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At least 307 records · Page 17Linked to original sources
PubMed1992

Initial studies on the N-glucosylation of phenobarbital by mouse liver microsomes using a radiochemical high-performance liquid chromatographic (HPLC) method.

A method is described for the assay of phenobarbital N-glucosylation using UDP-D-[6-3H]glucose. The radioactive phenobarbital N-glucoside conjugates [(5R)-PBG, (5S)-PBG] formed during the incubations were resolved from each other and from uncharacterized radioactive products by semipreparative HPLC. The product ratio of the N-glucosides of (5R)-PBG/(5S)-PBG was 2.9 for the crude liver homogenate and 3.0 +/- 0.5 for the microsomes. Magnesium was necessary for optimal activity. The Km values for formation of (5R)-PBG, (5S)-PBG, and (5R + 5S)-PBG were 1.55 +/- 0.35, 1.27 +/- 0.14, and 1.47 +/- 0.21 mM, respectively. The Vmax values for formation of (5R)-PBG, (5S)-PBG, and (5R + 5S)-PBG were 1.34 +/- 0.05 x 10(-6), 0.43 +/- 0.01 x 10(-6), and 1.77 +/- 0.04 x 10(-6) mumol/min/mg microsomal protein, respectively. It was observed that at concentrations greater than 5 mM sodium phenobarbital, inhibition of formation of phenobarbital N-glucosides occurred. The product ratio of (5R)-PBG/(5S)-PBG is comparable to that observed in the urinary excretion studies with the mouse and opposite to that observed in urinary excretion studies in humans.

Animals↗
PubMed1999

Purification, structural characterization, cloning and immunocytochemical localization of chemoreception proteins from Schistocerca gregaria.

Soluble low-molecular-mass protein isoforms were purified from chemosensory organs (antennae, tarsi and labrum) of the desert locust Schistocerca gregaria. Five genes encoding proteins of this group were amplified by PCR from cDNAs of tarsi and sequenced. Their expression products are polypeptide chains of 109 amino acids showing 40-50% sequence identity with putative olfactory proteins from Drosophila melanogaster and Cactoblastis cactorum. Direct structural investigation on isoforms purified from chemosensory organs revealed the presence in the expression products of two of the genes cloned. Two additional protein isoforms were detected and their molecular structure exhaustively characterized. MS analysis of all isoforms demonstrated that the four cysteine residues conserved in the polypeptide chain were involved in disulfide bridges (Cys29-Cys38 and Cys57-Cys60) and indicated the absence of any additional post-translational modifications. Immunocytochemistry experiments, performed with rabbit antiserum raised against the protein isoform mixture, showed selective labelling of the outer lymph in contact sensilla of tarsi, maxillary palps and antennae. Other types of sensilla were not labelled, nor were the cuticle and dendrites of the sensory cells. No binding of radioactively labelled glucose or bicarbonate was detected, in disagreement with the hypothesis that this class of proteins is involved in the CO2-sensing cascade. Our experimental data suggest that the proteins described here could be involved in contact chemoreception in Orthoptera.

Amino Acid Sequence↗
PubMed1988

Enzyme activities associated with maize kernel amyloplasts.

Activities of the enzymes of gluconeogenesis and of starch metabolism were measured in extracts of amyloplasts isolated from protoplasts derived from 14-day-old maize (Zea mays L., cv Pioneer 3780) endosperm. The enzymes triosephosphate isomerase, fructose-1,6-bisphosphate aldolase, fructose-1,6-bisphosphatase, phosphohexose isomerase, phosphoglucomutase, ADPG pyrophosphorylase, UDPG pyrophosphorylase, soluble and bound starch synthases, and branching enzyme were found to be present in the amyloplasts. Of the above enzymes, ADPG pyrophosphorylase had the lowest activity per amyloplast. Invertase, sucrose synthase and hexokinase were not detected in similar amyloplast preparations. Only a trace of the cytoplasmic marker enzyme alcohol dehydrogenase could be detected in purified amyloplast fractions. In separate experiments, purified amyloplasts were lysed and then supplied with radioactively labeled glucose-6-phosphate, glucose-1-phosphate, fructose-1,6-bisphosphate, dihydroxyacetone phosphate, glucose, fructose, sucrose, and 3-0-methylglucose in the presence of adenosine triphosphate or uridine triphosphate. Of the above, only the phosphorylated substrates were incorporated into starch. Incorporation into starch was higher with added uridine triphosphate than with adenosine triphosphate. Dihydroxyacetone phosphate was the preferred substrate for uptake by intact amyloplasts and incorporation into starch. In preliminary experiments, it appeared that glucose-6-P and fructose-1,6-bisphosphate may also be taken up by intact amyloplasts. However, the rate of uptake and incorporation into starch was relatively low and variable. Additional study is needed to determine conclusively whether hexose phosphates will cross intact amyloplast membranes. From these data, we conclude that: (a) Triose phosphate is the preferred substrate for uptake by intact amyloplasts. (b) Amyloplasts contain all enzymes necessary to convert triose phosphates into starch. (c) Sucrose breakdown must occur in the cytosol prior to carbohydrate transfer into the amyloplasts. (d) Under the conditions of assay, amyloplasts are unable to convert glucose or fructose to starch. (e) Uridine triphosphate may be the preferred nucleotide for conversion of hexose phosphates to starch at this stage of kernel development.

Journal Article↗
PubMed1977

Gluconeogenesis in the guinea pig. Effect of glucagon on gluconeogenesis from lactate by isolated perfused guinea-pig liver.

Gluconeogenesis was stimulated by glucagon in fed but not fasted isolated perfused guinea pig livers. Both the amount and the rate of incorporation of radioactivity into glucose from L-[U-14C]lactate were increased in fed livers by the addition of glucagon to the perfusate. The glucagon-stimulated increase in gluconeogenesis was accompanied by an increase in oxygen consumption, an increase in the amount of lactate carbon converted to glucose and a decrease in the amount of lactate carbon converted to CO2. The results are interpreted to indicate that glucagon affects gluconeogenesis from lactate in fed livers by redirecting the fate of substrate from other products toward glucose.

Animals↗
PubMed1989

Regional cerebral blood flow and glucose utilization during hypoglycemia in newborn dogs.

To assess alterations in regional cerebral blood flow and glucose utilization during perinatal hypoglycemia, newborn dogs (2-7 days postnatal age) were anesthetized with halothane, tracheostomized, paralyzed, and artificially ventilated with 70% N2O-30% O2 to maintain arterial normoxia and normocapnia (arterial PO2 greater than 60 mmHg; arterial PCO2: 35-42 mmHg; arterial pH: 7.35-7.45). Regional cerebral blood flow (rCBF) and glucose utilization (rCGU) were determined with iodo-[14C]antipyrine and 2-deoxy-[14C]glucose as the radioactive tracers, respectively. Hypoglycemia with blood glucose concentrations averaging 0.9 mmol/l was achieved within 90-120 min in 10 animals using intermittent intravenous injections of regular insulin; 10 control animals received 0.9% saline (blood glucose = 9 mmol/l). During hypoglycemia, mean arterial blood pressure was 81% of control, whereas heart rate was unchanged. Arterial O2 and acid-base balance were well maintained (arterial PO2 = 68 mmHg; PCO2 = 37 mmHg; pH = 7.35). Hypoglycemia was associated with significant increases in rCBF in all of 16 analyzed structures, ranging from 172% (parietal white matter) to 249% (thalamus) of control values (17-65 ml.100 g-1.min-1). During hypoglycemia, rCGU was relatively unchanged from normoglycemic values in 11 of 16 brain structures. Significant reductions in rCGU were seen only in occipital white matter (-31%) and in the cerebellar vermis and hemisphere (-31 and -43%, respectively). CGU actually increased slightly in the pons and medulla (+12 and +19%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Ventromedial hypothalamic knife-cut lesions in rats resistant to dietary obesity.

The effects of ventromedial hypothalamic (VMH) knife-cut lesions on food intake and body weight of S 5B/Pl rats, which are normally resistant to obesity when eating a high-fat diet, were examined in two experiments. In the first experiment body weight increased only slightly after VMH knife-cut lesions when animals were fed pelleted laboratory chow or a 10% corn oil diet. When eating the 30% corn oil diet, however, body weight increased in the VMH knife-cut rats. In the second experiment VMH knife-cut lesions produced a small weight gain in rats fed the 10% fat diet; this manipulation also increased food intake and disrupted the normal diurnal feeding pattern. Changes in the weight of the liver, interscapular brown adipose tissue, and white adipose tissue paralleled the changes in body weight. Plasma insulin increased in the rats eating the 30% corn oil diet ad libitum but not in the VMH-lesioned animals pair fed to the sham-operated rats. Incorporation of 3H from 3H2O into lipid was significantly increased in white fat of animals with VMH knife cuts. Similar results were obtained from incubation of adipose tissue in vitro with insulin and radioactively labeled glucose. These studies show that hypothalamic knife-cut lesions can remove the resistance of the S 5B/Pl rats to obesity when they are fed a high-fat diet.

Adipose Tissue↗
PubMed1984

Sulfated polysaccharides and cell differentiation in the sea urchin embryo.

The synthesis of sulfated polysaccharides during the embryonic development of Paracentrotus lividus has been investigated by incorporation of radioactive sulfate, glucose, glucosamine and fucose. The following substances become labelled: fucan sulfate (approximately 60%), heparan sulfate (approximately 20%) and dermatan sulfate (approximately 20%), and possibly a very slight amount of chondroitin sulfate. In animalized and vegetalized embryos, the rate of incorporation is significantly reduced, and furthermore dermatan sulfate is almost absent in animalized embryos. It is concluded that this substance is associated with the differentiation of vegetative cells, possibly the mesenchyme cells.

Animals↗
PubMed1980

The effects of applied electric fields on Micrasterias. I. Morphogenesis and the pattern of cell wall deposition.

Applied electric fields of approximately 14 V/cm have profound effects on the morphogenesis of the unicellular green alga, Micrasterias denticulata. This field corresponds to a potential drop of 15-40 mV across lobes oriented perpendicular to the applied field. These lobes show a galvanotropism toward the cathode. Lobes growing parallel to the field are stunted to varying degrees, depending on their orientation. As shown by other investigators, most cell wall material is normally deposited at the tips of growing lobes. If, however, cell expansion is osmotically inhibited in electric fields, wall material also accumulates along the cathode-facing (CF) sides of lobes oriented perpendicular to the field. Similarly, in cells growing under the influence of an applied field, radioactively labelled glucose and the methyl groups from methionine are incorporated along the CF sides of lobes as well as the lobe tips. This is also true when the label is added immediately after cells are removed from the fields, indicating that the wall-depositing machinery itself has been temporarily altered by the field. These results demonstrate that applied electric fields can be a valuable tool in elucidating the mechanisms of growth localization in Micrasterias cells.

Cell Wall↗
PubMed1978

Ribulose-peptide in human semen: II. Synthesis.

In order to study the metabolism of a naturally occurring peptide containing D-ribulose in the semen, a pathway of D-ribulose synthesis from radioactively labeled glucose was analyzed. Semen obtained from ten healthy adults was used in this study. The seminal fluid of each person sampled was divided into two equal parts and each one was incubated with glucose-1-14C or glucose-6-14C at room temperature for 1 hr. The rate of incorporation into ribulose from glucose-6-14C was higher than that of glucose-1-14C. This suggests that the ribulose in semen might be converted from glucose through the pentose-phosphate cycle, and incorporated into the ribulose-peptide through an unknown pathway. Incorporation of the labelled 14C was also found in all of the amino acids which were detected in the acid hydrolysate of the ribulose-peptide.

Adult↗
PubMed2006

Accurate noninvasive measurement of infarct size in mice with high-resolution PET.

UNLABELLED: Reliable, repeatable, and time-efficient noninvasive measurement of infarct size in mice with PET would benefit studies aimed at the exploration of biochemical and functional changes associated with acute myocardial infarction (MI). PET with the radioactively labeled glucose derivative (18)F-FDG is used in humans to distinguish between viable but dysfunctional and nonviable myocardium. In this study, the feasibility, accuracy, and time efficiency of (18)F-FDG PET for quantification of infarct size in mice using a high-resolution animal PET device was evaluated in comparison with histomorphometry. METHODS: Mice were subjected to surgery with permanent ligation of the left anterior descending artery. PET was performed before and 7 d after surgery. The infarct size was determined from the PET studies using both manual and automated delineation. The second PET scan was followed by histomorphometric analysis. RESULTS: An excellent correlation between PET and histomorphometry was found for both manual (R = 0.98) and automated (R = 0.98) delineation, with linear regression curves close to unity (manual: y = 1.10x - 0.01; automated: y = 1.12x - 0.02). Automated analysis required <1 min per study. CONCLUSION: The measurement of infarct size in mice with (18)F-FDG PET is feasible and highly accurate. This noninvasive methodology permits unique longitudinal studies of biochemical parameters in mice and facilitates studies that aim to assess the effect of surgical and pharmacologic intervention after acute MI.

Algorithms↗
PubMed1987

Cell phenomena in experimental viral-bacterial infections in mice. II. Phagocytic activity of granulocytes during infection with influenza viruses and staphylococci.

In the paper the influence of viral, bacterial and mixed viral-bacterial infections on phagocytic activity of mouse peritoneal granulocytes was estimated. Granulocytes isolated on the 3rd, 6th, 9th and 14th day of infection were incubated for 1 h at 37 degrees C together with S. aureus 209P cultivated in the presence of 14C labelled glucose. The radioactivity of samples was measured in the scintillatory counter. The results were shown as phagocytic index of granulocytes. The obtained data point to the decrease of granulocyte phagocytic activity in mice infected with bacteria in the first period of infection. When mice were infected with non-adapted influenza virus the decrease of granulocyte phagocytic activity was observed in the late stage of infection. The infection with adapted virus as well as mixed infection led to the complete disfunction of granulocyte phagocytic activity.

Adaptation, Physiological↗
PubMed1975

Glucose transport in Acholeplasma laidlawii B: dependence on the fluidity and physical state of membrane lipids.

The uptake of D-glucose by Acholeplasma laidlawii B occurs via a mediated transport process, as shown by the following observations: (i) glucose permeates A. laidlawii B cells at a rate at least 100 times greater than would be expected if its entry occurred only by simple passive diffusion; (ii) the apparent activation energy for glucose uptake in A. laidlawii is significantly lower than that expected and observed for the passive permeation of this sugar; (iii) glucose uptake appears to be a saturable process; (iv) glucose uptake can be completely inhibited by low concentrations of phloretin and phlorizin; and (v) glucose uptake is markedly inhibited at temperatures above 45 C, whereas the passive entry of erythritol continues to increase logarithmically until at least 60 C. The metabolism of D-glucose by this organism is rapid and, at low glucose concentrations, the intracellular radioactivity derived from D-[14-C]glucose is at any given time a reflection of the net effect of glucose transport, glucose metabolism, and loss from the cell of radioactive metabolic products. Care must thus be taken when attempting to determine the rate of glucose transport by measuring the accumulation by the cells of the total radioactivity derived from D-[14-C]glucose. The rate of uptake of D-glucose by A. laidlawii B cells is markedly dependent on the fatty acid composition and cholesterol content of the plasma membrane and exhibits a direct dependence on the fluidity of the membrane lipids as measured by their reversible, thermotropic gel to liquie-crystalline phase transition temperatures. In contrast to the transport rates, the apparent activation energy for glucose uptake above the phase transition temperature is not dependent on membrane lipid composition. At the temperature range within the membrane lipid phase transition region, the apparent activation energy of glucose uptake is different from the activation energy observed at temperatures above the phase transition. This may reflect the superimposed operation within the phase transition region of more than one temperature-dependent process.

Acholeplasma laidlawii↗
PubMed1989

Topographical assessment of accumulated radioactivity from [14C]2-deoxyglucose and [6(-14C)]glucose in rat forebrain at different survival periods.

The uptake and retention of radioactivity was measured in discrete areas of rat brain at different times after i.v. injection of [14C]2-deoxyglucose or [6(-14)C]glucose, in unrestrained rats. In most brain regions, the accumulation of radioactivity from the two compounds was similar when a 30-min survival period for [6(-14)C]glucose was compared to a 45-min survival period for [14C]2-deoxyglucose. However, at those times, autoradiographic images of the hippocampus and piriform cortex appeared distinctly different for [14C]2-deoxyglucose and [6(-14)C]glucose. Relatively more radioactivity accumulated from [14C]2-deoxyglucose, compared to [14C]glucose, in the stratum lacunosum-moleculare of the hippocampus and in layer 4 of the isocortex. In contrast, relatively more radioactivity accumulated from [6(-14)C]glucose, compared to [14C]2-deoxyglucose, in the molecular and granule cell layers of the dentate gyrus, the CA1 pyramidal cell layer of the hippocampus, and in layer 2 of the piriform cortex. When rats were killed 5 min after injection of [6(-14)C]glucose, the relative neuroanatomical distribution of radioactivity was similar to the 30-min survival period, except in layer 4 of the isocortex, where relatively more radioactivity was present at the early time. When rats were killed 5 min after injection of [14C]2-deoxyglucose, in 20 of 24 brain regions examined, the absolute and relative amounts of accumulated radioactivity were similar when compared to that of the 45-min survival period. In contrast, the absolute and relative amounts of radioactivity were significantly greater for the 5-min compared to the 45-min survival period, in the CA1 pyramidal cell field, dentate gyrus, and layer 2 of the piriform cortex. For those regions, the appearance of autoradiograms prepared from rats killed 5 min after administration of [14C]2-deoxyglucose is remarkably similar to the appearance of autoradiograms prepared from rats killed 5 or 30 min after injection of [6(-14)C]glucose. Possible mechanisms are discussed to explain the observed differences in the accumulation of radioactivity in discrete brain regions after injection of [6(-14)C]glucose and [14C]2-deoxyglucose at the different survival times examined.

Animals↗