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Biomedical subjects

S Rickard

Publications and source records attributed to S Rickard.

14 recordsLinked to original sources
PubMed2007

The value of in-utero magnetic resonance imaging in ultrasound diagnosed foetal isolated cerebral ventriculomegaly.

AIM: To assess whether magnetic resonance imaging (MRI) is a useful adjunct to ultrasound (US) when imaging cases of foetal isolated cerebral ventriculomegaly. To assess whether, in such cases, ventricular morphology is a useful indicator for the underlying pathology, as has recently been suggested. MATERIALS AND METHODS: A retrospective analysis was undertaken of 30 cases of isolated ventriculomegaly diagnosed using US and referred for in utero MRI. The gestational age of each case was noted and the MRI report. Both ventricles were measured and each case was categorized according to severity and morphology. The MRI report was compared to the final diagnosis. RESULTS: Of the 30 cases evaluated 18 had mild ventriculomegaly (<15 mm; gestational age range 20-31 weeks, mean 22.8, median 22) and 12 had severe ventriculomegaly (>15 mm; gestational age range 21-37 weeks, mean 28, median 28.5). Additional abnormalities were found in 50% of cases overall (44% mild, 58% severe) using MRI. CONCLUSIONS: Using MRI additional abnormalities were identified in 50% of the foetuses. The morphology of the cases did not suggest underlying pathology in this group. In utero MRI is a useful adjunct to US in cases of foetal cerebral ventriculomegaly referred after initial diagnosis using US.

Abnormalities, Multiple↗
PubMed2006

In utero magnetic resonance of non-isolated ventriculomegaly: Does ventricular size or morphology reflect pathology?

AIM: To confirm whether ventricular size or morphology reflects the underlying pathology in foetuses referred with a diagnosis of possible ventriculomegaly (Vm) and central nervous system (CNS) pathology. METHODS: Retrospective analysis of 40 in utero magnetic resonance (MR) examinations was undertaken. Ventricular size was measured on axial sections by two observers, and morphology was agreed by consensus. Results were analysed according to gestational age at referral, degree of Vm (mild 10-15 mm, moderate/severe >15 mm) and morphology. RESULTS: Nine cases had no Vm (mean gestational age 23.6 weeks, range 19-33), 17 had mild Vm (mean age 23.9 weeks, range 20-31), and 14 had moderate/severe Vm (mean age 25.9 weeks, range 20-35). All groups had a mix of morphology and pathology. Eighteen suspected cases of spina bifida were referred and 17 confirmed (mean age 22.6 weeks, range 19-30) using MR. The morphology was mixed, five cases (27.8%) had an angular appearance (this morphology was only seen in cases with spina bifida). Fourteen cases (77.8%) had Vm (eight mild, six severe). Of the thirteen cases of agenesis of the corpus callosum (ACC) suspected on ultrasound, seven were confirmed using MR (mean age 26.5 weeks, range 20-35). Of those seven cases with ACC confirmed on MR, and three additional cases only detected by in utero MR, five had colpocephaly, seven had Vm (four mild, three severe). CONCLUSION: Severity of Vm did not reflect the type, or presence, of underlying pathology. Morphology appears an indicator of pathology. Angular ventricles should initiate a search for spinal defects. Colpocephaly may indicate ACC.

Brain Diseases↗
PubMed2001

Oto-facio-cervical (OFC) syndrome is a contiguous gene deletion syndrome involving EYA1: molecular analysis confirms allelism with BOR syndrome and further narrows the Duane syndrome critical region to 1 cM.

Branchio-oto-renal (BOR) syndrome is an autosomal dominant disorder involving hearing loss, branchial defects, ear pits and renal abnormalities. Oto-facio-cervical (OFC) syndrome is clinically similar to BOR syndrome, with clinical features in addition to those of BOR syndrome. Mutations in the EYA1 gene (localised to 8q13.3) account for nearly 70% of BOR syndrome cases exhibiting at least three of the major features. Small intragenic deletions of the 3' region of the gene have also been reported in patients with BOR syndrome. We have developed a fluorescent quantitative multiplex polymerase chain reaction for three 3' exons (7, 9 and 13) of the EYA1 gene. This dosage assay, combined with microsatellite marker analysis, has identified de novo deletions of the EYA1 gene and surrounding region in two patients with complex phenotypes involving features of BOR syndrome. One patient with OFC syndrome carried a large deletion of the EYA1 gene region, confirming that OFC syndrome is allelic with BOR syndrome. Microsatellite analysis has shown that comparison of the boundaries of this large deletion with other reported rearrangements of the region reduces the critical region for Duane syndrome (an eye movement disorder) to between markers D8S553 and D8S1797, a genetic distance of approximately 1 cM.

Abnormalities, Multiple↗
PubMed2001

Genetic analysis of the connexin-26 M34T variant: identification of genotype M34T/M34T segregating with mild-moderate non-syndromic sensorineural hearing loss.

Mutations in the human gap junction beta-2 gene (GJB2) that encodes connexin-26 have been shown to cause non-syndromic sensorineural hearing loss (NSSNHL) at the DFNB1 locus on 13q11. Functional and genetic data regarding the disease causing potential of one particular GJB2 sequence variant, 101 T-->C (M34T), have proven contradictory. In this study, we found the prevalence of the M34T allele in a cohort of white sib pairs and sporadic cases with NSSNHL from the United Kingdom and Ireland to be 3.179% of chromosomes screened. Significantly, we identified the first M34T/M34T genotype cosegregating in a single family with mid to high frequency NSSNHL. Screening a control population of 630 subjects we identified 25 M34T heterozygotes; however, no M34T homozygotes were detected. Surprisingly, the majority of M34T alleles (88%) were in cis with a 10 bp deletion in the 5' non-coding sequence. This non-coding deletion was also homozygous in the homozygous M34T subjects. Microsatellite analysis of flanking loci in M34T heterozygotes and controls does not define an extensive ancestral haplotype but preliminary data suggest two common alleles in subjects with the M34T allele. In summary, we provide data that support M34T acting as a recessive GJB2 allele associated with mild-moderate prelingual hearing impairment.

Alleles↗
PubMed1999

[Wheat bran and breast cancer: revisiting the estrogen hypothesis].

Breast cancer is the most relevant form of cancer among women in Latin America. Many studies have evaluated the hormonal mechanisms involved in mammary carcinogenesis, although new focus is aimed towards factors that can potentially be used individually to reduce risk. Wheat bran seems to show a consistent protective effect in mammary carcinogenesis. Wheat bran, besides high level of insoluble fiber, also contains phytic acid and lignins, phytochemicals that have shown to inhibit in vitro and in vivo growth of mammary cancer. The protective effect of wheat bran in breast carcinogenesis is greatest at the promotional phase and when supplemented to a high fat diet. Doses of wheat bran in the 9-12% range have been consistently protective and the inconsistencies observed at higher doses may be dependent on the animal model used. This review examines the protective role of wheat bran in the development of breast cancer and the possible mechanisms involved.

Animals↗
PubMed1997

Metabolic and performance adaptations to interval training in endurance-trained cyclists.

This study examined the effects of sustained high-intensity interval training (HIT) on the athletic performances and fuel utilisation of eight male endurance-trained cyclists. Before HIT, each subject undertook three baseline peak power output Wpeak tests and two simulated 40-km time-trial cycling performance (TT40) tests, of which the variabilities were 1.5 (1.3)% and 1.0 (0.5)%, respectively [mean (SD)]. Over 6 weeks, the cyclists then replaced 15 (2)% of their 300 (66) km.week-1 endurance training with 12 HIT sessions, each consisting of six to nine 5-min rides at 80% of Wpeak, separated by a l-min recovery. HIT increased Wpeak from 404 (40) to 424 (53) W (P < 0.01) and improved TT40 speeds from 42.0 (3.6) to 43.0 (4.2) km.h-1 (P < 0.05). Faster TT40 performances were due to increases in both the absolute work rates from 291 (43) to 327 (51) W (P < 0.05) and the relative work rates from 72.6 (5.3)% of pre-HIT Wpeak to 78.1 (2.8)% of post-HIT Wpeak (P < 0.05). HIT decreased carbohydrate (CHO) oxidation, plasma lactate concentration and ventilation when the cyclists rode at the same absolute work rates of 60, 70 and 80% of pre-HIT Wpeak (P < 0.05), but not when they exercised at the same relative (% post-HIT Wpeak) work rates. Thus, the ability of the cyclists to sustain higher percentages of Wpeak in TT40 performances after HIT was not due to lower rates of CHO oxidation. Higher relative work rates in the TT40 rides following HIT increased the estimated rates of CHO oxidation from approximately 4.3 to approximately 5.1 g.min-1.

Adaptation, Physiological↗
PubMed1997

Physiological and subjective measures of workload when shovelling with a conventional and two-handled ('levered') shovel.

Previous studies have suggested that the two-handled (levered) shovel is advantageous over the conventional spade from a biomechanical point of view. The aim of this experiment was to determine whether less energy was consumed while shovelling a load of sand with this shovel compared to a conventional tool. Accordingly, an experiment was designed in which subjects (n = 10) shovelled 1815 kg sand under laboratory conditions using either a conventional or a levered shovel. Heart rate and oxygen consumption were measured continuously during the trial and subjective data on perceived exertion, general fatigue and body discomfort were recorded after the trial. Although total energy expenditure was similar under both conditions (120 +/- 20 and 125 +/- 25 kcal; conventional versus two-handled spade), average heart rate was 4% higher when the two-handled shovel was used (p < 0.05). In addition, the mass of sand per scoop was 4% less with the two-handled shovel (p < 0.05). In conclusion, subjects used similar energy expenditure to shovel 1815 kg sand with the conventional shovel and the two-handled tool despite lower mass of sand per scoop with the latter. This can be explained by the fact that the increased mass of the additional handle compensated for the lower mass of sand per scoop. The higher average heart rate while shovelling with the two-handled shovel can be explained by the more erect posture.

Adult↗
PubMed1996

Imprint switching on human chromosome 15 may involve alternative transcripts of the SNRPN gene.

Imprinting on human chromosome 15 is regulated by an imprinting centre, which has been mapped to a 100-kb region including exon 1 of SNRPN. From this region we have identified novel transcripts, which represent alternative transcripts of the SNRPN gene. The novel exons lack protein coding potential and are expressed from the paternal chromosome only. We have also identified intragenic deletions and a point mutation in patients who have Angelman or Prader-Willi syndrome due to a parental imprint switch failure. This suggests that imprint switching on human chromosome 15 may involve alternative SNRPN transcripts.

Alternative Splicing↗
PubMed1991

Interaction of regrowing PNS axons with transplanted aggregates of cultured CNS glia in vivo.

Aggregates of cultured neonatal mouse cerebellar astrocytes were implanted into adult mouse sciatic nerves. Two different experimental models were used: aggregates were either placed between proximal and distal stumps of totally transected nerves, or were placed in gaps in partially transected nerves in direct apposition with the cut surface of the proximal stumps. In the model where aggregates were not placed in contact with the proximal stump, regrowing axons rarely entered the aggregates. Where aggregates were placed in contact with the proximal stumps, axons entered the astrocyte-rich environment. Experimental depression of the supply of Schwann cells available to comigrate with regenerating axons proved to be unnecessary: astrocytes provided an alternative substrate for axons. Some axons became myelinated by oligodendrocytes which differentiated within the aggregates; however, few axons remained, unmyelinated, in long-term association with the transplanted astrocytes.

Animals↗