Simultaneous evaluation of pancreatic exocrine function and intestinal absorptive function in dogs with chronic diarrhea

The N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BT-PABA):xylose test was evaluated in 5 clinically normal dogs, 5 dogs with pancreatic exocrine insufficiency (PEI), and 7 dogs with intestinal malabsorption. A solution of BT-PABA (1 g/100 ml) and d-xylose (10 g/100 ml) was given orally (5 ml/kg of body weight) to dogs in each group. Plasma p-aminobenzoic acid (PABA) curves were decreased in dogs with PEI and intestinal malabsorption (P < 0.05) but were the lowest in dogs with PEI, compared with clinically normal dogs. Xylose values in dogs with malabsorption were decreased (P < 0.05), compared with clinically normal dogs. Dogs with PEI had plasma xylose values that were intermediate to values in clinically normal dogs and dogs with intestinal malabsorption. Results of BT-PABA:xylose testing were compared with results of sodium PABA:xylose testing, to determine whether decreased PABA values obtained by the BT-PABA:xylose test were caused by free PABA malabsorption or by maldigestion of BT-PABA. The sodium PABA:xylose test was performed in dogs from each group by oral administration of a solution (5 ml/kg) of sodium PABA (0.372 g/100 ml) and d-xylose (10.0 g/100 ml). Plasma PABA values obtained by the sodium PABA:xylose test were similar in each group. Thus, different PABA values obtained by the BT-PABA:xylose test were not caused by PABA malabsorption. Xylose values were similar to values obtained by the BT-PABA:xylose test. It was concluded that: (1) the BT-PABA:xylose test is a practical test for detecting maldigestion or malabsorption in the dog; (2) dogs with intestinal malabsorption may have functional PEI; and (3) decreased PABA plasma values obtained by BT-PABA:xylose testing are not caused by malabsorption of free PABA.

Virus-specified protease in poliovirus-infected HeLa cells

Previous studies have shown that primary cleavages in nascent picornavirus precursors are accomplished by cellular proteases. This study has characterized the enzyme in infected cells that produces the capsid polypeptides by secondary cleavages of viral precursors. The kinetics of the production of protease activity correlate with the time course of virus protein synthesis, and the new enzyme has characteristic pH and temperature optima. Guanidine and cycloheximide, which are inhibitors of virus RNA and protein synthesis, prevent production of the protease. As determined by introduction of amino acid analogs into the protease or inhibition by a leucyl chloromethyl ketone, the enzyme is synthesized at a time of infection when host cell proteins are not produced, and the enzyme copurified with a 40,000-dalton virus polypeptide present in the cytoplasm of infected cells. Wild-type levels of protease activity are produced by viral mutants that are defective in coat protein synthesis. The conclusion is that a non-structural poliovirus gene product participates in protein cleavages that produce the viral coat proteins.

Conceptual structure and conceptual tempo

College students selected for extremes of concrete and abstract conceptual structure were given 4 visual information-processing tasks: Matching Familiar Figures, Design Recall test, Embedded-figures test, and a task requiring identification of familiar objects presented tachistoscopically at 1/100 sec. Schroder's theory of conceptual structure provided a basis for predicting that abstract Ss would proceed more reflectively on the tasks than would concrete Ss, i.e., abstract Ss were expected to show longer response times and a higher proportion of correct responses. Results showed little generality of either speed or accuracy over tasks, and no support for the conceptual structure hypothesis. Non-parametric analysis of over-all performance indicated that abstract Ss and males tended to be both faster and more accurate in visual tasks than concrete Ss and females, respectively.

Crystallization Kinetics and Polymorphic Transformations in Polybutene-1

When subcooled from the melt to any temperature between about 90 to 110 °C, polybutene-1 transforms at a readily measurable rate to a crystalline phase denoted "form 2," which is typically spherulitic. The kinetics of this process have been measured by optical and dilatometric techniques. The results are consistent with the concepts that the initiation is heterogeneous, that the initiation is followed by spherical growth (Avrami n=3), and that the growth rate is nucleation controlled. Values arc obtained for the surface free energies and related quantities that are consistent with crystallization by chain folding: σ=7.2 erg/cm2 or 7.2 mJ/m2, σ e =15.5 erg/cm2 or 15.5 mJ/m2, and work of chain folding q=1.7 × 10-13 erg/fold. (For comparison, q is 2.1 × 10-13 erg/fold for polyethylene.) The work of chain folding of polybutene-1 is also compared with that of polychlorotrifluoroethylene, and it is shown that an increase of q is connected with an increase of equilibrium melting temperature. Crystal form 2 subsequently converts slowly near room temperature to a crystalline phase denoted "form 1" of different helicity and density, and the rate of this crystal-crystal transformation is also studied. The Avrami parameter for the form 2→form 1 process is n = 2. The process appears to be nucleation controlled. It is shown that form 1 is, everywhere below its melting point, the stable form. The equilibrium melting temperature for form 2 is estimated to be about 128 °C, and for form 1 about 141 °C. A degree of crystallinity scale based on specific volume is established. The degree of crystallinity of form 2 is about 52 percent, and after conversion to form 1, the crystallinity is about 77 percent.