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Biomedical subjects

J Mendez

Publications and source records attributed to J Mendez.

At least 37 records · Page 2Linked to original sources
PubMed2000

Mesigyna once-a-month combined injectable contraceptive: experience in Latin America.

A phase III clinical study was carried out among 534 fertile Latin American women to evaluate cycle control, side effects, and contraceptive efficacy of a once-a-month combined injectable, Mesigyna, consisting of 50 mg norethisterone enanthate and 5 mg estradiol valerate. The pregnancy rate at 1 year was 0 per 100 woman-years for a total experience of 4688 woman-months. The overall discontinuation rate at one year was 17.9%. Discontinuation rate for bleeding problems was 5.1%. The Colombian women had a significant increase (p <0.001) in bleeding problems compared to other countries. The discontinuation rate for amenorrhea was 1.1%. There were no significant differences between the groups regarding discontinuation for other medical or non-medical reasons. Mean weight gain after one year of use was 1.02 kg. Mesigyna is an appropiate once-a-month injectable contraceptive for Latin American women since it is highly effective and its perception of normal menstrual bleeding is of importance in the Latin American population.

Adolescent↗
PubMed2000

Molluscicidal and piscicidal activities of Venezuelan Chrysobalanaceae plants.

Extracts of increasing polarity of 6 Venezuelan plants belonging to the Chrysobalanaceae family were tested for possible letal toxicity against Biomphalaria glabrata Say, a snail intermediate hosts of Schistosoma mansoni Sambon. The piscicidal toxicity of the active extracts was also evaluated with the aim of findings compounds without toxicity in nontarget organisms, principally fishes and humans.

Animals↗
PubMed2000

Antimicrobial triterpenoids from Licania heteromorpha.

Six triterpenoids having a lupane and oleane skeleton were isolated from the leaves and young branches of Licania heteromorpha Bentham var. heteromorpha and were identified as: betulinic acid 1, alphitolic acid 2, 3 beta-O-trans-p-coumaroyl alphitolic acid 3, 3 beta-O-cis-p-coumaroyl alphitolic acid 4, 3 beta-O-trans-p-coumaroyl maslinic acid 5, 3 beta-O-cis-p-coumaroyl maslinic acid 6. The antimicrobial activity of these compounds was evaluated in vitro on clinically isolated microorganisms employing a microdilution method. Compounds 2, 3, 5, and 6 showed antimicrobial activity on Gram-positive bacteria and yeasts, whereas none of the six triterpenoids were active against Gram-negative organisms.

Anti-Bacterial Agents↗
PubMed1999

Plasmapheresis with intravenous immunoglobulin G is effective in patients with elevated panel reactive antibody prior to cardiac transplantation.

BACKGROUND: Patients with a PRA >10% are considered to be at greater risk for the development of not only acute cellular and humoral rejection but also increased mortality when compared to nonsensitized patients following transplantation. All patients with a PRA >10% at our institution are treated with plasmapheresis and intravenous immunoglobulin G immediately prior to cardiac transplantation. METHODS: Sixteen (Group 1) of 118 patients awaiting cardiac transplantation were found to be sensitized. These patients underwent plasmapheresis followed by 20 gm of intravenous immunoglobulin G (IVIG) immediately prior to cardiac transplantation. Group 1 was compared to the remaining 102 patients with a PRA <10% (Group 2). RESULTS: Despite more patients in Group 1 having a positive crossmatch, pulmonary hypertension, and requiring mechanical circulatory support, there was no statistically significant difference in length of stay or mortality at a mean follow-up of 21.6+/-15.0 months. There was no difference in the occurrence of mild, moderate or severe cellular rejection or humoral rejection in these sensitized patients when compared to Group 2. CONCLUSIONS: Pretransplant plasmapheresis followed by intravenous immunoglobulin G may be an effective therapy that obviates the need for a prospective crossmatch and allows sensitized patients to undergo cardiac transplantation. There is no increase in the post transplant length of stay, occurrence of rejection or short term mortality. Long term follow up is necessary to evaluate whether there is a difference in the development of late rejection, transplant vasculopathy and survival.

Adult↗
PubMed1999

Differential coupling of serotonin 5-HT1A and 5-HT1B receptors to activation of ERK2 and inhibition of adenylyl cyclase in transfected CHO cells.

Although the subtypes of serotonin 5-HT1 receptors have distinct structure and pharmacology, it has not been clear if they also exhibit differences in coupling to cellular signals. We have sought to compare directly the coupling of 5-HT1A and 5-HT1B receptors to adenylyl cyclase and to the mitogen-activated protein kinase ERK2 (extracellular signal-regulated kinase-2). We found that 5-HT1B receptors couple better to activation of ERK2 and inhibition of adenylyl cyclase than do 5-HT1A receptors. 5-HT stimulated a maximal fourfold increase in ERK2 activity in nontransfected cells that express endogenous 5-HT1B receptors at a very low density and a maximal 13-fold increase in transfected cells expressing 230 fmol of 5-HT1B receptor/mg of membrane protein. In contrast, activation of 5-HT1A receptors stimulated only a 2.8-fold maximal activation of ERK2 in transfected cells expressing receptors at 300 fmol/mg of membrane protein but did stimulate a 12-fold increase in activity in cells expressing receptors at 3,000 fmol/mg of membrane protein. Similarly, 5-HT1A, but not 5-HT1B, receptors were found to cause significant inhibition of forskolin-stimulated cyclic AMP accumulation only when expressed at high densities. These findings demonstrate that although both 5-HT1A and 5-HT1B receptors have been shown to couple to G proteins of the Gi class, they exhibit differences in coupling to ERK2 and adenylyl cyclase.

Adenylyl Cyclase Inhibitors↗
PubMed1999

Influence of dietary energy, supplemental fat and linoleic acid concentration on performance of laying hens at two ages.

1. The aim of this study was to investigate the influence of metabolisable energy (ME), supplemental fat (SFAT) and linoleic acid (LIN) content of the diet on the productive performance and weight of eggs and egg components of Isabrown hens of 22 or 74 weeks of age. 2. Six diets were formulated to contain the following concentrations of ME (MJ/kg), SFAT (g/kg) and LIN (g/kg), respectively: A) 11.8, 0 and 11.5; B) 11.8, 40 and 11.5; C) 11.8, 40 and 16.5; D) 11.2, 40 and 16.5; E) 11.2, 40 and 11.5; and F) 11.2, 0 and 11.5. Data were collected for 28 d and analysed using linear contrasts to test the effect of SFAT, LIN, ME and their interactions. 3. When the LIN content of the diets was maintained constant at 11.5 g/kg, an increase in the SFAT from 0 to 40 g/kg increased egg weight (63.8 vs 64.5 g; P<0.05), food intake (119 vs 124 g; P<0.01) and energy intake (1.36 vs. 1.42 MJ/d; P<0.01) and body weight change of the hens (-85 vs. 27 g; P<0.001). Supplemental fat also increased yolk (15.8 vs. 16.3 g; P<0.001) and albumen weight (40.8 vs. 42.3 g; P<0.01) but yolk to albumen ratio was not modified. 4. Egg and albumen weights were improved by SFAT in early but not in late producing hens. As a result, yolk to albumen ratio decreased in the younger hens, from 0.371 to 0.357, but increased in the older hens, from 0.408 to 0.415; P<0.01) with fat addition. 5. An increase in the LIN content of the diets from 11.5 to 16.5 g/kg did not modify any of the traits studied. 6. It was concluded that the LIN requirement of the hens for maximal productivity and weight of eggs is 11.5 g/kg or less. Supplemental fat increased the weight of eggs and albumen in the younger but not in older hens and the beneficial effect was independent of its LIN content.

Animal Feed↗
PubMed1999

Laying hen productivity as affected by energy, supplemental fat, and linoleic acid concentration of the diet.

A trial using 720 Isabrown hens was conducted to determine the influence of energy (AMEn), supplemental fat (SFAT), and linolenic acid (LIN) concentration of the diet on performance and weight of eggs and egg components throughout the laying cycle (22 to 65 wk of age). There were six treatments whose calculated AMEn, SFAT, and LIN content were, respectively: 1) 2,810 kcal/kg, 0%, 1.15%; 2) 2,810 kcal/kg, 4%, 1.15%; 3) 2,810 kcal/kg, 4%, 1.65%; 4) 2,680 kcal/kg, 0%, 1.15%; 5) 2,680 kcal/kg, 4%, 1.15%; and 6) 2,680 kcal/kg, 4%, and 1.65%. All diets were formulated to have the same crude protein, lysine, TSAA, calcium, and nonphytin phosphorus levels per kilocalorie of AMEn. The data were analyzed with SFAT constant (4%) and AMEn, and LIN variables (Diets 2, 3, 5, and 6) and with LIN constant (1.15%) and AMEn and SFAT variables (Diets 1, 2, 4, and 5). When LIN was maintained at a constant of 1.15%, an increase in the AMEn of the diets from 2,680 to 2,810 kcal/kg decreased feed intake by 4% (P < 0.001). Increasing AMEn also improved feed conversion per dozen eggs and per kilogram of eggs by 4.9 and 4.7% (P < 0.05), respectively, and increased BW gain by 55.7% (P < 0.05). Egg production rate, egg weight, egg mass output, and energy intake were not modified by treatments. An increase in SFAT within both energy levels from 0 to 4% improved all of the traits studied except feed conversion. Supplemental fat increased both yolk and albumen weight, but the effect was more pronounced on the latter. When SFAT was maintained constant at 4%, an increase in AMEn of the diets decreased feed intake and improved feed conversion per dozen and per kilogram of eggs by 5.7, 5.5, and 5.2%, respectively (P < 0.001). An increase in LIN content from 1.15 to 1.65% did not modify any of the parameters studied. The results indicate that SFAT consistently improves productivity of hens and egg weight and that the LIN requirement for maximal productivity is 1.15% or less. The beneficial effects of adding SFAT to diets containing more than 1.15% LIN are due to the fat itself rather than to an increase in LIN or AMEn of the diet.

Aging↗
PubMed1999

Congenital transmission of experimental chronic toxoplasmosis in rats.

A 10% transplacental transmission rate was observed in litters from 89 Wistar rats chronically infected with Toxoplasmosis gondii, as judging from bioassays. The rats had been fed T. gondii 2 mo prior to mating. Six of 7 isolates of T. gondii were transplacentally transmitted. The frequency of transmission did not appear to be affected by the strain of T. gondii or the size of the inoculum.

Animals↗
PubMed1998

Clinical significance of viral load in the diagnosis of cytomegalovirus disease after liver transplantation.

In a cohort of 43 liver transplant recipients who did not receive antiviral prophylaxis, qualitative and quantitative polymerase chain reactions (PCRs) from peripheral blood were prospectively compared to determine their value in the diagnosis of established cytomegalovirus (CMV) disease and for the early detection of CMV replication as a marker for preemptive antiviral therapy. Using a cutoff of 7000 copies of CMV DNA per sample, the specificity and positive predictive values of qualitative PCR for the diagnosis of established CMV disease increased from 33% to 89% and from 54% to 82%, respectively, without reducing the 100% sensitivity and negative predictive value. By contrast, quantification of viral load provided no additional advantage to qualitative PCR for the early diagnosis of CMV infection before development of disease.

Blood↗
PubMed1998

Growth hormone reduces mortality and bacterial translocation in irradiated rats.

Growth hormone stimulates the growth of intestinal mucosa and may reduce the severity of injury caused by radiation. Male Wistar rats underwent abdominal irradiation (12 Gy) and were treated with either human growth hormone (hGH) or saline, and sacrificed at day 4 or 7 post-irradiation. Bacterial translocation, and the ileal mucosal thickness, proliferation, and disaccharidase activity were assessed. Mortality was 65% in irradiated animals, whereas hGH caused a decrement (29%, p < 0.05). Bacterial translocation was also reduced by hGH (p < 0.05). Treating irradiated rats with hGH prevented body weight loss (p < 0.05). Mucosal thickness increased faster in irradiated hGH-treated animals. The proliferative index showed an increment in hGH-treated animals (p < 0.05). Giving hGH to irradiated rats prevented decrease in sucrose activity, and increment in lactase activity. In conclusion, giving hGH to irradiated rats promotes the adaptative process of the intestine and acute radiation-related negative effects, including mortality, bacterial translocation, and weight loss.

Abdomen↗
PubMed1998

Acute necrotizing Meckel diverticulitis due to biliary enterolithiasis.

BACKGROUND: Acute abdominal pain due to complicated Meckel's diverticulum is an unusual event. Even the presence of biliary enterolithiasis at the onset of inflamed congenital diverticulum has rarely been reported previously. RESULTS: Despite this unusual presentation, an episode of gallstone passage through the biliary tract has not yet been described. CONCLUSIONS: Whether the stones were primarily formed in the diverticulum as enterolithiasis, or secondary to gallstone passage is discussed. The complications of Meckel's diverticulum requiring surgical treatment are reviewed, focusing on the unusual finding of biliary stones in Meckel's diverticulum and the etiogenic mechanism of enterolithiasis.

Aged↗
PubMed1997

An evaluation of a chest pain diagnostic protocol to exclude acute cardiac ischemia in the emergency department.

BACKGROUND: Although accelerated diagnostic protocols are being increasingly used in emergency departments to diagnose acute cardiac ischemia, there have been no prospective evaluations of a chest pain diagnostic protocol with serial determinations of creatine kinase MB isoenzyme and mandatory exercise electrocardiography (ExECG). METHODS: Prospective cross-sectional study in which chest pain protocol results were compared with final (reference) diagnoses of acute cardiac ischemia (including acute myocardial infarction and unstable angina). Patients in need of hospital admission but at low probability (by a validated algorithm) for acute myocardial infarction were examined for exclusions: known coronary artery disease, cardiac complications, severe comorbidities, or inability to perform exercise testing. A 12-hour diagnostic protocol included serial measurements of creatine kinase MB, ECG, and clinical assessments followed by ExECG for those with negative initial serial testing. Reference diagnoses were established during hospitalization and diagnostic accuracy was assessed. RESULTS: The study group of 317 patients was 54% male and 65% black, and had a mean age of 46.6 years; 9.5% had a final diagnosis of acute cardiac ischemia. For this diagnosis, the protocol had a sensitivity of 90.0% (95% confidence interval, 72.3%-97.4%); specificity, 50.5% (95% confidence interval, 44.6%-56.4%); positive predictive value, 16.0%; and negative predictive value, 98.0%. Creatine kinase MB, serial ECGs, and ExECG each made a contribution to improved sensitivity and accuracy, whereas clinical reassessments were less discriminating, as indicated by protocol's receiver operating characteristic curve. CONCLUSIONS: A chest pain diagnostic protocol achieved high sensitivity and improved specificity over the standard emergency department workup. There were no adverse advents associated with early ExECG.

Algorithms↗
PubMed1997

Protein-primed DNA replication: a transition between two modes of priming by a unique DNA polymerase.

Phage phi29 from Bacillus subtilis is a paradigm of the protein-primed replication mechanism, in which a single-subunit DNA polymerase is involved in both the specific protein-primed initiation step and normal DNA elongation. To start phi29 DNA replication, the viral DNA polymerase must interact with a free molecule of the viral terminal protein (TP), to prime DNA synthesis once at each phi29 DNA end. The results shown in this paper demonstrate that the DNA polymerase-primer TP heterodimer is not dissociated immediately after initiation. On the contrary, there is a transition stage in which the DNA polymerase synthesizes a five nucleotide-long DNA molecule while complexed with the primer TP, undergoes some structural change during replication of nucleotides 6-9, and finally dissociates from the primer protein when nucleotide 10 is inserted onto the nascent DNA chain. This behaviour probably reflects the polymerase requirement for a DNA primer of a minimum length to efficiently catalyze DNA elongation. The significance of such a limiting transition stage is supported by the finding of abortive replication products consisting of the primer TP linked up to eight nucleotides, detected during in vitro replication of phi29 TP-DNA particularly under conditions that decrease the strand-displacement capacity of phi29 DNA polymerase.

Bacillus Phages↗
PubMed1996

Effect of 17 beta-estradiol on chondrocyte membrane fluidity and phospholipid metabolism is membrane-specific, sex-specific, and cell maturation-dependent.

In this study we examined the hypothesis that 17 beta-estradiol exerts both rapid and direct, nongenomic effects of cells in the endochondral pathway. To do this, we used a cell culture model in which chondrocytes at two distinct stages of cell maturation are isolated from the costochondral cartilage of male and female rats, and examined the short-term effect of 17 alpha- and 17 beta-estradiol on [14C]arachidonic acid turnover in the cell layer and phospholipase A2 specific activity in plasma membranes and extracellular matrix vesicles isolated from similarly prepared cultures. In addition, the effect of 17 alpha- and 17 beta-estradiol on plasma membrane and matrix vesicle membrane fluidity was assessed. The effect of hormone on arachidonic acid turnover was rapid, time- and concentration-dependent, stereo-specific, and cell maturation-specific. Only resting zone cells from female rats were affected, and only 17 beta-estradiol elicited a response. Similarly, only female rat resting zone chondrocytes exhibited a change in phospholipase A2 activity after a 24 h exposure to hormone, causing an increase in enzyme activity in the matrix vesicles, but not plasma membranes. When isolated membranes were incubated directly with hormone, membrane fluidity was decreased in both plasma membranes and matrix vesicles isolated from female rat resting zone chondrocyte cultures. This nongenomic effect was dose-dependent and stereo-specific and differentially expressed in the two membrane fractions with respect to time course and magnitude of response. These results support the hypothesis that 17 beta-estradiol has a rapid action on chondrocyte membrane lipid metabolism and suggest that specific membrane components, characteristic of a particular sex and state of cell maturation, are involved in the nongenomic effects of this sex hormone on isolated matrix vesicles and plasma membranes.

Animals↗
PubMed1996

The response of highly productive rabbits to dietary sulphur amino acid content for reproduction and growth.

This study investigated the sulphur amino acid (SAA) requirements of rabbits. Five diets, containing 0.48-0.72% crude SAA, were formulated by supplementing a basal diet with DL-methionine. The apparent methionine digestibility (%) was 71.4 +/- 1.1 in the basal diet and 102.9 +/- 0.9 for DL-methionine, as estimated by the difference method. Feeding trials were carried out using 370 rabbit does and 1 195 weanling rabbits slaughtered at 2-2.1 kg body weight. Milk production was measured in 80 lactations. Carcass traits were determined in 125 rabbits. The dietary SAA content affected several productive traits, such as milk production, parturition interval, growth rate, carcass quality and feed efficiency. When the diets were compared using orthogonal contrasts, a minimum requirement of 0.54% crude or 0.40% digestible SAA was determined. Further responses in performance were observed, however, when the data were analysed by regression methods. The values of crude and digestible SAA for optimal production were, respectively, 0.63 and 0.49% (rabbit does) and, at least, 0.72 and 0.58% (growing rabbits).

Amino Acids, Sulfur↗
PubMed1996

Hypersensitivity to carrot associated with specific IgE to grass and tree pollens.

This study deals with a 34-year-old female cook with no previous history of atopy, who was studied because of allergic rhinoconjunctivitis and contact urticaria in both hands associated with severe itching when she handled raw carrot. The patient had had anaphylactic episodes after accidental ingestion of raw carrots, but she tolerated cooked carrots. Skin prick tests with carrot, celery, and olive, and birch, grass, and mugwort pollens were positive. Total IgE was 411 UI/ml. Specific IgE to olive, grass, and weed pollens were 10.92, 6.17, and 2.4 AU/ml, respectively. The histamine release test was positive for carrot, celery, celeriac, and olive pollen up to a dilution of 1/10(6). Immunoblot of raw carrot showed a single IgE-binding 18-kDa band. IgE reactivity for raw carrot immunoblot was completely inhibited by carrot and by celery, but not by olive or grass pollens. Specific IgE to olive pollen was not inhibited by carrot. The existence of monosensitization to an 18-kDa protein in carrot and specific IgE to olive pollen has not been reported in the celery-carrot-mugwort-spice syndrome.

Adult↗