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Biomedical subjects

A Gow

Publications and source records attributed to A Gow.

31 records · Page 2Linked to original sources
PubMed1994

Effects of estradiol on lipoprotein lipase activity and lipid availability in exercised male rats.

The effects of 17 beta-estradiol 3-benzoate (10 micrograms.0.1 ml sunflower oil-1 x 100 g body wt-1) and exercise on tissue lipid content and lipoprotein lipase (LPL) activity were determined in male rats. Estradiol administration significantly (P < 0.05) increased fatty acid contents of resting adipose, plasma, and white and red vastus muscle tissues and red vastus muscle triacylglycerol. Adipose and plasma fatty acids and red and white vastus muscle triacylglycerol were significantly higher in exercised estradiol-administered animals than in exercised oil-administered animals. Estradiol administration significantly reduced resting adipocyte LPL activity by 71% and increased myocardial LPL activity by 96%. After exercise, red vastus LPL activity was significantly increased by 76% in estradiol-administered animals compared with oil-administered animals. Ratios of red vastus to adipose LPL activity and myocardial to adipose LPL activity at rest and after exercise were significantly greater in estradiol-administered than in oil-administered animals. Estradiol administration significantly increased the ratio of white vastus to adipose LPL activity of exercised animals. These data indicate that estradiol increases the availability of lipid substrate to exercising muscle from multiple sources, including adipose, plasma, and intracellular muscle triacylglycerol. The absolute increases in muscle LPL activity, combined with a greater ratio of muscle to adipose LPL activity, lead to increased distribution of plasma triacylglycerol-derived fatty acids toward muscle.

Adipose Tissue↗
PubMed1993

Intracellular distribution of transgenic bacterial beta-galactosidase in central nervous system neurons and neuroglia.

Bacterial beta-galactosidase is widely used as a marker for gene expression and in cell tracing experiments. In a survey of three transgenic mouse lines expressing beta-galactosidase in the central nervous system (CNS) under the control of different promoters, we find substantial variation in the intracellular distribution of the lacZ protein. In line M beta P5, transgene beta-galactosidase expression is driven by a promoter/enhancer fragment from the oligodendrocyte-specific myelin basic protein gene; however, electron microscopy of histochemically stained preparations reveals transgene expression not only in oligodendrocytes but also in some neurons. Immunofluorescence and immunoperoxidase staining show the beta-galactosidase protein distributed throughout the perikaryal cytoplasm of oligodendrocytes and in processes reaching to myelin sheaths. By contrast, immunoreactive protein appears restricted in neurons to one or a few small perikaryal immunoreactive granules. The granules are visible in the electron microscope as amorphous inclusion bodies of moderate electron density and lack a limiting membrane. Histochemical staining patterns with X-gal and Bluo-gal echoed the protein distribution: diffuse distribution of enzyme protein yielded cells filled with substrate, while punctate enzyme distribution yielded restricted or punctate histochemical staining. Examination of two other lines using different promoter/enhancers to drive expression in the CNS showed both diffuse and punctate beta-galactosidase immunolocalization and histochemical staining. The amount of protein synthesized or other properties, yet unidentified, intrinsic to the target cells may determine the intracellular distribution of beta-galactosidase. In retroviral marking studies, clone members have been identified as those cells filled with X-gal reaction product. This approach may underestimate both clone size and the minimum number of divisions separating the members of each clone.

Animals↗
PubMed1992

Myelin basic protein gene contains separate enhancers for oligodendrocyte and Schwann cell expression.

The DNA sequence between position +36 and -1907 of the murine myelin basic protein gene contains the enhancer and promoter elements necessary for abundant and cell specific expression in transgenic mice. Surprisingly, the pattern of expression promoted by this DNA fragment is a subset of that exhibited by the endogenous myelin basic protein (MBP) gene. Fusion genes prepared with this promoter/enhancer and a Lac Z reporter gene are expressed only in oligodendrocytes and not in Schwann cells, whereas the endogenous MBP gene is expressed in both cell types. The level of transgene expression measured by nuclear run-on experiments is very substantial and rivals that of the endogenous MBP gene. Furthermore, this 1.9-kb DNA fragment directs transcription on the same (or very similar) developmental schedule as the endogenous gene. These results indicate that the MBP promoter/enhancer sequences are at least tripartite: a core promoter, the oligodendrocyte enhancer elements, and a third component that either expands the specificity of the oligodendrocyte enhancer to include Schwann cells or acts independently to specifically stimulate transcription in Schwann cells.

Animals↗
PubMed1990

Preferential ligand binding to multi-state acceptor systems: the unexplored paradox of acceptor self-association that is ligand-mediated but detrimental to ligand binding.

Consideration is given to the interactions of ligand with self-associating acceptor systems for which preferential ligand binding is an ambiguous term, in that the acceptor species with greater affinity for ligand possesses relatively fewer binding sites. A paradoxical situation wherein ligand-mediated self-association is seemingly detrimental to ligand binding is shown to be the predicted outcome for a transient range of ligand concentrations. This outcome reflects the existence of a critical point in the dependence of the extent of acceptor self-association upon ligand concentration that coincides with a cross-over point of ligand-binding curves for different, fixed total concentrations of acceptor. By classical differentiation methods the conditions for the existence of these critical points are established not only for two-state acceptor systems but also for three-state acceptor systems in which the ligand-binding form of monomer also undergoes reversible isomerization to an inactive state. Similar procedures are used to comment upon the forms of binding curves for the three-state acceptor systems, the Scatchard representations of which may exhibit as many as three critical points (two maxima and a minimum). This delineation of quantitative expressions for critical points and other distinctive features associated with the conflicting interplay of ligand-binding and self-association behaviour should provide a more definitive means of characterizing systems with one acceptor state the preferred binding form on affinity grounds but with the other the preferred state from the viewpoint of binding-site numbers.

Animals↗
PubMed1990

Interactions between bovine myelin basic protein and zwitterionic lysophospholipids.

The binding of myelin basic protein to lysolauroylphosphatidylcholine (lysoLPC) and lysolauroylphosphatidylethanolamine was investigated at neutral pH using gel partition chromatography and equilibrium dialysis at 20 and 37 degrees C. The results show that the protein-lysolipid interactions are highly cooperative and that the free lysolipid concentration at which the binding commences is markedly influenced by both the chemical structure of the lysolipids and the temperature. The binding begins just below the critical micelle concentration for both lysolipids, which suggests that the forces governing micellization and the binding are similar. Circular dichroism (CD) spectroscopy was used to follow changes in the conformation of the protein caused by lysomyristoylphosphatidylcholine and lysoLPC. The CD results indicate that lysolipid association with the protein commences below the critical micelle concentration and continues above this concentration. Mechanisms for the lysolipid-protein interaction, which are consistent with the binding and CD data, are discussed.

Animals↗
PubMed1989

The thermodynamically stable state of myelin basic protein in aqueous solution is a flexible coil.

Conformational studies of myelin basic protein (MBP) in solution generally have used protein purified in organic solvents and acid. The use of such conditions raises the possibility that the secondary structure reported for the basic protein represents a denatured state. Therefore we have purified this protein by using a procedure that avoids denaturants. Bovine myelin was extracted with 0.2 M-CaCl2 and the protein was purified from the supernatant by chromatography on Sephadex G-75. The conformation of the basic protein was characterized by using c.d. and 1H-n.m.r. spectroscopy. In solution, it appeared to be predominantly randomly coiled, with only small segments of persistent structure. However, in the presence of myristoyl lysophosphatidylcholine the secondary structure of MBP became more ordered, and sedimentation-velocity experiments showed that MBP aggregated. Comparison of our results with published data indicates that Ca2+-extracted basic protein behaves similarly to the protein purified by traditional methods with respect to its ordered conformation in solution in the absence and in the presence of lipid and with respect to its self-association. Thus its thermodynamically stable structure in aqueous solution appears to be a highly flexible coil.

Animals↗
PubMed1987

Equilibrium binding of myristoyllysophosphatidylcholine to bovine myelin basic protein: an example of ligand-mediated acceptor association.

The interaction of myristoyllysophosphatidylcholine with bovine myelin basic protein at pH 7.4 and 4.5, I = 0.48, has been investigated by a recycling partition equilibrium technique with Bio-Gel P-2 as the gel phase. Important points to emerge from this direct binding study are that it is a monomeric (not micellar) amphiphile that binds to myelin basic protein, that the amphiphile binds preferentially to the monomeric form of myelin basic protein, that this binding to monomer is highly cooperative, that the similarity of binding behavior in the two environments tested is consistent with the dominance of a hydrophobic contribution to the protein-amphiphile interaction, and that the self-association of myelin basic protein in the presence of phospholipid [Smith, R. (1982) Biochemistry 21, 2697-2701] must reflect the aggregation of a protein-amphiphile complex(es) coupled with concomitant release of some lipid. These findings are then related to earlier nuclear magnetic resonance and circular dichroism studies in which the results were interpreted on the basis that myelin basic protein bound preferentially to micellar phospholipid.

Animals↗
PubMed1985

Pressure-induced dissociation of aggregates of myelin proteolipid protein.

Sedimentation velocity and equilibrium experiments have revealed an extremely pressure-sensitive aggregation of myelin proteolipid protein in the presence of Triton X-100, dissociation of the protein aggregate being observed at pressures that are several orders of magnitude lower than those effecting disaggregation of many other proteins. These results highlight the need to employ a range of angular velocities in sedimentation studies of intrinsic membrane protein.

Animals↗
PubMed1980

Survival of Aujeszky's disease virus in frozen pig meat.

The survival of Aujeszky's disease virus was studied in muscle, lymph node and bone marrow frozen at -18 degrees C, following infusion of a large dose of the virus into the hindquarter of a freshly killed pig. Previous attempts to induce an adequate viraemia for such studies, using intranasal and intravenous routes of inoculation of large doses of virus in live pigs, were unsuccessful. In frozen meat and marrow, the virus showed a biphasic inactivation curve with time, similar to that seen with cell-cultured virus. Most virus was rapidly inactivated initially but a small population of more stable virus persisted for a considerable period of time. In contrast, virus in lymph node showed a uniform inactivaton rate, like that of the more stable componet only. Virus was not detectable in any of the tissues after 35 days of storage at -18 degrees C.

Animals↗