Lymphocytes express Ia antigens of foreign haplotype following treatment with neuraminidase

Evidence is presented which indicates that neuraminidase (NA) treatment of spleen cells both destroys old Ia antigens and reveals new Ia specificities which are not normally expressed by splenocytes. It was found that NA treatment unmasked alien I-A^k-like specificities on A.TH (I ^s ) spleen cells, and I^s-like antigens on A.TL (I ^k ) spleen cells. These conclusions were based on direct testing of NA-treated targets with a range of alloantisera and on cell-absorption experiments. Furthermore, the cellular distribution of NA-exposed antigens resembled that of convential Ia antigens, the new antigens being expressed on more than 90 percent of splenic B cells and a subpopulation of splenic T cells. However, although some of the antigens exposed by NA on A.TH cells appeared to resemble the Ia. 3 and 15 specificities, additional antigens were involved which did not correlate with any previously described Ia antigens.Sugar inhibition experiments demonstrated the NA-exposed antigens to be carbohydrate in nature, D-galactose being an effective inhibitor in these studies. The proportion of- and-linked D-galactose residues associated with the new antigens depended upon the target cell used and the anti-Ia serum tested. Furthermore, glycolipid extracts from lymphoid cells were shown to contain the NA-exposed antigens.Collectively, these results support the existence of carbohydrate-defined Ia antigens. The simplest interpretation of the findings is that NA clips off terminal sialic acid residues from carbohydrate-defined Ia antigens on the cell surface and exposes subterminal sugars which resemble antigens expressed by otherI-region haplotypes.     

Partial trisomy 10p and familial translocation t(7;10)(p22;p12)

Summary A girl with partial trisomy for the short arm of chromosome 10(p12pter) due to mal chromosome segregation in the father 46,XY,t(7;10)(p22;p12) is described. The major abnormalities in this case are: mottled skin, mid-facial hypoplasia, low percentiles for weight, length, and head circumference, and club feet.To whom offprint requests should be sent     

A model for the density ofAeromonas hydrophila in Albemarle Sound,North Carolina

The abundance ofAeromonas hydrophila was measured monthly at 29 sites in Albemarle Sound, North Carolina and its tributaries from April 1977 through July 1979. Simultaneous measurements included heterotrophic plate count bacteria, fecal coliform bacteria, and 18 physical and chemical parameters. Using only 6 water quality parameters, multiple correlation and regression analysis of the data produced a best-fit regression which explained 38% of the variation observed inA. hydrophila density. The 6 water quality parameters included dissolved oxygen, temperature, orthophosphate, chlorophyll A trichromatic, total Kjeldahl nitrogen, and ammonia. Heterotrophic plate count bacteria and fecal coliform densities were highly correlated withA. hydrophila density, but made the model very unstable. The model was successfully tested against similar data collected for 2 other North Carolina reservoirs, Lake Norman and Badin Lake. Data from 10 sites in Badin Lake over 18 months and from 7 sites on Lake Norman over 5 months were not significantly different from the Albemarle Sound model. Conditions of water quality that may give rise to “blooms” ofA. hydrophila will simultaneously contribute to the probability of increased epizootics in fish in the southeastern United States.     

Effects of nitrogen limitation on species replacement dynamics during early secondary succession on a semiarid sagebrush site

Summary A soil nitrogen (N) availability gradient was induced on a disturbed sagebrush site in northwestern Colorado by fertilizing with nitrogen (high available N), applying sucrose (low available N), and applying neither nitrogen nor sucrose (control). Species composition was studied for 3 years. At the end of the study, N concentration of aboveground tissue of 3 major species was determined. The rate of species replacement was most rapid on plots receiving the sucrose treatment and was slowest on plots receiving the N treatment. Early-seral dominats had greater tissue N concentrations when availability of the resource was high but lower tissue N concentrations when available soil N became limited. Midseral dominants displayed the opposite pattern. These results suggest that the supply of available soil N, and therefore the dynamics of N incorporation in perennial plant tissue, is a primary mechanism in controlling the rate of secondary succession within this semiarid ecosystem.     

Effect of α-Methylphenylalanine and Phenylalanine on Brain Polyribosomes and Protein Synthesis

Abstract: A chronic hyperphenylalanemia was effectively produced in developing mice by daily administrations of phenylalanine (2 mg/g body wt) and a phenylalanine hydroxylase inhibitor α-methyl-D, L-phenylalanine (0.43 mg/g body wt). The presence of α-methylphenylalanine in newborn mice inhibited 65–70% of hepatic phenylalanine hydroxylase activity within 12 h. Since this maximum inhibition persisted for 24 h or longer, decreased enzyme activity was maintained by daily administrations. Whereas concentrations of phenylalanine increased approximately 40-fold in both plasma and brain following injection of α-methylphenylalanine and phenylalanine, plasma levels of tyrosine were not altered significantly. Concomitant with changes in phenylalanine concentrations we observed the brain polyribosomes' disaggregation, which reached a maximum 3 h after injection and persisted as long as 18 h. Polyribosomes did not become refractory to as many as 10 daily injections of α-methylphenylalanine and phenylalanine. In addition to polyribosome disaggregation, chronic hyperphenylalanemia reduced the rates of polypeptide chain elongation on polyribosomes isolated from brain homogenates.