SURFACE CHARACTERS OF DIVIDING CELLS IV. ALLOTMENT OF THE CORTEX AND PARTITIONING OF THE CYTOPLASM IN UNEQUAL DIVISION OF GRASSHOPPER SPERMATOCYTE UNDER THE TEMPERATURE GRADIENT

The allotment of cell surface and the allotment of cell volume between two daughter cells were observed in unequal division of spermatocytes of the grasshopper, Acrida lata, caused by steep temperature gradient. In applying a temperature gradient through the cell division, coincidence in position between the provisional division plane indicated by the tongue of mitochondria, and the actually formed furrow, has been established (i) by markers attached to cell surface and (ii) by calculated volumes of cytoplasm on the two sides of the planes. On removing a temperature gradient while a cell is dividing, equality is regained as far as the volume of the incipient daughter cells are concerned but territories of the surface once allotted are strictly observed. Unequal division, therefore, involves two different meanings; allocation of the surface, and apportionment of the cytoplasm both of which are dependent upon the development of asters.     

DEVELOPMENT OF THE EMBRYONIC CHICKEN THYMUS III. UNEQUAL DIVISION OF LYMPHOID CELLS

Cell division of thymus lymphoid cells from 11- to 17-day old embryonic chickens, as well as chickens just after hatch was investigated on cell smears stained with Giemsa. Unequally dividing cells were observed in the developmental stage of thymocytes. At the telophase of such cells, the cytoplasm of one of two future daughter cells was apparently larger in amount and was sometimes stained deeper than the cytoplasm of its counterpart. Unequal division was also observed in pro-, meta- and anaphase; sometimes a dividing cell had a large cytoplasmic process belonging to one hemisphere, suggesting that only one of the two daughter cells would receive the cytoplasmic process through cell division.
The incidence of unequal division calculated by a rough estimation was around 10% of the total cell division between 11 and 13 days of embryonic development, and decreased progressively thereafter.     

FORAGE LOSSES CAUSED BY GRASSHOPPER CHORTHIPPUS DUBIUS (ZUB.1 ON GRASSLAND IN INNER MONGOLIA OF CHINA

Abstract To quantitatively assess the losses of forage, we conducted experiments to determine the average amount of forage destroyed (forage consumed plus forage cut-off and dropped to the ground) per day by the grasshopper, Chorthippus dubius (Zub.), at its different life stages in laboratory and then extrapolated estimates of losses caused by the field grasshopper population from these results and the population densities of this grasshopper. The main results are as follows:

• 1 Ch. dubius is a late-occurring species of grasshoppers in Inner Mongolian grassland. It occurred from June to October. The duration for each instar and the longevity of the adult under natural conditions ranged from 9. 09–9. 81 fdays) and 17. 65–19. 441days) respectively.
• 2 Both consumption and forage defoliation rates by Ch. dubius increase with its developemnt. The consumption rates had significantly linear relationships with the grasshopper's body weights.
• 3 Average losses caused by one grasshopper in its whole lifespan were 487. 55–784. 4 mg (dry weight) and the average amount of forage consumed and wasted per day was 7. 64–11. 45 mg.
• 4 Total losses caused by Ch. dubius population in 1990 ranged from 0. 762–1. 647 g/m² in the three types of vegetation, and the largest value was found in restorative type. The seasonal courses of cumulative forage losses would fit logistic equations in the three vegetation types.
• 5 Population densities (18. 5, 194., 11. 8/m², 4th instar nymph predominantly) were suggested as the levels at which control should be initiated on the three types of pastures respectively.

     

内蒙古草原三种植物群落中狭翅雏蝗造成的牧草损失(英文)

狭翅雏蝗Chorthippus dubius是我国北方草原的重要蝗种之一,在大发生年对牧草的威胁很大。它对牧草的损失至今尚无较准确的定量估算。本文通过测定不同发育阶段狭翅雏蝗的取食率、掉落毁损率,结合野外自然种群数据,对内蒙古草原三种植物群落中狭翅雏蝗造成的牧草损失进行了估测,并对三种草场蝗虫的经济阈值进行了计算。主要研究结果如下: 1.狭翅雏蝗对羊草、冷蒿、大针茅的取食率相似;取食率与虫体体重存在显著的线性相关。 2.狭翅雏蝗每个个体在一生中平均造成牧草损失487.55—784.4mg(干重),每日消耗与浪费的牧草为7.64—11.45mg。 3.狭翅雏蝗种群造成的牧草损失在冷蒿群落、羊草-大针茅-羊草群落、羊草-大针茅群落分别为1.52,1.65,0.76g/m,占地上初级生产量的2.96％、1.18％、0.42％,表现为越退化的草场,狭翅雏蝗对牧草的压力越大。其累积损失量的季节程式可以刚logisuc方程拟合。 4.狭翅雏蝗的经济阈值在羊草、羊草+大针茅+冰草、冷蒿草原分别为每平方米18.5、19.4、11.8头四龄为主个体。     

SPERMATOGENESIS IN A TRICHUROID NEMATODE,TRICHURIS MURIS. II. FINE STRUCTURE OF PRIMARY SPERMATOCYTE AND FIRST MEIOTIC DIVISION

Ultrastructural observations indicate that the primary spermatocyte of Trichuris muris is larger than the spermatogonial stage with an increased cytoplasm to nucleus ratio. The cytoplasm contains an extensive reticular system, mitochondria, numerous free ribosomes and prominent Golgi complexes which may contribute to the formation of a sub-surface, vesicular complex. Although only two spermatocytes were seen to be linked by a cytoplasmic bridge it is suggested that the number of conjoined cells is probably greater. The rearrangement of mitochondria in a ring around the nucleus and the indentation and vesiculation of the nuclear envelope preceeded its disappearance and indicated the onset of meiosis. Centrioles were frequently resolved at this stage. They were composed of nine peripheral doublets surrounded by a dense pericentriolar sheath. Three dense chromatin areas indicative of haploid chromosomes were present in later meiotic stages. Each chromosome was surrounded by a number of mitochondria and there was a clear separation of the chromosome-mitochondrial clusters from the remainder of the cytoplasm. This was particularly evident at telophase when two daughter cells were partially separated by membrane infoldings. This reflects incomplete cytokinesis in the dividing spermatocyte of T. muris and is similar to that described in other trichuroid species. A close association with processes of the non-germinal, sustentacular cells was noted throughout the spermatocyte stage.     

PHOTOCONTROL OF THE ORIENTATION OF CELL DIVISION IN ADIANTUM. III. EFFECTS OF METABOLIC INHIBITORS

5-Fluorouracil, 8-azaguanine and ethionine were tested on the orientation of cell division to see whether the two-dimensional development of the fern Adiantum gametophytes was due to newly synthesized protein(s). Using the system in which the orientation of cell division was controlled experimentally by sequential treatment with red light, white light and darkness and by the direction of irradiation, all the inhibitors decreased the rates of cell elongation and cell division of the gametophytes, but did not specifically affect the two-dimensional differentiation at all.     

GROWTH REGULATION BY ETHYLENE IN FERN GAMETOPHYTES. II. INHIBITION OF CELL DIVISION

Ethylene, a natural product of sensitive fern (Onoclea sensibilis L.) gametophytes, has been demonstrated to inhibit cell division in light-grown prothallia. When plants were grown on Knop's solution plus 1 % sucrose under 300 ft-c or more of white light, all ethylene concentrations from 1–1000 μl/liter reduced the rate of increase of cell number by about one-half. The over-all rate of increase of cell number was regulated by various environmental and chemical factors, but regardless of the rate established in control cultures, ethylene treatment of 1–1000 μl/liter produced a relative 50 % depression of cell number. Ethylene was specific for inhibition of cell division and was not a general inhibitor of growth. The ethylene inhibition did not result from a reduction of photosynthesis or energy supply. Further demonstration of ethylene as the active gaseous component resulted when cultures were grown in small enclosed containers with an ethylene absorbent, mercuric perchlorate, and consequently the cell number of gametophytes was restored to the level of unenclosed controls.     

DE- AND RE-GENERATION OF CHLOROPLASTS IN THE CELLS OF CHLORELLA PROTOTHECOIDES: III. EFFECTS OF MITOMYCIN C ON THE PROCESSES OF GREENING AND DIVISION OF "GLUCOSE-BLEACHED" ALGAL CELLS

The "glucose-bleached" cells of Chlorella protothecoides, whoseplastids were profoundly degenerated containing no trace ofchlorophyll, were obtained by the method previously reported.Transferring the cells to the condition of re-generation ofchloroplasts (greening)—incubation in the light in a glucose-lessand nitrogen-rich medium—the effect of mitomycin C onthe recovery process was investigated. It was found that theantibiotic suppressed completely the cell division without affectingthe re-generation of chloroplasts. De novo formation of RNAand protein which has been observed to occur during the recoveryprocess was not affected by the antibiotic to any significantextent. It thus became clear that the re-generation of chloroplasts,accompanied by the formation of chlorophyll, RNA and protein,occurring under the said condition is not a phenomenon causedby the formation of new "normal" cells from previously degeneratedcells. As was expected, the antibiotic suppressed strongly theDNA synthesis, indicating that the new formation of DNA is nota necessary condition for the re-generation of chloroplastsin "glucose-bleached" algal cells. (Received March 1, 1965; )     

THE PHOTOINHIBITION OF GROWTH IN ETIOLATED STEM SEGMENTS. II. GROWTH CAUSED BY COBALT IN PISUM

Bertsch, Walter F. (Yale U., New Haven, Conn.) The photoinhibition of growth in etiolated stem segments. II. Growth caused by cobalt in Pisum. Amer. Jour. Bot. 50(3): 213–219. Illus. 1963.—Etiolated pea stem sections were utilized to study the effects of various metal ions on the red, far-red photoinhibition of stem growth. Excision of immature tissue results in loss of photosensitivity. All growth caused by cobalt, either in the presence or absence of sugar, was inhibited by brief exposure of the excised tissue to red light. Since growth caused by sugar is also light-sensitive, it may be said that either cobalt or sugar may induce photosensitivity in this immature tissue. Other divalent metal ions were tested, but only nickel promoted growth. Although cobalt and nickel showed the same optimal concentration (ca. 2 × 10⁻⁵ m), growth caused by nickel was not photosensitive, suggesting that cobalt and nickel promoted growth through separate mechanisms. Since growth caused by indole-3-acetic acid or gibberellic acid is also insensitive to light in this tissue, a photosensitive sugar-cobalt growth system has been experimentally separated from other growth-controlling systems. The photoinhibition of a growth system which utilizes sugars and is promoted by cobalt and the relation of this system to certain de-etiolation phenomena are discussed.     

SPERMATOGENESIS IN ANIMALS AS REVEALED BY ELECTRON MICROSCOPY : II. SUBMICROSCOPIC STRUCTURE OF DEVELOPING SPERMATID NUCLEI OF GRASSHOPPER

The submicroscopic structure of the maturing spermatid nucleus of the grasshopper, Gelastorrhinus bicoler de Haan, has been studied in thin tissue sections by electron microscopy. In the early spermatid the nucleus appears dense with no clearly resolvable fine structure. In the advanced spermatid with a conical-shaped nucleus, the karyoplasm begins to show a fibrillar structure. At subsequent stages, the elongated spermatid nucleus displays in cross-sections a hexagonal honeycomb pattern and in longitudinal sections an array of parallel lines, 70 A in diameter and spaced 100 to 220 A apart. As differentiation of the spermatid proceeds further, the space between the lines becomes narrower and narrower until it can no longer be resolved.     

DYNAMICS OF NERVE CELLS : II. THE TEMPERATURE COEFFICIENTS OF CARBON DIOXIDE PRODUCTION BY THE HEART GANGLION OF LIMULUS POLYPHEMUS.

1. It is possible to determine by the colorimetric method the rate of production of carbon dioxide by the cardiac ganglion of Limulus. 2. Carbon dioxide formation in the cardiac ganglion was found to run parallel to the rate of heart beat for different temperatures. 3. The conclusion seems justified that the rate of cardiac rhythm of Limulus depends upon a chemical reaction in the nerve cells of the cardiac ganglion and that this reaction is associated with the production of carbon dioxide since the rate of beat and the rate of CO₂ production are similarly affected by changes in temperature.     

ISOLATION AND PURIFICATION OF GLANDULAR SECRETORY CELLS FROM ARTEMISIA TRIDENTATA (SSP. VASEYANA) BY PERCOLL DENSITY GRADIENT CENTRIFUGATION

Glandular trichome heads (the secretory cells), obtained by mechanical homogenization of young floral buds and subtending leaves of Artemisia, were isolated and partially purified in discontinuous and continuous Percoll density gradients. With discontinuous gradients, the mixed-cell suspension was fractionated on four layers of Percoll with increasing densities: 0, 1.048, 1.068, and 1.084 g/ml. Gland heads banded primarily at the 0/1.048 interface, mesophyll cells at the 1.068/1.084 interface, and the hairs and hair fragments pelleted at the bottom of the tube. Twenty to thirty percent of the cells in the 0/1.048 band were intact gland heads, which represented about half of those recovered from the gradient. Hairs were the major contaminant. Over 90% of the gland heads excluded Evan's blue dye and were apparently viable. Similar results were obtained from preliminary experiments using continuous density gradients. The whole procedure for either method requires 3–6 hr, depending on the amount of starting material.     

SEPARATION OF HELA CELLS BY COLLOIDAL SILICA DENSITY GRADIENT CENTRIFUGATION : I. Separation and Partial Synchrony of Mitotic Cells

Using a colloidal silica density gradient, HeLa cells in mitosis were found to have a density of 1.040–1.046 g/cc, lighter than the remaining interphase cells. The mitotic cells could be harvested and cultured after centrifugation, showing growth synchrony by measurement of a peak in mitotic index 21 hr after establishing the culture. By using Colcemid or vinblastine sulfate, HeLa cells were arrested in metaphase and centrifuged on the colloidal silica density gradient. The blocked metaphase cells were lighter in density than the interphase cells but somewhat more dense than untreated cells selected by the density gradient centrifugation. Near-equilibrium conditions were established during the centrifugation of cells so that cell density measurements could be made, and the gradient medium employed was not measurably toxic to those cells tested.     

STUDIES ON CELL METABOLISM AND CELL DIVISION : III. OXYGEN CONSUMPTION AND CELL DIVISION OF FERTILIZED SEA URCHIN EGGS IN THE PRESENCE OF RESPIRATORY INHIBITORS

1. The effects of a number of respiratory inhibiting agents on the cell division of fertilized eggs of Arbacia punctulata have been determined. For eggs initially exposed to the reagents at 30 minutes after fertilization at 20°C., the levels of oxygen consumption prevailing in the minimum concentrations of reagents which produced complete cleavage block were (as percentages of the control): In 0.4 per cent O₂-99.6 per cent N₂, 32; in 0.7 per cent O₂-99.3 per cent CO, 32; in 1.6 x 10^–4 M potassium cyanide, 34; in 1 x 10^–3 M phenylurethane, 70; in 4 x 10^–3 M 5-isoamyl-5-ethyl barbituric acid, 20; in 3 x 10^–4 M iodoacetic acid, 53. 2. The carbon monoxide inhibition of oxygen consumption and cell division was reversed by light. The percentage inhibition of oxygen consumption by carbon monoxide in the dark is described by the usual mass action equation with K, the inhibition constant, equal to approximately 60, as compared to values of 5 to 10 for yeast and muscle. In 20 per cent O₂-80 per cent CO in the dark there was a slight stimulation of oxygen consumption, averaging 20 per cent. 3. Spectroscopic examination of fertilized and unfertilized Arbacia eggs reduced by hydrosulfite revealed no cytochrome bands. The thickness and density of the egg suspension was such as to indicate that, if cytochrome is present at all, the amount in Arbacia eggs is extremely small as compared to that in other tissues having a comparable rate of oxygen consumption. 4. Three reagents poisoning copper catalyses, potassium dithio-oxalate (10^–2 M), diphenylthiocarbazone (10^–4 M), and isonitrosoacetophenone (2 x 10^–3 M) produced no inhibition of division of fertilized Arbacia eggs. 5. These results indicate that the respiratory processes required to support division in the Arbacia egg may perhaps differ in certain essential steps from the principal respiratory processes in yeast and muscle.     

TEMPERATURE CHARACTERISTICS FOR THE METABOLISM OF CHLORELLA : III. THE CATALYTIC DECOMPOSITION OF HYDROGEN PEROXIDE BY CHLORELLA PYRENOIDOSA

The decomposition of hydrogen peroxide by intact Chlorella cells follows a first order course at very low temperatures, but at higher temperatures gives falling first order constants. Between 0.6° and 20°C. the value of µ is 10,500 calories.     

III. DECREASE OF LABELED DNA IN CELLS OF THE ADRENAL MEDULLA AFTER INTERMITTENT EXPOSURE TO COLD

Italico rats were injected with thymidine-³H 6 hr after the end of 300 hr of intermittent cold treatment. This plan of experiment ensured replacement in the adrenal medulla of lost DNA which is specifically sensitive to cold treatment and has a labeling index sufficiently high for statistical evaluation. The labeling index in the adrenal medulla decreases to one-half of the initial value within 10 days in animals subjected to further intermittent cold treatment and within 32 days in animals kept at room temperature. The very low mitotic index and the absence of doubling of the labeling index show that the observed labeling cannot be ascribed to pre-mitotic DNA synthesis. The concept of metabolic DNA adequately explains the findings.