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Biomedical subjects

X Shi

Publications and source records attributed to X Shi.

At least 451 records · Page 25Linked to original sources
PubMed1992

Rembrandt toothpaste stain prevention with and without the use of Peridex.

Sixty-five subjects were assigned to use Crest or Rembrandt dentifrice with either a placebo or Peridex rinse for eight weeks. One group, using Peridex, started with Crest and switched to Rembrandt at week four of the study. There were no significant differences among the groups on gingivitis, plaque, or calculus by the conclusion of the study. On the stain intensity index there was a significant statistical difference on buccal surfaces between Crest and Rembrandt with placebo compared to Crest with Peridex. On lingual surfaces, Rembrandt with placebo rinse was significantly lower than all Peridex rinse groups by the end of the study. From baseline to the conclusion of the study, Crest with placebo had no change in stain intensity, while Rembrandt with placebo had a significant drop on both buccal and lingual surfaces. The Peridex groups had increases on buccal stain intensity. On stain area scores, by the conclusion of the study both Crest and Rembrandt with placebo were significantly different from Crest with Peridex on buccal and lingual surfaces. Over time there was no significant change in stain area for the Crest with placebo groups. Rembrandt and placebo was significantly lower on stain area from baseline to week eight on buccal surfaces. The Peridex groups had increases in stain area over the study period.

Adolescent↗
PubMed1992

Rembrandt toothpaste: stain removal following the use of Peridex.

Eighteen subjects participated in a stain removal study following two months of Peridex use. The subjects were randomly assigned to use either Rembrandt dentifrice or Crest dentifrice for two months. Indices for stain area and intensity were taken at baseline, two, four, and eight weeks. After eight weeks' use, the Rembrandt group had a 37.1% lower stain area score on facial and 30% lower stain score on lingual surfaces compared to the Crest dentifrice group. On total surface stain area, the Rembrandt group was significantly lower than the Crest dentifrice group at p less than .05. Over eight weeks, the Rembrandt group had a significant drop in stain area while the Crest group had no significant change. On the stain intensity index, there was a 45.7% reduction on facial surfaces and 38.2% on lingual surfaces compared to the Crest dentifrice group which was significant at p less than .01.

Adult↗
PubMed1992

Comparison of the forearm and calf blood flow response to thermal stress during dynamic exercise.

To examine the hypothesis that the skin blood flow response to body heating is not uniform over the entire body surface, we compared forearm (FBF) and calf (CBF) blood flow responses to an increase in core temperature (esophageal temperature, Tes) during dynamic exercise. We studied 13 physically active men during semi-recumbent one leg exercise and/or intermittent supine cycle exercise at 35 degrees C. During 30 min of one leg exercise, Tes, FBF, and CBF in the nonactive leg increased from 36.94 +/- 0.09 degrees C, 5.7 +/- 1.2, and 5.6 +/- 0.6 ml.(min.100 ml)-1 at rest to 37.97 +/- 0.10 degrees C, 27.0 +/- 2.4, and 11.1 +/- 0.8 ml.(min.100 ml)-1, respectively. The increase in blood flow per unit increase in Tes was much less in the calf than in the forearm. The ratio of the peak to resting blood flow averaged 6.5 in the forearm and 2.5 in the calf. During 60 min of intermittent supine two leg exercise, Tes, FBF, and CBF increased from 36.96 +/- 0.06 degrees C, 7.9 +/- 1.5, and 5.6 +/- 0.7 ml.(min.100 ml)-1 at rest to 37.91 +/- 0.07 degrees C, 23.6 +/- 3.0, and 11.4 +/- 1.9 ml.(min.100 ml)-1, respectively. Skin blood flow (SkBF) in the forearm and calf was estimated by using a simple cylindrical model, assuming skin thickness and resting muscle blood flow to be 0.2 cm and 2 ml.(min.100 ml)-1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Prophylactic and therapeutic effects of acupuncture on simple obesity complicated by cardiovascular diseases.

In order to understand the prophylactic-therapeutic effects of acupuncture and moxibustion in simple obesity complicated by cardiovascular diseases, we have observed in 102 cases the changes of pathogenetic and hazardous factors and the regulating function of vegetative nerves on cardiovascular activities. The results showed that the therapeutic effect of acupuncture and moxibustion was good with a total effective rate of 88.24%. At the same time, acupuncture and moxibustion were found to have a benign conversion effect on the loin hip ratio (the pathogenetic factor), the arteriosclerotic index (the hazardous factor), and the vegetative nerve function of regulating the heart and blood vessels (the equilibrium indices of the vegetative nervous system). All this suggests that acupuncture is a treatment of choice for obesity and an important method of preventing and treating complicating cardiovascular diseases.

Acupuncture Therapy↗
PubMed1991

Studies on three structurally related phenylenediamines with the mouse micronucleus assay system.

Three structurally related compounds, 4-chloro-o-phenylenediamine (COP), 4-nitro-o-phenylenediamine (NOP) and p-phenylenediamine dihydrochloride (PPD), are used in fur dyes, inks and hair coloring formulations. COP has been reported to be carcinogenic in both rats and mice. NOP and PPD are non-carcinogens, but have consistently tested positive in short-term in vitro genotoxicity assays. Studies were undertaken to evaluate their genotoxicity with the in vivo mouse bone-marrow micronucleus assay. Five CD-1 male mice per dose were injected i.p. with the compounds and sacrificed at intervals of 24, 48 and 72 h. 2000 cells were scored per animal to determine the frequency of micronucleated-polychromatic erythrocytes (MPCE). COP induced significant dose-related increases in MPCE over the 3 doses tested at each of the sampling intervals. The peak response occurred at 24 h. No response was observed in animals treated with PPD or NOP.

Animals↗
PubMed1991

Antioxidant behaviour of caffeine: efficient scavenging of hydroxyl radicals.

Considerable controversy exists in the literature regarding the toxicity of coffee, including its possible carcinogenic and anticarcinogenic properties. This study reports on the reaction of 1,3,7-trimethylxanthine (caffeine) with the hydroxyl radical (.OH), as investigated by electron spin resonance (ESR) spin trapping. The .OH was generated by the Fenton reaction (Fe2+ + H2O2) as well as by the reaction of chromium(V) with H2O2. The results show that caffeine effectively scavenges .OH with a reaction rate constant of approximately 5.9 x 10(9) M-1 sec-1 that is comparable with those of other efficient .OH radical scavengers. ESR measurements provide evidence that a caffeine-derived oxygen-centred radical is formed in the reaction of caffeine with .OH and suggest a biochemical basis for the understanding of the reported anticarcinogenic properties of caffeine and related methylxanthine compounds.

Antioxidants↗
PubMed1991

Cardiopulmonary baroreflex control of forearm vascular resistance after acute blood volume expansion.

We report the stimulus-response characteristics of cardiopulmonary (CP) baroreflex control of forearm vascular resistance (FVR) in young adult male volunteers before and after: 1) blood volume expansion (8 ml/kg infusion of 5% human serum albumin solution, n = 5) and 2) a redistribution of blood volume toward the heart (6 degrees head-down tilt (HDT), n = 6). We assessed the relationship between reflex stimulus (i.e., changes in central venous pressure (CVP] and response (i.e., FVR) during unloading of CP mechanoreceptors with lower body negative pressure (0 to -20 mm Hg). Changes in CVP were estimated from changes in venous pressure of a large peripheral vein of the dependent arm with the subject in the right lateral decubitus position. In all conditions, reflex forearm vasoconstriction occurred in response to a reduction in estimated CVP. The absolute change in FVR per unit of CVP was reduced from -4.24 +/- 1.68 to -2.15 +/- 1.16 units/mm Hg (p less than 0.05) following blood volume expansion but was similar before (-3.34 +/- 0.89 units/mm Hg) and during 6 degrees HDT (-3.30 +/- 0.92 units/mm Hg). The reduced sensitivity of the CP baroreflex following volume expansion was manifested primarily as a smaller FVR response to LBNP (p less than 0.05). Blood volume expansion and 6 degrees HDT increased resting estimated CVP by 1.5 and 0.9 mm Hg, respectively (p less than 0.05) and resting levels of FVR decreased slightly.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Experimental research of the effect of polysaccharides in semen Ziziphis Spinosae and Ziziphis Spinosae on enhancing the immune function of mice injured by radiation].

This article surveys the pharmacological effect of the polysaccharides in Semen Ziziphis Spinosae and Ziziphis Spinosae. The result shows that oral administration of this polysaccharide (0.1g/kg/d) can strengthen the immune function of cells nd body fluids and to a certain extent protect mice from radioactive injuries.

Animals↗
PubMed1991

[The catabolism of radioiodinated anti-lung-cancer monoclonal antibodies in tumor-bearing nude mice].

Nude mice bearing humor lung cancer xenografts were injected intravenously or intraperitoneally with a mixture of radioiodinated anti-lung-cancer monoclonal antibodies, 2E3 and 6D1. The blood radioactivity versus time curve was fitted to a two-compartment open model with a 3.4 day blood radioactivity clearance half-life and a 636 ml/kg apparent distribution volume. Radioiodinated 2E3 and 6D1 given intraperitoneally were rapidly absorbed, with a 2.08 absorption half-life and 89% bioavailability. The highest radioactivity levels were found in the tumor, blood, liver and spleen 1-3 days after injection; next came the lung, kidney, stomach and intestine. The relative radioactivity increased in the tumor as levels in blood and normal tissues decreased. The in vivo deiodination of radioiodinated 2E3 and 6D1 was about 18.6% and free radioiodine was excreted in the urine.

Animals↗
PubMed1991

Two-day preservation of major organs with autoperfusion multiorgan preparation and hibernation induction trigger. A preliminary report.

A new autoperfusion multiorgan preparation was studied in which the heart and lungs were removed with the liver, pancreas, duodenum, and both kidneys en bloc while being perfused by the heart and oxygenated by the lungs. A respirator with 50% oxygen was used for ventilation. Fresh blood, glucose, electrolytes, mannitol, and antibiotics were given through the portal vein. Fifteen mongrel dogs were used. In the study group (seven dogs), 10 ml of plasma containing hibernation induction trigger, obtained from deeply hibernating woodchucks, was given intravenously 2 hours before the operation, and 4 ml was given every 4 hours during the preservation period. In the control group (eight dogs), no hibernation induction trigger was used. Survival time in the study group ranged from 33 to 56 hours (mean 43.4 +/- 4.1 hours), longer than that of the control group, which was 9 to 31 hours (mean 16.2 +/- 2.6 hours, p less than 0.001). In the study group aortic systolic pressure ranged from 64 +/- 5 to 92 +/- 7 mm Hg, arterial oxygen tension from 180 +/- 35 to 285 +/- 66 mm Hg. Urine output ranged from 15 to 70 ml/hour. Blood urea nitrogen declined from 15.6 +/- 2.5 to 6.6 +/- 1.3 mg/dl (p less than 0.01); creatinine declined from 0.8 +/- 0.03 to 0.3 +/- 0.01 mg/dl (p less than 0.01). Severe liver congestion and premature renal failure occurred in the control group but did not occur in the study group. In the study group one lung was transplanted after 33 hours of preservation with simultaneous contralateral pulmonary artery ligation. Good lung function was maintained after transplantation. Although the exact mechanism by which hibernation induction trigger extends tissue survival time is still not clear, its effect on organ preservation is profound. This study also produced one of the longest average survival times for organ preservation.

Animals↗
PubMed1991

Clinical evaluation of the Plak Trac toothbrush.

Three separate studies have been conducted to evaluate the clinical safety and efficacy of the Plak Trac mechanical toothbrush. In an exaggerated use study, volunteers used the product a minimum of five times a day for eight days. Soft tissue evaluations were conducted before and at various times after use of the Plak Trac brush throughout the study. No tissue irritation related to product use was observed or reported at any time in the study. In a thirty-day at-home use study the Plak Track brush was compared to the Colgate ADA-approved manual toothbrush. Plak Trac was consistently more effective than the Colgate brush on plaque removal, at higher statistical levels. Both brushes were effective in decreasing the gingival index during the study. In a one-time use test, Plak Trac, Interplak, and the Oral B 35 manual brush were evaluated for plaque removal efficacy. All brushes significantly reduced both smooth surface and interproximal plaque scores. On total smooth surfaces Plak Trac was significantly more effective than the Interplak brush.

Adolescent↗
PubMed1990

On the physicochemical properties of gellan gum.

This paper concerns the behavior in dilute and demidilute solutions of deacetylated gellan. The conformational transition, controlled by temperature and ionic strength, is investigated. It corresponds to a double-helix single-chain transition. Large ionic selectivity is observed in the helical conformation th at controls the degree of aggregation upon gelation. Potentiometry and conductivity measurements are interpreted in terms of the Manning polyelectrolyte theory in the sol state.

Carbohydrate Conformation↗
PubMed1989

Electron spin resonance investigation of laser and heated metal-tip-induced free radical formation in various tissues.

The short-lived free radical formation accompanying laser irradiation and laser-heated metal tip contact was examined using electron spin resonance (ESR) spin-trap methodology. Various tissues (canine myocardium, human aorta, liver, and spleen) were irradiated by argon-ion (continuous wave [CW] and pulse) and YAG (CW) lasers employing both naked fiber and a laser-heated metal tip. All showed the formation of primarily carbon-centered, not oxygenated, free radicals, together with some minor unidentified species. This implies that the backbones of amino acids, lipids, or other biological building blocks are cleaved during the irradiation or thermal treatment. Different tissues produce similar radicals but with different amounts when irradiated by argon-ion, YAG, and laser-heated metal tip sources. The amount of the free radicals formed depends on the laser power (within 5-15 W). Compared to the naked fiber, the laser-heated metal tip shows the generation of at least twice the amount of free radicals. The possible relationship of the free radical formation to tissue injury is briefly discussed.

Animals↗