Genetic mapping of the cleidocranial dysplasia (CCD) locus on chromosome band 6p21 to include a microdeletion

Cleidocranial dysplasia (CCD) is a generalized skeletal dysplasia with autosomal dominant inheritance. Recently, the CCD disease locus was localized to 23 [Mundlos et al., 1995] and 17 cM regions [Feldman et al., 1995], of chromosome band 6p21 by linkage studies of seven affected families. Of note, the 23 cM region contained a microdeletion detected in one family at D6S459, an interval that was excluded in the 17 cM overlapping region. Here, linkage of CCD to 6p21 was independently confirmed with a maximal two-point LOD score of Z = 5.12 with marker D6S452 at theta = 0.00. Recombinant events in two affected individuals defined a CCD region of 7 cM from D6S465 to D6S282, which overlapped with the CCD region containing the microdeletion but did not overlap with the 17 cM critical region from D6S282 to D6S291. These results suggest the refined localization of the CCD region to 6 cM spanning markers D6S438 to D6S282, thereby reviving the possibility that the CCD gene lies within the microdeletion at D6S459.

Linkage of pycnodysostosis to chromosome 1q21 by homozygosity mapping

Pycnodysostosis is an autosomal recessive sclerosing skeletal dysplasia of unknown aetiology which is inherited with complete penetrance. The clinical features, fully delineated in 1962 by Maroteaux & Lamy and by Andrén et al., include osteosclerosis, acro-osteolysis of the distal phalanges, bone fragility, clavicular dysplasia, reduced stature and skull deformities with delayed suture closure. Although rare, pycnodysostosis has attained prominence because the French artist Henri de Toulouse-Lautrec was retrospectively diagnosed as having been affected with this disorder. For rare autosomal recessive traits, homozygosity mapping provides a powerful approach to disease gene mapping. We have now used this approach to map the locus for pycnodysostosis. Following a genome-wide search in a large Arab family with 16 affected relatives, we established linkage to a narrow region on chromosome 1q21, with a maximal lod score of 11.72. A single marker, D1S498, was homozygous-by-descent in all affecteds and defined the gene locus to a region of 4 cM. Two candidate genes in the region--the interleukin-6 receptor gene (IL6R) and the myeloid cell leukaemia-1 gene (MCL1)--are involved in the differentiation of monocyte/macrophages into osteoclasts, the most likely site of the primary defect in pycnodysostosis.

Leigh syndrome and hypertrophic cardiomyopathy in an infant with a mitochondrial DNA point mutation (T8993G)

Mutation of mitochondrial (mt) DNA at nucleotide (nt) 8993 has been reported to cause neurogenic weakness, ataxia, retinitis pigmentosa (NARP), or Leigh syndrome (LS). We report a family in whom the mutation was expressed clinically as LS and hypertrophic cardiomyopathy (CMP) in a boy who presented with a history of developmental delay and hypotonia, and who had recurrent lactic acidosis. The mother's first pregnancy resulted in the birth of a stillborn female; an apparently healthy older brother had died suddenly (SIDS) at age 2 months. MtDNA analysis identified the presence of the T8993G point mutation, which was found to be heteroplasmic in the patient's skeletal muscle (90%) and fibroblasts (90%). The identical mutation was present in leukocytes (38%) isolated from the mother, but not from the father or maternal grandmother. Our findings expand the clinical phenotype of the nt 8993 mtDNA mutation to include hypertrophic cardiomyopathy and confirm its cause of LS.

Genomic structure of and a cardiac promoter for the mouse carnitine palmitoyltransferase II gene

The mouse carnitine palmitoyltransferase II gene has been isolated and its genomic structure determined. The gene contained five exons, including an unusually long 1305-nt exon 4. The exon/intron boundaries were sequenced and conformed to the consensus splice junction sequences. The transcription start site was determined from adult mouse heart mRNA by primer extension analysis and confirmed by 5' rapid amplification of cDNA ends. A promoter that differs from the previously published promoter for the carnitine palmitoyltransferase II gene was isolated and sequenced. When placed in a mammalian expression vector, this promoter was shown to drive the chloramphenicol acetyltransferase gene in mouse hepatoma cells. This new promoter is the major driver of carnitine palmitoyltransferase II gene expression in heart and may also be active in liver.

Transcatheter closure of residual atrial septal defect following cardiac transplantation

An almost 3-year-old boy had a residual atrial septal defect after cardiac transplantation. The patient was symptomatic and had arrhythmia and cardiac enlargement. An atrial septal defect occlusion device was employed to close the communication with excellent results. Transcatheter occlusion enabled the patient to avoid further surgery and did not interfere with follow-up endomyocardial biopsies.

Neurologic complications of heart transplantation in children

Neurologic complications can add significant morbidity to otherwise successful orthotopic heart transplantations in children. Complications have been reported to occur in up to 50% of children undergoing heart transplantation. The purpose of this study was to identify the prevalence and outcome of neurologic complications of heart transplantation in children. We reviewed all children who received orthotopic heart transplantation at Texas Children's Hospital from November 1984 to November 1990. Twenty-two patients (ages, 3 weeks to 17 years; mean, 8.5 years) underwent heart transplantation using cardiopulmonary bypass with moderate hypothermia. For analysis, we compared results during the first 3 years of our experience, 1984 through 1987 (group 1), to 1987 through 1990 (group 2). Survival was 45% (5 of 11 patients) for group 1 and 73% (8 of 11 patients) for group 2. A neurologic complication was defined as a change in the neurologic examination and/or status. Neurologic complications included seizures (6 of 22 patients), strokes (3 of 22 patients), unresponsiveness (3 of 22 patients), and change in mental status (2 of 22 patients). Early (within 2 weeks after operation) neurologic complications occurred in 45% (10 of 22 patients), were persistent (sequelae lasting more than 4 months) in 27% (6 of 22 patients), and resulted in death in 9% (2 of 22 patients). Late (after 2 weeks after operation) neurologic complications occurred in 23% (5 of 22 patients), were persistent in 9% (2 of 22 patients), and have occurred in only two survivors. Neurologic factors were not responsible for the cause of death in group 2. No neurologic complications (early or late) were seen in 1 of 11 patients in group 1 as compared with 7 of 11 patients in group 2 (p < 0.015). Serious neurologic morbidity decreased between the two groups after preoperative cyclosporine was avoided and postoperative hypertension was controlled. All survivors are functioning at age-appropriate levels. Although neurologic complications may be frequent, long-term neurologic disability in survivors is rare.

Characterization of human genomic yeast artificial chromosome inserts containing hexokinase 1 coding information on chromosome 10

Hexokinase 1 (HK1) is one of four mammalian HK isoenzymes and maps to human chromosome 10. Two yeast artificial chromosomes (YACs) were identified in the Washington University human YAC library using polymerase chain reaction (PCR) primers designed with knowledge of the human HK1 cDNA sequence. YAC B129B12 is 120 kb in length and maps entirely to chromosome 10. YAC A159D5 is 400 kb in length and appears to have resulted from a recombination of chromosome 10 with non-chromosome 10 material. We report these YACs as potential resources for those interested in HK1 gene organization and mapping, as well as those desiring additional genomic information and markers on chromosome 10.

Designing health promotion programs by watching the market

More health care providers and payors are beginning to see health promotion programs as a significant tool for attracting patients, reducing costs, or both. To help design programs that take into account the values and lifestyles of the target group, naturalistic observation can be useful. The authors illustrate the approach in a study of pipeline workers that provided input for the design of nutrition and smoking cessation programs.

Developmental expression of hexokinase 1 in the rat

Hexokinase 1 (HK1) activity varies in a developmental stage- and tissue-specific manner and is a key step in glucose homeostasis and energy metabolism. We conducted studies to determine if HK1 expression is regulated at the transcriptional level. Expression of HK1 was examined in selected pre- and postnatal rat tissues using Northern blot analyses and RNAase protection assays. We found that brain and kidney exhibited significantly higher expression than heart, lung, spleen and skeletal muscle. Brain HK1 expression was constant prenatally, peaked at 7 days of age and reached a constant level after weaning. In kidney, HK1 expression was essentially constant or perhaps gradually decreased after weaning. HK1 transcription in heart, skeletal muscle and liver was higher during fetal stages than postnatally. Lung expression was essentially constant except in the adult. HK1 mRNA levels were compared to phosphoglycerate kinase (PGK) mRNA. PGK steady state mRNA levels were relatively constant in all tissues and developmental stages, except in skeletal muscle where there was a postnatal rise. The developmental profiles of HK1 and PGK mRNA expression are not consistent with enzyme activity measurements in all the tissues examined. We conclude that regulation of HK1 expression involves both transcriptional and posttranscriptional mechanisms that are tissue and stage specific.

Targeting of hexokinase 1 to liver and hepatoma mitochondria

The proportion of hexokinase (HK; EC 2.7.1.1) isozyme 1 (HK1) that is bound to the outer mitochondrial membrane is tissue specific and developmentally regulated. HK activity is known to be markedly elevated in many cancer cells and a significant fraction is mitochondrial bound. This study examined the role of the 15-amino acid N-terminal domain of HK1 in binding to liver and hepatoma mitochondria. A chimeric reporter construct, pCMVHKCAT, encoding this HK1 domain coupled to the chloramphenicol acetyltransferase (CAT) gene was electroporated into mouse Hepa 1-6 hepatoma cells. After digitonin treatment, cell fractions were assayed for HK, lactate dehydrogenase, and CAT activities. Digitonin (75 micrograms/mg of protein) caused cytosolic leak but 70% of HK remained with the pellet. HKCAT, like HK, remained predominantly with the pellet; CAT form the control, pCMVCAT, remained mostly unbound. Binding of membrane-free cell extracts to rat liver mitochondria in vitro showed 91% of the HKCAT bound, whereas only 12% of CAT bound. Specificity of HKCAT binding to mitochondria was demonstrated by competition of HK1 for HKCAT binding sites on rat liver mitochondria as well as by blockage of HKCAT binding by N,N'-dicyclohexylcarbodiimide, which covalently binds to porin and blocks HK1 binding. Deletional mutant constructs of HKCAT showed reduced binding with increasing deletion size. In summary, these studies demonstrate that the 15-amino acid N-terminal domain of HK1 is necessary and sufficient to confer mitochondrial binding properties to CAT and that there is specificity for this binding to the mitochondria.

Does greater usage of a health plan reduce satisfaction?

As health care providers assess the future of managed care, the satisfaction of individual purchasers becomes an important issue. Do they become disenchanted after heavier use of managed care plans--and if so, does that contrast with purchasers of indemnity plans? The authors explore such issues.

Mammalian hexokinase 1: evolutionary conservation and structure to function analysis

We have amplified and sequenced the complete coding region of bovine hexokinase isoenzyme 1 (HK1) from brain RNA with PCR primers selected for sequence conservation. The sequence information was analyzed to evaluate the evolutionary and structure-function relationships among the mammalian and yeast HK isoenzymes. Structure to function analysis identified an unduplicated, invariant N-terminal domain involved in HK1 outer mitochondrial membrane targeting, as well as putative carbohydrate and nucleotide-binding sites in the regulatory and catalytic halves of HK1 essential to enzyme function. The ATP-binding site in the catalytic half of the HK1 protein resembles nucleotide-binding regions from protein kinases, with the single amino acid replacement (lysine to glutamate) in the ATP-binding site of the amino half explaining the loss of HK1 catalytic function in the regulatory domain. Sequence comparisons suggest that the 50-kDa mammalian and yeast glucokinases arose separately in evolution. In addition to providing valuable phylogenetic and structure-function insights, this work provides an efficient strategy for rapid cloning and sequencing of the coding regions for other HKs and related proteins.

Pseudoconduction of atrial flutter of a recipient atrium

A nine-year-old girl had an episode of atrial flutter and a nonsustained wide QRS tachycardia during her initial hospitalization after orthotopic heart transplantation. Evaluation of her ECG and telemetric tracing revealed atrial flutter of the recipient atrium and sinus rhythm of the donor atrium. The wide QRS tachycardia was an accelerated ventricular rhythm that was also found on subsequent 24-hour ambulatory ECG monitoring. Timely recognition of recipient atrial arrhythmias prevents inappropriate clinical intervention.

San Luis Valley recombinant chromosome 8 and tetralogy of Fallot: a review of chromosome 8 anomalies and congenital heart disease

Tetralogy of Fallot, the most common cyanotic heart defect, has not been closely associated with a specific chromosome defect. The San Luis Valley Recombinant Chromosome 8 [SLV Rec(8)] syndrome is strongly associated with congenital heart disease, particularly tetralogy of Fallot. This article reviews SLV Rec(8) syndrome and other chromosome 8 aberrations to suggest locations for cardiogenic genes. SLV Rec(8) [rec(8),dup q,inv(8)(p23q22)] syndrome has been found in Hispanic families in the southwestern United States. Congenital heart disease is found in 93.3% of SLV Rec(8) individuals (n = 45), with tetralogy of Fallot constituting 40.5% of all lesions and conotruncal defects, 55.6%. These frequencies exceed the incidence of tetralogy of Fallot (10%) and conotruncal defects (20%) among all children with heart defects (P less than 0.003 for both). Review of patients with deletion 8p (n = 13) showed heart defects in 84.6% with 27.3% being conotruncal defects. Among duplication 8q patients (n = 20), 45% had heart defects with conotruncal defects constituting 44%. Neither group differed significantly from expected in its incidence of conotruncal defects. Among patients with mosaic trisomy 8 (n = 47), 12 had heart abnormalities including one conotruncal defect. Among 3 patients with other rec(8) chromosomes, one had a ventricular septal defect. The cause of heart defects in SLV Rec(8) cannot be assigned to either the deletion of 8p or the duplication of 8q. The lack of an association between other chromosome 8 abnormalities and tetralogy of Fallot suggests that genes at the SLV Rec(8) breakpoints or an interaction between genes on both arms of chromosome 8 are important.

Protein kinase activity of rat brain hexokinase

Hexokinase 1 (HK1) purified from rat brain exhibits protein kinase activity, including autophosphorylation and phosphorylation of histone H2A. This protein kinase activity is observed only in the absence of the HK1 carbohydrate substrate, glucose. Analysis of the ATP-binding domains of the mammalian HK1 protein sequences shows significant homology with other mammalian protein kinases.

Scenarios: a planning tool for health care organizations

An organization's strategic planners require an understanding of future developments in the environment in which their decisions will be made. However, there is increasing recognition that there is no single predetermined "future." Therefore, the use of alternative future scenarios can be helpful. Scenario construction is a technique for combining possible environmental developments in a systematic way to help managers assess the potential consequences of alternative decisions. This article discusses the scenario technique and shows, as an example, its application to one organization in the health care field.

Prevalence of additional cardiovascular anomalies in patients referred for transcatheter closure of patent ductus arteriosus

Catheter closure of the patent ductus arteriosus is now a reality. The purpose of this study was to establish the prevalence of associated cardiovascular defects and the accuracy of echocardiography in patients referred for transvenous ductal closure. This study reviewed 146 patients seen from 1981 to 1988: 126 with only a patent ductus arteriosus (Group I) and 20 with additional cardiovascular anomalies (Group II). Groups I and II did not differ significantly in age, gender or physical examination except for the presence of a continuous murmur (Group I 100% versus Group II 80%, p less than 0.001). A left patent ductus arteriosus was visualized by two-dimensional echocardiography in 96% of patients and was evident by Doppler study in 100%. A patent ductus arteriosus was not seen in six patients including a patient who was found to have only a collateral network from the aorta to the main pulmonary artery. The 12 patients with noncardiovascular abnormalities such as Down's syndrome were more likely than the overall group to have additional cardiovascular anomalies (6 of 12, p = 0.001). The cardiovascular anomalies encountered were varied. Eight of the 20 patients with such anomalies had only a restrictive ventricular septal defect in addition to the patent ductus arteriosus. Significant anomalies found at catheterization included two thoracic arteriovenous malformations and an isolated right carotid artery draining into the right pulmonary artery by way of a right ductus arteriosus. This study indicates that echocardiography is an effective diagnostic technique in this patient group. A thorough cardiac catheterization with angiography should be performed before implantation of a ductal device.

Noninvasive discrimination of right atrial ectopic tachycardia from sinus tachycardia in "dilated cardiomyopathy"

Right atrial ectopic tachycardia (RAET) with secondary cardiac dysfunction can be difficult to differentiate from primary dilated cardiomyopathy (CMP) with sinus tachycardia. In an attempt to separate RAET from CMP by noninvasive testing, routine surface electrocardiograms (EGGs), 24-hour ambulatory ECGs (Holter monitors), and echocardiograms of patients with RAET (n = 34) and CMP (n = 33) were reviewed. RAET atrial rates were significantly faster than CMP rates on the resting ECG and on Holter monitoring; 12 of 33 patients with RAET had resting ECG rates greater than 150% of predicted normal values for age but none of 32 patients with CMPs had resting ECG rates in this range. Mean P wave axis in the horizontal plane was more posterior in patients with RAET and was less than 0 degrees (negative in lead V2) in 8 of 29 patients with RAET but in 1 of 33 patients with CMP. Second-degree atrioventricular (AV) block was observed in 12 of 33 patients with RAET but in none of 33 with CMP. Shortening fraction less than 10% was found in 13 of 33 individuals with CMP but in only 1 of 27 with RAET. We conclude that noninvasive studies can help identify RAET among patients with poor functioning hearts and right atrial tachycardia.

Telephoned appointment-scheduling by a physician's office: does it work?

Are phone calls reminding patients of recall appointments a worthwhile marketing tool? Evidence from a dermatologist's practice suggests that, though patients find the calls acceptable, such calls do not increase the short-term revenue of a practice. They do, however, appear to increase the likelihood that a patient will return.

Physicians and hospital decision making: a two-stage technique for improvement

A research technique that combines qualitative and quantitative stages can be useful in eliciting issues of importance to physicians and then in calculating the relative priority they place on each issue. The technique described here, physician focus groups plus conjoint analysis, has been used successfully in the health care setting. It offers opportunities for decision makers in any health care institution to "listen" to what physicians have to contribute.