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Biomedical subjects

R Nowak

Publications and source records attributed to R Nowak.

At least 181 records · Page 10Linked to original sources
PubMed1986

[Effect of various types of artificial respiration on raised intracranial pressure, associated with acute alcoholic intoxication].

The effects of spontaneous respiration and mechanical ventilation on ICP were examined by investigating the interaction between elevated pressure and alcohol intoxication. 200 ml ethanol 48% were infused in 11 young pigs with elevated cerebral pressure during mechanical ventilation (Group 1), 7 young pigs with elevated intracranial pressure during spontaneous respiration (Group 2), and 4 young pigs without elevated intracranial pressure during spontaneous respiration (Group 3). While the behaviour of intracranial pressure during mechanical ventilation in the animals from Group 1 was inhomogeneous with a tendency to rise (29 mmHg to 34 mmHg), intracranial pressure (28 mmHg to 55 mmHg) increased dramatically in Group 2. This increase was associated with a sharp rise of paCO2 (37.6 mmHg to 73.3 mmHg) and a decline of paO2 (74 mmHg to 13 mmHg). None of the animals in Group 2 survived. paCO2 also rose in alcoholized animals without elevated ICP (Group 3) (41.9 mmHg to 63.9 mmHg); intracranial pressure, however, remained within the normal range. All animals in Group 3 survived. Our findings indicate that elevated intracranial pressure and alcohol intoxication have a cumulative or potentiating effect on depression of the respiratory centre. Respiratory depression can be prevented by mechanical ventilation and, therefore, a further rise of intracranial pressure can be generally avoided.

Alcoholic Intoxication↗
PubMed1985

Immunoreactive calcitonin in brain regions and pituitary of sheep.

In this study we have investigated the presence of immunoreactive calcitonin in the central nervous system and pituitary of sheep. The calcitonin concentrations were determined radioimmunologically by two different antibodies. We have demonstrated calcitonin in extracts of areas of the central nervous system, whole pituitary, thyroid gland and plasma of 21 sheep. The concentrations were (ng/g wet weight, mean values +/- SE): thyroid 16.0 +/- 4.4, pituitary 2.03 +/- 0.34, reticular formation 1.64 +/- 0.25, substantia nigra 1.53 +/- 0.46, dentate nucleus 1.11 +/- 0.27, putamen 1.05 +/- 0.35, hippocampus 0.97 +/- 0.17, fornix 0.96 +/- 0.15, anterior thalamus 0.92 +/- 0.28, mammillary body 0.88 +/- 0.12, cerebellum 0.86 +/- 0.09, caudate nucleus 0.84 +/- 0.11, posterior hypothalamus 0.83 +/- 0.19, epiphysis 0.75 +/- 0.25, thalamus centralis 0.71 +/- 0.10, almond nucleus 0.69 +/- 0.16, medulla oblongata 0.67 +/- 0.15, anterior hypothalamus 0.66 +/- 0.20, precentral gyrus 0.66 +/- 0.16, globus pallidus 0.63 +/- 0.31, postcentral gyrus 0.36 +/- 0.08 and plasma (ng/ml) 0.058 +/- 0.013. Our results demonstrate that immunoreactive calcitonin is present in the central nervous system (CNS) of sheep, compatible with a neurotransmitter function for this hormone.

Animals↗
PubMed1985

Effect of intravaginal implants of melatonin on the onset of ovarian activity in adult and prepubertal ewes.

Melatonin was administered intravaginally in Silastic tubing to adult and prepubertal ewes. In Exp. 1, ewe lambs (born early March) were given intravaginal melatonin implants at a mean age (+/- s.e.m.) of 7.5 +/- 0.1 weeks (Group E, N = 10) or 19.4 +/- 0.2 weeks (Group L, N = 10). The third group (Group C, N = 10) received empty implants. In Exp. 2 mature ewes were given implants on 13 May (Group E, N = 10) or 18 July (Group L, N = 10) or received empty implants (Group C, N = 10) on one of these two dates. Blood samples were taken twice weekly for progesterone assay. In Exp. 1 the mean age (+/- s.e.m.) at puberty (progesterone greater than 2 nmol/l for two consecutive samples) was 35.4 +/- 0.8 weeks. Puberty was advanced by 5.2 weeks in Group L lambs, occurring at a mean age of 30.2 +/- 0.7 weeks (P less than 0.001). In Group E lambs the timing of puberty was unaltered, occurring at a mean age of 34.8 +/- 0.6 weeks. Mature ewes in Group L (Exp. 2) showed increased incidence of ovarian activity (9/10 ewes cycling by 26 September) compared with the control ewes (1/10) (P less than 0.001), but there was no effect in Group E ewes (3/10). The results demonstrate that continuous melatonin administration to adult and prepubertal ewes can mimic the effect of short days in terms of the reproductive response, and that the present and previous exposure to melatonin is critical in determining the response.

Animals↗
PubMed1983

Runaway pacemaker.

We report a case of a runaway cardiac pacemaker in a hemodynamically unstable patient requiring surgical intervention for correction of the malfunction. The technique for gaining rapid access to the permanent pacemaker and disarming it, and for the utilization of a portable pacemaker generator to establish a normal heart rate is presented.

Aged↗
PubMed1983

Antibodies to Epstein-Barr virus in nasopharyngeal carcinoma, tonsillar carcinoma and control groups.

In the sera of 17 patients with nasopharyngeal carcinoma (NPC) and of 19 patients with tonsillar carcinoma (TC) the titres of IgA, IgG and IgM antibodies to EBV VCA (viral capsid antigen) and of IgG antibodies to EBV EA (early antigen) were determined by the indirect immunofluorescence (IF) method. Significant difference was observed in the frequency of IgA antibodies to EBV VCA and IgG antibodies to EBV EA between NPC patients and controls. There was also a significant difference between the frequency of IgM antibody to EBV VCA and EBV EA antibody titres in TC patients and controls. The geometric mean titre (GMT) of IgG antibodies to EBV VCA was significantly higher in the NPC and TC patients as compared to controls.

Adult↗
PubMed1983

[Electrophysiological studies on the spectral sensitivity of the photoreceptors of the frog retina].

A new method for potential measurements is proposed to study the spectral sensitivity of more than two different types of photoreceptors by means of the mass receptor potential of the isolated retina. The studies were carried out on retinas of animals belonging to the European waterfrog group: Rana ridibunda, R. lessonae and R. esculenta. We were able to demonstrate two different spectral types of rods and two different types of cone responses in each retina. In connection with morphological findings the european waterfrogs are suggested to possess the same types of photoreceptors as Rana pipiens. The question is discussed whether the different types of both rods and cones show different thresholds.

Action Potentials↗
PubMed1982

Subclavian vein catheterization during cardiopulmonary resuscitation. A prospective comparison of the supraclavicular and infraclavicular percutaneous approaches.

Percutaneous access to the central venous circulation is indicated in the management of some cardiopulmonary arrests. We prospectively studied 89 attempted subclavian vein catheterizations in a total of 76 patients. There were 44 supraclavicular (SC) and 45 infraclavicular (IC) approaches. We found that the percutaneous SC route provides a better technique than the IC approach: it is associated with fewer failures, less difficulty in the mechanics of line insertion, a higher incidence of proper catheter tip location, and much less interference with cardiopulmonary resuscitation in normal, obese, and cachectic patient subgroups. Successful performance occurred despite a documented lack of physician experience with the SC technique, indicating that it should be taught during advanced cardiac life support training courses.

Cardiac Catheterization↗
PubMed1982

Interactions of adaptation and masking in the guinea pig cochlea.

Fast cochlear adaptation and masking phenomena, expressed as percent inhibition of the summed action potential, are studied from the guinea pig cochlea responses to click trains and tone bursts given previously or simultaneously to the click sequence. After preceding tone bursts, the click responses are superposed by inhibitory aftereffects dependent on the tone frequency. With interposed tone bursts, the click sequence response is masked, dependent on tone frequency.

Adaptation, Physiological↗
PubMed1981

Cochlear responses to dynamic click patterns in the guinea pig.

Fast cochlear adaptation, expressed as percent inhibition of the summed action potential, is studied from the guinea pig cochlea responses to click trains, ramps, and steps in both directions. The transition time function of adaptation to constant click trains does not depend on click strength, but rather on click interval. On the background of steady state adaptation, click steps produce only transient changes of the adaptive state, opposite to step direction. Compared to constant train stimulation, adaptation is enhanced by descending click ramps, and diminished or reversed (near threshold) by ascending ramps.

Acoustic Stimulation↗
PubMed1981

[Studies on the circulatory side-effects of 2-[3'-diethylaminopropyl-(1')-carbamoyl]-6,7-dimethoxy-1-thiaiso-chroman-1,1-di oxide ("16-252") (author's transl)].

In view of its application to human beings, the authors tested 3-[3'-diethylaminopropyl-(1')-carbamoyl]-6,7-dimethoxy-1-thiasiochroman-1,1-dio xide ("16-252"), which is a potential antidepressant by its basic neuropharmacological activities, for circulatory side-effects on the rat, the cat and the awake carotid-ligated dog and compared them with those of imipramine. "16-252" differs from imipramine in principle. Whereas imipramine exerts above all a sympathiocomimetic circulatory effect (characterized by tachycardia, increased cardiac output and increased arterial pressure), "16-252" induces bradycardia, a decrease in cardiac output and a reactive increase of the total peripheral resistance. The doses of "16-252" required to bring about more marked circulatory side-effects are about 3-fold higher than those of imipramine. Medium doses of "16-252" do not produce the cardiodepressant effects typical of imipramine and they do not potentiate the action of administered noradrenaline typical of tricyclic antidepressants. The results obtained are discussed from the aspects of cardiotoxic properties in case of long-term therapy.

Animals↗
PubMed1981

Net DNA synthesis catalysed by calf thymus DNA polymerase beta.

1. The amounts of deoxynucleotides incorporated during an extensive replication by DNA polymerase alpha into poly(dA)-oligo(dT)12-18 and damaged DNA containing 2.5 incisions per molecule and 3.7% single-stranded DNA, corresponded to the amounts of non-complexed poly(dA) and single-stranded fraction of DNA, respectively. The amounts of the corresponding DNA polymerase beta products were several times higher. In the case of activated DNA they exceeded input DNA. The DNA polymerase beta reaction on this template was continued till substrate exhaustion. 2. The reaction of DNA polymerase beta with activated DNA, leading to net DNA synthesis, was template-directed, required Mg2+ and four deoxynucleoside triphosphates; was not inhibited by DNA polymerase alpha inhibitors, but was sensitive to 2',3'-dideoxythymidine triphosphate. The DNA product was completely digestable by DNAse I and showed a base ratio typical of calf thymus DNA. 3. The essential difference in the reaction mechanism between DNA polymerase alpha and beta suggests the ability of the latter enzyme to synthesize DNA with displacement of the non-replicated strand.

Animals↗
PubMed1980

The DNA polymerase beta reaction with ultraviolet-irradiated DNA incised by correndonuclease.

Covalently closed circular Col E1 DNA was ultraviolet-irradiated with a dose of 60 J/m2, thus introducing about 3.2 pyrimidine dimers per DNA molecule. Treatment of irradiated Col E1 DNA with Micrococcus luteus correndonuclease resulted, in the vicinity of pyrimidine dimers, in an average of 3.3 incisions per DNA molecule, and converted DNA to the open circular form. Incised Col E1 DNA stimulated no reaction with calf thymus DNA polymerase alpha but was recognized as a template by DNA polymerase beta. The latter enzyme incorporated about 1.6 molecules of dTMP (corresponding to 6 molecules od dNMP) per one correndonuclease incision. The length of the DNA polymerase beta product was comparable to the anticipated length of the DNA region within which the hydrogen bonds were disrupted owing to dimer formation. The enzyme required Mg(2)=nd four dNTPs for reaction and was resistant to N-ethylmaleimide or p-mercuribenzoate. The average numbers of deoxynucleotides incorporated per one DNAase I incision or per one nonspecific break, measured in control samples, were equal, amounting to 0.3 dTMP molecule. This value corresponded to 1.2 dNMP molecule; in our opinion, this reflects contaminating nuclease activity of the system used. The present results testify to the ability of DNA polymerase beta to repair synthesis by the "patch and cut' mechanism.

Animals↗
PubMed1980

A study of substrate specificity of mammalian and bacterial DNA polymerases with 5-alkyl-2'-deoxyuridine 5'-triphosphates.

DNA polymerases from procaryotic sources can utilize a variety of dTTP analogues as substrates. We studied here in vitro DNA syntheses catalyzed by DNA polymerase alpha and beta of calf thymus, and for comparison, by the Escherichia coli DNA polymerase I large fragment enzyme in the presence of 5-alkyl derivatives of dUTP as dTTP substrate analogues, using activated DNA as template-primer. The alkyl substituents were n-alkyl (from ethyl to hexyl) and iso-alkyl (isopropyl and tert-butyl) groups. All enzymes were active in the presence of each modified dTTP, incorporation rates of [3H]dAMP or [3H]dGMP were, however, much lower with the analogues than with dTTP. According to relative incorporation rates, alpha-polymerase in DNA synthesis was found to be less sensitive to changes in the length of the alkyl substituent of 5-n-alkyl-dUTPs than beta-polymerase or the E. coli enzyme. Evidence for the incorporation of the analogues was presented for 5-[2-14C]isopropyl-dUTP.

Animals↗