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Biomedical subjects

M H Wilkinson

Publications and source records attributed to M H Wilkinson.

At least 37 records · Page 2Linked to original sources
PubMed1994

Shading correction and calibration in bacterial fluorescence measurement by image processing system.

An image processing system with applications in bacterial (immuno-)fluorescence measurement has been developed. To reach quantitative results, correction for non-uniformities in system sensitivity, both as a function of time (calibration for drifts) and as a function of image coordinates (shading correction), is essential. Both problems can be handled simultaneously by acquiring images of a uniformly fluorescent, solid standard as a reference image. To measure bacterial fluorescence, the average fluorescence intensity of isolated areas of interest (the bacteria) is computed, and corrected using the reference images. Two shading correction methods are theoretically and experimentally compared: direct averaging in the corrected image, and (weighted and unweighted) averaging using the raw image and a separate shading image to determine the weights and correct for shading during the averaging. The latter method proved computationally 3.5-6.5 times faster on average and reduced propagation of truncation errors during computation, resulting in 40% less noise, for 8-bits/pixel images.

Bacteria↗
PubMed1994

A simple data compression scheme for binary images of bacteria compared with commonly used image data compression schemes.

A run length code compression scheme of extreme simplicity, used for image storage in an automated bacterial morphometry system, is compared with more common compression schemes, such as are used in the tag image file format. These schemes are Lempel-Ziv and Welch (LZW), Macintosh Packbits, and CCITT Group 3 Facsimile 1-dimensional modified Huffman run length code. In a set of 25 images consisting of full microscopic fields of view of bacterial slides, the method gave a 10.3-fold compression: 1.074 times better than LZW. In a second set of images of single areas of interest within each field of view, compression ratios of over 600 were obtained, 12.8 times that of LZW. The drawback of the system is its bad worst case performance. The method could be used in any application requiring storage of binary images of relatively small objects with fairly large spaces in between.

Bacteria↗
PubMed1994

Computer processing of microscopic images of bacteria: morphometry and fluorimetry.

Several techniques that use computer analysis of microscopic images have been developed to study the complicated microbial flora in the human intestine, including measuring the shape and fluorescence intensity of bacteria. These techniques allow rapid assessment of changes in the intestinal flora and could apply equally to other complex microbial ecosystems.

Bacteria↗
PubMed1994

Fluorescence overlay antigen mapping of the epidermal basement membrane zone: I. Geometric errors.

To identify in tissue sections the relative positions of antigen distributions close to the resolving power of the microscope, we have developed the fluorescence overlay antigen mapping (FOAM) procedure. As this technique makes high demands on the geometric fidelity of the overlay image, it is essential to recognize geometric errors resulting from optical imperfections. This applies in particular to the image shift difference (ISD) that may routinely occur during fluorescence overlay. We describe here procedures for assessment and mechanical correction of the ISD in tissue sections. Furthermore, we describe an alignment verification test to assess the accuracy of the ISD correction procedure, using collagen Type VII as the geometric verification marker. These procedures should enable reliable evaluation of relative antigen distributions in tissue sections using photomicrographic multicolor fluorescence overlay. Further details of the FOAM technique, such as color fidelity and its utility for diagnostic and research purposes, will be published separately.

Basement Membrane↗
PubMed1993

Origin of tonic electrical activity patterns in the diaphragm of the fetal lamb.

The respiratory pattern generator in fetal and postnatal life activates the phrenic nucleus and diaphragm muscle with phasic bursts of activity. In the fetus, diaphragmatic activity is also characterized by tonic activity patterns of unknown origin. We have examined whether such activity is diaphragmatic, or radiated from nearby ribcage muscles, by placing two sets of electrodes side-by-side in the costal portion of the diaphragm in five fetuses. The rationale for this approach is that if tonic activity, radiates to the diaphragm it should be recorded by both sets of electrodes and there should be no delay between the action potentials from each set of electrodes. Of 24 single tonic units identified, 15 were recorded from only one of the two sets of electrodes in the diaphragm. In the 9 tonic units recorded from both sets of electrodes, there was a time delay between the appearance of the action potentials in the two recordings (mean +/- S.E.M. 1.6 +/- 0.2 ms). This is the expected conduction delay along the muscle fibres separating the two electrodes. Since tonic diaphragmatic activity persisted in fetuses with the spinal cord transected rostral or caudal to the phrenic nucleus, we conclude that the spinal cord alone is sufficient to produce the tonic activity recorded from the fetal diaphragm but that the brain may also generate such activity.

Animals↗
PubMed1993

Characterization of human faecal flora by means of an improved fluoro-morphometrical method.

The use of polyclonal antibodies in differentiating between samples of faecal microflora derived from ten healthy volunteers was assessed. The distribution of FITC-labelled antibodies (of the IgA, IgG and IgM isotype) over 144 morphologically distinct subsets of faecal bacteria ('morphotypes') was quantified by means of digital morphometry and quantitative immunofluorescence. Furthermore, a new dataprocessing algorithm was developed which makes objective quantitation of the antibody distributions over the faecal morphotypes possible. The results of this study imply that the antibody binding capacity of faecal morphotypes is a unique characteristic of faecal microflora.

Adult↗
PubMed1992

Circulating antibodies against faecal bacteria assessed by immunomorphometry: combining quantitative immunofluorescence and image analysis.

A new technique to study the prevalence of circulating antibodies directed against different morphological groups ('morphotypes') of bacteria in fresh faeces is presented. The technique combines quantitative indirect immunofluorescence with digital image analysis. Plasma antibody titres and patterns of IgA, IgG and IgM isotype against morphotypes of faecal bacteria were determined in ten healthy individuals.

Adult↗
PubMed1991

Objective quantitation of serum antibody titres against Enterobacteriaceae using indirect immunofluorescence, read by videocamera and image processing system.

A new way of measuring indirect immunofluorescence (IIF) of microscopic bacterial slide preparations by videocamera and an image processing system is presented. This method is compared with the conventional method of reading the slides by eye. The advantages of this new approach are objective reading, greater accuracy and easier performance. We have applied the method to measure serum antibody titres against endogenous Enterobacteriaceae. The method offers the opportunity to combine IIF with automatic morphological analysis, thereby maximally exploiting the possibilities of the immunofluorescence technique.

Antibodies, Bacterial↗
PubMed1991

Electromyographic changes in the isolated rat diaphragm during the development of fatigue.

To investigate whether the power spectrum of the electromyogram of a fatiguing muscle can be used to infer the degree to which the muscle is fatigued, we recorded isometric tension and two monopolar electromyograms from eight isolated rat diaphragm preparations suspended in an organ bath containing a balanced salt solution. Each preparation was excited with a fixed phrenic nerve impulse pattern made up of a 70-Hz train of impulses of supramaximal voltage delivered for 170 ms with a 500-ms recovery period. Tension fell rapidly over the first 60 s of the fatigue run and more slowly for the remaining 60 s analysed. The duration of extracellular action potentials increased and their amplitude decreased as the tension developed by the diaphragm decreased; conduction velocity along muscle fibres also decreased. The centroid frequency (fcen) of the power spectrum of the first action potential elicited by each train of stimuli decreased rapidly until tension fell to approximately 70% of the initial value; thereafter little change in fcen occurred, although tension continued to fall to 33% of its initial value. Our results demonstrated that under controlled conditions, fcen provided a sensitive index of fatigue in its early stages, but provided no information once fatigue was pronounced.

Animals↗
PubMed1991

Morphometrical parameters of gut microflora in human volunteers.

The morphology of faecal microflora of nine healthy human volunteers was studied by digital image analysis of microscopic slides. Weekly specimens were collected during an 8-week period. Seven morphometrical parameters were derived: the means and medians of components 1, 2 and 3, and morphometrical entropy. Statistically significant differences among subjects were found for means of components 1 and 2, medians of components 1, 2 and 3, and entropy. The stability in normal circumstances provides an excellent basis for the detection of pathological change in gut flora balance.

Analysis of Variance↗
PubMed1991

Effects of ceftriaxone on faecal flora: analysis by micromorphometry.

In order to elucidate the effect of ceftriaxone therapy on the morphology of gut microflora, 11 human volunteers were treated with ceftriaxone, 1 g daily, given intramuscularly in one dose. Treatment continued for 5 days. Faecal microflora was analysed by digital image processing before, during and after the treatment period. We derived simple numerical parameters which describe the morphologic composition of the flora. They were significantly influenced by the antibiotic, and returned to their baseline values more than 7 days after treatment was stopped. The procedure holds promise for clinical application.

Adult↗
PubMed1987

Progressive shortening of the periodic breathing cycle duration in normal infants.

Ten normal full-term neonates were monitored by oxycardiorespirography in hospital during the 1st wk of life, and subsequently at home at 4, 8, and 12 wk of age in a longitudinal study of the duration of the periodic breathing cycle during spontaneous sleep. Periodic breathing was observed in 25 of the 40 studies, with a total of 168 epochs of periodicity noted. Eighty-four percent of the periodic epochs occurring during nonrapid eye movements were preceded by a sigh, body movements, or sleep state transition, compared with 41% during rapid eye movements (p less than 0.005). There was a progressive reduction in the periodic breathing cycle duration, which fell significantly between the 1st and 4th wk, in both sleep states, (p less than 0.001). There was a further significant fall between 4 and 12 wk in nonrapid eye movement sleep (p less than 0.05), and there was no significant difference between sleep states at any postnatal age. The overall change in the duration of the periodic cycle, for both sleep states combined, was from 15.0 +/- 3.6 s at less than 1 wk to 12.4 +/- 1.8 s at 12 wk of age. The periodic breathing cycle duration progressively shortens over the first 3 months of life. We postulate that this shortening may be useful indicator of peripheral chemoreceptor maturation over this time period.

Apnea↗
PubMed1986

Phasic respiratory activity in the fetal lamb during late gestation and labour.

We quantified the respiratory activity of 9 fetal lambs using computer-analysis of the diaphragmatic electromyogram (EMG) obtained during 2 h recording sessions interspersed over the last 13 days of gestation. The fetuses delivered unassisted at an average gestational age of 145 days (term = 147 days). During the last 2 h of labour the number of phasic EMG bursts (breaths) averaged 3% of the peak recorded earlier in the study. This decline in breathing began at least 2 days before labour and resulted predominantly from the fetus spending an increasing proportion of time in apnoea. Respiratory rate within epochs of breathing also fell significantly 1 day before labour, and the proportion of time spent in the low voltage electrocortical state declined once labour commenced. No significant change occurred in arterial PO2, PCO2 or pH over the study period. We conclude that fetal respiratory activity falls well before the onset of labour, largely as a result of increased apnoea, and that the decline does not result from the development of a progressive hypoxaemia associated with labour.

Animals↗
PubMed1983

Computerised nutritional data management in neonatal intensive care.

We report a minicomputer based recording, reporting, and research system for patient data management in the neonatal intensive care unit (NICU). It is moderately priced, transportable, and independent of a central computer. It requires only a desk top and standard power supply, and successfully meets the medical documentation, communication, and research needs of the NICU. The first phase of programme development has enabled us to process growth and nutritional data from infants on complex parenteral and enteral nutrition. The system is well suited to medical users and provides a practical interactive data management system with many potential applications in the NICU.

Australia↗
PubMed1981

Development of patterns of respiratory activity in unanesthetized fetal sheep in utero.

Respiratory activity (diaphragmatic electromyogram) was recorded in six unanesthetized in utero fetal lambs, between 0.7 of gestation and term. Respiratory patterns generated by the fetus showed developmental changes that included 1) an emergence of a periodic modulation of respiratory rate producing alternating active and quite phases (mean cycle length of 37 min between 130 and 140 days' gestation; 2) an increase in percentage apnea (expiratory time greater than 10 s) from 20% at 110 days to 60% at 140 days; and 3) a linear decrease in the 2-h average respiratory rate, while mean rate during active phases showed no consistent gestational decline. Electrocortical and electroocular activity was monitored in three of six fetuses; however, discrete sleep state patterns could not be consistently identified. The results demonstrate a gestational change in the respiratory patterns of the developing fetus and suggest an orderly maturation of the mechanisms controlling respiratory neuronal output.

Anesthesia↗
PubMed1981

Hypercapnic stimulation of respiratory activity in unanesthetized fetal sheep in utero.

Respiratory responses to hypercapnia were studied in seven chronic in utero fetal lambs between 105 and 138 days' gestation (16 expts). Fetal arterial CO2 tension was raised (mean increase 9.9 Torr) by altering maternal inspired gas concentrations. Diaphragmatic electromyogram (EMG) was recorded as the index of respiratory activity. Electrocortical and electroocular activity (3 fetuses) were monitored in an attempt to define sleep state. Average respiratory rate increased (90%) and fetal apnea decreased (60%) during hypercapnia. Mean respiratory rate during "on" periods (greater than 6 EMG bursts/min) increased significantly during hypercapnia throughout the gestational epoch studied. Mean duration of the inspiratory time (TI) showed no significant change. Variability in both rate and TI decreased in response to CO2 at all gestations. Integrated EMG activity per burst divided by TI increased significantly at all gestations; however, no gestational increase in responsiveness to CO2 was seen. Sleep states were not able to be consistently identified, and a quantifiable electrocortical response to CO2 was not observed. These results indicate a relatively early functional maturation of fetal respiratory responses to CO2.

Animals↗