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Biomedical subjects

P J Morrison

Publications and source records attributed to P J Morrison.

At least 55 records · Page 3Linked to original sources
PubMed1999

Genotype-phenotype analysis in X-linked Emery-Dreifuss muscular dystrophy and identification of a missense mutation associated with a milder phenotype.

Direct sequencing of the emerin gene in 22 families with Emery-Dreifuss muscular dystrophy (EMD) revealed mutations in 21 (95%), confirming that emerin mutations can be identified in the majority of families with X-linked EMD. Most emerin mutations result in absence of the protein. In this study three mutations (a missense mutation Pro183Thr and two in-frame deletions removing residues 95-99 and 236-241, respectively) were unusual in being associated with expression of mutant protein. The phenotype in these families was compared in detail with the clinical features in cases with typical null mutations. For the in-frame deletions there were no significant differences. In the family with the missense mutation the phenotype was milder. Age at onset was later for first symptoms and for development of ankle contractures and muscle weakness. These findings have diagnostic implications as well as pointing to functionally important regions of the emerin protein.

Amino Acid Substitution↗
PubMed1998

Negative energy modes and gravitational instability of interpenetrating fluids.

We study the longitudinal instabilities of two interpenetrating fluids interacting only through gravity. When one of the constituents is of relatively low density, it is possible to have a band of unstable wavenumbers well separated from those involved in the usual Jeans instability. If the initial streaming is large enough, and there is no linear instability, the indefinite sign of the free energy has the possible consequence of explosive interactions between positive and negative energy modes in the nonlinear regime. The effect of dissipation on the negative energy modes is also examined.

Journal Article↗
PubMed1998

Invariants and labels in Lie-Poisson systems.

Reduction is a process that uses symmetry to lower the order of a Hamiltonian system. The new variables in the reduced picture are often not canonical: there are no clear variables representing positions and momenta, and the Poisson bracket obtained is not of the canonical type. Specifically, we give two examples that give rise to brackets of the noncanonical Lie-Poisson form: the rigid body and the two-dimensional ideal fluid. From these simple cases, we then use the semidirect product extension of algebras to describe more complex physical systems. The Casimir invariants in these systems are examined, and some are shown to be linked to the recovery of information about the configuration of the system. We discuss a case in which the extension is not a semidirect product, namely compressible reduced MHD, and find for this case that the Casimir invariants lend partial information about the configuration of the system.

Journal Article↗
PubMed1998

Nitric oxide availability in diabetes mellitus.

Diabetes mellitus is associated with early development of cardiovascular complications. Under physiological conditions the endothelium protects against the development of atherosclerosis. Endothelial cells produce, e.g., nitric oxide (NO), a substance which is capable of keeping vascular tone, coagulation and inflammation well balanced. However, in pathological conditions, such as in diabetes mellitus, impaired NO activity may be present. Decreased NO activity can be caused by impaired production of NO, due to uncoupling of receptor-mediated signal transduction, a deficiency of the NO synthase (NOS) substrate L-arginine, or a decreased availability of one or more cofactors essential for optimal functioning of NOS. However, hyperglycaemia also stimulates the production of advanced glycosylated end products, enhances the polyol pathway and activates protein kinase C. These conditions may lead to increased oxidative stress. Reactive oxygen species rapidly inactivate NO leading to the formation of peroxynitrite. Peroxynitrite is a toxic oxidant capable of damaging many biological molecules. Reduced NO availability may not only be of relevance to the development of atherosclerotic complications in diabetes but may also interfere with insulin-mediated postprandial glucose disposal and possibly contribute to the development of insulin resistance. Understanding of the complex metabolic disturbances interacting with the NO system may provide us with further therapeutic options to decrease cardiovascular morbidity and mortality in diabetes mellitus.

Animals↗
PubMed1998

New form of autosomal-recessive axonal hereditary sensory motor neuropathy.

Two siblings, a male and a female, had severe axonal neuropathy and sideroblastic anemia. Despite a distinct clinical picture with areflexia, ataxia, hypotonia, optic atrophy, and progressive sensory neural hearing loss, no definite diagnosis could be reached and the older sibling died at 6 years of age of respiratory failure. It is proposed that the two affected siblings have a new form of autosomal-recessive axonal hereditary sensory motor neuropathy.

Anemia, Sideroblastic↗
PubMed1998

Discordant repeat size and phenotype in Kennedy syndrome.

Previous reports in the literature have described correlation of increasing repeat length with severity of the phenotype, in Kennedy syndrome. We describe male siblings with different repeat lengths, with lack of expression of the phenotype in the sibling with the longer repeat length. The phenotype was identical to motor neurone disease. There is variability of expression in Kennedy syndrome and repeat length even in siblings cannot be taken as a conclusive indicator of severity. CAG repeat length cannot be used to predict the natural history of Kennedy disease. The diagnosis of Kennedy syndrome should be considered in male patients presenting with atypical motor neurone disease.

Diagnosis, Differential↗
PubMed1998

Familial primary spontaneous pneumothorax consistent with true autosomal dominant inheritance.

A family exhibiting spontaneous pneumothorax in a father and three offspring (two sons, and one daughter) is described. The mode of inheritance is apparently autosomal dominant with two episodes of male to male transmission in one family. The age of onset varied by up to 13 years within the family. Isolated autosomal dominant pneumothorax appears to be a distinct clinical entity.

Adolescent↗
PubMed1998

Early catastrophic tibial component wear after unicompartmental knee arthroplasty.

Unicompartmental knee arthroplasty is an appropriate method of treating selected patients with osteoarthritis of the medial compartment of the knee. The common causes of failure are aseptic loosening, infection, patellofemoral pain, and deterioration in the opposite compartment. Seven cases of a cohort of 32 Robert Brigham unicondylar knee replacements that failed because of early catastrophic wear of the polyethylene tibial component are reported. Possible reasons suggested for failure include inadequate thickness of polyethylene, fusion defects in the polyethylene structure as a result of the sterilization process, increased rotational freedom, and reduced conformity in the design of the prosthesis.

Aged↗
PubMed1998

Laryngeal atresia or stenosis presenting as second-trimester fetal ascites--diagnosis and pathology in three independent cases.

Congenital atresia of the larynx is a rare abnormality. We describe three cases where prenatal diagnosis during the second trimester showed massive abdominal fetal ascites and at post-mortem, laryngeal atresia was identified in two cases, and severe laryngeal stenosis in the third. All were associated with pulmonary hyperplasia. No additional abnormalities were found in other systems. Overdistended lung tissue and ascites are resultant from aberrant laryngeal growth; laryngeal anomalies are a cause of isolated fetal ascites. The association of ascites and voluminous lungs should arouse suspicion of laryngeal atresia and should be an indication for careful pathological study of the fetal larynx.

Adult↗
PubMed1997

Mosaic partial trisomy 17 due to a ring chromosome identified by fluorescence in situ hybridisation.

We report on a 3-year-old-girl with mosaic partial trisomy 17 due to an additional ring chromosome 17 in 13% of cells analysed. This was identified by fluorescence in situ hybridisation (FISH) using a whole chromosome 17 specific paint as well as probes specific for the Smith-Magenis and Miller-Dieker regions of chromosome 17p. This girl showed mild developmental delay with subtle facial and other minor abnormalities including single palmar creases, generalised joint laxity, and a scoliosis.

Charcot-Marie-Tooth Disease↗
PubMed1997

Analysis of spinocerebellar ataxia types 1, 2, 3, and 6, dentatorubral-pallidoluysian atrophy, and Friedreich's ataxia genes in spinocerebellar ataxia patients in the UK.

Accurate clinical diagnosis of the spinocerebellar ataxias (SCAs) can be difficult because of overlap in phenotype with other disorders and variation in clinical manifestations. Six SCA loci have been mapped and four disease causing genes identified, in addition to the causative gene for Friedreich's ataxia (FA). All of the identified mutations are expansions of trinucleotide repeat tracts. The SCA2 and SCA6 genes were published recently. The extent of the normal CAG size ranges at these loci and the relative frequencies of the known causes of SCA in the UK are not known. This study first investigated the normal size ranges of the SCA2 and SCA6 loci by genotyping control populations of West African and South African subjects, since African populations generally show the greatest allelic diversity. We found one allele larger than the previously determined normal range for SCA2, and our results at the SCA6 locus agreed with the previously reported normal range. The second component of the study assessed the relative frequencies of the SCA1, 2, 3, and 6, DRPLA, and FA trinucleotide repeat mutations in 146 patients presenting with SCA-like symptoms referred to genetic diagnostic laboratories in the UK. We detected mutations in 14% of patients referred with a diagnosis of autosomal dominant SCA, and in 15% of patients referred with spinocerebellar ataxia where we did not have sufficient family history data available to allow categorisation as familial or sporadic cases. Friedreich's ataxia accounted for 3% of the latter category of cases in our sample, but the most common causes of SCA were SCA2 and SCA6.

Adolescent↗