Differences in horizontal, neoclassical facial canons in Chinese (Han) and North American Caucasian populations

To better our ability to analyze the facial disproportions of patients of Chinese ancestry, we compared the validity of four neoclassical canons of facial proportion in Chinese and North American Caucasians populations. We tested the frequency of four horizontal facial canons and their eight variations in 206 healthy adults (105 males and 101 females, 18-25 years old) belonging to the predominant ethnic group (Han: 400 million) of the Chinese population, and compared them to those of 103 healthy young North American Caucasian adults. The nose width corresponded to one-quarter of the face width (the nasofacial canon) significantly more frequently in Chinese participants (51.5%) than in Caucasian adults (36.9%). The nose was narrower than one-quarter of the face width in 38.8% of North American Caucasians and in 21.8% of Chinese; this difference was also statistically significant. In defiance of the naso-oral canon, the mouths of Chinese people were significantly more often narrower than 1.5 times the nose width (71.8%), while in North American Caucasian ethnics the mouth was significantly more frequently wider (60.2%).

Adolescent smoking in Wuhan, China: baseline data from the Wuhan Smoking Prevention Trial

BACKGROUND

This study reports the prevalence of adolescent smoking in the urban and rural areas of Wuhan, China, the capital of Hubei Province, on the Yangtze River in central China.

METHODS

Smoking behavior was examined by age, gender, and urbanicity as part of the Wuhan Smoking Prevention Trial. Subjects included 6994 seventh- to ninth-grade students attending 22 randomly selected schools in urban and rural districts. Outcome measures included lifetime smoking, past-30-day smoking, established smoking (>100 cigarettes in lifetime), and susceptibility to smoking (absence of a firm commitment not to smoke).

RESULTS

Lifetime smoking prevalence was 47% among boys and 18% among girls. Past-30-day smoking prevalence was 16% among boys and 4% among girls. Established smoking prevalence was 2% among boys and 0% among girls. The prevalence of susceptibility to smoking was 31% among boys and 10% among girls. Smoking increased significantly with age (p<.0005). Susceptibility was more prevalent in rural areas than in urban areas (p<.05), but there were no urban-rural differences in lifetime, past 30-day smoking, or established smoking. Trend analyses revealed that smoking increased with age more rapidly among boys than among girls (p<.05). Smoking was more prevalent among rural boys than among urban boys, but it was more prevalent among urban girls than among rural girls (p<.05).

CONCLUSIONS

Adolescent smoking is a significant public health problem in China. Boys are at particularly high risk, as are girls living in urban areas. Effective smoking prevention programs for adolescents, as well as restrictions on tobacco industry marketing and youth access to tobacco, are needed to prevent tobacco-related morbidity and mortality in China.

Nanospace within metal-organic frameworks for gas storage and separation

Porous metal-organic frameworks (MOFs), also known as porous coordination polymers, represent a new class of porous materials, and one of their striking features lies in their tunable, designable, and functionalizable nanospace. This nanospace within MOFs provides virtually plenty of room for imagination, allowing designed incorporation of different size, shape, and functionalities for targeted gas storage and separation applications. Furthermore, the features of high porosities, tunable framework structures and pore sizes, and immobilized functional sites enable MOF materials to fully make use of their nanopore space for gas storage, to optimize their sieving effects, and to differentiate their interactions with gas molecules for gas separation. In this review article, we highlight some recent significant advances in developing microporous MOFs for some of the most important gas storage and separation applications.

3D Printed Zn-doped Mesoporous Silica-incorporated Poly-L-lactic Acid Scaffolds for Bone Repair

Poly-L-lactic acid (PLLA) lacks osteogenic activity, which limits its application in bone repair. Zinc (Zn) is widely applied to strengthen the biological properties of polymers due to its excellent osteogenic activity. In the present study, Zn-doped mesoporous silica (Zn-MS) particles were synthesized by one-pot hydrothermal method. Then, the particles were induced into PLLA scaffolds prepared by selective laser sintering technique, aiming to improve their osteogenic activity. Our results showed that the synthesized particles possessed rosette-like morphology and uniform mesoporous structure, and the composite scaffold displayed the sustained release of Zn ion in a low concentration range, which was attributed to the shield effect of the PLLA matrix and the strong bonding interaction of Si-O-Zn. The scaffold could evidently promote osteogenesis differentiation of mouse bone marrow mesenchymal stem cells by upregulating their osteogenesis-related gene expression. Besides, Zn-MS particles could significantly increase the compressive strength of the PLLA scaffold because of their rosette-like morphology and mesoporous structure, which can form micromechanical interlocking with the PLLA matrix. The Zn-MS particles possess great potential to improve various polymer scaffold properties due to their advantageous morphology and physicochemical properties.

Silver-doped bioglass modified scaffolds: A sustained antibacterial efficacy

Implant-related bacterial infection is a serious complication, which even causes implant failure. Silver (Ag) nanoparticles are broadly used antibacterial agents due to their excellent antibacterial ability and broad-spectrum bactericidal property. However, the significance of burst release cannot be entirely ignored. In this study, Ag doped mesoporous bioactive glasses (Ag-MBG) nanospheres were synthesized using modified Stöber method, then incorporated into poly L-lactic acid (PLLA) matrix to prepare the composite scaffolds via selective laser sintering (SLS) technology. Herein, Mesoporous bioactive glasses (MBG) sol had many negatively-charged silicon hydroxyl groups, which could adsorb positively-charged Ag ions by electrostatic interaction and eventually form Si-O-Ag bonds into MBG. Moreover, MBG promoted osteoblast colonization due to its continuous release of Si ions. The results showed the Ag-MBG/PLLA scaffold could sustainedly release Ag ions for 28 days, and exhibited significantly antibacterial ability against Escherichia coli, its bacterial inhibition rate was over 80%. In addition, the composite scaffold also showed good cytocompatibility. It may be concluded that the prepared Ag-MBG/PLLA scaffold has great potential to repair implant-associated bone infection.

Novel Strategy to Accelerate Bone Regeneration of Calcium Phosphate Cement by Incorporating 3D Plotted Poly(lactic-co-glycolic acid) Network and Bioactive Wollastonite

Inefficient bone regeneration of self-hardening calcium phosphate cement (CPC) increases the demand for interconnected macropores and osteogenesis-stimulated substances. It remains a challenge to fabricate porous CPC with interconnected macropores while maintaining its advantages, such as plasticity. Herein, pastes containing CPC and wollastonite (WS) are infiltrated into a 3D plotted poly(lactic-co-glycolic acid) (PLGA) network to fabricate plastic CPC-based composite cement (PLGA/WS/CPC). The PLGA/WS/CPC recovers the plasticity of CPC after being heated above the glass transition temperature of PLGA. The presence of the 3D PLGA network significantly increases the flexibility of CPC in prophase and generates 3D interconnected macropores in situ upon its degradation. The addition of WS is helpful to improve the attachment, proliferation, and osteogenic differentiation of mouse bone marrow stromal cells in vitro. The in vivo experimental results indicate that PLGA/WS/CPC promotes rapid angiogenesis and bone formation. Therefore, the plastic CPC-based composite cement with a 3D PLGA network and wollastonite shows an obviously improved efficiency for repairing bone defects and is expected to facilitate the wider application of CPC in the clinic.

trans-activation of the HIV promoter by a cDNA and its genomic clones of human herpesvirus-6

Human herpesvirus 6 (HHV-6) is a lymphotropic herpesvirus, and in vitro, it can productively infect human CD4+ T cells as HIV-1. Co-infection of T cells by HIV-1 and HHV-6 can lead to both activation of the HIV-1 promoter and acceleration of the cytopathic effects. An HHV-6 (GS) cDNA clone, pCD41, encoding for a 41-kDa nuclear protein was identified and characterized previously (Chang and Balachandran, J. Virol. 65, 2884-2894 and 7085, 1991). Sequence analyses show that this protein has significant homology with the human cytomegalovirus UL44 gene coding for the ICP36 family of early-late-class phosphoprotein. Using this cDNA as the probe, a 3.8-kb EcoRI genomic fragment encoding the HHV-6(GS)P41 was cloned and designated as pGD41. When cotransfected with the HIV LTR CAT into CV-1 cells, both the pCD41 and pGD41 clones trans-activated the HIV LTR. Sequence analyses of pCD41 indicate that there are two potential open reading frames (ORFs), A and B, which are homologous to the ORFs found in the genomic clone pGD41. Deletion constructs of the pCD41 clone demonstrated that ORF-A was critical for the HIV LTR activation. Deletion analyses of the pCD41 ORF-A and the use of promoter constructs further mapped an internal functional promoter within the pCD41 sequence that can direct the synthesis of the trans-activating protein. By using HIV LTR deletion mutants, the NF-kappa B binding sites were found to be critical for response to the pCD41 trans-activation.

Fabrication of β-tricalcium phosphate composite ceramic sphere-based scaffolds with hierarchical pore structure for bone regeneration

Polymer sphere-based scaffolds, which are prepared by bonding the adjacent spheres via sintering the randomly packed spheres, feature uniform pore structure, full three-dimensional (3D) interconnection, and considerable mechanical strength. However, bioceramic sphere-based scaffolds fabricated by this method have never been reported. Due to high melting temperature of bioceramic, only limited diffusion rate can be achieved when sintering the bioceramic spheres, which is far from enough to form robust bonding between spheres. In the present study, for the first time we fabricated 3D interconnected β-tricalcium phosphate ceramic sphere-based (PG/TCP) scaffolds by introducing phosphate-based glass (PG) as sintering additive and placing uniaxial pressure during the sintering process. The sintering mechanism of PG/TCP scaffolds was unveiled. The PG/TCP scaffolds had hierarchical pore structure, which was composed by interconnected macropores (>200 μm) among spheres, pores (20–120 μm) in the interior of spheres, and micropores (1–3 μm) among the grains. During the sintering process, partial PG reacted with β-TCP, forming β-Ca2P2O7; metal ions from PG substituted to Ca2+ sites of β-TCP. The mechanical properties (compressive strength 2.8–10.6 MPa; compressive modulus 190–620 MPa) and porosity (30%–50%) of scaffolds could be tailored by manipulating the sintering temperatures. The introduction of PG accelerated in vitro degradation of scaffolds, and the PG/TCP scaffolds showed good cytocompatibility. This work may offer a new strategy to prepare bioceramic scaffolds with satisfactory physicochemical properties for application in bone regeneration.

Enhancing bone scaffold interfacial reinforcement through in situ growth of metal-organic frameworks (MOFs) on strontium carbonate: Achieving high strength and osteoimmunomodulation

Bioceramics have been extensively used to improve osteogenesis of polymers because of their excellent bone-forming capabilities. However, the inadequate interfacial bonding between ceramics and polymers compromises their mechanical properties. In this study, zeolitic imidazolate framework-8 (ZIF-8) was grown in situ on strontium carbonate (SrCO3) to construct a core-shell SrCO3@ZIF-8, which was then added to poly-l-lactic acid (PLLA) to print a SrCO3@ZIF-8/PLLA composite scaffold using selective sintering technology. First, ZIF-8 characterized by its multiple organic ligands, forms a robust interface with PLLA. Second, SrCO3 characterized by its negative zeta potential in solution, exhibits the ability to adsorb positively charged zinc ions. This, in turn, promotes the in situ growth of ZIF-8 on SrCO3, eventually achieving perfect bonding between the second phase and the PLLA matrix. Our findings indicated that the composite scaffold exhibited the highest compressive strength (21.93 MPa) and significantly promoted the osteogenic differentiation of mouse mesenchymal stem cells. Moreover, the in vivo results established that the SrCO3@ZIF-8/PLLA scaffold significantly accelerated bone regeneration efficiency in rat femur defects. The prepared scaffold, with its favorable mechanical properties and osteogenic activity, shows considerable promise for applications in bone repair.

Recovery of heavy metals and stabilization of spent hydrotreating catalyst using a glass-ceramic matrix

Chemical analysis of spent Co/Mo/gamma Al(2)O(3) catalyst revealed the presence of carbon, molybdenum, sulfur, vanadium and cobalt at levels of 16.0, 10.9, 7.3, 4.6 and 4.0 wt.%, respectively. It was found that calcination at 500 degrees C provides an effective solution for the removal of carbon and sulfur and this generates the oxide form of the heavy metals. The removal of these heavy metals can be achieved through a two-stage leaching process. During the first stage, in which concentrated ammonia is used and it has been found that this process can be successful in removing as much as 83% (w/v) Mo. In a second stage, it was found that using 10% (v/v) of sulfuric acid, it was possible to account for up to 77% (w/v) Co and 4% (w/v) Mo removal. Leaching test results indicated that the vanadium present in the heated spent catalyst was almost stabilized but the molybdenum and cobalt were not. The combination of two solid wastes, ladle furnace slag (LFS) and treated residue of spent catalyst, could be used for making a high value-added anorthite glass-ceramic materials. Further leaching tests showed that ceramic glass materials provided a very effective method of Co, Mo and V heavy metals stabilization resulting in a product with a possible commercial value.

The effect of maternal low flow oxygen administration during the second stage of labour on umbilical cord artery pH: a randomised controlled trial

OBJECTIVE

To assess the effect of maternal low flow oxygen administration during the second stage of labour on umbilical cord artery pH.

DESIGN

A randomised controlled trial.

SETTING

A tertiary teaching hospital in China.

POPULATION

Women in the second stage of labour with no complications.

METHODS

About 443 women were randomly allocated to receive either supplemental oxygen at a flow rate of 2 l/min or a sham supplementation by nasal cannula. Healthcare providers, women and outcome assessors were blinded to allocation.

MAIN OUTCOME MEASURES

Umbilical cord artery pH and fetal heart rate (FHR) pattern.

RESULTS

Baseline characteristics were similar between the two groups. There were no significant differences between the two groups in the umbilical cord artery pH [median 7.261, interquartile range (IQR) 7.228-7.295 versus 7.266 (IQR 7.232-7.297), P = 0.64], the proportion with pH less than 7.2 [30/219 versus 34/224, P = 0.66, RR (relative risk) 0.9, 95% CI 0.57-1.42], and the proportion with normal FHR pattern (147/219 versus 153/224, P = 0.79, RR 0.98, 95% CI 0.86-1.12). Maternal partial pressure of dissolved oxygen was significantly higher in the oxygen group than in the sham group [median 150.0 mmHg (IQR 142.6-156.7) versus 112.0 (IQR 104.8-118.3), P < 0.001], whereas carbon dioxide was significantly lower in the oxygen group than in the sham group (mean difference -1.1, 95% CI -2.1 to -0.1, P = 0.03).

CONCLUSION

The use of 2 l/min maternal oxygen during the second stage of labour did not adversely affect either the umbilical artery pH or the FHR pattern distribution.

TWEETABLE ABSTRACT

No difference in abnormal fetal acid base or normal heart rate if maternal O₂ given, randomised trial finds.

Identification and characterization of glycoprotein gH of human herpesvirus-6

Sequence analysis of an 8-kb BamHI-G DNA fragment from human herpesvirus-6 variant A strain GS (HHV-6A(GS)) has identified a gene encoding a glycoprotein homologous to glycoprotein gH of other herpesviruses and this gene was designated as HHV-6 gH (Josephs et al., J. Virol. 65, 5597). The open reading frame (ORF) of HHV-6A(GS) gH gene was amplified by polymerase chain reaction and was expressed as a trpE fusion protein in bacteria. Stable fusion protein was made only with constructs containing amino acids 15 to 469 of the ORF and this fusion protein was used to raise rabbit antisera. In the in vitro transcription-translation analysis of the gH gene, addition of microsomal membranes resulted in the processing of an unprocessed precursor to a polypeptide product of about 108 K. These in vitro-synthesized precursor and product forms were immunoprecipitated by the rabbit antibodies against the gH fusion protein. Rabbit anti-gH antibodies neutralized the infectivity of both HHV-6 variant A strain GS and variant B strain Z-29, and immunoprecipitation reactions identified a virion envelope-associated 102 K polypeptide as the glycoprotein gH of HHV-6 variants A and B. In addition to the 102 K glycoprotein, nonglycosylated polypeptides of about 58 and 164 K with different partial peptide maps were also consistently coimmunoprecipitated from [35S]methionine-labeled HHV-6A(GS)-infected cells, but not from HHV-6B(Z-29)-infected cells. The similarity in the molecular weights of glycoprotein gH among the two strains belonging to the two variant groups of HHV-6 and neutralization of infectivity of both groups by rabbit antibodies against HHV-6A(GS) gH suggests conserved functions of glycoprotein gH among the two variant groups of HHV-6.

Mitochondrial ND3 G10398A mutation: a biomarker for breast cancer

Mitochondrial DNA mutations have been found to play important roles in carcinogenesis. The most common G10398A mutation, a non-conservative amino acid substitution from Thr to Ala, seems to be involved in the tumorigenesis of breast cancer. Results from studies concerning this mutation remain inconclusive. In the current study, we first took clinical and molecular datasets from case-control studies to determine the association between the G10398A mutation and breast cancer. We further used the Phylotree to determine the haplogroups of this mutation. The frequencies of this mutation in 500 unrelated healthy controls were also screened. We found that this mutation is very common in the human population, and may be a polymorph.

Silver-decorated black phosphorus: a synergistic antibacterial strategy

Black phosphorus (BP) exhibits great potential as antibacterial materials due to its unique photocatalytic activity. However, the unsatisfactory optical absorption and quick recombination of photoinduced electron-hole pairs restrain its photocatalytic antibacterial performance. In this work, silver nanoparticles (AgNPs) were decorated on BP to construct BP@AgNPs nanohybrids and then introduced into poly-l-lactic acid scaffold. Combining the tunable bandgap of BP and the LSPR effect of AgNPs, BP@AgNPs nanohybrids displayed the broaden visible light absorption. Furthermore, AgNPs acted as electron acceptors could accelerate charge transfer and suppress electron-hole recombination. Therefore, BP@AgNPs nanohybrids achieved synergistically enhanced photocatalytic antibacterial activity under visible light irradiation. Fluorescence probe experiment verified that BP@AgNPs promoted the generation of reactive oxygen species, which could disrupt bacteria membrane, damage DNA and oxide proteins, and finally lead to bacteria apoptosis. As a result, the scaffold possessed strong antibacterial efficiency with a bactericidal rate of 97% under light irradiation. Moreover, the scaffold also exhibited good cytocompatibility. This work highlighted a new strategy to develop photocatalytic antibacterial scaffold for bone implant application.

Blocking Notch1 signaling by RNA interference can induce growth inhibition in HeLa cells

The Notch proteins constitute a family of transmembrane receptors that play a pivotal role in cellular differentiation, proliferation, and apoptosis. RNA interference of Presenilin1 (PS1) and Notch1 was carried out in this research to determine whether it could block Notch signaling and induce growth inhibition in HeLa cells. We transfected synthesized target small interfering RNA (siRNA) into HeLa cells, and blocking of Notch signaling was detected by C-promoter binding factor-1 (CBF1) reporter. We then conducted cell proliferation assay. Cells transfected with PS1 and Notch1 siRNA showed great inhibition in proliferation compared to the controls in vitro and in vivo. We conclude that RNA interference of PS1 or Notch1 can block Notch signaling and consequently induce growth inhibition of HeLa cells.

Cannabinoid 1 receptors modulate intestinal sensory and motor function in rat

BACKGROUND

Cannabinoid receptors are involved in visceral pain perception and control of intestinal motility in vivo. The underlying mechanisms are not well characterized. We aimed to determine whether the cannabinoid-1 (CB(1)) receptor modulates intestinal afferent nerve discharge and the peristaltic reflex.

METHODS

Rats were anesthetized and intestinal segments were removed. Afferent nerve discharge from a mesenteric nerve was investigated in vitro in the presence of the CB(1) antagonist SR 141716A or the CB(1) agonist WIN 55212-2. The myenteric peristaltic reflex was induced by electrical field stimulation and influence of SR 141716A or WIN 55212-2 was recorded.

KEY RESULTS

Afferent nerve discharge to the algesic mediator bradykinin was reduced to 11 +/- 5.1 imp s(-1) following pretreatment with SR 141716A and unchanged after WIN 55212-2 compared to 63 +/- 15.4 imp s(-1) in controls. At maximum distension pressure (80 cmH(2)O) during ramp distension, 92 +/- 12.4 imp s(-1) were reached following SR 141716A compared to 260 +/- 13.2 in vehicle controls and 227 +/- 15.4 in WIN 55212-2 pretreated animals. In contrast, afferent discharge to 5-HT (500 micromol L(-1)) was increased to 75 +/- 24.6 imp s(-1) following WIN 55212-2 compared to 18 +/- 5.9 imp s(-1) in controls, whereas SR 141716A had no effect. Ascending neuronal contractions were dose-dependently attenuated in the presence of SR 141716A and latency of these contractions was reduced. WIN 55212-2 had opposite effects that were abolished by SR 141716A.

CONCLUSIONS & INFERENCES

Activation of the CB(1) receptor differentially alters afferent intestinal nerve sensitivity to bradykinin, 5-HT, and noxious mechanical distension, while it strengthens ascending neuronal contractions. Further studies are needed to determine the physiological relevance of these observations.

The chemical modification of E. coli L-asparaginase by N,O-carboxymethyl chitosan

E. coli L-asparaginase was modified with N,O-carboxymethyl chitosan in the presence of normal product L-aspartic acid, which protected the active site of the enzyme. The modified enzyme remained high catalytic activity, showed greater stability against trypsin and alpha-chymotrypsin, but lost its activity more rapidly at high temperature (> 45 degrees C) than did the native enzyme. When tested in vivo, the plasma half-life of the modified enzyme (t1/2 = 40 hr) was over 33 times longer than that of the native enzyme (t1/2 = 1.6 hr). The results showed that the modified L-asparaginase may be much more useful than did the native enzyme for clinical treatments of tumors.

A spatiotemporal drug release scaffold with antibiosis and bone regeneration for osteomyelitis

INTRODUCTION

Scaffolds loaded with antibacterial agents and osteogenic drugs are considered essential tools for repairing bone defects caused by osteomyelitis. However, the simultaneous release of two drugs leads to premature osteogenesis and subsequent sequestrum formation in the pathological situation of unthorough antibiosis.

OBJECTIVES

In this study, a spatiotemporal drug-release polydopamine-functionalized mesoporous silicon nanoparticle (MSN) core/shell drug delivery system loaded with antibacterial silver (Ag) nanoparticles and osteogenic dexamethasone (Dex) was constructed and introduced into a poly-l-lactic acid (PLLA) scaffold for osteomyelitis therapy.

METHODS

MSNs formed the inner core and were loaded with Dex through electrostatic adsorption (MSNs@Dex), and then polydopamine was used to seal the core through the self-assembly of dopamine as the outer shell (pMSNs@Dex). Ag nanoparticles were embedded in the polydopamine shell via an in situ growth technique. Finally, the Ag-pMSNs@Dex nanoparticles were introduced into PLLA scaffolds (Ag-pMSNs@Dex/PLLA) constructed by selective laser sintering (SLS).

RESULTS

The Ag-pMSNs@Dex/PLLA scaffold released Ag+ at the 12th hour, followed by the release of Dex starting on the fifth day. The experiments verified that the scaffold had excellent antibacterial performance against Escherichia coli and Staphylococcus aureus. Moreover, the scaffold significantly enhanced the osteogenic differentiation of mouse bone marrow mesenchymal stem cells.

CONCLUSION

The findings suggested that this spatiotemporal drug release scaffold had promising potential for osteomyelitis therapy.

Robust structure from motion estimation using inertial data

The utility of using inertial data for the structure-from-motion (SfM) problem is addressed. We show how inertial data can be used for improved noise resistance, reduction of inherent ambiguities, and handling of mixed-domain sequences. We also show that the number of feature points needed for accurate and robust SfM estimation can be significantly reduced when inertial data are employed. Cramér-Rao lower bounds are computed to quantify the improvements in estimating motion parameters. A robust extended-Kalman-filter-based SfM algorithm using inertial data is then developed to fully exploit the inertial information. This algorithm has been tested by using synthetic and real image sequences, and the results show the efficacy of using inertial data for the SfM problem.

Neutralization of SIVmac239/17E in lymphocyte cultures involves virus strain-specific linear and conformational epitopes encoded by different regions of the env gene including the "V3" domain

SIVmac251 and its closely related derivatives SIVmac239 and SIVmac239/17E vary greatly in their susceptibility to neutralization with homologous and heterologous antisera. Whereas SIVmac251 induces homologous neutralizing antibodies, the antibodies induced by SIVmac239 rarely neutralize infectivity of this virus in lymphocyte cultures. In contrast, SIVmac239/17E is remarkably susceptible to neutralization with homologous and heterologous antisera induced by other strains of SIVmac. In this study, we studied the molecular basis for the neutralization of SIVmac239/17E. Using chimeric viruses in which different regions of the env gene of both SIVmac239 and SIVmac239/17E were inserted into a background of either of the parental genomes, we showed that the newly acquired neutralization properties of SIVmac239/17E were attributable to amino acid substitutions between the V2 and V4 regions of gp 120. Site-directed mutagenesis of the env gene in this region showed that the arginine substitutions at positions 334 and/or 340 within the "V3" domain were fundamental to virus neutralization but other substitutions in the V2-V4 region added to the ease of its neutralization since it became neutralizable with much higher dilutions of serum. The molecular determinants for neutralization of this virus are distinct from those reported as responsible for neutralization of SIVmac251 and both are distinct from SIVmac239.