Search PubMed⌕ Search

Biomedical subjects

M Gregor

Publications and source records attributed to M Gregor.

At least 73 records · Page 4Linked to original sources
PubMed1999

Creatine kinase reaction in skinned rat psoas muscle fibers and their myofibrils.

The aim of this study was to evaluate myofibrillar creatine kinase (EC 2.7.3.2) activity on the background of the effect of substrate channeling by myosin ATPase and to compare it with creatine kinase (CK) activity of whole skinned fibers. In order to assess CK activity, skinned fibers were prepared from the rat psoas major muscles defined by light microscopy. The activity in permeabilized fibers after treatment with saponin, Triton X-100 and Ca(2+)-free medium reached 2.80, 6.97 and 3.32 micromol ATP min(-1) mg(-1) protein, respectively, when a coupled enzyme assay system with external hexokinase and glucose-6-phosphate dehydrogenase was used. Transmission electron microscopy (TEM) revealed a possible interference among activities of sarcolemmal, sarcoplasmic, myofibrillar and mitochondrial CK from persisting structures. For evaluation of the myofibrillar CK itself, a pure myofibrillar fraction was prepared. Fraction purity was confirmed by TEM and by enzymatic assays for marker enzymes. Two procedures, i.e. the coupled enzyme assay and the evaluation of phosphocreatine (PCr) concentration before and after the CK reaction, were used for measurement of CK activity in this fraction. The procedures resulted in 3.2 nmol ATP min(-1) mg(-1) protein and 7.6 nmol PCr min(-1) mg(-1) protein, respectively. These alternative approaches revealed a discrepancy between the reacting portions of PCr by more than 50 %, which provides information about the size of the effect, generally described as substrate channeling.

Adenosine Triphosphate↗
PubMed1999

Diagnostic significance of nuclear p53 expression in the surveillance of Barrett's esophagus--a longitudinal study.

The efficacy of currently performed surveillance in patients with Barrett's esophagus (BE) is substantially compromised by shortcomings of dysplastic lesions as diagnostic markers. The aim of this study was to evaluate the possible role of p53 protein expression as complementary method in the diagnosis of neoplastic transformation in BE. A longitudinal study was performed. 41 patients were enrolled. The median time of surveillance was 46 months. 234 archival paraffin blocks containing a total of 627 biopsies were retrieved. p53 protein immunostaining by application of the monoclonal antibody DO-1 was performed. The results of immunohistochemistry were compared with the exact histopathological diagnosis and grading of dysplasia (no dysplasia, indefinite for dysplasia, low-grade dysplasia, high-grade dysplasia, carcinoma). In merely four of 206 nondysplastic mucosal sites p53 expression was found. However, p53 expression was detected with increasing frequency in sites indefinite for dysplasia (2/9), specimens with low-grade dysplasia (9/15), high-grade dysplasia (3/3) and the one with a carcinoma. This study shows a close association of nuclear p53 protein expression to the process of neoplastic transformation in Barrett's epithelium. However, it apparently does not precede the appearance of dysplasia significantly. Thus, nuclear p53 expression as detected by immunohistochemistry may serve to confirm a suspected diagnosis of dysplasia in BE.

Adenocarcinoma↗
PubMed1999

Age at onset in geriatric bipolar disorder. Effects on clinical presentation and treatment outcomes in an inpatient sample.

The authors report on 62 inpatients over age 60 who met DSM-III-R criteria for bipolar disorder, divided into early- and late-onset groups by their median age at lifetime onset, 49 years, in order to examine differences in demographic and clinical characteristics, treatment parameters, and outcome in the two groups during a short-term hospitalization. The late-onset group was more likely to have psychotic features and to demonstrate cerebrovascular risk/burden. However, both groups had similar and highly significant improvements in the Brief Psychiatric Rating Scale, Global Assessment Scale, and the Mini-Mental State Exam, and 87% were able to be discharged to settings no more restrictive than those at admission.

Age of Onset↗
PubMed1998

Hypermethylation of the p16INK4a promoter in colectomy specimens of patients with long-standing and extensive ulcerative colitis.

Functional inactivation of the p16INK4a gene has been reported to be involved in the development of a variety of human malignancies. Recent evidence shows that transcriptional silencing as a consequence of hypermethylation of CpG islands is the predominant mechanism of p16INK4a gene inactivation in sporadic colon cancer. This study sought to identify the significance of p16INK4a methylation in the colonic epithelium of patients with long-standing ulcerative colitis. A total of 89 tissue samples was retrieved from three colectomy specimens. A methylation-specific PCR assay was applied. The methylation status was compared with histological findings and the flow cytometrically determined DNA index. Hypermethylation of the p16INK4a promoter region was detected in 12.7% of samples that were negative for dysplasia. However, 70.0% of samples with dysplasia and all of the samples with carcinomatous lesions revealed hypermethylation. Hypermethylation of the p16INK4a gene promoter was detected already in 40% of specimens with lesions indefinite for dysplasia and in 13.7% of samples with exclusively diploid cell populations. These results suggest that hypermethylation of the p16INK4a promoter region is a frequent and early occurring event during the process of neoplastic progression in ulcerative colitis.

Colectomy↗
PubMed1998

Magnetic cell sorting for parietal cell purification using a new monoclonal antibody without influence on cell function.

Conventional isolation protocols for the parietal type of the gastric mucosal cell population are based on physical criteria such as cell size and cell density. Time-consuming centrifugation techniques are required, which decrease the overall yield and exert a negative influence on the functional integrity of purified cells. As an alternative, we now have developed a phenotype-dependent magnetic selection method. A monoclonal antibody (P1.4D5) was raised against rat parietal cells. After immunohistochemical, biochemical and functional characterization, P1.4D5 was used for rapid antibody-mediated magnetic cell sorting (MACS) of enzymatically dispersed gastric mucosal cells, which resulted in a 2.2- to 3-fold enrichment of parietal cells. Characterization of P1.4D5 demonstrated its applicability for parietal cell-specific immunostaining of formalin treated and paraffin-embedded tissue samples and cryosections from both rat and man. In vitro studies of the 14C-aminopyrine accumulation showed no intrinsic effect of P1.4D5 on the acid production of the parietal cell or on the histamine-stimulated acid production. This absence of negative influence on the parietal cell function qualifies P1.4D5 for immunomagnetic cell sorting procedures.

Aminopyrine↗
PubMed1998

Comparative analysis of histology, DNA content, p53 and Ki-ras mutations in colectomy specimens with long-standing ulcerative colitis.

Neoplastic progression in patients with chronic ulcerative colitis is characterized by the development of epithelial dysplasia, which is accompanied by genetic alterations. This study determined the time of onset of p53 and Ki-ras mutations as well as DNA aneuploidy during histological progression towards carcinoma. In all, 278 samples of 7 colectomy specimens were analyzed by flow cytometry, histology and single-strand conformation polymorphism analysis. Of the samples, 22% (61/278) were dysplastic and 43% (122/278) aneuploid, while 25% (71/278) showed p53 and 4% (11/278) Ki-ras mutations. The correlation between aneuploid status and p53 mutations varied among the patients. A strong correlation was noticed between histological progression from low-grade dysplasia to carcinoma and p53 mutations as well as DNA aneuploidy. Ki-ras mutations were found in 40% (2/5) of the carcinomatous samples. The correlation between p53 mutations and the histological status of the samples suggest the involvement of this genetic event in the development of colon cancer in patients with ulcerative colitis. In contrast to Ki-ras mutations, the appearance of p53 mutations is an early event. Therefore p53 analysis might be helpful in the classification of indefinite dysplasia and in the identification of patients at risk for cancer development. Further studies are necessary to detect the additional genetic alterations preceding the development of DNA aneuploidy.

Aneuploidy↗
PubMed1998

[Focal liver diseases].

INTRODUCTION: Advanced therapies are improving significantly the survival of patients with malignant focal liver disease. For efficient implementation of these surgical and interventional techniques a clear concept of the diagnostic procedure is mandatory. METHODS: Based on a review of the current literature, the different imaging modalities, including ultrasound, computed tomography, magnetic resonance tomography, nuclear medicine and angiography, are discussed and evaluated for their diagnostic efficacy in focal hepatic disease. RESULTS: Considering clinical, diagnostic, and economical appropriateness, recommendations for diagnostic strategies in different clinical scenarios regarding focal heptic disease are presented. CONCLUSION: If the power of specific imaging methods are relevant clinical information is known, problem-based diagnostic strategies help to avoid unnecessary, expensive and time-consuming studies in the work-up of focal liver lesions.

Carcinoma, Hepatocellular↗
PubMed1998

Hypermethylation of the CDKN2/p16 promoter during neoplastic progression in Barrett's esophagus.

BACKGROUND & AIMS: Inactivation of the CDKN2/p16(INK4A) tumor-suppressor gene is one of the most frequent genetic alterations in human malignancies. In esophageal adenocarcinomas, mutations of the p16 gene or homozygous deletions of the gene locus 9p21 are rare. This study investigated whether p16 promoter hypermethylation is an alternative mechanism for p16 gene inactivation during neoplastic progression in Barrett's esophagus. METHODS: A methylation-specific polymerase chain reaction protocol was applied. A total of 95 specimens from 14 patients with Barrett's esophagus were analyzed longitudinally. The p16 promoter status was compared with histomorphological findings. RESULTS: p16 promoter hypermethylation was detected in 9 of the 10 patients who had displayed dysplasia at some time during surveillance, whereas none of the patients who had not displayed dysplasia during surveillance had p16 promoter hypermethylation. p16 promoter hypermethylation was detected in 3% (2 of 67) of the samples without dysplasia, 60% (3 of 5) of the samples with lesions indefinite for dysplasia, 55.6% (10 of 18) of the specimens with low-grade dysplasia, and 75% (3 of 4) of the specimens with high-grade dysplasia. CONCLUSIONS: These data suggest that p16 promoter hypermethylation is a common mechanism of p16 gene inactivation during neoplastic progression in Barrett's esophagus.

Barrett Esophagus↗
PubMed1998

Pseudotype formation of Moloney murine leukemia virus with Sendai virus glycoprotein F.

Mixed infection of cells with both Moloney murine leukemia virus (MoMLV) and related or heterologous viruses produces progeny pseudotype virions bearing the MoMLV genome encapsulated by the envelope of the other virus. In this study, pseudotype formation between MoMLV and the prototype parainfluenza virus Sendai virus (SV) was investigated. We report for the first time that SV infection of MoMLV producer cells results in the formation of MoMLV(SV) pseudotypes, which display a largely extended host range compared to that of MoMLV particles. This could be associated with SV hemagglutinin-neuraminidase (SV-HN) glycoprotein incorporation into MoMLV envelopes. In contrast, solitary incorporation of the other SV glycoprotein, SV fusion protein (SV-F), resulted in a distinct and narrow extension of the MoMLV host range to asialoglycoprotein receptor (ASGP-R)-positive cells (e.g., cultured human hepatoma cells). Since stably ASGP-R cDNA-transfected MDCK cells, but not parental ASGP-R-negative MDCK cells, were found to be transduced by MoMLV(SV-F) pseudotypes and transduction of ASGP-R-expressing cells was found to be inhibited by ASGP-R antiserum, a direct proof for the ASGP-R-restricted tropism of MoMLV(SV-F) pseudotypes was provided. Cultivation of ASGP-R-positive HepG2 hepatoma cells on Transwell-COL membranes led to a significant enhancement of MoMLV(SV-F) titers in subsequent flowthrough transduction experiments, thereby suggesting the importance of ASGP-R accessibility at the basolateral domain for MoMLV(SV-F) pseudotype transduction. The availability of such ASGP-R-restricted MoMLV(SV-F)-pseudotyped vectors opens up new perspectives for future liver-restricted therapeutic gene transfer applications.

Animals↗
PubMed1998

Different acid secretagogues activate different Na+/H+ exchanger isoforms in rabbit parietal cells.

Rabbit parietal cells express three Na+/H+ exchanger isoforms (NHE1, NHE2, and NHE4). We investigated the effects of carbachol, histamine, and forskolin on Na+/H+ exchange activity and acid formation in cultured rabbit parietal cells and tested the effect of NHE isoform-specific inhibition on agonist-induced Na+/H+ exchange. Carbachol (10(-4) M) was the weakest acid secretagogue but caused the strongest Na+/H+ exchange activation, which was completely blocked by 1 microM HOE-642 (selective for NHE1); histamine (10(-4) M) and forskolin (10(-5) M) were stronger stimulants of [14C]aminopyrine accumulation but weaker stimulants of Na+/H+ exchange activity. HOE-642 (1 microM) reduced forskolin-stimulated Na+/H+ exchange activity by 35%, and 25 microM HOE-642 (inhibits NHE1 and -2) inhibited an additional 13%, but 500 microM dimethyl amiloride (inhibits NHE1, -2, and -4) caused complete inhibition. The presence of 5% CO2-HCO-3 markedly reduced agonist-stimulated H+ efflux rates, suggesting that the anion exchanger is also activated. Hyperosmolarity also activated Na+/H+ exchange. Our data suggest that, in rabbit parietal cells, Ca2+-dependent stimulation causes a selective activation of NHE1, whereas cAMP-dependent stimulation activates NHE1, NHE2, and more strongly NHE4. Because intracellular pH (pHi) did not change in the presence of CO2-HCO-3 and concomitant activation of Na+/H+ and anion exchange is one of the volume regulatory mechanisms, we speculate that the physiological significance of secretagogue-induced Na+/H+ exchange activation may not be related to pHi but to volume regulation during acid secretion.

Aminopyrine↗
PubMed1998

Intestinal obstruction, progressive weight loss, and recurrent fever in two patients with mesenteric lesions.

We describe 2 patients who presented with fever and incomplete intestinal obstruction. Previously, both patients had had laparotomies showing unresectable lesions in the root of the mesentery which were histologically diagnosed as sclerosing mesenteritis in the first and mesenteric fibromatosis in the second patient. In spite of aggressive immunosuppressive therapy the first patient deteriorated with high-grade fever and progressive weight loss. Similar symptoms occurred in the second patient. Computed tomographic scanning revealed necrotic lesions in both patients which histologically were found to be an angiocentric T-cell lymphoma in the first and a superinfected necrotizing fibroma in the second patient. It is therefore clinically and radiologically impossible to distinguish between the different causes of mesenteric lesions. Reoperation for further biopsies needs to be considered if such patients do not respond to medical treatment.

Aged↗
PubMed1997

A functional CFTR protein is required for mouse intestinal cAMP-, cGMP- and Ca(2+)-dependent HCO3- secretion.

1. Most segments of the gastrointestinal tract secrete HCO3-, but the molecular nature of the secretory mechanisms has not been identified. We had previously speculated that the regulator for intestinal electrogenic HCO3- secretion is the cystic fibrosis transmembrane regulator (CFTR) channel. To prove this hypothesis, we have now measured HCO3- secretion by pH-stat titration, and recorded the electrical parameters of in vitro duodenum, jejunum and ileum of mice deficient in the gene for the CFTR protein ('CF-mice') and their normal littermates. 2. Basal HCO3- secretory rates were reduced in all small intestinal segments of CF mice. Forskolin, PGE2, 8-bromo-cAMP and VIP (cAMP-dependent agonists), heat-stable enterotoxin of Escherichia coli (STa), guanylin and 8-bromo-cGMP (cGMP-dependent agonists) and carbachol (Ca2+ dependent) stimulated both the short-circuit current (Isc) and the HCO3- secretory rate (JHCO3-) in all intestinal segments in normal mice, whereas none of these agonists had any effect on JHCO3- in the intestine of CF mice. 3. To investigate whether Cl(-)-HCO3- exchangers, which have been implicated in mediating the response to some of these agonists in the intestine, were similarly active in the small intestine of normal and CF mice, we studied Cl- gradient-driven 36Cl- uptake into brush-border membrane (BBM) vesicles isolated from normal and CF mouse small intestine. Both the time course and the peak value for 4,4'-diisothiocyanostilbene-2',2-disulphonic acid (DIDS)-inhibited 36Cl- uptake was similar in normal and CF mice BBM vesicles. 4. In summary, the results demonstrate that the presence of the CFTR channel is necessary for agonist-induced stimulation of electrogenic HCO3- secretion in all segments of the small intestine, and all three intracellular signal transduction pathways stimulate HCO3- secretion exclusively via activation of the CFTR channel.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1997

Hepatic retinopathia. Changes in retinal function.

In patients suffering from hepatic failure, the brain is subject to defined morphological and functional changes known as hepatic encephalopathia (HE). The morphological changes are dominated by glial cells (Alzheimer-type II astrocytes). It has recently been possible to demonstrate, that the retinal glia (Müller) cells undergo similar morphological changes. The present study was carried out in order to reveal if these Müller cell changes cause any characteristic functional deficits. We examined 11 patients with different stages of HE due to liver cirrhosis. Six patients were at stage 0 or 1 (group I) and five at stage 2 or 3 (group II). They underwent ophthalmological routine examination, colour vision testing and standard ERG recording. None of the patients reported impaired vision, in daylight or at night. There were no fundus abnormalities except very mild changes of the pigment epithelium and abnormal reflexes of the inner limiting membrane, especially in the higher HE stages. The number of confusions in the colour arrangement test increased with the higher stages of HE, preferably in the tritan axis. The scotopic a- and b-waves of the electroretinogram (ERG) were almost unchanged in group I and significantly decreased and delayed in group II. The photopic ERG b-wave amplitudes were changed in a similar fashion. Oscillatory potentials proved to be most sensitive to hepatotoxic changes. Their latencies were significantly delayed even in group I. Amplitudes were decreased significantly only in group II. Patients suffering from hepatic failure and accompanying HE display functional abnormalities of the retina. These are best demonstrated by the ERG, and correlate well with the degree of HE. A hypothesis is presented that relates the observed functional changes to altered neurotransmitter levels and impaired retinal glial-neuronal interaction, due to Müller cell damage caused by elevated ammonia levels.

Adult↗
PubMed1997

Shock wave permeabilization as a new gene transfer method.

Uptake of naked functional DNA into mammalian cells can be achieved by a number of physical methods. However, for most of these techniques possibilities for therapeutic in vivo applications--especially to solid organs--are often limited. In this report, we describe shock wave permeabilization as a new physical gene transfer method, which can be easily applied, provides great flexibility in the size and sequence of the DNA molecules to be delivered, and which should exhibit an advantageous security profile in vivo. Upon exposure to lithotripter-generated shock waves eukaryotic cells display a temporary increase in membrane permeability. This effect was shown to be caused by cavitation resulting in the transient generation of cell pores which allows the direct transfer of naked plasmid DNA. Shockwave transfection of a variety of cell lines was demonstrated. Since shock waves can be well focused within particular body regions, future applications of extracorporally generated shock waves to tissues simultaneously perfused with DNA solutions might open up the possibility of achieving a regionally enhanced in vivo gene transfer.

Animals↗
PubMed1997

Distribution of cell populations with DNA aneuploidy and p53 protein expression in ulcerative colitis.

OBJECTIVE: Patients with ulcerative colitis are at an increased risk for developing colorectal neoplasms. p53 mutations and the occurrence of DNA aneuploidies are common events in the development of sporadic colorectal neoplasias. This study tried to determine the frequency of these events during the development of colitis-associated colorectal neoplasms. DESIGN/METHODS: Four colectomy specimens with a total of 124 biopsies were investigated. DNA content was measured by flow cytometry and p53 protein expression was detected by immunohistochemistry. These results were correlated with histological findings. RESULTS: DNA aneuploidies were found in 58 (46.8%), and p53 protein expression in 30 samples (24.2%). The presence of DNA aneuploidy as well as of p53 protein expression correlated with the histological characteristics of neoplastic transformation. In areas without dysplasias or with indefinite dysplasias, 31.5% of the samples showed DNA aneuploidies and in about 9% of the samples p53 protein expression could be detected; 33.7% of samples without or with indefinite dysplasias showed p53 protein expression and/or DNA aneuploidies. CONCLUSION: These results show that the occurrence of DNA aneuploidies and nuclear p53 protein expression is a common event in the development of colitis-associated colorectal neoplasias. p53 protein expression seems to be an early event in this process. DNA aneuploidies occur even earlier and more frequently in the absence of p53 protein expression. Therefore, other genetic alterations besides p53 gene mutations might be involved in colitis-associated tumour development.

Adult↗
PubMed1997

Sendai virus efficiently infects cells via the asialoglycoprotein receptor and requires the presence of cleaved F0 precursor proteins for this alternative route of cell entry.

Biochemical evidence suggests that the asialoglycoprotein receptor (ASGP-R) can be used as an alternative receptor for a temperature-sensitive Sendai virus (SV) mutant. We now have investigated this possible alternative route of infection for SV wild-type (SV-wt) strain Fushimi by using a pair of cell lines which differ only with regard to ASGP-R expression. Infection studies after enzymatic destruction of conventional sialic acid-containing SV receptors (SA-R) revealed that only ASGP-R-expressing cells could be infected by SV-wt. This alternative route of cell entry could be completely blocked by incubation of cells with ASGP-R-specific antibodies prior to infection. Furthermore, cleavage of SV-F0 precursor protein into the subunits F1 and F2 was necessary to establish infection via ASGP-R, suggesting a fusion-mediated cell entry after binding of SV-wt to the ASGP-R on host cells. Interestingly, infection via ASGP-R was found to be nearly as efficient as infection via conventional sialic acid-containing SV receptors. A possible physiological role of the ASGP-R-mediated route of SV infection is discussed.

3T3 Cells↗
PubMed1997

[Argon plasma coagulation in endoscopic therapy of CREST syndrome associated upper gastrointestinal hemorrhage].

We report on the case of a 55-year-old patient suffering from progressive systemic sclerosis (PSS). The patient was sent to our department when clinical symptoms of an acute upper gastrointestinal hemorrhage occurred. Upper endoscopy showed a watermelon stomach and fresh blood in the stomach. The presence of teleangiectasias in the antrum could be proved histologically. Since the teleangiectasias found in the antrum were the only possible source of the hemorrhage three sessions of endoscopic argon plasma coagulation were performed. Macroscopically, a nearly complete disappearance of teleangiectasias could be achieved. After a follow-up of six months, there have been no clinical signs of another hemorrhage episode. This case shows that the existence of gastrointestinal teleangiectasias should be considered when chronic anemia or acute gastrointestinal hemorrhage occur in patients with PSS. Further it is demonstrated that even extended gastrointestinal teleangiectasias can be successfully treated by endoscopically performed argon plasma coagulation.

CREST Syndrome↗