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Biomedical subjects

H Hahn

Publications and source records attributed to H Hahn.

At least 253 records · Page 14Linked to original sources
PubMed1981

Progressive posttraumatic cystic myelopathy: neuroradiologic evaluation.

The neuroradiologic evaluation and findings in 25 symptomatic patients with surgically proven progressive posttraumatic cystic myelopathy are reviewed. To follow patients with spinal cord injury, neuroradiologic algorithms were developed to confirm and define cystic myelopathy. The algorithm used in the early and mid 1970s relied on the myelographic demonstration of a large cord for suspicion of a cyst. Review of this material found that in progressively symptomatic patients 14 of 25 proven cysts were in large cords. A more recent algorithm used computed tomographic metrizamide myelography. In nine of 11 patients studied in this fashion, the cyst filled with contrast material 2--4 hr after injection, yet it did not communicate with the subarachnoid space at subsequent surgery. The origin of the cyst fluid and mechanism of cyst demonstration with metrizamide may be associated with transneural migration of fluid. This condition must be clinically suspected and radiologically confirmed for surgical treatment (cyst-shunt procedure) if neurologic preservation of function is to be maintained.

Cysts↗
PubMed1981

Interaction between Entamoeba histolytica and the immune system. I. Mitogenicity of Entamoeba histolytica extracts for human peripheral T lymphocytes.

The effect of Entamoeba histolytica extracts (E.h.e.) on proliferation in vitro of human peripheral blood lymphocytes, cord blood lymphocytes, and lymphocytes enriched for T cells or non-T cells was investigated. As tested by 3H-thymidine uptake and by morphologic criteria, E.h.e. stimulate T lymphocyte proliferation. Non-T lymphocytes do not respond to E.h.e. The response of lymphocytes to E.h.e. differed from their response to Con A in several respects, indicating either that E.h.e. and Con A act on different subsets of T cells or that E.h.e. act by different mechanism on the Con A reactive cells.

Dose-Response Relationship, Immunologic↗
PubMed1981

Direct in vitro evidence for different susceptibilities to 4-hydroperoxycyclophosphamide of antigen-primed T cells regulating humoral and cell-mediated immune responses to sheep erythrocytes: a possible explanation for the inverse action of cyclophosphamide on humoral and cell-mediated immune responses.

Suppressor T cells of humoral immune responses, effector T cells mediating DTH, suppressor T cells of DTH, and helper T cells of humoral immune responses, all with specificity to SRBC, were produced in mice. The biologic activity was tested in adoptive transfer experiments. In vitro treatment with different doses of 4-hydroperoxycyclophosphamide (4-HPCy) yielded the result that the various activities tested were not uniformly sensitive to the action of this drug: Suppressor T cells of humoral immune responses and effector T cells mediating DTH were resistant to doses of 4-HPCy that eliminated the activities of suppressor T cells of DTH and helper cells of the humoral immune response. These findings help to explain the various effects cyclophosphamide has on the in vivo immune response and may help to form a basis for the rational manipulation of the immune response by drugs that selectively affect different subgroups of immune cells.

Animals↗
PubMed1981

Peritoneal exudate T lymphocytes with specificity to sheep red blood cells. IV. Fc receptors on specific peritoneal exudate lymphocytes and their role in delayed-type hypersensitivity reactions.

In mice, delayed-type hypersensitivity (DTH) to sheep red blood cells (SRBC) is mediated by T cells. Peritoneal exudate T cells (PETLs) from mice optimally sensitized for DTH to SRBC form rosettes when interacted with sensitized sheep red blood cells (EA). The binding of EA to PETLs is mediated by a receptor specific for the Fc portion of the antibody (FcR). Biological activity (mediation of DTH) depends on the unreacted state of PETLs and is lost when the latter are either rosetted with EA or reacted with aggregated IgG. Transfer of EA or aggregated IgG-treated PETLs from mice with DTH to SRBC does not lead to adoptive sensitization of recipients. It is suggested that FcR found on the membrane of T cells mediating DTH play a role in the regulation of the cellular immune response to SRBC.

Animals↗
PubMed1980

Transferable suppression and intrinsic unresponsiveness in delayed-type hypersensitivity to sheep red blood cells of mice: two distinct mechanisms?

In mice rendered unresponsive in DTH by the i.v. infection of 10(9) SRBC, two forms of specific unresponsiveness could be distinguished, referred to as intrinsic unresponsiveness and suppression. Suppression could be transferred by splenic T cells. It was short-lived and sensitive to cyclophosphamide (Cy, 100 mg/kg i.v.) given after sensitization. On the other hand, intrinsic unresponsiveness was not transferable by either serum or spleen cells. It was long-lived and resistant to Cy (200 mg/kg i.v.) given after sensitization. Induction of both transferable suppression and intrinsic unresponsiveness depended on Cy-sensitive (200 mg/kg i.v.) precursors. Since no evidence for clonal deletion could be obtained, it is suggested that unresponsiveness in general is mediated by complex cellular interactions which are readily perturbed in transfer experiments. In this way, cell recipients would end up possessing incomplete regulatory circuits, intact circuits still being present in donor animals.

Animals↗
PubMed1980

Mitogenicity of Entamoeba histolytica extracts for murine lymphocytes.

Aqueous extracts or aqueous extracts of delipidated Entamoeba histolytica (E.h.e.) contain a mitogenic principle for murine lymphocytes. As detected by [3H]-thymidine incorporation and blast transformation, E.h.e. acted predominantly on T cells of splenic origin, but not on thymocytes or bone marrow cells. Furthermore, E.h.e. induced proliferation of a subset of non-T-cells which is present in the spleen of athymic nude mice, adhered to nylon wool, but could not be activated to produce antibody. It seems possible that polyclonal activation of lymphocytes by E. histolytica might play a role in the disturbance of the immune system as manifested in the impaired cell mediated immune response of E. histolytica infected hosts.

Animals↗
PubMed1980

Relative susceptibilities of T cell subsets involved in delayed-type hypersensitivity to sheep red blood cells to the in vitro action of 4-hydroperoxycyclophosphamide.

4-Hydroperoxycyclophosphamide, a derivative of cyclophosphamide, in aqueous solution yields 4-hydroxycyclophosphamide, which acts on lymphocytes in vitro. This compound was employed to determine the relative susceptibilities of T cell subsets involved in delayed-type hypersensitivity to sheep red blood cells in vitro. The following ranking order could be established: precursors of suppressor T cells > antigen-activated suppressor T cells > T cells mediating DTH. These data provide direct in vitro evidence that the enhancement of the cellular immune response to sheep red blood cells by cyclophosphamide is due to selective inactivation of suppressor T cells or their precursors, respectively.

Animals↗
PubMed1980

[Antibacterial activity of co-trimoxazole and tetroxoprim/sulfadiazine in vitro (author's transl)].

The antibacterial activity of the newly developed combination, tetroxoprim/sulfadiazine, was evaluated and compared with that of the combination, trimethoprim/sulfamethoxazole. Tested strains were: Klebsiella pneumoniae, Proteus vulgaris, Proteus mirabilis, and Streptococcus faecalis. The components in both combinations were assayed in different ratios on a weight basis and activities measured as minimum inhibitory and minimum bactericidal concentrations employing serial dilution tests in Isosensitest bouillon in microtiter plates. It was found that the combination tetroxoprim/sulfadiazine acts synergistically -- as does the combination trimethoprim/sulfamethoxazole -- optimal antibacterial activities being achieved with a weight ratio benzylpyrimidine/sulfonamide of 1:1 or 1:5, respectively. In all instances, the combination trimethoprim/sulfamethoxazole proved to be of higher antibacterial in vitro activity than that of tetroxoprim/sulfadiazine.

Anti-Bacterial Agents↗
PubMed1979

Specific Lyt 123 cells are involved in protection against Listeria monocytogenes and in delayed-type hypersensitivity to listerial antigens.

Specific anti-Lyt antisera and complement were used to determine the Lyt phenotype of peritoneal exudate T lymphocytes from Listeria monocytogenes-immune mice. It was found that Lyt 123+ T cells are crucially involved both in protection against listerial infection and in delayed-type hypersensitivity (DTH) to listerial antigens. Thus, both functions critically depend on a T-cell subclass phenotypically different from that which mediates DTH to noninfectious antigens and help in antibody formation on the one hand, as well as those T cells mediating cytotoxic reactions on the other.

Animals↗
PubMed1979

[The antibacterial efficacy of cefaclor in routine testing of clinical material from two Berlin hospitals (author's transl)].

The agar diffusion method was used to test the antibacterial efficacy of cefaclor against bacterial strains isolated routinely from patients in two hospitals in Berlin. A comparison was made with the efficacy of oxacillin, azlocillin, amikacin, gentamicin, ampicillin, co-trimoxazole, tetracycline, penicillin, cefazolin, nalidixic acid and nitrofurantoin. A total of 1235 strains of Staphylococcus aureus, enterococci, Escherichia coli, Klebsiella, Enterobacter, Proteus species, Citrobacter and Pseudomonas aeruginosa were tested. Cefaclor was superior to the other substances in its activity against E. coli, Klebsiellae, and Proteus mirabilis. Co-trimoxazole and tetracycline, on the other hand, proved more effective against indole-positive Proteus species and Citrobacter. Tetracycline was also more effective against Enterobacter. Ampicillin was the most effective agent against enterococci, and oxacillin the most effective against S. aureus. Cefaclor showed good antibacterial activity against strains which were resistant to the orally administrable agents ampicillin, tetracycline and co-trimoxazole.

Bacteria↗
PubMed1979

[Cellular antibacterial immunity (author's transl)].

Facultatively intracellular bacteria (Mycobacteria, Brucellae, Listeria monocytogenes, Salmonella typhi etc.) may not necessarily be killed after having being phagocytosed by polymorphonuclear leucocytes or macrophages, cellular immunity having first to be built up. This results in the formation of specifically committed T-lymphocytes, which in turn release lymphokines after restimulation by homologous antigen. Under the effect of lymphokines, mononuclear phagocytes are chemotactically attracted to the site of infection, granulomas are formed and macrophages within the granuloma are activated. The granuloma represents the tissue reaction within which the interaction between facultatively intracellular bacteria and defence factors takes place. The experimental details underlying this concept are reviewed.

Animals↗
PubMed1979

Congenital duodenal obstruction. A review of 65 cases.

We report our experience with 65 patients with congenital duodenal obstruction, 36 with intrinsic and 29 with extrinsic lesions. Seventeen patients had trisomy 21 syndrome. Eight pregnancies were complicated by polyhydramnios. The diagnostic features encountered, the operative procedures used, and the postoperative management regimes used are presented. Thirty-two of the 36 patients with intrinsic lesions and 28 of the 29 patients with extrinsic lesions survived. The data on the five patients who died emphasize the effect of multiple congenital anomalies and prematurity on survival. This review suggests that the surgical procedures available for treating patients with congenital duodenal obstruction are well established and yield predictably good results.

Adolescent↗
PubMed1979

Peritoneal exudate T lymphocytes with specificity to sheep red blood cells. III. High dose of antigen induces suppressor T cells which influence the appearance in exudates of effector T cells for delayed-type hypersensitivity and helper T cells for humoral immune responses.

Antisera produced in rabbits against adherent cells of rat alveolar or peritoneal lavage fluid (anti-rat alveolar macrophage sera, ARAMS, or anti-rat peritoneal macrophage sera, ARPMS) were used to detect antigenic differences between alveolar (AM) and peritoneal (PM) macrophages in an indirect membrane immunofluorescence (IMF) test. Of all sera tested, the IMF titres were higher with cells of that population which was used for immunization. These differences were found before and after exhaustive absorptions with insolubilized rat plasma, rat erythrocytes, and non-adherant rat kidney, spleen, thymus and bone marrow cells. The differences were not due to antigens specific for one of the macrophage populations, as demonstrated by cross-adsorption studies with macrophages of different localization. It is assumed that two or more macrophage specific antigenic determinants are present in different density in the two macrophage populations.

Animals↗