Sodium transport is increased by vasopressin in the cortical collecting ducts of rats and rabbits. Here we investigate, by quantitative immunoblotting, the effects of vasopressin on abundances of the epithelial sodium channel (ENaC) subunits (alpha, beta, and gamma) in rat kidney. Seven-day infusion of 1-deamino-[8-D-arginine]-vasopressin (dDAVP) to Brattleboro rats markedly increased whole kidney abundances of beta- and gamma-ENaC (to 238% and 288% of vehicle, respectively), whereas alpha-ENaC was more modestly, yet significantly, increased (to 142% of vehicle). Similarly, 7-day water restriction in Sprague-Dawley rats resulted in significantly increased abundances of beta- and gamma- but no significant change in alpha-ENaC. Acute administration of dDAVP (2 nmol) to Brattleboro rats resulted in modest, but significant, increases in abundance for all ENaC subunits, within 1 h. In conclusion, all three subunits of ENaC are upregulated by vasopressin with temporal and regional differences. These changes are too slow to play a major role in the short-term action of vasopressin to stimulate sodium reabsorption in the collecting duct. Long-term increases in ENaC abundance should add to the short-term regulatory mechanisms (undefined in this study) to enhance sodium transport in the renal collecting duct.

The inflammatory response to acute endotoxemia down regulates V2 VP receptors and aquaporin-2 of the kidney inner medulla resulting in prolonged impairment of the renal capacity to concentrate urine.

The photoplethysmographic (PPG) signal has the potential to aid in the acquisition and analysis of heart rate variability (HRV) signal: a non-invasive quantitative marker of the autonomic nervous system that could be used to assess cardiac health and other physiologic conditions. A low-power wireless PPG device was custom-developed to monitor, acquire and analyze the arterial pulse in the finger. The system consisted of an optical sensor to detect arterial pulse as variations in reflected light intensity, signal conditioning circuitry to process the reflected light signal, a microcontroller to control PPG signal acquisition, digitization and wireless transmission, a receiver to collect the transmitted digital data and convert them back to their analog representations. A personal computer was used to further process the captured PPG signals and display them. A MATLAB program was then developed to capture the PPG data, detect the RR peaks, perform spectral analysis of the PPG data, and extract the HRV signal. A user-friendly graphical user interface (GUI) was developed in LabView to display the PPG data and their spectra. The performance of each module (sensing unit, signal conditioning, wireless transmission/reception units, and graphical user interface) was assessed individually and the device was then tested as a whole. Consequently, PPG data were obtained from five healthy individuals to test the utility of the wireless system. The device was able to reliably acquire the PPG signals from the volunteers. To validate the accuracy of the MATLAB codes, RR peak information from each subject was fed into Kubios software as a text file. Kubios was able to generate a report sheet with the time domain and frequency domain parameters of the acquired data. These features were then compared against those calculated by MATLAB. The preliminary results demonstrate that the prototype wireless device could be used to perform HRV signal acquisition and analysis.

The effects upon production of cortisol and dehydroepiandrosterone (DHA) by human fetal adrenal cells in tissue culture were studied using commercial hCG (0.5 and 5 IU/ml), purified hCG (0.7-6.7 IU/ml), the alpha-subunit of hCG (200 and 1000 ng/ml), human GH (50 and 200 ng/ml), human PRL (0.1-100 ng/ml), alpha-MSH (0.1-10 ng/ml), corticotropin-like intermediate lobe peptide (200 ng/ml), human beta-lipotropin (0.1 and 0.2 ng/ml), and beta-endorphin (100 ng/ml). Although each peptide was added to the culture medium in a concentration either similar to that observed in the fetal circulation or (where such information was not available) in amounts several times greater than those effective for ACTH in this system, none demonstrated any significant stimulation of steroid production. In particular, repeated studies with hCG showed that this hormone had no stimulating effect upon DHA production, neither in cultures of whole adrenals nor in cultures of separated fetal zone and definitive zone cells. Furthermore, none of these peptides showed a synergistic effect upon DHA production when they were added to cultures together with concentrations of alpha-ACTH-(1-24) (10(2)-10(3) pg/ml) previously demonstrated to represent the middle of the dose-response curve. Indeed, the only significant interactions with alpha-ACTH-(1-24) observed in these studies were a slight reduction in cortisol production produced by corticotropin-like intermediate lobe peptide and apparent inhibition of DHA production by beta-lipotropin and GH. The data do not lend credence to the suggestion that any of these peptides plays an important role in vivo in stimulating fetal adrenal steroidogenesis.

The analysis of time duration between consecutive R waves of electrocardiogram (ECG) is a standard method to evaluate the variations in heart rate. The physiological literature reveals that blood glucose levels modulate the autonomic nervous system (ANS) activity and heart rate variability (HRV) is representative of the cardiovascular autonomic function. In the research described here, a pilot investigation was carried out to investigate the relationship between HRV signal measures derived from ECG and arterial blood glucose changes in a female subject with type 1 diabetes mellitus (T1DM) subject during normoglycemic and mildly hyperglycemic conditions. A CleveLabs BioCapture wireless device was used to acquire ECG signals from a 160 Kg, 59.6 year old female volunteer with type 1 diabetes. The PhysioToolkit Software was used to extract the HRV signal and the Kubios software package was deployed to perform comprehensive HRV signal analysis. This software has an easy-to-use graphical user interface that displays the HRV signal and provides three options to calculate: Time-domain, Frequency-domain and Nonlinear Dynamics parameters from raw HRV signals. In its Frequency-domain analysis section, it provides frequency bands such as VLF (Hz), LF (Hz), and HF (Hz), with LF/HF as an index that reflects the sympathovagal balance of the ANS. ECG data were acquired for 30 minutes during normoglycemic condition and for another 30 minutes during mildly hyperglycemic conditions, while blood glucose levels were measured manually by the subject using a glucometer every 5 minutes. ECG signal segments of 5 minute durations were then processed to extract HRV signals and these in turn were analyzed to provide frequency-domain measures. The results indicated that blood glucose changes were inversely related to LF/HF. For this dataset, it was observed that mean ± std of the LF/HF decreased from 6.0 ± 1.04 to 0.91 ± 0.17 when blood glucose levels increased from 156 ± 22 mg/dl to 202 ± 29 mg/dl. Further investigation is underway to recruit more diabetic subjects to acquire a large dataset and explore the relationships between different HRV signal parameters and blood glucose changes under different gylcemic conditions in a comprehensive way.