RESUMEN
BACKGROUND: Several studies have shown inorganic nitrate/nitrite to reduce blood pressure in both healthy subjects and hypertensive patients. An effect presumably caused through bioconversion to nitric oxide. However, studies on inorganic nitrate/nitrite have shown inconsistent results on renal functions such as GFR and sodium excretion. The current study investigated whether orally administered nitrate would decrease blood pressure and increase GFR and urinary sodium excretion. METHODS: In a randomized, placebo-controlled, double-blinded, crossover study, 18 healthy subjects received a daily dose of 24 mmol potassium nitrate and placebo (potassium chloride) during 4 days in a randomized order. Subjects also ingested a standardized diet and completed a 24-h urine collection. GFR was determined by the constant infusion technique and during GFR measurement, brachial blood pressure (BP) and central blood pressure (cBP), heart rate, and arterial stiffness were measured every half hour using the Mobil-O-Graph®. Blood samples was analyzed for nitrate, nitrite, cGMP, vasoactive hormones and electrolytes. Urine was analyzed for nitrate, nitrite, cGMP, electrolytes, ENaCγ, NCC, CrCl, CH2O and UO. RESULTS: No differences in GFR, blood pressure or sodium excretion were found between the treatments with potassium nitrate and placebo. However, both nitrate and nitrite levels in plasma and urine were significantly increased by potassium nitrate intake and the 24-h urinary excretion of sodium and potassium were stable, showing adherence to the standardized diet and the study medication. CONCLUSION: We found no decrease in blood pressure or increase in GFR and sodium excretion of 24 mmol potassium nitrate capsules as compared to placebo after 4 days of treatment. Healthy subjects may be able to compensate the effects of nitrate supplementation during steady state conditions. Future research should focus on long-term studies on the difference in response between healthy subjects and patients with cardiac or renal disease.
Asunto(s)
Nitratos , Nitritos , Humanos , Presión Sanguínea , Nitratos/farmacología , Estudios Cruzados , Nitritos/farmacología , Voluntarios Sanos , Sodio , Riñón/fisiología , Método Doble CiegoRESUMEN
BACKGROUND: Isotonic saline (IS) is widely used to secure perioperative cardiovascular stability. However, the high amount of chloride in IS can induce hyperchloremic acidosis. Therefore, IS is suspected to increase the risk of acute kidney injury (AKI). Biomarkers may have potential as indicators. METHODS: In a double-blinded, placebo-controlled study, 38 patients undergoing primary uncemented hip replacement were randomized to IS or PlasmaLyte (PL). Infusion was given during surgery as 15 ml/kg the first hour and 5 ml/kg the following two hours. Urinary samples were collected upon admission and the day after surgery. As surgery was initiated, urine was collected over the course of 4 h. Hereafter, another urine collection proceeded until the morning. Urine was analyzed for markers of AKI neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1). Arterious and venous blood samples for measurements of pH and plasma electrolytes including chloride (p-Cl) were collected as surgery was initiated, at the end of surgery and the following morning. RESULTS: IS induced an increase in p-Cl (111 ± 2 mmol/L after IS and 108 ± 3 after PL, p = 0.004) and a decrease in pH (7.39 ± 0.02 after IS and 7.43 ± 0.03 after PL, p = 0.001). Urinary NGAL excretion increased in both groups (ΔNGAL: 5.5 [4.1; 11.7] µg/mmol creatinine p = 0.004 after IS vs. 5.5 [2.1;9.4] µg/mmol creatinine after PL, p < 0.001). No difference was found between the groups (p = 0.839). Similarly, urinary KIM-1 excretion increased in both groups (ΔKIM-1: IS 115.8 [74.1; 156.2] ng/mmol creatinine, p < 0.001 vs. PL 152.4 [120.1; 307.9] ng/mmol creatinine, p < 0.001). No difference between the groups (p = 0.064). FENa increased (1.08 ± 0.52% after IS and 1.66 ± 1.15% after PL, p = 0.032). ENaC excretion was different within groups (p = 0.019). CONCLUSION: A significantly higher plasma chloride and a lower pH was present in the group receiving isotonic saline. However, u-NGAL and u-KIM-1 increased significantly in both groups after surgery despite absence of changes in creatinine. These results indicate that surgery induced subclinical kidney injury. Also, the IS group had a delayed sodium excretion as compared to the PL group which may indicate that IS affects renal sodium excretion differently from PL. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02528448 , 19/08/2015.
Asunto(s)
Lesión Renal Aguda/etiología , Artroplastia de Reemplazo de Cadera/efectos adversos , Receptor Celular 1 del Virus de la Hepatitis A , Lipocalina 2/orina , Solución Salina/administración & dosificación , Sodio/orina , Lesión Renal Aguda/orina , Anciano , Biomarcadores/orina , Cloruros/sangre , Método Doble Ciego , Femenino , Gluconatos/administración & dosificación , Humanos , Concentración de Iones de Hidrógeno , Cloruro de Magnesio/administración & dosificación , Masculino , Persona de Mediana Edad , Cloruro de Potasio/administración & dosificación , Acetato de Sodio/administración & dosificación , Cloruro de Sodio/administración & dosificaciónRESUMEN
In the present investigation, we sought to (1) replicate previous reports of impaired word-stem completion (WSC) priming and cued recall performance in older adults, (2) gain a better understanding of the differential roles of search and selection processes in implicit and explicit WSC, and (3) determine the particular aspects of WSC performance that are influenced by age. Experiment 1 demonstrated that older adults primed and recalled fewer items on a WSC task than middle-aged adults did, who in turn primed and recalled fewer items than young adults did. A series of item analyses indicated that choice of a stem completion is influenced by two independent sources of information: the familiarity of the completion reflected by word frequency and the cue-specific match between the stem and the completion word based on the common pronunciation of the stem. Experiment 2 demonstrated that older adults utilized cue-specific matching to the same degree as young and middle-aged adults. However, the impact of target familiarity changed across the lifespan. Older adults produced and recalled high-frequency targets as well as young adults but produced and recalled fewer low-frequency targets than did young participants. The results are consistent with the view that older adults rely on familiarity to a greater degree than do young adults.
Asunto(s)
Envejecimiento/psicología , Recuerdo Mental , Aprendizaje Verbal , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Atención , Señales (Psicología) , Femenino , Humanos , Masculino , Persona de Mediana Edad , Aprendizaje por Asociación de Pares , Valores de Referencia , Retención en PsicologíaRESUMEN
Studies examining implicit memory performance in Alzheimer's disease (AD) have yielded inconsistent findings, with these patients demonstrating impaired performance within some priming studies and intact performance within others. The present study examined the role of task sensitivity in detecting impaired priming in memory-impaired patients. Twelve healthy older adults and 12 AD patients were administered a picture fragment identification test. Task sensitivity was increased by employing stimulus cues expected to produce larger and more variable priming effects than obtained in previous studies. A simple comparison of priming scores revealed that the AD patients demonstrated significantly impaired priming relative to normal control participants. However, further analysis of priming in relation to certain stimulus characteristics revealed that AD patients often demonstrated impaired priming when overall priming effects were large but relatively intact priming when priming effects were small. These findings suggest that the prevention of ceiling effects in control participants may aid in the detection of impaired priming in patient populations.
Asunto(s)
Enfermedad de Alzheimer/psicología , Memoria/fisiología , Anciano , Cognición/fisiología , Señales (Psicología) , Femenino , Humanos , Masculino , Desempeño Psicomotor/fisiologíaRESUMEN
Fifty-three volunteer participants were studied with the fade-in task (Ostergaard, 1998) to measure naming latency, word priming, and recognition-memory performance. and with morphometric magnetic resonance imaging (MRI) techniques to measure volumes of mesial temporal lobe, diencephalic, striatal, and neocortical structures. The relationship between measures of cerebral volume loss and performance deficits was modeled using simultaneous regression analyses in which the behavioral measures were dependent variables. The results suggested that damage in both hippocampal and amygdala/entorhinal areas as well as damage in the diencephalon and the nucleus accumbens all contributed independently to the severity of recognition-memory deficits. Both caudate nucleus damage and hippocampal damage contributed independently to increased naming latency (slowed single-word reading). Finally, only damage in the hippocampus appeared to result in decreased word priming. These results provide further evidence against the assertion that word priming represents a form of memory unaffected by damage to the mesial temporal lobes.
Asunto(s)
Cuerpo Estriado/fisiopatología , Diencéfalo/fisiopatología , Trastornos de la Memoria/diagnóstico , Trastornos de la Memoria/fisiopatología , Lectura , Lóbulo Temporal/fisiopatología , Vocabulario , Adulto , Anciano , Anciano de 80 o más Años , Afasia/diagnóstico , Afasia/fisiopatología , Núcleo Caudado/patología , Núcleo Caudado/fisiopatología , Cuerpo Estriado/patología , Diencéfalo/patología , Femenino , Lóbulo Frontal/fisiopatología , Hipocampo/patología , Hipocampo/fisiopatología , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Núcleo Accumbens/patología , Núcleo Accumbens/fisiopatología , Lóbulo Occipital/fisiopatología , Índice de Severidad de la Enfermedad , Lóbulo Temporal/patologíaRESUMEN
The rate with which perceptual information becomes available was manipulated in 2 word naming experiments. Word priming effects, in terms of reduced naming latencies for repeated items, and recognition memory measures were obtained with matched groups of amnesic patients and control participants. In both experiments, the amnesic patients evidenced significantly reduced priming effects compared to control participants under difficult task conditions. Under easy task conditions the baseline naming latencies of the amnesics were significantly longer than those of controls, but the difference in priming effects failed to reach significance. The findings are consistent with the Information Availability model of priming positing that both priming and explicit memory are mediated by episodic information from a study or information processing episode. It is argued that word priming does not represent a memory function that is spared in amnesia.
Asunto(s)
Amnesia/complicaciones , Trastornos del Lenguaje/etiología , Adulto , Amnesia/diagnóstico , Análisis de Varianza , Femenino , Humanos , Trastornos del Lenguaje/diagnóstico , Masculino , Persona de Mediana Edad , Modelos Psicológicos , Índice de Severidad de la Enfermedad , Vocabulario , Escalas de WechslerRESUMEN
Previous memory research has suggested that the effects of prior study observed in priming tasks are functionally, and neurobiologically, distinct phenomena from the kind of memory expressed in conventional (explicit) memory tests. Evidence for this position comes from observed dissociations between memory scores obtained with the two kinds of tasks. However, there is continuing controversy about the meaning of these dissociations. In recent studies, Ostergaard (1998a, Memory Cognit, 26:40-60; 1998b, J. Int. Neuropsychol. Soc., in press) showed that simply degrading visual word stimuli can dramatically alter the degree to which word priming shows a dissociation from word recognition; i.e., effects of a number of factors on priming paralleled their effects on recognition memory tests when the words were degraded at test. In the present study, cerebral blood flow changes were measured while subjects performed the word identification (reading) and recognition memory tasks used previously by Ostergaard. The results are the direct comparisons of the two tasks and the effects of stimulus degradation on blood flow patterns during the tasks. Clear differences between word identification and word recognition were observed: the latter task evoked considerably more prefrontal activity and stronger cerebellar activation. Stimulus degradation was associated with focal increases in bilateral fusiform regions within the occipital lobe. No task, degradation, or item repetition effects were demonstrated in mesial temporal regions, no repetition effects were observed in any region, and there was no evidence for different effects of stimulus degradation in the priming and recognition memory conditions. Power limitations may have contributed to the null effects.
Asunto(s)
Mapeo Encefálico , Corteza Cerebral/fisiología , Recuerdo Mental/fisiología , Lectura , Aprendizaje Verbal/fisiología , Adulto , Aprendizaje Discriminativo/fisiología , Dominancia Cerebral/fisiología , Femenino , Humanos , Masculino , Lóbulo Occipital/fisiología , Corteza Prefrontal/fisiología , Solución de Problemas/fisiología , Tomografía Computarizada de EmisiónRESUMEN
Conflicting findings with respect to the effects of experimental manipulations on priming have been reported in previous studies. It is argued that, in many priming tasks, large amounts of task-relevant information are available from various sources, and that, therefore, the information available from a specific study episode will have only a small impact on overall performance level. Under such circumstances, high levels of baseline performance and small priming effects will be observed. The experiments reported here investigated the hypothesis that a high baseline performance in information-processing tasks that are used to measure priming may constrain priming effects. In a series of word-naming experiments, perceptual difficulty and, therefore, baseline performance was manipulated. Under easy conditions, priming effects were relatively small and were not affected by word frequency, spaced repetition, or delay. Under more difficult conditions, priming effects were larger, and significant effects of all of the above-mentioned experimental manipulations were observed. Under conditions that produced the largest priming effects, a significant relationship between priming and explicit-memory performance could be observed. In the last experiment, it was shown that the characteristics of the retrieval task can substantially affect the magnitude of priming. It is argued that priming effects should be considered to reflect interactions between memory traces and the information-processing components of the priming task.
Asunto(s)
Cognición/fisiología , Lenguaje , Vocabulario , Humanos , Modelos Teóricos , Tiempo de ReacciónRESUMEN
Coagulation factor VIIa belongs to a family of homologous enzymes, including factors IXa and Xa and activated protein C, composed of two epidermal growth factor-like domains located between an N-terminal domain rich in gamma-carboxyglutamic acid residues and a C-terminal serine protease domain. The first epidermal growth factor-like domain in factor VIIa contains a Ca2+ binding site, the function of which is largely unknown. Site-directed mutagenesis of two Ca2+-liganding Asp residues in this domain abolished Ca2+ binding and resulted in a 2-3-fold decrease in amidolytic activity at optimal Ca2+ concentrations. The lower amidolytic activity persisted in complex with soluble tissue factor, apparently due to a lower kcat of the mutant factor VIIa. Mutant and wild-type factor VIIa bound to lipidated tissue factor were equally efficient activators of factor X. The dissociation constants, derived from amidolytic activity and surface plasmon resonance measurements, were 2-5 nM and 50-60 nM for the interactions between wild-type and mutant factor VIIa, respectively, and soluble tissue factor. Binding to lipidated tissue factor was characterized by dissociation constants of 7.5 pM for factor VIIa and 160 pM for the factor VIIa mutant. Hence, a functional Ca2+ binding site in the first epidermal growth factor-like domain added 7-8 kJ/mol to the total binding energy of the interaction with both lipidated and soluble tissue factor.
Asunto(s)
Calcio/metabolismo , Factor de Crecimiento Epidérmico/metabolismo , Factor VIIa/metabolismo , Tromboplastina/metabolismo , Ácido Aspártico/metabolismo , Sitios de Unión , Cromatografía de Afinidad , Factor VIIa/genética , Factor X/metabolismo , Humanos , Cinética , Modelos Moleculares , Mutagénesis Sitio-Dirigida , Conformación ProteicaRESUMEN
This experiment investigated the effects of verbal labels on recognition memory for ambiguous visual figures in patients with Alzheimer's disease (AD), patients with Huntington's disease (HD), and matched normal control subjects. The study employed ambiguous figures that could be interpreted in two different ways. During the study phase each figure was presented together with a verbal label that corresponded to one interpretation of the figure. After a 30-min retention interval a recognition memory test was given during which the study figures and distractor figures were presented one at a time without verbal labels. For each study figure two distractor figures were employed, each corresponding to a different interpretation of the study figure. The patients' overall recognition memory performance was severely impaired compared to control subjects. However, all subject groups tended to produce responses and response latencies to distractor items that were consistent with the verbal labels presented during the study phase. This bias effect occurred in the AD patients despite the fact that their recognition memory performance was at chance level. Indeed, there was no significant difference in the bias evidenced by the AD and HD patients and their respective matched control subjects. The bias effects were obtained in an explicit memory task, and the findings are discussed in terms of unconscious influences on explicit memory processes.
Asunto(s)
Enfermedad de Alzheimer/psicología , Atención , Enfermedad de Huntington/psicología , Recuerdo Mental , Reconocimiento Visual de Modelos , Aprendizaje Verbal , Adulto , Anciano , Enfermedad de Alzheimer/diagnóstico , Aprendizaje por Asociación , Femenino , Humanos , Enfermedad de Huntington/diagnóstico , Masculino , Persona de Mediana Edad , Pruebas Neuropsicológicas , Retención en PsicologíaRESUMEN
Repetition priming was measured in two different tasks within a single experiment--one in which subjects named briefly (tachistoscopically) presented words, and one requiring naming of visually fragmented/degraded words. Thirteen amnesic patients, 12 patients with Alzheimer's disease (AD), and 15 normal control subjects were tested under 4 experimental conditions involving the factorial combination of two variables: delay of test (10 minutes and 24 hours), and number of prior occurrences of the primed items (1 and 4). The two tasks produced very different patterns of priming effects, despite the fact that common study phases were employed. In one task the priming effect showed no decay and virtually no effect of the number of prior occurrences of the primed items, whereas both these variables affected priming in the other task. The AD patients evidenced impaired priming in both tasks. However, in the degraded-word-naming task the deficit was only apparent under some experimental conditions. The amnesics produced priming effects that in absolute terms were similar to those produced by control subjects. However, when group differences in overall performance level were taken into account in the tachistoscopic task, these patients also showed clear evidence of impaired priming. It is argued that the complex pattern of priming effects obtained is best explained by the characteristics of the retrieval cues provided in the tasks, and, generally, that such characteristics may determine whether or not experimental variables will affect measured priming.
Asunto(s)
Enfermedad de Alzheimer/complicaciones , Lenguaje , Trastornos de la Memoria/etiología , Anciano , Femenino , Humanos , Pruebas del Lenguaje , Masculino , Persona de Mediana Edad , Estimulación Luminosa , Semántica , Análisis y Desempeño de TareasRESUMEN
A large number of reports have been published on stochastic independence between implicit and explicit measures of memory. This is often taken to imply that different memory systems mediate implicit and explicit memory performance. In these cases, stochastic independence is inferred from contingency analysis of overall success rates in two memory tasks when performance in one or both of the tasks is, to a large extent, mediated by factors other than memory. Typically, the difference between performance with studied and nonstudied items is not large in implicit memory tasks. It is argued that this must be taken into account when evaluating the contingency analysis. A method is presented for estimating the relevant joint and conditional probabilities, assuming that the aspects of performance in the two tasks that are related to memory are dependent to the maximum possible extent. The method is applied to a number of published studies, and it is shown that the difference between these estimated probabilities and those given by stochastic independence is too small to allow any conclusion to be drawn about memory systems from contingency analysis of data reported in these studies.
Asunto(s)
Recuerdo Mental , Retención en Psicología , Procesos Estocásticos , Percepción de Profundidad , Humanos , Ilusiones Ópticas , Orientación , Reconocimiento Visual de ModelosRESUMEN
Recently, Wood and his colleagues (1989) presented a case of childhood amnesia as evidence against the distinction between declarative and procedural memory that has sometimes been applied to human amnesia. Their argument was based on the observation that their patient showed some progress in school over the years, i.e., acquired some declarative knowledge, despite severely impaired day-to-day memory ability. We briefly review their case, together with a carefully studied second case of childhood amnesia not mentioned by Wood et al. Their argument is wrong in several ways. First, the utility of the declarative/procedural distinction for amnesia, or the utility of any other distinction between memory systems, depends on whether or not one kind of memory is impaired selectively, not on the severity of the impairment. In particular there is no requirement that one kind of memory be totally absent. Second, they have not provided the data necessary to support their argument; namely, data showing that the amount of declarative knowledge accumulated during years in school was better than would have been expected given the capacity for moment-to-moment or day-to-day memory. Indeed, the patient's moment-to-moment memory ability is better than represented, and the patient's progress in school was abnormally slow. Third, it is not clear that academic achievement scores provide a direct measure of declarative memory abilities (skill learning and recovery of function may also have contributed). We conclude that the evidence from childhood amnesia is fully consistent with the proposal that amnesia reflects a selective impairment in the formation of long-term declarative memory.
Asunto(s)
Logro , Amnesia/diagnóstico , Discapacidades para el Aprendizaje/diagnóstico , Recuerdo Mental , Trastornos Neurocognitivos/diagnóstico , Amnesia/psicología , Daño Encefálico Crónico/diagnóstico , Daño Encefálico Crónico/psicología , Niño , Estudios de Seguimiento , Humanos , Discapacidades para el Aprendizaje/psicología , Trastornos Neurocognitivos/psicologíaRESUMEN
The aim of this study was to determine the effects of postural changes on lung function in pregnant women during the first, second, third trimester and post partum. A significant decrease in FRC, PEF and FEV1 was observed as a result of the postural changes. Arterial oxygenation, MVV and DLCO remained largely the same.
Asunto(s)
Pulmón/fisiología , Embarazo/fisiología , Supinación/fisiología , Adulto , Femenino , Humanos , Mediciones del Volumen Pulmonar , Oxígeno/sangreRESUMEN
To evaluate whether there is a difference in mental function after general anaesthesia and epidural analgesia, a homogeneous group of 40 elderly men (age between 60 and 80) undergoing transurethral prostatectomy was studied. The study was prospective, randomised and double blind. Patients with all types of complications believed to impair mental function were excluded. Long-term, short-term, verbal and visual memory were tested preoperatively, and 4 days, and 3 weeks postoperatively. In conclusion, we found a significant and equal decline in test performance on the fourth postoperative day. Three weeks postoperatively, however, both groups had returned to or exceeded preoperative levels of performance.
Asunto(s)
Analgesia Epidural , Bupivacaína , Procesos Mentales/efectos de los fármacos , Prostatectomía , Anciano , Anciano de 80 o más Años , Anestesia General , Bupivacaína/farmacología , Humanos , Masculino , Memoria/efectos de los fármacos , Persona de Mediana Edad , Periodo Posoperatorio , Estudios Prospectivos , Pruebas Psicológicas , Distribución Aleatoria , Factores de TiempoRESUMEN
The occurrence of group B streptococci in the lower urogenital tract of 150 women with signs of abortion and 100 women with uncomplicated pregnancy was studied. Group B streptococci appeared significantly more frequently in the urine (p less than 0.001) and in the uterine cervix (p less than 0.01) of women with abortion. Delivery resulted in 85% of patients with group B streptococci in the urine and in 42% of patients with no group B streptococci (p less than 0.001). Group B streptococci were cultured from amniotic fluid from three of eight women with intact membranes and were isolated from the urine and cervix. These bacteria were antibody coated as demonstrated by an immunofluorescence technique. Group B streptococci were recovered from blood or liver in six fetuses, including two who had group B streptococci in the amniotic fluid. The study demonstrates an association between the occurrence of group B streptococci in the urine and cervix and late abortions.
Asunto(s)
Aborto Espontáneo/microbiología , Streptococcus agalactiae/aislamiento & purificación , Sistema Urogenital/microbiología , Líquido Amniótico/microbiología , Bacteriuria , Cuello del Útero/microbiología , Femenino , Feto/microbiología , Humanos , Recién Nacido , Embarazo , Vagina/microbiologíaRESUMEN
The patient C.C. developed an amnesic syndrome at the age of 10 yr. Like adult amnesics, C.C. demonstrated impaired episodic memory for both verbal and visual materials although immediate memory span was spared. However, striking deficits were also observed on a wide variety of semantic memory tasks, including reading vocabulary and verbal fluency tests, semantic classification and lexical decision tasks and tests of verbal intelligence. On the other hand, C.C. showed normal learning and retention of two procedural tasks. It was argued that this evidence is inconsistent with the view that the amnesic syndrome represents a selective defect of episodic memory that leaves semantic memory relatively unaffected.