Preliminary assignments of the aromatic and some methyl group resonances of the 1H-NMR spectrum of the oxidized form of uteroglobin. Application to the interaction of oxidized uteroglobin with progesterone

Two-dimensional NMR methods have been used to assign aromatic and methyl group resonances in the 1H-NMR spectrum of oxidized uteroglobin. Assignments to specific amino acids are based on X-ray-determined structures of two crystal forms (C222(1) and P2(1] and on an energy-minimized X-ray structure of the C222(1) form of uteroglobin. These preliminary assignments are sufficient to probe the interaction of oxidized uteroglobin with progesterone in solution. The protein global structure is unmodified but some direct or indirect conformational changes are induced in the H1H4(H1'H4') pockets and close to Phe28 by progesterone.     

Radiometric assay for carboxypeptidase H (EC 3.4.17.10) and other carboxypeptidase B-like enzymes

Carboxypeptidase H, EC 3.4.17.10, also known as enkephalin convertase, carboxypeptidase E, and crino carboxypeptidase B, is an important enzyme involved in the biosynthesis of bioactive peptides. To assay the enzyme, tissues are homogenized in at least 20 vol (ml/g) of 0.025 M Tris-HCl buffer, pH 8, with 5 mg/ml of bovine serum albumin. After centrifugation, the supernatant is brought to pH 5.6 and centrifuged again. Following a 20-min preincubation in 2 mM CoCl2, the supernatant is incubated with 0.1 mM (final concentration) of the radioactive substrate [3H]benzoyl-Phe-Ala-Arg. The 100-microliters assay is stopped by the addition of 680 microliters of acetonitrile/0.25 M HCl (0.7/1). The 1.5-ml tube is transferred into a scintillation vial and is flushed with 4 ml of Econofluor, a water-immiscible scintillation fluid. The product, [3H]benzoyl-Phe-Ala, recovered in the organic phase, is counted directly with no interference from the substrate remaining in the aqueous phase. The blank is below 1%. Expressed in nanomoles per minute per milligram of tissue, the activity of the soluble enzyme in rat is 0.34 for striatum, 21.0 for pancreatic islet, 16.6 for anterior pituitary, 46.0 for intermediate pituitary, and 10.9 for neural pituitary. In every case 25 microM guanidinoethylmercaptosuccinic acid, an active site-directed inhibitor of carboxypeptidase H, completely inhibits the activity.     

The site of substrate and fructose 2,6-bisphosphate binding to rabbit liver fructose-1,6-bisphosphatase

The binding site(s) in rabbit liver fructose-1,6-bisphosphatase for the active site binding ligand, fructose 6-phosphate, and the inhibitor, fructose 2,6-bisphosphate, have been investigated by using nuclear magnetic resonance spectroscopy. The distance from a nitroxide spin label to the bound ligands and the distance from the structural metal site to the bound ligands are about the same within experimental error. These data indicate that the two ligands probably bind at the active site in the rabbit liver enzyme.     

Purification and immunochemical characterization of the cytoplasmic androgen-binding protein of rat liver

The cytoplasmic androgen-binding (CAB) protein of the male rat liver has been implicated to play a role in the androgen-dependent regulation of alpha 2u-globulin synthesis. The liver of the adult male rat contains about 50 fmol of specific high-affinity androgen-binding activity per milligram of total cytosolic protein. Photoaffinity labeling with [3H]R-1881 followed by SDS-polyacrylamide gel electrophoresis and autoradiography shows that the CAB is a 31-kilodalton protein. By means of DEAE-cellulose chromatography and preparative SDS-polyacrylamide gel electrophoresis, we have purified the CAB protein to electrophoretic homogeneity and have raised polyclonal rabbit antiserum that is monospecific to this protein. In the sucrose density gradient, the antiserum reacted with the androgen-binding component of the male liver cytosol prelabeled with tritiated dihydrotestosterone. Western blot analysis of the liver cytosol showed that the antiserum recognizes only the 31-kDa androgen-binding component. Such immunoblotting also showed that unlike the young adult, the androgen-insensitive states during prepuberty and senescence are associated with a marked reduction in the hepatic concentration of the immunoreactive CAB protein. No immuno-chemical cross-reactivity between CAB and another androgen-binding component of Mr 29K (which is associated with androgen insensitivity during prepuberty and senescence) was observed. The latter finding favors the possibility that 31- and 29-kDa androgen-binding components may have distinct sequence structure.     

Metabolic and morphologic properties of single muscle fibers in the rat after spaceflight, Cosmos 1887

The adaptation of a slow (soleus, Sol) and a fast (medial gastrocnemius, MG) skeletal muscle to spaceflight was studied in five young male rats. The flight period was 12.5 days and the rats were killed approximately 48 h after returning to 1 g. Five other rats that were housed in cages similar to those used by the flight rats were maintained at 1 g for the same period of time to serve as ground-based controls. Fibers were classified as dark or light staining for myosin adenosine triphosphatase (ATPase). On the average, the fibers in the Sol of the flight rats atrophied twice as much as those in the MG. Further, the fibers located in the deep (close to the bone and having the highest percentage of light ATPase and high oxidative fibers in the muscle cross section) region of the MG atrophied more than the fibers located in the superficial (away from the bone and having the lowest percentage of light ATPase and high oxidative fibers in the muscle cross-section) region of the muscle. Based on quantitative histochemical assays of single muscle fibers, succinate dehydrogenase (SDH) activity per unit volume was unchanged in fibers of the Sol and MG. However, in the Sol, but not the MG, the total amount of SDH activity in a 10-microns-thick section of a fiber decreased significantly in response to spaceflight. Based on population distributions, it appears that the alpha-glycerophosphate dehydrogenase (GPD) activities were elevated in the dark ATPase fibers in the Sol, whereas the light fibers in the Sol and both fiber types in the MG did not appear to change. The ratio of GPD to SDH activities increased in the dark (but not light) fibers of the Sol and was unaffected in the MG. Immunohistochemical analyses indicate that approximately 40% of the fibers in the Sol of flight rats expressed a fast myosin heavy chain compared with 22% in control rats. Further, 31% of the fibers in the Sol of flight rats expressed both fast and slow myosin heavy chains compared with 8% in control rats. Immunohistochemical changes in the MG were minimal. These data suggest that the magnitude and direction of enzymatic activity and cell volume changes are dependent on the muscle, the region of the muscle, and the type of myosin expressed in the fibers. Further, the ability of fibers to maintain normal or even elevated activities per unit volume of some metabolic enzymes is remarkable considering the marked and rapid decrease in fiber volume.     

Cryogenic changes in seminal protein of cattle and buffalo

The effect of subzero temperatures on the electrophoretic pattern of seminal plasma protein of cattle and buffalo was studied. The profiles of the seminal proteins of these two closely related species differed considerably. Cattle had 11 proteins in the anodic system (pH 8.6) and none in the cathodic system (pH 4.3), while buffalo have 19 in the anodic system (pH 8.6) and 2 proteins in the cathodic system (pH 4.3). Freezing of semen at -5 degrees C for 24 h caused aggregation of seminal proteins in both species. A higher aggregation and loss of proteins were observed when freezing was done in liquid nitrogen at -196 degrees C. The effect was more pronounced in buffalo than in cattle. Loss of more seminal plasma proteins due to cryoinjury in buffalo semen may account for its poorer freezability than that of cattle semen.     

Measurement of bacterial growth rates in subsurface sediments using the incorporation of tritiated thymidine into DNA

Microbial growth rates in subsurface sediment from three sites were measured using incorporation of tritiated thymidine into DNA. Sampling sites included Lula, Oklahoma, Traverse City, Michigan, and Summit Lake, Wisconsin. Application of the thymidine method to subsurface sediments required (1) thymidine concentrations greater than 125 nM, (2) incubation periods of less than 4 hours, (3) addition of SDS and EDTA for optimum macromolecular extraction, and (4) DNA purification, in order to accurately measure the rate of thymidine incorporation into DNA. Macromolecule extraction recoveries, as well as the percentage of tritium label incorporated into the DNA fraction, were variable and largely dependent upon sediment composition. In general, sandy sediments yielded higher extraction recoveries and demonstrated a larger percentage of label incorporated into DNA than sediments that contained a high silt-clay component. Reported results also indicate that the acid-base hydrolysis procedure routinely used for macromolecular fractionation in water samples may not be routinely applicable to the modified sediment procedure where addition of SDS and EDTA are required for macromolecule extraction. Growth rates exhibited by subsurface communities are relatively slow, ranging from 5.1 to 10.2×10⁵ cells g^–1 day^–1. These rates are 2–1,000-fold lower than growth rates measured in surface sediments. These data lend support to the supposition that subsurface microbial communities are nutritionally stressed.     

In vitro propagation ofMitragyna parvifolia Korth.

Multiple shoot formation and their elongation from excised apical vegetative shoots of a 40-year old-tree ofMitragyna parvifolia Korth. was achieved in Murashige and Skoog's medium supplemented with 4.44 M benzyl adenine. The in vitro regenerated shoots rooted when cultured on modified Murashige and Skoog's medium containing low inorganic salts and the three auxins. Regeneration by this method was suitable for mass propagation of the plant.