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Biomedical subjects

M Stark

Publications and source records attributed to M Stark.

At least 91 records · Page 5Linked to original sources
PubMed1994

MR diagnosis of head and neck tumors: comparison of contrast enhancement with triple-dose gadodiamide and standard-dose gadopentetate dimeglumine in the same patients.

OBJECTIVE: The purpose of this study was to compare the relative values of MR images obtained with a triple dose of gadodiamide and MR images obtained with the standard dose of gadopentetate dimeglumine for the detection and determination of the extent of tumors of the head and neck. MATERIALS AND METHODS: Forty-two patients with benign and malignant tumors of the head and neck were examined with contrast-enhanced MR imaging in a comparison of a triple dose of gadodiamide (0.3 mmol per kilogram body weight) and a standard dose (0.1 mmol per kilogram body weight) of gadopentetate dimeglumine. All patients underwent MR imaging with both doses of contrast material. Contrast-to-noise ratios and the percentage enhancement of normal and abnormal structures were calculated, and delineation of the lesion and the contrast between tumor and surrounding tissue were evaluated visually. RESULTS: Statistical analysis (Friedman test and Wilcoxon test) of the contrast-to-noise ratios between tumor and white matter, the percentage enhancement, and the visual assessment rating revealed a statistically significant superiority of the triple dose of gadodiamide over the standard dose of gadopentetate dimeglumine. Tumor/muscle contrast-to-noise ratios were not significantly different with the two doses. The detection rate for tumors was no better with the triple dose of gadodiamide than with the standard dose of gadopentetate dimeglumine. CONCLUSION: Use of the triple dose of gadodiamide results in a statistically significant improvement in the visual assessment rating, but it does not increase the number of tumors detected on MR images over the number detected with the standard dose of gadopentetate dimeglumine and does not appear to alter the differential diagnosis.

Contrast Media↗
PubMed1994

Microtiter assay for colorimetric detection of in vitro amplified Chlamydia trachomatis sequences.

An integrated diagnostic method for colorimetric detection of polymerase chain reaction (PCR) products in a microtitre format is described. The amplified material is labelled by using modified PCR primers introducing a biotin molecule and a lac operator handle. Positive samples are identified, after immobilization onto streptavidin-coated microtitre wells, using a reporter fusion protein consisting of the Escherichia coli lac repressor and beta-galactosidase. The analysis of the PCR products is thus, from a practical point of view, identical with the enzyme-linked immunosorbent assay (ELISA) using the enzymatic activity of beta-galactosidase. Here, we show that the assay can be used for rapid and simple detection of Chlamydia trachomatis in an automated format. The reported analysis of 90 urethral patient samples, using this microtitre assay, indicates that this technique is more sensitive and more specific than culture technique.

Base Sequence↗
PubMed1994

Endothelin and atrial natriuretic peptide in non-insulin-dependent diabetic versus nondiabetic patients on chronic hemodialysis.

Plasma levels of endothelin (ET) and atrial natriuretic peptide (ANP) are known to be elevated in patients on chronic hemodialysis. Since ET and ANP plasma levels are found to be raised in nonuremic diabetic versus nondiabetic subjects, we wanted to detect a possible difference in plasma levels of these hormones in diabetic versus nondiabetic patients who were on chronic renal replacement therapy. ET is a possible marker of increased vascular atherogenic activity. We measured plasma levels of ET and ANP pre- and posthemodialysis in 23 non-insulin-dependent (NIDDM) diabetic versus 23 nondiabetic patients who were matched according to age and time of day of hemodialysis, and who did not show clinical signs of overt cardiac decompensation. Mean plasma levels of ET and ANP did not differ in diabetic from nondiabetic patients, neither pre- nor postdialysis. In both patient groups, mean ET levels were twice the upper normal limit, did not change significantly pre- versus postdialysis, and did not correlate with blood pressure or with volume ultrafiltration during dialysis. Calcium channel blocker therapy was accompanied by a significant rise of ET pre- and postdialysis in nondiabetic patients but not in diabetic patients. In diabetic patients, ET plasma levels correlated positively with fructosamine levels as an indicator of short-term blood glucose control. Mean ANP plasma levels were about three times the upper normal limit and decreased significantly during dialysis, but this decrease correlated neither with volume ultrafiltration nor with blood pressure. In conclusion, we could not find a difference in plasma levels of ET and ANP for diabetic versus nondiabetic dialysis patients, but impaired short-term blood glucose control in diabetic and calcium channel blocker therapy in only nondiabetic dialysis patients showed concomitant increases in plasma ET levels and thus possibly different mechanisms of ET regulating pathways.

Aged↗
PubMed1994

Assessment and management of the care of children with nocturnal enuresis: guidelines for primary care.

Nocturnal enuresis is a common situation, which may or may not become pathological. The issue of nighttime control of urination is frequently raised in the primary care setting as parents deal with toilet training their children. All NPs who provide care to these families should be knowledgeable about the cause of enuresis and know when to intervene more aggressively. The majority of queries about enuresis will be successfully handled in the primary care setting with minimal intervention and sound anticipatory guidance, education, and support. This article describes the epidemiology, causes, assessment, and treatment for primary and secondary enuresis.

Child↗
PubMed1994

Segmental colonic gangrene: a previously unreported complication of adult hemolytic uremic syndrome.

Gastrointestinal manifestations, however slight, must be carefully observed in patients with HUS regardless of age. Both clinical and diagnostic evaluations must be weighed expeditiously to rule out any surgically correctable disease. Although most patients with HUS can be treated nonoperatively, a considerable mortality still exists, especially in adults. Once surgical intervention is required, overall mortality is still favorable, especially with early diagnosis and proper treatment.

Colectomy↗
PubMed1993

Semi-automated cervical smear pre-screening systems: an evaluation of the Cytoscan-110.

This paper reports a test of a system for provision of machine assistance in cervical cytology screening. The hypothesis tested was that if the results of examination by a screener of a small number of high-ploidy cells on specially prepared monolayers, automatically selected and presented by the system, were combined with machine measurement of cell and cell population characteristics, it would be possible to distinguish conditions requiring further action on the part of a cytology service from those in which the patient could safely be signed out. The system appeared broadly capable of this discrimination, with a false-negative error not significantly different (for the numbers tested) on CIN1 and more severe cases to that obtaining for routine screening of the parallel PAP smears, and also to results obtained by a panel of three observers. The machine system appeared to do better than other systems in selecting borderline cases for review, but this may have been an artefact of the method of evaluation used: all results were compared with a 'reference diagnosis', which was computed using statistical techniques to integrate diagnostic information from all available sources. The false-negative error-rate of the system amounted to 5% of high-grade cases, 17% of CIN1's and 29% of borderlines, but were not substantially different from the FN rates for other reporting systems on the same material. The proportion of negative cases referred back for full cytological diagnosis was 34%. Despite this high false-positive rate, the system is potentially cost-effective in use.

Automation↗
PubMed1992

[Jacuzzi-immersion for obstetric analgesia].

The effect of immersion in a jacuzzi in relieving labor pains, and on cervical dilatation was examined in 40 parturients. They were immersed in the jacuzzi during labor for an average of 25.5 minutes. Labor pains decreased during immersion by 2.59 degrees (scale of 0-10) compared with an average increase in labor pains of 0.25 degrees in 40 control women who were not immersed (p < 0.01). The cervical opening increased during immersion by an average of 1.5 cm in the test group, compared with 0.3 cm in the controls (p < 0.01). Immersion in a jacuzzi during labor is apparently associated with analgesia and accelerated cervical dilatation.

Analgesia, Obstetrical↗
PubMed1992

Analysis of segregation and expression of an identified mutation at the neurofibromatosis type 1 locus.

A previously identified complex mutation, affecting exon 28 of the neurofibromatosis type 1 gene, was employed for the analysis of the expression pattern in primary cultures of neurofibroma cells and melanocytes from a café-au-lait macule of the patient, respectively. Reverse transcription and subsequent polymerase chain reaction amplification of the segment carrying the mutation revealed that both alleles were expressed in both cell types analysed, thus excluding loss of heterozygosity in this particular instance. Segregation of the alleles of the intragenic Alu sequence length-polymorphism disclosed the paternal origin of the mutated allele. Detection of this mutation was also used for presymptomatic direct DNA diagnosis in the younger child of the patient.

Adult↗
PubMed1992

Retinoic acid increases CD15 expression in immortalized rat astrocytes.

We have studied the expression of the CD15 (3-fucosyl-N-acetyl-lactosamine) epitope on immortalized astroglial cells derived from embryonic (E 19/20) rat brain. Immortalization was achieved by pulse-treatment of primary culture with 5-azacytidine. Seventy-three permanent cell lines were established by repeated cell cloning. Clones expressing GFAP, A2B5, and vimentin were regarded as immature astrocytes. One of these clones expressing CD15 was selected for manipulation studies. Monoclonal antibody was used for immunocytochemical detection of CD15 epitope and in immunoblot analysis. CD15 expression was visible in about 20% of the cells and was associated with a special morphological appearance. In the presence of retinoic acid the proportion of CD15-positive cells increased in a time-dependent manner, reaching about 90% within four days. Again, this expression was associated with the formation of distinct morphological features, including immunoreactive perinuclear granula, tips of processes and contact sites. After treatment with neuraminidase, all cells showed CD15-positive immunoreaction, revealing the presence of the epitope masked by sialylation. Immunoblot patterns of glycoproteins from trypsinized and mechanically detached cell preparations suggest that proteins, carrying sialylated CD15, might represent intracellular precursors of extracellularly active molecules.

Animals↗
PubMed1992

Inactivation of the protein phosphatase 2A regulatory subunit A results in morphological and transcriptional defects in Saccharomyces cerevisiae.

We have determined that TPD3, a gene previously identified in a screen for mutants defective in tRNA biosynthesis, most likely encodes the A regulatory subunit of the major protein phosphatase 2A species in the yeast Saccharomyces cerevisiae. The predicted amino acid sequence of the product of TPD3 is highly homologous to the sequence of the mammalian A subunit of protein phosphatase 2A. In addition, antibodies raised against Tpd3p specifically precipitate a significant fraction of the protein phosphatase 2A activity in the cell, and extracts of tpd3 strains yield a different chromatographic profile of protein phosphatase 2A than do extracts of isogenic TPD3 strains. tpd3 deletion strains generally grow poorly and have at least two distinct phenotypes. At reduced temperatures, tpd3 strains appear to be defective in cytokinesis, since most cells become multibudded and multinucleate following a shift to 13 degrees C. This is similar to the phenotype obtained by overexpression of the protein phosphatase 2A catalytic subunit or by loss of CDC55, a gene that encodes a protein with homology to a second regulatory subunit of protein phosphatase 2A. At elevated temperatures, tpd3 strains are defective in transcription by RNA polymerase III. Consistent with this in vivo phenotype, extracts of tpd3 strains fail to support in vitro transcription of tRNA genes, a defect that can be reversed by addition of either purified RNA polymerase III or TFIIIB. These results reinforce the notion that protein phosphatase 2A affects a variety of biological processes in the cell and provide an initial identification of critical substrates for this phosphatase.

Amino Acid Sequence↗
PubMed1992

One-year clinical evaluation of an anterior composite resin.

An anterior composite resin was evaluated in a clinical study of 93 Class III and Class IV restorations placed in patients aged 12 to 50 years. The restorations were evaluated at baseline, 6 months, and 1 year. Sixty-four (79%) of the 81 restorations examined at the 1-year recall were unchanged. Marginal discoloration and changes in surface appearance and marginal adaptation accounted for most of the changes. All changes appeared in patients younger than 14 years, which may indicate that the patients had problems in oral hygiene. Replicas of randomly selected restorations showed smooth surfaces and well-sealed margins with a smooth transition from restoration to enamel. Some restorations showed marginal breakdown and a pitted irregular surface.

Adolescent↗
PubMed1991

cDNA cloning of mouse NKR-P1 and genetic linkage with LY-49. Identification of a natural killer cell gene complex on mouse chromosome 6.

NK cells lyse tumor cells and virally infected cells, but the molecular basis for this phenomenon has not been defined. A mAb specific for the rat cell surface molecule, NKR-P1, stimulates rat NK cell lytic activity and is reactive with all rat NK cells, suggesting that this molecule may play a significant role in NK cell function. We have previously described another NK cell-specific Ag, Ly-49, that belongs to a family of cross-hybridizing genes on distal mouse chromosome 6. The rat NKR-P1 Ag shares several features with the mouse Ly-49 Ag, including selective cell surface expression on NK cells, homology to the C-type lectins, expression as a type II integral membrane protein, and disulfide-linked homodimeric structure. To further examine the relationship of NKR-P1 to Ly-49, we have cloned the cDNA encoding a mouse homologue of NKR-P1 (mNKR-P1). The mouse and rat NKR-P1-deduced polypeptide sequences are highly conserved, suggesting a similar tertiary structure. By examination of DNA from informative recombinant inbred mice with Southern blot analysis, we have determined that mNKR-P1 is encoded by a distinct gene that is genetically linked to the Ly-49 locus, lying within 0.5 centi-Morgan (cM) of Ly-49. Although the deduced amino acid sequences of mNKR-P1 and Ly-49 reveal that these proteins are structurally similar, they are only 24% identical at the amino acid level and the cDNA sequences do not demonstrate significant nucleotide homology. Our studies suggest that we have identified a region on mouse chromosome 6 that includes distinct NK-specific genes that encode structurally related proteins (type II integral membrane proteins, C-type lectin super-gene family) but which demonstrate considerable heterogeneity. We have termed this genetic region the NK complex.

Amino Acid Sequence↗
PubMed1991

A small deletion and an adjacent base exchange in a potential stem-loop region of the neurofibromatosis 1 gene.

A single-strand conformational polymorphism found in the DNA of a patient with neurofibromatosis 1 (NF1) was shown to be caused by a deletion of a CCACC or CACCT sequence and an adjacent transversion, located about 500 base pairs downstream from the region that codes for a functional domain of the NF1 gene product. This mutation could also be detected in the patient and in his affected daughter by heteroduplex analysis. The deletion removes the proximal half of a small potential stem-loop and interrupts the reading frame in exon 1. A severely truncated protein with a grossly altered carboxy terminus lacking one third of its sequence is expected to be formed from the mutant allele.

Adult↗
PubMed1991

Radiation dosimetry by automatic image analysis of dicentric chromosomes.

A system for scoring dicentric chromosomes by image analysis comprised fully automatic location of mitotic cells, automatic retrieval, focus and digitization at high resolution, automatic rejection of nuclei and debris and detection and segmentation of chromosome clusters, automatic centromere location, and subsequent rapid interactive visual review of potential dicentric chromosomes to confirm positives and reject false positives. A calibration set of about 15,000 cells was used to establish the quadratic dose response for 60Co gamma-irradiation. The dose-response function parameters were established by a maximum likelihood technique, and confidence limits in the dose response and in the corresponding inverse curve, of estimated dose for observed dicentric frequency, were established by Monte Carlo techniques. The system was validated in a blind trial by analysing a test set comprising a total of about 8000 cells irradiated to 1 of 10 dose levels, and estimating the doses from the observed dicentric frequency. There was a close correspondence between the estimated and true doses. The overall sensitivity of the system in terms of the proportion of the total population of dicentrics present in the cells analysed that were detected by the system was measured to be about 40%. This implies that about 2.5 times more cells must be analysed by machine than by visual analysis. Taking this factor into account, the measured review time and false positive rates imply that analysis by the system of sufficient cells to provide the equivalent of a visual analysis of 500 cells would require about 1 h for operator review.

Cells, Cultured↗
PubMed1991

Immediate postoperative oral hydration after caesarean section.

A study was carried out to assess the effects of immediate postoperative oral rehydration in 51 unpremedicated women undergoing caesarean section under epidural anesthesia. The patients were randomly assigned to 2 groups: group 1 (n = 22)--fasting at least until 24 hours after the end of the operation, and group 2 (n = 29)--receiving immediate oral intake of fluids (water, tea or coffee with sugar) without limitation of quantity. The 2 groups were compared for the occurrence of postoperative nausea and vomiting, onset of peristalsis, rectal gas emission, first bowel movement, and possible complications. The results demonstrate no significant differences between the parturients who drank immediately postoperatively as compared to those in whom oral fluid intake was delayed for 24 hours or more. It is concluded that immediate postoperative oral rehydration had no harmful effect upon peristalsis post-caesarean section.

Adult↗
PubMed1991

Psychotic exacerbation attributed to low-dose bromocriptine treatment of galactorrhea and hyperprolactinemia.

Low-dose bromocriptine administered for antipsychotic drug-induced hyperprolactinemia and galactorrhea precipitated an acute psychotic state in a female patient. Discontinuation of the bromocriptine and increase in antipsychotic dosage resulted in complete remission. We advise caution in the use of bromocriptine especially in patients with a pre-existing psychiatric history and recommend monitoring for changes in mental status when bromocriptine is prescribed.

Acute Disease↗