柚花头香化学成分的研究(一)

本文首次报道柚花的香气成分。作者利用憎水性树脂XAD-4吸附柚鲜花的头香,并以毛细管气相色谱和毛细管气相色谱-质谱-计算机联用方法研究头香的化学组分,分离鉴定了17个已知化学成分。它们是芳樟醇、β-蒎烯、β-水芹烯、橙花叔醇等。     

Distribution and frequency of neuro-epithelial bodies in post-natal rabbit lung: Quantitative study with monoclonal antibody against serotonin

Summary The distribution, frequency and size of neuroepithelial bodies (NEB) were studied in lungs of rabbits during different stages of development (27-day fetus, newborn, 6, 11, 21, 28 and 56 days postnatally). NEB were visualized by immunostaining with monoclonal antibody against serotonin. Detailed quantitiation of NEB was performed by use of camera lucida drawings of immunostained serial sections from the same anatomical region, i.e. the lower lobe of the left lung. The total number of NEB was counted and expressed per epithelial length of airway, surface area and volume. The size of NEB defined as surface area as well as the position of NEB in relation to the airway bifurcations was assessed in airways of different sizes. The overall number and size of NEB were found to increase during the immediate perinatal period followed by a sharp decline at 56 days of age. The number of NEB peaked at 6 days postnatally (mean 175.5 NEB/mm³ of airway epithelium) and declined significantly (3.0 NEB/mm³) at 56 days of postnatal age. The size of NEB reached its maximum at 11 days (mean surface area 659.54 m², with the largest NEB measuring 1839.98 m²). By 56 days of age, NEB became significantly smaller (mean surface area 177.29 m²) consisting of small clusters of cells situated deep within the airway epithelium. At all ages, about half of all NEB (mean 47.6%) were localized within the small peripheral airways with up to 63.9% located at airway bifurcations. These findings indicate that the functional activity of NEB may be confined predominantly to the perinatal period. The postulated functions of NEB include those of intrapulmonary hypoxia-sensitive chemoreceptors and/or endocrine-paracrine activity in the lung. Such function(s) may be important during adaptation to extrauterine life as well as for growth and development of the lung.     

Metabolism of d-xylose in Schizosaccharomyces pombe cloned with a xylose isomerase gene

Summary The Escherichia coli xylose isomerase gene was transformed into Schizosaccharomyces pombe for direct d-xylose utilization. In order to understand d-xylose metabolism and determine the limiting factors on d-xylose utilization by the transformed yeast, d-xylose transport, xylose isomerization, and xylulose phosphorylation were investigated. The results indicated that low activity of xylose isomerization in the cloned yeast was the limiting step for d-xylose fermentation. An in vitro study showed that yeast proteases decreased xylose isomerase activity. Xylitol, a by-product of d-xylose fermentation, had no effect on the activity of xylose isomerase.     

Calcitonin gene-related peptide (CGRP) in normotensive and spontaneously hypertensive rats

With the techniques of specific radioimmunoassay and gel filtration it was found that CGRP was distributed in various tissues of normotensive (WKY) and spontaneously hypertensive rats (SHR) with the highest concentration in the lumbar spinal cord (1197 +/- 94.8 pg/mg tissue) and the lowest in the auricle (15.0 +/- 2.1 pg/mg tissue). In comparison with WKY, CGRP concentration in the plasma was decreased and in the abdominal aorta and hypothalamus was increased in SHR. Gel filtration revealed only one major CGRP molecular form in the tissues. In addition, CGRP reduced the mean arterial pressure (MAP) in SHR in a dose-dependent manner. These data suggest that CGRP may play an important role in the pathogenesis of hypertension and its possible therapy.     

鼎突多刺蚁群体结构和生活史的研究

本文报告了鼎突多刺蚁(Polyrhachis vicina Roger)的群体结构和生活史。通过研究表明,鼎突多刺蚁一年发生一代,以蚁后、雄蚁、工蚁、幼虫和卵越冬。卵和幼虫在冬天发育停滞(或极慢)。到了春天,随着气温的上升,卵和幼虫又恢复正常发育。据室内人工饲养观察,卵的发育历期为23.8±2.5天(平均温度26℃)幼虫为20.4±4.4天(26℃),工蚁蛹为19.8±5.5天(27℃)。成长工蚁在5—11月出现;8—11月,雄蚁从蛹中羽化;10月,雌蚁从蛹中羽化。雌蚁分飞交尾后,进入邻近蚁巢或回到原巢,脱翅成为蚁后。蚁巢内存在着多后现象。     

Competition in the gradostat: the role of the communication rate

In this paper we study a mathematical model of competition between two species of microorganisms for a single limiting nutrient in a laboratory device called a gradostat. A gradostat consists of several (we consider only two) chemostats (CSTR's) connected together so that material can flow between the vessels in such a way that a nutrient gradient is established. Our model is a slightly modified version of one considered recently by Jäger et al. [3], in that the rate of exchange of material between the two vessels (the communication rate) is allowed to differ from the dilution rate. The outcome of competition turns out to be surprisingly sensitive to variation of the communication rate. We identify several coexistence regimes in parameter space and describe a method for obtaining operating diagrams for given pairs of competing microorganisms.Research supported in part by NSF Grant DMS 8521605     

Base and conformational specificity of an amine modification of DNA

We have investigated the site and conformational preference of the reaction of a formaldehyde/amine reagent with DNA. Previous investigations of this laboratory have established that this reagent will react with native DNA, placing a positively charged amine moiety on the duplex that will survive exhaustive dialysis. The resulting adduct is duplex and base stacked in character, possessing B backbone geometry with a higher average winding angle and exhibiting remarkable stability with respect to the A-form, Z-form, or the single-strand denaturated species. In this current investigation, we have found that the stability of the adduct is dramatically reduced if the DNA is converted to mononucleotides, thus obviating the usual approach of nuclease digestion and chromatography for the identification of the modified nucleotides. Using indirect approaches, we have established that the reactive site that survives removal of the equilibrium concentrations of CH2O and amine is the exocyclic amino group of the guanine bases. This conclusion is based on (1) the positive correlation between GC content and the extent of adduct formation under standard reaction conditions (27 degrees C, 0.63M CH2O, 0.007M n-butylamine, pH 7); (2) decreases in the level of substitution of amine in DNA, which has this site blocked by trinitrobenzene modification; and (3) failure of poly(dI-dC) to retain amine upon dialysis. Raman spectra of the derivatized poly(dG-dC) show enhanced 2'-endo B character, with no marked shifts in the position of any of the lines, indicating the absence of any ring structures involving the N7 and the 06 of G. In standard reaction mixtures, other sites may react but this phenomenon appears to be minimal under conditions that do not favor fluctuational opening of base pairs. In the latter case, excess loading of amine on high GC content polymers produces a CD spectrum that is similar to one produced by poly(dA-dT) in the "X"-form [M. Vorlickova, E. Minyat, and J. Kypr (1984) Biopolymers 23, 1-4]. This conformation is lost, however, upon removal of excess reagents by dialysis and cannot be reestablished, in the absence of unbound amine and formaldehyde. The reaction is specific for the B-form of polynucleotides as demonstrated by the failure of poly(dG-m5dC) in the stable Z-form to exhibit substantial reaction. The B-form of this polymer will react readily with the retention of 0.23 moles amine/mole nucleotide under our standard reaction conditions.(ABSTRACT TRUNCATED AT 400 WORDS)