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Biomedical subjects

B Biagi

Publications and source records attributed to B Biagi.

15 recordsLinked to original sources
PubMed1993

Influence of different harvesting techniques on the arterial wall of the internal mammary artery graft: microscopic analysis.

An histological comparison was made between left internal mammary arteries (LIMAs) harvested and prepared with different techniques prior to coronary artery bypass grafting. The mobilization of LIMA was made as follows: conventional technique (group I), extra pleural takedown with lysis of the endothoracic fascia (group II), and LIMA skeletonization (group III). Each group was divided into two other sub-groups according to the LIMA graft preparation: papaverine-saline solution sprayed on the pedicle (sub-group A) and intraluminal hydrostatic dilatation (sub-group B). Free blood flow from the LIMAs was measured immediately before cardiopulmonary bypass and ultrasonic duplex scanning (UDS) was performed to analyze the flow patterns and velocities during the early postoperative course. The results showed that the technique by which the LIMA is harvested bears no significant relationship to microscopical graft damage, while intimal lesions were observed in all sub-groups that adopted intraluminal hydrostatic dilatation (sub-group B). No difference in intraoperative LIMA flows were noted between groups and sub-groups of patients except in the case of group I-sub-group B, in which the flow was markedly reduced. Intramural haematoma or subadventitial blood effusion was observed with low incidence and magnitude in all groups and subgroups of patients, without any reduction of blood flow, and all LIMAs were patent at UDS measurements. In conclusion, the results showed that the method by which the IMA is harvested bears little and insignificant relationship to arterial wall damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Extrapleural takedown of the internal mammary artery as a pedicle.

Four hundred thirty-three patients underwent coronary bypass grafting using both internal mammary artery (IMA) and saphenous vein graft. In 233 patients the IMA was exposed with a conventional technique (group 1), whereas in the remaining patients the IMA was harvested leaving the pleura intact and performing an associated lysis of the endothoracic fascia (group 2). Postoperative course and complications of these groups were studied and compared in a period of time ranging from 8 to 28 months. Postoperatively, the blood transfused was significantly less in group 2 patients than in group 1; group 2 also had a reduction of surgical reexploration. Pleural effusion and hemidiaphragm impairment were infrequent or absent in group 2 patients, whereas pericarditis, severe postoperative chest pain, and respiratory insufficiency were noted only in group 1 patients. Our data suggest that extrapleural access without pleurotomy may be preferred owing to its low rate of chest wall complications.

Adult↗
PubMed1991

Tricuspid valve incompetence caused by nonpenetrating thoracic trauma.

Tricuspid valve incompetence from ruptured papillary muscle or chordae as a result of nonpenetrating trauma is uncommon. Blunt trauma causing partial detachment of a leaflet from the annulus is very rare. We report the case of a young adult involved in a car accident who had these findings. Operative repair with resuture of the leaflet to the annulus and annuloplasty using a Carpentier ring resulted in complete recovery.

Adult↗
PubMed1991

Haemorrhagic shock in cardiac surgery. Pharmacological treatment with ACTH (1-24).

Spontaneous rupture of one or more cardiac chambers following open heart surgery is not common. A case is reported of a 45 year-old woman who sustained a spontaneous rupture of the right atrium in the intensive care unit after mitral valve replacement. Exsanguination of the patient was very rapid. On the basis of clinical and experimental convincing studies in this case a high dose of ACTH was used to prevent the damaging effect of haemorrhagic shock. During the reopening manoeuvre and initial conventional management, 10 mg ACTH (1-24) was injected into a peripheral vein. Although the blood lost was 93% of her circulating blood volume and a lot of fluid transfused via the central venous catheter was lost into the pericardium and hemithorax, the patient's condition improved rapidly after the occlusion of the atrial tear with initial small volume of transfusion. Based on the review of recent investigations the use of ACTH is emphasized.

Adrenocorticotropic Hormone↗
PubMed1990

Effects of tetrodotoxin on chloride secretion in rabbit distal colon: tissue and cellular studies.

The effects of tetrodotoxin (TTX) were examined in muscle-stripped segments of rabbit distal colon and in cells of isolated colonic crypts. Electrical field stimulation (EFS) of the submucosa/mucosa evoked an increase in short-circuit current (ISC) that was due to an increase in chloride secretion. The EFS-evoked response was reduced 81% by 10(-7) M TTX and 30% by 5 X 10(-6) M atropine. Vasoactive intestinal peptide (VIP), carbachol, aminophylline, and 1,1-dimethyl-4-phenylpiperazinium increased ISC. Bumetanide reduced the responses to neural stimulation, aminophylline, and VIP. To determine whether TTX had direct effects on crypt epithelial cells, crypts were isolated and cells were impaled with microelectrodes. Mean resting potential (Vbl) was -67 +/- 1.1 mV (n = 63). VIP and aminophylline depolarized Vbl by 34 +/- 4.6 (n = 13) and 34 +/- 3.5 mV (n = 18), respectively. TTX had no significant effect on resting Vbl or on the responses to VIP or aminophylline. We conclude that stimulation of submucosal neurons in the rabbit distal colon evokes a TTX- and bumetanide-sensitive increase in net chloride secretion that is dependent on the release of acetylcholine and other secretory neurotransmitters. Electrophysiological studies rule out a direct effect of TTX on colonic crypt cells.

Amiloride↗
PubMed1990

Opposing actions of Bay K 8644 enantiomers on calcium current, prolactin secretion, and synthesis in pituitary cells.

Dihydropyridine (DHP) Ca2+ channel modulators were used to explore the relationship between voltage-gated Ca2+ channels and PRL secretion, synthesis, and mRNA in PRL-secreting pituitary cells. Optical isomers of the Ca2+ channel agonist Bay K 8644 produced stereospecific and opposing effects on L-type Ca2+ current, PRL release, and synthesis in GH3 and GH4C1 cells. (-)-Bay K 8644 (R5417) behaved as a pure agonist, enhancing Ca2+ current several-fold while shifting the current-voltage curve 10-15 mV in the hyperpolarizing direction. The agonist effect was independent of holding potential, but decreased during prolonged Ba2+ or Ca2+ entry. R5417 produced a concentration-dependent increase in acute PRL release and enhanced PRL production by GH cells several-fold during a 72-h period. (+)-Bay K 8644 (R4407) behaved as a weak Ca2+ channel antagonist, inhibiting L-type Ca2+ current, KCl-stimulated PRL secretion, and PRL production at concentrations of 0.5-5 microM. These two isomers produced similar effects on PRL production by normal rat pituitary cells in dispersed culture. R5417 (500 nM) increased PRL produced in 72 h to 233 +/- 8% of the control value. R4407 reduced this quantity by 36 +/- 9%. The effects of the DHPs on PRL mRNA levels were consistent with the effects observed for acute secretion and hormone production. The agonist R5417 increased PRL mRNA 147 +/- 5% over a 30-h period, and the potent DHP Ca2+ channel blocker nimodipine inhibited PRL mRNA production 2-fold. These results demonstrate that racemic Bay K 8644 interacts with L-type Ca2+ channels in normal and transformed pituitary cells as a mixed agonist-antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1982

Active potassium transport by rabbit descending colon epithelium.

Previous studies of rabbit descending colon have disagreed concerning potassium transport across this epithelium. Some authors reported active K+ secretion under in vitro short-circuited conditions, while others suggested that K+ transport occurs by passive diffusion through a highly potassium-selective paracellular route. For this reason, we re-examined potassium fluxes across the colon in the presence of specific and general metabolic inhibitors. In addition, electrochemical driving forces for potassium across the apical and basolateral membranes were measured using conventional and ion-sensitive microelectrodes. Under normal conditions a significant net K+ secretion was observed (JK net = -0.39 +/- 0.081 mueq/cm2hr) with 42K fluxes, usually reaching steady-state within approximately 50 min following isotope addition. In colons treated with serosal addition of 10(-4)M ouabain, JKsm was lowered by nearly 70% and JKms was elevated by approximately 50%. Thus a small but significant net absorption was present (JKnet = 0.12 +/- 0.027 mueq/cm2hr). Under control conditions, the net cellular electrochemical driving force for K+ was 17mV, favoring K+ exit from the cell. Cell potential measurements indicated that potassium remained above equilibrium after ouabain, assuming that passive membrane permeabilities are not altered by this drug. Net K+ fluxes were abolished by low temperature. The results indicate that potassium transport by the colon may occur via transcellular mechanisms and is not solely restricted to a paracellular pathway. These findings are consistent with our previous electrical results which indicated a nonselective paracellular pathway. Thus potassium transport across the colon can be modeled as a paracellular shunt pathway in parallel with pump-leak systems on the apical and basolateral membranes.

Animals↗
PubMed1982

Control mechanisms of bicarbonate transport across the rat proximal convoluted tubule.

Bicarbonate transport (JHCO3) was studied in rat proximal convoluted tubules by luminal and peritubular microperfusion, and the effects on tubular bicarbonate transport of selective changes in luminal and peritubular bicarbonate concentrations and of changes in luminal flow rate were evaluated. A pH glass electrode was used to measure [HCO3(-)] and gave results similar to those of a microcalorimetric method. Increasing the tubular and peritubular [HCO3(-)] at constant luminal perfusion rate (10 nl.min-1) augmented JHCO3, but JHCO3 increased more when pH changes were prevented by PCO2 adjustments (constant peritubular pH) than when pH was allowed to rise with the increase in [HCO3(-)] (constant PCO2). Elevation of the tubular HCO3(-) load by raising [HCO3(-)] stimulated JHCO3 more than when the HCO3(-) load was raised by enhancing luminal perfusion rate at constant [HCO3(-)] An increase in PCO2 at constant peritubular pH increased JHCO3. Diamox and benzolamide inhibited JHCO3 at luminal concentrations of 2-4 X 10(-4) M, yet a small but significant fraction of JHCO3 remained intact. Capillary perfusion with 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (5 X 10(-4) M) depressed JHCO3 by 70%. Acute changes in luminal and peritubular potassium concentrations (range, 2-6 meq/liter) had no effect on JHCO3, but JHCO3 increased moderately but significantly in severe dietary hypokalemia.

Animals↗
PubMed1981

Intracellular potentials in rabbit proximal tubules perfused in vitro.

Conventional microelectrodes were used to measure the basolateral membrane potential (VBL) in isolated perfused superficial proximal convoluted (sPCT) and superficial proximal straight (sPST) tubules of the rabbit kidney. Stable recordings for periods up to 2 h can be obtained. The mean +/- SE (n = number of cells) values of VBL were sPCT = -51.0 +/- 1.63 (24) and sPST = -47.0 +/- 0.97 (94) mV. Inhibitors of active transport, ouabain (10(-5) M) and low bath potassium (0.1 mM), caused a significant depolarization of VBL in sPST. In contrast, short-duration bath cooling (10 degrees C) had no significant effect. Removal of luminal glucose caused a larger hyperpolarization in sPCT (-13.9 +/- 1.77 (9) mV) than in sPST (-3.8 +/- 1.02 (5) mV). Removal of luminal glucose and alanine resulted in an even larger hyperpolarization of VBL in sPCT (-19.0 +/- 0.44 (6) mV). Perfusion of the lumen with a solution resembling late proximal tubular fluid in sPST resulted in hyperpolarization of VBL (-4.3 +/- 0.85 (4) mV). Reducing bath pH to 6.7 depolarized VBL (39.9 +/- 1.77 (13) mV). This effect can be associated with a decrease in the relative potassium permeability of the basolateral membrane. These results demonstrate the feasibility of using intracellular electrical measurements to determine both luminal and basolateral membrane characteristics in isolated proximal tubular segments.

Animals↗
PubMed1981

Intracellular potassium activity in the rabbit proximal straight tubule.

Double-barreled liquid ion-exchanger microelectrodes were used to measure basolateral membrane potential (VBL) and intracellular potassium activity (aiK) in superficial proximal straight tubules (sPST) of the rabbit perfused in vitro. The mean +/- SE (number of cells in parentheses) value of VBL was -37.8 +/- 2.49 (20) vM and aiK was 48.6 +/- 2.27 (20) mM. The calculated Nernst equilibrium potential (EK) across the basolateral membrane was -68 mV. Lowering both potassium concentration to 0.1 mM reversibly decreased both VBL and aiK to -12.2 +/- 1.21 (19) mV and 11.3 +/- 1.29 (19) mM, respectively. Bath ouabain (10(-5) resulted in similar changes. These results demonstrate that intracellular potassium is actively accumulated in sPST perfused in vitro and that accumulation results primarily from Na-K-ATPase activity in the basolateral membrane. During recovery from low K bath, the temporal relationship between VBL and aiK and the effects of ouabain and high K bath on recovery are used to demonstrate directly electrogenic pumping. Lowering bath pH to 6.7 (HCO-3 = 5 mM) and the presence of 0.5 mM BaCl2 in the bath resulted in a large and rapid depolarization of VBL with little or no change in aiK. These results suggest that the response of VBL to both maneuvers is caused by a decrease in potassium permeability of the basolateral membrane.

Animals↗