Human immunodeficiency virus neutralizing antibodies recognize several conserved domains on the envelope glycoproteins.

Serum neutralizing antibodies against the human immunodeficiency virus were frequently detected in infected individuals, and low or absent serum neutralizing titers correlated with poor prognosis. Multiple diverse human immunodeficiency virus isolates were found to exhibit similar susceptibility to neutralization by a panel of human seropositive sera, suggesting that neutralizing antibodies are largely directed against conserved viral domains. Furthermore, utilizing antisera raised against a library of synthetic env peptides, four regions which are important in the neutralization process have been identified within both human immunodeficiency virus envelope glycoproteins (gp41 and gp120). Three of these are in conserved domains and should be considered for inclusion in a candidate vaccine.     

PHYSIOLOGICAL MODIFICATIONS RELATED TO DENSITY INCREASE IN PERIPHYTIC ASSEMBLAGES 1

Periphytic communities in running waters were examined as they developed on granite rocks, concrete balls and glass slides. At equivalent cell densities, no differences in pigment concentrations, species diversity or production levels were found among the different substrata examined. Development of the assemblage appeared to result from the elongation of short algal filaments which had initially settled on the surface. As these communities matured, a distinct canopy and understory developed. Cellular metabolisms were comparable among the communities. In the understory of the communities, even though the cellular content of chl a and b did not differ, chl c and carotenoid pigment concentrations were higher than those in the over-story. Bicarbonate assimilation of Tabellaria fenestrata (Lyng.) Külz. and Eunotia pectinalisi var. pectinalis (O. F. Müll?) Rabh. was higher than that of the more abundant Tabellaria flocculosa (Roth.)Kütz. var. flocculosa IV (sensu Koppen) at both high and low cell densities. This probably reflects a seasonal succession of colonizing species. Glucose assimilation appeared to be mainly attributable to bacterial activity, and algal cells of the upper layer were less active than those of the bottom. The small amount of glucose that was incorporated by the algal cells was probably absorbed passively since its amount was in direct proportion to cell volumes.     

A note on the hatching and viability ofCeriodaphnia ephippia collected from lake sediment

Ephippia ofCeriodaphnia pulchella Sars were collected at 2 sites from successive sediment layers. Hatching observed in the laboratory gave information about the duration of their viability. Conclusions about the hatching situation in the lake were drawn from the ratio of intact to total ephippia at various lake depths. The results are discussed.     

Differences among immune complexes: association of C1q in SLE immune complexes with renal disease

Studies that made use of multiple assay systems demonstrated increased levels of immune complexes (IC) in patients with systemic lupus erythematosus (SLE), but no consistent correlations of IC concentration to patterns or activity of disease have been observed. Furthermore, consistent associations between qualitative differences in IC and disease manifestations have been elusive. IC interaction with erythrocytes and mononuclear phagocytic cells is another variable in SLE that may also mediate some of the biological effects of IC. The present report concerns studies of the composition of purified IC obtained from individuals with SLE and other rheumatic diseases; a 64,000 dalton component identified as the A-B subunit of C1q was detected in purified IC from 27 of 51 SLE patients (53%). The presence of this 64,000 dalton component was not related to either IC concentration or to the serum C1q level. However, the presence of the C1q component in isolated SLE IC did correlate with the presence of renal disease (p less than 0.02). These observations are interpreted relative to a recently described kinetic model of IC clearance.     

Evolution of the secondary haustoria to a primary haustorium in the parasiticScrophulariaceae/Orobanchaceae

In the parasiticScrophulariaceae andOrobanchaceae, two types of contact organs exist: secondary and primary haustoria. Secondary haustoria are lateral organs, developing in large numbers and only when the seedling is fully established. In contrast, a primary haustorium represents the first developmental stage of the seedling itself. In the root system of the parasiticLesquereuxia syriaca (=Siphonostegia syriaca) there are only secondary haustoria, but a few of them apparently develop in a terminal position. This is achieved by transferring the haustorial initiation region closer to the root apex. One can interpret this as a transformation of the apical meristem into a meristematic haustorial tissue. On the condition that an extreme shortening (abbrevation) of the primary root could happen, we discuss the transformation of the terminal secondary into a primary haustorium.     

New details on the morphology of fossil onagraceous pollen grains

Fossil onagraceous pollen grains from two Upper Miocene localities in E. Austria were investigated by LM and EM. Exine structure and sculpture as well as viscin threads suggest affinities with the extant genusCircea.     

Dominant expression of an amino-acid uptake deficiency in carrot somatic fusion hybrids

Somatic hybrids were selected previously by their ability to grow in medium containing normally inhibitory levels of the two amino acid analogs aminoethylcysteine (AEC) and 5-methyltryptophan (5MT) following fusion of protoplasts from a cell strain resistant to AEC with protoplasts resistant to 5MT. The hybrid nature of the selected clones was shown by several criteria including the presence of another resistance, azetidine-2-carboxylate (A2C), carried by one of the parental strains which was not selected for in the initial hybrid selection scheme. The characterization presented here shows that the AEC resistance in the parental strain, as well as the two somatic hybrids, was due to decreased AEC uptake. Also the 5MT resistance in the hybrids, as in the parent was caused by a feedback altered form of the tryptophan biosynthetic control enzyme, anthranilate synthase which leads to increases in free tryptophan. The A2C resistance was caused by the accumulation of free proline by a mechanism which has not been studied. These studies confirm that AEC resistance caused by decreased uptake can be expressed dominantly in protoplast fusion hybrids.Abbreviations A2C Azetidine-2-carboxylate - AEC Aminoethylcysteine - 5MT 5-methyltryptophan