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Biomedical subjects

H Lim

Publications and source records attributed to H Lim.

72 records · Page 4Linked to original sources
PubMed1990

Restriction site and genetic map of Cucurbita pepo chloroplast DNA.

A detailed restriction map of squash chloroplast DNA (cpDNA) was constructed with five restriction endonucleases, SalI, PvuII, BglI, SacII, and PstI. The cleavage sites were mapped by sequential digestion of cpDNA using low-gelling temperature agarose. The restriction map shows that squash cpDNA is an approximately 153 kilobase (kb) circle with a large inverted repeat sequence of 23.3 kb, separated by a large (83.7 kb) and a small (22.7 kb) single copy region. Genes for a number of chloroplast polypeptides were localized on the map by hybridizing the cpDNA restriction fragments to heterologous gene-specific probes from tobacco, pea, tomato, maize, and spinach chloroplasts. The gene locations and organization of squash cpDNA are highly conserved and similar to chloroplast genomes of tomato, pepper, and Ginkgo.

Chloroplasts↗
PubMed1989

Pharmacokinetics of N-4-hydroxyphenyl-retinamide and the effect of its oral administration on plasma retinol concentrations in cancer patients.

Concurrent with a phase-II trial of 4HPR in patients with various cancers, we studied the plasma pharmacokinetics of both 4HPR and its major metabolite 4MPR as well as the effect of 4HPR administration on plasma retinol concentrations using a simple, specific and sensitive HPLC procedure. Initial estimates of plasma pharmacokinetic parameters after oral administration of 4HPR (300 mg/day) [corrected] in 3 cancer patients were the following: 4HPR, t beta 1/2 = 13.7 hr, AUC = 3.49 micrograms.hr/ml, CL = 56.57 L/hr/m2; 4MPR, t beta 1/2 = 23.0 hr, AUC = 1.15 micrograms.hr/ml, CL = 239.29 L/hr/m2. We also found that oral administration of 4HPR resulted in a rapid, profound and significant reduction in plasma retinol concentrations. The mean plasma retinol concentrations for 9 patients decreased 60% from baseline to below 200 ng/ml within 1-2 weeks of 4HPR dosing initiation. In addition, there was a concurrent, significant reduction in plasma retinol-binding protein levels in these patients. The mechanism whereby 4HPR reduces plasma retinol levels in vivo has not been determined. The addition of 4HPR to pooled human plasma at 37 degrees C in vitro did not reduce endogenous retinol levels, suggesting no direct chemical interaction between these 2 retinoids.

Administration, Oral↗
PubMed1988

The excretion of large vitamin C loads in young and elderly subjects: an ascorbic acid tolerance test.

An ascorbic acid tolerance test is described for assessing vitamin C status. The test is simple to administer and suitable for elderly patients. It involves giving an oral load of 1 g ascorbic acid in water and then measuring urinary excretion of vitamin C over the next 6 h. The excretion pattern at dosing has been studied in ten young subjects. The result of the ascorbic acid tolerance test in these young subjects was significantly different after supplementation with 1 g ascorbic acid daily for 1 month. Two series of elderly patients were also studied with the ascorbic acid tolerance test. They had low initial plasma ascorbic acid levels and much less vitamin C was excreted in the urine after dosing. Seven of these elderly patients were then supplemented with 1 g ascorbic acid for 1 month. After supplementation the initial plasma levels and their response to the ascorbic acid tolerance test became similar to that seen in younger subjects.

Administration, Oral↗
PubMed1986

Isozyme-specific enzyme inhibitors. 12. C- and N-methylmethionines as substrates and inhibitors of methionine adenosyltransferases of normal and hepatoma rat tissues.

The 2-, 3-, and 4-mono-C-methyl derivatives of D,L-methionine (Met) have been resolved into the 10 possible enantiomeric forms having the configurations 2-Me-D, 2-Me-L, 3(alpha or beta)-Me-D, 3(alpha or beta)-Me-L, 4(alpha or beta)-Me-D, and 4(alpha or beta)-Me-L (the alpha designation was given to enantiomeric pairs that had higher Rf values on silica gel chromatograms than their diastereomeric counterparts). All compounds were weak, poorly selective inhibitors of the rat M-2 (normal tissue) and M-T (Novikoff ascitic hepatoma) variants of Met adenosyltransferase. Kinetic analysis of the three most effective showed them to be competitive inhibitors with respect to Met with both variants; the strongest inhibition (KM(Met)/Ki = 0.03) was that of M-T by 3 beta-Me-L-Met. The Me-Met enantiomers had low substrate efficiencies (Vmax/KM) in the range (0.5-2.2) X 10(-4) that of L-Met with M-2 (0.2-1.3) X 10(-3) with M-T among seven compounds studied. At a 4 mM level, seven of the enantiomers were converted to adenosylmethionine derivatives more rapidly by M-T than by M-2. Among these, 2-Me-L-Met, 3 alpha-Me-L-Met, 3 alpha-Me-D-Met, and 4 beta-Me-D-Met had little or no substrate activity with M-2. These differences in substrate specificity are potentially exploitable in the design of compounds with selective toxicity for rat tumor tissue. N-Me- and N-(n-Bu)-Met, and the Met analogue in which NH is substituted for S, were weak inhibitors of M-T and M-2 and showed no substrate activity at a level of 4 mM.

Animals↗
PubMed1979

Proteolytic denaturation and methods of improving the stability of glucose isomerase preparations.

Evidence is provided in support of proteolytic denaturation of free and immobilized preparations of glucose isomerase from a Bacillus species. A number of methods to improve the stability with respect to proteolysis have been tested and their advantages as well as shortcomings are discussed. These methods include hollow-fiber treatment, gel permeation, thermal treatment, and addition of protease inhibitors. The half-life of the free and the cellulose acetate fiber-entrapped preparations of glucose isomerase can be significantly improved. For example, the hollow-fiber treatment can improve the half-life by an order of magnitude.

Acetates↗
PubMed1978

Concurrent cutaneous and hepatic hemangiomata in infancy: report of a case and a review of the literature.

Fifty-eight cases of concurrent cutaneous and hepatic hemangiomatosis in infants have been reported in the world literature. A fifty-ninth case is herewith reported and the literature is reviewed. Untreated cases have a mortality rate of 81%, whereas the mortality of treated cases is 29%. The main cause of death appears to be the consequence of arteriovenous shunting in the liver. Early and aggressive treatment by prednisone, radiotherapy to the liver, partial resection of liver, and ligation of the hepatic artery, each alone or in combinations, have been effective.

Digoxin↗
PubMedDate not supplied

Role of heat shock protein 60 (HSP60) on paraquat intoxication.

The possibility of establishing a new method of treatment against pulmonary fibrosis caused by acute paraquat intoxication, which takes into consideration the role of heat shock protein 60 (HSP60), was investigated in paraquat-exposed rat lung mitochondria. In polyacrylamide electrophoresis, mitochondrial protein bands appeared, especially in the range of molecular weight 60 kDa and higher, whereas protein bands disappeared in the 20-40 kDa range on the 4th day after paraquat exposure. The protein profile was normalized on the 7th day and no remarkable changes were seen thereafter up to the 56th day. The changes seen during the observation period were thought to reflect the course of paraquat-induced dysfunction and subsequent repair. The malondialdehyde concentration in mitochondria decreased until the 7th day but subsequently increased and recovered to normal levels by the 56th day. The relative density of HSP60 increased until the 7th day but subsequently decreased and recovered to normal levels by the 56th day. These two parameters therefore showed symmetrical changes. The change in the malondialdehyde concentration was thought to reflect the course of activation of the antioxidation function in mitochondria and the progression of repair. The change in the relative density of HSP60 was thought to have increased to repair the proteins affected by the paraquat radical and to have normalized with the progression of healing. These results suggest that HSP60 may play an important role in preventing the progression of pulmonary fibrosis induced by paraquat.

Animals↗
PubMedDate not supplied

PPAR delta functions as a prostacyclin receptor in blastocyst implantation.

Peroxisome proliferator-activated receptors (PPARs), members of the nuclear hormone superfamily, are the target of extensive investigation because of their role in various pathophysiological processes. Recently, a novel biological function of PPAR delta, a less studied member of the family, was observed in the mouse. Evidence suggests that cyclooxygenase 2-derived prostacyclin mediates blastocyst implantation via this receptor. In this review, this new function of PPAR delta in implantation is highlighted, and future directions to investigate its mechanism of action are discussed.

Animals↗
PubMedDate not supplied

High-performance liquid chromatographic analysis of a new neuroprotective agent for ischemia-reperfusion damage, KR-31378.

A high-performance liquid chromatographic method was developed for the determination of a neuroprotective agent for ischemia-reperfusion damage, KR-31378, in human plasma and urine and in rat tissue homogenates. The method involved deproteinization of the the biological samples with 0.5 volumes of saturated Ba(OH)2, 0.5 volumes of 0.04 M ZnSO4 and 1 volume of acetonitrile. A 80-microl aliqout of the supernatant was injected onto a reversed-phase C18 column. The mobile phase, 50 mM triethylamine acetate : acetonitrile : tetrahydrofuran (65:30:5, v/v/v), was run at a flow rate of 1.0 ml/min. The column effluent was mornitored by a ultraviolet detector set at 310 nm. The retention time of KR-31378 was approximately 6.5 min. The detection limits of KR-31378 in human plasma and urine and rat tissue homogenates were 0.2, 0.5 and 0.5 microg/ml, respectively. The coefficients of variation (within-day and between-day) were below 13.6% for human plasma and urine and rat homogenates. No interferences from endogenous substances were found.

Animals↗