Nonlinear dynamic behavior of cardiac oscillators

By studying a mathematical model of the effects of brief current impulses on the oscillation of cardiac cells, we have simulated the phase transition curves of the oscillators. This has permitted discussions of the interactions of two coupled sinus oscillators and the periodic stimulation of one ventricular oscillator. The results have been compared with findings from the normal electrocardiogram and applied to explain the mechanisms of some arrhythmias.

Prevalence survey of cytomegalovirus infection in children in Chengdu

Cytomegalovirus (CMV) is a common worldwide perinatal infection. Although usually asymptomatic, it may cause deafness in up to 15% of these infants. A cross-sectional study was performed to determine the age-specific prevalence of CMV seropositivity in Chinese children and to determine if any risk factors for infection could be identified. In a two-stage sampling procedure, nine districts were randomly selected from 70 citizenship districts in Chengdu, Sichuan Province, People's Republic of China. Then, 1,950 households were randomly selected from 11,886 households and interviewed. Blood was obtained from all children aged less than seven years and assayed using an enzyme-linked immunosorbent assay method. A subgroup of sera was retested at the research laboratory and also sent to the National Reference Laboratory in Beijing. Kappa values for the test agreement with the reference laboratory and retesting within the study laboratory were 0.94 and 0.86, respectively. Seropositivity averaged 52% in those aged less than one year and 60% in those between four and seven years. A higher rate of seropositivity was observed in urban versus rural children (odds ratio (OR) = 2.55), breast feeding in urban areas only (OR = 1.87), and day care versus home care setting (OR = 1.59). High CMV seroprevalence, even in the first year of life, was observed in this population of well children in Chengdu, China. An association was observed between seroprevalence and residence, method of feeding, and day care attendance.

On the relationships between rural labor productivity, family investment in education, and population quality

The authors consider "the relationships between labor productivity and population quality in order to demonstrate the importance of economic development, and of improving population quality in rural areas. This study is made on the basis of surveys conducted in 1979 and 1986 on the age-specific VP and VC [volume of production and volume of consumption] in certain areas of Jiangsu Province [China]." Population quality is defined primarily in terms of the educational status of the labor force.

Involvement of the nigral output pathways in the inhibitory control of the substantia nigra over generalized non-convulsive seizures in the rat

Activation of GABAergic transmission within the substantia nigra has been shown to suppress several forms of generalized seizures in experimental models of epilepsy. More especially, such pharmacological manipulations suppress spontaneous and chemically-induced generalized non-convulsive seizures in the rat. The aim of the present study was to examine the role of the dopaminergic and GABAergic thalamic and collicular nigral outputs in this antiepileptic effect. For this purpose, we examined the effects of output destruction on the antiepileptic effect of intranigral injections of a GABA agonist or pharmacological blockade of the neurotransmission at the nerve terminal level in rats with spontaneous absence seizures. After selective destruction of dopaminergic neurons within the substantia nigra with 6-hydroxydopamine (5 micrograms/side) or hemisection of the ascending nigral output, bilateral intranigral injection of muscimol (2 ng/side) still significantly suppressed generalized non-convulsive seizures. Bilateral lesioning of the ventromedial nucleus of the thalamus did not abolish the antiepileptic effects of intranigral muscimol (2 ng/side) and the GABA antagonist, picrotoxin, when given into this thalamic nucleus (10 ng/side) also failed to induce suppression of spike and wave discharges. The antiepileptic effects of intranigral injection of muscimol (2 ng/side) was reversed by bilateral electrolytic lesions of the superior colliculus. Blockade of the GABAergic transmission at this level with picrotoxin (40 ng/side) significantly suppressed generalized non-convulsive seizures. Finally, excitation of collicular cell bodies with low doses of kainic acid (4 and 8 ng/side) also resulted in a suppression of spike and wave discharges. These results demonstrate that the GABAergic nigrocollicular pathway is critical for the inhibitory control of the substantia nigra over generalized non-convulsive seizures. The data further suggest that antiepileptic effects observed following potentiation of GABAergic transmission in the substantia nigra result from a disinhibition of collicular cell bodies.

[Affective disturbances in patients with breast cancer]

40 cases of breast tumor (cancer group 20 cases, benign tumor group 20 cases) hospitalized from October, 1986 to April, 1987 were investigated by interview, HAMD, SCL-90 and so on. Results showed that 10 cases met diagnostic criteria of organic affective syndrome defined by DSM-III. The morbidity of depression among all cases was 25 per cent, but the morbidity of depression in breast cancer group was higher than in benign tumor group. Causes of depression in breast cancer were analysed. Authors consider that causes of depression are not relating to operation on breast, but probably relating to biological and psychosocial factors.

[Changes of glomerular fixed anionic charge sites in adriamycin nephrosis in rats]

A single intravenous injection of adriamycin (5mg per kg.) into rats induced nephrosis. In the various periods of the model, alterations of glomerular anionic sites stained with colloidal iron were analyzed quantitatively by image analyzer for the first time at home and abroad. The results showed that there was a significant decrease in glomerular anionic charge sites at 3 hours after administration of adriamycin as compared with that of the control animals (P less than 0.01). Marked loss of the anionic charge sites preceded the onset of proteinuria and was steadily increasing along with progress of the disease. The results suggest that loss of glomerular anionic charge sites may play an important role in the development of proteinuria in nephrotic syndrome.

Environmental factors and Parkinson's disease: a case-control study in China

We studied the role of environment in the development of Parkinson's disease (PD) in China, where industrialization is relatively recent and the population geographically stable. Using a case-control method, we investigated the relationship between PD and exposure to the following factors before disease onset: place of residence, source of drinking water, environmental and occupational exposure to various agricultural and industrial processes. Occupational or residential exposure to industrial chemicals, printing plants, or quarries was associated with an increased risk of developing PD. In contrast, living in villages and exposure to the common accompaniments of village life, wheat growing and pig raising, were associated with a decreased risk for PD. PD cases and controls did not differ with respect to other factors investigated. These findings are consistent with the hypothesis that environmental exposure to certain industrial chemicals may be related to the development of PD.

Computer simulations of figure-ground discrimination in the visual system of the fly

Figure-ground discrimination and pattern discrimination represent one of the most important problems in computer vision. Based on computational neuronal network model proposed by Reichardt et al. for figure-ground discrimination in the visual system of the fly, entire systematic computer simulations were carried out under nonstationary conditions. Results show that the model network and simulations have predictive power for behavioural experimental results. This paper proposes that motion perception and elementary pattern discrimination in human visual system may be mediated by some kind of figure-ground system with movement detectors as input layer.

Urban-rural and educational differentials in marital status in China

Since 1950, laws aimed at delaying marriage have been 1 of the major means of slowing population growth in China, where marriage is nearly universal. Age at marriage has risen in recent decades, but not to the same extent in all localities. This article uses cross-tabulated data from China's 1982 census to assess the effects of urban-rural residence and educational level on the ages at which men and women have been marrying. The data also reveal the effects of residence and education on widowhood, divorce, and current marital status. As expected, exposure to development, indicated by urban residence and higher education, is associated with later marriage, but it also increases the likelihood of ever marrying, especially for men. Women's tendency to seek social mobility by marrying men from economically more developed areas results in bachelorhood for a substantial percentage of rural men, especially those who are illiterate.

Pontentiometric cyanine dyes are sensitive probes for mitochondria in intact plant cells : kinetin enhances mitochondrial fluorescence

Selected fluorescent dyes were tested for uptake by mitochrondria in intact cells of barley, maize, and onion. The cationic cyanine dye 3,3'-diheptyloxacarbocyanine iodide [DiOC(7)(3)] accumulated in mitochondria within 15 to 30 minutes without appreciable staining of other protoplasmic constituents. The number, shape, and movement of the fluorescent mitochondria could be seen readily, and the fluorescence intensity of the mitochondria could be monitored with a microscope photometer. Fluorescence was eliminated in 1 to 5 minutes by the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) indicating that maintenance of dye concentration was dependent on the inside-negative transmembrane potential maintained by functional mitochondria. Fluorescence of prestained mitochondria was enhanced within 5 to 10 minutes after addition of 0.1 millimolar kinetin to cells. The fluorescence in kinetintreated cells was dissipated by CCCP. These results suggest that kinetin interacted with respiratory processes resulting in higher potential across the mitochondrial membrane.

Calcium-41 Concentration in Terrestrial Materials: Prospects for Dating of Pleistocene Samples

Calcium-41 has been suggested as a new tool for radiometric dating in the range of 10(5) to 10(6) years. The concentration of cosmogenic calcium-41 in natural samples of terrestrial origin has now been determined by high-sensitivity accelerator mass spectrometry after pre-enrichment in calcium-41 with an isotope separator. Ratios of calcium-41 to total calcium between 2 x 10(-14) and 3 x 10(-15) were measured for samples of contemporary bovine bone and from limestone deposits. Some prospects for the use of calcium-41 for dating Middle and Late Pleistocene bone and for other geophysical applications are discussed.