Measurement of extracellular space in the rabbit AV node

We used quantitative histochemistry to measure the size of the extracellular space (ESC) in various regions of the rabbit heart. When inulin, sucrose, and sorbitol were used as ECS markers, the ECS of the AV-nodal tissue was found to be, respectively, 2.4, 2.2, and 2.5 times larger than that of left ventricular muscle. Glucose was also measured over a 50-fold serum concentration range as an extracellular marker for AV-nodal tissue, left ventricular muscle, and Purkinje fibers. Measurements with glucose also revealed that the ECS of the AV node was 2.5-2.8 times larger than that of ventricular muscle. In contrast, the ECS of the AV node was the same as that of Purkinje fibers when glucose was used as an extracellular marker. ATP content, measured as an intracellular marker, was similar in both AV-nodal and contractile tissue. Collectively, the data obtained with all extracellular markers indicate that the ECS of the AV-nodal region is approximately 2.5 times larger than that of adjacent contractile tissue. Differences in the size of the ECS in various regions of the heart probably have functional significance and should be considered appropriately during the interpretation of data obtained by biochemical and densitometric approaches.     

A Correspondence between Individual Differences in the Brain's Intrinsic Functional Architecture and the Content and Form of Self-Generated Thoughts

Although neural activity often reflects the processing of external inputs, intrinsic fluctuations in activity have been observed throughout the brain. These may relate to patterns of self-generated thought that can occur while not performing goal-driven tasks. To understand the relationship between self-generated mental activity and intrinsic neural fluctuations, we developed the New York Cognition Questionnaire (NYC-Q) to assess the content and form of an individual''s experiences during the acquisition of resting-state fMRI data. The data were collected as a part of the Nathan Kline Rockland Enhanced sample. We decomposed NYC-Q scores using exploratory factor analysis and found that self-reported thoughts clustered into distinct dimensions of content (future related, past related, positive, negative, and social) and form (words, images, and specificity). We used these components to perform an individual difference analysis exploring how differences in the types of self-generated thoughts relate to whole brain measures of intrinsic brain activity (fractional amplitude of low frequency fluctuations, regional homogeneity, and degree centrality). We found patterns of self-generated thoughts related to changes that were distributed across a wide range of cortical areas. For example, individuals who reported greater imagery exhibited greater low frequency fluctuations in a region of perigenual cingulate cortex, a region that is known to participate in the so-called default-mode network. We also found certain forms of thought were associated with other areas, such as primary visual cortex, the insula, and the cerebellum. For example, individuals who reported greater future thought exhibited less homogeneous neural fluctuations in a region of lateral occipital cortex, a result that is consistent with the claim that particular types of self-generated thought depend on processes that are decoupled from sensory processes. These data provide evidence that self-generated thought is a heterogeneous category of experience and that studying its content can be helpful in understanding brain dynamics.     

Partial trisomy 11q as the result of sporadic translocation

Summary Partial trisomy 11q due to a sporadic translocation was found in a mentally retarded girl with multiple abnormalities. The proportion of sporadic translocations involved in the total incidence of partial trisomies is discussed.     

Radiology: angiographic diagnosis and therapy for impotence

The Scientific Board of the California Medical Association presents the following inventory of items of progress in radiology. Each item, in the judgment of a panel of knowledgeable physicians, has recently become reasonably firmly established, both as to scientific fact and important clinical significance. The items are presented in simple epitome, and an authoritative reference, both to the item itself and to the subject as a whole, is generally given for those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, research workers or scholars to stay abreast of these items of progress in radiology that have recently achieved a substantial degree of authoritative acceptance, whether in their own field of special interest or another.The items of progress listed below were selected by the Advisory Panel to the Section on Radiology of the California Medical Association and the summaries were prepared under its direction.     

Heat treatment of ripening apples: Differential effects on physiology and biochemistry

Apples ( Malus domestica Borkh.) were heated for 4 days at 38°C immediately after harvest and then placed at 20°C for 7–10 days. Protein synthesis, ethylene production and fruit softening were reversibly inhibited by the heat treatment. Fruit respiration, membrane permeability and chlorophyll degradation in the fruit peel were enhanced during the treatment. The heat-treated apples ripened normally but more slowly than untreated apple We hypothesize that heat treatment differentially affects processes which normally increase simultaneously during fruit ripening, by inhibiting those processes which require tie novo protein synthesis and enhancing those that do not.     

Protein Synthesis and Breakdown during Heat Shock of Cultured Pear (Pyrus communis L.) Cells

Cultured pear (Pyrus communis L. cv Passe Crassane) cells were subjected to temperatures of 39, 42, and 45[deg]C. Heat-shock protein (hsp) synthesis was greater at 30[deg]C than at temperatures above 40[deg]C and continued for up to 8 h. Both cellular uptake of radiolabeled methionine and total protein synthesis were progressively lower as the temperature was increased. Polysome levels decreased immediately when cells were placed at 39 or 42[deg]C, although at 39[deg]C the levels began to recover after 1 h. In cells from both temperatures, reassembly occurred after transfer of cells to 25[deg]C Four heat-shock-related mRNAs[mdash]hsp17, hsp70, and those of two ubiquitin genes[mdash]all showed greatest abundance at 39[deg]C and decreased at higher temperatures. Protein degradation increased with time at 42 and 45[deg]C, but at 39[deg]C it increased for the first 2 h and then decreased. In the presence of cycloheximide, which prevented hsp synthesis, protein degradation at 39[deg]C was as great as that at 45[deg]C in the absence of cycloheximide. The data suggest that hsps may have a role in protecting proteins from degradation at the permissive temperature of 39[deg]C. At temperatures high enough to inhibit hsp synthesis, protein degradation was enhanced. Although ubiquitin may play a role in specific protein degradation, it does not appear to be involved in increased protein degradation occurring above 40[deg]C.     

Mutation spectrum in gamma-irradiated shuttle vector replicated in ataxia-telangiectasia lymphoblasts.

Cells from ataxia-telangiectasia (AT) patients are hypersensitive to the lethal effects of ionizing radiation. To assess radiation mutagenesis in these cells, the SV40-based shuttle vector, pZ189, was used to analyze gamma-ray-induced mutations following the plasmid's replication in AT lymphoblasts. Progenies from the AT line GM2783 exposed to 50 Gy showed a mutation frequency of 7.6 x 10(-3), 63-fold over background; surviving plasmids were 3.4% of control. Both values were essentially the same as those of irradiated plasmids replicated in a normal lymphoblast line, GM606. In addition, pZ189 exposed to 25 Gy of gamma radiation and replicated in another normal lymphoblast line and in cells of two additional AT lymphoblast lines showed similar mutation frequencies and percentages of surviving plasmids. Qualitative comparison of plasmid mutations from AT and normal cells showed no significant differences, indicating that the damaged DNA was repaired with similar fidelity in AT and normal cells. These studies suggest that there is no correlation between the enhanced sensitivity of AT cells to killing by ionizing radiation and gamma-radiation-induced mutagenesis of plasmid DNA processed in these cells.     

Variability in host plant resistance of Sorghum to Striga Hermonthica infestation in West Africa

Fourteen elite sorghum lines were evaluated for their resistance to Striga hermonthica at three locations in Nigeria and Mali. Results showed that many of the lines especially MALISOR 84-1, SAMSORG 41, 97-SB-F5DT-64 (Keninkédié) and the check SRN 39 remained resistant to Striga in all locations with low emerged Striga counts, while SAMSORG 14 had the highest Striga infestation in all locations. Considerable variation in reaction to Striga infestation was observed on Séguètana, 97-SB-F5DT-63 (Wasa), 97-SB-F5DT-65, CMDT 38, CMDT 39 and CMDT 45 which were susceptible to Striga at Samaru, Nigeria but were resistant to Striga at both locations in Mali. Based on low Striga resistance and high grain yield, lines MALISOR 84-1, SAMSORG 41, 97-SB-F5DT-64, 97-SB-F5DT-65, CMDT 39 and SAMSORT 14 have been nominated for wider evaluation across more West African countries.