Showing papers by "University of Miami published in 1973"
TL;DR: Purkinje cells in the infarcted zone showed distinctive alterations in electrophysiological properties which were probably related to deleterious factors that accumulated in that zone.
Abstract: Electrophysiological mechanisms which underlie the ectopic ventricular beats occurring 1 day after occlusion of the anterior descending coronary artery of dogs were explored. In intact dogs, bipolar electrograms were recorded in the infarcted and normal zones. Both Purkinje and ordinary myocardial potentials were recorded from the endocardial surface of the normal zone, but only Purkinje potentials were recorded from the infarcted zone. The Purkinje potentials in the infarcted zone were diminished in amplitude and rapidity. The threshold for endocardial pacing was higher in the infarcted zone than it was in the normal zone. The refractory periods of Purkinje cells were longer in the infarcted zone than they were in the normal zone. Excised specimens of endocardial surface containing the infarcted zone were superfused with Tyrode's solution. No ordinary myocardial cells were electrically active at the endocardial surface of the infarcted zone. Purkinje cells showed diminished resting and action potentials, reduced upstroke velocity, enhanced automaticity and phase 4 depolarization, and long action potentials with prolonged phase 3. Excitability was depressed within the infarcted zone. During superfusion, even with Tyrode's solution poor in oxygen and free of dextrose, Purkinje cells recovered toward normal with respect to amplitude of resting and action potentials, upstroke velocity, automaticity, and excitability. The prolonged action potentials persisted. Repetitive firing was easily elicited within the infarcted zone. Various types of pacemaker activity were detected within the infarcted zone. Thus Purkinje cells in the infarcted zone showed distinctive alterations in electrophysiological properties which were probably related to deleterious factors that accumulated in that zone. It is likely that the arrhythmia which occurred in the intact dogs at this time originated within the altered Purkinje cells of the infarcted zone.
250 citations
TL;DR: Evidence from vascular, uterine and intestinal smooth muscle demonstrates that the large transmembrane Ca $^{2+}$ gradient depends on cellular [ATP] but not on the Na $^+$ gradient.
Abstract: The study of cellular Ca $^{2+}$ exchange in smooth muscle has been severely limited by extensive extra-cellular Ca $^{2+}$ binding. This problem was solved by using La $^{3+}$ to trap Ca $^{2+}$ inside the cells while displacing extracellular bound Ca $^{2+}$ . It was then shown that cytoplasmic Ca $^{2+}$ could be raised by Ca $^{2+}$ influx during high K $^+$ depolarization, Na $^+$ elimination and high pH. Ca $^{2+}$ influx was inhibited by other multivalent cations, local anaesthetics and low pH. In the rabbit aortae norepinephrine and angiotensin increase cytoplasmic Ca $^{2+}$ by release from intra-cellular membrane surfaces. In this same smooth muscle relaxation is brought about by intracellular Ca $^{2+}$ binding. Evidence from vascular, uterine and intestinal smooth muscle demonstrates that the large transmembrane Ca $^{2+}$ gradient depends on cellular [ATP] but not on the Na $^+$ gradient. ATP depletion abolishes the Ca $^{2+}$ gradient by increasing Ca $^{2+}$ influx.
248 citations
TL;DR: In this article, the authors studied the chemical composition of pelagic sediments for 73 locations in the Pacific and for 11 in the Indian Ocean and showed that many elements accumulate rapidly close to the continents and slowly in the central part of the ocean, and that significant quantities of basaltic matter (oceanic crust) are incorporated into the sediments only in areas of very low total sedimentation rates in the vicinity of oceanic island groups such as Polynesia and Hawaii.
226 citations
TL;DR: Regulation by ethylene extends to abscission, to flower formation and fading, and to fruit growth and ripening, as well as certain other instances, since auxins induce ethylene formation.
Abstract: Ethylene inhibits cell division, DNA synthesis, and growth in the meristems of roots, shoots, and axillary buds, without influencing RNA synthesis. Apical dominance often is broken when ethylene is removed, apparently because the gas inhibits polar auxin transport irreversibly, thereby reducing the shoot's auxin content just as if the apex had been removed. A similar mechanism may underly ethylene-induced release from dormancy of buds, tubers, root initials, and seeds. Often ethylene inhibits cell expansion within 15 min, but delays differentiation so that previously expanding cells eventually grow to enormous size. These cells grow isodiametrically rather than longitudinally because their newly deposited cellulose microfibrils are laid down longitudinally rather than radially. Tropistic responses are inhibited when ethylene reversibly and rapidly prevents lateral auxin transport. In most of these cases, as well as certain other instances, ethylene action is mimicked by application of an auxin, since auxins induce ethylene formation. Regulation by ethylene extends to abscission, to flower formation and fading, and to fruit growth and ripening. Production of ethylene is controlled by auxin and by red light, auxin acting to induce a labile enzyme needed for ethylene synthesis and red light to repress ethylene production. Numerous cases in which a response to red light requires an intervening step dependent upon inhibition of ethylene production have been identified. Ethylene action requires noncovalent binding of the gas to a metal-containing receptor having limited access, and produces no lasting product. The action is competitively inhibited by CO2, and requires O2. Ethylene is biosynthesized from carbons 3 and 4 of methionine, apparently by a copper-containing enzyme in a reaction dependent upon an oxygen-requiring step with a Km = 0.2% O2. The oxidative step appears to be preceded by an energy-requiring step subsequent to methionine formation.
223 citations
TL;DR: The long range forces in physics are those which fall off according to the inverse square law as mentioned in this paper, and the short range forces, on the other hand, fall off exponentially, so that after a very short distance they become effectively zero.
Abstract: The long range forces in physics are those which fall off according to the inverse square law. The short range forces, on the other hand, fall off exponentially, so that after a very short distance they become effectively zero. The short range forces play an important role in the physics of nuclei and of elementary particles. There are just two long range forces known, the gravitational force and the electromagnetic force. These are the ones that I shall be speaking about today.
207 citations
University of Miami1, Cleveland Clinic2, University of California, San Francisco3, Barts Health NHS Trust4, New York University5, Newcastle upon Tyne Hospitals NHS Foundation Trust6, Duke University7, Lund University8, Icahn School of Medicine at Mount Sinai9, University College London10, Aarhus University11
TL;DR: Of 247 patients with biopsyproven fibrosis or cirrhosis, 88 patients had no recorded abnormalities in history, physical examination, or laboratory test results which casts serious doubt on the reliability of detecting fibrosis without a liver biopsy.
Abstract: An international cooperative study was organized to evaluate whether the treatment of severe psoriasis with methotrexate significantly affects the liver of these patients. From a study population of 550 patients, 742 liver biopsy specimens together with pertinent clinical and laboratory data were evaluated as a function of methotrexate usage. Factors found to be significantly associated with histologic liver damage include: increased alcohol intake, the daily orally administered methotrexate dosage schedule, obesity, and diabetes. The evidence implicating increasing cumulative methotrexate dosage as a cause of hepatic fibrosis is not clear. Of 247 patients with biopsyproven fibrosis or cirrhosis, 88 patients had no recorded abnormalities in history, physical examination, or laboratory test results which casts serious doubt on the reliability of detecting fibrosis or cirrhosis without a liver biopsy.
205 citations
TL;DR: In this article, a decomposition of the complex-valued series into polarized components is proposed for the cross spectrum analysis of pairs of two-dimensional velocity vectors or pairs of complexvalued time series in general.
203 citations
TL;DR: Methods were devised for the selective alteration of parasympathetic control over the sinoatrial (SA) or the atrioventricular (AV) node in anesthetized, thoracotomized mongrel dogs and, except for the SA speeding produced by stimulation at the site near the coronary sinus, the effects were blocked by atropine.
Abstract: Methods were devised for the selective alteration of parasympathetic control over the sinoatrial (SA) or the atrioventricular (AV) node in anesthetized, thoracotomized mongrel dogs. Two epicardial sites were located at which parasympathetic nerve fibers enroute to the SA or the AV node could be stimulated or blocked. Selective nerve stimulation was accomplished with brief pulses (0.05 msec), and blockade was accomplished with topically applied lidocaine. At the intercaval site, only the SA node was affected. At the site near the coronary sinus ostium, only the AV node was affected in terms of parasympathetic control, but sometimes there were modest sympathetic effects on the SA node. The effects of stimulation at these sites, except for the SA speeding produced by stimulation at the site near the coronary sinus, were blocked by atropine. The effects were also blocked by ganglionic blockade. Probably, preganglionic parasympathetic fibers to the nodes are concentrated at these sites.
174 citations
TL;DR: The cup reefs of Bermuda demonstrate the reef-building ability of a community of encrusting organisms that form only crusts in the intertidal zone of the Mediterranean and Northern Brazil as discussed by the authors.
Abstract: Small charges of explosives were used to section cup-shaped reefs that occur on the margins of the Bermuda Platform. Study of these artificial outcrops, up to 10 m high, and the samples collected from them show how the reef-building community is rapidly converted to well-lithified reef rock in the marine development.
The reefs, known locally as boilers and breakers, occur along the wave-swept south shore of the Bermuda Islands and around the northeast and northwest margins of the Platform. They are cup-shaped, up to 30 m in long dimensions, and rise up to the sea surface as much as 12 m above the surrounding sea floor. The reefs are built by an intergrowth of encrusting organisms, principally crustose coralline algae, an encrusting hydrozoan, Millepora sp., and an attached gastropod, Dendropoma irregulare.
The growth framework of these algal cup reefs has extensive voids: large and intermediate-sized growth framework and shelter pores; borings of bivalves and sponges; and both intra- and inter-particle pores. A variety of vagile and sessile organisms (coelobites) inhabit these pores: an encrusting Foraminifera, Homotrema rubrum, is the most abundant attached coelobite; the tests of a variety of benthic Foraminifera and ostracods are common: branched coralline algae, barnacles, bivalves, ahermatypic corals, bryozoans, and burrowing crustaceans occur in varying abundance.
Beginning millimetres below the living surface, internal sediments accumulate in the extensive voids. Coarse-grained skeletal sand derived from the surface of the reefs is characteristic of the larger voids; lime mud with the tests of planktonic Foraminifera and planktonic algae occurs generally in the smaller voids. Most specimens from the interior of the reefs show multiple generations of internal sediment that vary in grain size, composition, and colour. The sand-sized sediments are pumped into the voids by the frequent and intense wave action; the lime mud settles out in the smaller, less agitated pores.
Cementation of internal sediments and surrounding growth frame begins centimetres below the living surface; it is so pervasive that marble-hard reef rock is developed within 1/2 m or less. The cement is principally high-magnesium calcite of micrite size, and subordinately acicular aragonite, but there are locally wide variations in crystal size and morphology. The occurrence of the cement within the reefs well below sea level, the isotope ratios of the cement crystals, the mineralogy, and the age inferred from radiocarbon age determinations of the growth frame all indicate that the cement is submarine and deposited from water of oceanic composition.
The algal cup reefs of Bermuda demonstrate the reef-building ability of a community of encrusting organisms that form only crusts in the intertidal zone of the Mediterranean and Northern Brazil. The cup reefs of the northern margins of the Bermuda Platform are true reefs, not merely veneers covering eroded blocks of Pleistocene limestone. In their composition, location, and early diagenesis, the cup reefs closely resemble the algal or lithothamnion ridge of Pacific atolls. Synsedimentary cementation of internal sediments and growth frame makes a major contribution to the rigidity of these ocean-facing reefs and atoll rims.
The assemblage of features that characterize the submarine fossilization of the cup reefs is widespread elsewhere in the modern seas: the floors of the Persian Gulf and parts of the Mediterranean; the margins of Pacific atolls; and the reefs off the north coast of Jamaica. This fossilization is characterized by reiterated generations of coelobites, internal sediments, and synsedimentary cements that can in time replace a major part of the original growth framework. Major variations in the sequence of these generations from pore to pore is the signature of this kind of fossilization. The same features of fossilization are described from reefs in the Devonian, Permian, and Triassic.
157 citations
141 citations
TL;DR: Spontaneous diastolic depolarization and automaticity also occurred occasionally without pharmacological or other experimental interventions; moreover, spontaneous activity originating in the mitral valve leaflet could propagate into and activate the atrial wall.
Abstract: Transmembrane action potentials were recorded from multiple sites in isolated canine anteromedial left atrial wall preparations with the anterior mitral valve leaflet attached. The preparations were superfused with Tyrode's solution. When the left atrial wall was electrically stimulated, activity propagated into the mitral valve leaflet. Typical atrial action potentials occurred in atrial wall fibers. However, maximum diastolic potential, total action potential amplitude, and rate of depolarization decreased markedly in the atrium overlying the fibrous annulus (junctional region), and repolarization characteristics were altered in this region. Mitral valve muscle fibers demonstrated still lower maximum diastolic potential, action potential amplitude, and rate of depolarization. Electrical excitation of single discrete regions in the mitral valve leaflet did not result in conduction to the atrium; conduction block occurred in the junctional region. However, simultaneous excitation of several mitral valve sites did cause an impulse to propagate to the atrium, but transmembrane action potentials of junctional fibers were characteristically different from those recorded from the same junctional fibers during activation from the atrium. Muscle fibers in the mitral valve leaflet were capable of developing spontaneous diastolic depolarization, which resulted in automatic impulse initiation, when they were exposed to epinephrine or norepinephrine (1 x 10-7 to 1 x 10-5M) or when they were stretched. Spontaneous diastolic depolarization and automaticity also occurred occasionally without pharmacological or other experimental interventions; moreover, spontaneous activity originating in the mitral valve leaflet could propagate into and activate the atrial wall. Acetylcholine abolished spontaneous activity. These data suggest that the mitral valve could act as a site of ectopic impulse initiation in the left atrium.
TL;DR: Fragments of spleen autotransplanted to subcutaneous tissue of the abdomen in the rat undergo almost complete necrosis and then regenerate into splenic tissue with a microscopic structure indistinguishable from the structure of the original organ.
01 Apr 1973
TL;DR: Replicas of fractured chromaffin cells are indicative of a range of activities thought to characterize exocytosis, including attachment of secretory vesicles to the plasma membrane, fusion, extrusion of contents, and membrane retrieval.
Abstract: Replicas of fractured chromaffin cells are indicative of a range of activities thought to characterize exocytosis, including attachment of secretory vesicles to the plasma membrane, fusion, extrusion of contents, and membrane retrieval. Exocytosis sites are abundant on stimulated cells but are infrequent when calcium is omitted from the system.
TL;DR: It was demonstrated that the formation of PGE(2) from arachidonic acid by the microsomal fraction from human skin could be inhibited by polyunsaturated fatty acids, suggesting a possible regulatory role of fatty acids released from endogenous phospholipids on prostaglandin synthesis in this tissue.
TL;DR: A steady decline of the accumulation of cyclic AMP in the Graafian follicle between the ovulatory stimulus and the actual rupture of the follicle, precedes similar changes in steroidogenesis observed by others and suggests that the decline in cyclicAMP accumulation is causally related to the process of ovulation.
TL;DR: It appears that the mutation in shrunken-4 affects the activities of more than one enzyme, and the defective starch synthesis seen in this mutant could be due to the low activities of ADPglucose pyrophosphorylase and starch synthetase rather than the low activity of phosphorylases.
Abstract: Soluble ADPglucose-α-glucan 4-α-glucosyltransferase (starch synthetase), ADPglucose pyrophosphorylase, UDPglucose pyrophosphorylase and phosphorylase were assayed in extracts from developing kernels of maize (Zea mays). Normal, waxy and amylose-extender maize at stages of development ranging from 8 days to 28 days after pollination were studied. Shrunken-4 maize at the 22-day stage was also studied. There is adequate activity of both ADPglucose pyrophosphorylase and starch synthetase at all stages of development to account for the synthesis of starch. Thus all starch could be synthesized via the ADPglucose pathway. High levels of UDPglucose pyrophosphorylase and of phosphorylase activities were also found at all stages of development. The possible role of phosphorylase in starch synthesis could not be discounted. The levels of phosphorylase, ADPglucose pyrophosphorylase, starch synthetase, and UDPglucose pyrophosphorylase activities in shrunken-4 kernels were about 20 to 40% of that found in normal maize kernels. It appears that the mutation in shrunken-4 affects the activities of more than one enzyme. The defective starch synthesis seen in this mutant could be due to the low activities of ADPglucose pyrophosphorylase and starch synthetase rather than the low activity of phosphorylase.
TL;DR: An increased degree of shielding of mineral embryos provided by adjacent protein cores of aggregated proteoglycans is hypothesized to explain the inhibitory action of fast-sedimenting proteoglyCans on mineral growth in vitro.
Abstract: The effect of proteoglycans on growth of seeding minerals in synthetic lymph was studied with special reference to regulation of endochondral calcification. Proteoglycans were isolated from bovine nasal cartilage by three published methods. By each method two fractions were separated which differed in respect to presence or absence of fast-sedimenting components on analytical ultracentrifugation. Each fraction was tested for its capacity to inhibit mineral growth in a buffered synthetic lymphin vitro. At concentrations of proteoglycans estimated to occur in the interstitial fluid of endochondral plates from 6- to 7-week-old rats, the fractions containing fast-sedimenting components were inhibitory to mineral growth; whereas fractions containing the slow-sedimenting components and a glycoprotein (link protein) had no inhibitory activity demonstrable in these systems. Comparison of calcium-binding capacity of certain proteoglycan fractions as well as their computed effect upon reduction of calcium activity under conditions of equilibrium dialysis revealed no differences in the behavior of a proteoglycan fraction rich in fast—as opposed to fractions composed entirely of slow-sedimenting components. An increased degree of shielding of mineral embryos provided by adjacent protein cores of aggregated proteoglycans is hypothesized to explain the inhibitory action of fast-sedimenting proteoglycans on mineral growthin vitro.
TL;DR: Opponensplasty using the extensor indicis proprius routed subcutaneously around the ulnar side of the forearm and across the palm to theextensor pollicis longus tendons in the region of the thumb metacarpophalangeal joint restored excellent thumb function in fifty-seven of sixty-five forearms.
Abstract: Opponensplasty using the extensor indicis proprius routed subcutaneously around the ulnar side of the forearm and across the palm to the extensor pollicis longus tendons in the region of the thumb metacarpophalangeal joint restored excellent thumb function in fifty-seven of sixty-five forearms: nine
TL;DR: A new microassay method with precision of ±5% was developed to quantitate pyrophosphate in synovial fluid and plasma with starting volumes of 0.5 ml, finding a highly significant elevation in some patients with osteoarthritis and gouty arthritis and in subjects with pseudogout.
Abstract: A new microassay method with precision of ±5% was developed to quantitate pyrophosphate in synovial fluid and plasma with starting volumes of 0.5 ml. A highly significant elevation of synovial fluid pyrophosphate concentration was found in some patients with osteoarthritis and gouty arthritis in addition to the well-established elevation in synovial fluid of subjects with pseudogout. No gradient of pyrophosphate between plasma and synovial fluid of patients with rheumatoid arthritis or in normal subjects was detectable. Studies of various parameters reflecting inflammation failed to show a correlation with the concentration of pyrophosphate in patients with pseudogout.
TL;DR: Marked hemodynamic changes are frequent in the course of ventricular tachycardia with systemic arterial hypotension, a decrease in cardiac output, and evidence of cerebral, coronary, and renal vascular insufficiency in congenital complete heart block.
Abstract: The hemodynamic consequences of cardiac arrhythmias depend on various factors, including the ventricular rate and the duration of the abnormal rate, the temporal relationship between atrial and ventricular activity, the sequence of ventricular activation, the functional state of the heart, the irregularity of the cycle length, associated drug therapy, the peripheral vascular vasomotor system, disease in organ systems other than the heart, and the degree of anxiety caused by the disease processes. Sinus bradycardia, even with rates as low as 40 beats/min, may not be associated with significant hemodynamic consequences unless the stroke volume is limited by myocardial or valvular disease, as in acute myocardial infarction. Cardiac output usually, but not invariably, falls when atrial fibrillation replaces normal sinus rhythm, even at comparable ventricular rates, both at rest and during exercise. Similar observations have been made during the development of atrial flutter despite the persistence of effectiv...
01 Mar 1973
TL;DR: In this article, the effect of varying light intensities on the rates of calcification and CO2 fixation in the coralMontastrea annularis is described, and high light intensity, above the saturation point of symbiont photosynthesis, are shown to inhibit the rate of calcifying in both shallow and deep specimens, while light enhanced calcification in reef-building corals appears to be an energy-requiring process involving the active transport of calcium and carbonate ions.
Abstract: 1. The effect of varying light intensities on the rates of calcification and CO2 fixation in the coralMontastrea annularis is described. 2. High light intensities, above the saturation point of symbiont photosynthesis, are shown to inhibit the rate of calcification in both shallow and deep specimens. 3. Light enhanced calcification in reef-building corals appears to be an energy-requiring process involving the active transport of calcium and carbonate ions, and the translocation of symbiont photosynthate.
TL;DR: Results indicate that 17βC is an antiandrogen, which acts by inhibition of testosterone 5α–reductase, which is an androgen—dependent sebaceous structure.
Abstract: 4–Androsten–3–one–17β–carboxylic acid (17βC), an inhibitor of testosterone 5α–reductase, as discovered in our enzymic studies of human skin, was tested for its antiandrogenic potency in the hamster flank organ, which is an androgen—dependent sebaceous structure The organ in the female animals enlarged in size and increased in pigmentation after topical application of testosterone propionate, 4 μg per day for 2 to 3 weeks This response was completely inhibited by the concomitant application of 17βC or its methyl ester (400 μg per day) Topical application of 5α–dihydrotestosterone (DHT, 4 jig per day) also caused the enlargement of the flank organ, but the action of DHT was not inhibited by 17βC Incubation of [14C] testosterone with homogenates of the flank organ produced DHT and androstane–3α,17β–diol (ADIOL) as the major metabolites The formation of these two 5asteroids was inhibited by 17βC added in the incubation medium These results indicate that 17βC is an antiandrogen, which acts by inhibition
TL;DR: Skin infections in Colombia were studied over one month to determine the effect of climate on the prevalence and flora of bacterial pyoderma, and to acquire first-hand information on cutaneous infections of military importance in tropical Latin America.
TL;DR: In this paper, it was shown that ventricular rate depended on the duration of the effective refractory period of the accessory pathway and when it was longer than that of thenormal AVpathway (and AVnodal block was not present).
Abstract: known to alternate but the reasons why the ratescould vary so muchhave been a matter of debateandspeculation. Thepresent communicationandaprevious study (Castellanos et al., I973) suggestedthat ventricular rate depended on the duration ofthe effective refractory period of the accessorypathway. When it was longer than that of thenormal AVpathway (and AVnodal block was notpresent) the majority of the impulses were trans-mitted across the normal AVpathwaythrough the