Responses of Ribulose-1,5-Bisphosphate Carboxylase,Cytochrome f,and Sucrose Synthesis Enzymes in Rice Leaves to Leaf Nitrogen and Their Relationships to Photosynthesis

The photosynthetic gas-exchange rates and various biochemical components of photosynthesis, including ribulose-1,5-bisphosphate carboxylase (Rubisco) content, cytochrome (Cyt) f content, and the activities of two sucrose synthesis enzymes, were examined in young, fully expanded leaves of rice (Oryza sativa L.) grown hydroponically in different nitrogen concentrations. The light-saturated rate of photosynthesis at an intercellular CO2 pressure of 20 Pa (CO2-limited photosynthesis) was linearly dependent on leaf nitrogen content, but curvilinearly correlated with Rubisco content. This difference was due to a greater than proportional increase in Rubisco content relative to leaf nitrogen content and the presence of a CO2 transfer resistance between the intercellular air spaces and the carboxylation sites. CO2-limited photosynthesis was proportional to Cyt f content, one of the key components of electron transport, but was not proportional to the activities of cytosolic fructose-1,6-bisphosphatase and sucrose phosphate synthase, the two regulatory enzymes of sucrose synthesis. Light-saturated photosynthesis above an intercellular CO2 pressure of 60 Pa (CO2-saturated photosynthesis) was curvilinearly dependent on leaf nitrogen content. This CO2-saturated photosynthesis was proportional to Cyt f content in the low- and normal-nitrogen leaves, and correlated better with the activities of cytosolic fructose-1,6-bisphosphatase and sucrose phosphate synthase in the high-nitrogen leaves. The increase in the activities of these two enzymes with increasing leaf nitrogen was not as great as the increase in Cyt f content. Thus, as leaf nitrogen increased, the limitation caused by the activities of sucrose synthesis enzymes came into play, which resulted in the curvilinear relationship. However, this limitation by sucrose synthesis enzymes did not affect photosynthesis under normal ambient air.     

Cellular localization of NADH-dependent glutamate-synthase protein in vascular bundles of unexpanded leaf blades and young grains of rice plants

Tissue and cellular localization of NADH-dependent glutamate synthase (NADH-GOGAT, EC 1.4.1.14) in the unexpanced leaf blades and young grains of rice (Oryza sativa L.) was investigated using tissue-print immunoblot and immunocytological methods with an affinity-purified anti-NADH-GOGAT immunoglobulin G. Tissue-print immunoblots showed that the NADH-GOGAT protein was mostly located in large and small vascular bundles of the unexpanded blades. When the cross-sections (10μ in thickness) prepared from the paraffin-embedded blades were stained with the antibody, the NADH-GOGAT protein was detected in vascular-parenchyma cells and mestome-sheath cells. In developing grains, the NADH-GOGAT protein was detected in both phloem- and xylem-parenchyma cells of dorsal and lateral vascular bundles, and in the nucellar projection, nucellar epidermis, and aleurone cells. On the other hand, ferredoxin (Fd)-dependent GOGAT (EC 1.4.7.1) was located mainly in mesophyll cells of the leaf blade and in chloroplast-containing cross-cells of the pericarp of the grains. The spatial expression of these GOGAT proteins indicates distinct and non-overlapping roles in rice plants. In the leaf blades and young grains, NADH-GOGAT could be involved in the synthesis of glutamate from the glutamine that is transported through the vascular system from roots and senescing tissues.     

Fractionation of Nitrogen Isotopes by Glutamine Synthetase Isolated from Spinach Leaves

The isotopic fractionation of nitrogen in the reaction in vitroof glutamine synthetase isolated from spinach (Spinacia oleraceaL.) leaves was calculated from the changes in natural ¹⁵N abundance(     

A histochemical study of the innervation of cerebral blood vessels in the snake

Summary Dual innervation of snake cerebral blood vessels by adrenergic and cholinergic fibres was demonstrated with the use of histochemical methods. Although the nerve plexuses are somewhat less dense, the essential features of innervation of the blood vessels are similar to those of mammals with the exception that the adrenergic plexuses are more prominent than the cholinergic plexuses. The major arteries of the cerebral carotid system have a rich nerve supply. However, the innervation is less rich in the basilar and poor in the spinal (vertebral) arteries. Although the arteries supplying the right side of head are poorly developed, three pairs of arteries, cerebral carotids, ophthalmics and spinals, supply the snake brain. The carotids and ophthalmics are densely innervated and are accompanied by thick nerve bundles, suggesting that the nerves preferentially enter the skull along those arteries. Some parenchymal arterioles are also dually innervated. Connection between the brain parenchyma and intracerebral capillaries via both cholinergic and adrenergic fibres was observed. In addition cholinergic nerve fibres, connecting capillaries and the intramedullary nerve fibre bundles, were noticed. Capillary blood flow may be influenced by both adrenergic and cholinergic central neurons. The walls of capillaries also exhibit heavy acetylcholinesterase activity. This may indicate an important role for the capillary in the regulation of intracerebral blood flow.     

Chromosomal loci of genes controlling site-specific restriction endonucleases of Bacillus subtilis

Molecular Genetics and Genomics - We constructed transformants of B. subtilis 168 which acquired genes for site-specific restriction endonucleases. These endonucleases originated from various...     

Immunohistochemical study of NGF and its receptors in the synovial membrane of the ankle joint of adjuvant-induced arthritic rats

To study the role of nerve growth factor (NGF) in local inflammation, we investigated the expression of NGF and its receptors, trkA and p75, in the ankle joints of adjuvant-induced arthritic rats. Infiltrated mononuclear cells revealed a positive immunoreactivity for NGF and trkA; they were also positive for immunostaining for W3/25 and ED1, which mainly stain T cells and macrophages, respectively. Changes in the ratios of NGF-positive cells to mononuclear cells showed a relatively similar pattern for trkA-positive cells, which peaked at weeks 2 to 3 after the adjuvant injection. In double-immunofluorescence staining, 80% and 65% of NGF-positive cells stained for W3/25 and ED1, respectively. Similarly, 67% and 80% of trkA-positive cells also corresponded to W3/25- and ED1-positive cells, respectively. However, p75 immunoreactivity localized on the nerve fibers but not on the cells of the ankle joints. Dense meshworks of p75-positive nerve fibers with numerous terminal varicosities were observed at weeks 2 to 4. The present findings suggest that infiltrated mononuclear cells may secrete NGF in an autocrine or paracrine manner in the inflamed synovium. An upregulation of NGF in these mononuclear cells and an increase in density of the synovial nerve fibers may be involved in the development of adjuvant arthritis in rats.     

Recent events in alcoholic liver disease V. effects of ethanol on liver regeneration

Liver regeneration is necessary to recover from alcoholic liver injury. Herein, we review evidence that ethanol interferes with liver regeneration. Briefly, alcoholic fatty livers demonstrate increased rates of hepatocyte death. The latter provides a regenerative stimulus. However, unlike mature hepatocytes in healthy adult livers, most surviving mature hepatocytes in alcoholic fatty livers cannot replicate. Therefore, less mature cells (progenitors) must differentiate to replace dead hepatocytes. Little is known about the general mechanisms that modulate the differentiation of liver progenitors in adults. Delineation of these mechanisms and clarification of how ethanol influences them might suggest new therapies for alcoholic liver disease.     

Hyperthermia using magnetite cationic liposomes for hamster osteosarcoma

BACKGROUND: We have developed magnetite cationic liposomes (MCLs) and applied them to local hyperthermia as a mediator. MCLs have a positive charge and generate heat under an alternating magnetic field (AMF) by hysteresis loss. In this study, the effect of hyperthermia using MCLs was examined in an in vivo study of hamster osteosarcoma. METHOD: MCLs were injected into the osteosarcoma and then subjected to an AMF. RESULTS: The tumor was heated at over 42 degrees C, but other normal tissues were not heated as much. Complete regression was observed in 100% of the treated group hamsters, whereas no regression was observed in the control group hamsters. At day 12, the average tumor volume of the treated hamsters was about 1/1000 of that of the control hamsters. In the treated hamsters, no regrowth of osteosarcomas was observed over a period of 3 months after the complete regression. CONCLUSION: These results suggest that this treatment is effective for osteosarcoma.