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Biomedical subjects

B A Mast

Publications and source records attributed to B A Mast.

At least 19 recordsLinked to original sources
PubMed2001

Comparison of magnetic resonance angiography and digital subtraction angiography for visualization of lower extremity arteries.

Objective vascular assessment is frequently required before microvascular reconstruction involving the lower extremities. The purpose of this study was to evaluate the reliability of magnetic resonance angiography (MRA) for preoperative assessment before free flap surgery. Five patients underwent preoperative MRA: one before fibula harvest for oromandibular reconstruction, and four before muscle free flap reconstruction of the lower extremity. In all patients, the tibioperoneal trunk, anterior tibial, posterior tibial, and peroneal arteries were well visualized to the ankle, including pathological occlusions. The radiographic findings were demonstrated at surgery and were confirmed to be accurate. These findings facilitated and guided the surgical procedure. This study strongly suggests the accuracy and surgical relevance of MRA before free flap surgery. MRA is desirable over angiography because of its noninvasive nature. It may also be better than ultrasonography because the latter is highly dependent on the technician (particularly in identifying the peroneal artery). MRA may likely replace angiography as the objective procedure of choice before microvascular surgery.

Adult↗
PubMed2001

The nasolabial flap revisited as an adjunct to floor-of-mouth reconstruction.

Composite free tissue reconstruction for floor-of-mouth defects are thought of as single-stage procedures. However, postoperative wound complications often require additional soft-tissue coverage to salvage the initial reconstruction. Nasolabial flaps interpolated into the oral cavity offer an expedient solution to soft-tissue deficits encountered during complicated floor-of-mouth reconstructions. The records of 39 patients undergoing free tissue reconstruction, from July 1995 to December 1999 at Shands Hospital and the Gainesville VA Medical Center, for floor-of-mouth defects were reviewed. Six patients developed postoperative wound complications that compromised the initial reconstruction. In all patients, inferiorly based nasolabial flaps were used to provide additional soft-tissue coverage and wound closure. Radiation therapy and facial artery ligation did not affect the outcome. Complete wound healing and salvage of the initial reconstruction was achieved in all 6 patients.

Humans↗
PubMed1999

Keratinocyte collagenase-1 expression requires an epidermal growth factor receptor autocrine mechanism.

In response to cutaneous injury, expression of collagenase-1 is induced in keratinocytes via alpha2beta1 contact with native type I collagen, and enzyme activity is essential for cell migration over this substratum. However, the cellular mechanism(s) mediating integrin signaling remain poorly understood. We demonstrate here that treatment of keratinocytes cultured on type I collagen with epidermal growth factor receptor (EGFR) blocking antibodies or a specific receptor antagonist inhibited cell migration across type I collagen and the matrix-directed stimulation of collagenase-1 production. Additionally, stimulation of collagenase-1 expression by hepatocyte growth factor, transforming growth factor-beta1, and interferon-gamma was blocked by EGFR inhibitors, suggesting a required EGFR autocrine signaling step for enzyme expression. Collagenase-1 mRNA was not detectable in keratinocytes isolated immediately from normal skin, but increased progressively following 2 h of contact with collagen. In contrast, EGFR mRNA was expressed at high steady-state levels in keratinocytes isolated immediately from intact skin but was absent following 2 h cell contact with collagen, suggesting down-regulation following receptor activation. Indeed, tyrosine phosphorylation of the EGFR was evident as early as 10 min following cell contact with collagen. Treatment of keratinocytes cultured on collagen with EGFR antagonist or heparin-binding (HB)-EGF neutralizing antibodies dramatically inhibited the sustained expression (6-24 h) of collagenase-1 mRNA, whereas initial induction by collagen alone (2 h) was unaffected. Finally, expression of collagenase-1 in ex vivo wounded skin and re-epithelialization of partial thickness porcine burn wounds was blocked following treatment with EGFR inhibitors. These results demonstrate that keratinocyte contact with type I collagen is sufficient to induce collagenase-1 expression, whereas sustained enzyme production requires autocrine EGFR activation by HB-EGF as an obligatory intermediate step, thereby maintaining collagenase-1-dependent migration during the re-epithelialization of epidermal wounds.

Animals↗
PubMed1999

Functional outcomes of microsurgical reconstruction of delayed complications following head and neck cancer ablation.

Treatment of large and/or invasive head and neck cancers results in defects that are complex, such that immediate free tissue transfer provides the best functional outcomes. Consequently, delayed use of free flaps in such patients is seldom seen in today's practice. The purpose of this study was to analyze a recent experience of such delayed microsurgical procedures to evaluate their efficacy and outcomes. Between November 1995 and May 1997, 13 patients underwent free flap reconstruction of residual or secondary defects following initial head and neck cancer ablation. Preoperative status was categorized as open wounds in 8 patients, oral incontinence in 9 patients, poor speech in 5 patients, and difficulty swallowing in 7 patients. Microvascular reconstruction was performed for the mandible and floor of the mouth/chin in 7 patients, cervical esophagus in 2 patients, sinus cavity in 2 patients, and one patient each underwent microvascular reconstruction of the orbit and cranial base. The free flaps utilized were fibular osteocutaneous (N = 6), radial forearm fasciocutaneous (N = 2), rectus abdominis (N = 2), jejunum (N = 1), radial forearm osteocutaneous (N = 1), and serratus (N = 1). There were no flap failures and the overall complication rate was 62%. Functional outcomes were best for the static conditions of open wound and oral incontinence, each demonstrating a 75% and 78% substantial improvement respectively. Conversely, functional improvement in dynamic functions such as poor speech and difficulty swallowing fared less well. Only 60% of patients with poor speech and 14% with difficulty swallowing showed significant improvement despite aggressive speech and swallowing therapy. These data show that the functional outcomes of free flap reconstruction of delayed head and neck cancer complications are inferior to those expected with immediate reconstruction using free tissue transfer. Nevertheless, reconstruction can be very useful with a high likelihood of flap survival and patient improvement.

Adult↗
PubMed1999

Subtotal maxillectomy for melanotic neuroectodermal tumor of infancy.

Melanotic neuroectodermal tumor of infancy is a rare pigmented neoplasm occurring in infants before 1 year of age. It is a rapidly growing tumor that most frequently affects the craniofacial skeleton. Although melanotic neuroectodermal tumor of infancy is benign in the vast majority of cases, inadequate excision, occasional multicentricity, and a small malignant potential result in a fairly high recurrence rate. On the basis of data obtained from the literature and our clinical experience, we advocate an aggressive surgical approach consisting of complete surgical excision when vital structures are not involved. Histopathologic confirmation of complete excision is mandatory to minimize the risk of recurrence and provide the patient with curative treatment and minimal morbidity.

Humans↗
PubMed1999

Painful pectoralis major myospasm as a result of sternal wound reconstruction: complete resolution with bilateral pectoral neurectomies.

We report a patient with a highly unusual and previously unreported complication with the use of the pectoralis major muscle to treat the infected median sternotomy. The diagnosis of painful myospasm was made by a combination of physical findings and exclusion of other conditions such as recurrent infection. Treatment by pectoral denervation was relatively simple and highly successful. Patients with chest-wall pain after sternal wound reconstruction should have myospasm entertained as a possible cause.

Aged↗
PubMed1998

Tissue repair in the fetal intestinal tract occurs with adhesions, fibrosis, and neovascularization.

Cutaneous wound healing in the fetus can occur in a nonfibrotic, regenerative manner. However, other fetal tissues such as bone and stomach heal with scar formation. In light of potential ramifications for adult hollow visceral scarring (biliary and intestinal strictures), this study was undertaken to determine if tubular visceral tissue repair in the fetus is regenerative or fibrotic. Fetal rabbits underwent laparotomy on day 24 of gestation, during which a controlled intestinal enterotomy was created and suture repaired immediately using microsurgical techniques. Maternal rabbits and adult male rabbits also underwent enterotomy and repair. After 5 days all animals were sacrificed and the wounds analyzed histologically by a pathologist in a blinded fashion. All animals demonstrated a similar degree of peri-intestinal adhesion formation. Fetal and maternal wounds contained fibroblastic and smooth muscle cell proliferation, mild inflammatory infiltration, and new blood vessel formation. The male adult wounds demonstrated a more pronounced fibrovascular healing response. Immunohistochemical staining for CD31 (endothelial cell marker) was quantitated on a scale of 0 to 4+, indicating degree of neovascularization. The mean scores for the fetal and maternal groups were similar (1.70 +/- 0.68 and 1.23 +/- 1.07 respectively), but were significantly greater for male adults (2.93 +/- 0.12; p = 0.001 by analysis of variance). The results of this study indicate that hollow visceral tissue repair in the fetal rabbit intestine occurs in a similar fibrotic manner as adult healing. This provides further evidence that regenerative healing in the fetus is not ubiquitous. Differences in the degrees of fibrosis and neovascularization between adult male and pregnant female wounds deserve further investigation.

Animals↗
PubMed1997

Healing in other tissues.

Wound healing in many tissue types is essentially the same as that which occurs in skin. The repair processes that occur in bone, tendon, the alimentary tract, skin grafts, and bone grafts are substantially different from cutaneous wound repair. Because surgeons frequently encounter these tissues, it is essential to understand how they heal.

Anastomosis, Surgical↗
PubMed1996

Aggressive use of free flaps in children for burn scar contractures and other soft-tissue deficits.

Free flap reconstruction in children is often undertaken with trepidation due to a variety of perceived technical difficulties and variable reports of success. The present report examines the efficacy of free tissue transfer in children, with particular attention given to the use of fasciocutaneous flaps in burn reconstruction. Over a 12-year period, 38 free flaps were done on 30 patients with an average age of 10 years (range, 16 months-17 years). Twenty-five flaps were done for burn deformities; 6 were done for chronic back wounds; 2 each were done for chronic lower extremity wounds, lower extremity traumatic defects, and a craniofacial deformity; and 1 flap was done following the resection of a large thigh vascular malformation. The vast majority of the flaps (84%) were fasciocutaneous: 13 groin, 9 scapula, 5 radial forearm, and 4 others. The mean hospital stay was 10 days and there were 11 major complications (29%). Five of 6 flaps were salvaged by reoperation following vascular thrombosis. Six flaps were unsuccessful (84% total success). Three of these flaps were aborted intraoperatively due to technical difficulties, while 3 others were lost postoperatively due to cellulitis, thrombosis, and patient-inflicted flap removal. During follow-up (range, 1-103 months), 39% of patients underwent a minor secondary revision of the flap reconstruction. This series demonstrates the efficacy of free tissue transfer in children in providing the majority of these patients with a successful, one-stage reconstruction with morbidity similar to that reported for adult patients. Moreover, the use of fasciocutaneous free flaps for pediatric burn reconstruction is shown to provide a durable and aesthetically superior treatment of these difficult problems.

Adolescent↗
PubMed1994

Platelet-derived growth factor induces fetal wound fibrosis.

The fetal response to cutaneous injury differs markedly from that of the adult, proceeding with only minimal inflammation, minimal fibroblast proliferation, and only essential collagen deposition. Although the sequence of events in adult wound healing is well defined and thought to be controlled in part by potent polypeptide cytokines, relatively sparse information exists regarding growth factor involvement in fetal wound repair. Thus, the authors sought to examine the effect of platelet-derived growth factor (PDGF), a putative adult wound healing regulator, on the cellular and extracellular matrix events at a fetal wound site. SILASTIC wound implants containing 0, 1.0, 5.0, or 10.0 ng of human PDGF were placed subcutaneously on the backs of 24-day-gestation fetal rabbits (full term, 31 days) and then harvested after either 1, 3, or 5 days in utero. The specimens underwent standard histological processing and were evaluated in a blinded fashion. Compared with controls, PDGF-treated implants had a marked increase in acute inflammation, fibroblast recruitment, and collagen and hyaluronic acid deposition; these differences appeared to be largely time- and PDGF dose-dependent. Thus, the fetal system is responsive to an adult wound healing mediator, and these data suggest that fetal repair proceeds in the absence of PDGF.

Animals↗
PubMed1993

Hyaluronic acid modulates proliferation, collagen and protein synthesis of cultured fetal fibroblasts.

Fetal wound healing is characterized by minimal inflammation, mild fibroplasia and rapid, but organized collagen deposition such that scarring is not apparent. The matrices of fetal wounds differ greatly from adult wounds in that fetal wounds are persistently enriched with hyaluronic acid (HA). It has been shown that a reduction in fetal rabbit wound HA results in an adult-like healing response with increased fibroplasia and neovascularization. These observations suggest that HA can modulate cellular activity in fetal repair. Therefore, this study was designed to define the effect of HA on fetal fibroblast function. Fibroblasts from the skin of fetal rabbits were isolated and maintained in culture medium containing either no HA (controls), 1 microgram/ml, 10 micrograms/ml or 100 micrograms/ml of HA (n = 6 for each group). Fibroblast proliferation was quantitated by DNA content in each culture, and collagen and noncollagen protein synthesis were analyzed by incorporation of [3H] proline into collagenase-digestible and collagenase-nondigestible protein, respectively. At all concentrations tested, HA significantly inhibited fetal fibroblast proliferation (p < 0.02), but stimulated collagen (p < 0.002) and noncollagen protein (p < 0.005) synthesis. These findings provide further evidence that HA affects the function of fetal fibroblasts. Moreover, this study in conjunction with previous in utero findings suggests that HA may have a regulatory influence in scarless fetal healing by affecting cellular function during the repair process.

Animals↗
PubMed1992

Biology of fetal wound healing: collagen biosynthesis during dermal repair.

The rapid restoration of tissue integrity and breaking strength in healing fetal wounds is mainly a function of fetal wound collagen. In this study, the fetal and adult tissue responses to injury were characterized in terms of changes in collagen biosynthesis. Linear wounds and unwounded skin were incubated with radioactive proline, and collagen synthesis was measured as isotope incorporation into collagenase-sensitive protein. Likewise, noncollagen protein synthesis was represented by isotope incorporation into collagenase-resistant protein. Adult wounds demonstrated a preferential stimulation of collagen as compared with noncollagen protein synthesis after wounding. In contrast, both collagen and noncollagen protein synthesis were significantly elevated in the fetus during the first 5 days postwounding. Despite marked increases in fetal wound collagen synthesis above both unwounded fetal skin and adult wound levels, fetal wounds exhibited no evidence of excessive collagen deposition or scar formation after wounding. These findings suggest that the fetal response to tissue injury is a function of the distinctive qualities of fetal fibroblasts associated with the extracellular wound matrix and may involve rapid collagen turnover and degradation.

Animals↗
PubMed1992

In vivo degradation of fetal wound hyaluronic acid results in increased fibroplasia, collagen deposition, and neovascularization.

Fetal tissue repair occurs without acute inflammation, prominent fibroplasia, or marked neovascularization. The fetal wound extracellular matrix is rich in hyaluronic acid (HA), while collagen is deposited in an organized normal dermal pattern. In various biologic systems, including regeneration and development, the controlled accumulation and subsequent degradation of hyaluronic acid is associated with distinct cellular and matrix events. Therefore, it is hypothesized that the abundance of hyaluronic acid in fetal wounds may influence cellular and/or matrix events such that tissue repair is highly organized and adult-like scarring does not occur. To test this hypothesis, the hyaluronic acid content of fetal rabbit wounds was reduced by specific degradation with Streptomyces hyaluronidase. Control wounds were treated with either enzyme buffer (n = 12) or denatured enzyme solution (n = 8) and exhibited a normal fetal healing response with scattered peripheral fibroblasts, a matrix of hyaluronic acid, and no infiltrating collagen. In marked contrast, the hyaluronidase-treated wounds (n = 14) demonstrated increased fibroblast infiltration, collagen deposition, and capillary formation. A significant reduction in the hyaluronic acid content of the hyaluronidase-treated wounds was confirmed biochemically. Since the degradation of hyaluronic acid resulted in an altered healing response, this study demonstrates that hyaluronic acid affects the cellular and matrix events in fetal healing and may be partially responsible for the unique qualities of this regenerative repair process.

Animals↗
PubMed1992

Scarless wound healing in the mammalian fetus.

Fetal wound healing is a remarkable process that is fundamentally different than postnatal healing. Healing of primarily closed, linear wounds occurs rapidly and without scarring. In late gestational age fetal sheep, a transition to adult-like healing occurs as evidenced by minimal scar formation. Acute inflammation is not involved, fibroblast recruitment and proliferation is minimal, the matrix of the wounds is enriched with HA and collagen deposition is highly organized so that scarring is minimal or nonexistent. Open wounds in several species do not contract, an observation that may be because of an inhibitor of contraction in amniotic fluid. The underlying mechanisms that regulate fetal wound repair are currently not well understood. An altered supply or activity of growth factors may be instrumental. Fibroblasts may preferentially produce HA secondary to a factor present within the fetal system, and HA may influence cellular and matrix events within the wound. As greater knowledge of the biologic factors of scarless healing in the fetus is gained, applications to abnormal adult healing may be developed. As the age of fetal surgery is approaching, it is essential to understand the injury response in these new patients.

Adult↗
PubMed1991

Hyaluronic acid is a major component of the matrix of fetal rabbit skin and wounds: implications for healing by regeneration.

The extracellular matrix (ECM) of fetal rabbit wounds contains an abundance of the glycosaminoglycan hyaluronic acid (HA) but is devoid of excessive collagen. Thus, fetal wounds heal without scarring, such that tissue repair grossly resembles regeneration. To obtain further insight into the process of fetal wound healing, the ECM of normal fetal rabbit skin was analyzed, thus providing a comparative endpoint for the ECM of healing fetal wounds. Similarities between the matrices would support the theory of healing by regeneration. The glycosaminoglycan (GAG) component of fetal rabbit skin from 24- and 29-day gestational age fetuses was extracted and then quantitated using an alcian blue binding assay. The extracted GAG was characterized by cellulose acetate electrophoresis and HA was identified by its selective digestion by Streptomyces hyaluronidase. The mean GAG content, measured as ng GAG per mg dry weight skin, was 260 +/- 200 for the 24-day group (n = 28) and 280 +/- 220 for the 29-day group (n = 26). The only GAG identified at both times of gestation was HA. This study has demonstrated that HA is the predominant GAG present in fetal rabbit skin and its quantity is stable during the period studied late in gestation. A major component of the ECM of both wounded and normal fetal skin is HA, indicating a close compositional similarity. These observations provide biochemical support for the hypothesis that the reparative process of injured tissue in the fetal rabbit proceeds in an attempt to reconstitute normality, i.e. regeneration.

Animals↗
PubMed1990

Use of gastrointestinal contrast studies in obstruction of the small and large bowel.

Gastrointestinal contrast studies were performed in 96 (27 percent) of 342 patients with small-bowel obstruction including 57 upper gastrointestinal and 39 barium-enema examinations. In 34 patients, upper gastrointestinal examination disclosed either obstruction or failure of contrast to reach the cecum in 24 hours; all 34 patients required surgery. The remaining 23 patients who had upper gastrointestinal studies recovered with tube decompression. Barium enema demonstrated obstruction in 13 (33 percent) of 39 cases of suspected small-bowel obstruction and localized obstruction in the colon rather than small bowel in 9 of 13 cases. Barium enema was 100 percent predictive of surgery when obstruction was shown, but was not helpful in predicting surgery when obstruction was not demonstrated. Surgery was required in 42 percent of patients whose barium enema did not show obstruction. Barium enema also was performed in 19 of 23 patients with large-bowel obstruction and showed the level of obstruction in all cases. All patients with large-bowel obstruction required surgery except for three who recovered after barium-enema reduction of intussusception or volvulus. Barium upper gastrointestinal examination is recommended in small-bowel obstruction when plain films are nondiagnostic, and in selected cases of small-bowel obstruction that do not resolve with a short trial of tube decompression. Barium enema is not recommended in suspected small-bowel obstruction but should be performed in all cases of large-bowel obstruction, except when perforation is a possibility or when the cecum measures 10 cm or larger in diameter.

Barium Sulfate↗