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Biomedical subjects

B M Evans

Publications and source records attributed to B M Evans.

At least 19 recordsLinked to original sources
PubMed2006

Using a GIS transfer model to evaluate pollutant loads in the Lake Kinneret watershed, Israel.

Lake Kinneret (Sea of Galilee) is the only large surface water body in Israel, encompassing an area of 167 km2 and supplying some 30% of the country's fresh water. Pollution from anthropogenic sources and water abstraction for domestic and agricultural uses has long been threatening the water quality of the lake. Point-source pollution in the watershed has decreased drastically with the development of wastewater treatment. However, diffuse pollution from agricultural activities is still an unresolved issue. In this paper we present an application of AVGWLF (a GIS-based watershed load model) to the Lake Kinneret watershed. The model allows one to simulate daily stream flows and monthly sediment, nitrogen, and phosphorus loads discharged to the lake from the surrounding watershed. Results from simulations yield a satisfactory correspondence between simulated and measured daily water volume. Partition by source of total phosphorus delivered to the lake in the period of 2000-04 confirms the reduction in point source nutrient contribution due to improvement of wastewater treatment facilities in the area. Future management should focus on reduction of nutrients originating from septic systems (point sources) and pasture and cropland areas (diffuse sources). Results from simulations will enable watershed managers to prioritize effective management alternatives for protecting the water quality in the lake.

Fresh Water↗
PubMed2004

Discordant PKU phenotype in one family due to disparate genotypes and a novel mutation.

Classical phenylketonuria (PKU) and mild hyperphenylalaninaemia (MHP) are two ends of the broad diagnostic spectrum in phenylalanine hydroxylase (PAH) deficiency. We have analysed a family in which classical PKU, MHP and a normal phenotype occurred in family members with different mutations. Sequence analysis revealed three mutations segregating in the family. The individual with classical PKU had two previously reported deleterious mutations. A third novel mutation was identified in the other two individuals. This report demonstrates that when discordant phenotypes occur in a family, without protein loading or phenylalanine tolerance test, complete analysis of the PAH gene may be performed in order to support the diagnosis and assist in accurate genetic counselling and patient management.

Alleles↗
PubMed2003

Sleep, consciousness and the spontaneous and evoked electrical activity of the brain. Is there a cortical integrating mechanism?

The physiological mechanisms that underlie consciousness and unconsciousness are the sleep/wake mechanisms. Deep sleep is a state of physiological reversible unconsciousness. The change from that state to wakefulness is mediated by the reticular activating mechanism. The reverse change from wakefulness to sleep is also an active process effected by an arousal inhibitory mechanism based on a partial blockade of the thalamus and upper brain stem, associated with thalamic sleep spindles and also with cortical sub-delta activity (<1 Hz). The deactivation of the thalamus has been demonstrated both electrically and by positron emission tomography during deep sleep. Normally, wakefulness is associated with instant awareness (defined as the ability to integrate all sensory information from the external environment and the internal environment of the body). Awareness may be a function of the thalamo-cortical network in the cerebral hemispheres, which forms the final path of the sleep/wake mechanism. Anatomical and physiological studies suggest that there may be a double thalamo-cortical network; one relating to cortical and thalamic areas with specific functions and the other global, involving all cortical areas and so-called 'non-specific' thalamic nuclei. The global system might function as a cortical integrating mechanism permitting the spread of information between the specific cortical areas and thus underlying awareness. The global system may also be responsible for much of the spontaneous and evoked electrical activity of the brain. The cognitive change between sleep and wakefulness is accompanied by changes in the autonomic system, the cerebral blood flow and cerebral metabolism. Awareness is an essential component of total consciousness (defined as continuous awareness of the external and internal environment, both past and present, together with the emotions arising from it). In addition to awareness, full consciousness requires short-term and explicit memory and intact emotional responses.

Arousal↗
PubMed2000

Environmental and geographical factors contributing to watershed contamination with Cryptosporidium parvum oocysts.

Cryptosporidium parvum is a waterborne parasite which infects cattle and produces life-threatening zoonosis in people with impaired immune systems. Digital maps of 100-year floodplain boundaries, land use/cover, and livestock operations were used to select and characterize cattle farms in the floodplain area in Lancaster County, Pennsylvania, U.S.A. Over 21% of the cattle farms were located within 100-year floodplain boundaries. On average, a single farm comprised 12.8 ha of pasture (including buildings and farmyard) at risk of inundation. In all farms cattle had unlimited access to the creek. Manure samples collected from closed-in calf pens, cow/heifer yard runoff, and cattle paths through the creek were tested for C. parvum. On 64% of the farms (n=50) at least one sample was positive for C. parvum, and 44% of the farms had oocysts in all manure samples. Concentration varied from 90 to 371 oocysts/g and was significantly higher (P<0.02) in calf samples than in manure from cow and cow/heifer.

Animal Husbandry↗
PubMed1995

Prediction of outcome in severe head injury based on recognition of sleep related activity in the polygraphic electroencephalogram.

This study shows that the continuing presence of activity similar to normal sleep in the EEG in conjunction with the EEG polygraph (EEGP) can be used to determine the severity of brain damage after head injury. Recordings were taken within seven days of head injury from 154 unselected patients after resuscitation and emergency surgery. Sixteen patients with ongoing seizures were excluded. In the remaining 138 patients the presence of activity in the EEG, EEGP, or both, which can also be recognised in normal alertness and sleep, was noted. Particular attention was paid to the presence or absence of arousal related phasic activity involving EEG, motor, and autonomic changes. The traces were allocated to one of five groups: group 1, wakeful traces with normal alpha in at least one hemisphere; group 2, sleep-like traces with K complexes responsive to stimulation; group 3, traces with phasic activity related to abnormal spontaneous arousal including EEG changes; group 4, traces with abnormal spontaneous arousal activity without EEG changes; group 5, traces with no spontaneous arousal activity. The mean follow up was 21.5 months. Groups 2 and 3 were significantly associated with a good outcome and group 5 with death or a vegetative state. Comparison between the EEG/EEGP findings and the Glasgow coma scale at the time of the recording showed the EEG/EEGP to be the better predictor of outcome, particularly for individual patients.

Adolescent↗
PubMed1993

Cyclical activity in non-rapid eye movement sleep: a proposed arousal inhibitory mechanism.

The presence of an endogenous arousal cycle in stage 1 sleep with a dominant length of 15-18 sec has been previously demonstrated. This allows the division of the electroencephalogram (EEG) into naturally occurring epochs consisting of periods of higher arousal, associated with a shift towards wakefulness and an alpha burst, and periods of lower arousal with a shift towards sleep and a theta period. The present study seeks to determine the changes in arousal as sleep progresses to stage 4. The polygraphic traces of 63 subjects with no demonstrable EEG abnormality or sleep disturbance were examined. When vertex sharp waves appeared in late stage 1 sleep the dominant cycle length increased to 30-34 sec (P < 0.001 Kolmogorov-Smirnov). In stage 2 arousals showing a definite shift towards wakefulness (Definite Arousals) occurred at intervals predominantly 51-60 sec in length (P < 0.0005, chi square). Few Definite Arousals were seen during stage 3 and none in stage 4 apart from awakening or sleep stage change. These findings suggest a steady decline in arousal between waking and stage 4, parallelled by the EEG changes of stage 1-4 sleep. It is suggested that there may be an arousal inhibitory mechanism operating during stages 1, 2 and 3 of NREM sleep.

Adolescent↗
PubMed1992

Periodic activity in cerebral arousal mechanisms--the relationship to sleep and brain damage.

Periodic activity during light sleep is well recognised in many physiological systems, particularly respiration. In damaged brains this activity can become exaggerated. It involves the autonomic nervous system, the muscles, the cerebrospinal fluid (CSF) pressure, the cerebral blood flow and the electroencephalogram (EEG). It is related to the level of arousal. The EEGs of 52 subjects were studied. In stage 0-1 sleep, periods of alpha activity alternated with periods of theta activity related to the level of arousal. The intervals between the alpha onsets were measured and the data pooled. There was a dominant interval of about 16 sec. It is suggested that this is a physiological cerebral rhythm involving the cortex and the brain-stem activating mechanisms, responsive to outside stimuli but essentially endogenous. It is related to the controls of the autonomic, motor, and some cerebral auto-regulatory mechanisms. It may be severely disturbed in brain damage.

Adolescent↗
PubMed1992

The differentiation of peripheral effector neuron failure from acute brain stem dysfunction in a critically ill patient.

A patient appeared to be in coma following pneumococcal meningitis, an intracerebral haemorrhage, and a cardiac arrest. Late in the course of his illness neurophysiological investigations confirmed a proposal that he also had a fulminant acute demyelinating polyneuropathy which, for a period of five days, rendered the patient completely unresponsive. The patient recovered and is now working without any disability.

Adult↗
PubMed1990

A prospective study of genital infections in a family-planning clinic. 1. Microbiological findings and their association with vaginal symptoms.

A prospective study of genital infection was conducted in four inner-city family-planning clinics. Fifteen per cent of routine attenders had symptoms and signs of vaginal infection and many more women attended primarily because of symptoms. Among the women with both signs and symptoms, 70% had positive laboratory findings, Trichomonas vaginalis, Candida albicans and bacterial vaginosis being equally prevalent. Measurement of vaginal pH in the clinic was the single most useful clinical finding for directing empirical therapy. Among patients with a discharge confirmed on examination and an abnormally high pH, 72% had either T. vaginalis or bacterial vaginosis. Neisseria gonorrhoeae was isolated from 4% of women with, and 1% of those without, symptoms. We believe that it is worthwhile to investigate patients presenting to family-planning clinics with vaginal symptoms. No single specimen was found ideal for all pathogens, a cervical swab is better for gonococci and also for T. vaginalis but a vaginal swab is needed for candida and bacterial vaginosis.

Bacterial Infections↗
PubMed1981

Electroencephalographic changes as prognostic indicators after psychosurgery.

Thirty-five patients were studied by EEG with recordings taken the day before, two weeks after, and six months after psychosurgery. Most showed a characteristic frontal slow activity of varying degrees after operation with varying enhancement of background activity. The amount and spread of the frontal slow waves two weeks after operation showed a significant positive correlation with the clinical outcome one year later, which suggests a relatively objective and very early indication of the subsequent clinical response to psychosurgery.

Adult↗
PubMed1979

Semen separation technique monitored with greater accuracy by B-body test.

A fluorescent staining technique, the B-body test, is utilized to ascertain the proportion of male and female spermatozoa in separated semen. This test is also used to monitor progress of Thermal Convection Counterstreaming Sedimentation and Forced Convection Galvanization processes for separating heavier electropositive (female) and lighter electronegative (male) spermatozoa into the two constituent fractions. Biological field tests using separated semen with 1,115 cows resulted in 510 progeny showing close correlation in the percentage of male versus female and B-body positive in the male spermatozoa fractions, while a control group with nonseparated semen, usually 46% B-body positive, yielded 55% male offspring and 72.0% pregnancy. Thus, the accuracy of the separation techniques has been established to the extent of producing more females with heavier and electropositive and more males with the lighter and electronegative spermatozoa fractions. However, the pregnancy rate slopes downward as the positive electropotential and density of the spermatozoa are successively increased.

Animals↗