PubMed Health⌕ Search

Biomedical subjects

R Cheng

Publications and source records attributed to R Cheng.

At least 91 records · Page 5Linked to original sources
PubMed1992

Arbitrarily primed PCR fingerprinting of RNA.

Fingerprinting of RNA populations was achieved using an arbitrarily selected primer at low stringency for first and second strand cDNA synthesis. PCR amplification was then used to amplify the products. The method required only a few nanograms of total RNA and was unaffected by low levels of genomic double stranded DNA contamination. A reproducible pattern of ten to twenty clearly visible PCR products was obtained from any one tissue. Differences in PCR fingerprints were detected for RNAs from the same tissue isolated from different mouse strains and for RNAs from different tissues from the same mouse. The strain-specific differences revealed are probably due to sequence polymorphisms and should be useful for genetic mapping of genes. The tissue-specific differences revealed may be useful for studying differential gene expression. Examples of tissue-specific differences were cloned. Differential expression was confirmed for these products by Northern analysis and DNA sequencing uncovered two new tissue-specific messages. The method should be applicable to the detection of differences between RNA populations in a wide variety of situations.

Animals↗
PubMed1992

Current status of education and training in occupational health and their development programs in China.

There are 40 post graduate schools of public health in China, from where 1,400 students are graduating every year. Fourteen percent of them are going into occupational health field. A total of about 25,000 specialists are now working in the occupational health field. However, this number is only 1 percent of all health workers in China. Facts on the educational resources in China including responsible institutions and programs for such occupational health specialists are introduced and discussed. Finally a program for increasing the number of occupational health specialists in the Eighth Five-year Plan of China is introduced.

China↗
PubMed1992

Computer-assisted three-dimensional reconstruction and simulations of vestibular macular neural connectivities.

The macular neuroepithelium is morphologically organized as a weighted neural network for parallel distributed processing of information. The network is continuous across the striola, where some type II hair cells synapse with calyces containing type I cells with tufts of opposite directional polarities. Whether other hair cell to calyx appositions that lack synapses interact because of intercellular potassium accumulation remains an open question. A functionally important inference of macular organization is that just as arrays of hair cells communicate an entire piece of information to a nerve fiber, so do macular subarrays of nerve fibers (not single units) carry the whole coded message to the brain stem. Moreover, the size of the network subarray can expand or become more limited depending upon the strength and/or duration of the input. It is the functioning of the network and its subarrays that must be understood if we are to learn how maculas carry out their work and adapt to new environments. Simulations of functioning maculas, or subparts, based on precise morphology and known physiology are useful tools to gain insights into macular information processing. The current simulations of afferent collateral electrical activity are a prelude to development of a 3-D model. The simulations demonstrate a relationship between geometry and function, with the diameter of the stem apparently being a major determinant of electrical activity transmitted to the base in the case of collaterals with short stems. Thus, while changes in synaptic number and/or size may be an important adaptive mechanism in an altered g environment, changes in diameter of the stem is another means of altering outflow. Research on the effects of microgravity should be extremely useful in examining the validity of this and other concepts of neural adaptation, since maculas are biological linear accelerometers ideally suited to the task. Maculas are also extremely interesting to study in detail because of the richness of connectivities and submicroscopic organization they present. Many of their features are common with more complex parts of the brain. It seems possible that knowledge of the three-dimensional geometric relationships operative in a functioning macula will contribute much to the understanding of the dynamics underlying more complex behavior. Computerized approaches greatly facilitate this task and provide an objective method of analysis. It is likely that, in the end, simple rules will be found to govern optimal neural architectural organization, even at higher cognitive levels. The architecture only appears complex because we do not yet grasp its meaning.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Maculae↗
PubMed1991

Monoclonal antibody-based therapy of a human tumor xenograft with a 177lutetium-labeled immunoconjugate.

177Lutetium (177Lu) is a member of the family of elements known as lanthanides or rare earths. Monoclonal antibody (MAb) CC49, a murine IgG1, which is reactive with the tumor-associated antigen, TAG-72, has been shown previously to react with a wide range of human carcinomas; CC49 reacts to a different epitope on the TAG-72 molecule than MAb B72.3 and has a higher binding affinity. We report here the first use of a 177Lu-labeled immunoconjugate, 177Lu-CC49, in an experimental therapy model for human carcinoma. 177Lu-CC49 was shown to delay the growth of established LS-174T human colon carcinomas in athymic mice at a single dose of 50 microCi. Overt toxicity was observed with the administration of approximately 500 microCi of 177Lu-CC49 in which 5 of 9 mice died of apparent marrow toxicity. A single administration of 200 or 350 microCi of 177Lu-CC49, however, was shown to eliminate established tumors through the 77-day observation period after MAb administration. Dose fractionation experiments revealed that at least 750 microCi of 177Lu-CC49 (250 microCi/week for 3 consecutive weeks) was well tolerated in that 9 of 10 mice survived. Moreover, this dose schedule was able to eliminate the growth of relatively large (300 mm3) human colon tumor xenografts in 90% of the animals treated. Single-dose and dose fractionation studies were also carried out with an isotype-matched control MAb, 177Lu-MOPC-21. In all dose schedules, a large differential was seen between the therapeutic effects of the 177Lu-CC49 versus that of the 177Lu-control MAb. The merits and limitations of the use of 177Lu-labeled immunoconjugates (in particular, 177Lu-CC49) are discussed in terms of potential novel therapeutics for human carcinoma.

Adenocarcinoma, Mucinous↗
PubMed1990

[Chemical constituents of Isodon parvifolia (Batalin) Hara].

Twelve compounds were isolated from the leaves and stems of Isodon parvifolia. This paper deals with the isolation and identification of two diterpenes epinodosinol (I), lasiodonin (II) and two triterpenes alpha-amyrin (XI a) and beta-amyrin (XI b).

Antineoplastic Agents, Phytogenic↗
PubMed1989

Measurement of methionine enkephalin and leucine enkephalin in rat brain regions by high-performance liquid chromatography with coulometric electrochemical detection.

A method is described for the determination of two pentapeptides, methionine enkephalin (H-Tyr-Gly-Gly-Phe-Met-OH) (ME) and leucine enkephalin (H-Tyr-Gly-Gly-Phe-Leu-OH) (LE) in discrete rat brain regions. Separation and quantitation were performed by reversed-phase high-performance liquid chromatography with coulometric detection. Perchloric acid extracts of the tissue after enzyme inactivation by heat treatment were passed through a normal-phase solid-phase extraction diol (COHCOH) column, and endogenous ME and LE were subsequently eluted with methanol. The mobile phase was 1-propanol-phosphate buffer (pH 5.5) (9:91). Eluted samples were detected electrochemically using dual coulometric electrodes operated in screen mode. Each of these enkephalins gave a linear response over the range 40-160 ng/ml cerebellar homogenate (0.8-3.2 ng absolute amount on column). Analytical recoveries of synthetic ME and LE, added to the homogenates, were 70 +/- 3 and 70 +/- 10%, respectively, when compared with enkephalins dissolved in water. The mean between-assay coefficients of variation for synthetic ME and LE were lower than 10.7 and 7.4%, respectively, over the concentration range studied. The within-assay coefficients of variation for synthetic ME and LE were 11.4 and 9.5%, respectively, at the lowest concentration. The present method has been applied to a study determining the levels of endogenous ME and LE in discrete rat brain regions.

Animals↗
PubMed1985

Differential expression of the Leu-7 antigen on human lung tumor cells.

The HNK-1 monoclonal antibody detects an antigen (Leu-7) on a subpopulation of large granular lymphocytes which have natural killer cell function. Recently this antigen has been found on nonhemopoietic tissues. In the present study human lung tumor cells were examined for the presence of Leu-7 antigen using an enzyme-linked immunosorbent assay, immunoperoxidase staining, and fluorescence-activated cell sorter analysis. All small cell lung tumor cells tested were Leu-7 positive. In contrast only two of seven biopsy specimens from small cell lung cancer patients were Leu-7 positive. Several large cell lung tumor lines were Leu-7 positive while an adenocarcinoma and squamous cell carcinoma were negative. These results indicate that expression of Leu-7 antigen on lung tumor cells is heterogeneous both in vitro and in vivo. Small cell lung tumor lines have been reported to undergo histological conversion in vitro accompanied by the loss of a number of biochemical markers. In our study histologically converted cells exhibited much less reactivity with HNK-1 than did the parent cells. These results indicate that the degree of expression of Leu-7 antigen may be under the control of differentiation-related events. Thus monoclonal antibody HNK-1 has been very useful in studying heterogeneity within and among lung tumor cells.

Antibodies, Monoclonal↗
PubMed1980

Electroacupuncture elevates blood cortisol levels in naive horses; sham treatment has no effect.

It was hypothesized that electroacupuncture releases beta-endorphin and ACTH from the pituitary. Since ACTH induces the release of cortisol from the adrenal glands, blood cortisol level should be enhanced by electroacupuncture. The present result shows that the blood cortisol levels of horses are significantly increased after 30 min of electroacupuncture treatment while the sham treatment (control) shows an insignificant effect.

Acupuncture Therapy↗
PubMedDate not supplied

Enzyme-linked immunoassay for respiratory syncytial virus is not predictive of bronchiolitis in sudden infant death syndrome.

Although respiratory syncytial virus (RSV)-infected infants may present with apnea, the role that RSV plays in sudden infant death syndrome (SIDS) is speculative. To determine whether RSV is associated with bronchiolitis in these patients, we examined histologic sections of lungs from 41 apparent SIDS cases and compared the results with those of enzyme-linked immunofluorescent assay (EIA) from nasal washings. Bronchiolitis was defined by a bronchiolar inflammatory cell infiltrate plus epithelial necrosis. A positive EIA was associated with bronchiolitis in 8 instances, compared with 6 having a positive EIA and negative histology, 14 having a negative EIA and positive histology, and 13 having EIA and histology both negative. These results yield a predictive value of a positive test of 57% and a predictive value of a negative test of 48% (P > .9 by chi square analysis). Although RSV of the upper respiratory tract may be related to SIDS, our results indicate that EIA of nasal washings is not predictive of bronchiolitis, and we recommend other means of verification of histologic results.

Antibodies, Viral↗