Evaluation of consistency for multiple experiments of a single combination in the time-dependence mixture toxicity assay.

Test-to-test consistency was evaluated for a single binary combination of organic chemicals using an assay that examined toxicity over multiple exposure times. Six experiments were conducted. The toxicities of 3-chloro-2-butanone (3C2B), methyl crotonate (MC) and the mixture of both (MX) were evaluated in each experiment at 15, 30 and 45 min of exposure using the Microtox® system. Concentration-response (x/y) curves were generated via the five-parameter logistic minus one-parameter (5PL - 1P) curve-fitting function and were used to develop predicted x/y curves for the dose-addition (DA) and independence (I) models of combined effect. A variety of toxicity (e.g. effective concentration, EC50) and time-dependent toxicity (TDT) endpoints, 5PL - 1P parameters and various combined-effects metrics (e.g. MX/DA) were calculated. Test-to-test consistency was evaluated via the coefficient of variation (CV) or, for TDT, the standard deviation of mean values. In the study, CVs obtained for single-chemical and mixture toxicity endpoints (EC25, EC50 and EC75) at each exposure time were <20, as were those for the predicted DA and I curves. For the MX/DA metric, mixture toxicity was consistent with that predicted for DA at each exposure time in each experiment with CVs <6, despite some substantial variation in TDT for MC-alone at the EC25 and for the 30-45 min time-interval. There was a lower variation in TDT for 3C2B and MX. Mean and CV values for 5PL - 1P-derived slope and asymmetry parameters were also assessed to provide bases for comparisons in future reports.

Mixture toxicity of SN2-reactive soft electrophiles: 3. Evaluation of ethyl α-halogenated acetates with α-halogenated acetonitriles.

Mixture toxicity for each of four ethyl α-halogenated acetates with each of three α-halogenated acetonitriles (xANs) was assessed. Inhibition of bioluminescence in Vibrio fischeri was measured after 15, 30, and 45 min of exposure. Concentration-response curves were developed for each chemical at each exposure duration and used to develop predicted concentration-response curves for the dose-addition and independence models of combined effect. Concentration-response curves for each mixture and each exposure duration were then evaluated against the predicted curves using three metrics per model: (1) EC50-based additivity quotient (AQ) or independence quotient (IQ) values; (2) mean AQ (mAQ) or mean IQ (mIQ) values, which were calculated by averaging the EC25, EC50, and EC75 AQ or IQ values; and (3) deviation values from additivity (DV-A) or independence (DV-I). Mixture toxicity for ethyl iodoacetate was dose-additive with each of the xANs at all exposure durations and was also often consistent with independence. The same was true for mixture toxicity of ethyl bromoacetate with each xAN. However, for the two more slowly reactive chemicals, ethyl chloroacetate (ECAC) and ethyl fluoroacetate (EFAC), mixture toxicity with each xAN only became consistent with dose-addition on increasing exposure duration. Consistency with independence for both ECAC and EFAC with the xANs was essentially limited to the EC50-IQ metric, thereby showing the utility of calculating the mean quotient (mAQ, mIQ) and deviation value (DV-A, DV-I) metrics. On review of these findings with those from the first two studies in the series, the results suggest that instances in which mixture toxicity was not consistent with dose-addition relate (1) to differences in the capability of the chemicals to form strong H-bonds with water; and (2) to differences in relative reactivity and time-dependent toxicity levels of the chemicals.

Maternal effects and heritability of annual productivity.

Within-individual consistency and among-individual heterogeneity in fitness are prerequisites for selection to take place. Within-individual variation in productivity between years, however, can vary considerably, especially when organisms become older and more experienced. We examine individual consistency in annual productivity, the covariation between survival and annual productivity, and the sources of variation in annual productivity, while accounting for advancing age, to test the individual-quality and resource-allocation life-history theory hypotheses. We use long-term data from a pedigreed, wild population of house sparrows. Within-individual annual productivity first increased and later decreased with age, but there were no selective mortality due to individual quality and no correlation between lifespan and productivity. Individuals were consistent in their annual productivity (C = 0.49). Narrow-sense heritability was low (h(2) = 0.09), but maternal effects explained much of the variation (M = 0.33). Such effects can influence evolutionary processes and are of major importance for our understanding of how variation in fitness can be maintained.

Genetic diversity and population structure in contemporary house sparrow populations along an urbanization gradient.

House sparrow (Passer domesticus) populations have suffered major declines in urban as well as rural areas, while remaining relatively stable in suburban ones. Yet, to date no exhaustive attempt has been made to examine how, and to what extent, spatial variation in population demography is reflected in genetic population structuring along contemporary urbanization gradients. Here we use putatively neutral microsatellite loci to study if and how genetic variation can be partitioned in a hierarchical way among different urbanization classes. Principal coordinate analyses did not support the hypothesis that urban/suburban and rural populations comprise two distinct genetic clusters. Comparison of FST values at different hierarchical scales revealed drift as an important force of population differentiation. Redundancy analyses revealed that genetic structure was strongly affected by both spatial variation and level of urbanization. The results shown here can be used as baseline information for future genetic monitoring programmes and provide additional insights into contemporary house sparrow dynamics along urbanization gradients.

Antisocial behavioral syndromes and 3-year quality-of-life outcomes in United States adults.

OBJECTIVE: To examine 3-year quality-of-life (QOL) outcomes among United States adults with Diagnostic and Statistical Manual of Mental Disorders - Fourth Edition (DSM-IV) antisocial personality disorder (ASPD), syndromal adult antisocial behavior without conduct disorder (CD) before age 15 [adulthood antisocial behavioral syndrome (AABS), not a DSM-IV diagnosis], or no antisocial behavioral syndrome at baseline. METHOD: Face-to-face interviews (n = 34 653). Psychiatric disorders were assessed using the Alcohol Use Disorder and Associated Disabilities Interview Schedule - DSM-IV Version. Health-related QOL was assessed using the Short-Form 12-Item Health Survey, version 2 (SF-12v2). Other outcomes included past-year Perceived Stress Scale-4 (PSS-4) scores, employment, receipt of Supplemental Security Income (SSI), welfare, and food stamps, and participation in social relationships. RESULTS: Antisocial personality disorder and AABS predicted poorer employment, financial dependency, social relationship, and physical health outcomes. Relationships of antisociality to SSI and food stamp receipt and physical health scales were modified by baseline age. Both antisocial syndromes predicted higher PSS-4, AABS predicted lower SF-12v2 Vitality, and ASPD predicted lower SF-12v2 Social Functioning scores in women. CONCLUSION: Similar prediction of QOL by ASPD and AABS suggests limited utility of requiring CD before age 15 to diagnose ASPD. Findings underscore the need to improve prevention and treatment of antisocial syndromes.

Mixture toxicity of S(N)2-reactive soft electrophiles: 2-evaluation of mixtures containing ethyl α-halogenated acetates.

Four ethyl α-halogenated acetates were tested in (1) sham and (2) nonsham combinations and (3) with a nonreactive nonpolar narcotic. Ethyl iodoacetate (EIAC), ethyl bromoacetate (EBAC), ethyl chloroacetate (ECAC), and ethyl fluoroacetate (EFAC), each considered to be an SN2-H-polar soft electrophile, were selected for testing based on their differences in electro(nucleo)philic reactivity and time-dependent toxicity (TDT). Agent reactivity was assessed using the model nucleophile glutathione, with EIAC and EBAC showing rapid reactivity, ECAC being less reactive, and EFAC lacking reactivity at ≤250 mM. The model nonpolar narcotic, 3-methyl-2-butanone (3M2B), was not reactive. Toxicity of the agents alone and in mixture was assessed using the Microtox acute toxicity test at three exposure durations: 15, 30 and 45 min. Two of the agents alone (EIAC and EBAC) had TDT values >100%. In contrast, ECAC (74 to 99%) and EFAC (9 to 12%) had partial TDT, whereas 3M2B completely lacked TDT (<0%). In mixture testing, sham combinations of each agent showed a combined effect consistent with predicted effects for dose-addition at each time point, as judged by EC(50) dose-addition quotient values. Mixture toxicity results for nonsham ethyl acetate combinations were variable, with some mixtures being inconsistent with the predicted effects for dose-addition and/or independence. The ethyl acetate-3M2B combinations were somewhat more toxic than predicted for dose-addition, a finding differing from that observed previously for α-halogenated acetonitriles with 3M2B.

Sociodemographic and psychopathologic predictors of first incidence of DSM-IV substance use, mood and anxiety disorders: results from the Wave 2 National Epidemiologic Survey on Alcohol and Related Conditions.

The objective of this study was to present nationally representative findings on sociodemographic and psychopathologic predictors of first incidence of Diagnostic and Statistical Manual of Mental Disorders, 4th edn (DSM-IV) substance, mood and anxiety disorders using the Wave 2 National Epidemiologic Survey on Alcohol and Related Conditions. One-year incidence rates of DSM-IV substance, mood and anxiety disorders were highest for alcohol abuse (1.02), alcohol dependence (1.70), major depressive disorder (MDD; 1.51) and generalized anxiety disorder (GAD; 1.12). Incidence rates were significantly greater (P<0.01) among men for substance use disorders and greater among women for mood and anxiety disorders except bipolar disorders and social phobia. Age was inversely related to all disorders. Black individuals were at decreased risk of incident alcohol abuse and Hispanic individuals were at decreased risk of GAD. Anxiety disorders at baseline more often predicted incidence of other anxiety disorders than mood disorders. Reciprocal temporal relationships were found between alcohol abuse and dependence, MDD and GAD, and GAD and panic disorder. Borderline and schizotypal personality disorders predicted most incident disorders. Incidence rates of substance, mood and anxiety disorders were comparable to or greater than rates of lung cancer, stroke and cardiovascular disease. The greater incidence of all disorders in the youngest cohort underscores the need for increased vigilance in identifying and treating these disorders among young adults. Strong common factors and unique factors appear to underlie associations between alcohol abuse and dependence, MDD and GAD, and GAD and panic disorder. The major results of this study are discussed with regard to prevention and treatment implications.

Avian genome evolution: insights from a linkage map of the blue tit (Cyanistes caeruleus).

We provide a first-generation linkage map of the blue tit (Cyanistes caeruleus), a passerine within the previously genetically uncharacterized family Paridae, which includes 91 orthologous loci with a single anchored position in the chicken (Gallus gallus) sequence assembly. The map consists of 18 linkage groups and covers 935 cM. There was highly conserved synteny between blue tit and chicken with the exception of a split on chromosome 1, potential splits on chromosome 4 and the translocation of two markers from chromosome 2 and 3, respectively, to chromosome 5. Gene order was very well conserved for the majority of chromosomes, an exception being chromosome 1 where multiple rearrangements were detected. Similar results were obtained in a comparison to the zebra finch (Taeniopygia guttata) genome assembly. The recombination rate in females was slightly higher than in males, implying a moderate degree of heterochiasmy in the blue tit. The map distance of the blue tit was approximately 78% of that of the Wageningen chicken broiler population, and very similar to the Uppsala chicken mapping population, over homologous genome regions. Apart from providing insights into avian recombination and genome evolution, our blue tit linkage map forms a valuable genetic resource for ecological and evolutionary research in Paridae.

Mixture toxicity of SN2-reactive soft electrophiles: 1. Evaluation of mixtures containing α-halogenated acetonitriles.

The concept of multiple modes of toxic action denotes that an individual chemical can induce two or more toxic effects within the same series of concentrations, for example, reactive toxicity and narcosis. It appears that such toxicity confounds the ability to develop precise predictions of mixture toxicity and makes it more difficult to clearly link a dose-additive combined effect to agents in the mixture having a single common mechanism of toxic action. This initial study of a three-part series begins to examine this issue in greater detail by testing three α-halogenated acetonitriles: (1) in sham combinations, (2) in true combinations, and (3) with a nonreactive nonpolar narcotic. Iodo-, bromo-, and chloro-derivatives of acetonitrile were selected for testing based on their electro(nucleo)philic reactivity, via the S(N)2 mechanism, and their time-dependent toxicity individually. Reactivity of each agent was assessed in tests with the model nucleophile glutathione (GSH). Each acetonitrile was reactive with GSH, but the nonpolar narcotic 3-methyl-2-butanone was not. In addition, toxicity of the agents alone and in mixtures was assessed using the Microtox(®) acute toxicity test at three time points: 15, 30, and 45 min of exposure. Each of the three agents alone had time-dependent toxicity values of about 100%, making it likely that most of the toxicity of these agents, at these times, was due to reactivity. In contrast, the nonpolar narcotic agent lacked time-dependent toxicity. In mixture testing, sham combinations of each acetonitrile showed a combined effect consistent with predicted effects for dose-addition at each time point, as did the sham combination of the nonpolar narcotic. Mixture toxicity results for true acetonitrile combinations were also consistent with dose-addition, but the acetonitrile-nonpolar narcotic combinations were generally not consistent with either the dose-addition or independence models of combined effect. Based on current understanding of mixture toxicity, these results were expected and provide a foundation for the second and third studies in the series.

Age and Periodontal Health - Immunological View.

PURPOSE OF THE REVIEW: Aging clearly impacts a wide array of systems, in particular the breadth of the immune system leading to immunosenescence, altered immunoactivation, and coincident inflammaging processes. The net result of these changes leads to increased susceptibility to infections, increased neoplastic occurrences, and elevated frequency of autoimmune diseases with aging. However, as the bacteria in the oral microbiome that contribute to the chronic infection of periodontitis is acquired earlier in life, the characteristics of the innate and adaptive immune systems to regulate these members of the autochthonous microbiota across the lifespan remains ill defined. RECENT FINDINGS: Clear data demonstrate that both cells and molecules of the innate and adaptive immune response are adversely impacted by aging, including in the oral cavity, yielding a reasonable tenet that the increased periodontitis noted in aging populations is reflective of the age-associated immune dysregulation. Additionally, this facet of host-microbe interactions and disease needs to accommodate the population variation in disease onset and progression, which may also reflect an accumulation of environmental stressors and/or decreased protective nutrients that could function at the gene level (ie. epigenetic) or translational level for production and secretion of immune system molecules. SUMMARY: Finally, the majority of studies of aging and periodontitis have emphasized the increased prevalence/severity of disease with aging, all based upon chronological age. However, evolving areas of study focusing on "biological aging" to help account for population variation in disease expression, may suggest that chronic periodontitis represents a co-morbidity that contributes to "gerovulnerability" within the population.

Acute focal ischemia-induced alterations in MAP2 immunostaining: description of temporal changes and utilization as a marker for volumetric assessment of acute brain injury.

The utility of microtubule-associated protein 2 (MAP2) immunostaining as a marker of acute focal ischemic injury was investigated. Permanent middle cerebral artery occlusion (MCAO) elicited a rapid reduction in MAP2 immunostaining that was visible 1 h post-MCAO and that increased in intensity and area encompassed over time. The ischemic lesion borders were well defined by loss of MAP2 immunostaining, but alterations in staining within the lesion were more heterogeneous. Lesion volume increased significantly from 1 to 4 h post-MCAO (from 63.8 +/- 10.8 to 111.3 +/- 19.0 mm3, mean +/- SD). Thus, MAP2 immunostaining is a sensitive, quantifiable indicator of acute brain injury following focal ischemia.

Inhibition of nitric oxide synthesis: effects on cerebral blood flow and glucose utilisation in the rat.

The consequences of inhibition of nitric oxide synthesis on local CBF and glucose utilisation have been studied in the conscious rat using the specific nitric oxide synthase inhibitor Ng-nitro-L-arginine methyl ester (L-NAME; 30 mg kg-1 i.v.). Local CBF and glucose utilisation were assessed with the [14C]iodoantipyrine and the 2-deoxy-D-[14C]glucose autoradiographic techniques, respectively. L-NAME induced prolonged (> 3 h) reductions in local CBF throughout the CNS with concomitant increases in arterial blood pressure. For example, 1 h post L-NAME, CBF dropped from 79 +/- 4 to 45 +/- 1 ml 100 g-1 min-1 in cerebellum, from 76 +/- 4 to 47 +/- 2 ml 100 g-1 min-1 in medulla oblongata, and from 117 +/- 6 to 72 +/- 2 ml 100 g-1 min-1 in cortex. L-NAME produced sustained elevations (e.g., 46 +/- 2 mm Hg at 1 h after bolus administration) in mean arterial blood pressure throughout the period evaluated. Despite evidence implicating nitric oxide in neuronal signalling, L-NAME did not significantly influence CNS functional activity, as measured by local rates of glucose utilisation, in any neuroanatomical region examined. Consequently, the normal ratio of blood flow to glucose use throughout the brain was significantly reduced in the presence of L-NAME, although the hierarchy of blood flow levels in different neuroanatomical regions was preserved. These results are consistent with the involvement of nitric oxide in the tonic control of cerebral tissue perfusion.

Cerebrovascular hemodynamics and ischemic tolerance: lipopolysaccharide-induced resistance to focal cerebral ischemia is not due to changes in severity of the initial ischemic insult, but is associated with preservation of microvascular perfusion.

Lipopolysaccharide (LPS), administered 72 hours before middle cerebral artery (MCA) occlusion, confers significant protection against ischemic injury. For example, in the present study, LPS (0.9 mg/kg intravenously) induced a 31% reduction in infarct volume (compared with saline control) assessed 24 hours after permanent MCA occlusion. To determine whether LPS induces true tolerance to ischemia, or merely attenuates initial ischemic severity by augmenting collateral blood flow, local CBF was measured autoradiographically 15 minutes after MCA occlusion. Local CBF did not differ significantly between LPS- and saline-pretreated rats (e.g., 34 +/- 10 and 29 +/- 15 mL x 100 g(-1) x min(-1) for saline and LPS pretreatment in a representative region of ischemic cortex), indicating that the neuroprotective action of LPS is not attributable to an immediate reduction in the degree of ischemia induced by MCA occlusion, and that LPS does indeed induce a state of ischemic tolerance. In contrast to the similarity of the initial ischemic insult between tolerant (LPS-pretreated) and nontolerant (saline-pretreated) rats, microvascular perfusion assessed either 4 hours or 24 hours after MCA occlusion was preserved at significantly higher levels in the LPS-pretreated rats than in controls. Furthermore, the regions of preserved perfusion in tolerant animals were associated with regions of tissue sparing. These results suggest that LPS-induced tolerance to focal ischemia is at least partly dependent on the active maintenance of microvascular patency and hence the prevention of secondary ischemic injury.

Anti-ischaemic efficacy of a nitric oxide synthase inhibitor and a N-methyl-D-aspartate receptor antagonist in models of transient and permanent focal cerebral ischaemia.

1. We have recently developed a new model of transient focal ischaemia in the rat utilising topical application of endothelin-1 to the left middle cerebral artery (MCA). In order to validate this approach the present study assessed the neuroprotective efficacy of the NMDA receptor antagonist dizocilpine (MK-801) in the endothelin-1 model. The anti-ischaemic efficacy of the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) was subsequently evaluated, and contrasted with its efficacy against permanent focal ischaemia, to determine the utility of the endothelin-1 model for identification of novel pharmacoprotective agents. 2. MK-801 (0.12 mg kg-1 bolus, 108 micrograms kg-1 h-1 infusion i.v., either 1 or 2.5 h pre-transient MCA occlusion (MCAO)) induced hypotension that persisted for approximately 1.5 h so that mean arterial blood pressure (MABP) at the time of MCAO was significantly lower in the 1 h group compared with control (MABP: 86 +/- 11, 68 +/- 6 and 84 +/- 4 mmHg (mean +/- s.d.) for saline, 1 h MK-801 and 2.5 h MK-801 groups respectively). The 2.5 h pretreatment schedule resulted in significant reduction (71%) in the volume of hemispheric damage (assessed 4 h post onset of ischaemia) while the 1 h pretreatment schedule did not (volumes of hemispheric damage: 59 +/- 38, 51 +/- 51 and 17 +/- 28 mm3 for saline, 1 h and 2.5 h MK-801 groups). 3. Thus the considerable neuroprotective effect of MK-801 in the endothelin-1 model of transient focal cerebral ischaemia was highly sensitive to drug-induced hypotension. This result is in contrast to previous studies of permanent MCAO where MK-801-induced hypotension did not compromise its neuroprotective action.4. L-NAME (3 mg kg-1, i.v. 30 min pre-MCAO) moderately, but significantly, reduced (16%) the volume of ischaemic damage 4 h post-permanent MCA occlusion, whereas the 29% reduction in volume of damage achieved in the model of transient focal ischaemia did not attain significance due to the greater variability associated with this model. L-NAME did not significantly alter MABP in either model.5. The modest neuroprotection achieved with NO synthase inhibition suggests NO is of relatively minor importance as a mediator of neurotoxicity following permanent focal cerebral ischaemia. In addition the comparable efficacy of L-NAME against transient focal ischaemia suggests the presence of reperfusion does not enhance the contribution of NO to neuronal injury in the acute (4 h) phase following a focal ischaemic insult.

Family structure and children's health: United States, 1988.

This report describes the family arrangements of children 17 years of age and under and the association between family structure and various demographic and socioeconomic characteristics of the children and their families. The focus of the report is on the relationship between family structure and children's health and well-being. Physical health, educational attainment, and emotional health are compared for children in the four most common types of family. Data are from the 1988 National Health Interview Survey on Child Health.

Polymorphonuclear leukocytes and microcirculatory perfusion in acute stroke in the SHR.

In order to determine the effect of depleting circulating polymorphonuclear neutrophils (PMN's) on brain microcirculation and lesion size in an acute stroke model, Spontaneously Hypertensive Rats (SHR) were injected intraperitoneally with either 2 ml RP-3 antineutrophil antibody followed in 4 hours by MCAO (n = 5), 2 ml saline followed in 4 hours by middle cerebral artery occlusion (MCAO) (n = 6), or 2 ml saline followed in 4 hours by sham operation (n = 3). After 4 hours of ischemia or a 4 hour interval (sham-operated animals), microvascular perfusion was assessed by means of an intravascular fluorescent tracer technique: FITC-dextran and Evans blue were injected intravenously 10 seconds and 5 seconds, respectively, before decapitation. Lesion volume was calculated by interpolation from histologic sections cut from 8 predefined stereotactic levels. MCAO with the normal complement of neutrophils led to significant impairment of perfusion in nutrient vessels and a maximal ischemic lesion volume. Depletion of circulating leukocytes by RP-3 significantly attenuated the microvessel perfusion impairment and reduced the volume of ischemic brain injury.

Analysis of the combined osteolathyritic effects of beta-aminopropionitrile and diethyldithiocarbamate on xenopus development.

In order to examine the mechanistic basis between combined effects and mechanisms of action, two osteolathyrogens, beta-aminopropionitrile (betaAPN) and diethyldithiocarbamate (DTC), were tested together on Xenopus embryos. In a separate test, DTC was also tested with copper sulfate to determine the importance of copper in DTC-induced osteolathyrism. Frog embryos (Xenopus laevis) were exposed for 96 h, with daily solution removal and replacement. Preserved tadpoles were evaluated for osteolathyritic lesions. For the betaAPN:DTC test, a 1.2-factor matrix design was used, producing two single chemical and seven mixture-response curves. The chi(2) goodness-of-fit test was used to compare the experimental mixture-response curves with theoretical effects for two combined effects models, dose-addition and independence. All seven mixture curves were consistent with expected results for dose-addition, but the correlations were generally not high. For the DTC:copper test, the three mixture-response curves generated showed that added copper increased the DTC-alone EC(50), but there was no corresponding right shift at the top of the response curves, as observed previously with betaAPN and copper. In the betaAPN:DTC and DTC:copper tests, DTC alone showed a biphasic concentration-osteolathyrism curve, and the slope of the response curve for DTC alone in each test was statistically different than the slope for the betaAPN alone response curve. Taken together, the results suggest the potential for a second osteolathyritic effect of DTC that affected the combined toxicity enough to produce a dose-addition correlation without the chemicals necessarily having the same mechanism.

A comparative assessment of the efficacy and side-effect liability of neuroprotective compounds in experimental stroke.

There are many examples of compounds showing neuroprotective efficacy in animal models of stroke but not in clinical trials. It is possible that some or all of these compounds possess poor therapeutic ratios, which results in the administration of sub-efficacious doses in order to avoid the emergence of side-effects. In order to explore this possibility, this study compared the therapeutic ratios of a number of neuroprotective agents that have undergone clinical trials. Neuroprotective efficacy was established using the mouse permanent (24 h) middle cerebral artery occlusion model. Side-effect liability was determined by assessment of motor coordination using the rotarod test. The therapeutic ratio was calculated as the ratio between the minimum effective dose (MED) for significant impairment in rotarod performance and the MED for significant neuroprotection. Compounds were administered i.p. 30 min prior to rotarod testing or onset of ischemia. Drugs such as Ifenprodil, Cerestat and Selfotel, that have failed in clinical trials, were found to have very low therapeutic ratios of < or = 1, whereas compounds with more tolerable clinical side-effect profiles were found to have higher therapeutic ratios (2, 10 and 10 for Sipatrigine, Remacemide and sPBN, respectively). It is concluded that the lack of efficacy of a number of neuroprotectants in clinical trials may well be a consequence of their poor therapeutic ratios.

Temporal impairment of microcirculatory perfusion following focal cerebral ischemia in the spontaneously hypertensive rat.

Microcirculatory impairments have theoretically been proposed as a potential factor in the development of ischemic injury, but few attempts have been made to directly assess microvascular patency following stroke. To address this issue we investigated the temporal changes in microvascular perfusion induced by permanent focal ischemia. Halothane-anesthetized spontaneously hypertensive rats were subjected to middle cerebral artery occlusion (MCAO) of 5 min to 4 h duration. Two fluorescent tracers (FITC-dextran and Evans blue) were then sequentially administered i.v. and allowed to circulate for 10 and 5 s respectively. Tissue sections were examined by fluorescent microscopy, and the mean number of perfused microvessels/mm2 calculated for cortical areas representing non-ischemic (Region A), perifocal/penumbral (Region B) and core ischemic (Region C) regions. For sham-operated controls, virtually all microvessels perfused with tracer within 5 s. In contrast MCAO induced significant reductions in the number of perfused microvessels in Regions B and C. The most marked impairments in perfusion were observed in core MCA territory (e.g. 2-10% of control values for 5 s circulation period) while, initially, the deficit was less severe in penumbral cortex. However, a secondary perfusion impairment developed over time in the perifocal/penumbral region, so that the deficit was greater 4 h after MCAO than at earlier time points (e.g. 72%, 71% and 22% of control value for 0.5, 1 and 4 h MCAO respectively; 10 s circulation period). In conclusion, MCAO induced severe impairments in microcirculatory perfusion within the core ischemic region, and to a lesser extent in the penumbra. However, the development of a more severe perfusion deficit in the penumbra within 4 h of MCAO supports the hypothesis that microcirculatory failure in this region contributes to its recruitment to the ischemic infarct.

Autoradiographic evaluation of forskolin and D1 dopamine receptor binding in a rat model of focal cerebral ischaemia.

Post-ischaemic changes in forskolin and D1 dopamine receptor (labelled with SCH23390) binding sites were evaluated in a rat unilateral middle cerebral artery occlusion (MCA) model. The changes in binding were assessed acutely (2 h post-MCA occlusion) in relation to local cerebral blood flow (lCBF) and chronically (24 h post-MCA occlusion) in relation to histopathological alterations. Two hours following occlusion lCBF was significantly reduced throughout the territory of the MCA. Despite the widespread hypoperfusion, significant reductions in binding were only observed in the dorsolateral caudate nucleus--the region with the most profound reduction in blood flow (6% of the control contralateral lCBF value). Forskolin binding sites were reduced to 40% of the contralateral value while D1 binding sites were reduced to 80% of the contralateral value. Analysis of the relationship between forskolin binding and CBF in the caudate nucleus revealed that the ischaemic threshold for alteration in forskolin binding sites 2 h after MCA occlusion was approximately 34 ml/100 g/min. Twenty-four h post-occlusion forskolin binding sites were further reduced in the dorsolateral caudate nucleus (to 6% of contralateral) while D1 binding showed minimal reduction from that observed at 2 h. The areas of reduced binding corresponded to the area of histopathological change in the caudate nucleus and rostral neocortex. In conclusion, reduction in forskolin binding progresses further than reduction in D1 binding within the first 24 h following focal cerebral ischaemia. For both forskolin and D1 binding sites, the areas of reduced binding 24 h post-MCA occlusion predicted the area of histopathological change.