Intercontinental circulation of human influenza A(H1N2) reassortant viruses during the 2001-2002 influenza season

Reassortant influenza A viruses bearing the H1 subtype of hemagglutinin (HA) and the N2 subtype of neuraminidase (NA) were isolated from humans in the United States, Canada, Singapore, Malaysia, India, Oman, Egypt, and several countries in Europe during the 2001-2002 influenza season. The HAs of these H1N2 viruses were similar to that of the A/New Caledonia/20/99(H1N1) vaccine strain both antigenically and genetically, and the NAs were antigenically and genetically related to those of recent human H3N2 reference strains, such as A/Moscow/10/99(H3N2). All 6 internal genes of the H1N2 reassortants examined originated from an H3N2 virus. This article documents the first widespread circulation of H1N2 reassortants on 4 continents. The current influenza vaccine is expected to provide good protection against H1N2 viruses, because it contains the A/New Caledonia/20/99(H1N1) and A/Moscow/10/99(H3N2)-like viruses, which have H1 and N2 antigens that are similar to those of recent H1N2 viruses.

Molecular epidemiology of influenza A(H3N2) virus reinfections

Between 1979 and 1989, families enrolled in the Houston Family Study were prospectively monitored for influenza virus infections. Reinfection with the H3N2 subtype occurred in a number of family members, and 6 pairs of isolates (interval between collection of first and second isolate, 2-5 years) were available for molecular analysis. Changes in the hemagglutinin genes of pairs of viruses isolated from the same individuals were examined to determine the molecular basis for reinfection. The findings of this study indicate that reinfection of an individual by viruses of the same subtype may occur within a relatively short period of time when the paired strains have genetically distinct hemagglutinin genes in which amino acid changes are present in the defined antigenic sites.

Genetic and antigenic analysis of the first A/New Caledonia/20/99-like H1N1 influenza isolates reported in the Americas

From February through May of 1999, 13 cases of Influenza A virus (FLUAV), type H1N1 were reported at a Department of Defense influenza surveillance sentinel site in Lima, Peru. Genetic and antigenic analysis by hemagglutination inhibition and direct nucleotide sequencing of the HA1 region of the hemagglutinin gene were performed on two isolates, A/Peru/1641/99 and A/Peru/1798/99. Both isolates were distinct from the Bayern/7/95-like viruses circulating in the Americas and closely related to a Beijing/262/95-like variant, A/New Caledonia/20/99. With the exception of travel-related cases, the detection of these isolates represents the first appearance of New Caledonia/20/99-like viruses in the Americas. Since the characterization of these Peru isolates, a number of New Caledonia/20/99-like viruses have been reported worldwide. For the 2000/01 and 2001/02 influenza seasons, the World Health Organization (WHO) has recommended the inclusion of A/New Caledonia/20/99 as the H1N1 vaccine component for both the southern and northern hemispheres.

Stability of green fluorescent protein using luminescence spectroscopy: is GFP applicable to field analysis of contaminants?

Green fluorescent protein (GFP) was first isolated in the early 1970s for experimental use from coelenterates or the Pacific jellyfish. Aequorea victoria (Morin and Hastings, 1971). GFP has since become a favored biomarker in the photophysical analysis of molecular and cell biology because of its strong intrinsic visible fluorescence and the feasibility of fusing it to other proteins without affecting their normal functions (Creemers et al., 2000). Here we report using Bacillus subtilis expressing GFP to evaluate the influence of different environmental pH conditions on GFP fluorescence. Emission acquisitions were configured to excite at 471 nm and detect at an emission from 490 to 650 nm at 1-nm increments. Fluorescence intensity was significantly better at pH 7 (4.2 x 105 cps; P-value < 0.01) than at acid or alkaline conditions. GFP is a good biomarker for environments near netural conditions: however, GFP may be unsuitable where soils or waters are below or above pH 7 because of loss in fluorescence intensity. Alternative fluorescent markers and delivery systems must be examined in different environments to optimize responses from bioreporter molecules.

A polymeric sodium complex of 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine

The ligand 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine forms a 1:1 complex with Na[BPh4], which has been structurally characterised as a one-dimensional polymeric system with an unusual coordination geometry about the sodium.

The effect of the primary structure of the polypeptide catalyst on the enantioselectivity of the Juliá-Colonna asymmetric epoxidation of enones

Epoxidation of chalcone (1), using basic hydrogen peroxide, catalysed by polypeptides with defined primary structures demonstrates that the residues in the chain near to the N-terminus determine the stereochemical outcome of the reaction.

Estimation of the number of "true" null hypotheses in multivariate analysis of neuroimaging data

The repeated testing of a null univariate hypothesis in each of many sites (either regions of interest or voxels) is a common approach to the statistical analysis of brain functional images. Procedures, such as the Bonferroni, are available to maintain the Type I error of the set of tests at a specified level. An initial assumption of these methods is a "global null hypothesis," i.e., the statistics computed on each site are assumed to be generated by null distributions. This framework may be too conservative when a significant proportion of the sites is affected by the experimental manipulation. This report presents the development of a rigorous statistical procedure for use with a previously reported graphical method, the P plot, for estimation of the number of "true" null hypotheses in the set. This estimate can then be used to sharpen existing multiple comparison procedures. Performance of the P plot method in the multiple comparison problem is investigated in simulation studies and in the analysis of autoradiographic data.

Role of muscle tone in peristalsis in guinea-pig small intestine

We investigated the involvement of muscle tone and circular muscle (CM) contraction in peristalsis in isolated guinea-pig small intestine. A segment of jejunum (approximately 13 cm) was mounted into a three chambered partitioned bath. Peristaltic waves were initiated in the oral chamber either by: (1) infusing fluid into the oral end of the jejunum; the ejected fluid was diverted via a cannula from reaching the intermediate and anal chambers, or by (2) intraluminal balloon distension of the empty oral segment. Tension of the circular muscle was measured in all three chambers. Peristaltic waves elicited by fluid infusion were evoked at an abrupt threshold. In contrast, peristaltic waves elicited by distension could be graded in amplitude according to stimulus intensity. Peristaltic waves evoked in an empty intestine exhibited similar propagation velocities to peristaltic waves associated with fluid propulsion. Nifedipine (200-400 nM) added to the intermediate chamber to block muscle contraction did not prevent peristaltic waves elicited by either stimulus from propagating into the anal chamber, although their amplitude was attenuated. Nifedipine to the site of stimulation (oral chamber) abolished peristaltic waves generated by either stimulus. Tetrodotoxin (1-2 microM), or a low Ca2+-high Mg2+ solution to the intermediate chamber abolished the propagation of peristalsis from the oral to anal chambers. In conclusion, graded peristaltic waves can occur in an empty intestine. Therefore peristalsis is not necessarily an "all-or-none" phenomenon. Peristalsis depends on the spread of nervous activity along the bowel, rather than the reactivation of neural circuits caused by displacement of fluid in the lumen. However, local muscle tone and contraction are important for the initiation and maintenance of peristaltic propagation.

Molecular correlates of influenza A H5N1 virus pathogenesis in mice

Highly pathogenic avian influenza A H5N1 viruses caused an outbreak of human respiratory illness in Hong Kong. Of 15 human H5N1 isolates characterized, nine displayed a high-, five a low-, and one an intermediate-pathogenicity phenotype in the BALB/c mouse model. Sequence analysis determined that five specific amino acids in four proteins correlated with pathogenicity in mice. Alone or in combination, these specific residues are the likely determinants of virulence of human H5N1 influenza viruses in this model.

Cerebral protein synthesis in a genetic mouse model of phenylketonuria

Local rates of cerebral protein synthesis (lCPS(leu)) were measured with the quantitative autoradiographic [1-(14)C]leucine method in a genetic mouse model (Pah(enu2)) of phenylketonuria. As in the human disease, Pah(enu2) mice have a mutation in the gene for phenylalanine hydroxylase. We compared adult homozygous (HMZ) and heterozygous (HTZ) Pah(enu2) mice with the background strain (BTBR). Arterial plasma concentrations of phenylalanine (Phe) were elevated in both HMZ and HTZ mutants by 21 times and 38%, respectively. In the total acid-soluble pool in brain concentrations of Phe were higher and other neutral amino acids lower in HMZ mice compared with either HTZ or BTBR mice indicating a partial saturation of the l-amino acid carrier at the blood brain barrier by the elevated plasma Phe concentrations. In a series of steady-state experiments, the contribution of leucine from the arterial plasma to the tRNA-bound pool in brain was found to be statistically significantly reduced in HMZ mice compared with the other groups, indicating that a greater fraction of leucine in the precursor pool for protein synthesis is derived from protein degradation. We found reductions in lCPS(leu) of about 20% throughout the brain in the HMZ mice compared with the other two groups, but no reductions in brain concentrations of tRNA-bound neutral amino acids. Our results in the mouse model suggest that in untreated phenylketonuria in adults, the partial saturation of the l-amino acid transporter at the blood-brain barrier may not underlie a reduction in cerebral protein synthesis.

Glucose transporter expression in brain: relationship to cerebral glucose utilization

Glucose is the principle energy source for mammalian brain. Delivery of glucose from the blood to the brain requires its transport across the endothelial cells of the blood-brain barrier and across the plasma membranes of neurons and glia, which is mediated by the facilitative glucose transporter proteins. The two primary glucose transporter isoforms which function in cerebral glucose metabolism are GLUT1 and GLUT3. GLUT1 is the primary transporter in the blood-brain barrier, choroid plexus, ependyma, and glia; GLUT3 is the neuronal glucose transporter. The levels of expression of both transporters are regulated in concert with metabolic demand and regional rates of cerebral glucose utilization. We present several experimental paradigms in which alterations in energetic demand and/or substrate supply affect glucose transporter expression. These include normal cerebral development in the rat, Alzheimer's disease, neuronal differentiation in vitro, and dehydration in the rat.

Selection of an adaptive test statistic for use with multiple comparison analyses of neuroimaging data

Statistical analysis of neuroimages is commonly approached with intergroup comparisons made by repeated application of univariate or multivariate tests performed on the set of the regions of interest sampled in the acquired images. The use of such large numbers of tests requires application of techniques for correction for multiple comparisons. Standard multiple comparison adjustments (such as the Bonferroni) may be overly conservative when data are correlated and/or not normally distributed. Resampling-based step-down procedures that successfully account for unknown correlation structures in the data have recently been introduced. We combined resampling step-down procedures with the Minimum Variance Adaptive method, which allows selection of an optimal test statistic from a predefined class of statistics for the data under analysis. As shown in simulation studies and analysis of autoradiographic data, the combined technique exhibits a significant increase in statistical power, even for small sample sizes (n = 8, 9, 10).

Effects of passage history and sampling bias on phylogenetic reconstruction of human influenza A evolution

In this paper we determine the extent to which host-mediated mutations and a known sampling bias affect evolutionary studies of human influenza A. Previous phylogenetic reconstruction of influenza A (H3N2) evolution using the hemagglutinin gene revealed an excess of nonsilent substitutions assigned to the terminal branches of the tree. We investigate two hypotheses to explain this observation. The first hypothesis is that the excess reflects mutations that were either not present or were at low frequency in the viral sample isolated from its human host, and that these mutations increased in frequency during passage of the virus in embryonated eggs. A set of 22 codons known to undergo such "host-mediated" mutations showed a significant excess of mutations assigned to branches attaching sequences from egg-cultured (as opposed to cell-cultured) isolates to the tree. Our second hypothesis is that the remaining excess results from sampling bias. Influenza surveillance is purposefully biased toward sequencing antigenically dissimilar strains in an effort to identify new variants that may signal the need to update the vaccine. This bias produces an excess of mutations assigned to terminal branches simply because an isolate with no close relatives is by definition attached to the tree by a relatively long branch. Simulations show that the magnitude of excess mutations we observed in the hemagglutinin tree is consistent with expectations based on our sampling protocol. Sampling bias does not affect inferences about evolution drawn from phylogenetic analyses. However, if possible, the excess caused by host-mediated mutations should be removed from studies of the evolution of influenza viruses as they replicate in their human hosts.

Genetic characterization of H3N2 influenza viruses isolated from pigs in North America, 1977-1999: evidence for wholly human and reassortant virus genotypes

Since 1998, H3N2 viruses have caused epizootics of respiratory disease in pigs throughout the major swine production regions of the U.S. These outbreaks are remarkable because swine influenza in North America had previously been caused almost exclusively by H1N1 viruses. We sequenced the full-length protein coding regions of all eight RNA segments from four H3N2 viruses that we isolated from pigs in the Midwestern U.S. between March 1998 and March 1999, as well as from H3N2 viruses recovered from a piglet in Canada in January 1997 and from a pig in Colorado in 1977. Phylogenetic analyses demonstrated that the 1977 Colorado and 1997 Ontario isolates are wholly human influenza viruses. However, the viruses isolated since 1998 from pigs in the Midwestern U.S. are reassortant viruses containing hemagglutinin, neuraminidase and PB1 polymerase genes from human influenza viruses, matrix, non-structural and nucleoprotein genes from classical swine viruses, and PA and PB2 polymerase genes from avian viruses. The HA proteins of the Midwestern reassortant swine viruses can be differentiated from those of the 1995 lineage of human H3 viruses by 12 amino acid mutations in HA1. In contrast, the Sw/ONT/97 virus, which did not spread from pig-to-pig, lacks 11 of these changes.

Cerebral glucose utilization and glucose transporter expression: response to water deprivation and restoration

The relationship between local rates of cerebral glucose utilization (ICMRglc) and glucose transporter expression was examined during physiologic activation of the hypothalamoneurohypophysial system. Three days of water deprivation, which is known to activate the hypothalamoneurohypophysial system, resulted in increased ICMRglc and increased concentrations of GLUT1 and GLUT3 in the neurohypophysis; mRNA levels of GLUT1 and GLUT3 were decreased and increased, respectively. Water deprivation also increased ICMRglc in the hypothalamic supraoptic and paraventricular nuclei; mRNA levels of GLUT1 and GLUT3 appeared to increase in these nuclei, but the changes did not achieve statistical significance. Restoration of water for 3 to 7 days reversed all observed changes in GLUT expression (protein and mRNA): restoration of water also reversed changes in ICMRglc in both the neurohypophysis and the hypothalamic nuclei. These results indicate that under conditions of neural activation and recovery, changes in ICMRglc and the levels of GLUT1 and GLUT3 are temporally correlated in the neurohypophysis and raise the possibility that GLUT1 and GLUT3 transporter expression may be regulated by chronic changes in functional activity. In addition, increases in the expression of GLUT5 mRNA in the neurohypophysis after dehydration provide evidence for involvement of microglial activation.

Effects of diazepam and ketamine administered individually or in combination on regional rates of glucose utilization in rat brain

The effects of diazepam, which acts at GABAA receptors to enhance the effects of GABA, and ketamine, a non-competitive N-methyl-D-aspartate receptor antagonist, on local rates of cerebral glucose utilization (ICMRglc) were examined in unrestrained rats. Four groups were studied: vehicle-injected controls; and ketamine-treated, diazepam-treated and combined ketamine- and diazepam-treated animals. Ketamine alone produced a heterogeneous pattern of changes in ICMRglc (e.g. significant increases in the corpus callosum, olfactory tubercle and the entire Papez circuit, in addition to other limbic areas, and significant decreases in lateral habenula and some components of the auditory system). Diazepam alone statistically significantly decreased ICMRglc in the brain as a whole and in most areas of the cerebral cortex, thalamus and limbic system. The most remarkable effects of the two drugs administered together on ICMRglc occurred in the limbic system where the dramatic increases observed with ketamine alone were prevented by treatment with diazepam.

Suppression of protein synthesis in brain during hibernation involves inhibition of protein initiation and elongation

Protein synthesis (PS) has been considered essential to sustain mammalian life, yet was found to be virtually arrested for weeks in brain and other organs of the hibernating ground squirrel, Spermophilus tridecemlineatus. PS, in vivo, was below the limit of autoradiographic detection in brain sections and, in brain extracts, was determined to be 0.04% of the average rate from active squirrels. Further, it was reduced 3-fold in cell-free extracts from hibernating brain at 37 degreesC, eliminating hypothermia as the only cause for protein synthesis inhibition (active, 0.47 +/- 0.08 pmol/mg protein per min; hibernator, 0.16 +/- 0.05 pmol/mg protein per min, P < 0.001). PS suppression involved blocks of initiation and elongation, and its onset coincided with the early transition phase into hibernation. An increased monosome peak with moderate ribosomal disaggregation in polysome profiles and the greatly increased phosphorylation of eIF2alpha are both consistent with an initiation block in hibernators. The elongation block was demonstrated by a 3-fold increase in ribosomal mean transit times in cell-free extracts from hibernators (active, 2.4 +/- 0.7 min; hibernator, 7.1 +/- 1.4 min, P < 0.001). No abnormalities of ribosomal function or mRNA levels were detected. These findings implicate suppression of PS as a component of the regulated shutdown of cellular function that permits hibernating ground squirrels to tolerate "trickle" blood flow and reduced substrate and oxygen availability. Further study of the factors that control these phenomena may lead to identification of the molecular mechanisms that regulate this state.

Effects of thiopental anesthesia on local rates of cerebral protein synthesis in rats

We have examined the effects of a surgical level of thiopental anesthesia in adult male rats on local rates of cerebral protein synthesis with the quantitative autoradiographic L-[1-14C]leucine method. The relative contribution of leucine derived from protein breakdown to the intracellular precursor amino acid pool for protein synthesis was found to be statistically significantly decreased in the anesthetized rats compared with controls. In the brain as a whole and in 30 of the 35 brain regions examined, rates of protein synthesis were decreased (1-11%) in the anesthetized rats. Decreases were statistically significant (P < or = 0.05) in the brain as a whole and in six of the regions, and they approached statistical significance in an additional 13 regions, indicating a tendency for a generalized but small effect.

Plasticity of cerebral metabolic whisker maps in adult mice after whisker follicle removal--I. Modifications in barrel cortex coincide with reorganization of follicular innervation

We investigated alterations of the metabolic whisker map of barrel cortex after the removal of the follicles of left whiskers C1, C2 and C3 in adult albino mice. The quantitative autoradiographic [14C]deoxyglucose method was used to measure local cerebral metabolic rates for glucose in barrel cortex of mice two, four, eight, 64, 160 and 250 days after the lesion. Metabolic rates were measured in three groups of animals: (i) mice with lesions that had all whiskers clipped; (ii) mice with lesions that had left whiskers B1-3 and D1-3 stimulated; and (iii) unoperated mice that had left whiskers B1-3 and D1-3 stimulated. Compared with the metabolic rates in barrels C1-3 of stimulated unoperated mice, barrels C1-3 of stimulated mice with lesions showed the first discernible increase in metabolic rate four days after the lesion. The increase became distinct at 64 days, but attained statistical significance only approximately 160 days after the lesion. The lesion per se, i.e. without whisker stimulation, caused only a small increase in metabolic rate in barrels C1-3 accounting for not more than one fourth of the increase in metabolic rate measured after whisker deflection. The removal of whisker follicles C1-3 led, therefore, to an enlargement of the metabolic representations of the adjacent whiskers into the barrels deprived by the lesion. The gradual consolidation of the alterations of the metabolic whisker map coincided with the regeneration of follicular nerves in the whiskerpad. We detected anomalous deep nerves innervating follicles surrounding the lesion at approximately 64 days, and the number of myelinated nerve fibres in the deep nerves of these follicles was increasing with increasing time after the lesion. The coincidence of peripheral and central change suggests that the reorganization of the innervation of the sensory periphery plays an important role in the persistent alterations of the cortical somatotopy in adults following a lesion in the sensory periphery.

Plasticity of cerebral metabolic whisker maps in adult mice after whisker follicle removal--II. Modifications in the subcortical somatosensory system

The follicles of whiskers C1-3 were removed from the left side of the snout of adult mice. Adjacent whiskers B1-3 and D1-3 were stimulated while local rates of glucose utilization were measured with the [14C]2-deoxyglucose method two, four, eight, 64, 160 and approximately 250 days after follicle removal. Local metabolic activity in the trigeminal sensory brainstem and somatosensory thalamus was compared with that of unoperated mice with the same stimulation and of mice with the same lesion that had all whiskers clipped. Actual rates of glucose utilization were measured in brainstem subnuclei caudalis and interpolaris whereas metabolic activation was only assessable by colour-coded imaging in brainstem nucleus principalis and in the thalamic ventrobasal complex. Whisker stimulation activated the somatotopically appropriate loci in brainstem and thalamus. In addition, the territory deprived by follicle removal was metabolically activated in subnuclei caudalis and interpolaris at all time intervals examined. The activation was statistically significant in subnucleus interpolaris at two days, indicating that the metabolic representations of whiskers neighbouring the lesion rapidly expanded into the deprived territory. Nucleus principalis showed a broad metabolic activation at two and four days that was absent at the longer time intervals examined. Instead, at approximately 250 days the metabolic representations of the whiskers adjacent to the lesion were enlarged into the deprived territory as in the subnuclei. Since metabolic whisker representation in the ventrobasal complex appeared to have changed in the same fashion, follicle removal apparently resulted in congruent modifications of the whisker map in the three nuclei of termination as well as in the thalamic relay at the longest time interval examined. Since metabolic responsiveness of the deprived barrels in barrel cortex of the same animals increased statistically significantly only several months after follicle removal, the novel neural responses in the brainstem were not effectively transmitted to barrel cortex immediately and the slowly evolving cortical modifications are more likely to be associated with regrowth of the connectivity of primary neurons. By contrast, unmasking of hitherto suppressed inputs may underlie the early expansion of metabolic whisker representation in the brainstem.

The future of Veterans Affairs Medical Centers

In the past four years, the Department of Veterans Affairs (VA) has experienced unprecedented changes in the ways it provides medical care, trains medical residents, and supports its clinical research program. For the most part, these changes have improved the quality and efficiency of care provided to veterans, and they have improved the chances that the VA will survive in an increasingly competitive medical market place. While the changes in priorities for training medical residents and funding clinical research have been designed to be more consistent with the overall mission of the VA, these changes have been stressful for many of the VA/medical school affiliations. Our challenge is to understand and manage these changes so that the many benefits that have derived from more than fifty years of VA/medical school affiliations can be retained.