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Biomedical subjects

K Walsh

Publications and source records attributed to K Walsh.

At least 199 records · Page 11Linked to original sources
PubMed1994

The gene encoding rat phosphoglycerate mutase subunit M: cloning and promoter analysis in skeletal muscle cells.

The expression of the gene encoding the muscle-specific (M)-subunit of phosphoglycerate mutase (PGAM-M) is restricted to adult skeletal and cardiac muscle. In order to study its expression in muscle, the rat PGAM-M gene has been isolated and sequenced. Rat PGAM-M spans about 2.2 kb and is composed of three exons: 442, 181 and 186-bp long, and two introns of 97 bp and 1.3 bp. The analysis of the 5'-flanking region reveals a promoter which contains multiple DNA regulatory elements and constitutes an ideal model to study muscle gene transcriptional regulation. Thus, the elements responsible for rat PGAM-M muscle-specific expression have been identified by transient transfection in chicken embryo primary cultures, using chimeric constructs of the rat promoter linked to a cat reporter gene. Here, we report that in spite of the abundance of E-box motifs in the rat PGAM-M promoter known for their involvement in muscle gene expression, two DNA elements regulate the muscle-specific transcription of rat PGAM-M: an A/T motif, the putative MEF-2-binding site (myocyte-specific enhancer-binding factor 2), and a proximal 27-bp element which is conserved between the rat and human genes. These two elements define a small promoter (170 bp) sufficient to support potent and skeletal-muscle-specific expression. The conserved 27-bp region contains a transcriptional regulatory element able to confer muscle-specific expression when located upstream from a heterologous TATA box.

Amino Acid Sequence↗
PubMed1994

The mouse creatine kinase paired E-box element confers muscle-specific expression to a heterologous promoter.

E-box elements, with the CANNTG sequence motif, occur in numerous promoters and enhancers. We evaluated the tissue-specific expression properties of the paired murine E-box element from the mouse muscle creatine kinase (MCK) enhancer in a minimal heterologous promoter construct. A 46-bp fragment containing the paired E-box element in its wild-type (wt) configuration conferred high levels of muscle-specific expression in transfected embryonic chicken cell cultures. The expression from this paired E-box element was similar to that of the simian virus 40 (SV40) promoter/enhancer, but a 21-bp fragment containing a single E-box was inactive. We conclude that the paired E-box element from the MCK enhancer is sufficient for high levels of muscle-specific expression when placed upstream from a non-muscle TATA element.

Actins↗
PubMed1994

Molecular cloning and localization of the human GAX gene to 7p21.

The GAX homeobox gene is expressed in the cardiovascular tissues of the adult rat, including heart, lung, kidney, and blood vessels. In the vasculature it is specifically expressed in quiescent smooth muscle cells, but its expression is rapidly down-regulated when these cells are stimulated to proliferate with mitogens. Since vascular smooth muscle cell proliferation is important in the pathology of blood vessel disorders, the human GAX gene was isolated and characterized. The human GAX cDNA was obtained by an anchored-PCR approach using cDNA templates from cardiovascular tissues and amplification primers designed from sequence information of the rat GAX cDNA and the homeodomain-containing exon of the human GAX gene. The human and rat GAX gene coding sequences are 98% conserved at the amino acid level and 83% conserved at the nucleotide level. Similar to rat, the human homolog contains a CAX trinucleotide repeat N-terminal to the homeodomain that encodes for a stretch of 17 consecutive histidine or glutamine residues. The human GAX locus was mapped by fluorescence in situ hybridization to the short arm of chromosome 7 at band p21. The human cDNA sequence will be useful for analyses of GAX gene expression in cardiovascular diseases.

Amino Acid Sequence↗
PubMed1994

Guidelines for the prevention and control of tuberculosis in the elderly.

Tuberculosis (TB) in the elderly is on the rise although the disease is both preventable and curable. The primary practitioner plays a pivotal role in the diagnosis and prevention of TB. The article provides guidelines designed to bring the practitioner up-to-date on the latest recommendations for the prevention and control of TB in the elderly. An overview of TB, current epidemiology, and information on the uniqueness of this disease as it presents in the elderly client is addressed. An in-depth guideline and explanation for all aspects of care are included for both the institutionalized and community-based elder. Current Centers for Disease Control and Prevention recommendations and research are presented. The role of the primary practitioner in the prevention and control of this disease is included with a quick reference tool. The guidelines also address the current diagnostic testing and recommended treatment for TB.

Aged↗
PubMed1994

Incidence and prognosis of obstruction of the left ventricular outflow tract in Liverpool (1960-91): a study of 313 patients.

OBJECTIVE: To determine the incidence of the various types of obstruction of the left ventricular outflow tract in patients born in the five health districts of Liverpool and to compare their prognosis into early adult life. DESIGN: Notes of all patients with obstruction of the left ventricular outflow tract born in the study area between 1960 and 1991 were reviewed. Patients with hypoplastic left ventricle, mitral valve atresia, and those with discordant atrioventricular or ventriculoarterial connections were excluded. Survivors were traced and assessed clinically; eight were lost to follow up. RESULTS: Obstruction of the left ventricular outflow tract occurred in 313 patients (67% male), giving an incidence of 6.1/10,000 live births. The median (range) age at presentation was 13.9 months (0-20 yr). Aortic valve stenosis occurred in 71.2%: subvalve in 13.7%, supravalve in 7.7%, and multilevel in 7.4%. The median (range) duration of follow up was 10.0 (1-29) yr. Aortic regurgitation at presentation occurred more often (p < 0.001) in patients with subvalve stenosis than in those with other types of obstruction, but there was an increased incidence (p < 0.001) at follow up in patients with valve stenosis. Ninety eight patients (31.3%) underwent operation. The reoperation rate was 27% for valve stenosis and 9% for subvalve obstruction. No patients with supravalve stenosis underwent reoperation. The median duration from first operation to aortic valve replacement (17 patients) was 12.3 years. Hazard analysis confirmed that the risk of death was higher in patients presenting at a younger age, with more severe stenosis, and those with subaortic, multilevel obstruction or a syndrome. Hazard analysis also showed that the risk of a clinical event (surgery, balloon dilatation, or endocarditis) was greater in patients who presented at a younger age, with more severe stenosis or aortic regurgitation, and in those with subvalve or multilevel obstruction. CONCLUSIONS: Aortic valve stenosis was the most common type of obstruction. Hazard analysis indicates that the age and severity of obstruction at presentation have a significant effect on survival and freedom from a clinical event. The risk of premature death in patients presenting with moderately severe valve stenosis is reasonably small, but increases considerably in those with subvalve, supravalve, and multilevel obstruction. Patients who present with mild valve stenosis have a good prognosis. The risk of sudden death is less than previous predictions. Patients with subvalve and multilevel obstruction, even when mild at presentation, are more likely to undergo intervention or develop endocarditis than those with valve or supravalve stenosis. Follow up into adult life is essential.

Adolescent↗
PubMed1994

Morphology of left ventricular outflow tract structures in patients with subaortic stenosis and a ventricular septal defect.

OBJECTIVE: To compare the incidence and prognosis of subaortic stenosis associated with a ventricular septal defect and to define the morphological basis of subaortic stenosis. DESIGN: Presentation and follow up data on 202 patients with subaortic stenosis seen at the Royal Liverpool Children's Hospital between 1 January 1960 and 31 December 1991 were reviewed. Survivors were traced to assess their current clinical state. Necropsy specimens of 291 patients with lesions associated with subaortic stenosis were also examined. RESULTS: In the clinical study; 65 (32.1%) of the 202 patients with subaortic stenosis had a ventricular septal defect (excluding an atrioventricular septal defect). 32 of these patients had a short segment (fibromuscular) subaortic stenosis. 33 had subaortic stenosis produced by deviation of muscular components of the outflow tracts. In 17 patients (51.5%) this was caused by posterior deviation or extension of structures into the left ventricular outflow tract, resulting in obstruction above the ventricular septal defect. In the other 16 patients (48.5%) there was over-riding of the aorta with concordant ventriculoarterial connections, (without compromise to right ventricular outflow) producing subaortic stenosis below the ventricular septal defect. Additional fibrous obstruction occurred in 39% of the patients with deviated structures. The age at presentation was lower (P < 0.01) in patients with deviated structures (median (range) 0.4 (0 to 9.2) months) than in those with short segment obstruction (median (range) 4.2 (0 to 84.9) months). The incidence of aortic arch obstruction was higher (P < 0.002) in patients with deviated structures than in those with short segment obstruction (38%). In the morphological study 35 pathological specimens showed obstructive muscular structures in the left ventricular outflow tract either above or below the ventricular septal defect. 16 had either posterior deviation of the outlet septum or extension of the right ventriculoinfundibular fold, or both of these together into the left ventricle. 19 had anterior deviation of the outlet septum into the right ventricle with overriding of the aorta (without compromise to right ventricular outflow). The earliest age at which additional fibrous obstruction was seen was 9 months. The aortic valve circumference was small in 18% of specimens. FOLLOW UP: The median (range) duration of follow up in survivors from the clinical study was 6.6 (1 to 25.7) years. 16 patients with deviated musculature (49%) and 16 with short segment fibromuscular stenosis (50%) underwent operation for subaortic stenosis. Patients with deviated structures were younger at operation than those with short segment stenosis (P < 0.005). Patients with posterior deviation or extension of structures into the left ventricular outflow tract underwent operation for subaortic stenosis more frequently (P < 0.05) than those with anterior deviation of the outlet septum and aortic override. The ventricular septal defect required surgical closure more frequently (P < 0.005) in patients with deviation (93.9%) than in those with short segment obstruction (21.9%). There was no significant difference in the mortality between patients with deviation (27%) and those with short segment obstruction (12%). CONCLUSIONS: 32% of patients in the clinical study with subaortic stenosis had a ventricular septal defect. Only 51% of these had obstructive and deviated muscular structures in the left ventricular outflow tract. These patients had a significantly higher incidence of aortic arch obstruction and required surgery for subaortic stenosis at a younger age than those with short segment obstruction. The ventricular septal defect also required surgical closure more frequently in those patients with deviation. The morphological study defined the two sites of obstruction. The presence or absence and type of deviation should be clearly defined in all patients with a ventricular septal defect,

Aortic Stenosis, Subvalvular↗
PubMed1994

Cloning and sequence analysis of homeobox transcription factor cDNAs with an inosine-containing probe.

Much effort has been directed toward the isolation and characterization of homeobox cDNAs from numerous cell types because they encode transcription factors important to many cellular processes, including pattern formation in the embryo, cell growth and cell differentiation. Many novel homeobox cDNAs have been isolated by screening libraries by hybridization with degenerate oligonucleotides designed from conserved amino acid sequences in the third helix of the homeodomain. However, the degeneracy of the genetic code necessitates that these oligonucleotides be highly degenerate, often precluding their use as sequencing primers to rapidly determine clone identity. Here we describe a screening protocol for homeobox cDNAs that utilizes a short oligonucleotide probe with inosine residues incorporated at positions of maximum codon degeneracy. This probe specifically hybridizes to many classes of homeobox transcription factor cDNAs, but its primary advantage is that it also serves as an effective sequencing primer, which allows the investigator to rapidly determine whether the clones encode a protein of interest. In a screen of 500,000 plaques of a rat aorta cDNA library by this method, we identified 13 positive plaques of which 12 were found to contain homeobox cDNAs representing 5 distinct genes, and, using this probe, it was possible to obtain initial high-quality sequence information from every clone isolated that contained a homeodomain.

Animals↗
PubMed1994

Evaluation of the use of general practice age-sex registers in epidemiological research.

AIM: This study set out to show how well samples from general practice registers compare with census data, to describe those characteristics of the population and of the register that influence the response to postal surveys, and to demonstrate how general practice records can be used to assess non-response bias. METHOD: The data for this study were obtained from a large postal survey about low back pain among the general adult population aged 20-59 years in eight areas of the United Kingdom, using general practice age-sex registers as the sampling frame. RESULTS: The overall response rate was 59%. In the areas chosen, general practice registers yielded samples of size and age-sex composition close to that predicted from national census data. Responses were more likely to be obtained from women, from older age groups and from practices where the sample lists had been inspected for errors. The use of computerized registers and a letter of recommendation from the general practitioner had no effect on the response rate. Inspection of the general practice records of subsamples of respondents and non-respondents to determine consultation rates suggested that there was little response bias in respect of the subject of the survey. CONCLUSION: General practice registers can provide a suitable sampling frame for epidemiological purposes. Inaccuracies in the register can be reduced to some extent by careful inspection, but an irreducible minimum remain. Information held in general practice records can be useful in assessing response bias in health surveys.

Adult↗
PubMed1993

The progression of mild congenital aortic valve stenosis from childhood into adult life.

UNLABELLED: We studied 187 patients who presented with mild congenital aortic valve stenosis or a bicuspid aortic valve without stenosis at presentation; 63% were males. Information on all clinical events was obtained, and patients were traced to assess current clinical status. RESULTS: The median age at presentation was 2 years (range, 0-15). Additional cardiac lesions occurred in 51 patients, more commonly in patients presenting under 1 year of age (P < 0.0001). The median duration of follow-up was 10 years (range, 1-28); seven patients were lost to follow-up. Thirty-two patients progressed to require intervention (28 surgical, five balloon valvuloplasty) at a median age of 10.5 years. No patient who presented with a bicuspid aortic valve required intervention. Two patients developed endocarditis. There were eight deaths; four after surgery for aortic stenosis and four due to other cardiac lesions. There were no sudden deaths. Actuarial and hazard analysis showed that progression beyond mild stenosis was closely related to duration of follow-up. CONCLUSIONS: Congenital aortic valve stenosis is most frequently mild at presentation. Progression is related to duration of follow-up. Fewer than 20% of patients are likely to still have mild stenosis after 30 years. Follow-up into adult life is essential.

Actuarial Analysis↗
PubMed1993

Spectral Doppler flow profiles in neonates with obstructive lesions of the aortic arch.

The aim was to assess the value of continuous and pulsed wave Doppler ultrasound in the detection and differentiation of obstructive lesions of the aortic arch in neonates. In 31 neonates with proven arch obstruction (pre- or juxtaductal coarctation in 19 patients; postductal coarctation in five patients; interrupted aortic arch in four patients; aortic arch atresia in three patients), continuous wave Doppler interrogation of the descending aorta from the suprasternal notch revealed a high velocity jet (greater than 2.2 m/s) directed away from the transducer in 12 patients. Of these, four neonates had preductal coarctation, and five postductal coarctation. The remaining three patients had arch interruption or atresia. Image guided pulsed Doppler ultrasound recordings were obtained from the arch upstream from the obstruction, the descending aorta distal to the obstruction, and from the arterial duct. Patients with coarctation had a prominent diastolic flow directed away from the transducer in the arch upstream from the obstruction, representing a diastolic coarctation gradient, or diastolic steal either by the patent arterial duct or by collateral vessels. In contrast, patients with arch interruption or atresia had only a systolic flow signal in the proximal arch. Ductal flow was either bidirectional (preductal coarctation, arch interruption, arch atresia), continuous right to left flow from pulmonary artery to aorta (one case each of juxtaductal coarctation and arch atresia), or continuous left to right flow from aorta to pulmonary artery (postductal coarctation). In neonates wide patency of the duct often precludes the development of a large pressure drop across a coarctation. Conversely, a high velocity signal may be recorded from a patent but restrictive duct. In conjunction with imaging, pulsed Doppler velocity profiles from the arch and patent duct permit a meaningful interpretation of the haemodynamics of arch obstruction.

Analysis of Variance↗
PubMed1993

Ethylene glycol monomethyl ether (EGME) exposure of male mice produces a decrease in cell proliferation of preimplantation embryos.

In this study using an aggregation chimera assay we examined male mice exposed to a nonmutagenic reproductive toxicant, EGME, for the transmission of impaired viability to their progeny preimplantation embryos. Prior to their aggregation into pairs, one of the embryos was labeled with a viable dye fluorecein isothiocyanate (FITC) to determine the relative cellular contribution from each partner embryo when chimeras were dissociated 30 to 35 h later (2 to 3 cell cycles). Direct cell-cell contact of embryos derived from exposed males and embryos from control males creates a competitive situation that has been shown to confer a cell proliferation disadvantage to the embryo from an exposed parent. The cell proliferation disadvantage is expressed as a "proliferation ratio": number cells from an experimental embryo/total chimera cell number. Male mice were exposed to EGME by gavage for 5 days with 0, 50, 200, 750, or 1500 mg/kg and were serially mated with unexposed female mice for the next 7 weeks. Proliferation ratios were significantly decreased in the 50, 200, and 750 mg/kg dose groups at week 4, which corresponds to the pachytene spermatocyte stage of spermatogenesis. Proliferation ratios were also significantly decreased in the 1500 mg/kg group at week 5. Due to transient infertility in this dose group, there were not sufficient numbers of embryos to evaluate for week 4. These results indicate that male mice exposed to EGME transmitted adverse effects to their progeny embryos that were expressed as an embryonic cell proliferation disadvantage in the chimera assay.

Animals↗
PubMed1993

Different regulatory sequences control creatine kinase-M gene expression in directly injected skeletal and cardiac muscle.

Regulatory sequences of the M isozyme of the creatine kinase (MCK) gene have been extensively mapped in skeletal muscle, but little is known about the sequences that control cardiac-specific expression. The promoter and enhancer sequences required for MCK gene expression were assayed by the direct injection of plasmid DNA constructs into adult rat cardiac and skeletal muscle. A 700-nucleotide fragment containing the enhancer and promoter of the rabbit MCK gene activated the expression of a downstream reporter gene in both muscle tissues. Deletion of the enhancer significantly decreased expression in skeletal muscle but had no detectable effect on expression in cardiac muscle. Further deletions revealed a CArG sequence motif at position -179 within the promoter that was essential for cardiac-specific expression. The CArG element of the MCK promoter bound to the recombinant serum response factor and YY1, transcription factors which control expression from structurally similar elements in the skeletal actin and c-fos promoters. MCK-CArG-binding activities that were similar or identical to serum response factor and YY1 were also detected in extracts from adult cardiac muscle. These data suggest that the MCK gene is controlled by different regulatory programs in adult cardiac and skeletal muscle.

Animals↗
PubMed1993

Molecular cloning of a diverged homeobox gene that is rapidly down-regulated during the G0/G1 transition in vascular smooth muscle cells.

Adult vascular smooth muscle cells dedifferentiate and reenter the cell cycle in response to growth factor stimulation. Here we describe the molecular cloning from vascular smooth muscle, the structure, and the chromosomal location of a diverged homeobox gene, Gax, whose expression is largely confined to the cardiovascular tissues of the adult. In quiescent adult rat vascular smooth muscle cells, Gax mRNA levels are down-regulated as much as 15-fold within 2 h when these cells are induced to proliferate with platelet-derived growth factor (PDGF) or serum growth factors. This reduction in Gax mRNA is transient, with levels beginning to rise between 8 and 24 h after mitogen stimulation and returning to near normal by 24 to 48 h. The Gax down-regulation is dose dependent and can be correlated with the mitogen's ability to stimulate DNA synthesis. PDGF-AA, a weak mitogen for rat vascular smooth muscle cells, did not affect Gax transcript levels, while PDGF-AB and -BB, potent mitogens for these cells, were nearly as effective as fetal bovine serum. The removal of serum from growing cells induced Gax expression fivefold within 24 h. These data suggest that Gax is likely to have a regulatory function in the G0-to-G1 transition of the cell cycle in vascular smooth muscle cells.

Animals↗
PubMed1993

Incidence and prognosis of congenital aortic valve stenosis in Liverpool (1960-1990).

OBJECTIVE: To determine the incidence and prognosis of congenital aortic valve stenosis in the five Health Districts of Liverpool that make up the Merseyside area. DESIGN: The records of the Liverpool Congenital Malformations Registry and the Royal Liverpool Children's Hospital identified 239 patients (155 male, 84 female) born with aortic valve stenosis between 1960 and 1990. Patients were traced to assess the severity of stenosis at follow up. Information on the severity at presentation and all subsequent events was obtained. RESULTS: Congenital aortic valve stenosis occurred in 5.7% of patients with congenital heart disease born in the Merseyside area. The median age at presentation was 16 months (range 0-20 years). Stenosis was mild at presentation in 145 patients, moderate in 33, severe in one and critical in 21 and 39 had a bicuspid valve without stenosis. Additional cardiac lesions were significantly more common in children presenting under one year of age and in those with critical stenosis. The median duration of follow up was 9.2 years (range 1-28 years) and seven patients were lost to follow up. 81 operations were performed in 60 patients. The reoperation rate was 28.3% after a median duration of 8.7 years (range 2.5-18 years). 15% of patients who presented with mild stenosis subsequently required operation compared with 67% of those with moderate stenosis. There were no sudden unexpected deaths and no deaths after aortic valvotomy, except in those presenting with critical stenosis. Mortality was 16.7% but patients presenting with critical aortic stenosis had a much worse prognosis. Actuarial and hazard analysis showed that the survival and absence of serious events (aortic valve surgery or balloon dilatation, endocarditis, or death) were significantly better in patients who presented with mild aortic stenosis than in those who presented with moderate aortic stenosis. 75% of patients presenting with mild stenosis had not progressed to moderate stenosis after 10 years of follow up. CONCLUSIONS: Congenital aortic valve stenosis may be progressive even when it is mild at presentation. Patients presenting with mild stenosis, however, have a significantly better prognosis than those presenting with moderate stenosis. An accurate clinical and echocardiographic assessment of the severity of aortic valve stenosis at presentation provides a good guide to prognosis into early adult life.

Actuarial Analysis↗
PubMed1993

Recanalisation of an occluded modified Blalock-Taussig shunt by balloon dilatation.

A four year old boy with pulmonary atresia and ventricular septal defect had an acute cyanotic episode three years after undergoing a right-sided, 6 mm diameter, modified Blalock-Taussig shunt. On admission no continuous murmur could be heard from the shunt and the typical high velocity, continuous flow profile of the shunt could not be identified by Doppler echocardiography. At catheterisation a right subclavian artery angiogram confirmed shunt occlusion. From the subclavian artery, an 0.035 inch wire was used to enter the occluded shunt and then the pulmonary artery. Balloon angioplasty of the entire length of the shunt was performed with 6 mm diameter balloon. After angioplasty the arterial oxygen saturation increased from 63% to 83%. The patient was treated with intravenous heparin followed by warfarin. Repeat catheterisation and angiography eight days later confirmed wide patency of the shunt.

Blood Vessel Prosthesis↗