The distribution and localization of drug-induced secondary constrictions in human chromosomes

BUdR, mitomycin C and hydroxylamine hydrochloride induce secondary constrictions in particular human chromosomes. The increased frequency of constriction formation in certain chromosomes is time and drug dependent, and correlates well with the timing of DNA synthesis. The frequency at which some of these constrictions can be induced by specific drugs at specific times increases the usefulness of these landmarks in chromosome identification.

Observations on Aeromonas hydrophila septicaemia in a patient with leukaemia

A Gram-negative bacillus isolated from the blood of a leukaemic patient with septicaemia was identified on the basis of common tests as Escherichia coli. However, the organism's antibiogram was atypical of E. coli and led to its re-examination and correct identification as Aeromonas hydrophila. A. hydrophila is sensitive to chloramphenicol and tetracycline, characteristics useful in differentiation from E. coli. A simple test differentiating this organism from the Enterobacteriaceae is the oxidase test. A. hydrophila is oxidase positive.

Photomorphogenesis in Arabidopsis thaliana (L.) Heynh: Threshold Intensities and Blue-Far-red Synergism in Floral Induction

Arabidopsis seeds were germinated on sterile mineral agar supplemented with 1% glucose and cultured under continuous light regimes. With 4-hour incandescent plus 20-hour monochromatic illumination in the region from 400 to 485 nanometers there was effective floral induction at an intensity of 100 microwatts per square centimeter. Exclusion of far red wave lengths from the 4-hour incandescent period sharply reduced the effectiveness of subsequent monochromatic blue light in promoting floral induction. Delayed floral induction occurred under continuous incandescent light lacking far red and was attributable to the blue wave lengths. Continuous 485 nanometer (100 microwatts per square centimeter) exposure without any white light treatment during the postgermination growth period was ineffective in floral induction and meristem development. Light at 730 nanometers under the same conditions was partially effective, whereas energy between 500 and 700 nanometers was completely ineffective. When continuous monochromatic light at a 3-fold higher energy level was administered, all photomorphogenic responses were accomplished with 485 nanometer light, including germination and 100% floral induction without any white light treatment at any time during the experiment. Almost equal quantum effectiveness was calculated when equivalent quantum flux densities in the region from 710 to 740 nanometers or at 485 nanometers were used. It is postulated that floral induction in Arabidopsis may be the result of a continuous excitation of a stable form of far red-absorbing phytochrome localized in or on a membrane, and that excitation can be either by direct absorption of energy by far red-absorbing phytochrome or by transfer from an accessory pigment.

Effectiveness of hypoglycemic agents in guinea pigs exposed to mixed gamma-neutron radiations

The effect of 200, 1000, and 5000 rads of mixed gamma-neutron radiations on total blood reducing sugar and blood glucose levels in guinea pigs was investigated 2 and 24 hours, and 9, 22, and 60 days postirradiation. In addition, the effectiveness of insulin and tolbutamide in these animals was evaluated before and after irradiation. Glucose increased to a lesser degree and later than did the nonglucose fraction of the blood sugar. Insulin and tolbutamide were at least as effective in irradiated animals as in unirradiated ones except after 5000 rads, when tolbutamide was significantly less effective. These results suggest that: (1) insufficient insulin is released by the pancreas in response to elevated blood sugar levels following irradiation; (2) the pancreas does produce insulin at these times and is able to release it in response to tolbutamide; and (3) a decrease in insulin production occurs following supralethal doses of radiation.

Effect of ionizing radiation on total protein-bound neutral hexoses in the plasma of mice

Total protein-bound carbohydrates (PBC), as neutral hexoses, were quantified in the plasma of C3H mice as a function of time relative to whole-body exposure to either monoenergetic 14-MeV neutrons or mixed gamma-neutron radiations delivered at a rate of approximately 20 rads/ min. The reported doses, 365 to 530 rads, were those which yielded survivors under the stress of daily bleeding. A striking difference was observed between those radiosensitive animals which died after exposure and the more resistant individuals which, although exposed to identical doses, survived the observation period. In the former population, the PBC concentration rose to high values and remained elevated until the death of the animal. By contrast, the survivors showed little change in PBC, deviating only slightly from their preirradiation base-line values. The mean preirradiation PBC concentration in the mice which survived 30 days, while statistically significant (p < 0.01) only at the lowest reported dose, was consistently lower than that of those which died during the same period. The magnitude of the difference was inversely related to the radiation dose. The refinement of these data to provide an index to radiosensitivity prior to and prognosis after irradiation in otherwise healthy individuals is proposed.

A Suspected Case Of Infectious Synovitis In Alberta

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