The bothridial hooks of Acanthobothrium quadripartitum Williams, 1968 (Cestoda: Tetraphyllidea): Their growth and use in taxonomy

McVicar A. H. 1977. The bothridial hooks of Acanthobothrium quadripartitum Williams, 1968 (Cestoda: Tetraphyllidea): their growth and use in taxonomy. International Journal for Parasitology7: 439–442. Bothridial hooks are absent from juvenile Acanthobothrium quadripartitum in Raja naevus but develop to full size before there is much growth of the bothridia and strobila. There is a linear relationship between the lengths of the different components of the hooks during their development and it is suggested that the ratios of these lengths to the total hook length may be useful parameters in dstinguishing between species of Acanthobothrium. Principal component analysis of published hook dimensions gave good separation of most species of Acanthobothrium.     

Roles of auxin and gibberellic acid in growth and maturation of epicotyls of Vigna angularis: Cell wall changes

The effects of auxin and gibberellic acid on cell wall composition in various regions of epicotyls of azuki bean ( Vigna angularis Ohwi and Ohashi cv. Takara) were investigated with the following results. (1) Young segments excised from apical regions of the epicotyl elongated in response to added 10⁻⁴ M indole-3-acetic acid (IAA). When the segments were supplied with 50 m M sucrose, the IAA-induced segment growth was accompanied by enhanced overall synthesis of cell wall polysaccharides, such as xyloglucans, polyuronides and cellulose. This IAA effect on the cell wall synthesis is a consequence of extension growth induced by IAA. Gibberellic acid (GA) at 10⁻⁴ M synergistically enhanced the IAA-induced cell wall synthesis as well as IAA-induced extension growth, although GA by itself neither stimulated the cell wall synthesis nor extension growth. In the absence of sucrose, cell wall synthesis was not induced by IAA or GA. (2) In mature segments excised from basal regions of the epicotyl, no extension growth was induced by IAA or GA. GA enhanced the synthesis of xylans and cellulose when the segments were supplied with 50 m M sucrose. IAA had no effect on the cell wall synthesis. These findings indicate that synthesis of polyuronides, xyloglucans and cellulose, which occurs during extension growth of the apical region of the epicotyl, is regulated chiefly by auxin whereas synthesis of xylans and cellulose during cell maturation in the basal region of the epicotyl is regulated by GA.     

Studies on the size,location and turnover of calcium pools accessible to growing Tetrahymena cells

Tetrahymena pyriformis cells in the logarithmic phase of growth accumulate 2.5–3.75 times as much calcium per unit volume as is present in the growth medium. It appears that most of this calcium is stored in a non-ionic form, with approximately 30% existing in the cilia, near its site of action in effecting ciliary reversal. The exchange of extracellular ⁴⁵Ca²⁺ with the major internal pools is extremely rapid, exhibiting a $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ of less than 0.5 h. Sites located on the cilia are responsible for 35–50% of Ca²⁺ influx, with the remainder entering through other positions on the cell surface.     

Papyrus swamp development in the Upemba Basin, Zaïre: studies of population structure in Cyperus papyrus stands

The ecology and distribution of papyrus swamps are briefly reviewed together with the ecology, distribution structure and growth characteristics of Cyperus papyrus.
Three age-classes of culm are recognized and girth and density of each are recorded along transects through mree swamps in the Upemba Basin of Zaïre. A regression of culm-unit biomass on culm girth, developed for Ugandan swamps, is used to convert Upemba measurements into biomasses. It is shown that simple measurements, taken at only a single point in time, yield much information on both the structure and the dynamics of papyrus populations.
It is suggested that the standing-crops of such populations are determined by available light, and by local temperature regimes, and are therefore constant, irrespective of site quality (nutrient status), for any particular climatic zone. Culm-duration (life-time) is not significantly influenced by climate and the ratio culms/rhizomes provides a useful indicator of comparative productivity. Unlike community biomass, productivity can be limited by site quality.     

Regulation of growth in larvae of the crab : The effect of cyclic temperatures

Experiments were designed to demonstrate that growth is precisely regulated in crustacean larvae and that cyclic temperatures act as a perturbation on growth regulation. Newly hatched larvae were exposed to either the specific a cyclic temperature, cumulative growth was significantly inhibited. Also, the specific growth rate ( ) of larvae in the cyclic temperature regime was found to oscillate with decreasing amplitude around the of the larvae exposed to constant temperature. This oscillatory pattern has been observed in a wide variety of self-regulating systems. Evidence is presented to demonstrate that this regulatory mechanism also adapts to long-term exposure to cyclic temperatures. These findings increase our understanding of how larvae cope with and adapt to changing environmental temperatures. More significantly, the mechanism could provide a sensitive tool for estimating the effects of specific environmental disturbances on fitness.     

Effect of sodium butyrate on the hepatoma cell cycle: Possible use for cell synchronization

Summary Exposure of HTC cells to sodium butyrate caused inhibition of growth. The site of growth inhibition was studied by time-lapse cinematography and [³H]thymidine incorporation studies. Evidence is presented that sodiunm butyrate affected the cell cycle at a specific point immediately after mitosis. Inasmuch as it does not modify the interphase duration after its removal, butyrate may be used for HTC synchronization. This work was supported by l'Institut Nationale de la Santé et de la Recherche Médicale and la Centre Nationale de la Recherche Scientifique (L. T. and J. K.).     

Prostaglandin D2, a potential antineoplastic agent

Cytotoxic actions of various prostaglandins were examined on L1210 mouse leukemia and several human leukemia cell lines, and prostaglandin D₂ (PGD₂) was found most active. PGD₂ exerted a dose dependent inhibition of L1210 cell growth over 3.6 μ$\text{M}$. At 14.3 μ$\text{M}$ growth was completely inhibited, and the number of viable cells remarkably decreased during culture. Microscopically the remaining cells showed degenerative changes with many vacuoles in their cytoplasm. The IC₅₀ value of PGD₂ on L1210 cell growth was calculated to be 6.9 μ$\text{M}$ (2.4 μg/ml), and at this concentration the DNA synthesis in 24 hr cultured cells was also decreased to a half of the level in the control cells. Such growth inhibition by PGD₂ was also found at similar concentrations with several human leukemia cell lines such as NALL-1, RPMI-8226, RPMI-8402, and Sk-Ly-16. Among other prostaglandins tested, PGA₂ showed a comparable, and PGE₂ a less but significant growth inhibitory activity, while PGB₂, PGF_2α and PGI₂ had no such effects on cell proliferation at 14.3 μ$\text{M}$ concentration. These results suggest a potential antineoplastic activity of PGD₂.     

Growth and morphology of neuronal cell lines cultured in perfusion

Summary To optimize culture conditions and gain a more reliable culturing system for studies of metabolic properties of neuronal cells, a simplified perfusion chamber was developed. It consists of two parts: a perfusion block and a standard plastic culture dish. To confirm the suitability of this chamber for continuous culturing of anchorage-dependent cells, the growth and morphology of the four neuronal cell lines glioma C6 and glioma 138MG, neuroblastoma C1300, clones N1E115 and N18 were followed for 4 d using both traditional and perfusion techniques. A marked increase in growth and a decrease in the degree of morphological differentiation were obtained with the latter technique compared to the former. This work was supported by grants from the National Swedish Board for Technical Development (Grant 81-5009), the Swedish Work Environmental Foundation (Grant 76-53), and Ollie and Elof Ericssons Foundation for Scientific Research.     

Calcium and phosphate effects on growth and alkaloid production in Coffea arabica: experimental results and mathematical model

Plant, mammalian, and microbial cells are commonly immobilized in calcium alginate gels for the production of valuable secondary metabolites. However, calcium ions are known to inhibit growth in various types of cells, and calcium is an integral part of such gels. Therefore, an investigation was conducted to evaluate the effect of calcium on the growth and alkaloid production of a model cell-line, Coffea arabica, in suspension culture before, attempting to immobilize such cells in alginate. A kinetic model was then developed from the results to describe cell growth and alkaloid production and the mechanism by which calcium influences these variables. In addition, it was observed that there was a characteristic relationship between the concentration of calcium in the external medium and the concentration of extra cellular and intracellular phosphate. The intracellular phosphate level was, in turn, related to the production of alkaloids. Using these results, a dynamic mathematical model of cell growth and alkaloid production was developed based on the proposed roles of calcium and phosphate. The model showed satisfactory agreement with three sets of experiments at different calcium concentrations. A possible linkage between the calcium and phosphate results is postulated based on the limited solubility of calcium phosphate.     

Estimation of growth yield and maintenance coefficient of plant cell suspensions

Methodology is presented for the determination of growth yield (Y(g)) and maintenance coefficient (m) for carbon utilization of plant cells grown in suspension culture. Estimation of Y(g) and m requires measurements of specific growth rate (micro) and specific rate of substrate uptake (q) at different growth limiting substrate concentrations. Batch culture of tobacco cells did not permit evaluation of Y(g) and m because micro is constant and maximal during most of the growth cycle. In batch culture, the period of declining specific growth rate is extremely brief because of the rapid transition from logarithmic growth to stationary phase. This occurs because the K(m) for growth is relatively small compared to the initial sucrose concentration. Thus, when the substrate level reaches the K(m), the large mass of cells rapidly depletes the remaining substrate. In contrast, semicontinuous culture facilitates the determination of Y(g) and m because various steady-state growth rates can be achieved. Mathematical expressions were developed to determine the effective values of micro and q over the semicontinuous replacement interval. The validity of this approach was verified by conducting simulations using experimentally determined parameters.