Search PubMed⌕ Search

Biomedical subjects

V Maier

Publications and source records attributed to V Maier.

At least 19 recordsLinked to original sources
PubMed2000

Cesium-137 source strength verification.

Over the years, the protocol for Cesium-137 source calibration has undergone a number of revisions based on updated data. The 3M Corporation issued product alerts and a revision of the calibration protocol in the early 1980s. We verified the activity of clinically used cesium tubes and found the difference with the activity stated by 3M in the range of 6-13%, which exceeds the recommended by 3M adjustment of 5% for all sources issued before 1979. Therefore, the verification and adjustment of activity should be recommended for each affected tube individually.

Cesium Radioisotopes↗
PubMed1999

Angiotensinogen M235T polymorphism is associated with plasma angiotensinogen and cardiovascular disease.

BACKGROUND: Genes encoding components of the renin-angiotensin system have been associated with elevated blood pressure (BP) and an increased risk of coronary artery disease. To explore the role of the angiotensinogen (AGT) gene in coronary atherosclerosis and thrombosis, we studied the effect of the AGT M235T gene variant on plasma AGT levels and BP in patients with coronary artery disease and in the subgroup of survivors of myocardial infarction as compared with angiographically defined control subjects. METHODS AND RESULTS: This was a case-control study of 301 white male subjects examined at Frankfurt University medical center. Plasma AGT levels increased stepwise according to the number of T235 alleles present (no T235 allele, 14.8 +/- 3.9 nmol/L; 1 allele, 15.7 +/- 5.1 nmol/L; 2 alleles, 17.3 +/- 4.7 nmol/L; P =.006). In a multivariate model, circulating AGT emerged as the most important predictor of diastolic pressure (P =.001). In addition, AGT M235T gene polymorphism remained a significant predictor of diastolic BP in a multivariate model adjusted for age, body mass index, fasting glucose, apolipoprotein B, presence of coronary artery disease, and treatment with antihypertensive agents ( P <.05). Finally, homozygosity for T235 was associated with increased univariate risk of coronary artery disease and myocardial infarction (odds ratio estimates 1.5; 95% confidence intervals 1.1 to 2.1, P =.03, and 1.0 to 2.1, P =.05, respectively). CONCLUSIONS: The significant relations observed between the AGT M235T variant, its protein product, and the cardiovascular disease phenotypes provide evidence for a possible role of elevated circulating AGT in the pathogenesis of coronary artery disease.

Alleles↗
PubMed1996

Physical training improves endothelial function in patients with chronic heart failure.

BACKGROUND: Chronic heart failure is associated with endothelial dysfunction including impaired endothelium-mediated, flow-dependent dilation (FDD). Since endothelial function is thought to play an important role in coordinating tissue perfusion and modulating arterial compliance, interventions to improve endothelial dysfunction are imperative. METHODS AND RESULTS: To assess the potential of physical training to restore FDD, 12 patients with chronic heart failure were studied and compared with FDD of 7 age-matched normal subjects. With a recently developed high-resolution ultrasound system, diameters of radial artery were measured at rest, during reactive hyperemia (with increased flow causing endothelium-mediated dilation), and during sodium nitroprusside, causing endothelium-independent dilation. Determination of FDD was repeated after intra-arterial infusion of NG-monomethyl-L-arginine (L-NMMA, 7 mumol/min) to inhibit endothelial synthesis and release of nitric oxide. The protocol was performed at baseline, after 4 weeks of daily handgrip training, and 6 weeks after cessation of the training program. FDD was impaired in heart failure patients compared with normal subjects. L-NMMA attenuated FDD, indicating that the endothelial release of nitric oxide is involved in FDD. Physical training restored FDD in patients with heart failure. In particular, the portion of FDD inhibited by L-NMMA (representing FDD mediated by nitric oxide) was significantly higher after physical training (8-minute occlusion: 8.0 +/- 1% versus 5.4 +/- 0.9%; P < .05; normal subjects: 9.2 +/- 1%). CONCLUSIONS: These results indicate that physical training restores FDD in patients with chronic heart failure, possibly by enhanced endothelial release of nitric oxide.

Adult↗
PubMed1996

Statistical approach for evolutionary relationship of alpha-conotoxins and members of insulin-superfamily.

Similar conserved structures appear in apparently unrelated protein families. Thus, the superfamily of insulin shows an evolutionary relationship with the alpha-conotoxins of marine fish-hunting snails as indicated by methods of protein comparison. In order to reach statistical significance, the A-chains of different insulins, insulin-like growth factors, relaxins, insulin related peptides from invertebrates were drawn for comparison. These data were correlated with sequences from randomly chosen proteins. The alpha-conotoxins show identity scores up to 37.5% and similarity up to 56.2% toward the members of the insulin-superfamily. These scores conform to values achieved by comparing the relaxin and the insulin/IGF-sequences. The data show clearly that the identity and similarity values obtained in the comparison with the insulins are significantly higher than the scores of randomly chosen protein primary structures. According to our calculated data, this hormone system regulating metabolism and growth in vertebrates and the mentioned toxin-receptor system share the same evolutionary ancestor. However, this statistical approach has to be substantiated on gene level.

Amino Acid Sequence↗
PubMed1995

Red-cell and serum folate levels in depressed inpatients who commit violent suicide: a comparison with control groups.

There has been some discussion in the recent literature regarding the possible relationship between peripheral levels of folate and serotonin deficiency in the CNS. At the same time, such a serotonin deficiency has been implicated in the biology of suicidal behavior. Thus, decreased peripheral folate levels may be expected in patients who commit violent suicide. In this study, the red-cell and serum folate levels in nine persons who later committed suicide are compared with those in age- and sex-matched control groups. A one-way analysis of variance showed no significant difference between the groups.

Adult↗
PubMed1995

Folate deficiency, anticonvulsant drugs, and psychiatric morbidity.

The folic acid (FOA) level was determined in serum and erythrocytes in 100 epileptic patients and 100 control patients using a luminescence assay. A lowered FOA concentration in serum, erythrocytes, or both was observed in 15% of the epileptic patients and in 2% of the control group. In the epileptic patients, the FOA in the serum and in the erythrocytes was significantly lower than that in the control group. Patients receiving carbamazepine monotherapy had a significantly lower FOA level in the erythrocytes than did patients receiving phenytoin monotherapy. The FOA level showed a negative correlation to the duration of epilepsy. None of the patients with lowered FOA had a normal mental status. The course of the supplementation treatment with 5 mg folinic acid (or FOA) of four patients with FOA deficiency could be monitored psychopathometrically. All four patients showed an improvement in their well-being and the majority of measured variables of the cognitive performance.

Adult↗
PubMed1994

Effect of corticotropin releasing factor on atrial natriuretic peptide release from the isolated perfused rat heart.

The effect of corticotropin releasing factor (CRF) on atrial natriuretic peptide (ANP) release and its possible modulation by indomethacin, norepinephrine, propranolol and nitro-L-arginine (an inhibitor of the endothelium-derived relaxing factor (EDRF) release) was investigated, using an isolated perfused rat heart preparation. Bolus injection of 5 micrograms CRF, dissolved in 100 microliters perfusion buffer, provoked a significant (p < 0.01 vs. control) short-time increase of ANP release. Indomethacin (3 x 10(-5) mol/l) inhibited the CRF-stimulated increase of ANP release and decreased the basal ANP secretion (p < 0.01 vs. CRF group). Norepinephrine (10(-9) mol/l) slightly, but not significantly, decreased the CRF-stimulated ANP release and did not change the basal ANP output. Propranolol (3 x 10(-6) mol/l) did not alter ANP release. Nitro-L-arginine (3 x 10(-5) mol/l) increased the basal ANP release (p < 0.01 vs. CRF group) and prolonged the CRF-induced rise of the ANP secretion. The present data suggest that prostaglandins are important mediators of basal and CRF-stimulated ANP release and that EDRF might be a physiological inhibitor of ANP release.

Animals↗
PubMed1993

A fast protein liquid chromatography (FPLC) method for study of thyrotropin-releasing hormone (TRH) and its metabolite histidyl-proline diketopiperazine (CHP) in human blood: degradation in liver and pancreatic diseases.

We have developed a convenient method combining fast protein liquid chromatography (FPLC) with sensitive radioimmunoassay (RIA) for thyrotropin-releasing hormone (TRH) to separate and identify TRH and its metabolite histidyl-proline diketopiperazine (CHP) and applied this to study inactivation of TRH by blood extracts from patients with liver cirrhosis (LC) and acute edematous pancreatitis (AP). Blood samples spiked with TRH and CHP were extracted by cold methanol and injected on a reverse-phase FPLC column. A linear gradient was applied for separation. Subsequent analyses of fractions by RIA for TRH revealed that only fractions 9-10 contained TRH. Separation by retention time (9.9 +/- 0.8 min for TRH, 10.5 +/- 0.6 min for CHP, mean +/- SEM) was highly reproducible. For degradation studies, pooled sera from patients with LC and AP were incubated with TRH and CHP for 60 min. Inactivation of TRH was less rapid in the presence of blood extract from LC patients than that from normal subjects or AP patients. CHP was more stable than TRH. These data suggest that activity of TRH-degrading enzymes is reduced in liver disease, whereas it does not appear to be altered in AP. Degradation of CHP does not closely reflect metabolic processing of its major precursor. This rapid and sensitive method may be applicable for further investigations on the metabolism of TRH in organic fluids.

Acute Disease↗
PubMed1993

Fluctuations of carbohydrates in haemolymph of honeybee (Apis mellifica) after fasting, feeding and stress.

The haemolymph of honeybee contains trehalose, a non-reducing disaccharide, glucose and fructose. The aim of this work was to describe changes of haemolymph sugar induced by different physiological situations. Gas chromatography for the determination of carbohydrate concentrations in the haemolymph was introduced. The individual bee was anesthetized by CO2 and punctured at tergum III in order to gain 1 microliter haemolymph using a glass capilette. The main sugars in the haemolymph were determined as silylated derivatives by gas chromatography. Bees living under exactly standardized conditions in an artificial bee-house were observed after feeding and fasting. In addition saccharides were determined after "run-stress" along different distances.

Animals↗
PubMed1993

[Folic acid deficiency in patients hospitalized with depression? A pilot study of clinical relevance].

Seventy-seven depressive inpatients were studied in a pilot study to determine their serum and red cell folate levels at admission. Only one depressive inpatient with a low serum folate value had a history of an illness-related lack of nutrition prior to admission, and the low value was only on day 1 of the study. Our results demonstrate that folate acid deficiency is not as common in depressive inpatients as reported, especially in British studies for two reasons: different eating habits and a methodological problem.

Adult↗
PubMed1992

Dilatory and inotropic effects of corticotropin-releasing factor (CRF) on the isolated heart. Effects on atrial natriuretic peptide (ANP) release.

The effects of CRF administration on cardiac performance, coronary flow and ANP release were investigated in the rat heart. Isolated hearts were perfused at a constant filling pressure according to working heart model with a Krebs-Henseleit solution containing glucose and insulin, saturated with a gas mixture containing 95% O2 and 5% CO2. Administration of CRF via a cannula into the left atrium elicited a prolonged increase in the coronary flow rate and a transient increase in the aortic pressure resulting in an overall increase in the pressure-volume work. The oxygen consumption, after the administration of CRF, increased in accordance with the cardiac effort. No changes were observed in the spontaneous heart rate. Furthermore, administration of CRF induced a short-term increase of ANP release into the coronary perfusate. Our experiments suggest that administration of CRF produces a prolonged dilatory effect on the coronary arteries while producing a transient positive inotropic effect and a transient increase of ANP release on the isolated rat heart.

Animals↗
PubMed1992

Contribution of postprandial amino acid levels to stimulation of insulin, glucagon, and pancreatic polypeptide in humans.

The present study was designed to examine the contribution of the postprandial increase of plasma amino acids after ingestion of a protein-rich meal to the rise of the three pancreatic hormones insulin, glucagon, and pancreatic polypeptide (PP). A mixed amino acid solution was designed, which permitted a fairly close imitation of the arterial plasma pattern of the 21 amino acids that rise after ingestion of a 200-g porcine steak meal. In 10 healthy subjects the intravenous infusion of this mixed amino acid solution at a rate of 10 g/h elicited a rise of the 21 amino acids examined that correlated well with the postprandial increase (r = 0.89, p < 0.001). The maximal rise of plasma insulin (64 +/- 5 pmol/L) and glucagon (630 +/- 21 ng/L) was not significantly different from the postprandial increase of these two hormones (49 +/- 4 pmol/L and 780 +/- 28 ng/L, respectively). PP levels rose by 316 +/- 33 ng/L postprandially, which was clearly above the increase of 112 +/- 13 ng/L during intravenous amino acids (p < 0.01). In conclusion, the present data demonstrate that the postprandial rise of amino acid levels in arterialized venous plasma can account for most if not all of the postprandial increase of insulin and glucagon during the ingestion of a protein-rich meal. In contrast, only 35% of postprandial PP levels can be ascribed to the rise of plasma amino acids. In contrast to the effect of carbohydrate-rich meals, an enteric augmentation of insulin release seems to be of minor and possibly of no importance during ingestion of protein-rich meals.

Adult↗
PubMed1991

Periodic hypersomnia: case report with biochemical and EEG findings.

We report on a 23-year-old patient with periodic hypersomnia. Electroencephalographic (EEG) background activity for this individual was slightly slowed in the EEG during an episode of hypersomnia, and intermittent slow activity was found in addition. Usual laboratory parameters were normal; however, leucine-enkephalin was markedly elevated in the plasma at that time, whereas free cysteine could not be demonstrated. Clinical findings were normal in the following years, and the EEG background activity returned to normal; leucine-enkephalin and cysteine also returned to normal values.

Adult↗
PubMed1991

Comparison of neural activity in the supplementary motor area and in the primary motor cortex in monkeys.

Neuronal activity recorded from the primary motor cortex (MI) and from the supplementary motor area (SMA) was compared in two monkeys trained to perform conditioned arm movements. A handle had to be held in a central waiting position until a visual go and cueing signal indicated to the monkey to move the handle either to a medial or to a lateral target zone (choice reaction time paradigm). Unit and representative electromyographic data were analyzed in relation either to the go signal or to movement onset. In 240 penetrations, 431 SMA neurons and 353 MI neurons were found with activity related to the task. The majority of neurons (303 in MI, 290 in SMA) displayed activity changes after the go signal and before movement onset. Of these "short-lead neurons", 71% in MI and 41% in SMA were clearly related to movement execution. The distribution of lead times in MI and SMA neurons was completely overlapping without any statistical difference among subgroups. The remaining neurons were as well related to the go signal as to movement onset, or were better related to the visual go signal. The response latencies to this signal were not statistically different in SMA and MI neurons. Activity changes during the waiting period was observed more frequently in SMA (47%) than in MI (32%); modulations restricted to the waiting period occurred in 14% of SMA neurons, but were exceptional in MI neurons (3%). It is concluded from these experiments that a surprisingly large proportion of SMA neurons have "MI-like" properties, in that they are temporally recruited together with MI neurons, with similar patterns of discharges during the task. This then suggests that the two interconnected areas operate in parallel. A population of SMA neurons is involved in some processing that is not as predominantly expressed in MI. This activity could relate to sensory, timing, or other higher-order aspects of response preparation, and/or motor functions such as postural stabilization.

Animals↗
PubMed1991

Effect of CCK on food intake in man: physiological or pharmacological effect?

The present study was designed to determine in humans the dose of CCK which suppresses food intake. 18 male subjects received in randomized order either i.v. saline or Thr28 Nle31 CCK 25-33 (CCK-9) at 100 or 500 pmol/kgh, respectively. In addition, 7 subjects received CCK together with the opiate receptor antagonist naloxone to examine if activation of endogenous opioids might interfere with the potential satiating effect of CCK. Food intake during saline was 32 +/- 2 sandwiches (mean +/- SEM), during CCK-9 100 pmol/kgh 28 +/- 2 (n.s.) and only 12 +/- 3 during CCK-9 500 pmol/kgh (p less than 0.01). The respective water intake was 730 +/- 70 ml, 590 +/- 60 ml (n.s.) and 320 +/- 50 ml (p less than 0.01). Naloxone further reduced food and water intake during high but not low dose CCK or saline. During saline postprandial insulin levels rose by 49 +/- 6 microU/ml within 45 min which was attenuated during low dose (23 +/- 6 microU/ml; p less than 0.01) and high dose CCK-9 (1 +/- 1 microU/ml; p less than 0.001). Plasma glucagon did not change in control or CCK experiments. The postprandial rise of pancreatic polypeptide was attenuated during high dose CCK. Naloxone had no effect on the hormonal response except for a prolonged reduction of insulin and glucose levels following high dose CCK + naloxone. Plasma CCK levels rose by 5.4 pmol/l in controls but by 55 and 255 pmol/l during the low and high dose CCK infusion, respectively. These data demonstrate that suppression of food intake in man by i.v. CCK is a pharmacological rather than a physiological effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Ultrastructural localization of prolactin-like antigenic determinants in neurosecretory cells in the brain of the honeybee (Apis mellifica).

With two different antisera to human prolactin (hPRL), the ultrastructural localization of PRL-like material in the bee brain is examined by means of the protein-A-gold method at the electron microscopical level. Labelling is found in electron-dense granules of medium size (150-200 nm in diameter) for the first time in insects. Such granules are distributed in the cytoplasm of the neurosecretory cells, their axons and their axon-terminals. The electron-dense granule is one criterion for identifying a neurosecretory cell. In the honeybee, hPRL-like material may serve as an old neurohormone with respect to its evolution.

Animals↗
PubMed1989

Immunocytochemical localization of prolactin-like antigenic determinants in the neuroendocrine system of the honeybee (Apis mellifica).

In the brain of the adult worker bee (Apis mellifica) prolactin-like (PRL) immunoreactive cells were localized in the lateral neurosecretory cell region and the subesophageal ganglion by means of the PAP procedure. These cells emit nerve fibers which pass through the neuropile of the brain to the corpora cardiaca where a great number of immunoreactive axon terminals is present. Test with antisera against rat pituitary prolactin and human luteinizing hormone were negative. These results indicate that hPRL material is produced in neurosecretory cells of the bee brain and transferred via axons to the corpora cardiaca for storage and subsequent release into haemolymph.

Animals↗