An oceanographic radiance distribution camera system

An oceanographic optical instrument has been designed and constructed to record the radiance distribution of natural radiant energy underwater. The instrument contains two cameras placed back-to-back, each equipped with a fisheye (180 degrees field of view) lens and is fabricated so that film can be exposed by remote control. The instrument is designed to operate at depths up to 100 m. Values of underwater radiance can be obtained from the exposed films by means of photographic photometry. Radiance distributions obtained in natural waters will provide basic information needed for the study and solution of several problems in optical oceanography. First, the radiance distribution is an important input for the study of the interaction of electromagnetic radiation with the sea. From the distribution of radiance in the natural light fields in the ocean, many of the important optical properties which relate to radiative transfer processes in the ocean can be calculated. Second, from these optical properties one can compute the magnitude of the deterioration of image contrast of submerged objects and thus furnish information for the study and solution of underwater visibility problems, which include problems in underwater television and photography. Finally, since radiant energy is critical to the beginning of the marine food chain through photosynthetic plankton, radiance distribution measurements will provide information of fundamental importance to the problem of primary productivity in natural waters.

Time course of exudation from excised corn root segments of different stages of development

Xylem exudates were collected at hourly intervals from short segments which had been excised from two portions of the primary root of corn (Zea mays L.) seedlings and partially immersed in experimental salt solution containing (86)Rb. All segments showed variation in rates of output of both volume and ions for several hours, after which a steady state was attained which persisted for many hours. Apical segments produced little or no exudate for several hours and did not reach a steady state until 18 or more hours after excision. Basal segments produced exudate containing detectable quantities of isotope within an hour and they reached a steady state about 12 hours after excision. During their respective steady states, apical segments produced three times the volume per hour and translocated eight times as much Rb per hour as did basal segments.These differences in the time course of exudation and the large differences in output are interpreted as indicating that two independent systems of ion transport operate simultaneously in intact roots. If this interpretation is correct, then it would appear that one of these systems has a greater potential capacity for ion transport than the other.

S-Adenosylethionine as an inhibitor of tRNA methylation

S-Adenosylethionine was shown to inhibit the methylation of tRNA by S-adenosylmethionine. Lineweaver–Burk plots of kinetic data suggested that the inhibition was competitive. Another known inhibitor of tRNA methylation, adenine, also exhibited competitive inhibition kinetics. A derivative of S-adenosylethionine, ethylthioadenosine, also inhibited the reaction and displayed a competitive inhibition pattern. These data were obtained using Escherichia coli K12W6 as a source of methyl-deficient tRNA and methylase enzymes. Preliminary data indicate that S-adenosylethionine is even a better inhibitor of rat methylases.Methylase activity of ethionine-fed rats was elevated, which suggested that the inhibition reaction with S-adenosylethionine and the increased methylase activity may proceed by two different pathways.

Inhibition by ethionine of the growth of Neurospora crassa

A wild-type strain of Neurospora crassa was inhibited 30% by 0.1 μg/ml of L-ethionine. With 1 μg/ml the cultures failed to grow for the first 5 days of incubation and then they grew at a rate comparable to that of a control culture. However, the final weight of the inhibited cultures was less than that of the untreated cultures. L-Ethionine at 2.5 μg/ml completely inhibited growth of the cultures. The growth of a methionine-requiring strain of N. crassa was inhibited about 90% when the ratio of ethionine to methionine was at least 10:1. Ethionine at 0.6 μg/ml inhibited the growth of a choline-requiring mutant. α-Methylmethionine and norleucine at 1 mg/ml did not inhibit growth of the wild-type N. crassa in liquid medium. S-Ethyl-cysteine inhibited growth much less than ethionine. p-Fluorophenylalanine was as effective an inhibitor as ethionine.

Growth and nucleic acid synthesis of Salmonella typhimurium inhibited by alpha-methylmethionine

The addition of α-methylmethionine to exponentially growing cultures of Salmonella typhimurium or Escherichia coli resulted in an immediate cessation of growth with low concentrations of the analogue. After a lag period, the length of which was dependent on the optical density of the culture, growth resumed at a rate characteristically slower than that of an untreated culture. Chemical analyses showed that the rate of synthesis of ribonucleic acid and protein by S. typhimurium had a pattern similar to the curve for optical density. However, deoxyribonucleic acid and cell numbers continued to increase at the normal rate for about 30 minutes, then slowed, and changed to the rate characteristic of cells treated with the analogue. Incorporation of thymine-14C, uracil-14C, and leucine-14C by the thymine auxotroph E. coli 15T− confirmed the chemical analyses. After 25 minutes the cells of the culture treated with α-methylmethionine had incorporated only 15% of the uracil and 26% of the leucine as that of a control culture. The optical density was 30% that of a control culture. Thymine incorporation was 92% that of a control culture.