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Biomedical subjects

M A King

Publications and source records attributed to M A King.

At least 19 recordsLinked to original sources
PubMed1995

A method for labeling embryonic rat medial septal region projection neurons, in vitro, using fluorescent tracers.

A retrograde labeling method is described in which rat embryonic (E18, E21) and postnatal (P1) medial septal neurons were labeled with succinyl wheat germ agglutin-fluorescein, fluorescent green microspheres, or 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate (Dil) following in vitro hippocampal injections. The brains were removed and immediately immersed in oxygenated Tyrode solution. Dye was pressure injected into the hippocampus bilaterally. After incubating the brain in oxygenated Tyrode, the medial septal region was removed. The neurons were dissociated and cultured at medium density in 35 mm dishes with a hole in the bottom covered by a coverslip with a grid. The neurons were observed with a low light system, and cell counts were made at 5, 24, and 48 h. Labeled and unlabeled neurons showed considerable neurite outgrowth and acetylcholinesterase activity in culture. Highly reproducible labeling was obtained, with Dil giving the best results. Dil labeled the neurons in vitro, was retained during culture for 1 week, and was compatible with cell survival.

Acetylcholinesterase↗
PubMed1992

Chronic ethanol consumption reduces the neurotrophic activity in rat hippocampus.

The effect of chronic ethanol treatment (CET) for 21-26 weeks on the neurotrophic activity contained in the rat hippocampus (HPC) was determined with a bioassay in cultures of dissociated dorsal root ganglion cells (DRG) obtained from E7-8 chick embryos. Extracts of the HPC from CET or pair-fed control rats were used as experimental media, and neuronal survival and neurite-outgrowth of DRG cultures were determined. Both neuronal survival (-25%) and neurite-outgrowth (-50%) were reduced in the presence of HPC extracts from CET rats relative to controls. These data suggest that CET reduces the neurotrophic content of the HPC which may result in damage to septohippocampal neurons.

Animals↗
PubMed1992

Severe botulism after eating home-preserved asparagus.

OBJECTIVE: To present a case of adult botulism acquired in Queensland. CLINICAL FEATURES: After eating home-preserved asparagus, a 33-year-old man presented with internal and external ophthalmoplegia, bilateral facial nerve palsies, and descending muscle weakness culminating in a sudden respiratory arrest. Electrophysiological testing demonstrated normal nerve conduction velocities and an incremental response of evoked motor potentials on repetitive stimulation, confirming the clinical diagnosis of botulism. INTERVENTION AND OUTCOME: Treatment with trivalent antitoxin, oral treatment with vancomycin and supportive mechanical ventilation for four weeks resulted in complete clinical recovery. Plasmapheresis was also used but its contribution to the patient's improvement is dubious. CONCLUSIONS: Although botulism is rare in Australia, clinicians should be aware of the clinical presentation and the rapidity of confirmation of the diagnosis by electrophysiological testing. Patients should be nursed in an intensive care setting. Regular testing of vital capacity should be performed to determine the need for mechanical ventilation.

Adult↗
PubMed1992

Quantitative single photon emission tomography: verification for sources in an elliptical water phantom.

Accurate absorbed dose calculations are important for a proper dose planning in internal radionuclide therapy. The activity distribution must be measured and the target volume defined. This can be done with single photon emission tomography (SPET) if proper attenuation and scatter correction are employed. This study investigated the calculation of the activity and the volume of different spherical sources. These two parameters are essential for a proper dose calculation. The scatter and attenuation correction method is based on spatially variant scatter functions and density maps. The volume calculation method is based on obtaining a threshold from a grey-level histogram. Both point sources and spheres of different diameters containing technetium-99m were placed in different locations in an elliptical water phantom and imaged by SPET. The activity and the volume of the spheres were calculated from the SPET images and compared with known activities. Results show a quantification of activity within 10% for most of the sources. Important influences on the quantification are (a) the presence of artefacts due to improper reconstruction and (b) the finite spatial resolution which affects the total number of counts within the determined volume.

Humans↗
PubMed1992

Monitoring circulating B cells in patients with multiple myeloma at diagnosis or in plateau phase: how prevalent is light chain isotype suppression?

Peripheral blood lymphocytes from 25 patients with multiple myeloma at diagnosis or in plateau phase, and from 18 healthy subjects, were analysed for the surface expression of CD19 and immunoglobulin (Ig) light chain isotypes by dual parameter flow cytometry. The aim was to test for the existence of light chain isotype suppression (LCIS). LCIS is a hypothetical suppressor mechanism which supposedly operates in myeloma patients with stable disease, causing a drop in the number of circulating B cells bearing the same Ig light chain isotype as the myeloma paraprotein. Our experiments emphasized that the use of a non-Ig, pan-B cell marker, combined with dual antigen analysis, is necessary to distinguish Ig on B cells form (cytophilic) Ig on some non-B cells. We found good correlation between results obtained using polyclonal versus monoclonal anti-light chain antibodies, and washed blood versus peripheral blood mononuclear cells. There was no evidence of an abnormal ratio of CD19+, K+ to CD19+, lambda + cells in any of the patients. Thus, these patients did not manifest LCIS, and these experiments raise doubts about the existence of this phenomenon. The results also illustrate the problem that may arise in the interpretation of one parameter flow cytometry.

Antigens, CD↗
PubMed1992

Clinical experience and physiologic results with an implantable intratracheal oxygen catheter.

Ten patients with chronic lung disease received an implanted ITOC. Seven patients continue to use their catheters after a mean period of 14.75 months. Four catheters were removed, 2 at 1 month, 1 after 10 months and 1 after 13 months. One patient requested a second catheter. Three patients experienced mucus plug formation; this was transient in two patients, but led to removal of the catheter in the third. To determine the degree of oxygen-saving afforded by the ITOC, SaO2 was measured at rest and during exercise for eight of the ten subjects using a double-blind technique. The calculated oxygen savings were around 40 percent both at rest and during exercise. The ITOCs were well received by the majority of our patients and were shown to produce a useful saving of oxygen which is of benefit to patients using portable systems and those who require high oxygen flow rates.

Adult↗
PubMed1992

A dual-photopeak window method for scatter correction.

The imaging of scattered photons degrades contrast and is a major source of error in the quantitation of activity. It was hypothesized that, if the photopeak was divided into two nonoverlapping energy windows, a regression relation could be obtained between the ratio of counts within these windows and the scatter fraction for counts within the total region. This idea was tested by acquiring dual photopeak window acquisitions of a 99mTc point source in an elliptical attenuator, and at the same locations in air. From these, a regression between the scatter fraction and window ratio was determined. When this regression was applied to estimate the scatter distribution for acquisitions in both uniform and nonuniform elliptical attenuators, the residual scatter fraction was reduced approximately ten-fold and the estimated scatter line spread functions matched very closely the tails of the total line spread functions. In SPECT acquisitions, dual-photopeak window scatter correction was observed to significantly increase the contrast of "cold" spheres, improve the accuracy of estimating activity at the center of "hot" spheres, and return the three-dimensional modulation transfer function for point sources in an elliptical attenuator to near their in-air shape.

Gamma Cameras↗
PubMed1992

Inter-machine variability in the stability of continuous positive airway pressure.

Two studies were performed to investigate the differences in pressure stability performance of the continuous positive airway pressure (CPAP) machines used by our patients. The variations of mask pressures during each respiratory cycle were measured during overnight studies of two groups of patients with obstructive sleep apnoea, who were using either a Sleep-Easy III CPAP machine or a Si-Plan CPAP unit. The patients were well-matched for age, weight and neck circumference. The group using the Si-Plan unit had more constant mask pressures and were using lower CPAP pressures (mean 10.6 cmH2O) than those using the Sleep-Easy III machine (mean 13.8 cmH2O) (p less than 0.02). The pressure stability performance of five CPAP machines used by our patients was also compared using standardized simulated patient breaths produced by a negative pressure cuirass pump. There were large differences between the machines in ability to maintain a constant pressure. Using a tidal volume of 0.5 l and peak flow rates of between 20-40 l.min-1 the pressure variation ranged from 0-67% of the minimum inspiratory pressure. The maintenance of a constant pressure during inspiration and expiration lowers the mean pressure required to eliminate obstructive sleep apnoeas and reduces the likelihood of pressure related side-effects.

Adult↗
PubMed1992

Bremsstrahlung imaging using the gamma camera: factors affecting attenuation.

Quantitative imaging of bremsstrahlung from pure beta emitters is proposed as a means for in vivo management of antibody therapy. The method involves the use of high-energy collimation, an empirically selected broad photon energy window to enhance detector sensitivity, and a Wiener restoration filter to compensate for system blur. The measured and filtered data were obtained for an idealized scattering medium and isolated spherical sources. An effective linear attenuation coefficient of about 0.13 cm-1 was determined from the raw image data of 32P. A coefficient of 0.14 cm-1 was determined after the images were restored using the Wiener filter. The measured attenuation was not significantly dependent on the size of the region of interest or the size of the source. Its variation was within the experimental error of measurement (+/- 5%). The measured sensitivity (6 x 10(-6) cps/Bq) was sufficient for imaging therapy doses of 32P or 90Y.

Filtration↗
PubMed1991

Magnetic resonance imaging detection of early experimental periostitis. Comparison of magnetic resonance imaging, computed tomography, and plain radiography with histopathologic correlation.

This study characterizes the appearance of periosteal reaction by magnetic resonance imaging (MRI), and evaluates the efficacy of MRI versus computed tomography (CT), and plain film radiography (PF) in detecting early, experimentally induced periostitis. Acute Staphylococcus aureus osteomyelitis was induced in 30 legs of 20 New Zealand white rabbits. The rabbits were then imaged with MR, contrast-unenhanced CT, and PF 4 days after infection. Histologically, periosteal elevation was present in 27 cases. Periosteal ossification was seen in 23 cases, and cellular reaction without ossification in 4 cases. Periosteal reaction was demonstrated by PF in 21 (78%) and by CT in 20 (74%) cases. Evidence of periostitis was seen by MR in all 27% (100%) cases. MR resulted in two false-positive diagnoses. Multiple concentric, alternating high and low signal arcs demonstrated by MR in 19 (70%) cases represented periosteal ossification surrounded by fibrous or granulation tissue. These findings demonstrate the ability of MR to detect periostitis despite the absence of periosteal ossification. MR was more sensitive than CT (P less than .05) or PF (P less than .05) in the detection of experimentally induced periostitis.

Acute Disease↗
PubMed1991

Status epilepticus.

Status epilepticus, especially the convulsive type, is a medical emergency. Initial treatments include clearing the airway and giving diazepam intravenously (preferably) or rectally. Clonazepam is equally effective. A loading dose of phenytoin should be given to maintain seizure control.

Humans↗
PubMed1990

High-risk STD/HIV behavior among college students.

The current sexually transmitted disease (STD) epidemic in adolescents has led to concern about the potential for spread of the human immunodeficiency virus (HIV). In 1988, a total of 5514 students in first-year community college and university classrooms across Canada were surveyed to assess STD/HIV-related knowledge, attitudes, and risk behavior. The students' mean age was 19.7 years; the male-to-female ratio was 1:1.4. Students knew more about HIV/acquired immunodeficiency syndrome than other STDs. Of the 74.3% of the men and 68.9% of the women who were coitally active, 14.3% of the men and 18.6% of the women had participated in anal intercourse and 5.5% reported a previous STD. Only 24.8% of the men and 15.6% of the women always used a condom during sexual intercourse. Among the 21.3% of the men and 8.6% of the women with 10 or more partners, regular condom use was reported in only 21% and 7.5%, respectively. In this subgroup, anal intercourse was practiced by 26.9% of the men and 34.8% of the women, and previous STD was reported by 10.6% and 24.2%, respectively. Factors associated with not using a condom included number of sexual partners, embarrassment about condom purchase, difficulty discussing condom use with a partner, use of oral contraceptives, insufficient knowledge of HIV/STDs, and the belief that condoms interfere with sexual pleasure. These factors are potentially amenable to change. Effective, behaviorally focused educational programs are needed to improve condom use and reduce STD/HIV risk.

Adolescent↗
PubMed1990

Lyme disease: a seasonal hazard.

Cutaneous markers are usually the first signs of Lyme disease, a multisystem infection that affected about 7,000 people last year. This article reviews its clinical features, diagnosis, and treatment.

Anti-Bacterial Agents↗
PubMed1989

Biocytin: a versatile anterograde neuroanatomical tract-tracing alternative.

Biocytin, a naturally occurring low molecular weight analog of biotin, was evaluated as a neuroanatomical tract-tracing marker in the adult rat brain. Since it retains high-affinity binding to avidin, biocytin can be labelled with avidinylated visualization reagents. Iontophoretic or pressure injections resulted in filling of cell bodies and dendrites around the injection site and their efferent axonal processes and boutons. Retrogradely labelled neurons were occasionally observed at a distance but only with large injections. Anterograde tracing with biocytin is successful even in animals that are quite old, in contrast to lectins and HRP conjugates, and offers advantages in delivery, tissue processing, selection of light and/or electron microscopic labels, time to obtain results, and cost over many conventional tracers.

Alkaline Phosphatase↗