Theiler's murine encephalomyelitis virus contrasts with encephalomyocarditis and foot-and-mouth disease viruses in its functional utilization of the StopGo non-standard translation mechanism.

The picornaviruses' genome consists of a positive-sense ssRNA. Like many picornaviruses, cardioviruses synthesize two distinct polyprotein precursors from adjacent but non-overlapping genome segments. Both the [L-1ABCD-2A] and the [2BC-3ABCD] polyproteins are proteolytically processed to yield mature capsid and non-structural proteins, respectively. An unusual translational event, known as 'StopGo' or 'Stop-Carry on', is responsible for the release of the [L-1ABCD-2A] polyprotein from the ribosome and synthesis of the N-terminal amino acid of the [2BC-3ABCD] polyprotein. A common feature of these viruses is the presence of a highly conserved signature sequence for StopGo: -D(V/I)ExNPG(↓)P-, where -D(V/I)ExNPG are the last 7 aa of 2A, and the last P- is the first amino acid of 2B. Here, we report that, in contrast to encephalomyocarditis virus and foot-and-mouth disease virus, a functional StopGo does not appear to be essential for Theiler's murine encephalomyelitis virus viability when tested in vitro and in vivo.

In vitro replication models for the hepatitis C virus.

Soon after the discovery of the hepatitis C virus (HCV), attention turned to the development of models whereby replication of the virus could be investigated. Among the HCV replication models developed, the HCV RNA replicon model and the newly discovered infectious cell culture systems have had an immediate impact on the study of HCV replication, and will continue to lead to important advances in our understanding of HCV replication. The aim of this study is to deal with developments in HCV replication models in a chronological order from the early 1990s to the recent infectious HCV cell culture systems.

Safety of endobronchial biopsy in children with cystic fibrosis.

There is little found in the published literature regarding the use of endobronchial biopsy (EBB) in children with cystic fibrosis (CF). One concern over the use of the technique may relate to safety, in particular increased risk of bleeding from a hypertrophied bronchial circulation. The aim of this retrospective study was to compare the safety of EBB in children with CF and those with other conditions, the most frequent of which included primary ciliary dyskinesia and recurrent lower respiratory tract infections. Case notes of all children undergoing EBB in our institution between February 2003 and May 2004 were reviewed. EBB was performed during 45 bronchoscopies in 42 CF patients (19 males, group mean age 7.13 +/- 4.48 years) and in 39 controls (20 males, group mean age 6.59 +/- 4.48 years). There were no significant differences between disease groups in the number, type, or severity of complications occurring during or in the first 12 hr after the procedure. We conclude that EBB performed as part of fibreoptic bronchoscopy (FOB) under general anaesthesia can be performed safely in children with CF, when both bronchoscopist and anaesthetist are suitably experienced. Studies of such samples would allow us to determine the early pathological changes in the CF airway and possibly find new treatments to prevent the progression to bronchiectasis and end stage airway destruction.

Investigation of young children with severe recurrent wheeze: any clinical benefit?

The management of young children with severe recurrent wheeze is difficult because symptoms are often refractory to conventional asthma therapy and other diagnoses must be excluded. The present authors aimed to evaluate the outcome of detailed, invasive investigations in such patients. Children aged between 3 months and 5 yrs with severe recurrent wheezing, who had been referred to a tertiary centre, underwent a protocol of investigations including a chest computed tomography scan, blood tests, nasal ciliary brushings, fibreoptic bronchoscopy, bronchoalveolar lavage (BAL), endobronchial biopsy and passage of an oesophageal pH probe. A total of 47 children (25 males) with a median age of 26 (range 5-58) months underwent investigation. Of these, 39% were atopic, two-thirds had evidence of gastro-oesophageal reflux and 37 out of 47 had an abnormal bronchoscopy. Findings included structural abnormalities (13 out of 37), excessive mucus (20 out of 37) and macroscopic inflammation (10 out of 37). BAL revealed bacterial growth in 12 out of 44 (27%) patients. Good quality endobronchial biopsies were obtained from 36 out of 46 (78%) patients; of these, 44% had tissue eosinophilia and 28% had a thickened reticular basement membrane. Additional investigations (including bronchoscopy) in young children with severe wheeze may help to identify positive diagnoses and provide information to support a clinical diagnosis of asthma. This hypothesis-generating work should form the basis of future interventional studies.

A strategy for obtaining near full-length HCV cDNA clones (assemblicons) by assembly PCR.

Hepatitis C virus (HCV) genotype is a predictor of response, and guides the duration of antiviral therapy. However, with the exception of HCV genotype 1a, 1b and 2a, a limited number of clones from other genotypes exist. Here we report the optimization of long RT-PCR to generate three overlapping amplicons that span the near full length HCV genome from a panel of HCV genotypes (1a, 1b, 2a, 2b, 3a, 4a, 5a). Assembly-PCR (As-PCR) was used to construct near full-length cDNA clones (assemblicons) for each genotype. The optimization of the long RT-PCR on genotype 1a and 1b indicated that QIAamp Viral RNA kit (Qiagen, UK), Expand RT and Expand Long Template PCR system (Roche, UK), were the most efficient in producing the requisite three overlapping amplicons and assemblicons for each genotype. The genotype of each assemblicon was confirmed. Assemblicon generation was only possible when the overlapping amplicons were biotinylated. As-PCR obviated the need for time consuming ligations and cloning. The use of three overlapping amplicons in the construction of HCV assemblicons minimised the chimeric nature of the resultant clone. As-PCR may prove a methodological avenue through which a larger panel of consensus HCV clones could be made available for HCV in vitro investigation.

Airway inflammation in children with difficult asthma: relationships with airflow limitation and persistent symptoms.

BACKGROUND: The effective management and development of new treatments for children with difficult asthma requires investigation of the underlying airway pathology and its relationships with persistent symptoms and airflow limitation. METHODS: The density of immunologically distinct inflammatory cells and cells expressing interleukin (IL)-4, IL-5, and RANTES was determined in paraffin-embedded endobronchial biopsy specimens from 27 children with difficult asthma (6-16 years) following treatment with systemic corticosteroids. Eleven non-asthmatic children (7-16 years) acted as controls. Reticular basement membrane (RBM) thickness was also recorded and forced expiratory volume in 1 second (FEV(1)) and exhaled nitric oxide (FE(NO)) measured, the latter in asthmatic children only. RESULTS: RBM thickness was greater in the asthmatic than the control group (median (range) 7.4 (3.1-11.1) v 5.1 (3.5-7.5) microm, p = 0.02). No other significant tissue difference was seen, nor was there a difference between asthmatic subjects with daily symptoms after systemic corticosteroids and those who became asymptomatic. CD4+ T lymphocyte density was higher in asthmatic subjects with persistent airflow limitation (post-bronchodilator FEV(1)<80% predicted) than in those without (9.1 (5.5-13.6) v 3.5 (0.6-34.9)%, p = 0.027). Analysing all asthmatic subjects together, there were negative correlations between CD4+ T lymphocytes and both pre-bronchodilator FEV(1) (r = -0.57 (95% CI -0.79 to -0.23), p = 0.002) and post-bronchodilator FEV(1) (r = -0.61 (95% CI -0.81 to -0.29), p<0.001). There were no significant correlations between FE(NO) and inflammatory cells of any type. CONCLUSION: In children with difficult asthma treated with systemic corticosteroids, persistent airflow limitation is associated with a greater density of CD4+ T lymphocytes in endobronchial biopsy specimens.

The safety and quality of endobronchial biopsy in children under five years old.

BACKGROUND: Little is known about the airway pathology of wheezing disorders in infants and preschool children, partly owing to the difficulty of undertaking invasive studies in this age group. The safety of endobronchial biopsy and the quality of biopsies obtained were reviewed in infants and preschool children. METHODS: Case notes of children under five years of age who underwent bronchoscopy and endobronchial biopsy were reviewed. The safety of the procedure was compared in a control group matched for weight and age, undergoing bronchoscopy without endobronchial biopsy. A consultant histopathologist assessed biopsy quality. RESULTS: 33 patients (mean age 31 months, range 4 to 59) underwent bronchoscopy and endobronchial biopsy, and were matched with 33 controls (mean age 28 months, range 3 to 52). There was no significant difference between groups in the number, type, or severity of complications occurring during or after the procedure. Biopsies from 30 of the 33 subjects could be assessed. Reticular basement membrane was identified in all 30; inflammation could be assessed in 26; areas of smooth muscle were present in 23. CONCLUSIONS: In a group of preschool children undergoing bronchoscopy under general anaesthetic, performance of endobronchial biopsy carried no extra risk. The quality of biopsies obtained was usually sufficient to allow an assessment of remodelling and inflammation.

Relationship between exhaled nitric oxide and mucosal eosinophilic inflammation in children with difficult asthma, after treatment with oral prednisolone.

Exhaled nitric oxide (FE(NO)) has been proposed as a noninvasive marker of airway inflammation in asthma, and may reflect airway eosinophilia. We examined the relationship between FE(NO) and eosinophilic inflammation in endobronchial biopsies from 31 children with difficult asthma (mean age [range] 11.9 [6-17] yr), following 2 wk of prednisolone (40 mg/d). Endobronchial biopsy was also performed in seven children without asthma. Biopsy eosinophils were detected using antibody to major basic protein, and point-counting used to derive an "eosinophil score." FE(NO) readings and suitable biopsies for analysis were both obtained in 21 of 31 children with asthma. Adherence to prednisolone was demonstrated in 17 of these 21. Within this group, there was a correlation between FE(NO) and eosinophil score (r = 0.54, p = 0.03). The relationship was strongest in patients with persistent symptoms after prednisolone, in whom FE(NO) > 7 ppb was associated with a raised eosinophil score. For all patients, FE(NO) < 7 ppb was associated with an eosinophil score within the nonasthmatic range, regardless of symptoms. We propose that FE(NO) is associated with eosinophilic inflammation in children with difficult asthma, following prednisolone, and may help in identifying patients in whom persistent symptoms are associated with airway eosinophilia.

Oxygen consumption after cardiopulmonary bypass surgery in children: determinants and implications.

OBJECTIVE: We sought to assess oxygen consumption and its determinants in children shortly after undergoing cardiopulmonary bypass operations. METHODS: Twenty children, aged 2 months to 15 years (median, 3.75 years), undergoing hypothermic cardiopulmonary bypass operations were studied during the first 4 hours after arrival in the intensive care unit. Central and peripheral temperatures were monitored. Oxygen consumption was continuously measured by using respiratory mass spectrometry. Oxygen delivery was calculated from oxygen consumption and arterial and mixed venous oxygen contents, which were sampled every 30 minutes. Oxygen extraction was derived by the ratio of oxygen consumption and oxygen delivery. Arterial blood lactate levels were measured every 30 minutes. RESULTS: There was a correlation between oxygen consumption and age in patients older than 3 months (r = -0.76). Mean oxygen consumption increased by 14.7% during the study. The increase in oxygen consumption was correlated with the increase in central temperature (r = 0.73). Nine patients had an arterial lactate level above 2 mmol/L on arrival. There were no significant differences in oxygen consumption, oxygen delivery, and oxygen extraction between the group with lactate levels between 2 and 3 mmol/L and the groups with normal lactate levels both on arrival and at 2 hours. One patient with a peak lactate level of 6.8 mmol/L had initially low oxygen delivery (241.3 mL. min(-1). m(-2)). CONCLUSIONS: During the early hours after a pediatric cardiac operation, the increase in oxygen consumption is mainly attributed to the increase in central temperature. Oxygen consumption is negatively related to age. Mild lactatemia is common and does not appear to reflect oxygen delivery or oxygen consumption or a more complicated recovery.

Aurothiolates enhance the replication of Semliki Forest virus in the CNS and the exocrine pancreas.

The A7(74) strain of Semliki Forest virus (SFV) is avirulent and the L10 strain virulent in adult mice. A7(74) infection of adult mouse brain gives rise to small discrete foci of infection which, in immunocompetent animals, are cleared within 10 days. In contrast L10 infection results in a widespread and fatal central nervous system infection. Aurothiolates are linear, 2-coordinate complexes in which two ligands are covalently bound on either side of a gold nucleus in a +1 oxidation state (gold (I)). Pretreatment of A7(74) infected mice with two distinct aurothiolates (sodium aurothiomalate and aurothioglucose) resulted in significantly increased brain virus titers, and large confluent areas of infection in the brain similar to the pattern of infection seen with the L10 strain. The gold (I) moiety of aurothiolates was demonstrated to be the active component, since thiomalic acid when administered alone had no potentiating effect on the infection. Although both aurothiolates allowed productive replication and spread of A7(74) within the nature mouse brain, enhanced neuronal destruction was not apparent. There were no significant changes in virus distribution in any other tissue except for the exocrine pancreas and the myocardium where widespread infection of the acinar cells and occasional infected myocytes were observed.

Cationic lipid-mediated CFTR gene transfer to the lungs and nose of patients with cystic fibrosis: a double-blind placebo-controlled trial.

BACKGROUND: We and others have previously reported significant changes in chloride transport after cationic-lipid-mediated transfer of the cystic fibrosis transmembrane conductance regulator (CFTR) gene to the nasal epithelium of patients with cystic fibrosis. We studied the safety and efficacy of this gene transfer to the lungs and nose of patients with cystic fibrosis in a double-blind placebo-controlled trial. METHODS: Eight patients with cystic fibrosis were randomly assigned DNA-lipid complex (active) by nebulisation into the lungs followed 1 week later by administration to the nose. Eight control patients followed the same protocol but with the lipid alone (placebo). Safety was assessed clinically, by radiography, by pulmonary function, by induced sputum, and by histological analysis. Efficacy was assessed by analysis of vector-specific CFTR DNA and mRNA, in-vivo potential difference, epifluorescence assay of chloride efflux, and bacterial adherence. FINDINGS: Seven of the eight patients receiving the active complex reported mild influenza-like symptoms that resolved within 36 h. Six of eight patients in both the active and placebo groups reported mild airway symptoms over a period of 12 h following pulmonary administration. No specific treatment was required for either event. Pulmonary administration resulted in a significant (p<0.05) degree of correction of the chloride abnormality in the patients receiving active treatment but not in those on placebo when assessed by in-vivo potential difference and chloride efflux. Bacterial adherence was also reduced. We detected no alterations in the sodium transport abnormality. A similar pattern occurred following nasal administration. INTERPRETATION: Cationic-lipid-mediated CFTR gene transfer can significantly influence the underlying chloride defect in the lungs of patients with cystic fibrosis.

Modified ultrafiltration improves global left ventricular systolic function after open-heart surgery in infants and children.

OBJECTIVES: Modified ultrafiltration increases blood pressure and cardiac index following open-heart surgery in children, but it is unclear if this is secondary to an improvement in global left ventricular function. A previous report has suggested that left ventricular systolic function as assessed in a single chord is improved by ultrafiltration (Davies MJ, Nguyen K, Gaynor JW, Elliott MJ. Modified ultrafiltration improves left ventricular systolic function in infants after cardiopulmonary bypass. J Thorac Cardiovasc Surg 1998;115:361--370). The prominent vascular actions of modified ultrafiltration necessitate left ventricular assessment using load-independent indices of systolic and diastolic function. METHODS: In 22 consecutive infants and children undergoing open-heart surgery, left ventricular function was assessed following bypass and then 10 min later. Sixteen children (median weight 8.1 kg) underwent modified ultrafiltration during this period, the remainder (median weight 7.3 kg) were controls for spontaneous recovery without ultrafiltration. Real-time pressure-volume loops, with transient inferior caval vein snaring were generated from conductance and microtip pressure catheters inserted through the LV apex. From these, load-independent (slope of the end-systolic pressure-volume [Ees] and end-diastolic pressure-volume [Eed] relationships) and load-dependent (Pmax, maximum LV pressure; Ped, end-diastolic LV pressure; maximum [dP/dtmax] and minimum [dP/dtmax] time derivatives of LV pressure; tau, time constant of isovolumic relaxation) indices of left ventricular function were measured. RESULTS: Haemoconcentration was achieved in all modified ultrafiltration patients, median increase in haematocrit 34% (interquartile range 21%, 42%), final haematocrit 0.40 (0.35, 0.41). Ees increased 58% (9, 159, P = 0.005). The changes in Eed, Pmax, Ped, dP/dtmax, dP/dtmin, and tau were not significantly different from the control group. CONCLUSION: Modified ultrafiltration improves global left ventricular systolic function in infants and children following open-heart surgery.

Sexual transmission of GB virus C/hepatitis G virus.

Although it is established that infection with GB virus C (GBV-C) or hepatitis G virus (HGV) can be transmitted parenterally, the prevalence of GBV-C/HGV viremia in the general population (2-5%) is relatively high compared with other parenterally borne viruses such as hepatitis C virus. To investigate the possibility of sexual transmission of GBV-C/HGV, we determined the frequency of viremia by the polymerase chain reaction and serological reactivity to the E2 protein by ELISA in samples collected from individuals at risk for sexually transmitted diseases attending a city genitourinary medicine clinic. GBV-C/HGV viremia was detected in 27 of 87 male homosexuals (31%) and 9 of 50 prostitutes (18%), frequencies significantly greater than those in matched controls (2/63) and local blood donors (2.3%). Among nonviremic individuals, a high frequency of serological reactivity to the E2 protein of GBV-C/HGV was also observed in the risk groups (male homosexuals: 14/60; prostitutes: 11/41), although these figures are likely to be underestimates of the frequency of past infection as detectable anti-E2 reactivity may attenuate rapidly over time following resolution of infection. Infection with GBV-C/HGV was more frequent among those coinfected with human immunodeficiency virus type 1. Among male homosexuals from whom retrospective samples were available, evidence for de novo infection was found in 9 of 22 individuals over a mean sampling time of 2.9 years, predicting an annualized incidence of GBV-C/HGV infection of approximately 11% in this group. The high prevalence and incidence of GBV-C/HGV infection in these individuals and prostitutes provides strong evidence for its spread by sexual contact. Further studies are required to investigate the mechanism of its transmission and the clinical significance of acute and persistent infection in these risk groups.

Left ventricular dysfunction after open repair of simple congenital heart defects in infants and children: quantitation with the use of a conductance catheter immediately after bypass.

OBJECTIVE: Quantification of myocardial injury after the simplest pediatric operations by load-independent indices of left ventricular function, using conductance and Mikro-Tip pressure catheters (Millar Instruments, Inc., Houston, Tex.) inserted through the left ventricular apex. METHODS: Sixteen infants and children with intact ventricular septum undergoing cardiac operations had left ventricular function measured, immediately before and after bypass. Real-time pressure-volume loops were generated by conductance and Mikro-Tip pressure catheters placed in the long-axis via the left ventricular apex, and preload was varied by transient snaring of the inferior vena cava. RESULTS: Good quality pressure-volume loops were generated in 13 patients (atrial septal defects, n = 11; double-chambered right ventricle, n = 1; supravalvular aortic stenosis, n = 1; age 0.25 to 14.4 years, weight 3.1 to 46.4 kg). Their mean bypass time was 41 +/- 14 minutes and mean aortic crossclamp time 27 +/- 11 minutes. End-systolic elastance decreased by 40.7% from 0.34 +/- 0.17 to 0.21 +/- 0.15 mm Hg-1.ml-1.kg-1 (p < 0.001). There were no significant changes in the slope of the stroke work-end-diastolic volume relationship, end-diastolic elastance, time constant of isovolumic relaxation, and normalized values of the maxima and minima of the first derivative of developed left ventricular pressure. CONCLUSION: Load-independent indices of left ventricular function can be derived from left ventricular pressure-volume loops generated by conductance and Mikro-Tip pressure catheters during the perioperative period in infants and children undergoing cardiac operations. Incomplete myocardial protection was demonstrated by a deterioration in systolic function after even short bypass and crossclamp times.

Virus infection induces neuronal apoptosis: A comparison with trophic factor withdrawal.

Multicellular organisms can employ a number of defences to combat viral replication, the most dramatic being implementation of a cell autonomous apoptotic process. The overall cost to the viability of an organism of losing infected cells by apoptosis may be small if the dying cells can be substituted. In contrast, suicide of irreplaceable cells such as highly specialised neurons may have a more dramatic, even fatal consequence. Previous in vitro approaches to understanding whether neurotropic viruses cause neurons to apoptose have utilised transformed cell lines. These are not in the appropriate state of differentiation to provide an accurate indication of events in vivo. We have chosen to characterise the ability of a model CNS disease-causing virus, Semliki Forest virus (SFV), to infect and trigger apoptosis in primary cultures of nerve growth factor (NGF)-dependent sensory neurons. These cells are known to die when deprived of NGF and constitute a useful indicator of apoptosis. We observe that infection causes cell death which bears the morphological hallmarks of apoptosis, this occurs even in the present of survival promoting NGF and is concomitant with new virus production. Using the TUNEL (transferase dUTP nick end labelling) technique we show that SFV-induced apoptosis involves DNA fragmentation and requires caspase (CED-3/ICE cysteine protease) activation, as does apoptosis induced by NGF-deprivation. Extensive areas of apoptosis, as defined using a combination of ultrastructural analysis and TUNEL occur in infected neonatal mouse brains. The novel evidence that infection of primary neurons with SFV induces apoptosis with activation of one or more caspases defines a system for the further anlaysis of apoptosis regulation in physiologically relevant neurons.

Susceptibility to a neurotropic virus and its changing distribution in the developing brain is a function of CNS maturity.

Many major physiological changes occur within the rodent central nervous system (CNS) during the first few postnatal weeks. These include axonogenesis, synaptogenesis and myelination. Concomitant with CNS development over this period, there is a decrease in susceptibility to many neurotropic virus infections in that infection of suckling animals results in lethal encephalitis whereas infection of weanling animals is not lethal. The events underlying this dramatic change in susceptibility have been unclear. Here we demonstrate that age-related virulence of the neurotrophic alphavirus, Semliki Forest virus is dependent upon ability of the infection to spread in the CNS. This is not determined by maturity of interferon, or specific immune responses or the blood brain barrier, but by maturity of neuronal systems. Detailed study of the course of infection in the cortex, hippocampus and cerebellum during their postnatal development indicates that as these and other neuronal systems mature they become resistant to spread of the virus and the pattern of infection changes from widespread to focal.

bcl-2 acts early to restrict Semliki Forest virus replication and delays virus-induced programmed cell death.

As characterized by morphological assessment and terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling, Semliki Forest virus (SFV) infection of rat prostatic adenocarcinoma cells triggers an apoptotic cell response. Cell death proceeded more rapidly following infection with the neurovirulent L10 strain of SFV than with the avirulent A7 strain. Overexpression of the antiapoptotic proto-oncogene bcl-2 allowed survival of cultures infected with either strain of virus. bcl-2 overexpression drastically reduced the numbers of productively infected cells within the cultures. In situ hybridization for viral message-sense RNA coupled with immunostaining for viral protein indicated that bcl-2 functions at an early stage of the virus life cycle, at entry, pretranscriptional events or at transcription, to inhibit virus replication. Double-immunofluorescent labeling for bcl-2 and viral glycoproteins revealed double-positive cells, demonstrating that with time, this early block in replication can be overcome. These productively infected bcl-2-expressing cells do, with time, undergo apoptosis. As a result of changing the balance between cell death and cell division by restricting productive virus replication and delaying virus-induced cell death, bcl-2 expression led to the establishment of chronically infected cell lines which could be passaged.

Role of immune responses in protection and pathogenesis during Semliki Forest virus encephalitis.

The course of Semliki Forest virus (SFV) A7(74) infection in immunocompetent BALB/c, athymic nu/nu and severe combined immunodeficient (SCID) mice was compared. BALB/c mice remained healthy and exhibited transient viraemia and infectious virus in the brain from days 2 to 7. Antibodies were detectable by day 5. In comparison, SCID mice displayed a high incidence of paralysis and died: the average day of death was day 23. From infection until death, virus was present in blood and brain. No antibodies were detectable. Athymic mice were intermediate with a transient viraemia and a persistent (> 210 days) sub-clinical central nervous system (CNS) infection. These mice produced anti-viral IgM but not IgG. The pattern of infection in BALB/c or nu/nu mice could be recreated in infected SCID mice by transfer of immune serum from BALB/c or nu/nu mice with the important exception that although BALB/c immune serum could abolish infectivity titres in the CNS, scattered cells positive for viral RNA remained. Transfer of serum decreased mortality and delayed the onset of paralysis. Transfer to infected SCID mice of a non-neutralizing IgG anti-E2 monoclonal antibody did not affect the viraemia but could also reduce brain virus titres. Irrespective of specific immune responses, virus replication in CNS cells was restricted, was generally non-cytopathic and in the absence of specific immune responses could persist. From day 14 lesions of inflammatory, primary demyelination were observed throughout the CNS of BALB/c mice. In contrast, despite prolonged brain virus titres, no demyelinating lesions were observed in infected nu/nu or SCID mice. Lesions could be initiated in the latter by transfer of spleen cells but not antibody. In summary, the focal restricted infection in the CNS of adult mice infected with SFV A7(74) is independent of specific immune responses. IgM antibodies clear the viraemia. IgG antibodies including non-neutralizing antibodies reduce and clear infectious virus but cells positive for viral RNA remain. These may normally be cleared by T cell responses which are damaging and give rise to lesions of demyelination.

Cerebral lactate release after circulatory arrest but not after low flow in pediatric heart operations.

Arteriovenous (jugular bulb) differences in blood lactate were followed throughout the procedure and until 18 hours postoperatively in 17 children undergoing congenital heart operations during profound hypothermia. Transcranial Doppler sonography was used to monitor changes in blood flow velocity in the middle cerebral artery. Ten children had a period of total circulatory arrest (39 +/- 6 minutes) during profound hypothermia (arrest group). Another 7 children had continuous but reduced pump flow (0.6 to 1.2 L/m2) throughout hypothermic cardiopulmonary bypass (low-flow group). The mean age was 7.3 +/- 1.3 months in the arrest group and 7.9 +/- 2.2 months in the low-flow group. The mean time on bypass was 90 +/- 10 minutes in the arrest group and 75 +/- 9 minutes in the low-flow group. The velocity of blood flow in the middle cerebral artery decreased significantly (p < 0.05) in both groups to less than 50% of the preoperative level during hypothermia and increased during and after rewarming. Differences in blood lactate level were significantly less than zero (p < 0.05) from the start of rewarming until 3 hours after the end of cardiopulmonary bypass in the arrest group, whereas differences in blood lactate level remained close to zero in the low-flow group. We conclude that circulatory arrest during profound hypothermia is followed by a period with release of lactate from the brain, indicating anaerobic cerebral metabolism and possibly disturbed cerebral aerobic metabolism. This study argues for the avoidance of circulatory arrest whenever possible.