Localization of immunoreactive cholecystokinin precursor to amacrine cells and bipolar cells of the macaque monkey retina.

We used antisera that recognized precursors of the neuropeptide cholecystokinin extended at the carboxyl terminus in an immunocytochemical study of the macaque retina. A subpopulation of bipolar cells with long, obliquely oriented dendrites was labeled. Their axons terminated exclusively in the fifth stratum of the inner plexiform layer, where they contacted processes of amacrine and ganglion cells. Based on their morphology, these cells appeared to be the type that contacts short-wavelength cones selectively. Two types of amacrine cells were also labeled, and processes from both types formed dense plexuses in the second and fourth strata of the inner plexiform layer. The majority of their synaptic connections were with other amacrine cells, but they had more contacts with bipolar cell axons and retinal ganglion cell dendrites than any other peptidergic cells in the macaque retina. We studied extracts of macaque retina with gel-filtration chromatography and radioimmunoassays to confirm our immunohistochemical results. We found cholecystokinin octapeptide and other immunoreactive forms that were amidated at their carboxyl termini and were therefore likely to be biologically active. Unlike most other regions of the CNS, however, the retina had relatively low concentrations of amidated forms, and forms with extended carboxyl termini that are presumably their precursors were far more abundant. These findings suggest that the rate of cholecystokinin synthesis in the retina is quite high, as we would expect if the peptide were found in tonically active neurons.

The binding of somatostatin to the mouse retina is altered by the pearl mutation.

Pearl mutants have a night-blind phenotype and abnormal optokinetic nystagmus. Preliminary results from another study showed that the light responses of retinal ganglion cells of pearl mutant mice were affected by bathing the isolated retina with low (less than 1 nM) concentrations of either somatostatin-14 or -28, whereas the responses in wild-type retinas were affected only by somatostatin-28. In order to test the possibility that these physiological differences resulted from alterations in receptor affinity, we studied the binding of 125I-[Tyr11]-somatostatin-14 and 125I-[Leu8,D-Trp22,Tyr25]-somatostatin-28 to frozen, unfixed sections of eyes of wild-type (C57BL/6J +/+) and congenic pearl mutant (C57BL/6J-pin pe(pin)/pe(pin)) mice. As found previously for wild-type mice, specific binding occurred in 3 maxima in pearl mutants: a broad band extending from the retinal ganglion cell to the inner nuclear layer, a narrow and inconstant band over the outer plexiform layer, and a band over the pigment epithelium and choroid. We quantified the label over the inner plexiform layer and found evidence for a single saturable site in both genotypes. However, several results indicate that somatostatin-14 binds more avidly to pearl mutant retinas than to wild-type retinas. In saturation binding studies, Kd for 125I-[Tyr11]-somatostatin-14 was 600 pM in pearl mutants vs 1.5 nM in wild-type; whereas, for 125I-[Leu8,D-Trp22,Tyr25]-somatostatin-28, Kd was nearly equal in the two genotypes (500 and 625 pM, respectively). Bmax was nearly equal for both ligands in both genotypes (63-69 fmol/mg protein).(ABSTRACT TRUNCATED AT 250 WORDS)

Localization and characterization of somatostatin binding sites in the mouse retina.

We studied the binding of [125I]Tyr11-somatostatin-14 and [125I]Leu8,D-Trp22,Tyr25-somatostatin-28 to frozen, unfixed sections of C57BL/6J mouse eyes with autoradiography. Specific binding of both ligands occurred in 3 maxima, a broad band extending from the retinal ganglion cell to the inner nuclear layers, a narrow and inconstant band over the outer plexiform layer, and a band over the retinal pigment epithelium and choroid. We quantified the label over the inner plexiform layer and found evidence for a single, saturable binding site after Scatchard analysis of saturation binding data. With [125I]Tyr11-somatostatin-14 the dissociation constant (Kd) was 1.48 nM and the total number of binding sites (Bmax) was 68 fmol/mg protein; in competition experiments the inhibitory binding constant (Ki) was 900 pM for somatostatin-14 and 350 pM for somatostatin-28. With [125I]Leu8,D-Trp22,Tyr25-somatostatin-28, Kd was 625 pM and Bmax was 69 fmol/mg protein; in competition experiments Ki was 4.58 nM for somatostatin-14 and 710 pM for somatostatin-28. These results demonstrate the existence of somatostatin receptors in the inner plexiform layer of the retina that appear to have greater specificity for somatostatin-28 than for somatostatin-14.

Distinguishing features of idiopathic flushing and carcinoid syndrome.

We compared the clinical and biochemical profiles of 11 patients with idiopathic flushing (IF) with those of eight patients with carcinoid syndrome (CS). Patients with IF were more often women, had a longer duration of symptoms, and were younger. Palpitations, syncope, and hypotension occurred only in patients with IF, while wheezing and abdominal pain occurred only with CS; diarrhea occurred in both types of patients. Elevated blood serotonin levels were present primarily in CS. Increased levels of urine 5-hydroxyindoleacetic acid was specific for CS but unsufficiently sensitive to detect all cases. Abnormalities of gut and vasoactive peptides failed to distinguish the two conditions. Flushing in carcinoid patients responds uniformly to octreotide (Sandostatin), but only one third of the patients with IF are relieved of the symptom. Patients with IF have features that distinguish them from individuals with flushing from other causes, such as CS, postmenopausal state, chlorpropamide-alcohol flush, panic attacks, medullary thyroid carcinoma, and autonomic epilepsy. Familiarity with the clinical and biochemical features of IF should facilitate evaluation and identification of these patients.

Pulmonary function in thyroid carcinoma metastatic to the lung.

Pulmonary testing was carried out in 12 of 35 consecutive cases of differentiated thyroid carcinoma metastatic to the lung, which were identified in a retrospective analysis covering the 22-yr period from 1962-1984. In 7 of the 12 patients, pulmonary function tests showed abnormalities. Impaired pulmonary function was associated with a poor prognosis. Four of the twelve patients died; each had impaired pulmonary function and their ages (12-65 yr) were similar to those still living (13-65 yr). Specific types of functional abnormalities were not associated with pulmonary metastases, and underlying pulmonary disease contributed to the findings in some patients. Four patterns were defined on chest radiographs: macronodular, micronodular, miliary, and normal, but these patterns did not correlate with outcome. Scintiscan patterns varied from normal to diffuse concentration of 131I. Generally, following therapy with radioiodine, fewer abnormalities on chest x-ray and less uptake of 131I in the lungs was noted. However, therapy with radioiodine did not improve pulmonary function. Pulmonary function testing appears to be a better predictor of outcome in patients with thyroid carcinoma metastatic to lung than chest x-ray appearance or scintigraphic scanning.