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Biomedical subjects

Zaki Kraiem

Publications and source records attributed to Zaki Kraiem.

11 recordsLinked to original sources
PubMed2005

Human thyrotropin (TSH) variants designed by site-directed mutagenesis block TSH activity in vitro and in vivo.

TSH is a heterodimeric glycoprotein hormone synthesized in the pituitary and composed of a specific beta-subunit and a common alpha-subunit shared with FSH, LH, and human chorionic gonadotropin. The heterodimer was previously converted into a biologically active single chain protein by genetic fusion of the genes coding to both subunits in the presence of the carboxy-terminal sequence of human (h) chorionic gonadotropin-beta subunit as a linker [hTSHbeta-carboxyl-terminal peptide (CTP)-alpha]. N-linked carbohydrate-free single-chain TSH variants were constructed by site-directed mutagenesis and overlapping PCR: one devoid of both N-linked oligosaccharide chains on the alpha-subunit (hTSHbeta-CTP-alpha(deg)) and the other lacking also the oligosaccharides on the beta-subunit (hTSHbeta(deg)-CTP-alpha(deg)). These variants were expressed in Chinese hamster ovary cells and secreted into the culture media. We have previously reported that the variants block the activities of hTSH and thyroid-stimulating immunoglobulins in cultured human thyroid follicles. In the present study, binding affinity of hTSH variants to hTSH receptor and the localization of the antagonistic effect were examined. Moreover, the effect of these variants on TSH activity was tested in vivo. The results of the present study indicate that the hTSH variants bind to the hTSH receptor with high affinity. Experiments using forskolin also indicated that the N-linked carbohydrate-free TSH single-chain variants inhibit TSH activity at the receptor-binding site and not at a postreceptor level. Moreover, the variants significantly inhibited (about 50%) TSH activity with respect to thyroid hormone secretion in vivo in mice. These variants may offer a novel therapeutic strategy in treating hyperthyroidism.

Animals↗
PubMed2005

Selective agonists and antagonists to thyroid hormone action.

Selective thyromimetics have been designed and shown to exhibit some of the beneficial effects of thyroid hormones, such as lowering of cholesterol and weight reduction, without the adverse thyroid hormone action on muscle, bone, and heart rate. Progress has also been made in attempting to treat hyperthyroidism by synthesizing antagonists that block thyroid hormone action, at the level of the thyroid hormone receptor or of the thyrotropin receptor. Clinical trials are still awaited, however, to verify whether these potentially promising agents will indeed prove to be of clinical therapeutic value.

Animals↗
PubMed2004

Early embryo-endometrial signaling modulates the regulation of matrix metalloproteinase-3.

OBJECTIVE: To examine matrix metalloproteinase-3 (MMP-3) expression in human stromal cell culture after P stimulation and the effect of conditioned medium from human embryo-epithelial cells coculture on its expression and activity. DESIGN: Metabolic and endocrine studies on human tissue. SETTING: In vitro fertilization (i.v.f.) unit and endocrine research unit. PATIENT(S): Infertile patients undergoing endometrial tissue sampling for dating at the luteal phase before i.v.f. INTERVENTION(S): Endometrial sampling and collection of human embryos culture media. MAIN OUTCOME MEASURE(S): Expression and activity of secreted MMP-3 by P-induced stromal cells, and in stromal cells exposed to conditioned medium from embryo-epithelial cell coculture. RESULT(S): Expression and activity of MMP-3 in human stromal cells decrease after P induction. Following incubation of these stromal-derived decidual cells with conditioned medium from embryo-epithelial cell coculture, MMP-3 expression and activity increased in a statistically significant manner. CONCLUSION(S): Progesterone inhibition of MMP-3 expression and its support of endometrial integrity were prevented by local expression of MMP-3 in response to embryonic signaling.

Adult↗
PubMed2003

Decreased expression of tissue inhibitor of matrix metalloproteinases in follicular fluid from women with polycystic ovaries compared with normally ovulating patients undergoing in vitro fertilization.

OBJECTIVE: To compare activity of matrix metalloproteinases (MMP) and expression of their tissue-specific inhibitor (TIMP) in the follicular fluid of normally ovulating women and women with the polycystic ovary syndrome (PCOS). DESIGN: Prospective study. SETTING: IVF unit and endocrine research unit. PATIENT(S): Fourteen patients undergoing IVF treatment (seven with normal ovulation and seven with PCOS). MAIN OUTCOME MEASURE(S): Activity of MMP-2 and MMP-9 and expression of MMP-1, TIMP-1, and TIMP-2 was measured in follicular fluid of the leading follicles by using gel zymography and immunoblot analysis. RESULT(S): The activity of MMP-2 and MMP-9 and expression of MMP-1 was similar in follicular fluid of normally ovulating patients and patients with PCOS. Significantly lower expression of TIMP-1 was found in follicular fluid of patients with PCOS women compared with normally ovulating patients. CONCLUSION(S): Because MMPs and TIMPs play a role in the physical and chemical structure of the follicular compartment, the decreased expression of TIMP in patients with PCOS may be part of a compensatory process to overcome the physical properties of the thick ovarian capsule.

Adult↗
PubMed2003

Stimulation of Fos- and Jun-related genes during distraction osteogenesis.

Bone cells respond to mechanical stimulation by gene expression. The molecular events involved in the translation of mechanical stimulation into cell proliferation and bone formation are not yet well understood. We looked for the expression of early-response genes of the AP-1 transcription factor complex in an in vivo bone regeneration system subjected to mechanical forces because these genes were found to be related to mechanotransduction and important for bone development. Sheep maxillary bone was distracted daily for 15 days. c-Jun and c-Fos were evaluated by Northern blotting analysis and immunohistochemistry in biopsy specimens removed at 8 and 15 days and were compared with post-osteotomy but not distracted repair tissue. Elevated levels of c-Jun and c-Fos mRNA were found after 8 days of distraction. Likewise, mesenchyme-like and fibroblast-like cells composing the 8-day distracted regeneration tissue showed increases in the intensity of immunostaining compared to cells in the corresponding non-distracted fracture repair tissue. After 15 days of distraction, when bone trabeculae start to form distally and proximally in the distracted regeneration tissue, mostly preosteoblasts and osteoblasts retained c-Fos and c-Jun immunoreactivity, similar to bone-associated cells in control non-distracted fracture repair tissue. We propose that the elevated expression of c-Jun and c-Fos is related to mechanical stimulation in this in vivo bone regeneration system.

Animals↗
PubMed2003

Enhanced expression of nicotinamide N-methyltransferase in human papillary thyroid carcinoma cells.

To gain an understanding of the molecular pathogenesis of thyroid cancer, we used DNA microarray to study the expression profiles of 10 different human thyroid carcinoma cell lines. These included papillary lines BHP 2-7, BHP 7-13, BHP 10-3, BHP 18-21, NPA 87, and TPC1; anaplastic lines ARO 81-1 and DRO 90-1; follicular line WRO 82-1; and medullary line HRO 85-1. Among the genes with increased expression in the cancer cell lines, a gene coding for nicotinamide N-methyltransferase (NNMT) was identified for being highly expressed only in the papillary cell lines. NNMT catalyzes N-methylation of nicotinamide and other structurally related compounds and is highly expressed in the human liver. The results were further confirmed by semiquantitative RT-PCR and Northern blot analysis. NNMT catalytic activities were determined in all of the cells described above and in additional cell lines. Significantly higher NNMT enzyme activities were detected in eight of 10 of the papillary lines and three of six of the follicular cell lines tested. Normal thyroid tissue, thyroid primary cultures, anaplastic cancer cells, and medullary cancer cells showed no or low enzyme activity. Immunohistochemical staining for NNMT of human thyroid specimens showed strong and abundant cytoplasmic reactions in the sections of papillary carcinomas, and weak or scanty reaction in the normal thyroid tissues. These results indicate that NNMT is a potential biomarker for papillary thyroid carcinoma.

Biomarkers, Tumor↗
PubMed2003

Recent advances in thyroid research: selective thyroid hormone receptor modulators (STRMs).

Compounds have been designed and tested exhibiting some of the beneficial effects of thyroid hormones, such as lowering of cholesterol and weight reduction, without the adverse thyroid hormone action on heart rate. Progress has also been made in attempting to treat hyperthyroidism by synthesizing antagonists that block thyroid hormone action, at the level of the thyroid hormone receptor or of the thyrotropin receptor. Clinical trials are still awaited, however, to verify whether these potentially promising agents will indeed prove to be of clinical therapeutic value.

Animals↗
PubMed2002

Impaired light chain allelic exclusion and lack of positive selection in immature B cells expressing incompetent receptor deficient of CD19.

Positive signaling is now thought to be important for B cell maturation, although the nature of such signals has not yet been defined. We are studying the regulatory role of B cell Ag receptor (BCR) signaling in mediating positive selection of immature B cells. To do so, we use Ig transgenic mice (3-83Tg) that are deficient in CD19, thus generating a monoclonal immature B cell population expressing signaling-incompetent BCR. Immature 3-83Tg CD19(-/-) B cells undergo developmental arrest in the bone marrow, allowing maturation only to cells that effectively compensate for the compromised receptor by elevated levels of BCR. We find that developmentally arrested 3-83Tg CD19(-/-) B cells fail to impose L chain allelic exclusion and undergo intensive V(D)J recombination to edit their BCR. Furthermore, immature 3-83Tg CD19(-/-) B cells, which were grown in vitro, failed to undergo positive selection and to survive when adoptively transferred into normal recipients. However, elevation of BCR expression levels, obtained by transgene homozygosity, effectively compensated for the compromised BCR and completely restored BCR-mediated Ca(2+) influx, allelic exclusion, and positive selection. Our results suggest that the BCR signaling threshold mediates positive selection of developing B cells, and that a receptor-editing mechanism has an important role in rescuing cells that fail positive selection because of incompetent receptors.

Alleles↗
PubMed2002

Increased expression of matrix metalloproteinase-2: a diagnostic marker but not prognostic marker of papillary thyroid carcinoma.

BACKGROUND: Matrix metalloproteinases are proteolytic enzymes that degrade extracellular matrix components. Numerous studies have demonstrated that individual MMPs play a crucial role in tumor invasion and metastasis. OBJECTIVE: To examine the expression of MMPs and their inhibitor TIMP-2 in neoplastic and normal thyroid tissues. METHODS: We examined 33 cases of thyroid tumor (papillary, follicular and medullary carcinoma, follicular adenoma and multinodular goiter). MMP protein content and activity were measured by enzyme-linked immunosorbent assay and gel zymography. Immunohistochemistry was also performed. RESULTS: The thyroid tissues examined secreted MMP-2 and 9 as well as TIMP-2, but only MMP-2 was significantly higher in papillary carcinoma cases compared to the adjacent normal tissue or to the other tumor entities. Increased MMP-2 immunohistochemical staining was demonstrated in the neoplastic papillary epithelial component. No significant difference was seen between papillary carcinomas with lymph node metastases and those without. CONCLUSIONS: Increased MMP-2 expression may be useful as a diagnostic marker to differentiate papillary carcinoma from other thyroid neoplasms, but it cannot serve as a useful prognostic marker.

Biomarkers, Tumor↗
PubMedDate not supplied

Presence of matrix metalloproteinases and tissue inhibitor of matrix metalloproteinase in human sperm.

The matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that degrade protein components of the extra-cellular matrix. The necessity of breakdown of physical barriers in the fertilization process suggests that MMPs, along with their tissue inhibitors (TIMPs), might be involved in this task. We have examined the presence of MMP and TIMP in normal and abnormal human sperm samples by gel zymography and Western blot analysis. Thirty-five normal sperm samples and 35 abnormal sperm samples were examined in this study. Gel zymography showed 92-, 72-, 62-, and 28-kd molecular-weight bands exhibiting gelatin-degrading activity in both normal and abnormal sperm samples. The 92-, 72-, and 62-kd bands with gelatinolytic activity are consistent with pro-MMP-9, pro-MMP-2, and active MMP-2, respectively (pro-MMP being the zymogen of MMP). Western blot analysis showed the presence of TIMP-1 in both normal and abnormal sperm samples. A higher 28-kd activity and a lower 92-kd MMP activity in normal sperm samples relative to abnormal samples were detected. No marked difference in TIMP-1, 72-kd, and 62-kd release was observed between normal and abnormal sperm samples. In conclusion, this is the first report of MMP activity in normal and abnormal human sperm samples and of TIMP presence in sperm samples. The data indicate a different MMP profile between normal and abnormal sperm samples, with a higher 28-kd activity and a lower 92-kd MMP activity in normal relative to abnormal samples.

Humans↗