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Biomedical subjects

E F Pfeiffer

Publications and source records attributed to E F Pfeiffer.

At least 199 records · Page 11Linked to original sources
PubMed1979

[Scurvy].

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Diet, Reducing↗
PubMed1979

Differential and integral corticosteroid feedback effects on ACTH secretion in hypoadrenocorticism.

Recent work suggests the existence of a dual corticosteroid feedback mechanism of stress-induced ACTH secretion in the rat. This possibility led us to study the kinetics of suppression of ACTH levels by corticosteroid administration in patients with nonstress ACTH hypersecretion secondary to hypoadrenocorticism. Cortisol was administered according to different protocols, which were chosen to provide extreme variations of the input signal. By this means, two phases of suppression of ACTH levels could be differentiated. A first decrease occurred without latency whenever, and as long as, plasma cortisol levels were rising. There was a linear regression between the logarithm of the increments in cortisol concentrations and the decrease in ACTH levels per minute (r = 0.951) (differential or rate-sensitive feedback mechanism). Neither the absolute doses of cortisol, nor plasma cortisol concentrations were closely correlated with the degree of suppression of ACTH by this rapid mechanism. A second decrease in ACTH levels began congruent with30 min after corticosteroid administration. In this case there was a significant linear regression between the degree of inhibition of ACTH levels and the cortisol doses (r = 0.997) (integral or dose-sensitive feedback mechanism). The dose-sensitive feedback effects of dexamethasone were less than might have been predicted from its relative anti-inflammatory potency. No rate-sensitive effects were seen with dexamethasone doses of 1.0 or 1.25 mg.

Adrenal Cortex Hormones↗
PubMed1979

Positive rate-sensitive corticosteroid feedback mechanism of ACTH secretion in Cushing's disease.

To define the nature of the disturbance of the corticosteroid feedback mechanism in Cushing's disease, the dynamic aspects of the ACTH response to corticosteroid administration have been studied in patients with Cushing's disease after total adrenalectomy (C.d. post adx.). The results were compared with those obtained in patients with Addison's disease (control group). Different experimental designs for administration of cortisol were chosen to provide extreme variations in the input signal. The response of the system was evaluated by measuring plasma ACTH concentrations (radioimmunoassay) at short time intervals. Infusion of cortisol at constant rate (50 mg/h for 2 h) resulted in a transient, paradoxical rise in ACTH levels with a maximum at 15 min. (315+/-65%, mean+/-SEM). In contrast, in the control group there was an immediate and rapid decrease in ACTH levels with a significant inhibition after 15 min (80+/-6%, mean+/-SEM). Infusion of 50 mg cortisol for 5 and 15 min, respectively, produced an increase in ACTH levels, which was confined to the time when cortisol levels were rising (maximum: 137+/-30% and 139+/-10% at 5 and 15 min, respectively, mean+/-SEM). This increase corresponded in time to the first decrease in ACTH levels in the Addisonian patients. With bolus injections of 25 mg cortisol, ACTH levels remained unchanged during the first 15 min. The time-course in the patients with C.d. post adx. was essentially the same as in the Addisonian patients. From these results it is concluded that in the patients with C.d. post adx. the rapid, rate-sensitive feedback mechanism was converted into a positive one, whereas the delayed, dose-sensitive mechanism was completely undisturbed. The capacity of dexamethasone to activate rate-sensitive feedback elements was markedly diminished. Accordingly, there were only minor positive feedback effects upon ACTH secretion in the patients with C.d. post adx.

Addison Disease↗
PubMed1979

[Postoperative blood-sugar regulation in pancreatectomized patients using the artificial "beta cell"].

Seven patients who had undergone total duodenopancreatectomy were connected postoperatively to an artificial 'beta cell', which is a computer-regulated, glucose-controlled-insulin-infusion-system. Despite high-calorie parenteral nutrition, the apparatus enabled successful regulation of the diabetes that followed removal of the pancreas in our patients during the immediate postoperative period (7 days). The artificial beta cell is capable of exogenously regulating the carbohydrate metabolism of pancreatectomized diabetics, even in the extreme conditions immediately following operation.

Artificial Organs↗
PubMed1979

D-Trp8-D-Cys14-somatostatin--demonstration of its differential suppressive activity in juvenile diabetics.

In 8 insulin-dependent diabetics, the effect of D-Trp8-D-Cys14-somatostatin on blood glucose, growth hormone, and glucagon levels as well as on insulin requirements from an artificial endocrine pancreas was studied during a balanced meal. The somatostatin analogue was infused at a rate of 25 microgram/h preceeded by a bolus injection of 25 microgram 30 minutes before ingestion of the meal. At this dose the analogue had no effect on glucagon levels and insulin requirements from the artificial pancreas. On the other hand, there was a significant lowering effect on fasting blood glucose levels, possibly indicating a direct inhibition of hepatic glucose production. Furthermore, there might be a slight effect on growth hormone levels, as was demonstrated by a rebound increase after termination of analogue infusion.

Adolescent↗
PubMed1979

Application of an artificial endocrine pancreas in the management of the diabetic surgical patient.

Application of the artificial endocrine pancreas in 12 patients undergoing total duodenopancreatectomy and 3 diabetics in whom different operations were performed proved to be safe for the patients with respect to blood glucose control and prevention of ketosis. In the postoperative period, essentially normal blood glucose values were obtained despite high caloric parenteral nutrition.

Adult↗
PubMed1979

Influence of insulin infusion kinetics of an artificial beta cell on blood glucose control in insulin-dependent diabetics.

The influence of different control modes for insulin infusion with an artificial beta cell was examined in 41 insulin-dependent diabetics. In 21 Patients, oral glucose tolerance tests were performed with control modes characterized either by low dynamic and high static gain (type I, 10 patients) or high dynamic and low static gain (type III, 11 patients). The change from type I to type III control mode effected an increase of initial insulin infusion rates (91 +/- 59 to 313 +/- 81 mU/min 10-20 min after glucose ingestion) and a decrease of infusion rates during the following phase of the 3-hour observation period (28.2 +/- 4.2 to 18.1 +/- 2.8 U) in patients whose blood glucose curves were completely normalized. Suppression of plasma glucagon levels, observed in 5 healthy control subjects, was not fully restored to normal in these patients. In another 20 insulin-dependent diabetics, daily insulin requirements form the artificial beta cell were determined by employing two control modes (types II and III) comparable in static control but different in dynamic control. Gain of dynamic control, especially in the range of falling glucose levels, was higher in type III control mode (15 patients) than in type II mode (5 patients). These insulin requirements were compared to the insulin doses necessary for subcutaneous treatment. While intravenous insulin requirements were much higher when type II control mode was employed (78.2 +/- 10.2%), during application of type III mode, intravenous insulin requirements were only 10.8 +/- 5.5% higher than subcutaneous doses. We conclude from these data that early increases in insulin infusion rates followed by a rapid decrease seem to reduce insulin requirements after glucose ingestion. A high-gain dynamic control is the basis for this insulin infusion profile.

Adolescent↗
PubMed1979

The effect of three days of blood glucose normalization by means of an "artificial endocrine pancreas" on the concentrations of growth hormone, glucagon, and cortisol in juvenile diabetics.

Glucagon, growth hormone, and cortisol secretion was studied in seven male insulin-dependent diabetics under conventional subcutaneous insulin therapy and after three days of blood glucose normalization attained by the artificial endocrine pancreas (Biostator-GCIIS). The diurnal hormonal profiles under the two types of therapy were compared. Six healthy male students served as control group. A three-day period of blood glucose normalization in insulin-dependent diabetic can restore glucagon secretion to normal. Growth hormone secretion is decreased but not completely normalised. Cortisol secretion is slightly decreased. It is concluded that prolonged normoglycemia achieved by means of an artificial endocrine pancreas may completely control endocrine abnormalities in insulin-dependent diabetics.

Adult↗
PubMed1979

Feedback inhibition of insulin in healthy and overweight subjects studied by use of an artificial endocrine pancreas.

Insulin self-inhibition is still a controversial subject. The majority of data is in favour of an inhibition; however, whether this mechanism is of physiologic relevance in the regulation of insulin secretion is open to discussion. We examined the effect of exogenous insulin on beta cell secretion in 16 volunteers, including 3 who were overweight. Blood glucose (BG) was clamped by means of the dextrose infusion unit of the artificial beta cell, and the secretion of the pancreatic beta cell was monitored by immunomeasureable C-peptide (IMCP) before, during, and after infusion of insulin. The subjects were divided into 3 experimental groups. The inhibition of the basal insulin secretion was examined in group I by clamping BG at the fasting level. The inhibition of the glucose-stimulated insulin secretion was examined in group II by clamping BG at a raised level. The stimulation of insulin secretion by glucose during insulin infusion was examined in group III by stepwise BG rises from the fasting level. An inhibition of the basal insulin secretion was observed in all volunteers examined according to the protocol for group I (n = 9, including 3 overweight volunteers). The lowest insulin infusion rate applied was 1.75 U/h. An inhibition occurred at this low infusion rate corresponding to 44 mu U immunomeasurable insulin (IMI) per ml of serum. However the inhibition was impaired in the overweight participants, who, in addition, were the only ones showing a rebound rise of IMCP after stopping the insulin infusion. An inhibiting effect of exogenous insulin appeared as likely in only 1 of 5 participants examined according to the protocol for group II. Sudden rises of BG abolished the inhibition, while a total or partial inhibition was found at a constantly raised BG level in both participants examined according to protocol III. We conclude that exogenous insulin inhibits beta cell secretion, depending on the BG level, the mode of glucose stimulation, and the time relation between glucose and insulin application. Physiologically occuring IMI levels in peripheral serum were sufficient to cause an inhibition. A disturbance of the negative feedback inhibition of insulin should be discussed as a pathogenetic factor of adipositas.

Adult↗