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J H Fuller

Publications and source records attributed to J H Fuller.

At least 145 records · Page 8Linked to original sources
PubMed1976

Determination of antidromic excitation by the collision test: problems of interpretation.

Extracellular unit recordings were made from pontine reticular neurons in the cat and cells of the motor cortex in monkeys. In all cases, the characteristics of responses to electrical stimulation were studied using the tests of invariance of latency, high frequency following, and collision for determining the orthodromic or antidromic nature of the responses. The results of these tests show that their conclusions are not always consistent. A systematic error was found between the experimental and predicted values of the collision interval. It is argued that this error is due to differences in the application of measured parameters in calculating the collision interval. The collision test can be considerably improved by repeating the test with stimuli of progressively greater strengths.

Animals↗
PubMed1976

Brain stem reticular units: synaptic responses to stimulation within the ascending reticular pathways.

When the ascending reticular axonal system is stimulated, the responses of distal structures (e.g., the cerebral cortex) appear to outlast the stimulus; these longlasting effects could reflect the intrinsic nature of the distal structure, or the response could reflect an interaction among the reticular cells which tends to prolong the effects of stimulation. To examine the latter hypothesis, single units with ascending axons (projecting units) were recorded in the cat rostral rhombencephalon in acute experiments conducted under halothane-nitrous oxide anesthesia. Stimulation of areas to or through which axons of reticular neurons projected (midbrain tegmentum and lower tectum, medial thalamus, and basal forebrain) produced a consistent and specific response which was elicited only from these areas: suppression of spontaneous activity which was typically elicited from several areas having ascending axons. One-half of these responses were accompanied by a short latency-single spike synaptic excitation. Stimulating areas more than 1.0 mm from the ascending trajectory never produced this response, whereas the number of responses was directly related to the number of projecting axons identified in any one experiment from a given site. Thus, the predominant effect of stimulating within the ascending axonal trajectory was suppression of spontaneous activity in the projecting units, not an 'en cascade' activation of these units; on the contrary, the only type of excitation encountered was a single, short latency spike. Therefore, any effects of stimulation within the ascending reticular pathway which appear to outlast the stimulus (as previously described in the literature) cannot be ascribed to a reverberating (excitatory) circuit among projecting units. A possible source of the synaptic responses of projecting units is a retrograde activation of collaterals interconnecting the reticular cells. If such interaction exists, it is specifically distributed among cells with ascending axons, as the responses were only observed in a very few units not identified by antidromic excitation; however, other evidence is adduced to support the belief that these few units were projecting units whose axons were beyond the reach of the stimulating electrodes. Futhermore, the axons may be bundled such that units with axons nearest that of a given projecting unit give rise to the most extensive synaptic interactions; the activation of these nearby axons suppresses spontaneous activity, while axons farther away have a greater possibility of being excitatory in nature. Should such a medium for interaction exist, reticular collateral interactions might be seen to exist specifically for the purpose of decreasing the activity of cells destined for similar rostral target structures.

Animals↗
PubMed1975

Visual tracking and the primate flocculus.

Purkinje cells in the primate flocculus discharge specifically in relation to visual tracking, effectively generating a velocity profile of the target during pursuit. It is suggested that these neurons supply oculomotor centers with the velocity command signals needed to support pursuit eye movements.

Action Potentials↗
PubMed1975

Brain stem reticular units: some properties of the course and origin of the ascending trajectory.

Experiments were conducted in acutely prepared cats anesthetized with halothane-nitrous oxide. Single units were recorded in the mesencephalic and rostral rhombencephalic reticular core, and their ascending axons were stimulated in the mesencephalon, diencephalon, and telencephalon. The locations of stimulation and recording sites were determined by histological examination of the brains. Antidromic spikes were elicited by electrodes with a stimulus spread of approximately 300 mum and were collided with spontaneous (orthodromic) spikes to confirm antidromicity. Projecting axons were found to be scattered diffusely in the central mesencephalon in both the tegmentum and tectum. At the mesodiencephalic junction, the dorsal extent of the pathway lay in the posterior commissure and the ventral extent in the substantia nigra. More rostrally, a ventral group of axons was found in or near the supraoptic nucleus in the hypothalamus, and near the floor of the forebrain in the basal telencephalon. In agreement with previous reports, a dorsal component was located in the medial thalamus, most often in the nucleus centralis lateralis. The conduction velocity of each axon was determined, and they suggest a wide range of axon size in the ascending pathways. There may be a slight predominance of smaller fibers in the dorsal component and of larger fibers in the ventral component; however, all parts of the pathways were relatively heterogenous. The units from which projecting axons arose were found in the rostral rhombencephalon, and no units sending their axons along the restricted pathways investigated were identified rostral or caudal to this region. However, no conclusion is drawn concerning units within the region extending from 0.0 to 0.6 mm of the midline or other brain stem regions known to be monoamine-rich and to have ascending axons; these cellular populations were not examined.

Anesthesia, Inhalation↗
PubMedDate not supplied

Microalbuminuria is not rare before 5 years of IDDM. EURODIAB IDDM Complications Study Group and the WHO Multinational Study of Vascular Disease in Diabetes Study Group.

Microalbuminuria is thought to be rare in people with insulin-dependent diabetes mellitus (IDDM) for less than 5 years. We measured its prevalence in 733 clinic-attending IDDM patients with diabetes duration of 1-5 years in two large multicenter studies [EURODIAB IDDM Complications Study and the World Health Organization (WHO) Multinational Study]. We also compared characteristics of microalbuminuric patients with IDDM for 1-5 years versus more than 5 years' duration. Albumin excretion rate was measured from a timed 24-h urine collection in the EURODIAB Study. Proteinuria was measured by the salicylsulphonic acid test in the WHO Study. The prevalence of microalbuminuria (20-200 micrograms/min, EURODIAB) was 18% [95% confidence interval (CI) 13%-22%)]. The prevalence of light proteinuria was 15% (9%-20%, WHO study). Raised protein excretion was a consistent finding in 34 of the 36 centers. The increased cardiovascular risk (raised blood pressure and total cholesterol) associated with microalbuminuria in patients with IDDM for more than 5 years was also apparent in those with diabetes for 1-5 years. However, repeat urine testing suggested that microalbuminuria before 5 years was more likely to be transient or reversible. In conclusion, these two studies in 36 centers, which used different methods more than 10 years apart, show consistently that raised urinary albumin excretion occurs before 5 years of IDDM. The clinical significance of this needs to be examined by prospective observation.

Adult↗
PubMedDate not supplied

Psychosocial factors and the onset of type 1 diabetes.

Stress has been proposed as a possible precipitating factor for the development of Type 1 diabetes in genetically susceptible individuals. A validated in-depth psychometric instrument (The Life Events and Difficulties Schedule) was used to investigate the role of psychosocial factors in the onset of Type 1 diabetes in islet cell antibody (ICA)-positive family members. Families with ICA-positive members had higher scores for subject focused severe life events in the 5-year period prior to the diagnosis of diabetes in a second family member compared with matched control families (1.50 +/- 0.68 (+/- SD) vs 0.32 +/- 0.37; p less than 0.03). In the same time period, these families also experienced a higher mean number of severe long-term difficulties compared with control families (1.34 +/- 0.52 vs 0.14 +/- 0.17; p less than 0.01). Scores for current total visual social contacts were greater for control families compared with case family members (12.10 +/- 1.90 vs 9.64 +/- 2.70; p less than 0.05). These results suggest that global family stress possibly in conjunction with a reduced number of social contacts may act as a trigger for the development of diabetes in a second family member and that social support may act as a buffer to stress and disease onset.

Adolescent↗
PubMedDate not supplied

Validity of routinely collected hospital admissions data on diabetes.

Data from the clinical records of patients known to have diabetes and admitted to hospital in North West London, Cambridge or Newcastle were compared with data on the same admissions taken from the system responsible for recording information on all acute hospital admissions (Hospital Activity Analysis). In 89 out of 751 admissions (12%), either the sex, date of birth or marital status of the patient was incorrectly recorded. The diagnosis of diabetes was omitted in 32 (10%) of 315 admissions in which diabetes or a complication of diabetes was regarded as the principal cause of admission and in 12 (23%) out of 53 in which the principal cause was closely related to diabetes. These included cases in which the diagnosis had not been stated (by the clinician) on the discharge summary (the source document for Hospital Activity Analysis) as well as instances in which the coding clerk had failed to record the diagnosis. The validity of information collected on hospital admissions is dependent on the presentation of data by the clinician to the coding clerk. There may be a lack of awareness of the importance of the clinical discharge summary as a source document for such systems.

Diabetes Mellitus↗