Quality-of-care appraisal in primary care: a quantitative method

A reproduceable method has been developed for measuring the quality of clinical care provided by physicians and nurse practitioners. The distinctive features of the method are the extended use of the tracer disease concepts, the evaluation of referrals, new procedures for probing the clinical operation of practices, a single blind design, emphasis on the use of the untouched medical record, the ability to compare results with measurements of concurrent outcome, and a relatively low cost. Three simultaneous approaches used in the method are described: surveillance of the management of indicator conditions, evaluation of clinical use drugs, and the assessment of referral decisions. The three approaches gave consistently similar results about the relative performances of the practices compared and were in agreement with concurrent outcome studies. The method was successfully implemented in a health care experiment.

Effects of Hormones on the Polysaccharide-Synthesizing Membrane Systems of Lettuce Pith

Changes have been induced in the polysaccharides laid down in the cell walls of lettuce pith by administration of the hormones auxin and zeatin. This polysaccharide derives from the membrane systems of the cells and radioactive precursor has been used to follow the accompanying changes which occurred in the polysaccharide contained within isolated Golgi and endoplasmic reticulum fractions. Zeatin-induced division and differentiation was accompanied by up to 12-fold increases in the amount of radioactivity in polysaccharide of isolated membrane fractions, and the pattern of distribution of label between the sugars of this polysaccharide was qualitatively different in the presence of zeatin. The change in this pattern was evident in the Golgi fraction at an earlier stage in the induction of the response than that in the endoplasmic reticulum.

The relationship of root-cap slimes to pectins

1. The patterns of incorporation of radioactivity from d-[U-(14)C]glucose into the pectic components of sections of sycamore roots changed so that sections nearer the tip incorporated relatively more label into arabinose and galactose compared with uronic acid. 2. Radioactive maize root-cap slime was prepared and found to contain three water-soluble component polymers which were electrophoretically (i) neutral, (ii) weakly acidic and (iii) strongly acidic at pH6.5. The neutral component was a glucan. The other components, which could be degraded by trans-elimination, consisted of an acidic backbone chain composed of galacturonic acid and glucose, attached to which were different proportions of neutral sugars. Arabinose, galactose and fucose, the main neutral sugars of the weakly and strongly acidic materials, were absent from the neutral fraction. 3. Fucose was a major sugar in maize-root slime and in a slime of similar composition synthesized by a maize callus of shoot origin. Only trace amounts were found in sycamore, pea and wheat root tips, and in pectin prepared from maize roots and coleoptiles. A high proportion of fucose is therefore a chemical characteristic of maize slime, and slime synthesis indicated a state of differentiation of the tissue. 4. The similarity between the slime and pectin is discussed; slime is a form of pectin modified in such a way as to provide a hydrated protective coating around the root tip.

Differences in Ploidy and Degree of Intercellular Contact in Differentiating and Non-Differentiating Sycamore Calluses

Comparisons have been made between a sycamore callus (S4) isolated in 1970 and one first isolated in 1958 (S2). Incubation of S4 on media containing different concentrations of auxin and kinetin showed that the ratio of the hormones was the factor which controlled the growth pattern within the tissue. High ratios of auxin: cytokinin favoured a white friable tissue, whereas a compact callus with a much harder texture was formed at low ratios. Roots were differentiated at intermediate values.

Callus (S2) has not been induced to undergo cellular differentiation. No soluble factors which were capable of stimulating differentiation in S2 were produced during the differentiation of S4, and S2 did not affect the ability of S4 to form roots.

Divisions seen in suspension cultures of S4 callus were mainly diploid; the cells of S2 were predominantly tetraploid. When S2 suspensions were grown in the cytokinin-free medium used for S4 a considerable number of diploid cells were seen. A number of S2 clones have been isolated and all these developed chloroplasts on exposure to continuous light and, when grown on the medium used to induce differentiation in S4, five of them showed a growth pattern in which the cells were more closely packed than is usually the case in S2 callus.

A greater degree of cell contact has also been induced by including polyethylene glycol in the medium and so restricting the availability of water to the callus. Under these conditions the cells must have a greater capacity for interaction with one another. The effect of tissue texture on the extent of cell contact and adhesion between the cells is discussed in relation to the composition of the plant cell wall and ideas on the totipotency of plant tissue cultures.

Induced Root Differentiation in Sycamore Callus

A sycamore callus (S 4) has been isolated and grown on a medium containing salts, vitamins, a casein digest, 2% sucrose and 1 mg/l. NAA. The callus, which would not grow in the absence of the added auxin, was much firmer in texture than a sycamore callus (S 2) isolated in this laboratory in 1958 which has not been induced to differentiate. When kinetin over the range 0.05-0.5 mg/l. was included in the growth medium of S 4 nodules of xylem and phloem were induced within the tissue and roots frequently grew from the surface of the callus. Some roots developed geotropic sensitivity although the majority grew radially outwards from the callus surface. The roots also varied with respect to the number of root hairs they carried. No roots were produced at sucrose concentrations less than 2%, although histological examination revealed extensive xylem and phloem differentiation relative to the amount of growth which had taken place. When sugars other than sucrose were supplied in the medium at a concentration of 3% (w/v) roots were also induced in those calluses where the carbon source had supported good growth. Sucrose, glucose and fructose were identified in the ethanol-soluble extracts of all these calluses. Radioactivity was incorporated into sucrose when S 4 was incubated on a medium containing D-[U-14C]glucose for 24 h.

Any sugar which supported growth and differentiation was therefore one which was capable of entering the common metabolic pathway used by the plant for glucose and sucrose. The cells could undergo differentiation so long as the sugar they were supplied with supported active growth and division. The possibility of a physiological role for sucrose is discussed.