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Biomedical subjects

R Castillo

Publications and source records attributed to R Castillo.

At least 109 records · Page 6Linked to original sources
PubMed1990

Alfentanil potentiates midazolam-induced unconsciousness in subanalgesic doses.

The effects of alfentanil on the midazolam dose-response curve for hypnosis was studied with response to the verbal command as an end point in 95 patients. The analgesic effect of alfentanil was studied by measuring the threshold for pain caused by pressure on the trapezius muscle with the use of a dolorimeter in 21 patients. The study was randomized, double-blind, and performed on the unpremedicated patients with ASA physical status I or II. Alfentanil was found to reduce the midazolam ED50 value for the induction of anesthesia in a dose-dependent fashion. The smallest dose of alfentanil (3 micrograms/kg) that caused a marked shift of the midazolam dose-response curve to the left along the dose axis (from the ED50 of 270 micrograms/kg to the ED50 of 142 micrograms/kg, P less than 0.0005) represents approximately 2% of the alfentanil ED50 for induction of unconsciousness (130 micrograms/kg). Alfentanil (10 micrograms/kg) caused only a tendency for increase in the pain threshold, whereas a dose of 15 micrograms/kg significantly increased the pain threshold by 37% (P less than 0.05). The results demonstrate that alfentanil potentiates the hypnotic effect of midazolam in very small doses. The high potency of alfentanil in this respect, as compared to its analgesic potency, suggests a very specific mechanism of alfentanil-midazolam hypnotic interaction, one that most likely is based on a functional relationship between the GABA receptor-benzodiazepine receptor system and the opioid receptor system in mediation of hypnosis.

Adult↗
PubMed1990

[Update on the role of vascular, plasmatic and cellular components in the regulation of the interaction of platelets with the subendothelium].

The interaction of platelets (Plts) with subendothelium (SE) or with extracellular matrices (ECM) generated by endothelial cells was studied under flow conditions. The role of: a) platelet membrane glycoproteins (GPS) or subunits; b) plasma adhesive proteins such as von Willebrand factor (VWF) and fibronectin (Fn); and c) structural proteins of the SE such as laminin (Lm). Specific antibodies or purified proteins were added to the perfusates. GPS. Monoclonal antibodies (MoAb) directed against distinct epitopes of the GPIIb-IIIa affected in different manner the deposition of platelets. MoAb EDU3 decreased (p less than 0.01) the surface of the vessel covered by platelets (% CS) and increased the presence of platelets in contact (% C) with the SE. MoAb C17 did not modify the % CS but altered the morphological characteristics of the aggregates. A monoclonal antibody against GPIIb, decreased the % CS (p less than 0.01) without influencing % C; VWF. A linear progression of the % CS was observed for VWF levels ranging from 0.1 to 0.6 U/mL. A plateau was reached for concentrations of vWF above 0.6 U/mL; Fn. Perfusions in which blood was reconstituted with Fn-depleted plasma showed the cooperation of this protein facilitating Plt-Plt interaction. No statistical differences were observed in the % CS when ECM were incubated with a MoAb against Fn (3E3); Lm. The % CS decreased statistically (p less than 0.01) when SE or ECM were incubated with an antibody to Lm. These results show the critical role of vascular, plasmatic and cellular components in the maintenance of and adequate platelet function.

Animals↗
PubMed1989

Role for platelet von Willebrand factor in supporting platelet-vessel wall interactions in von Willebrand disease.

Twelve infusions of plasma concentrates of von Willebrand factor (vWF) were given to four patients with severe (type III) von Willebrand disease (vWD). Their prolonged bleeding times were either completely or partially corrected after five infusions and had not changed after the remaining seven. In contrast, the low platelet coverage of the subendothelial surface of rabbit aorta perfused with normal washed platelets and red cells resuspended in preinfusion patient plasma was completely or partially corrected in ten instances by replacing preinfusion plasma with postinfusion plasma and remained unchanged in two. Postinfusion improvement in surface coverage was greater than that in bleeding time, suggesting that vWF from normal platelets is needed to support optimal platelet-vessel wall interactions in vWD. This possibility was further explored through other perfusion experiments. The subendothelial surface covered by platelets from an untreated patient with type III vWD (containing no measurable vWF) or from a type IIA vWD patient (containing dysfunctional vWF) resuspended in normal plasma was much smaller than that covered by normal platelets resuspended in normal plasma. These results establish that platelet vWF is important in supporting platelet-vessel wall interactions in vWD and also provide experimental support in favour of the therapeutic transfusion of normal platelets in addition to vWF concentrates to correct the bleeding time in vWD patients.

Blood Platelets↗
PubMed1989

Development and initial validation of a dual-language English-Spanish format for the Arthritis Impact Measurement Scales.

Language, cultural, and educational barriers complicate efforts to validate health status questionnaires that have been translated into Spanish. To overcome these problems, a prototype dual-language format was developed for the Arthritis Impact Measurement Scales. Validity testing with 72 patients diagnosed as having rheumatoid arthritis indicated high levels of test-retest reliability, item-to-scale internal consistency, and construct validity for both Anglo and Hispanic subjects. A technique for developing and pilot-testing a questionnaire written in a regional Spanish dialect is described. Linguistic considerations, questionnaire design, and other applications are discussed in light of the results obtained.

Arthritis↗
PubMed1989

[Clinical experience in diabetes and pregnancy].

We followed patients with pregnancy and diabetes in an outpatient clinic. 240 had gestational diabetes, 16 had type II and 5 type I diabetes. 85% of 110 patients with gestational diabetes had normal glucose tolerance test post partum (AGT). Type I patients were younger (25 years old) than AGT (32) or type II (33) patients. Complications frequently observed among diabetics included hypertension, premature membrane rupture and polyhydroamnios (the latter only among AGT and type II patients). Insulin was required for diabetes control in 14% of cases. Cesarean section was more frequent in diabetics than in a control population (21%): AGT 45%, type II 45% and type I 60%. Larger newborns occurred in 21% of AGT and 22% of type II as compared to 6% in controls. Neonatal mortality was 2.1% in AGT patients (0.8% in controls). Hyperbilirrubinemia, polyglobulia and hypocalcemia were more frequent among newborns of diabetic patients.

Adult↗
PubMed1989

Uremic plasma after infusion of desmopressin (DDAVP) improves the interaction of normal platelets with vessel subendothelium.

Effects of 1-deamino-8-D-arginine vasopressin (DDAVP; 0.4 microgram/kg iv) were studied in 11 patients with uremia. Bleeding time, platelet retention on glass beads, factor VIII activities, plasma catecholamine levels, and studies on platelet interaction with the subendothelium were performed before, 1 hour after, and 6 hours after DDAVP infusion. Perfusates consisting of normal washed platelets, uremic platelet-poor plasma (u-PPP) and washed red blood cells were perfused through the Baumgartner perfusion system at a shear rate of 800 sec-1. One hour after DDAVP infusion, a shortening in the bleeding time and an increase in platelet retention on glass beads were noticed in these patients (p less than 0.01). Simultaneously, plasma levels of noradrenaline, factor VIII coagulant (FVIII:C), and von Willebrand factor (vWF) activities were statistically increased. Platelet deposition and platelet aggregate formation on subendothelium were consistently increased (p less than 0.05) in perfusions carried out with blood reconstituted with u-PPP obtained 1 hour after DDAVP. The "in vitro" addition of 1 U/ml vWF or 1 U/ml vWF plus 1 U/ml factor VIII to the pretreatment u-PPP had no significant influence on the parameters that quantify platelet-subendothelium interaction. However, after the addition of 10 ng/ml noradrenaline to a similar system containing basal u-PPP, a clear improvement (p less than 0.05) in platelet deposition was noticed. Our results confirm the hemostatic effectiveness of DDAVP in patients with uremia and reveal an increased platelet interaction with subendothelium mediated by a factor present in uremic plasma after DDAVP administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[Use of FMC macromolecular medium for determination of the erythrocyte ABO group using microtiter plates].

Several blood group determination techniques have been developed in recent years which provide easy handling, fine reproducibility and similar or even higher sensitivity than the procedures commonly employed, aimed to be used in the automation of blood bank work. A microtitration plate technique for ABO determination on red cells is presented in this report. A macromolecular medium, comprised of a mixture of the polymers Ficoll 400 and carboxymethyl cellulose (FMC) is used ad coadjuvant for the reaction. This medium increases by 15- the score units and by 4-fold (or more) the intensity of haemagglutination (titration) in typing the ABO antigenicity of red cell A, B, O and AB groups.

ABO Blood-Group System↗
PubMed1988

Asialo von Willebrand factor enhances platelet adhesion to vessel subendothelium.

Native von Willebrand factor (N-vWF) binds to platelets activated by thrombin, ADP or ristocetin. Asialo vWF (As-vWF) induces platelet aggregation in absence of platelet activators. N-vWF mediates platelet adhesion to vessel subendothelium at high shear rates. We have investigated the role of As-vWF in supporting platelet deposition to rabbit vessel subendothelium at a shear rate of 2,000 sec-1, using the Baumgartner perfusion system. We have studied the effects of the addition of As-vWF (from 2 to 12 micrograms/ml) to perfusates consisting of washed red blood cells, 4% human albumin and washed platelets. Our results show a significant increase in platelet deposition on subendothelium (p less than 0.01) in perfusions to which As-vWF had been added. Blockage of the platelet glycoproteins Ib and IIb/IIIa (GPIb and GPIIb/IIIa) by specific monoclonal antibodies (LJIb1 and LJCP8, respectively) resulted in a decrease of platelet deposition in both types of perfusates prepared with N-vWF and As-vWF. Our results indicate that As-vWF enhances platelet deposition to vessel subendothelium under flow conditions. Furthermore, they suggest that this effect is mediated by the binding of As-vWF to platelet membrane receptors, which in turn, promote platelet spreading and adhesion to the subendothelium.

Antibodies, Monoclonal↗
PubMed1988

Ristocetin induces platelet aggregation: a morphological demonstration.

Changes in the morphology of human platelets induced by ristocetin in platelet-rich plasma (PRP) have been analysed at the ultrastructural level by means of a tannic acid procedure. Studies were also undertaken to measure the release of serotonin. Modifications of the aggregation tests induced by apyrase, a monoclonal antibody (Mab) to GPIIb/IIIa and by EDTA were also investigated. Transmission electron microscopy revealed that ristocetin precipitated adhesive proteins on the platelet membrane. An electron-dense deposit was seen within 20 s after ristocetin was added. When experiments were carried out in the aggregometer cuvette during stirring, groups of platelets became activated, changed their shape, and finally aggregated releasing part of their contents. The morphology of aggregates did not differ from those formed in the presence of ADP. Aggregation studies demonstrated that a Mab to GPIIb/IIIa modified the extent and the rate of the aggregation curve when RIPA was performed in citrated platelet-rich plasma (c-PRP), while apyrase modifies the extent, but not the slope, of the curve. Neither the antibody nor apyrase modified RIPA when it was performed in PRP obtained in the presence of EDTA. All this evidence suggests that RIPA in c-PRP, besides reflecting the interaction of GPIb with vWF, may also test other mechanisms of the platelet function including: assembly of GPIIb/IIIa complex, interaction of fibrinogen with this glycoprotein complex, and possibly the release reaction.

Antibodies, Monoclonal↗