Isolation of cell cycle mutants of Physarum polycephalum

Summary Asynchronous amoebal cultures of temperature-sensitive mutants of Physarum polycephalum were examined cytologically, and two cell cycle mutants were identified. Genetic analysis indicated that each mutant carried a single mutation that was expressed in both amoebal and plasmodial phases. Thus it is possible to isolate cell cycle mutations expressed in plasmodia by initial isolation and analysis of amoebal mutants, a quicker procedure than the alternative of isolating plasmodial mutants directly. The two mutants were studied further by measuring nuclear DNA contents and synthesis of macromolecules. Both mutants gave results consistent with a block in nuclear division.     

The role of enteric bacteria in the anerobic metabolism of 5-aminosalicylate

The primary (and inactive) enteric metabolite of 5-aminosalicylate is N-acetyl-5-amino-salicylate. Previous studies have demonstrated acetylation of this anti-inflammatory agent by intestinal and bacterial homogenates. To assess the contribution of anerobic bacteria to the N-acetylation in vivo, we have measured the production of N-acetyl-5-aminosalicylate in anerobic microculture. Our results indicate that enteric bacteria play a minor role in N-acetylation, but may contribute to the production of other metabolites of pharmacologic and toxicological interest.     

Tricyclic quinoxalines as ligands for the strychnine-insensitive glycine site

The synthesis of a series of tricyclic quinoxalines is described. These compounds exhibit good affinity for both the strychnine-insensitive glycine site of the NMDA receptor and the AMPA receptor.     

Human brain tubulin purification: Decrease in soluble tubulin with age

The soluble tubulin of human cerebral cortex, as assessed by [³H]colchicine binding of the 100,000g supernatant fraction, decreases drastically with age, 75 percent from age 0 to age 90. There is also a considerably lower concentration of high molecular weight proteins in the soluble fraction of postmortem human cerebral cortex than in that of nonhuman species. Human brain tubulin can be polymerized into microtubules with DEAE-dextran. The DEAE-dextran induced microtubules are stable to cold temperature (4°) and calcium. However, in the presence of 1 M glutamate, the microtubules become cold labile and depolymerize at 4°. Thus we have developed a novel method for purifying polymerization competent tubulin from fresh or frozen human cerebral cortex. Human brain tubulin purified by our novel method is very similar to tubulin from the brains of other mammals in molecular weight, amino acid composition, polymerization-depolymerization parameters, and structural dimensions of the microtubules formed.Some aspects of this work have been published as an abstract in 1981. Fed. Proc. 40:1548.     

Unusual lesion morphology and skin test reaction for Mycobacterium avium complex in macaques

Three rhesus (Macaca mulatta) and one cynomolgus (M. fascicularis) monkey were euthanized because of positive reactions to intradermal tests with mammalian Old Tuberculin (mOT). All the animals had gross or microscopic lesions consisting of unitized macro- or microgranulomas with central necrosis, involving the lung or mesenteric lymph nodes. Small numbers of acid fast organisms were demonstrated in the lesions. Mycobacterium avium complex, serotype 2 was isolated from three of the cases. The cases were unusual because the lesion morphology and mOT hypersensitivity were more typical of mammalian tuberculosis than avian tuberculosis in monkeys.     

ECOLOGY OF THE RED-NECKED FALCON FALCO CHICQUERA IN ZAMBIA

The Red-necked Falcon in southern Zambia is a year-long resident in its breeding territory. The study was conducted on a floodplain and the adjacent acacia savannah in an undisturbed natural environment. The falcon principally nests in natural depressions on frond bases on the leeward side of Borassus Palms but also utilizes old crow and raptor nests. Incubation averaged 33 days and was undertaken by the female. The young fledged after a 36-day nestling period and remained under parental care for up to three weeks after that. Nesting success averaged 1.3 young per nest or 44% of the eggs laid. The post-juvenal moult commenced when the young were five to six months old and continued for six months. Birds comprised 98% of the diet of the falcons. The adults selected larger prey as the nestlings increased in size. The 69-day incubation and nesting period is up to 14 days longer than in similar-sized falcons.     

Glutaraldehyde fixation and protochlorophyll transformations in etiolated peas

Summary Glutaraldehyde causes protochlorophyllide and newly formed chlorophyllide in etiolated peas to absorb at shorter wavelemgths. Fixation completely inhibits photoconversion in a cell free preparation of protochlorophyll in 1 min but in intact infiltrated leaves inhibition is only partial after 24 hr. It is suggested that procedures which indicate that fixation has occurred at a broad level of structural organization may be inadequate to establish that fixation has occurred at a macromolecular level.     

Successful maintenance of suckling rat ileum in organ culture.

Ileum from rats 4, 9, 11, 12, and 15 days old can best be maintained for 24 hours in a system using Hanks' Balanced Salt Solution without fetal calf serum, at 25 degrees C and 21% O2. Suckling rat duodenum and jejunum were difficult to maintain well for 24 hours in this system or a variety of other systems that were tried. A temperature of 37 degrees C hastened deterioration of duodenum, jejunum or ileum. With ileum, 3H-thymidine and 14C-leucine were increasingly incorporated into DNA and protein over the 24-hour period. Light microscopy, as well as scanning and transmission electron microscopy, showed very good preservation of the ileum after 24 hours. The addition to the medium of hydrocortisone, 1 micron, and thyroxine, 0.01 micron, alone or in combination, did not change DNA or protein synthesis, or morphology, possibly because of the relatively short (24 hour) time period. Our organ culture system emphasizes the differences between suckling rat ileum and the rest of the intestine, and provides a new tool for evaluating, over a 24-hour period, the developing rat small intestine.