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Biomedical subjects

M Stark

Publications and source records attributed to M Stark.

At least 55 records · Page 3Linked to original sources
PubMed1998

Phosphatidate phosphatase--a key enzyme in glycerolipid biosynthesis. Studies on the yeast enzyme.

Phosphatidate phosphatase is an important enzyme in glycerolipid biosynthesis, but difficult to purify. A purified preparation of N-ethylmaleimide-sensitive phosphatidate phosphatase from the yeast Saccharomyces cerevisiae was obtained by a five-step protocol, using chromatography on DE-53/DEAE FF, Affi-Gel Blue, hydroxyapatite, Mono-Q, and Superdex 200. A protease-deficient yeast strain gave preparations similar to those of the wild-type strain. In exclusion chromatography, the enzyme activity of all preparations eluted at approximately the same position as albumin. However, the behavior on SDS/PAGE differed considerably among preparations, suggesting a multimeric subunit structure or degradation during purification. A 35-kDa and a 40-kDa protein band which coincided with activity were found in all preparations. Glycerol in the buffers could be excluded without rapid loss of enzyme activity, and Tris could be substituted for ammonium bicarbonate, while at least 0.6% sodium cholate in the buffers was essential.

Electrophoresis, Polyacrylamide Gel↗
PubMed1998

Strong prognostic impact of tumor-associated urokinase-type plasminogen activator in completely resected adenocarcinoma of the esophagus.

The serine protease system has been shown to play an important role in the invasive potential of a variety of tumors. To date, however, there are little data about the expression of these proteases in esophageal carcinoma. To determine the level of expression and the significance of urokinase-type plasminogen activator (uPA) and its plasminogen activator inhibitor type 1 (PAI-1) in adenocarcinoma of the esophagus, we studied 54 tumor cases and a control group of normal gastric mucosa cases with ELISA using detergent-extracted samples. uPA and PAI-1 were significantly elevated as compared to control tissue by factors of 16 and 14, respectively. Median levels of both uPA and PAI-1 showed significant correlation with tumor pT, pN, and pM categories, whereas the presence of lymphatic invasion correlated only with the uPA content and tumor grade correlated only with PAI-1 content. Using maximally selected statistics, a cutoff value was found for uPA (2.85 ng/mg protein) but not for PAI-1, which divided the study group into significantly poorer and better survival subgroups. By univariate analysis, depth of tumor invasion (pT), lymph node involvement (pN), number of involved lymph nodes, lymph node ratio, distant nodal metastases [pM1(Iym)], lymphatic invasion, and uPA showed significant correlations with patient survival. By multivariate analysis, uPA (first rank), pN, and pM (lym) were identified as independent prognostic factors, with relative risks of 8.4, 4.1, and 4.3, respectively. In a second survival analysis method, a prognostic model was developed using classification and regression trees analysis, in which a significant difference among three patient survival groups was distinguished using the variables "number of involved lymph nodes" and "uPA content." In summary, tumor uPA content as determined by ELISA appears to be a powerful, independent prognostic factor for survival in adenocarcinoma of the esophagus.

Adenocarcinoma↗
PubMed1998

Dose-effect relationship of idebenone in an experimental cerebral deficit model. Pilot study in healthy young volunteers with piracetam as reference drug.

Within a general cerebral deficit model--inspiratory hypoxia-the dose--effect relationship of idebenone (CAS 58186-27-9), an antioxidant, was studied with regard to selected electrophysiological and psychometric parameters. Seventeen healthy male volunteers (mean age = 32 years, mean BW = 75 kg) received three different oral medications: placebo, idebenone and piracetam (CAS 7491-74-9) as reference. The test drug idebenone was administered in five different dosages, ranging--in 60 mg steps--from 60 to 300 mg t.id. Piracetam was given at a dose level of 800 mg t.i.d. A strict dose-regimen was used in idebenone for safety reasons. Each dosage/medication--except idebenone 300 mg t.i.d.--was given for one week without washouts in between. On each 7th treatment day, pharmacodynamic assessments comprising electroretinography (ERG), auditory evoked potentials (AEP) and visual analogue scales (VAS) were run. Immediately after the phases with the lower dosages, the study was continued with the highest dosage of idebenone (300 mg t.i.d.) for a period of four weeks with pharmacodynamic assessments on the 7th, 14th and 28th day. In this pilot study, the target variable, the amplitude of the ERG b-wave indicated a definite antihypoxidotic effect after the highest dosage of idebenone. With 300 mg idebenone t.i.d., ERG b-wave amplitudes increased linearily with increasing duration of treatment. The 'central' AEP P2-amplitude demonstrated a different dose-effect relationship. AEP P2-amplitudes increased with increasing dosages of idebenone. The prolongation of treatment with 300 mg t.i.d. resulted in no further improvement of this parameter (ceiling effect). Subjective ratings (VAS) by the volunteers confirmed the results seen in electrophysiological variables. The findings, however, remain to be confirmed within an adequate double-blind, crossover study design.

Adult↗
PubMed1997

A multisite study of sexual orientation and injection drug use as predictors of HIV serostatus in out-of-treatment male drug users.

The risk groups of men who have sex with men and injection drug users (IDUs) together account for 90% of all male AIDS cases. The extent to which each risk behavior contributes to seroprevalence among IDUs has not been determined and is critical for intervention development. Analysis of data on sexual orientation, injection drug use, and HIV serostatus was undertaken in a multisite study of 3002 male drug injectors and crack smokers recruited for HIV prevention projects. Overall HIV seroprevalence was 8.4%; 57.1% for gay men, 25.4% for bisexual men, and 7.4% for heterosexuals (p = 0.001). Logistic regression analyses indicated being gay (OR = 24.08) and coming from an area where seroprevalence is high among IDUs (OR = 4.07) were the best predictors of serostatus. Ever having injected was significant only in interaction with moderate (OR = 3.09) or high (OR = 4.71) IDU seroprevalence areas. Among this multisite sample of drug users, being a gay drug user is the strongest predictor of serostatus. Drug injection is significant only in areas of moderate or high seroprevalence among injectors. This indicates the importance of targeted outreach and intervention efforts.

Adult↗
PubMed1997

The mouse atlas and graphical gene-expression database

The large amounts of gene-expression data on mouse development are now too extensive to be stored in any format other than that of a database. Furthermore, as this data is intrinsically graphical and as, in the early developmental stages at least, its boundaries do not map directly to those of anatomical tissues, the natural way to store it is in graphical format. We are therefore constructing a database able to handle such graphical gene-expression data by mapping it onto 3-D reconstructions of mouse embryos whose tissues have been delineated. This article reviews the progress that has been made in this project and describes its two major components, CD-ROMs of the 3-D reconstructions to be held on the user's computer and a gene-expression database that will be maintained at a host site, the two being linked over the internet by a complex Java-based interface for submitting data and querying the database.Copyright 1997 Academic Press Limited Copyright 1997Academic Press Limited

Journal Article↗
PubMed1997

Analysis of fused maxillary incisor dentition in p53-deficient exencephalic mice.

Out of a total of 21 exencephalic p53-deficient embryonic and newborn mice, 6 (28.6%) possessed fused maxillary incisor teeth. On histological analysis of the 5 examples seen on day 19.5 of gestation and newborn mice, 3 varieties were observed: an example of 'simple' fusion, 3 examples of simple fusion each of which contained a 'dens in dente' ('tooth within a tooth'), and a single example in which the fused teeth were associated with a median supernumerary incisor tooth which, while deeply indenting the labial surface of the fused teeth, was in all locations a completely separate unit. 3-D reconstructions of the fused teeth demonstrated that they were all of the fusio subtotalis variety. No gross abnormalities were observed in the other dentition in these mice. It is noted that in mice fused maxillary incisor teeth are relatively commonly associated with both hypervitaminosis A-induced and trypan blue-induced exencephaly. It is believed that the presence of dens in dente within fused maxillary incisor teeth has only once been reported in mice, and the association between fused maxillary incisor teeth and a median supernumerary incisor tooth has not previously been reported in this species.

Animals↗
PubMed1997

Familial nontoxic multinodular thyroid goiter locus maps to chromosome 14q but does not account for familial nonmedullary thyroid cancer.

Thyroid goiter is a common condition that is often associated with iodine deficiency. Familial forms of goiter in areas not known to feature iodine deficiency are much less common. We have performed a genomic search on a single large Canadian family with 18 cases of nontoxic multinodular goiter in which 2 individuals also had papillary lesions highly suggestive of papillary carcinoma. A locus on chromosome 14q (MNG1 [multinodular goiter 1]) has been identified, with a maximal two-point LOD score of 3.8 at D14S1030 and a multipoint LOD score of 4.88 at the same marker, defined by D14S1062 (upper boundary) and D14S267 (lower boundary). The gene encoding thyroid-stimulating hormone receptor (TSHR), which is located on chromosome 14q, is outside the linked region. To determine the role of this gene in familial nonmedullary thyroid cancer (NMTC), we studied 37 smaller pedigrees each containing at least two cases of NMTC. Analysis by both parametric and nonparametric methods indicates that only a very small proportion of familial NMTC (point estimate 0.001, support intervals 0-.6 under a dominant model) is attributable to MNG1.

Canada↗
PubMed1997

A multicentre evaluation of the CA 15-3 assay, CA 19-9 assay and CA 125 II assay on the Bayer Immuno 1 System.

The analytical performance of the tumour markers CA 15-3 assay, CA 19-9 assay and Ca 125 II assay on the Bayer Immuno I System was studied according to a revised version of the ECCLS guidelines (Haeckel R. In: Evaluation methods in laboratory medicine, Weinheim, VCH Verlag 1993:47-69) in a multicentre evaluation involving five laboratories. Determination of the 3 analytes generated more than 6000 data. On the Bayer Immuno I System, the imprecisions of the CA 15-3 assay, CA 19-9 assay and CA 125 II assay were better than those found for comparison methods. The median recovery over all five laboratories of system assigned values in control sera was within the 1-s range for the three tumour marker assays. No deviation of linearity could be detected experimentally for all assays. Results for patients' samples showed acceptable agreement between the Bayer Immuno 1 system and several different comparison methods in most cases. One exception was the CA 15-3 assay in comparison with the MCA assay from Roche Diagnostic Systems, where the large difference in values is due to the use of different antibodies and calibrators in the two assays. No carry-over effects could be detected. The selective Bayer Immuno 1 system is fully automated; its practicability was rated as high.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1996

Difficulties in the assay of phosphatidate phosphohydrolase activity. Influence of ionic strength, detergent, and selection of substrate.

In the present paper, problems in connection with assay of the activity of magnesium-dependent rat liver phosphatidate phosphohydrolase (PAP) are discussed. PAP activity is usually measured by following the production of diacylglycerol or inorganic phosphate from the substrate phosphatidate. These two methods may give widely different results due to a number of factors that may affect the assay. One such factor is the composition of the substrate. Higher apparent enzyme activity was observed with dioleoyl-phosphatidate than with dipalmitoyl-phosphatidate. This substrate-dependent difference in apparent PAP activity was 2-2.5-fold in the absence and 10-fold in the presence of Triton X-100, respectively. Triton X-100 reduced the activity as measured with the dipalmitoyl-phosphatidate substrate. In contrast, the activity of PAP as measured with dioleoyl-phosphatidate was stimulated by Triton X-100. The stimulatory effect of Triton was reduced or abolished when the ionic strength in the assay mixture was increased. Assays based on 32P-labeled substrate are rapid and sensitive. It is shown here that 33P can be used as an alternative. This radionuclide has a longer half-life and also emits particles with lower energy, thus posing less potential health hazards for the user.

Animals↗
PubMed1996

How can the bioavailability of timolol be enhanced? A pharmacokinetic pilot study of novel hydrogels.

BACKGROUND: Carbomerbased hydrogels with timolol maleate (T-Gel) were chosen to study the vehicle effect on ocular bioavailability. Pharmacokinetic profiles of T-Gel 0.05% (0.05% timolol), T-Gel 0.025% (0.025% timolol) and commercial timolol ophthalmic solution (TOS 0.1%; 0.1% timolol) were determined and compared. METHODS: A single dose was administered to rabbits' eyes. Timolol was determined by HPLC in aqueous humour, blood samples and washings of the ocular surface (as a measure of residence time). Sampling times were 0.5 h, 1 h and 4 h after instillation. RESULTS: Concentration versus time curves (AUC) of timolol in aqueous humour demonstrate no significant differences between TOS 0.1% and T-Gel 0.025% (P = 0.19), whereas the difference between T-Gel 0.05% and TOS 0.1% is significant (P = 0.006); the AUC ratio of T-Gel 0.05%:TOS 0.1%:T-Gel 0.025% was 2.14:1:0.87. Timolol blood levels were highest with TOS 0.1% at every time point. Peak levels occurred after 0.5 h with all test products; the ratio of peak levels (Cmax) for T-Gel 0.05%:TOS 0.1%:T-Gel 0.025% was 0.55:1:0.17. Timolol was detected in the washings up to 1 h after instillation of test products; the highest levels were observed after T-Gel 0.05%. CONCLUSION: The new vehicle obviously improves the bioavailability of topically applied timolol.

Administration, Topical↗
PubMed1996

Cloning and sequence of a region of Vibrio cholerae O139 Bengal and its use in PCR-based detection.

We isolated and characterized a Vibrio cholerae O139 Bengal-specific DNA region by arbitrary PCR. The fragment contains open reading frames encoding two potential glycosyltransferases possibly involved in capsular polysaccharide or lipopolysaccharide biosynthesis. In order to evaluate the possibility that this region could be used for the specific detection of V. cholerae O139 Bengal, a PCR system was established. The specificity and sensitivity of the PCR were investigated by analyzing 240 strains within the family Vibrionaceae and 178 stains of other gram-negative bacteria. All V. cholerae O139 Bengal strains tested were positive, and none of the 384 control strains were amplified. The sensitivity of the assay was 10(2) CFU/ml.

Amino Acid Sequence↗
PubMed1996

Immunomagnetic separation and solid-phase detection of Bordetella pertussis.

In the present study, novel solid-phase methods were used for both sample preparation and PCR detection of Bordetella pertussis. The sample preparation was performed by immunomagnetic separation with paramagnetic beads coated with polyclonal antibodies directed toward the surface antigens of the bacteria. The precoated immunobeads were directly used on nasopharyngeal aspirates to capture the bacteria on the solid support and were subsequently transferred to the PCR tube with no further manipulations. The region encompassing the pertussis toxin promoter was analyzed to allow direct discrimination between the three major Bordetella species (B. pertussis, B. parapertussis, and B. bronchiseptica). The resulting amplicons were captured on a second magnetic solid phase, allowing detection and restriction analysis of the target sequence. A colorimetric detection system based on a DNA binding fusion protein enabled the use of standardized enzyme-linked immunosorbent format tests both for the detection of Bordetella spp. and for species evaluation. When the optimized system was evaluated on 55 clinical aspirate samples, 21 of 22 (95%) culture-positive samples were positive by the system that we developed. In addition, two samples were positive by the PCR-based assay, while the culture assay was negative. The implications of these results are discussed.

Base Sequence↗
PubMed1996

Successful outcome of idiopathic nonimmune hydrops fetalis treated by maternal digoxin.

Nonimmune hydrops fetalis (NIHF), occurring in 1 in 2,500-3,000 live births has a reported mortality rate of 50-98%. A similar mortality rate for intrauterine death of fetuses with NIHF probably exists. Many fetal pathological entities have been implicated as causing the condition, but to date, treatment has only been found for cases of fetal tachycardia complicated with hydrops. During a routine ultrasonographic survey of a woman at 32 weeks of gestation, we detected a fetus with severe ascites. There was no apparent etiology, and although no tachycardia was evident, low dosage transplacental digoxin therapy was immediately initiated. The hydropic condition completely resolved within 17 days and at 39 weeks of gestation, a perfectly normal baby was born after a spontaneous and uneventful labor. This is the first report of successful treatment of idiopathic NIHF with maternal digoxin.

Administration, Oral↗
PubMed1995

Crystallization and preliminary X-ray diffraction studies of an a1/alpha 2/DNA ternary complex.

Crystals have been obtained of a ternary complex containing the yeast a1/alpha 2 homeodomain heterodimer bound to a 21-base pair DNA site containing two 5' overhanging bases at each end. The crystals are grown from cobaltic hexamine and form in space group P6(1) or P6(5) with a = b = 133 A, c = 45.4 A. Crystals that are flash-frozen at -179 degrees C diffract to 2.7 A along the c-axis and to 2.4 A in perpendicular directions. The crystals contain one protein-DNA complex in the crystallographic asymmetric unit.

Base Sequence↗