Cellular requirements for simulation by the purified streptococcal antigen DSR

Delayed skin reactor (DSR) was prepared from streptokinase-streptodornase. Peripheral blood mononuclear cells, were collected from a Ficoll-Hypaque gradient and subsequently subdivided into T cell-, B cell-, or monocyte-depleted populations. Mononuclear cells with complement receptors (B cells) were removed by a nylon-wool column adsorption. Sheep erythrocyte rosette forming cells (T cells) were removed by centrifugation on a second gradient. Populations of cells which did not adhere to plastic and/or ingest iron filings were monocyte-depleted. While response to DSR as measured by incorporation of tritiated thymidine into DNA was not affected by removing B lymphocytes, it was significantly diminished by removing T lymphocytes. Monocyte-depleted cells incorporated less tritiated thymidine into DNA in both antigen stimulated and control cells, but the stimulation index was not significantly altered.

The choice of practice location

A ten per cent sample survey of all general practitioners in England and Wales in 1969-70 included two questions about the choice of practice location. The most common reasons given were the absence of any real alternatives (in the immediate post-war period), the influence of family or friends, the existence of medical contacts in the area, and favourable points about the practice itself.In considering possible future moves, general practitioners would pay closest attention to the educational facilities of an area, its rural or coastal location, its social and cultural amenities, and the practice conditions. The conclusion is drawn that financial incentives are unlikely to contribute much towards a more equal distribution of general-practitioner manpower. More thought should be given to recruitment to the medical profession in under-doctored areas through the development of the highest professional standards and facilities in such places.

Fine structural changes at Entamoeba histolytica rabbit kidney cell (RK 13) interface

When bacteria-free trophozoites of Entamoeba histolytica were added to a monolayer of rabbit kidney cells, cellular injury occurred at the sites of contact. Changes appeared within the cell cytoplasm before there was any generalized cell membrane damage. At some points of contact there was apparent fusion of amoebic and cell cytoplasm. Electron-dense bodies, here interpreted as liposomes, were present in the amoebic cytoplasm and beneath the surface membrane. No surface lysosomes were seen. Various modes of cell damage and enzyme transfer from amoeba to cell are suggested, together with the possibility that cytopathic amoebae are infected with virus particles.

Surveys for amoebiasis; interpretation of data and their implications

In survey work, stool microscopy for cysts and serology are the only really practicable measures of amoebic infection. The diagnostic sensitivity of stool microscopy should be estimated. Using a simple deterministic mathematical model, the rates of gain and loss of infection and seropositivity may be estimated from survey data. The low value of the constants creates difficulties but they can be estimated from: (1) cumulative data from frequently sampled cohorts; (2) analysis of the curves of age prevalence; (3) analysis of curves of long-term follow-up studies. The second method is the simplest and normally gives valid results. Appropriate epidemiological studies can give useful information about protective immunity, incubation period, superinfection, and interactions between amoebic infection and various host factors, including other disease states. Knowledge of the rate constants of infection allows predictions to be made about the likely effect of control measures.

The relation between hybrid vigour and genotype-environment interactions

Consideration was given to the response curves and response surfaces that are obtained when genotypes are grown at various levels of environmental factors. These curves and surfaces were used to illustrate genotype-environment interactions and possible relations between two parents and their F 1.When a hybrid had a response exactly intermediate between its parents, the metric values for the hybrid were not intermediate but varied with the environment, exhibiting different degrees of dominance including overdominance (hybrid vigour). A range in dominance for the metric also was found when the response of the hybrid was more similar to one parent than the other.A hybrid with an intermediate response has a lower phenotypic variance across environments than the mean variance of its parents. In some situations the hybrid's variance is less than that of either parent.A component of the error variation for a genotype was shown to vary with the environment having a minimal value when the environment was optimal.An algebraic treatment of response curves and surfaces was presented. In some instances the metric values for two parents and their F 1 in a range of environments may be related in the form of a multiple regression.

In vitro evaluation of tobramycin, a new aminoglycoside antibiotic

One hundred fifty-two strains of Escherichia coli, Klebsiella-Enterobacter, Pseudomonas aeruginosa, Proteus species, and Staphylococcus aureus were inhibited by 3.1 mug of tobramycin/ml in a broth-dilution method and showed zones of inhibition of 16 mm or more around a 10-mug tobramycin disc in the Kirby-Bauer method. Tobramycin was most active against S. aureus, 100% of strains being inhibited by 0.1 mug/ml. All strains of E. coli, K. pneumoniae, P. aeruginosa, and indole-positive Proteus species, and 80% of Enterobacter species were inhibited by 0.8 mug of tobramycin/ml, whereas only 48% of P. mirabilis strains were inhibited by this concentration. Tobramycin was approximately twice as active as gentamicin against S. aureus, four times as active against P. aeruginosa, slightly more active against E. coli and Enterobacter species, equally active against P. mirabilis, and slightly less active against K. pneumoniae. The minimal bactericidal concentrations of tobramycin and gentamicin were the same as or twice the minimal inhibitory concentrations for all strains except those of P. aeruginosa, against which greater concentrations of both gentamicin and tobramycin were required for bactericidal activity. Tobramycin sterilized cultures of S. aureus, E. coli, and P. aeruginosa, but the rate of bactericidal action was faster with a combination of tobramycin and carbenicillin than with either antibiotic alone in the same concentrations. Tobramycin retained potency in the presence of 200 to 600 mug of carbenicillin/ml for at least 6 hr of incubation at 37 C, but lost potency in the presence of 600 mug of carbenicillin/ml by 24 hr of incubation and in the presence of 800 mug/ml by 2 hr of incubation.

A multiple regression analysis of hybrid vigour in single crosses ofDactylis glomerata L

Thirty-six crosses ofDactylis glomerata together with their parents were assessed for seasonal yield at twelve successive harvests during a 16 month period. The yields varied with the environment provided by the climatic seasons of the year. For some crosses, the hybrid approximated to its mid-parental value at one environment but exceeded both parents in another, showing hybrid vigour.The twelve yield values for a hybrid and for each of its parents were analysed as a multiple regression in the form -[Formula: see text] wherey ij,P i andp j are the yields of the hybrid and parents at any one harvest,b i andb j are regression coefficients pertaining to the respective parents and a is a constant. It was found that such a regression accounted for a great part of the seasonal yield variation of each cross, including the situation of a hybrid approximating to the mid-parental value or exceeding both parents.Theb value pertaining to an individual parent varied according to the parent with which it was crossed. In the discussion the values ofb anda were considered in relation to the incidence of hybrid vigour, and the use of a multiple regression is compared with other analyses of quantitative inheritance.

Relapsing amoebic colitis of 12 year's standing exacerbated by corticosteroids

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Intraperitoneal blood transfusion in African adults with hookworm anaemia

Twenty-nine patients were given an intraperitoneal transfusion of blood. The procedure was found to be free of serious complications. Study of the absorption of an (51)Cr-labelled cells from the peritoneum in 14 patients showed that between 35 and 100% of the blood was absorbed intact in 6 to 10 days. Intraperitoneal transfusion may be indicated as an alternative or as an addition to exchange transfusion in severe hookworm anaemia.

The in vitro digestibility of parents and hybrids of cocksfoot (Dactylis glomerata L.)

The digestibility of a range of genotypes of cocksfoot (Dactylis glomerata L.) and their hybrids was estimated by an in vitro technique at eight harvests over a period of 14 months. The material for analysis was grown in a Mediterranean type environment with summer irrigation and obtained by recurrent defoliation of sward plots. Digestibility values tended to be lower in summer than in winter, although some material showed a fall in digestibility in the middle of winter. Within a harvest there were correlations between general combining ability and parental performance, but there was little uniformity in ranking of parents or their progenies from one harvest to the next, which would make selection for uniform high digestibility very difficult. Reasons for the fluctuations are not known, and were not obviously correlated with any aspect of the growth rhythm apart from a correlation with heading on one harvest occasion.

The seasonal growth rhythm of some cultivars of cocksfoot (Dactylis glomerata)

The seasonal yields of twenty-seven introduced cultivars of Dactylis glomerata were compared under irrigation with Australian cultivars and ecotypes from the Mediterranean basin. Very large differences in winter yield were obtained between cultivars, some French ones having yields three times larger than those from continental climates in Europe and North America. The material in the trial was also assessed for heading date and a range of three months was obtained between the earliest and latest cultivars, with the French cultivars as a group being the earliest. Survival of the introduced cultivars was low over the summer when not irrigated, emphasizing the need for hybridization with drought resistant material.

The performance of hybrids between Mediterranean and Northern European parents of cocksfoot (Dactylis glomerataL.) in a mediterranean type environment

Hybrids were produced between seven different parents of Mediterranean origin and two parents of Northern European origin. A special technique of controlled flowering, emasculation, and pollination was used to effect the hybridization. Hybrid plants were grown in undefoliated swards and assessed for cumulative growth, variation in the reproductive phase, tillering, and summer survival. The combining abilities of the parents were estimated for these characters. Hybrids between Mediterranean and Northern European parents were able to respond to summer showers at a time when Mediterranean material was still summer dormant and Northern European material severely affected by dry summer conditions. This out-of-season growth was reflected in the higher yields of the hybrids in the autumn after the main start to the growing season. During midwinter when the Mediterranean material was growing actively the growth of Northern European material ceased and some combinations of Mediterranean and Northern European parents ceased growing. The cessation of growth was attributed to winter dormancy. Plant survival during the summer was 97% for the purely Mediterranean families, 88% for Mediterranean x Northern European families, and 59% for the purely Northern European families. Some of the Mediterranean x Northern European families survived as well as the best Mediterranean families. The potential agricultural value of the Mediterranean x Northern European hybrids and a possible breeding programme with them are discussed.

The relation between yield and the reproductive phase in cocksfoot (Dactylis glomerata L.) in a winter rainfall environment

Studies were made of six genotypes of Dactylis glomerata grown in defoliated clonal swards in the Mediterranean-type environment of southern Australia. Differences between genotypes in timing of reproductive phase stem elongation was the main cause of yield differences for 5 months of the growing season. This latter period compares with the 3–4 weeks for differentiation of ecotypes found in northern temperate regions, and is a result of the winter growing season and lower latitude. High yields were obtained under midwinter conditions from early genotypes. The yield of late genotypes was affected by moisture stress in the spring of some years, and their production was very erratic from year to year. The ranking of the genotypes was affected by the date of the previous harvest. Initiation of reproductive buds was variable between genotypes, and some genotypes carried initiated buds throughout the year.

The relation between tillering and dry matter production in cocksfoot (Dactylis glomerata L.). Grown under spaced and sward conditions

A study of nine clones of cocksfoot (Dactylis glomemta) showed that differences between clones in dry matter production were not associated with tillering ability. The clones, seven of Mediterranean origin and two from Great Britain, were grown under the spacing conditions of a breeding nursery and in swards, but were not defoliated. Individual plant weight and tiller number were greatly reduced by sward conditions, as compared with plants under spaced conditions. Tiller weight was much less affected. Thus the lower individual plant weight in swards was associated mainly with fewer tillers. Tiller numbers in the swards rose to a peak during the second year, followed by a decline to the end of the growing season. The decline, which differed between clones, was related to plant weight and was probably correlated with the mutual shading of the plants.

The growth of cocksfoot (Dactylis glomerata L.) under spaced plant and sward conditions

The cumulative growth of nine clones of Dactylis glomerata was compared under two conditions of spacing. The first spacing was chosen to provide conditions similar to those of a breeding nursery, the second, conditions met with in swards. Data were obtained for two growing seasons, the individual plant and its parts being considered at each harvest. Of the nine clones seven were developed from plants obtained from the Mediterranean region and two from Great Britain. There was a poor correlation between plants under the two spacing conditions, particularly as later in the life of the swards clones reacted differently to competition. Competition did not lead to a uniformity of top weight for the clones in the swards. These results are discussed in relation to the conflicting results of similar studies and the reaction of genotypes to factors of the environment affecting growth. It is suggested that plants in the vegetative phase are affected by competition differently from plants in the reproductive phase. Some clones were found to regenerate after summer dormancy more rapidly than others, but initial advantages were not maintained. The relative development of parts of the plants differed between clones, some having high proportions of their total weight below ground. At the time of reproduction, despite very large differences in total weight between plants of a clone under the two spacing conditions, the percentages of plant parts were very similar. A high mortality was shown during the summer by the two clones from northern European plants, but only a negligible mortality by the Mediterranean plants.