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Biomedical subjects

P P Wong

Publications and source records attributed to P P Wong.

At least 19 recordsLinked to original sources
PubMed2001

Heavy metal concentrations in marine fishes collected from fish culture sites in Hong Kong.

The levels of six heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) in different tissues of three species of cultured marine fishes (Epinephelus areolatus, Lutjanus russelli, and Sparus sarba) collected from three fish culture sites in Hong Kong were evaluated. Metal pollution problems in the fish culture sites were serious, as reflected by the high metal concentrations recorded in sea water, sediments, and the biomonitor Perna viridis. In general, tissues of all three species contained high concentrations of Zn and Cu, but much lower concentrations of Ni, Pb, Cd, and Cr. Similar pattern of heavy metal concentrations was observed in sea water, sediment, and P. viridis. Metal concentrations in various tissues varied greatly among species and among fish culture sites. Different tissues showed different capacity for accumulating heavy metals. Gonad of all three species contained high concentrations of Zn. On the other hand, liver seemed to be the primary organ for Cu accumulation. Overall, metal concentrations in the tissues of culture marine fishes were much lower than those in P. viridis. Despite high metal levels in sea water and sediments, concentrations of Cd, Cr, and Pb in edible tissues, including muscle and skin, did not exceed permissible levels recommended by the Hong Kong Government for human consumption.

Animals↗
PubMed2001

Mathematical models of cognitive recovery.

Longitudinal psychological test results are used as dependent variables to explore the complex relationship between length of coma, time of testing on the recovery curve, and corresponding cognitive status after traumatic brain injury (TBI). A database containing 319 TBI patients with a broad spectrum of coma duration was used. Statistical analysis of mixed effects modelling was applied to longitudinal WAIS-R (Wechsler Adult Intelligence Scale-Revised) scores to construct two mathematical models (verbal IQ and performance IQ). The models predict the course of recovery (initial cognitive level post-coma, eventual recovery level, and level of cognitive functioning at any point on the recovery curve) when the duration of coma is known. Performance IQ was found to recover at a rate that is almost four times slower than verbal IQ. The results have important clinical rehabilitation implications. This statistical modelling technique also enables the medical researcher to investigate disease progression or recovery using structured assessments, which would normally be part of the routine medical monitoring.

Adult↗
PubMed1997

SNAP-23 is located in the basolateral plasma membrane of rat pancreatic acinar cells.

The SNARE hypothesis proposes that specificity of exocytosis is regulated by the appropriate interactions between the vesicle (v-) SNARE and the target membrane (t-) SNAREs. We show here that pancreatic acinar cells express the SNAP-25 t-SNARE homolog SNAP-23, and find that this t-SNARE is most highly concentrated on the basolateral plasma membrane while being expressed below detectable levels in endocrine islets within the same tissue. This is the first localization of SNAP-23 within a polarized tissue and suggests that this t-SNAREs may interact with syntaxin-4 to mediate basolateral secretion.

3T3 Cells↗
PubMed1997

Tissue distribution of SNAP-23 and its subcellular localization in 3T3-L1 cells.

The SNARE hypothesis of vesicular traffic proposes that three proteins, VAMP/synaptobrevin, syntaxin, and SNAP-25, constitute a complex that docks the vesicle at the target membrane. VAMP and syntaxin isoforms have been identified outside the nervous system, and a cDNA to a SNAP-25 related protein, SNAP-23, was recently identified in human lymphocytes. Here we report the generation of isoform-specific antibodies to SNAP-23 cloned from human melanoma cells, and their use in detecting the expression and localization of the endogenous SNAP-23 protein in several tissues and cell lines. SNAP-23 was readily detected in liver, lung, kidney, and spleen, to a lesser extent in muscle and heart, and was almost undetectable in brain. The protein was also abundant in fibroblast, muscle, and fat cell lines, but relatively less enriched in neuroendocrine PC12 cells. SNAP-23 abundance did not change during differentiation of 3T3-L1 fibroblasts into adipocytes. In both, SNAP-23 was membrane-bound and below detectable levels in the cytosolic fraction. Subcellular fractionation of 3T3-L1 adipocytes revealed that the majority of the protein was associated with plasma membranes. These findings support the conclusion that a tripartite SNARE complex exists outside of the nervous system, and suggest that SNAP-23 may play a role in vesicle traffic in most cell types.

3T3 Cells↗
PubMed1997

How well does epidemiological evidence hold for the relationship between smoking and adverse obstetric outcomes in New South Wales?

This study examines whether the established epidemiological relationship between cigarette-smoking exposure in pregnancy and adverse obstetric outcomes are confirmed in Australian data from the NSW Midwives Data Collection (MDC). These data were analysed to compare the obstetric complications and pregnancy outcomes between smoking and nonsmoking women confined in 1994. Results showed that smoking mothers had higher rates of antepartum haemorrhage due to placental abruption and placenta praevia. They were also at higher risk of giving birth to low birth-weight babies and preterm delivery. Infants born to smoking mothers were 17% more likely to be admitted to hospital special care nurseries or neonatal intensive care units. Moreover, the risk of reported perinatal death among babies of smoking mothers was 20% higher than babies of nonsmoking mothers. However, smoking during pregnancy was found to confer a protective effect against the development of pregnancy-induced hypertension. These results were compared with existing evidence from the literature. Published research reports on the corresponding smoking effects were identified to assess the consistency of evidence and typical risk ratios. Findings from the literature search showed a near-perfect concordance with the associations in the NSW MDC data. The paper documents the likely complications which might be prevented if smoking in pregnancy were eliminated. There remains a real need for effective programmes to reduce smoking prevalence in pregnancy.

Apgar Score↗
PubMed1996

Exercise increases the plasma membrane content of the Na+ -K+ pump and its mRNA in rat skeletal muscles.

Muscle fibers adapt to ionic challenges of exercise by increasing the plasma membrane Na+-K+ pump activity. Chronic exercise training has been shown to increase the total amount of Na+-K+ pumps present in skeletal muscle. However, the mechanism of adaptation of the Na+-K+ pump to an acute bout of exercise has not been determined, and it is not known whether it involves alterations in the content of plasma membrane pump subunits. Here we examine the effect of 1 h of treadmill running (20 m/min, 10% grade) on the subcellular distribution and expression of Na+-K+ pump subunits in rat skeletal muscles. Red type I and IIa (red-I/IIa) and white type IIa and IIb (white-IIa/IIb) hindlimb muscles from resting and exercised female Sprague-Dawley rats were removed for subcellular fractionation. By homogenization and gradient centrifugation, crude membranes and purified plasma membranes were isolated and subjected to gel electrophoresis and immunoblotting by using pump subunit-specific antibodies. Furthermore, mRNA was isolated from specific red type I (red-I) and white type IIb (white-IIb) muscles and subjected to Northern blotting by using subunit-specific probes. In both red-I/IIa and white-IIa/IIb muscles, exercise significantly raised the plasma membrane content of the alpha1-subunit of the pump by 64 +/- 24 and 55 +/- 22%, respectively (P < 0.05), and elevated the alpha2-polypeptide by 43 +/- 22 and 94 +/- 39%, respectively (P < 0.05). No significant effect of exercise could be detected on the amount of these subunits in an internal membrane fraction or in total membranes. In addition, exercise significantly increased the alpha1-subunit mRNA in red-I muscle (by 50 +/- 7%; P < 0.05) and the beta2-subunit mRNA in white-IIb muscles (by 64 +/- 19%; P < 0.01), but the alpha2- and beta1-mRNA levels were unaffected in this time period. We conclude that increased presence of alpha1- and alpha2-polypeptides at the plasma membrane and subsequent elevation of the alpha1- and beta2-subunit mRNAs may be mechanisms by which acute exercise regulates the Na+-K+ pump of skeletal muscle.

Animals↗
PubMed1994

Clover development during spaceflight: a model system.

The development of legume root nodules was studied as a model system for the examination of gravitational effects on plant root development. In order to examine whether rhizobial association with clover roots can be achieved in microgravity, experiments were performed aboard the KC-135 parabolic aircraft and aboard the sounding rocket mission Consort 3. Binding of rhizobia to roots and the initial stages of root nodule development successfully occurred in microgravity. Seedling germination experiments were performed in the sliding block device, the Materials Dispersion Apparatus, aboard STS-37. When significant hydration of the seeds was achieved, normal rates of germination and seedling development were observed.

Cell Differentiation↗
PubMed1992

Antipeptide antibodies that can distinguish specific subunit polypeptides of glutamine synthetase from bean (Phaseolus vulgaris L.).

The amino acid sequences of the beta and gamma subunit polypeptides of glutamine synthetase from bean (Phaseolus vulgaris L.) root nodules are very similar. However, there are small regions within the sequences that are significantly different between the two polypeptides. The sequences between amino acids 2 and 9 and between 264 and 274 are examples. Three peptides (gamma 2-9, gamma 264-274, and beta 264-274) corresponding to these sequences were synthesized. Antibodies against these peptides were raised in rabbits and purified with corresponding peptide-Sepharose affinity chromatography. Western blot analysis of polyacrylamide gel electrophoresis of bean nodule proteins demonstrated that the anti-beta 264-274 antibodies reacted specifically with the beta polypeptide and the anti-gamma 264-274 and anti-gamma 2-9 antibodies reacted specifically with the gamma polypeptide of the native and denatured glutamine synthetase. These results showed the feasibility of using synthetic peptides in developing antibodies that are capable of distinguishing proteins with similar primary structures.

Amino Acid Sequence↗
PubMed1991

Late consolidative radiation therapy in the treatment of limited-stage small cell lung cancer.

Two hundred twenty-three patients were enrolled on this randomized Phase III trial testing the value of late consolidative involved-field radiation therapy in the treatment of limited-stage small cell lung cancer (SCLC). Patients were treated with induction chemotherapy consisting of alternating cycles of procarbazine, vincristine, lomustine, and cyclophosphamide (POCC) and etoposide, doxorubicin, and methotrexate (VAM) for 6 to 9 months. Responding patients were then randomized at 6 or 9 months to chemotherapy alone or to involved-field radiation therapy. All partial and complete responders received prophylactic cranial irradiation. Of the 180 eligible and evaluable patients, 80 (44%) achieved a complete response and 39 (22%) achieved a partial response (overall rate of response, 66%). Actuarial median survival time was 11.6 months, with 16% of patients surviving 2 years and 11% surviving 5 years. Forty-eight patients were randomized to chemotherapy alone (24 patients) versus chemotherapy plus involved-field radiation therapy (24 patients). There were no significant differences in time to progression or survival between those patients receiving or not receiving involved-field radiation therapy. The thorax was the site of first relapse in 58% of patients randomized to chemotherapy alone versus 29% in patients randomized to chemotherapy plus involved-field radiation therapy (P equals 0.042). The major acute toxicity was reversible myelosuppression, and the major late toxicity was chronic central nervous system dysfunction. The authors conclude that the addition of late consolidative radiation therapy to induction chemotherapy in the treatment of limited-stage SCLC is well tolerated and improves local control, but does not improve time to progression or rates of survival.

Adult↗
PubMed1991

Immunocytochemical Localization of Glutamine Synthetase in Organs of Phaseolus vulgaris L.

Glutamine synthetase was localized in nodules, roots, stems, and leaves of red kidney bean (Phaseolus vulgaris L.) by immunocytochemistry. Affinity purified antibodies reactive with glutamine synthetase were prepared using purified nodule-enhanced glutamine synthetase. Immunogold labeling was observed in the cell cytoplasm in each plant organ. In nodules, the labeling was more intense in the infected cells than in the uninfected cells. No labeling was observed in nodule bacteroids, peribacteroid spaces, or in peribacteroid membranes, while previous reports of glutamine synthetase immunolabeling of legume nodules showed labeling in the bacteroid fraction. Significant labeling was observed in nodule proplastids which contained starch granules. Substantial labeling was also observed in leaf chloroplasts. No labeling was observed in other organelles including mitochondria, peroxisomes, and endoplasmic reticulum. Preimmune IgGs did not bind to any structure in the tissues examined.

Journal Article↗
PubMed1990

Binding of isolated plant lectin by rhizobia during episodes of reduced gravity obtained by parabolic flight.

Development of a legume root nodule is a complex process culminating in a plant/bacterial symbiosis possessing the capacity for biological dinitrogen fixation. Formation of root nodules is initiated by the binding and stabilization of rhizobia to plant root hairs, mediated in part by a receptor/ligand recognition system composed of lectins on the plant root surface and lectin-binding sites on the rhizobial cell surface. The dinitrogen fixation activity of these root nodules may be an important feature of enclosed, space-based life support systems, and may provide an ecological method to recycle nitrogen for amino acid production. However, the effects on nodule development of varied gravitational fields, or of root nutrient delivery hardware, remain unknown. We have investigated the effects of microgravity on root nodule formation, with preliminary experiments focused upon the receptor/ligand component. Microgravity, obtained during parabolic flight aboard NASA 930, has no apparent effect on the binding of purified lectin to rhizobia, a result that will facilitate forthcoming experiments using intact root tissues.

Fabaceae↗
PubMed1989

Subunit Composition of Glutamine Synthetase Isozymes from Root Nodules of Bean (Phaseolus vulgaris L.).

Glutamine synthetase from bean nodules can be separated into two isoforms, GS(n1) and GS(n2). A purification protocol has been developed. It included protamine sulfate precipitation, ammonium sulfate fractionation, anthranilate-affinity chromatography, Dye-Matrex (Orange A) chromatography, and diethylaminoethyl-cellulose ion-exchange chromatography. GS(n1) and GS(n2) have been purified to homogeneity. Subunit structure analysis using two-dimensional polyacrylamide gel electrophoresis revealed that GS(n1) was composed of two different types of subunit polypeptides. They differed in isoelectric points (6.0 and 6.3) but had the same molecular weights (46,000 Daltons). GS(n2) was composed of only one type of subunit polypeptide. It had an isoelectric point of 6.0 and a molecular weight of 46,000 Daltons. It was apparently identical to one of the polypeptides found in GS(n1). Glutamine synthetase holoenzyme consisted of eight subunits. In the nodule there are two different types of glutamine synthetase subunit polypeptides. Random combinations of the polypeptides should generate nine different isozymes. Our electrophoretic analysis revealed that GS(n2) was but one of the isozymes, and GS(n1) was a composite of the other eight. Hence, nodule glutamine synthetase isozymes were homo-octameric as well as hetero-octameric.

Journal Article↗
PubMed1987

Gabaculine Inhibition of Chlorophyll Biosynthesis and Nodulation in Phaseolus lunatus L.

Gabaculine (3-amino-2,3-dihydrobenzoic acid) was an inhibitor of in vivo chlorophyll biosynthesis in lima bean (Phaseolus lunatus L. cv Henderson). When applied to roots of 9-day-old plants, 10 micromolar gabaculine was sufficient to terminate biosynthesis of new chlorophyll. The trifoliolate leaves which emerged after gabaculine treatment were yellow. Gabaculine-treated plants had slightly lower dry weights; yet, overall plant size showed very little change. Chlorophyll fluorescence induction kinetics and CO(2) exchange measurements were used to monitor both immediate and long-term effects of gabaculine on photosynthesis. A lowered rate of the decline from the maximum level of fluorescence was observed after 10 hours for nitrate-supplemented plants, and all treated plants showed a slightly increased level of original fluorescence after 6 days. No change was observed in the rate of photosynthesis by unifoliolate leaves. The trifoliolate leaves, though not able to photosynthesize, were able to continue respiration. This suggested that heme biosynthesis for mitochondrial cytochromes was not abolished. In untreated lima bean, root nodules were induced by Rhizobium sp. 127E15. Following gabaculine treatment, root nodules formed, but were largely ineffective in nitrogen fixation. Nodule dry weight, nitrogen fixation activity, and leghemoglobin content were decreased by gabaculine.

Journal Article↗
PubMed1986

Isozymes of Glutamine Synthetase in Phaseolus vulgaris L. and Phaseolus lunatus L. Root Nodules.

The glutamine synthetase (GS) isozymes in the plant fraction of nodule extracts from 62 cultivars of Phaseolus vulgaris L. and one cultivar of Phaseolus lunatus L. were analyzed by polyacrylamide gel electrophoresis. All P. vulgaris nodule extracts displayed two GS activity bands: a nodule-specific band (GS(n1)) and a band (GS(n2)) similar to the single band (GS(r)) present in root extracts. In nodule extracts of P. lunatus, the GS(n1) band was detected, but the GS(n2) band was barely detectable. In contrast to P. vulgaris, the GS(n2) band and the GS(r) band of P. lunatus appeared to be different. The electrophoretic mobility of the GS(n1) band in P. vulgaris was governed by both the plant cultivar and the development stage of the nodule. In nodule extracts of P. vulgaris and P. lunatus, the zone of GS(n1) activity coincided with six to nine distinct protein bands as revealed after treatment of gels, which had previously been stained for GS activity, with Coomassie blue. All these protein bands were shown to consist of polypeptides of identical molecular weight (approximately 47,000 daltons) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Our results indicate that P. vulgaris continuously generates isozymes of GS(n1) of increasing electrophoretic mobility during the course of nodule development.

Journal Article↗
PubMed1982

Recognition of leguminous hosts by a promiscuous Rhizobium strain.

The lima bean (Phaseolus lunatus L.) and the pole bean (Phaseolus vulgaris L.) are nodulated by rhizobia of two different cross-inoculation groups. Rhizobium sp. 127E15, a cowpea-type Rhizobium, can induce effective nodules on the lima bean and partially effective nodules on the pole bean. Rhizobium phaseoli 127K14 can induce effective nodules on the pole bean but does not reciprocally nodulate the lima bean. Root hairs of the lima bean when inoculated with Rhizobium sp. 127E15 showed tip curling and swelling and infection thread formation as observed by light microscopy and scanning electron microscopy. When lima bean root hairs were inoculated with R. phaseoli 127K14, no host-specific responses were observed. Pole bean root hairs that had been inoculated with R. phaseoli 127K14 or Rhizobium sp. 127E15 also showed tip curling and swelling and infection thread formation. Colonization of lima bean root hairs by Rhizobium sp. 127E15 and pole bean root hairs by R. phaseoli 127K14 or Rhizobium sp. 127E15 appeared to involve the elaboration of microfibrils. This study showed that when Rhizobium sp. 127E15 nodulates a host of a different cross-inoculation group, it elicits the same specific host responses as it does from a host of the same cross-inoculation group.

Journal Article↗
PubMed1982

Nodulation of Pole Bean (Phaseolus vulgaris L.) by Rhizobium Species of Two Cross-Inoculation Groups.

Physiology and morphology of pole bean (Phaseolus vulgaris L. cv Kentucky Wonder) root nodules induced by two Rhizobium species of different cross-inoculation groups have been compared. Root nodules induced by Rhizobium sp. 127E15, which is a strain of the cowpea group Rhizobium, were pinkish, had irregular shapes, and were only partially effective. Their peak acetylene reduction activity was 4.36 mumol of C(2)H(4) formed per g of fresh nodules per h at 30 days after inoculation. The effective nodules induced by Rhizobium phaseoli 127K14, which is a strain of the bean group Rhizobium, were dark red, spherical, and showed peak acetylene reduction activity of 15.95 mumol of C(2)H(4) formed per g of fresh nodules per h at 15 days after inoculation. The partial effectiveness of 127E15-induced nodules was associated with fewer infected cells, a delay in the increase of bacteroid population within the host cells, abundance of cytoplasmic vesicles in the host cells, more bacteroids within a membrane envelope (peribacteroid membrane), and the inability of bacteroids to completely fill up the host cytoplasmic space. The 127K14-induced nodules were fully mature, with host cells filled with bacteroids by 12 days after inoculation. In contrast, the 127E15-induced nodules did not reach a similar developmental stage even 30 days after inoculation.

Journal Article↗