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Biomedical subjects

A K Jensen

Publications and source records attributed to A K Jensen.

8 recordsLinked to original sources
PubMed1999

Human T cell responses to the ESAT-6 antigen from Mycobacterium tuberculosis.

Human T cell responses to ESAT-6 and eight synthetic overlapping peptides were investigated in tuberculosis (TB) patients and control subjects from regions of high and low endemicity for TB. ESAT-6 was recognized by 65% of all tuberculin purified protein derivative-responsive TB patients, whereas only 2 of 29 bacille Calmette-Guérin-vaccinated Danish healthy donors recognized this molecule. In Ethiopia, a high frequency (58%) of healthy contacts of TB patients recognized ESAT-6. All of the peptides were recognized by some donors, indicating that the molecule holds multiple epitopes. Danish and Ethiopian patients differed in the fine specificity of their peptide responses. Recognition of the C-terminal region (aa 72-95) was predominant in Danish patients, whereas recognition of aa 42-75 was predominant in Ethiopia. The relationship of these differences to the distribution of HLA types in the two populations is discussed. This study demonstrates that ESAT-6 is frequently recognized during early infection and holds potential as a component of a future TB-specific diagnostic reagent.

Antigens, Bacterial↗
PubMed1995

The role of cytokines in mediating the bystander effect using HSV-TK xenogeneic cells.

We have previously demonstrated that genetically modified syngeneic murine tumor cells (KBALB) expressing the herpes simplex virus thymidine kinase gene (HSV-STK) can kill nearby unmodified tumor cells in the presence of ganciclovir (GCV). The killing was mediated by a 'bystander effect' as evidenced by the prolonged animal survival when syngeneic HSV-TK gene-modified tumor cells were inoculated into mice with an intraperitoneal tumor. In this study we investigated whether irradiated xenogeneic HSV-TK gene-modified tumor cells, a human colon carcinoma cell line (HCT) transfected with the HSV-TK gene, can mediate the 'bystander effect' when used in vitro and in vivo. In vitro experiments indicate that irradiated HSV-TK gene-modified xenogeneic cells (HCT) can mediate a bystander effect on the adjacent cells when the tumor population consisted of as few as 10% of the HSV-TK expressing HCT tumor cells. In vivo, animal survival experiments demonstrate that the xenogeneic gene-modified tumor cells could generate the 'bystander effect' in mice with intraperitoneal tumors as evidenced by prolonged animal survival. In addition, histologic examination of the tumors from experimental animals showed extensive tumor necrosis 3 days post HSV-TK/GCV treatment in comparison to control animals. To evaluate the cause of necrosis in vivo, we assayed for cytokines, which may be involved in mediating this process, by performing RT-PCR and immunohistochemistry on tumor RNA and tumor cells, respectively. Production of IL-1 alpha and IL-6 mRNA within the experimental tumors was observed by RT-PCR. However, mRNA expression for other cytokines including IFN-gamma, IL-2 and IL-4 was not present. Immunohistochemical analysis for IL-1 alpha protein showed reactivity within the infiltrating mononuclear cells indicating the release of this soluble factor. These results indicate that the bystander effect can be generated using irradiated xenogeneic cells both, in vitro and in vivo. Furthermore, this process is mediated by the release of cytokines such as IL-1 alpha, IL-6 which enhances the bystander effect in vivo by immunostimulation.

Animals↗
PubMed1993

Comparison of four second generation kits for detection of IgG antibodies against Helicobacter pylori in adults.

Four serological kits for detection of IgG antibodies against H. pylori were tested on 132 adult patients with dyspeptic symptoms. Presence of H. pylori infection was established when either culture or microscopy of gastric biopsies were positive. The prevalence of H. pylori infection was 55% in the test population. With Anti-H. pylori MTP-assay (Roche), Pylori stat test kit (Whittaker), HM-CAP (Enteric Products Inc.) and Pyloriset EIA-G (Orion) the sensitivities were 97%, 95%, 81% and 68% respectively, the specificities were 53%, 56%, 71% and 69% respectively, the positive predictive values 72%, 74%, 79% and 74% respectively and the negative predictive values were 94%, 92%, 79% and 64% respectively.

Adolescent↗
PubMed1993

Evaluation of eight commercial kits for Helicobacter pylori IgG antibody detection.

Eight commercial kits and an in-house ELISA for detection of IgG antibodies against Helicobacter pylori were evaluated for their use in diagnosis of H. pylori infection and in epidemiological research: Helico-GTM (Porton-Cambridge), G. A. P. test (Bio-Rad), H. pylori antibodies ELISA (Biometra), Anti-H. pylori IgG EIA (Roche), 2nd generation H. pylori EIA (Roche), Anti-H. pylori MTP-assay (Roche), Pylori stat test kit (Whittaker), Pyloriset latex agglutination kit (Orion), and the in-house ELISA based on heat-stable antigens. Fifty-four patients with dyspepsia (31 H. pylori positive by culture or microscopy) and 68 asymptomatic persons were tested. Sensitivities for the eight kits were 71%, 77%, 90%, 84%, 87%, 94%, 90%, 87%, and 87%, specificities were 74%, 65%, 74%, 74%, 83%, 83%, 70%, 65%, and 65%, respectively. For epidemiological use the estimated seroprevalence varied within approximately 15% in all age groups. Sensitivities and specificities obtained in different studies reveal as great differences in the results with the same kit as between results obtained with different kits in the same study. Kits with the highest sensitivities tend to be the same in all studies. It is therefore more important to test a kit in the population to which it is to be applied than to choose a specific kit.

Adolescent↗
PubMed1986

Effect of pretreatment with 0.9% sodium chloride or insulin solutions on the delivery of insulin from an infusion system.

The effect of pretreating a polyvinyl chloride i.v. administration system with sodium chloride or insulin solution on the delivery of insulin was studied. Insulin labeled with iodine 125 was added to human insulin, which was added to 0.9% sodium chloride injection packaged in flexible polyvinyl chloride containers and to 0.9% sodium chloride injection placed in empty ethylene vinyl acetate containers. Samples were tested for insulin content by gamma spectrometry after storage in the bags and after infusion through four different polyvinyl chloride administration sets at different flow rates. Effluent samples were collected at 10 times (6-50 minutes) after the start of the infusion. The 0.9% sodium chloride injection had a conditioning effect on the polyvinyl chloride administration sets, indicating an electrostatic sorption mechanism for insulin. Sorption to the untreated polyvinyl chloride sets and the ethylene vinyl acetate bags was substantial and followed a Langmuir adsorption isotherm. Insulin sorption to the untreated administration sets was greatest from the first 100 mL of effluent and did not differ by flow rate or type of set investigated. Storing the sodium chloride injection in the tubing for one hour or flushing the tubing with 100 mL of sodium chloride injection or 100 mL of the insulin admixture decreased sorption by half. Storing the insulin admixture in the tubing for 30 minutes caused sorption to be reduced by a factor of three. When either of the solutions was stored in the set and then the set was flushed with the solution, sorption was even further suppressed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗