Investigation of immunosuppressive properties of inactivated human immunodeficiency virus and possible neutralization of this effect by some patient sera

Retroviral infections are accompanied by immunosuppression in a variety of species. For feline leukemia virus, the immunosuppression has been ascribed to the transmembrane envelope protein, p15E, which suppresses the proliferative responses of cat, mouse, and human lymphocytes. A similar suppressive effect has been shown for a lysate of human immunodeficiency virus (HIV), strain HTLV-IIIB. Here we determined that detergent-disrupted HTLV-IIIB lystate exerted a strong suppressive effect on PHA-stimulated lymphocytes. Preparations of whole virions, a lysate of a local HIV isolate grown on MP-6 cells, and a commercially obtained UV and psoralene-inactivated lysate were examined and demonstrated to have a similar suppressive effect. The HIV lysate was not directly cytotoxic to lymphocytes and did not contain tumor necrosis factor or lymphotoxin. The HIV lysate specifically suppressed the proliferation of a range of hemopoietic cell lines from man and mouse including three EBV transformed CD4- and IL-2 receptor-negative B-cell lines. The lysate also suppressed the formation of human bone marrow colonies, whereas the lysate had only a slight or no effect on fibroblasts. The suppression of lymphocyte proliferation was not abrogated by addition of IL-2 or IL-1 and the HIV lysate inhibited the expression of IL-2 receptors on suboptimal PHA-stimulated mononuclear cells. The suppressive factor(s) has not been characterized in molecular terms, but suppressive activity was recovered in fractions with a molecular weight of about 67,000 and in both the glycoprotein fraction and in the glycoprotein-depleted fraction of the HIV lysate. Sera from one-third of a small series (N = 13) of individuals with antibodies to HIV seem to be able to neutralize the suppressive properties of HIV lysate in cultures.     

Relative performance of monohaploid potato clones and their diploid parents at plant level and after protoplast isolation and subsequent fusion

Summary Plant growth performance was studied in 118 potato monohaploids and in their diploid parents. Of these monohaploids 76 were also investigated at the protoplast level and eight of these were used in protoplast fusion experiments as well. No correlation was found between relative performance of greenhouse grown and in vitro grown plants. No or only weak correlations were found between different in vitro characteristics such as plant growth, protoplast yield per gram plant material, plating efficiency and callus growth. This indicates the unpredictability of these characters.The protoplast fusion experiments indicated that only in some genotype combinations increased callus growth rates may be found. However, it is not clear whether such calli were hybrids or not. In protoplast monocultures only diploid and tetraploid regenerants were obtained. After fusion, tetraploids but also some triploids could be regenerated. The finding of triploids indicates that monoploid protoplasts were involved in fusion. Isozyme analysis and morphological assessment of the plants pointed out that the majority of the fusion regenerants were hybrids. The implications of these results are discussed.     

Isolation of an amylose-free starch mutant of the potato (Solanum tuberosum L.)

Summary An amylose-free potato mutant was isolated after screening 12,000 minitubers. These minitubers had been induced on stem segments of adventitious shoots, which had been regenerated on leaf explants of a monoploid potato clone after Röntgen-irradiation. The mutant character is also expressed in subterranean tubers and in microspores. Starch granules from the mutant showed a strongly reduced activity of the granule bound starch synthase and loss of the major 60 kd protein from the starch granules.     

A morphometric and ultrastructural study of lithium-induced changes in the medullary collecting ducts of the rat kidney

Summary Rats were given a lithium-containing diet (40 mmol/kg) to Study the effect of lithium on the structure of collecting ducts from the inner stripe of the outer medulla. The results show that there is a significant increase in the volume density of collecting ducts already after one week on this diet. The volume density of both intercalated and principal cells increases, whereas the volume density of mitochondria in the cytoplasm increases in the intercalated cells only. The increased volume of both principal and intercalated cells seems to be part of a general hyperplasia and hyperactivity of the collecting duct, which may in some way be related to the effects of lithium on vasopressinmediated water transport. The specific changes in the intercalated cells may be a consequence of the effects of lithium on distal nephron potassium and hydrogen ion transport in the distal nephron.     

Extracellular and cell-bound lipase activity in relation to growth of Geotrichum candidum

Summary The imperfect fungus Geotrichum candidum produced extracellular lipase in a basic peptone-salt medium. By adding olive oil or Tween 80 to the basic medium the lipase yields could be enhanced and the maximal yields were found with Tween 80, which resulted in a sixfold increase in extracellular lipase activity as compared with basic medium. During the early phase of growth in medium with olive oil the proportion of cell-bound activity was higher than that of extracellular activity, and a delay in the secretion of extracellular lipase was found. The proportion of cell-bound activity from growth in basic medium and in basic medium with Tween 80 was lower than that of extracellular activity during the entire growth phase. Analyses by polyacrylamide gel electrophoresis showed that the lipase activity from growth in all three media could be ascribed to equivalent protein bands at 57 000 and 61 000 daltons. Immunodiffusion showed that the cell-bound preparation contained lipase that was immunologically identical with purified extracellular lipase from G. candidum.     

Evidence for precursor forms of the low isoelectric point alpha-amylase isozymes secreted by barley aleurone cells

Gibberellin-treated barley (Hordeum vulgare L.) aleurone cell protoplasts have been shown previously to contain two α-amylase isozymes which are not secreted (JV Jacobsen, JA Zwar, PM Chandler 1985 Planta 13: 430-438). This report shows that these intracellular forms are immunochemically related to the low isoelectric point but not the high isoelectric point group of α-amylase isozymes and that they arise by new synthesis like the secreted forms. Pulse-chase studies show that the intracellular isozymes are precursors to the secreted isozymes. Conversion of the intra- to the extracellular forms involves decreases in isoelectric points with no change in size detectable by SDS-PAGE. The precursor isozymes were also detected in aleurone layer homogenates but they were unstable. They could be stabilized by various treatments including heating the homogenate to 70°C for 10 minutes indicating that the instability was enzymically mediated. Using purified radioactive precursor isozymes, it was shown that instability did not involve inactivation but the conversion to secreted forms. The nature of the covalent modification associated with conversion was not determined but available data indicate that it does not involve glycosylation.     

Mechanisms of Mutagenesis by a Bulky DNA Lesion at the Guanine N7 Position

The RpII215 locus encodes the large subunit of RNA polymerase II (polII). Three of 22 RpII215 alleles cause a synergistic enhancement of the mutant phenotype elicited by mutations in the Ultrabithorax (Ubx) locus. We have recovered and analyzed three new mutations that suppress this enhancement. All three mutations map to the RpII215 locus. In addition to suppressing the Ubx enhancement of other RpII215 alleles, two of the new mutations, JH1 and WJK2, themselves enhance Ubx. RpII215 alleles can be placed into three classes based on their ability to enhance Ubx. Class I alleles, including Ubl, C4, C11, JH1, and WJK2, enhance Ubx when heterozygous with class II alleles, which include wild-type RpII215. Class III alleles, which include amorphic alleles, do not enhance Ubx. The third new mutation, WJK1, is a conditional amorphic allele, which behaves like a class III allele at 29 degrees but like a class II allele at 19 degrees. Another mutant phenotype is caused by certain RpII215 alleles, including all class I alleles. This phenotype is a synergistic enhancement of a mutant phenotype elicited by mutations at the Delta (Dl) locus. Unlike the enhancement of Ubx, the enhancement of Dl is not dependent upon antagonistic interactions between different classes of RpII215 alleles.     

Phosphorus in sediments — speciation and analysis

Characterization of sediment phosphorus is commonly based on sequential chemical extractions, in which phosphorus is supposed to be selectively removed from different compounds in the sediments. The first extraction schemes were designed to quantify discrete chemical or mineralogical compounds. As extraction schemes have been tested on different sediments, several systematic errors have been detected and the schemes have been modified and simplified accordingly. Other chemical extractions or treatments have attempted to determine phosphorus bound to particles with a certain strength or binding energy, the purpose being to determine the labile, loosely bound, exchangeable, mobile or algal-available fraction of sediment phosphorus. All extraction procedures yield operationally defined fractions and cannot be used for identification of discrete phosphorus compounds. The many methodological modifications make it necessary to be cautious when comparing results from the literature in this field.     

Antibody-nucleic acid interactions. Monoclonal antibodies define different antigenic domains in 2',5'-oligoadenylates

To define the epitopes involved in binding anti-oligonucleotide antibodies, several hybridomas producing monoclonal antibodies directed against 2',5'-oligoadenylate were established. A solid-phase enzyme-linked immunoassay that employed microtiter wells coated with Ficoll-2',5'-oligoadenylate conjugates proved useful in screening and characterizing hybridoma supernatants. Control experiments demonstrated that the conjugates were irreversibly adsorbed to polystyrene wells under the conditions employed in the assay. Reactivity of monoclonal antibodies with numerous analogues of 2',5'-oligoadenylate was measured by using a competition assay. Several monoclonal antibodies originating from different mice immunized with the same or different immunogens possessed distinctive fine specificities. At least one 2',5'-phosphodiester bond was important in forming each epitope, suggesting that the ribose phosphate backbone is a critical element in defining an antigenic domain of an oligonucleotide. The purine bases were also important, and modification of the bases had varied effects on the extent of antibody recognition. The length of the oligonucleotide and the nature of the termini were also of some importance. In several instances the modification created by linkage of 2',5'-oligoadenylate to carrier protein also contributed to the determinant. The monoclonal antibody most specific for 2',5'-oligoadenylates was relatively insensitive to ionic strength. In contrast, a monoclonal antibody with a 2',5'-oligopurine specificity appeared to bind 2',5'-oligoadenylate through one ion pair, whereas the binding of a monoclonal antibody with a low degree of base specificity appeared to bind through two ion pairs. The results demonstrated that 2',5'-linked oligoadenylate-protein complexes possess at least three distinct oligonucleotide-related antigenic surfaces that can be recognized with high apparent affinity by monoclonal antibodies. A model for the three epitopes is presented.