Thyroid status influences rat serum but not brain TRH pyroglutamyl aminopeptidase activities

Serum and brain cytosol contains pyroglutamyl aminopeptidase activity that converts TRH to His-ProNH2 (TRH PAPase). Whereas serum TRH PAPase has specificity for TRH, this is not the case for brain cytosol PAPase. Recent reports indicate that a brain membrane fraction contains TRH PAPase that is specific for TRH and has a remarkable similarity to serum TRH PAPase. In the present studies, a method for measuring serum TRH PAPase activity and the activities of the membrane and cytosol brain TRH PAPase enzymes are described. The effect of thyroid status on these different TRH PAPase activities was determined. In hypothyroid rats serum TRH PAPase activity was decreased, whereas in rats treated with supraphysiological doses of T4 it was increased. In contrast, the cytosolic and the membrane TRH PAPase enzymes in brain were not affected by thyroid status. It is concluded that the membrane-associated brain TRH PAPase differs from the serum TRH PAPase in terms of its response to thyroid hormone. In addition, the previously reported effects of thyroid status on rat serum TRH degrading activity are explained by the finding that thyroid hormone increases serum TRH PAPase activity.

A Drosophila mutation that eliminates a calcium-dependent potassium current

A mutation of Drosophila, slowpoke (slo), specifically abolishes a Ca2+-dependent K+ current, IC, from dorsal longitudinal flight muscles of adult flies. Other K+ currents remain normal, providing evidence that IC is mediated by a molecularly distinguishable set of channels. The pharmacological properties of IC are similar to those of Ca2+-dependent currents in some vertebrate cells. The muscle action potential was significantly lengthened in slo flies, indicating that IC plays the major role in its repolarization.

Differentiation and central projections of peripheral sensory cells with action-potential block in Drosophila mosaics

The ultrastructural differentiation and central projection of identified bristle mechanosensory neurons were examined in Drosophila mutants lacking action potentials. Two mutations, parats1 and napts, are known to block axonal conduction in centrally located neurons at high temperatures. Their effects on epithelial sensory cells, which are derived from imaginal disks during pupation, have not been determined. Furthermore, the parats1 napts double-mutant flies are lethal at all temperatures; thus the synergistic effect of these mutations on neurons has not yet been studied. It is possible to examine the above questions in genetic mosaics. By monitoring a reflex response involving identified bristle sensory cells, we found that the 2 mutations exert similar effects on these epithelial sensory cells as seen in central neurons. This also indicates that the action potential mechanisms in both epithelial sensory cells and central neurons are under similar genetic control. The parats1 napts double-mutant sensory cells in mosaics are nonfunctional at all temperatures, providing an opportunity to examine, at the single cell level, the development of neurons with activity block. Ultrastructural specializations typical of epithelial sensory cells were found in the double-mutant cells. Cobalt backfilling experiments showed that central projections of these nonfunctional sensory cells were not altered, as compared with the active contralateral sensory cells. Therefore, blockage of the action potential mechanism in individual sensory cells has no effect on their pathfinding and arborization.

Clinical significance of bifid T waves

An attempt was made to analyze bifid T waves which appeared in different clinical conditions. Bifid T waves occurred in 16% of 600 normal children, 92% of 37 cases of childhood ventricular septal defect (VSD), 6 of 10 cases of tetralogy of Fallot (children) and 33% of 193 patients with cerebrovascular accidents (including 3 children). Sixteen cases of bifid T waves which appeared after amiodarone treatment were also analyzed. It was thought that in normal children, bifid T waves might be due to right ventricular preponderance. In VSD, the bifid T waves assumed a peculiar "dome and dart" appearance. In cerebrovascular accidents, autonomic imbalance might be at fault. In cases of treatment with adriamycin, myocardial toxicity is the most probable cause. The conclusion was made that bifid T waves can appear in different clinical settings, which must be considered individually.

Synthesis of 6-anilino-2-thiouracils and their inhibition of human placenta iodothyronine deiodinase

Several 6-anilino-2-thiouracils were synthesized and tested for their ability to inhibit the inner-ring iodothyronine deiodinase from human placenta. The p-ethyl and p-n-butyl analogues were strongly inhibitory to the enzyme and were much more effective than the standard deiodinase inhibitor, 6-propyl-2-thiouracil. The degree of inhibition caused by 6-(p-n-butylanilino)-2-thiouracil was, moreover, unaffected by high concentrations of reducing agent in the enzyme assay. Attempts to prepare 3-alkyl derivatives via S-debenzylation of 2-benzylthio intermediates led to rearrangement to, for example, 3-methyl-5-benzyl-6-amino-2-thiouracil. This compound also strongly inhibited the deiodinase reaction. Preliminary results suggest that these compounds are useful to study in vitro and in vivo metabolism of thyroid hormones and may be clinically useful to enhance the availability of active thyroid hormones to certain organs.

Inner-ring deiodination of 3,5,3'-triiodothyronine in the in situ perfused guinea pig placenta

Broken cell preparations of rat and human placentas contain an inner (tyrosyl)-ring iodothyronine deiodinase enzyme with greatest activity when the substrate is 3,5,3'-triiodothyronine (T3). This report describes the deiodination of T3 in the intact placenta and the effect of sodium iopanoate (IA) and propylthiouracil (PTU) on T3 deiodination. Under nembutal anesthesia, the placenta of 60-65-d-old pregnant guinea pigs was surgically exposed, a single umbilical artery and the umbilical vein were cannulated, and the fetus was removed. In a temperature-controlled chamber (37 degrees C), the fetal side of the placenta was perfused through the umbilical artery at a rate of 1 ml/min with 3% bovine serum albumin Krebs-Henseleit buffer containing 0.14 nM outer ring labeled [125I]T3. Placenta effluent fractions were collected at timed intervals from the umbilical vein cannula throughout a 120-min perfusion period. The contents of the perfusion buffer and the various effluent fractions were analyzed for their iodothyronine content by high pressure liquid chromatography. In five experiments, the percent composition of 125I-labeled iodothyronines in the perfusion buffer and placenta effluent was 95.3 +/- 1.0 (mean +/- SE) and 70.2 +/- 2.1 for T3 (P less than 0.01), 2.5 +/- 0.7 and 20.1 +/- 1.8 for 3,3'-T2 (P less than 0.01), and 0 and 8.2 +/- 0.9 for 3'-T1. There was no difference between the percent [125I]iodide in the perfusion buffer and in the placenta effluents. When placentas were perfused with IA and [125I]T3, after perfusion with [125I]T3 alone, there was a significant increase (P less than 0.01) in the percent [125I]T3 in the placenta effluents, and a significant decrease in [125I]3,3'-T2 (P less than 0.01) and [125I]3'-T1 (P less than 0.01). In contrast, PTU did not affect the composition of labeled iodothyronines in the placenta effluents, despite the fact that the addition of PTU significantly (P less than 0.001) inhibits the inner-ring deiodination of [125I]T3 in human or guinea pig placenta microsomes in the presence of low (0.25 mM) concentrations of dithiothreitol. The present studies demonstrate that T3 is actively deiodinated in the inner ring to 3,3'-T2 by the intact guinea pig placenta. A portion of 3,3'-T2 is further deiodinated in the inner ring to generate 3'-T1. No outer ring deiodination of T3 was seen under the conditions employed. IA, but not PTU, inhibits T3 deiodination in the placenta perfused in situ. We conclude that the placenta is probably a site for fetal T3 metabolism.

Voltage clamp analysis of membrane currents in larval muscle fibers of Drosophila: alteration of potassium currents in Shaker mutants

The body wall muscles in Drosophila larvae are suitable for voltage clamp analysis of changes in membrane excitability caused by mutations. Both inward and outward ionic currents are present in these muscle fibers. The inward current is mediated by voltage-dependent Ca2+ channels. In Ca2+-free saline, the inward current is eliminated. The remaining outward K+ currents consist of two distinct components, an early transient IA and a delayed steady IK, which are separable by differences in the rate and voltage dependence of activation and inactivation. The steady-state and kinetic properties of the activation and inactivation processes of these two currents are analyzed. The results provide a basis for quantitative analysis of altered membrane currents in behavioral mutants of Drosophila. Previous studies indicate that mutations in the Shaker (Sh) locus alter excitability in both nerve and muscle in Drosophila. Our results support the idea that the channels mediating IA are molecularly distinct from those mediating IK. All Sh mutations studied specifically affect IA without changing the properties of the calcium current and IK. In certain alleles (ShKS133, Sh102, and ShM) IA is eliminated, permitting detailed studies of IK in isolation of IA. Studies of the alleles that do not eliminate IA provide additional information of the channels. In one such allele, Sh5, voltage dependence of IA activation is shifted to more positive potentials. This is accompanied by a less pronounced shift in the voltage dependence of inactivation. These results suggest that Sh5 mutation affects the voltage-sensitive mechanism of both activation and inactivation processes and that these two processes are not controlled by independent parts of the channel. Furthermore, the differential effects of these alleles on different excitable membranes imply that other genes take part in the control of IA. The effects of Sh5 on muscle depend on developmental stage. In larval muscle, Sh5 reduces the amplitude of IA because of the shift in the current-voltage (I-V) relation. In contrast, in adult Sh5 muscles, IA is reported to be normal in amplitude but shows abnormally rapid inactivation (Salkoff, L., and R. Wyman (1981) Nature 293: 228-230). A different allele, ShrK0120, causes a clear defect in nerve excitability, but analysis of IA in ShrK0120 larval muscle reveals I-V relations, inactivation, and recovery from inactivation similar to those seen in normal fibers. We suggest a possible mechanism of combinations of multiple interacting genes participating in the control of potassium channels to account for the presence of a variety of potassium channels in different excitable membranes.

The pharmacokinetics of thyrotropin-releasing hormone (TRH) and deamido-TRH in the rat

The pharmacokinetics of TRH and its metabolite deamido-TRH (TRH-OH) were evaluated and compared. After a 60- to 90-min infusion of the appropriate peptide into rats, the MCR, half-life of disappearance (t 1/2), and volume of distribution were calculated. The MCR of TRH averaged 4 ml/min, whereas that of TRH-OH was 6.5 ml/min. The serum concentrations of both TRH and TRH-OH decreased in a biexponential manner after stopping the corresponding peptide infusions. The t 1/2 values were 2.4 and 3.9 min for the initial phase of disappearance and 14.1 and 20.6 min for the later phase of disappearance for TRH and TRH-OH, respectively. The volume of distribution of TRH-OH was twice that of TRH. The fractional conversion rate of TRH to TRH-OH, based on serum TRH-OH concentrations measured during TRH infusions, was 0.7-1.4%. Less than 1 ng TRH-OH was excreted in the urine during the last 30 min of TRH infusion. The rapid clearance of TRH-OH and low fractional conversion of TRH to TRH-OH, as measured in serum, suggest that little TRH secretion will be reflected in serum TRH-OH concentrations.

Altered sensitivity to sodium channel-specific neurotoxins in cultured neurons from temperature-sensitive paralytic mutants of Drosophila

In vitro culture of central nervous system neurons from Drosophila larvae enables direct examination of effects of neurological mutations at a single-cell level not readily amenable to in vivo experimentation. Using this system, we examined the cytotoxic effect of veratridine, which selectively causes persistent activation of sodium channels, on the mutants parats1 and napts known to have a temperature-dependent block in propagation of nerve action potentials. Even at a permissive temperature (22 degrees C) for the mutant flies, the veratridine-induced neuronal lethality was significantly lower in both parats1 and napts cultures than in normal cultures. At a temperature (35 degrees C) causing paralysis of mutant flies, napts neurons showed the same high degree of resistance to veratridine; while parats1 neurons showed an increased resistance to a level similar to that of napts neurons. A similar reduction in the veratridine-induced neuronal death was also observed in normal cultures that were pretreated with the sodium channel blocker tetrodotoxin. These results support the idea that both parats and napts affect sodium channel functions at the level of isolated single neurons. It was also found that parats1 and napts mutations, like the sodium channel blocker tetrodotoxin, do not affect the morphological differentiation and survival of central nervous system neurons in culture. These findings indicate that functional sodium channels are not required for neurite outgrowth and survival of neurons at this developmental stage.

Neurogenetic analysis of potassium currents in Drosophila: synergistic effects on neuromuscular transmission in double mutants

Recombinational dissection of the ShrK0120 strain of Drosophila melanogaster demonstrated that its extremely prolonged neuromuscular transmission, a defect qualitatively different from other Sh alleles, results from a synergistic interaction with a second site mutation. This new mutation caused spontaneous repetitive firing in motor axons and increased transmitter release. Complementation tests showed that it is allelic to eag. Combining either eag allele with various Sh alleles reproduced the same extreme defect observed in the original ShrK0120 strain. Thus, from their effects on neuromuscular transmission no qualitative difference among Sh alleles is apparent while Sh, eag, and eag Sh double mutant individuals can be uniquely distinguished. Pharmacological experiments indicated that Sh affects a membrane component sensitive to the potassium channel blockers 4-AP and TEA while eag affects a component sensitive to TEA but not 4-AP. We suggest that eag and Sh preferentially disrupt different potassium currents explaining their synergistic interaction.

Dissociated neurons from normal and mutant Drosophila larval central nervous system in cell culture

A primary dissociated cell culture of Drosophila larval central nervous system is reported. Divisions of neuroblasts and vigorous outgrowth of neurites could be observed in culture. Within 24 hr cultured cells exhibited characteristic neuronal morphology and unimpaired ability to synthesize and accumulate acetylcholine. This cell culture system renders easy access to experimental analysis of normal neuronal properties and the altered mechanisms in neurological mutants. Single-channel currents induced by acetylcholine and regenerative action potentials were studied in the somata of the dissociated neurons. The appearance of Na channels in these cultured neurons was demonstrated by the cell lethality induced by veratridine and inhibition of the effect by tetrodotoxin. Dissociated neurons from a temperature-sensitive paralytic mutant napts, in which nerve conduction fails at high temperature, were studied in culture. Neuronal growth was not affected by this mutation, nor by tetrodotoxin. However, napts neurons showed greatly reduced sensitivity to veratridine even at 21 degrees C, a temperature at which napts individuals behave normally. This finding indicates expression of the napts phenotype at a level of isolated single cells and provides independent evidence that napts affects Na channel function.

Potassium currents in Drosophila: different components affected by mutations of two genes

Electrophysiological analysis of the Drosophila behavioral mutants Eag and Sh and the double mutant Eag Sh indicates that the products of both genes take part in the control of potassium currents in the membranes of both nerve and muscle. In voltage-clamped larval muscle fibers, Sh affects the transient A current, whereas Eag reduces the delayed rectification and, to a lesser extent, the A current.

Acetylcholine synthesis and accumulation in the CNS of Drosophila larvae: analysis of shibirets, a mutant with a temperature-sensitive block in synaptic transmission

A radiochemical method is applied to the study of neurotransmitter metabolism in Drosophila. The larval CNS is a favorable system for analyzing acetylcholine (ACh) metabolism, since the pool of [3H]ACh rapidly reaches a steady state with a high ratio of intracellular [3H]ACh to [3H]choline. A temperature-sensitive paralytic mutant, shibirets, shows reduced [3H]ACh accumulation at the restrictive temperature. This reduction is not the result of decreased synthesis of [3H]ACh, but rather an abnormally rapid rate of release, which is not prevented by blocking tetrodotoxin-sensitive nerve activity.

Thyrotropin-releasing hormone metabolism in visceral organ homogenates of the rat

TRH, which is found in a number of sites outside the central nervous system, is degraded by serum and homogenates of brain, liver, and kidney. The presence of TRH deamidase activity in the brain is well documented. In view of the widespread distribution of TRH, the present study was undertaken to evaluate whether TRH deamidase activity is present in visceral organs and to determine the extent to which TRH degradation, as observed under broken cell conditions, can be accounted for by deamidation. Organs from Sprague-Dawley rats were homogenized in 150 mM sodium maleate, pH 7, and aliquots of the 700 X g supernatant were incubated separately with equimolar amounts of synthetic TRH or the deamidated form of TRH, pGlu-His-Pro. The amount of peptide remaining and the conversion of TRH to deamindated TRH in tubes incubated with TRH were measured by specific RIAs at multiple time points. TRH deamidase activity was found in rat liver, kidney, heart, lung, pancreas, ileum, and skeletal muscle. It was time and temperature dependent and was not observed in boiled tissues. Under relative high substrate conditions, approximately 56%, 50%, and 24% of TRH degradation was via the TRH deamidase pathway in liver, kidney, and lung, respectively. In other tissues, the presence of nondeamidase pathways, in addition to the deamidase pathway, could not be ruled out. TRH deamidation accounted for little or no TRH degradation in serum.

Indirect Suppression Involving Behavioral Mutants with Altered Nerve Excitability in DROSOPHILA MELANOGASTER

Two classes of X-linked behavioral mutants of Drosophila melanogaster, leg-shaking mutants and bang-sensitive mutants, are suppressed by nap(ts) (no action potential, temperature-sensitive), an autosomal temperature-sensitive paralytic mutation. So far, nap(ts) is found to suppress thirteen mutations at seven loci, two of which produce leg shaking and five bang-sensitivity. Suppression is recessive, occurs at temperatures permissive for nap(ts), and is indirect and function-specific rather than allele-specific. At restrictive temperatures, nap(ts) is known to completely block all nerve activity. Several of the mutants suppressed by nap(ts) are shown by neurophysiological experiments to have increased nerve excitability. The physiological defect of these mutants as well as their behavioral defect is suppressed by nap(ts). Thus, suppression occurs within individual neurons at the level of excitable membranes and apparently depends on the reduction in membrane excitability caused by nap(ts) even under permissive conditions. We suggest that all mutants suppressed by nap(ts) may have related defects leading to enhanced nerve excitability. Genetic interactions of this type help reveal functional relationships between different behavioral mutants and suggest ways of isolating new mutants with altered excitable membranes.

Myocardial composition and function in diabetes. The effects of chronic insulin use

This study was undertaken in an animal model of mild diabetes to determine if provision of chronic insulin replacement during postprandial hyperglycemia may modify the abnormalities of myocardium. Group 1 served as controls with normal glucose tolerance by intravenous testing. Two additional groups were made diabetic with low doses of alloxan. Diabetic animals of Group 2 were untreated (n = 6). Group 3 animals (n = 6) received regular insulin daily to reduce postprandial hyperglycemia. After one year with maintained body weight, the animals were studied in the intact anesthetized state using the indicator dilution technique for left ventricular volume determinations. Basal left ventricular function and contractility were similar to normals in both diabetic groups. During intraventricular infusion of saline, end-diastolic pressure rose to higher levels in untreated diabetes (14.8 +/- 2 mm Hg) than normals (8.8 +/- 0.84), despite similar basal levels. Insulin treatment was associated with higher filling pressures than in group 1 as well as reduced end-diastolic volume response. Collagen concentrations were enhanced an average of 50% in layers from the inner to outer myocardium in both untreated and treated diabetics, associated with sodium and water accumulation. Since hypertrophy was not present, the diminished compliance appeared related to increased collagen levels. On electron microscopy, the subcellular organelles of the cardiac cell appeared normal in both diabetic groups. Thus, collagen accumulation and abnormal myocardial function in this model of diabetes is not affected by control of postprandial hyperglycemia, but a potential role for sustained hormone replacement is not excluded.

A Drosophila mutant with a temperature-sensitive block in nerve conduction

A mutant, napts (no action potential, temperature-sensitive), is described in which axonal conduction fails at high temperature. Synaptic transmission at the larval neuromuscular junction is unimpaired. Larvae and adults are rapidly paralyzed at restrictive temperatures; they recover rapidly when the temperature is decreased. The mutant gene is recessive and is located on the second chromosome at map position 56.

Light-induced voltage noise in the photoreceptor of Drosophila melanogaster

The Drosophila photoreceptor potential is thought to be composed of discrete unit potentials called bumps. The steady-state receptor potential and the accompanying voltage fluctuations were recorded intracellularly under steady illumination. The occurrence rate, effective amplitude, and duration of the bumps were deduced by assuming a shot noise model. Over a wide range of light intensity, the duration of bumps remained essentially constant (25-30 ms). Below the saturation intensity for the receptor potential, the bump rate was roughly proportional to the intensity, and the adjustment of bumps to smaller size at higher intensity was mainly responsible for the nonlinear behavior of the receptor potential. The reduction in size of bumps at increasing light intensity was found to be due mainly to the diminishing magnitude of the bump current, and not to some other secondary effects. The bump rate saturated at about 3 x 105-106 events/s.

Frequency characteristics in the visual system of Drosophila: genetic dissection of electroretinogram components

Various drosophila mutants were used to dissect the electroretinogram (ERG) frequency response into components of different origins. The ommochrome granules in the receptor cell body are known to migrate in response to light, limiting the amount of light entering the rhabdomere. Comparison between the ERG frequency responses of the wild type and the mutant lacking the ommochrome granules indicates that the pigment migration reduces the amplitude gain at frequencies below 0.5 Hz. The ERG of drosophila compound eyes consists of contributions from receptor cells and the second-order cells in the lamina. Mutants with defective laminae showed a high-frequency cutoff with a corner frequency of about 20 Hz, while in wild type the response peaked in that frequency region. These results suggest that the lamina contributes mainly to the high-frequency components of the ERG transfer function. The shot noise model (Dodge et al., 1968) has been tested in drosophila by comparing the frequency response of the superimposed on the intracellular receptor potential. The results are consistent with the hypothesis that the receptor potential consists of a summation of small discrete potentials (bumps). In a mutant in which the bumps exhibit latency dispersion in response to a dim flash, the receptor showed a poor high-frequency response, the corner frequency being lowered to about 1-2 Hz. The slope of the cutoff was approximately 20 dB/dec indicating that the latency dispersion in this mutant is the major limiting factor in temporal resolution. Light-evoked high frequency oscillations have been observed in the ERG of another mutant. The oscillation was found sharply turned to light flickering at about 55 Hz.

The effects of tolbutamide on the myocardium in experimental diabetes

The effects of chronic tolbutamide treatment were examined in a diabetic animal model in which abnormal myocardial function and composition have previously been demonstrated. Eight diabetic dogs were given tolbutamide 250 mg/day orally and compared with seven untreated diabetics, five healthy dogs receiving tolbutamide, and eight normal controls. After one year, resting hemodynamic studies in the intact anesthetized state showed that treated diabetic dogs had a significantly higher left ventricular end-diastolic pressure of 12.1+/-1.3 mm Hg associated with normal end-diastolic volume, compared to 6.1+/-0.8 mm Hg in untreated diabetics (P less than 0.01) and 6.3+/-0.5 in normals. Stroke work and ejection fraction were similar to normals. Acute volume expansion revealed a larger rise of left ventricular end-diastolic pressure in treated and untreated diabetics than normals, without a significant stroke volume response in treated diabetics. Enhanced stiffness of myocardium appeared to be related to interstitial accumulation of periodic acid-Schiff staining material, further intensified in treated diabetics by triglyceride accumulation observed on electron microscopy and by chemical analysis. Thus treatment of diabetes with tolbutamide, despite improved glucose tolerance, effected further reduction of left ventricular function and altered morphology of myocardium.

Photoreceptor mutant of Drosophia: is protein involved in intermediate steps of phototransduction?

In norpA mutants of Drosophila melanogaster the phototransduction process is either partially or completely blocked. By using a temperature-sensitive allele, we have found that that norpA mutation has little or no effect on either the rhodopsin-metarhodopsin transition or the machinery of quantum bump production. Thus, the norpA lesion appears to be localized in the intermediate process of phototransduction. Because a temperature-sensitive allele of norpA has been isolated, the norpA gene probably encodes a protein involved in the process.

Quantal basis of photoreceptor spectral sensitivity of Drosophila melanogaster

Small potential fluctuations ("bumps"), boyh spontaneous and light induced, can be recorded intracellularly from the photoreceptors of Drosophila melanogaster. Statistical analyses of these bumps in the spectral range, 400-600 nm, lead to the following interpretations; (a) For weak stimuli at least, these bumps are the quantal units of the receptor potential. (b) Quanta of various wavelengths, when effectively absorbed, will elicit bumps of the same average size. (c) The spectral sensitivity of the receptor potential appears to have its origin in the relative efficiency of quantum bump production at different wavelengths, and not in the intrinsic difference in the properties of bumps produced by quanta of differenct wavelengths.

Acute myocardial infarction in toxic cardiomyopathy without coronary obstruction

Confluent left ventricular scar without significant coronary obstruction has been found in alcoholic subjects at autopsy. To evaluate the pathogenesis, 12 patients with chronic alcoholism and severe precordial pain persisting 4-24 hours were observed clinically. Cardiac isoenzymes of lactic dehydrogenase rose in serum. ST segment was elevated in anterior or posterior ECG leads, and abnormal Q waves appeared. Hypertnesion and hypercholesterolemia were present in two (group B) but not in the ten (group A). The latter exhibited no significant obstructive disease, based on coronary angiography in seven survivors and postmortem examination of the remaining three. Clinical evidence, as well as the quantitative assessment of platelets, made arterial thromboembolism an unlikely cause for the symptoms. Neither hemotologic or systemic disease affecting myocardium was present. The morphology of the left ventricle in three autopsies was compared with that of patients with alcoholism who had no cardiac disease, cardiomyopathy, or an asymptomatic scar. All had accumulation of Alcian positive glycoprotein in the interstitium. The patients with cardiac disease also had interstitial fibrosis which was characterized, particularly in the acute infarction group, by concentric periarterial fibrosis. Restriction of coronary vasodilation by this process during periods of high blood flow requirements was postulated as a basis for infarction.