Biomedical subjects

H Liu

Publications and source records attributed to H Liu.

At least 919 records · Page 51Linked to original sources

PubMed1996

Increased density of senile plaques (SP), but not neurofibrillary tangles (NFT), in non-demented individuals with the apolipoprotein E4 allele: comparison to confirmed Alzheimer's disease patients.

The apolipoprotein E genotype and cortical senile plaque (SP) and cortical and hippocampal neurofibrillary tangle (NFT) densities were determined in non-demented individuals and neuropathologically confirmed AD patients. The non-demented population was further subdivided according to presence or absence of pathologically established critical coronary artery disease (cCAD), hypertension (HyperT), or neither (non-heart disease; non-HD). The apolipoprotein E4 (APOE4) allele incidence and dose frequencies were increased in the AD, cCAD and HyperT groups compared to the non-HD controls. The mean number of SP and NFT was significantly increased with the presence of the APOE4 allele within the entire population. After grouping the non-demented subjects according to cardiac status, SP but not NFT density was increased among those individuals with the APOE4 genotype. In HyperT, the increased density of SP also correlated to the APOE4 allele dose frequency. The density of SP and NFT was increased in all regions of AD brain compared to all other non-demented groups, but no significant difference was found between AD patients with or without an APOE4 allele. These two AD groups were age-matched, but could not be matched for disease duration. The data suggest a relationship between heart disease, APOE4 genotype and the presence of SP regardless of cognitive status.

Aged↗

PubMed1996

V2-receptor blockade enhances pressor response to vasopressin: gender difference.

The present study was performed to determine if the attenuated pressor response to vasopressin in conscious non-estrous female rats is due in part to an enhanced V2-like receptor vasodilator action. In male rats, infusion of vasopressin at a rate of 1 ng.min(-1).kg body weight-1 (wt) resulted in an increase in mean arterial blood pressure (MABP) of about 20 mm Hg. Thirty minutes after beginning the infusion of vasopressin, the iv bolus injection of a non-peptide V2-receptor antagonist, OPC-31260 (2 mg.kg body wt-1), resulted in a further gradual increase in MABP of approximately 8 mm Hg in the next 60 min (p < 0.05). Thus, the pressor response to vasopressin was greater in OPC-31260-treated than in vehicle-treated male rats (p < 0.01). The pressor response to vasopressin 30 min after the start of its infusion was lower (about 8 mm Hg) in non-estrous female rats than in males. During the next 60 min of vasopressin infusion, there was a small further increase (p < 0.05) in MABP in the females given either OPC-31260 or its saline vehicle. In contrast to the male rats, however, there was no difference in MABP between the OPC-31260 and vehicle treated females. Thus, the present study has provided additional evidence for a V2-like receptor related vasodilator effect in male rats. However, since female rats do not appear to express a V2-receptor mediated vasodilator response, the sexually dimorphic pressor response to vasopressin cannot be due to a gender difference in V2-receptor vasodilator activity.

Animals↗

PubMed1996

Drinking and blood pressure responses to central injection of L-NAME in conscious rats.

The drinking behavior and blood pressure responses to i.c.v. administration of artificial cerebrospinal fluid (aCSF) or NG-nitro-L-arginine methyl ester (L-NAME, 10, 250, or 500 micrograms), an inhibitor of nitric oxide synthase, were examined in conscious rats following either osmotic stimulation (1.0 M NaCl, 15 ml/kg, s.c.) or induction of hemorrhage (0.7 ml/min to a 20% blood volume loss). Water intake increased in all animals. L-NAME at doses of 250 and 500 micrograms, but not 10 micrograms, significantly attenuated water consumption induced by both stimuli. The mean arterial blood pressure (MABP), which increased after osmotic stimulation, was maintained at pressor levels by 250 and 500 micrograms of L-NAME, but decreased progressively and reached basal levels after treatment with aCSF and the lowest dose of L-NAME (i.e., 10 micrograms). Hemorrhage significantly decreased MABP in all rats. The fall in blood pressure associated with hemorrhage returned to control levels in animals treated with 250 and 500 micrograms of L-NAME but not in those treated with aCSF or 10 micrograms of L-NAME. These results indicate that nitric oxide is involved in the regulation of drinking behavior and may play an important role in the central control of blood pressure during osmotic stimulation and hypotensive hemorrhage.

Animals↗

PubMed1996

A competitive chemiluminescent enzyme-linked immunosorbent assay for the determination of RMP-7 in human blood.

RMP-7, a bradykinin agonist, is a synthetic nonapeptide designed to enhance the delivery of therapeutics to the central nervous system. A sensitive, competitive chemiluminescent enzyme-linked immunosorbent assay (ELISA) for quantifying RMP-7 in human blood samples has been developed. Rabbit antibodies against RMP-7 were produced using the conjugate of RMP-7 to keyhole limpet hemocyanin through glutaraldehyde. Biotinylated RMP-7, conjugated via N-hydroxysuccinimide ester, was used as the tracer. A premixed solution of biotinylated alkaline phosphatase and avidin was used to quantify the tracer, with a dioxetane-based compound as the chemiluminescent substrate. The method involves treating blood samples with organic solvents to precipitate proteins, evaporating the supernatants to dryness, reconstituting residues in PBS and assaying the buffer solutions with the ELISA. The assay, using 1.0 ml of whole blood, has precision and accuracy within +/- 20% over the concentration range 25-800 pg ml-1. There are no significant endogenous interferences. The assay has been successfully used to support clinical trials of RMP-7.

Alkaline Phosphatase↗

PubMed1996

The reduction of glutathione disulfide produced by t-butyl hydroperoxide in respiring mitochondria.

Factors affecting the reduction of GSSG by rat liver mitochondria after a t-butyl hydroperoxide-induced (t-BOOH) oxidative stress were studied. The amounts of ADP and mitochondrial protein were adjusted to consume less than 50% of the available oxygen during the 8-min experimental period. A 4-min treatment of mitochondria with 24 nmol t-BOOH/mg protein (60 microM) oxidized 91% of total glutathione. In the presence of glutamate/malate, succinate or ascorbate/N,N,N',N'-tetramethyl-p- phenylenediamine (TMPD) (state 4 respiration), 84, 84, and 28% of the GSSG formed during t-BOOH treatment was reduced after 4 min, respectively. A similar extent of reduction was seen during state 3 respiration (1.5 mM ADP) with glutamate/malate, but no reduction occurred during state 3 respiration with either succinate or ascorbate/TMPD. The succinate-supported reduction of GSSG was completely blocked by rotenone, antimycin A, carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP), or 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). In contrast, oligomycin potentiated GSSG reduction using either glutamate/malate or succinate as substrates. Rotenone partially blocked glutamate/malate-supported GSSG reduction. NADPH levels were altered in direct proportion to the effects on GSSG reduction. The current data indicate that the reduction of GSSG in oxidatively-stressed isolated rat liver mitochondria occurs most efficiently during state 4 respiration and is independent of ATP synthesis. Both transhydrogenation and the transmembrane proton gradient appear to be important in NADPH regeneration and consequent GSSG reduction.

Animals↗

PubMed1996

Identification and functional characterization of conserved promoter elements from glass: a retinal development gene of Drosophila.

The Drosophila melanogaster glass transcription factor acts in photoreceptor cell development, glass transcription in the developing eye begins in the morphogenetic furrow. We report a deletion analysis which shows that a 5147 bp fragment can confer near wild-type expression in the developing eye. We completed the sequence of a similar Drosophila virilis fragment and comparison of these two genomic sequences reveals seven perfectly conserved sequence elements of 15 bp (or longer). We placed oligomers of each element 5' to an hsp70 promoter-lacZ fusion construct, and examined the patterns of beta-galactosidase expression produced in transgenic files. Three of these elements drive beta-galactosidase expression in the developing eye, and one is inhibitory.

Animals↗

PubMed1996

Interstitial cells of Cajal in human colon and in Hirschsprung's disease.

BACKGROUND & AIMS: Subpopulations of interstitial cells of Cajal are regarded as the source of spontaneous slow waves of the gut musculature (pacemaker cells). Their ontogeny remains unclear, but a role of the tyrosine kinase receptor c-kit in their development has recently been recognized. This study examined the interstitial cells in the human colon and in Hirschsprung's disease (aganglionosis). METHODS: The distribution of the c-kit receptor was studied using specific antibodies in 5 normal patients, 10 patients with Hirschsprung's disease, and 3 patients with diversion loop enterostomies. c-kit immunohistochemistry was also combined with reduced nicotinamide adenine dinucleotide phosphate diaphorase histochemistry or with c-kit ligand (stem cell factor) immunohistochemistry. Transmission electron microscopy was performed in 1 patient with Hirschsprung's disease. RESULTS: c-kit immunoreactivity labeled a network of interstitial cells at the outer edge of the submucosa, in the muscular layers, and around the myenteric plexus. In aganglionic segments, interstitial cells were scarce and its network appeared disrupted. Interstitial cells of Cajal were identified in aganglionic regions by electron microscopy. Interstitial cells of Cajal are identifiable in newborns and exhibit similar distribution in diversion loops independent of contact with luminal nutrients. CONCLUSIONS: Our morphological data may explain the abnormal spontaneous electrical activity in aganglionic segments of Hirschsprung's disease and may give new insight into the ontogeny of interstitial cells.

Child, Preschool↗

PubMed1996

The pathology of infantile hypertrophic pyloric stenosis after healing.

INTRODUCTION: Infantile hypertrophic pyloric stenosis (IHPS) is a common surgical affection of unknown etiology. The muscular hypertrophy is known to resolve within a few months after pyloromyotomy (PM). The pathology of IHPS has been studied extensively at the time of PM, but the fate of the pylorus after healing remains unknown. MATERIALS AND METHODS: We had the rare opportunity to study two pyloric biopsy specimens obtained 4 months and 2 years (respectively) after an uncomplicated PM for IHPS. They were compared with the initial specimen in one case, with 26 other specimens of IHPS, and with five normal controls. Immunohistochemistry using the avidin-biotin complex (ABC) system was performed for S-100 and nerve growth factor receptor, as markers for the enteric nervous system, and for the tyrosine kinase receptor c-kit, as a marker for the interstitial cells of Cajal (pacemaker cells). NADPH-diaphorase histochemistry was performed as a marker for the neuronal enzyme nitric oxide synthase, which produces the inhibitory neurotransmitter nitric oxide. RESULTS: In both cases of IHPS, after healing, the circular musculature was not hypertrophic. For all markers studied, the distribution appeared similar to that in the normal pylorus. In contrast, all specimens obtained at the time of PM displayed a severe reduction of the different markers in the hypertrophic musculature. DISCUSSION: The pathological features observed in the circular layer in IHPS appear to resolve within a few months after PM. This suggests that the involvement of the enteric nervous system in IHPS might be milder than generally assumed. The etiology remains obscure, but our occasional observations may provide new insight into the pathophysiology of IHPS, and are in agreement with the excellent longterm clinical outcome for IHPS.

Biomarkers↗

PubMed1996

Inhibition of vein graft intimal and medial thickening by periadventitial application of a sulfated carbohydrate polymer.

PURPOSE: The purpose of this study was to determine whether the wall thickening observed in vein grafts after they were placed into the arterial circulation could be inhibited by periadventitial delivery of an insoluble sulfated polymer of beta-cyclodextrin (P-CDS) capable of tightly binding heparin binding growth factors. METHODS: Thirty-four New Zealand white rabbits underwent implantation of reversed autologous jugular vein interposition grafts in the common carotid artery and were randomized to receive either 20 mg P-CDS (n = 18) topically around the graft or no additional therapy (n = 16). Before being killed at 28 days, animals were given bromodeoxyuridine to assess smooth muscle cell proliferation. Histomorphometric analyses were performed after perfusion fixation. RESULTS: Compared to controls, treatment with P-CDS was associated with reduced mean intimal thickness (24 +/- 3 vs 38 +/- 4 microns; mean SEM, p < 0.01) and intimal area (0.25 +/- 0.03 vs 0.54 +/- 0.09 mm2; p < 0.01). There was also significantly less medial thickness in the P-CDS group (45 +/- 3 vs 63 +/-3, p < 0.001). There was no significant difference in intimal or medial smooth muscle cell proliferation between P-CDS-treated and control vein grafts at 28 days. The polymer persisted in the adventitia with a mild foreign body reaction. CONCLUSION: Periadventitial placement of P-CDS, a novel, insoluble, sulfated carbohydrate polymer, inhibits intimal and medial thickening of vein bypass grafts in this model of vein grafting. The persistence of P-CDS in vivo for prolonged periods, and the ease of topical application of P-CDS during vascular bypasses may have important implications for its future use in vascular surgery.

Administration, Topical↗

PubMed1996

Pulsed electromagnetic fields influence hyaline cartilage extracellular matrix composition without affecting molecular structure.

Pulsed electromagnetic fields (PEMF) influence the extracellular matrix metabolism of a diverse range of skeletal tissues. This study focuses upon the effect of PEMF on the composition and molecular structure of cartilage proteoglycans. Sixteen-day-old embryonic chick sterna were explanted to culture and exposed to a PEMF for 3 h/day for 48 h. PEMF treatment did not affect the DNA content of explants but stimulated elevation of glycosaminoglycan content in the explant and conserved the tissue's histological integrity. The glycosaminoglycans in sterna exposed to PEMF were indistinguishable from those in controls in their composition of chondroitin sulfate resulting from chondroitinase ABC digestion. Specific examination with [35S]-sulfate labels showed that PEMF treatment significantly suppressed both the degradation of pre-existing glycosaminoglycans biosynthetically labeled in ovo and the synthesis of new [35S]-sulfated glycosaminoglycans. The average size and aggregating ability of pre-existing and newly synthesized [35S]-sulfated proteoglycans extracted with 4 M guanidinium chloride from PEMF-treated cartilage explants were identical to controls. The chain length and degree of sulfation of [35S]-sulfated glycosaminoglycans also were identical in control and PEMF-treated cultures. PEMF treatment also reduced the amount of both unlabeled glycosaminoglycans and labeled pre-existing and newly synthesized [35S]-sulfated glycosaminoglycans recovered from the nutrient media. [35S]-Sulfated proteoglycans released to the media of both control and PEMF-treated cultures were mostly degradation products although their glycosaminoglycan chain size was unchanged. These results demonstrate that exposure of embryonic chick cartilage explants to PEMF for 3 h/day maintains a balanced proteoglycan composition by down-regulating its turnover without affecting either molecular structure or function.

Animals↗

PubMed1996

Pulmonary parenchymal manifestations surrounding small peripheral masses: pathologic correlation with chest radiographs and diagnostic value.

RATIONALE AND OBJECTIVES: We evaluated pathologic correlations of pulmonary parenchymal manifestations surrounding small peripheral masses and their usefulness in differentiating small peripheral bronchogenic carcinomas from tuberculomas. METHODS: We evaluated 29 resected lobe specimens with 1.5- to 3.5-cm solitary pulmonary masses, including 24 carcinomas and five tuberculomas. These specimens were prospectively studied with preoperative chest radiographs, postoperative specimen radiographs, 10- to 15-microns-thick wholemount sections, and 5-microns-thick slices. A total of 100 chest X-rays and conventional tomography scans of 1- to 3-cm peripheral pulmonary masses, including 60 carcinomas and 40 tuberculomas, were retrospectively reviewed and analyzed. RESULTS: The pulmonary parenchymal manifestations surrounding the masses presented as small infiltrates and nodular protrusions, thickened strands, and "double track" shadows, which extended from the proximal margin of five tuberculomas (100%, 5 of 5) and from the distal margin of 17 carcinomas (71%, 17 of 24). These pulmonary changes represented caseous material spreading from tuberculomas into the proximal bronchus and alveolar inflammatory exudation distal to the carcinomas. The proximal pulmonary manifestations were significantly more frequent in tuberculomas than in carcinomas (p < .01), whereas the distal pulmonary manifestations were more often found in carcinomas than in tuberculomas (p < .01). CONCLUSION: The radiologic findings of the pulmonary parenchymal manifestations proximal or distal to the masses may be valuable radiologic signs for distinguishing between tuberculomas and small peripheral bronchogenic carcinomas, even though there is still considerable crossover between the two disease populations in the findings.

Carcinoma, Bronchogenic↗

PubMed1996

Signal-to-noise ratio and detective quantum efficiency analysis of optically coupled CCD mammography imaging systems.

RATIONALE AND OBJECTIVES: Design considerations for x-ray systems with optically coupled charge-coupled devices require an understanding of the characteristics of cascaded multistage imaging chains. Performance evaluations rely on accurate analyses of signal-to-noise ratio, noise power spectrum, and detective quantum efficiency. METHODS: Theoretic models of signal-to-noise ratio, noise power spectrum, and detective quantum efficiency were extended to analyze the optically coupled charge-coupled device and other electronic x-ray imaging systems. The descriptions of how to measure or compute these parameters are provided. RESULTS: The results of our quantitative analysis illustrate that x-ray quantum-noise limitation can be obtained without an image intensifier by using a low additive noise charge-coupled device. CONCLUSION: This theoretic model and experimental method provide a useful tool for developing optoelectronic x-ray imaging systems for digital mammography and other radiologic procedures.

Female↗

PubMed1996

Observer performance in the localization of tubes and catheters on digital chest images: the role of expertise and image enhancement.

RATIONALE AND OBJECTIVES: To determine whether observer performance in the localization of tubes and catheters on computed radiography (CR) chest images can be improved by using an automatic image-processing algorithm. METHODS: Comparisons were made of CR hard-copy, CR soft-copy, and CR enhanced soft-copy images obtained with an image-processing algorithm. The enhanced images used gray-level optimization and nonlinear unsharp masking to emphasize the edges of the devices. Chest radiologists (n = 4), general radiologists (n = 4), and interns (n = 6) read 45 images that contained endotracheal tubes, pulmonary artery catheters, and central venous catheters. RESULTS: Chest radiologists had the smallest mean interobserver localization variability (4 mm), followed by general radiologists (6 mm) and interns (8 mm). Localization variability was greatest for hard-copy images and least for enhanced soft-copy images. CONCLUSION: Use of an automatic imaging-processing algorithm reduced localization variability and enabled the medical interns to perform at approximately the same level as the chest radiologists.

Algorithms↗

PubMed1996

Study of the interstitial cells of Cajal in infantile hypertrophic pyloric stenosis.

BACKGROUND & AIMS: The interstitial cells of Cajal form a network in close association with the smooth muscle of the gut. They are regarded as pacemaker cells and might be involved in motility disorders. Their distribution was studied in a common disorder with a dysfunction of the pyloric sphincter called infantile hypertrophic pyloric stenosis. METHODS: Specimens from 27 infants with pyloric stenosis and 12 controls were processed for immunohistochemistry using a specific antiserum raised against c-kit, a tyrosine kinase receptor expressed by interstitial cells. RESULTS: In the normal pylorus, numerous interstitial cells were labeled throughout the tissue. In pyloric stenosis, c-kit immunoreactivity was absent in the major part of the tissue. Interstitial cells were observed only in the inner part of the musculature, near the submucosal edge, and in the antrum, at the proximal end of the biopsy specimens. CONCLUSIONS: The lack of interstitial cells in the pylorus possibly contributes to the motility disturbance of infantile pyloric stenosis.

Female↗

PubMed1996

Identification and characterization of autosomal genes that interact with glass in the developing Drosophila eye.

The glass gene encodes a zinc finger, DNA-binding protein that is required for photoreceptor cell development in Drosophila melanogaster. In the developing compound eye, glass function is regulated at two points: (1) the protein is expressed in all cells' nuclei posterior to the morphogenetic furrow and (2) the ability of the Glass protein to regulate downstream genes is largely limited to the developing photoreceptor cells. We conducted a series of genetic screens for autosomal dominant second-site modifiers of the weal allele glass3, to discover genes with products that may regulate glass function at either of these levels. Seventy-six dominant enhancer mutations were recovered (and no dominant suppressors). Most of these dominant mutations are in essential genes and are associated with recessive lethality. We have assigned these mutations to 23 complementation groups that include multiple alleles of Star and hedgehog as well as single alleles of Delta, roughened eye, glass and hairy. Mutations in 18 of the complementation groups are embryonic lethals, and of these, 13 show abnormal adult retinal phenotypes in homozygous clones, usually with altered numbers of photoreceptor cells in some of the ommatidia.

Animals↗

PubMed1996

Saccharomyces cerevisiae S288C has a mutation in FLO8, a gene required for filamentous growth.

Diploid strains of baker's yeast Saccharomyces cerevisiae can grow in a cellular yeast form or in filaments called pseudohyphae. This dimorphic transition from yeast to pseudohyphae is induced by starvation for nitrogen. Not all laboratory strains are capable of this dimorphic switch; many grow only in the yeast form and fail to form pseudohyphae when starved for nitrogen. Analysis of the standard laboratory strain S288C shows that this defect in dimorphism results from a nonsense mutation in the FLO8 gene. This defect in FLO8 blocks pseudohyphal growth in diploids, haploid invasive growth, and flocculation. Since feral strains of S. cerevisiae are dimorphic and have a functional FLO8 gene, we suggest that the flo8 mutation was selected during laboratory cultivation.

Alleles↗

PubMed1996

Frequent deletion of chromosome 1p sequences in an aggressive histologic subtype of endometrial cancer.

The molecular genetic events underlying endometrial tumorigenesis are ill-defined at present. We have identified a region on the short arm of chromosome 1 which is frequently deleted in endometrial cancers. The region of deletion has been localized to bands 1p32-33. Deletion of 1p32-33 is seen more frequently in cancers of the highly aggressive papillary serous type than in cancers of the less-aggressive endometrioid type. These data suggest the presence of a tumor suppressor gene on 1p32-33 which is specifically involved in the development of endometrial cancers with poor outcome.

Adenocarcinoma, Clear Cell↗

PubMed1996

Vascular manifestations of small solitary pulmonary masses. Angiographic-pathologic correlations and clinical significance.

RATIONALE AND OBJECTIVES: By performing pulmonary specimen angiographies, the authors attempted to determine the pathologic correlations of the vascular-related radiologic manifestations within, at the edge of, and adjacent to the small solitary pulmonary masses, and to evaluate their usefulness in differentiating small bronchogenic carcinomas from tuberculomas. METHODS: A total of 29 resected lobe specimens with 1.5- to 3.5-cm solitary pulmonary masses, including 24 carcinomas and 5 tuberculomas, were studied prospectively with preoperative radiographs, postoperative specimen arteriographies (in 19 carcinomas and 5 tuberculomas), and venographies (in 5 carcinomas), 10- to 15 micrograms-thick whole-mount sections, and 5-micrograms-thick slices for the examination of angiographic-pathologic correlation. Another series of chest radiographs and conventional tomographs of 100 patients with 1- to 3-cm peripheral pulmonary masses, including 60 carcinomas and 40 tuberculomas, were reviewed retrospectively and analyzed with the chi-square test. RESULTS: Specimen angiographies showed the intralesion avascularity, small arterial speculation, and lobulation or notch at the mass margin with arterial compression, as well as vascular convergence to the mass, in both carcinoma and tuberculoma groups. The irregular arterial wall (79.2%) and venous dilation distal to the mass (100%) were found in the carcinoma group only. Microscopically, arterial or venous fibrous hyperplasia was observed in both carcinomas and tuberculomas, whereas the arterial erosion by tumor tissue and tumor emboli within the vessels were found in carcinomas only. The retrospective review of the 100 patients showed that two radiologic signs of the vascular convergence to the mass and the vascular dilation distal to the mass occurred at similar frequencies (12%-13%) between the carcinoma and tuberculoma groups. CONCLUSIONS: In addition to compression of vessels by tumor and vessel occlusion by tumor embolus, pulmonary vascular fibrotic hyperplasia can cause intramass avascularity. Small vessels running vertically into or from the mass margin can construct the spiculation sign of the tuberculomas. Any evidence of pulmonary vascular irregularity will indicate a bronchogenic carcinoma. The vascular convergence to the mass and the vascular dilation distal to the mass are not specific radiologic signs for small solitary bronchogenic carcinomas.

Adenocarcinoma↗