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C K Yeung

Publications and source records attributed to C K Yeung.

At least 19 recordsLinked to original sources
PubMed2001

Modulation of the growth and guidance of rat brain stem neurons using patterned extracellular matrix proteins.

Dissociated neuronal cultures on substrates patterned with extracellular matrix (ECM) proteins have yielded much information regarding the physiological characteristics of neuronal cells behaviour in vitro. However, neuronal patterning using long term embryonic brain slice cultures has not been comprehensively demonstrated to-date. Structuring was performed by micro contact printing of laminin. The slice cultures were evaluated by means of phase contrast microscopy at 3-22 days in culture. We were able to consistently achieve outgrowth of neurons, neurites and filopodia from brain stem slices cultured on ECM proteins structures of grid- and line-shapes. We believe that brain slice cultures on patterned substrates is a favourable approach to study functional synapses in vitro under defined conditions. The use of appropriate structures and the subsequent cell patterning may help to gain further understanding of axonal, dendritic and synaptic signal transductions and processes.

Animals↗
PubMed2001

Purification and characterization of hexahistidine-tagged cyclohexanone monooxygenase expressed in Saccharomyces cerevisiae and Escherichia coli.

Cyclohexanone monooxygenase (CMO) is a soluble flavoenzyme originally isolated from Acinetobacter spp. which carries out Baeyer-Villiger reactions with cyclic ketone substrates. In the present study we cloned the Acinetobacter CMO gene and modified it for facile purification from heterologous expression systems by incorporation of a His(6)-tag at its C-terminus. A single purification step employing metal (Ni(2+))-affinity column chromatography provided essentially homogeneous enzyme in yields of 69-72%. The properties of the purified, recombinant enzymes (rCMO) were compared with that of native CMO (nCMO) isolated from Acinetobacter cultures grown in the presence of cyclohexanone. The specific activities of His(6)-tagged rCMO and nCMO toward their index substrate, cyclohexanone, were similar and ranged from 14 to 20 micromol/min/mg. nCMO and rCMO from the Escherichia coli expression system exhibited molecular masses, determined by electrospray mass spectrometry, of 60,800 and 61,615 Da, respectively, an increase for the recombinant enzyme equivalent to the mass of the His(6)-tag. However, rCMO expressed in Saccharomyces cerevisiae consistently exhibited a mass some 50 Da larger than rCMO expressed in bacteria. Edman degradation confirmed that rCMO purified from the E. coli system and nCMO shared the same N-terminal sequence, whereas no sequence information could be obtained for rCMO expressed in yeast. Therefore, the yeast-expressed enzyme possesses an additional posttranslational modification(s), possibly acylation, at the N-terminus. Expression in E. coli is the preferred system for future site-directed mutagenesis studies and crystallization efforts.

Acinetobacter↗
PubMed2001

Video cystometry in young infants with renal dilation or a history of urinary tract infection.

Cystometry is increasingly being used in infants to diagnose bladder dysfunction. However, infantile urodynamic patterns have not been fully established. In this study we investigated the urodynamic patterns in young infants with renal dilation or a history of urinary tract infection, but with no apparent lower urinary tract symptoms. We use video cystometry with simultaneous perineal EMG recording. Thirty-five infants (27 male and 8 female) with congenital renal dilatation or a history of urinary tract infection at age 2 days to 24 months old were involved. We found that detrusor instability occurred in 8.6% of these subjects. Bladder capacity increased with age but less than would nomally be expected. An intermittent voiding pattern was observed in 57% (20/35) of subjects and was characterized by a single or recurring increase in sphincter activity with a simultaneous rise in the voiding detrusor pressure curve. The maximum voiding detrusor pressure with pelvic floor overactivity was significantly higher than that with no pelvic floor overactivity (105+/-44 cmH2O vs 69+/-22 cmH2O, P < 0.001). The median post-voiding residual volume was 2 (range 0 to 65) ml. We conclud that in infants with no apparent lower urinary tract symptoms, bladder instability is uncommon, and the capacity is lower than the normally expected range; an intermittent voiding pattern is common and the residual urine volume showed great variation. This probably represents an immature detrusor-sphincter function.

Dilatation, Pathologic↗
PubMed2001

Cardiomyocyte-transistor-hybrids for sensor application.

An extracellular recording system has been designed for the detection of electrical cell signals using p-channel or n-channel field-effect transistor (FET) arrays with non-metallized gates. Signals from rat heart muscle cell were recorded by these devices and the results described on the basis of an equivalent circuit. This technique is sensitive enough to detect minute changes of the extracellular membrane voltage and has potential applications in drug screening. We show that known cardiac stimulants (isoproterenol, norepinephrine) and relaxants (verapamil, carbamylcholine) have characteristic effects on the heart cells in terms of the changes of beat frequencies in the absence or presence of corresponding agents.

Action Potentials↗
PubMed2001

The relationship between early renal status, and the resolution of vesico-ureteric reflux and bladder function at 16 months.

OBJECTIVE: To examine, in infants presenting with vesico-ureteric reflux (VUR), the relationship between the presence of initial renal abnormalities with the outcome of VUR and bladder function at 16 months of age. PATIENTS AND METHODS: The study group comprised 40 infants (32 boys) presenting consecutively (29 after prenatal detection) with VUR grade III or greater (bilateral in 29) on the initial micturating cystogram (median age 8 weeks). The initial presence of abnormal kidneys was determined from isotopic renography and/or ultrasonography. These data were correlated with the outcome of VUR, from direct isotope cystography, and bladder function assessed by natural filling urodynamics, examined at age 16 months (mean 16.4 months, SD 2.1). RESULTS: Three groups were identified. Group 1 (eight boys and six girls) had normal kidneys bilaterally; initially grade III VUR was common. At 16 months bladder function was normal in 10 children and none had VUR (complete resolution). Group 2 (14 boys and two girls) had unilateral renal abnormalities; initially VUR was predominantly grade IV or grade V. At 16 months bladder function was normal in eight children and VUR resolved in eight, five of these with normal bladder function. Group 3 (10 boys) had bilateral renal abnormalities. Initially grade V VUR predominated; at 16 months the bladder function was normal in only one, and in the rest the emptying dynamics were abnormal. All 10 boys had persisting VUR (no resolution). CONCLUSIONS: In infants with moderate or severe VUR, resolution at 16 months old is associated with normal kidneys in a similar proportion of boys and girls. Resolution also correlates well with normal bladder function. Presentation in infancy with bilateral abnormal kidneys, associated with severe VUR in boys, is a poor prognostic sign for the early outcome of VUR and for bladder function.

Female↗
PubMed2001

Retroperitoneoscopic dismembered pyeloplasty for pelvi-ureteric junction obstruction in infants and children.

OBJECTIVE: To report our initial experience of endoscopic dismembered pyeloplasty through a retroperitoneal approach in infants and children with pelvi-ureteric junction (PUJ) obstruction. PATIENTS AND METHODS: Thirteen infants and children with PUJ obstruction underwent retroperitoneoscopic dismembered pyeloplasty (mean age at operation 2.7 years, range 0.25-10). Nine patients presented with complications secondary to PUJ obstruction, including urinary tract infection, pyonephrosis and increasing hydronephrosis with impairment in renal function. The other four patients had recurrent loin pain secondary to intermittent PUJ obstruction. The patient was placed in semi-prone (for left-sided) or a semilateral position (for right-sided PUJ obstruction). The retroperitoneal space was entered via a 1-cm incision over the mid-axillary line and further developed using a glove balloon. Video-retroperitoneoscopy was undertaken using a 5-mm laparoscope. Dismembered pyeloplasty was carried out with the pelvi-ureteric anastomosis fashioned using fine polydioxanone sutures over a double-pigtail ureteric stent. RESULTS: The retroperitoneoscopic dismembered pyeloplasty was successful in 12 patients, while one with previous percutaneous nephrostomy drainage for pyonephrosis required open conversion because of difficulties in developing the retroperitoneal space. The mean (range) operative duration was 143 (103-235) min. All patients had a rapid and uneventful recovery. The drainage was satisfactory in all 12 patients on a follow-up scan. CONCLUSIONS: Retroperitoneoscopic dismembered pyeloplasty is effective and safe in infants and young children giving a good early outcome, although the long-term results await further studies.

Anastomosis, Surgical↗
PubMed2001

Laparoscopic excision of prostatic utricles in children.

OBJECTIVE: To report our experience of laparoscopic excision of symptomatic prostatic utricles in children. PATIENTS AND METHODS: Prostatic utricles were excised laparoscopically in four boys (mean age 6.3 years, range 1.5-17). Cysto-urethroscopy and cannulation of the prostatic utricle was initially undertaken with a cystoscope that was left in situ inside the prostatic utricle to facilitate subsequent identification and mobilization during the laparoscopic procedure. Laparoscopy was conducted via a 5-mm port inserted through a supra-umbilical incision. Two more 5 mm working ports were inserted at the right and left mid-abdomen. The prostatic utricle was easily identified with the guidance of cystoscopic transillumination. Dissection was further facilitated by lifting and counter-traction of the prostatic utricle using the indwelling cystoscope. The prostatic utricle was completely mobilized and divided at its confluence with the urethra using an ultrasonic scalpel. RESULTS: Laparoscopic excision of the prostatic utricle was successful in all four patients. The urethral defect was closed by intracorporeal suturing in three patients while the defect was small enough to be adequately closed by ultrasonic coagulation in one. One patient also had a nonfunctioning dysplastic kidney associated with an ectopic ureter joining into the prostatic utricle, and underwent nephroureterectomy at the same setting. The mean (range) operative duration was 148 (105-225) min. All four patients recovered uneventfully with no complications. CONCLUSIONS: Laparoscopic excision under cystoscopic guidance is effective for symptomatic prostatic utricles, offering a good surgical view and allowing easy dissection in a deep and narrow pelvic cavity.

Adolescent↗
PubMed2001

Effect of process parameters upon the dopamine and lipid peroxidation activity of selected MIG welding fumes as a marker of potential neurotoxicity.

There is growing concern over the neurotoxic effects of chronic occupational exposure to metal fume produced by welding. Elevated iron and manganese levels in the brain have been linked to an increase in lipid peroxidation, dopamine depletion and predisposition to the development of a Parkinson's type condition in advanced cases. Chemical and toxicological analysis of selected welding fumes, generated by model processes, were used in order to evaluate their potential to release solutes that promote oxidation of dopamine and peroxidation of brain lipids in cell free assays. This study compared the effect of shield gas, electrode type and voltage/currect upon the dopamine and brain lipid peroxidation potential of selected welding fume, obtained from metal inert gas (MIG) welding systems. Overall, fume extracts were found to enhance dopamine oxidation and inhibit lipid peroxidation. Significant differences were also found in the oxidising potential of fume generated under differing process conditions; it may therefore be possible to determine the potential neurotoxicity of fumes using this system.

Animals↗
PubMed2001

Invasive disease due to Mucorales: a case report and review of the literature.

OBJECTIVE: To review the mycology, pathogenesis, clinical characteristics, investigations, and treatment modalities of mucormycosis. DATA SOURCES: A local case of mucormycosis; MEDLINE and non-MEDLINE search of the literature. STUDY SELECTION: Key words for the literature search were 'mucormycosis' and 'Mucorales'; all available years of study were reviewed. DATA EXTRACTION: Original articles, review papers, meta-analyses, and relevant book chapters were reviewed. DATA SYNTHESIS: Mucormycosis is a fungal infection that is rare but increasingly recognised in the growing population of immunocompromised patients. It is caused by saprophytic non-septate hyphae of the order Mucorales. The pulmonary and disseminated forms commonly occur in patients with haematological malignancy, especially acute leukaemia and lymphoma, and those receiving treatment with immunosuppressive effects. The rhinocerebral form is more prevalent in patients with diabetes mellitus, particularly those with the complication of diabetic ketoacidosis. The use of amphotericin B combined with surgery remains the mainstay of treatment. The prognosis largely depends on prompt correction of the underlying risk factors. New strategies to combat this life-threatening infection will result from better understanding of its pathogenesis. CONCLUSION: A high index of suspicion is needed, in appropriate clinical settings, to diagnose and aggressively treat this infection in view of the high mortality rate for susceptible patients.

Humans↗
PubMed2000

Cystometry techniques in female infants and children.

Cystometry is increasingly used in children, being an important diagnostic tool for congenital and acquired malformations such as neurogenic bladder, vesicoureteric reflux, urinary tract infection, urge syndrome, nocturnal enuresis, urinary incontinence and anorectal malformations. During cystometry bladder storage and voiding function can be evaluated. Carefully conducted urodynamic studies provide an insight into the pathophysiologic mechanisms involved in voiding dysfunctions that cannot be obtained by any other diagnostic technique. A variety of methods are available, the most sophisticated being filling and voiding cystometry with flowmetry and electromyography (EMG) under fluoroscopy, i.e. videocystometry. A detailed home recording of the frequency and volume of micturition can provide important clues as to the underlying bladder dysfunction, and can significantly aid in the choice of appropriate investigative techniques, as well as in the interpretation of subsequent urodynamic findings. It must be realized that urodynamic studies are invasive procedures and that artifacts may occur and influence the correct interpretation of the results. Infants and children have a different spectrum of bladder dysfunctions from adults and are generally much less cooperative during a urodynamic study. Therefore, cystometric techniques must be significantly modified. This article reviews cystometry techniques and their application in female infants and children. Cystometry/flow/EMG studies with or without fluoroscopy, ambulatory urodynamics and telemetric urodynamic measurement and their application are outlined.

Adult↗
PubMed2000

The use of laparoscopy in the management of adnexal pathologies in children.

BACKGROUND: The authors' experience of using laparoscopy in the management of 23 girls (mean age: 8.9 years; range: 3 months-15 years) with various adnexal pathologies over a 3-year period is reviewed. METHODS: Of the 23 patients, seven were evaluated for congenital gonadal pathologies, 15 presented with abdominal pain and one patient had an antenatally diagnosed adnexal mass. Detailed laparoscopic examination of the pelvic cavity and laparoscopic gonadectomy were successfully performed in all seven patients with congenital gonadal pathologies: mosaic Turner's syndrome (n = 2), gonadal dysgenesis (n = 3) and testicular feminization syndrome (n = 2). Of 15 patients presenting with abdominal pain, 11 had an adnexal mass, two had acute appendicitis and two had pelvic inflammatory disease. RESULTS: Laparoscopic excision of the adnexal masses were successfully performed in 10 of 11 patients. Conversion to open surgery was required in one patient with a huge teratoma. Laparoscopic appendicectomy was successfully performed in both patients with acute appendicitis while diagnostic laparoscopy was the only procedure required in the two patients with pelvic inflammatory disease. Laparoscopy in the infant with an antenatally diagnosed adnexal mass confirmed this to be an omental cyst, which was successfully excised. All patients recovered without complications and good cosmetic result was universally achieved. CONCLUSION: Laparoscopy is safe and effective in both diagnosis and treatment of adnexal pathologies in children.

Adnexa Uteri↗
PubMed2000

Atrophy and intestinal metaplasia one year after cure of H. pylori infection: a prospective, randomized study.

BACKGROUND & AIMS: Helicobacter pylori-infected gastric mucosa evolves through stages of chronic gastritis, intestinal metaplasia (IM), glandular atrophy (GA), and dysplasia before carcinoma develops. We studied if H. pylori eradication would alter the course of premalignant histologic changes in the stomach. METHODS: Volunteers from the Yantai County in China underwent upper endoscopy with biopsy specimens obtained from the antrum and corpus. H. pylori-infected subjects were randomized to receive either a 1-week course of omeprazole, amoxicillin, and clarithromycin (OAC) or placebo. At 1 year, endoscopies with biopsies were repeated. RESULTS: A total of 587 H. pylori-infected subjects were randomized to OAC (n = 295) and placebo (n = 292). At 1 year, H. pylori was eradicated in 226 subjects assigned to OAC. In the placebo group, 245 patients remained H. pylori infected. Analysis of paired samples obtained from the same patients showed that acute and chronic gastritis decreased in both the antrum and corpus after H. pylori eradication (P<0.001) and activity of IM decreased in antrum (P = 0.014). In the H. pylori-infected group, antral biopsy specimens had more pronounced acute gastritis (P = 0.01), whereas corpus specimens showed increased acute and chronic gastritis (P<0.001) and a marginal increase in GA (P = 0.052). When histologic changes were compared between the 2 groups, decrease in acute and chronic gastritis was more frequent after H. pylori eradication (P<0.001) but changes in IM were similar. In the H. pylori-infected group, increase in GA was seen in the corpus (P = 0.01). CONCLUSIONS: At 1 year, H. pylori eradication is beneficial in preventing progression of pathologic changes of the gastric mucosa.

Adult↗
PubMed2000

Laparascopy for definitive diagnosis and treatment of gastrointestinal bleeding of obscure origin in children.

BACKGROUND/PURPOSE: Gastrointestinal bleeding (GIB) in children with no identifiable source found after upper endoscopy and colonoscopy or GIB of obscure origin can pose a great management problem for pediatric surgeons. The recent advent of laparoscopy in children has provided a useful solution. METHODS: The authors reviewed their experience of using laparoscopy in the management of 17 children (13 boys) with GIB of obscure origin over an 8-year period. The mean age was 9.8 years (range, 3 to 17 years). RESULTS: In all patients, upper endoscopy and colonoscopy results did not show a bleeding source. Pertechnetate technetium Tc 99m scan showed positive uptake in 6 patients. Of these, 4 were found on laparoscopy to have a Meckel's diverticulum, 1 had intestinal duplication, and the remaining patient had nodular lymphoid hyperplasia at the terminal ileum. Ten patients had a negative pertechnetate scan. Of these, 3 had a Meckel's diverticulum, 1 had lymphoid hyperplasia, 1 had intestinal duplication, 1 had vascular enteritis, and 4 had normal findings on videolaparoscopy. Pertechnetate scan was not performed in 1 patient and, on laparoscopy, it turned out to be Meckel's diverticulum. Laparoscopic-assisted small bowel resection was performed successfully in all patients with Meckel's diverticulum, intestinal duplication, and nodular hyperplasia. Conversion to open surgery was required in the patient with extensive ileal vascular enteritis secondary to Henoech Scholein purpura. All patients, including the 4 with normal findings on laparoscopy, had made uneventful recovery without further episode of bleeding. CONCLUSION: Laparoscopy is a useful diagnostic as well as therapeutic tool in children with GIB of obscure origin.

Adolescent↗
PubMed2000

Laparoscopic cecostomy for anterior ectopic anus with constipation: a new and technical proposal.

A female patient of 26 years of age with faecal incontinence is presented. The anal opening was anteriorly located just posterior to the vagina. This had resulted in overflow faecal incontinence due to severe chronic constipation. NMR showed a normal musculature of the pelvic floor and sphincter. Since the patient did not agree to surgery, laparoscopic cecostomy was performed for the first time for antegrade rinsing.

Adult↗