Studies on vitamin D metabolism: Catabolism of 1α, 25-dihydroxyvitamin D3 and 1α-hydroxyvitamin D3 to a metabolite inactive on bone mineral mobilization

A heretofore unknown metabolite of vitamin D₃ was isolated from the 1α,24,25-trihydroxyvitamln D₃ fraction of lipid extracts obtained from plasma of rats which were given intravenous or oral doses of 100 pmol/100 g of either 1α-hydroxyvitamin D₃ or 1α, 25-dihydroxy-vitamin D₃. Doses of 25–250 pmoles of the new metabolite when given to a vitamin D deficient rat were completely inactive in terms of stimulating the classic vitamin D response of bone calcium mobilization. The nature of the metabolism of 1α-hydroxyvitamin D₃ or 1α, 25-dihydroxy-vitamin D₃ to the metabolite is not clear at the present time, but it is probable that neither of these steroids undergo side-chain cleavage to yield the new metabolite.     

Late ventricular fibrillation following successful resuscitation from postinfarction cardiogenic shock with intraaortic balloon pumping

Early ventricular fibrillation occurs in approximately 5% of patients admitted for acute myocardial infarction. Although late ventricular fibrillation (> 48 hours postinfarction) may occur in stable patients, it occurs more commonly when severe left ventricular power failure is present. We have encountered late ventricular fibrillation in three of 42 (7%) patients treated with intraaortic balloon pumping (IABP) for profound cardiogenic shock secondary to myocardial infarction. These patients progressed to our hemodynamic Class A prior to weaning, and were thought to be stable prior to IABP removal. They were the only ones who expired after achieving Class A status. The episodes of late ventricular fibrillation occurred after the patients had been successfully weaned from IABP and were free of arrhythmias. This experience suggests that prolonged antiarrhythmic therapy may be indicated for postinfarction patients who have had ventricular dysrhythmias during IABP support.     

Persistent atrial paralysis: Case report with light microscopy and ultrastructural analyses

Persistent atrial paralysis in a patient with complete heart block and mild mitral insufficiency is presented. Left atrial specimens obtained during implantation of a permanent cardiac pulse generator showed evidence of hypertrophy and fibrosis; subcellular degenerative changes ranged from near normal to irreversible, thus suggesting that atrial paralysis may be due to the replacement of normal atrial muscle with nonfunctional fibrous tissue.     

Biology of Azospirillum-Sugarcane Association: Enhancement of Nitrogenase Activity

Azospirillum brasilense was reisolated from associations with callus tissue cultures of sugarcane and compared with stock cultures of the inoculated bacterium and related strains. Although the reisolate had a growth rate similar to stock cultures, it exhibited a severalfold increase in maximum specific activity of nitrogenase. The reisolate and the parent culture had similar ultrastructure. The general ultrastructure of Azospirillum is described. The bacterium was capsulated when grown on nitrogen-free nutrient agar plates and on callus, but was not capsulated when growing in a subsurface zone in N-free semisolid nutrient agar, except rarely in aging cultures. Capsulation may be a protective mechanism against unfavorable pO₂ under dinitrogen-fixing conditions. Pleomorphism occurred in capsulated forms, and the ultrastructure of these forms is described.     

Comparison of renografin density gradient centrifugation and ion-exchange chromatography for purification of phony peach bacterium from plant extracts

Renografin density gradient centrifugation and carboxymethyl (CM)-and diethylaminoethyl (DEAE)-cellulose ion-exchange chromatography were compared for purification of cells of phony peach, rickettsia-like bacterium (RLB) from plant extracts. Centrifugation on 30–40% linear gradients resulted in four bands. Cells of RLB sedimented into the third band located 4.9–5.4 cm below the meniscus. Phase-contrast microscopy, plant peroxidase activity, and viable bacterial assays showed the resulting cells ofRLB to be relatively free of host contaminants. A typical purification from 120 ml of extract containing 7.2×10⁹ RLB cells resulted in the recovery of 7.0×10⁷ RLB cells. Cells ofRLB were not successfully purified byCM andDEAE chromatography. Unitil a medium is available for cultivation of plantRLB, Renografin density gradient centrifugation should be a useful tool for obtaining cells ofRLB for biochemical and serological investigations.     

A putative pathway of glyconeogenesis in skeletal muscle

Evidence is presented in support of a pathway in skeletal muscle of glyconeogenesis (glycogen biosynthesis de novo) from L-glutamate and related amino acids involving the enzyme phosphoenolpyruvate carboxykinase (PEP CK). In the rat hemidiaphragm in vitro, not only did L-[U-¹⁴C]glutamate exert a glycogen-sparing action, but¹⁴C-label was incorporated into glycogen. The incorporation is thought not to be simply via label randomization and was decreased by factors that increased glycolysis or pyruvate oxidation. 3-Mercaptopicolinate and amino-oxyacetate, specific inhibitors of PEP CK and aminotransferase-type enzymes, respectively, decreased¹⁴C-incorporation from L-[U-¹⁴C]glutamate into glycogen. No quantitative determination of apparent glyconeogenic flux was made, and it remains to be established whether glyconeogenesis via PEP CK and/or via PEP CK coupled with 'malic' enzyme (or pyruvate carboxylase) is functionally important in skeletal muscle.     

THE HEXOSE MONOPHOSPHATE PATHWAY IN ETHYLNITROSOUREA INDUCED TUMORS OF THE NERVOUS SYSTEM

Respiration studies in vitro, in which tissue slices were incubated with [1-¹⁴C]glucose or [6-¹⁴C]glucose and ¹⁴CO₂ collected, resulted in C-1/C-6 ¹⁴CO₂ ratios that were higher in slices of tumor and newborn brain than in slices of adult brain. In adult brain, the C-1/C-6 ¹⁴CO₂ ratio averaged close to unity. In slices of tumor and newborn brain however, the mean C-1/C-6 ratio was greater than three. Addition of phenazine methosulfate (PMS) increased conversion of [1-¹⁴C]glucose to ¹⁴CO₂ in slices of normal adult brain 5-fold, and in slices of newborn brain and tumor, approx 12-fold. Injection of animals with 6-aminonicotinamide (6-AN) decreased conversion of [1-¹⁴C]glucose in slices of normal brain 30% but decreased conversion in tumor slices by 80%. Evidence supports the presence of an active hexose monophosphate pathway (HMP) in tumors of the nervous system regulated in part by available NADP⁺ levels. Inhibition by 6-AN was more effective in tumors than in normal adult brain.     

SUCCESSFUL AORTOCORONARY BYPASS SURGERY IN A PATIENT WITH CLASSICAL HEMOPHILIA A

A patient with documented Factor VIII deficiency (classical Hemophilia A) and a history of previous severe intra- and postoperative hemorrhage and transfusion reaction underwent myocardial revascularization for advanced triple vessel coronary artery occlusive disease. The coagulation status was investigated, and a replacement regimen was instituted. The surgical procedure and postoperative course were uneventful.