Biomedical subjects

R Chen

Publications and source records attributed to R Chen.

At least 415 records · Page 23Linked to original sources

PubMed1996

A meta-analysis of mortality among workers exposed to organic solvents.

It has been suggested that organic solvent exposure may contribute to an increased risk of blood disorders, neurological, liver and renal disease, and cancer. A meta-analysis has been performed of 55 published mortality studies which involved solvent exposure and provided standardised mortality ratios (SMR) or relative risk (RR). The combined results showed the overall SMR to be 86.7 (95% confidence interval [Cl] = 83.7-89.9), while that for all sites of cancer was 92.3 (Cl = 87.5-97.4). Risk of death from leukaemia was increased (SMR = 112.2, Cl = 101.6-146.9) as was that from cancer of liver and biliary passages (SMR = 119.7, Cl = 104.4-137.2), even though the risk of death from cirrhosis was reduced (SMR = 81.5, Cl = 68.1-97.4). No excess risk of death from other diseases has been found. The favourable mortality might be from a "healthy worker effect', but the increase in death from liver cancer in the absence of excess deaths from cirrhosis is biologically plausible and justifies further investigation. The increase in mortality from leukaemia is likely to have been associated with exposure to benzene.

Chemical Industry↗

PubMed1996

The influence of study characteristics on the healthy worker effect: a multiple regression analysis.

The so-called 'healthy worker effect' (HWE) describes a reduced mortality rate in occupational populations. From 85 occupational cohorts of workers exposed to organic solvents, we have previously found a low weighted standardized mortality ratio (SMR) for all causes (SMR = 89.5, 95 per cent confidence interval [Cl] = 89.0-90.2). Characteristics of the cohorts were examined for association with the HWE. A multiple regression analysis revealed that, for overall deaths, the closer the comparison group, the smaller the HWE (p = 0.001); the more hazardous the potential exposures, the higher the SMR (p = 0.02); the higher the social class, the greater the HWE (p = 0.02); and the higher the rates of loss to follow up, the greater the HWE (p = 0.04). These results have shown that, in addition to time-related modifiers, the comparison group, type of occupational exposure, social class and rates of loss to follow-up significantly influence the size of the so-called HWE. Differences in the HWE related to gender and race were probably attributable to different rates of loss to follow-up.

Cohort Studies↗

PubMed1996

Prediction of outcome in patients with anoxic coma: a clinical and electrophysiologic study.

OBJECTIVE: To evaluate and compare the predictive powers of clinical examination, electroencephalography (EEG), and studies of short-latency somatosensory evoked potentials in determining the prognosis in anoxic coma. DESIGN: Prospective case series of patients in anoxic coma, whose prognoses were uncertain based on previously established clinical criteria. The clinical features, EEG, and somatosensory evoked potentials results were correlated with outcome. SETTING: A 40-bed intensive care unit in a university teaching hospital. PATIENTS: Thirty-four consecutive patients admitted over a 2-yr period with anoxic coma as the principal diagnosis. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Twenty-seven (79%) patients never recovered consciousness and seven (21%) patients made a good recovery. One of six patients whose pupillary reflexes were present but whose other cranial nerve reflexes were absent on day 1 recovered, but none of the seven patients with these features still present on day 3 survived. None of the patients with motor responses of extension to painful stimuli or worse on days 1 or 3 recovered. The EEGs were classified into benign, uncertain, and malignant categories. The results of both EEG and somatosensory evoked potentials studies were strongly associated with outcome. With malignant EEG, the sensitivity was 74%, the specificity was 71%, and the positive predictive value was 90% [corrected] for the prediction of no recovery (death or persistent vegetative state). However, two patients with an initially malignant EEG eventually made a good recovery. The sensitivity for low amplitude or absent somatosensory evoked potentials for prediction of no recovery was 66%. There were no falsely pessimistic predictions with somatosensory evoked potentials, as all 18 patients with absent or low-amplitude responses had no recovery (specificity and positive predictive value were 100%). EEG and somatosensory evoked potentials studies were complementary to clinical examination in the determination of prognosis. Using a combined clinical and electrophysiologic approach, 63% of patients who had no recovery could be identified by day 3. Repeat EEG and somatosensory evoked potentials studies were of value in patients whose prognoses were uncertain, as their evolution invariably correlated with outcome. CONCLUSIONS: Based on the present data and a literature review, we propose that clinical examination combined with the results of EEG and somatosensory evoked potentials can be used to establish an early, definitive prognosis in a significant proportion of patients in anoxic coma. On day 3 or thereafter, patients with motor response of extension to pain or worse and malignant EEG, or those patients with flexor posturing or worse and bilaterally absent cortical somatosensory evoked potentials invariably have poor outcome. However, some patients with initially malignant EEG and normal somatosensory evoked potentials may recover and should be supported until their prognoses become more definitive.

Adolescent↗

PubMed1996

Differential diagnosis and management of very low second trimester maternal serum unconjugated estriol levels, with special emphasis on the diagnosis of X-linked ichthyosis.

Incorporation of maternal serum unconjugated estriol into the calculation of risk may increase the yield of serum screening performed during pregnancy for detection of fetal chromosomal and structural anomalies. The differential diagnosis of very low and undetectable levels of unconjugated estriol in maternal serum is discussed, with special emphasis on the prenatal diagnosis of X-linked ichthyosis. The prenatal detection of these findings dictates skilled genetic counseling, targeted sonographic evaluation and examination of fetal karyotype and fetal cDNA for Xp 22.32 with amniotic fluid levels of cortisol, STS, and ASC.

Adult↗

PubMed1996

A periplasmic protein (Skp) of Escherichia coli selectively binds a class of outer membrane proteins.

A search was performed for a periplasmic molecular chaperone which may assist outer membrane proteins of Escherichia coli on their way from the cytoplasmic to the outer membrane. Proteins of the periplasmic space were fractionated on an affinity column with sepharose-bound outer membrane porin OmpF. A 17 kDa polypeptide was the predominant protein retained by this column. The corresponding gene was found in a gene bank; it encodes the periplasmic protein Skp. The protein was isolated and it could be demonstrated that it bound outer membrane proteins, following SDS-PAGE, with high selectivity. Among these were OmpA, OmpC, OmpF and the maltoporin LamB. The chromosomal skp gene was inactivated by a deletion causing removal of most of the signal peptide plus 107 residues of the 141-residue mature protein. The mutant was viable but possessed much-reduced concentrations of outer membrane proteins. This defect was fully restored by a plasmid-borne skp gene which may serve as a periplasmic chaperone.

Bacterial Outer Membrane Proteins↗

PubMed1996

Respiratory electrophysiological studies in Guillain-Barré syndrome.

Respiratory failure is a common and potentially life threatening complication in patients with Guillain-Barré syndrome. The incidence of phrenic nerve involvement and the predictive value of phrenic nerve conduction and diaphragmatic needle EMG were studied in 40 patients with Guillain-Barré syndrome within the first three days of admission to hospital. The negative peak onset latency of the diaphragmatic compound muscle action potential (CMAP), and its amplitude, duration, and area were abnormal in 83%. The need for ventilation was correlated with diaphragmatic CMAP amplitude (P = 0.005), and area (P = 0.001), but not with latency or duration. Abnormalities in diaphragmatic needle EMG were found in 45%, mainly a decreased number of motor unit potentials. The abnormalities correlated with the need for ventilation (P = 0.013). Of the 40% who required ventilation, all had either abnormal phrenic conduction, abnormal diaphragmatic needle EMG, or both. Eighty one per cent of the ventilated patients had abnormal forced vital capacity on the day of the electrophysiological examination. The results indicate that phrenic nerve conduction studies and diaphragmatic EMG are useful in detecting respiratory involvement in patients with Guillain-Barré syndrome and in identifying those at risk of respiratory failure.

Adolescent↗

PubMed1996

Motor neuron disease presenting as acute respiratory failure: a clinical and pathological study.

Respiratory failure is rarely a presenting symptom of motor neuron disease. Seven patients with motor neuron disease who presented with acute respiratory failure of unknown cause and required mechanical ventilation were studied. They all had symptoms and signs suggestive of diaphragmatic weakness. Respiratory involvement seemed disproportionately severe, as six were ambulatory and only three noted limb weakness. Only one had tongue weakness and none had swallowing difficulty. Electrophysiological studies showed widespread denervation and, in particular, diaphragmatic involvement to explain the severe respiratory failure. Weaning from the ventilator was unsuccessful in all cases. The four patients examined at necropsy showed severe loss of anterior horns cells in the cervical cord, with only minimal upper motor neuron involvement. Motor neuron disease should be recognised as a cause of acute respiratory failure, secondary to diaphragmatic paralysis from involvement of phrenic motor neurons.

Acute Disease↗

PubMed1996

Peripheral artery disease and cardiovascular risk factors in the elderly. The Honolulu Heart Program.

Peripheral vascular disease as measured by the ankle/brachial blood pressure index (ABI) is associated with increased risk of mortality and morbidity. Few sources of data on the relationship of risk factors to ABI are available for the elderly, especially those > 80 years of age, and minority populations. ABI measurements from the Honolulu Heart Program's fourth reexamination of 3450 ambulatory, elderly Japanese American men indicate that the prevalence of an abnormal ABI, defined as a ratio of < 0.9, was 13.6%, increasing from 8.0% in those 71 to 74 years of age to 27.4% in those 85 to 93 years. Associations that were U or J shaped were present for a number or risk factors (higher rates of abnormality [ABI < 0.9] in those in the lowest and highest risk factor quintiles) in a cross-sectional analysis. Risk factors measured at baseline were also predictive of an abnormal ABI 25 years later, even after adjustment for multiple risk factors. The odds ratio (OR) for an ABI < 0.9 at the 80th percentile of cholesterol compared with that at the 20th percentile was 1.4; the OR for 1-hour postload glucose was 1.3, and for alcohol intake 1.2. The OR associated with hypertension was 1.8 and that for smoking, 2.9 (P < .05 for all ORs). These findings are consistent with ABI being a marker for generalized atherosclerotic disease in old and very old Japanese American men.

Aged↗

PubMed1996

The use of ondansetron in the treatment of nausea and vomiting associated with acetaminophen poisoning.

BACKGROUND: Nausea and vomiting associated with poisoning can complicate treatment and in some cases delay potential antidote administration. Side effect such as lowering the seizure threshold may at times discourage the use of traditional phenothiazine and butyrophenone antiemetics. METHODS: We performed a prospective, single arm, observational study examining the effectiveness of the 5HT3 receptor antagonist ondansetron in the management if nausea and vomiting associated with acetaminophen poisoning. Patients with a history or laboratory evidence of acetaminophen poisoning were eligible for inclusion in the study. Exclusion criteria included age less than 18 or greater than 65, use of other antiemetic therapy within the previous 12 hours, history of preexisting hepatic or hematologic disease, pregnancy, or significant ingestion of other substances. Upon meeting entry criteria, patients were administered 8 mg of intravenous ondansetron. Nausea was graded on a 100 mm scale with number of emetic episodes recorded before and after treatment. RESULTS: Six patients were entered in the study. All patients had nausea and at least one emetic episode prior to ondansetron and prior to administration of N-acetylcysteine. All patients reported relief of nausea after ondansetron. The degree of nausea decreased by an average of 52% at 30 min and 88% at 60 min following ondansetron administration. No significant vital sign changes were recorded in any patient, and there were no complications related to therapy. Three patients were administered N-acetylcysteine, and all tolerated this therapy without vomiting after ondansetron. CONCLUSIONS: Ondansetron appears to be a potentially useful adjunct in the management of nausea and vomiting associated with acetaminophen poisoning.

Acetaminophen↗

PubMed1996

[Subconjunctival 5-fluorouracil polyphase liposome interference with scar formation in experimental filtration surgery].

OBJECTIVE: A comparative study was made to determine the effect of 5-fluorouracil (5-Fu) polyphase liposome and 5-Fu solution on the prevention of scar formation in filtration surgery. METHOD: 20 New Zealand white rabbits that underwent a standard trabeculectomy in both eyes were divided into two groups and each group consisted of 10 rabbits. Postoperatively, according to randomized fashion, in the first group, one eye received daily subconjunctival injection of 5 mg (0.2 ml) 5-Fu solution and the fellow eye received equal subconjunctival amount of normal saline serving as the control, in the second group, one eye received once subconjunctival injection of 5 mg (0.2 ml) of 5-Fu ployphase liposome with every 3 days apart and the fellow eye received the equal amount of subconjunctival injection of polyphase liposome serving as the control. RESULTS: Two weeks after the surgery, the eyes treated with 5-Fu solution in the first group and 5-Fu polyphase liposome in the second group showed marked reduction of intraocular pressure (IOP, P < 0.05) and the control eyes of both groups did not reveal any marked reduction of IOP as compared with preoperative IOP respectively. Morphometric analysis of the areas of fibrosis in histologic section demonstrated a significant decrease (P < 0.002) in episcleral fibrosis in the eyes treated with 5-Fu solution and 5-Fu polyphase liposome as compared with their control eyes respectively. Superficial punctate keratopathy occurred in two of the 5-Fu solution-treated eyes (20%) and no toxic reaction was noted in the 5-Fu polyphase liposome-treated eyes. CONCLUSION: Postoperatively, subconjunctival 5-Fu polyphase liposome instead of 5-Fu solution inhibits the scar formation at filtering site, and the therapy is safe and effective, leading to a higher success rate.

Animals↗

PubMed1996

High level expression of oryzacystatin in Escherichia coli.

A rice cDNA library of immature seeds has already been constructed, from which colonies carrying oryzacystatin cDNA were isolated. The coding region of the oryzacystatin (a thiol proteinase inhibitor) gene was amplified by the Polymerase Chain Reaction (PCR) and inserted downstream of lambdaPRPL promoter of E. coli thermal-inducible expression vector pBV220. An oryzacystatin expression plasmid pBVC9 was therefore obtained. Shifting the culture temperature of E. coli DH5 alpha (pBVC9) from 30 degrees C to 42 degrees C led to a high level expression of oryzacystatin. The result of SDS-PAGE showed a distinct band of 12.0 kDa which accounts for at least 10% of the total soluble proteins. The inhibitory activity of the total soluble proteins of E. coli DH5 alpha (pBVC9) toward papain was confirmed by using that of E. coli DH5 alpha (pBV220) as a control.

Cloning, Molecular↗

PubMed1996

The respiratory system.

Neurological disorders frequently contribute to respiratory failure in critically ill patients. They may be the primary reason for the initiation of mechanical ventilation, or may develop later as a secondary complication. Disorders of the central nervous system leading to respiratory failure include metabolic encephalopathies, acute stroke, lesions of the motor cortex and brain-stem respiratory centres, and their descending pathways. Guillan-Barré syndrome, critical illness polyneuropathy and acute quadriplegic myopathy are the more common neuromuscular causes of respiratory failure. Clinical observations and pulmonary function tests are important in monitoring respiratory function. Respiratory electrophysiological studies are useful in the investigation and monitoring of respiratory failure. Transcortical and cervical magnetic stimulation can assess the central respiratory drive, and may be useful in determining the prognosis in ventilated patients, with cervical cord dysfunction. It is also helpful in the assessment of failure to wean, which is often caused by a combination of central and peripheral nervous system disorders. Phrenic nerve conduction studies and needle electromyography of the diaphragm and chest wall muscles are useful to characterize neuropathies and myopathies affecting the diaphragm. Repetitive phrenic nerve stimulation can assess neuromuscular transmission defects. It is important to identify patients at risk of respiratory failure. They should be carefully monitored and mechanical ventilation should be initiated before the development of severe hypoxaemia.

Critical Care↗

PubMed1996

Metabolic encephalopathies.

Metabolic encephalopathies are common among patients in the critical care unit. Septic, hypoxic-ischaemic, hepatic and uraemic encephalopathies are most frequently seen. They produce global neurological dysfunctions ranging from lethargy or mild confusion to coma. Metabolic encephalopathies must be distinguished from other conditions such as structural brain lesions, infections of the central nervous system or drug reactions. Neurological manifestations are often present in the early stages of systemic illness and may be the first symptom. The severity of encephalopathy generally correlates with that of the systemic illness. Appropriate investigations often include drug and metabolic screens, cultures of blood and cerebrospinal fluids and neuro-imaging studies. Electroencephalogram is useful to grade the severity of encephalopathy. With some exceptions such as hypoxic-ischaemic encephalopathy, most metabolic encephalopathies are reversible unless secondary complications such as brain herniation occurred. Treatment is generally that of the underlying systemic illness and supportive measures.

Brain Diseases, Metabolic↗

PubMed1996

An analysis program for occupational cohort mortality and update cancer risk in copper miners.

Author has developed a computer analysis system to deal with data from occupational follow-up studies, including: (1) input and administration of data; (2) calculation of person-years at risk and follow-up rate; (3) standardised mortality ratios for all cause-of-death categories; (4) the differences and trends of the cancer risks among subcategories defined by variables such as year and age at death, year and age at start of exposure, duration of exposure and time since first exposure, and job titles; and (5) life expectancy analysis. It is explained and applied in an updated cohort of copper miners. The computed results showed that the SMR for all cancer was elevated to 129 (95% CI 117-142). The SMR increased with calendar periods and a higher risk of cancer deaths was found in the miners employed in the 1950s. The miners who were exposed at a younger age had more chance of developing cancer. The risk of cancer deaths increased with the time since first exposure and more strongly with the duration of exposure. The SMR of cancer in underground miners reached up to 137 significantly. All analysis suggests that the occupational exposure (possibly silica dust) could be considered as a risk factor of cancer among the copper miners. The analysis of life expectancy indicated that deaths from circulatory system disease shorten more life expectancy for the miners.

Adolescent↗

PubMed1996

Repeated recurrence of osteosarcoma treated by resections and chemotherapy.

This paper presents 5 patients with repeated recurrence of osteosarcoma (RROS). The primary focus of 3 patients were in the distal portion of femur, and 2 patients were in the proximal portion of tibia. Three patients, whose chest X ray film were negative, were treated by amputation and chemotherapy. Two patients had isolated metastatic focus 1.5 cm in diameter in lung, were treated by amputation after 1 week of chemotherapy and then treated by lobectomy after 2 weeks of chemotherapy. After operation, the chemotherapy was carried out for 3 courses of treatment. The roentgenogram of chest and affected limb were taken once every two months. There were metastatic focuses found in the lung of 1 patient and in the distal portion of femur of 2 patients. One patient was operated on for 4 times. Up to now, 3 patients have been living for 5 years and 2 patients for 6 years after operation.

Adolescent↗

PubMed1996

[A new speech training method for patients following cleft palate repair].

A new method of speech training in Chinese was established according to investigations of articulatory phonetics and speech pathology of 50 patients following cleft palate operations. All of these patients were examined thoroughly and were considered to have good velopharyngal function. However, in all of them, the articulation score was lower than 70%. 33 of these 50 patients were treated with the method for a period of 22 to 120 days (average 63 days). Results showed that their articulation improved from 38.4% to 89.5% on average, the improvement in speech was highly significant statistically (P < 0.0001). In addition, the question of correct timing for speech therapy is discussed.

Adolescent↗

PubMed1995

A highly active decarboxylating dehydrogenase with rationally inverted coenzyme specificity.

The isocitrate dehydrogenase of Escherichia coli, which lacks the Rossmann fold common to other dehydrogenases, displays a 7000-fold preference for NADP over NAD (calculated as the ratio of kcat/Km). Guided by x-ray crystal structures and molecular modeling, site-directed mutagenesis has been used to introduce six substitutions in the adenosine binding pocket that systematically shift coenzyme preference toward NAD. The engineered enzyme displays an 850-fold preference for NAD over NADP, which exceeds the 140-fold preference displayed by a homologous NAD-dependent enzyme. Of the six mutations introduced, only one is identical in all related NAD-dependent enzyme sequences--strict adherence to homology as a criterion for replacing these amino acids impairs function. Two additional mutations at remote sites improve performance further, resulting in a final mutant enzyme with kinetic characteristics and coenzyme preference comparable to naturally occurring homologous NAD-dependent enzymes.

Amino Acid Sequence↗

PubMed1995

Low serum cholesterol and mortality. Which is the cause and which is the effect?

BACKGROUND: Many studies have reported an association between a low or lowered blood total cholesterol (TC) level and subsequent nonatherosclerotic disease incidence or death. The question of whether low TC is a true risk factor or alternatively a consequence of occult disease at the time of TC measurement remains unsettled. To shed new light onto this problem, we analyzed TC change over a 6- year period (from exam 1 in 1965 through 1968 to exam 3 in 1971 through 1974) in relation to subsequent 16-year mortality in a cohort of Japanese American men. METHODS AND RESULTS: The study was based on 5941 men 45 to 68 years of age without prior history of coronary heart disease, stroke, cancer, or gastrointestinal-liver disease at exam 1 who also participated in exam 3 of the Honolulu Heart Program. The association of TC change with mortality end points was investigated with two different approaches (continuous and categorical TC change) with standard survival analysis techniques. Falling TC level was accompanied by a subsequent increased risk of death caused by some cancers (hemopoietic, esophageal, and prostate), noncardiovascular noncancer causes (particularly liver disease), and all causes. The risk-factor-adjusted rate of all-cause mortality was 30% higher (relative risk, 1.30; 95% CI, 1.06 to 1.59) among persons with a decline from middle (180 to 239 mg/dL) to low (< 180 mg/dL) TC than in persons remaining at a stable middle level. By contrast, there was no significant increase in all-cause mortality risk among cohort men with stable low TC levels. Nonillness mortality (deaths caused by trauma and suicide) was not related to either TC change or the average of TC levels in exams 1 and 3. CONCLUSIONS: These results add strength to the reverse-causality proposition that catabolic diseases cause TC to decrease.

Aged↗