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Biomedical subjects

F Lopez

Publications and source records attributed to F Lopez.

At least 109 records · Page 6Linked to original sources
PubMed1989

Persistent alterations in GABAA receptor binding and function after prenatal lorazepam administration in the chick.

Behavioral abnormalities have been reported in young and adult animals exposed to benzodiazepines prenatally. The presence of neurochemical alterations in the GABAergic system after prenatal benzodiazepine exposure was assessed in a chick model which avoids prenatal and postnatal maternal effects. The GABAA receptor complex, the presumed site of benzodiazepine action, was altered in adult chickens previously exposed to lorazepam for 10 days in ovo. Binding was decreased at the putative chloride channel site labeled by [35S]TBPS, coupling was decreased between this site and the GABA binding site, and function of the GABAA receptor in chloride uptake was diminished in animals exposed to prenatal lorazepam. Persistent neurochemical alterations in the GABAergic system accompany prenatal benzodiazepine exposure, and may influence subsequent behavior and development.

Animals↗
PubMed1989

Lorazepam discontinuation promotes 'inverse agonist' effects of benzodiazepines.

1. The effects of lorazepam discontinuation on responses to benzodiazepine agonists and antagonists were studied in mice. 2. The convulsant dose of pentylenetetrazol was decreased after an acute dose of lorazepam (0.5 mg kg-1) at 4 days after drug discontinuation, compared to 1 or 7 days after discontinuation or to vehicle treatment. 3. The percentage of mice undergoing convulsions after an acute dose of FG 7142 (40 mg kg-1) was increased at 4 days after lorazepam discontinuation, compared to 1 or 7 days after discontinuation or to vehicle treatment. 4. After an acute dose (0.5 mg kg-1), lorazepam concentrations in cortex tended to be greater in lorazepam-treated compared to vehicle-treated mice at 4 days after discontinuation compared to 1 and 7 days. 5. These data indicate a shift toward reduced agonist sensitivity and increased inverse agonist sensitivity in mice 4 days after lorazepam discontinuation.

Animals↗
PubMed1989

Capillary gas chromatographic analysis of mycolic acid cleavage products, cellular fatty acids, and alcohols of Mycobacterium xenopi.

The fatty acids, alcohols, and mycolic acids of 26 strains of Mycobacterium xenopi were studied by capillary gas chromatography and thin-layer chromatography. All strains contained alpha-, keto-, and omega-carboxymycolates. The primary mycolic acid cleavage product was hexacosanoic acid. The fatty acid patterns and, especially, the presence of 2-docosanol are characteristic markers of M. xenopi.

Alcohols↗
PubMed1989

Dietary choline intake modulates benzodiazepine receptor binding and gamma-aminobutyric acidA receptor function in mouse brain.

Several lines of evidence suggest that dietary choline intake influences the metabolism of membrane phospholipids with possible effects on GABAergic neurotransmission. Based on these findings, the present experiments determined whether chronic choline supplementation or deficiency alters GABAergic function at the level of the gamma-aminobutyric acid (GABA)/benzodiazepine-chloride channel complex. To accomplish this, mice were fed diets containing 0% (deficient), 0.2% (basal) or 2.0% (supplemented) choline chloride for 28 days, and behavior, ligand binding at several sites in the complex and chloride uptake were determined in various brain regions. For both rotarod ataxia and open-field activity, mice receiving choline supplementation had a decreased response to clonazepam compared to those receiving basal and deficient diets. Choline supplementation significantly increased the in vivo binding of [3H]Ro15-1788 to cortex and cerebellum by 19% and 24%, respectively, and in vitro studies in cortical membranes indicated a significant 36% increase in the maximal number of [3H]flunitrazepam binding sites without a change in affinity, as compared to basal controls. In contrast, [3H]Ro15-1788 binding in vivo in all brain regions from mice fed the deficient diet decreased significantly to 20 to 58% of control values. Dietary choline intake did not alter GABA levels in brain, the binding of [35S]t-butylbicyclophosphorothionate to the chloride channel or the coupling between GABA and either the t-butylbicyclophosphorothionate site or the benzodiazepine site. However, the function of the GABAA receptor, determined by muscimol-stimulated chloride uptake into cortical synaptoneurosomes, was increased significantly in tissue from the supplemented group as compared to both control and deficient groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Chronic benzodiazepine administration. III. Upregulation of gamma-aminobutyric acidA receptor binding and function associated with chronic benzodiazepine antagonist administration.

Chronic administration of a benzodiazepine agonist appears to downregulate benzodiazepine receptors and gamma-aminobutyric acid (GABA) receptor function. To examine the effects of chronic treatment with a benzodiazepine antagonist, we administered Ro15-1788, 1, 2 and 5 mg/kg/day to mice via implanted s.c. osmotic pumps for 1 to 14 days. Plasma and cortex (CX) concentrations of Ro15-1788 remained constant between days 1 and 7, indicating no change in pharmacokinetics. Open-field activity studies showed no change in distance traveled or ambulatory time at days 1, 2 and 4, but an increase in both parameters at days 7 and 14 in mice receiving Ro15-1788, 2 mg/kg/day. Benzodiazepine receptor binding was unchanged in CX, cerebellum (CB), hypothalamus, hippocampus and ponsmedulla at 1, 2 and 4 days at a dose of 2 mg/kg/day. Binding was increased in CX, CB and hippocampus at day 7 compared to days 1 and 2, and remained elevated at day 14. Similar results were observed at Ro15-1788 doses of 1 and 5 mg/kg/day. Benzodiazepine binding assessed in vitro in CX and CB also was increased at day 7 compared to day 1, due to an increase in receptor number rather than a change in apparent affinity. Binding of t-[35S]butylbicyclophosphorothionate to the chloride channel site in CX after Ro15-1788, 2 mg/kg/day, was increased at days 7 and 14 compared to days 1, 2 and 4 and controls due to an increase in number of binding sites. t-Butylbicyclophosphorothionate binding in CB was unchanged throughout.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Clinical patterns and treatment complications of 1000 cases of carcinoma of the uterine cervix.

One thousand consecutive cases of carcinoma of the uterine cervix treated in the General Hospital Kuala Lumpur between January 1977 to December 1979 were studied. Epidemiological breakdown by race, age, parity, occupation, stage and histology of the disease were obtained. Treatment complications in survivors available for follow-up were analysed. The Chinese had the highest incidence, followed by the Indians and the Malays. Ninety six percent were squamous cell cancers, the remaining were adenocarcinomas. Eighty percent of patients were seen at an advanced stage (Stage IIB-IV). Late radiation complications were mainly proctitis, cystitis and fistula; (5%, 7.2% and 1.4% respectively). These figures are comparable to many centres but the incidence of cystitis is relatively higher. This is believed to be related to irradiation techniques in these cases.

Adult↗
PubMed1988

Low-dose alprazolam augments motor activity in mice.

The triazolobenzodiazepine alprazolam appears to have a unique clinical spectrum, and recent studies indicate unusual binding properties at the benzodiazepine receptor when assessed in vivo at low doses (0.02-0.05 mg/kg). To assess the behavioral activity of alprazolam at low doses, we examined open-field activity after one hour in mice treated with alprazolam, triazolam, and clonazepam. Following triazolam and clonazepam administration, open-field activity decreased in a dose-dependent fashion. In contrast, low doses of alprazolam resulted in an increase in open-field activity, whereas higher doses decreased activity. For all three drugs, activity was linearly related to receptor binding. Pretreatment with a dose of the benzodiazepine antagonist Ro15-1788 sufficient to fully occupy receptors had no effect on open-field activity, but when administered concurrently with alprazolam (0.05 mg/kg) prevented the increase in activity seen with alprazolam alone. Increased open-field motor activity represents a behavioral correlate to the increases in receptor binding seen with low-doses of alprazolam. Changes in activity appear to be mediated at the benzodiazepine receptor, since an antagonist prevents increased activity. These data suggest that the unique clinical effects of alprazolam may be due in part to unusual interactions with the benzodiazepine receptor.

Alprazolam↗
PubMed1988

[Non-invasive methods for vascular studies in the diagnosis of deep venous thrombosis].

The sonographic diagnosis of deep venous thrombosis must be made up of a functional continuous wave Doppler study of the whole deep venous system of the limbs, including leg veins, as well as saphenous veins. Then, high resolution B-mode real time sonography is used for the detection of direct (echogenic thrombus) or indirect (incompressible vein) signs of thrombosis. This noninvasive approach offers a good sensitivity (about 96%) and a high level of specificity (about 98%). Moreover, B-mode sonography can ensure the differential diagnosis (hematoma, extrinsic compression...) in most cases. So, X-Ray venography is required only when an interventional therapy is planned (thrombectomy, fibrinolysis, inferior vena cava interruption...), or when the noninvasive techniques are not able to show the upper limit of the thrombosis (especially for iliac veins or inferior vena cava), or when there is still a doubt about deep venous thrombosis. Therefore, the number of X Ray venographies can be consistently reduced, thus decreasing both cost and risks.

Angiography↗
PubMed1986

Cytoplasmic and nuclear estrogen binding capacity in the rat uterus during treatment with danazol and testosterone.

Danazol, testosterone and dihydrotestosterone (DHT) were tested as competitors for estrogen receptors on immature rat uterus cytosol. No competitive binding could be demonstrated for any of these steroids. After that, prepubertal Wistar rats were exposed to danazol, testosterone or propylene glycol (control) for 3 days or 17 days. After the appropriate exposure to medication, the animals were killed. Both danazol and testosterone appeared to be uterotropic after 3 days of treatment, although the increase in the uterine weight was significant only in the danazol-treated group (p less than 0.05). This effect was lost after 17 days of treatment. Estradiol receptor binding assays were done on the cytosolic and nuclear fractions of the homogenized uterine tissue of each group. The estrogen binding capacity of cytosols was increased in both the danazol (p less than 0.05) and the testosterone (p less than 0.01) groups after 3 days of treatment. A parallel increase was found in the nuclear fraction of both groups. After 17 days of treatment, the comparison between the 3 groups showed no differences in the cytosolic or nuclear estrogen binding capacity. The information provided by this study suggests that some effects of danazol may be due to an androgenic action and that may be associated to increases in the free fraction of testosterone.

Animals↗
PubMed1985

Effects of the intraventricular administration of 5,7-dihydroxytryptamine on FSH, LH and prolactin secretion in neonatally estrogenized male rats.

The role of the serotoninergic system in the control of LH, FSH and prolactin secretion was analyzed in control and neonatally estrogenized male rats. Animals injected s.c. with 500 micrograms of estradiol benzoate (EB) on day 1 of life, or their corresponding sham-treated controls, were divided on day 75 into the following groups: (1) orchidectomized; (2) injected intraventricularly with 5,7-dihydroxytryptamine (5,7-DHT); (3) orchidectomized and treated with 5,7-DHT, and (4) sham operated. 15 days later, the animals were decapitated and their FHS, LH and prolactin plasma values measured by specific RIA systems. After the treatment with 5,7-DHT, control animals showed a decline in basal prolactin levels but no modification in basal LH and FSH values. After castration, 5,7-DHT-treated animals showed a reduced LH increase and a more marked prolactin decrease. In neonatal estrogen-treated animals, the 5,7-DHT injection did not change FSH, LH or prolactin levels but did partially or completely abolish the post-castration rise in FSH and LH levels, respectively. These data seem to indicate that neonatal estrogenization induced a modification of the serotoninergic role in the control of LH, FSH and prolactin.

Animals↗
PubMed1984

Fluoroscopic imaging: quantitation of image lag or smearing.

Image lag (smearing or persistence of the image) is a characteristic of video imaging systems that is exhibited when rapidly moving objects are blurred due to motion. Video pick-up tubes can exhibit differing amounts of image lag depending on the age of the tube, the amount of light reaching the tube, the set-up parameters used (e.g., beam current and target voltages, etc.), and the tube type. We describe a new quantitative method for measuring image lag that requires only a storage oscilloscope and an inexpensive shutter. Examples of lag measurements on different systems under varying clinical conditions are given. Suggested limits for clinically acceptable amounts of image lag range from 10% to 50% depending on the particular application.

Data Display↗
PubMed1983

The effects of three different regimens of oral contraceptives and three different intrauterine devices on the levels of hemoglobin, serum iron and iron binding capacity in anemic women.

The effects on hemoglobin, iron and iron binding capacity (IBC) in 150 moderately anemic women of 1) a 21-day low-dose combined pill, 2) the same low-dose combined pill for 21 days, followed by 7 days of an iron-containing pill, 3) the same low-dose combined pill administered for 63 consecutive days, followed by 7 days of no pill intake, 4) Lippes IUD, 5) TCu 220C and 6) Progestasert were studied. The three pill regimens were associated with an increase in hemoglobin and serum iron after 12 months. However, the iron pill and 63-day schedule groups produced an increase in hemoglobin and iron at the 6th month ans a diminution of IBC at 12 months. The Lippes and TCu 220C groups did not show any change in hemoglobin, iron or iron binding capacity after 12 months. The Progestasert group showed an increase in hemoglobin and iron levels at 6 and 12 months, and a diminution of IBC at 12 months. The pill and Progestasert have advantages as contraceptives in anemic women.

Adolescent↗
PubMed1983

Effects of partial anti-G suit inflation on thoracic volume and breathing pattern.

The purpose of this study was to determine the changes in thoracic volume and pattern of breathing during partial anti-G suit (PAGS) inflation by respiratory inductive plethysmography (RIP). Nine normal subjects donned the PAGS, with bladders over legs and thighs, and rested for about 10 min in 60 degrees head-up tilt position. The subjects breathed with closed glottis at functional residual capacity while PAGS was suddenly inflated to 140 mmHg using a calves to thighs sequence. The increase in thoracic volume, as measured from deflection of RIP baseline was 252 ml (S.D. 43 ml), which reflected displacement of blood from the lower extremities into the thorax. On resuming normal breathing, thoracic volume returned to baseline level. Breathing pattern was then monitored for a 15 min baseline period, PAGS was inflated, expiratory reserve volume (ERV) was measured by spirometry, and breathing pattern was monitored another 15 min. ERV decreased 227 ml (+/- 60) after PAGS inflation, which did not differ from the change in thoracic volume expected from displacement of blood into the thorax. Breathing pattern was monitored for another 15 min after PAGS was deflated. No changes took place in minute ventilation, tidal volume, frequency, inspiratory time, fractional inspiratory time, and mean inspiratory flow from deflation to PAGS inflation. Thus, 1) increase in thoracic volume produced by displacement of blood from the calves and thighs is balanced by a decrease in gas volume and, 2) no changes in breathing pattern occur after partial anti-G suit inflation, probably because the pulmonary blood vessels and heart are sufficiently distensible to accept a 250 ml volume increment without leakage of fluid into pulmonary tissues.

Adult↗