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Biomedical subjects

M Johnson

Publications and source records attributed to M Johnson.

At least 37 records · Page 2Linked to original sources

Biosonar performance of foraging beaked whales (Mesoplodon densirostris).

Toothed whales (Cetacea, odontoceti) emit sound pulses to probe their surroundings by active echolocation. Non-invasive, acoustic Dtags were placed on deep-diving Blainville's beaked whales (Mesoplodon densirostris) to record their ultrasonic clicks and the returning echoes from prey items, providing a unique view on how a whale operates its biosonar during foraging in the wild. The process of echolocation during prey capture in this species can be divided into search, approach and terminal phases, as in echolocating bats. The approach phase, defined by the onset of detectable echoes recorded on the tag for click sequences terminated by a buzz, has interclick intervals (ICI) of 300-400 ms. These ICIs are more than a magnitude longer than the decreasing two-way travel time to the targets, showing that ICIs are not given by the two-way-travel times plus a fixed, short lag time. During the approach phase, the received echo energy increases by 10.4(+/-2) dB when the target range is halved, demonstrating that the whales do not employ range-compensating gain control of the transmitter, as has been implicated for some bats and dolphins. The terminal/buzz phase with ICIs of around 10 ms is initiated when one or more targets are within approximately a body length of the whale (2-5 m), so that strong echo returns in the approach phase are traded for rapid updates in the terminal phase. It is suggested that stable ICIs in the search and approach phases facilitate auditory scene analysis in a complex multi-target environment, and that a concomitant low click rate allows the whales to maintain high sound pressure outputs for prey detection and discrimination with a pneumatically driven, bi-modal sound generator.

Acoustics↗

Aerated rock filters for enhanced nitrogen and faecal coliform removal from facultative waste stabilization pond effluents.

Facultative waste stabilization ponds in the UK, loaded at 80 kg BOD/ha day, produce effluents which comply with the European Urban Waste Water Treatment Directive (i.e., < or = 25 mg filtered BOD/l and < or = 150 mg SS/l). However, the Environment Agency of England and Wales typically requires a higher effluent quality of < or = 40 mg/l unfiltered BOD and < or = 60 mg/l SS, both on a 95-percentile basis. An ammonium-nitrogen requirement might also be applied. Traditionally, maturation ponds and reedbeds have been used to upgrade facultative pond effluents, requiring large land areas. This paper describes and compares aerated and unaerated rock filter performance for BOD, SS, nitrogen and faecal coliform removals, and highlights the land-saving opportunities as maturation ponds and reedbeds become redundant.

Aerobiosis↗

Outcome of patients with HIV-related germ cell tumours: a case-control study.

Testicular germ cell tumour (GCT) is not an AIDS-defining illness despite an increased incidence in men with HIV infection. We performed a matched case-control study comparing outcomes in HIV-positive men and the general population with GCT, using three age and stage matched controls for each case. There was no difference in the 5-year GCT-free survival between cases and controls. However, overall survival was significantly decreased in the cases (log rank P=0.03). HIV was responsible for 70% of this mortality. The relapse-free survival for stage I patients treated with orchidectomy and surveillance was not affected by HIV status (log rank P=0.68). There was no difference in disease free survival in patients with metastatic disease (log rank P=0.78). The overall survival has not improved since the introduction of highly active antiretroviral therapy (log rank P=0.4). Thus, HIV-related GCT is not more aggressive than GCT in the general population.

Adult↗

What is the daily practice of mechanical ventilation in pediatric intensive care units? A multicenter study.

OBJECTIVE: To describe the daily practice of mechanical ventilation (MV), and secondarily, its outcome in pediatric intensive care units (PICUs). DESIGN: Prospective cohort of infants and children who received MV for at least 12 h. SETTING: Thirty-six medical surgical PICUs. PATIENTS: All consecutive patients admitted to the PICUs during 2-month period. MEASUREMENTS AND MAIN RESULTS: Of the 1893 patients admitted, 659 (35%) received MV for a median time of 4 days (25th percentile, 75%: 2, 6). Median of age was 13 months (25th percentile, 75%: 5, 48). Common indications for MV were acute respiratory failure (ARF) in 72% of the patients, altered mental status in 14% of the patients, and ARF on chronic pulmonary disease in 10% of the patients. Median length of stay in the PICUs was 8 days (25th percentile, 75%: 5, 13). Overall mortality rate in the PICUs was 15% (confidence interval 95%: 13-18) for the entire population, 50% (95% CI: 25-74) in patients who received MV because of acute respiratory distress syndrome, 24% (95% CI: 16-35) in patients who received MV for altered mental status and 16% (95% CI: 9-29) in patients who received MV for ARF on chronic pulmonary disease. CONCLUSION: One in every 3 patients admitted to the PICUs requires ventilatory support. The ARF was the most common reason for MV, and survival of unselected infants and children receiving MV for more than 12 h was 85%.

Child, Preschool↗

Design and application of a novel brain slice system that permits independent electrophysiological recordings from multiple slices.

We describe a novel brain slice system 'SliceMaster' that allows electrophysiological recordings from eight brain slices independently. The system consists of two autonomous units each supporting four modular brain slice chambers enabling high signal-to-noise ratio recordings, each chamber has one stimulation electrode, one recording electrode, a twin camera system and a solution application system. The positioning of both electrodes and cameras are controlled from a remote user console. The software both acquires and performs on-line analysis of the data. We have demonstrated utility of this system in obtaining recordings of spontaneous firing activity and evoked synaptic activity from mouse hippocampal slices, with reduced variability within and between experiments. Furthermore, we show recordings of population spikes from the perirhinal cortex, indicating applicability of this system for further brain regions. In addition, stable recordings could be maintained until recording was terminated after 3 h, permitting investigation of the induction and maintenance of synaptic plasticity. Recordings of spontaneous and synaptic activity, and effects of pharmacological and electrophysiological manipulation, were consistent with reports using conventional methods. However, the described system permits concurrent and independent recordings from eight brain slices, thus improving throughput, statistical design, and reducing animal use.

Action Potentials↗

Selective changes in nicotinic acetylcholine receptor subtypes related to tobacco smoking: an immunohistochemical study.

Increases in neuronal nicotinic receptors (nAChRs) in response to nicotine exposure have been reported in cell cultures, rodent brains, and in the brains of human smokers. The present study examines alterations in alpha4 and alpha7 nAChR subunit cellular expression in human hippocampus and entorhinal cortex from normal elderly individuals with known smoking history. There were significant increases in the intensity of alpha4 immunoreactive neuropil, but not the number of cell bodies, in many regions of hippocampus and entorhinal cortex in smokers compared to age-matched non-smokers and ex-smokers. There was also an increase in alpha7 immunoreactive perikarya in the granular cell layer of dentate gyrus in smokers but not other regions examined. There was, in contrast, a significant reduction in alpha7 immunoreactive astrocytes in smokers and ex-smokers compared to non-smokers. These findings suggest exposure to tobacco smoke acutely up-regulates alpha4 receptors in axon terminals and dendrites but not perikarya, whereas tobacco smoking induced down-regulation of alpha7 expression on astrocytes is a long-term effect. As the alpha4 subunit decreases with ageing and degenerative diseases such as Alzheimer's disease, whereas alpha7 increases in astrocytes in Alzheimer's disease, the findings further indicate the therapeutic relevance of nicotinic agonists such as nicotine.

Aged↗

Depletion of normal B cells with rituximab as an adjunct to IL-2 therapy for renal cell carcinoma and melanoma.

BACKGROUND: We postulated that in patients with metastatic renal cell carcinoma (RCC) or melanoma, depletion of normal B cells using the anti-CD20 mAb rituximab before treatment with low-dose interleukin (IL)-2 would improve clinical outcome. PATIENTS AND METHODS: Rituximab (375 mg/m(2)) weekly for 4 weeks. IL-2 [11 (million units) daily] s.c., 4 days a week for weeks 5-8, followed by a 2-week rest (weeks 9 and 10). Patients without disease progression continued on IL-2. Disease re-evaluation was performed after rituximab and after every course of IL-2. RESULTS: Fifteen patients with RCC and six with melanoma were enrolled. One patient had a partial response and seven patients had stable disease. Toxicities were similar to those expected with IL-2 alone, and there were no grade 4 events. Circulating B cells were depleted in all patients. The subsequent low-dose IL-2 increased absolute numbers of natural killer cells, activated CD4(+) and activated CD8(+) T cells. Expanded T cells produced interferon-gamma, but not IL-4. Proliferation of peripheral blood lymphocytes to phytohemagglutinin was diminished following rituximab treatment, suggesting that B cells participate in this response in vitro. CONCLUSIONS: Our results suggest that depletion of circulating B cells with rituximab does not increase the response rate, alter the toxicity profile or change the biological activity in response to low-dose IL-2 in patients with RCC or melanoma.

Adult↗

Inactivation of pathogenic bacteria by cucumber volatiles (E,Z)-2,6-nonadienal and (E)-2-nonenal.

The effects of (E,Z)-2,6-nonadienal (NDE) and (E)-2-nonenal (NE) on Bacillus cereus, Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium were investigated. A suspension of each organism of 6 to 9 log CFU/ml was incubated for 1 h at 37 degrees C in brain heart infusion solution that contained 0 to 500 or 1,000 ppm of NDE or NE. Depending on concentration, exposure to either NDE or NE caused a reduction in CFU of each organism. Treatment with 250 and 500 ppm NDE completely eliminated viable B. cereus and Salmonella Typhimurium cells, respectively. L. monocytogenes was the most resistant to NDE, showing only about a 2-log reduction from exposure to 500 ppm for 1 h. Conversely, this concentration of NDE caused a 5.8-log reduction in E. coli O157:H7 cells. NE was also effective in inactivating organisms listed above. A higher concentration of NE, 1,000 ppm, was required to kill E. coli O157:H7, L. monocytogenes, or Salmonella Typhimurium compared with NDE. In conclusion, both NDE and NE demonstrated an apparent bactericidal activity against these pathogens.

Aldehydes↗

Efficacy trial of an irradiated cattle lungworm vaccine in red deer (Cervus elaphus).

Lungworm (Dictyocaulus sp.) is the parasite of most concern to the New Zealand deer industry. Although lungworm can be controlled by anthelmintics there is an increasing concern over excessive drenching programmes and reliance on chemicals for parasite control. A live irradiated larval vaccine developed for cattle has been available in Europe for the past 40 years but has never been evaluated in red deer in New Zealand. Four groups of red deer and two of cattle were hand reared from birth in parasite-free conditions. The cattle acted as a control group to ensure that the vaccine was still efficacious on arrival in New Zealand. Two groups of deer were vaccinated, and all four groups were challenged with either D. viviparus or deer origin Dictyocaulus, tentatively identified as D. eckerti. The vaccine provided excellent protection to cattle under New Zealand conditions, there was no larval output in the vaccinated cattle and no adults were found in their lungs at necropsy. In red deer, patency was delayed in the vaccinated groups regardless of challenge species and larval output was lower but was not prevented. Adult lungworms were found in the lungs of all deer at necropsy but fewer were recorded in the vaccinated deer. Although Huskvac provided a degree of protection for red deer it was not effective enough to recommend its use.

Animals↗

Seasonality and water quality trends in a maturing recreated reed bed.

The socio-economic and ecological value of wetland ecosystems is widely acknowledged. As a result, considerable efforts are now being made to rehabilitate and in some cases recreate wetlands throughout Europe. An option for the restoration of worked-out peat pits is to establish reed beds. Ham Wall, located in Somerset in the UK, comprises reed bed and a mosaic of other wetland habitats that has been constructed as a wildlife area. Since 1996, water chemistry has been monitored for a 16.5 ha wetland compartment planted with reeds in July 1995. Water is pumped into the reed bed from Ham Wall Rhyne, a drainage ditch supplied with nutrient-rich runoff from the surrounding agricultural land. The principal objectives of the research described in this paper were to investigate differences in the chemistry of water from different locations in the vicinity of the wetland and to evaluate seasonal changes and trends in water quality as the reeds matured. The results obtained provide insight into the biogeochemical functioning of the wetland system.

Conservation of Natural Resources↗

Multicenter study of human immunodeficiency virus-related germ cell tumors.

PURPOSE: Testicular germ cell tumors (GCT) occur at increased frequency in men with human immunodeficiency virus (HIV). This multicenter study addresses the characteristics of these tumors. PATIENTS AND METHODS: Patients with HIV-related GCT were identified from six HIV treatment centers. The incidence was calculated from the center with the most complete linked oncology and HIV databases. RESULTS: Thirty-five patients with HIV-related GCT were identified. The median age at GCT diagnosis was 34 years (range, 27 to 64 years). The median CD4 cell count was 315/mm3 (range, 90 to 960/mm3) at this time. The histologic classification was seminoma in 26 patients (74%) and nonseminomatous GCT in nine patients (26%). Twenty-one patients (60%) had stage I disease and 14 patients had metastatic disease. Overall six patients relapsed, three died from GCT, and seven died from HIV disease, resulting in a 2-year overall survival rate of 81%. HIV-related seminoma occurred more frequently than in the age- and sex-matched HIV-negative population, with a relative risk of 5.4 (95% confidence interval, 3.35 to 8.10); however, nonseminomatous GCT did not occur more frequently, and there was no change in the incidence of GCT since the introduction of highly active antiretroviral therapy. CONCLUSION: Testicular seminoma occurs significantly more frequently in HIV-positive men than in the matched control population. Patients with HIV-related GCTs present and should be treated in a similar manner to those in the HIV-negative population. After a median follow-up of 4.6 years, 9% of the patients died from GCT. Most of the mortality relates to HIV infection.

Adolescent↗

Investigation of mitochondrial function in hereditary spastic paraparesis.

Following the association of hereditary spastic paraparesis (HSP) with mutation in the paraplegin gene (SPG7) and mitochondrial dysfunction, we wished to investigate whether mitochondrial dysfunction might be associated with other forms of HSP. Five cases of HSP caused by mutation in the spastin gene (SPG4) and nine cases with HSP with mutation in the spastin and paraplegin genes excluded (non-SPG4/SPG7), were investigated for mitochondrial dysfunction. Muscle tissue from the HSP groups and a control group was analysed histochemically and spectrophotometrically for mitochondrial dysfunction. A significant decrease in mitochondrial respiratory chain complexes I and IV was demonstrated in the non-SPG4/SPG7 group. No abnormality was detected in the SPG4 group. We therefore conclude that there is evidence for mitochondrial dysfunction in non-SPG4/SPG7 HSP. There is no evidence for mitochondrial dysfunction in the pathogenesis of spastin-related HSP.

ATPases Associated with Diverse Cellular Activitie↗

Effects of repeated anaesthesia on central cholinergic function in the rat cerebral cortex.

BACKGROUND AND OBJECTIVE: General anaesthesia may contribute to postoperative cognitive decline in the elderly. The aim was to determine the effects of repeated pentobarbital anaesthesia throughout life on central cholinergic function in the rat. METHODS: Young Lewis rats were randomly allocated to two groups. The anaesthesia group (n = 15) was anaesthetized with pentobarbital 20 mg kg(-1) intraperitoneally at 6, 8.5, 11, 13.5, 16, 18.5, 21 and 23.5 months of age. The control group (n = 12) was treated identically, apart from the anaesthesia. At 26 months of age, the animals were killed and the brain dissected and stored for analysis. Central cholinergic function in the cortex and hippocampus was assessed by measuring [3H]-epibatidine and [125I]alpha-bungarotoxin binding to nicotinic receptors and choline acetyltransferase (ChAT) activity. RESULTS: Tissue from nine rats in the anaesthesia group and eight in the control group was available for analysis. There was a significant reduction in alpha-bungarotoxin binding in the anaesthetized compared with the control group in the superior cortex (P < 0.0002) and molecular cortex (P < 0.04). There were no significant differences between the groups for epibatidine binding or ChAT. CONCLUSIONS: Repeated anaesthesia in rat reduces central nicotinic cholinergic binding in the cortex. The findings may have implications for postoperative cognitive function studies.

Anesthesia, General↗

Susceptibility of oral bacteria to Melaleuca alternifolia (tea tree) oil in vitro.

The in vitro activity of Melaleuca alternifolia (tea tree) oil against 161 isolates of oral bacteria from 15 genera was determined. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) ranged from 0.003 to 2.0% (v/v). MIC90 values were 1.0% (v/v) for Actinomyces spp., Lactobacillus spp., Streptococcus mitis and Streptococcus sanguis, and 0.1% (v/v) for Prevotella spp. Isolates of Porphyromonas, Prevotella and Veillonella had the lowest MICs and MBCs, and isolates of Streptococcus, Fusobacterium and Lactobacillus had the highest. Time kill studies with Streptococcus mutans and Lactobacillus rhamnosus showed that treatment with > or = 0.5% tea tree oil caused decreases in viability of >3 log colony forming units/ml after only 30 s, and viable organisms were not detected after 5 min. These studies indicate that a range of oral bacteria are susceptible to tea tree oil, suggesting that tea tree oil may be of use in oral healthcare products and in the maintenance of oral hygiene.

Actinomyces↗

Dictyocaulus species: cross infection between cattle and red deer.

AIM: To discover whether cross infection between red deer (Cervus elaphus) and cattle is possible with either a bovine isolate of the cattle lungworm, Dictyocaulus viviparus, or with a cervine isolate of the lungworm, Dictyocaulus eckerti which is thought to be maintained primarily in deer. METHOD: Twelve cattle and 12 red deer were reared parasite-free from birth. At 3-4 months of age, half of each species (n=6) were experimentally infected with D. viviparus and the other half with D. eckerti. The course of infection was monitored for 34 days, after which the animals were slaughtered and the lungs removed to assess levels of infection. RESULTS: Faecal larval counts demonstrated that patent Dictyocaulus infections occurred in all groups. At necropsy, adult worms were found in the lungs in all groups except the cattle that were infected with D. eckerti. The largest numbers of adult worms were found in the red deer infected with D. eckerti. CONCLUSION: It was demonstrated that both cattle and red deer could be infected with either D. viviparus or D. eckerti. However, D. eckerti larvae that originated from deer established more successfully in deer and D. viviparus larvae that originated from cattle established more successfully in cattle.

Journal Article↗

Complete sequencing shows a role for MSX1 in non-syndromic cleft lip and palate.

MSX1 has been proposed as a gene in which mutations may contribute to non-syndromic forms of cleft lip and/or cleft palate. Support for this comes from human linkage and linkage disequilibrium studies, chromosomal deletions resulting in haploinsufficiency, a large family with a stop codon mutation that includes clefting as a phenotype, and the Msx1 phenotype in a knockout mouse. This report describes a population based scan for mutations encompassing the sense and antisense transcribed sequence of MSX1 (two exons, one intron). We compare the completed genomic sequence of MSX1 to the mouse Msx1 sequence to identify non-coding homology regions, and sequence highly conserved elements. The samples studied were drawn from a panethnic collection including people of European, Asian, and native South American ancestry. The gene was sequenced in 917 people and potentially aetiological mutations were identified in 16. These included missense mutations in conserved amino acids and point mutations in conserved regions not identified in any of 500 controls sequenced. Five different missense mutations in seven unrelated subjects with clefting are described. Evolutionary sequence comparisons of all known Msx1 orthologues placed the amino acid substitutions in context. Four rare mutations were found in non-coding regions that are highly conserved and disrupt probable regulatory regions. In addition, a panel of 18 population specific polymorphic variants were identified that will be useful in future haplotype analyses of MSX1. MSX1 mutations are found in 2% of cases of clefting and should be considered for genetic counselling implications, particularly in those families in which autosomal dominant inheritance patterns or dental anomalies appear to be cosegregating with the clefting phenotype.

Amino Acid Sequence↗