A single- and double-flash flash photolysis study of the sequential biphotonic photoprocesses of Cu(I) phenanthrolines. Comparison of the helicate complex, [Cu2(1,3-bis(9-methyl-1,10-phenanthrolin-2-yl)propane)2]2+, and [Cu(2,9-dimethyl-1,10-phenanthroline)2]+ photoprocesses.

Photochemical processes induced when two photons are sequentially absorbed by the helicate complex [Cu2(mphenpr)2](2+), where mphenpr = 1,3-bis(9-methyl-1,10-phenanthrolin-2-yl)propane, and [Cu(dmp)2](+) were investigated in CH2Cl2 containing solvents. A strong resemblance was observed between the fs-ns photophysics of [Cu2(mphenpr)2](2+) and Cu(I) phenanthroline complexes having a large steric hindrance. In the biphotonic regime, single-flash flash-photolyzed solutions were used for the determination of the product concentrations and quantum yields. The concentration of Cl(-) produced by the photoinduced decomposition of CH2Cl2 increases linearly with flash intensity as expected for a monophotonic process. In contrast, the concentration of a decomposed Cu(I) complex exhibits the quadratic dependence on flash intensity of a biphotonic process. Results of a sequential double-flash flash photolysis experiment are consistent with the decomposition of CH2Cl2 ahead of the flattened excited state formation and with the absorption of the second photon by the flattened MLCT excited state.

Unfolding of the [Cu2(1,3-bis(9-methyl-1,10-phenanthrolin-2-yl)propane)2]2+ helicate. Coupling of the chlorocarbon dehalogenation to the unfolding process.

A new helical dimeric copper(I) complex [Cu(2)(mphenpr)(2)](ClO(4))(2) where mphenpr is 1,3-bis(9-methyl-1,10-phenanthrolin-2-yl)propane has been prepared and characterized by X-ray crystallography and NMR. In the solid state, the metal centers are 6.42 A apart, and the electronic structure has been investigated with use of density functional theory (DFT) calculations. In solution the dimer equilibrates with a monomeric form [Cu(mphenpr)](ClO(4)), and the mechanism of unfolding of the dimer into monomer has been studied. In the presence of CCl(4), formation of the monomer is coupled to the reductive dehalogenation of the halocarbon. The mechanism of this process has been probed by the study of short-lived potential reaction intermediates using fast kinetic pulse radiolysis techniques and comparisons with DFT calculations. The copper(II) product [Cu(mphenpr)Cl](ClO(4)) and an analogue [Cu(mphenpr)](ClO(4))(2) have been isolated and characterized by X-ray crystallography.

[First SIBEN clinical consensus: diagnostic and therapeutic approach to patent ductus arteriosus in premature newborns]. / Primer consenso clínico de SIBEN: enfoque diagnóstico y terapéutico del ductus arterioso permeable en recién nacidos pretérmino.

OBJECTIVE: To report the process and results of the first neonatal clinical consensus of the Ibero-American region. DESIGN AND METHODS: Two recognized experts in the field (Clyman and Van Overmeire) and 45 neonatologists from 23 countries were invited for active participation and collaboration. We developed 46 questions of clinical-physiological relevance in all aspects of patent ductus arteriosus (PDA). Guidelines for consensus process, literature search and future preparation of educational material and authorship were developed, reviewed and agreed by all. Participants from different countries were distributed in groups, and assigned to interact and work together to answer 3-5 questions, reviewing all global literature and local factors. Answers and summaries were received, collated and reviewed by 2 coordinators and the 2 experts. Participants and experts met in Granada, Spain for 4.5 h (lectures by experts, presentations by groups, discussion, all literature available). RESULTS: 31 neonatologists from 16 countries agreed to participate. Presentations by each group and general discussion were used to develop a consensus regarding: general management, availability of drugs (indomethacin vs. ibuprofen), costs, indications for echo/surgery, etc. Many steps were learnt by all present in a collaborative forum. CONCLUSIONS: This first consensus group of Ibero-American neonatologists SIBEN led to active and collaborative participation of neonatologists of 16 countries, improved education of all participants and ended with consensus development on clinical approaches to PDA. Furthermore, it provides recommendations for clinical care reached by consensus. Additionally, it will serve as a useful foundation for future SIBEN Consensus on other topics and it could become valuable as a model to decrease disparity in care and improve outcomes in this and other regions.

In vitro hypoxia differentially affects constriction and relaxation responses of isolated pulmonary arteries from broiler and leghorn chickens.

Under normoxic conditions in vitro, isolated pulmonary arteries from broilers exhibit reduced endothelium-dependent relaxation responses when compared with Leghorns. In vivo, hypoxia increases the susceptibility of broiler chickens to pulmonary hypertension syndrome (PHS), whereas Leghorns are considered resistant to PHS. Because L-arginine supplementation decreases the incidence of PHS in vivo and improves the relaxation responses of broiler isolated pulmonary arteries in vitro, we hypothesized that in vitro hypoxia would further reduce the relaxation responses of broilers to endothelium-derived nitric oxide (EDNO)-dependent vasodilators and that L-arginine supplementation would alleviate this impairment. As a test of this hypothesis, pulmonary arteries from broiler and Leghorn chickens were isolated and exposed to normoxia or hypoxia in the presence or absence of L-arginine while their constriction and relaxation responses to vasoactive compounds were recorded. In broilers, hypoxia did not affect the constriction responses of isolated pulmonary arteries but decreased EDNO-dependent acetylcholine-induced relaxation responses. In contrast, in Leghorns hypoxia increased endothelin-1-induced vasoconstriction responses and reduced the EDNO-dependent relaxation responses only to the lowest concentration of acetylcholine used. L-Arginine supplementation augmented the relaxation responses to acetylcholine in broilers and Leghorns under normoxia but failed to augment them under hypoxia. Relaxation responses to the NO donor, sodium nitroprusside, were not affected by hypoxia in Leghorns but were increased by hypoxia in broilers. These results suggest that the increased incidence of PHS in broiler chickens reared under hypoxia may be associated with a hypoxia-induced reduction in the synthesis or activity of EDNO in the pulmonary circulation.

Pulmonary artery vasoactivity in broiler and Leghorn chickens: an age profile.

Vascular function plays a preponderant role in the pulmonary changes that occur with maturation, during birth, and in the development of pulmonary hypertension. This study was designed to characterize the changes in vasoactivity occurring in broiler and Leghorn chickens from late embryonic life to 5 wk of age. Pulmonary arteries were isolated from 19- and 20-d-old embryos, hatchlings, and 1-, 2-, 3-, 4- and 5-wk-old chickens of both lines and subjected to KCl (45.4 mM)- and endothelin-1 (10(-7.5) M)-induced vasoconstrictions followed by acetylcholine (ACh; 10(-5), 10(-6) and 10(-7) M)- and papaverine (10(-4) M)-induced vasodilations. Vasoconstrictions were greatest at hatch and rapidly declined thereafter, whereas vasodilations were greatest in 20-d-old embryos except with 10(-7) M ACh. Broilers grew faster than Leghorns and had lower vasodilation responses to all concentrations of ACh at 2 and 5 wk of age. Broilers also had greater right-to-total ventricular weight ratios at 5 wk of age, whereas ratios were greater in Leghorn embryos at 20 d of incubation and at hatch. Thus, for a brief period before hatch there is a significant increase in pulmonary endothelium-dependent vasodilation capacity in the chicken embryo, which may aid in the transition from chorioallantoic to pulmonary respiration. The absence of differences in vasodilator capacity between broilers and Leghorns before hatch suggests that the differences in pulmonary artery relaxation capacity and pulmonary hypertension observed after hatch in broilers are not necessarily acquired during incubation but may be related to rapid growth of the broiler chicken.

Probing the cortical neuronal correlates of a sensory discrimination process.

Key to understanding perception is the form of how sensory stimuli are represented in the evoked activity of the brain. Here, we addressed the question of which components of the evoked neuronal activity in the somatosensory cortex represent the stimulus features while trained monkeys discriminated the difference in frequency between two vibrotactile stimuli. We probed whether these cortical neuronal representations are essential to perception. The results show a strong link between the cortical representation of the stimulus and perception.

[Neural codes for perception]. / Códigos neurales para la percepción.

OBJECTIVE: This article describes experiments designed to show the neural codes associated with the perception and processing of tactile information. DEVELOPMENT: The results of these experiments have shown the neural activity correlated with tactile perception. The neurones of the primary somatosensory cortex (S1) represent the physical attributes of tactile perception. We found that these representations correlated with tactile perception. By means of intracortical microstimulation we demonstrated the causal relationship between S1 activity and tactile perception. In the motor areas of the frontal lobe is to be found the connection between sensorial and motor representation whilst decisions are being taken. CONCLUSIONS: S1 generates neural representations of the somatosensory stimuli which seen to be sufficient for tactile perception. These neural representations are subsequently processed by central areas to S1 and seem useful in perception, memory and decision making.

Códigos neurales para la percepción / Neural codes for perception

Objetivo. Este artículo describe experimentos diseñados para poner en evidencia los códigos neurales asociados a la percepción y el procesamiento de información táctil. Desarrollo. Los resultados obtenidos en estos experimentos han revelado la actividad neural correlacionada con la percepción táctil. Las neuronas de la corteza somatosensorial primaria (S1) representan los atributos físicos de los estímulos táctiles. Se encontró que estas representaciones se correlacionan con la percepción táctil. Se comprobó por medio de la microestimulación intracortical la relación causal entre la actividad de S1 y la percepción táctil. En las áreas motoras del lóbulo frontal se encontró el enlace entre las representaciones sensoriales y motoras durante la toma de decisiones. Conclusiones. S1 genera representaciones neurales de los estímulos somatosensoriales que parecen ser suficientes para la percepción táctil. Estas representaciones neurales son posteriormente procesadas por áreas centrales a S1 y parecen ser útiles para la percepción, memoria y la toma de decisiones (AU)

Interaction of Leishmania mexicana promastigotes with the plasminogen-plasmin system.

The binding of human plasminogen and plasmin to the promastigote form of Leishmania mexicana was investigated. L. mexicana was capable to bind both molecules, the binding being inhibited by epsilon-aminocaproic acid. Scatchard plot analysis revealed a dissociation constant (Kd) value of 2.4+/-0.8 microM and 0.9+/-0.1 x 10(4) binding sites per cell for plasminogen and a Kd value of 1.2+/-0.4 microM and 1.6+/-0.2 x 10(5) binding sites per cell for plasmin. C-terminal lysine residues are involved in plasminogen binding to cells, since carboxypeptidase B treatment reduced this binding by 34%. Ligand blotting analysis showed a group of proteins, with molecular masses between 105 and 115 kDa, capable to interact with plasminogen. Zymogram analysis showed that the protease activity acquired by L. mexicana, due to the interaction with either plasminogen or plasmin, comprises an important fraction of the total protease activity at pH 7.7. Plasminogen activation by tissue-type plasminogen activator (t-PA) was enhanced by the presence of L. mexicana promastigotes. These results raise the question whether the interaction of L. mexicana with components of the fibrinolytic system is involved in the virulence of the parasite.

Sensing without touching: psychophysical performance based on cortical microstimulation.

Unequivocal proof that the activity of a localized cortical neuronal population provides sufficient basis for a specific cognitive function has rarely been obtained. We looked for such proof in monkeys trained to discriminate between two mechanical flutter stimuli applied sequentially to the fingertips. Microelectrodes were inserted into clusters of quickly adapting (QA) neurons of the primary somatosensory cortex (S1), and the first or both stimuli were then substituted with trains of current pulses during the discrimination task. Psychophysical performance with artificial stimulus frequencies was almost identical to that measured with the natural stimulus frequencies. Our results indicate that microstimulation can be used to elicit a memorizable and discriminable analog range of percepts, and shows that activation of the QA circuit of S1 is sufficient to initiate all subsequent neural processes associated with flutter discrimination.

Echocardiographic study of pulmonary hypertension syndrome in broiler chickens.

Echocardiography was used to study cardiovascular structure and function during the development of pulmonary hypertension syndrome (PHS) in broiler chickens. Body weight-normalized right and left ventricular diameters at both end-diastole (RVDD, LVDD) and end-systole (RVDS, LVDS) were determined weekly in broilers reared under either normobaric (altitude, 96.7 m) or hypobaric conditions (simulated altitude, 2900 m) until 5 wk of age. Hypobaric-exposed broilers had larger RVDD at 3 and 4 wk of age and larger RVDS at 3, 4, and 5 wk of age. Hypobaric-exposed broilers also had larger LVDD at 2, 3, 4, and 5 wk of age and larger LVDS at 4 wk of age. Right (RVFS) and left ventricular fractional shortening (LVFS) were smaller in hypobaric- vs. normobaric-exposed broilers at 3, 4, and 5 wk of age and at 4 wk of age, respectively. Among hypobaric-exposed birds, PHS-positive (+) broilers had larger RVDD and RVDS than PHS-negative (-) broilers on week 3 and on weeks 1 and 3 after hypobaric exposure, respectively. PHS-positive (+) broilers also had smaller RVFS on week 1 after hypobaric exposure. Electrocardiographic and post-mortem data indicated that PHS+ broilers also developed right ventricular hypertrophy when compared with PHS-negative (-) broilers. These results are consistent with the hypothesis that PHS develops as a result of pulmonary hypertension and cardiac overload and suggest that PHS+ broilers have a greater and more persistent reaction to hypoxia than PHS- broilers.

Application of phonocardiography for detecting hypoxia-induced cardiovascular adaptation in the chicken.

Phonocardiography was evaluated as a noninvasive technique for diagnosis of cardiovascular adaptation and disease in broiler chickens. Heart sounds (HSs) were compared in a fast-growing (FG) commercial broiler line that is highly susceptible to chronic right heart failure resulting from pulmonary hypertension syndrome (PHS) and in a non-selected slow-growing (SG) broiler line that is resistant to PHS. HSs were analyzed in broilers reared in hypobaric hypoxia (HYP) and normobaric (CON) conditions. PHS was induced by a combination of embryonic hypoxia and HYP exposure. HSs were recorded with a microphone placed at the thoracic inlet of each chicken. Electrocardiograms were used to mark the sampling interval for the first, second, and total HS. Digitized HS signals were analyzed for peak frequency, mean peak frequency, and band width. Birds were examined for PHS lesions when 6 wk of age, at the end of each experiment. HSs were compared by line and treatment (Experiment 1) or by treatment and week (Experiment 2). In addition, HS frequencies were analyzed within the HYP treatment group for differences between birds with severe or no gross PHS lesions. HS frequencies generally decreased with age and were also lower in the FG than the SG line. Hypobaric exposure decreased all HS frequencies in the SG line and components of the first HSs in the FG line. The SG line did not develop gross lesions of PHS. In the FG line, significant differences in HS frequencies were observed between HYP and CON groups but not between PHS- and PHS+ broilers. Frequency changes described in humans with PHS were not observed. Further development to maximize the resolution of the HS waveforms and improved matching of the sampling interval to the electrical or hemodynamic output of the chicken heart may allow its use as a diagnostic tool for differentiating broilers with normal cardiac function or physiologic adaptation from those with cardiovascular disease.

Pulmonary artery endothelium-dependent vasodilation is impaired in a chicken model of pulmonary hypertension.

Among chicken strains, broilers are prone to pulmonary hypertension, whereas Leghorns are not. Relaxations to endothelium-dependent (ACh, A23187) and endothelium-independent [sodium nitroprusside (SNP), papaverine (PPV)] vasodilators were compared in preconstricted pulmonary artery (PA) rings from these chicken strains. ACh (10(-7), 10(-6), and 10(-5) M)- and A23187 (10(-6) and 10(-5.5) M)-induced relaxations were smaller (P < 0.05) in broilers than Leghorns. N(G)-nitro-L-arginine methyl ester (10(-3.5) M) caused similar reductions in ACh-induced relaxations in both strains. L-Arginine (10(-4) M) enhanced ACh-induced relaxations more in broilers than Leghorns. Relaxations to 10(-10)-10(-6) M SNP did not differ between strains, but were greater (P < 0.05) in broilers than Leghorns at higher concentrations (10(-5) and 10(-4) M). PPV (10(-4) M)- and SNP (10(-4) M)-induced maximal relaxations were greater in broilers than in Leghorns (176.2 +/- 14.7 vs. 120.9 +/- 14.7% and 201.3 +/- 7.8 vs. 171.2 +/- 10.7%, respectively, P < 0.05). Broiler PA rings appear to have increased intrinsic tone and reduced endothelium-derived nitric oxide activity, both of which may contribute to the susceptibility of broiler chickens to pulmonary hypertension.

Neuronal correlates of parametric working memory in the prefrontal cortex.

Humans and monkeys have similar abilities to discriminate the difference in frequency between two mechanical vibrations applied sequentially to the fingertips. A key component of this sensory task is that the second stimulus is compared with the trace left by the first (base) stimulus, which must involve working memory. Where and how is this trace held in the brain? This question was investigated by recording from single neurons in the prefrontal cortex of monkeys while they performed the somatosensory discrimination task. Here we describe neurons in the inferior convexity of the prefrontal cortex whose discharge rates varied, during the delay period between the two stimuli, as a monotonic function of the base stimulus frequency. We describe this as 'monotonic stimulus encoding', and we suggest that the result may generalize: monotonic stimulus encoding may be the basic representation of one-dimensional sensory stimulus quantities in working memory. Thus we predict that other behavioural tasks that require ordinal comparisons between scalar analogue stimuli would give rise to monotonic responses similar to those reported here.

[The neurological complications of infectious endocarditis]. / Complicaciones neurológicas de la endocarditis infecciosa.

We review the neurologic complications of 131 episodes of infective endocarditis, and the influences of some factors that are considered risk factors at its presentation, like the presence of vegetations detected by echocardiography, type and location of involved valve, or bacterial culture. Neurologic complications occurred in 28 patients (21.4%), 4 of them were excluded because of the absence of neuroimaging studies. In 21 patients the underlying cardiac pathology was valve disease and in the remaining 3 patients was congenital heart disease. 11 patients had native valve endocarditis and 10 prosthetic valve endocarditis. The cultured bacteria were Streptococcus viridans in 8 cases and Staphylococcus aureus in 7. The most frequent complication was cerebrovascular with incidence of cerebral embolism, and intracerebral hemorrhage of 62.5% and 8.3% respectively. Echocardiographic evidence of vegetation was seen in 18 patients, and cerebral embolism were noted in 12. Death occurred in 29% of patients with neurologic complications and 27% without. Two of nine patients who underwent open-heat surgery died. We conclude that there is no difference in the incidence of neurologic complications between mitral and aortic valve groups, neither when comparing native and prosthetic valve groups. Open-heart surgery does not increase mortality in this group of patients.

[Coxiella burnetii endocarditis. A report of the first case diagnosed in Mexico]. / Endocarditis por Coxiella burnetii. Informe del primer caso diagnosticado en México.

The first case of Q fever endocarditis that has been diagnosed in Mexico is presented. A 10-year-old girl with discrete subaortic stenosis (SAS) and patent ductus arteriosus (PDA) was seen in December of 1996 with fever, hepatomegaly and splenomegaly. She presented also anemia, leukopenia, hypergammaglobulinemia, positive rheumatoid factor, cryoglobulinemia, antinuclear and anticytoplasmic antibodies (anti-RNA-proteins and anti-DNA). An aortic valve vegetation was seen by echocardiogram. Blood-cultures were negative. Antibody test for Coxiella burnetii was positive. Treatment with doxicyclin was initiated as soon the diagnosis was done. PDA was closed, SAS was liberated and two aortic vegetations were resected. Endocarditis in Q fever occurs when there is predisposing heart disease and/or immunodeficiency. Effective therapy has not yet been established. The diagnosis of Q fever endocarditis is difficult; it should be considered, in case of clinical suspicion of endocarditis with negative blood-cultures.

Echocardiographic evaluation of cardiac structure and function in broiler and Leghorn chickens.

This study was conducted to validate echocardiography in chickens, and to compare cardiac structure and function between broiler and Leghorn chickens. Diameters of the right and left ventricles, and thicknesses of the left ventricular free wall and the interventricular septum were measured echocardiographically in 5- and 7-wk-old chickens from both lines. Images were obtained from minimally restrained, standing birds using a 7.5 MHz probe placed in a parasternal position. End-systolic and end-diastolic echocardiographic measurements were compared with post-mortem measurements of the same variables. Comparisons resulted in correlation coefficients greater than 0.70 between in vivo (echocardiographic) and post-mortem measurements of the same variables, with post-mortem measurements more closely resembling end-diastolic echocardiographic measurements. After being normalized to body weight, post-mortem myocardial thicknesses, aortic and left ventricular diameters, heart weight at 5 wk of age, and left ventricular weight at 7 wk of age were smaller in broiler than in Leghorn chickens. Echocardiographic parameters, including ventricular wall thicknesses, ventricular diameters, and left ventricular fractional shortening, were also smaller in the broiler chicken. Right ventricular fractional shortening did not differ between the chicken lines. These results indicate that echocardiography is a useful noninvasive technique for in vivo evaluation of cardiac structure and function in the chicken, and that broiler chickens have a relatively smaller structural and functional heart than Leghorn chickens.

[Infectious endocarditis at the National Institute of Cardiology "Ignacio Chavez". Five year's experience (1990-1994)]. / Endocarditis infecciosa en el Instituto Nacional de Cardiología "Ignacio Chávez". Experiencia de cinco años (1990-1994).

BACKGROUND: Infective endocarditis (IE) is one of the most life threatening infections in both medical and surgical practices. In the last few years, changes in its epidemiology, diagnostic methods and therapeutical trends have appeared. We analysed our experience in the diagnosis and treatment of IE. METHODS: The clinical records of patients admitted to our hospital with definitive (Group I) and highly probable (Group II) diagnosis of IE, during a period of five years (1990-1994), were retrospectively reviewed. Age, sex, clinical features, risk, factors, echocardiographic abnormalities, microbiologic and surgical findings, as well as mortality were recorded. In addition, an evaluation was made of the accuracy of the diagnostic criteria proposed by Von Reyn versus those brought forward by Duke University. RESULTS: One hundred thirty one patients were included, 99 in Group I and 32 in Group II. The mean age was 35 years. Native valve endocarditis was present in 88 patients and prosthetic valve endocarditis in 43 patients. Streptococcus sp. (48%) was the most frequently causative german and 16.7% of cases were culture negative. The sensitivity of transesophageal echocardiography was higher than transthoracic echocardiography in the diagnosis of both vegetations (76% vs 55%) and abscesses (30% vs 16.5%), (p < 0.05). Vegetations (95%) were the most frequent surgical finding followed by abscesses (23%). Inpatient mortality was 22% in Group I and 45% in Group II (p < 0.05). The sensitivity of Von Reyn's diagnostic criteria and that of Duke's University group was 49% and 85.8% (p < 0.05). Mean follow up was 531 days. Two patients had a new event of IE and no outpatient deaths were recorded. CONCLUSION: IE is a medical and surgical emergency. Because of the high mortality rate, in the medically treated group, surgery should be considered in all cases as early as possible in the course of the disease.

Depressed T-cell proliferation associated with susceptibility to experimental Taenia crassiceps infection.

Peritoneal infection with Taenia crassiceps cysticerci of naturally resistant (C57BL/10J and C57BL/6J) and susceptible (BALB/cAnN) mice induces a cellular immune depression. T-cell proliferation in response to concanavalin A (ConA) or anti-CD3 was significantly depressed in infected mice of all strains tested. However, in resistant mice, the diminished response to ConA was transient and animals recovered normal responsiveness at day 40, whereas susceptible mice remained suppressed throughout the 40 days of the experiment. In contrast, the proliferative response to anti-CD3 was lower in infected mice than in noninfected controls regardless of differences in natural susceptibility of the strains. Intraperitoneal injection of mice with a parasite extract also induced a depression of the response to ConA, although not as strong as that produced by the parasite itself. This depression is not due to direct effects by parasite antigens over host lymphocytes, as proliferation is not affected by the presence of cysticercal antigens added in vitro. Diminished interleukin-2 production during the parasitosis accounts at least in part for the diminished responses to ConA. A primary infection favors parasite establishment after a second challenge, pointing to the relevance of the immunodepression in generating a host environment favorable to the parasite.

The effect of unequal transversion rates on the accuracy of evolutionary parsimony.

Evolutionary parsimony is an easy-to-use method of phylogenetic inference that is based on nucleic acid sequences and that does not require the assumption that evolutionary processes in the various sites on the molecule are identical. It does, however, require a parameter constraint, known as the "balanced transversion" assumption. We show that the accuracy of the procedure is fairly insensitive to moderate violations of this assumption--and that the procedure thus is applicable under more general conditions than previously thought.