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Biomedical subjects

B He

Publications and source records attributed to B He.

At least 253 records · Page 14Linked to original sources
PubMed1993

Body surface Laplacian mapping of cardiac excitation in intact pigs.

Relating body surface electrocardiographic signals to regional myocardial events has been a major effort in cardiac electrophysiology. Conventional electrocardiographic means do not provide sufficient spatial resolution to resolve distributed cardiac electrical activity. The purpose of this investigation was to evaluate and study the validity of a new technique--body surface Laplacian mapping--in a well-controlled experimental setting, and to test the hypothesis that the body surface Laplacian map (BSLM) can resolve normal and abnormal ventricular depolarization patterns and localize the initial site of ventricular depolarization with high spatial resolution. In this study, BSLMs were constructed from direct measurements of the surface Laplacian of the body surface potentials using an array of 64 concentric bipolar Laplacian electrodes. BSLMs were compared to body surface potential maps (BSPMs) during normal and ectopic ventricular activation in intact anesthetized pigs. The BSLM displayed highly localized images of cardiac electrical activity, indicating its ability to resolve myocardial events. The BSLM in pigs identified the pacemaking focus overlying the known location of the epicardial pacing electrode, and imaged the activation sequence associated with exogenous ventricular pacing. In contrast, in all cases the BSPM revealed a diffuse distribution of activity over the chest. The present results suggest that the BSLM provides sufficient spatial resolution to relate body surface recordings to regional myocardial events and is able to detect ventricular depolarization patterns with greater resolution than the conventional BSPM.

Animals↗
PubMed1993

Regulation of Escherichia coli glnB, prsA, and speA by the purine repressor.

A strategy was devised to identify Escherichia coli genes subject to coregulation by purR. From a data base search, similarities to the pur regulon cis-acting control site were found in 26 E. coli genes. Of five genes examined in which the putative pur operator is upstream of the coding sequence, glnB, prsA, and speA bound purified purine repressor in vitro. Binding of the repressor to a pur operator in these genes was dependent upon a corepressor. The pur operator in glnB is located between two major transcription start sites that were located by primer extension mapping. The effect of purR on expression of glnB, prsA, and speA was examined by using a lacZ reporter. The results indicated two- to threefold repression of these genes by purR. Coregulation by purR provides evidence that expands the pur regulon to include glnB, prsA, and speA. These genes have functions related to nucleotide metabolism.

Bacterial Proteins↗
PubMed1993

[Possible involvement of atrial natriuretic factor and vasopressin in antihypertensive mechanism of clonidine in humans].

To appreciate the role of some neuropeptides in the antihypertensive mechanism of clonidine, 17 patients with essential hypertension were given po clonidine 150 micrograms tid for 3 d. Plasma atrial natriuretic factor (ANF), vasopressin (Vas), and dynorphin A (Dyn A) were measured by radioimmunoassay. After the treatment, mean blood pressure (MBP), heart rate and 24 h urine norepinephrine, epinephrine were decreased, but no change was found in plasma Dyn A. The magnitudes of increased ANF and decreased Vas were correlated with the decreased MBP (r = -0.57 and 0.53, respectively, P < 0.05). These results suggest that both ANF and Vas are involved in the antihypertensive mechanism of clonidine.

Adult↗
PubMed1993

Studies on immobilization of aminoacylase on the functionalized polymethyl acrylate.

Functionalized polymethyl acrylate was used for the immobilization of aminoacylase of Aspergillus oryzae. The effects of the degree of cross-linking, the amount of pore-forming agent and their mixing rates on the activity of immobilized aminoacylase were investigated. The results showed that the activity of the immobilized aminoacylase was the highest when the carrier was a combination of 20% cross-linking and 100% pore-forming agent. The effects of substrate concentration, ionic concentration, temperature and pH on the immobilized aminoacylase were compared with those on soluble aminoacylase, on the other hand, the effects of some organic solvents and protein denaturants on immobilized aminoacylase were also investigated. A column reactor packed with immobilized aminoacylase was used to resolve continuously N-acyl-DL-phenylalanine for a month, and 90% activity of immobilized aminoacylase was retained.

Amidohydrolases↗
PubMed1993

[Analysis of estrogen receptors in normal bone and bone tumor tissues].

Thirteen human normal bone and fifteen bone tumor tissues were assayed for estrogen receptor (ER) by Dextran-coated Charcoal method (Scatchard plot). The results showed that the concentrations of ER in normal bone tissues (15.12 +/- 14.68 fmol/mg pro) were higher than that of bone malignant tumors (8.04 +/- 6.71 fmol/mg pro) P < 0.05). The binding dissociation constants (Kd) of ER in bone tumors (18.46 +/- 27.10 x 10(-11) mol/L) was lower than those in normal ones (39.91 +/- 20.13 x 10(-11) mol/L) (P < 0.025). The percentages for positive score of ER in normal and tumor ones (23.1%, 26.7%) were not significantly different (P > 0.05). Our study indicated that the variations of concentration and affinity of ER in bone related to the tumor incidence. That cytosol ER content was decreased in malignant bone tumors whereas that of affinity increase suggests an impairment or change of an intact receptor mechanism in this tissues.

Adolescent↗
PubMed1993

[Study on estrogen and progesterone receptors in endometriosis and adenomyosis].

Estrogen and progesterone receptors (ER and PR) in 18 cases of ovarian endometriosis and 13 cases of adenomyosis were determined with dextran coated charcoal (DCC) method. The levels of ER and PR in those specimens were lower than those of normal endometrium. Among the 18 cases of ovarian endometriosis, 6 (33.4%) were negative for PR, which accounted for the unsatisfactory results of progesterone treatment for some endometriosis. In the 13 cases of adenomyosis there were 10 (76.9%) showing positive PR. It is suggested that the hormone therapy may be useful to treat those young patients with adenomyosis instead of surgery. The correlation of the ER and PR levels, the treatment and prognosis in endometriosis and adenomyosis are worth further studying.

Adult↗
PubMed1993

[Change of beta tubulin gene expression in the motoneurons of spinal cord during nerve regeneration].

After crushing the right sciatic nerve of rat, the contents of both tubulin and beta tubulin mRNA increased significantly in the ventral horns of spinal cord. Analysis of tubulin in bilateral ventral horns by SDS-PAGE showed that tubulin in the injured side increased by 17%-121% of the control side. The results of in situ hybridization indicated with the signals of hybridization with beta tubulin cDNA probes were 27%-70% higher in motoneurons of the ventral horns in the injury side than the control. Northern blotting analysis of tubulin mRNA in ventral horns also revealed an increase of tubulin gene expression.

Animals↗
PubMed1992

Equivalent dipole estimation of spontaneous EEG alpha activity: two-moving dipole approach.

A method of estimating equivalent moving and fixed dipoles from the scalp-recorded EEG alpha waves, with the realistic geometry of the head taken into account, is presented. Twenty-one silver electrodes were used to collect spontaneous EEG alpha waves on the scale. Four models, the single-moving dipole model, the single-fixed dipole model, the two-moving dipole model and the two-fixed dipole model were applied to approximate the EEG alpha field on the scalp. The algorithm, based on a least-squares fit for estimating the moving and the fixed dipoles by using a realistically shaped head model, is described. The numerical accuracy of the algorithm is also evaluated by a computer simulation. It is found that the spontaneous EEG alpha activity observed on the scalp can be represented by two equivalent moving dipoles, simultaneously located separately in the occipital regions of the right and the left hemisphere, at a depth of 4-6 cm beneath the scalp, with a goodness-of-fit of up to 97 per cent for all subjects examined. The excellent fit of the two-moving dipole model to the EEG human alpha activity is also compared with the single-dipole fit.

Adult↗
PubMed1992

Body surface Laplacian ECG mapping.

A new noninvasive approach has been developed to resolve spatially distributed cardiac electrical activity by measuring the surface Laplacian of the body surface potential. Computer simulations demonstrate the ability of the Laplacian map compared with the potential map to image spatially distributed dipole sources embedded in a semi-infinite volume conductor. Body surface Laplacian mapping has been implemented in human subjects utilizing dry bipolar Laplacian electrodes and compared with potential maps obtained using the central terminal of each bipolar Laplacian electrode. The body surface Laplacian ECG distribution was found to provide better spatial resolution than the body surface potential distribution. The body surface Laplacian map appears to resolve depolarization and repolarization of different regions of the heart. Further improvements of the body surface Laplacian mapping may permit noninvasive mapping of spatially distributed intracardiac events.

Body Surface Area↗
PubMed1992

Escherichia coli purB gene: cloning, nucleotide sequence, and regulation by purR.

Escherichia coli purB encodes adenylosuccinate lyase (ASL), the enzyme that catalyzes step 8 in the pathway for de novo synthesis of IMP and also the final reaction in the two-step sequence from IMP to AMP. Gene purB was cloned and found to encode an ASL protein of 435 amino acids having a calculated molecular weight of 49,225. E. coli ASL is homologous to the corresponding enzymes from Bacillus subtilis and chickens and also to fumarase from B. subtilis. Gene phoP is 232 bp downstream of purB. Gene purB is regulated threefold by the purine pool and purR. Transcriptional regulation of purB involves binding of the purine repressor to the 16-bp conserved pur regulon operator. The purB operator is 224 bp downstream of the transcription start site and overlaps codons 62 to 67 in the protein-coding sequence.

Adenosine Monophosphate↗
PubMed1992

Repression of Escherichia coli purB is by a transcriptional roadblock mechanism.

Escherichia coli purB is regulated by a repressor-operator interaction. The purB operator is 242 bp downstream from the transcription start site and overlaps condons 62 to 67 in the protein-coding sequence (B. He, J. M. Smith, and H. Zalkin, J. Bacteriol. 174:130-136, 1992). The mechanism by which the repressor-operator interaction functions to repress transcription was investigated by a combination of promoter replacement experiments and RNA analyses. By using a trp promoter replacement that deleted 5' flanking DNA to position -986, purB expression was increased sevenfold, yet normal two- to threefold regulation was maintained. This indicates that repressor-operator control is independent of the purB promoter and other 5' flanking sequences. Transcriptional regulation was likewise independent of coupled translation. An approximately 260-nucleotide truncated in vivo purB mRNA was identified which was dependent upon repressor-operator interaction. Thus, binding of purine repressor to the purB operator inhibits transcription elongation by a roadblock mechanism. The roadblock was not influenced by a sevenfold increase in promoter strength or by an operator mutation resulting in a 2.5-fold increase in repressor-operator affinity.

Base Sequence↗
PubMed1992

[Study of the estrogen receptor and progesterone receptor in human cervical carcinoma].

Three hundred and twelve different cervical specimens have been tested for estrogen (ER) and progesterone receptor (PR) content with dextran-coated charcoal method (DCC). The results showed that the concentrations of ER and PR in normal cervical tissues were higher than those in malignant cervical tissues, and that the percentage of positive scores for ER and PR in cervical squamous epithelial tissues were higher than that in malignant cervical tissues. That the variances of ER and PR in cervical malignant tumors were not parallel suggested that the production or/and the mechanism of receptor action might be impaired. The percentage of positive scores for ER was not correlated with the clinical stages whereas that of PR was inversely proportional to clinical stages. That some patient with cervical cancer had high level of PR and had both ER and PR positive implied the possibility for endocrine therapy. The content and distribution of ER and PR in normal cervical tissues are consistent with the effects of sex hormone.

Carcinoma, Squamous Cell↗
PubMed1992

Immobilization of aminoacylase from Aspergillus oryzae on synthetic modified polyacrylamides.

A series of acrylamide-bisacrylamide copolymers modified by the Mannich Reaction was prepared. The immobilization of aminoacylase from Aspergillus oryzae on the copolymers was studied. All the polymers adsorbed the enzyme and the activity of the immobilized enzyme dependent on the amine used, viz. secondary amine, diamine, or aniline derivative. However, the activity was also influenced by the degree of crosslinking of the polymer. The surface morphology of the dimethylamine-modified polymer, with varying degrees of crosslinking, was analyzed by scanning electron microscope; the polymers having the largest pore diameter possessed the highest enzyme activity. One of the best polymers (DMA-A9B8) was used for immobilization of aminoacylase and its properties were studied. It had high enzymatic activity and good operational stability, i.e., retaining 90% of its original activity after being used for 42 days. The use of these copolymers for the preparation of immobilized enzymes is discussed.

Acrylic Resins↗
PubMed1992

[Cerebrospinal fluid (CSF) cytochemistry of acute cerebrovascular diseases with clear CSF: observation of nonspecific esterase activity of mononuclear phagocytes].

CSF nonspecific esterase (ANAE) activities of mononuclear phagocytes of 35 patients with intracerebral hematoma (ICH) with clear CSF and 25 with cerebral thrombosis and 17 normals were observed. The ANAE activities of ICH were much higher than those of thrombosis significantly (P less than 0.01). Furthermore, the distributions of ANAE activities of all cases suggested that there were few overlaps between both diseases. The CSF cytochemical detection was obviously superior to routine CSF cytological examination in differentiating strokes with clear CSF. The authors concluded that these results provided a simple inexpensive and relatively accurate method to differentiate hemorrhagic from ischemic cerebrovascular diseases in case of without CT.

Cerebral Hemorrhage↗
PubMed1991

RAM2, an essential gene of yeast, and RAM1 encode the two polypeptide components of the farnesyltransferase that prenylates a-factor and Ras proteins.

In the yeast Saccharomyces cerevisiae, mutations in either of two unlinked genes, RAM1 or RAM2, abolish the farnesyltransferase activity responsible for prenylation of Ras proteins and the a-factor mating pheromone. Here we report that the function of RAM1 and RAM2 genes is required for the membrane localization of Ras proteins and a-factor. The RAM2 gene was sequenced and can encode a 38-kDa protein. We examined the functional interaction of RAM2 and RAM1 by expressing the genes in Escherichia coli. Extracts derived from an E. coli strain that coexpressed RAM1 and RAM2 efficiently farnesylated a-factor peptide and Ras protein substrates. In contrast, extracts derived from E. coli strains that expressed either RAM gene alone were devoid of activity; however, when the latter extracts were mixed, protein farnesyltransferase activity was reconstituted. These results indicate that the yeast farnesyl-protein transferase is comprised of Ram1 and Ram2 polypeptides. Although Ram1 is a component of the enzyme, disruption of the RAM1 gene in yeast was not lethal, indicating that the Ram1-Ram2 farnesyltransferase is not essential for viability. In contrast, disruption of RAM2 was lethal, suggesting that Ram2 has an essential function in addition to its role with Ram1 in protein farnesylation.

Alkyl and Aryl Transferases↗
PubMed1991

Structural homology among mammalian and Saccharomyces cerevisiae isoprenyl-protein transferases.

Farnesyl-protein transferase (FTase) purified from rat or bovine brain is an alpha/beta heterodimer, comprised of subunits having relative molecular masses of approximately 47 (alpha) and 45 kDa (beta). In the yeast Saccharomyces cerevisiae, two unlinked genes, RAM1/DPR1 (RAM1) and RAM2, are required for FTase activity. To explore the relationship between the mammalian and yeast enzymes, we initiated cloning and immunological analyses. cDNA clones encoding the 329-amino acid COOH-terminal domain of bovine FTase alpha-subunit were isolated. Comparison of the amino acid sequences deduced from the alpha-subunit cDNA and the RAM2 gene revealed 30% identity and 58% similarity, suggesting that the RAM2 gene product encodes a subunit for the yeast FTase analogous to the bovine FTase alpha-subunit. Antisera raised against the RAM1 gene product reacted specifically with the beta-subunit of bovine FTase, suggesting that the RAM1 gene product is analogous to the bovine FTase beta-subunit. Whereas a ram1 mutation specifically inhibits FTase, mutations in the CDC43 and BET2 genes, both of which are homologous to RAM1, specifically inhibit geranylgeranyl-protein transferase (GGTase) type I and GGTase-II, respectively. In contrast, a ram2 mutation impairs both FTase and GGTase-I, but has little effect on GGTase-II. Antisera that specifically recognized the bovine FTase alpha-subunit precipitated both bovine FTase and GGTase-I activity, but not GGTase-II activity. Together, these results indicate that for both yeast and mammalian cells, FTase, GGTase-I, and GGTase-II are comprised of different but homologous beta-subunits and that the alpha-subunits of FTase and GGTase-I share common features not shared by GGTase-II.

Alkyl and Aryl Transferases↗