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Biomedical subjects

D J Field

Publications and source records attributed to D J Field.

At least 55 records · Page 3Linked to original sources
PubMed1990

Shortfall of equipment for neonatal intensive care and the introduction of budget holding contracts.

As adequate allowance must be made for the costs of purchasing, maintaining, and updating equipment during the development of contracts the current standing of neonatal units with regard to available equipment was assessed. Data were collected as part of a one year prospective survey of the 17 perinatal units in the Trent region. Adequacy of provision of equipment for recognised intensive care cost was assessed using the recommendations of the British Paediatric Association and British Association of Perinatal Paediatrics. It was assumed that units without recognised intensive care cost had to be able to equip one cot to a standard of intensive care level 1 in the short term. Equipment more than 5 years old was considered likely to warrant replacement or major maintenance within the next two years. With these guidelines over 600,000 pounds would be required to provide sufficient equipment for all recognised level 1 intensive care cost and to allow units without funded cost to provide this level of care in the short term and to replace existing equipment more than 5 years old for these cost alone. This amount could be reduced by 25% by subdividing intensive care cost into levels 1 and 2, thereby reducing equipment requirements, but this would impair the units' ability to perform level 1 care at funded provision, which has already been shown to need expansion. Neither figure takes account of equipment requirements for infants requiring special care. In addition, no allowance has been made for purchase or update of ultrasound scanners or blood gas analysers. If the government's proposed reforms are to be implemented clinicians need to revise guidelines regarding essential equipment, and plans must be made to correct any existing shortfalls so that they do not become inherited financial liabilities for future budget holders.

Budgets↗
PubMed1990

Attitudes to viability of preterm infants and their effect on figures for perinatal mortality.

OBJECTIVE: To examine how local attitudes to management of extreme preterm labour can influence data on perinatal mortality. DESIGN: One year prospective study in a geographically defined population. SETTING: The 17 perinatal units of Trent region. PATIENTS: All preterm infants of less than or equal to 32 weeks' gestation in the Trent region. INTERVENTIONS: Infants who had been considered viable at birth were referred for intensive care; those who had been considered non-viable received terminal care. MAIN OUTCOME MEASURES: Whether each infant was born alive, dead, or alive but considered non-viable. RESULTS: Large differences were observed among units in the rates of delivery of infants of less than or equal to 27 weeks' gestation (rates varied from 7.2 to 0 per 1000 births). These differences were not present in the data relating to infants of between 28 and 32 weeks' gestation. The variation seemed to result from different approaches to the management of extreme preterm labour--that is, whether management took place in a labour ward or a gynaecology ward. CONCLUSIONS: Place of delivery of premature babies (less than or equal to 27 weeks' gestation) may influence classification and hence figures for perinatal mortality. In addition, the fact that the onus of judgment regarding viability and classification is often placed on relatively junior staff might also affect the figures for perinatal mortality. The introduction of a standard recording system for all infants greater than 500 g would be advantageous.

Attitude to Health↗
PubMed1990

Circulatory effects of fast ventilator rates in preterm infants.

High frequency positive pressure ventilation has been suggested to result in a lower incidence of respiratory complications in preterm infants with idiopathic respiratory distress syndrome compared with ventilation at conventional rates. A possible disadvantage is compromise of the infant's cardiovascular condition secondary to inadvertent positive end expiratory pressure (PEEP). In a group of 20 such infants treated with high frequency positive pressure ventilation (rates of up to 100/minute) and analysed, changes in arterial blood pressure and cerebral blood flow velocity were largely influenced by changes in arterial blood gases, and no effect could be attributed to inadvertent PEEP. In addition, the observed fall in both arterial carbon dioxide and oxygen tensions could be readily predicted for theoretical reasons. Under certain conditions at the fastest rates used, cerebral blood flow velocity was significantly influenced by changes in blood pressure, which may indicate impaired cerebrovascular regulation. Though other factors (such as the severity of the infants' illness or the use of paralysis) may have been responsible for this apparent blood pressure passivity, the role of high frequency positive pressure ventilation in such infants warrants further study.

Blood Flow Velocity↗
PubMed1989

A group II intron in the Neurospora mitochondrial coI gene: nucleotide sequence and implications for splicing and molecular evolution.

The temperature-sensitive Neurospora nuclear mutant cyt18-1 is deficient in splicing many Group I mitochondrial introns when grown at its non-permissive temperature; however, splicing of intron 1 in the coI gene of the Adiopodoume (formerly called North Africa) strain is unaffected (R.A. Collins and A.M. Lambowitz, J. Mol. Biol. 184: 413-428, 1985). Here we show that coI intron 1 is a typical Group II intron, the only one identified to date in Neurospora. The differential effect of the cyt18-1 mutation suggests that splicing of certain introns could be regulated independently of others by nuclear-encoded proteins. The intron contains a long open reading frame (ORF) resembling that of the Neurospora Mauriceville mitochondrial plasmid. The intron and plasmid ORFs share unusual features of codon usage that suggest both evolved outside of the Neurospora mitochondrial genetic system.

Amino Acid Sequence↗
PubMed1989

The demand for neonatal intensive care.

In a one year prospective study within the Trent Regional Health Authority the demand for neonatal intensive care was estimated to be 1.1 cots per 1000 births. Intensive care level 1 (as defined by the British Paediatric Association and British Association for Perinatal Paediatrics) was determined by two separate techniques, which showed close agreement. Intensive care level 2 could not be measured directly, as the definition was too subjective. This aspect of demand was therefore estimated by using data derived from the treatment of babies transferred for intensive care. These findings represent a minimum estimate of need, as the data were obtained from a service constrained by having facilities well below the estimated level (roughly 60% of estimated demand). In the future other factors such as increased survival of extremely preterm infants will be likely to increase demand still further.

Bed Occupancy↗
PubMed1988

Analysis of tubulin proteins and peptides in neuronal and non-neuronal tissues using immobilized pH gradients.

The accurate identification of the individual protein products of multi-gene families is essential to the interpretation of data from a wide range of experimental approaches including molecular biology, protein chemistry, and cell biology. We have adapted immobilized pH gradient isoelectric focusing to provide high resolution of tubulin proteins. Here we use these techniques to investigate the heterogeneity of tubulin in several neuronal and non-neuronal tissues to provide an accurate evaluation of isotubulin composition. Of the ten sources examined, the greatest number of isotubulins was found in whole adult brain. Tubulin isolated from either neonate human or rat brain consists predominantly of the more basic alpha and beta isotubulins found in adult brain. Cerebrum, cerebellum, medulla and caudate nucleus all contain the same large number of isotubulins as in whole brain, but in varying proportions. Liver, kidney and spleen isotubulin populations are all similar to each other and consist of a simpler distribution than any neuronal tissue examined. The majority of the tubulin protein in these non-neuronal tissues is composed of only the most basic alpha tubulins and intermediately-charged beta tubulins. No isotubulins were identified that were unique to these three non-neuronal tissues. Tubulin from neuroblastoma cells has an isotubulin distribution grossly similar to non-neuronal sources but additionally contains two basic beta isotubulins found in adult brain that are absent from non-neuronal tissues.

Animals↗
PubMed1988

Is perinatal mortality still a good indicator of perinatal care?

The increasing influence of very immature infants on perinatal mortality rates (PMR) led us to question the usefulness of this parameter in assessing perinatal care. To examine this further we have compared the incidence of perinatal asphyxia amongst mature babies (greater than or equal to 35 weeks gestation) for two geographically-defined populations of over 500,000 people. Both areas have a teaching hospital-based maternity service and comparable perinatal mortality rates. The incidence of severe post-asphyxial encephalopathy showed a marked excess in one population (1.93 vs 0.61 per 1000 births), which was not obviously explicable. Taken in conjunction with the figures for stillbirth in labour, this represented a 2.8 times greater risk for either fetal death in labour or severe asphyxial insult. It would appear that perinatal mortality rates do not accurately reflect important differences in those perinatal outcomes most likely to be affected by perinatal care.

Asphyxia Neonatorum↗
PubMed1987

Relations between the statistics of natural images and the response properties of cortical cells.

The relative efficiency of any particular image-coding scheme should be defined only in relation to the class of images that the code is likely to encounter. To understand the representation of images by the mammalian visual system, it might therefore be useful to consider the statistics of images from the natural environment (i.e., images with trees, rocks, bushes, etc). In this study, various coding schemes are compared in relation to how they represent the information in such natural images. The coefficients of such codes are represented by arrays of mechanisms that respond to local regions of space, spatial frequency, and orientation (Gabor-like transforms). For many classes of image, such codes will not be an efficient means of representing information. However, the results obtained with six natural images suggest that the orientation and the spatial-frequency tuning of mammalian simple cells are well suited for coding the information in such images if the goal of the code is to convert higher-order redundancy (e.g., correlation between the intensities of neighboring pixels) into first-order redundancy (i.e., the response distribution of the coefficients). Such coding produces a relatively high signal-to-noise ratio and permits information to be transmitted with only a subset of the total number of cells. These results support Barlow's theory that the goal of natural vision is to represent the information in the natural environment with minimal redundancy.

Humans↗
PubMed1986

The structure and symmetry of simple-cell receptive-field profiles in the cat's visual cortex.

Receptive fields of simple cells in the cat visual cortex have recently been discussed in relation to the 'theory of communication' proposed by Gabor (1946). A number of investigators have suggested that the line-weighting functions, as measured orthogonal to the preferred orientation, may be best described as the product of a Gaussian envelope and a sinusoid (i.e. a Gabor function). Following Gabor's theory of 'basis' functions, it has also been suggested that simple cells can be categorized into even- and odd-symmetric categories. Based on the receptive field profiles of 46 simple cells recorded from cat visual cortex, our analysis provides a quantitative description of both the receptive-field envelope and the receptive-field 'symmetry' of each of the 46 cells. The results support the notion that, to a first approximation, Gabor functions with three free parameters (envelope width, carrier frequency and carrier phase) provide a good description of the receptive-field profiles. However, our analysis does not support the notion that simple cells generally fit into even- and odd-symmetric categories.

Animals↗