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Biomedical subjects

A Castro

Publications and source records attributed to A Castro.

At least 19 recordsLinked to original sources
PubMed1992

In vitro antiviral activity of four isothiazole derivatives against poliovirus type 1.

The in vitro effects of four isothiazoles [5,5'-diphenyl-3,3'-diisothiazole disulfide, 5-phenyl-3-mercapto-isothiazole, 5,5'-(4-chlorophenyl)-3,3'- diisothiazole disulfide, and 5-(4-chlorophenyl)-3-mercapto-isothiazole] on poliovirus type 1 were studied. The derivatives tested demonstrated remarkable viral inhibition, with a higher selectivity index than the previously studied iminodithiole precursors. Under one-step growth conditions, all the isothiazole derivatives caused the greatest activity if added during or after (within 1 h) poliovirus adsorption. These data suggest interference with early events of viral replication. [5-3H]Uridine incorporation into RNA showed that the compounds tested reduced poliovirus RNA synthesis, which was completely shut off after 2 h of incubation and reduced by 50-60% after 4 h. Also, pretreatment of the cell cultures with the compounds for 24 h caused a substantial inhibition of viral replication. The data suggest that the four isothiazole derivatives may have a multi-step antiviral mode of action different from their iminodithiole precursors.

Antiviral Agents↗
PubMed1992

[A topical solution of 40% idoxuridine in dimethyl sulfoxide compared to oral acyclovir in the treatment of herpes zoster. A double-blind multicenter clinical trial].

BACKGROUND: Both topical 40% idoxuridine in dimethylsulfoxide (IDU) and oral acyclovir (ACV) are useful in herpes zoster (HZ). This is the first clinical trial which compares the efficacy of both drugs in the course of the disease and in the prevention of post-herpetic neuralgia (PHN). METHODS: Patients of both sexes older than 18 years, with a HZ of less than 4 days were selected. Patients with otic or ophthalmic zoster, serious concomitant illness or pregnant or breast-feeding women were excluded. Following a double dummy design, the patients received at random topical IDU and oral placebo, or oral ACV and topical placebo. Topical treatment was applied during 4 days and oral treatment during 7 days. The evolution of the disease (number of individual lesions, evolution of symptoms, use of analgesic drugs and eventual appearance of complications) was controlled on days 0, 2, 4, 6, 8, and weekly until its resolution. RESULTS: The group of patients treated with IDU (85) showed a better evolution of the disease than those treated with ACV (86) in some of the parameters controlled: day of first and all vesicles drying (p less than 0.05), last day of moderate-intense pain (p less than 0.05), hyperaesthesia (p less than 0.05) and itching (p less than 0.05) and last day of analgesic use (p less than 0.01). The appearance of new vesicles during treatment was lower in the IDU treated group (p less than 0.01). A tendency favouring IDU can be observed in the appearance of PHN. CONCLUSIONS: In our study topical 40% idoxuridine in DMSO was better than oral acyclovir in 7 of the 14 clinical parameters studied.

Acyclovir↗
PubMed1992

Pathogenesis of arterial hypotension in cirrhotic rats with ascites: role of endogenous nitric oxide.

Nitric oxide is a vasodilator tonically secreted by endothelial cells that is involved in the regulation of arteriolar tone. This study, which includes two protocols, was performed to investigate whether nitric oxide plays a role in the pathogenesis of arterial hypotension in cirrhosis with ascites. In protocol 1, the administration of increasing doses (25, 50, 250, 500 and 1,000 micrograms.kg-1.min-1) of the nitric oxide biosynthesis inhibitor N omega-nitro-L-arginine to 18 conscious rats with cirrhosis and ascites produced, at each dose tested, a significantly greater increase in arterial pressure than in 17 conscious control rats. At the lowest dose of N omega-nitro-L-arginine, arterial pressure significantly rose in cirrhotic rats but not in controls. In protocol 2, arterial pressure, estimated renal plasma flow, glomerular filtration rate and sodium excretion were measured in 12 cirrhotic rats with ascites and 10 control rats before and during the sequential infusion of previously selected doses of N omega-nitro-L-arginine (25, 50 and 250 micrograms.kg-1.min-1). Changes in arterial pressure reproduced those observed in protocol 1. In control rats, N omega-nitro-L-arginine caused a decrease in estimated renal plasma flow without affecting glomerular filtration rate or sodium excretion. In contrast, N omega-nitro-L-arginine administration to cirrhotic animals did not produce any appreciable renal vasoconstrictor effect, and it increased glomerular filtration rate and sodium excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Intramedullary spinal cord abscess.

We report a patient with a chronic intramedullary spinal cord abscess who suffered an episode of acute meningitis due to rupture of the abscess into the subarachnoid space.

Abscess↗
PubMed1992

[Incidence of and mortality from malignant tumors inthe municipality of++Vila Nova de Gaia: 1981-1987].

Data from the population based Cancer Registry of Vila Nova de Gaia for the 1981-1987 period are presented. Cancer is becoming a disease increasingly frequent in Portugal, causing progressively higher mortality rates. Population and geographic characteristics of Vila Nova de Gaia country is presented. Information sources of this Registry are hospitals, pathology labs, Health Authority files and death certificates. Net (229.2, 216.6) and standardized for european population (369.9, 245.9) incidence rates are presented for respectively men and women. Comparisons with registries from other countries (e.s.) are made.

Adolescent↗
PubMed1992

[The results of drug holiday in Parkinson's disease].

The transitory suppression of L-dopa in patients with advanced Parkinson's disease improves motor response upon reintroduction of the drug although this improvement is not constant. The degree and duration of clinical improvement obtained following L-dopa drug holiday were studied and the factors which may intervene in the result of 32 patients with Parkinson's disease were analyzed. Improvement was found in 100% (24.9 +/- 6.7%) with significant differences being observed in the degree of disability (p < 0.05) and the final decrease of the doses of L-dopa (p < 0.05). Improvement was maintained during 10.3 +/- 7.9 weeks. Linear regression studies did not show any relation between the length of the drug holiday, longer than 4 days, and the degree and maintenance of improvement or final decrease of the doses of L-dopa. The authors consider this procedure useful in patients with important fluctuations in treatment response or with important refractory side effects to other measures.

Adult↗
PubMed1992

Tissue expanders in the gut: a histological and angiographic study.

A study to assess the effects of an intraluminally placed tissue expander in the rabbit jejunum was performed. Oval expanders (8 cm3) were placed via a midline coeliotomy through an enterotomy on the antimesenteric border of the jejunum. The reservoir was tunnelled subcutaneously through the abdominal wall. Expansion was carried out through this port at 7-10-day intervals using 0.5-cm3 increments. At the end of the experiment, angiography was performed and routine haematoxylin and eosin-stained sections were produced. Angiography revealed an increase in vessel diameter and vascular density of the specimen. Histology showed an increase in villi size, an increase in the number of goblet cells and a marked increase in the thickness of the muscular layer. The possible applications of this technique are discussed.

Animals↗
PubMed1992

Purification of streptokinase by affinity chromatography on immobilized acylated human plasminogen.

Streptokinase is an extracellular protein produced by several strains of streptococci. It functions in the species-specific conversion of plasminogen to plasmin. In this paper we describe the purification of streptokinase by affinity chromatography on human plasminogen acylated with p'-nitrophenyl p-guanidinobenzoate. The acylated and non-acylated plasminogen and plasmin were coupled to cyanogen bromide-activated Sepharose 4B and evaluated for streptokinase purification. These results show that a homogeneous preparation of streptokinase with high specific activity and high yield can be obtained using acylated plasminogen. This method permits the binding of one milligram of streptokinase per milliliter of swollen gel.

Acylation↗
PubMed1991

Induction of tumor necrosis factor and macrophage-mediated cytotoxicity by horseradish peroxidase and other glycosylated proteins: the role of enzymatic activity and LPS.

Recent studies by these investigators have shown that horseradish peroxidase (HRP) can cause murine thioglycollate-induced peritoneal macrophages (M phi) to produce both tumor necrosis factor (TNF) and enhance macrophage-mediated cytotoxicity (MMC) to 3T12 target cells. The present study identifies the roles of both enzymatic activity and contaminating lipopolysaccharides (LPS) (less than or equal to 1 ng) on these activities. The addition of 100 ng/ml of polymyxin B (PB) to enzymatically active HRP significantly reduced TNF production but did not affect MMC. Enzymatically inactive HRP (DHRP) was more effective than HRP in both TNF production and MMC but was not affected by PB. The inability of PB to modify DHRP-induced TNF suggests that LPS was not required. The induction of TNF and MMC in the absence of LPS was also corroborated by similar studies using M phi from endotoxin-resistant C3H/HeJ mice. Glycosylated proteins such as HRP, DHRP, and mannosylated bovine serum albumin (M-BSA) are known to bind to mannose receptors (mannosyl-fucosyl receptor [MFR]) on the surface of M phi. In the present studies, M-BSA behaved similarly to DHRP in that it induced both TNF secretion and MMC. These results suggest that binding to the MFR may be sufficient to induce TNF secretion and MMC. In addition, the data suggest that neither enzymatic activity nor LPS was required for DHRP-induced TNF.

Animals↗
PubMed1991

Localization of microfilaments and a tubulin-like protein in crustacean (Rhynchocinetes typus) spermatozoon.

Sperm from the decapod crustacean Rhynchocinetes typus undergo dramatic shape changes as they pass from the vas deferens to seawater and interact with the oocyte envelopes. Using FITC-phalloidin and antitubulin antibodies, we were able to localize microfilaments and a tubulin-like protein in R. typus spermatozoon. Microfilaments and the tubulin-like protein were associated with the sperm rays and spines, but were absent at the spike and at its base. Folded and unfolded spermatozoa display similar fluorescence patterns. SDS-PAGE of whole spermatozoa and electrotransfer to nitrocellulose confirmed the presence of actin and two proteins at 97 kd and 120 kd that bind to tubulin antibodies (tubulin-like proteins). These results demonstrate the presence of actin, but not tubulin, and localize microfilaments in these sperm. It is proposed that this cytoskeletal component is active in sperm during crustacean fertilization.

Actin Cytoskeleton↗
PubMed1991

Effect of V1-vasopressin receptor blockade on arterial pressure in conscious rats with cirrhosis and ascites.

Angiotensin II blockade with saralasin in human cirrhosis with ascites is associated with a significant reduction in arterial pressure, indicating that endogenous angiotensin II plays an important role in the maintenance of systemic hemodynamics in this condition. The aim of the current study was to investigate whether vasopressin also contributes to the maintenance of arterial pressure in cirrhosis with ascites. The study was performed using three groups of cirrhotic rats with ascites and three groups of control animals. The administration of d(CH2)5Tyr(Me)AVP, a selective antagonist of the vascular effect of vasopressin, to 10 cirrhotic rats induced a significant reduction in mean arterial pressure (from 94 +/- 4 to 85 +/- 4 mm Hg; P less than 0.001) and a significant increase in plasma renin activity (from 24.3 +/- 4.9 to 34.3 +/- 5.9 ng/mL.h; P less than 0.02) and plasma norepinephrine concentration (from 1474 +/- 133 to 2433 +/- 253 pg/mL; P less than 0.01). Similar results were observed following saralasin administration in a second group of 5 cirrhotic rats [mean arterial pressure decreased from 97 +/- 4 to 85 +/- 5 mm Hg (P less than 0.0001); and plasma renin activity and norepinephrine concentration increased from 18.4 +/- 5.8 to 40.3 +/- 5.7 ng/mL.h (P less than 0.02) and from 1383 +/- 70 to 2312 +/- 334 pg/mL (P less than 0.05), respectively]. The simultaneous blockade of angiotensin II and vasopressin in a third group of cirrhotic rats resulted in a significantly greater reduction of mean arterial pressure (from 97 +/- 6 to 74 +/- 6 mm Hg; P less than 0.05). No changes in arterial pressure were observed in the three groups of control rats. These findings indicate that endogenous vasopressin is as important as angiotensin II in the maintenance of arterial pressure in cirrhotic rats with ascites and support the contention that arterial hypotension is the initial event leading to the stimulation of the renin-angiotensin system and vasopressin in this animal model of cirrhosis.

Angiotensin II↗
PubMed1991

Doses of endothelin have natriuretic effects in conscious rats with cirrhosis and ascites.

MAP, RPF, GFR, V and UNaV were measured in nine conscious control and in 11 conscious cirrhotic rats with ascites before and following two bolus injections (100 and 600 pmol/kg body wt) of endothelin (ET). PRA and plasma concentration of aldosterone and ANP were measured in basal conditions and following the high dose ET. ET induced similar increase in MAP and decrease in RPF and GFR in control and cirrhotic rats. High-dose ET produced a significant reduction in UNaV in control rats (from 2.22 +/- 0.46 to 1.14 +/- 0.28 microEq/min, P less than 0.01). By contrast, it induced marked natriuresis in cirrhotic rats (from 0.76 +/- 0.18 to 2.31 +/- 0.70 microEq/min, P less than 0.05). ET significantly increased aldosterone (control rats: 59.3 +/- 2.2 vs. 85.4 +/- 7.4 ng/dl, P less than 0.025; cirrhotic rats: 115.0 +/- 15.8 vs. 163.9 +/- 30.8, ng/dl, P less than 0.05) and ANP (control rats: 20.1 +/- 3.4 vs. 42.7 +/- 7.7, fmol/ml, P less than 0.025; cirrhotic rats: 107.5 +/- 17.3 vs. 214.2 +/- 41.1, fmol/ml, P less than 0.025) and significantly suppressed PRA (control rats: 2.5 +/- 0.5 vs. 0.2 +/- 0.04, ng/ml.hr, P less than 0.025; cirrhotic rats: 16.6 +/- 2.9 vs. 5.0 +/- 1.1, ng/ml.hr, P less than 0.01) in both groups of animals. These results indicate that ET has marked natriuretic properties in cirrhosis with ascites due to inhibition of tubular sodium reabsorption.

Animals↗