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Biomedical subjects

A K Bal

Publications and source records attributed to A K Bal.

At least 19 recordsLinked to original sources
PubMed1993

Roles of plant homologs of Rab1p and Rab7p in the biogenesis of the peribacteroid membrane, a subcellular compartment formed de novo during root nodule symbiosis.

The peribacteroid membrane (PBM) in legume root nodules is derived from plasma membrane following endocytosis of Rhizobium by fusion of newly synthesized vesicles. We studied the roles of plant Rab1p and Rab7p homologs, the small GTP-binding proteins involved in vesicular transport, in the biogenesis of the PBM. Three cDNAs encoding legume homologs of mammalian Rab1p and Rab7p were isolated from soybean (sRab1p, sRab7p) and Vigna aconitifolia (vRab7p). sRab1p was confirmed to be a functional counterpart of yeast Ypt1p (Rab1p) by complementation of a yeast ypt1-1 mutant. Both srab1 and vrab7 genes are induced during nodulation with the level of vrab7 mRNA being 12 times higher than that in root meristem and leaves. This induction directly correlates with membrane proliferation in nodules. Antisense constructs of srab1 and vrab7, under a nodule-specific promoter (leghemoglobin, Lbc3), were made in a binary vector and transgenic nodules were developed on soybean hairy roots obtained through Agrobacterium rhizogenes-mediated transformation. Both antisense srab1 and vrab7 nodules were smaller in size and showed lower nitrogenase activity than controls. The antisense srab1 nodules showed lack of expansion of infected cells, fewer bacteroids per cell and their frequent release into vacuoles. In contrast, antisense vrab7 expressing nodules showed accumulation of late endosomal structure and multivesicular bodies in the perinuclear region. These data suggest that both Rab1p and Rab7p are essential for the development of the PBM compartment in effective symbiosis.

Amino Acid Sequence↗
PubMed1992

Changes in the amount and distribution of neuronal alkaline and acid phosphatase after chronic exposure of cultures of cingulate cortex to antidepressant drugs.

Enzyme histochemistry was used to examine alkaline and acid phosphatases in cultures of embryonic rat cingulate cortex after 14 days exposure in vitro to two tricyclic antidepressants (amitriptyline and desipramine) and two non-tricyclic antidepressants (mianserin and citalopram). An increased amount of acid phosphatase reaction product was observed in lysosomes of neurons in cultures treated chronically with the non-tricyclic antidepressants, mianserin or citalopram. More strikingly, reaction product was also present in the inner lamellae of the Golgi apparatus after this treatment, but never in controls. These observations suggest that non-tricyclic antidepressants significantly increase the rate of degradative processes in cingulate neurons. In cultures, treated chronically with desipramine or amitriptyline, pre- and postsynaptic membranes contained heavy deposits of alkaline phosphatase reaction product, whereas in control cultures not exposed to these drugs the corresponding membranes were entirely devoid of reaction product. An increase in the amount of alkaline phosphatase reaction product was also observed on the plasma membranes of neuronal cell bodies. These observations suggest that chronic exposure to antidepressants may influence transmembrane transport in cingulate neurons.

Acid Phosphatase↗
PubMed1990

Localization of plant lipids for light microscopy using p-phenylenediamine in tissues of Arachis hypogaea L.

p-Phenylenediamine (pPD) can be used en bloc to preserve and differentiate cell lipids in aldehyde-fixed peanut plant tissues treated with osmium tetroxide during dehydration in 70% ethanol. Semithin plastic sections for light microscopy need no further staining and can be mounted in Histoclad after drying on a slide. Brown staining above background differentiates lipid-containing structures. Nonspecific staining can be distinguished in control preparations extracted en bloc with lipid solvents.

Lipids↗
PubMed1987

Use of tannic acid for the ultrastructural visualization of periplasm in gram-negative bacteria.

Tannic acid mordanting reveals the periplasm, the area between the outer membrane and the inner membrane of gram-negative bacteria, Rhizobium sp., Escherichia coli and Enterobacter aerogenes, as an electron-dense layer continuous with the inner leaflet of the outer membrane. The method involves 18 hr of tannic acid treatment after fixation in aldehyde prior to osmium tetroxide postfixation, followed by conventional electron microscopy.

Bacteriological Techniques↗
PubMed1985

Vacuolation and infection thread in root nodules of soybean.

Profuse vacuolation takes place in the soybean root nodule cells where infection threads carry rhizobia. After the rhizobia are released the disappearance of the infection thread is attributed to its degradation within large vacuoles which result from fusion of small vacuoles.

Microscopy, Electron↗
PubMed1980

Fractionation and characterization of two morphologically distinct types of cells in Rhizobium japonicum broth culture.

Differential centrifugation of stationary phase broth culture of Rhizobium japonicum yielded two distinct morphological types of bacterial cells, rods, and small coccoid forms with capsulated and non-capsulated cells in each group. The rods usually had polar capsules which resulted in "star" formation. The coccoid bacteria were either free with thick capsular material surrounding the cells or held together in a common capsular sheath forming clusters and chains. 125I soybean. lectin bound to the two types of cells. The binding sites were localized in the capsular material as revealed by colloidal gold- and ferritin-labelled lectin. Both fractions were capable of nodule formation in the soybean.

Lectins↗
PubMed1980

Changes in the outer cell wall of Rhizobium during development of root nodule symbiosis in soybean.

Treatment of soybean root nodule tissue with a nonionic detergent. Nonidet P-40, after aldehyde fixation, results in a selective solubilization of membranes. The cell wall membrane of bacteroids and of free-living Rhizobium is resistant to this treatment. Fragments of "extra" membrane present inside the membrane envelope enclosing the bacteroids are also resistant to the detergent and are morphologically similar to the outer membrane of the cell wall of Rhizobium grown in broth culture. These observations, along with electrophoretic profiles of detergent resistant membranes from nodules, free-living Rhizobium, and isolated nodule bacteroids, suggest that the Rhizobium cell wall membrane undergoes significant changes during establishment of the root nodule symbiosis.

Cell Membrane↗
PubMed1978

Isolation and characterization of the membrane envelope enclosing the bacteroids in soybean root nodules.

The membrane envelope enclosing the bacteroids in soybean root nodules is shown by ultrastructural and biochemical studies to be derived from, and to retain the characteristics of, the host cell plasma membrane. During the early stages of the infection process, which occurs through an invagination, Rhizobium becomes surrounded by the host cell wall and plasma membrane, forming the infection thread. The cell wall of the infection thread is degraded by cellulolytic enzyme(s), leaving behind the enclosed plasma membrane, the membrane envelope. Cellulase activity in young nodules increases two- to threefold as compared to uninfected roots, and this activity is localized in the cell wall matrix of the infection threads. Membrane envelopes were isolated by first preparing bacteroids enclosed in the envelopes on a discontinuous sucrose gradient followed by passage through a hypodermic needle, which released the bacteroids from the membranes. This membrane then sedimented at the interface of 34--45% sucrose (mean density of 1.14 g/cm3). Membranes were characterized by phosphotungstic acid (PTA)-chromic acid staining. ATPase activity, and localization, sensitivity to nonionic detergent Nonidet P-40 (NP-40) and sodium dodecyl sulfate (SDS) gel electrophoresis. These analyses revealed a close similarity between plasma membrane and the membrane envelope. Incorporation of radioactive amino acids into the membrane envelope proteins was sensitive to cycloheximide, suggesting that the biosynthesis of these proteins is primarily under host-cell control. No immunoreactive material to leghemoglobin antibodies was found inside or associated with the isolated bacteroids enclosed in the membrane envelope, and its location is confined to the host cell cytoplasmic matrix.

Adenosine Triphosphatases↗
PubMed1978

Ultrastructure of Rhizobium japonicum in relation to its attachment to root hairs.

In Rhizobium japonicum strain Nitragin 61A76, morphologically distinct types of bacteria were found to occur in yeast extract-mannitol broth cultures, at both mid-log and stationary phases. Of these only the capsular form, characterized by a smooth cell envelope, storage granules (glycogen and poly-beta-hydroxybutyric acid), and an amorphous extracellular capsule, bound soybean lectin. The binding site was localized in the capsular material. Less than 1% of the bacterial population differentiated into these capsular forms, which were also able to attach to the soybean root hair surface.

Cell Membrane↗
PubMed1976

Subcellular localization of cellulases in auxin-treated pea.

Two forms of cellulase, buffer soluble (BS) and buffer insoluble (BI), are induced as a result of auxin treatment of dark-grown pea epicotyls. These two cellulases have been purified to homogeneity. Antibodies raised against the purified cellulases were conjugated with ferritin and were used to localize the two cellulases. Tissue sections were fixed in cold paraformaldehyde-glutaraldehyde and incubated for 1 h in the ferritin conjugates. The sections were washed with continuous shaking for 18 h and subsequently postfixed in osmium tetroxide. Tissue incubated in unconjugated ferritin was used as a control. A major part of BI cellulase is localized at the inner surface of the cell wall in close association with microfibrils. BS cellulase is localized mainly within the distended endoplasmic reticulum. Gogli complex and plasma membrane appear to be completely devoid of any cellulase activity. These observations are consistent with cytochemical localization and biochemical data on the distribution of these two cellulases among various cell and membrane fractions.

Cell Membrane↗
PubMed1974

Cellulase localization in hyphae of Achlya ambisexualis.

Cellulase (EC 3.2.1.4; beta-1, 4-glucan glucanohydrolase) was localized at the ultrastructural level and found to occur in dictyosomes and vesicles, around the periphery of unidentified storage bodies, between the plasmalemma and the cell wall, and on the outer surface of the cell wall in the male strain (E87) of Achlya ambisexualis after treatment with the sex hormone antheridiol.

Cell Wall↗