A reinvestigation of the role of the grey crescent in axis formation in xenopus laevis

Gravitationally induced displacements of the contents of the frog egg can predictably determine the orientation of the subsequent dorsal-ventral axis of the embryo, regardless of the original position of sperm entry or of the grey crescent. In certain conditions, these displacements in the egg can also lead to the formation of a second axis, that is, to twinning. The previously reported ability of grafts of grey crescent cortex to induce secondary axes in recipient eggs is interpreted here as an unrecognized twinning effect of gravity. Our results lead to question the classic interpretation of the grey crescent as a dorsal determinant in amphibian development.

Oxygen consumption for lower extremity exercises in normal subjects and burned patients

The purpose of this study was to compare the oxygen requirements for normal subjects and burned patients during rest and while performing two separate exercises of the quadriceps femoris muscles. The oxygen consumption of 10 normal subjects and 10 burned patients while at rest and while performing each exercise was measured. The resting and exercising oxygen-consumption levels for burned patients were significantly greater (p < .01) than for normal subjects. However, the mean difference in increased oxygen consumption during two exercises for normal subjects and for burned patients was not significant (p > .05). The elevated resting and exercising oxygen-consumption levels in burned patients were considered to be related to the hypermetabolic response characteristic of thermally injured patients.

Retinal changes in rats flown on Cosmos 936: A cosmic ray experiment

Ten rats, five centrifuged during flight to simulate gravity and five stationary in flight and experiencing hypogravity, orbited the Earth. No differences were noted between flight-stationary and flight-centrifuged animals, but changes were seen between these two groups and ground controls. Morphological alterations were observed comparable to those in the experiment flown on Cosmos 782 and to the retinal cells exposed to high-energy particles at Berkeley. Affected cells in the outer nuclear layer showed swelling, clearing of cytoplasm, and disruption of the membranes. Tissue channels were again found, similar to those seen on 782. After space flight, preliminary data indicated an increase in cell size in montages of the nuclear layer of both groups of flight animals. This experiment shows that weightlessness and environmental conditions other than cosmic radiation do not contribute to the observed damage of retinal cells.

Hydrogen bonding in solution between the uracil ring and the peptide backbone demonstrated by nuclear magnetic resonance spectroscopy

Proton and 13C nuclear magnetic resonance measurements indicate that uracil derivatives dissolved in chloroform bind to glycine and phenylalanine tripeptide derivatives through pairs of hydrogen bonds. The N(3)--H and C(4)=0 groups of the uracil ring appear to interact with the C=0 and N--H groups, respectively, of individual amino acid residues, suggesting a fundamental complementarity between uracil and the peptide backbone. The binding occurs in the same concentration range as the hydrogen bonding between derivatives of adenine and uracil under comparable conditions.

Cosmic ray effects on the eyes of rats flown on Cosmos No. 782, experimental K-007

The eyes from six rats were fixed at the recovery site in Russia after they had circled the earth for 19.5 d in a 62.8 degree orbit. The eyes of six more flight rats were fixed 25 d later. These two preparations and eyes exposed to 1000 rad of neon and argon were compared to obtain data on possible radiation effects on the retina. Most of the flight eye tissue was normal; however, necrotic nuclei were found in the outer nuclear layer and channels were located in the outer segment area. Macrophages were seen between the pigment layer and outer segments. Comparison of the Day zero znd 25-d postflight eyes suggested some possible recovery. Light flashes seen by space travelers and damage from cosmic rays appear to arise from two different sites of interaction. The flashes are created by cosmic ray transversal of the outer segments while pathologic change, when it occurs, is quite possibly from interaction with some part of the nucleus. Nevertheless, direct interaction with other cellular components could also occur. Other factors, such as secondaries from spacecraft shielding, may play an important role.

Binding of uracil derivatives to hydrophobic peptides and sodium dodecyl sulfate

The capacities of five hydrophobic peptides to bind 13 alkyl uracil derivatives have been assessed as a first step toward constructing polymeric molecules, related to the nucleic acids, that specifically complement protein molecules. The peptides were Phe-Phe-Phe-Glu-Glu and its structural analogs with leucine, isoleucine, methionine, and valine substituted for phenylalanine. Uracils with the following substituents in position 5' were used: i-propyl, i-butyl, i-pentyl, sec-butyl, n-butyl, phenyl, benzyl, phenylethyl, methylthioethyl, ethylthiomethyl, and ethylthioethyl. 6-Benzyl and 6-i-pentyl uracils were also tested. The variations in base binding patterns are unique for each peptide, and the general effectiveness of the peptides in binding is related to the order in which their hydrophobic amino acid constituents occur in the uracil column of the genetic codon table. Although the method used does not permit precise determination of binding constants, it is apparent that many of them are much lower than 1 mM. 5-Ethylthioethyluracil quite selectively forms a large metastable aggregate with Phe3Glu2. Its close homologues do not. Also, 5-ethylthioethyluracil binds in some measure to Met3Glu2 but not significantly to Ile3Glu2 and Val3Glu2, whereas its homologue, 5-ethylthiomethyluracil, binds better to the latter two than to Met3Glu2. Thus, the two homologues might serve to form hypothetical polymers that discriminatively bind polymers of isoleucine and valine. It is argued that evolution would most reasonably have begun with such crude mechanisms.

The effects of cosmic particle radiation on pocket mice aboard Apollo XVII: V. preflight studies on tolerancee to oxygen and heat. Part III. effects on eyes

A study was made of the eyes of eight pocket mice exposed to oxygen at partial pressures of 8, 10, or 12 psi over a period of 7 d. At the termination of the exposure, the animals were decompressed to sea-level O2 either immediately or over a period of 30, 60, or 90 min. No pathological changes were found in any of the eyes, except in the retina of one of the animals exposed to 12 psi O2. Here, only a single rod photoreceptor was found damaged, an observation not regarded as significant. Hence, an oxygen partial pressure as high as 12 psi in the camister in which pocket mice were expected to fly on Apollo XVII would probably have no deleterious effect on the eyes of the animals.

The flicker-fusion threshold in schizophrenia and depression

The flicker-fusion threshold was determined in 76 patients who complained of depression and who were diagnosed as suffering from either schizophrenia or depression. It was found to be lowered in schizophrenia and lowered further in depression as compared with 28 healthy volunteers. The differences between the three groups were all highly significant with P less than 0.0005 in each case. The flicker-fusion threshold was found to be lowered by intravenous chlorpromazine and raised by intravenous amitriptyline, so it is unlikely that these differences were due to medication that the patients had been taking.

Spasm and operative cholangiography

Operative cholangiography is a commonly employed adjunct to biliary operation and is useful in identifying unsuspected common duct calculi. Spasm of the sphincter of Oddi from administration of anesthetic agents like fentanyl citrate (Sublimaze) and morphine sulfate and from operative manipulation may lead to misinterpretation of the cholangiograms and unnecessary surgical procedures that increase morbidity and mortality. Six case reports illustrate these hazards, and the influence of medications that exacerbate spasm of the sphincter of Oddi is emphasized. Recognition of the factors that cause spasm of the sphincter of Oddi will prevent unnecessary common duct explorations and reduce morbidity and mortality in biliary tract operations.