The specific localization and the characterization of the parathyroid hormone (PTH) receptor in bone have been studied using 18-d embryonic chick calvariae and biologically active, electrolytically labeled [1251] bovine PTH(I-34). Binding was initiated by adding [12Sl]-bPTH(I-34) to bisected calvariae at 30°C. Steady state binding was achieved at 90 min at which time 10 mg dry wt of calvaria specifically bound 17% of the added [12Sl]bPTH (I-34). Nonspecific binding in the presence of 244 nM unlabeled bPTH(1-34) was <2%. Insulin, glucagon, and calcitonin (I/~g/ml) did not compete for PTH binding sites. Half-maximal inhibition of binding was achieved at concentrations of unlabeled bPTH(1-34) or bPTH(I-84) of about 10 nM. The range of concentration (2-100 nM) over which bPTH(1-34) and bPTH(I-84) stimulated cyclic 3'5'adenosine monophosphate (cAMP) production was similar to that which inhibited the binding of [12Sl]bPTH(I-34). Light microscope autoradiograms showed that grains were concentrated over cells (osteoblasts and progenitor cells) at the external surface of the calvariae and in trabeculae. In the presence of excess unlabeled PTH, labeling of control autoradiograms was reduced to near background levels. No labeling of osteocytes or osteoclasts was observed. At the electron microscopic level, grains were localized primarily over cell membranes. A quantitative analysis of grain distribution suggested that cellular internalization of PTH occurred.Parathyroid hormone (PTH) acts directly on bone acutely to increase bone resorption and decrease bone formation (1, 2) and chronically to increase both bone resorption and bone formation (3). These actions are mediated by the ceUular elements of bone by mechanisms involving, at least in part, the stimulation of cyclic Y,5' adenosine monophosphate (cAMP) production (4, 5). The evidence available indicates that PTH directly or indirectly influences all bone cells (osteogenic precursors, osteoblasts, osteocytes, and osteoclasts) (6-9); however, recent reports (10, 11) which describe the effect of PTH on cAMP production in osteoblastlike or osteoclastlike cells in monolayer culture implicate the osteoblast as the major osseous target cell of PTH.During the past five years, major advances in the production of biologically active, high specific-activity, radioiodinated preparations of PTH have made it possible to investigate the previously elusive PTH receptor in kidney (12). It is only recently that similar progress has been made in the identification and characterization of PTH receptors in bone: using electrolytically [L2SI]-labeled, receptor-purified, synthetic bo-

Electron microscope autoradiographs were prepared of IM-9 human cultured lymphocytes incubated with iodine-125-labeled insulin. With the use of [125I]insulin and Ilford L-4 emulsion, the technique had a resolution half-distance of approximately 0.085 micrometer. Autoradiographs revealed a time-dependent entry of insulin into the cell interior that was maximal after 30 minutes of incubation. At this time point nearly 40 percent of the [125I]insulin was in the interior of the cell at a distance 1 micrometer or greater from the plasma membrane. Grain distribution and volume density analyses revealed that the intracellular insulin was concentrated in the endoplasmic reticulum and nuclear membrane.

No abstract

Electron microscope autoradiographs were prepared from diabetic rat pancreatic acini that had been incubated with 125I-insulin. Distribution histograms of the distance of the 125I-insulin silver grains from the nearest plasma membrane were prepared and compared with a histogram of an 125I line source. After 3 min of incubation, insulin was located predominately on the plasma membrane, but even at this early time 15% of the grains had an intracellular location. After 30 min of incubation, there was a decrease in grains on the plasma membrane and an increase (to 45%) in grains localized in the cell. At both times of incubation, a comparison of the distribution of the insulin grains overlying subcellular organelles to a theoretical random grain distribution pattern indicated that the intracellular distribution of insulin grains was nonrandom. At 3 min, there was a relative concentration of grains over the plasma membrane and vesicles with an average diameter of 100 nm. At 30 min, there was a concentration of grains over the plasma membrane, 100-nm vesicle, and Golgi. These studies suggest that 125I-insulin is internalized into pancreatic acinar cells in a time-dependent manner and then is nonrandomly distributed inside the cell.

Aims To compare the efficacy of the high specificity Frequency Doubling Technology (FDT) Perimeter Screening Program (C-20-1) to standard threshold automated perimetry in the diagnosis of open-angle glaucoma. Methods A total of 100 consecutively presenting patients attending a glaucoma clinic who volunteered for the study (approximately 30% of whom were attending for an initial visit) were examined with the FDT C-20-1 Screening Program and with the Humphrey Field Analyzer (HFA) SITA Fast algorithm and Program 24-2. Results Of the patients, 17 were excluded due to unreliable visual field results or nonglaucomatous ocular abnormalities. In all, 10 patients were diagnosed as normal, 54 with open-angle glaucoma, eight with ocular hypertension, and 11 as glaucoma suspects. Of the 54 glaucomatous patients, 45 exhibited high-tension glaucoma and nine normal tension glaucoma. Perimetry with the HFA gave a sensitivity of 81.5% for the combined category of glaucoma and glaucoma suspect and a specificity of 83.3% for the combined category of normal and ocular hypertension. Perimetry with the FDT gave a sensitivity of 74.5% and a specificity of 85.2% compared to that of the HFA. Conclusion In the detection of glaucoma, Program C-20-1 of the FDT perimeter exhibits high specificity. It exhibits low sensitivity for the detection of mild loss but high sensitivity for advanced field loss relative to Program 24-2 and the SITA Fast algorithm of the HFA.