Progressive release of carboxylating enzymes during mechanical grinding of sugar cane leaves.

The progressive release of protein, chlorophyll, phenol oxidase activity and phenolic compounds during the mechanical disruption of sugar cane leaves has been correlated with the release of carboxylating enzymes. Enzymes of the photosynthetic carbon reduction cycle were released in parallel with chlorophyll, the bulk of which was recovered in grana-containing chloroplasts. PEP carboxylase activity followed the release of total protein.

Interaction effects of visual contours on the discharge frequency of simple striate neurones.

1. The discharge frequency of simple neurones in the cat striate cortex responding to the two edges of a slit of light moving over their receptive fields was studied as a function of slit width. While one edge of the slit was discharging the cell, the other edge had a modifying influence on that discharge either by way of facilitation or of inhibition.

Responses to visual contours: spatio-temporal aspects of excitation in the receptive fields of simple striate neurones.

1. The properties of the receptive fields of simple cells in the cat striate cortex have been studied by preparing average response histograms both to moving slits of light of different width and to single light-dark edges or contours.2.

Effects of some phenoloxidase inhibitors on chloroplasts and carboxylating enzymes of sugar cane and spinach.

A number of additives have been tested for their effects on o-diphenol: O2 oxidoreductase activity of cane leaves. The most inhibitory compounds were thioglycollate, β-mercaptoethanol, polyethylene glycol and bovine serum albumin. Sulphydryl (SH) compounds did not affect rates of photosynthetic CO2 assimilation when used at concentrations below 10(-2) M.

Phenols, phenoloxidase, and photosynthetic activity of chloroplasts isolated from sugar cane and spinach.

Sugar cane chloroplasts isolated in simple media possessed little photochemical activity, but showed rapid O2 uptake, independent of light. A similar rapid consumption of O2 was observed with brei prepared from cane leaves. This was not observed in brei of spinach leaves.

Studies on the biochemistry and fine structure of silica-shell formation in diatoms : Chemical Changes in the wall of Navicula pelliculosa during its formation.

Wall formation in Navicula pelliculosa was studied in Si-starvation synchrony. Electron microscopy of walls, prepared by mechanical shaking, indicated that they were free, of cytoplasmic contamination. Removal of the frustule, using HF, indicated that a higher ratio of organic material to silica occurred in the girdle bands below the punctae and in the raphe region.

Studies on the biochemistry and fine structure of silica shell formation in diatoms. Photosynthesis and respiration in silicon-starvation synchrony of Navicula pelliculosa.

Rates of photosynthesis, measured by oxygen electrode or by (14)CO(2) fixation, dark respiration and (32)P-phosphate incorporation are reported for the silicon-starvation synchrony of the fresh water diatom Navicula pelliculosa. During late exponential growth the rates were consistent with increase in carbon mass. During silicon starvation, rates of carbon dioxide fixation, oxygen evolution and (32)P incorporation fell, and the saturating light intensity decreased from 27,000 lux to 5000 lux.

Studies on the biochemistry and fine structure of silica shell formation in diatoms. Chemical composition of Navicula pelliculosa during silicon-starvation synchrony.

Changes are reported in total cellular organic carbon, nucleic acids, proteins, carbohydrates, lipids and chlorophylls during the course of silicon-starvation synchrony of Navicula pelliculosa. All constituents increased at the same rate, relative to cell number, for 30 hours of exponential growth during which silicon was depleted from the medium. Increase in cell number then stopped, but net synthesis of most components continued for a further 5 to 7 hours before ceasing.