Hemocyanin from E. californicum encapsulated in silica gels: Oxygen binding and conformational states

Cooperativity depends on the existence of equilibria among functionally distinct conformational states that are affected by homo and heterotropic effectors. In order to isolate the quaternary conformations of hemocyanin from E. californicum, the 24-meric giant protein was encapsulated in wet, nanoporous silica gels, either in the absence or presence of oxygen. The deoxy- and oxy-hemocyanin gels exhibit a p50 for oxygen of 11 and 2.5 torr, respectively, values in close agreement with those for hemocyanin in solution. The observed Hill coefficients are lower than unity, indicating a conformational heterogeneity within each locked conformational state, a finding in agreement with the assumption that at least four conformational states are required to explain the oxygen binding properties of E. californicum hemocyanin in solution.

Pharmacokinetics of intravenous trovafloxacin in critically ill adults

The pharmacokinetic disposition of numerous antimicrobial agents is altered in critically ill patients. Pharmacokinetics of trovafloxacin, a fluoroquinolone indicated specifically for severe, life-threatening infections in the intensive care unit, have not been well studied in this population. We characterized the pharmacokinetic disposition of trovafloxacin after administration of alatrofloxacin, the intravenous prodrug, in critically ill adults. Seven patients (3 men, 4 women; mean +/- SD age 59.4 +/- 20.6 yrs; baseline aspartate aminotransferase [AST]/alanine aminotransferase [ALT] 66.0 +/- 40.6/51.5 +/-37.5 IU/L; median Acute Physiology and Chronic Health Evaluation [APACHE II] score 27, range 15-32) were studied at estimated steady state. Calculated (mean +/- SD) half-life, clearance at steady state, and volume of distribution in all patients were 10.9 +/- 1.8 hours, 161.3 +/- 41.1 ml/minute, and 1.4 +/- 0.4 L/kg. In patients receiving 300 mg, maximum concentration, minimum concentration, and area under the curve from 0-24 hours were 3.6 +/- 0.5 mg/L, 0.6 +/- 0.3 mg/L, and 34.2 +/- 10.6 mg x hr/L, respectively. These results are consistent with published values in other patient populations, indicating that trovafloxacin pharmacokinetics are not substantially altered in critically ill patients with normal or mildly impaired hepatic function.

Idiopathic hemochromatosis in a 45-year-old infertile man

The clinical manifestations of primary or idiopathic hemochromatosis include mainly hepatomegaly, diabetes mellitus, and hypogonadism. Most investigators postulated that the hypogonadism is caused by pituitary dysfunction and that the deposition of iron in the testes is of little importance. We found not only pituitary failure in a 45-year-old man with idiopathic hemochromatosis (low LH and FSH levels, no response to GnRH) but could also detect by light microscopy deposition of iron in capillary endothelial cells and in the perivascular space of the testicular tissue. Electron microscopic study of tissue from the testes showed intracytoplasmic hemosiderin deposits in capillary endothelial cells. Abundant lipofuscin granules were present in Sertoli cells and Leydig cells. The serum testosterone levels were also lowered. In our opinion, the androgenic deficiency in idiopathic hemochromatosis is not only caused by pituitary failure but also by testicular dysfunction due to deposits of hemosiderin and lipofuscin in the testes.