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Biomedical subjects

G Thomas

Publications and source records attributed to G Thomas.

At least 235 records · Page 13Linked to original sources
PubMed1998

Inhibition of soluble recombinant furin by human proteinase inhibitor 8.

Furin is a ubiquitous prototypical mammalian kexin/subtilisin-like endoproteinase that is involved in the proteolytic processing of a variety of proteins in the exocytic and endocytic pathways, with cleavage occurring at the C terminus of the minimal consensus furin recognition sequence Arg-Xaa-Xaa-Arg. In this study, human proteinase inhibitor 8 (PI8), a widely expressed 45-kDa ovalbumin-type serpin that contains two sequences homologous to the minimal sequence for recognition by furin in its reactive site loop, was tested for its ability to inhibit a recombinant soluble form of human furin. PI8 formed an SDS-stable complex with furin and inhibited its amidolytic activity via a two-step mechanism with a kappa assoc of 6.5 x 10(5) M-1 S-1 and an overall Ki of 53.8 pM. Thus, PI8 inhibits furin in a rapid, tight binding manner that is characteristic of physiological serpin-proteinase interactions. PI8 is not only the first human ovalbumin-type serpin to demonstrate inhibitory activity toward furin, but it is also the first significant inhibitor of furin identified that is not a serpin reactive site loop mutant, either naturally occurring or engineered.

Amino Acid Sequence↗
PubMed1998

In search of a dose-response relationship with radiotherapy in the management of recurrent rectal carcinoma in the pelvis: a systematic review.

PURPOSE: A systematic review of the literature was undertaken to address the question: "What is the most effective dose fractionation schedule for the relief of symptoms in patients with pelvic recurrence from rectal or colorectal carcinoma?" METHODS AND MATERIALS: Cancerlit/Medline-computerized databases were searched between the years 1966-1996. Studies that explored the response to radiotherapy in patients with pelvic recurrence from rectal/rectosigmoid carcinoma were included. Factors that may contribute to differences in results were postulated in advance and the variations encountered between articles were presented. Articles with data applicable to recurrent disease only were included in the primary analysis. The effect of including articles that reported outcomes of recurrences with unresectable primaries and residual disease was presented as a sensitivity analysis. RESULTS: Only retrospective series (level V evidence) were available. The many sources of potential bias inherent in retrospective analyses make the data suitable for hypothesis generation only. Comparison of response was made between "lower" vs. "higher" doses, using 45-50 Gy as the dividing dose, base on the primary analysis. There were no significant differences observable in terms of initial response and the proportion maintaining a response at 6 months, within the range of doses employed. When data from articles that reported outcomes of recurrent disease with primary untreated cancers and postoperative residual disease were included, there was a suggestion for a more favorable response with higher doses. This requires cautious interpretation within the methodological limitations of the data. CONCLUSION: The optimal dose fractionation schedule for the palliation of pelvic recurrence from rectal carcinoma remains undefined. Well-designed randomized studies, with study arms that are sufficiently diverse biologically to allow the detection of a dose-response relationship if one existed, equipped with suitable symptom control end points, are necessary to provide a clinically relevant answer.

Dose-Response Relationship, Radiation↗
PubMed1998

Germline mutation profile of the VHL gene in von Hippel-Lindau disease and in sporadic hemangioblastoma.

von Hippel-Lindau (VHL) disease is a dominantly inherited disorder predisposing those afflicted to hemangioblastomas of the central nervous system and the retina, renal cell carcinomas, pheochromocytomas, and pancreatic tumors. The disease has been associated with mutations of the VHL gene. The screening of 92 unrelated patients with VHL disease for point mutations in this gene revealed 61 DNA variants. In addition, a search for EcoR1 rearrangements revealed germline anomalies in 5 patients. The 61 variants could be subdivided in 20 mutations predicted to alter the open reading frame (8 nonsense mutations, 8 frame shift mutations, and 4 mutations in consensus splicing sites) and 43 DNA sequence variants of a priori unknown biological consequence (4 in-frame insertions or deletions, 36 missense mutations, and 3 apparently silent variations). The 3' end of the coding sequence of the VHL gene, which encodes the Elongin binding domain was the site of 5 of 20 truncating mutations (25%) and of 18 of 41 DNA variants (44%) causing uncertain functional impairment. A similar screening in 18 patients with sporadic hemangioblastoma revealed 2 missense DNA variants. In order to corroborate this latter observation, a systematic screening for germline alteration of the VHL gene might be performed in a larger series of sporadic hemangioblastoma. If this preliminary result is confirmed, more than 10% of sporadic hemangioblastoma might be related to a mild VHL disease, thus a follow-up program similar to that recommended in cases of VHL disease should probably be discussed in the corresponding families.

Adult↗
PubMed1998

Determination of the replication error phenotype in human tumors without the requirement for matching normal DNA by analysis of mononucleotide repeat microsatellites.

Microsatellite instability (MI) characterizing tumors with replication errors (RER+ tumors) was first described in colorectal tumors from hereditary non-polyposis colorectal cancer (HNPCC) patients as well as in sporadic cases. It has also been observed in subgroups of extracolonic sporadic tumors, but there is no consensus as to the number of microsatellite loci to examine, and the threshold percentage of unstable loci required to classify a tumor as RER+. We have recently shown that BAT-26, a mononucleotide repeat microsatellite, was quasi-monomorphic in DNA from normal individuals and from colorectal RER- samples, and showed important size variations in RER+ samples. In the present work, we analyzed BAT-26 allelic profiles in tumors of the breast (n = 107), brain (n = 78), stomach (n = 59), prostate (n = 49), esophagus (n = 36), thyroid (n = 31), endometrium (n = 12), and cervix (n = 10) whose RER status was already known, thus extending BAT-26 analysis to a total of 542 human solid tumors. BAT-26 alleles were quasi-monomorphic in RER- samples (475/481) and shortened in RER+ tumors (57/61), including four tumors shown to have been misclassified on the basis of dinucleotide repeat microsatellite analysis. In 3/481 RER- and 4/61 RER+ cases, BAT-26 size variation was important enough to attract attention, but not sufficient to establish the RER status of the corresponding tumors. In these cases, the analysis of BAT-25 and BAT-34C4, two other mononucleotide repeat microsatellites, was necessary to resolve the ambiguity. There were only 3 false positive cases. In conclusion, BAT-26 was able to identify the RER status of 539 out of 542 tumors from various origins (99.5% efficiency) in a single-step experiment without the requirement for matching normal DNA.

Breast Neoplasms↗
PubMed1998

A randomized trial of standard versus partially hyperfractionated radiation with or without concurrent 5-fluorouracil in locally advanced cervical cancer.

The objective of this study was to determine whether the addition of concurrent 5-fluorouracil (5-FU) and/or a change in radiation fractionation improves pelvic control and survival or decreases complications in advanced cervical cancer, FIGO stages IB/IIA (>=5 cm) to IVA inclusive. After stratification by pelvic disease extent, 234 of a planned 292 patients were randomized to receive one of four possible treatments: (a) standard external beam pelvic irradiation (RT) 5000 cGy in 25 fractions versus (b) RT as in arm (a) with infusional IV 5-FU 1g/m2 daily in the first and last 4 days of RT, (c) partially hyperfractionated RT, 5280 cGy in 33 fractions, two fractions per day on the first and last 4 days of RT, or (d) arm (c) with the same FU. All were followed with a linear source of intracavitary RT to deliver 40 Gy. The median duration of follow-up for the 221 evaluable patients was 59 months. The 5-year Kaplan-Meier disease-free survival (DFS) in arm (a), (c), (d), and (b), respectively, were 45, 53, 58, and 61%. The differences in survival and pelvic control were not statistically significant. An exploratory subset analysis was performed within stratum 1 and stratum 2 to generate hypotheses for future studies. Only for the 99 patients in stratum 1 (IB/IIA or medial parametrial IIB disease) was the 5-year DFS significantly better (long rank P = 0.05) for standard RT and 5-FU. The DFS was 39% for arm (a), 76% for arm (b), 58% for arm (c), and 65% for arm (d). A multivariate analysis of patient, tumor, and treatment related prognostic factors identified only the use of 5-FU to account for the observed difference. The crude serious late bowel or bladder complication rate was 5.9%. Overall concurrent infusional 5-FU was not beneficial when added to standard RT in this study. The possible benefit for patients in stratum 1 requires exploration in a further randomized trial with appropriate accrual.

Adult↗
PubMed1998

[Surgery of acute aortic valve endocarditis: prognosis in paravalvular abscess].

The occurrence of paravalvular abscesses in the course of an acute endocarditis of the aortic valve indicates an advanced stadium of the disease. The infection has spread beyond the limits of the valve leaflets, and ongoing destruction of the paravalvular tissue is to be expected, if the endocarditis is continually treated by antibiotics alone. Surgery of acute endocarditis with paravalvular abscess, however, supposedly carries an increased risk of early mortality and late morbidity. The following prospective study was carried out to determine whether a radical surgical approach together with aggressive postoperative antibiotic therapy could help to improve results. Between 1988 and 1995, 138 patients were operated during the acute phase of infective endocarditis; in 102 the aortic valve was involved. Among these, 44 had paravalvular abscesses at the time of surgery. The mean age of both groups was the same, but there was a higher rate of concomitant coronary artery disease, multiple valve involvement, advanced NYHA-class, and staphylococcal disease among the patients with abscesses. All interventions were carried out with cardiopulmonary bypass and cardioplegic arrest. The aortic valve was resected, abscesses were removed, and each part of potentially infected or necrotic tissue was resected as complete as possible, irrespective of the possibility to jeopardize the conduction system or to create large tissue defects. The aortic valve was replaced with a mechanical prosthesis in each case. The postoperative antibiotic regimen was specifically directed against the microorganisms isolated preoperatively; therapy was only modified, if signs of systemic infection did not disappear three days after surgery. The operative mortality was 10% among patients without an abscess and 11% in patients with a paravalvular abscess. Early recurrent endocarditis was recorded in two patients without and in only one patient with an abscess. Late recurrent endocarditis was noted in three patients; none of them had abscesses at the time of surgery. We conclude that the operative risk of acute endocarditis of the aortic valve with a paravalvular abscess does not have to be inevitably higher compared to cases without paravalvular involvement. To achieve these results, it is necessary to use a radical surgical approach and to adjust postoperative antibiotic therapy, if infectious signs do not disappear shortly after surgery.

Abscess↗
PubMed1998

Preclinical review of cerivastatin sodium--a step forward in HMG-CoA reductase inhibition.

Epidemiological studies have established that elevated concentrations of plasma cholesterol, particularly the low density lipoprotein (LDL) cholesterol, is one of the major risk factors for the development of arteriosclerosis and ischemic heart disease. Treatment with HMG-CoA reductase inhibitors (vastatins) has become the most successful drug treatment in lowering total plasma and LDL cholesterol concentrations in the last years. The vastatins already available for treatment are therapeutically used in a dose-range between 10 and 80 mg/day. The new enantiomerically pure pyridine derivative cerivastatin sodium has demonstrated its efficacy in significantly lower doses in the microgram-range, not only in preclinical but also in clinical studies with daily doses of only 0.1-0.3 mg. The differences in the therapeutic doses are reflected by the Ki- and IC50-values from enzyme inhibition tests in comparison with various HMG-CoA reductase inhibitors. Cerivastatin sodium exhibits much higher enzyme affinity with factors between 70 and almost 200. The Ki-value for cerivastatin sodium was 1.3 x 10(-9) M in comparison to 150 x 10(-9) M for lovastatin. The extremely high enzyme affinity of cerivastatin sodium was also reflected in its high activity in vivo. In acute in vivo studies cerivastatin sodium inhibited the hepatic [14C]cholesterol synthesis from [14C]acetate in both rats and dogs by 50% after oral administration at doses of 0.002 mg/kg body weight (ED50-values). This dose was comparable to 0.3 mg/kg of lovastatin. In subchronic dog studies a dose of 0.03 mg/kg lowered the serum LDL cholesterol concentration by 35% which is comparable with doses of 8-10 mg lovastatin/kg. Interesting results were observed in cholestyramine-primed dogs when 0.1 mg cerivastatin sodium/kg p.o. markedly decreased the serum triglycerides up to 70%. Cerivastatin shows a favourable pharmacokinetic profile with high liver selectivity. Rat studies have shown almost complete absorption and rapid hepatic clearance. Cerivastatin was highly bound to plasma proteins of rats, dogs and humans (>98%). Cerivastatin metabolites were excreted mainly via feces. The metabolism of cerivastatin sodium in man follows two metabolic pathways, demethylation to metabolite M1 and stereospecific hydroxylation to M23. The three major metabolites M1, M23 and the hydroxylated and demethylated metabolite M24 are highly active inhibitors not only in vitro but also in vivo. The human specific metabolites M23 and M24 inhibited the HMG-CoA reductase isolated from rat liver with the same potency as the parent compound cerivastatin sodium (IC50: 1.0-1.2 x 10(-9) M). M1 was slightly less active. Corresponding pharmacological activity was observed in vivo. M23 and M24 inhibited [14C]cholesterol synthesis from [14C]acetate in rat liver with ED50)-values between 0.001 and 0.002 mg/kg body weight which is similar to cerivastatin sodium and M1 exhibited an ED50-value of <0.006 mg/kg The strong inhibitory activity of these metabolites, in addition to cerivastatin's high enzyme affinity may explain the extraordinary pharmacological activity of cerivastatin and its ultra-low dose in man and demonstrates cerivastatin to be the most active HMG-CoA reductase inhibitor amongst all vastatins.

Animals↗
PubMed1998

Pathogen-free granulomatous diseases of the central nervous system.

Pathogen-free granulomatous diseases (PFGD) of the central nervous system (CNS) are a group of disorders with protean clinical and pathological findings. Failure to identify a causative organism leads to considerable diagnostic difficulty. The neuropathology records between 1985 and 1995 were retrospectively reviewed, and the medical records of all patients in whom a diagnosis of PFGD of the CNS was made were retrieved. Patients in whom an infective agent was shown either by culture, special staining techniques, or by immunohistochemical methods were excluded. We identified 11 patients (eight male, three female) who fulfilled the pathological criteria for this condition. Average age at diagnosis was 38.7 years (range, 17 to 78). Neurological symptoms were the presenting feature in nine patients. Neuroimaging findings included hydrocephalus (54.5%), meningeal enhancement (45.5%), and mass lesions (45.5%). Seven patients had antemortem CNS biopsies (brain/meninges [n = 6], spinal [n = 1]), which showed noncaseating granulomas. Eight patients died (mortality rate: 72.7%). Postmortem examination showed granulomatous involvement of the leptomeninges and cerebral parenchyma in all cases with systemic involvement in 50%, chiefly in the form of noncaseating granulomas of the hilar nodes. Six patients fulfilled the clinical, radiological, and pathological diagnostic criteria for neurosarcoidosis. The remaining five patients had an unclassifiable pathogen-free granulomatous disease of the CNS. PFGD of the CNS are associated with a poor prognosis. Although neurosarcoidosis may account for some of the cases, there remains an unclassifiable subgroup that continues to be a diagnostic and management challenge.

Adolescent↗
PubMed1998

Cytophagic histiocytic panniculitis--a syndrome associated with benign and malignant panniculitis: case comparison and review of the literature.

Many cases of hemophagocytic syndromes with cytophagic histiocytic panniculitis (CHP) are being classified and considered as a natural disease progression of subcutaneous panniculitic T-cell lymphoma (SPTL). Review of the literature on both CHP and SPTL discloses distinct patterns suggesting these disorders may not be equivalent, even though a terminal hemophagocytic syndrome may be associated with each. Some SPTL appear to have association with Epstein-Barr virus (EBV), show malignant histopathology in the skin, and may disseminate terminally, with a majority of cases showing a rapidly fatal progression. On the other hand, classic cases of CHP without proven lymphoma may not be associated with EBV, appear to be histologically benign, and have an indolent course unless terminal hemophagocytic syndrome develops. We compared and contrasted a case of CHP and a case of SPTL and reviewed the literature. Our observations suggest that the often fatal hemophagocytic syndrome may be associated with both benign and malignant subcutaneous panniculitis.

Adult↗
PubMed1998

Antidepressant effect of an ethanolic extract of the leaves of Cissampelos sympodialis in rats and mice.

An ethanolic extract of the leaves of Cissampelos sympodialis Eichl. (Menispermaceae) was found to potentiate the toxicity of pentylenetetrazol in mice. Similar to imipramine, the extract also reduced the immobility period in the forced swimming test in mice and reversed the degree of ptosis and catalepsy induced by reserpine in rats. These results suggest that the extract possesses antidepressant activity and the reported phosphodiesterase inhibitory activity of the plant may account for the observed antidepressant effect.

Animals↗
PubMed1998

Analysis of the p21 gene in gliomas.

The p21 gene encodes a cyclin dependent kinase inhibitor protein (p21) which has a tumor suppressive activity in a variety of tumor cell lines. Since, the p21 gene is up-regulated by the p53 tumor suppressor gene, which is frequently mutated in gliomas, acting therefore in the same control pathway, it constitutes a good candidate gene to be also inactivated in these tumors. To test this hypothesis, DNAs from 81 gliomas (48 glioblastomas, 11 anaplastic astrocytomas, 10 low-grade astrocytomas, 12 oligodendrogliomas and mixed gliomas), were investigated for mutations in the p21 coding sequence by denaturant gradient gel electrophoresis followed by sequencing. All these tumors have been previously screened for p53 mutations. Three different DNA variants were identified on codon 31 (17 cases), 27 (1 case) and 117 (1 case) and shown to be also present in matching constitutional DNA, suggesting they were polymorphisms. None of the tumors demonstrated a somatic mutation. No significant correlation between the presence of a p21 variant and the p53 mutation tumor status was observed. In conclusion, mutation in the p21 gene unlikely contributes to the development of gliomas.

Alleles↗
PubMed1998

NF2 gene in neurofibromatosis type 2 patients.

Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder that predisposes to nervous system tumors. The schwannomin (also termed merlin) protein encoded by the NF2 gene shows a close relationship to the family of cytoskeleton-to-membrane proteins linkers ERM (ezrin-radixin-moesin proteins). Even though penetrance of the disease is >95% and no genetic heterogeneity has been described, point mutations in the NF2 gene have been observed in only 34-66% of the screened NF2 patients, depending on the series. In order to generate tools that would enable an exhaustive alteration screening for the NF2 gene, we have deduced its entire genomic sequence. This knowledge has provided the delineation of a mutation screening strategy which, when applied to a series of 19 NF2 patients, has revealed a high recurrence of large deletions in the gene and has raised the efficiency of mutation detection in NF2 patients to 84% of the cases in this series. The remaining three patients who express two functional NF2 alleles are all sporadic cases, an observation compatible with the presence of mosaicism for NF2 mutation.

Cells, Cultured↗
PubMed1998

Impaired interaction of naturally occurring mutant NF2 protein with actin-based cytoskeleton and membrane.

Although schwannomin, the product of the neurofibromatosis type 2 gene, shares homology with three cytoskeleton-to-membrane protein linkers defining the ERM family, the mechanism by which it exerts a tumor suppressive activity remains elusive. Based on the knowledge of naturally occurring mutations, a functional study of schwannomin was initiated. Constructs encoding the two wild-type isoforms and nine mutant forms were transfected into HeLa cells. Transiently expressed wild-type isoforms were both observed underneath the plasma membrane. At this location they were detergent insoluble and redistributed by a cytochalasin D treatment, suggesting interaction with actin-based cytoskeletal structures. Proteins with single amino acid substitutions at positions 219 and 220 demonstrated identical properties. Three different truncated schwannomins, that are prototypic for most naturally occurring NF2 mutations, were affected neither in their location nor in their cytochalasin D sensitivity. However, they were revealed to be detergent soluble, indicating a relaxed interaction with the actin-based structures. An increased solubility was also observed for a mutant with a single amino acid substitution at position 360 in the C-terminal half of the protein. Mutant proteins with either a single amino acid deletion at position 118 or an 83 amino acid deletion within the N-terminal domain had lost the submembraneous localization and tended to accumulate in perinuclear patches that were unaffected by cytochalasin D treatment. A similar behavior was observed when the N-terminal domain was entirely deleted. Taken together these observations suggest that the N-terminal domain is the main determinant that localizes the protein at the membrane where it interacts weakly with actin-based cytoskeletal structures. The C-terminal domain potentiates this interaction. With rare exceptions, most naturally occurring mutant schwannomins that have lost their tumor suppressive activity are impaired in an interaction involving actin-based structures and are no longer firmly maintained at the membrane.

Actins↗
PubMed1998

Comparative rearing of Wohlfahrtia magnifica (Diptera: Sarcophagidae) in dead and living tissues and the impact of cold storage on pupal survival.

Larvae from adults of Wohlfahrtia magnifica (Schiner) emerging from pupal cold storage (4 degrees C for 80-100 d) were reared in wound and dead tissues. Of 2,150 first instars placed on a mixture of muscle + liver in a climate-controlled room, 47.1% molted to 2nd instar, 6.1% to 3rd instar, and 4.6% pupated. Two females emerged from these pupae after 14 d. To synchronize adult emergence, 191 pupae that were reared in living or dead tissues and were 2, 8, and 11 d old were cold-stored in lots according to age. Adult emergence was greatest in pupae of 2-d-old (57.1%) and, pupae developing in living and dead tissues, 22.5 and 8.7%, respectively. When the experiment was repeated with cold-stored pupae from 0 to 11 d old, developing in living tissues, the highest emergence was again in 2-d-old pupae (55.0%). These data have important implications for the control of adult emergence which may be used in further biological studies.

Animals↗