Rune Nilsen

In situ characterization of mononuclear cells in human dental periapical inflammatory lesions using monoclonal antibodies

Mononuclear cells in cryostat sections of human dental periapical inflammatory lesions were studied with the aid of murine monoclonal antibodies and with indirect immunofluorescence microscopy. T lymphocytes (OKT3-positive cells) made up a major part of the cells in the infiltrates. They were found mainly in clusters, although single cells were also seen. T helper cells (OKT4) were more numerous than suppressor/cytotoxic T cells (OKT8-positive cells), with a ratio of approximately 2:1. Langerhans cells (OKT6-positive cells) were not demonstrated: only a few scattered HNK 1-positive cells, probably natural killer cells, were detected. A large number of OKM1- and OKIa 1-positive cells were detected in the infiltrates. Their size and number varied considerably in the different areas of the sections. These cells are probably macrophages. Sheets of small OKIa 1-positive cells were also demonstrated, indicating the presence of B lymphocytes or activated T lymphocytes. The results indicate that immune reactions may be of importance in the pathogenesis of periapical inflammatory lesions.

Increased Expression of Fas Ligand on Mycobacterium tuberculosis Infected Macrophages: A Potential Novel Mechanism of Immune Evasion by Mycobacterium tuberculosis?

We have studied the location and mechanism of apoptosis within the granulomas in the lungs at various stages of slowly progressive primary murine Mycobacterium tuberculosis infection. Parallel sections were analyzed for detection of mycobacterial antigens, Fas, and Fas ligand (FasL) by immunohistochemistry, and for apoptotic cells by terminal deoxynucleotidyl-transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) method. The frequency of apoptosis was high in the macrophage aggregates as compared to the lymphocyte aggregates and at the interface between them. Five to seven percent of the vacuolated macrophages in the granulomas expressed FasL intensely. These cells contained large amounts of mycobacterial antigens. These findings suggest that M. tuberculosis infection can induce increased expression of FasL in a population of infected macrophages. As a consequence the infected macrophages will be protected from the attack of cytotoxic T cells and activation of bactericidal mechanisms by Th1 type lymphocytes. This constitutes a novel evasion mechanism for M. tuberculosis possibly explaining the chronic course of infection.

A Mouse Model for Slowly Progressive Primary Tuberculosis

The progression from primary Mycobacterium tuberculosis infection to disease is usually slow in humans. The aim of this study was to develop and characterize a mouse model for slowly progressive primary tuberculosis, using the intraperitoneal (i.p.) route of infection, and to compare it with our previously described model of latent M. tuberculosis infection. B6D2F1 hybrid mice inoculated with 1.5 × 106 colony‐forming units (CFUs) of M. tuberculosis H37Rv were followed‐up for 70 weeks. Lungs, livers and spleens were examined for bacillary growth, histopathological changes and mycobacterial antigens (MPT64, ManLAM and multiple antigens of M. tuberculosis), by immunohistochemical staining. The infection was found to pass through three distinctive phases. During phase 1, mice were healthy despite development of small granulomas and an increasing number of bacilli in the lungs. During phase 2, mice were unwell but mortality was low. The count of M. tuberculosis and the granuloma size stabilized. The granulomas contained an increasing population of large, vacuolated macrophages. During phase 3, mice became moribund and died rapidly, but the M. tuberculosis count remained relatively stable. The inflammatory infiltrates filled ≈ 80% of the lung parenchyma and the lesions were not well demarcated. Rapidly progressing inflammation, rather than an increase in the M. tuberculosis count, seems to contribute more to mortality.

INCREASED EXPRESSION OF FAS LIGAND IN HUMAN TUBERCULOSIS AND LEPROSY LESIONS: A POTENTIAL NOVEL MECHANISM OF IMMUNE EVASION IN MYCOBACTERIAL INFECTION

To study the location and mechanism of apoptosis within the human tuberculosis (TB) and leprosy lesions, parallel sections were analyzed for mycobacterial antigens (M.Ag), Fas ligand (FasL), Fas, CD68 and Mac387 by immunohistochemistry, and apoptotic cells by the terminal deoxynucleotidyl‐transferase‐mediated dUTP‐digoxigenin nick end labelling method. Cutaneous leishmaniasis and foreign body granulomas were analyzed for comparison. The heavily infected macrophages in multibacillary TB and leprosy granulomas very strongly expressed FasL, indicating that a mycobacterial infection can induce an increased expression of FasL in a population of infected macrophages, which may protect them from the attack of Fas‐expressing lymphocytes. However, macrophages with high levels of leishmania amastigotes did not selectively express FasL, suggesting that this phenomenon is specific for the mycobacteria. Interestingly, in the well‐formed TB granulomas, 84% of the multinucleated giant cells strongly expressed FasL. The expression of Fas was weak (34%) or absent. A higher number (33%) of epithelioid cells expressed FasL than Fas (23%). Lymphocytes were scanty among the epithelioid cells. The frequency of apoptotic cells was higher in the epithelioid cells (0.25%) than the mononuclear cells in the mantle zone (0.14%). Thus, the epithelioid cells and the multinucleated giant cells by virtue of the increased expression of FasL may make these granulomas an immune privileged site for mycobacteria.

A Mouse Model for Latent Tuberculosis

The aim of the study was to establish a reproducible murine model for latent tuberculosis. We propose an operational definition of latent murine tuberculosis as a stable Mycobacterium-tuberculosis count in lungs and spleens without clinical signs or obvious histopathological changes in the lungs over a long period of time and without spontaneous reactivation of disease. B6D2F1Bom mice were inoculated with a wide range of Mycobacterium tuberculosis doses intraperitoneally or intravenously and followed for a long period to determine suitable conditions to produce latent infection. No anti-tuberculosis drug treatment was used. Microbiological and histopathological studies were carried out. Corticosterone challenge was used to reactivate the latent infection. Mice infected with 4 x 10(4) and 4 x 10(5) bacilli i.p. were followed up to 107 weeks without spontaneous reactivation. The present model is discussed in comparison with previous latent tuberculosis mouse models as well as the possible mechanisms of shift to stationary phase from multiplying bacilli.

Mutations of the p53 gene in oral squamous-cell carcinomas from sudanese dippers of nitrosamine-rich toombak and non-snuff-dippers from the Sudan and Scandinavia

Using PCR‐SSCP/DNA sequencing methods, we analyzed 14 oral squamous‐cell carcinomas (OSCCs) and 8 pre‐malignant oral lesions from different Sudanese patients for prevalence of mutations in exons 5 to 9 of the p53 gene in relation to toombak‐dipping status. OSCCs (14 from Sudan, 28 from Scandinavia), and 3 pre‐malignant oral lesions from Sudanese non‐dippers were used as controls. A statistically significant increased incidence in mutations of the p53 gene was found in OSCCs from toombak dippers (93%; 13/14), as compared with those from non‐dippers in Sudan (57%; 8/14) and in Scandinavia (61%; 17/28) respectively. In OSCCs from dippers, mutations were found in exons 5 to 9, while in those from non‐dippers they were found in exons 5, 7, 8, 9, and no mutations were found in exon 8 in any of the OSCCs from Sudan. Certain types of mutations, however, were similar with respect to exposure to toombak. OSCCs from dippers showed 15 transversions, 9 transitions, 3 insertions and one deletion, compared with 7 transversions, 2 transitions and one deletion found in OSCCs from Sudanese non‐dippers, and 9 transversions, 17 transitions and 2 insertions found in those from non‐dippers in Scandinavia. No mutations were found in any of the non‐malignant oral lesions in relation to dipping or non‐dipping status. These findings suggest that (i) the use of toombak plays a significant role in induction of increased p53 gene mutations, (ii) mutations observed were similar to those induced by tobacco‐specific N‐nitrosamines (TSNAs) in experimental animal models and those already reported in toombak dippers, (iii) types of mutations associated with TSNAs were similar in the exposed and the control groups, (iv) a novel mutation in exon 6 was found in the OSCCs from toombak dippers, (v) the p53 exons 5 (codon 130), 6 (codons 190, 216) and 7 (codons 229, 249, 252) mutations are probable hot spots for toombak‐related OSCCs. Further studies are necessary to validate the increased incidence and exon locations of the p53‐gene mutations as a biomarker of malignant transformation in populations in which the oral use of tobacco is habitual. Int. J. Cancer 81:527–534, 1999.

Effect of processing (sprouting and/or fermentation) on sorghum and maize. I: Proximate composition, minerals and fatty acids

Abstract Sorghum and maize porridge are used as infant weaning foods in many African countries. Porridges prepared from the cereals have high viscosity; to reduce viscosity, the cereals are initially sprouted and made into flour or fermented before use. This paper compares the effects of these preparatory methods on the proximate composition, mineral and fatty acid characteristics of the sprouted and/or fermented sorghum and maize. The preparatory methods had no effect on the proximate composition. The cereals are poor in calcium, iron and zinc. They are low in ω3 fatty acids but rich in the ω6 fatty acids. Germination increased the gross energy of the cereals. Porridges prepared from these cereals need to be supplemented by other foods.

Electron microscopy of induced heterotopic bone formation in guinea pigs

Abstract A high yield of osteoid and some mineralized bone was induced in the abdominal muscles following implantation of allogenic demineralized and lyophilized dentine. The following types of cells and reactions were found: A. Resorptive reaction mediated by monocytes, macrophages and dentinoclasts. B. Fibroblastic reaction, as an unspecific capsulation process. C. Osteoblastic reaction with osteoid formation. Dentinoclasts were observed before remineralization of the implanted dentine. Macrophages were active in the resorption of dentine, especially in the earliest stages. In dentinoclasts near remineralized dentine, crystals were observed in the ruffled border. Channels to the surface were found in osteoblasts, possibly originating from endoplasmic reticulum.

Effect of processing (sprouting and/or fermentation) on sorghum and maize: II. Vitamins and amino acid composition. Biological utilization of maize protein

Abstract The use of sprouted and or fermented maize and sorghum in improving weaning food nutrient quality was investigated. The cereals were studied for their thiamin, niacin, pyridoxine and amino acid composition and for their protein quality by nitrogen retention in young rats and by protein synthesis in vitro. Germination (sprouting) improved the vitamin content whereas fermentation had no substantial effect. The amino acids were slightly improved, but not enough to meet the nutritional needs of infants. Germination and/or fermentation neither improved nor had any detrimental effect on the overall protein quality. In-vitro protein synthesis was not affected by the processing methods.

Localization of Fcγ receptors and complement receptors CR1 on human peripheral nerve fibres by immunoelectron microscopy

The localization of receptors for the Fc part of IgG (Fc gamma R) and for the complement C3b/C4b components (CR1) on human peripheral nerve fibres was investigated by indirect immunoperoxidase staining of frozen nerve sections with monoclonal antibodies. Transmission electron microscopy revealed that Fc gamma R and CR1 are localized to the entire surface membrane and inner membrane (axolemma) of the Schwann cell. Myelin and axons were not stained. The presence of Fc gamma R and CR1 in human Schwann cells adds further evidence for the immunocompetence of these cells.