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Biomedical subjects

T Wong

Publications and source records attributed to T Wong.

At least 145 records · Page 8Linked to original sources
PubMed1991

Detection of immunoglobulin gene rearrangement in acute and chronic lymphoid leukemias of B-cell lineage by polymerase chain reaction gene amplification.

Polymerase chain reaction (PCR) was used to amplify the DNA fragments of the complementarity determining region 3 of the immunoglobulin (Ig) gene heavy chain from the leukemic cell specimens of patients with acute and chronic lymphoid leukemias of B-cell lineage. Two different pairs of primers were tested. Fourteen of the 17 (82%) cases of acute lymphoblastic leukemia (ALL), and all 15 cases (100%) of B-cell chronic lymphocytic leukemia, who had rearrangement of the Ig gene heavy chain by Southern analysis, were positive by PCR with either one or both pairs of primers. This technique was able to detect leukemic cells at the level of 0.1%. Applying it to study the remission marrow specimens following induction chemotherapy was more useful than morphology alone in predicting early relapse of the leukemia.

Burkitt Lymphoma↗
PubMed1991

Dynamic measurements of the platelet membrane glycoprotein IIb-IIIa receptor for fibrinogen by flow cytometry. I. Methodology, theory and results for two distinct activators.

Platelet aggregation, which occurs within seconds of activation, is generally considered to be mediated by fibrinogen binding to glycoprotein IIb-IIIa which becomes expressed as a fibrinogen receptor (FbR) on the activated platelet surface. This receptor expression has, however, only been measured to date at relatively long activation times (greater than 15 min). We have therefore developed a theoretical and experimental approach for determining FbR expression within seconds of platelet activation using flow cytometry. The fluorescently labeled IgM monoclonal antibody FITC-PAC1, was used to report on the GPIIb-IIIa receptor for Fb (FbR). Human citrated platelet-rich plasma (PRP; diluted 1:10) was incubated with adenosine diphosphate (ADP) or phorbol myristate acetate (PMA) for varying times (tau = 0-10 s, out to 60 min), followed by incubation with fluorescein isothiocyanate (FITC)-PAC1 antibody at saturating concentrations. The time course of FITC-PAC1 binding was then measured for these variously preactivated samples (different tau) from the mean platelet-bound fluorescence (Fl), determined for greater than or equal to 5 s of PAC1 addition by dilution quenching and determination of fluorescence intensity histograms with the FACSTAR or FACSCAN (Becton-Dickinson Canada, Mississauga, Ontario) flow cytometers. Both rapid, initial rate of increase in Fl (nu) (related to PAC1 on-rates) and maximal extent of increase (Flmax) were thus determined for different tau values. These measurements yield the rate of formation of FbR (k1), and both the rate (k2) and efficiency (alpha) of binding of PAC1 to FbR as a function of activator type and time of action. We have found that ADP appears to cause rapid, maximal expression of FbR within 1-3 s (k1 greater than 20 min-1), whereas PMA expresses FbR in a slow, biphasic manner (k1 - 0.01 and 0.2 min-1). However, k2 and alpha for maximal PMA activation are about two and three times greater, respectively, than for maximal ADP-activation. Moreover, k2 decreases with post ADP activation time. These differences are discussed in terms of altered FbR organization and accessibility. This kinetic approach can be widely used to analyze the dynamics and organization of molecules on cell surfaces by flow cytometry, including studies of size-dependent subpopulations (see Part II, Frojmovic, M., and T. Wong. 1991. Biophys. J. 59:828-837).

Adenosine Diphosphate↗
PubMed1991

Dynamic measurements of the platelet membrane glycoprotein IIb-IIIa receptor for fibrinogen by flow cytometry. II. Platelet size-dependent subpopulations.

Platelet aggregation has previously been shown to occur within 1 s of activation with 100 microM adenosine diphosphate (ADP) for both large (L) and small (S) platelet subpopulations, but L platelets were about twofold more sensitive and more rapidly recruited into microaggregates than were S platelets after correcting for differences in platelet surface area. Because platelet aggregation normally requires fibrinogen binding to glycoprotein IIb-IIIa receptors (FbR) expressed on the activated platelet surface, we wished to compare the kinetics and nature of FbR expression induced by ADP for L versus S platelets, and to measure size-dependent differences in FbR expression for platelets maximally activated with phorbol myristate acetate (PMA). We presented the theory and methodology in Part I (Frojmovic, M., T. Wong, and T. van de Ven. 1991. Biophys. J. 59:815-827) for measuring the rate of FbR expression (k1) and both the rate (k2) and efficiency (alpha) of binding of PAC1 to FbR as a function of activation conditions from the initial on-rate of FITC-PAC1 to FbR (V) and the maximal number of FbR expressed: these are measured, respectively, from the initial rate of increase in platelet-bound fluorescence (v) and the maximal increase in mean fluorescence (Flmax). We extended these analyses to L and S platelets, selected by electronic gating of forward scatter profiles (FSC), with corresponding fluorescence (Fl) histograms retrieved analytically. Platelet size (V) and surface area (SA), determined directly for cells separated with a cell sorter, were highly correlated with FSC, allowing v and Flmax values to be expressed per unit area of membrane for L:S comparisons. Surprisingly, ADP activation appeared to express all FbR within 1-3 s of ADP activation for both L and S platelets, whereas k1 was similar for PMA activation. In addition, L platelets maximally expressed two and three times more FbR per unit area than did S platelets when maximally stimulated, respectively, with ADP or PMA. Whereas k2 was independent of platelet size for a given activator, the efficiency of PAC1 binding (alpha), per unit area of membrane, was two times greater for L than for S platelets, for either ADP or PMA activation. Our data suggest that the FbR structure, its microenvironment, or its surface organization may vary with platelet size or activator type. Major reorganization of FbR and/or its environment appears to occur after approximately 5 min of ADP activation equally for both L and S platelets. A model is presented to account for size-dependent differences in FbR expression with implications for regulation of platelet aggregation.

Adenosine Diphosphate↗
PubMed1991

Intestinal absorption of calcium from yogurt in lactase-deficient subjects.

Fractional intestinal absorption of calcium (FACa) was measured using radioactive calcium and 200 mg of calcium carrier provided either by yogurt or by CaCl2 in 7 lactase-deficient (L(-] and 7 normal (L(+] subjects. During the control period prior to yogurt consumption, mean calcium intake was 819 mg per day in L(-) and 931 mg per day in L(+) subjects (NS). In both groups of subjects yogurt increased FACa from 20.8 +/- 3.9% to 26.9 +/- 7.2% (P = 0.065) in L(+) subjects and from 20.2 +/- 5.6% to 23.5 +/- 6.4% (P = 0.050) in L(-) subjects. The significant increase in FACa observed in L(-) subjects indicates that yogurt, which is an autodigesting source of lactose, does not impair calcium absorption. FACa increase could reflect the lower dietary calcium intake in L(-) subjects when compared with L(+) subjects, due to avoidance of milk and non-fermented dairy products which could cause intestinal discomfort. It is concluded that yogurt is a well-tolerated and efficient source of calcium in subjects with lactase deficiency.

Adult↗
PubMed1991

Plasma sodium-potassium ATPase inhibition activity in low- and normal-renin hypertension.

Thirty-seven subjects with low- and normal-renin hypertension (plasma renin activity less than 0.45 ng/L/sec on a 100 mmol Na diet) were studied on a 10 and 100 mmol sodium diet (100 mmol K and 25 mmol Ca) to examine the effect of varied sodium intake on plasma Na,K-ATPase inhibitory activity (NKAIA) (% inhibition). On the 10 mmol Na diet, plasma NKAIA correlated with mean arterial pressure (MAP) (r = 0.384, P = .019). On the 100 mmol Na diet, plasma NKAIA correlated with daily urinary sodium excretion (r = 0.384, P = .019). With the increase in sodium intake, the mean change in MAP was 0.5 +/- 7.8 mm Hg (range -12.7 to 16.3) and the mean change in plasma NKAIA was -4.2 +/- 11.2% inhibition (range -37.5 to 16). The change in MAP was correlated to the change in plasma NKAIA (r = 0.384, P = .019). Plasma NKAIA is related to mean arterial pressure or urinary sodium excretion depending on the dietary sodium intake, and is related to sodium-induced changes in MAP in low and normal renin hypertensive patients.

Adult↗
PubMed1990

The platelet extinction coefficient measured by aggregometry is dependent on platelet composition rather than size: implications for studies of platelet heterogeneity and abnormalities.

Extinction (E) or light transmission measurements of platelet suspensions have been widely used to evaluate platelet structure and aggregation for platelet populations of varying mean platelet size (V). However, useful comparisons of platelet suspensions from donors having abnormally-sized platelets with those from healthy controls require a knowledge of the dependence of E on V. We have analyzed the extinction per platelet (e) as a function of the geometric scattering cross-section of equivalent spheres, V2/3, related to the apparent mean platelet optical efficiency, k. Such an analysis using data previously reported by Holme et al., for healthy controls and a variety of platelet-associated disorders showed e/V2/3 or k to be constant over an eight-fold variation in V. The outstanding exception was platelet suspensions from myeloproliferative disorder patients (MPD) which showed approximately 25% reduction in k values. When we analyzed e/V2/3 data for different-sized platelet subpopulations which were isolated by elutriation from healthy donors, we found that k doubled with a doubling in V from small to large platelets. It appears that the use of aggregometry devices with wide light acceptance angles yields k values for platelets which are insensitive to variations in V, but rather are sensitive to the expected variations in refractive index associated with distinct platelet internal composition and organization expected for different-sized normal subpopulations and "diseased" platelets as found in MPD. We relate these observations to photometric studies of platelet heterogeneity and of aggregation of platelets with different V and k values.

Adult↗
PubMed1990

Synthesis and use of a lysolecithin analog for the purification of UDP-glucuronosyltransferase.

Because of their high cost, lysolecithins are generally not considered useful detergents for the purification of membrane-bound enzymes. Therefore, we have synthesized a structural analog of lysolecithin with similar physical properties for which synthesis is straightforward. This analog is 1-palmitoylpropanediol-3-phosphocholine. To compare the efficacy of the two detergents for the purification of a membrane-bound enzyme, we have purified UDP-glucuronosyltransferase from pig liver microsomes using lysophosphatidylcholine or the synthetic analog. The catalytic properties of UDP-glucuronosyltransferase purified with 1-palmitoylpropanediol-3-phosphocholine or lysolecithin were identical. Sodium dodecyl sulfate-gel electrophoresis indicated that the purity of the UDP-glucuronosyltransferase preparation was the same whether lysophosphatidylcholine or its synthetic analog was used. The advantage of using 1-palmitoylpropanediol-3-phosphocholine in preference to lysophosphatidylcholine is that the former can be synthesized for about 1% the cost of the latter. In addition, the method for synthesis of 1-palmitoylpropanediol-3-phosphocholine is general in that the structural features of the polymethylene chain can be varied, allowing for the inexpensive synthesis of a series of detergents.

Electrophoresis, Polyacrylamide Gel↗
PubMed1990

Brain tumors diagnosed in the first year of life in five Far-Eastern countries. Statistical analysis of 307 cases.

A statistical survey is presented of brain tumors diagnosed in the first year of life (from five Far-Eastern countries) in relation to the racial differences in tumor types, congenital factors, and general clinical features. Of the 307 cases collected, 262 were verified histologically, and astrocytomas comprised 23.3%, medulloblastomas 17.2%, ependymomas 11.1%, choroid plexus papillomas 10.7%, teratomas 8.4%, primitive neuroectodermal tumors 4.2%, meningiomas 2.3%, and others 22.9%. There were statistically significant racial differences in comparison with the worldwide survey done by the International Society for Pediatric Neurosurgery Education Committee (1987) on the same subject. In the Far-Eastern population, medulloblastoma and teratoma were more common (P less than 0.05), whereas astrocytoma was less frequent (P less than 0.01) than reported in the worldwide survey. The malformative factors were suggested in 18 cases in which various associated congenital anomalies were observed. Vascular anomalous lesions, mostly in the extracranial organs, were most common, comprising 61.1% of the associated malformations. Hereditary factors were less commonly demonstrated in these tumors than were anomalies in the major congenital central nervous system. Among the 307 cases, there was one instance (0.3%) of nearly identical tumors occurring in twin brothers. The specific clinical manifestations of brain tumors involving the immature brain were again apparent in this survey, as were the poor survival rates and poor functional prognosis.

China↗
PubMed1990

Effect of brief treatment at alkaline pH on the properties of UDP-glucuronosyltransferase.

The kinetic properties of UDP-glucuronosyltransferase were measured after brief treatment of liver microsomes at alkaline pH, followed by assay with p-nitro-phenol as aglycone, at pH 7.5. Enzyme activity increased in a graded fashion as the pH of pretreatment was increased above 8.0, with apparent maximal activation of eight-fold for a pretreatment pH of 11.1. The pH for half maximal activation was 10.6. Brief treatment at alkaline pH prior to assay at pH 7.5 was associated too with a graded conversion of the kinetics of the enzyme from non-Michaelis-Menten to Michaelis-Menten at pH 11.7. Sensitivity to the allosteric modulator, UDP-N-acetylglucosamine decreased as the pH increased. A fifty percent loss of sensitivity to UDP-N-acetylglucosamine-induced activation occurred at pH 10.6. Thus, pretreatment at alkaline pH had irreversible effects on the properties of UDP-glucuronosyltransferase in microsomes. In order to establish the cause for the irreversibility of the changes induced by alkaline pH, microsomes were treated at pH 11.6 prior to purifying UDP-glucuronosyltransferase. Enzyme purified from alkali-treated and untreated microsomes had approximately the same specific activity. More importantly, responses to activation by lipids, and regeneration of allosteric properties were the same for both purified enzymes (from alkali-treated and control microsomes). Pure enzyme was not activated by pretreatment at alkaline pH. We interpret these data to mean that the irreversible effects of alkaline pH on the properties of UDP-glucuronosyltransferase in microsomes were not due to direct effects on the enzyme, but to how the enzyme interacted normally with molecules within the plane of the membrane.

Animals↗
PubMed1990

Dietary supplementation with oils rich in (n-3) and (n-6) fatty acids influences in vivo levels of epidermal lipoxygenase products in guinea pigs.

Certain dietary oils may have therapeutic potential in the treatment of inflammatory skin disorders. Presumably, the fatty acid constituents of these dietary oils exert their effects by altering the levels of cutaneous eicosanoids. Prompted by this possibility, we investigated whether supplementation of guinea pig diets with fish oil [rich in 20:5(n-3)] or borage oil [rich in 18:3(n-6)] could significantly alter epidermal levels of eicosanoids compared with control animals supplemented with olive oil. After feeding periods of 4, 8 or 12 wk, the epidermis from the animals was analyzed for: 1) fatty acid composition of individual epidermal phospholipids, 2) levels of lipoxygenase products, and 3) levels of cyclooxygenase products (prostaglandins). Our results demonstrated that the animals supplemented with dietary fish oil had elevated levels of 20:5(n-3) in epidermal phospholipids and elevated epidermal levels of 15-hydroxyeicosapentaenoic acid (15-HEPE) [the 15-lipoxygenase product of 20:5(n-3)] compared with guinea pigs fed olive oil or borage oil. Similarly, the animals supplemented with dietary borage oil had elevated levels of 20:3(n-6) [the epidermal elongase product of 18:3(n-6)] in epidermal phospholipids and elevated epidermal levels of 15-hydroxyeicosatrienoic acid [15-HETrE, the epidermal 15-lipoxygenase product of 20:3(n-6)] compared with guinea pigs fed olive oil or fish body oil. There were no significant changes in epidermal levels of prostaglandins. Both 15-HEPE and 15-HETrE have been identified as possible anti-inflammatory metabolites, and their elevated presence in the epidermis of animals fed oils rich in 20:5(n-3) or 18:3(n-6) may provide a mechanism for the beneficial effects of these oils on inflammatory conditions.

Analysis of Variance↗
PubMed1990

[Continuous hemodialysis with low blood flow and low dialysate flow in the treatment of acute renal insufficiency].

Slow continuous hemodialysis (SCHD) was performed in 9 patients with oliguric acute renal failure and cardiovascular instability. The vascular access was a Scribner's shunt in 7 patients and a double lumen venous catheter with a BSM22 blood system in 2 patients. Three different dialyzers were tested. The mean urea clearance was 10.8 +/- 1.5 ml/min with the 0.2 m2 polysulfone hollow fiber dialyzer, 14.3 +/- 2.7 ml/min with the 0.5 m2 AN 69 S parallel plate dialyzer and 13.8 +/- 1.8 ml/min with the 0.6 m2 AN 69 hollow fiber dialyzer. The mean dialysate flow rate was 15.6 +/- 1.9 ml/min, 15.2 +/- 0.7 ml/min and 15.1 +/- 1.6 ml/min for the three dialyzers, respectively. A linear relationship was documented for blood urea clearance and dialysate flow rate indicating clearly that low blood flow from 60 to 100 ml per min was appropriate for optimal diffusive transfer. The technic required continuous heparin anticoagulation. Three patients died of causes not related to the SCHD technic. When used in critically ill patients, SCHD is a simple method, suitable for intensive care unit staff with no trained dialysis nurses and allows an adequate control of uremia, fluid removal, acid base homeostasis and parenteral nutrition.

Acute Kidney Injury↗
PubMed1989

Platelet size affects both micro- and macro-aggregation: contributions of platelet number, volume fraction and cell surface.

The relationship between platelet size (v), platelet number (N0), platelet volume fraction (phi) and platelet aggregation was evaluated in human platelet subpopulations separated on the basis of volume using counterflow centrifugation. The original platelet population and three size-dependent platelet fractions were concentrated and resuspended in autologous citrated platelet-poor plasma at varying N0. Micro-aggregation (PA) and macro-aggregation (TA) were determined respectively by electronic particle counting and light transmission (turbidimetry). At similar N0, large platelets were about two-fold more sensitive and more rapidly recruited into both micro (PA) and macro (TA) aggregates in response to ADP than the small platelets (v were respectively 7.3 +/- 0.2 and 4.2 +/- 0.2 fl, each 16 +/- 4% of the total population). At volume fractions favouring the small platelets, however, the above differences persisted for PA, but not for TA. Similar size-dependent differences were observed for two other receptor-mediated platelet activators, namely a stable thromboxane A2 analogue (U46619) and platelet activating factor (PAF), but not for ristocetin-induced agglutination. Increasing platelet size appears to optimize platelet aggregation due to (i) the simple geometric advantage of large-sized platelets associated with any given N0, seen for both PA and TA, and (ii) intrinsic differences in size-dependent subpopulations which favour more efficient platelet membrane surface changes associated with receptor-mediated micro-aggregation (PA), for which a likely model is proposed.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1989

Montreal platelet syndrome: a defect in calcium-activated neutral proteinase (calpain).

Platelets from patients with Montreal platelet syndrome (MPS) consistently display a defect in the mechanisms that regulate platelet size during shape change and undergo spontaneous aggregation and stir-induced microaggregate formation. We now provide data that the surface glycoprotein composition of MPS platelets is indistinguishable from that of normal platelets. However, a defect in calcium-activated neutral proteinase (calpain) was detected in MPS platelets. The specific activity of calpain in the cytosolic fraction of platelets from four MPS patients was found to be only 30% of that in platelets from normal control donors (n = 18, P less than .001). Additionally, platelets from MPS patients (n = 3) contained only 50% (P less than .001) of the calpain I catalytic subunit antigen found in platelets from normal control donors (n = 9). Platelets from the asymptomatic father/grandfather of the MPS patients had normal amounts of both total calpain proteolytic activity and calpain I catalytic subunit antigen. This represents the first report of a defect in calpain in human cells. The abnormally low calpain activity in MPS platelets may account for the platelet defects characteristic of this disorder.

Blood Platelet Disorders↗
PubMed1989

Seizure in gradual clonazepam withdrawal.

Convulsions from abrupt clonazepam withdrawal in patients with a seizure history or concurrent neuroleptic use have been described in the literature. This is a report of a patient without these precipitating factors developing seizure despite "gradual" reduction of clonazepam by .5 mg every 4 days. The possibility of clonazepam withdrawal seizures should be kept in mind even in patients not considered at risk for developing seizures. Clonazepam cessation should be more gradual, even slower than .5 mg every 4 days.

Adult↗
PubMed1989

An evaluation of conventional cephalometric appraisals.

Although lateral cephalographic diagnosis is central to craniofacial skeletal assessment, their classification (categorization) remains largely empiric. In this study, pre- and post-treatment lateral cephalographic dimensional arrays were subjected to the classic numerical taxonomic technique of cluster analysis. The resultant patient groupings (clusters) were not only inconsistent with respect to their Angle malocclusion categories, but also the composition of each cluster group varies depending upon the dimensional arrays analyzed. These findings demonstrate that lateral cephalometric categorization remains largely subjective.

Adolescent↗