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Biomedical subjects

D Kohn

Publications and source records attributed to D Kohn.

At least 127 records · Page 7Linked to original sources

[Meniscus insertion].

In meniscus replacement procedures anatomically correct fixation of the graft is one of the prerequisites for a successful outcome. An anatomical cadaver study was carried out to identify the insertion areas in the femur and tibia as well as the peripheral meniscus length. Ninety-two fresh knees from 46 human donors were included. The tibial insertions of the medial meniscus could be defined by bony landmarks. The peripheral length was 111 +/- 11 mm for the medial and 110 +/- 13 mm for the lateral meniscus. Wrisberg's ligament was present in 76% of all knee specimens and Humphry's ligament could be found in 50%. The correlation between the right and left knee in the same individual was poor concerning the presence of the meniscofemoral ligaments and the size of the tibial meniscal insertions to bone.

Adolescent↗

Autograft meniscus replacement: experimental and clinical results.

Because of the risks related to allograft meniscus replacement an attempt was made to replace the medial meniscus by autograft tissue. In animal experiments the free middle third of the patellar tendon was transformed to a meniscus-like structure within one year after insertion. Early arthroscopic results after autograft meniscus replacement in a clinical series comprising 20 patients are promising.

Animals↗

Langerhans' cells of elderly patients with decubital ulcers.

An ultrastructural and morphometric study compared Langerhans' cells in sacral epidermis, 8-10 cm from the lesion of patients (mean age 70) with decubital ulcers, with those in the patients' own normal epidermis from the upper leg and with those in the epidermis from the upper leg of normal age-matched volunteers. The Langerhans' cell section area was significantly lower in patients' control leg epidermis (25.86 +/- 2.29 microns2) than in that from normal controls (35.74 +/- 3.76 microns2) or that from patients' sacral epidermis near the lesion (41.26 +/- 3.45). The number of Langerhans' cell granules was higher in control leg epidermis of patients (10.22 +/- 1.26) and was significantly higher in lesioned sacral epidermis (12.94 +/- 1.90) than in normal controls (6.97 +/- 1.47). In Langerhans' cells in patients' epidermis, formative stages of Langerhans' cell granules were observed. The findings may indicate that Langerhans' cells in patients' epidermis are in an active state.

Aged↗

A role for complement as the major opsonin in the sequestration of erythrocytes from elderly and young donors.

Erythrocytes from elderly donors (> 70 years), but not young donors (18-35 years), are shown to undergo sequestration in an in vitro erythrophagocytosis assay. Comparable levels of sequestration are observed for high density erythrocytes from young individuals and both low density and high density erythrocytes from elderly individuals. These cells, which are susceptible to phagocytosis with no additional treatment are collectively termed 'in situ aged' erythrocytes. We present evidence for the involvement of complement in the sequestration of 'in situ aged' erythrocytes and correlate levels of complement bound to 'in situ aged' erythrocytes from young and elderly donors with levels of phagocytosis. We also demonstrate that the in vitro sequestration of erythrocytes from elderly donors can be inhibited by beta-galactosyl sugars and arginine-glycine-aspartic acid (RGD) but not by mannose nor by Protein-G, a specific inhibitor of Fc-gamma mediated phagocytosis. These experiments show that IgG is not the major opsonin in the sequestration of red cells from elderly donors. In support of the role of complement rather than IgG as the major opsonin in red cell sequestration, we further demonstrate that C'3 bearing immune complexes block in vitro sequestration of erythrocytes from elderly donors. This competition is not dependent upon the isotype of the immunoglobulin (IgM or IgG) in the complex but rather on the presence of active complement.

Adolescent↗

T lymphocyte ontogeny in adenosine deaminase-deficient severe combined immune deficiency after treatment with polyethylene glycol-modified adenosine deaminase.

Adenosine deaminase (ADA) deficiency causes severe combined immune deficiency (SCID) by interfering with the metabolism of deoxyadenosine, which is toxic to T lymphocytes at all stages of differentiation. Enzyme replacement with polyethylene glycol-modified ADA (PEG-ADA) has been previously shown to correct deoxyadenosine metabolism and improve mitogen-induced T lymphocyte proliferation. We studied the biochemical and immunologic effects of PEG-ADA in two infants with ADA-deficient SCID. While in a catabolic state, higher doses of PEG-ADA than previously described were required to normalize deoxyadenosine metabolism. After biochemical improvement, the patients recovered immune function in a pattern similar to that observed in normal thymic ontogeny and in patients with immunological reconstitution after bone marrow transplantation. Immune reconstitution was marked by the sequential appearance in the peripheral blood of phenotypic T lymphocytes corresponding to successive stages of thymic differentiation. Functional reconstitution was marked by the successive appearance of mitogen responses dependent on exogenous in vitro IL-2, mitogen responses not requiring exogenous IL-2, antigen-specific responses dependent on exogenous IL-2, and finally, antigen-specific responses not requiring exogenous IL-2. Natural killer function was tested in one patient and normalized with PEG-ADA therapy. Optimal PEG-ADA therapy appears to normalize thymic differentiation in ADA-deficient SCID, resulting in normal antigen-specific immune function.

Adenosine Deaminase↗

[Revision surgery after failed anterior cruciate ligament repair].

Not every reconstruction of the anterior cruciate ligament is successful. Possible reasons for failure are renewed severe trauma, inadequate fixation of the transplant, an isometric mistake, weak transplant material, an anterior cruciate ligament reconstruction performed in isolation in a complex unstable knee, or prosthetic ligaments. Revision surgery is indicated when patients complain about the recurrence of knee instability. Preoperative diagnostic procedures must include X-rays with the knee in defined positions in order to determine drill hole courses and visualize any signs of arthrosis and the patellar position. Revision surgery is hampered by disadvantageously placed drill holes, exhaustion of the supply of transplant material, secondary instabilities, gonarthrosis or a possible arthrofibrosis. During rehabilitation a variable knee position is imperative, because of the different procedures that might need to be implemented.

Anterior Cruciate Ligament↗

Lack of changes in histomorphometric, bone mass, and biochemical parameters in ovariohysterectomized dogs.

A predictable animal model with skeletal remodeling characteristics similar to those of humans is needed to facilitate the understanding of the mechanism of postmenopausal osteoporosis. We have utilized the ovariohysterectomized (Ovh) dog to examine cellular and biochemical responses to estrogen depletion and PTH stimulation. Histomorphometric measurements of bone biopsies taken prior to (first biopsy) and five months after the operation (second biopsy) showed no significant differences in static and dynamic parameters. Bone mineral density of the excised vertebrae displayed the same values between the two groups six months after surgery. Between the second biopsy and sacrifice, two infusion studies were performed. A two-hour infusion of EDTA followed by a two-hour recovery period elicited a rapid response in PTH production, highly correlated to the changes in ionized calcium, but no significant difference in response was observed between Sham and Ovh groups. A short-term (24-h) infusion of 1-34 hPTH increased circulating ionized calcium and 1,25-(OH)2-D levels to a similar extent in both groups. The levels of alkaline phosphatase were constant and both groups showed a small but nonsignificant increase in osteocalcin. The lack of sizable responses in histomorphometric, bone mass, and biochemical parameters may limit the utility of dogs for the study of cancellous bone loss in ovarian-dysfunction osteoporosis.

Animals↗

[The value of dynamic examination methods in instability of the shoulder joint].

We prospectively examined 25 patients with shoulder instability by clinical examination and by fluoroscopic and sonographic imaging. 14 patients were classified as recurrent, posttraumatic instabilities, 12 of these anterior and two posterior. Clinical examination revealed the direction of instability in 5 patients, fluoroscopy in 5 and sonography in 3 patients. 11 patients had non-traumatic recurrent instabilities. Of these, clinical examination and fluoroscopy demonstrated identical directions of laxity in 8. Sonography concurred with the other techniques in only three cases. We recommend manual instability testing followed by fluoroscopy for evaluation and documentation of patients with non-traumatic, recurrent shoulder instability. Posttraumatic instabilities should be diagnosed with other, static procedures.

Adolescent↗

Medial meniscus replacement by a tendon autograft. Experiments in sheep.

In 20 skeletally mature female merino sheep, divided into four groups, we performed total medial meniscectomy, removal of the middle third of the patellar tendon, and tenotomy of the calcaneal tendon of the right hind leg. Group I (control) had no additional procedures. In the other three groups the medial meniscus was replaced by the middle third of the patellar tendon from the ipsilateral knee. The animals were killed at three (group II), six (group III), or 12 months (group IV) and the tendon-meniscus examined macroscopically, by light and scanning electron microscopy, and biomechanically. Remodelling of the tissue had taken place by 12 months but the failure stress and tensile modulus for the tendon-meniscus were lower than for the normal meniscus. Our evidence suggests that, in sheep, replacement of a meniscus by a tendon autograft may decrease the severity of the degenerative changes that occur after meniscectomy.

Animals↗

Health information management using optical storage technology: case studies.

All the health care facilities examined in the case studies addressed several important organizational issues before and during the installation of their systems. All the facilities examined employee commitment. The prudent managers considered how easily their employees adapt to changes in their jobs and work environment. They considered how enthusiastic cooperation can be fostered in the creation of a liberated and reengineered office. This was determined not only by each individual's reaction to change, but also by the health care facility's track record with other system installations. For example, document image, diagnostic image, and coded data processing systems allow the integration of divergent health care information systems within complex institutions. Unfortunately, many institutions are currently struggling with how to create an information management architecture that will integrate their mature systems, such as their patient care and financial systems. Information managers must realize that if optical storage technology-based systems are used in a strategic and planned fashion, these systems can act as focal points for systems integration, not as promises to further confuse the issue. Another issue that needed attention in all the examples was the work environment. The managers considered how the work environment was going to affect the ability to integrate optical image and data systems into the institution. For example, many of these medical centers have created alliances with clinics, HMOs, and large corporate users of medical services. This created a demand for all or part of the health information outside the confines of the original institution. Since the work environment is composed of a handful of factors such as merged medical services, as many work environment factors as possible were addressed before application of the optical storage technology solution in the institutions. And finally, the third critical issue was the organization of work. "Organizations that understand their business processes are having no trouble whatsoever justifying the cost of optical storage-based information management systems," said Thornton May, director of imaging research at Nolan Norton Institute. "It is only confusing to organizations that do not have a feel for what is happening in the flow of work in the company. If an organization has on-line performance measurements with regard to time, cost, quality, error rates, and customer service, the move to optical image and data management technology is a no-brainer."(ABSTRACT TRUNCATED AT 400 WORDS)

CD-ROM↗

The legal issues.

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Liability, Legal↗