Biomedical subjects

J Chou

Publications and source records attributed to J Chou.

At least 73 records · Page 4Linked to original sources

PubMed1986

Functional domains within the a sequence involved in the cleavage-packaging of herpes simplex virus DNA.

Newly replicated herpes simplex virus (HSV) DNA consists of head-to-tail concatemers which are cleaved to generate unit-length genomes bounded by the terminally reiterated a sequence. Constructed defective HSV vectors (amplicons) containing a viral DNA replication origin and the a sequence are similarly replicated into large concatemers which are cleaved at a sequences punctuating the junctions between adjacent repeat units, concurrent with the packaging of viral DNA into nucleocapsids. In the present study we tested the ability of seed amplicons containing specific deletions in the a sequence to become cleaved and packaged and hence be propagated in virus stocks. These studies revealed that two separate signals, located within the Ub and Uc elements of the a sequence, were essential for amplicon propagation. No derivative defective genomes were recovered from seed constructs which lacked the Uc signal. In contrast, propagation of seed constructs lacking the Ub signal resulted in the selection of defective genomes with novel junctions, containing specific insertions of a sequences derived from the helper virus DNA. Comparison of published sequences of concatemeric junctions of several herpesviruses supported a uniform mechanism for the cleavage-packaging process, involving the measurement from two highly conserved blocks of sequences (pac-1 and pac-2) which were homologous to the required Uc and Ub sequences. These results form the basis for general models for the mechanism of cleavage-packaging of herpesvirus DNA.

Animals↗

PubMed1986

Effects of alpha and beta adrenergic blockade on hepatic glucose balance before and after oral glucose. Role of insulin and glucagon.

In conscious dogs, phentolamine infusion significantly increased fasting portal vein insulin, glucagon, and decreased net hepatic glucose output and plasma glucose. Propranolol significantly decreased portal vein insulin, portal flow, and increased hepatic glucose production and plasma glucose. Phentolamine, propranolol, and combined blockade reduced glucose absorption after oral glucose. alpha, beta, and combined blockade abolished the augmented fractional hepatic insulin extraction after oral glucose. Despite different absolute amounts of glucose absorbed and different amounts of insulin reaching the liver, the percent of the absorbed glucose retained by the liver was similar for control and with alpha- or beta blockade, but markedly decreased with combined blockade. Our conclusions are: (a) phentolamine and propranolol effects on basal hepatic glucose production may predominantly reflect their action on insulin and glucagon secretion; (b) after oral glucose, alpha- and beta-blockers separately or combined decrease glucose release into the portal system; (c) net hepatic glucose uptake is predominantly determined by hyperglycemia but can be modulated by insulin and glucagon; (d) direct correlation does not exist between hepatic delivery and uptake of insulin and net hepatic glucose uptake; (e) alterations in oral glucose tolerance due to adrenergic blockers, beyond their effects on glucose absorption, can be, to a large extent, mediated by their effects on insulin and glucagon secretion reflecting both hepatic and peripheral glucose metabolism.

Administration, Oral↗

PubMed1986

Effect of dexamethasone on hepatic glucose and insulin metabolism after oral glucose in conscious dogs.

To examine whether hyperinsulinemia associated with glucocorticoid treatment results solely from hypersecretion of insulin or also involves altered fractional hepatic extraction, oral glucose (1 g/kg body wt) was administered to dogs with or without dexamethasone treatment (2 mg/d for 2 d). Dexamethasone significantly increased basal glucose and insulin concentrations in the portal vein, hepatic vein, and femoral artery, reduced basal fractional hepatic extraction of insulin from 43 +/- 4% to 22 +/- 4%, and, after oral glucose, increased retention by the liver of net glucose released into the portal system from 27 +/- 4% to 53 +/- 13%. Intraportal insulin infusion (1 and 2 mU/kg per min) after 7 d of dexamethasone treatment (2 mg/d) caused less suppression of endogenous glucose production, and less exogenous glucose was required to maintain an euglycemic clamp than in control animals. Dexamethasone treatment is associated with: decreased basal fractional hepatic insulin extraction contributing to hyperinsulinemia; and less suppression of endogenous glucose production and increase in peripheral uptake in response to insulin, but no reduction in net hepatic glucose uptake after oral glucose.

Administration, Oral↗

PubMed1985

Isomerization of herpes simplex virus 1 genome: identification of the cis-acting and recombination sites within the domain of the a sequence.

Previous studies have shown that the a sequence located at the termini and at the junction between the L and S components is the site-specific, cis-acting sequence mediating the inversions of herpes simplex virus 1 DNA. We constructed mutated a sequences, inserted them into the thymidine kinase gene, and recombined them into the L component of the viral genome. Deletion of Uc or Ub domains of the a sequence did not affect inversions, whereas the deletion of direct repeat #4 (DR4) drastically reduced their frequency. Deletion of both direct repeat #2 (DR2) and DR4 abolished inversions. Recombinational events leading to inversions appear to occur through DR2, and possibly DR4. These results complement previous studies showing that most of one DR1 sequence can also be dispensed with and are consistent with the hypothesis that DR4 and possibly DR2 are the cis-acting sites for the inversions mediated by the a sequence.

Base Sequence↗

PubMed1985

The HLA-A, -B, and -DR phenotypes and tuberculosis.

The HLA-A, -B, and -DR antigens were studied in black Americans to analyze deviation in phenotype distribution between ATS Class 3 patients with tuberculosis disease and ATS Class 2 healthy persons with significant tuberculin reaction, but no tuberculosis. Statistical analyses with Fisher's exact test revealed a significant difference in frequency distribution of HLA-B5 (p = 0.046), HLA-DR5 (p = 0.0276), and HLA-DR6y (p = 0.0095) between ATS Class 2 and ATS Class 3 patients. There was a significant decrease in HLA-DR6y (p = 0.01) but increase in HLA-B5 and HLA-DR5 phenotypes in ATS Class 3 patients.

Black People↗

PubMed1985

Effects of atropine and gastric inhibitory polypeptide on hepatic glucose uptake and insulin extraction in conscious dogs.

Previous studies comparing the effects of oral, intraportal, and peripheral venous administration of glucose in conscious dogs demonstrated a significant increase in hepatic extraction of insulin only after oral glucose, but similar hepatic uptake of glucose after oral and intraportal glucose, which was greater than that after peripheral intravenous glucose infusion. This study evaluated the effect of atropine blockade of the parasympathetic nervous system on the increased fractional hepatic extraction of insulin and the role of gastric inhibitory polypeptide (GIP) on augmented hepatic uptake of oral glucose in conscious dogs with chronically implanted Doppler flow probes on the portal vein and hepatic artery, and catheters in the portal and hepatic veins and carotid artery. Since atropine infusion decreased absorption of glucose, and in order to achieve comparable portal vein levels of glucose and insulin, the dogs receiving atropine were given 1.9 +/- 0.1 g/kg glucose, compared with the control dogs who received 1.1 +/- 0.1 g/kg. The percentage of the glucose load that was absorbed was greater in the dogs not given atropine (80 +/- 4 vs. 44 +/- 7%), but because of the different loads, the absolute amount of glucose absorbed was similar in both groups (20.2 +/- 1.6 vs. 21.7 +/- 4.1 g). Although delayed by atropine, the peak portal vein glucose and insulin concentrations and the amounts presented to the liver were similar in both groups. However, the increased portal vein plasma flow and fractional hepatic extraction of insulin observed after oral glucose was not observed in the dogs infused with atropine. The net hepatic glucose uptake after oral glucose was significantly less at 10, 20, and 45 min in the atropine-treated dogs, and the area under the curve over the 180-min period was 44% less. However, the latter was not statistically significant. Infusion of GIP with peripheral intravenous glucose did not increase hepatic uptake of glucose or the fractional hepatic extraction of insulin compared with peripheral intravenous glucose alone. These results indicate an important role for parasympathetic innervation in the augmented fractional hepatic extraction of insulin, and increased portal vein plasma flow after oral glucose. Although a relationship between the augmented fractional extraction of insulin and the net hepatic glucose uptake may exist, it does not necessarily indicate that the former is required for the latter. Such parasympathetic innervation may be involved in the greater removal of glucose by the liver after oral compared with peripheral glucose administration. The augmented hepatic uptake of glucose and fractional hepatic extraction of insulin after oral glucose doesn not appear to be mediated by gastric inhibitory polypeptide.

Administration, Oral↗

PubMed1985

Effect of metabolic clearance rate and hepatic extraction of insulin on hepatic and peripheral contributions to hypoglycemia.

Effects of alterations in metabolic clearance rates, hepatic extraction, and plasma concentrations of insulin on hepatic and peripheral contribution to hypoglycemia and glucose counterregulation were studied in conscious dogs. Since insulin and sulfated insulin had markedly different metabolic clearance rates (34 +/- 1 vs. 16 +/- 1 ml/kg per min, respectively) and fractional hepatic extraction (42 +/- 1% vs. 15 +/- 2%, respectively), biologically equivalent amounts infused intraportally produced twofold higher hepatic vein and artery sulphated insulin concentrations and concentrations that were 30% higher in the portal vein. This significantly larger arterial/portal concentration ratio (0.67 vs. 0.45, respectively) permitted assessment of differential distribution of insulin on glucose turnover using [3-3H]glucose. Insulin and sulfated insulin (1 and 2 mU/kg per min) caused similar hypoglycemia. While insulin transiently suppressed glucose production and increased glucose disappearance, sulfated insulin had significantly greater effects on glucose disappearance and clearance, without suppression of glucose production. Despite similar hypoglycemia, sulfated insulin caused greater increment in glucagon. 3 mU/kg per min insulin caused more rapid and greater hypoglycemia, greater glucose clearance, and greater glucagon increments without suppression of glucose production, which indicates that with larger doses of insulin counterregulation can absolutely mask the suppressive effect of insulin. The effects of insulin and sulfated insulin were evaluated using euglycemic clamp to eliminate interference from stimulated counterregulation. Sequential infusion of 1 and 2 mU/kg per min of both insulins suppressed endogenous glucose production to 0 at 150 min, which indicates that the apparent lack of a hepatic effect of sulfated insulin during hypoglycemia was masked by greater counterregulation. This greater counterregulation may reflect greater peripheral glucose clearance, and prevented greater hypoglycemia than after the same insulin doses. The results indicate that the different rates of removal and the total metabolic clearance rate caused different concentrations and relative distribution between the portal and arterial blood compartments, leading to the significantly different contributions by the liver and peripheral tissues to the same hypoglycemia.

Animals↗

PubMed1984

Age-related and diurnal changes in Met5-Enk-Arg6-Phe7 and Met5-enkephalin contents of pituitary and rat brain structures.

The beta-endorphin, met5-enkephalin-arg6-phe7 (MEAP) and met5-enkephalin (ME) changes related to age and diurnal rhythms were studied in various regions of rat brain and in the pituitary by specific radioimmunoassays. The contents of MEAP, met5-enkephalin and beta-endorphin were higher in the pituitary of old rats (18 months old) than that of young rats (23 days old) while the content of these opioid peptides was higher in the hypothalamus of young rats than in that of old rats. Beta-endorphin was also higher in the striatum of 23 days old rats, but no age-associated changes were observed in the hippocampus, brain stem or cortex. In the diurnal rhythm study, it was found that in the hypothalamus and striatum of the adult rat (2-3 months old), both MEAP and ME contents were higher at mid-dark than at mid-light and that in the intermediate posterior lobe of the pituitary, the ME content was also higher at mid-dark.

Age Factors↗

PubMed1984

Proglumide prevents and curtails acute tolerance to morphine in rats.

The antagonism of the antinociceptive action of morphine elicited by CCK-8-SO4 can be counteracted by proglumide, a CCK antagonist. The addition of morphine (10(-6)M) to the artificial spinal fluid perfusing the subarachnoidal space of rat spinal cord increases the CCK content of the perfusate. Proglumide can potentiate morphine analgesia without changing the half life of morphine. After seven to eight subcutaneous injections of morphine (4 mg/kg) repeated every two hrs there is tolerance to the antinociceptive action of morphine. Proglumide can partially block or reverse this acute tolerance to morphine.

Animals↗

PubMed1984

In vivo formation of gene fusions encoding hybrid beta-galactosidase proteins in one step with a transposable Mu-lac transducing phage.

A Mu-lac bacteriophage transposon, MudII301 (Ap, lac), was constructed to form hybrid protein gene fusions. When it integrates into structural genes in the appropriate direction and reading phase, transcription and translation from outside gene controlling regions can proceed across 116 nucleotides from the right end of Mu into lacZ codons to form hybrid proteins that are enzymatically active for beta-galactosidase. Integration can be obtained either by infection to form lysogens or by transposition during growth of a lysogen. The size of the hybrid protein product either corresponds to or, in the cases of translation restart or protein degradation, is a minimal estimate of the distance of the Mu insertion from the translation initiation site of the gene. Hybrid proteins formed by insertions in randomly selected genes and in the araB and A genes were examined by polyacrylamide gel electrophoresis.

Bacteriophage mu↗

PubMed1984

Hepatic extraction of exogenous insulin in depancreatized conscious dogs.

Hepatic and mesenteric extraction of exogenous insulin and glucose appearance and clearance were compared in conscious depancreatized and normal dogs after intraportal or peripheral intravenous insulin infusion. Portal vein insulin levels were higher, whereas arterial insulin levels were lower after intraportal compared with intravenous peripheral infusion of insulin. During the intraportal infusion of 1 and 2 mU X kg-1 X min-1 insulin, 40 +/- 3% of the insulin presented to the liver was extracted by that organ in the diabetic dogs, similar to the value obtained in normal dogs (39 +/- 5%). Hepatic extraction of insulin after intravenous peripheral infusion of that hormone was similar in normal and diabetic dogs and was not significantly different from intraportal infusion. Mesenteric extraction of insulin in the diabetic dogs (13 +/- 2%) was similar to the 19 +/- 3% in the normal animals. The blood sugar changes were similar after both routes of insulin infusion. Suppression of glucose appearance in diabetic dogs was also similar during both routes of infusion. Glucose clearance during the peripheral intravenous infusion of insulin in diabetic dogs was greater than during intraportal insulin. These findings indicate that hepatic extraction of exogenous insulin was similar in normal and depancreatized dogs and was not influenced by the different infusion routes. Suppression of glucose appearance in diabetic dogs was similar after both routes despite different portal vein insulin levels. The peripheral action of intravenous peripheral infused insulin in diabetic dogs was greater than that of intraportal insulin reflecting the higher arterial insulin levels.

Animals↗

PubMed1984

Effects of portal and peripheral venous insulin infusion on glucose production and utilization in depancreatized, conscious dogs.

The relation between portal vein insulin concentrations and suppression of hepatic glucose production, as well as peripheral venous insulin level and increase of peripheral glucose utilization, was compared in conscious, depancreatized, diabetic dogs after infusion of insulin at 0.25 and 0.5 mU/kg/min into either the portal system or the peripheral circulation. Glucose appearance and clearance was measured using [3-3H]-glucose. Before infusion of insulin, portal vein insulin concentrations were undetectable. The intraportal infusion of insulin at 0.25 mU/kg/min increased portal vein insulin to 16 +/- 1 microU/ml, significantly higher than the arterial concentration (9 +/- 1 microU/ml). Infusion of the same amount of insulin into a peripheral vein raised peripheral insulin levels to 14 +/- 1 microU/ml and portal vein concentrations to 12 +/- 1 microU/ml. When 0.5 mU/kg/min of insulin was infused into the portal system, the portal vein insulin level was 28 +/- 2 microU/ml and significantly greater than the arterial concentration (16 +/- 1 microU/ml). After the same amount of insulin was infused into a peripheral vein, the arterial insulin level was higher than that of the portal vein (25 +/- 1 microU/ml versus 20 +/- 1 microU/ml, respectively). The ensuing hypoglycemia was greater after the 0.5 mU/kg/min infusion compared with the 0.25 mU/kg/min infusion. At each dose there was no significant difference between the peripheral venous or the portal route.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Action of peptidase inhibitors on methionine5-enkephalin-arginine6-phenylalanine7 (YGGFMRF) and methionine5-enkephalin (YGGFM) metabolism and on electroacupuncture antinociception.

In the spinal cord Met5-enkephalin-Arg6-Phe7 (YGGFMRF) is located in small interneurons of the dorsal and ventral horns. From these storage sites, YGGFMRF can be released by perfusing the subarachnoidal spaces of the spinal cord with artificial spinal fluid containing substance P. In vitro YGGFMRF can be hydrolyzed readily by a dipeptidyl carboxypeptidase. In order to ascertain whether this reaction is physiologically relevant, we measured the content of YGGFMRF and Met5-enkephalin (YGGFM) in subarachnoidal space perfusate in presence and in absence of captopril, bestatin and thiorphan using substance P to activate the release of opioid peptides. Without peptidase inhibitors, the efflux of YGGFMRF and YGGFM was hardly detectable. The addition of captopril to the perfusion medium increased the substance P (10(-7) M)-induced release of YGGFMRF markedly but it increased the efflux of YGGFM to a much smaller extent. When captopril and bestatin were added together the amount of YGGFMRF present in the perfusate was further increased slightly. In contrast, the YGGFM content in the same perfusate was increased greatly by bestatin and only slightly by thiorphan. To characterize the pharmacological profile of these peptidase inhibitors, we compared electroacupuncture antinociception with and without intrathecal injections of captopril and bestatin. This antinociception, as measured by tail-flick latency, was potentiated by the intrathecal injection of captopril and bestatin. These results taken together suggest that YGGFMRF released in the perfusate of the arachnoidal space by substance P is metabolized by both dipeptidyl carboxypeptidase and aminopeptidase.

Acupuncture Therapy↗

PubMed1984

Increase of striatal Met5-enkephalin-Arg6-Phe7 (YGGFMRF) content elicited by long-term treatment with haloperidol.

In rats, daily doses of haloperidol repeated for various time periods increase striatal Met5-enkephalin-Arg6-Phe7 (YGGFMRF) immunoreactivity in a time- and dose-dependent manner. This increase occurred also in other dopamine-rich brain areas. After intraventricular captopril (0.5 mg), the accumulation rate of immunoreactive YGGFMRF was greater in haloperidol- than in saline-injected rats. Intraventricular captopril inhibits the YGGFMRF degradation; hence the greater accumulation rate of YGGFMRF caused by captopril in haloperidol-treated rats suggests that this drug increases the YGGFMRF biosynthesis. A slower rate of YGGFMRF release in haloperidol-treated rats can be excluded as a cause for the drug-induced increase in striatal content of this peptide because the release rates of YGGFMRF elicited by K+ were similar in striatal slices of haloperidol- and saline-treated rats. The similarities between the accumulation rate of immunoreactive YGGFMRF and of Met5-enkephalin induced by haloperidol suggest that haloperidol increases the biosynthesis of the specific messenger RNA for preproenkephalin, an opioid peptide precursor, which contains one copy of YGGFMRF and several copies of Met5-enkephalin.

Animals↗

PubMed1983

Met5-enkephalin-arg6-phe7 content of human and rabbit plasma.

Using an adsorption technique combined with high pressure liquid chromatography and a specific radioimmunoassay, the met5-enkephalin-arg6-phe7 (YGGFMRF) content was measured in human and rabbit plasma. This heptapeptide content was 0.16 +/- 0.03, 0.20 +/- 0.05 pmol/10 ml plasma, for human and rabbit plasma, respectively. The degradation of YGGFMRF injected intravenously (rabbit) or that of the opioid heptapeptide added to rabbit plasma is rapid. The biological half life (T 1/2) of 125I-YGGFMRF in rabbit plasma was about 45 seconds (in vivo) and 1 minute and 8 seconds (in vitro). The metabolic clearance rate of YGGFMRF is slower than that of met5-enkephalin. The YGGFMRF content of rabbit plasma increased following inhibition of dipeptidyl peptidase activity by an intravenous injection of captopril. The presence of met5-enkephalin-arg6-phe7 into circulation indicates that it may have some physiological role, however it is unknown whether circulating YGGFMRF originates from adrenal medulla, intermediate lobe of pituitary or some other site.

Adult↗

PubMed1983

Met5-enkephalin-arg6-phe7 and its receptor in lung.

The presence of met5-enkephalin-arg6-phe7 (YGGFMRF) and opiate receptors in rat, guinea pig and human lung was investigated with specific and sensitive radio immuno- and radio-receptor assays. 1) High and low molecular weight YGGFMRF-like immunoreactivity were detected in lung extracts using Bio-Gel P-2 column chromatography followed by radioimmunoassay. Using HPLC, we determined that the low molecular weight YGGFMRF-like immunoreactivity is authentic YGGFMRF. 2) The contents of YGGFMRF were 0.68 +/- 0.08, 0.76 +/- 0.12 and 0.63 pmol/mg protein in lung of rat, guinea pig and human, respectively. In the lung of these three species, the content of YGGFMRF is much greater than that of met5-enkephalin. 3) 47 mM KCl released YGGFMRF from rat lung slices in a Ca++ dependent manner. 4) Rat lung membranes were shown to bind [3H]-etorphine in a saturable manner. There are two populations of binding sites with a Kd = 0.6 and 7.1 nM and a Bmax = 7.8 and 28.5 fmol/mg protein, respectively. This binding could be displaced by YGGFMRF with high affinity, the other endogenous opioid peptides were poor displacers. From these results, we infer that YGGFMRF might be a putative neurotransmitter or neuromodulator, its role in the regulation of lung function can now be investigated.

Animals↗

PubMed1983

Relationships among DNA sequences of the 1.3 kb EcoRI family of mouse DNA.

The genome of the mouse (Mus musculus) contains a family of repeated DNA sequences defined by a 1.3 kb EcoRI fragment. Restriction maps of ten cloned fragments from this family have been determined. The fragments were of seven different types, based on the patterns of digestion obtained with AvaII, HindIII, and TaqI restriction enzymes. These seven unique sets of sequences fell into two classes, as defined by the position of a single HindIII site. Portions of fragments from each of the two classes were sequenced. Although certain regions of the repeat were highly conserved between classes, there was more intraspecific sequence divergence among the sequenced regions than has been observed for the short interspersed Alu family of repeated sequences in mammals. Sequences of both HindIII classes were found to be present within the mouse X chromosome; we can conclude that both classes must also be present on other mouse chromosomes.

Animals↗

PubMed1983

The effect of peptidase inhibitors on the release of Met5-Enk-Arg6-Phe7 (YGGFMRF) and Met5-enkephalin (YGGFM) from spinal cord induced by substance P in vivo.

Using a preparation for the perfusion of the subarachnoidal spaces of the spinal cord of rats it was found that substance P can stimulate the release of YGGFMRF and YGGFM. We have studied the effect of several peptidase inhibitors (captopril, bestatin, thiorphan) on the recovery of YGGFMRF and YGGFM released from spinal cord by substance P. The recovery of released YGGFMRF was increased by adding captopril to the perfusion medium. A combination of captopril and bestatin in the perfusion medium further increases this YGGFMRF recovery. Intrathecal injection of captopril and bestatin also potentiated the analgesic effect of YGGFMRF and electroacupuncture. These results suggest that substance P may act as a "releaser" of enkephalins in spinal cord and that the dipeptidyl carboxypeptidase and aminopeptidase may be important in the degradation of YGGFMRF in vivo.

Animals↗