Degenerative changes in fresh aortic root homografts in a canine model: evidence of an immunologic influence.
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Animals↗
Biomedical subjects
J Bianchi
Publications and source records attributed to J Bianchi.
[Value of the D-xylose test in elderly subjects].
To ten patients who have more than sixty years old (medium: 75.5), the test of D-Xylose with 25 g was carried out. They have not intestinal or extraintestinal disease, that difficult the results. A control group was, ten adults young (medium: 23.7). The xylose in blood was in the first hours, between the normals limits in both groups. It does not occurred with the xylose in urine of five hours. This work support that the absorption of D-Xylose is carried out normally in old people, when the detection is in blood not in urine. Although we purpose the detection of xylose in blood during the first two hours in both groups, as an easy way for this test.
Adolescent↗
Dehydroascorbic acid and cell membranes: possible disruptive effects.
Exposure of cellular membranes to dehydroascorbic acid can result in a loss of membrane integrity. Renal brush border or basolateral membrane vesicles pre-incubated with dehydroascorbic acid demonstrate a decrease in initial transport rates of D-glucose and a loss of intravesicular volume. The activity of brush border membrane specific leucine aminopeptidase is increased in vesiculated membrane preparations following exposure of the vesicles to either dehydroascorbic acid or Triton X-100. Erythrocytes in isotonic buffer with dehydroascorbic acid lose membrane integrity as demonstrated by a release of hemoglobin.
Animals↗
Dehydroascorbic acid and ascorbic acid transport systems in the guinea pig ileum.
The transport properties of dehydroascorbic acid and ascorbic acid in membrane vesicle preparations of guinea pig ileum were evaluated. Na-dependent transport of ascorbic acid in the brush-border membrane was confirmed, and an Na-independent mechanism was found in the basolateral membrane. The electrically neutral oxidized form of vitamin C is transported by an Na-independent mechanism at both cell surfaces. Transport of each substrate is saturable and exhibits cis-inhibition and trans-stimulation in the presence of structural analogues. Additional studies on ascorbate metabolism will be necessary to support a comprehensive model of intestinal handling of vitamin C.
Animals↗
Glucose-independent transport of dehydroascorbic acid in human erythrocytes.
It has been previously reported that glucose and its structural analogs inhibit dehydroascorbic acid (DHA) transport across the membranes of nonpolar cells, which led to the suggestion that the hexose transporter mediates dehydroascorbic acid transport. The present study examines the role of the erythrocyte hexose transport system in dehydroascorbic acid uptake. We have confirmed that dehydroascorbic acid may be a ligand of the hexose transport system under certain experimental conditions. However, there is an additional pathway of dehydroascorbic acid transport that is uninfluenced by external glucose. This pathway is one of facilitated diffusion, demonstrating saturation kinetics of transport, cis-inhibition, and trans-stimulation. The Km for the system is 412 microM. It is suggested that this previously undescribed sugar-independent transporter is the physiologically important route of DHA uptake in erythrocytes.
Adult↗
Effective use of renal cortical slices in transport and metabolic studies.
The uptake and metabolism of two water-soluble vitamins were measured in rat renal cortical slices, isolated tubules, and vesicles of the brush-border and basolateral cell membranes to determine (a) whether it is possible to produce slices that have open tubules and, (b) whether slices and tubules metabolize vitamins similarly. Transport of ascorbic acid is sodium-dependent in slices and in brush-border vesicles but is sodium-independent in basolateral vesicles, suggesting that the brush-border membrane of slices is accessible to components of the bathing solution. Nicotinic acid was metabolized similarly (97-98%) in both slices and isolated tubules. Oxygen consumption by slices maintained in a closed chamber was constant as pO2 decreased from 88% to 58%. Slices are concluded to be a suitable model for transport and metabolic studies providing that care is taken in their preparation and use.
Animals↗
Transport of L-ascorbic acid and dehydro-L-ascorbic acid across renal cortical basolateral membrane vesicles.
The uptake of L-ascorbic acid and dehydro-L-ascorbic acid into renal cortical basolateral membrane vesicles has been characterized. The uptake systems for both solutes demonstrate saturation kinetics. The presence of structural analogs of L-ascorbic acid and dehydro-L-ascorbic acid results in cis-inhibition and trans-stimulation. Uptake of each substrate is Na+-independent, proceeding to an endpoint of substrate equilibrium across the vesicular membrane. The transport mechanism(s) for L-ascorbic acid and dehydro-L-ascorbic acid appears to be facilitated diffusion.
Animals↗
Na+-independent dehydro-L-ascorbic acid uptake in renal brush-border membrane vesicles.
A membrane preparation enriched in the brush-border component of the plasma membrane was isolated from rat renal superficial cortex by a divalent cation precipitation procedure. Uptake of dehydro-L-ascorbic acid, the oxidized form of L-ascorbic acid, by the brush-border membrane vesicles was studied. The uptake mechanism was found to be sodium-independent and insensitive to the trans-membrane electrical potential difference. Uptake was saturable and subject to cis-inhibition. Concentrative uptake was demonstrated only under conditions of trans-stimulation by structural analogs. The results suggest a mechanism of facilitated diffusion for the uptake of dehydro-L-ascorbic acid in renal brush-border membranes.
Animals↗
The role of the phase relation between the atrial excitatory waves in determining the functional refractory properties of the atrioventricular node.
Through programme stimulation of the two basic inputs of the atrioventricular node (AVN)--crista terminalis and interatrial septum--different spatial and temporal relations between the excitatory waves passing from the atrium into the node were modelled in intact rabbit heart preparation. The essential role of the spatial-temporal organization for the determination of the refractory properties is demonstrated. The functional refractory curves depend not only on the basic rhythm, but also on the direction of the atrial excitation front. It is shown that interaction of the input waves is possible in intact preparation as well. At optimum phase regimes combined stimulation of the two inputs leads to prolongation or shortening of the initial H1H2 interval. The qualitative characteristic of the observed effects is very varied. It is defined predominantly by the stimulation programme, but it does not depend on which of the two inputs the basic rhythm is applied. The view is expressed that in order to obtain a more accurate characterization of the AVN-conduction, it is necessary to consider the interaction of the atrial excitatory waves arriving at the posterior and anterior inputs of AVN and the reflection of this interaction on its refractory properties.
Animals↗
Supernormal response and conduction in depressed isolated canine ventricular muscle exposed to high potassium concentration.
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Action Potentials↗
Tachycardia and apparent sino-atrial block due to concealed sinus node re-entry.
The role of the middle intercaval area ("internodal pathway") in the genesis of atrial re-entry was studied using microelectrode techniques and the extrastimulus method in the rabbit heart. Following surgical interruption of the anterior and posterior internodal tracts, two patterns of re-entry were observed using the middle internodal pathway manifesting alternatively as tachy- and brady-arrhythmias. Re-entry which was produced by critically timed extrastimulation at the septal branch of the crista terminalis (CT) caused tachycardia reciprocating between the sinus node (SN) and intercaval area. Spontaneous re-entrant impulses were also observed, particularly following the addition of cedilanid (0.04 mg/L). In addition, in association with critical prolongation of conduction in the sino-septal area, premature discharge of the dominant pacemaker fibers was observed and resulted in the appearance of bradyarrhythmias. These were commonly manifest as bigeminy and trigeminy on the surface septal electrogram. Hence concealed sinus node re-entry could manifest itself as apparent sino-atrial block or sino-atrial re-entry tachycardia.
Action Potentials↗
Atrioventricular nodal conduction during atrial fibrillation in rabbit heart.
Atrial fibrillation was induced in 15 superfused rabbit atrial-atrioventricular nodal preparations in which surface bipolar electrograms were recorded simultaneously from the crista terminalis, interatrial septum, and His bundle along with microelectrode action potentials from cells in the atrionodal (AN), nodal (N), and nodal-His (NH) regions of the atrioventricular node. Effective engagement of the atrioventricular node with propagation to the His bundle was critically dependent on the relative timing of activation at the crista terminalis and interatrial septal input regions of the atrioventricular node. Conduction through the AN and N regions appeared dependent on the relative timing of activation wave fronts emerging from the two input regions. Asynchronous engagement of AN and N regions resulted in both distortion of action potentials and concealed conduction, with delayed conduction and block to the NH region and His bundle. Successful engagement of the NH region always produced a 1:1 NH-to-His bundle relationship. It is concluded that during atrial fibrillation 1) activation of the AN region occurs as a result of the variable interaction of inputs from the crista terminalis and interatrial septum; 2) predictably, effective synchronous engagement of the AN and consequently the N region is responsible for conduction to the NH and His bundle regions; 3) conversely, asynchronous activation inputs from the crista terminalis and interatrial septum result in fragmented, asynchronous as well as concealed conduction within the AN and N regions with block in the atrioventricular node and variable conduction to the His bundle.
Action Potentials↗
The mechanism of AV junctional reentry: role of the atrionodal junction.
Mapping of atrial-AV nodal (AVN) activation patterns was performed in 10 superfused rabbit AVN preparations utilizing 3 bipolar electrodes placed simultaneously at the crista terminalis (CT), interatrial septum (IAS) and His bundle (H) regions in close proximity to the AVN, along with two or three microelectrodes in the AN, N and NH regions of the AVN. Basic and premature stimuli were introduced at either or both the CT and IAS regions of the AVN. The timing of the premature stimuli was varied to induce close interaction of inputs to the AVN. Summation and/or cancellation, as evidenced by changes in the morphology of the action potentials and alteration of H1-H2 intervals, were observed. Apparent reentry phenomena could be induced or terminated by appropriately timed stimulation at the CT and IAS inputs. Reentry was critically related to both the patterns and timing of the spread and excitation within AVN and surrounding atrial tissue. Slow conduction and unidirectional block were observed in various portions of the reentry circuit. It is concluded that 1) interaction between input waves engaging the AVN produced either summation or fragmentation; 2) slow conduction and reentry resulted from a critical collision of wavefronts; 3) in this preparation, AVN reentry circuits always appeared to involve conduction through atrial tissue immediately surrounding AVN; and 4) remarkably, reentry confined to the intranodal region was never observed.
Action Potentials↗
Conduction disturbances in the middle internodal tract of the rabbit heart.
Conduction properties between the sinus node and the septal branch of the crista terminalis, the so-called middle internodal tract, were studied in the isolated rabbit right atrium. Recordings were obtained from two simultaneously impaled microelectrodes using the extrastimulation technique after cutting the anterior and posterior internodal tracts. Several types of conduction block were observed associated with steplike prepotentials and distortions of perinodal fibers in the absence of pharmacological intervention. Prolongation of sino-septal conduction time occurred with decreasing coupling intervals. The return cycle of the atria gradually increased with prolongation of the retrograde conduction time of premature impulses to the SN until entrance block was seen. Several observations in this data demonstrate the influence of concealed or manifest retrograde conduction into the perinodal fibers of the sinus node after premature stimulation of the atria, as critical delay within the perinodal region could alter conduction time of the premature depolarization, reset the sinus node, and influence subsequent antegrade conduction alone or in various combinations.
Action Potentials↗
Iodoflex and Iodosorb in the treatment of venous leg ulcers.
This article reviews the use of Iodoflex and Iodosorb in chronic venous leg ulcers. A description of prevalence and quality of life issues is given. Application and method of use of Iodoflex and Iodosorb in venous leg ulcers is then detailed along with relevant clinical evidence. A case study describes the use of Iodoflex in a difficult-to-heal venous leg ulcer.
Bandages↗
The management of leg ulcers in a patient with B cell cutaneous lymphoma.
Some patients suffer the consequences of skin ulceration more severely than others. Patients with B cell cutaneously lymphoma are one such group and this article reviews their special needs.
Aged↗
The management of a patient with lymphoedema of the legs.
Lymphoedema is a much under-publicised condition, yet it affects many people. Janice Bianchi and Marie Todd outline the implications of the condition and examine the treatment options of a typical case study.
Activities of Daily Living↗
[Urinar estriol variations during labor and puerperium].
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Estriol↗