Basic statistics of PM2.5 and PM10 in the atmosphere of Mexico City

The high levels of fine particulate matter in Mexico City are of concern since they may induce severe public health effects as well as the attenuation of visible light. Sequential filter samplers were used at six different sites from 23 February to 22 March 1997. The sampling campaign was carried out as part of the project 'Investigación sobre Materia Particulada y Deterioro Atmosferico-Aerosol and Visibility Evaluation Research'. This research was a cooperative project sponsored by PEMEX and by the US Department of Energy. Sampling sites represent the different land uses along the city, the northwest station, Tlalnepantla, is located in a mixed medium income residential and industrial area. The northeast station, Xalostoc, is located in a highly industrialized area, Netzahualcoyotl is located in a mixed land use area, mainly commercial and residential. Station La Merced is located in the commercial and administrative district downtown. The southwest station is located in the Pedregal de San Angel, in a high-income neighborhood, and the southeast station located in Cerro de la Estrella is a mixed medium income residential and commercial area. Samples were collected four times a day in Cerro de la Estrella (CES), La Merced (MER) and Xalostoc (XAL) with sampling periods of 6 h. In Pedregal (PED), Tlalnepantla (TLA) and Netzahualcoyot1 (NEZ) sampling periods were every 24 h. In this paper the basic statistics of PM2.5 and PM10 mass concentrations are presented. The average results showed that 49, 61, 46, 57, 51 and 44% of the PM10 consisted of PM2.5 for CES, MER, XAL, PED, TLA and NEZ, respectively. The 24-h average highest concentrations of PM25 and PM10 were registered at NEZ (184 and 267 microg/m3) and the lowest at PED (22 and 39 microg/m3). The highest PM10 correlations were between XAL-CES (0.79), PED-TLA (0.80). In contrast, the highest PM2.5 correlations were between CES-PED (0.74), MER-CES (0.73) and TLA-PED (0.72), showing a lower correlation than the PM10 one. The results of the PM10 from 12.00 to 18.00 h at CES and MER presented the highest variability and also the highest median concentrations, meanwhile XAL showed them from 06.00 to 12.00 h. The highest variability and median concentrations of PM2.5 were from 06.00 to 12.00 h for the three stations.

[Serotypes and antibiotic susceptibility of the genus Salmonella in Elche, Spain]

Salmonellosis is one of the main public health problems in developed countries. The most common serotype is Salmonella enteritidis, followed by S. typhimurium, S. hadar and S. virchow. Each serotype's sensitivity to antibiotics is different, but in general, there has been an increase in the number of isolates resistant to antibiotics. This is especially true for S. hadar and nalidixic acid, although we have not isolated any strains resistant to ciprofloxacin. Our study provides data that may help to control these infections and draws attention to the increase in resistance to certain antibiotics. This should give rise to the implementation of measures to protect public health and control the use of antibiotics, especially in animals.

Alternate splicing of the shal gene and the origin of I(A) diversity among neurons in a dynamic motor network

The pyloric motor system, in the crustacean stomatogastric ganglion, produces a continuously adaptive behavior. Each cell type in the neural circuit possesses a distinct yet dynamic electrical phenotype that is essential for normal network function. We previously demonstrated that the transient potassium current (I(A)) in the different component neurons is unique and modulatable, despite the fact that the shal gene encodes the alpha-subunits that mediate I(A) in every cell. We now examine the hypothesis that alternate splicing of shal is responsible for pyloric I(A) diversity. We found that alternate splicing generates at least 14 isoforms. Nine of the isoforms were expressed in Xenopus oocytes and each produced a transient potassium current with highly variable properties. While the voltage dependence and inactivation kinetics of I(A) vary significantly between pyloric cell types, there are few significant differences between different shal isoforms expressed in oocytes. Pyloric I(A) diversity cannot be reproduced in oocytes by any combination of shal splice variants. While the function of alternate splicing of shal is not yet understood, our studies show that it does not by itself explain the biophysical diversity of I(A) seen in pyloric neurons.

Influence of fitness on the integrated neuroendocrine response to aerobic exercise until exhaustion

A group of trained and sedentary men performed an incremental graded exercise-test to exhaustion in order to assess the organic response of the two main stress-activated systems: the sympathetic nervous system with its endocrine component (the adrenal medulla), and the hypothalamic-pituitary-adrenal (HPA) axis. Maximal plasma concentrations of ACTH, cortisol and endogenous opioids (beta-endorphins) were obtained at the end of the exercise-test in the trained group. Thus ACTH increased from basal value of 21.25 +/- 2.5 pg/ml to 88.78 +/- 11.8 pg/ml at the end of the exercise (p<0.01); cortisol, from 16.56 microg/dl +/- 4.94 microg/dl to 23.80 +/- 4.57 microg/dl in min 15 of the recovery period (p<0.001); and beta-endorphin from 21.80 +/- 8.33 pmol/ml to 64.36 +/- 9.8 pmol/ml in min 3 of the recovery period (p<0.05). Catecholamine levels were increased from initial values at the end of the effort test in both control and trained groups. Control subjects exhibited a higher responsiveness compared to trained and showed superior intrinsic stimulation of the sympathetic nervous system. These results reveal a different response according to fitness in a physical stress situation.

Activator protein 2alpha transcription factor expression is associated with luminal differentiation and is lost in prostate cancer

PURPOSE

Prostate cancer progression is associated with deregulation of genes like E-cadherin, p21/WAF1, MMP-2, VEGF, and IGF-binding protein, 3 and 5, all of which are target genes for the transcription factor activator protein 2alpha (AP-2alpha). We, therefore, hypothesize that the development/progression of prostate cancer is associated with changes in the expression of AP-2alpha.

EXPERIMENTAL DESIGN

We used immunofluorescent staining to assess the presence of AP-2alpha in normal, benign, and malignant human prostate tissues and to correlate its expression with tumor grade and stage.

RESULTS

We found that although AP-2alpha was expressed in normal prostate epithelium, it was not expressed in 30 prostate cancer specimens of different Gleason scores. Moreover, AP-2alpha protein was present in the luminal cell layer but not in the basal cell layer of the normal epithelium, which indicated that the loss of AP-2alpha staining in the prostate cancer specimens was not attributable to a lack of AP-2alpha-expressing cells. Further analysis demonstrated the presence of AP-2alpha in 2 (40%) of 5 atrophic normal epithelium, in 4 (24%) of 17 cases of benign prostatic hyperplasia, and in 2 (13%) of 13 cases of high-grade prostatic intraepithelial neoplasia. Loss or reduction in AP-2alpha expression was also observed in LNCaP, LNCaP-LN3, and PC3M-LN4 cell lines.

CONCLUSIONS

Our data demonstrate that AP-2alpha expression is associated with normal luminal differentiation and that a loss of AP-2alpha expression occurs early in the development of prostate adenocarcinoma. Loss of AP-2alpha may lead to deregulation in AP-2alpha target genes that normally regulate cellular growth and differentiation.

[Dyspepsia-related quality of life. Spanish adaptation and validation of the questionnaire Dyspepsia-Related Health Scale]

BACKGROUND

Dyspepsia affects about 25 % of the population and may cause an important decrease in quality of life. The aim of this work was to perform a Spanish validation and adaptation of the questionnaire DRHS (Dyspepsia Related Health Scale), a tool that assesses dyspepsia-related quality of life.

PATIENTS AND METHOD

The study was carried out in 234 subjects, 163 with symptoms of dyspepsia and 71 health volunteers. Two rheumatologists, 2 general practitioners, 1 gastroenterologist, 1 clinical pharmacologist, 1 pharmacoepidemiologist and 1 psychologist were involved in the work. The process of adaptation and validation included translation and re-translation, pilot study in 16 patients, dimensionality, reliability and validity (of content, of construct, convergent, predictive and discriminative).

RESULTS

The mean age was 49.1 years (SD: 18) and 60.7 % were females. The between-judges agreement rate of Hambleton and Rovinelli, which evaluates the content validity, was lower than 0.41. The construct validity assessed by the factorial analysis of responses showed that each subscale may be considered unidimensional in both health volunteers and individuals with dyspepsia. Reliability was satisfactory (Cronbach's alpha = 0.92) and stability of measures (test-retest) was excellent with a correlation coefficient of 0.95. The convergent validity, assessed by means of the EuroQoL, was only moderate with a correlation coefficient of 0.54 (p < 0.001). The predictive validity, assessed by administering the questionnaire 12 days after treating dyspepsia, showed a correlation coefficient of 0.47 between the two measures (p < 0.001). There was also a relationship between scores variation and outcome.

CONCLUSIONS

The Spanish version of the DRHS, so-called QoL-PEI (questionnaire of quality of life related with problems of stomach and intestine), displays good metric properties and is able to predict the evolution of dyspepsia. The results of this study show that this tool is essentially unidimensional, yet it can be used on a multidimensional form to perform a differentiated assessment of each evaluated case.

Pharmacological stress myocardial perfusion imaging with the potent and selective A(2A) adenosine receptor agonists ATL193 and ATL146e administered by either intravenous infusion or bolus injection

BACKGROUND

Adenosine (Ado) and dipyridamole are alternatives to exercise stress for myocardial perfusion imaging. Though generally safe, side effects frequently occur that cause patient discomfort and sometimes lead to premature termination of the study or require aminophylline administration. Recently, a new class of A(2A) Ado receptor agonists was synthesized. ATL193 and ATL146e are 2-propynylcyclohexyl-5'-N-ethylcarboxamido derivatives of Ado. The study goals were to evaluate the potency and selectivity of these new compounds on recombinant canine Ado receptors and to evaluate their hemodynamic properties in dogs to assess their usefulness as vasodilators for myocardial perfusion imaging.

METHODS AND RESULTS

In assays of recombinant canine Ado receptors, ATL-193 and ATL-146e were highly selective for the A(2A) over the A(1) and A(3) receptors and were more potent than MRE-0470 and CGS-21680. In 16 anesthetized dogs, the agonists were administered by infusion (ATL-193; n=7 normal) or bolus injection (ATL-146e; n=9 critical left anterior descending coronary artery stenosis), and hemodynamic responses were compared with those of Ado. Both agonists produced dose-dependent coronary flow (CF) elevation without provoking the hypotension observed with Ado. After an ATL-146e bolus, the CF increase was sustained for several minutes, providing ample time for injection and myocardial uptake of (99m)Tc-sestamibi, and CF returned to baseline within 20 minutes. The CF increase was completely blocked by the selective A(2A) antagonist ZM241385 (3 microgram. kg(-1). min(-1)).

CONCLUSIONS

ATL-193 and ATL-146e are highly potent and selective Ado A(2A) receptor agonists with excellent potential for use as vasodilators for myocardial perfusion imaging. An important advantage of ATL-146e is the ability to administer it by bolus injection.

Characterization of two novel mutations in the glucocorticoid receptor gene in patients with primary cortisol resistance

OBJECTIVE

Primary glucocorticoid resistance is characterized by decreased sensitivity to cortisol signalling. We have performed genetic analysis of the glucocorticoid receptor (GR) gene in 12 unrelated patients with primary cortisol resistance as defined by a pathological dexamethasone suppression test.

METHODS

Exon specific polymerase chain reaction amplification of the GR gene and sequencing of each exon was carried out. The two mutations were characterized in vitro in terms of glucocorticoid driven reporter gene activity in a transient transfection assay and in a ligand binding assay. Molecular modelling of the R477H mutant was performed based on the X-ray structure of the GR-DNA binding domain.

RESULTS

Two novel mutations in the GR gene were found: R477H in the DNA-binding domain which is the first reported mutation in that region of the human GR gene and G679S in the ligand binding domain. The R477H mutation showed no transactivating capacity, whereas the G679S mutation had reduced transactivation capacity compared to the wild-type (wt) GR. When tested for ligand binding capacity, the G679S mutation had 50% binding affinity compared to the wt GR. The effect of the point mutation R477H was deduced by a comparison between the wt structure and the model of the mutant. The wt GR has direct and water mediated contact with the phosphate groups of the glucocorticoid responsive element (GRE) whereas, in the model, the mutation R477H has no contact with the GRE. The G679S mutation is located on the surface of the ligand binding domain, at a distance from the steroid-binding site. A previously reported polymorphism, AAT to AAC at amino acid position 766, was found in four of the patients.

CONCLUSIONS

In two of 12 patients with clinical glucocorticoid resistance, mutant forms of GR could be found. The glucocorticoid resistance in vivo in these two patients corresponds to impaired function of the two mutated GR forms in two in vitro assays. The relevance of the conservative polymorphism for the glucocorticoid insensitivity noted in these patients remains to be clarified.

Assessment of residual coronary stenoses using 99mTc-N-NOET vasodilator stress imaging to evaluate coronary flow reserve early after coronary reperfusion in a canine model of subendocardial infarction

Reperfusion is often incomplete after recanalization therapy because of the presence of residual coronary stenoses. Detecting mild to moderate stenoses requires assessing coronary flow reserve with vasodilator stress. 99mTc-(N-ethoxy-N-ethyl-dithiocarbamato)nitrido (N-NOET) is a viability-independent flow tracer and thus may be well suited for assessing coronary flow reserve in the acute phase of reperfusion.

METHODS

Twelve open-chest dogs underwent 60 min of total left anterior descending artery (LAD) occlusion followed by either full reperfusion (group 1; n = 4) or reperfusion through a residual critical stenosis (group 2; n = 8). 99mTc-N-NOET was given during peak vasodilator stress 165 min after reperfusion, and initial and 60-min delayed images were acquired. Regional blood flow was assessed with radiolabeled microspheres.

RESULTS

Infarct size was similar in both groups (9% +/- 2% vs. 8% +/- 2% of left ventricle). Both initial (0.61 +/- 0.02 vs. 0.73 +/- 0.01; P < 0.01) and 60-min (0.67 +/- 0.02 vs. 0.80 +/- 0.01; P < 0.01) defect count ratios (LAD/left circumflex coronary artery [LCx]) differentiated between the 2 groups, reflecting the greater diminution in coronary flow reserve in group 2 dogs (LAD/LCx flow ratios = 0.37 +/- 0.04 vs. 0.57 +/- 0.09; P < 0.01). Interestingly, coronary flow reserve in the reperfused zone of group 1 was diminished despite the absence of a stenosis. Thus, the difference in 99mTc-N-NOET uptake between the 2 groups was less than expected.

CONCLUSION

In this canine myocardial infarction model with some coronary flow reserve preservation, 99mTc-N-NOET imaging can detect residual coronary stenoses. However, with more prolonged occlusion resulting in more severe endothelial or microvascular dysfunction, it may be difficult to distinguish varying degrees of vessel patency using any coronary flow reserve technique.

Transcription factor AP-2alpha is preferentially cleaved by caspase 6 and degraded by proteasome during tumor necrosis factor alpha-induced apoptosis in breast cancer cells

Several reports have linked activating protein 2alpha (AP-2alpha) to apoptosis, leading us to hypothesize that AP-2alpha is a substrate for caspases. We tested this hypothesis by examining the effects of tumor necrosis factor alpha (TNF-alpha) on the expression of AP-2 in breast cancer cells. Here, we provide evidence that TNF-alpha downregulates AP-2alpha and AP-2gamma expression posttranscriptionally during TNF-alpha-induced apoptosis. Both a general caspase antagonist (zVADfmk) and a caspase 6-preferred antagonist (zVEIDfmk) inhibited TNF-alpha-induced apoptosis and AP-2alpha downregulation. In vivo tests showed that AP-2alpha was cleaved by caspases ahead of the DNA fragmentation phase of apoptosis. Recombinant caspase 6 cleaved AP-2alpha preferentially, although caspases 1 and 3 also cleaved it, albeit at 50-fold or higher concentrations. Activated caspase 6 was detected in TNF-alpha-treated cells, thus confirming its involvement in AP-2alpha cleavage. All three caspases cleaved AP-2alpha at asp(19) of the sequence asp-arg-his-asp (DRHD(19)). Mutating D(19) to A(19) abrogated AP-2alpha cleavage by all three caspases. TNF-alpha-induced cleavage of AP-2alpha in vivo led to AP-2alpha degradation and loss of DNA-binding activity, both of which were prevented by pretreatment with zVEIDfmk. AP-2alpha degradation but not cleavage was inhibited in vivo by PS-431 (a proteasome antagonist), suggesting that AP-2alpha is degraded subsequent to cleavage by caspase 6 or caspase 6-like enzymes. Cells transfected with green fluorescent protein-tagged mutant AP-2alpha are resistant to TNF-alpha-induced apoptosis, further demonstrating the link between caspase-mediated cleavage of AP-2alpha and apoptosis. This is the first report to demonstrate that degradation of AP-2alpha is a critical event in TNF-alpha-induced apoptosis. Since the DRHD sequence in vertebrate AP-2 is widely conserved, its cleavage by caspases may represent an important mechanism for regulating cell survival, proliferation, differentiation, and apoptosis.

[Clinical results of double versus single mammary artery myocardiac revascularization: 15 years of follow-up]

INTRODUCTION

Use of the left internal mammary artery to bypass the left anterior descending coronary artery reduces cardiac events and increases survival. However, there is some controversy as to the benefits of using both mammary arteries.

OBJECTIVES

To assess the long-term outcome of the use of both mammary arteries in comparison with the use of only one.

PATIENTS AND METHOD

A retrospective cohort study with a mean follow-up of 9.0 +/- 4.2 years was performed including 108 patients consecutively revascularized using both mammary arteries (II) and 108 patients randomly chosen in whom one mammary artery (I) was used for this purpose.

RESULTS

Both groups were similar. There were no differences between the groups in operative morbidity or mortality. The survival at 10 years was similar (II: 84.61 +/- 4%; I: 85.18 +/- 3.8%), whereas recurrence of angina (II: 29.63 +/- 5.3%; I: 47.55 +/- 5.6%) (p = 0.012), the requirement for percutaneous angioplasty (II: 3.98 +/- 2%; I: 12.99 +/- 4.1%) (p = 0.009) and cardiologic events (II: 33.48 +/- 5.5%; I: 48.48 +/- 5.5%)(p = 0.022) were all lower in the group in which both mammary arteries were used. In the multivariate analysis, the use of both mammary arteries was an independent protective factor against angina recurrence (RR = 0.55), angioplasty (RR = 0.18) and cardiologic event (RR = 0.60).

CONCLUSIONS

The use of both mammary arteries for revascularization does not increase operative morbidity. Since this procedure acts as an independent factor against angina recurrence, angioplasty and cardiologic event

Immunization with a tumor-associated CTL epitope plus a tumor-related or unrelated Th1 helper peptide elicits protective CTL immunity

Immunization with cytotoxic T cell epitope SPSYVYHQF (AH1), derived from MuLV gp70 envelope protein expressed by CT26 tumor cells, does not protect BALB/c mice against challenge with CT26 tumor cells. By contrast, immunization with AH1 plus T helper peptides OVA(323-337) or SWM(106-118) eliciting Th1 and Th0 profiles, protected 83% and 33% of mice, respectively. Interestingly, immunization with AH1 plus both helper peptides reverted the efficacy to 33%. We identified the endogenous T helper peptide p(320-333) from gp70 which elicits a Th1 profile and is naturally processed. As for OVA(323-337), immunization with p(320-333) alone did not protect against tumor challenge. However, p(320-333) plus AH1 protected 89% of mice at day 10 after vaccination. Only 20% of mice vaccinated with AH1 + OVA(323-337) or AH1 + p(320-333) were protected when challenged 80 days after immunization. Treatment with OVA(323-337) or with p(320-333) around established tumors delayed tumor growth. Our results show that tumor-related as well as tumor-unrelated but strong Th1 peptides may be useful for inducing CTL responses in tumor immunotherapy.

[Acquired partial lipodystrophy. Insulin resistance, hepatic lipase activity and small and dense LDL particles]

Partial lipodystrophy (PLD) is an infrequent condition characterized by symmetric loss of subcutaneous adipose tissue in the upper or lower part of the body, although occasionally it affects only the extremities. In all cases it appears along with acantosis nigricans (AN), insulin resistance and impairment in the metabolism of lipids and carbohydrates. The case depicted pertains to a 49 year old female with no family history involving loss of adipose tissue in face and upper body. No fat in lower part of body was observed. The patient showed facial thinning at age 8, AN at 11 and gestational diabetes during her fourth pregnancy at 33. At present, the patient presents severe hyperglycemia and hyperinsulinemia with a marked insulin resistance. Type IV hyperlipoproteinemia (OMS), declined C-HDL and Apo A1 and low C-LDL but with a high proportion of small and dense LDL particles were present. Non esterified fatty acids were high. Lipoprotein lipase and hepatic lipase activities are in the lower limit and increased respectively. Fraction C3 of the complement was diminished. No mutations were observed either in codons 170, 809 and 972 of the IRS-1 receptor or in codon 276 of the adrenergic beta 2 gene.

In vitro activity of four fluoroquinolones against Mycobacterium tuberculosis

The in vitro activity of ciprofloxacin, ofloxacin, levofloxacin and moxifloxacin against strains of Mycobacterium tuberculosis was studied. Moxifloxacin and levofloxacin showed the greatest activity having an MIC(90) of 1 mg/l. The MIC(90) for ofloxacin was 2 mg/l and for ciprofloxacin 4 mg/l. Further studies should be made to determine the role played by these compounds in the treatment of tuberculosis.

Tc-99m sestamibi defect magnitude predicts the amount of viable myocardium after coronary reperfusion despite the presence of severe residual stenosis

BACKGROUND

Whether technetium-99m-labeled methoxyisobutyl isonitrile (Tc-99m sestamibi) imaging early after reperfusion can detect the amount of salvaged viable myocardium in the presence of a severe residual stenosis remains controversial.

METHODS AND RESULTS

Nine dogs underwent total left anterior descending coronary artery (LAD) occlusion for 40 to 180 minutes followed by reperfusion through a flow-limiting stenosis. They were divided into 2 groups based on infarct size (group 1, <15% of risk area; group 2, > or =15%). Triphenyl tetrazolium chloride infarct size was measured by planimetry, and regional flow was quantified by radiolabeled microspheres. Mean infarct size was 9.3% +/- 3.0% of risk area in group 1 versus 51.1% +/- 4.8% in group 2 (P <.01). Tc-99m sestamibi was injected 30 minutes after reperfusion, when the LAD flows were comparable for group 1 (9 +/- 2 mL. min(-1)) and group 2 (9 +/- 1 mL. min(-1)). Left circumflex coronary artery flows were 33 +/- 5 and 32 +/- 9 mL. min(-1) for groups 1 and 2, respectively. Despite administration of Tc-99m sestamibi during diminished residual LAD flow after reperfusion, defect magnitude on ex vivo images in group 1 was significantly less severe than that in group 2, which had larger infarcts (0.71 +/- 0.02 vs 0.42 +/- 0.05, P <.01). This reflects greater salvage and more viability in group 1.

CONCLUSION

Resting perfusion imaging with Tc-99m sestamibi accurately determined viability of the infarct zone despite reperfusion through a residual stenosis. Tc-99m sestamibi imaging may prove useful in the clinical setting for the prediction of the amount of salvaged myocardium.

[The "quality of life" concept in medical students and postgraduate residents in a university hospital]

We investigated the quality of life's concept and its uses by both residents and interns as well as last year medical students in the University Hospital in Caracas (HUC). A random sample by strata, without replacement of 123 persons, completed a self administered questionnaire which included a set of closed questions and one of open questions related to the quality of life's concept. The mean age was 29 years for both sexes (3.55 standard deviation or SD). There was not a statistically significant difference between males and females. More than 50% read about quality of life in either newspapers, journals and fiction literature. There was no difference among the groups (p = 0.25). Only 68% had heard in a different sort of academical institution the term "quality of life" such as in the school of medicine, highschool or in some discussion groups with no differences among the groups (p = 0.15). However, there was no agreement as from whom and where they learned about quality of life (p < 0.001). Although everybody considered that the quality of life was an important element in medical actions such as diagnostic or therapeutics, its importance was reduced for diagnosis compared to treatment (p < 0.0001). All the elements that were considered as part of the concept were also considered as important, regardless of the group and was statistically significant (p < 0.05). The open question analysis showed that the non-medical definitions represent 85.15% of the group, 50% out of them included terms of potentiality or condition. Among the elements included in the definition was the social in 27.65%, psychological in 23.53% and, the economical in 12.35% of the questionnaires. The great majority of the "quality of life" definitions did not include a clearly defined subject and in many cases it was exclusively related to ill persons. Finally, there is an informal and not well oriented form of learning about "quality of life" in residents, interns and last year medical students with a lack of a good applicability in the medical practice. Therefore, there is a need for a formal training on quality of life along the medical studies and its uses in the medical practice in general and with special emphasis on diagnosis and therapeutics.

Diagnosis of pneumonia and monitoring of infection eradication

Pneumonia can be classified as community-acquired (CAP) or hospital-acquired (nosocomial). Both are frequent infections that demand a great amount of medical resources. The diagnosis of CAP is based on clinical signs and the presence of a pulmonary infiltrate visible on chest radiograph. For practical purposes, CAP has been classified as typical, with an acute onset in which the most representative microorganism is Streptococccus pneumoniae, and atypical, with a subacute onset (Mycoplasma pneumoniae). Nevertheless, so far no studies have clearly demonstrated the utility of this classification in predicting the aetiology. Guidelines on CAP recommend associating the aetiology of CAP with comorbidity, age and severity. The microbiological diagnosis relies mainly on Gram stain and sputum culture, but this technique has disadvantages such as frequent contamination of the sample with oropharyngeal commensal flora, frequent sterile cultures associated with previous antibiotic treatment, and the fact that approximately 40% of patients are not able to expectorate. Other diagnostic techniques such as blood cultures, serological tests and fibreoptic bronchoscopy must be reserved for patients who are hospitalised, especially if they need admission to an intensive care unit. Compared with CAP, nosocomial pneumonia has major diagnostic problems due to the presence of other diseases able to mimic pneumonia and frequent bacterial colonisation of the lower respiratory tract. Most of the diagnostic techniques produce a high percentage of false-negative and false-positive results. This is especially true for ventilator-associated pneumonia. There is controversy over using a comprehensive aetiological work-up based on bronchoscopic techniques or only on quantitative culture of endotracheal aspiration. By contrast, there is consensus about the importance of the adequacy of empirical antibiotic treatment, since mortality rates are higher in patients who are inadequately treated. Once treatment of pneumonia has begun, it must be maintained for 48 to 72 hours because this is the minimum time to evaluate a clinical response. Antibacterial agents have to be adjusted according to microbiological findings. In nonresponding patients, pneumonia-related complications and the presence of multiresistant micro-organisms or non-covered pathogens must be ruled out.

Aberrant development of hippocampal circuits and altered neural activity in netrin 1-deficient mice

Diffusible factors, including netrins and semaphorins, are believed to be important cues for the formation of neural circuits in the forebrain. Here we have examined the role of netrin 1 in the development of hippocampal connections. We show that netrin 1 and its receptor, Dcc, are expressed in the developing fimbria and in projection neurons, respectively, and that netrin 1 promotes the outgrowth of hippocampal axons in vitro via DCC receptors. We also show that the hippocampus of netrin 1-deficient mice shows a misorientation of fiber tracts and pathfinding errors, as detected with antibodies against the surface proteins TAG-1, L1 and DCC. DiI injections show that hippocampal commissural axons do not cross the midline in these mutants. Instead, when axons approach the midline, they turn ventrally and form a massive aberrant projection to the ipsilateral septum. In addition, both the ipsilateral entorhino-hippocampal and the CA3-to-CA1 associational projections show an altered pattern of layer-specific termination in netrin 1-deficient mice. Finally, optical recordings with the Ca(2+) indicator Fura 2-AM show that spontaneous neuronal activity is reduced in the septum of netrin 1-mutant mice. We conclude that netrin 1 is required not only for the formation of crossed connections in the forebrain, but also for the appropriate layer-specific targeting of ipsilateral projections and for the control of normal levels of spontaneous neural activity.