Limited entry of adenovirus vectors into well-differentiated airway epithelium is responsible for inefficient gene transfer

Investigations of the efficiency and safety of human adenovirus vector (AdV)-mediated gene transfer in the airways of patients with cystic fibrosis (CF) in vivo have demonstrated little success in correcting the CF bioelectrical functional defect, reflecting the inefficiency of AdV-mediated gene transfer to the epithelial cells that line the airway luminal surface. In this study, we demonstrate that low AdV-mediated gene transfer efficiency to well-differentiated (WD) cultured airway epithelial cells is due to three distinct steps in the apical membrane of the airway epithelial cells: (i) the absence of specific adenovirus fiber-knob protein attachment receptors; (ii) the absence of alphavbeta3/5 integrins, reported to partially mediate the internalization of AdV into the cell cytoplasm; and (iii) the low rate of apical plasma membrane uptake pathways of WD airway epithelial cells. Attempts to increase gene transfer efficiency by increasing nonspecific attachment of AdV were unsuccessful, reflecting the inability of the attached vector to enter (penetrate) WD cells via nonspecific entry paths. Strategies to improve the efficiency of AdV for the treatment of CF lung disease will require methods to increase the attachment of AdV to and promote its internalization into the WD respiratory epithelium.

Predicting susceptibility and incubation time of human-to-human transmission of vCJD

BACKGROUND

Identification of possible transmission of variant Creutzfeldt-Jakob disease (vCJD) via blood transfusion has caused concern over spread of the disease within the human population. We aimed to model iatrogenic spread to enable a comparison of transmission efficiencies of vCJD and bovine spongiform encephalopathy (BSE) and an assessment of the effect of the codon-129 polymorphism on human susceptibility.

METHODS

Mice were produced to express human or bovine prion protein (PrP) by direct replacement of the mouse PrP gene. Since the human PrP gene has variation at codon 129, with MM, VV, and MV genotypes, three inbred lines with an identical genetic background were produced to express human PrP with the codon-129 MM, MV, and VV genotypes. Mice were inoculated with BSE or vCJD and assessed for clinical and pathological signs of disease.

FINDINGS

BSE was transmitted to the bovine line but did not transmit to the human lines. By contrast, vCJD was transmitted to all three human lines with different pathological characteristics for each genotype and a gradation of transmission efficiency from MM to MV to VV.

INTERPRETATION

Transmission of BSE to human beings is probably restricted by the presence of a significant species barrier. However, there seems to be a substantially reduced barrier for human-to-human transmission of vCJD. Moreover, all individuals, irrespective of codon-129 genotype, could be susceptible to secondary transmission of vCJD through routes such as blood transfusion. A lengthy preclinical disease is predicted by these models, which may represent a risk for further disease transmission and thus a significant public-health issue.

A structure-based mechanism for copper-zinc superoxide dismutase

A reaction cycle is proposed for the mechanism of copper-zinc superoxide dismutase (CuZnSOD) that involves inner sphere electron transfer from superoxide to Cu(II) in one portion of the cycle and outer sphere electron transfer from Cu(I) to superoxide in the other portion of the cycle. This mechanism is based on three yeast CuZnSOD structures determined by X-ray crystallography together with many other observations. The new structures reported here are (1) wild type under 15 atm of oxygen pressure, (2) wild type in the presence of azide, and (3) the His48Cys mutant. Final R-values for the three structures are respectively 20.0%, 17.3%, and 20.9%. Comparison of these three new structures to the wild-type yeast Cu(I)ZnSOD model, which has a broken imidazolate bridge, reveals the following: (i) The protein backbones (the "SOD rack") remain essentially unchanged. (ii) A pressure of 15 atm of oxygen causes a displacement of the copper ion 0.37 A from its Cu(I) position in the trigonal plane formed by His46, His48, and His120. The displacement is perpendicular to this plane and toward the NE2 atom of His63 and is accompanied by elongated copper electron density in the direction of the displacement suggestive of two copper positions in the crystal. The copper geometry remains three coordinate, but the His48-Cu bond distance increases by 0.18 A. (iii) Azide binding also causes a displacement of the copper toward His63 such that it moves 1.28 A from the wild-type Cu(I) position, but unlike the effect of 15 atm of oxygen, there is no two-state character. The geometry becomes five-coordinate square pyramidal, and the His63 imidazolate bridge re-forms. The His48-Cu distance increases by 0.70 A, suggesting that His48 becomes an axial ligand. (iv) The His63 imidazole ring tilts upon 15 atm of oxygen treatment and azide binding. Its NE2 atom moves toward the trigonal plane by 0.28 and 0.66 A, respectively, in these structures. (v) The replacement of His48 by Cys, which does not bind copper, results in a five-coordinate square pyramidal, bridge-intact copper geometry with a novel chloride ligand. Combining results from these and other CuZnSOD crystal structures, we offer the outlines of a structure-based cyclic mechanism.

The utility of the Digi-walker step counter to assess daily physical activity patterns

PURPOSE

The Digi-Walker step counter is a promising and cost-effective tool to measure physical activity under free-living conditions. Two specific studies were conducted to evaluate the number of steps required to meet current physical activity guidelines.

METHODS

Thirty-one adults (17 men, 14 women) served as participants. In study 1, we determined the number of steps to complete a mile under two different conditions and three paces. In study 2, we conducted a field trial to examine the relationship between daily step counts and other indices of physical activity. Participants in this study wore a Digi-Walker for 2 consecutive weeks and completed the 7-d physical activity recall (PAR) after each week.

RESULTS

In study 1, there were no differences in step counts by site, but steps were inversely related to pace, with values ranging from 1330 to 1996. Individual step counts at a specific pace were negatively correlated with height, weight, leg length, and stride length and were positively correlated with body fatness. In study 2, participants had average daily step counts of 11,603 when structured vigorous activity was included and 8265 when only light and moderate activity were measured. Modest correlations were found between step counts and estimated energy expenditure. Similar correlations were observed when step counts were related to minutes of activity per day and minutes of sitting per day.

CONCLUSIONS

Pedometers provide a useful indicator of daily step counts but variability in activity patterns make it difficult to establish step count guidelines that correspond with other public health guidelines.

The crystal structure of a 3D domain-swapped dimer of RNase A at a 2.1-A resolution

The dimer of bovine pancreatic ribonuclease A (RNase A) discovered by Crestfield, Stein, and Moore in 1962 has been crystallized and its structure determined and refined to a 2.1-A resolution. The dimer is 3D domain-swapped. The N-terminal helix (residues 1-15) of each subunit is swapped into the major domain (residues 23-124) of the other subunit. The dimer of bull seminal ribonuclease (BS-RNase) is also known to be domain-swapped, but the relationship of the subunits within the two dimers is strikingly different. In the RNase A dimer, the 3-stranded beta sheets of the two subunits are hydrogen-bonded at their edges to form a continuous 6-stranded sheet across the dimer interface; in the BS-RNase dimer, it is instead the two helices that abut. Whereas the BS-RNase dimer has 2-fold molecular symmetry, the two subunits of the RNase A dimer are related by a rotation of approximately 160 degrees. Taken together, these structures show that intersubunit adhesion comes mainly from the swapped helical domain binding to the other subunit in the "closed interface" but that the overall architecture of the domain-swapped oligomer depends on the interactions in the second type of interface, the "open interface." The RNase A dimer crystals take up the dye Congo Red, but the structure of a Congo Red-stained crystal reveals no bound dye molecule. Dimer formation is inhibited by excess amounts of the swapped helical domain. The possible implications for amyloid formation are discussed.

Beta blockers in the management of chronic kidney disease

The sympathetic nervous system modulates renal function through its receptors namely beta1 (cardiac output and renin release), alpha1 (systemic and renovascular constriction), and beta2 renovascular dilation. Sympathetic overactivity is commonly seen in chronic kidney disease (CKD) and is an important contributor to increasing the risk of cardiovascular events as well as increasing renal disease progression. Recent evaluations of drug use in people with CKD shows a remarkably low percentage of patients receiving beta-blockers, especially in more advanced stage CKD when cardiovascular risk is higher. This is in large part due to tolerability of these agents. Moreover, water-soluble beta-blockers such as atenolol and metoprolol are dialyzable and require supplementation to avoid exacerbation of arrhythmias following dialysis. Newer vasodilating beta-blockers have better tolerability and different effects on renal hemodynamics as well as metabolic variables. These effects are related to the relative alpha1-blocking effect of agents such as carvedilol and labetolol, with carvedilol having relatively greater alpha-blocking effects. Few studies evaluate beta-blockers on cardiovascular risk in CKD patients. Studies with carvedilol demonstrate attenuated increases in albuminuria as well as reduction in cardiovascular events in CKD patients with hypertension. This paper reviews the animal and clinical trial data that evaluate beta-blockers in CKD highlighting the vasodilating beta-blockers. It is apparent that greater use of this drug class for blood pressure control would further enhance reduction of risk of heart failure, the most common cause of death in the first year of starting dialysis.

A missing link in cupredoxins: crystal structure of cucumber stellacyanin at 1.6 A resolution

Stellacyanins are blue (type I) copper glycoproteins that differ from other members of the cupredoxin family in their spectroscopic and electron transfer properties. Until now, stellacyanins have eluded structure determination. Here we report the three-dimensional crystal structure of the 109 amino acid, non-glycosylated copper binding domain of recombinant cucumber stellacyanin refined to 1.6 A resolution. The crystallographic R-value for all 18,488 reflections (sigma > 0) between 50-1.6 A is 0.195. The overall fold is organized in two beta-sheets, both with four beta-stands. Two alpha-helices are found in loop regions between beta-strands. The beta-sheets form a beta-sandwich similar to those found in other cupredoxins, but some features differ from proteins such as plastocyanin and azurin in that the beta-barrel is more flattened, there is an extra N-terminal alpha-helix, and the copper binding site is much more solvent accessible. The presence of a disulfide bond at the copper binding end of the protein confirms that cucumber stellacyanin has a phytocyanin-like fold. The ligands to copper are two histidines, one cysteine, and one glutamine, the latter replacing the methionine typically found in mononuclear blue copper proteins. The Cu-Gln bond is one of the shortest axial ligand bond distances observed to date in structurally characterized type I copper proteins. The characteristic spectroscopic properties and electron transfer reactivity of stellacyanin, which differ significantly from those of other well-characterized cupredoxins, can be explained by its more exposed copper site, its distinctive amino acid ligand composition, and its nearly tetrahedral ligand geometry. Surface features on the cucumber stellacyanin molecule that could be involved in interactions with putative redox partners are discussed.

Uclacyanins, stellacyanins, and plantacyanins are distinct subfamilies of phytocyanins: plant-specific mononuclear blue copper proteins

The cDNAs encoding plantacyanin from spinach were isolated and characterized. In addition, four new cDNA sequences from Arabidopsis ESTs were identified that encode polypeptides resembling phytocyanins, plant-specific proteins constituting a distinct family of mononuclear blue copper proteins. One of them encodes plantacyanin from Arabidopsis, while three others, designated as uclacyanin 1, 2, and 3, encode protein precursors that are closely related to precursors of stellacyanins and a blue copper protein from pea pods. Comparative analyses with known phytocyanins allow further classification of these proteins into three distinct subfamilies designated as uclacyanins, stellacyanins, and plantacyanins. This specification is based on (1) their spectroscopic properties, (2) their glycosylation state, (3) the domain organization of their precursors, and (4) their copper-binding amino acids. The recombinant copper binding domain of Arabidopsis uclacyanin 1 was expressed, purified, and shown to bind a copper atom in a fashion known as "blue" or type 1. The mutant of cucumber stellacyanin in which the glutamine axial ligand was substituted by a methionine (Q99M) was purified and shown to possess spectroscopic properties similar to uclacyanin 1 rather than to plantacyanins. Its redox potential was determined by cyclic voltammetry to be +420 mV, a value that is significantly higher than that determined for the wild-type protein (+260 mV). The available structural data suggest that stellacyanins (and possibly other phytocyanins) might not be diffusible electron-transfer proteins participating in long-range electron-transfer processes. Conceivably, they are involved in redox reactions occurring during primary defense responses in plants and/or in lignin formation.

Chitinases, chitosanases, and lysozymes can be divided into procaryotic and eucaryotic families sharing a conserved core

Barley chitinase, bacterial chitosanase, and lysozymes from goose (GEWL), phage (T4L) and hen (HEWL) all hydrolyse related polysaccharides. The proteins share no significant amino-acid similarities, but have a structurally invariant core consisting of two helices and a three-stranded beta-sheet which form the substrate-binding and catalytic cleft. These enzymes represent a superfamily of hydrolases which are likely to have arisen by divergent evolution. Based on structural criteria, we divide the hydrolase superfamily into a bacterial family (chitosanase and T4L) and a eucaryotic family represented by chitinase and GEWL. Both families contain the core but have differing N- and C-terminal domains. Inclusion of chitinase and chitosanase in the superfamily suggests the archetypal catalytic mechanism of the group is an inverting mechanism. The retaining mechanism of HEWL is unusual.

Cloning and characterization of a Kv1.5 delayed rectifier K+ channel from vascular and visceral smooth muscles

We have cloned and characterized the expression of a Kv1.5 K+ channel (cKv1.5) from canine colonic smooth muscle. The amino acid sequence displayed a high level of identity to other K+ channels of the Kv1.5 class in the core region between transmembrane segments S1-S6; however, identity decreased to between 74 and 82% in the NH2 and COOH terminal segments, suggesting that cKv1.5 is a distinct isoform of the Kv1.5 class. Functional expression of cKv1.5 in oocytes demonstrated a channel highly selective for K+, which activates in a voltage-dependent manner on depolarization to membrane potentials positive to -40 mV. At room temperature the channel showed fast activation (time to half of peak current, 5.5 ms) and slow inactivation that was incomplete after 20-s depolarizations. Single channel analysis of the channel expressed in oocytes displayed a linear current-voltage curve and had a slope conductance of 9.8 +/- 1.1 pS. Northern blot analysis demonstrated differential expression of cKv1.5 in smooth muscles of the gastrointestinal tract and abundant expression in several vascular smooth muscles. We propose that cKv1.5 represents a component of the delayed rectifier current in both vascular and visceral smooth muscles.

Subunit asymmetry in the three-dimensional structure of a human CuZnSOD mutant found in familial amyotrophic lateral sclerosis

The X-ray crystal structure of a human copper/zinc superoxide dismutase mutant (G37R CuZnSOD) found in some patients with the inherited form of Lou Gehrig's disease (FALS) has been determined to 1.9 angstroms resolution. The two SOD subunits have distinct environments in the crystal and are different in structure at their copper binding sites. One subunit (subunit[intact]) shows a four-coordinate ligand geometry of the copper ion, whereas the other subunit (subunit[broken]) shows a three-coordinate geometry of the copper ion. Also, subunit(intact) displays higher atomic displacement parameters for backbone atoms ((B) = 30 +/- 10 angstroms2) than subunit(broken) ((B) = 24 +/- 11 angstroms2). This structure is the first CuZnSOD to show large differences between the two subunits. Factors that may contribute to these differences are discussed and a possible link of a looser structure to FALS is suggested.

Enhanced drug metabolism in cigarette smokers

The effect of cigarette smoking on salivary antipyrine disappearance rate, and as an index of hepatic drug metabolism, was studied in 42 healthy subjects. Antipyrine half life was significantly shorter in smokers compared with non-smokers. To determine whether this difference was due solely to tobacco consumption eight subjects were restudied two months after they stopped smoking. The mean antipyrine disappearance rate in this group increased by 23% in contrast to that of a control group, which did not alter. Cigarette smoking contributes to the considerable variation in interindividual rates of drug metabolism.

Unusual trigonal-planar copper configuration revealed in the atomic structure of yeast copper-zinc superoxide dismutase

The three-dimensional structure of yeast copper-zinc superoxide dismutase (CuZnSOD) has been determined in a new crystal form in space group R32 and refined against X-ray diffraction data using difference Fourier and restrained crystallographic refinement techniques. The unexpected result is that the copper ion has moved approximately 1 angstrom from its position in previously reported CuZnSOD models, the copper-imidazolate bridge is broken, and a roughly trigonal planar ligand geometry characteristic of Cu(I) rather than Cu(II) is revealed. Final R values for the two nearly identical room temperature structures are 18.6% for all 19 149 reflections in the 10.0-1.7 angstrom resolution range and 18. 2% for 17 682 reflections (F > 2 sigma) in the 10.0-1.73 angstrom resolution range. A third structure has been determined using X-ray data collected at -180 degrees C. The final R value for this structure is 19.0% (R(free) = 22.9%) for all 24 356 reflections in the 10.0-1.55 angstrom resolution range. Virtually no change in the positions of the ligands to the zinc center is observed in these models. The origin of the broken bridge and altered Cu-ligand geometry is discussed.

Cloning and expression of a Kv1.2 class delayed rectifier K+ channel from canine colonic smooth muscle

A cDNA (CSMK1) encoding a delayed rectifier K+ channel of the Kv1.2 class was cloned from canine colonic circular smooth muscle and expressed in Xenopus oocytes. These channels appear to be uniquely expressed in gastrointestinal muscles and may participate in the electrical slow wave activity. Functional expression of CSMK1 in Xenopus oocytes demonstrated a K+ current that activated in a voltage-dependent manner upon depolarization. This current was highly sensitive to 4-aminopyridine (IC50, 74 microM). A low-conductance K+ channel was identified in inside-out patches from oocytes injected with CSMK1. This channel displayed a linear current-voltage relation with a slope conductance of 14 pS. The channels were blocked in a concentration-dependent manner by 4-aminopyridine. Northern blot analysis demonstrated that CSMK1 is expressed in a wide variety of gastrointestinal smooth muscles. Portal vein, renal artery, and uterus do not express CSMK1, suggesting that, among smooth muscles, expression of this K+ channel may be restricted to gastrointestinal smooth muscles. CSMK1 is 91% homologous to RAK, a delayed rectifier K+ channel cloned from rat heart, but displays unique pharmacological properties and tissue distribution.

Visualization of secreted Hrp and Avr proteins along the Hrp pilus during type III secretion in Erwinia amylovora and Pseudomonas syringae

Pili are required for protein and/or DNA transfer from bacteria to recipient plant or bacterial cells, based on genetic evidence. However, it has never been shown directly that the effector proteins or DNA are localized along or inside the pili in situ. Failure to visualize an association of effector proteins/DNA with pili is the central issue in the debate regarding the exact function of pili in protein and DNA transfer. In this study, a newly developed in situ immunogold labelling procedure enabled visualization of the specific localization of type III effector proteins of Erwinia amylovora and Pseudomonas syringae pv. tomato along the Hrp pilus, but not along the flagellum or randomly in the intercellular space. In contrast, PelE, a pectate lyase secreted via the type II protein secretion system, was not associated with the Hrp pilus. These results provide direct evidence that type III secretion occurs only at the site of Hrp pilus assembly and that the Hrp pilus guides the transfer of effector proteins outside the bacterial cell, favouring the 'conduit/guiding filament' model.

Crystal structure of an endochitinase from Hordeum vulgare L. seeds

Higher plants contain multiple constitutively expressed proteins for defense against infection by viruses, bacteria, and fungi. One such class of proteins, the chitinases, are effective antifungal agents because they hydrolyze the insoluble beta-1,4-linked polymer of N-acetylglucosamine (chitin), which is the major component of the mycelial cell wall of many fungi. We report here the three-dimensional, 2.8 A, crystal structure of a 26 kDa endochitinase from barley (Hordeum vulgare L.) seeds. The 243 amino acid residue molecule is rich in alpha-helices and has three disulfide bonds. A prominent elongated cleft runs the length of the molecule, and is presumably the region responsible for substrate binding and catalysis. Endochitinases from various species of plants show a high degree of similarity in their amino acid sequences. It is therefore likely that the barley endochitinase structure can serve as a model for other plant endochitinases and that catalytic models based on that structure will be applicable to the entire enzyme family.

Acute fatty liver of pregnancy associated with short-chain acyl-coenzyme A dehydrogenase deficiency

There is a correlation between pregnancy complications such as acute fatty liver of pregnancy and long-chain 3-hydroxyacyl-coenzyme A dehydrogenase (LCHAD) deficiency. We diagnosed another fatty acid beta-oxidation defect, short-chain acyl-coenzyme A dehydrogenase deficiency, in an infant when evaluating him because his mother had acute fatty liver of pregnancy. Other beta-oxidation defects, in addition to LCHAD deficiency, should be considered in children born after pregnancies complicated by liver disease.

Expression of cystic fibrosis transmembrane regulator Cl- channels in heart

Cyclic AMP (cAMP)-dependent chloride channels modulate changes in resting membrane potential and action potential duration in response to autonomic stimulation in heart. A growing body of evidence suggests that there are marked similarities in the properties of the cAMP-dependent chloride channels in heart and cystic fibrosis transmembrane regulator (CFTR) chloride channels found in airway epithelia or in cells expressing the CFTR gene product. We isolated poly A+ mRNA from rabbit ventricle and converted it to cDNA for amplification using the polymerase chain reaction (PCR). A fragment corresponding to the nucleotide-binding domain 1 (NBD1) of the CFTR transcript was cloned. Comparison of the amino acid sequence of NBD1 of human CFTR with the deduced sequence of the rabbit heart PCR product indicated 98% identity. Northern blot analysis, using the heart amplification product as a cDNA probe, demonstrated expression of homologous transcripts in human atrium, guinea pig and rabbit ventricle, and dog pancreas. Xenopus oocytes injected with poly A+ mRNA extracted from rabbit and guinea pig ventricle or dog pancreas expressed robust time-independent chloride currents in response to an elevation of cAMP. We conclude that CFTR chloride channels are expressed in heart and are responsible for the observed cAMP-dependent chloride conductance.

Seasonal variation in hypothalamic content of gonadotropin-releasing hormone (GnRH), pituitary receptors for GnRH, and pituitary content of luteinizing hormone and follicle-stimulating hormone in the mare

Seasonal changes in the hypothalamic-hypophyseal axis were investigated using tissue from 49 light-horse mares, of mixed breeding. Hypothalamic and pituitary tissues were collected at 5 intervals throughout the years 1981 and 1982, representing midbreeding season (July, n = 10), transition out of the breeding season (October, n = 11), midanestrus (December, n = 8), transition into the breeding season (March, n = 10), and again in the following midbreeding season (July, n = 10). The hypothalamic region was dissected into preoptic area, body and median eminence. Gonadotropin-releasing hormone (GnRH) was extracted from hypothalamic samples with methanol-formic acid and quantified by radioimmunoassay. The anterior pituitary was homogenized and receptors for GnRH were quantified in a crude membrane fraction. Concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured in the resulting supernatant. Content of GnRH in each of the 3 hypothalamic areas varied with season (P less than 0.01) and was lowest during midanestrus (P less than 0.05). There was no effect of season (P greater than 0.01) on either concentration or total number of receptors for GnRH, or concentration of FSH in the anterior pituitary. Concentrations of LH in the anterior pituitary varied with season (P less than 0.001). Means (+/- SEM) for the 5 collection times were 15.5 +/- 2.7, 9.7 +/- 2.4, 2.3 +/- 0.5, 2.7 +/- 0.4 and 11.7 +/- 1.5 microgram LH/mg anterior pituitary, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuroendocrine aspects of primary endogenous depression. II. Serum dexamethasone concentrations and hypothalamic-pituitary-adrenal cortical activity as determinants of the dexamethasone suppression test response

To determine the contribution of serum dexamethasone concentrations and hypothalamic-pituitary-adrenal cortical activity before dexamethasone administration to the dexamethasone suppression test (DST) response, a series of stepwise discriminant function analyses were performed for 40 patients with definite endogenous depression and 40 matched normal control subjects. The 24-hour serum cortisol concentration before dexamethasone administration and the serum dexamethasone concentrations at 8, 16, and 24 hours after administration served as the independent variables, and the DST "escaper"/"suppressor" dichotomy served as the dependent variable. While both types of independent variables significantly influenced the DST response, the major factor that contributed to the discrimination of escapers from suppressors was the 24-hour cortisol concentration before dexamethasone administration. Sixteen hours after dexamethasone administration, when the DST had the highest positive predictive value, serum dexamethasone concentrations significantly influenced DST outcome only when they were below a certain threshold level. At this time, hypothalamic-pituitary-adrenal cortical hyperactivity before dexamethasone administration accounted for approximately two thirds of the incidence of DST nonsuppression.

Cystic fibrosis gene encodes a cAMP-dependent chloride channel in heart

cAMP-dependent chloride channels in heart contribute to autonomic regulation of action potential duration and membrane potential and have been inferred to be due to cardiac expression of the epithelial cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. In this report, a cDNA from rabbit ventricle was isolated and sequenced, which encodes an exon 5 splice variant (exon 5-) of CFTR, with >90% identity to human CFTR cDNA present in epithelial cells. Expression of this cDNA in Xenopus oocytes gave rise to robust cAMP-activated chloride currents that were absent in control water-injected oocytes. Antisense oligodeoxynucleotides directed against CFTR significantly reduced the density of cAMP-dependent chloride currents in acutely cultured myocytes, thereby establishing a direct functional link between cardiac expression of CFTR protein and an endogenous chloride channel in native cardiac myocytes.

Atrial septal aneurysm: a cause for midsystolic click. Report of a case and review of the literature

A patient who was evaluated for a midsystolic click was found to have an aneurysm of the atrial septum as an isolated anomaly. Bulging of this aneurysm into the right atrium was associated with the production of the click. Echo-, phono-, and angiocardiographic features are presented, with a review of the literature on atrial septal aneurysms. These aneurysms, although rare, should be considered in the differential diagnosis of patients with midsystolic click.