Biomedical subjects

R Kwok

Publications and source records attributed to R Kwok.

At least 19 recordsLinked to original sources

PubMed2006

Genetic association study of insulin-like growth factor-I (IGF-I) gene with curve severity and osteopenia in adolescent idiopathic scoliosis.

UNLABELLED: IGF-I has a pivotal role in bone growth and could be one of the putative disease-modifier genes in AIS. Two SNPs in IGF-I gene promoter region were studied for any association with occurrence of AIS and for their effect on the curve severity among AIS. METHODS: 506 AIS girls (Cobb>20 degrees) and 227 age-matched Chinese girls were recruited. The spine (L2-L4) and hip BMD of the subjects were measured by DXA. A subgroup of AIS patients (N=340) who were followed-up to skeletal maturity and the maximum Cobb's angle was recorded. Two SNPs were genotyped by PCR-RFLP (rs5742612 and rs2288377). The chi-square test and one-way ANOVA were used to test the association between genotypes and quantitative parameters, respectively. RESULTS: No association was between the genotypes and the occurrence of AIS and the BMD of the spine and hip. The allelic frequency of T allele was 0.69 in AIS and control. However, the Cobb's angle was higher in patients with the homozygous T allele (Mean Cobb's angle: 38.1 degrees in TT vs 35.9 degrees in TC vs 33.2 degrees in CC group; p=0.04). DISCUSSION: Interestingly, IGF-I polymorphism affects the curve severity of AIS though it was not associated with onset of AIS per se. It indicates that IGF-I may be a disease modifying gene. The importance of IGF-I in skeletal growth makes it a good candidate gene which would play a role in the documented association of rapid growth with curve progression in AIS.

Adolescent↗

PubMed2005

Phe-Gly-Leu-amide allatostatin in the termite Reticulitermes flavipes: content in brain and corpus allatum and effect on juvenile hormone synthesis.

In the subterranean termite Reticulitermes flavipes, allatostatins (ASTs) with the C-terminus Phe-Gly Leu-amide were localized by immunocytochemistry with antibody against a cockroach AST, Dippu AST-7. AST-immunoreactivity occurred in the corpus cardiacum and corpus allatum and in the lateral and medial neurosecretory cells of the brain that innervate these organs as well as in many other nerve cells of the brain. This was observed in workers, nymphs, soldiers and secondary reproductives. A radioimmunoassay, using anti-Dippu AST-11, demonstrated about 40 fmole equivalents of AST in brains of soldiers and secondary reproductives. The product of the corpora allata in this species was determined to be juvenile hormone III. Its synthesis by corpora allata of secondary reproductives, determined by in vitro radiochemical assay, was inhibited in a dose-dependent fashion by two cockroach allatostatins, Dippu AST-7 and Dippu AST-11. Thus, as in cockroaches and crickets, allatostatin-containing nerves innervate the corpora allata of this termite species and their production of juvenile hormone is inhibited by these neuropeptides.

Animals↗

PubMed2002

Preliminary experience in radionuclide therapy of hepatocellular carcinoma using hepatic intra-arterial radio-conjugates.

INTRODUCTION: In a minority of the cases, resection of hepatocellular carcinoma (HCC) is potentially curative but local recurrence is common. Adjuvant intra-arterial radio-conjugate therapy could potentially reduce the rate of local recurrence and increase disease-free and overall survival. However, in the majority of cases, treatment of HCC is largely palliative. A wide range of palliative treatment options are available and these include external radiation, hepatic intra-arterial chemo-embolisation, systemic chemotherapy and percutaneous ethanol injection. The long-term survival rate is poor. Hepatic intra-arterial radio-conjugate therapy provides a new and promising means of palliation. MATERIALS AND METHODS: We share our initial experience in the treatment of patients with HCC. A total of 32 patients were recruited between October 1999 and June 2001. Group 1 comprised 15 patients who had potentially curative resection of HCC who were treated with Iodine-131 (I131) lipiodol as a form of adjuvant therapy. Group 2 comprised 17 patients with unresectable HCC, 12 of whom were treated with Yttrium-90 (Y90) microspheres and 5 with Rhenium-188 (Re188) lipiodol. The radio-conjugates were administered via the intra-arterial route. RESULTS: Thirteen of the 15 patients in group 1 who were treated with I131 lipiodol following curative resection of HCC were free of disease, 1 patient died and 1 patient who developed recurrence was retreated with Re188 lipiodol and was subsequently free of disease. The 6-month disease-free survival rate was 100% and the 12-month disease-free and overall survival rates were 72% and 85%, respectively. Of the 12 patients in group 2 who were treated with Y90 microspheres for unresectable HCC, 6 had stable disease, 2 showed tumour regression and 4 died. The 6-month and 12-month survival rates were 75% and 66%, respectively. Of the 5 patients in group 2 who were treated with Re188 lipiodol for unresectable HCC, 4 had stable disease and 1 had regression of the right lobe tumour but progression of the left lobe tumour. CONCLUSION: Our results in the adjuvant treatment of patients with I131 lipiodol following curative resection of early HCC and in the palliative treatment of unresectable HCC using Y90 microspheres and Re188 lipiodol are preliminary and not fully conclusive. These preliminary results have to be confirmed in larger groups of patients and by prospective, randomised, controlled trials. This study highlights the preliminary experience in radionuclide therapy of HCC using hepatic intra-arterial radio-conjugates in a local context.

Carcinoma, Hepatocellular↗

PubMed2000

Water exchange between the subglacial Lake Vostok and the overlying ice sheet

It has now been known for several years that a 200-km-long lake, called Lake Vostok, lies beneath the ice sheet on which sits Vostok Station in Antarctica. The conditions at the base of the ice sheet above this subglacial lake can provide information about the environment within the lake, including the likelihood that it supports life. Here we present an analysis of the ice-sheet structure from airborne 60-MHz radar studies, which indicates that distinct zones of basal ice loss and accretion occur at the ice-water interface. Subglacial melting and net ice loss occur in the north of the lake and across its 200-km-long western margin, whereas about 150 m of ice is gained by subglacial freezing in the south. This indicates that significant quantities of water are exchanged between the base of the ice sheet and the lake waters, which will enrich the lake with gas hydrates, cause sediment deposition and encourage circulation of the lake water.

Journal Article↗

PubMed2000

When knowing becomes remembering: individual differences in susceptibility to suggestion.

In two experiments, the authors explored factors that might influence a person's tendency to make source-monitoring errors about autobiographical memories. In the first experiment, undergraduates retrieved a memory from childhood (a) that was known about but not remembered, (b) that was remembered, or (c) for which they were unsure of their memory's source. After writing down the memory, experimental groups listened to a guided visualization tape and answered questions about the event--interventions designed to help them focus on details of their memory. Controls also retrieved and wrote down a memory; however, instead of visualizing the memory, they were instructed to conduct a visual search task. Results indicated that guided visualization led participants to rate known memories closer to remembered events. A second experiment examined individual difference variables that might be related to this know-to-remember shift. Results indicated that extraversion, external locus of control, a memory that conveyed fear, and overall affective content predicted this rating. The applicability of these findings to the psychotherapy process is discussed.

Adult↗

PubMed2000

Use of a continuous nephelometer to measure personal exposure to particles during the U.S. Environmental Protection Agency Baltimore and Fresno Panel studies.

In population exposure studies, personal exposure to PM is typically measured as a 12- to 24-hr integrated mass concentration. To better understand short-term variation in personal PM exposure, continuous (1-min averaging time) nephelometers were worn by 15 participants as part of two U.S. Environmental Protection Agency (EPA) longitudinal PM exposure studies conducted in Baltimore County, MD, and Fresno, CA. Participants also wore inertial impactor samplers (24-hr integrated filter samples) and recorded their daily activities in 15-min intervals. In Baltimore, the nephelometers correlated well (R2 = 0.66) with the PM2.5 impactors. Time-series plots of personal nephelometer data showed each participant's PM exposure to consist of a series of peaks of relatively short duration. Activities corresponding to a significant instrument response included cooking, outdoor activities, transportation, laundry, cleaning, shopping, gardening, moving between microenvironments, and removing/putting on the instrument. On average, 63-66% of the daily PM exposure occurred indoors at home (about 2/3 of which occurred during waking hours), primarily due to the large amount of time spent in that location (an average of 72-77%). Although not a reference method for measuring mass concentration, the nephelometer did help identify PM sources and the relative contribution of those sources to an individual's personal exposure.

Activities of Daily Living↗

PubMed1999

Locustatachykinin isoforms in the locust: distribution and quantification in the central nervous system and action on the oviduct muscle.

The presence of locustatachykinin (LomTK)-like immunoreactivity is demonstrated in the central nervous system (CNS) of Locusta migratoria with the use of a polyclonal antiserum raised against LomTK1. By developing a radioimmunoassay with the same antiserum, we have demonstrated picomolar amounts of LomTK-like material in the tissues of the central nervous system. In contrast, only femptomolar amounts of LomTK-like material are associated with the oviduct tissue. The relative amounts of the different LomTK isoforms in the brain and the abdominal ganglionic chain were examined by separating the native peptides on high-performance liquid chromatography and comparing their retention times to synthetic LomTK standards. The amounts of the different isoforms of LomTK differed between and within the two regions of the central nervous system. However, the ratios of the different isoform amounts were similar between the two regions. The myostimulatory activities of LomTKs 1 to 4 were characterized by using the locust oviduct bioassay. LomTKs 1, 2, and 3 appeared to be more efficacious than LomTK4.

Animals↗

PubMed1993

Use of magnetic resonance imaging in the evaluation of nasopharyngeal cancer.

Computerised tomographic (CT) scanning is an established modality in the diagnosis and evaluation of tumours of the nasopharynx. Magnetic resonance (MR) imaging is a newer tool which has rapidly gained acceptance in the same regard due to its innate ability to better characterise and detail soft tissue structures, and its multiplanar scanning ability. This study reviews our experience, in a series of 30 cases, with the use of MR imaging in lesions of the nasopharynx, in particular nasopharyngeal carcinoma. Most of our patients showed involvement of the pharyngeal mucosal and parapharyngeal spaces, as expected. A large number also had intracranial extension. Our sample was probably biased as patients with neurological involvement are more likely to be assessed by MR than CT. Soft tissue infiltration, particularly intracranial extension, was very clearly delineated, especially when intravenous contrast (gadolinium DTPA) was administered. Bone erosion was not well demonstrated. In current clinical practice where radiotherapy is the most common form of treatment for nasopharyngeal carcinoma however, there does not in general, appear to be any clear advantage of MR over CT in the imaging of this particular disease, although there are some exceptions.

Adult↗

PubMed1992

Management and epidemiologic analyses of an outbreak due to methicillin-resistant Staphylococcus aureus.

PURPOSE: Following implementation of special measures to control a nosocomial outbreak of methicillin-resistant Staphylococcus aureus (MRSA), we used immunoblot typing in conjunction with antimicrobial susceptibility testing to investigate the epidemiology of this event and to determine whether this outbreak represented the failure of infection control measures to limit the spread of previously endemic MRSA strains or the introduction of a new strain of MRSA. MATERIALS AND METHODS: Isolates of MRSA recovered from hospitalized patients were initially categorized on the basis of antimicrobial susceptibility results. Organisms susceptible to ciprofloxacin and/or trimethoprim/sulfamethoxazole were recovered from patients at a relatively constant rate prior to December 1988 and were categorized as endemic isolates. Subsequently, there was an outbreak due to organisms resistant to both of these antibiotics; these were therefore categorized as outbreak isolates. Isolates were later characterized by immunoblot typing. Prior to this analysis, isolates were given code numbers so that clinical and epidemiologic data as well as resistance patterns were not known until this testing was complete. RESULTS: Between January 1986 and November 1988, an average of 3.9 patients per month acquired nosocomial MRSA in the Sepulveda Veterans Administration Medical Center. In contrast, from December 1988 to October 1989, 369 MRSA isolates were collected from 125 patients (an average of 11.4 patients per month). Prior to December 1988, all tested nosocomial isolates of MRSA were susceptible to ciprofloxacin and/or to trimethoprim/sulfamethoxazole. In contrast, the outbreak was due to spread of MRSA isolates resistant to these antibiotics. Immunoblot typing of 204 isolates from 98 individuals identified five distinct immunoblot types of which types B and C were by far the most common. Type B was highly associated with outbreak isolates, whereas type C was associated with endemic isolates (p less than 0.001). All sequential isolates from single patients that belonged to different susceptibility categories demonstrated discordant immunoblot types. In contrast, concordant immunoblot types were observed for 25 of 27 sequential isolates that displayed minor variations in antimicrobial resistance. The institution of more stringent infection control measures was followed by the return of nosocomial MRSA acquisition rates to pre-outbreak levels. Although novobiocin and trimethoprim/sulfamethoxazole were extensively used to treat patients harboring outbreak and endemic isolates, respectively, in no instance was the initial MRSA isolate from any patient resistant to novobiocin and only 6% of initial endemic isolates displayed trimethoprim/sulfamethoxazole resistance. A modest, significant increase in the resistance of endemic isolates to various other antimicrobial agents was noted however. CONCLUSION: Immunoblot analyses provided strong, corroborative evidence that at least two separate strains of MRSA were present during the outbreak and that a newly introduced strain with a distinctive antimicrobial resistance pattern was primarily responsible for the rapid spread of MRSA during the outbreak. The observation that previously effective infection control measures failed to prevent the nosocomial spread of a newly introduced community-acquired MRSA strain suggests that a single set of control measures may not be equally efficacious against all strains of MRSA. In this regard, previously reported variations in resistance to topical antimicrobials and/or antiseptics, and differences in virulence factors such as colonization potential, invasiveness, and survival on fomites, may warrant further study. Control of the outbreak strain of MRSA in our institution did occur after the implementation of more strenuous isolation procedures.(ABSTRACT TRUNCATED)

California↗

PubMed1989

Percutaneous ultrasonic lithotripsy--its role in the management of renal and upper ureteric stones.

Percutaneous ultrasonic lithotripsy (PUL), a new technique used in the treatment of renal stones has been shown to be safe and effective with low morbidity. 54 of the 57 patients (95%) were successfully treated by this method and all were done as a single stage procedure. 39 patients (68%) in this series were either unsuitable or had failed extracorporeal shock wave lithotripsy (ESWL). No mortality occurred in this series and one patient with staghorn stone required a nephrectomy due to severe secondary haemorrhage. Though PUL is technically more difficult to perform, it is a better alternative than open renal surgery and is complementary to ESWL especially in the treatment of the more complicated renal stones.

Adult↗

PubMed1989

Antegrade ureteroscopy and ultrasonic lithotripsy in the treatment of difficult upper and middle ureteric stones.

34 patients with difficult upper and middle ureteric stones were treated by antegrade ureteroscopy with ultrasonic lithotripsy over a 2-year period. 14 patients (41 percent) had failed extracorporeal wave lithotripsy and another 20 patients (59 percent) were considered unsuitable for extracorporeal shock wave lithotripsy due either to obstruction associated with urosepsis or renal failure. Thirty patients (88 percent) had large stones with a transverse diameter from 10 to 20mm in size. Thirty-three of the 34 patients (97 percent) were successfully treated by this method with minimal morbidity. Of the 7 patients with residual stones, only one needed transurethral ureteroscopic removal and another by piezoelectric extracorporeal shock wave lithotripsy. This technique is a safe and effective method in removing impacted upper and middle ureteric stones for patients who have failed or are unsuitable for extra-corporeal shock wave lithotripsy treatment.

Endoscopy↗

PubMed1988

Clostridium difficile plasmid isolation as an epidemiologic tool.

A large hospital outbreak of Clostridium difficile diarrhea at the Minneapolis Veterans Administration Medical Center (MVAMC) was studied by plasmid profile typing. Plasmids were obtained from 30 (37%) of 82 clinical isolates from MVAMC patients and 10 (67%) of 15 non-MVAMC isolates. While bacteriophage plus bacteriocin typing and polyacrylamide gel electrophoresis (PAGE) plus bacterial agglutination typing proved more universally applicable, plasmid profiles may be useful for tracing isolated epidemic outbreaks, reinfections and relapses caused by plasmid-bearing strains.

Bacteriocins↗

PubMed1988

Vasoactive intestinal peptide secreting tumours in children: a case report with literature review.

A 3 year old Chinese girl with watery diarrhoea, abdominal distension and hypokalaemia due to a thoracic paraspinal vasoactive intestinal peptide (VIP) secreting ganglioneuroma is reported. The pre-operative serum VIP was 314 pmol/l (normal less than 30). Her diarrhoea stopped after the removal of the tumour. The VIP was 14 pmol/l 6 months post-operatively. Review of the 19 reported cases in children with documented elevated serum VIP showed that many of the cases presented with watery diarrhoea for prolonged duration before the diagnosis was made. Earliest age of onset was 2 weeks of age. The male to female ratio was 9:10. Ganglioneuroma and ganglioneuroblastoma were the commonest tumours. Pancreatic non-beta cell hyperplasia and neurofibroma were also reported. Location of the tumour was variable: neck, chest or abdomen. Increased urinary catecholamine excretion was reported in 50% of the cases. Abdominal distension, flushing, episodic hypertension and failure to thrive were the other associated features.

Adenoma, Islet Cell↗

PubMed1988