Biomedical subjects
Publications and source records attributed to M Valente.
The paper reports a case of cholestatic icterus caused by a large calculus in the infundibulum of the gallbladder with a cholecysto-choledochal fistula and hepato-choledochal block (Mirizzi's type II syndrome). The diagnostic iter complicated the evolution, raising questions regarding the therapeutic strategy.
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Durability of a new bioprosthesis, the Meadox-Gabbay unileaflet pericardial xenograft, was evaluated by reviewing a series of 12 patients who received this device in the mitral position from 1983 to 1985. Bioprosthetic failure necessitated reoperation in 5 patients 21, 22, 53, 66, and 81 months after placement. Three patients died of cardiac failure after 31, 52, and 70 months; no postmortem examinations were done. In 2 of the 3 patients, an echocardiographic study had shown signs of valvular dysfunction. Pathological examination of five available explants revealed the presence of redundancy and stretching of the single pericardial leaflet in all of them; in one, this lesion alone caused severe prosthetic incompetence. Other pathological findings included cusp and commissural calcification and commissural tears with or without calcification. Histologic examination and electron microscopy showed intrinsic calcification involving both collagen bundles and cellular debris and various degrees of collagen disruption. In this limited series of patients, the Meadox-Gabbay pericardial xenograft demonstrated various modes of failure that markedly impair its durability and render it unsuitable as a cardiac valve substitute.
Between September 1984 and December 1990, seven patients underwent right pneumonectomy and carinal reconstruction. All patients but one had squamous-cell lung cancer. Anterior thoracotomy through the 4th space was the surgical access in all cases. The mean time needed to perform the operation was 190 min and the mean blood infusion 340 ml. There were no intraoperative deaths. Of three deaths, only one was attributable to cancer, while two occurred after 84 and 94 days, respectively, as a result of cardiorespiratory failure. The median disease-free interval was 12 months, but the median survival had not been reached (51%) after a median follow-up of 47 months. Calculation of predicted and observed FEV1 showed that a mean decrease of 286 ml (range 145-439) occurred in the observed FEV1. More attention to pulmonary function is therefore required, and anterior thoracotomy is recommended as the surgical approach.
The overall results of salvage surgery for lung metastases were evaluated on 174 consecutive patients with primary osteosarcoma below the age of 20, resected in Milan between 1970 and 1988. Seventy-two children treated in the years 1970-1981 were compared with 102 children treated in the years 1982-1988. In the latter period, adjuvant chemotherapy was replaced by neo-adjuvant programs and salvage surgery was applied systematically to all patients with resectable lung metastases through median sternotomy. During the last period, the overall 5 year survival improved significantly from 35% to 58% (P less than 0.001), while the disease free survival rose from 38% to 45% (median 15 vs. 33 months, P = 0.3). The proportion of patients with completely resected lung metastases rose from 17% (7/42) to 55% (27/49), without operative mortality, and the overall survival from detection of lung metastases (including unresected cases) improved from 0 to 28% at 5 years (P less than 0.001). The survival benefit was observed only in the group of children with resected metastases. These data indicate that systematic bilateral pulmonary resection, combined with neoadjuvant chemotherapy, has contributed to improve the final cure rate of childhood osteosarcoma.
The ideal prosthetic conduit for surgical repair of complex congenital heart disease has yet to be found. Twenty conduits were implanted between the right ventricle and pulmonary artery in growing sheep as follows: four Dacron porcine valve conduits (mean time in place, 142 days); four avalved glutaraldehyde-fixed bovine iliac veins (mean 132 days); and 12 glutaraldehyde-fixed bovine iliac veins containing a porcine valve (mean 180 days). Fifteen conduits were left in place from 167 to 244 days (mean 204 days), and five were explanted earlier (mean 54 days). Pathological study included gross, x-ray, histological, and ultrastructural investigation. Five conduits failed because of infective endocarditis. The valved Dacron conduits showed significant tissue ingrowth and calcification of the valve graft. The valved bovine iliac veins presented calcification at the valve level and vein wall, as well as a valvelike calcific fibrous ridge at the proximal anastomosis with the right ventricle. The avalved bovine iliac veins also presented calcific deposits along the wall and a valvelike calcific ridge at the ventricular anastomosis. Histological and ultrastructural studies of the vein tunica media revealed the phenomena of inflammatory rejection and foreign body reaction with loss of smooth muscle cells (medionecrosis) and fibrotic replacement. In conclusion, bovine iliac veins undergo inflammation with medionecrosis indicating that smooth muscle cell antigenicity is not attenuated by glutaraldehyde fixation.
Sixty postmenopausal women were randomly assigned to three types of treatment with intranasal salmon calcitonin (SCT) plus calcium 500 mg daily (group A: 100 IU daily of SCT; group B: 100 IU daily of SCT for alternate cycles of 2 months with a 1-month interval; group C: 100 IU daily of SCT for alternate cycles of 3 months of treatment followed by a 3-month interval) or calcium 500 mg daily alone (control group). Lumbar density significantly decreased in the control group while it maintained the initial value in both continuously or cyclically treated groups. The bone density of the proximal and distal forearm in treated and control groups did not show significant changes after 12 months.
Accurate parameter estimation of allometric equations is a question of considerable interest. Various techniques that address this problem exist. In this paper it is assumed that the measured values are normally distributed and a maximum likelihood estimation approach is used. The computations involved in this procedure are reducible to relatively simple forms, and an efficient numerical algorithm is used. A listing of the computer program is included as an appendix.
Bovine pericardium has been widely employed as a xenograft tissue for the manufacture of bioprosthetic valve substitutes. Early three-leaflet valve models showed poor tissue preservation and shortcomings in valve design, which accounted for tissue wear and prosthesis failure due to cuspal tear. Reducing the number of cusps in the unicusp pericardial valve has proved unsuccessful due to stretching of the single pericardial leaflet with consequent valvular incompetence. The new generation of pericardial xenografts present basic changes in valve design and optimal tissue preservation after industrial processing, with no evidence of leaflet tear at medium term follow up. However, clinical experience is limited and, similarly to porcine xenografts, dystrophic calcification still appears to be a major problem.
Between 24 November 1977 and 16 September 1988, 18 consecutive chest wall resections for recurrent breast cancer after failure of radiotherapy, were evaluated as of 1 January 1990. Chest wall involvement was the only site of recurrence in 14 patients (Group I), and the most painful of the multiple recurrences in the remaining four (Group II). Of Group I, chest wall recurrence was local in eight patients (four with necrosis after radiotherapy), regional in four, and distant in two. Chest wall reconstruction was effected by contralateral breast flap in six, by random cutaneous flap in seven and by myocutaneous flap in the remaining five. Cosmetic results were better if both marlex mesh and myocutaneous flap were used. Of Group I, at surgical/pathological staging, one recurrence with sarcomatous findings, two multiple recurrences and residual cancer in all necrosed local recurrences were found: in three of these cases radionecrosis was prominent. Mortality was 0% and surgical morbidity 5%. For Group I, median disease-free interval from mastectomy was extended from 1611 days to 3220 by recurrence resection, and disease-free interval from chest wall resection was 28% cancer-free at 1657 days, without any difference between the local vs regional-distant recurrence. Correlation factor between first and second disease interval was 0.99 and R2 was 0.98. For Group II, survival was 0% at 635 days. Chest wall resection must be considered as an important part of palliative treatment in breast cancer, but the results reflects the biology of the disease more than the chest wall surgery.
Long-term experience with first generation porcine valve xenografts enabled identification of the major limitations to their durability: (1) prosthetic-ventricular mismatch due to the high profile of the stent in patients with mitral stenosis and a small left ventricle; (2) high-pressure fixation with loss of natural collagen crimping in the fibrosa, and wash-out of proteoglycans in the spongiosa; (3) xenograft tissue autolysis, due to the long interval between animal slaughter and aortic valve removal fixation; (4) muscle shelf in the right coronary cusp, which created a gradient and could undergo accelerated calcification and/or spontaneous perforation with time; (5) a flexible polypropylene stent, which could creep or even fracture with consequent inward bending of the stent; (6) progressive time-related dystrophic calcification; (7) host fibrous tissue ingrowth. An awareness of these limitations stimulated technical modifications, which frequently brought about distinct improvements: (1) the reduction of the stent profile eliminated the problem of mismatch, but resulted in a higher tendency towards cusp prolapse and earlier commissural tearing; (2) natural collagen waviness, proteoglycans and cusp extensibility were preserved by employing low or even zero pressure during the fixation process; (3) earlier valve fixation enabled preservation of cell integrity; (4) a new orifice for small valves was designed by replacing the right muscular cusp, thus achieving less gradient and avoiding muscle-shelf-related complications; (5) polypropylene was replaced by Delrin as stent material; (6) calcium-retarding agents like T6 and toluidine blue were applied during commercial processing and storage in order to mitigate tissue mineralization.(ABSTRACT TRUNCATED AT 250 WORDS)
Benefits of high-frequency audiometry in monitoring hearing sensitivity of patients administered ototoxic medications are well established. Thresholds obtained within a sound suite have been proven reliable. It may, however, often be necessary for the audiologist to evaluate the patient at bedside. The primary purpose of this study was to determine if significant differences are present between high-frequency thresholds measured in a sound suite versus thresholds measured in a hospital room. In addition, the test-retest reliability of high-frequency thresholds was determined when measured in a hospital room. For 25 normal hearing subjects, results revealed that significant differences were not observed between thresholds measured in a sound suite versus those measured in a typical hospital room. In addition, differences between the initial and repeated thresholds obtained in the hospital room were not significant, and the differences were, for the most part, within +/- 10 dB at all test frequencies.
Benefits of high-frequency audiometry in monitoring hearing sensitivity of patients administered ototoxic medications are well established. High-frequency thresholds have been reported to be variable, due in part to small differences in the placement of the earphone diaphragm over the opening of the ear canal. Reliability may be improved by using insert earphones (ER-2) when obtaining high-frequency thresholds. The purposes of this study were to determine high-frequency threshold test-retest reliability using Koss HV/1A+ and ER-2 earphones and to determine if significant differences are present between high-frequency thresholds obtained using these two earphones. Results obtained on 40 ears of 20 normal hearing adults revealed that differences between the test and retest thresholds for each earphone were not significant. Intrasubject threshold differences between the test and retest thresholds for each earphone were, for the most part, within +/- 10 dB at all test frequencies. Further, significantly greater intensity was required to measure threshold when using the ER-2 earphone when compared to the Koss HV/1A+ at all test frequencies.
A large segment of the hearing impaired population does not utilize amplification. this paper reviews several factors which may account for the under-utilization of hearing aids by the hearing impaired population. In addition, this paper reviews several recent developments in procedures used to select and fit hearing aids.
Loading of the fluorescent Ca2+ probe fura 2 in rat platelets is highly inhibited by a plasmatic factor that is removed by gel filtration through a Sepharose C-2B column. Rat plasma also inhibits fura 2 loading in human platelets. The inhibitory effect is abolished by perchloric acid-deproteinization or heat denaturation of plasma suggesting a proteic nature of the inhibitory compound. Indeed the 10,000 x g supernatant of the heat denaturated plasma shows a positive effect on fura 2 accumulation, most likely by partially inhibiting its cellular effux. These effects are only negligibly shown by the corresponding fractions of human plasma. Results obtained by fractionation of rat plasma proteins by means of ion exchange DEAE Sepharose C-6B chromatography and ultracentrifugation through high density saline solutions indicate that the inhibition of cellular fura 2 loading is due to the HDL fraction of rat plasma.
The laboratory findings in patients receiving high-dose vitamin A as adjuvant treatment for stage I lung cancer are here reported. A group of 283 patients were randomized to either treatment with retinyl palmitate (300,000 IU daily for 12 months) or standard follow-up, and are now evaluable after a median observation period of 28 months. At regular intervals, all the patients underwent a physical examination, chest roentgenogram, blood chemistries, haematological assays, hepatic and renal function tests and determinations of serum triglycerides and cholesterol. Serum transaminase abnormalities were of similar magnitude in cases and controls, while gamma-glutamyltransferase levels were abnormally elevated in 69% of the treated patients compared to 39% of controls (mean values 149 vs 57 IU/l at 24 months, P less than 0.05). Serum triglyceride concentrations over 150 mg/dl were seen in 74% of treated patients compared to 43% of controls at 12 months, the average concentration was 283 mg/dl compared to 179 mg/dl (P less than 0.05). Cholesterol levels showed a modest, non-significant rise with time in both groups, and there was no other laboratory evidence of toxicity attributable to vitamin A. Serum retinol and retinol-binding protein, assessed on a limited sample of patients, were higher in the treatment arm (P less than 0.05) at 12 months. In our experience 300,000 IU/day of retinyl palmitate can be administered as a possible chemopreventive agent with reasonable safety for up to 2 years.
Intratester test-retest reliability of the real ear unaided response (REUR) was determined on 49 ears using the Frye 6500 real ear analyzer. Results revealed mean differences of less than 1 dB for repeat measurements at seven test frequencies between 250 and 4000 Hz. The average peak resonant frequency of the repeated measure was within 16 Hz of the initial measure. In addition, the intersubject variability of the amplitude of REUR was quite large. A range of 7 dB was found at 250 to 500 Hz with the range expanding to 15 to 20 dB at 2000 to 4000 Hz. Also, the peak resonant frequency varied between 2100-4800 Hz. These results are discussed in terms of those dispensers who use the REUR to "custom" order hearing aids.
The paper reports on the efficacy and side effects of high-dose vitamin A, administered as adjuvant treatment for resected stage I lung cancer in a randomized clinical trial. After a median follow-up of 28 months, 283 patients were evaluable: 138 allocated to treatment with retinol palmitate (300,000 IU daily for at least 12 months) and 145 to standard observation. The clinical results available to date do well justify a continuation of the study. Skin dryness and desquamation were the most frequent symptoms, affecting 60% of all treated patients. Other symptoms such as dyspepsia, headache, nosebleeds and mild hair loss occurred in less than 10% of patients, and were self-terminating. Only in 4 patients (3%) was the treatment interrupted because of symptoms potentially related to vitamin A administration. As for laboratory tests, gamma-GT levels were abnormally elevated in 69% of treated patients vs. 39% of controls at 24 months (mean 149 vs. 58 IU/l; p less than 0.05). Serum triglyceride concentrations over 150 mg/dl were seen in 74% of treated patients vs. 43% of controls at 12 months (mean 283 vs. 179 mg/dl; p less than 0.05). There were no other laboratory signs of toxicity attributable to vitamin A. In our experience, high-dose retinoyl palmitate administration was a well-tolerated and safe treatment. The long-term impact on lipid metabolism still remains to be determined.