Liquid chromatographic determination of L-ascorbate 2-polyphosphate in fish feeds by enzymatic release of L-ascorbate

An accurate method was devised to assay L-ascorbic 2-polyphosphate esters (AsPP) in fish feed by phosphatase digestion followed by determination of the released L-ascorbic acid (AsA). Compressed yeast and dithiothreitol are added to the phosphatase reaction mixture to give 95-100% recovery of AsA, which is quantitated by reverse-phase liquid chromatography (LC) with electrochemical detection. Chromatograms of all feed digests showed baseline resolution of AsA. In 3 feeds, to which 75-125 ppm AsA equivalents in the form of AsPP were added, the assay procedure gave 98-100% recovery of AsA.

cDNA cloning and deduced amino acid sequence of microvitellogenin, a female specific hemolymph and egg protein from the tobacco hornworm, Manduca sexta

Microvitellogenin is a female-specific yolk protein from the tobacco hornworm moth Manduca sexta. A cDNA library was constructed from poly(A)+ RNA isolated from adult female fat body. cDNA clones of mRNA for microvitellogenin were isolated by using antiserum against microvitellogenin. Northern blot analysis of poly(A)+ RNA isolated from different life stages and sexes reveals that mRNA coding for microvitellogenin is only present in adult female fat body. Immunoprecipitation of the protein product translated from hybrid selected mRNA indicates that the cDNA clone is specific for microvitellogenin. The complete nucleotide sequence of the 834-base pair cDNA insert has been determined by the dideoxy chain termination method. The cDNA sequence predicts that microvitellogenin is a protein of 232 residues with a calculated molecular weight of 26,201. The cDNA also predicts an amino-terminal extension of 17 residues which are not present in the mature form. This sequence appears to be a signal peptide. A comparison of the translated amino acid sequence with the sequences in the National Biomedical Foundation protein library did not establish any sequence homology with other known proteins.

Growth hormone promoted tyrosyl phosphorylation of growth hormone receptors in murine 3T3-F442A fibroblasts and adipocytes

Because many growth factor receptors are ligand-activated tyrosine protein kinases, the possibility that growth hormone (GH), a hormone implicated in human growth, promotes tyrosyl phosphorylation of its receptor was investigated. 125I-Labeled human GH was covalently cross-linked to receptors in intact 3T3-F442A fibroblasts, a cell line which differentiates into adipocytes in response to GH. The cross-linked cells were solubilized and passed over a column of phosphotyrosyl binding antibody immobilized on protein A-Sepharose. Immunoadsorbed proteins were eluted with a hapten (p-nitrophenyl phosphate) and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. The eluate from the antibody column contained an Mr 134,000 125I-GH-receptor complex. A similar result was obtained when the adipocyte form of 3T3-F442A cells was used in place of the fibroblast form. O-Phosphotyrosine prevented 125I-GH-receptor complexes from binding to the antibody column, whereas O-phosphoserine and O-phosphothreonine did not. In studies of GH-promoted phosphorylation in 3T3-F442A fibroblasts labeled metabolically with [32P]Pi, GH was shown to stimulate formation of a 32P-labeled protein which bound to immobilized phosphotyrosyl binding antibodies. The molecular weight of 114,000 obtained for this protein is similar to that expected for non-cross-linked GH receptor. The Mr 114,000 phosphorylated protein could be immunoprecipitated with anti-GH antibody, indicating that GH remained noncovalently bound to this protein during absorption to and elution from the immobilized phosphotyrosyl binding antibody. Phosphoamino acid analysis after both limited acid hydrolysis and extensive base hydrolysis of the Mr 114,000 phosphoprotein confirmed the presence of phosphotyrosyl residues.(ABSTRACT TRUNCATED AT 250 WORDS)

Freeze-fracture cytochemistry of rat glomerular capillary tuft. Determination of wheat germ agglutinin binding sites and localization of anionic charges

We propose here the use of freeze-fracture to gain access and to label in vitro glomerular components and locate WGA receptors and anionic sites. Tissues are frozen, fractured under liquid nitrogen, and thawed. Freeze-fracture rendered all glomerular structures directly accessible to the reagents. This made possible study of the nature and topology of cationized ferritin and WGA binding sites. WGA-gold complexes were observed over plasma membranes of podocytes and of endothelial and mesangial cells. Labeling of podocytes and endothelial cells was similar in the mesangial area and in the peripheral part of the capillary loop. Cross-fractures of extracellular matrices showed that WGA bound uniformly to the glomerular basement membrane (GBM) as well as to mesangial matrix. In fractured specimens treated with neuraminidase, WGA was no longer observed over podocytes but it consistently labeled the surface of endothelial and mesangial cells. Whereas in GBM cross-sections WGA binding was greatly reduced or even abolished, it remained unmodified in the mesangium. This shows that only NeuNAc (sialic acid) might account for the binding of WGA to podocytes, whereas GlcNAcs appear to be the main WGA binding sites on endothelial and mesangial cells and in the mesangial matrix. Both NeuNAc and GLcNAc residues are probably associated in GBM. With cationized ferritin (pI 8.3) at pH 7.4, intense, continuous labeling was seen all over the different plasma membranes, denser in podocytes than in endothelial cells. CF was also observed in cross-fractured profiles of extracellular matrices and never appeared agglutinated in discrete sites.

Nalbuphine as an analgesic component in balanced anesthesia for cardiac surgery

The efficacy and safety of nalbuphine hydrochloride as an IV analgesic used in combination with pretreatment and supplemental doses of diazepam with and without N2O were assessed in 15 patients scheduled to undergo aortocoronary bypass (n = 11) or valve replacement surgery (n = 4). The loading infusion of 3.0 mg/kg nalbuphine given in 20 min 5 min after conclusion of IV injection of 0.4 mg/kg/5 min diazepam caused no significant changes in systolic or diastolic systemic and pulmonary arterial blood pressures or in heart rate, cardiac index, stroke index, systemic and pulmonary vascular resistance, or right and left ventricular stroke work index. After the initial 1-hr loading infusion of 6.66 +/- 0.89 mg/kg nalbuphine (mean +/- SE), additional nalbuphine infusion maintenance doses of 4.73 +/- 0.77, 1.87 +/- 0.31, 2.16 +/- 0.23, 1.65 +/- 0.22, and 2.35 +/- 0.44 were used in the subsequent hourly periods to maintain a pain-free state throughout surgery. Hemodynamic changes during the three most stressful periods, tracheal intubation, skin incision, and sternotomy, were not statistically significant. Normal plasma catecholamine and cortisol levels indicate that these patients experienced neither stress nor pain during the maintenance of anesthesia. Nalbuphine caused no significant histamine release. All patients had uncomplicated maintenance of and emergence from anesthesia.

Endocrine and hemodynamic effects of antagonism of fentanyl-induced respiratory depression by nalbuphine

Endocrine and hemodynamic changes associated with the antagonism of fentanyl by nalbuphine have not been reported. Therefore, the authors studied ten patients after anesthetic induction with thiopental, fentanyl, tracheal intubation aided by succinylcholine and maintenance with diazepam, pancuronium, N2O, and further doses of fentanyl. Eight of the patients underwent cholecystectomy, one had a hysterectomy, and another had an abdominoplasty. After reversal of neuromuscular block at the conclusion of surgery, normal ventilation was restored by 0.22 +/- 0.02 mg/kg intravenous nalbuphine (mean +/- SEM). Plasma levels of free norepinephrine, histamine, and cortisol did not increase after antagonism of the fentanyl-induced respiratory depression, but plasma concentration of epinephrine increased significantly but without significant hemodynamic changes. Minute ventilation was 1.5 +/- 0.4 L/min before and 11 +/- 1, 10 +/- 1, 11 +/- 1, and 10 +/- 1 L/min at 15, 30, 45, and 60 min after antagonism; corresponding PaCO2 levels were 56 +/- 2, 44 +/- 1, 49 +/- 7, 49 +/- 1, 42 +/- 1 mm Hg. The mean analogue pain score remained below 1.5. We conclude that nalbuphine effectively antagonizes fentanyl-induced respiratory depression without adverse endocrine and circulatory changes or loss of analgesia.

Structural and cytochemical differentiation of membrane elements of the apical membrane of amphibian urinary bladder epithelial cells. A label fracture study

It is now generally accepted that ADH-induced increase in water permeability in responsive epithelia is associated with the insertion of specific structures in the apical membrane of epithelial cells. Up to now, these structures have only been recognized in freeze-fractured preparations and their chemical nature is still unknown. In this study, we used the label-fracture method (Pinto da Silva and Kan, J. Cell Biol., 99, 1156-1161, 1984) to investigate the distribution of wheat germ agglutinin (WGA) on the luminal plasma membrane of freeze-fractured frog urinary bladder epithelial cells. With label-fracture, the cytochemical markers are seen superimposed with the conventional high resolution image of the E face. Label-fracture of tissue treated for 15 min with WGA and subsequently labeled with colloidal gold coated with ovomucoid showed uniform distribution of gold particles along the exoplasmic fracture face. Stereomicrographs show that the gold label is under the fracture face as it is attached to the outer surface of the membrane. Preincubation of the bladder with WGA for 3 hr induced a segregation of the intramembranous particles of the apical plasma membrane. In this condition, we observed a co-distribution of WGA-gold complexes with the segregated particles on the E face. This indicates that WGA-binding sites are located on glycoproteins which probably comprise the large intramembranous particles dispersed on the exoplasmic faces of freeze-fractured luminal membranes. In contrast, the numerous small intramembrane particles observed on P faces remained evenly distributed even after exposure to WGA and are, therefore, unrelated to WGA receptor sites. After WGA treatment, ADH still induced the formation of aggregates inside the smooth domains. A few WGA-binding sites appeared to be associated to these aggregates.

The inhibitory effect of glycopyrrolate on human plasma-cholinesterase

The in vitro inhibitory effect of glycopyrrolate and atropine on the hydrolysis of benzoylcholine at 50.0 microM concentration was determined in the plasma of 6 healthy volunteers at 37 degrees C and at 240 nm by the ultraviolet spectrophotometric method of Kalow. The 50 per cent inhibitory concentration (I50) of glycopyrrolate was found to be 1.0 mM and the I50 of atropine was 0.9 mM. This inhibitory effect of glycopyrrolate and atropine is moderate but its interaction with the in vivo hydrolysis of succinylcholine or that of ester-type of local anaesthetics in patients should be further studied. Although both glycopyrrolate and atropine inhibit PChE to the same extent, glycopyrrolate should be utilized in patients in whom inhibition of brain PChE or central effects ought to be avoided, since glycopyrrolate does not penetrate the blood-brain barrier.