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Biomedical subjects

L Méndez

Publications and source records attributed to L Méndez.

At least 19 recordsLinked to original sources
PubMed2000

Control of ticks resistant to immunization with Bm86 in cattle vaccinated with the recombinant antigen Bm95 isolated from the cattle tick, Boophilus microplus.

The recombinant Bm86-containing vaccine Gavac(TM) against the cattle tick Boophilus microplus has proved its efficacy in a number of experiments, especially when combined with acaricides in an integrated manner. However, tick isolates such as the Argentinean strain A, show low susceptibility to this vaccine. In this paper we report on the isolation of the Bm95 gene from the B. microplus strain A, which was cloned and expressed in the yeast Pichia pastoris producing a glycosylated and particulated recombinant protein. This new antigen was effective against different tick strains in a pen trial, including the B. microplus strain A, resistant to vaccination with Bm86. A Bm95-based vaccine was used to protect cattle against tick infestations under production conditions, lowering the number of ticks on vaccinated animals and, therefore, reducing the frequency of acaricide treatments. The Bm95 antigen from strain A was able to protect against infestations with Bm86-sensitive and Bm86-resistant tick strains, thus suggesting that Bm95 could be a more universal antigen to protect cattle against infestations by B. microplus strains from different geographical areas.

Animals↗
PubMed1999

Vaccination against ticks (Boophilus spp.): the experience with the Bm86-based vaccine Gavac.

The control of tick infestations and the transmission of tick-borne diseases remain a challenge for the cattle industry in tropical and subtropical areas of the world. Traditional control methods have been only partially successful and the parasites continue to result in significant losses for the cattle industry. Recently, vaccines containing the recombinant B. microplus gut antigen Bm86 have been developed. Our vaccine formulation (Gavac, Heber Biotec S.A., Havana, Cuba) has been registered and is commercially available in Cuba, Colombia, Dominican Republic, Brazil and Mexico. In controlled pen trials, Gavac has been effective for the control of artificial infestations of B. annulatus, B. decoloratus and chemical-sensitive and resistant B. microplus strains from Australia, Africa, America and Iran. In controlled field trials in Cuba, Brazil, Argentina and Mexico, Gavac has shown a 55-100% efficacy in the control of B. microplus infestations in grazing cattle 12-36 weeks after the first vaccination. Field trials under production conditions have been conducted in Cuba, Colombia, Brazil and Mexico in pure and cross-bred cattle herds. The application of Gavac has increased the time between acaricide treatments by an average of 32 /-21 days (P = 0.0005) resulting in important savings for the cattle industry. In Cuba, a cost-effectiveness analysis was conducted in more than 260000 animals. The cost-effectiveness analysis showed a 60% reduction in the number of acaricide treatments, together with the control of tick infestations and transmission of babesiosis, which resulted in savings of 23.4 dollars animal(-1) year (-1). These results clearly demonstrate the advantage of vaccination and support the application of Gavac for the control of Boophilus spp. infestations.

Animals↗
PubMed1999

Sequence variations in the Boophilus microplus Bm86 locus and implications for immunoprotection in cattle vaccinated with this antigen.

Cattle tick infestations constitute a major problem for the cattle industry in tropical and subtropical regions of the world. Traditional control methods have been only partially successful, hampered by the selection of chemical-resistant tick populations. The Boophilus microplus Bm86 protein was isolated from tick gut epithelial cells and shown to induce a protective response against tick infestations in vaccinated cattle. Vaccine preparations including the recombinant Bm86 are used to control cattle tick infestations in the field as an alternative measure to reduce the losses produced by this ectoparasite. The principle for the immunological control of tick infestations relies on a polyclonal antibody response against the target antigen and, therefore, should be difficult to select for tick-resistant populations. However, sequence variations in the Bm86 locus, among other factors, could affect the effectiveness of Bm86-containing vaccines. In the present study we have addressed this issue, employing data obtained with B. microplus strains from Australia, Mexico, Cuba, Argentina and Venezuela. The results showed a tendency in the inverse correlation between the efficacy of the vaccination with Bm86 and the sequence variations in the Bm86 locus (R2 = 0.7). The mutation fixation index in the Bm86 locus was calculated and shown to be between 0.02 and 0.1 amino acids per year. Possible implications of these findings for the immunoprotection of cattle against tick infestations employing the Bm86 antigen are discussed.

Amino Acid Sequence↗
PubMed1998

Field studies and cost-effectiveness analysis of vaccination with Gavac against the cattle tick Boophilus microplus.

The control of tick infestations and the transmission of tick-borne diseases remains a challenge for the cattle industry in tropical and subtropical areas of the world. Traditional control methods have been only partially successful and the parasites continue to result in significant losses for the cattle industry. Recently, vaccines containing the recombinant Boophilus microplus gut antigen Bm86 have been developed. These vaccines have been shown to control tick infestations in the field. However, extensive field studies investigating the efficacy and cost-effectiveness of vaccination have not been reported and are needed to appraise the effect of this new approach for tick control. Here is reported the results of the application of Gavac in a field trial including more than 260,000 animals in Cuba. In this study the correlation between the antibody response to vaccination and the effect on ticks fertility is determined. Physiological status of the animals was found to affect the primary response to vaccination but not the antibody titers after revaccination. A cost-effectiveness analysis showed a 60% reduction in the number acaricide treatments, together with the control of tick infestations and transmission of babesiosis, which resulted in savings of $23.4 animal-1 year-1. These results clearly demonstrate the advantage of vaccination and support the application of Gavac for tick control.

Animals↗
PubMed1998

Effect of particulation on the immunogenic and protective properties of the recombinant Bm86 antigen expressed in Pichia pastoris.

The recombinant Bm86 tick antigen expressed in Pichia pastoris is obtained in a highly particulated form, as a distinguish feature of this expression system. This particulated protein, the active principle of the recombinant vaccine Gavac against the cattle tick, have shown high immunogenic and protective properties, probably associated with its own characteristics. To evaluate the effects of particulation on the properties of Bm86, three groups of calves were immunized with particulated or non-particulated recombinant Bm86 and the anti-Bm86 antibody response determined. Animals were challenged with a controlled tick infestation and the protective capacities of both proteins assessed. Humoral immune response and protection in cattle vaccinated with the particulated antigen were higher. These experiments suggested that particulation of the Bm86 expressed in P. pastoris is an important feature for the protective properties of the antigen in vaccine preparations.

Animals↗
PubMed1995

Bioavailability of medication delivered via nasogastric tube is decreased in the immediate postoperative period.

BACKGROUND: A study was performed to determine bioavailability of medication delivered via nasogastric tube in patients after abdominal surgery. METHODS: Acetaminophen (20 mg/kg) was administered to each patient per os at least 48 hours prior to abdominal surgery and via nasogastric tube 3 hours postoperatively. The nasogastric tube was clamped for 30 minutes after drug administration, prior to resuming suction. Serum levels of acetaminophen were measured 0, 40, and 90 minutes after each dose. RESULTS: Acetaminophen levels were significantly lower (P < 0.001) when the drug was administered via nasogastric tube postoperatively. CONCLUSIONS: Decreased bioavailability of medications delivered via nasogastric tube may have important clinical implications and should be taken into consideration during the postoperative period.

Abdomen↗
PubMed1995

Bioavailability of medication after laparoscopic cholecystectomy.

Bioavailability of medication after laparoscopic cholecystectomy has not been studied previously. There is concern about the ability of patients to tolerate oral medication postoperatively and the optimal timing of hospital discharge. In this study, each subject received 20 mg/kg acetaminophen (po) preoperatively, with a repeat dose at 6 (group 1), 12 (group 2), or 24 h (group 3) postoperatively. Serum levels were obtained 40 and 90 min after each ingestion. Bioavailability of medication was significantly decreased (p < 0.01) 6 h (group 1) and 12 h (group 2) postoperatively. Bioavailability returned to baseline by 24 h after laparoscopic cholecystectomy (group 3). This study indicates that oral medication should be used judiciously during the first 12 h after laparoscopic surgery.

Acetaminophen↗
PubMed1995

Immunophenotype analysis of dendritic cells and lymphocytes associated with cutaneous malignant melanomas.

The purpose of this study was to investigate the relationship between changes in density and distribution of dendritic cells, both in epidermis and in peritumoral infiltrate, and lymphocyte subset variations in malignant melanomas (MM) of patients belonging to different risk groups. The collective immunoreactive expression of six markers (S100 protein, CD1-a, HLA-DR, CD4, CD8 and CD25) was analyzed in 13 cutaneous malignant melanomas. Changes were observed in density and distribution of Langerhans cells (LC) (S100+, CD1-a+) in the epidermis overlying the tumor, as well as in peritumoral and intratumoral locations, independently of the tumor-invasion level. A decrease was recorded in LC (S100+, CD1-a+) in the epidermis overlying six tumors, whereas most of the MM studied showed an increase of LC (S100+, CD1-a+) in peritumoral infiltrate. The expression of HLA-DR in tumor cells was controversial; it was observed in three moderate-risk MM, but it was negative in high-risk tumors. The percentage of CD4+ cells was in most cases greater than that of CD8+ in the peritumoral infiltrate, irrespective of the degree of histopathological malignancy. The concomitant expression of the lymphocytic activation marker CD25 (receptor for interleukin 2) in lymphocytic infiltrate was variable. Peritumoral infiltrate in three high risk MM contained few CD25+ cells, and a concomitant decrease was recorded in LC. This preliminary report shows that alterations in the density and distribution of LC may be responsible for determining the degree or T lymphocyte activation, and this may be critical for the development of effective tumor-directed immunity. Further studies are required to demonstrate these hypothetical interrelations.

Adult↗
PubMed1994

Conservative management of endoscopic sclerotherapy-induced esophageal perforation.

Esophageal perforation is a rare though potentially lethal complication of variceal sclerotherapy. Diagnosis is usually made after recognition of often subtle clinical symptoms. Surgical and nonsurgical modalities have been proposed, and nonoperative management can be successful even in patients thought to have absolute indications for surgery.

Adult↗
PubMed1994

[Pelvic exenteration, morbidity and survival].

Between 1985 and 1990, 17 patients have undergone pelvic exenteration at the Obstetric and Gynecology Hospital 4, Mexican Social Security Institute, Mexico City. Sixteen patients had undergone radiation therapy previously. Most operative procedures were performed for cancer of the cervix, recurrent or persistent. The major type of pelvic neoplasm was epidermoid carcinoma, occurring in 15 patients. No exenterations were performed in presence of pelvic lymph nodes. Operative mortality was 5.8%. One or more major surgical complications occurred in nine patients, three patients required one or more surgical procedures to correct these complications. There was no mortality in patients undergoing reoperation. Nonsurgical complications were encountered in five patients. All patients were followed for at least 2 years or until time of death. The cumulative 5-year survival was significantly related to type of tumor. All patients with recurrent tumor were alive and disease free in the last follow-up compared to only 33% of patients with persistent tumor. Four patients underwent anterior surgical procedure, all with persistent tumour. Three had documented recurrence and none survived beyond 14 months.

Adnexa Uteri↗
PubMed1994

[Colorectal polyps. Treatment and clinical course].

We report the results of the treatment and follow up of 61 patients with polyps of the colon and rectum, who underwent surgical intervention between 1983 through 1991. The mean age was 56 years (range from 41 to 56 y.) and 53% of the patients were males. The majority of the polyps were located in the anorectal region, n = 32 (52.4%) and sigmoid colon n = 17 (27.8%). Tubular adenomas in n = 38 patients and villous adenoma in n = 19, were the most frequent histological types. We have found polyps with invasive carcinoma in 15 (24.6%) cases. The polyps were resected by transanal resection in 15 patients, by colectomies in 11, and 10 patients underwent colectomy for removal of their polyps. Surgery was indicated when the polyp had a base too wide to be removed by colonoscopy or when malignancy was demonstrated by biopsy. There were 10 (19.6%) recurrences during the first three years of follow up. The histological examination showed malignant changes in 4 polyps. Villous adenomas, n = 7 constituted the histological type with more recurrences. Recurrences were treated by local resection in half of the cases. The morbidity was 9.8% and mortality was 3.3%. Surgery when indicated, allows to obtain free margins from tumor, to determine lymph node involvement and to establish the stage.

Adenomatous Polyps↗
PubMed1993

The attitudes toward psychiatry of physicians and medical students in Venezuela.

Attitudes toward psychiatry were assessed in 490 medical students and 362 physicians from two universities in Venezuela: Universidad de Los Andes (ULA) and Universidad Centro-Occidental Lisandro Alvarado (UCLA). A modified version of the Attitude Toward Psychiatry-30 scale was used. The attitude toward psychiatry of all the students and physicians was moderately positive. Students from ULA displayed a more positive attitude than UCLA students, whereas physicians from UCLA displayed a more positive attitude than ULA physicians. The most negative attitude toward psychiatry was observed in students planning to select obstetrics and gynecology (ULA + UCLA), in physicians working in Surgery, obstetrics and gynecology (ULA + UCLA) and in basic sciences (ULA). Female students tended to display a more positive attitude than male students. The attitude toward psychiatry was similar in students with low and high academic achievement in the courses in psychiatry. A large number of years in the profession did not modify the attitude of the physicians. It is recommended to improve teaching and communication with the students and physicians that displayed the most negative attitudes toward psychiatry.

Adult↗