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Biomedical subjects

S Sun

Publications and source records attributed to S Sun.

At least 307 records · Page 17Linked to original sources
PubMed1992

Positive and negative cis-acting regulatory elements mediate expression of the mouse vascular smooth muscle alpha-actin gene.

Segments of the 5'-flanking region of the mouse vascular smooth muscle alpha-actin gene were assayed for promoter activity in transfected mouse BC3H1 myogenic cells and AKR-2B embryonic fibroblasts. The region between -150 and -191 that functions as a positive transcriptional element in myogenic and fibroblastic cells contains a mammalian-specific inverted CC(A/T)6GG-type consensus sequence. Expression was restricted to fully differentiated myogenic cells when an additional sequence spanning -191 to -224 was included in reporter gene constructs. This 33-base pair (bp) negative regulatory element is 70% conserved between the mouse and human genes and contains a 10-bp motif at its 3' end that only partially resembles a CC(A/T)6GG element. Retention of a GGGA motif at the 3' boundary of the 33-bp region is sufficient to maintain full transcriptional repression in fibroblasts and is partly responsible for repression in undifferentiated myoblasts. Complete muscle tissue-restrictive expression requires an additional 8 bp from the CC(A/T)6GG-like element immediately 5' to the GGGA motif, since replacement of this region with an unrelated 10-bp sequence completely eliminated restrictive transcriptional behavior in undifferentiated myoblasts. The distal portion of the 5'-flanking region between -224 and -1074 contains six E-box motifs (CANNTG) and mediates high level transcription only in postconfluent BC3H1 myoblasts. Analysis of reporter gene constructs including either the proximal E-box at -240 or all six E-boxes indicate that the five distal E-boxes are not required for high level transcription. A 724-bp segment of the 5'-flanking region consisting of the proximal E-box flanked upstream by a mammalian-specific 352-bp region was sufficient for maximal transcriptional activation in postconfluent BC3H1 myoblasts. Deletion of the 352-bp region restricts the early transcriptional response to high cell density in temporal studies of promoter activity during BC3H1 myogenic cell differentiation.

Actins↗
PubMed1992

Molecular cloning of the cDNA encoding a 42 kDa antigenic polypeptide of Anisakis simplex larvae.

The gene encoding an antigenic polypeptide of Anisakis simplex larvae was studied using recombinant DNA techniques. cDNA synthesized from poly(A)-rich mRNA from A. simplex larvae was ligated into phage vector lambda gtll DNA and packaged in vitro. The phages were propagated on Escherichia coli and a lambda gtll expression library was constructed. A cDNA clone encoding a 42 kDa antigenic polypeptide was selected by immunoscreening of the library and identified by the epitope selection method. A clone containing cDNA for a 42 kDa protein was isolated. The gene encoding this 42 kDa antigenic polypeptide was characterized by DNA and RNA blot analysis using the cDNA as a probe. The gene was transcribed to mRNA with approximately 1400 nucleotides and translated to 42 kDa polypeptide. The antigenic beta-galactosidase fusion protein synthesized by bacteria had no cross-reactivity with other parasite-infected sera.

Amino Acid Sequence↗
PubMed1992

The identity of Anisakis type II larvae with Anisakis physeteris confirmed by restriction fragment length polymorphism analysis of genomic DNA.

The identity of Anisakis type II larvae with adult A. physeteris was confirmed by comparison of restriction fragment length polymorphisms (RFLPs) of 25S ribosomal DNA (rDNA). Patterns of RFLPs in larvae were almost identical with those in adult worms. Directly labelled 25S rDNA might serve as an appropriate probe with highly specific activity for examining RFLPs of larvae and adult worms.

Animals↗
PubMed1992

Stage-specific expression of a developmentally regulated gene in Dirofilaria immitis.

A previously reported cDNA clone encoding 34 kDa antigenic polypeptide of Dirofilaria immitis (lambda cD34) was studied to elucidate the mechanism of stage-specific gene expression. The 34 kDa polypeptide was a larva-specific antigen and the mRNA was detectable in microfilariae but not in adult worms and eggs. The lambda cD34 gene was not sex linked and was contained in the genome of D. immitis at each stage. The stage-specific expression of the developmentally regulated gene in D. immitis may be controlled primarily at the mRNA level.

Animals↗
PubMed1992

Immunodiagnosis of human dirofilariasis by enzyme-linked immunosorbent assay using recombinant DNA-derived fusion protein.

An enzyme-linked immunosorbent assay (ELISA) using antigenic beta-galactosidase-Dirofilaria immitis recombinant fusion protein (FP) obtained by the recombinant DNA technique provided a useful diagnostic tool for human dirofilariasis. D. immitis-infected human sera reacted strongly with FP that was immobilized with anti-beta-galactosidase monoclonal antibody on microplates. However, the FP did not react with sera from patients with other filariasis. In detection of anti-D. immitis IgG antibody. ELISA using FP was highly sensitive and specific compared to that using crude somatic antigen.

Animals↗
PubMed1992

Noncontiguous injuries of the spine.

A total of 372 consecutive spinal injury patients were evaluated at the Regional Spinal Cord Injury Center of Delaware Valley. Of these, 39 patients (10.5%) were found to have noncontiguous spinal column injuries. Fewer than half of the patients in our series could be classified into previous classification systems (Calenoff, Gupta) of noncontiguous spinal fractures. Fifteen fractures in 12 patients were missed on presentation on admission and 25% of these patients had a progressive neurologic deficit as a result of improper initial immobilization. The location of missed fractures were found to be primarily at the extremes or junctures of the spine (i.e., cervicothoracic, thoracolumbar). Complete spinal roentgenographic evaluation is recommended in the workup of suspected spinal column injury patients, and additional imaging modalities (i.e., tomograms, computed tomography scans, and magnetic resonance imaging) may be necessary in those areas of the spine difficult to visualize.

Adolescent↗
PubMed1992

Production of an Amylase-Sensitive Bacteriocin by an Atypical Leuconostoc paramesenteroides Strain.

An atypical Leuconostoc paramesenteroides strain isolated from retail lamb produced a bacteriocin, leuconocin S, that was inactivated by alpha-amylase, trypsin, alpha-chymotrypsin, protease, and proteinase K but not by lipase or heat treatment at 60 degrees C for 30 min. Supernatants from culture broths produced two glycoprotein bands on sodium dodecyl sulfate-polyacrylamide gels; these had molecular weights of 2,000 and 10,000 and activity against Lactobacillus sake ATCC 15521. The crude bacteriocin preparation was bacteriostatic and dissipated proton motive force. Bacteriocin activity was produced over a wide pH range (5.2 to 7.9) on buffered agar medium, with an optimum pH of pH 6.15. The optimum pH for production in broth was 6.5 to 7.0.

Journal Article↗
PubMed1992

Internal carotid arterial flow velocity during exercise in Tibetan and Han residents of Lhasa (3,658 m).

Cerebral blood flow increases with acute exposure to high altitude, but the effect of hypoxia on the cerebral circulation at rest and during exercise appears influenced by the duration of high-altitude exposure. To determine whether internal carotid artery flow velocity increased with exercise in long-term residents of high altitude and whether resting values and the response to exercise differed in lifelong vs. acclimatized newcomer male residents of high altitude, we studied 15 native Tibetan and 11 Han ("Chinese") 6 +/- 2-yr residents of Lhasa (3,658 m), Tibet Autonomous Region, China. Noninvasive Doppler ultrasound was used to measure internal carotid artery diameter, mean flow velocity, and, in combination, hemoglobin and arterial O2 saturation to assess cerebral O2 delivery. Tibetan and Han groups were similar in body size and resting internal carotid artery diameter, blood pressure, hemoglobin concentration, internal carotid artery mean flow velocity, and calculated cerebral O2 delivery. Submaximal exercise increased internal carotid artery mean flow velocity and cerebral O2 delivery in the Tibetan and Han subjects. At peak exercise, the Tibetans sustained the increase in flow velocity and cerebral O2 delivery, whereas the Hans did not. Across all exercise levels up to and including peak effort, the Tibetans demonstrated a greater increase in internal carotid artery flow velocity and cerebral O2 delivery relative to resting values than did the Hans. The greater cerebral O2 delivery was accompanied by increased peak exercise capacity in the Tibetan compared with the Han group. Our findings suggest that the cerebral blood flow response to exercise is maintained in Tibetan lifelong residents of high altitude.

Adult↗
PubMed1992

[Anti-carcinogenic and anti-promoting effects of retinoid R8605].

R8605 belongs to the third generation retinoid and was found during the systematic screening of cancer chemopreventive agents in our institute. Based on the theory of multistage carcinogenesis, the anti-carcinogenic and anti-promoting effects of R8605 as well as its possible anti-promoting mechanisms were studied. Experiments proved that R8605 (50 mg/kg and 25 mg/kg, i.g.) significantly inhibited the growth of skin papillomas induced by 7, 12-dimethylbenz[a]anthracene and croton oil in mice and exhibited a potent anti-promoting action. In addition, R8605 (50 mg/kg and 25 mg/kg, i.g.) strongly inhibited the induction of ornithine decarboxylase (ODC) activity of mouse skin epidermis by croton oil. At a dose of 100 mg/kg of R8605 (i.g.) croton oil-induced ear edema in mice was suppressed. These results suggest that the anti-promoting effect of R8605 might be associated with its anti-inflammatory action and its inhibitory effect on ODC activity.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1992

Cardiac anaphylaxis in the Sprague-Dawley rat.

Anaphylactic shock was induced in pentobarbital-anesthetized, mechanically ventilated Sprague-Dawley rats that had been sensitized 21 days earlier to crystallized ovalbumin. The sensitization was confirmed by passive cutaneous anaphylaxis test. Antigen challenge produced an immediate reduction in mean aortic pressure from 168 to 67 mm Hg within 1 minute after intravenous injection of ovalbumin. Plasma histamine increased from 4.5 to 128 ng/ml within 5 minutes after injection of antigen. There were no changes in airway or esophageal pressures after antigen challenge. Left ventricular diastolic pressure was increased, and contractility, as measured by the rate of change of left ventricular pressure (dP/dt), was decreased over an interval exceeding 90 minutes. When isolated, constant flow--perfused hearts from sensitized Sprague-Dawley rats were challenged with antigen, decreases in left ventricular function were observed associated with decreased positive and negative maximum rate of change of left ventricular pressure (dP/dtmax). This experimental model in the rat therefore demonstrated selective myocardial impairment with reduced inotropism and lusitropism after anaphylaxis.

Anaphylaxis↗
PubMed1991

Stability of monoclonal antibody-defined epitopes.

Epitope instability can limit the applications of monoclonal antibody (mAb) technology in laboratory and clinical research. We exposed a group of representative antigens on human hepatocellular carcinoma (HCC) cells to physiochemical insults to study epitope stability as measured by mAb immunoreactivity. Each epitope was found to have a unique pattern of instability which serves to biophysically characterize the antigen and defines the conditions to which the antigen can be exposed during laboratory and clinical investigations. Individual antigens were found to be unstable within a surprisingly well defined window of solvent polarities while being stable on either side of that window. Several antigens were observed to be unstable when exposed to transient changes in pH. When a critical temperature between 42 degrees C and 65 degrees C was achieved, epitopes which were thermosensitive underwent a sudden loss in immunoreactivity. This critical temperature was found to be pH dependent. The effects of polarity, pH, and temperature on epitope stability are consistent with changes in protein structural conformation. In addition, we found that certain fixatives cause a time and concentration dependent loss of epitope immunoreactivity. This study provides a rapid and easy determination of monoclonal antibody-defined epitope stability; the results of which serve to guide further studies on the antigen and to characterize the antigen on the basis of its unique physiochemical stability.

Animals↗
PubMed1991

Ab initio study of the electrostatic multipole nature of torsional potentials in CH3SSCH3, CH3SSH, and HOOH.

The origin of torsional potentials in H3CSSCH3, H3CSSH, and HOOH and the anisotropy of the local charge distribution has been analyzed in terms of atomic multipoles calculated from the ab initio LCAO-MO-SCF wave function in the 6-31G* basis set. The results indicate that for longer -S-S-bonds the major contribution to these torsional barriers are electrostatic interactions of the atomic multipoles located on two atoms forming the rotated bond. This finding demonstrates the important role of electrostatic 1-2 interatomic interactions, usually neglected in conformational studies. It also opens the possibility to derive directly from accurate ab initio wave functions a simple nonempirical torsional potential involving atomic multipoles of two bonded atoms defining the torsional angle. For shorter -O-O- bonds, use of more precise models and inclusion of 1-3 interactions seems to be necessary.

Chemistry, Organic↗
PubMed1991

Pulmonary ventilation/perfusion defects induced by epinephrine during cardiopulmonary resuscitation.

BACKGROUND: Epinephrine has been shown to impair pulmonary excretion of CO2 during resuscitation. This phenomenon was investigated in a rodent model of cardiac arrest and conventional resuscitation. METHODS AND RESULTS: The effects of racemic epinephrine were compared with the selective alpha 1-agonist methoxamine and with saline placebo during cardiac resuscitation in 15 Sprague-Dawley rats mechanically ventilated with gas containing 70% oxygen. Epinephrine and methoxamine but not saline placebo significantly increased coronary perfusion pressure from approximately 32 to 55 mm Hg. Following epinephrine, end-tidal PCO2 decreased from approximately 10 to 5 mm Hg. This was associated with a time-coincident decrease in PaO2 from approximately 130 to 74 mm Hg and an increase in PaCO2 from approximately 26 to 40 mm Hg. These changes indicated increases in alveolar dead space ventilation concomitant with increases in pulmonary arteriovenous admixture. No such effects were observed after administration of either methoxamine or saline placebo. Each of the 15 rats was successfully resuscitated. However, a significantly larger number of transthoracic countershocks were required after epinephrine compared with methoxamine or placebo before return of spontaneous circulation. CONCLUSIONS: Epinephrine induced ventilation/perfusion during cardiopulmonary resuscitation as a result of redistribution of pulmonary blood flow.

Animals↗
PubMed1991

[Ultrastructure of mast cells in nasal polyps].

More mast cells were found in the base of nasal polyps and most of them showed varying degrees of degranulation. There were three types of granules in the cytoplasm, namely: high electron-dense granules with crystalline structure; low electron-dense granules with netlike structure and some granules containing a mixture of components of different electron density. The appearance of cell degeneration in nasal polyps and granules broken away from mast cells through the dissolved cellular membrane were noted. These findings suggested that mast cells degranulation in nasal polyps might be in some way different from the more rapid changes found in cells activated by the classical IgE-mediated pathway and showed that mast cell degranulation may play a part in formation and growth of the nasal polyps.

Cell Degranulation↗