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Biomedical subjects

S Goldenberg

Publications and source records attributed to S Goldenberg.

At least 55 records · Page 3Linked to original sources
PubMed1995

Hypergastrinemia following gastrocystoplasty in rats.

Gastrocystoplasty has been previously described as an effective method of bladder augmentation or replacement. Twenty-four female Wistar rats were divided into three groups of eight animals each: control (G1), partial gastrectomy with the gastric body (G2) and gastrocystoplasty with the gastric body (G3). The period of observation was 2 months and the parameter assessed was serum gastrin. Increases in serum gastrin were seen in 62.5% (5/8) of rats in group 2 and in 50% (4/8) of rats in group 3. Our results suggest that, in rats, hypergastrinemia is induced by the partial surgical removal of the gastric body and is not due to gastrocystoplasty.

Animals↗
PubMed1994

Characteristics of P388/VMDRC.04, a simple, sensitive model for studying P-glycoprotein antagonists.

Cross-resistance to chemotherapeutic drugs is a significant problem in the treatment of patients with cancer. The discovery that this phenomenon is associated with the overexpression of a membrane glycoprotein, P-glycoprotein, which acts as a drug efflux pump, has provided a new target for drug development. To develop a model for identifying new compounds which can block the function of P-glycoprotein, we infected P388 mouse leukemic cells with a retrovirus containing a cloned human MDR1 complementary DNA. The new cell line, P388/VMDRC.04, incorporated and overexpressed the human gene as evidenced by Southern blots, increased mRNA and protein synthesis, and recognition by the MRK16 monoclonal antibody. P388/VMDRC.04 was cross-resistant to colchicine, vincristine, and doxorubicin, and the degree of resistance correlated with a reduction in cellular drug accumulation. Unlike many cell lines selected for resistance by growth in increasing concentrations of drug for prolonged periods of time, these cells did not show alternative mechanisms of resistance such as increased synthesis of glutathione or alterations in topoisomerase II. In addition, the sensitivity of P388/VMDRC.04 cells was completely restored by cyclosporin A and trans-flupenthixol. P388/VMDRC.04 cells were subcloned and 10 clones were picked for in vivo evaluation. One subclone grew similarly to parental cells in female BALB/c x DBA/2 F1 mice and showed no responsiveness to therapeutic doses of vincristine or etoposide. The combination of vincristine with cyclosporin A significantly increased the survival of mice inoculated with P388/VMDRC.04 cells. The availability of a cell line that displays the MDR phenotype, overexpresses human P-glycoprotein, but does not contain alterations in at least two well-defined alternative mechanisms of resistance, and that can be grown in simple animal models should facilitate the development of new agents active against this form of chemotherapeutic drug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Favourable results of treatment of narrowed saphenous vein grafts with Palmaz-Schatz stent implantation.

Although conventional balloon angioplasty of saphenous vein grafts can be performed with an acceptable acute success and complication rate, restenosis remains a major problem. However, this may be overcome by the implantation of Palmaz-Schatz stents. Palmaz-Schatz stent deployment was performed in our institution in 43 patients who were referred for PTCA of stenosed saphenous vein grafts. Thirty-seven were located at the mid-portion of the graft, seven at the ostium and six at the distal anastomosis. Overall, we used 59 standard length (15 mm) Palmaz-Schatz stents and 22 short (7 mm) stents. In 15 lesions (30%) multiple stents were implanted in tandem to treat diffuse disease. Angiographic success was achieved in 47 of the 50 attempted lesions (94%). Major cardiac complications occurred in three patients. Two patients had procedures complicated by the development of a Q wave myocardial infarction, one of whom underwent urgent CABG. One patient died. There was no episode of subacute thrombosis. The angiographic follow-up of 37 lesions (80% of eligible lesions) at a mean time of 5 +/- 2 months (range 1-8) showed a restenosis rate of 11% and residual post-stent diameter stenosis was associated with a significantly higher restenosis rate. However, no restenosis occurred in lesions receiving multiple stents. Clinical follow-up was performed in all patients, and at a mean of 25 months after the procedure, 64% were free from clinical events, including recurrent angina. Palmaz-Schatz stent implantation is an effective and safe procedure to treat narrowed vein grafts.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Characterization of proteinases in trypanosomatids.

Proteinases are important factors in the pathogenicity of many parasitic diseases. In this study, the proteolytic activities of 10 trypanosomatids from five different genera (Crithidia, Phytomonas, Endotrypanum, Trypanosoma and Leishmania) were determined by SDS-PAGE containing copolymerized gelatin as substrate. In almost all species we could detect two proteolytic classes, cysteine- and metalloproteinases, based on the inhibition of their activities by E-64 and 1,10-phenanthroline, respectively. In all cases, the metalloproteinase activities did not change over a broad pH range (from 5.5 to 10). E. schaudinni, T. mega, T. dionisii, C. luciliae, C. fasciculata, C. oncopelti and C. guilhermei expressed one or two metalloproteinases of 45-66 kDa, whereas in P. serpens and P. hyssopifolia a double band of this endopeptidase was detected at 94 kDa. In contrast, no metalloproteinase activity was observed in L. tarentolae. The optimal pH for the cysteine-proteinase activities was acidic (about 5.5). In E. schaudinni, T. mega and in Crithidia sp., these proteinases had an apparent molecular weight of 66-94 kDa, while L. tarentolae expressed a broad band from 29 to 45 kDa. In Phytomonas sp., this class of endopeptidase showed a unique feature, in that major cysteine-proteinases were found at 29-66 kDa, but multiple, low-activity bands were detected from 116 to 200 kDa. The most striking characteristic, however, was the very intense cysteine-proteinase activity expressed by T. dionisii (29-66 kDa). We conclude that these differences in the proteolytic profiles could be useful markers to characterize and compare trypanosomatids.

Animals↗
PubMed1993

Targeted disruption of the mouse mdr1b gene reveals that steroid hormones enhance mdr gene expression.

To evaluate the role of P-glycoprotein in steroid secretion in adrenal cells, we have used gene targeting to introduce a null mutation into one allele of the mdr1b gene in mouse Y1 adrenal cells. Characterization of both the wild-type and the mutant cell lines revealed the following. 1) The expression of mdr1b is enhanced by steroid hormones, in a feedback regulatory mechanism. Inhibition of steroid biosynthesis by 2-aminoglutethimide blocks the adrenocorticotropin (ACTH)-induced increase in mdr1b mRNA levels. 2) ACTH-stimulated steroid secretion is markedly decreased in the mutant cell line. This decreased steroid secretion in the mutant cells occurs despite an increase in the levels of mdr1b mRNA and P-glycoprotein. Kinetic analyses of vinblastine and daunomycin accumulation in both the wild-type and the mutant cell lines during ACTH-stimulated steroidogenesis show that in the mutant cells both drugs accumulated to higher levels than in Y1 cells, suggesting that the remaining mdr1b allele in the mutant cells is relatively inactive as an exporter of steroids, or that the targeted disruption of the mdr1b allele is associated with other changes in the mutant cells which block ACTH-stimulated steroid secretion.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1993

Cloning and characterization of the gene encoding ATP-dependent phospho-enol-pyruvate carboxykinase in Trypanosoma cruzi: comparison of primary and predicted secondary structure with host GTP-dependent enzyme.

The complete nucleotide (nt) sequence of the PEPCK gene encoding Trypanosoma cruzi phospho-enol-pyruvate carboxykinase (PEPCK; ATP dependent, EC 4.1.1.49) has been determined. The predicted primary sequence has 473 amino acids (aa) with a calculated molecular mass of 52.5 kDa. The ubiquitous spliced leader is present at nt position -60 from the AUG start codon in PEPCK mRNA; the coding region is followed by a long 3'-non-coding region of 777 nt. Northern and Southern blot analysis showed that the PEPCK mRNA is 2.7 kb long and that the PEPCK gene is polymorphic in T. cruzi, with more than one copy in the genome of the epimastigote form. Comparison of the available aa sequences of ATP(protozoa, yeast and bacteria)- and GTP(vertebrates, insects, helminths and fungi)-dependent PEPCKs showed that the former lack two characteristic, highly conserved regions present in the GTP-dependent enzymes: one is associated with the binding of PEP while the second is frequently labeled as 'catalytic' and contains a conserved Cys residue of unusual reactivity. On the other hand, two consensus sequences with conserved predicted secondary structure were identified in all PEPCKs, independent of their nt specificity; one of them is a divalent metal-binding site previously identified in pyruvate kinase by X-ray crystallographic studies.

Adenosine Triphosphate↗
PubMed1993

The effect of ion channel blockers, immunosuppressive agents, and other drugs on the activity of the multi-drug transporter.

The MDRI protein is an energy-dependent transport protein responsible for the multi-drug resistance seen in many tumors. A variety of drugs have been shown to inhibit the function of this pump, including compounds known to block various ion channels. The mouse lymphoma cell line L5178Y has been transduced with the human mdrI gene. Using this cell line, we have tested a number of compounds to determine whether there is a correlation between the ability to block a specific type of ion channel, or shift membrane potential, and the ability to act as an MDR-reversing agent using the fluorescent substrates Rhodamine 123 and daunorubicin as test compounds. Our results show no apparent correlation between the ability to block a specific ion channel and reversal of MDR transport ability. We have found active MDR inhibitors in compounds that affect K+, Na+, Ca++, H+, but not Cl- channels. Our data suggest that Cl- channel activity may be distinct from MDR activity. Several immunosuppressive compounds and analogs were also tested and found to be active reversing agents. Measurements suggest a significant difference in resting membrane potential between the L5178YvMDR line and the L5178Y parental cell line used in these experiments. No correlation was found between the ability of drugs to alter membrane potential and to inhibit MDR transport activity. Our results suggest that MDR transport function may be independent of the physiological movement of ions and show that a wide variety of compounds can inhibit MDR transport.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

cDNA cloning and expression of Rhodnius prolixus vitellogenin.

It was shown that Rhodnius prolixus vitellogenin (Vg) is synthesized as precursors of 205 and 190 kDa. Each Vg subunit is antigenically related to a domain in the precursor molecules. Since Vg has been previously detected in R. prolixus male adults, protein synthesis by fat bodies from 5th instar male nymphs was investigated and no Vg synthesis could be detected. Also, a 6.1 Kb RNA is present in female adults but not in 5th instar male nymphs. Therefore, cDNAs from female adult and 5th instar male fat bodies were used for differential screening of a female fat body cDNA library leading to the isolation of several female specific clones. All the clones hybridizing to the female specific 6.1 Kb RNA species were identical. We also describe the construction of new expression vectors, pGex-A and pGex-B, derived from the previously described plasmid pGex-1N. The new vectors, together with pGex-3X, comprise a set of expression plasmids with cloning sites in all three possible reading frames that give a fusion polypeptide with the glutathione S-transferase. This carrier protein can be cleaved by digestion with factor Xa in all three plasmids; one of the Vg cDNA clones was subcloned in pGex-A. Antibodies affinity purified from the fusion protein Vg/glutathione S-transferase recognized both large Vg subunits, suggesting an antigenic relationship between them. Furthermore, the small Vg subunits were not recognized, indicating that they may be localized at the N-terminal region of Vg precursors.

Amino Acid Sequence↗
PubMed1993

Trypanosoma cruzi topoisomerase II: a target enzyme for the chemotherapy of Chagas' disease? Cloning and characterization of its encoding gene.

The study of Trypanosoma cruzi type II DNA-topoisomerase should provide new clues for the rational development of new drugs for the chemotherapy of Chagas' disease. This enzyme is very likely involved in the processes leading to T. cruzi replication and differentiation since both processes are blocked by bacterial type II DNA topoisomerase inhibitors. In this article, we review and discuss our recent data related to the cloning, sequencing, and expression of T. cruzi type II topoisomerase.

Amino Acid Sequence↗
PubMed1992

Cloning and characterization of the gene encoding Trypanosoma cruzi DNA topoisomerase II.

The gene encoding Trypanosoma cruzi type II topoisomerase (TcTOP2) was isolated from a genomic library with a heterologous probe corresponding to part of the Trypanosoma brucei type II topoisomerase (TBrTOP2) gene. Nucleotide sequencing of TcTOP2 showed that the gene consists of an open reading frame of 3696 nucleotides (1232 amino acids), predicting a polypeptide product of 138,413 Da. Comparison of the amino acid sequence with that of type II topoisomerases from T. brucei (TBrTOP2) and Crithidia fasciculata (CfaTOP2), shows a high degree of conservation with estimated identities of 78% and 69%, respectively. TcTOP2 is a single copy gene in the genome of T. cruzi Dm28c and is expressed as a 4.5-kb mRNA. PCR mapping showed two distinct mini-exon addition sites at positions 225 and 203 upstream from the initiator AUG.

Amino Acid Sequence↗
PubMed1992

Trypanosoma cruzi flagellar repetitive antigen expression by recombinant baculovirus: towards an improved diagnostic reagent for Chagas' disease.

We constructed a recombinant baculovirus that expressed part of a Trypanosoma cruzi flagellar repetitive antigen (FRA). Both cell- associated and secreted forms of recombinant FRA were detected in cultures of virus-infected Spodoptera frugiperda (Sf9) cells. These forms show a complex pattern after polyacrylamide gel electrophoresis and Western blot analysis using either an anti-FRA rabbit serum or human Chagasic sera. Competitive Western-blot experiments revealed that all bands react with the same antibodies as a bacterially-derived FRA. Polymerase chain reaction and Southern blots of the recombinant viral DNA also showed a complex pattern, suggesting the presence of more than one repeat unit in the viral genome. When tested against a panel of human sera from an endemic area for Chagas' disease, FRA recombinant-Sf9 culture supernatant showed the same reactivity as purified FRA produced in bacteria.

Animals↗