ordinal data, polychoric correlation,

point polyserial correlation, dichotomous variables, polychotomous variables, latent variables,

The paper is concerned with the consequences for maximum likelihood factor analysis which may follow if the observed variables are ordinal with only a few scale steps, which are assigned integer values. It is hypothesized that the observed variables are obtained through a classification of some true variables, which are multivariate normal and for which a factor model holds. Using simple formulas for the relations between true correlations and correlations based on the classified variables, we demonstrate numerically the relationships between true factor models and results obtained from classified data. This is done for several choices of thresholds, true factor loadings and numbers of variables, assuming a one-factor model. The results indicate that classification may lead to a substantial lack of fit of the model, i.e. an erroneous indication that more factors are needed. This is especially true if the variables are skewed in opposite direction and have high true loadings, but does not depend much on the number of scale steps. The classification also attenuates the loading estimates, and this effect is increased with a decreasing number of scale steps and increasing variation in skewness among the variables.

Serum thymidine kinase (sTK) activity was evaluated as a tumor marker for canine malignant lymphoma (ML). The objective was to investigate if sTK, as in humans, could be used as a prognostic marker for survival time in dogs with ML and if sTK could identify early signs of progression of disease in treated dogs. Serum samples from 52 dogs with ML were tested for initial TK activity. Samples from 21 normal dogs and 25 dogs with nonhematologic neoplasms were used for comparison. Forty-four dogs with ML were treated. Serum TK activity was measured in treated dogs before each treatment and every 4 weeks thereafter until relapse. Dogs with ML had 2-180 times higher TK activity (TK 5-900 U/L) than normal dogs (TK Ͻ7 U/L) based on the mean ϩ 2 standard deviations. In the group of other neoplasms, only 2 dogs had a moderate increase (6.4 and 7.5 U/L) compared with the controls. Mean sTK activities in the dogs with ML that had gone into complete remission (CR) were not significantly different from activities in healthy controls (P ϭ .68). Mean sTK at least 3 weeks before and at the time of relapse was significantly higher than activity measured at CR (P Ͻ .0001). Dogs with ML that initially had sTK Ͼ30 U/L had significantly shorter survival times (P Ͻ .0001). Furthermore, sTK activity reflected the clinical staging of ML. Measuring sTK can be used as a powerful objective tumor marker for prognosis and for predicting relapse before recurrence of clinically detectable disease in dogs with ML undergoing chemotherapy.

Four barley varieties with no significant difference in aphid acceptance were sown in pure stands and in pairwise combinations with varieties side by side in separate rows. Settling tests were done in situ in the field plots with apterae of Rhopalosiphum padi (L.) (Homoptera:Aphididae) and showed that aphid acceptance was changed in some combinations of cultivars. In a laboratory test, in which plants of one cultivar were exposed to air from the other cultivars, aphid acceptance was significantly reduced in three of the four cultivars when treated with air from certain other cultivars. Two of these three cultivars showed the same reduction under field conditions. This supports the hypothesis that plant/plant communication may release responses in neighbouring plants that change aphid host plant acceptance. The results also show that this mechanism is not restricted to optimal growing conditions in the laboratory, although it may be modified under field conditions depending on plant genotype.

Hemodynamic factors may play a role in the development of acute renal failure following administration of contrast media (CM). In this study the effect of intravenous injection of contrast media and mannitol on red blood cell velocity (VRBC) and red blood cell aggregation in renal medullary vessels was studied in 58 rats. Renal medullary blood flow was investigated by a cross-correlation technique and by a visual aggregation score. The CM, namely diatrizoate, iopromide, iohexol, ioxaglate, iotrolan, were given in iodine equivalent doses (1600 mg/kg body wt). Mannitol (950 mOsm/liter) and Ringer's solution were used as controls. The same vessels were studied 30 minutes before and 30 minutes after injections. VRBC decreased significantly after injection of diatrizoate, iopromide, iohexol, iotrolan and mannitol. Ringer's solution and ioxaglate did not significantly alter medullary blood flow, while iotrolan and mannitol caused the largest decreases in VRBC. All CM and mannitol caused both red cell aggregation and cessation of blood flow. The decrease in blood flow and increase in red blood cell aggregation after injection of CM and mannitol may partly explain the occurrence of contrast medium-induced acute renal failure.

No abstract

Today the family is seen as a unit for food choice and consumption. The influence of family members on food choice comprises several stages that can be carried out both in the private home and in the public sphere, such as the grocery store. This makes the grocery store a context in which ordinary family life can be observed. The aim was to study families and the interaction between children and adults in the grocery store, focusing on young people's involvement in food shopping. Hidden observation and family interview methods were used. A total of 338 people were observed in seven different grocery stores in Stockholm during the summer and autumn of 2003. Seven family interviews, involving a total of 29 persons, were conducted in Uppsala in the spring of 2003. In the interviews, parents reported avoiding shopping for food together with children as they experienced it as stressful and exhausting. The observations showed that family life in the grocery store comprises not only the food purchase, but also bringing up children and consumer education. Young people's involvement in the food purchase varied depending on their age and the specific product. The different behaviour observed may be interpreted as reflecting the variation in ways of bringing up children at home. Another conclusion is that a public place such the grocery store facilitates pedagogical situations and can work as a tool for informal education.