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Biomedical subjects

J Knapowski

Publications and source records attributed to J Knapowski.

64 records · Page 4Linked to original sources
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Paraquat effect on the bioelectric parameters of the rabbit small intestine and its in vitro penetration.

The effect of paraquat (in concentrations of 10(-4) and 10(-3) mol/l) was studied on the bioelectric parameters of rabbit small intestine. A short-lasting rise in the potential difference (PD) and some decrease of tissue resistance (R) were observed, particularly after the higher concentration. These changes indicate stimulation of the transport function of the rabbit small intestine as a result of administration of this herbicide. Other tested parameters included determination of the rate of paraquat penetration (at concentration gradient 10(-3) mol/l) across the intestinal wall from the serosal side to the mucosal side and conversely. In the latter case three experimental models were used: first--complete intestinal wall, second--intestinal wall with the serosa stripped off, and third--intestinal wall with the mucosa and serosa removed. Differences were found in these rates depending on the model used. The importance of epithelial cells of the mucosa and subepithelial layers, and mesothelium of the serosa in limiting the penetration of bipirydylium herbicides is stressed.

Animals↗
PubMedDate not supplied

Monocrotophos effect on the bioelectric parameters of rabbit intestine and frog skin.

The effect of monocrotofos (in a concentration of 4.5 X 10(-3)M) on the bioelectric parameters of rabbit intestinal epithelium was compared with a similar effect on these parameters of frog skin. It was demonstrated that the tested pesticide added to the medium on the mucosal side of the intestinal wall or on the external side of frog skin caused no evident changes in the potential difference (PD), short-circuit current (CC) and resistance of the studied tissues. This suggested absence of monocrotophos-binding receptors on the external surface of these epithelial structures. The pesticide applied to the serosal side of the intestine decreased PD and SCC without changing the resistance. Applied to the internal surface of frog skin it raised the PD and SCC with some decrease of the resistance. The different pattern of the response could be due to structural differences and to species-specific differences of these epithelia.

Action Potentials↗
PubMedDate not supplied

Sodium transport across isolated epithelial structures in vitro--Ledakrin in the liposomes as a moderator of the bioelectric activity of frog skin.

The effect of Ledakrin (an acridine derivative with antineoplastic action), free or liposome-bound, on the bioelectric activity of frog skin was studied by the method of Ussing and it was shown that this activity (being a function of sodium transport) depended on the chemical composition of the liposomes as well as on the calcium content of the experimental medium. Two conclusions have been drawn: 1) the first phase of the response triggered by Ledakrin is due to its action on the cell membrane, 2) the second phase depends on an intracellular mechanism due, probably, to Ledakrin effect on the cytoskeleton.

Action Potentials↗
PubMedDate not supplied

Effect of ethacrynate sodium on transmesothelial transfer of solutes.

The effect of ethacrynate sodium on transmesothelial fluxes of solutes was studied in vitro. Ethacrynate sodium increased the mesothelial permeability to urea, chloride and sodium. The increase was transient, reproducible and not dependent on cellular metabolism.

Animals↗
PubMedDate not supplied

Early effect of ledakrin -- a nitro-derivative of acridine -- on cell membrane.

Ledakrin effect on the bioelectrical parameters of sodium ion transport (potential difference -- PD and short-circuit current -- SSC) and on Na22 transport across frog (R. esculenta) skin was studied in vitro. Ledakrin induced a biphasic action, after a phase of increase of PD, SCC and sodium flux the transport of sodium ions decreased gradually. The effect of this nitro-derivative of acridine was compared with that of Amiloride. When both these agents were given simultaneously only one phase developed, that is inhibition of sodium ion transport. In both situations there was a significant stimulation of outflux. The obtained results suggest that the external apical cell membrane of epithelial cells is the site of action of Ledakrin.

Acridines↗
PubMedDate not supplied

Effect of certain pesticides on active sodium transport in the epithelium of isolated frog skin.

Investigations were carried out on the effects of several pesticides (Lindan, 2,4-D, p,p-Metoxychlor, Carbaryl, Monolinuron) on the transport ability of the plasma membrane. The experiments were done on isolated skin of the frogs Rana temporaria. The so called short-circuit current technique was used for quantitative evaluation of the transport activity in relation to sodium ions. The effect of the studied substances was studied during 3 hours after their addition to the medium on the external surface of frog skin after a preceding control period of 1-2 hours. A series of long-term experiments was performed also in which the animals were exposed to those pesticides for 14-20 days. The results of the acute experiments failed to demonstrate any significant effect of the studied substances on the plasma membrane, but some weak effects could have been observed in some experiments, at least. The results obtained in the long-term experiment showed that an effect on the plasma membrane could be postulated as regards 2,4-D and Carbaryl. It does not mean, however, that this effect is the only mechanism of the toxic action of these substances on the organism.

Animals↗
PubMedDate not supplied

Insulin stimulates the activity of Na+/K(+)-ATPase in human peritoneal mesothelial cells.

OBJECTIVE: To assess the effect of insulin on the Na+/K(+)-ATPase expression and activity in human peritoneal mesothelial cells (HPMC). METHODS: HPMC were isolated from the omental tissue of non-uremic patients, grown to confluence and rendered quiescent by serum deprivation for 24 hours. The activity of Na+/K(+)-ATPase was determined by measuring the ouabain-sensitive 86Rb uptake. To assess whether the effect of insulin was related to changes in [Na+]i the sodium influx was measured with 22Na and the activity of Na+/K(+)-ATPase was assessed in the presence of amiloride. Expression of Na+/K(+)-ATPase alpha 1,alpha 2 and beta 1-subunit mRNAs was determined by RT/PCR. RESULTS: Exposure of HPMC to insulin resulted in a time- and dose-dependent increase in the Na+/K(+)-ATPase activity. After 60 minutes the ouabain-sensitive 86Rb uptake (cpm/10(4) cells) was increased from 6650 +/- 796 in control cells to 9763 +/- 1212 in HPMC exposed to 100 mU/mL insulin (1.5-fold increase; n = 4, P < 0.05). In addition, incubation of HPMC with 100 mU/mL insulin resulted in a time-dependent increase in the 22Na influx. Pre-exposure of HPMC to 1mM amiloride reduced the activity of Na+/K(+)-ATPase but did not block the stimulatory effect of insulin. RT/PCR analysis revealed that HPMC constitutively expressed alpha 1- and beta 1-subunit mRNAs while the alpha 2-subunit mRNA was barely detectable. Exposure of HPMC to insulin for up to 24 hours was not associated with any changes in the expression of either alpha 1, alpha 2 or beta 1-subunit. CONCLUSION: Insulin stimulates the Na+/K(+)-ATPase activity in HPMC in a time- and dose-dependent manner. This effect appears to mediated by an increase in [Na+]i and is not related to alterations in Na+/K(+)-ATPase subunit mRNAs expression.

Cells, Cultured↗