REGIONAL CHANGES IN BRAIN CATECHOLAMINES AFTER PROTON IRRADIATION OF THE STRIATE CORTEX IN THE SQUIRREL MONKEY

To establish possible functional relationships between anatomically distinct cortical centres in primates, we compared changes in visual acuity, nucleic acids, protein, enzymes and catecholamines in cortical and subcortical areas six months after 10,000 and 20,000 rd of proton irradiation of striate area 17 of the visual cortex of the squirrel monkey. Minimum separable acuity was reduced from 1 minute of arc in controls to 4 minutes in the 20,000-rd group. DNA, RNA and protein contents were not altered, but the activity of acetylcholinesterase was increased significantly in area 17. A decrease of norepinephrine occurred in the hypothalamus, hippocampus, caudate nucleus, putamen and brain stem of the irradiated brains. Since no ultrastructural basis has been found to account for these changes, we assume that a sustained chemical change occurred at the irradiated site and that the effect was transmitted to non-irradiated regions of the brain.     

Transport Phenomena in Zonal Centrifuge Rotors: I. Velocity and Shear-Stress Distributions of Fluid During Acceleration

An analysis is presented for the evaluation of velocity components and shear-stress distributions of fluid in zonal centrifuge rotors during acceleration. Analytical expressions for the distribution of tangential and radial velocity components and the tangential shear-stress and the radial shear-stress distributions of fluid are obtained for the transient case. Characteristics of each distribution for a typical density gradient liquid in a zonal centrifuge rotor are computed from the relations derived, and are presented as figures. An unusual phenomenon—the tangential velocity of the gradient exceeding the velocity of the rotor during a particular period of acceleration—is demonstrated.     

The influences of mechanical loads on the form of a growing elastic body

In this paper the influences of certain classes of mechanical loads on the configuration of a growing body are studied for a special class of linear material. The specific problem is: If the form to which a body grows under no externally applied loads is known, what will be the form of the body if some mechanical loads are applied to it during growth? Constitutive equations are formulated for the particular class of materials satisfying the following requirements:

1. (a) The material grows isotropically in normal growth.

2. (b) The material is normal.

3. (c) The state of growth of the material is completely determined by the current mechanical conditions.

4. (d) The growth is relatively slow and the stress field is quasi-static.

The cases of simple tension and simple shear are analyzed for various boundary conditions and the resulting effects of stress on growth are discussed.     

Immunofluorescence and Cytochemical Studies of Visna Virus in Cell Culture

Sequential morphological changes occurring in sheep choroid plexus cells infected with visna virus were studied by direct immunofluorescence, acridine orange, and hematoxylin and eosin staining methods. Specific immunofluorescence was first detected in the perinuclear cytoplasm of solitary cells 24 hr after infection. As the infection progressed, viral antigen appeared in an increasing number of cells, and rounded globular cells with long slender processes harboring intense fluorescence were seen. Nuclear fluorescence was not observed in infected monolayers. Polykaryocytes formed within 6 hr after inoculation due to the direct cell-fusing effect of the virus inoculum did not show specific fluorescence. Viral antigen was found, however, in the cytoplasm of multinucleated giant cells in cover slips harvested after new infective virus had been released, and later in the course of infection circular fluorescent inclusions were seen in the cytoplasm of polykaryocytes. Comparable eosinophilic inclusions were observed in hematoxylin and eosin preparations, and acridine orange staining of infected monolayers demonstrated similar inclusions which fluoresced with the color characteristic of single-stranded nucleic acid and were susceptible to digestion with ribonuclease. Visna virus appears to be a ribonucleic acid virus which replicates in the cytoplasm.     

Determination of Giardia lamblia cyst infective dose for the Mongolian gerbil (Meriones unguiculatus).

The purpose of this study was to determine the 50% infective dose for Giardia lamblia (CDC:0284:1) cysts in Mongolian gerbils (Meriones unguiculatus). The log10 50% infective dose results calculated by probit analysis and the Spearman-Karber method were 2.45 and 2.50, respectively.     

A strategy for efficient characterization of macromolecular heteroassociations via measurement of sedimentation equilibrium.

A method is proposed for the selection of experimental conditions for sedimentation equilibrium experiments that will provide maximal information about the values of equilibrium association constants within a given scheme for heteroassociation of two solute components. A discriminator function is proposed that indicates the sensitivity of the experimentally observed gradient or gradients to alterations in the underlying association constants. The value of this function is plotted or tabulated as a function of the concentrations of the two components, over a broad range of solution compositions. It is suggested that experiments performed with loading compositions corresponding to large absolute values of the discriminator function will yield the most information with respect to determination of the underlying association constants. This method was tested by predicting optimal conditions for three different types of sedimentation equilibrium experiments: (i) measurement of total (natural) solute absorbance; (ii) measurement of individual component gradients via measurement of tracer absorbance; and (iii) global analysis of multiple experiments. Experimental data resulting from sedimentation equilibrium experiments carried out under the specified conditions were simulated by addition of realistic levels of random error to calculated equilibrium gradients. The simulated data were then analyzed exactly as real experimental data, i.e., without prior knowledge of the underlying association constants. It was found that the highest accuracy and precision in determination of heteroassociation constants are obtained by global analysis of multiple experiments performed using significantly different loading compositions, each of which is selected from 'sensitive' regions of the discriminator map.     

Fragments of the internal transcribed spacer 1 of pre-rRNA accumulate in Saccharomyces cerevisiae lacking 5''----3'' exoribonuclease 1.

The portion of the internal transcribed spacer 1 found on 20S pre-rRNA accumulates in Saccharomyces cerevisiae lacking 5'----3' exoribonuclease 1, showing that an endonucleolytic cleavage at the 3' terminus of 18S rRNA is involved in the 20S pre-rRNA to 18S mature rRNA conversion. Smaller fragments of the spacer sequence are also found. The exoribonuclease may be involved as a cytoplasmic RNase in the hydrolysis of the spacer.     

Hemoglobin E: a common hemoglobinopathy among children of Southeast Asian origin.

With the recent immigration of Southeast Asians to Canada, hemoglobin E has become a frequent diagnosis. The clinical and hematologic findings in 42 children (mean age 4.3 years) with hemoglobin E are presented. There were 33 heterozygotes (having hemoglobin E trait), 6 homozygotes (having hemoglobin EE) and 3 double heterozygotes (having hemoglobin E-beta-thalassemia). The heterozygotes had low-normal hemoglobin levels and mean corpuscular volumes; coexisting iron deficiency, present in 62% of these children, resulted in substantially lower hemoglobin levels, very low mean corpuscular volumes and lower than expected levels of hemoglobin E on electrophoresis. The children with hemoglobin EE were only slightly anemic, but those with hemoglobin E-beta-thalassemia had severe anemia and required long-term transfusion therapy. Nutritional factors and parasitic infestations were the main causes of iron depletion, which was common, particularly in children less than 2 years old (87%). Physicians of patients of Southeast Asian origin should be aware of the clinical and hematologic presentation of these hemoglobinopathies.     

Sustained Nicotine Exposure Differentially Affects α3β2 and α4β2 Neuronal Nicotinic Receptors Expressed in Xenopus Oocytes

Abstract: To determine whether prolonged exposure to nicotine differentially affects α3β2 versus α4β2 nicotinic receptors expressed in Xenopus oocytes, oocytes were coinjected with subunit cRNAs, and peak responses to agonist, evoked by 0.7 or 7 µ M nicotine for α4β2 and α3β2 receptors, respectively, were determined before and following incubation for up to 48 h with nanomolar concentrations of nicotine. Agonist responses of α4β2 receptors decreased in a concentration-dependent manner with IC₅₀ values in the 10 n M range following incubation for 24 h and in the 1 n M range following incubation for 48 h. In contrast, responses of α3β2 receptors following incubation for 24–48 h with 1,000 n M nicotine decreased by only 50–60%, and total ablation of responses could not be achieved. Attenuation of responses occurred within the first 5 min of nicotine exposure and was a first-order process for both subtypes; half-lives for inactivation were 4.09 and 2.36 min for α4β2 and α3β2 receptors, respectively. Recovery was also first-order for both subtypes; half-lives for recovery were 21 and 7.5 h for α4β2 and α3β2 receptors, respectively. Thus, the responsiveness of both receptors decreased following sustained exposure to nicotine, but α4β2 receptors recovered much slower. Results may explain the differential effect of sustained nicotine exposure on nicotinic receptor-mediated neurotransmitter release.