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Biomedical subjects

L Shi

Publications and source records attributed to L Shi.

At least 253 records · Page 14Linked to original sources
PubMed1995

[The mitochondrial DNA diversity of pigs in southwest China].

Twenty restriction endonucleases, ApaI, AvaI, BamHI, BclI, BglI, BglII, ClaI, EcoRI, EcoRV, HindIII, HpaI, KpnI, PstI, PvuII, SacI, SalI, ScaI, SmaI, XbaI, XhoI were used to investigate the mitochondrial DNA polymorphism of pigs from 11 localities in southwest China. Among the 28 animals analyzed, 27 restriction morphs were detected, which can be sorted into 6 haplotypes. The average genetic distance among haplotypes (P) is 0.004, and the value of average sequence variation in pig population (pi) is 0.122%. Our results suggest that the genetic diversity within the pigs is remarkably scarce. The pigs in southwest China may have origineted from a late common ancester, and were likely impacted by the founder effect.

Animals↗
PubMed1995

[Influence of changing Ca++ concentration in neiguan (PC 6) on the effect of acupuncture treating experimental arrhythmia of rabbits].

We have made two kinds of experimental arrhythmia of rabbits by injecting aconitine and stimulating hypothalamus. Acupuncture could improve arrhythmia, after Ca++ in Neiguan (PC6) was chelated with EDTA solution the effect of acupuncturing Neiguan (PC6) was abolished. It indicates that Ca++ may be the key factor of acupuncture effect and one of the important material bases of the functional activity of meridians and collaterals.

Aconitine↗
PubMed1995

Effect of NDGA on beef heart mitochondria and EMT6 mouse mammary carcinoma cells.

The inhibition of mitochondrial succinate cytochrome c reductase by nordihydroguaiaretic acid (NDGA) was measured in vitro under aerobic and hypoxic conditions. The photodynamic effect of NDGA on EMT6 mouse mammary carcinoma cells was also investigated in vitro under aerobic and hypoxic conditions. NDGA strongly inhibited succinate cytochrome c reductase, which contains the mitochondrial electron transport Complexes II and III. By comparing the I50 values of aerobic and hypoxic assays, NDGA inhibition was found to be oxygen-independent. This finding suggests that oxygen is not involved in the inhibitory effect of mitochondrial respiration by NDGA. Similarly, our data demonstrate that NDGA-induced cytotoxicity towards EMT6 tumor cells is neither light-dependent nor oxygen-dependent. A dose-dependent loss of viability of EMT6 cell was observed although the toxicity of NDGA towards EMT6 cells was not strong, with an LC50 in the 200 microM range. NDGA caused a depletion of mitochondrial sulfhydryl groups. Sulfhydryl compounds, GSH and cysteine, prevented the inhibition of succinoxidase activity by NDGA. This suggests that NDGA exerts its biological effects by the depletion of sulfhydryl groups in key biochemical systems related to mitochondrial function.

Aerobiosis↗
PubMed1995

[A transplantable model of human laryngeal squamous carcinoma in nude mice].

We have successfully established a human laryngeal squamous carcinoma model in nude mice by transplantation of surgical specimen from patients with laryngeal carcinoma. Histopathological study revealed squamous carcinoma. We named it HLC14. Light and electron microscopy showed that the morphology was similar to that of the original tumor. The transplanted tumor has maintained for more than two years through 25 passages. The tumor grew steadily and fast. The successful rate of transplantation was 100%. Pingyangmycine was then used to treat the transplantable model. The result was satisfactory.

Animals↗
PubMed1994

Protein conformational changes induced by 1,1'-bis(4-anilino-5-naphthalenesulfonic acid): preferential binding to the molten globule of DnaK.

1,1'-Bis(4-anilino-5-naphthalenesulfonic acid) (bis-ANS), a hydrophobic fluorescent molecular probe which has been shown to bind to compact intermediate states of proteins (molten globules) and also to many nucleotide binding sites, induces a conformational change in DnaK by preferentially binding to its partially folded intermediate state (I) and thus shifting the equilibrium from favoring the native state (N) to favoring the I state. The conformational change was detected by CD, fluorescence emission, size exclusion chromatography, and small-angle X-ray scattering. The presence of bis-ANS significantly decreases the midpoint, Tm, of the initial transition (N-->I) in the thermal unfolding of DnaK, resulting in the apparent destabilization of the native state of DnaK. There is a linear correlation between the apparent free energy (reflected by Tm) of this transition and the concentration of bis-ANS. Bis-ANS does not affect the midpoint of the transition for DnaK from the intermediate to the unfolded state (U). An additional small transition from I to I*, a more expanded intermediate state, was observed, suggesting that the thermal denaturation of DnaK proceeds via a four-state (N-->I-->I*-->U) unfolding process. The addition of nucleotides, ADP or ATP, to the DnaK-bis-ANS complex causes a decrease in bis-ANS fluorescence emission due to the release of bound bis-ANS from the intermediate state of DnaK. This is due to preferential binding of the nucleotide to the native state of DnaK, resulting in a shift in the equilibrium from the intermediate toward the native state rather than the direct displacement of bis-ANS bound in the nucleotide binding site. Denaturation of DnaK induced by bis-ANS can be minimized by working at a temperature much lower than the Tm of the protein, at low dye concentration, and in the presence of nucleotide. Under these conditions, bis-ANS binds to the native state of DnaK.

Adenosine Diphosphate↗
PubMed1994

hsp70-protein complexes. Complex stability and conformation of bound substrate protein.

The presence of bound substrate protein increases the thermostability of hsp70 molecular chaperones (heat shock proteins of molecular mass 70 kDa). Complexes between hsp70 and unfolded substrate proteins were isolated by size-exclusion high performance liquid chromatography. The isolated complexes were observed to dissociate at a significant rate even in the absence of ATP. The presence of ADP caused a substantial increase in the stability of the complex. Both ADP and inorganic phosphate were found to inhibit the ATP-induced dissociation of complex. ADP was also observed to increase both the rate of complex formation and its stability as a function of temperature, suggesting an important regulatory role for nucleotides during heat shock. Circular dichroism and fluorescence studies of the complex between DnaK and a thermally unstable mutant of staphylococcal nuclease indicate that the bound substrate protein is significantly unfolded. A model for hsp70 cycle of complex formation and dissociation, which accounts for the regulatory role of nucleotides, is proposed.

Adenosine Diphosphate↗
PubMed1994

Premature p34cdc2 activation required for apoptosis.

Activation of the serine-threonine kinase p34cdc2 at an inappropriate time during the cell cycle leads to cell death that resembles apoptosis. Premature activation of p34cdc2 was shown to be required for apoptosis induced by a lymphocyte granule protease. The kinase was rapidly activated and tyrosine dephosphorylated at the initiation of apoptosis. DNA fragmentation and nuclear collapse could be prevented by blocking p34cdc2 activity with excess peptide substrate, or by inactivating p34cdc2 in a temperature-sensitive mutant. Premature p34cdc2 activation may be a general mechanism by which cells induced to undergo apoptosis initiate the disruption of the nucleus.

Amino Acid Sequence↗
PubMed1994

Gibberellin-induced changes in the translatable mRNA populations of stamens and shoots of gibberellin-deficient tomato.

The gib1 mutant of tomato (Lycopersicon esculentum Mill.) is deficient in endogenous gibberellins and exhibits phenotypes including extreme dwarfism, reduced germination, and abnormal flower development, which are reversed by the application of gibberellic acid (GA3). Previous work has demonstrated that, in stamens of the gib1 mutant, pollen mother-cell development arrests at the premeiotic G1 stage (Jacobsen and Olszewski 1991, Plant Physiol. 97, 409-414). Following GA3 treatment of developmentally arrested flowers, pollen mother-cell development resumes and is synchronous. The present study examines gibberellin-induced changes in the translatable mRNA populations of developmentally arrested stamens and of vegetative shoots of the gib1 mutant. Following rescue of developmentally arrested stamens by treatment with GA3, we consistently detected increases and decreases in the abundance of 14 and 20 in-vitro translation products, respectively. Some of these changes were first detected 8 h post treatment and therefore represent the first changes observed in stamens whose development has been rescued by GA3 treatment. In vegetative gib1 shoots, the abundance of 13 in-vitro translation products decreased within 6-24 h after GA3 treatment. However, no in-vitro translation products that increased in abundance after GA3 treatment were detected.

Gene Expression↗
PubMed1994

Elderly support in rural and suburban villages: implications for future support system in China.

This study compares current elderly support between rural and suburban elderly, drawn from a 1987 and 1989 cluster sample involving 6 Chinese villages purposely selected to reflect geographic variations and different standards of living. The results of the study indicate that social support for the elderly through pension and subsidy is improving, particularly in suburban villages where there is greater level of economic development and there are increasingly more industrial enterprises. The current pension or subsidy status is mainly a function of the presence of well-developed economy (as represented by our proxy variables RURALITY, and PRIORJOB). In terms of family support, our study shows it serves largely as a substitute for social support. Elderly not receiving pension support are more likely to receive monetary support from their children. The implications of these findings are analyzed in the context of the socioeconomic and demographic transitions in China and alternative solutions to elderly support are discussed.

Aged↗
PubMed1994

Alcoholic beverages and breast cancer: some observations on published case-control studies.

We identified 38 case-control studies investigating possible associations between alcoholic beverage consumption and cancer of the female breast. Each study was characterized according to design features such as: control type (hospital or community based), risk factors controlled for, matching strategy, and statistical power. We examined the effect of these design variables on several outcome variables including identification of any significant elevation in odds ratio and characterization of any dose-response effect. The major finding of this study is that of a striking difference between hospital and community based controlled studies with respect to (1) the level of any estimated dose-response effect, and (2) the finding of statistically significant elevations in odds ratios at levels of consumption below 4 drinks per week. In summary, the generally weak associations reported in these case-control studies along with the measurement and/or selection biases implied by our findings would lead one to the conclusion that present evidence does not support a causal association. This conclusion seems to be in accord with results from cohort studies and with similar conclusions from several other reviews.

Alcohol Drinking↗
PubMed1994

A suppressor of a mating-type limited zygotic lethal allele also suppresses uniparental chloroplast gene transmission in Chlamydomonas monoica.

Uniparental inheritance of Chlamydomonas chloroplast genes is thought to involve modification of maternal (mt+) chloroplast genomes to protect against a nuclease that is activated after gamete fusion. The mating-type limited mtl-1 mutant strain of Chlamydomonas monoica is unable to protect mt(+)-derived chloroplast DNA. Zygotes homozygous for mtl-1 lose all chloroplast DNA and fail to germinate. We have selected for suppression of this zygote-specific lethality, and have obtained 20 mutant strains that produce viable homozygotes despite the continued presence of the mtl-1 allele. Genetic analysis indicates that the suppressor mutations are all recessive alleles at a single locus (sup-1) which is unlinked to mtl-1. Crosses between sup-1 strains carrying distinctive chloroplast antibiotic resistance markers also show predominantly biparental chloroplast gene transmission. Chloroplast nucleoids of both parental origins (stained with the DNA-specific fluorochrome, DAPI) are retained in the zygotes homozygous for sup-1. The data are compatible with the idea that the sup-1 (suppressor of uniparental inheritance) locus may encode a chloroplast DNA nuclease that is expressed from both parental genomes.

Alleles↗
PubMed1994

Rural primary care program survival: an analysis of financial variables.

This study examines the effect of financial characteristics of rural primary care programs on the probability of their continuing as federally funded entities. A randomly selected national cohort of rural primary care programs (n = 162) was used to compare financial measures of programs that were continuing and those that were noncontinuing. Financial data were obtained from 1978-1987 Bureau Common Reporting Requirements (BCRR) forms submitted to the Bureau of Health Care Delivery and Assistance of the Department of Health and Human Services as part of the requirement to receive federal grant support for the programs. The results emphasize the importance of both outside funding and increased level of self-sufficiency in the continuation of rural primary care programs. Noncontinuing programs often suffer from both a lack of self-sufficiency and a lack of outside funding, mostly from federal sources. To a lesser extent, the number of patients also affects the program's chance of continuation. From a policy perspective, government intervention is both necessary and likely if rural primary care programs are to succeed and fulfill their mission of providing primary care for the medically underserved who are primarily poor, uninsured, and unable to pay.

Cohort Studies↗
PubMed1994

Sequential action of two-component genetic switches regulates the PHO regulon in Bacillus subtilis.

Bacillus subtilis has an alkaline phosphatase (APase) gene family composed of at least four genes. All members of this gene family are expressed postexponentially, either in response to phosphate starvation or sporulation induction or, in some cases, in response to both. The phoA gene (formerly called phoAIV) and the phoB gene (formerly called phoAIII) products have both been isolated from phosphate-starved cells, and a mutation in either gene decreased the total APase expressed under phosphate starvation conditions. Data presented here show that a phoA phoB double mutant reduced APase production during phosphate starvation by 98%, indicating that these two genes are responsible for most of the APase activity during phosphate-limited growth. The promoter for phoA was cloned and used, with the phoB promoter, to examine phosphate regulation in B. subtilis. phoA-lacZ reporter gene assays showed that the expression of the phoA gene commences as the culture enters stationary phase as a result of limiting phosphate concentrations in the growth medium, thereby mimicking the pattern of total APase expression. Induction persists for approximately 2 h and is then turned off. phoA is transcribed from a single promoter which initiates transcription 19 bp before the translation initiation codon. PhoP and PhoR are members of the two-component signal transduction system believed to regulate gene expression in response to limiting phosphate. The expression of phoA or phoB in response to phosphate starvation was equally dependent on PhoP and PhoR for induction. lacZ-promoter fusions showed that both phoA and phoB were hyperinduced, or failed to turn off induction after 2 h, in a spo0A strain of B. subtilis. Mutations in genes which are required for phosphorylation of Spo0A, spo0B and spo0F, also resulted in phoA and phoB hyperinduction, suggesting that phosphorylation of Spo0A is required for the repression of both APases in wild-type strains. The hyperinduction of either APase gene in a spo0A strain was dependent on PhoP and PhoR. Analysis of a phoP-lacZ promoter fusion showed that the phoPR operon is hyperinduced in a spo0A mutant strain, suggesting that Spo0A approximately P represses APases by repressing phoPR transcription. We propose a model for PHO regulation in B. subtilis whereby the phoPR operon is transcribed in response to limiting phosphate concentration, resulting in activation of the PHO regulon transcription, including transcription of phoA and phoB. When the phosphate response fails to overcome the nutrient deficiency, signals for phosphorylation of Spo0A result in production of Spo0A approximately P, which represses transcription of phoPR, thereby repressing synthesis of the PHO regulon.

Alkaline Phosphatase↗
PubMed1994

Effect of CD4 gene expression on adenovirus replication.

The gene encoding the CD4 receptor was introduced into KB cells to establish the KBT4 cell line, a cell line susceptible to infection with human immunodeficiency virus type 1. Adenovirus replication was found to be significantly less in these cells than in the parental KB cells. Similar decreased adenovirus type 5 (Ad5) replication occurred in HeLaT4 cells compared with the original HeLa cells. The presence of CD4 did not alter the cell surface population of KB cell adenovirus receptors, since viral adsorption was similar in the two cell lines. Moreover, addition of soluble CD4 did not reduce viral replication in either KB or KBT4 infected cells. Uncoating of viral DNA was also unchanged in KBT4 cells compared with the parental KB cells. In contrast, migration to or entrance of viral DNA into nuclei and synthesis of early viral RNAs was delayed and reduced in KBT4 cells. These effects were more pronounced for Ad7 than for Ad5. The yields of infectious viruses were the same in both cell lines, however, after transfection of naked viral DNAs to initiate infection. These results imply that the expression of the CD4 gene in KBT4 cells interfered with passage of uncoated virus across endosomal vesicles and/or transfer of uncoated core viral DNA into the nucleus.

Adenoviridae↗
PubMed1994

Primary care, specialty care, and life chances.

The relationship between the availability of primary care and specialty care and certain life chance indicators such as mortality rates and life expectancy is analyzed using the multiple regression procedure. Dependent variables are life chance indicators; independent variables were selected based on Starfield's and Blum's health determinant models and include socioeconomic environment, lifestyles, demographics, and medical care. The author also examines the rankings of states in terms of these indicators, using Spearman's rho coefficient. Among the medical care variables, primary care is by far the most significant variable related to better health status, correlating with lower overall mortality, lower death rates due to diseases of the heart and cancer, longer life expectancy, lower neonatal death rate, and lower low birth weight. In contrast, the number of specialty physicians is positively and significantly related to total mortality, deaths due to heart diseases and cancer, shorter life expectancy, higher neonatal mortality, and higher low birth weight. From a policy perspective, a likely implication is to reorient the medical profession from its current expensive, clinically based, treatment-focused practice to a more cost-effective, prevention-oriented primary care system.

Health Services Accessibility↗
PubMed1994

[Causes of death of the host of no. 2 Chu Grave in Baoshan, Jingmen, Hubei Province: a preliminary study].

On the bamboo slips found in the No. 2 Chu Grave unearthed in Baoshan, Jingmen, Hubei Province in 1986, there were records about its host, Shao Tuo, consulting a sorcerer for his disease from March 4 (Chu Calendar) 317 B.C. to May 7th (Chu calendar), 316 B.C. As a result of textual research on the name of disease recorded as heart disease, lower heart disease and abdominal heart disease; the symptoms such as short breath, upper abdominal distension and dropsy; the characteristics of the disease such as sudden and intermittent onset, more and more severe condition, relatively rapid death and so on, it is considered that Shao Tuo died of cardiac disease. The two possible reasons why Shao Tuo suffered from cardiac disease are also discussed.

China↗
PubMed1994

[IL-1 and TNF-alpha bioassay and PGE2 immunoassay of supernatant of cultured synovia in patients with rheumatic diseases].

Using arthroscopy technique, synovia were adopted and cultured, and the supernatant was harvested on 1, 4, 7, 14 and 28 days. The bioactivity of supernatant IL-1 were measured in 33 cases (RA 11 cases), TNF-alpha in 30 cases (RA 9 cases); the content of supernatant PGE2 were measured in 44 cases (RA 11 cases). The results showed that IL-1 Growth Index (GI) and TNF-alpha Killing Rate (KR) in RA group are higher than in non-synovitis group (negative control) with statistically significant difference and that the cultured time of the IL-1 highest value is consistent with TNF-alpha. In RA group, the cases treated with disease-modifying anti-rheumatic drugs (DMARDs), especially using the combined therapy, the activity of IL-1 and TNF-alpha decreased. The contents of PGE2 in RA+ synovitis group were higher than osteoarthritis (OA) + nonsynovitis group with statistically significant difference. In conclusion, cytokines such as IL-1 and TNF-alpha have very important status in the pathogenesis of RA. This work provides some clues for new approaches and strategies in the treatment of RA.

Adult↗