Effect of fat pre-feeding on bile flow and composition in the rat

Studies were conducted in rats to determine if the increase in lymph triacylglycerol output on pre-feeding a 20% glyceryltrioleate diet (Mansbach, C.M., II and Arnold, A. (1986) Am. J. Physiol. 251, G263-269) was due to an increase in phosphatidylcholine output into bile. Rats who were fed chow or pre-fed the 20% fat diet were equipped with biliary and duodenal cannulas and infused with glucose-saline while bile was collected hourly. The next day a taurocholate-glyceryltrioleate infusion was given and bile collected for 5 h. Bile flow, bile acid, phosphatidylcholine and cholesterol output were greater in the chow fed group than controls during the 6 h of the glucose saline period. Outputs were low overnight. During the taurocholate-glyceryltrioleate infusion, bile flow, bile acid, phosphatidylcholine and cholesterol output were all greater in the fat pre-fed group than the chow fed controls. We conclude that fat pre-feeding profoundly influences biliary composition and flow. The 2-fold increase in biliary phosphatidylcholine output during duodenal lipid infusion offers a potential explanation for the increased delivery of triacylglycerol into the lymph in rats on a similar fat pre-feeding program.     

Lanthanum-induced alterations in cellular electrolytes and membrane potential in Ehrlich ascites tumor cells

We have investigated the effect of varying La⁺³ concentrations (0.01 mM to 2.0 mM) on membrane potential and electrolyte composition of Ehrlich ascites tumor cells. La⁺³ concentrations less than 0.02 mM had no effect. Above 0.02 mM, La⁺³ induced concentration-dependent loss of electrolytes and water from the cells. At 1.0 mM the effect was maximal and resulted in an 87% reduction in cellular K⁺, 79% in Cl^? and 21% in Na⁺ within 4.8 minutes. The Na⁺ loss occurred even in the face of an electrochemical potential gradient favoring Na⁺ entry. La⁺³ increased the recorded values of membrane potential; the magnitude of the effect was related to the external La⁺³ concentration, and was maximal at 1.0 mM. Studies using ¹⁴⁰La showed that La⁺³ binds rapidly to the cell surface and does not enter the cells. The amount of La⁺³ bound to the cells was related to the external La⁺³ concentration by a sigmoidal curve and was maximal at about 1.0 mM. The bound La⁺³ could not be displaced by either added La⁺³ or Ca⁺². Agents known to effect the integrity of the cell membrane, such as phospholipase C, neuraminidase, pronase and Hg⁺² were tested for their ability to displace bound La⁺³. Only pronase displaced bound La⁺³, indicating that La⁺³ associates with cell protein. It is hypothesized that La⁺³ rapidly interacts with membrane protein causing alterations in membrane permeability and capacity to actively transport ions.     

Metabolic Requirements for Microcycle Sporogenesis of Bacillus megaterium

Spores of Bacillus megaterium QM B1551 germinated, elongated, and resporulated (microcycle sporogenesis) in simple chemically defined media which permitted no cell division. The second-stage spores thus produced were heat-stable and required heat activation for germination. The original amount of spore deoxyribonucleic acid tripled before completion of the cycle. Acetate and a small amount of a tricarboxylic acid cycle intermediate were the minimal organic metabolic requirements for microcycle sporogenesis. During this cycle, germinated cells oxidized acetate only after a delay, whether or not glucose was initially present. Spores that were germinated in the absence of a carbon source first oxidized an endogenous substrate, and then developed the ability to oxidize acetate.     

Rapid Method for Measuring Extracellular Water in Yeast Preparations

A rapid procedure for the quantitative determination of extracellular water in bulk bakers' yeast was developed on the basis of the solute dilution principle. A reagent is prepared by synthesizing the diazonium ion of p-aminobenzoic acid and coupling it to peptone. This "azopeptone reagent" permits direct colorimetric measurement, which accounts for the rapidity and simplicity of the test. Potential errors due to osmotic effects are avoided by supplementing the reagent with saline and, more importantly, minimizing the duration of contact between reagent and cells. The new method has acceptable accuracy and precision, and may also be suitable for use with other microorganisms.     

CARDIAC CATHETERIZATION IN ADULT CONGENITAL HEART DISEASE—A Preliminary Report

The diagnosis of uncomplicated ventricular septal defect and uncomplicated patent ductus arteriosus presents few hazards. Differential diagnosis of atrial septal defect and of transposed pulmonary veins is technically more difficult. The complex nature of most types of cyanotic congenital heart disease requires the combined use of catheterization, determination of circulation times, ventilation studies, and possibly angiocardiography.Reports of eight cases in which cardiac catheterization was carried out illustrate the common forms of acyanotic and cyanotic heart disease and the factors in diagnosis.     

Intrinsic growth control in the imaginal primordia of Drosophila, and the autonomous action of a lethal mutation causing overgrowth

Cell proliferation in Drosophila imaginal discs appears to be regulated by a disc-intrinsic mechanism involving local cell interactions that also control the formation of patterns of differentiation. This growth-control mechanism breaks down in animals homozygous for the mutation lethal (2) giant discs (l(2)gd) which remain as larvae for up to 9 days longer than normal. During this time cell proliferation continues in the imaginal discs as well as in the imaginal rings for the salivary glands, foregut, and hindgut, so that these tissues become greatly overgrown. When wild-type wing discs from mid-third instar larvae were removed and cultured for up to 28 days in wild-type female adult hosts, they grew and terminated growth at a cell number close to that which would be attained in situ by the time of pupariation. On the other hand, wing discs from l(2)gd homozygotes grew rapidly and continuously when cultivated in wild-type hosts, reached an enormous size, and acquired abnormal folding patterns. Overgrowth of mutant imaginal rings also continued during culture of these tissues in wild-type hosts. We conclude that overgrowth in this mutant is due to an autonomous defect in the imaginal primordia, which requires an extended larval period for its expression in situ.