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T Popescu

Publications and source records attributed to T Popescu.

At least 19 recordsLinked to original sources
PubMed1998

Mutation spectrum and phenylalanine hydroxylase RFLP/VNTR background in 44 Romanian phenylketonuric alleles.

The mutation spectrum and polymorphic haplotype background in 22 Romanian families have been analysed in this study using the restriction digestion of phenylalanine hydroxylase (PAH) regions specifically amplified or the DGGE/direct sequencing methods. Eleven PAH mutations specifically associated with six mutant haplotypes were detected. In spite of the relative heterogeneity of the molecular defects in the PAH gene, three mutations covered almost 70% of all alleles: R408W, 47.72%, 21/44; K363fsdelG 13.63%, 6/44; and P225T 6.81%, 3/44. Among these, R408W, the most frequent mutation in our population, represented 50% of all the phenylketonuric (PKU) chromosomes. Splice mutation IVS12nt1g-->a affected two PAH alleles (4.54%); the remaining seven mutations were rare, each having an effect on just one chromosome (1/44), resulting in a relative frequency of 2.27%. A high frequency was observed in our PKU samples for the relatively uncommon mutations, K363fsdelG and P225T mutation, suggesting a possible founder effect at origin. Within the investigated panel, these mutations, both very rare among other Caucasians were exclusively linked to haplotype 5.8 and 1.7, respectively. These results provide a basis for the development of a routine molecular analysis of Romanian PKU families.

Adult↗
PubMed1992

Kinetics of melittin induced pore formation in the membrane of lipid vesicles.

We have investigated the permeabilization of POPC unilamellar vesicle bilayers upon the addition of melittin. This process was measured in an early time range of a few minutes by means of monitoring the release of an entrapped marker, the self-quenching fluorescent dye carboxyfluorescein. Pore formation is indicated by an apparent 'all-or-none' efflux out of individual vesicles and a higher than linear dependence on melittin concentration. Applying a recently developed evaluation procedure, the data are readily converted into the gross number of pores per vesicle formed within the elapsed measuring time t. The results can be generally described in terms of a fast initial rate of pore formation that slows down to a much lower value after a period of about 1 to 2 minutes, following a single exponential time course. The three rate parameters involved are shown to be power functions of the concentration of melittin that is actually associated with the vesicle membrane. These findings are in excellent quantitative agreement with a proposed scheme of reaction steps where the formation of lipid associated peptide dimers becomes rate determining once an initial fast deposit is exhausted.

Ion Channel Gating↗
PubMed1989

A Novel Effect in Phycomyces Phototropism : Positive Bending and Compensation Spectrum in Far UV.

A novel effect-positive phototropic bending under far UV irradiation (between 260 and 305 nanometers) at low intensities-is reported. Natural compensation points (intensities which cause no bending under unilateral irradiation) have been determined for different wavelengths. The curve connecting these points, the compensation spectrum, divides the intensity-wavelength plane into areas of negative and positive tropism. It is further shown that a highly asymmetrical pattern of light stimulus within the sporangiophore underlies the symmetrical growth response at each compensation point. This suggests that some unknown additional factor is involved in perceiving a UV stimulus at the level of the photoreceptor. It is also demonstrated here that positive tropism in the UV range is due to a lens effect. We conclude that the hypothesis of optical attenuation of the stimulus (considered until now as the most plausible explanation of negative tropism in the UV spectral range) must be dismissed. The results presented here represent the first application of our quantitative theoretical consideration of spatial factors in phototropism heretofore neglected by others.

Journal Article↗
PubMed1987

A nonclassical radiation process (Comorosan effect) studied by a photographic technique.

Unconventional and highly unexpected results in the Comorosan Effect have been obtained in a photographic study using N-methyl-4-aminophenol (metol) as the developer. Before dissolving the developer was irradiated with green light (lambda = 546 nm) for various distinct periods of time (5, 10 and 15 seconds). A significant difference was observed in the rates of the developing process for different samples of the developer which had been irradiated for 5 seconds compared to non-irradiated controls, but no differences were observed for samples irradiated for 10 or 15 seconds, respectively. This unusual radiation phenomenon is similar to the Comorosan Effect by which rates of enzymatic reactions are manifested and significantly influenced by prior irradiation of the enzyme substrates, but only for times which are certain multiples of 5 seconds.

Enzymes↗
PubMedDate not supplied

Essential arterial hypertension and polymorphism of angiotensinogen M235T gene.

Several candidate genes, chosen from the renin- angiotensin system, were examined for their association with essential hypertension. The genes of the renin- angiotensin system (RAS) are good candidates for such an approach because this system is well known to be involved in the control of blood pressure. One of these candidate genes is the gene encoding for angiotensinogen (the most important gene of the RAS associated with essential hypertension in the most population, is the gene for angiotensin-converting enzyme- ACE). One DNA polymorphism within exon 2- with threonine instead of methionine at position 235 (M235T) was found to be significantly associated with hypertension. The objective of this study is the analysis of M235T polymorphism in angiotensinogen gene in Romanian patients with essential hypertension as well as controls. We examined 38 patients with essential hypertension and 21 normotensive patients. In order to identify the M235T angioteninogen variant, we used the following methods: DNA extraction, PCR amplification and enzymatic digestion of the PCR product using Tth 111I restriction endonuclease enzyme. In the study groups, the M235T variant (Met?Thr in aminoacid position 235) was found more frequently in hypertensive patients (81,57%), than in control subjects (66,66%). We identified 52,63% M235T heterozygotes in the hypertensive group compared with 47,61% in the control group, and 28,94% T235T homozygotes in the hypertensive group compared with 19,04% in the control group. The results of our study suggest an association of the M235T polymorphism in the gene encoding angiotensinogen with essential hypertension.

Adult↗
PubMedDate not supplied

Influence of pregnancy, birth and abortion on the evolution of systemic lupus erythematosus.

The effect of pregnancy, birth and abortion on systemic lupus erythematosus (SLE) was studied in 225 patients with or without a history of pregnancy and abortion. It was observed that pregnancy, birth and abortion aggravate the evolution of disease in patients with active SLE. The tissue autoantibodies studies presented a low titer in patients in whom pregnancy had occurred in the course of disease. Antimeasles antibodies presented a high titer in patients with a history of gestation. These data suggest that gestation induces immune changes which aggravate SLE.

Abortion, Spontaneous↗