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Biomedical subjects

S Klein

Publications and source records attributed to S Klein.

At least 37 records · Page 2Linked to original sources
PubMed1999

Systematic analysis of S. cerevisiae chromosome VIII genes.

To begin genome-wide functional analysis, we analysed the consequences of deleting each of the 265 genes of chromosome VIII of Saccharomyces cerevisiae. For 33% of the deletion strains a growth phenotype could be detected: 18% of the genes are essential for growth on complete glucose medium, and 15% grow significantly more slowly than the wild-type strain or exhibit a conditional phenotype when incubated under one of 20 different growth conditions. Two-thirds of the mutants that exhibit conditional phenotypes are pleiotropic; about one-third of the mutants exhibit only one phenotype. We also measured the level of expression directed by the promoter of each gene. About half of the promoters direct detectable transcription in rich glucose medium, and most of these exhibited only low or medium activity. Only 1% of the genes are expressed at about the same level as ACT1. The number of active promoters increased to 76% upon growth on a non-fermentable carbon source, and to 93% in minimal glucose medium. The majority of promoters fluctuated in strength, depending on the medium.

DNA Primers↗
PubMed1999

Functional analysis of 150 deletion mutants in Saccharomyces cerevisiae by a systematic approach.

In a systematic approach to the study of Saccharomyces cerevisiae genes of unknown function, 150 deletion mutants were constructed (1 double, 149 single mutants) and phenotypically analysed. Twenty percent of all genes examined were essential. The viable deletion mutants were subjected to 20 different test systems, ranging from high throughput to highly specific test systems. Phenotypes were obtained for two-thirds of the mutants tested. During the course of this investigation, mutants for 26 of the genes were described by others. For 18 of these the reported data were in accordance with our results. Surprisingly, for seven genes, additional, unexpected phenotypes were found in our tests. This suggests that the type of analysis presented here provides a more complete description of gene function.

Cell Differentiation↗
PubMed1999

Activity of O6-methylguanine DNA methyltransferase in mononuclear blood cells of formaldehyde-exposed medical students.

A recent study reported that exposure of student embalmers in Cincinnati to high concentrations of formaldehyde (2 mg/m3) reduced the activity of the DNA repair protein O6-methylguanine DNA methyltransferase (MGMT). Reduction in a DNA repair enzyme may strongly increase the cancer risk not only with respect to the repair-enzyme causing agent but with respect to all carcinogens causing lesions subject to repair by the enzyme in question. Thus, we examined whether formaldehyde exposure of 57 medical students during their anatomy course at two different Universities in Germany influenced MGMT activity in mononuclear blood cells. Mean formaldehyde exposure of 41 students was 0.2 +/- 0.05 mg/m3 for 6 h per week. MGMT activity was 133.2 +/- 14.9 fmol MGMT/10(6) cells before the beginning of the formaldehyde exposure, 131.1 +/- 15.8 fmol MGMT/10(6) cells after 50 days (P = 0.56) and 128.2 +/- 19.0 fmol MGMT/10(6) cells after 111 days of exposure (P = 0.92). Similarly, no significant influence of formaldehyde exposure was observed, when smoking habits, alcohol consumption, allergic disease and sex of students were considered. In addition no significant difference was obtained in MGMT activity between 16 students with mean formaldehyde exposure of 0.8 +/- 0.6 mg/m3 and students without formaldehyde exposure (n = 51; P = 0.37). In conclusion, exposure of the medical students in western Europe to formaldehyde did not decrease MGMT activity in mononuclear blood cells.

Adult↗
PubMed1999

The effects of the participation of patients with cancer in teaching communication skills to medical undergraduates: a randomised study with follow-up after 2 years.

The importance of good doctor-patient communication is widely recognised. The aims of this study were to evaluate the immediate effects of the participation of patients with cancer on the attitudes and skills of undergraduate medical students receiving an interview skills training programme, and to assess the effects of the participation of patients with cancer on the attitudes and interview performance of students 2 years later. It was hypothesised that the participation of cancer patients would have specific beneficial effects on attitudes and interview performance. Before participating in a 6-session interview methods course in third year, students were randomised to be taught with patients who had cancer (experimental group) or with patients with other diagnoses (control group). Before and after participating in the course, 233 students (94% response rate) completed an Attitudes Questionnaire. When they reached their fifth year, 54 students again completed the Attitudes Questionnaire and, in addition, made a video recording of an interview with a patient who had gynaecological cancer. These recordings were rated independently by two researchers using the Interview Rating Instrument. Immediately after the course, a number of differences were found between the two groups. For example, students in the experimental group were more likely to consider the ability to listen an extremely important characteristic of hospital doctors and to consider more strongly that trust is an essential part of the doctor-patient relationship. 2 years after the course, the ability of hospital doctors to communicate with patients, and the need for clinical decisions to reflect patients' wishes, were considered to be more important by students in the experimental group, although even 96% of controls felt both these issues were very or extremely important. As hypothesised, the experimental group had better ratings in terms of responding empathically, showing regard and concern for the patient, and assessing the impact of the symptoms on the patient's life. The participation of patients with cancer has beneficial and enduring effects on the attitudes and interview performance of medical undergraduates. Medical schools should consider how best patients with cancer can make an important contribution to communication skills training.

Clinical Competence↗
PubMed1999

IL-10 expression by CT26 colon carcinoma cells inhibits their malignant phenotype and induces a T cell-mediated tumor rejection in the context of a systemic Th2 response.

In spite of the evidence that IL-10 has Th1-immunosuppressive and anti-inflammatory effects, it has been shown that IL-10 may reduce the tumorigenic capacity of certain tumor cell types. In order to characterize the responses elicited by IL-10, we explored the effect of transducing murine CT26 colon carcinoma cells with a recombinant retrovirus expressing mIL-10. IL-10 gene transfer of CT26 cells had no effect on tumor cell growth on plastic surface but inhibited the anchorage-independent growth capacity of tumor cells and their metastatic potential as assessed by their invasive and migration ability. Expression of IL-10 also elicited an antitumor immune response involving both CD4+ and CD8+ T cells. Assessment of the immune status of the animals demonstrated that mice injected with CT26-IL10 cells showed prevalence of a systemic and tumor-specific Th2 response. Spleen cells obtained from these mice showed an increased production of IL-4 and no changes in IFNgamma levels, characteristic of a Th2 response. These results demonstrate that IL-10 affects CT26 tumor cell growth by both inhibiting the malignant phenotype and by recruiting and activating a T cell-mediated antitumor response. This T cell response occurs in the context of a shift towards a Th2 response.

Analysis of Variance↗
PubMed1999

A multicentre evaluation of the laser assisted ratio analyser (LARA): a novel device for measurement of 13CO2 in the 13C-urea breath test for the detection of Helicobacter pylori infection.

BACKGROUND: The laser assisted ratio analyser (LARA) was developed as a novel device to measure 13CO2 in the urea breath test for the detection of H. pylori infection. The analyser was tested in a prospective multicentre study in 444 patients in North America (Phase 1) followed by second study involving 160 patients (Phase 2). METHODS: Patients undergoing endoscopy for clinical indications had antral and gastric biopsies taken for histological examination, culture and CLO test. One hour after endoscopy, a baseline breath sample was obtained, 100 mg of 13C-urea were ingested and breath samples were obtained at 30 and 60 min post ingestion. Data obtained with the LARA were compared with the results of culture, rapid urease testing and central pathology in two different combinations {reference standards}. The study was conducted in two phases: in Phase 2, a modification was made to the LARA that improved the removal of water vapour from the breath sample. RESULTS: In Phase I, data from 331 patients were analysed using a cut off of (delta) 7.8 +/- 0.8, the sensitivity of the method was 91.7% and the specificity was 86.5%, using the reference standard of 2 of 3 tests (CLO, culture or histology) being positive. Positive and negative predictive values were, respectively, 85.2% and 92.5%. In Phase 2 of the study, 160 patients were enrolled and 141 patients were analysed using the same standards. We used the same reference standards but with a cut off of (delta) 6.1 +/- 0.6. The sensitivity and specificity increased to 96.8% and 98.6%, respectively. Positive and negative predictive values were, respectively, 98.4% and 97.3%. The detection rates for H. pylori were similar in patients with peptic ulcer or H. pylori associated gastritis. CONCLUSIONS: The LARA provides an accurate non-invasive means of detecting 13CO2 in the 13C-urea breath test for H. pylori in a multicentre clinical environment that compares well with invasive 'gold standard' methods.

Adolescent↗
PubMed1999

Regional leptin kinetics in humans.

BACKGROUND: Leptin is known to be cleared by the kidney, a tissue with substantial leptin receptor mRNA expression; however, lung, liver, and muscle tissues also express leptin receptor messenger RNA and it is not known whether these tissues also clear leptin from the circulation. OBJECTIVE: This study was conducted to determine whether net leptin clearance takes place in the pulmonary, splanchnic, and leg tissue beds to a similar extent as in the kidney. DESIGN: Plasma leptin concentrations were measured in blood entering and exiting the renal bed, pulmonary bed, splanchnic bed, and leg in 4 groups of subjects. Regional plasma flow was measured in 3 of the 4 groups. RESULTS: Renal leptin uptake was substantial, whereas no net uptake of leptin by the splanchnic or pulmonary vascular beds was detected; leg tissue was a net leptin producer. Net leptin release by leg tissue, relative to leg adipose tissue mass, was comparable with that reported previously for abdominal subcutaneous adipose tissue. CONCLUSION: These results confirm that the kidney is a significant site of leptin clearance in humans, whereas pulmonary and splanchnic beds are not.

Absorptiometry, Photon↗
PubMed1999

Effect of short-term fasting on lipid kinetics in lean and obese women.

We evaluated whole body and regional adipose tissue lipid kinetics and norepinephrine (NE) spillover during brief fasting in six lean [body mass index (BMI) 21 +/- 1 kg/m2] and six upper-body obese (UBO; BMI 36 +/- 1 kg/m2) women. At 14 h of fasting, abdominal adipose tissue glycerol and free fatty acid (FFA) release rates were lower (P = 0.07), but whole body glycerol and FFA rates of appearance (Ra) were greater (P < 0.05) in obese than in lean subjects. At 22 h of fasting, glycerol and FFA Ra increased less in obese (19.8 +/- 7.0 and 87.1 +/- 30.3 micromol/min, respectively) than in lean (44.2 +/- 6.6 and 137.4 +/- 30.4 micromol/min, respectively; P < 0.05) women. The percent increase in glycerol Ra correlated closely with the percent decline in plasma insulin in both groups (r2 = 0.85; P < 0.05). Whole body NE spillover declined in lean (P < 0.05) but not obese subjects with continued fasting, whereas regional adipose tissue NE spillover did not change in either group. We conclude that, compared with lean women, in UBO women 1) basal adipose tissue lipolysis is lower, but whole body lipid kinetics is higher because of their greater fat mass; 2) the increase in lipolysis during fasting is blunted because of an attenuated decline in circulating insulin; and 3) downregulation of whole body sympathetic nervous system activity is impaired during fasting.

Adipose Tissue↗
PubMed1999

Endurance exercise training does not alter lipolytic or adipose tissue blood flow sensitivity to epinephrine.

We evaluated the relationship between lipolysis and adipose tissue blood flow (ATBF) in response to epinephrine and the effect of endurance exercise training on these responses. Five healthy untrained men underwent a four-stage incremental epinephrine infusion (0.00125, 0.005, 0.0125, and 0.025 microgram. kg fat free mass(-1). min(-1)) plus hormonal clamp before and after 16 wk of cycle ergometry exercise training. Whole body glycerol and free fatty acid (FFA) rates of appearance (R(a)) in plasma were determined by stable isotope methodology, and ATBF was assessed by (133)Xe clearance. After each training session, subjects were fed the approximate number of calories expended during exercise to prevent changes in body weight. Glycerol R(a), FFA R(a), and ATBF increased when plasma epinephrine concentration reached 0.8 nM, but at plasma epinephrine concentrations >1.6 nM ATBF plateaued, whereas lipolysis continued to increase. Exercise training increased peak oxygen uptake by 24 +/- 7% (2.9 +/- 0.2 vs. 3.6 +/- 0.1 l/min; P < 0. 05) but did not alter body weight [70.5 +/- 3.8 vs. 72.0 +/- 3.8 kg; P = nonsignificant (NS)] or percent body fat (18.4 +/- 1.6 vs. 17.8 +/- 1.9%; P = NS). Lipolytic and ATBF responses to epinephrine were also the same before and after training. We conclude that the lipolytic and ATBF responses to epinephrine are coordinated when plasma epinephrine concentration is </=1.6 nM, but that at higher epinephrine concentrations, lipolysis continues to increase while ATBF remains constant. Endurance exercise training does not change lipolytic or ATBF sensitivity to epinephrine infusion in vivo during resting conditions.

Adipose Tissue↗
PubMed1999

A comparison of single fraction radiosurgery tumor control and toxicity in the treatment of basal and nonbasal meningiomas.

Between July 1993 and October 1997, 107 patients with 118 meningiomas were treated with Gamma Knife radiosurgery (GKRS). The most frequent site of tumor origin was the skull base (54%). The mean tumor diameter and volume were 2.5 cm and 9.4 cm3, respectively. The mean dose to the tumor periphery was 17 Gy, prescribed to a mean iso-dose of 47%. At a mean follow-up of 28 months, tumor control for basal and nonbasal meningiomas was 80%. Deteriorating peritumoral edema associated with symptoms was observed in 1 of 49 (2%) skull-base tumors and in 4 of 39 (10%) non-basal tumors, without associated tumor growth. (p=0.l5 and 0.234 respectively, z-test). Stereotactic radiosurgery can achieve acceptable tumor control with low morbidity in the treatment of most meningiomas. However, when the tumor is nonbasal, the potential morbidity from peritumoral edema should be recognized and other treatment options considered, such as adjuvant surgery, partial fractionated irradiation or stereotactic radiotherapy.

Adolescent↗
PubMed1999

[Sexual violence in the reality of life in mentally handicapped young girls and women--results of a research project].

Subject of the study is the situation of 12- to 25-year-old girls and women from Berlin with a mental handicap who have experienced sexualised violence. 367 residential institutions of the Behindertenhilfe Berlin (aid for the handicapped) as well as 15 selected advice and consultancy facilities with amongst others a range of offers on problems of sexual violence. The return from the residencies was 68.7%. The gained individual data for the first time show the belonging to a sex for the residents. The group that was relevant for the study--altogether 147 girls and young women--was cared for in 31 institutions. The heads of the institutions provided information about more than 116 of these inhabitants. Every third to fourth resident (32 out of 116) was concerned by sexualised violence. This high extend of experience of sexualised violence in mentally handicapped female residents is directly opposed to an utterly insufficient psychosocial care situation. On one side the access to the questioned advice and consultancy centres is considerably limited for this clientele. Furthermore, heads of institutions of the Behindertenhilfe rather fall back on experts with medical-psychiatric knowledge, but not necessarily with knowledge of the handling of problems of sexual violence. Suggestions for the necessary improvement of the care situation of concerned girls and women with a mental handicap are being made.

Adolescent↗
PubMed1999

Validation of a new procedure to determine plasma fatty acid concentration and isotopic enrichment.

Assessment of free fatty acid (FFA) concentration and isotopic enrichment is useful for studies of FFA kinetics in vivo. A new procedure to recover the major FFA from plasma for concentration and isotopic enrichment measurements is described and validated. The procedure involves extraction of plasma lipids with hexane, methylation with iodomethane (CH(3)I) to form fatty acid methyl esters (FAME), and subsequent purification of FAME by solid phase extraction (SPE) chromatography. The new method was compared with a traditional method using thin-layer chromatography (TLC) to recover plasma FFA, with subsequent methylation by BF(3)/methanol. The TLC method was found to be less reliable than the new CH(3)I method because of contamination with extraneous fatty acids, chemical fractionation of FFA species, and incomplete recovery of FFA associated with TLC. In contrast, the CH(3)I/SPE method was free of contamination, did not exhibit chemical fractionation, and had higher recovery. The iodomethane reaction was specific for free fatty acids; no FAME were formed when esterified fatty acids (triglycerides, cholesteryl esters, phospholipids) were subjected to the methylation reaction. We conclude that the CH(3)I/SPE method provides rapid and convenient recovery of plasma fatty acids for quantification or GC/MS analysis as methyl esters, and is not subject to the problems of contamination, reduced recovery, and chemical fractionation associated with recovery of FFA by TLC.

Chromatography↗
PubMed1998

Frequent nitric oxide synthase-2 expression in human colon adenomas: implication for tumor angiogenesis and colon cancer progression.

An increased expression of nitric oxide synthase (NOS) has been observed in human colon carcinoma cell lines as well as in human gynecological, breast, and central nervous system tumors. This observation suggests a pathobiological role of tumor-associated NO production. Hence, we investigated NOS expression in human colon cancer in respect to tumor staging, NOS-expressing cell type(s), nitrotyrosine formation, inflammation, and vascular endothelial growth factor expression. Ca2+-dependent NOS activity was found in normal colon and in tumors but was significantly decreased in adenomas (P < 0.001) and carcinomas (Dukes' stages A-D: P < 0.002). Ca2+-independent NOS activity, indicating inducible NOS (NOS2), is markedly expressed in approximately 60% of human colon adenomas (P < 0.001 versus normal tissues) and in 20-25% of colon carcinomas (P < 0.01 versus normal tissues). Only low levels were found in the surrounding normal tissue. NOS2 activity decreased with increasing tumor stage (Dukes' A-D) and was lowest in colon metastases to liver and lung. NOS2 was detected in tissue mononuclear cells (TMCs), endothelium, and tumor epithelium. There was a statistically significant correlation between NOS2 enzymatic activity and the level of NOS2 protein detected by immunohistochemistry (P < 0.01). Western blot analysis of tumor extracts with Ca2+-independent NOS activity showed up to three distinct NOS2 protein bands at Mr 125,000-Mr 138,000. The same protein bands were heavily tyrosine-phosphorylated in some tumor tissues. TMCs, but not the tumor epithelium, were immunopositive using a polyclonal anti-nitrotyrosine antibody. However, only a subset of the NOS2-expressing TMCs stained positively for 3-nitrotyrosine, which is a marker for peroxynitrite formation. Furthermore, vascular endothelial growth factor expression was detected in adenomas expressing NOS2. These data are consistent with the hypothesis that excessive NO production by NOS2 may contribute to the pathogenesis of colon cancer progression at the transition of colon adenoma to carcinoma in situ.

Adenoma↗
PubMed1998

[Success and failure in laparoscopic "gastric banding". A report of 3 years experience].

During 3 years, the adjustable gastric band (AGSB) was laparoscopically implanted in 224 of 873 patients with morbid obesity. The operation was done by 7 surgeons. Problems arising from the operative technique are: early pouch dilatation, gastric slippage, gastric perforation, penetration of the band, port infection, penetration of the port, defect of the band catheter. These can be avoided by care and increasing experience. The late pouch dilatation and the insufficient loss of excess weight arise from the unsatisfactory compliance of the patient. Critical selection of patients is necessary. Total morbidity in this seria was 19%, the letality 0.4% and the average excess weight loss within 2 years was 50 +/- 28%. The results may be improved by restrictive selection of patients and great operative routine.

Adult↗
PubMed1998

Metabolic alteration in patients with cancer: nutritional implications.

During the past 20 years, efforts have been made to elucidate the metabolic changes observed in patients with cancer by using stable and radioactive isotopic tracers. These metabolic changes in patients with cancer may be similar to those in other stress conditions, in which glucose production and utilization, lipolysis and free fatty acid flux, and net protein catabolism are increased. Stress hormones, such as glucagon and catecholamines, and certain cytokines may be responsible for these metabolic changes. Although it has been shown that cachexia in patients with cancer signals a poor prognosis, efforts to improve the clinical outcomes with nutritional support have been disappointing. The failure of cancer patients to respond to nutritional support may be related to an alteration in the intermediate metabolism. Therefore, further research evaluating the metabolic abnormalities associated with cancer may lead to more effective nutritional therapies.

Cachexia↗
PubMed1998

Improved accuracy and precision of gas chromatography/mass spectrometry measurements for metabolic tracers.

The use of stable-isotope tracer methodology to study substrate metabolic kinetics requires accurate measurement of the tracer to tracee ratio (TTR), often by gas chromatography/mass spectrometry (GC/MS). Many approaches for measurement of the TTR by GC/MS do not use standards of known isotopic enrichment to control for variability in instrument response. In addition, most GC/MS applications exhibit some degree of concentration dependency whereby the measured ion abundance ratio varies with the quantity of sample analyzed, thereby placing a limitation on the accuracy of isotopic enrichment standard curves unless the quantities of standards and samples analyzed are closely matched. We document the degree to which day-to-day variability can affect the instrument response for several GC/MS analyses of metabolic tracers when isotopic enrichment standards are not used to control for variable instrument response. Furthermore, we report a new approach that incorporates concentration dependencies within a standard curve to improve the accuracy and precision of TTR measurements over a range of sample quantities analyzed. The new approach was applied to plasma samples obtained from experimental protocols performed in human subjects with three commonly used tracers: 2H2-palmitate, 15N2-urea, and 13C-leucine. Variability in the day-to-day instrument response was 84% and 26% for 2H2-palmitate and 15N2-urea, respectively; in addition, up to 10% variability due to concentration dependency was noted for these applications. The new approach virtually eliminated these sources of variability. After controlling for concentration dependency, a threefold reduction in the standard error was noted when the enrichment of 13C-leucine measured by electron-impact (EI) ionization GC/MS was correlated against negative chemical ionization (NCI) GC/MS. These data demonstrate that our new approach decreases the errors in TTR determination caused by variations in instrument response and concentration dependency. This approach is generically applicable, and can improve the accuracy and precision of TTR determinations for most GC/MS analyses.

Adolescent↗