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Biomedical subjects

S Leong

Publications and source records attributed to S Leong.

At least 37 records · Page 2Linked to original sources
PubMed1993

Regulation of the response to bacterial lipopolysaccharide by endogenous and exogenous lipopolysaccharide binding proteins.

Bactericidal/permeability-increasing protein (BPI) is a natural constituent of human neutrophils. Recombinant BPI has been shown to bind to bacterial lipopolysaccharide (LPS), and to neutralize the ability of LPS to stimulate inflammatory cells in vitro and in vivo. BPI shares sequence homology and immunocrossreactivity with another endogenous LPS binding protein, lipopolysaccharide binding protein (LBP). Despite the homology, these proteins have opposite effects on LPS. LBP mediates cell activation by low, otherwise nonstimulatory concentrations, while BPI neutralizes LPS bioactivity. Exogenous LPS binding proteins in the form of monoclonal antibodies have been developed with the goal of generating antiendotoxin therapeutics to treat gram-negative sepsis and related syndromes. Here we show that LPS-binding and neutralizing properties of BPI compare favorably with two monoclonal antibodies tested, HA-1A and XMMEN-OE5. BPI also competes effectively with LBP for LPS. Thus, BPI may represent an endogenous LPS-regulatory molecule suitable for use as a potent antiendotoxin therapeutic.

Animals↗
PubMed1992

Bv: a distinct category of B sub-group among Chinese blood donors in Hong Kong.

During the period 1984-1989, a total of 46 examples of Bv phenotype were encountered out of a total of 567,210 donors, giving an incidence of 1 in 12,330 among the Chinese in Hong Kong. The Bv determinant corresponds to the portion of the B antigen that is present on rabbit red cells, and gives a negative reaction with polyclonal anti-B reagents absorbed with rabbit red cells that still react with B3. Some potent monoclonal anti-B reagents confirm the absence of a B epitope from Bv red cells even by adsorption and elution techniques. The failure of some monoclonal anti-B reagents to detect Bv demonstrates the need to select or blend monoclonal anti-B reagents for use in typing Oriental bloods. Cell-conversion techniques failed to convert O cells to B cells using Bv serum with the appropriate substrate, whereas sera from most of the other B variants were capable of doing so. The Bv phenotype, therefore, represents a distinct category of B subgroups that is easily distinguishable from B3 and other B variants.

ABO Blood-Group System↗
PubMed1992

A study of hepatitis C virus antibodies and serum alanine amino transferase in blood donors in Hong Kong Chinese.

The reference range of serum alanine amino transferase (ALT) for the local population was established by testing 5,000 random voluntary Chinese blood donors of various age groups of both sexes. In addition, 1,769 serum samples with elevated ALT levels were also collected for anti-HCV assays using both the Abbott and Ortho anti-hepatitis C virus (HCV) assay kits. The relationship between serum ALT and anti-HCV tests was studied and the performances of both kits used were compared. It was found that while the prevalence of serum anti-HCV was 0.4% among hepatitis B surface antigen-negative donors with normal ALT, subjects with ALT between 2 and 3 standard deviations (SD) and greater than 3 SD above the mean level had respective prevalence of anti-HCV 3 and 9.5 times that of the normal ALT subjects. Both anti-HCV kits were found to identify in majority the same positive population among the different groups of subjects studied. In addition, it was observed that for subjects who were anti-HCV-positive, the higher the serum ALT level, the higher the mean anti-HCV ELISA ratio and this observation was similar for both anti-HCV kits used. We conclude that: (1) there is a direct relationship between serum ALT level and anti-HCV positivity by EIA; (2) there is a direct correlation between serum ALT level and anti-HCV ELISA ratio, and (3) both Abbott and Ortho anti-HCV kits perform similarly in the identification of positive serum samples.

Adult↗
PubMed1992

Pseudomelanosis duodeni and the controversial pigment--a clinical study of 4 cases.

Despite the common practice of upper gastrointestinal endoscopy, the unique phenomenon of punctate black pigmentation of the duodenal mucosa, now known as pseudomelanosis duodeni, still remains a rare entity. Four patients with normal renal function at presentation were found to have this pigment on endoscopy. One developed renal failure subsequently but the pigmentation persisted and this observation has not been reported before. Histochemical and ultrastructural studies were made. It is postulated that the pigment is heterogenous and represents a form of stored iron. Anti-hypertensive drugs may have a role in the causation of the pigmentation formation.

Aged↗
PubMed1992

Evoked response study among Malaysian multiple sclerosis patients.

A study of visual evoked potential (VEP), brainstem evoked potential (BAEP) and median nerve somatosensory evoked potential (SSEP) in 26 Malaysian patients with clinically definite Multiple Sclerosis (MS). This study showed an overall high rate of abnormality, with 85% of patients for VEP, 31% for BAEP and 65% for median nerve SSEP. The rate of abnormality was particularly high for patients who were symptomatic, reaching 100% of patients for VEP, 50% of patients in BAEP, 83% of nerves for median nerve SSEP. The rate of abnormality among those who were asymptomatic was lower, varying from 32% of eyes in VEP, 27% of patients in BAEP and 31% of nerves in median nerve SSEP. Three out of 10 patients with optic spinal form of MS have abnormal BAEP. These show the usefulness of the evoked potential studies in confirming the clinical lesions as well as demonstrating subclinical involvement. The rate of abnormal evoked responses for the asymptomatic patients in this study is generally lower than that published elsewhere.

Adult↗
PubMed1991

The MiIII phenotype among Chinese donors in Hong Kong: immunochemical and serological studies.

The incidence of the MiIII phenotype among Chinese blood donors in Hong Kong was found to be 6.28%. Eleven individuals apparently homozygous for the MiIII gene were detected by immunoblotting with monoclonal antibodies R1.3 and R18. R1.3 detects an identical epitope on both glycophorins A and B and R18 detects a different epitope on glycophorin A. Immunoblotting with R1.3 showed an absence of bands corresponding to normal glycophorin B. Immunoblotting with R18 showed an absence of a 58 K band, which corresponds to a heterodimer of normal glycophorin B complexing with the MiIII component, found in MiIII heterozygotes. In two families with apparent MiIII homozygous individuals, both parents of the propositi had the MiIII phenotype which implies normal autosomal inheritance of the MiIII gene. In another family, only one parent had the MiIII phenotype and the presence of an Su gene is postulated to explain the immunochemical and serological findings.

Animals↗
PubMed1991

Complications associated with needle localization biopsy of the breast.

A review of 144 consecutive needle localization biopsies of the breast (NLBB) was performed to assess complications associated with this procedure. Thirty-four complications occurred in 27 patients. There were 11 wound infections associated with NLBB. During this time period, there were 1,583 clean general surgical operations performed, other than biopsy of the breast, yielding an over-all wound infection rate of 1.2 per cent (p less than 0.001). A trend was noted, suggesting that use of drains may have contributed to wound infection versus no drainage (25 versus 5 per cent, respectively). Electrocautery burns requiring local wound care occurred during seven biopsies and four of these patients subsequently had a wound infection develop. Four lesions required more than one excision to remove the abnormal mammary tissue, and in four, there was a failure to remove the lesion at the first operation. Fifty-three localization procedures were performed using methylene blue. In this group, only one patient required more than one biopsy to remove the abnormal mammary tissue, and there were no failures with this technique. Also, a smaller mean volume of tissue was removed in this group versus the standard NLBB (30.2 +/- 3.0 versus 53.3 +/- 4.6 cubic millimeters, respectively) (p less than 0.01). Four cardiovascular complications occurred, requiring overnight admission. All of these patients were more than 65 years old and had the procedure performed while under general anesthesia. Patient age, type of anesthesia, resident versus attending surgeon and length of procedure had no independent effect on local complication rate.

Aged↗
PubMed1990

Highly virulent strains of Pseudomonas solanacearum that are defective in extracellular-polysaccharide production.

Extracellular polysaccharide (EPS) has long been regarded as one of the most important factors involved in wilting of plants by Pseudomonas solanacearum. By means of transposon Tn5 mutagenesis, we have isolated a class of mutants that have an afluidal colony morphology but retain the ability to cause severe wilting and death of tobacco plants. One such mutant, KD700, was studied in detail. By marker exchange mutagenesis, the altered colony morphology was shown to be the result of a single Tn5 insertion in a 14.3-kilobase EcoRI fragment. This defect could be corrected by introducing a homologous clone from a cosmid library of the wild-type, parental strain K60. The Tn5-containing fragment was introduced into other P. solanacearum wild-type strains by marker exchange, and these altered strains had the same afluidal phenotype as KD700. N-Acetylgalactosamine (GalNac), the major constituent of EPS of all wild-type strains of P. solanacearum, was not detected by gas chromatography-mass spectrometry analysis of vascular fluids from wilting plants infected by KD700. In contrast, GalNac was readily detected in similar fluids of plants infected by K60. Polysaccharides extracted from culture filtrates of KD700 contained approximately one-fifth of the GalNac present in polysaccharides from K60. No differences in growth rates in culture or in planta between the mutant and the parental strains were observed. Since strains that are deficient in EPS production can remain highly virulent to tobacco, we conclude that EPS, or at least its GalNac-containing component, may not be required for disease development by P. solanacearum.

Carbohydrates↗
PubMed1989

Detection of supercoiled hepatitis B virus DNA and related forms by means of molecular hybridization to an oligonucleotide probe.

A novel assay for supercoiled and other fully double-stranded forms of hepatitis B virus (HBV) DNA in blood is presented that utilizes molecular hybridisation to a radiophosphorous-labeled oligonucleotide probe. The probe [5'-d(ACGTGCAGAGGTGAAGCGA)] is complementary to the S(+)-strand sequence furthest downstream, at the end of the gap. We examined blood specimens from 137 healthy HBsAg-positive individuals, applying the probe to dots representing 2-3.5 ml serum or plasma. We found that supercoiled HBV is present in many HBV DNA-positive blood specimens albeit in small quantities. Of the 104 specimens that were positive for HBV DNA of any form, 53 annealed to the probe. Serial specimens from the same subject taken over a period of months showed that the proportion of supercoil to other HBV DNA forms was variable. The presence of supercoil HBV DNA was not closely correlated with the level of serum HBV DNA polymerase. The supercoil is an HBV DNA form that can persist in the liver in the presence or absence of other replicative intermediates. This assay may enable further characterization of the status of HBV infection.

Base Sequence↗
PubMed1989

Cloning and expression of the cDNA for the murine interferon gamma receptor.

A murine interferon gamma (IFN-gamma) receptor cDNA was isolated by screening a murine T-cell hybridoma library prepared in lambda gt10 with probes prepared from a human IFN-gamma receptor cDNA. The 2.1-kilobase (kb) cDNA encoded a serine-rich polypeptide of 477 amino acids that was 52% identical to the human protein. Southern and Northern (RNA) blot analyses indicated the presence of a single receptor gene and a single predominant 2.3-kb receptor transcript. Human embryonic kidney fibroblasts, stably transfected with the murine IFN-gamma receptor cDNA, expressed murine IFN-gamma receptors as detected by flow cytometry with either ligand or a receptor-specific monoclonal antibody. Nontransfected cells bound neither ligand nor antibody. Radioligand-binding analysis demonstrated that the transfectants expressed 530,000 murine IFN-gamma receptors per cell and bound murine IFN-gamma with a Ka of 1 x 10(9) M-1. However, despite high-level expression of murine IFN-gamma receptors, the transfected human cells responded only to human and not to murine IFN-gamma as detected by enhancement of major histocompatibility class I antigen expression and induction of antiviral activity. These results thus document the isolation and expression of a full-length murine IFN-gamma receptor cDNA and suggest that additional species-specific components may be necessary to form a biologically active IFN-gamma receptor.

Amino Acid Sequence↗
PubMed1988

Influence of preovulatory estradiol concentration on diurnal and pulsatile prolactin secretion patterns.

We evaluated the effect of preovulatory concentrations of estradiol on the 24-hour profile of prolactin secretion in women with regular menstrual cycles. An estradiol preparation was chosen to allow comparison with physiologic events. Estradiol benzoate, 1 mg intramuscularly, was administered for 7 days to achieve estradiol concentrations just above preovulatory levels (424 +/- 54 pg/ml); 24-hour mean prolactin concentrations increased threefold (14.0 +/- 2.1 to 40.6 +/- 7.1 ng/ml). Prolactin pulse frequency increased significantly (p less than 0.001) during waking hours after estradiol benzoate administration. The diurnal pattern of prolactin secretion was maintained with estradiol benzoate, although the sleep acrophase often reached high concentrations (86 +/- 11 ng/ml). These results suggest in women with regular menstrual cycles: (1) that estrogen administration that achieves slightly greater than preovulatory estradiol concentrations can stimulate prolactin release, (2) that estradiol may elevate prolactin by increasing its pulsatile secretion, (3) that estradiol does not alter the diurnal pattern of prolactin secretion, (4) that estradiol concentrations just above preovulatory levels can be associated with markedly elevated prolactin concentrations.

Adult↗
PubMed1988

Molecular cloning of genes that specify virulence in Pseudomonas solanacearum.

The suicide plasmid pSUP2021 was used to introduce Tn5 into the Pseudomonas solanacearum wild-type strain K60. We isolated eight avirulent mutants after screening 6,000 kanamycin-resistant transconjugants by inoculating eggplant (Solanum melongena L. cv. Black Beauty) and tobacco (Nicotiana tabacum L. cv. Bottom Special) seedlings. The Tn5-containing EcoRI fragments from the eight mutants were unique, suggesting that numerous genes specify virulence in this species. These EcoRI fragments were cloned into pBR322 or pUC12, and one of the clones, pKD810, was transformed into K60. All of the kanamycin-resistant, ampicillin-sensitive transformants were avirulent. Three randomly selected avirulent transformants were shown to carry the Tn5-containing fragment in place of the wild-type fragment and to exhibit the same hybridization pattern as the original KD810 mutant did. With pKD810 as a probe, we identified cosmids carrying the wild-type virulence genes by using a genomic library of K60 prepared in pLAFR3. Two of the homologous cosmids, pL810A and pL810C, when introduced into KD810 by transformation, restored virulence and normal growth of this mutant in tobacco. Altogether, these data indicate that the gene(s) interrupted by Tn5 insertion in KD810 is essential for the virulence of P. solanacearum. Further characterization of this gene is now being completed by subcloning, transposon mutagenesis, and complementation analysis.

Cloning, Molecular↗
PubMed1987

Fatal pancreatitis presenting with subcutaneous fat necrosis. Evidence that lipase and amylase alone do not induce lipocyte necrosis.

We report a case of fatal pancreatitis heralded by the presence of cutaneous panniculitis without abdominal pain or other stigmata of the disease. Although cutaneous fat necrosis has been associated with pancreatitis, it is unusual as the presenting complaint of this relatively common disease. In vitro evidence suggests that human pancreatic amylase or lipase alone is not responsible for the observed panniculitis.

Acute Disease↗