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Biomedical subjects

J Cheng

Publications and source records attributed to J Cheng.

531 records · Page 30Linked to original sources
PubMedDate not supplied

Association between metabolic gene polymorphisms and susceptibility to peripheral nerve damage in workers exposed to n-hexane: a preliminary study.

Chronic exposure to n-hexane may result in peripheral neuropathy. 2,5-Hexanedione (2,5-HD) has been identified as a toxic metabolite of n-hexane. The CYP2E1, CYP1A1 and GST genes are involved in the formation of 2,5-hexanedione from n-hexane as well as the elimination of 2,5-HD-formed electrophile, and these genes are highly polymorphic in the general population. A nested case-control study in an industrial cohort was conducted to evaluate the associations between polymorphisms in these metabolic genes and n-hexane-induced peripheral nerve damage. The study subjects included 22 cases, who worked in a printing factory with symptoms of peripheral nerve damage, and 163 controls, who came from the same factory of cases. DNA was extracted from blood samples and genotyping was conducted for CYP2E1 Pst, CYP2E1 Dra, CYP2E1 Ins96, CYP1A1 Msp, GSTT1 null, GSTM1 null and GSTP1 105V. Unconditional logistic regression was applied to estimate the odds ratio and 95% confidence intervals. There were no significant differences between the two groups regarding age, sex, smoking and alcohol status. A significant association between Dra polymorphism and peripheral nerve damage was found. The frequency of CYP2E1 Dra homozygous mutation in the case group (18.2%) was higher than that in the control group (3.7%, p=0.015). Individuals with homozygote genotype (CC) of CYP2E1 Dra had a significantly higher risk of peripheral nerve damage compared with those with DD genotype (adjusted OR=?.58, 95% CI=1.32-23.65) after n-hexane exposure duration, sex, age, smoking and alcohol status were adjusted. No significant association was found that CYP2E1 Pst, CYP2E1 Ins96, CYP1A1 Msp, GSTT1, GSTM1, GSTP gene polymorphisms associated with the susceptibility of peripheral nerve damage. These findings suggested that CYP2E1 gene might increase the susceptibility to n-hexane-induced peripheral damage.

Adult↗
PubMedDate not supplied

A study of thyrotropin-releasing hormone for the treatment of spinal muscular atrophy: a preliminary report.

OBJECTIVE: To determine whether thyrotropin-releasing hormone (TRH) can increase muscle strength in children with spinal muscular atrophy types 2 and 3. DESIGN: A randomized, double-blinded, controlled, 5-wk drug trial of six subjects and three controls. Subjects and controls ranged from 4 to 8 yr of age and were randomly assigned to treatment and placebo groups in a ratio of 2:1. TRH (protirelin) or placebo was delivered intravenously through percutaneous intravenous catheters at a dose of 0.1 mg/kg (in 50 ml of normal saline) for a total of 29 days. Patients were evaluated using electromyography and handheld dynamometry of the deltoids, biceps, triceps, wrist extensors, hip flexors, quadriceps, hamstrings, and grip strength before and immediately after 5 wk of treatment. A unidirectional t test was used to compare mean values. RESULTS: Dynamometry improved significantly only for the six treated subjects (P < 0.02). Peroneal nerve conduction velocities were significantly faster in the treatment group (paired t test, P = 0.036). The parents of the treated children also provided anecdotal evidence of improvements in function. Improvements lasted 6-12 mo. CONCLUSIONS: TRH may be a useful treatment for spinal muscular atrophy. A larger, crossover design group comparison study is warranted.

Action Potentials↗
PubMedDate not supplied

Time-frequency analyses of TEOAE recordings from normals and SNHL patients.

This study evaluated the characteristics of transient evoked otoacoustic emission (TEOAE) time-frequency (TF) representations from normal and hearing-impaired ears. Linear and non-linear TEOAE recordings from normally-hearing subjects (40) and non-linear recordings from patients with sensorineural hearing loss (SNHL) (40) were analysed using the short-time-Fourier-transform spectrogram, the Gabor spectrogram, and the adaptive spectrogram. The TF representations of the TEOAE recordings indicated a considerable dispersion of energy across frequencies and TEOAE time segments >4.0 ms. The linear and non-linear recordings from the normal subjects showed common frequency peaks. The TF representations from the patients with SNHL indicated that the significantly reduced energy in the mid-to-high TEOAE frequencies did not correlate closely with the threshold elevation. As in the recordings from the normal subjects, a high percentage of the TEOAE cumulative energy was found within a short TEOAE segment (4-14 ms).

Acoustic Stimulation↗
PubMedDate not supplied

Novel targets for therapeutic intervention against ischemic brain injury.

Ischemic stroke is a major health care problem worldwide, and the mechanisms that lead to ischemic brain injury are not completely defined. In the past few years, the identification of many molecules that participate in neuronal death and particularly in apoptosis, has shed light on the development of neuroprotective therapy. Glycine site antagonism of N-methyl-D-aspartate (NMDA) receptors may offer an alternative means to a blockade of glutamate neurotoxicity, which lacks most side effects associated with competitive and noncompetitive NMDA receptor antagonists. Inflammatory processes executed by some proinflammatory molecules contribute to secondary brain injury. Neutral protease calpain is capable of degrading critical cytoskeletal and regulatory proteins, mainly causing postischemic neuronal necrosis. Caspases, a family of cysteine proteases, are at the heart of the apoptotic pathway. Severe DNA damage induced by oxidative stress or apoptotic stimuli activates poly(ADP-ribose) polymerase, causing a rapid depletion of nuclear NAD pools, cellular energy, and thiols. Inhibition of these inducible molecules is expected to achieve effective neuroprotection without serious side effects because the molecules seem relatively unimportant in normal neurotransmission. In the future, the efficacy of these novel strategies should be confirmed in larger study populations, individually and in combinations, before considering clinical application.

Animals↗
PubMedDate not supplied

Cyclosporin in the treatment of severe aplastic anemia: report of one case.

According to recent reports, cyclosporin (CsA) has been proven to be a cure for some patients with severe aplastic anemia (SAA). The use of CsA to treat SAA is based on both experimental and clinical evidences showing that this disease is sometimes caused by immune-mediated mechanisms. This report describes a fourteen-year-old boy who recovered from SAA after being treated with CsA, together with to a lesser extent prednisolone. In June of 1986, when he failed to improve after receiving six months of corticosteroid treatment, CsA was introduced. Following three weeks of CsA therapy no further blood transfusion was needed. Danazol was added on the 28th day of CsA therapy. On the 105th day the blood counts began to improve, and on the 375th day bone marrow aspirate revealed normal hematopoiesis. Along with these improvements, however, some side effects from the CsA treatment were observed. These included: hirsutism, hypertension and gingival hyperplasia, all of which eventually subsided on tapering and finally terminating CsA. For the time being, no side effects have been observed in the six-months period since CsA was stopped and the patient is leading a normal life.

Adolescent↗
PubMedDate not supplied

Papanicolaou smears in pregnancy. Positivity of exfoliated cells for human chorionic gonadotropin and human placental lactogen.

Trophoblastic cells are seen rarely in cervical exfoliative cytology during normal pregnancy but are thought to occur with increasing frequency in the clinical setting of threatened abortion. We performed a clinicopathologic and immunologic study to determine the significance of multinucleate syncytiotrophoblastic and cytotrophoblastic cells in cervicovaginal smears from 13 women identified by cytomorphologic screening during a six-year period. Control groups included 11 patients who subsequently had spontaneous abortions and 15 patients with uneventful pregnancies. Immunocytochemistry was performed using a cocktail of antihuman chorionic gonadotropin and antihuman placental lactogen antisera. Five of the 13 screen-positive cases, 1 of the 11 spontaneous abortion cases and 0 of the 15 normal pregnancies were positive on immunostaining. Clinical follow-up showed that none of the screen-positive pregnancies, including those also positive on immunostaining, ended in spontaneous abortion. Further, there was no significant difference in fetal weight or Apgar scores between the controls and the screen-positive group. The presence of trophoblastic cells on cervicovaginal smears during pregnancy is not a reliable indicator of impending abortion.

Abortion, Spontaneous↗
PubMedDate not supplied

Antithrombotic therapy after intracoronary stenting.

Conventional percutaneous transluminal coronary angioplasty may result in complications such as abrupt closure and late restenosis. This has led to increased application of mechanical revascularization techniques including intracoronary stents. In the past, subacute thrombosis after intracoronary stenting mandated anticoagulation with warfarin for a minimum of 1 month, with aspirin (ASA) started before the procedure and continued indefinitely. New information suggests that high-pressure balloon inflation, with or without intracoronary ultrasound guidance to ensure successful stent placement, may permit reduction in the antithrombotic regimen to ASA, continued indefinitely, and ticlopidine, continued for 1-3 months. However, the majority of trials supporting this practice are primarily small, nonrandomized, observational studies. One randomized study found a lower frequency of cardiac events, including thrombosis, as well as fewer bleeding complications with combined antiplatelet therapy with ticlopidine compared with anticoagulant therapy with phenprocoumon. Intracoronary stenting without anticoagulation, would permit shorter hospitalization and lead to cost-savings. This has led many cardiologists to administer ASA and ticlopidine without benefit of data from randomized, blinded clinical trials. Antithrombotic therapy after coronary artery stenting is in an evolutionary stage, and additional information regarding the safety and efficacy of ASA and ticlopidine is necessary.

Angioplasty, Balloon, Coronary↗
PubMedDate not supplied

Modulation of cerebral somatosensory evoked potentials arising from tibial and sural nerve stimulation during rhythmic active and passive movements of the human lower limb.

The magnitudes of cerebral somatosensory evoked potentials (SEPs), following stimulation of cutaneous or muscle afferents in the upper limb, are reduced during active and passive movements of the fingers. The generalizability of such a movement effect was tested for lower limb events. We measured SEP magnitudes following activation of cutaneous (sural) and mixed (tibial) nerves during the flexion phase of active and passive rhythmic movements of the human lower limb. In eight volunteers, 150 SEPs per condition were recorded from Cz' referenced to Fpz'. Compared to stationary controls, both active and passive movements significantly depressed the early SEP components (P1-N1) [mean values, to 12.8%, 9.9% respectively for tibial nerve and to 29.6%, 25.6% for sural nerve stimulation, p < 0.05]. The attenuation was still observed when only one leg was moved and with stimulation at an earlier point in the flexion phase of movement. Visual fixation did not significantly affect P1-N1 amplitudes, compared to eyes closed. As previously shown, soleus H reflexes with stable M waves were significantly depressed during the movements (p < 0.05). The general construct may be that centripetal flow initiated from somatosensory receptors during limb movement leads to modulation of both spinal and cortical responses following large diameter cutaneous or muscle afferent activation.

Adult↗