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Biomedical subjects

V Suarez

Publications and source records attributed to V Suarez.

At least 19 recordsLinked to original sources
PubMed2004

Resistance to benzimidazole and macrocyclic lactone anthelmintics in cattle nematodes in Argentina.

In April 2003, persistent scouring and ill-thrift that was reported in calves form an intensive beef rearing operation in central Argentina despite treatments with benzimidazole and ivermectin. In order to conduct a controlled faecal egg count reduction test on this herd, 40 calves 5-8-months-old were selected on the basis that they had a nematode eggs per gram (epg) of faeces count greater than 150. Animals were divided into four groups (1-4) of 10 calves. Calves of groups 1-3 were treated, respectively, with subcutaneous injection of ivermectin (200 mcg/kg), ricobendazole (4 mg/kg) and levamisole (7.5 mg/kg), while calves of group 4 remained as untreated controls. The egg count reductions carried out 10 days later were lower than 15% in calves treated with ivermectin and ricobendazole, but 100% in animals receiving levamisole. Pooled post-treatment faecal cultures showed larval percentages of 92 and 95 for Haemonchus and 8 and 5 for Cooperia in the faeces of calves treated with ivermectin and ricobendazole, respectively. This is the first reported case of Haemonchus parasiting cattle showing simultaneous resistance to avermectins and benzimidazole type anthelmintics.

Albendazole↗
PubMed2001

Substrate specificity and antifungal activity of recombinant tobacco class I chitinases.

Endochitinases contribute to the defence response of plants against chitin-containing pathogens. The vacuolar class I chitinases consist of an N-terminal cysteine-rich domain (CRD) linked by a glycine-threonine-rich spacer with 4-hydroxylated prolyl residues to the catalytic domain. We examined the functional role of the CRD and spacer region in class I chitinases by comparing wild-type chitinase A (CHN A) of Nicotiana tabacum with informative recombinant forms. The chitinases were expressed in transgenic N. sylvestris plants, purified to near homogeneity, and their structures confirmed by mass spectrometry and partial sequencing. The enzymes were tested for their substrate preference towards chitin, lipo-chitooligosaccharide Nod factors of Rhizobium, and bacterial peptidoglycans (lysozyme activity) as well as for their capacity to inhibit hyphal growth of Trichoderma viride. Deletion of the CRD and spacer alone or in combination resulted in a modest <50% reduction of hydrolytic activity relative to CHN A using colloidal chitin or M. lysodeikticus walls as substrates; whereas, antifungal activity was reduced by up to 80%. Relative to CHN A, a variant with two spacers in tandem, which binds chitin, showed very low hydrolytic activity towards chitin and Nod factors, but comparable lysozyme activity and enhanced antifungal activity. Neither hydrolytic activity, substrate specificity nor antifungal activity were strictly correlated with the CRD-mediated capacity to bind chitin. This suggests that the presence of the chitin-binding domain does not have a major influence on the functions of CHN A examined. Moreover, the results with the tandem-spacer variant raise the possibility that substantial chitinolytic activity is not essential for inhibition of T. viride growth by CHN A.

Amino Acid Motifs↗
PubMed2001

Graft transmission of induced and spontaneous post-transcriptional silencing of chitinase genes.

Sense and antisense tobacco chitinase (CHN) transgenes, Luciferase-CHN transcriptional fusions, and promoterless CHN cDNAs were introduced biolistically into CHN transformants of tobacco that never exhibit spontaneous gene silencing. All of the constructs tested induced systemic silencing of the resident CHN transgene and endogenes. Nuclear run-on transcription assays showed that local introduction of additional gene copies triggers systemic post-transcriptional gene silencing (PTGS). Together, this provides evidence that additional transgene copies need not be either highly transcribed or produce sense transcripts to evoke production of systemic PTGS signals. CHN PTGS was transmitted by top grafting, but not by reciprocal grafting of mature stems or the exchange of tissue plugs. Thus, the commonly encountered difficulties in achieving graft-transmission could reflect the method used. Silencing in sense but not antisense transformants was transmitted by grafting to a high-expressing sense CHN scion suggesting that the elaboration of mobile signals may not be an essential feature of antisense-mediated gene silencing.

Chitinases↗
PubMed1996

Epithelial ovarian cancer: influence of polymorphism at the glutathione S-transferase GSTM1 and GSTT1 loci on p53 expression.

The importance of polymorphism in the glutathione S-transferase GSTM1, GSTT1 and, cytochrome P450, CYP2D6 loci in the pathogenesis of epithelial ovarian cancer has been assessed in two studies; firstly, a case-control study designed to determine the influence of these genes on susceptibility to this cancer, and secondly, the putative role of these genes in the protection of host cell DNA has been studied by comparing p53 expression in patients with different GSTM1, GSTT1 and CYP2D6 genotypes. The frequencies of GSTM1, GSTT1 and CYP2D6 genotypes in 84 cases and 325 controls were not different. Immunohistochemistry was used to detect p53 expression in 63 of these tumours. Expression was found in 23 tumours. Of the patients demonstrating immunopositivity, 20 (87%) were GSTM1 null. The frequency distributions of GSTM1 genotypes in p53-positive and -negative samples were significantly different (P = 0.002) and those for GSTT1 genotypes approached significance (exact P = 0.057). The proportion of patients with both GSTM1 null and GSTT1 null was also significantly greater in the immunopositive (4/22) than in the immunonegative group (1/40) (P = 0.0493). Single-strand conformational polymorphism (SSCP) analysis was used to detect mutations in the 23 tumour samples demonstrating p53 positivity. A shift in electrophoretic mobility of amplified fragments was found in 11 patients (exons 5, 6, 7 and 8) and these exons were sequenced. In eight samples a mutation was found. No SCCP variants were identified in the other 12 immunopositive patients. Sequencing of exons 4-9 of p53 from these tumours resulted in the detection of mutations in two patients (exons 5 and 7). Thus, in 23 patients who demonstrated immunopositivity, p53 mutations were found in nine patients with GSTM1 null (90.0%). In the 13 patients in whom no mutations were identified, 11 were GSTM1 null (84.6%). The data show that overexpression of p53 is associated with the GSTM1 null genotype. We propose the data are compatible with the view that GSTM1 and GSTT1 are critical in the detoxification of the products of oxidative stress produced during the repair of the ovarian epithelium. Thus, failure to detoxify products of this stress may result in damage to various genes in the host cell, including to p53, resulting in persistent expression of mutant protein. In other patients, oxidative stress effects damage to various genes, but not including p53, resulting in overexpression of wild-type p53.

Case-Control Studies↗
PubMed1995

Isolation and enzymic properties of levansucrase secreted by Acetobacter diazotrophicus SRT4, a bacterium associated with sugar cane.

Acetobacter diazotrophicus, a nitrogen-fixing bacterium associated with sugar cane, secretes a levansucrase (sucrose-2,6-beta-D-fructan 6-beta-D-fructosyltransferase; EC 2.4.1.10). This enzyme is constitutively expressed and represents more than 70% of the total proteins secreted by strain SRT4. The purified protein consists of a single 58 kDa polypeptide with an isoelectric point of 5.5. Its activity is optimal at pH 5.0. It catalyses transfructosylation from sucrose to a variety of acceptors including water (sucrose hydrolysis), glucose (exchange reaction), fructan (polymerase reaction) and sucrose (oligofructoside synthesis). In vivo the polymerase activity leads to synthesis of a high-molecular-mass fructan of the levan type. A. diazotrophicus levansucrase catalyses transfructosylation via a Ping Pong mechanism involving the formation of a transient fructosyl-enzyme intermediate. The catalytic mechanism is very similar to that of Bacillus subtilis levansucrase. The kinetic parameters of the two enzymes are of the same order of magnitude. The main difference between the two enzyme specificities is the high yield of oligofructoside, particularly 1-kestotriose and kestotetraose, accumulated by A. diazotrophicus levansucrase during sucrose transformation. We discuss the hypothesis that these catalytic features may serve the different biological functions of each enzyme.

Acetobacter↗
PubMed1993

Species and morphs in the Ostertagiinae: an allozyme study of seven species.

Five enzymes, malate dehydrogenase, lactate dehydrogenase, mannose-phosphate isomerase, glucose-phosphate isomerase and phosphoglucomutase from seven putative species of Ostertagiinae were compared using starch-gel electrophoresis. The Nei distances were not much affected by origin of specimens or host species. Six of the putative species could form polymorphic pairs: Ostertagia ostertagi and Ostertagia lyrata, Ostertagia leptospicularis and Ostertagia kolchida, Teladorsagia circumcincta and Teladorsagia trifurcata. The Nei distance was of the same magnitude (> 0.6) between species pairs, O. ostertagi, O. leptospicularis, T. circumcincta and Spiculopteragia spp.

Animals↗
PubMed1991

Red tattoo reactions: X-ray microanalysis and patch-test studies.

Eighteen patients who developed cutaneous reactions to red tattoos were studied to identify the chemicals responsible for the reactions to modern red tattoo pigments. Biopsies from the tattoos were examined histologically and the chemical composition of the red pigments was analysed by X-ray microanalysis. A variety of metallic elements including aluminium, iron, calcium, titanium, silicon, mercury and cadmium were detected. Patch tests were performed to the relevant chemicals in nine cases, and only one patient reacted to mercury. This study demonstrates that although reactions to mercury still occur, other red dyes containing a variety of inorganic pigments may provoke a cutaneous inflammatory response.

Adult↗
PubMed1991

A new breast screening programme--an audit of the first year.

The experience of a new breast screening unit is reported. In the first 12 months there was a 72.1% response rate with 9890 women being screened. After the initial screen 598 (5.8%) were referred to the Assessment clinic. Following repeated mammography and clinical examination 166 patients were referred for a surgical opinion; 105 (1.06% of the total screened) were considered to be possibly malignant; 61 further patients with clinical and mammographically benign disease were kept under review by a single surgeon; 101 patients had excision biopsies; 28 of 32 palpable breast lumps and 36 of 69 non-palpable lesions proved to be malignant.

Biopsy↗
PubMed1990

Stomal adenocarcinoma in Crohn's disease.

Malignant change occurring at the site of a stoma in two patients with proved Crohn's disease is described. Patients with ulcerative colitis have an increased risk of colonic malignancy and Crohn's disease is also associated with both small and large bowel carcinoma. Most previous reports of stomal carcinoma have been associated with ulcerative colitis although Crohn's disease seems to carry a greater risk of associated small bowel carcinomas. This is the first report of stomal carcinoma complicating Crohn's disease. Epithelial dysplasia is associated with gastrointestinal carcinomas in both ulcerative colitis and Crohn's disease and a dysplasia-carcinoma sequence has been suggested as the origin of these tumours. In both our patients with stomal adenocarcinoma, dysplasia was identified in adjacent tissues, which suggests a similar mechanism. Malignant change should be suspected if epithelial dysplasia is discovered in a biopsy specimen from the mucosa of an ileostomy in Crohn's disease, and this risk is increased if the dysplasia is of a high grade.

Adenocarcinoma↗
PubMed1989

The value of NOR numbers in neoplastic and non-neoplastic epithelium of the stomach.

Using a silver staining technique, nucleolar organizer region-associated proteins (AgNORs) have been studied in paraffin sections of 15 benign gastric ulcers, seven early gastric cancers, 13 gastric adenocarcinomas and 10 control cases. A significant difference in the mean number of AgNORs per nucleus was found when control and benign groups were compared with the malignant group. However, there was an overlap between each category. Further studies are warranted to determine if this may be of value in differentiating regenerative epithelium from early malignancy.

Adenocarcinoma↗
PubMed1989

Nucleolar organizer regions in transitional cell tumors of the bladder.

The traditional silver staining technique that identifies nucleolar organizer region-associated proteins has recently been adapted and applied to paraffin sections, and used to examine changes in nucleolar organizer region numbers in a variety of benign and malignant conditions. We describe herein the enumeration of nucleolar organizer regions in a variety of benign and malignant conditions of the transitional epithelium of the urinary bladder. While there is a statistical separation between normal and neoplastic groups, there is a degree of overlap between normal, inflammatory, dysplastic, and neoplastic urothelium.

Carcinoma in Situ↗
PubMed1988

Carcinoma developing in ileostomies after 25 or more years.

Primary carcinoma of the ileal mucosa in patients who have had an ileostomy has been documented rarely. This report describes 4 patients seen within the last 4 yr with ileal carcinoma adjacent to the mucocutaneous junction of an ileostomy 25, 29, 30, and 34 yr after the stoma was formed. The incidence of this serious complication may be increasing.

Adenocarcinoma↗
PubMed1988

Early onset high grade dysplasia in ulcerative colitis.

We report a patient with ulcerative colitis who underwent colectomy when aged 25 years for multifocal high grade dysplasia which had developed within 2 years of diagnosis, and only 5 1/2 years after his first symptoms. The implications of this case for the management of ulcerative colitis are discussed.

Adult↗