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Biomedical subjects

C He

Publications and source records attributed to C He.

At least 163 records · Page 9Linked to original sources
PubMed1994

Multiple p53 protein isoforms and formation of oligomeric complexes with heat shock proteins Hsp70 and Hsp90 in the human mammary tumor, T47D, cell line.

At least eleven isoforms of p53 protein were observed in a human mammary tumor cell line. T47D. Comparative 33P and 35S incorporation analysis showed an equal distribution of P53 isoforms within cytoplasmic and nuclear compartments, although phosphorylation was unequal among isoforms and the most basic p53 species was unphosphorylated. Using a combination of immunoprecipitation with monoclonal antibodies for p53 and heat shock proteins Hsp70 & Hsp90, and two-dimensional gel electrophoretic analysis, T47D p53 protein oligomers were observed with several species of Hsp70 and Hsp90. The p53/Hsp70/Hsp90 aggregate dissociates after nuclear translocation. Immunoprecipitation of Hsp70 and Hsp90 using monoclonal antibodies showed formation of a heteroligomer between Hsp70 and Hsp90 in cytoplasm but not nucleus. This suggests these Hsp proteins can form a complex in the cytoplasm but undergo a conformational change after nuclear translocation such that Hsp/Hsp binding sites are no longer recognized. These data indicate T47D cells have multiple p53 precursor molecules probably at different stages of phosphorylation, and which may be sequestered from proteases by binding to Hsp proteins. Hsp proteins also can heterocomplex in the cytoplasm, also possibly as protection against protease degradation until bound to p53. After translocation, p53 is freed from Hsp proteins for binding to DNA where Hsp70 and Hsp90 are no longer able to form a nuclear complex probably rendering Hsp's labile to proteolysis.

Antibodies, Monoclonal↗
PubMed1994

Mouse cells with null p53 mutation have all p53 isoforms deleted and lose negative growth control.

Embryonic mouse cells containing a disrupted p53 gene (-/-) were compared to the heterozygote (+/-) and homozygote control (+/+) for growth characteristics and the presence of p53 protein isoforms. There were considerable morphological differences between the null cells and homozygote, with the null cells having irregular shapes and sizes, and densely staining pleomorphic nuclei. Growth curves showed the null cells to have essentially remained in log phase growth during the course of these studies, losing contact inhibition. Losses of all protein isoforms indicate a single locus origination, and suggest that the multiple protein isoforms observed are due to different net charges on the protein as a result of post-translational modification. These results confirm deactivation of the p53 gene by site-specific disruption of exon 5 as described by Donehower (Donehower et al., 1992).

Animals↗
PubMed1993

Evaluation of the critical value of driving fatigue based on the fuzzy sets theory.

Applying the newly developed multistage evaluation method based on the fuzzy sets theory, we have evaluated the sense of driving fatigue of 8 male drivers who covered 400 km in 8 hr in the daytime, empirically revealing the distribution of the degree of driving fatigue. The critical values from "no" to "a bit" and "a bit" to "fatigued" are 1 and 5.5 hr, respectively. Finally, a tentative study of the psychophysical relations between driving time and driving fatigue has been made, leading to a curve of driving fatigue under the conditions of this experiment.

Adult↗
PubMed1993

Two-dimensional gel electrophoresis of major cytosolic proteins derived from spleen mononuclear cells of normal and leukemic rats.

Proteins from leukemic spleen cells derived from a F344 rat transplant model were investigated by 2D gel electrophoresis. The cell line was maintained in vivo by serial transplant of mononuclear spleen cells from leukemic donors into syngeneic recipients. Cytosolic proteins from mononuclear cells (MNC) were isolated from spleens of normal and leukemic rats and separated by electrophoresis. Replicate data from silver-stained gels for each preparation were compiled into Master Images using image analysis algorithms in order to characterize the normal and leukemic protein profiles. Comparative analysis showed a total of 458 proteins that were reproducibly detected in normal MNC, while almost twice the number of proteins (828) were found in leukemic MNC, suggestive of the more mitotically active tumor cells. Profile analysis showed that normal and leukemic preparations shared 228 common proteins, with 600 proteins observed only in leukemic MNC, and 230 proteins found only in normal MNC. Differences in protein patterns between normal and leukemic MNC in rats probably reflects a shift in spleen leukocyte populations and a relative induction of gene expression in leukemic MNC as compared to the normal MNC.

Animals↗
PubMed1992

Three-dimensional structure of Theiler murine encephalomyelitis virus (BeAn strain).

Depending on the strain, Theiler murine encephalomyelitis virus (TMEV) may cause acute encephalitis or chronic demyelinating disease, which is associated with viral persistence in mice. Persistent central nervous system infection and demyelination by the less-virulent TMEV has provided a useful animal model for the human demyelinating disease multiple sclerosis. The less-virulent BeAn strain of TMEV was crystallized and its atomic structure was determined by x-ray crystallography. The alpha-carbon coordinates of the closely related Mengo virus were used to calculate the initial phases to 3.5 A resolution and the interpretable electron density map was produced by 10 cycles of 30-fold noncrystallographic molecular replacement averaging. The structure revealed a high degree of overall structural similarity to Mengo virus as well as substantial differences in the surface loops. These structural changes might be correlated with TMEV host-specific recognition, pH-related stability, and neurovirulence.

Animals↗
PubMed1992

Enhancement of motor nerve regeneration by nerve growth factor.

The sciatic nerves of adult Wistar rats were severed bilaterally. Each nerve was sutured into a silicone tube used as a conduit, leaving a 5 mm gap in length between the nerve ends. Nerve growth factor in a saline solution vehicle was injected into the silicone chamber on the right side and normal saline solution (control) on the left. Six weeks after surgery, electrophysiological studies were performed. The motor nerve conduction velocities (MNCV) were significantly increased in the NGF-treated nerves. In one rat, the MNCV on the NGF-treated side was 66.6 m/s, in the range of normal nerves. There was no significant difference between the two sides in the amplitudes of evoked muscle action potentials. There are apparently no reports on the effect of NGF on motor neuron regeneration in vitro. In this study, NGF was found to enhance motor nerve regeneration.

Action Potentials↗
PubMed1992

[Alpha 2 megaloglobulin inhibits the activation of rabbit platelet by Chinese Agkistrodon acutus venom].

An in vitro study of alpha 2-mengaloglobulin (alpha 2MG) in the inhibition of the activation of washed rabbit platelet by Chinese Agkistrodon acutus venom (CAAV) was reported. Results showed that CAAV induced aggregation rate of washed rabbit platelet was positively related to the CAAV concentration, and the maximal aggregation rate was 43.8 +/- 9.9% at the concentration of 100 micrograms/ml. Meanwhile the release of serotonin (5-HT) and platelet factor 4(PF4) from the platelet reached maximum at the CAAV concentrations of 0.81 +/- 0.07 microgram/ml and 39.08 +/- 2.78%, respectively. Platelet aggregation and the release of 5-HT and PF4 induced by CAAV could be inhibited by the addition of 0.25% alpha 2 MG into the platelets both 1 minute before and 1 minute after the addition of CAAV. When alpha 2 MG was added to the platelets 1 minute prior to the addition of CAAV, the platelet aggregation and the ultrastructural changes which could be induced by CAAV were not observed, and the morphology of the rabbit platelets was the same as that of the normal counterparts.

Animals↗
PubMed1992

Two-dimensional polyacrylamide gel electrophoretic characterization of proteins from organs of C3H mice expressing the scurfy (sf) genetic mutation during early and late stages of disease progression.

Scurfy (sf), is an X-linked recessive lethal mutation that occurs spontaneously in the C3H mouse. The disease is characterized by lymphoid and hematopoietic dysfunction. Affected males are of small stature and exhibit scaliness and crusting of the eyelids, ears, tail, and feet, marked splenomegaly, moderate hepatomegaly, enlarged lymph nodes, and atrophy of the thymus. The average lifespan of the affected hemizygous males (sf/y) is 24 +/- 0.7 days. Total cellular proteins were extracted from pooled samples of thymus and spleen obtained from combined litters of mice. Tissue-specific protein profiles characteristic of either sf mutant or normal mice were analyzed by two dimensional polyacrylamide gel electrophoresis (2DPAGE) at different stages of the phenotypic expression of the sf mutation, to identify changes in protein patterns that might be associated with the progression of the disease. The resultant gels were silver stained, digitized, and analyzed, by image analysis utilizing a pipelined image processor connected to a host computer. At 14 +/- 1 days of age, protein patterns from sf mutant and normal mice control organs showed considerable homogeneity, although there were proteins identified unique to the sf mutant and to the normal controls. At 20 +/- 1 days of age, the pattern differences between the sf mutant and normal control increased markedly. Differences were expressed as the percent of proteins that were unique to either the sf mutant or the normal control from the total number of each type. The percent of proteins that increased or decreased in the three organs utilized in this study ranged between 21%-39% at 14 days and were between 25%-54% at 20 days. Differences in protein expression between the normal and sf mutant as the disorder progressed for each of the three tissues examined. In addition, thymus protein profiles from 9 day old littermates that were phenotypically normal but genotypically unknown were evaluated to determine if marker proteins could be identified for the sf mutation. Limited protein changes were noted at relative molecular weights of 66, 60, 54, 39, 37, 33, 25, 23, 27, and 11 kDa. These data suggest that the sf mutation follows a trackable pattern of protein expression and repression different than the normal control C3H mouse. Several potential marker proteins associated with the sf mutation were identified in 9 day thymus prior to the phenotypic expression of the disease. These putative biomarkers may be useful for characterizing the sf mutation and the mutant may act a possible model the Wiskott-Aldrich syndrome (WAS).

Abnormalities, Multiple↗
PubMed1992

Activation of extracellular matrix metalloproteases by proteases and organomercurials.

Extracellular matrix metalloproteases are synthesized as proenzymes and are activated by certain physiological agents after secretion into the extracellular space. The identity of these agents and the stimulus that elicits their response in vivo is only recently becoming clear, but a variety of agents or stimuli are capable of activating these metalloproteases in vitro also. Of these, the most well studied and characterized are trypsin, plasmin and the organomercurials. These agents appear to have in common an ability to disrupt the structure of the stable latent enzyme in such a way as to allow the generation of a proteolytic active site. In the case of organomercurial activation, intramolecular proteolytic cleavage of the amino-terminus of the enzyme occurs subsequent to generation of activity. A similar intramolecular process is seen with trypsin and plasmin activation except that it is initiated by a single trypsin or plasmin catalyzed cleavage in the amino-terminus prior to the autocatalytic cleavages. A possible explanation for organomercurial activation is that the mercurial disrupts a cysteinyl residue coordination bond with the active site zinc that prevents interaction with substrate. Disruption of this complex would allow productive enzyme-substrate interaction via the newly available coordination site. In addition, activated stromelysin is capable of increasing the specific activity of active interstitial collagenase by approximately ten-fold through what appears to be proteolytic removal of a small peptide.

Amino Acid Sequence↗
PubMed1991

Hepatitis B virus DNA in sera of virus carriers positive exclusively for antibodies to the hepatitis B core antigen.

The prevalence of serum HBV DNA in individuals positive for anti-HBc alone was determined by the polymerase chain reaction in two groups with endemic HBV infection from Canton (group A) and Hainan (group B), provinces of China. Twenty-one out of 294 individuals in group A (7.2%) and 193 out of 1995 in group B (9.7%) were positive for anti-HBc but negative for other markers of ongoing or past HBV infection (HBsAg and anti-HBs). HBV DNA was detected in 6/21 sera in group A (28.6%) and 68/193 in group B (35.2%) in their initial serum specimen. One of the six HBV-DNA-positive individuals in group A became negative after 6 months and four of the 58 positive in group B became negative at 4 years of follow-up. All of the individuals remained positive for anti-HBc and negative for anti-HBs, but one of them became positive for HBsAg on follow-up. None of the anti-HBc- and HBV-DNA-positive subjects had symptoms of liver diseases. They were, therefore, defined as chronic asymptomatic HBV carriers with undetectable HBsAg. This type of carrier should be added to the typical HBsAg-positive carrier, who constitutes about 10-15% of the general Chinese population, to give a more complete estimate of asymptomatic HBV carriers in China.

Adolescent↗
PubMed1991

Expression of OKM5 antigen on keratinocytes in some dermatoses.

Employing an avidin-biotin complex immunoperoxidase technique, it was found that there was OKM5 but no OKM1 antigen expression on the keratinocytes of the upper epidermis from all the studied specimens of seborrheic keratosis, verrucous nevus, Bowen's disease, BCC, SCC, MM, lichen planus, psoriasis vulgaris, condyloma acuminatum, and sporotrichosis as well as in two of eight cases of nevus pigmentosus. Our findings indicate that OKM5 antigen expression on epidermal keratinocytes is usually associated with dermal infiltration. It is assumed that human keratinocytes in cutaneous lesions, like the OKM1- OKM5+ monocyte/macrophage lineages, might play certain roles in immune responses and possibly function as antigen-presenting cells.

Adolescent↗
PubMed1991

Site-specific mutagenesis method which completely excludes wild-type DNA from the transformants.

A highly efficient site-specific mutagenesis method has been devised to exclude wild-type DNA from incorporation into the transformed cells. Two complementary oligonucleotides, corresponding to a target sequence of a DNA molecule and containing an insertion mutation which created an endonuclease restriction site, were synthesized. By using the wild-type DNA molecule flanked by two restriction sites on each side of the target region as a template, the two oligonucleotide primers were extended, enriched, and isolated. The extended products, in turn, were used as templates in a polymerase chain reaction to obtain a mutagenized double-stranded DNA fragment which was conveniently cloned into plasmids by using the flanking restriction sites. Escherichia coli cells transformed by these plasmids were subject to large-scale analysis. One hundred percent of the transformants examined by colony hybridization, restriction enzyme analysis, and DNA sequencing were found to contain the mutant DNA sequence.

Base Sequence↗
PubMed1991

Carnivora: the primary structure of the hemoglobin from the silver fox (Vulpes vulpes var., Canidae).

The primary structure determination of the hemoglobin alpha- and beta-chains from the silver fox (Vulpes vulpes var., Canidae) is described. The separation of the chains could be achieved directly from the hemoglobin by RP-HPLC as well as by column chromatography of the globin using carboxymethyl-cellulose. Following tryptic digestion of the chains, the peptides were isolated by RP-HPLC. Amino-acid sequences were determined by Edman degradation in liquid and gas phase sequencers. The peptides could be aligned by homology with human and other Carnivora hemoglobins. Compared to human hemoglobin the alpha- and beta-chains of the silver fox exhibit 24 and 13 amino-acid exchanges, respectively. They differ by one alpha- and two beta-chain replacements from the domestic dog and the coyote. The substitutions affecting contact positions are discussed.

Amino Acid Sequence↗
PubMed1990

Secreted proteases. Regulation of their activity and their possible role in metastasis.

Extracellular matrix metalloproteases are secreted by the resident cells of the tissue in a proenzyme form, and their extracellular activity is regulated at the level of gene expression, proenzyme activation, and interaction with inhibitors. To understand the molecular mechanisms that control the activity of ECM metalloproteases and their effect on the cellular phenotype, we have established cell lines in which the transcription of the protease genes is repressed. We also have undertaken a detailed study of the pathway of extracellular activation of interstitial procollagenase. Stable transfection of three human tumor cell lines--H-ras-transformed bronchial epithelial cells TBE-1, fibrosarcoma cells HT1080, and melanoma cells A2058--with the adenovirus E1A gene dramatically repressed the expression of the secreted proteases, type IV and interstitial collagenases, and urokinase-type plasminogen activator. Concomitantly, E1A-expressing cells showed reduced metastatic activity in vivo and reduced ability to traverse a reconstituted basement membrane in vitro. Monospecific anti-type IV collagenase antibody inhibited the invasive activity of parental tumor cell lines in the in vitro system, suggesting a possible causal relationship between the effect of E1A on the expression of secreted proteases and the reduced metastatic potential of the E1A-expressing transformants. We have also studied the mechanism of regulation of metalloprotease activity at the level of extracellular activation by investigating the cascade of proteolytic events that results in the activation of interstitial procollagenase. Cocultivation of the major cellular components of skin, dermal fibroblasts, and epidermal keratinocytes induces activation of interstitial procollagenase and prostromelysin in the presence of plasminogen. This activation occurs through a uPA-plasmin-dependent pathway in which plasmin catalyzes the first step in activation of both collagenase and stromelysin by amino-terminal processing. Activated stromelysin can in turn convert plasmin-activated collagenase into a fully active enzyme by removal of approximately 15 amino acid residues from the carboxyl end of the enzyme. This second step of activation results in a 5-8-fold further increase in specific activity of collagenase. This cascade of proteolytic events may constitute a major physiologic pathway of collagenase activation.

Adenovirus Early Proteins↗
PubMed1990

Carnivora: the primary structure of hemoglobin from the Masked Palm Civet (Paguma larvata, Viverridae).

The primary structure of the alpha- and beta-chains of hemoglobin from the Masked Palm Civet (Paguma larvata, Viverridae) is described. The chains were separated directly from hemoglobin by RP-HPLC. After tryptic digestion of the chains, the peptides were separated by RP-HPLC. Amino acid sequences were determined by Edman degradation in liquid and gas-phase sequencers. The alignment of the tryptic peptides was made by homology with human and other Carnivora hemoglobins. Paguma and human hemoglobin differ with respect to 23 amino-acid residues. Some of these amino-acid substitutions, which occur in both the alpha- and beta-chains, occur at contact sites between the subunits, and at the binding sites of heme and of organic phosphate, as well as involving residues responsible for the alkaline Bohr effect.

Amino Acid Sequence↗
PubMed1990

[Influence of microinjection of dynorphin antibody into periaqueductal gray (PAG) on analgesia induced by electroacupuncture of different frequencies in rats].

Previous studies have shown that 2 Hz but not 100 Hz electroacupuncture (EA) stimulation released beta-endorphin in PAG of the rat to induce analgesia. The present study was undertaken to see whether dynorphin plays a role in PAG in mediating analgesia induced by low and high frequency EA. Injection of affinity purified dynorphin antibody (1:350,000 in RIA titer) 1 microliter into PAG blocked 2 Hz EA analgesia almost completely, and 15 Hz EA analgesia partly, leaving 100 Hz EA analgesia intact. This blocking effect was totally disappeared when the antibody was diluted to 1/10 of its original concentration (1:35,000). Besides, injection of dynorphin into PAG through chronically implanted cannula showed no analgesic effect. The results suggest that the blockade of 2 Hz EA analgesia by high titer dynorphin antibody injected into PAG may have been the result of cross reactivity of the antibody to other opioid peptides (such as beta-endorphin, enkephalin, etc) released in the PAG area. The data also stress the importance of using antibodies of proper titer and concentration to exclude false positive or false negative conclusions in adopting the antibody microinjection techniques, as was repeatedly shown in the immunohistochemical studies.

Acupuncture Analgesia↗