A randomised, controlled, crossover study to investigate the safety and response of 1R,2S-methoxamine hydrochloride (NRL001) on anal function in healthy volunteers.

AIMS: This study aimed to assess the dose and volume effects of suppository preparations and safety of NRL001 (one of four possible stereoisomers of methoxamine hydrochloride) on anal sphincter tone using rectal suppositories in healthy adult volunteers. METHODS: This was a Phase I, single-centre, randomised, double-blind, three-way crossover study during which subjects received three single doses of 1 g rectal suppositories (containing 5 or 10 mg NRL001 or matching placebo) or 2 g rectal suppositories (containing 10 or 15 mg NRL001 or matching placebo) on three separate dosing days. The outcome measures were mean anal resting pressure (MARP) variables (monitored continuously for 20-30 min before and up to 6 h after dosing), pharmacokinetics (PK) and safety assessments. RESULTS: Twenty-six subjects were dosed with study medication. Two subjects were withdrawn prematurely and were not included in the main analysis. There was a dose-dependent increase in anal sphincter tone (MARP) when comparing the 5 and 10 mg doses of NRL001; however, the 15 mg dose did not have a significantly greater effect than the 10 mg dose. Suppository size (1 or 2 g) did not appear to have an effect on sphincter tone. There was no evidence against dose proportionality for the PK variables, but the mean maximum plasma concentration (Cmax ) for the 1 g suppository group was higher than for the 2 g group. Twenty-one adverse events were reported in 8 (30.8%) subjects. A dose dependent decrease in heart rate was noted; however, there were no adverse events reported that were related to this reduction in heart rate. CONCLUSIONS: The increase in anal sphincter tone supports the potential therapeutic use of NRL001 in treating faecal incontinence, with further studies in patients required. NRL001 was well tolerated in single doses of up to 15 mg.

The structure of lombricine kinase: implications for phosphagen kinase conformational changes.

Lombricine kinase is a member of the phosphagen kinase family and a homolog of creatine and arginine kinases, enzymes responsible for buffering cellular ATP levels. Structures of lombricine kinase from the marine worm Urechis caupo were determined by x-ray crystallography. One form was crystallized as a nucleotide complex, and the other was substrate-free. The two structures are similar to each other and more similar to the substrate-free forms of homologs than to the substrate-bound forms of the other phosphagen kinases. Active site specificity loop 309-317, which is disordered in substrate-free structures of homologs and is known from the NMR of arginine kinase to be inherently dynamic, is resolved in both lombricine kinase structures, providing an improved basis for understanding the loop dynamics. Phosphagen kinases undergo a segmented closing on substrate binding, but the lombricine kinase ADP complex is in the open form more typical of substrate-free homologs. Through a comparison with prior complexes of intermediate structure, a correlation was revealed between the overall enzyme conformation and the substrate interactions of His(178). Comparative modeling provides a rationale for the more relaxed specificity of these kinases, of which the natural substrates are among the largest of the phosphagen substrates.

The Canadian Glomerulonephritis Registry (CGNR) and Translational Research Initiative: Rationale and Clinical Research Protocol.

Background: Glomerulonephritis (GN) is a leading cause of kidney failure and accounts for 20% of incident cases of end-stage kidney disease (ESKD) in Canada annually. Reversal of kidney injury and prevention of progression to kidney failure is possible; however, limited knowledge of underlying disease mechanisms and lack of noninvasive biomarkers and therapeutic targets are major barriers to successful therapeutic intervention. Multicenter approaches that link longitudinal clinical and outcomes data with serial biologic specimen collection would help bridge this gap. Objective: To establish a national, patient-centered, multidimensional web-based clinical database and federated virtual biobank to conduct human-based molecular and clinical research in GN in Canada. Design: Multicenter, prospective observational registry, starting in 2019. Setting: Nine participating Canadian tertiary care centers. Patients: Adult patients with a histopathologic pattern of injury consistent with IgA nephropathy, focal and segmental glomerulosclerosis, minimal change disease, membranous nephropathy, C3 glomerulopathy, and membranoproliferative GN recruited within 24 months of biopsy. Measurements: Initial visits include detailed clinical, histopathological, and laboratory data collection, blood, urine, and tonsil swab biospecimen collection, and a self-administered quality of life questionnaire. Follow-up clinical and laboratory data collection, biospecimen collection, and questionnaires are obtained every 6 months thereafter. Methods: Patients receive care as defined by their physician, with study visits scheduled every 6 months. Patients are followed until death, dialysis, transplantation, or withdrawal from the study. Key outcomes include a composite of ESKD or a 40% decline in estimated glomerular filtration rate (eGFR) at 2 years, rate of kidney function decline, and remission of proteinuria. Clinical and molecular phenotypical data will be analyzed by GN subtype to identify disease predictors and discover therapeutic targets. Limitations: Given the relative rarity of individual glomerular diseases, one of the major challenges is patient recruitment. Initial registry studies may be underpowered to detect small differences in clinically meaningful outcomes such as ESKD or death due to small sample sizes and short duration of follow-up in the initial 2-year phase of the study. Conclusions: The Canadian Glomerulonephritis Registry (CGNR) supports national collaborative efforts to study glomerular disease patients and their outcomes. Trial registration: NCT03460054.

Contexte: Les glomérulonéphrites (GN) sont des causes importantes d'insuffisance rénale; elles représentent 20 % des cas incidents d'insuffisance rénale terminale (IRT) au Canada chaque année. Inverser la néphropathie et prévenir la progression vers l'insuffisance rénale est possible, mais deux obstacles majeurs freinent la réussite de l'intervention thérapeutique: une compréhension limitée des mécanismes sous-jacents de la maladie, de même que l'absence de biomarqueurs non invasifs et de cibles thérapeutiques. Les approches multicentriques reliant les données cliniques longitudinales et les résultats de santé à la collecte d'échantillons biologiques en série permettraient de combler cette lacune. Objectif: Créer une base de données cliniques nationale en ligne, multidimensionnelle et axée sur le patient, de même qu'une biobanque virtuelle fédérée pour permettre de mener des recherches moléculaires et cliniques humaines sur les GN au Canada. Type d'étude: Registre d'observation prospectif multicentrique débuté en 2019. Cadre: Neuf centres de soins tertiaires canadiens. Sujets: Des patients adultes recrutés dans les 24 mois suivant la biopsie et présentant un profil histopathologique de lésion compatible avec une néphropathie à IgA, une hyalinose segmentaire et focale, une maladie à changement minime, une glomérulonéphrite extra-membraneuse, une glomérulopathie à C3 et une glomérulonéphrite membranoproliférative. Mesures: La première visite comporte une collecte détaillée des données cliniques, histopathologiques et de laboratoire, la collecte d'échantillons biologiques (sang, urine et écouvillonnage des amygdales), ainsi qu'un questionnaire autoadministré sur la qualité de vie. Pour le suivi, la collecte des données cliniques et de laboratoire, la collecte des échantillons biologiques et les questionnaires s'effectuent tous les six mois. Méthodologie: Les patients reçoivent des soins comme établi par leur médecin, et les visites d'étude sont programmées tous les six mois. Les patients sont suivis jusqu'au décès ou jusqu'à la dialyse, à la transplantation ou au retrait de l'étude. Un critère de jugement combiné (IRT, ou diminution de 40 % du débit de filtration glomérulaire estimé après deux ans), ainsi que le taux de déclin de la fonction rénale et la rémission de la protéinurie sont les principaux critères de jugement. Les données phénotypiques cliniques et moléculaires seront analysées par sous-types de GN afin d'identifier les prédicteurs de la maladie et de découvrir de nouvelles cibles thérapeutiques. Limites: Le recrutement des sujets demeure un des principaux défis puisque les maladies glomérulaires prises individuellement sont relativement rares. La faible taille des échantillons et la courte durée du suivi pendant les deux ans de la phase initiale de l'étude pourraient faire en sorte que les études initiales issues du registre ne soient pas assez puissantes pour détecter de légères différences dans les résultats cliniquement significatifs comme l'IRT ou le décès. Conclusion: Le Canadian Glomerulonephritis Registry (CGNR) appuie les efforts de collaboration nationale visant à étudier les patients atteints de maladies glomérulaires et leur évolution clinique. Enregistrement de l'essai: NCT03460054.

Microtubules: evidence for 13 protofilaments.

When microtubules are fixed in glutaraldehyde in the presence of tannic acid and thin sections cut, the subunit structure of the microtubule is readily observed without the need of image reinforcement. Seven types of microtubules were analyzed: those in the heliozoan axoneme, the mitotic apparatus, the contractile axostyle, repolymerized microtubules derived from the chick brain, the central pair in flagella, and the A tubules of flagella and the basal body. In all cases microtubules were composed of 13 equally spaced protofilaments. The B tubules in flagella and the basal body appear to be composed of 11 subunits. The connections of the B to the A and the C to the B are described. A model of a microtubule is presented.

Inhibition of tumor promotion by a biomimetic superoxide dismutase.

A low molecular weight, lipophilic, copper coordination complex with superoxide dismutase-mimetic activity inhibited biochemical and biological actions of a tumor promoter in mouse epidermis. Such inhibitory effects implicate reactive oxygen species in the tumor promotion process.

Sec-independent protein translocation by the maize Hcf106 protein.

The bacterial Sec and signal recognition particle (ffh-dependent) protein translocation mechanisms are conserved between prokaryotes and higher plant chloroplasts. A third translocation mechanism in chloroplasts [the proton concentration difference (DeltapH) pathway] was previously thought to be unique. The hcf106 mutation of maize disrupts the localization of proteins transported through this DeltapH pathway in isolated chloroplasts. The Hcf106 gene encodes a receptor-like thylakoid membrane protein, which shows homology to open reading frames from all completely sequenced bacterial genomes, which suggests that the DeltapH pathway has been conserved since the endosymbiotic origin of chloroplasts. Thus, the third protein translocation pathway, of which HCF106 is a component, is found in both bacteria and plants.

Reduction of atherosclerosis by administration of dehydroepiandrosterone. A study in the hypercholesterolemic New Zealand white rabbit with aortic intimal injury.

Dehydroepiandrosterone (DHEA) is an endogenous steroid that blocks carcinogenesis, retards aging, and exerts antiproliferative properties. In vitro, it is a potent inhibitor of glucose-6-phosphate dehydrogenase, the first committed step of the pentose phosphate pathway. In man, serum levels of DHEA and its sulfate peak in early adulthood and drop markedly with age. Epidemiologic evidence indicates that low levels of DHEA or its sulfate conjugate are linked to an increased risk of developing cancer or of death from cardiovascular disease. Like cancer, atherosclerosis is a proliferative process characterized by both initiation and promotion phases. This similarity provided a framework in which to study the antiatherogenic effects of DHEA. Rabbits were randomly assigned to four groups. Two groups of rabbits received aortic endothelial injury by balloon catheter and were fed a 2% cholesterol diet for 12 wk. DHEA, 0.5%, was incorporated into the diet of one group receiving the 2% cholesterol diet and endothelial injury and also into the diet of one of the control groups. Animals were killed after 12 wk and aortas, hearts, and livers were studied. Plasma samples were analyzed for total cholesterol, VLDL, LDL, HDL, triglycerides, DHEA, and DHEA-sulfate levels. The atherogenic insult resulted in severe atherosclerosis in animals not treated with DHEA. In those receiving DHEA there was an almost 50% reduction in plaque size (P = 0.006), inversely related to the serum level of DHEA attained. Fatty infiltration of the heart and liver were also markedly reduced. These beneficial actions were not attributable to differences in body weight gain, food intake, total plasma cholesterol or distribution of cholesterol among the VLDL, LDL, or HDL fractions. The results show that high levels of plasma DHEA inhibit the development of atherosclerosis and they provide an important experimental link to the epidemiologic studies correlating low DHEA-sulfate plasma levels with an enhanced risk of cardiovascular mortality.

Steroid administration after myocardial infarction promotes early infarct expansion. A study in the rat.

Whether steroids lead to thinner scars and larger aneurysms by delaying collagen deposition or worsening infarct expansion before significant collagen deposition begins is unknown. Rats underwent either transmural infarction by left coronary ligation or sham operation. Both infarct and sham rats were randomized to methylprednisolone 50 mg/kg i.p. X 4 or saline treatment within 24 h after operation. Sacrifice occurred before (3 d) or after (7 d) collagen deposition typically begins. Despite similar infarct size, infarct wall thickness was 1.35 +/- 0.08 mm in the saline and 0.99 +/- 0.12 mm in the methylprednisolone group (P less than 0.001) at 3 d. This decrease in wall thickness was explained by a decrease in the number of myocytes across the infarct wall (r = 0.99; P less than 0.001), suggesting that steroids promote myocyte slippage. Furthermore, methylprednisolone caused no further infarct thinning or cavity dilatation beyond 3 d. Thus, high-dose methylprednisolone given within 24 h after transmural infarction worsens infarct expansion before collagen is laid down by promoting the slippage of necrotic myocytes.

Non-invasive quantification of small bowel water content by MRI: a validation study.

Substantial water fluxes across the small intestine occur during digestion of food, but so far measuring these has required invasive intubation techniques. This paper describes a non-invasive magnetic resonance imaging (MRI) technique for measuring small bowel water content which has been validated using naso-duodenal infusion. Eighteen healthy volunteers were intubated, with the tube position being verified by MRI. After a baseline MRI scan, each volunteer had eight 40 ml boluses of a non-absorbable mannitol and saline solution infused into their proximal small bowel with an MRI scan being acquired after each bolus. The MRI sequence used was an adapted magnetic resonance cholangiopancreatography sequence. The image data were thresholded to allow for intra- and inter-subject signal variations. The MRI measured volumes were then compared to the known infused volumes. This MRI technique gave excellent images of the small bowel, which closely resemble those obtained using conventional radiology with barium contrast. The mean difference between the measured MRI volumes and infused volumes was 2% with a standard deviation of 10%. The maximum 95% limits of agreement between observers were -15% to +17% while measurements by the same operator on separate occasions differed by only 4%. This new technique can now be applied to study alterations in small bowel fluid absorption and secretion due to gastrointestinal disease or drug intervention.

Sugar transporters in plant biology.

Sugar transporters are key players in many fundamental processes in plant growth and development. Recent results have identified several new transporters that contribute to a wide array of physiological activities, and detailed molecular analysis has provided exciting insights into the structure and regulation of these essential membrane proteins.

Modulation of azaserine-induced pancreatic foci by phenolic antioxidants in rats.

Effects of the dietary phenolic antioxidants butylated hydroxyanisole [(BHA) CAS: 25013-16-5; (1,1-dimethylethyl)-4-methoxyphenol] and butylated hydroxytoluene [(BHT) CAS: 128-37-0; 2,6-di-tert-butyl-p-cresol] on pancreatic tumorigenesis were examined. Male LEW inbred rats were given injections of 30 mg azaserine [CAS: 115-02-6; diazoacetate (ester) serine] per kg body weight once a week for 3 weeks and maintained on either a control diet or 0.45% BHA- or 0.45% BHT-supplemented control diet throughout the initiation and post-initiation phases of the experiment. At 4 months post initiation, pancreatic tissue sections were quantitatively examined for the number and size of preneoplastic foci. BHT and BHA treatments reduced the number of acidophilic foci per pancreas by 32 and 48%, respectively, but were without effect on focal size. By contrast, basophilic foci were not subject to modulation by these antioxidants. A constellation of enzyme activities involved in carcinogen inactivation and known to be perturbed by antioxidant treatment was examined in liver and pancreas. The hepatic activities of glucose-6-phosphate dehydrogenase, glutathione reductase, and glutathione-S-transferases were markedly elevated while catalase and superoxide dismutase activities were unchanged. Glutathione peroxidase activity was diminished. In the pancreas, only glutathione peroxidase activity was affected, and it was reduced in both the BHA and BHT treatment groups. Although the pancreas is refractory to the enzyme inductive effects of these antioxidants, morphometric analysis of foci demonstrated chemoprevention by BHA and BHT of azaserine-induced foci. Whether this reduction reflected inhibition of an initiation, postinitiation , or a combination of effects was not known.

Effect of testing temperature on internal egg quality measurements.

The objective of this study was to determine the effect of egg testing temperature on quality measurements of shell eggs. The quality measurements compared included 3 Haugh unit (HU) devices (electronic Haugh, tripod Haugh, and Haugh meter), egg weight, albumen height, albumen width, albumen index, yolk width, yolk height, yolk index, percentage of thin albumen, and vitelline membrane strength at 3 temperatures of 5, 13, and 23 degrees C from 2 strains of laying hens (Hyline W36 and Bovans White) at 2 storage times. The HU measurements averaged 72.44 at time zero and 59.99 at 7 wk. At 7 wk for all devices, HU values decreased 6 units with increased temperature (P < 0.05). The electronic Haugh and tripod Haugh devices gave equal measurements for all testing conditions. The Haugh meter gave equal values at 5 degrees C for fresh eggs but lower HU at higher temperatures and 7 wk storage. Thus, it is recommended that egg testing temperature be reported when HU are measured. Coefficient of variation generally increased for all HU methods with increasing temperature. Although there was a proportionately different amount of thin albumen detected between the strains of laying hens, no significant difference was seen in HU. From the evaluated methods for measuring quality, the electronic Haugh, which electronically measures albumen height and calculates HU, provided the lowest coefficient of variation, was sensitive to quality loss, and gave the highest quality measurement (5 degrees C).

Amino acid transporters in plants.

Amino acid transporters are essential participants in the resource allocation processes that support plant growth and development. Recent results have identified several new transporters that contribute to a wide array of physiological activities, and detailed molecular analysis has provided fundamental insights into the structure, function and regulation of these integral membrane proteins.

Permanent epicardial pacing in pediatric patients: seventeen years of experience and 1200 outpatient visits.

BACKGROUND: The purpose of this study was to evaluate the long-term outcome of all pediatric epicardial pacing leads. METHODS AND RESULTS: All epicardial leads and 1239 outpatient visits between January 1, 1983, and June 30, 2000, were retrospectively reviewed. Pacing and sensing thresholds were reviewed at implant, at 1 month, and at subsequent 6-month intervals. Lead failure was defined as the need for replacement or abandonment due to pacing or sensing problems, lead fracture, or phrenic/muscle stimulation. A total of 123 patients underwent 207 epicardial lead (60 atrial/147 ventricular, 40% steroid) implantations (median age at implant was 4.1 years [range 1 day to 21 years]). Congenital heart disease was present in 103 (84%) of the patients. Epicardial leads were followed for 29 months (range 1 to 207 months). The 1-, 2-, and 5-year lead survival was 96%, 90%, and 74%, respectively. Compared with conventional epicardial leads, both atrial and ventricular steroid leads had better stimulation thresholds 1 month after implantation; however, only ventricular steroid leads had improved chronic pacing thresholds (at 2 years: for steroid leads, 1.9 muJ [from 0.26 to 16 mu]; for nonsteroid leads, 4.7 muJ [from 0.6 to 25 muJ]; P<0.01). Ventricular sensing was significantly better in steroid leads 1 month after lead implantation (at 2 years: for steroid leads, 8 mV [from 4 to 31 mV]; for nonsteroid leads, 4 mV [from 0.7 to 10 mV]; P<0.01). Neither congenital heart disease, lead implantation with a concomitant cardiac operation, age or weight at implantation, nor the chamber paced was predictive of lead failure. CONCLUSIONS: Steroid epicardial leads demonstrated relatively stable acute and chronic pacing and sensing thresholds. In this evaluation of >200 epicardial leads, lead survival was good, with steroid-eluting leads demonstrating results similar to those found with historical conventional endocardial leads.

Pharmacokinetics of an intravenous-oral versus intravenous-mesna regimen in lung cancer patients receiving ifosfamide.

PURPOSE: To compare the pharmacokinetics of the approved I.V. (intravenous) mesna regimen and an investigational I.V.-oral regimen that could be used in outpatients who receive ifosfamide. PATIENTS AND METHODS: The I.V. regimen consisted of three I.V. mesna doses given at 0, 4, and 8 hours after ifosfamide administration. The investigational regimen included an I.V. mesna dose given concurrently with ifosfamide, followed 2 and 8 hours later by oral administration of mesna tablets. I.V. and oral mesna doses equaled 20% and 40%, respectively, of the ifosfamide dose. The study subjects were 12 lung cancer patients who received ifosfamide 1.2 g/m2 daily for 5 days. The patients were randomized to receive either the I.V.-oral or I.V. mesna regimen on day 1, followed by crossover to the other regimen on days 2 through 5 of ifosfamide treatment. The urinary profiles of mesna and dimesna excretion were determined on days 1, 2, and 5; pharmacokinetic parameters for blood samples were determined only on day 5. RESULTS: During the first 12 hours after ifosfamide administration, the amount of mesna excreted and the profile of urinary mesna excretion was similar for both regimens; however, the I.V.-oral regimen showed less fluctuation in the excretion rate and higher trough values. During hours 12 to 24, about eightfold more mesna was excreted by patients given the I.V.-oral than the I.V. regimen. CONCLUSION: These pharmacokinetic data show that the I.V.-oral regimen should be at least as uroprotective as the I.V. mesna regimen. Patients may also benefit from the I.V.-oral regimen because of the higher trough values during hours 0 through 12 and the sustained urinary mesna excretion during hours 12 through 24.

Fibronectin fragments modulate human retinal capillary cell proliferation and migration.

Capillary morphogenesis involves cell-cell and cell-matrix interactions. Proteases elaborated by capillary cells modify the extracellular matrix (ECM) to facilitate capillary tube formation. Previously, we detected the presence of fibronectin fragments (Fn-f) associated with the proform of matrix metalloprotease-2 (MMP-2) in conditioned medium of human retinal endothelial cells (HRECs). Association of this fragment to latent MMP-2 prevented autocatalytic activation of MMP-2, suggesting a modulatory role of Fn-f in MMP-2 activation. In this report, we examined the potential role of Fn-f on two processes involved in angiogenesis, proliferation and migration of vascular cells. The effects of Fn-f on proliferation were determined by DNA synthesis and cell counts. Their effects on migration were assessed using modified Boyden chambers. Seven Fn-f were tested on vascular cell migration and/or proliferation. Three Fn-f induced migration. Fn-f of 30-kDa and 120-kDa size positively affected proliferation of microvascular cells but not macrovascular cells. A 45-kDa gelatin binding fragment of Fn inhibited HREC proliferation but stimulated pericyte and smooth muscle cell proliferation. The potency of these fragments exceeded that of the known angiogenic growth factor, basic fibroblast growth factor (bFGF), on HREC migration. ECM components such as fibronectin may influence capillary morphogenesis by the generation of fragments that can modulate proliferation, migration, and protease activation. In the setting of diabetes, excess Fn is generated and is available for degradation. Thus, the production of Fn-f may be specifically relevant to the angiogenesis observed in proliferative diabetic retinopathy.

Seasonal pattern of acute myocardial infarction in the National Registry of Myocardial Infarction.

OBJECTIVES: The purpose of this study was to determine whether the rate of hospital admission for acute myocardial infarction (AMI) varies seasonally in a large, prospective U.S. registry. BACKGROUND: Identification of specific patterns in the timing of the onset of AMI is of importance because it implies that there are triggers external to the atherosclerotic plaque. Using death certificate data, most investigators have noted a seasonal pattern to the death rate from AMI. However, it is unclear whether this observation is due to variation in the prevalence of AMI or to other factors that may alter the likelihood of a fatal outcome. METHODS: We examined the seasonal mean number of cases of AMI (adjusted for the length of days in each season) that were submitted to the National Registry of Myocardial Infarction (NRMI) by 138 high volume core hospitals over a 3-year period (December 21, 1990 through December 20, 1993) during which the number of hospitals participating in the Registry was stable. Data were analyzed using general linear modeling and analysis of variance. RESULTS: High volume core hospitals reported 83,541 cases of AMI to the Registry during the study period. Approximately 10% more such cases were entered into the Registry in winter or spring than in summer (p < 0.05). The same trends were seen in both northern and southern states, men and women, patients < 70 versus > or = 70 years of age and those with Q wave versus non-Q wave AMI. CONCLUSIONS: We conclude that there is a seasonal pattern to the reporting rate of cases of AMI in the NRMI. This observation further supports the hypothesis that acute cardiovascular events may be triggered by events that are external to the atherosclerotic plaque.

Global cardiac remodeling after acute myocardial infarction: a study in the rat model.

Infarct expansion, regional dilation and thinning of the infarct zone, occurs within 1 day after myocardial infarction. Whether the early change in regional shape of infarct expansion affects the architecture of remote normal regions is unknown. To study this question, 45 rats with a transmural infarct were killed at 1, 2 and 3 days after infarction and their hearts were examined for infarct size and extent of expansion. Wall thickness and radius of curvature were measured within, adjacent to and remote from the infarct zone. Equivalent regions were analyzed in eight control hearts. The extent of disproportionate wall thinning and increased radius of curvature within the infarct zone of hearts with expansion was not dependent on infarct size. Significant wall thinning and increased regional radius of curvature were also seen in adjacent and remote regions of the hearts with expansion (p less than 0.001). These structural changes outside of the infarct occurred independent of infarct age and size, and were not seen in hearts without infarct expansion. Thus, when disproportionate thinning and dilation occur in the infarct region, they are accompanied by a distortion in shape of the entire heart including remote normal myocardium. This remote remodeling of noninfarcted myocardium correlates with extent of expansion, but not with age or size of the infarct.

Increased afterload aggravates infarct expansion after acute myocardial infarction.

After acute transmural myocardial infarction, the heart may undergo major remodeling characterized by thinning and dilation of the infarct zone and overall enlargement of the heart. The effect of increased left ventricular pressure on infarct expansion and the extent to which it alters postinfarction remodeling were studied in a rat model. Rats with either aortic banding or a sham operation and a survival period of 3 weeks were further randomized to sham thoracotomy or left coronary ligation. Surviving rats were killed 7 days later and the hearts were fixed in diastole for morphologic analysis. Hearts with aortic banding had a mean peak to peak gradient of 20.7 +/- 4.9 mm Hg across the aortic band at death and a significantly thicker heart than that of the comparison group without an aortic band. Infarct size, as a percent of total left ventricular mass, at the time of death was less in the group with aortic banding, yet infarct expansion was more marked. However, when original infarct size was estimated taking into account the effects of aortic banding, scar formation, infarct expansion and infarct-induced hypertrophy, it was found to be similar in both infarct groups (45.50 +/- 4.2 versus 47.90 +/- 3.1%). Infarct expansion, as measured by cavity dilation and infarct thinning, occurred in both infarct groups but was greater in the group with aortic banding.(ABSTRACT TRUNCATED AT 250 WORDS)