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Biomedical subjects

R Pamphlett

Publications and source records attributed to R Pamphlett.

At least 19 recordsLinked to original sources
PubMed2006

Ubiquitin-positive inclusions and progression of pathology in frontotemporal dementia and motor neurone disease identifies a group with mainly early pathology.

Frontotemporal lobar degeneration (FTLD) with tau-negative, ubiquitin-positive inclusions has been a topic of major interest in recent years, with this group now accounting for the majority of tau-negative cases of frontotemporal degeneration. The severity of neurodegeneration in FTLD is dependent on the stage of disease and is substantial even in the earliest stages. Elucidating the pathogenesis of FTLD requires evaluation of changes during the earliest possible stage of disease. However, the long survival of most frontotemporal dementia cases means that cases with early neuropathology are not frequently encountered. Cases of FTLD with the shortest survival are those with coexisting motor neurone disease (FTLD + MND), making these the ideal group for studying early FTLD pathology. It is not clear, however, what the pathological contribution of MND is in these cases. This study evaluates the pathology of 20 cases of FTLD (11 with no clinical signs of MND and nine with FTLD + MND) as well as 10 cases of MND without dementia. Our findings indicate that the deposition of ubiquitin does not play a key role in the neurodegenerative process in FTLD, and that the severity of neurodegeneration in FTLD is similar in cases with and without clinical MND.

Aged↗
PubMed2005

Denaturing high performance liquid chromatography: high throughput mutation screening in familial hypertrophic cardiomyopathy and SNP genotyping in motor neurone disease.

AIMS: To evaluate the usefulness of denaturing high performance liquid chromatography (DHPLC) as a high throughput tool in: (1) DNA mutation detection in familial hypertrophic cardiomyopathy (FHC), and (2) single nucleotide polymorphism (SNP) discovery and validation in sporadic motor neurone disease (MND). METHODS: The coding sequence and intron-exon boundaries of the cardiac beta myosin heavy chain gene (MYH7) were screened by DHPLC for mutation identification in 150 unrelated patients diagnosed with FHC. One hundred and forty patients with sporadic MND were genotyped for the A67T SNP in the poliovirus receptor gene. All DHPLC positive signals were confirmed by conventional methods. RESULTS: Mutation screening of MYH7 covered 10 kb with a total of 5700 amplicons, and more than 6750 DHPLC injections were completed within 35 days. The causative mutation was identified in 14% of FHC cases, including seven novel missense mutations (L227V, E328G, K351E, V411I, M435T, E894G, and E927K). Genotyping of the A67T SNP was performed at two different temperatures both in MND cases and 280 controls. This coding SNP was found more frequently in MND cases (13.6%) than in controls (6.8%). Furthermore, 19 and two SNPs were identified in MYH7 and the poliovirus receptor gene, respectively, during DHPLC screening. CONCLUSIONS: DHPLC is a high throughput, sensitive, specific, and robust platform for the detection of DNA variants, such as disease causing mutations or SNPs. It enables rapid and accurate screening of large genomic regions.

Algorithms↗
PubMed2002

Consensus neuropathological diagnosis of common dementia syndromes: testing and standardising the use of multiple diagnostic criteria.

The aim of this study was to assess the variation between neuropathologists in the diagnosis of common dementia syndromes when multiple published protocols are applied. Fourteen out of 18 Australian neuropathologists participated in diagnosing 20 cases (16 cases of dementia, 4 age-matched controls) using consensus diagnostic methods. Diagnostic criteria, clinical synopses and slides from multiple brain regions were sent to participants who were asked for case diagnoses. Diagnostic sensitivity, specificity, predictive value, accuracy and variability were determined using percentage agreement and kappa statistics. Using CERAD criteria, there was a high inter-rater agreement for cases with probable and definite Alzheimer's disease but low agreement for cases with possible Alzheimer's disease. Braak staging and the application of criteria for dementia with Lewy bodies also resulted in high inter-rater agreement. There was poor agreement for the diagnosis of frontotemporal dementia and for identifying small vessel disease. Participants rarely diagnosed more than one disease in any case. To improve efficiency when applying multiple diagnostic criteria, several simplifications were proposed and tested on 5 of the original 20 cases. Inter-rater reliability for the diagnosis of Alzheimer's disease and dementia with Lewy bodies significantly improved. Further development of simple and accurate methods to identify small vessel lesions and diagnose frontotemporal dementia is warranted.

Alzheimer Disease↗
PubMed2001

Severe infantile axonal neuropathy with respiratory failure.

We describe 5 infants (4 male, 1 female) with a severe intractable form of motor-sensory axonal neuropathy. All became ventilator-dependent, 4 have since died and 1 remains static. Diaphragmatic paralysis was an early feature with generalized neuropathy evolving rapidly. Nerve conduction studies and biopsies were consistent with axonal disease. This disorder could be a new condition or part of the spectrum of inherited neuropathies of the axonal degenerative type. It may be that there is a "switching-off" in the infant's Schwann cell-axonal interactions in utero or in the early postnatal period, resulting in severe progressive deterioration and then a static period without recovery.

Biopsy↗
PubMed2001

Blood levels of toxic and essential metals in motor neuron disease.

Toxic and essential metals have been implicated in the pathogenesis of sporadic motor neuron disease (SMND), but attempts to measure blood levels of these metals have led to contradictory results. We, therefore, measured blood levels of various metals using paired SMND/controls. In 20 subjects with SMND (15 males, five females, mean age 56.8 years) and 20 partner controls (15 females, five males, mean age 55.0 years) cadmium, lead, mercury, copper, zinc and selenium levels were measured in blood, plasma and red cells with inductively coupled plasma mass spectrometry and manganese levels with atomic absorption spectrophotometry. Results were analysed using non-parametric tests. Hypo-osmotic red blood cellfragility was estimated in six SMND/control pairs to see if hemolysis could account for increased metal levels. The plasma cadmium level was significantly raised in SMND cases (P = 0.005), but with considerable overlap between SMND and controls. No other metal levels were significantly different, though plasma lead in SMND had a tendency to be higher than controls. No difference in red cell fragility was found between groups. In conclusion, plasma levels of cadmium were raised in this SMND group, but the biological significance of this is uncertain. The measurement of metals in the blood of SMND cases seems unwarrranted for routine diagnostic testing.

Adult↗
PubMed2000

Tissue uptake of bismuth from shotgun pellets.

Shotgun pellets containing bismuth have been suggested to be less environmentally toxic than those containing other metals. We sought to find if bismuth from shotgun pellets embedded within an animal enters the tissues of that animal. Five bismuth-containing shotgun pellets were placed intraperitoneally into adult mice. Four or 9 weeks later the tissue distribution of bismuth was examined histologically using silver lactate autometallography. Bismuth was seen in the nervous system of the mice, either in cells with processes outside the nervous system or in cells not protected by the blood-brain barrier. Bismuth was also seen in the kidney, liver, spleen, and lung. The amount of bismuth within tissues varied widely between animals at both time intervals. Bismuth from shotgun pellets enters the tissues of mice, with some mice taking up more bismuth than others. Some animals wounded with bismuth pellets are therefore likely to accumulate large amounts of potentially toxic bismuth in their tissues.

Animals↗
PubMed2000

Bismuth autometallography: protocol, specificity, and differentiation.

We provide a detailed protocol of the autometallographic bismuth technique and evaluate the specificity of the technique. We show by the multi-element technique "proton-induced X-ray microanalysis" (PIXE) that the autometallographic grains contain silver, bismuth, and sulfur, proving that autometallography can be used for specific tracing of bismuth bound as bismuth sulfide clusters in tissue sections from Bi-exposed animals or humans. In sections from animals exposed concurrently to selenium and bismuth, the autometallographic grains also contain selenium. This demonstrates that, if present in excess in the organisms, selenium will bind to exogenous bismuth, creating bismuth selenide clusters. As a further possible control for specificity and as a tool for differentiating among autometallographically detectable metals in sections containing more than one, we describe how bismuth sulfide clusters can be removed from Epon-embedded tissue sections by potassium cyanide.

Animals↗
PubMed1999

Vertebral artery compression resulting from head movement: a possible cause of the sudden infant death syndrome.

OBJECTIVE: Vertebral artery compression causing brainstem ischemia has been suggested to underlie the sudden infant death syndrome. Vertebral artery distortion from neck movements has been demonstrated by angiography in infants, but direct evidence for arterial compression is lacking. In an attempt to demonstrate vertebral artery compression from head movement, we examined at postmortem the vertebral arteries of infants after neck extension or rotation. METHODS: The C1-C7 spinal column, together with a 2-cm rim of skull base, was removed from 20 infants dying from sudden infant death syndrome or other causes. In 5 cases the neck was extended, in 9 cases it was rotated 90 degrees to the right, and in 6 cases the neck was held in the neutral position. The neck was maintained in these positions during formalin fixation, and serial sections of selected blocks were examined microscopically. RESULTS: In 3 of 5 extended cases, bilateral vertebral artery compression was seen between the occipital bone and C1. In 3 of 9 rotated cases, the left vertebral artery was compressed adjacent to C1 before the artery entered the transverse foramen. No vertebral artery compression was seen in the necks held in the neutral position. CONCLUSIONS: The vertebral arteries of some infants can be compressed by neck movement. This could induce lethal brainstem ischemia in infants with inadequate collateral blood flow or with poor compensatory arterial dilatation, and may underlie some cases of sudden infant death syndrome.

Brain Ischemia↗
PubMed1998

Oxidative damage to nucleic acids in motor neurons containing mercury.

Heavy metals have been implicated in the pathogenesis of sporadic motor neuron disease (MND). We were interested to see if inorganic mercury leads to oxidative damage in motor neurons since free radicals have been suspected to be involved in MND, so a method to examine oxidatively-damaged DNA in situ was used to examine individual motor neurons. Mice were exposed to 500 microg/m3 of mercury vapour for 2 h. Two, five, or ten days later sections from formalin-fixed, paraffin-embedded blocks of cervical spinal cord were incubated in avidin-FITC. Sections were examined under a fluorescence microscope and photographs of pairs of mercury-exposed and control spinal motor neurons were analysed semi-quantitatively for the amount of fluorescence using an image analysis program. Avidin fluorescence was seen in the perikaryon of both control and mercury-exposed motor neurons. In each control-mercury pair (four pairs per group) significantly more perikaryal fluorescence was seen in mercury-containing than in control motor neurons (Mann-Whitney testing). Mercury within the motor neuron perikaryon therefore leads to increased avidin binding, an indicator of oxidative damage to DNA. The findings support the hypothesis that an environmental toxin such as mercury can enter and damage motor neurons.

Animals↗
PubMed1998

Mercury in human spinal motor neurons.

Inorganic mercury has been proposed as a neurotoxin that could cause sporadic motor neuron disease (SMND). We were therefore interested to see if mercury could be detected in the upper and lower motor neurons of SMND patients, and if mercury accumulated within motor neurons during life. Paraffin sections of formalin-fixed spinal cord (22 control adults, 20 SMND adults, 25 infants) and frontal primary motor cortex (9 control adults, 18 SMND adults, 20 infants) were stained with silver nitrate autometallography to detect ionic mercury. Mercury was found in the spinal motor neurons of 36% of adult control cases and 45% of adult SMND cases, with no significant difference between groups. No mercury was seen in infant spinal motor neurons, or in any adult or infant corticomotoneurons. In conclusion, many humans appear to accumulate mercury in their spinal motor neurons by the time they are adults, but mercury does not appear to play a major role in the loss of upper or lower motor neurons in SMND.

Adult↗
PubMed1998

Shrinkage of motor axons following systemic exposure to inorganic mercury.

Systemically-administered inorganic mercury localizes to motor neurons, but it is not known if mercury injures these neurons. We therefore looked for signs of damage to the motor and sensory neurons of mice that had been exposed to inorganic mercury. Young adult mice were injected intraperitoneally with either 1 or 2 microg/g of mercuric chloride and perfused 1 or 30 weeks later. The cellular distribution of mercury in the spinal cord was examined with silver nitrate autometallography. The numbers and sizes of myelinated axons in the L5 anterior and posterior roots were quantitated using an image analysis program. Mercury was found throughout the cytoplasm of motor neuron cell bodies after 1 week and in paranuclear aggregations after 30 weeks. Thirty weeks after exposure to either 1 or 2 microg/g of mercury, fewer large myelinated axons were seen in mercury-injected groups than in controls, though total numbers of myelinated axons did not differ between groups. A slight increase in numbers of small axons was seen in the posterior roots of mice exposed to 1 microg/g of mercury. In conclusion, inorganic mercury remains within mouse neurons for prolonged periods and causes a reduction in the size of myelinated axons in the anterior root and to a lesser extent the posterior spinal root. Inorganic mercury within motor neurons therefore appears to behave as a slowly-acting neurotoxin that shrinks motor axons.

Animals↗
PubMed1998

Neuroradiological features of six kindreds with MELAS tRNA(Leu) A2343G point mutation: implications for pathogenesis.

OBJECTIVE: To determine the neuroradiological abnormalities associated with subjects carrying the mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS) tRNA(Leu)(UUR) A3243G point mutation METHODS: Mitochondrial genetic analysis was performed on 24 subjects from six kindreds with the MELAS tRNA(Leu)(UUR) A3243G point mutation. Cerebral CT and MRI were performed on 24 patients and 15 patients respectively. Previous neuroradiological investigations including cerebral CT from four deceased members of the families were also reviewed. Histological examination of postmortem specimens of two patients within the kindreds was performed. RESULTS: The commonest radiological finding was basal ganglia calcification. Other abnormalities included focal lesions and cerebellar and cerebral atrophy. Basal ganglia calcification was progressive, symmetric, and asymptomatic. Histologically, basal ganglia calcification in one patient was found to be in the pericapillary regions of the globus pallidus, with no neuronal involvement. Focal lesions most commonly involved the grey matter of the parietal and occipital lobes and cerebellum. Histopathological examination suggested that these were due to cellular rather than vascular dysfunction. Enlargement of the fourth ventricle was the first sign of cerebellar atrophy. Cerebral and cerebellar atrophy were only present with severe disease. CONCLUSIONS: These radiological findings, when considered in the context of the clinical and pathological findings, seem to reflect two major disease processes: an intermittent abrupt loss of function associated with cell injury from which there is at least partial recovery and a slowly progressive degenerative process causing basal ganglia calcification, and cerebral and cerebellar atrophy. The clinical and radiological features resulting from these processes are distinctive and provide insight into the consequences of mitochondrial dysfunction on the brain.

Adolescent↗
PubMed1998

Entry of low doses of mercury vapor into the nervous system.

Inorganic mercury remains within neurons indefinitely and has been implicated in some human neurodegenerative diseases. We were interested in finding the lowest dose of mercury vapor that resulted in mercury deposition in neurons. Female BALB/c mice were exposed to 25 micrograms mercury/m3 for 2-20 hr or 500 micrograms mercury/m3 for 5-240 min. To see if female mouse neurons were more susceptible to mercury vapor than male neurons, male and female BALB/c mice were exposed to 50 micrograms mercury/m3 for 4-24 hr. Mice were perfused with formalin 1-30 weeks after exposure and paraffin sections of brain, spinal cord and kidney were stained for mercury with silver nitrate autometallography. On light microscopy, spinal motor neurons contained mercury granules after 12 hr exposure to 25 micrograms mercury/m3 or after 30 min exposure to 500 micrograms mercury/m3. Mercury remained in motor neurons 30 weeks after exposure. In female mice, mercury was seen in motor neurons at half the exposure times of male mice. In conclusion, low doses of mercury vapor, well within WHO guidelines for safe human occupational exposure, enter and remain within motor neurons of mice.

Administration, Inhalation↗
PubMed1997

Increased c-fos expression in the brain during experimental murine cerebral malaria: possible association with neurologic complications.

Cerebral expression of c-fos protein was studied by immunocytochemistry in murine cerebral malaria (CM) and malaria without cerebral involvement (non-CM). c-fos expression, low in the brains of uninfected mice, increased in frequency, intensity, and distribution during the course of fatal CM (e.g., a 70-fold increase on day 7 after inoculation). These changes paralleled the timing and degree of the neurologic complications and histopathologic changes. Only a slight increase in c-fos expression was detectable in non-CM mice on day 7 after inoculation. Dexamethasone treatment (days 0 and 1 after inoculation) of the CM mice largely prevented the increased cerebral c-fos expression, histopathologic changes, cerebral complications, and death. Increased c-fos expression may indicate the specific neuronal pathways activated by the immunopathologic process of fatal murine CM and could be associated with the behavioral changes and neurologic complications in this model.

Animals↗
PubMed1996

Phrenic nerve maturation in the sudden infant death syndrome.

It has been suggested that delayed development in either the peripheral or central nervous system could underlie the sudden infant death syndrome (SIDS). We studied the phrenic nerve in an attempt to find if maturation in this nerve was delayed in SIDS, and to see if fiber size differences could explain the paucity of type I muscle fibers described in SIDS diaphragms. Samples of phrenic nerves were taken at post mortem from 11 SIDS and 10 control infants. Myelinated fibers were quantitated in 1-micron silver-stained resin sections using a semi-automatic image analysis system. The numbers and sizes of all myelinated fibers in the right phrenic nerve were compared between SIDS and control groups. The proportion of small (less than 6-microns diameter) phrenic nerve fibers was similar in SIDS (53.1%, SD 12.8%) and control (53.6%, SD 14.0%) cases. The proportion of small fibers decreased with increasing age at an equivalent rate in both SIDS and control groups. Total numbers of myelinated fibers were similar in the right phrenic nerves of SIDS (3429, SD 440) and control (3457, SD 507) infants, but varied widely between cases and were not correlated with age. Maturation of the phrenic nerve, as judged by increasing size of myelinated fibers, is therefore similar in SIDS and control infants. This argues against a widespread development delay in SIDS. No changes in phrenic nerve fiber sizes were found to account for the finding of fewer type I fibers in SIDS diaphragms.

Age Distribution↗