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Biomedical subjects

M Nowak

Publications and source records attributed to M Nowak.

At least 127 records · Page 7Linked to original sources
PubMed1994

[Comparison of bacterial flora isolated from the urinary tract of patients examined in the Department of Microbiology and Immunology of the Pomeranian Academy of Medicine and from the bacteriology laboratory of the Municipal Health Care Group in Szczecin].

The authors have analyzed 5305 urine samples from patients with significant bacteriuria, examined in 1988-1992 at the Department of Microbiology and Immunology of the Pomeranian Academy of Medicine, performing analyses for the State Clinical Hospital No. 2 in Szczecin, and in the Bacteriology Laboratory of the Municipal Health Care Group in Szczecin. The results obtained demonstrate a dominance of Escherichia coli among patients of general medicine ambulatories and internal medicine departments (70%), while patients of the urologic department and urologic out-patient clinic were positive for this bacteria in only 30-40%. It should be mentioned that a significant increase in the number of infections by Pseudomonas, Acinetobacter, and Serratia strains has been observed, mainly among patients after urologic operations.

Ambulatory Care Facilities↗
PubMed1994

Results of topical treatment of HPV infection in the uterine cervix using interferon beta, 13-cis-retinoic acid and TFX.

Local treatment was administrated to 130 women, in whom colposcopy, cytology and (if the latter was abnormal) histology pointed to HPV infection in uterine cervix. The best results were obtained with 13-cis-retinoic acid (provitamin A) in conjunction with interferon beta (94.2% cured patients), followed by interferon beta in combination with TFX (90% cured patients) and interferon beta administered alone (88% cured patients).

Administration, Topical↗
PubMed1993

A strategy of win-stay, lose-shift that outperforms tit-for-tat in the Prisoner's Dilemma game.

The Prisoner's Dilemma is the leading metaphor for the evolution of cooperative behaviour in populations of selfish agents, especially since the well-known computer tournaments of Axelrod and their application to biological communities. In Axelrod's simulations, the simple strategy tit-for-tat did outstandingly well and subsequently became the major paradigm for reciprocal altruism. Here we present extended evolutionary simulations of heterogeneous ensembles of probabilistic strategies including mutation and selection, and report the unexpected success of another protagonist: Pavlov. This strategy is as simple as tit-for-tat and embodies the fundamental behavioural mechanism win-stay, lose-shift, which seems to be a widespread rule. Pavlov's success is based on two important advantages over tit-for-tat: it can correct occasional mistakes and exploit unconditional cooperators. This second feature prevents Pavlov populations from being undermined by unconditional cooperators, which in turn invite defectors. Pavlov seems to be more robust than tit-for-tat, suggesting that cooperative behaviour in natural situations may often be based on win-stay, lose-shift.

Biological Evolution↗
PubMed1993

Chaos and the evolution of cooperation.

The "iterated prisoner's dilemma" is the most widely used model for the evolution of cooperation in biological societies. Here we show that a heterogeneous population consisting of simple strategies, whose behavior is totally specified by the outcome of the previous round, can lead to persistent periodic or highly irregular (chaotic) oscillations in the frequencies of the strategies and the overall level of cooperation. The levels of cooperation jump up and down in an apparently unpredictable fashion. Small recurrent and simultaneous invasion attempts (caused by mutation) can change the evolutionary dynamics from converging to an evolutionarily stable strategy to periodic oscillations and chaos. Evolution can be twisted away from defection, toward cooperation. Adding "generous tit-for-tat" greatly increases the overall level of cooperation and can lead to long periods of steady cooperation. Since May's paper [May, R. M. (1976) Nature (London) 261, 459-467], "simple mathematical models with very complicated dynamics" have been found in many biological applications, but here we provide an example of a biologically relevant evolutionary game whose dynamics display deterministic chaos. The simulations bear some resemblance to the irregular cycles displayed by the frequencies of host genotypes and specialized parasites in evolutionary "arms races" [Hamilton, W. D., Axelrod, R. & Tanese, R. (1990) Proc. Natl. Acad. Sci. USA 87, 3566-3573; Seger, J. (1988) Philos. Trans. R. Soc. London B 319, 541-555].

Biological Evolution↗
PubMed1992

Comparison of the effects of neurotensin and vasopressin on the adrenal cortex of dexamethasone-suppressed rats.

Neurotensin (NT) and vasopressin (AVP) share some similarities as far as their actions on the adrenal weight and secretion are concerned. The present study aimed to compare the in vivo chronic effect of these two peptides on the adrenal cortex of dexamethasone (Dx)-treated rats. NT or AVP were ip. infused at a rate of 2 micrograms/rat/d for 7 d. In the animals concomitantly treated with 15 micrograms Dx/100 g/d for 7 d, both NT and AVP partially prevented adrenal atrophy. AVP enhanced plasma aldosterone concentration (PAC), but not that of corticosterone (PBC). On the other hand, NT did not affect either PAC or PBC. In rats treated with 35 micrograms Dx/100 g/d for 14 d, neither NT nor AVP administered for the last 7 d exerted any effect on the adrenal weight. However, also under these conditions of profound adrenal atrophy AVP was still able to notably raise PAC, while NT was ineffective. Our findings indicate that the mechanism underlying the aldosterone secretagogue action of AVP does not require, unlike that of NT, the presence of ACTH. Moreover, in light of many recent literature data they could suggest the possibility that in vivo NT acts on the rat adrenal cortex via AVP.

Adrenal Cortex↗
PubMed1992

[Public health and citizen involvement--guidelines and general practice in Herne].

Health problems cannot be solved only by expanding medical and other systems of service. Limitations of these services are not only set by costs, but also by the disease patterns themselves. The traditional role of the patient must be redefined. It is necessary to develop personal health-coping strategies outside medical care, and for the citizen to participate in improving conditions of health in general. The public health system has the specific duty of initiating and establishing these new approaches to health promotion and coping with disease. A model for these new municipal health policies is presented with reference to medical practice in the city of Herne in the Ruhr area of Germany.

Community Participation↗
PubMed1991

Periodic and chaotic host-parasite interactions in human malaria.

It has been recognized since ancient times that malaria fever is highly periodic but the mechanism has been poorly understood. Malaria fever is related to the parasite growth cycle in erythrocytes. After a fixed period of replication, a mature parasite (schizont) causes the infected erythrocyte to rupture, releasing progeny that quickly invade other erythrocytes. Simultaneous rupture of a large number of schizonts stimulates a host fever response. Febrile temperatures are damaging to Plasmodium falciparum, particularly in the second half of its 48-hr replicative cycle. Using a mathematical model, we show that these interactions naturally tend to generate periodic fever. The model predicts chaotic parasite population dynamics at high multiplication rates, consistent with the classical observation that P. falciparum causes less regular fever than other species of parasite.

Animals↗
PubMed1991

The evolution of viruses. Competition between horizontal and vertical transmission of mobile genes.

The transmission dynamics of viruses in a replicating cell population is investigated, assuming that viral mutants differ in their efficiencies of horizontal and vertical transmission. As a genetic result we find that competition between such different viral strategies need not select for increasing basic reproductive rates. We illustrate evolutionary trajectories that lead to increased viral latency even at the expense of lower basic reproductive rates and lower equilibrium abundance. In some cases oscillations in the prevalence of different mutants are obtained.

Biological Evolution↗
PubMed1991

Effect of bombesin on the structure and function of the rat adrenal cortex.

Intact and dexamethasone-treated adult female Wistar rats were infused (Alzet osmotic minipumps) with bombesin (0.75 micrograms/rat per day) for 7 days. Bombesin depressed body weight and capacity of adrenal homogenate to secrete corticosterone; the latter effect was reflected in intact rats by a drop in serum corticosterone level. Bombesin had no effect on pituitary and serum adrenocorticotropic hormone (ACTH) concentration and serum aldosterone level. In intact animals, infusion of bombesin resulted in lowering of the number of parenchymal cells in adrenal cortex connected with the hypertrophy of glomerulosa and fasciculata cells. Moreover, bombesin lowered basal corticosterone secretion by isolated rat adrenocortical cells; however, neuropeptide applied did not change the response of isolated cells to ACTH stimulation. The data obtained clearly demonstrate inhibitory effect of bombesin on basal corticosterone secretion by the rat adrenal cortex.

Adrenal Cortex↗
PubMed1991

Comparison of the effects of neurotensin and ACTH on the pituitary-adrenocortical axis of dexamethasone-suppressed rats.

Neurotensin (NT) (12-48 micrograms/kg-1/day-1, for 2 days, s.c.), like ACTH (60 micrograms/kg-1/day-1, for 2 days, s.c.), counteracted the dexamethasone (Dx)-induced (120 micrograms/kg-1/day-1, for 4 days, s.c.) adrenal zona-fasciculata cell atrophy. NT notably raised, in Dx-suppressed rats, the plasma concentration of ACTH, which reached about that found after exogenous ACTH administration. However, at variance with ACTH, NT did not enhance either plasma corticosterone (B) level or B production by adrenal quarters in vitro. The conclusion is drawn that NT modulates the function of the rat pituitary-adrenocortical axis, by simultaneously stimulating hypophyseal ACTH release and inhibiting steroidogenesis at the adrenal level.

Adrenocorticotropic Hormone↗
PubMed1991

Effects of arginine vasopressin on the pituitary-adrenocortical axis of intact and dexamethasone-suppressed rats.

Weekly infusion with arginine vasopressin (AVP) (2 micrograms.kg-1.day-1) exerted a slight stimulatory effect on the adrenal growth of intact female rats and induced a 2-fold rise in plasma aldosterone concentration (PAC), without apparently affecting corticosterone (B) and ACTH secretions. Weekly dexamethasone (Dx) administration (125 micrograms.kg-1.day-1) caused a marked adrenal atrophy, a conspicuous suppression of B and ACTH productions, and a 5-fold increase in PAC. AVP infusion reversed the Dx-induced adrenal atrophy. It did not counteract the suppression of B and ACTH secretions, nor did it change PAC. These findings suggest that chronic AVP treatment is able to stimulate adrenal growth by a Dx-insensitive mechanism (i.e. independent of any change in ACTH secretion). Conversely, AVP may enhance the steroid secretory capacity only in adrenocortical cells in which the maintenance of the steroidogenic machinery is assured by normal levels of circulating ACTH.

Adrenocorticotropic Hormone↗
PubMed1991

Effects of neurotensin on the pituitary-adrenocortical axis of intact and dexamethasone-suppressed rats.

A 7-day infusion with neurotensin (NT) (10 micrograms.kg-1.day-1) stimulated adrenal growth in intact female rats, and raised ACTH blood concentration, without altering corticosterone (B) plasma level and output by adrenal homogenates. For a week dexamethasone (Dx) administration (125 micrograms.kg-1.day-1) caused a notable adrenal atrophy, a marked lowering of ACTH and B blood concentrations, and a profound depression of B output by adrenal homogenates. NT infusion reversed Dx-induced adrenal atrophy and plasma ACTH-level drop, but not the impairment in adrenal-cortex secretory activity. In vitro studies showed that NT (10(-6) mol/l) significantly reduced basal, but not ACTH-stimulated B release by isolated rat inner adrenocortical cells. These findings suggest that NT exerts a direct inhibitory effect on B production by rat adrenals, while it is able to enhance ACTH secretion and consequently adrenal growth. Moreover, they indicate that NT evokes a striking, and at present unexplained dissociation between structure and function in the adrenal cortex of Dx-suppressed rats.

Adrenocorticotropic Hormone↗
PubMed1991

[Occurrence of anti-Mycobacterium antibodies detected by the indirect immunofluorescence method in patients with pulmonary tuberculosis and in healthy controls].

Due to an unfavorable epidemiological situation in tuberculosis in Poland and diagnostical difficulties the authors suggest the need to enlarge the diagnostical tests used in detecting M. tuberculosis with modern immunological methods. In this study we analysed serum of patients with pulmonary tuberculosis determining with the indirect immunofluorescence method the levels of specific antibodies of the IgG class directed against Mycobacteria. The heat attenuated H37Rv strain was used as a standard. Significantly higher levels of antibodies were seen in patients with tuberculosis in comparison with control. These preliminary results suggest diagnostic utility of antimycobacterial antibodies assessed with immunofluorescence in diagnosing infections and suggest the possible comparability with the ELISA method.

Antibodies, Bacterial↗
PubMed1990

HIV mutation rate.

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Acquired Immunodeficiency Syndrome↗
PubMed1990

Sex differences in adrenocortical structure and function. XXVII. The effect of ether stress on ACTH and corticosterone in intact, gonadectomized, and testosterone- or estradiol-replaced rats.

Studies were performed on the reactivity of the hypothalamo-pituitary-adrenocortical axis of intact, gonadectomized, and testosterone- or estradiol-replaced rats to standard ether stress. Plasma ACTH and corticosterone (B) levels, anterior pituitary ACTH, and adrenal B content were estimated 20 and 40 min after stress application and in unstressed animals. Ether stress resulted in an increase in plasma ACTH and B levels and in adrenal B content while pituitary ACTH content was notably lower when compared with unstressed rats. The response was markedly higher in female than in male rats. After orchiectomy and testosterone replacement, plasma ACTH and B responses to ether stress were similar to those observed in intact male rats. On the other hand, ovariectomized females responded to ether stress like intact males, while after estradiol replacement the pattern of plasma ACTH and B concentration and adrenal B content was similar to that in intact female rats. Thus, the higher responsiveness of the pituitary-adrenal cortex axis of female rats to ether stress depends on stimulatory or facilitatory effect of estradiol.

Adrenal Glands↗
PubMed1990

Gestational changes in hamster adrenal cortex: stereologic and functional studies.

Pregnancy in hamsters evoked a prompt increase in adrenal weight, with the highest value at day 5 and a subsequent fall toward the end of gestation. The surface densities of mitochondrial cristae and smooth endoplasmic reticulum did not display significant changes in the course of gestation, while 11 beta-hydroxylase and 3 beta-hydroxysteroid dehydrogenase/isomerase activity (two enzymes located in these two organelles) underwent significant increases at day 5 and day 10 of pregnancy, respectively. Neither the adrenal content of cortisol nor cortisol output by adrenal homogenates changed, but cortisol production measured in adrenal slices gradually rose during the course of pregnancy. Blood cortisol concentration increased about ten-fold toward the end of gestation, whereas the plasma ACTH level remained unchanged and plasma aldosterone concentration was significantly lowered. The conclusion is drawn that the pregnant hamster's adrenal glands possess an enhanced capacity to secrete cortisol, but the factor(s) involved remain unknown.

3-Hydroxysteroid Dehydrogenases↗