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Biomedical subjects

M Chen

Publications and source records attributed to M Chen.

At least 973 records · Page 54Linked to original sources
PubMed1973

Automated detection of Haemophilus influenzae.

Addition of heme (X factor) and pyridine nucleotide (V factor) to the medium permits rapid growth of Haemophilus influenzae, with evolution of easily detectable amounts of (14)CO(2). Radiometric media containing X and V factor should be used when evaluating clinical specimens which might contain Haemophilus species.

Aerobiosis↗
PubMedDate not supplied

Improved sonographic visualization of choledocholithiasis.

Ultrasonographic diagnosis of gallstones in the distal part of extrahepatic duct is not easy. A number of new techniques have been used by the authors to improve the detection rate of these stones. They include filling the duodenum and gastric antrum with drinking water, scanning after a fatty meal, and changing the patient's position during scanning. Ultrasound successfully identified choledocholithiasis in 78 of 104 patients for a sensitivity of 75%. There were 26 false-negative cases. The chief causes of the false negatives were obscuration of the distal duct by overlying bowel gas, missing of small stone in a nondilated bile duct, and misdiagnosis of soft pigment or an impacted stone having an atypical hypoechoic image in the distal duct as a tumor. False-positive diagnosis occurred in 32 out of 188 noncalculous cases, giving a specificity of 83%. These cases represent various hyperechoic lesions in the neck of gallbladder, cystic duct, and periampullary region. The overall diagnostic accuracy of gallstones in the extrahepatic bile duct by ultrasound was 80% (234/292).

Gallstones↗
PubMedDate not supplied

Imaging of ovarian cancer.

Cross sectional imaging continues to play an increasingly important role in ovarian cancer diagnosis, staging, and treatment follow-up. Screening for ovarian cancer remains a controversial subject. The combined use of clinical examination, CA-125, and endovaginal ultrasound (US) are being advocated for high risk patients but consensus recommendation for screening awaits further studies. In characterization of an ovarian neoplasm US is indisputedly the primary imaging approach. Only when US is inconclusive are further studies warranted. Magnetic resonance imaging (MRI) is generally preferred to computer tomography (CT). A prospective MRI-CT clinical trial has not been performed as yet. Preoperative staging by imaging is slowly gaining its acceptance. This is mostly due to the awareness of the difficulties and inaccuracy in surgical staging when unsuspected extensive disease is present. Furthermore, in known resectable ovarian cancer, primary chemotherapeutic cytoreduction may be a better treatment option. Accuracy of CT and MRI in staging ovarian cancer is similar, CT, however, is faster, more widely available, and less expensive; these are important attributes that are decisive in this time of health reimbursement constraints.

Female↗
PubMedDate not supplied

An in vivo 19F NMR study of isoflurane elimination as a function of age in rat brain.

In vivo 19F NMR at 4.7 T has shown that the biphasic elimination of the vapor anesthetic isoflurane from rat brain is ca 15% slower in old (23-24 months) animals compared with young (5-6 months) animals. The fast kinetic component has a t1/2 of ca 7-9 min and the slow event, 100-115 min. Gas chromatographic measurement of arterial blood elimination displays age attenuation to the same extent, although a monophasic kinetic process (6-7 min). The slow wash-out from brain is thought to involve elimination from intracranial fatty tissue as postulated by others in rabbit brain. Longitudinal relaxation time measurements show monoexponential recovery and essentially identical values for young (1.09 + 0.11 s) and old (1.04 +/- 0.09 s) animals. For dipalmitoylphosphatidylcholine vesicles the monoexponential recovery also suggests rapidly exchanging averaged homogeneous lipid environments for the anesthetic, but the longer T1s (2.75 +/- 0.25 s) imply less restricted mobility compared with brain. Single T2 values were obtained in vivo, indicating either a single compartment or rapid exchange between multiple environments. These measurements were inconsistent, undoubtedly as a result of B1 inhomogeneity. The age-attenuated elimination kinetics for isoflurane are consistent with poorer cardiopulmonary function, whereas the T1 data suggest similar environments for the anesthetic in young and old brain tissue.

1,2-Dipalmitoylphosphatidylcholine↗
PubMedDate not supplied

Role of opioid receptors in cardioprotection of cold-restraint stress and morphine.

Since cold exposure confers cardioprotection, the present study attempted to determine the role of opioid receptors (OR). Stress with cold exposure and restraint for 3 h, shown previously to induce peptic ulcer in a synergistic manner, attenuated infarct size induced by myocardial ischemia and reperfusion in the isolated perfused rat heart from 36.64 +/- 1.8 to 22.85 +/- 2.6%. This is similar to protecting the rat with morphine at 8 mg/kg, which also attenuated the infarct size from 36.26 +/- 1.6 to 20.30 +/- 2.1%. The effects of cold-restraint or morphine were abolished by naloxone, a non-selective OR antagonist; nor-binaltorphimine, a selective kappa-OR antagonist; naltrindole, a selective delta-OR antagonist, or CTOP, a selective mu-OR antagonist. The effects were also attenuated by blockade of protein kinase C or the mitochondrial K(ATP) channel. The finding is first evidence that all three OR subtypes mediate cardioprotection of cold-restraint stress in the rat.

Adenosine Triphosphate↗
PubMedDate not supplied

A research-oriented medical cost accounting system.

Prospective research into factors affecting health care costs for individual patients requires a hybrid information management system with some features usually associated with a medical billing package and other features common to research databases. Furthermore, data collection for such a project must often be done in the field where a portable computer is most convenient. A software program is described which has been developed to address these disparate needs. It allows classification by study protocol assignment and provides multiple summary formats for the assessment of costs. For example, charges can be stratified by specialty, by category of service (pharmacy, room, surgery, respiratory therapy, etc.), by magnitude of expense ('big' vs 'little' ticket items) and so forth. The system design described may prove useful to other investigators studying variation in health care costs.

Accounting↗
PubMedDate not supplied

Analysis of a myosin-like protein and the role of calcium in the E. coli cell cycle.

For a number of years now, we have argued that current models for the control of initiation of DNA synthesis, chromosomal partitioning and septum formation in Escherichia coli are unsatisfactory. Indeed, we could argue that despite considerable efforts, with the possible exception of dnaA and ftsZ, no genes specifically implicated in these control processes have been identified. In the cases of DnaA and FtsZ, no evidence has appeared to indicate how such molecules might be regulated to act once per cycle. In 1988, we formulated a specific proposal that the timing of cell cycle events in E. coli might be determined by a Ca++ flux, mediated by calcium-binding proteins and protein kinases and culminating, in the case of chromosome segregation and division, in the action of force-generating proteins such as myosin (Norris et al., 1988). In formulating this proposal, we took the view that the fundamental elements of cell cycle regulation are likely to be highly conserved across all species including prokaryotes. In this presentation, we shall describe the approaches we have been taking in order to test this hypothesis and to summarize the data obtained, in particular in relation to new genes identified which may play a role in the E. coli cell cycle. We shall also briefly indicate recent data from other laboratories consistent with our general hypothesis.

Bacterial Proteins↗