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Biomedical subjects

L Wong

Publications and source records attributed to L Wong.

At least 217 records · Page 12Linked to original sources
PubMed1987

Biogenesis of very-low-density lipoproteins in rat liver. Intracellular distribution of apolipoprotein B.

The hepatic subcellular distribution of apolipoprotein B (apo B) was studied quantitatively by using an enzyme immunoassay developed for apo B and by immunoadsorption-precipitation of [3H]leucine-labelled apo B. Over 50% (of 0.59 microgram/mg protein) of the apo B was located in the microsomal fraction. Further subfractionation of the microsomes revealed that 47% of the microsomal apo B was in the Golgi apparatus, while another 43% was associated with the rough endoplasmic reticulum. The smooth endoplasmic reticulum accounted for only 4% of the total. When rat livers were labelled with [3H]leucine for 10 min, the rough endoplasmic reticulum accounted for 80% of the total immunoadsorbed precipitable apo B radioactivity while the smooth accounted for 20%, with no contribution from the Golgi. However, only 8.7% of the total radioactive immunoadsorbed precipitable apo B was lipoprotein-associated, the remainder being membrane-bound. Lipoprotein-associated apo B radioactivity in the smooth endoplasmic reticulum accounted for 40%, with the rough contribution attributed at 50% and the Golgi at 9%. We concluded that (a) there are two major pools of apo B in rat liver microsomes; (b) although the apo B mass may be negligible in the smooth endoplasmic reticulum, the latter does play a role in lipoprotein biogenesis. The possible function of apo B associated with membranes of the microsomes is also discussed.

Animals↗
PubMed1987

Immunological heterogeneity of rat apolipoprotein B epitope expression. A study using monoclonal antibodies to rat apolipoprotein B.

Epitope expression of rat apolipoprotein B on lipoproteins was investigated with the help of six monoclonal antibodies produced from mice. Through a variety of techniques, which include cotitrations, ELISAs and quantitative immunoadsorption precipitation, we concluded that the six monoclonal antibodies recognize five different epitopes. LRB 110 and LRB 260 recognize epitopes that may be overlapping. LRB 240 and LRB 250 recognize epitopes that are preferentially expressed in triacylglycerol-rich particles. LRB 220 recognizes an epitope that is expressed by all apolipoprotein-B-containing lipoproteins. We have also determined that apolipoprotein B epitope expression in rat lipoproteins is very similar to its human counterpart. Both rat and human apolipoprotein B epitope expression on lipoproteins showed heterogeneities even in homologous lipoprotein preparations. We concluded that a variety of techniques are necessary to fully characterize monoclonal antibodies to apolipoproteins. The possible implications of epitope expression in pathophysiology are also discussed.

Animals↗
PubMed1987

Lepromin-induced suppressor cells in lepromatous leprosy.

The presence or absence of suppressor cells in leprosy patients was investigated by measuring peripheral blood lepromin-induced suppression of the Con A response. Significant suppressor activity was measured in 15 of 15 untreated or recently treated patients with lepromatous leprosy and 3 of 5 patients with borderline lepromatous leprosy. In addition, in patients with lepromatous leprosy, suppressor cell activity was found in 10 of 14 patients that had been under treatment for more than 1 year but in only 2 of 27 patients who had active or thalidomide controlled erythema nodosum leprosum. Suppression was observed in only 5 of 29 tuberculoid leprosy patients, 1 of 6 patient contacts, and 0 of 11 normal controls. The differences between the lepromatous or borderline lepromatous group as compared with the tuberculoid group were statistically significant (P less than 0.001). Our findings confirm the presence of lepromin-triggered suppressor cells in the peripheral blood of patients with lepromatous leprosy. These suppressor cells may contribute to the selective unresponsiveness of lepromatous patients to the antigens of Mycobacterium leprae.

Concanavalin A↗
PubMed1987

Calmodulin and calbindin D28K in Alzheimer disease.

The calcium binding proteins, calmodulin and calbindin D28K, were measured by radioimmunoassay in cerebral cortex from brains with degenerative brain diseases associated with dementia. Samples were obtained from 17 normal control brains, 18 Alzheimer affected brains, and 15 brains of patients who died of a dementia process other than Alzheimer disease. Calmodulin content in the non-Alzheimer group was not significantly different from control. However, in the Alzheimer group, frontal, temporal, parietal cortex, and subjacent white matter calmodulin content was significantly reduced (66% of that found in the other 2 groups). Calmodulin extracted from temporal cortex also demonstrated reduced efficacy as an activator of 3',5' cyclic nucleotide phosphodiesterase. Calbindin D28K was reduced both in Alzheimer and non-Alzheimer dementia brains. Reduced concentrations of these important proteins may affect calcium homeostasis and the regulation of a large number of calcium mediated brain functions.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1987

The influence of incorporated and adsorbed fluoride on the dissolution of powdered and pelletized hydroxyapatite in fluoridated and non-fluoridated acid buffers.

The effects of fluoride (F) incorporated into hydroxyapatite (HA), adsorbed onto the HA surface, and fluoride in solution were studied during HA dissolution. Dissolution rates at pH 5.0 and 25 degrees C were determined in fluoridated (0.1, 5.0 micrograms/mL) and non-fluoridated buffers for the following powdered and pelletized synthesized HAs: non-fluoridated HA, partially-fluoridated (100, 1000, 37,000 micrograms/g) HA, and surface-adsorbed fluoridated (100, 1000 micrograms/g) HA. The dissolution rate curves were used to derive two components we have called 'diffusion' and 'surface chemical reactivity'. With powders, the rate-determining factor was surface chemical reactivity during the first 60 min. Diffusion was reduced by increasing the F levels in the apatite or buffer. In non-fluoridated buffers, diffusion was reduced 29% for apatite with 100 micrograms/g incorporated F and 99% with 37,000 micrograms/g. Diffusion was reduced by 37% and 81% by 0.1 and 5.0 micrograms/mL F, respectively, in the buffer. With pelletized HA, the rate-determining factor during the first 10 min was surface chemical reactivity. Diffusion then became relatively more important, but the diffusion rate was independent of F content. During the dissolution of powdered apatites, F was taken up by the remaining apatite solid, as evidenced by the lower F concentration in solution than that calculated to be released during dissolution. There was also a decrease in the F concentration of the 0.1 microgram/mL buffer as reaction progressed. Pelletized apatites did not release enough F to influence dissolution significantly. Surface-adsorbed F was more effective than incorporated F in reducing HA dissolution.(ABSTRACT TRUNCATED AT 250 WORDS)

Acids↗
PubMed1987

Cold provocation test results from a 1985 survey of hard-rock miners in Ontario.

A total of 143 miners, 6 ex-miners, and 42 referents from five mines in northern Ontario were examined with a cold provocation test. The skin temperatures, measured by thermocouples at the tips of the fingers and thumbs were recorded at 5-s intervals throughout the immersion in cold water (10 degrees C) for 10 min and during the recovery period. The finger skin temperature was followed until 99% recovery had occurred as compared to the starting temperature. For the referents and the vibration-exposed subjects, the results by separate stage of the Taylor-Pelmear scale for hand-arm vibration syndrome were compared. There were statistically significant differences in the mean finger temperature at the 50, 75, 90, and 95% recovery times between stages 0, 0T/0N, and stages 1 through 3 combined, as well as significant differences between stages 1, 2, and 3. The mean temperature at 10 min and the mean hyperemia temperature for eight fingers combined were compared between the miners and referents. There were significant differences in the mean temperature at 10 min and in the hyperemia temperature between the referents and miners in stage 0T/0N, as well as between the referents and the miners in stages 1 through 3 combined. For the worst finger (defined as that with the lowest temperature at 10 min) there was an increasing trend towards a lower hyperemia temperature and delay in recovery time from stage 0 to stages 2 and 3 combined.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Interaction between flurazepam and ethanol.

The interaction of a representative benzodiazepine, flurazepam, and ethanol has been assessed in ICR albino mice. Tests done included loss of "rotarod" performance, light sedation, deep sedation, loss of righting reflex, anesthesia, and lethality. LD50 and ED50s were plotted as isobolograms (plots of equieffective dose combinations). Data for anaesthesia and lethality showed little or no interaction between the two drugs. In contrast, the four motor and behaviour tests showed synergism, especially with higher doses of ethanol (over 2 g/kg) for righting reflex, and (over 1.5 g/kg) for deep sedation. Synergism occurred over all doses for light sedation and rotarod performance. It is expected that concurrent use of benzodiazepines and ethanol can result in a significantly higher accident risk in humans, but little additional risk of death from simple overdose.

Anesthesia↗
PubMed1986

Effect of cyclosporine A in erythema nodosum leprosum.

Erythema nodosum leprosum (ENL) is a reactional state of lepromatous leprosy in which the loss of suppressor cell function, decrease in suppressor cell numbers, and increase of interleukin 2 production are observed. We reasoned that cyclosporine A (CsA), by opposing these immune responses, could suppress the ENL reaction and restore patients to the quiescent lepromatous state. We tested this hypothesis in vitro by measuring the effect of CsA on M. leprae-triggered suppressor cells. In 24 of 25 patients with ENL, suppressor cell activity was restored by CsA. The target of CsA appeared to be macrophages. These findings are significant in that they provide the first evidence for the potential efficacy of CsA in the treatment of ENL. Preliminary clinical trials indicate a beneficial therapeutic effect associated with increased T suppressor cells in lesions.

Cyclosporins↗
PubMed1986

Suppressor T lymphocytes from lepromatous leprosy skin lesions.

The immune response in leprosy forms a spectrum with lepromatous leprosy patients exhibiting specific unresponsiveness to antigens of Mycobacterium leprae. This unresponsiveness is thought to be related to the prevalence of T8-positive lymphocyte in these lepromatous lesions. To analyze the immunoregulatory function of these T8 cells, we developed simple procedures to extract lymphocytes from skin biopsy specimens of patients with leprosy. These lymphocytes were sorted for T8 and T4 positive cells, and cell lines were established by expansion with interleukin 2 (IL 2) and irradiated feeder cells. All T8 positive lines tested were positive for IL 2 receptors and HLA-DR determinants. These lines were additionally assayed for lepromin-induced suppression of the normal peripheral blood lymphocyte Con A proliferative response. Thirteen of 32 lines from six lepromatous patients showed significant suppressor activity, whereas nine lines from six tuberculoid patients and one line from normal peripheral blood failed to show suppression (p less than 0.001). Taken together, the finding of M. leprae-triggered suppressor cells within lepromatous skin lesions may in part explain the M. leprae unresponsiveness of lepromatous leprosy patients.

Antigens↗
PubMed1986

Counterion distribution around DNA: variation with conformation and sequence.

The three-dimensional Poisson-Boltzmann equation for the distribution of counterion charge density around double helical DNA has been solved by an iterative procedure. These computations have been performed for 0.01M monovalent salt solutions. A systematic study of the ten possible sequences found among adjacent nucleotide base pairs is presented for the A, B, and C conformations of DNA. In addition, calculations of the electrostatic stabilities of these conformations of DNA allows for comparison of the charge accumulation around each of the three conformers.

Base Sequence↗
PubMed1986

Deuterium NMR study of the interaction of alpha-tocopherol with a phospholipid model membrane.

The effects of 5, 10, and 20 mol % incorporation of alpha-tocopherol (vitamin E) on 50 wt % aqueous multilamellar dispersions of sn-2-substituted [2H31]palmitoylphosphatidylcholine (PC-d31), a saturated, deuterated phospholipid prepared from egg lysophosphatidylcholine, have been studied by deuterium nuclear magnetic resonance (2H NMR) and differential scanning calorimetry (DSC). Moment analysis of the 2H NMR spectra as a function of temperature and DSC heating curves demonstrate that the main gel to liquid-crystalline phase transition is progressively broadened and its onset temperature lowered by increasing concentrations of alpha-tocopherol. Below the transition temperature (40 degrees C) for PC-d31 bilayers, the 2H NMR spectra indicate that acyl chain motion is increased by addition of alpha-tocopherol and that this effect extends to lower temperatures with higher alpha-tocopherol content. Above the transition, average carbon-deuterium bond order parameters calculated from the first spectral moment establish that alpha-tocopherol increases acyl chain ordering within the PC-d31 bilayer by as much as 17% at 20 mol % incorporation. Profiles of order parameter vs. chain position, constructed from 2H NMR spectra following application of the depaking technique, show that despite higher order the general form of the profile is not significantly altered by alpha-tocopherol.

Calorimetry, Differential Scanning↗
PubMed1986

Carcinogenic effects of antimony trioxide and antimony ore concentrate in rats.

This study was initiated because of a suspected increase in incidence of lung cancer in antimony smelter workers in England. Three groups of 8-mo-old Wistar-derived rats (90 males and 90 females per group) were exposed by inhalation to either Sb2O3 [time-weighted average (TWA) 45 mg/m3], Sb ore concentrate (TWA 36 + 40 mg/m3), or filtered air (controls) for 7 h/d, 5 d/wk, for up to 52 wk and sacrificed 20 wk after terminating exposures. Serial sacrifices (5 rats/sex/group) were performed at 6, 9, and 12 mo. Autopsies and histopathological examinations were performed on all animals. The dusts and animal tissues were analyzed for Sb, arsenic, and other inorganic elements by atomic absorption and proton-induced X-ray emission methods. The most significant findings were the presence of lung neoplasms in 27% of females exposed to Sb2O3 and 25% of females exposed to Sb ore concentrate (p less than 0.01). None of the male rats in any group or the female controls developed lung neoplasms. There were no significant differences in incidences of cancer of other organs between exposed and control rats. These results were compared with other published results, including an animal inhalation study with Sb2O3 in which lung tumors were also induced. Higher concentrations of arsenic were found in tissues from female rats than from male rats. For example, arsenic levels in blood of control males, control females, Sb2O3 males, Sb2O3 females, Sb ore males, and Sb ore females were 60, 123, 115, 230, 71, and 165 micrograms arsenic/g dry blood, respectively, 9 mo after initiating exposures.

Animals↗
PubMed1986

The role of serum isoamylase and lipase determinations in clinical practice.

To determine the clinical utility of routine determination of serum isoamylase (pancreatic/salivary) and/or lipase activity, sera were tested from 109 consecutive patients with elevated total serum amylase. Without knowledge of the isoamylase and lipase results, an assessment was made of the confidence with which the attending medical staff had made or excluded a diagnosis of acute pancreatitis. The attending staff had considered acute pancreatitis to be probable in 78, possible in 12 and unlikely in 19 patients. The confidence of the clinical diagnosis of acute pancreatitis was directly related to the degree of elevation of the serum total amylase: (mean IU/l +/- s.e.m.) probable pancreatitis 1807 +/- 313, possible pancreatitis 680 +/- 74, pancreatitis unlikely 493 +/- 50. Pancreatic isoamylase was elevated in 97% of patients with probable pancreatitis, 92% with possible pancreatitis and 68% in whom pancreatitis had been considered unlikely. Lipase elevations generally parallelled these results. Although gall-stones were usually sought among patients with probable pancreatitis, they were rarely sought in patients in the other categories. In conclusion, amylase isoenzyme or lipase determinations add little information in cases of clinically suspected acute pancreatitis with marked hyperamylasemia. The tests may have a role in the evaluation of patients with clinically unexplained hyperamylasemia by defining more precisely the origin of the amylase.

Acute Disease↗
PubMed1986

Characterization of messenger RNA from the cerebral cortex of control and Alzheimer-afflicted brain.

A detailed comparative study of RNA transcripts isolated from the neocortex of control and Alzheimer postmortem brains was made to determine whether morphological changes in the chromatin of Alzheimer neurons and glia, which we reported earlier, are accompanied by changes in the products of transcription. A number of parameters were determined including the yields of total and mRNA per gram of tissue, the relative proportions of polyadenylated [poly(A)+] mRNA in the total RNA, the size distribution of the transcripts and the length of their poly(A) tails, and the nature of their in vitro translation products. The levels of endogenous RNase activity were also measured. The effect of the agonal process on the transcript complement was examined by Northern blotting of a cloned human heat-shock cDNA to total human brain RNA. Our results reveal that the yields of total RNA, unadenylated mRNA, and poly(A) tail lengths from Alzheimer neocortex samples do not differ significantly from those of control and non-Alzheimer dementia neocortex. On the other hand we find a significant reduction in the levels and proportion of poly(A)+ mRNA in the Alzheimer samples as compared to control brain samples. Quantitative rather than qualitative differences were observed in the in vitro translation products when programmed with control and Alzheimer mRNA. No differences were found in the levels of RNase activity between control and Alzheimer samples. Heat-shock mRNA transcripts were detected in brain samples from patients in whom fever was associated with death. The direct correlation of reduced poly(A)+ mRNA and chromatin condensation in Alzheimer neocortex suggests a cause-and-effect relationship. Whether all transcribed genes are affected or only a specific subset has yet to be determined.

Aged↗