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P M MacLeod

Publications and source records attributed to P M MacLeod.

At least 19 recordsLinked to original sources
PubMed2001

Early gastric cancer in young, asymptomatic carriers of germ-line E-cadherin mutations.

BACKGROUND: Germ-line truncating mutations in the E-cadherin (CDH1) gene have been found in families with hereditary diffuse gastric cancer. These families are characterized by a highly penetrant susceptibility to diffuse gastric cancer with an autosomal dominant pattern of inheritance, predominantly in young persons. We describe genetic screening, surgical management, and pathological findings in young persons with truncating mutations in CDH1 from two unrelated families with hereditary diffuse gastric cancer. METHODS: Mutation-specific predictive genetic testing was performed by polymerase-chain-reaction amplification, followed by restriction-enzyme digestion and DNA sequencing in Family 1 and by heteroduplex analysis in Family 2. A total gastrectomy was performed prophylactically in five carriers of mutations who were between 22 and 40 years old. In each case, the entire mucosa of the stomach was extensively sampled for microscopical analysis. RESULTS: Superficial infiltrates of malignant signet-ring cells were identified in the surgical samples from all five persons who underwent gastrectomy. These early diffuse gastric cancers were multifocal in three of the five cases, and in one person infiltrates of malignant signet-ring cells were present in 65 of the 140 tissue blocks analyzed, representing in aggregate less than 2 percent of the gastric mucosa. CONCLUSIONS: We recommend genetic counseling and consideration of prophylactic gastrectomy in young, asymptomatic carriers of germ-line truncating CDH1 mutations who belong to families with highly penetrant hereditary diffuse gastric cancer.

Adenocarcinoma↗
PubMed2001

Rett syndrome: review of biological abnormalities.

The Rett syndrome (RS) is a peculiar, sporadic, atrophic disorder, almost entirely confined to females. After the first six months of life there is developmental slowing with reduced communication and head growth for about one year. This is followed by a rapid destructive stage with severe dementia and loss of hand skills (with frequent hand wringing), apraxia and ataxia, autistic features and irregular breathing with hyperventilation. Seizures often supervene. Subsequently there is some stabilization in a pseudo-stationary stage during the preschool to school years, associated with more emotional contact but also abnormalities of the autonomic and skeletal systems. After the age of 15-20 years, a late motor deterioration occurs with dystonia and frequent spasticity but seizures become milder. RS has generally been considered an X-linked disorder in which affected females represent a new mutation, with male lethality. Linkage studies suggested a critical region at Xq28. In 1999, mutations in the gene MECP2 encoding X-linked methyl cytosine-binding protein 2 (MeCP2) were found in a proportion of Rett girls. This protein can bind methylated DNA. Analyses are leading to much further investigation of mutants and their effects on genes. Neuropathological and electrophysiological studies of RS are described. Description of neurometabolic factors includes reduced levels of dopamine, serotonin, noradrenaline and choline acetyltransferase (ChAT) in brain, also estimation of nerve growth factors, endorphin, substance P, glutamate and other amino acids and their receptor levels. The results of neuroimaging are surveyed, including volumetric magnetic resonance imaging (MRI) and positron emission tomography (PET).

Animals↗
PubMed2001

High incidence rate and absent family histories in one quarter of patients newly diagnosed with Huntington disease in British Columbia.

The advent of the direct mutation test for Huntington disease (HD) has made it possible to identify a previously unrecognized symptomatic population of HD, including those with an atypical presentation or patients without a family history of HD. The present study investigated the uptake of this test in the province of British Columbia (BC), Canada and assessed the incidence rate and rate of identification of new mutations for HD. All symptomatic individuals residing in BC who were referred for the genetic test for HD between 1993 and 2000 (n=205) were analyzed for CAG expansion, baseline demographics and clinical data, and a family history of HD. A total of 141 (or 68.8%) had a CAG expansion > or =36. Of these, almost one-quarter (24.1%) did not have a family history of HD. An extensive chart review revealed that 11 patients (or 7.8%) had reliable information on both parents (who lived well into old age) and therefore possibly could represent new mutations for HD. This indicates a three to four times higher new mutation rate than previously reported. Our findings also show that the yearly incidence rate for HD was 6.9 per million, which is two times higher than previous incidence studies performed prior to the identification of the HD mutation. We also identified five persons with a clinical presentation of HD but without CAG expansion (genocopies) (2.4%).

Adolescent↗
PubMed1997

Inherited mutations in PTEN that are associated with breast cancer, cowden disease, and juvenile polyposis.

PTEN, a protein tyrosine phosphatase with homology to tensin, is a tumor-suppressor gene on chromosome 10q23. Somatic mutations in PTEN occur in multiple tumors, most markedly glioblastomas. Germ-line mutations in PTEN are responsible for Cowden disease (CD), a rare autosomal dominant multiple-hamartoma syndrome. PTEN was sequenced from constitutional DNA from 25 families. Germ-line PTEN mutations were detected in all of five families with both breast cancer and CD, in one family with juvenile polyposis syndrome, and in one of four families with breast and thyroid tumors. In this last case, signs of CD were subtle and were diagnosed only in the context of mutation analysis. PTEN mutations were not detected in 13 families at high risk of breast and/or ovarian cancer. No PTEN-coding-sequence polymorphisms were detected in 70 independent chromosomes. Seven PTEN germ-line mutations occurred, five nonsense and two missense mutations, in six of nine PTEN exons. The wild-type PTEN allele was lost from renal, uterine, breast, and thyroid tumors from a single patient. Loss of PTEN expression was an early event, reflected in loss of the wild-type allele in DNA from normal tissue adjacent to the breast and thyroid tumors. In RNA from normal tissues from three families, mutant transcripts appeared unstable. Germ-line PTEN mutations predispose to breast cancer in association with CD, although the signs of CD may be subtle.

Adenoma↗
PubMed1993

Evidence for multi-site closure of the neural tube in humans.

Four separate initiation sites for neural tube (NT) fusion have been demonstrated recently in mice and other experimental animals. We evaluated the question of whether the multisite model vs. the traditional single-site model of NT closure provided the best explanation for neural tube defects (NTDs) in humans. Evidence for segmental vs. continuous NT closure was obtained by review of our recent clinical cases of NTDs and previous medical literature. With the multi-site NT closure model, we find that the majority of NTDs can be explained by failure of fusion of one of the closures or their contiguous neuropores. We hypothesize that: Anencephaly results from failure of closure 2 for meroacranium and closures 2 and 4 for holoacranium. Spina-bifida cystica results from failure of rostral and/or caudal closure 1 fusion. Craniorachischisis results from failure of closures 2, 4, and 1. Closure 3 non-fusion is rare, presenting as a midfacial cleft extending from the upper lip through the frontal area ("facioschisis"). Frontal and parietal cephaloceles occur at the sites of the junctions of the cranial closures 3-2 and 2-4 (the prosencephalic and mesencephalic neuropores). Occipital cephaloceles result from incomplete membrane fusion of closure 4. In humans, the most caudal NT may have a 5th closure site involving L2 to S2. Closure below S2 is by secondary neurulation. Evidence for multi-site NT closure is apparent in clinical cases of NTDs, as well as in previous epidemiological studies, empiric recurrence risk studies, and pathological studies. Genetic variations of NT closures sites occur in mice and are evident in humans, e.g., familial NTDs with Sikh heritage (closure 4 and rostral 1), Meckel-Gruber syndrome (closure 4), and Walker-Warburg syndrome (2-4 neuropore, closure 4). Environmental and teratogenic exposures frequently affect specific closure sites, e.g., folate deficiency (closures 2, 4, and caudal 1) and valproic acid (closure 5 and canalization). Classification of NTDs by closure site is recommended for all studies of NTDs in humans.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Gonadal mosaicism in a family with adrenoleukodystrophy: molecular diagnosis of carrier status among daughters of a gonadal mosaic when direct detection of the mutation is not possible.

Adrenoleukodystrophy is a severe, X-linked neurological disease that has been shown to be linked to DNA markers from Xq28. We tested several families with these markers and, in one family, found two apparent recombination events between DXS52 and the disease. Expansion of the study to include other tests and several others markers from Xq28 led us to conclude that recombination probably had not occurred and that, instead, the mutation in this family had a mitotic origin and that the grandmother was a gonadal mosaic. For genes that have been cloned, it is often possible to demonstrate the presence or absence of a specific mutation in such families and to determine carrier status on that basis. This is not possible when the gene has not been cloned. We therefore describe a method that can be employed by a molecular diagnostic laboratory to discriminate between people who inherit the same RFLP haplotype, with or without the mutation, from a parent with gonadal mosaicism in diseases where direct gene analysis is not yet possible.

Adrenoleukodystrophy↗
PubMed1992

The Machado-Joseph disease locus is different from the spinocerebellar ataxia locus (SCA1).

Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative spinocerebellar ataxia that has been described primarily in families of Azorean or Portuguese descent. MJD and chromosome 6p-linked spinocerebellar ataxia (SCA1) are difficult to differentiate clinically, and it has been suggested that they may be allelic variants of the same disorder. We have tested MJD families for linkage to six DNA sequence polymorphisms located on chromosome 6p, including the highly informative dinucleotide repeat, D6S89. Seventeen centimorgans telomeric to and 41 cM centromeric to D6S89, a region that includes the SCA1 locus reported to be within 3 cM of D6S89, have been excluded. These data provide conclusive evidence that MJD and SCA1 are nonallelic.

Alleles↗
PubMed1991

Carrier detection and prenatal diagnosis of Pelizaeus-Merzbacher disease using a combination of anonymous DNA polymorphisms and the proteolipid protein (PLP) gene cDNA.

We report carrier identification and a prenatal diagnosis using DNA polymorphisms in 2 families with X-linked Pelizaeus-Merzbacher disease (PMD). In both families, the proteolipid protein (PLP) gene in the single affected male could be traced back to his unaffected maternal grandfather. Therefore, each family contains a new mutation. In the case of the prenatal diagnosis, the fetus was shown by cytogenetic analysis to be a female, who we predict will be a noncarrier of PMD based on her genotype with the PLP intragenic polymorphism.

DNA↗
PubMed1991

Recurrent respiratory infections in a child with fucosidosis: is the mucus too thin for effective transport?

Fucosidosis is caused by a deficiency of the lysosomal enzyme alpha-L-fucosidase (ALF) leading to an accumulation of glycoproteins in a variety of cells. Infants and young children with this disorder are prone to recurrent sinus and pulmonary infections and often die of pneumonia. We studied the mucociliary and systemic immune function in a 6 year old girl with fucosidosis and recurrent respiratory infections. All measurements of systemic immune function were normal. Sweat chloride was normal when measured on angiokeratotic skin but was greater than 65 mg/L on uninvolved areas. During the placement of tympanic ventilation tubes, tracheal mucus was gently aspirated and a mucosal biopsy was taken. Tracheal mucus transport was not measured. The biopsy material was examined under phase contrast microscopy and revealed ciliated cells with apparently normal beating. TEM of these cells showed a characteristic pattern of vacuoles in the cytoplasm as described in other tissues from patients with fucosidosis. Ciliary ultrastructure was normal. Mucus viscoelasticity was measured in a magnetic microrheometer. The loss tangent was 2 SD above the mean for normal mucus and mechanical impedance was about 2 SD below the mean. These changes are similar in direction but double in magnitude to what has been described with methacholine administration in dogs. The high compliance of the mucus may be due to incomplete assembly of mucus glycoprotein or to decreased secretion of glycoproteins in respiratory secretions. This leads to mucus that is abnormally watery and thus difficult to clear from the airway.

Child↗
PubMed1990

The role of radiotherapy in in-situ carcinoma of the larynx.

Twenty patients with in situ carcinoma of the vocal cord treated with radical radiotherapy over a 16-year period have been assessed for local control and survival. Seventy-one patients with Stage T1 invasive carcinomas treated in the same period have been similarly assessed and the results are compared. All patients were treated with megavoltage wedge pair techniques using fields of mean size 4.5 x 4.5 cm. Patients were treated to radical intent, the Tis group receiving a mean nominal standard dose (NSD) of 1759 ret and the T1 invasive group a mean NSD of 1743 ret. In the Tis group, radiotherapy resulted in local control in 70% (14/20) of patients with an ultimate local control, after surgery, of 90% (18/20). This is not statistically different to the primary local control rate for T1 invasive lesions of 83% (59/71) with an ultimate control rate, after surgery, of 94% (68/71), chi 2 p greater than 0.2. Five and 10-year actuarial survival rates were 100% in the Tis group and 96.8% and 92.6%, respectively, in the T1 invasive group (chi 2 p = 0.275). Five and 10-year actuarial recurrence-free survival rates were 78.8% and 69% for the Tis group and 86.1% and 78.4% for the T1 invasive group (chi 2 p = 0.548). Analysis of failures suggests that extent of disease, field size, and total dose given are not contributory factors to local control or survival in this group of patients. There is no indication that in situ lesions respond to radiotherapy less favorably than T1 invasive lesions and we would support the use of radiotherapy as a therapeutic option in this condition.

Adult↗
PubMed1990

Megestrol acetate in relapsed carcinoma of prostate.

A series of 22 patients with advanced carcinoma of the prostate who had failed first-line hormonal therapy (orchiectomy, stilboestrol, luteinising hormone-releasing hormone agonist) were treated with 160 mg megestrol acetate daily. Treatment was well tolerated, side effects were minimal and 21 patients were evaluable. There were no complete or partial responses, although 8 patients had a good subjective response. In 6 patients the disease was stabilised for 6 to 12 months and there was a 40 to 50% reduction in their prostatic acid phosphatase (PAP) levels. It was concluded that megestrol acetate has a role as second-line hormonal therapy in the management of prostatic carcinoma.

Carcinoma↗
PubMed1989

Growth and development in thanatophoric dysplasia.

Two cases of prolonged survival of thanatophoric dysplasia are presented, in which ventilatory support was initiated in the neonatal period because of respiratory distress. Both patients required a ventriculoperitoneal shunt for hydrocephalus and had decompression of the posterior fossa. The history of each patient has been characterized by profound developmental delay and dramatic growth failure.

Arm↗
PubMed1989

Methylcitrate in maternal urine during a pregnancy with a fetus affected with propionic acidaemia.

Patients homozygous for propionic acidaemia have high levels of methylcitric acid in urine while heterozygotes have normal levels. Methylcitric acid was determined by stable isotope dilution gas chromatography-mass spectrometry in maternal urine during a pregnancy with a fetus affected with propionic acidaemia. Although the levels increased linearly between 23 and 39 weeks of gestation, the levels were not significantly elevated above normal until after 30 weeks of gestation. Thus, determination of methylcitric acid in maternal urine is not of value for early prenatal diagnosis of propionic acidaemia.

Amino Acid Metabolism, Inborn Errors↗
PubMed1989

The use of simultaneous radiotherapy and 5-flurouracil in patients with inoperable squamous cell lung cancer.

Over a 2-year period, 17 patients with histologically proven squamous cell carcinoma of the bronchus, assessed as inoperable or incurable on surgical or medical grounds, were treated with palliative radiotherapy and a concurrent 120-h infusion of 5-flurouracil, at a dosage of 1 g/day. The treatment was found to be well tolerated with no major toxicity. The degree of palliation and survival obtained was found to be no different to that of a historical matched control group, treated with radiotherapy alone, with median survival in the two groups of 35 weeks and 42 weeks respectively (log rank test P greater than 0.69). We conclude that although a non-toxic treatment regime, no benefit was obtained by the addition of 5-flurouracil to palliative radiotherapy.

Aged↗
PubMed1988

Ultrastructural studies as a method of prenatal diagnosis of neuronal ceroid-lipofuscinosis.

Ultrastructural studies of uncultured amniotic fluid cells obtained by genetic amniocentesis at 16 wk of gestation demonstrated 3 major cell types. Membrane bound curvilinear cytosomes were observed in about 30% of a subpopulation of dark, elongated cells. These are considered typical of the inclusions of the late infantile variant of neuronal ceroid-lipofuscinosis. This technique was used to monitor 6 at-risk pregnancies of which 2 were identified as affected. We have followed 6 of the 7 fetuses through to delivery with confirmation of our findings by skin biopsy in 4 and with clinical observations of a fifth child. There are major problems involved in the use of uncultured amniotic fluid cells for prenatal diagnosis. In addition to a great deal of heterogeneity of cell type, there is a considerable amount of tissue debris and a very high proportion of nonviable cells. We have examined chorionic villus tissues of 3 fetuses known to have inborn errors of lysosomal metabolism without finding any evidence of storage material. This is taken as an indication that the mutant gene(s) is not expressed in these tissues at this early stage of pregnancy. Notwithstanding these limitations, the usefulness of this technique in monitoring at-risk pregnancies has to be determined.

Amniocentesis↗