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Biomedical subjects

G Ritter

Publications and source records attributed to G Ritter.

At least 91 records · Page 5Linked to original sources
PubMed1991

Ganglioside antigens expressed by human cancer cells.

Gangliosides are normal cell surface components of all animal cells. Altered ganglioside biosynthesis during malignant transformation results in expression of a qualitatively and quantitatively different ganglioside profile in many tumors. While their physiological function is largely unclear, gangliosides expressed by cancer cells, e.g. GD3, GD2 and GM2 in malignant melanoma, have proven to be suitable targets for passive immunotherapy with monoclonal antibodies and for active immunotherapy with vaccines. Studies aimed at further augmenting the effectiveness of these approaches are currently underway.

Animals↗
PubMed1991

[The light-cured composite CuRAY-FIL. A clinical and experimental animal study].

This article presents a animal study on 36 teeth by dogs without definite race. By the histological observation we cannot assess a damage of the pulp by application of CuRAY-FIL with a basic material. The clinical and REM observations after 11 and 24 months by 76 patients pointed out: CuRAY-FIL has a good colour stability and adhesion, however the claims on a optimal filling material for the restoration in the visible area are not accomplished in all points.

Acid Etching, Dental↗
PubMed1991

[Interpretation of MR tomography findings in trauma surgery].

MR-Imaging is well established as the most sensitive method for the diagnosis of avascular necrosis of the femoral head. In this paper preliminary results are analyzed in an attempt to clarify whether as in a vascular necrosis of the femoral head. MR changes after trauma or surgery allow conclusions concerning the vitality of the bone. Comparison of clinical, MR and histological findings revealed that we cannot yet differentiate between fibrosis of the bone marrow with sustained vitality of the osteocytes and bone necrosis. Therefore, conclusions with implications for therapy should be drawn with extreme care.

Adult↗
PubMed1991

[Compression osteosyntheses with the new AO universal nail. Functional principle and biomechanical prerequisites].

The new AO universal nail, with its special construction, allows extremely stable compression osteosynthesis in correctly selected fractures. Compression osteosynthesis with an intramedullary brace has definite advantages for fracture healing and biomechanics. The basic requirement, especially for the long-term maintenance of pressure, is truly stable anchorage of the locking bolts in the bone. Previous investigations by the author have shown that this is only possible in the shaft of the bone. Anchoring stability is not sufficient in the cancellous juxta-articular bone. Five years of clinical experience fully confirm the theoretical expectations.

Biomechanical Phenomena↗
PubMed1991

[Diagnosis, therapy and results of biceps tendon ruptures].

During 1980 and 1988 a total of 29 male patients suffering from ruptures of the biceps tendons were treated operatively. In 21 cases the long tendon was involved, in two the short tendon, and in 6 cases the distal tendon. All ruptures of the long tendon and one of the short tendon had resulted from degeneration without any adequate trauma. Refixation of the long biceps tendon was performed with drill holes along the bicipital sulcus. In ruptures of the short and distal tendon various procedures were applied. Results of operative treatment were better in ruptures of the long biceps tendon than in ruptures of the short tendon. An operation may be successful even some months after injury.

Adult↗
PubMed1990

Effect of empiric antiarrhythmic therapy in resuscitated out-of-hospital cardiac arrest victims with coronary artery disease.

The effect of empiric antiarrhythmic therapy with quinidine and procainamide on long-term mortality was examined in 209 patients with coronary artery disease resuscitated after out-of-hospital cardiac arrest. The antiarrhythmic agent used was determined by the patient's private physician without knowledge of the study ambulatory electrocardiogram. Of the 209 patients, procainamide was prescribed in 45 (22%), quinidine in 48 (23%) and no antiarrhythmic therapy in 116 (55%). Digoxin therapy was initiated in 101 patients. The 2-year total survival rate for the quinidine, procainamide and nontreated patients was 61, 57 and 71% (p less than 0.05), and for sudden death was 69, 69 and 89% (p less than 0.01), respectively. These observations suggest that empiric antiarrhythmic therapy in survivors of out-of-hospital cardiac arrest did not affect total mortality and was associated with an increased frequency of sudden death.

Aged↗
PubMed1990

Retinol is essential for growth of activated human B cells.

When EBV-transformed human B cells are removed from conventional cell cultures, washed, and seeded at a low cell density in serum-free medium, their growth potential is greatly diminished. Fresh serum restores the growth of low density B cell cultures. We have traced this restorative effect to an essential factor present in the lipid fraction of serum and have identified it as all-trans retinol. The identification is based on the close similarities of the factor isolated from serum with authentic all-trans retinol as revealed by mass spectrometry, HPLC chromatography, and the ability to stimulate the growth of lymphoblastoid cells in the bioassay. Retinol is active at concentrations equal to its concentration in serum. Retinol is also a requirement for growth in suspension cultures at cell densities of 3 x 10(5)/ml. Cells removed at any time from such exponentially growing cultures and transferred to retinol-free medium cease to grow and consequently die, whereas in the continued presence of retinol, cell growth is unabated. All-trans retinal can substitute for retinol, but retinoic acid fails to stimulate the growth of lymphoblastoid cells at physiological concentrations. Normal human B lymphocytes also require retinol as a costimulator of proliferation after activation by anti-mu antibody or Staphylococcus aureus (Cowan strain) bacteria. In serum, retinol is bound to retinol-binding protein, which in turn forms a complex with prealbumin. Accordingly, we find that B cells respond to retinol bound to its physiological serum carrier, retinol-binding protein. In conclusion, human B cells are critically dependent for optimal growth in cell culture on an external supply of retinol.

B-Lymphocytes↗
PubMed1990

Biochemical and serological characteristics of natural 9-O-acetyl GD3 from human melanoma and bovine buttermilk and chemically O-acetylated GD3.

Because its expression appears to be largely restricted to human melanomas, 9-O-acetyl-GD3 is a candidate antigen for vaccine construction. Searching for potential sources, we compared chemically O-acetylated calf brain GD3 and 9-O-acetyl-GD3 extracted from bovine buttermilk with 9-O-acetyl-GD3 from human melanoma. Three fractions (F1-F3) of chemically O-acetylated GD3 differed in the number and position of O-acetyl groups. O-Acetylation sites were the lactose portion in F1 and lactose as well as sialic acid in F2 and F3. Natural (melanoma- or buttermilk-derived) 9-O-acetyl-GD3 was O-acetylated solely on the sialic acid moiety. While F1 was not reactive with monoclonal antibodies against 9-O-acetyl-GD3, F2 and F3 were as reactive as the natural products. Immunization with the natural products induced high-titer antibodies against natural 9-O-acetyl-GD3 as well as F2 and F3. In contrast, mice immunized with the synthetic fractions produced antibodies only against the immunogen but not against natural 9-O-acetyl-GD3. Only immunization with the natural products induced production of antibodies reactive with surface antigens of melanoma cells expressing 9-O-acetyl-GD3. The findings suggest (a) that C-9 of the subterminal sialic acid is the site of chemical O-acetylation in F2 and F3, as opposed to C-9 of the terminal sialic acid in the natural products; (b) that O-acetylation of both the terminal and subterminal sialic acid moieties of GD3 results in recognition by three murine monoclonal antibodies (D1.1, ME 311, and Jones) reactive with human melanoma cells; (c) that O-acetylation of the terminal sialic acid is critical, on the other hand, for inducing an immune response against melanoma 9-O-acetyl-GD3; and (d) that O-acetyl GD3 from bovine buttermilk can substitute as immunogen for inducing an immune response against human melanoma cell surface antigens in the mouse.

Acetylation↗
PubMed1990

Kinematics of the patellofemoral joint. Investigations on a computer model with reference to patellar fractures.

Patellofemoral kinematics were studied on a computer model. The articulating point of the patella moves from distal to proximal during flexion, until the quadriceps tendon starts to turn around the femur tendo-femoral gliding. The pattern of patellofemoral movement consists of a gliding and rolling component, the latter at its maximum at the beginning of flexion. The pathway of the instant centers of motion moves from dorsal to ventral during flexion. Stress analysis shows that the contact area is at all times the area of maximum bending stress. The distal part of the patella is the part with mechanical stress at all angles of flexion. The conclusions to be drawn for treatment are that fractures within the proximal and central part of the patella need a very high stability of internal fixation, the distal part of the patella less so. Postoperative treatment must take into account the changing contact area, because the peak stress is always at the contact area.

Biomechanical Phenomena↗
PubMed1990

[Tension band wiring osteosynthesis--studies on tension and fixation of the osteosynthesis wire].

In tension band wiring different tensioners and wire-connections are in use. Both of these were examined on tensile force during and after connection with help of a material-testing machine. Additionally the different connections were examined under traction-load. The results show that none of the tensioners for monofilament wire are capable of establishing a permanent tension at the end of the fixation-procedure. Consequently we must ask if the theoretical principle of B. G. Weber concerning tension band wiring is efficient in practice. Only the use of twisted wires in combination with fixation clamps could produce a permanent tension. The limit of elasticity is 2 to 3% for monofilament wires as well as for twisted wires. Further stretching causes plastic, i.e. irreversible deformation in monofilament wire and its connections. In twisted wires further tension stress causes ruptures especially at the border of the fixation clamp. In conclusion extreme active exercise of fractures treated with tension band wiring should not be emphasized.

Bone Wires↗
PubMed1990

[Experimental determination of sliding friction during insertion of femoral intramedullary nails].

No data have published concerning the procedure of driving in intramedullary nails. An extensive experimental device consisting of a contact-free distance measurement, a dynamograph connected to strain gages and an accelerometer now enabled this investigation. Among other things we determined the range of sliding friction for each stroke at different levels of nail-progression. Depending of the depth of nail-progression forces between 200 N und 400 N were measured. When the nail is stuck these values rise to over 1000 N. The sliding-process lasted between 10 ms and 20 ms. Knowledge of these data is of major importance for improvement of surgical technique and possible development of mechanical nail-insertion aids.

Biomechanical Phenomena↗
PubMed1990

[Experimental studies on the stability of femoral head spongiosa in reference to a new type blade profile of a 130-degree angle plate].

The fracture of the trochanter major during and after angle plate-osteosynthesis of pertrochanteric fractures in mind, we made a 130 degrees-angle plate for experimental investigations with an only 6 mm broad blade profile. Therefore the lateral femoral corticalis will be weakened much less. The question was, whether this blade would be stable enough in the spongiosa of the femoral head with regard to the stability of the osteosynthetic system. For this the two methods of osteosynthesis were exposed to dynamic stress. The investigations were done with bone specimens by right-left-comparison with the new plate on the one side and the well-known 130 degrees-angle plate on the other side. The results show, that the new blade with the narrow profile has rather the same stability in the spongiosa of the femoral head as the AO-angle plate.

Biomechanical Phenomena↗
PubMed1990

Antibody response to immunization with purified GD3 ganglioside and GD3 derivatives (lactones, amide and gangliosidol) in the mouse.

GD3 is the ganglioside most abundantly expressed on the cell surface of human melanoma, and treatment with a monoclonal antibody recognizing GD3 has induced major responses in a small proportion of patients. However, we have been unable to induce production of GD3 antibodies in melanoma patients by active immunization with GD3-expressing melanoma cells or purified GD3. In this report we describe attempts to increase the immunogenicity of GD3 in the mouse by chemical modification. GD3 lactone I and II, GD3 amide and GD3 gangliosidol were synthesized, and the humoral immune response to these derivatives was compared with the response to unmodified GD3. The GD3 derivatives were more immunogenic than GD3. At a low dose all congeners induced an IgM response, with antibody titers higher than those elicited by low-dose GD3. The gangliosidol and amide derivatives also induced an IgG response. IgM antibodies induced by immunization with GD3 lactone I cross-reacted with purified GD3 and GD3-expressing melanoma cells. Titers of GD3 cross-reactive antibodies were slightly higher than after immunization with GD3 itself at the same low dose. IgM and IgG antibodies induced by the other congeners did not cross-react with GD3.

Amides↗
PubMed1990

[Scapholunar dissociation--when an accident sequela, when a normal congenital variant?].

The scapholunate dissociation is an instability of the wrist which shows characteristic signs in the X-rays. It is commonly believed to be caused by trauma. During the past two years four cases of idiopathic scapholunate dissociations were identified by the typical radiologic signs on both sides without any trauma or symptoms. Before operative treatment of an injured hand X-rays of the uninjured side should be examined.

Carpal Bones↗
PubMed1990

[Detection and effects of bone marrow intravasations in operations in the area of the femoral marrow cavity].

In recent years, during total hip replacement and intramedullary nailing large sonographic echoes some centimeters in length have been observed on transesophageal echocardiography of the right heart. The echoes have always appeared after rise in pressure in the femoral cavity. The substrate of the echoes was not known. We could not imagine that particles of bone marrow of the size observed were passing through the vessels of the femur, but on the other hand there was no other suitable explanation. For clarification of the substrate of the sonographic echoes an animal study was performed in sheep. After the application of a known pressure on the femoral cavity the distal vena cava was investigated sonographically through a laparotomy; proximally blood was taken from the vein. The study identified the large sonographic echoes as "mixed emboli" consisting of a core of bone marrow and surrounding apposition of thrombotic material. The observations explain the frequent observations of pulmonary impairment after elevation of the intrafemoral pressure. It seems possible that the intravasation of bone marrow is involved in the pathogenesis of thrombosis after orthopedic surgery.

Animals↗