Biomedical subjects

B He

Publications and source records attributed to B He.

At least 55 records · Page 3Linked to original sources

PubMed1998

On the algorithm for computing body surface Laplacians in an inhomogeneous volume conductor of arbitrary shape.

In this short communication, a corrected version of algorithm for calculating the body surface Laplacian (BSL) in an inhomogeneous volume conductor of arbitrary shape is described. The present computer simulation results show that the corrected algorithm can give an accurate numerical solution. This algorithm was then applied to examine the effect of the lung inhomogeneity on the BSL's in a realistically shaped torso model. The simulation results show that the low-conductivity lungs have little effect on both topology and magnitudes of body surface Laplacian maps (BSLM's) for a single dipole source.

Algorithms↗

PubMed1998

A computer simulation study of cortical imaging from scalp potentials.

In this paper, computer simulation studies were conducted to test the feasibility of imaging brain electrical activity from the scalp electroencephalograms. The inhomogeneous three-concentric-sphere head model was used to represent the head volume conductor. Closed spherical dipole layers, consisting of several thousand uniformly distributed dipoles, were used to reconstruct the cortical potential maps corresponding to neuronal sources located inside the brain. Simulation results indicate that the present procedure can image both cortical and deep sources, and for the cortical sources, a spatial resolution as high as 1.2 cm can be achieved.

Brain↗

PubMed1998

Body surface Laplacian mapping in patients with left or right ventricular bundle branch block.

Body surface Laplacian maps (BSLMs) have been previously reported to provide enhanced capability in localizing and resolving multiple spatially separate myocardial events. However, only a few studies have been reported on the clinical applications of BSLM. To test the clinical utility of BSLMs, BSLMs and body surface potential maps (BSPMs) during ventricular depolarization for complete right or left ventricular bundle branch block (CRBBB or CLBBB) were studied in ten patients in each group. As a control group, ten healthy subjects were also studied using the same procedure. One hundred and twenty-eight electrodes were placed uniformly over the entire chest and back of the subjects. BSLMs were computed from recorded potentials, using a numerical algorithm. The BSLMs showed multiple and more localized positive and negative activities compared with the BSPMs. In healthy subjects, the BSLMs showed multiple areas of positive activity overlying the RV, LV, and the RV outflow, and negative activity corresponding to RV free-wall breakthrough and LV anterolateral breakthrough sites, whereas the BSPMs could not separate RV and LV activities. In the patients with CRBBB, the BSLMs showed more localized areas of activity corresponding to the LV apex breakthrough and LV lateral breakthrough, and separated LV lateral and posterior activation. In the patients with CLBBB, the BSLMs showed multiple RV activation, and propagating activation of LV from lateral to posterior. The BSLMs appear to provide enhanced capability in detecting multiple ventricular electrical events associated with normal and abnormal conduction and a more detailed activation sequence of both ventricles in healthy subjects and in the patients with CRBBB and CLBBB. BSLM may provide an important alternative to other imaging modalities in localizing cardiac electrical activity noninvasively.

Action Potentials↗

PubMed1998

The myelin basic protein gene in multiple sclerosis: identification of discrete alleles of a 1.3 kb tetranucleotide repeat sequence.

Myelin basic protein (MBP) is a potential autoantigen in multiple sclerosis (MS) and its gene therefore is an attractive candidate to confer genetic susceptibility to this disease. Linkage and association with certain alleles of a 1.2 kb tetranucleotide repeat region 5' to the MBP gene with MS have been reported in Finnish patients, and an association has been reported from Denmark. However, these findings have not been confirmed in subsequent analyses in other populations. A limitation of previous studies has been the low resolution of the typing procedure. We have investigated the same polymorphism in thirty-four Swedish nuclear families with 2 or 3 MS patients. and in 149 unrelated Swedish MS patients and 95 healthy controls using a fluorescence-based semi-automated technique which allowed the identification of discrete tetrarepeat numbers. Neither parametric two-point linkage analysis nor a nonparametric affected pedigree members analysis showed any sign of linkage. In addition, the distribution of alleles was similar in patients and controls. We conclude that the MBP gene does not influence susceptibility to MS in Swedish patients.

Alleles↗

PubMed1998

Glycogen synthase kinase 3beta and extracellular signal-regulated kinase inactivate heat shock transcription factor 1 by facilitating the disappearance of transcriptionally active granules after heat shock.

Heat shock transcription factor 1 (HSF-1) activates the transcription of heat shock genes in eukaryotes. Under normal physiological growth conditions, HSF-1 is a monomer. Its transcriptional activity is repressed by constitutive phosphorylation. Upon activation, HSF-1 forms trimers, acquires DNA binding activity, increases transcriptional activity, and appears as punctate granules in the nucleus. In this study, using bromouridine incorporation and confocal laser microscopy, we demonstrated that newly synthesized pre-mRNAs colocalize to the HSF-1 punctate granules after heat shock, suggesting that these granules are sites of transcription. We further present evidence that glycogen synthase kinase 3beta (GSK-3beta) and extracellular signal-regulated kinase mitogen-activated protein kinase (ERK MAPK) participate in the down regulation of HSF-1 transcriptional activity. Transient increases in the expression of GSK-3beta facilitate the disappearance of HSF-1 punctate granules and reduce hsp-70 transcription after heat shock. We have also shown that ERK is the priming kinase for GSK-3beta. Taken together, these results indicate that GSK-3beta and ERK MAPK facilitate the inactivation of activated HSF-1 after heat shock by dispersing HSF-1 from the sites of transcription.

Calcium-Calmodulin-Dependent Protein Kinases↗

PubMed1998

Inactivating mutation in the human parathyroid hormone receptor type 1 gene in Blomstrand chondrodysplasia.

A single homozygous nucleotide exchange in exon E3 of the gene encoding the parathyroid hormone receptor type 1 (PTHR1) was identified in an infant with Blomstrand chondrodysplasia born to consanguineous parents. This alteration changes a strictly conserved proline residue at position 132 in the receptor's amino terminal extracellular domain to leucine. COS-1 cells expressing the mutant receptor did not accumulate cyclic adenosine 3',5'-monophosphate in response to PTH or PTH-related peptide (PTHrP) and did not bind the radiolabeled ligand. Expression of the mutant protein on the cell surface of transiently transfected COS-1 cells and in growth plate chondrocytes derived from the affected infant suggests that proline 132 is critical for the receptor's intrinsic binding activity. These findings suggest that the Blomstrand form of human short-limbed dwarfism arises from defective PTHR1 signaling in the developing cartilaginous skeleton.

Amino Acid Sequence↗

PubMed1998

Mutations in the promoter of adenylyl cyclase (AC)-III gene, overexpression of AC-III mRNA, and enhanced cAMP generation in islets from the spontaneously diabetic GK rat model of type 2 diabetes.

Glucose-induced insulin release is decreased in the spontaneously diabetic GK rat, a nonobese rodent model of type 2 diabetes. Forskolin restores the impaired insulin release in both the isolated perfused pancreas and isolated islets from these rats (Abdel-Halim et al., Diabetes 45:934-940, 1996). We demonstrate here that the insulinotropic effect of forskolin in the GK rat is due to increased generation of cAMP and that it is associated with overexpression of adenylyl cyclase (AC)-III mRNA and gene mutations. The AC-III mRNA overexpression was demonstrated by in situ hybridization using oligonucleotide probes binding to different regions of the rat AC-III mRNA. It was associated with the presence of two point mutations identified at positions -28 bp (A --> G) and -358 bp (A --> C) of the promoter region of the AC-III gene and was demonstrable in both GK rat islets and peripheral blood cells. Transfection of COS cells with a luciferase reporter gene system revealed up to 25-fold increased promoter activity of GK AC-III promoter when compared with normal rat promoter (P < 0.0001). In conclusion, forskolin restores the impaired insulin release in islets of the GK rat through enhanced cAMP generation. This is linked to overexpression of AC-III mRNA in GK islets due to two functional point mutations in the promoter region of the AC-III gene.

Adenylyl Cyclases↗

PubMed1998

Longer-term fourth ventricular 5-thioglucose infusion increases body fat in the rat.

5-Thioglucose (5-TG) has been shown to increase food intake after acute administration. To determine the longer-term effects of 5-TG on feeding and body composition, thirty-four female Sprague-Dawley rats were cannulated into the fourth ventricle and infused with artificial CSF and either 0.01 M 5-TG or 0.1 M 5-TG using osmotic pumps. Food intake and body weight were monitored daily. Rats were killed after 14 days of infusion. Carcass and fatpad weights were measured, and body compositions were determined. Food intake was not different during the first week of infusion; however, cumulative food intake was decreased in the 0.1 M 5-TG group during the second week as compared to the CSF control group. Body weight and carcass weight of this group also decreased as compared to the control. The group receiving the higher dose of 5-TG (0.1 M) had increased fatpad weights in all three depots examined (inguinal, retroperitoneal, and perimetrial depot); the group with lower dose of 5-TG infusion (0.01 M) increased the fatpad weights in the retroperitoneal and perimetrial depot, as compared to the CSF group. Data from the body composition analysis were consistent with the results of the fatpad weights. In conclusion, the present study demonstrated that chronic fourth ventricular 5-TG infusion increased body fat without increasing food intake, suggesting that energy expenditure is decreased under this condition. The results of this study indicate that glucose metabolism in the hindbrain is important in the control of energy expenditure, body fat deposition, and thus energy balance regulation.

Adipose Tissue↗

PubMed1998

Antibiotic activities and affinities for bacterial cell wall analogue of N-demethylvancomycin and its derivatives.

N-Demethylvancomycin, which has been clinically used in China, is one member of vancomycin group (glycopeptide) antibiotics. It differs from vancomycin only in that methyl group on the amino group of the N-terminal residue of vancomycin has been replaced by H. By reductive alkylation of N-demethylvancomycin, we synthesized N-alkyl and N,N'-dialkyl N-demethylvancomycins, which closely correlated with vancomycin in structure. The association constants of the complexes of N-demethylvancomycin and its analogues with di-N-Ac-L-Lys-D-Ala-D-Ala and the antibiotic activity against Staphylococcus aureus of the glycopeptides were determined. Results showed that N-demethylvancomycin has higher affinity for bacterial cell wall analogue di-N-Ac-L-Lys-D-Ala-D-Ala and more potent antibiotic activity against Staphylococcus aureus than vancomycin. Both N-alkylation and N,N'-dialkylation of N-demethylvancomycin reduced the affinity and antibiotic activity. The longer the alkyl groups, the less potent antibiotic activities and lower affinities have the glycopeptides. The antibiotic activities against Staphylococcus aureus of N-demethylvancomycin and its analogues roughly parallel their affinities for di-N-Ac-L-Lys-D-Ala-D-Ala.

Alkylation↗

PubMed1998

[Antagonistic action of organic selenium on lead poisoning].

Ninety white rats were treated with liquid lead acetate. When the concentration of lead in urine was more than (0.81 +/- 0.26) mg/L and blood lead was more than (4.8 +/- 0.33) mg/L, the rats were divided into three groups randomly. The oxygenic damage indicators in serum showed SOD activity decreased and MDA content increased. In one group of lead rats fed with an organic selenium compound (code FCQY) the SOD activities were high and the lipid peroxidation was inhibited compared with controls without selenium supplementation. The lead contents of bone, kidney and liver were measured. The results suggested that the organic selenium compound could interfere with the absorption and accumulation of lead.

Animals↗

PubMed1998

Dissociation of creatine kinase under different denaturation conditions.

Dissociation of dimeric creatine kinase under different denaturation conditions was investigated using the cleavable cross-linker 3, 3;-dithiobis(succinimidyl propionate). The results show that at low denaturant concentrations or at low denaturation temperatures the creatine kinase was mostly inactivated, but the enzyme was still either in the dimeric state or very slightly dissociated. It appears, therefore, that for several denaturation conditions, inactivation of the enzyme is not due to the dissociation of the active dimer.

Animals↗

PubMed1997

Recovery of infectious SV5 from cloned DNA and expression of a foreign gene.

A complete cDNA clone of the genome (15,246 nucleotides) of the paramyxovirus SV5 was constructed from cDNAs such that an anti-genome RNA could be transcribed by T7 RNA polymerase and the correct 3' end generated by cleavage using hepatitis delta virus ribozyme. The plasmid encoding the antigenome sequence was transfected into cells previously infected with recombinant vaccinia virus that expressed T7 RNA polymerase, together with helper plasmids that expressed the viral replication proteins, NP, P, and L, under the control of the T7 polymerase promoter. Rescue of the RNA genome from DNA was demonstrated by recovering SV5 with the tag restriction sites introduced into the DNA clone, using RT-PCR of the genome RNA and nucleotide sequencing. Rescue of SV5 from DNA did not require expression of the viral V protein as a helper plasmid, suggesting that V protein is not essential for initial replication. The infectious cDNA of SV5 was also manipulated to express green fluorescent protein (GFP) under the control of SV5 transcriptional start and stop signals introduced between the HN and L genes. The amount of GFP that was expressed varied depending on the nature of the newly introduced transcription signals.

DNA, Complementary↗

PubMed1997

Mutant bacteriophage T7 RNA polymerases with altered termination properties.

We have identified mutants of bacteriophage T7 RNA polymerase (RNAP) that are altered in their ability to pause or terminate at a variety of signals. These signals include a terminator found fortuitously in the human preproparathyroid hormone (PTH) gene, a pause site found in the concatamer junction (CJ) of replicating T7 DNA, and termination signals that are also utilized by Escherichia coli RNAP (e.g. rrnB T1 and T2). Whereas the mutant enzymes terminate normally at the late terminator in T7 DNA (T(phi)) and rrnB T2, they fail to terminate at one of the termination sites of rrnB T1, and also fail to recognize the PTH and CJ signals. The mutant enzymes exhibit normal processivity on linear templates, but show a slightly reduced processivity on supercoiled templates and terminate more efficiently when synthesizing poly(U) tracts. The mutant enzymes also show a decreased tendency to produce aberrant transcription products from DNA templates having protruding 3' ends. T7 lysozyme (an inhibitor of T7 RNAP) has been shown to exert its action by preventing the transition of the RNAP from an unstable initiation complex (IC) to a stable elongation complex (EC). We have found that T7 lysozyme enhances recognition of CJ by wild-type T7 RNAP, and that mutant T7 RNAPs that show increased sensitivity to lysozyme show enhanced recognition of this signal, even in the absence of lysozyme. These results, together with the observation that the mutations that result in the termination-deficient phenotype affect a region of the RNAP that has been implicated in RNA binding and upstream promoter contacts, support the hypothesis that, in some cases, termination represents a reversal of the events that occur during initiation.

Amino Acid Sequence↗

PubMed1997

Elevated hypothalamic neuropeptide Y levels in rats with dorsomedial hindbrain lesions.

Lesions centered on the area postrema (AP) and adjacent nucleus of the solitary tract (AP/mNTS-lesions) are reported to result in increased consumption of highly palatable diets. Recent studies suggest that neuropeptide Y (NPY) may cause a preference for carbohydrate-rich diets. Thus, it is possible that NPY may play a role in the enhanced intake of highly palatable diets by AP/mNTS-lesioned rats. In the studies reported here, we found that lesions centered on the AP result in increased levels of NPY-immunoreactivity in the paraventricular nucleus of the hypothalamus. Additionally, steady-state NPY mRNA in the basomedial hypothalamus including the arcuate nucleus was elevated. Enhanced NPY was not found throughout the hypothalamus however, as NPY-immunoreactivity was not elevated in the lateral hypothalamus or the tissue bordering the anteroventral third ventricle. These data suggest the possibility that elevated hypothalamic NPY, particularly in the arcuate and paraventricular nuclei, may contribute to the altered food intake and energy balance observed in rats with lesions centered on the AP.

Animals↗

PubMed1997

Conserved and sexually dimorphic behavioral responses to biogenic amines in decapitated Drosophila.

A preparation of decapitated Drosophila melanogaster has been used for direct application of drugs to the nerve cord. Serotonin, dopamine, and octopamine stimulate locomotion and grooming, showing distinguishable effects that often are potentiated by addition of the vertebrate monoamine oxidase-inhibitor hydrazaline. Many of the hydrazaline-induced effects are sexually dimorphic, with males showing greater responses than females. Behaviors similar to those induced by dopamine can be induced by application of the vertebrate dopamine D2-like receptor agonist quinpirole, whose effects are also sexually dimorphic. In contrast, vertebrate D2-like and D1-like dopamine antagonists result in akinesic states, and D1-like agonists selectively stimulate grooming. These data indicate that Drosophila nerve cord amine receptors are coupled to reflexive behaviors similar to those stimulated by brain dopamine receptors in vertebrates.

Animals↗

PubMed1997

The gamma(1)34.5 protein of herpes simplex virus 1 complexes with protein phosphatase 1alpha to dephosphorylate the alpha subunit of the eukaryotic translation initiation factor 2 and preclude the shutoff of protein synthesis by double-stranded RNA-activated protein kinase.

In human cells infected with herpes simplex virus 1 the double-stranded RNA-dependent protein kinase (PKR) is activated but phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2) and total shutoff of protein synthesis is observed only in cells infected with gamma(1)z34.5- mutants. The carboxyl-terminal 64 aa of gamma(1)34.5 protein are homologous to the corresponding domain of MyD116, the murine growth arrest and DNA damage gene 34 (GADD34) protein and the two domains are functionally interchangeable in infected cells. This report shows that (i) the carboxyl terminus of MyD116 interacts with protein phosphatase 1alpha in yeast, and both MyD116 and gamma(1)34.5 interact with protein phosphatase 1alpha in vitro; (ii) protein synthesis in infected cells is strongly inhibited by okadaic acid, a phosphatase 1 inhibitor; and (iii) the alpha subunit in purified eIF-2 phosphorylated in vitro is specifically dephosphorylated by S10 fractions of wild-type infected cells at a rate 3000 times that of mock-infected cells, whereas the eIF-2alpha-P phosphatase activity of gamma(1)34.5- virus infected cells is lower than that of mock-infected cells. The eIF-2alpha-P phosphatase activities are sensitive to inhibitor 2. In contrast to eIF-2alpha-P phosphatase activity, extracts of mock-infected cells exhibit a 2-fold higher phosphatase activity on [32P]phosphorylase than extracts of infected cells. These results indicate that in infected cells, gamma(1)34.5 interacts with and redirects phosphatase to dephosphorylate eIF-2alpha to enable continued protein synthesis despite the presence of activated PKR. The GADD34 protein may have a similar function in eukaryotic cells. The proposed mechanism for maintenance of protein synthesis in the face of double-stranded RNA accumulation is different from that described for viruses examined to date.

Animals↗

PubMed1997

A mutant T7 RNA polymerase that is defective in RNA binding and blocked in the early stages of transcription.

We have identified a mutation (E148A) in T7 RNA polymerase (RNAP) that results in an enzyme which aborts transcription primarily when the nascent RNA achieves a length of 5 nt. This phenomenon is observed at a consensus promoter, but is even more strongly observed at promoters that are altered in the initiation region. Although the abortive product is of a fixed length (5 nt), the positions of the base substitutions in the initiation region that enhance this effect do not appear to be fixed, and we have observed the effect with a variety of initiation-region promoter variants. The phenomenon is also observed during promoter-independent transcription when transcribing a homopolymeric template such as poly(dC). Under conditions where the active site of the RNAP cannot extend beyond the third nucleotide in the template strand and the maximum length of the RNA:DNA hybrid cannot exceed three base-pairs (i.e. when synthesizing oligoG products due to transcript slippage at a promoter that initiates with the sequence +1 GGG...) the mutant RNAP gives rise to a normal spectrum of products 2 to 14 nt in length with no evidence of a block at 5 nt. Neither promoter binding nor promoter melting appears to be involved in this phenotype, as the mutant RNAP binds normally to promoter sequences and the behavior of the enzyme is unaffected by removal of the non-template strand in the initiation region of the promoter or on a supercoiled template. Importantly, the mutant RNAP is defective in binding single strand oligomers of RNA. These results suggest that the affected region of the RNAP may form part of the RNA product binding site and may be involved in the transition from an unstable initiation complex to a stable elongation complex, perhaps by sensing the presence of a nascent RNA and/or RNA:DNA hybrid.

Amino Acids↗

PubMed1997

Rapid mutagenesis and purification of phage RNA polymerases.

We have developed plasmid-based expression systems that encode modified forms of T7 RNA polymerase (RNAP) having 6-12 histidine residues fused to the amino terminus. The histidine-tagged RNAPs (His-T7 RNAPS) are indistinguishable from the wild-type (WT) enzyme in nearly all biochemical assays. Similar plasmids that encode His-tagged T3 and SP6 RNAPs have also been constructed. To facilitate site-directed mutagenesis of the RNAP gene, the size of the target plasmid was minimized by using T7 RNAP itself as a selectable marker. BL21 (DCAT4) cells (which carry a chromosomal copy of the chloramphenicol acetyltransferase cat gene under control of a T7 promoter) are resistant to chloramphenicol when functional T7 RNAP is expressed, thus allowing the selection and maintenance of the target plasmid in these cells. Mutagenesis is accomplished by denaturing the plasmid, annealing mutagenic DNA primers, and repairing the plasmid with T4 DNA polymerase. Two DNA primers are used: one corrects a defect in the bla gene, the other introduces the desired mutation into the RNAP gene; 30-85% of the ampicillin-resistant transformants carry the desired mutation in the RNAP gene. By using BL21 (DCAT4) cells as a recipient for transformation the functional integrity of the RNAP gene may conveniently be monitored by assessing the level of chloramphenicol resistance in vivo. Methods for rapid, simultaneous purification of multiple samples of modified (His-tagged) and conventional RNAPs are described. Together, these developments greatly enhance our ability to characterize this important class of enzymes.

Amino Acid Sequence↗