Biomedical subjects

P D Costas

Publications and source records attributed to P D Costas.

9 recordsLinked to original sources

PubMed1998

Transcutaneous access to retrograde axonal flow.

Transcutaneous entry of fluorescent tracer and subsequent retrograde neuronal transport achieved by the use of dimethyl sulfoxide (DMSO) as a vehicle fluorescent dye dissolved in DMSO and applied topically to the hind limb of rats was found in corresponding dorsal root ganglia; aqueous absorption of tracer dye by neuronal tissue was not demonstrated. This example of transcutaneous access and retrograde transport may have implications as to the entry of various toxins, viruses, chemicals, and therapeutic agents to the nervous system.

Administration, Cutaneous↗

PubMed1995

Hyaluronic acid through a new injectable nerve guide delivery system enhances peripheral nerve regeneration in the rat.

The use of non-neural conduits to bridge gaps in peripheral nerves has been noted in the literature for many years. A logical extension of this concept is the introduction of neurotrophic or growth promoting factors into the lumen. We present here an injectable nerve guide that allows percutaneous access to the microenvironment of the regenerating peripheral nerve within the guide's lumen. Hyaluronic acid, a compound associated with decreased scarring and improved fibrin matrix formation, is added sequentially to the regenerating peripheral rat sciatic nerve via this injectable nerve guide. Assessment of nerve regeneration and reinnervation shows better conduction velocity, higher axon counts, and a trend toward earlier myelination with hyaluronic acid compared with saline. This work not only implies hyaluronic acid's role as an agent that aids nerve growth but also describes a new tool that allows percutaneous access to the milieu of a regenerating nerve.

Animals↗

PubMed1995

Inside-out vein graft repair compared with nerve grafting for nerve regeneration in rats.

The inside-out vein graft is a vein conduit pulled through itself to invert the normal orientation and place the adventitial layer within the lumen of the conduit. Our study compares regeneration of peripheral nerves in the rat through two conduits: inside-out graft of the jugular vein and autogenous nerve graft. In 10 rats, the right jugular vein was harvested, turned inside out, and used to bridge a 10 mm defect created in the right sciatic nerve. The 10 mm nerve segment from the right was then used as a standard nerve graft to bridge a 10 mm gap created in the left sciatic nerve. Rats were sacrificed at 8 and 12 weeks. Regeneration on the inside-out vein graft side showed superior functional results (faster conduction velocities) and improved histological results (greater axon counts) compared with the nerve grafted side. We feel the adventitial surface of the wall of the vein promotes nerve regeneration by providing an environment rich with collagen, laminin, and Schwann cells and promotes increased vascularization of the new nerve.

Action Potentials↗

PubMed1994

Normal sensation of the human face and neck.

A total of 116 adult volunteers were studied to determine normal values for static two-point discrimination and sensation of pressure of the head and neck. Thirteen regions of the head and neck corresponding to major sensory innervation were examined bilaterally for static two-point discrimination with the Mackinnon-Dellon Disk-Criminator and for sensation of pressure with Semmes-Weinstein monofilaments. Perception of two-point discrimination improved from lateral and posterior areas (17 to 25 mm) to the midline toward the lips (3 to 7 mm). Semmes-Weinstein monofilaments proved inadequate in determining sensitivity to cutaneous pressure because of low thresholds in the face and neck. Static two-point discrimination is a reliably reproducible method for assessing sensation of the face and neck.

Adult↗

PubMed1993

Inside-out vein graft promotes improved nerve regeneration in rats.

Vein grafts have been used both experimentally and clinically to bridge gaps in peripheral nerves. This study describes a modification of the vein graft technique in which vein graft conduits are pulled inside-out before anastomosis with proximal and distal nerve stumps. This technique creates an autogenous vein conduit with the collagen-rich adventitial surface exposed to the regenerating axons. The inside-out technique is a fast and simple modification of the standard vein graft technique and produces an accelerated rate of nerve regeneration and significantly earlier myelination compared with the results obtained from the use of polyethylene nerve guides and standard vein graft conduits.

Animals↗

PubMed1993

Sleeve insertion and collagen coating improve nerve regeneration through vein conduits.

Vein grafts have been used as conduits for nerve regeneration in both research protocols and clinical situations. Results to date are encouraging. This study investigated several variations in the vein graft model in an attempt to enhance peripheral nerve regeneration. Results showed that the jugular vein, with an improved suture technique made possible by its larger diameter, is superior to the femoral vein as a conduit for regeneration of the sciatic nerve in the rat. The larger diameter of the jugular vein and its lack of valves provided less hinderance to regenerating axons. Results also showed that coating the luminal epithelium of the jugular vein with type I collagen gel greatly improved regeneration.

Animals↗

PubMed1993

Total versus partial musculofascial coverage for steroid-containing double-lumen breast implants in augmentation mammaplasty.

The use of intraluminal steroids in double-lumen breast implants is effective in preventing fibrous capsular contraction around the implant. This technique has not been accepted widely, however, and remains controversial primarily because steroid-related complications, including extrusion, late inferior migration, and atrophy of the skin, have been associated with their use. This nonrandomized retrospective study of 76 patients (146 breasts) who underwent submuscular augmentation of the breast through inframammary and periareolar incisions compares results after total musculofascial coverage of the implant with partial muscle coverage of the implant. In patients with partial muscle coverage of the implant, 7.8% steroid-related complications were observed. In the group with total musculofascial coverage of the implant, no steroid-related complications and no symptomatic contractions of the capsule were observed. Our study suggests that total musculofascial coverage provides a statistically significant margin of protection from steroid-related complications compared with techniques using only partial muscle coverage of the implant in patients who underwent cosmetic augmentation mammaplasty.

Contracture↗

PubMed1993

Immunocytochemistry of skeletal muscle basal lamina grafts in nerve regeneration.

The influence on nerve regeneration of the extracellular matrix glycoprotein laminin was studied after sciatic nerve transection in 90 outbred Sprague-Dawley rats. Nerve regeneration through basal lamina grafts was comparable with regeneration through traditional nerve grafts across gaps up to 2.0 cm in length. True axonal regeneration rather than axonal branching was demonstrated by retrograde horseradish peroxidase labeling of nerve cables. Pretreatment of basal lamina grafts with antilaminin antibodies reduced the total number of regenerated axons by 90 percent with a significant decrease of nerve conduction velocity and a significant impairment of walking track patterns. The basement membrane glycoprotein laminin serves a critical role in the regeneration of peripheral nerves through basal lamina grafts.

Animals↗

PubMed1983

Transformation of a rabbit progesterone receptor from an 8S form to 5.5S and 4S forms.

The 8S form of the rabbit uterine progesterone receptor transforms slowly at 0 degree C to a 4S form with an intermediate 5.5S form. The transformation is accelerated by either heat, increased ionic strength and dilution of cytosol. The transformation, which is reversibly inhibited by sodium molybdate, is unrelated to total cytosolic alkaline phosphatase activity. The transformation is accompanied by a positive change in receptor surface charge and a decrease in the rate of progesterone dissociation. The stability of the 8S progesterone-receptor complex is reduced and the sedimentation coefficient increased by acidic conditions; acid does not affect the 4S receptor as drastically.

Animals↗