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Biomedical subjects

R Pettigrew

Publications and source records attributed to R Pettigrew.

12 recordsLinked to original sources
PubMed2007

CNS hypomyelination in Rat Terrier dogs with congenital goiter and a mutation in the thyroid peroxidase gene.

Arrested physical development and neurologic abnormalities were identified in 3 of 5 Rat Terrier puppies at 9 weeks of age. Bilaterally firm symmetrical masses were palpated in the region of the thyroid glands. Low serum total (T4) and free thyroxine (FT4, by equilibrium dialysis) and markedly elevated thyroid stimulating hormone (TSH) concentrations supported the diagnosis of hypothyroidism. At necropsy, the thyroid gland was grossly enlarged and histologically exhibited severe, diffuse hyperplasia of the follicular epithelium. Gross examination of the central nervous system revealed a myelin deficiency, most evident in the corpus callosum. Regional distribution of hypomyelination was confirmed histologically, affecting the corpus callosum and, to a lesser degree, the corona radiata, the longitudinal fibers of the pons, the pyramids, and the lateral funiculi of the spinal cord. Myelin reduction was paralleled by axon reduction, suggesting that hypomyelination was a consequence of reduced axonal formation. A homozygous nonsense mutation in the thyroid peroxidase gene was identified in the affected puppies. The dam and a clinically normal litter mate were heterozygous for this mutation, confirming simple autosomal recessive inheritance of the disease trait. The same mutation, causing congenital hypothyroidism with a goiter was previously described in the Toy Fox Terrier breed. Given the ongoing practice of introducing the Toy Fox Terrier genetic background into some Rat Terrier breeding programs to obtain a smaller stature and the apparent relative incidence of the disorder in the 2 breeds, it is likely that this mutation crossed into the Rat Terrier breed from Toy Fox Terriers fairly recently.

Animals↗
PubMed2001

Six unaffected livebirths following preimplantation diagnosis for spinal muscular atrophy.

Spinal muscular atrophy (SMA) is a severe neurodegenerative autosomal recessive disorder, second only in frequency to cystic fibrosis. In its most severe form, SMA type I (Werdnig-Hoffman), death invariably ensues before age 2 years from respiratory failure or infection. Around 98% of clinical cases of SMA are caused by the homozygous absence of a region of exons 7 and 8 of the telomeric copy of the SMN gene (SMN1) on chromosome 5. We have developed a novel means of preimplantation diagnosis of SMA using a nested polymerase chain reaction (PCR) amplification of exon 7 of SMN, followed by a HinfI restriction digest of the PCR product enabling the important SMN1 gene to be distinguished from the centromeric SMN2 gene which has no clinical phenotype. This method was designed to reduce the likelihood of misdiagnosis. Five couples were treated using this method. Four proceeded to embryo transfer which resulted in six liveborns (one singleton, one twin and one triplet), all free of SMA. Embryo transfer was not performed in one cycle because of PCR contamination.

Adult↗
PubMed2000

A pregnancy following PGD for X-linked dominant [correction of X-linked autosomal dominant] incontinentia pigmenti (Bloch-Sulzberger syndrome): case report.

Incontinentia Pigmenti (Bloch-Sulzberger syndrome) is a rare multisystem, ectodermal disorder associated with dermatological, dental and ocular features, and in <10% of cases, severe neurological deficit. Pedigree review suggests X-linked dominance with lethality in affected males. Presentation in female carriers is variable. Following genetic counselling, a mildly affected female carrier diagnosed in infancy with a de novo mutation was referred for preimplantation sexing, unusually selecting for male gender, with an acceptance of either normality or early miscarriage in an affected male. Following standard in-vitro fertilization and embryo biopsy, fluorescence in situ hybridization (FISH) unambiguously identified two male and two female embryos. A single 8-cell, grade 4 male embryo was replaced. A positive pregnancy test was reported 2 weeks after embryo transfer, although ultrasonography failed to demonstrate a viable pregnancy. Post abortive fetal tissue karyotyping diagnosed a male fetus with trisomy 16. This is an unusual report of preimplantation genetic diagnosis (PGD) being used for selection of males in an X-linked autosomal dominant disorder and demonstrates the value of PGD where amniocentesis or chorion villus sampling followed by abortion is not acceptable to the patient. This case also demonstrates the importance of follow-up prenatal diagnosis.

Adult↗
PubMed2000

Fluid mechanic assessment of the total cavopulmonary connection using magnetic resonance phase velocity mapping and digital particle image velocimetry.

The total cavopulmonary connection (TCPC) is currently the most promising modification of the Fontan surgical repair for single ventricle congenital heart disease. The TCPC involves a surgical connection of the superior and inferior vena cavae directly to the left and right pulmonary arteries, bypassing the right heart. In the univentricular system, the ventricle experiences a workload which may be reduced by optimizing the cavae-to-pulmonary anastomosis. The hypothesis of this study was that the energetic efficiency of the connection is a consequence of the fluid dynamics which develop as a function of connection geometry. Magnetic resonance phase velocity mapping (MRPVM) and digital particle image velocimetry (DPIV) were used to evaluate the flow patterns in vitro in three prototype glass models of the TCPC: flared zero offset, flared 14 mm offset, and straight 21 mm offset. The flow field velocity along the symmetry plane of each model was chosen to elucidate the fluid mechanics of the connection as a function of the connection geometry and pulmonary artery flow split. The steady flow experiments were conducted at a physiologic cardiac output (4 L/min) over three left/right pulmonary flow splits (70/30, 50/50, and 30/70) while keeping the superior/inferior vena cavae flow ratio constant at 40/60. MRPVM, a noninvasive clinical technique for measuring flow field velocities, was compared to DPIV, an established in vitro fluid mechanic technique. A comparison between the results from both techniques showed agreement of large scale flow features, despite some discrepancies in the detailed flow fields. The absence of caval offset in the flared zero offset model resulted in significant caval flow collision at the connection site. In contrast, offsetting the cavae reduced the flow interaction and caused a vortex-like low velocity region between the caval inlets as well as flow disturbance in the pulmonary artery with the least total flow. A positive correlation was also found between the direct caval flow collision and increased power losses. MRPVM was able to elucidate these important fluid flow features, which may be important in future modifications in TCPC surgical designs. Using MRPVM, two- and three-directional velocity fields in the TCPC could be quantified. Because of this, MRPVM has the potential to provide accurate velocity information clinically and, thus, to become the in vivo tool for TCPC patient physiological/functional assessment.

Biomedical Engineering↗
PubMed1997

Obesity and female reproductive function.

Obesity has consistently been demonstrated to have a detrimental effect upon the female reproductive system. This review explores the common association of obesity with polycystic ovary syndrome (PCOS), the effect of obesity on the clinical and endocrinological parameters, and the role of insulin resistance in the expression of this disorder. An improvement in menstrual function, a decrease in the clinical androgenic profile, and significant increase in spontaneous pregnancy rates have been reported following weight loss. Obesity is associated with poor pregnancy outcome and miscarriage in both women with PCOS, and in those with normal ovarian morphology. The optimal weight gain during pregnancy remains controversial, but obesity is a risk factor for both maternal and fetal complications, and dietary advice should be offered on an individual basis according to the pre-pregnancy BMI. Weight gain at the time of menopause is common, and dietary advice is paramount as obesity is an independent risk factor for thrombosis, coronary heart disease (CHD), and breast and endometrial cancer. Effective nutritional counselling should be offered at all stages of the female reproductive lifecycle.

Adult↗
PubMed1996

Diagnosis of cardiac sarcoidosis aided by MRI.

We describe herein a case of dilated cardiomyopathy. The diagnosis of myocardial sarcoid was suggested by abnormal findings on an MRI of the chest. This was subsequently confirmed by a histology of a subcutaneous nodule. MRI is well suited in imaging myocardial scarring associated with sarcoidosis. Its use should be considered where sarcoidosis is suspected. Early detection and intervention with steroids may improve function.

Adult↗
PubMed1988

Donor indium-111 leukocyte scan in a nonleukopenic patient.

Indium-III leukocytes are useful in localizing infection and abscess with excellent sensitivity and specificity. In this case report, heterologous Indium-III leukocytes provided the same diagnostic information as autologous leukocytes without adverse effects to the patient. A potential application of donor Indium-III leukocytes in the nonleukopenic patient is discussed.

Adult↗
PubMed1986

Fundamentals of 180 degree acquisition and reconstruction in SPECT imaging.

The accuracy of the reconstructed images obtained from a 180 degrees SPECT acquisition is directly related to the effects of resolution and attenuation in the acquired projection data. Computer simulation studies show that the tomographic point spread functions and the quality of 201Tl myocardial perfusion transaxial images depend upon the specific 180 degrees arc used for reconstruction. Significant distortions are predicted in 201Tl myocardial images reconstructed from both 180 degrees and 360 degree scans; with signal to noise being significantly better for 180 degree scans. An anterior 180 degrees scan with a starting angle between right lateral and 45 degrees RAO in 201Tl myocardial imaging is recommended. Reconstructed images acquired from 180 degrees and 360 degree elliptical orbits are predicted to show more distortion than those obtained from circular acquisitions.

Heart↗