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Biomedical subjects

A R Bahrami

Publications and source records attributed to A R Bahrami.

7 recordsLinked to original sources
PubMed2005

Embryonic stem (ES) cells and embryonal carcinoma (EC) cells: opposite sides of the same coin.

Embryonal carcinoma (EC) cells are the stem cells of teratocarcinomas, and the malignant counterparts of embryonic stem (ES) cells derived from the inner cell mass of blastocyst-stage embryos, whether human or mouse. On prolonged culture in vitro, human ES cells acquire karyotypic changes that are also seen in human EC cells. They also 'adapt', proliferating faster and becoming easier to maintain with time in culture. Furthermore, when cells from such an 'adapted' culture were inoculated into a SCID (severe combined immunodeficient) mouse, we obtained a teratocarcinoma containing histologically recognizable stem cells, which grew out when the tumour was explanted into culture and exhibited properties of the starting ES cells. In these features, the 'adapted' ES cells resembled malignant EC cells. The results suggest that ES cells may develop in culture in ways that mimic changes occurring in EC cells during tumour progression.

Animals↗
PubMed2003

Comparative study of lung function in Iranian factory workers exposed to silica dust.

The study compared lung function among 322 workers in pottery, ceramic, stone-cutter and stone-grinder factories in the west of the Islamic Republic of Iran. Concentrations of silica particles <2 microm were measured in the ambient air of factories. Forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) were significantly lower in stone-grinders compared with pottery, ceramic or stone-cutter workers and a control group. No difference in lung function was found in pottery and stone-cutter workers with less than 20 years occupation compared with controls. The prevalence of respiratory symptoms in stone-grinders was higher than other workers. The concentration of silica particles of stone-grinder factories was 40-110 times higher than in ceramic and potteries factories. More attention is needed to ventilation systems and health care of stone-grinders.

Air Pollutants, Occupational↗
PubMed2001

Ripening-related occurrence of phosphoenolpyruvate carboxykinase in tomato fruit.

Phosphoenolpyruvate carboxykinase (PEPCK) is present in ripening tomato fruits. A cDNA encoding PEPCK was identified from a PCR-based screen of a cDNA library from ripe tomato fruit. The sequence of the tomato PEPCK cDNA and a cloned portion of the genomic DNA shows that the complete cDNA sequence contains an open reading frame encoding a peptide of 662 amino acid residues in length and predicts a polypeptide with a molecular mass of 73.5 kDa, which corresponds to that detected by western blotting. Only one PEPCK gene was identified in the tomato genome. PEPCK is shown to be present in the pericarp of ripening tomato fruits by activity measurements, western blotting and mRNA analysis. PEPCK abundance and activity both increased during fruit ripening, from an undetectable amount in immature green fruit to a high amount in ripening fruit. PEPCK mRNA, protein and activity were also detected in germinating seeds and, in lower amounts, in roots and stems of tomato. The possible role of PEPCK in the pericarp of tomato fruit during ripening is discussed.

Amino Acid Sequence↗
PubMed2000

The HIC signalling pathway links CO2 perception to stomatal development.

Stomatal pores on the leaf surface control both the uptake of CO2 for photosynthesis and the loss of water during transpiration. Since the industrial revolution, decreases in stomatal numbers in parallel with increases in atmospheric CO2 concentration have provided evidence of plant responses to changes in CO2 levels caused by human activity. This inverse correlation between stomatal density and CO2 concentration also holds for fossil material from the past 400 million years and has provided clues to the causes of global extinction events. Here we report the identification of the Arabidopsis gene HIC (for high carbon dioxide), which encodes a negative regulator of stomatal development that responds to CO2 concentration. This gene encodes a putative 3-keto acyl coenzyme A synthase--an enzyme involved in the synthesis of very-long-chain fatty acids. Mutant hic plants exhibit up to a 42% increase in stomatal density in response to a doubling of CO2. Our results identify a gene involved in the signal transduction pathway responsible for controlling stomatal numbers at elevated CO2.

Algal Proteins↗
PubMed1999

Expression of a proteasome alpha-type subunit gene during tobacco development and senescence.

Proteasomes degrade specific proteins that have been targeted for proteolysis by ubiquitination. In animals and yeast nuclear-localised proteasomes play a role in regulating the cell cycle, and other developmental processes, via control of the levels of regulatory nuclear proteins such as cyclins and transcription factors. A cDNA, NtPSA1, isolated from tobacco styles was found to have high similarity to human and yeast genes, PRCI_human and PRCI_yeast with 63.4% and 51.6% overall identity respectively. These genes are believed to encode non-catalytic alpha-type subunits of 26S proteasomes and like NtPSA1 have putative nuclear localisation signals. NtPSA1 RNA was found to accumulate to varying levels in different parts of the plant and at different developmental stages. In particular, the level of NtPSA1 RNA was high in young dividing and expanding tissues, and declined during the senescence of both leaves and flowers. These results suggest that a role of proteasomes in plant nuclei may be to regulate developmental events by controlling the levels of regulatory proteins in proliferating and developing tissues, rather than to degrade and recycle proteins during senescence.

Amino Acid Sequence↗
PubMedDate not supplied

Distribution of volatile organic compounds in ambient air of Tehran.

Transportation sources have created a major hydrocarbon pollution problem in the ambient air of Tehran. The authors used a Carbotrap tube to determine volatile organic compounds in air. Such compounds can be desorbed thermally and analyzed with gas chromatography-mass spectrometry. Samples were obtained from 8 sites in Tehran at which traffic flow varied between 500 and 2,500 vehicles/hr. A total of 54 hydrocarbons were identified in the ambient air of Tehran, and the average measured concentrations of benzene, toluene, m- and p-xylene, ethyl benzene, and o-xylene were 127.6 microg/m3, 201.1 microg/m3, 110.7 microg/m3, 58.1 microg/m3, and 57.6 microg/m3, respectively (standard deviation = 3.8-51.7 microg/m3). Emissions of individual pollutants in south Tehran exceeded those in north Tehran, and these emissions were higher during the afternoon than during the morning. The geographical parameters and the photochemical reaction also played important roles in the pollution conditions.

Air Pollution↗