De novo synthesis of 3'-nucleotidase in germinating wheat embryo

The enzyme 3′-AMP nucleotidase was purified 2,500- to 5,000-fold from extracts of an acetone powder of wheat (Triticum aestivum) embryonic axes germinated for 40 hours. Sodium dodecyl sulfate acrylamide gel electrophoresis and chromatography on Biogel-P100 indicate that the enzyme is monomeric with a molecular weight of 39,000. Extracts of embryos germinated up to 6 hours have only 1% of the 40-hour level of enzyme activity. To see if the increase to 40 hours represents de novo synthesis, extracts were compared for their ability to react with a rabbit antibody prepared against the enzyme. In immunodiffusion tests, 40-hour extracts showed a strong precipitin line coincident with that of the purified enzyme, whereas no precipitation was observed with 1-hour extracts. When the enzyme present in 40-hour extracts was partially inactivated by EDTA, it still blocked the ability of the antibody to inhibit enzyme activity. Extracts of 1-hour embryos, in contrast, were not able to block the inhibitory activity of the antibody. Embryos allowed to take up ³⁵SO₄ between 40 and 46 hours of germination synthesized ³⁵S-labeled 3′-nucleotidase. In contrast, no radioactive protein synthesized by embryos during the first 6 hours of germination coincided on gel electrophoresis with the enzyme. These results indicate that the increase in 3′-nucleotidase activity is a consequence of de novo synthesis of the enzyme.     

Early growth of wheat embryonic axes and the synthesis of RNA and DNA

The requirement for the synthesis of RNA and DNA in early germination of wheat (Triticum aestivum var Newana) embryonic axes has been studied by incubating embryos in the presence of appropriate inhibitors and monitoring both embryo growth and the rates of specific metabolic processes. Experiments with 5-fluorouridine showed that both rRNA and DNA synthesis could be curtailed by 60 to 70% without affecting embryo growth to 24 hours. Similarly, the presence of mitomycin C and methotrexate inhibited DNA synthesis 70%, with only a small effect on growth. Experiments with a range of concentrations of cordycepin and α-amanitin indicated that mRNA synthesis could be curtailed by 30 to 40% within the first 8 hours of germination with only a small effect on embryo growth. Thus, at least the initial phases of seed embryo germination are not closely linked to the synthesis of mRNA, rRNA, or DNA. Maximal sensitivity of embryo growth was obtained with cycloheximide and 2-(4-methyl-2,6-dinitroanilino)-N-methyl propionamide, supporting the idea that protein synthesis is the macromolecular process most closely linked to early germination.     

History of total nasal reconstruction with particular emphasis on the folded forehead flap technique

The history of plastic surgery is identified throughout the centuries with the history of rhinoplasty. The Indian Koomas first and later the Italian surgeons found valid solutions to the problems caused by partial loss of the nasal pyramid. However, the idea of rebuilding, with a single forehead flap, the tip and columella and providing at the same time a lining of skin for the newly formed nose goes back to the middle of the nineteenth century. The Italian Natale Petrali (1842) and the Germans Johann Friedrich Dieffenbach (1845) and Ernst Blasius (1848) contend for precedence in carrying out this important procedure still used today, which, barring postoperative contracture, represented a great advance in successful total rhinoplasty.     

Physiological effects of an allozyme polymorphism: Glutamate-pyruvate transaminase and response to hyperosmotic stress in the copepod Tigriopus californicus

In order to regulate cell volume during hyperosmotic stress, the intertidal copepod Tigriopus californicus, like other aquatic crustaceans, rapidly accumulates high levels of intracellular alanine, proline, and glycine. Glutamate-pyruvate transaminase (GPT; EC 2.6.1.2), which catalyzes the final step of alanine synthesis, is genetically polymorphic in T. californicus populations at Santa Cruz, California. Spectrophotometric studies of homogenates derived from a homozygous isofemale line of each of the two common GPT alleles indicated that the GPT^F allozyme has a significantly higher specific activity than the GPT^S allozyme. Under conditions of hyperosmotic stress, individual adult copepods of GPT^F and GPT^F/S genotypes accumulated alanine, but not glycine or proline, more rapidly than GPT^S homozygotes. When young larvae were subjected to the same hyperosmotic conditions, GPT^S larvae suffered a significantly higher mortality than GPT^F or GPT^F/S larvae. These results suggest that the biochemical differences among GPT allozymes result in specific physiological variation among GPT genotypes and that this physiological variation is manifested in differential genotypic survivorships under some naturally occurring environmental conditions.This work was supported in part by a grant from the Lerner Fund for Marine Research of the American Museum of Natural History, an NIH Training Grant in Integrative Biology, and NIH Grants GM 28016 and GM 10452.     

Postural influence on maternal capillary oxygen and carbon dioxide tension

The effect of posture on maternal capillary blood Po₂ and Pco₂ was studied in pregnant and non-pregnant women. There was a significant decrease of Po₂ (mean 13·0 mm. Hg) and significant decrease of Pco₂ (mean 2·4 mm. Hg) when pregnant women sat up, but these changes did not occur in the non-pregnant. These findings may be relevant to debate on the optimum posture for labour.     

Genetic Analysis of the Glutamate Permease in Escherichia coli K-12

The glutamate permeation system in Escherichia coli K-12 consists of three genes: gltC, gltS, and gltR. The genes gltC and gltS are very closely linked, and are located between the pyrE and tna loci, in the following order: tna, gltC, gltS, pyrE; gltR is located near the metA gene. The three glt genes constitute a regulatory system in which gltR is the regulator gene responsible for the formation of repressor, gltS is the structural gene of the glutamate permease, and gltC is most probably the operator locus. The synthesis of glutamate permease is partially repressed in wild-type K-12 strains, resulting in the inability of these strains to utilize glutamate as the sole source of carbon. Derepression due to mutation at the gltC locus enables growth on glutamate as a carbon source both at 30 C and at 42 C. Temperature-sensitive gltR mutants capable of utilizing glutamate for growth at 42 C but not at 30 C were found to be derepressed for glutamate permease when grown at 42 C and partially repressed (wild-type phenotype) upon growth at 30 C. These mutants produce an altered thermolabile repressor which can be inactivated by mild heat treatment (10 min at 44 C) in the absence of growth.     

Genetic and Physiological Analysis of Glutamate Decarboxylase in Escherichia coli K-12

No correlation was found between glutamate decarboxylase (GAD) activity and the ability of Escherichia coli K-12 strains to grow on glutamate. A gene, gad, determining GAD activity maps near gltC, which controls glutamate permease.     

Occurrence, isolation, and characterization of polyribosomes in yeast

This report details the procedural requirements for preparing cell-free extracts of yeast rich in polyribosomes. This enabled us to demonstrate the occurrence of polyribosomes in yeast, to show their role in protein synthesis, and to devise methods for their resolution and isolation. When certain precautions are met (the use of log phase cells, rapidly halting cell growth, gentle methods of disruption, sedimentation through exponential density gradients, etc.), individual polyribosome size classes ranging up to the heptosome can be fractionated and separated from their nearest neighbors. Larger size classes are resolved partially among themselves, free of smaller polyribosomes. This was confirmed by extensive electron micrographic studies of material from the various fractions obtained upon density gradient centrifugation of yeast extracts. Modifications of the gradients and procedure should allow fractionation and isolation of the larger polyribosomes, including those containing polycistronic messages. Yeast polyribosomes are disaggregated to single ribosomes by longer term grinding, cell disruption by the French pressure cell, the Hughes press, or by incubation with dilute RNAse. Yeast polyribosomes are active in the incorporation of amino acids into polypeptide; the single ribosomes exhibit only slight activity. The latter activity is probably due to the presence of a small fraction of monosomes still containing mRNA. Poly-U stimulates amino acid incorporation only in the single ribosomes.