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Biomedical subjects

J Ricotta

Publications and source records attributed to J Ricotta.

10 recordsLinked to original sources
PubMed2000

Biophysical characteristics of gap junctions in vascular wall cells: implications for vascular biology and disease.

The role gap junction channels play in the normal and abnormal functioning of the vascular wall is the subject of much research. The biophysical properties of gap junctions are an essential component in understanding how gap junctions function to allow coordinated relaxation and contraction of vascular smooth muscle. This study reviews the properties thus far elucidated and relates those properties to tissue function. We ask how biophysical and structural properties such as gating, permselectivity, subconductive states and channel type (heteromeric vs homotypic vs heterotypic) might affect vascular smooth muscle tone.

Biophysical Phenomena↗
PubMed1998

Ambient pulsatile pressure modulates endothelial cell proliferation.

Many studies over the last decade have indicated that circulatory forces such as shear stress and cyclic strain can influence the endothelial cell (EC) phenotype. However, very little is known about the in vitro effects of pressure on EC. To study this, cultured bovine aortic EC were grown in custom designed pressure chambers with carefully regulated CO2/air environment. EC were exposed to either atmospheric, static (135 mmHg) or pulsatile pressure (160/110 mmHg). A pulsed pressure frequency of 60 cycles/min was maintained by computer-controlled solenoid valves, placed in series with pressure lines. EC proliferation was determined both by cell count after trypsin release on days 1,3 and 5 and by 3H-thymidine incorporation. By day 5, a significant decrease in cell number occurred in both pressure groups, confirmed by the thymidine studies. No changes were observed in cell morphology and cell viability as assessed by LDH activity studies. To investigate the mechanism of this effect, EC conditioned media from the three pressure conditions were transferred to non-exposed, control EC. Significant cell growth inhibition was demonstrated in the control EC group treated with conditioned media from EC cultured under pulsatile pressure conditions. This finding suggests that EC exposed to pulsatile pressure secrete an autocrine factor with growth inhibitory properties. This effect was not mediated by the growth factors TGFbeta and IL-1 as shown by Northern blot analysis and antibody-neutralization studies.

Animals↗
PubMed1997

Effect of pressure on cultured smooth muscle cells.

Recent studies indicate that smooth muscle cell (SMC) growth and morphology can be modulated by repetitive strain. However, there is very little known about the influence of pressure, without an associated cell stretch, on SMC phenotype. To study this, cultured bovine aortic SMC were grown on a rigid surface and placed in a custom-designed plexiglass pressure chamber with a carefully regulated 5% CO2/air environment. SMC were exposed to either atmospheric, 105 mm Hg or 120/90 mm Hg pressure at a frequency of 60 cycles/min (0.5 s systole, 0.5 s diastole). SMC number was determined on days 1, 3, 5, 7 and 9. SMC exposed to pressure were more elongated and displayed a significant increase in cell number by day 5 which persisted until day 9. Lactate dehydrogenase (LDH) in the conditioned media, an index of cytotoxicity, was not different between the groups at each time point. There was also no difference in pH or pCO2 of the media of SMC in any group. This is the first report of the effects of increased static and pulsatile pressure on SMC in vitro and indicates an increased proliferative rate. We hypothesize that the systemic pressure that the blood vessel is exposed to in vivo may have a significant regulatory influence on the phenotype of the smooth muscle cells which may affect the SMC response to injury or stimuli.

Animals↗
PubMed1994

Increased ambient pressure stimulates proliferation and morphologic changes in cultured endothelial cells.

Very little is known about the effects of pressure within the vascular system on EC phenotype. To study this, bovine aortic EC were seeded on rat type I collagen plates (2,000/cm2) and allowed to attach for 24 hours. The cells were exposed to either atmospheric, 40, 80, or 120 mm Hg pressure by placing them in a plexiglass pressure chamber loaded with 5% CO2/air and maintained at 37 degrees C inside an incubator. Chamber pressure was continuously monitored with an amplified voltage transducer connected to a digital monitor. EC were maintained in DMEM supplemented with 10% calf serum and substrates for up to 9 days. The results indicate that EC proliferation is influenced by their ambient pressure. EC subjected in vitro to pressures comparable to mean systemic blood pressures had a significant increase in cell number compared to EC exposed to atmospheric pressures. EC were elongated and appeared to align randomly. We hypothesize that the systemic pressure which the endothelium is exposed to in vivo may have a significant regulatory influence on the ability of the endothelium to proliferate which may affect the endothelial cell response to injury.

Animals↗
PubMed1992

Utility of an oral examination in a surgical clerkship.

To evaluate the utility of the oral examination in a surgical clerkship, we designed a prospective and randomized study to relate the subjective impressions of experienced examiners with an objective measure of cognitive knowledge. The examiners were asked to score the student's performance as honors, high satisfactory, satisfactory, or unsatisfactory, according to their subjective impression of the student's ability. Student performance was grouped according to oral examination performance. The cognitive performance in the honors group was significantly better than that of the other groups (Student's t-test, p = 0.05). There was a significant difference in cognitive performance for oral examination groups throughout the rotations (analysis of variance, p = 0.000; Kruskal Wallis, p = 0.05). The oral examination is useful to identify a high level of cognitive achievement but cannot discriminate between groups of median to low competence. It should be used for educational feedback, career counseling, residency recommendations, and professional development.

Achievement↗
PubMed1992

Experience as a surgeon determines resident knowledge.

BACKGROUND: This is a prospective study that compares operative experience with performance on the American Board of Surgery Inservice Training Examination (ABSITE) to establish the primacy of procedural experience in the graduate training environment. METHODS: Operative experience was determined from a computerized log of surgical procedures. The Report D of the 1991 ABSITE was used to assign each test item to specific operative procedures and to determine the frequency of the correct response (Fcr) for each item. The fraction of operative procedures (Fs) was determined for each category of surgical procedures (Fs = Number of procedures as surgeon/Total number of procedures). The Fcr was compared to the Fs by use of the Pearson correlation coefficient with significance at 95% confidence. RESULTS: Forty-two residents reported doing 8357 surgical procedures as surgeon in 12 months. Report D contained 209 test items. Of these, 162 items could be assigned to 26 categories of surgical procedures. The Fcr correlated directly with the Fs (p = 0.002, r = 0.605). CONCLUSIONS: A significant correlation exists between the experience of surgical residents as surgeon and their performance on the ABSITE:

Clinical Competence↗
PubMed1981

The multiple sequential distal bypass graft: improving nature's alternatives.

Sequential femoral-distal bypass grafts were employed to revascularize 21 ischemic limbs. An end-to-side distal anastomosis plus an additional side-to-side anastomosis to an isolated popliteal segment or an additional distal tibial vessel were employed. If one graft that underwent successful early revision is included, the initial patency rate was 100%. After a median follow-up of 8 months, complete graft failure had occurred in three patients. A previously unreported occurrence in two patients was proximal graft segment occlusion, with patency of th distal segment that was successfully revascularized. One additional patient had occlusion of the distal graft segment. Limb salvage was achieved in 20 of the 21 patients. This approach offers several hemodynamic advantages and may be the procedure of choice in patients with distal runoff that si not ideal for a routine femoropopliteal bypass graft.

Aged↗
PubMed1981

Construction of an ileocecal valve and its role in massive resection of the small intestine.

A method of construction a nonrefluxing valve to use as a substitute for the ileocecal valve in patients with massive resection of the small intestine has been described. We believe that this represents a safe and simple alternative to other valve mechanisms previously reported in the literature. Results using this valve in one patients and also in the laboratory are presented and discussed. The use of this valve significantly decreased mortality in laboratory dogs following massive resection of the small intestine and is associated with a decrease in weight loss and bacterial overgrowth when compared with the dogs in the group without the valve. It also results in an increase in intestinal transit time. While the final mechanism of the action of the valve is unclear, prevention of stasis of the small intestine and of regurgitation of the colonic contents seems to be of major importance.

Adolescent↗
PubMed1980

The extended retroperitoneal approach for treatment of extensive atherosclerosis of the aorta and renal vessels.

The aorta was exposed by a standard "nephrectomy" incision through the eleventh interspace in 53 patients with aneurysmal or occlusive disease. The plane posterior to the kidney and ureter was developed easily, enabling exposure of the aorta above the level of the celiac axis to its bifurcation by dividing only the crus of the diaphragm and the lumbar branch of the left renal vein. Twenty-five patients with abdominal aortic aneurysms were treated in this fashion. In all but four there were significant risk factors, including extension of the aneurysm to or above the level of the renal arteries in eight and coexisting renal artery stenosis with hypertension in two. Twenty-eight patients with occlusive vascular disease were treated surgically. In eight, this was the second operation on the aorta while in 11, major occlusive disease involved the aorta as well as the renal/visceral arteries. The operative mortality rate was 8%. Eighty-nine percent of the patients were alive at this writing. Of 18 hypertensive patients, 9 were not taking medication and only 3 have not improved significantly. We recommend this approach for reoperations on the aorta and for patients who have extensive aneurysmal and/or occlusive disease of the aorta, renal, and visceral arteries.

Adolescent↗