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Biomedical subjects

P Chan

Publications and source records attributed to P Chan.

At least 181 records · Page 10Linked to original sources
PubMed1994

Left vocal cord palsy: an unusual presentation of a mycotic aneurysm of the aorta caused by Salmonella cholerasuis.

A 67-year-old man was admitted to hospital because of fever, productive cough and a concomitant hoarseness. A para-aortic lesion was found on chest X-ray, and bronchoscopy revealed a left vocal cord palsy. Due to rapid enlargement of the lesion, angiography was performed, which revealed a pseudoaneurysm at the descending aorta. Operation disclosed an infected aneurysm with rupture, and tissue culture yielded Salmonella cholerasuis. The findings of a mycotic aneurysm and hoarseness due to compression of the left recurrent laryngeal nerve is a rare and serious combination caused by salmonella, previously unreported in the medical literature.

Aged↗
PubMed1994

Fatal and nonfatal methamphetamine intoxication in the intensive care unit.

Methamphetamine poisoning was confirmed in eight patients admitted to intensive care 1989 through 1992 because of altered mental status and hemodynamic instability. Four patients were male and four were female, ages 20 to 34 years. Five patients were addicts and three were attempted suicides. The most common clinical cardiovascular manifestations were tachycardia and palpitations. Neurological abnormalities included agitation, hallucinations, pupillary dilatation and muscle twitching; profuse sweating was also common. All patients had rhabdomyolysis and four had remarkable elevation of creatinine kinase > 10,000 U/L. Leucocytosis was noted in seven cases. Therapy included aggressive circulatory support with Swan-Ganz monitoring, external cooling and other modalities. The three fatalities (two addicts, one suicide) presented with coma, shock, body temperature 39 degrees-42 degrees C, acute renal failure, metabolic acidosis and hyperkalemia (K 5.6-8.5 mmol/L).

Adult↗
PubMed1994

Aging and the nigrostriatal dopamine system: a non-human primate study.

The present study examined neurochemical, morphological and functional markers of the nigrostriatal dopamine system in young, intermediate-aged and old squirrel monkeys. Striking reductions in motoric activity were observed with advancing age. significant age-related loss of dopamine occurred in the substantia nigra (70%) and the putamen (30%) but not in the caudate. There was a strong correlation between the reductions in motoric activity and the loss of putamen dopamine. However, nigrostriatal dopamine loss did not appear to be the consequence of age-related loss of dopaminergic nigral neurons since the number of tyrosine immunoreactive cells was not significantly different among the three age groups. These results suggest that the aging squirrel monkey demonstrates the age-related loss of nigrostriatal dopamine thought to occur in humans and identify this non-human primate as a useful model to further investigate the underlying mechanism(s) and functional consequences of age-related decline of the nigrostriatal dopamine system. In addition, the selective loss of dopamine in the putamen but not the caudate parallels the regional vulnerability observed in Parkinson's disease, an age-related neurodegenerative disorder, raising the possibility of a relationship between normal aging and the development of this disease. Finally, because the number of tyrosine hydroxylase (TH) positive cells remains constant with age, these results raise the possibility that therapeutic strategies aimed at increasing dopamine concentrations may benefit elderly individuals.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Risk factors associated with recurrent carotid stenosis.

The incidence of restenosis following carotid endarterectomy reported with duplex scanning has ranged from 6-19%. The aim of this study was to determine the importance of risk factors in the development of carotid stenosis following carotid endarterectomy. Two hundred-thirty patients who underwent carotid endarterectomy (nineteen bilateral carotid endarterectomies) and had complete follow-up with duplex scanning for at least one year have been studied between February 1983 and April 1989. Forty six patients developed restenosis (18.5% of carotid endarterectomies) whereas 184 patients did not restenose. All patients were studied for the following risk factors: age, sex, ischemic heart disease, smoking habit, family history of cardiovascular disease diabetes mellitus, hyperlipidemia and peripheral vascular disease. The incidence of ischemic heart disease, a positive family history of cardiovascular disease, hyperlipidemia and diabetes mellitus was significantly increased (p < 0.05) in patients with recurrent carotid stenosis (80.4%, 71.7%, 58.7%, 32.6% respectively) as compared to patients without a recurrent stenosis (55.7%, 33.5%, 31%, 10.5%). None of the above significant risk factors was strongly associated with early (< 2 years) carotid restenosis. There is an increased prevalence of clinical atherosclerotic risk factors such as family history of cardiovascular disease, diabetes mellitus, ischemic heart disease and hyperlipidemia in patients who develop carotid restenosis.

Aged↗
PubMed1994

Cell biology of human vascular smooth muscle.

Vascular smooth muscle is the cellular substrate of most significant arterial diseases. Restenosis after angioplasty and surgery mainly represents vascular smooth muscle reaction to trauma, a process which is also significant in the early stages of atherogenesis. Empirical approaches, based on findings in animal models of vascular injury, have notably failed to make any impact on human restenosis. We have developed and validated growth of the human VSMC in culture as a model of restenosis. Intimal hyperplastic lesions producing vascular restenosis contain cells that have reduced sensitivity to physiological growth inhibition by heparin in cell culture conditions, compared with cells from normal vascular tissue. Undiseased saphenous vein obtained from patients with intimal hyperplastic restenoses also contain cells that are relatively resistant to heparin inhibition. Arterial healing that progresses to restenosis may have distinct and fundamental differences at the cellular level from the normal process of arterial healing after injury.

Arterial Occlusive Diseases↗
PubMed1993

Developmentally regulated transcription of the four liver-specific genes for inter-alpha-inhibitor family in mouse.

The inter-alpha-inhibitor family is composed of the plasma-protease inhibitors inter-alpha-inhibitor, pre-alpha-inhibitor and bikunin. Inter-alpha-inhibitor and pre-alpha-inhibitor are distinct assemblies of bikunin with distinct sets from three heavy (H) chains designated H1, H2 and H3. These H chains are encoded by a set of three evolutionarily related H genes, and bikunin by an alpha-1-microglobulin/bikunin precursor gene (AMBP). This precursor is cleaved to yield bikunin, a member of the Kunitz-type protease-inhibitor superfamily, and alpha-1-microglobulin, which belongs to the lipocalin superfamily. Northern-blot experiments with RNAs obtained from various tissues in fetal and in adult mice indicated that the transcription of the four AMBP and H genes is liver-restricted, although there is expression of H3 in brain. An analysis of the H1, H2, H3 and AMBP transcripts, as well as of transcripts for other control genes, in liver during development showed a progressive increase in the amounts of the H1, H2, H3 and AMBP RNAs, which all peak transiently at day 5 after birth. This was shown by a nuclear run-on experiment to originate from a change in transcription rate. The transient and postnatal increase in transcription could be explained neither by the liver-restricted expression nor by a common origin of these four genes, nor by a perinatal requirement for many lipocalins or protease inhibitors. This suggests that all four genes are perinatally triggered at the level of similar elements in their transcriptional regulatory regions, a conclusion strengthened by the weak expression of the four genes that is seen in a mutant mouse strain (albino) that is deficient in some liver-specific transcription factors.

Aging↗
PubMed1993

Mouse alpha-1-microglobulin/bikunin precursor: cDNA analysis, gene evolution and physical assignment of the gene next to the orosomucoid locus.

alpha-1-Microglobulin (A1m) is a member of the lipocalin superfamily whereas bikunin is a Kunitz-type proteinase inhibitor. A1m and bikunin originate from a shared precursor. A comparison of mammalian cDNAs for the precursor indicates a highly conserved amino acid sequence along with muridae-specific deletions in both A1m and bikunin. In rodents, the gene for this precursor is less than 300 kb apart from the orosomucoid gene, another lipocalin gene. This precursor likely results from the assembly of two lipocalin and Kunitz-type genes, between 270 and 80 million years ago.

Alpha-Globulins↗
PubMed1993

Neurologic and histologic evaluation of almitrine+raubasine (Duxil) in middle cerebral artery occlusion in cats.

Impairment of energy metabolism is the fundamental mechanism leading to cell death in ischemia. Using the middle cerebral artery (MCA) occlusion model in cats, we studied the effect of Duxil (almitrine and raubasine combination), which was given either before and after or only after MCA occlusion, on ischemia in terms of neurological function and histological changes. Neurological function was assessed consecutively for 7 days after MCA occlusion using a categorical rating scale in 18 cats. Neurological function was significantly improved in treated animals than in non-treated controls regarding to the motor and sensory function, walking, posture and stepping reflex. Animals were killed on the 8th day and histological changes were examined by light and electron microscopies. Significant improvement in the morphological scores based on the light-microscopy changes were found in animals treated with Duxil compared to non-treated ones. Under the electron microscopy, the protective effects of Duxil were characterized by retaining glycogen and mitochondria. Morphological improvement was associated with the recovery of neurological function and especially profound in penumbra areas of MCA infarction. These results suggest that Duxil has a protective effect against ischemic damage induced by occlusion of MCA in cats.

Almitrine↗
PubMed1993

Abnormal growth regulation of vascular smooth muscle cells by heparin in patients with restenosis.

Proliferation of vascular smooth muscle cells (VSMC) underlies myointimal hyperplasia, which can lead to restenosis after angioplasty and vascular surgery. We propose that some individuals have an intrinsic capacity for this exaggerated response to vascular injury, partly through decreased sensitivity to the physiological growth inhibitor heparin. We investigated the effect of heparin on VSMC from restenotic lesions and from apparently normal vessels of the same patients, and VSMC from control patients undergoing primary bypass procedures. Cells from patients with restenosis (both restenotic lesion and undiseased vein) showed much lower sensitivity to growth inhibition by heparin than the controls (median inhibition 8 [95% Cl -2 to 25] vs 22 [15-44]%, p < 0.001); this finding suggests aberrant growth regulation in these cells.

Arterial Occlusive Diseases↗
PubMed1993

Detection of superior mesenteric and coeliac artery stenosis with colour flow Duplex imaging.

Measurements of blood velocity in the coeliac axis (CA) and the superior mesenteric artery (SMA) before and after a standard meal in normal people have been studied by several authors. However, information about the ability to detect stenotic lesions is lacking. The aim of our study was to determine the accuracy of Duplex scanning in detecting angiographically proven lesions. Twenty normal volunteers (13 males and seven females) and 24 patients (19 males and five females) with visceral artery stenosis on angiography were examined in the supine position (angle of insonation 60.5) with colour flow Duplex imaging (CFDI) (3.5 MHz probe), in the fasting state and after a standard meal at 15, 40, 60 and 90 min. Peak systolic velocity (PSV) and end diastolic velocity (EDV) were determined in both CA and SMA. The PSV was the best indicator of stenosis. After the meal, there was an increase in both PSV and EDV but neither of the postprandial measurements improved the accuracy of the test. The results indicate that CFDI can detect the presence of significant stenosis (> 50% in the CA and SMA with a sensitivity and specificity of > 80%.

Arterial Occlusive Diseases↗
PubMed1993

Cellular biology of human intimal hyperplastic stenosis.

Restenosis after angioplasty and vascular surgery remains a major unsolved clinical problem. Vascular smooth muscle cell (VSMC) hyperplasia is an invariable response, but in 20-50% of cases proceeds to compromise the vessel lumen. We sought to identify cellular characteristics of human VSMC which are associated with restenosis. Human VSMC were grown from 135 samples of vascular tissue derived from patients undergoing primary cardiovascular surgery and revision surgery for restenosis. Cells derived from normal vein and artery, atherosclerotic plaques and from stenotic lesions were studied for successful proliferation in cell culture. Furthermore, growth rates were measured in response to 15% foetal calf serum +/- inhibition with heparin (100 micrograms/ml). Significantly fewer cells from atherosclerotic plaques progress to the third passage in cell culture than those derived from stenoses and controls (p < 0.001, Chi square) and growth rates after the third passage could not be studied in these cells. Of cells that progress to this stage, growth rates do not differ between stenosis-derived and normal cells under standard conditions. VSMC from mature atherosclerotic plaques may have undergone senescent changes. Stenosis-derived cells do not grow more rapidly than normal cells, but are significantly less sensitive to heparin (p < 0.001, Mann-Witney test), which is a major physiological inhibitor of VSMC growth. Differences in biological characteristics of human VSMC, observed in cell culture, may provide important insights into human vascular disease.

Actins↗
PubMed1993

Complete membranous obstruction of the inferior vena cava: clinical characteristics of Chinese patients.

OBJECTIVES: To analyse the clinical presentations of membranous-type Budd-Chiari syndrome and the long-term outcome of balloon angioplasty. DESIGN: A case-control study. Patients who received abdominal sonography and were suspected of having hepatic venous outflow obstruction were advised to receive cardiac catheterization and angiography. SETTING: Patients were collected from Chung Hisao Hospital and Chang Gung Medical Centre. Angioplasty was done at Chang Gung Medical Centre. SUBJECTS: Seventeen patients who had the symptoms and signs of portal hypertension were suspected of having hepatic venous outflow obstruction after abdominal sonography and a radionuclide liver scan and eight of them were confirmed as having membranous-type obstruction. INTERVENTIONS: Simultaneous catheterization and contrast angiography was performed via the right brachial and femoral veins. Angioplasty was performed afterwards. MAIN OUTCOME MEASURES: The remission of clinical symptoms and signs and a decrease of the pressure gradient between the right atrium and inferior vena cava were used as indicators of successful intervention. RESULTS: All patients had remarkable remission of symptoms and signs. The average pressure gradient between right atrium and inferior vena cava dropped from 16.5 +/- 1.6 to 6.5 +/- 1 mmHg (mean +/- SD). CONCLUSION: The clinical presentations of membranous-type Budd-Chiari syndrome are somewhat different from hepatic vein occlusion. Balloon angioplasty may be a modality for curing this disease. A larger patient population is necessary to confirm this study.

Adult↗
PubMed1993

2-deoxyglucose enhances 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced ATP loss in the mouse brain.

The effects of 2-deoxyglucose (2-DG), an inhibitor of the uptake and use of glucose, on ATP loss caused by the neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were determined in the mouse brain. 2-DG alone had no effect on brain ATP levels, but when administered 30 min before MPTP exposure, 2-DG significantly enhanced MPTP-induced ATP reduction. This was reflected as an increase in ATP loss in the striatum (from 15 to 27%) as well as a significant decrease in ATP in the cerebellar cortex, an area of the brain that was not affected after exposure to MPTP alone. In mice pretreated with 2-DG, striatal ATP levels remained significantly decreased for > 8 h after MPTP administration. In contrast, ATP levels in the cerebellar cortex returned to normal values within 4 h from MPTP exposure. Mazindol, a catecholamine uptake blocker, completely protected against MPTP-induced loss of striatal ATP in the absence of 2-DG, but it only partially prevented striatal ATP decrease after administration of both 2-DG and MPTP; mazindol was also ineffective in protecting against ATP loss caused by 2-DG and MPTP in the cerebellar cortex. 2-DG/MPTP-induced ATP loss appeared to be associated with the presence of the 1-methyl-4-phenylpyridinium (MPP+) metabolite because (1) the pattern of ATP recovery in the striatum and cerebellar cortex appeared to reflect the pattern of MPP+ clearance from these areas of the brain (i.e., significant MPP+ levels persisted longer in the striatum than in the cerebellar cortex), and (2) ATP decrease was completely prevented by blocking the conversion of MPTP to MPP+ with the monoamine oxidase B inhibitor deprenyl.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1993

Identification of a single amino acid residue in the capsid protein VP1 of coxsackievirus B4 that determines the virulent phenotype.

To identify the molecular determinants of virulence for coxsackievirus B4, a panel of recombinant, chimeric viruses were constructed from cDNA clones of a virulent virus, CB4-V, and a nonvirulent virus, CB4-P. Initial studies mapped a major determinant of virulence to the 5' end of the viral genome, which contained the 5' untranslated and the P1 regions (A. Ramsingh, A. Hixson, B. Duceman, and J. Slack, J. Virol. 64:3078-3081, 1990). To determine whether the 5' untranslated region contributed to the virulent phenotype, a chimeric virus (vCB403) containing this region of the virulent virus on an avirulent background was tested in mice. The vCB403 construct displayed a phenotype similar to that of CB4-P, suggesting that the 5' untranslated region did not significantly contribute to virulence. Analysis of the sequence data of the P1 regions of both CB4-V and CB4-P revealed five mutations that resulted in amino acid substitutions in VP1, VP2, and VP4 (A. Ramsingh, H. Araki, S. Bryant, and A. Hixson, Virus Res. 23:281-292, 1992). Analysis of individual mutations in both VP1 and VP2 revealed that a single residue (Thr-129 of VP1) determined the virulent phenotype.

Animals↗
PubMed1993

MK-801 temporarily prevents MPTP-induced acute dopamine depletion and MPP+ elimination in the mouse striatum.

The acute effects of the noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist 5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine [(+)-MK-801] on 1) dopamine depletion caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP); 2) the biodisposition of the MPTP metabolite 1-methyl-4-phenylpyridinium (MPP+) and 3) MPTP-induced ATP loss were investigated in the mouse striatum. Systemic administration of a single dose of MPTP (40 mg/kg s.c.) to C57BL/6 mice rapidly decreased striatal dopamine levels to 30% of control values. A single injection of (+)-MK-801 (1 mg/kg i.p.) 30 min before MPTP treatment completely prevented striatal dopamine depletion at 1.5 and 4 hr. The competitive NMDA antagonist CGS-19755 also completely protected against MPTP-induced acute dopamine depletion at 4 hr in the striatum. The action of (+)-MK-801 was only temporary, however, because at 12 hr, the degree of dopamine depletion was not different between the (+)-MK-801/MPTP-treated animals and mice treated with MPTP alone. Repeated injections of (+)-MK-801 at 4-hr intervals did not provide any additional protective effect. (+)-MK-801 administration before MPTP exposure did not appear to affect the production of MPP+, but it did significantly delay its elimination from the striatum. There was a significant correlation between levels of dopamine and MPP+ both in the presence and in the absence of (+)-MK-801. Finally, MPTP-induced striatal ATP loss was not affected by pretreatment with (+)-MK-801.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1993

Progression of carotid atherosclerosis. Three year follow-up and analysis of risk factors.

OBJECTIVE: To elicit the risk factors associated with increasing grades of stenosis in patients with carotid plaque. STUDY DESIGN: Retrospective review of serial duplex scans of the carotid bifurcation. Case note review for documented risk factors. SETTING: Irvine Laboratory of the Academic Department of Surgery, Vascular Section. PATIENTS AND RESULTS: Review of serial duplex scans of the carotid bifurcation was performed on 200 unselected patients who each had a follow-up of at least three years. Definite progression of carotid atherosclerosis was defined as an unequivocal increase in at least one grade by the criteria of Strandness, and was documented in 50 patients (25%). Even if the initial situation is normal or minimal disease (< 15% stenosis), once definite plaque progression is observed, the lesion will progress to a hemodynamically significant one (> 50%) in 67% of this patient population. The only risk factor for plaque progression that we defined is hypertension, and this may be spurious. There are no risk factors associated with the subgroup of plaques that progress rapidly above those that progress at a slower rate. CONCLUSIONS: There are no risk factors defined in this population which are associated with advancing carotid atherosclerosis.

Aged↗
PubMed1993

The effect of elastic stockings on the elasticity of varicose veins.

The aim of this study was to establish the long-term effect of graduated elastic compression on venous elasticity in patients with superficial or deep venous disease and to determine the possible relationship between elasticity and the duration of the disease. The elastic modulus of 29 patients, 19 with superficial vein incompetence and 10 with deep vein incompetence was assessed by the simultaneous measurement of calf volume (determined using strain gauge) and venous pressure (obtained via a dorsal foot vein) during venous occlusion. The measurements were obtained before and after 4 weeks of elastic compression stockings. The elastic modulus K, was defined as stress/strain when the veins were full and was calculated from the pressure/volume relationship. The results show a clear difference in elasticity before and after elastic stockings. Two groups of patients were identified: group 1 with increased elasticity and group 2 with decreased elasticity. There was a negative linear relationship (r = 0.88) between increase in elasticity after treatment and duration of venous disease.

Bandages↗