Ocean acidification may negatively impact the early life stages of some marine invertebrates including corals. Although reduced growth of juvenile corals in acidified seawater has been reported, coral larvae have been reported to demonstrate some level of tolerance to reduced pH. We hypothesize that the observed tolerance of coral larvae to low pH may be partly explained by reduced metabolic rates in acidified seawater because both calcifying and non-calcifying marine invertebrates could show metabolic depression under reduced pH in order to enhance their survival. In this study, after 3-d and 7-d exposure to three different pH levels (8.0, 7.6, and 7.3), we found that the oxygen consumption of Acropora digitifera larvae tended to be suppressed with reduced pH, although a statistically significant difference was not observed between pH conditions. Larval metamorphosis was also observed, confirming that successful recruitment is impaired when metamorphosis is disrupted, despite larval survival. Results also showed that the metamorphosis rate significantly decreased under acidified seawater conditions after both short (2 h) and long (7 d) term exposure. These results imply that acidified seawater impacts larval physiology, suggesting that suppressed metabolism and metamorphosis may alter the dispersal potential of larvae and subsequently reduce the resilience of coral communities in the near future as the ocean pH decreases.

We examined the potential role of myosin and actin in the release of human immunodeficiency virus type 1 (HIV-1) from infected cells. Wortmannin (100 nM to 5 ,uM), an effective inhibitor of myosin light chain kinase, blocked the release of HIV-1 from infected T-lymphoblastoid and monocytoid cells in a concentration-dependent manner. Cytochalasin D, a reagent that disrupts the equilibrium between monomeric and polymeric actin, also partially inhibited the release of HIV-1 from the infected cells. At the budding stage, myosin and HIV-1 protein were detected in the same areas on the plasma membrane by using dual-label immunofluorescence microscopy and immunoelectron microscopy. In the presence of 5 ,uM wortmannin, viral components were observed on the plasma membrane by using immunofluorescence microscopy and electron microscopy, implying that wortmannin did not disturb the transport of viral proteins to the plasma membrane but rather inhibited budding.The infection and release of human immunodeficiency virus (HIV) from lymphocytes, monocytes, and macrophages involves several distinct steps including binding to a specific surface receptor, entry into the host cell, reverse transcription of the RNA genome, replication, transcription, protein synthesis, intracellular transportation, recognition of release sites, and budding (for reviews, see refs.

Although macrophages are major targets for human immunodeficiency virus (HIV) infection in vivo, study of HIV-macrophage interactions in vitro was hindered because many laboratory strains of HIV would not replicate in macrophages, and because survival of macrophages in culture was poor. Addition of purified macrophage colony-stimulating factor (M-CSF) to cultured macrophages markedly improves their survival, but does not induce proliferation. HIV isolates that replicate in macrophages will also replicate in lymphocytes; however, isolates adapted to lymphoid cells (such as HIV-HTLVIIIB) will not replicate in macrophages. The envelope gene appears to be a major determinant of the cell tropism of viral isolates. T-cell grown virus stocks synthesize abundant gp120, while virus grown in macrophages contains relatively much less gp120. Electron microscopy of virions from macrophages shows them to be depleted of gp120 surface "spikes." Recombination studies show that the portion of the genome coding for the envelope glycoprotein appears to determine cell tropism. Lastly, rsCD4 neutralized macrophage-tropic isolates less efficiently than T-cell tropic isolates. HIV replication in macrophages is partially under the control of cellular factors, although these have been less well characterized than they have in lymphocytes.

The amino acid sequences of proteins determine their three-dimensional structures and functions. However, how sequence information is related to structures and functions is still enigmatic. In this study, we show that at least a part of the sequence information can be extracted by treating amino acid sequences of proteins as a collection of English words, based on a working hypothesis that amino acid sequences of proteins are composed of short constituent amino acid sequences (SCSs) or “words”. We first confirmed that the English language highly likely follows Zipf's law, a special case of power law. We found that the rank-frequency plot of SCSs in proteins exhibits a similar distribution when low-rank tails are excluded. In comparison with natural English and “compressed” English without spaces between words, amino acid sequences of proteins show larger linear ranges and smaller exponents with heavier low-rank tails, demonstrating that the SCS distribution in proteins is largely scale-free. A distribution pattern of SCSs in proteins is similar among species, but species-specific features are also present. Based on the availability scores of SCSs, we found that sequence motifs are enriched in high-availability sites (i.e., “key words”) and vice versa. In fact, the highest availability peak within a given protein sequence often directly corresponds to a sequence motif. The amino acid composition of high-availability sites within motifs is different from that of entire motifs and all protein sequences, suggesting the possible functional importance of specific SCSs and their compositional amino acids within motifs. We anticipate that our availability-based word decoding approach is complementary to sequence alignment approaches in predicting functionally important sites of unknown proteins from their amino acid sequences.

Previous studies have demonstrated that the principal neutralizing determinant of human iunodeficiency virus type 1 (HIV-1) is located in the V3 loop of glycoprotein gpl20. Antibodies prepared against this region using gp120 or peptides as immunogens have been predonminantly HIV-1-isolate-specific. In the present studies, murine monoclonal antibodies (mAbs) were prepared against the HIV-1MN strain. One mAb, designated NM-01, was selected for its ability to neutralize both the MN and TUB strains. Neutralization of H9-cell infectivity as determined by reverse transcriptase assay demonstrated an lDl5 of <1 jig/ml for both MN and ITB. mAb NM-01 also blocked MN and IIIB infectivity in the MT-2 assay and inhibited their reactivity in syncytium formation. The results further demonstrate that mAb NM-01 binds to the V3 loop of gpl20 at amino acids 312-326. This mAb reacted equally well with loop peptides from the MN, TUB, RF, and CDC4 isolates. In contrast, there was less afflnity with a similar peptide from the NY5 strain and little if any reactivity with ioop peptides from the Z2, Z6, and ELI strains. We also demonstrate that peptides corresponding to the V3 loops of MN and IIIB, but not Z6, block neutralization of TUB virus by mAb NM-O1. These rindings indicate that mAb NM-01 reacts with diverse HIV-1 isolates through the Gly-Pro-Gly-Arg sequence of the V3 loop.Human immunodeficiency virus type 1 (HIV-1) infects a variety oflineages, such as T cells, monocytes/macrophages, and neuronal cells, that express CD4 (1, 2). Studies demonstrating binding of gpl20, the major HIV-1 external envelope glycoprotein, to the CD4 receptor supported the role of this viral glycoprotein in HIV-1 infectivity (3-7). Moreover, several epitopes on gpl20 have been associated with the development of neutralizing antibodies. A conserved domain of gpl20 implicated in HIV-1 infectivity elicits specific neutralization (8). Other conformation-dependent epitopes on gpl20 have resulted in the development of antibodies that broadly neutralize diverse strains of this virus (9, 10). However, the principal neutralizing determinant (PND) has been located in the V3 loop of gp120 (11)(12)(13)(14).The V3 loop consists of a hypervariable 36-amino acid (aa) domain (aa 302-338) that is cross-linked by disulfide bonds (12,14). Recombinant and synthetic protein fragments containing the V3 loop elicit isolate-specific neutralizing antibodies (14-16). More recent studies have demonstrated that the type 2 P-turn structure of the V3 loop, which contains the relatively conserved Gly-Pro-Gly-Arg (GPGR) sequence, is the site recognized by isolate-specific antibodies (11,17). This epitope has been identified by a variety of neutralizing monoclonal antibodies (mAbs) prepared in rodents, whereas other findings indicate that the PND also induces MN-isolatespecific antibodies during HIV-1 infection in humans (18).The hypervariable PND domain may account for the isolatespecific neutralizing activity generated by this epitope. However, several studies have indicated t...