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111.
The forms, disposition, and cytoskeletal contents of astroglia in immature mouse cerebellum were studied by immunocytochemical staining with antisera against two intermediate filament proteins, vimentin (Vim) (58,000 daltons) and glial filament protein (GF) (51,000 daltons). From embryonic (E) Day 15 to postnatal (P) Day 2, Vim is expressed in cells throughout the cerebellar anlage, including radial glia and Bergmann fibers, cells with amorphous shapes and 2–3 processes, and thick longitudinal elements oriented parallel to axons within axon tracts. GF is not expressed during the first few postnatal days, but by P7, there is a dramatic increase in GF-positive astrocyte-like cells in the putative white matter that are more densely stained and more crowded than at any other age. Between P7 and P14 all astrocytes throughout the cerebellum express both Vim and GF. From P21 on, Vim expression is progressively rarer in all astrocytes except for Bergmann fibers, and GF-positive astrocytes become less numerous. These findings raise two issues: (a) the lineage and relationships of cells expressing Vim and GF; (b) Since GF-positive cells appear as axon ingrowth ceases, axons must grow in a terrain comprised of glial cells that have a different cytoskeletal composition (vimentin), reflecting a less differentiated state, than mature astrocytes or than the GF-rich astrocytes that proliferate after injury in adult CNS. 相似文献
112.
Cathepsin L was purified from rabbit liver by a method involving whole-tissue homogenization, pH precipitation, ammonium sulphate fractionation and chromatography on CM-Sephadex C-50, phenyl-Sepharose and Sephadex G-75. Pure enzyme was obtained without the necessity of laborious subcellular fractionation techniques. The Mr of the enzyme was determined to be 29 000 by gel filtration, and affinity for concanavalin A-Sepharose indicated that it was a glycoprotein. A novel technique for detection of enzyme activity in agarose isoelectrofocusing gels showed that the enzyme existed in multiple isoenzymic forms with pI values ranging from 5.0 to 5.9. The enzyme catalysed the hydrolysis of azocasein, collagen and Z-Phe-Arg-NMec (where Z and NMec indicate benzyloxycarbonyl and N-methylcoumarin derivative respectively) optimally at pH 5.2, 3.3 and 6.0 respectively. In addition, cathepsin L was found to degrade benzoyl-Phe-Val-Arg-NMec and 3-carboxypropionyl-Ala-Phe-Lys-NMec. However, cathepsin B also cleaved all of these substrates. One major difference between these two enzymes was in their Michaelis constants for Z-Phe-Arg-NMec; cathepsin B had Km 75 microM whereas that of cathepsin L was 0.7 microM. Cathepsin L was inhibited by all of the usual chemical inhibitors of thiol proteinases as well as the more specific inhibitors Z-Phe-Phe-CHN2, Z-Phe-Ala-CHN2, compound E-64 and compound Ep-475. Active-site titration with compound E-64 showed that the purified sample contained 80% active protein, which had kcat. 20s-1 for the substrate Z-Phe-Arg-NMec. Antibodies were raised to active cathepsin L, and these did not cross-react with cathepsin B, thus demonstrating that these two enzymes are immunologically distinct. 相似文献
113.
P Mason J Adams D V Morris M Tucker J Price Z Voulgaris Z M Van der Spuy I Sutherland G R Chambers S White et al. 《BMJ (Clinical research ed.)》1984,288(6412):181-185
Ovulation was successfully induced with luteinising hormone releasing hormone in 28 women with hypothalamic amenorrhoea who had failed to respond to treatment with clomiphene. Luteinising hormone releasing hormone was administered in a pulsatile manner with miniaturised automatic infusion systems. The rate of ovarian follicular maturation, as monitored by serial pelvic ultrasonography, was similar to that observed in spontaneous cycles. Endocrine assessment by serial measurement of gonadotrophin, oestradiol, and progesterone concentrations showed hormone concentrations to be within the normal range. Intravenous treatment was required in only two patients, the remainder responding satisfactorily to subcutaneous infusion. All patients conceived within six cycles of treatment, and only one multiple pregnancy occurred. 相似文献
114.
C. F. Mason 《Hydrobiologia》1977,56(1):17-20
The troglobitic amphipod crustacean Crangonyx antennatus populates two distinct habitats in southern Appalachian caves, mud-bottom pools and gravel-bottom streams. An investigation was conducted to determine if stream populations possess behavioral adaptations to lotic conditions. Observations on the thigmotactic behavior of C. antennatus were made seasonally in six Lee Co., Virginia caves, three containing pool habitats and three with stream habitats. Stream-dwelling amphipods were found to exhibit more cryptic behavior than those inhabiting pools under natural conditions and when disturbed. Artificial stream experiments indicate that stream-dwelling C. antennatus are better adapted behaviorally to lotic conditions than pool-dwelling amphipods. 相似文献
115.
116.
S Gutteridge D B Winter W J Bruyninckx H S Mason 《Biochemical and biophysical research communications》1977,78(3):945-951
After mild dissociation of cytochrome oxidase protomers, and polyacrylamide gel electrophoresis, copper was found predominantly in polypeptides of Bands V (m.w. 12,100) and VII (m.w. 3,400), and heme a predominantly in polypeptides of Bands I (m.w. 35,300) and II (m.w. 21,000). Some copper was found in Band II – III, and heme a in Band V. 相似文献
117.
R P Mason F J Peterson J L Holtzman 《Biochemical and biophysical research communications》1977,75(3):532-540
An ESR spectrum is observed during the anaerobic incubation of the diazonaphthol dye sulfonazo III, with rat hepatic microsomes and NADPH. This spectrum is characterized by a partially resolved 17-line hyperfine pattern and g = 2.0043, as is consistent with the spectrum of an azo anion free radical, [R-N-N-R′]. Oxygen, which strongly inhibits microsomal azoreductase, destroys the ESR signal. The oxidation of the azo anion radical metabolite by oxygen to the parent azo dye may account for the oxygen inhibition of microsomal azoreductase. 相似文献
118.
A coupled assay was devised for the assay of liver microsomal epoxide hydratase using the ability of alcohol dehydrogenase to transfer electrons from diols to NAD+: epoxide hydratase activity was continuously monitored at 340 nm. Rates of hydrolysis of octene-1,2-oxide and styrene-7,8-oxide measured utilizing this assay were similar to those determined using gas-liquid chromatography and radiometric thin-layer chromatography, respectively. The assay was used to examine the ability of rat liver microsomes and highly purified rat liver microsomal epoxide hydratase fractions to hydrolyze 15 other epoxides. 相似文献
119.
The basic equations for multicomponent transport through partially sieving or leaky membranes are discussed from a statistical-mechanical viewpoint. They have the same mathematical form as the corresponding equations for open membranes, but differ in a discontinuous way from the equations for semipermeable membranes (since a "leak" in a semipermeable membrane constitutes a discontinuous or singular perturbation). Partially sieving membranes can be made to mimic semipermeable behavior through the introduction of characteristic time scales. They may approximate semipermeable behavior at short times, but always deviate at longer times. 相似文献
120.
Peter Mason 《European biophysics journal : EBJ》1978,4(1):15-25
Small sinusoidal vibrations at 300 Hz were applied to frog sartorius muscle to measure the dynamic stiffness (Young's modulus) throughout the course of tetanus. For a peak-to-peak amplitude of 0.4% the dynamic Young's modulus increased from 1.5×105 Nm–2 in the resting state to 2×107 Nm–2 in tetanus. After correction for the external connective tissue, the dynamic Young's modulus of the muscle was almost directly proportional to the tension throughout the development of tetanus. The ratio of dynamic Young's modulus to tensile stress thus remained constant (with a value at 300 Hz of approximately 100), consistently with Huxley and Simmons' identification of the crossbridges as the source of both tension and stiffness.For a single crossbridge the ratio of stiffness to tension was 8.2×107 m–1 at 300 Hz; it is deduced from literature data that the limiting value at high frequencies is about 1.6×108 m–1. This ratio is interpreted on Harrington's (1971) model to show that crossbridge action can be explained by a helix-coil transition of about 80 out of the 260 residues in each S-2 myosin strand. It is also shown that a helix-coil model can account for the observed rapid relaxation of muscle without invoking any complex behaviour of the crossbridge head. 相似文献