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Biomedical subjects

P Lamont

Publications and source records attributed to P Lamont.

At least 19 recordsLinked to original sources
PubMed2003

A locus on chromosome 15q for a dominantly inherited nemaline myopathy with core-like lesions.

Nemaline myopathy is a congenital neuromuscular disorder characterized by muscle weakness and the presence of nemaline rods. Five genes have now been associated with nemaline myopathy: alpha-tropomyosin-3 (TPM3), alpha-actin (ACTA1), nebulin (NEB), beta-tropomysin (TPM2) and troponin T (TNNT1). In addition, mutations in the ryanodine receptor gene (RYR1) have been associated with core-rod myopathy. Here we report linkage in two unrelated families, with a variant of nemaline myopathy, with associated core-like lesions. The clinical phenotype consists of muscle weakness in addition to a peculiar kind of muscle slowness. A genome-wide scan revealed a locus for nemaline myopathy with core-like lesions on chromosome 15q21-q23 for both families. Combining the two families gave a two-point LOD score of 10.65 for D15S993. The alpha-tropomyosin-1 gene (TPM1) located within this region is the strongest candidate gene. However, no mutations were found in the protein-coding region of TPM1, although small deletions or mutations in an intron cannot be excluded. The critical region contains few other candidate genes coding for muscle proteins and several genes of unknown function, and has not yet been sequenced completely. The novel phenotype of nemaline myopathy in the two presented families corresponds to an also novel, as yet uncharacterized, genotype.

Adolescent↗
PubMed2003

Principal mutation hotspot for central core disease and related myopathies in the C-terminal transmembrane region of the RYR1 gene.

The congenital myopathies are a group of disorders characterised by the predominance of specific histological features observed in biopsied muscle. Central core disease and nemaline myopathy are examples of congenital myopathies that have specific histological characteristics but significantly overlapping clinical pictures. Central core disease is an autosomal dominant disorder with variable penetrance which has been linked principally to the gene for the skeletal muscle calcium release channel (RYR1). Two recent reports have identified the 3' transmembrane domain of this gene as a common site for mutations. Two other studies have reported single families that have features of both central core disease and nemaline myopathy (core/rod disease) caused by mutations in RYR1. Screening of the 3' region (exons 93-105) of the RYR1 gene for mutations in 27 apparently unrelated patients with either central core disease or core/rod disease by single strand conformation polymorphism analysis and DNA sequencing identified three described and nine novel mutations in 15 patients.

DNA Mutational Analysis↗
PubMed2001

Determinants of carotid microembolization.

PURPOSE: Earlier studies have highlighted risk factors for perioperative stroke after carotid endarterectomy, such as female sex, preoperative symptoms, and cerebral infarction. In this study, we investigated the relationship between these factors and perioperative microembolization. METHODS: A total of 235 patients were entered in the study at two centers. Transcranial Doppler ultrasound scanning was possible in 190 patients (81%) and was performed for 1 hour preoperatively and continuously intraoperatively as a means of detecting microemboli and monitoring mean middle cerebral artery velocity. The findings of transcranial Doppler ultrasound scanning were related to perioperative risk factors by means of univariate analysis. RESULTS: Microemboli were detected in 28 (15%), 79 (42%), and 98 (52%) patients preoperatively, during carotid artery dissection, and after closure of the artery, respectively. Having 10 or more emboli after carotid artery closure was more common in women (P = .04) and in patients with symptomatic carotid artery disease (P = .04) and was demonstrated in three of the six patients who had a perioperative stroke. These three patients also had preoperative evidence of cerebral infarction and an intraoperative middle cerebral artery velocity less than 40 cm/s. CONCLUSION: In this study, perioperative microembolization was more common in women and patients with symptomatic carotid artery disease. These findings may explain the increased risk of carotid surgery in these patients.

Adult↗
PubMed1995

Differences in diaphragm fiber types in SIDS infants.

The diaphragm is a vital respiratory muscle in the sleeping infant. Any changes in diaphragm fiber type number or size could represent either a primary developmental delay or a secondary reaction to increased workload, and could give a clue as to the pathogenesis of sudden infant death syndrome (SIDS). We therefore quantitated by point counting on ATPase histochemistry the numbers and areas of type 1 and 2 fibers in the diaphragm, external intercostal and psoas muscles of 37 SIDS and 20 control infants. The amount of slow, fast and fetal myosin in the diaphragm and psoas muscles was measured by electrophoresis to check the ATPase quantitation. There were fewer type 1 fibers in SIDS (median 30.0%) compared with control (median 40.0%) infants (p < 0.02), whereas the diameter of type 1 fibers in SIDS (median 33.9 microns) was larger than in control (median 30.3 microns) infants (p < 0.007). The total cross-sectional area occupied by type 1 and 2 fibers was similar in both groups. No changes were found in the external intercostal or psoas. The amount of slow and fast myosins correlated well with type 1 and type 2 fibers, respectively. The finding of fewer type 1 (fatigue-resistant) fibers of large diameter in SIDS diaphragms suggests that differences in muscle fiber types may predispose these infants to diaphragm fatigue and respiratory failure.

Diaphragm↗
PubMed1995

Brain stem nuclei in sudden infant death syndrome (SIDS): volumes, neuronal numbers and positions.

It has been suggested that the defect underlying the sudden infant death syndrome (SIDS) lies in brain stem nuclei involved in cardiac and respiratory function. However, most studies have not used rigorous quantitative techniques to assess brain stem nuclear volumes and neuronal numbers. We have measured the volume, neuronal numbers and position of brain stem nuclei in 11 SIDS and 11 aged-matched control infants. Using serial sagittal sections, nuclei involved in maintaining airway patency (hypoglossal, ambiguus and retroambiguus), heart rate (dorsal vagal) and generation of respiratory rhythm (ambiguus and dorsal vagal) were studied. No significant differences were found in nuclear volume increase with age, total neuronal number or nuclear position between SIDS and control cases. These findings support the hypothesis that the nervous system in SIDS may be normal until the final event that kills these infants.

Age Factors↗
PubMed1995

Myelin in SIDS: assessment of development and damage using MRI.

OBJECTIVE: Abnormalities of myelin that have been reported in Sudden Infant Death Syndrome (SIDS) include a delay in development and focal lesions presumed to be secondary to hypoxia. Magnetic resonance imaging (MRI) gives excellent images of white matter and can be used to map the progress of myelination and to demonstrate focal lesions. It was the aim of this study to determine whether any MRI abnormality of myelin could be detected in the brains of SIDS compared to control infants. METHODS: The brains of 28 SIDS and 14 control infants were fixed in formalin and scanned with MRI. The proton density, T2-weighted, and inversion recovery scans were assessed for the presence of focal white matter lesions. The amount of myelin in 26 sites was measured in the proton density scans, using a densitometer. The amount of myelin present could be assessed in 21 of 26 sites. RESULTS: In 15 of 21 sites the amount of myelin for age was the same in SIDS and controls. In three sites the rate of myelination was greater in SIDS than control and in another three sites the amount of myelin for age was greater in SIDS than control infants, but these differences were not seen in infants aged less than 8 months. No focal abnormalities of white matter were seen in either SIDS or control infants. CONCLUSIONS: The development of white matter in brains of SIDS infants less than 8 months old is the same as in controls, and in older SIDS infants white matter development may be slightly advanced compared to controls. No hypoxic changes can be seen in SIDS white matter on MRI.

Brain↗
PubMed1994

Magnetic resonance imaging of postmortem infant brains.

In order to obtain postmortem magnetic resonance images of infant brains, the formalin-fixed brains of 37 infants, ranging in age from 17 days to 17 months, were studied. Factors that improved scan resolution included formalin fixation, not washing the formalin from the brain, imaging the brain with a thin film of water over it, and the use of an extremity coil. The scan resolution was of sufficient quality to direct the histopathologist to regions requiring microscopic examination and to map the progress of myelination.

Autopsy↗
PubMed1994

Subclavian artery aneurysm: the role of magnetic resonance imaging.

Subclavian artery aneurysms are rare. Diagnosis is important as complications can be life threatening. A case is reported which is diagnosed by magnetic resonance imaging; moreover it is suggested that magnetic resonance imaging is now the initial imaging modality of choice in the investigation of these lesions.

Aged↗
PubMed1992

Combined cardiac and abdominal aortic aneurysm operations. The dual operation on cardiopulmonary bypass.

Eight patients underwent both cardiac operation and repair of abdominal aortic aneurysm. All had respiratory impairment and significant impairment of left ventricular function, whereas six patients had severe diffuse distal coronary disease. In all patients the cardiac procedure was performed first, and the patients continued to receive cardiopulmonary bypass. Rewarming was not commenced until the abdominal repair was well under way, to protect the vital organs. There were no problems in weaning the patients from bypass, and six of the patients were extubated within 24 hours; one required ventilation for 36 hours. One patient died of colonic infarction complicated by kidney failure without being extubated. Another patient who was initially extubated in 11 hours required reintubation because of poor lung function and eventually died of multisystem organ failure caused by bilateral lower limb ischemia that persisted despite embolectomies. All survivors are well and in New York Heart Association functional class I or II between 3 and 18 months postoperatively. We conclude that for patients considered unfit for abdominal aortic aneurysm operations because of the nature of the cardiac disease, the combined operation with cardiopulmonary bypass is both safe and effective.

Aged↗
PubMed1990

Commencement of a paediatric EEG-video telemetry service.

The diagnosis of epilepsy is sometimes difficult in childhood. The events witnessed in children may be atypical and the interictal electroencephalogram (EEG) may be normal or contain non-specific abnormalities. The problems may be overcome by recording events on video-EEG telemetry. Over the first 18 months of this service, 82 patients were monitored--42 males and 40 females. Forty-two were daytime studies, 37 day and night, and 3 night only. Surface electrodes only were used. The system used was the 24-channel la Mont Video-telemetry unit from Medical Systems International. Parents served as observers. Events and a sample of interictal data were analysed. The commonest reason for referral was to determine whether an event was ictal. Other reasons included seizure frequency, classification or localization of onset. Presenting events were unusual motor activity, staring, change of behaviour, distressing visceral sensations, combinations of the above and miscellaneous phenomena. Events occurred during the recording in 66 of 82 subjects. Of these, 23 were judged to be ictal. These were complex partial seizures, absence seizures, myoclonic jerks, generalized tonic seizures, gelastic seizures and mixed seizure disorders. The non-ictal events were commonly habit tics or normal sleep phenomena, although pertussis, pallid syncopal attacks and extrapyramidal movements occurred. In 76% of cases the management of the child's condition was influenced by the telemetric study.

Adolescent↗
PubMed1989

Femoro-popliteal versus femoro-distal bypass grafting for limb salvage in patients with an "isolated" popliteal segment.

In a prospective, multicentre trial, 59 patients with an ischaemic limb and an "isolated" popliteal segment on angiography were randomised to undergo infrainguinal bypass grafting to either the popliteal segment or to a reconstituted distal vessel lower in the calf. Limb salvage was attained with 88% of the femoro-popliteal grafts and 80% of the femoro-distal grafts. There was no difference in the one year graft patency rate between the femoro-popliteal group (79%) and the femoro-distal group (70%). Mean postoperative increase in ankle/brachial pressure index was similar in the two groups despite the presence of occluded or significantly diseased vessels distal to the popliteal anastomoses. Technical difficulties were encountered in 8% of the popliteal group and 24% of the distal group. Femoro-distal bypass grafting confers no apparent benefit over femoral bypass grafting into a patent popliteal segment, even though the popliteal run-off is impaired or occluded.

Aged↗
PubMed1986

Effects of muramyl dipeptide and lead acetate on carbon clearance and endotoxin-induced mortality in mice.

Muramyl dipeptide (MDP) is a nonspecific immune adjuvant thought to affect the macrophage. MDP had been used safely without immunosuppressive or toxic side effects in our laboratory and others. Endotoxin, or lipopolysaccharide (LPS), is thought to be responsible for many of the systemic toxic effects of gram-negative infection. Lead acetate potentiates the lethal effects of endotoxin, an effect attributed to increased hepatotoxicity involving both hepatocytes and Kupffer macrophages. This study was undertaken to examine putative mechanism of action of MDP relating to the reticuloendothelial system. Endotoxin was given intraperitoneally to susceptible mice that were pretreated with MDP, lead acetate, or both, and to unmodified controls. Lead acetate significantly enhanced lethality due to LPS, but pretreatment with MDP did not alter mortality. Carbon clearance was measured in mice treated with MDP, lead, or both. There was no difference in the phagocytic index of control mice and those mice treated with lead acetate at various times prior to the injection. Carbon clearance increased significantly in mice pretreated with MDP but was unaltered by the addition of lead acetate. We conclude that if hyperphagocytosis of endotoxin occurs in MDP-pretreated mice, it does not cause additional mortality. Muramyl dipeptide appeared to be a safe reticuloendothelial stimulant that did not enhance the toxicity of lead or LPS in this experimental model.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1985

Muramyl dipeptide and polymorphonuclear leukocyte chemotaxis in vitro.

Muramyl dipeptide (MDP) is an immunostimulatory agent that has been shown repeatedly to provide protection against the effects of some forms of experimental surgical infection. The mechanisms of this protection are incompletely understood, and in order to further define them, the impact of MDP upon in vitro polymorphonuclear (PMN) leukocyte chemotaxis was examined in the presence of both normal and opsonic depleted serum. We have also evaluated the effect of MDP as a chemoattractant itself and the response of neutrophils along with MDP to a standard chemoattractant, n-formyl-L-methionyl-L-leucyl-L-phenyl-alanine (FMLP), using the agarose assay for chemotaxis. MDP has weak but significant chemotactic activity itself, with a peak effect at a concentration of 5 X 10(-8) micrograms/ml for neutrophils. These effects are enhanced by the addition of 10% serum. MDP more strongly enhances neutrophil chemotaxis to FMLP. The enhancement of chemotaxis may be a factor in the protection that MDP exerts against some experimental bacterial challenges.

Acetylmuramyl-Alanyl-Isoglutamine↗