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Biomedical subjects

L J Barratt

Publications and source records attributed to L J Barratt.

26 records · Page 2Linked to original sources
PubMed1976

The effect of amiloride on the transepithelial potential difference of the distal tubule of the rat kidney.

Microelectrodes with relatively large tips (3-5 mu O.D.) were used to measure the transepithelial potential difference (PD) of the distal tubule of the rat kidney in the control state and following i.v. administration of amiloride. This drug produced an increase in the magnitude of the positive PD in early distal segments (from +8.0 to +10.5 mV) and a change in polarity of the PD in late distal segments (from -18.0 to +2.5 mV). These data suggest that the potassium-conserving properties of the drug are due to its ability to induce an unfavorable electrochemical gradient opposing passive potassium secretion along the distal tubule.

Amiloride↗
PubMed1975

Transepithelial potential difference profile of the distal tubule of the rat kidney.

In a recent micropuncture study electrodes with relatively large tips (3 to 5 mu O.D.) and, hence, low tip resistances were used to measure the transepithelial potential difference (PD) across the proximal tubule of the rat kidney. The present study reexamines the PD of the distal tubule of the rat kidney using such electrodes. In contrast to previous studies where a negative PD has been uniformly found in the distal tubule, the transtubular PD was found to be positively oriented (+3.7 mv) when particular efforts were made to puncture the earliest accessible segments. In accord with previous observations, the PD of the late segment was consistently negative (mean, -19.6 mv). Morphologic examination of the epithelium at the site of puncture suggests that in the very early distal tubule where positive potentials are recorded, the epithelium is characteristic of the distal convoluted tubule. By contrast, in the latter part of the distal tubule, where negative potentials are recorded, the epithelium displays the morphologic characteristics of the cortical collecting duct. The results of these studies suggest that the net transport properties of the distal tubule, that is the region of the nephron beginning just beyond the macula densa and extending to the first junction with another renal tubule, are a composite of activities of at least two types of epithelium.

Animals↗
PubMed1975

Pyelo-ureteritis cystica associated with a urinary tract infection due to a coagulase-negative staphylococcus.

A young female presenting with a history suggestive of renal colic was found by intravenous pyelography to have Pyeloureteritis Cystica. In association with this condition she had a urinary tract infection due to a coagulase-negative staphylococcus. Following a two week course of appropriate antibiotic therapy, her urine became sterile and repeat pyelography revealed no abnormality.

Adult↗
PubMed1975

Dialysis-associated dementia.

Two patients from an Australian Dialysis Centre developed a progressive neurological disorder with features similar to those recently discribed as the snydrome of Dementia Dialytica. These two patients are reported here and this newly recognised syndrome reviewed.

Adult↗
PubMed1974

Factors governing the transepithelial potential difference across the proximal tubule of the rat kidney.

Previous measurements of the transepithelial potential difference (PD) of the proximal tubule have yielded widely conflicting values (range -20 to +3 mV). In a recent study, Kokko has demonstrated that the PD of the in vitro perfused isolated proximal tubule of the rabbit varies in a predictable way from -6 to +3 mV, depending on the concentration of chloride, bicarbonate, glucose, and amino acids in the perfusing solution. The present micropuncture study examines the effect of tubular fluid composition on the PD profile along the proximal tubule of the in vivo rat kidney. Low resistance measuring electrodes with large tips (3-5 microns OD) filled with 3 M KCl, were used to provide stable PD recordings. Experiments were performed to validate the use of these electrodes. Transepithelial PD measurements were made in immediate postglomerular segments identified by injection of dye into Bowman's space of accessible surface glomeruli and in randomly selected more distal segments of the proximal tubule. In the control state, the first loop was found to have a small but consistently negative PD which could be obliterated by an infusion of phloridzin. In contrast, the PD in later segments was consistently positive. Infusion of acetazolamide abolished the positive PD in the later segments. Acetazolamide and glucose infusion resulted in a negative PD which was abolished by the additional infusion of phloridzin. These data provide evidence that glucose reabsorption is electrogenic and can account for the small negative PD normally present in the early proximal tubule. The positive PD in later segments appears to be a passive chloride diffusion potential. This positive potential is discussed as an important electrochemical driving force for significant passive reabsorption of sodium in the proximal tubule.

Acetazolamide↗