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Biomedical subjects

I Albrecht

Publications and source records attributed to I Albrecht.

At least 19 recordsLinked to original sources
PubMed1979

Total RNA content and blood flow in rat brain after RNA administration.

The changes in blood flow through selected brain structures and the changes in the total RNA content of cells of these structures were examined after a single administration of yeast RNA to 6-month-old male rats. The total content of ribosomal RNA in cells of the limbic system (septum, hippocampus, hypothalamus) increased 48 hrs after the administration of 100 mg i.p. yeast RNA , dropped after 7 days (in hypothalamus), 21 and 30 days (in hippocampus), 30 days (in septum). In cells of the limbic system as a whole there is a higher total RNA content in experimental rats. No changes were observed in the cells of parietal brain cortex. Blood flow increased in limbic structures 21 and 30 days after RNA administration and in septum and in hippocampus also 90 days after application. No changes were observed in parietal brain cortex, bulbi olfactorii, cerebellum and brain stem. Histochemical changes correlated positively with blood flow changes in the limbic system 14, 21, 30 and 90 days after RNA application. The body weight of experimental rats did not differ from that of control animals. The changes in haemodynamic parameters were transient and were demonstrated as fluctuations in heart rate, cardiac output, and peripheral resistance. Blood pressure experienced no changes.

Animals↗
PubMed1978

Contraceptive efficacy determination by postcoital testing.

A new vaginal contraceptive method that offers the ease of use with none of the potentially harmful physiologic effects of hormonal contraception was subjected to direct in vivo tests of its efficacy in immobilizing spermatozoa and preventing their entry into the cervical canal. The new contraceptive, a small avoid only 2.8 cm long and 1.4 cm wide, is easily inserted into the vagina without the need for special applicators. It offers protection through the delivery of a highly effective spermicide by the effervescent formation of foam that disperses over the uterine opening. In the trials, no motile spermatozoa could be found in any samples obtained from the vagina, the os externum, or the cervical canal immediately after intercouse protected with the new agent. In no case were any sperm, even immotile sperm, observed in the cervical canal. By contrast, examination of 30 samples obtained immediately after coitus protected with another contraceptive agent (used as a control) revealed motile spermatozao in the cervical canal in nine cases, and propulsive motility was seen on five occasions. The new contraceptive proved highly effective in preventing conception.

Coitus↗
PubMed1977

Water deprivation for 24 hours increases selectively blood flow in posterior pituitary of conscious rats.

Blood flow was measured by means of 125I-Antipyrin distribution and was found to be increased in the posterior pituitary of conscious rats following water deprivation for 24 h as compared to either normohydrated control or to force hydrated rats (2.86 ml min-1 g-1 vs. 2.36 ml or 2.08 ml, respectively). Other parameters of systemic haemodynamics, blood flow in the brain or in the hypothalamus and in anterior pituitary did not differ in three experimental groups of rats subjected to various water intake. The increased blood flow in the posterior pituitary in dehydrated rats presumably parallels the locally intensified metabolic rats due to the enchanged stimulation of the antidiuretic hormone release.

Animals↗
PubMed1975

Regional and systemic haemodynamic effects of some vasopressins: structural features of the hormone which prolong activity.

Cardiac output and regional blood flows to myocardium, gut, uterus and kidney were determined in anaesthetised female rats by a single injection of 86RbCl. The haemodynamic responses were measured at various time intervals up to 2 h after single I.V. injections of lysine-vasopressin and the following of its analogues: a) with extended peptide chains at the N-terminal (including "hormonogens") Nalpha-glycyl-glycyl-lysine-vasopressin, Nalpha-glycyl-glycyl-glycyl-arginine-vasopressin and Nalpha-D-valyl-lysine-vasopressin, b) "carba" modifications desamino-carba6-arginine-vasopressin, desamino-carba6-D-arginine8-vasopressin, desamino-carba6-ornithine8-vasopressin, desamino-dicarba-arginine-vasopressin and c) other steric alterations - desamino-D-arginine8-vasopressin and desamino-N-methylarginine8-vasopressin. Sub-pressor doses of lysine-vasopressin were followed by marked reductions in gut and uterus blood flows which reached a peak at 10 min. and had completely receded by 60 min. The presence of steric alterations in the C-terminal tripeptide of the molecule- D-arginine or N-methylarginine in sequence position 8 - practically completely eliminated vascular activity. The same was true for Nalpha-D-valyl-lysine-vasopressin. None of the latter three analogues showed any inhibitor properties to the action of lysine-vasopressin. The two hormonogens (triglycyl N-terminal extensions) had to be given in doses 10 times greater to obtain a vasoconstrictor effect in gut and uterus equivalent in amplitude to that of a lysine-vasopressin, but this effect was still present to the same degree 2 h later with the hormonogen of lysine-vasopressin, and was only starting to return to baseline values at the same time with the arginine-vasopressin hormonogen. The vascular potency of both mono-carba L-analogues was higher than that of lysine-vasopressin, and the effect was as prolonged as with the hormonogens. The dicarba analogue also showed a prolonged action, but with much reduced potency. No significant changes in renal or myocardial blood flows were observed at all. Molecular features of vasopressin smooth muscle activity were discussed, and a receptor model was proposed. It was suggested that the -S-S-, -CH2CH2-bridges in the above analogues are not directly bound in the peptide-receptor complex and constitute the limiting factor determining complex duration, or persistence of the active peptide in the "receptor compartment". These results provide an experimental basis for possible clinical application of triglycyl-vasopressin and carba-vasopressin in bleeding from both gut and uterus and for induction of menstruation.

Amino Acid Sequence↗
PubMed1975

Arterial pressure, cardiac output and systemic resistance before and after pithing in normotensive and spontaneously hypertensive rats.

After complete cardiovascular denervation mean arterial pressure (MAP) falls to almost equally low levels in spontaneously hypertensive rats (SHR) and normotensive control rats (NCR). This has earlier been suggested to indicate a dominance of neurogenic mechanisms in established SHR hypertension. -- In the present study, total peripheral resistance (TPR) remains, however, some 35 per cent higher in adult SHR than in NCR after pithing while cardiac output (CO), and stroke volume, is 35 per cent lower in SHR. These opposite differences in TPR and CO after denervation, resulting in equal MAP levels in SHR and NCR, seem rather to be a consequence of the rapidly established structural adaptation that affects all SHR high-pressure cardiovascular sections. Thus, the SHR precapillary resistance vessels display thickened walls and luminal narrowing, which keeps TPR higher than in NCR even during maximal vasodilatation. Due to hypertrophy, the SHR left ventricle exhibits a reduced myocardial stretch for a given filling pressure and stroke volume is consequently reduced more than in NCR after complete denervation. -- Paradoxically, therefore, rather than reflecting any dominance of neurogenic mechanisms in established SHR hypertension the MAP equalization in SHR and NCR after cardiovascular denervation emphasizes the hemodynamic importance of cardiovascular structural changes present in hypertension.

Animals↗
PubMed1975

Methodological aspects of blood flow measurement in ovaries containing corpora lutea.

Ovarian blood flow measurements were carried out in pseudopregnant anesthetized rabbits in order to compare three different techniques. Direct measurement by venous cannulation and flow determination by 15-mum radioactive microspheres resulted in values 5 and 10 times higher, respectively, than indicator fraction technique using -86Rb. The direct method inevitably involves surgical handling of the ovary and its vessels, which may account for the lower values found with this method than with microspheres. A comparison between the dynamics of -86Rb uptake in the luteal ovary and the hindleg tissues, mainly consisting of striated muscle, indicated that this technique will underestimate ovarian blood flow due to a low ovarian extraction of the radionuclide. In the preparation for direct measurement the relation between blood pressure and flow was linear. This lack of autorgeulation is an important factor to consider in studies of ovarian steroid secretion rates. The radioactive microsphere technique appears to reflect physiological blood flow in the ovary and corpus leteum of the rabbit and can be useful in studies of vascular mechanisms in this gland.

Animals↗
PubMed1975

Effects of prostaglandin f2a on ovarian blood flow and vascular resistance in the pseudopregnant rabbit.

In the search for data supporting the hypothesis that the luteolytic effect of prostaglandins (PG) is initiated by a vascular mechanism, some haemodynamic parameters including ovarian blood flow and vascular resistance were measured in pseudopregnant anaesthetized rabbits before and after exogenous administration of PGF2a. The measurements were performed on days 5-10 of pseudopregnancy induced by 500 IU HCG iv.

Animals↗