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Biomedical subjects

G Rojas

Publications and source records attributed to G Rojas.

At least 37 records · Page 2Linked to original sources
PubMed1999

Neutralization, by a monospecific Bothrops lanceolatus antivenom, of toxic activities induced by homologous and heterologous Bothírops snake venoms.

A monospecific Bothrops lanceolatus antivenom, currently used in Martinique, was tested for its efficacy in the neutralization of several toxic and enzymatic activities of the venoms of B. lanceolatus, B. atrox and B. asper. When tested by the i.p. route in mice, B. lanceolatus venom had an LD50 of 12.8 microg/g. In addition, it induced local tissue damage (hemorrhage, edema and myotoxicity) and showed indirect hemolytic activity, but was devoid of coagulant effect on human plasma in vitro and of defibrinating activity in mice. Antivenom was fully effective in the neutralization of lethal, hemorrhagic, edema-forming, myotoxic and indirect hemolytic effects of B. lanceolatus venom in assays involving preincubation of venom and antivenom. When tested against the venoms of B. asper and B. atrox, the antivenom completely neutralized the lethal, hemorrhagic, myotoxic and indirect hemolytic effects, and was partially effective in neutralizing edema-forming activity. In contrast, the antivenom was ineffective in the neutralization of in vitro coagulant and in vivo defibrinating effects induced by these two venoms.

Animals↗
PubMed1999

A randomized blinded clinical trial of two antivenoms, prepared by caprylic acid or ammonium sulphate fractionation of IgG, in Bothrops and Porthidium snake bites in Colombia: correlation between safety and biochemical characteristics of antivenoms.

A randomized blinded clinical trial was performed in 53 patients bitten by Bothrops sp. and Porthidium sp. in Antioquia and Chocó, Colombia, in order to compare the efficacy and safety of two antivenoms made of whole IgG obtained by either ammonium sulphate (monovalent anti-B. atrox) or caprylic acid (polyvalent) fractionation. Additionally, antivenoms were compared by electrophoretic and chromatographic analyses and anticomplementary activity in vitro. With a protocol of 2, 4 and 6 antivenom vials for the treatment of mild, moderate and severe envenomings, respectively, both antivenoms were equally efficient to neutralize the most relevant signs of envenoming and to clear serum venom levels in patients from the first hour and later on. Three patients with severe envenoming and initially treated with less than six vials on admission had persistent or recurrent venom antigenemia within 12-48 h. Monovalent antivenom fractionated by ammonium sulphate precipitation had higher amounts of protein aggregates and nonimmunoglobulin proteins than polyvalent antivenom fractionated by caprylic acid precipitation. Both antivenoms presented anticomplementary activity in vitro, being higher in the monovalent product. In agreement, monovalent antivenom induced a significantly higher incidence of early antivenom reactions (52%) than polyvalent antivenom (25%).

Adolescent↗
PubMed1999

Sexual dimorphism in circulating monomeric and dimeric inhibins in normal boys and girls from birth to puberty.

BACKGROUND AND OBJECTIVE: Inhibins are peptides, mainly of gonadal origin, that suppress FSH production. Dimeric forms of inhibin (A and B) have been proposed as peripheral markers of Sertoli and granulosa cell function. The aim of this study was to establish the relationship between circulating dimeric and monomeric inhibins, and gonadotrophins and sex steroids, in normal boys and girls from birth to puberty. SUBJECTS: One hundred and forty-six normal children (females: 57; males: 89) were studied. MEASUREMENTS: Serum LH and FSH were measured by an immunofluorometric assay. Serum oestradiol and testosterone were measured by radioimmunoassay. Serum inhibin A and B, and Pro-alphaC, were measured by specific two-site enzyme-linked immunosorbent assays. RESULTS: In boys from birth to 6 months of age, the mean serum inhibin B concentration was as high (477 +/- 53.7 ng/l) as that found at puberty (400 +/- 70.2 ng/l). After the first year, inhibin B gradually decreased to reach its lowest concentration (153 +/- 23.6 ng/l) at age 4-6 years. At approximately age 10, it rose progressively to reach pubertal concentrations. Pro-alphaC showed a similar pattern but at lower concentrations. Inhibin A was not detected at any age. In girls from birth to 6 months, inhibin B levels (83.0 +/- 18.3 ng/l) were approximately 50% lower than those found at puberty (181 +/- 25.7 ng/l). After 6 months of age, these levels dropped (17.5 +/- 1.6 ng/l) and remained low until the prepubertal years. Thereafter, they increased to pubertal concentrations. The serum inhibin A concentration after birth (29.9 +/- 8.7 ng/l) was similar to that found at puberty (18.3 +/- 5.7 ng/l); after 6 months, it fell to undetectable levels until the prepubertal years. CONCLUSION: The sex difference in serum levels of gonadotrophins is associated with sex differences in the levels and proportions of circulating dimeric and monomeric inhibins.

Adolescent↗
PubMed1999

Reoperations for bleeding portal hypertension. Surgical rescue of surgical failures.

BACKGROUND: Surgery for portal hypertension has a low rebleeding rate. Patients that rebleed can be grossly divided into those who die as a consequence of the episode, those who don't die but develop liver failure (remaining as Child-Pugh C) and those who, in spite of the bleeding episode, retain good liver function (Child-Pugh A or B). At our hospital, the latter group is considered for further surgical treatment. We report here the results of surgical rescue of surgical failures. METHODS: In a twenty year period, 36 patients (30 Child-Pugh A, 6 Child-Pugh B) were reoperated. The files of these patients were reviewed. RESULTS: Average age was 33 years. Cirrhosis was present in 31 cases. All patients were electively reoperated with portal blood flow preserving procedures. Operative mortality for the whole group was 12% and for the Child-Pugh A group 6.6%. Rebleeding was observed in 5.5%. Postoperative incapacitating encephalopathy was recorded in one case (2.7%). Good quality of life was recorded in 84% of the cases. Survival (Kaplan-Meier) was 78% at 6 months and 69% at 5 years. CONCLUSIONS: Surgical failures in low risk patients (Child-Pugh A or B) can be treated by means of surgery, and a low mortality, re-bleeding and encephalopathy rate can be expected. The performance of a portal blood flow preserving procedure is recommended.

Adolescent↗
PubMed1999

Comparative study on the ability of IgG and F(ab')2 antivenoms to neutralize lethal and myotoxic effects induced by Micrurus nigrocinctus (coral snake) venom.

A comparative study was performed on the ability of IgG and F(ab')2 antivenoms to neutralize lethal and myotoxic activities of Micrurus nigrocinctus venom. Both antivenoms were adjusted to a similar neutralizing potency in experiments where venom and antivenoms were preincubated prior to injection. No significant differences were observed between IgG and F(ab')2 antivenoms concerning neutralization of lethal effect in rescue experiments, i.e., when antivenom was administered intravenously after envenomation. However, F(ab')2 antivenom was more effective in prolonging the time of death when subneutralizing doses were administered immediately after venom injection. Both products partially reversed the binding of M. nigrocinctus alpha-neurotoxins to acetylcholine receptor in vitro. The IgG and F(ab')2 antivenoms effectively neutralized venom-induced myotoxicity when administered intravenously immediately after envenomation, although neutralization was poor if antivenom injections were delayed. Intramuscular injection of venom promoted diffusion of antivenom antibodies throughout muscle tissue, and F(ab')2 diffused to a higher extent than IgG molecules. Thus, despite the observation that F(ab')2 antivenom was more effective than IgG antivenom in prolonging the time of death when subneutralizing doses were administered immediately after envenomation, no major differences were observed in antivenom neutralization of lethal and myotoxic effects or in their capacity to reverse neurotoxin binding to the acetylcholine receptor.

Animals↗
PubMed1998

Inhibition by CaNa2EDTA of local tissue damage induced by Bothrops asper (terciopelo) venom: application in horse immunization for antivenom production.

The ability of the chelating agent CaNa2EDTA to inhibit local tissue damage induced by Bothrops asper venom was studied in mice and in horses used for polyvalent (Crotalinae) antivenom production. CaNa2EDTA was devoid of toxicity when injected i.m. or s.c. inducing only a mild edema. Preincubation of B. asper venom with CaNa2EDTA inhibited hemorrhagic and dermonecrotic activities, but did not reduce edema-forming and myotoxic effects. A group of horses initially immunized with native venoms developed less severe local tissue reactions when injected with booster doses of venom and CaNa2EDTA than when receiving booster injections of venom alone, although they showed a similar antivenom response. Moreover, antivenoms produced from plasmas of horses that received booster injections of either venom alone or venom plus CaNa2EDTA had similar neutralizing activity against lethal, hemorrhagic and coagulant effects induced by B. asper venom. The similar antibody response was corroborated by Western blotting using crude venom and by an ELISA that estimates anti-myotoxin titer. It is concluded that the chelating agent CaNa2EDTA reduces the extent of local tissue damage induced by B. asper venom, without affecting the immune response of horses against pharmacologically-relevant venom components.

Animals↗
PubMed1998

Neutralization of local tissue damage induced by Bothrops asper (terciopelo) snake venom.

Local tissue damage represents a serious consequence of Bothrops asper envenomations. It encompasses a complex series of alterations, including myonecrosis, dermonecrosis, hemorrhage and edema. Due to its rapid development it is difficult to neutralize by antivenoms, especially if there is a delay in serotherapy. Experimental studies with this venom and the polyvalent (Crotalinae) antivenom produced in Costa Rica indicate that antivenom is effective in neutralizing these toxic activities when incubated with the venom prior to injection. However, if venom and antivenom are injected independently in mice, neutralization of these effects is only partial. Moreover, neutralization is not complete even if homologous or heterologous antibodies are present in the circulation before venom is injected. Despite differences in their pharmacokinetic profiles, equine whole IgG and F(ab')2 antivenoms show similar efficacy in the neutralization of edema, hemorrhage and myonecrosis induced by B. asper venom, suggesting that the use of antivenoms made of antibody fragments may not improve neutralization of these effects. This is due, at least in part, to the fact that microvessel disruption by venom components favors a similar antibody concentration in the affected tissues. Recent advances in the development of neutralizing substances of rapid diffusion, that could be injected locally in the field, may contribute to the neutralization of metalloproteinases and phospholipases A2. In addition, the rapid administration of antivenoms with high antibody titers against locally-acting toxins is very important in the treatment of these effects.

Animals↗
PubMed1998

Conceptual bases and methodology for the evaluation of women's and providers' perception of the quality of antenatal care in the WHO Antenatal Care Randomised Controlled Trial.

In this paper, we describe the conceptual bases and methodology used to assess women's and providers' perception of the quality of antenatal care, as part of a large randomised trial in four developing countries. Information has been obtained by applying both qualitative and quantitative methodologies. The focus group discussions and in-depth interviews have contributed useful insights into the cultural milieu in which care is provided, users' and providers' expectations, and their concept of quality. Based on these findings, we developed two standardised questionnaires, one being administered to a representative sample of pregnant women (n = 1600) and the other for all care providers. In this paper we present some of the findings of the focus group discussions and in-depth interviews with women in one country as an example of the kind of information we have obtained. Women expressed their point of view concerning a reduced number of visits, type of provider, information that they get during clinical encounters and interpersonal relations with health professionals. The qualitative information, together with the data we obtain from the surveys, will highlight the aspects that will have be to considered if the new model of care is to be introduced on a routine basis.

Argentina↗
PubMed1998

Antimicrobial compounds detected in Bocconia arborea extracts by a direct bioautographic method.

BACKGROUND: Among the numerous in vitro methods for studying the antimicrobial activity of plant drugs, bioautography has found widespread applications, especially for the detection of new compounds in complex plant extracts. METHODS: This paper describes the results obtained during the application of the bioautographic method to detect antimicrobial compounds in a chloroformic extract of leaves and stems of Bocconia arborea, a plant used profusely in traditional medicine for the treatment of diverse infectious diseases. RESULTS AND CONCLUSIONS: The methods allows for the detection of spots of growth inhibition of cultures directly in the extract thin layer chromatographic plate previously dispersed with a broth culture containing the microorganisms. The procedure also allowed for the detection of the presence of several products in the B. arborea extract with considerable activity against five different microorganisms. Additionally, the method allowed the determination that the antimicrobial activity is due to compounds of probable alkaloid origin.

Anti-Infective Agents↗
PubMed1998

[Common mental disorders, depression and public health].

Common Mental Disorders (CMD), particularly depressive disorders, are problems of public health importance and it would seem appropriate to approach them from a public health point of view. In this paper only psychosocial aspects are dealt with, because biological factors are less important in the pathogenesis of CMD. Although there are significant associations between socioeconomic variables and CMD, the association between poverty and CMD seems to be one of the most robust. There is good evidence that low income is associated with CMD, and this relationship may be causal. There is therefore a possibility that changes in social and economic policy that would reduce poverty might also reduce the prevalence of CMD. Future research should try to unravel the mechanisms and causal factors that underlie these common and disabling disorders.

Depression↗
PubMed1997

Changes in gallbladder surgery: comparative study 4 years before and 4 years after laparoscopic cholecystectomy.

Operative procedures on the gallbladder and biliary ducts have undergone a profound transformation since the introduction of laparoscopic techniques in general surgery. As the benefits of minimally invasive procedures become universally known, patients are seeking surgery at an earlier stage, resulting in an increased number of cases for elective surgery and a considerable reduction in emergency operations, morbidity, need for intraoperative cholangiography (IOC), fewer common bile duct (CBD) explorations, shortened hospital stay, and reduced overall costs. The early criteria for IOC and the need for CBC explorations must be reevaluated in view of the observed changes and appropriate modifications made. Looking at the present trends, it seems that the routine use of IOC is not justified in the average patient who presents for laparoscopic cholecystectomy with no history of jaundice or pancreatitis, normal liver function tests, and a normal-size CBD on ultrasonography. Under those conditions, the chance of leaving an unsuspected stone in the CBD is less than 1%; and if it happens the stone can be easily retrieved by endoscopic sphincterotomy as an outpatient procedure.

Cholangiography↗
PubMed1997

Immunoglobulin G and F(ab')2 polyvalent antivenoms do not differ in their ability to neutralize hemorrhage, edema and myonecrosis induced by Bothrops asper (terciopelo) snake venom.

The ability of whole immunoglobulin G (IgG) and F(ab')2 polyvalent (Crotalinae) antivenoms to neutralize the hemorrhagic, edema-forming and myotoxic activities of Bothrops asper venom was studied. Both antivenoms were adjusted to the same neutralizing potency against lethal and hemorrhagic activities in experiments where venom and antivenoms were incubated before injection. Thus, in these experimental conditions, differences in the neutralizing ability in experiments involving independent injection of venom and antivenoms would depend mainly on the different pharmacokinetic profiles of whole IgG and F(ab')2 antivenoms. Experiments involving local injection of venom followed by intravenous administration of antivenom at either 0, 15 or 30 min after envenomation did not reveal any significant difference between whole IgG and F(ab')2 products concerning neutralization of hemorrhage, edema and myonecrosis induced by B. asper venom. The three effects were neutralized by antivenoms only to a partial extent and neutralization decreased as the time-lapse between envenomation and antivenom administration increased. Moreover, with the exception of one time-interval, no significant differences in the neutralization of hemorrhage were observed when antivenom was administered by the intramuscular or intraperitoneal route. The results do not support the assumption that F(ab')2 antivenom is more effective than whole IgG antivenom in the neutralization of local hemorrhage, edema and myonecrosis induced by B. asper venom in mice.

Animals↗
PubMed1997

Snakebite mortality in Costa Rica.

The mortality rate due to snakebite envenomation in Costa Rica was estimated from 1952 to 1993. The highest mortality was observed during the 1950s and 1960s, with the highest rate of 4.83 per 100,000 population in 1953. In contrast, a rate of 0.2 per 100,000 population per year was estimated from 1990 to 1993. The most conspicuous decline in mortality occurred after 1970. The highest mortality rates were observed in the provinces of Limón and Puntarenas, especially in regions where tropical rain forests had been transformed into agricultural fields. The lowest mortality was in the province of Guanacaste, where tropical dry forest predominates and Bothrops asper (terciopelo), the most important poisonous snake in the country, is not abundant. The majority of fatalities occurred in the age groups from 10 to 19 years old. Males were more affected than females in a ratio of 3.6:1. Before 1980 most fatal cases did not receive medical attention in hospitals, whereas after 1980 the majority of cases with fatal outcome were attended in hospitals.

Adolescent↗
PubMed1997

Genetically engineered large animal model for studying cone photoreceptor survival and degeneration in retinitis pigmentosa.

Patients with retinitis pigmentosa (RP) typically develop night blindness early in life due to loss of rod photoreceptors. The remaining cone photoreceptors are the mainstay of their vision; however, over years or decades, these cones slowly degenerate, leading to blindness. We created transgenic pigs that express a mutated rhodopsin gene (Pro347Leu). Like RP patients with the same mutation, these pigs have early and severe rod loss; initially their cones are relatively spared, but these surviving cones slowly degenerate. By age 20 months, there is only a single layer of morphologically abnormal cones and the cone electroretinogram is markedly reduced. Given the strong similarities in phenotype to that of RP patients, these transgenic pigs will provide a large animal model for study of the protracted phase of cone degeneration found in RP and for preclinical treatment trials.

Animals↗
PubMed1997

An assessment of residents' competence in the delivery of bad news to patients.

PURPOSE: To assess the level of residents' competence in delivering bad news to patients. METHOD: In June 1995, 25 residents (of 116) in the Wayne State University general internal medicine residency program volunteered to participate in the study, which consisted of videotaped interviews of a simulated patient whose profile had been developed to highlight the delivery of a diagnosis of lung cancer. The residents were evaluated using an instrument based on a review of the current literature regarding the skills considered necessary for giving bad news in a caring and informative manner. The instrument contained 16 items, seven in the informative category and nine in the affective category. Each item was rated on a five-point Likert scale (from 1 = "doesn't do this" to 5 = "does this very well"). A rating of > or = 4 on any item indicated competence in the skill area measured by that item. All interviews included in the study were rated by all six of the authors. Interrater reliability was calculated to be .91. RESULTS: In all, 22 interviews (three by women, 19 by men) were included in the study. The residents' ages ranged from 26 to 35 years; the numbers of years since graduation from medical school ranged from two to six. Twenty were third- or fourth-year residents ready to graduate; the other two were completing their first year. Mean ratings in the informative category ranged from 1.51 to 4.51; for three items, mean ratings were > or = 4. The total mean rating for all the items in this category was 3.42. Mean ratings in the affective category ranged from 1.15 to 4.75; for three items, mean ratings were > or = 4. The total mean rating for all the items in this category was 3.45. CONCLUSION: The residents showed a general lack of competence in delivering bad news. The skill items with the lowest ratings were primarily related to eliciting the patient's perspective, which may represent a weakness on the part of the residency program in teaching the residents to use a "patient-centered" interviewing style. The results of this study will form the basis of a curriculum to improve residents' comfort with and skills for delivering bad news to patients.

Adult↗
PubMed1996

Diabetic muscle infarction: radiologic evaluation.

OBJECTIVE: Diabetic muscle infarction (DMI) is frequently misdiagnosed clinically as abscess, neoplasm, or myositis, and is often biopsied. Clinical and radiologic findings are presented here to enable the radiologist to suggest the correct diagnosis. DESIGN AND PATIENTS: Four patients with severe diabetes mellitus presenting with acute thigh pain, tenderness, and swelling were evaluated by imaging techniques and biopsy. RESULTS AND CONCLUSIONS: Edema in the affected muscles was seen in two patients with MRI studies. Femoral artery calcification and mild muscle swelling was present in one patient who underwent CT. Decreased echogenicity was seen in the involved muscle in a patient studied with ultrasound. Serum enzymes were normal or mildly elevated in three patients (not reported in one). Biopsy demonstrated necrosis and regenerative change in all cases. MRI, although nonspecific, is the best imaging technique to suggest the diagnosis of DMI in the appropriate clinical setting, thereby obviating biopsy.

Adult↗
PubMed1996

Antimicrobial evaluation of some plants used in Mexican traditional medicine for the treatment of infectious diseases.

Twelve methanolic plant extracts from botanical species used in traditional medicine in Morelos, México to cure infectious diseases have been subjected to a screening study to detect potential antimicrobial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. The antimicrobial activity of the products was evaluated using colonies growing in solid medium, establishing the minimal concentration required to inhibit their in vitro growth (MIC). The results showed that extracts from Eucalyptus globolus Labill, Punica granatum L., Artemisia mexicana Wild., and Bocconia arborea Watt. possess strong in vitro antimicrobial activity against the tested microorganisms.

Candidiasis↗