Extracorporeal irradiation and incorporation of bone grafts. Autogeneic cortical grafts studied in rats.

The incorporation of resected, extracorporeally irradiated (1, 5, 25 and 50 kGy) and orthotopically reimplanted autogeneic cortical bone was investigated in 116 adult Wistar rats. 7 mm-long diaphyseal segments of the tibia were resected, irradiated and reimplanted using K-wire osteosynthesis. Autogeneic fresh grafts served as controls. Graft healing was evaluated by radiography and histomorphometric study at 3, 6, 9, and 12 weeks. At 3 weeks, two thirds of the 50 kGy irradiated grafts were fractured and therefore the series with this dose was interrupted because of mechanical graft insufficiency. After 3 and 6 weeks there were no statistically significant differences among the control group and 1 or 5 kGy irradiated grafts. The healing of 25 kGy irradiated grafts was delayed from the sixth week onwards and continued until the end of the experiment at 12 weeks (50% reduction of incorporation). The incorporation of 1 and 5 kGy irradiated grafts showed a 16% (1 kGy) to 24% (5 kGy) delay at 12 weeks, compared to autogeneic fresh grafts. 1 and 5 kGy irradiated autogeneic bone grafts retain most of their biological potential. Resection, extracorporeal irradiation and reimplantation of bone tumors may therefore be a possible alternative to allografting.

[Mechanical stability of hip joint endoprosthesis shafts of carbon fiber composite materials]. / Mechanische Sicherheit von Hüftgelenkendoprothesenschäften aus Kohlenstoffaserverbundwerkstoff.

The use of composite materials in orthopaedic surgery permits the design of implants with varying degrees of stiffness. A system of carbon fibre reinforced epoxy hip stems was investigated and compared to the mechanical safety of metal ones. Special attention has been paid to the fact that torsional moments are the common failure mechanism of composite materials. In total 74 hip stems (three different sizes) have been tested under static and dynamic loading conditions according to ISO 7206. A group of 27 implants was pre-conditioned for 75 days in 80 degrees C Ringer's solution to discover potential degradation effects of absorbed fluids. The carbon fibre hip stems proved to reach run-out loads higher than conventional metal ones. Moisture absorption didn't influence the mechanical properties within the range of the experimental accuracy. The calculated fatigue stress of 750 MPa permits further optimization of stiffness parameters without the risk of implant fracture.

Sulfated polysaccharide anticoagulants suppress natural killer cell activity in vitro.

In contrast to the well studied anticoagulant activity of sulfated polysaccharides (SPS), little is known about their influence on immune competent cells. Using two naturally derived SPSs (unfractionated heparin and low molecular weight heparin), one semi-synthetic SPS (pentosanpolysulfate), and one synthetic SPS (lactobionic acid) as well as the polypeptide hirudin we investigated the effect of these drugs on natural killer cell activity in vitro. We demonstrate that all SPSs tested significantly suppress the activity of natural killer cells at clinically relevant dosages. At all concentrations and at all effector:target ratios tested pentosanpolysulfate was the most potent natural killer cell inhibitor. In contrast, hirudin had no effect on natural killer cell function. Furthermore, scanning electron microscopy revealed that reduced natural killer cell activity is paralleled by decreased lymphocyte cell size and altered cell surface structures. Our results indicate that defined therapeutically applied SPSs can interfere with the tumor cell killing process.

A versatile flow cytometry-based assay for the determination of short- and long-term natural killer cell activity.

A flow cytometry based method has been developed to assess natural killer (NK) cell activity in both short-term (4 h) and long-term (18 h) NK assays. Target cells were either labeled with PKH-2, c'FDA or D275. Simultaneously, dead cells were identified by counter-staining with the nuclear dye propidium iodide. Using flow cytometry, only D275 in combination with propidium iodide permits the differentiation of four cell populations: live target cells, dead target cells, live effector cells, and dead effector cells. Even after the extended incubation periods (18 h) necessary for the determination of NK activity in some domestic animals these four populations remain clearly distinguishable. Comparison of results with cells of normal human individuals obtained using this D275/propidium iodide flow cytometry assay with data derived from fluorescence microscopy or an endogenous lactate dehydrogenase release assay shows a strong correlation. Since in long-term NK assays a high proportion of dead effector cells is constantly observed this cell population frequently limits the use of the lactate dehydrogenase release assay but does not interfere with the flow cytometry assay presented here. Using this novel assay, we have demonstrated the suppressive effects of defined glycosaminoglycans on long-term porcine NK activity.

[Preservation and sterilization of cortical bone--biomechanical studies of the rat]. / Konservierung und Sterilisation von Kortikalis--biomechanische Untersuchungen an der Ratte.

The biomechanical properties of cryopreserved, autoclaved, irradiated and chemically treated cortical bone harvested from rat tibiae were evaluated in three-point bending. Biomechanical parameters (maximum bending load, deflection, failure energy and stiffness) are not altered by cryopreservation (-70 degrees C, 28 days) or irradiation with doses of 1 kGy or 5 kGy. The maximum bending load of autoclaved (134 degrees C, 3 min) or irradiated (25 kGy) cortical bone is reduced to 82% and 74% compared that of controls tested immediately after death (100% = 74.4 +/- 6.6 N). Extension of the autoclaving time from 3 to 5 min or irradiation with 50 kGy diminishes the bending load (28% after autoclaving, 48% after irradiation), deflection and failure energy. Stiffness is altered by autoclaving only. If a sterilization process is combined with deep freezing, better biomechanical values are obtained by sterilizing the bone before deep freezing than vice versa. The bending loads for autoclaving and irradiation before deep freezing are 68.8 +/- 9.4 N and 50.8 +/- 7.9 N, as against 51.7 +/- 2.7 N and 43.1 +/- 3.9 N for autoclaving and irradiation of previously cryopreserved bone. Whereas treating bone with tetrahydrofurane does not alter its biomechanical behavior, 80% ethanol leads to a reduction of structural properties.

[Fulminating malignant hyperthermia in swine--an alternative therapy concept]. / Die fulminante maligne Hyperthermie beim Schwein--Ein alternatives Therapiekonzept.

An inexpensive therapeutic concept compared to the dantrolene-therapy to counter the malignant hyperthermia (MH) is to be discussed, using a case-study from swine-anaesthesia. Hyperventilating the animals (with O2), administering metamizol, beta-blocker, bicarbonate and sufficiently cooling the patient can, if the symptoms are recognized early enough, arrest the hypermetabolic cascade in its track. All the animals that were treated according to this scheme survived the (MH) crisis without any lasting post operative damage.

[Change in subchondral mineralization after reconstruction of the anterior cruciate ligament of the sheep]. / Veränderung der subchondralen Mineralisierung nach Rekonstruktion des vorderen Kreuzbands beim Schaf.

The cruciate ligaments are generally regarded as regulators of the joint kinematics, but also increasingly as a "Sensory organ" regulating the periarticular musculature, which influences the position of the contact surfaces and the direction and magnitude of the resultant forces. Indirectly, therefore, they influence the long-term stress distribution, which is itself reflected in the distribution of the subchondral mineralisation. An experimental investigation was therefore undertaken to see whether, in terms of this distribution, the distribution of the stress alters postoperatively, since this could be regarded as an early cause of degenerative change. We examined the distribution of the subchondral mineralisation of six tibiae from six adult Merino sheep 1 year after anterior cruciate ligament reconstruction with patellar tendon. The contralateral tibia we used as controls. Maximum subchondral mineralisation of both the medial and the lateral joint surfaces in all the control joints was found to be central. In the treated knees, however, the medial joint surface maxima were found to have been displaced towards the dorsomedial edge of the surface in every case. If the density pattern on the control side is accepted as the expression of a normal stress distribution, the distribution patterns on the treated side must indicate a pathologic distribution of stress. Reconstruction of the anterior cruciate ligament is therefore--at least in the animal model--not able to prevent the development of a pathologic stress distribution.(ABSTRACT TRUNCATED AT 250 WORDS)

Monitoring of right ventricular function using a conventional slow response thermistor catheter.

OBJECTIVE: To investigate whether determination of right ventricular end-diastolic volume (RVEDV) and right ventricular ejection fraction (RVEF) can be performed with reasonable accuracy and reproducibility using a conventional slow response thermistor pulmonary artery catheter (CPAC) applying an adaptive algorithm. DESIGN: To study RVEDV and RVEF simultaneously with pulmonary artery catheters equipped with slow and fast response thermistors (FRPAC) under a broad range of cardiac output. SETTING: Laboratory of Institute of Experimental Surgery, Technical University. ANIMALS: 11 anaesthetised piglets. INTERVENTIONS: Hypovolemia (V-) was induced by withdrawal of blood up to 50 ml/kg, hypervolemia (V+) was produced by retransfusing blood and adding up to 30 mg/kg hydroxyethyl starch. In 5 animals in phases V- and V+ beta-adrenergic stimulation was achieved with dobutamine. Finally pulmonary artery hypertension was induced by infusion of small air bubbles. MEASUREMENTS AND RESULTS: Cardiac output (CO), RVEDV and RVEF were determined simultaneously with FRPAC and CPAC placed in the same pulmonary artery branch. Measurements were repeated 8 times sequentially in steady state normovolemia. A total of 130 measurements could be analysed. The coefficient of variation was 6.7 +/- 4.2% for CO(FRPAC) and 4.6 +/- 1.7% for CO(CPAC); for RVEF it was 9.7 +/- 6.2% (FRPAC) and 9.9 +/- 3.9% (CPAC); for RVEDV it was 11.6 +/- 4.8% (FRPAC) and 8.54 +/- 3.2 (CPAC). Mean difference (bias) was 0.06 +/- 0.39 l/min for CO measured with both methods, 19 +/- 35 ml for RVEDV and -3.3 +/- 6.5% for RVEF. CO(CPAC) displayed a strong correlation to CO(FRPAC) (R = 0.97, p = 0.001) as well as RVEF (R for RVEF(CPAC) versus RVEF(FRPAC) = 0.90, p = 0.001). R for RVEDV(CPAC) versus RVEDV(FRPAC) was 0.67, p = 0.001. We conclude that this animal study demonstrates good agreement between RVEF and RVEDV obtained with catheters equipped with a fast response thermistor or with a conventional slow response thermistor allowing accurate monitoring of right ventricular function with a conventional pulmonary artery catheter.

Effects of preservation and sterilization on cortical bone grafts. A scanning electron microscopic study.

The effects of preservation and sterilization on the structural properties of cortical bone were investigated. Specimens of cortical bone from rat tibiae were frozen (-70 degrees C for 28 days), freeze-dried, irradiated (1, 5, 25 and 50 kGy) or autoclaved (at 134 degrees C for 3 or 5 min), and examined by scanning electron microscopy. Cryopreservation and irradiation had no deleterious effects on the surface structure of the cortical bone. Freeze-drying caused microcracks running parallel to the mineralized fiber bundles. After autoclaving, a time-dependent distension, swelling and amalgamation of the fibrillary matrix was observed. This denaturation of the organic matrix was more pronounced after 5 min than 3 min autoclaving. The alterations of the fibrillary structure described above might be due to a preservation- and sterilization-induced decrease of the biological and biomechanical potential of bone grafts.

[Blood coagulation and fibrinolysis in prostate surgery]. / Blutgerinnung und Fibrinolyse in der Prostatachirurgie.

In 23 patients undergoing transurethral resection of the prostate (n = 11) or suprapubic prostatectomy (n = 12), hemostasis and fibrinolysis were studied. In addition to basic coagulation tests, antithrombin III, plasminogen, antiplasmin and fibrin degradation products were determined preoperatively, intra-operatively and postoperatively over a period of 6 days. Evaluation of the results revealed slightly activated blood coagulation and fibrinolysis intraoperatively and postoperatively, with no significant differences being seen between the two groups. Routine use of antifibrinolytic drugs in patients undergoing surgery of the prostate is not recommended.

Coagulation in aortofemoral bifurcation bypass grafting.

Few data are available on the pathophysiology of the coagulation system during aortic surgery. Cross-clamping of the aorta, intestinal eventeration and circulatory shock in ruptured aortic aneurysms are thought to cause coagulation disturbances and hyperfibrinolysis. A prospective study of several parameters of the clotting system, i.e. standard clotting tests, platelet count, indicators of fibrinolysis, inhibitors of the clotting cascade and proteases were measured perioperatively in aortobifemoral bypass grafts. Ten patients undergoing elective procedures and two emergency cases with ruptured aortic aneurysms were included. The standard clotting tests reflected the use of heparin. A similar course of ATIII, C1-inhibitor, alpha 2-antiplasmin, plasminogen and fibrinogen with a decrease during the operation and a return to almost normal values postoperatively, were due to intra-operative blood loss, haemodilution and a slight activation of the clotting cascade, as well as, hyperfibrinolysis. This observation was supported by the increased levels of euglobulin lysis and PMN-elastase and the resultant increase in some fibrinogen degradation products, indicating non-specific proteolysis. These changes were more pronounced in the two emergency cases, except for the heparin induced changes in PTT and thrombin time. It is concluded that non-specific proteolysis may be an important factor in the pathogenesis of clotting disorders in surgery of the aorta. Further research is needed to discover the pathways of non-specific proteolysis and its prevention by protease inhibitors.

Study of a dose-dependent effect of the glycosaminoglycan polysulfate on various parameters of blood coagulation.

In a double-blind study the dose-dependent effect of 10, 20, 40, and 70 mg of SSHA was tested in volunteers. Whereas only a minor prolongation of the aPTT was noted, a clear anti-factor Xa effect was proven (method of Yin), as well as the release of lipoprotein lipase. In a subsequent study, 12 volunteers were treated daily with a dose of 40 mg for 11 days. On the first day of treatment a dosage of 40 mg SC was administered three times every 90 min. There was no cumulative effect with this dose and a clear plateau effect was recorded daily after each application. Repeated administration therefore results in an identical reproducible effect. Thus, no tachyphylaxis occurred under long-term treatment with 40 mg SSHA.

[Light and scanning electron microscopy studies of the pleura. A contribution to the pathogenesis of spontaneous pneumothorax in young patients]. / Licht- und rasterelektronenmikroskopische Untersuchungen der Pleura. Ein Beitrag zur formalen Genese des Spontanpneumothorax beim jungen Menschen.

In a prospective study of 10 patients (7 men, 3 women, mean age 26.2 years), who underwent thoracotomy because of recurrent spontaneous pneumothorax, we performed light and scanning electron microscopic investigations of the resected pleura. The purpose of our work was to explain pleural changes which allowed the penetration of air through the intact wall of the blebs. In 8 of 10 cases we found small bullae at the top of the upper lobe, the remaining 2 showed up with massive pleural scar. The morphological and ultrastructural findings indicated that the presence of air induced a reactive process at the visceral pleura which led to degeneration and scarification. The changes consisted of simple membrane formation up to complete destruction of the pleural layer. The development of blebs is due to an air fistula coming out of the lung parenchyma. Penetration of air through the bleb's wall is explained with the increasing pressure inside and the dehiscence of degenerated pleural structure. In our opinion spontaneous pneumothorax in young people is caused by a localized disease of the upper lobe. The pleural changes are the visible effects of a degenerative process induced by air fistula from lung parenchyma. Therefore wedge-resection of that region is a rational therapy in patients with spontaneous pneumothorax.

[Combination anesthesia in sheep with ketamine-(fentanyl)-guaifenesin (My 301)-laughing gas-halothane]. / Die Kombinationsanästhesie beim Schaf mit Ketamin-(Fentanyl-)Guaifenesin (My 301-) Lachgas-Halothan.

The concept of combined anaesthesia, the centrally-acting muscle relaxant guaifenesin (My 301) in a 5% solution with ketamine (and/or fentanyl) in addition to the inhalation of nitrous oxide and halothane is based upon the principle of "balanced anaesthesia". Guaifenesin amplifies the effect of several anaesthetics, which complement one another, allowing the dosage to be decreased and thereby reducing the cardiovascular stress. To induce anaesthesia, the combination of a cataleptic anaesthetic (ketamine = Ketanest, Ketolar) and a centrally acting skeletal muscle relaxant (guaifenesin = Myolaxin, My 301) is used. Because of the risk of aspiration the animal should be intubated as soon as possible. Anaesthesia will be prolonged by the carrier gas nitrous oxide (65%, weakly analgesic)/oxygen (65%), low concentrations of halothane (1.0 to 0.6 to 0.4%, weakly hypnotic and analgesic) and by a continuous drip infusion of 5% guaifenesin (relaxing, mild analgesic and sedative). The effect of all the other anaesthetics is increased by guaifenesin. To increase the analgesia and to control the cardiovascular parameters the additional injection of ketamine or fentanyl is recommended. The recovery period is short and the general condition is good both after a lengthy anaesthesia of 9 hours (n = 32) and after anaesthesia of 2 hours. No significant adverse effects on the cardiovascular system were detected.

[Bone healing--an immunoreactive process?]. / Die Knochenheilung--ein immunreaktiver Vorgang?

Cell mediated immune reactions, demonstrated by leukocyte migration assay and histological analysis of spleen and lymph nodes, could be observed after fresh autografting of cortical segments in rats. The detected immune answer showed a bone-specific reaction pattern. In consideration of the temporal correlation of the observed immune reactions and the histological signs of graft incorporation, a connection of bone healing and immune system may be possible.

[Orotracheal intubation in rats]. / Orotracheale Intubation an Ratten.

A detailed description of the technique of orotracheal intubation under visual control in rats is given. This method was used successfully in 190 animals, the complication rate being 3.2%. The hazards consisted of laryngospasm (1.6%) and fatal bleeding (0.5%). Intubation was proved to be a safe, reliable, simple and atraumatic way to establish a patent airway in this laboratory animal.