Communication from Abroad Does Secretin Influence Rat Colonic Absorption and Secretion?

In rats, a secretin (Jorpes) intravenous infusion superimposed on an intracolonic sodium acetate perfusion elicits, with respect to control values, a significant depression of Na+ absorption (0.16 mEq./h-0.00 mEq./h.) and mucus secretion (230-40 mg.). When the hormone is superimposed upon an intracolonic infusion of acetic acid, mucus secretion is also significantly inhibited (790-340 mg.). The influence of secretin on organic anion movement was pH related. At pH values of 7.0, absorption was unchanged (0.34--0.33 mEq./h.), at pH values of 2.9, absorption was significantly reduced (0.67-0.41 mEq./h). The secretin impairment of colonic mucus secretion could influence the transport of watersoluble (Na+) and lipid soluble (acetic acid) substances, probably through changes at the "unstirred layer" level.     

Age at commencing smoking and number of cigarettes smoked in an Ialian Population Survey

The objective of the study was to describe a group of adolescentswho have no smokers in their social environment and to examinetheir beliefs regarding the benefits of smoking. The designwas a telephone survey. A population-based survey was conductedin California in 1990. There were 7,767 adolescent respondentsbetween 12 and 17 years of age, 373 (5%) of whom were unexposedto smokers in their social environment. A positive responseto any 1 of 5 questions concerning a belief in the benefitsof smoking was the main outcome measure. In teenagers unexposedto smokers in their social environment 70% were 12 or 13 yearsof age compared to only 35% of teenagers exposed to smokers.Unexposed teenagers were more often female and more often whiterather than Hispanic, African-American or Asian. After adjustingfor demographic factors, unexposed teenagers were only one-quarteras likely as exposed teenagers to harbour a belief in the benefitsof smoking. However, 40% of unexposed teenagers held such abelief with 28% believing that smoking helps people feel morecomfortable in social situations, 19% believing that smokinghelps people relax and 13% believing that smoking helps peoplekeep their weight down. It is unlikely that the group of teenagersunexposed to smokers in their social environment acquired theirbeliefs about the benefits of smoking through contact with smokers.Cigarette advertising might be a likely source of these perceptions.     

Physiological Sensitivity of Respiratory-Dependent Cardiac Pacing: Four-Year Follow-Up

Clinical and physiological data on long-term follow-up of 143 patients with respiratory-dependent pacemakers (RDP3) are reported; 121 patients received ventricular (VVI-RD) and 22 patients atrial (AAI-RD) respiratory-dependent stimulation. Functional evaluation was based on the exercise testing (130 pts) with oxygen uptake VO2, ventilation, ECG and arterial pressure monitoring and the dynamic Holter electrocardiogram (95 pts). In each patient, the stimulation rate curve selected was that which produced the best work tolerance and moved the anaerobic threshold to the right. Respiratory levels were assessed by telemetry verifying proper sensing of tidal volume variations and absence of interference and artefacts. In patients with VVIR or AAIR stimulation, exercise tolerance, oxygen uptake and anaerobic threshold increased significantly in comparison with VVI or AAI pacing respectively. The physiological sensitivity of the stimulation system (i.e., a linear relationship of the pacing rate with metabolic requirements) was excellent (up to exhaustion) in 70%, very good (up to anaerobic threshold) in 20% and erratic (no relationship between pacing rate and VE/VO2) in 10% of patients. In dynamic electrocardiographic monitoring, the automatic pacing rate was always predominant during the night and during rest periods; the pacing rate increased properly with daily activity; myopotential inhibition (none longer than 3,500 ms) was observed in 38 patients, but without subjective complaints. The incidence of the RDP3 malfunction was less than 8%; it may have stemmed from the pacing system itself, or from other clinical conditions. Oversensing of impedance system pulses has not been recorded in the last 3 years. Partial respiration undersensing results from incorrect accessory lead position, pulmonary emphysema, marked obesity or other causes. Respiratory sensing becomes erratic at the anaerobic threshold point in such patients, but functions well at submaximum exercise levels. In patients with left ventricular failure, exercise tolerance was improved by setting a lower ratio between the pacing rate and respiration, which prevented the occurrence of excessive pacing rates.     

THE EFFECT OF CHRONIC ETHANOL CONSUMPTION ON IRON ABSORPTION IN RATS

Alcoholics often have an increased amount of iron in the liverwhich may contribute to the development of alcoholic liver disease,although the mechanism is unknown. It has been shown that chronicethanol intake decreases the enterocyte turnover and enhancesgalactose absorption. Whether it affects iron absorption isstill controversial. The aim of this study was to investigatethe effect of chronic ethanol ingestion on whole body iron absorptionin rats. Twenty-eight adult male Sprague-Dawley rats were pair-fed aliquid diet containing either ethanol as 36% of total caloriesor an isocaloric diet where fat was substituted, for ethanol.On the 28th day, four-hour fasted rats were given an oral doseof ⁵⁹Fe (0.5µCi) and were immediately counted by a wholebody counter. ⁵⁹Fe levels were then monitored over the followingnine days. Although ethanol- and control-fed rats had a similarhepatic iron content (59.5±5.8 vs 60.2±7.4 µg/100mg dry liver weight) (mean±S.E.M.), the ⁵⁹Fe total bodycontent was greater in the ethanol group (75%±3%) comparedwith the control group (45%±4%). These results show thatchronic ethanol ingestion increased iron absorption in rats.A reduction of enterocyte turnover may play a role in determiningthis effect.     

Wavelength Index at Three Atrial Sites in Patients with Paroxysmal Atrial Fibrillation

PADELETTI, L., et.al .: Wavelength Index at Three Atrial Sites in Patients with Paroxysmal Atrial Fibrillation . The purpose of this study was to evaluate the wavelength index (WLI) at three atrial sites in a group of 23 patients with recurrent episodes of lone paroxysmal atrial fibrillation (LPAF) and a control group (n = 20). All patients underwent programmed atrial stimulation (paced cycle length = 600 ms) at high, medium, and low lateral right atrial wall. P wave duration, sinus cycle length, and corrected sinus node recovery time were not significantly different between the two study groups. WLI was calculated according to the following formulas: atrial effective refractory period (AERP)/duration of atrial extrastimulus electrogram (A₂) or AERP/A₂+ atrial latency; and atrial functional refractory period (AFRP)/A₂. WLI was significantly shorter in LPAF than in the control group at each of the paced atrial sites independently of the formula used. Duration of premature atrial electrogram appeared to play the major role in determining the difference in WLI between patients with paroxysmal atrial fibrillation and the control group.     

Multiple Shocks Affect Thoracic Electrical Impedance During External Cardioversion of Atrial Fibrillation

Background: Thoracic impedance (TI) influences the success of external cardioversion (ECV) or defibrillation because current intensity traversing the heart is inversely related to TI. Experimental data suggest that TI decreases after multiple shocks. We undertook a clinical study to determine changes of TI values in patients with atrial fibrillation or flutter requiring ECV. Methods: We enrolled 222 consecutive patients (age 73 ± 11 years; males 67%; body weight 75 ± 13 kg) who underwent ECV between January 2004 and February 2007. Biphasic shocks were delivered through adhesive pads placed in the anteroposterior position. The initial energy was set at 1 J/kg, with progressive increases up to a maximum of 180 J in case of failure. In the last 39 elective patients, plasma concentration of interleukin‐6 (IL‐6) and tumor necrosis factor (TNF)‐α were determined before and 6 hours after ECV. Results: Sinus rhythm was restored in 202 patients (91.0%). Of these, 155 (69.8%) required more than one shock (on average, 2.5 ± 1.5 shocks/patient). Final values of energy and peak current intensity were 136 ± 47 J and 50 ± 14 A, respectively. TI decreased significantly by 6.2% from baseline after ≥2 shocks (P < 0.001). The absolute reduction was correlated with baseline TI, number of delivered shocks, and hemoglobin oxygen saturation. IL‐6 and TNF‐α increased with ECV (P < 0.001 and P = 0.014, respectively). Conclusions: TI decreases significantly after multiple shocks, possibly by activation of acute inflammation.     

GROWTH HORMONE SECRETION IN PRIMARY DEGENERATIVE DEMENTIA: CORRELATIONS WITH COGNITIVE IMPAIRMENT

Changes in brain peptides and neurotransmitters are thought to elicit alterations of growth hormone (GH) secretion in dementia. Baseline GH levels and hormone responses to GH-releasing hormone (GHRH)—administered alone or after pyridostigmine pretreatment—were evaluated in 17 patients, aged 52–83, with primary degenerative dementia quantified by the Clinical Dementia Rating (CDR) Scale and the Mini-Mental State Examination (MMSE) with a view to detecting correlations between neuroendocrine and clinical data. Basal GH levels were not statistically different in patients and in age-matched controls. However, when patients were split into the three CDR groups of disease severity, basal GH levels were significantly higher in those with more severe dementia than in all other patients and in controls. GH responses to GHRH, evaluated both in terms of peaks attained after simulation and of secretion areas under the curve (AUC), were significantly higher in patients than in controls after pyridostigmine pretreatment, but not after the infusion of GHRH alone. Patients with mild to moderate dementia had GH peaks after GHRH higher than more severe patients. Pyridostigmine did not potentiate GHRH effects in the more severe cases. The scores on Rey's 15-word test for memory function were directly correlated with GH peaks after GHRH. No correlations were found between GH data, age, body weight, disease duration and scores at other psychometric assessments such as MMSE, Raven's matrices, verbal fluency or WAIS tests.     

KIDNEYS DERIVED FROM MICE TRANSGENIC FOR HUMAN COMPLEMENT BLOCKERS ARE PROTECTED IN AN IN VIVO MODEL OF HYPERACUTE REJECTION

Purpose

The major obstacle to successful discordant kidney xenotransplantation is hyperacute rejection (HAR). Complement plays a key role in the induction of HRA, defined by endothelial cell activation, loss of vascular integrity, hemorrhage and thrombosis. The activation of complement is tightly controlled by a number of species-specific regulatory proteins which inhibit, at different points, the cascade of events leading to the formation of the membrane attack complex (MAC). We have tested the hypothesis that kidneys derived from transgenic mice expressing two human complement inhibitors, Decay Accelerating Factor (hDAF) and Membrane Cofactor Protein (MCP), could be protected from human complement-mediated damage.

Materials and Methods

Control and transgenic mice were perfused with human plasma by cannulation of the right jugular vein, at a perfusion rate of 10 micro L./min. for two hours. Complement C3 deposition was detected on kidney sections by immunohistochemistry using specific FITC antibody. Complement-induced tissue damage was evaluated by histopathological examination.

Results

Heavy deposition of complement C3 was observed on kidneys derived from perfused control mice. This was associated with a characteristic HAR pathology of severe interstitial hemorrhage, inflammatory reaction, loss of glomerula and tubuli structure. Kidneys derived from mice transgenic for hDAF or hMCP were partially protected from both complement C3 deposition and tissue damage. The expression of both dDAF and hMCP in double transgenic mice significantly increases the protection from human complement-mediated damage.

Conclusions

A novel model of in vivo perfusion with human plasma has been adopted to recreate the initial event of HAR. Our data show that this murine model could be very valuable to determine the effect of transgenic human molecules in protecting vascularized organs from human complement attack.     

Atrial Septal Pacing:

Atrial pacing may prevent the onset of atrial fibrillation (AF) because of: (1) prevention of the relative bradycardia that triggers paroxysmal AF; (2) prevention of the bradycardia induced dispersion of refractoriness; (3)suppression or reduction of premature atrial contractions that initiate reentry and predispose to AF; (4) preservation of AV synchrony, which might prevent switch induced changes in atrial repolarization predisposing to AF. Atrial pacing locations that decrease atrial activation and dispersion of refractoriness may be preferable in patients with a history of AF. Two different interatrial septum sites have been proposed: the Bachmann's bundle and the coronary sinus ostium. The results of two prospective randomized studies indicate that septal pacing, when compared to the traditional right atrial appendage pacing, significantly reduces : (1) paroxysmal AF recurrences and burden; and (2) progression to chronic AF. (PACE 2004; 27[Pt. II]:850–854)