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Biomedical subjects

M H Lee

Publications and source records attributed to M H Lee.

At least 19 recordsLinked to original sources
PubMed1992

Preliminary crystallographic studies of urease from jack bean and from Klebsiella aerogenes.

Ureases from both jack bean (Canavalia ensiformis) seeds and Klebsiella aerogenes have been crystallized by the hanging drop method. The plant-derived urease crystals are regular octahedra analogous to those obtained by Sumner. Preliminary X-ray diffraction studies show that the crystals belong to the cubic space group F4(1)32, with a = 364 A, and appear to contain one or two subunits in the asymmetric unit. Using a synchrotron source, the crystals diffract to near 3.5 A resolution. Crystals of urease from K. aerogenes belong to the cubic space group I23 or I2(1)3, with a = 170.8 A and appear to contain a single catalytic unit per asymmetric unit. The crystals diffract to better than 2.0 A resolution and are well suited for structural analysis.

Bacterial Proteins↗
PubMed1992

Supplementation of the phosphatidyl-L-serine requirement of protein kinase C with nonactivating phospholipids.

The mechanism of protein kinase C (PKC) activation by phosphatidyl-L-serine (PS) is highly specific and occurs with high cooperativity [Lee, M.-H., & Bell, R. M. (1989) J. Biol. Chem. 264, 14797-14805]. To further investigate the multiplicity and specificity of PS cofactor requirement, some of the PS molecules present in Triton X-100 mixed micelles were substituted with nonactivating phospholipids devoid of required amino or carboxyl functional groups. The ability of these phospholipids to spare or reduce the mole percent of PS required was determined. Addition of phosphatidyl-(3-hydroxypropionate) (PP) or phosphatidate (PA) reduced the mole percent of PS required for maximal activity from 10 to 4 mol %, and also reduced the cooperativity of activation with PS. In contrast, phosphatidylethanolamine did not alter the dependence on PS. Phosphatidylethanol (P-Et) reduced the PS requirement to 2-4 mol % and cooperatively less efficiently than PP or PA. Phosphatidylglycerol and phosphatidylinositol resemble P-Et in their ability to reduce PS requirements and cooperativity. Therefore, it appears that the ability of phospholipids to substitute for PS in PKC activation depends on the negative charge in the phospholipid head group and the efficiency of substitution appears to be directly related to the negative charge density. The presence of two acyl groups within the phospholipid cofactor proved important since lyso-PS and lyso-PA replaced a portion of PS molecules required less efficiently than P-Et. Sodium oleate and sodium dodecyl sulfate behaved like lyso-PS. When other anionic lipids are present, approximately four molecules of PS per micelle are required for maximal PKC activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Serum alpha 1-antitrypsin in patients with hepatocellular carcinoma.

To evaluate the diagnostic value of alpha 1-antitrypsin (alpha-AT) as a tumor marker for hepatocellular carcinoma (HCC), we studied the serum levels of alpha-AT by rocket immunoelectrophoresis and alpha-fetoprotein (alpha-FP) by radioimmunoassay in 46 proven HCC patients, 43 cirrhosis patients and 200 healthy blood donors. The mean alpha-AT level of the 46 patients with HCC (4.8 +/- 2.7 mg/ml) was significantly higher than that of 200 healthy control subjects (1.7 +/- 0.7 mg/ml) (P less than 0.0001). The sensitivity of alpha-AT in 24 patients with high level of alpha-FP (greater than 400 ng/ml) and 22 patients with low level of alpha-FP (less than 400 ng/ml) were 96% and 64%, respectively. There was no substantial correlation between alpha-FP and alpha-AT in the two groups (alpha-FP greater than 400 ng/ml, alpha-FP less than 400 ng/ml) (r = 0.078, 0.064). The sensitivity for HCC using alpha-FP level alone (greater than 400 ng/ml) was only 52%, and the sensitivity using alpha-AT level alone (greater than 3.2 mg/ml) was 76% of the 46 patients. Combining both tests, sensitivity was improved only to 80%.

Adolescent↗
PubMed1992

Cisplatin-based chemotherapy for the treatment of advanced transitional-cell carcinoma of the urinary tract--a preliminary report.

The CMV (cisplatin, methotrexate, and vinblastine) and M-VAC (methotrexate, vinblastine, doxorubicin, and cisplatin) regimens were used to treat 19 patients with advanced transitional-cell carcinoma (TCC) of the urothelial tract. In the CMV group, the partial response rate was 45.5% and the mean response duration was 6.3 months. No complete response was obtained in our series. The median duration of survival was 15.8 and 8.3 months in responders and nonresponders, respectively. The toxic symptoms included one case of sepsis and three cases of renal toxicity. However, nausea and vomiting were experienced by most patients and required the administration of antiemetics. In the M-VAC group, the median duration of survival for responders was longer than that of nonresponders (greater than 10.2 vs 7.2 months), although the number of patients was too small for this difference to reach statistical significance. The toxic symptoms included one case of sepsis, two cases of renal toxicity, and nausea and vomiting in most patients. Bone metastasis in three patients did not respond to chemotherapy (CMV), a finding that is compatible with the results reported by other investigators. In summary, chemotherapy with the CMV or M-VAC regimen was effective in improving the response rate of patients. However, the duration of response was short, toxicity was severe in some cases, and the efficacy against bone lesions was poor. These problems must be solved to improve the outcome of patients with TCC following chemotherapy with the CMV or M-VAC regimens.

Adult↗
PubMed1992

A non-radioisotopic reverse transcriptase assay using biotin-11-deoxyuridinetriphosphate on primer-immobilized microtiter plates.

We developed a non-radioisotopic (non-RI) reverse transcriptase assay (RTA). The reverse transcriptase (RT) incorporates biotin-11-deoxyuridine-triphosphate (bio-dUTP) using a poly(rA) template hybridized with oligo(dT) primer that is immobilized on the surface of a 96-well microtiter plate. This assay is thus semi-automated by adapting it to an ELISA testing format. The incorporation of bio-dUTP was enhanced by adding cold dTTP to the reaction mixture, optimally in a molar ratio 4:1 (dTTP:bio-dUTP). This non-RI RTA is more sensitive than the conventional RI assay for the detection of purified Rous-associated virus 2 (RAV-2) and of human immunodeficiency virus type 1 (HIV-1) lysate. Because of its simple procedure, higher sensitivity and non-use of RI materials, the assay can be utilized not only for virological studies but also for routine safety screening of biological products for retroviral contamination.

Avian Leukosis Virus↗
PubMed1992

The distribution of coagulation factors VII and VIII and fibrinogen in adults over 65 years. Results from the Cardiovascular Health Study.

The Cardiovascular Health Study (CHS) was designed to examine cardiovascular disease and its risk factors in older adults. We report here the distributions of the coagulation factors fibrinogen, factor VII, and factor VIII in a population-based cohort of men and women 65 years or older. In other studies of middle-aged individuals, these factors were shown to be associated with cardiovascular risk. In the CHS cohort, all three factors were elevated, compared to levels reported in middle-aged individuals, and fibrinogen and factor VIII values were higher in each successive age group; factor VII values, in contrast, declined slightly with age in the CHS cohort. Compared to white subjects, blacks had higher values for fibrinogen and factor VIII and lower values for factor VII. While women had markedly higher values for factor VII and factor VIII than men at all ages in the CHS, mean fibrinogen values were not different between men and women.

Age Factors↗
PubMed1992

Decreased systemic clearance of diltiazem with increased hepatic metabolism in rats with uranyl nitrate-induced acute renal failure.

The effect of uranyl nitrate (UN)-induced acute renal failure (ARF) on the pharmacokinetics of diltiazem (DTZ) was examined in rats through in vitro and in vivo studies. In vitro homogenate studies demonstrated that DTZ was metabolized to deacetyl diltiazem (DAD) predominantly in the liver. Metabolism in the small intestine, kidney, or blood pool was negligible compared with that in the liver. UN-induced ARF (UN-ARF) increased the in vitro hepatic clearance (CLvit) of DTZ 1.4-fold. In vivo pharmacokinetic studies following intravenous (iv) and portal venous (pv) administration revealed that UN-ARF increased the intrinsic clearance (CLi) of DTZ from 243.0 to 414.5 ml/min/kg but decreased its total plasma clearance (CLt) from 90.3 to 64.3 ml/min/kg. The increase in CLi was consistent with the increase in CLvit of the liver. The in vitro plasma free fraction of DTZ (fp) was decreased from 0.25 to 0.14 by UN-ARF, but the in vitro blood/plasma partition of DTZ (Rb) remained constant at unity. From the CLi and fp changes, the plasma intrinsic clearance for unbound DTZ (CLi') was calculated to be increased 2.7-fold, from 1104.5 to 2960.7 ml/min/kg, by UN-ARF. The fp decrease was also reflected in the steady-state distribution volume (Vdss) of DTZ, which was decreased significantly from 3595.5 to 2528.3 ml/kg. The absolute bioavailability of pv DTZ (Fpv) was decreased by UN-ARF from 37.5 to 15.5% but was still much higher than the reported oral bioavailability (6%), indicating poor absorption of DTZ from the GI tract. From the calculation based on a well-stirred pharmacokinetic model, DTZ was found to increase the hepatic blood flow (HBF) of the control rats more than twofold at doses of 3 mg/kg (iv) or 10 mg/kg (pv), possibly due to the vasodilating effect of DTZ. However, the effect of DTZ on HBF was not present in the UN-ARF rats. It is not clear at present whether this could be attributed to vasoconstricting effects of UN-ARF or blockade of the vasodilating effect of DTZ.

Acute Kidney Injury↗
PubMed1992

Klebsiella aerogenes urease gene cluster: sequence of ureD and demonstration that four accessory genes (ureD, ureE, ureF, and ureG) are involved in nickel metallocenter biosynthesis.

The region located immediately upstream from the Klebsiella aerogenes urease structural genes was sequenced and shown to possess an open reading frame capable of encoding a 29.8-kDa peptide. Deletions were generated in this gene, denoted ureD, and in each of the genes (ureE, ureF, and ureG) located immediately downstream of the three structural genes. Transformation of the mutated plasmids into Escherichia coli resulted in high levels of urease expression, but the enzyme was inactive (deletions in ureD, ureF, or ureG) or only partially active (deletions in ureE). Ureases were purified from the recombinant cells and shown to be identical to control enzyme when analyzed by gel filtration chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis; however, in every case the activity levels correlated to nickel contents as analyzed by atomic absorption analysis. UreD, UreE, UreF, and UreG peptides were tentatively identified by gel electrophoretic comparison of mutant and control cell extracts, by in vivo expression of separately cloned genes, or by in vitro transcription-translation analyses; the assignments were confirmed for UreE and UreG by amino-terminal sequencing. The latter peptides (apparent M(r)s, 23,900 and 28,500) were present at high levels comparable to those of the urease subunits, whereas the amounts of UreF (apparent M(r), 27,000) and UreD (apparent M(r), 29,300) were greatly reduced, perhaps because of the lack of good ribosome binding sites in the regions upstream of these open reading frames. These results demonstrate that all four accessory genes are necessary for the functional incorporation of the urease metallocenter.

Amino Acid Sequence↗
PubMed1992

Modified indirect hemagglutination test for detection of treponemal antibodies in finger-prick blood.

A modified indirect hemagglutination test for the detection of treponemal antibodies was developed for use with finger-prick blood. By using paired serum and absorbed finger-prick blood from 58 patients from an area previously endemic for yaws and 12 patients without yaws, the modified hemagglutination test was compared with a hemagglutination test for Treponema pallidum and the fluorescent treponemal antibody absorption test. The modified hemagglutination test showed 100% specificity and an overall agreement of 96.5% with the hemagglutination test for T. pallidum and 94.8% with the fluorescent treponemal antibody test. The modified hemagglutination test appears to be a simple and economical test that is suitable for use in large epidemiological surveys for yaws.

Adult↗
PubMed1992

Biliary proteins in patients with and without gallstones.

BACKGROUND: Nucleation from supersaturated bile of calcium salts of cholesterol and bilirubinate is essential in the formation of gallstone. Nucleation requires gallbladder mucin and its main component, glycoprotein, may contribute to gallstone formation by providing a nidus or matrix for precipitation of lipid components. However, biliary protein patterns of patients with gallstones have not been completely explored. METHODS: We have tried to extract, isolate and characterize the proteins in patients with gallstones and without gallstones. 21 bile samples were obtained from patients with different types of gallstones and with no stones at cholecystectomy. Biliary protein concentrations were measured by Lowry and Bensadoun methods, and individual glycoproteins from each of the patients were compared by silver staining and densimetric quantification of Sodium Dodesyl Sulfate Polyacrylamide Gel Electrophoresis. RESULTS: 1) Among 16 gallstones, 5 were cholesterol stones, 5 were calcium bilirubinate stones, and 6 were black pigment stones. 2) The mean protein concentration was highest in bile with cholesterol stones (47.6 mg/ml), 24.2 mg% in bile without gallstones, and 15.9 mg/ml in brown pigment stones. 3) Cholesterol gallstones were found to have 14.2 KD glycoproteins, whereas pigment stones were found to have 66 KD glycoproteins. CONCLUSIONS: Gallbladder proteins from both cholesterol and pigment stones play an important role in the nucleation and growth of calcium salt crystals.

Bile↗
PubMed1992

A new ensemble averaging technique in impedance cardiography for estimation of stroke volume during treadmill exercise.

In this study, a new ensemble average technique is developed to measure cardiac output during treadmill exercise. Each dz/dt peak is used as a starting point for ensemble averaging, instead of the conventionally used R point of the ECG, in order to prevent the peak dz/dt waveform (C point) from smoothing, which results in increased dz/dtmax. The R-Z interval from the R point of the ECG to the peak dz/dt varies for each heart beat especially during strenuous exercise. Signal-to-noise ratios of five subjects obtained with the new technique are 0-32.6% higher than those obtained with the conventional technique at rest and during four levels of treadmill exercise. Power spectral densities of the averaged dz/dt waveforms by the peak dz/dt and R point references are also analyzed. Stroke volumes of the five subjects averaged by the peak dz/dt are 0-23.5% higher than those obtained by the R point at rest and during four levels of exercise.

Cardiography, Impedance↗
PubMed1992

Modulation of hematologic and immunologic effects of high dose chemotherapy by interleukin-2 in a murine tumor model.

To determine if intensive chemotherapy consisting of cyclophosphamide (C), etoposide (E), and cisplatin (P) (CEP) may be usefully combined with recombinant human interleukin-2 (rhIL-2), we examined a murine tumor model designed to approximate a common clinical situation: macroscopic, drug-resistant cancer. Using C57BL/6 mice with extensive tumor burden 10 days after intravenous B16 melanoma cell injection, we observed (1) C, E, and P synergize to enhance survival but do not cure mice at the highest tolerable dose (C = 200 mg/kg, E = 60 mg/kg, and P = 3 mg/kg); (2) rhIL-2 at 3 x 10(5) U (subcutaneously) daily for 4 days administered 10-18 days after B16 injection significantly improves survival; (3) CEP plus rhIL-2 is more effective than CEP alone only when rhIL-2 is administered before CEP; (4) CEP suppresses IL-2-induced lymphokine-activated killer cell activity in the spleen; and (5) rhIL-2 protects mice incompletely from the immunologic and hematologic suppression of CEP. Our results suggest that intensive chemotherapy combined with rhIL-2 may be beneficial. The success of any such combination may be schedule dependent.

Animals↗
PubMed1992

Left-sided superior vena cava: a not-so-unusual vascular anomaly discovered during central venous and pulmonary artery catheterization.

OBJECTIVE: To report our ICU experience with patients noted to have a left-sided superior vena cava after central venous and pulmonary artery catheterization. DESIGN: Retrospective review. SETTING: Surgical ICUs in a University and Veterans Administration Medical Center. PATIENTS: Five patients who had insertion of central venous or pulmonary artery catheters were noted to have abnormal placement. RESULTS: Five patients were noted to have a left-sided superior vena cava that was not appreciated on preinsertion radiography after central venous (two patients) or pulmonary artery catheterization (three patients). The finding of left-sided superior vena cava was confirmed by computed tomography scan (one patient), transesophageal echocardiography (one patient), bolus contrast injection (two patients), and intraoperative inspection (one patient). CONCLUSIONS: Left-sided superior vena cava occurs infrequently, most often in association with a right-sided superior vena cava. It is often associated with cardiac septal defects. The intensivist should be aware of its occurrence in order to not mistake catheters placed in it as being present in the arterial circulation or malpositioned outside of the venous circulation.

Adult↗
PubMed1991

Simultaneous determination of haloperidol and its metabolite, reduced haloperidol, in plasma, blood, urine and tissue homogenates by high-performance liquid chromatography.

A high-performance liquid chromatographic method was developed for the simultaneous determination of haloperidol and reduced haloperidol in human plasma, urine and rat tissue homogenates using bromperidol as an internal standard. The method involved extraction followed by injection of 50-80 microliters of the aqueous layer onto a C18 reversed-phase column. The mobile phase was 0.5 M phosphate buffer-acetonitrile-methanol (58:31:11, v/v/v) and the flow-rate was 0.6 ml/min. The column effluent was monitored by ultraviolet detection at 214 nm. The retention times for reduced haloperidol, haloperidol and bromperidol were 5.4, 7.2 and 8.4 min, respectively. The detection limits for haloperidol and reduced haloperidol in human plasma were both 0.5 ng/ml, and the corresponding values in human urine were both 5 ng/ml. The coefficients of variation of the assay were generally low (below 10.7%) for plasma, urine, blood and tissue homogenates. No interferences from endogenous substances or any drug tested were found.

Animals↗
PubMed1991

Fibrinogen Ledyard (A alpha Arg16----Cys): biochemical and physiologic characterization.

Fibrinogen Ledyard was discovered in a 10-year-old boy with a mild bleeding history. His father had the same defect and a bleeding history after surgery. Both patients were heterozygous. The plasma fibrinogen concentration was normal immunologically (335 mg/dL) and very low functionally (52 mg/dL). Purified fibrinogen Ledyard had a prolonged polymerization, which was somewhat corrected by addition of Ca2+ ions. High performance liquid chromatography (HPLC) analyses of the fibrinopeptides released by thrombin showed 1 mol of fibrinopeptide A (FPA) and 2 mol of fibrinopeptide B (FPB) released per mole of fibrinogen Ledyard. Steady-state kinetic parameters were evaluated for release of FPA by thrombin. When the concentration of fibrinogen Ledyard was corrected to 50% of total protein, because only 50% of fibrinogen Ledyard can release FPA, the kinetic constants were similar to those of control fibrinogen (Km = 7.5 mumol/L for A alpha chain, kcat = 54 s-1). This finding indicates that the cleavage site of the A alpha chain in these abnormal molecules may not interact with the catalytic site of thrombin. The three chains of fibrinogen Ledyard were isolated on reverse-phase C4-HPLC. The sequence of the amino terminus of A alpha chain showed that Arg in position 16 was replaced by Cys in the abnormal molecules. Approximately half of fibrinogen Ledyard (52%) was clotted by reptilase, suggesting that fibrinogen Ledyard may consist of 50% normal homodimers (A alpha Arg16 . A alpha Arg16) and 50% abnormal homodimers (A alpha Cys16 . A alpha Cys16). Abnormal molecules could form disulfide bond between the A alpha Cys16 residues. Thus, the abnormal molecules have a different structure that does not bind to thrombin. Probably the abnormality of polymerization of fibrinogen Ledyard results from the interaction of the abnormal molecules with normal fibrin monomers, so that the growth of fibrin protofibrils is inhibited. This abnormal fibrinogen supports adenosine diphosphate-induced platelet aggregation in a normal manner.

Amino Acid Sequence↗