Tachykinin involvement in cutaneous anaphylaxis in the guinea pig

Permeability changes in the guinea-pig skin following intradermal (i.d.) injection of tachykinin agonists or antigen were monitored through the extravasation of 99mTc-labelled human serum albumin and blood flow changes through the accumulation of 51Cr-labelled microspheres. A variety of synthetic and natural tachykinins, including substance P and neurokinins A and B, were shown to be potent inducers of permeability changes. Neurokinins A and B, but not substance P, were also shown to be apparent vasoconstrictor agents. Permeability responses in sensitized guinea pigs to i.d. injection of antigen and substance P, but not histamine, were abolished by pretreatment with the tachykinin antagonists [D-Arg1, D-Pro2, D-Trp7,9, Leu11]-substance P and [D-Pro2, D-Trp7,9]-substance P. Interpretation of such results was complicated by the fact that such antagonists may in themselves induce mast cell activation. Depletion of substance P containing neurons by pretreatment of guinea pigs with capsaicin also produced significant inhibition of antigen-induced permeability changes. These results indicate a possible role for tachykinins, such as substance P, in cutaneous anaphylaxis in the guinea pig.     

An experimental model of ameboma in guinea pig.

Among the wide variety of clinicopathological manifestations of intestinal amebiasis, amebomas occur rarely and their pathogenesis is not well understood. When cholesterol-fed, 2- to 4-week-old guinea pigs were infected intracecally with a virulent, monoaxenic strain of Entamoeba histolytica, gross and histologically characteristic amebomas developed in 85% of the animals by the 3rd day, in 94% by the 9th day, and in 96% by the 12th day postinfection, by which time most of them had died. Amebomas were confirmed by histopathology. Thus, a model of consistent production of amebomas was documented.     

The effects of starvation and experimental diabetes on phosphoenol-pyruvate carboxykinase in the guinea pig.

1. Approx. 85% of liver phosphoenolpyruvate carboxykinase is associated with the mitochondrial fraction in the fed guinea pig. Enzyme activity is unchanged in diabetes, but doubles during starvation. In contrast with earlier reports, both cytoplasmic and mitochondrial activities were found to be increased. 2. In kidney cortex, total enzyme activity is increased in both starved and diabetic animals. These changes are associated with increases in the cytoplasmic activity alone. 3. In diabetic animals the mean blood-glucose concentration was 23.1 mM. Other blood metabolites were lower than those in the rat, and the animals did not show significant ketosis. 4. Changes in the rates of gluconeogenesis from lactate and propionate paralleled those in phosphoenolpyruvate carboxykinase activity.