Biomedical subjects

M Hejazi

Publications and source records attributed to M Hejazi.

6 recordsLinked to original sources

PubMed2004

Modulation of thyroidal radioiodine uptake by theophylline.

Diagnostic and therapeutic use of radioiodine in the management of thyroid disorders depends on the ability of thyroid cells to concentrate radioiodine, a process regulated by thyrotropin and dependent on the intracellular increase in cAMP. We tested the ability of theophylline, a drug known to increase intracellular cAMP via inhibition of phosphodiesterase, to modulate the thyroidal radioiodine uptake in FRTL-5 cells, in mice and in humans. In FRTL-5 cells, theophylline increased the uptake of radioactive iodine and intracellular cAMP only at low concentrations (1 microM). In mice, theophylline increased slightly the radioiodine uptake, although this increase varied from 1.5- to 6.6-fold. In humans, theophylline decreased slightly the radioiodine uptake, a decrease that became more pronounced with time after radioiodine administration. These studies suggest that theophylline modulates the radioiodine uptake in a dose-dependent fashion, although the modulation is mild and probably not applicable to the clinical setting.

Adult↗

PubMed2002

Use of hop (Humulus lupulus) agricultural by-products for the reduction of aqueous lead(II) environmental health hazards.

The agricultural by-products of the hop plant (Humulus lupulus L.) were investigated to determine their potential for use in the removal of heavy lead(II) ions from contaminated aqueous solutions. Separate batch laboratory experiments were performed to establish the optimal binding pH, time exposures, and capacity of the metal adsorption for lead(II) ions by dried and ground hop leaves and stems biomass. Results from these studies have shown a pH dependent binding trend from pH 2-6, with optimum binding occurring around pH 5.0. Time dependency experiments showed a rapid adsorption of lead(II) ions within the first 5 min of contact. Binding capacity experiments demonstrated that 74.2mg of lead(II) were bound per gram of leaf biomass. Similarly overall capacity was seen for the leaves and stems. Desorption of 99% of the bound lead(II) ions was achieved by exposing the metal laden biomass to 0.5M sodium citrate. Further experiments were performed with silica-immobilized hop tissues to determine the lead(II) binding ability under flow conditions. Comparison studies were performed with ion-exchange resins to evaluate the binding ability and to gain further insight into the metal binding mechanism. X-ray absorption spectroscopy experiments were also utilized to gain further insight into the possible lead(II) binding mechanism by the hop plant tissue. Results from these studies indicate that carboxyl ligands are involved in the binding of lead(II) from aqueous solution. These findings show that the use of hop agricultural waste products may be a viable alternative, for the removal and recovery of aqueous lead(II) ions from contaminated waters.

Adsorption↗

PubMed2000

Hypothyroidism in transgenic mice expressing IFN-gamma in the thyroid.

IFN-gamma has been implicated with contradictory results in the pathogenetic process of autoimmune (Hashimoto's) thyroiditis, the most common cause of hypothyroidism in adults. To test whether the local production of IFN-gamma can lead to thyroid dysfunction, we have generated transgenic mice that express constitutively IFN-gamma in the thyroid follicular cells. This expression resulted in severe hypothyroidism, with growth retardation and disruption of the thyroid architecture. The hypothyroidism derived from a profound inhibition of the expression of the sodium iodide symporter gene. Taken together, these results indicate a direct role of IFN-gamma in the thyroid dysfunction that occurs in autoimmune thyroiditis.

Animals↗

PubMed1999

Mouse thyroid primary culture.

Technological advances have drastically decreased the number of cells required to analyze expression of the genes and functions of the encoded proteins, making even a small organ like a mouse thyroid amenable to study in vitro. We have established primary cultures of mouse thyroids that showed, for up to 14 days after seeding, strong cytoplasmic staining for thyroglobulin. The staining then gradually decreased and was present in only 5-10% of thyrocytes at day 28. Furthermore, cultured thyrocytes expressed the thyroperoxidase and thyrotropin-receptor genes, and, although at lower levels, the sodium-iodide symporter gene. Finally, cultured thyrocytes could be transiently transfected by lipofection, using FuGENE 6. Thus, we report that it is possible to cultivate functional primary mouse thyrocytes that can be used for a variety of biological studies. This system is appealing because it permits the use of the ever-increasing number of transgenic, knock-out and knock-in mouse strains in studying thyroid pathophysiology.

Animals↗

PubMed1999

Cyanophycinase, a peptidase degrading the cyanobacterial reserve material multi-L-arginyl-poly-L-aspartic acid (cyanophycin): molecular cloning of the gene of Synechocystis sp. PCC 6803, expression in Escherichia coli, and biochemical characterization of the purified enzyme.

The branched polypeptide multi-L-arginyl-poly-L-aspartic acid, also called cyanophycin, is a water-insoluble reserve material of cyanobacteria. The polymer is degraded by a specific hydrolytic enzyme called cyanophycinase. By heterologous expression in Escherichia coli, a gene encoding cyanophycinase has been identified in the sequenced genome of Synechocystis sp. PCC 6803. The gene, designated cphB, codes for a protein of 29.4 kDa. The high level of expression of active cyanophycinase in E. coli from the Synechocystis gene allowed for its purification to electrophoretic homogeneity. The enzyme, which appears to be specific for cyanophycin, hydrolysed the polymer to a dipeptide consisting of aspartic acid and arginine. Based on inhibitor sensitivity and primary sequence, cyanophycinase appears to be a serine-type exopeptidase related to dipeptidase E [Conlin, C.A., Haakensson, K., Liljas, A. & Miller, C.G. (1994) J. Bacteriol. 176, 166-172].

Amino Acid Sequence↗

PubMed1987

Temporal lobe epilepsy with schizophrenia.

I have reported a case of coexisting schizophrenia and complex partial seizures to augment earlier reports of schizophrenia and psychomotor seizures masquerading as one another. I have attempted to clarify the differential diagnosis and reinforce the need to do thorough studies in such cases.

Aged↗