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Biomedical subjects

M Ivanova

Publications and source records attributed to M Ivanova.

At least 55 records · Page 3Linked to original sources
PubMed1989

Expression of repetitive human calcitonin genes in Escherichia coli.

In order to stabilize recombinant human calcitonin (rhCT) against Escherichia coli proteases a series of concatemeric hCT genes with varying degrees of repetition were synthesized and expressed in E. coli under the control of a constitutive synthetic phage promoter. The series of expression vectors thus constructed was used as a model to study the effect of gene repetition on the efficiency of expression (both transcription and translation), stability of mRNA, proteolytic stability of recombinant protein, genetic stability of expression plasmids, etc. The oligomerization of the hCT gene resulted in stabilization of the mRNA increasing its half-life from 60-70 s (as in the hCT monomer, dimer, and trimer genes) to 100-120 s (for the hCT tetramer gene). This effect held true as well for the proteins coded by the corresponding repetitive hCT genes. The genetic stability (segregation and recombination) of the expression plasmids containing hCT oligomeric genes also depended on the number of hCT gene repeats. The expression plasmid containing the hCT tetramer gene segregated from one of the best producers of rhCT (E. coli LE392) up to 100% after 100 cell generations in nonselective media (free of antibiotics). One of the plasmids most sensitive to recombination events was that containing the hCT pentamer gene. The series of expression plasmids bearing hCT oligomeric genes was used for transformation of various E. coli strains in order to find the optimal host for production of rhCT. The highest yield (44-100 mg rhCT per 1 liter of bacterial culture) was obtained with the strains LE392, JM107, and DH1.

Calcitonin↗
PubMed1987

[Ambulatory treatment of paroxysmal supraventricular arrhythmias with verapamil (isoptin)].

Twenty patients, seven of them with paroxysmal supraventricular tachycardia; 8 with paroxysmal auricular flutter; 3 with paroxysmal auricular fibrillation and 2 with paroxysmal atrial tachycardia, with stage II of A-V block, were treated intravenously with isoptin, with an average dose of 0.1 mg/kg body mass. Ten, out of them, restored their sinus rhythm, 7 considerably slowed down the heart rate and 3 failed to respond. Adverse effects were observed only in one patient--transitory hypotension.

Adult↗
PubMed1986

Hormonal regulation of sodium-fluid balance and some hemodynamic parameters in the rat. I. Effect of indomethacin and vasopressor-vasodepressor hormonal systems in the regulation of blood pressure.

A study based on sodium depletion, sodium loading and indomethacin treatment was conducted on rats. After sodium depletion significant activation of renin-angiotensin-aldosterone system and insignificantly increased kallikrein excretion without changes in prostaglandin excretion and plasma vasopressin were found. After sodium loading significant decrease of PRA (-83%), prostaglandin excretion (-34%), insignificant decrease of aldosterone and kallikrein excretion and significant increase of vasopressin (134%) were established. Indomethacin (5 mg/kg b.w.) administered for 8 days showed an antidiuretic and an anti-natriuretic effect, inhibition of PG-synthesis by 57% and of PRA by 68%, a significant increase of plasma volume (21%), blood volume (24%) and mean arterial pressure (14%). The relationships between vasopressor and vasodepressor hormonal systems in the rat are discussed.

Animals↗
PubMed1985

The renal prostaglandin kallikrein-kinin-system in Brattleboro rats with hereditary hypothalamic diabetes insipidus.

The results of estimation of renal prostaglandin (PG) excretion showed a significantly decreased excretion of PGE2 by 71% and that of PGF2 alpha--by 28% in rats with hereditary diabetes insipidus (DI), compared to the control Long Evans (LE) rats. The results suggested an inhibition of renal PG synthesis in DI rats due to the absence of stimulatory effect of ADN in DI rats lacking ADH. An inverse correlation between plasma renin activity and renal PG excretion was found (r = --0.36). The renal kallikrein excretion of DI rats was not significantly different compared to that of LE rats. An attempt for explanation of these results was made.

Animals↗
PubMed1984

Insulin effect on some biochemical and biophysical characteristics of lung surfactant.

The incorporation of [14C]palmitic acid into rat alveolar wash total phospholipids and phospholipid fractions has been followed for 6, 8, 10 and 12 hr after insulin administration, indicating a considerable enhancement. The fatty acid profiles of phosphatidylcholines, phosphatidylethanolamines and phosphatidylglycerols were found changed after the hormone administration. Eight hours post insulin treatment the precursor incorporation was highest in all phospholipid fractions studied, as well as the contribution of long chain fatty acids. Dynamic monolayer studies of the lung wash lipid extracts indicated a maximally expanded lipid film corresponding to the highly unsaturated phospholipids present.

Animals↗
PubMed1984

Humoral factors involved in the regulation of sodium-fluid balance in normal man. II. Effect of indomethacin on sodium concentration, renal prostaglandins, vasopressin and renin-angiotensin-aldosterone system.

The effect of drastic sodium chloride changes (performed by using low-Na diet + furanthril and high-Na diet) on renin-angiotensin-aldosterone system, vasopressin and renal prostaglandins was studied in normal subjects after inhibition of prostaglandin synthesis by indomethacin (0.35 mg/kg three times daily for 13 days). The purpose of the investigation was to evaluate the mechanism of prostaglandin-vasopressin interrelationship. Indomethacin inhibition of PG-synthesis was performed, and after high-Na provocation, an increase of vasopressin and cyclic AMP excretion by 15% and 376% more than that without indomethacin was found. Indomethacin by itself caused sodium retention and antidiuretic effect. The results confirmed the assumption that renal prostaglandins are modulators of renin release from the kidney and that they alternate vasopressin effect on urine concentration, most probably through adenylate cyclase-cAMP system.

Adult↗
PubMed1984

Humoral factors involved in the regulation of sodium-fluid balance in normal man. I. Effect of dietary sodium chloride intake on renal prostaglandins, vasopressin and renin-angiotensin-aldosterone system.

Animal and human studies demonstrate the dependence of renal prostaglandin (PG) production on dietary sodium chloride intake. The effect of 5 days' low salt diet (10 mmol Na/day plus 0.5 mg/kg Furanthril daily), and 5 days' high salt diet (250 mmol Na/day) on PGE2 and PGF2 alpha plasma levels and their excretion, on plasma renin activity (PRA) aldosterone (A) and vasopressin (VP) was evaluated on 30 normal subjects. Sodium restriction significantly increased plasma PGE2 and PGF2 alpha and their excretion in the urine. High salt intake reduced renal PG production to normal levels. Under low salt conditions PRA and A increased significantly and fell to normal values on high salt regimen. A negative correlation between renal PG production and VP plasma levels and excretion was demonstrated during the changes of dietary sodium intake.

Adult↗
PubMed1979

[Correlation between the degree of reaction to the rapid mastitis test and the changes in the chemical makeup and properties of bulk cow's milk].

Samples of trade cow milk from the milk combine in Stara Zagora were investigated using the quick mastitis tests "Sofia" and "Bernburg". It was established that 38% of the samples studied react positively (+). The samples reacting in a varying degree to the test were investigated for content of total protein, caseine, whey protein, lactose, chlorides, calcium and number of somatic cells. An electrophoretic separation of the caseine fractions was performed on acrylamide gel. The refraction number of milk serum was determined. No composition and property changes were observed in milk samples reacting positively to the test and having a cell content lower than 1 000 000/cm3. Changes of the protein components in favour of whey proteins were evident in milk samples having a positive reaction to the test as well as cell content higher than 1 000 000/cm3. The electrophoretic picture of caseine from milk samples reacting positively to the test and having higher than 1 000 000/cm3 cell content includes all caseine fractions typical for cow milk, but a reduction in the Ls and beta caseine fractions and an increase of kappa- and gamma fractions is observed.

Animals↗
PubMedDate not supplied

Experimental immune oophoritis as a model for studying the thymus-ovary interaction: 1. Morphological studies.

The experimental immune oophoritis (EIO) model was used to study the functional relationship between the ovary and organs of the immune system. EIO was developed in Balb/c mice by twofold subcutaneous injection of saline ovarian extract in complete Freund's adjuvant. The ovary, thymus, and spleen were investigated histologically, histoautoradiographically, and electromicroscopically on days 7, 14, 21, and 28 after immunization. EIO was manifested by massive atresia of follicles and perivascular mononuclear cell infiltration. The appearance of the germinal center like structures in the thymus and increased T cell mitotic activity and B cell stimulation in the spleen pointed out that EIO is mediated both by T and B cells.

Animals↗