Biomedical subjects

H G Machens

Publications and source records attributed to H G Machens.

At least 19 recordsLinked to original sources

PubMed2006

The influence of medium composition and matrix on long-term cultivation of primary porcine and human hepatocytes.

The differentiated hepatocyte phenotype remains difficult to maintain in culture. The duration over which phenotypically stable hepatocytes can be cultured ranges from a couple of days to a few weeks. Shortcomings in medium formulation may be a factor in this lack of success. We have investigated effects of medium formulation on primary porcine and human hepatocyte cultures. We tested seven culture medium compositions (DMEM, ExCell 400, HepatoZYME-SFM, L-15 Leibovitz, SF-3, Waymouth, and Williams' E) and the effects of serum, fibronectin and biomatrix in a sandwich culture configuration. Albumin, urea, cholesterol, GOT, GPT, LDH and triglyceride concentrations were measured over 14 days. For both human and porcine cultures, the best results were obtained with SF-3 medium. Cells cultivated with Williams' E medium and FCS had good morphology and synthetic function during the first days of culture. However, continued addition of serum, was associated with a subsequent loss of differentiated phenotype. Addition of fibronectin was associated with improved function in cultures maintained in SF-3 medium whilst biomatrix had no effect. In contrast, addition of fibronectin did not influence cultures maintained in Williams' E medium, but cultures with biomatrix were associated with improved function at longer time points.

Animals↗

PubMed2005

A technique to detect and to quantify fasciocutaneous blood vessels in small laboratory animals ex vivo.

PURPOSE: A microangiographical technique is described, which allows visualization of small and capillary blood vessels and quantification of fasciocutaneous blood vessels by means of digital computer analysis in very small laboratory animals. MATERIALS AND METHODS: The left carotid artery of 20 nu/nu mice was cannulated (26 gauge) and a mixture of gelatin, bariumsulfate, and green ink was injected according to standardized protocol. Fasciocutaneous blood vessels were visualized by digital mammography and analyzed for vessel length and vessel surface area as standardized units [SU] by computer program. RESULTS: With the described microangiography method, fasciocutaneous blood vessels down to capillary size level can be clearly visualized. Regions of interest (ROIs) can be defined and the containing vascular network quantified. Comparable results may be obtained by calculating the microvascular area index (MAI) and the microvascular length index (MLI), related to the ROIs size. Identical ROIs showed a high reproducibility for measured [SU] < 0.01 +/- 0.0012%. CONCLUSION: Combining microsurgical techniques, pharmacological knowledge, and modern digital image technology, we were able to visualize small and capillary blood vessels even in small laboratory animals. By using our own computer analytical program, quantification of vessels was reliable, highly reproducible, and fast.

Angiography↗

PubMed2005

[A microangiography technique to quantify fasciocutaneous blood vessels in small laboratory animals].

PURPOSE: A microangiographic technique is described, which allows visualization of small blood vessels with a diameter of approximately 20 microm and quantification of fasciocutaneous blood vessels by means of digital computer analysis in very small laboratory animals. METHOD: The left carotid artery of 45 nu/nu mice was cannulated (26 gauge) and a mixture of gelatine, barium sulfate and green ink was injected according to standardized protocol. Fasciocutaneous blood vessels were visualized by digital mammography and analyzed for vessel length and vessel surface area as standardized units (pixel) by computer program. RESULTS: With the described microangiography method fasciocutaneous blood vessels can be clearly visualized. Regions of interest (ROIs) can be defined and the containing vascular network quantified. Identical ROIs showed a high reproducibility for measured unit (pixel) < 6.5 +/- 2.4 %. By the use of digital image, processing the quantification of vessels was reliable, reproducible and fast. CONCLUSION: Combining microsurgical techniques, pharmacological knowledge and modern computer imaging analysis systems, we were able to visualize and quantify blood vessels with a diameter of approximately 20 microm even in small laboratory animals.

Angiography↗

PubMed2002

Hydroxyethyl starch does not cross the blood-brain or the placental barrier but the perineurium of peripheral nerves in infused animals.

Therapy with hydroxyethyl starch (HES) is associated with a high incidence of persistent pruritus due to HES storage in cutaneous nerves. Up to now it has been unknown if HES also accumulates in the extracutaneous peripheral or central nervous system. To study this, five rats including one pregnant one were infused with a single dose (34-150 mg) of HES (70/200/450 kDa molecular weight) conjugated with fluorescein isothiocyanate (FITC). In addition, four sheep were infused with a cumulative dosage of 30 g, 120 g, and 420 g HES (200 kDa), respectively. After 7-13 days, biopsies from the adult rats, four fetal rats and sheep were taken from various organs. The specimens were analyzed by light, electron, and confocal laser scanning microscopy. Typical HES storage vacuoles were found in macrophages of the skin, liver, spleen, lung, and kidney. HES storage in healthy animals was not associated with signs of either inflammation or apoptosis contrary to a previously described animal hemorrhagic shock model. Beyond that, fetus biopsies did not show any storage phenomenon, confirming that HES does not cross the placental barrier. Deposits of HES could be detected in Schwann cells of cutaneous nerve fibers as well as in perineural and endoneural cells of sciatic nerve in one rat (HES 450 kDa) and three of four sheep. No HES storage was found in the central nervous system. Our findings clearly demonstrate that storage of HES is detectable only in small peripheral nerves, suggesting a cutaneous origin of the HES-induced pruritus.

Animals↗

PubMed2001

Computer-guided microsurgery: surgical evaluation of a telerobotic arm.

A new telerobotic arm was evaluated in different microsurgical procedures. The system consisted of a robotic arm bearing a microsurgical forceps controlled by a joystick-like master unit operated by the surgeon's hand. The robotic arm functioned as an operating as well as assisting instrument. Advantages of the system were its precise functioning, which was especially important when tissue or instruments had to be held for a longer period of time, as well as its ability to replace an assisting person to some extent. Deficiencies of the system were its 10-min startup, the spatial conflict with in the operative field, and the poor rotation of the robotic tip. In some procedures, the telerobotic arm could replace the standard microsurgical instrument guided by the surgeon's second hand; in other maneuvers it could function as the surgeon's third hand with precision and void of tremor.

Anastomosis, Surgical↗

PubMed2001

[Value of EEG monitoring in intensive care patients in plastic surgery--indications and experiences].

EEG monitoring can be performed at the patients' bedside and it is a valuable support in therapeutic decision making providing unique information about the functional state of the brain. Due to newer technical developments, EEG monitoring can be conducted rather easily. In this article, indications for EEG monitoring in plastic surgical patients are presented: controlling the level of sedation, use in states of increased intracranial pressure, screening the cerebral state in comatose patients, diagnosis and therapy of epileptic seizures, and the search for circumscribed cerebral abnormalities. Furthermore, practical experience with the use of the new EEG monitor Narcotrend, which is provided with an automatic EEG classification, is described.

Cerebral Cortex↗

PubMed2000

[Gene therapy possibilities in plastic surgery].

Advances in gene technologies have meanwhile reached plastic surgery. Important contributions in this field (which are not all included in the paper) come not only from plastic surgeons, but also from neighboring specialities like dermatology, trauma surgery, orthopedics and vascular surgery. The uniting principle for all this work is improving wound healing and reconstructing tissue defects taking into consideration functional and aesthetic aspects. Gene-therapy is gaining further importance in the clinical field of plastic surgery. In this regard, every clinician has to be aware of the fact that progress in experimental and experimental-clinical work will be achieved only with the help of basic science. On the other hand, basic science needs the clinical input to get relevant patient-oriented studies started. Further intensive cooperation between clinicians and basic scientists is therefore mandatory. In plastic surgery, 2 years ago we founded a forum called ECSAPS (European Conference of Scientists and Plastic Surgeons), which takes place in European city every year.

Animals↗

PubMed2000

[Administration of Integra on primary burn wounds and unstable secondary scars].

We report on our experience with Integra application in 22 patients treated from February 1996 through April 1999. Nine patients suffered a primary burn injury and 13 patients had secondary unstable scars. Integra is artificial skin that consists of a collagen/glycosaminoglycane matrix and a silicon layer. It was first used by Burke and Yannas in 1980 in the USA. The mechanical and biological features of Integra protect the tissue from fluid loss and bacterial invasion in the acutely burned patient. The integra-induced formation of a neodermis leads to functionally and aesthetically highly acceptable scar formation. We present our clinical experience with Integra in long-term follow-up.

Adult↗

PubMed2000

[Factitious wounds in plastic surgery].

Self-inflicted disorders of wound healing were diagnosed in two women (aged 24 and 25 years) after long years of history. A detailed medical history and the characteristic course helped to confirm the diagnosis. The artificial wounds were an expression of a severe psychic disturbance in both young women. Operative therapy was able to restore the local findings, the basic psychological disorder required a long-term psychotherapeutic treatment to prevent irreversible, partially iatrogenic co-induced somatic mutilations, due to an exceptionally high recurrence rate.

Adult↗

PubMed2000

[Does tissue perfusion after free microvascular tissue transplantation remain autonomous?].

In a retrospective study, including 60 patients, after free latissimus dorsi transplantation (FLDT) to the lower leg, we found persistent pedicle blood flow up to ten years postoperatively. After uncomplicated FLDT, the pedicle supported the flap in all cases. After complicated FLDT (hematoma, thrombosis, infection) only 50% of all flaps after ten years were perfused by the vascular pedicle.

Adolescent↗

PubMed2000

Indications and limitations of angiography before free-flap transplantation to the distal lower leg after trauma: prospective study in 36 patients.

The necessity for routine angiography in evaluation of the vasculature of recipient legs prior to microsurgical free-tissue reconstruction still remains controversial. This prospective study was designed to determine the indications and limitations of angiography pertinent to this issue. The protocol consisted of palpation of dorsalis pedis and posterior tibial artery pulsation and lower-limb angiography prior to surgery, as well as intraoperative observation of the posterior tibial, anterior tibial, and peroneal arteries. Thirty-six patients were included who were treated from November, 1993 to December 1998. In five patients either the posterior tibial pulse (1), the dorsalis pedis pulse (3), or both pedal pulses, including the popliteal pulse (1) were not palpable preoperatively. These clinical findings correlated with the vascular lesion images on angiography. In two patients, pedal pulse palpation could not clearly be evaluated because of the injury. Among the 29 patients with both pedal pulses palpable, three patients angiographically presented an injury of the peroneal artery, and one patient a pseudoaneurysm of the anterior tibial artery. In none of the cases with at least one palpable pedal pulse (33), did preoperative angiography add relevant information which led to a plan change in the free-flap transfer. However, in two cases, severe scarring and fibrosis required an intraoperative change of the recipient vessel in one case, and a change of the anastomosis level and use of a vein graft, in the other case, although the angiography had demonstrated normal vascularity in both. The authors conclude that preoperative angiography is indicated only when both pedal pulses are not palpable, and that normal preoperative angiography does not guarantee the presence of vessels suitable for anastomosis.

Adolescent↗

PubMed2000

Free flap to the arteria peronea magna for lower limb salvage.

A 36-year-old woman sustained an amputation of her right leg at the thigh level and a degloving injury of her left foot and ankle region in an accident during a suicide attempt. Primarily, her left foot was covered with a split skin graft, resulting in a soft-tissue defect at the medial malleolus and at the calcaneus bone. Reconstruction was planned with a free latissimus dorsi muscle flap. Preoperative examinations revealed an arteria peronea magna with a hyperplastic peroneal artery solely providing arterial blood supply to the foot. The arteria peronea magna divided into two branches proximal to the upper ankle joint, replacing the dorsal pedis artery and the medial plantar artery. Tibial posterior and tibial anterior arteries were hypoplastic-aplastic. Microvascular end-to-end anastomoses of the flap vessels to the medial branch ("medial plantar artery") of the arteria peronea magna and its concomitant vein at the medial malleolar bone level were successfully performed. The postoperative course was uneventful. Four weeks postoperatively, the patient started walking assisted by a prosthesis on her right thigh stump. This experience demonstrates that even in a case of arteria peronea magna, free flap surgery for lower limb salvage is a reliable and worthwhile method.

Adult↗

PubMed2000

Flap perfusion after free musculocutaneous tissue transfer: the impact of postoperative complications.

In a previous study, the authors found persistence of pedicle blood flow up to 10 years after uncomplicated free latissimus dorsi transfer. In this study, the impact of postoperative complications (hematoma, thrombosis, infection) and successful surgical revision was tested. Since 1982, more than 1200 free tissue transfers have been performed at the authors' institution (Hannover Medical School). Of these, the authors selected two groups of 30 patients each who had received a free latissimus dorsi transfer to the lower leg without microsurgical nerve coaptation for wound coverage. All patients included in this study were carefully selected for clinical homogeneity, with one difference: group I comprised patients who had no postoperative complications after free latissimus dorsi transfer. Group II included only patients with major postoperative complications after the procedure. All flaps in group II survived after successful surgical revision. The arteries, which nourished the lower leg, were visualized and documented by means of a duplex scanner in both groups. Three different time intervals were chosen for measurements of blood flow: 4 to 6 months (groups I.I and II.I), 4 to 6 years (groups I.II and II.II), and 8 to 10 years (groups I.III and II.III). Quantitative measurements of local flap perfusion in milliliters per minute per 100 g tissue were performed by means of the hydrogen clearance technique. In each patient, a total of nine measurements was performed in three phases: phase A, before closing the vascular pedicle by manual compression (n = 3); phase B, with a closed pedicle (n = 3); and phase C, after releasing the vascular pedicle from manual compression (n = 3). Each measurement took approximately 10 minutes. One hundred percent closure of each pedicle in phase B was confirmed by the duplex scanner. Furthermore, all patients were monitored both clinically and by means of the hydrogen clearance technique during phase B for adequate blood supply to the lower leg. Lower leg perfusion showed no statistical differences for phases A, B, and C in all groups of patients. In group I, no statistical differences in local flap perfusion were encountered for phases A and C. In phase B, however, a statistically significant (p < 0.01) complete extinction of local flap perfusion was registered in all patients of group I at the site of the flap's skin paddle. In group II, however, persistent flap perfusion was registered during phase B in up to 50 percent of cases in one subgroup (II.III). No statistically significant alterations of local blood flow were registered in the surrounding tissue of group II during phases A, B, and C. Patients with thrombosis of the venous anastomosis (n = 7) seemed to have the highest incidence of loss of autonomous blood supply through the vascular pedicle (5 out of 11 cases). No inconstant results were found during the repetitive measurements (n = 3) for each patient in each phase. After uncomplicated free tissue transfer, the flap's intact vascular pedicle seems to play an important role in permanent flap survival up to 10 years after the procedure. Postoperative complications after free tissue transfer with successful surgical revision, especially venous thrombosis of the vascular anastomosis, may lead to loss of vascular flap autonomy over time.

Adult↗

PubMed2000

Bioartificial skin.

The loss of skin has been one of the oldest, yet most frequent and costly problems in our health care system. To restore functional and esthetic integrity in patients with unstable or hypertrophic scars, in burn patients and after skin loss for hereditary, traumatic or oncological reasons, an armamentarium of reconstructive surgical procedures including autogenous, allogenous and xenogenous tissue transfer as well as implantation of alloplastic materials has been favored. For several decades there has been increasing interest focused on 'tissue engineering' of dermal, epidermal and full thickness skin substitutes by both biological and synthetic matrices. At our institution (Hannover Medical School), a collagen/glycosaminoglycan dermal regeneration matrix has been used for immediate dermal coverage after escharectomy in burn injuries as well as for dermal replacement in chronically unstable scars. This article gives an overview on the current state of the art in bioartificial skin as well as our personal experience with the collagen/glycosaminoglycan matrix for dermal replacement in different clinical situations.

Adolescent↗

PubMed1999

[Techniques for postoperative monitoring of tissue circulation after free microvascular tissue transplantation].

Success rates after free tissue transplantation (FTT) have greatly improved over the last 20 years, partly due to improved technical performance of microvascular anastomoses with better optical and instrumental aids. However, flap failure is still a clinical problem and occurs in 5 to 10%, mainly due to blood vessel thrombosis within the first 24 postoperative hours. The clinical results after FTT can be optimized by in-time diagnosis of irreversibly compromised tissue blood flow and immediate operative reexploration. Therefore, there is a special demand for adequate and reliable postoperative monitoring techniques. This article reviews all monitoring techniques which have been performed in the experimental-clinical setting after FTT thus far.

Follow-Up Studies↗

PubMed1998

Genetically modified fibroblasts induce angiogenesis in the rat epigastric island flap.

METHODS: Gene therapy was tested for inducing functional angiogenesis in the superficial rat epigastric island flap to allow earlier pedicle division. Autologous rat fibroblasts were grown, harvested, cultured and retrovirally transfected to produce platelet-derived growth factor AA (PDGF-AA), an angiogenetically active protein. Stable gene expression was monitored by PDGF-AA enzyme-linked immunosorbent assay (ELISA). One hundred and eighty animals were divided into three groups (I-III) and a bilateral flap created in each animal. In all experiments, the right-sided flap was subjected to experimental treatment and the left-sided flap served as control (1ml saline 0.9%). During flap elevation, group I received 5X10(6) GMFB (genetically modified fibroblasts) plus 1 ml Dulbecco's modified Eagle's medium. Group II was treated with 5x10(6) NMFB (non-modified fibroblasts) plus 1 ml medium and group III received 1 ml medium only. The flaps were sutured back and the vascular pedicle was bilaterally ligated and divided in each of ten animals during the following 6 days. After 7 days, the flaps were harvested, the amount of necrosis measured and histologically examined. RESULTS: The GMFB produced up to 560 times more PDGF-AA than the NMFB, measured by ELISA. The GMFB-treated flaps tolerated surgical division of the vascular pedicle significantly earlier than groups II and III. Histologically, fibroblasts persisted in all flaps of groups I and II, without major inflammatory reaction. In all GMFB-treated flaps, massive angiogenesis could be demonstrated. CONCLUSION: By means of retroviral gene transfer, autologous rat fibroblasts can be genetically modified for stable expression of the PDGF-A gene to produce high amounts of PDGF-AA, which is angiogenetically active. After injection into the panniculus carnosus, these cells induce functional angiogenesis to permit earlier division of the vascular pedicle in this flap model.

Animals↗

PubMed1998

Intrabronchial surfactant application in cases of inhalation injury: first results from patients with severe burns and ARDS.

Damage to the respiratory tract caused by inhalation of toxic products of combustion with subsequent development of an acute respiratory distress syndrome (ARDS) is one of the main causes of death in burn patients. Treatment with an exogenous surfactant is a therapeutic option for which there has previously been no empirical data. We report on four severely burned patients with deep partial thickness and full thickness burns of between 40 and 70 per cent body surface area (BSA), and with inhalation injury complicated by ARDS. These patients were treated once or more than once with bovine surfactant replacement (Alveofact). In addition to biophysical and biochemical analysis, the influence of this substance on oxygenation and lung function were evaluated. After the limits of mechanical ventilation had been reached, bronchoscopic intrabronchial administration of surfactant was followed by temporarily improved gas exchange with an increase in arterial O2 partial pressure (PaO2), accompanied by a reduction in inspiratory O2 concentration (FiO2), and also improved lung compliance. All the patients survived in spite of an initially unfavourable prognosis. Replacement of exogenous surfactant in the treatment of inhalation traumatized severe burn patients with ARDS appears to show considerable promise as an approach to improving the survival chances of these high-risk patients.

Adolescent↗

PubMed1998

Gynecomastia of the male nipple.

Diseases of the male nipple can be responsible for severe problems for the patient. The location of gynecomastia can be restricted to the nipple. Carcinoma should also be considered. The therapy of choice is operative treatment. A subtle microsurgical procedure is helpful to achieve a good functional and cosmetic result.

Adult↗