Chicken oocyte growth: receptor-mediated yolk deposition

During the rapid final stage of growth, chicken oocytes take up massive amounts of plasma components and convert them to yolk. The oocyte expresses a receptor that binds both major yolk lipoprotein precursors, vitellogenin (VTG) and very low density lipoprotein (VLDL). In the present study, in vivo transport tracing methodology, isolation of coated vesicles, ligand- and immuno-blotting, and ultrastructural immunocytochemistry were used for the analysis of receptor-mediated yolk formation. The VTG/VLDL receptor was identified in coated profiles in the oocyte periphery, in isolated coated vesicles, and within vesicular compartments both outside and inside membrane-bounded yolk storage organelles (yolk spheres). VLDL particles colocalized with the receptor, as demonstrated by ultrastructural visualization of VLDL-gold following intravenous administration, as well as by immunocytochemical analysis with antibodies to VLDL. Lipoprotein particles were shown to reach the oocyte surface by passage across the basement membrane, which possibly plays an active and selective role in yolk precursor accessibility to the oocyte surface, and through gaps between the follicular granulosa cells. Following delivery of ligands from the plasma membrane into yolk spheres, proteolytic processing of VTG and VLDL by cathepsin D appears to correlate with segregation of receptors and ligands which enter disparate sub-compartments within the yolk spheres. In small, quiescent oocytes, the VTG/VLDL receptor was localized to the central portion of the cell. At onset of the rapid growth phase, it appears that this pre-existing pool of receptors redistributes to the peripheral region, thereby initiating yolk formation. Such a redistribution mechanism would obliterate the need for de novo synthesis of receptors when the oocyte's energy expenditure is to be utilized for plasma membrane synthesis, establishment and maintenance of intracellular topography and yolk formation, and preparation for ovulation.

Reversal of cytochrome P-4501A1 and P-450-EF expression in MCA-C3H/10T1/2 cell-derived tumors as compared to cultured cells

The 3-methylcholanthrene-transformed tumorigenic cell line, MCA-C3H/10T1/2 CL15 (MCA), expresses the novel benz(a)anthracene (BA)-inducible polycyclic aromatic hydrocarbon-metabolizing cytochrome P-450 (P-450-EF). The level of expression is comparable to that reported for the nontumorigenic C3H/10T1/2 CL8 (10T1/2) cells (Pottenger, L. H., Christou, M., and Jefcoate, C. R. Arch. Biochem. Biophys., 286: 488-497, 1991). Sarcomas (3-12 mm in diameter) generated in athymic "nude" mice by s.c. injection of MCA cells exhibited much lower 7,12-dimethylbenz(a)anthracene-metabolizing activities (5-15% of the levels in cultured cells), both constitutively and after in vivo treatment with BA. A sharp decrease in P-450-EF expression was observed both at the functional level (10- to 30-fold) (as determined by antibody inhibition studies) and at the apoprotein level (50- to > 100-fold) (as determined by Western immunoblots). However, in contrast to the BA-treated MCA cells in which P-450-EF comprises essentially the total spectrally detectable P-450 content (approximately 30 pmol/mg) with virtually undetectable cytochrome P-4501A1, tumors from these cells expressed substantial levels of P-4501A1 immunodetectable protein in response to BA treatment (approximately 0.5-3 pmol/mg). In these tumors, P-450-EF expression decreased to undetectable or barely detectable levels (< 0.2-0.5 pmol/mg). P-4501A1-expressing cells were localized in tumor sections immunocytochemically and were morphologically identical to other MCA cells, which formed the majority of the sarcoma. At the functional level, antibody inhibition studies and product ratios demonstrated that P-4501A1 accounted for only 40% of the total dimethylbenz(a)anthracene-metabolizing activity of BA-induced tumor microsomes, whereas the remaining activity was due to P-450-EF. This low catalytic activity for P-4501A1 (35-95 pmol/mg/h) indicated that the majority of BA-inducible P-4501A1 in the tumors (> 95%) was expressed as apoprotein. The contribution from P-450-EF was consistent with full expression of hemoprotein. Tumor size affected the total dimethylbenz(a)anthracene-metabolizing activities/mg microsomal protein (small tumors were 2- to 3-fold more active than large tumors) but had no effect on the ratio of activities dependent on, respectively, P-450-EF and P-4501A1 holoenzymes (1.5:1), thus suggesting controlled coexpression of these proteins. Reculturing of tumor-derived cells effected partial restoration of P-450-EF expression and eliminated the expression of P-4501A1, confirming a unique contribution from tumor environment to the regulation of these genes. Possible mechanisms for an environment-dependent concerted regulation of the P-4501A1 and P-450-EF genes are discussed.

An observation on flash evoked cortical potentials and Qigong meditation

The purpose of this study was to investigate the functional state of the cerebral cortex during Qigong meditation with flash visual evoked potentials (F-VEPs) recorded from the occipital scalp in four groups of adults. The first group included 14 subjects who had exercised in Neiyang Gong for 0.5-5.5 years. The second group was composed of 12 subjects who had practiced Neiyang Gong for only 0.5-3 months. Eleven subjects who had never practiced Qigong before made up the third group and served as control. Eleven Qigong practitioners constituted the fourth group. It was found that F-VEP amplitudes were increased in the first group and decreased in the fourth group with the exception of one subject during Qigong meditation. No significant changes were found in the second group and controls. The results were discussed and it is shown that Qigong mediation may have either facilitative or inhibitory effects on the visual cortex depending on the Qigong methods practiced by different individuals.

Formation of the excited ferryl species following Fenton reaction

A concomitant chemiluminescence burst can be detected when hydrogen peroxide is injected into the solution containing either free or chelated ferrous iron. The duration of the burst is slightly longer than the time for the oxidation of Fe2+. The luminescence intensity is a quadratic function of the initial concentration of H2O2 and is dependent on Fe2+ concentration. The scavengers of hydroxyl radical effectively inhibit, while the previously added ferric ions enhance, the luminescence. It is proposed that the excited species responsible for the luminescence is created by the reaction of hydroxyl radical with ferric iron. The theoretical analysis based on such a mechanism can fairly well interpret the experimental observation. The present study suggests that an excited ferryl species may be formed in Fenton reaction.

The laying hen expresses two different low density lipoprotein receptor-related proteins

We have identified, by a combination of ligand, 45Ca2+, and immunoblotting, two large membrane proteins akin to the mammalian so-called low density lipoprotein (LDL) receptor-related protein (LRP) in chicken tissues. LRP has thus far been demonstrated only in mammalian species where it is thought to act as a receptor for proteinase-alpha 2-macroglobulin complexes and/or chylomicron remnants, lipoproteins not produced in birds. One of the chicken LRPs was demonstrated in liver, and has the same apparent Mr and hallmark biochemical properties as rat liver LRP. The other chicken LRP is smaller (approximately 380 kDa) and is expressed in ovarian follicles, but is undetectable in liver. Immunological analysis demonstrated a lack of cross-reactivity between the two LRPs, as well as between them and the previously identified chicken oocyte-specific 95-kDa receptor for the yolk precursors, very low density lipoprotein, and vitellogenin (Stifani, S., Barber, D. L., Nimpf, J., and Schneider, W. J. (1989) Proc. Natl. Acad. Sci. U.S.A. 87, 1955-1959). As shown by ligand blotting, both chicken LRPs have the ability to interact with vitellogenin, a property they share not only with rat LRP, but also with mammalian LDL receptors. To obtain independent confirmation of the ligand blotting results, the smaller (follicular) LRP was purified and high-affinity binding of vitellogenin to it was demonstrated by a solid-phase filtration binding assay. Amino acid sequences of tryptic fragments of the smaller LRP were obtained, and its homology with human LRP demonstrated through unambiguous alignment of three fragments. Both chicken LRPs, the chicken oocyte 95-kDa receptor, as well as rat LRP, could be shown by ligand blotting to interact specifically with chicken serum alpha 2-macroglobulin. In addition, human apolipoprotein E, a ligand implicated in receptor-mediated metabolism of chylomicron remnants, also binds to the smaller chicken LRP, further emphasizing the similarities between LDL receptors and related proteins from a variety of species. In analogy to the known dichotomy of chicken LDL receptors, which is characterized by the production of the 95-kDa oocyte-specific receptor on one hand and a 130-kDa LDL receptor that is exclusively expressed in somatic cells (Hayashi, K., Nimpf, J., and Schneider, W. J. (1989) J. Biol. Chem. 264, 3131-3139), it appears that the smaller and larger chicken LRPs also may be restricted to the oocyte and somatic cells, respectively.

[A clinical trial of treating asthma of moderate severity with beclomethasone dipropionate aerosol]

In order to investigate the efficacy of steroid inhalation in treating asthma of moderate severity, a single-blind, randomized short-term (3-4 weeks) trial was performed in 25 asthmatics uncontrolled by salbutamol inhalation, oral aminophylline and beta 2-agonist. 22 patients finished the trial. Among them, twelve received beclomethasone dipropionate 300 mcg/day and ten received placebo. There was significant improvement in asthmatic symptoms and pulmonary function (FEV1.0, V50, V25) in the group treated with steroid inhalation at the end of this trial, whereas no significant changes were observed in the placebo group. The results demonstrated that steroid inhalation could effectively control asthma of moderate severity.

[Steroidal constituents from Saussurea gossypiphora D. Don]

Four steroids were isolated from the Saussurea gossypiphora for the fist time. They were determined as 3-stigmastanol, beta-sitosterol, stigmast-7-en-3-ol and ergostan-3,24-diol by spectral and chemical methods.

Induced rotary motion and ocular torsion

When a large patterned annulus rotates around a stationary sectored disc the latter appears to rotate in the opposite direction. Such induced rotary motion was examined with central discs subtending 5, 20 and 40 deg at the eye, with the surround filling the remainder of the visual field. The annular surround or the central disc could be oscillated sinusoidally around the fixation point through 20 deg at 0.2 Hz. In each case, subjects estimated the angles through which the moving and stationary parts of the display appeared to rotate on one half-cycle. Subjects also estimated the angle of rotation of an oscillating display that filled the visual field. Induced rotation of the centre was around 100% of the inducing amplitude for all disc sizes, but there was no induced motion of the surround when the centre rotated. Ocular torsion was measured under the same conditions, using the scleral search-coil technique. The amplitude of ocular torsion was a function of the size of the stationary or rotating field. Thus, variations in stimulus conditions affected induced rotary motion and ocular torsion in different ways. The implications of the results for theories of induced motion in terms of underregistered eye movements are discussed.

[Effect of radix Astragalus on the contents of collagen in the aorta and lung of old rats]

The result of experiments shows that the collagen contents in the aorta and lung of old rats are higher than in those of young rats, whereas the contents in the old rats given Radix Astragalus appear lower than those in the control group, close to those in young rats.

NMR study on the major components in hematoporphyrin derivative YHPD

The hematoporphyrin derivative YHPD, a China-made product, has been clinically used in photodynamic therapy of tumors as a good photosensitizing drug. The NMR study on the structure of its major components is reported here. In terms of high performance liquid chromatography (HPLC) four major components A, B, C and D were isolated. The NMR results showed that the component A is O-acetylhematoporphyrin, B and C are two isomers of vinyldeuteroporphyrin. The spectra of 2-dimensional homonuclear correlation NMR, 2-dimensional NOE (nuclear overhauser enhancement), 13C-NMR and off-resonance as well as FAB (fast atom bombarding) mass spectrum of component D indicate that it is a protoporphyrin dimer linked by carbon-carbon bond. This finding may provide a chemical basis for understanding the difference in biological activity between YHPD and other foreign commercial HPD, as well as the composition of clinically used alkali-treated HPD and its effective component.

[High resolution electrophoresis of urinary proteins from unconcentrated samples with silver staining]

We have evaluated an electrophoretic technique on agarose gel with silver staining on one hundred pathological urine samples. This method allows to study low proteinuria and to characterize glomerular, tubular electrophoretic patterns and also to detect monoclonal immunoglobulin light chains.

Flash photolysis study of insulin

The transient absorption spectra of the initial UV-photolysis products of insulin and des-pentapeptide (B26-30)-insulin (DPI) were determined and compared with that of free tyrosine. The far-UV band of the spectra (less than 300 nm) has not been reported before. Their main initial photoproducts are p-alanylphenoxyl radical (lambda max = 410,390 nm) and an unidentified radical (lambda max = 270 nm). The photolysis yields are closely correlative with the dissociation rate of hydroxyl group on phenol ring of tyrosine residues, which in turn depends on the exposed degree of these residues. The quantum yields of the phenoxyl radicals formed in photolysis of insulin and DPI were determined and compared with that of free tyrosine. Based on the comparison, the number of light accessible tyrosine residue in insulin and DPI can be calculated, which provides more quantitative information on the exposed degree of tyrosine residues in these two proteins.

Isolation of genome-enzyme complex from cytoplasmic polyhedrosis virus of silkworm Bombyx mori

The genome-enzyme complex is isolated from the silkworm cytoplasmic polyhedrosis virus with DEAE-Sephadex column chromatography after ultraviolet irradiation. The genome-enzyme complex shows both RNA-polymerase and methyltransferase activities while using 3H-UTP and [3H-methyl]-S-adenosyle-L-methionine as substrates. Like the double-stranded RNA genome of CPV, the genome-enzyme complex could be separated into nine segments on polyacrylamide gel electrophoresis. It is demonstrated that the RNA polymerase and methyl-transferase are tightly bound to the double-stranded RNA genome and that the individual segments of the genome-enzyme complex all possess RNA-polymerase and methyltransferase activities. It appears that each segment of the double-stranded RNA genome is transcribed independently.