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Biomedical subjects

D M Power

Publications and source records attributed to D M Power.

At least 19 recordsLinked to original sources
PubMed2000

Genomic structure and expression of parathyroid hormone-related protein gene (PTHrP) in a teleost, Fugu rubripes.

In this study we describe the isolation and characterisation of the parathyroid hormone-related protein (PTHrP) gene from the teleost Fugu rubripes. The gene has a relatively simple structure, compared with tetrapod PTHrP genes, composed of three exons and two introns, encompassing 2.25kb of genomic DNA. The gene encodes a protein of 163 amino acids, with a putative signal peptide of 37 amino acids and a mature peptide of 126 amino acids. The overall homology with known tetrapod PTHrP proteins is low (36%), with a novel sequence inserted between positions 38 and 65, the absence of the conserved pentapeptide (TRSAW) and shortened C-terminal domain. The N-terminus shows greater conservation (62%), suggesting that it may have a hypercalcaemic function similar to that of tetrapod PTHrP. In situ localisation and RT-PCR have demonstrated the presence of PTHrP in a wide range of tissues with varying levels of expression. Sequence scanning of overlapping cosmids has identified three additional genes, TMPO, LDHB and KCNA1, which map to human chromosome 12, with the latter two mapping to 12p12-11.2. PTHrP in human also maps to this chromosome 12 sub-region, thus demonstrating conservation of synteny between human and Fugu.

Amino Acid Sequence↗
PubMed2000

Cloning of the cDNA for sea bream (Sparus aurata) parathyroid hormone-related protein.

This paper reports cloning of the cDNA for sea bream (Sparus aurata) parathyroid hormone-related protein (PTHrP). The gene codes for a 125-amino acid mature protein with a 35-residue prepeptide. The total gene sequence is 1.8 kb with approximately 75% noncoding. The N-terminus of the protein resembles mammalian and chicken PTHrP peptides with 12 of the first 21 amino acids identical and for which there is homology with mammalian parathyroid hormone. Toward the C-terminus, the nuclear transporter region between residues 79 and 93 in sea bream is 73% homologous to tetrapod PTHrP, and the RNA binding domain, 96-117, is 50% homologous, moreover starting with the conserved lysine and terminating with the lysine/arginine sequence. Sea bream PTHrP differs significantly from mammalian and chicken PTHrP, having a novel 16-amino acid segment between residues 38 and 54 and completely lacking the terminal domain associated in mammals with inhibition of bone matrix lysis. RT-PCR and in situ hybridization of sea bream tissues show that the gene is expressed widely and the results confirm observations of a PTHrP-like factor in sea bream detected with antisera to human PTHrP.

Amino Acid Sequence↗
PubMed2000

Evolution of the thyroid hormone-binding protein, transthyretin.

Transthyretin (TTR) belongs to a group of proteins, which includes thyroxine-binding globulin and albumin, that bind to and transport thyroid hormones in the blood. TTR is also indirectly implicated in the carriage of vitamin A through the mediation of retinol-binding protein (RBP). It was first identified in 1942 in human serum and cerebrospinal fluid and was formerly called prealbumin for its ability to migrate faster than serum albumin on electrophoresis of whole plasma. It is a single polypeptide chain of 127 amino acids (14,000 Da) and is present in the plasma as a tetramer of noncovalently bound monomers. The major sites of synthesis of TTR in eutherian mammals, marsupials, and birds are the liver and choroid plexus but in reptiles it is synthesised only in the choroid plexus. The observation that TTR is strongly expressed in the choroid plexus but not in the liver of the stumpy-tailed lizard and the strong conservation of expression in the choroid plexus from reptiles to mammals have been taken as evidence to suggest that extrahepatic synthesis of TTR evolved first. The identification and cloning of TTR from the liver of an amphibian, Rana catesbeiana, and a teleost fish, Sparus aurata, and its absence from the choroid plexus of both species suggest an alternative model for its evolution. Protein modelling studies are presented that demonstrate differences in the electrostatic characteristics of the molecule in human, rat, chicken, and fish, which may explain why, in contrast to TTR from human and rat, TTR from fish and birds preferentially binds triiodo-l-thyronine.

Amino Acid Sequence↗
PubMed2000

Outcome from poor grade aneurysmal subarachnoid haemorrhage--which poor grade subarachnoid haemorrhage patients benefit from aneurysm clipping?

Patients with poor grade aneurysmal subarachnoid haemorrhage (SAH) are associated with high mortality and morbidity, and hence are often treated conservatively. This study has set out to determine the outcome for all poor grade subarachnoid haemorrhage patients, and attempts to identify a subgroup with a more favourable prognosis. During a prospective audit of patients with aneurysmal SAH, patients of poor grade [World Federation of Neurological Surgeons (WFNS) IV (and not obeying commands) and V] were sedated, paralysed and ventilated for transfer to the Regional Neurosurgical Unit. Any intraventricular blood and/or hydrocephalus was treated by external ventricular drainage. Following a 24-h period for active blood gas, fluid and electrolyte resuscitation, patients were assessed after reversal of sedation. Selection for angiography and potential aneurysm surgery was restricted to those who showed a purposeful response to painful stimulation. Patients who could readily obey commands were not considered 'true' poor grade and were excluded from analysis. In 102 patients with 'true' poor grade SAH admitted between 1991 and 1997, the overall management outcome at 6 months was poor (favourable outcome 25%, mortality 67%). Following reversal of sedation, 55 patients demonstrated a purposeful response and proceeded to angiography, of whom 37 underwent clipping and three coiling of aneurysm. The outcome in this aneurysm treated subgroup was favourable in 53% (mortality 28%). If patients over the age of 65 years are excluded, the management outcome was favourable in 35% (mortality 58%), with those patients proceeding to clipping or coiling of aneurysms having a favourable outcome in 57% (mortality 27%). Patients over the age of 65 years with poor grade SAH had a favourable outcome in only 6% (mortality 85%). The mortality for poor grade SAH patients remains high. However, following resuscitation and correction of any acute hydrocephalus, a patient subgroup identified on simple clinical criteria can be identified who can expect a better outcome.

Adolescent↗
PubMed2000

Two estrogen receptors expressed in the teleost fish, Sparus aurata: cDNA cloning, characterization and tissue distribution.

Estrogen is an essential hormone for many reproductive and non-reproductive functions. The function of estrogen in the reproductive cycle of seabream (Sparus aurata), a protandrous hermaphrodite teleost fish, is complex but it is understood to be involved in sex inversion, a process that occurs in some individuals during the second reproductive season. Estrogen action is mediated by two estrogen receptor (ER) subtypes designated alpha and beta. As a step to understanding the mechanisms of estrogen action during natural and induced sex reversal in seabream, we have isolated two cDNAs encoding distinct forms of ER homologous to mammalian ERalpha and ERbeta. The seabream ERalpha clone (sbERalpha1), which was truncated in the A/B domain, corresponded to a variant differing in five amino acids from another recently cloned sbERalpha. The ERbeta clone (sbERbeta) encoded a protein 559 amino acids long and showed only 40% identity to sbERalpha. Northern blot analysis of liver and ovary mRNA indicated the presence of several transcripts of the two receptor subtypes. PCR analysis showed that the two receptors differed in their expression pattern. sbERalpha had a more restricted distribution, occurring mainly in testis, liver and heart, and sbERbeta was present in most tissues, being more abundant in ovary, testis, liver, intestine and kidney. The presence in seabream of two ERs with several ER transcripts and their pattern of distribution are consistent with the widespread effects of estrogen in different tissues.

Amino Acid Sequence↗
PubMed1999

Helical computed tomography and three-dimensional reconstruction of a bipedicular developmental anomaly of the C2 vertebra.

STUDY DESIGN: A case of bilateral failure of fusion of the C2 neural arch resembling a bipedicular fracture in a 9-year-old boy involved in a motor vehicle accident. OBJECTIVES: To describe the use of helical computed tomography and three-dimensional reconstruction images to identify the defect as congenital. SUMMARY OF BACKGROUND DATA: Congenital defects in the C2 neural arch are rare. Diagnostic difficulties arise when they are discovered during the assessment of patients after trauma, when they may resemble C2 arch fractures. METHODS: Lateral cervical spine radiograph, transverse section computed tomography, and three-dimensional reconstruction images were used to delineate the anatomy of the defect. RESULTS: The three-dimensional reconstruction views showed that normal alignment of the vertebrae was maintained, despite the pedicle defects. CONCLUSIONS: Differentiation of a C2 fracture from a congenital defect may be difficult. Reconstruction in three dimensions from helical computed tomography is a useful adjunct to conventional computed tomography in the evaluation of such patients.

Cervical Vertebrae↗
PubMed1999

Cloning, expression, and tissue localisation of prolactin in adult sea bream (Sparus aurata).

A major action of prolactin (PRL) in teleost fish is the maintenance of hydromineral balance in euryhaline species in fresh water. The function of PRL in marine teleosts is less certain and unlike euryhaline teleosts, such as tilapia and salmon, there is relatively little information about protein or gene structure. Associated with studies to determine potential functions of PRL, pituitary prolactin cDNA has been cloned and sequenced from sea bream (Sparus aurata), a marine teleost. The sequence obtained spanned 1349 bp and contained an open reading frame encoding a protein of 212 amino acids composed of a putative signal peptide of 24 residues and a mature protein of 188 amino acids. N-terminal sequencing of the native protein confirmed unambiguously the cleavage site, Ala24, Val25, predicted from alignments of the sea bream PRL cDNA with that of other teleosts. The presence of only one form of PRL in sea bream was supported by identification using Northern blots of only a single transcript of 1.35 kb. Reverse transcription and polymerase chain reaction techniques coupled with Southern blot analysis resulted in the detection of PRL in the pituitary but also in the intestine, liver, ovary, and testes.

Amino Acid Sequence↗
PubMed1999

Identification of transthyretin in fish (Sparus aurata): cDNA cloning and characterisation.

Transthyretin (TTR) has been proposed to have first evolved in reptiles and is one of the three plasma proteins important in the transport of thyroid hormones in higher vertebrates. A full-length cDNA encoding TTR was isolated from a sea bream (Sparus aurata) liver cDNA library using a homologous TTR cDNA probe generated by RT-PCR. Comparison of the deduced amino acid sequence of sea bream TTR with other published sequences, revealed an overall identity of 47-54%, although the amino acids in the active binding site were almost 100% conserved. Distribution of TTR was studied in sea bream adult tissue by RT-PCR and was detected in liver, brain, pituitary, gills, kidney, intestine and testis, although northern blot analysis only revealed TTR in the liver, suggesting that in sea bream, liver is the main source of this protein. TTR was also expressed in larvae from the first day post-hatch (48 h post-fertilisation). Analysis of thyroxine (T4) and triiodo-L-thyronine (T3) binding to sea bream serum proteins demonstrated that both T4 and T3 bind to albumin and TTR. By demonstrating the existence of TTR in teleost fish this study indicates TTR must have evolved in a common fish ancestor of the tetrapod evolutionary line.

Amino Acid Sequence↗
PubMed1999

Anatomy, demonstrating and basic surgical training.

Calmanisation of surgical training has led to the introduction of the concept of a two-year basic surgical training (BST) rotation. Successful completion of this training is assessed by the new MRCS/AFRCS examination. Within these constraints there is no room for the previously popular anatomy demonstrating posts. The aim of this study, therefore, was to examine the views of FRCS and MRCS surgical trainees about their own demonstrating experience, their current anatomical knowledge and on the future value of anatomy demonstrating.

Anatomy↗
PubMed1998

Cloning, characterisation and expression of the apolipoprotein A-I gene in the sea bream (Sparus aurata).

A full length cDNA clone representing apolipoprotein A-I was isolated from a sea bream (Sparus aurata) liver library. The clone encodes a 261 amino acid protein which shows highest amino acid identity (38%) with salmon apolipoprotein A-I. Northern blot analysis showed strong expression of a 1.4 kb transcript in liver with lower expression in intestine. Expression of apolipoprotein A-I in intestine was markedly reduced by treatment with triiodothyronine (T3).

Amino Acid Sequence↗
PubMed1998

Parathyroid hormone-related protein in lower vertebrates.

1. Parathyroid hormone-related protein (PTHrP) is an important mediator of humoral hypercalcaemia of malignancy in humans. Normal human subjects have very low levels of PTHrP in their circulation. 2. Parathyroid hormone-related protein has recently been demonstrated in high levels in the circulation and tissues of the sea bream and the dogfish, leading to the hypothesis that PTHrP may be a 'classical' hormone in fish. 3. Immunohistochemistry and in situ hybridization were performed to investigate the evolutionary history of PTHrP. Tissues were examined from a number of lower vertebrates, including lungfish, lamprey and several species of bony and cartilaginous fish. Parathyroid hormone-related protein was localized to the skin and to kidney tubules in all animals studied. In the developing lungfish, PTHrP was observed in the notochord, developing brain and skeletal muscle layers. These results suggest that PTHrP is of ancient origin and has a basic and fundamental function in vertebrates.

Animals↗
PubMed1997

Cloning and sequencing of a full-length sea bream (Sparus aurata) beta-actin cDNA.

A full-length cDNA clone encoding beta-actin (beta-actin) was isolated from a sea bream (Sparus aurata) liver cDNA library. Sequencing of this clone reveals an open reading frame encoding a 375 amino acid protein that shares a high degree of conservation to other known actins. The sea bream beta-actin sequence showed 98% identity to carp and human beta-actin and 95% and 94% identity to sea squirt and Dictyostelium cytoplasmic actins, respectively.

Actins↗
PubMed1996

Immunochemical detection of parathyroid hormone-related protein in the saccus vasculosus of a teleost fish.

Using antisera to regions of human parathyroid hormone-related protein (PTHrP) the saccus vasculosus (SV) of the sea bream (Sparus aurata) has been shown to contain immunoreactive PTHrP. By immunohistochemistry (IHC) the epithelial coronet cells in fixed and wax-embedded SV tissue reacted with antisera to the prepro region of human PTHrP (-13 to +2), the N-terminus PTHrP (1-16), and the midmolecule PTHrP (50-69). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of saccus extracts and incubation media contained two major proteins of 14.3 and 15 kDa. By Western blotting these two proteins both reacted with the three antisera used for IHC, suggesting that they are immunochemically similar to human PTHrP (1-84). Ultrastructurally the coronet cells of Sparus saccus vasculosus resembled coronet cells described for other teleosts, with an abundant smooth endoplasmic reticulum (SER) which was more highly organized in the coronets. IHC at EM level showed reaction mainly with the membranes of the SER. These results suggest that S. aurata saccus vasculosus may produce a PTHrP-like molecule similar to human PTHrP.

Animals↗
PubMed1996

Somatotropin release-inhibiting factor and galanin innervation in the hypothalamus and pituitary of seabream (Sparus aurata).

The distribution of galanin (GAL) and somatotropin-release-inhibiting-factor (SRIF) immunoreactivity in the hypothalamus and pituitary of the sea bream (Sparus aurata) was studied by immunocytochemistry. An extensive system of neurons immunoreactive with antisera to the two peptides was identified throughout the brain with staining particularly in the hypothalamus. In the hypothalamus, GAL immunoreactive perikarya were detected principally in the nucleus preopticus and nucleus tuberis. Major nerve tracts were observed to sweep down from the hypothalamic nuclei and reached the pituitary via the preoptico-hypophysial tract. Many of the fibers had varicose swellings indicating they were secretory. SRIF immunoreactivity was distributed similarly to GAL but the network of nerve fibers was less dense; no colocalization of these two peptides was seen. SRIF immunoreactive perikarya were present in the preoptic nucleus, the tuberal nucleus, and the basolateral hypothalamus. These perikarya were large and densely staining and were predominately bipolar, although some multipolar perikarya were observed. In the pituitary GAL and SRIF immunoreactivities were confined principally to the pars distalis where fibers infiltrated between growth hormone, prolactin, and adrenocorticotrophic cells. More of the fibers were immunoreactive for SRIF than for GAL. There was no immunoreaction for GAL or SRIF in any of the pituitary cells. There is thus morphological evidence for a neuroendocrine control of the pars distalis by GAL and SRIF and for a possible functional interaction between these two systems.

Animals↗
PubMed1995

Cloning and characterisation of a fish aldolase B gene.

A full length cDNA clone representing an aldolase mRNA was isolated from a sea bream (Sparus aurata) liver cDNA library. Sequencing of this clone revealed it to encode a 364 amino acid protein with 74% amino acid identity to human aldolase B and slightly lower similarity to human aldolase A and C. In view of the sequence data and of Northern blot analysis showing strong expression of a 1.6 kb transcript in liver it was concluded that the cloned gene represents aldolase B. This clone represents the first aldolase gene to be sequenced from any fish species thus providing new data on the evolution of the vertebrate aldolase gene family.

Amino Acid Sequence↗
PubMed1993

Parathyroid hormone-related protein is a factor in normal fish pituitary.

Using antibodies to the amino-terminal region of human parathyroid hormone-related protein (PTHrP) we have demonstrated PTHrP immunoreactivity in pituitaries and plasma of the sea bream (Sparus aurata). Pituitary cells at two distinct locations contained immunodetectable PTHrP; an anterior group in the rostral pars distalis which also contained immunoreactive thyroid stimulating hormone (TSH), and a posterior group lying at the border of the pars intermedia and proximal pars distalis between cells which stained with antibody to human corticotrophin-like intermediate lobe peptide. By Western blot analysis pituitary extracts contained two immunoreactive isoforms of PTHrP, one of 29 kDa and the other of 26 kDa. Media of pituitaries incubated for up to 14 days in Krebs-Ringer bicarbonate also had several isoforms of immunodetectable PTHrP, two of them corresponding to the 29- and 26-kDa molecular forms but there were in addition both larger and smaller molecules. The concentration of PTHrP in sea bream plasma was comparable with levels observed in human subjects with humoral hypercalcaemia of malignancy. There was no reaction between pituitary cells or pituitary extracts and antibody to human parathyroid hormone. Thus sea bream pituitary contains immunoreactive PTHrP, which appears to be released into medium during in vitro incubation and which may be a significant source of plasma immunoreactive PTHrP in vivo.

Animals↗