Nurse practitioners in primary care III. The southern Ontario randomized trial

A group of nurses who formerly had performed office functions received a special university-based educational program designed to prepare them to assume much of primary care management as nurse practitioners. The associated family physicians would shift their role to general supervision and attention to difficult clinical problems. To test this new form of practice, two complementary randomized trials have been conducted in south-central Ontario. The particular trial reported here was intended to assess the influence of the educational program on the changing roles of the professional personnel. The nurses of 14 family medical practices, with the physicians'' support and commitment to participation, applied for the new training. Seven applicants were randomly selected to receive the training and their corresponding practices became the experimental group, while the remaining nurses and practices were retained as controls. During the subsequent year of investigation important changes occurred in professional roles of the experimental group. Nurse practitioners spent more time in clinical activities than conventional office nurses. The shift was not at the expense of time devoted to clinical work by physicians. Doctors delegated more professional activities to nurse practitioners than to conventional nurses. Except for remuneration (affected by legal constraints) job satisfaction among experimental physicians and nurses remained high after one year of experience with the new method.     

Production of Hydrocinnamic Acid by Clostridia

Hydrocinnamic acid was found in acid extracts of spent growth medium from cultures of Clostridium sporogenes. The acid was identified by mass spectrometry and its identity was confirmed by gas chromatography. The acid was produced in relatively large amounts (2 to 3 μmoles/ml of medium) by C. sporogenes, toxigenic types A, B, D, and F of C. botulinum, and some strains of C. bifermentans. Other strains of C. bifermentans and strains of C. sordellii and C. caproicum produced only small amounts (0.1 to 0.4 μmoles/ml) of the acid. The acid was not detected in spent medium from toxigenic types C and E of C. botulinum or from 25 other strains representing eight Clostridium species. Resting cell suspensions exposed to l-phenylalanine produced hydrocinnamic and cinnamic acid; the latter compound probably functions as an intermediate in the metabolism of l-phenylalanine.     

Regulation of Nitrate Uptake in Penicillium chrysogenum by Ammonium Ion

A nitrate uptake system is induced (along with nitrate reductase) when NH₄⁺-grown Penicillium chrysogenum is incubated with inorganic nitrate in synthetic medium in the absence of NH₄⁺. Nitrate uptake and nitrate reduction are probably in steady state in fully induced mycelium, but the ratios of the two activities are not constant during the induction period. Substrate concentrations of ammonium cause a rapid decay of nitrate uptake and nitrate reductase activity. The two activities are differentially inactivated (the uptake activity being more sensitive). Glutamine and asparagine are as effective as NH₄⁺ in suppressing nitrate uptake activity. Glutamate and alanine were about half as effective as NH₄⁺. Cycloheximide interferes with the NH₄⁺-induced decay of nitrate uptake activity. The ammonium transport system is almost maximally deinhibited (or derepressed) in nitrate-grown mycelium.     

Intracellular localization of the active process in polar transport of auxin

Summary The cytoplasm of maize coleoptile cells was displaced to either the apical or basal ends of the cells by centrifuging (1750xg for 10 min) segments in which protoplasmic streaming had been stopped by pretreatment with cytochalasin B. Centrifugation toward the base of the segment promotes the subsequent basipetal transport of indole-3-acetic acid, whereas apical centrifugation dramatically inhibits this transport. Apical centrifugation neither promotes acropetal transport nor reverses the polarity of auxin transport. Experiments in which the amyloplasts were separated from the bulk of the cytoplasm indicate that the basipetal transport is independent of both the position and pressure exerted by the amyloplasts but is strongly dependent on the amount of cytoplasm at the basal end of the cells. These effects of centrifugation on auxin transport lead to the conclusion that the metabolic component of the transport is a polar secretion of auxin localized in the basal plasma membrane of each cell.     

Do Flies Have A Red Receptor?

(1) The compound eye of Musca exhibits characteristics which have heretofore frequently been considered evidence for color receptors: (a) The spectral sensitivity curve has several peaks whose relative heights can be altered by selective adaptation to colored lights, and (b) the shape of the retinal action potential varies with wave length. (2) The action spectrum for the red enhancement of on and off responses is compared with the "red receptor" calculated by Mazokhin-Porshnyakov from colorimetric data obtained in rapid color substitutions. Both have maxima at 615 to 620 mµ and appear to be different expressions of the same phenomenon. (3) A red receptor is absent. The evidence which suggests different types of receptors in the region 500 to 700 mµ can be accounted for by variations in the numbers of receptors stimulated. In red light there is a recruitment of additional ommatidia caused by leakage of long wave lengths through the pigment screen, and this spatial summation potentiates the on and off responses. The principal evidence is: (a) a white eye mutant which has no accessory screening pigments also lacks the peak of sensitivity in the red, even when adapted to violet light; (b) white-eyed flies give identical responses with large on and off effects at all wave lengths from 500 to 700 mµ; and (c) reducing the number of excited ommatidia by decreasing the size of the test spot makes the on and off transients smaller relative to the receptor component.     

What controls variation in carbon use efficiency among Amazonian tropical forests?

Why do some forests produce biomass more efficiently than others? Variations in Carbon Use Efficiency (CUE: total Net Primary Production (NPP)/ Gross Primary Production (GPP)) may be due to changes in wood residence time (Biomass/NPP_wood), temperature, or soil nutrient status. We tested these hypotheses in 14, one ha plots across Amazonian and Andean forests where we measured most key components of net primary production (NPP: wood, fine roots, and leaves) and autotrophic respiration (R_a; wood, rhizosphere, and leaf respiration). We found that lower fertility sites were less efficient at producing biomass and had higher rhizosphere respiration, indicating increased carbon allocation to belowground components. We then compared wood respiration to wood growth and rhizosphere respiration to fine root growth and found that forests with residence times <40 yrs had significantly lower maintenance respiration for both wood and fine roots than forests with residence times >40 yrs. A comparison of rhizosphere respiration to fine root growth showed that rhizosphere growth respiration was significantly greater at low fertility sites. Overall, we found that Amazonian forests produce biomass less efficiently in stands with residence times >40 yrs and in stands with lower fertility, but changes to long‐term mean annual temperatures do not impact CUE.