THE EFFECTS OF ULTRAVIOLET RADIATION ON SPORES OF THE FUNGUS ASPERGILLUS NIGER

The survival ratio of Aspergillus spores exposed to ultraviolet radiation has been measured as a function of total incident energy for wave lengths of 2537 Å, 3022 Å, 3129 Å, and 3650 Å. The effect of humidity on killing of Aspergillus spores by ultraviolet radiation has been found to be negligible. A delay in germination as a result of irradiation has been found. The Bunsen-Roscoe reciprocity law has been found to hold within the limits of the radiation intensities studied. Certain morphological changes have been observed.     

NATURE OF THE ACTION CURRENT IN NITELLA : IV. PRODUCTION OF QUICK ACTION CURRENTS BY EXPOSURE TO NACl

Treatment of Nitella with NaCl greatly reduces the time required for the action current and produces an action curve with one peak instead of the customary two. The time may be reduced to 0.6 second in place of the usual 15 to 30 seconds. This might be expected if the treatment increased the conductivity of the aqueous part of the protoplasm. The experiments favor this idea although they do not prove its correctness. This effect is prevented by calcium, possibly because calcium inhibits penetration of salts. That penetration is an important factor is indicated by the fact that salts which might be expected to penetrate rapidly have the most effect. Thus NaSCN is more effective than NaCl but Na₂SO₄ has little or no effect. The action of NH₄Cl and LiCl is similar to that of NaCl.     

静止和充气培养条件下短期紫外辐射对钝顶螺旋藻光化学效率的影响

为了研究短期太阳紫外辐射对钝顶螺旋藻的影响,作者将静止和充气培养的藻体,暴露在全波长太阳辐射PAB(PAR UVA UVB),去除UVB辐射PA(PAR UVA)及切断所有紫外辐射的光合有效辐射P(PAR)三种光处理条件下,测定了其光化学效率的变化。结果表明,紫外辐射(UVP)及光合有效辐射(PAR)均能导致钝顶螺旋藻的光化学效率降低,表现出了明显的光抑制,但是,UVR可导致更大程度的光抑制。充气培养条件下,与早晨(07:00)初始值相比,PAR导致了11%~20%的光抑制,而UVR(PAB-P)所产生的额外光抑制占9%~31%;静止培养条件下,UVR的存在使得螺旋藻的光化学效率趋近于零(无法检出)。在两种培养条件下,藻细胞所受最大光抑制均发生在中午,下午(17:00)表现出不同程度的恢复。紫外辐射使得类胡萝卜素及藻蓝蛋白与叶绿素a含量的比例增大。与PAB和P相比,PA处理使得螺旋藻类胡萝卜素和藻蓝蛋白与叶绿素含量之比明显升高,UVA可能会诱导类胡萝卜素及藻蓝蛋白的合成。     

THE INACTIVATION OF BACILLUS SUBTILIS SPORES IN PENICILLIN BY GAMMA RADIATION

SUMMARY: Sodium benzylpenicillin, contaminated with Bacillus subtilis spores by freeze-drying a suspension of spores in an aqueous penicillin solution ( c . 50% w/v), was exposed to gamma radiation and a 70-tube dilution method was used to determine the surviving spores after various doses. The correlation coefficient between log₁₀ percentage survival and dose was −0.9523. The regression of the former on the latter was calculated and the decimal reduction dose found to be 20.2 × 10⁴ rads. The regression and the decimal reduction dose were similar to those obtained when suspensions of spores in distilled water were irradiated.     

缓冲神经在刺激兔下丘脑诱发室性期前收缩中的作用

1.静脉注射氰化钾(0.3mg/kg)可引起血压升高和室性心律失常,并能使刺激下丘脑诱发的室性期前收缩增多。去除双侧窦神经后,上述现象消失。2.刺激降压神经时,刺激下丘脑诱发的室性期前收缩显著减少。3.切断双侧缓冲神经后短时内,刺激下丘脑诱发的室性期前收缩极度增多,并且不易被躯体传入冲动所抑制。二小时后,这种室性期前收缩减少,且可为刺激腓深神经所抑制。4.电刺激延髓中线区不仅可以降低血压,而且能减弱刺激下丘脑诱发的升压反应、抑制刺激下丘脑诱发的室性期前收缩。损毁该区后,刺激腓深神经不再能抑制刺激下丘脑诱发的室性期前收缩。5.上述结果表明:化学感受性反射能易化刺激下丘脑诱发的室性期前收缩,而压力感受性反射可以抑制这种室性期前收缩,但躯体传入冲动对这种心律失常的抑制作用并不依赖于缓冲神经的存在,而有赖于延髓中线核群的完整性。     

~(60)CO-γ射线诱发的德国蜚蠊精母细胞中心体畸变

德国蜚蠊经不同剂量的~(60)Co-γ射线照射,以光镜和电镜观察精母细胞巨大中心体结构和数目的变化,发现:γ射线可诱发各种类型中心体畸变,如棒状、断裂、不分离、超数和微小中心体等;畸变率随剂量增加而升高;畸变类型和辐射剂量有密切关系,低剂量(500—1000r)诱发较多的棒状中心体和中心体断裂、中等剂量(2000r)诱发较多的超数中心体和中心体不分离、高剂量(5000r)诱发较多的微小中心体,看来低剂量γ射线主要影响中心体结构,高剂量则对中心体的生长发育有明显的阻滞作用。本文还讨论了中心体畸变的可能产生机制及在遗传毒理研究中应用的前景。     

噪声短时暴露所致的耳蜗电位改变

本实验观察115dB(SPL)白噪声暴露20min对豚鼠耳蜗直流电位(EP),复合听神经动作电位(CAP),微音器电位(CM)的影响。发现此种噪声暴露确可提高源于血管纹的正EP(P-EP),说明有血管纹功能的代偿性增强;而负EP(N-EP)变化不大。AP及CM输入-输出函数的变化说明噪声首先影响外毛细胞的主动运动功能。EP与耳蜗电图的对照分析表明,血管纹功能的改变确能影响噪声性听损伤的发展。     

SALTANT PRODUCTION BY WAVE LENGTHS OF VISIBLE AND LONG ULTRAVIOLET MONOCHROMATIC IRRADIATION,AND A COMPARISON WITH SALTANTS PRODUCED BY SHORT WAVE LENGTHS OF MONOCHROMATIC ULTRAVIOLET IRRADIATION IN THE FUNGUS CHAETOMIUM GLOBOSUM

1. Saltants have been produced in the fungus Chaetomium globosum by longer wave lengths than previously reported—by 365 mµ and by a visible line 404 mµ. 2. Absence at these wave lengths of the K saltant, which is so abundant at short wave lengths, is marked. 3. Ratio of percentage irradiated spores germinating to control spores germinating decreases from 83 per cent at 265 mµ, a short ultraviolet wave length, to 57 per cent at 404 mµ, a visible violet wave length.     

THE BACTERICIDAL EFFECT OF ULTRAVIOLET RADIATION ON ESCHERICHIA COLI IN LIQUID SUSPENSIONS

1. The irradiation of bacteria in liquid suspension has been made possible through: (a) the use of a specially balanced physiological salt solution which is practically non-absorbing for the wave lengths used, and which is of such composition that subsequent dilution of the bacterial suspension gives the proper number of organisms; (b) special design of the exposure cell and a very thorough method of stirring which subjects each organism equally to the radiation; (c) practically complete absorption of the incident radiation, through the use of very dense suspensions, thus eliminating the necessity for a separate determination of the absorption coefficients of the bacteria for the wave lengths used. 2. The method also provides a means for determining the effects of sub-lethal doses. 3. A formula is given for calculating from observed survival ratios the energy required to inactivate bacteria with ultraviolet radiation. The formula corrects for the protective action of non-viable organisms. 4. Data are given for the inactivation of 15 hour and 240 hour cultures of E. coli, washed and unwashed) and for 6–7 hour cultures, unwashed. These data are compared with those of other investigators. 5. A possible explanation for the differences in energy required to inactivate old, young, and standard cultures of bacteria is suggested. 6. The possible mechanism of the action of ultraviolet radiation on microorganisms is discussed.     

THE ACTION SPECTRUM OF SENSITIZATION TO HEAT WITH ULTRAVIOLET LIGHT

1. Heat does not sensitize paramecia to ultraviolet light but ultraviolet light sensitizes them to heat. Paramecia of two species (Paramecium caudatum and P. multimicronucleate) are much more readily killed by heat at 42.3° C. if they are first exposed to ultraviolet light. 2. From studies on paramecia irradiated with a given dosage at various wave lengths before being killed by heat, an action spectrum of the compound in the protoplasm being sensitized to heat can be determined. Proteins with absorption similar to that of pseudoglobulin are suggested by these experiments. 3. The effect upon living things differs from that on pure protein systems in that paramecia are not rendered more sensitive to temperatures below the lethal temperature whereas proteins are. 4. Almost complete recovery from ultraviolet light as judged by heat sensitivity occurs within 4 to 5 days. 5. By a study of the rate of recovery from doses at different wave lengths evidence suggesting effects on nucleic acid is obtained. 6. The possible significance of the data and the action spectrum is discussed.     

颗石球缓解紫外辐射对颗石藻光合作用的胁迫

正颗石藻(Coccolithophore)是一类胞外具有数层钙质颗石粒(Coccolith)的海洋钙化金藻,在绝大部分海域均有分布。颗石藻通过光合固碳向深海沉降有机碳颗粒,同时其钙化作用形成的颗石粒是海底的重要沉积物。它们与钙化浮游动物翼足类(Petropod)钙化量可占海洋生物钙化量的80%,对于海洋碳、钙循环有重要意义~([1,2])。颗石藻在条件合适时,可形成大面积藻华(全球每年可达上百万平方公里)~([3])。促进藻华形成的环境因素很     

A STUDY OF THE BACTERICIDAL ACTION OF ULTRA VIOLET LIGHT : I. THE REACTION TO MONOCHROMATIC RADIATIONS

In this first paper of a series on the bactericidal action of ultra violet light the methods of isolating and measuring monochromatic radiations, of preparing and exposing the bacteria, and of estimating the effects of exposure, are given in detail. At all the different wave lengths studied the reactions of S. aureus followed similar curves, but occurred, at each wave length, at a different energy level. The general similarity of these curves to those for monomolecular reactions provokes a discussion of their signifiance, and emphasis is laid upon variations in susceptibility of individual organisms, due especially to age and metabolic activity, so that the typical curve seems to be best interpreted as one of probability.     

紫外线^60Co照射对蛇毒毒性的影响

选择体重20g 左右小白鼠分别使用眼镜蛇毒、蝮蛇毒以及经过紫外线、~(60)Co 照射灭菌后的这两种蛇毒进行半数致死量的测定,结果经紫外线照射后的眼镜蛇毒和白眉蝮蛇毒的毒性降低了6.98%和6.41%.经~(60)Co 照射的眼镜蛇毒和蝮蛇毒的毒性降低了21%和33%.     

THE ACTION OF NISIN ON SPOILAGE BACTERIA. I. THE EFFECT OF NISIN ON THE HEAT RESISTANCE OF BACILLUS STEAROTHERMOPHILUS SPORES

SUMMARY: Spores of two strains of Bacillus stearothermophilus were heated for various times both in the absence and presence of nisin and in the latter case both with and without subsequent destruction of the nisin with trypsin. The results obtained on enumeration of the survivors indicated that the reduction of heat resistance which was observed was apparent rather than real and was due to the adsorption of nisin on the spores. When this was removed by means of trypsin the heat resistance was restored almost to normal.     

CARBON UPTAKE IN A MARINE DIATOM DURING ACUTE EXPOSURE TO ULTRAVIOLET B RADIATION: RELATIVE IMPORTANCE OF DAMAGE AND REPAIR1

Experiments on a marine diatom, Thalassiosira pseudonana (Hustedt) clone 3H, demonstrate that under moderate photon flux densities (75 μmol quanta·m^?2·s^?1) of visible light the inhibition of photosynthesis by supplemental ultraviolet (UV) radiation (UV-B: 280–320 nm) is well described as a hyperbolic function of UV-B irradiance for time scales of 0.5–4 h. Results are consistent with predictions of a recently developed model of photosynthesis under the influence of UV and visible irradiance. Although net destruction of chlorophyll occurs during a 4-h exposure to UV-B, and the effect is a function of exposure, the principal effect of UV-B is a decrease in chlorophyll-specific photosynthetic rate. The dependence of photoinhibition on dosage rate, rather than cumulative dose, and the hyperbolic shape of the relationship are consistent with net photoinhibition being an equilibrium between damage and repair. The ratio of damage to repair is estimated by a mathematical analysis of the inhibition of photosynthesis during exposures to UV-B. A nitrate-limited culture was much more sensitive to UV-B than were the nutrient-replete cultures, but the kinetics of photoinhibition were similar. The analysis suggests that the nutrient-limited culture was more sensitive than the nutrient-replete cultures because repair or turnover of critical proteins associated with photosynthesis is inhibited. An inhibitor of chloroplast protein synthesis was used to suppress repair processes. Photoinhibition by UV-B was enhanced, and inhibition was a function of cumulative dose, as would be expected if damage were not countered by repair. The fundamental importance of repair processes should be considered in the design of field experiments and models of UV-B effects in the environment, especially in the context of vertical mixing. Repair processes must also be considered whenever biological weighting functions are developed.     

EFFECTS OF VISIBLE AND ULTRAVIOLET RADIATION ON THE GERMINATION OF PHACELIA TANACETIFOLIA

Schulz , Sister M. Richardis , O.P., and Richard M. Klein . (N. Y. Bot. Gard., N. Y., N. Y.) Effects of visible and ultraviolet radiation on the germination of Phacelia tanacetifolia. Amer. Jour. Bot. 50(5): 430–434. Illus. 1963.—Germination of Phacelia tanacetifolia was suppressed by exposure to white light increasing with intensity and length of illumination. The light effect decayed during 24 hr of darkness. Seeds were most sensitive to the suppressive effects of light 13–17 hr after the beginning of imbibition. Light suppression was caused by a photocatalytic reaction. Wavelengths causing the suppression lie in the far-red, red, blue, near-ultraviolet and far-ultraviolet regions of the spectrum. At equal energies, blue light was less effective than far-red, red or ultraviolet radiation. There was no evidence for the existence of the phytochrome system. Simultaneous irradiation with red and blue light or simultaneous irradiation with red and far-red induced a synergistic repression of germination. The presentation of different wavelengths in various sequential patterns markedly altered the germination response. An interaction between elevated temperatures and visible radiation affecting germination response was also noted.