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Biomedical subjects

R S Liu

Publications and source records attributed to R S Liu.

At least 109 records · Page 6Linked to original sources
PubMed1994

Temporal lobectomy in adults with intractable epilepsy.

We report on 30 adult patients with intractable complex partial seizure (CPS) of the temporal lobe origin who received anterior temporal lobectomy. The average follow-up period was 41 months. The age of onset was younger and the duration of epilepsy was longer in the non-mass lesion group than in the mass lesion group. Postoperatively, 21 patients (70%) were seizure-free, four patients (13%) had only rare seizures (less than three attacks per year), three patients (10%) achieved a remarkable reduction (more than 50%) of seizure frequency, and two patients (7%) showed no worthwhile improvement. Based on our experience, anterior temporal lobectomy is an effective and safe procedure for adult patients with intractable CPS. For diagnosis, magnetic resonance imaging (MRI) yielded a higher sensitivity rate than computed tomography (CT), especially in the group without mass lesions. Positron emission tomography using 18F-fluorodeoxyglucose (FDG-PET) was superior to single photon emission computed tomography (SPECT) which had a relatively high false localization rate. With high resolution MRI and FDG-PET, localization of the epileptogenic zone was more accurate. A preresection electrocorticogram (ECoG) was used to confirm the epileptogenic focus during the operation. The residual spikes on the postresection ECoG did not necessarily predict a poor seizure control outcome after anterior temporal lobectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Divergent pathways in photobleaching of 7,9-dicis-rhodopsin and 9,11-dicis-12-fluororhodopsin: one-photon-two-bond and one-photon-one-bond isomerization.

Through low-temperature photochemistry, UV/vis spectroscopy, and chromophore extraction experiments, we have established that 7,9-dicis-rhodopsin undergoes one-photon-two-bond photoisomerization to a batho intermediate (its absorption maximum is slightly blue shifted from that of bathorhodopsin) containing the all-trans geometry, while 9,11-dicis-12-fluororhodopsin undergoes one-photon-one-bond isomerization to the corresponding 9-cis isomer and then the all-trans batho intermediate. The difference in the photochemical properties of the two dicis pigment analogs was rationalized by possible local protein perturbation, lability of the 11-cis geometry, and photochemical properties of the chromophores.

Animals↗
PubMed1993

Technetium-99m hexamethylpropylene amine oxime single photon emission tomography of the brain in early Parkinson's disease: correlation with dementia and lateralization.

Regional cerebral blood flow was assessed in 19 patients with early idiopathic Parkinson's disease (PD) and 12 control subjects of similar age by single-photon emission tomography using technetium-99m hexamethylpropylene amine oxime (HMPAO). Of the patients with PD, seven were mildly demented and 15 presented with hemiparkinsonism. Mean HMPAO cortical or basal ganglia/cerebellum activity ratios were calculated. Mean cortical and regional uptake ratios in non-demented PD patients were not significantly different from values in the controls. In contrast, besides generalized cortical hypoperfusion, demented PD patients had significantly lower HMPAO uptake in the frontal and basal ganglia regions than non-demented patients. These observations support the hypothesis of impaired neuronal activity in both cortical and subcortical regions of the brain in demented PD patients. In hemiparkinsonian patients, the only asymmetrical finding was a relative hypoperfusion in the contralateral parietal region. This may be due to deafferentation of the thalamoparietal pathways. The lack of asymmetrical uptake in basal ganglia in our PD patients may be explained by their staging at the time of the investigation (stage I and II, Hoehn and Yahr scale).

Aged↗
PubMed1993

Analyzing the red-shift characteristics of azulenic, naphthyl, other ring-fused and retinyl pigment analogs of bacteriorhodopsin.

Prompted by the near infrared-absorbing properties of some of the azulenic bacteriorhodopsin (bR) analogs, we have analyzed their absorption characteristics along with 11 new related ring-fused analogs and the corresponding Schiff bases (SB) and protonated Schiff bases (PSB). The following three factors are believed to contribute to the total red shift of each of the pigment analogs (sigma RS): perturbation of the basic chromophore (SB shift, delta SB), protonation of the SB (PSB shift, PSBS) and protein perturbation (the opsin shift, OS). For each factor, effects of structural modifications were examined. For the red-shifted pigments, percent OS has been suggested as an alternate way of measuring protein perturbation. Computer-simulated chromophores provided evidence against any explanation involving altered shapes of the binding pocket as a major cause for absorption differences. Implications of the current bR results on preparation of further red-shifted bR and possible application to visual pigment analogs are discussed.

Absorption↗
PubMed1993

Posterior ischemia during an attack of transient global amnesia.

BACKGROUND: The popular concept that cerebral ischemia causes transient global amnesia has been difficult to prove by cerebral blood flow studies during attacks because the transient global amnesia attacks are so short. CASE DESCRIPTION: We performed single-photon emission computed tomography (SPECT) of the brain and neuropsychological assessment in a 37-year-old woman during a 10-hour attack and twice thereafter. A neuropsychological evaluation 3 hours after the onset of transient global amnesia revealed severe impairment of recent memory and verbal fluency, both of which returned to normal 2 and 28 days later, respectively. A 99mTc-labeled hexamethylpropyleneamine oxime SPECT of the brain performed 6 hours after the onset showed multiple perfusion defects in both occipital lobes, the medial left temporal lobe, and the left thalamus. A second brain SPECT performed 3 days later showed perfusion defects in only the occipital regions. A third brain SPECT performed 28 days later was normal. The patient's brain computed tomographic scan, electroencephalogram, duplex ultrasound of the carotid artery, and echocardiogram were normal. CONCLUSIONS: The perfusion defects revealed by the brain SPECT during the transient global amnesia attack indicated ischemia in the territory of the posterior cerebral arteries, which partially resolved in 3 days and completely resolved by 28 days.

Adult↗
PubMed1993

Reactivation of hepatitis B virus in two chronic GVHD patients after transplant.

We report two cases of hepatitis B virus reactivation following allogeneic bone marrow transplantation (BMT) for severe aplastic anemia and acute myelocytic leukemia. The presence of antibodies to HBsAg, HBeAg and HBcAg prior to transplant indicated previous infection with hepatitis B virus (HBV). These antibodies disappeared 2 and 4 months after the onset of chronic graft versus host disease (GVHD) following immunosuppressive treatment, but HBsAg reappeared in their sera 6 and 10 months later, respectively. This suggests that chronic GVHD and immunosuppressive drugs can reactivate HBV in HBsAb-positive patients, most likely because of the decrease in quality and function of helper T cells and B cells during chronic GVHD to induce clearance of HBV antibodies and reactivation of HBV. Our observation confirms that patients with HBsAb, HBeAb and HBcAb present in their sera should not be considered to have 'immunity' to HBV after BMT.

Adult↗
PubMed1992

Diagnosis of venous leakage by 133Xe corporeal clearance after intracavernous injection of prostaglandin E1 in poorly responding patients.

133Xe corporeal clearance after intracavernous (IC) prostaglandin E1 (PGE-1) injection was assessed in detecting venous leakage (VL) in a group of impotent patients with poor clinical response to PGE-1 injection. 133Xe corporeal washouts were done in the flaccid state and at full erection or at 20 min after the IC injection of 20 micrograms PGE-1 in cases where no full erection occurred in sequence on two separate days. In each case, data were acquired in frame mode after intracorporeal injection on one side of the midline just behind the glans of 0.1 ml, namely, 1-2 mCi (34-74 MBq) 133Xe in saline for 20 min. A time-activity curve was generated from the region of interest (ROI) at the site of injection and a computer routine was used to calculate clearance half-time (T1/2) in min and flow rate (Q) in ml per 100 g tissue per min. The data of 20 patients with equivocal response to IC PGE-1 were analysed. Of them, 14 had venous leakage and six had no vascular impairment (NVI). Venous leakage was proved by Doppler analysis, cavernosography after PGE-1, and/or selective arteriography. Twelve of 14 patients with VL had enhanced 133Xe corporeal clearance after PGE-1 with a significant decrease in T1/2 (mean +/- S.D.) from 115.9 +/- 196.0 to 13.3 +/- 13.4 (P less than 0.05) and increase in Q from 2.1 +/- 2.2 to 7.5 +/- 5.6 (P less than 0.01). In contrast, all six patients with NVI had decreased 133Xe corporeal clearance.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Single photon emission computed tomography using 99Tcm-HMPAO in Alzheimer's disease.

Brain single photon emission computed tomography (SPET) using 99mTcm-hexamethylpropyleneamine oxime (HMPAO) was performed in 37 patients satisfying the standard clinical criteria of Alzheimer's disease (AD), correlating results with patient's age of onset, duration of illness, severity of dementia, neuropsychological impairment, computed tomography (CT) and EEG findings. All patients had abnormal SPET: 23 were bilaterally symmetric, 10 were bilaterally asymmetric and four showed unilateral low regional cerebral perfusion. Low perfusion in bilateral parietal regions was the most consistent finding and was present alone or with other abnormal regions in 31 patients (84%). The only significant clinical correlation was found between asymmetric SPET changes and onset of disease before the age of 65 years. Fifty per cent of patients with presenile onset, but only 19% with senile onset had asymmetric low regional cerebral perfusion. Fifteen of the 36 patients had normal brain CT scans, and 9 of 31 patients receiving EEG examination had normal results. Although clinical evaluation is the most valuable diagnostic tool, brain SPET is a sensitive test for physiological investigation in AD.

Aged↗
PubMed1992

9,11-Dicis-12-fluororhodopsin. Chromophore properties from 19F-NMR studies.

From a 19F-NMR study of 9,11-dicis-12-fluororhodopsin and its photobleached product, we concluded that the initially formed chromophore retained its configuration and the photoproduct corresponded to the two-bond isomerized all-trans. Upon standing, it slowly isomerized to the 9-cis isomer. The method represents a direct, non-destructive procedure for determining configuration purity of the pigment formed. Its unique fluorine opsin shift value is consistent with the expected different orientation of the fluoro-substituent in a dicis pigment.

Magnetic Resonance Spectroscopy↗
PubMed1992

Modeling rhodopsin, a member of G-protein coupled receptors, by computer graphics. Interpretation of chemical shifts of fluorinated rhodopsins.

An attempt has been made to construct a 3-D model of rhodopsin, a member of G-protein coupled receptors. Sequence homology of rhodopsin with the latter was a factor considered in the modeling procedure. The constructed model has been used to compare currently available specific protein/substrate interaction information, the shape of the binding cavity derived from shape of binding retinal isomers and analogs and challenged to explain recently available results from a series of fluorinated rhodopsins.

Amino Acid Sequence↗
PubMed1992

Plasma ammonia in patients with acute leukemia.

Plasma ammonia level (PAL) was studied in 43 cases of acute leukemia (AL). PAL was 39.21 +/- 26.2 mumol/L in normal controls and 38.8 +/- 16.6 mumol/L in leukemic patients before chemotherapy. High PAL was found in 40 cases after chemotherapy. Six cases showed clinical manifestations due to severe hyperammonemia, including dizziness, lethargy, confusion, coma and mental changes of various degree, and there was also respiratory alkalosis. After ammonia-trapping therapy, 4 of the 5 patients recovered. The authors believe that high PAL is not uncommon after chemotherapy in leukemic patients. Respiratory alkalosis and unexplained mental and neurologic changes following intensive chemotherapy are useful clues for the diagnosis of hyperammonemia syndrome. Early diagnosis and treatment with ammonia-trapping may improve the rates of remission and survival.

Adolescent↗
PubMed1992

[Tc-99m MIBI myocardial scintigraphy in evaluation of the effect of percutaneous transluminal coronary angioplasty on coronary artery stenosis].

Tc-99m 2-Methoxy-Isobutyl-Isonitrile, a newly developed myocardial perfusion radiopharmaceutical for myocardial perfusion imaging, provides an accurate, noninvasive detection of coronary artery disease. The potential advantages of Tc-99m MIBI over T1-201 have been reported extensively. The purpose of this study is to evaluate the detectability of the diseased vessels and the effectiveness of percutaneous transluminal coronary angioplasty (PTCA) on Tc-99m MIBI myocardial perfusion scan. Twenty cases of coronary artery disease were included. Single photon emission computed tomographic (SPECT) imagings were used. Forty myocardial imagings were done before and after PTCA. Twenty nine segments of perfusion defect were found preoperatively. The sensitivity and specificity for the images to detect the individual coronary arteries were 88% and 94%, respectively. After PTCA, 25 out of 29 perfusion defects (86%) resolved. Among these, 14 were transient defects (93%) and 11 were persistent defects (79%). Persistent defects on serial thallium and Tc-99m MIBI scans are commonly thought to represent fibrosis or scar. Some investigators suggest that the recovered persistent defects on thallium scan represent hypoperfusion of viable myocardium. In our study, we found that regions of persistent defects on Tc-99m MIBI scan often revert to normal-state after PTCA (79%), indicating the similar results on thallium scans. In conclusion, Tc-99m MIBI myocardial imaging is useful in detecting coronary artery disease and monitoring success of PTCA.

Aged↗
PubMed1992

[Iron absorption in HbH disease].

We have reported that many cases of Hb H disease have a complication of iron overload without a history of multiple blood transfusion or prolonged iron therapy. We determined their iron absorption by 59Fe whole body counting in 13 such cases. Also 10 normal subjects were studied as a control group. The results showed a significant increase in iron absorption to 20.3%, in contrast to 6.9% in the normal control. This was further documented by their RBC incorporation (i.e. the percentage of orally administered) 59Fe recovered in the total RBC mass) on day 14 (13.7% vs 6.1%). The degree of ineffective erythropoiesis might not be severe considering their similar 59Fe utilization by RBC (i.e. the percentage of absorbed 59Fe recovered in the RBC) to the normals (86.3% vs. 84.3%).

Absorption↗
PubMed1992

Comparison of effective renal plasma flow (ERPF) and endogenous creatinine clearance (Ccr) in evaluation of the differential kidney function: an in vivo study.

Eleven patients with obstructive uropathy were inserted with a pigtail catheter either for urinary diversion, endopyelotomy or percutaneous nephrolithotomy. Differential kidney functions were obtained by single-sample technique with I-131 orthoiodohippurate (OIH) and separate endogenous creatinine clearance (Ccr). Good linear correlation was noted between effective renal plasma flow (ERPF) and Ccr (r = 0.84, p less than 0.005), but there was still some discrepancy between these two examinations, chiefly found in two severely obstructed kidneys. Determination of ERPF by I-131-OIH single-sample technique is a simple, rapid, inexpensive and relative accurate test to measure the differential kidney function. But if the ERPF is at extremely low level, further investigations such as sonography of kidney and separate endogenous creatinine clearance should be done to avoid unnecessary nephrectomy.

Adolescent↗