Biomedical subjects

J W Siebert

Publications and source records attributed to J W Siebert.

At least 37 records · Page 2Linked to original sources

PubMed1995

Transient postoperative stenosis in small-vessel anastomoses.

Using a newly developed Doppler probe, we have found that a standard suture anastomosis in a rat femoral artery is accompanied by significant (30-60%) cross-sectional area stenosis, which dissipates to baseline levels within 24 hours. We hypothesized that spasm, deposition of coagulation products, or the suture technique itself was responsible. Topical vasodilators (papaverine, sodium nitroprusside, lidocaine) and intravenous thromboxane A2 synthetase inhibitor and receptor blocking agent (Ridogrel, 4 mg/ml), anticoagulants heparin and SC4992 (an experimental platelet inhibitor/arginine-glycine-aspartic acid analogue), were administered. No drug had any significant effect on preventing postoperative stenosis. Varied suture bites affected stenosis measurements. Scanning electron microscopy and light microscopy displayed "bunching" of vessel wall in the suture ties. This was confirmed with methyl methacrylate corrosion casts and microangiography. "Sham" anastomoses also produced stenosis, which was relieved when sutures were removed. We conclude that suture anastomosis of small vessels is accompanied by significant cross-sectional stenosis caused by the physical action of tensioned sutures. This effect dissipates over a 24-hour postoperative period. The mechanism behind these changes and the clinical importance of this effect are still under investigation.

Anastomosis, Surgical↗

PubMed1995

Microvascular free-flap correction of severe hemifacial atrophy.

Romberg's disease is a progressive hemifacial atrophy of unknown etiology. Microsurgical reconstruction, focusing on the correction of facial asymmetry and restoration of contour, has become the "gold standard." We report our experience with 15 patients involving 16 free-tissue transfers with a minimum of 1 year of follow-up who were treated from July of 1989 to January of 1993. All patients were classified as having severe atrophy. There were 7 males and 8 females in the series. Distribution of disease was a coup de sabre type or segmental pattern in 6 patients, whereas 9 patients had a hemifacial distribution. Fourteen patients had unilateral disease (7 right and 7 left), and 1 patient had bilateral atrophy. The average age of onset of disease was 11.9 years. The average duration of atrophy was 6.7 years. No patient was operated on with a quiescent interval of less than 2 years. Average age at operation was 28.7 years, with a range from 6 to 46 years. Follow-up ranged from 1 to 4.5 years. Two patients had facial hematomas as the only complication. No flaps were lost. Flap revisions consisting of minor contour corrections were performed in 10 patients. Limited recurrence of facial atrophy was seen in a single patient 2 years postoperatively. All patients rated their improvement as excellent. The deepithelialized extended parascapular flap with large fascial extensions of dorsal thoracic fascia is our procedure of choice. This fascia can be folded into variable thicknesses to correct subtle contour defects of the upper lip, medial canthus, eyelids, and ear that have reportedly been difficult to reconstruct.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

The in vivo effect of hyaluronan associated protein-collagen complex on wound repair.

Fetal skin wounds heal without scarring, however the underlying mechanisms remain unknown. Immunohistochemical staining and biochemical studies indicate the deposition of a collagen repair matrix that is highly organized. We have previously described a unique hyaluronan associated protein-collagen complex (HA-PC) profile present during the period of scarless healing in the sheep fetus. In this study, we examined the biologic activity of this HA-PC in an in vivo model of adult rat wound repair. A total of 84 incisional and 84 excisional wounds were examined by histology, TGF-beta immunocytochemistry and computer planimetry (excisional wounds only). Planimetry of the excisional wounds demonstrated the mean wound area remaining at day 1 was 88.7% for the control and 63.6% for the treated (p<0.01). At day 2, mean wound area was 81.5% for the control and 63.6% for the treated (p<0.01). At day 4, mean wound area was 56.6% for the control and 41.9% for the treated (p<0.01). At day 7, mean wound area was 26.9% for the control and 16.8% for the treated (p<0.01). At day 14, mean wound area was 7.9% for the control and 3.4% for the treated (p<0.05). Collagen organization was judged to be greater in the treated compared to control wounds, with a mean organization score of 2.3 vs. 1.9 (p=0.0596; Wilcoxon Signed Rank Sum Test). There were significantly more neutrophils at the wound margin of the treated compared to control wounds, 4.0 vs. 2.7 (p=0.038; Paired Two Tailed Student's t-Test). There was no difference in the number of microphages at the wound margin of the treated compared to control wounds, 6.15 vs. 6.0 (p>0.05). TGFbeta1 and beta2 staining was decreased whereas TGFbeta3 staining was increased in the HA-PC treated wounds. These results suggest that compared to control wounds HA-PC treated wounds heal more quickly, with more organized collagen, more neutrophils at the wound margin and increased TGFbeta3 expression. Furthermore, these data suggest that the manipulation of scarring in adult wounds is possible by the addition of proteins present in fetal skin.

Animals↗

PubMed1994

Improved technique for rodent microarteriography.

We have developed new techniques in rodent microarteriography which provide excellent two-plane views of the rat femoral artery. These techniques employ routine mammography film and equipment for imaging as well as standard intravenous catheters for vascular access. The use of mammographic equipment provides high quality, finely detailed, orthogonal X-ray images. The elective outpatient nature of mammography allows microsurgical investigators convenient access to the necessary equipment without interfering with patient care. The standard intravenous catheters permit easy and inexpensive vascular access via the contralateral femoral artery. The technique avoids the more invasive thoracic and abdominal aortic approaches without compromising X-ray image quality. Additionally, the same rat can be imaged multiple times if care is taken to repair the vascular access route.

Anastomosis, Surgical↗

PubMed1994

Prefabricated flap size limitations utilizing an omental carrier.

Several researchers and clinicians have taken advantage of the omentum's rich vascular arcades to support skin grafts. We have previously described an experimental model using the omentum as a vascular carrier for prefabricated free flaps in the rat. In this study, we used this model to compare three different sizes of free flaps using the same size omental carrier. Twenty-four male Sprague-Dawley rats were used for this study. A 2.5 x 4 cm patch of omentum with gastroepiploic vessels and its rich vascular arcades was transferred under a bipedicled 2.5 x 6 cm (group I), a 2.5 x 8 cm (group II), and a 4 x 10 cm (group III) right abdominal panniculocutaneous flap. On the seventh postoperative day, the skin pedicles were divided and the skin flap raised as a composite island flap vascularized only by the underlying omental patch. The composite flap was then sutured back in place. Prefabricated flaps examined 7 days postoperatively demonstrated a dye florescence index percent (DFI) of 38.19 +/- 7.52 and 98.13 +/- 3.72% flap survival (FS) in the 6 x 2.5 cm skin flap group; a DFI of 39.96 +/- 6.81% and FS 94.88 +/- 7.08% in the 8 x 2.5 skin flap group (P > 0.05) and a DFI 29.71 +/- 2.85% and FS 57.06 +/- 9.52% in the 10 x 4 cm skin flap group (P < 0.05). India ink injection study and histologic examination confirmed revascularization of the overlying skin at 7 days. This study confirms that omentum can be used as a vascular carrier for prefabricated flaps. However, there is a limit to the size of the flap. A 10 cm2 carrier can support 57% of a 40 cm2 (10 x 4 cm) flap for a total area of 22.8 cm2, more than twice the area of the carrier.

Animals↗

PubMed1994

Breast capsule contracture: is fibroblast activity associated with severity?

Factors responsible for breast capsule contracture remain elusive. Using an in vitro model of wound contraction, the fibroblast-populated collagen lattice (FPCL), breast capsule fibroblasts and control dermal fibroblasts from ten patients were analyzed. Comparison was made to determine (1) if the activity of dermal fibroblasts on a collagen lattice correlated with the activity of breast capsule fibroblasts or if capsular fibroblasts are unique, and (2) if the degree of fibroblast-driven collagen contraction correlated with clinical severity of breast capsule contracture. If so, a preoperative predictor of breast capsule contracture would be available. Dermal fibroblasts and breast capsule fibroblasts were cultured and mixed with media and collagen to form a matrix, and then the degree of lattice contraction was measured. A correlation between breast capsule fibroblasts and control dermal fibroblasts with respect to collagen matrix contraction was confirmed. Collagen lattice contraction coordinated by fibroblasts derived from breast capsules did not correlate with clinical severity of capsular contracture. These results indicate that the degree of breast capsule contracture can not be predicted by fibroblast activity alone. An interaction between inflammatory cells, extracellular matrix, and fibroblasts is hypothesized. Further work is needed to delineate the mechanisms responsible for breast capsule contracture.

Breast↗

PubMed1994

Microvascular anastomoses utilizing new intravascular stents.

Evolving microsurgical technique has allowed for the anastomosis of smaller diameter vessels. Standard suture anastomoses cause a measure of stenosis and intimal damage during application and therefore cannot be dependably used in the anastomosis of very small vessels. We developed and tested a fibrin glue-based anastomosis applied over a meltable stent made of mono- di- and tri-glycerides. In vivo rodent studies using the 0.35 mm diameter inferior epigastric artery have shown immediate and short-term patency rates better than those associated with suture technique. The stent technique is significantly faster and easier than the suture technique. The glyceride stent method suffers from decreased late patency due to aneurysm formation. In addition, we developed a glyceride-coated polyethylene glycol-based stent for use in lasered anastomoses. Work on both projects is ongoing.

Anastomosis, Surgical↗

PubMed1994

Fetal fibroblast contraction of collagen matrices in vitro: the effects of epidermal growth factor and transforming growth factor-beta.

Wound contraction is an important component of healing but, in the extreme, may lead to excessive scar formation and pathological wound contracture. Fetal rabbit wounds heal without contraction or scarring, whereas excisional fetal sheep wounds have been shown to contract, but no scarring or pathological wound contracture is noted. We used an in vitro model, the fibroblast-populated collagen lattice, to study the ability of fetal fibroblasts to coordinate contraction of a collagen matrix and the modulating effects of epidermal growth factor and transforming growth factor-beta 1 on this contraction. With increasing gestational age, fibroblasts increased the degree of collagen lattice contraction. Epidermal growth factor inhibited contraction by fetal fibroblasts, whereas transforming growth factor-beta 1 stimulated it. These findings suggest that while intrinsic differences between fetal and adult fibroblasts exist, polypeptide growth factors may operate at the site of tissue repair to alter cell phenotype. Further work is underway to delineate the role of soluble protein factors responsible for the absence of scarring and contracture seen in the fetal wound.

Animals↗

PubMed1994

Microvascular free-flap salvage of the diabetic foot: a 5-year experience.

This study reviews 21 microvascular free flaps to the diabetic foot in 19 patients over a 65-month period. All flaps were either to the plantar surface of the foot or to cover exposed Achilles tendon. Twenty of the flaps survived. The operations required a long, costly hospitalization with frequent recipient- and donor-site complications. All patients eventually ambulated on their flaps. Five patients came to proximal amputation from 6 to 37 months after surgery. Only one amputation was for flap breakdown.

Adult↗

PubMed1993

Successful microvascular replantation of a completely amputated ear.

A case of successful microvascular replantation of a traumatically amputated ear is presented. The postoperative course was complicated by venous thrombosis requiring the use of medicinal leeches and systemic heparinization for salvage. This is the tenth successful microvascular ear replantation reported in the literature.

Adult↗

PubMed1993

Comparison of the effects of interleukin-1 beta on proteoglycan synthesis by human skin and post-burn normal scar explant cultures.

The effect of interleukin (IL)-1 beta on proteoglycan (PG) synthesis and secretion, into culture medium by normal human skin and post-burn human normal scar using tissue explants in culture, was investigated. Following exposure of different tissues to labeling with Na2[35SO4] in the presence and absence of IL-1 beta, the extractable [35SO4]PG (isolated from 0.15 M NaCl and 4 M Gdm. Cl extracts), non-extractable [35SO4]PG (isolated after papain treatment of residual tissue), and [35SO4]PG secreted into culture medium were analyzed for contents and distribution. The contents of [35SO4]PG as measured by [35SO4] incorporation indicate differences in [35SO4]PG production of extractable and non-extractable PGs and also in the PGs released into the culture medium. Examination of the sizes of [35SO4]PGs on Sepharose CL-6 beta columns with and without treatment of IL-1 beta shows that the size of non-extractable [35SO4]PG decreases after IL-1 beta treatment. Cellulose acetate plate electrophoresis of these [35SO4]PG fractions shows that the distribution of PGs alters after treatment with IL-1 beta. These results indicate that burn wound healing abnormalities (scarring) is related to a change in the level of PGs, and may be modified by IL-1 beta treatment.

Adolescent↗

PubMed1993

Serial quantitation of hyaluronan and sulfated glycosaminoglycans in fetal sheep skin.

Fetal wounds are abundant in hyaluronic acid (HA), but little is known as to the total HA content of fetal tissues as a function of gestational age. Previous studies demonstrated scarless healing prior to approximately 130 days gestation, after which disorganized collagen deposition became prevalent. Glycosaminoglycans (GAGs) have been shown to play an important role in wound healing, cytodifferentiation, and morphogenesis. In this study, we examined the HA and GAG content of fetal sheep skin of increasing gestational age. We found that the total amount of HA and GAGs declined from a high at 80 days gestation (528 +/- 9 micrograms/gm) to a low at 130 days (174 +/- 11). Analysis of the various GAG species revealed that HA comprised the largest fraction (75-96%). The sulfated GAGs, Heparan Sulfate (HS) and Dermatan Sulfate (DS), were not present in the extracellular matrix until 120 days gestation. Both the trough of HA content and the appearance of sulfated GAGs in the extracellular fraction correspond to the appearance of scarring in fetal sheep wound repair.

Animals↗

PubMed1992

Prefabrication of free flaps using the omentum in rats.

The omentum used as a vascular carrier is a new experimental model for prefabrication of free flaps in the rat. A 2.5 x 4 cm patch of omentum with gastroepiploic vessels and its rich vascular arcades was transferred under a bipedicled 2.5 x 6 cm right abdominal panniculocutaneous flap. At subsequent time intervals (postoperative days 0, 3, 5, 7, and 14), the skin pedicles were divided and the skin flap was raised as a composite island flap vascularized only by the underlying omental patch. The composite flap was then sutured back in place. Prefabricated flaps examined postoperatively demonstrated a dye fluorescence index (DFI) of 4.60% +/- 2.82% and 1.67% +/- 4.08% flap survival (FS) in the day 0 group; in the day 3 group, 9.83% +/- 1.47% of DFI and 15.00% +/- 10.35% of FS; in the day 5 group, 28.39% +/- 5.25% of DFI and 86.0% +/- 12.74% of FS (P less than 0.05); in the day 7 group, 38.19% +/- 7.52% of DFI and 98.13% +/- 3.72% of FS (P less than 0.05); and, in the day 14 group, 49.55% +/- 6.70% of DFI and 100% of FS (P less than 0.05). India-ink injection and histologic examination confirmed revascularization of the overlying skin by day 5.

Animals↗

PubMed1992

The effect of tissue expansion on dermal fibroblast contraction.

Tissue expansion alters the function of skin cells. We studied the effects of expansion on the contractile function of dermal fibroblasts using an in vitro model, the fibroblast-populated collagen lattice (FPCL). Spherical expanders were placed dorsally in 30 Sprague-Dawley rats; one-half were serially inflated. One, 2, and 4 weeks later, 5 rats from each group were killed. Fibroblasts were cultured from dermis overlying the expanders and mixed with collagen, medium, and serum in petri dishes to form FPCL. Fibroblasts from 5 rats that had not undergone surgery were cultured to make control FPCL. Contraction was assessed by measuring the areas of the FPCL. At 48 hours, FPCL containing expanded fibroblasts had contracted significantly less than those containing unexpanded or control fibroblasts. Four weeks of expansion resulted in less contraction than 1 or 2 weeks. Tissue expansion inhibits the in vitro contractile function of dermal fibroblasts in the rat in a time-related fashion.

Animals↗

PubMed1992

Isolation and partial characterization of hyaluronan-protein-collagen complex (HA-PC) from fetal sheep skin of different gestational ages.

Hyaluronic acid (HA) has a positive effect on cell migration, differentiation and wound healing. Earlier work from our laboratory has shown the presence of biologically active proteins associated with HA. The protein associated with HA of fetal sheep skin varies in molecular weight depending on its gestational age. Specifically, the protein profile changes at 125 days of gestation, from a 60 KDa protein to a smaller protein of about 21 KDa. This time period coincides with the time that scarring becomes apparent in fetal sheep skin wounds. In this study, we have quantified changes in the proteins associated with HA with increasing gestational age, obtained amino acid profiles of these proteins with increasing gestational age, and proposed the existence of an HA-associated protein-collagen complex (HA-PC) which may serve as a scaffold for wound healing. Our results indicate that HA-PC content decreases from 42% of the dry weight at 75 days of gestation to 22% at 125 days of gestation. Protein content, in contrast, increases to 40% of the dry weight at 140 days of gestation. At the same time, collagen content increases from < 1% of the dry weight at 75 days to > 10% at 140 days. The increase in collagen content may account for the increase in total protein seen at 140 days. The expression of varying HA-PC's at different gestational ages may influence the kinetics of collagen fibrillogenesis and thus account for the previously noted late gestational change from "scarless" wound healing to "adult-like" wound healing in fetal sheep.

Amino Acids↗

PubMed1991

Simultaneous comparison of pre- and post-microanastomotic hemodynamic profiles using a Tandem Doppler Probe.

The use of High-Frequency Pulsed Doppler Ultrasound (HFPDU) for evaluation of microvascular hemodynamics is well established. Due to technical limitations of existing probes, quantitation of anastomotic stenoses and detailed waveform analyses are difficult to perform and impractical for clinical use. We present a new Tandem Doppler Probe (TDP) for simple and accurate study of blood flow in vessels smaller than 1 mm in diameter. Its unique ability to compare the pre- and post-anastomotic waveforms simultaneously allows for quantitative detection of anastomotic narrowing of as little as 5%, as well as identification of subtle pathologic anastomotic waveform changes not seen with single probes. Such early and precise delineation of anastomotic problems in the operating room can provide an invaluable, objective assessment of the technical adequacy of the anastomoses as well as an important baseline for later post-operative monitoring of free-tissue transfers with implantable Doppler devices.

Anastomosis, Surgical↗

PubMed1991

A new technique for microvascular sleeve anastomosis.

This study describes our experience using an improved technique for microsurgical sleeve anastomosis of arteries. Modifications of previously described techniques include utilization of a sidecut and placement of the two stitches within separate vertical planes. In 40 arteries, we attained a patency rate of 97.5%. Histology, in vivo observation, and flow study using high-frequency pulsed ultrasound Doppler at 2 hr to 8 weeks demonstrate that the sidecut sleeve anastomosis shows patency and flow characteristics similar to those of standard end-to-end anastomosis, but with a dramatic decrease in operative time.

Anastomosis, Surgical↗

PubMed1991

A new vascularized bone graft for scaphoid nonunion.

Nonunion and avascular necrosis after scaphoid fractures continue to be problem sequelae because of unrecognized injuries, inadequate immobilization techniques, or insufficient treatment time. Screw fixation and inlay bone grafting techniques remain the options of choice, with successful union reported in approximately 90% of patients. However, prolonged immobilization with plaster up to 4 to 6 months is required with conventional techniques. With the use of standard latex injection techniques with vascular filling of vessels to less than 0.1 mm diameter in ten fresh cadaver dissections, we discovered a consistent vascularized bone graft source from the distal dorsoradial radius. We have used this vascularized bone graft source with good results in eleven patients with long-standing nonunion of the scaphoid. It is technically easy and seemingly offers the advantages of a decreased period of immobilization and a higher union rate.

Adolescent↗