Sensitivity of the human circadian pacemaker to nocturnal light: melatonin phase resetting and suppression

Ocular exposure to early morning room light can significantly advance the timing of the human circadian pacemaker. The resetting response to such light has a non-linear relationship to illuminance. The dose-response relationship of the human circadian pacemaker to late evening light of dim to moderate intensity has not been well established. Twenty-three healthy young male and female volunteers took part in a 9 day protocol in which a single experimental light exposure6.5 h in duration was given in the early biological night. The effects of the light exposure on the endogenous circadian phase of the melatonin rhythm and the acute effects of the light exposure on plasma melatonin concentration were calculated. We demonstrate that humans are highly responsive to the phase-delaying effects of light during the early biological night and that both the phase resetting response to light and the acute suppressive effects of light on plasma melatonin follow a logistic dose-response curve, as do many circadian responses to light in mammals. Contrary to expectations, we found that half of the maximal phase-delaying response achieved in response to a single episode of evening bright light ( approximately 9000 lux (lx)) can be obtained with just over 1 % of this light (dim room light of approximately 100 lx). The same held true for the acute suppressive effects of light on plasma melatonin concentrations. This indicates that even small changes in ordinary light exposure during the late evening hours can significantly affect both plasma melatonin concentrations and the entrained phase of the human circadian pacemaker.

Molecular cloning of a cDNA encoding human antihaemophilic factor

A complete copy of the mRNA sequences encoding human coagulation factor VIII:C has been cloned and expressed. The DNA sequence predicts a single chain precursor of 2,351 amino acids with a relative molecular mass (Mr) 267,039. The protein has an obvious domain structure, contains sequence repeats and is structurally related to factor V and ceruloplasmin.

Children with autism fail to orient to naturally occurring social stimuli

Children with autism were compared to developmentally matched children with Down syndrome or typical development in terms of their ability to visually orient to two social stimuli (name called, hands clapping) and two nonsocial stimuli (rattle, musical jack-in-the-box), and in terms of their ability to share attention (following another's gaze or point). It was found that, compared to children with Down syndrome or typical development, children with autism more frequently failed to orient to all stimuli, and that this failure was much more extreme for social stimuli. Children with autism who oriented to social stimuli took longer to do so compared to the other two groups of children. Children with autism also exhibited impairments in shared attention. Moreover, for both children with autism and Down syndrome, correlational analyses revealed a relation between shared attention performance and the ability to orient to social stimuli, but no relation between shared attention performance and the ability to orient to nonsocial stimuli. Results suggest that social orienting impairments may contribute to difficulties in shared attention found in autism.

Inositol phospholipid hydrolysis in rat cerebral cortical slices: I. Receptor characterisation

Characterisation of receptor-mediated breakdown of inositol phospholipids in rat cortical slices has been performed using a direct assay which involves prelabelling with [3H]inositol. When slices were preincubated with [3H]inositol, lithium was found to greatly amplify the capacity of receptor agonists such as carbachol, noradrenaline, and 5-hydroxytryptamine to increase the amount of radioactivity appearing in the inositol phosphates. Using a large variety of agonists and antagonists it could be shown that cholinergic muscarinic, alpha 1-adrenoceptor, and histamine H1 receptors appear to be linked to inositol phospholipid breakdown in cortex. The large responses produced by receptor agonists allowed a clear discrimination between full and partial agonists as well as quantitative analysis of competitive antagonists for each receptor. Whereas carbachol and acetylcholine (in the presence of a cholinesterase inhibitor) were full agonists, oxotremorine and arecoline were only partial agonists. Very low concentrations of atropine shifted the carbachol dose-response curve to the right and allowed inhibition constants for the antagonist to be easily calculated. The nicotinic antagonist, mecamylamine, was ineffective. Noradrenaline adrenaline were full agonists at alpha 1-adrenoceptors, but phenylephrine and probably methoxamine were partial agonists. Prazosin, but not yohimbine, potently and competitively antagonised the noradrenaline inositol phospholipid response. Mepyramine but not cimetidine competitively antagonised the histamine response. These data provide strong confirmation for the potentiating effect of lithium on neurotransmitter inositol phospholipid breakdown and emphasise the ease with which functional responses at a number of cortical receptors can be characterised.

The premenstrual symptoms screening tool (PSST) for clinicians

A variety of instruments have been used in an attempt to operationalize DSM-IV criteria for premenstrual dysphoric disorder (PMDD) and to understand clinically significant premenstrual syndrome (PMS). The objectives of this research were to devise a simple user friendly screening tool to identify women who suffer from severe PMS/PMDD and who are likely to benefit from treatment. Five hundred and nineteen women, between the ages of 18 and 55 yrs, who were seen at a primary care facility completed "The Premenstrual Symptoms Screening tool" (PSST). The PSST reflects and 'translates' categorical DSM-IV criteria into a rating scale with degrees of severity. The results are in line with reported prevalence rates from several recent large prospective studies. We believe that the PSST applies a necessary degree of measure of severity and impact of premenstrual symptoms, establishes quickly if women qualify for PMDD, and is less time consuming and more practical than two cycles of prospective charting. This fast simple tool is an effective screening tool and an important starting point for further assessment.

Integrin-associated protein: a 50-kD plasma membrane antigen physically and functionally associated with integrins

Phagocytosis by monocytes or neutrophils can be enhanced by interaction with several proteins or synthetic peptides containing the Arg-Gly-Asp sequence. Recently we showed that an mAb, B6H12, specifically inhibited this enhancement of neutrophil phagocytosis by inhibiting Arg-Gly-Asp binding to the leukocyte response integrin (Gresham, H. D., J. L. Goodwin, P. M. Allen, D. C. Anderson, and E. J. Brown. 1989. J. Cell Biol. 108:1935-1943). Now, we have purified the antigen recognized by B6H12 to homogeneity. Surprisingly, it is a 50-kD molecule that is expressed on the plasma membranes of all hematopoietic cells, including erythrocytes, which express no known integrins. On platelets and placenta, but not on erythrocytes, this protein is associated with an integrin that can be recognized by an anti-beta 3 antibody. In addition, both the anti-beta 3 and several mAbs recognizing the 50-kD protein inhibit Arg-Gly-Asp stimulation of phagocytosis. These data demonstrate an association between integrins and the 50-kD protein on several cell types. For this reason, we call it Integrin-associated Protein (IAP). We hypothesize that IAP may play a role in signal transduction for enhanced phagocytosis by Arg-Gly-Asp ligands.

Clinical outcomes, quality of life, and costs in the North Thames Dialysis Study of elderly people on dialysis: a prospective cohort study

BACKGROUND

Evidence-based health policy is urgently needed to meet the increasing demand for health services among elderly people, particularly for expensive technologies such as renal-replacement therapy. Age has been used to ration dialysis, although not always explicitly, despite the lack of rigorous empirical evidence about how elderly people fare on dialysis. We undertook a comprehensive assessment of outcomes in patients 70 years or over.

METHODS

We did a 12-month prospective cohort study of outcomes in 221 patients with end-stage renal failure aged 70 years or over recruited from four hospital-based renal units. We assessed 1-year survival in 125 incident patients (70-86 years) and disease burden (hospital admissions, quality of life, costs) in 174 prevalent patients (70-93 years).

FINDINGS

1-year survival rates were: 71% overall; 80%, 69%, and 54% in patients 70-74 years, 75-79 years, and 80 years and older, respectively (p=0.008); and 88%, 71%, and 64% in patients with no, one, or two or more comorbid conditions, respectively (p=0.056). Cox regression analyses showed that mortality was significantly associated with age 80 years and older (relative risk 2.79 [95% CI 1.28-6.93]) and peripheral vascular disease (2.83 [1.29-6.17]), but not with diabetes, ischaemic heart disease, cerebrovascular disease, chronic obstructive airways disease, sex, or treatment method. In terms of disease burden, hospital admissions represent a low proportion of costs and was not required by a third of patients, mental quality of life in elderly dialysis patients was similar to that of elderly people in the general population, and the average annual cost per patient of 20802 (US$31200) (68% dialysis treatment, 1% transport, 19% inpatient hospital admissions, 12% medications) was within the range of other life-extending interventions.

INTERPRETATION

Our results suggest that age alone should not be used as a barrier to referral and treatment and emphasise the need to consider the benefits of dialysis in elderly people. Indicators of the ability to benefit from treatment, rather than chronological age, should be used to develop policies that ensure equal access to care for all.

Transient hyperthermia protects against subsequent forebrain ischemic cell damage in the rat

We heated Wistar rats (n = 10) to 41.5 +/- 0.2 degrees C for 15 minutes, 24 hours before the induction of forebrain cerebral ischemia. We subjected 23 rats to forebrain ischemia without prior heating. Ischemic cell damage in the medial, lateral, and overall CA 1/2 hippocampus, inferior frontal cortex, and dorsal-lateral striatum was significantly (p less than 0.05) less severe in heated animals than in nonheated animals.

Evaluation of the TREX1 gene in a large multi-ancestral lupus cohort

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disorder with a complex pathogenesis in which genetic, hormonal and environmental factors have a role. Rare mutations in the TREX1 gene, the major mammalian 3'-5' exonuclease, have been reported in sporadic SLE cases. Some of these mutations have also been identified in a rare pediatric neurological condition featuring an inflammatory encephalopathy known as Aicardi-Goutières syndrome (AGS). We sought to investigate the frequency of these mutations in a large multi-ancestral cohort of SLE cases and controls. A total of 40 single-nucleotide polymorphisms (SNPs), including both common and rare variants, across the TREX1 gene, were evaluated in ∼8370 patients with SLE and ∼7490 control subjects. Stringent quality control procedures were applied, and principal components and admixture proportions were calculated to identify outliers for removal from analysis. Population-based case-control association analyses were performed. P-values, false-discovery rate q values, and odds ratios (OR) with 95% confidence intervals (CI) were calculated. The estimated frequency of TREX1 mutations in our lupus cohort was 0.5%. Five heterozygous mutations were detected at the Y305C polymorphism in European lupus cases but none were observed in European controls. Five African cases incurred heterozygous mutations at the E266G polymorphism and, again, none were observed in the African controls. A rare homozygous R114H mutation was identified in one Asian SLE patient, whereas all genotypes at this mutation in previous reports for SLE were heterozygous. Analysis of common TREX1 SNPs (minor allele frequency (MAF)>10%) revealed a relatively common risk haplotype in European SLE patients with neurological manifestations, especially seizures, with a frequency of 58% in lupus cases compared with 45% in normal controls (P=0.0008, OR=1.73, 95% CI=1.25-2.39). Finally, the presence or absence of specific autoantibodies in certain populations produced significant genetic associations. For example, a strong association with anti-nRNP was observed in the European cohort at a coding synonymous variant rs56203834 (P=2.99E-13, OR=5.2, 95% CI=3.18-8.56). Our data confirm and expand previous reports and provide additional support for the involvement of TREX1 in lupus pathogenesis.

The metabolic effects of mild hypothermia on global cerebral ischemia and recirculation in the cat: comparison to normothermia and hyperthermia

The metabolic effects of graded whole body hypothermia on complete global cerebral ischemia and recirculation was investigated in the cat. Hypothermia was induced to one of three levels prior to ischemia; T = 26.8 degrees +/- 0.5 degrees C (n = 4), T = 32.1 degrees +/- 0.2 degrees C (n = 5), and T = 34.6 degrees +/- 0.3 degrees C (n = 6), and maintained constant throughout 16 min of ischemia and 1.5-2 h of recirculation. Intracellular cerebral pH and relative concentrations of high-energy phosphate metabolites were continuously monitored, using in vivo 31P nuclear magnetic resonance (NMR) spectroscopy. Except for the first 4 min of ischemia, no significant differences were detected in the response of adenylate intensities and intracellular pH to ischemia and recirculation between the hypothermic groups. The three hypothermic groups were then pooled into one group, and the data compared to previously published data from a normothermic group, T = 38.4 degrees +/- 0.6 degrees C (n = 14), and a hyperthermic group, T = 40.6 degrees +/- 0.2 degrees C (n = 9), subjected to the identical ischemic and NMR measurement protocols. The hypothermic animals exhibited a statistically significant reduction of cerebral intracellular acidosis, both during ischemia and recirculation, as well as a more rapid return of adenylate intensities during recirculation, compared to the normothermic or hyperthermic groups. The data thus suggest that mild hypothermia has an ameliorative affect on brain energy metabolism and intracellular pH under conditions of complete global cerebral ischemia and recirculation.

The Ca2+-sensing receptor: a target for polyamines

The Ca2+-sensing receptor (CaR) is activated at physiological levels of external Ca2+ (Ca(o)) but is expressed in a number of tissues that do not have well-established roles in the control of Ca(o), including several regions of the brain and the intestine. Polyamines are endogenous polyvalent cations that can act as agonists for the CaR, as shown by our current studies of human embryonic kidney (HEK-293) cells transfected with the human CaR. Cellular parameters altered by polyamines included cytosolic free Ca2+ (Ca(i)), inositol phosphate production, and the activity of a nonselective cation channel. Spermine stimulated Ca(i) transients in CaR-transfected HEK cells, with a concentration producing a half-maximal response (EC50) of approximately 500 microM in the presence of 0.5 mM Ca2+, whereas sustained increases in Ca(i) had an EC50 of approximately 200 microM. The order of potency was spermine > spermidine >> putrescine. Elevation of Ca(o) shifted the EC50 for spermine sharply to the left, with substantial stimulation below 100 microM. Addition of subthreshold concentrations of spermine increased the sensitivity of CaR-expressing HEK cells to Ca(o). Parathyroid hormone secretion from bovine parathyroid cells was inhibited by 50% in the presence of 200 microM spermine, a response similar to that elicited by 2.0 mM Ca(o). These data suggest that polyamines could be effective agonists for the CaR, and several tissues, including the brain, may use the CaR as a target for the actions of spermine and other endogenous polycationic agonists.

Dark Matter Search Results from a One Ton-Year Exposure of XENON1T

We report on a search for weakly interacting massive particles (WIMPs) using 278.8 days of data collected with the XENON1T experiment at LNGS. XENON1T utilizes a liquid xenon time projection chamber with a fiducial mass of (1.30±0.01)  ton, resulting in a 1.0 ton yr exposure. The energy region of interest, [1.4,10.6]  keV_{ee} ([4.9,40.9] keV_{nr}), exhibits an ultralow electron recoil background rate of [82_{-3}^{+5}(syst)±3(stat)]  events/(ton yr keV_{ee}). No significant excess over background is found, and a profile likelihood analysis parametrized in spatial and energy dimensions excludes new parameter space for the WIMP-nucleon spin-independent elastic scatter cross section for WIMP masses above 6  GeV/c^{2}, with a minimum of 4.1×10^{-47}  cm^{2} at 30  GeV/c^{2} and a 90% confidence level.

Role of biofilms in the survival of Legionella pneumophila in a model potable-water system

Legionellae can infect and multiply intracellularly in both human phagocytic cells and protozoa. Growth of legionellae in the absence of protozoa has been documented only on complex laboratory media. The hypothesis upon which this study was based was that biofilm matrices, known to provide a habitat and a gradient of nutrients, might allow the survival and multiplication of legionellae outside a host cell. This study determined whether Legionella pneumophila can colonize and grow in biofilms with and without an association with Hartmannella vermiformis. The laboratory model used a rotating disc reactor at a retention time of 6.7 h to grow biofilms on stainless steel coupons. The biofilm was composed of Pseudomonas aeruginosa, Klebsiella pneumoniae and a Flavobacterium sp. The levels of L. pneumophila cells present in the biofilm were monitored for 15 d, with and without the presence of H. vermiformis, and it was found that, although unable to replicate in the absence of H. vermiformis, L. pneumophila was able to persist.

What gives a face its gender?

An experiment is reported in which the attribution of gender to isolated facial features and to faces whose features have been interchanged with those of a face of the opposite gender has been examined. Sixteen male faces were averaged to create a prototype male face and sixteen female faces averaged to create a prototype female face. The prototypes were then masked to exclude ears, neck, hair, and hairline. Individual features (brows, eyes, nose, mouth, and chin) and pairs of features (brows & eyes, eyes & nose, nose & mouth, mouth & chin) from the prototypes were then presented in isolation for classification according to their perceived gender. The results showed that, for the faces used, the brows & eyes, brows alone, eyes alone, the whole jaw, the chin, the nose & mouth, the mouth alone (in descending order), ie all the features except the nose, carried some information about gender when they were seen in isolation. In the second part of the experiment different features from one prototype face were grafted into the prototype of the opposite gender and the resulting composite faces classified by their perceived gender. The results of this feature substitution showed the jaw, brows & eyes, chin, and brows (in descending order) effecting significant change in perceived gender. The difference in gender information carried by feature(s) when they were viewed in isolation from that when they were substituted for each other is attributed to the role of configuration in the perception of the gender of a face.

Size constancy at birth: newborn infants' responses to retinal and real size

Two experiments are described whose aim was to investigate whether perception of size at birth is determined solely by proximal (retinal) stimulation, or whether newborn babies have the ability to perceive an object's real size across changes in distance. In Experiment 1, preferential looking between pairs of stimuli which varied in real size and viewing distance was found to be solely determined by retinal size, suggesting that changes to proximal stimulation can have profound effects on newborns' looking behavior. However, in Experiment 2 newborns were desensitized to changes in distance (and retinal size) during familiarization trials, and subsequently strongly preferred a different sized object to the familiar one, suggesting that the real size had been perceived as constant across the familiarization trials. These results confirm Granrud's (1987) findings that size constancy is present at birth.

Safety and metabolic effects of L-glutamine administration in humans

A series of dose-response studies was conducted to evaluate the clinical safety, pharmacokinetics, and metabolic effects of L-glutamine administered to humans. Initial studies in normal individuals evaluated the short-term response to oral loads of glutamine at doses of 0, 0.1, and 0.3 g/kg. A dose-related increase in blood glutamine occurred after oral loading and elevation of amino acids known to be end products of glutamine metabolism occurred (including alanine, citrulline, and arginine). No evidence of clinical toxicity or generation of toxic metabolites (ammonia and glutamate) was observed. Glutamine was infused intravenously in normal subjects over 4 hr at doses of 0.0125 and 0.025 g/kg/hr. In addition, glutamine was evaluated as a component of parenteral nutrition solutions (0.285 and 0.570 g/kg/day) administered for 5 days to normal subjects. Intravenous administration of glutamine was well tolerated without untoward clinical or biochemical effects. Subsequent studies in patients receiving glutamine-enriched parenteral nutrition for several weeks confirmed the clinical safety of this approach in a catabolic patient population. In addition, nitrogen retention appeared to be enhanced when glutamine was administered at a dose of 0.570 g/kg/day in a balanced nutritional solution providing adequate calories (145% of basal) and protein (1.5 g/kg/day). Nitrogen balance in patients receiving lower doses of glutamine (0.285 g/kg/day) was similar to that in patients receiving standard formulations. Further controlled clinical trials of the metabolic efficacy, tolerance, and dose response of glutamine in other patient groups are necessary to determine the appropriate use of glutamine enrichment of nutrient solutions.

Interventions to improve antibiotic prescribing practices for hospital inpatients

BACKGROUND

Up to 50% of antibiotic usage in hospitals is inappropriate. In hospitals infections caused by antibiotic-resistant bacteria are associated with higher mortality, morbidity and prolonged hospital stay compared with infections caused by antibiotic-susceptible bacteria. Clostridium difficile associated diarrhoea (CDAD) is a hospital acquired infection that is caused by antibiotic prescribing.

OBJECTIVES

To estimate the effectiveness of professional interventions that alone, or in combination, are effective in promoting prudent antibiotic prescribing to hospital inpatients, to evaluate the impact of these interventions on reducing the incidence of antimicrobial resistant pathogens or CDAD and their impact on clinical outcome.

SEARCH STRATEGY

We searched the Cochrane Effective Practice and Organisation of Care (EPOC) specialized register, Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE from 1980 to November 2003. Additional studies were obtained from the bibliographies of retrieved articles

SELECTION CRITERIA

We included all randomised and controlled clinical trials (RCT/CCT), controlled before and after studies (CBA) and interrupted time series (ITS) studies of antibiotic prescribing to hospital inpatients. Interventions included any professional or structural interventions as defined by EPOC.

DATA COLLECTION AND ANALYSIS

Two reviewers extracted data and assessed quality.

MAIN RESULTS

Sixty six studies were included and 51 (77%) showed a significant improvement in at least one outcome. Six interventions only aimed to increase treatment, 57 interventions aimed to decrease treatment and three interventions aimed to both increase and decrease treatment. The intervention target was the decision to prescribe antibiotics (one study), timing of first dose (six studies), the regimen (drug, dosing interval etc, 61 studies) or the duration of treatment (10 studies); 12 studies had more than one target. Of the six interventions that aimed to increase treatment, five reported a significant improvement in drug outcomes and one a significant improvement in clinical outcome. Of the 60 interventions that aimed to decrease treatment 47 reported drug outcomes of which 38 (81%) significantly improved, 16 reported microbiological outcomes of which 12 (75%) significantly improved and nine reported clinical outcomes of which two (22%) significantly deteriorated and 3 (33%) significantly improved. Five studies aimed to reduce CDAD. Three showed a significant reduction in CDAD. Due to differences in study design and duration of follow up it was only possible to perform meta-regression on a few studies.

AUTHORS' CONCLUSIONS

The results show that interventions to improve antibiotic prescribing to hospital inpatients are successful, and can reduce antimicrobial resistance or hospital acquired infections.

CD45 regulates Src family member kinase activity associated with macrophage integrin-mediated adhesion

BACKGROUND

Adhesion of leukocytes to the extracellular matrix and to other cells is mediated by members of the integrin family of adhesion molecules. Src family kinases are activated upon integrin-mediated adhesion. In lymphocytes, CD45 is a leukocyte-specific transmembrane protein tyrosine phosphatase that activates Src family kinases associated with B-cell and T-cell antigen receptor signaling by constitutive dephosphorylation of the inhibitory carboxy-terminal tyrosine phosphorylation site. Here, we show that CD45 is also important in downregulating the kinase activity of Src family members during integrin-mediated adhesion in macrophages.

RESULTS

We found that CD45 colocalized with beta2 integrin and the Src family kinase p53/56(lyn) to adhesion sites in bone marrow-derived macrophages. Macrophages from CD45(-/-) mice were unable to maintain integrin-mediated adhesion. In adherent macrophages, absence of CD45 led to the hyperphosphorylation and hyperactivation of p56/59(hck) and p53/56(lyn), but not of p58(c-fgr). CD45 directly inactivated p59(hck) but not p56(lck) in transient transfection assays. Furthermore, coexpression of CD45 with p59(hck) or p56(lyn) containing a tyrosine to phenylalanine mutation at the carboxy-terminal negative regulatory site resulted in decreased tyrosine phosphorylation of the Src family member kinases due to dephosphorylation of the potentiating tyrosine phosphorylation site within the kinase domain.

CONCLUSIONS

Using primary bone marrow macrophages, these studies demonstrate that CD45 regulates Src family kinases and is required to maintain macrophage adhesion. CD45 decreases Src family kinase activity by dephosphorylating the tyrosine residue located within the kinase domain.

"Depression" increases "craving" for sweet rewards in animal and human models of depression and craving

This study consisted of two experiments, one in rats and one in human volunteers, that used the identical progressive ratio (PR) operant procedure. In both experiments, responding was reinforced under a progressively increasing work requirement, and different groups of subjects received reinforcers that varied in sweetness. In experiment 1, rats were subjected to chronic mild stress, a well-validated animal model of depression. Performance under the PR schedule increased in subjects reinforced with conventional precision pellets (which contain 10% sucrose) or very sweet pellets, but not in subjects reinforced with sugar-free pellets. In experiment 2, volunteers were subjected to a depressive musical mood induction. Performance under the PR schedule increased in subjects reinforced with chocolate buttons, but not in subjects reinforced with with buttons made from the relatively unpalatable chocolate substitute carob. In experiment 2, depressive mood induction also increased chocolate craving, as measured by a novel questionnaire, and there were significant correlations between chocolate craving and chocolate-reinforced PR performance. These results suggest that performance under the PR schedule provides a measure of craving rather than reward, and that craving for sweet rewards is increased by depressive mood induction in both animal and human models. Implications for the interpretation of pharmacological studies using the PR procedure are also discussed.

Viruses of the Serengeti: patterns of infection and mortality in African lions

1. We present data on the temporal dynamics of six viruses that infect lions (Panthera leo) in the Serengeti National Park and Ngorongoro Crater, Tanzania. These populations have been studied continuously for the past 30 years, and previous research has documented their seroprevalence for feline herpesvirus, feline immunodeficiency virus (FIV), feline calicivirus, feline parvovirus, feline coronavirus and canine distemper virus (CDV). A seventh virus, feline leukaemia virus (FeLV), was absent from these animals.

2. Comprehensive analysis reveals that feline herpesvirus and FIV were consistently prevalent at high levels, indicating that they were endemic in the host populations. Feline calici‐, parvo‐ and coronavirus, and CDV repeatedly showed a pattern of seroprevalence that was indicative of discrete disease epidemics: a brief period of high exposure for each virus was followed by declining seroprevalence.

3. The timing of viral invasion suggests that different epidemic viruses are associated with different minimum threshold densities of susceptible hosts. Furthermore, the proportion of susceptibles that became infected during disease outbreaks was positively correlated with the number of susceptible hosts at the beginning of each outbreak.

4. Examination of the relationship between disease outbreaks and host fitness suggest that these viruses do not affect birth and death rates in lions, with the exception of the 1994 outbreak of canine distemper virus. Although the endemic viruses (FHV and FIV) were too prevalent to measure precise health effects, there was no evidence that FIV infection reduced host longevity.

Role of complement activation in a model of adult respiratory distress syndrome

The adult respiratory distress syndrome is characterized by arterial hypoxemia as a result of increased alveolar capillary permeability to serum proteins in the setting of normal capillary hydrostatic pressures. Because bacterial sepsis is prominent among the various diverse conditions associated with altered alveolar capillary permeability, we studied the effect of bacteremia with attendant complement activation on the sequestration of microorganisms and the leakage of albumin in the lungs of guinea pigs. Pneumococci were injected intravenously into guinea pigs and their localization was studied. Unlike normal guinea pigs, complement-depleted guinea pigs did not localize injected bacteria to the lungs. Preopsonization of organisms did not correct this defect in pulmonary localization of bacteria in complement-depleted animals, suggesting that a fluid-phase component of complement activation was required. Genetically C5-deficient mice showed no pulmonary localization of bacteria. C5-sufficient mice demonstrated the usual pulmonary localization, thus further suggesting that the activation of C5 might be important in this localization. The infusion of activated C5 increased alveolar capillary permeability to serum proteins as assayed by the amount of radioactive albumin sequestered in the lung. Neutropenic animals did not develop altered capillary permeability after challenge with activated C5. Thus, complement activation through C5, in the presence of neutrophils, induces alterations in pulmonary alveolar capillary permeability and causes localization of bacteria to the pulmonary parenchyma. Complement activation in other disease states could potentially result in similar clinical manifestations.

Imaging intact human organs with local resolution of cellular structures using hierarchical phase-contrast tomography

Imaging intact human organs from the organ to the cellular scale in three dimensions is a goal of biomedical imaging. To meet this challenge, we developed hierarchical phase-contrast tomography (HiP-CT), an X-ray phase propagation technique using the European Synchrotron Radiation Facility (ESRF)'s Extremely Brilliant Source (EBS). The spatial coherence of the ESRF-EBS combined with our beamline equipment, sample preparation and scanning developments enabled us to perform non-destructive, three-dimensional (3D) scans with hierarchically increasing resolution at any location in whole human organs. We applied HiP-CT to image five intact human organ types: brain, lung, heart, kidney and spleen. HiP-CT provided a structural overview of each whole organ followed by multiple higher-resolution volumes of interest, capturing organotypic functional units and certain individual specialized cells within intact human organs. We demonstrate the potential applications of HiP-CT through quantification and morphometry of glomeruli in an intact human kidney and identification of regional changes in the tissue architecture in a lung from a deceased donor with coronavirus disease 2019 (COVID-19).