Novel technology for the provision of power to implantable physiological devices.

We report the development of a novel technology that enables the wireless transmission of sufficient amounts of power to implantable physiological devices. The system involves a primary unit generating the magnetic field and a secondary pickup unit deriving power from the magnetic field and a power conditioner. The inductively coupled system was able to supply a minimum of 20 mW at all locations and pickup orientations across a rat cage, although much higher power of up to 10 W could be achieved. We hypothesized that it would be possible to use this technology to record a high-fidelity ECG signal in a conscious rat. A device was constructed in which power was utilized to recharge a battery contained within a telemetry device recording ECG signal sampled at 2,000 Hz in conscious rats (200-350 g) living in their home cage. Attributes of the ECG signal (QT, QRS, and PR interval) could be obtained with a high degree of accuracy (<1 ms). ECG and heart rate changes in response to treatment with the beta blocker propranolol and the proarrhythmic alkaloid aconitine were measured. Transmitters were implanted for up to 4 mo, and the characteristic circadian variation in heart rate was recorded. Such technology allows potentially lifetime monitoring without the need for implant refurbishment. The ability to provide suitable power levels to implanted devices without concern to the orientation of the device and without causing heating provides the basis for the development of new devices to record or influence physiological signals in animals or humans over significantly longer time periods than can currently be accommodated.     

Transformation and Deoxyribonucleic Acid Size: Extent of Degradation on Entry Varies with Size of Donor

The fate of label introduced as donor deoxyribonucleic acid (DNA) into competent cells of Diplococcus pneumoniae was determined immediately after entry at 25 C, as a function of the size of the donor DNA. Part of the label is found to be acid soluble, part has been incorporated into chromosomal DNA, apparently through reincorporation of degraded donor DNA, and part is found in single strands of length smaller than that of the input donor DNA strands. The last fraction apparently constitutes the precursor for integration of intact donor genetic markers and is referred to as the intact fraction. For large donor DNA the intact fraction contains over 80% of the total intracellular label, but the median strand length has been reduced to 2.2 x 10(6) daltons. For small donor molecules (1 x 10(5) to 6 x 10(5) daltons per strand) the fraction intact increases with donor size from 10 to 50% of the total intracellular label, and the median strand length of this fraction is half that of the donor strands. By combining these results with earlier data on the size dependence of the yield of transformants per unit of total intracellular donor label, we have calculated the probability that a marker in the intact fraction will be integrated, as a function of the length of the donor strand after entry. This probability has a linear dependence on strand length for activities below 40% of maximum, and extrapolates to zero activity at 77,000 daltons per strand.     

Pore positioning: Current concepts in Pannexin channel trafficking

Pannexins (Panxs) are a multifaceted family of ion and metabolite channels that play key roles in a number of physiological and pathophysiological settings. These single membrane large-pore channels exhibit a variety of tissue, cell type, and subcellular distributions. The lifecycles of Panxs are complex, yet must be understood to accurately target these proteins for future therapeutic use. Here we review the basics of Panx function and localization, and then analyze the recent advances in knowledge regarding Panx trafficking. We examine several intrinsic features of Panxs including specific post-translational modifications, the divergent C-termini, and oligomerization, all of which contribute to Panx anterograde transport pathways. Further, we examine the potential influence of extrinsic factors, such as protein-protein interactions, on Panx trafficking. Finally, we highlight what is currently known with respect to Panx internalization and retrograde transport, and present new data illustrating Panx1 internalization following an activating stimulus.     

Destruction of low efficiency markers is a slow process occurring at a heteroduplex stage of transformation

Summary Direct evidence is presented that the mechanism which discriminates against low efficiency markers in transformation of Diplococcus pneumoniae of genotype hex ⁺ acts on them after the formation of donor-recipient heteroduplexes. This conclusion is based on assays of the transforming activity of donor markers in lysates made after various times of incubation of recipient cells following exposure to DNA. The activity of a low efficiency marker rises substantially, indicating formation of native-like heteroduplex structures, and then falls. At 37° C the process is essentially completed 10 minutes after entry, and the apparent half life of a susceptible heteroduplex is 1.5 to 2 minutes. Data from these and other experiments imply that about as many of the surviving low efficiency markers have simply escaped attack as have been inserted into both strands by the excision-repair process suggested by Ephrussi-Taylor.