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Biomedical subjects

C Henriques de Jesus

Publications and source records attributed to C Henriques de Jesus.

6 recordsLinked to original sources
PubMed1978

A molecular basis for an irreversible thermodynamic description on non-electrolyte permeation through lipid bilayers.

The non-electrolyte permeability of liposomal membranes has been investigated according to the concepts of irreversible thermodynamics. A strong interaction between the permeation of solute and water was observed. This solute-solvent interaction can be fully described by assuming that a number of water molecules will copermeate with each molecule of solute. This number of copermeating water molecules is independent of the nature of the permeant and of temperature, but depends on the osmotic concentration of impermeants inside the liposomes.

Glucose↗
PubMed1978

Non-electrolyte permeability as a tool for studying membrane fluidity.

1. The reflection coefficient for the permeation of thiourea through bilayers of phosphatidylcholine is a function of the fatty-acid composition of the lipid molecules. By means of these reflection coefficients an index for membrane fluidity has been given to each of those lipids, relative to that of egg phosphatidylcholine. 2. The maximum number of water molecules that can copermeate with each molecule of solute by means of solute-solvent interaction is a function of the packing of the lipid molecules in the bilayer. This parameter has been used in this paper for characterizing the fluidity of cholesterol-containing membranes and for membranes with their lipids in the gel state.

Chemical Phenomena↗
PubMed1977

Short-circuit current and total conductance measurements on rabbit ileum.

1. Short-curcuit current (SCC) and total conductance (Gt) measurements were made in in vitro preparations of rabbit terminal ileum. 2. Successive additions of D-glucose increased the SCC and Gt in a stepwise way and both effects were seen to correlate linearly. 3. Measurements of SCC ant Gt were also made after replacing Na in the Krebs solution by K or sucrose. The SCC decreased to nearly zero in both cases but the decrease in Gt was larger when sucrose was used. 4. SCC and Gt were monitored after the addition of ouabain. SCC decreased to nearly zero but Gt remained constant. 5. On successive additions of sucrose after the preparation was mounted in 1/4 Na Krebs without osmolal compensation, SCC decreased and Gt increased, a linear relationship being found between both changes. 6. Successive additions of 2-deoxy-td-glucose caused a stepwise decrease of SCC and an increase in Gt. These effects seemed independent of the presence of glucose. 7. A model in which a resistance in series is added to the basic model by Ussing & Windhager (1964), modified by Rose & tschultz (1971), is proposed to account for these findings.

Animals↗
PubMed1974

Sodium transport by the small intestine of new-born and suckling pigs.

1. Sodium transport has been measured across in vitro preparations of pig ileum taken at birth or during the first 10 days of post-natal life.2. Both the unidirectional and net fluxes of sodium fell shortly after colostrum was ingested by the new-born piglet. These changes were associated with falls in short-circuit current, open-circuit voltage and tissue conductance and with the appearance of protein-filled vacuoles within the mucosal epithelium.3. Overnight fasting of piglets following a period of suckling caused all sodium fluxes to revert to values similar to those found in the new-born animal. The short-circuit current also increased on fasting but the magnitude of this effect decreased with age.4. The suckling-dependent inhibition of sodium transport was not associated with any change in the level of adenine nucleotides within the mucosa. However the rate at which sodium entered the intestinal mucosa of suckled pigs was found to be only half that of the new-born.5. It is suggested that pinocytosis might use up or chemically modify the microvillar membrane making it less permeable to sodium. Subsequent fasting would, by replenishment or further modification of existing membrane surface, allow the epithelium to recover its original permeability to sodium and possibly regain the ability to undergo a further cycle of pinocytotic activity.

Adenosine Diphosphate↗
PubMed1974

Protein and glucose-induced changes in sodium transport across the pig small intestine.

1. The effect of glucose and of bovine gamma-globulin on short-circuit current and sodium transport was measured using new-born pig ileum before and after suckling.2. Glucose increased the short-circuit current with an apparent K(m) of 1.9 and 19.5 mM for new-born unsuckled and suckled intestines respectively. The V(max) was about 80 muA cm(-2) in each case.3. Bovine gamma-globulin applied to new-born pig ileum caused a 20% increase in sodium chloride influx without change of short-circuit current. The tissue conductance was also greater in the presence of globulin. These effects were not seen in ileum taken from suckled pigs.4. p-Chloromercuriphenyl sulphonic acid (PCMPS) inhibited the globulin induced increase in sodium influx in new-born pig ileum without changing the measured short-circuit current. 0.1 mM-PCMPS also changed the characteristics of the glucose-dependent increase in short-circuit current, so that this response came to resemble that seen in ileum taken from suckled pigs. Dithioerythritol reversed this effect of PCMPS.5. The suckling-dependent difference in results is explained in terms of a change in microvillar function taking place as a consequence of long-term pinocytosis in vivo. The ability of PCMPS to simulate some of these changes suggests that sulphydryl groups might be important regulators of microvillar membrane stability.

Animals↗