广东省农业生态学三十年发展概要

广东省农业生态学近三十年的发展过程可以大致以十年为一段分为:(1)为现代农业生态学发展的奠基阶段,(2)为农业可持续发展的探索阶段和(3)推动农业生态学长远发展的平台建设阶段。广东省生态学工作者在改革开放初期为我国农业生态学体系的建设、科研教学的人才培养和农业生态系统的科学研究奠定了坚实的基础。在上个世纪九十年代,我省农业生态学工作者积极参与广东省和全国的生态农业建设,组织了跨学科、跨单位的大规模农业可持续发展研究。跨入新世纪,我省农业生态学家不仅积极推动全国农业生态学有关组织的活动,而且通过重点学科和重点实验室的建设,为学科长远发展建立了高水平的硬件平台,通过活跃的重大项目研究把农业生态学研究逐步推向深入,系列农业生态学著作和教材的出版更为未来农业生态学的发展建立了丰厚的思想平台。     

Causation and Disease: The Henle-Koch Postulates Revisited

The Henle-Koch postulates are reviewed in terms of their full validity in Koch's day and in light of subsequent developments. The changing guidelines developed for viral diseases, for viruses in relation to cancer and to chronic central nervous system infection, and for causative agents in chronic diseases are discussed chronologically. A set of guidelines for both acute infectious and chronic diseases is presented. The need for recognizing the role of the host and the spectrum of host responses, for sound biologic sense in evaluating causal roles of agents in disease, and for flexibility in adapting our guidelines to new knowledge are emphasized.     

Improved simultaneous determination method of beta-carotene and retinol with saponification in human serum and rat liver

Among the many simultaneous determination methods for carotenoid and retinoid, there are only a few reports including the saponification process. However, the yields of beta-carotene and retinol were higher when using this process. In this study, the analytical conditions, including saponification, were investigated. The extraction solvent was n-hexane and the sample solvent was HPLC mobile phase in the beta-carotene and retinol analysis. BHT as an antioxidant was added at concentrations of 0.125 and 0.025%, respectively, to ethanol and n-hexane phase in the extraction process for serum. The recovery rates were 99.7, 93.7 and 98.3% for beta-carotene, retinol and retinyl palmitate in serum, respectively, and 107.1, 92.8 and 98.8% for beta-carotene, retinol and retinyl palmitate in liver, respectively. The within-day coefficients of variation (C.V.) were 6.0% for serum and 4.7% for liver in the case of beta-carotene, 7.1% for serum, and 5.1% for liver in the case of retinol. The between-day coefficients of variation were 2.7% for serum and 2.7% for liver in the case of beta-carotene, and for retinol, 6.4% for serum and 2.7% for liver.     

菜豆种质资源RAPD多样性的研究Ⅱ

本研究收集了我国43个栽培品种,国际热带农业中心13个半野生品种,波兰4个矮生品种共60个菜豆品种资源,将其分成三大类型,即蔓生种35个,矮生种12个,半野生种13个,从RAPD标记上进行了研究,探明种内及各种群间的遗传相似度、遗传距离,绘制聚类分析图。综合RAPD标记聚类图,表明:蔓生种群分为五大类;矮生种群分为二大类;半野生种群分为二大类。我国是菜豆的主要育种、栽培地区,收集国内外菜豆种质资源,开展DNA水平的分子标记将有助于了解菜豆种内、各种群间的遗传基础,确定各资源材料间的亲缘关系,为我国菜豆种质资源的保存及培育优良品种工作提供一定的理论依据。     

Circannual and Circa-Hemiannual Rhythms of Basal and Stimulated Gastric Secretion in Conscious Cats

Conscious cats equipped with a gastric fistula and a denervated Heidenhain pouch were submitted to weekly measurements of the basal and pentagastrin-stimulated gastric secretion for 1 to 14 years. Rhythms of basal secretion were documented in 37 cats for the group studies, in 25 cats only for the individual studies which required at least whole year data. Twelve-month or 6-month rhythms were detected for each variable studied, i.e. volume, acid, pepsin, fucose and uronic acid outputs in the group studies, with peaks for volume, acid and pepsin in Winter, peaks for uronic acid in Spring and Fall indicating different rhythms for oxyntic, chief and mucous cells. Individual studies detected rhythms in 25% of the analyses, and demonstrated male and female and cat to cat differences. Spectral analysis in 3 cats confirmed the differences in the individual rhythms with prominent peaks differing from 365 days in 50% of the cases. Chronopharmacological responses to pentagastrin were documented for volume, acid and pepsin outputs in 5 male and 6 female cats. Group analysis detected a Winter acrophase for volume and acid secretion and a Summer acrophase for pepsin secretion. Analysis of the stimulated response data showed interindividual variation but a higher percentage of detection for rhythms, i.e. 38% for all variables and 50% for pepsin secretion. Different rhythms in acid and pepsin secretion documented in individual studies could provide the basis of a better understanding of the discrepancies reported in the literature concerning the seasonal incidence of peptic ulcer disease.     

Demography of the human sex ratio in some Latin American countries, 1967-1986.

A sample based on hospital births recorded for the Latin American Collaborative Study on Congenital Malformations (ECLAMC) program was used in the present study to determine sex ratios for live births and for stillbirths. Sixty-four cities and 147 hospitals in 11 countries (Uruguay, Chile, Argentina, Brazil, Bolivia, Peru, Paraguay, Ecuador, Venezuela, Colombia, and Costa Rica) were included in the present analyses. The number of live births was 1,886,653 in the period 1967-1986, and the number of stillbirths was 24,818 in the period 1978-1986. The sex ratio for the total sample was 0.5112 for live births and 0.5477 for stillbirths. The sex ratio as a whole is decreasing with time in a parabolic fashion. Each country in our study behaved differently. Except for Peru and Uruguay, the countries experienced a significant decrease in the sex ratio after 1978 for live births; only Brazil did not show a temporal trend for the sex ratio for stillbirths.     

Circannual and Circa-Hemiannual Rhythms of Basal and Stimulated Gastric Secretion in Conscious Cats

Conscious cats equipped with a gastric fistula and a denervated Heidenhain pouch were submitted to weekly measurements of the basal and pentagastrin-stimulated gastric secretion for 1 to 14 years. Rhythms of basal secretion were documented in 37 cats for the group studies, in 25 cats only for the individual studies which required at least whole year data. Twelve-month or 6-month rhythms were detected for each variable studied, i.e. volume, acid, pepsin, fucose and uronic acid outputs in the group studies, with peaks for volume, acid and pepsin in Winter, peaks for uronic acid in Spring and Fall indicating different rhythms for oxyntic, chief and mucous cells. Individual studies detected rhythms in 25% of the analyses, and demonstrated male and female and cat to cat differences. Spectral analysis in 3 cats confirmed the differences in the individual rhythms with prominent peaks differing from 365 days in 50% of the cases. Chronopharmacological responses to pentagastrin were documented for volume, acid and pepsin outputs in 5 male and 6 female cats. Group analysis detected a Winter acrophase for volume and acid secretion and a Summer acrophase for pepsin secretion. Analysis of the stimulated response data showed interindividual variation but a higher percentage of detection for rhythms, i.e. 38% for all variables and 50% for pepsin secretion. Different rhythms in acid and pepsin secretion documented in individual studies could provide the basis of a better understanding of the discrepancies reported in the literature concerning the seasonal incidence of peptic ulcer disease.     

Aging process of leg muscle endurance in males and females

In order to estimate muscle endurance during knee extension (KME) and plantar flexion (PME) using a simple method, holding times for the half-squatting posture for KME and for the calf-raising posture for PME were measured in 3,792 males and 3,620 females aged between 6 and 79 years. The regression lines of the aging process for KME and PME in both sexes were determined. Peak values were found at 13 years in males and 12 years in females for KME, and at 15 years in males and 16 years in females for PME. The mean values increased sharply with age up to each peak and then decreased abruptly to a low level at around 20 years, thereafter declining gradually. The values of KME as a percentage of the peak value were 71, 75 and 34 at the ages of 6, 20 and 70-79 years respectively in males, while the corresponding values were 80, 77 and 36 for females. The values of PME at these ages were 34, 93 and 69 in males and 54, 91 and 73 in females. The mean values for males were generally higher than those for females. These results suggest that endurance of the leg muscles differs according to age, sex and the region of the leg muscle. These data will be useful as standard values for evaluating endurance and for prescribing suitable exercise for the promotion of physical fitness.     

Relationships in Canada between mortality from tumours of the gastrointestinal tract and marital status.

The mortality from tumours of the gastrointestinal tract in the Canadian population in 1970-72 was 16% higher in single than in married men (on the basis of age-adjusted rates), 25% higher in widowed men and 28% higher in divorced men. All these differences were unlikely to be due to chance. The rates were 4% higher for single women, 14% higher for widows and 22% higher for divorced women, compared with the married. The differences for single and divorced women were not significant. Substantial excess mortality was found in the unmarried for tumours of the mouth, pharynx and esophagus, and rectum; for tumours of the stomach and colon the excess was small or nonexistent. This variation between sites suggests that systematic errors in the census data used as denominators are not responsible for the high mortality for the unmarried from certain tumours. The effect is found in conditions for which treatment can have made little difference (e.g., a 75% excess mortality for tumours of the esophagus in single men compared with married) and in conditions for which differences in the use of medical facilities may have been important (e.g., a 44% excess mortality for tumours of the rectum in widowers).     

Stark effect spectroscopy of carotenoids in photosynthetic antenna and reaction center complexes

The effects of electric fields on the absorption spectra of the carotenoids spheroidene and spheroidenone in photosynthetic antenna and reaction center complexes (wild-type and several mutants) from purple non-sulfur bacteria are compared with those for the isolated pigments in organic glasses. In general, the field effects are substantially larger for the carotenoid in the protein complexes than for the extracted pigments and larger for spheroidenone than spheroidene. Furthermore, the electrochromic effects for carotenoids in all complexes are much larger than those for the Qx transitions of the bacteriochlorophyll and bacteriopheophytin pigments which absorb in the 450-700 nm spectral region. The underlying mechanism responsible for the Stark effect spectra in the complexes is found to be dominated by a change in permanent dipole moment of the carotenoid upon excitation. The magnitude of this dipole moment change is found to be considerably larger in the B800-850 complex compared to the reaction center for spheroidene; it is approximately equivalent in the two complexes for spheroidenone. These results are discussed in terms of the effects of differences in the carotenoid functional groups, isomers and perturbations on the electronic structure from interactions with the organized environment in the proteins. these data provide a quantitative basis for the analysis of carotenoid bandshifts which are used to measure transmembrane potential, and they highlight some of the pitfalls in making such measurements on complex membranes containing multiple populations of carotenoids. The results for spheroidenone should be useful for studies of mutant proteins, since mutant strains are often grown semi-aerobically to minimize reversion.     

Identification of overweight in children in the United States: a simplified approach

The objective of this study was to develop a screening instrument for easy identification of overweight in children and adolescents in the United States. Data derived from the 2000 Growth Charts published by the Centers for Disease Control and Prevention (CDC) were utilized to compute gender-specific screening values for identification of overweight in children and adolescents. Computations were based on age- and gender-specific 85th percentile BMI calculated for the various height percentiles at 6-month age intervals. The simplified approach for identification of overweight in children and adolescents consisted of two tables, one each for males and females. Each table described the screening values for overweight at 6-month age intervals for all the nine height percentiles described in the CDC Stature for Age Tables. Two screening tables for identification of obesity were also developed in a similar manner using age- and gender-specific 95th percentile BMI. The simplified approach described for identification of overweight uses only the child's height and weight measurements and obviates the need to compute BMI or assess BMI percentile scores.     

Is the PRC for Dark Pulses in LL a Mirror Image of the PRC for Light Pulses in DD in Mice?

The phase-response curves (PRC) for light pulses in continuous darkness (DD) have been described in many mammals, especially in nocturnal rodents. The PRC for dark pulses in continuous light (LL), however, has been described in a few mammals only, in nocturnal for bat and for hamster and in diurnal for Octodon degus, suggesting that this PRC is mirror imaging the PRC for light pulses. Therefore, the effect of 1-h and 3-h lasting dark pulses on the circadian wheel-running activity rhythm of mice in continuous light was investigated and then the PRC for dark pulses in LL was drawn up. For comparison, the effect of 1-h lasting light pulses on the circadian wheel-running activity rhythm of mice in DD was examined and the PRC for light pulses in DD was constructed. It appeared that the PRC for dark pulses, to a certain degree, represents a mirror image of the PRC for light pulses in mice. However, the advance region of this PRC is longer than that of delay. The mechanism of dark pulses action is discussed.     

Is the PRC for Dark Pulses in LL a Mirror Image of the PRC for Light Pulses in DD in Mice?

The phase-response curves (PRC) for light pulses in continuous darkness (DD) have been described in many mammals, especially in nocturnal rodents. The PRC for dark pulses in continuous light (LL), however, has been described in a few mammals only, in nocturnal for bat and for hamster and in diurnal for Octodon degus, suggesting that this PRC is mirror imaging the PRC for light pulses. Therefore, the effect of 1-h and 3-h lasting dark pulses on the circadian wheel-running activity rhythm of mice in continuous light was investigated and then the PRC for dark pulses in LL was drawn up. For comparison, the effect of 1-h lasting light pulses on the circadian wheel-running activity rhythm of mice in DD was examined and the PRC for light pulses in DD was constructed. It appeared that the PRC for dark pulses, to a certain degree, represents a mirror image of the PRC for light pulses in mice. However, the advance region of this PRC is longer than that of delay. The mechanism of dark pulses action is discussed.     

Perspectives for malaria vaccination

The need for vaccines to relieve the current global resurgence of malaria is apparent. Immunity is specific for each species of human malaria and for each stage in the life cycle. Once protective immunogens have been identified for one species, the homologous molecules in other species may lead to protection. The usefulness of a particular immunogen will be determined, in part, by its antigenic diversity in the population and the potential for boosting during natural infection. Successful immunization with malarial antigens may require adjuvants to induce effective, long-lived immunity. If different vaccines become available against each stage in the life cycle, then the composition of a particular vaccine may be tailored for different objectives: protection for short periods (for example, during epidemics and for tourists), decrease in disease and death, and malaria eradication.     

Twinning rates in a rural area of Bangladesh

In this study we investigate the incidence of twin births over a period of 16 years in a rural area of Bangladesh using data from the Demographic Surveillance System of the International Centre for Diarrhoeal Disease Research. Over the study period twinning rates fluctuated between 7.8 and 11.2 per 1000 live births. The twinning rate was strongly correlated with maternal age; the rate for mothers over 35 years of age was about 3 times higher than for mothers younger than 20 years. The variation in twinning rate with maternal age is due to the variation in dizygotic twinning; the rate of monozygotic twinning is almost constant for all ages. Twinning rates were higher in the treatment area than in the comparison area after controlling for maternal age and parity. The rates were lower for monozygotic twinning and higher for dizygotic twinning in the treatment area than in the comparison area. Seasonality was observed for both twins and singletons, but the peak for twinning precedes that for singleton births by more than a month.     

Alginate/carbon composite beads for laccase and glucose oxidase encapsulation: application in biofuel cell technology

Alginate–carbon beads were prepared in order to develop a biocompatible matrix for laccase and glucose oxidase immobilization for application in biofuel cell technology. The enzyme loading capacity was high (91%) in pure alginate beads for glucose oxidase. For laccase, the loading capacity was enhanced from 75% to 83% by introducing carbon. Desorption out of the matrix was controlled by the enzymes’ diffusion and reached a plateau after 40 h for laccase and 70 h for glucose oxidase. Two-thirds of both enzymes was irreversibly retained inside the alginate beads. This proportion increased to 80% for laccase in combined alginate/carbon beads. Half-life of the adsorbed enzyme was enhanced to 74 days for laccase in carbon/alginate beads and 45 days for glucose oxidase in pure alginate as compared to 38 days and 23 days for free enzymes, respectively.