Biomedical subjects

C K Ho

Publications and source records attributed to C K Ho.

At least 55 records · Page 3Linked to original sources

PubMed2000

A yeast-based genetic system for functional analysis of viral mRNA capping enzymes.

Virus-encoded mRNA capping enzymes are attractive targets for antiviral therapy, but functional studies have been limited by the lack of genetically tractable in vivo systems that focus exclusively on the RNA-processing activities of the viral proteins. Here we have developed such a system by engineering a viral capping enzyme-vaccinia virus D1(1-545)p, an RNA triphosphatase and RNA guanylyltransferase-to function in the budding yeast Saccharomyces cerevisiae in lieu of the endogenous fungal triphosphatase (Cet1p) and guanylyltransferase (Ceg1p). This was accomplished by fusion of D1(1-545)p to the C-terminal guanylyltransferase domain of mammalian capping enzyme, Mce1(211-597)p, which serves as a vehicle to target the viral capping enzyme to the RNA polymerase II elongation complex. An inactivating mutation (K294A) of the mammalian guanylyltransferase active site in the fusion protein had no impact on genetic complementation of cet1Deltaceg1Delta cells, thus proving that (i) the viral guanylyltransferase was active in vivo and (ii) the mammalian domain can serve purely as a chaperone to direct other proteins to the transcription complex. Alanine scanning had identified five amino acids of vaccinia virus capping enzyme-Glu37, Glu39, Arg77, Glu192, and Glu194-that are essential for gamma phosphate cleavage in vitro. Here we show that the introduction of mutation E37A, R77A, or E192A into the fusion protein abrogates RNA triphosphatase function in vivo. The essential residues are located within three motifs that define a family of viral and fungal metal-dependent phosphohydrolases with a distinctive capacity to hydrolyze nucleoside triphosphates to nucleoside diphosphates in the presence of manganese or cobalt. The acidic residues Glu37, Glu39, and Glu192 likely comprise the metal-binding site of vaccinia virus triphosphatase, insofar as their replacement by glutamine abolishes the RNA triphosphatase and ATPase activities.

Acid Anhydride Hydrolases↗

PubMed2000

An unusual case of organophosphate intoxication of a worker in a plastic bottle recycling plant: an important reminder.

A young man was sent to our emergency unit because he had suffered from vomiting and cold sweating for 2 days. At the time he was admitted, he had no acute abdominal pains or gastrointestinal symptoms, and a physical examination revealed nothing but a faster heart rate and moist, flushing skin. The patient had worked for 6 years at a plastic bottle-recycling factory, but none of his co-workers had the same symptoms. Nevertheless, because the plant also recycled pesticide bottles, we suspected organophosphate pesticide intoxication. The patient's plasma acetylcholinesterase level was checked, revealing 1498.6 microU/L (normal range: 2,000-5, 000) on the first day and 1,379 microU/L on the second day. Upon questioning, the patient recalled that one of his shoe soles had been damaged and that his foot had been wet from walking all day in rain collected on the factory floor on the day that his symptoms first occurred. We conducted a study in the change of preshift and postshift acetylcholinesterase levels among six of his co-workers on a rainy day. We used the Wilcoxon signed rank test to compare the preshift and postshift plasma acetylcholinesterase levels; no significant difference was revealed (p = 0.600), leaving contamination via the damaged shoe sole suspect. We reviewed the literature on organophosphate intoxication; pesticide bottle-recycling factories were reported to be at a low risk of organophosphate toxicity in the working environment. However, because the potential risk of intoxication is still present, protective equipment such as clothing, gloves, and water-proof shoes should be worn, and employees should be educated on the potential risks.

Acetylcholinesterase↗

PubMed1999

An essential surface motif (WAQKW) of yeast RNA triphosphatase mediates formation of the mRNA capping enzyme complex with RNA guanylyltransferase.

Saccharomyces cerevisiae RNA triphosphatase (Cet1p) and RNA guanylyltransferase (Ceg1p) interact in vivo and in vitro to form a bifunctional mRNA capping enzyme complex. Cet1p binding to Ceg1p stimulates the guanylyltransferase activity of Ceg1p. Here we localize the guanylyltransferase-binding and guanylyltransferase-stimulation functions of Cet1p to a 21-amino acid segment from residues 239 to 259. The guanylyltransferase-binding domain is located on the protein surface, as gauged by protease sensitivity, and is conserved in the Candida albicans RNA triphosphatase CaCet1p. Alanine-cluster mutations of a WAQKW motif within this segment abolish guanylyltransferase-binding in vitro and Cet1p function in vivo, but do not affect the triphosphatase activity of Cet1p. Proteolytic footprinting experiments provide physical evidence that Cet1p interacts with the C-terminal domain of Ceg1p. Trypsin-sensitive sites of Ceg1p that are shielded from proteolysis when Ceg1p is bound to Cet1p are located between nucleotidyl transferase motifs V and VI.

Acid Anhydride Hydrolases↗

PubMed1999

Mutational analysis of Escherichia coli DNA ligase identifies amino acids required for nick-ligation in vitro and for in vivo complementation of the growth of yeast cells deleted for CDC9 and LIG4.

We report that the NAD-dependent Escherichia coli DNA ligase can support the growth of Saccharomyces cerevisiae strains deleted singly for CDC9 or doubly for CDC9 plus LIG4. Alanine-scanning mutagenesis of E.coli DNA ligase led to the identification of seven amino acids (Lys115, Asp117, Asp285, Lys314, Cys408, Cys411 and Cys432) that are essential for nick-joining in vitro and for in vivo complementation in yeast. The K314A mutation uniquely resulted in accumulation of the DNA-adenylate intermediate. Alanine substitutions at five other positions (Glu113, Tyr225, Gln318, Glu319 and Cys426) did not affect in vivo complementation and had either no effect or only a modest effect on nick-joining in vitro. The E113A and Y225A mutations increased the apparent K (m)for NAD (to 45 and 76 microM, respectively) over that of the wild-type E. coli ligase (3 microM). These results are discussed in light of available structural data on the adenylylation domains of ATP- and NAD-dependent ligases. We observed that yeast cells containing only the 298-amino acid Chlorella virus DNA ligase (a 'minimal' eukaryotic ATP-dependent ligase consisting only of the catalytic core domain) are relatively proficient in the repair of DNA damage induced by UV irradiation or treatment with MMS, whereas cells containing only E.coli ligase are defective in DNA repair. This suggests that the structural domains unique to yeast Cdc9p are not essential for mitotic growth, but may facilitate DNA repair.

Alanine↗

PubMed1999

Mutational analyses of yeast RNA triphosphatases highlight a common mechanism of metal-dependent NTP hydrolysis and a means of targeting enzymes to pre-mRNAs in vivo by fusion to the guanylyltransferase component of the capping apparatus.

Saccharomyces cerevisiae Cet1p is the prototype of a family of metal-dependent RNA 5'-triphosphatases/NTPases encoded by fungi and DNA viruses; the family is defined by conserved sequence motifs A, B, and C. We tested the effects of 12 alanine substitutions and 16 conservative modifications at 18 positions of the motifs. Eight residues were identified as important for triphosphatase activity. These were Glu-305, Glu-307, and Phe-310 in motif A (IELEMKF); Arg-454 and Lys-456 in motif B (RTK); Glu-492, Glu-494, and Glu-496 in motif C (EVELE). Four acidic residues, Glu-305, Glu-307, Glu-494, and Glu-496, may comprise the metal-binding site(s), insofar as their replacement by glutamine inactivated Cet1p. E492Q retained triphosphatase activity. Basic residues Arg-454 and Lys-456 in motif B are implicated in binding to the 5'-triphosphate. Changing Arg-454 to alanine or glutamine resulted in a 30-fold increase in the K(m) for ATP, whereas substitution with lysine increased K(m) 6-fold. Changing Lys-456 to alanine or glutamine increased K(m) an order of magnitude; ATP binding was restored when arginine was introduced. Alanine in lieu of Phe-310 inactivated Cet1p, whereas Tyr or Leu restored function. Alanine mutations at aliphatic residues Leu-306, Val-493, and Leu-495 resulted in thermal instability in vivo and in vitro. A second S. cerevisiae RNA triphosphatase/NTPase (named Cth1p) containing motifs A, B, and C was identified and characterized. Cth1p activity was abolished by E87A and E89A mutations in motif A. Cth1p is nonessential for yeast growth and, by itself, cannot fulfill the essential role played by Cet1p in vivo. Yet, fusion of Cth1p in cis to the guanylyltransferase domain of mammalian capping enzyme allowed Cth1p to complement growth of cet1Delta yeast cells. This finding illustrates that mammalian guanylyltransferase can be used as a vehicle to deliver enzymes to nascent pre-mRNAs in vivo, most likely through its binding to the phosphorylated CTD of RNA polymerase II.

Acid Anhydride Hydrolases↗

PubMed1999

A conserved domain of yeast RNA triphosphatase flanking the catalytic core regulates self-association and interaction with the guanylyltransferase component of the mRNA capping apparatus.

The 549-amino acid yeast RNA triphosphatase Cet1p catalyzes the first step in mRNA cap formation. Cet1p consists of three domains as follows: (i) a 230-amino acid N-terminal segment that is dispensable for catalysis in vitro and for Cet1p function in vivo; (ii) a protease-sensitive segment from residues 230 to 275 that is dispensable for catalysis but essential for Cet1p function in vivo; and (iii) a catalytic domain from residues 275 to 539. Sedimentation analysis indicates that purified Cet1(231-549)p is a homodimer. Cet1(231-549)p binds in vitro to the yeast RNA guanylyltransferase Ceg1p to form a 7.1 S complex that we surmise to be a trimer consisting of two molecules of Cet1(231-549)p and one molecule of Ceg1p. The more extensively truncated protein Cet1(276-549)p, which cannot support cell growth, sediments as a monomer and does not interact with Ceg1p. An intermediate deletion protein Cet1(246-549)p, which supports cell growth only when overexpressed, sediments principally as a discrete salt-stable 11.5 S homo-oligomeric complex. These data implicate the segment of Ceg1p from residues 230 to 275 in regulating self-association and in binding to Ceg1p. Genetic data support the existence of a Ceg1p-binding domain flanking the catalytic domain of Cet1p, to wit: (i) the ts growth phenotype of 2mu CET1(246-549) is suppressed by overexpression of Ceg1p; (ii) a ts alanine cluster mutation CET1(201-549)/K250A-W251A is suppressed by overexpression of Ceg1p; and (iii) 15 other cet-ts alleles with missense changes mapping elsewhere in the protein are not suppressed by Ceg1p overexpression. Finally, we show that the in vivo function of Cet1(275-549)p is completely restored by fusion to the guanylyltransferase domain of the mouse capping enzyme. We hypothesize that the need for Ceg1p binding by yeast RNA triphosphatase can by bypassed when the triphosphatase catalytic domain is delivered to the RNA polymerase II elongation complex by linkage in cis to the mammalian guanylyltransferase.

Acid Anhydride Hydrolases↗

PubMed1999

Circulating levels of thrombopoietic and inflammatory cytokines in patients with clonal and reactive thrombocytosis.

The regulation of megakaryocytopoiesis and thrombopoiesis appears to be under the control of an array of hematopoietic growth factors. To determine the relationship between endogenous cytokine levels and circulating platelet counts, we measured the serum levels of both thrombopoietic and inflammatory cytokines in the peripheral blood and bone marrow samples from 70 patients with clonal thrombocytosis (CT) caused by myeloproliferative disorders, 28 patients with reactive thrombocytosis (RT), and 35 normal control subjects. The levels of thrombopoietin (TPO), interleukin-6 (IL-6), soluble IL-6 (sIL-6) receptor, IL-11, stem cell factor (SCF), IL-3, and IL-8 were determined by enzyme-linked immunosorbent assay (ELISA). Platelet counts were significantly higher in both CT and patients with RT (699+/-399x10(9)/L, P<.001; 642+/-200 x 10(9)/L, P<.001; respectively) as compared with the normal control subjects (240+/-47x10(9)/L). The concentrations of cytokines in the bone marrow correlated well with those in the peripheral blood. The endogenous levels of TPO, IL-6, and sIL-6 receptor were significantly higher in both CT and patients with RT than those in normal control subjects. The median level of IL-6 was significantly higher in patients with RT than in patients with CT (40 pg/mL vs. 5 pg/mL; P<.001); however, there was no detectable difference in TPO and sIL-6 receptor levels between the two groups. Significantly higher levels of SCF and IL-8 were also found in patients with CT as compared with those found in normal control subjects (median 2460 pg/mL vs 1995 pg/mL, P<.05; 20 ng/mL vs. 5 ng/mL, P = .001; respectively). Finally, IL-11 and IL-3 levels were undetectable in most patients with thrombocytosis. Our results reveal that the endogenous levels of TPO, IL-6, sIL-6 receptor, IL-8, and SCF are elevated in patients with CT or RT. These cytokines appear to be active mediators involved in the regulation of thrombopoiesis during clonal and reactive thrombocytosis.

Adult↗

PubMed1999

Distinct roles for CTD Ser-2 and Ser-5 phosphorylation in the recruitment and allosteric activation of mammalian mRNA capping enzyme.

Capping is targeted to pre-mRNAs through binding of the guanylyltransferase component of the capping apparatus to the phosphorylated CTD of RNA polymerase II. We report that mammalian guanylyltransferase binds synthetic CTD peptides containing phosphoserine at either position 2 or 5 of the YSPTSPS heptad repeat. CTD peptides containing Ser-5-PO4 stimulate guanylyltransferase activity by enhancing enzyme affinity for GTP and increasing the yield of the enzyme-GMP intermediate. A CTD peptide containing Ser-2-PO4 has no effect on guanylyltransferase activity. This implies an allosteric change in guanylyltransferase conformation that is specified by the position of phosphoserine in the CTD. Stimulation of guanylyltransferase increases with the number of Ser-5-phosphorylated heptads. Our results underscore how mRNA production may be regulated by the display of different CTD phosphorylation arrays during transcription elongation.

Allosteric Regulation↗

PubMed1999

In vitro effect of granulocyte-colony stimulating factor and all-trans retinoic acid on the expression of inflammatory cytokines and adhesion molecules in acute promyelocytic leukemic cells.

Differentiation therapy with all-trans retinoic acid (ATRA) represents a landmark approach in the treatment of acute promyelocytic leukemia (APL). However, a potentially fatal complication of retinoic acid (RA) syndrome occurs in about a quarter of patients and its pathophysiology is still unclear. In order to investigate whether or not the treatment with ATRA leads to increased elaboration of inflammatory cytokines and adhesion molecules by the APL cells, the expression of interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, IL-8, L-selectin and intercellular adhesion molecule-1 (ICAM-1) was examined in the APL cells after induction of differentiation with ATRA in the presence or absence of granulocyte-colony stimulating factor (G-CSF) or IL-3 in the present study. Cytokine elaboration by the treated cells was detected using both Northern blotting and enzyme-linked immunosorbent assay. Our results have shown that ATRA induces an increased expression of IL-8, IL-1beta, TNF-alpha and ICAM-1 in APL cells, which can be amplified by the addition of G-CSF. These data imply that the induction of inflammatory cytokines in APL cells may play an important role in the pathogenesis of RA syndrome. Furthermore, G-CSF, through its potent differentiating activity, may increase the risk of such complications during ATRA treatment.

Antineoplastic Agents↗

PubMed1999

Modulating influence of cytochrome P-450 MspI polymorphism on serum liver function profiles in coke oven workers.

OBJECTIVES: It was reported previously that topside oven workers with heavy exposure to coke oven emissions had increased serum activities of hepatic aminotransferase in one coke oven plant. This study was conducted to investigate the modifying effect of CYP1A1 MspI polymorphism on liver function profiles in coke oven workers. METHODS: 88 coke oven workers from a large steel company in Taiwan were studied in 1995-6. Exposure was categorised by work area: topside oven workers and sideoven workers. Liver function profiles including serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), r-glutamyl transpeptidase (GGT), alkaline phosphatase (ALP), and total bilirubin (BIL) were examined in the morning after personal exposure measurements. The MspI polymorphism was determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). RESULTS: Five of 23 (22%) topside oven workers and seven of 65 (11%) sideoven workers had the CYP1A1 MspI homozygous variant genotype. With sideoven workers with the combined wild type and heterozygous variant as the reference group in multiple regression models, it was found that topside oven workers with the combined traits had mean AST and ALT activities that were 21% and 46% higher (95% confidence interval (95% CI) 4% to 42% and 12% to 91%, respectively) than the reference group after adjusting for appropriate confounders. Also, topside oven workers with the homozygous variant trait had mean AST, ALT, and GGT activities that were 59%, 68%, and 157% higher (95% CI 21% to 109%, 6% to 168%, and 39% to 374%, respectively) than the reference group. The prevalence of an abnormal hepatocellular pattern (AST > 37 IU/l or ALT > 39 IU/l) was more common in the topside oven workers with the homozygous variant than in the sideoven workers with the other combined genotypes (adjusted odds ratio 9.9, 95% CI 1.2 to 82.3) after adjusting for appropriate confounders. CONCLUSIONS: The CYP1A1 MspI polymorphism may modify the biotransformation of coke oven emissions, which results in hepatocellular damage in coke oven workers.

Adult↗

PubMed1999

Fungal corneal ulcers of onion harvesters in southern Taiwan.

Fungal corneal ulcers related to agriculture has been reported throughout the world, especially in tropical areas. Most of them were sporadic and had histories of ocular trauma or use of topical corticosteroids and topical antibiotics. Five onion harvesters had fungal corneal ulcers during the same harvest period in Southern Taiwan. The authors think that this is the first report of a group occurrence relating to agricultural workers. Although all of the patients improved after medical and surgical management, their vision was greatly decreased. It is suggested that the tropical climate, the harvest procedure, the characteristic monsoon, and lack of eye protection were involved. Therefore, the importance of the eye protection, hygiene education, and improving medical care to reduce the occurrence of fungal corneal ulcer in agriculture workers must be emphasised.

Adult↗

PubMed1999

Suspected nasopharyngeal carcinoma in three workers with long-term exposure to sulphuric acid vapour.

Sulphuric acid vapour has been suspected of being an industrial carcinogen. In this study, a cluster is presented of three patients with nasopharyngeal carcinoma (NPC) who worked in the same building of a telecommunications conveyance station in southern Taiwan with long term exposure to sulphuric acid vapour concentrations as high as 0.18 mg/m3. All three workers were diagnosed with NPC within a 5 month period between September 1992, and March 1993. Compared with 19 other healthy workers from the same building, these three workers with NPC had worked significantly longer in this building than had the others (mean (SD) (years): 12.7 (0.6) v 7.4 (4.4); p = 0.01). With an in situ nucleic acid hybridisation and immunostaining method for colocalised Epstein-Barr virus (EBV) and secretory component (SC) protein among biopsy specimens of these three patients with NPCs, it was found that some tumour cells did not contain EBV and SC protein staining signals. These results indicate that EBV infection is not the only risk factor for NPC and long term exposure to relatively low concentrations of sulphuric acid vapour may be associated with the development of NPC.

Adult↗

PubMed1999

Regulation of 11beta-hydroxysteroid dehydrogenase isoforms and glucocorticoid receptor gene expression in the rat uterus.

Glucocorticoids are known to have diverse effects on the uterus, generally believed to be mediated by the glucocorticoid receptor (GR). To date, two isoforms of the enzyme 11beta-hydroxysteroid dehydrogenase (11betaHSD) have been identified, namely 11betaHSD1 and 11betaHSD2, which interconvert active and inactive glucocorticoids and regulate local levels of hormones available to the GR in target tissues. The aim of the present study was to examine the uterine expression of 11betaHSD and GR mRNA. The interplay of these parameters is probably an important factor in determining actions of glucocorticoids on the uterus. Using Northern analysis we investigated the uterine expression of 11betaHSD1, 11betaHSD2 and GR mRNA in relation to serum levels of sex steroid hormones and uterine progesterone receptor mRNA expression in an animal model. Immature female rats were treated with 10 IU pregnant mare serum gonadotrophin (PMSG) followed by 10 IU human chorionic gonadotrophin (hCG) 48 h afterwards, and then killed at 0, 3, 6, 9, 12 and 24 h and 5 days after the hCG injection. Expression of both 11betaHSD1 and 11betaHSD2 mRNA in total uterine RNA was found to be up-regulated by more than 50% at 48 h after PMSG injection when oestradiol levels were also high. Following hCG treatment the expression of 11betaHSD1 and 11betaHSD2 further increased to reach maximal levels at 24 and 12 h respectively. GR mRNA expression was down-regulated by more than 50% by PMSG but gradually recovered after hCG injection. The results show that mRNA expression of 11betaHSD1, 11betaHSD2 and GR in the uterus is developmentally regulated, suggesting that these key determinants of glucocorticoid action may play an important role in uterine function.

11-beta-Hydroxysteroid Dehydrogenases↗

PubMed1998

Yeast and viral RNA 5' triphosphatases comprise a new nucleoside triphosphatase family.

Saccharomyces cerevisiae Cet1p catalyzes the first step of mRNA capping, the hydrolysis of the gamma phosphate of triphosphate-terminated RNA to form a 5' diphosphate end. The RNA triphosphatase activity of Cet1p is magnesium-dependent and has a turnover number of 1 s-1. Here we show that purified recombinant Cet1p possesses a robust ATPase activity (Km = 2.8 microM; Vmax = 25 s-1) in the presence of manganese. Cobalt is also an effective cofactor, but magnesium, calcium, copper, and zinc are not. Cet1p displays broad specificity in converting ribonucleoside triphosphates and deoxynucleoside triphosphates to their respective diphosphates. The manganese- and cobalt-dependent nucleoside triphosphatase of Cet1p resembles the nucleoside triphosphatase activities of the baculovirus LEF-4 and vaccinia virus D1 capping enzymes. Cet1p, LEF-4, and D1 share three collinear sequence motifs. Mutational analysis establishes that conserved glutamate and arginine side chains within these motifs are essential for the RNA triphosphatase and ATPase activities of Cet1p in vitro and for Cet1p function in vivo. These findings are in accord with the effects of single alanine mutations at analogous positions of vaccinia capping enzyme. We suggest that the metal-dependent RNA triphosphatases encoded by yeast and DNA viruses comprise a novel family of phosphohydrolase enzymes with a common active site.

Acid Anhydride Hydrolases↗

PubMed1998

The guanylyltransferase domain of mammalian mRNA capping enzyme binds to the phosphorylated carboxyl-terminal domain of RNA polymerase II.

We have conducted a biochemical and genetic analysis of mouse mRNA capping enzyme (Mce1), a bifunctional 597-amino acid protein with RNA triphosphatase and RNA guanylyltransferase activities. The principal conclusions are as follows: (i) the mammalian capping enzyme consists of autonomous and nonoverlapping functional domains; (ii) the guanylyltransferase domain Mce1(211-597) is catalytically active in vitro and functional in vivo in yeast in lieu of the endogenous guanylyltransferase Ceg1; (iii) the guanylyltransferase domain per se binds to the phosphorylated RNA polymerase II carboxyl-terminal domain (CTD), whereas the triphosphatase domain, Mce1(1-210), does not bind to the CTD; and (iv) a mutation of the active site cysteine of the mouse triphosphatase elicits a strong growth-suppressive phenotype in yeast, conceivably by sequestering pre-mRNA ends in a nonproductive complex or by blocking access of the endogenous yeast triphosphatase to RNA polymerase II. These findings contribute to an emerging model of mRNA biogenesis wherein RNA processing enzymes are targeted to nascent polymerase II transcripts through contacts with the CTD. The phosphorylation-dependent interaction between guanylyltransferase and the CTD is conserved from yeast to mammals.

Amino Acid Sequence↗

PubMed1998

The influence of cryopreservation on cytokine production by human T lymphocytes.

Human T lymphocytes isolated from peripheral blood were cryopreserved at -196 degreesC for different periods of 3, 14, 21, 35, and 50 days. Viability and cytokine-producing activity of T cells were examined before and after cryopreservation. A high recovery (90 +/- 1%) of viable T cells was obtained at each frozen period, indicating that a 10% loss of cells was due to the freezing process rather than the duration of cryopreservation. There was no difference in cell cycle distribution between PHA-treated fresh and frozen lymphocytes. Resting human T cells produced little or no cytokine. After stimulation of fresh T cells with PHA, an apparent increase in cytokine production was noted in IL-2 (35.5 +/- 8.3 pg/ml), IL-6 (1280.4 +/- 64.7 pg/ml), tumor necrosis factor-alpha (874.3 +/- 71.7 pg/ml), interferon-gamma (58.9 +/- 2.2 pg/ml), and granulocyte macrophage-colony-stimulating factor (59.5 +/- 4.4 colonies/5 x 10(4) bone marrow cells). Compared with PHA-activated fresh T cells, all the above cytokines did not diminish in their levels in conditioned medium from PHA-treated frozen T cells thawed at each storage period, suggesting that cryopreservation could well retain the cytokine-producing activity of human T lymphocytes. In addition, our results also revealed that cryopreservation rendered T lymphocytes more responsive to PHA in IL-2 production than fresh T cells.

Cryopreservation↗

PubMed1998

Perineal seeding of prostate cancer as the only evidence of clinical recurrence 14 years after needle biopsy and radical prostatectomy: molecular correlation.

Perineal needle tract seeding of prostate cancer is an unusual complication of perineal prostate biopsy. We report a case with the longest known interval from biopsy to perineal recurrence--14 years. The prostate-specific antigen did not become detectable until 12 years after biopsy and no other metastases were apparent, suggesting that the patient's perineal disease was an isolated recurrence. Immunohistochemical staining of the perineal recurrence and the original biopsy and prostate for the p53 tumor suppressor gene and bcl-2 oncogene proteins revealed rare/absent p53 expression but marked increased bcl-2 expression. This unusual molecular pedigree may help to explain this rare clinical scenario.

Aged↗

PubMed1998

HLA DR2 and DQ1 frequency among narcoleptic patients in Hong Kong Chinese.

Narcolepsy is a life-long crippling sleep disorder with significant physical and psychosocial impairments. Although its exact etiology and neuropathology is not clear, a strong association with specific human leucocyte antigen (HLA) subtype, particularly DR2 (DRw15) and DQw1 (DQw6), has been demonstrated across different ethnic groups including Caucasians and Japanese. The presence of 100% association with HLA DR2 in a series of Hong Kong Chinese narcoleptic patients has previously been reported. The report can now be extended, and as far as could be ascertained in the available subjects, all were HLA DQw1 (DQw6)-positive. This is concordant with the experiences of Japanese narcoleptic patients who are 100% HLA DR2- and DQw1-positive. However, the definitive account of the population prevalence of narcolepsy in Chinese could be determined only by a well-conducted epidemiological study with laboratory confirmation.

Adolescent↗