The binding of pentaammineruthenium (III) to RNase B and RNase A+d(pA)4 in the crystalline state

The binding of pentaammineruthenium (III) to ribonuclease A and B both free and complexed with d(pA)₄ has been examined in the crystalline state through the application of X-ray diffraction and difference Fourier techniques. In crystals of native RNase B, the reagent was observed to have many binding sites, some entirely electrostatic in nature and others consistent with coordination to histidine residues. The primary histidine in the latter case was 105 with 119 also partially substituted. In crystals of RNase A+d(pA)₄ complex only a single, extremely strong site of substitution was observed, and this was 2.4 Å from the native position of the imidazole ring of histidine 105. Thus, the results of these X-ray diffraction studies appear to be quite consistent with the findings of earlier NMR studies and with the results obtained in crystals of the gene 5 DNA binding protein.     

A critical examination of the evidence for the reactions of the pentose pathway in animal tissues

There are two pentose pathway reaction sequences in tissues. The classical textbook reaction scheme is present in adipose tissue and is now called the F-type pathway. A new pathway has been found in liver, photosynthetic and other tissues and is called the L-type pathway. The evidence for the L-type pathway is reviewed.     

Enhancement of the binding of 3H-diazepam to rat brain membranes in vitro by SQ 20009, A novel anxiolytic, gamma-aminobutyric acid (GABA) and muscimol.

SQ 20009, a compound with anxiolytic-like activity, was found to cause an enhancement of the binding of ³H-diazepam to rat brain membranes in a concentration-dependent manner with inhibition of binding occuring at 10^?4 M. Both GABA and the GABA agonist, muscimol, were also found to enhance ³H-diazepam binding while the GABA antagonist (+)-bicuculline decreased binding. The effects of SQ 20009, the GABA agonists and (+)-bicuculline were reflected as a change in the affinity rather than number of binding sites. The effects of SQ 20009 and GABA and muscimol are discussed in terms of an interaction with an endogenous diazepam-like factor.     

Inhibition of HIV infection by a novel CD4 domain 2-specific monoclonal antibody. Dissecting the basis for its inhibitory effect on HIV-induced cell fusion.

HIV use the CD4 molecule as their primary cellular receptor. Residues in the N-terminal domain (D1) of CD4 are crucial to HIV attachment through the gp120 envelope component. However, other regions of CD4 appear to be required subsequently for virus- and cell-cell fusion. Little is understood of the post-binding steps which may differ between HIV variants. We report a novel anti-CD4 mAb that does not block CD4/gp120 binding, but that does efficiently block both viral infection and cell-cell syncytia formation, and define its contact site as residues in CD4 D2 using both mouse/human CD4 chimeras and CD4 substitution mutants. We also investigated the basis for its antiviral effect. Using the CD4 D2 specific mAb, we identify another conserved step in HIV infection, as evidenced by its ability to neutralize a broad range of primary isolates and T cell-line passaged strains. Monovalent forms of the mAb were used to determine if its activity was due to masking of the D2 epitope, to steric inhibition, or bivalency. Our data indicate that both binding site and bivalency of the mAb underlie its potency. The need for bivalency is not simply explained by affinity, because monovalent forms can displace the intact mAb and reverse its protective effect. These results provide evidence that binding of the D2-specific mAb prevents structural alterations necessary for membrane fusion.     

Determination of fetal biparietal diameter without the use of ultrasound in squirrel monkeys

This study evaluated manual caliper measurement of fetal BPD in Saimiri through the abdomen of the dam (TBPD) for correlation with paired ultrasound measurements, prediction of delivery date, subspecies variation, prediction of pregnancy outcome, and correlation between postpartum BPD and TBPD. Regression analysis revealed a close relationship between TBPD measurements and those obtained by ultrasound (P < 0.001). TBPD for Saimiri boliviensis boliviensis increased from a mean of 14.8 ± 0.3 mm for 11 weeks prepartum to a delivery week measurement of 33.2 ± 0.2mm. Delivery-week TBPD of Saimiri boliviensis peruviensis were significantly smaller than Saimiri sciureus sciureus (P < .05). Delivery week TBPD had a correlation coefficient of 0.64 with paired post-patrum measurements. No complications were associated with the technique. Delivery date could be predicted within two weeks. TBPD is an inexpensive, safe, rapid method of approximating fetal growth during the last half of pregnancy in Saimiri.     

Arachidonic acid metabolism and prostaglandin production by primate preimplantation blastocysts.

Preimplantation embryos of many species are known to synthesize prostaglandins. These tissue hormones are believed to influence embryonic metabolism, as well as embryo-maternal interaction during implantation although their putative role(s) remains obscure. Here, prostaglandin production by blastocysts from cynomolgus monkeys (Macaca fascicularis) was examined qualitatively during in vitro culture. Tritium labelled arachidonic acid was metabolized to 6 keto-prostaglandin F1 alpha, 2,3-dinor-prostaglandin F1 alpha and thromboxane B2, as characterized by HPLC separation. Also, 6-keto-prostaglandin F1 alpha, and thromboxane B2 as characterized by HPLC separation. Also, 6-keto-prostaglandin F1 alpha and thromboxane B2 were identified by specific RIA's. Our data suggest that the main arachidonic acid metabolites produced by blastocysts of cynomolgus monkeys are prostacyclin and thromboxane.     

7-Azaindole-3-acetic acid derivatives: Potent and selective CRTh2 receptor antagonists

High throughput screening identified a 7-azaindole-3-acetic acid scaffold as a novel CRTh2 receptor antagonist chemotype, which could be optimised to furnish a highly selective compound with good functional potency for inhibition of human eosinophil shape change in whole blood and oral bioavailability in the rat.     

The role of carbohydrate reserves in the growth, resilience, and persistence of cabbage palm seedlings (Sabal palmetto)

Sabal palmetto (Walt.) Lodd. ex Schultes (cabbage palm) is an arborescent palm common in many plant communities throughout Florida, U.S.A., and the Caribbean. Although its seedlings grow very slowly in forest understories, they survive damage and defoliation well, and the species may increase in dominance following disturbances such as fire, logging, and hurricanes. We investigated the potential importance of total nonstructural carbohydrate (TNC) pools in the ability of cabbage palm seedlings to recover from the loss of aboveground tissue such as that caused by fire, grazing, or shallow burial by storm debris. TNC concentrations in belowground organs of seedlings from a forest understory were high, and TNC pools were sufficient to theoretically replace >50% of a seedling's canopy. The largest fraction of the belowground TNC pool was in stem tissue, where TNC in unclipped plants accounted for 26–54% of stem dry mass. Experimental reduction of TNC pools by repeated defoliation slowed seedling regrowth, and seedlings with inherently smaller pools (smaller seedlings) suffered higher mortality after repeated defoliation than did larger seedlings. Although regrowth and recovery after the loss of aboveground tissue was related to the size of the TNC pool in belowground organs, even the smallest seedlings with the smallest pools had sufficient stores to withstand at least two defoliations at frequent (7-week) intervals. Large belowground TNC pools in S. palmetto seedlings appear to enable them to survive all but the most frequent defoliations (e.g., frequent grazing or mowing). Allocation of resources to these stores, however, may contribute to the slow growth rates of S. palmetto seedlings in natural communities. Received: 13 April 1998 / Accepted: 28 August 1998