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Biomedical subjects

R Schick

Publications and source records attributed to R Schick.

At least 19 recordsLinked to original sources
PubMed2004

Detection of aquatic colloids in drinking water during its distribution via a water pipeline network.

Laser-induced Breakdown Detection (LIBD) is a highly sensitive method for the direct detection of nano-particles (colloids). During the detection process plasmas are generated on single particles by a focused laser beam, the resulting plasma light emissions are detected optically. The method is based on the difference in breakdown thresholds of liquid and solid matter, it is lower for solid material. The laser pulse energy is adjusted precisely so that in the pure liquid no breakdown events occur, and only in the presence of colloids is the breakdown threshold in the focal volume exceeded. The spatial distribution of several thousand recorded plasma flashes within the focal volume reveals the mean particle diameter. The evaluation of the number of breakdown events per number of laser pulses results in a breakdown probability, together with the particle size the concentration is calculated using specially-designed computer software. Compared to conventional laser light scattering methods the LIBD is approximately 6 orders of magnitude more sensitive for particles smaller than ca. 0.05 pm. Together with laser light obscuration the LIBD technique has been used successfully for the quantification of aquatic nano-particles during drinking water processing and its distribution via a pipeline network of nearly 1,700 km total length. In addition, the particulate content of several brands of mineral water has been investigated.

Colloids↗
PubMed2002

Erythropoiesis and performance after two weeks of living high and training low in well trained triathletes.

The purpose of our study was to evaluate hematologic acclimatization during 2 weeks of intensive normoxic training with regeneration at moderate altitude (living high-training low, LHTL) and its effects on sea-level performance in well trained athletes compared to another group of equally trained athletes under control conditions (living low - training low, CONTROL). Twenty-one triathletes were ascribed either to LHTL (n = 11; age: 23.0 +/- 4.3 yrs; VO 2 max: 62.5 +/- 9.7 [ml x min -1 x kg -1]) living at 1956 m of altitude or to CONTROL (n = 10; age: 18.7 +/- 5.6 yrs; VO 2 max: 60.5 +/- 6.7 ml x min -1 x kg -1) living at 800 m. Both groups performed an equal training schedule at 800 m. VO 2 max, endurance performance, erythropoietin in serum, hemoglobin mass (Hb tot, CO-rebreathing method) and hematological quantities were measured. A tendency to improved performance in LHTL after the camp was not significant (p < 0.07). Erythropoietin concentration increased temporarily in LHTL (Delta 14.3 +/- 8.7 mU x ml -1; p < 0.012). Hb tot remained unchanged in LHTL whereas was slightly decreased from 12.5 +/- 1.3 to 11.9 +/- 1.3g x kg -1 in CONTROL (p < 0.01). As the reticulocyte number tended to higher values in LHTL than in CONTROL, it seems that a moderate stimulation of erythropoiesis during regeneration at altitude served as a compensation for an exercise-induced destruction of red cells.

Acclimatization↗
PubMed1995

Identification and partial characterization of a domain in CFTR that may bind cyclic nucleotides directly.

BACKGROUND: The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel that is activated by cAMP-dependent phosphorylation. CFTR channel activity is also stimulated by cGMP-dependent protein kinase and protein kinase C. RESULTS: Here, we show that CFTR channel activation by cGMP may also occur directly. In oocytes from one-third of Xenopus donors, the activation of CFTR by cGMP averaged 87% of the level achieved by cAMP. The currents activated by either cyclic nucleotide displayed similar current-voltage relationships, kinetics, pharmacology and halide selectivity. Sequential stimulation by cAMP and cGMP was not additive, suggesting that both cyclic nucleotides activate the same channel; cGMP was one order of magnitude more potent than cAMP, and its action was insensitive to protein kinase inhibitors. Analysis of the amino-acid sequence of CFTR revealed a domain in the amino-terminal portion of the third cytoplasmic loop that resembles a class of cyclic-nucleotide-binding domains related to that of the catabolite-gene activator protein, CAP. Two CFTR residues in this domain--Val397 and Lys420--were identified which, when changed to alanine, altered the response to cGMP independently of the response to cAMP. CONCLUSIONS: We conclude that direct cyclic nucleotide binding may play a role in channel gating of CFTR. The cGMP-binding domain may provide a useful target for pharmacologic intervention in cystic fibrosis.

Amino Acid Sequence↗
PubMed1990

An analysis of the validity of the three-mile run as a field test of aerobic capacity in college males.

The purpose of the present investigation was to examine the concurrent and construct validity of the three-mile (4.83 km) run as a field test of aerobic capacity. Subjects included 109 college-aged males whose three-mile run time (M = 1310.31 +/- 184.48 s) was measured. Fifty of the subjects were given a maximal treadmill stress test, and their peak oxygen consumption (VO2peak) (M = 54.23 +/- 7.08 ml.kg-1.min-1) was measured. The three-mile run was conducted on an outdoor 0.25 mile (0.425 km) track, and split times were recorded each 110 yds (100.32 m) for the first and last laps and total time was recorded for laps 2 through 11. The correlation coefficient between the run time and VO2peak was -.58, indicating only moderate concurrent validity for the run as a field test for aerobic capacity. A factor analysis conducted on the split time data revealed a three-factor structure of a stable pace phase, an initial sprint, and a final sprint with the stable pace factor accounting for most of the common factor variance (69%). The three-mile run time was used to discriminate successfully between two known groups of subjects in aerobic capacity. These data provide a degree of support for the construct validity of the three-mile run as a field test of aerobic capacity.

Adult↗
PubMed1986

Modulatory effect of glucose, amino acids, and secretin on CCK-8-induced somatostatin and pancreatic polypeptide release in dogs.

Protein- and fat-rich test meals elicit a strong stimulatory effect on postprandial somatostatin (SLI) and pancreatic polypeptide (PP) release, whereas carbohydrate-rich meals rather attenuate the response of both hormones. Since there is evidence that intestinal hormones might contribute to the postprandial SLI and PP response, it was the aim of the present study to determine in dogs the effect of low-dose cholecystokinin octapeptide (CCK-8) on basal hormone levels and also during a background infusion of amino acids or glucose. In a group of six conscious dogs, sulfated CCK-8 was infused intravenously (i.v.) via a hindleg vein at stepwise increasing infusion rates of 10, 30, and 50 pmol X kg-1 X h. The infusion of CCK was applied during a background infusion of saline (2 ml/min), glucose (0.2 g/min), or an amino acid mixture (8.5%, 2 ml/min). CCK-8 had no effect on plasma insulin and glucagon levels under all experimental conditions. Plasma SLI levels were significantly stimulated by all doses of CCK. This stimulatory effect was similar during background infusions of either saline, glucose, or amino acids, respectively. Pancreatic polypeptide (PP) levels rose 200-300 pg/ml during CCK plus saline. This was slightly attenuated by glucose. During CCK plus amino acids, the PP response was augmented to 600-800 pg/ml. Since secretin is also released after the ingestion of a meal and intraduodenal acidification is a potent stimulus not only of secretin but also of gastric and pancreatic SLI release, the effect of secretin was examined additionally.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1985

Physiological, pathophysiological and pharmacological aspects of exogenous and endogenous opiates.

Endogenous opioid peptides have been detected not only in the central nervous system but also in the peripheral autonomic nervous system of the gastrointestinal tract and pancreas and several other organs. In addition opioid active peptides have been found in certain nutrients such as wheat gluten and bovine and human milk. Functional studies have presented evidence for a participation of endogenous opioids in the regulation of certain pituitary and gastrointestinal functions. Apart from being a physiological neuroregulator there is evidence that endogenous opioids might play a role as a pathogenetic factor in various clinical disorders. The evidence for these different aspects of opioid function is reviewed in the present article.

Animals↗
PubMed1983

Effect of beta-casomorphins on somatostatin release in dogs.

In the present study, the effects of orally administered beta-casomorphins (beta-CM) and met-enkephalin on postprandial plasma somatostatin-like immunoreactivity (SLI) were assessed in conscious dogs. The intragastric instillation of a liver extract-sucrose test meal containing 12 mg beta-CM or 10 mg met-enkephalin, respectively, augmented the postprandial rise of peripheral vein plasma SLI levels significantly. This effect was inhibited by the additional administration of the specific opiate-receptor antagonist, naloxone. When liver extract-sucrose was dissolved in fresh bovine milk the increase of plasma SLI levels was significantly greater than liver extract-sucrose dissolved in water. This milk-induced augmentation of SLI levels was also reduced by naloxone. Since these opiate-active compounds have an influence upon insulin release when given iv, the effect of beta-CM-7, beta-CM-5, beta-CM-4 beta-CM-4-amide, and met-enkephalin on SLI levels was assessed during their iv infusion at a rate of 1 nmol/kg . h during an iv background infusion of a glucose-amino acid mixture. The infusion of beta-CM-5 elicited a stimulation of peripheral vein SLI levels, whereas the infusion of met-enkephalin resulted in a significant decrease of SLI levels. beta-CM-7, beta-CM-4, and beta-CM-4-amide had no effect on plasma SLI levels at the dose employed. The present data demonstrate that in dogs the ingestion of opiate-active peptide stimulates postprandial SLI release, indicating that nutrient-contained opiate-active material (exorphins) might participate in the regulation of postprandial gastrointestinal endocrine function.

Amino Acids↗
PubMed1975

Correlation of "sneaking through" of tumor cells with specific immunological impairment of the host.

The preferential take of tumors after small-size inocula of transplantable tumor cells has been described for many systems. The phenomenon has been named "sneaking through" or "dilution escape". Using a BALB/c mastocytoma, we have analyzed the immunological parameters accompanying sneaking through that can be observed upon injection of 10(1) to 10(3) living cells. Mice can also be conditioned by injection of low, subimmunogenic numbers of irradiated cells to show increased tumor incidences upon injection of living cells in doses two orders of magnitude above the sneaking through dose. The general immune reactivity of the animals is not impaired under these conditions. However, determinant-specific unresponsiveness is found which can be transferred by spleen cells and therefore seems to be actively maintained. It is concluded that sneaking through of tumor cells is the result of specific immunological impairment of the host's immune system by subimmunogenic small-size inocula of tumor cells.

Animals↗
PubMedDate not supplied

Modulation of motilin-induced somatostatin release in dogs by naloxone.

Somatostatin release in dogs is modulated by exogenous and endogenous opioids. Since postprandial somatostatin secretion is in part due to the stimulatory effect of postprandially activated gastrointestinal hormones as well as endogenous opioids, it was of interest to determine the interaction between motilin, a known stimulus of somatostatin release, and endogenous opioids with regard to activation of D-cell function. In a group of eight conscious dogs the infusion of synthetic porcine motilin at doses of 0.05, 0.25 and 0.5 micrograms/kg X hr elicited a significant increase of peripheral vein plasma somatostatin-like immunoreactivity (SLI), confirming previously reported data. The additional infusion of the opiate receptor antagonist naloxone attenuated this SLI response, suggesting that endogenous opioids participate in motilin-induced SLI release. Since previous studies have shown that the interaction between endogenous opioids and postprandial somatostatin secretion is modified by elevated plasma glucose levels, the experiments were repeated during an IV glucose (0.2 g/min) background infusion increasing circulating glucose levels by 20-30 mg/dl. During IV glucose, the SLI response to motilin was almost abolished. In this group the addition of naloxone restored the SLI response, indicating that the inhibitory effect of elevated glucose on D-cell function is, at least in part, mediated by endogenous opioids. These data suggest that motilin has to be considered as one regulatory factor which participates in the previously observed interaction between glucose and endogenous opioids during postprandial SLI release.

Animals↗
PubMedDate not supplied

Osteogenesis imperfecta associated with basilar impression and cerebral atrophy: a case report.

Osteogenesis imperfecta is a disease of bone formation subdivided into two types, congenita and tarda. It is associated with bony fragility, blue sclerae and abnormality of tooth dentin. Rarely the tarda form is associated with basilar invagination or infolding of the foramen magnum and upper cervical segments into the posterior fossa. This results in hydrocephalus and a spectrum of neurologic dysfunction known as the foramen magnum compression syndrome. Many radiologic methods have been used to evaluate basilar invagination including plain film and CT. We describe a patient with osteogenesis imperfecta tarda examined with CT, with a unique finding of diffuse cerebral atrophy associated with basilar invagination.

Adult↗