Steven Price

Electrical responses of pancreatic islet cells to secretory stimuli

Abstract The electrical activity of beta-cells of mouse islets of Langerhans was recorded in response to varying concentrations of glucose, mannose, and calcium. The electrical activity parallels insulin secretion and is reversible and independent of time within the periods recorded. The results suggest that sugars stimulated insulin secretion by adsorption to a membrane glucoreceptor which induces electrical activity.

Specific anosmia to geraniol in mice

The ability of Swiss mice to detect geraniol, menthol, benzaldehyde, and salicylaldehyde was tested by an active avoidance paradigm. Fourteen animals with specific anosmia to geraniol were obtained. Of these, seven were also unable to detect phenylethyl alcohol. Both compounds have similar odor quality in humans and are believed to stimulate the same receptors. The data on the specifically anosmic mice suggest that these structurally dissimilar compounds are detected by the same receptors in mice.

Pancreatic islet cell membranes: Extraction of a possible glucoreceptor

Abstract Solubilized cell membranes of dog pancreatic islets, in contrast to membranes from acinar cells, include a component which forms complexes with glucose, mannose, and fructose, each of which is a stimulus to insulin secretion. Galactose and 3-O- methylglucose , which are not secretory stimuli, are not complexed. Thus, this component has the specificity expected of the receptor site through which these cells are stimulated to secrete insulin.

Effects of antibodies against odorant binding proteins on electrophysiological responses to odorants

Monoclonal antibodies against two olfactory mucosal proteins, one with affinity for anisole-like and the other for benzaldehyde-like compounds, were applied to mouse olfactory epithelium. Responses to three odorants (anisole, benzaldehyde and amyl acetate) were measured. Of 26 antibodies, three (12%) inhibited responses only to the odorant with affinity for the antigen, nine (35%) inhibited responses to all three odorants, and 14 (54%) were without effect. None reduced responses by as much as 50%. The data support the hypothesis that there is a class of related proteins in olfactory neuronal cell membranes that function as receptor molecules and that other mechanisms also mediate odorant stimulation.

Effects of odorant mixtures on olfactory receptor cells.

The general mechanisms by which chemical stimuli may influence the firing frequency of olfactory neurons were briefly described. They include specific mechanisms mediated by receptor molecules and nonspecific mechanisms involving general properties of the chemicals and of cells. It is difficult to imagine that odorant mixtures influence receptor cells by mechanisms that are fundamentally different from those by which homogeneous chemicals act. It is argued that even under the best experimental conditions the presentation of odorants usually or always involves exposing the receptor cells to more than one additional molecular species compared to the unstimulated condition. This is because odorants invariably have contaminants that may be of potency such that their contribution to the odor is large even though their contribution to the number of molecules in the stimulus stream is small. Furthermore, the partition coefficients of the major and minor components are unlikely to be identical; therefore, their relative concentrations in the aqueous environment of the receptor cells can differ greatly from that in the gas phase. Finally, metabolic transformations of odorants in the olfactory mucosa can result in the exposure of receptor cells to mixtures of odorant and metabolites, with the mixture composition varying with time. Finally, some pitfalls in analyzing the effects of odorant mixtures are discussed. At the very least, it is necessary to determine the relation of concentration to response for each odorant in the mixture in order to interpret results in terms of interactions. Even with such data caution must be used, especially in attaching significance to reductions in the apparent maximal responses to one odorant induced by the presence of the other.

An alternative to allosteric interactions as causes of sigmoid dose versus response curves application to glucose-induced secretion of insulin

It is shown that a sigmoid dose vs. response curve will occur in any biological system in which the stimulant compound must diffuse significant distances to reach responding cells, even when the cells themselves respond according to Michaelis-Menten kinetics. Isolated pancreatic islets releasing insulin in response to glucose stimulation have been used as a specific example. Since diffusion and/or other physical processes can produce global effects which could account for the sigmoidal nature of a dose vs. response curve, the existence of complex molecular mechanisms of hormone-receptor interaction can not be inferred solely from the character of a dose vs. response relation.

Benzaldehyde Binding Protein from Dog Olfactory Epitheliuma

A protein with a high affinity for o-methyl phenols, of which the odorant anisole is the simplest compound, has been extracted from dog olfactory epithelium.’ Called anisole binding protein, it was hypothesized to be a receptor for odorants of the anisole type. Further studies on it and isolation of a benzaldehyde binding protein are reported here. “Anisole” and “benzaldehyde” columns were prepared by covalently coupling panisic acid and p-carboxybenzaldehyde, respectively, to o-aminobutyl agarose via the carboxyl groups. Olfactory epithelium from dog nasal septum was extracted with 0.1 M Tris buffer, pH 7.2, and the residue was reextracted with the same buffer to which 0.1% sodium dodecyl sulfate had been added. The resulting extract was subjected to affinity chromatography on the two columns consecutively, and the anisole and benzaldehyde binding proteins were displaced from the columns by addition of 1 mMpanisic acid or p-carboxybenzaldehyde, respectively. The eluates from the columns were subjected to polyacrylamide gel slab electrophoresis? Protein on the slabs was visualized by silver ~taining.~ Rabbits were immunized with anisole or benzaldehyde binding protein, and sera from them were tested for their effects on electroolfactograms (EOGs) of sagitally bisected heads of male ICR mice? Except for the method of EOG recording and the use of slab rather than disc electrophoresis, the methods used in this study were essentially the same as those described previously.’ The electrophoretic patterns obtained from elution of the columns are shown in FIGURE 1. Nearly all the protein passes through the columns freely, eluting with Tris buffer (tracks B and E). After the buffer-elutable protein has cleared the column (tracks C and F), p-anisic acid and p-carboxybenzaldehyde displace additional protein from the anisole and benzaldehyde columns, respectively (tracks D and G). These are the anisole and benzaldehyde binding proteins. From their mobilities relative to those of the standards, their molecular masses are estimated to be about 61,000 daltons. Effects of antisera and control sera (sera from the same rabbits, taken before immunization) on EOG responses to anisole, benzaldehyde and isoamyl acetate are shown in TABLE 1. The control sera have no significant effects. The serum from the rabbit immunized with anisole binding protein abolished the response to anisole and reduced the responses to the other odorants to about one-third. Serum from the rabbit immunized with benzaldehyde binding protein reduced responses to all three odorants to about one-third.

Dimethyl Sulfoxide Failure to Penetrate Encysted Artemia Embryos

Summary These results demonstrate the impermeability of Artemia cysts to DMSO. There was no evidence of DMSO penetration even after 9 days, and hydrated cysts shrunk rapidly when placed into hyperosmotic DMSO solutions. DMSO, at 2.1%, appears to have no particular toxicity to the eggs or to the free-swimming nauplii.