Five-year results of the peer assessment program of the College of Physicians and Surgeons of Ontario.

The office practices of 918 physicians selected through stratified random sampling from the College of Physicians and Surgeons of Ontario (CPSO) registry were assessed by peers and the Peer Assessment Committee of the CPSO from 1981 to 1985. The sample comprised 662 general practitioners (GPs) and family physicians (FPs) and 256 specialists in 11 fields. Of the physicians 749 (82%) had neither deficient records nor an unsatisfactory level of patient care. Of the GPs and FPs 97 (15%) had serious deficiencies in one or both areas, as compared with 4 (2%) of the specialists (p2 less than 0.00001). The proportions of certificants of the Royal College of Physicians and Surgeons of Canada and of the College of Family Physicians of Canada (CFPC) with serious deficiencies were low (2% and 3% respectively). Three statistically significant predictors of physician performance were found among the GPs and FPs: age, CFPC membership status and type of practice. Of the 56 physicians who were reassessed 6 to 12 months later 29 (52%) had made the improvements recommended by the committee. Our findings demonstrate the need, feasibility and acceptance of a peer assessment program of office practices in Ontario.     

Spectral responses of sustaining fibers in the optic tracts of crayfish (Procambarus)

Summary Spectral response curves were recorded for 60–70 individual sustaining fibers in the optic nerve of the crayfish Procambarus. These cells belong to at least 8 of the 14 classes of sustaining fibers described by Wiersma and Yamaguchi (1966) on the basis of receptive fields. About 90 percent of the cells receive predominant input from yellow-green receptors and are maximally sensitive at 560 to 570 nm; a much smaller number receive principal input from blue receptors and are maximally sensitive near 460 nm.The wavelength sensitivity of optic fibers receiving their major input from yellow-green receptors depends on the state of dark adaptation of the animal and the intensity of illumination. Early in dark adaptation and at high intensities of stimulation the spectral response curve is distorted by light which has been filtered through the sleeves of red-brown shielding pigment. During dark adaptation a shift in maximum spectral response to shorter wavelengths parallels the retraction of the migratory pigment to the dark position and the development of retinal glow. The effects are reversed by injecting into a dark-adapted animal an extract of eyestalks containing the hormone controlling pigment migration: the pigment sleeves lengthen, retinal glow disappears, and shoulders or peaks of sensitivity appear in the red region of the spectrum.This work was supported by USPHS research grant EY 00222 to Yale University. A. E. R. W. was aided by a Fulbright-Hays travel grant. We are grateful to Prof. C. A. G. Wiersma and Dr. R. M. Glantz for a helpful demonstration of the recording technique.     

Differential wavelength sensitivity in the receptive fields of sustaining fibers in the optic tract of the crayfishProcambarus

Summary Spike discharges were measured at 473 nm and at 573 nm in 40–50 individual sustaining fibers (slowly-adapting units signaling intensity levels over large receptive fields). The units belonged to five of the 14 classes of sustaining fibers recognized by Wiersma and Yamaguchi (1966) on the basis of the positions of their receptive fields. The test wavelengths were selected because they lie near the peaks of sensitivity of the two spectral types of receptor known to be present in the ommatida. Relative sensitivity was measured at 5 ° intervals as the test lights were moved around the eye on various arcs, and the receptive fields were described in terms of contours of equal sensitivity for each wavelength.No large differences in relative spectral sensitivity were observed as a function of position in the receptive field, but there was a consistent tendency for sensitivity to blue light to be relatively greater in the dorsal region of the eye. The difference was modest, generally being 0.5 log units or less. This effect could be caused either by regional variation in the population density of the blue and yellow-green receptors, or by weighting of inputs in the optic neuropile.This work was supported by USPHS research grant EY00222 to Yale University. A.E.R.W. was aided by a Fulbright-Hays travel grant.     

Quantitative predictions for the chemiosmotic uptake of auxin

1. The predictions of a general kinetic model for the chemiosmotic uptake of auxin and other weak acids are compared with experimental results for the auxin indoleacetic acid. The proposed mechanism involves diffusional flux of undissociated acid, a saturable, voltage-sensitive flux of anion (A^-), and a carrier-mediated symport of H⁺ and A^-, all operating in parallel. During much of uptake, the electrochemical gradients are such that the net symport and the net anion flux are in opposition: the symport contributes more to influx; the anion path, to efflux. The voltage-sensitive flux of A^- therefore constitutes a leak. 2. The presence of a symport, whose carrier can distribute across the membrane in response to the internal and external concentrations of auxin, can speed the rate of uptake, but does not by itself alter the accumulation of auxin at equilibrium. 3. The accumulation ratio at equilibrium is less at low concentrations of auxin than at higher concentrations, indicating the presence of a saturable anion path. The concentration dependence of the transition depends on several factors, and is not a reliable indicator of the A^--carrier binding constant. 4. Observed uptake near neutral pH appears larger than is consistent with a voltage-sensitive anion flux being the only carrier-mediated path across the membrane. This observation provides indirect evidence for the presence of an auxin-proton symport in addition to a saturable A^- carrier. 5. The change in kinetics of uptake of [³H]indole-3-acetic acid (IAA), observed as the total concentration of IAA is raised from 0.1 to 100 M, is consistent with either (i) a symport that saturates at low concentrations, or (ii) activation of an A^- efflux by intermediate concentrations of auxin. 6. The data on the concentration dependence of uptake of auxin are not consistent with a multi-proton symport.Abbreviations A^- auxin anion - HA weak acid, particularly IAA - HXA carrier in electroneutral complex with a proton and the auxin anion - H₂XA carrier in electroneutral complex with two protons and the auxin anion - IAA indole-3-acetic acid - X auxin carrier - XA carrier-auxin anion complex     

The action of specific inhibitors of auxin transport on uptake of auxin and binding of N-1-naphthylphthalamic acid to a membrane site in maize coleoptiles

Using both 1-mm segments of corn (Zea mays L.) coleoptiles and a preparation of membranes isolated from the same source, we have compared the effectiveness of several inhibitors of geotropism and polar transport in stimulating uptake of auxin (indole-3-acetic acid, IAA) into the tissue and in competing with N-1-naphthylphthalamic acid (NPA) for a membrane-bound site. Low concentrations of 2,3,5-triiodobenzoic acid (TIBA), NPA, 2-chloro-9-hydroxyfluorene-9-carboxylic acid (morphactin), and fluorescein, eosin, and mercurochrome all stimulated net uptake of [³H]IAA by corn coleoptile tissues while higher concentrations reduced the uptake of both [³H]IAA and another lipophilic weak acid, [¹⁴C]benzoic acid. Since low concentrations of fluorescein and its derivatives competed for the same membrane-bound site in vitro as did morphactin and NPA, the basis for both the specific stimulation of auxin accumulation and the inhibition of polar auxin transport by all these compounds may be their ability to interfere with the carrier-mediated efflux of auxin anions from cells. At higher concentrations, the decrease in accumulation of weak acids was nonspecific and thus may be the result of acidification of the cytoplasm and a general decrease in the driving force for uptake of the weak acids. Triiodobenzoic acid was an exception. Low concentration of TIBA (0.1–1 M) were much less effective than NPA in competing for the NPA receptor in vitro, but little different from NPA in ability to stimulate auxin uptake. One possibility is that TIBA, a substance which is polarly transported, may compete with auxin for the polar transport site while NPA, morphactin, and the fluorescein derivatives may render this site inactive.Abbreviations C1-NPA 2,3,4,5-tetrachloro-N-1-naphthylphthalamic acid - IAA indole-3-acetic acid - -NAA -naphthaleneacetic acid - -NAA -naphthalenacetic acid - NPA N-1-naphthylphthalamic acid - TIBA 2,3,5-triiodobenzoic acid     

Four Years' Experience with Indwelling Silastic Cannulae for Long-term Peritoneal Dialysis

Indwelling silicone rubber cannulae have been used for peritoneal dialysis in 41 uraemic patients for periods of up to 46 months. The simplicity of this treatment is particularly suited to patients awaiting transplantation.     

Polar auxin transport and auxin-induced elongation in the absence of cytoplasmic streaming

Summary When cytoplasmie streaming in oat and maize coleoptile cells is completely inhibited by cytochalasin B (CB), polar transport of auxin (indole-3-acetic acid) continues at a slightly reduced rate. Therefore, cytoplasmic streaming is not required for polar transport. Auxin induces elongation in CB-inhibited coleoptile and pea stem segments, but elongation rate is reduced about 40% by CB. Therefore, stimulation of cytoplasmic streaming cannot be the means by which auxin promotes cell elongation, but streaming may be beneficial to elongation growth although not essential to it. A more severe inhibition of elongation develops after several hours in CB. With coleoptiles this could be due to inhibition of sugar uptake; in pea tissue it may be due to permeability changes and cytoplasmic degeneration. CB does not disorganize or disorient microfilament bundles when it inhibits streaming in maize, but appears instead to cause hypercondensation of microfilament material.