Photoaffinity labeling of mammalian alpha 1-adrenergic receptors. Identification of the ligand binding subunit with a high affinity radioiodinated probe

We have synthesized and characterized a novel high affinity radioiodinated alpha 1-adrenergic receptor photoaffinity probe, 4-amino-6,7-dimethoxy-2-[4-[5-(4-azido - 3 - [125I]iodophenyl) pentanoyl] - 1 - piperazinyl] quinazoline. In the absence of light, this ligand binds with high affinity (KD = 130 pM) in a reversible and saturable manner to sites in rat hepatic plasma membranes. The binding is stereoselective and competitively inhibited by adrenergic agonists and antagonists with an alpha 1-adrenergic specificity. Upon photolysis, this ligand incorporates irreversibly into plasma membranes prepared from several mammalian tissues including rat liver, rat, guinea pig, and rabbit spleen, rabbit lung, and rabbit aorta vascular smooth muscle cells, also with typical alpha 1-adrenergic specificity. Autoradiograms of such membrane samples subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis reveal a major specifically labeled polypeptide at Mr = 78,000-85,000, depending on the tissue used, in addition to some lower molecular weight peptides. Protease inhibitors, in particular EDTA, a metalloprotease inhibitor, dramatically increases the predominance of the Mr = 78,000-85,000 polypeptide while attenuating the labeling of the lower molecular weight bands. This new high affinity radioiodinated photoaffinity probe should be of great value for the molecular characterization of the alpha 1-adrenergic receptor.     

Preparation and biological activity of taxol acetates

Synthesis and biological activity of 2′-acetyltaxol and 7-acetyltaxol are reported. Activity is measured $\text{in}\text{vivo}$ by cytotoxicity toward the macrophage-like cell line J774.2, and $\text{in}\text{vitro}$ by promotion of microtubule assembly in the absence of exogenous GTP. Addition of an acetyl moiety at C-2′ results in loss of $\text{in}\text{vitro}$ activity but not cytotoxicity. The properties of 7-acetyltaxol are similar to those of taxol in its effects on cell replication and on $\text{in}\text{vitro}$ microtubule polymerization. Therefore a free hydroxyl group at C-7 is not required for $\text{in}\text{vitro}$ activity and this position is available for structural modifications.     

Sperm chromosome analysis in a man heterozygous for a paracentric inversion of chromosome 7 (q11q22)

Summary Human sperm chromosomes were studied in a man heterozygous for a paracentric inversion of chromosome 7 (q11q22). The pronuclear chromosomes were analysed after in vitro penetration of golden hamster (Mesocricetus auratus) eggs. Ninety-four sperm chromosome spreads were examined, of which 34 contained the normal number 7 chromosome and 59 the inverted 6. This segregation was significantly different from the expected 1:1 ratio. The number of X- to Y-bearing sperm was 48 and 46 respectively. No sperm contained a recombinant chromosome caused by a crossover within the inversion. The frequency of chromosomal abnormalities in other chromosomes was 9.6%, which is not significantly different from the frequency observed in normal donors (8.9%) in our laboratory. These result suggest that the risk of chromosomally unbalanced sperm is not high for this paracentric inversion.     

Plasma alpha natriuretic peptide in cardiac impairment.

Regional plasma alpha human atrial natriuretic peptide concentrations were measured, and their relation to intracardiac pressures assessed, in an unselected series of 45 patients undergoing diagnostic cardiac catheterisation. Arteriovenous gradients in plasma concentrations of alpha human atrial natriuretic peptide were consistent with its cardiac secretion and its clearance by the liver and kidneys. Plasma concentrations of the peptide in the pulmonary artery, aorta, and superior vena cava correlated closely with the mean right atrial and pulmonary arterial pressures, and similar, though weaker, positive relations were seen with the left ventricular end diastolic and pulmonary artery wedge pressures. Concentrations of both atrial natriuretic peptide and renin showed significant inverse relations with serum sodium concentrations. Plasma concentrations of alpha human atrial natriuretic peptide are an additional objective indicator of the severity of haemodynamic compromise in patients with cardiac impairment.     

Histone H1: Ultracentrifugation studies of the effects of ionic strength and denaturants on the solution conformation

The conformation of histone H1 has been examined under native and denaturing conditions in the absence of DNA or chromatin. Sedimentation coefficients were determined for Histone H1 in 0.1 m KCl and in 6 m guanidine hydrochloride solutions at pH 7.4. The influence of ionic strength on the conformation of histone H1 has been determined by measurement of the sedimentation coefficient in tetramethylammonium chloride solutions of up to 2.5 m and extrapolated to infinite ionic strength. Results from these experiments suggest that the native conformation of histone H1 is very asymmetric in shape. The molecule is best described as a prolate ellipsoid with axes of 312 Å (2a) and 16 Å (2b) in low ionic strength media and also as a prolate ellipsoid with axes of 202 Å (2a) and 20 Å (2b) at high ionic strength or when associated with polyanions, e.g., DNA. Denaturation of histone H1 by guanidine hydrochloride was found to be completely reversible. In 6 m guanidine hydrochloride, the H1 molecule collapses to a sphere but the original extended conformation of the protein is readily restored on dialysis. This suggests rigid conformational requirements for the H1 molecule as incorporated into chromatin. The shape and dimensions for the H1 molecule at high ionic strength are not sufficiently conclusive to locate H1 in the chromatin structure. It is proposed, however, that viable models for chromatin architecture must be consistent with the histone H1 solution dimensions obtained here.     

Response of end bud cells from immature rat mammary gland to hormones when cultured in collagen gel

End buds from 4- to 5-week-old rat mammary glands were isolated and cultured within a rat tail tendon collagen gel matrix. Media containing equine serum or porcine serum and cholera toxin promoted growth, but not the production of casein or thioesterase II, nor did they induce a state of differentiation as assessed by cell ultrastructure. Medium supplemented with only 5% porcine serum, insulin and cholera toxin did not support growth or differentiation. However, when prolactin, estradiol, progesterone and hydrocortisone were added to this medium, growth was stimulated greatly and a differentiated state was induced as assessed by the production of casein and thioesterase and by the appearance of a highly secretory ultrastructure.     

Competition of Rhizobium japonicum Strains in Early Stages of Soybean Nodulation

The effects of preexposure of soybean (Glycine max L. Merrill) roots to Rhizobium japonicum strains and subsequent establishment of other strains in the nodules were investigated by using combinations of effective strains (USDA 110 and USDA 138) and effective-ineffective strains (USDA 110 and SM-5). Strain USDA 110 was a better competitor than either USDA 138 or SM-5 on cultivars Lee and Peking. However, when either of the two less-competitive strains was inoculated into 2-day-old seedlings before USDA 110 was, their nodule occupancy increased significantly on both cultivars. With USDA 138 as the primary inoculum and USDA 110 delayed for 6, 48, and 168 h, the incidence of USDA 138 nodules increased on cultivar Peking from 6% (at zero time) to 28, 70, and 82% and on cultivar Lee from 17% (at zero time) to 32, 88, and 95% for the three time delays, respectively. Preexposure of 2-week-old roots of cultivar Lee to USDA 138 had essentially the same effect: the incidence of USDA 138 nodules increased from 23% at zero time to 89 and 97% when USDA 110 was delayed for 24 and 72 h, respectively. When the ineffective strain SM-5 was used as the primary inoculum, followed by USDA 110 72 h later, the percentage of nodules containing SM-5 increased from 7 to 76%. These results indicate that the early events in the nodulation process of soybeans are perhaps the most critical for competition among R. japonicum strains.