The expression, purification and crystallization of the epsilon subunit of the F1 portion of the ATPase of Escherichia coli.

The epsilon subunit of the F0F1-ATPase from Escherichia coli has been expressed in E. coli as a fusion protein with glutathione S-transferase from the parasitic helminth Schistosoma japonicum. The epsilon subunit released by thrombin treatment of the purified fusion protein carried two amino acid changes, A1G and M2S, and was obtained in a yield of about five milligrams per litre of cultured cells. The two amino acid changes were shown not to affect function. The protein has been crystallized in a form suitable for X-ray diffraction structure analysis. The crystals are hexagonal, space group P6(1)22 (or P6(5)22), with a = b = 94.9 A, c = 57.1 A and gamma = 120 degrees. The diffraction from small crystals extends to at least 2.9 A resolution.     

Serologic evidence of a Rickettsia akari-like infection among wild-caught rodents in Orange County and humans in Los Angeles County, California.

We detected antibodies reactive with Rickettsia akari, the etiologic agent of rickettsialpox in humans and in 83 of 359 (23%) rodents belonging to several species, collected in Orange County, CA. Reciprocal antibody titers >1:16 to R. akari were detected in native mice and rats (Peromyscus maniculatus, P. eremicus, and Neotoma fuscipes) and in Old World mice and rats (Mus musculus, Rattus rattus, and R. norvegicus), representing the first time that antibodies reactive with this agent have been detected in four of these species and the first report of these antibodies in rodents and humans west of the Mississippi River. We then tested serum samples from individuals who used a free clinic in downtown Los Angeles and found that 25 of 299 (8%) of these individuals had antibody titers >1:64 to R. akari. Serologic evidence suggested that R. akari or a closely related rickettsia is prevalent among several rodent species at these localities and that infection spills over into certain segments of the human population. Isolation or molecular confirmation of the agent is needed to conclusively state that R. akari is the etiologic agent infecting these rodents.     

Postnatal changes in enzyme activities of rat myocardial adenine nucleotide catabolic pathway

Three catabolic enzymes, 5'-nucleotidase (5'NT), adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP) and one anabolic enzyme, myokinase (MK) involved in adenine nucleotide (AN) metabolism were studied in myocardium from 4 to 105 day old rats. The specific enzyme activities (nmoles/min/mg protein) at day 4 were 35.3 for 5'NT, 28.4 for ADA, 43.3 for PNP, and 5 X 10(3) for MK. At day 7, 5'NT, activities rose to 450%; PNP and ADA 150%; and MK 120%; of the day 4 level. The activities of the three catabolic enzymes were elevated for one or two weeks then declined rapidly. By day 34, they were slightly above the adult values. MK activity displayed a different time course. It continued to increase slowly with age after the initial surge. Compared to the adult heart, the total activities of these catabolic enzymes in the one- to three-week-old heart were 30% to 220% higher. This transient elevation in AN catabolic enzyme activities may be related to active DNA synthesis and cell proliferation occurred in the rat myocardium during the same period.     

The influence of diet on the growth of Stenonema vicarium (Walker) (Ephemeroptera: Heptageniidae)

Laboratory studies compared the growth rate of Stenonema vicarium (Walker) nymphs on diets of detritus and natural stream periphyton. In three consecutive runs of the experiment, growth rates were consistently higher on periphyton (mean growth rate = 2.1% wet wt. d⁻¹) than detritus (mean = 1.8% wet wt. d⁻¹). The starting date of each run also significantly influenced growth rates. In each treatment growth rates generally decreased over the course of the 3 runs, and ca. one-half of the nymphs in the last run did not molt or grow. It appeared that growth of S. vicarium may be partially controlled by seasonal factors.