Biomedical subjects

E Kwan

Publications and source records attributed to E Kwan.

At least 37 records · Page 2Linked to original sources

PubMed1996

Aftercare telephone contacts with problem drinkers can serve a clinical and research function.

Research staff typically gather treatment outcome data, whereas clinicians perform aftercare contacts. To date no alcohol treatment outcome study has examined the utility of therapists collecting outcome data through aftercare contacts. Using the Alcohol Timeline Followback (TLFB) method modified for clinical aftercare contacts, 154 problem drinkers who were part of a cognitive-behavioral intervention completed the modified TLFB with their primary therapist during aftercare telephone contacts conducted 1 and 3 months after their last treatment session. Clients reported their daily alcohol use over the past 30 days using four consumption categories (i.e. 0 drinks, 1-4 drinks, 5-9 drinks and 10+ drinks). At a 6-month follow-up research interview, a trained research assistant gathered standard TLFB data from the clients that included the time period for aftercare contacts. Correlations between the two TLFB formats showed good alternate form reliability, especially for frequency of alcohol use. Discrepancies between reports were positively associated with heavier pre-treatment and post-treatment drinking, suggesting possible memory biases among heavier drinkers. Subject reports also closely paralleled collateral reports of the subjects' drinking. These results support the utility of a brief TLFB instrument for use by therapists in assessing clients' outcomes by telephone during aftercare contacts.

Adolescent↗

PubMed1996

Characterization of CenC, an enzyme from Cellulomonas fimi with both endo- and exoglucanase activities.

The cenC gene, encoding beta-1,4-glucanase C (CenC) from Cellulomonas fimi, was overexpressed in Escherichia coli with a tac-based expression vector. The resulting polypeptide, with an apparent molecular mass of 130 kDa, was purified from the cell extracts by affinity chromatography on cellulose followed by anion-exchange chromatography. N-terminal sequence analysis showed the enzyme to be properly processed. Mature CenC was optimally active at pH 5.0 and 45 degrees C. The enzyme was extremely active on soluble, fluorophoric, and chromophoric glycosides (4-methylumbelliferyl beta-glycosides, 2'-chloro-4'-nitrophenyl-beta-D-cellobioside, and 2'-chloro-4'-nitrophenyl-lactoside) and efficiently hydrolyzed carboxymethyl cellulose, barley beta-glucan, lichenan, and, to a lesser extent, glucomannan. CenC also hydrolyzed acid-swollen cellulose, Avicel, and bacterial microcrystalline cellulose. However, degradation of the latter was slow compared with its degradation by CenB, another C. fimi cellulose belonging to the same enzyme family. CenC acted with inversion of configuration at the anomeric carbon, in accordance with its classification as a family 9 member. The enzyme released mainly cellobiose from soluble cellodextrins and insoluble cellulose. Attack appeared to be from the reducing chain ends. Analysis of carboxymethyl cellulose hydrolysis suggests that CenC is semiprocessive enzyme with both endo- and exoglucanase activities.

Base Sequence↗

PubMed1996

Hepatic first-pass uptake of diphenhydramine. A comparative study between fetal and adult sheep.

In this study, two factors that could affect fetal drug exposure were examined: 1) the extent of elimination of drug delivered to the fetal liver from the placenta via the umbilical vein; and 2) the degree to which there is preferential distribution of drug in umbilical venous blood to the fetal upper body, as is the case with oxygen and other endogenous substances. Studies were conducted with the histamine H1 antagonist, diphenhydramine (DPHM), in chronically instrumented nonpregnant and pregnant sheep (115-138 days gestation). Hepatic presystemic DPHM elimination was assessed using simultaneous and separate administration of DPHM and stable isotope labeled DPHM ([2H10]DPHM) via the umbilical vein (test route) and abdominal inferior vena cava (control route) in fetal lambs by either bolus injection (N = 6) or 90-min infusion (N = 5), and in nonpregnant sheep (N = 5), by simultaneous and separate bolus injections of the two forms of the drug via the mesenteric vein (test route) and abdominal inferior vena cava (control route). With the bolus injection protocol, hepatic presystemic elimination was estimated by the ratio of the area under the arterial drug concentration vs. time curve for the test and control routes of drug administration, whereas with the fetal infusion study it was calculated as the difference in fetal DPHM clearance values for the test and control routes of administration. To test for isotope effects in the disposition of [2H10]DPHM in the ewe or fetus, both DPHM and [2H10]DPHM were simultaneously injected via the inferior vena cava; however, no isotope effects were noted. In the ewe, there was extensive (93.2 +/- 1.4%) presystemic elimination of DPHM (F 0.068 +/- 0.014). However, in the fetus, this did not occur with bolus drug injection (F = 1.10 +/- 0.07), nor were there differences in the fetal DPHM clearance values estimated from the tarsal and umbilical venous infusions. During the latter experiments, DPHM levels were higher in the femoral artery than in carotid artery, with both umbilical venous and inferior vena caval drug infusion, and this was opposite of the differences in the concentrations of glucose, lactate, and oxygen between these two vessels. Thus, there is extensive hepatic presystemic elimination of DPHM in adult sheep, but no evidence for this phenomenon in the fetus. Furthermore, the preferential distribution of umbilical venous blood to the upper body of the fetal lamb does not result in higher drug levels in ascending aortic blood.

Age Factors↗

PubMed1995

Sensitive fused-silica capillary gas chromatographic assay using electron-capture detection for indomethacin in ovine fetal fluids.

A sensitive gas chromatographic (GC) method with electron-capture detection (ECD) has been developed to quantitate indomethacin (IND) in plasma, urine, amniotic, and tracheal fluids obtained from the pregnant sheep model. IND and the internal standard, alpha-methylindomethacin (alpha-Me-IND) are extracted by a simple liquid-liquid extraction procedure using ethyl acetate and derivatized with N-methyl-N-(tert.-butyldimethyl-silyl)trifluoroacetamide (MTBSTFA) at 60 degrees C for 50 min. The limit of quantitation (LOQ) is 1 ng/ml with a C.V. < 10% and signal-to-noise ratio > 10. Recoveries from all fluids were greater than 80%. Calibration curves were linear over the range of 1-32 ng/ml with a coefficient of determination (r2) > 0.999. Inter- and intra-day coefficients of variation were < 10% at concentrations of 2-32 ng/ml, and < 20% at the LOQ. Applicability of the developed method is demonstrated for a pharmacokinetic study of IND samples collected following long-term infusion of IND in a chronically instrumented ovine fetus.

Acetamides↗

PubMed1995

Increased retinoic acid receptor gamma expression suppresses the malignant phenotype and alters the differentiation potential of human neuroblastoma cells.

Human neuroblastoma (NB) tumor cell lines treated in vitro with the retinoid, all-trans-retinoic acid (aRA), form neurites and undergo growth arrest. Retinoids exert their diverse morphologic effects through a signalling pathway which involves the nuclear retinoid receptors. Defective retinoic acid receptor (RAR) function contributes to the malignant phenotype of several human and experimental tumors. Considerable evidence from gene disruption studies now suggests that one of the RARs, RAR gamma, may directly mediate some retinoid effects on embryonic and malignant cells. We, firstly, examined primary NB tumor tissue for a correlation between endogenous RAR gamma expression and clinical stage of the tumor and secondly, the effects of exogenous over-expression of the RAR gamma gene on a human NB tumor cell line. RAR gamma mRNA expression in 32 primary NB tumor tissue samples were significantly higher in clinically localised tumors compared with advanced or disseminated tumors. The human NB tumor cell line, BE(2)-C, was stably transfected with a mammalian expression vector (pREP4) over-expressing the human RAR gamma cDNA. Two selected clones over-expressing RAR gamma (BE/G1 and 2) exhibited a reduced growth rate compared to control cells. Tumorigenicity was inhibited for BE/G1 cells and there was a delayed onset to tumor formation for BE/G2 cells. aRA caused growth inhibition but not neuritic differentiation of the BE/G clones, while 9-cis-retinoic acid caused both growth arrest and neuritic differentiation. Taken together these results suggest that reduced endogenous RAR gamma expression may contribute to the malignant phenotype of human NB. In NB cells the retinoid signalling pathway for neuritic differentiation may be distinct from that causing growth inhibition.

Adrenal Glands↗

PubMed1995

Enhancement of the endo-beta-1,4-glucanase activity of an exocellobiohydrolase by deletion of a surface loop.

In the commonly accepted mechanism for enzymatic hydrolysis of cellulose, endo-beta-1,4-glucanases randomly cleave glucosidic bonds within glucan polymers, providing sites for attack by exo-cellobiohydrolases (EC 3.2.1.91). It has been proposed that hydrolysis by Trichoderma reesei cellobiohydrolase II is restricted to the ends of cellulose polymers because two surface loops cover its active site to form a tunnel. In a closely related endoglucanase, E2 from Thermomonospora fusca, access to the substrate appears to be relatively unhindered because the carboxyl-proximal loop is shortened, and the amino-proximal loop is displaced. The hypothesis was examined by deletion of a region in Cellulomonas fimi cellobiohydrolase A corresponding to part of the carboxyl-proximal loop of T. reesei cellobiohydrolase II. The mutation enhanced the endoglucanase activity of the enzyme on soluble O-(carboxymethyl)cellulose and altered its activities on 2',4'-dinitrophenyl-beta-D-cellobioside, insoluble cellulose, and cellotetraose.

Amino Acid Sequence↗

PubMed1995

Blood volume restitution and growth in fetal lambs after acute hemorrhage.

The effects of 15-50% fetal hemorrhage (at approximately 1%/min) were studied in 13 pregnant ewes at 130-135 days of gestation for up to 5 days posthemorrhage. The upper limit of acute blood loss appears to be approximately 45%, and the rate of restoration of blood volume decreases with the severity of hemorrhage, particularly with hemorrhage > 30-40%. The restoration of fetal blood volume was due primarily to the restoration of plasma volume; in the animals subject to 40-45% blood loss (n = 9), red cell mass was still only 69.1 +/- 3.9% of the prehemorrhage value at day 5 posthemorrhage. There appear to be two phases in the restoration of plasma: 1) plasma volume was restored by 2 h posthemorrhage and 2) the restoration of plasma protein mass occurred primarily from 2 to 24 h. There was a significant correlation between blood volume and plasma protein mass. However, the regression line for the posthemorrhage days was shifted significantly upward in relation to that for the hemorrhage day because of a significant rise of plasma protein concentration. This may be important for the maintenance of blood volume after hemorrhage. Finally, fetal growth rate was determined by comparing fetal weight estimated in utero (from blood volume) with birth weight in 12 nonhemorrhaged control fetuses and in the 9 fetuses subject to 40-45% hemorrhage. The average rate of growth per day was 1.57 +/- 0.34% and -1.82 +/- 1.02%, respectively. The latter value is not significantly different from zero, suggesting that the acute blood loss impaired fetal growth.

Acute Disease↗

PubMed1995

Oxygen consumption, acid-base status, and behavior during and after acute, severe hemorrhage in fetal lambs.

The metabolic and behavioral effects of 40-45% hemorrhage (at approximately 1%/min) were studied in nine fetal lambs in utero (130-135 days of gestation) until 2 days posthemorrhage. Umbilical blood flow (Qum) fell from 192 +/- 14 to 100 +/- 9 ml.min-1.kg-1 at the end of blood loss, and on the day of hemorrhage it was linearly related to blood volume. However, on the posthemorrhage days, Qum was restored even though blood volume was still reduced. Fetal O2 delivery (DO2) fell with the decrease in Qum and later due to anemia (decrease in hematocrit from 33.4 +/- 1.2 to 23.6 +/- 1.2%), from 946 +/- 81 to 494 +/- 47 mumol.min-1.kg-1, but the decrease was lessened because of a rise in umbilical venous PO2 (31.7 +/- 2.6 to 45.9 +/- 2.8 mmHg). Fetal O2 consumption was reduced during and for 2 h after hemorrhage (262 +/- 17 to 190 +/- 16 mumol.min-1.kg-1), and this was associated with modest lactic acidemia (1.25 +/- 0.11 to 2.91 +/- 0.43 mM). There was also a temporary reduction in fetal breathing activity, low voltage electrocortical state, and rapid eye movements, but this was not associated with hypoxemia. It is concluded that reductions in fetal DO2 achieved via fetal blood loss are better tolerated than during hypoxemia and that the associated depression in fetal biophysical activities involves mechanisms other than systemic hypoxia.

Acid-Base Equilibrium↗

PubMed1995

Characterization of clonal immunoglobulin heavy chain and I cell receptor gamma gene rearrangements during progression of childhood acute lymphoblastic leukemia.

Instability of antigen receptor gene rearrangements during progression of acute lymphoblastic leukemia (ALL) has important implications for polymerase chain reaction (PCR)-based techniques using these genes for the detection of minimal residual disease (MRD). Antigen receptor gene instability may lead to false negative results in bone marrow samples taken during remission. Utilizing the PCR and consensus primers for rearranged immunoglobulin heavy chain (IgH) and T cell receptor gamma (TCR gamma) gene sequences, we analyzed the bone marrow samples at diagnosis and first relapse for 37 children with ALL. The incidence of clonal evolution at the IgH locus was 9/33 (27%) and at the TCR gamma locus 1/15 (7%). In four of the nine patients with clonal evolution at the IgH locus, the sequence at relapse retained the diversity and joining region (D-N-J) sequences from diagnosis. Patients with clonal evolution were characterized by a higher incidence of more than one IgH PCR band at diagnosis and by late relapse (> 18 months from diagnosis). These results suggest that, where possible, patients with more than one IgH PCR rearrangement at diagnosis should be monitored using another antigen receptor gene, such as TCR gamma, since evolution for this gene was found to be a rare event. By combining this approach with a strategy directed at the more stable D-N-J region of the IgH gene, MRD false negativity would have occurred in less than 10% of patients in the present study.

Adolescent↗

PubMed1995

Detection of evolving immunoglobulin heavy-chain gene rearrangements in acute lymphoblastic leukemia: a PCR-based assay employing overlapping DJH primers.

The use of the polymerase chain reaction (PCR) to amplify clonal immunoglobulin heavy-chain (IgH) gene rearrangements appears to be a particularly promising technique for detecting minimal residual disease (MRD). However, a major obstacle to successful implementation of this technique involves the problem of clonal evolution, in which instability of the VHDJH region leads to the generation of further rearrangements of the IgH gene over time. Such clonal evolution results in a high likelihood of false negative results when detecting MRD using clone-specific primers based on the rearrangement present at diagnosis. Since in acute lymphoblastic leukemia (ALL), clonal evolution commonly involves alterations of the VHD joining but not the DJH joining, we have devised a novel PCR strategy to circumvent the problem of false negativity in these evolved leukemias. The strategy, which involves construction of overlapping clone-specific DJH primers for use with a consensus VH segment primer, can be used to amplify both evolved and nonevolved ALL populations with high sensitivity and specificity. The method does not require radioactivity and should prove valuable for improving the effectiveness of PCR-based detection of residual leukemia.

Base Sequence↗

PubMed1995

The pharmacokinetics of valproic acid in pregnant sheep after maternal and fetal intravenous bolus administration.

The pharmacokinetics and disposition of valproic acid (VPA) have been assessed in pregnant sheep after both maternal and fetal iv bolus administration. The time course of VPA and 16 of its metabolites was followed in maternal and fetal arterial blood, amniotic fluid, and fetal tracheal fluid for 48 hr after administration. Fetal blood gas, acid-base, metabolic, cardiovascular, and fetal breathing activity parameters were also monitored. The disposition of VPA in maternal serum is best described by a biexponential function with a terminal elimination half-life of 2.13 +/- 0.49 hr and volume of distribution of 0.242 +/- 0.036 liter/kg. VPA transfer to fetal serum and other fetal fluids was rapid after drug administration. There was significant fetal exposure to VPA after maternal dosing (mean AUCinfinityFA/AUCinfinityMA = 0.410 +/- 0.118). Similarly, the disposition of VPA in fetal serum after fetal dosing is best described by a biexponential decay with a terminal elimination half-life of 3.37 +/- 1.37 hr. Once again, VPA transfer to other fluids was rapid. However, unlike basic compounds studied previously, VPA did not accumulate extensively in either amniotic or fetal tracheal fluid. The following metabolites were detected after drug administration in these experiments: (E)- and (Z)-2-ene VPA, (E)- and (Z)-3-ene VPA, 4-ene VPA, 3-keto VPA, 4-keto VPA, 3-OH VPA, 4-OH VPA, 5-OH VPA, and 2-PGA. Both maternal and fetal bolus administration of VPA elicited a significant reduction in fetal breathing movements, which may be attributed to the drug's action on gamma-aminobutyric acid dynamics in the central nervous system (CNS). This suggests that the significant fetal exposure to VPA may produce further CNS-related effects in utero.

Amniotic Fluid↗

PubMed1994

Cellobiohydrolase A (CbhA) from the cellulolytic bacterium Cellulomonas fimi is a beta-1,4-exocellobiohydrolase analogous to Trichoderma reesei CBH II.

The gene cbhA from the cellulolytic bacterium Cellulomonas fimi encodes a protein of 872 amino acids designated cellobiohydrolase A (CbhA). Mature CbhA contains 832 amino acid residues and has a predicted molecular mass of 85,349 Da. It is composed of five domains: an N-terminal catalytic domain, three repeated sequences of 95 amino acids, and a C-terminal cellulose-binding domain typical of other C. fimi glycanases. The structure and enzymatic activities of the CbhA catalytic domain are closely related to those of CBH II, an exocellobiohydrolase in the glycosyl hydrolase family B from the fungus Trichoderma reesei. CbhA is the first such enzyme to be characterized in bacteria. The data support the proposal that extended loops around the active site distinguish exohydrolases from endohydrolases in this enzyme family.

Amino Acid Sequence↗

PubMed1994

Screening test for growth hormone deficiency: usefulness of L-dopa-propranolol provocative test.

This is a retrospective review of 185 short children who were tested for growth hormone (GH) secretion using the L-dopa-propranolol provocative test. One hundred and thirty-three children were deemed to have passed the screening test when a GH concentration of greater than 15 miu/L was elicited after stimulation. Fifty-two failed the screening test, of which 33 were diagnosed as having growth hormone deficiency (GHD) when they had inadequate growth hormone response to insulin-induced hypoglycaemia. The other 19 were low-responders since they showed adequate GH response to insulin tolerance test (ITT). The low-responder rate to L-dopa-propranolol provocative test among short children who are not GH deficient was 12.5%. The low cost of L-dopa and propranolol, the simplicity and safety of the test, and the acceptable rate of low-responders make the test an effective screening test for GHD.

Adolescent↗

PubMed1994

Lateralization of memory for the visual attributes of objects: evidence from the posterior cerebral artery amobarbital test.

We used the posterior cerebral artery amobarbital test to examine how each temporal lobe mediates memory for objects. Temporal lobectomy candidates were presented with four objects while one hemisphere was anesthetized. We assessed recall and recognition following recovery from the drug. Verbal recall was significantly better following object presentation to the left hemisphere when the left hemisphere was not the seizure focus. Recognition memory, tested with two identical objects, two objects that shared the same name but had different physical characteristics, and two foils, was superior following object presentation to the right hemisphere. Only the right hemisphere could discriminate identical objects from same-name foils. These data confirm that the left temporal lobe has an advantage in encoding the verbal representation of an object and suggest that the right temporal lobe is critical for memory of specific visual attributes of objects.

Adult↗

PubMed1993

The ftf gene encoding the cell-bound fructosyltransferase of Streptococcus salivarius ATCC 25975 is preceded by an insertion sequence and followed by FUR1 and clpP homologues.

Analysis of the region downstream of the ftf gene of Streptococcus salivarius led to the detection of two open reading frames (ORFs). The deduced amino acid sequences of these ORFs were homologous to proteins encoded by genes not previously described and/or sequenced in Gram-positive bacteria. The deduced amino acid sequence of the first of these (orf2) showed strong homology to the product of the FUR1 gene of Saccharomyces cerevisiae, which codes for a uracil phosphoribosyltransferase. The over-expression of the product of this gene appeared to be the source of the detrimental effect observed with phagemids carrying orf2 in Escherichia coli hosts. The deduced amino acid sequence of the second ORF (orf3) was homologous to the ClpP family of proteases. Examination of the upstream region of the ftf gene led to the discovery of a new insertion sequence-like element which has been designated IS1161.

ATP-Dependent Proteases↗

PubMed1993

Transplacental and nonplacental clearances, metabolism and pharmacodynamics of labetalol in the fetal lamb after direct intravenous administration.

Labetalol has been previously shown to cause significant maternal and fetal metabolic effects in pregnant sheep after maternal administration. To investigate these observations further, the present study describes the pharmacokinetics, metabolism and pharmacodynamics of labetalol in the fetal lamb after direct fetal i.v. bolus (4 mg) administration. The fetal total body clearance of labetalol (50.45 +/- 1.37 ml m-1 kg-1), which was significantly higher than that previously determined in the ewe, was composed of transplacental and nonplacental CLs of 23.4 +/- 8.99 ml m-1 kg-1 and 27.05 +/- 10.36 ml m-1 kg-1, respectively. The maternal to fetal plasma labetalol area under the curve ratio was 0.031 +/- 0.002 and the CLmp and CLmn were 7.27 +/- 2.11 ml m-1 kg-1 and 30.5 +/- 5.94 ml m-1 kg-1, respectively. Labetalol concentrations in fetal tracheal fluid were consistently higher than that in fetal plasma. The glucuronide conjugate of labetalol was found in the amniotic fluid at up to 20 times the free drug concentration but the oxidative metabolite, 3-amino-1-phenyl-butane, was not detected in plasma or amniotic fluid samples. The fetal effect of labetalol was characterized by an acute lactic acidosis. The calculated hind limb arteriovenous lactate flux showed a net output of lactic acid equal to 3.85 +/- 2.05 g from the hind limb over 24 h after labetalol administration. Although the fetal exposure to labetalol in this study was roughly 4 times that after a 100-mg maternal bolus administration, the magnitude of fetal lactic acidosis was not significantly different in these studies. The clinical implications of the observations made in this study remain to be investigated.

Animals↗

PubMed1992

Crystallization and preliminary X-ray diffraction analysis of the catalytic domain of Cex, an exo-beta-1,4-glucanase and beta-1,4-xylanase from the bacterium Cellulomonas fimi.

Single crystals of the catalytic domain of Cex, an exo-beta-1,4-glucanase and beta-1,4-xylanase from the cellulolytic bacterium Cellulomonas fimi, have been grown in the presence of polyethylene glycol 4000 using the vapour diffusion technique. The crystals, which diffract to better than 2.0 A resolution, belong to space group P4(1)2(1)2 or P4(3)2(1)2 and have cell constants: a = b = 88.21 A, c = 81.10 A; alpha = beta = gamma = 90 degrees.

Actinomycetales↗

PubMed1992

Identification and quantitation of an oxidative metabolite of labetalol in sheep: pharmacokinetic and metabolic implications.

A sensitive and selective assay has been developed for the identification and quantitation of 3-amino-1-phenyl butane (3-APB), a metabolite of labetalol, in biological fluids using electron impact gas chromatography/mass-selective detection. Samples were extracted with n-hexane, derivatized with heptafluorobutyric anhydride and chromatographed on a cross-linked fused-silica capillary column. A positive EI spectrum was obtained using a mass-selective detector. Identification of the metabolite was accomplished using an authentic standard; quantitation was performed in the selected ion monitoring mode using ions m/z 345 (M+) and 132. The assay was linear over the calibration range of 0.5-1000 ng of the analyte and the intra-sample coefficients of variation were less than 12% in all cases. The absolute recovery of 3-APB following extraction from urine and bile was found to be 102.9 +/- 4.9% and 98.3 +/- 1.45% (mean +/- SEM) respectively. The minimum quantitation limit of the assay was 0.5 ng ml-1 (approximately 2 pg injected). Application of the assay in a pharmacokinetic-pharmacodynamic study of labetalol in sheep is demonstrated. The metabolite was detected in urine and bile samples obtained from adult non-pregnant sheep following labetalol administration. The cumulative amount of 3-APB excreted in urine over 24 h was found to be 71.55 micrograms in one animal following a 100 mg dose of labetalol. Evidence for biliary excretion, glucuronidation and sulfation of 3-APB was also found.

Animals↗