Persistent atrial paralysis: Case report with light microscopy and ultrastructural analyses

Persistent atrial paralysis in a patient with complete heart block and mild mitral insufficiency is presented. Left atrial specimens obtained during implantation of a permanent cardiac pulse generator showed evidence of hypertrophy and fibrosis; subcellular degenerative changes ranged from near normal to irreversible, thus suggesting that atrial paralysis may be due to the replacement of normal atrial muscle with nonfunctional fibrous tissue.     

Critical importance of microsome concentration in mutagenesis assay with V79 Chinese hamster cells.

For optimum mutagensis in V79 Chinese hamster cells, the amount of liver postmitochondrial fraction in the assay was found to be of critical importance, depending on the chemicals being tested. Benzo[a]pyrene (BP) required lower (1-5%) concentrations of the liver 15 000 X g supernatant (S15) from methylcholanthrene pretreated rats for a maximum induction of cytotoxicity and mutagenicity, as determined by 8-azaguanine- and ouabain-resistance. A sharp peak of mutagenicity and cytotoxicity was induced by 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (7,8-diol BP) at a concentration of 1% of the S15 fraction. Little or no response was induced by these compounds with the S15 concentrations of more than 10%. Similarly, aflatoxin B1 induced a sharp peak of mutagenicity and cytotoxicity at a concentration of 2% of the liver S15 fraction from Aroclor-pretreated rats. Under the same condition, non-carcinogenic aflatoxin G2 did not induce cytotoxicity and mutagenicity. Analysis of BP metabolites by high-pressure liquid chromatography indicates that with the 30% S15 fraction, more than 80% of BP was metabolized during the first 15 min, while with the 2% S15 fraction, 7,8-diol BP increased continuously throughout the 120-min incubation period, suggesting a strong metabolic competition to rapidly remove BP and 7,8-diol BP with a high concentration of the S15. In contrast with these compounds, N-nitrosodimethylamine induced mutagenicity and cytotoxicity which increased linearly in proportion to the increasing amount of the S15 fraction from phenobarbitone- and Aroclor-pretreated rats. Various nitrosamines with different lipophilicity were examined at a high (30%) and low (2%) concentration of the S15 fraction from Aroclor-pretreated rats, in which ratios of mutation frequencies at 30% and 2% correlated inversely with lipophilicity of the compound. This result suggests that the lipid solubility of test compounds may be one factor which determines the concentration of post-mitochondrial supernatant for optimum mutagenesis.     

SUCCESSFUL AORTOCORONARY BYPASS SURGERY IN A PATIENT WITH CLASSICAL HEMOPHILIA A

A patient with documented Factor VIII deficiency (classical Hemophilia A) and a history of previous severe intra- and postoperative hemorrhage and transfusion reaction underwent myocardial revascularization for advanced triple vessel coronary artery occlusive disease. The coagulation status was investigated, and a replacement regimen was instituted. The surgical procedure and postoperative course were uneventful.     

Protein modules

As the database of protein sequences grows it is becoming apparent that many proteins are constructed from relatively few modular units that appear many times. Determination of the three-dimensional structure of such modules by NMR has been possible due to their production in relatively large quantities by recombinant DNA techniques. The knowledge gained about the structure of individual modules can then be used to predict their properties in a variety of intact proteins.     

ON MISSING ENTRIES IN CLADISTIC ANALYSIS

Abstract The exact algorithms of two commonly used parsimony programs, Hennig86 by J. S. Farris and PAUP by D. Swofford, sometimes produce different solutions, and sometimes produce resolutions that are not supported by the data being analysed. The discrepancies apparently involve the treatment of missing entries, which can currently represent unknown data, inapplicable character and/or polymorphic taxa. Each of those potential sources of ambiguity is logically (if not computationally) different; with regard to binary characters, unknown data could be either 0 or 1, inapplicable characters are neither 0 nor 1 and polymorphisms are both 0 and 1. Resolutions that cannot be supported by any possible combination of known state attributions should either be flagged as such or suppressed entirely.     

Fixed action patterns and neural Darwinism

Summary The stereotopy of the Fixed Action Pattern of classical ethology is customarily attributed to hard wiring. We submit that this explanation is akin to the 17th century use of the homunculus to explain development. We propose extendingEdelman's notions of neural Darwinism to explain the emergence of species-characteristic (innate) motor patterns.

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Angeborene, Stereotype Verhaltensweisen und Neuraler Darwinismus

Zusammenfassung Die in der klassischen Ethologie beschriebenen angeborenen Verhaltensweisen (sensuLorenz &Tinbergen) wurden meist durch die Annahme erklärt, daß bestimmte genetisch bedingte Nervennetze die stereotypen Bewegungen in reflektorischer Weise bestimmen. Im Computerjargon heißt das hard wiring. Wir meinen, daß diese Formulierung eher einer modernen Form des Homunculus des 17. Jh. als einer echten Erklärung entspricht, weil sie nicht erklären kann, wie das exakt reproduzierbare Nervennetz entsteht. Außerdem ist bekannt, daß dasselbe Verhalten auch bei enormen Unterschieden in der Neuralanatomie auftreten kann; stereotype Bewegungen brauchen keine spezifischen Nervennetze.G. Edelmann hat bereits vorgeschlagen, daß Nervennetze für angeborene Auslösemechanismen durch eine darwinistische Auslese von Neuronen entstehen können. Wir schlagen vor, dieses Prinzip auch zur Erklärung der Entwicklung stereotyper, artspezifischer Verhaltensweisen heranzuziehen und dadurch die sogenannte hard wiring-Erklärung abzulösen.

     

The induction of sensitivity to gibberellin in aleurone tissue of developing wheat grains

Aleurone tissue from undried immature developing wheat grains (Triticum aestivum L. cv. Sappo), normally insensitive to gibberellic acid, can be made to respond to the hormone by a series of temperature treatments. Incubation of the de-embryoed grains at temperatures above 27° C for at least 8 h causes the tissue to become sensitive. Prolonged incubation at temperatures below 27° C does not effect a change in sensitivity. In addition to the requirement for exposure to an elevated temperature for a period of several hours the tissue must also subsequently be subjected to a period at a lower temperature for just a few seconds for the response to be observed. Once sensitized, the tissue remains responsive to gibberellic acid for substantial periods of time. Exposure of the tissue to temperatures which induce sensitivity to gibberellic acid also results in an increased leakage of amino acids. It is suggested that the increase in sensitivity to gibberellin requires two separate processes to take place. One could be a homeoviscous adaptation of the cell membranes in response to elevated temperature, the other a subsequent, permanent change in conformation of membrane components.     

Trypanosoma musculi: Passive hemagglutination technique to measure antibody in mice

A passive hemagglutination assay was developed to measure Trypanosoma musculi-specific antibody in mice. Indicator-erythrocyte donor mice received 550 rad ⁶⁰Co 24 hr before intraperitoneal injection of 3 × 10⁴T. musculi. T. musculi antigen-coated erythrocytes were obtained from these mice on Day 9 postinfection. T. musculi antigen-coated erythrocytes obtained in this manner were used as indicator erythrocytes in a passive hemagglutination procedure. Serum from hyperimmunized mice (three consecutive infections at 21-day intervals) gave titers as high as 1:1024. Titers of 1:256 and 1:512 were obtained from singly infected mice on Days 18 and 28 postinfection, respectively. In marked contrast, nude mice infected with T. musculi did not produce a detectable agglutinating antibody response. Erythrocytes obtained from either irradiated (550 rad ⁶⁰Co) uninfected mice, nonirradiated infected mice, or normal mice did not agglutinate when combined with any of the sera tested. These data suggest the usefulness of this passive hemagglutination assay for the measurement of antibody to T. musculi in the serum of infected mice.