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Biomedical subjects

J Zhou

Publications and source records attributed to J Zhou.

At least 721 records · Page 40Linked to original sources
PubMed1996

N-terminal mutants of chloroplast cytochrome f. Effect on redox reactions and growth in Chlamydomonas reinhardtII.

The N-terminal tyrosine of cytochrome f, which provides the sixth ligand to the heme group, has been changed by site-directed mutagenesis in Chlamydomonas reinhardtii to evaluate the role of this amino acid in assembly and function. The second and third residues, proline and valine, respectively, have also been mutated. Y1P is the only strain that did not grow photoautotrophically. The other strains show cytochrome b6f complex/photosystem I reaction center chlorophyll, photosystem I unit size and chlorophyll a+b/cell ratios comparable with wild-type cells. Rates of cytochrome f photooxidation in all strains were similar (t1/2 approximately = 300 microsec), whereas the rate of re-reduction sensitive to stigmatellin (at Eh = 0 mV, (where Eh is the ambient redox potential) for wild-type, Y1W, Y1F, Y1S, P2V, and V3P had a tl/2 of 3, 4, 5, 9, 40, and 2 ms, respectively. Rates of oxygen evolution by whole cells of P2V, Y1F, and Y1S were 67, 80, and 80% of wild-type rates, respectively. At low light intensity, all competent strains had the same growth rate whereas at saturating intensities, only P2V showed a significant inhibition. These results are considered in relation to structure-function relationships in the cytochrome f molecule.

Animals↗
PubMed1996

Epithelial cells display separate receptors for papillomavirus VLPs and for soluble L1 capsid protein.

We examined the distribution of putative receptors for papillomavirus (PV) capsid proteins on various cell types, using either Hexahis HPV6b L1 fusion protein or synthetic HPV6b virus-like particles (VLPs). Specific, saturable binding of VLPs to CV-1 cells was demonstrated using 35S-labeled VLPs, with an average receptor number of 1 x 10(4)/cell and a binding affinity constant (Ka) of 4 x 10(7) M. VLP binding was quantitated by flow cytometry using a monoclonal antibody to the L1 capsid protein. Intense staining of epithelial and mesenchymal cells was observed. Some immature bone marrow-derived cells bound VLPs weakly, while the majority of B lymphoma cells demonstrated no binding. Binding to 12 of 16 VLP receptor positive cell lines was abolished by trypsin pretreatment of cells. Removal of cellular sialic acid or O-linked oligosaccharides separately did not affect VLP binding, which was enhanced about 25% when cells were pretreated with both neuraminidase and O-glycosidase. Culture of cells with sufficient tunicamycin to inhibit Concanavalin A binding did not diminish the binding of VLPs. Denatured L1 protein, either from VLPs or expressed from Escherichia coli as a Hexahis fusion protein, bound to a trypsin-resistant structure on a range of cell types and did not block the binding of VLPs to cells. Dual-fluorescence assay with a Burkitt lymphoma line BL72 demonstrated that Hexahis L1 protein and VLPs bind to separate cell surface molecules on BL72 cells. We conclude that the first binding of PV virus to cells is via a widely distributed membrane protein receptor(s) and that subsequent processing of particles may involve other non-trypsin-sensitive structure(s) also displayed on the cell membrane.

Animals↗
PubMed1996

Dual-electrode detection for capillary electrophoresis/electrochemistry.

The extremely low sample volumes required for capillary electrophoresis and the high sensitivity and selectivity of electrochemical detection make capillary electrophoresis/electrochemistry (CEEC) a very useful method for bioanalysis. In this paper, two types of dual-electrode detectors for CEEC are described. The first employs a ring-disk microelectrode placed in a wall-jet configuration and is used for the selective detection of substances undergoing chemically reversible oxidations. Collection efficiencies obtained for catecholamines with this configuration were between 25 and 35%. The second electrode design consists of two adjacent carbon fibers embedded in an epoxy matrix and is analogous to the parallel dual-electrode configuration used in liquid chromatography/electrochemistry. This configuration can be used to confirm peak identity and purity by operating the electrodes at two different potentials. Alternatively, it is possible to perform simultaneous oxidative and reductive electrochemical detection.

Catecholamines↗
PubMed1996

Transfected neu oncogene induces human prostate cancer metastasis.

c-erb B2/neu has been demonstrated to be a transforming oncogene in both rodent and human prostatic epithelial cells. To understand the potential role of neu in human prostatic cancer progression, we used a transfer procedure to determine whether neu amplification/overexpression leads to increased tumor growth and metastasis. We chose an androgen-independent human prostatic epithelial cell line, PC-3, as the target for gene transfer. PC-3 cells were cotransfected with pSVneu-T (a point-mutated rat neu oncogene construct) and pSV2neo, and single-cell cloned. Fifty cell clones were isolated and characterized, of which two neu-transfected clones (N17 and N35) and a neo control clone (C32) were studied extensively with respect to neu gene integration, levels of neu mRNA and protein expression, anchorage-independent growth, and tumorigenic and metastatic potential. Results showed that: 1) Clone N35 contained 70 copies of the neu oncogene and a high level of neu mRNA transcripts. It acquired increased anchorage-independent growth potential in vitro and increased tumorigenicity in vivo. 2) Clone N17 contained 10 copies of the neu oncogene and a low level of neu mRNA transcripts. It did not acquire additional capability for anchorage-independent growth and tumorigenic potential as compared to the controls. 3) Despite an increased level of neu mRNA transcripts present in clone N35, there was no corresponding increase of the steady-state levels of neu protein in this particular clone. 4) When administered subcutaneously, none of the cell clones tested, including the control neomycin-resistant clone, acquired metastatic potential. However, clone N35 exhibited marked metastatic potential when administered orthotopically; this cell clone was found to disseminate widely to the lymph nodes, kidney, skeletal muscle, lung, liver, and bone. 5) When neu-transfected cell subclones from N35-induced primary and metastatic lymph node, kidney, and bone tumors were analyzed for cytoskeletal, extracellular matrix, and cell adhesion protein expression, the bone metastatic subclone exhibited increased levels of vimentin and collagen IV and decreased levels of cytokeratin and ICAM-1. These results, taken together, suggest that neu transfection induces secondary changes, which, rather than neu protein per se, are responsible for the acquisition of tumorigenic and metastatic potential of prostate cancer cells when an appropriate host microenvironment is present.

Animals↗
PubMed1996

Expression of an Msx homeobox gene in ascidians: insights into the archetypal chordate expression pattern.

The Msx homeobox genes are expressed in complex patterns during vertebrate development in conjunction with inductive tissue interactions. As a means of understanding the archetypal role of Msx genes in chordates, we have isolated and characterized an Msx gene in ascidians, protochordates with a relatively simple body plan. The Mocu Msx-a and McMsx-a genes, isolated from the ascidians Molgula oculata and Molgula citrina, respectively, have homeodomains that place them in the msh-like subclass of Msx genes. Therefore, the Molgula Msx-a genes are most closely related to the msh genes previously identified in a number of invertebrates. Southern blot analysis suggests that there are one or two copies of the Msx-a gene in the Molgula genome. Northern blot and RNase protection analysis indicate that Msx-a transcripts are restricted to the developmental stages of the life cycle. In situ hybridization showed that Msx-a mRNA first appears just before gastrulation in the mesoderm (presumptive notochord and muscle) and ectoderm (neural plate) cells. Transcript levels decline in mesoderm cells after the completion of gastrulation, but are enhanced in the folding neural plate during neurulation. Later, Msx-a mRNA is also expressed in the posterior ectoderm and in a subset of the tail muscle cells. The ectoderm and mesoderm cells that express Msx-a are undergoing morphogenetic movements during gastrulation, neurulation, and tail formation. Msx-a expression ceases after these cells stop migrating. The ascidian M. citrina, in which adult tissues and organs begin to develop precociously in the larva, was used to study Msx-a expression during adult development. Msx-a transcripts are expressed in the heart primordium and the rudiments of the ampullae, epidermal protrusions with diverse functions in the juvenile. The heart and ampullae develop in regions where mesenchyme cells interact with endodermal or epidermal epithelia. A comparison of the expression patterns of the Molgula genes with those of their vertebrate congeners suggests that the archetypal roles of the Msx genes may be in morphogenetic movements during embryogenesis and in mesenchymal-epithelial interactions during organogenesis.

Amino Acid Sequence↗
PubMed1996

Preparation and properties of pure, full-length IclR protein of Escherichia coli. Use of time-of-flight mass spectrometry to investigate the problems encountered.

IclR protein, the repressor of the aceBAK operon of Escherichia coli, has been examined by time-of-flight mass spectrometry, with ionization by matrix assisted laser desorption or by electrospray. The purified protein was found to have a smaller mass than that predicted from the base sequence of the cloned iclR gene. Additional measurements were made on mixtures of peptides derived from IclR by treatment with trypsin and cyanogen bromide. They showed that the amino acid sequence is that predicted from the gene sequence, except that the protein has suffered truncation by removal of the N-terminal eight or, in some cases, nine amino acid residues. The peptide bond whose hydrolysis would remove eight residues is a typical target for the E. coli protease OmpT. We find that, by taking precautions to minimize Omp T proteolysis, or by eliminating it through mutation of the host strain, we can isolate full-length IclR protein (lacking only the N-terminal methionine residue). Full-length IclR is a much better DNA-binding protein than the truncated versions: it binds the aceBAK operator sequence 44-fold more tightly, presumably because of additional contacts that the N-terminal residues make with the DNA. Our experience thus demonstrates the advantages of using mass spectrometry to characterize newly purified proteins produced from cloned genes, especially where proteolysis or other covalent modification is a concern. This technique gives mass spectra from complex peptide mixtures that can be analyzed completely, without any fractionation of the mixtures, by reference to the amino acid sequence inferred from the base sequence of the cloned gene.

Amino Acid Sequence↗
PubMed1996

Synthesized surface anatomy scanning (SSAS) for surgical planning of brain metastasis at the sensorimotor region: initial experience with 5 patients.

Surface anatomy scanning (SAS) is a powerful technique that uses T2-weighted magnetic resonance images (MRI) to visualize brain surface structures, and to precisely localize subcortical lesions. To overcome technical limitations of this method, synthesized SAS (SSAS) superimposes MR angiography (MRA) data on the SAS images. We describe our initial experience with surgical planning for the resection of metastases at the sensorimotor region in 5 patients using SSAS. Neurological deficits were assessed before and after surgical resection. Although 4 of 5 patients had mild to severe neurological deficits before surgery, three became symptom-free and no patient had an increased deficit after surgery. Our results undoubtedly provide palliative surgery for sensorimotor metastases. As SSAS is non-invasive and requires a short scanning time, this method could become a useful technique for the routine pre-operative simulation for surgery on brain surface lesions such as sensorimotor metastases.

Adenocarcinoma↗
PubMed1996

Deep hypothermia cardiopulmonary bypass and direct surgery of two large aneurysms at the vertebro-basilar junction.

This paper highlights two interesting cases of radial clipping of large aneurysms at the vertebro-basilar junction accompanied by a vascular anomaly, consisting of fenestration of the split basilar artery at its origin. Description of the inner and outer surface of the aneurysm were obtained pre-operatively, from analysis by 3D CT and 3D CT endoscopy of the form of the neck, parent vessels of the vertebral arteries on both sides, basilar artery and split basilar artery, as well as other details of branching. The neck exhibited a broad base in both cases. The height of the neck extended to the internal acoustic meatus, and it was possible to expose the circumference of the aneurysmal neck, peripheral basilar artery and both vertebral arteries proximally with an anterior, transpetrosal approach. Based on the size of the aneurysm and the site being the anterior surface of the brain stem, clipping (consisting of interruption of the occluded portion and reconstruction of the parent vessels) was performed. In the first case it was achieved protecting the brain by hypothermia and barbiturates under deep hypothermia with extracorporal circulation, and in the second case, a state of circulatory arrest was used. This paper documents the report of two cases along with other cases treated so far.

Adult↗
PubMed1996

A comparison of the nucleotide sequences of the adk and recA genes of pathogenic and commensal Neisseria species: evidence for extensive interspecies recombination within adk.

The sequences of the adenylate kinase gene (adk) and the RecA gene (recA) were determined from the same isolates of Neisseria gonorrhoeae, N. meningitidis, N. lactamica, N. polysaccharea, N. cinerea, N. mucosa, N. pharyngis var. flava, N. flavescens, and N. animalis. The patterns of sequence divergence observed at adk and recA were very different. Dendrograms constructed from the recA data using two different algorithms were statistically robust and were congruent with each other and with the relationships between the species previously proposed using other data. In contrast, the dendrograms derived from the adk data were noncogruent with each other, and with those from the recA data, and were statistically poorly supported. These results, along with the uniform distribution of pairwise sequence divergences between the species at adk, suggest there has been a history of interspecies recombination within the adk gene of the human Neisseria species which has obscured the phylogenetic relationships between the species. This view was supported by Sawyer's runs test, and the Index of Association (IA) between codons, which provided significant evidence for interspecies recombination between the adk genes from the human Neisseria species, but no evidence of interspecies recombination between the recA sequences.

Adenylate Kinase↗
PubMed1996

Molecular evolution of nitrate reductase genes.

To understand the evolutionary mechanisms and relationships of nitrate reductases (NRs), the nucleotide sequences encoding 19 nitrate reductase (NR) genes from 16 species of fungi, algae, and higher plants were analyzed. The NR genes examined show substantial sequence similarity, particularly within functional domains, and large variations in GC content at the third codon position and intron number. The intron positions were different between the fungi and plants, but conserved within these groups. The overall and nonsynonymous substitution rates among fungi, algae, and higher plants were estimated to be 4.33 x 10(-10) and 3.29 x 10(-10) substitutions per site per year. The three functional domains of NR genes evolved at about one-third of the rate of the N-terminal and the two hinge regions connecting the functional domains. Relative rate tests suggested that the nonsynonymous substitution rates were constant among different lineages, while the overall nucleotide substitution rates varied between some lineages. The phylogenetic trees based on NR genes correspond well with the phylogeny of the organisms determined from systematics and other molecular studies. Based on the nonsynonymous substitution rate, the divergence time of monocots and dicots was estimated to be about 340 Myr when the fungi-plant or algae-higher plant divergence times were used as reference points and 191 Myr when the rice-barley divergence time was used as a reference point. These two estimates are consistent with other estimates of divergence times based on these reference points. The lack of consistency between these two values appears to be due to the uncertainty of the reference times.

Base Composition↗
PubMed1996

A scintigraphic study on gastric emptying in patients with non-ulcer dyspepsia.

Solid gastric emptying rates (GER) were determined with scintigraphic techniques in 20 patients with non-ulcer dyspepsia (NUD) and 9 healthy volunteers. GER were significantly decreased in NUD patients compared with controls, especially 45 min (P < 0.05), 60 and 90 min (P < 0.01) and 120 min (P < 0.05) after ingestion. In 13 out of 20 NUD patients who demonstrated lower GER, only 4 cases gave a lower GER at all stages throughout the determination, the other 9 showed their abnormal GER only after 60 min. In 3 cases who received repeated GER studies after cisapride therapy, 2 patients showed symptomatic relief accompanied by GER improvement. It is concluded that gastric emptying delay may be present with a high percentage in patients with non-ulcer dyspepsia. Scintigraphic gastric emptying test is a safe and reliable technique with good reproducibility. It may be helpful in quantitative study about gastric motion disorders.

Adolescent↗
PubMed1996

Changes in monoamines and their metabolite concentrations in REM sleep-deprived rat forebrain nuclei.

Rapid eye movement sleep deprivation (REMSD) is a potent stressor in rats. Behavioral abnormalities such as passive and active avoidance, locomotor activity, problem solving, sensory information processing, and the development of adaptive copping strategy in response to repeated stress are among the earliest obvious symptoms of REMSD, the mechanism for which remain largely unknown. The aim of this study was to determine whether 96 h of REMSD causes changes in monoamine neurotransmitters concentrations in rat forebrain regions (frontal cortex, FC; parietal cortex, PC, and striatum) that are involved in mediating higher brain functions such as attentional mechanisms, sensory information processing, and locomotor activity, which are severely affected in REMSD conditions. Rats were subjected to 96 h of REMSD using inverted flower pot water tank technique. To account for the stress associated with water tanks, a tank control group (TC) was included where the animals could reside comfortably on a large pedestal in the water tank. Regional brain concentrations of norepinephrine (NE), dopamine (DA), dihydroxyphenyacetic acid (DOPAC), L-3,4-dihydroxyphenylalanine (L-DOPA), homovanillic acid (HVA), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (HIAA) were determined by electrochemical detection using high-performance liquid chromatography. The concentrations of serotonin and its metabolite, HIAA, was reduced in the frontal and parietal cortexes of REMSD rats compared with TC or cage control (CC) group. NE, DA, DOPAC, and HVA concentrations in FC and PC of REMSD animals were remained unchanged compared with TC or CC rats. A significant increase in the concentrations of DA metabolites was observed in the striatum of REMSD rats when compared with CC and TC rats. There was a 29 and 31% increase in the concentration of striatal DA in REMSD group compared to the TC and CC groups, respectively; however, these percentages were not statistically different. Striatal NE, 5-HT, and HIAA concentrations were not significantly different among the three groups. These results suggest that 96 h of REMSD alters dopaminergic and serotonergic systems in different locations in rat brain. The effect of REMSD on the serotonergic systems are localized in the cerebral cortex, whereas dopaminergic metabolism is increased in the striatum.

Animals↗
PubMed1996

Expression of early lung cancer detection marker p31 in neoplastic and non-neoplastic respiratory epithelium.

In an immunocytochemical study of sputum, two antibodies, including a mouse monoclonal antibody (703D4) to a 31 kDa protein (p31) antigen, have been previously shown to detect lung cancer earlier than routine cytomorphology or chest X-ray. To understand the basis of p31 expression, the distribution of this antigen in the respiratory epithelium of individuals known to have lung cancer was mapped. These individuals are likely to demonstrate extensive changes throughout the epithelium due to field cancerization. p31 immunoreactivity was examined in primary tumors and surrounding non-neoplastic lungs containing both histologically normal and abnormal areas obtained from 28 Stage I non-small cell lung cancer (NSCLC) patients. Distribution and intensity of p31 expression was scored in three lung compartments (bronchi, bronchioli, alveoli). While p31 was present in histologically unremarkable bronchial and bronchiolar epithelium, no expression was detected in bronchi or bronchioli containing histologic abnormalities. Furthermore, in the peripheral lung p31 staining was frequently observed in alveolar type II cells and was most commonly detected in reactive, hyperplastic type II cells. When p31 immunoreactivity was correlated with clinicopathological features, a statistically significant increase in p31 expression was found both in bronchioli and alveoli of older individuals a well as in bronchioli of patients with most extensive smoking exposure. We conclude that p31 expression occurs in both non-neoplastic and neoplastic epithelium of the human respiratory tract. The increased expression of p31 in the peripheral lung may be potentially informative as to what critical cell populations are involved in the development of invasive cancers. Moreover, this study provides a model approach for analysis of the nature of early epithelial changes leading to the development of lung cancer.

Antibodies, Monoclonal↗
PubMed1996

Automated analytical systems for drug development studies. V. A system for enzyme kinetic studies.

Two similar automated analytical systems using liquid chromatography (LC) and microdialysis as an on-line sampling technique were applied to studies of enzyme kinetics. 2',3',5'-Triacetyl-6-azauridine (azaribine) with porcine liver esterase (PLE) and N-acetylphenylalanyl-3,5-diiodotyrosine (AcFY') with pepsin were used as model compounds. The microdialysis sampling technique permitted the rapid separation of low molecular weight analytes from macromolecules, thus simultaneously achieving clean-up of the samples and quenching of the reaction. The combination of rapid LC analysis and microdialysis sampling provided selectivity and automation. The systems are rugged and give reproducible results in agreement with those from manual sampling methods.

Animals↗
PubMed1996

The use of differential transverse relaxation to detect mobile species in solids.

Delayed acquisition of the proton NMR in selected organic molecular solids (L-alanine, durene, ethyl fumarate, and p-hydroxybenzoic acid) is shown to allow the observation of mobile species in the presence of relatively rigid bulk molecules. The mobility is found to be thermally activated. The combination of the thermally activated motion and magic-angle spinning leads to a fraction of these species moving nearly isotropically on the time scale of the inverse of the homonuclear dipolar splitting. In the case of ethyl fumarate and alanine, there exist populations with differing values of T1 and T1 row. This indicates the co-existence of relatively rigid and relatively mobile molecules in the same sample. The intensities under delayed acquisition cannot always be trusted to yield quantitative information. Comparison of spectra taken under delayed acquisition and under the CRAMPS (B.C. Gerstein, R.G. Pembleton, R.C. Wilson and L.M. Ryan, J. Chem. Phys., 66 (1977)361) technique is made.

Alanine↗
PubMed1996

High resolution 1H spectra of powdered solids observed by Hahn echo pulse sequence with magic-angle spinning.

The 1H magic-angle spinning (MAS) spectrum for a typical powdered solid is composed of a high resolution component and a broadline component. The high resolution component can be well isolated from the broadline component by the Hahn echo sequence with a long echo time. Compared with CRAMPS experiment, which measures the proton system as a whole, the high resolution echo-MAS method measures only a fraction of the solid, which is usually small at room temperature and quite different from the majority of the solid in both molecular motion and chemical environment. It is shown that for a sample of fumaric acid monoethyl ester, the chemical shifts of the high resolution component are apparently distinguishable from the isotropic chemical shifts of the broadline component in the CRAMPS spectrum as the temperature approaches the melting point. In addition, for a sample of malonic acid, the echo-MAS spectrum is sensitive to moisture and temperature, while its corresponding CRAMPS spectrum is not. It is suggested that the molecules which produce the high resolution component are related to the lattice defects in a solid, including the surface disorder of the polycrystallites, while the molecules that generate the broadline component are located on the rigid lattice of the solid.

Chemical Phenomena↗