Adrenaline and the relationship between neurosomatism, aerobic fitness and mental task performance.

The influence of neurotic instability as manifested by functional somatic complaints (neurosomatism) and aerobic fitness on responses to mental stress and to intravenous adrenaline infusions were investigated in 44 university students. Adrenaline-induced changes from resting levels in state anxiety and somatic anxiety were significantly more pronounced in high than in low neurosomatic subjects and all anxiety ratings were generally negatively related to aerobic fitness. Cardiovascular reactivity was induced by mental stress and by adrenaline infusions, but was not altered by neurosomatism. In individuals assumed to be characterized by a susceptibility to adrenergic effects, interference of adrenaline-induced arousal with cognitive performance may not occur. In contrast, a further increase in performance may occur when adrenaline is infused. Performance measures correlated negatively with anxiety during the baseline task and the placebo task, but this negative relation was absent during the adrenaline infusion and was replaced by positive relations between performance and aerobic power. The complex relations between bodily symptoms of anxiety, aerobic fitness and mental stress are discussed.

Platelet catecholamine contents as related to trait anxiety and aerobic fitness.

Platelet catecholamines (CA) are derived from plasma and are considered as a cumulative index of sympathoadrenal activity. We investigated whether trait anxiety (TA) and aerobic fitness, two interrelated long-term determinants of sympathoadrenal activity, affect platelet CA concentration as measured in rest and after acute increments of plasma epinephrine (Epi). For that purpose, platelet CA were measured 15 min before and after Epi infusion (5-160 ng.kg-1.min-1, increased in 6 steps) in 45 healthy male students with high (n = 21) and low (n = 24) TA, of whom maximal aerobic power (VO2max) was assessed. Plasma CA and electrolytes were measured during each infusion rate. Epi infusion significantly raised platelet Epi by 67% and decreased platelet and plasma norepinephrine (NE) by 23 and 17%. Plasma potassium significantly decreased by 32% and plasma sodium slightly increased. Platelet Epi increase was inversely related to basal platelet Epi (r = -0.58, P less than 0.001). Platelet NE decrease was positively associated with basal platelet NE and plasma potassium levels (r = 0.50, P less than 0.01). TA and VO2max were not related to basal levels and responses of electrolytes and platelet NE. VO2max was correlated with platelet Epi increase in low TA (r = 0.62, P = 0.002), whereas no such relationship existed in high TA (r = 0.008). We conclude that fitness positively influences platelet Epi accumulation, but that high TA interferes with this relationship.

Preservatives in insulin preparations impair leukocyte function. In vitro study.

m-Cresol and methyl p-hydroxybenzoate are preservatives in insulin preparations. As previously reported, in diabetic patients on continuous subcutaneous insulin infusion, users of insulin-containing m-cresol had significantly more inflamed infusion sites than users of insulin with methyl p-hydroxybenzoate. This study assessed the influence of insulin with and without these preservatives on leukocyte function. Leukocyte function was investigated in a killing experiment, expressed as the percentage of bacteria killed after 60 min incubation of bacteria (Staphylococcus aureus), polymorphonuclear leukocytes, serum, and insulin preparations. Because preservative is retained by the infusion device, insulin with preservative was tested before and after 1 and 4 days perfusion with a PVC pump catheter. After perfusion, the amount of preservative was reduced (percentage of original concentration after 1 and 4 days 8 and 30% m-cresol and 42 and 72% methyl p-hydroxybenzoate, respectively). The killing percentage in insulin with m-cresol reduced compared with insulin without preservative (mean +/- SE 95.4 +/- 0.8%) and the control without insulin (95.8 +/- 0.8%), both before and after 1 and 4 days perfusion (74.8 +/- 0.7, 80.2 +/- 2.8, and 80.6 +/- 1.6%, respectively; P less than 0.01). The same occurred in insulin with methyl p-hydroxybenzoate (85.0 +/- 0.9% before and 88.4 +/- 0.9 and 86.2 +/- 0.8% after 1 and 4 days perfusion; P less than 0.05). All insulin preparations with m-cresol caused lower killing percentages than corresponding insulin preparations with methyl p-hydroxybenzoate (P less than 0.05). These results demonstrate that both preservatives impaired leukocyte function, but m-cresol was the most noxious in this respect.(ABSTRACT TRUNCATED AT 250 WORDS)

Carriage of Staphylococcus aureus and inflamed infusion sites with insulin-pump therapy.

The most common complication of continuous subcutaneous insulin infusion (CSII) is inflammation at the infusion site. To determine possible risk factors to these infections, we studied several factors in the management of CSII and compared the pyogenic skin inflammation rate, the carriage rate of Staphylococcus aureus, and the HbA1 level among 50 CSII-treated diabetic patients, 50 diabetic patients on insulin injections, 48 diabetic patients on oral medication, and 40 healthy volunteers. There was no increased carriage rate of S. aureus among CSII-treated patients (42%) as compared with the other groups. An unexpected inverse relationship existed between HbA1 level and carriage rate in the CSII-treated group (HbA1 5-8%, n = 16, 69%; HbA1 8-10% n = 15, 40%; HbA1 greater than 10, n = 19, 21% P = .02). Pyogenic skin inflammations were reported by 24 (48%) CSII-treated patients, of which 18 had infected infusion sites, 6 (12%) insulin injecting patients, 2 (4%) patients on oral medication, and 3 (8%) healthy volunteers (P less than .01). The occurrence of inflamed infusion sites was not associated with carriage of S. aureus, the indwelling time of the needle, or the insulin dosage per day. There was an association, however, with the type of insulin preparation classified according to the added preservative: m-cresol-containing insulin (n = 24, 54%); methyl p-hydroxybenzoate-containing insulin (n = 26, 19%, P = .02). We concluded that the carriage of S. aureus is not increased among diabetic patients on CSII treatment and is not a risk factor in the occurrence of inflammation at the infusion site.(ABSTRACT TRUNCATED AT 250 WORDS)

Repetitive stimulation of insulin secretion with arginine and glucose.

Glucose and arginine are both known to be potent insulin secretagogues and to potentiate each others insulin secretion. We investigated if repetitive infusion of arginine leads to comparable insulin secretion during fasting and if the additional infusion of glucose leads to a change in the pattern of the insulin secretion during repeated infusion of arginine. Repeated continuous infusions of arginine (0.3 g/kg in 30 min) in six normals led to a lower second phase insulin secretion during the third infusion (p less than 0.05). Pre-stimulus blood glucose levels were lower before the third infusion than before the first infusion (p less than 0.05). Repeated hyperglycaemic clamps (17.5 mmol/l during 30 min) led to comparable insulin secretion during three infusion. Combined infusion of arginine and glucose (hyperglycaemic clamps) did not lead to a decrease during the third infusion. We conclude first, that concomitant hyperglycemia potentiates second phase insulin secretion and second, that prolonged fasting leads to an adaptation of the pancreas B-cell leading to diminished arginine-induced insulin secretion, which can be overcome by additional infusion of glucose. This potentially confounding factor will have to be taken into account in planning future investigations of arginine-induced insulin secretion.