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Biomedical subjects

F Louis

Publications and source records attributed to F Louis.

At least 55 records · Page 3Linked to original sources
PubMed1980

Natriuretic factor in rats acutely expanded by Ringer's versus albumin solution.

Previous studies have shown that it is possible to extract a natriuretic factor from the renal tissue of rats. This substance, which can be isolated by fractionation through a G-25 Sephadex column, shows a strong correlation with sodium elimination by the kidney. The present work was designed to compare the effects of expansion by a Ringer's solution versus an albumin solution on the presence of this factor and the natriuretic response in the rat. Albumin-expanded rats, like control nonexpanded rats, which have no natriuretic response, do not exhibit any active natriuretic factor in their kidneys. In contrast, significant activity of the natriuretic factor is found in the kidneys of Ringer-expanded rats, which also respond by a significant natriuresis (P less than 0.001). We conclude that the expansion of the extracellular fluid volume, as opposed to the expansion of the intravascular volume, only determines both the presence of the natriuretic factor and the physiologic natriuretic response. As the difference in the sodium transport by the renal tubule in these two modes of expansion takes place in the collecting duct, we suggest that the natriuretic factor acts at this level.

Albumins↗
PubMed1980

Basal activity of the natriuretic factor extracted from the rat kidney as a function of the diet and its role in the regulation of the acute sodium balance.

1. The effect of the sodium content of the diet on the natriuretic activity of an extract from the kidneys was studied in non-expanded and volume-expanded rats. 2. The kidney tissue was homogenized and the supernatant fractionated by gel filtration of Sephadex G-25. A single low-molecular-weight fraction eluted after the salt possessed the natriuretic activity and was tested on a rat bioassay. 3. The natriuretic activity of the fraction obtained from the kidneys of non-expanded rats was related to the sodium intake. 4. After an acute extracellular volume expansion, the natriuretic activity obtained from the fraction extracted from the kidneys was much greater than before expansion and was related to the dietary intake of sodium.

Animals↗
PubMed1979

Role of the basal sodium intake in the rats on their response to a natriuretic factor.

A previously described natriuretic factor found in urine from man and dogs receiving a high salt diet has been postulated to be of hormonal nature. In order to test this hypothesis, natriuretic factor obtained from a pool of human urine of a standard activity has been injected into rats fed 0.55 (group A), 3.55 (group B), 6.55 (group C) mEq sodium a day as it has been shown that the endogenous activity of this factor depends on the sodium content of the diet. This material induces an increment of the UNaV and FENa in the rats averaging respectively 429.6 +/- 150.1% and 317.5 +/- 71.14% for the rats from group A, 103 +/- 29% and 99.7 +/- 26.25% for the rats from group B, 56.3 +/- 34.4% and 63.2 +/- 35.8% for the rats from group C reflecting the degree of statistical significance observed between the absolute values obtained during the control and experimental periods for each group. In addition, a dose-response curve has been established. Altogether the results suggest the hormonal nature of the natriuretic factor and design the kidney as the target organ. These data allow to define the best conditions under which the rats have to be in order to provide a valuable bioassay for this natriuretic material.

Animals↗
PubMed1979

Lipoid cell tumor of the ovary.

An androgen-secreting tumor of the left ovary was preoperatively localized in a 55-year-old virilized woman by radioimmunoassay of blood androgens. The blood sample was obtained by bilateral catheterization of the ovarian and adrenal veins using a percutaneous retrograde femoral approach. A total abdominal hysterectomy and bilateral salpingo-oophorectomy were performed, and revealed a lipoid cell tumor of the left ovary and right ovarian stromal hyperplasia. Despite early postoperative return of plasma adrogens to the normal range, virilizing signs persisted almost unchanged 1 year after surgery.

Adrenal Rest Tumor↗
PubMed1977

Relation between optical density at 650 nm and L/S ratios.

A simple and rapid test that correlates with L/S ratios has been developed. By centrifuging fresh, unfrozen amniotic fluids at 200g for 10 minutes and measuring the optical density at at 650 nm, correlation with L/S ratios is obtained. Optical density readings of 0.15 or greater correlate 100% with L/S ratios of 2.0 or greater. Optical readings below 0.15 correlate 94% with L/S ratios below 2.0.

Amniotic Fluid↗
PubMed1976

Chlorination, decarboxylation and bactericidal activity mediated by the MPO-H2O2-C1- system.

1. MPO, H2O2 and C1- form a complex that undergoes intramolecular rearrangement yielding the chlorinium ion. 2. The chlorinium ion can interact with MPO, bacteria and amino acids. 3. The reaction can occur at a wide range of pH, H2O2 concentration and C1- concentration. 4. The chlorinium ion can attack different protein molecules to cause structural changes. 5. Preincubation of MPO with bacteria results in greater bactericidal activity. 6. Diffusible bactericidal agents are also produced by the MPO-H2O2-C1- system.

Animals↗
PubMed1976

Correlation between amniotic fluid optical density and L/S ratio.

A test that circumvents the complex methodology needed for the determination of L/S ratios has been developed. It has been observed that the optical density, measured at 400 nm, of supernatants collected from fresh amniotic fluids centrifuged at 2000 g for 10 minutes correlates with L/S ratios.

Amniotic Fluid↗
PubMedDate not supplied

Presence of neurophysins I and II in the human pineal gland: comparison with the content of neurohypophyseal hormones.

We have previously measured the individual content of immunoreactive vasopressin (AVP), oxytocin (OT) and vasotocin (AVT) in 155 human pineal glands, and report here identification and measurement of the neurophysin (Np) content of the same glands, using specific homologous human neurophysin I (HNp I) and neurophysin II (HNp II) radioimmunoassays. Median values for HNp I were for men 47 ng/gland (range, 5 to 1360) and for women 24 ng/gland (range, 5 to 1000); median values for HNp II were respectively 7 ng/gland (range, 2 to 191) and 15 ng/gland (range, 2 to 356) with no significant difference between men and women for HNp I and HNp II but a significant difference (p less than 0.001) between HNp I and HNp II for both sexes. Gel filtration showed that pineal neurophysins were eluted at the same volume as both standard Np and Np from human posthypophyses used as controls. HNp I correlated both with AVP (rs = 0.54 for men and 0.55 for women) and OT (rs = 0.86 for men and 0.57 for women) but not with AVT, while HNp II correlated with AVP (rs = 0.52 for men and 0.53 for women) and OT (rs = 0.92 for men and 0.50 for women) but not with AVT. This study thus confirms the presence of two neurophysins in the human pineal gland and further indicates that they are related to AVP and OT concentrations in the same gland. The results also imply, however, that the presence of immunoreactive AVT (more probably a closely related peptide) is independent of the neurophysins.

Arginine Vasopressin↗
PubMedDate not supplied

Presence of vasopressin, oxytocin and neurophysin in the retina of mammals, effect of light and darkness, comparison with the neuropeptide content of the neurohypophysis and the pineal gland.

Arginine vasopressin (AVP) and oxytocin (OT) as well as their CNS carrier neurophysins (Np) have been found in the pineal gland. In view of the analogy between the pineal gland and the retina, the contents of these neuropeptides in rat, human and bovine retinae were determined. AVP, OT and Np were detected by specific radioimmunoassay (RIA) and their presence confirmed by RIA measurements (1) in rat and human retinae on HPLC fractions and (2) by the detection of the C-terminal portion of the precursor to AVP and its associated Np = propressophysin (CPP). The AVP and OT content in the retina of the rat was modified by light: AVP and OT content was smaller at 2 a.m. than at 2 p.m., but was increased by a 7 day constant exposure to darkness. In contrast, pituitary content was decreased after 7 days of constant darkness. If one optic nerve was cut we observed a decrease in retinal AVP content compared to the contralateral side and a decrease in pituitary AVP content. Our data clearly demonstrated the presence of AVP, OT and Np in the retina and their variation induced by light. It is probable that these peptides are of central origin.

Animals↗