سال:1379 | دوره: | شماره: |تعداد مقالات:8

In recent years the science of tissue engineering has emerged as a powerful tool for the development of a novel set of tissue replacement parts and technologies. Recent advances in the fields of biomaterials, stem cell technologies, growth factor field and biomimetics have created a unique set of opportunities for investigators to fabricate lab-grown tissues from combination of extracellular matrices (scaffolds), cells, and bioactive molecules. Despite these breakthrough advances, the major challenges facing this new emerging field of bioengineering remain unresolved as lab-grown tissues still exhibit a general lack of functional and biomechanical stability needed for transplantation. A successful strategy to develop true human replacement parts requires a multidisciplinary approach that converges recent advances in tissue, matrix, growth factor and developmental biology with recent technological breakthroughs in tissueinformatics, bioinformatics, highthrouput combinatorial chemistry and stem cell technologies.

A murine IgM monoclonal antibody (MA-2C6) with k-light chains directed against an antigenic determinant of outer surface protein A (OspA) of the Lyme disease spirochete, Borrelia burgdorferi, is produced. This antibody could bind specifically to OspA antigen of several isolates of B. burgdorferi, but not to the non-Lyme disease bacteria such as T. pallidum and B. hermsii. Antibody MA-2C6 was purified by ion-exchange chromatography and used for purification of OspA antigen from Borrelia burgdorferi cell lysate. This antibody together with an IgG1 monoclonal antibody specific for OspA, that was previously characterized, were used to test whether these antibodies recognize different epitopes on OspA antigen of Borrelia burgdorferi. For this test, ELISA double antibody binding was used. Two antibodies were added to the antigen either separately or simultaneously, and the amount of bound antibody was quantitatively measured by the use of rabbit anti-mouse IgG conjugated with alkaline phosphatase. Additivity of the bound enzymatic activity was observed when the monoclonal antibodies bind to distinct epitopes. With this test, two distinct epitopes were recognized on the OspA molecule. This antibody can be used not only for the purification and subtyping of OspA, but also for neutralization and immunotherapy

The mechanism by which bi-and trivalent cations affect human liver phosphatidate phosphohydrolase (PAP) activity was investigated. Bivalent cations up to 1 mM increased PAP activity whereas at higher concentrations the activity of the enzyme decreased. The stimulatory concentration for trivalent cations such as Al3+ and Cr3+, however, was much lower being 2 m M and 1 m M, respectively. All cations affecting PAP activity were also able to induce phase transition of phosphatidate from lamellar (La) to inverted hexagonal (HII) form. The rate of La-HII transition was different for each cation. At 100 mM concentration of Mg2+ only 26% of the original phosphatidate remained in La form and for other cations tested ranged from 14.5% to 76%. The phase transition was blocked by EDTA. Magnesium from 0.8 to 1.5 mM concentration raised PAP activity (3-fold) with La form of substrate but not with the HII phase. Monovalent cations such as Na+ and K+ neither affected enzyme activity nor substrate configuration. These data suggest that cation-induced PAP activation is not as a result of cation-protein interaction, but is due to formation of a suitable substrate configuration for the enzyme catalysis during phosphatidate phase transition. It appears that the real substrate configuration for PAP activity is situated between La and HII phases.

Data on the effects of serotonin reuptake inhibitors on learning and memory processes are not consistent. In the present study, the effects of citalopram, a very potent and completely selective inhibitor of the serotonin reuptake on spatial discrimination in the T-maze and Morris water maze, were assessed in mice and/or rats. Animals received different doses of citalopram (1, 2, 4, 8 or 16 mg/kg, i.p.) or its vehicle (saline) 30 min before training each day. The results showed no significant effects of citalopram on T-maze discrimination task in mice and rats. However, there was dose-dependent increases in latencies to find the invisible platform and traveled distances in citalopram received groups compared to the control group with the peak effect at doses of 4 and 8 mg/kg in Morris task. Therefore, it appears that citalopram can cause learning deficits in complex spatial tasks. Iran. Biomed.

Experimental autoimmune vitiligo was induced by the intradermal injection of the purified mushroom tyrosinase emulsified in Complete Freund’s Adjuvant (CFA) in female C57BL/6 mice. The onset of vitiligo was characterized by hair hypopigmentation and total melanocyte depletion in the basal layer of the epidermis. Oral administration of semipurified mushroom tyrosinase prevented experimental autoimmune vitiligo (EAV). Suppression of clinical and histological disease was observed when animals received mushroom tyrosinase. A decrease in lymphocyte proliferation, delayed type hypersensitivity responses, increase in humoral immunity of the mice may all suggest that the suppression of the disease is correlated with cellular immune responses suppression. Based on our data, it may be concluded that the oral administration of the mushroom tyrosinase may have practical implications in vitiligo

DNA coding for the core antigen from hepatitis B Virus (HBcAg) was amplified, cloned and propagated in E. coli. The core protein was expressed in E. coli and the product was readily detected by Western blot. This protein can be used as a diagnostic material in serum screening tests. To increase the level of expression of this antigen in bacteria, two plasmids were constructed in which the gene coding for N-terminal part of the human IL-2 has been fused to 5¢ -terminus of the core antigen gene under control of the tryptophan promoter. Although the expression level of core antigen from hepatitis B Virus in E. coli was increased in fusion forms, but the size of fusion partner could affect the antigenicity, particle formation and assembly of the core antigen. The native and the two fusion forms of the core antigens from hepatitis B Virus were evaluated as a diagnostic material in serum screening.

There are extensive evidences that show axonal processes of the nervous system (peripheral and/or central) may be degenerated after nerve injuries. Wallerian degeneration and chromatolysis are the most conspicuous phenomena that occur in response to injuries. In this research, the effects of post-operative time following sciatic nerve crush on the number of spinal motoneurons were investigated. Twelve adult male Wistar rats, whose left sciatic nerves were highly compressed for 30 s, assigned to experimental groups 1 and 2 (n = 6). After 3 and 8 weeks post-operative (in groups 1 and 2 respectively) the lumbar segments of spinal cord were sampled, processed, sectioned serially and stained with toluidine blue (pH 4.65). By using stereological quantitative technique (physical disector), the number of alpha motoneurons in the right and the left ventral horns of spinal cord were counted and compared with each other. Statistical analyses showed a remarkable reduction in the number of alpha motoneurons in the left side (experimental or operated) when compared with the right side (control or unoperated) both in 3 and 8 weeks post-operative groups. This reduction may be due to the blockade of retrograde axonal transport.

Elevated amount of the free radicals due to ionizing radiation causes deteriorating damage on immune system. Therefore, we made attempts to investigate the protective effect of vitamin E (vit-E), a biological antioxidant in BALB/c mice, so as to find an affordable prophylactic supplementation for individuals who are at risk. Several groups of mice were selected and exposed to sub-lethal g -irradiation with or without vit-E supplementation. At the end of exposure, mice were immunized by either live attenuated Brucella melitensis vaccine or sheep red blood cell (SRBC). Consequently, the following parameters were assayed: specific antibody response, delayed type hypersensitivity and lymphocyte proliferation. We showed that vit-E supplementation restored the immune response in g -irradiated mice. These findings might have implications for individuals who are at risk of exposure to ionizing radiation. Iran. Biomed.