Evidence for insect transmission of rabbit haemorrhagic disease virus

The spread of rabbit haemorrhagic disease (RHD) virus from quarantine on Wardang Island to mainland Australia in 1995 suggested that insects could be potential vectors. Field observations and laboratory experiments were conducted to address aspects of this hypothesis. Firstly, the variation in insect populations on the island during the field trials was examined. There was approximately a 1,000-fold increase in the number of bushflies, Musca vetustissima, shortly before the spread of the virus. Secondly, M. vetustissima were tested in the laboratory as potential vectors of RHD virus, and it was demonstrated that disease could be transmitted between rabbits by flies. Finally, 13 of 16 insect samples, collected from Wardang Island and from several sites on the mainland following the spread of virus off the island, were positive for the presence of RHD virus by a specific polymerase chain reaction (PCR). Only one sample contained sufficient infectious virus to kill a susceptible rabbit. These data, combined with previously published information on fly biology, suggested that flies, particularly bushflies, may be involved in the transmission of RHD virus. Other possible routes of spread were not assessed in this study.     

Distribution of [(3)H]BU224, a selective imidazoline I(2) binding site ligand,in rat brain

BU224 (2-(4,5-dihydroimidaz-2-yl)-quinoline) is a selective imidazoline I(2) binding site ligand characterised in both competition binding assays and functional studies. However, in some studies, BU224 has been reported to have a different functional effect from that seen with another selective imidazoline I(2) binding site ligand 2-BFI (2-(2-benzofuranyl)-2-imidazoline). This effect may reflect differing efficacies of the ligands or a difference in their brain distribution. The present study has investigated the distribution of the tritiated form of BU224 in rat brain and correlated this distribution with other imidazoline I(2) binding site ligands, [(3)H]idazoxan and [(3)H]2-BFI. Saturation studies revealed binding of [(3)H]BU224 was of high affinity and saturable. The central distribution of [(3)H]BU224 was similar to that previous reported for imidazoline I(2) binding site in rat brain. Autoradiography revealed that the highest levels of binding were in the arcuate nucleus, interpeduncular nucleus, area postrema, pineal gland and ependymal cell layer lining the ventricles. Correlation analysis of the binding distribution with our previous published studies revealed a highly significant correlation between [(3)H]BU224 and both [(3)H]idazoxan (r=0.94) and [(3)H]2-BFI (r=0.96). These data indicate [(3)H]BU224 labels the same population of imidazoline I(2) binding site in rat brain as seen with [(3)H]idazoxan and [(3)H]2-BFI. Therefore, the differences in functional effects observed with these compounds may reflect agonist and antagonist properties.     

Dicaffeoyltartaric acid analogues inhibit human immunodeficiency virus type 1 (HIV-1) integrase and HIV-1 replication at nontoxic concentrations

The human immunodeficiency virus type 1 (HIV-1) is a major health problem worldwide. In this study, 17 analogues of L-chicoric acid, a potent inhibitor of HIV integrase, were studied. Of these analogues, five submicromolar inhibitors of integrase were discovered and 13 compounds with activity against integrase at less than 10 microM were identified. Six demonstrated greater than 10-fold selectivity for HIV replication over cellular toxicity. Ten analogues inhibited HIV replication at nontoxic concentrations. Alteration of the linkages between the two bis-catechol rings, including the use of amides, mixed amide esters, cholate, and alkyl bridges, was explored. Amides were as active as esters but were more toxic in tissue culture. Alkyl and cholate bridges were significantly less potent against HIV-1 integrase in vitro and were inactive against HIV-1 replication. Two amino acid derivates and one digalloylderivative of L-chicoric acid (L-CA) showed improved selectivity over L-CA against integration in cell culture. These data suggest that in addition to the bis-catechols and free carboxylic acid groups reported previously, polar linkages are important constituents for optimal activity against HIV-1 integrase and that new derivatives can be developed with increased specificity for integration over HIV entry in vivo.     

Non-ahr gene susceptibility Loci for porphyria and liver injury induced by the interaction of 'dioxin' with iron overload in mice

Among the actions of 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin) in mice is the induction of hepatic porphyria. This is similar to the most common disease of this type in humans, sporadic porphyria cutanea tarda (PCT). Evidence is consistent with the actions of dioxin being mediated through binding to the aryl hydrocarbon receptor (AHR) with different Ahr alleles in mouse strains apparently accounting for differential downstream gene expression and susceptibility. However, studies of dioxin-induced porphyria and liver injury indicate that the mechanisms must involve interactions with other genes, perhaps associated with iron metabolism. We performed a quantitative trait locus (QTL) analysis of an F(2) cross between susceptible C57BL/6J (Ahr(b1) allele) and the highly resistant DBA/2 (Ahr(d) allele) strains after treatment with dioxin and iron. For porphyria we found QTLs on chromosomes 11 and 14 in addition to the Ahr gene (chromosome 12). Studies with C57BL/6.D2 Ahr(d) mice confirmed that the Ahr(d) allele alone did not completely negate the response. SWR mice are syngenic for the Ahr(d) allele with the DBA/2 strain but are susceptible to porphyria after elevation of hepatic iron. Analysis of SWRxD2 F(2) mice treated with iron and dioxin showed a QTL on chromosome 11, as well as finding other loci on chromosomes 1 (and possibly 9), for both porphyria and liver injury. These findings show for the first time the location of genes, other than Ahr, that modulate the mechanism of hepatic porphyria and injury caused by dioxin in mice. Orthologous loci may contribute to the pathogenesis of human sporadic PCT.     

Regulation of the neuronal glutamate transporter excitatory amino acid carrier-1 (EAAC1) by different protein kinase C subtypes

In previous studies, we have shown that activation of protein kinase C (PKC) rapidly (within minutes) increases the activity and cell surface expression of the glutamate transporter EAAC1 in two systems that endogenously express this transporter (C6 glioma cells and cocultures of neurons and astrocytes). However, the magnitude of the increase in activity is greater than the increase in cell surface expression. In addition, certain compounds completely block the increase in cell surface expression but only partially attenuate the increase in activity. We hypothesized that PKC increases EAAC1 activity by increasing cell surface expression and catalytic efficiency and that two different subtypes of PKC mediate these effects. To address these hypotheses, the PKC subtypes expressed by C6 glioma cells were identified. Of the PKC subtypes that are activated by phorbol esters, only PKCalpha, PKCdelta, and PKCepsilon were observed. G?6976, a compound that blocks PKCalpha at concentrations that do not inhibit PKCdelta or PKCepsilon, partially inhibited the increase in uptake but completely abolished the increase in EAAC1 cell surface expression. The 'G?6976-insensitive' increase in activity was not associated with a change in total transporter expression but was associated with an increase in the V(max). Na(+)-dependent glycine transport was not increased, providing indirect evidence that the G?6976-insensitive increase in activity was not caused by a change in the Na(+) electrochemical gradient required for activity. Finally, by down-regulating different subtypes of PKC, we found evidence that PKCepsilon mediates the increase in EAAC1 activity that is independent of changes in cell surface expression and found further evidence that PKCalpha mediates the increase in cell surface expression. The potential relationship of the present work with a previously identified role for PKCalpha in certain forms of synaptic plasticity is discussed.     

Use of psychoactive substances and sexual risk behavior in adolescents

This study investigated the relationship between the use of illicit drugs and sexual-risk-behavior in a sample of students aged 14 to 21 years at a public high school in S?o Paulo in 1997. A total of 689 useable questionnaires documented the sample in consumption of psychoactive substances and sexual behavior. Sexual behavior of drug users and non-users was compared regarding history of complete sexual intercourse, age at first sexual intercourse, use of condoms, sexual intercourse with sex workers, and prostitution. Drug users (N = 366) presented a higher frequency of complete sexual intercourse (80.8% of users versus 53.5% of non-users), (N = 323, p < .001), a younger age at first sexual intercourse (on average 15.2 years in users versus 15.7 among non-users, p < .005), a trend toward lower use of condoms (56.7% among users versus 65.3% among non-users, p < .1), and more sexual intercourse with sex workers (31.1% among users versus 15% among non-users, p < .001). Sexual-risk-behavior increased with the number of drugs used. Alcohol and marijuana use were associated with the highest sexual-risk-behavior. These data are essential for the development of more specific preventive strategies, focusing on male alcohol and marijuana users.     

Drug delivery systems based on sugar-macromolecule conjugates

The specificity of carbohydrate-protein interactions can greatly outstrip that of many other ligand-binding systems; such is the enormous density of information that sugars can convey. In addition, macromolecules allow for the fine-tuning of active drug delivery through their great ability to undergo site-specific modification and their inherent physicochemical properties. Once combined, these two factors suggest that sugar-macromolecule conjugates, targeted using endogenous carbohydrate binding proteins, are a promising route to the 'magic bullet'.