DYNAMICS OF NERVE CELLS : I. THE TEMPERATURE COEFFICIENT OF THE NEUROGENIC RHYTHM OF THE HEART OF LIMULUS POLYPHEMUS.

In the case of the heart of Limulus polyphemus the same magnitude and variation of the temperature coefficient (Q ₁₀) is obtained from the whole heart as from the ganglion alone. From the magnitude of the temperature coefficients and their variation with changes of temperature we may conclude that the rate of the heart beat is determined by alteration of chemical processes in the ganglion cells.     

THE ECOLOGICAL GENETICS OF INTRODUCED POPULATIONS OF THE GIANT TOAD,BUFO MARINUS. III. GEOGRAPHICAL PATTERNS OF VARIATION

The allele frequencies at ten polymorphic loci are described from 31 Bufo marinus populations in the Moreton Bay region in southeastern Queensland, Australia and the variation of these is found to be non-random in all cases. The pattern of non-randomness varies among loci, being clinal in two instances. The allele frequencies at the same ten loci are also described for 12 populations sampled from throughout B. marinus' Australian range. The frequency variation on this larger geographical scale is non-random at all but two loci (Mpi and Hbdh) and also varies among loci, in this case being clinal in four instances. In both cases, the patterns of variation are most reasonably explained as having resulted from genetic drift occurring during the recent range expansion which B. marinus is known to have experienced in Australia. It seems that natural selection has played little, if any, role in generating the observed gene frequency patterns. These results emphasize the need for caution in interpreting geographical patterns of variation. They show that even when clinal patterns exist at some loci but not at others, one cannot conclude that the patterns result from natural selection, unless the demographic histories of the studied populations are known and are inconsistent with the alternative hypothesis that the patterns result from genetic drift.     

天山北麓历史时期的环境演变信息

近 2 0 0 0年以来 ,天山北麓的气候有冷暖干湿波动 ,但总体干旱的基本面貌未发生根本变化。植被在森林的上下界限、平原河谷林的发育程度、平原低地草甸的面积上 ,随气候的变化而发生波动。山地生态系统比较稳定 ,平原生态系统相对不稳定。尤其是平原河流和湖泊抗干扰性极差 ,容易发生改变 ,同时也引起局地小气候及生物群的变化。由于气候变化和人类活动的影响 ,平原地区的水系变化很大 ,河流流量减少、流程缩短、尾闾湖消失、地下水位降低、扇缘溢出带北移等成为普遍现象。天山北麓是自然绿洲发育比较好的地带 ,由于人类活动的影响 ,自然绿洲大多为人工绿洲取代 ,自然绿洲功能弱化 ,基本失去了改善荒漠环境、生物栖息地、保护荒漠区生物多样性等多种生态功能。该区新石器时代以来就有人为活动 ,早期以狩猎、牧业活动为主 ;中期以牧业为主 ,农业为辅 ;后期以农业为主 ,牧业为辅 ,人类对环境的影响有相当长的时间。清朝以来 ,尤其是解放后 ,人类对环境的影响作用急剧加强 ,成为近代环境变化的主导因素 ,主要表现在对水的控制而产生的一系列水系、植被、沙漠变化     

ANALYSIS OF THE GEOTROPIC ORIENTATION OF YOUNG RATS. VIII

The upward geotropic orientation (angle θ) of adult rats (race A) has been measured as a function of slope of substratum. The relative variation of orientation angle is a declining rectilinear function of θ. The fraction of the total observable variation of performance (θ) which is controlled by the intensity of excitation (56 per cent) is identical with that found for young rats of the same strain, although the total variation is a little greater. Injection of adrenin distorts the θ vs. α graph in a manner quite concordant with the effect obtained in young rats. With the adults the absolute magnitudes of the variations of θ, at corresponding intensities of excitation, are not affected by the action of adrenin, and, as with the young, the proportion of modifiable variation of θ is not altered. The variability of performance, considered as a function of the performance, must therefore be regarded as an organic invariant. Certain consequences of this finding are referred to.     

NOTES ON THE TAXONOMY OF THE CLAPPER LARKS OF SOUTH AFRICA.

A case is made out for grouping the various forms of clapper lark in southern Africa, other than those included in the species Mirafra rufocinnumomea (olim fischeri ), as a single polytypic species, Mirafra apiata Vieillot. Many of the described forms are listed as geographical races. The conclusions reached can only be regarded as a very early stage in the understanding of variation in this rather little-known and highly variable species.     

THE ANTIPROTEOLYTIC ACTIVITY OF SERUM : I. THE NATURE AND EXPERIMENTAL VARIATION OF THE ANTIPROTEOLYTIC ACTIVITY OF SERUM

1. An equation is derived for the calculation of a constant which, experimental results indicate, may be a more reliable index of the antiproteolytic activity of serum than those equations hitherto used. 2. (a) Intramuscular administration of trypsin resulted in a slow rise in the antiproteolytic activity of the serum, followed by a lesser decline. (b) Intravenous administration resulted in no appreciable variation. (c) Oral administration resulted in a rapid rise, which was sustained during the period of administration. (d) Intramuscular, intravenous, or oral administration of denatured trypsin resulted in no appreciable variation. (e) The extent of the local necrosis following subcutaneous injection of trypsin varied inversely with the antiproteolytic activity of the serum. 3. The experimental results indicate that the products of protein hydrolysis in the intestine and parenterally are an important factor in the antiproteolytic activity of the serum. They also indicate that antibodies to trypsin are not an important factor in the antiproteolytic activity of the serum.     

THE PHYSIOLOGY OF THE RESPIRATION OF FISHES IN RELATION TO THE HYDROGEN ION CONCENTRATION OF THE MEDIUM

1. The ability of marine fishes to absorb oxygen at low tension from the sea water is more or less dependent upon the hydrogen ion concentration of the water. 2. The ability of fishes to withstand wide variations in the range of hydrogen ion concentration of the sea water can be correlated with their habitats. The fishes that are most resistant to a wide variation in the hydrogen ion concentration are most cosmopolitan in their habitat. Those that are least resistant to a variation in the hydrogen ion concentration are the most restricted in their range of habitat. 3. There is a close correlation between the optimum condition of the sea water for the absorption of oxygen at low tension by the herring (Clupea pallasii), the condition of the sea water to which they react positive and that in which they are found most abundantly. 4. It is suggested that the variation in the ability to absorb oxygen at low tension at a given pH of individuals of a species is dependent upon the alkaline reserve of the blood of the individual fish.     

PROTEIN SYNTHESIS IN THE MEDULLA OF THE RAT BRAIN. REPRODUCIBILITY OF THE RESULTS

Abstract— [¹⁴C]Leucine was injected intracranially into the brainstem reticular formation at the level of the upper medulla by the stereotaxic method. Subcellular fractions prepared 3 hr after injection showed that the specific activities of leucine-incorporated proteins decreased in the order soluble, microsomal, nuclear and mitochondrial fractions. Specific activities of proteins in the sera were 2·2 per cent of whole homogenate proteins.
The results from 27 experiments showed that 66·6 per cent of the mean specific activities of proteins extracted from whole homogenates fell within ·1 s.d . and 100 per cent within ± 2 s.d . (close to a normal distribution). The coefficients of variation were between 40 and 50 per cent for whole homogenates, sera and all subcellular fractions. Reproducibility of results and factors concerned with possible errors in the technique are discussed.     

THE SIGNIFICANCE OF GENETIC EROSION IN THE PROCESS OF EXTINCTION. IV. INBREEDING LOAD AND HETEROSIS IN RELATION TO POPULATION SIZE IN THE MINT SALVIA PRATENSIS

If, because of genetic erosion, the level of homozygosity in small populations is high, additional selfing will result in small reductions of fitness. In addition, in small populations with a long inbreeding history selection may have purged the population of its genetic load. Therefore, a positive relationship between population size (or level of genetic variation) and level of additional inbreeding depression, here referred to as inbreeding load, may be expected. In a previous study on the rare and threatened perennial Salvia pratensis, a positive correlation between population size and level of allozyme variation has been demonstrated. In the present study, the inbreeding load in six populations of varying size and allozyme variation was investigated. In the greenhouse, significant inbreeding load in mean seed weight, proportion of germination, plant size, regenerative capacity, and survival was demonstrated. In a field experiment with the two largest and the two smallest populations, survival of selfed progeny was 16% to 63% lower than survival of outcrossed progeny. In addition, survival of outcrossed progeny was, with the exception of the largest population, lower (16% to 37%) than of hybrid progeny, resulting from crosses between populations. Effects on plant size were qualitatively similar to the effects on survival, but these effects were variable in time because of differential survival of larger individuals. In all populations the total inbreeding load, that is, the effects on size and survival multiplicated, increased in time. It was demonstrated that inbreeding load in different characters may be independent. At no time and for no character was inbreeding load or the heterosis effect correlated to the mean number of alleles per locus, indicating that allozyme variation is not representative for variation at fitness loci in these populations. Combined with results of previous investigations, these results suggest that the small populations are in an early phase of the genetic erosion process. In this phase, allozyme variation, which is supposed to be (nearly) neutral, has been affected by genetic erosion but the selectively nonneutral variation is only slightly affected. These results stress the need for detailed information about the inbreeding history of small populations. The relative performance of selfed progeny was lowest in all populations, in the greenhouse as well as in the field, and inbreeding depression could still influence the extinction probabilities of the small populations.     

THE GENETIC BASIS OF THE ECOLOGICAL AMPLITUDE OF SPARTINA PATENS. II. VARIANCE AND CORRELATION ANALYSIS

Reciprocal transplantations of Spartina patens genotypes from adjacent salt marsh, swale, and dune habitats provided evidence for genetic differentiation among subpopulations, due at least in part to contrasting selection regimes. Genet survival in the different habitats was related to the amount of genetic divergence. In the dune habitat, marsh ramets showed the lowest survival, swale ramets showed intermediate survival, and dune ramets showed the highest survival. This relationship was not reciprocal, however. The marsh habitat afforded an environment where survival was maximal for all genotypes. Thus, by comparison, the dune environment appeared to impose a more intense selection pressure, and the swale an intermediate selection pressure on Spartina patens. In each site resident genotypes tended to show greater relative fitness than aliens. This evidence for genetic divergence corroborates that previously reported on morphometric (Silander and Antonovics, 1979) and allozymic traits (Silander, 1984). High levels of phenotypic plasticity may permit greater adaptation to the spatially and temporally heterogeneous environment occupied by S. patens than would genetic variation alone. Dune and swale genets were more phenotypically plastic across traits examined than were marsh genotypes. The higher plasticity in these peripheral subpopulations may confer increased fitness among residents and compensate for observed declines in genetic variation. A slight decrease in genetic variability was evident from marsh to dune subpopulations. However, since the differences in genetic variation among subpopulations were small, and disparities did occur, it is unlikely that evolutionary divergence is retarded primarily by a lack of genetic variability in the characters considered. Evidence is presented to indicate that evolutionary divergence among subpopulations may be retarded by negative or unfavorable correlations among characters being selected simultaneously. These negative correlations may increase extinction probabilities in small peripheral populations, such as those represented by the dune or swale, and are likely to lower fitness. Based on these observations, I hypothesize that further microevolution may be retarded in peripheral dune and swale subpopulations, primarily by unfavorable genetic correlation structures among fitness components or characters under simultaneous selection. Contributing factors may include lowered genetic variance and higher levels of phenotypic plasticity.     

ANALYSIS OF THE GEOTROPIC ORIENTATION OF YOUNG RATS. IX

Adult hybrid rats from the cross of races A x B show a total capacity to vary their geotropic performance which is identical with that of their B parents. The proportionate modifiable variability of geotropic orientation also agrees quantitatively with that for the B parents. These relationships are not disturbed by the action of adrenin, which leads to a distortion of the θ vs. α curve. Young rats of the F ₁ generation show a greater proportion of unmodifiable variation of geotropic orientation. It is pointed out that the present findings support the conclusion that the capacity of rats to exhibit variation of geotropic orientation is limited by their genetically determined composition and that the special condition in the young hybrids may be understood as due to a kind of temporary disharmony of developmental events.     

ANALYSIS OF THE GEOTROPIC ORIENTATION OF YOUNG RATS. VII

The intraperitoneal injection of standard young rats of race A with 2/5 cc. of adrenalin chloride 1:50,000 results in increased speed of geotropically oriented creeping upon an inclined surface. It was expected that the effect of such increased frequency of stepping must be analogous to that due to imposition of added loads carried by the rats during geotropic progression. This is verified. The curve connecting θ with log sin α is distorted, under adrenalin, so as to be comparable to that obtained with an added mass of approximately 2.5 gm. upon the young rat''s saddle; the threshold slope of surface for orientation is accordingly lowered, from α = 20° to α = 12.5°; at the new threshold slope of surface the mean orientation angle θ is the same as in the absence of adrenalin at the corresponding threshold slope of surface. The total variation of performance is significantly increased in the injected rats, and at given slope of surface the variation is slightly increased. The proportionate modifiable variation of response is quite unaffected by the distortion of the θ – α curve, and is the same as in standard young A rats untreated or carrying additional loads. It is pointed out that for the consideration of the problem as to whether a given experimental treatment, or a given natural situation, affects in any way the variation of performance of a living system, it is necessary to obtain indices of variability which involve the expression of variation of performance as a function of measured conditions governing the performance.     

视网膜电图振荡电位参数的稳定性

用系列强度１１档刺激闪光记录２０例３０只眼的视网膜电图（ＥＲＧ）振荡电位（ＯＰ）,研究ＯＰ的光强特性和参数稳定性。结果表明,ＯＰ各子波峰时和刺激光强呈指数曲线相关,相关性很高;而振幅和光强的函数关系的变异很大,相关性较低,不同对象间ＯＰ各子波振幅的变异系数较大,而峰时的变异系数较小,ＯＰ的峰时改变比振幅改变更为稳定。     

LIFE-HISTORY VARIATION WITHIN A POPULATION OF THE COLONIAL ASCIDIAN BOTRYLLUS SCHLOSSERI. I. THE GENETIC AND ENVIRONMENTAL CONTROL OF SEASONAL VARIATION

Many empirical analyses of life-history tactics are based on the assumption that demographic variation ought to be greatest among populations or species living in different environments. However, in a single population of the sessile colonial sea squirt Botryllus schlosseri, there are two discrete life-history morphs. Semelparous colonies are characterized by a) death immediately following the production of a single clutch, b) early age at first reproduction, c) rapid growth to first reproduction, and d) high reproductive effort. In contrast, iteroparous colonies a) produce at least three clutches before dying, b) postpone sexual reproduction until they are nearly twice the age of semelparous colonies, c) grow at about half the rate of semelparous colonies, and d) invest roughly 75% less in reproductive effort than semelparous colonies. Semelparous colonies numerically dominate the population through midsummer; later in the summer, iteroparous colonies are most numerous. Field and laboratory common-garden experiments, along with breeding studies, indicate that the demographic differences between the morphs are genetically determined. Consequently, the seasonal switch from dominance by semelparous colonies to dominance by iteroparous colonies may be an evolved response to a seasonally changing environment. On theoretical grounds, temporal variation in selection is thought to play a relatively unimportant role in maintaining genetic polymorphism; nonetheless, the seasonally recurrent life-history polymorphism shown in this study indicates that temporal variation in selection can lead to the maintenance of genetic polymorphism for traits strongly affecting fitness.     

STUDIES ON THE MECHANISM OF DIURNAL VARIATION OF PROLIFERATIVE INDICES IN THE SMALL BOWEL MUCOSA OF THE RAT

In the rat small bowel mucosa significant variation was found in both the labelling and the mitotic indices with time of day. The zenith and the nadir of labelling and mitotic activity coincided at 15.00 and 02.00 hours respectively. Small changes were found in the ‘cut-off’ position, but this variation in proliferative compartment size was insufficient to account for the comparatively wider fluctuations in proliferative indices. Measurements of the rate of entry into mitosis, using metaphase arrest with vincristine at three widely separated times during the day, showed no significant change. Changes in the growth fraction or in the birth rate as measured cannot account for diurnal variation in the proliferative activity of the small bowel mucosa. We propose a hypothesis which involves diurnal fluctuations in the transit times through G₁ and through G₂.     

离子注入烟草种子引起的M1代变异分析

利用随机引物扩增ＤＮＡ（ＲＡＰＤ）技术及ＳＤＳ－聚丙烯酰胺蛋白电泳技术,对３０ｋｅｖＮ＋离子注入后的烟草Ｍ１代ＤＮＡ及叶片水溶性蛋白进行分析,通过ＲＡＰＤ反应,检测到ＰＣＲ条带的缺失和增加,而对照植株未发现条带明显变化,并且条带变异率随剂量的增加而上升。６０次的剂量对烟草（红花大金元）诱变效果较好,有相对较高的成活率和变异率。还发现Ｎ＋离子注入后,Ｍ１代叶片水溶性蛋白与对照相比有明显变异;Ｍ１代植株株高普遍高于对照,并出现少数表型变异。     

白刺不同自由授粉家系的生长变异性研究

反映甘肃民勤县白刺分布区生态变化特征信息的55个白刺自由授粉家系,一、二、三年生植株的生长均存在极显著差异,说明这些家系可能属于不同的遗传变异群体。白刺生长的家系间变异较大,且变异性有逐年增大的趋势;不同生长指标间的同一指标上下年度间的生长变异有很大相关性。家系内变异与家系的个体生长状态呈极显著的负相关,生长越好的家系,变异越小,且变异与母株果实和种子特征无关。研究结果为优良生长家系选择奠定了基础。     

THE RELATIONSHIP BETWEEN DIURNAL VARIATION OF THE NUMBER OF CELLS IN MITOSIS AND OF THE NUMBER OF CELLS SYNTHESIZING DNA IN THE EPITHELIUM OF THE HAMSTER CHEEK POUCH

1. The numbers of cells in mitosis and in DNA synthesis in the epithelium of the hamster cheek pouch have been studied at different times of the day and night. 2. By accumulation of mitotic cells using colcemid, both the rate of entry of cells into mitosis and the duration of mitosis have been estimated at two different times of day. 3. A diurnal variation has been demonstrated in both the mitotic index and in the tritiated thymidine labelling index. Although these variations are of different amplitude and timing, the experimental data fit closely to the hypothesis that the diurnal mitotic variation is the result of a partially synchronous population moving through the DNA synthetic period. No direct action on the mitotic process need be postulated. 4. From the results of mitotic accumulation, it is clear that the rate of entry of cells into mitosis depends on the time of day at which this is studied. There is also the possibility that the duration of mitosis is slightly longer when the mitotic index is high. 5. It is concluded that, at least in the epithelium of the hamster cheek pouch, the diurnal rhythm in the number of mitoses present is a reflection of the diurnal variation in the number of cells synthesizing DNA at some time earlier. Small fluctuations in the mitotic pattern imposed by this partially synchronous population moving from S into mitosis, could be caused by slight variations in the duration of mitosis.     

层粘连蛋白与膜受体结合下膜受体构象与膜脂有序性的研究

配体蛋白与细胞膜受体蛋白结合后,可引起膜受体的构象与膜脂的有序性变化.本文研究外源性层粘连蛋白与腹水肝癌细胞膜受体结合后膜热量变化,膜序参数改变和膜电荷及细胞迁移率的变更.就膜蛋白构象与膜脂有序性以及膜电荷等方面改变的生理意义与层粘连蛋白抗癌细胞脱落转移寻找理论关系.本文应用微量量热法、顺磁共振和细胞电泳等技术,得知层粘连蛋白与癌细胞膜作用后细胞膜有放热效应,膜流动性增大,细胞电泳动变慢.癌细胞膜的这些变化对于限制癌的恶性生长与脱落均起重要作用.