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Biomedical subjects

K Narayanan

Publications and source records attributed to K Narayanan.

At least 91 records · Page 5Linked to original sources
PubMed1986

Studies on the nature of the flap/bed interaction in rodents--Part II: Morphological and fluorescein kinetic data.

The current study in rats concerns two aspects of the flap/bed interaction: fluorescein kinetics and histological finding. In the control group of animals in the fluorescein kinetics experiment, flaps were raised and then reattached. In one experimental group, the flaps were raised and placed on a sterile polyethylene film. In two other groups, the flaps were raised and then the pedicle was cut, either immediately or at specific intervals. At intervals up to 24 hours several animals were injected with 5% fluorescein. In the control group fluorescein penetration increased with time, while it decreased in the polyethylene-film group. There was virtually no fluorescein staining in both cut-pedicle groups. To study histological events, the animals were divided into groups with flaps and groups in which the distal end of each flap was severed to form a contiguous skin graft. Other conditions were varied. All flaps were cultured, and biopsy specimens were obtained from three areas at several time intervals. Histological sections from the distal flap were markedly different from the corresponding skin grafts. These results corroborate previously noted survival rates.

Animals↗
PubMedDate not supplied

Residual silicone detection using MRI following previous breast implant removal: case reports.

The current controversy surrounding the safety of silicone gel breast implants has resulted in an increasing number being removed. Although previous reports have suggested that remnants of the implant capsule are reabsorbed after explantation surgery, the persistence of the capsule in fact may be associated with implant fragments and silicone gel leakage. In this study we have used magnetic resonance imaging (MRI) to identify residual silicone gel and silicone granulomas following the removal of silicone gel breast implants. Four representative clinical case reports are presented. These patients, who had residual silicone present in their bodies, presented to us with breast pain, palpable masses, or abnormal calcific mass densities apparent on a mammogram. High-resolution MRI images were found to be helpful in identifying local and remote collections of silicone gel, silicone granulomas, and residual capsules that were incompletely removed from previous explantation surgery. MRI breast images demonstrated high resolution and provided the accurate anatomical locations of residual silicone gel and silicone granulomas in all the regions of breast parenchyma, chest wall muscles, and axillae. Patients with persistent local symptoms following explantation surgery may benefit from an evaluation of the breast using MRI.

Adult↗
PubMedDate not supplied

Carotenoids of an Antarctic psychrotolerant bacterium, Sphingobacterium antarcticus, and a mesophilic bacterium, Sphingobacterium multivorum.

The major carotenoid pigments of an Antarctic psychrotolerant bacterium, Sphingobacterium antarcticus, and a mesophilic bacterium, Sphingobacterium multivorum, were identified as zeaxanthin, beta-cryptoxanthin, and beta-carotene. Analysis was based on ultraviolet-visible spectroscopy, mass spectroscopy, and reversed-phase HPLC. Photoacoustic spectroscopy of intact bacterial cells revealed that the bulk of the pigments in S. antarcticus and S. multivorum was associated with the cell membrane. In vitro studies with synthetic membranes of phosphatidylcholine demonstrated that the major pigment was bound to the membranes and decreased their fluidity. The relative amounts of polar pigments were higher in cells grown at 5 degrees C than in cells grown at 25 degrees C. In the mesophilic strain, the synthesis of polar carotenoids was quantitatively less than that of the psychrotolerant strain.

Antarctic Regions↗
PubMedDate not supplied

Magnetic ports in tissue expanders--a caution for MRI.

Although a great deal is known about the potential hazards of ferromagnetic materials relative to MRI, little has been written about the safety of tissue panders. Recently a new modification of the existing ports has been made available by incorporating a magnet for ease of identification of the injection site. Despite its low mass, the intrinsic magnetic field presents a contra-indicating factor due to the potential for torque and movement in the presence of the strong magnetic field found in the clinical MR imagers. With any evidence of tissue expander prosthesis obtained in the history, a careful questioning about the possibility of a magnetic port should be carried out.

Equipment Safety↗
PubMedDate not supplied

NF-kappaB is essential for induction of pro-inflammatory cytokine genes by filarial parasitic sheath proteins.

The transcription factor NF-kappaB plays critical roles in immune and inflammatory responses. Here we show that filarial parasitic sheath proteins cause activation of NF-kappaB in the airway epithelial HEp-2 cell line. This activation was transient and saturable, and involved degradation of the cytoplasmic inhibitor protein IkappaBalpha. Stable expression of IkappaBalpha mutated at Ser32 and Ser36 to Ala caused inhibition of NF-kappaB activation, indicating that this activation involves the IkappaB kinase-mediated pathway. Moreover, while it did not influence the HEp-2 cell survival, selective blockade of NF-kappaB activation resulted in inhibition of the expression and the secretion of pro-inflammatory cytokines, tumor necrosis factor-alpha, interleukin-6 and interleukin-8. Thus, initial transient activation of NF-kappaB resulted in profound and long-term effects on epithelial cell responses to filarial parasitic proteins. These findings implicate an important role for NF-kappaB in orchestrating inflammatory reactions associated with tropical pulmonary eosinophilia.

Animals↗