Serious Adverse Events Are Uncommon with Combination Neonatal Antiretroviral Prophylaxis: A Retrospective Case Review

Six weeks of zidovudine (ZDV) is recommended for postnatal prophylaxis of HIV-exposed infants, but combination antiretrovirals are indicated if HIV transmission risk is increased. We investigated the frequency and severity of adverse events (AE) in infants receiving multiple drug prophylaxis compared to ZDV alone. In this retrospective review of 148 HIV-exposed uninfected infants born between 1997–2009, we determined clinical and laboratory AE that occurred between days of life 8–42. Thirty-six infants received combination prophylaxis; among those, a three-drug regimen containing ZDV, lamivudine, and nevirapine was most common (53%). Rates of laboratory AE grade ≥1 were as follows for the combination prophylaxis and ZDV alone groups, respectively: neutropenia 55% and 39%; anemia 50% and 39%; thrombocytopenia 0 and 3%; elevated aspartate aminotransferase 3% and 3%; elevated alanine aminotransferase 0 and 1%; hyperbilirubinemia 19% and 42%. Anemia occurred more frequently in infants who received three-drug prophylaxis compared to infants who received ZDV alone (63% vs. 39%, p = 0.04); all anemia AE were grade 1 or 2 in the three-drug prophylaxis group. Overall, 75% of infants on combination prophylaxis and 66% of infants on ZDV alone developed grade ≥1 AE (p = 0.32), and 17% of infants in either group developed grade ≥3 AE. Stavudine was substituted for ZDV in 23 infants due to anemia or neutropenia. After this antiretroviral change, 50% of evaluable infants demonstrated improvement in AE grade, and 25% had no change. In conclusion, low grade anemia, neutropenia, and hyperbilirubinemia occurred frequently regardless of the prophylactic regimen, but serious AE were uncommon. Although most AE were typical of ZDV toxicity, the combination of ZDV with lamivudine and nevirapine resulted in an increased frequency of low-grade anemia. Further studies are needed to identify prophylactic regimens with less toxicity for infants born to HIV-infected mothers.     

Bleb-driven chemotaxis of Dictyostelium cells

Blebs and F-actin–driven pseudopods are alternative ways of extending the leading edge of migrating cells. We show that Dictyostelium cells switch from using predominantly pseudopods to blebs when migrating under agarose overlays of increasing stiffness. Blebs expand faster than pseudopods leaving behind F-actin scars, but are less persistent. Blebbing cells are strongly chemotactic to cyclic-AMP, producing nearly all of their blebs up-gradient. When cells re-orientate to a needle releasing cyclic-AMP, they stereotypically produce first microspikes, then blebs and pseudopods only later. Genetically, blebbing requires myosin-II and increases when actin polymerization or cortical function is impaired. Cyclic-AMP induces transient blebbing independently of much of the known chemotactic signal transduction machinery, but involving PI3-kinase and downstream PH domain proteins, CRAC and PhdA. Impairment of this PI3-kinase pathway results in slow movement under agarose and cells that produce few blebs, though actin polymerization appears unaffected. We propose that mechanical resistance induces bleb-driven movement in Dictyostelium, which is chemotactic and controlled through PI3-kinase.     

Transport of proteins into chloroplasts. Organization, orientation, and lateral distribution of the plastocyanin processing peptidase in the thylakoid network

Plastocyanin is synthesized in the cytoplasm as a larger precursor and transported into the thylakoid lumen of the chloroplast. Maturation of preplastocyanin involves successive cleavages by a stromal peptidase and a distinct thylakoidal peptidase. In this report we have analyzed the precise location and orientation of the thylakoidal peptidase with respect to the thylakoid membrane. Experiments involving differential centrifugation of thylakoid extracts and sonication of isolated vesicles indicate that the peptidase is tightly bound to the thylakoid membrane but not intimately associated with any of the major thylakoid protein complexes. Analysis of the lateral distribution of the peptidase has shown that the enzyme is exclusively located in the non-appressed lamellae of the thylakoid network. The active site of the peptidase is on the lumenal face of the thylakoid membrane.     

Circular dichroism and fluorescence studies on protein synthesis initiation factor eIF-4E and two mutant forms from the yeast Saccharomyces cerevisiae

Circular dichroism studies have shown that eukaryotic initiation factor 4E contains low amounts of alpha-helix; the main elements of secondary structure are beta-sheets/turns and aperiodic regions. Interactions with cap analogs are accompanied by small but reproducible changes in overall secondary structure, which may also involve more significant perturbations of localized regions containing certain phenylalanine residues. Dissociation constants for interactions with nucleotides have been established from fluorescence titrations. Results show that the (N-7) methylated guanosine nucleotides bound more strongly than their nonmethylated counterparts. Involvement of a key tryptophan residue in the cap binding site was suggested. Additional studies with two cap binding mutant forms of the protein, designated SK-4 (W----75----L) and SK-6 (W----115----L), confirmed and extended these observations. Fluorescence melting experiments indicated that binding of cap analogs stabilized the protein against thermal perturbation and demonstrated subtle differences in folding between the wild-type and mutant forms of the protein. These subtle differences in folding may account for the observed loss in cap specificity of both mutant forms.     

Convenient uses of polymerase chain reaction in analyzing recombinant cDNA clones

We have used polymerase chain reaction to accelerate our analysis of recombinant lambda-cDNA clones. We have amplified the inserts of lambda gt10 or lambda gt11 recombinants starting with bacteriophage in cored plaques or isolated DNA. The amplifications made with simple or complex oligonucleotide primers have allowed convenient sizing, subcloning and translation of the phage inserts into protein.     

The molecular structure of different polymorphic forms of canine C3 and C4

The subunit composition of different electrophoretic forms of canine C3 and C4 was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of reduced immune precipitates. Canine C4 comprises alpha, beta, and gamma chains of approximate molecular weight 90 000–95 000, 72 000, and 33 000, respectively. The molecular weight of the alpha chain of the C4 1 allelic product was approximately 95 000, but 90 000 for the C4 2 and C4 4 allotypes. No differences were observed in the molecular weights of the beta or gamma chains of any canine C4 phenotype tested. Canine C3 appears to be encoded by a single locus. The subunit composition comprises an alpha and beta chain with molecular weights of approximately 106 000 and 71000, respectively. Unlike C4, no differences in the molecular weights of the subunits were observed in different electrophoretic forms of canine C3.     

Control of ornithine decarboxylase activity in stimulated human lymphocytes by putrescine and spermidine

Ornithine decarboxylase activity in extracts of phytohaemagglutinin-stimulated human lymphocytes is rapidly and extensively inhibited by additions of micromolar concentrations of putrescine or spermidine to the culture medium. This inhibition is not due to feedback inhibition of the enzyme by putrescine, spermidine or their metabolites. Inhibition is dependent on the continuation of protein synthesis, but does not require RNA synthesis. The effect of putrescine is abolished when its conversion into spermidine by the cells is prevented.