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Biomedical subjects

P Chan

Publications and source records attributed to P Chan.

At least 199 records · Page 11Linked to original sources
PubMed1992

Glutathione in Parkinson's disease: a link between oxidative stress and mitochondrial damage?

Several links exist between the two mechanisms of neuronal degeneration (i.e., oxygen radical production and mitochondrial damage) proposed to have a role in Parkinson's disease. Indeed, mitochondria are critical targets for the toxic injury induced by oxygen radicals, and experimental evidence suggests that mitochondrial damage may cause an increased generation of oxygen radicals. A potentially important link between these two mechanisms of neurodegeneration is glutathione. Because of the scavenging activity of glutathione against accumulation of oxygen radicals, its decrease in the brains of parkinsonian patients has been interpreted as a sign of oxidative stress; however, this change may also result from or lead to mitochondrial damage. It is conceivable therefore that regardless of whether oxidative stress or mitochondrial damage represents the initial insult, these toxic mechanisms may both contribute to neuronal degeneration via changes in glutathione levels.

Animals↗
PubMed1992

Budd-Chiari syndrome treated successfully by percutaneous transluminal balloon angioplasty: two cases followed-up for 6 years.

We report 2 cases of Budd-Chiari syndrome that are due to complete membranous obstruction between the junction of the inferior vena cava and the right atrium. Both cases were treated successfully by King's bioptome breakthrough followed by balloon dilatation of the membrane. The patients showed remarkable symptomatic improvement and promising hemodynamic and angiographic results immediately after the procedure and 6 years later. We conclude that balloon angioplasty is a safe and effective method for treating this rare disease in selected cases.

Adult↗
PubMed1992

Popliteal vein entrapment in the normal population.

The aim of this study was to determine the incidence and severity of popliteal vein compression by full knee extension in the normal population. The popliteal veins in 100 healthy volunteers (200 limbs) with no history of previous deep vein thrombosis (DVT) or venous obstruction were examined using duplex scanning with the knee slightly flexed and then fully extended. Knee extension produced complete obstruction in 17 subjects and severe obstruction (< 50% decrease in diameter) in a further 10 subjects. Thirteen subjects had unilateral compression and 14 bilateral. The 27 subjects were tested for functional venous outflow obstruction with air plethysmography. In flexion, the outflow fraction was normal (> 40%) in all subjects. With the knee fully extended, severe or complete venous obstruction (outflow fraction < 10%) was found in eight subjects. Moderate obstruction (outflow fraction 10-40%) was found in all the remaining 19 subjects. When digital compression of the long saphenous vein was performed, these subjects also demonstrated severe outflow obstruction. Although the incidence of symptoms of functional venous obstruction is rare in the general population, these findings have important implications for venous stasis for patients on the operating table and in those having prolonged bed rest. Studies investigating the association between popliteal vein compression and postoperative deep venous thrombosis are needed.

Adult↗
PubMed1992

High output cardiac failure caused by multiple giant cutaneous hemangiomas.

A 59-year-old Chinese woman had multiple giant cutaneous cavernous hemangiomas on her right upper limb which resulted in high output heart failure because they presented as a large peripheral arteriovenous (A-V) fistula. Selective right subclavian arteriography showed extremely hypertrophic arteries of the patient's right arm with a tremendous blood supply to the soft tissues; neither superselective embolization nor surgery seemed applicable to this patient. The patient's heart failure was not satisfactorily controlled by conservative treatment.

Angiography↗
PubMed1992

Radiological manifestations of cardiovocal syndrome.

Cardiovocal syndrome is a rare clinical diagnosis that signifies vocal cord palsy associated with various cardiovascular diseases. The radiological manifestations of six cases of clinically diagnosed cardiovocal syndrome are reviewed retrospectively. The common clinical presentation of these six cases was hoarseness that was due to left vocal cord palsy. By means of chest X-rays (CXR) and cardioangiography, four cases were respectively diagnosed to have atrial septal defect (n = 1), ventricular septal defect (n = 1) and mitral stenosis (n = 2), all of which were associated with a common radiological finding of dilatation of pulmonary trunk. The other two cases were separately diagnosed to have proximal descending aortic saccular aneurysm (n = 1) by means of CXR and angiography, and fusiform ascending aortic aneurysm (n = 1) by computed tomography and magnetic resonance image. All these radiological presentations of either aortic aneurysm or dilated pulmonary trunk were associated with encroachment of aorticopulmonary window for which the left recurrent laryngeal nerve was presumably compressed with the result of left vocal cord palsy. Hoarseness that is caused by these underlying cardiovascular diseases is correctable after treatment of the underlying diseases. Hence, clinicians and radiologists should pay attention to the radiological manifestations of patients whose chief complaints are hoarseness and cardiovocal syndrome.

Adult↗
PubMed1992

Cardiovocal (Ortner's) syndrome left recurrent laryngeal nerve palsy associated with cardiovascular disease.

Five patients with cardiovascular disease presented with hoarseness due to left recurrent laryngeal nerve palsy. One had secundum atrial septal defect, one had ventricular septal defect, two had mitral stenosis and the other had aortic aneurysm. All except the patient with aortic aneurysm had pulmonary artery dilatation and moderate to severe pulmonary hypertension. Four patients' hoarseness resolved after successful interventional therapy. As for the patient with the aortic aneurysm, hoarseness persisted; the patient died before surgery. We postulate that the dilated pulmonary artery or aortic arch was responsible for the compression of the left recurrent laryngeal nerve.

Adult↗
PubMed1991

Rapid ATP loss caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in mouse brain.

The effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on ATP levels in different areas of mouse brain were studied after rapid fixation of cerebral tissue in situ by microwave irradiation. ATP levels in the striatum, ventral mesencephalon, and cerebellum of untreated C57BL/6 mice killed by microwave irradiation were 2-3 times greater than values measured in the brains of animals killed by cervical dislocation. In microwaved mice, administration of MPTP (40 mg/kg s.c.) caused a 10-20% decrease in ATP concentrations as compared to control animals injected with saline. This decrease was relatively rapid and selective because it occurred in both the striatum and ventral mesencephalon, but not in the cerebellar and frontal cortex, at 30, 60, 120, and 240 min after MPTP exposure. Furthermore, ATP loss in the striatum was prevented by mazindol, a catecholamine uptake blocker, indicating a rather selective effect of MPTP on the ATP content of dopaminergic terminals. Results of this study are consistent with mitochondrial damage in the MPTP model of parkinsonism and provide the first direct experimental evidence in vivo that a decrease in ATP may play a role in MPTP-induced neurotoxicity.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1990

The use of human epidermal keratinocytes in culture as a model for studying the biochemical mechanisms of sulfur mustard toxicity.

Human epidermal keratinocytes in culture were studied to evaluate their usefulness in demonstrating toxic events following exposure to sulfur mustard. Exposure of keratinocytes to sulfur mustard over a concentration range of 1-1000 microM HD, reduced NAD + levels from 96% to 32% of control levels. When keratinocytes were exposed to a concentration of 300 microM HD, NAD + levels began to fall at 1 hour and reached a plateau of 47% of control levels at 4 hours. Niacinamide, an inhibitor of the enzyme poly(ADP-ribose) polymerase, partially protected mustard-exposed cells against NAD + depletion. It also protected cellular viability as assessed by vital staining 24 hours after exposure. This protection was not seen in long-term (72 hr) cultures. These studies suggest that human epidermal keratinocytes in culture can serve as a useful in vitro model for research into the biochemical mechanisms of sulfur mustard-induced cutaneous injury.

Cell Survival↗
PubMed1990

Coarctation of aorta coexisting with pheochromocytoma: report of a case.

A patient was admitted for a study of his hypertension because coarctation of the aorta (COA) was suspected. His history also provided clues of pheochromocytoma. A computed tomography (CT) scan revealed a right-side supraadrenal tumor. A study of urine catecholamine showed a strong positive result. Cardiac catheterization revealed that the patient had a postductal COA and a supraadrenal tumor. Surgery and pathology confirmed that the patient had pheochromocytoma.

Adrenal Gland Neoplasms↗
PubMed1990

Effectiveness of stimulated menstrual cycles and Percoll sperm preparation in intrauterine insemination.

To examine the usefulness of intrauterine insemination in women with various fertility factors, we retrospectively analyzed data from women treated during 1986 and 1987. Ninety-three patients underwent 1-11 cycles of single or double procedures, for a total of 423 inseminations in 263 treatment cycles. Twenty-six patients (28%) conceived, for a 10% total pregnancy rate per cycle, with 58% of the pregnancies resulting from double inseminations per cycle. An average of two treatment cycles was required to achieve pregnancy. Eight pregnancies (31%) occurred in spontaneous cycles, while 18 (69%) occurred in stimulated cycles. While clomiphene citrate therapy was useful in anovulatory patients, it was of no benefit in ovulatory patients being treated with intrauterine insemination. Human menopausal gonadotropin therapy was of benefit in both ovulatory and anovulatory patients when combined with intrauterine insemination. The live birth rate was higher (75%) in spontaneous cycles than in stimulated cycles (44%). Semen preparation was accomplished by sperm washing in 61% of the pregnancies and by Percoll preparation in 39%. The effectiveness of the discontinuous Percoll gradient for semen preparation for insemination was suggested by a pregnancy rate of 9% per cycle. While the mean sperm count in the pregnant group was 44 million, successful pregnancy was accomplished with a double insemination of 880,000 and 1.16 million rapidly progressive sperm in the first and second inseminate, respectively. The data confirm the important role of intrauterine insemination for the treatment of infertility.

Adult↗
PubMed1989

Salmonella cholerasuis bacteremia and mycotic aneurysm of abdominal aorta--report of five cases.

From August 1986 to October 1987, there were 5 cases of primary mycotic aneurysm of the lower abdominal aorta in Chang Gung Memorial Hospital at Kaoshiung. All patients were proved to have Salmonella cholerasuis (Sal. chol.) septicemia by blood culture. The ages ranged from 60 to 80 years old, the mean age was 71.6 years old. The male to female ratio was 4 to 1, 3 patients had diabetes mellitus (DM) and 3 had hypertension. The duration of symptoms lasted from 1 week to 2 months before diagnosis. Clinically, all patients had sepsis with fever, chills, leucocytosis, and complained of pain in the lower abdomen (80%), at flank (20%) or low back (20%). Abdominal tenderness was present in 3 (60%). Two patients underwent surgery, 1 expired during the operation, the other expired 1 month after operation because of retroperitoneal abscess and sepsis. Three were discharged in septic shock and expired within 1 day. The mortality rate was 100%. The diagnosis of complicated aneurysm of the lower abdominal aorta was established in all by computed tomography (CT). In conclusion, when there are clinical manifestations of sepsis, positive blood culture for Sal. chol., and pain or tenderness in the lower abdomen, flank area or back, one should consider the possibility of mycotic aneurysm of the lower abdominal aorta. Although the prognosis is poor, early surgical intervention may improve the outcome. And the diagnosis is best established by CT.

Aged↗
PubMed1989

Tricuspid valve endocarditis.

TVE is mainly a disease of intravenous drug abusers. Although the infecting organisms are often highly virulent, they frequently respond to medical treatment. The prognosis for patients with TVE is fairly good. About 25% of TVE patients require surgical intervention. Persistent sepsis and intractable congestive heart failure are indications for surgery. Tricuspid valvulectomy without prosthetic replacement is the surgical intervention of choice. Right-sided heart failure is the principal complication after valvulectomy without a prosthesis. A significant percentage of patients require insertion of prosthetic valves at a future date.

Adult↗
PubMed1989

In vitro cyclosporine toxicity. The effect of verapamil.

The epithelial cell line LLC-PK1, which expresses many proximal tubular characteristics, was used to investigate the relationship between calcium, the calcium channel blocker verapamil, and cyclosporine toxicity. The LLC-PK1 cells took up cyclosporine when this was added in a concentration of 2 micrograms/ml, and this uptake was maximal at 30 min (112 +/- 3 ng cyclosporine/mg cell protein). At 12 micrograms/ml it inhibited the sodium glucose cotransporter, as assessed by phlorizin-inhibitable 14C-alpha-methyl glucopyranoside (alpha-MG) uptake (control 37.2 +/- 6.3, 12 micrograms/ml 21.2 +/- 1.1 mumol/hr/mg protein). Cyclosporine at 2 micrograms/ml did not affect cell growth after 5 days (control 945 +/- 60 micrograms cell protein per 25 cm2 flask, 2 micrograms/ml cyclosporine/ml 1046 +/- 32 micrograms protein/flask), even in the presence of 7.6 mM ionized calcium (862 +/- 37 micrograms protein/flask). Cyclosporine at 12 micrograms/ml inhibited cell growth (286 +/- 27 micrograms protein/flask), and raising the ambient ionized calcium concentration to 7.6 mM reduced cell growth further (91 +/- 6 micrograms protein/flask). Cyclosporine at concentrations of 2 and 12 micrograms/ml produced increasing cell vacuolation, as seen in vivo. Short-term uptake of 2 micrograms/ml cyclosporine could be inhibited by 1.0 mM and 0.5 mM verapamil (49 +/- 9.5 and 71 +/- 6.4 ng cyclosporine/mg cell protein, respectively, at 30 min). However, in the presence of 2 micrograms/ml cyclosporine 0.1 mM verapamil was toxic to the cells grown over five days (44 +/- 5 micrograms protein/flask). At 0.01 mM verapamil was not toxic to cell growth (921 +/- 29 micrograms protein/flask), but raising the medium calcium to 7.6 mM reduced cell growth (652 +/- 96 micrograms/ml). Inhibition of cyclosporine uptake did not occur with 0.01 mm verapamil (control 145.6 +/- 12.3 vs. 0.01 mM verapamil 150.4 +/- 3.8 ng cyclosporine/mg cell protein). The LLC-PK1 cell line represents a good in vitro model for cyclosporine renal tubular toxicity, as the in vivo observation of glycosuria and proximal tubular cell vacuolation in cyclosporine nephrotoxicity can be reproduced. In vitro this is shown to be associated with inhibition of sodium-dependent glucose cotransport. Verapamil inhibited cyclosporine uptake, but only at concentrations that were toxic to the cells. Verapamil potentiated rather than reduced the increased cyclosporine toxicity produced by increasing the medium calcium concentration. The suggested protective effect of verapamil against cyclosporine nephrotoxicity is therefore unlikely to be due to inhibition of cyclosporine uptake or of calcium entry into proximal tubular cells.

Calcium Channels↗