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Query: UMLS:C0029713 (immaturity)
 4,335 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Clearance experiments concerning the influence of hypophysin + (0.1 vol. unit/kg) and desoxycorticosterone-21-acetate (0.1 mg/kg) on sodium, potassium, calcium, magnesium and inorganic phosphorus excretion in urine have been carried out on 12 bulls at the age of 2-5 weeks of life. After hypophysin injection kidney purification of sodium, potassium and chloride ions has been noticed and hypophysin effect on tubular absorption processes turned out to be clearly late in relation to its influence on glomerular filtration decrease. After desoxycorticosterone-21-acetate injection, lowering of clearances of both sodium and potassium has been noticed and it may prove that kidney mechanisms responsible for potassium ion regulation show functional immaturity. Hypophysin and desoxycorticosterone-21-acetate in calves at the age 2-5 weeks have not affected kidney processes of calcium, magnesium and inorganic phosphorus excretion in urine.
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PMID:[Effect of hypophysin and desoxycorticosterone-21-acetate on renal function in calves in the neonatal period. II. Urinary excretion of electrolytes]. 248 70

To assess the influence of immaturity on the responsiveness of enterocytes to specific pathogens, a dose-response curve for cholera toxin (CT)-induced fluid secretion was determined in the proximal small intestine of rats at 2 and 4 wk of age. The suckling rat was approximately 50 times more sensitive to CT in triggering the secretory response than the weaned rat, when estimated by the medium-effective dose (ED50, 0.8 vs. 38.9 nM). Cortisone, known to promote enterocyte maturation, when injected into suckling rats, decreased host sensitivity approximately 1,000 times. Neither age nor cortisone decreased the receptor binding of 125I-labeled CT to intestinal microvillus membranes. In contrast, cortisone treatment caused a threefold increase in receptor density from 14.5 to 43.0 pmol/mg protein. The enzyme responsible for the sodium pump, Na+-K+-ATPase, showed a threefold increase in activity both after weaning and after a cortisone treatment. These data indicate that the immature gut exhibited an increased host sensitivity to CT stimulation that was not correlated with initial receptor binding but was related to a lowered Na+-K+-ATPase activity, suggesting that an underdeveloped sodium pump may be partially responsible for the high incidence of secretory diarrhea in neonates.
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PMID:Age and cortisone alter host responsiveness to cholera toxin in the developing gut. 253 37

Nippostrongylus brasiliensis infection of the rat resulted, at day 10 of infection, in decreased levels of jejunal enterocyte sodium-potassium-activated adenosine triphosphatase (Na,K-ATPase) and potassium-activated p-nitrophenyl phosphatase (K-pNPPase) activities. Parallel decreases occurred in active sodium efflux from jejunal enterocytes in the presence and absence of actively transported monosaccharides. Ileal enterocyte Na,K-ATPase and K-pNPPase activities were significantly increased, as was active sodium efflux. In contrast to controls, the presence of monosaccharides produced a stimulation of active sodium efflux from ileal enterocytes derived from infected rats. Enzyme and sodium transport changes in the jejunal enterocytes probably reflect cellular immaturity. Functional changes in ileal enterocytes probably represent a compensatory phenomenon.
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PMID:Changes in Na,K-ATPase, sodium ion, and glucose transport in isolated enterocytes in an experimental model of malabsorption. 255 21

Postnatal development of mossy fiber afferents from the vestibular and the visual system to the vestibulocerebellum was studied electrophysiologically and morphologically. In kittens anesthetized with pentobarbital sodium and N2O plus halothane, extracellular simple and complex spikes of Purkinje cells were recorded in the flocculus, nodulus and uvula. In the flocculus, stimulation of the VIIIth, but not the optic nerve, evoked simple spike responses with a latency of 16 ms at the day of birth which decreased to 5 ms by day 15 (short latency group). On the other hand, another group of simple spike responses with much longer latencies (50-80 ms) began to be elicited on day 7 via both the optic and VIIIth nerves. The latency decreased to 24 ms by day 15 and 10 ms on day 30. These latencies further shortened with development to the adult latency value (3-5 ms). Simple spike responses of the short latency group were also evoked in the nodulus and uvula from the VIIIth nerve with a slightly longer latency than that in the flocculus (23 ms on day 3 and 12 ms on day 17). Because of the immaturity of granule cells in early postnatal days, short latency simple spike responses from the VIIIth nerve suggested the direct synaptic connection of vestibular mossy fibers with Purkinje cells. Horseradish peroxidase was injected into the white matter of the flocculus, nodulus and uvula in slice preparations. Mossy fibers labeled with horseradish peroxidase showed fine branches extending to reach Purkinje cell somata from mossy swellings in the internal granular layer during days 2-20. Electron microscopy showed that the labeled mossy fibers made intimate contacts with Purkinje cell somata and the terminals contained many round synaptic vesicles. Pre and postsynaptic densities were occasionally found. After day 20, direct mossy fiber connections with Purkinje cells could not be observed. During days 7-20, these direct connections, as well as mossy fiber-granule cell connections could be observed. It was demonstrated that during early postnatal development, vestibular mossy fibers temporarily make direct contact with Purkinje cells, through which impulses could be transmitted to elicit simple spikes in Purkinje cells.
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PMID:Transient direct connection of vestibular mossy fibers to the vestibulocerebellar Purkinje cells in early postnatal development of kittens. 258 54

The circulating levels of vasopressin, catecholamines and renin activity before, during and following a 10-20% fall in mean arterial blood pressure induced by sodium nitroprusside were measured in six chronically catheterized lambs during the first week of life. No significant changes in pHa, PaO2, PaCO2, Plasma sodium or osmolality were observed during or following the infusion of sodium nitroprusside at an average of 12 g.kg-1.min-1 (table I). However, the fall in blood pressure at the end of 60 minutes infusion, was associated with significant increases in the plasma levels of vasopressin from a control value of 2.4 +/- 0.57 to a maximum of 35.1 +/- 16.3 pg/ml (p = .002), renin activity from 6.7 +/- 1.56 to 27.4 +/- 11.44 ng.ml-1.hr-1 (p = .003), and catecholamines from 189.3 +/- 42.15 to 543.3 +/- 100.52 pg.ml-1 (p = .0001). The increase in vasopressin is lower, while that of PRA was higher and catecholamines similar to those found in the ewe. Plasma renin activity (PRA) and catecholamine levels remained elevated for at least 30 minutes following the end of the infusion while the mean blood pressure rose significantly above control levels and remained elevated for twenty minutes. We speculate that the persistent elevated levels of vasoactive mediators are responsible for the prolonged rebound hypertension following the cessation of the nitroprusside infusion and is the result of an immaturity of either a feedback process or metabolism of the vasoactive mediators or a combination of both mechanisms. This rebound hypertension could have adverse effects particularly in the very immature neonate.
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PMID:Plasma vasopressin, renin and catecholamines during nitroprusside-induced hypotension in the newborn lamb. 269 75

The endocrine control of electrolyte balance during development is reviewed. It is suggested that the high urinary sodium excretion observed in premature infants may be secondary to the immaturity of the adrenal gland to adequately increase the secretion of aldosterone (Sulyok et al, 1979b), and to the inability of the distal tubule to respond appropriately to a rise in circulating aldosterone levels (Sulyok et al, 1979a). On the other hand, the elevated plasma aldosterone levels observed in term newborn infants may play an important role in the blunted response of the newborn kidney to saline loading (Sulyok et al, 1979a; Spitzer, 1982). The ability of ANP to induce a natriuresis and to contribute to fluid and electrolyte homeostasis during development has been investigated. It has been found that the immature kidney is less responsive to ANP than later in life (Chevalier et al, 1988; Robillard et al, 1988). On the other hand, it has been suggested that a rise in plasma ANP during the first five days of life may contribute to the physiological weight loss associated with the extracellular volume contraction occurring shortly after birth (Tulassay et al, 1987). The role of glucocorticoids, prostaglandins and the kallikrein-kinin system in regulating electrolyte balance during development is also reviewed.
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PMID:Endocrine control of electrolyte balance during development. 269 49

Electron microscopic observations of an originally established mouse mastocytoma cell line (BSP-MST-2) revealed that the cytoplasm of many of the MST-2 cells contained small and low osmiophilic granules and a few mature electron-dense granules. Fluorescent- and immuno-histochemical examinations also suggested the immaturity of granules as the cytoplasmic reaction for serotonin (5-HT) was weak. Induction of further maturation of granules was investigated by administration of various chemical agents. Among the chemicals examined, sodium butyrate and hydrocortisone were effective. In the presence of 1 mM sodium butyrate for 24 h, the cytoplasmic granules contained an abundant dense matrix. MST-2 cells incubated with hydrocortisone at 5 micrograms/ml for 24 h showed a somewhat different granulopoietic pattern from those incubated with sodium butyrate, including numerous electron-dense progranules. Fluorescent- and immuno-histochemical studies showed increased reactions of cytoplasmic 5-HT of both butyrate- and hydrocortisone-treated MST-2 cells. The specificity of these morphological and cytochemical changes was confirmed by treatment with reserpine, a drug which depletes cellular 5-HT; electron-dense materials were virtually diminished and cytochemical reactions were significantly decreased. The mode of induced production of 5-HT in mastocytoma granules is discussed, in relation to mastocyte differentiation.
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PMID:Induction of granulopoiesis of mastocytoma cells: ultrastructural and cytochemical studies on production of serotonin in a cultured mouse mastocytoma cell line. 288 33

Bicarbonate reabsorption by the immature kidney in response to acute acid-base changes was assessed in 50 anesthetized newborn rabbits before the end of nephrogenesis. The normal newborn rabbit (age 5-12 days) is in a state of hypochloremic metabolic alkalosis (PHCO3-, 31.9 +/- 0.6 mmol/l; PCl-, 83.1 +/- 1.0) and excretes a hypertonic (Uosmol = 578 +/- 41 mosmol/kgH2O), alkaline (UpH = 7.40 +/- 0.15) urine containing 50 +/- 9 mmol/l Cl- and 13 +/- 4 mmol/l Na+. The alkalosis is probably generated by an alkaline load contained in the mother's milk and maintained by a state of chloride wasting and volume contraction. In this alkalotic model, bicarbonate reabsorption, expressed per milliliter glomerular filtration rate (GFR), correlates positively with arterial CO2 pressure (PaCO2). The ability of the immature kidney to reclaim filtered bicarbonate in response to an elevation of the plasma carbon dioxide tension remains unlimited up to PaCO2 of 110 mmHg (y = 20.7 + 0.15 x, r = 0.82, P less than 0.001). Hypercapnia is associated with a marked fall in GFR, so that the positive correlation between bicarbonate reabsorption and PaCO2 vanishes when the bicarbonate reabsorption rate is expressed in absolute terms. Bicarbonate reabsorption is strongly dependent on the filtered load during both acutely induced metabolic acidosis and alkalosis. The acid-base state of the newborn rabbit is in sharp contrast with that of most animal species, and the renal handling of bicarbonate as a function of GFR does not show signs of tubular immaturity.
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PMID:Bicarbonate reabsorption by the kidney of the newborn rabbit. 291 64

The present studies were undertaken to determine, by recollection micropuncture, the effect of a synthetic atrial natriuretic peptide (ANP) on the absolute and fractional deliveries of water and sodium to the juxtamedullary end-descending limb. Two groups of young female Munich-Wistar rats were studied: control (n = 8) received the vehicle only; and ANP (n = 12) received a prime followed by the constant infusion of a synthetic rat atrial peptide (28 amino acids). With the infusion of ANP, clearance of p-[14C]aminohippurate [( 14C]PAH) and glomerular filtration rate (GFR) fell significantly. Despite this fall in GFR and renal plasma flow, ANP produced a 2-fold increase in urine volume and a 10-fold increase in sodium excretion. Absolute and fractional sodium deliveries to the end-descending limb increased by approximately 30% in the ANP group, whereas mean juxtamedullary single-nephron glomerular filtration rate (SNGFR) remained stable. In three additional rats prepared for micropuncture of the superficial end-accessible proximal tubule, ANP reduced cortical SNGFR by approximately 15%. By contrast, GFR did not decline in response to ANP in larger rats, when treated identically. We conclude that in young rats ANP can produce a natriuresis in the absence of a rise in GFR; the fall in GFR observed following ANP is due presumably to the immaturity of the animals used in these studies; and ANP produces a rise in absolute and fractional water and sodium deliveries to the end-descending limb that cannot be attributed to a change in SNGFR.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of synthetic ANP on renal and loop of Henle functions in the young rat. 294 65

The transport of ions and solutes at the epithelial surface of the renal proximal tubule increases during periods of reduced dietary intake and decreases with dietary excess. We have used the sulfur-containing beta-amino acid, taurine, as a probe of this renal adaptive response to altered dietary sulfur amino acid intake to better understand the mechanisms of renal amino acid reabsorption. There exists an age-related precession of taurine uptake values by brush border membrane vesicles prepared from nursing rats from youngest to oldest. However, despite the immaturity of this transport mechanism, epithelial membranes become able to display a full renal adaptive response to altered sulfur amino acid intake sometime between the 7th and 14th day of life. This adaptive response is expressed in both "up regulation" and "down regulation" by means of a change in the initial rate of Na(+)-taurine cotransport. No changes in the lipid microenvironment of the membrane, as assessed by measurements of membrane fluidity, are evident. The lack of adaptation observed in 7-day-old pups may be due to immaturity of the Na+ transporting mechanism which energizes the uptake of amino acids.
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PMID:Renal adaptation to dietary amino acid alteration is expressed in immature renal brush border membranes. 315 88


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