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C Wang

Publications and source records attributed to C Wang.

At least 991 records · Page 55Linked to original sources
PubMed1994

Isolation of a cDNA encoding a 70 kDa heat-shock cognate protein expressed in vegetative tissues of Arabidopsis thaliana.

A cDNA encoding a 70 kDa heat shock 'cognate' protein (hsc70) was isolated from Arabidopsis thaliana by using a rat hsc70 cDNA as probe. Sequence analysis demonstrated the conservation of functional domains and important amino acid residues among hsc70s in plants and animals. The expression of this gene was stress-inducible, and was found at a substantial level during normal growth in root, stem, leaf and flower tissues, but not in siliques. Multiple copies of this gene exist in the Arabidopsis genome.

Amino Acid Sequence↗
PubMed1994

Non-dominant suppression in the dorsal lateral geniculate nucleus of the cat: laminar differences and class specificity.

Binocular non-dominant suppression (NDS) in the dorsal lateral geniculate nucleus (LGNd) of the cat was studied by recording from single neurons in the LGNd of anaesthetized, paralysed cats while stimulating the non-dominant eye with a moving light bar. The maintained discharge rate of LGNd neurons was varied by stimulating the dominant eye in various ways: by varying the size or contrast of a flashed spot, by varying the inner diameter of a flashed annulus of large outer diameter, by varying the velocity of a moving light bar, and by covering the eye. Non-dominant suppression was quantified either as the decrease in the maintained discharge rate (the "dip"), expressed as spikes per second, or as the ratio of the dip to the maintained discharge rate (the "dip ratio"). At low maintained discharge rates the dip, although low in value, frequently approached the maintained rate, i.e. the dip ratio approached unity. As the maintained discharge rate increased the dip value also increased, but more slowly than the maintained discharge rate, i.e. the dip ratio decreased. At maintained discharge rates above about 30 spikes/s, in many neurons the dip appeared to be approaching a constant value. This strong dependence of NDS on the maintained discharge rate of the LGNd neuron suggests that the inhibitory input to the cell arises from a region of the brain that receives an input both from the non-dominant eye and from the LGNd cell. Reasons are given for thinking that this region is the perigeniculate nucleus. Because of the strong dependence of dip and dip ratio on the maintained discharge rate, it was necessary to adopt stringent criteria when comparing NDS in two different sets of neurons or of the same set of neurons in different conditions. We recognized a significant difference in NDS between two classes of neurons or between two states only if: (1) there was no significant difference between the maintained discharge rates, and (2) there was a significant difference for both dip and dip ratio between the two classes or states. Using these criteria we found: (1) no difference between non-lagged X (XNL) and non-lagged Y (YNL) cells, (2) no difference between on-centre and off-centre cells for either XNL or YNL cells, (3) no difference between XNL cells and lagged X (XL) cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Anesthesia↗
PubMed1994

Hyaluronan and CD44 in psoriatic skin. Intense staining for hyaluronan on dermal capillary loops and reduced expression of CD44 and hyaluronan in keratinocyte-leukocyte interfaces.

The distributions of hyaluronan (HA) and its presumptive receptor, CD44, were studied in skin samples from 13 psoriasis vulgaris patients, using an HA-specific probe (HABC), and monoclonal antibodies, respectively. The general distribution of HA and CD44 in psoriatic lesional epidermis resembled that in normal epidermis. However, areas of epidermis invaded by leukocytes showed a local depletion of HA and CD44, particularly at the contact areas of keratinocytes to lymphocytes and neutrophils. Removal by cellular uptake or extracellular degradation of CD44 and HA may be required for tight adherence between a keratinocyte and a leukocyte. On the dermal side, the tips of the prolonged dermal papillae in psoriatic lesions were intensively stained with HABC. The dilated capillaries and the space below the tip basal lamina, in particular, were heavily covered with HA. Occasionally, a similar intense staining was seen around an enlarged capillary in uninvolved psoriatic skin. CD44-positive leukocytes were found around the affected capillaries. The accumulation of HA in the dermal papillae may support the growth of psoriatic lesions, since HA stimulates the growth of capillaries as well as attracting inflammatory cells.

Adult↗
PubMed1994

A method for co-registering three-dimensional multi-modality brain images.

A method has been developed for co-registering three-dimensional multi-modality images of the human brain. The interactive program allows users to specify the interhemispheric fissure plane in three dimensions by identifying the endpoints of the centerline within transaxial slices. Translations and rotations within transaxial and coronal planes are determined to align the interhemispheric fissure planes of the two image sets to be co-registered. After reslicing the two partially co-registered image volumes, the intercommissural lines are detected by using three internal landmarks. A transformation including translation and rotation in the sagittal plane finally co-registers the two image sets in three-dimensional space. Single photon emission computed tomography (SPECT) images and magnetic resonance (MR) images have been used to validate the method for co-registering three-dimensional functional and anatomic brain images. This new co-registration method requires neither special head positioning procedures nor external fiducial markers, thereby making it appropriate for the routine clinical practice.

Brain↗
PubMed1994

A role for polysialylated neural cell adhesion molecule in lesion-induced sprouting in hippocampal organotypic cultures.

By mediating cell-cell interactions, the neural cell adhesion molecule (N-CAM) has been implicated in various events such as axonal pathway formation, neurite outgrowth or synaptic remodelling. One mechanism by which N-CAM could contribute to these events has been proposed to involve modifications of the content of the molecule in polysialic acid. Here we have tested this possibility using an in vitro model of lesion-induced reactive synaptogenesis in hippocampal organotypic cultures. We present evidence that the sprouting reaction triggered by a section of CA3-CA1 connections in these cultures is associated with the expression of the highly sialylated form of N-CAM on regenerating neurites. In addition, we have examined the functional importance of this sialylation mechanism by analysing the effect of treating sectioned cultures with endo-neuraminidase-N which removes the polysialic acid portions of N-CAM. Measurements of the time course of recovery from the lesion, as assessed by the formation of new functional synaptic contacts across the section, showed that removal of the polysialic acid moieties of N-CAM significantly delays the sprouting reaction. The results support the idea that up regulations of highly sialylated forms of N-CAM are of functional importance in neurite sprouting and synapse regeneration in this in vitro model.

Animals↗
PubMed1994

Noradrenergic abnormalities in the genetically epilepsy-prone rat.

The genetically epilepsy-prone rat (GEPR) has central nervous system noradrenergic deficits as compared to normal rats. It is possible that these deficits contribute to seizure predisposition because they are exhibited by seizure-naive as well as by seizure-experienced GEPRs. On the basis of pharmacological studies, it is hypothesized that there is an inverse relation between seizure predisposition and levels of noradrenergic activity in brain. Neurochemical studies indicate that deficits exist in areas innervated by both the locus ceruleus and the lateral tegmental noradrenergic systems. These deficits exist in GEPRs without seizure experience and are more pronounced in the severe seizure strain as compared to the moderate seizure strain. We review eight experimental steps undertaken to identify more precisely the anatomical location of noradrenergic determinants of seizure predisposition. These steps illustrate the theoretical bases for the studies and describe the specific experiments completed. Evidence supports the hypothesis that noradrenergic deficits in the superior colliculus and/or ventrally adjacent regions are determinants of seizure predisposition.

Animals↗
PubMed1994

Noradrenergic terminal fields as determinants of seizure predisposition in GEPR-3s: a neuroanatomic assessment with intracerebral microinjections of 6-hydroxydopamine.

The genetically epilepsy-prone rat (GEPR) and other mammals with genetically based epilepsy are characterized by an innate predisposition to seizures evoked by a wide variety of stimuli (including those of endogenous origin). The present investigation was undertaken to identify the anatomical location of the noradrenergic terminal fields responsible for regulation of seizure predisposition. In this study, audiogenic seizure severity was used as the index of seizure predisposition. The effect of widespread destruction of noradrenergic terminal fields was compared with the effect of destroying regionally distinct terminal fields. These lesions were produced by microinfusion of 6-hydroxydopamine (6-OHDA) into the locus ceruleus, the A1 noradrenergic area, the noradrenergic dorsal bundle, the cerebellar peduncles and spinal intrathecal space. Selective depletion of norepinephrine in the forebrain, the cerebellum, or the spinal cord failed to alter audiogenic seizure severity. An increase in seizure severity was always associated with marked depletion of norepinephrine in the midbrain excluding the inferior colliculus. Also a significant correlation existed between the seizure intensification and reduction of norepinephrine in this structure in all instances where a seizure intensification was observed. An association of seizure intensification also existed in all cases except one with depletion in the pons/medulla. The present findings support the hypothesis that the noradrenergic terminal fields of the midbrain excluding the inferior colliculus are determinants of seizure predisposition. Inasmuch as audiogenic seizures are a type of brainstem seizure, the present findings do not a priori pertain to the noradrenergic regulation of forebrain seizures.

Acoustic Stimulation↗
PubMed1994

Lignans and flavonoids inhibit aromatase enzyme in human preadipocytes.

Lignans and flavonoids are naturally-occurring diphenolic compounds found in high concentrations in whole grains, legumes, fruits and vegetables. Seven lignans and six flavonoids were evaluated for their abilities to inhibit aromatase enzyme activity in a human preadipose cell culture system. The lignan, enterolactone (Enl) and its theoretical precursors, 3'-demethoxy-3O-demethylmatairesinol (DMDM) and didemethoxymatairesinol (DDMM) decreased aromatase enzyme activity, with Ki values of 14.4, 5.0 and 7.3 microM, respectively. The flavonoids, coumestrol, luteolin and kaempferol also decreased aromatase enzyme activity, with Ki values of 1.3, 4.8 and 27.2 microM, respectively. Aminoglutethimide, a pharmaceutical aromatase inhibitor, showed a Ki value of 0.5 microM. Kinetic studies showed the inhibition by all compounds to be competitive. Smaller decreases in aromatase activity were observed with the lignan, enterodiol (End) and its theoretical precursors, O-demethylsecoisolariciresinol (ODSI), demethoxysecoisolariciresinol (DMSI) and didemethylsecoisolariciresinol (DDSI). The flavonoids, O-demethylangolensin (O-Dma), fisetin and morin showed no inhibitory effects. The inhibition of human preadipocyte aromatase activity by lignans and flavonoids suggests a mechanism by which consumption of lignan- and flavonoid-rich plant foods may contribute to reduction of estrogen-dependent disease, such as breast cancer.

Adipose Tissue↗
PubMed1994

Hyaluronan and the hyaluronan receptor RHAMM promote focal adhesion turnover and transient tyrosine kinase activity.

The molecular mechanisms whereby hyaluronan (HA) stimulates cell motility was investigated in a C-H-ras transformed 10T 1/2 fibroblast cell line (C3). A significant (p < 0.001) stimulation of C3 cell motility with HA (10 ng/ml) was accompanied by an increase in protein tyrosine phosphorylation as detected by anti-phosphotyrosine antibodies using immunoblot analysis and immunofluorescence staining of cells. Tyrosine phosphorylation of several proteins was found to be both rapid and transient with phosphorylation occurring within 1 min of HA addition and dissipating below control levels 10-15 min later. These responses were also elicited by an antibody generated against a peptide sequence within the HA receptor RHAMM. Treatment of cells with tyrosine kinase inhibitors (genistein, 10 micrograms/ml or herbimycin A, 0.5 micrograms/ml) or microinjection of anti-phosphotyrosine antibodies inhibited the transient protein tyrosine phosphorylation in response to HA as well as prevented HA stimulation of cell motility. To determine a link between HA-stimulated tyrosine phosphorylation and the resulting cell locomotion, cytoskeletal reorganization was examined in C3 cells plated on fibronectin and treated with HA or anti-RHAMM antibody. These agents caused a rapid assembly and disassembly of focal adhesions as revealed by immunofluorescent localization of vinculin. The time course with which HA and antibody induced focal adhesion turnover exactly paralleled the induction of transient protein tyrosine phosphorylation. In addition, phosphotyrosine staining colocalized with vinculin within structures in the lamellapodia of these cells. Notably, the focal adhesion kinase, pp125FAK, was rapidly phosphorylated and dephosphorylated after HA stimulation. These results suggest that HA stimulates locomotion via a rapid and transient protein tyrosine kinase signaling event mediated by RHAMM. They also provide a possible molecular basis for focal adhesion turnover, a process that is critical for cell locomotion.

Antibodies↗
PubMed1994

A subgraph problem from restriction maps of DNA.

Computing the minimum number of edge removals needed to convert a bipartite graph into an interval graph was proposed by Waterman and Griggs in the study of restriction maps of DNA. We show that this problem is N P-complete and we give a polynomial algorithm that finds an edge-maximum interval subgraph for trees. Then various heuristics can be devised using this algorithm.

Algorithms↗
PubMed1994

Comparison of clonidine with fentanyl on phrenic nerve activity and their interaction in anaesthetized rabbits.

We have compared the effects of clonidine and fentanyl on phrenic nerve activity in anaesthetized rabbits during artificial ventilation. Both drugs caused dose-dependent inhibition of phrenic nerve activity and complete abolition in all experiments. The calculated ED50 values were 3.7 micrograms kg-1 for clonidine and 3.9 micrograms kg-1 for fentanyl. Pretreatment with clonidine 1 microgram kg-1 i.v. depressed phrenic nerve activity to 81.8% of control values. This effect was additive with subsequent doses of fentanyl which was confirmed with an ED50 isobologram. We conclude that clonidine has the potential for deleterious respiratory effects at doses similar to those of fentanyl, but the interaction between the two drugs is additive and hence differs from their known synergistic antinociceptive interaction.

Anesthesia, General↗
PubMed1994

Clonidine has comparable effects on spontaneous sympathetic activity and afferent A delta and C-fiber-mediated somatosympathetic reflexes in dogs.

BACKGROUND: Clonidine, an alpha 2-adrenergic agonist, has been studied as an adjunct or alternative to spinal opioids in the management of moderate to severe pain. This study examined the relative effects of clonidine on efferent spontaneous sympathetic activity and afferent A delta and C fiber-mediated somatosympathetic responses. METHODS: Spontaneous and evoked sympathetic activity in renal sympathetic nerves, mediated by A delta and C fibers by means of supramaximal electrical stimulation of the radial and tibial nerves, were observed in anesthetized dogs. Incremental doses of clonidine were administered intrathecally or intravenously in each of five preparations followed by intravenous naloxone 2 mg and yohimbine 5 mg. RESULTS: Both spontaneous sympathetic outflow and afferent A delta- and C fiber-mediated somatosympathetic responses evoked by tibial nerve stimulation were depressed in a similar dose dependent manner by clonidine administered intrathecally or intravenously in a dose ratio of approximately 1:4. Intrathecal clonidine inhibited and eliminated both local spontaneous sympathetic outflow and tibial nerve evoked sympathetic responses but had no significant depressant effect on the radial nerve evoked sympathetic reflexes. When administered intravenously clonidine had a similar depressant effect on both radial and tibial nerve elicited reflexes and spontaneous sympathetic activity. CONCLUSIONS: Clonidine, administered intrathecally or intravenously, has a similar depressant effect on both spontaneous sympathetic outflow and afferent A delta- and C fiber-mediated somatosympathetic reflexes. When administered intrathecally it has little effect on reflexes evoked via the descending pathway by radial nerve stimulation.

Animals↗
PubMed1994

NNERVE: neural network extraction of repetitive vectors for electromyography--Part I: Algorithm.

Artificial neural network (ANN) based signal processing methods have been shown to have significant robustness in processing complex, degraded, noisy, and unstable signals. A novel approach to automated electromyogram (EMG) signal decomposition, using an ANN processing architecture, is presented in this paper. Due to the lack of a priori knowledge of motor unit action potential (MUAP) morphology, the EMG decomposition must be performed in an unsupervised manner. An ANN classifier, consisting of a multilayer perceptron neural network and employing a novel unsupervised training strategy, is proposed. The ANN learns repetitive appearances of MUAP waveforms from their suspected occurrences in a filtered EMG signal in an autoassociative learning task. The same training waveforms are fed into the trained ANN and the output of the ANN is fed back to its input, giving rise to a dynamic retrieval net classifier. For each waveform in the data, the network discovers a feature vector associated with that waveform. For each waveform, classification is achieved by comparing its feature vector with those of the other waveforms. Firing information of each MUAP is further used to refine the classification results of the ANN classifier. Then, individual MUAP waveform shapes are derived and their firing tables are created.

Algorithms↗
PubMed1994

NNERVE: neural network extraction of repetitive vectors for electromyography--Part II: Performance analysis.

We have presented a new method for the decomposition of clinical electromyographic signals, NNERVE, which utilizes a novel "pseudo-unsupervised" neural network approach to signal decomposition. In this paper, we present a detailed performance analysis. We present definitions for quantitative performance criteria. NNERVE is shown to be highly reliable over a wide range of neural network architectures. It is also minimally sensitive to learning parameters. The degradations of performance over a wide range of signals and parameters are shown to be gradual, slight and graceful. These characteristics are shown to translate directly into a high degree of robustness over widely varying signals. Real signals obtained from the entire range of patients encountered in clinical situations are shown to be correctly handled without any modifications or adjustments of any parameters. This neural network method is then directly compared to a prior traditional signal processing method and is shown quantitatively to have consistently superior performance on both simulated and real signals. Clinically acceptable performance over a wide range of signals, recorded using standard clinical methodology, and the lack of a need for user interaction, will facilitate the use of motor unit quantitation in routine clinical electromyography.

Algorithms↗
PubMed1994

Induction of spermatogenesis with gonadotrophins in Chinese men with hypogonadotrophic hypogonadism.

The effects of gonadotrophin administration to 17 Chinese patients with hypogonadotrophic hypogonadism (HH) on testicular volume and induction of spermatogenesis were studied. Ten subjects had isolated HH and seven had hypopituitarism. Twelve of the subjects had prepubertal onset of HH and five of them had been treated previously with hCG for induction of puberty. None had a history of cryptorchidism. During hCG treatment for induction of spermatogenesis, all subjects had an increase in serum levels of testosterone into the normal adult male range and their testes increased in size from 3 (1-20) ml to 11.6 (5-20) ml [median(range), p < 0.02]. Six subjects required treatment with hCG alone. However, the remaining 11 subjects, after at least 6 months treatment with hCG, required the addition of human menopausal gonadotrophin (hMG) to induce spermatogenesis. Two subjects remained azoospermic. One had a history of mumps orchitis and the other had isolated elevation of blood FSH levels, suggestive of primary testicular failure in addition to HH. Excluding one subject with fertile eunuch syndrome, the mean duration for first appearance of spermatozoa was 13 (4-52) months. Twelve subjects became fertile and pregnancy was achieved in their partners after 20 (4-78) months. The weekly doses for hCG and hMG were 4000 (3000-10,000) IU and 225 (225-450) IU, respectively. Patients who responded to hCG alone had a significantly larger pretreatment testicular volume, suggesting that they had only partial gonadotrophin deficiency. Prepubertal onset of hypogonadism was not a determining factor for requirement of hMG treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Multicopy single-stranded DNAs with mismatched base pairs are mutagenic in Escherichia coli.

Retrons are genetic elements that encode multicopy single-stranded DNAs called msDNAs. They are clonally distributed in Escherichia coli and retrons in different clones produce DNAs with different nucleotide sequences. msDNAs consist of an RNA molecule covalently linked to a single-stranded DNA molecule. The latter contains an inverted repeat, resulting in a stem-loop structure. In two retrons, Ec83 and Ec78, the DNA is cleaved off from the RNA. All known retrons except Ec78, have one or more mismatched base pairs in the stem-loop structure. We found that two retrons, Ec86 and Ec83, when present in high copy numbers are mutagenic. The ratios of mutation frequencies observed in Lac- indicator strains were similar to the ratios observed for a mutant defective in mismatch repair. It is known that some proteins required for mismatch repair bind to mismatched base pairs prior to carrying out repair. The similarity in the mutation frequency ratios suggested that the mutagenesis caused by msDNAs of retrons Ec86 and Ec83 might be due to sequestration of a mismatch repair protein by msDNA. Strong support for this interpretation was obtained from the finding that the msDNA produced by retron Ec78 is not mutagenic.

Base Sequence↗