Search PubMed⌕ Search

Biomedical subjects

R Chen

Publications and source records attributed to R Chen.

At least 343 records · Page 19Linked to original sources
PubMed1998

[Immunodiagnosis of cysticercosis by simplified western blotting using recombinant fusion protein as antigen].

AIM: To provide simple and useful method for the immunodiagnosis of cysticercosis. METHODS: Fusion protein of beta-galactosidase-Cysticercus cellulosae cDNA was analysed with simplified Western blot. RESULTS: The positive rate was 93.5% when detecting 124 cases of human cysticercosis sera with four clones (cC1, cC2, cP1 and cH1) and 100% when detecting 38 cases of porcine cysticercosis sera with three clones (cC1, cC2 and cP1), being higher than those using monoclone fusion protein alone. Moreover, the fusion proteins did not react with other parasitosis sera. CONCLUSION: Simplified Western blot analysis using recombinant fusion protein as antigen was highly sensitive and specific and easy to be operated.

Animals↗
PubMed1998

[Detection of TT virus DNA and sequence analysis of partial gene of TTV in sera from blood donors].

In order to investigate TTV infection in blood donors, 262 sera samples from blood donors were detected by nested--PCR method using primers from ORF1 of TTV genome DNA. The results showed that 18 of 58(31.0%) serum samples from blood donors with elevated transaminase level were positive for TTV DNA. 30 of 204 (14.7%) sera samples from blood donors with normal transaminase levels were positive for TTV DNA. There were significant difference between them (chi 2 = 38.1, P < 0.05). Five products of PCR for TTV DNA were purified and cloned to T Vector. The sequence analysis showed that there were above 97% nucleotide identity among AB008394 (from Japan), TTVCHNI (from China) and our 5 isolates from blood donors. The results suggest that there exists TTV infection among blood donors in China. TTV may be transmitted by blood transfusion. Our isolates, AB008394 and TTVCHN1 share a same genotype.

Base Sequence↗
PubMed1998

[Crackle detection and classification based on matched wavelet transform].

In this paper, we present a method for crackle detection which is based on 'matched' wavelet transform. We first modeled crackles as a mathematical function. Then we designed a matched mother wavelet based on this model. Applying a soft-threshold to the results of the continuous wavelet transform to suppress noise further, we obtained the optimal scale Crackles were detected based on the envelope of the signal at optimal scale, and could be classified based on energy distribution with scale. The theory, methods and experimental results are given in detail.

Algorithms↗
PubMed1998

Analysis of data associated with seemingly temporal clustering of a rare disease.

Three statistical tests aimed at detecting temporal clustering within a given short series of diagnoses are presented. These tests are based on a standardized time interval between consecutive diagnoses. Two of the tests (the Cuscore and the Sets tests) are derived from sequential monitoring techniques which are sensitive to temporal clustering within the data set. The third test (R test) is not sequential and its sensitivity is focused on the average increase in the overall rate of the disease rather than on clustering within the series. Power curves are presented for conditions related to the intensity level of the subtle epidemic, the cluster size and the number of diagnoses. None of the techniques showed highest efficiency over all the specified conditions. The R test is the most efficient when the relative risk is 2 or less, and the Cuscore test is the most efficient method when the relative risk is > or = 2.5.

Decision Support Techniques↗
PubMed1998

Evaluation of night vision disturbances in contact lens wearers.

PURPOSE: We quantitatively recorded and evaluated night vision disturbances with physiologically dilated pupils. We compared the amount of image degradation experienced in eyes wearing spherical soft contact lenses with the amount of image degradation experienced by subjects wearing spectacles. METHODS: We prospectively evaluated 69 eyes from 35 myopic subjects with no ocular pathology. The subjects ranged in age from 22 to 35 years. We designed a test to quantitatively record image degradation with physiologically dilated pupils in scotopic conditions of dim ambient light. Previously, we have shown that this test accurately measures image degradation. We used this test to compare image degradation between new spherical soft contact lens and spectacle correction. Hyperopes and eyes with greater than 1.50 D of astigmatism were excluded. RESULTS: Adequately correcting myopic refractive error decreased recorded image degradation (P < or = 0.0001). There was no significant difference in the amount of image degradation between spectacle trial frames and new spherical soft contact lenses (P < or = 0.2885). CONCLUSIONS: Our test offers an objective method of assessing night vision disturbances in contact lens wearers. Our results suggest that image degradation, which may contribute to the sensation of glare experienced by some patients, is influenced equally by contact lens and spectacle correction.

Adult↗
PubMed1998

Detection of CD5 antigen on B cell lymphomas in fixed, paraffin embedded tissues using signal amplification by catalyzed reporter deposition.

CD5 surface antigen is expressed on some categories of B cell lymphomas. The detection of CD5 coexpression on malignant B cell infiltrates, particularly in small biopsy specimens, is useful in distinguishing between small lymphocytic lymphoma, mantle cell lymphoma, low grade marginal zone B cell lymphoma, and follicular small cleaved cell lymphoma. However, conflicting results have been reported with regard to the detection of CD5 antigen expression on B cell non-Hodgkin's lymphomas (B-NHLs) in fixed, paraffin embedded tissues using routine immunohistochemical (IHC) staining techniques. We used catalyzed reporter deposition (CARD) as a strategy to amplify the IHC signal and consequently increase the sensitivity of antigen detection. CARD improved detection of CD5 antigen without sacrificing specificity of the test. In our study, virtually all malignant B-NHLs with CD5 antigen expression showed strong immunoreactivity for a commercially available anti-CD5 monoclonal antibody using CARD, whereas the majority of the same lymphomas did not label for CD5 using routine IHC without CARD amplification. The concordance between CD5 antigen detection by immunophenotyping of fresh or frozen tissues and immunostaining with CARD amplification on paraffin fixed tissue sections was 100%. It appears that this method can be applied in the diagnostic evaluation of B-NHLs or in other situations that a weak antigen signal is present.

Biotin↗
PubMed1998

Focal dystonia and repetitive motion disorders.

It commonly is observed that focal hand dystonias, such as writer's cramp or musician's cramp, are associated with repetitive movements, although definitive proof of a causal relationship is lacking. These focal dystonias are often task specific, with involuntary muscle contractions occurring only when patients perform specific acts such as writing or playing a musical instrument. Physiologic studies show deficiencies in spinal reciprocal inhibition and abnormalities of central sensory processing and motor output that may be related to reduced cortical inhibition. Recent studies in primates support the notion that repetitive motions can induce plasticity changes in the sensory cortex leading to degradation of topographic representations of the hand, and raise the possibility that sensory training may be beneficial. Current treatment options for focal dystonia include botulinum toxin injections, anticholinergics, baclofen, benzodiazepines, and occupational therapy.

Cumulative Trauma Disorders↗
PubMed1998

[The types and distributive features of gene mutation on beta-thalassemia in three districts in northwest China].

OBJECTIVE: To sum up the results of gene analyses on beta-Thalassemia in three districts in northwest China and discuss the types and distributive features of the mutation. METHODS: Polymerase china reaction in combination with dot-blot hybridization of allele-specific oligonucleutide probes(PCR-ASO). RESULTS: In the gene analysis carried out in 85 probands with beta-Thalassemia, twelve types of gene mutation were identified from five nationalities. CD8(-AA), CDs8-9(+G), CDs27-28(+C) heterozygote and [-28(A-->uG). CD17(A-->uT)/N] double heterozygote were firstly assayed in these districts besides the common types in Chinese, of which, [-28(A-->uG). CD17(A-->uT)/N] as double gene mutation in the same chromosome is rare. CONCLUSION: There are significant differences in the distribution and nationality features of gene mutation types for beta-Thalassemia in the three districts, so the three districts as a whole is an area with special distributive features of the disease.

Adolescent↗
PubMed1998

Calculation and comparison of average standardised mortality ratio in occupational cohort study.

The average standardised mortality ratios (SMRs) were calculated, by the methods of median, mean, Poisson and meta-analysis, across 85 occupational cohorts. The difference of average SMR between these methods was reduced with increasing number of cases. The SMRs from the Poisson and fixed/random effects models were close, however, the fixed and random effects models should be more appropriate as the Poisson model ignores variation from the characteristics of different cohorts. There were also wider confidence intervals for the random effects model than for the fixed effects model. Based on such calculations and comparisons of average SMRs, we would suggest that if a total cohort consists of several subcohorts, a summary SMR should be calculated by the fixed effects or random effects models, instead of the Poisson model.

Chi-Square Distribution↗
PubMed1997

Dachshund and eyes absent proteins form a complex and function synergistically to induce ectopic eye development in Drosophila.

The eyeless, dachshund, and eyes absent genes encode conserved, nuclear proteins that are essential for eye development in Drosophila. Misexpression of eyeless or dachshund is also sufficient to induce the formation of ectopic compound eyes. Here we show that the dachshund and eyes absent genes act synergistically to induce ectopic retinal development and positively regulate the expression of each other. Moreover, we show that the Dachshund and Eyes Absent proteins can physically interact through conserved domains, suggesting a molecular basis for the genetic synergy observed and that a similar complex may function in mammals. We propose that a conserved regulatory network, rather than a linear hierarchy, controls retinal specification and involves multiple protein complexes that function during distinct steps of eye development.

Animals↗
PubMed1997

Structural constraints in protein engineering--the coenzyme specificity of Escherichia coli isocitrate dehydrogenase.

In a previous study we reported on the successful inversion of coenzyme specificity in isocitrate dehydrogenase (IDH) from NADP to NAD [Chen, R., Greer, A. & Dean, A. M. (1995) A highly active decarboxylating dehydrogenase with rationally inverted coenzyme specificity, Proc. Natl Acad. Sci. USA 92, 11666-11670]. Here, we explore alternative means to generate NAD dependence in the NADP-dependent scaffold of Escherichia coli IDH. The results reveal that engineering a preference for NAD is constrained by the architecture of the IDH coenzyme binding pocket and confirms that the substituted Asp344 in the engineered enzyme is the major determinant of coenzyme specificity. Mutations in the 316-325 loop, which forms part of the coenzyme binding site, reduce activity through transmission of long-range conformational changes into the active site some 14 A distant. Conformational changes seen upon substituting Cys332-->Tyr are not directly involved with improving activity. Replacements at Cys201 reveal that subtle changes in the packing of hydrophobic residues (Met and Ile versus Leu) can elicit markedly different responses. We caution against using sequence alignments as the sole guide for mutagenesis and show how a combination of rational design of active-site residues based on X-ray structures and random substitutions at surrounding residues provides an efficient means to improve enzyme preference and catalytic efficiency towards novel substrates.

Amino Acid Sequence↗
PubMed1997

The affected gene underlying the class K glycosylphosphatidylinositol (GPI) surface protein defect codes for the GPI transamidase.

The final step in glycosylphosphatidylinositol (GPI) anchoring of cell surface proteins consists of a transamidation reaction in which preassembled GPI donors are substituted for C-terminal signal sequences in nascent polypeptides. In previous studies we described a human K562 cell mutant, termed class K, that accumulates fully assembled GPI units but is unable to transfer them to N-terminally processed proproteins. In further work we showed that, unlike wild-type microsomes, microsomes from these cells are unable to support C-terminal interaction of proproteins with the small nucleophiles hydrazine or hydroxylamine, and that the cells thus are defective in transamidation. In this study, using a modified recombinant vaccinia transient transfection system in conjunction with a composite cDNA prepared by 5' extension of an existing GenBank sequence, we found that the genetic element affected in these cells corresponds to the human homolog of yGPI8, a gene affected in a yeast mutant strain exhibiting similar accumulation of GPI donors without transfer. hGPI8 gives rise to mRNAs of 1.6 and 1.9 kb, both encoding a protein of 395 amino acids that varies in cells with their ability to couple GPIs to proteins. The gene spans approximately 25 kb of DNA on chromosome 1. Reconstitution of class K cells with hGPI8 abolishes their accumulation of GPI precursors and restores C-terminal processing of GPI-anchored proteins. Also, hGPI8 restores the ability of microsomes from the mutant cells to yield an active carbonyl in the presence of a proprotein which is considered to be an intermediate in catalysis by a transamidase.

Acyltransferases↗
PubMed1997

Clustering of leukaemia cases in a city in Israel.

A temporal cluster of cases may result from exposure to a new carcinogen, but it may also occur under stable conditions or as result of another factor, such as changes in medical practice. In this study, we used several complementary methods to detect a cluster and to conduct an initial investigation regarding its cause. The analyses included three stages, and were based on the time interval between consecutive diagnoses. First, we applied the sets monitoring technique to detect clustering. Following the detection (alarm), a confirmatory analysis was conducted in order to confirm or refute it as a true alarm. We applied this analysis to the first five cases diagnosed subsequent to the alarm. With a graphical display of the temporal pattern of the diagnoses, we considered the possible causes leading to the cluster. The data included registered diagnoses of leukaemia cases made from 1960 to 1990 among residents of Ashkelon, Israel. Clustering was detected for acute lymphatic leukaemia and for chronic myeloid leukaemia. We found that the temporal patterns of the diagnoses consistent with the possibility that these two clusters are due to exposure to a common local carcinogen. We cannot however, rule out the possibility that these clusters are due to unknown factors.

Adolescent↗
PubMed1997

Risk of chronic arthropathy among women after rubella vaccination. Vaccine Safety Datalink Team.

CONTEXT: A review by the Institute of Medicine found a possible relationship between rubella vaccination and chronic arthritis among women. OBJECTIVE: To evaluate the risk of persistent joint and neurologic symptoms in rubella seronegative women subsequently vaccinated with RA 27/3 rubella vaccine. DESIGN: Retrospective cohort study based on computerized laboratory data and medical record review. Records were reviewed for symptoms occurring within 2 years before and after the date of serological testing and to identify vaccinees. Possible cases were evaluated by a rheumatologist blinded to serological findings and vaccination status. SETTING: Large health maintenance organization in northern California. PATIENTS: Women aged 15 to 59 years serotested for rubella during 1990 with continuous health plan membership for 2 years before and after the date of their serological test. Seronegative women immunized within 1 year of serotesting (n=971) were defined as exposed. Primary comparison groups included all unvaccinated, seronegative women (n=924) and randomly selected seropositive, unvaccinated women (n=2421) matched to exposed subjects on serological test date and age (+/-3 years). MAIN OUTCOME MEASURES: Prevalence and incidence of chronic joint and neurologic symptoms during 1-year follow-up period stratified by age and serological findings, immunization, and postpartum status. RESULTS: No significantly increased risk was associated with receipt of rubella vaccine for any outcome except for prevalence of carpal tunnel syndrome in vaccinated women at least 30 years old compared with seropositive, unvaccinated women (2.9% vs 1.4%; P=.03). A total of 34 women had onset of conditions within the 1-year follow-up period; 9 of these were in the group of seronegative, immunized women, of whom 6 had onset of symptoms within 6 weeks of vaccination. Among these 6 women, symptoms included transient arthritis or arthralgias (<6 weeks duration) in 4 women, arthralgia of indeterminate chronicity in 1 woman, and carpal tunnel syndrome in 1 woman. Postpartum women across all groups were less likely to be seen for nontraumatic arthropathies than nonpostpartum women (4.5% vs 7.2%, P=.08 in vaccinated women; 4.8% vs 8.1%, P=.09 in seronegative controls; and 4.8% vs 10.0%, P=.01 in seropositive controls). CONCLUSIONS: In this large retrospective cohort analysis there was no evidence of any increased risk of new onset chronic arthropathies or neurologic conditions in women receiving the RA 27/3 rubella vaccine. These data support the continued vaccination of rubella-susceptible women to reduce the risk of congenital rubella syndrome.

Adolescent↗
PubMed1997

The efficiency of the sets and the cuscore techniques under biased baseline rates.

Statistical techniques used for surveillance of disease incidence rates are generally based on the assumption of known baseline rate of the disease monitored, whereas actually it is an estimate obtained from a large sample. As a result, the time interval until true or false alarm is shorter or longer than assumed. In this study, we evaluate the performance of the sets and of the cuscore techniques when the estimate of the baseline rate is biased. We evaluate the effect of an underestimated baseline rate with respect to frequency of false alarms and to that of an over estimated rate with respect to the delay until elicitation of a true alarm. We evaluate the effects of 5 per cent and 10 per cent bias in the estimated baseline rate for specified conditions associated with sparse data. The results show that the effect of plus or minus 5 per cent bias in the estimate are moderate and those of 10 per cent are substantial. In general, the effect of an overestimated baseline rate is greater on the sets technique than it is on the cuscore technique and the effect of an underestimated rate is greater on the cuscore technique than it is on the sets technique. However, the differences between the two techniques are small on both perspectives. The two methods differ also with respect to the expected time until true alarm when the specified baseline rate is unbiased. The sets technique is the more efficient in detecting a two-fold increased rate when the number of diagnoses expected annually (E(X)) is less than 1.62, and the cuscore is the more efficient technique when E(X) > 1.62. We use the term 'turning point' to define the regions in which the sets technique and the cuscore techniques are preferred. With an estimated baseline rate that is 5 per cent higher than the actual rate, the turning point falls from 1.62 to 1.45 when the rate is twice the baseline rate, and from 5.75 to 4.34 when the rate is triple the baseline rate.

Bias↗
PubMed1997

The exchange between proglycogen and macroglycogen and the metabolic role of the protein-rich glycogen in rat skeletal muscle.

The aim of this study is to determine if proglycogen and macroglycogen are kinetically related in rat skeletal muscle. Eight groups of anesthetized fasted rats (seven hepatic-occluded and one nonoccluded) were intravenously infused with [3-3H]glucose at a rate of 1.7 microCi x min(-1) for 20 min. At the end of infusion, hindlimb muscles were excised and rapidly frozen in liquid nitrogen. Proglycogen was extracted by precipitation in 10% TCA; and macroglycogen as a part of total glycogen by precipitation in 20% KOH-65% ethanol. Along with the tracer, the occluded rats were also infused with: saline (group 1); insulin at rates ranging from 5 to 50 mU x min(-1) (groups 2 to 5); and insulin at a rate of 10 mU x min(-1) plus glucose at rates of 10.2 and 20.4 micromol x min(-1), respectively (groups 6 and 7). The infusion regimens resulted in up to 30-fold difference in whole-body glucose utilization among the rats. In the rats infused with saline and insulin at a rate of 5 mU x min(-1), [3H]glucose was found to be exclusively incorporated into proglycogen. Incorporation into macroglycogen was found in the rats infused with insulin at rates > 10 mU x min(-1). Supplementary glucose infusion increased the synthesis of [3H]proglycogen (four- to sixfold), and equilibrated the two extractable forms of glycogen in the insulin-infused rats. In the saline-infused nonoccluded rats, only proglycogen was found to be labeled. In conclusion, our data indicate that in the intact and hepatic-occluded rats, proglycogen in the skeletal muscles may undergo synthesis and degradation of its own more readily than exchange between itself and depot macroglycogen.

Animals↗
PubMed1997

Subacute uremic and diabetic polyneuropathy.

We present 4 patients who had a subacute, predominantly motor polyneuropathy associated with diabetes mellitus and end-stage renal disease. Electrophysiological studies and muscle biopsy indicated a primary axonal degeneration of nerve with secondary segmental demyelination, and mild to moderate, acute and chronic denervation of muscle. A relative absence of denervation potentials on needle electromyography was an unusual feature. Three of our patients improved with a switch from conventional to high-flux hemodialysis. We speculate on possible mechanisms.

Aged↗