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Biomedical subjects

J C Liu

Publications and source records attributed to J C Liu.

At least 91 records · Page 5Linked to original sources
PubMed1997

Operationalization of clinical practice guidelines using fuzzy logic.

There are a number of obstacles to successful operationalization of clinical practice guidelines, including the difficulty in accurately representing a statement's decidability or an action's executability. Both require reasoning with incomplete and imprecise information, and we present one means of processing such information. We begin with a brief overview of fuzzy set theory, in which elements can have partial memberships in multiple sets. With fuzzy inferencing, these sets can be combined to create multiple conclusions, each with varying degrees of truth. We demonstrate a fuzzy model developed from a published clinical practice guideline on the management of first simple febrile seizures. Although the creation of fuzzy sets can be an arbitrary process, we believe that fuzzy inferencing is an effective tool for the expression of guideline recommendations, and that it can be useful for the management of imprecision and uncertainty.

Age Factors↗
PubMed1997

Peritoneoscintigraphy using Tc-99m MAA for diagnosis of diaphragmatic disruption in a peritoneal dialysis patient.

Massive hydrothorax is an infrequent but well-recognized complication of continuous ambulatory peritoneal dialysis (CAPD), and is often regarded as a contraindication to its use. We describe here a patient with massive hydrothorax that appeared during CAPD. Peritoneoscintigraphy was performed to demonstrate the clinical suspicion of a pleuroperitoneal communication and the pleurodesis using tetracycline was commenced and this allowed the successful continuance of CAPD.

Female↗
PubMed1996

Polymorphisms of dopamine D2-like (D2, D3, and D4) receptors in schizophrenia.

The result of most association studies and linkage analyses have suggested a negative association between schizophrenia and D2-like (D2, D3, and D4) receptor polymorphisms. Although the polymorphisms of the D2-like receptor in themselves may not account for the etiology of schizophrenia, they can contribute to the severity of the symptoms. Thus, we studied the associations between the polymorphisms and their combinations, and the vulnerability of schizophrenics. Fragments of the D2-like receptor genes were amplified by means of the polymerase chain reaction, and the polymorphisms were identified by the restriction fragment length polymorphism and single-stranded conformation polymorphism methods. There were no statistically significant differences in the polymorphisms and their combinations between schizophrenics and controls. Schizophrenics with D4E1(A1/A2), which contains 2 and 1 tandem repeats of a 12-base-pair sequence in exon 1, had a lower total positive symptom score before medication than schizophrenics with D4E1(A1/A1). There was no association between the polymorphisms and negative symptoms.

Adult↗
PubMed1996

Reversal of the temperature-shift-induced growth restriction of a temperature-sensitive simian virus 40 T-antigen-transformed human fibroblast cell line by treatment with retinoic acid.

We previously established a human fibroblast cell line, HFL 6-2, that contains a temperature sensitive simian virus 40 (SV40) T antigen, permitting cell growth at 35 degrees C but restricting growth at 39 degrees C. p21 (Waf1/Cip1) was significantly induced by temperature shifts in HFL 6-2 cells. Here we show that all-trans-retinoic acid (RA) treatment prevented the growth restriction of HFL 6-2 cells at 39 degrees C. In the presence of RA, HFL 6-2 cells proliferated into sizeable colonies even at 39 degrees C. [3H]Thymidine incorporation and flow cytometry analysis revealed that cells exposed to RA maintained DNA synthesis at 39 degrees C. Prevention of growth restriction by RA was correlated with a lack of induction of p21 at the transcription level. These observations suggest that RA may prevent the senescence process by repressing p21 gene expression, and perturb the growth regulation of somatic cells.

Antigens, Polyomavirus Transforming↗
PubMed1996

Contralateral temperature changes of the finger surface during video endoscopic sympathectomy for palmar hyperhidrosis.

One hundred and eight consecutive patients with primary palmar hyperhidrosis were surgically managed by coagulation of bilateral T2 sympathetic ganglia using video thoracoscopic techniques. Patients were divided into two groups. In the first group (N = 46), finger surface temperature of the ipsilateral index finger was recorded before and after T2 ganglionectomy. The average increase of post-operative temperature was 2.74 +/- 0.27 degrees C (mean +/- SE) on the right side and 2.67 +/- 0.33 degrees C on the left (P < 0.05). The significant rise of temperature resulting from sympatholytic vasodilatation was only noted in cases of exact ablation of the T2 ganglion. In the second group (N = 62), surface temperatures of both index fingers were monitored and recorded simultaneously. These patients were arbitrarily subdivided into Group 2-A (N = 29) when right side ganglionectomy was performed first and Group 2-B (N = 33) when left side ganglionectomy was done initially. After the first ganglionectomy was completed, an ipsilateral increase with a contralateral decrease of temperature was observed; the average increase of temperature was 1.92 +/- 0.35 degrees C and 2.19 +/- 0.30 degrees C, and the average decrease was 1.50 +/- 0.51 degrees C and 1.67 +/- 0.39 degrees C for Group 2-A and 2-B respectively (P < 0.05). The authors postulate that a cross-inhibitory effect by the post-ganglionic neurons innervating blood vessels of the upper extremities may exists in humans and this effect is released after ganglionectomy, resulting in contralateral vasoconstriction and decrease of finger surface temperature.

Adolescent↗
PubMed1996

The mode of action of hirsutellin A on eukaryotic cells.

A 16-kDa protein toxin was purified from Hirsutella thompsonii var thompsonii and named hirsutellin A (HtA). At 0.5 and 5.0 microM concentrations, HtA caused detectable cytopathic effects on Spodoptera frugiperda cells (Sf-9) within 2-4 hr and completely inhibited Sf-9 cell growth at 4 days posttreatment. Electron microscope data showed that the HtA treated Sf-9 cells became hypotrophied and internal organelles and cell membranes were disrupted. At the same concentration, HtA effectively inhibited Brome mosaic virus protein synthesis of both rabbit reticulocyte and wheat germ in vitro translation system. The ribosomal RNA extracted from HtA treated Sf-9 cells produced a smaller RNA (approximately 528 bases) than untreated Sf-9 cells. In summary, HtA is the first mycotoxin of a invertebrate mycopathogen determined to possess ribosomal inhibiting activity and appears to possess some specificity to invertebrate cells.

Animals↗
PubMed1996

Intact 5-HT2A receptor exons and the adjoining intron regions in schizophrenia.

Genes that regulate serotonergic (5-HT) systems may underlie the etiology of schizophrenia. In this study the gene encoding the 5-HT2A receptor in schizophrenics and healthy controls was examined. First, we sequenced all exons and the flanking introns of the 5-HT2A receptor gene in 10 schizophrenics and 10 controls. The substitution of C for T at position 102 in exon, which had been reported by Warren et al. (1993), was confirmed. Restriction fragment length polymorphism (RFLP) analysis revealed no association between polymorphism and schizophrenia. There was no association between the polymorphism and subdiagnosis, family history, age of onset, amounts of antipsychotics, or positive and negative symptoms before or after medication. Other polymorphisms in the gene were screened in 100 schizophrenics by the single-strand conformation polymorphism method, but none was found. Our results suggest that an abnormality in the 5-HT2A receptor gene in schizophrenia is unlikely.

Adult↗
PubMed1996

Radiation protection systems for the final focus test beam at SLAC.

The Final Focus Test Beam (FFTB) is a new beam line at the Stanford Linear Accelerator Center designed to test new beam optics concepts, hardware, and techniques necessary to achieve and measure the small spot sizes required for future generations of high-energy e+e- linear colliders. The FFTB takes a 47 GeVc-1, 1 kW electron beam at the end of the Stanford Linear Accelerator Center linear accelerator and transports it to the FFTB beam dump. A radiation protection system was designed and installed for the FFTB with the primary goal that the integrated dose equivalent outside the shielding resulting from beam loss would not exceed 10 mSv y-1. This system is comprised of shielding, a beam containment system and a personnel protection system. This paper presents various aspects of radiation safety at Stanford Linear Accelerator Center that were considered in the design of the FFTB radiation protection system. Beam tests were conducted in which the performance of various beam containment devices and the shielding effectiveness were evaluated. Preliminary results from these tests are presented.

California↗
PubMed1996

Descending pressor pathways from the dorsomedial and ventrolateral medulla of cats.

Descending pathways of the pressor areas in dorsomedial (DM) and ventrolateral (VLM) medulla were studied physiologically and anatomically. The electrically induced pressor response from either DM or VLM that previously responded to glutamate (Glu) was slightly but not significantly decreased after splitting the medulla at midline. After electrolytic lesion in the ipsilateral lateral tegmental field (LTF) of caudal medulla, 4 mm caudal to the obex, electrically induced pressor responses from DM and VLM previously responded to Glu decreased significantly from 71% to 20% and from 57% to 7%, respectively. The dorsomedial LTF was found to be responsible for the DM responses, while the ventrolateral LTF for the VLM responses. Following electrolytic lesion in the ipsilateral dorsolateral funiculus (DLF) between C4 and C5, the magnitude of DM-induced pressor responses decreased significantly from 74% to 37% and that of the VLM from 75% to 14%. After electrolytic lesion at the ipsilateral intermediolateral cell column (IML) of T2 spinal cord, the pressor responses on DM and VLM stimulations also decreased significantly. Lesioning the remaining IML almost completely abolished the induced pressor responses. Seven to ten days following kainic acid injections into DM or VLM to destroy neurons therein, degenerative fibers (silver impregnation) were found to descend from the medulla to thoracic spinal cord, principally ipsilaterally, but with some fibers crossing to the controlateral medulla. Data from both physiological and anatomical studies suggest that fibers from DM and VLM descend ipsilaterally through different pathways and converge at LTF 4 min caudal to the obex, and then further descend to DLF before reaching the thoracic IML.

Animals↗
PubMed1996

Effects of precollicular decerebration on the vasomotor and sympathetic nerve responses to locus coeruleus stimulation.

In 25 cats under intraperitoneal alpha-chloralose (40 mg/kg) and urethane (400 mg/kg) anesthesia, cardiovascular reactive sites of locus coeruleus (L.C) were stimulated by rectangular pulses (0.5 ms, 80 Hz, 100 to 200 microA) and/or by microinjection of sodium glutamate (Glu, 0.25 M, 70-150 nl). Changes of systemic arterial blood pressure (SAP) and sympathetic vertebral (VNA) and renal (RNA) nerve activities following stimulations were analyzed and, furthermore, SAP responses were compared before and after precollicular decerebration (PD). Microinjection of Glu in this region often produced a moderate increase and less often decrease in SAP. Depressor points were located dorsal to the sites eliciting pressor responses. In the majority of LC stimulations (69%) VNA increased along with the increase of SAP, while the RNA decreased. In a few stimulations marked increase in VNA and decrease in RNA occurred with little change in SAP. PD itself produced various degrees of a temporary (lasted for 5 to 15 min) decrease in SAP from 40 to 100 mmHg. Following PD, three types of change in the LC induced SAP responses were observed in a decreasing order, i.e., the responses were slightly reduced or slightly augmented, or the LC induced depressor responses were converted to a pressor one. Findings of the present study showed that neural mechanism in LC responsible for the changes of SAP and sympathetic nerve activities may exist in a topographic organization. LC is different from the gigantocellular tegmental field (FTG) located in the same rostral pons. The marked pressor responses elicited by activation of the FTG depend entirely on the rostral brain structure, while LC is not. Some brain structures rostral to superior colliculi may exert both inhibitory and excitatory influences over LC in cardiovascular integration.

Animals↗
PubMed1995

Differential regulation of cyclin A, cyclin B and p21 concentrations in a growth-restricted human fibroblast cell line.

When the culture temperature was shifted from 35 degrees C to 39 degrees C, human fibroblasts immortalized by the temperature-sensitive simian virus 40 T antigen became larger and acquired the morphological characteristics of senescent fibroblasts. After culture at 39 degrees C for 48 h, most cells had ceased to proliferate. A rapid depletion of cells with S-phase DNA content was observed after the temperature shift. To elucidate the mechanism governing this rapid arrest of proliferation, we studied the expression of genes involved in the regulation of cell cycle progression. Cyclin A, cyclin B and p34cdc2 concentrations were not changed during growth restriction, whereas p21 was rapidly induced in these growth-restricted cells. Transient expression of exogenous p21 in cells cultured at 35 degrees C led to growth restriction and morphological changes characteristic of senescence. Furthermore, we studied the reversibility of growth restriction induced by the temperature increase. The results showed that senescent morphology and growth arrest were not reversible. In these cells the p21 concentration remained high and p34cdc2 remained undetectable. This indicates that p21 accumulation might be responsible for the maintenance of senescence. Our findings provide information on the use of growth restriction of immortalized fibroblasts induced by a temperature shift as a model system to study senescence.

CDC2 Protein Kinase↗
PubMed1995

Cloning and characterization of the endogenous retroviral-tRNA(Glu) multigene family from human genomes of different racial backgrounds.

An 8.3-kb human endogenous retroviral-tRNA(Glu) (HERV-E)-encoding cDNA clone and a 1.5-kb genomic clone were isolated from a Chinese-derived cervical cancer cell line, CC7T, and their sequences determined. The former is a full-length endogenous retroviral cDNA containing corresponding u5-gag-pol-env-u3-r regions. The latter is a partial retroviral DNA segment, covering the gag and pol genes. Analysis of normal human DNA by Southern blot hybridization with three specific HERV-E molecular DNA probes revealed complex restriction-fragment length polymorphisms (RFLP), implying that the human genome contains diverse proviral structures and dispersed integration sites. The complex patterns were virtually identical between DNAs from African-Americans, Asians and Caucasians, with only a few minor variations. The data suggest that these proviral sequences were mostly incorporated into the human genome before racial divergence and, hence, may serve as markers for distinct chromosomal sites.

Amino Acid Sequence↗
PubMed1995

Human ventromesencephalic grafts restore dopamine release and clearance in hemiparkinsonian rats.

We and others reported previously that transplantation of fetal ventromesencephalic homograft restores the apomorphine-induced rotational behavior and electrochemical indices of dopamine (DA) depletion in the 6-hydroxydopamine (6-OHDA)-lesioned rat. We found that regeneration of KCl-evoked DA release and tyrosine hydroxylase (TH) immunoreactivity was limited to the graft area even 4 months after transplantation. In the present experiments, we transplanted human fetal ventromesencephalic tissue to the 6-OHDA-lesioned rats. After transplantation, rats received chronic cyclosporin and vibramycin treatment. We found that human fetal grafts from the substantia nigra can restore the effects of DA depletion in 6-OHDA-lesioned rats; these fetal grafts were found to reduce the apomorphine-induced rotational behavior and restore K(+)-evoked DA release as well as DA clearance in the striatum. The area with active DA release is far beyond the transplantation site, unlike that seen in the homografted rats. These electrochemical responses correspond to the extended outgrowth of TH-positive neuronal fibers distal to the graft area. Taken together, our data suggest that rats that received human mesencephalic graft had much greater DA innervation and more complete restoration of function than those that received homografts.

Animals↗
PubMed1995

Gas bremsstrahlung and associated photon-neutron shielding calculations for electron storage rings.

The EGS4 electron-photon Monte Carlo code has been used to study the characteristics of the bremsstrahlung x rays generated from the interaction of circulating electrons with the residual gas in accelerator storage rings. Gas bremsstrahlung dose rates are given for various opening angles as a function of the electron beam energy ranging from 0.5-10 GeV. Photon and neutron dose rates, generated from various devices struck by gas bremsstrahlung in a synchrotron radiation beamline, are also presented along with the photon spectral and transmission results. The EGS4-predicted results are found to be in basic agreement with the measurements made at the Stanford Synchrotron Radiation Laboratory. Figures, equations, and a simple method useful for the photon-neutron shielding design for beamlines are provided.

Neutrons↗
PubMed1995

Nucleotide sequence and transcriptional analysis of the gp41 gene of Spodoptera frugiperda nuclear polyhedrosis virus.

The Spodoptera frugiperda multiple nucleocapsid nuclear polyhedrosis virus (SfMNPV) gp41 structural protein gene was located in the 1.9 kbp EcoRI-S fragment and sequenced. An open reading frame (ORF) of 999 nucleotides was detected that encoded a protein of 332 amino acids. The gp41 gene transcript was detected after 12 h post-infection (p.i.) and remained detectable at 48 h p.i. Two major mRNAs, about 1.6 and 2.8 kb in length, were determined by Northern blot analysis. Primer extension analysis demonstrated that the gp41 gene promoter region contains three transcription start sites. Two of the gp41 gene transcription start sites were located at -42 and -41 nucleotides from the ATG translation start codon within a consensus late transcription start site (TAAG) and another transcription start site was located at -140 nucleotides from the ATG translation start codon for which no consensus motif has been determined. Comparison of SfMNPV gp41 nucleotide and amino acid sequences with the gp41 genes from Autographa californica, Bombyx mori, and Helicoverpa zea NPVs showed 60% homology of nucleotide sequences and 70% similarity of amino acid sequences.

Amino Acid Sequence↗
PubMed1995

Brainstem tethering in Dandy-Walker syndrome: a complication of cystoperitoneal shunting. Case report.

Treatment of the Dandy-Walker syndrome has included placement of a ventriculoperitoneal shunt alone or in combination with a posterior fossa cystoperitoneal shunt. Complications in shunting are common and are usually related to malfunction or infection. The authors present a case in which the patient developed headaches and focal cranial nerve deficits following infection caused by a cystoperitoneal shunt. Magnetic resonance imaging showed tethering of the brainstem. A posterior fossa craniotomy with microsurgical untethering and cyst fenestration achieved two goals: improvement of the focal cranial nerve deficits and elimination of the cystoperitoneal shunt.

Brain Stem↗
PubMed1995

Dopamine-modulated potassium channels on rat striatal neurons: specific activation and cellular expression.

We have used cell-attached patch-clamp electrophysiology to characterize the activation and distribution of an 85 pS K+ channel on freshly dissociated rat striatal (caudate-putamen) neurons. In recordings from 643 cells, openings of this channel showed an absolute dependence on the presence of dopamine or the D2-like dopamine receptor agonist quinpirole in the cell-attached patch pipette, but were never seen when the D2 antagonist domperidone was applied along with quinpirole, or in the absence of drug. This channel displayed inward rectification at depolarized membrane potentials, but its activation was otherwise voltage insensitive. It was largely restricted to a subset of dissociated cells with diameters > or = 10 microns, with channel openings seen in about 25% of patches. When present, there were typically multiple channels per patch. Cells of this size were immunocytochemically stained for neuron-specific enolase but not glial fibrillary acidic protein; about 40% were also labeled for gamma-amino butyric acid (GABA) and about 60% for NADPH diaphorase, with GABAergic cells displaying a shape most similar to that of cells expressing the channel. A large number of distinct types of other channels were also present, comprising inwardly rectifying channels of 5-35 pS conductance and voltage-activated channels of 100-250 pS, but the frequencies of occurrence and fractional open times of these channels were independent of the presence or absence of dopaminergic agonists. Thus, the 85 pS K+ channel uniquely requires activation by a D2-like dopamine receptor on rat striatal neurons, and is selectively expressed by a subset of these cells, which are most likely to be GABAergic neurons.

Animals↗