Motor activity and neurotransmitter release in the gastric fundus of streptozotocin-diabetic rats.

As deficiencies of the cholinergic and non-adrenergic non-cholinergic innervation of the gastrointestinal tract have been described in diabetic rats, we studied the simultaneous release of, and muscular response to, acetylcholine, vasoactive intestinal polypeptide and adenosine-5'-triphosphate in isolated preparations of gastric fundus from control and 8-week streptozotocin-treated diabetic rats. Muscular responses were measured in longitudinal muscle strips prepared from one half of the gastric fundus and release was studied in the other half. The contractile response to acetylcholine and electrical field stimulation was not different in control and diabetic rats. In the presence of atropine, and when tone was increased with prostaglandin F2 alpha, electrical field stimulation, vasoactive intestinal polypeptide and adenosine-5'-triphosphate induced relaxation with a similar response in control and diabetic rats. The basal release of acetylcholine, vasoactive intestinal polypeptide and adenosine-5'-triphosphate was not significantly different in control and diabetic rats. Electrical field stimulation significantly increased the release of the three substances and this increase was tetrodotoxin-sensitive. While the stimulation-induced increase of acetylcholine and vasoactive intestinal polypeptide was not different in control and in diabetic rats, the stimulation-induced release of adenosine-5'-triphosphate increased 3-fold in diabetic compared to control gastric fundus. Desensitization to alpha,beta-methylene adenosine-5'-triphosphate reduced the relaxant response to adenosine-5'-triphosphate and to electrical field stimulation, suggesting a role of adenosine-5'-triphosphate in non-adrenergic non-cholinergic neurotransmission of rat gastric fundus. The reduction of the non-adrenergic non-cholinergic relaxation by alpha,beta-methylene adenosine-5'-triphosphate was greater in diabetic tissues. This, with the increase in stimulation-induced adenosine-5'-triphosphate release, suggests that the purinergic component of the vagal non-adrenergic non-cholinergic response of the stomach may be increased in diabetics.     

Correlating digit span performance and event-related potentials to assess working memory.

Event-related brain potentials (ERPs) were recorded during a computerized and modified version of the Digit Span Backwards (DB) task from the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III). The modified DB version (ERP-DB task) was divided into two sections of 2, 4, 6 and 8 digits in length (Group 1) and 3, 5 and 7 digits in length (Group 2). Each trial had a study phase and a test phase. For the study phase, a series of digits was presented sequentially and aurally to 20 participants (10 for each group). For the test phase, a second series of digits was also presented sequentially and aurally that either corresponded to the reverse order of the digits in the study phase (correct condition) or had one digit in the sequence replaced by an incorrect digit (incorrect condition). The traditional DB task of the WAIS-III was also administered for comparison purposes. A prolonged positive slow wave (PSW) peaking between 450 and 750 ms was elicited to incorrect condition trials. For each participant, a derived measure was calculated from the ERP differentiation between correct and incorrect conditions. The derived measure was defined as the mean of the t-values obtained from the correct and incorrect waveform comparison, within the temporal interval that encompassed this component. The strongest statistical correlations between the derived measure and the traditional DB test scores were found at the Pz site (Group 1: r=0.79; Group 2: r=0.59). This statistical approach shows that it is possible to adequately relate an individual's performance on a traditional measure of working memory and ERP patterns. Overall, we believe that this kind of ERP approach holds promise as a technique for assessing quantitatively non-communicative patients.     

Defective implant osseointegration under protein undernutrition: prevention by PTH or pamidronate.

Protein deficiency is associated with impaired titanium osseointegration. We studied whether systemic treatment with PTH or pamidronate could influence the resistance to pull-out of titanium rods implanted into rats proximal tibia under normal and isocaloric low protein intake. PTH or pamidronate prevented the deleterious effects of protein undernutrition on bone microarchitecture close to the implant and on mechanical fixation. PTH even significantly improved implant osseointegration. INTRODUCTION: Protein deficiency is highly prevalent among elderly patients hospitalized in orthopedic wards. Reduced protein intake impairs titanium osseointegration in rats. Whether stimulator of bone formation or inhibitor of bone resorption could improve implant osseointegration under protein deprivation is not known. We studied the effects of systemic treatment with PTH or pamidronate on the resistance to pull-out of titanium rods implanted into rats proximal tibia under normal and isocaloric low protein intake. MATERIALS AND METHODS: We measured the resistance to pull-out 1-mm-diameter titanium rods implanted into the proximal tibias of 49 adult female rats receiving a normal or an isocaloric low protein diet. After 2 wk on either diet, the implants were inserted, and the rats received PTH(1-34), pamidronate or saline vehicle for 8 wk. The tibias were removed for microCT morphometry, followed by the evaluation of pull-out strength. RESULTS: Pull-out strength was lower in rats fed an isocaloric low protein diet compared with rats fed a normal protein intake (-29%). PTH and pamidronate significantly increased pull-out strength in animals fed a normal or a low protein diet, the effect of PTH being of higher magnitude. The PTH- or pamidronate-mediated increase in pull-out strength was associated with significant increases of relative bone volume, bone-to-implant contact, and trabecular thickness, whereas trabecular spacing was reduced, in the vicinity of the implants. CONCLUSIONS: We confirmed that isocaloric low protein intake impairs titanium implant osseointegration. PTH or pamidronate prevented the deleterious effects of protein undernutrition and even significantly improved the implant osseointegration. These results indicate that systemic administration of PTH or pamidronate could be considered for preventing uncemented arthroplasty loosening in protein undernourished patients.