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Biomedical subjects

J He

Publications and source records attributed to J He.

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

Role of sodium reduction in the treatment and prevention of hypertension.

Evidence relating dietary sodium and blood pressure comes from a variety of sources: animal experiments, observational epidemiologic studies, migration studies, and randomized controlled trials. In this review, we examine new findings in each of these areas published during 1995 and 1996. Results from both observational epidemiologic studies and randomized controlled trials demonstrated a dose-response association between dietary sodium and blood pressure in humans. The relationship of dietary sodium to blood pressure was modified by age, race, body weight, and initial level of blood pressure. On average, a 100-mmol decrease in urinary sodium was associated with a reduction of approximately 3 mm Hg in systolic and a 2 mm Hg in diastolic blood pressure. In a general population, this blood pressure reduction would substantially reduce the societal burden of cardiovascular and renal diseases.

Animals↗
PubMed1997

Kidney damage in 'benign' essential hypertension.

During the past 12 months additional evidence has emerged from observational studies indicating that high blood pressure is an important independent predictor of incident renal damage, progression of existing renal disease, and morbidity and mortality in patients with renal failure. Several of these studies suggest that elevation of systolic blood pressure is a stronger predictor of risk than a corresponding increase in diastolic blood pressure. Furthermore, the relationship between blood pressure and incident renal disease appears to be positive and continuous throughout the entire spectrum of blood pressure, including in the 'normotensive' range. Recent clinical trial experience in patients with renal insufficiency of diverse etiology supports the beneficial effect of treatment with angiotensin-converting enzyme inhibitors noted in earlier studies confined to patients with type II diabetes. Ongoing trials should help clarify optimal choice of antihypertensive medications and goals for reduction of blood pressure in prevention of renal disease. In the interim, two new guidelines for management of hypertension in patients with existing renal disease provide helpful guidance for the clinician.

Antihypertensive Agents↗
PubMed1997

A dynamic neuromuscular model for describing the pendulum test of spasticity.

Both dynamic and static thresholds, as well as the gain in the stretch reflex loop, affect the sensitivity of motoneurons to muscle stretch. How the variation in each parameter will influence the mechanical behavior of patients with spasticity is not well understood because of the difficulty in experimentally isolating individual parameters. A neuromuscular dynamic model, based on the pendulum test of spasticity, has been developed to study the specific contribution of individual parameter abnormalities in stretch reflex loops to the observed mechanical abnormalities. The model contains detailed nonlinear dynamics of muscle force generation and stretch reflexes. A computer simulation of the model indicates that the stretch reflex thresholds and the gain have different influences on the leg swing in the pendulum test of spasticity. Individual changes in the static stretch reflex threshold, in the dynamic threshold, or in the gain can not stimulate the whole spectrum of spasticity severity. When simultaneous changes in all three parameters of the stretch reflex loop occur, a small variation of the gain coupled with changes in both static and dynamic thresholds can produce increasing severity of spasticity as the thresholds further decrease. The model is also successful in simulating the effect of posture changes on spasticity.

Adult↗
PubMed1997

Rapid tyrosine phosphorylation of HS1 in the response of mouse lymphoma L5178Y-R cells to photodynamic treatment sensitized by the phthalocyanine Pc 4.

The ability of photodynamic treatment (PDT) with the phthalocyanine Pc 4 to activate cellular signal transduction pathways in murine lymphoma L5178Y-R cells has been assessed by observing increases in protein tyrosine phosphorylation at early times post-PDT. Western blot analysis with an anti-phosphotyrosine antibody revealed a dramatic increase in phosphorylation of two major protein bands of Mr approximately 80,000 and approximately 55,000 in response to PDT. The increase was PDT dose-dependent, occurred as early as 20 s after initiation of light exposure of Pc 4-preloaded cells and was amplified by the presence of the protein tyrosine phosphatase inhibitor, sodium orthovanadate (NaVO4). By immunoprecipitation, one of the Mr approximately 80,000 phosphorylated proteins has been identified as HS1, a substrate of nonreceptor-type protein tyrosine kinases. Although vanadate greatly enhanced the level and extent of PDT-induced phosphorylation, it had no influence on overall photocytotoxicity or on the rate of apoptotic DNA fragmentation. Genistein, an inhibitor of protein tyrosine kinases, diminished tyrosine phosphorylation of the Mr approximately 80,000 and other proteins and dramatically potentiated cell killing induced by PDT but did not significantly affect PDT-induced apoptosis. The results suggest that PDT rapidly activates a membrane-associated src family kinase(s) in L5178Y-R cells, one substrate of which is HS1, and that protein tyrosine phosphorylation is part of a stress response, protecting a portion of the cells from the lethal effects of PDT but not altering the mechanism by which they die.

Adaptor Proteins, Signal Transducing↗
PubMed1997

The synthesis, photophysical and photobiological properties and in vitro structure-activity relationships of a set of silicon phthalocyanine PDT photosensitizers.

Four silicon phthalocyanine photosensitizers have been prepared and studied in an effort to learn more about the structural features that a silicon phthalocyanine must have in order to be a good photodynamic therapy (PDT) photosensitizer. The compounds that have been studied are the known phthalocyanines HOSiPcOSi(CH3)2-(CH2)3N(CH3)2, Pc 4; and SiPc[OSi(CH3)2(CH2)3N(CH3)2]2, Pc 12; and the new photosensitizers HOSiPcOSi(CH3)2- (CH2)3N(CH2CH3)(CH2)2N(CH3)2, Pc 10; and SiPc[OSi (CH3)2(CH2)3N(CH2CH3)(CH2)2N(CH3)2]2, Pc 18. The triplet lifetimes of the four photosensitizers, their singlet oxygen quantum yields, their ability to photoenhance the generation of lipid peroxidation products in human erythrocyte ghosts, their ability to partition into V79 cells and their ability to photokill V79 and L5178Y-R cells have been determined. It is concluded that the presence of a small axial ligand (e.g. an OH ligand) is not necessary for efficient photosensitization, the presence of two aminosiloxy ligands generally provides at least as good photosensitization as one such ligand, and the presence of an elongated diaminosiloxy axial ligand rather than a short aminosiloxy ligand is less desirable. Further, it is concluded that the presence of structural features leading to improvement in the association between the photosensitizers and important cellular targets are more useful than those leading to improvements in their already acceptable photophysical and photochemical properties.

Animals↗
PubMed1997

Modulatory effects of regional cortical activation on the onset responses of the cat medial geniculate neurons.

Corticofugal modulation on activity of the medial geniculate body (MGB) was examined by locally activating the primary auditory cortex (AI) and looking for effects on the onset responses of MGB neurons to acoustic stimuli. Of 103 MGB neurons recorded from 13 hemispheres of 11 animals, 91 neurons (88%) showed either a facilitatory or inhibitory effect or both; of these neurons, 72 showed facilitatory effects and 25 inhibitory effects. The average facilitatory effect was large, with a mean increase of 62.4%. Small inhibitory effects (mean: -16.2%) were obtained from a few neurons (6 of 103) when a pure tone stimulus was used, whereas the effect became larger and more frequent when a noise burst stimulus was used (mean: -27.3%, n = 22 of 27 neurons). Activation of an AI site having the same best frequency (BF) as the MGB neuron being recorded from produced mainly a facilitatory effect on MGB neuronal responses to pure tones. Activation of AI at a site neighboring the BF site produced inhibitory effects on the MGB response when noise burst stimuli were used. We found that the effective stimulation sites in AI that could modulate MGB activity formed patchlike maps with a diameter of 1.13 +/- 0.09 (SE) mm (range 0.6-1.9 mm, n = 15) being larger than the patches of thalamocortical terminal fields. Examining the effects of sound intensities, of 18 neurons tested 9 neurons showed a larger effect for low-sound-intensity stimuli and small or no effects for high-sound-intensity stimuli. These were named low-sound-intensity effective neurons. Five neurons showed high sound intensity effectiveness and four were non-intensity specific. Most low-sound-intensity effective neurons were monotonic rate-intensity function neurons. The AI cortical modulatory effect was frequency specific, because 15 of 27 neurons showed a larger facilitatory effect when a BF stimulus was used rather than a stimulus of any other frequency. The corticothalamic connection between the recording site in MGB and the most effective stimulation site in AI was confirmed by injecting wheat germ agglutinin-horseradish peroxidase tracer at the stimulation site and producing a small lesion in the recording site. The results suggest that 1) the large facilitation effects obtained by AI activation at the region that directly projected to the MGB could be the result mainly of the direct projection terminals to the MGB relay neurons; 2) the large size patches of the effective stimulation site in AI could be due to widely ramifying corticothalamic projections; and 3) the corticofugal projection selectively gates auditory information mainly by a facilitatory effect, although there is also an inhibitory effect that depends on the sound stimulus used.

Acoustic Stimulation↗
PubMed1997

Rapid sensitivity changes on flickering backgrounds: tests of models of light adaptation.

To investigate mechanisms underlying sensitivity changes that are capable of following rapid variations in intensity of the background field, we measured the threshold radiance needed to detect a 2-ms probe flash presented at various phases relative to a sinusoidally flickering background. The temporal frequency, mean luminance, and modulation of the background were systematically varied. The sensitivity change consisted of two components: a phase-insensitive increase in threshold that occurs at all the phases of the background field (a change in the dc level of the threshold), and a phase-dependent variation in threshold. Both components can reliably be measured at temporal frequencies up to approximately 50 Hz. On a 30-Hz background, the threshold varied with phase over roughly 0.5 log unit within a half-cycle (17 ms). For background flicker rates of 20-40 Hz the probe threshold increased with increasing instantaneous background radiance, following a typical threshold-versus-radiance template, and approaching Weber-law behavior during the peak of the background flicker. This pattern of threshold elevation was measured at mean background illuminances from 580 to 9100 Td (trolands), with the dimmer backgrounds being slightly less effective in producing threshold elevations. The measured increase in the dc level commenced as soon as the modulation of the background flicker began, and the amount of threshold elevation followed the envelope of the background flicker, ruling out modulation gain control explanations for the change in sensitivity on flickering backgrounds. The threshold elevations measured on a 30-Hz, 25% modulation background were lower than those measured on a 30-Hz, 100% modulation background at all phases. The measured changes in threshold with changes in background modulation rule out all adaptation models consisting of a multiplicative and a subtractive adaptation processes followed by a single, late, static nonlinearity.

Adaptation, Ocular↗
PubMed1997

An abundant zebrafish cDNA clone encodes a ras-like protein which is expressed ubiquitously.

An abundant clone from a zebrafish embryonic cDNA library was identified and sequenced. It encodes a ras-like protein, being 94-95% identical to vertebrate Ran, ras-related nuclear protein. The zebrafish Ran mRNA is expressed in all tissues examined and throughout embryogenesis; therefore, it is likely that the Ran protein functions in all types of cells.

Amino Acid Sequence↗
PubMed1997

[A simple nitric oxide exposure system for small animals].

A nitric oxide exposing system was designed for experimental research, which consist of equipments such as plexiglass chamber, blower, flowmeter, NO/N2 cylinder, pure O2 cylinder, NOx analyzer, and O2/CO2 monitor. The efficacy of the whole system has been verified through our practice as shown by the following results: measured NO inside the chamber were close to designed NO concentration, measured O2 concentrations in the chamber were similar to that of the atmosphere, and the highest nitrogen dioxide (NO2) and carbon dioxide (CO2) concentrations were lower than 3 ppm and 0.3% respectively. The experimental facility is simple in construction, easy to be operated and convenient for research on effects and toxicity of long-term inhaled nitric oxide in small animals.

Administration, Inhalation↗
PubMed1997

[Clinical application of a modified small posterolateral thoracotomy in general thoracic surgery].

To assess the application of a modified thoracotomy approach in general thoracic operation. 311 general thoracic operations were performed using a modified small posterolateral thoracotomy surgical procedures included lobectomy plus lymph nodes dissection in 186, pneumonectomy in 23, esophagectomy for esophageal cancer in 23. The modified method of thoracotomy had following advantages: (1) reduce postoperative morbidity; (2) reduce bleeding and bank blood transfusion; (3) shorter operating time. This study suggested that the modified small posterolateral thoracotomy have some advantages than standard approach. It should be used in some selected thoracic operations.

Adolescent↗
PubMed1997

[The relation of the changes of SOD and PGE2 in aqueous humor with the transient rise of intraocular pressure after argon laser iridectomy].

OBJECTIVE: To study the mechanism of transient rise of the intraocular pressure (IOP) after argon laser iridectomy (ALI). METHODS: The rabbit changes of IOP, the activity of superoxide dismutase (SOD) and the concentration of prostaglandin E2 (PGE2) in aqueous 15 min, 60 min, 6 hr, 24 hr, 48 hr after ALI, the relationships of these changes with the transient rise of IOP, and the effects of using indomethacin, cortisone, vitamin E and C before ALI on the transient rise of IOP were observed. RESULTS: After ALI, the transient rise of IOP took place within postoperative 6 hr. Following the postoperative transient rise of IOP, the concentration of PGE2 in the aqueous was markedly increased, but the activity of SOD in the aqueous markedly decreased. When indomethacin, cortisone, vitamin E and C were used before ALI, the concentration of PGE2 was not markedly increased, the activity of SOD was not markedly decreased and the postoperative transient rise of IOP did not take place. CONCLUSIONS: The transient rise of IOP after ALI is related to the increase of concentration of PGE2 and the decrease of activity of SOD in the aqueous. Using indomethacin, cortisone, vitamin E and C before ALI can effectively prevent the postoperative transient rise of IOP.

Animals↗
PubMed1997

[Determination of trace silver in surface water samples by flame atomic absorption with continuous flow on-line absorption preconcentration].

In a continuous flow on-line preconcentration system, trace silver was adsorbed onto activated carbon particles packed in micro colum at pH 1, eluted with 0.3 ml of 10 g/L Na2S2O3 solution and determined by flame atomic absorption spectrometry. For surface water samples, 25 ml sufficed precise determination of silver at level of microgram/L. The relative standard deviation of 10 parallel sample determinations was 6.9%. The proposed method was successfully applied to water samples with recoveries ranging from 93.2% to 104.6% and a throughout of 7-8 sampling/h.

Silver↗
PubMed1997

[Adsorption of permanganate onto activated carbon particles].

In this paper, the adsorption behavior of permanganate onto activated carbon particles was studied as a function of pH, flow rate and the concentration of permanganate. It was found that permanganate was not adsorbed but reduced by activated carbon particles. The percent of reduction of permanganate was strongly pH-dependent. The reducing product of permanganate was mainly Mn2+ which was adsorbed onto the activated carbon particles by surface complexation.

Adsorption↗
PubMed1997

[A three-dimensional finite element stress analysis of implant-supported prosthesis and its supporting tissue in the edentulous mandible. Part 5. The influence of implant type in complete implant overdenture and its supporting tissue].

The stress distribution of implant, implant-bone interface, alveolar ridge surface and the overdenture when supported by cylindrical-type or blade-type implants under three kinds of occlusion, were investigated respectively in this study. The results showed that the extreme principle stress was greater when the denture was supported by blade-type implants than by cylindrical type one. The stress distribution of the system with application of cylindrical type implant is more acceptable.

Alveolar Process↗
PubMed1997

[A three-dimensional finite element stress analysis of implant-supported prosthesis and its supporting tissue in the edentulous mandible. Part 6. The influence of superstructure in mandibular complete implant overdenture and its supporting tissue].

The effect of superstructure, including telescope, conventional-bar and modified-bar, on the stress distribution of mandibular complete implant overdenture and its supporting tissue was investigated in this study. The results demonstrated that bar could lower the extreme principle stress of the implant, but the stress distribution of implant-bone interface was better when the implants were not linked with each other. Modified-bar is not preferred because it increases the stress of implant and its interface.

Alveolar Process↗
PubMed1997

[Study on the micellar electrokinetic capillary chromatography (MECC) for several water soluble vitamins].

In the paper, the influences of the concentration of sodium dodecyl sulphate (SDS) and borax (Na2B4O7), pH value and applied voltage on the MECC of water soluble vitamins--VB1, VB2, VB6, VB12 and VC in fused silica capillary were studied. In the system of SDS-Na2B4O7, the retention times of the vitamins mentioned above increase with the increase of concentration of SDS and Na2B4O7. But if SDS concentration is too high the separation will become worse, and if Na2B4O7 concentration is too high the peak will be broad because the increase of retention time will lead to the increase of diffusion of molecules. With the pH increasing, the separation efficiency is always increasing. The change of the applied voltage has little effect on the separation efficiency. However, at higher pH and applied voltage, the high ionic strength and large current will produce more Joule heat and cause higher background noise. The optimum run buffer for this separation contains 18mmol/L Na2B4O7 and 25mmol/L SDS, with pH at 8.5 by adjusted with hydrochloric acid. The separation was completed within 4min at an applied voltage of 14.0kV. The separation efficiencies ranged from 1.1 x 10(5) to 2.4 x 10(5) theoretical plates/meter. The application of this method to drug analysis is demonstrated.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed1997

The study of the relationship between the activity of phospholipase A2 and acute hypoxic pulmonary arterial pressure.

The role of phospholipase A2 (PLA2) and related inflammatory mediators in the mechanism of hypoxic pulmonary arterial hypertension was studied. Thirty Sprague-Dawley rats were equally divided into three groups at random: group A was the normal control group; group B was given 10% oxygen ventilation; group C was given 10% oxygen ventilation too and, at the same time, dexamethasone was injected into the external jugular vein. The pulmonary arterial pressure (PAP) was measured by inserting a microcatheter into pulmonary artery. After 30 minutes of hypoxia, the activity of PLA2, platelet activating factor (PAF), prostaglandin E2 (PGE2) and tromboxane B2 (TXB2) were measured in blood and lung tissue. After hypoxia, the mean pulmonary arterial pressure (mPAP), the PLA2 activity, PGE2, TXB2 and PAF in blood and lung tissue of group B were significantly higher than in group A; in group C the same parameters were lower than in group B. In hypoxia, a positive correlations was found between the PLA2 activity and mPAP, PAF, PGE2, TXB2 respectively; positive correlations were also found between PAF, PGE2, TXB2 and mPAP. PLA2 induced release of inflammation mediators, plays an important role in the mechanism of the acute hypoxic pulmonary arterial hypertension.

Acute Disease↗