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Biomedical subjects

M Engelhardt

Publications and source records attributed to M Engelhardt.

At least 91 records · Page 5Linked to original sources
PubMed1997

Relative contribution of normal and neoplastic cells determines telomerase activity and telomere length in primary cancers of the prostate, colon, and sarcoma.

Telomerase and telomere length are increasingly investigated as potential diagnostic and prognostic markers in human tumors. Among other factors, telomerase and telomere length may be influenced by the degree of tumor cell content in tumor specimens. We studied telomerase activity and telomere length with concomitant integration of histopathological data to determine whether both were influenced by the amount of tumor cells. We measured telomerase in 153 specimens: in 51 solid tumor blocks; in 51 cryostat sections; and in 51 adjacent normal tissues from patients with sarcoma (n = 10) and colorectal (n = 11) and prostate cancer (n = 30) using the sensitive and rapid detection telomeric repeat amplification protocol assay. Telomere length was determined by telomere restriction fragment Southern blot analysis. From cryostat sections, tumor cell infiltration was assessed. Telomerase activity was detected in all colorectal tumors and sarcomas, as expected. In primary prostate cancer, however, telomerase activity was less frequently observed (14 of 30, 47%). Moreover, a decreased intensity compared to colon cancer and sarcoma was evident (P < 0.001). The median tumor cell infiltration was significantly higher in sarcoma (65%) and colon (30%) compared to prostate cancer (5%; P < 0.001). There was a positive correlation between tumor cell infiltration and telomerase activity (r = 0.89; P < 0.001). Telomere restriction fragments in tumors were shorter compared to the normal tissues with peak differences in colon, sarcoma, and prostate of 1.8, 2.8, and 1 kilobase pairs, respectively (P < 0.002). Our data suggest the presence of a positive correlation between the degree of tumor cell content in human solid tumors and the level of telomerase activity detected. We demonstrated that the amount of tumor cells also affects telomere restriction fragment analysis. Therefore, with the predominance of normal cells in tumor specimens, telomerase activity measured may not reflect the malignant phenotype, and telomere loss may be underestimated. This phenomenon was most evident in prostate cancer. Our results will have implications for the future when telomerase activity and telomere lengths may be used for early screening, diagnosis, and prognosis determinations and when telomerase inhibitors are applied to clinical practice.

Adenocarcinoma↗
PubMed1997

Telomerase and telomere length in the development and progression of premalignant lesions to colorectal cancer.

Telomerase and telomere length are increasingly studied as prognostic markers in malignancy. Telomerase is also known to be expressed in certain nonmalignant cells, although generally at low levels. We investigated telomerase activity and telomere length in premalignant, malignant, inflammatory, and normal colon specimens to determine whether significant differences exist and whether telomerase may serve as a marker for early- or late-stage colorectal cancer. Telomerase activity was evaluated in 130 frozen specimens from human colon cancer (n = 50), adjacent normal colon tissue (n = 50), colon polyps (n = 20), and colitis (n = 10) using a modified telomeric repeat amplification protocol assay, and telomere length was assessed by terminal restriction fragment analysis. High to moderate levels of telomerase activity were detected in 90% of colorectal tumors. Weakly positive activity was detected in 10%. None of the normal tissues exhibited telomerase activity. In polyps and colitis, telomerase activity was found in 60% (12 of 20) and 40% (4 of 10), respectively. Telomerase activity in both nonmalignant lesions was 25- to 54-fold lower than that detected in colon cancer (P < 0.001). We found a positive correlation between tumor cell infiltration determined in cryostat sections and telomerase activity (r = 0.886; P > 0.0001). Late-stage tumors (Dukes C + D) demonstrated increased telomerase activity compared to early-stage tumors (Dukes A + B). Telomere restriction fragments in colon tumors had peak values of 4.8 +/- 1 kbp that were significantly and consistently shorter than those of the adjacent normal tissues (7.54 +/- 1.3 kbp), polyps (7.5 +/- 0.7 kbp), and colitis specimens (7.7 +/- 0.5kbp; P < 0.0001). Telomeres were 0.6 kbp longer in tumors with high telomerase activity and in late-stage cancers (Dukes C + D) compared to those in tumors with low telomerase activity and in early-stage cancers (Dukes A + B). Our data demonstrate that telomerase in colon cancer was commonly acquired, and activity was higher than that in polyps and colitis. However, weak telomerase activity was detected in premalignant and inflammatory lesions. Telomeres in colon cancer were considerably shorter, an indication of extensive cell proliferation and population divisions, whereas adjacent normal colon specimens, polyps, and colitis had comparable telomere lengths. Our results indicate that increased telomerase activity occurs in colon cancer cells that have undergone extensive telomere shortening relative to surrounding normal tissues and in which telomerase-induced stabilization of telomeres may be critical for the continued proliferation of the malignant clone. The link between telomerase activity and stage suggests that telomerase is up-regulated as a function of increased tumor cell invasion, tumor progression, and metastatic potential in colon cancer.

Adult↗
PubMed1996

Differential expression of perforin in muscle-infiltrating T cells in polymyositis and dermatomyositis.

Polymyositis (PM) and dermatomyositis (DM) are the prototypical inflammatory diseases of skeletal muscle. In PM, CD8+ T cells invade and destroy muscle fibers, whereas humoral effector mechanisms prevail in DM. We studied the expression of the cytotoxic mediator perforin in inflammatory cells in PM and DM muscle by semiquantitative PCR, immunohistochemistry and confocal laser microscopy. Similar levels of perforin mRNA were expressed in PM and DM, and abundant perforin-expressing CD3+CD8+ and CD3+ CD4+ T cells were observed in both diseases. However, there was a striking difference in the intracellular localization of perforin. In DM, perforin was distributed randomly in the cytoplasm of the inflammatory T cells. In contrast, 43% of the CD8+ T cells that contacted a muscle fiber in PM showed perforin located vectorially towards the target muscle fiber. The results suggest (a) that the random distribution of perforin in the cytoplasm of muscle-infiltrating T cells observed in DM reflects nonspecific activation, and (b) that the vectorial orientation observed only in PM reflects the specific recognition via the T cell receptor of an antigen on the muscle fiber surface, pointing to a perforin- and secretion-dependent mechanism of muscle fiber injury.

Base Sequence↗
PubMed1996

Mobilization of peripheral blood progenitor cells for allogeneic transplantation: efficacy and toxicity of a high-dose rhG-CSF regimen.

Mobilization of PBPC was investigated in 19 healthy matched sibling donors using two different rhG-CSF regimens. Five donors (median age 39 years, range 17 to 57 years) received 10 micrograms rhG-CSF/kg bw once daily subcutaneously (s.c.), while 14 donors (median age 34 years, range 19 to 56 years) were treated with 10-12 micrograms rhG-CSF/kg bw twice daily s.c.. Leukapheresis was started on day 4 of rhG-CSF administration. Cytokine priming as well as collection of PBPCs were well tolerated. Application of twice daily rhG-CSF resulted in a higher yield of CD34+ cells in leukapheresis products than injection of once daily rhG-CSF. This high-dose twice daily rhG-CSF regimen is well tolerated and results in reliably high numbers of progenitor cells in the leukapheresis product in healthy donors, therefore collection as well as subsequent selection has been facilitated.

Adolescent↗
PubMed1996

Latex allergy and the student with spina bifida.

This article discusses the potential problem of latex allergy in the school, particularly among students with spina bifida. The origin of the problem, its symptoms, and prevention and management of latex allergy in the school environment are described. The individual roles of school administrator, school nurse, parent, student and other service providers are listed within an Individual Healthcare Plan (IHP). The IHP is proposed as a guide to schools to assist with identification of latex allergy reactions as well as response procedures if an allergic reaction is identified.

Child↗
PubMed1995

Leukocytoclastic vasculitis and long-term remission in a patient with secondary AML and post-remission treatment with low-dose interleukin-2.

Interleukin-2 (IL-2) has been licensed for the treatment of renal cell carcinoma and is currently being evaluated as a therapeutic agent in hematological malignancies. It is associated with a variety of side effects due to induction of a nonspecific inflammatory response. However, phenomena of autoimmunity have also been reported. Here we describe a patient with secondary acute myeloid leukemia who developed a leukocytoclastic vasculitis during long-term post-remission treatment with very low doses of IL-2.

Adrenal Cortex Hormones↗
PubMed1994

Intragraft events after heart transplantation: an experimental study comparing cytology in coronary sinus blood, peripheral blood, and daily histology.

Acute rejection is a frequent consequence after heart transplantation. To expand our knowledge of the rejection process and to investigate some intragraft events during acute rejection, the following experimental transplantation model was designed. Right cervical heart transplantation was performed in 12 mongrel dogs. Two experimental groups of six animals each received different immunosuppressive regimens. All animals were treated with daily triple drug therapy. In contrast to group 1, the animals in group 2 received high-dose steroids during rejection. The condition of the hearts was examined by daily transmural biopsies, graded according to the Billingham classification. To detect and quantify alterations in the mononuclear cell subsets of the myocardial venous return, blood samples from the coronary sinus blood (CS) and from peripheral blood (PB) were taken simultaneously with the biopsy. The total number of lymphoblasts and activated lymphocytes was determined and an activation index (AI) was calculated. The data referred to was established from 337 transmural biopsies. The AI of PB (n = 287) correlated well with the different stages of acute rejection (grade B0: AI = 2.2 +/- 2.1; grade B1 + 2: AI = 6.3 +/- 1.7; grade B3: AI = 10.0 +/- 4.7; P < 0.001). The rejection kinetics of both groups, including the rejection-free interval following high-dose steroid administration in group 2, could be expressed accurately by the AI. The time course of the total number of lymphoblasts in CS versus PB demonstrated that the lymphoproliferative response started 4 days prior to the first intramyocardial signs of rejection (mean = 3.8 +/- 0.7; n = 12).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1992

Allogeneic heart transplantation following xenogeneic bridging.

Xenografting seems to be a solution to bridge the time intervals when an essential allograft cannot be obtained. A subsequent allograft was never tried. Eight dogs (20-24 kg) of 2 years of age underwent right cervical heart transplantation. Donors were silver foxes (3-4 kg). The animals were treated by triple drug therapy consisting of cyclosporin A, methylprednisolone and azathioprine in clinical dosages. For control, six recipients received allogeneic heart transplantation (AHTP) and the identical immunosuppression. After rejection of the xenograft, a second allogeneic heart was anastomosed to the same right cervical vessels. Routine histology and immunohistology were performed. Thromboxane B2 and 6-keto-prostaglandin Fla were determined daily in peripheral blood. After final rejection sensitization of the recipient was controlled by haemagglutination tests. Survival times of the xenografts were 9.6 +/- 1.2. The subsequent hearts under the same therapy beat for 4.5 +/- 5.0 days. The average survival time of control hearts was 18 +/- 1.9 days. The five hyperacute second allografts showed signs of humoral rejection by absence of inflammation. The release of thromboxane B2 was different in hyperacute, accelerated or cellular rejection. In contrast to the long-functioning grafts, thromboxane B2 persisted during hyperacute rejection at a high level. However 6-keto-prostaglandin Fla showed no significant differences between long-time survivors and hyperacute rejecting hearts. After xenogeneic transplantation all recipients showed haemagglutinating titres between 1:4 and 1:16. Allogeneic grafts have different kinetics of rejection following xenogeneic heart transplantation (XHTP) compared with control hearts. Thromboxane B2 seems to be an important mediator in hyperacute rejection. This type of rejection is not associated with a change in 6-keto-prostaglandin Fla levels. These results indicate, that xenogeneic bridging under a common immunosuppressive regimen could lead to accelerated rejection of the following allograft. Under this condition clinical bridging is not advisable.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Comparison of acute rejection in sensitized ("domino") and unsensitized donor hearts following heterotopic transplantation.

Right cervical heart transplantation was performed in 18 mongrel dogs. Three experimental groups (6 dogs in each) were set up. Group I and II dogs received unsensitized donor hearts, while Group III dogs received the potentially sensitized native hearts of Group I and II dogs, following final rejection episodes in those animals. We call the transplantation of a native heart out of a previous recipient "domino" transplantation. Immunosuppression consisted of standard triple-drug therapy in all dogs. Groups II and III received, additionally, high-dose steroids during acute rejection episodes. The donor hearts were assessed daily via transmural biventricular biopsy (graded according to Billingham's criteria), and these results were compared with results of daily cytoimmunologic monitoring (n=259 for activation-index), used as a noninvasive method. Supplementally, antimyosin scintigraphy (n=25, heart-to-lung ratio) was employed for rejection diagnosis. The rejection type was determined by calculating T-cell/B-cell ratios with the aid of fluorescein-conjugated monoclonal antibodies. The invasive data consisted of 587 transmyocardial biopsy results, which were used to establish the rejection kinetics. In the domino grafts of Group III, acute rejection had an earlier onset (an average of 3.2 days) and was permanent, despite repeated cortisonepulse therapy. In contrast, acute rejection followed a biphasic course in Group II (average rejection-free interval, 6.8 days) and was non-uniform in Group I (onset after an average of 5.7 days). Cytoimmunologic monitoring corresponded significantly (p < 0.001) with daily histologic findings in Groups I and II, but not with those in Group III (domino grafts). The T-cell/B-cell ratio increased in Groups I and II (to an average of 3.9), as would be expected during acute cellular rejection. In contrast, the T-cell/B-cell ratio decreased in Group III (to an average of 1.1). The heart-to-lung ratio, as determined by antimyosin scintigraphy, accurately revealed the various stages of acute rejection in all groups (p < 0.001). We conclude that the native heart appears to become sensitized during acute rejection episodes of a heterotopically transplanted heart. Cytoimmunologic monitoring and calculation of T-cell/B-cell ratios support this conclusion. In addition, we conclude that cyto-immunologic monitoring and antimyosin scintigraphy are highly specific and sensitive tools for diagnosis of cellular rejection.

Journal Article↗
PubMed1990

Cation-dependent solubilization of rat thymocyte chromatin is closely related to decondensation of the nuclei.

The cation-dependent solubilization of rat thymocyte chromatin has been compared with decondensation of the nuclei as a function of sodium phosphate-mediated changes in the concentration of Mg2+ and Na+. After digestion of the nuclei with DNase I or Micrococcus nuclease for a time just sufficient to permit extraction of a maximal amount of chromatin (minimum digestion), solubilization of most of the chromatin was found to occur with the same cation dependency as decondensation of untreated nuclei, while further digestion changed the ionic requirements for solubilization. The cation-dependency of the chromatin solubility and of the nuclear decondensation also exhibited the same variations with temperature. The chromatin in the nuclei became up to 4-times more sensitive to DNase I by decondensation, which also induced a shift in the DNase I cleavage mode from a 200 bp to a 100 bp repeat pattern. In contrast, the sensitivity to Micrococcus nuclease appeared to be nearly unchanged. These results suggest that solubilization of chromatin prepared by a mild endonuclease treatment occurs as a direct consequence of structural changes in the chromatin which take place during decondensation of the nuclei.

Animals↗