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Biomedical subjects

M Franz

Publications and source records attributed to M Franz.

At least 19 recordsLinked to original sources
PubMed2000

Effective "penetration depth" in the vortex state of a d-wave superconductor.

The temperature and the field dependence of the effective magnetic penetration depth (lambdaeff) in the vortex state of a d-wave superconductor, as measured by muon spin rotation (muSR) experiments, is calculated using a nonlocal London model. We show that at temperatures below [EQUATION: SEE TEXT], the linear T dependence of lambda-2eff crosses over to a T3 dependence. This could provide an explanation for the low temperature flattening of the lambda-2eff curve observed in a recent muSR experiment.

Journal Article↗
PubMed2000

Recombinant human granulocyte colony-stimulating factor after kidney transplantation: a retrospective analysis to evaluate the benefit or risk of immunostimulation.

BACKGROUND: Leukopenia due to immunosuppressive drugs represents a well-known complication in graft recipients, which might put patients at an increased risk for infections. In this study, recombinant human granulocyte colony-stimulating factor (rhG-CSF), a hematopoietic growth factor that selectively stimulates neutrophil colony formation and neutrophil cell differentiation, was tested for safety and efficacy. METHODS: We evaluated 30 episodes of leukopenia (<2000/mm3) in 19 kidney graft recipients treated with rhG-CSF. This cohort was compared with an age- and sex-matched historical control group without therapy. Peripheral and differential blood cell counts were analyzed, and the duration of leukopenia was estimated. Furthermore, the occurrence of infections associated with leukopenia was investigated. RESULTS: All patients responded to rhG-CSF therapy. Peripheral leukocyte counts increased from 1756+/-582 to a peak of 8723+/-3038/mm3 (P<0.0001). On the average, the peak was reached after 2.7 days (range 1 to 8). Furthermore, the effect was fairly persistent, because in 22 of 30 episodes leukocyte counts were within the normal range after 7 days. The elevation of total leukocytes was mainly due to a specific increase in neutrophil granulocytes from 1143+/-514 to 6895+/-1950/mm3 on the peak day (P<0.0001). Patients in the G-CSF group were leukopenic for a mean of 1.29+/-0.59 days, whereas in the control group leukopenia persisted for at least 7 days. Consequently, the rate of infections was significantly higher (P<0.045) in nontreated patients. CONCLUSION: rhG-CSF was safe and effective in leukopenic kidney graft recipients. Leukopenic episodes in treated patients were significantly shorter, and infections occurred at a significantly lower rate. No evidence was found that rhG-CSF therapy might trigger rejection episodes, and no side effects were observed.

Antilymphocyte Serum↗
PubMed2000

Computer-controlled impalement of cells in retinal wholemounts visualized by infrared CCD imaging on an inverted microscope.

We present a computer-guided microelectrode positioning system that is routinely used in our laboratory for intracellular electrophysiology and functional staining of retinal neurons. Wholemount preparations of isolated retina are kept in a superfusion chamber on the stage of an inverted microscope. Cells and layers of the retina are visualized by Nomarski interference contrast using infrared light in combination with a CCD camera system. After five-point calibration has been performed the electrode can be guided to any point inside the calibrated volume without moving the retina. Electrode deviations from target cells can be corrected by the software further improving the precision of this system. The good visibility of cells avoids prelabeling with fluorescent dyes and makes it possible to work under completely dark adapted conditions.

Animals↗
PubMed2000

Quasiparticles in the vortex lattice of unconventional superconductors: bloch waves or landau levels?

A novel singular gauge transformation is developed for quasiparticles in the mixed state of a strongly type-II superconductor which permits a full solution of the problem at low and intermediate fields, H(c1)<B<<H(c2). For a periodic vortex lattice the natural low-energy quasiparticle states are Bloch waves rather than Landau levels discussed in the recent literature. The new representation elucidates the physics considerably and provides fresh insights into the spectral properties of such systems.

Journal Article↗
PubMed2000

Release measurements for materials out of controlled areas

Large amounts of dismantled materials from nuclear power plants show such a weak level of radioactivity that they could be released after decision measurements. Till some years ago, the decision measurements taken for the release were based only on determining the mass-specific activity of samples by means of gamma spectrometry and/or manual sequential measurements of the surface activity with large area gas flow counters. The choice of an appropriate measuring method, the layout of the release measurement facility (RMF), the way of preparing the material and the development of smart release procedures are very important for a large throughput and an economic performance of the release process. NIS and RADOS have developed RMF based on gross gamma activity. The NIS-RMFs have been applied for the last 10 years for decision measurements in different operated but also in dismantled nuclear power plants. Together with RMFs from RADOS, more than 12,000 Mg of various types of materials have been measured up to now with this method in Germany.

Journal Article↗
PubMed2000

Sertoli cells as a target for reproductive hazards.

Male fertility can be impaired by various toxicants. Some of them are known to target mainly Sertoli cells, which play an essential role in spermatogenesis. In this study, the in vitro response of immature rat Sertoli cells to various environmental pollutants, including pesticides, oestrogenic compounds and heavy metals, has been investigated. Mitochondrial dehydrogenase activity has been used to measure Sertoli cell viability, while production of lactate and secretion of inhibin B have been used as general and specific cell markers. Sertoli cell viability was not affected after 24-h exposure to lindane, DDT, ethinyloestradiol or bisphenol A in the concentration range analysed (up to 100, 25 or 50 microM, respectively). In contrast, mercury(II) (EC50 = 31 microM) and cisplatin (15% decrease in viability at 100 microM) induced some cytotoxic effect. With the exception of the pesticide DDT, all chemicals investigated induced a significant dose-dependent increase in lactate production after 24-h exposure to Sertoli cells. Owing to the cytotoxic effect of mercury(II), lactate levels dropped again at concentrations above 20 microM. The pesticide lindane (but not DDT) and both oestrogens significantly increased the production of the Sertoli cell specific hormone inhibin B without affecting cell viability. In contrast, the heavy metals mercury(II) and platinum(II) markedly decreased inhibin B levels. This sharp decrease was already significant at metal concentrations that reduced Sertoli cell viability only moderately (10-15%). In conclusion, the secretion of lactate and inhibin B by immature rat Sertoli cells seems to be a useful and sensitive marker with which to explore potential Sertoli cell toxicants.

Animals↗
PubMed2000

N-terminal fragments of the proatrial natriuretic peptide in patients before and after hemodialysis treatment.

BACKGROUND: Fragments derived from the prohormone of alpha-human atrial natriuretic peptide (alpha-ANP) in patients with cardiac failure are more closely related to the disease state than intact alpha-ANP. METHODS: Specific immunoassays have been developed to detect proANP 1-30, proANP 31-67, and proANP 1-98. Plasma concentrations of these fragments were determined in 122 hemodialysis patients with and without cardiac dysfunction, with and without hypertension, as well as with and without dialysis-associated hypotensive episodes either before or after a regularly scheduled hemodialysis session. The effects of different dialyzer membranes were also evaluated. The results of these assays along with other markers of volume regulation such as alpha-ANP and cyclic 3',5' guanosine monophosphate (cGMP) were compared with those of healthy controls. RESULTS: Predialytic and postdialytic plasma concentrations of the proANP fragments were markedly higher in uremic patients than in controls (98-fold for proANP 1-98, 56-fold for proANP 31-67, and 35-fold for proANP 1-30). All proANP fragments, alpha-ANP, and cGMP decreased during hemodialysis. A strong linear correlation was found between predialytic and postdialytic plasma levels. There was no correlation, however, with the amount of fluid removed during hemodialysis. Patients with altered left ventricular hemodynamics displayed significantly higher plasma concentrations of all proANP fragments and alpha-ANP, but not cGMP, than patients with normal cardiac function. Hemodialysis patients with moderate or severe hypertension had higher concentrations of proANP fragments, alpha-ANP, and cGMP than patients with normal blood pressure or patients with only mild hypertension. There was no significant difference in circulating levels of proANP peptides, alpha-ANP, and cGMP between patients with and without frequent dialysis-associated hypotensive episodes. Cellulose-triacetate dialyzers reduced plasma levels of proANP 1-30, proANP 31-67, and proANP 1-98 significantly more than polysulfone dialyzers, but alpha-ANP and cGMP levels were not different. CONCLUSIONS: Circulating alpha-ANP and proANP fragments are influenced by a variety of factors such as end-stage renal disease, hemodialysis treatment, dialyzer membrane material, cardiac dysfunction, and hypertension. Therefore, these are not useful markers to accurately estimate volume status in hemodialysis patients.

Adult↗
PubMed2000

Expression of HSV-TK suicide gene in primary T lymphocytes: the dog as a preclinical model.

Expression of suicide genes (e.g. herpes simplex virus thymidine kinase,HSV-TK) in T cells is an appealing approach to regulate graft-versus-host disease in adoptive immunotherapy. Here we report the optimization of retroviral infection of canine T cells. Canine T cells were stimulated either with phytohemagglutinin (PHA, 2 microg/ml) for 24-72 hours or with 100 U/ml interleukin-2 for seven days. Stimulated cells were co-cultivated with irradiated virus-producing cells. Transduction efficiencies ranged from 4% to 45% using PG13, a gibbon ape leukemia virus envelope (env) pseudotyped packaging cell line. Infection of cells with GPenvAM12, expressing the amphotropic Moloney murine leukemia virus env, did not yield a satisfactory percentage of transduced cells. Enrichment of transduced cells was performed using immunoselection, and gave a purity of up to 98%. Transfusion of 1 x 10(6) transduced cells per kilogram body weight showed that transduced cells could convert mixed chimerism to 100% and transfer immunity to a specific antigen. Transduced cells were repeatedly detected in peripheral blood and bone marrow by polymerase chain reaction with primers specific for the HSV-TK gene. We have demonstrated the feasibility of using the canine model to study gene therapy as a preclinical model.

Animals↗
PubMed2000

A prospective study of dietary glycemic load, carbohydrate intake, and risk of coronary heart disease in US women.

BACKGROUND: Little is known about the effects of the amount and type of carbohydrates on risk of coronary heart disease (CHD). OBJECTIVE: The objective of this study was to prospectively evaluate the relations of the amount and type of carbohydrates with risk of CHD. DESIGN: A cohort of 75521 women aged 38-63 y with no previous diagnosis of diabetes mellitus, myocardial infarction, angina, stroke, or other cardiovascular diseases in 1984 was followed for 10 y. Each participant's dietary glycemic load was calculated as a function of glycemic index, carbohydrate content, and frequency of intake of individual foods reported on a validated food-frequency questionnaire at baseline. All dietary variables were updated in 1986 and 1990. RESULTS: During 10 y of follow-up (729472 person-years), 761 cases of CHD (208 fatal and 553 nonfatal) were documented. Dietary glycemic load was directly associated with risk of CHD after adjustment for age, smoking status, total energy intake, and other coronary disease risk factors. The relative risks from the lowest to highest quintiles of glycemic load were 1.00, 1.01, 1. 25, 1.51, and 1.98 (95% CI: 1.41, 2.77 for the highest quintile; P for trend < 0.0001). Carbohydrate classified by glycemic index, as opposed to its traditional classification as either simple or complex, was a better predictor of CHD risk. The association between dietary glycemic load and CHD risk was most evident among women with body weights above average ¿ie, body mass index (in kg/m(2)) >/= 23. CONCLUSION: These epidemiologic data suggest that a high dietary glycemic load from refined carbohydrates increases the risk of CHD, independent of known coronary disease risk factors.

Adult↗
PubMed2000

American College of Sports Medicine position stand. Exercise and type 2 diabetes.

Physical activity, including appropriate endurance and resistance training, is a major therapeutic modality for type 2 diabetes. Unfortunately, too often physical activity is an underutilized therapy. Favorable changes in glucose tolerance and insulin sensitivity usually deteriorate within 72 h of the last exercise session: consequently, regular physical activity is imperative to sustain glucose-lowering effects and improved insulin sensitivity. Individuals with type 2 diabetes should strive to achieve a minimum cumulative total of 1,000 kcal x wk(-1) from physical activities. Those with type 2 diabetes generally have a lower level of fitness (VO2max) than nondiabetic individuals. and therefore exercise intensity should be at a comfortable level (RPE 10-12) in the initial periods of training and should progress cautiously as tolerance for activity improves. Resistance training has the potential to improve muscle strength and endurance, enhance flexibility and body composition, decrease risk factors for cardiovascular disease, and result in improved glucose tolerance and insulin sensitivity. Modifications to exercise type and/or intensity may be necessary for those who have complications of diabetes. Individuals with type 2 diabetes may develop autonomic neuropathy, which affects the heart rate response to exercise, and as a result, ratings of perceived exertion rather than heart rate may need to be used for moderating intensity of physical activity. Although walking may be the most convenient low-impact mode, some persons, because of peripheral neuropathy and/or foot problems, may need to do non-weight-bearing activities. Outcome expectations may contribute significantly to motivation to begin and maintain an exercise program. Interventions designed to encourage adoption of an exercise regimen must be responsive to the individual's current stage of readiness and focus efforts on moving the individual through the various "stages of change."

Cardiovascular Diseases↗
PubMed1999

Ultrasound measurements of the diameter of the fetal trachea, larynx and pharynx throughout gestation applicability to prenatal diagnosis of obstructive anomalies of the upper respiratory-digestive tract.

The purpose of the present study was to obtain normative data for the fetal upper respiratory tract by using high-resolution ultrasound techniques. Furthermore, we wanted to test the potential utility of the resulting normograms in diagnosing obstructive lesions of the trachea and oesophagus. Sonographic measurements of the diameters of the trachea, larynx and pharynx were obtained at well-defined planes from a prospective cross-sectional sample of 198 normal patients of known gestational age between 15 and 40 weeks' gestation. All measurements were performed during fetal apnea and in the absence of swallowing. The same measurements were also obtained from two cases with laryngeal atresia and three cases with oesophageal atresia, all of which were diagnosed prenatally. The data obtained were plotted on the constructed normograms. In normal fetuses approximately linear relationships existed between tracheal, laryngeal and pharyngeal diameter, on the one hand, and gestational age, on the other, with the measurements correlating significantly (p<0.0001) with gestational age. The linear regression coefficients (r2) for the tracheal, laryngeal and pharyngeal diameters were 0.66, 0.55 and 0.32, respectively. The 95 per cent prediction limits were also calculated. In fetuses with laryngeal atresia only the tracheal diameter was significantly higher as compared with that of normal fetuses. Data of the fetuses with oesophageal atresia showed that there were no changes in the upper airway anatomy. Our study provides normative data for the upper respiratory tract. In the prenatal diagnosis of obstructive neck anomalies the usefulness of the data would seem to be limited to those affecting the respiratory tract. Among the structures measured, only the trachea may prove to be of clinical significance.

Cross-Sectional Studies↗
PubMed1999

[Feelings without speech or speech without feelings? Further evidence for the decoupling hypothesis of alexithymia].

The theoretical background of the present investigation was the decoupling hypothesis of alexithymia, which presumes for alexithymic individuals a dissociation of psychophysiological indicators of emotion from verbal cognitive awareness of one's emotional state. To study alterations in reactivity to emotionally distressing stimuli in alexithymic individuals, 12 high-alexithymic and 14 low-alexithymic subjects (separated by TAS) out of a general sample of 54 were investigated. All subjects were exposed to cognitive (CPT) and affect inductive (film sequences) distress. During stimulus exposition electrodermal activity (spontaneous fluctuations) was recorded. After stimulus exposition the subjects assessed their emotional reaction towards the film sequences (DAS). Concerning electrodermal activity no differences were found between high and low alexithymics under cognitive distress. In any case a significant autonomous arousal was registered. However, only the low alexithymic subjects but not the high alexithymics showed a significant increase of spontaneous fluctuations as expression of autonomous arousal during presentation of affect inductive stimuli. The altered psychophysiological reactivity found in high alexithymics in contrast to low alexithymic subjects was revealed specifically for the processing of emotional qualified stimuli. However, there was no difference between the groups in cognitive self assessment of emotional response towards the film sequences. The findings are discussed with reference to neurophysiological and psychodynamic models and the decoupling hypothesis of alexithymia.

Adult↗
PubMed1999

A decade of spontaneous long-term course of psychogenic impairment in a community population sample.

BACKGROUND: Our epidemiological study demonstrates the spontaneous long-term course of predominantly psychosocially influenced ("psychogenic") disorders (neurotic spectrum disorders, personality disorders, stress reactions and somatoform disorders) in a representative community sample of the normal adult population of Mannheim, an industrial and university town in Germany. The natural spontaneous course of these disorders in a population sample over a long period remains largely unknown. METHOD: Beginning in 1979 (nt1 = 600) a random population sample was investigated three times over a mean period of approximately 11 years. The last follow-up study ended in 1994 (nt3 = 301). The follow-up sample was representative of the t1 sample. Psychodynamically trained and clinically experienced interviewers used a semi-structured interview and standardized clinical and psychometric instruments. Psychogenic impairment was assessed using a standardized expert rating (Impairment Score, IS). RESULTS: The mean sum-score of psychogenic impairment after 11 years exceeded the value at t1. The case rate (point prevalence, ICD diagnosis + clinical cut-off/IS) increased from 21.6% at t1 to 26.2% at t3 in the investigated follow-up sample. Intra-individual correlation of psychogenic impairment between t1 and t3 was high (r = 0.55). We found strong evidence for an unfavorable long-term course of psychogenic impairment and only a weak tendency (23.1%) for spontaneous remission of clinically relevant psychogenic impairment. Within a regression model clinical variables, childhood development conditions and personality traits at t1 predicted psychogenic impairment at t3. CONCLUSION: All clinical variables conclusively indicate an unfavorable spontaneous long-term course of psychogenic impairment. Together with the well-known high prevalence of psychogenic disorders in the normal population, this underlines the need for early therapeutic and preventive intervention.

Adult↗
PubMed1999

The fatigue strength of the interface between Ag-Pd alloy and hydrothermal ceramic.

OBJECTIVE: The purpose of this paper was to investigate the fatigue strength of a hydrothermal ceramic fused to Ag-Pd alloy. This study compared the values with those of other metal-ceramic systems previously reported by other authors. METHODS: This investigation was performed on 48 specimens made of Ag-Pd alloy frames (45 x 12 x 4 mm) on which the hydrothermal ceramic was fused (25 x 12 x 2 gmm). The specimens were divided into two groups. The first group of specimens was dynamically loaded immediately after casting and fusing, while the other group of specimens was thermocycled (1000 times at 0 degree C and 55 degrees C) before dynamic loading. The dynamic loading tests were carried out by using a modified three-point load method in a universal testing machine. RESULTS: The determined dynamic loading limit was up to 550 N for thermocycled, and up to 850 N for non-thermocycled specimens. These results are very respectable in comparison with other metal-ceramics. A statistically significant difference between maximal dynamic forces and number of loading cycles for thermocycled and non-thermocycled samples was determined. SIGNIFICANCE: From the data obtained in this study and current literature profiles, it is concluded that the tested metal-ceramic system is more durable than other metal-ceramic systems.

Hot Temperature↗