Histochemical changes in the developing abscission layer in fruits of Prunus cerasus L.

Summary Abscission layer formation in the sour cherry (Prunus cerasus L.) during fruit maturation occurred in the transition zone between the fruit and the pedicel. The abscission layer, consisting of 5–8 rows of cells, was first identified by its low affinity for haematoxylin. The walls of cells in the abscission layer contained less total polysaccharides than adjacent cells. The pectins were degraded and the cellulose was partially broken down resulting in cell separation. The Ca level in the abscission zone decreased and Ca and Mg were lost from the walls of cells in the layer during abscission. After the abscission layer formed, cells associated with the layer had a lower capacity to bind ⁴⁵Ca than cells distal or proximal to the layer.Michigan Agricultural Experiment Station Journal Article No. 4607     

Isocitrate Dehydrogenase and Glutamate Synthesis in Acetobacter suboxydans

Acetobacter suboxydans is an obligate aerobe for which an operative tricarboxylic acid cycle has not been demonstrated. Glutamate synthesis has been reported to occur by mechanisms other than those utilizing isocitrate dehydrogenase, a tricarboxylic acid cycle enzyme not previously detected in this organism. We have recovered alpha-ketoglutarate and glutamate from a system containing citrate, nicotinamide adenine dinucleotide (NAD), a divalent cation, pyridoxal phosphate, an amino donor, and dialyzed, cell-free extract. Aconitase activity was readily detected in these extracts, but isocitrate dehydrogenase activity, measured by NAD reduction, was masked by a cyanide-resistant, particulate, reduced NAD oxidase. Isocitrate dehydrogenase activity could be demonstrated after centrifuging the extracts at 150,000 x g for 3 hr and treating the supernatant fluid with 2-heptyl-4-hydroxyquinoline N-oxide. It is concluded that A. suboxydans can utilize the conventional tricarboxylic acid cycle enzymes to convert citrate to alpha-ketoglutarate which can then undergo a transamination to glutamate.     

DNA base composition of Microcyclus species and organisms of similar morphology

Summary From studies of the DNA base composition of Microcyclus species, it is concluded that the genus is to be regarded as a taxonomically heterogeneous group. This agrees with morphological observations of the different species.     

The presence of parvalbumin in a nonmuscle cell line attenuates progression through mitosis

Based on studies that have examined the effect of calcium chelators on cells, it has been proposed that this cation plays a role in regulating cell proliferation. In this study a novel approach was used to indirectly examine the role of calcium in cell cycle progression. A cDNA for the Ca2+-binding protein parvalbumin has been expressed in mouse C127 cells, using a bovine papilloma virus-based expression vector. The normal role of parvalbumin is that of a calcium buffer in vertebrate fast twitch muscle, and the C127 cells do not normally express this protein. The presence of parvalbumin had several effects on the growth of C127 cells. The most striking phenotype was an increase in cell cycle duration which analysis showed was the result of an increase the length of G1 and mitosis (predominantly at prophase). Since changes in cell cycle duration typically occur as a result of changes in G1 duration, the observed increase in the length of mitosis is most unusual. The present results indicate that the previously observed increase in the rate of cell proliferation in cells with elevated calmodulin levels is not the result of a general increase in the level of cytoplasmic calcium-binding protein, but is specific to calmodulin. In addition, the results suggest that calcium regulates progression through mitosis by both calmodulin-dependent (metaphase transition) and -independent (prophase) mechanisms.     

Poly- and Monoclonal Antibodies Against Recombinant Rat Brain Calbindin D-28K Were Produced to Map Its Selective Distribution in the Central Nervous System

Many processes in the CNS depend on calcium. The calcium signal is transduced into an intracellular response via Ca2(+)-binding proteins, including calbindin D-28K. In many laboratories, polyclonal antibodies against chicken intestinal calbindin D-28K have been used to study its localization in the brain (normal and degenerated) of various species, including humans, but some of these antisera cross-reacted with other proteins, including calretinin. We purified recombinant rat brain calbindin D-28K to raise antisera in rabbits and purified a recombinant rat-chicken calbindin D-28K hybrid protein to immunize mice for the generation of monoclonal antibodies. These antisera were highly specific for calbindin D-28K, as demonstrated by two-dimensional Western blotting analysis. Immunohistochemical analyses combined with in situ hybridization studies demonstrated that calbindin D-28K in the Purkinje cells of the cerebellum is independent of vitamin D. The antibodies described here will be important tools for studying the regulation of expression of calbindin D-28K and its biological function in the brain and in the PNS.     

Immunogold localization of chymotrypsin inhibitor-2, a lysine-rich protein,in developing barley endosperm

Chymotrypsin inhibitor-2, a lysine-rich protein in the barley endosperm, has been localized at the ultrastructural level by immunocytochemistry in developing barley endosperm cells 14 days post anthesis. The protein is deposited in the protein bodies. Two morphologically distinct types of protein bodies, small spherical and large irregularly shaped, are present. Golgi-apparatus-derived vesicles whose content is labelled by chymotrypsin inhibitor-2 antibody-gold particles are observed at the Golgi complex and around the vacuoles. These observations indicate that the transport of the protein to the site of deposition is mediated by the Golgi apparatus.Abbreviations CI chymotrypsin inhibitor - DPA days post anthesis - ER endoplasmic reticulum The authors wish to thank Dr. V.R. Franceschi (Department of Botany, Washington State University, Pullman, USA) for many helpful discussions and advice during the work, and the staff at the Electron Microscope Center at Washington State University for technical assistance.     

The role of secreted acid hydrolases in the utilization of complex nutrients byTetrahymena

In an attempt to extend our knowledge of the biology of feeding of the ciliateTetrahymena thermophila, this organism was grown axenically on complex organic material. The nutrient substrate was based on autoclaved wheat grains and adjusted to either pH 5.5 or 7.5. In wild type cultures the cells grew and multiplied only under acidic conditions. In cultures of a mutant cell line blocked in the secretion of acid hydrolases the cells did not grow at either pH value. Thus released acid hydrolases may play a key role in the utilization of complex nutrients in combination with uptake of small organic molecules. Mechanisms in the feeding biology ofTetrahymena thermophila andParamecium tetraurelia are compared.     

Metabolism of i.v. administered 45 kDa epidermal growth factor in the rat

The 45 kDa epidermal growth factor (EGF-(45 kDa)) has been purified from rat urine. We have investigated the distribution and the processing of i.v. injected 125I-labeled EGF-(45 kDa) in the rat. 2.5 min after the i.v. injection only 12% of the label remained in the blood. Most of the label was found in the liver (54%), in the kidneys (7%) and in the skin (4%). The submandibular glands, stomach, small intestine, colon, spleen and lungs contained 1% or less of the radioactivity. Some of the 125I-EGF-(45 kDa) was processed to 125I-EGF-(6 kDa) immunoreactivity in the liver and in the kidneys. The kidneys excreted 125I-EGF-(45 kDa) in the urine, but we were not able to demonstrate 125I-EGF-(6 kDa) in urine. In conclusion, this study shows that homologous EGF-(45 kDa) is cleared from the circulation of rats within a few minutes, mainly by the liver and the kidneys. In vivo both the liver and the kidneys are able to process some of the EGF-(45 kDa) to EGF-(6 kDa) immunoreactivity.