PEDB: the Prostate Expression Database

Naloxone is generally considered to be a pure antagonist, but it may produce several behavioral effects, such as hyperalgesia or stimulation of respiration. We studied the effect of naloxone on gastric emptying and gastrointestinal transit in rats. Six to eight Wistar rats (200-250 g) were used for each experiment. Either saline or naloxone (0.01-10 mg/kg) was injected intraperitoneally at 0 min. At 30 min, radiolabeled saline or milk 1 mL was infused into the stomach. At 60 min, gastric emptying and gastrointestinal transit were calculated by measuring the radioactivity in the gastrointestinal tract. Naloxone significantly inhibited gastric emptying of saline (P = 0.002) and of milk (P < 0.05), but not the gastrointestinal transit of either (P > 0.05). Gastric emptying of saline showed a significant peak (P < 0.05) in the dose-response curve at 0.7 mg/kg. Therefore, naloxone significantly inhibits gastric emptying of saline and milk, but not the gastrointestinal transit of either. IMPLICATIONS: Although naloxone is generally considered to be a pure opioid receptor antagonist, it delays gastric emptying of saline or milk, as does morphine in the rat. However, it is uncertain from our results whether naloxone inhibited gastric emptying by antagonizing the effects of endogenous opioids.     

Deformation of concrete and cement paste loaded at constant temperatures from 140 to 724°C

Constant temperature creep of unsealed pure cement paste, gravel and lightweight concretes obtained under constant uniaxial compressive load are reported for temperatures between 140°C and 724°C. The work suggests that it is possible, within certain limits, to uncouple the time, stress and temperature functions of constant high temperature creep, which can be represented mathematically by a simple multiple of the three functions. The time functions of all three mixes were best represented by a power law with an exponent slightly influenced by temperature. It is suggested that the temperature function may not be sufficiently described by the Arrhenius relation during first heating. The temperature function indicated a sharp increase in creep for gravel concrete above 350°C caused by break-up of the aggregate. However, the sharp increase in creep for both lightweight concrete and cement paste above 600°C is seated in the cement paste and appears to be a function of “current” temperature. A rheological criterion therefore limits the structural usefulness of Portland cement concretes to temperatures below 600°C. Similarities in constant high temperature creep behaviour with other materials have been noted.     

Human Myt1 is a cell cycle-regulated kinase that inhibits Cdc2 but not Cdk2 activity

Activation of the Cdc2.cyclin B kinase is a pivotal step of mitotic initiation. This step is mediated principally by the dephosphorylation of residues threonine 14 (Thr14) and tyrosine 15 (Tyr15) on the Cdc2 catalytic subunit. In several organisms homologs of the Wee1 kinase have been shown to be the major activity responsible for phosphorylating the Tyr15 inhibitory site. A membrane-bound kinase capable of phosphorylating residue Thr14, the Myt1 kinase, has been identified in the frog Xenopus laevis and more recently in human. In this study, we have examined the substrate specificity and cell cycle regulation of the human Myt1 kinase. We find that human Myt1 phosphorylates and inactivates Cdc2-containing cyclin complexes but not complexes containing Cdk2 or Cdk4. Analysis of endogenous Myt1 demonstrates that it remains membrane-bound throughout the cell cycle, but its kinase activity decreased during M phase arrest, when Myt1 became hyperphosphorylated. Further, Cdc2. cyclin B1 was capable of phosphorylating Myt1 in vitro, but this phosphorylation did not affect Myt1 kinase activity. These findings suggest that human Myt1 is negatively regulated by an M phase-activated kinase and that Myt1 inhibits mitosis due to its specificity for Cdc2.cyclin complexes.     

An automated radiopharmaceutical dispenser

Residential proximity to electrical power lines of different voltage in relation to childhood leukemia was investigated through a case-control study undertaken in Greece during 1993-1994. The study comprised 117 incident cases of childhood leukemia and 202 age-, gender- and place-of-residence-matched controls. Four measures of exposure to magnetic fields were developed, using data provided by the Public Power Corporation of Greece: Voltage (V) divided by the distance (d), V/d2, V/d3 and an adaptation of the Wertheimer-Leeper code. Conditional-logistic-regression modeling was used to adjust for potential confounding influences of 18 variables. No significant trends of childhood leukemia risk with increasing exposure levels were noted, nor were there statistically significant elevations of disease risk at the higher exposure levels in each measure of exposure. These results do not support a causal link between residential proximity to electrical high-voltage wires and childhood leukemia risk, but in themselves do not refute a weak empirical association.     

Apolipoprotein B and AI distributions in the United States, 1988-1991: results of the National Health and Nutrition Examination Survey III (NHANES III)

Serum apolipoproteins (apo) B and AI were measured in a probability sample of the noninstitutionalized US civilian population, ages > or = 4 years, which included non-Hispanic whites, non-Hispanic blacks, and Mexican-Americans. Apo B concentrations were the same in males and females, lower in black males than in other males, low in childhood (approximately 0.80 g/L) and increasing to approximately 1.2 g/L in adults, and higher in younger women on hormones. Apo AI was higher in females than males, higher in blacks than in others, remained constant from childhood to adulthood (approximately 1.35 g/L) in males, but increased with age (approximately 1.30 g/L to approximately 1.55 g/L) in females, and was higher in women taking hormones. These are the first national probability estimates of apo B and apo AI in the US and are referable to the WHO-IFCC First International Reference Materials for apo AI and B.     

Dynamics of the N-terminal alpha-helix unfolding in the photoreversion reaction of phytochrome A

Time-resolved circular dichroism spectroscopy in the far-UV spectral region was used to examine the intermediates of the phytochrome photoreversion reaction (Pfr --> Pr). Three intermediates, lumi-F (tau = 320 ns), meta-Fa (tau = 265 micros) and meta-Fb (tau = 5.5 ms), have been identified in a simple sequential kinetic photoreversion mechanism by absorption spectroscopy [Linschitz, H., Kasche, V., Butler, W. L., & Siegelman, H. W. (1966) J. Biol. Chem. 241, 3395-3403; Pratt, L. H., & Butler, W. L. (1968) Photochem. Photobiol. 8, 477-485; Burke, M., Pratt, D. C., & Moscowitz, A. (1972) Biochemistry 11, 4025-4031; Spruit, C. J. P., Kendrick, R. E., & Cooke, R. J. (1975) Planta (Berlin) 127, 121-132; Eilfeld, P., & Rüdiger, W. (1985) Z. Naturforsch. 40c, 109-114; Chen, E., Lapko, V. N., Lewis, J. W., Song, P.-S., & Kliger, D. S. (1996) Biochemistry 35, 843-850]. In order to correlate the unfolding of the N-terminal alpha-helical segment with one or more of the intermediate species, time-resolved methods were coupled with the structurally sensitive probe of CD in the far-UV spectral region. Analysis of the TRCD data associates the decrease in alpha-helical content that occurs upon formation of Pr with decay of the meta-Fa intermediate. This unfolding process occurs with a time constant of 310 +/- 125 micros, which is consistent with the 265-micros lifetime for meta-Fa.     

Enantioselective analysis of praziquantel in plasma samples

In prokaryotes, DnaK-DnaJ chaperon is involved in the protein degradation catalyzed by proteases La and ClpA/B complex as shown in E. coli. To extend this into eukaryotic cells, we examined the effects of hsp70 genes, SSA1 and SSB1, and DnaJ genes, SIS1 and YDJ1, on the growth of proteasome subunit mutants of the yeast S. cerevisiae. The results identified SSB1 and SIS1 as a pair of chaperon genes specifically involved in efficient protein turnover in the yeast, whose overexpression suppressed the growth defects caused by the proteasome mutations. Moreover, a single amino acid substitution in the putative peptide-binding site of SSB1 protein profoundly enhanced the suppression activity, indicating that the activity is mediated by the peptide-binding activity of this chaperon. Thus SSB1, with its partner DnaJ, SIS1, modulates the efficiency of protein turnover through its chaperon activity.     

Riboflavin-mediated delivery of a macromolecule into cultured human cells

The effects of perivascular nerve stimulation and phenylephrine on osmolyte release were studied in the intact perfused rat liver and isolated liver parenchymal cells (PC) and nonparenchymal cells. In the perfused liver, electrical stimulation of perivascular nerves (20 Hz/2 ms/20 V) led to a phentolamine-sensitive increase of cell hydration by 6.5% +/- 1.2% (n = 3) and a transient phentolamine-sensitive stimulation of taurine and inositol, but not betaine, release. These nerve effects were mimicked by phenylephrine, but not prostaglandin F2alpha, and were not affected by sodium nitroprusside (SNP) or ibuprofen. Nerve stimulation-induced taurine, but not inositol, release was inhibited by 4, 4'-di-isothiocyanatostilbene-2,2'-disulphonic acid (DIDS) (50 micromol/L). Single-cell fluorescence studies with isolated liver PC, Kupffer cells (KC), sinusoidal endothelial cells (SEC), and hepatic stellate cells (HSC) revealed that phenylephrine induced an increase in cytosolic free Ca2+ only in PC and HSC, but not in KC and SEC, whereas extracellular uridine triphosphate (UTP) produced Ca2+ transients/oscillations in all liver cell types studied. Phenylephrine had no effect on osmolyte release from isolated KC and SEC, but increased taurine (but not inositol) release from PC and inositol (but not taurine) efflux from HSC. The data suggest that: 1) liver cell hydration and-consecutively-osmolyte content are modulated by hepatic nerves via an alpha-adrenergic mechanism, which does not involve eicosanoids or hemodynamic changes; 2) that PC and HSC are the primary targets for nerve-dependent alpha-adrenergic activation, whereas 3) KC and SEC probably do not express alpha-adrenoceptors coupled to Ca2+ mobilization or osmolyte efflux.     

Evaluation of biochemical changes during in vivo erythrocyte senescence in the dog

One hypothesis to explain the age-dependent clearance of red blood cells (RBCs) from circulation proposes that denatured/oxidized hemoglobin (hemichromes) arising late during an RBC's life span induces clustering of the integral membrane protein, band 3. In turn, band 3 clustering generates an epitope on the senescent cell surface leading to autologous IgG binding and consequent phagocytosis. Because dog RBCs have survival characteristics that closely resemble those of human RBCs (ie, low random RBC loss, approximately 115-day life span), we decided to test several aspects of the above hypothesis in the canine model, where in vivo aged cells of defined age could be evaluated for biochemical changes. For this purpose, dog RBCs were biotinylated in vivo and retrieved for biochemical analysis at various later dates using avidin-coated magnetic beads. Consistent with the above hypothesis, senescent dog RBCs were found to contain measurably elevated membrane-bound (denatured) globin and a sevenfold enhancement of surface-associated autologous IgG. Interestingly, dog RBCs that were allowed to senesce for 115 days in vivo also suffered from compromised intracellular reducing power, containing only 30% of the reduced glutathione found in unfractionated cells. Although the small quantity of cells of age >/=110 days did not allow direct quantitation of band 3 clustering, it was nevertheless possible to exploit single-cell microdeformation methods to evaluate the fraction of band 3 molecules that had lost their normal skeletal linkages and were free to cluster in response to hemichrome binding. Importantly, band 3 in RBCs >/=112 days old was found to be 25% less restrained by skeletal interactions than band 3 in control cells, indicating that the normal linkages between band 3 and the membrane skeleton had been substantially disrupted. Interestingly, the protein 4.1a/protein 4.1b ratio, commonly assumed to reflect RBC age, was found to be maximal in RBCs isolated only 58 days after labeling, implying that while this marker is useful for identifying very young populations of RBCs, it is not a very sensitive marker for canine senescent RBCs. Taken together, these data argue that several of the readily testable elements of the above hypothesis implicating band 3 in human RBC senescence can be validated in an appropriate canine model.