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Biomedical subjects

M B Singh

Publications and source records attributed to M B Singh.

62 records · Page 4Linked to original sources
PubMed1984

Invertases of Lilium Pollen : Characterization and Activity during In Vitro Germination.

Two different forms of invertase are found in pollen of lily (Lilium auratum). One form is cytoplasmic (Invertase 1) and the other is bound to the pollen wall (Invertase 2). Invertase 1 has been partially purified and is a glycoprotein (apparent molecular weight, 450 kilodaltons) with a K(m) of 0.65 millimolar for sucrose. The two invertases differ in pH optimum and thermal stability. Invertases of lily pollen are beta-fructofuranosidases which can hydrolyze sucrose but not melizitose. The mature pollen grains have enzyme activity in both cytoplasmic and wall fractions, and no increase in the activity of either occurs during germination. The wall-bound enzyme could not be released by treatments with detergents or high salt concentrations.

Journal Article↗
PubMed1979

Studies on the physiology of pollen and pollen tube growth. IV Eschscholtzia californica Cham.

Eschscholtzia californica stigmas with germinating pollen at different stages of development were the subject of histochemical studies which aimed the localization of several enzymes like phosphorylase, leucine amino peptidase, nonspecific esterase, cytochrome oxidase, aldolase, alpha-glycerophosphate dehydrogenase, succinate dehydrogenase, malate dehydrogenase, monoamine oxidase, alpha-galactosidase, beta-glucosidase and beta-galactosidase. Pollen and pollen tubes were shown to contain starch, lipid, proteins and soluble sugars as the storage products. These storage products were utilized during germination and tube growth. The role of different enzymes in the process of germination and tube growth is discussed. From the distribution of oxidoreductases it is inferred that respiration plays an essential role in the tube growth. During pollen germination probably the reserve proteins were transported to pollen tube tip. The increase of activity of alpha-and beta-galactosidase in pollen tubes indicates on their involvement in carbohydrate metabolism. The role of alpha-galactosidase in the metabolism of galactolipids is also inferred. Similarly, the reaction catalysed by beta-glucosidase resulted in the production of aglycon and glucose; of these the former possibly act as a substrate of peroxidase. Some of the glycosidases diffused out of pollen wall on the stigma and participated in the release of free sugars of the female tissue.

Electron Transport Complex IV↗
PubMed1976

Histochemical studies on reserve substances and enzymes in female gametophyte of Zea mays.

Cytochemical changes during the early development of maize caryopsis are reported. Changes in the localization of different reserve substances (e.g. polysaccharides, proteins, nucleic acids and lipids) and enzymes (acid phosphatase, esterase, lipase, phosphorylase, succinate dehydrogenase, cytochrome oxidase and peroxidase) have been studied in unfertilized and fertilized ovules. Before pollination very feeble enzyme activity (acid phosphatase, succinate dehydrogenase, cytochrome oxidase and peroxidase) was observed. Reserve substances were present in low amounts before pollination. Pollination stimulated the accumulation of several substances and enzymes in the tip of the nucellus, micropylar zone. Just prior to, during and after fertilization, the cells in the micropylar zone had strong reaction for several enzymes indicating temporary enhancement of metabolic activity in the micropylar zone. The role of antipodals in the storage of reserve food products and nutrition of embryo and early stages of endosperm development is discussed. The pattern of enzymatic changes within the embryo sac reflected the biochemical changes operative during quiescent and active stages. The nucellus of Zea mays contains many enzymes required for hydrolysis of reserved food substances. A role of acid phosphatase in autolysis of nucellar cells, after fertilization is suggested. Post-fertilization increase in the activity of enzymes and accumulation of reserve materials is interpreted as reflecting a presumed increase in the metabolic rate relative to growth and differentiation.

Acid Phosphatase↗
PubMedDate not supplied

Reduction in allergenicity of grass pollen by genetic engineering.

BACKGROUND: Hay fever and allergic asthma triggered by grass pollen allergens affect approximately 20% of the population in cool temperate climates. Ryegrass is the dominant source of allergens due to its prodigious airborne pollen production. Lol p 5 or group 5 is among the most important and widespread grass pollen allergen because it reacts with IgE antibodies of more than 90% of grass pollen-allergic patients, contains most of the grass pollen-specific IgE epitopes and elicits strong biological responses. Significant efforts have been made in developing diagnostic and therapeutic reagents for designing new and more effective immunotherapeutic strategies for treatment of allergic diseases. An alternative approach to this problem could be to reduce the amount of allergen content in the source plant. METHODS: High velocity microprojectile bombardment was used to genetically engineer ryegrass. Antisense construct targeted to one of major allergen, Lol p 5, was introduced. The expression of antisense RNA was regulated by a pollen-specific promoter. Pollen was analysed for IgE reactivity. RESULTS: Analysis of proteins with allergen-specific monoclonal and polyclonal antibodies did not detect Lol p 5 in the transgenic pollen. The transgenic pollen showed remarkably reduced allergenicity as reflected by low IgE binding capacity of pollen extract as compared to control pollen. The transgenic ryegrass plants in which Lol p 5 gene expression is perturbed showed normal fertile pollen development. CONCLUSIONS: Our studies showed that it is possible to selectively 'switch off' allergen production in pollen of ryegrass demonstrating feasibility of genetic engineering of plants for reduced allergenicity.

Allergens↗