The visual system can be considered as a multi-layered and dynamic image processing system. According to experimental evidence, the receptive field (RF) organization is characterized by spatio-temporal properties. The modified extended Gabor (MEG) function model was proposed to describe the main spatio-temporal properties of RF at different levels of visual pathway. Based on the MEG model, a three-layered dynamic coding model was constructed for a complex cell. The responses of the complex cell depend on synaptic events from a simple cell assembly within a time window. The membrane potential evolution equation was applied to the analysis of the length of a time window. The simulation results demonstrated that a complex cell plays as a coincidence detector in encoding synaptic events within the time window.

Mathematics↗

PubMedDate not supplied

Branched-chain transaminase and keto acid dehydrogenase activities in burned rats: evidence for a differential adaptation according to sex.

Female and male rats show differences in nitrogen metabolism after trauma, and the contribution of the branched-chain amino acid oxidizing pathway following thermal injury was evaluated. Female and male rats were subdivided into baseline, burned and unburned, pair-fed groups. Burned and pair-fed rats were sacrificed on days 1, 2, and 3 postburn, and branched-chain amino acid transaminase (BCTA), branched-chain alpha-keto acid dehydrogenase (BCKDH) activated and total, and succinate dehydrogenase (SDH) activities were measured in red and white muscle and in liver, BCTA was not measured in liver. Baseline and pair-fed groups had similar enzyme activities. Changes following thermal injury were: (1) elevated SDH in all tissues for both sexes; (2) increased BCTA activity in red and white muscles from male rats; and (3) increased percentage of activated BCKDH in red and white muscles on days 2 and 3 for male rats. All other activities were unchanged. These findings agree with previous post trauma differences in urinary nitrogen losses in female and male rats. The results show that the enzymes for oxidation of the branched-chain amino acids in males respond to injury while those do not in females.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗

PubMedDate not supplied

Synthesis and structural characterization of highly chlorinated, brominated, iodinated, and methylated carborane anions, 1-H-CB9X9-, 1-NH2-CB9X9- (X = Cl, Br, I), and 1-H-CB9(CH3)9-.

The highly chlorinated, brominated, and iodinated carborane anions 1-R-CB9X9- (R = H, NH2; X = Cl, Br, I) were prepared in high yields by treatment of [Me3NH][1-R-CB9H9] with excess ICl, Br2/triflic acid, and I2/triflic acid, respectively, in sealed tubes at 180-240 degrees C. With the aid of a Pd catalyst, B-I bonds could be converted into the B-Me bonds by treatment with excess MeMgBr, which led to the preparation of the permethylated species 1-H-CB9Me9- in good yield. These new anions were fully characterized by 1H, 13C, and 11B NMR, IR, and negative-ion MALDI MS spectroscopy. Some were further characterized by single-crystal X-ray analyses. The weakly coordinating nature of these new anions was probed by 29Si chemical shifts.

Journal Article↗

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Non-parametric estimation of age-related centiles over wide age ranges.

A new method for estimating age-related centile curves has been developed, which is suitable for measurement covering a wide age range. The method was used to calculate weight centile curves of 8995 children from birth to 6 years obtained by the Collaborating Centre for Physical Growth and Psychosocial Development of Children in Shanghai, China.

Aging↗

PubMedDate not supplied

Technical note: reference values of haematocrit in young people and relationship with altitude.

The purpose of this paper is to provide scientific basis for a unified standard reference value of haematocrit in young people in China. The reference values of haematocrit levels in healthy young people have been collected according to the Wintrobe methods; the relationship between the reference values of haematocrit in young people and altitude has been tested in this paper. It has been found that the reference value of haematocrit in young people increases when the altitude gradually increases, and such relationship is quite significant, The method of mathematical univariate regression analysis is used to deduce two regression equations: Y1 = 44.3 + 0.00357X +/- 3.7, and Y2 = 39.7+0.00318X +/- 2.6. If the altitude value of a s known, the particular area of China is known, the reference value of haematocrit in young people there can be calculated by means of the regression equations. Furhermore depending on the altitude, China can be divided into three districts: Qingzang District, Central District and Eastern District.

Adolescent↗

PubMedDate not supplied

Comparison of in vitro and in vivo release characteristics of sustained release ofloxacin microspheres.

The sustained release nature of ofloxacin microspheres--to eradicate bacterial biofilm associated with chronic infections from sensitive strains of bacteria--was determined both in vitro and in vivo. Ofloxacin microspheres were prepared by emulsion solvent evaporation procedure using poly(glycolic acid-co-dl-lactic acid) (PLGA) as the biodegradable polymer. The microspheres were characterized by scanning electron microscopy, in vitro release in an incubator, and in vivo release in the rat subcutaneous model. The microspheres were highly spherical with a very smooth surface. Approximately 45% of the drug was released from microspheres in sizes of 125-250 microns and 250-425 microns in 2 days compared with approximately 22% from microspheres of size range 37-125 microns indicating that surface area of the microspheres did not control the kinetics of in vitro release. However, about 96% of the drug was released from the three different size ranges in 35 days. The in vitro release profile of microspheres of size range 125-250 microns is not significantly different from microspheres in sizes of 250-425 microns. The peak plasma level of ofloxacin in animals that received the drug suspension occurred within 2 hr and was higher than that of the microspheres that occurred by the end of the second day. The plasma of animals that received the free drug was depleted of ofloxacin by the end of the first day, but the drug was sustained above 0.5 microgram/mL in the plasma of animals that received the microspheres for about 3 weeks. The results suggest that biodegradable ofloxacin microspheres can be prepared that release the antibiotic in vivo for about 3 weeks. This should provide a means for continuous treatment of chronic infections in which bacterial biofilm can occur.

Animals↗

PubMedDate not supplied

Controlled release tacrine delivery system for the treatment of Alzheimer's disease.

Alzheimer's disease is a neurodegenerative condition that affects approximately 5 million people and is the fourth leading cause of death in America. Tacrine is one of the three drugs approved by the FDA for the treatment of Alzheimer's disease. However, the drug has a short biologic half-life of 2-3 hr and gastrointestinal, cholinergic, and hepatic adverse reactions that are associated with high doses of the drug. The aim of our study was to formulate a controlled release delivery system of tacrine that could be used to minimize the side effects associated with the drug. Microparticles of tacrine were formulated using poly(D,L-lactide-co-glycolide) (PLG). PLG and tacrine were dissolved in mixed organic solvents and added to a polyvinyl alcohol solution that was stirred at a constant rate. The organic solvent was evaporated overnight and the formed microparticles were collected by filtration, dried, and sieve-sized. The effects of such formulation variables, as molecular weight of polymer, stir speed during preparation, and drug loading on encapsulation efficiency (EEF), and in vitro release profiles of tacrine were investigated. An increase in the molecular weight of polymer from 8,000 to 59,000 and 155,000 resulted in approximately 10-fold increase in EEF, but the rate of release decreased with increasing molecular weight. Stir speed during preparation had an effect on the EEF but not on the rate of release. Drug loading did not have a significant effect on the EEF but had an effect on the rate of tacrine release. The results suggest that tacrine could be delivered at controlled levels for weeks for the treatment of Alzheimer's disease.

Alzheimer Disease↗

PubMedDate not supplied

Inheritance and allelism of resistance to soybean mosaic virus in Zao18 soybean from China.

Soybean mosaic disease caused by soybean mosaic virus (SMV) occurs wherever soybean [Glycine max (L.) Merr.] is grown and is considered one of the most important soybean diseases in many areas of the world. Use of soybean cultivars with resistance to SMV is a very effective way of controlling the disease. China has rich soybean germplasm, but there is very limited information on genetics of SMV resistance in Chinese soybean germplasm and reaction of the resistance genes to SMV strains G1-G7. There also is no report on allelic relationships of resistance genes in Chinese soybeans with other named genes at the three identified loci Rsv1, Rsv3, and Rsv4. The objectives of this study were to examine reactions of Chinese soybean cultivar Zao18 to SMV strains G1-G3 and G5-G7, to reveal the inheritance of SMV resistance in Zao18 and to determine the allelic relationship of resistance genes in Zao18 with previously reported resistance genes. Zao18 was crossed with the SMV-susceptible cultivar Lee 68 to study the inheritance of resistance. Zao18 was also crossed with the resistant lines PI96983, L29, and V94-5152, which possess Rsv1, Rsv3, and Rsv4, respectively, to examine the allelic relationship between the genes in Zao18 and genes at these three loci. Our research results indicated that Zao18 possesses two independent dominant genes for SMV resistance, one of which is allelic to the Rsv3 locus; the other is allelic with Rsv1. The presence of both genes (Rsv1 and Rsv3) in Zao18 confers resistance to SMV strains G1-G7.

Alleles↗

PubMedDate not supplied

Risk factors for trisomy 21: maternal cigarette smoking and oral contraceptive use in a population-based case-control study.

PURPOSE: We examined maternal smoking and oral contraceptive use as possible risk factors in the genesis of cases of trisomy 21 of maternal origin. This is the first epidemiological study to categorize cases of trisomy 21 by parent of origin and timing of the meiotic error before assessing possible risk factors. METHODS: We used chromosome 21-specific DNA markers to assign origin to each case. Structured interviews were employed to determine maternal smoking and oral contraceptive use around conception. RESULTS: The odds ratio (OR) for maternal smoking was significantly increased among younger mothers (OR = 2.98; 95% CI = 1.01-8.87), but only in a particular subset of meiotically-derived cases. The combined use of cigarettes and oral contraceptives increased the risk further (OR = 7.62; 95% CI = 1.63-35.6); however, oral contraceptive use alone was not a significant risk factor. CONCLUSION: Our results indicate that categorizing cases of trisomy 21 by parent and timing of the meiotic error allows more precision in identifying risk factors and may shed light on mechanisms of meiotic nondisjunction.

Adult↗

PubMedDate not supplied

On the use of population-based registries in the clinical validation of genetic tests for disease susceptibility.

PURPOSE: Many new genetic tests for susceptibility to adult-onset diseases are developed on the basis of selected and high-risk groups. Before such tests can be used in medical practice, however, epidemiologic studies must be conducted to evaluate their clinical sensitivity, specificity, and positive predictive value in the general population. For many common adult-onset diseases, this process may take decades of follow-up. METHOD: We illustrate how clinical validation of new predictive genetic tests can be done retrospectively using case-control studies that are derived from population-based registries of diseases. We use the examples of birth defects and cancer registries to illustrate a hypothetical process by which such tests can be clinically validated. RESULTS: We demonstrate how such epidemiologic studies can be successfully used to derive measures of a test's sensitivity, specificity, positive predictive value, negative predictive value, and of the population attributable fraction of disease due to the disease-susceptibility genes. Under certain assumptions, data derived from population-based case-control studies provide adequate estimates of lifetime risks for disease (penetrance) among people with specified genotypes. CONCLUSIONS: With adequate protections of human subjects, studies involving population-based registries of disease will increasingly become valuable in validating the numerous genetic tests that will emerge from advances in human genetic research and the Human Genome Project.

Adult↗

PubMedDate not supplied

Arsenic trioxide induces apoptosis in cisplatin-sensitive and -resistant ovarian cancer cell lines.

Arsenic trioxide (As(2)O(3)), has been used for centuries in traditional Chinese medicine; it has considerable efficacy in the treatment of relapsed acute promyelocytic leukemia, inducing partial differentiation and promoting apoptosis of malignant promyelocytes. Although a number of studies have demonstrated that As(2)O(3) has potent activity against cell growth in a series of leukemia cell lines, little information is available regarding this compound's effect on cell growth in solid tumor cell lines. In this study, we investigated the effects of As(2)O(3)in vitro on ovarian cancer cell lines sensitive (3AO) and resistant (3AO/CDDP) to cisplatin. The 3-(4,5-dimethy-thiazoyl-2-yl)-2,5-diphenyl-tetrazolium bromide assay was used to evaluate cytotoxicity. Flow cytometric analysis was used to determine the apoptosis, cell cycle distribution. We clearly demonstrated that As(2)O(3) induced cell apoptosis and inhibition of cell growth in both the cell lines. Furthermore, we identified that As(2)O(3)-induced apoptosis involved Fas pathway. As(2)O(3) is an active agent against ovarian cancer cells and could be effective in the clinical treatment of ovarian cancer.

Apoptosis↗

PubMedDate not supplied

Adjusting for confounding due to population admixture when estimating the effect of candidate genes on quantitative traits.

When analyzing the relationship between allelic variability and traits, a potential source of confounding is population admixture. An approach to adjusting for potential confounding due to population admixture when estimating the influence of allelic variability at a candidate gene is presented. The approach involves augmenting linear regression models with additional regressors. Family genotype data are used to define the regressors, and inclusion of the regressors ensures that, even in the presence of population admixture, the estimates of the regression coefficients that parameterize the influence of allelic variability on the trait are unbiased. The approach is illustrated through an analysis of the influence of apolipoprotein E genotype on plasma low density lipoprotein cholesterol concentrations.

Alleles↗

PubMedDate not supplied

Cytologic grading of invasive breast carcinoma. Correlation with clinicopathologic variables and predictive value of nodal metastasis.

OBJECTIVE: To estimate cytologic grade and correlate it with the other known prognostic factors, such as tumor differentiation, growth fraction, estrogen receptor status and nodal status. STUDY DESIGN: Fine needle aspirates from 104 invasive ductal carcinomas were stained by the Papanicolaou method and examined for necrosis, cellular size, nuclear/cytoplasmic ratio, nuclear pleomorphism, nucleoli, chromatin granularity and density of chromatin. We established a semiquantitative scoring system based on the above features and correlated cytologic findings with clinicopathologic variables. RESULTS: Histologic grade correlated positively with cytologic grade and negatively with estrogen receptor positivity. Moreover, high cytologic grade was associated with nodal metastasis and proliferative index labeling by MIB-1. CONCLUSION: This study showed that our grading system for breast cancer on fine needle aspiration cytology is feasible on a routine diagnostic basis. Cytologic grading can provide more information than usual on tumor biologic behavior.

Antigens, Nuclear↗

PubMedDate not supplied

Upper gastrointestinal tract bleeding: assessing the diagnostic contributions of the history and clinical findings.

Various strategies can be used in the diagnosis of upper gastrointestinal tract bleeding. This study investigates the relevance of anamnestic and clinical findings for the diagnosis of the bleeding source. The authors introduced a computer-aided diagnostic system using Bayes' theorem and compared it with clinicians' predictions using anamnestic and clinical findings only. There was no difference in the overall accuracy rates, but a difference was observed in the diagnostic behaviors of the two "systems." In addition, the discriminatory ability of the computer-aided system, the sharpness of the predictions obtained, and the reliability of the posterior probabilities were analyzed. It is concluded that the clinician and the computer-aided system are not able to discriminate well between the disease categories. Derived classification matrices and probability-based measures show the reasons for the inadequacy of diagnostic information obtainable from the clinical history and physical findings.

Bayes Theorem↗