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Biomedical subjects

X Yu

Publications and source records attributed to X Yu.

At least 307 records · Page 17Linked to original sources
PubMed1996

Production of cellulose II by Acetobacter xylinum in the presence of 2,6-dichlorobenzonitrile.

This report provides X-ray diffraction and Raman spectral evidence that, when 2,6-dichlorobenzonitrile is present in the culture medium, Acetobacter xylinum, which is a model system for investigation of the biosynthesis of native cellulose, produces cellulose II, as well as cellulose I. The significance of the observations with respect to the mechanism of biosynthesis of cellulose is discussed briefly.

Cellulose↗
PubMed1996

Evidence for expression of vasopressin V2 receptor mRNA in human lung.

Studies using fetal sheep, goats, and guinea pigs indicate that vasopressin may play a role in preparing the fetal lung for the transition from a uterine to an air-breathing environment by slowing lung liquid secretion. The mechanism of vasopressin action is believed to occur through V2 receptors with subsequent activation of amiloride-sensitive sodium channels. However, the presence of the V2 receptor in human lung has not yet been documented. In the present study, expression of the vasopressin V2 receptor in fetal and adult human lung was examined using reverse transcription-polymerase chain reaction (RT-PCR), Northern blot analysis, and DNA sequencing. Using RT-PCR and primer pairs specific for the human V2 receptor, PCR products of the predicted sizes of 512 and 862 bp were obtained from adult human lung. DNA sequencing of the cloned PCR products revealed exact identity with the published sequence for the V2 receptor. Northern blot analysis revealed the expression of a approximately 1.9 kb mRNA in adult human lung as well as in kidney, but not in fetal human lung at 22-24 weeks of gestation. However, using the more sensitive RT-PCR assay the 862-bp product was successfully amplified from human fetal lung, although the data indicate the mRNA for this receptor is expressed in lower levels than in adult human lung or kidney. Using RT-PCR and primers specific for the rat V2 receptor, a PCR product of the predicted size of 461 bp was amplified from adult rat lung and kidney, despite an earlier report that this receptor mRNA is absent from the lung of this species. The role for the V2 receptor in adult human lung is unknown at this time, but, as in the human kidney and lungs of fetal sheep, goats, and guinea pigs, this receptor may play a role in fluid balance.

Adult↗
PubMed1996

Inhibition of GABA-gated chloride channels in brain by the arachidonic acid metabolite, thromboxane A2.

Previously, we showed that arachidonic acid and prostaglandin metabolites inhibited GABAA responses in rat cerebral cortex. Thromboxane A2 (TXA2), a metabolite of arachidonic acid, has potent actions on blood vessels and platelets, but its actions on neurons are not known. Here, we examined the effects of several TXA2 analogs on the functional and binding characteristics of GABAA receptors in rat brain. The stable analogs of TXA2, pinane and carbocyclic TXA2, and the TXA2 agonist, U-46619, inhibited muscimol-induced 36Cl- uptake in cerebral cortical synaptoneurosomes. Carbocyclic TXA2 decreased the maximal response to muscimol, consistent with a non-competitive interaction. The TXA2 antagonist, SQ 25,548, did not block the effects of either arachidonic acid or carbocyclic TXA2. Neither the biologically inactive metabolite of TXA2, TXB2, nor carbacyclin, a stable analog of prostacyclin (prostaglandin I2) had an effect on GABAA responses. Thus the pharmacology differs from that in vascular smooth muscle and platelets. To determine if GABAA receptors were sensitive to the thromboxanes, the effect of pinane TXA2 on the binding of [35S]t-butylbicyclophosphorothionate ([35S]TBPS) to GABA-gated Cl- channels was measured using receptor autoradiography. Pinane TXA2 inhibited [35S]TBPS binding in a regionally selective and non-competitive manner; the greatest inhibition was in the cerebral cortex, hippocampus and striatum, areas which are selectively vulnerable to cerebral ischemia. We conclude that TXA2 can interact with neuronal membranes to inhibit GABA receptor function, independent of its actions on the cerebrovasculature and on glial cells. This may be important during pathologic states such as ischemia, when TXA2 accumulates in extracellular spaces.

Animals↗
PubMed1996

CD95-induced apoptosis of lymphocytes in an immune privileged site induces immunological tolerance.

We examined the relationship between cell death and tolerance induction following antigen injection into the anterior chamber of the eye. Our data show that when inflammatory cells undergo apoptosis following infection with HSV-1, tolerance to the virus was observed. In contrast, when cell death was absent due to defects in Fas or FasL, immune tolerance was not observed. Further studies revealed that cell death and tolerance required that the lymphoid cells be Fas+ and the eye be FasL+. Additionally, we show that while Fas/FasL-mediated apoptosis occurred in the eye, it was apoptotic cell death that was critical for tolerance induction. Our results further demonstrate immune privilege is not a passive process involving physical barriers, but is an active process that employs an important natural mechanism to induce cell death and immune tolerance.

Animals↗
PubMed1996

Interaction between effects of parathyroid hormone and bisphosphonate on regulation of osteoclast activity by the osteoblast-like cell line UMR-106.

Treatment of osteoblasts by either parathyroid hormone (PTH) or bisphosphonate can affect their regulation of the bone-resorbing activity of osteoclasts in vitro, leading to increased and decreased resorption, respectively. To address this issue, we have examined the interaction between the effects of PTH and bisphosphonate on the regulation of osteoclast activity by the PTH-responsive osteoblast-like cell line UMR-106. When rat osteoclasts were cocultured with UMR-106 cells on bovine bone slices in the presence of 10(-8) mol/L PTH, the number of resorption pits was increased 4.2-fold, whereas the addition of UMR-106 cells or PTH alone had no effect. Pretreatment of the UMR-106 cells for 5 min with increasing concentrations of either of the bisphosphonates, clodronate, and ibandronate before coculture with osteoclasts in 10(-8) mol/L PTH, caused a dose-dependent reduction in the formation of resorption pits, reaching the maximal inhibition level (60%-75% below the control) at approximately 10(-9) mol/L clodronate and 10(-11) mol/L ibandronate. Addition of conditioned medium (CM) from untreated UMR-106 cells to rat osteoclasts had no effect on pit formation, whereas CM from UMR-106 cells pretreated with ibandronate reduced the osteoclastic bone resorption by approximately 40%. However, this effect was abolished by the subsequent culture of the ibandronate-pretreated UMR-106 cells in 10(-8) mol/L PTH before harvesting the CM, because both this CM and CM from non-pretreated UMR-106 cells cultured in 10(-8) mol/L PTH caused an approximately 75% increase in pit formation when added to rat osteoclasts. In conclusion, osteoclastic bone resorption can be directly affected independently as well as at the same time by the ibandronate-induced osteoclast-inhibiting factor and the PTH-induced osteoclast-stimulating factor. The final level of bone resorption depends on the relative concentration of these two factors.

Animals↗
PubMed1996

Ret 1, a cis-acting element of the rat opsin promoter, can direct gene expression in rod photoreceptors.

The Ret 1 element, located at -136 to -110 in the rat opsin promoter, binds developmentally regulated retinal nuclear proteins. A similar sequence is found up-stream of opsin genes, from humans to Drosophila, as well as many other photoreceptor-specific genes. The function of the Ret 1 element was tested both in vitro and in two sets of transgenic mice. A mutated Ret 1 element did not bind retinal nuclear proteins in vitro. The same mutations in an otherwise normal 1.9-kb rat opsin promoter failed to drive expression of a lacZ reporter gene in nine of 12 lines. In the three other lines, expression in photoreceptors was very faint. Four tandem copies of the Ret 1 element maintained the Ret 1 binding specificity in vitro and were able to direct expression of a lacZ transgene in photoreceptors of all nine mouse lines obtained. In two lines, expression was also detected in the ganglion cell layer and the ciliary epithelium. In three lines, a characteristic pattern of expression was found in the nervous system in addition to the normal retinal expression. These results indicate that Ret 1 can and is necessary to drive gene expression in rod photoreceptors. Furthermore, our results suggest that Ret 1-like elements may also be important in the developing nervous system.

Animals↗
PubMed1996

Changes in average blood pressure and incidence of high blood pressure 1983-1984 to 1987-1988 in four population cohorts in the People's Republic of China. The PRC-USA Cardiovascular and Cardiopulmonary Epidemiology Research Group.

OBJECTIVE: To assess comparative changes in systolic and diastolic blood pressure and incidence of high blood pressure over 4 years, and factors related to these changes, in northern and southern, urban and rural adults in the People's Republic of China. SETTING: This is a prospective study of populations surveyed by standardized methods in 1983-1984 and 1987-1988 in north China, Beijing area steel mill workers and farmers, and south China, Guangzhou area shipyard workers and farmers. SUBJECTS: The subjects were 8805 men and women aged 35-54 years at baseline (1983-1984), of whom 7338 were non-hypertensive (systolic blood pressure < 140, diastolic blood pressure < 90 mmHg, not being administered antihypertensive drugs). MAIN OUTCOME MEASURES: The main outcome measures were 4-year changes in systolic and diastolic blood pressures and the 4-year incidence of high blood pressure in persons not hypertensive at baseline. RESULTS: At baseline, the average systolic and diastolic blood pressures were higher for Beijing than for Guangzhou cohorts. At resurvey the average systolic blood pressure had increased for seven of eight sex-city-setting cohorts (all but Guangzhou urban men). The Beijing urban cohorts had the greatest increases (men 6.2 mmHg, women 4.9 mmHg, slopes of 1.6 and 1.2 mmHg/year). The incidence of high blood pressure was higher for Beijing than for Guangzhou cohorts in all four comparisons (men and women, urban and rural). Beijing men, urban and rural, had the highest incidence rates (about 21%). In multiple logistic analyses by sex, variables significantly related to 4-year high blood pressure incidence were city, baseline systolic blood pressure and body mass index, change in weight, and, for men, baseline alcohol use and heart rate. CONCLUSION: Modifiable lifestyle traits, previously shown to be related to blood pressure and high blood pressure in cross-sectional studies, also relate to the incidence of hypertension.

Adult↗
PubMed1996

Emergency department walk-in patients study.

We conducted a 25-week study of the emergency department's (ED) walk-in patients at a university hospital, covering 20% of the total period by a Latin square method of 6-h blocks. One thousand eight hundred walk-in patients entered the study group. The walk-in population represents approximately 44% of the total ED population. Our results reveal that the study population was predominantly male, aged less than 40 years but somewhat younger than the general population and had a relatively stable place of abode. Trauma and medical patients were respectively 46% and 53%. Eight-six per cent of the trauma patients came to the ED on their own initiative and less than 3 h after the accident or injury, while 43% of the medical patients were referred by a medical practitioner and had a relatively longer duration of symptoms. Forty-eight per cent of the medical patients visited the ED 12 h after the onset of symptoms. Although this study only concerned ED walk-in patients, the admission rate of medical patients is relatively high: 47% as opposed to the trauma patients' 10%. About 10% of the walk-in patients were classified as 'symptoms, signs and ill-defined conditions' according to the International Classification of Diseases 9. Fifty-two per cent of these patients were discharged home. This group of patients requires further investigation.

Acute Disease↗
PubMed1996

Transcriptional activation of promoters of the superoxide and multiple antibiotic resistance regulons by Rob, a binding protein of the Escherichia coli origin of chromosomal replication.

The Rob protein, isolated on the basis of its ability to bind to the right arm of the Escherichia coli origin of chromosomal replication, is about 50% identical in amino acid sequence to SoxS and MarA, the direct regulators of the superoxide (soxRS) and multiple antibiotic resistance (mar) regulons, respectively. Having previously demonstrated that SoxS (as a MalE-SoxS fusion protein) and MarA are essentially identical in their abilities to activate in vitro transcription of genes of the sox-mar regulons, we investigated the properties of Rob as a transcriptional activator. We found that Rob (i) activates the transcription of zwf,fpr,fumC, micF, nfo, and sodA, (ii) requires a 21-bp soxbox-marbox-robbox sequence to activate zwf transcription, (iii) protects the soxbox/marbox/robbox from attack by DNase 1, (iv) is ambidextrous, i.e., requires the C-terminal domain of the alpha subunit of RNA polymerase for activation of zwf but not fumC or micF, (v) bends zwf and fumC DNA, and (vi) binds zwf and fumC DNA as a monomer. Since these transcription activation properties of Rob are virtually identical to those of MalE-SoxS and MarA, it appears as if the E. coli genome encodes three genes with the same functional capacity. However, in contrast to SoxS and MarA, whose syntheses are induced by specific environmental stimuli and elicit a clear defense response, Rob is expressed constitutively and its normal function is unknown.

Bacterial Proteins↗
PubMed1996

Human immunodeficiency virus type 1 envelope protein endocytosis mediated by a highly conserved intrinsic internalization signal in the cytoplasmic domain of gp41 is suppressed in the presence of the Pr55gag precursor protein.

The mechanisms involved in the incorporation of viral glycoproteins into virions are incompletely understood. For retroviruses, incorporation may involve interactions between the Gag proteins of these viruses and the cytoplasmic domains of the relevant envelope (Env) glycoproteins. Recent studies have identified within the cytoplasmic tail of the human immunodeficiency virus type 1 (HIV-1) Env protein a tyrosine-containing internalization motif similar to those found in the cytoplasmic domains of certain cell surface proteins that undergo rapid constitutive endocytosis in clathrin-coated pits. Given that surface expression of the HIV-1 Env protein is essential for the production of infectious virus, the presence of this internalization motif is surprising. We show here that in contrast to the rapid rate of Env protein internalization observed in cells expressing the Env protein in the absence of other HIV-1 proteins, the rate of internalization of Env protein from the surfaces of HIV-1-infected cells is extremely slow. The presence of the Pr55gag precursor protein is necessary and sufficient for inhibition of Env protein internalization, while a mutant Pr55-gag that is incapable of mediating Env incorporation into virions is also unable to inhibit endocytosis of the Env protein. The failure of the Env protein to undergo endocytosis from the surface of an HIV-1-infected cell may reflect the fact that the proposed interaction of the matrix domain of the Gag protein with Env during assembly prevents the interaction of Env with host adaptin molecules that recruit plasma membrane molecules such as the transferrin receptor into clathrin-coated pits. When the normal ratio of Gag and Env proteins in the infected cells is altered by overexpression of Env protein, this mechanism allows removal of excess Env protein from the cell surface. Taken together, these results suggest that a highly conserved system to reduce surface levels of the Env protein functions to remove Env protein that is not associated with Gag and that is therefore not destined for incorporation into virions. This mechanism for the regulation of surface levels of Env protein may protect infected cells from Env-dependent cytopathic effects or Env-specific immune responses.

Amino Acid Sequence↗
PubMed1996

Promoters for synthesis of the pre-C and pregenomic mRNAs of human hepatitis B virus are genetically distinct and differentially regulated.

Two similar, yet functionally distinct genomic RNAs are transcribed from the DNA genome of the human hepatitis B virus. The pre-C RNAs encode the precore protein which is proteolytically processed to yield e antigen. The pregenomic RNAs encode both the nucleocapsid protein and reverse transcriptase and serve as the templates for viral DNA replication. To determine whether synthesis of these two RNAs is directed from a single or a closely spaced pair of promoters, we introduced point and insertion mutations into the basal elements of the promoter that directs their synthesis. Transcription from these mutants was examined both in cell-free transcription systems derived from hepatoma (HepG2) and nonliver (HeLa) cell lines and by transient transfection of hepatoma cell lines (Huh7 and HepG2). The data from these experiments indicated that synthesis of the pre-C and pregenomic RNAs is directed by two distinct promoters and that the basal elements of these two promoters partially overlap, yet are genetically separable, with each consisting of its own transcriptional initiator and a TATA box-like sequence situated approximately 25 to 30 bp upstream of its sites of initiation. A 15-bp insertion was found to be sufficient to physically separate these two promoters. Furthermore, these two promoters can be differentially regulated, with the transcriptional activator Sp1 specifically activating transcription from the pregenomic promoter and the hepatocyte nuclear factor 4 specifically repressing transcription from the pre-C promoter. Thus, we conclude that the promoters used in synthesis of the pre-C and pregenomic mRNAs are genetically distinct and separately regulated.

Base Sequence↗
PubMed1996

decapentaplegic, a target gene of the wingless signalling pathway in the Drosophila midgut.

dishevelled, shaggy/zeste-white 3 and armadillo are required for transmission of the wingless signal in the Drosophila epidermis. We show that these genes act in the same epistatic order in the embryonic midgut to transmit the wingless signal. In addition to mediating transcriptional stimulation of the homeotic genes Ultrabithorax and labial, they are also required for transcriptional repression of labial by high wingless levels. Efficient labial expression thus only occurs within a window of intermediate wingless pathway activity. Finally, the shaggy/zeste-white 3 mutants revealed that wingless signalling can stimulate decapentaplegic transcription in the absence of Ultrabithorax, identifying decapentaplegic as a target gene of wingless. As decapentaplegic itself is required for wingless expression in the midgut, this represents a positive feed-back loop between two cell groups signalling to each other to stimulate each other's signal production.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Stereotactic intratumour irradiation with nuclide for craniopharyngiomas.

OBJECTIVE: Craniopharyngiomas is a kind of intractable tumor in neurosurgery. Since the radical excision is very difficult and occasionally hazardous because of its deep location and close neighbouring to critical cerebral structures, it is necessary to look for a simple and effective method. PATIENTS AND METHODS: Stereotactic intratumour irradiation with instillation of nuclide colloid was performed in 220 patients with craniopharyngiomas (altogether 265 times), of whom, 130 were male and 90 female. Their ages ranged from 5 to 69 years. The syndromes of optic path's impairment were present in all of the patients. CT or MRI scan showed cystic tumour in 125 patients, solid and cystic in 80 and solid in 15. No severe complications and death were related to the operation. RESULTS: 150 patients were followed up for 2 months to 7 years (average 3.5 years). Tumours disappeared in 92 patients (61.4%), decreased dramatically in 20 (13.4%), decreased less than 50% in 19 (12.6%), and increased in 15 (10%); and there were 4 deaths (2.6%). CONCLUSIONS: Stereotactic intratumour irradiation with instillation of nuclide colloid is effective in the patients with craniopharyngiomas. Beta-emitting isotopes (P-32 and Y-90) are the preferred internal radiation source because of their limited penetration of the energy released and the greater ease of handling. A calculated dose of 20 000 rads to the cyst wall is recommended.

Adolescent↗
PubMed1996

[US-guided microwave in the treatment of liver cancer: experimental study and preliminary clinical application].

OBJECTIVE: To completely coagulate deep tumor and protect normal tissue by using microwave electrode is vivo and in vitro animal experimental study, under US-guided percutaneous microwave coagulation. METHOD: The Ultrasound Microwave Therapy-I (UMT-I) equipment was utilized at 2450 MHz in frequency. RESULTS: Microwave coagulation could produce a stable necrosis area of 2cm in diameter with irradiation at 60-80W for 60-180 seconds, and the corresponding temperature at its surrounding area was 61.95 +/- 5.81 degrees C. Microwave induced coagulation of tumor correlated well with the sonographic changes. The shape of coagulated area was elliptic when 27 mm or 9 mm of the inner conductor of electrode was exposed, and the temperature of the shaft of the electrode raised smaller and slowly based on our animal experimental study, 15 nodules of 12 patients with liver cancer were microwave-coagulated under US-guide. The temperature of tumor surrounding area raised to 54-69.5 degrees C during operation. After treatment, all lesions had smaller size, hypoechogenicity and disappearance of blood flow. AFP titer dropped in 7 patients and normalized in 4. CONCLUSION: US-guided microwave for the treatment of liver cancer is effective in coagulating deep tumor and protecting normal tissue.

Animals↗
PubMed1996

[Clinical analysis of bacterial vaginosis in 76 cases].

OBJECTIVE: To study the clinical manifestation and treatment of bacterial vaginosis (BV). METHODS: The criteria used for diagnosis were the presence of clue cells by wet mount slide or gram stain, plus at least 2 of the following 3 signs and symptoms: (1) vaginal discharge with pH > 4.5; (2) an increased thin homogeneous vaginal discharge; (3) positive amine test. From 1994, 1 to 1995, 3, a total of 76 cases with BV who had good follow up were diagnosed and treated by Kejunning (a combination of chinese traditional herb medicine), Shuangzuotai (combined metronidazole vaginal suppository), metronidazole, etc. RESULTS: For BV, the presence of clue cells is a prerequisite for diagnosis. Vaginal discharge with pH > 4.5 and positive amine test were present in all the cases. Increased white thin homogeneous vaginal fluid were found in 96.1% (73/76) of the cases. 79.0% of the patients complained of fishy odor vaginal discharge. Treatment with antibiotics or Shuangzuotai were effective. Kejunning had a cure rate of 70.0% one month after treatment. CONCLUSIONS: The detection of clue cell is an important diagnostic criterion. Besides metronidazole, Kejunning had a good result for the treatment of BV as well.

Adult↗