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Biomedical subjects

A S Reddy

Publications and source records attributed to A S Reddy.

70 records · Page 4Linked to original sources
PubMed1989

Molecular cloning and sequencing of a cDNA for plant calmodulin: signal-induced changes in the expression of calmodulin.

A cDNA clone (pPCM-1) for plant calmodulin was isolated by screening a potato stolon tip cDNA library with a chicken calmodulin cDNA. Nucleotide sequence analysis of pPCM-1 revealed that it contained 80 base pairs of 5' untranslated region, the entire coding region, and 376 base pairs of 3' untranslated region. Comparison of the nucleotide sequence of coding regions of potato and chicken calmodulin mRNA showed 78% homology. Comparison of the predicted amino acid sequence of potato calmodulin with other known calmodulin sequences indicated a high degree of homology with a few exceptions. Three changes in the amino acid sequence were found to be unique to the potato calmodulin sequence. In our earlier studies we showed the involvement of calcium and calmodulin in potato tuberization. The pPCM-1 clone was used as a probe to study the expression of calmodulin mRNA during tuberization and to monitor calmodulin mRNA level in various parts of the potato plant. Stolon tips showed the highest levels of calmodulin mRNA, suggesting a role for calmodulin in the tuberization process. In addition, pPCM-1 was used to investigate the effect of auxin and light on calmodulin gene expression in auxin-responsive strawberry fruit and light-responsive Merit corn roots, respectively. Both auxin and light signals were found to increase the level of mRNA for calmodulin. These results suggest that the altered calmodulin gene expression could be one of the molecular events involved in the signal transduction process in plants.

Amino Acid Sequence↗
PubMed1989

Isolation and characterisation of satellite DNA from Brassica juncea (L.) Czern.

Nuclear DNA isolated from hypocotyls (H), proliferating callus (PC) and differentiating callus (DC) of Brassica juncea contains a satellite DNA which can be resolved in actinomycin-D/CsCl gradients. The satellite DNA undergoes changes, when an in vitro culture is raised from hypocotyl tissue and forms a higher percentage of the genome in PC and DC than in mature differentiated tissue (hypocotyl). All the three satellite DNAs are GC-rich compared to main band DNAs. Satellite DNA of H has higher Tm and GC content than that of the PC and DC satellites. A 200 bp basic repeat unit from hypocotyl nuclear DNA has been cloned and characterised.

Brassica↗
PubMed1987

Signal transduction in plants: evidence for the involvement of calcium and turnover of inositol phospholipids.

Involvement of calcium and turnover of inositol phospholipids in signal transduction was investigated using roots of a variety of corn (Zea mays L., cv. Merit) which require light to develop gravitropic sensitivity. Depletion of calcium in root tips by EGTA plus calcium ionophore A23187 prior to light treatment resulted in the loss of light-dependent gravisensitivity. Replenishment of calcium to depleted roots restored the light-dependent gravisensitivity. Light treatment of dark-grown roots resulted in an increased level of inositol trisphosphate as compared to controls. Furthermore, 5-hydroxytryptamine, which is known to promote the hydrolysis of phosphoinositides, sensitized dark-grown roots to gravity and increased inositol trisphosphate levels. These results support the hypothesis that calcium and inositol phospholipid turnover play a role in signal transduction in plants.

Calcium↗
PubMed1987

Accumulation of a glycine rich protein in auxin-deprived strawberry fruits.

Growth of strawberry (Fragaria ananassa Duch. cv. Ozark Beauty) receptacles is regulated by auxin supplied from the achenes. The receptacle growth can be stopped at any stage by deachening the fruits, and can be resumed by exogenous application of auxin. In our earlier studies we demonstrated auxin regulated polypeptide changes at different stages of strawberry fruit development. Removal of achenes from fruits and growing the receptacles without auxin resulted in the time-dependent accumulation of 52,000 Mr polypeptide. Amino acid analysis revealed that the protein is rich in glycine. Our studies, with normal and variant strawberry receptacles, indicate that the synthesis and accumulation of this glycine-rich protein correlates with cessation of receptacle growth. These results suggest a possible role for the glycine-rich protein in cessation of growth.

Indoleacetic Acids↗
PubMed1987

Auxin-regulated changes in protein phosphorylation in pea epicotyls.

Auxins regulate various aspects of plant growth and development. However, the mechanism by which these hormones elicit diverse physiological processes is not clear. We present evidence for the role of auxin in protein phosphorylation and the possible involvement of calmodulin in auxin-induced changes. In the presence of auxin, phosphorylation of 23,000, 82,000, 105,000 and 110,000 molecular weight polypeptides markedly decreased whereas phosphorylation of 19,000, 24,000 and 28,000 molecular weight polypeptides increased. These results open up a new experimental approach in understanding the molecular mechanism by which auxins regulate various physiological processes in plants.

Fabaceae↗
PubMed1987

Inositol 1,4,5-trisphosphate induced calcium release from corn coleoptile microsomes.

The effect of inositol 1,4,5-trisphosphate (IP3) on Ca2+ release from microsomes of corn coleoptiles was investigated. Addition of micromolar concentrations of IP3 to Ca2+ loaded microsomes resulted in rapid release of 20-30% of sequestered Ca2+. Maximal and half maximal Ca2+ release occurred at 20 and 8 microM of IP3 respectively. Part of the Ca2+ released by IP3 was reaccumulated into microsomes within 4 min. The amount of Ca2+ released by IP3 was found to be dependent on free Ca2+ concentration in the incubation medium at the time of release. Maximum Ca2+ release was observed around 0.1 microM free Ca2+ concentration in the assay medium. These data suggest that IP3 might act as a second messenger in plants in a manner similar to animal systems by altering cytosolic levels of calcium.

Calcium↗
PubMed1987

Calcium-regulated in vivo protein phosphorylation in Zea mays L. root tips.

Calcium dependent protein phosphorylation was studied in corn (Zea mays L.) root tips. Prior to in vivo protein phosphorylation experiments, the effect of calcium, ethyleneglycol-bis-(beta-aminoethyl ether)-N-N' -tetraacetic acid (EGTA) and calcium ionophore (A-23187) on phosphorus uptake was studied. Calcium increased phosphorus uptake, whereas EGTA and A-23187 decreased it. Consequently, phosphorus concentration in the media was adjusted so as to attain similar uptake in different treatments. Phosphoproteins were analyzed by two-dimensional gel electrophoresis. Distinct changes in phosphorylation were observed following altered calcium levels. Calcium depletion in root tips with EGTA and A-23187 decreased protein phosphorylation. However, replenishment of calcium following EGTA and ionophore pretreatment enhanced phosphorylation of proteins. Preloading of the root tips with 32P in the presence of EGTA and A-23187 followed by a ten minute calcium treatment, resulted in increased phosphorylation indicating the involvement of calcium, calcium and calmodulin-dependent kinases. Calmodulin antagonist W-7 was effective in inhibiting calcium-promoted phosphorylation. These studies suggest a physiological role for calcium-dependent phosphorylation in calcium-mediated processes in plants.

Calcimycin↗
PubMed1987

Regulation of Protein Synthesis in Plant Embryo by Protein Phosphorylation : I. Purification and Characterization of a cAMP-Independent Protein Kinase and Its Endogenous Substrate.

A cyclic AMP-independent protein kinase, which strongly inhibits in vitro protein synthesis, was purified to homogeneity from barley embryo by affinity and ion exchange chromatography. The M(r) of the purified enzyme is 95,000 with two nonidentical subunits of M(r) 58,000 and 39,000. The enzyme activity is not stimulated by cAMP, cGMP, or calmodulin. The endogenous phosphate acceptor of this kinase is a protein of M(r) 52,000, was isolated by purified protein kinase immobilized Sepharose column. Using antibodies raised against this protein kinase, the levels of the enzyme during embryogenesis and germination are determined. An inverse relationship has been observed between protein kinase level and rate of protein synthesis.

Journal Article↗
PubMed1987

The role of calcium ions in gravity signal perception and transduction.

Ca2+ is implicated as a messenger in coupling various environmental stimuli, such as gravity and light, to response. In recent years, it has become evident that Ca2+ plays a central role in all three phases of gravitropism--perception, transduction and response. The root cap, which is known to contain high amounts of Ca2+ and calmodulin, is the primary site of gravity perception. The possible role of phosphoinositide turnover and Ca(2+) - and Ca(2+) -calmodulin-dependent enzymes such as Ca(2+) -ATPase and protein kinases in gravitropism is discussed. A model is proposed to describe the role of Ca2+ in both normal and light-dependent gravity response in roots.

Calcium↗
PubMedDate not supplied

Electromyographic analysis of the deltoid and rotator cuff muscles in persons with subacromial impingement.

The purpose of this study was to compare subjects with subacromial impingement and subjects with normal shoulders with respect to muscle activity. Fifteen subjects in each group were studied by means of fine-wire electromyography. The middle deltoid and rotator cuff muscles were evaluated during isotonic scaption from 30 to 120 degrees. Overall, the impingement group demonstrated decreased mean muscle activity in comparison with the group of normal subjects. The magnitude of diminished activity was statistically significantly different (P < .05) during the 30- to 60-degrees arc for the infraspinatus, subscapularis, and middle deltoid muscles; in addition, the infraspinatus muscle demonstrated significantly depressed activity during the 60- to 90-degrees arc. In the impingement group, the supraspinatus and teres minor revealed a diminution of muscle function in comparison with shoulders in the normal group; the difference was not significant. This study demonstrates that muscle activity in subjects with impingement is most notably decreased in the first arc of motion. Also of clinical relevance is the fact that the inferior force vector (from the infraspinatus and subscapularis) is less functional in subjects with impingement than is the superior compressive vector (from the supraspinatus). Thus, humeral head depression during the critical first portion of elevation may be insufficient in people with subacromial impingement.

Adult↗
PubMedDate not supplied

Evaluation of the intraosseous and extraosseous blood supply to the distal femoral condyles.

Osteonecrosis of the distal femur occurs more often in the medial femoral condyle than in the lateral femoral condyle, but the vascular supply to these regions has not previously been described. Twelve fresh adult cadaver legs were injected with india ink or latex via the femoral artery and then meticulously dissected to evaluate the extraosseous blood supply. After all soft tissue was removed, the intraosseous blood supply was evaluated using a modified Spateholtz technique. The vascular structures at risk during posterior cruciate ligament reconstruction were also identified. The analysis of the extraosseous arterial supply demonstrated that the superior and inferior lateral genicular arteries combine to supply the lateral femoral condyle. The medial femoral condyle is supplied primarily by the superior medial genicular artery and other lesser branches of the popliteal artery. The intraosseous supply to the lateral condyle was shown to consist of an arcade of vessels providing multiple branches to the subchondral bone with no obvious "watershed" region of limited vascularity. The intraosseous supply to the medial condyle appeared to consist of a single nutrient vessel supplying the subchondral bone with an apparent watershed area of limited supply. A potentially significant difference exists between the intraosseous and extraosseous blood supply to the medial and lateral femoral condyles that may explain the higher frequency of ischemic events occurring in the medial femoral condyle. The close proximity of the extraosseous vessels to the medial femoral condyle and the standard femoral tunnel used during posterior cruciate ligament reconstruction may explain the occurrence of avascular necrosis after this procedure.

Cadaver↗