Fungal populations of the haulm base of wheat

Abstract In a 2-year field survey, the phylloplane mycoflora on the haulm base of wheat was studied by the dilution plate technique. No significant colonisation was registered before the end of May. Cladosporium spp., 'white' and 'red' yeasts were found to be the most abundant fungi.     

Modulation of murine hemopoiesis in vivo by a synthetic hemoregulatory pentapeptide (HP 5b)

Abstract. Degeneration of the archenteron in middle gastrulae occurred in the presence of α,α'-dipyridyl or Zn²⁺, inhibitors of prolyl hydroxylase. In the presence of these substances the archenteron degenerated and was eventually destroyed. Adding Fe²⁺ to the embryo culture containing α,α'-dipyridyl protected the archenteron from further degeneration, but the collapsed archenteron was not restored to the upright position. At the late gastrula stage, α,α'-dipyridyl did not cause the degeneration of the archenteron. Treatment of the embryos by α,α'-dipyridyl, starting at the swimming blastula stage, resulted in the production of many mesenchyme-like cells but archenteron was not produced in the embryos. Addition of Fe²⁺ to α,α'-dipyridyl culture, just before the beginning of gastrulation of normal embryos, resulted in the formation of normal archenteron. α,α'-Dipyridyl inhibited hydroxylation of proline residues of collagen in sea urchin embryos and Fe²⁺ prevented the inhibition by α,α'-dipyridyl. Respiration was not inhibited by α,α'-dipyridyl.     

A simple,rapid, and sensitive method for measuring protein concentration in subcellular membrane fractions prepared by sucrose density ultracentrifugation

The Multiskan spectrophotometric system and Coomassie brilliant blue G-250 protein-dye binding method have been used together to measure NaOH-solubilized protein in subcellular membrane fractions prepared from isolated rat adipose cells. Forty-eight samples can be read in duplicate within 1 min. Sucrose in concentrations up to 0.7 m interfere only moderately with the assay. A rapid and convenient method is, therefore, now available for multiple protein determinations following sucellular fractionation on sucrose gradients.     

The cellular dynamics of hepatic receptors for alpha 2-macroglobulin.protease complex and for insulin are different

Making freshly isolated rat hepatocytes permeable by 0.4 g/liter digitonin doubled the number of binding sites for alpha 2-macroglobulin.trypsin complex without changing the affinity. Thus, digitonin unmasked a receptor pool, probably of intracellular origin. The total cellular binding capacity was measured in the presence of digitonin, the surface-exposed in its absence. Upon preincubation of the cells at 37 degrees C, the total cellular binding capacity for alpha 2-macroglobulin.trypsin decreased over a 2-h period to 0.26 of the initial value. By contrast, the surface-exposed binding capacity initially increased in response to a preincubation at 37 degrees C, reached after 20 min a peak value 1.74 times that at 0 time, followed by a decrease. Neither the increase in nor the loss of surface-exposed binding capacity was influenced by inhibitors of lysosomal functions, protein synthesis and glycosylation. Colchicine abolished the increase in surface-exposed binding capacity but not the disappearance. By contrast, phenylarsine oxide (inhibitor of endocytosis), N-ethylmaleimide, and phenylmethanesulphonyl fluoride inhibited the receptor loss, suggesting that the loss occurred by proteolysis. The insulin receptor concentration, studied in parallel, remained practically constant in the investigated period in the presence and absence of digitonin. Thus, the hepatic receptor for alpha 2-macroglobulin.protease complexes is regulated independently of other specialized plasma membrane proteins.     

Receptor-mediated degradation of insulin in isolated rat adipocytes. Formation of a degradation product slightly smaller than insulin

More than 90% of the radioactivity associated with isolated rat adipocytes incubated with [TyrA14-125I]monoiodoinsulin represented at steady state iodoinsulin possessing full binding affinity. In contrast, about half of the radioactivity dissociating from the cells was [125I]monoiodotyrosine. The other half was of a molecular size similar to that of iodoinsulin as judged from gel-filtration chromatography. However, the descending limb of the 'insulin' peak (i.e., the smaller molecules) possessed a reduced binding activity compared with native iodoinsulin, material from the ascending limb, or a similar fraction isolated from dissociation medium from IM-9 lymphocytes, a cell type devoid of receptor-mediated insulin degradation. The cells, thus, release an intermediary degradation product.     

Characterization, size estimation and solubilization of α-macroglobulin complex receptors in liver membranes

Receptors for α₂-macroglobulin-proteinase complexes have been characterized in rat and human liver membranes. The affinity for binding of ¹²⁵I-labelled α₂-macroglobulin · trypsin to rat liver membranes was markedly pH-dependent in the physiological range with maximum binding at pH 7.8–9.0. The half-time for association was about 5 min at 37°C in contrast to about 5 h at 4°C. The half-saturation constant was about 100 pM at 4°C and 1 nM at 37°C (pH 7.8). The binding capacity was approx. 300 pmol per g protein for rat liver membranes and about 100 pmol per g for human membranes. Radiation inactivation studies showed a target size of 466 ± 71 kDa (S.D., n = 7) for α₂-macroglobulin · trypsin binding activity. Affinity cross-linking to rat and human membranes of ¹²⁵I-labelled rat α₁-inhibitor-3 · chymotrypsin, a 210 kDa analogue which binds to the α₂-macroglobulin receptors in hepatocytes (Gliemann, J. and Sottrup-Jensen, L. (1987) FEBS Lett. 221, 55–60), followed by SDS-polyacrylamide gel electrophoresis, revealed radioactivity in a band not distinguishable from that of cross-linked α₂-macroglobulin (720 kDa). This radioactivity was absent when membranes with bound ¹²⁵I-α₁-inhibitor-3 complex were treated with EDTA before cross-linking and when incubation and cross-linking were carried out in the presence of a saturating concentration of unlabelled complex. The saturable binding activity was maintained when membranes were solubilized in the detergent 3-[(3-cholamidopropyl)dimethylammonio]profane sulfonate (CHAPS) and the size of the receptor as estimated by cross-linking experiments was shown to be similar to that determined in the membranes. It is concluded that liver membranes contain high concentrations of an approx. 400–500 kDa α₂-macroglobulin receptor soluble in CHAPS. The soluble preparation should provide a suitable material for purification and further characterization of the receptor.