B-MuX: A unique murine C-type virus containing the “env” gene of xenotropic viruses and the “gag” gene of the ecotropic virus

A unique C-type virus, B-MuX, was isolated from nonproducer, BALB/c-transformed fibroblasts after IdUrd induction. B-MuX has the envelope gp70 properties of the endogenous BALB:virus-2 genome as determined by neutralization, interference, host-range characteristics and competition radioimmunoassays. Tryptic peptide analysis of gp70 from B-MuX revealed that B-MuX gp70 contains peptides in common to xenotropic virus gp70s and overall was very similar in structure to the xenotropic BALB: virus-2 gp70. In contrast, the gag gene products are serologically identical with the p15 and p12 of the endogenous, ecotropic virus. The p30 of B-MuX is structurally similar to that of the endogenous, ecotropic virus, and differs from the p30 of BALB/c xenotropic viruses as determined by tryptic peptide analysis. The results suggest that either B-MuX is a new type of endogenous, xenotropic virus or a recombinant between the endogenous xenotropic and ecotropic viruses. The unaltered xenotropic behavior of B-MuX demonstrates that the gag gene region does not contribute to this virological property.     

A simple computerized system for plotting the locations of cells of specified sizes in a histological section

A computerized plotting system is described which generates an outline of a histological section on an oscilloscope screen, and displays within its boundaries the positions of labeled neurons whose coordinates are sent to the computer electronically. Measured cell diameters can also be entered, allowing the computer to generate displays of the distributions of cells within specified size ranges. All data are saved by the computer, and any portion of a distribution may be examined oscilloscopically at several levels of magnification; moreover, three-dimensional displays may be generated with appropriate programs.     

Structure of the 3' extremity of barley stripe mosaic virus RNA: evidence for internal poly(A) and a 3'-terminal tRNA-like structure

The results of a previous study suggested that the poly(A) sequence in barley stripe mosaic virus (BSMV) RNA is intercalated between a 3'-terminal tyrosine-accepting structure and the 5'-terminal coding part of the BSMV genome. Here we show that poly(A)+ and poly(A)- fractions of BSMV RNA can be cleaved into two fragments specifically at the position of poly(A) or oligo(A) sequence with RNase H from Escherichia coli in the presence of oligo(dT)10. The shorter fragment (Sh) retains the ability of intact viral RNA to be aminoacylated, i.e., it represents the 3'-terminal part of BSMV RNA. Electrophoretic analysis of Sh-RNA reveals three closely positioned subspecies with an average length of about 210 nucleotides. The long 5'-terminal RNA fragment (L) produced by RNase H treatment has electrophoretic mobility similar to that of intact BSMV RNA, but displays neither amino acid-accepting ability nor infectivity. Nevertheless, L-RNA possesses the same messenger activity as the intact viral RNA and codes for the same pattern of polypeptides in rabbit reticulocyte lysate in vitro translation assays.     

Developmental changes in bombesin,substance P,somatostatin and vasoactive intestinal polypeptide in the rat brain

The regional distribution of the 4 neuropeptides, bombesin, substance P, somatostatin and vasoactive intestinal polypeptide (VIP) were investigated in the developing rat brain. Specific radioimmunoassay and immunocytochemistry were employed. VIP and bombesin were undetectable in the foetal brain whereas substance P and somatostatin were shown to be present in all regions as early as 14 days postcoitus. There was a dramatic postnatal increase in all 4 peptides in most regions. These results are discussed and compared with results of previous investigations of the ontogeny of the classic neurotransmitters.     

Age-associated changes in the micronuclear cycle of Tetrahymena thermophila A1III heterokaryons. A brief note

The micronuclear cycle of Tetrahymena thermophila A¹III heterokaryons is shown to change with increasing clonal age. Autoradiographic and cytofluorimetric studies suggest that alteration may be due to (1) loss of late replicating sequences, or (2) (more likely) changes in the timing of micronuclear division and S with respect to cytokinesis.     

beta-Endorphin is present in high concentration in the hypophysial portal vessels of rats

beta-Endorphin-like immunoreactivity (beta-ELI) was measured in hypophysial portal and arterial blood of intact, adrenalectomized and hypophysectomized rats. beta-ELI levels were 61 times higher in the long portal vessels than in the general circulation. Circulating, and especially portal, levels of beta-ELI were significantly increased after adrenalectomy. After removal of the pituitary gland, the mean level of beta-ELI in portal blood was significantly lower than in intact rats. beta-ELI in portal blood displayed the same chromatographic properties as synthetic beta-endorphin.     

Structural studies of murine I-E and human DR antigens.

The structures of murine I-E antigens from two strains of mice were compared to each other and to human DR antigens. Murine and human antigens were isolated by using allo- and xenoantiserum, respectively, and purified by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The murine I-E and human DR antigens consist of two polypeptide chains designated α and β. The E_α and DR_α chains display a high degree of amino acid sequence homology as do the E_β and DR_β chains, provided a gap is inserted at position 1 of the DR_β chain. Comparison of N-terminal sequences reveals several differences between the β chains of I-E antigens from the two strains of mice. In contrast no sequence differences between the two α chains are observed. In addition, comparison of tryptic peptides examined by isoelectrofocusing reveals several differences between the two E_β chains, but not between the two E_α chains. Thus, the polymorphism of murine I-E antigens and by analogy human DR antigens, may result from structural differences in the smaller (β) chain.     

Dendrite bundles in nuclei raphe dorsalis and centralis superior of the rabbit: A possible substrate for local control of serotonergic neurons

A Golgi-Cox, cresyl violet, and histofluorescence study has revealed the presence of dendrite bundles in nuclei raphe dorsalis (NSR) and centralis superior (CNS) in the rabbit brain stem. In NRD, bundles were found in the midline, traversing the medial longitudinal fasciculus (MLF) and in a circumferential location around the MLF. In NCS, bundles were found oriented vertically in the midline. Serotonergic dendrites predominnted in these bundles, but non-serotonergic denddites from cells of the dorsal tegmental nucleus, adjacent reticular formation, and NCS also were present. Lond descending shafts from tanycytes on the floor of the rostral fourth ventricle were also found in the dendrite bundles of both NRD and NCS. We suggest that the dendrite bundles constitute a local neuronal system for regulating the activity of these raphe neurons.     

Comparison of the antinociceptive activity of intraventricularly administered acetylcholine to narcotic antinociception

Intraventricularly administered acetylcholine inhibits mouse tail-flick latency in a dose-dependent manner with an ED₅₀ of about 20 μg. This antinociceptive activity is not mimicked by biogenic amine neurotransmitters (i.e. norepinephrine, epinephrine, dopamine, serotonin or histamine) and is not markedly affected by selective depletors of brain catecholamines or serotonin. However, pretreatment with reserpine or tetrabenazine dramatically reduces acetylcholine-induced antinociception. Tolerance develops rapidly to the antinociceptive effects of acetylcholine. Cross-tolerance to morphine in acetylcholine-tolerant mice is minimal, but the antinociceptive activity of acetylcholine is markedly reduced in mice chronically pretreated with morphine. Acetylcholine-induced antinociception differs from narcotic antinociception in the reversed stereoselectivity of several narcotic antagonists and in the in vivo pA₂ values for inhibition by naloxone. Therefore, the antinociceptive activity of intraventricularly administered acetylcholine cannot be described as a specific narcotic action.     

Sequence variation at the 3′ end of the neuraminidase gene from 39 influenza type A viruses

Thirty-nine influenza virus strains belonging to eight serologically distinct neuraminidase subtypes (N1 to N8) were examined in order to study the genetic variation which occurs within a subtype of influenza neuraminidase. RNA segment 6, which codes for neuraminidase, was sequenced from the 3′ end using the dideoxy method. The sequences obtained for the different subtypes reveal that there are several kinds of variation: (a) point mutations in the RNA which sometimes change the amino acid sequence, (b) short regions of many nucleotide and amino acid changes, (c) small insertions and/or deletions (usually three nucleotides or one amino acid at a time), and (d) large deletions (from 33 to 48 nucleotides in length).     

Relationship between the magnitude of myocardial ischemia and ultrastructural alterations

Previous studies have defined the sequence and time course of ultrastructural alterations in markedly ischemic myocardial tissue. In order to determine the effects of various levels of ischemia on myocardial ultrastructure we evaluated myocardial segments from the perfuse-fixed left ventricle 12 hr after occlusion of the left anterior descending artery. Radioactive microspheres, injected before and after occlusion, were employed to calculate segmental blood flow, and six samples from each segment were excised for electron microscopy. Ultrastructural analysis indicated that cellular changes follow a sequence which is related to the extent of myocardial ischemia. When flow declined to 50–75% of control values cellular swelling became evident and enlarged mitochondria with a relatively translucent matrix were common, although focal. In contrast a reduction in blood flow below 50% of control precipitated more marked mitochondrial changes—including the appearance of amorphous dense bodies—as as well as glycogen depletion, disruption of the contractile elements, and the appearance of contraction bands. In segments with blood flows between 25 and 50% of control, these alterations were less marked and somewhat variable as were nuclear changes, but became widespread and characteristic of all cells when blood flow was reduced below 25%. On the basis of these findings and other studies which have defined reversible and irreversible myocardial injury, it is suggested that (1) irreversible cell injury occurs in many cells when tissue perfusion falls below 50% of control, and (2) advanced stages of irreversible damage characterize virtually all cells when blood flow falls below 25% of control.     

Age-dependent changes in glutamate oxidation by non-synaptic and synaptic mitochondria from rat brain

The oxidation of glutamate by non-synaptic and synaptic mitochondria from brains of 3-, 12- and 24-month-old rats was studied. With glutamate plus malate as substrates, non-synaptic mitochondria showed higher respiration rates than synaptic mitochondria in all the three age groups studied. The rate of oxidation of L-[1-¹⁴C] glutamate and the activities of NAD-glutamate dehydrogenase and aspartate aminotransferase were also higher in non-synaptic mitochondria compared with synaptic mitochondria in three age groups. With glutamate plus malate as substrates, a significant reduction in state 3 respiration was observed in both mitochondrial populations from 12- and 24-month-old rats compared with 3-month-old animals. Although an age-dependent decrease in the oxidation of L-[1-¹⁴C] glutamate was observed in both non-synaptic and synaptic mitochondria from aging rats, the oxidation of [1-¹⁴C]-2-oxoglutarate was unaltered in non-synaptic and synaptic mitochondria from senescent rats. The activity of NAD-glutamate dehydrogenase was decreased with age in both mitochondrial populations, whereas aspartate aminotransferase was not altered with age. The results indicate that the oxidation rate of glutamate in rat brain mitochondria is decreased during aging.     

Evidence against a presynaptic mechanism for kainate neurotoxicity in the cochlear nucleus.

Kainic acid produces a selective pattern of degeneration in the cochlear nucleus of the guinea pig. This pattern is not altered by destruction of the putative glutamatergic primary afferent innervation, even with minimal doses of kainic acid. Thus, kainate neurotoxicity does not require intact presynaptic terminals in the cochlear nucleus.     

Recovery from ozone-induced injury in the lungs of the Syrian golden hamster

In order to examine the morphological and cytokinetic changes in the hamster pulmonary epithelium after a high dose of ozone, Syrian golden hamsters were exposed to 15 ppm of ozone for 6 hr and killed 2 hr to 96 days later. Two hours before death, each animal was injected intraperitoneally with tritiated thymidine. Autoradiographs were prepared from 1-μm glycol methacrylate sections of lung tissue. Ozone produced immediate epithelial desquamation in all airways, leaving a single layer of either squamous cells or nonciliated cells which began to proliferate within 1 day of the exposure. The overall morphology of the airway epithelium returned to normal within 7 days. Damage in the alveolar region was localized to alveoli near the terminal bronchioles and consisted of desquamation of Type I epithelial cells and endothelial cells and the presence of inflammation. Hyperplastic regions of cuboidal, squamous, and ciliated cells formed at the bronchiolar-alveolar junction within 2 days of exposure. The greatest increase in proliferation was seen in airway epithelial cells which reached a maximal labeling index of 50%. We conclude that the hamster pulmonary epithelium has a great proliferative capacity to repair damage due to a high concentration of ozone. Foci of hyperplasia in both airway and alveolar epithelium appear during this repair process.     

Isolation of t cell membrane proteins (IgT) with antisera to non-isotypic determinants of immunoglobulins: Evidence thaT IgT ‘Light’ chains are not identical to B cell kappa chains

Radiolabelled cell membrane proteins obtained by detergent lysis of murine T cells labelled by lactoperoxidase-catalysed radioiodination were specifically immunoprecipitated with an antiserum to immunoglobulin Fab determinants. Absorption of the antiserum by myeloma proteins or normal immunoglobulins coupled to Sepharose and the use of antibody proteins eluted from these absorbents indicated that the antibody activity in the serum responsible for binding detergent-soluble T cell membrane proteins was directed towards variable region and not to the constant region determinants of kappa light chains. Immunoglobulin light chain sized polypeptides isolated from T cells with this antiserum were found to possess serological characteristics which differed from serum or B cell membrane immunoglobulin kappa chains. Evidence is presented which suggests that a portion of the light chain sized polypeptides isolated from T cells may be proteolytic fragments of a larger polypeptide chain. The results suggest that immunoglobulin-like detergent-soluble T cell membrane proteins isolated with antisera to immunoglobulins (IgT) possess neither immunoglobulin heavy nor light chain constant regions determinants but do carry determinants associated with immunoglobulin variable regions.     

Analysis of ribosomal proteins from adult Drosophila melanogaster in relation to age.

Analysis of high salt washed ribosomal proteins by two-dimensional polyacrylamide electrophoresis revealed no detectable qualitative differences in ribosomal proteins from young (4-day) and old (30-day) male flies.     

Cortical projections to the periaqueductal gray in the monkey: A retrograde and orthograde horseradish peroxidase study

Stereotaxic fluid microinjections of horseradish peroxidase (HRP) into the periaqueductal gray (PAG), coupled with cortical HRP gel placements in macaque and cebus monkeys, have provided substantive retrograde and orthograde evidence that the rostral dorsal convexity and rostral medial prefrontal cortex are the principal sources of cortical-PAG projections. The prefrontal cortex projects to the dorsolateral quadrant of the PAG, precisely the area shown to receive spinothalamic inputs in mammals, including monkey. The findings are discussed in terms of a possible affective role in central analgesic mechanisms.     

The effect of 2-amino-4-phosphonobutyrate (APB) on acetylcholine release from the rabbit retina: evidence for on-channel input to cholinergic amacrine cells

The light-evoked release of acetylcholine (ACh) from the rabbit retina was taken as a measure of cholinergic amacrine cell activity. The glutamate analogue DL-(+/-)-2-amino-4-phosphonobutyric acid (APB) prevented the light-evoked release of ACh and also selectively abolished the ON-responses of ganglion cells and the ERG b-wave. It is concluded that the input to cholinergic amacrine cells involves mainly the depolarizing bipolar cells, which subserve ON-channels. L-(+)-stereoisomer of APB was 15 times more potent than the D-(-)-isomer in suppressing ACh release and the b-wave, suggesting that the mechanism of action of APB does not involve antagonism of excitatory amino acids.     

Characterization of avian lymphocyte surface proteins which bind to membrane and circulating immunoglobulins

Lactoperoxidase-catalyzed cell surface radioiodination was employed to label membrane proteins of chicken cells from bursa, and spleen cells from normal or bursectomized (Aγ) chickens. Detergent lysates of labelled cells were precipitated with rabbit anti-chicken Ig Fab antisera to isolate membrane immunoglobulins and with chicken anti-human gamma globulin: human gamma globulin immune complexes or insoluble, heat-aggregated chicken Ig to isolate Fc receptors (FcR). Resolution of bursa or normal spleen cell membrane proteins bound by anti-Fab antibodies by SDS-PAGE under reducing conditions revealed three molecular species (70,000, 45,000 and 25,000 dallons) specifically precipitated. All membrane proteins bound by the anti-Fab reagents were bound by antisera specific for chicken IgM. Bursa lymphocyte membrane proteins which bound to immune complexes were resolved into two major molecular species (55,000 and 45,000 daltons). The 45,000-dalton FcR exhibited an isoeleclric point and detergent sensitivily idenlical to a 45,000-dalton protein coprecipitated with membrane Ig. Two-dimensional gel analysis of Fc receptors obtained from spleen cells of bursectomized birds revealed that these proteins can be distinguished by size and/or charge from bursa Fc receptors. The results suggest that chicken lymphocyte Fc receptors comprise a group of proteins which can be distinguished by size, charge, and cellular origin.