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Biomedical subjects

C Li

Publications and source records attributed to C Li.

At least 1,045 records · Page 58Linked to original sources
PubMed1994

[Direct determination of tin in water by oscillopolarography].

Sn(IV) has a sensitive polarographic wave in the system of H2SO4-KI-VitC-V (IV). We examined the factors influencing the polarographic wave and found that the concentration of sulfuric acid and temperature were critical factors for the determination. The sensitivity of the method was increased nearly 50-fold by decreasing the concentration of sulfuric acid from 0.8 mol/L to 0.1 mol/L. The coefficient of variation (CV) percentages of the method were less than 5% and 8% for 6-7 determinations of Sn (IV) standard and sample respectively. The recovery ranged from 97.3% to 101%. The proposed method is suitable for direct determination of trace Sn (IV) in most natural water samples.

Polarography↗
PubMed1994

[The observation of the bulbar conjunctival microcirculation in patients with retinitis pigmentosa].

The detection of the bulbar conjunctival microcirculation (BCM) of 73 cases (146 eyes) with retinitis pigmentosa (RP) showed that there were some abnormal changes of BCM in the pathologic progress of RP. The older the patient, the longer the disease history and the more the loss of visual field, the more serious the abnormal changes of BCM. The disease in male patients was in general more serious than in female patients. Its characteristics were the followings: increase in the number of tortuous vessels; the different widths of vessels in a few cases; obvious increase of microangioma; abnormal proportion of artery to vein; decelerated blood flow and aggregated erythrocytes. Some abnormal changes in the nailfold microcirculation (left ring finger) were observed in the meantime, and compared with those in the BCM of 56 cases. It was found that they were positively interrelated (gamma's = 0.9965, P < 0.001).

Adolescent↗
PubMed1994

[Biochemical analysis of protein homogenates in skin stored at different temperatures].

The amount and constitution of protein, its ultraviolet photo-absorption ability, and the amount of esterase of homogenates of cadaver, guinea pig and mouse skin, which were stored under various temperatures of 4 degree C, -20 degree C, -80 degree C and -196 degree C, were assayed by using ultraviolet spectrophotometer and polyacrylamide gel electrophoresis. The results show that there are changes in various degree in biochemical components of skin protein and esterase after being stored at different temperatures as compared with fresh skin.

Animals↗
PubMed1994

[An investigation on the distribution of leptospirae interrogans in water and soil in southwest of Yunnan Province].

The conservation of pathogenic leptospirae in water and soil is one of the important problems of geography-epidemiological survey of leptospirosis. We have conducted this investigation by using of filtration-culture isolation method in five counties in the west and southwest of Yunnan during 1988-1992. The results showed that the isolates from samples of water and soil collected between July and September in Menglian and Huaping county were leptospirae biflexa while in the samples of water and soil collected between November and December in three counties, 8 strains of L. interrogans were isolated from the samples of Gengma and Baoshan county. The total positive rate was 3.31% (8/242). The positive rate of water and soil was 2.14% (3/140) and 4.9% (5/102) respectively. Strains obtained in this investigation belong to six serogroups: Icterohaemorrhagiae and Pyrogenes in 2 respectively. Canicola, Grippotyphosa, Sejroe and Australis in 1 respectively. These serogroups of leptospirae obtained from water and soil were corresponded with the serogroups obtained from the patients and animals with leptospirosis in local area. This survey provided new data for expounding the structure of the focus of leptospirosis.

China↗
PubMed1994

[Polarographic determination of N,N'-methylene-bis(2-amino-1,3,4-thiadiazole) in water].

The polarographic behavior of the product of N,N'-methylene-bis(2-amino-1,3,4-thiadiazole) (I) with nitrite and N-(1-naphthyl)-ethylendiamine is reported. The effects of acidity and reagents on the polarography was studied, and a polarographic method was established for the determination of (I). The relative standard deviation was 2.2-8.4%, and the recovery in the range of 80-103%. The proposed method was sensitive, accurate, reproducible and suitable for the determination of microamount of (I) in water.

Insecticides↗
PubMed1994

[Observation on parasite density in the early stage of vivax malaria].

Thirty-eight cases were artificially infected with local Plasmodium vivax sporozoites and experienced onsets of acute attacks after a short incubation period. The parasite densities upon the patent of malaria parasites in the peripheral blood and the primary clinical onset were 0.2-1.6 and 0.6-4 040/microliters, respectively. Such significant difference in parasitaemia level seems to be closely related to the interval between the initial parasitaemia and the first onset, as indicated by the fact that for the majority of cases, the earlier the appearance of clinical attack after sporozoite inoculation, the lower the parasite density at the beginning of the patent period, while primary onsets of later occurrence, in those with higher initial parasitemia. The biological and epidemiological significance of the evidence was discussed.

Animals↗
PubMed1994

[Experimental studies in effect of limb lengthening using metaphyseal osteotomy on epiphyseal growth plate].

The experimental results in effect of limb lengthening using metaphyseal osteotomy at proximal tibia on epiphyseal growth plate in 28 young sheep were reported. Radiographic, microscopic and electronmicroscopic findings showed that lengthening of 7.5% the growth plate resulted in narrowing in varying degrees in one third of the sheep with a lengthening rate of 0.25 mm every six hours. Narrowing of epiphyseal growth plate was seen in half of sheep with lengthening of 10% and in all sheep with lengthening of 12.5% and 15%. Degeneration and necrosis of chondrocytes happened in one sheep of lengthening of 15%. Thickening of growth plate was seen in all sheep of the control group. Our conclusion from this series of experimental studies was that depression caused by compression stress effect in limb lengthening of less than 7.5% on epiphyseal growth plate is minimal.

Animals↗
PubMed1993

DNA-binding properties and secondary structural model of the hepatocyte nuclear factor 3/fork head domain.

An 84-amino acid segment of QRF-1 [glutamine (Q)-rich factor 1], a newly cloned, B-cell-derived DNA-binding protein, shows significant sequence homology with the DNA-binding domains of the hepatocyte nuclear factor 3/fork head family of proteins. Here we demonstrate that this 84-amino acid domain is necessary and sufficient for DNA binding. We also propose a secondary structural model for the domain. At the N-terminal portion of the model, a basic hook structure is followed by two amphipathic helices separated by a turn. Invariant amino acid residues within the two proposed helices form the hydrophobic cores. An aromatic kink and a third amphipathic helix comprise the center of the domain. At the C terminus, two variable-length loops flank a putative 7-amino acid helix followed by a short basic region.

Amino Acid Sequence↗
PubMed1993

apl-1, a Caenorhabditis elegans gene encoding a protein related to the human beta-amyloid protein precursor.

The major component of senile plaques found in the brains of Alzheimer disease patients is the beta-amyloid peptide, which is derived from a larger amyloid precursor protein (APP). Recently, a number of APP and APP-related proteins have been identified in different organisms and constitute the family of APP proteins. We have isolated several cDNAs encoding an APP-related protein in the nematode Caenorhabditis elegans and have designated the corresponding gene as apl-1. The apl-1 transcripts undergo two forms of posttranscriptional modification: trans-splicing and alternative polyadenylylation. In vitro translation of an apl-1 cDNA results in a protein of approximately the expected size. Similar to the Drosophila, human, and mouse APP-related proteins, APL-1 does not appear to contain the beta-amyloid peptide. Because APP-related proteins seem to be conserved through evolution, the apl-1 gene from C. elegans should be important for determining the normal function of human APP.

Alternative Splicing↗
PubMed1993

Pedicle and antler development following sectioning of the sensory nerves to the antlerogenic region of red deer (Cervus elaphus).

Sensory nerves supplying the deer antlerogenic region were sectioned about 60 days prior to pedicle initiation to determine the extent of neural influence on pedicle and first antler growth. Our results from a combination of histological examination and immunohistochemical localization showed that all 12 antlerogenic regions were successfully deprived of sensory nerve supply, but in 10 of 12 cases there was partial regeneration during the experimental period. In the two cases where no sensory reinnervation occurred, pedicle growth did not show any differences compared with partially sensory reinnervated or intact pedicles. With or without reduced sensory nerve supply, first antlers were initiated, grown, cleaned of velvet, cast, and regenerated in the normal way, but they were smaller than controls. Consequently, we conclude that a sensory nerve supply is not necessary for normal pedicle formation and for the first antler cycle, but plays a role in determining antler size.

Animals↗
PubMed1993

Zn2+ potentiates excitatory action of ATP on mammalian neurons.

Despite the increasing recognition that ATP is an important extracellular excitatory mediator in the nervous system, the regulation of ATP receptors is poorly understood. Because the extracellular Zn2+ concentration is regulated in a variety of biological tissues, we studied modulation of the ATP-gated cation channel by Zn2+ in mammalian neurons using the whole-cell patch-clamp technique. In approximately 73% of cells tested, the amplitude of ATP-activated membrane ion current increased up to 5-fold in the presence of micromolar concentrations of Zn2+. The characteristics of this action suggest that Zn2+ increases the apparent affinity of the receptor for ATP. In addition, Zn2+ increased membrane depolarization and action potential firing elicited by ATP. These observations suggest that Zn2+ may play a physiological role in regulating the excitatory action of ATP on mammalian neurons.

Adenosine Triphosphate↗
PubMed1993

Mechanisms of inhibition of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone bioactivation in mouse by dietary phenethyl isothiocyanate.

The tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1- butanone (NNK), induces lung tumors in mice, rats, and hamsters. Phenethyl isothiocyanate (PEITC), which occurs as gluconasturtiin in cruciferous vegetables, is a potent inhibitor of NNK-induced carcinogenesis. The present study investigated the enzymatic basis for the bioactivation of NNK and the mechanisms of the inhibition of this process by dietary PEITC in mice. The apparent Km for the formation of keto aldehyde, keto alcohol, and NNK-N-oxide in lung microsomes was 4.9, 2.6, and 1.8 microM and, in liver microsomes, 5.5, 5.1, and 8.8 microM, respectively. Immunoinhibition studies suggested that cytochrome P450s (P450s) 2A1 and 2B1 or related forms are the major enzymes involved in the oxidative metabolism of NNK in mouse lung microsomes. When female A/J mice were fed diets containing 0, 1, or 3 mumol of PEITC/g of diet for 4 wk, the dietary PEITC had no significant effects on the food consumption and body weight of the mice. NNK oxidation in the lung microsomes of mice consuming the 1 or 3 mumol of PEITC/g of diet was decreased by 13 to 27% or 30 to 50%, respectively. In liver microsomes, whose NNK oxidative metabolism rates were about twice those of lung microsomes on a per mg of protein basis, the activities were decreased by 14 to 31% by the 3 mumol of PEITC/g of diet. The apparent Km remained unchanged, and the apparent Vmax decreased in the lung and liver microsomes of PEITC-fed mice, suggesting a noncompetitive nature of the inhibition. When added to the incubation mixture, PEITC decreased NNK metabolism in a concentration-dependent manner and exhibited a competitive inhibition with apparent Ki values of 51 to 93 nM. Dietary PEITC decreased the hepatic P450 content by 25%, but increased (2-fold) the O-dealkylase activities of 7-pentoxyresorufin (indicative of P450 2B1) and 7-ethoxyresorufin (indicative of P450 1A) in the liver microsomes of mice consuming the 3 mumol of PEITC/g of diet. The P450 2B level was increased in liver microsomes but slightly decreased in the lung microsomes. The p450 2E1 level was increased by dietary PEITC by 1.2- and 1.6-fold in the liver and lung microsomes, respectively. The activities of glutathione S-transferase and NAD(P)H-quinone oxidoreductase in liver and lung microsomes were not affected appreciably by the dietary PEITC treatment. The results suggest that chronic consumption of PEITC decreases the rate of metabolic activation of NNK by chemical inactivation and competitive inhibition of the enzyme(s) responsible for NNK oxidation.

Animals↗