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Biomedical subjects

A Ng

Publications and source records attributed to A Ng.

At least 19 recordsLinked to original sources
PubMed1995

Intracoronary stenting in the treatment of acute or threatened closure in angiographically small coronary arteries (< 3.0 mm) complicating percutaneous transluminal coronary angioplasty.

The effect of the Flex-Stent on immediate and long-term angiographic and clinical results for acute and threatened closure was evaluated in 42 consecutive patients with coronary arterial segments < 3.0 mm in diameter after percutaneous transluminal coronary angioplasty (PTCA). Forty-two consecutive patients were treated with Flex-Stent (2.0 or 2.5 mm) for acute or threatened closure complicating PTCA. Ten patients (24%) had acute closure and 32 (76%) had threatened closure with a residual luminal stenosis of > 50%. Successful stent deployment was achieved in 40 patients (95%) with a primary clinical success rate of 90% (freedom from myocardial infarction, coronary artery surgery, and death). In-hospital complications occurred in 5 patients (some patients fell into more than one category): 3 (7.1%) had coronary bypass surgery, 1 (2.4%) had acute stent thrombosis, 1 (2.4%) had subacute stent thrombosis, 2 (4.8%) had myocardial infarction, and 1 (2.4%) had dextran allergy. There was no hospital death. Clinical follow-up was complete at a mean of 14.8 +/- 7.6 months, and recurrence of angina was noted in 20 of 38 eligible patients (53%). Angiographic restenosis was found in 19 of 29 patients (66%) (76.3% of eligible patients) on follow-up angiography (mean 5.9 +/- 4.6 months). Fourteen patients (74%) underwent successful repeat PTCA at the stented site, 4 of 38 patients (11%) had bypass surgery. Intracoronary stenting in the treatment of acute or threatened closure in arteries < 3.0 mm is effective in improving the acute clinical outcome and is a viable nonsurgical alternative for this subset of patients.

Acute Disease↗
PubMed1994

Radiofrequency catheter ablation of accessory pathways: the initial experience in Singapore.

Radiofrequency catheter ablation is a recently introduced non-surgical technique for curing patients with arrhythmias as a result of conduction over an accessory pathway in patients with the Wolff-Parkinson-White (WPW) syndrome. We present our initial experience with this technique. There were 90 patients (61 males, 29 females) with a mean age of 37 +/- 14.4 years (range: 13-73 years). All except one were symptomatic with a mean duration of symptoms of 10 +/- 9.4 years (range: 0.1-40 years). The indications for catheter ablation were failure of drug therapy in 71, patient's preference in 10, increased risk of sudden death in 6 and almost incessant tachycardia in 3. The radiofrequency ablation was performed using a deflectable 7 French 4 mm tip electrode catheter positioned at the mitral or tricuspid annulus. The site of the accessory pathway was localised by electrophysiological study and radiofrequency energy applied via the tip of the catheter. There were 100 accessory pathways as 10 (10%) patients had multiple accessory pathways. There were 69 (69%) left free wall, 11 (11%) posteroseptal, 13 (13%) right free wall, 6 (6%) right anteroseptal accessory pathways and one (1%) midseptal accessory pathways. Ninety-six percent (96%) of the accessory pathways were successfully ablated on the first ablation. Two of the 4 initially unsuccessful ablations were successfully reablated, giving an overall success rate of 98%. There were no major complications. In conclusion, radiofrequency catheter ablation of accessory pathways is highly successful and safe and provides a definitive cure for patients with the WPW syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Intra-operative blood loss during elective lower segment caesarean section.

OBJECTIVE: To measure intra-operative blood loss at elective lower segment caesarean section and to compare estimated with measured blood loss. DESIGN: Prospective observational study. Blood loss was measured in patients who underwent lower segment caesarean section in the course of routine hospital activity. SETTING: Tsan Yuk Hospital (Hong Kong), which is affiliated to the University of Hong Kong, 1990-1991. SUBJECTS: Forty women (mean age 29 years) with singleton pregnancies (mean gestation 38 weeks) delivered by elective lower segment caesarean section under general anaesthesia (mean birthweight 3177 g). MAIN OUTCOME MEASURE: Intra-operative blood loss measured by the alkaline haematin method (intra-assay co-efficient of variation 2.2%). RESULTS: The mean measured blood loss was 487 ml (SE 40, range 164-1438). The mean estimated blood loss was 425 ml (SE 31) range 100-1300; mode 400). Observer error in estimating blood loss was higher if measured blood loss greater than 600 ml. One patient received a blood transfusion and another had a post-operative haemoglobin level less than 10.0 g/dl. CONCLUSION: Blood loss at elective lower segment caesarean section was usually less than 500 ml and was estimated with reasonable accuracy. However, there was a tendency to under-estimate blood loss when the measured loss exceeded 600 ml.

Adult↗
PubMed1991

Determination of disulfide bond pairs and stability in recombinant tick anticoagulant peptide.

Tick anticoagulant peptide (TAP) is a potent and selective inhibitor of blood coagulation factor Xa (Waxman, L., Smith, D.E., Arcuri, K.E., and Vlasuk, G.P. (1990) Science 248, 593-596). The 60-amino acid sequence of TAP shows limited homology to Kunitz-type inhibitors, including cysteines at positions 5, 15, 33, 39, 55, and 59. For detailed biochemical and pharmacological studies, a recombinant version of TAP (rTAP) has been produced in yeast. To determine the arrangement of the disulfide bonds, rTAP was cleaved with trypsin and chymotrypsin and the purified peptides sequenced using a gas-phase sequenator. The positions of the disulfide bonds were assigned by identifying the cycle(s) at which di-phenylthiohydan-toin-cystine was released. The specific disulfide bridges, Cys-5 to Cys-59, Cys-15 to Cys-39, and Cys-33 to Cys-55, are analogous to those in the prototype Kunitz-type inhibitor, bovine pancreatic trypsin inhibitor (BPTI). While treatment of BPTI with dithiothreitol rapidly and specifically reduced one disulfide bond, the reduction of disulfide bonds in rTAP proceeded at a slower rate and appeared to be nonspecific, reaching a maximum of two disulfides reduced. Reduced rTAP derivatized with either iodoacetic acid or iodoacetamide lost 59% of its inhibitory activity. In contrast, BPTI alkylated with iodoacetic acid inhibited trypsin half as well as the iodoacetamide derivative. Although the arrangement of disulfides in the two inhibitors is the same, their susceptibility to reduction is markedly different.

Amino Acid Sequence↗
PubMed1990

Nonfunctioning paraganglioma of the liver, gallbladder and common bile duct.

Paragangliomas are rare extra-adrenal neoplasms of neural crest origin. Although most of these lesions are of retroperitoneal origin, paragangliomas have been reported at a host of remote sites, including the urinary bladder, larynx, orbit and lung. In our review of the literature, we discovered only solitary case reports of such neoplasms involving the gallbladder and hepatic duct. We report a case of paraganglioma simultaneously involving the liver, gallbladder and common bile duct, as well as celiac and portal lymph nodes. Our findings add paraganglioma to the list of differential diagnoses for hypervascular portacaval space lesions. Furthermore, the radiographic appearance of this unusual tumor may be sufficiently distinctive to suggest the correct histologic diagnosis preoperatively.

Cholangiopancreatography, Endoscopic Retrograde↗
PubMed1990

Six-month combination chemotherapy for cervical tuberculous lymphadenitis.

A prospective study was undertaken to determine the effectiveness of a 6-month four-drug regimen in the treatment of 123 patients with cervical tuberculous lymphadenitis. The results showed that the disease was satisfactorily controlled with residual lymph nodes which did not necessitate further chemotherapy in 14.6% of patients at 3 years follow-up. Recurrence requiring further chemotherapy occurred in 3.3% of patients between 9 and 28 months. Wound sinuses occurred in 3.3% of patients and all healed with conservative treatment. The culture results and numbers of lymph nodes at presentation had no effect on outcome at 3 years. An excisional procedure was associated with a lower incidence of residual lymph nodes than an incisional biopsy. Minor gastrointestinal upset from drug treatment was common, but only 2.4% of patients needed a change of regimen. Six months of combination chemotherapy is adequate for the treatment of the disease.

Adolescent↗
PubMed1989

Malignant fibrous histiocytoma of the pancreas.

A case of fibrous histiocytoma of low grade malignancy arising from the uncinate lobe of the pancreas is reported. This is an unusual site for these extremely rare tumours. Survival up to 4 years has been achieved in our patient following surgical resection.

Aged↗
PubMed1989

The validity of a portable accelerometer for estimating energy expenditure in bicycle riding.

The purpose of the investigation was to determine the validity of a portable vertical accelerometer and a Large-Scale Integrated Motor Activity Monitor (LSI) for estimating energy expenditure in riding a bicycle at various velocities. Instrument placement was either at the knee or ankle. Energy consumption, i.e. oxygen consumption (VO2) was determined during bicycle rides after steady state metabolism was reached. Standard errors of estimate were used to express the accuracy of estimating VO2 from accelerometer or LSI recordings. The reliability of the vertical accelerometer was found to be satisfactory. The vertical accelerometer was also effective for estimating VO2 in bicycling (standard errors of estimate = 3.3 to 4.4 ml.kg-1.min-1). The accuracy of the LSI was not as good; the standard errors of estimate being = 5.9 to 8.5 ml.kg-1.min-1.

Adolescent↗
PubMed1989

Ultrasound guided drainage of pleural fluid.

Ultrasound guided drainage has been reported as a highly successful drainage procedure. Computed tomography (CT) and fluoroscopy also have been cited as favorable imaging modalities for the treatment of pleural effusion. With its extreme sensitivity to fluid collections and rapid and accurate localization of fluid, real-time ultrasound has become the primary imaging modality for the interventional drainage of pleural fluid. This is a retrospective study of patients with radiographically suspected pleural effusion, using ultrasonic scanning for possible drainage. A special bedside drainage technique in critically ill patients also is described.

Drainage↗
PubMed1988

Tuberculous cervical abscess: comparing the results of total excision against simple incision and drainage.

In 40 patients with tuberculous cervical abscesses a prospective study was undertaken to determine the results of surgical treatment by either total excision or incision and drainage, together with 6 months of chemotherapy in both groups. While both procedures were well tolerated, the results showed that 17/22 (77 per cent) of those having a simple drainage procedure required a second operation to excise the residual infected lymph glands because of persistent sinus discharge, recurrent abscesses or enlarging lymphadenopathy. In contrast, 17/18 (94 per cent) of those having total excision as the primary procedure had no local ward problem afterwards. Most of the patients remained asymptomatic after completion of the chemotherapy but small painless lymph nodes might still be palpable during follow-up at 2 years.

Abscess↗
PubMed1987

Protection of neonates from transfusion-associated AIDS by the use of CMV-seronegative blood before availability of specific serologic tests for HTLV-III (HIV).

Concern over possible acquisition of acquired immune deficiency syndrome (AIDS) following blood transfusions has caused considerable anxiety for hospitalized patients who require blood products as part of their medical management. This anxiety is heightened due to the long incubation period between exposure and the development of symptoms of AIDS. Sick preterm neonates frequently require multiple blood transfusions for replacement of blood loss as a result of frequent blood sampling associated with laboratory testing. Availability of HTLV-III (HIV [human immunodeficiency virus]) antibody testing has markedly improved the safety of blood products. However, parents of neonates who received blood before routine HTLV-III (HIV) antibody testing have expressed their concern that their children may have received "tainted" blood. Since preterm neonates are also at risk for serious disease due to post-transfusion cytomegalovirus (CMV) infection, many institutions administer CMV-seronegative blood products to their neonatal patients in order to prevent infection with CMV. Information obtained from recent HTLV-III (HIV) and CMV antibody screening by the American Red Cross Blood Services Central Ohio Region suggests that the use of CMV-seronegative blood in neonates offered protection against transfusion-associated AIDS. This information may allay the fears of parents of newborns or other populations that routinely received CMV-seronegative blood before availability of HTLV-III (HIV) antibody testing.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Hyperexcitability of cutaneous afferents during the supernormal period. Relevance to paraesthesiae.

The excitability of cutaneous afferents in the median nerve of 20 normal human subjects was investigated using a supramaximal conditioning stimulus and a submaximal test stimulus that produced an afferent volley of 20 to 40% of maximum. The intensity of the test stimuli was 1.1 to 1.25 times threshold for the first recruited axons (defined as a compound action potential of approximately 0.5 microV). The amplitude of the test volley did not reach the control amplitude until conditioning-test intervals of 3.4 ms. This was followed by a period of increased axonal excitability which reached a peak at intervals of 5 to 8 ms and declined gradually into a late phase of subnormality at 15 to 20 ms. The amplitude of the submaximal test potential was potentiated by, on average, 47% (range 9-146%) during the supernormal period. There were no significant changes in latency. The time course and the degree of potentiation were reproducible in the same subject on separate occasions. When the limb was cooled, the latency of the onset of supernormality was increased and the degree of supernormality was decreased and ultimately abolished. There was an inverse relationship between the degree of potentiation and the size of the test volley. High-frequency repetitive stimulation of the digital nerves for 10 min modified axonal excitability and produced spontaneous paraesthesiae that lasted for 20 min after the stimulation. Following this prolonged stimulus train, single submaximal stimuli evoked larger cutaneous afferent potentials than before the train, and the extent of the potentiation during the supernormal period was increased. It is concluded that prolonged repetitive stimulation of cutaneous afferents has two effects, one on axonal threshold, the second on the supernormal period. It is suggested that, in this experimental model, paraesthesiae result from ectopic impulses generated when axonal excitability is highest, namely at the peak of the supernormal period.

Adult↗
PubMed1987

Salivary cortisol for monitoring adrenal activity during marathon runs.

In non-elite male runners (n = 8), changes in adrenal activity were monitored by measurement of salivary cortisol in samples collected at 4-mile intervals during marathon runs. These changes were compared with those in similarly timed samples collected on rest days. Immediately prior to the Cardiff marathon, at 09.00 h, mean salivary cortisol concentrations (21.5 nmol/l) were higher than those in similarly timed rest day samples (14.9 nmol/l). Cortisol concentrations increased during the marathon, and although values at 25 miles were high (79.4 nmol/l), maximum values (87.9 nmol/l) were observed in samples collected 30 min after completion of the run. Some Cardiff marathon runners also participated in the Bristol marathon (n = 4) and a non-competitive event (n = 3). The changing pattern in secretory activity was similar in all events. The easy collection of saliva without cessation of exercise is ideal for monitoring the hormonal response to exercise.

Adrenal Cortex↗
PubMed1986

Loss of viability and induction of DNA damage in human leukemic myeloblasts and lymphocytes by m-AMSA.

The effects of m-AMSA on in vitro viability and on the induction of DNA damage were examined in low-growth-fraction cell populations of human leukemic myeloblasts and normal lymphocytes. A significant individual variation in the drug-induced reduction of in vitro viability was observed in studies with five selected leukemic patients. The concentration of m-AMSA required to reduce viability by 50% within 48 h ranged from 0.25 microM to in excess of 5.0 microM for the leukemic myeloblasts as against about 2.0 microM for the samples of normal lymphocytes. Alkaline elution studies showed that m-AMSA induced protein-associated DNA strand breaks (PADB) in both myeloblasts and lymphocytes. Depending upon the m-AMSA concentration, there was a 4- to 9-fold difference in the level of PADBs induced by a given drug concentration in the myeloblasts of eight patients studied. The level of PADBs was saturable with respect to both drug concentration (5-10 microM) and exposure time (45-10 microM). The PADBs were repaired rapidly in all the lymphocyte and myeloblast samples studied, with over 90% of this DNA damage being repaired within 45 min after resuspension of the cells in drug-free medium. These studies of m-AMSA in low-growth-fraction samples of human lymphocytes and myeloblasts show both similarities and differences in the action of this drug compared with previously published studies using the high-growth-fraction mouse L1210 system.

Aminoacridines↗
PubMed1986

Centrifugal cytology: a new technique for urine cytology.

A new technique, centrifugal cytology, appears to have a high recovery rate of malignant cells from voided urine specimens resulting in a high probability of early disease detection and should be considered a good supplement to cytoscopic evaluation of high-risk populations.

Centrifugation↗
PubMed1986

A semi-quantitative assessment of the histopathology of oral lichen planus.

In a retrospective study of 112 cases, an attempt has been made to further delineate the histopathological parameters which are useful in making a diagnosis of oral lichen planus. The results of this study show that mononuclear infiltration beneath and adjacent to the epithelium, parakeratosis and degeneration of the basal layer of the epithelium were consistent features. Linear regression analyses of the parameters studied provided partial support for a cell-mediated immune mechanism.

Adult↗
PubMed1985

Evaluation of the posterior approach for subfascial ligation of perforating veins.

A posterior midline incision was used for subfascial ligation of incompetent medial and lateral perforating veins in 32 patients. The indications for surgery were recurrent ulceration in 31 limbs and stasis dermatitis in six limbs. Incompetent perforating veins were found on the medial aspect of the leg in all cases and lateral aspect of the leg in 69% of cases. Postoperative mild skin edge necrosis and wound infection each occurred in seven limbs. Follow-up of these patients from 5 months to 4 years showed that there were 11 recurrent ulceration, 10 mild leg oedema and three recurrent varices. This operation was successful in preventing further leg ulceration in 70% of patients, and a further 21.6% had benefited from the operation in that ulcers which recurred in the follow-up period were small in size compared to the original ones, and healed quickly.

Adult↗