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Biomedical subjects

H Mandin

Publications and source records attributed to H Mandin.

50 records · Page 3Linked to original sources
PubMed1982

Studies of the sensing mechanism in the tubuloglomerular feedback pathway.

Two aspects of the single nephron feedback response previously observed by us have been reexamined. The first, the effect of modifying the composition of fluid used to perfuse the loop of Henle of a single nephron, was studied in rats by comparing flow-induced changes in stop-flow pressure (PSF) with three different perfusion solutions: artificial tubule fluid (ATF); 0.3 M mannitol (M); and mannitol plus 25 to 30 mM sodium chloride (M + E). The second, triggering of the feedback response by injection of ionic current into the distal tubule, was studied in similarly prepared rats by monitoring PSF while passing current. Increasing the rate of loop of Henle perfusion with either ATF or M + E resulted in similar decreases in PSF. In contrast, with M, changes in PSF were usually transient and if persistent were smaller than the changes observed with the other two solutions. When loops of Henle were perfused with ATF at a constant rate, injection of current into the early distal tubule making the lumen more negative resulted in decreases in PSF. Currents of opposite polarity caused no change in PSF if loop flow rate was low; these currents increased PSF if the loop flow rates had previously been high. Current-induced feedback responses were obtained with micropipette electrodes filled with either potassium chloride or lithium acetate. Addition of 10(-4) M furosemide blocked the current-induced feedback responses.

Animals↗
PubMed1981

Effect of arachidonic acid and indomethacin on renal function of dogs with pericardial tamponade.

Previous studies revealed persistent sodium retention in dogs with chronic pericardial tamponade (induced by injection of Freund adjuvant into pericardial sacs) and pericardiocentesis, revealed in increased sodium excretion. Three groups of dogs were studied. Group 1 was treated with indomethacin (2.5 mg/kg, iv) prior to pericardiocentesis. Compared with experiments without indomethacin, sodium excretion did not increase flowing pericardiocentesis in animals treated with indomethacin despite similar changes in arterial pressure, venous pressure, hematocrit, plasma protein concentration, and renin activity. This effect of indomethacin was presumably mediated through prostaglandin (PG) synthesis inhibition. Group 2 dogs received an infusion of arachidonic acid (AA) (to increase PG synthesis) into the left renal artery (20 micrograms.kg-1. min-1). Sodium excretion increased after AA infusion during tamponade (11.2 to 30.9 mequiv.min-1) with a further increase occurring after pericardiocentesis (84.4 mequiv.min-1). Animals in group 3 were infused with both 20 and 80 micrograms. kg-1. min-1 doses of AA. Although sodium excretion following 80 micrograms.kg-1.min-1 AA(21 mequiv.min-1) was higher than that seen during 20 micrograms.kg-1.min-1 (14.2 mequiv.min-1), a further increase in sodium excretion to 45.6 mequiv.min-1 followed pericardiocentesis. During tamponade, AA did not change any of the measured parameters other than sodium excretion, a result compatible with the proposed distal tubular site of action of PG. Absolute but not fractional cortical blood flow distribution increased during the time sodium excretion increased following pericardiocentesis in all experiments. It is proposed that increased PG synthesis may be one possible mechanism involved in the natriuresis seen following pericardiocentesis. One cannot exclude the possibility that increased absolute blood flow to the superficial cortex also contributes to the observed natriuresis. Changes in arterial pressure, venous pressure, hematocrit, plasma protein concentration, and renin activity appear to contribute to the observed natriuresis but only when PG synthesis is not blocked.

Animals↗
PubMed1979

Cardiac edema in dogs: distribution of renal blood flow and glomerular filtrate.

The injection of Freund's adjuvant into the pericardial sac of 29 dogs resulted in chronic pericardial tamponade with persistent sodium retention. Micropuncture, clearance, and radioactive microsphere experiments were initiated 6--13 days after pericardial injection and 60 min after pericardiocentesis. Pericardiocentesis increased sodium excretion (from 12.2 to 41.3 microequiv./min) and mean arterial pressure (+ 20 mmHg (1 mmHg = 133.322 Pa)). Central venous pressure decreased 6.5 mmHg, as did hematocrit (from 45.7 to 39.8%) and plasma protein concentration (from 5.88 to 5.15 g%). Pericardiocentesis had no significant effect on renal blood flow (RBF), nor plasma flow. Redistribution of glomerular filtrate was suggested by the observation that superficial nephron glomerular filtration rate increased (from 91 to 108 nL/min) while glomerular filtration rate remained unaltered. Determination of intrarenal distribution of RBF revealed that cortical blood flow also distributed superficially. A significant increase in the fraction of RBF perfusing zone 1 (outer cortex) and a decrease in fractional perfusion of zones 2, 3 and 4 (juxtamedullary cortex) were observed in each experiment following pericardiocentesis. RBF distribution examined in a series of six animals prior to and during the development of pericardial tamponade showed the opposite effect. These results indicate that pericardiocentesis causes redistribution of both glomerular filtrate and RBF to superficial nephrons. The development of pericardial tamponade was associated with increased fractional juxtamedullary blood flow. These changes may have been the result of altered blood pressure, hematocrit, plasma protein concentration, or altered renal resistance.

Animals↗
PubMed1979

Urinary ionic calcium and binding sites in normocalciuric idiopathic calcium urolithiasis.

Total bindings sites, ionic calcium, and other crystalloids were measured in 41 normocalciuric patients with idopathic calcium urolithiasis and in 34 normocalciuric healthy subjects. Twenty-six stoneformers were treated with thiazide to determine the effect of the drug. The average total calcium excretion was higher in patients than in controls and patients receiving therapy. The fraction of total calcium ionized was higher in patients than in normal subjects; thiazide therapy did not seem to cause a decrease in this fraction in stoneformers. The 24-hr excretion of ionic calcium was equal in normal subjects and in patients receiving thiazide therapy, but was higher in patients without therapy. Normal subjects have a significantly higher concentration and total excretion of magnesium and citrate. Apparent binding constants for calcium were significantly different for all three groups. The concentration of total binding sites was lower in patients with and without therapy than in normal subjects; this was partly attributed to the higher urinary concentration of citrate in normal subjects. However, citrate accounted for less than 20 per cent of the total bindings sites in urine. There was no significant differential 24-hr excretion of binding sites. Measurement of the specific excreting pattern of binding sites on proteins, peptides, nucleotides, and amino acid may emerge with a characteristic pattern in patients with urolithiasis.

Benzothiadiazines↗
PubMed1973

Mechanism of natriuresis after closure of chronic arteriovenous shunts.

Animals subjected to certain cardiovascular manipulations, such as arteriovenous fistulas, diminish their urinary sodium excretion. It has been shown that closure of such fistulas results in a prompt increase in the rate of sodium excretion. However, the nature of the renal mechanisms increasing the excretion of sodium when the initial cardiovascular abnormality is corrected has remained unclear. Since the elucidation of such mechanisms might provide information pertinent to other sodium-retaining states, the effect of closure of chronic Teflon-Silastic arteriovenous shunts was studied in desoxycorticosterone acetate (DOCA)-treated dogs by utilizing micropuncture techniques.Nephron filtration rates were measured first during a control period with open arteriovenous shunts and then again after closure of the shunts in 12 dogs. Nephron filtration rate rose 32% while total glomerular filtration rate (GFR) decreased 8%. After closure of the arteriovenous shunt, fractional reabsorption increased 6%, while total kidney filtration fraction increased from 0.31 to 0.35. Renal plasma flow decreased from a mean of 111 ml/min to 90 ml/min. Closure of the arteriovenous shunts increased sodium excretion from a mean of 21 mueq/min to 45 mueq/min. Concomitantly, a redistribution of filtrate to superficial nephrons occurred. Since pharmacological doses of DOCA were being administered while total GFR was not increased and fractional reabsorption of sodium in the proximal tubule was not inhibited, it was concluded that filtrate distribution to superficial nephrons may have contributed to the observed natriuresis, although alternate explanations were also deemed possible.

Animals↗
PubMed1971

Effect of saline infusions on intrarenal distribution of glomerular filtrate and proximal reabsorption in the dog.

The effect of acute extracellular volume expansion with saline on the intrarenal distribution of glomerular filtrate, was studied in dogs utilizing micropuncture techniques in which samples were obtained by both recollection and from new tubules. Recollection was examined in seven dogs during continuous hydropenia and in five dogs during continuous saline diuresis. Recollection was associated with an increase in nephron flow rate of 8% during hydropenia and 27% during saline diuresis. In addition, during continuous saline diuresis, shortened transit times and lowered intratubular pressures were recorded in previously punctured tubules. Despite increased tubular flow, fractional reabsorption was unchanged. Nephron glomerular filtration rates (gfr) were measured during hydropenia and then after acute volume expansion in 10 dogs. In the repunctured tubules gfr rose 38% more than total glomerular filtration rate (GFR). In contrast, when new tubules were punctured during volume expansion, nephron gfr and total GFR changed proportionately. The disproportionate rise in nephron gfr after volume expansion noted with the recollection technique appears to be artifactual when contrasted to micropuncture of new tubules. With acute volume expansion, fractional reabsorption decreased 15% in recollected samples and 16% in newly sampled tubules. Increased nephron gfr cannot account for the fall in fractional reabsorption. It is concluded that in dogs, saline diuresis is not associated with redistribution of filtrate from deep to superficial nephrons, and that the fall in proximal fractional reabsorption is caused by diminished absolute reabsorption.

Animals↗
PubMed1966

Intermittent hemodialysis in terminal chronic renal failure.

Seven patients with chronic renal failure underwent intermittent hemodialysis for five to 37 months (111 patient-months on a twice-weekly basis) employing arteriovenous Teflon-Silastic cannulas and the modified two-layer Kiil hemodialyzer. A single-pass 37 degrees C. dialysate system has been used. One patient died of an indirectly related cause. All other patients have been successfully rehabilitated and now carry on normal activity of moderate sedentary type. Complications included recurring infection and clotting of arteriovenous cannulas. Hypertension and anemia were common complications requiring careful control. Peripheral neuropathy was noted in five of the seven patients but was of clinical significance in only one patient. Metastatic calcification, osteoporosis and urolithiasis also occurred in this patient. Peptic ulcers with hemorrhage developed in two patients. The degree of rehabilitation and psychological adjustment achieved by this group of patients strongly indicates the need for expansion of dialysis facilities and further research into the medical and economic aspects of dialysis.

Adolescent↗
PubMedDate not supplied

Denial as a defense against depression in end-stage renal disease: an empirical test.

End-stage renal disease (ESRD) is recognized as imposing severe psychosocial stresses upon patients with the result that depression is believed to be highly prevalent. A number of studies have reported low levels of depression, however, and this contradictory finding has been explained via the construct of defensive denial-i.e., patients may minimize the impact of illness-related experiences upon their overall experiences of life. The present study tested this hypothesis in a sample of seventy ESRD patients. Participants rated a series of twelve life dimensions (e.g., work, family and martial relations, recreation) in terms of perceived intrusiveness and control as well as indicating their perceived similarity using a card sort task. Standard measures of depression, positive and negative moods, somatic symptoms of distress, self-esteem, and life happiness were also obtained via structured interviews. A multidimensional scaling analysis applied to the card sort data indicated that ESRD patients do, indeed, perceive illness-related and nonillness aspects of life as independent. However, an analysis of partial variance-controlling for age and nonrenal health-failed to provide evidence of defensive denial. The suggestion is forwarded that previous findings of a high prevalence of depression in ESRD may be in error due to the misidentification of uremic symptoms as symptoms of depression.

Denial, Psychological↗