The effects of insulin on the counterregulatory response to equivalent hypoglycemia in patients with insulin-dependent diabetes mellitus

We previously demonstrated that hyperinsulinemia can amplify the counterregulatory response to hypoglycemia in normal subjects. The aim of the present study was to determine if differing concentrations of insulin can modify the counterregulatory response to equivalent fixed hypoglycemia in insulin-dependent-diabetic subjects (IDDM). Experiments were carried out in seven lean, overnight-fasted, moderately controlled (hemoglobin A1c, 10.9%; normal range, 5-9) IDDM subjects with a disease duration of 13 +/- 3 yr. All were maintained normoglycemic overnight so that basal plasma glucose (5.6 +/- 0.2 and 5.4 +/- 0.2 mmol/L) and insulinemia (63 +/- 18 and 48 +/- 10 pmol/L) were similar at the start of each study. Insulin was infused for 120 min in two separate randomized protocols, so that steady state levels (mean +/- SE) of 742 +/- 212 pmol/L (low) and 3360 +/- 710 pmol/L (high) were obtained. Glucose was infused during both protocols to ensure that the rate of fall of plasma glucose (0.09 mmol/L.min) and the hypoglycemic plateau (2.8 +/- 0.1 mmol/L) were similar. In response to hypoglycemia, plasma levels of epinephrine, norepinephrine, cortisol, GH, and pancreatic polypeptide increased similarly during both insulin infusions. During the final 30 min, despite similar levels of counterregulatory hormones, hepatic glucose production was significantly reduced in the presence of high compared to low insulin levels (1.7 +/- 2.8 vs. 8.3 +/- 1.7 mumol/kg.min; P < 0.05). Similarly, plasma nonesterified fatty acids (472 +/- 94 vs. 787 +/- 105 mumol/L) and blood 3-hydroxybutyrate levels (30 +/- 12 vs. 106 +/- 29 mumol/L) were significantly reduced (P < 0.05) during high compared to low dose infusions. Cardiovascular parameters (heart rate and systolic, diastolic, and mean arterial pressures) responded similarly during both infusions. We conclude that 1) insulin per se does not amplify the counterregulatory response to equivalent hypoglycemia in individuals with moderately controlled, long duration IDDM; and 2) there may be a relative autonomic adrenomedullary deficit in some IDDM subjects that prevents the amplified epinephrine response to hyperinsulinemia during hypoglycemia.

Effects of insulin on the counterregulatory response to equivalent hypoglycemia in normal females

The aim of this study was to determine if insulin could augment the counterregulatory response to equivalent hypoglycemia in normal females similarly to males. Experiments were carried out in nine normal lean overnight-fasted female subjects. Insulin was infused in two separate randomized protocols so that steady-state levels of 794 +/- 62 (low) and 3,620 +/- 476 pM (high) were obtained. Despite an identical plasma glucose level (2.8 +/- 0.1 mM), epinephrine (5.7 +/- 0.9 vs. 3.9 +/- 0.6 nM), norepinephrine (2.7 +/- 0.4 vs. 1.8 +/- 0.3 nM), cortisol (918 +/- 55 vs. 826 nM), and growth hormone (35.8 +/- 3.7 vs. 28.4 +/- 2.7 micrograms/l) were increased (P < 0.05) during high compared with low insulin infusion, respectively. Glucagon and pancreatic polypeptide levels increased significantly but were not different during the two insulin infusions. Hepatic glucose production was increased during the high-compared with low-dose infusions (9.5 +/- 1.1 vs. 5.1 +/- 2.2 mumol.kg-1 x min-1; P < 0.05). Lipolysis, as indicated by the blood glycerol level, increased significantly during high- compared with low-dose insulin infusions (121 +/- 29 vs. 65 +/- 13 microM; P < 0.05). The hormonal and metabolic responses to hypoglycemia were significantly different in females compared with previous results in males.(ABSTRACT TRUNCATED AT 250 WORDS)

Labyrinthine Pattern Formation in Magnetic Fluids

A quasi two-dimensional drop of a magnetic fluid (ferrofluid) in a magnetic field is one example of the many systems, including amphiphilic monolayers, thin magnetic films, and type I superconductors, that form labyrinthine patterns. The formation of the ferrofluid labyrinth was examined both experimentally and theoretically. Labyrinth formation was found to be sensitively dependent on initial conditions, indicative of a space of configurations having a vast number of local energy minima. Certain geometric characteristics of the labyrinths suggest that these multiple minima have nearly equivalent energies. Kinetic effects on pattern selection were found in studies of fingering in the presence of timedependent magnetic fields. The dynamics of this pattern formation was studied within a simple model that yields shape evolutions in qualitative agreement with experiment.

Detection and significance of myocardial ischemia in stable patients after recovery from an acute coronary event. Multicenter Myocardial Ischemia Research Group

OBJECTIVE

To determine the clinical significance of silent and symptomatic myocardial ischemia detected by noninvasive testing in stable postcoronary patients.

DESIGN

Cohort study with a mean 23-month follow-up.

SETTING

Ambulatory outpatients after recent hospitalization for an acute coronary event.

PATIENTS

Nine hundred thirty-six patients (76% male; mean age, 58 years) who were clinically stable 1 to 6 months after hospitalization for acute myocardial infarction or unstable angina.

INTERVENTIONS

Noninvasive testing involved rest, ambulatory, and exercise electrocardiograms and stress thallium-201 scintigraphy.

MAIN OUTCOME MEASURES

Cox regression analysis was used to evaluate the risk (hazard ratio) of first recurrent primary events (cardiac death, nonfatal infarction, or unstable angina) or restricted events (cardiac death or nonfatal infarction) associated with ischemic noninvasive test results.

RESULTS

ST segment depression on the rest electrocardiogram was the only noninvasive test variable that identified a significantly increased risk (P = .05) for first recurrent primary events (hazard ratio; 95% confidence limits): rest electrocardiogram ST depression (1.5; 1.00, 2.25); ambulatory electrocardiogram ST depression (0.86; 0.49, 1.51); exercise electrocardiogram ST depression (1.13; 0.82, 1.56); and stress thallium-201 reversible defects (1.3; 0.96, 1.74). Test results were similar for first recurrent restricted events, and in patients with and without angina. Significantly increased risk (P < .05) was noted when exercise-induced ST depression occurred in patients who also had reduced exercise duration (hazard ratio, 3.4) or when reversible thallium-201 defects occurred in patients who also had increased lung uptake (hazard ratio, 2.8). Each high-risk subset made up less than 3% of the population and contained less than 6% of patients with first primary events.

CONCLUSION

Detection of silent or symptomatic myocardial ischemia by non-invasive testing in stable patients 1 to 6 months after an acute coronary event is not useful in identifying patients at increased risk for subsequent coronary events.

The effects of differing insulin levels on the hormonal and metabolic response to equivalent hypoglycemia in normal humans

The aim of this study was to determine if differing concentrations of insulin can modify the counterregulatory response to equivalent hypoglycemia in normal humans. Experiments were conducted in 9 normal, lean men, who had fasted overnight. Insulin was infused in two separate, randomized protocols so that steady-state levels of 486 +/- 33 (low) and 3056 +/- 236 pM (high) were obtained. Glucose was infused during both protocols to ensure that the rate of fall of plasma glucose (0.07 mM/min) and hypoglycemic plateau (2.8 +/- 0.1 mM) were similar. Despite similar plasma glucose levels, EPI (8.7 +/- 0.7 vs. 5.5 +/- 0.7 nM), NE (3.3 +/- 0.3 vs. 2.3 +/- 0.2 nM), and cortisol (811 +/- 36 vs. 611 +/- 72 nM) significantly increased during high compared with low insulin infusion, respectively (P < 0.05). Glucagon, growth hormone, and pancreatic polypeptide levels increased briskly and significantly but were not different during the two insulin infusions. HGP rose significantly from 12.1 +/- 0.3 to 18.1 +/- 1.1 mumol.kg-1 x min-1 in response to the high insulin level (P < 0.05) but remained unchanged (12.1 +/- 0.4 and 11.7 +/- 1.4 mumol.kg-1 x min-1) in the presence of th low insulin level. GRa increased significantly during high insulin levels (3.4 +/- 0.3 to 4.8 +/- 0.7 mumol.kg-1 x min-1, P < 0.05) but remained at a basal rate (3.0 +/- 0.3 to 2.7 +/- 0.6 mumol.kg-1 x min-1) in the presence of low insulin levels. sBP and heart rate increased more during high insulin infusion (18 +/- 5 vs. 6 +/- 5 mmHg and 18 +/- 4 vs. 7 +/- 2 beats/min, respectively, P < 0.05). In summary, the 6-fold higher insulin level resulted in significantly greater increases in catecholamine and cortisol secretion, HGP, lipolysis, heart rate, and sBP despite equivalent hypoglycemia. We conclude that at moderate hypoglycemia, high doses of insulin can augment certain aspects of the counterregulatory response in normal humans.

Effects of chronic elevation in plasma cortisol on hepatic carbohydrate metabolism

This study was undertaken to investigate the effects of chronic physiological elevations in plasma cortisol on glycogenolysis and gluconeogenesis in conscious, overnight-fasted dogs. Experiments consisted of an 80-min tracer and dye equilibration period and a 40-min sampling period. Infusions of D-[3-3H]glucose, L-[U-14C]alanine, and indocyanine green dye were used to assess glucose production (Ra) and gluconeogenesis using tracer and arteriovenous (a-v) difference techniques. In the cortisol group, (n = 10), a continuous infusion of hydrocortisone (3.5 micrograms.kg-1 x min-1) was begun 5 days before the experiment and continued throughout the sampling period. In the saline group (n = 10), there was no infusion of cortisol. The fivefold elevation in plasma cortisol increased plasma insulin from 12 +/- 2 to 19 +/- 2 microU/ml. Glucose Ra was elevated in the cortisol group (3.5 +/- 0.2 vs. 2.8 +/- 0.2 mg.kg-1 x min-1) but net hepatic glucose output was markedly diminished (1.2 +/- 0.4 vs. 2.7 +/- 0.3 mg.kg-1 x min-1). Gluconeogenic conversion of alanine to glucose was increased slightly by cortisol (0.60 +/- 0.13 to 0.99 +/- 0.12 mumol.kg-1 x min-1), but the gluconeogenic efficiency of the liver was unchanged. Cortisol increased hepatic glycogen content evident at the end of the study greater than twofold (76.4 +/- 7.9 vs. 30.0 +/- 4.7 g/liver). These results suggest that cortisol 1) promotes glucose cycling through glycogen, 2) greatly inhibits nonhepatic glucose utilization, 3) increases hepatic gluconeogenesis in vivo primarily through enhanced substrate delivery to the liver, and 4) raises plasma insulin levels, which restrains intrahepatic gluconeogenesis.

The effects of acute elevations in plasma cortisol levels on alanine metabolism in the conscious dog

The present study was undertaken to determine whether an acute physiological increase in plasma cortisol level had significant effects on alanine metabolism and gluconeogenesis within 3 hours in conscious, overnight-fasted dogs. Each experiment consisted of an 80-minute tracer and dye equilibration period, a 40-minute basal period, and a 3-hour experimental period. A primed, continuous infusion of [3-3H]glucose and continuous infusions of [U-14C]alanine and indocyanine green dye were initiated at the start of the equilibration period and continued throughout the experiment. Dogs were studied with (1) a hydrocortisone infusion ([CORT] 3.0 micrograms.kg-1.min-1, n = 5), (2) hydrocortisone infused as in CORT, but with pancreatic hormones clamped using somatostatin and basal intraportal replacement of insulin and glucagon (CLAMP+CORT, n = 5), or (3) saline infusion during a pancreatic clamp (CLAMP, n = 5). Glucose production and gluconeogenesis were determined using tracer and arteriovenous difference techniques. During CLAMP, all parameters were stable except for a modest 67% +/- 6% increase in gluconeogenic conversion of alanine to glucose and a 53% +/- 26% increase in gluconeogenic efficiency. When plasma cortisol levels were increased fourfold during CLAMP+CORT, there was no change in the concentration, production, or clearance of glucose. Gluconeogenic conversion of alanine to glucose increased 10% +/- 34% and gluconeogenic efficiency increased 65% +/- 43%, while net hepatic alanine uptake (NHAU) increased 60% +/- 19% and hepatic fractional extraction of alanine increased 38% +/- 12%. Cortisol did not cause an increase in the arterial glycerol level or net hepatic glycerol uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Patient maintenance of esthetic restorations

There are probably as many ways to maintain esthetic restorations as there are restorations. After esthetic treatment is completed, schedule a mandatory postoperative appointment to make certain that whatever technique the patient uses is effective. At the postoperative visit, it should be apparent that the patient's tissue is healthy. If the tissue has not healed, some change in home care or additional periodontal or restorative treatment may be necessary. There are virtually hundreds, perhaps even thousands of home plaque removal devices. The ones mentioned here have worked for us and are therefore discussed. It isn't the type of device that is critical, however, but patient compliance. The described regimens have worked effectively for us in overcoming this obstacle of compliance. Appropriate recall visits with the hygienist should be made at one- to six-month intervals. In the final analysis, your success with esthetic restorations may well depend on your patients' success with esthetic maintenance.

Cardiovascular effects of platelet-activating factor

Sudden release of platelet-activating factor (PAF) into the circulation can cause hypotension, tachycardia, and circulatory collapse. To further examine this response, we performed detailed studies of cardiovascular function after PAF administration to young domestic pigs and newborn piglets. Our results indicate that circulatory dysfunction after PAF reflects severe constriction of pulmonary resistance vessels and consequent acute right ventricular failure. Although PAF-induced coronary artery constriction and contractile depression may be complicating problems, left ventricular underperfusion and dysfunction after PAF are mainly the result of systemic arterial hypotension and diminished left ventricular filling. The adverse hemodynamic effects of PAF are accompanied by substantial release of thromboxane A2 (TxA2). These effects are mimicked by the TxA2 agonist U-46619 and partially blocked by specific and nonspecific inhibitors of TxA2 synthesis (OKY-046 and indomethacin). Even more potent blockade of PAF action is exerted by the TxA2 receptor blocker, SQ 29,548. Taken together, these findings indicate that severe pulmonary vascular constriction and hemodynamic collapse soon after intravenous PAF are at least partially mediated by PAF-induced TxA2 release. Tachyphylaxis to PAF influence has been observed in studies of leukocyte and platelet function. We hypothesized that tachyphylaxis to PAF might also occur in our studies of constrictor responses in pulmonary vessels. Recently, we have examined the capacity of PAF to produce sustained pulmonary vasoconstriction in open-chested, anesthetized newborn piglets. Infusions sufficient to produce 100% increase in mean pulmonary artery pressure after 3 min showed no loss of efficacy when sustained for 30 min.(ABSTRACT TRUNCATED AT 250 WORDS)