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Biomedical subjects

G B Stark

Publications and source records attributed to G B Stark.

At least 91 records · Page 5Linked to original sources
PubMed1989

[Results of the treatment of hepatic echinococcosis by hydatectomy].

In 72 patients with hydatid disease results and complications of different operation techniques are compared. Whereas we previously preferred pericystectomy and resecting methods we now perform irrigation and drainage in hydatid cysts of the liver. By use of a simple, flexible instrument even poorly accessible cysts can be transferred to irrigation and drainage therapy. Results of this procedure are good. The complication rate was decreased.

Adolescent↗
PubMed1989

Failed tissue expansion in a patient with osteogenesis imperfecta.

This is a report of a failure of tissue expansion in a 43-year-old patient suffering from a mild form of osteogenesis imperfecta tarda. Filling of the expander was not possible. Skin histology showed thrombosis of the blood vessels and vessel wall necrosis. This finding supports the theory that tissue expansion does not depend as much on mechanical skin laxity as on the proliferative potential of the skin.

Adult↗
PubMed1989

The influence of the calcium channel blocker nimodipine on flap survival.

The calcium channel blocker nimodipine has been used successfully in neurological patients for the treatment of vasospasm after subarachnoid hemorrhage and stroke. In this study of experimental random pattern skin flaps in rats, an increase of nearly 50% in the survival rate to 94.33% (+/- 7.3% standard deviation) under nimodipine treatment versus 66.00% (+/- 16.5% standard deviation) in the controls could be demonstrated (p less than 0.001). Vital dye injections in a separate experiment indicated that the increased flap survival is mainly due to improved microcirculation. The distance traveled by the dye was 8.01 +/- 1.21 cm in the experimental versus 6.61 +/- 1.25 cm in the control group (p less than 0.05).

Animals↗
PubMed1987

Rapid elongation of arteries and veins in rats with a tissue expander.

The saphenous arteries and veins of 40 rats were elongated with 20-cc tissue expanders underlying the leg adductor muscles. The mean rate of successful elongation of the vessels was 84 +/- 47 percent SD, with a maximum gain of 140 percent. The fastest mean elongation velocity reached 45 percent per day. Thrombosis occurred only with stretching velocities of more than 10 percent per day, which seemed to be a safe margin. Distribution of the volume into many intervals was safer than infrequent high-volume injections. Histology showed no reduction in vessel wall diameter or loss intimal integrity. Subendothelial cellular proliferation was an indicator of this rapid regeneration. Microvascular anastomoses performed in elongated arteries and veins had the same patency rate (90 percent) as in controls.

Animals↗
PubMed1987

Enhanced neovascularization of rat tubed pedicle flaps with low perfusion of the wound margin.

To study the role of ischemia due to low perfusion as the inciter of neovascularization, caudally based 3 X 9 cm skin flaps were created on the dorsum of 50 Sprague-Dawley rats. After injection of 0.2 ml 10% fluorescein, the animals were divided into two groups. In group I (n = 25), the distal margin of the flap tip was 1 cm proximal to the border of the fluorescence (good perfusion). In group II (n = 25), the flap was cut 1 cm distally in the nonfluorescent part (poor perfusion). The tips of the tubed flaps were transferred to a wound bed on the right flank. After 10 days, the pedicles were ligated, so that flap survival depended totally on the new vascular supply from the inset area of the flap. The flaps in group I showed a significantly higher rate of necrosis of 52.4 +/- 15.1 percent versus 1.7 +/- 1.4 percent in group II (p less than 0.0001), although the flap length in group I (5.85 +/- 1.16 cm) was less than in group II (7.15 +/- 0.95 cm; p = 0.0001). A nearly three times larger amount of tissue based on the new blood supply survived in group II compared to group I. Xerograms after injection of PbO2-gelatine on day 10 showed an increased ingrowth of blood vessels in group II. After excluding the delay phenomenon as the cause for the difference in necrosis rate, it is concluded that the only possible explanation is an enhancement of neovascularization by a perfusion gradient between the wound margins.

Angiography↗
PubMed1987

Elongation of axial blood vessels with a tissue expander.

The authors present a rat model and a surgical technique for the study of elongation of axial blood vessels using a tissue expander. The successful demonstration of elongation of axial vessels while maintaining patency further encourages use of the concept in other organ systems such as bowel, ureter, and so on.

Animals↗
PubMed1982

[Control of serum levels of tobramycin and amikacin during clinical routine treatment conditions (author's transl)].

576 serum levels at peak and before the next dosage (end level) were determined during clinical treatment conditions using radioimmunoassay in 131 patients treated with tobramycin or amikacin because of life-threatening infections. Only 42.8% of tobramycin serum peak levels were within the therapeutic range. 3.6% were potentially toxic, however, 53.6% were in a subtherapeutic range. After amikacin administration only 25% of serum peak levels were in a subtherapeutic range. 54.2% were therapeutic and 20.8% were potentially toxic. The main reason for increased peak and end serum levels was diminished renal function. Infusion treatment with more than 3 1/24 hrs lowered serum peak levels of tobramycin by 38% and of amikacin by 31%. Single doses of 80 mg of tobramycin lead to subtherapeutic concentrations too frequently, whereas single doses of 500 mg of amikacin too frequently lead to potentially toxic serum levels. Control of serum levels during aminoglycoside treatment is recommended particularly in patients at risk with life-threatening infections.

Amikacin↗
PubMedDate not supplied

Effect of ultrasonic assisted lipectomy (UAL) on breast tissue: histological findings.

As the use of ultrasound-assisted liposuction (UAL) increases, the technique grows more popular in breast surgery, especially in reduction mammaplasty and treatment of gynecomastia. The aim of our study was to investigate the effect of UAL on breast tissue using histological examinations, and analyze the effect of this technique on a cellular level. Biopsies from 10 patients undergoing ultrasonically assisted lipectomy prior to classic reduction mammaplasty were taken from the treated areas of the breast. Biopsies were fixed in formalin and embedded in paraffin. Sections were stained with hematoxilin-eosin, and analyzed for defective adipocytes, and the effects of UAL on breast tissue. Untreated breast tissue and breast tissue that had been treated only with conventional aspiration lipectomy served as controls. Sections were analyzed using light microscopy. Compared to the breast tissue treated only with conventional lipectomy, a stronger destruction of the cellular structure of adipocytes could be detected. The destruction was visible even in areas more distant from the aspiration channel. In contrast, the breast tissue was mostly intact, no signs of ultrasonic-induced cellular destruction were visible. The glandular structure was kept intact. Beside the direct mechanical destruction by the probe and the canula, no further alterations of the cellular integrity of the glandular parts were visible. In conclusion our results indicates that UAL is also a safe technique for use in breast surgery. Besides easy handling and improved modelling, the destructive effect of the ultrasound does not include the glandular breast tissue.

Breast↗
PubMedDate not supplied

Modulation of in vitro angiogenesis in a three-dimensional spheroidal coculture model for bone tissue engineering.

One of the major challenges in tissue engineering of bone substitutes remains vascularization of the transplant. We have developed a three-dimensional collagen-based coculture system to assess interactions between human endothelial cells (hECs) and human osteoblasts (hOBs) in vitro. Human umbilical vein endothelial cells (HUVECs) were grown as three-dimensional multicellular spheroids and seeded in a collagen matrix to assess sprouting of the spheroids, that is, formation of tubelike structures resembling early capillaries. Direct cell contact between hOBs and HUVECs was established by incorporating hOBs into the EC spheroids, thus forming heterogeneous cospheroids. Spatial organization of cospheroids and sprout configuration were assessed by immunohistochemical wholemount staining techniques and confocal laser microscopy. Cumulative sprout length of spheroids was quantitatively analyzed by digital imaging planimetry. In this model HUVECs and hOBs formed heterogeneous cospheroids with distinct spatial organization. The ability of HUVEC spheroids to form tubelike structures on angiogenic stimulation with vascular endothelial growth factor and basic fibroblast growth factor was suppressed in heterogeneous HUVEC/hOB cospheroids. The model system introduced in this study may be useful to assess the mechanisms involved in regulating angiogenesis during bone formation and to further investigate the mechanisms by which heterotypic cell-cell interactions inhibit endothelial tube formation for applications in bone tissue engineering.

Bone Substitutes↗
PubMedDate not supplied

Reconstitution of basement membrane after 'sandwich-technique' skin grafting for severe burns demonstrated by immunohistochemistry.

Reconstitution of basement membrane structures after "sandwich-technique" grafting of severe deep burns is demonstrated with use of immunohistochemical techniques. Cryosections of human skin after epifascial burn wound excision and sandwich grafting were stained with monoclonal antibodies against type IV and VII collagen, polyvalent antiserum against type VI collagen, and polyvalent antibody against laminin. Standard hematoxylin and eosin histologies were performed for morphologic correlation. Reorganization of the mesenchymal border zone (basement membrane), after transplantation of extremely expanded split-thickness skin autografts overlaid with glycerolized split-thickness skin allografts onto debrided human full-thickness wounds, occurred from day 5 to day 35. The autografts reepithelize the spaces between the mesh structure, which has been covered primarily exclusively with allogenic skin, and form a layered squamous epithelium, with an underlying three-dimensional basket-weave array of collagen in the remodeled neodermis after epifascial excision. Immunochemical techniques detect the reconstitution of a basement membrane zone with a typical architecture and distribution of laminin, type IV, and type VII collagen being built up 1 week to 5 weeks after sandwich grafting. These structures can be seen in the autografts during the first 2 weeks and are consistent in the whole reconstituted skin after day 35. To our knowledge this is the first report of the expression of type VI collagen in these types of wounds. The findings are compared with the expression of type VI collagen in healthy skin. The results indicate that the modified sandwich-grafting technique is an adequate means for early burn wound closure and resurfacing of third-degree burn wounds and leads to the reconstitution of dermal qualities.

Basement Membrane↗
PubMedDate not supplied

Radiologic findings in lymphangioma of the posterior tibial nerve.

A case of lymphangioma of the posterior tibial nerve is reported. MRI showed an elongated multiseptated cystic lesion along the tibial nerve leading to axonal degeneration and progressive left calf pain. A similar cystic lesion in a second patient was shown to be a ganglion. The diagnosis was made by surgical resection.

Adult↗
PubMedDate not supplied

Impact of electrical stimulation on three-dimensional myoblast cultures - a real-time RT-PCR study.

Several focal skeletal muscle diseases, including tumours and trauma lead to a limited loss of functional muscle tissue. There is still no suitable clinical approach for treating such defects. A promising approach could be the tissue engineering of skeletal muscle. However, a clinically reliable differentiation stimulus for three-dimensional (3-D) cultures is necessary for this process, and this condition has not yet been established. In order to quantify and analyze the differentiation potential of electrical cell stimulation, primary myoblasts were stimulated within a 3-D fibrin- matrix. Gene expression of MyoD, myogenin and AChR-epsilon were measured by real-time RT-PCR over a time period of eight days, showing immediate down-regulation of all marker genes. For tissue engineering approaches, cell multiplication is crucial for acquisition of sufficient tissue volumes for reconstruction. Therefore, all experiments were performed with high and low passaged myoblasts, demonstrating higher transcript rates of marker genes in lowpassage cells. Our findings strongly suggest a reconsideration of electrical stimulation in muscle tissue engineering.

Animals↗
PubMedDate not supplied

Evaluation of processed bovine cancellous bone matrix seeded with syngenic osteoblasts in a critical size calvarial defect rat model.

INTRODUCTION: Biologic bone substitutes may offer alternatives to bone grafting procedures. The aim of this study was to evaluate a preformed bone substitute based on processed bovine cancellous bone (PBCB) with or without osteogenic cells in a critical size calvarial defect rat model. METHODS: Discs of PBCB (Tutobone) were seeded with second passage fibrin gel-immobilized syngenic osteoblasts (group A, n = 40). Cell-free matrices (group B, n = 28) and untreated defects (group C; n=28) served as controls. Specimens were explanted between day 0 and 4 months after implantation and were subjected to histological and morphometric evaluation. RESULTS: At 1 month, bone formation was limited to small peripheral areas. At 2 and 4 months, significant bone formation, matrix resorption as well as integration of the implants was evident in groups A and B. In group C no significant regeneration of the defects was observed. Morphometric analysis did not disclose differences in bone formation in matrices from groups A and B. Carboxyfluorescine-Diacetate-Succinimidylester (CFDA) labeling demonstrated low survival rates of transplanted cells. DISCUSSION: Osteoblasts seeded into PBCB matrix display a differentiated phenotype following a 14 days cell culture period. Lack of initial vascularization may explain the absence of added osteogenicity in constructs from group A in comparison to group B. PBCB is well integrated and represents even without osteogenic cells a promising biomaterial for reconstruction of critical size calvarial bone defects.

Animals↗