Formation, manipulation, and elasticity measurement of a nanometric column of water molecules

Nanometer-sized columns of condensed water molecules are formed by an atomic-resolution force microscope operated in ambient conditions. An unusual stepwise decrease of the force gradient associated with the ultrathin water bridge in the tip-substrate gap is observed during its stretch, exhibiting regularity in step heights (approximately 0.5 N/m) and plateau lengths (approximately 1 nm). Such "quantized" elasticity is indicative of an atomic-scale stick slip at the tip-water interface. A thermodynamic-instability-induced rupture of the water meniscus (5 nm long and 2.6 nm wide) is also found. This work opens a high-resolution study of the structure and interface dynamics of a nanometric aqueous column.

Angiotensin-converting enzyme 2: a functional receptor for SARS coronavirus

Cellular entry of enveloped viruses is often dependent on attachment proteins expressed on the host cell surface. Viral envelope proteins bind these receptors, and, in an incompletely understood process, facilitate fusion of the cellular and viral membranes so as to introduce the viral core into the cytoplasm. Only a small fraction of viral receptors have been identified so far. Recently, a novel coronavirus was identified as the etiological agent of severe acute respiratory syndrome (SARS). The fusion protein gene of SARS coronavirus (SARS-CoV) was cloned and characterized, and shortly thereafter, angiotensin-converting enzyme 2 (ACE2) was shown to be its functional receptor. Identification of ACE2 as a receptor for SARS-CoV will likely contribute to the development of antivirals and vaccines. It may also contribute to the development of additional animal models for studying SARS pathogenesis, and could help identify the animal reservoir of SARS-CoV.

Spatial and temporal ontogenies of glutathione peroxidase and glutathione disulfide reductase during development of the prenatal rat

Spatial and temporal expression and regulation of the antioxidant enzymes, glutathione peroxidase (GSH-Px), glutathione disulfide reductase (GSSG-Rd) may be important in determining cell-specific susceptibility to embryotoxicants. Creation of tissue-specific ontogenies for antioxidant enzyme activities during development is an important first step in understanding regulatory relationships. Early organogenesis-stage embryos were grouped according to the somite number (GD 9-13), and fetuses were evaluated by gestational day (GD 14-21). GSH-Px activities in the visceral yolk sac (VYS) increased on consecutive days from GD 9 to GD 13, representing a 5.7-fold increase during this period of development. GSH-Px activities in VYS decreased after GD 13, ultimately constituting a 37% decrease at GD 21. Head, heart, and trunk specific activities generally increased from GD 9 to GD 13 albeit not to the same magnitude as detected in the VYS. GSSG-Rd activities showed substantial increases in the VYS from GD 9 to GD 13, 6.3-fold and decreased thereafter to 50% by GD 21. The greatest changes in enzyme activities were noted in the period between GD 10 and GD 11, where the embryo establishes an active cardiovascular system and begins to convert to aerobic metabolism. Generally, from GD 14-21, embryonic organ GSH-Px and GSSG-Rd activities either remained constant or increased as gestation progressed. These studies suggest the importance of the VYS in dealing with ROS and protecting the embryo. Furthermore, understanding the consequences of lower antioxidant activities during organogenesis may help to pinpoint periods of teratogenic susceptibility to xenobiotics and increased oxygen.

Sialylated O-glycans and sulfated tyrosines in the NH2-terminal domain of CC chemokine receptor 5 contribute to high affinity binding of chemokines

The chemokine receptor CCR5 plays an important role in leukocyte chemotaxis and activation, and also acts as a coreceptor for human and simian immunodeficiency viruses (HIV-1, HIV-2, and SIV). We provide evidence that CCR5 is O-glycosylated on serine 6 in the NH2 terminus. The O-linked glycans, particularly sialic acid moieties, significantly contribute to binding of the chemokine ligands. By contrast, removal of O-linked oligosaccharide exerted little effect on HIV-1 infection. Sulfation of specific tyrosine residues in the CCR5 NH2 terminus was important for efficient beta-chemokine binding. Thus, as has been observed for the binding of selectins and their ligands, O-linked carbohydrates and tyrosine sulfates play major roles in promoting the interaction of chemokines with CCR5. The resulting flexible arrays of negative charges on the CCR5 surface may allow specific, high-affinity interactions with diverse chemokine ligands. Although this is the first example of O-linked oligosaccharides and tyrosine sulfates playing a role in chemokine binding, the high density of serines, threonines and tyrosines in the N-termini of many CC chemokine receptors suggests that these posttranslational modifications may commonly contribute to chemokine binding.

Gating properties of inward-rectifier potassium channels: effects of permeant ions

Two inward-rectifier K+ channels, ROMK2 (Kir1.1b) and IRK1 (Kir2.1), were expressed in Xenopus oocytes and their gating properties were studied in cell-attached membrane patches. The gating properties depended strongly on the ion being conducted (K+, NH4+, Rb+, or Tl+), suggesting tight coupling between permeation and gating. Mean open times were strongly dependent on the nature of the conducted ion. For ROMK2 the order from the longest to the shortest times was K+ > Rb+ > Tl+ > NH4+. For IRK1 the sequence was K+ > NH4+ > Tl+. In both cases the open times decreased monotonically as the membrane voltage was hyperpolarized. Both the absolute values and the voltage dependence of closed times were dependent on the conducted species. ROMK2 showed a single closed state whose mean lifetimes were biphasic functions of voltage. The maxima were at various voltages for different ions. IRK1 had at least two closed states whose lifetimes decreased monotonically with K+, increased monotonically with Tl+, and were relatively constant with NH4+ as the conducted ion. We explain the ion-dependence of gating by assuming that the ions bind to a site within the permeation pathway, resulting in a stable, ion-dependent, closed state of the channel. The patterns of voltage-dependence of closed-state lifetimes, which are specific for different ions, can be explained by variations in the rate at which the bound ions leave the pore toward the inside or the outside of the cell.

Magnesium sulfate does not reduce postoperative analgesic requirements

BACKGROUND

Because magnesium blocks the N-methyl-D-aspartate receptor and its associated ion channels, it can prevent central sensitization caused by peripheral nociceptive stimulation. However, transport of magnesium from blood to cerebrospinal fluid (CSF) across the blood-brain barrier is limited in normal humans. The current study was designed to evaluate whether perioperative intravenous magnesium sulfate infusion affects postoperative pain.

METHODS

Sixty patients undergoing abdominal hysterectomy received 50 mg/kg intravenous magnesium sulfate as a bolus dose followed by a continuous infusion of 15 mg x kg(-1) x h(-1) for 6 h (magnesium group) or the same volume of isotonic saline (control group). At the end of surgery, serum and CSF magnesium concentration were measured in both groups. The cumulative postoperative analgesic consumption was measured to assess the analgesic effect using a patient-controlled epidural analgesia device. Pain intensities at rest and during forced expiration were evaluated at 6, 24, 48, and 72 h postoperatively.

RESULTS

At the end of surgery, patients in the magnesium group had significantly greater postoperative serum magnesium concentrations compared with both preoperative and control group values (P < 0.001). Despite significantly higher serum magnesium concentrations in the magnesium group, there was no significant difference in magnesium concentration measured in postoperative CSF. Cumulative postoperative analgesic doses were similar in both groups. However, there was observed an inverse relation between cumulative postoperative analgesic consumption and the CSF magnesium concentration in both groups. Visual analog pain scores at rest and during forced expiration were similar and less than 4 in both groups.

CONCLUSIONS

Perioperative intravenous administration of magnesium sulfate did not increase CSF magnesium concentration and had no effects on postoperative pain. However, an inverse relation between cumulative postoperative analgesic consumption and the CSF magnesium concentration was observed. These results suggest that perioperative intravenous magnesium infusion may not be useful for preventing postoperative pain.

Transscleral infrared laser for retinal ablation without retinal visualization in an experimental model

PURPOSE

To investigate whether transscleral diode laser can create retinal photocoagulation reliably without creating retinal holes under conditions simulating opaque media.

METHODS

In New Zealand pigmented rabbits, optimal infrared diode laser power settings were determined, and transscleral retinal photocoagulation was then applied 4 mm and 6 mm from the limbus without retinal visualization. Transscleral testing was done using retina and cyclophotocoagulation probes placed directly on the sclera, on conjunctiva, and on silicone scleral buckles.

RESULTS

A retina probe placed on the sclera achieved moderate retinal photocoagulation intensity in 75% of spots 4 mm from the limbus and in 50% of spots 6 mm from the limbus. Retinal holes were only formed when using the transscleral cyclophotocoagulation (TSCPC) probe. An association between burn intensity and the presence of conjunctiva was seen for the TSCPC probe (P = 0.0001) but not for the retina probe (P = 0.125). Photocoagulation spots did not exceed moderate intensity through any of the silicone scleral buckles tested.

CONCLUSIONS

Transscleral infrared photocoagulation applied without retinal visualization did not cause retinal hole formation with a retina probe placed directly on conjunctiva, sclera, or scleral buckle material. A TSCPC probe created retinal holes when placed directly on sclera. A decrease in power was required for all treatments closer to the limbus.

Regulation of ROMK by extracellular cations

The effect of external potassium (K) and cesium (Cs) on the inwardly rectifying K channel ROMK2 (K(ir)1.1b) was studied in Xenopus oocytes. Elevating external K from 1 to 10 mM increased whole-cell outward conductance by a factor of 3.4 +/- 0.4 in 15 min and by a factor of 5.7 +/- 0.9 in 30 min (n = 22). Replacing external Na by Cs blocked inward conductance but increased whole-cell conductance by a factor of 4.5 +/- 0.5 over a period of 40 min (n = 15). In addition to this slow increase in conductance, there was also a small, rapid increase in conductance that occurred as soon as ROMK was exposed to external cesium or 10 mM K. This rapid increase could be explained by the observed increase in ROMK single-channel conductance from 6.4 +/- 0.8 pS to 11.1 +/- 0.8 pS (10 mM K, n = 8) or 11.7 +/- 1.2 pS (Cs, n = 8). There was no effect of either 10 mM K or cesium on the high open probability (P(o) = 0.97 +/- 0.01; n = 12) of ROMK outward currents. In patch-clamp recordings, the number of active channels increased when the K concentration at the outside surface was raised from 1 to 50 mM K. In cell-attached patches, exposure to 50 mM external K produced one or more additional channels in 9/16 patches. No change in channel number was observed in patches continuously exposed to 50 mM external K. Hence, the slow increase in whole-cell conductance is interpreted as activation of pre-existing ROMK channels that had been inactivated by low external K. This type of time-dependent channel activation was not seen with IRK1 (K(ir)2.1) or in ROMK2 mutants in which any one of 6 residues, F129, Q133, E132, V121, L117, or K61, were replaced by their respective IRK1 homologs. These results are consistent with a model in which ROMK can exist in either an activated mode or an inactivated mode. Within the activated mode, individual channels undergo rapid transitions between open and closed states. High (10 mM) external K or Cs stabilizes the activated mode, and low external K stabilizes the inactivated mode. Mutation of a pH-sensing site (ROMK2-K61) prevents transitions from activated to inactivated modes. This is consistent with a direct effect of external K or Cs on the gating of ROMK by internal pH.

Apelin, the natural ligand of the orphan seven-transmembrane receptor APJ, inhibits human immunodeficiency virus type 1 entry

In addition to the CCR5 and CXCR4 chemokine receptors, a subset of primary human immunodeficiency virus type 1 (HIV-1) isolates can also use the seven-transmembrane-domain receptor APJ as a coreceptor. A previously identified ligand of APJ, apelin, specifically inhibited the entry of primary T-tropic and dualtropic HIV-1 isolates from different clades into cells expressing CD4 and APJ. Analysis of apelin analogues demonstrated that potent and specific antiviral activity was retained by a 13-residue, arginine-rich peptide. Antiviral potency was influenced by the integrity of methionine 75, which contributes to APJ-binding affinity, and by the retention of apelin residues 63 to 65. These studies demonstrate the ability of a small peptide ligand to block the function of APJ as an HIV-1 coreceptor, identify apelin sequences important for the inhibition, and provide new reagents for the investigation of the significance of APJ to HIV-1 infection and pathogenesis.

A tyrosine-sulfated peptide based on the N terminus of CCR5 interacts with a CD4-enhanced epitope of the HIV-1 gp120 envelope glycoprotein and inhibits HIV-1 entry

The sequential association of the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein gp120 with CD4 and a seven-transmembrane segment coreceptor such as CCR5 or CXCR4 initiates entry of the virus into its target cell. The N terminus of CCR5, which contains several sulfated tyrosines, plays a critical role in the CD4-dependent association of gp120 with CCR5 and in viral entry. Here we demonstrate that a tyrosine-sulfated peptide based on the N terminus of CCR5, but not its unsulfated analogue, inhibits infection of macrophages and peripheral blood mononuclear cells by CCR5-dependent, but not CXCR4-dependent, HIV-1 isolates. The sulfated peptide also inhibited the association of CCR5-expressing cells with gp120-soluble CD4 complexes and, less efficiently, with MIP-1alpha. Moreover, this peptide inhibited the precipitation of gp120 by 48d and 23e antibodies, which recognize CD4-inducible gp120 epitopes, but not by several other antibodies that recognize proximal epitopes. The ability of the sulfated peptide to block 48d association with gp120 was dependent in part on seven tropism-determining residues in the third variable (V3) and fourth conserved (C4) domains of gp120. These data underscore the important role of the N-terminal sulfate moieties of CCR5 in the entry of R5 HIV-1 isolates and localize a critical contact between gp120 and CCR5.

BACE2, a beta -secretase homolog, cleaves at the beta site and within the amyloid-beta region of the amyloid-beta precursor protein

Production of amyloid-beta protein (Abeta) is initiated by a beta-secretase that cleaves the Abeta precursor protein (APP) at the N terminus of Abeta (the beta site). A recently identified aspartyl protease, BACE, cleaves the beta site and at residue 11 within the Abeta region of APP. Here we show that BACE2, a BACE homolog, cleaves at the beta site and more efficiently at a different site within Abeta. The Flemish missense mutation of APP, implicated in a form of familial Alzheimer's disease, is adjacent to this latter site and markedly increases Abeta production by BACE2 but not by BACE. BACE and BACE2 respond identically to conservative beta-site mutations, and alteration of a common active site Arg inhibits beta-site cleavage but not cleavage within Abeta by both enzymes. These data suggest that BACE2 contributes to Abeta production in individuals bearing the Flemish mutation, and that selective inhibition of these highly similar proteases may be feasible and therapeutically advantageous.

Adaptation of a CCR5-using, primary human immunodeficiency virus type 1 isolate for CD4-independent replication

The gp120 envelope glycoprotein of the human immunodeficiency virus type 1 (HIV-1) promotes virus entry by sequentially binding CD4 and chemokine receptors on the target cell. Primary, clinical HIV-1 isolates require interaction with CD4 to allow gp120 to bind the CCR5 chemokine receptor efficiently. We adapted a primary HIV-1 isolate, ADA, to replicate in CD4-negative canine cells expressing human CCR5. The gp120 changes responsible for the adaptation were limited to alteration of glycosylation addition sites in the V2 loop-V1-V2 stem. The gp120 glycoproteins of the adapted viruses bound CCR5 directly, without prior interaction with CD4. Thus, a major function of CD4 binding in the entry of primary HIV-1 isolates can be bypassed by changes in the gp120 V1-V2 elements, which allow the envelope glycoproteins to assume a conformation competent for CCR5 binding.

Structural determinants of gating in inward-rectifier K+ channels

The gating characteristics of two ion channels in the inward-rectifier K+ channel superfamily were compared at the single-channel level. The strong inward rectifier IRK1 (Kir 2.1) opened and closed with kinetics that were slow relative to those of the weakly rectifying ROMK2 (Kir 1.1b). At a membrane potential of -60 mV, both IRK and ROMK had single-exponential open-time distributions, with mean open times of 279 +/- 58 ms (n = 4) for IRK1 and 23 +/- 1 ms (n = 7) for ROMK. At -60 mV (and no EDTA) ROMK2 had two closed times: 1.3 +/- 0.1 and 36 +/- 3 ms (n = 7). Under the same conditions, IRK1 exhibited four discrete closed states with mean closed times of 0.8 +/- 0.1 ms, 14 +/- 0.6 ms, 99 +/- 19 ms, and 2744 +/- 640 ms (n = 4). Both the open and the three shortest closed-time constants of IRK1 decreased monotonically with membrane hyperpolarization. IRK1 open probability (Po) decreased sharply with hyperpolarization due to an increase in the frequency of long closed events that were attributable to divalent-cation blockade. Chelation of divalent cations with EDTA eliminated the slowest closed-time distribution of IRK1 and blunted the hyperpolarization-dependent fall in open probability. In contrast, ROMK2 had shorter open and closed times and only two closed states, and its Po was less affected by hyperpolarization. Chimeric channels were constructed to address the question of which parts of the molecules were responsible for the differences in kinetics. The property of multiple closed states was conferred by the second membrane-spanning domain (M2) of IRK. The long-lived open and closed states, including the higher sensitivity to extracellular divalent cations, correlated with the extracellular loop of IRK, including the "P-region." Channel kinetics were essentially unaffected by the N- and C-termini. The data of the present study are consistent with the idea that the locus of gating is near the outer mouth of the pore.

Tyrosine sulfation of the amino terminus of CCR5 facilitates HIV-1 entry

Chemokine receptors and related seven-transmembrane-segment (7TMS) receptors serve as coreceptors for entry of human and simian immunodeficiency viruses (HIV-1, HIV-2, and SIV) into target cells. Each of these otherwise diverse coreceptors contains an N-terminal region that is acidic and tyrosine rich. Here, we show that the chemokine receptor CCR5, a principal HIV-1 coreceptor, is posttranslationally modified by O-linked glycosylation and by sulfation of its N-terminal tyrosines. Sulfated tyrosines contribute to the binding of CCR5 to MIP-1 alpha, MIP-1 beta, and HIV-1 gp120/CD4 complexes and to the ability of HIV-1 to enter cells expressing CCR5 and CD4. CXCR4, another important HIV-1 coreceptor, is also sulfated. Tyrosine sulfation may contribute to the natural function of many 7TMS receptors and may be a modification common to primate immunodeficiency virus coreceptors.

Chemokine receptors in HIV-1 and SIV infection

Seven transmembrane segment (7TMS) receptors for chemokines and related molecules have been demonstrated to be essential, in addition to CD4, for HIV and SIV infection. The beta-chemokine receptor CCR5 is the primary, perhaps sole, coreceptor for HIV-1 during the early and chronic phases of infection, and supports infection by most primary HIV-1 and many SIV isolates. Late-stage primary and laboratory-adapted HIV-1, HIV-2, and SIV isolates can use other 7TMS receptors. CXCR4 appears especially important in late-stage HIV infection; several related receptors can also be used. The specificity of SIV viruses is similar. Commonalities among these receptors, combined with analyses of mutated molecules, indicate that discrete, conformationally-dependent sites on the chemokine receptors determine their association with the third variable and conserved regions of viral envelope glycoproteins. These studies are useful for elucidating the mechanism and molecular determinants of HIV-1 entry, and of inhibitors to that entry.

Permeation and gating of an inwardly rectifying potassium channel. Evidence for a variable energy well

Permeation, gating, and their interrelationship in an inwardly rectifying potassium (K+) channel, ROMK2, were studied using heterologous expression in Xenopus oocytes. Patch-clamp recordings of single channels were obtained in the cell-attached mode. The gating kinetics of ROMK2 were well described by a model having one open and two closed states. One closed state was short lived (approximately 1 ms) and the other was longer lived (approximately 40 ms) and less frequent (approximately 1%). The long closed state was abolished by EDTA, suggesting that it was due to block by divalent cations. These closures exhibit a biphasic voltage dependence, implying that the divalent blockers can permeate the channel. The short closures had a similar biphasic voltage dependence, suggesting that they could be due to block by monovalent, permeating cations. The rate of entering the short closed state varied with the K+ concentration and was proportional to current amplitude, suggesting that permeating K+ ions may be related to the short closures. To explain the results, we propose a variable intrapore energy well model in which a shallow well may change into a deep one, resulting in a normally permeant K+ ion becoming a blocker of its own channel.

Stabilization of human immunodeficiency virus type 1 envelope glycoprotein trimers by disulfide bonds introduced into the gp41 glycoprotein ectodomain

Biochemical and structural studies of fragments of the ectodomain of the human immunodeficiency virus type 1 (HIV-1) gp41 transmembrane envelope glycoprotein have demonstrated that the molecular contacts between alpha helices allow the formation of a trimeric coiled coil. By introducing cysteine residues into specific locations along these alpha helices, the normally labile HIV-1 gp160 envelope glycoprotein was converted into a stable disulfide-linked oligomer. Although proteolytic cleavage into gp120 and gp41 glycoproteins was largely blocked, the disulfide-linked oligomer was efficiently transported to the cell surface and was recognized by a series of conformationally dependent antibodies. The pattern of hetero-oligomer formation between this construct and an analogous construct lacking portions of the gp120 variable loops and of the gp41 cytoplasmic tail demonstrates that these oligomers are trimers. These results support the relevance of the proposed gp41 structure and intersubunit contacts to the native, complete HIV-1 envelope glycoprotein. Disulfide-mediated stabilization of the labile HIV-1 envelope glycoprotein oligomer, which has been suggested to possess advantages as an immunogen, may assist attempts to develop vaccines.

The orphan seven-transmembrane receptor apj supports the entry of primary T-cell-line-tropic and dualtropic human immunodeficiency virus type 1

Human immunodeficiency virus type 1 (HIV-1) enters target cells by sequential binding to CD4 and specific seven-transmembrane-segment (7TMS) coreceptors. Viruses use the chemokine receptor CCR5 as a coreceptor in the early, asymptomatic stages of HIV-1 infection but can adapt to the use of other receptors such as CXCR4 and CCR3 as the infection proceeds. Here we identify one such coreceptor, Apj, which supported the efficient entry of several primary T-cell-line tropic (T-tropic) and dualtropic HIV-1 isolates and the simian immunodeficiency virus SIVmac316. Another 7TMS protein, CCR9, supported the less efficient entry of one primary T-tropic isolate. mRNAs for both receptors were present in phytohemagglutinin- and interleukin-2-activated peripheral blood mononuclear cells. Apj and CCR9 share with other coreceptors for HIV-1 and SIV an N-terminal region rich in aromatic and acidic residues. These results highlight properties common to 7TMS proteins that can function as HIV-1 coreceptors, and they may contribute to an understanding of viral evolution in infected individuals.

Low-NaCl diet increases H-K-ATPase in intercalated cells from rat cortical collecting duct

Extracellular K+-dependent H+ extrusion after an acute acid load, an index of H/K exchange, was monitored in intercalated cells (ICs) from rat cortical collecting tubule (CCT) using ratiometric fluorescence imaging of the intracellular pH (pHi) indicator, 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). The hypothesis tested was that 12- to 14-day NaCl deprivation increases H-K-ATPase in rat ICs. The rate of H/K exchange in the low-NaCl ICs was double that of controls. In control ICs, H/K exchange was inhibited by Sch-28080 (10 microM). In the low-NaCl ICs, it was partially blocked by Sch-28080 or ouabain (1 mM). Simultaneous addition of both inhibitors abolished K-dependent pHi recovery. The induced H/K exchange observed with NaCl restriction was not due to elevated plasma aldosterone as evidenced by experiments on ICs from rats implanted with osmotic minipumps administering aldosterone such that plasma levels were comparable to those of NaCl-deficient rats. The results suggest that NaCl deficiency induces two isoforms of H-K-ATPase in ICs and that this effect is not mediated by elevated plasma aldosterone.

Structural interactions between chemokine receptors, gp120 Env and CD4

Seven transmembrane segment (7TMS) receptors for chemokines and related molecules have been demonstrated to be essential, in addition to CD4, for HIV and SIV infection. The beta-chemokine receptor CCR5 is the primary, perhaps sole, co-receptor for HIV-1 during the early and chronic phases of infection and supports infection by most primary HIV-1 and many SIV isolates. Late-stage primary and laboratory-adapted HIV-1, HIV-2, and SIV isolates can use other 7TMS receptors. CXCR4 appears especially important in late-stage HIV infection; several related receptors can also be used. The specificity of SIV viruses is similar. Commonalities among these receptors, combined with analyses of mutated molecules, indicate that discrete, conformationally-dependent sites on the chemokine receptors determine their association with the third variable and conserved regions of viral envelope glycoproteins. These studies are useful for elucidating the mechanism and molecular determinants of HIV-1 entry, and of inhibitors to that entry.

The bis-azo compound FP-21399 inhibits HIV-1 replication by preventing viral entry

The bis-azo compound FP-21399 inhibits HIV-1 infection. We now show that FP-21399 acts on the HIV-1 envelope glycoprotein to prevent viral replication. This compound targets the entry step of the HIV-1 replication cycle as demonstrated by time-of-addition and single cycle viral entry assays. The entry of SIVmac239, which uses the same coreceptors (CD4/CCR5) as HIV-1, was not inhibited by FP-21399, indicating that the antiviral effect of FP-21399 is specific for the HIV-1 envelope glycoprotein and is not dependent upon the cellular receptors CD4 and CCR5. FP-21399 inhibits neither the activity of HIV-1 reverse transcriptase nor the expression of HIV-1 early mRNA. Finally, this compound inhibits gp120 shedding of the T-tropic virus. Our results suggest that the anti-HIV activity of FP-21399 is due to its interaction with HIV-1 gp120/41 complex during viral entry.

Epidural verapamil reduces analgesic consumption after lower abdominal surgery

In this double-blind study, we administered lumbar epidural bupivacaine or bupivacaine plus verapamil to investigate the possible role of the calcium channel blocker, verapamil, in postoperative pain. One hundred patients (ASA physical class I or II) scheduled for lower abdominal surgery were randomly assigned to one of four groups. Group 1 received 10 mL of 0.5% epidural bupivacaine injected 15 min before incision, followed by 10 mL of epidural normal saline 30 min after incision. Group 2 received 10 mL of epidural normal saline injected before incision, followed by 10 mL of 0.5% epidural bupivacaine 30 min after incision. Group 3 received 10 mL of 0.5% epidural bupivacaine plus 5 mg of verapamil injected before incision, followed by 10 mL of epidural normal saline 30 min after incision. Group 4 received the same drugs as Group 3, in the reverse order. Pain and mood numeric rating scores, sedation scores, Prince Henry scores, patient-controlled cumulative postoperative analgesic consumption, and the incidence of side effects were assessed 2, 6, 12, 24, and 48 h after the operation in each group. Cumulative postoperative analgesic consumption in Groups 3 and 4 was significantly lower (P < 0.05) than that in Groups 1 and 2 24 and 48 h after surgery. There were no differences in the pain, mood, and sedation scores and the incidence of side effects among the four groups. We conclude that epidural verapamil decreases postoperative pain, possibly by interfering with normal sensory processing and by preventing the establishment of central sensitization.

IMPLICATIONS

Calcium plays an important role in pain physiology at the spinal cord level. We examined the effect of bupivacaine plus verapamil (calcium channel blocker) and of bupivacaine alone. We demonstrated that the combination, administered epidurally, resulted in less postoperative analgesic consumption than bupivacaine alone.