The human amylin analog, pramlintide, corrects postprandial hyperglucagonemia in patients with type 1 diabetes.

Mealtime amylin replacement with the human amylin analog pramlintide as an adjunct to insulin therapy improves postprandial glycemia and long-term glycemic control in type 1 diabetes. Preclinical animal studies indicate that these complementary effects may result from at least 2 independent mechanisms: a slowing of nutrient delivery to the small intestine and a suppression of nutrient-stimulated glucagon secretion. The former effect of pramlintide has previously been demonstrated in patients with type 1 diabetes. The present studies characterize the effect of pramlintide on postprandial glucagon secretion in this patient population. Plasma glucagon and glucose concentrations were measured before and after a standardized liquid meal in 2 separate randomized, double-blind, placebo-controlled studies of pramlintide administration to patients with type 1 diabetes. In a 2-day crossover study, 18 patients received a 5-hour intravenous infusion of pramlintide (25 microg/h or 50 microg/h) or placebo in addition to subcutaneous (SC) insulin injections. In a 14-day parallel-group study, 84 patients received SC injections of 30, 100, or 300 microg of pramlintide or placebo 3 times daily in addition to SC injections of insulin. In both studies plasma glucagon concentrations increased in response to the meal in the placebo-plus-insulin group but not in any of the pramlintide-treated groups (all pramlintide treatment arms v placebo, P <.05). We conclude that mealtime amylin replacement with pramlintide prevents the abnormal meal-related rise in glucagonemia in insulin-treated patients with type 1 diabetes, an effect that likely contributes to its ability to improve postprandial glucose homeostasis and long-term glycemic control.

Adsorption and desorption of chemotherapeutic drugs from a magnetically targeted carrier (MTC).

Magnetically targeted carriers (MTCs) are composite microparticles made from metallic iron and activated carbon. Particles, loaded with doxorubicin in the pharmacy (MTC-DOX), are infused intra-arterially through the artery feeding the tumor. With the aid of an externally positioned permanent dipole magnet, they can be localized and retained within a tumor mass. MTC-DOX is currently in use in a Phase I/II clinical study as a delivery vehicle for doxorubicin in primary hepatocellular carcinoma. The adsorption and desorption of doxorubicin, mitomycin C, camptothecin, methotrexate, verapamil and 9AC onto MTCs have been analyzed. Each of these chemotherapeutic agents has a different mechanism of action, suggesting that some benefit may be derived from combined delivery to a tumor using MTCs and magnetic targeting. Each drug displays different behavior with respect to adsorption and desorption. However, this behavior can be described for each drug with a non-linear thermodynamic model. The thermodynamic model predicts a controlled release rate by adjusting a number of parameters, including initial drug loading concentrations. This is confirmed with in vitro extraction experiments using human plasma as the extraction medium.

A Unified Scaling Law in Spiral Galaxies.

We investigate the origin of a unified scaling relation in spiral galaxies. Observed spiral galaxies are spread on a plane in the three-dimensional logarithmic space of luminosity L, radius R, and rotation velocity V. The plane is expressed as L~&parl0;VR&parr0;alpha in the I passband, where alpha is a constant. On the plane, observed galaxies are distributed in an elongated region which looks like the shape of a surfboard. The well-known scaling relations L-V (Tully-Fisher [TF] relation), V-R (also the TF relation), and R-L (Freeman's law) can be understood as oblique projections of the surfboard-like plane into two-dimensional spaces. This unified interpretation of the known scaling relations should be a clue to understand the physical origin of all the relations consistently. Furthermore, this interpretation can also explain why previous studies could not find any correlation between TF residuals and radius. In order to clarify the origin of this plane, we simulate formation and evolution of spiral galaxies with the N-body/smoothed particle hydrodynamics method, including cooling, star formation, and stellar feedback. Initial conditions are set to 14 isolated spheres with two free parameters, such as mass and angular momentum. The cold dark matter (h=0.5, Omega0=1) cosmology is considered as a test case. The simulations provide the following two conclusions: (1) The slope of the plane is well reproduced but the zero point is not. This zero-point discrepancy could be solved in a low-density (Omega0<1) and high-expansion (h>0.5) cosmology. (2) The surfboard-shaped plane can be explained by the control of galactic mass and angular momentum.

Stenosis of the internal auditory canal with VIIth and VIIIth cranial nerve dysfunctions.

We report the case of a 37-year-old woman with a history of long-standing right-sided sensorineural hearing loss who presented with an acute onset of vertigo and ipsilateral facial palsy. A computed tomographic scan study showed a stenosis of the right internal auditory canal (IAC). Neither generalized skeletal disease nor bony tumors, which may cause the IAC stenosis, were evident. The IAC stenosis found in this patient may be due to congenital malformation. Inflammation, compression or ischemia in the stenosed IAC may have resulted in the vertigo and facial palsy. This is the only case that we are aware of in which IAC stenosis is accompanied by vertigo and facial palsy.

Plasma amylin concentrations in fasted and fed rats quantified by a monoclonal immunoenzymometric assay.

Amylin is a 37-amino acid peptide co-secreted from the pancreatic beta-cell with insulin in response to nutrient stimuli. Plasma amylin concentrations in the rat are reported to vary widely. We have employed a recently-developed immunoenzymometric assay to quantify plasma amylin concentrations in fasted, fed and glucose-administered rats. Fasted amylin concentrations ranged between 1.02+/-0.09 and 1.63+/-0.15pM among three different common rat strains, and increased up to 7.70+/-0.80 pM after feeding. The differences among strains and between fasted and fed rats were all significant at P<0.01 or less. Intravenous glucose administration (5.2 mmol/kg) also significantly increased plasma amylin concentrations in fasted rats from 1.5+/-0.3pM to 3.4+/-0.5pM, and in fed rats from 4.6+/-1.1 pM to 9.1+/-1.7 pM. Plasma amylin/insulin molar ratios ranged between 2.3+/-0.2% and 3.6+/-0.5% (mean 3.0%), but did not differ among strains, or between the fasted vs fed state in any strain. In conclusion, a new sensitive immunoenzymometric assay revealed fasting plasma concentrations which are lower than previously reported, and which are significantly increased by stimulation with feeding or glucose administration.

Plasma amylin immunoreactivity and insulin resistance in insulin resistant relatives of patients with non-insulin-dependent diabetes mellitus.

To explore the potential relationship between concentrations of circulating amylin and the insulin resistance observed in first-degree relatives of patients with non-insulin-dependent-diabetes mellitus (NIDDM), we studied 40 relatives compared to 35 matched controls. Two newly developed immunoassays that measure either non-glycosylated or total amylin were applied. All subjects were examined by an oral glucose tolerance test (OGTT) and by a hyperinsulinemic euglycemic clamp (insulin infusion: 0.6 mU/kg/min). Glucose tolerance was normal in all, but insulin-stimulated glucose uptake (Rd) was diminished in the relatives (p < 0.001). Area under the curves (AUCs) during OGTT for plasma glucose (p < 0.01) and serum insulin (p=0.08), but not for plasma total and non-glycosylated amylin, were higher in relatives versus controls. In both groups, inverse correlations were found between Rd and AUC for plasma total and non-glycosylated amylin (p [all]<0.05). However, in multiple linear regression analyses, plasma total and non-glycosylated amylin failed to influence Rd independent of serum insulin and family history-of NIDDM. In conclusion, this study demonstrated inverse correlations between Rd and circulating concentrations of plasma total and non-glycosylated amylin in relatives and matched controls. These data, however, do not support the hypothesis that physiological amylin concentration are a major importance for the insulin resistance in relatives of NIDDM patients.

Pramlintide: a human amylin analogue reduced postprandial plasma glucose, insulin, and C-peptide concentrations in patients with type 2 diabetes.

In order to determine the influence of a 5 h infusion of pramlintide compared to placebo on postprandial glucose, lactate, insulin, and C-peptide concentrations in patients with Type 2 diabetes, a single-blind, randomized, cross-over study was conducted in 24 patients; 12 treated with exogenous insulin and 12 managed with diet and/or oral hypoglycaemic agents. One hour after initiation of infusion, patients consumed a Sustacal test meal. The protocol was repeated on the following day with each patient receiving the alternate study medication. Pramlintide infusion in the insulin-treated patients resulted in statistically significant reductions in mean glucose, insulin, C-peptide, and lactate concentrations during the 4-h period after the Sustacal test meal. Pramlintide infusion also resulted in significant reductions of mean insulin, C-peptide, and lactate concentrations, but not glucose concentrations, in the patients treated with diet and/or oral hypoglycaemic agents. Within this latter group, reduction in postprandial glucose concentrations in individual patients correlated with glycated haemoglobin values. These results suggest that administration of pramlintide may improve glycaemic control in patients with Type 2 diabetes treated with insulin or poorly controlled on diet and/or oral hypoglycaemic agents.

Development and characterization of monoclonal antibodies specific for amylin.

Highly selective monoclonal antibodies to the peptide hormone human amylin have been produced and characterized. These antibodies are produced by hybridomas resulting from the fusions of BALB/c-derived myelomas and splenocytes from either inbred or outbred mouse strains. Certain of these antibodies recognize epitopes at the amino-terminus or the amidated carboxy-terminus, as well as conformational epitopes within the central region of the 37 amino acid peptide. Several of these antibodies show less than 0.1% cross-reactivity with related peptide hormones such as calcitonin and calcitonin gene-related peptide (CGRP) and have apparent affinities in the low nanomolar range. Antibody pairs were selected for use in two-site assays for the direct measurement of endogenous amylin and the synthetic human amylin analogue, pramlintide (25, 28, 29 tripro-human amylin), which is presently under clinical investigation for improving glucose control in patients with both Type I and Type II diabetes treated with insulin.

Effect of race and hypertension on plasma amylin concentrations.

Amylin is a recently discovered peptide hormone composed of 37 amino acids that is cosecreted with insulin by pancreatic beta cells. Amylin has been reported to be present in increased amounts in insulin-resistant subjects who are hyper-insulinemic. Because blacks and whites differ in the prevalence of both hypertension and diabetes, we examined amylin levels in 77 individuals; 42 were black (11 hypertensive and 31 normotensive) and 35 were white (10 hypertensive and 25 normotensive) individuals who were either healthy control subjects or hypertensive subjects not receiving antihypertensive medication. Plasma amylin concentrations were measured in two separate monoclonal antibody-based immunofluorescent sandwich-type assays. The F002-2 capture antibody binds amylin plus at least two additional amylin-like peptides, and the F024-4 capture antibody detectably binds only the amylin peptide. There was a significant race-by-diagnosis interaction for levels of amylin immunoreactivity during a 2-hour glucose tolerance test (P<.005 for F002-2 antibody and P<.05 for F024-4 antibody). Highest levels were found in black hypertensive subjects. The results appear to fit with previously observed differences in metabolic status between blacks and whites and with the association between hypertension and alterations in metabolic status.

Development of sensitive immunoassays to detect amylin and amylin-like peptides in unextracted plasma.

Amylin is a 37-amino-acid polypeptide synthesized in and secreted from pancreatic beta cells along with insulin. Its biological actions include the slowing and reduction of postmeal increases in plasma glucose concentrations. Studies of the basic amylin biology in humans have been hampered by the lack of a rapid, sensitive assay capable of measuring physiological concentrations of amylin in small volumes of plasma. We report here two sandwich-type immunoassays that use pairs of monoclonal antibodies, the fluorescent substrate 4-methylumbelliferyl phosphate, and the enzyme alkaline phosphatase. The minimum detectable concentration of amylin in 50 microL of plasma was 0.5 to 2 pmol/L, and the dynamic range was 2 to 100 pmol/L. The assays had average intraassay CVs of <10%, average interassay CVs of <15%, and good linearity on dilution and recovery of added amylin. The two assays use the same detection antibody, which binds to the carboxyl terminus of the molecule, but different capture antibodies. One of the assays measures only human amylin; the other also detects amylin-like peptides. Examples of measurements in human plasma are provided in subjects with impaired glucose tolerance and in nondiabetic controls.

Pharmacokinetics and pharmacodynamics of AC137 (25,28,29 tripro-amylin, human) after intravenous bolus and infusion doses in patients with insulin-dependent diabetes.

A study was conducted to evaluate the effect of 30-mug, 100-mug, and 300-mug 2-minute bolus doses and 2-hour infusion doses of AC137 (25,28,29 tripro-amylin, human) on plasma AC137 concentrations and plasma glucose and lactate responses in patients with insulin-dependent diabetes mellitus (IDDM). The study design was an imbedded two-way cross-over wherein patients received placebo and active boluses in one period and placebo and active infusions in the other period. Two patients in each dose group received placebo throughout the two periods. Pharmacokinetics and pharmacodynamics (PK/PD) were determined during the 6-hour period after initiation of dosing. Data were fitted with a linked PK/PD model. Pharmacokinetics were linear over the dose range studied, and attenuation of glucose and lactate responses to a mixed meal was dose and concentration dependent. The results of the PK/PD model indicate that the attenuation of glucose and lactate responses was greater after AC137 infusion doses than after the same doses given as a bolus. Glucose and lactate responses to a mixed meal were essentially negated by the 300-mug infusion dose.

Molecular physiology of amylin.

Amylin is a 37-amino acid peptide first isolated, purified, and characterized from the amyloid deposits in the pancrease of type 2 diabetics. It is synthesized and secreted primarily from pancreatic beta cells along with insulin. The ability of amylin to potently reduce insulin-stimulated incorporation of glucose into glycogen in skeletal muscle requires both an intact 2Cys-7Cys disulfide bond and a COOH-terminal amide. Amylin has structural and functional relationships to two other messenger proteins, calcitonin and CGRP. Amylin has relatively potent calcitonin-like activity on bone metabolism and weaker CGRP-like activity on the vasculature. CGRP is a slightly weaker agonist than amylin for metabolic responses. Although rat calcitonins are weak, teleost fish calcitonins are very potent agonists for amylin's metabolic effects. This group of peptides appears to act on a family of related G protein-coupled receptors; several variant calcitonin receptors have recently been cloned and expressed. These receptors appear to be coupled to adenylyl cyclase in many instances; recent evidence supports the view that amylin's effects on skeletal muscle occur, at least in large part, through activation of the cAMP pathway.

Structure and biology of amylin.

Amylin is a recently discovered 37 amino acid peptide secreted into the bloodstream, along with insulin, from pancreatic beta-cells. It is about 50% identical to calcitonin gene-related peptides (CGRP alpha and CGRP beta) and structurally related to the calcitonins. Amylin can elicit the vasodilator effects of CGRP and the hypocalcaemic actions of calcitonin, while these peptides can mimic newly discovered actions of amylin on carbohydrate metabolism. The different relative potencies of these peptides suggest that they act with different selectivities at a family of receptors. Amylin is deficient in insulin-dependent diabetes mellitus, while plasma levels are elevated in insulin-resistant conditions such as obesity and impaired glucose tolerance. In this Viewpoint article, Tim Rink and colleagues propose that amylin is an endocrine partner to insulin and glucagon; deficiency or excess of amylin may therefore contribute to important metabolic diseases.

An evaluation of laryngeal muscle activation in patients with voice tremor.

Eight patients with voice tremor were studied to characterize laryngeal muscle involvement. Electromyographic (EMG) recordings were made from intrinsic laryngeal muscles, simultaneously with some extrinsic laryngeal muscles, respiratory movement, and voice recordings during respiration, whisper, and phonation. Spectral measures were used to determine the tremor frequency and the prominence of spectral peaks in the EMG, respiratory and acoustic signals, while correlation coefficients were computed between pairs of tremulous EMG signals to measure the synchrony of tremor between muscles. The intrinsic laryngeal muscles were tremulous during respiration and speech, with the thyroarytenoid most often involved. Tremor was also detected in some of the extrinsic muscle recordings and the percentage of muscles with tremor was higher during phonation than during whisper or respiration. Time delays were found between tremor oscillations in laryngeal muscles. Because the thyroarytenoid was affected in all the patients studied, botulinum toxin injections may be beneficial in treatment of this voice disorder.

Characteristics of late responses to superior laryngeal nerve stimulation in humans.

To characterize human thyroarytenoid and cricothyroid muscle responses to stimulation of the internal (sensory) and external (motor) branches of the superior laryngeal nerve (SLN), three awake subjects were studied at rest and during muscle activation with stimulation at different current levels. When only the external branch was stimulated, direct cricothyroid muscle responses were obtained without responses in either thyroarytenoid muscle. When only the internal branch was stimulated, no cricothyroid responses were obtained, but two late thyroarytenoid responses occurred (R1 and R2). The R1 response was usually ipsilateral and had a mean onset latency of 18 milliseconds, while the R2 response was bilateral and occurred between 66 and 70 milliseconds. Both responses tended to decrease in latency and increase in amplitude with increased stimulation level. The similarity of R1 to the adductor response and R2 to other late responses is discussed.

Hyperamylinemia, hyperinsulinemia, and insulin resistance in genetically obese LA/N-cp rats.

The experimental evidence supporting a direct role for hyperinsulinemia as a cause of insulin resistance remains equivocal. Amylin, an islet beta-cell peptide cosecreted with insulin in response to nutrient stimuli, causes insulin resistance when infused into intact animals or applied to isolated skeletal muscles. We compared measures of amylin and insulin gene expression between control and genetically obese, insulin-resistant Lister Albany/NIH-(LA/N-cp) rats. Pancreatic amylin messenger RNA levels were increased 7.8 +/- 0.7-fold (mean +/- SEM), and plasma amylin-like immunoreactive material was increased 10.9 +/- 1.1-fold (LA/N-lean, 14 +/- 4 pM; LA/N-cp, 153 +/- 16 pM; p less than 0.0001) in obese rats. Pancreatic insulin I mRNA levels were increased 7.4 +/- 0.5-fold, and plasma insulin levels 20.0 +/- 5.0-fold, in these rats (LA/N-lean, 308 +/- 84 pM; LA/N-cp 6,120 +/- 1,540 pM; p less than 0.0001). The EC50 for insulin-stimulated incorporation of glucose into glycogen was about fourfold higher in muscles isolated from obese rats. The present results, coupled with previous observations, support the hypothesis that hyperamylinemia, rather than hyperinsulinemia per se, could have directly caused the insulin resistance in the obese LA/N-cp rats. Hyperamylinemia needs to be considered in future experimental studies probing the relation between hyperinsulinemia and insulin resistance.

Serum levels and biochemical characteristics of cancer-associated antigen CA-549, a circulating breast cancer marker.

CA-549 is a circulating breast cancer-associated antigen that reacts with monoclonal antibody BC4E 549. Biochemical characterization of CA-549 revealed that it is an acidic (isoelectric point 5.2) glycoprotein that exhibits two bands by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions of apparent molecular weights of 400,000 and 512,000. Immunohistochemical staining of unfixed frozen tissue sections of human breast tumors and a variety of benign tissues with BC4E 549 revealed no preferential staining of tumor over benign breast tissue and cross-reactivity with a wide range of other benign tissues including kidney, liver, lung, colon, pancreas, ovary, and spleen. Serum levels of CA-549 were initially tested by an enzyme-linked immunosorbent assay inhibition using BC4E 549. This assay showed that CA-549 concentrations were elevated in 19 of 27 sera from patients with advanced breast cancer compared to 0 of 22 and 0 of 129 sera from benign breast disease patients and healthy females, respectively. These preliminary data suggested that CA-549 was a useful breast tumor marker; thus BC4E 549 was adapted to a sandwich immunoradiometric assay format suitable for routine use in the clinical laboratory and its performance was evaluated on a panel of 668 serum samples. The test detected significant concentrations of CA-549 in the sera of 40 of 80 patients with advanced breast cancer, 1 of 30 with early breast cancer, 4 of 19 with advanced lung cancer, 2 of 40 with advanced colon cancer, and 5 of 29 with advanced prostate cancer. The test showed a high degree of specificity, producing false-positives in only 3 of 79 benign breast patients, 2 of 25 benign liver patients, 2 of 70 benign colon patients, 2 of 19 benign lung patients, 0 of 20 benign prostate patients, and 3 of 257 healthy individuals. These data represent an overall 50% sensitivity and 98% specificity as a test for advanced breast cancer. These data indicate that this immunoradiometric assay is a useful test for the detection of circulating CA-549 in advanced breast cancer patients and suggest that it may prove useful as a monitor in the management of that disease.