Effects of package, extender, and light on stored frozen bull spermatozoa.

Spermatozoa were analyzed when fresh, freshly frozen, and stored at --196 C for 6 and 18 mo after processing in egg yolk-citrate and Promine-D extender with varying exposure to light and packaging in straws or glass ampules. Over all treatments there were decreases with time in spermatozoal motility, oxygen uptake, and cellular glutamic oxaloacetic transaminase due to freezing-thawing. Percent progressive motility decreased from spermatozoa freshly frozen (36.

Preparation of biological tissues for electron microscopy by freeze-drying.

A dependable method for freeze-drying tissues for electron microscopy has been developed. Thin slices of fresh tissue were frozen by bringing them into direct contact with a polished copper bar at liquid nitrogen temperature. The tissue was transferred to a copper specimen block equipped with a thermocouple and heating circuit for accurate control of the environmental temperature of the tissue, and evacuated in a glass freeze-drier using clean high vacuum techniques for keeping the system free of hydrocarbons.

The effect of keto-analogues of essential amino acids in severe chronic uremia.

Alpha keto-analogues of valine, leucine, isoleucine, methionine, phenylalanine, and (in one instance) tryptophan and histidine, along with the remaining essential amino acids, were administered orally to 10 patients with severe chronic uremia fed a diet low in protein but adequate in calories. Ketoacid dosage varied from 6 to 14 g daily, as sodium or calcium salts. Net nitrogen intake, calculated as intake minus urinary protein nitrogen, averaged 1.

Physiological studies of an oligosporogenous strain of Bacillus popilliae.

A relatively small but consistent increase in the frequency of spore formation by an oligosporogenous strain of Bacillus popilliae (NRRL B-2309M) was obtained by adding 0.1% sodium pyruvate to the sporulation medium. The frequency of spore formation was essentially the same when a low level of glucose, trehalose, or glucose-6-phosphate or a high level of alpha-methyl-d-mannoside was added as the carbon and energy source.

Base pairing in 5-chlorouridine.

5-Chlorouridine has been found to crystallize from water with the molecules of the nucleoside arranged in a base-paired, parallel-stranded ribbon. This type of polymer structure has not been previously considered for nucleic acids. We have constructed a model of polyuridylic acid based upon the 5-chlorouridine crystal structure and wish to suggest it as a plausible molecular complex for this and perhaps other polynucleotides.

Production, purification, and composition of staphylococcal alpha toxin.

Coulter, John R. (Institute of Medical and Veterinary Science, Adelaide, Australia). Production, purification, and composition of staphyloccocal alpha toxin.

ELECTRON MICROSCOPY OF INFECTION THREADS AND BACTERIA IN YOUNG ROOT NODULES OF MEDICAGO SATIVA.

Jordan, D. C. (Ontario Agricultural College, Guelph, Canada), I.

PORPHYRIN COMPOUNDS DERIVED FROM BACTERIA.

The pigment contained in the extracts obtained from B. phosphorescens by freezing and thawing, and in the alkaline extracts of B. phosphorescens and yeast, resembles the "cytochrome c" of Hill and Keilin (6) and the "porphyratin B" of Schumm (7) in giving absorption bands at mmicro 552-550 and 522-520) but shows in addition a band about 575, as in the "hemochromogen A" obtained by Keilin (3) by prolonged treatment of yeast with strong alkali.

THE OCCURRENCE OF PORPHYRINS IN CULTURES OF C. DIPHTHERIAE.

A complex porphyrin which has not been hitherto described is found in liquid cultures of C. diphtheriae. The porphyrin is a combination of coproporphyrin with both iron and copper, and shows an oxidation-reduction change.