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Biomedical subjects

M L Marin

Publications and source records attributed to M L Marin.

At least 19 recordsLinked to original sources
PubMed1992

Natural history, duplex characteristics, and histopathologic correlation of arterial injuries in a canine model.

The treatment of patients with penetrating extremity trauma in proximity to major arteries as well as the nonoperative treatment of clinically occult arterial injuries remain controversial. Duplex ultrasonography (DUS) has recently been advocated in this setting. We therefore studied experimentally induced arterial injuries in dogs to correlate the natural history, duplex findings, and histopathologic condition of different injuries and to help define criteria for operation. Fifty-two canine femoral and carotid arteries were randomized to have surgically created intimal flaps (n = 15), crush injuries (n = 15), or lacerations (n = 15) or to be controls (n = 7). An experienced sonographer, blinded to the presence or type of injury, evaluated the vessels every 10 days for 1 month. Histopathologic study was performed 1 month after injury when the arteries were retrieved. The sensitivity (96.5%), specificity (86.4%), and accuracy (95.1%) of DUS in evaluating arterial injuries at 1 month correlated well with histopathologic evaluation. All arteries subjected to crush injuries showed abnormal duplex findings. These findings correlated well with the histologic picture of severe injury (arterial wall thickness = 2.72 x +/- 0.23 x control; intramural hemorrhage, 93%; mural thrombus, 60%). DUS and histologic study revealed healing of intimal flaps in 27% of the arteries. Other intimal flaps deteriorated (stenoses, 47%; dilation, 13%; occlusion, 13%). Most lacerations (86%) revealed duplex evidence of healing within 10 days of injury. This was confirmed by histologic study at 1 month in 73% of lacerated arteries. This study confirms the accuracy of DUS in diagnosing various arterial injuries and shows that the natural history of these injuries varies with the mechanism of injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Human leukocyte A and B antigen, gene and haplotype frequencies in the population of the city of São Paulo in Brazil.

1. Antigen, gene and haplotype frequencies are important data for population analysis, paternity exclusion testing, genetic studies, and for organ transplantation selection. 2. We have studied the Class I histocompatibility antigens of 617 unrelated individuals from the city of São Paulo, Brazil, to determine antigen and gene frequencies of 16 HLA-A and 28 HLA-B antigens. Estimated haplotype frequencies were also determined, as well as the genetic distances of this population from European Caucasian and Negro populations. 3. A previously unknown linkage disequilibrium was detected for A23-B49 and a clear trend towards antigen frequencies intermediate between Caucasoid and Negro populations was observed.

Adult↗
PubMed1992

Unsuspected preexisting saphenous vein disease: an unrecognized cause of vein bypass failure.

Our prior anecdotal experience with unsuspected preexisting saphenous vein disease prompted us to study its incidence, its relation to graft failure, and to identify techniques for its detection. Thick-walled, postphlebitic sclerotic occluded, postphlebitic sclerotic recanalized, calcified, and varicose vein lesions were detected in 63 (12%) of 513 infrainguinal vein bypasses. In 13 (2% to 5%) cases, severe saphenous vein disease precluded use of the vein. In the remaining 50 cases, the entire vein or a portion thereof, with minimal or unsuspected disease, was used for bypass. Early graft failures occurred in 10 (20%) of the 50 cases. The cumulative primary patency rate at 30 months for bypasses performed with diseased veins was 32%. This was significantly less than the 73% cumulative primary patency rate for bypasses with veins without detectable disease (p less than or equal to 0.001). Retrospective evaluation of preoperative duplex ultrasonography (n = 21) originally used to evaluate saphenous vein length and diameter correctly identified thick-walled, occluded, calcified, and varicose veins in 62% of cases. Intraoperative methods of vein evaluation included inspection, palpation, irrigation, catheter or valvulotome insertion to identify obstruction, and intraoperative arteriography. Histologic examination of diseased veins demonstrated a spectrum of disease with thickening of the intima and media, vein wall calcification, and luminal recanalization. We conclude that (1) unsuspected preexisting saphenous vein disease occurs in approximately 12% of cases and results in both early and late graft failures; (2) detection, in some cases, is possible with duplex ultrasonography and intraoperative techniques; and (3) diseased veins that are recanalized, calcified, or thick-walled should not be used if an alternative vein is available.

Chi-Square Distribution↗
PubMed1991

Development of functional sex differences in the larynx of Xenopus laevis.

Three laryngeal properties associated with the production of masculine song--laryngeal muscle tension, fiber twitch type, and fiber recruitment--are markedly sexually dimorphic in adult Xenopus laevis frogs. To elucidate the pattern of sexual differentiation, tension and fiber recruitment in male and female larynges and fiber twitch type in male larynges were examined throughout postmetamorphic development. Masculinization of male laryngeal properties begins early in postmetamorphic development and continues until adulthood. In contrast, tension and fiber recruitment in females do not change after the end of metamorphosis. Laryngeal muscle tension and fiber type are gradually and progressively masculinized; the temporal pattern of masculinization is very similar for these properties. Fiber recruitment, on the other hand, appears to masculinize in a stepwise manner. Masculinization of all three properties is highly correlated with larynx weight in males. We have used this relation to divide postmetamorphic development into seven stages associated with key events in sexual differentiation. This staging scheme provides an important experimental tool for studying the hormonal regulation of sexual differentiation, the subject of the accompanying paper.

Animals↗
PubMed1991

Temporal constraints on androgen directed laryngeal masculinization in Xenopus laevis.

Temporal constraints on androgen regulated masculinization of three sexually dimorphic laryngeal properties--tension, fiber type, and fiber recruitment--were examined in Xenopus laevis frogs. Endocrine state was manipulated at PM0 when the larynx is similar in males and females, at PM2 when the larynx begins sexual differentiation, and at PM6 when sexual differentiation is complete. Removing the testes in developing males (PM0 or PM2) completely arrests laryngeal masculinization. Masculinization resumes when testosterone is replaced later in development (PM2 or PM6, respectively). Thus, testicular secretions, in particular androgens, are required for laryngeal masculinization. The ability of androgens to masculinize tension, fiber type, and fiber recruitment in developing and adult larynges was also determined. Five weeks of testosterone treatment in PM0 or PM2 males and females completely masculinizes laryngeal tension and fiber type, but only partially masculinizes fiber recruitment. However, fiber recruitment can be fully masculinized in PM6 males castrated at PM2. We conclude that androgen induced masculinization of tension and fiber type are not temporally constrained but that androgen induced masculinization of fiber recruitment is. Prolonged androgen treatment can override the temporal constraints on masculinization of the larynx. Testosterone treatment for more than 6 months fully masculinizes fiber recruitment in developing (PM0 or PM2) females. In addition, prolonged treatment (greater than 9 months) completely masculinizes tension, fiber type, and fiber recruitment in adult females; these properties were not fully masculinized by shorter (1-3 months) treatments in adult females. Testosterone induced masculinization in females is maintained for up to 8 months following testosterone removal; thus androgen effects are long lasting and possibly permanent.

Aging↗
PubMed1991

A ten-year experience with one hundred fifty failing or threatened vein and polytetrafluoroethylene arterial bypass grafts.

Between Jan. 1, 1980, and Dec. 31, 1989, 2187 infrainguinal revascularization procedures were performed. In 130 of these cases with patent bypasses, hemodynamic deterioration was suspected, and urgent arteriography was performed. Twenty additional patients with aortofemoral, femorofemoral, or axillofemoral bypasses demonstrated hemodynamic deterioration. In 93% of failing grafts the condition was suspected because of recurrent symptoms or changes in the pulse examination. Two hundred eighty-five high-grade stenotic or occlusive lesions were identified in inflow arteries, outflow arteries, within the graft, or at proximal or distal anastomoses associated with these 150 grafts. One hundred sixty-one (57%) of these lesions were in patients with failing vein grafts; 115 (40%) were in patients with failing polytetrafluoroethylene (PTFE) grafts; and 9 (3%) were associated with failing composite vein/PTFE grafts. Stenotic lesions less than 5 cm in length were initially treated with percutaneous transluminal balloon angioplasty (PTA). Occlusive lesions, stenoses greater than 5 cm in length, and PTA failures were treated surgically. The overall 6-year cumulative secondary patency rate for failing grafts was 65%, and the limb salvage rate was 75%. The extended patency rate after the first intervention in the failing state was 56% at 5 years. The 5-year secondary patency rate for grafts initially treated with PTA (58%) was not significantly different (p = 0.25) from that for grafts treated initially with surgery (71%). Percutaneous transluminal angioplasty was effective for inflow stenoses of the iliac, femoral, and popliteal arteries and for some outflow lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1991

Bronchogenic cyst: a case report emphasizing the role of magnetic resonance imaging.

The article describes a patient with a right paratracheal bronchogenic cyst in whom the preoperative diagnosis was unclear. The fluid component of the cyst was not readily apparent by CT or T1-weighted MR images. Very intense signal on T2-weighted MR images suggested a cystic lesion. Inhomogeneities evident on MR but not CT images provided further soft tissue characterization. These soft tissue elements correlated with a macroscopic ring of hyaline cartilage in the resected specimen. The usefulness of MRI for the differential diagnosis of mediastinal tumors is discussed.

Adult↗
PubMed1990

Immunomodulation of vascular endothelium. 1. Ultrastructural changes following ultraviolet B irradiation of peripheral veins.

Immunologic function of endothelial cells is especially important in consideration of vein allografting for arterial reconstruction and in organ allotransplantation. Ultraviolet B radiation (UVB) has previously been shown to modulate graft immunogenicity, and to alter cell surface receptor function. In this study, superficial epigastric veins were UVB irradiated with 10, 24, 40, 80, and 150 mJ/cm2 while control veins were not irradiated; all specimens were examined for endothelial ultrastructural changes. Veins were perfuse-fixed at 1, 3, 7, 14, and 28 days after irradiation, and were evaluated by transmission electron microscopy and scanning electron microscopy. Control veins had a normal appearing endothelial lining, composed of elongated, attenuated endothelial cells. Veins irradiated with more than 24 mJ/cm2 displayed injured endothelial cells characterized by altered microvilli, defects in the cell surface, and a change in cell shape. The degree of cell damage correlated closely with increasing UVB dose. At doses of 80 mJ/cm2 or greater there was moderate to severe endothelial cell separation from the underlying basement membrane and an increase in cellular lysosomes. The effects of UVB were maximal at 3 days with virtual recovery in resurfacing of all specimens with endothelium 28 days after irradiation. These data suggest that UVB has a dose-dependent effect on venous endothelium that is morphologically reversible with time. Cell membrane changes seen following exposure to UVB may contribute to altered cell surface receptor function.

Animals↗
PubMed1990

Hormone-sensitive stages in the sexual differentiation of laryngeal muscle fiber number in Xenopus laevis.

The number of muscle fibers in the vocal organ of the adult male African clawed frog, Xenopus laevis, exceeds that of adult females. This sex difference is the result of rapid fiber addition in males between the end of metamorphosis, post-metamorphic stage 0 (PM0) and PM2. At PM0, male and female frogs have similar numbers of laryngeal muscle fibers. Males then add more muscle fibers than females and achieve an adult value that is 1.7 times the female number. Males castrated at PM0 have the same fiber number as females. Ovariectomy at PM0 does not alter muscle fiber addition in females. Gonadectomy at PM2 has no effect on fiber addition in either sex. Females attain masculine muscle fiber number if their ovaries are replaced with a testis at metamorphosis. Exogenous testosterone treatment at PM0 significantly increases fiber number in females but not in males. Exogenous testosterone given at PM2 has no effect on fiber number in females but decreases fiber number in males. We conclude that the testes are necessary for the marked addition of laryngeal muscle fibers seen in male X. laevis between PM0 and PM2. The masculine pattern of muscle fiber addition can be induced in females provided with a testis. Androgen secretion from the testes most probably accounts for masculinization of laryngeal muscle fiber number. After PM2, androgens are no longer necessary for muscle fiber addition and cannot increase fiber number in females.

Androgens↗
PubMed1990

Immunomodulation of vascular endothelium: effects of ultraviolet B irradiation on vein allograft rejection.

Prosthetic grafts of vein allografts are inadequate as small-diameter vessel substitutes. We have applied ultraviolet B (UVB) irradiation to modulate the immunogenicity of vein allografts to avoid immunologic injury. The veins of male ACI rats were irradiated with UVB (60 mJ/cm2) in situ and transplanted to male ACI rats (autografts) and female Lewis rats (allografts). Nonirradiated veins served as controls. At 4, 7, 14, and 28 days, all grafts were patent and were studied for morphologic changes by scanning electron microscopy and for immunogold labeling of major histocompatibility complex class II antigen expression. In autografts, scanning electron microscopy demonstrated minimal endothelial loss after grafting, regardless of UVB irradiation. Untreated allografts showed severe endothelial injury 4, 7, and 14 days after transplantation. UVB irradiation of veins protected allografts from injury to the endothelium and basement membrane. Major histocompatibility complex class II-positive endothelial cells were not seen in autografts but were seen in 40% of cells 4 days after transplantation in untreated allografts. UVB-treated allografts showed MHC class II antigen expression labeling of 20% of the endothelial cells. Barr body analysis demonstrated the donor origin of these endothelial cells. UVB irradiation of rat vein allografts prolongs endothelial survival while decreasing endothelial surface expression of class II antigens. These data suggest that modification of vein immunogenicity with UVB irradiation may permit functional survival of small-vessel allografts without chronic immunosuppression.

Abdomen↗
PubMed1989

Elastofibroma dorsi: benign chest wall tumor.

Elastofibroma dorsi was diagnosed in seven patients at the Columbia-Presbyterian Medical Center between 1976 and 1986. The ages of the patients ranged from 6 to 79 years (mean 49.3 years). No sex predominance was seen. Five cases of unilateral subscapular tumor and two cases of bilateral masses were identified. Four patients had pain with arm motion, and the remaining patients were free of symptoms. A nonencapsulated soft tissue mass elevating the scapula was identified by computed tomography. Incisional biopsy was performed in all cases, followed by local excision of the tumor. On gross examination, these lesions were firm and rubbery. Histologic evaluation demonstrated a slightly hypercellular fibrous tissue that contained variable numbers of fragmented elastic fibers. All patients with symptomatic tumors had complete relief of their pain after the operation. No recurrences were observed. Clinically, elastofibroma may mimic sarcoma and fibromatosis (extraabdominal desmoid tumors). Whether elastofibroma is a true neoplasm or a reactive fibrous lesion that produces not only collagen, but also abnormal elastic fibers, has been the subject of controversy and remains undetermined.

Adolescent↗
PubMed1989

Immunomodulation of vascular endothelium: induction of Ia antigen expression in rejecting venous allografts.

MHC class II antigens (Ia) are important to the primary transplantation response. The present study investigates the kinetics of expression of Ia antigens on endothelial cells of rat vein autografts and allografts. The superficial epigastric veins of 15 ACI rats were anastomosed to the femoral artery of Lewis recipients using standard microsurgical technique. Eighteen Lewis-to-Lewis or ACI-to-ACI autografts served as controls. Veins were studied for Ia expression at 1, 4, and 7 days after grafting using the immunogold electron microscopic technique. All grafts remained patent for the duration of the experiment. Endothelial cells from control grafts did not demonstrate labeling of Ia antigens on their cell surfaces. Similarly, few mononuclear-adventitial cells in control grafts were Ia positive. When endothelial cells from vein allografts were studies for Ia antigen expression, 40% of the endothelial cells showed labeling for Ia at 4 days after transplantation. At 1 week following grafting, endothelial survival was inadequate for study because of cell loss secondary to rejection. In comparison to autografts, rejecting vein allografts showed numerous Ia-positive mononuclear cells permeating the vessel adventitia. Expression of Ia antigens by vascular endothelium may enable these cells to perform tasks traditionally ascribed to monocytes or dendritic cells. Effort to alter Ia expression may suggest an approach to long-term vein allograft survival.

Animals↗
PubMed1984

Freeze-fracture analysis of epithelial cell lysosomal inclusions in Crohn's disease.

Ileal epithelial cells from patients with Crohn's disease contain many large electron-dense lysosomal granules. Freeze-fracture electron microscopy was utilized to evaluate granule membrane ultrastructure and the interaction between granule contents and granule-limiting membranes. Large apical granules contained 0.1-0.6 micron vesicular inclusions as well as whorl-like myelin figures. The P-fracture face contained discrete membrane specializations on the granule surface that were composed of circular arrays of intramembranous particles. Areas of membrane devoid of intramembranous particles were also seen. These circular arrays and particle-poor regions resemble previously documented areas of membrane fusion. These results are discussed and a number of possible interpretations for their significance in terms of the pathogenesis of Crohn's disease are presented.

Adult↗
PubMed1983

A freeze fracture study of Crohn's disease of the terminal ileum: changes in epithelial tight junction organization.

Freeze fracture replicas of the plasma membrane and tight junctions of epithelial cells of the terminal ileum from 10 patients with Crohn's disease involving the small bowel and from the terminal ileum of two patients without inflammatory bowel disease were studied to determine if significant morphological variations could be documented. Samples of diseased tissue were taken from: 1) macroscopically normal ileal resection margins, 2) pinpoint aphthoid ulcers, 3) small 5 mm ulcers, 4) cobblestone mucosa. Samples of ileal mucosa from the proximal margin of ileocolic resections for carcinoma of the right colon were identically processed and served as controls. Control specimens showed normal villus structures lined by absorptive and goblet cells linked to adjacent cells by four to seven tight junction strands, arranged as an anastomosing network of fibrils oriented perpendicularly to the long axis of the cell. Crohn's disease specimens taken from the cobblestone area displayed the greatest degree of tight junction disorganization. Tight junctions commonly formed bizarre patterns, were fragmented, and often showed misalignment in a direction parallel to the cell axis. Specimens taken from areas 2 and 3 displayed a less severe form of tight junction rearrangement. Junctional strand fragmentations, as well as areas of plasma membrane lacking strands, were apparent. The resection margins had minor irregularities in junctional structure in some, but not all, cases. The predominant alteration in those cases which showed change was varying degrees of strand fragmentation. We postulate that the tight junction abnormalities of epithelial cells from the terminal ileum of patients with Crohn's disease may contribute to a disturbance in barrier functions.

Adult↗