Linear relationship between the maintenance of hippocampal long-term potentiation and retention of an associative memory.

The hypothesis that the maintenance or decay of an associative memory trace after an extended retention interval is a function of the residual strength of the synapses originally strengthened during learning was examined in a classical conditioning paradigm in which high-frequency stimulation of a hippocampal input--the medial perforant path--served as a conditioned stimulus. Rats received perforant path stimulus-foot shock pairings while engaged in a previously acquired food-motivated lever-pressing task. Conditioned suppression of lever pressing was the behavioral measure of learning and retention of the association. Stimulus trains to the perforant path at an intensity above the threshold for eliciting a population spike induced long-term potentiation of synaptic transmission in the dentate gyrus. Synaptic potentials recorded extracellularly in the dentate gyrus were subsequently monitored for 31 days to examine quantitatively the decay of synaptic potentiation, a period after which retention of the learned association was assessed. All rats learned the association to a similar extent and displayed equivalent amounts of long-term potentiation by the end of conditioning. A slowly decaying function of synaptic potentiation was observed in remembering rats, i.e., rats with high retention performance after the 31-day learning-to-retention interval, while forgetting was associated with a rapid decay of long-term potentiation. Behavioral performance at the long-term memory test was linearly correlated with the amplitude of long-term potentiation maintained just prior to the retention test. The results favor the hypothesis that long-term associative memory depends, at least in part, on the maintenance of elevated synaptic strengths in the pathway activated during learning and suggest a role for the lasting component of long-term potentiation in the maintenance of memory.     

The prognostic value of evoked responses from primary somatosensory and auditory cortex in comatose patients.

OBJECTIVE: To evaluate somatosensory and auditory primary cortices using somatosensory evoked potentials (SEPs) and middle latency auditory evoked potentials (MLAEPs) in the prognosis of return to consciousness in comatose patients. METHODS: SEPs and MLAEPs were recorded in 131 severe comatose patients. Latencies and amplitudes were measured. Coma had been caused by transient cardiac arrest (n=49), traumatic brain injury (n=22), stroke (n=45), complications of neurosurgery (n=12) and encephalitis (n=3). One month after the onset of coma patients were classified as awake, still comatose or dead. Three months after (M3), they were classified into one of the 5 categories of the Glasgow outcome scale (GOS). RESULTS: At M3, 41.2% were dead, 47.3% were conscious (GOS 3-5) and 11.5% had not recovered consciousness. None of the patients in whom somatosensory N20 and auditory Pa were absent did return to consciousness and in the post-anoxic group, reduced cortical amplitude too was always associated with bad outcome. Conversely, N20 and Pa were present, respectively, in 33/69 and 34/69 patients who did not recover. CONCLUSIONS: The prognostic value of SEPs and MLAEPs in comatose patients depends on the cause of coma. Measurement of response amplitudes is informative. Abolition of cortical SEPs and/or cortical MLAEPs precludes post-anoxic comatose patients from returning to consciousness (100% specificity). In any case, the presence of short latency cortical somatosensory or auditory components is not a guarantee for return to consciousness. Late components should then be recorded.     

Effect of low dietary calcium on bone metabolism in the SENCAR mouse

The SENCAR (sensitive to carcinogenesis) mouse is a unique tool for investigating the interaction between a specific defect in intracellular signaling, dietary calcium, and metabolic bone disease. The SENCAR mouse was developed by selective breeding for enhanced sensitivity to two-stage carcinogenesis. Its major genetic defect, which renders it exquisitely sensitive to stimulation with diacylglycerol or phorbol esters, is in the regulatory domain of protein kinase C, one of the primary intracellular mediators of hormonal effects. At sexual maturity, SENCAR mice are large and have big bones, but our previous pharmacokinetic studies showed that they accumulate lesscalcium under normal conditions and lose more calcium under adverse conditions than do other, standard strains of mice. To histologically define the effect of low dietary calcium on bone metabolism, we performed histomorphometric analysis of tetracycline-labeled sections of femoral bone from male SENCAR mice maintained on calcium-sufficient and calcium-deficient diets during the critical period from 10 to 14 weeks of age. The bone volume, absolute osteoid volume, and mineral apposition rate were lower at 14 than at 10 weeks of age in SENCAR mice fed 0.02 or 0.6% calcium diets. Calcium deficiency increased the architectural disarray and the probability of observing focal discontinuities in the growth plate. Thus, characteristic features of impaired bone metabolism (low bone volume and apposition rate) develop early in SENCAR mice and are exacerbated by low dietary calcium. Detailed examinations of the histology and biochemistry of SENCAR mouse bone will provide insights into the mechanisms by which specific defects in the signal transduction of protein kinase C contribute to impaired bone metabolism.     

Evidence for a direct stimulatory effect of cibenzoline on insulin secretion in rats.

The effect of cibenzoline succinate, a new antiarrhythmic agent, was studied on insulin secretion in rats. Experiments were performed both in vivo and in vitro using two preparations: the isolated perfused pancreas and isolated islets. In anaesthetized rats, cibenzoline was able to increase plasma insulin levels and to reduce glycaemia. These effects were observed at 1 mg/kg i.v. in fed rats and at 3 mg/kg i.v. in fasted rats. In the isolated pancreas perfused in the presence of a slightly stimulating glucose concentration (8.3 mM), cibenzoline (2 and 6 microM) elicited a progressive and sustained insulin response in a concentration-dependent manner. In the presence of a non-stimulating glucose concentration (4.2 mM), cibenzoline was ineffective at 2 microM and slightly increased basal insulin release at 6 microM. In isolated islets incubated with 8.3 mM glucose, cibenzoline (6 and 20 microM) caused a concentration-dependent stimulation of insulin release. It is concluded that cibenzoline stimulates insulin secretion by a direct action on pancreatic B cells in rats.     

La prothèse totale du coude GUEPAR

Résumé Un grand nombre de prothèses du coude sont actuellement disponibles, beaucoup de critères les opposent les unes aux autres. Après les premières prothèses à charnière contrainte, les prothèses semicontraintes et plus récemment les prothèses à glissement se sont imposées. La prothèse à glissement GUEPAR se situe dans l'évolution récente des implants du coude. Nous rapportons ici les résultats des trente-neuf premières arthroplasties réalisées au sein du Guepar de 1986 à 1991, sur 33 coudes rhumato?des, 4 destructions post-traumatiques, 1 spondylarthrite ankylosante et 1 arthrose sur chondrocalcinose.

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The Guepar total elbow arthroplasty

Summary The Guepar total elbow replacement is a low friction, minimally constrained gliding prosthesis. The humeral and ulnar components are of metal with intramedullary stems, which are cemented. There is a sigmoid shaped, high density polyethylene interposition bearing. The authors have used the prosthesis in 33 patients with rheumatoid arthritis, 4 with post-traumatic problems, one with chondrocalcinosis and another with degenerative changes of uncertain aetiology. In the patients with rheumatoid arthritis, one sustaine a posterior dislocation and two suffered deep infection. In the remaining 30, the overall results were good at an average review of 32 months. The mean range of movement had increased by 31° and pain was absent in 28 elbows. In the management of rheumatoid arthritis total elbow arthroplasty must be part of an overall plan of treatment. Severe involvement of the wrist and shoulder must be dealt with before elbow replacement is considered.

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Nous remercions Mr J. H. Aubriot, M. Condamine, A Deburge, B Lassale, T Le Balc'h, J. Y. Nordin et J Witvoet, membres du GUEPAR (Groupe pour l'utilisation et l'étude des prothèses articulaires) de nous avoir donné leurs observations     

An unusual case of sundown syndrome subsequent to a traumatic head injury

An unusual case of sundown syndrome is here reported, in which a bilingual patient would involuntarily change languages at sunset. Numerous theories have been advanced in attempting to account for sundowning. Cameron [1] has suggested that nocturnal delirium was based on an inability to maintain a spatial image without the assistance of repeated visualization. Krai [2] and Wolanin and Phillips [3] have argued for a more psychogenic account, by stating that psychosocial stressors may, in concert with impaired cognitive functioning, account for sundowning. The present case concerns a 42-year-old white male who in January 1989 suffered a closed head injury. A thorough personal history as well as a detailed examination of the patient's daily activities allowed us to account for the unusual manner in which the sundowning manifested itself. The uniqueness of this case allows us to underscore both the psychological as well as environmental and neurological factors involved in sundowning. Thus, we have as a consequence been able to synthesize the seemingly disparate accounts of both Cameron and more recent published literature [2, 3].     

A Half-Century Perspective on World Nutrition and the International Nutrition Agencies

Editors' note: As we approach the end of the 20th century, we will, in Nutrition Reviews, take an occasional look back at developments of the last half-century that have established the underpinnings of public health nutrition as we know it and practice it today. This is also a span of time over which this journal, having begun publication in 1942, has addressed important developments in nutrition and health. Our first retrospective is contributed by Dr. José Maria Bengoa, one of the fathers of international public health nutrition. Dr. Bengoa, whose career has spanned more than 50 years, witnessed the origins of the international nutrition agencies and served in leadership roles at the Pan American Health Organization and the World Health Organization (WHO) from 1955 to 1964, and as director of the WHO Office of Nutrition from 1964 to 1974.     

Treatment of muscle spasticity in patients with cerebral palsy using BTX-A: a pilot study

This study was designed to verify the safety and efficacy of botulinum toxin type A (BTX-A) used as a neuromuscular block on spastic masticatory musculature of children with cerebral palsy. Six patients who had spastic-tetraplegic cerebral-palsy, aged 5 to 20 years were selected. All patients had spasticity of the jaw muscles, bruxism, lower lip trauma, limited mouth opening, and difficulties in cleaning the oral cavity. The patients were sedated under general anesthesia, while the dentist injected the masseter and temporalis muscles bilaterally with 150 and 75 units of BTX-A each. Clinical examinations were conducted at 7, 14, 30, and 90 days after the initial appointment. We found statistically significant decreases in muscle spasticity and bruxism ( p = 0.002), improved inter-incisal opening ( p = 0.002), improved oral hygiene ( p = 0.031), and less lower lip trauma ( p = 0.060) after the neuromuscular blocking.     

NDT competence of nurses caring for patients with stroke.

Neurodevelopmental treatment (NDT) is the most used rehabilitation approach in the treatment of patients with stroke in the Western world today, despite the lack of evidence for its efficacy. The aim of this study was to conduct an intervention check and measure the nurses' competence, in positioning stroke patients according to the NDT approach. The sample consisted of 144 nurses in six neurological wards who were observed while positioning stroke patients according to the NDT approach. The nurses' combined mean competence scores within the wards was 195 (70%) of 280 (100%) possible, and for each ward the mean score varied between 181 (65%) and 206 (74%). This study indicates that nurses working in hospitals where the NDT approach has been implemented have the knowledge and skills to provide NDT nursing.