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.

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.

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.

Molecular cloning of a homeobox transcription factor from adult aortic smooth muscle

We report here the cloning of a cDNA encoding a homeobox transcription factor from vascular smooth muscle and describe its unique pattern of mRNA expression at different stages in development. The cDNA isolated is 1576 base pairs in length not including the poly(A) tail and contains an open reading frame coding for a predicted 372-amino acid homeobox protein. During early embryogenesis, expression was detected in the neural tube with a sharp expression boundary occurring at an anterior position, in the myelencephalon, in the third and fourth branchial arches, and in vessels leading from the heart. In adults, however, transcripts were only detected in aortic smooth muscle and lung but were undetectable in cardiac or skeletal muscle, visceral smooth muscle, and many other tissues including brain. In neonates, expression was detected in the outflow tracts of the heart as well as in the cardiomyocytes. The expression pattern of this gene suggests that, although it likely has multiple roles during development, in the adult, it may participate in the control of vascular smooth muscle differentiation and proliferation.

Profiles, correlates, and trajectories of intelligence in Prader-Willi syndrome

Three aspects of intellectual functioning in persons with Prader-Willi syndrome were examined in two, related studies. In study 1, 21 subjects were evaluated with a psychometric instrument that assesses neuropsychological styles of cognitive processing, the Kaufman Assessment Battery for Children. Prader-Willi subjects showed deficits in sequential processing, and strengths in academic achievement tasks such as reading and vocabulary. In contrast to previous reports on the syndrome, no relationship was found between weight and degree of intellectual impairment. Study 2 included a cross-sectional examination of the trajectory of IQ in 21 subjects aged 13 to 46 years, as well as a longitudinal analysis of 31 subjects aged 5 to 30 years who were tested twice with the same IQ test. No evidence of the previously described decline in IQ over time was noted in either the cross-sectional or longitudinal analyses. The implications of these findings for interventions are discussed.

Adaptive and maladaptive behavior in Prader-Willi syndrome

The development and profiles of adaptive and maladaptive behavior of 21 adolescents and adults with Prader-Willi syndrome were cross-sectionally examined with the Vineland Adaptive Behavior Scales and Achenbach's Child Behavior Checklist (CBCL). Adaptive strengths emerged for the group as a whole in daily living skills, and this strength became more pronounced with increasing age. A relative weakness was found in socialization, most notably in coping skills. CBCL findings indicated that externalizing behaviors were particularly heightened in adolescence and that many behaviors previously described as either emerging or worsening in adolescence also persist into the adult years (e.g., temper tantrums, arguing, irritability, stubbornness, lying, skin picking, obsessions, defiance). Certain elevated CBCL behaviors were unique to young versus old age groups, and aging in this syndrome may be associated with heightened confusion, withdrawal, and fatigue. The need to study adaptive and maladaptive features in a wider age range of subjects with Prader-Willi syndrome was emphasized.

A prospective cytogenetic study of 36 cases of DiGeorge syndrome

Cytogenetic analysis was carried out in a prospective series of 36 children with DiGeorge syndrome. High-resolution banding (> 850 bands/haploid set) was achieved in 30 cases. Monosomy 22q11.21-->q11.23 was found in 9 of these 30 cases. In each of these cases monosomy 22q11.21-->q11.23 resulted from an interstitial deletion and not from a translocation. No other chromosome abnormalities were seen.

Functional antagonism between YY1 and the serum response factor

The rapid, transient induction of the c-fos proto-oncogene by serum growth factors is mediated by the serum response element (SRE). The SRE shares homology with the muscle regulatory element (MRE) of the skeletal alpha-actin promoter. It is not known how these elements respond to proliferative and cell-type-specific signals, but the response appears to involve the binding of the serum response factor (SRF) and other proteins. Here, we report that YY1, a multifunctional transcription factor, binds to SRE and MRE sequences in vitro. The methylation interference footprint of YY1 overlaps with that of the SRF, and YY1 competes with the SRF for binding to these DNA elements. Overexpression of YY1 repressed serum-inducible and basal expression from the c-fos promoter and repressed basal expression from the skeletal alpha-actin promoter. YY1 also repressed expression from the individual SRE and MRE sequences upstream from a TATA element. Unlike that of YY1, SRF overexpression alone did not influence the transcriptional activity of the target sequence, but SRF overexpression could reverse YY1-mediated trans repression. These data suggest that YY1 and the SRF have antagonistic functions in vivo.

Patency of Blalock-Taussig shunt assessed by Doppler colour flow imaging

A neonate with pulmonary atresia and intact ventricular septum underwent a modified right sided Blalock-Taussig shunt. Following the procedure, the patient developed a right sided haemothorax, which required drainage. A murmur was not audible subsequently. Echocardiography with colour flow imaging enabled identification of patency of the right sided shunt. It was then possible to discontinue intravenous prostaglandin medication.

MyoD binds to the guanine tetrad nucleic acid structure

A high affinity interaction between a protein and the guanine tetrad nucleic acid structure is described. Recombinant MyoD, a transcription factor that can initiate myogenesis, specifically bound to helical structures formed by stacks of guanine residues in square planar arrays. The N-7 methylation of a set of consecutive dG residues in a single-stranded probe of the creatine kinase enhancer interfered with the formation of this nucleic acid structure and prevented protein binding. Recombinant MyoD also bound to a guanine tetrad formed with a telomeric DNA probe, and it had a higher affinity for the four-stranded structure than for the double-stranded E-box-binding site. These data are the first report of a direct interaction between a protein and this nucleic acid conformation. The potential biological significance of this finding is discussed.

Giant right atrial diverticulum: an unusual cause of Wolff-Parkinson-White syndrome

A case of a giant right atrial diverticulum associated with neonatal supraventricular tachycardia is reported. The electrocardiogram in sinus rhythm showed pre-excitation that may have been caused by the right atrial diverticulum adhering to the right ventricle.

Spectrum and frequency of pediatric illness presenting to a general community hospital emergency department

Knowledge of the range of pediatric illness presenting to a general emergency department (ED) is needed to optimize the quality of care delivered there. It was hypothesized that the pediatric population treated at a general ED exhibited a broad range of medical complaints, while differing significantly from children seen in a pediatric ED. General ED records from 1 week each season were reviewed, and patient age, chief complaint, diagnosis, time of arrival, season, and disposition were recorded. Data on 874 patients were analyzed and compared with pediatric ED data. General ED patient age affected chief complaint, diagnosis, and admission rate (9.5% less than or equal to 1 year admitted vs 2.6% greater than 1 year, P less than .001). General ED patients were older (7.9 vs 6.0 years, P less than .001) and admitted less frequently (3.8% vs 11%, P less than .001). Admission rates varied by arrival time only at the general ED, where minor trauma was more common (41% vs 22%, P less than .001). It is concluded that a wide range of pediatric illness is treated in a general ED, supporting the decision to have pediatric emergency physicians on staff, and that significant differences exist in the spectrum and frequency of pediatric illness seen in a general ED and pediatric ED.

Low back pain in eight areas of Britain

STUDY OBJECTIVE

The aim was to assess the geographical variation in low back pain and associated disability in Britain.

DESIGN

This was a cross sectional survey with information collected by postal questionnaire.

SETTING

General practices in seven British towns and one rural district.

SUBJECTS

1172 men and 1495 women aged 20-59 years were selected from the age-sex registers of 136 general practitioners in the study areas.

MAIN RESULTS

The overall lifetime and one year period prevalences of low back pain were 58.3% and 36.1%. Rates in men and women were similar. Symptoms were more common in men with manual occupations than in those with non-manual jobs, but in women there was no clear trend in relation to social class. Geographical differences in prevalence were small, but the threshold for consulting general practitioners about symptoms varied markedly from place to place. After allowance for age, sex, social class, and severity of symptoms, subjects in the northern towns of Arbroath and Peterlee who had suffered from low back pain in the past year were three to four times as likely to have consulted their doctor about the problem as those living in the southern towns of St Austell and Dorking. Consultation rates in the Midlands were intermediate.

CONCLUSIONS

Geographical variation in rates of general practice consultation for low back pain in Britain is due largely to differences in patient behaviour once symptoms have developed. The distribution of important causes of low back back pain across the country is probably fairly uniform.

Diagnosis of total anomalous pulmonary venous drainage by Doppler color flow imaging

Over a 2.5-year period, 16 consecutive infants were prospectively diagnosed as having total anomalous pulmonary venous drainage. The sites of drainage were cardiac (to the coronary sinus) in four patients, supracardiac in nine, infracardiac in two and mixed in one patient. In every case, two-dimensional echocardiography with color flow imaging enabled complete and correct diagnosis of the sites of drainage and the presence or absence of pulmonary venous obstruction. The echocardiographic findings were verified at surgery or autopsy in all. Color flow imaging rapidly provided information about the direction and mean velocity of flow through abnormal vascular structures in any two-dimensional echocardiographic plane. It facilitated the acquisition of quantitative velocity information with standard Doppler ultrasound techniques by identifying areas of high velocity or turbulent flow and was invaluable in the assessment of anomalous pulmonary venous drainage occurring either as an isolated anomaly or in conjunction with complex intracardiac lesions.

Risk of low back pain in people admitted to hospital for traffic accidents and falls

STUDY OBJECTIVE

The aim was to assess the risk of back symptoms in people admitted to hospital because of traffic accidents and falls.

DESIGN

The study was a cross sectional survey with information collected by postal questionnaire. Main outcome measures were associations between hospital admission for a traffic accident or fall and reported first onset of back symptoms at the same age and at later ages.

SETTING

General practices in seven towns and one rural district.

SUBJECTS

1172 men and 1495 women aged 20-59 years were selected from the age-sex registers of 136 general practitioners in the study areas.

MAIN RESULTS

Low back pain was reported by 1556 subjects and hospital admission for a traffic accident or fall by 362. The incidence of low back pain was unusually high during the year of age at which subjects were first admitted to hospital for trauma (RR = 5.5, 95% CI 3.8-7.8). The risk of first developing symptoms in subsequent years was lower, but still significantly increased (RR = 1.3, 95% CI 1.1-1.6). Low back pain which started at the age of an accident tended to last longer than that occurring in other circumstances, and was more often ascribed to injury (56% of cases). However, this proportion was smaller than the calculated attributable proportion for traffic accidents and falls (82%).

CONCLUSIONS

The data suggest that a person under age 60 years who is admitted to hospital for a traffic accident or fall has a 7% chance of developing low back pain as result of the injury. However, the link between the injury and subsequent symptoms is often not obvious to the patient.

Primary structure and functional expression of the beta 1 subunit of the rat brain sodium channel

Voltage-sensitive sodium channels are responsible for the initiation and propagation of the action potential and therefore are important for neuronal excitability. Complementary DNA clones encoding the beta 1 subunit of the rat brain sodium channel were isolated by a combination of polymerase chain reaction and library screening techniques. The deduced primary structure indicates that the beta 1 subunit is a 22,851-dalton protein that contains a single putative transmembrane domain and four potential extracellular N-linked glycosylation sites, consistent with biochemical data. Northern blot analysis reveals a 1,400-nucleotide messenger RNA in rat brain, heart, skeletal muscle, and spinal cord. Coexpression of beta 1 subunits with alpha subunits increases the size of the peak sodium current, accelerates its inactivation, and shifts the voltage dependence of inactivation to more negative membrane potentials. These results indicate that the beta 1 subunit is crucial in the assembly, expression, and functional modulation of the heterotrimeric complex of the rat brain sodium channel.

Nucleic acid specificity of a vertebrate telomere-binding protein: evidence for G-G base pair recognition at the core-binding site

A factor from avian cells formed complexes with telomeric sequences and other single-stranded probes that contained tracts of guanine residues. Nucleoprotein complexes with telomere probes required two or more of the telomeric repeats that were incapable of Watson-Crick base-pairing. Methylation interference and protection experiments identified guanine N7 residues that were critical for the formation of the nucleoprotein complex and for the formation of a higher-order structure that occurred in the absence of the protein. Substitutions of deoxyinosine (dI) for deoxyguanosine (dG) demonstrated that the exocyclic N2 amino groups in the internal telomeric repeat, but not the terminal repeat, were required for the formation of the chemically protected structure and for protein binding. On the basis of these data we propose that the factor specifically recognizes a hairpin DNA structure that is stabilized by intramolecular G-G base-pairing between the telomere repeats. The positions of the critical guanine N2 and N7 groups indicate a G-G base-pairing configuration, where guanines function as hydrogen bond donors at the internal telomeric repeat and hydrogen bond acceptors at the terminal telomeric repeat.

Professional challenges in the coming decade

Last month, as part of our observance of the 15th anniversary of Physician Assistant journal, members of our Editorial Board offered their views on turning points in the history of the PA profession. In this issue, we jump from the past to the future, with perspectives on the main crises or changes facing the profession in the coming decade. You may agree or disagree with these viewpoints. Diversity of opinion keeps the PA profession dynamic and strong--which is exactly why Physician Assistant journal provides an open forum for letters and guest editorials.

Absent left-sided atrioventricular connexion, with right atrium connected to left ventricle: prospective diagnosis in infancy, and outcome

Prospective echocardiographic diagnosis of absence of the left atrioventricular connexion, with the right atrium connected to a morphologic left ventricle through a bileaflet morphologically mitral valve, was made in six infants. The rudimentary right ventricle was left-sided in all patients, and separated from the left atrium by sulcus tissue. The ventriculoarterial connexions were discordant. Associated defects included subpulmonary stenosis (2 patients), pulmonary atresia (1 patient), and a patent duct (4 patients). All patients developed early left atrial hypertension due to a restrictive interatrial septum, and required transcatheter septostomy (5 patients), or surgical septectomy (3 patients). One patient who had a severely restrictive ventricular septal defect died following cardiac catheterization. In three others the ventricular septal defect has become progressively restrictive on serial catheterization. Successful intermediate term palliation has been performed in two patients using a bidirectional Glenn anastomosis, together with enlargement of the ventricular septal defect and a Damus-Kay-Stansel procedure in one. It is possible to distinguish this malformation from "mitral atresia" using cross-sectional echocardiography. The long-term outlook is influenced by early relief of left atrial hypertension. Balloon atrial septostomy alone is usually inadequate, and either blade septostomy or surgical septectomy are required. Serial cardiac catheterization is mandatory for planning definitive palliation.