Biomedical subjects
Publications and source records attributed to A C Leung.
130 hospital-discharged elderly patients received our comprehensive assessment by using a Chinese Minimum Data Set-Home Care (MDS-HC). Our case manager developed and implemented care plans with reference to the computer-generated Clients Assessment Protocols. Results showed that the MDS-HC was sensitive to identify elderly persons' holistic needs, and helpful in formulating all-inclusive care plans.
Leydig cell tumors of the testis are the underlying cause in about 10% of the cases of precocious puberty in boys. Leydig cell hyperplasia is a less well-characterized cause, with an undocumented frequency. We describe a boy with precocious puberty associated with ipsilateral testicular enlargement and focal Leydig cell hyperplasia with spermatogenesis limited to the local adjacent testicular tissue.
A group of 43 patients requiring tooth extraction after radiotherapy for nasopharyngeal carcinoma (NPC) was studied retrospectively to determine the incidence of post-extraction complications. It was found that because of the method used in the delivery of radiation, extraction of maxillary posterior teeth resulted in the greatest risk of complications (28.9 per cent), including a 10.5 per cent risk of osteoradionecrosis (ORN). Based on the findings, a protocol was established for the dental care of such patients. It was concluded that when extraction of maxillary posterior teeth was necessary, prophylactic antibiotics were not sufficient to prevent the complication of delayed healing. The risk of ORN was 10.5 per cent within the field of maximal radiation dose. Hyperbaric oxygen may be the better choice of preventive measures. However, in view of the low risk of ORN, wholesale prescription of hyperbaric oxygen therapy may not be indicated. An additional patient who had tooth extraction two weeks prior to radiotherapy was included to show that if adequate time for wound healing was not allowed, ORN could develop.
An ultrasensitive HPLC method has been developed for measuring NADP+, NADPH, NAD+, and NADH. A simple, rapid reaction of the oxidized nucleotides with cyanide in basic solution leads to two stable fluorescent products and allows all four nucleotides to be separated and quantitated on one chromatogram. Furthermore, only one extraction is needed, rather than prior procedures which require one acid extraction (for oxidized species) and one basic extraction (for reduced species). This method is particularly useful in quantitating pyridine dinucleotides in rodent brain, where no current method is adequate to quantitate the small amounts contained in various brain regions. The assay is sensitive enough to measure individual brain regions down to 10 mg of tissue. Due to the involvement of NAD(P)H enzymatic systems in combating oxidative stress it is important to be able to assess levels regionally in brain diseases.
A retrospective study was carried out in 100 adult patients with advanced malignant disease. They were given subcutaneous continuous infusions of medication for symptom relief. The drugs were administered through a butterfly needle inserted subcutaneously in the anterior chest wall using a battery-operated infusion pump. The indications for using this technique were inability to swallow due to deteriorating general condition, oesophageal obstruction, intestinal obstruction, severe nausea and vomiting, terminal dyspnoea and poor pain control with oral opiates. All patients received morphine; other drugs administered through the syringe driver included hyoscine, metoclopramide, cyclizine, dexamethasone and midazolam. Ninety-four patients continued subcutaneous infusion until death. The mean duration of treatment was 9.1 days. The treatment was well tolerated by the patients and controlled their symptoms satisfactorily in the great majority. The use of continuous subcutaneous infusion via a syringe driver gives good symptom control. In the last days of life when the patients have difficulty tolerating oral medication, continuous subcutaneous infusion is a superior alternative to frequent intermittent parenteral injections.
MPP+ is redox active in the presence of cytochrome P450 reductase and induces the formation of O2.- and HO(.). In this study, we report the redox cycling capability of MPP+ with additional enzymes and with UV photolysis detected through ESR techniques. The treatment of MPP+ with UV light resulted in the production of HO. trapped as a spin adduct. Two of the enzymes examined in this study, xanthine oxidase and aldehyde dehydrogenase, produced O2.- in the presence of substrate. However, when MPP+ was added to the incubations, the radical trapped by DMPO was HO(.). This indicates that MPP+ redox cycles in the presence of these two enzymes or UV light, which produces HO.. Our data also suggest that MPP+ is reduced by lipoamide dehydrogenase. MPP+ stimulated the oxidation of reduced nicotinamide adenine dinucleotide (NADH) by the enzyme at concentrations between 2 mM and 8 mM of MPP+. Higher concentrations of MPP+ inhibited lipoamide dehydrogenase. MPP+ appears to be redox active with a number of redox enzymes. The mechanism involved may be hydride transfer from the enzymes to MPP+, rather than a direct single-electron reduction.
MPP+ has been reported to inhibit reduced nicotinamide adenine dinucleotide (NADH) dehydrogenase in mitochondria, which results in the formation of O2(.-). The current report demonstrates that H2O2 and HO. are also products of MPP+ interaction with NADH dehydrogenase. It is possible that MPP. formation precedes the formation of some of these active oxygen species. Reducing equivalents for radical formation come from NADH. MPP+ may be capable of interacting with submitochondrial particles at a site other than the rotenone site, which results in some formation of oxygen radicals. Plasma amine oxidase incubations with MPDP+ resulted in O2.- H2O2, and perhaps HO. formation. This is probably due to MPP. formation from the oxidation of MPDP+. This study presents new findings that indicate the potential importance of oxygen radical formation in mitochondria during MPTP toxicity.
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Ninety-one Chinese in the community, aged between 18 and 45, with mental health problems ranging from mild to moderate degree, were treated by cognitive behavioural group therapy (CBGT) for a period of 3 months. All subjects were assessed on multiple measures at 4 time points: screening, pre-treatment (after 3 months), post-treatment and at 3-month follow-up. Attendance was good. A standard practice manual was developed to ensure consistent treatment by 2 group workers. After controlling for the placebo effect in the waiting period, treatment effect was demonstrated which was sustained after a three month period. The all-round improvement included a decrease in psychiatric symptoms, improvement in self-assessment, better and more social activities and being more able to cope with problems. In terms of psychiatric diagnosis, depressed subjects gained the most benefit and personality disorder subjects the least. Parents seemed to benefit more than non-parents.
Sclerosing peritonitis (SP) is an uncommon but serious complication of CAPD with various suggested etiologies. We have documented 14 cases of SP in 18 patients who had used chlorhexidine in alcohol (ChA) in the connection procedure for CAPD. Thirteen died. Nine of the 14 patients had been transferred to hemodialysis or renal transplantation, yet all still developed symptoms of SP within a few months after transfer - even the 5 who were originally asymptomatic. The main symptoms of SP were peritoneal ultrafiltration failure, exudative bloody ascites and intestinal obstruction. They presented at around 5 years (30-80 months) after commencement of CAPD. Most deaths were related to intestinal obstruction. Four other patients with a comparable duration of ChA exposure were continued on CAPD with the Travenol Spike System (TSS), without further exposure to ChA. They were all asymptomatic of SP after 9-12 months. Comparing the 2 groups of asymptomatic patients, those transferred to TSS had a much better outcome after 9 months than those transferred to HD or renal transplantation (P = 0.0476). We suggest that ChA is the main cause of SP in our patients and that continuing CAPD without further exposure to ChA is a better alternative than stopping CAPD to prevent the progression of SP.
Although much is now known with regard to the processes of mammalian mitochondrial gene expression, relatively little is known concerning the quantitative regulation of this pathway in response to hormones or other physiological stimuli. In this paper the potential coupling of mitochondrial metabolism to mitochondrial protein synthesis was investigated and the concentration of nucleotides and substrates for optimal translation in isolated rat heart mitochondria was determined. It was demonstrated that optimal isolated heart mitochondrial protein synthesis required the presence of an oxidizable substrate. Of the substrates tested, glutamate (20 mM) supported translation best followed by malate, succinate, and alpha-ketoglutarate, whereas pyruvate supported synthesis poorly. Unlike other recent mammalian mitochondrial systems, the presence of an oxidizable substrate was required for translation even in the presence of medium ATP and an exogenous energy-generating system. Mitochondrial translation also required the presence of adenine nucleotide that could be added as ADP or ATP; however, ATP added above 0.5 mM became progressively inhibitory. As a result, synthesis was supported significantly better by ATP synthesized by the system from added ADP, than by ATP added directly to the system. However, if the phosphorylation of ADP was prevented by limiting the phosphate concentration, ADP itself strongly inhibited mitochondrial protein synthesis. This inhibition appeared to be closely related to the energy charge of the system rather than to absolute levels of ADP, indicating for the first time that mitochondrial translation, like its cytoplasmic counterpart is regulated by energy charge. Last, this system did not require the inhibition of guanine nucleotide or exogenous energy-generating systems.(ABSTRACT TRUNCATED AT 250 WORDS)
The goal of this paper was to determine the effects of 3,5,3'-triiodothyronine (T3)-thyroxine-induced cardiac hypertrophy on the rates of synthesis of mitochondrial proteins by both the cytoplasmic and mitochondrial protein synthesis systems and to compare the results with total protein synthesis and cardiac enlargement. Daily injections of T3-thyroxine in the rat resulted in a 25% increase in the growth of the ventricle compared with controls. The cytoplasmic synthesis of both mitochondrial and total proteins as measured in the isolated perfused heart was stimulated by T3-thyroxine injection to a peak of 155 and 146%, respectively, of vehicle-injected controls after 3 days of hormone treatment. This peak was followed by a gradual decline in stimulation in total protein synthesis to 132% of control by 9 days of injection, whereas the decline in stimulation of cytoplasmic synthesis of mitochondrial proteins was significantly steeper, falling to 119% of vehicle control. The rate of protein synthesis within the mitochondrial compartment was also measured during the time course of T3-thyroxine-induced hypertrophy. These rates were measured in an isolated intact heart mitochondrial protein synthesis system described and characterized in the companion papers [E. E. McKee, B. L. Grier, G. S. Thompson, and J. D. McCourt. Am. J. Physiol. 258 (Endocrinol. Metab. 21): E492-E502, 1990; and E. E. McKee, B. L. Grier, G. S. Thompson, A. C. F. Leung, and J. D. McCourt. Am. J. Physiol. 258 (Endocrinol. Metab. 21): E503-E510, 1990]. Rates of mitochondrial protein synthesis were dramatically stimulated by T3-thyroxine injection.(ABSTRACT TRUNCATED AT 250 WORDS)
Sclerosing peritonitis (SP) is an uncommon but serious complication of CAPD with various suggested etiology. We have documented 14 cases of SP in 18 CAPD patients using chlorhexidine in alcohol (ChA) in the connection procedure; 13 died. Nine of the 14 patients had been transferred to haemodialysis or renal transplantation, yet all still developed symptoms of SP within a few months after transfer even though 5 of them were originally asymptomatic. The main symptoms of SP were peritoneal ultrafiltration failure, exudative bloody ascites and intestinal obstruction. They present at around 5 years (30-80 months) after commencement of CAPD. Four other patients with a comparable duration of ChA exposure were continued on CAPD with a Travenol Spike System (TSS) without further exposure to ChA. They were all asymptomatic of SP after 9-12 months. Comparing the 2 groups of asymptomatic patients at 9 months after transfer, those transferred to TSS have a much better outcome than those transferred to HD or renal transplantation (P = 0.0476). We concluded that ChA is the main cause of SP in our patients and continuing CAPD without further exposure to ChA is a better alternative than stopping CAPD in preventing the progression of SP.
Primary IgA nephropathy is generally considered an indolent disease, but progression to chronic renal failure is not uncommon, and a rapidly progressive course is observed in some cases, especially when extensive fibrocellular crescents are present. The therapeutic benefit of immunosuppression and plasma exchange remains controversial. We described two patients with primary IgA nephropathy and rapidly progressive renal failure. Both patients showed extensive glomerulosclerosis and crescent formation in their renal biopsies. Corticosteroid and immunosuppressive therapy failed to control the progression of the disease, and plasma exchanges were performed. In both cases, the serum creatinine and creatinine clearance initially improved with plasma exchange and the rapid progression of renal failure was apparently halted. In one patient, the serum creatinine rose when treatment was discontinued and fell again when plasma exchange was recommenced. Nevertheless, the long-term benefit of plasma exchange in crescentic IgA nephropathy was unsatisfactory as the renal function continued to deteriorate in the following 12 months despite an initial stabilization.
The practice of multiple use of hemofilter was examined on 16 patients in our dialysis center. The hemofilters were cleaned by reverse ultrafiltration using positive pressure in the blood and filtrate compartment of the hemofilter. Ten hemofilters used for continuous arteriovenous hemofiltration, 6 hemofilters used for pump-assisted acute hemofiltration and seventy hemofilters used for chronic maintenance hemofiltration were studied for the clearances of urea nitrogen and creatinine and sieving coefficients of albumin and electrolytes. Hemofilters were successfully reused in pump-assisted acute hemofiltration and chronic hemofiltration. In continuous arteriovenous hemofiltration, hemofilters could not be reused mainly because of clotting of fibers. The practice is safe, efficient and highly cost-saving.
We report a case of polyarteritis in a 54 year old woman who presented with marked thrombocytosis and acute blindness in one eye secondary to central retinal vein thrombosis. She also developed bilateral pulmonary infiltrates and renal failure. The diagnosis was confirmed by histological changes in the renal biopsy. Treatment with immunosuppressives, plasma exchange and antiplatelet drugs led to rapid clinical improvement and recovery of renal function and prevented further thromboembolic episodes. Plasma exchange and antiplatelet drugs should be considered in polyarteritis group of systemic vasculitis especially in the presence of thromboembolic complications or thrombocytosis.
The authors studied eight cases of IgA nephropathy presenting with nephrotic syndrome. Renal biopsy revealed only mild mesangial proliferation or minor glomerular changes on light microscopic examination but typical features of IgA nephropathy on immunofluorescent and electron microscopic examination. A satisfactory response characterized by correction of hypoalbuminemia, clearance of proteinuria, and an increase of endogenous creatinine clearance occurred with corticosteroid therapy. These cases represent a variant of IgA nephropathy associated with a nephrotic syndrome that resembles lipoid nephrosis in its responsiveness to steroid.
A 67 year old man presented with a polyarteritis nodosa-like syndrome with renal, pulmonary joint and neurological involvement during the 'preleukaemic' stage of monocytic leukaemia. The association between these two conditions is discussed.