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Biomedical subjects

M Weck

Publications and source records attributed to M Weck.

At least 19 recordsLinked to original sources
PubMed2001

[Spinal meningioma as differential diagnosis of diabetic polyneuropathy].

HISTORY AND ADMISSION FINDINGS: A 70 year old woman had suffered from diabetes mellitus type 2 since she was 52. Three years before the surgery she had begun to experience weakness together with altered sensitivity in the right leg, which was regarded as having been caused by diabetic polyneuropathy. During the admission examination the level for algesia on the right-hand side was at about D 11, a distal paraparesis of the leg (3-4 degrees, Janda's classification), more intense on the right, hyperactive deep tendon reflexes, Babinski's reflex on both sides, and depressed abdominal cutaneous reflexes. The sensitivity to vibrations on the Malleolus medialis on both sides was 0/8. The patient could walk only with the help of a Rollator. INVESTIGATIONS: Over the three-year period following onset of symptoms the following tests were carried out: motor nerve conduction speeds of the N. tibialis and N. peronaeus, electromyogram of the N. tibialis anterior and the M. gastrocnemius, somatosensory evoked potentials (SSEP) of the N. tibialis, which indicated a lesion in the peripheral nerves or nerve roots. Cranial computed tomography (CCT), CT scan of the lumbar spine (L3-S1) and angiological investigation elicited no significant pathological findings. An MRI of the thoracal spine showed a vertebra-sized dorsal tumor pressing on the spinal cord from left to right. TREATMENT AND COURSE: By means of microsurgery the spinal tumor was completely removed. Suspected meningeoma was confirmed by histological analysis. During the post-surgical period, the incomplete paraplegia quickly regressed, and 7 weeks after the removal of the spinal meningeoma the patient was able to climb stairs. CONCLUSION: In case of slowly-developing paresis of the legs in diabetic patients, diabetic polyneuropathy should not be diagnosed without careful consideration, and rare spinal tumors should be considered as part of the differential diagnosis, especially if the blood glucose level is normal, and intensive physiotherapy brings no improvement in the patient's condition.

Aged↗
PubMed2001

Molecule-mimetic chemistry and mesoscale self-assembly.

Molecules are structured aggregates of atoms joined by chemical bonds; crystals are aggregates of molecules, interacting covalently or noncovalently. The work described in this Account uses molecules, crystals, and other forms of atomic/molecular matter to suggest principles that can be used in generating structured aggregates of millimeter-scale components, interacting through capillary interactions. The properties of these aggregates--that is, their "chemistry"--mimic aspects of the chemistry of molecules.

Crystallization↗
PubMed2001

Spontaneous baroreflex sensitivity and heart rate variability are not superior to classic autonomic testing in older patients with type 2 diabetes.

BACKGROUND: Early detection of cardiac autonomic neuropathy (CAN) permits individual risk stratification. Spontaneous heart rate variability (HRV) and baroreflex sensitivity (BRS) are suggested to be superior to classic autonomic testing in that they detect CAN earlier, with greater reliability, and do not require the patient's undue attention. METHODS: To test that hypothesis, we studied 53 diabetic patients (mean age, 55 years) and 38 age-matched healthy control subjects (HC). Subjects underwent deep breathing, Valsalva maneuver, and orthostatic testing. Each abnormal test was counted as 1 point. A change in systolic blood pressure during standing of more than 10 mm Hg was graded with a single point; a decrease of more than 20 mm Hg received 2 points. A total score of zero was regarded as no CAN (noCAN), a score > or =4 as severe CAN (sCAN), and scores of 1 to 3 as mild CAN (mCAN). Spontaneous BRS was determined using the sequence technique. HRV was calculated as coefficient of variation (CV), high frequency power (HF) and low frequency power (LF). RESULTS: Mean group values for HRV and BRS were: CV = 3.9+/-1.3; 4.0+/-1.3; 2.4+/-1.1; and 1.2+/-0.4; BRS = 8+/-3; 8+/-5; 5+/-2; and 2+/-2 msec/mm Hg for HC n = 38, noCAN n = 15, mCAN n = 26, and sCAN n = 12, respectively. BRS was similar in HC and patients with noCAN. In sCAN, BRS detected only 10 of 12 patients. HRV and BRS did not improve reclassification based on discriminant analysis. CONCLUSION: BRS and HRV did not detect CAN in older diabetic patients better than classic autonomic testing.

Aged↗
PubMed2000

Patterning electro-osmotic flow with patterned surface charge.

This Letter reports the measurement of electro-osmotic flows (EOF) in microchannels with surface charge patterned on the 200 microm scale. We have investigated two classes of patterns: (1) Those in which the surface charge varies along a direction perpendicular to the electric field used to drive the EOF; this type of pattern generates multidirectional flow along the direction of the field. (2) Those in which the surface charge pattern varies parallel to the field; this pattern generates recirculating cellular flow, and thus causes motion both parallel and perpendicular to the external field. Measurements of both of these flows agree well with theory in the limit of thin double layers and low surface potential.

Electrochemistry↗
PubMed2000

Reference values of indices of spontaneous baroreceptor reflex sensitivity.

Spontaneous baroreceptor reflex sensitivity (BRS) is a well established method for determining baroreflex function, which can be used to assess the potential impact on survival after myocardial infarction, to detect autonomic dysfunction in diabetic patients and in human essential hypertension. The assessment of impaired spontaneous baroreflex function in individual patients contains important clinical information, but age-dependent reference values are still lacking. In the present study we evaluated spontaneous BRS in healthy human controls to determine reference values as a function of age. Two hundred and sixty-two healthy volunteers divided into six age groups (I: <20 years, f = 11, m = 9, II: 20-29 years, f = 42, m = 37, III: 30-39 years, f = 23, m = 37, IV: 40-49 years, f = 27, m = 22, V: 50-59 years, f = 19, m = 17, VI: 60-69 years, f = 5, m = 13). Electrocardiograms (ECG) and finger arterial BP were measured with each subject in the supine position (sup, 7 min) and during deep breathing (dB, 6/min, 15 cycles). BRS was assessed using the sequence technique and the alpha coefficients as obtained from a power spectrum density estimate. Due to the normal logarithmic distribution of the BRS, the limits for impaired baroreflex function at rest were defined from logarithmic data. The limits for the BRS at rest (P = .025) were calculated as (-0.0283 x age) + 2.5198 for the sequence technique. We did not find significant differences in BRS among the female and male healthy volunteers. Our analysis of the six age groups showed the expected significant decrease in BRS, which was most prominent at the transition from group III (<40 years) to group IV (<50 years). BRS at rest and during deep breathing as well as sequential and spectral BRS indices did differ significantly. The results underline the necessity of reference values to evaluate impaired baroreflex function in individual patients.

Adolescent↗
PubMed1999

Influence of Perfluoroarene-Arene Interactions on the Phase Behavior of Liquid Crystalline and Polymeric Materials.

A stabilization of the liquid-crystalline mesophase and thus an enlarged temperature range of the mesogenic phase is achieved by adding perfluorotriphenylene to a chiral liquid-crystalline triphenylene. This mesophase is based on 1:1 perfluoroarene-arene interactions (see picture). In a polymer with triphenylenes as mesogens in the side chains, the addition of perfluorotriphenylene led to crystallization.

Journal Article↗
PubMed1999

Effect of obesity and insulin resistance on resting and glucose-induced thermogenesis in man. EGIR (European Group for the Study of Insulin Resistance).

OBJECTIVE: To assess the impact of obesity and insulin sensitivity on resting (REE) and glucose-induced thermogenesis (GIT). DESIGN: Data from 322 studies carried out in non-diabetic subjects of either gender, covering a wide range of age (18-80y) and body mass index (BMI, 18-50 kg/m2). MEASUREMENTS: Insulin sensitivity and thermogenesis were measured by combining the euglycaemic insulin clamp technique with indirect calorimetry. RESULTS: REE was inversely related to age (P = 0.001) and the respiratory quotient (P = 0.03), and positively related to BMI, lean body mass (LBM), fat mass, and percentage fat mass (all P<0.0001). In a multiple regression model, LBM-adjusted REE was estimated to decline by 9% between 18 and 80 y, independently of obesity and insulin sensitivity. In contrast, GIT was strongly associated with insulin sensitivity (P<0.0001) but not with gender, age or BMI. By multiple regression analysis, GIT was linearly related to insulin sensitivity after controlling for gender, age, BMI and steady-state plasma insulin levels. Furthermore, both of the main components of insulin-mediated glucose disposal (glucose oxidation and glycogen synthesis) correlated with GIT independently of one another. In the subset of subjects (n = 89) in whom waist-to-hip ratio (WHR) measurements were available, GIT was inversely associated with WHR (P<0.001 after adjustment by gender, age, BMI, insulin sensitivity and steady-state plasma insulin concentration). In this model, a significant interaction between WHR and gender indicated a stronger adverse effect on GIT of a high WHR in women than in men. CONCLUSIONS: In healthy humans, age, lean mass and respiratory quotient are the main independent determinants of resting thermogenesis. In contrast, insulin sensitivity and, to a lesser extent, abdominal obesity are the principal factors controlling glucose-induced thermogenesis.

Adolescent↗
PubMed1997

Impaired activation of the baroreflex loop as early sign of sympathetic damage in diabetics with normal heart rate variability at rest.

The objective of the study was to define the impairment of sympathovagal balance in patients with diabetes mellitus (DM) and coronary heart disease (CHD) compared to healthy controls (HC) showing similar heart rate variability (HRV) at supine rest. 88 DM (41 m, 47 f; age 62 +/- 1 years; BMI 27.1 +/- 1.5 kg/m2; HbA1c 7.9 +/- 0.4%), 49 CHD (27 m, 22 f; age 62 +/- 1 years; BMI 27.1 +/- 1.6 kg/m2; HbA1c 5.2 +/- 0.1%) and 16 HC (8 m, 8 f; age 59 +/- 1 years; BMI 26.4 +/- 0.5 kg/m2; HbA1c 5.0 +/- 0.1%) were investigated. Time series of heart period duration (HPD) were obtained during 2 min deep breathing (6/min), 5 min of supine rest and for 5 min at upright position using a RR memory device (BHL 6000, Baumann-Haldi Switzerland, modified ECG lead, 1 kHz). Mean HPD, coefficient of variation (CV), total power (TP) and integral power in the HF (0.15 to 0.5 Hz), MF (0.05 to 0.15 Hz) and LF (0.015 to 0.05 Hz) frequency bands as well as (MF-HF)/(MF + HF) as spectral index were calculated. As to be expected we found significantly lower values of CV, TP and HPD in DM compared to HC. The CV of HRV did not differ significantly between DM and CHD but TP and HPD of CHD patients were significantly higher in comparison to DM. Therefore, the deterioration of HRV was most pronounced in the DM group. For further analysis we calculated data of subjects with CV's in the upper quartile (> or = 3.52) of the CV at supine rest. The aim of this procedure was to compare subjects with similar high HRV at supine rest. With this method we obtained from all subjects 12 HC, 11 DM and 12 CHD. These DM had a significant decrease of CV, TP and the integral power at the HF frequency band during active orthostasis compared to HC and CHD. The spectral index increased significantly during standing in HC and CHD but was unchanged in DM. These changes were accompanied by a nearly similar increase of HRV during deep breathing. In conclusion, DM with normal reaction to deep breathing did not activate the sympathetic baroreflex loop during active orthostasis. This could be an early sign of sympathetic dysfunction in DM with normal HRV at supine rest.

Autonomic Nervous System Diseases↗
PubMed1997

Reduced gastric emptying and mesenteric blood flow in IDDM with cardiac autonomic neuropathy.

Our objective was to investigate the relationship between gastric emptying and mesenteric blood flow in type 1 diabetic patients with (CAN+) and without (CAN-) cardiac autonomic neuropathy. CAN was determined by a series of cardiovascular reflex tests and power spectral analysis of heart rate variations (HRV) using a computerized system. We calculated from these data a score for cardiac autonomic neuropathy with a maximum of 7 points (1 point for abnormal value of: CV of HRV at supine rest, CV of HRV during deep breathing, Valsalva ratio, lying-to-standing ratio, PSA of HRV in the low frequency band, PSA of HRV in the mid frequency band, blood pressure response to standing). Patients were considered to have CAN if at least 3 of the 7 parameters were found to be abnormal (CAN score > or = 3). The resulting groups (CAN-, n = 14 vs. CAN+, n = 16) were well matched with respect to age (53 +/- 11 vs. 51 +/- 12 years), BMI (27.2 +/- 3.3 vs. 25.9 +/- 3.6 kg/m2), duration of diabetes (162 +/- 157 vs. 158 +/- 100 months), fasting blood glucose (6.9 +/- 2.6 vs. 6.8 +/- 2.4 mmol/l) and HbA1c (7.2 +/- 1.5 vs. 7.3 +/- 2.0%). Gastric emptying was determined by real-time ultrasonography (antral planimetry) during 60 min after a semiliquid test meal (Fresubin diabetes 300 ml, 53% carbohydrate, 32% lipid, 15% protein) and the blood flow of the superior mesenteric artery was measured by Doppler ultrasound technique. Type I diabetic patients with CAN had a significantly higher CAN score than those without CAN (6.1 +/- 0.4 vs. 1.3 +/- 0.7). Mean preprandial (before ingestion of the test meal) as well as postprandial (immediately after ingestion of test meal) antral areas of CAN+ (5.2 +/- 2.0v/10.9 +/- 2.8 cm2) and CAN- (5.1 +/- 1.5/10.8 +/- 2.2 cm2) were comparable. CAN+ had significantly slower decrease of postprandial antral areas at 15, 30, 45 and 60 min after ingestion of test meal (-1.7 +/- 0.4/-8.3 +/- 1.2/-9.5 +/- 0.9/-19.5 +/- 2.0 delta % compared to postprandial value) compared to CAN- (-8.9 +/- 1.8/-22.5 +/- 2.6/-29.1 +/- 2.9/-35.5 +/- 2.9 delta %). The increase in mesenteric blood flow at 15, 30 and 45 min after the meal was significantly reduced in CAN+ compared to CAN- patients. Significantly negative correlations were found between the CAN score and the decrease of antral area as well as between CAN score and the increase of diastolic mesenteric blood flow and significantly positive correlations between the decrease of antral area and the increase of diastolic mesenteric blood flow. In conclusion, type 1 diabetic patients with cardiac autonomic neuropathy showed delayed gastric emptying and diminished mesenteric blood flow during 60 min after ingestion of a semiliquid test meal.

Adult↗
PubMed1995

Hemodynamic regulation during postural tilt assessed by heart rate- and blood-pressure variability combined with impedance cardiography.

Assessment of heart rate and heart rate variability (HRV) are used in sports medicine and space medicine to give conclusions about the functional state of the autonomic nervous system. Furthermore, reduced HRV and changed blood pressure variability (BPV) are accepted as risk factors in patients with cardiovascular diseases, metabolic syndrome and neurologic disorders. The aim of the first studies was to combine the evaluation of central hemodynamic (impedance cardiography) with HRV and BPV evaluation in the time and frequency domain (fft tracking) based on a standardized clinical test with automated protocol output. Data acquisition and -analysis was realized beat to beat (Kohto Ltd., Moscow) during forced breathing (150 s, 6 breath/min) and postural tilt (7 min, supine, transition to 55 degrees in 4 s, 7 min upright) allowing one to evaluate: orthostatic response type including impedance cardiography; activation of vagal afferences and efferences by forced breathing; vagal and sympathetic components during initial heart rate and blood pressure responses; characteristic changes of spectral balance of HRV and BPV (measured at the finger) during early regulation. First investigations on 34 normal volunteers subdivided into two age groups and on 13 patients with different diseases indicate that besides the age dependent changes (reduced HRV, reduced cardiac performance, reduced regulatory amplitudes and baroreflex sensitivity) individual response types can be described and dysfunction of different reflex loops can be detected. Consequently, the assessment of specific influences onto circulatory control by therapy, sport and rehabilitative training is possible and further studies are necessary.

Adult↗
PubMed1994

Glucocorticoid hormone binding to rat adipocytes.

Previous quantification of glucocorticoid receptor (GR) binding in adipose tissue has been performed in cytosol preparations, which did not allow the determination of the total number of GR in the cell. Therefore, GR binding was determined in intact adipocytes. Dexamethasone (dex) was used as a ligand in adipocytes isolated from epididymal (Epi), retroperitoneal (Ret), inguinal (Ing) and mesenteric (Mes) adipose tissue regions in male rats. The binding was saturable and specific with a Kd in the nanomolar range, not different from previously reported affinity of binding in cytosol preparations from adipocytes. Binding capacity rose after removal of endogenous glucocorticoids either by adrenalectomy (ADX) or culture in a glucocorticoid-free medium. Binding capacity of adipocytes was in general higher in Mes adipose cells than in adipocytes from Epi, Ing and Ret tissues from intact and ADX animals when expressed per unit of triglyceride weight of adipose tissues. This seemed to be largely explainable by a higher cellular density in Mes than in other adipose tissues. When comparisons were performed with binding per adipocyte, intraabdominal (Epi, Ret and Mes) cells bound more dex than adipocytes from subcutaneous (Ing) adipose tissue. It is suggested that in comparison with other adipose tissues Mes tissue has a higher density of the GR in situ, due mainly to a higher cellular density. Intraabdominal adipocytes in general seem to have a higher GR density than subcutaneous cells. This might explain the high activity of glucocorticoid-regulated metabolic pathways in intraabdominal particularly Mes adipose tissue.

Adipocytes↗
PubMed1989

Very low calorie diet therapy in obese non-insulin dependent diabetes patients.

VLCD is an effective and safe measure to reduce overweight in NIDDM. It substantially improves glucose control and corrects associated coronary risk factors, in particular dyslipoproteinaemia and hypertension. Both insulin secretion and insulin resistance were ameliorated by perfect glucose control with VLCD. Reliable data on long term efficacy and factors determining weight loss and success in permanent glucose control are urgently needed.

Blood Glucose↗
PubMed1987

Loss of fat, water, and protein during very low calorie diets and complete starvation.

The magnitude and composition of weight loss obtained in obese women on two forms of very low calorie protein-supplemented diets (Cambridge diet, Dresden drink) as well as by complete starvation has been investigated. With the VLCD, nitrogen equilibrium was reached on the 10th day of fasting, the cumulative nitrogen balance also being compensated. Nearly half of the body weight loss is due to loss of fat. In order to assess the benefit of fasting regimes, we propose to measure at least two parameters which are independent of each other, e.g., nitrogen balance and total body water. Both types of VLCD were equally effective, safe, and acceptable in achieving rapid body weight reduction.

Adipose Tissue↗
PubMed1987

Predictive value of the index of desirable body weight for total body fat mass as measured by dilution of tritiated water--problems and limitations.

The index of desirable body weight is currently used for classification of patients' weights. We examined how it is related to the degree of adiposity, and whether it can serve in the prediction of body fat to the same degree as Quetelet's index. Sixty-five women and 142 men comprising a wide range of weight indices were studied. Body fat (F) was measured by the tritium dilution technique with a precision of +/- 1.26 kg. Regressions of F/W0 on the index of desirable weight W/W0 gave a correlation coefficient of 0.969 for women and 0.939 for men. Regressions of F/H2 on Quetelet's index W/H2 had correlation coefficients of the same order, i.e. 0.971 for women and 0.936 for men. Hence both indices are equally powerful for calculation of body fat within the study population. Further progress was achieved by multiple regression of F on W and W0 which yielded correlation coefficients of 0.976 for women and 0.953 for men. The residual standard deviation reflecting the mean difference between calculated and estimated fat was 3.4 kg for women and 3.8 kg for men. Despite this self-consistency, prediction of body fat for persons outside the study population is only possible within wide limits. These are given by about twice the residual standard deviation. Therefore, prediction of body fat from weight indices can only be used for detection of larger abnormalities in body composition.

Adult↗