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Biomedical subjects

K L Li

Publications and source records attributed to K L Li.

31 records · Page 2Linked to original sources
PubMed1993

Multinuclear and magic-angle spinning NMR investigations of molecular organization in phospholipid-triglyceride aqueous dispersions.

The supramolecular organization of multi-bilayers formed by aqueous egg phosphatidylcholine-triolein (PC-TO) mixtures has been investigated using 31P, 13C, and 1H nuclear magnetic resonance (NMR). For these emulsions, which mimic substrates in the early hydrolytic stages of fat digestion, the NMR spectra obtained with magic-angle spinning (MAS) exhibit resolution comparable to that of sonicated vesicles and integrated peak intensities consistent with their chemical composition. Both 31P line shapes and MAS sideband patterns from the phosphocholine group indicate that mixing with triolein produces a PC bilayer which remains predominantly liquid crystalline in its organization; nevertheless, anomalous spectral features in MAS spectra may be attributed to additional phases in which the headgroups adopt a different orientation with respect to the bilayer normal, and tight packing enhances phosphorus-phosphorus interactions. 13C and 1H line widths monitored as a function of PC mole fraction, spinning speed, and decoupling strength show that the choline headgroups and glycerol backbones are anchored preferentially in the phospholipid-triglyceride assemblies, whereas all acyl chains become very fluid. The average degree of chain order also decreases for the mixed dispersions, as judged from spinning-sideband intensities in 1H MAS NMR spectra. The absence of proton spin-diffusion effects in the PC-TO multilayers is demonstrated by examination of their spinning sidebands and relaxation times, making it possible to use MAS-assisted two-dimensional NMR to assign overlapped 1H resonances and to identify proximal interactions between the two constituents. The usefulness of these NMR strategies in mechanistic studies of gastric fat digestion is also discussed.

Carbon Isotopes↗
PubMed1993

Hepatic injury during propylthiouracil therapy in patients with hyperthyroidism. A cohort study.

OBJECTIVE: To evaluate the incidence, severity, and course of propylthiouracil-induced hepatic injury in patients with hyperthyroidism. DESIGN: Cohort study. SETTING: Outpatient clinic of a university-based hospital. PATIENTS: Fifty-four patients with normal aspartate aminotransferase (AST) and alanine aminotransferase (ALT) values and a definite diagnosis of hyperthyroidism. INTERVENTION: Treatment with propylthiouracil, 300 mg/d for 2 months followed by 100 to 150 mg/d for 3 months and a subsequent maintenance dose of 100 mg/d. MEASUREMENTS: Liver biochemical tests were studied before therapy and 2 months and 5 months after starting propylthiouracil therapy. The patients were monitored with clinical evaluation and weekly liver biochemical tests after AST or ALT levels became abnormal. Serologic markers of hepatitis A, B, C, and delta virus infection were also studied when appropriate. RESULTS: Fifteen (28%; 95% CI, 16% to 42%) of the 54 patients showed ALT elevations 2 months after propylthiouracil therapy. The mean peak ALT level for these patients was 1.35 mu kat/L (range, 0.65 3.85 mu kat/L). None of these patients had symptoms or hyperbilirubinemia. Liver biopsy in three patients showed mild perivenular focal necrosis or ill-defined granuloma composed of foamy histiocytes with ceroid pigment and mild fatty metamorphosis. Despite continued propylthiouracil therapy at a reduced dose, ALT levels returned to normal in 13 of 15 patients in the following 3 months. None of these ALT elevations resulted from hepatitis A, B, C, or delta virus infection. No statistical difference was seen in the pretreatment characteristics between patients with and those without ALT elevation, except that the former had a higher pretreatment T4 level (270 +/- 12.9 compared with 237 +/- 7.72 nmol/L, P = 0.027) and T3 level (7.22 +/- 0.72 compared with 5.85 +/- 0.39 nmol/L, P = 0.048). CONCLUSIONS: Propylthiouracil-induced subclinical liver injury is common and is usually transient and asymptomatic. Therapy with propylthiouracil may be continued with caution in the absence of symptoms and hyperbilirubinemia.

Adult↗
PubMed1993

Changes in inflammatory mediators in experimental periodontitis in the rhesus monkey.

Ligature-induced periodontitis was monitored for 6 months in eight Macaca mulatta monkeys to examine clinical status, radiographic bone level, and crevicular fluid (CF) levels of prostaglandin E2 (PGE2), thromboxane B2 (TxB2), interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha, and leukotriene B4 (LTB4). A split-mouth design was used, with eight ligated teeth and eight contralateral nonligated teeth which develop soft-chow-promoted (spontaneous) disease. Ligated sites experienced an average attachment loss of 0.94 mm per site and linear bone loss of 0.88 mm per site, with spontaneous-periodontitis sites experiencing approximately half the loss of ligated sites. The CF mediator levels showed increased levels of PGE2 and TxB2 at the ligated sites, as compared with the spontaneous sites, with no significant contralateral differences in the IL-1 beta or LTB4 responses. The concentrations of LTB4 in CF reached an early threefold peak over the baseline level at 1 month. By 2 months there was a statistically significant threefold elevation in CF-PGE2 in the ligated sites and a twofold elevation in the spontaneous sites as compared to the baseline level (P = 0.041 and 0.008, respectively). The monocyte product IL-1 beta increased sharply at 2 months and returned to the baseline level by 6 months at both ligated and nonligated sites. Tumor necrosis factor alpha in CF was below the limit of detection at all sites throughout the experiment (i.e., < 2 ng/ml). The selective elevation of both PGE2 and TxB2 in ligated sites, compared with levels in spontaneous sites, in the presence of similar levels of LTB4 and IL-1 beta provides further evidence that these molecules regulate the magnitude of the tissue-destructive response in progressive periodontitis.

Animals↗
PubMed1991

Evaluation of the effect of butyl p-hydroxybenzoate on the proteolytic activity and membrane function of human spermatozoa.

The inhibition of the proteolytic activity of acrosin in human spermatozoa by butyl p-hydroxybenzoate was assessed by the gelatin substrate film method. Compared with a typical acrosin inhibitor, TLCK, the inhibitory activity of butyl p-hydroxybenzoate to acrosin was much more effective (20 times) than that of TLCK, proving that butyl p-hydroxybenzoate was a potent acrosin inhibitor. The effect of butyl p-hydroxybenzoate on membrane function of human spermatozoa was evaluated using a sperm-tail hypoosmotic swelling test and supravital stain method. A good correlation (r = 0.92) was observed between the % spermatozoa with normal membrane function and the % live spermatozoa after treatment of the spermatozoa with butyl p-hydroxybenzoate for 1 min, indicating that the death of spermatozoa caused by butyl p-hydroxybenzoate is probably due to impairment of sperm membrane function. Both the inhibitory effect on acrosin and the adverse effect on membrane function suggest that butyl p-hydroxybenzoate could be developed as a new vaginal contraceptive.

Acrosin↗
PubMed1991

Agranulocytosis associated with anti-thyroid drug in patients with Graves' thyrotoxicosis--report of 11 cases.

Retrospective analysis of 11 Chinese patients with Graves' thyrotoxicosis developing agranulocytosis during anti-thyroid treatment was done. Seven of them received methimazole and 4 received carbimazole. None of the 11 patients had taken propylthiouracil. The major chief complaints were high fever (100%), chillness (91%), and sore throat (73%). The duration of drug treatment prior to the detection of agranulocytosis ranged from 13 to 63 days (mean +/- 1SE: 33.1 +/- 16.1). At the time of agranulocytosis detected, the peripheral leukocyte counts were 0.5 to 2.1 X 1000/mm3 (mean +/- 1SE: 1.05 +/- 0.47 X 1000/mm3), absolute neutrophil counts 0 to 450/mm3 (mean +/- 1SE: 54.27 +/- 132.12/mm3), and hemoglobin 8.2 to 15.9 g/dl (mean +/- 1SE: 11.85 +/- 2.24 gm/dl). Three of the 11 patients had positive bacterial blood cultures. The recovery time of absolute neutrophil counts above 500/mm3 ranged from 3 to 25 days (mean +/- 1SE: 10.5 +/- 6.6) after discontinuation of antithyroid drugs. Mortality was found in 2 of them (18%).

Adolescent↗
PubMed1990

Sulfadiazines reduce gingivitis and plaque formation in beagle dogs.

The effect of zinc sulfadiazine (ZnSD) and silver sulfadiazine (AgSD) on reducing plaque formation and gingivitis was studied in 12 beagle dogs over a 14-week period. 12 beagle dogs were scaled, root planed and pumiced to bring them to a similar level of gingival health, prior to placing them on a diet of Purina Dog Chow softened with canned gravy and molasses to promote the build-up of plaque and the initiation of gingivitis. At the end of 8 weeks, the dogs were determined to have substantial bacterial plaque accumulation and apparent gingivitis. Thereafter, 4 dogs were treated 2 x daily with topical applications of 3% zinc sulfadiazine; 4 dogs were treated with 2% silver sulfadiazine while 4 dogs were treated with placebo gel serving as control over a 14-week treatment period. By week 2, the zinc and silver sulfadiazine dogs showed a significant decrease in gingival index which was maintained throughout the study. Additionally, by week 2, the % of sites with bleeding was also seen to decrease significantly in the experimental groups. The plaque index remained consistent in all 3 groups until week 6 when the 2 experimental groups indicated significant decrease in plaque accumulation as compared to controls. Probing depths were also seen to decrease significantly in the experimental groups after 10 weeks of therapy. The mean stain index was similar in all 3 groups of dogs throughout the study. Data indicate that both zinc and silver sulfadiazine inhibit plaque formation and reduce existing gingivitis in beagle dogs.

Administration, Topical↗
PubMed1990

Sulfadiazines prevent plaque formation and gingivitis in beagles.

The effect of zinc sulfadiazine (ZnSD) and silver sulfadiazine (AgSD) on developing plaque formation and gingivitis was studied in 12 beagle dogs over a 14-week period. Plaque and gingival indices were used to measure plaque formation and gingivitis. During a 2-wk baseline period each dog was brought to optimal gingival health with prophylaxis and tooth brushing. Thereafter, 4 dogs were treated twice daily with topical application of 3.0% zinc sulfadiazine; 4 dogs were treated with 2.0% silver sulfadiazine while 4 dogs treated with placebo gel served as controls over a 12-wk treatment period. At wk 2 of treatment, all three groups of dogs showed an increase in plaque build-up on their teeth from baseline. By wk 6, plaque accumulation on the teeth was significantly less in dogs treated with either ZnSD or AgSD compared to control dogs. At wk 2 of treatment, gingival inflammation was increased from baseline in all three groups. Thereafter, over the course of the 12-wk treatment period, gingival inflammation in the ZnSD and the AgSD treated dogs was significantly less than the placebo treated dogs. The data indicate that both ZnSD and AgSD inhibit developing plaque formation in beagles. This significant inhibition of plaque formation was accompanied by a significant reduction in gingival inflammation.

Administration, Topical↗
PubMed1988

Structural requirements for binding of nonsteroidal anti-inflammatory drugs to human serum albumin.

The binding of representative chemical classes of nonsteroidal anti-inflammatory drugs (NSAIDs) to human serum albumin (HSA) was investigated by equilibrium dialysis. Warfarin enantiomers were used as specific markers in displacement studies. Data were analyzed by a computerized nonlinear least squares approach designed for binding of small ligands to macromolecules at equilibrium. The binding data indicated comparable affinities to the primary site by the warfarin enantiomers, phenylbutazone, and meclofenamate sodium. Naproxen, sulindac, and zomepirac showed lower affinity by one order of magnitude. The displacement data revealed stereoselectivity. The R(+) isomer was displaced to a significantly greater extent than the S(-) isomer by meclofenamate sodium, while the reverse was observed for phenylbutazone. Naproxen displaced both isomers to the same extent. No significant displacement of either isomer was seen with sulindac or zomepirac. Examination of the chemical structures of the high affinity compounds indicated the common feature of a hydrophobic area bearing a widely delocalized negative charge. Hydrophobic binding of these compounds to HSA at the warfarin site is possibly stabilized by the attraction of the delocalized negative charge to the basic lysine and arginine residues adjoining the lone tryptophan.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1979

Stability-indicating assay of acetaminophen in an effervescent tablet by ion-pair high-performance liquid chromatography.

A stability-indicating analytical method is described for determining acetaminophen and its degradation product, p-aminophenol, in an affervescent tablet. Tablets assayed by ion-pair high-performance reversed-phase liquid partition chromatography required no sample cleanup. The method applied to tablets containing 325 mg of acetaminophen yielded an average recovery of 99.6% with a relative standard deviation of 0.70% (n = 10). As little as 0.005% p-aminophenol could be detected.

Acetaminophen↗
PubMedDate not supplied

Cocaine-induced changes in time course of regional cerebral blood volume and transit time as determined by dynamic MR imaging.

We examined cocaine-mediated change in regional cerebral blood volume (rCBV) and mean transit time (MTT) in central brain structures of rats using functional MR imaging techniques. Changes in MTT and rCBV in animals who had previously been given cocaine depended on the length of time between the last pretreatment injection and the acute injection and seemed to parallel cocaine-mediated changes in extracellular dopamine concentrations.

Animals↗