Biomedical subjects

L Shi

Publications and source records attributed to L Shi.

317 records · Page 18Linked to original sources

PubMedDate not supplied

Alterations in free radical activity in aging Drosophila.

Drosophila were examined to see if there is an increase in damage associated with free radical activity in older flies. The levels of superoxide radical and of lipid peroxides were higher in membrane samples from older flies. Also, in older Drosophila there was a significant decrease in membrane fluidity, as determined by fluorescence polarization, and an increase in ATP-dependent calcium uptake. In homogenates from whole flies, the concentration of inorganic peroxides and activity of the proteolytic enzyme, cathepsin B, increased with age. During their lifetime, vestigial wing Drosophila displayed a greater level of free radical activity than wild-type flies and a significantly shorter life span (26.7 +/- 0.7 days vs. 34.4 +/- 1.0, p < 0.01). These results indicate that the level of oxidative stress is closely coupled to cellular damage and to life span, and they indicate that free radicals may play a central role in the aging process in Drosophila.

Aging↗

PubMedDate not supplied

Uterine electromyography and light-induced fluorescence in the management of term and preterm labor.

OBJECTIVE: Understanding the physiology of the uterus and cervix during term and preterm parturition is crucial for developing methods to control their function and is essential to solving clinical problems related to labor. To date, only crude, inaccurate, and subjective methods are used to assess changes in uterine and cervical function in pregnancy. METHODS: In the past several years, we have developed noninvasive methods to quantitatively evaluate the uterus and cervix based on recording of uterine electrical signals from the abdominal surface (uterine electromyography) and measurement of light-induced fluorescence (LIF) of cervical collagen (Collascope), respectively. Both methods are rapid and allow immediate assessment of uterine contractility and cervical ripening. RESULTS: Studies in animals and humans indicated that uterine and cervical performance can be monitored successfully during pregnancy using those approaches and that these techniques can be used during labor to better define management in a variety of conditions associated with labor. CONCLUSION: The potential benefits of the proposed instrumentation and methods include reducing the rate of preterm delivery, improving maternal and perinatal outcome, monitoring treatment, decreasing cesarean rate and providing research methods to understand uterine and cervical function.

Animals↗

PubMedDate not supplied

The use of conventional antipsychotic medications for patients with schizophrenia in a medicaid population: therapeutic and cost outcomes over 2 years.

OBJECTIVE: To evaluate the association between drug therapy patterns achieved with conventional antipsychotics and direct healthcare costs over 2 years. METHODS: Paid claims data from the California Medicaid (Medi-Cal) program were used to identify 2476 patients with schizophrenia for whom 2 years of data were available. Ordinary least squares (OLS) regression models were used to estimate the association between lack of antipsychotic drug therapy, delayed therapy, changes in medications, and continuous therapy on healthcare costs over a 2-year period. RESULTS: Nearly 99% of Medi-Cal patients with schizophrenia were treated with conventional antipsychotics. Patients with schizophrenia consumed nearly $48,000 in direct costs over 2 years. Over 16% of patients did not use any antipsychotic medication for 2 years. Untreated patients used more healthcare resources than treated patients did ($10,833, P = .0422), especially psychiatric hospital care ($8,027, P = .0004). However, treated patients frequently experienced suboptimal drug use patterns. Nearly 33% of treated patients delayed antipsychotic therapy for up to 2 years. Delayed therapy was associated with increased costs of $12,285 (P = .070). Over 56% of patients experienced changes in therapy that were associated with higher total direct costs ($17,644, P < .0001). Finally, only 3.2% of treated patients used an antipsychotic medication consistently for 2 years. However, continuous drug therapy was not associated with lower costs. CONCLUSION: Suboptimal drug use patterns are common and costly in Medi-Cal patients with schizophrenia who initiated therapy with conventional antipsychotics.

Adult↗

PubMedDate not supplied

Control and assessment of the uterus and cervix during pregnancy and labour.

Preterm labour and resultant preterm birth are the most important problems in perinatology. Countless efforts have failed to establish a single effective treatment of preterm labour, partly because the mechanisms regulating the uterus and cervix during pregnancy are not well understood. New knowledge is needed to inhibit early progression of labour (uterine contractility and cervical ripening), and adequate quantitative tools to evaluate the uterus and cervix during pregnancy are lacking. In this review, we outline studies showing that the uterus (myometrium) and cervix pass through a conditioning step in preparation for labour. This step is not easily identifiable with present methods to assess the uterus or cervix. In the uterus, this seemingly irreversible step consists of changes in the electrical properties to make muscle more excitable and responsive to produce forceful contractions. In the cervix, the step consists of softening of the connective tissue components. Progesterone appears to have a dominant role in controlling both the uterus and cervix, as antiprogestins induce early, preterm conditioning leading to preterm labour. Apparently, nitric oxide (NO) also controls conditioning of the uterus and cervix. In the uterus, NO, in concert with progesterone, inhibits uterine contractility. At term, NO production by the uterus and placenta are decreased and allow labour to progress. In contrast, NO in the cervix increases at the end of pregnancy and it may be the final pathway for stimulating cervical ripening by activation of metalloenzymes. The progress of labour can be assessed non-invasively using electromyographic (EMG) signals from the uterus (the driving force for contractility) recorded from the abdominal surface. Uterine EMG bursts detected in this manner characterize uterine contractile events during human and animal pregnancy. A low uterine EMG activity, measured transabdominally throughout most of pregnancy, rises dramatically during labour. EMG activity also increases substantially during preterm labour in humans and rats. This method may be used one day to predict impending preterm labour and identify control steps and treatments. A quantitative method also assesses the cervix, using an optical device which measures collagen fluorescence in the cervix. The collascope estimates cervical collagen content from a fluorescent signal generated when collagen cross-links are illuminated with excitation light of about 340 nm. The system has proved useful in rats and humans at various stages of pregnancy, and indicates that cervical softening occurs progressively in the last one-third of pregnancy. In rats, collascope readings correlate with resistance measurements made in the isolated cervix, which may help to assess cervical function during pregnancy, and indicate control and treatments.

Animals↗

PubMedDate not supplied

Expressed sequence tags for the chicken genome from a normalized 10-day-old White Leghorn whole embryo cDNA library: 1. DNA sequence characterization and linkage analysis.

Expressed sequence tags (ESTs) provide a rapid and reliable method for gene discovery as well as a resource for the large-scale analysis of gene expression of known and unknown genes. Here we describe a normalized cDNA library developed from a 10-day-old White Leghorn chicken whole embryo. The utility of the library was evaluated by partial sequencing of 99 randomly selected insert-containing clones and the analysis of EST-targeted genomic regions for single nucleotide polymorphisms (SNPs) in the East Lansing chicken reference DNA mapping panel. Using stringent match criteria of percent identity of 80 or higher across a length of 50 or more bases, 46 ESTs matched database sequences including previously reported Gallus gallus genes. Thirty-seven of the 50 primer pairs developed from 50 unique ESTs amplified a single fragment. The size of the 37 amplicons ranged from 276 to 693 bp for a total of 17,508 and an average of 473. About 70% of the SNPs detected were either G-->A or C-->T transition. The number of SNPs detected within the amplicons from EST-targeted genomic regions ranged from 0 to 4 for a total of 65 and a frequency of about 1 every 470 bases. About 35% of the amplicons contained only 1 SNP, while 19% had 4 SNPs. Using the SNPs that were informative in the East Lansing reference panel, 17 ESTs were mapped on the East Lansing chicken genetic map. The ESTs described, as well as the nucleotide variants identified within the EST-targeted genomic regions, represent significant resources for genome analysis in the chicken.

Animals↗

PubMedDate not supplied

Soybean chromosome painting: a strategy for somatic cytogenetics.

Cytological identification of soybean mitotic metaphase chromosomes (2n = 40) has been severely limited by their small size and uniform karyomorphology. We have developed fluorescent in situ hybridization (FISH), PCR-primed in situ labelling (PCR-PRINS) procedures, and molecular probes for routine cytological identification and for the physical mapping of soybean somatic chromosomes. Chromosome preparation has been achieved by modifications of previous protocols and through the preparation of root-tip protoplasts prior to chromosome spreading. Initially our probe selection focused on highly repeated DNAs that provide very intense localized hybridization signals. Repetitive gene probes that have proven valuable include the rDNA loci (5S and 45S) which are chromosome specific. We have also developed satellite DNA probes for two different sequence families: the SB92 and the STR120 satellites. Both of these are tandemly arranged at multiple chromosomal loci. By using different cloned examples of each family, we have been able to selectively label unique subsets of soybean chromosomes. Double hybridization with biotin and digoxigenin labeled probes has allowed us to determine the chromosomal overlap between different probes. In addition, we have joined portions of the metaphase chromosome painting patterns with the genetic map by single-copy FISH and PCR-PRINS detection of the RFLP loci G8.15, G17.3, and A199a and A199b. Total genomic DNA in situ hybridization (GISH) patterns were also used to characterize the soybean chromosomes.

Chromosome Mapping↗

PubMedDate not supplied

[The reactions of the cat motor cortex neurons to electrical stimulation of the base of the forebrain as a conditioned signal for the reflex of placing the forelimb on a support].

Electrical stimulation of the globus pallidus (500 ms, 300 Hz) in the area restricted by the stereotaxic coordinates AP 14-AP 16, L5-L8 at the level of the anterior commissura (HO) evoked food reactions in the form of mouth opening, chewing, and licking in the absence of food. There were no visible motor effects in the case of electrical stimulation of the subcommissural area (H-2-H-4) corresponding to the ventral pallidum and substantia innominata. The conditioned forepaw placing reaction was elaborated with the basal forebrain stimulation used as a conditioned stimulus. After conditioning, the short (3-5 pulses) conditioned basal forebrain stimulation evoked a prolonged (up to 500-1000 ms) activation of neurons in the motor cortex. This activation did not change in the absence of the movement, i.e., after acute extinction of the contralateral forepaw placing or transfer of placing reaction to the ipsilateral forepaw.

Animals↗

PubMedDate not supplied

Analysis of multivariables during porcine liver digestion to improve hepatocyte yield and viability for use in bioartificial liver support systems.

In order to achieve optimal BALSS function, preparation of porcine hepatocytes with high yield, viability, and P450 activity is known to be important. To date hepatocyte yields have varied from 0.58 x 10(10) to 3.45 x 10(10) and viabilities from 75% to 95% within and between laboratories, even when using the same digestion methods and procedures, indicating that hepatocyte isolation during porcine liver digestion is not fully optimized. The aim of this work was to identify the critical parameters affecting cell recovery during porcine liver harvesting by investigating 21 variables involved in the process, including pig body and liver weight, different digestion times of perfusates, pH, a range of concentrations of sodium and chloride in EDTA, and collagenase perfusates. Univariate and multivariate analysis of a retrospective study (n = 23) revealed that low perfusate pH during the process of digestion had a positive effect on hepatocyte yield (p < 0.05), while high (relative) concentrations of sodium and chloride in the perfusates had significant negative effects on hepatocyte viability (both p < 0.05). Sodium and chloride had narrow optimal ranges for achieving a >90% viability. These findings were then tested in a prospective study (n = 10) and further verified. High hepatocyte viabilities (91.8+/-1.6% p = 0.036) and yields (2.56+/-0.48 x 10(10)) were achieved consistently, and P450IA1 activity was increased after sodium and chloride concentrations and pH in the perfusates were controlled. The physiological mechanism by which sodium and chloride affects hepatocyte viability during porcine liver digestion is discussed.

Animals↗

PubMedDate not supplied

An epidemiological analysis of leprosy from 1951-1996 in Sichuan.

Through the leprosy surveillance system established in 1990s the authors analysed the epidemiology of leprosy in Sichuan province from 1951 to 1996. By the end of 1996, the total number of registered cases was 32,772, the peak incidence rate (2.44/100,000) was in 1958. The annual average progressively decreasing speed (AAPDS) of the number of new cases, incidence rate, incidence rate among children, number of newly detected patients, detection rate, number of registered cases and registered prevalence rates were 4.7% (xg = 0.9534), 5.9% (xg = 0.9407), 7.4% (xg = 0.9263), 6.7% (xg = 0.9326), 8.1% (xg = 0.9195), 10.9% (xg = 0.8913) and 11.7% (xg = 0.8828) respectively. Among newly detected cases, the proportion of children gradually declined with an AAPDS of 2.9% (xg = 0.9712), but that of household contacts gradually increased, showing a gradual decline of source of infection. The multibacillary (MB) rate among new cases, newly registered cases and active cases also increased gradually. The MB rate among child cases was much lower than that among adults. The disability rates among newly registered cases tended to decline. The peak incidence was in the 20 to 35 years age group, the average age at onset being 31.92 years. Average age at onset gradually increased to 34.19 during 1991-1995. The average interval between onset of symptoms and diagnosis was 4.89 years and that had reduced gradually to 3.24 years during 1991-1995. The authors conclude that: (1) the epidemiological trend of leprosy in Sichuan province shows decline; (2) the case-finding activities have improved and intensified; but (3) the disability rate among newly detected cases is still high (> 20%) and the average delay in diagnosis is still too long, showing that early case finding is still not satisfactory.

Adolescent↗

PubMedDate not supplied

A rural-urban comparative study of nonphysician providers in community and migrant health centers.

This is a study of the employment of nonphysician providers--nurse practitioners, physician assistants, and certified nurse midwives--in both rural and urban Community and Migrant Health Centers and of factors associated with their employment, based on a 1991 national survey of 383 Centers. Results of the survey suggest that nonphysician providers, in particular nurse practitioners and certified nurse midwives, primarily serve as physician substitutes, and are more likely to be employed by Centers that are larger and have affiliations with nonphysician provider training programs. Rural or urban location is not significantly related to the employment of nonphysician providers after controlling for center size. The fact that rural centers employ fewer nonphysician providers than urban centers can primarily be accounted for by their relatively small size, rather than a lack of interest. These findings demonstrate that the use of nonphysician providers is an important way both to achieve cost containment and improve access to primary care for those residing in medically underserved areas.

Community Health Centers↗

PubMedDate not supplied

A cost-benefit analysis of a California county's back injury prevention program.

Back-related injuries have become a major health problem in the workplace, affecting as many as 35 percent of the work force and accounting for about 25 percent of all compensation claims. This study evaluates a back injury prevention program among employees in a northern California county in 1989-90. Six divisions of the county government were selected for the study because they had the highest prevalence of back pain experienced and the most back-related injuries in recent years. Four of the six divisions were randomly selected as the intervention group and the remaining two, the control group. Overall, 77 percent or 205 of the targeted employees in the intervention group participated in the study. The intervention group was given an identical health risk assessment (HRA) before and after the 1-year back injury prevention program that offered employees a combination of education, training, physical fitness activities, and ergonomic improvement. The control group was neither given the HRA nor offered the program. The back injury and cost data of both the control and intervention groups were collected before and after the 1-year intervention. The results showed a modest overall decline in back pain prevalence rates, but significant improvement in satisfaction and reduction in risky behaviors. Cost-benefit analysis showed the net benefit of introducing back injury prevention program was $161,108, and the return on investment is 179 percent. Therefore, the study offers suggestive evidence for the initial benefits of a back injury prevention program and lends support to the widely held belief that health promotion in the workplace can reduce employee health risks, increase healthful behaviors and attitudes, and improve attitudes toward the employer organization.Whether such intervention will continue to reap benefits in future years depends, to a large extent,on a favorable work environment and the maintenance and continuation of positive behavioral changes.

Adult↗