Inhibition of (Na,K)-ATPase by tetravalent vanadium

Vanadyl, the tetravalent state of vanadium and a divalent cation, VO2+, was a relatively powerful inhibitor of highly purified membrane-bound sodium and potassium ion transport adenosine triphosphatase. The sensitivity of the ATPase activity to vanadyl characteristically correlated positively with the specific activity of the enzyme preparation. Inhibition ranged from nearly complete inhibition at less than 5 microM vanadyl for some of the purest fractions (specific activity approximately 45 mumol/min/mg of protein) to no observable inhibition at 300 microM vanadyl in one crude preparation of the enzyme with a specific activity of 10 mumol/min/mg of protein. The level of free vanadyl was reduced by incubation with these membranes, but this reduction was not sufficient to account for the low sensitivity to vanadyl observed in crude preparations. A reduction in specific activity by partial inactivation of a sensitive preparation by treatment with FeCl3 and ascorbate reduced its sensitivity to vanadyl. Anionic ligands of the enzyme, vanadate or ATP, increased the rate of recovery from inhibition after chelation of free vanadyl. At pH 6.1, the inhibition was characteristically fully reversible (t1/2 approximately 10 min), whereas at pH 8.1 it was stable for hours. The degree and stability of enzyme inhibition by vanadyl increased for several hours during incubation of the vanadyl-enzyme mixture, and at pH 6.1 the properties of the inhibitor itself also changed with time. Preincubation of the ion at that pH for 5 h before addition of the enzyme produced a more stable inhibition. The time- and pH-dependent changes in the degree and stability of enzyme inhibition probably relate to the complex chemistry of the vanadyl ion in solution.     

Campylobacter Enteritis on Hopi and Navajo Indian Reservations—Clinical and Epidemiologic Features

From June 22 through September 30, 1981, stool specimens from 522 Hopi and Navajo outpatients were cultured because of diarrheal illnesses at the Keams Canyon Indian Health Service Hospital, Arizona. Campylobacter jejuni was isolated from the specimens of 26 (5%) of the patients. This pathogen was found as frequently as Shigella in patients younger than 2 years or older than 20 years, but was significantly less common in the 2 to 20-year age group (P<.000001). Campylobacter enteritis was indistinguishable clinically from shigellosis in adult patients, but in children younger than 5 years, a rectal temperature higher than 38°C (100.5°F) was significantly more common with Shigella than with Campylobacter infection (P=.003). In a field study of 20 families, we found that households with a case of Campylobacter enteritis were more likely than age- and community-matched controls to own farm animals (P=.05), but were not more likely to own household pets. C jejuni is less common than Shigella as a cause of summer seasonal diarrhea and dysentery among the Hopi and Navajos; the striking differences in the age-specific rates of these two infections suggest different routes of transmission.     

尖柱线虫属一新种：圆线亚目：毛圆科

本文报道草兔胃内的四川尖柱线虫，新种Ｏｂｅｌｉｓｃｏｉｄｅｓ ｓｉｃｈｕａｎｅｎｓｉｓ ｓｐ．ｎｏｖ．本新种同已知种有明显不同。     

The evolution of skeletal muscle performance: gene duplication and divergence of human sarcomeric α‐actinins

In humans, there are two skeletal muscle α‐actinins, encoded by ACTN2 and ACTN3, and the ACTN3 genotype is associated with human athletic performance. Remarkably, approximately 1 billion people worldwide are deficient in α‐actinin‐3 due to the common ACTN3 R577X polymorphism. The α‐actinins are an ancient family of actin‐binding proteins with structural, signalling and metabolic functions. The skeletal muscle α‐actinins diverged ～250–300 million years ago, and ACTN3 has since developed restricted expression in fast muscle fibres. Despite ACTN2 and ACTN3 retaining considerable sequence similarity, it is likely that following duplication there was a divergence in function explaining why α‐actinin‐2 cannot completely compensate for the absence of α‐actinin‐3. This paper focuses on the role of skeletal muscle α‐actinins, and how possible changes in functions between these duplicates fit in the context of gene duplication paradigms.