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Y Lu

Publications and source records attributed to Y Lu.

At least 775 records · Page 43Linked to original sources
PubMed1995

Roles of the three transcriptional attenuators of the Bacillus subtilis pyrimidine biosynthetic operon in the regulation of its expression.

Expression of the Bacillus subtilis pyr operon is regulated by exogenous pyrimidines and the protein product of the first gene of the operon, PyrR. It has been proposed that PyrR mediates transcriptional attenuation at three untranslated segments of the operon (R.J. Turner, Y. Lu, and R.L. Switzer, J. Bacteriol., 176:3708-3722, 1994). In this study, transcriptional fusions of the pyr promoter followed by the pyr attenuation sequences, either individually or in tandem to a lacZ reporter gene, were used to examine the physiological functions of all three attenuators through their ability to affect beta-galactosidase expression. These fusions were studied as chromosomal integrants in various B. subtilis strains to examine the entire range of control by pyrimidines, PyrR dependence, amd developmental control of pyr gene expression. The nutritional regulation of each attenuator separately was roughly equivalent to that of the other two and was totally dependent upon PyrR, and that of tandem attenuators was cumulative. The regulation of a fusion of the spac promoter followed by the pyrP:pyrB intercistronic region to lacZ produced results similar to those obtained with the corresponding fusion containing the pyr promoter, demonstrating that attenuator-dependent regulation is independent of the promoter. Extreme pyrimidine starvation gave rise to two- to threefold-higher levels of expression of a pyr-lacZ fusion that lacked attenuators, independent of PyrR, than were obtained with cells that were not starved. Increased expression of a similar spac-lacZ fusion during pyrimidine starvation was also observed, however, indicating that attenuator-independent regulation is not a specific property of the pyr operon. Conversion of the initiator AUG codon in a small open reading frame in the pyrP:pyrB intercistronic region to UAG reduced expression by about half but did not alter regulation by pyrimidines, which excludes the possibility of a coupled transcription-translation attenuation mechanism. Developmental regulation of pyr expression during early stationary phase was found to be dependent upon the attenuators and PyrR, and the participation of SpoOA was excluded.

Bacillus subtilis↗
PubMed1995

Identification and characterization of a serine-like proteinase of the murine coronavirus MHV-A59.

Gene 1 of the murine coronavirus, MHV-A59, encodes approximately 800 kDa of protein products within two overlapping open reading frames (ORFs 1a and 1b). The gene is expressed as a polyprotein that is processed into individual proteins, presumably by virus-encoded proteinases. ORF 1a has been predicted to encode proteins with similarity to viral and cellular proteinases, such as papain, and to the 3C proteinases of the picornaviruses (A. E. Gorbalenya, A. P. Donchenko, V. M. Blinov, and E. V. Koonin, FEBS Lett. 243:103-114, 1989; A. E. Gorbalenya, E. V. Koonin, A. P. Donchenko, and V. M. Blinov, Nucleic Acids Res. 17:4847-4861, 1989). We have cloned into a T7 transcription vector a cDNA fragment containing the putative 3C-like proteinase domain of MHV-A59, along with portions of the flanking hydrophobic domains. The construct was used to express a polypeptide in a combined in vitro transcription-translation system. Major polypeptides with molecular masses of 38 and 33 kDa were detected at early times, whereas polypeptides with molecular masses of 32 and 27 kDa were predominant after 30 to 45 min and appeared to be products of specific proteolysis of larger precursors. Mutations at the putative catalytic histidine and cysteine residues abolished the processing of the 27-kDa protein. Translation products of the pGpro construct were able to cleave the 27-kDa protein in trans from polypeptides expressed from the noncleaving histidine or cysteine mutants. The amino-terminal cleavage of the 27-kDa protein occurred at a glutamine-serine dipeptide as previously predicted. This study provides experimental confirmation that the coronaviruses express an active proteinase within the 3C-like proteinase domain of gene 1 ORF 1a and that this proteinase utilizes at least one canonical QS dipeptide as a cleavage site in vitro.

Amino Acid Sequence↗
PubMed1995

Discrimination of DNA binding sites by mutant p53 proteins.

Critical determinants of DNA recognition by p53 have been identified by a molecular genetic approach. The wild-type human p53 fragment containing amino acids 71 to 330 (p53(71-330)) was used for in vitro DNA binding assays, and full-length human p53 was used for transactivation assays with Saccharomyces cerevisiae. First, we defined the DNA binding specificity of the wild-type p53 fragment by using systematically altered forms of a known consensus DNA site. This refinement indicates that p53 binds with high affinity to two repeats of PuGPuCA.TGPyCPy, a further refinement of an earlier defined consensus half site PuPuPuC(A/T).(T/A) GPyPyPy. These results were further confirmed by transactivation assays of yeast by using full-length human p53 and systematically altered DNA sites. Dimers of the pentamer AGGCA oriented either head-to-head or tail-to-tail bound efficiently, but transactivation was facilitated only through head-to-head dimers. To determine the origins of specificity in DNA binding by p53, we identified mutations that lead to altered specificities of DNA binding. Single-amino-acid substitutions were made at several positions within the DNA binding domain of p53, and this set of p53 point mutants were tested with DNA site variants for DNA binding. DNA binding analyses showed that the mutants Lys-120 to Asn, Cys-277 to Gln or Arg, and Arg-283 to Gln bind to sites with noncanonical base pair changes at positions 2, 3, and 1 in the pentamer (PuGPuCA), respectively. Thus, we implicate these residues in amino acid-base pair contacts. Interestingly, mutant Cys-277 to Gln bound a consensus site as two and four monomers, as opposed to the wild-type p53 fragment, which invariably binds this site as four monomers.

Base Sequence↗
PubMed1995

Secretin at physiological doses inhibits gastric motility via a vagal afferent pathway.

Secretin is an important modulator of gastric motility. In this study, we investigated the site(s) and mechanism(s) of action of secretin to inhibit gastric motility, using an in vivo rat model. Intragastric pressure response to graded doses of secretin was recorded in anesthetized rats by a balloon attached to a catheter passed through an incision in the duodenum into the body of the stomach. The intragastric pressure was set at 10 cmH2O with balloon distension. Intravenous infusion of secretin (1.4, 2.8, 5.6, 11.2, and 22.4 pmol.kg-1.h-1) decreased intragastric pressure in a dose-dependent manner. The threshold dose was 2.8 pmol.kg-1.h-1, and the effective dose at 50% (ED50) was 5.6 pmol.kg-1.h-1, which produced physiological levels of plasma secretin. Pretreatment with hexamethonium (10 mg/kg) markedly reduced gastric motor response to secretin (5.6 pmol.kg-1.h-1). Bilateral truncal vagotomy also significantly diminished gastric motor responses to secretin. In contrast, secretin (5.6 pmol.kg-1.h-1) had no effect on gastric contraction evoked by electrical vagal stimulation (1.25-5 Hz) or carbachol (10(-6) to 3 x 10(-5) M). These observations indicate that physiological concentrations of secretin act via stimulation of presynaptic cholinergic neurons in a vagally mediated pathway. In subsequent studies, we demonstrated that perivagal treatment 4 days before with the sensory neurotoxin, capsaicin, abolished gastric motor response to secretin but did not affect contraction evoked by electrical vagal stimulation. Similarly, we also showed that gastroduodenal application of capsaicin for 30 min also markedly reduced gastric response to secretin. These observations indicate that physiological doses of secretin act on vagal afferent pathways originating from the gastroduodenal mucosa to induce gastric relaxation.

Afferent Pathways↗
PubMed1995

Quantification of the volume of articular cartilage in the metacarpophalangeal joints of the hand: accuracy and precision of three-dimensional MR imaging.

OBJECTIVE: Cartilage loss is central to the development of joint failure in arthritis. However, radiographic assessment of cartilage loss is highly unreliable. This study examined the accuracy and reproducibility of a noninvasive technique for quantifying the volume of articular cartilage in the metacarpophalangeal joints of the hand by use of three-dimensional (3D) MR imaging. SUBJECTS AND METHODS: Eight metacarpophalangeal joints (four normal, one rheumatoid arthritic, and three normal cadaveric) each were imaged three times with a 1.5-T clinical MR imaging scanner with a small partial volume coil and a fat-saturated 3D spoiled gradient-echo sequence optimized for delineating articular cartilage. The volumes of cartilage over the metacarpal and phalangeal surfaces were quantified by summing the voxels within segmented 3D reconstructions of the images. Cartilage volumes in the three cadaver joints also were estimated by scraping cartilage off the articular surfaces and measuring water displacement in graduated cylinders. These values were used as the gold standard for assessing the accuracy of cartilage volume quantification by MR imaging. RESULTS: The fat-saturated sequence discriminated the articular cartilage from adjacent joint structures with high contrast and high spatial resolution. Cartilage volumes determined by MR imaging for the different subjects ranged from 115 microliters to 222 microliters for metacarpal cartilage and from 34 microliters to 86 microliters for proximal phalangeal cartilage. Accuracy errors for quantifying cartilage volume by MR imaging were -1.8% (95% confidence interval, -3.5% to -0.7%) for metacarpal cartilage and 9.1% (4.3% to 14.7%) for proximal phalangeal cartilage. Reproducibility errors were 5.2% (95% confidence interval, 2.9% to 7.6%) and 9.9% (5.4% to 15.1%), respectively. CONCLUSION: Fat-suppressed T1-weighted 3D MR imaging provides sufficient contrast and spatial resolution to allow accurate and reproducible quantification of articular cartilage volume in the metacarpophalangeal joints of the hand. This technique may be useful for monitoring cartilage loss in patients with arthritis.

Adult↗
PubMed1995

Transformation of primary cultures of shrimp (Penaeus stylirostris) lymphoid (Oka) organ with Simian virus-40 (T) antigen.

Primary cultures of lymphoid (Oka) organ from Penaeus stylirostris were transformed with naked or Lipofectin-mediated pSV-3 neo, a shuttle vector containing the tumor (T) antigen gene from Simian virus-40. The transformed cells, OKTr-1 and OKTr-23, exhibited the following characteristics: rounded morphology forming grapelike aggregates, loosely adhesive, increased growth rate in Medium-199, resistance to G-418 (a neomycin analog marker in the shuttle vector), cloning efficiencies of 68.7% and 36.7% in soft agarose, respectively, and stability in liquid nitrogen storage. Immunofluorescence staining (IFA) of the transformed cells using a monoclonal antibody against SV-40 tumor antigen showed positive results. In contrast, primary cell cultures exhibited fibroblast-like morphology and formed a tight, adhesive monolayer on the surface of the culture vessel. They were sensitive to G-418, and showed negative results with IFA. To date, OKTr-1 and OKTr-23 have undergone 44 and 18 passages, respectively. Primary cultures of the lymphoid organ have not been successfully passaged beyond the primary stage.

Animals↗
PubMed1995

The effects of the interosseous membrane and partial fibulectomy on loading of the tibia: a biomechanical study.

The biomechanical basis for the treatment of delayed union of tibial fractures by partial fibulectomy has yet to be fully evaluated. To gain further insight into this problem, nine intact cadaveric lower extremities were instrumented with strain gauges on the surfaces of the tibia and fibula. The limbs were then subjected to axial loading with the ankle and subtalar joints placed in multiple positions. The specimens were loaded either through the distal femur or by direct loading of the tibial plateau. All specimens were first tested intact then after sectioning of the interosseous membrane and finally after partial fibulectomy. It was shown that during loading of the leg, the primary effects of the interosseous membrane were to stabilize the fibula and constrain its posterolateral bending. The fibular strains were not reduced to zero following sectioning of the interosseous membrane. Tibial strains measured on the anteromedial and anterolateral surfaces were consistently in relative tension, indicating a posterior bending force (anterior bowing) of the tibia. After partial fibulectomy, strains on these surfaces became relatively more compressive. With the ankle and subtalar joints in neutral position (0 degree flexion, 0 degree inversion/eversion) the strains on the anterior surface averaged approximately 10% more compressive relative to the intact condition. Tibial strains were observed to vary with the position of the ankle and subtalar joints. The fact that the anteromedial and anterolateral tibia surfaces were always in tension may explain why partial fibulectomy has not proved to be a uniformly successful treatment method for delayed union of the tibia. Furthermore, it points to the important role of "fracture personality" in the selection of treatment.

Aged↗
PubMed1995

Changes of endothelin during cerebral vasospasm after experimental subarachnoid hemorrhage.

Laser-Doppler flowmetry was employed in the observation of regional cortical blood flow (rCBF) after experimental subarachnoid hemorrhage (SAH) in anesthetized rats and the contents of endothelin (ET) in the cerebral-spinal fluid (CSF), plasma, hypothalamus, cerebral cortex, cerebellum and medulla were simultaneously measured. There was a biphasic change of rCBF after SAH. The contents of ET in CSF, plasma and hypothalamus rose prominently in the early stage after SAH, and the ET-increase in CSF and hypothalamus was earlier than that in plasma. The changes of ET contents in CSF correlated well with that in hypothalamus. Our results suggest that ET probably is an early important factor which induces cerebral vasospasm (CVS) after SAH. The increase of ET in CSF, which may originate from the hypothalamus, might play a more important role in the development of CVS after SAH than that in plasma.

Animals↗
PubMed1995

The glenohumeral-biceps reflex in the feline.

The existence of a reflex arc from the anterior aspects of the glenohumeral capsule to the long head of the biceps was determined in a feline. A single articular branch of the musculocutaneous nerve terminating in the capsule was identified and stimulated with 100 microseconds supramaximal pulse train at 10 pulses per second. It was shown tht stimulation of the musculocutaneous articular nerve elicited myoelectric discharge in the biceps muscle. Transection of the articular nerve just distal to its emergence from the main trunk of the musculocutaneous nerve abolished the myoelectric discharge in the biceps, confirming the afferent nature of this articular nerve. The mean (+/- standard deviation) time delay from the application of the stimulus to the articular nerve to the recording of the corresponding myoelectric discharge in the biceps was 2.7 (+/- 0.3) milliseconds. The existence of a reflex arc from the capsule to the biceps confirms and extends the concept of passive (ligaments) and active (muscles) restraints of a joint and the synergy between them toward maintaining shoulder stability. If demonstrated in the human, such a reflex may have significant implications in modification of surgical procedures and the design of new rehabilitation modalities for treatment of shoulder defects.

Action Potentials↗
PubMed1995

[Constituents of lignanoids in Siphonostegia chinensis Benth].

A trace monomeric compound was isolated from the aerial part of Siphonostegia chinensis, and determined by X-ray diffraction as a lignanoid compound named syringaresinol. It is obtained from this plant as well as from Scrophulariaceae for the first time.

Drugs, Chinese Herbal↗
PubMed1995

[Radiologic study of ossifying fibroma of the facial and jaw bones].

83 cases with ossifying fibroma were diagnosed by clinical, histopathological and radiological criteria, and were analyzed radiologically. Four distinct radiographic patterns were identified according to the radiodensity and shape: (1) cystic radiolucent (42.2%), (2) ground-grass (7.2%), (3) sclerotic change (9.6%), (4) mixed change of radiolucent and radiopaque (41.0%). The lesions showed a growth pattern of round expanding in all directions with well-defined margin and frequent involvement of teeth. A preliminary analysis of the relationship among the clinical, radiological and histopathological manifestations was presented. The diagnostic criteria was proposed and differentiate diagnosis was discussed.

Adolescent↗
PubMed1995

[Clinical use of conservative surgery in hypopharyngeal carcinomas].

Fifty-one cases of hypopharyngeal carcinoma treated with conservative hypopharyngectomy (CH) and 29 cases of total larygectomy hypopharyngectomy (the Control) were retrospectively analyzed. In patients with CH, laryngeal function restored completely in 36 cases, and partially in 15. Severe complication rate (including graft necrosis, fistulae and structure) was 23.5% (12/51). Successful deglutition rate was 98%; mean resumption of oral intake was 29 days (10-150 days) and mean hospitalization 40 days (16-160 days). Three-year survival rate was 58.8% and 5-year survival rate 49.0% (25/51). No significant difference was found between the patients with CH and the control in the aspects of severe complication rate, successful deglutition rate, mean resumption of oral intake, mean hospitalization and 5-year survival rate (P > 0.05).

Adult↗
PubMed1995

[Mental status and personality of infertile women].

Mental status and personality were investigated in 130 infertile women from November 1992 to May 1993 in the infertility clinic of The Second Hospital of Hunan Medical University. Causes of their infertility attributed to female (n = 65), male (n = 53), unexplained infertility (n = 12). Fifty four fertile women were recruited as normal control. A women consulting questionnaire, Eysenck personality questionnaire (EPQ), symptom checklist-90 (SCL-90), self-rating anxiety scale (SAS) and Hamilton depressive scale (HDS) were used in this study. The result showed that any level of mental pressure were found in 83.8% of infertile women, and moderate and severe in 52%. In comparison with the control, the prevalence of psychiatric symptoms were significantly higher in infertile than fertile women (P < 0.01). Infertile women were more likely to suffer from severe depression and anxiety. Their mental status were more unstable than fertile women and correlated with their personality traits. Authors emphasized that not only the somatic treatment, but also the psychological consultation and mental support should be provided in the program of the infertility management.

Adult↗
PubMed1995

Analysis of animal carcinogenicity experiments with multiple tumor types.

Because of the occult nature of tumors, the time-to-tumor is usually unobservable in animal studies of chemical carcinogenicity. In this paper, we propose new test approaches for simultaneous comparison of the marginal tumor incidence rates with several tumor types. We first set forth a model for tumor development and discuss the identifiability of parameters in this model. We then combine the results of tests for each marginal tumor incidence rate to develop simultaneous tests of all marginal tumor incidences. We apply the proposed methods to data from the ED01 study. This study, which used about 24,000 mice, was designed to determine the carcinogenic effect of the compound 2-acetylaminofluorene (2-AAF) at low dosages. We also present some simulation results to illustrate the application of simultaneous test methods to small experiments using 100 mice per dose group.

2-Acetylaminofluorene↗
PubMed1995

[Image analysis for intercellular adhesion molecule-1 expression in MRI/lpr mice: effects of Chinese herb medicine].

To clarify the role of intercellular adhesion molecule-1 (ICAM-1) on pathogenesis of autoimmune lupus nephritis in MRL/lpr mice and the effects of Chinese herb medicine (stragalin), a computer image analysis system was used to study immunodepositions of ICAM-1, immunoglobulins and C3 in renal tissue sections of the mice. ICAM-1 was found in the mesangial area and deposited along the glomerular capillary walls in MRL/lpr mice. The distribution intensity of ICAM-1, immunoglobulins and C3 were significantly decreased after treatment with stragalin in form of decoction per os in the mice. We found that ICAM-1 might play an important role in pathogenesis of autoimmune lupus nephritis in MRL/lpr mice and Chinese herb medicine has some inhibition effects on immunodepositions in renal tissue of MRL/lpr mice.

Animals↗