Effect of fixation time on measurement of 2''-deoxyribonucleoside 5''-triphosphate pools in the rat embyro.

Values for the concentrations of deoxyribonucleoside triphosphates in rat embryos on day 12 of gestation, determined by high-pressure liquid chromatography, were artifactually two to three times as high in embryos fixed by cooling in ice/water followed by freezing on solid CO2, in 20s, as in those more rapidly/fixed in liquid N2, in 1 s.     

Analysis of the principles underlying chemo-immunotherapy of mouse tumours

Summary A CBA mouse fibrosarcoma (M4) growing as a solid tumour was treated with a single high dose (200 mg/kg) of cyclophosphamide (CY) followed by C. parvum (CP) immunotherapy. The optimal time for the administration of both nonspecific (CP IV) and active specific (SC CP-irradiated tumour cell mixtures) immunotherapy after CY was 4 days, compared with 1, 8, or 12 days. Optimal combinations of CY and CP were synergistic in that they provided a stronger antitumour effect than the sum of the individual effects of the two agents. In keeping with the finding that a 4-day interval between CY and CP was better than only 1 day, studies in normal mice show that when CP is given early during the suppressive phase of CY the onset of both specific and nonspecific antitumour effects are delayed. CY increased the susceptibility of mice to the toxic effects of a subsequent high systemic dose of CP.     

Femoral stiffness and jumping in grasshoppers and locusts

There is a close relationship between maximal jumping force and animal mass. Likewise, the relative stiffness of the hind femoral exoskeletal cuticle is very highly correlated with both animal mass and the force exerted during a jump. It is suggested that femoral stiffness has functional importance in the extensor energy storage system utilized in jumping by grasshoppers and locusts.     

The effects of dogfish MSH''s and of corticotrophin-like intermediate lobe peptides (CLIP''s) on avoidance behavior in rats

Recently purified melanocyte-stimulating hormones (MSH's) from dogfish pituitary tissue were tested on extinction of a conditioned avoidance response (CAR). Corticotrophin like intermediate lobe peptides (CLIP's) from dogfish and porcine origin were tested for an effect on avoidance extinction as well. All peptides appeared to delay extinction of the CAR.The results suggest that the pituitary contains various peptides which influence adaptive behavior. The observation that MSH is more potent in delaying extinction of the CAR then CLIP leads to the conclusion that the behavioral active sequence of the ACTH molecules is located in the N terminal part rather than in the C terminal part of the polypetide.     

Effects of ischemia on forelimb weight and lymph protein concentration.

The aim of this study was to determine if edema develops in the canine forelimb after relief of prolonged ischemia. Two hours of ischemia was induced either by interrupting brachial artery inflow in collateral-free innervated, naturally and constantly perfused preparations or by applying a pressure cuff in intact preparations. Changes in extravascular fluid volume were inferred from changes in limb weight. Relief of ischemia produced a transient 1.7% increase in weight in the collateral-free, naturally perfused preparation but had no effect on weight in the collateral-free, constantly perfused or intact preparations. Skin lymph flow failed to change significantly and total lymph protein concentration increased only slightly. Thus, relief of 2 hr of ischemia does not produce marked edema or a large increase in microvascular permeability to plasma proteins in the dog forelimb.