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Biomedical subjects

H K Tan

Publications and source records attributed to H K Tan.

At least 55 records · Page 3Linked to original sources
PubMed1996

Spectrum of roller-blading injuries.

We studied 32 patients who presented to the Accident and Emergency Department of Toa Payoh Hospital with injuries sustained while roller-blading (in-line roller skating). This sporting activity carries risk of injuries, often fractures, due to 3 principal mechanisms of injury. The first and main mechanism of injury is that of a forward fall with the arms outstretched as a protective gesture. This is associated with fractures of the distal radius in the majority of cases, although other injuries to the upper limb can occur. The second important mechanism is that of a backward fall with resulting injury to the back of the head. Lastly, the patient may fall sideways, often together with a twisting force to the lower limbs, resulting in ankle sprains and meniscus injuries to the knee. The vast majority of patients are young teenagers who are beginners and had not been properly clad in protective gear. Roller-blading therefore carries a very real risk of sporting injury.

Adolescent↗
PubMed1996

Laparoscopic treatment of ectopic pregnancies--a study of 100 cases.

The experience of laparoscopic treatment of ectopic pregnancies (EPs) in a single institution was studied. Of the 358 cases of EPs treated between January 1990 and December 1995, 100 (27.9%) were treated laparoscopically. The mean age of these patients was 27.6 years and 65% were parous. The preoperative haemoglobin levels ranged between 7.1 and 13.2 g/dl. Haemoperitoneum was present in 83% of these cases and ectopic gestation was sited within the ampullary region in 66% of cases. Of the 100 cases of laparoscopically-treated EPs, 63 were treated by salpingectomy and 37 by linear salpingostomy. The mean operative time was 58 min (range 30 to 90 min). Except one patient with deteriorating vital signs in the immediate postoperative period needing a repeat laparoscopy, no other intra or postoperative morbidity was encountered. Majority of patients were ambulant within 12 hours of surgery and 84% were discharged home within 36 hours of their surgery. Laparoscopic treatment of EPs is safe and effective. Resident specialists in Obstetrics and Gynaecology should be trained in therapeutic laparoscopy early in their career so that more patients with EP can benefit from this minimally invasive surgery.

Adolescent↗
PubMed1995

Detection of p53 gene alteration in renal-cell cancer by micropreparation techniques of tumor specimens.

Alterations in the p53 tumor-suppressor gene have been identified in a variety of human malignancies, including renal-cell cancer. A technique for the isolation of tumor areas from tissue specimens to analyze formalin-fixed and paraffin-embedded tumors and try to avoid a disturbance of the results due to genetic background signal by the presence of tumor-infiltrating lymphocytes, was established. The presence of lymphocytes within the tumor areas investigated was determined by immunohistochemical staining for CD3, a lymphatic surface antigen. Following the isolation of about 100-200 tumor cells, PCR-directed molecular genetic analysis was performed. A highly informative allelotyping approach for the detection of loss of heterozygosity (LOH), determining BstU1- and VNTR-polymorphisms, a 100-bp marker directly localized in intron 1 of the p53 gene, as well as screening for mutations by single-strand conformation polymorphism analysis (SSCP) in exons 5-8, were used. Out of 44 renal-cancer specimens, 33 (75%) were informative for PCR-directed RFLP-analysis. Allelic loss at the p53 gene locus was observed in 10 of 33 cases (33%). No correlation between p53 gene alteration and T-stage, histological grade or histological differentiation could be observed. Alterations in the p53 gene, as detected by a molecular genetic as well as an immunohistochemical approach, were correlated to overall survival. During univariate analysis histological grade, lymphnode status and the presence of distant metastases could be identified as prognostic parameters for overall survival. During multivariate analysis none of the factors investigated remained an independent prognosticator for survival. Summarizing these results, it seems unlikely that p53 gene alterations will serve as an important new factor for the clinical prognosis of patients with renal-cell cancer.

Adult↗
PubMed1995

CHESS classification of bladder-outflow obstruction. A consequence in the discussion of current concepts.

The present discussion on the natural history, growth rate pathophysiology, morbidity, and possible treatment of benign prostatic hyperplasia (BPH) reinforces the need to objectify mechanical BPH-induced obstruction with pressure-flow study. Different methods for the quantification of BPH-induced obstruction exist and the grade of simplification depends on their working mechanism. To review the limitations of the current concepts, 118 BPH patients were selected for computerized pressure-flow data analysis according to quadratic passive urethral resistance relation (PURR) function. The CHESS classification differs from all other concepts due to its two-dimensional character and was developed as a result of the following way of thinking: (1) the whole individual pressure-flow plot is the most accurate basis for further analysis; (2) PURR as the true low-pressure flank of the individual plot is the most favorable definition for mechanical obstruction; (3) PURR quantification requires at least two parameters, footpoint and curvature/slope, with regard to the documented missing significant correlation of both; and (4) a two-parameter-based classification is two-dimensional (CHESS classification).

Aged↗
PubMed1995

p53 overexpression as a prognostic factor for advanced stage bladder cancer.

Overexpression of the TP53 gene protein detected by immunohistochemistry appears to identify those patients with superficial bladder cancer at risk of the development of muscle invasive or metastatic disease. However, the role of p53 overexpression in patients with advanced or metastatic bladder cancer is not yet well established. In the present study, 44 specimens from 44 patients with advanced stage bladder tumours (T2-T4) undergoing radical cystectomy were investigated for different biological and clinical characteristics as possible prognostic factors: sex, age, depth of tumour infiltration, T-stage, histological grade, lymph node status, application of adjuvant systemic chemotherapy (MVAC), proliferative activity (staining for proliferating cell nuclear antigen (PCNA) by monoclonal antibody (PC10) as well as overexpression of the p53 oncoprotein (monoclonal antibody pAb 1801)). After a median follow-up of 22 months, 16 of the 23 patients (70%) with more than 40% of tumour cells stained positively for p53 (Group B) died from tumour progression compared with 7 of the 21 patients (33%) with less than 40% of tumour cells positive for p53. During univariate analysis, p53 overexpression (P = 0.008), staining for PCNA (> or = 80% of cells positive) (P = 0.01) and tumour stage (P = 0.01) were significant prognostic factors for survival, among which p53 overexpression (P = 0.023) as well as T-stage (P = 0.012) remained independent significant predictors during multivariate analysis. Prospective studies are needed to confirm the independent prognostic potential of p53 overexpression in patients with advanced bladder cancer. The availability of more refined prognostic factors should assist decision making regarding the value of more aggressive treatment options, such as adjuvant or neoadjuvant chemotherapy, for prognostically defined subgroups of patients.

Adult↗
PubMed1995

p53 immunohistochemistry as an independent prognostic factor for superficial transitional cell carcinoma of the bladder.

Although patients with superficial bladder cancer (Ta, T1) have a generally good prognosis, those patients who develop muscle-invasive tumours or metastatic disease at recurrence do poorly clinically. In the current study 69 patients undergoing complete transurethral resection for superficial transitional cell cancer of the bladder were investigated for different clinical and biological characteristics as possible prognostic factors: age, sex, performance of instillation therapy and immunohistochemical determination of mutational inactivation of p53 tumour-suppressor gene (monoclonal antibody PAb 1801) as well as immunohistochemical determination of the proliferation rate by staining for PCNA (proliferating cell nuclear antigen) (monoclonal antibody PC 10). After a median follow-up of 45.8 months, 12 of 14 patients (85.7%) with more than 20% of cells positive for p53 had disease progression with muscle-invasive growth compared with only one of 55 patients (1.8%) negative for p53 (P < 0.01, chi 2 test). During univariate analysis histological grade (G1 vs G2) (P = 0.0373), positivity for PCNA (> 60% of cells) (P = 0.0033) and positivity for p53 (P < 0.001) were significant prognostic factors for disease progression (log-rank test), while during multivariate analysis only positivity for p53 was a significant predictor for relapse of bladder cancer (P = 0.0029) (multivariate Cox regression analysis). The immunohistochemical detection of mutations of the p53 gene has been demonstrated to be a reliable, easily performed and thereby widely available technique for the investigation of fresh-frozen or paraffin-embedded tumour specimens. The results demonstrate the important role of the p53 tumour-suppressor gene protein in the development and for the progression of bladder cancer. If the high prognostic value of p53 mutations in superficial bladder cancer is confirmed in larger prospective trials, more aggressive therapeutic strategies could be discussed for patients with p53 mutations in their tumour specimens.

Aged↗
PubMed1995

[Thermotherapy of benign prostatic hyperplasia].

Transurethral microwave thermotherapy (TUMT) differs from hyperthermia in the higher intraprostatic temperatures reached and in the irreversible damage it causes to intraprostatic tissue. Both subjective symptoms and objective data, such as peak flow and residual urine, are influenced differently by TUMT and by sham treatment. As expected, no improvement of the objective data was documented with TUMT, in contrast to transurethral resection of the prostate (TURP), whereas the improvement in subjective symptoms was comparable. The complication rate in terms of morbidity is clearly lower with TUMT than with TURP. TUMT can be performed as an outpatient procedure without a general anaesthetic. TUMT had a specific effect on outflow obstruction, but it was less pronounced than that achieved with TURP. Therefore, TUMT is indicated for patients with typical symptoms of BPH and a mild mechanical obstruction. In this patient group TUMT seems to be the optimal treatment, whereas TURP would constitute "overtreatment" owing to its higher complication rate and the unnecessary tissue resection. At this stage of BPH, TURP is justifiable only with reservations; it should be reserved for BPH with moderate and severe mechanical obstruction.

Follow-Up Studies↗
PubMed1994

An unusual cause of stridor in a neonate.

We report an unusual case of unilateral vocal fold palsy due to intracranial haemorrhage in a neonate with undiagnosed haemophilia A. Bleeding disorders in neonates are briefly discussed and the importance of a systemic investigation of stridor in children is emphasized.

Brain↗
PubMed1993

Effects of disinfecting irreversible hydrocolloid impressions on the resultant gypsum casts: Part I--Surface quality.

This study evaluated the effects of disinfection time (10, 30, and 60 minutes) on the surface quality of stone casts poured against an alginate impression material (Jeltrate). Five antimicrobial agents were tested: Sporicidin spray, sodium hypochlorite, and iodophor for spray; and Sporicidin cold sterilization solution and Cidexplus glutaraldehyde solution for immersion. Impressions, flushed with water and stored for 0, 10, 30, and 60 minutes before pouring, served as untreated controls. On completion of the disinfection treatments, the impressions were rinsed and poured in Velmix stone. The effects on cast surface were evaluated under a stereomicroscope by three experienced raters. A 1-to-4 scoring system was developed to rate the surface quality in terms of smoothness and detail reproduction. Both immersion disinfectants proved to be unacceptable for treating alginate impressions. The mean scores of other disinfectant-time combinations were compared with the use of the Tukey-Kramer method with a 95% confidence interval. The results indicated that treatment time had statistically significant effects on the quality of cast surface in Sporicidin spray, sodium hypochlorite, and untreated control groups but not in the iodophor spray group.

Analysis of Variance↗
PubMed1993

Effects of disinfecting irreversible hydrocolloid impressions on the resultant gypsum casts: Part III--Dimensional changes.

This study evaluated the effect of disinfection time (10, 30 and 60 minutes) on the dimensional changes of stone casts poured against an irreversible hydrocolloid impression material (Jeltrate). Impressions were made of a stainless steel analog of a maxillary arch. The impressions were sprayed with bleach, iodophor, phenol, and water and were stored for designated times before poured in a type IV stone (Vel-mix). The arch width, length, and depth of the vault of the resultant casts were measured by use of a contact measuring device (MicroVal) capable of measuring to 0.0001 mm. Data were analyzed with two-way analysis of variance at the 95% confidence level. Results indicated that disinfection treatment of alginate impressions with surface disinfectants did not cause significant dimensional changes in the resultant stone casts from statistical and clinical points of view.

Analysis of Variance↗
PubMed1993

An alternate procedure for making a remount cast for a locking type removable partial denture.

This procedure describes the use of silicone impression material to make an index that will correctly position a hinge and latch removable partial denture when a remount cast is being made. This procedure ensures that the partial denture can be retrieved with the index without stressing the retentive components of the partial denture and the remaining dentition. Recovering the remount cast is easier because the latch can be released before the impression index is separated from the cast.

Dental Impression Technique↗
PubMed1993

Single potential analysis of cavernous electrical activity. Four years' experience in more than 500 patients with erectile dysfunction.

Since the recent introduction of cavernous electromyography by Gerstenberg and Wagner, a new too for the study of erectile dysfunction in man is available. The refinement of this method, single potential analysis of cavernous electrical activity (SPACE), offers a straightforward approach to the diagnosis of cavernous autonomic neuropathy and smooth muscle myopathy by minimal invasive means. SPACE was done in more than 500 consecutive patients with erectile dysfunction and in 85 normal control subjects. With increasing experience the methodology was refined with respect to the used hardware as well as cut-off frequencies. In normal control subjects, SPACE showed a reproducible regular activity with potentials of low frequency and electrical silence inbetween. The potentials were synchronous throughout the cavernous bodies. In patients with peripheral autonomic denervation, asynchronous potentials with higher frequencies and irregular shape were found. Normal and abnormal potentials were found in patients with upper spinal cord lesions. Recordings obtained with surface electrodes showed similar characteristics when compared with recordings obtained with needle electrodes. Recent studies show that SPACE provides independent information about the autonomic and myogenic intactness of the cavernous tissue. Currently, a computerized expert system and a graded classification for easier interpretation is being developed with first results. We conclude that cavernous electrical activity can be recorded. SPACE is a reproducible diagnostic tool for erectile dysfunction.

Action Potentials↗
PubMed1993

Single potential analysis of cavernous electrical activity (SPACE). Experiences, limitations and perspectives.

Cavernous electromyography was first introduced by Wagner and Gerstenberg in 1989. The authors developed a refined method of cavernous electromyography by means of single potential analysis in introduced this method into clinical Urology as a diagnostic procedure for the evaluation of patients presenting with erectile dysfunction. To date, our experience with single potential analysis of cavernous electrical activity (SPACE) includes more than 500 patients with erectile dysfunction of various etiologies and 92 normal control subjects. Several technical modifications and refinements have been adopted during the last 4 years. In normal control subjects, SPACE shows a regular pattern of activity with long phases of electrical silence at the usual amplification interrupted by synchronous low frequency, high amplitude potentials. In patients with disruption of the peripheral autonomic supply, typical asynchronous potentials with higher frequencies and irregular shape are observed. In complete spinal cord lesions, abnormal as well as normal electrical activity is found. In patients with a long history of insulin-dependent diabetes and presumably cavernous smooth muscle degeneration, SPACE recordings show irregular potentials with low amplitudes and slow depolarization speed. Synchronization of electrical activity is usually absent. Recent studies on patients with venous leakage show that SPACE provides independent clinical information about the cavernous smooth musculature. The recording of cavernous electrical activity is possible and reproductible. In the future, a new software for one-line date processing, storage and interpretation of SPACE signals will be available.

Action Potentials↗
PubMed1991

Metabolic evaluation in stone patients in relation to extracorporeal shock wave lithotripsy treatment.

No information exists in the literature about the optimal time for metabolic evaluation of stone patients in relation to extracorporeal shock wave lithotripsy (ESWL) treatment. It is uncertain whether the presence of a stone, ESWL treatment itself or subsequent colic episodes influence the urinary risk factors. A prospective study was performed to determine the optimal period for metabolic evaluation. Two 24-hour urine samples were collected directly before, and 1 week, 1 month and 3 months after therapy in an outpatient setting and tested for total volume, calcium, uric acid, oxalate, citrate and creatinine levels. A total of 66 patients was available for evaluation. Comparison of the 4 subsequent collecting periods showed no statistically significant differences in the excretion values. Also, in subgroups of patients with colic (16%), on a calcium oxalate restricted diet (12%) and with repeated treatments within 3 months (33%) no differences were noted. This means that the presence of a stone, treatment itself or subsequent colic episodes have no adverse effect on the urinary risk factors. For practical reasons metabolic evaluation directly before ESWL treatment seems most attractive. In the pre-ESWL samples hypercalciuria (greater than 7.5 mmol./24 hours), hyperuricosuria (greater than 6 mmol./24 hours), hyperoxaluria (greater than 0.5 mmol./24 hours) and hypocitraturia (less than 2 mmol./24 hours) were found in 31%, 12%, 18% and 27%, respectively, of the patients. It is concluded that metabolic evaluation before ESWL is practical, applicable and reliable.

Adolescent↗
PubMed1989

Adaptation of a visible light-cured denture base material.

The Triad light-cured resin system appears to have potential for making processed record bases for special patients. The close adaptation of this material to the dental cast often results in internal voids and defects. These defects are greatly reduced when a dry cast is used instead of one with a high moisture content. Vacuum-assisted adaptation using a sheet of rubber dam in connection with a vacuum adaptor also results in an improved internal surface. Finger pressure alone is not a dependable method of adaptation.

Composite Resins↗
PubMed1987

Reaction of chlorine dioxide with amino acids and peptides: kinetics and mutagenicity studies.

Chlorine dioxide (ClO2) is currently being considered as an alternate to chlorine as a disinfectant for water treatment. Many organic compounds present in water and food treated with ClO2 are subject to oxidation. 21 amino acids and 3 peptides (L-aspartyl-L-phenylalanine methyl ester (aspartame), L-glycyl-L-tryptophan and L-tryptophylglycine) were studied for their reactivity with ClO2. Chlorine dioxide reacted only with 6 amino acids in 0.1 M sodium phosphate buffer, pH 6.0. The reaction with cysteine, tryptophan and tyrosine was too rapid to be monitored either iodometrically or spectrophotometrically. The reaction with histidine, hydroxyproline and proline was found to be pseudo-first order. ClO2 readily reacted with L-glycyl-L-tryptophan and L-tryptophylglycine but not with aspartame. Mutagenicity studies with the Salmonella microsome assay of the reaction mixtures of ClO2 with those 6 reactive amino acids and the 3 peptides indicated that the reaction products of the 3 peptides, hydroxyproline, and tyrosine exerted mutagenic activity toward both tester strains of TA98 and TA100 in the presence and absence of rat-liver S9 mix.

Amino Acids↗
PubMed1980

Effect of magnesium deficiency on erythrocyte aging in rats.

Rats placed on a magnesium-deficient diet show decreased erythrocyte magnesium concentration, shortened erythrocyte survival, and erythrocyte membrane ultrastructure defects and become progressively anemic. Whether these pathologic processes are due to abnormal erythropoiesis or occur in the peripheral circulation is unknown. In the present study, magnesium and hemoglobin concentrations, reticulocyte count, erythrocyte pyrophosphatase, and pyruvate kinase activities were determined at weekly intervals for 6 weeks in whole blood and age-dependent erythrocyte fractions isolated from inbred Fisher rats fed a diet deficient in magnesium or the same diet with added magnesium. Freeze-fracture electron microscopic examinations were performed on age-dependent erythrocyte fractions to evaluate the membrane defect. The youngest red cells from magnesium-deficient rats were similar to those of control animals with respect to erythrocyte magnesium concentrations, pyrophosphatase activities, and membrane morphology. The older erythrocyte fractions from magnesium-deficient rats showed significant decreases in magnesium concentrations, pyrophosphatase activity, and the presence of membrane abnormalities. Thus, new erythrocytes produced in magnesium-deficient rats appear to be normal but rapidly develop biochemical and morphologic abnormalities with aging in a magnesium-deficient plasma environment.

Animals↗