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Biomedical subjects

S Dasgupta

Publications and source records attributed to S Dasgupta.

At least 181 records · Page 10Linked to original sources
PubMedDate not supplied

In vivo effect of the tus mutation on cell division in an Escherichia coli strain where chromosome replication is under the control of plasmid R1.

The phenotypic effect of the tus::kan mutation in an Escherichia coli strain, where the chromosome is replicated unidirectionally by an integrated R1 miniplasmid, was examined by flow cytometry and phase fluorescence microscopy. The tus+ cells exhibited perturbed cell division, as indicated by the presence of many elongated cells and filaments. Inactivation of the tus gene led to a reduction in the frequency of such elongated cells, presumably by eliminating Tus-mediated polar arrests of replication forks at ter sites, thereby shortening the time required for completion of chromosome replication.

Bacterial Proteins↗
PubMedDate not supplied

Analysis of the bacterial cell cycle using strains in which chromosome replication is controlled by plasmid R1.

As an alternative approach in the study of the Escherichia coli cell cycle, we have constructed strains in which chromosome replication is under the control of various plasmid R1 derivatives, IntR1 strains. The physiological properties of such strains are described. In intR1 strains, chromosome replication can be manipulated independently of cell-cycle-related control mechanisms, and the effects on cell division can be analysed. Using this approach, we have found that the timing of replication during the cell cycle is random in intR1 strains, that overreplication of the chromosome is lethal, and that chromosome replication does not trigger cell division. Current investigations include the study of the E. coli cell cycle in the absence of the DnaA protein, the effect on cell division of a specific inhibition of the initiation of chromosome replication, and the molecular basis of uni- and bidirectional replication.

Cell Cycle↗
PubMedDate not supplied

Additional alkaloids of Pachygone ovata.

Pachygone ovata (Menispermaceae), indigenous to the sandy seashores of southern India, is a woody climber whose fruits have been used as a rodenticide and fish poison. Chromatography of the extract of the roots resulted in the reisolation of the alkaloids liriodenine, coclaurine, trilobine (1), and magnoflorine and the isolation of stepholidine, coreximine, isoboldine, norjuziphine, and nortrilobine (2). Nortrilobine (2) is a new dibenzo-p-dioxin bisbenzylisoquinoline alkaloid whose structure was established by a consideration of spectral data and conversion to isotrilobine (3).

Alkaloids↗
PubMedDate not supplied

Transpectoral anterior approach to the axilla for lymph node dissection in association with mastectomy preserving both pectoral muscles and their neurovascular bundles.

In Patey's mastectomy, which is still the most common operation for breast cancer, axillary node dissection (AND) is performed through the base of the axilla after retracting the pectoralis major muscle and excising the pectoralis minor muscle (some surgeons preserve the latter). This has the disadvantage of inadequate exposure of the axilla and the risk of damage to the neurovascular bundles supplying the pectoral muscles, which in the long run may lead to atrophy of these muscles. A transpectoral anterior approach to the axilla for AND in association with mastectomy was attempted in 115 cases to obviate the above-mentioned disadvantages. The approach included: 1) splitting of the pectoralis major between the clavicular and sternal fibers; 2) mobilization and swinging of the pectoralis minor into different directions by means of a sling to facilitate AND at selected levels. The major advantages of this approach were: 1) total preservation of both pectoral muscles with their neurovascular bundles maintained the normal anatomy and function of the shoulder; 2) the axilla was directly approached through the anterior wall instead of through the base; in this way the axillary contents were exposed almost at surface level; 3) the dissection plane could be limited to anterior to and below the axillary vein and the risk of postoperative lymphedema could thus be minimized; 4) change of position of the ipsilateral arm was not necessary; 5) the duration of surgery was reduced. Monoblock ablation of significant and suspected tissues, maintaining the normal anatomy and function of the shoulder, could be easily accomplished with this approach.

Adult↗