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Biomedical subjects

T Li

Publications and source records attributed to T Li.

At least 541 records · Page 30Linked to original sources
PubMed1991

A field study of cold effects among cold store workers in China.

A field study was carried out among cold store workers in China. A self administrative questionnaire and health check-up were taken among 463 male workers from two different types of cold stores, all during their whole daily work. 296 men from Lower Temperature Stores (LTS), where the air temperature was between -10 to -25 degrees C, and 167 men from Ice Stores (IS), where the air temperature was between -5 and +5 degrees C participated. Another group of 152 men working in normal stores and exposed to an air temperature between 20 and 30 degrees C served as a control group. The study did not indicate any special disease attributable to the cold environment. The number of complaints of lower back pain and knee pain in the cold exposed group were significantly higher than that of the control group (in LTS: 42.3%, 46.6%; IS: 52.7%, 50.8%; control group: 9.2%, 14.5%; low back and knee pain, respectively). After 5 years of cold exposure work, the lower back and knee symptoms were very frequent. The point press pain on the knees of the cooler group (LTS) was higher than in the moderate cold group (IS). We suppose that the cold factor contributed to lower back and knee pain. 12.2% of 463 cold exposed workers had frostbite on the body extremities viz: hand, foot and ear. Self estimation of health indicated more problems among cold exposed workers (28.0%) than control group (2.7%).

Adult↗
PubMed1991

[Determination of naphthoquinones in tissue cultured Zicao].

A simple, sensitive and accurate method for the separation and determination of the naphthoquinones, deoxyshikonin (I), acetylshikonin (II) and beta-beta-dimethylacrylshikonin (III) in tissue cultured Zicao is described. The sample solution was applied at a point 1 cm from the bottom edge of the TLC silica gel plate (10 x 15 cm). A mixture of n-hexane-acetone-chloroform-glacial acetic acid (13:0.3:0.2:0.05 v/v) was used as the developing solvent. The plate was saturated for 30 min and then developed twice for 15 cm using ascending technique. The spots were scraped off and extracted with CHCl3, then determined spectrophotometrically. The standard curve was linear in the range of 0.65-2.25 micrograms for the naphthoquinones. The method has been applied to the analysis of different samples. This method can be used for the quality control of naphthoquinones in tissue culture products.

Chromatography, Thin Layer↗
PubMed1990

Retinal degeneration in the rd mouse is caused by a defect in the beta subunit of rod cGMP-phosphodiesterase.

Mice homozygous for the rd mutation display hereditary retinal degeneration and the classic rd lines serve as a model for human retinitis pigmentosa. In affected animals the retinal rod photoreceptor cells begin degenerating at about postnatal day 8, and by four weeks no photoreceptors are left. Degeneration is preceded by accumulation of cyclic GMP in the retina and is correlated with deficient activity of the rod photoreceptor cGMP-phosphodiesterase. We have recently isolated a candidate complementary DNA for the rd gene from a mouse retinal library and completed the characterization of cDNAs encoding all subunits of bovine photoreceptor phosphodiesterase. The candidate cDNA shows strong homology with a cDNA encoding the bovine phosphodiesterase beta subunit. Here we present evidence that the candidate cDNA is the murine homologue of bovine phosphodiesterase beta cDNA. We conclude that the mouse rd locus encodes the rod photoreceptor cGMP-phosphodiesterase beta subunit.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1990

Beta-subunit of bovine rod photoreceptor cGMP phosphodiesterase. Comparison with the phosphodiesterase family.

A group of cDNA clones encoding the beta-subunit of bovine rod photoreceptor cGMP phosphodiesterase were isolated for structural analysis. The encoded polypeptide has 853 residues with a calculated molecular mass of 98 kDa. The beta-subunit is 72% identical to the rod cGMP phosphodiesterase alpha-subunit. Like the alpha-subunit and the cone alpha'-subunit, the beta-subunit belongs to the family of phosphodiesterase genes. The beta- and alpha-subunits are more similar to each other than either is to the cone alpha'-subunit, suggesting either that the beta- and alpha-subunits diverged more recently or that their divergence was restrained by the rod functional environment.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1990

Genetic mapping demonstrates that the alpha-subunit of retinal cGMP-phosphodiesterase is not the site of the rd mutation.

In the inherited degenerative retinal disease of the rd mouse, rod cGMP levels rise above normal due to depressed cGMP-phosphodiesterase (cGMP-PDE) function a few days before degeneration begins. The subnormal activity of the cGMP-PDE may be due to a lesion in the enzyme itself, or in any of several proteins that regulate it. We have used a bovine cDNA for the alpha-subunit of cGMP-PDE to map its gene Pdea to mouse chromosome 18 at a distance of 21 centimorgans (cM) from the Mbp locus. Since the locus of the rd mutation is on mouse chromosome 5, a defect in the Pdea gene is ruled out as the cause of this inherited retinal degeneration.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1990

Effects of MDL 11,939 on action potential and contractile force in cardiac tissues: a comparison with bretylium, clofilium, and sotalol.

The effect of MDL 11,939 hydrochloride [alpha-phenyl-1-(2-phenylethyl)-4-piperidinemethanol HCl], a novel antiarrhythmic agent, was studied using microelectrode recording techniques. MDL 11,939 (10(-7) - 10(-6) M increased the action potential (AP) duration in both guinea pig papillary muscle and dog Purkinje fiber with a maximum effective concentration of 10(-6) to 3 x 10(-6) M. MDL 11,939 up to and including 10(-6) M did not alter upstroke velocity (Vmax) of the AP in either tissue but 10(-5) M decreased the Vmax in Purkinje fibers. Compared to the other class III antiarrhythmic agents (bretylium, clofilium, and d-sotalol), MDL 11,939 was among the most potent in increasing AP duration in the papillary muscle, while being relatively less effective in increasing AP duration in Purkinje fiber. Bretylium did not increase the AP duration in papillary muscle unless it was reserpinized. MDL 11,939, clofilium, and d-sotalol all produced negative inotropic effects in papillary muscle, whereas bretylium produced a positive inotropic effect. The positive inotropic effect of bretylium was abolished by reserpinization. In papillary muscle preparations depolarized with 22 mM K+, MDL 11,939 at concentrations greater than or equal to 10(-5) M depressed Vmax of the slow AP, suggesting that it inhibited the inward Ca2+ current, and such an effect may contribute to the negative inotropic effect of this agent. In the depolarized preparations, the slow AP duration was still increased by concentrations of MDL 11,939 greater than or equal to 10(-6) M. In conclusion, MDL 11,939 has cellular electrophysiological properties that suggest a class III antiarrhythmic activity.

Action Potentials↗
PubMed1990

In vivo comparison of renal and femoral vascular sensitivity and local angiotensin generation.

Experiments were conducted to compare the relative importance of the local renin-angiotensin systems in the rabbit renal and femoral vascular beds and their functional role in hemodynamic regulation. Angiotensin I (Ang I) (0.15 microgram/kg i.v.) elevated mean arterial blood pressure by 18 +/- 1 mm Hg in the renal experimental group and 19 +/- 1 mm Hg in the femoral experimental group; it decreased renal blood flow by 35 +/- 3% but increased femoral blood flow by 31 +/- 8%. All these effects were blocked by intravenous administration of captopril (2 mg/kg bolus injection plus 1 mg/kg/hr). Captopril also lowered mean arterial pressure by 17 +/- 3 and 16 +/- 2 mm Hg in the renal and femoral experimental groups, respectively, and it increased renal blood flow by 32 +/- 10% but reduced femoral blood flow by 21 +/- 4%. As a result, renal vascular resistance was decreased by 36 +/- 5%, but femoral vascular resistance remained unchanged. After captopril, plasma angiotensin II (Ang II) levels were decreased and Ang I levels increased in the two groups. The renal venous-arterial difference of Ang I was increased by captopril, but the femoral venous-arterial difference of Ang I was not, suggesting greater generation of Ang I in the kidney. In a separate group of bilateral nephrectomized rabbits, plasma Ang II levels as well as mean arterial pressure, femoral blood flow, and femoral vascular resistance were not changed by intravenous administration of captopril.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin I↗
PubMed1990

Localization of classical neurotransmitters in interneurons of the larval tiger salamander retina.

Autoradiography was used to visualize the neurons in the tiger salamander retina that exhibit high-affinity uptake of 3H-dopamine, [3H]-serotonin, [3H]-glycine, and [3H]-GABA. Both [3H]-dopamine and [3H]-serotonin were accumulated by amacrine cells and by displaced amacrine cells. [3H]-glycine was taken up by amacrine cells, displaced amacrine cells, bipolar cells, and displaced bipolar cells. [3H]-GABA was accumulated by amacrine cells and by cells in the ganglion cell layer that may be displaced amacrine or ganglion cells. [3H]-GABA was also taken up by horizontal cells, bipolar cells, and displaced bipolar cells.

Animals↗
PubMed1990

[Dissolution of metronidazole stilus].

Metronidazole stilus is a new preparation to be inserted into periodontal pockets for treatment of periodontitis. The certificate and file number of approval given to this new product were issued by the Ministry of Public Health in August, 1989. Its shape looks like a toothpick and the width, thickness and length are 1.5mm, 0.7mm and 3 cm, respectively. The content of metronidazole in each cm of the stilus is 2.2 mg. We have studied the dissolution of the new preparation by rotation basket method. The kinetic process of dissolution approximates first order kinetics. The K, t0.5 and t0.9 are 0.0624 min-1, 12.8 and 38.6 minutes, respectively. The requirement is that the dissolved percentage should not be lower than 60% of the added amount in 30 minutes. In order to have a dissolution test similar to that of the stilus in dental pockets, we examined the dissolution in static condition. The results showed that a very high dissolution rate appeared in the beginning, but it decreased quickly, and 71.76% of metronidazole was not dissolved until 48 hours. So one insertion per two days for clinical use is suggested.

Metronidazole↗
PubMed1990

[Smooth muscle tumors of gastrointestinal tract: a study on correlation between pathology and prognosis and histogenesis].

Seventy three cases of gastrointestinal smooth muscle tumors (GISMT) were collected and their correlation between pathology and prognosis and their histogenesis was studied, microscopically, the following parameters were evaluated: 1. cellularity; 2. grade of differentiation; 3. nuclear pleomorphism; 4. mitotic rate/10 HPF. All cases were followed up, but from only 47 information was elicited. To study the histogenesis, the technique of immunohistochemical staining to desmin, S-100 protein was used in all the cases and five were examined by EM. The results showed that the mitotic rate was the most important and reliable pathological parameter used to differentiate between benign and malignant tumors, and to evaluate the prognosis of a given tumor; in the cases which showed active mitosis, tumor size was important to evaluate the prognosis; the other histologic parameters of less, if any, significance in evaluation of prognosis. The authors supported the hypothesis that GISMT might mainly be derived from primary mesenchymal cells potentiated with smooth muscle cells differentiation. The hypothesis that GISMT are derived from nerve tissue waits for further evidence.

Adolescent↗
PubMed1990

[Effects of processing on volatile oil constituents in nutmeg and on the contents of myristicin].

This paper reports a GC analysis of the volatile oil contained in the nutmeg (Semen Myristicae) prepared by simmering wrapped in flour in hot purified talc, scalding in hot purified talc and stir-frying in smoking wheat bran. The experimental results showed that before and after processing the volatile oil compounds in nutmeg are the same and during processing no known compounds disappeared. The contents of the main volatile oil compounds in nutmeg changed, however, before and after processing, including the amounts of myristicin, one of the toxic compounds in nutmeg. It is suggested that the amounts of myristicin could be decreased notably under certain processing conditions.

Allylbenzene Derivatives↗
PubMed1990

[Cyclic GMP phosphodiesterase from bovine retina. Amino acid sequence of beta-subunit and nucleotide sequence of corresponding cDNA].

Primary structure of beta-subunit of the cyclic GMP phosphodiesterase has been determined by the parallel analysis of the protein amino acid sequence and the corresponding cDNA nucleotide sequence. The beta-subunit contains 852 amino acid residues, its molecular mass is 98291 Da. A significant homology is found between beta- and alpha-subunit of the cGMP phosphodiesterase.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1990

[Effects of processing methods on the amounts of volatile oil of nutmeg and on isolation and characterization of the volatile oil constituents].

In this paper, the authors investigated the effects of various processing methods, i.e., scalding in hot purified talc, simmering wrapped in flour in hot purified talc and stir-frying in smoking wheat bran, on nutmeg (Semen Myristicae) in terms of the quantities of the volatile oil. The experimental results revealed that the amounts of volatile oil contained in nutmeg vary remarkably with the lengths of cooking time and the fluctuation of temperature. Detected by GC-MS-computer, 32 compounds of nutmeg were characterized, and their contents were determined by GC respectively.

Allylbenzene Derivatives↗
PubMed1990

[Involvement of sulfhydryls in the protective mechanism of gastric mucosa].

The present work have studied the role of nonproteinsulfhydryl (NPSH) in the protective mechanism of gastric mucosa. During the development of gastric injury induced by acidified ethanol (AE) gavage or restraint-cold stress (RCS), NPSH content in gastric mucosa markedly decreased. Pretreatment with cysteamine (cys) or reductive glutathione (GSH) could prevent gastric mucosa from injury induced by AE. The activity of glutathione reductase in gastric mucosa was inhibited consistently in the time course with NPSH decrease after AE gavage or RCS. Malondialdehyde (MDA) level in the mucosa increased after AE gavage and dimethyl suloxide, a free radical scavenger, could reduce AE induced injury. The above results suggest that NPSH in gastric mucosa might be involved in the local protective mechanism through its free radical scavenging activity, and the decrease of NPSH in gastric mucosa resulted by the inhibition of glutathione reductase activity and the increase of free radical production may be an important step in the development of injury.

Animals↗