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Biomedical subjects

N Dan

Publications and source records attributed to N Dan.

26 records · Page 2Linked to original sources
PubMed1996

Formation of ordered domains in membrane-bound DNA.

The interactions between DNA molecules adsorbed on fluid membranes are calculated. The adsorbing DNA perturbs the equilibrium packing of the lipids, thereby giving rise to membrane-induced, attractive interactions. These balance the direct repulsive interactions between DNA molecules. As a result, DNA adsorbed on membranes is predicted to form ordered domains characterized by a finite spacing, which varies with the membrane characteristics and the solution Debye screening length. Comparing the model predictions to recent experiments (Yang et al. 1996) yields excellent agreement with only one free (i.e., experimentally unknown) parameter.

Adsorption↗
PubMed1996

Bone replacement in head and neck surgery: a biocompatible alternative.

BACKGROUND: Defects in the skull have presented difficult reconstructive problems. Recently glass-ionomer cement and preformed. implants have been used to repair bony defects in the skull base and in cranio-facial surgery. Three patients are reported to illustrate possible applications for this new material. METHODS: Ionocap cement and Ionoroc-skull standardized implants have been used. The cement is available as a two component blister pack. When mixed and blended a gel is produced which can be worked for approximately 5 min before hardening. It can then be contoured and drilled to the required shape. The resultant material is biocompatible and biostable, is non-toxic and permanently bonds to bone with no increase in temperature or shrinkage. RESULTS: The material has been used to fill the temporal defect left by transplantation of the temporalis muscle for oral reconstruction, the anterior and lateral walls of the maxilla and following craniofacial resection, the posterior wall of the frontal sinus and anterior skull base. CONCLUSIONS: Three patients with different reconstructive problems have been presented to illustrate the use of an alloplastic material that has a tensile strength similar to bone and firmly adheres to it. The material was found to be safe and easy to use. All three patients have now been followed for 12 months with no adverse affects.

Aged↗
PubMed1994

Transcytosis and processing of intrinsic factor-cobalamin in Caco-2 cells.

Intracellular events within enterocytes following receptor-mediated endocytosis of intrinsic factor-cobalamin (IF-Cbl) are poorly understood. We have examined the fate of IF and Cbl in filter-grown Caco-2 cells which express both IF receptors and transcobalamin II and which transcytose Cbl. Uptake of IF-Cbl from the apical surface leads to the intracellular accumulation of Cbl in a process that reaches an equilibrium between internalization and secretion only after a 20-h continuous incubation. Transcytosed Cbl is detectable in the basolateral medium 4 h after the onset of endocytosis. Cbl is released from the basolateral surface with the same kinetics irrespective of from which cell surface endocytosis of IF-Cbl took place. Following uptake, internalized IF is degraded with a half-time of 4 h. Leupeptin causes a partial block in the proteolysis of IF, an intracellular accumulation of Cbl bound to IF, and a decrease in transcytosis of Cbl. Finally, an analysis of intracellular Cbl during transcytosis shows that free Cbl is present within cells during transcytosis.

Biological Transport↗
PubMed1992

An extraskeletal chondrosarcoma arising in the brachial plexus.

A case of extraskeletal chondrosarcoma of the left brachial plexus is described with emphasis on the diagnostic and therapeutic difficulties of this site. With combination therapy the patient survived 6 years. Recurrent disease in the plexus region and adjacent spinal cord resulted in a painful, flail limb.

Brachial Plexus↗
PubMed1989

[Scavenging effects of probimane on active oxygen free radicals by electron spin resonance].

Probimane, dl-1,2-bis (4-morpholine-methyl-3, 5-dioxopiperazin-1-yl) propane, is a new antitumor agent synthesized by Shanghai Institute of Materia Medica, Chinese Academy of Sciences. The scavenging effects of probimane on active oxygen radicals produced in 3 different systems were studied with the ESR spin trapping methods. In Fenton's reaction, probimane remarkably scavenged hydroxyl radicals (.OH) and the rate of scavenging .OH by probimane 0.05 mmol/L was 47%, compared to 5% by vitamin E (VE) and 30% by ascorbic acid (AA). In irradiation riboflavin system, in which superoxide (O2-.) was produced, the agent also had the scavenging effects on O2(-.). The rate of scavenging O2-. by probimane 0.05 mmol/L was 13%, higher than that by VE (7%) but lower than that by AA (90%). In cell system where the active oxygen radicals were produced during the respiratory burst of human neutrophils (Neu) stimulated by TPA (tetradecanoylphorbol acetate), probimane exhibited a dose-dependent scavenging action on the radicals. The rate of the radical scavenging by probimane 0.05 mmol/L was 37%, much higher than that by VE (9%) but lower than that by AA (68%). Probimane had no effect on the rate of oxygen consumption by human Neu, measured with spin probe oxymetry.

Antineoplastic Agents↗
PubMed1980

Urinary retention and intervertebral disc protrusion.

The case histories of 17 patients in whom urinary retention was associated with an intervertebral disc protrusion which occurred, most commonly, centrally at the lumbar 4/5 level are presented. Strong pleas are made for consideration of this entity in patients with unexplained urinary retention.

Adult↗