Interaction of lymphocytes and high endothelial venules in irradiated lymph nodes

After total-body exposure to various doses of ionizing radiation, the ability of lymphocytes to interact specifically with high endothelial venules of rat cervical and mesenteric lymph nodes was analyzed in frozen sections. Following a radiation dose of 1.5 Gy, high endothelial venules remained intact and the binding of unirradiated lymphocytes to the venules was enhanced relative to unirradiated controls. At radiation doses above 5.0 Gy, damage to high endothelial venules was observed histologically as well as assessed functionally. There was a significant decrease in specific lymphocyte-venule binding and a significant increase in nonspecific binding. These findings suggest that radiation-induced damage to high endothelial venules might play a role in radiation-induced immunosuppression by interfering with the normal passage of lymphocytes from the blood into lymph nodes via a specific interaction between lymphocytes and high endothelial venules.     

Additional mapping of mouse chromosome 2 genes

The purpose of this work was to elucidate the genetic fine structure of the central portion of mouse chromosome (Chr) 2. Seven Chr 2 congenic mouse strains [B10.PA(L)-pa we un a ^t , B10.PA(L)-pa A ^w , B10.PA(L)-we un a ^t , B10.PA(J)-pa a, B10.FS-we A ^w , B10.C-we A ^w , and B10.YBR-a] were produced. Breeding studies were carried out using strains B10.PA(L)-pa we un a ^t and B10.LP-H-13 ^b to accurately determine the recombination frequencies between marker genes pa and we (1.9%±0.3), we and un (8.8%±0.5), and un and a ^t (4.5%±0.4) of strain B10.PA(L)-pa we un a ^t . These strains and other Chr 2 congenic strains were typed for immunologically defined loci using monoclonal antibody (mAb) C23 reactive with the gene product of B2m ^b T-lymphocyte clone C1 reactive with the gene product of H-3 ^a and H-3 ^c , and lymphocyte clone H1.8 reactive with the gene product of Hd-1 ^a . B2m and H-3 typing located a recombinational event separating [pa B2m H-3] from we (the order of bracketed genes is not known). Hd-1 typing indicated that Hd-1 maps distal to [H-42, H-44] and proximal to un. The gene order [pa, B2m, H-3], we, [H-42, H-45], Hd-1, un, H-13, a ^t , with H-44 mapping centromeric to Hd-1, is indicated by the data. Address correspondence and offprint requests to: R. J. Graff.     

Characterization of the central region containing the X-inactivation center and terminal region of the mouse X Chromosome using irradiation and fusion gene transfer hybrids

The irradiation and fusion gene transfer (IFGT) procedure provides a means of isolating subchromosomal fragments for use in the mapping of loci and for cloning probes from a particular area of a chromosome. Using this procedure, two large panels of somatic cell hybrids that contain mouse X Chromosome (Chr) fragments have been generated. These hybrid panels were generated by irradiating the monochromosomal mouse-hamster hybrid HYBX, which retains the mouse X Chr, with either 10 K or 50 K rads of X-irradiation followed by fusion with a recipient Chinese hamster cell line. IFGT hybrids retaining mouse material were generated at high frequency. These hybrids were used to orient loci in the X-inactivation center region that had not been resolvable in our interspecies backcross panel and also to map, within the terminal region of the X Chr, repeat elements detected by the probe p15-4. These hybrids not only complement existing interspecies meiotic mapping panels for the detailed analysis of specific regions of particular chromosomes, but also provide a potential source of material for chromosome-specific probe isolation.     

Apoptosis: final control point in cell biology

The discovery of apoptosis, a widespread and morphologically distinct form of physiological cell death, has had an extraordinary impact on cell biology. The importance of apoptosis stems from its active nature and its potential for controlling biological systems. The growing appreciation of the significance of this process has stimulated intense investigation into the molecular mechanisms involved and into its fundamental implications for developmental biology, immunology and oncology.     

d-Hydantoinase from anaerobic microorganisms

Summary Of 373 anaerobic microbial isolates screened for the enzymatic conversion of dihydrouracil to N-carbamyl--alanine, several strains of Clostridium spp., C. glycolicum, C. subterminale and Peptococcus anaerobius were positive. These Clostridium and Peptococcus strains produced also N-carbamyl-d-amino acids from the respective 5-monosubstituted hydantoins. The d-hydantoinase activity from whole cell suspensions of P. anaerobius strain CRDA 303 was characterized with regard to pH and temperature stability and activity by using dihydrouracil (DHU) and isopropylhydantoin (IPH) as substrates. The d-hydantoinase from P. anaerobius was optimal at 60°C and at pH 6.5–9.5 for the substrate DHU. It was stable up to 55°C and at pH 5.0–9.5 and could be stored at 4°C under an aerobic atmosphere for at least 14 days. Offprint requests to: A. Morin     

Activin-A binding and biochemical effects in osteoblast-enriched cultures from fetal-rat parietal bone.

Activin, a disulfide-linked polypeptide dimer first isolated from gonadal tissue extracts, has amino acid sequence and structural homology with transforming growth factor beta (TGF beta). Along with other activities, TGF beta regulates replication and differentiation and interacts with a defined set of binding sites on isolated bone cells. To determine if activin shares these properties, recombinant human activin-A (A-chain homodimer) was examined in osteoblast-enriched cultures obtained from fetal-rat parietal bone. After 23 h of treatment, 60 to 6,000 pM activin-A increased the rate of [3H]thymidine incorporation into DNA 1.5- to 4.0-fold, and at 600 to 6,000 pM, it enhanced the rate of [3H]proline incorporation into collagen and noncollagen protein by up to 1.7-fold. Like earlier studies with TGF beta in primary osteoblast-enriched cultures, the stimulatory effects of activin-A on DNA and protein synthesis were opposed by parathyroid hormone, and the influence of activin-A on collagen synthesis was independent of cell replication. Binding studies with 125I-activin-A indicated approximately 8,000 high-affinity (Kd = 0.4 nM) and 300,000 low-affinity (Kd = 40 to 50 nM) binding sites per cell. Polyacrylamide gel analysis revealed 125I-activin-A-binding complexes of Mr greater than 200,000 and 73,000 which did not appear to correspond to primary TGF beta-binding sites. These results indicate that activin-A produces TGF beta-like effects in bone and that some of these effects may be mediated, at least in part, by distinct activin receptors on bone cells.     

Phycological studies in the North Channel,Lake Huron

The phytoplankton of North Channel in Lake Huron and its productivity was studied at 8 stations distributed across the channel during May to October, 1974. The phytoplankton analysis was conducted using the Utermohl technique. The mean percent biomass at each station indicated Diatomeae (59–77%) and phytoflagellates such as Chrysophyceae (4–21%) and Cryptophyceae (7–19%) as the dominant contributors. Seasonal variations of biomass ranged from 0.2 to 0.35 g·m^–3 with a single peak during stratified conditions. Diatomeae dominated throughout the period of investigation followed by Chrysophyceae and Cryptophyceae. Biomass composition by size revealed the dominance of ultraplankton (5–20 m) which contributed 29–68% to the total biomass. Species such as Fragilaria crotonensis, Tabellaria fenestrata, Synedra acus var. radians, Cyclotella comta and C. bodanica made substantial contributions during the unstratified and stratified conditions.Ultraplankton contributed overwhelmingly to the primary productivity as measured by carbon-14 uptake. The contaminant bioassays with single metals, metals in combination and a mixture of metals demonstrated that the ultraplankton's carbon assimilation was inhibited significantly, revealing their sensitivity to contaminants. Phytoplankton ecology of the Channel appears to be affected by tributary inflows, industrial/municipal inputs, and short flushing rates. However, statistical treatment of the ultraplankton biomass showed correlations with temperature and nutrients. Based on phycological and limnological characteristics, the Channel appears to be oligotrophic. The chlorophyll/biomass ratios and Activity Coefficient (P/B) align it with the most oligotrophic Lake Superior in its metabolic efficiency.     

Genetic transformation system in the archaebacterium Methanobacterium thermoautotrophicum Marburg.

A wild-type strain of Methanobacterium thermoautotrophicum Marburg was transformed by DNA from strains resistant to 5-fluorouracil. Recipient cells were grown without selection on gellan gum (GELRITE) plates with DNA. Drug-resistant cells were recovered by replica plating the resulting colonies onto drug plates. Transformation required high-molecular-weight DNA with appropriate markers and was not observed on agar or in liquid media under a variety of conditions.     

Structural studies of alpha-bungarotoxin. 3. Corrections in the primary sequence and X-ray structure and characterization of an isotoxic alpha-bungarotoxin

The most plausible set of chemical shift assignments for alpha-bungarotoxin as deduced from the combined use of two-dimensional J-correlated and two-dimensional nuclear Overhauser effect 1H nuclear magnetic resonance (NMR) spectroscopy was in conflict with the accepted amino acid sequence between residues 8 and 12 and residues 66 and 70 [Basus, V. J., Billeter, M., Love, R. A., Stroud, R. M., & Kuntz, I. D. (1988) Biochemistry (first paper of three in this issue]). Furthermore, NMR spectra of alpha-bungarotoxin, purified by conventional methods, evidenced a second species at the level of approximately 10% total protein. The minor component was separated from alpha-bungarotoxin by Mono-S (cationic) chromatography. Sequencing of Mono-S-purified alpha-bungarotoxin and one of its tryptic peptides showed that the correct sequence for alpha-bungarotoxin is Ser-Pro-Ile at positions 9-11 and Pro-His-Pro at positions 67-69. The electron density map of alpha-bungarotoxin [Love, R. A., & Stroud, R. M. (1986) Protein Eng. 1, 37] was refined with the new sequence data. Improvements in the structure were found primarily for residues 9-11. Sequence analysis of two overlapping tryptic peptides proved that the minor species differed from alpha-bungarotoxin by replacement of a valine for an alanine at position 31. This new toxin, alpha-bungarotoxin(Val-31), binds to the acetylcholine receptor with an affinity that is comparable to that of alpha-bungarotoxin.