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Biomedical subjects

X Shi

Publications and source records attributed to X Shi.

At least 289 records · Page 16Linked to original sources
PubMed1997

Interaction of central venous pressure, intramuscular pressure, and carotid baroreflex function.

Seven healthy volunteer men participated in an experiment involving lower body positive pressure (LBPP) of 30 Torr and acute volume expansions of 5-6% (VE-I) and 9-10% (VE-II) of their total blood volume (TBV) to differentiate the effect of increased intramuscular pressure and central venous pressure (CVP) on the maximal gain (Gmax) of the carotid baroreflex. During each experimental condition, the heart rate (HR), mean arterial pressure (MAP; intraradial artery or Finapres), and CVP (at the 3rd-4th intercostal space) were monitored continuously. Gmax was derived from the logistic modeling of the HR and MAP responses to ramped changes in carotid sinus transmural pressure using a protocol of pulsatile changes in neck chamber pressure from +40 to -65 Torr. The increase in CVP during +30-Torr LBPP was 1.5 mmHg (P < 0.05) and was similar to that observed during VE-I (1.7 mmHg, P > 0.05). The Gmax of the carotid baroreflex of HR and MAP was significantly decreased during LBPP by -0.145 +/- 0.039 beats x min(-1) x mmHg(-1) (38%) and -0.071 +/- 0.013 mmHg/mmHg (25%), respectively; however, VE-I did not affect Gmax. During VE-II, CVP was significantly greater than that elicited by LBPP, and the Gmax of the carotid baroreflex of the HR and MAP responses was significantly reduced. We conclude that carotid baroreflex responsiveness was selectively inhibited by increasing intramuscular pressure, possibly resulting in an activation of the intramuscular mechanoreceptors during LBPP. Furthermore, it would appear that the inhibition of the carotid baroreflex, via cardiopulmonary baroreceptor loading (increased CVP), occurred when a threshold pressure (CVP) was achieved.

Adult↗
PubMed1997

Involvement of NF-kappaB in silica-induced cyclooxygenase II gene expression in rat alveolar macrophages.

The role of nuclear factor (NF)-kappaB transcription factor in silica-induced cyclooxygenase (COX) II gene expression was examined in the rat alveolar macrophage cell line NR8383. Our results indicate that NF-kappaB can be activated in this cell line by silica exposure. Suppression of NF-kappaB activation in these cells leads to an attenuation of COX II mRNA accumulation induced by silica. Using an electrophoretic mobility shift assay and a reporter gene assay, we provide evidence that at least two kappaB sites in the 5'-flanking region of the rat COX II gene are involved for silica-induced transcriptional control of the COX II gene. The first motif, -404 GGGGATTCCC -395, is absolutely conserved in sequence and is localized in a similar position among the COX II genes found in humans, rats, and mice. The second motif, -91 GGGGAAAGCC -82, was conserved only in the mouse and rat COX II genes in sequence and in location. Aspirin, a COX inhibitor, was shown to suppress silica-induced NF-kappaB activation. However, prostaglandin E2, one of the important downstream reaction products catalyzed by the COX enzyme, was also shown to attenuate silica-induced NF-kappaB activation by retarding the degradation of silica-induced inhibitor NF-kappaB. These results suggest that an interdependent regulation may exist between NF-kappaB activation and COX or its products.

Animals↗
PubMed1997

The role of oxygen free radicals in occupational and environmental lung diseases.

Oxygen free radicals and their metabolites, collectively described as reactive oxygen species (ROS), have been implicated in the pathogenesis of many diseases. The pulmonary system is particularly vulnerable to ROS-induced injury because of its continuous exposure to toxic pollutants from a wide variety of sources in the ambient air. Additionally, lungs are exposed systemically to ROS generated from xenobiotic compounds and endogenous sources. This review describes the sources of endogenous and exogenous ROS generation in the lung. Special emphasis is given to major sources of ROS in occupational and environmental exposures to asbestos, crystalline silica, coal, chromium, herbicides, bleomycin, and cigarette smoke. ROS-induced lung injury at different target levels may contribute to similar patterns of cell injury and alterations at the molecular level by initiation, propagation, and autocatalytic chain reactions. Intracellular signalling, activation and inactivation of enzymes, stimulation, secretion, and release of proinflammatory cytokines, chemokines, and nuclear factor activation and alterations are also common events. Understanding the interactions of these intricate mechanistic events is important in the prevention and amelioration of lung injury that results from acute and chronic exposures to toxins in ambient air.

Environmental Exposure↗
PubMed1997

[Protective effect of ciliary neurotrophic factor against the ototoxicity of gentamicin in guinea pigs].

The effect of ciliary neurotrophic factor (CNTF) on gentamycin induced deafness was observed by Preyer's reflex, auditory brainstem evoked potential, bioelectric response of the cochlea and histomorphological examination of surface preparation of cochlea. It was found that CNTF was capable of reducing ototoxicity of gentamicin in guinea pigs, thus protecting hair cells of cochlea and auditory nerves.

Animals↗
PubMed1997

[A continuous and constant rate administration method--mini-osmotic pump].

Mini-osmotic pump is a delicate administration method. When it is activated by water, mini-osmotic pump can deliver a variety of solutions or suspensions at a constant rate for days even up to several weeks. Since it is drived by osmotic pressure, the pumping rate is independent on the physical and chemical feature of the drugs. The pump from inside to outside consists of a cylindrical reservior, osmotic driving agent and semipermeable membrane.

Animals↗
PubMed1997

[Wildervanck or cervico-oculo-acoustic syndrome].

In 1952, Wildervanck described the first case of what he called the Cervico-Oculo-Acoustic (COA) syndrome, which comprises Klippel-Fetl anomalad (congenitally fused cervical vertebrae), congenital deafness and Duane's retraction syndrome (abducen's paralysis and retraction on adduction). Since the first case was reported, there have been more reports describing this triad, either completely or incompletely. A further case of this syndrome with CSF leakage is reported here and exploratory tympanotomy was performed. Abnormalities of both inner and middle ear were found. In addition, MRI and CT scan of the head revealed an abnormal cerebellum which is the second case reported in the world. And a review of literature concerning this syndrome is also presented here.

Abnormalities, Multiple↗
PubMed1997

[Surgical treatment of optic neuropathy after head trauma].

We studied the surgical treatment of patients with optic nerve injury following craniocerebral trauma. Fifteen patients aged 17 to 42 years sustained optic neuropathy after head trauma. Single lateral frontal injury occurred in 11 patients, bilateral frontal injury in 3 and temporal injury in one. After head trauma, 8 patients with visual acuity impairment had no light perception, including 3 patients who had bilateral eyelosing light perception, 5 patients who had only light perception, one who patient can count fingers. In addition, 2 patients compromised supraorbital fissure syndrome, 3 patients complicated exophthaloms, and one patients did enophthaloms. Thirteen patients underwent frontal craniotomy with bicoronal skin flap. Operative procedure obtained the lift of depressed orbital fragment, debridement of hemorrhage, and stabilization of displacement bone. The suprawall of optic canal was opened with microb drill, and longitudinal incision was performed in relatively avascular regions of the optic nerve sheath. Lateral orbital wall approach through peritoneal incision entered the orbital apex in 2 patients with supraorbital fissure syndrome, in who in decompression of suprorbital fissure and optic nervous canal were completed. For the purpose of analysis, the outcome of improvements of visual acuity after surgery was classified into five grades: no light perception, light perception, hand motion, counting fingers, and seeing acuity chart. Visual acuity improvements reaching 2 grade or more were determined as effective, and less than 2 grade as inefficient. All patients were followed up for intervals of 1 month, 3 months, and 6 months. Ten of 15 patients, who had no postoperative complication, showed the improvement of their visual acuity. Exophathaloms was recovered in 3 patients, and so did in one patient enophthalmos. Transcranial approach may be a safe and effective treatment for the treatment of traumatic optic neuropathy in the orbital, intracranial, and optic canal segments after head trauma.

Adolescent↗
PubMed1997

[The stress reaction induced by intensive noise exposure in rats].

To study the effects of sustained intensive noise on rats, fifty SD male rats were randomly divided into: control group and 1 d, 3 d, 7 d and 14 d noise exposure groups (120 dBSPL, broadband noise, 2 h daily). The results showed that after noise exposure, the ACTH level and the corticosterone level in serum increased, but the content of DA in diencephalon decreased, the weight of adrenal gland increased, while that of thymus and spleen decreased. Change of weight of adrenal gland and thymus became maximum after 7d-exposure. The ACTH level in serum and the content of DA in diencephalon decreased and the later reached the lowest value and the weight of adrenal gland and thymus returned to normal level after 14 d exposure. It indicated that the acute response began to decrease after 7d-exposure, and the response turned into a chronic inhibitory state after 14d-exposure.

Adrenal Glands↗
PubMed1997

[Effect of noise in submarine compartment on signal discrimination and arithmetic performance].

To study the effects of noise level in submarine compartment on signal discrimination and arithmetic performance, experiments were carried out on 13 subjects. The results showed that as noise level raised from moderate (73 dBA) to higher levels (85-92 dBA), work efficiency showed a progressive decrease, but when noise level reached 96 dBA the decrease in efficiency reached a steady state. The results indicated that impairment of efficiency apparently occurred at a level of 85 dBA and that the interference effect of noise was more pronounced on task performance with mental strain.

Auditory Perception↗
PubMed1997

[Preliminary study on the arsenic trioxide-induced NB4 cell apoptosis and its molecular mechanisms].

OBJECTIVE: To illustrate the possible cellular and molecular mechanisms of arsenic trioxide (As2O3) in the treatment of acute promyelocytic leukemia (APL). METHODS: APL cell line NB4 was used for in vitro studies. The effect of As2O3 on APL was studied by using flow cytometry, DNA electrophoresis, Narthern blotting and Western blotting. RESULTS: As2O3 induced NB4 cell apoptosis, while not inhibiting the growth and survival of two other leukemic cell lines (HL-60 and U937). Furthermore, As2O3 effectively down-regulated the expression of bcl-2 gene without changing the mRNA levels of other apoptosis-associated genes (including p53, c-myc, bax and bcl-XL). CONCLUSION: These might be one of the molecular mechanisms of As2O3 induced NB4 cell apoptosis.

Animals↗
PubMed1997

[In vitro study on arsenic trioxide-inducing apoptosis in primary acute promyelocytic leukemie cells].

OBJECTIVE: To illustrate mechanisms of arsenic trioxide(As2O3) in the treatment of acute promyelocytic leukemia (APL). METHODS: Cell-DNA content distribution, CD11b and CD33 antigens and nitroblue tetrazolium (NBT) reduction were evaluated in fresh APL cells from six APL patients treated in vitro with As2O3. RESULTS: As2O3 had double effects on the cells inducing apoptosis and inducing partial differentiation at higher and at lower drug concentrations, respectively. As2O3 (0.1 approximately 2.0 micromol/L) could rapidly modulate and degrade APL-specific marker molecule PML-RARalpha protein, which could play an important role in the effects of As2O3 on APL cells. CONCLUSION: As2O3 had double effects (induction of apoptosis and partial differentiation) on APL cells through the modulation and degradation of PML-RARalpha proteins.

Apoptosis↗
PubMed1997

[Comparative study on the lysis of leukemia cells by IL-2 activated bone marrow and cord blood].

OBJECTIVE: To explore the antitumor activity of IL-2 activated bone marrow (ABM) and cord blood (ACB) mononuclear cells. METHODS: The antitumor activity of ABM and ACB mononuclear cells to the K562 (NK sensitive) and HL-60 (NK resistant) cells was studied by 3H-TdR release assay and semisolid culture method. The progenitor cell activity (PCA) of ABM and ACB was also assayed. RESULTS: After coculturing for 24 hrs with IL-2, the tumor-killing activities of ABM to K562 cells and to HL-60 cells were identical, while the activity of ACB to K562 cells was higher than that to HL-60 cells. After 72 hr coculturing, the activities of ABM to K562 and HL-60 cells were still higher than that of ACB. The optimum conditions for the activation of ABM and ACB were 1000U/ml IL-2, 1 x 10(6)/ml cells, 100 : 1 effector to target ratio and 72 hr culturing. PCA was not affected after IL-2 activation, while the immunophenotypic markers changed greatly. TNFalpha and IL-6 were detectable after culturing for 24 hrs, and went higher at 72 hrs. Large granular lymphocytes were generated both in cord blood and bone marrow after 24 hr culturing with IL-2. CONCLUSION: Both bone marrow and cord blood could be activated by IL-2 and gained cytotoxic effects, but the cytotoxicity of ACB was slightly lower than that of ABM under the same culturing condition. The mechanism of cytotoxicity might be cell mediated cytotoxicity and releasing of cytokines such as TNFalpha and IL-6.

Biomarkers↗
PubMed1997

[Simultaneous determination of carotenoids and chlorophylls in algae by high performance liquid chromatography].

An isocratic reversed-phase HPLC method for the simultaneous determination of carotenoids and chlorophylls in algae is presented. Both carotenoids and chlorophylls were separated by using a C18 column and a mobile phase consisting of dichloromethane/acetonitrile/methanol/water (22.5:9.5:67.5:0.5). The flow rate was 1.0mL/min. These pigments were detected by a UV-VIS absorbance detector set at 450nm. The average recoveries of these pigments by standard addition method were 99.1% for lutein, 98.5% for alpha-carotene, 99.4% for beta-carotene, 100.6% for chlorophyll a and 99.9% for chlorophyll b. The relative standard deviations of these pigments were 2.4% for lutein, 5.6% for alpha-carotene, 6.0% for beta-carotene, 4.1% for chlorophyll a and 4.0% for chlorophyll b. The calibration curves for these pigments gave good linearity over a wide range of 0-50mg/L (r = 0.9992-0.9999). The retention times were 3.0 min for lutein, 4.7 min for chlorophyll b, 6.3 min for chlorophyll a, 14.1 min for alpha-carotene, and 14.7 min for beta-carotene. Using this method, carotenoids and chlorophylls were determined in Spirulina platensis, Chlorella vulgaris and Haematococcus lacustris. Chlorella vulgaris and Haematococcus lacustris samples were ground in a B. Braun homogenizer. Spirulina platensis sample was smashed by supersonic wave. Acetone was used as extractant.

Carotenoids↗
PubMed1997

Baroreflex regulation of blood pressure during dynamic exercise.

From the work of Potts et al. Papelier et al. and Shi et al. it is readily apparent that the arterial (aortic and carotid) baroreflexes are reset to function at the prevailing ABP of exercise. The blood pressure of exercise is the result of the hemodynamic (cardiac output and TPR) responses, which appear to be regulated by two redundant neural control systems, "Central Command" and the "exercise pressor reflex". Central Command is a feed-forward neural control system that operates in parallel with the neural regulation of the locomotor system and appears to establish the hemodynamic response to exercise. Within the central nervous system it appears that the HLR may be the operational site for Central Command. Specific neural sites within the HLR have been demonstrated in animals to be active during exercise. With the advent of positron emission tomography (PET) and single-photon emission computed tomography (SPECT), the anatomical areas of the human brain related to Central Command are being mapped. It also appears that the Nucleus Tractus Solitarius and the ventrolateral medulla may serve as an integrating site as they receive neural information from the working muscles via the group III/IV muscle afferents as well as from higher brain centers. This anatomical site within the CNS is now the focus of many investigations in which arterial baroreflex function, Central Command and the "exercise pressor reflex" appear to demonstrate inhibitory or facilitatory interaction. The concept of whether Central Command is the prime mover in the resetting of the arterial baroreceptors to function at the exercising ABP or whether the resetting is an integration of the "exercise pressor reflex" information with that of Central Command is now under intense investigation. However, it would be justified to conclude, from the data of Bevegard and Shepherd, Dicarlo and Bishop, Potts et al., and Papelier et al. that the act of exercise results in the resetting of the arterial baroreflex. In addition, if, as we have proposed, the cardiopulmonary baroreceptors primarily monitors and reflexly regulates cardiac filling volume, it would seem from the data of Mack et al. and Potts et al. that the cardiopulmonary baroreceptor is also reset at the beginning of exercise. Therefore, investigations of the neural mechanisms of regulation involving Central Command and cardiopulmonary afferents, similar to those being undertaken for the arterial baroreflex, need to be established.

Animals↗
PubMed1997

Engineering factors affecting the granulation of sludge in the UASB reactor.

The influence of inoculum sludge involving different microbial populations, different modes of stream flow and different flow rates in a bioreactor on the granulation of sludge was studied. In the granulation process there were four periods: formation of microbial floccus, formation of subcore, growth of subcore, and maturity of granules. The production of microfloccus could be attributed to acid-forming bacteria. The hydrodynamic momentum transfer caused by moving phases and the hydraulic shear effect are the crucial factors affecting the formation of the subcore. For this a new concept-the lowest limited flow rate-is proposed, i.e., the lowest flow rate to form an expanded sludge bed. A sufficient feed rate (higher than the lowest flow rate), an appropriate sludge load, and an equal distribution of feed, as well as a suitable alkalinity in the medium are the essential factors for the scaling-up and process-control of the UASB reactor.

Anaerobiosis↗
PubMed1997

Interproximal access efficacy of Sonicare Plus and Braun Oral-B Ultra compared to a manual toothbrush.

A laboratory testing method, which has previously been shown to correlate with in vivo plaque removal results, was used to test the interproximal access efficacy (IAE) of two powered toothbrushes (Sonicare Plus and Braun Oral-B Ultra), and a manual toothbrush. This method tests IAE by means of simulated interdental spaces covered with pressure-sensitive paper tightly apposed to the surface. Testing was performed under wet conditions using 70, 100 and 140 grams of brushing force. Brushing was done for 15 seconds. The pressure-sensitive papers were removed, dried, and the IAE was quantified by a blinded investigator who measured the markings on the papers with calipers. The Sonicare Plus interproximal access scores were significantly greater than both the Braun Oral-B Ultra and the manual toothbrush at all three brushing forces tested (p < 0.001). These findings demonstrate that in vitro methodology previously used for testing manual toothbrushes is also adaptable for testing powered brushes. While additional studies are needed to confirm the clinical relevance of the present study, these results demonstrate the superiority of interproximal access of the Sonicare Plus sonic toothbrush over the Braun Oral-B Ultra powered brush and a manual toothbrush using this method.

Analysis of Variance↗
PubMed1997

[Method and significance of removal of dermal epithelial components in the study of composite skin].

UNLABELLED: In order to investigate the possible re-epithelialization originated from the dermal epithelial components after trypsinization of the allo-dermis, microscopic observation, tissue culture study and histological observation after allo-grafting were adopted. The number of the hair follicles in dermal layer was counted in the study process. The results showed that a few of hair follicles in the structure of allo-dermis remained after trypsin digestion for 80 minutes. After culturing and grafting of such trypsinized dermis, none of the newly formed epithelium was observed. CONCLUSION: 1. Trypsinization of allo-dermis eliminates the antigenic epithelial components of dermis preventing the possibility of re-epithelization; 2. Strictly controled time is required while digesting the allo-dermis with trypsin.

Animals↗