Identification of novel subgroup a variants with enhanced receptor binding and replicative capacity in primary isolates of anaemogenic strains of feline leukaemia virus

<b>BACKGROUND:</b> The development of anaemia in feline leukaemia virus (FeLV)-infected cats is associated with the emergence of a novel viral subgroup, FeLV-C. FeLV-C arises from the subgroup that is transmitted, FeLV-A, through alterations in the amino acid sequence of the receptor binding domain (RBD) of the envelope glycoprotein that result in a shift in the receptor usage and the cell tropism of the virus. The factors that influence the transition from subgroup A to subgroup C remain unclear, one possibility is that a selective pressure in the host drives the acquisition of mutations in the RBD, creating A/C intermediates with enhanced abilities to interact with the FeLV-C receptor, FLVCR. In order to understand further the emergence of FeLV-C in the infected cat, we examined primary isolates of FeLV-C for evidence of FeLV-A variants that bore mutations consistent with a gradual evolution from FeLV-A to FeLV-C.<p></p> <b>RESULTS:</b> Within each isolate of FeLV-C, we identified variants that were ostensibly subgroup A by nucleic acid sequence comparisons, but which bore mutations in the RBD. One such mutation, N91D, was present in multiple isolates and when engineered into a molecular clone of the prototypic FeLV-A (Glasgow-1), enhanced replication was noted in feline cells. Expression of the N91D Env on murine leukaemia virus (MLV) pseudotypes enhanced viral entry mediated by the FeLV-A receptor THTR1 while soluble FeLV-A Env bearing the N91D mutation bound more efficiently to mouse or guinea pig cells bearing the FeLV-A and -C receptors. Long-term in vitro culture of variants bearing the N91D substitution in the presence of anti-FeLV gp70 antibodies did not result in the emergence of FeLV-C variants, suggesting that additional selective pressures in the infected cat may drive the subsequent evolution from subgroup A to subgroup C.<p></p> <b>CONCLUSIONS:</b> Our data support a model in which variants of FeLV-A, bearing subtle differences in the RBD of Env, may be predisposed towards enhanced replication in vivo and subsequent conversion to FeLV-C. The selection pressures in vivo that drive the emergence of FeLV-C in a proportion of infected cats remain to be established

Age, anger regulation and well-being

Emotion regulation has been argued to be an important factor in well-being. The current study investigated the effects of adult aging on emotional expression, emotional control and rumination about emotional events, focusing on an emotion which is particularly important in social interaction: anger. Measures of anger regulation and well-being were obtained in a sample of 286 adults aged between 18 and 88. Older adults expressed anger outwardly less often, and reported more inner control of anger using calming strategies compared to their younger counterparts. These age differences were not explained by variance in social desirability of responding. Age improvements in negative affect and anxiety were partly explained by age differences in anger regulation suggesting an important role for anger management in good mental health amongst older adults. Further, age improvements in quality of life were explained by variance in anger regulation indicating that improved management of emotions with age is an important factor in maintaining well-being in old age

Anticonvulsant potencies of the enantiomers of the neurosteroids androsterone and etiocholanolone exceed those of the natural forms

RATIONALE: Androsterone [(3α,5α)-3-hydroxyandrostan-17-one; 5α,3α-A] and its 5β-epimer etiocholanolone [(3α,5β)-3-hydroxyandrostan-17-one; 5β,3α-A)], the major excreted metabolites of testosterone, are neurosteroid positive modulators of GABA(A) receptors. Such neurosteroids typically show enantioselectivity in which the natural form is more potent than the corresponding unnatural enantiomer. For 5α,3α-A and 5β,3α-A, the unnatural enantiomers are more potent at GABA(A) receptors than the natural forms. OBJECTIVES: The aim of this study was to compare the anticonvulsant potencies and time courses of 5α,3α-A and 5β,3α-A with their enantiomers in mouse seizure models. METHODS: Steroids were administered intraperitoneally to male NIH Swiss mice 15 min (or up to 6 h in time course experiments) prior to administration of an electrical stimulus in the 6-Hz or maximal electroshock (MES) seizure tests or the convulsant pentylenetetrazol (PTZ). RESULTS: In the 6-Hz test, the ED(50) values of ent-5α,3α-A was 5.0 mg/kg whereas the value for 5α,3α-A was 12.1 mg/kg; the corresponding values in the PTZ seizure test were 22.8 and 51.8 mg/kg. Neurosteroid GABA(A) receptor positive allosteric modulators are generally weak in the MES test and this was confirmed in the present study. However, the atypical relative potency relationship was maintained with ED(50) values of 140 and 223 mg/kg for ent-5α,3α- A and 5α,3α-A, respectively. Similar relationships were obtained for the 5β-isomers, except that the enantioselectivity was accentuated. In the 6-Hz and PTZ tests, the ED(50) values of ent-5β,3α-A were 11.8 and 20.4 mg/kg whereas the values for 5β,3α-A were 57.6 and 109.1 mg/kg. Protective activity in the 6-Hz test of ent-5α,3α-A persisted for somewhat longer (~5 h) than for 5α,3α-A (~4 h); protection by ent-5β,3α-A also persisted longer (~3 h) than for 5β,3α-A (~2 h). CONCLUSIONS: The unnatural enantiomers of 17-keto androgen class neurosteroids have greater in vivo potency and a longer duration of action than their natural counterparts. The more prolonged duration of action of the unnatural enantiomers could reflect reduced susceptibility to metabolism. Unnatural enantiomers of androgen class neurosteroids could have therapeutic utility and may provide advantages over the corresponding natural isomers due to enhanced potency and improved pharmacokinetic characteristics