School refusal: issues of conceptualisation, assessment, and treatment.

Developments in the assessment and treatment of school refusal have often been hampered by a failure to recognise its essentially heterogeneous nature. This paper provides a review of major conceptual complexities that have helped to undermine developments in clinical practice. In particular, it considers the distinction between school refusal and truancy, and school phobia and separation anxiety. Common approaches to the assessment and treatment of school refusal are outlined. Although behavioural and cognitive behavioural approaches are now widely accepted as central to treatment, it is increasingly recognised that individually tailored programmes, utilising a range of approaches, are most likely to prove successful. An approach focusing upon the functions, rather than the symptoms, of school refusal is advocated as having most promise for assessment and the subsequent formulation of individual prescriptive treatment.

In vitro characterisation of the interaction between newly synthesised proteins and a pancreatic isoform of protein disulphide isomerase.

The lumen of the endoplasmic reticulum (ER) contains an array of molecular chaperones and folding factors that modulate the folding and assembly of newly synthesised proteins entering the secretory pathway. One of these components, protein disulphide isomerase (PDI), facilitates the formation of the correct disulphide bonds within newly synthesised polypeptides, and is the archetype for a family of sequence related PDI-like proteins. We have investigated the interaction between a recently identified, pancreas-specific PDI-like protein (PDIp), and in vitro synthesised secretory and membrane proteins produced in the presence of ER-derived canine pancreatic microsomes. We have previously established that a second PDI-like protein, ERp57, interacts specifically with N-glycosylated proteins. In contrast, we find that the interaction of PDIp with newly synthesised proteins occurs independently of any requirement for N-linked glycosylation. In this respect, the properties of PDIp mirror those of archetypal PDI. When the carbohydrate-dependent interactions between glycoproteins and ERp57 are blocked by drug treatment, the association of these precursors with both PDIp and PDI is enhanced. We propose that PDI-like proteins have overlapping specificity and may exhibit some degree of functional redundancy.

The thiol-dependent reductase ERp57 interacts specifically with N-glycosylated integral membrane proteins.

The lumen of the endoplasmic reticulum contains a number of distinct molecular chaperones and folding factors, which modulate the folding and assembly of newly synthesized proteins and protein complexes. A subset of these luminal components are specific for glycoproteins, and, like calnexin and calreticulin, the thiol-dependent reductase ERp57 has been shown to interact specifically with soluble secretory proteins bearing N-linked carbohydrate. Calnexin and calreticulin also interact with glycosylated integral membrane proteins, and in this study we have examined the interaction of ERp57 with these substrates. As with soluble proteins, the binding of ERp57 to an integral membrane protein is dependent upon the protein bearing an N-glycan that has undergone glucose trimming. Furthermore, ERp57 binds to newly synthesized glycoproteins in combination with either calnexin or calreticulin. We propose that ERp57 acts in concert with calnexin and calreticulin to modulate glycoprotein folding and enforce the glycoprotein specific quality control mechanism operating in the endoplasmic reticulum.

Bioavailability of iron to rats from processed soybean fractions determined by intrinsic and extrinsic labeling techniques.

Intrinsic and extrinsic labeling techniques were used to measure iron bioavailability from soybean fractions (isolated soy protein, defatted flour, soy hulls, insoluble material and whey) by iron-depleted and non-iron-depleted rats. As expected, absorption of iron was higher in the iron-depleted than in the non-iron-depleted rats. In the iron-depleted group, significantly more iron was absorbed from soy whey than from other fractions. No other significant difference in iron absorption associated with iron source was observed. The higher absorption rate of iron from whey by the iron-depleted rats probably was related to a lower quantity of food consumed during the test meal by this group. Intrinsic and extrinsic labeling techniques produced similar assessments of bioavailability of iron.

Radiolabeled iron in soybeans: intrinsic labeling and bioavailability of iron to rats from defatted flour.

Soybeans can be efficiently labeled with radiolabeled iron by supplying the iron via a nutrient culture medium as an iron salt or as a chelate. By using dual labeled iron and EDTA, it was determined that none of the chelator was transported to the shoots with the iron. Therefore, the use of chelated iron as the iron source in the nutrient medium should not affect assessments of bioavailability of iron from plants. Bioavailability (determined from whole-body retention curves of 59Fe in rats) of iron from defatted soy flour was relatively high and addition of vitamin C did not significantly enhance absorption of iron from defatted soy flour.

Apparent nitrogen digestibility data: AACC-ASTM collaborative study.

Apparent nitrogen digestibility data were obtained from 4 laboratories for 6 protein sources and 2 diet levels, 6 and 10% protein, after a 2-day adaptation period during the AACC-ASTM protein efficiency ratio (PER) and net protein ratio (NPR) collaborative studies. For 5 protein sources fed as 10% of the diet, the interlaboratory variation as measured by coefficient of variation (CV) values was low (1.5-3.5%), indicating high precision of the method. Wheat flour (6% protein diet) had the highest variation and, therefore, the lowest precision (CV of 7.10%). The interlaboratory variation (CV value) for 3 of the 4 laboratories was considerably lower, less than half that for the 4 laboratories. An analysis of variance of apparent nitrogen digestibility data indicated significant (P less than 0.05) effects for the 4-laboratory group due to laboratories and protein diets at both 10 and 6% protein levels, and for the 3-laboratory group at the 10% protein level. The 3-laboratory ANOVA for the 6% diets indicated a significant effect (P less than 0.05) due to diet only.

Net protein ratio data: AACC-ASTM collaborative study.

Seven- and 14-day net protein ratio (NPR) data were obtained from 7 laboratories for 6 protein sources: ANRC casein, lean beef, lactalbumin, textured vegetable protein, and peanut flour were fed as 10% protein (N X 6.25) in the test diet. Wheat flour, casein, and textured vegetable protein were fed as 6% protein (N X 6.25) in the test diet. Weighed dry ingredients for each diet were sent to each collaborator , who mixed the dry ingredients, then added specified amounts of corn oil and water and mixed each complete diet thoroughly. Rats were adapted for 0, 2, or 4 days, and then were fed the test diets for 28 days for protein efficiency ratio (PER) diets. The animal weight gain and feed consumption data obtained after 7 or 14 days of feeding were used to calculate NPR values. Analyses of data were done before [net protein ratio (NPR)] and after (R-NPR [relative-NPR]) adjustment of the data from each laboratory by its results for the reference protein casein. From the analysis of variance for NPR, significant (P less than 0.05) interactions were observed among laboratories, protein sources, and adaptation times of the animals (0, 2, or 4 days). Inter- and intralaboratory variability were decreased by use of 14-day values compared with 7-day values. Adjustment of the NPR data to R-NPR did not lower the intralaboratory variability but did lower the interlaboratory variability of the data. Increasing adaptation time did not consistently decrease interlaboratory or intralaboratory variability or decrease coefficients of variation (CV) of R-NPR values.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein efficiency ratio: AACC/ASTM collaborative study.

Eight laboratories (7 of the laboratories conducted animal experiments) participated in a collaborative study to standardize some of the methodology associated with animal bioassays for determining protein efficiency ratios and to suggest improvements which would reduce the variation among laboratories. One-, 2-, 3-, and 4-week protein efficiency ratios (PER) with 0-, 2-, or 4-day adaptation periods were obtained from each laboratory, respectively, for 6 protein sources: casein, lean beef, lactalbumin, textured vegetable protein, peanut flour, and wheat flour. Analyses were computed for PER and adjusted PER (APER). From the analysis of variance for PER and APER, significant (P less than 0.05) effects were observed due to laboratories, adaptation length, protein sources, and/or interactions among these variables. In general, APER values show much less variation among laboratories than PER values. The reproducibility and repeatability variances were significantly (P less than 0.05) greater for an assay length of 2 weeks than they were for 3- or 4-week assays. Two protein sources, casein and textured vegetable protein, were fed at both high (10%) and low (6%) levels of protein. Analysis of variance of PER values shows a significant (P less than 0.05) laboratory by protein level by assay length interaction.

Sources of variance in the bioassay of protein value.

A factorial design was used to simultaneously evaluate the relative effect of 8 experimental factors and their interactions on the weanling rat bioassay of protein value: (1) source of protein: ANRC casein, lactalbumin, high-protein wheat flour; (2) protein level of the diet: 5 and 10%; (3) dietary fat level: 10 and 20% corn oil; (4) animal: ARS-Sprague-Dawley, from Taconic Farms; (5) age of animal: 21 and 28 days; (6) acclimation time: 2 and 4 days; (7) replication: 2 complete replications in time; and (8) duration of the test: food consumption and body weights were measured at 3, 7, 10, 14, 17, 21, 24, and 28 days after starting the test diet and converted to the ratio of grams of weight gained per gram of protein consumed for each weigh day. The official AOAC method for determining the protein efficiency ratio was followed with minor modifications. All 8 factors and many of their possible interactions appeared to significantly influence the measured ratios. When the ratios were adjusted by reference to the corresponding value for casein as a control, fat level, rat source, rat age, and acclimation time were no longer significant sources of variation. Plots of measured ratios and their coefficients of variation against time suggest that the optimum assay time varies with the protein but that the assay time should not be less than 21 days. The generally used 28-day assay time seems to offer no increase in precision over 21 days.

Food eating patterns and health: a reexamination of the Ten-State and HANES I surveys.

Dietary, clinical, and biochemical data from the Ten-State Nutrition Survey (1968 to 1970) and the Health and Nutrition Examination Survey I (1971 to 1974), have been reexamined by factor analysis to focus attention on eating patterns as a means of relating food intake to health. The seven statistically different eating patterns generated were characterized by disproportionate consumption of different food groups. The relationship between the combination of foods that people ate and the state of their nutritional health was examined for both samples in total, and for various age, sex, race, region, and income groups within the Health and Nutrition Examination Survey I sample. Significantly different associations between the seven eating patterns and the absence of clinical symptoms and biochemical deficiencies were found. Some eating patterns consistently stood out as being significantly better or worse in this regard (p less than 0.05). This food eating pattern model should prove useful for 1) examining the association between food consumption and the incidence of disease states, such as obesity, hypertension, cardiovascular disease, cancer, and periodontal disease for various large scale dietary-health surveys, 2) establishing food regulatory policies, 3) setting national dietary goals, and 4) educating the public on nutrition and health issues.

Effects of vitamin A and ascorbic acid on in vitro cholesterol biosynthesis in the rat.

In order to determine the effect of various doses of vitamin A and the interaction between vitamin A and ascorbic acid on cholesterol synthesis, male weanling rats were fed four levels of vitamin A as retinyl acetate (0, 20, 436 and 6,666 IU/g diet) and two levels of ascorbic acid (0 and 1 mg/g diet) for 28 days except the highest level of retinyl acetate which was fed for only 3 days. The incorporation of [2-14C]mevalonic acid into cholesterol intermediates, fatty acids and bile acids was determined in liver slices prepared from rats fed the above diets. The results may be summarized as follows: (a) ascorbic acid synthesis was reduced in both a deficiency and excess of vitamin A; (b) ascorbic acid in the diet prevented or blocked the decrease in liver ascorbic acid in vitamin A deficiency but not at the highest level of retinyl acetate (6,666 IU/g); (c) retinyl acetate inhibited the incorporation of [2-14C]mevalonic acid into cholesterol, lanosterol, dimethylallyl alcohol, geranol and farnesol, but had no inhibitory effect on the incorporation into squalene, nerolidol or bile acids, and (d) ascorbic acid had no inhibitory effect on cholesterol synthesis and no interaction between retinyl acetate and ascorbic acid was observed.