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C P Lechene

Publications and source records attributed to C P Lechene.

28 records · Page 2Linked to original sources
PubMed1977

Absence of significant secretory flux of phosphate in the proximal convoluted tubule.

The presence of phosphate secretion by the renal tubule in mammals has been controversial. Recently, in a micropuncture and microperfusion study, net secretion of phosphate was reported for the proximal tubule of rats which were infused with parathyroid hormone (PTH) and phosphate. Since the finding of net secretion of phosphate by the proximal tubule is in contradiction to other reports, the question was reinvestigated with the use of microperfusion techniques that were modified to allow identification of sample contamination. Studies were performed in intact dogs, phosphate- and PTH-loaded intact rats, and phosphate-loaded, acutely thyroparathyroidectomized rats. After exclusion of contaminated samples, no significant influx of phosphate was found in any of the three groups. Neither increased plasma phosphate concentration nor the infusion of parathyroid hormone unmasked a secretory process for phosphate. It is concluded that phosphate transport in the proximal tubule is essentially a unidirectional phenomenon, i.e., reabsorption is not opposed by significant backflux of phosphate.

Animals↗
PubMed1977

Electron probe microanalysis: its present, its future.

Electron probe microanalysis (EPM) is a method of elemental ultramicroanalysis based on the spectrometry of the characteristic X rays which are emitted when a target sample is excited by an electron beam. In the same sample many more elements (from carbon and up in the periodic table) in much smaller volumes (less than 1 micronm3 or 10(-15) liter) can be analyzed with EPM than with any other ultramicroanalytical method. Quantitation down to 10(-15) g is relatively easy. Any application of EPM in biology depends on the development of suitable methods for biological sample preparation. Liquid droplets of 10(-11)-liter volumes are routinely analyzed. Elemental content in isolated cells can be quantitated. The analysis of cellular, extracellular, and intercellular content in the same preparation is in sight: a general method for the analysis of diffusible elements in different compartments in tissue relies on the manipulation of frozen hydrated tissue near liquid nitrogen temperature. Localization in the same preparation of several organic compounds at high resolution will be possible by use of appropriate tags. All fields of microphysiology are likely to benefit from this new discipline.

Cells↗
PubMed1976

Effect of parathyroid hormone on phosphate reabsorption in the presence of acetazolamide.

The hypothesis that parathyroid hormone and carbonic anhydrase inhibitors have a common mechanism or site of action on phosphate reabsorption by the renal tubule was tested by administration of parathyroid hormone in the absence and presence of acetazolamide in thyroparathyroidectomized dogs. Re-collection micropuncture and electron probe microanalysis methodologies were utilized. In the absence of acetazolamide, parathyroid hormone increased fractional delivery of phosphate (and volume) from the proximal tubule from 25 +/- 2 to 38 +/- 3%, P less than 0.025, and increased fractional phosphate excretion from 3.8 +/- 1.2 to 19.9 +/- 3.7%, P less than 0.005 (eight dogs). In the presence of acetazolamide, parathyroid hormone increased fractional delivery of phosphate (but not volume) from the proximal tubule from 50 +/- 4 to 58 +/- 5%, P less than 0.025, and increased fractional excretion of phosphate from 8.7 +/- 2.2 to 31.0 +/- 4.3%, P less than 0.001 (12 dogs). Thus, the effects of parathyroid hormone were additive to the effects of maximal inhibition of carbonic anhydrase indicating that parathyroid hormone and carbonic anhydrase inhibitors have different mechanisms of action on phosphate reabsorption by the renal tubule. In addition, phosphate reabsorption beyond the point of micropuncture in the late proximal tubule was much more markedly inhibited by parathyroid hormone than by acetazolamide.

Acetazolamide↗
PubMedDate not supplied

The effect of estrogen administration in vivo on the elemental composition of the intraluminal fluids of the seminiferous tubules, rete testis, and epididymis of the rat.

The maturation of spermatozoa in the epididymis is dependent upon the presence of androgens. This study examined the effects of androgen suppression by estradiol valerate on the elemental composition of the intraluminal fluids of the testis and epididymis. In the fluid from the caput epididymidis, the concentrations of sodium (106.1 +/- 3.4 to 182.8 +/- 16.9 mmol/1, P less than 0.01) and chloride (16.5 +/- 2.2 to 79.3 +/- 10.8 mmol/1, P less than 0.01) rose after treatment with estradiol valerate. By contrast, this treatment reduced the concentrations of phosphorus (63.7 +/- 1.6 to 47.8 +/- 3.2 mmol/1, P less than 0.01), sulfur (18.4 +/- 1.0 to 10.8 +/- 1.0 mmol/1, P less than 0.01), calcium (0.93 +/- 0.09 to 0.50 +/- 0.07 mmol/1, P less than 0.01), and magnesium (2.21 +/- 0.41 to 0.76 +/- 0.16 mmol/1, P less than 0.01). In the distal cauda epididymidis, the concentration of chloride rose after treatment with estradiol valerate (24.4 +/- 1.7 to 54.9 +/- 3.9 mmol/1, P less than 0.01), but the concentrations of the other measured elements (sodium, potassium, phosphorus, calcium, magnesium, and sulfur) were not altered by estrogen treatment. In rete testis fluid the concentration of phosphorus fell (2.00 +/- 0.30 to 0.67 +/- 0.12 mmol/1, P less than 0.01), while that of calcium rose (0.66 +/- 0.15 to 1.55 +/- 0.21 mmol/1, P less than 0.01). Estrogen treatment did not appear to affect the elemental composition of seminiferous tubular fluid or serum. Therefore, estradiol valerate had a marked impact on the elemental composition of luminal fluid only in the caput epididymidis--where sperm maturation is initiated--and a minor effect on that of cauda epididymidal fluid--in which mature spermatozoa are stored.

Animals↗