Spatial relationship of sites for atrial fibrillation drivers and atrial tachycardia in patients with both arrhythmias.

Introduction: Atrial fibrillation (AF) often converts to and from atrial tachycardia (AT), but it is undefined if these rhythms are mechanistically related in such patients. We tested the hypothesis that critical sites for AT may be related to regional AF sources in patients with both rhythms, by mapping their locations and response to ablation on transitions to and from AF.

Methods: From 219 patients undergoing spatial mapping of AF prior to ablation at 3 centers, we enrolled 26 patients in whom AF converted to AT by ablation (n=19) or spontaneously (n=7; left atrial size 42±6cm, 38% persistent AF).

Frequency analysis of atrial action potential alternans: a sensitive clinical index of individual propensity to atrial fibrillation.

Background: Few clinical indices identify the propensity of patients to atrial fibrillation (AF) when not in AF. Repolarization alternans has been shown to indicate AF vulnerability, but is limited in its sensitivity to detect changes in action potential (AP) duration (APD), which may be subtle. We hypothesized that spectral analysis would be a more sensitive and robust marker of AP alternans and thus a better clinical index of individual propensity to AF than APD alternans.

Ablating persistent atrial fibrillation successfully.

The ablation of persistent atrial fibrillation (AF) poses many challenges compared with ablation for paroxysmal AF, including greater procedural complexity, longer procedural time, unclear endpoints, increased patient comorbidity with a greater risk of procedural complications, and lower success rate. Nevertheless, using a combination of patient selection, careful procedural planning of both ablation strategy and endpoints, and by setting realistic patient expectations, successful ablation may be achieved. Further improvements will come from continued technical advances as well as from greater mechanistic understanding of persistent AF, including the physiologically-targeted ablation of localized rotors and focal sources that have recently been shown to maintain human AF.

Reduced thin filament length in nebulin-knockout skeletal muscle alters isometric contractile properties.

Nebulin (NEB) is a large, rod-like protein believed to dictate actin thin filament length in skeletal muscle. NEB gene defects are associated with congenital nemaline myopathy. The functional role of NEB was investigated in gastrocnemius muscles from neonatal wild-type (WT) and NEB knockout (NEB-KO) mice, whose thin filaments have uniformly shorter lengths compared with WT mice.

Interrogating rodents regarding their object and spatial memory.

Today, neuroscientists have access to a host of advanced techniques -- ranging from targeted genetic interventions to brain imaging -- that are rapidly providing new insights. Ultimately, however, memory must be inferred from its behavioral read-out. Thus, to fully utilize the advanced technologies available today, we must select the most appropriate behavioral procedures from those currently available, or else devise novel behavioral techniques to meet a specific demand.

Role of Sgk1 in salt and potassium homeostasis.

Aldosterone plays a pivotal role in NaCl and K(+) homeostasis by stimulation of Na(+) reabsorption and K(+) secretion in the aldosterone-sensitive distal nephron (ASDN). Recent studies demonstrated that the serum- and glucocorticoid-regulated kinase 1 (Sgk1) is induced by aldosterone in the ASDN and that polymorphisms of the kinase associate with arterial blood pressure in normotensive subjects. This review discusses the role of Sgk1 in NaCl and K(+) homeostasis as evidenced by in vivo studies, including those in Sgk1-deficient mice.

In vivo expression of myosin essential light chain using plasmid expression vectors in regenerating frog skeletal muscle.

It is well established that mutations in specific structural elements of the motor protein myosin are directly linked to debilitating diseases involving malfunctioning striated muscle cells. A potential way to study the relationship between myosin structure and function is to express exogenous myosin in vivo and determine contractile properties of the transgenic muscle cells. However, in vivo expression of functional levels of contractile proteins using transient transgenesis in skeletal muscle has not been demonstrated.

Identification and treatment of sleep problems in the elderly.

For many adults, changes in sleep occur with aging. An estimated 15 million elderly, or 50% of older Americans, experience some sleep problem. The elderly complain that their sleep is more fragmented and that as they have gotten older, they experience more daytime sleepiness.

Polyamine transport system mediates agmatine transport in mammalian cells.

Agmatine is a biogenic amine with the capacity to regulate a number of nonreceptor-mediated functions in mammalian cells, including intracellular polyamine content and nitric oxide generation. We observed avid incorporation of agmatine into several mammalian cell lines and herein characterize agmatine transport in mammalian cells. In transformed NIH/3T3 cells, agmatine uptake is energy dependent with a saturable component indicative of carrier-mediated transport.

Quantitative computed tomography in the evaluation of spinal osteoporosis following spinal cord injury.

Disuse osteoporosis occurs in the lower extremities of patients with spinal cord injury (SCI). However, spinal osteoporosis is not usually observed in these patients. We investigated lumbar spine bone mineral density (BMD) in SCI patients using single energy quantitative computed tomography (QCT) and dual-energy X-ray absorptiometry (DXA).

Stress fractures of the lateral metatarsal bones in metatarsus adductus foot deformity: a previously unrecognized association.

Objective: To document a distinctive pattern of stress fractures in the lateral metatarsal bones of patients with metatarsus adductus foot deformity.

Design And Patients: Conventional radiographs and available medical records were reviewed in 11 patients (6 women, 5 men; ages 25-61 years) with stress fractures of the lateral (fourth or fifth) metatarsal bones and metatarsus adductus. Evaluation included the number and location of fracture(s), forefoot adduction angle, and qualitative assessment of bone mineral density.

Post-traumatic and stress-induced osteolysis of the distal clavicle: MR imaging findings in 17 patients.

Objective: To describe the MR imaging findings in patients with osteolysis of the distal clavicle and to compare the MR imaging appearance of clavicular osteolysis following acute injury with that related to chronic stress.

Design And Patients: MR imaging examinations were reviewed in 17 patients (14 men, 3 women; ages 16-55 years) with the diagnosis of post-traumatic or stress-induced osteolysis of the clavicle. A history of a single direct injury was present in seven patients and a history of weight-lifting, participation in sports, or repetitive microtrauma was present in 10 patients.

Agmatine suppresses proliferation by frameshift induction of antizyme and attenuation of cellular polyamine levels.

Polyamines are required for entry and progression of the cell cycle. As such, augmentation of polyamine levels is essential for cellular transformation. Polyamines are autoregulated through induction of antizyme, which represses both the rate-limiting polyamine biosynthetic enzyme ornithine decarboxylase and cellular polyamine transport.