The postnatal emergence of dehydration anorexia in rats is temporally associated with the emergence of dehydration-induced inhibition of gastric emptying.

Osmotic dehydration produced by systemic hypertonic NaCl (HS) inhibits gastric motility and emptying and also inhibits feeding in adult rats. Conversely, in neonatal rats, dehydration does not inhibit feeding. The present study examined whether the postnatal emergence of dehydration anorexia is temporally associated with the emergence of dehydration-induced inhibition of gastric emptying. Rat pups 4 to 19 days old were injected subcutaneously with HS (0.75 M NaCl; 200 microL/10 g body weight). Control rats were injected with isotonic saline (0.15 M NaCl). Thirty minutes later, rats were given access to milk that could be lapped from paper towels on the floor of a warm testing chamber. Other HS-treated and control rats were given an intragastric load of 0.15 M NaCl (2% body weight) and then killed after 30 min to determine how much of the load had emptied from the stomach. Consistent with previous reports, HS-treated rats consumed significantly more milk than control rats from postnatal Day 4 (P4) through P11 but consumed significantly less milk than controls at P19. HS treatment did not affect gastric emptying of 0.15 M NaCl at P4 or P11. Conversely, HS treatment significantly inhibited gastric emptying at P19. These findings suggest that the hypophagic effects of dehydration develop in tandem with inhibitory effects on gastric motility and are consistent with the view that the full complement of mature homeostatic responses to plasma hyperosmolality requires coordinated activation of forebrain and hindbrain neural circuits that are only partially formed in neonatal rats.

Improvements in accuracy and reproducibility of quantitative clotting factor assays by use of a novel approach for modeling reference curves.

A method for creating a reference model in the quantitative assay of specific clotting factor activities is described. This method incorporates the use of a piecewise function with two component polynomials. This function allows more accurate representation of the global coagulation reaction, a sequential activation of multiple serine protease enzymes and cofactors, leading to improvements over traditional methods in range, accuracy, precision and robustness in reported activity levels. Clotting factor assay results using this method are compared with traditional and other candidate methods.

A high-sensitivity thromboplastin reagent prepared from cultured human cells.

High-sensitivity thromboplastin reagents suitable for use in the prothrombin time (PT) assay are typically prepared from human brain and placenta, tissues that are in limited supply and subject to viral contamination. Cloning and expression of recombinant human tissue factor (TF) has enabled production of a new generation of thromboplastin reagents whose performance and utility are under active investigation. The purpose of this study was to determine the feasibility of producing a sensitive human thromboplastin reagent from a non-recombinant source: cultured human cells. Several human cell lines with apparently high constitutive TF synthesis were identified, and a viable thromboplastin reagent (Humaplastin) was produced from a human lung cell line via a non-conventional process that did not require reconstitution or rehydration of TF in cell membranes. When calibrated against BCT/253, a human brain international reference thromboplastin, Humaplastin exhibited a mean normal prothrombin time of 12.6 +/- 0.7 s (mean +/- SD: n = 20) and an International Sensitivity Index of 1.09 +/- 0.019. The performance of this reagent was well correlated (r = 0.983) with Thromborel S, a commercially available human placental thromboplastin reagent. Orthogonal least squares regression of the log PT values from the placental thromboplastin reagent versus Humaplastin and two recombinant TF-based thromboplastin reagents suggested that the latter three reagents are somewhat more sensitive than the placental thromboplastin reagent, although such differences should not be expected to have a significant impact on clinical utility. It is concluded that cultured human lung cells represent a suitable source of tissue thromboplastin for production of a high-sensitivity non-recombinant thromboplastin reagent.