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The effect on cognitive test scores of generating differences in postprandial glycaemia using test foods or beverages has been inconsistent. Methodological issues may account for some of the variable results requiring further investigation using strong study designs into the relationship between glycaemia and cognitive functioning. The objective of this study was to determine the effects of postprandial glycaemia on cognitive function by examining cognition after consumption of foods that differ only by the rate of digestion of available carbohydrate in a population of young adults. In a double-blind, randomised, crossover trial, sixty-five participants received trifle sweetened either with a higher-glycaemic index (GI) sugar (sucrose; GI 65) or a lower-GI sugar (isomaltulose; GI 34). Cognitive tests were completed prior to trifle consumption, and 60 and 120 min after. There was no between-trifle difference at 60 min in performance on free word recall (0·0 (95 % CI -0·6, 0·5)), short delay word recall (0·0 (95 % CI -0·5, 0·5)), long delay word recall (0·0 (95 % CI -0·6, 0·6)), letter-number sequence recall (0·3 (95 % CI - 0·2, 0·7)) and visuo-spatial recall (-0·2 (95 % CI -0·6, 0·2)) tests. At 120 min, no difference was detected in any of these tests. The participants performed 7·7 (95 % CI 0·5,14·9) s faster in Reitan's trail-making test B 60 min after the higher-GI trifle than the lower-GI trifle (P = 0·037). Our findings of a null effect on memory are generally consistent with other works in which blinding and robust control for confounding have been used.

The effect that blood glucose concentration has on feelings of satiety is unclear. Our aims were to assess satiety and subsequent energy intake following the ingestion of trifle sweetened with sucrose or isomaltulose whilst measuring plasma glucose concentration to confirm glycemic differences between trifles. Seventy-seven healthy adults participated in a double-blind crossover trial where trifle sweetened with sucrose or isomaltulose was consumed on separate days with a two-week washout. Blood was sampled at the baseline, 1 and 2 h postprandially, and satiety assessed using visual analogue scales (VAS). Weighed diet records were taken on test days. A statistically significant difference in blood glucose concentration between trifles was found at 60 min following consumption, with the isomaltulose trifle having a 0.69 mmol/L (95% confidence interval: -1.07, -0.31) lower concentration when compared with the sucrose trifle. Mean satiety response by area-under-the-curve (AUC) was not significantly different between trifles. Mean (SD) appetite scores for the sucrose and isomaltulose trifles were 4493 (2393) and 4527 (2590) mm·min, respectively, with a between trifle difference of -9 (95% CI: -589, 572) mm·min. Mean (SD) energy intake for the remainder of the day following trifle consumption was 3894 kJ (1950 kJ) and 3530 kJ (1926 kJ) after the sucrose and isomaltulose trifles, respectively, and was not significantly different ( p = 0.133). The differing glycemic response to trifle was not related to satiety or to subsequent energy intake.

1. The preparation is described of a deep red protein dye, R-salt-azo-benzidine-azo-crystalline egg albumen, which contains no more than traces of protein with the original egg albumen specificity. 2. Based on previous publications of the writers, a quantitative method is given for the micro estimation of precipitin in the antisera to the dye. The method gives the actual weight of precipitin and may be applied to the determination of the maximum amount of precipitable antibody in any antiserum. 3. Data are given (1) on the influence of the period between the final injection and the bleeding on the precipitin content of rabbit antisera to the azo protein; (2) on the magnitude of the antibody response following the injection of multiple doses of the antigen varying within wide limits; (3) on the variations in the precipitin content of the sera of rabbits given successive courses of antigen injections; and (4) on the stability of antisera stored in the cold. 4. Four antisera were obtained in which over 100 times as much precipitin was recovered as the amount of antigen injected. This supplements the growing mass of evidence against the theory that specific antigen fragments are actually incorporated into the antibody molecule.

A method, based on the precipitin reaction, is given for the micro determination of the specific polysaccharide of Type III pneumococcus. As little as 0.01 mg. of S III can be determined. The method should be applicable to any specific polysaccharide upon standardization of an homologous antibody solution or antiserum in the region of excess antibody.

The experiments recorded above show that in the case of antipneumococcus horse serum or purified antibody the arbitrary immunological procedure (37 degrees for 2 hours, overnight in the ice box) does not permit either the establishment of a true equilibrium or the precipitation of the maximum amount of antibody nitrogen. Analyses of such horse sera for antibody content should therefore be carried out at 0 degrees and the determinations should be allowed to stand in the cold for at least 24 hours in order to insure the completion of the reaction. It is believed that the similarity of the nitrogen: S III ratios in the specific precipitate, whether obtained from whole serum or from purified antibody, and the failure of added serum to influence the amount of nitrogen precipitated show that the absolute chemical method for the estimation of antibody actually measures antibody and not antibody plus a more or less indefinite amount of non-specific protein. An objection to the use of the method is thus shown to be unfounded.

1. The reaction between the specific polysaccharide of Type III pneumococcus and homologous antibody in rabbit sera is quantitatively accounted for by expressions similar to those derived from the mass law for the corresponding horse sera. Preliminary data are also given for the Type I reaction. 2. Differences and similarities of the reaction with antibodies produced by the two animals are discussed. 3. Calculations are made of the equivalent composition of the specific precipitate at various reference points in the reaction range. 4. Certain theoretical and practical implications of the findings are pointed out.

1. Quantitative data are given on the effect of changes in hydrogen ion concentration and of salt solutions of high concentration on certain immune precipitates obtained at lower salt concentration. 2. Advantage is taken of the shift in reaction equilibrium brought about by the salt in the case of pneumococcus carbohydrate-anti-carbohydrate precipitates to enable the preparation, in a single step from unconcentrated serum, of antibody solutions in which up to 93 per cent of the total nitrogen is immune nitrogen. The method permits successive absorptions of a serum to be made with the same specific precipitate. 3. A modification of Felton's alkaline earth hydroxide dissociation procedure is proposed which yields highly purified antibody with precipitates which have been subjected to several successive salt dissociations.

1. Antisera to R-salt-azo-benzidine-azo-crystalline egg albumin give precipitates with crystalline egg albumin by virtue of their antidye content. 2. The quantitative course of the reactions with increasing amounts of antigen is very similar for the dye-antidye and egg albumin-anti-egg albumin systems, but differs markedly for the cross reaction between egg albumin and antidye. 3. A possible explanation for the occurrence of this one-sided crossreaction is given in terms of reactive groupings on the antigen and antibody. 4. A qualitative expression of the course of the cross-reaction is given in terms of the laws of classical chemistry.

1. A quantitative theory of the precipitin reaction based on the laws of classical chemistry has been tested on an azoprotein-antiprotein system and found to apply. 2. With its aid relationships may be deduced which permit the calculation of the behavior of an antidye serum over its entire range after a few quantitative chemical analyses have been made for antigen and antibody in the precipitate. 3. An empirical relation is also presented which further reduces the number of analyses necessary. 4. A study of supernatants in the inhibition zone has shown that the entire amount of dissolved antigen-antibody compound present is precipitated when supernatants are analyzed for antigen by the precipitin method.

1. A quantitative study of the reaction between the soluble specific substance of Type III pneumococcus and its homologous antibody has been made. 2. The entire reaction, from excess of antibody, to excess of specific substance with its accompanying inhibition zone effect, may be expressed by three mass-law equations. 3. The significance of these findings is discussed.

The precipitin reaction between the specific polysaccharide of Type III pneumococcus and homologous antibody formed in the horse can be accounted for quantitatively by assuming the chemical combination of the components in a bimolecular reaction, followed by a series of competing bimolecular reactions which depend upon the relative proportions of the components. These reactions would lead to the formation of larger and larger aggregates until precipitation ultimately occurred. The mathematical formulation of this theory on the basis of the mass law is described. The derived expressions are shown to be in accord with the experimental findings and the constants used in these expressions are shown to have definite significance. In spite of the wide variation in the properties of individual sera these expressions permit the complete description of the behavior of an unknown serum with S III without an unduly burdensome number of analyses. The quantitative theory presented has been found applicable to other instances of the precipitin reaction, as will be shown in subsequent papers.

1. Rats fed l-cystine at excessive levels excrete large amounts of sulfate sulfur in the urine and develop liver necrosis and cirrhosis. 2. Rats fed dl-methionine at excessive levels excrete large amounts of sulfate sulfur, but do not develop liver necrosis and cirrhosis. 3. Rats fed cysteic acid at high levels excrete relatively small amounts of sulfate, but do develop liver necrosis and cirrhosis. 4. In conclusion, there is no apparent correlation between the amount of sulfate formed and the development of liver damage in rats fed l-cystine, dl-methionine, and cysteic acids.

1. A quantitative theory of the precipitin reaction based on the laws of classical chemistry has now been found applicable to the crystalline egg albumin-antibody system. Equations derived from the theory permit the calculation of the behavior of an anti-egg albumin serum over most of the reaction range after a few quantitative analyses have been made for the nitrogen precipitated. Data of other workers also conform to the proposed equations. 2. The empirical relation, shown to have advantages in the dye antidye system, may also be used for the Ea-A reaction. 3. Serum from the same animal after successive courses exhibits progressive changes which have been described graphically and quantitatively. These changes are believed to consist in the formation of more and more antibody capable of reacting with a larger number of chemically different groupings in the antigen molecule. 4. Evidence is presented that anti-egg albumin is not homogeneous, and that even after prolonged immunization the antiserum contains much low-grade antibody, incapable of forming precipitates unless more reactive precipitin is present. 5. Factors affecting the equivalence point ratio are discussed.

1. Partial hydrolysis products of the specific polysaccharide of Type III pneumococcus ranging from 550 to 1,800 in formula weight can be quantitatively freed from unhydrolyzed polysaccharide. 2. The fractions yield specific precipitates with Type III antipneumococcus horse serum but fail to precipitate homologous rabbit antisera, giving rise only to specific inhibition. The aldobionic acid, the structural unit of S III, does not precipitate antisera. 3. A possible explanation and a possible application of the findings are pointed out.

1. A tentative method is described for extracting a labile nucleo-protein from scarlatinal Streptococcus hemolyticus. 2. The product differs chemically and serologically from the fractions prepared by subsequent alkaline extraction of the cell residues, and from protein obtained by the classical method for extraction of bacterial "nucleoproteins." 3. The new nucleoprotein is sensitive to very weak alkalies and readily loses nucleic acid under these conditions. The protein degradation products resemble the alkaline-extracted protein fractions of the cell residues. 4. The bearing of the properties of the new nucleoprotein on the chemistry of nucleoproteins in general is discussed, also the possible relation of the fractions obtained to the analysis of streptococcus antigens made by Lancefield.

1. A quantitative study has been made of the effect on the precipitin reaction between the specific polysaccharide of Type III pneumococcus and the homologous antibody of salt concentrations ranging from O.1 M to 1.79 M, including the effect of ions of higher valence. 2. Within these limits, observed decreases in precipitated antibody with increasing salt concentration appear to be due to a decrease in the amount of antibody combined with the S III, rather than to an increase in solubility of the S III-antibody compounds. 3. The egg albumin-antibody reaction is far less sensitive to changes in salt concentration than is the S III-antibody reaction.

1. A rapid and simple method is given for the approximate determination of the specifically precipitable protein in Type I antipneumococcus sera. 2. It is shown that a close parallel exists between the specifically precipitable protein and the number of mouse protection units in a wide variety of Type I antipneumococcus sera. 3. Owing to the consistent results obtained and the rapidity, simplicity, and economy of the method, its use is proposed instead of the mouse protection test as a basis for the titration of standard sera and the comparison of others with a standard. 4. A method is given for conveniently preparing highly purified specific polysaccharide of Type I pneumococcus.