Leaf shelter-building caterpillars harness forces generated by axial retraction of stretched and wetted silk

Leaf shelter-building caterpillars generate most of the force required to pull leaf surfaces together by stretching silk strands while spinning. Axially retractive forces produced by columns of stretched strands enabled caterpillars in our study to generate forces as great as 0.3 Newtons (i.e., a 30-g force). We found that caterpillar silk also contracts instantly when wetted, producing an additional, though smaller, axially retractive force. Contraction ratios (final length/ original length) of the wetted silk of 19 species ranged from 0.21 to 0.93 and were smallest among species that use their silk to make leaf shelters. Our study, the first to identify the specific sources of the energy harnessed by caterpillars to tie, roll, or fold leaves, indicates that silk properties and caterpillar behavior have coevolved to facilitate the leaf shelter-building process.     

Enxymological characterization of a putative canine analogue of primary hyperoxaluria type 1

This paper concerns an enzymological investigation into a putative canine canalogue of the human autosomal recesive disease primary hyperoxaluria type 1 (alanine:glyoxylate / serine:pyruvate aminotransferase deficiency). The liver and kidney activities of alanine:glyoxylate aminotransferase and seribe:pyruvate aminotransferase in two Tibetan Spaniel pups with familial oxalate nephripathy were markedly reduced when compared with a variety of controls. There were no obvious deficiencies in a number of other enzymes including d-glycerate dehydrogenese / glyoxylate reductase which have been shown previously to be deficient in primary hyperoxaluria type 2. Immunoblotting of liver and kidney homogenates from oxalotic dogs also demonstrated a severe deficiency of immunoreactive alanine:glyoxylate aminotransferase. The developmental expression of alanine:glyoxylate / serine:pyruvate aminotransferase was studied in the livers and kidneys of control dogs. In the liver, enzyme activity and immunoreactive protein were virtually undetectable at 1 day old, but then increased to reach a plateau between 4 and 12 weeks. During this period the activity was similar to that found in normal humanb liver. The enzyme activities and the levels of immunoreactive protein in the kidneys were more erratic, but they appeared to increase up to 8 weeks and then decrease, so that by 36 weeks the levels were similar to those found at 1 day. The data presented in this paper suggest that these oxalotic dogs have a genetic condition that is anlogous, at least enzymologically, to the human disease primary hyperoxaluria type 1.     

CMP-N-acetylneuraminic acid synthetase of Escherichia coli: high level expression, purification and use in the enzymatic synthesis of CMP-N-acetylneuraminic acid and CMP-neuraminic acid derivatives.

The gene encoding CMP-N-acetylneuraminic acid (CMP-NeuAc) synthetase (EC 2.7.7.43) in Escherichia coli serotype O7 K1 was isolated and overexpressed in E.coli W3110. Maximum expression of 8-10% of the soluble E.coli protein was achieved by placing the gene with an engineered 5'-terminus and Shine-Dalgarno sequence into a pKK223 vector derivative behind the tac promoter. The overexpressed synthetase was purified to greater than 95% homogeneity in a single step by chromatography on high titre Orange A Matrex dye resin. Enzyme purified by this method was used directly for the synthesis of CMP-NeuAc and derivatives. The enzymatic synthesis of CMP-NeuAc was carried out on a multigram scale using equimolar CTP and N-acetylneuraminic acid as substrates. The resultant CMP-NeuAc, isolated as its disodium salt by ethanol precipitation, was prepared in an overall yield of 94% and was judged to be greater than 95% pure by 1H NMR analysis. N-Carbomethoxyneuraminic acid and N-carbobenzyloxyneuraminic acid were also found to be substrates of the enzyme; 5-azidoneuraminic acid was not a substrate of the enzyme. N-Carbomethoxyneuraminic acid was coupled to CMP at a rate similar to that observed with NeuAc, whereas N-carbobenzyloxyneuraminic acid was coupled greater than 100-fold more slowly. The high level of expression achieved with the E.coli synthetase, together with the high degree of purity readily obtainable from crude cell extracts, make the recombinant bacterial enzyme the preferred catalyst for the enzymatic synthesis of CMP-N-acetylneuraminic acid.     

Tryptophan and tryptophan pyrrolase in haem regulation. The role of lipolysis and direct displacement of serum-protein-bound tryptophan in the opposite effects of administration of endotoxin, morphine, palmitate, salicylate and theophylline on rat liver 5-aminolaevulinate synthase activity and the haem saturation of tryptophan pyrrolase

1. The increase in the haem saturation of rat liver tryptophan pyrrolase caused by tryptophan administration was previously shown to be associated with a decrease in 5-aminolaevulinate synthase activity. 2. It is now shown that similar reciprocal effects are caused by palmitate and salicylate, both of which increase tryptophan availability to the liver by direct displacement of the serum-protein-bound amino acid. 3. The reciprocal effects on the former two parameters caused by endotoxin and morphine are associated with an increase in liver tryptophan concentration produced by a lipolysis-dependent, non-esterified fatty acid-mediated, displacement of the serum-protein-bound amino acid. 4. All these changes and those caused by another lipolytic agent, theophylline, are prevented by the β-adrenoceptor-blocking agent propranolol and by the opiate-receptor antagonist naloxone, whose anti-lipolytic nature is demonstrated. 5. High correlation coefficients have been obtained for one or more pairs of the following parameters: serum non-esterified fatty acid concentration, free serum tryptophan concentration, liver tryptophan concentration, liver 5-aminolaevulinate synthase activity, liver holo-(tryptophan pyrrolase) activity and the haem saturation of liver tryptophan pyrrolase. 6. It is suggested that liver tryptophan concentration may play an important role in the regulation of 5-aminolaevulinate synthase synthesis, and that the latter may be subject to control by changes in lipid metabolism and may be influenced by pharmacological agents that affect tryptophan disposition. 7. Preliminary evidence suggests that tryptophan may be bound in the liver and that such a possible binding may control its availability for its hepatic functions.     

A simple and novel method for radiometric analysis of glucose utilization by adrenal chromaffin cells

Glucose utilization by cells and tissues can be followed by measuring the release of [³H]H₂O from added -[5-³H]glucose, and we have developed a method whereby the whole reaction and assay can be performed in a single scintillation vial. The basic principle behind our new assay is that the released tritiated hydrogen ion in water can be quantitatively exchanged with the hydroxyl proton of simple alcohols such as isoamyl alcohol. The radiolabeled alcohol can then be extracted into an organic solvent to which 2,5-diphenyloxazole and p-bis[2-(5-phenyloxazoyl)]benzene have been previously added. Using this new assay we studied isolated chromaffin cells and found them to utilize glucose at a linear rate for at least 30 min. The assay was precise and reproducible enough to allow detailed analysis of various inhibitors of glycolysis and of oxidative phosphorylation. The new method is simple and rapid, can be done in open test tubes, requires no complex equipment, and is intrinsically highly accurate.     

Purification and phosphorylation of initiation factor eIF-2 from rabbit skeletal muscle

Core particle DNA unfolding and refolding are followed by stopped-flow circular dichroism technique. When core particles are dissociated in the stopped-flow cuvette, the high CD deviation corresponding to the dissociated state is reached in the first millisecond, which means that the dissociation process is completed within the dead time of the apparatus which is ～1 ms. The same conclusion can be drawn when core particles are reassociated, since the low CD value, typical of the associated state, is immediately reached. Similarly histone release from chromatin is a very fast process. We also include some points of discussion about core particle assembly process.     

Anhydrobiosis in Nematodes II: Carbohydrate and Lipid Analysis in Undesiccated and Desiccate Nematodes

Glycogen, trehalose, glucose, and total lipid contents of six nematode species were studied. Anhydrobiotic Anguina tritici and Ditylencbus dipsaci stored trehalose in preference to glycogen and only small amounts of glucose were detected. Glycogen content was also reduced in anhydrobiotic Aphelenchus avenae. Conversely, Panagrellus redivivus and Turbatrix aceti contained large amounts of glycogen, appreciable amounts of glucose, and minimal amounts of trehalose. Ditylenchus myceliophagous "curds" contained low amounts of glycogen and very little trehalose; total lipid was 60% of that in fresh samples. The lipid contents of fresh samples of P. redivivus, T. aceti, and A. avenae were high (23.1, 21.9, and 36.7% dry weight, respectively), but in anhydrobiotic A. avenae larvae the level was reduced by over 60%. In contrast, lipid levels remained high in anhydrobiotic A. tritici and D. dipsaci larvae (40.6 and 38.3%, respectively). Analysis of lipid composition in anhydrobiotic A. tritici and A. avenae did not indicate any specific metabolic adaptations to desiccation survival.