The orchid bee Euglossa imperialis sucks nectars through a slender proboscis. I tested how nectar properties influence this suction pressure and whether ambient air pressure sets the upper limit for suction feeding. Nectar intake rate was measured as a function of sucrose concentration (5-75% w/w), nectar viscosity (2-80 mPa s), and ambient pressure (101-40 kPa). Intake rate declines from about...

1. Treatment of washed rat liver microsomes in a medium containing 0.12m-sucrose, 12.5mm-potassium chloride, 2.5mm-magnesium chloride and 25mm-tris-hydrochloric acid buffer, pH7.6, with 2m-lithium chloride at 5 degrees for 16hr. leads to the formation of membranes free of ribosomes and ribosomal subunits. 2. Confirmation of the absence of ribosomes from lithium chloride-prepared membranes was o...

The outer membrane (OM) of the mammalian pathogen Leptospira kirschneri was isolated in the form of membrane vesicles by alkaline plasmolysis and separated from the protoplasmic cylinder by sucrose density gradient ultracentrifugation. All four components of the alkaline plasmolysis buffer, including 1.0 M NaCl, 27% sucrose (wt/vol), 2 mM EDTA, and 10 mM Tris (pH 9), were required for efficient...

Cytosolic retinoic acid receptor in carcinoma, chronic pancreatitis, and normal pancreatic tissue were examined using sucrose density gradient centrifugation, isoelectric focussing on agarose gel and saturation analysis. Thirteen patients were studied. Cytosolic retinoic acid binding protein (cRABP) was detected in all the samples with chronic pancreatitis and pancreatic carcinoma, but not in t...

Human peripheral lymphocytes were incubated in the presence of Phaseolus vulgaris phytohemagglutinin. ACtivities of both glutamine-utilizing carbamyl phosphate synthetase (EC 2.7.2.5) and aspartate transcarbamylase (EC 2.1.3.2), the initial enzymes of the de nouo pathway for pyrimidine biosynthesis, increased simultaneously during the blastogenesis of lymphocytes. A very close connection betwee...

Growth of a strain of Bacillus subtilis that requires uracil, thymine, adenine, and tryptophan in the presence of 5-fluorouracil (FU) results in the synthesis of ribonucleic acid (RNA) and ribosomes in which 55 to 65% of the RNA uracil has been replaced by the fluorine derivative. Examination of analogue-containing ribosomes by sucrose density gradient centrifugation and thermal denaturation st...

A polysome extract from salivary glands of C. tentans was sedimented in a 15-60% sucrose gradient. Fractions from the heavy polysome region (1,000-2,000S) and fractions from the light polysome region (200-1,000S) were pooled separately, and the long-term labeled RNA was released by Sarkosyl/pronase and analysed by in situ hybridization. The results showed that BR 1 and BR 2 sequences were prese...

1. Enterocytes were isolated from rat jejunum and characterized morphologically. 2. Attempts to separate the enterocyte subcellular organelles, characterized by their marker enzymes, with isopycnic centrifugation were unsuccessful but good separation of peroxisomes, lysosomes and mitochondria was achieved by sedimentation through a shallow sucrose density gradient with a super-imposed inverse g...

1. Isoelectric focusing of human liver alkaline phosphatase in a sucrose density gradient with LKB Ampholine as carrier ampholytes is described. 2. Problems due to the chelating properties of the ampholytes and the pH gradient were examined. 3. A reactivation procedure to counter these effects was devised that can probably be used for other alkaline phosphatases. 4. The isoelectric point of hum...

A procedure is described for preparing intact mitochondria from leaves of Sedum praealtum D.C., a plant showing Crassulacean acid metabolism. These mitochondria oxidized malate, pyruvate, alpha-ketoglutarate, succinate, NADH, NADPH, and isocitrate with good respiratory control and ADP/O ratios better than those observed in mitochondria from other photosynthetic tissues.Malate oxidation was very...