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Biomedical subjects

F Hess

Publications and source records attributed to F Hess.

At least 37 records · Page 2Linked to original sources
PubMed1989

Neointima formation in expanded polytetrafluoroethylene vascular grafts with different fibril lengths following implantation in the rat aorta.

Expanded polytetrafluoroethylene (PTFE) prostheses with fibril lengths of 30 and 60 microns were implanted in the rat infrarenal aorta. Sequential scanning electron and light microscopic studies of the prostheses after implantation demonstrated a different pattern of endothelialization. Prostheses with a fibril length of 60 microns had a continuous multilayered neointima at week 25 postimplantation, whereas prostheses with a 30-microns fibril length had a discontinuous and single layer of endothelium after the same interval. It was concluded, therefore, that a prerequisite for the development of a lining in a vascular prosthesis is for the inner surface of the prosthesis to have adequate pores for effective anchoring of the invading endothelioid cells. Expanded PTFE prostheses with an internodular distance of 60 microns provided sufficient anchoring possibilities for invading endothelioid cells to form a continuous neointima.

Actin Cytoskeleton↗
PubMed1989

Auxiliary liver transplantation in jaundiced rats with UDP-glucuronyltransferase deficiency and defective hepatobiliary transport.

In this study auxiliary liver transplantation (ALT) has been tested as a means of correcting the UDP-glucuronyltransferase deficiency in Gunn rats and the UDP-glucuronyltransferase deficiency and impaired hepatobiliary bilirubin transport in double mutant rats. In both groups serum bilirubin normalized and remained low until the end of the study at 12 weeks after transplantation in 4 out of 6 rats. Excretion of 99mTc-HIDA in non-transplanted double mutants was considerably slower than in Gunn rats (kel 0.9 x 10(-3) versus 4.3 x 10(-3) s-1). HIDA excretion by transplants in double mutants and Gunn rats was about equal (kel 1.6 x 10(-3) and 1.1 x 10(-3) s-1). Experiments with bile duct-cannulated transplants showed that in double mutants bile flow, bile acid and bilirubin excretion was 2-4 times higher than in Gunn rats. This study shows that auxiliary liver transplants can conjugate and excrete bilirubin when one of these or both functions are lacking in the recipient's liver.

Animals↗
PubMed1989

[Blood vessel replacement by new large (over 6 mm) and small (to 1.5 mm) lumen vascular prostheses].

Histologic studies on 1,672 functionally implanted synthetic vascular grafts of various fabrics revealed 1. an industrially coated large-porous textile prosthesis to heal faster and without less complications than conventionally preclotted ones, 2. a neointimal endothelium to regenerate only from the vascular stumps, 3. the fate of neointima and of in vitro seeded endothelium to depend on the type of the vascular graft and 4. a new type of fine fibrillar vascular (polyurethane) microprostheses to have functioned in clinically relevant lengths with excellent results.

Animals↗
PubMed1988

Patency rate of small caliber fibrous polyurethane vascular prostheses implanted in the dog carotid and femoral artery improved by use of acetylsalicylic acid and dipyridamol.

Segments of 3 mm diameter fibrous polyurethane vascular prosthesis of length 3-4 cm were prepared. They were bilaterally implanted in the carotid and femoral arteries of male and female beagles. Four groups consisting of animals receiving either no medication or thrombocyte aggregation drugs were studied: Group A (8 dogs), no medication: group B (19 dogs), 500 mg acetylsalicylic acid (ASA) once daily and 25 mg dipyridamol (DIP) three times daily orally for 6 weeks after the implantation operation; group C (14 dogs), 250 mg ASA and 25 mg DIP three times daily orally for 6 weeks after the implantation operation; group D (12 dogs), 250 mg ASA and 25 mg DIP three times daily orally for 25 weeks after the implantation operation. Medication was started one week prior to the implantation operation. In group A, all prostheses were occluded at week 6. There was a significant difference in patency rates between groups B-D and C-D. No significant differences in patency rates could be found between groups B and C. The best patency rates were obtained 25 weeks after implantation in group D for both the right and left carotid and right and left femoral implantation sites. Highest patency rates were observed when ASA and DIP were given for 25 weeks.

Animals↗
PubMed1988

Implantation of 20 cm long polyurethane vascular prostheses in the femoral artery of dogs. Preliminary results.

In a preliminary experiment externally reinforced polyurethane prostheses measuring 20 cm in length, with an inner diameter of 3 mm, were implanted in a loop in the femoral artery of six dogs. The dogs received 250 mg acetylsalicylic acid and 25 mg dipyridamol three times a day as anti-thrombocyte aggregation therapy starting three weeks prior to surgery. Anti-thrombocyte aggregation therapy was continued throughout the study. All prostheses remained patent 8, 9, 15 and 17 months after implantation. Patency was confirmed by palpation and Doppler ultrasound measurements. Preliminary results suggest that in clinically relevant situations, these prostheses could function well over prolonged periods of time.

Animals↗
PubMed1988

[Success and long-term results of radiotherapy of periarthritis humeroscapularis].

The results in 164 patients receiving radiotherapy for humeroscapular periarthritis were evaluated on the basis of questionnaires. In all, 76% of the patients reported an improvement. A long-term study over an average of 5 years showed 61 patients (49%) to have experienced long-lasting freedom from pain. However, 38 patients (24%) noticed no improvement. Criteria affecting the success of therapy seem to include the length of the history of the disease as well as inadequate differential diagnosis. No influence is attributed to age, sex or previous types of treatment.

Adult↗
PubMed1988

Augmentation by L-dopa of growth inhibition and melanin formation of X-irradiated Harding-Passey melanoma cells in culture.

Treatment of exponentially proliferating melanogenic Harding-Passey melanoma cells in monolayer culture (HPM-73 line) with a single dose of X-irradiation (up to 8 Gy) or continuously (for several weeks) with L-3,4-dihydroxyphenylalanine (L-Dopa) up to 5 X 10(-4) M resulted in a dose-dependent inhibition of cell proliferation, but not in death of all cells. Actually, 8 Gy-irradiated or L-Dopa (2 X 10(-4) M)-treated cultures finally reached the cell number and cell density of controls. However, a combination of a single dose of radiation (8 Gy) followed by L-Dopa (2 X 10(-4) M)-treatment resulted in destruction of all cells. Melanin formation was stimulated by L-dopa-treatment or X-irradiation, and was further elevated by the combined application of radiation and L-Dopa-exposure. Whether the effects of exogenously applied L-Dopa, an intermediary metabolite of melanin synthesis, are due to the conversion to growth-inhibitory metabolites (quinones, radicals, etc.) inside or outside the cell, was discussed. The latter might result from release (due to membrane damage or cell disintegration) of tyrosinase or/and melanosomes into the culture medium with the consequence of extracellular synthesis of potentially cytotoxic metabolites from medium substrates. Further, endocytosis of exogenous melanosomes and tyrosinase with potentially harmful effects is feasible. An application of such a combination therapy of melanoma to clinical medicine should be considered.

Animals↗
PubMed1987

Determination of the patency of vascular prostheses implanted in the rat aorta by means of ultrasonic blood-flow measurements.

Patency of vascular prostheses implanted in the rat aorta is usually confirmed by reoperation and inspection of the distal stump of the aorta for pulsations. Repeated reoperation on rats included in long-term investigations is not possible because of the increasing formation of scar tissue and adhesions at the site of the distal aorta. Consequently, noninvasive ultrasonic Doppler measurement was investigated to determine whether this method could provide accurate information about the patency of an implanted prosthesis. A total of 37 rats with 10-cm-long prostheses implanted in the aorta (groups C nonsupported prostheses, n = 12; and D supported prostheses, n = 25), eight normal nonoperated controls (group A), and three rats with a ligated aorta (negative controls, group B) were studied over a period of 12 weeks. The Dopplerrecordings obtained in the normal animals served as controls for the recordings of rats with an implanted prosthesis. A prosthesis was considered patent if the Dopplermeasurements obtained from the femoral artery resembled that of the normal pattern. In seven cases a prosthesis was suspected to be occluded since the Dopplermeasurements resembled those obtained after aortic ligation. Autopsy confirmed the Dopplermeasurements in all cases. No Dopplermeasurements returned to normal in the femoral artery in the aorta-ligated rats even after longer periods post-operation. It is concluded that Dopplermeasurements can accurately provide information about the patency of a vascular prosthesis implanted in the rat aorta.

Animals↗
PubMed1987

The formation of a neo-intima in textile prostheses implanted in the aorta of rats and dogs.

The formation of a neo-intima in textile prostheses implanted in the rat and dog aorta was studied by means of light- and scanning electron microscopy. Two independent cellular layers (the superficial and deep ingrowth layers) developed on the free surface and under the fibrin layer initially deposited on the inner surface of the prostheses. The superficial ingrowth layer invades the prosthesis from both the proximal and distal aortic stumps and extends over the primary fibrin layer, or replaces it. This layer consists mainly of smooth muscle cells of the triangular aortic type covered by endothelial-like cells. The deep ingrowth layer originates from cellular elements of the prosthetic bed. Fibroblasts, myofibroblasts and spindle-shaped smooth muscle cells invade the fibrin layer through the interstices of the fabric structure of the prosthesis. Precursors of endothelial cells, however, are absent from this population. The superficial and the deep ingrowth layers may become joined by progressive replacement of the fibrin layer, but remain distinguishable because of their different cellular components. When a continuous cellular layer is established on the inner surface of the prosthesis, and this is then covered by endothelial-like cells, the neo-intima formed remains stable during long-term studies.

Animals↗
PubMed1987

[Effect of neuraminidase and x-rays (2 Gy and 8 Gy) on microvilli and membrane invaginations of Ehrlich ascites tumor cells in monolayer culture].

A monolayer culture (Eagle basal medium plus 10% of fetal calf serum) of Ehrlich ascites tumor cells was exposed to X-radiation with 2 Gy and 8 Gy and treated with Vibrio cholerae neuraminidase alone or combined with sublethal X-ray irradiation (2 Gy). Pictures of the Ehrlich ascites tumor cells taken with the electron microscope were investigated in order to find out any cell surface modifications due to membrane invaginations and microvilli. The results showed that the rate of microvilli as well as that of membrane invaginations became higher with the increasing X-ray dose (2 Gy; 8 Gy). Following to neuraminidase treatment there was a considerable augmentation of membrane invaginations as compared to control cells, whereas the number of microvilli was slightly reduced. As it has been already described before, the influence of neuraminidase produced an increased endocytosis activity and a strengthening of the cytoskeleton. Combined treatment with neuraminidase and sublethal X-radiation (2 Gy) caused a higher rate of membrane invaginations than each method alone; the number of microvilli was slightly increased by combined treatment. The conclusion is drawn that these structure modifications are due to reparation processes induced by radiation on the one hand and to an enzymic action of neuraminidase on the cell surface on the other hand.

Animals↗
PubMed1986

The inner prosthetic surface structure and re-endothelialization: an experimental study in the rat using two types of microvascular prostheses for aortic implantation.

Two types of microvascular prostheses were implanted in the rat infrarenal aorta. Operations were carried out with clean, nonsterile instruments under ether anesthesia. Anastomoses were made with a continuous 8-0 suture. In group A, a 1-cm-long piece of expanded polytetrafluorethylene (PTFE) and in group B a 1-cm-long fibrous polyurethane prosthesis were implanted. Both groups consisted of 18 rats. Three rats from each group were killed at days 3, 5, 10, 20, 40, and 60 postimplantation. Prostheses were examined by scanning electron and light microscopy for the re-endothelialization. All prostheses in both groups were patent at the time of death. Re-endothelialization started in both types of prostheses the fifth day after implantation and had advanced 1-3 mm in the PTFE prostheses at day 60. However, in the fibrous polyurethane prostheses, re-endothelialization progressed and a complete new lining was achieved between days 20 and 40 postimplantation. The endothelium/neointima in the fibrous prosthesis was firmly anchored onto the prosthetic wall by means of cellular protrusions between the polyurethane fibers. In contrast to this observation, the endothelium/neointima developed in the PTFE prostheses was not anchored to the wall of the prosthesis. It is emphasized that the development of a new lining in a prosthesis may reduce the risk of endogenous, hematogenous infections. From the results of this study, we have concluded that there is a correlation between the inner surface structure and the extent of the re-endothelialization of a prosthesis. A prosthesis with a fibrous structure is much more rapidly and completely re-endothelialized than an expanded PTFE prosthesis.

Animals↗
PubMed1986

Amsacrine-associated cardiotoxicity: an analysis of 82 cases.

Amsacrine is an antileukemia drug being widely used in North America, Europe, Australia, and New Zealand. In the initial clinical trials, patients treated with amsacrine developed occasional instances of acute cardiac arrhythmias and cardiomyopathy. We review and analyze the features of cardiac abnormalities associated with amsacrine in 82 patients, 27 of whom have not been previously reported. The rest have been reported in the literature, but we have included a large amount of additional information about these patients in our analysis. We conclude that amsacrine-related cardiac events are less common than those related to anthracycline chemotherapeutic agents. Manifestations of such toxicity include ECG abnormalities, ventricular and atrial arrhythmias, sudden death, and congestive heart failure. There is little or no cumulative dose effect. Hypokalemia may be a risk factor for development of serious tachyarrhythmias, but such problems can occur despite a normal serum potassium level. Amsacrine appears to affect depolarization and repolarization of the heart, but the mechanism is unknown.

Adolescent↗
PubMed1985

History of (micro) vascular surgery and the development of small-caliber blood vessel prostheses (with some notes on patency rates and re-endothelialization).

The historical development of vascular surgery is reviewed from ancient times (Ruphus of Ephesus, Aëtius of Amida) to recent developments (sutured anastomosis by Carrel). Attempts to anastomose blood vessels by means of nonsuturing technique, using a ring or short tube of diverse materials called prostheses, were undertaken at the start of this century and continued until shortly after World War II. With the advent of modern polymeric materials, prostheses of different types, sizes, structures, and fabrics have been used to substitute for blood vessels, both experimentally and clinically. Recently, blood vessel prostheses with small (1-1.5 mm) internal diameters became available and have been implanted experimentally. Patency rates, biophysical and structural properties, the re-endothelialization and the neointima formation of several types of microvascular prostheses are briefly reviewed.

Animals↗
PubMed1985

Three years experience with experimental implantation of fibrous polyurethane microvascular prostheses in the rat aorta.

The results of a 3-year study in which a series of 355 implantations of 1-cm-long fibrous polyurethane microvascular prostheses into the infrarenal aorta of the rat (group A) were evaluated with respect to patency and formation, structure, and fate of the neo-intima. Rats were sacrificed at various intervals from 1 day to 2 years in order to obtain a time-related impression of the re-endothelialization and stability of the neo-intima. A second series of 51 implants was done with prostheses 10 cm in length, placed in a 1.5-cm loop in the abdominal aorta (group B). An overall patency rate of 92.7% was achieved in group A. Initially, eight technical failures caused early thrombosis of the prostheses. Sixteen prostheses became infected and subsequently occluded. The overall patency in group B was 52.9%, due to kinking from adhesion formation and normal growth of the rat. In both the long and short prostheses, a continuous multilayered neo-intima developed, growing from the aortic stumps into the prosthesis from both sides. According to the growth rate of 0.3 mm/day, a 1-cm prosthesis was re-endothelialized after +/- 20 days and a 10-cm prosthesis after +/- 9 months. Once developed, the neo-intima, consisting of myofibroblasts and smooth muscle cells covered with a flat endothelium, remained stable and continuous, throughout the observation period. The neo-intima was firmly anchored onto the prosthetic wall by means of cellular protrusions extending between the polyurethane fibres. The significance of rapid healing of an implanted prosthesis is emphasized with respect to preventing (late) hematogenous, endogenous infection of the prosthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Significance of the inner-surface structure of small-caliber prosthetic blood vessels in relation to the development, presence, and fate of a neo-intima. A morphological evaluation.

Microvascular prostheses with three different inner surface structures were examined morphologically 1-18 months after implantation to evaluate the presence and structure of the neo-intima. Fibrous polyurethane tubes (length: 5-10 mm, inner diameter: 1.5 mm) were implanted in the rat abdominal aorta in group A with a fibrillar inner structure (pore sizes 20-50 microns), and in group B the inner fibrillar structure was coated with an impermeable continuous silicon sheet. Expanded polytetrafluorethylene vascular prostheses (length: 40 mm, inner diameter: 4 mm) were implanted in the dog carotid artery (group C). The specimens were examined by light microscopy and scanning electron microscopy. A continuous and permanent neointima was only found in the prostheses with the porous fibrillar inner structure (group A). The thin new lining sheet was well attached to the prosthetic wall by cellular protrusions. In the silicon-coated prostheses (group B) also a continuous neo-intima had developed which, however, was irregular, thicker, and not anchored to the prosthetic wall. The expanded polytetrafluorethylene prostheses (group C) showed also after 1 year only incomplete lining with a neo-intima. Fresh blood cell deposits could be observed in the unlined prosthetic wall. It is concluded that a continuous lining of vascular grafts with a thin neo-intima is only achieved if the cells invading the prostheses from the anastomotic areas can anchor their cytoplasmic protrusions onto an appropriately structured inner surface. If these anchoring facilities are not provided, the unattached neo-intima will thicken, interfering with the patency of these microvascular prostheses, or fragments of the neo-intima or alternatively mural thrombi may constantly strip off and embolize.

Animals↗
PubMed1984

Patency and neo-intima development in 10 cm-long microvascular polyurethane prostheses implanted into the rat aorta.

Microvascular fibrous polyurethane prostheses (inner diameter 1.5 mm, length 10 cm) were implanted in the abdominal aorta of rats. The prostheses were fixed in a loop. All rats (n = 37) were reoperated 6 weeks after implantation to verify the patency of the prostheses. Eight prostheses were obliterated from various causes. The remaining 29 prostheses were found to be patent 3 months after implantation, which gives a patency rate of 79%. Six weeks and 3 months after implantation 7 and 4 rats, respectively, with patent prostheses were sacrificed. The remaining 18 rats of this study are still alive, more than 4 months after implantation, and will be included in long-term observation studies. The prostheses were examined using both light and scanning electron microscopy. The patent prostheses exhibited macroscopically a clear and transparent inner surface. No obliterative processes could be found either macroscopically or microscopically. Neo-intima ingrowth had advanced +/- 10 mm into the prostheses over the anastomotic line from both ends 3 months after implantation, and was continued by a single endothelium layer for several centimeters. An acellular, stable fibrin film was found inbetween the cellular lining. The neo-intima was anchored at the prosthesis by cellular protrusions extending between the polyurethane fibers. Though 10 cm long prostheses were implanted under unfavorable hemodynamic conditions, a patency rate of 79% was achieved, both 6 weeks and 3 months after implantation. This patency rate could have been higher if evident technical failures had been avoided.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗