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Biomedical subjects

D Frommel

Publications and source records attributed to D Frommel.

At least 109 records · Page 6Linked to original sources
PubMed1970

Conformational significance of the intrachain disulfide linkages in immunoglobulins.

Biophysical studies of intact immunoglobulins, enzymatically derived immunoglobulin subunits, and chemically derived immunoglobulin chains are reported. All the forms studied lacked optical activity associated with the alpha-helix conformation. A dichroism band centered near 217 nm, which has been assigned to the beta-sheet conformation, was present in all subunits that contained at least two covalently linked intrachain disulfide loop regions. This dichroism band could not be detected in Component II, the C-terminal 120 amino acids of the heavy chain. The reduction and alkylation of the intrachain disulfide linkages caused a large conformational change associated with short range interactions. The cleavage of the intrachain disulfide also produced a large change in the environment of two aromatic amino acids, tyrosine and tryptophan. These observations indicate some unique conformational relationships for immunoglobins which may be related to the functional demands placed on this class of macromolecule.

Alkylation↗
PubMed1969

Localization of immunological complexes fixing beta1C (C3) in germinal centers of lymph nodes.

28 human and 60 experimentally stimulated rabbit lymph nodes were studied by means of light microscopy and immunofluorescence. 21 of the 28 human lymph nodes showed well-developed germinal centers. IgM, IgG, and the beta(1C) component of complement were found in the same distribution within germinal centers when examined in serial cryostat sections. 36 rabbits were stimulated with Brucella antigen, and 24 rabbits with BSA. A strikingly consistent correlation between distribution and appearance of specific staining for rabbit beta(1C), IgM, and IgG was observed; when lymph nodes were stimulated with BSA, antigen and specific antibody were present. Treatment of unfixed sections with citrate-buffered saline at low pH resulted in complete elution of immunoglobulins, beta(1C), and BSA from rabbit germinal centers, and in marked diminution of IgG and IgM in human germinal centers, while at the same time plasma cells remained strongly fluorescent. Specific selective fixation of heterologous (human) complement in rabbit germinal centers positive for beta(1C), IgG, IgM, and BSA was also obtained. These data present strong evidence for the existence within germinal centers of antigen-antibody complexes which fix at least the beta(1C) component of complement in vivo. The possibility of complete elution of immunoglobulins from rabbit germinal centers can be taken as evidence that, at least for 20 days after primary and secondary stimulation, a major component of the immunoglobulins present in germinal centers is not produced locally but accumulates at the surface of cells.

Animals↗
PubMedDate not supplied

The use of DNA hybridization for the detection of Leishmania aethiopica in naturally infected sandfly vectors.

Hybridization with kinetoplast deoxyribonucleic acid (kDNA) probes was used to detect Leishmania aethiopica in naturally infected sandflies in south-west Ethiopia, an endemic area for cutaneous leishmaniasis. 396 sandflies were dissected; microscopy revealed flagellates in the midgut of 5 Phlebotomus pedifer. The infecting flagellates were confirmed as L. aethiopica by isoenzyme typing. Gut specimens for all dissected sandflies were hybridized with total L. aethiopica kDNA as well as with a cloned kDNA probe specific for L. aethiopica. Samples from sandflies which were found to be infected microscopically also hybridized with the L. aethiopica kDNA probes. One additional sandfly hybridized but was not shown to be infected by microscopical examination. Hybridization experiments with 65 whole squash-blotted sandflies gave results that correlated very well with results obtained using microscopy. Our results indicate that DNA probing is a useful method to detect Leishmania infection in sandfly midguts as well as in whole squash-blotted sandflies, and can be used to follow changes of infection rate. DNA probing is therefore an alternative to microscopy in large-scale epidemiological studies as well as monitoring control programmes aimed at human leishmaniasis.

Animals↗
PubMedDate not supplied

Cutaneous leishmaniasis in south-western Ethiopia: Ocholo revisited.

The borough of Ocholo, on the western side of the Ethiopian Rift Valley, is an endemic focus for Leishmania aethiopica infection and has been surveyed thrice between 1987 and 1990. In 1989, 3022 inhabitants (> 95% of the population) were interviewed and examined. The overall prevalence of localized cutaneous leishmaniasis (LCL) was 3.6-4.0%, with a peak value of 8.5% in the 0-10 years old age group. In half of the patients the active disease was estimated to last for 9.6 +/- 6 months; in 10%, it exceeded 3 years. Scars of LCL were present in 34.3% of the residents. Leishmanin skin tests were positive in 54% of 120 school-children without signs of the disease. Therefore, in Ocholo a minimum of 71.6% of the population has been exposed to L. aethiopica infection. Two cases of the diffuse form of cutaneous leishmaniasis were observed. In this highland biotope, Phlebotomus pedifer was found to be the major, and possibly the only, vector for L. aethiopica.

Adolescent↗
PubMedDate not supplied

Aminosidine and its combination with sodium stibogluconate in the treatment of diffuse cutaneous leishmaniasis caused by Leishmania aethiopica.

Treatment of diffuse cutaneous leishmaniasis (DCL) caused by Leishmania aethiopica remains unsatisfactory as the parasite is relatively insensitive to antimonial compounds. Reports of the clinical effectiveness of aminosidine sulphate, especially in combination with sodium stibogluconate, in visceral leishmaniasis and the finding that this antibiotic is potent against L. aethiopica in vitro, prompted us to evaluate its usefulness in DCL. Two patients with long-standing, active DCL were treated for 60 d with aminosidine sulphate, 14 mg/kg/d parenterally. The skin lesions resolved completely in both patients although they relapsed subsequently. Synergism between aminosidine and stibogluconate was demonstrated in vitro against parasites isolated from the patients. This led us to administer combined therapy, aminosidine sulphate 14 mg/kg/d and sodium stibogluconate 10 mg/kg/d, to the 2 patients in relapse and to another, third patient. Treatment was continued for 2 months beyond parasitological cure. Side effects were minimal. Following treatment, a return of specific cell-mediated immunity occurred, as expressed by a moderate infiltration of lymphocytes into the lesions and by lymphocyte proliferation in vitro in the presence of live Leishmania antigen, with synthesis of interleukin-2 and interferon gamma with one patient and interleukin 4 with the other. During follow-up periods of 2 to 21 months after treatment, no sign of relapse was seen.

Animals↗
PubMedDate not supplied

Ethiopian visceral leishmaniasis patients co-infected with human immunodeficiency virus.

This communication reports 7 Ethiopian visceral leishmaniasis (VL) patients co-infected with human immunodeficiency virus (HIV). The clinical and laboratory findings in 6 patients did not differ from classical VL. All patients had highly elevated anti-leishmanial antibody titres, determined by immunoglobulin G-based enzyme-linked immunosorbent assay; they most probably acquired the Leishmania infection before HIV. Amastigotes were identified in the splenic aspirates of 6 patients and in the lymph node aspirate of the 2 patients whose lymph nodes were examined. The CD4:CD8 lymphocyte ratio was depressed in those patients whose ratio was determined. Most patients showed some initial response to pentavalent antimonial therapy.

Adult↗
PubMedDate not supplied

Detection of cutaneous Leishmania infection in paraffin-embedded skin biopsies using the polymerase chain reaction.

In this study the polymerase chain reaction (PCR) with previously developed oligonucleotide primers was used to detect Leishmania aethiopica in paraffin-embedded skin biopsy specimens. The Leishmania-specific 120 base pair fragment of the kinetoplast deoxyribonucleic acid (kDNA) minicircles has been amplified from all parasitologically or histologically confirmed cases of cutaneous leishmaniasis (CL), as demonstrated by gel electrophoresis and hybridization with L. aethiopica kDNA. Control specimens from patients with skin diseases other than CL were all negative. Using PCR, Leishmania were demonstrated in the skin lesions of 7 cases in a group of 40 patients in whom the parasites could not be demonstrated by histopathology or culture in vitro although lesions were clinically suggestive of CL. These data indicate that PCR, carried out on DNA extracted from formalin-fixed and paraffin-embedded tissue specimens, is a valuable method for the diagnosis of CL, especially in chronic cases where the parasite load in the lesion is low.

Animals↗
PubMedDate not supplied

[The time is ripe for listening to the voice of the half of the world].

Has the world of women changed? So wonders a one-time champion of what was then called women's rights, and is now known as women's empowerment, in the Third World. She recalls her surprise when she listened to advocates of birth spacing as a young mother. She remembers the debates she attended: "Today development, tomorrow the Pill", "Women's education is the key to progress", the speculations of western feminists ignorant of the burden of traditions kept alive elsewhere. She is now concerned about the resolution of the Beijing conference, assigning the protection of the environment and responsibility for domestic husbandry to women. Is this not yet another abdication of male responsibility? Should she once again stand up and deliver a harangue at an international meeting or should she instead pursue the quiet, self-effacing weaving of networks between the women of the North and South?

Contraception↗