R-factor from the natural strain of Salmonella derby carrying a DNA-polymerase gene

A R-factor which determines multiple stability to antibiotics (Cm, Pn, Sm) was found in a Salmonella derby strain isolated from the clinical material. The plasmid was eliminated by treatment with ethidium bromide; the DNA-polymerase activity in the antibiotic-sensitive derivatives measured under conditions optimal for DNA-polymerase I from E. coli was found to be decreased 10-50-fold. Plasmid DNA of S. derby K89 was fractionated by electrophoresis in agarose gel; individual zones I-IV were obtained, using a preparative technique. Upon transformation of S. derby K82 pol- cells, only plasmid DNA in zone II (designed as pSD Cm pol) gave Cm-resistant transformants, in which the DNA-polymerase activity decreased to the normal level. The experimental results pont to the binding of the DNA-polymerase gene to the S. derby plasmid.     

Role of lipid peroxidation in changes in the structure of Ca-ATPase in skeletal muscle sarcoplasmic reticulum during hypercholesterolemia

Using the method of spin labels it was shown that in hypercholesterolemia (HCh), the following parameters decreased: the velocity of maleimide spin label binding to sarcoplasmic reticulum (SR) Ca-ATPase of rabbit skeletal muscles, the accessibility of spin-labeled thiol groups of the enzyme to potassium ferricyanide and sodium ascorbate, and the mobility of the Ca-ATPase molecule fragment to which the spin label was attached. In addition, intensification of lipid peroxidation was demonstrated in SR membranes. Supplementation of the high-cholesterol diet with alpha-tocopherol resulted in the decreased rates of lipid peroxidation in SR membranes and increased values of the above parameters relative to the values found under HCh. It is concluded that the effect of alpha-tocopherol in vivo on the structure of the Ca-ATPase proteolipid complex in HCh is due mainly to antioxidant properties of the diet-supplementing substance.     

Effects of fat content in the diet on hepatic peroxisomes of the rat

Effects of fat content in the diet on rat liver peroxisomes was examined. In the livers of rats fed for one week on the high-fat diet containing 30% fat, the cyanide-insensitive palmitoyl-CoA oxidation was accelerated to eight times that of control and the enzymic activities of catalase, carnitine acetyltransferase and carnitine palmitoyltransferase were elevated by the factors of 1.3, 5 and 2, respectively. In contrast, the activities of D-amino acid oxidase in addition to the three enzymes mentioned above were all lowered by 20% when the animals were maintained on a fat-free diet for the same period of time. It appears that the high-fat diet-induced increase in the activity of carnitine palmitoyltransferase is a result of the raised activity of this enzyme in mitochondria only while the apparent high activity reflects stimulation of carnitine acetyltransferase in all the subcellular fractions. Another notable effect of the high-fat diet was a remarkable increase in the quantity of a peroxisome-associated polypeptide which was separable by sodium dodecyl sulfate polyacrylamide gel electrophoresis. It is noteworthy that this effect of the high-fat diet resemble that of clofibrate. If the diet was deprived of fat, however, this polypeptide species, with an estimated molecular weight of 80 000, decreased to a level slightly lower than normal. On the basis of the electron micrographic criteria, the high-fat diet provoked a marked proliferation of hepatic peroxisomes.     

Intraneuronal amyloid precursor protein (APP) and appearance of extracellular β‐amyloid peptide (aβ) in the brain of aging kokanee salmon

Antibodies to human amyloid precursor protein (APP₆₉₅) and beta‐amyloid peptide (Aβ_1‐42) were used to determine timing of amyloidosis in the brain of kokanee salmon (Oncorhynchus nerka kennerlyi) in one of four reproductive stages: immature (IM), maturing (MA), sexually mature (SM), and spawning (SP), representing a range of aging from somatically mature but sexually immature to spawning and somatic senescence. In IM fish, immunoreactive (ir) intracellular APP occurred in 18 of 23 brain regions. During sexual maturation and aging, the number of neurons expressing APP increased in 11 of these APP‐ir regions. Aβ‐ir was absent in IM fish, present in seven regions in MA fish, moderately abundant in 15 regions in SM fish, and was most abundant in all brain regions of SP fish exhibiting Aβ‐ir. Intracellular APP‐ir was observed in brain regions involved in sensory integration, olfaction, vision, stress responses, reproduction, and coordination. Intra‐ and extracellular Aβ_1‐42 immunoreactivity (Aβ‐ir) was present in all APP‐ir regions except the nucleus lateralis tuberis (hypothalamus) and Purkinje cells (cerebellum). APP‐ir and Aβ deposition increase during aging. APP‐ir is present in IM fish; Aβ‐ir usually appears first in MA or SM fish and increases in SM fish as does APP‐ir. Extracellular Aβ deposition dramatically increases between SM and SP stages (1–2 weeks) in all fish, indicating an extremely rapid and synchronized process. Rapid senescence observed in pacific salmon could make them a useful model to investigate timing of amyloidosis and neurodegeneration during brain aging. © 2002 Wiley Periodicals, Inc. J Neurobiol 53: 11–20, 2002