A third DNA polymerase from Spiroplasma citri and two other spiroplasmas.

Recently, two DNA polymerases (ScA and ScB) were isolated and characterized from Spiroplasma citri. We now have found a third DNA polymerase (ScC) not only in S. citri but also in the serologically related honeybee spiroplasma BC3 and the unrelated flower spiroplasma BNR1. Enzyme ScC is N-ethylmaleimide (NEM) sensitive. The three DNA polymerases from the honeybee spiroplasma seem to be similar to the respective enzymes of S. citri. However, whereas the NEM-resistant enzyme ScA from S. citri and that from the BC3 honeybee spiroplasma are retained on DEAE-cellulose and require 0.09 M KCl for elution, the NEM-resistant enzyme A from the flower spiroplasma BNR1 is not retained.     

The effect of monochromatic radiation in the range 350 to 750 nm on the carotenogenesis in Verticillium agaricinum

An action spectrum for carotenogenesis in V. agaricinum has maxima at 395, 433, 660 and 737 nm. In a previous study it had been shown that a light-minus-dark difference spectrum of a crude extract from V. agaricinum had maxima at 390 and 420 nm, and furthermore a red, far-red interaction suggesting phytochrome involvement has been proposed. All these data suggest that there may be at least two photoreceptor systems operating in the photoinduction process here; one for the near-ultraviolet (UV-A)-mediated carotenogenesis, presumably a novel pigment, and the other for the red, far-red region, most likely phytochrome.     

Polyploidy and aspartate-transcarbamylase activity in Hippocrepis comosa L.

The DNA content of plants which were sampled in natural di-, tetra- and hexaploid populations of Hippocrepis comosa L. was estimated and the aspartate transcarbamylase activities of the corresponding cell-free extracts were compared. The amount of DNA is not exactly proportional to the number of genomes. The three kinds of populations do not differ in their aspartate transcarbamylase specific activity. While the enzyme properties are identical in the extracts derived from the diploid and hexaploid plants, the aspartate transcarbamylase present in the tetraploid cytotype shows a slightly lower affinity for one of its substrates and a significantly lower sensitivity to the feedback inhibitor UTP which is still observed after partial purification. These properties might be related to the previously reported greater ability of the tetraploid cytotype to adapt to a variety of biotopes.Abbreviations ATCase aspartate transcarbamylase - CAP carbamylphosphate - EDTA ethylenediaminetetracetic acid - Tris trihydroxymethylaminomethane - AMP adenosine monophosphate - ATP adenosine triphosphate - CMP cytidine monophosphate - CTP cytidine triphosphate - UMP uridine monophosphate - UTP uridine triphosphate     

Energization of the sugar transport mechanism in the plasmalemma of isolated mesophyll protoplasts

The mechanism of 3-O-methyl-d-glucose transport through the plasmalemma has been investigated in protoplasts isolated from the mesophyll of Pisum sativum L. var. Dan.Analysis of the fluxes after 50 minutes of uptake showed that the gradual decrease in slope of the net uptake curve with time was not due to any decline in uptake capacity; it represented the approach to flux equilibrium of a small compartment of the protoplast, probably the cytoplasm.The energy of activation for initial flux into this compartment was 20 kilocalories per mole between 17 and 27 C. Very high discrimination was shown with regard to sugar isomers. Light strongly promoted flux (by a factor of 2.5 in the case of methyl glucose). Initial flux showed sharply contrasting inhibitor sensitivity in the light and the dark. Light uptake was sensitive to the proton conductor carbonyl cyanide m-chlorophenylhydrazone (CCCP), but stable for at least the first 10 minutes to the ATPase inhibitors quercetin, rutin, and diethylstilbestrol, as well as to arsenate. Dark uptake, on the other hand, was stable to CCCP but was immediately depressed by quercetin, rutin, diethylstilbestrol, and arsenate.Protoplasts which received a light pretreatment before incubation in the dark took up methyl glucose at the accelerated light rate for the first 7 minutes. Moreover, the light pretreatment sensitized subsequent initial dark uptake to CCCP, and conferred on it the stability to ATPase inhibitors and arsenate characteristic of light uptake. After about 7 minutes the characteristic inhibitor responses of dark uptake were resumed.It is proposed that more than one mode of energy-coupling for sugar transport may operate in these protoplasts.     

The brief survival of free-ranging baboon infants (Papio cynocephalus) after separation from their mothers

The importance of mother — infant attachment in free-ranging primates is illustrated by events culminating in the deaths of two baboon infants a few days after losing their mothers. These two cases are contrasted with those of a severely injured infant, not separated from its mother, which lived, and an animal which lost and refound its troop. Protective behavior of adult males is described. In captivity, separation sometimes produces infant depression; in nature, such depression may be fatal.     

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.     

Light and electron microscopic structure of golgi-stained neurons in the vertebrate brain (new rapid Golgi procedure)

Summary After application of a rapid, selective silver impregnation procedure for light (LM) and electron (EM) microscopy, individual neurons are distinguishable by a light silver precipitation. The silver content is sufficient that entire nerve cells can be observed light microscopically; on the other hand, electron microscopically the cytological details are still visible. Brains of mice were fixed by phosphate-buffered aldehyde perfusion, and pieces of tissue left in a 1 % K₂Cr₂O₇ solution for 13 h before impregnation in a 0.5 % AgNO₃ solution for 2h. Thick sections (30–50 m) of the impregnated tissue were cut; from these sections, suitably stained neurons were dissected out and re-embedded for ultrathin sectioning, thereby allowing observations on the same neurons at the EM level. A thin silver deposit was observed along the delimiting neuronal membrane, the microtubules and the smooth ER, including the spinal apparatus of the dendritic spines. The fine cytoplasmic details of the impregnated neurons and the surrounding tissue are well preserved and, therefore, suitable for subsequent determination of synaptic relationships of the impregnated neurons with the adjacent neuronal elements.     

Bovine coronavirus genome.

The tissue culture-adapted strain (Mebus) of the bovine coronavirus was grown to titers of greater than 10(7) 50% tissue culture infective doses per ml in secondary bovine embryo kidney cells, and the RNA was isotopically labeled with [3H]uridine. The RNA was extracted from purified virus and was found to have the following properties. (i) It consisted primarily of a homogeneous large-molecular-weight species which comigrated electrophoretically with vesicular stomatitis viral RNA and therefore had an apparent molecular weight of 3.8 X 10(6). (ii) It remained as a 3.8 x 10(6)-molecular-weight molecule after heat denaturation when rapidly harvested virus was examined. (iii) It was 80% susceptible to pancreatic RNase A digestion in high (0.3 M) NaCl, and the 20% resistant fraction was 4S to 7S in size. (iv) It was polyadenylated to the extent that 40 and 60% of the native RNA bound to polyuridylic acid-Sepharose and oligodeoxythymidylic acid-cellulose, respectively, under conditions of high (0.5 M) NaCl.     

A stochastic model of a temperature-dependent population

The theoretical basis is developed for a population model which allows the use of constant temperature experimental data in predicting the size of an insect population for any variable temperature environment. The model is based on a stochastic analysis of an insect's mortality, development, and reproduction response to temperature. The key concept in the model is the utilization of a physiological time scale. Different temperatures affect the population by increasing an individual's physiological age by differing rates. Conditions for the temperature response properties are given which establish the validity of the model for variable temperature regimes. These conditions refer to the relationship between chronological and physiological age. Reasonable agreement between the model and field populations demonstrates the practicality of this approach.