Developmental changes in eye-blink conditioning and neuronal activity in the cerebellar interpositus nucleus.

Neuronal activity was recorded in the cerebellar interpositus nucleus in infant rats during classical conditioning of the eye-blink response. The percentage and amplitude of eye-blink conditioned responses increased as a function of postnatal age. Learning-specific neuronal activity in the cerebellum emerged ontogenetically in parallel with the eye-blink conditioned response. There were also age-specific changes in neuronal activity after the onset of the conditioned and unconditioned stimuli. The results indicate that the development of the eye-blink conditioned response may depend on the development of stimulus-evoked neuronal responses and learning-specific plasticity in the cerebellum. Functional immaturity in the afferent neural pathways may limit the induction of neural plasticity in the cerebellum and thereby limit the development of the eye-blink conditioned response.

Developmental changes in eye-blink conditioning and neuronal activity in the inferior olive.

Neuronal activity was recorded in the dorsal accessory inferior olive in infant rats during classical conditioning of the eye-blink response. The percentage and amplitude of eye-blink conditioned responses (CRs) increased as a function of age. The magnitude of the neuronal response to the unconditioned stimulus (US) decreased with age. There were also age-specific modifications of US-elicited inferior olive neuronal activity during paired trials in which a conditioned eye-blink response was performed. The results indicate that the development of the conditioned eye-blink response may depend on dynamic interactions between multiple developmental processes within the eye-blink circuitry. Differences in the functional maturity of olivo-cerebellar pathways may limit the induction of plasticity in the cerebellum and thereby limit the development of eye-blink conditioned responses.

Synapses with a segmented, completely partitioned postsynaptic density express more AMPA receptors than other axospinous synaptic junctions.

Axospinous perforated synapses of one morphological subtype exhibit multiple transmission zones, each one being formed by an axon terminal protrusion apposing a postsynaptic density (PSD) segment and separated from others by complete spine partitions. Such segmented, completely partitioned (SCP) synapses have been implicated in synaptic plasticity and postulated to be exceptionally efficacious. The present study explored the validity of this supposition. Postembedding immunogold electron microscopy was used for quantifying the postsynaptic AMPA receptor (AMPAR) expression, which is widely regarded as a major determinant of synaptic efficacy. Various subtypes of axospinous synapses were examined in the rat CA1 stratum radiatum. The results showed that the number of immunogold particles for AMPARs in SCP synapses markedly and significantly exceeded that in other perforated subtypes (by 101% on the average) and in nonperforated immunopositive synapses (by 1086%). Moreover, the particle number per single PSD segment, each of which also contained NMDA receptors, was significantly higher than that per nonperforated PSD (by 485%). SCP synapses also exhibited a higher particle density per unit PSD area, as well as a larger overall PSD area as compared with other synaptic subtypes. Analysis of covariance revealed that the high AMPAR expression in SCP synapses was related to the segmented PSD configuration, not only to the PSD size. Moreover, the subpopulations of SCP and other perforated synapses with either overlapping or equal PSD sizes differed in AMPAR content and concentration, with both measures being significantly higher in SCP synapses. Thus, the elevated AMPAR expression in SCP synapses is associated with the presence of separate PSD segments, not only with their large PSD area. These findings are consistent with the idea that SCP synapses have a relatively greater efficacy and may support maximal levels of synaptic enhancement characteristic of certain forms of synaptic plasticity such as the early LTP phase.

Hiatus hernia: a comparison between two methods of fundoplication by evaluation of the long-term results.

This paper presents a comparative study of two methods of fundoplication, a Belsey-like procedure and a Nissen-Rossetti operation in the management of 283 cases of hiatal hernia from 1962 to 1974. The methods, history, and preoperative findings are described, and the mortality and morbidity rates, particularly related to recurrence, are discussed. A short historical review is included in the discussion, which also deals with the anatomic and physiologic factors thought to be involved in the maintenance of the competence of the cardia. The author's reasons for preferring a Nissen operation are outlined. The management of peptic stricture and of shortening due to periesophagitis by modification of this technique is described.

Lesions of the perirhinal cortex impair sensory preconditioning in rats.

The effects of lesions of the perirhinal cortex on the development of associations between two conditioned stimuli (CSs) were examined with a sensory preconditioning procedure. Rats were given either bilateral electrolytic lesions of the perirhinal cortex or control surgery. They were then given either paired or unpaired presentations of a light CS and a tone CS. All of the rats were then given eyeblink conditioning procedures that involved paired presentations of either the light or tone and a periorbital shock unconditioned stimulus (US). The rats were finally given a test session that consisted of unpaired presentations of the tone and light CSs. Sensory preconditioning was established in the control group, but not in the lesion group. The findings are consistent with the view that the perirhinal cortex is involved in forming associations between neutral stimuli (even in the absence of reinforcement).

Neuronal activity in the cerebellar interpositus and lateral pontine nuclei during inhibitory classical conditioning of the eyeblink response.

Single-unit neuronal activity was recorded from the cerebellar interpositus nucleus and lateral pontine nuclei during conditioned inhibition of the eyeblink response in rats. Conditioned inhibition training sessions included 100 trials/day for 12 days. During each training session, the rats were given 50 presentations of a tone conditioned stimulus (CS) that was paired with a brief periocular shock unconditioned stimulus (US). They were also given 50 presentations of a compound stimulus that included the tone-CS and a light-CS. The compound-CS was not paired with the US. The two types of trials were mixed throughout the session and presented in an irregular sequence. This training procedure resulted in significant inhibition of the eyeblink response during the compound-CS. Neurons in the interpositus and lateral pontine nuclei exhibited significantly less activity during the compound-CS relative to the tone-CS. The suppression of cerebellar and pontine learning-related neuronal activity during the inhibitory CS may be critical for inhibiting the conditioned eyeblink response.

Review article: endoscopic ultrasound of the stomach.

Endoscopic ultrasound (EUS) is the adopted term for the technique which enables endoluminal ultrasound to be performed using a specially designed endoscope with a fixed piezoelectric transducer. Since initial reports described the use of this technique in patients, its use in clinical practice in Europe, the Far East and the USA has been steadily increasing over the past few years. At present the technique is only practised in a very few centres in the UK but it is likely that this will increase in the future. This article describes the present day value of EUS in evaluating gastric pathology.

The influence of type of tube and experience of the operator on performance of small bowel enema.

Seventy patients underwent small bowel enema (SBE) to assess the influence of experience of the radiologist on the ease of jejunal intubation and the adequacy of SBE using two types of tubes. Comparing intubation time, intubation screening time, total screening time and total room time, we conclude that jejunal intubation is achieved easily, in a reasonable time with both types of tube, by all grades of radiologist, although the experienced operator using the Silk tube achieved intubation in a significantly shorter time. Overall patient acceptability was satisfactory (75%) but was better using the Silk tube, with which entero-gastric reflux and vomiting were less.

Management of intra-abdominal abscesses in Crohn's disease.

Over a 5-year period, 54 intra-abdominal abscesses were observed in 40 (20.8%) of 192 patients with Crohn's disease. The median age was 39 years (range 17-76 years); median interval from diagnosis, 7.5 years (range 0-24 years) and the median number of surgical operations was 2 (range 0-7). Forty abscesses (74.1%) were spontaneous and 14 (25.9%) were postoperative. Thirty abscesses were initially managed by laparotomy, 14 by percutaneous drainage, nine by incision and drainage and in one case the abscess drained spontaneously. Intra-abdominal abscesses were managed successfully by laparotomy in 23 (76.7%) of 30 patients, with a 93% success rate (13 of 14) for spontaneous abscesses managed by resection and primary anastomosis. Three of 8 (37.5%) spontaneous abscesses were managed successfully by percutaneous drainage, a temporising effect being achieved in a further two cases. There was no significant difference in sepsis score or duration of hospital stay for patients managed initially by laparotomy and those managed by drainage. However, patients with stricturing or fistulating Crohn's disease were much more likely to have initial management by laparotomy and in these patients surgical intervention was found to be an effective initial strategy.

Ontogenetic changes in the neural mechanisms of eyeblink conditioning.

The rodent eyeblink conditioning paradigm is an ideal model system for examining the relationship between neural maturation and the ontogeny of associative learning. Elucidation of the neural mechanisms underlying the ontogeny of learning is tractable using eyeblink conditioning because the necessary neural circuitry (cerebellum and interconnected brainstem nuclei) underlying the acquisition and retention of the conditioned response (CR) has been identified in adult organisms. Moreover, the cerebellum exhibits substantial postnatal anatomical and physiological maturation in rats. The eyeblink CR emerges developmentally between postnatal day (PND) 17 and 24 in rats. A series of experiments found that the ontogenetic emergence of eyeblink conditioning is related to the development of associative learning and not related to changes in performance. More recent studies have examined the relationship between the development of eyeblink conditioning and the physiological maturation of the cerebellum, a brain structure that is necessary for eyeblink conditioning in adult organisms. Disrupting cerebellar development with lesions or antimitotic treatments impairs the ontogeny of eyeblink conditioning. Studies of the development of physiological processes within the cerebellum have revealed striking ontogenetic changes in stimulus-elicited and learning-related neuronal activity. Neurons in the interpositus nucleus and Purkinje cells in the cortex exhibit developmental increases in neuronal discharges following the unconditioned stimulus (US) and in neuronal discharges that model the amplitude and time-course of the eyeblink CR. The developmental changes in CR-related neuronal activity in the cerebellum suggest that the ontogeny of eyeblink conditioning depends on the development of mechanisms that establish cerebellar plasticity. Learning and the induction of neural plasticity depend on the magnitude of the US input to the cerebellum. The role of developmental changes in the efficacy of the US pathway has been investigated by monitoring neuronal activity in the inferior olive and with stimulation techniques. The results of these experiments indicate that the development of the conditioned eyeblink response may depend on dynamic interactions between multiple developmental processes within the eyeblink neural circuitry.

ABC of emergency radiology. The ankle.

The os trigonum is a common normal variant of the talus and is due to a separate ossification centre arising from the posterior tubercle. The appearance may resemble an old ununited fracture fragment. However, it is triangular, well corticated, in a classic location, and usually bilateral, which enables it to be distinguished from a fracture. Transverse, sclerotic, linear lines located at the metaphysis of growing long bones are due to short periods of growth arrest and have no clinical importance (fig 5). They may be confused with compression fractures, but again these lines are usually bilateral. Fibrous cortical defects are the most commonly seen benign lesions of long bones and are usually identified incidentally in radiographs taken for another reason. The defect is limited to the cortex, commonly found at the metaphysis, but may be located in the diaphysis as the bone grows. The lesion is well corticated (sclerotic margins) and usually does not produce signs or symptoms.

ABC of emergency radiology. The wrist.

History including detailed mechanism of injury. Meticulous clinical examination. Appropriate radiograph and systematic assessment.