Biomedical subjects

John D Pollard

Publications and source records attributed to John D Pollard.

7 recordsLinked to original sources

PubMed2006

Expression of the antioxidant enzyme peroxiredoxin 5 in the human peripheral nervous system.

Peroxiredoxins (PRDXs) belong to a family of peroxidases that are highly expressed in mammalian tissues. Comparatively, little is known about their expression in the nervous system. In this study, we examined in human sural nerve, the expression of PRDX5, the most recently defined peroxiredoxin family member. Immunohistochemical staining of paraffin sections showed that PRDX5 expression was mainly localised to the axon and, to a lesser extent, to the Schwann cells. Immunogold labelling electron microscopy further revealed that PRDX5 is widely distributed in multiple cellular compartments, most importantly in mitochondria but also in axoplasm, Schwann cell cytosol, nucleus, and myelin. A progressive decline in PRDX5 expression with advancing age was identified in human nerves at different ages. The wide distribution of PRDX5 in cellular and sub-cellular structures indicates that it may play important roles in a wide range of tissue components in normal peripheral nerves.

Adolescent↗

PubMed2005

Isolated hypoglycorrachia: leptomeningeal carcinomatosis causing subacute confusion.

We report a 76-year-old caucasian man who presented with a 3-week history of progressive confusion. His past medical history included a left nephro-uretectomy for poorly differentiated transitional cell carcinoma 9 years previously. Besides his confusion, his clinical and neurological examination was unremarkable. Extensive investigation revealed only isolated hypoglycorrachia and mildly elevated CSF protein. Cerebral CT and MRI scans without contrast did not reveal any abnormalities. As his condition continued to decline, an MRI scan of the brain with gadolinium was performed which revealed extensive nodular enhancement of the surface of the cerebellum and brainstem and both temporal lobe convexities. Repeat lumbar puncture showed malignant cells in the CSF and confirmed the diagnosis of leptomeningeal carcinomatosis. This case illustrates that leptomeningeal carcinomatosis should be considered in the differential diagnosis of cognitive decline in the elderly, after other common aetiologies have been excluded. The index of suspicion should be increased in patients with a prior history of cancer.

Aged↗

PubMed2005

Autosomal dominant hereditary sensory neuropathy with chronic cough and gastro-oesophageal reflux: clinical features in two families linked to chromosome 3p22-p24.

Autosomal dominant hereditary sensory neuropathy (HSN I) is a clinically and genetically heterogeneous group of disorders, and in some families it is due to mutations in the serine palmitoyltransferase (SPTLC1) gene. We have characterized two families with HSN I associated with cough and gastro-oesophageal reflux (GOR). From a large Australian family, 27 individuals and from a smaller family, 11 individuals provided clinical information and blood for genetic analysis. Affected individuals had an adult onset of paroxysmal cough, GOR and distal sensory loss. Cough could be triggered by noxious odours or by pressure in the external auditory canal (Arnold's ear-cough reflex). Other features included throat clearing, hoarse voice, cough syncope and sensorineural hearing loss. Neurophysiological and pathological studies demonstrated a sensory axonal neuropathy. Gastric emptying studies were normal, and autonomic function and sweat tests were either normal or showed distal hypohidrosis. Cough was likely to be due to a combination of denervation hypersensitivity of the upper airways and oesophagus, and prominent GOR. Most affected individuals were shown on 24 h ambulatory oesophageal pH monitoring to have multiple episodes of GOR, closely temporally associated with coughing. Hoarse voice was probably attributable to acid-induced laryngeal damage, and there was no evidence of vocal cord palsy. No other cause for cough was found on most respiratory or otorhinological studies. Linkage to chromosome 3p22-p24 has been found in both families, with no evidence of linkage to loci for known HSN I, autosomal dominant hereditary motor and sensory neuropathy, hereditary GOR or triple A syndrome. These families represent a genetically novel variant of HSN I, with a distinctive cough owing to involvement of the upper aerodigestive tract.

Adult↗

PubMed2004

Chronic axonal neuropathy with triosephosphate isomerase deficiency.

A patient with triosephosphate isomerase deficiency resulting from compound heterozygote mutation is described. Chronic axonal neuropathy was identified on clinical and neurophysiologic grounds and confirmed by sural nerve biopsy. This report describes the first biopsy-proven case confirming that peripheral neuropathy can occur with triosephosphate isomerase deficiency.

Axons↗

PubMed2003

Neurophysiological changes in demyelinating and axonal forms of acute experimental autoimmune neuritis in the Lewis rat.

Myelin-sensitized T- and B-cells (lymph node cells) induced experimental autoimmune neuritis (EAN) in Lewis rats after passive transfer to naive recipients. After 6 days, all recipient rats developed tail paresis that progressed to limb paresis within 12-72 h. Progressive nerve conduction changes consistent with demyelination in the sciatic nerve (conduction block and prolongation of the distal motor latencies) and lumbar nerve roots (initial low F-wave frequencies followed by later prolongation in F-wave latencies) were observed during the disease. For comparison, adoptive transfer experimental autoimmune neuritis (AT-EAN) of differing disease severity was induced by titrating the dose of P2-specific T-cells. In contrast to EAN induced by myelin-sensitized T- and B-cells, AT-EAN was predominantly associated with rapid nerve conduction changes consistent with axonal dysfunction and degeneration. These findings demonstrate that distinct forms of EAN with different pathophysiological mechanisms are induced by the passive transfer of P2-specific T-cell lines or myelin-specific T-cells and B-cells. The electrophysiological changes in EAN induced by myelin-specific T- and B-cells are very similar to those seen clinically during acute inflammatory demyelinating polyneuropathy, whereas AT-EAN has less resemblance to axonal forms of Guillain-Barré syndrome.

Action Potentials↗

PubMed2003

Peripheral neuropathies of infancy.

Over a 33-year period, 260 patients (< 17 years of age; 119 males, 141 females) from New South Wales, Australia who had peripheral neuropathies confirmed by nerve biopsy, were studied. Of these, 50 infants presented with symptoms or signs of neuropathy under 1 year of age: including 24 patients with demyelinating neuropathies and 21 axonal neuropathies; a further five patients had spinal muscular atrophy with associated secondary sensory axonopathy. Nineteen infants had hereditary motor sensory neuropathy, of whom 13 had myelin protein mutations confirmed by molecular genetic studies. Peripheral neuropathy is not an unusual diagnosis in infancy. Awareness of this association will aid early diagnosis and prognosis as well as facilitate interventional patient management.

Adolescent↗

PubMed2002

Chronic inflammatory demyelinating polyradiculoneuropathy.

In chronic inflammatory demyelinating polyradiculopathy differing clinical subtypes are beginning to emerge as has already occurred with the Guillain-Barré syndrome. However, neither pathogenic correlates nor particular therapeutic approaches have yet been defined for these subgroups. The neurophysiological techniques of terminal latency index and of modified F ratio help differentiate chronic inflammatory demyelinating polyradiculopathy from IgM paraproteinaemic neuropathy. Diagnosis may be assisted by magnetic resonance imaging studies in which enlarged nerve roots and plexuses and gadolinium enhancement may be evident. Further insight into pathogenesis has come from studies showing pathogenic antibodies in a small percentage of patients. Immunohistological studies examining the presence of adhesion, co-stimulatory and antigen presenting molecules in nerve biopsies have shown that T cell activation can be initiated and perpetuated within nerve and that Schwann cells possess the necessary markers to function as antigen presenting cells. Recent clinical trials have confirmed the therapeutic short term efficacy of intravenous immunoglobulin and Prednisone.

Autoantibodies↗