植物冷锻炼对于胁强敏感度的影响(英文)

前文由柑桔枝条在不同低温下、不同冷冻时间的电解质外渗测定,提出胁强(stress)、作用时间与胁变(strain)之间关系的数学模型。在这个模型中共有3个参数:屈服点温度(yield point temperature),胁强敏感度(stress sensitivity)和作用时间敏感度(sensitivity to duration),用以描述植物的抗性。抗性强的植物应表现为屈服点温度较低,胁强敏感度或者时间敏感度较低。为验证此数学模型,本工作以经冷锻炼与未经冷锻炼的盆栽柑桔枝条为材料,作不同温度与时间处理的电解质外渗率的测定,研究了冷锻炼对于上述3个参数的影响。发现胁强敏感度和屈服点温度受冷锻炼影响而下降,时间敏感度未表现明显变化。对于田间柑桔、油桐与毛竹的定期测定,在固定冷冻时间下,得到了类似于盆栽柑桔的结果。入冬时,植物抗冻性提高,3种植物都表现出下列两种变化:1.胁强敏感度的明显下降;2.屈服点温度和/或时间敏感度亦下降。开春时的变化则相反。胁强敏感度的变化与后一种变化有各自的规律,且因植物种类而不同。拐点胁强(stress at inflection point)具有与半致死温度(50％killing point temperature)不同的意义,它的变化是上述两种变化的综合结果。本试验结果表明,冷锻炼对于植物胁强敏感度有明显影响,用本数学模型的3个抗性指标描述     

Self-Reported Substantial 1-Year Weight Change Among Men and Women in the United States

Population-based data have not been readily available on relatively short-term changes in weight. Therefore, we sought to determine the nature of self-reported substantial (> 10%) weight change over one year in a representative sample of the US population which participated in the 1989 National Health Interview Survey (NHIS). Across all ages, a larger proportion of women than men reported both weight loss as well as weight gain of any amount (18.9% vs. 16.1% for weight loss and 20.0% vs. 16.1% for weight gain). In sex-specific logistic regression analyses, significant risk factors common to both sexes for substantial weight loss included divorced/separated marital status, smoking, increased number of blood pressure checks, increased BMI (body mass index) and increased number of bed days. Black race reduced the risk of weight loss for both men and women. Sex-specific risk factors for weight loss in men only were widowhood or never married marital status, while increasing age was a protective factor in women only. Concerning weight gain > 10% over the past year, increased number of blood pressure checks and having one or more diabetic parents were significant risk factors among both men and women; while never being married, increased age, BMI, and education exerted a protective effect in both sexes. For women only, risk factors for weight gain included black race, increased number of contacts with a health professional, and being unemployed. Intention to lose weight was associated with both weight gain and weight loss in both sexes, although it did not serve as a confounder in any of these relationships. A greater likelihood of substantial weight loss among women relative to men was diminished for persons with higher BMI, higher number of blood pressure checks, being widowed, divorced or separated, and intention to lose weight. A greater likelihood of substantial weight gain among women relative to men was diminished for persons with low BMI. The results of this cross-sectional study of weight change, involving a one-year follow-up period, generally correspond with the results obtained by longitudinal studies involving a longer follow-up.     

The periodicities in and biometeorological relationships with bed occupancy of an acute psychiatric ward in Antwerp,Belgium

Recently, some investigators have established a seasonal pattern in normal human psychology, physiology and behaviour, and in the incidence of psychiatric psychopathology. In an attempt to elucidate the chronopsy and meteotropism in the latter, we have examined the chronograms of, and the biometeorological relationships to bed occupancy of the psychiatric ward of the Antwerp University Hospital during three consecutive calendar years (1987–1989). Weather data for the vicinity were provided by a local meteorological station and comprise mean atmospheric pressure, air temperature, relative humidity, wind speed and minutes of sunlight and precipitation/day. The number of psychiatric beds occupied during the study period exhibited a significant seasonal variation. Peaks in bed occupancy were observed in March and November, with lows in August. An important part of the variability in the number of beds occupied could be explained by the composite effects of weather variables of the preceding weeks. Our results suggest that short-term fluctuations in atmospheric activity may dictate some of the periodicities in psychiatric psychopathology.     

微生物发酵法生产S-腺苷甲硫氨酸的研究进展

S-腺苷甲硫氨酸(S-adenosyl-l-methionine, SAM)广泛存在于生物体内,主要参与生物体内的转甲基过程、转硫过程及转氨丙基过程,具有重要的生理功能,其生产备受重视。目前SAM生产的研究主要集中于微生物发酵法,该方法与化学合成法和酶催化法相比,成本较低且更容易实现工业化生产。随着需求量的迅速增加,通过菌种改良提高SAM产量备受关注。当前SAM生产菌种改良的主要策略包括常规育种和代谢工程。本文综述了提高微生物生产SAM能力的近期研究进展并探讨了SAM生产中的瓶颈问题及解决方法,以期为进一步提高SAM产量提供思路。     

Macrophage activation for tumor cytotoxicity: induction of tumoricidal macrophages by supernatants of PPD-stimulated Bacillus Calmette-Guérin-immune spleen cell cultures.

Resident peritoneal macrophages from normal mice were activated for tumor cytotoxicity in vitro by co-cultivation with BCG1-immune spleen cells and PPD and by incubation with supernatants of PPD-stimulated BCG-immune spleen cell cultures (lymphokine supernatants). Lymphokine activation of macrophages occurred in unfractionated PC suspensions as well as in macrophage monolayers depleted of nonadherent PC. Tumor cytotoxicity by lymphokine-activated macrophages was evident by 3 to 4 hr of culture in active supernatants, reached maximal levels by 8 to 12 hr. and was absent by 20 hr. Continued incubation in lymphokines or even re-exposure after washing did not maintain macrophage cytotoxicity. The capacity of normal resident macrophages to be activated by lymphokines in vitro progressively decreased and was absent by 20 hr in culture. This decrease did not necessarily reflect cell death; macrophage viability as estimated by exclusion of trypan blue or by phagocytic responses did not change over the 20-hr culture period. The short lived nature of both macrophage tumoricidal capacity and capacity of precursor cells to be activated by lymphokines may function as negative feedback mechanisms in immune reactions.     

Biochemical and genetic characterization of three hamster cell mutants resistant to diphtheria toxin

We describe here three different hamster cell mutants which are resistant to diphtheria toxin and which provide models for investigating some of the functions required by the toxin inactivates elongation factor 2 (EF-2). Cell-free extracts from mutants Dtx(r)-3 was codominant. The evidence suggests that the codominant phenotype is the result of a mutation in a gene coding for EF-2. The recessive phenotype might arise by alteration of an enzyme which modifies the structure of EF-2 so that it becomes a substrate for reaction with the toxin. Another mutant, Dtx(r)-2, contained EF-2 that was sensitive to the toxin and this phenotype was recessive. Pseudomonas aeruginosa exotoxin is known to inactivate EF-2 as does diphtheria toxin and we tested the mutants for cross-resistance to pseudomonas exotoxin. Dtx(r)-1 and Dtx(r)-3 were cross-resistant while Dtx(r)-2 was not. It is known that diphtheria toxin does not penetrate to the cytoplasm of mouse cells and that these cell have a naturally occurring phenotype of diphtheria toxin resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance of the hybrid cells to diphtheria toxin. Intraspecies hybrids containing the genome of mutants Dtx(r)-1 and Dtx(r)-3 had some resistance while those formed with Dtx(r)-2 were as sensitive as hybrids derived from fusions between wild-type hamster cells and mouse 3T3 cells.     

Effect of morphine, beta-endorphin and leu-enkephalin on 3H-spiroperidol binding to bovine pituitary membranes.

The ability of morphine, leu-enkephalin and β-endorphin to antagonize the binding of ³H-spiroperidol to bovine anterior pituitary membranes was studied. All three drugs were virtually inactive despite their ability to stimulate prolactin secretion $\text{in}$$\text{vivo}$ and the reported ability of morphine to antagonize the inhibitory effect of dopamine on prolactin release from rat hemi-pituitaries. These results suggest that opiates do not produce their direct effect on prolactin secreation at the pituitary level through an effect on the ³H-spiroperidol binding site. The opiates may antagonize the effect of dopamine at a component of the dopamine receptor which is independent of the ³H-spiroperidol binding site, or the opiates may stimulate prolactin secretion by an effect on the lactotrophes which is independent of dopamine.     

Defective tumoricidal capacity of macrophages from C3H/HeJ mice

Peritoneal macrophages from C3H/HeN mice treated i.p. with T cell mitogens or viable BCG organisms were cytotoxic to syngeneic tumor cells in vitro. Macrophages from endotoxin-unresponsive C3H/HeJ mice treated with BCG or T cell mitogens, however, were not tumoricidal. Furthermore, unlike cells from C3H/HeN mice, macrophages from C3H/HeJ mice could not be activated for tumor cytotoxicity after in vitro treatment with bacterial endotoxins or with lymphokine-rich supernatants. The subnormal induction of cytotoxic macrophages after in vitro or in vivo treatments in C3H/HeJ mice appears to be a highly selective defect. Macrophage responses (yield, phagocytosis, or peroxidase staining) in inflammatory exudates induced by BCG, T cell mitogens, or heterologous serum in C3H/HeJ or C3H/HeN mice were identical. C3H/HeJ macrophages also responded normally in vitor to chemotactic lymphokines. Thus, C3H/HeJ macrophages possess a profound and selective defect in tumoricidal capacity. This defect was not dependent upon exogenous endotoxins. Defective macrophage cytotoxic responses may reflect non-LPS related functions regulated by the LPS gene.     

Effects of enkephalin in analogues on prolactin release in the rat.

The effects of nineteen enkephalin analogues on the circulating levels of prolactin in the male rat following intraventricular injection of the peptides were determined and compared with that of Met- and Leu-enkephalin. Eleven of the 19 analogues stimulated prolactin secretion. It was found, in general, that the structure activity relationship for enkephalin stimulation of prolactin secretion was similar to that for opiate receptor activity. Analogues which contained a [DAla²] substitution were generally effective in stimulating prolonged prolactin release. Some, but not all analogues containing [DTrp²] or [DLeu⁵] were active. Analogues containing the [DTrp¹], [DPhe⁴] or [DMet⁵] substitutions were ineffective. The prolactin releasing effect of intravenous Tyr-DAla-Gly-Phe-DLeu was reversed by naloxone. Naloxone had no effect on the haloperidol- and alpha-methylparatyrosine induced increases in plasma prolactin levels. The results of these studies are discussed in the light of the suggestion that the enkephalins may function as neuroendocrine modulators.