Biomedical subjects

M T Longaker

Publications and source records attributed to M T Longaker.

At least 19 recordsLinked to original sources

PubMed1992

Large induction of keratinocyte growth factor expression in the dermis during wound healing.

Recent studies have shown that application of basic fibroblast growth factor (basic FGF) to a wound has a beneficial effect. However, it has not been assessed whether endogenous FGF also plays a role in tissue repair. In this study we found a 160-fold induction of mRNA encoding keratinocyte growth factor (KGF) 1 day after skin injury. This large induction was unique within the family of FGFs, since mRNA levels of acidic FGF, basic FGF, and FGF-5 were only slightly induced (2- to 10-fold) during wound healing, and there was no expression of FGF-3, FGF-4, and FGF-6 detected in normal and wounded skin. High levels of FGF receptor 1 and FGF receptor 2 mRNA and low levels of FGF receptor 3 mRNA were found in both normal and wounded skin. No change in the levels of these transcripts was detected during wound healing. In situ hybridization studies revealed highest levels of KGF mRNA expression in the dermis at the wound edge and in the hypodermis below the wound. In contrast, mRNA encoding the receptor of this growth factor (a splice variant of FGF receptor 2) was predominantly expressed in the epidermis. These results suggest that basal keratinocytes are stimulated by dermally derived KGF during wound healing and implicate a unique role of this member of the FGF family in wound repair.

Animals↗

PubMed1992

New techniques in fetal surgery.

Optimal fetal management during and after fetal surgery has been limited by an inability to reliably monitor the fetal heart rate and temperature, and by a lack of access to the fetal circulation. In order to solve these problems, we used early third trimester fetal sheep to develop: (1) an implantable radiotelemetry device that transmits the fetal electrocardiogram and temperature, and (2) an intraosseous access technique. A miniaturized radiotelemeter was implanted subcutaneously in the axilla of four fetal sheep. Safe implantation of the radiotelemeter was technically feasible and the device reliably recorded the fetal electrocardiogram and temperature both intraoperatively and postoperatively. Although many possible routes for access to the fetal circulation have been tried experimentally and clinically for both resuscitation and blood sampling, none have proven satisfactory. We assessed the use of intraosseous access in fetal sheep (n = 6) for both infusion and blood sampling. Access with an intraosseous needle was obtained in both sheep fetuses and human fetal cadavers. Blood gas values (pH, PCO2, and PO2) obtained from the medullary cavity of fetal sheep accurately reflected peripheral venous values. Resuscitation drugs reached the fetal circulation via the intraosseous route: sodium bicarbonate elevated venous bicarbonate levels from 28.4 +/- 1.7 to 31.8 +/- 2.1 mEq/dL (P < .05); injected glucose increased venous glucose levels by 520 +/- 108 mg/dL (P < .01); and injection of calcium chloride elevated venous calcium levels from 11.8 +/- 0.7 to 15.2 +/- 2.2 mEq/dL (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Necrotizing fasciitis in two children with acute lymphoblastic leukemia.

Necrotizing fasciitis is a severe, soft tissue infection, and is an unusual condition in children. The cornerstone of therapy is prompt, aggressive surgical treatment. Despite vigorous treatment, mortality rates are high. We report the occurrence of necrotizing fasciitis in two children during the granulocytopenic phase of induction chemotherapy for acute lymphoblastic leukemia. The diagnosis and treatment of necrotizing fasciitis in these two children was made more difficult by their underlying disease and its chemotherapy. The successful treatment of their infections relied on a multimodality approach. Aggressive surgical debridement was the mainstay of therapy. Adjuvant therapy was vital to the successful outcomes and included meticulous wound care, intravenous hyperalimentation, appropriate antibiotics, and granulocyte transfusions.

Agranulocytosis↗

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

Scarless fetal healing. Therapeutic implications.

The purpose of this report is to call attention to the fetal wound healing process as a blueprint for ideal tissue repair. Wound healing in the fetus is fundamentally different from healing in the adult. Fetal tissue repair occurs rapidly and in the absence of scar formation. Because scarring and fibrosis dominate some diseases in every area of medicine, an understanding of fetal wound healing should help develop therapeutic strategies to avert the devastating consequences of excessive scar formation.

Adult↗

PubMed1992

An in utero model of craniosynostosis.

To define better the pathophysiology of craniosynostosis, we developed an in utero model in rabbits. Premature fusion of the sutures was achieved by osteoinduction using demineralized bone matrix (DBM). Thirty-six fetuses from 18 time-dated pregnant rabbits underwent coronal strip craniectomies and implantation of DBM at 25 days of gestation (term = 31 days). Seventeen (47%) survived vaginal delivery and 10 (28%) survived for long-term follow-up. Surviving, operated animals demonstrated bony fusion across the coronal sutures presumably due to osteoinduction by the DBM. Coronal computed tomographic scans with sagittal reconstructions revealed that experimental animals had taller and wider skulls than nonoperated control animals. We conclude that employing DBM to create craniosynostosis in the fetal rabbit is technically feasible. Such a model may be used to more clearly define the pathophysiology of craniosynostosis and to evaluate methods of treatment.

Animals↗

PubMed1992

A model for fetal cleft lip repair in lambs.

Fetal wounds heal without inflammation and scar formation. This phenomenon may, in the future, be applicable to human cleft lip and palate repair. However, extensive experimental work must first be done to document the benefits of in utero repair. We developed a large animal model for creation and repair of a complete cleft lip and alveolus using fetal lambs. The cleft lip and alveolus deformity was created in eight 75-day-gestation fetuses (term = 145 days) and either repaired in three layers or left unrepaired. There were four sham-operated fetuses, and all animals were alive at harvest. Repaired, unrepaired, and control fetuses were harvested at 7, 14, 21, and 70 days following surgery. The unrepaired fetuses demonstrated a complete cleft lip and alveolus with an oronasal fistula. The maxilla was asymmetrical, with the greater segment deviated toward the cleft and with decreased anterior maxillary width. In contrast, repaired cleft lip and alveolus animals showed no scar, normal thickness of the lip, and a symmetrical maxilla. Histologic analysis of the repaired wounds showed evidence of tissue regeneration without scar formation. The results of this preliminary study indicate that the fetal lamb cleft lip and alveolus model is technically feasible with an excellent survival rate. Healing occurs without scar formation. In the repaired animals, the maxilla was symmetrical. This model will be used to document facial growth following in utero repair of a cleft lip and alveolus.

Alveolar Process↗

PubMed1992

Scarless wound repair: a human fetal skin model.

Animal studies demonstrate that the fetus heals cutaneous wounds by reformation of normal tissue architecture without scar formation. We have developed a new model to study human fetal skin wound healing. Grafts of human fetal skin placed onto athymic mice retain the morphologic features of normal development, although they differentiate at an accelerated rate when placed cutaneously compared to subcutaneously. Full-thickness skin grafts from human fetuses at 15 (n = 12), 17 (n = 11), 18 (n = 25), 19 (n = 20) and 22 (n = 13) weeks gestational age were placed onto athymic (nu/nu) mice in 2 locations: (1) cutaneously onto a fascial bed and thereby exposed to air or (2) subcutaneously in a pocket under the murine panniculus carnosus. Linear incisions were made in each graft 7 days after transplantation. Grafts were harvested at 7, 14 and 21 days postwounding and analyzed histologically for scar formation. By hematoxylin & eosin and Mallory's trichrome stains, complete epidermal and dermal graft wound healing without scar formation was demonstrated in the subcutaneous grafts at each gestational age studied. In contrast, scar was seen at all time points in the cutaneous grafts in both the incisional wound and at the interface of the fetal human skin graft and adult mouse skin, regardless of fetal skin gestational age.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1992

Endoscopic creation and repair of fetal cleft lip.

In utero repair of several life-threatening malformations in the human fetus is now a clinical reality, yet fetal surgery still poses significant risks to both the mother and the unborn child. Preterm labor is a major problem and is directly related to the large hysterotomy required for fetal exposure. Endoscopic surgical manipulation of the fetus, through small uterine "ports," solves this problem and may eventually permit fetal intervention for non-life-threatening malformations. In this pilot study we demonstrated the feasibility of performing endoscopic surgery on the fetus in situ. A lip incision was created and repaired using endoscopic microsurgical techniques in midgestation fetal lambs. This represents the first application of this technique for in utero fetal intervention.

Animals↗

PubMed1992

Fetal fracture healing in a lamb model.

A large animal model to assess fetal fracture repair and the ability to close excisional bony defects is presented. Incisional and excisional ulnar fractures were made in 14 midgestation fetal lambs, harvested at serial time points, and subjected to high-resolution low-kilovolt magnification radiographs, magnetic resonance imaging scans, and histologic analysis. Fetal fracture healing was characterized by early closure of excisional defects and rapid fracture healing with minimal or no soft-tissue inflammation or callus formation. Magnetic resonance imaging scans of the fractures revealed a characteristic pattern compatible with the histologic findings, namely, minimal inflammation in soft tissue adjacent to the fracture site. Histologic and magnification radiographic findings indicated that complete bony repair occurred within 21 days in incisional defects and within 40 days in excisional defects. In both cases, healed fetal bone resembled normal bone matrix. Excisional defects, including periosteum, of greater than three times the width of the bony cortex closed rapidly with virtually normal-appearing bony matrix and with minimal or no callus formation.

Animals↗

PubMed1991

Hyaluronidase levels in urine from Wilms' tumor patients.

The pathophysiology of Wilms' tumor is associated with major alterations in hyaluronic acid metabolism. Elevated levels of both hyaluronic acid and a hyaluronic acid-stimulating activity occur in the urine and serum of patients with this tumor. In the current study, we describe elevated levels of urinary hyaluronidase in five patients with Wilms' tumor. Following surgical removal of the tumor, enzyme levels decreased toward normal. Characterization of enzyme activity indicates that hyaluronidase may be produced by the tumor itself. Alternatively, normal renal tissue may also be producing enzyme in a compensatory response to the elevated hyaluronic acid levels in these patients. We suggest that urinary hyaluronidase can be used as an additional marker for Wilms' tumor.

Biomarkers, Tumor↗

PubMed1991

Intraoperative radiation therapy for Wilms' tumor in situ or ex vivo.

Patients with bilateral Wilms' tumor who have local recurrence after undergoing maximum-dose multitechnique therapy are problematic. The role of surgery in the management of these patients is changing from ablation to preservation of renal tissue. Bilateral nephrectomy is reserved as a last resort. Intraoperative radiation therapy (IORT) is advantageous to conservative management, as illustrated by the current cases of two children with recurrent Wilms' tumors in their remaining kidneys. Both children underwent limited surgery and precisely directed IORT. In one patient the nephron-sparing surgery and IORT were performed in situ. In the other the kidney was removed, treated with ex vivo bench surgery and radiation surgery, and then reimplanted. The adjuvant use of IORT, either in situ or ex vivo, in nephron-sparing surgery permits complete obliteration of gross and microscopic disease while maximizing residual renal function.

Child↗

PubMed1991

Maternal outcome after open fetal surgery. A review of the first 17 human cases.

A few fetal diseases may benefit from surgical treatment before birth, but hysterotomy and subsequent delivery by cesarean section pose a risk to the otherwise unaffected mother. To assess maternal risk of mortality, morbidity, and reproductive potential after fetal surgery, we reviewed our experience with 17 highly selected women who underwent fetal surgery. Fifteen of these procedures were performed for one of two congenital anomalies: severe bilateral hydronephrosis and congenital diaphragmatic hernia. There were no deaths or serious maternal injuries. In the 14 women who continued pregnancy after hysterotomy, uterine irritability and preterm labor were frequent complications, requiring early confinement in most cases. There has been no detectable effect on future fertility, as indicated by eight subsequent normal pregnancies. We conclude that hysterotomy for fetal surgery can be accomplished without unduly endangering the mother's life or her future reproductive potential. However, morbidity related to premature labor remains a serious problem, and our ability to control uterine contractions after hysterotomy remains the limiting factor in human fetal surgery.

Adolescent↗

PubMed1991

Sheep amniotic fluid has a protein factor which stimulates human fibroblast populated collagen lattice contraction.

Sutured incisional wounds made in fetal sheep and rabbits heal without scarring. Fetal sheep excisional wounds can close by contraction, but those in fetal rabbits do not. In vivo and in vitro evidence suggests that rabbit amniotic fluid inhibits wound contraction. The question arises: does sheep amniotic fluid promote wound contraction because their fetal wounds close by contraction? Sheep amniotic fluid (SAF) from 100 and 125 days gestation was tested in fibroblast populated collagen lattice (FPCL) system, an in vitro model of wound contraction. SAF stimulated FPCL contraction in a dose responsive manner. SAF from a 100 day fetus was more stimulating than a 125 day SAF. SAF enhanced FPCL contraction in the presence or absence of serum. SAF was fractionated by size, using column chromatography. It yielded a fraction with an estimated molecular weigh near 40,000 daltons, which stimulated FPCL contraction. The factor was inactivated by proteolytic digestion and heat denaturation. This protein fraction which stimulates FPCL contraction is not related to 1) actin-myosin filaments enhanced contraction by ATP-induced cell contraction, 2) promotion of fibroblast elongation on glass surface or in collagen, or 3) increased cell number by enhanced fibroblast duplication in a collagen matrix. A mechanism for SAF promotion of FPCL contraction was investigated but not identified.

Adenosine Triphosphate↗

PubMed1991

Hyaluronic acid in a cardiac myxoma: a biochemical and histological analysis.

Cardiac myxoma is the most common primary tumor of the heart. This tumor has a gelatinous stroma that is thought to be composed of glycosaminoglycans, the classical acid mucopolysaccharide ground substance. We examined both biochemically and histologically the hyaluronic acid in a case of cardiac myxoma using a newly developed hyaluronic acid-binding protein probe. We observed that hyaluronic acid was localized in the amorphous stroma and occurred at levels 30 times that found in normal atrial septum.

Heart Neoplasms↗

PubMed1991

In utero arterial embolism from renal vein thrombosis with successful postnatal thrombolytic therapy.

Thromboembolic events in the pediatric age group occur most commonly in neonates, and newborns of diabetic mothers are particularly at risk. We report a newborn with right renal vein and inferior vena cava thrombosis who apparently embolized across the foramen ovale antenatally with resultant right brachial artery occlusion. The baby was delivered by cesarean section from an insulin-dependent diabetic mother. At the time of birth, there was severe right arm ischemia with absent brachial and radial pulses. There was clinical evidence of distal embolization with a "trash" lesion of the distal right middle finger as well as a midforearm area of full-thickness skin loss. Ultrasound demonstrated a right renal vein thrombosis and a 95% occlusion of the inferior vena cava. Regional urokinase therapy was instituted through a lower extremity vein with a 5,000 U/kg bolus and then 5,000 U/kg/h continuous infusion. Twelve hours of infusion of urokinase led to clinical resolution of the right arm ischemia, with return of pulses. Follow-up ultrasound showed the right renal vein thrombosis and inferior vena cava clot to be completely resolved. The right middle finger and forearm lesions subsequently have healed primarily. We report this as a case of in utero arterial embolization with successful postnatal therapy using regional urokinase infusion.

Arm↗

PubMed1991

Ontogeny of fetal sheep polymorphonuclear leukocyte phagocytosis.

Premature infants and neonates are vulnerable to bacterial sepsis. This susceptibility may be due to the relative immaturity of their immune systems. To determine if neonates and, in particular, premature infants have decreased polymorphonuclear leukocyte (PMN) phagocytosis, we tested PMN phagocytosis of Staphylococcus aureus as a function of gestational age in the fetal lamb model. Because phagocytosis is made more efficient by the presence of opsonins in plasma, fetal and postnatal PMN phagocytosis were also measured after exposure to fetal and adult plasma. PMNs were isolated from fetal lambs at 104, 114, 124, and 141 days' gestation (term gestation for the fetal lamb is 145 days), as well as from 10-day-old neonatal sheep and adult sheep. Labeled S aureus were opsonized by incubation in either fetal or adult plasma, or left unopsonized for baseline values. Phagocytosis was measured as a percent of adult PMN phagocytosis after adult plasma opsonization. It was found that fetal PMN function is limited by two factors during the early third trimester: a primary defect in the ability of the PMN to phagocytose S aureus despite adequate opsonization, and the diminished ability of autologous fetal plasma to opsonize bacteria. The defect in PMN phagocytosis disappears late in the third trimester, but the inability of the fetal plasma to opsonize effectively continues until after birth.

Age Factors↗

PubMed1991

Midgestational excisional fetal lamb wounds contract in utero.

Clinical observations and experimental data suggest that fetal wound healing is very different from adult wound healing. An understanding of the biology of scarless fetal wound healing has tremendous clinical potential for modulating postnatal wound problems. In this study, the fetal lamb model was used to assess excisional fetal skin wound contraction in utero. Full-thickness 9-mm punch biopsy wounds were created on fetal lambs at 100 days' gestation (term, 145 days). Half of the wounds remained exposed to amniotic fluid, whereas the other half were covered by a silastic patch to exclude amniotic fluid. Wounds were harvested 3, 7, or 14 days later and wound areas were calculated. Exposure to amniotic fluid retarded wound contraction significantly at 3 days, but by 14 days all wounds had completely contracted and reepithelialized. Myofibroblasts are an important cellular element of wound contraction. The presence of wound myofibroblasts was documented by both transmission electronmicroscopy and immunocytochemistry with antimuscle actin antibody. It is concluded that fetal lamb wounds contract in utero and exposure to amniotic fluid appears to retard fetal skin wound contraction only during the early healing process.

Amniotic Fluid↗