prolonged homologous desensitization of its contractile response but did not affect the responses mediated by carbachol, histamine, serotonin, substance P, and PLA2. High-affinity binding sites for 125I-labelled ET-1 were identified on microsomal membranes prepared from GPILM with Kd and Bmax values obtained by Scatchard analysis of 3.5 +/- 0.6 x 10(-10) M and 2138 +/- 159 fmol/mg protein, respectively. The binding of 125I-labelled ET-1 to GPILM microsomes was characterized by a rapid association (kob value of 0.077 min-1 at a radioligand concentration of 0.45 nM and an extremely slow dissociation (k1 value of 0.011 min-1; t1/2 value of 793 min). The binding was unaffected by the calcium channel antagonists nifedipine, verapamil, and diltiazem (10(-6) M); the receptor antagonists phenoxybenzamine, atropine, and naloxone (10(-6) M) and propranolol; and the peripheral benzodiazepine receptor antagonists Ro 5-4864 and PK 11195 and psychotomimetic drug phencyclidine (10(-5) M).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Subcutaneous growth hormone-releasing hormone therapy in growth hormone-deficient children: first year of therapy.

The purpose of this study was to determine the efficacy and safety of GH-releasing Hormone [GHRH-(1-44)] therapy in GH-deficient children. Twenty previously untreated prepubertal children with GHRH deficiency were treated for 1 yr in a multicenter, open label, company-sponsored study with at least 20 micrograms/kg GHRH-(1-44), sc, half at bedtime and half upon awakening. The main effects were enhancement of linear growth, advancement in bone age, and alteration in general blood chemistries and hormonal values. The mean velocity of the entire group increased from 3.6 +/- 1.1 to 8.1 +/- 1.5 cm/yr (P < 10(-4)) at 1 yr of therapy. After 6 months of therapy, 16 were growing at a mean of 9.4 +/- 2.0 cm/yr and were continued on this dose. In 4 patients who were growing at a rate of 5.5 +/- 1.7 cm/yr, the dose was increased to 40 micrograms/kg daily for the second 6 months. The high dose group increased their mean linear growth velocity for the second 6 months while on the higher dose to 7.6 +/- 0.4 cm/yr (P < 10(-2)). This was equal to the mean velocity for the second 6 months of therapy of the 16 subjects who remained on the 20 micrograms/kg daily therapy (7.6 +/- 1.2 cm/yr). Mean advancement of bone age was 1.3 +/- 0.6 yr during the first year of therapy. No adverse changes in general biochemical, hormonal, or pituitary radiographic analyses were noted. No change in fasting glucose or insulin concentrations, or excessive generation of insulin-like growth factor-I concentrations occurred. We conclude that GHRH in a daily dose of 20-40 micrograms/kg for 1 yr was effective in increasing growth velocity in most GHRH-responsive GH-deficient patients. It was well tolerated without side-effects. Glucose intolerance was not noted.

Adolescent↗
PubMed1992

Cardiac responses and binding sites for endothelin in normal and cardiomyopathic hamsters.

The effects of endothelin-1 in the spontaneously beating atrium and the field-stimulated right ventricular strip preparation and the binding of [125I]endothelin-1 to membrane preparations from the atrium, ventricle, lung parenchyma, kidney and brain were compared using the 90-day-old dystrophic hamster strain CHF 147 (a strain displaying marked cardiomyopathologies at this age) and its age/genetically matched normal control, CHF 148. In the atrium, endothelin-1 produced dose-dependent positive inotropic and positive chronotropic effects in both CHF 148 and CHF 147 over the dose range of 10(-8) M to 3 x 10(-7) M. However, although no significant difference between CHF 148 and CHF 147 was observed for the positive chronotropic effects of endothelin-1, it produced a small, but significantly less positive inotropic effect in CHF 147 compared to CHF 148 at endothelin-1 concentrations of 2 x 10(-8) M and 3 x 10(-8) M. Field-stimulated right ventricular strips from CHF 148 contracted with a greater force compared to those from CHF 147. Endothelin-1 produced a dose-dependent decrease in the developed tension of the field-stimulated ventricular strip preparation, the extent of which did not differ between CHF 148 and CHF 147. [125I]Endothelin-1 bound with high affinity and in an apparently irreversible manner to membranes from both CHF 148 and CHF 147 atrium, ventricle, lung parenchyma, kidney and brain. No significant differences were noted between CHF 148 and CHF 147 for [125I]endothelin-1 binding to membranes prepared from the various tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Vascular reactivity, tissue levels, and binding sites for endothelin: a comparison in the spontaneously hypertensive and Wistar-Kyoto rats.

The role of endothelin (ET-1) in mediating the development of blood pressure was investigated in the spontaneously hypertensive (SHR) rat using the Wistar-Kyoto (WKY) rat as the normotensive control. The following were characterized in both rat strains: age-dependent changes in mean arterial blood pressure (MAP), tissue (blood, lung, heart, and kidney) levels of immunoreactive ET-1 like related peptides (ET-1RP), aortic ring responses to ET-1, and specific high-affinity tissue (lung, atrium, ventricle, aorta, and kidney) binding sites for 125I-labelled ET-1. Commencing at age 10 weeks through to 12 weeks, SHR rats but not WKY rats developed a significant increase in MAP (from 152 +/- 7 to 189 +/- 3 mmHg) (1 mmHg = 133.32 Pa). However, in both WKY and SHR rats immunoreactive levels of ET-1RP increased (100 and 80%, respectively) throughout the same measurement period. The potency of ET-1 to contract aortic rings from SHR rats was slightly but not significantly greater than that for aortic rings from WKY rats, although aortic rings from SHR rats contracted in the presence of 0.5 nM ET-1, while those from WKY rats did not. The levels of immunoreactive ET-1RP were significantly reduced (32%) in the kidney and unchanged in the heart and lung of SHR rats compared with WKY rats. Specific 125I-labelled ET-1 binding sites displayed an increase and a significant decrease (24%) of density in the atrium and ventricle, respectively, a significant increase (31%) of affinity in the lung, and were unchanged in the kidney and aorta of SHR rats compared with WKY rats following the development of hypertension. The lack of a correlation between circulating levels of immunoreactive ET-1RP and the development of hypertension coupled with a lack of significant differences in vascular reactivity suggest that ET-1 is not the sole mediator of hypertension in this animal model. However, the tissue-specific changes in immunoreactive ET-1RP and 125I-labelled ET-1 binding sites suggest that ET-1 may be a partial mediator of hypertension and is subject to compensatory changes in response to the increased total peripheral resistance in SHR rats.

Animals↗
PubMed1991

Interactions between endothelin and atrial natriuretic factor in the rat aortic ring preparation.

The potential interaction (s) between atrial natriuretic factor (ANF) and porcine--human endothelin (ET-1) was investigated in the endothelium-denuded rat aortic ring preparation. ET-1 produced a sustained contraction of aortic rings with an ED50 of 3.6 +/- 0.49 x 10(-9) M. Within the concentration range of 10(-9) to 10(-7) M, both rat ANF 103-126 and rat ANF 99-126 when preincubated with tissues reduced the contractile efficacy of ET-1 especially at low concentrations resulting in a small but significant rightward shift of the dose--response curve to ET-1. In contrast, at a concentration of 10(-10) M, rANF 99-126 but not rANF 103-126 produced a significant leftward shift of the dose--response curve to ET-1 and an increase in the maximal developed tension for the dose--response curve to ET-1. For tissues incubated in the absence of extracellular calcium or in the presence of the calcium channel blocker nifedipine (5 x 10(-7) M), both ANF derivatives produced a dose-dependent decrease in the maximum contraction, but no change in potency to ET-1. Addition of either rANF 103-126 or rANF 99-126 to tissues maximally contracted with ET-1 resulted in relaxation, reaching a maximum of 70%. The ED50 values for relaxation were 2.7 +/- 0.51 x 10(-8) and 3.5 +/- 0.60 +/- 10(-8) M for rANF 103-126 and rANF 99-126, respectively. ET-1 did not interact with biologically responsive and clearance receptors for ANF.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Synthesis and biological activity of atrial natriuretic factor analogues: effect of modifications to the disulfide bridge.

A series of atrial natriuretic factor (ANF) analogues with modifications to the disulfide bridge and lacking the exocyclic N-terminal sequence was synthesized. The native cystine residue was substituted by isofunctional deamino carba, beta,beta-dimethyl carba and dehydro dicarba spanners that bridge residues 106 and 120. The compounds were prepared by segment condensation coupling using the base-labile (9-fluorenylmethyl)carboxyl protecting group. Biological evaluation revealed that the exocyclic N-terminal segment of ANF is not necessary for expression of high biological activity. The compounds retained high affinity for ANF receptors in bovine adrenal zona glomerulosa cells and were found to be potent antihypertensive and diuretic agents, indicating that the native disulfide bridge can be mimicked by isosteric spanning residues. It was noted that the reported analogues, unlike the endogenous hormone, show marked reduced inhibitory activity on PGE1-stimulated aldosterone secretion from adrenal zona glomerulosa cells. This lack of inhibition may be a contributing element to the low saluresis in spite of the high level of diuresis observed with some analogues.

Amino Acid Sequence↗
PubMed1990

Tissue selectivity and calcium dependence of contractile responses to endothelin.

The tissue selectivity and calcium dependence of endothelin, a potent vasoconstrictor peptide obtained from endothelial cells, were investigated in a number of rat and guinea pig tissues. Endothelin produced a significant dose-dependent contraction of rat tissues with the following rank order of efficacy: aorta greater than portal vein greater than trachea much greater than vas deferens = lung parenchyma much greater than bladder. In the rat atrium and ventricle, endothelin possessed positive inotropic effects at low doses and arrhythmogenic effects at high doses. Endothelin also produced a significant contraction of guinea pig lung parenchyma and induced relaxations of guinea pig taenia coli precontracted with potassium chloride. The aortic ring contractile response to endothelin was characterized by both rapid and slow phases of contraction. The rapid phase of contraction was abolished by removal of extracellular calcium or preincubation of tissues with the dihydropyridine calcium channel antagonist, nifedipine. Removal of the endothelium from aortic rings resulted in an increase of approximately 10-fold in the contractile potency of endothelin. In comparison, the potency of the dihydropyridine calcium channel activator, (-)-S-BAY K 8644, was increased approximately 15-fold by the same treatment. These findings suggest that endothelin, while displaying some selectivity as a vascular smooth muscle spasmogen, is a general smooth and cardiac muscle spasmogen which utilizes both intra- and extracellular sources of calcium to support its contractions.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1990

Tissue specificity of endothelin binding sites.

A measurement was made of the binding of 125I-labeled endothelin (125I-ET) to crude membrane fractions prepared from rat aorta, atrium, ventricle, portal vein, trachea, lung parenchyma, vas deferens, ileum, bladder, and guinea-pig taenia coli and lung parenchyma. Scatchard analysis of 125I-ET binding in all tissues indicated binding to a single class of saturable sites. The affinity and density of 125I-ET binding sites varied between tissues. The Kd of 125I-ET binding was approximately 0.5 nM for rat aorta, trachea, lung parenchyma, ventricle, bladder, and vas deferens, and guinea-pig taenia coli and lung parenchyma, 1.8 nM for rat portal vein and atrium, and 3.3 nM for ileum. The Bmax of 125I-ET binding had the following rank order of density in rat tissues: trachea greater than lung parenchyma = vas deferens much greater than aorta = portal vein = atrium greater than bladder greater than ventricle = ileum. The properties of 125I-ET endothelin binding were characterized in rat ventricular membranes. 125I-ET binding was time dependent, reaching a maximum within 45-60 min at 25 degrees C. The calculated microassociation constant was 9.67 x 10(5) s-1 M-1. Only 15-20% of 125I-ET dissociated from its binding site even when dissociation was studied as long as 3 h. Preincubation of ventricular membranes with ET prevented binding of 125I-ET. 125I-ET binding was destroyed by boiling of ventricular membranes and was temperature, pH, and cation (Ca2+, Mg2+, and Na+) dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Resistance of the diabetic rat nerve to ischemic inactivation.

The resistance of the action potential to ischemic inactivation observed in diabetic patients has been reproduced in vivo in rat rendered diabetic with streptozotocin and, acutely, in normal rats given p.o. a load of glucose. The resistance phenomenon was not detected in galactosemic rats. The preservation of the action potential was reversed by the administration of insulin, but not by treatment with an aldose reductase (AR) inhibitor. The ischemic resistance is attributed to the metabolic availability of excess glucose to the nerve. AR does not appear to be involved in the phenomenon.

Action Potentials↗
PubMed1984

Cetamolol: a new cardioselective beta-adrenoceptor blocking agent without membrane-stabilizing activity.

Cetamolol, a new beta-adrenoceptor blocker with partial agonist activity and cardioselectivity, was studied in vivo to determine its membrane-stabilizing effects. Comparisons were carried out with atenolol, pindolol, practolol, propranolol, timolol, dexpropranolol, lidocaine, and procaine. The following results indicated that cetamolol lacked membrane-stabilizing activity: (i) failure to cause local anesthesia on the rabbit cornea and motor nerve of the rat tail; (ii) ineffectiveness in reversing ventricular arrhythmias induced by coronary artery litigation in dogs; (iii) failure to reduce cardiac automaticity in catecholamine-depleted dogs as determined by the rate of a subatrial rhythm during ventricular (vagal) escape; and (iv) lack of a significant increase in atrioventricular conduction time in vagotomized or atropinized dogs in contrast to the effect in normal dogs indicating a reflex effect of cetamolol. Other results include a restoration of sinus rhythm in dogs with ventricular tachycardia induced by ouabain, and a dose-related decline in the force of cardiac contraction in anesthetized dogs at doses from 3 to 15 mg/kg, which occurred after an initial increase in force owing to intrinsic sympathomimetic activity. Although the mechanisms for the latter two effects are not clear at this time, explanations other than membrane-stabilizing activity have been considered in view of the other findings. It is concluded that cetamolol lacks membrane-stabilizing activity even at inordinately high doses.

Acetamides↗
PubMed1983

Sex differences in secretion pattern of neonatal rat Harderian gland under various environmental lighting conditions.

1. Secretion pattern of Harderian gland of neonatal rats maintained under (a) diurnal lighting conditions; (b) continuous light or (c) continuous darkness was studied at light microscopy level. 2. All animals were placed in especially designed cages at 13:00 hr on day 1 and studied on day 7 at 13:00 and 23:00 hr, respectively. 3. Acini with intraluminal secretion were counted in glands from each animal and the results were separately grouped for male and female animals. 4. A diurnal rhythm in secretion pattern of rat Harderian gland in neonatal period was demonstrated. 5. A statistically significant difference was observed in the gland secretion pattern between males and females at both, 13:00 and 23:00 hr when the animals were kept under diurnal lighting conditions. 6. Under continuous light or continuous darkness, the diurnal rhythm in secretion pattern was lost and no significant differences were seen when data from males were compared to those from female neonates. 7. Results are discussed in terms of the possible function of Harderian gland as element of an extraretinal photoreceptor system involved in the regulation of pineal function in neonatal rats.

Animals↗
PubMed1983

A comparative study of the acute effects of cetamolol (AI-27,303), atenolol, propranolol, and dexpropranolol on blood pressure, sympathetic nerve and ganglion activity of cats.

The effects of cetamolol (AI-27,303, Betacor), atenolol, propranolol, and dexpropranolol were evaluated in 36 chloralose-urethane anesthetized cats. Blood pressure, sympathetic nerve discharge, and ganglionic activity (from the superior cervical ganglion) were recorded after the intravenous administration of 2.5, 5.0, and 10 mg/kg doses of the compounds. The results indicate that cetamolol and atenolol decreased blood pressure and discharge in the postganglionic sympathetic nerve and impaired transmission at the level of sympathetic ganglia. Propranolol and dexpropranolol given at the same doses produced a larger decrease in blood pressure, but increased the sympathetic discharge and had no effect on ganglionic spike amplitude.

Acetamides↗
PubMed1979

Assessment of the anaesthetic and metabolic activities of dioxychlorane, a new halogenated volatile anaesthetic agent.

The ability of dioxychlorane to depress cortical activity in rats with implanted electrodes was compared to that reported previously for methoxyflurane, halothane and enflurane. Dioxychlorane was eight times more potent than enflurane, five times more potent than halothane and twice as potent as methoxyflurane. Serum fluoride concentrations after the administration of dioxychlorane and enflurane were not different from controls. In contrast, serum fluoride concentrations after methoxyflurane reached a value of 105 mumol litre-1 and remained increased for at least the next 48 h. Urine fluoride concentrations in the dioxychlorane and enflurane groups were a half and a quarter, respectively, of those recorded in the methoxyflurane group. Polyuria and polydipsia were observed only in the methoxyflurane group. Dilatation of the proximal convoluted tubules was noted in the rats anesthetized with methoxyflurane. These changes were most marked at the 6- and 24-h periods following anaesthesia. Haemorrhage and ulcerative cystitis were noted in the bladders of the rats subjected to methoxyflurane. Cellular swelling in the proximal tubule was observed in the rats sacrificed 24 h after the administration of dioxychlorane. Enflurane produced no pathological changes.

Anesthetics↗
PubMed1979

Quantitative electroencephalographic and metabolic studies of midaflur, a new anesthetic agent.

Midaflur [4-amino-2,2,5,5-tetrakis(trifluoro methyl)-3-imidazoline] was tested for its ability to induce changes in (i) the EEG of Sprague-Dawley rats with chronically implanted electrodes and (ii) metabolic and kidney functions on Fischer 344 rats. Ataxia and loss of righting reflex were observed in animals given the smaller doses (2 to 5 mg/kg of body weight, intraperitoneally), with little or no effect on the EEG. At higher dose rates, a significant linear dose-response relationship was found for midaflur in depressing brain activity. Changes in body weight and feed and water intake occurred in rats given single doses of midaflur (2 to 20 mg/kg). These effects seemed to be due, in part, to the drug-induced inactivity and to the vehicle in which midaflur has been formulated (equal parts of ethyl alcohol, propylene glycol, and water). Urinary volumes were reduced after injection of midaflur, possibly as a consequence of the changes in water intake. Since midaflur is highly fluorinated, studies were done to detect possible release of inorganic fluoride due to metabolic breakdown. Serum fluoride concentrations in rats given single doses of midaflur (2 to 20 mg/kg) were consistently lower than those of control (untreated) animals, reflecting a reduction in the daily intake of fluoride as a consequence of the diminished feed intake. Significant changes were not observed in the urinary fluoride concentrations in treated rats as compared with these values in control animals given the vehicle alone.

Anesthetics↗
PubMed1978

Pharmacological studies on tandamine hydrochloride, a potential heterocyclic antidepressant.

Tandamine, a potential heterocyclic antidepressant, was compared with imipramine for its ability to modify: (a) the contractions induced by noradrenaline (NA) and 5-hydroxytryptamine (5-HT) on the normal and chronically denervated nictitating membrane of the cat, (b) the neuron blocking effect induced by guanethidine in the guinea pig vas deferens, (c) the electroencephalograph and the physostigmine arousal in the rabbit and (d) the sleep pattern of the rat. Both tandamine and imipramine potentiated the NA and 5-HT induced contractions of the normalnictitating membrane and antagonized the effects of gaunethidine on the vas deferens. The potentiation by tandamine and imipramine of the NA and 5-HT contraction of the nictitating membrane disappeared after chronic denervation of the membrane. These results are consistant with the ability of the substances to block the neural uptake of catechol- and indoleamines. Tandamine did not induce EEG synchronization and did not affect the arousal reaction induced by physostigmine. Tandamine also reduced or abolished REM (rapid eye movement) sleep with a concomitant decrease in NREM (non-rapid eye movement) sleep.

Animals↗