Acceptability of voluntary HIV testing by pregnant women in developing countries: an international survey. Ghent International Working Group on Mother-to-Child Transmission of HIV

OBJECTIVE: To evaluate acceptability of voluntary HIV counselling and testing (VCT) by pregnant women in the context of clinical trials assessing interventions to reduce mother-to-child transmission (MCT) of HIV in developing countries. METHODS: During September-October 1997, 13 studies located in West (Abidjan, Bobo Dioulasso), East (Nairobi, Mombasa, Dar Es Salaam, Blantyre, Lusaka, Harare) and South Africa (Soweto, Durban), and Thailand (Bangkok) were included in a cross-sectional mailing survey about the acceptability of VCT in antenatal clinics. Acceptance rate, return rate, overall acceptability of VCT (acceptance of both pre- and post-VCT sessions) were obtained using a standardized questionnaire. RESULTS: The median overall acceptability of VCT was 69% (range, 33-95%). Overall acceptability of VCT most frequently depended on return rates because acceptance rates were generally high. Where several studies were conducted in parallel in the same city or the same country, overall acceptability rates of HIV testing were generally comparable even if the intervention programmes differed. Overall acceptability rates of VCT were high in antenatal clinics where a particular effort in implementing VCT programmes had been made. CONCLUSIONS: This international survey shows that despite many obstacles, VCT is feasible and acceptable for pregnant women aiming to reduce their risk of transmitting HIV to their children.     

Opioids activate G proteins in REM sleep-related brain stem nuclei of rat

Mu opioid receptors within the pontine reticular formation contribute to opioid-induced rapid eye movement (REM) sleep inhibition. Mu receptors are coupled to guanine nucleotide binding (G) proteins and this study tested the hypothesis that the micro opioid agonist [D-Ala2,N-Me-Phe4,Gly-ol5]enkephalin (DAMGO) would activate G proteins in rat brain stem nuclei known to regulate REM sleep. In vitro autoradiography of DAMGO-stimulated [35S]GTPgammaS binding showed that, compared with basal [35S]GTPgammaS binding, DAMGO significantly increased G protein activation in the nucleus pontis oralis (56.2%), nucleus pontis caudalis (57.3%), laterodorsal tegmental nucleus (75.8%), pedunculopontine tegmental nucleus (72.4%), nucleus locus coeruleus (77.2%) and dorsal raphe nucleus (73.4%). DAMGO stimulation of [35S]GTPgammaS binding in nuclei regulating REM sleep suggests that opioid-induced REM sleep inhibition involves activation of G proteins.     

Interrelationship between the duration of HIV infection, viral load and CD4 positive lymphocyte count

BACKGROUND: The decline in CD4+ lymphocytes occurs at different rates in patients with HIV infection. A longer duration of HIV infection and a higher level of viral replication, represented by the viral load, are associated with a lower CD4+ lymphocyte count. However, the interelationship between these variables is still not well known. PATIENTS AND METHODS: 107 HIV-infected patients for whom the date of infection was known, were included in a transversal study, in which the CD4+ lymphocyte count and the plasma viral load were analysed, the last using an isothermal amplification method (NASBA). Patients were not receiving antiretroviral drugs or suffered intercurrent infections at the time of the study. RESULTS: The mean duration of HIV infection was 8.6 +/- 2.9 years. The mean CD4+ lymphocyte count was 366 +/- 264 x 10(6)/l. The mean plasma viraemia was 4.3 +/- 0.9 logs. In a linear regression model, the CD4+ lymphocyte count was explained in 21.7% of cases by the duration of HIV infection, meanwhile the viral load justified up to 36.2 of CD4+ cell variability. When both parameters were combined, up to 58.4% of CD4+ lymphocyte values were explained. In this model, changes of 1 log in viral load had a 4-fold higher effect on the CD4+ cell count than each year of HIV infection. CONCLUSIONS: The duration of HIV infection and, particularly the viral load strongly influences the current CD4+ lymphocyte count, although other variables should exist (virus with syncytium-inducing phenotype, age of the patient and his immunegenetic repertoire) influencing the different decline seen in CD4+ T-cells.     

Increased transversions in a novel mutator colon cancer cell line

We describe a novel mutator phenotype in the Vaco411 colon cancer cell line which increases the spontaneous mutation rate 10-100-fold over background. This mutator results primarily in transversion base substitutions which are found infrequently in repair competent cells. Of the four possible types of transversions, only three were principally recovered. Spontaneous mutations recovered also included transitions and large deletions, but very few frameshifts were recovered. When compared to known mismatch repair defective colon cancer mutators, the distribution of mutations in Vaco411 is significantly different. Consistent with this difference, Vaco411 extracts are proficient in assays of mismatch repair. The Vaco411 mutator appears to be novel, and is not an obvious human homologue of any of the previously characterized bacterial or yeast transversion phenotypes. Several hypotheses by which this mutator may produce transversions are presented.     

Apolipoprotein(a) enhances platelet responses to the thrombin receptor-activating peptide SFLLRN

Elevated levels of lipoprotein(a) [Lp(a)] are correlated with an increased risk of atherosclerotic disease. We examined the effect of recombinant apolipoprotein(a) [r-apo(a)] and Lp(a) on responses of washed human platelets, prelabeled in the dense granules with [14C]serotonin and suspended in Tyrode's solution, to ADP and the thrombin receptor-activating peptide SFLLRN. No effect of the 17 kringle (K), 12K, or 6K r-apo(a) derivatives (at concentrations of 0.35 and 0.7 micromol/L) or Lp(a) (up to 0.1 micromol/L) on primary ADP-induced platelet aggregation was observed. In contrast, weak platelet responses stimulated by 7.5 micromol/L SFLLRN were significantly enhanced by the r-apo(a) derivatives; eg, 0.7 micromol/L 17K r-apo(a) increased aggregation from 15+/-4% to 58+/-6%, release of [14C]serotonin from 9+/-3% to 36+/-6%, and formation of thromboxane A2, measured as its stable metabolite thromboxane B2, from 7+/-1 to 29+/-5 ng/10(9) platelets (n=3; P<0.04 to 0.015). Significant enhancement of aggregation and release of granule contents was observed at a concentration of 17K r-apo(a) as low as 0.175 micromol/L. Purified Lp(a) (0.25 to 0.1 micromol/L) also enhanced SFLLRN-induced aggregation and release in a dose-dependent manner. Although plasminogen (0.7 and 1.5 micromol/L) and low density lipoprotein (0.025 to 0.1 micromol/L) both exhibited potentiating effects on SFLLRN-mediated platelet aggregation, the magnitude of the responses was less than that observed with either the r-apo(a) derivatives or Lp(a). The enhanced responses of platelets via the protease-activated receptor- thrombin receptor in the presence of Lp(a) may contribute to the increased risk of thromboembolic complications of atherosclerosis associated with this lipoprotein.     

Traumatic brain injury in the developing rat: effects of maturation on Morris water maze acquisition

Previous work has demonstrated that postnatal and adult rats show different physiological responses to lateral fluid percussion (FP) brain injury. Compared to adult animals, the younger rats showed longer apnea and shorter unconsciousness, and sustained hypotension at all injury severities, with higher mortality following severe traumatic brain injury (TBI). To determine if these younger rats exhibit differential cognitive impairments, the Morris water maze (MWM) was used to compare the degree of spatial learning deficits between moderately injured postnatal day 17 (P17), P28, and adult rats, as well as their age-matched controls. Comparisons between shams of different ages showed a maturational time course for MWM acquisition, where adult rats learned the task 34-58% faster than younger age groups. Injured adults showed escape latency deficits throughout the entire training period, took 39% fewer direct paths to the platform during training, took 24% longer to reach criterion performance, and showed poor probe trial performance than adult shams. Injured P28s exhibited escape latency deficits during the first week, with 23% more trials to criterion and 24% fewer direct paths compared to P28 shams. In contrast, injured P17 rats showed no significant difference from age-matched controls in terms of escape latency, number of direct paths taken, or time to criterion performance. This work suggests that, upon surviving the insult, P17 injured rats show remarkable sparing compared to P28 and adult injured animals.     

GDP-fucose synthetase from Escherichia coli: structure of a unique member of the short-chain dehydrogenase/reductase family that catalyzes two distinct reactions at the same active site

BACKGROUND:. In all species examined, GDP-fucose is synthesized from GDP-mannose in a three-step reaction catalyzed by two enzymes, GDP-mannose 4,6 dehydratase and a dual function 3, 5-epimerase-4-reductase named GDP-fucose synthetase. In this latter aspect fucose biosynthesis differs from that of other deoxy and dideoxy sugars, in which the epimerase and reductase activities are present as separate enzymes. Defects in GDP-fucose biosynthesis have been shown to affect nodulation in bacteria, stem development in plants, and are associated with the immune defect leukocyte adhesion deficiency type II in humans. RESULTS:. We have determined the structure of GDP-fucose synthetase from Escherichia coli at 2.2 A resolution. The structure of GDP-fucose synthetase is closely related to that of UDP-galactose 4-epimerase and more distantly to other members of the short-chain dehydrogenase/reductase family. We have also determined the structures of the binary complexes of GDP-fucose synthetase with its substrate NADPH and its product NADP+. The nicotinamide cofactors bind in the syn and anti conformations, respectively. CONCLUSIONS:. GDP-fucose synthetase binds its substrate, NADPH, in the proper orientation (syn) for transferring the 4-pro-S hydride of the nicotinamide. We have observed a single binding site in GDP-fucose synthetase for the second substrate, GDP-4-keto,6-deoxy-mannose. This implies that both the epimerization and reduction reactions occur at the same site in the enzyme. As is the case for all members of the short-chain family of dehydrogenase/reductases, GDP-fucose synthetase retains the Ser-Tyr-Lys catalytic triad. We propose that this catalytic triad functions in a mechanistically equivalent manner in both the epimerization and reduction reactions. Additionally, the X-ray structure has allowed us to identify other residues that are potentially required for substrate binding and catalysis.     

Sickle cell adhesion to laminin: potential role for the alpha5 chain

Sickle red blood cell (RBC) adhesion to the endothelium and to exposed, underlying subendothelial proteins is believed to contribute to vascular occlusion in sickle cell disease. Laminin, a major component of the subendothelium, supports significant adhesion of sickle, but not normal RBCs. The purpose of this study was to define the adhesive region for sickle RBCs within a human laminin preparation using a flow adhesion assay designed to mimic physiologic flow through postcapillary venules. Because sickle RBCs did not adhere to the common laminin contaminants entactin or collagen type IV, neither of these proteins are likely to contribute to the observed adhesion to laminin. Known adhesive regions of laminin neither supported nor inhibited sickle RBC adhesion to laminin, suggesting a mechanism of adhesion previously uncharacterized in other laminin adhesion studies. Moreover, sickle RBCs did not adhere to mouse EHS laminin or to human laminin-2 (merosin), eliminating the alpha1, alpha2, beta1, and gamma1 chains as mediators of sickle cell adhesion. The monoclonal antibody 4C7, which binds at or near the G-domain of the laminin alpha5 chain, significantly inhibited sickle RBC adhesion. These results suggest that an adhesive region for sickle RBCs is contained within the laminin alpha5 chain.     

Hypomyelination alters K+ channel expression in mouse mutants shiverer and Trembler

Voltage-gated K+ channels are localized to juxtaparanodal regions of myelinated axons. To begin to understand the role of normal compact myelin in this localization, we examined mKv1.1 and mKv1.2 expression in the dysmyelinating mouse mutants shiverer and Trembler. In neonatal wild-type and shiverer mice, the focal localization of both proteins in axon fiber tracts is similar, suggesting that cues other than mature myelin can direct initial K+ channel localization in shiverer mutants. In contrast, K+ channel localization is altered in hypomyelinated axonal fiber tracts of adult mutants, suggesting that abnormal myelination leads to channel redistribution. In shiverer adult, K+ channel expression is up-regulated in both axons and glia, as revealed by immunocytochemistry, RNase protection, and in situ hybridization studies. This up-regulation of K+ channels in hypomyelinated axon tracts may reflect a compensatory reorganization of ionic currents, allowing impulse conduction to occur in these dysmyelinating mouse mutants.     

Comparisons of highly virulent H5N1 influenza A viruses isolated from humans and chickens from Hong Kong

Genes of an influenza A (H5N1) virus from a human in Hong Kong isolated in May 1997 were sequenced and found to be all avian-like (K. Subbarao et al., Science 279:393-395, 1998). Gene sequences of this human isolate were compared to those of a highly pathogenic chicken H5N1 influenza virus isolated from Hong Kong in April 1997. Sequence comparisons of all eight RNA segments from the two viruses show greater than 99% sequence identity between them. However, neither isolate's gene sequence was closely (>95% sequence identity) related to any other gene sequences found in the GenBank database. Phylogenetic analysis demonstrated that the nucleotide sequences of at least four of the eight RNA segments clustered with Eurasian origin avian influenza viruses. The hemagglutinin gene phylogenetic analysis also included the sequences from an additional three human and two chicken H5N1 virus isolates from Hong Kong, and the isolates separated into two closely related groups. However, no single amino acid change separated the chicken origin and human origin isolates, but they all contained multiple basic amino acids at the hemagglutinin cleavage site, which is associated with a highly pathogenic phenotype in poultry. In experimental intravenous inoculation studies with chickens, all seven viruses were highly pathogenic, killing most birds within 24 h. All infected chickens had virtually identical pathologic lesions, including moderate to severe diffuse edema and interstitial pneumonitis. Viral nucleoprotein was most frequently demonstrated in vascular endothelium, macrophages, heterophils, and cardiac myocytes. Asphyxiation from pulmonary edema and generalized cardiovascular collapse were the most likely pathogenic mechanisms responsible for illness and death. In summary, a small number of changes in hemagglutinin gene sequences defined two closely related subgroups, with both subgroups having human and chicken members, among the seven viruses examined from Hong Kong, and all seven viruses were highly pathogenic in chickens and caused similar lesions in experimental inoculations.