Norman C Nelson

Portal and Peripheral Vein Immunoreactive Insulin Concentrations Before and After Glucose Infusion

Catheterization of the portal vein via the umbilical vein was performed under local anesthesia in twelve nondiabetic subjects prior to exploratory laporatomy for a variety of conditions. Immunoreactive insulin (IRI) in simultaneously obtained portal and peripheral vein plasma was determined before, during, and after a two-minute glucose infusion (25 gm.). Two phases of insulin secretion were apparent from portal vein IRI concentrations. A rapid secretory phase beginning one minute after start of the infusion and lasting three to four minutes was followed by a slower secretory phase beginning approximately ten minutes after start of the glucose infusion. The absolute amount of “big” insulin (proinsulin-like material) in the portal vein was similar during the first phase and the early part of the second phase of insulin secretion. A significant positive correlation between portal vein and peripheral vein IRI responses to glucose was noted.

A Technique for Retinal Pigment Epithelium Transplantation for Age-Related Macular Degeneration Secondary to Extensive Subfoveal Scarring

We describe the surgical excision of submacular scar in end-stage age-related macular degeneration and transplantation of autologous and homologous retinal pigment epithelial (RPE) cells. The technique involves the preparation of a large retinal flap encompassing the macula and the arcades, removal of the submacular scar, and replacement of the RPE cells, using either an autologous pedicle graft or homologous RPE cells and Bruchs membrane. Fourteen months following the procedure, visual acuity in a patient with a pedicle graft had improved from counts fingers to 20/400 and the patient fixated over the transplanted RPE cells. After 10 months, a homologous graft in a second patient had become encapsulated with a fine subretinal membrane without neovascular tissue; visual acuity had not improved. No intraoperative or postoperative complications resulting from the surgery occurred in either patient.

Portal and Peripheral Vein Immunoreactive Glucagon Concentrations After Arginine or Glucose Infusions

Catheterization of the portal vein via the umbilical vein was performed under local anesthesia in eight nondiabetic subjects before exploratory laparotomy for a variety of conditions. Levels of immunoreactive glucagon (IRG) and immunoreactive insulin (IRI) were determined in simultaneously obtained portal and peripheral vein plasma before, during and after a fifteen minute arginine infusion (30 gm.) in five subjects. The mean portal vein to peripheral vein glucagon ratio in the postabsorptive state was 1.7 ± 0.5. A biphasic portal vein IRG response to arginine was observed, with the initial glucagon peak occurring within one minute of the beginning of the infusion. Peripheral IRG concentrations did not reflect the biphasic response. The portal vein IRI response to arginine was also mildly biphasic, and the first phase occurred before a detectable increase in blood glucose. The portal vein IRG peak either preceded or coincided temporally with the portal vein IRI peak. In three nondiabetic subjects, portal vein IRG decreased rapidly to its nadir within two minutes after a two minute glucose infusion (25 gm.) was started.

Portal Vein Insulin Concentrations in Diabetic Subjects

Portal vein immunoreactive insulin (IRI) concentrations following intravenous glucose were compared in diabetics and nondiabetics. Diminished pancreatic insulin secretion rather than extrapancreatic factors explains the peripheral insulinopenia observed in diabetics. Early insulin release (acute pool) was impaired more than delayed release (chronic pool) in the diabetics.

Posterior relaxing retinotomies: analysis of anatomic and visual results.

Fifteen eyes with complicated retinal detachments--11 with proliferative vitreoretinopathy (C3 D3), 2 with posterior segment trauma, and 2 with inflammatory retinopathy--were treated with vitrectomy, membrane peeling, and large posterior retinotomy. All posterior relaxing retinotomies were circumferential, including temporal quadrants in all cases. With a minimum follow up of 6 months, 12 eyes (80%) were attached posterior to the retinotomy. Reproliferation resulted in redetachment in 3 eyes (20%). Visual acuity improved in 53%, remained unchanged in 20%, and decreased in 27%. Of the 11 eyes that achieved stable or improved visual acuity, 5 (45%) achieved 20/400 to 20/25 vision, 5 achieved counts fingers perception, and 1 patient remained stable at hand motion perception. Of all the eyes undergoing surgery, hypotony (intraocular pressure < 5 mm Hg) occurred in 6 eyes (40%); 3 of these were among the 12 eyes with attached retinas.

Influence of the Vagus Nerves on Pancreatic Insulin Secretion

The effect of short and long-term faradic stimulation of the vagus nerves on pancreatic immunoreactive insulin (IRI) release was assessed in dogs. In the present study stimulation of the vagus nerves at the level of the diaphragm or in the neck did not enhance pancreatic IRI release. The only significant effect was a transient fall in pancreatic vein IRI values immediately after stimulation was begun.

Internal choroidectomy of posterior uveal melanomas under a retinal flap

Local excision of uveal melanoma is an intriguing therapeutic modality in selected cases. An internal choroidectomy under a retinal flap has been developed as an alternative to retinochoroidectomy in managing posterior pole melanomas. This technique offers more adequate preservation of retinal architecture, thus potentially enhancing central visual function in patients with tumors located close to the fovea.

Surgical management of incarcerated retina in the sclerotomy

We used perfluoroperhydrophenanthrene (Vitreon) to release an incarcerated retina successfully from the pars plana sclerotomy site.

Bimanual technique of subfoveal neovascular membrane removal in presumed ocular histoplasmosis

We describe a bimanual technique of subfoveal neovascular membrane removal in a patient with presumed ocular histoplasmosis syndrome. His postoperative vision has improved from 20/400 to 20/100 at 3 months follow-up. No recurrence of the membrane was noted.