Kinetics of Carboxylmethylation of the Charge Isoforms of Myelin Basic Protein by Protein Methyltransferase II

The charge isoforms (C1-C5) of bovine myelin basic protein (MBP) were used as substrates for the rat brain enzyme protein carboxylmethyltransferase (PM II). The objective of these experiments was to ascertain whether the kinetic behavior of the MBP isoforms reflected differences in the structures of this molecular family. Initial velocity plots as a function of the MBP-isoform concentration showed significnt differences ( p > 0.05) among the assayed isoforms except for isoforms C2 and C4. Under the conditions of our experiment all the curves exhibited a consistent sigmoidicity. The kinetic data were best fitted by a model, previously described for the enzyme D-Β-hydroxybutyrate dehydrogenase, in which two independent sites must be randomly occupied before any catalytic activity can occur. This mechanism is substantially different from that proposed by other investigators for similar PM II enzymes and other substrates. The differences in the rates of isoform carboxylmethylation are largely accounted for by the different apparent dissociation constants K s and is explained on the basis of inherent structural differences among the charge isoforms.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65821/1/j.1471-4159.1989.tb09257.x.pd

A Semi-Distributed Electric Demand-Side Management System with PV Generation for Self-Consumption Enhancement

This paper presents the operation of an Electrical Demand-Side Management (EDSM) system in a real solar house. The use of EDSM is one of the most important action lines to improve the grid electrical efficiency. The combination between the EDSM and the PV generation performs a new control level in the local electric behavior and allows new energy possibilities. The solar house used as test-bed for the EDSM system owns a PV generator, a lead-acid battery storage system and a grid connection. The electrical appliances are controllable from an embedded computer. The EDSM is implemented by a control system which schedules the tasks commanded by the user. By using the control system, we define the house energy policy and improve the energy behavior with regard to a selected energy criterion, self-consumption. The EDSM system favors self-consumption with regard to a standard user behavior and reduces the energy load from the grid

Cryopreservation of Brown Bear Skin Biopsies

Genetic resource banks and assisted reproductive technologies support the conservation of endangered or threatened species. In this study we assessed two procedures to cryopreserve skin biopsies from live brown bears. Skin biopsies were taken from six live, anesthetized brown bears. Single biopsies (n = 3) of each animal were cut into small pieces and assigned to one of the three experimental groups: freezing, vitrification, or untreated fresh. There were no differences on cell attachment. However, both freezing and fresh culture allowed for higher cell proliferation (p < 0.05) and less days to reach 70% to 80% confluence (p < 0.03) than vitrification. Skin biopsies from brown bears can be preserved long term, allowing fibroblasts to proliferate in culture. Slow freezing was effective to cryopreserve skin biopsies from brown bears

Flow cytometric cell cycle analysis of cultured brown bear fibroblast cells

The aim of this study was to assess by flow cytometry the cell cycle of brown bear fibroblast cells cultured under different growth conditions. Skin biopsies were taken in Cantabria (Spain) from a live, anaesthetized brown bear. DNA analysis was performed by flow cytometry following cell DNA staining with propidium iodide. Serum starvation increased (P < 0.01) the percentage of G0/G1 phase cells (92.7 0.86) as compared to cycling cells (39.7 0.86) or cells cultured to confluency (87.3 0.86). DMSO included for 48 h in the culture significantly increased (P < 0.01) the percentage of G0/G1 phase of the cell cycle at all concentrations used and decreased percentages of S phase in a dose-dependent fashion. Roscovitine increased the G0/G1 phase of the cell cycle (P < 0.01) at 15 mM concentration. Interestingly, the G2/M stage significantly increased at 30 and 50 mM compared to the control and 15 mM (P < 0.02). The cell cycle of brown bear adult fibroblast cells can be successfully synchronized under a variety of culture conditions