Sepsis and multiple brain abscesses caused by Salmonella paratyphi B in an infant: successful treatment with sulbactam-ampicillin and surgical drainage.

Abscess formation by Salmonella species is an uncommon but significant manifestation of salmonellosis, because this type of infection has high morbidity and mortality rates and is a potential nosocomial hazard. In infants, history of consumption of contaminated water should be especially quired. We report a case who had sepsis and multiple brain abscesses due to Salmonella paratyphi B and who responded to sulbactam-ampicillin (SAM) therapy. Sulbactam-ampicillin combination may be preferable due to its immunomodulator effect.

Relationship between extra- and intracellular calcium in distal segments of the renal tubule. Role of the Ca2+ receptor RaKCaR.

The effect of extracellular calcium ([Ca2+]e) on cytosolic calcium ([Ca2+]i) was investigated in thick ascending limbs and collecting ducts from the rat kidney, using the fluorescent dye fura-2. In cortical collecting ducts, basolateral but not apical changes in [Ca2+]e were associated with parallel changes in [Ca2+]i. Basal [Ca2+]i was hardly modified by nifedipine and verapamil but was decreased by 60% by basolateral La3+. Increasing peritubular [Ca2+]e triggered Ca2+ release from intracellular stores. This effect was not reproduced by agonists of the renal Ca2+-receptor RaKCaR, e.g., Ba2+, Mg2+, Gd3+, and neomycin, but was reproduced by Ni2+. Ni2+-induced mobilization of intracellular Ca2+ was larger in the inner medullary collecting duct, a segment which poorly responds to increasing [Ca2+]e. In the cortical thick ascending limb, removing basolateral Ca2+ hardly altered [Ca2+]i but increasing [Ca2+]e or adding Ba2+, Mg2+, Gd3+ and neomycin released intracellular calcium. These data demonstrate that (1) basolateral influx of calcium occurs in cortical collecting ducts, under basal conditions; (2) this influx occurs through nonvoltage gated channels, permeable to Ba2+, insensitive to verapamil and nifedipine, and blocked by La3+; (3) increasing [Ca2+]e stimulates the influx and triggers intracellular calcium release, independently of the phospholipase C-coupled receptor RaKCaR; (4) RaKCaR is functionally expressed in thick ascending limbs; (5) another membrane receptor, sensitive to Ni2+ but not to Ca2+ is present in the collecting duct.

Calcitonin stimulates H+ secretion in rat kidney intercalated cells.

Calcitonin (CT) modulates rat intercalated cell (IC) functions of the rat cortical collecting duct (CCD) [E. Siga, B. Mandon, N. Roinel, and C. de Rouffignac. Am.J. Physiol. 264 (Renal Fluid Electrolyte Physiol. 33): F221-F227, 1993]. To characterize the specific function regulated by CT, rat CCDs were perfused in vitro. Total CO2 net fluxes (JtCO2, pmol.mm-1.min-1) and transepithelial voltage (Vt) were measured. Bath CT induced a significant tCO2 reabsorption. This effect was higher on CCDs harvested from acid-loaded than from control rats. When HCO3- secretion was blocked, CT also raised JtCO2 and Vt. When H+ secretion was blocked, CT was ineffective on JtCO2 and Vt. When HCO3- secretion was increased and H+ secretion was inhibited, CT did not change JtCO2, whereas isoproterenol (ISO) increased tCO2 secretion from -13.5 +/- 2.0 (control) to -19.0 +/- 2.4 (ISO). In rat CCD studied under these same preceding conditions plus luminal amiloride to block the Na(+)-dependent Vt, CT did not alter Vt, whereas ISO increased it by 4.5 +/- 0.7 mV. We conclude from these data that, in the rat CCD, calcitonin stimulates H+ secretion, likely by so-called alpha-intercalated (alpha-IC) cells, whereas ISO stimulates HCO3- secretion, likely by so-called beta-IC cells.

Molecular analysis of beta-adrenergic receptor subtypes in rat collecting duct: effects on cell cAMP and Ca2+ levels.

Expression and functional properties of beta-adrenergic receptors (beta-ARs) were studied in rat collecting tubules isolated by microdissection. Reverse transcription-polymerase chain reaction experiments demonstrated that the beta 1- and beta 2-AR mRNAs, but not the beta 3-subtype, are expressed in the cortical collecting duct (CCD). Quantitation of mRNAs, carried out using mutant RNAs as internal standards, further showed that beta 1- and beta 2-ARs transcripts are present at comparable amounts in CCD (3,000-4,000 copies/mm of tubular length), but reach 6-8 times lower levels in the outer medullary collecting duct (OMCD: beta 1, 480 +/- 180; beta 2, 590 +/- 110 copies/mm of tubular length). Functional studies, carried out in CCD, corroborated the expression of these two receptor subtypes. The rank order of potency of beta-agonists for stimulating adenosine 3',5'-cyclic monophosphate (cAMP) accumulation was isoproterenol > norepinephrine = epinephrine, and similar efficiencies were found for a beta 1- and a beta 2-antagonist to inhibit isoproterenol-dependent cAMP formation. Fura 2 fluorescence measurements revealed that isoproterenol (10 microM) induces a biphasic rise of intracellular free Ca2+ concentration ([Ca2+]i), consisting of an initial fast increase (delta [Ca2+]i = 122 nM) followed by a plateau phase (delta [Ca2+]i = 58 nM). In the absence of basolateral Ca2+, the initial peak was still observed, suggesting intracellular Ca2+ release. Norepinephrine and epinephrine, as well as selective beta 1- and beta 2-agonists, also increased [Ca2+]i in CCD. Only slight [Ca2+]i variations were produced by isoproterenol in the OMCD (delta [Ca2+]i = 21 nM) and the cortical thick ascending limb (delta [Ca2+]i = 25 nM). These results show that both beta 1- and beta 2-ARs are expressed in the collecting tubule and that they predominate in the CCD. The two receptor subtypes contribute to cAMP accumulation induced by beta-agonists. They also trigger [Ca2+]i variations, indicating their possible coupling to several transduction pathways in the rat CCD.

cAMP-dependent effects of vasopressin and calcitonin on cytosolic calcium in rat CCD.

Fura 2 fluorescence measurements were carried out on microperfused rat cortical collecting ducts (CCD) to investigate the effect of adenosine 3',5'-cyclic monophosphate (cAMP) and adenylate cyclase-stimulating hormones on free cytosolic calcium ([Ca2+]i). Forskolin, 3-isobutyl-1-methylxanthine, and 8-(4-chlorophenylthio)-cAMP (CPT-cAMP) all triggered marked and sustained [Ca2+]i variations. Maximal increases elicited by 100 microM CPT-cAMP amounted to 101 +/- 11 nM (mean +/- SE, n = 18). This effect was mostly dependent on the presence of basolateral calcium and totally independent of luminal calcium. It remained unchanged in CCD perfused with sodium-free luminal fluid (82 +/- 10 nM, n = 5), pretreated with 1 mM bath ouabain (113 +/- 20, n = 4), or superfused with sodium-free bath in the presence of ouabain (82 +/- 22, n = 5). The V2 agonist 1-desamino-8-D-arginine vasopressin (DDAVP, 10 nM) increased [Ca2+]i by 57 +/- 5 nM (n = 27), a value 40% lower than that achieved with 10 nM AVP (141 +/- 7, n = 34) but similar to that observed with AVP + a V1a antagonist (57 +/- 6, n = 6). Significant effects could also be obtained with 200 pM DDAVP (31 +/- 6, n = 8) and arginine vasopressin (AVP) (72 +/- 6, n = 16). Rat calcitonin also raised [Ca2+]i by 43 +/- 10 (n = 8) and 66 +/- 8 nM (n = 17) at 1 and 10 nM, respectively, and its effect was not additive to that of CPT-cAMP. Calcitonin and DDAVP effects, like those of CPT-cAMP and forskolin, were nearly abolished in Ca(2+)-free bath, but AVP action on intracellular release persisted. These results show that, in rat CCD, cAMP effects on [Ca2+]i mainly result from basolateral calcium entry. In contrast to rabbit CCD the mechanism is independent on Na reabsorption and basolateral Na+/Ca2+ exchange. Calcitonin and DDAVP effects on [Ca2+]i are probably secondary to increased cAMP production.

Insulin stimulates Na+, Cl-, Ca2+, and Mg2+ transports in TAL of mouse nephron: cross-potentiation with AVP.

Insulin (Ins) decreases Na+ delivery in the final urine. To determine whether the loop of Henle participates in this reduction, the effects of Ins were tested on cortical (CTAL) and medullary thick ascending limbs (MTAL) of the mouse nephron, microperfused in vitro. In the MTAL, Ins increased the transepithelial potential difference (Vt) and the Na+ and Cl- net reabsorption fluxes (JNa and JCl, respectively) in a dose-dependent manner, the threshold being below 10(-9) M. At 10(-7) M, Ins reversibly increased JNa and JCl, leaving Mg2+ and Ca2+ fluxes (JMg and JCa, respectively) close to zero. In the CTAL, 10(-7) M Ins reversibly increased Vt, JNa, JCl, JMg, and JCa. In CTAL segments perfused under asymmetrical conditions, with a bath-to-lumen-directed NaCl gradient (lumen 50 mM NaCl, bath 150 mM NaCl), addition of 10(-7) M Ins to the bath resulted in a large increase in JMg and JCa. Thus the responses of CTAL and MTAL to Ins are in all ways similar to those already reported for the adenosine 3',5'-cyclic monophosphate (cAMP)-generating hormones acting on these nephron segments. When 10(-10) M arginine vasopressin (AVP) and 10(-7) M Ins were used in combination, previous addition of one hormone to the bath potentiated the response to the second hormone. In cAMP accumulation experiments, performed in the presence of a phosphodiesterase inhibitor, the amounts of cAMP formed with 10(-7) M Ins and 10(-10) M AVP (which elicit maximal physiological responses in these segments) were in the same range.(ABSTRACT TRUNCATED AT 250 WORDS)

Ca2+, Mg2+ and K+ transport in the cortical and medullary thick ascending limb of the rat nephron: influence of transepithelial voltage.

Isolated segments of rat cortical (cTAL) and medullary (mTAL) thick ascending limbs were microperfused and the transepithelial net fluxes (JX) were determined by measuring the composition of the collected fluid with an electron microprobe. When perfused with symmetrical solutions both segments showed similar JNa and JCl and lumen-positive transepithelial voltage (Vte = 7-8 mV). JMg, JCa and JK were not significantly different from zero. When perfused with asymmetrical solutions (lumen 50 mM, bath 150 mM NaCl), the mean Vte were 23 mV and 17 mV in the cTAL and mTAL respectively; this rise was accompanied by significant increases in JMg and JCa in the cTAL, but not in the mTAL, and a marked increase in JK in both segments. It is concluded that, in the rat, divalent cations can be reabsorbed in the cTAL, and K+ can be reabsorbed in the cTAL and mTAL. The transport is voltage-dependent. The mTAL can reabsorb neither Mg2+ nor Ca2+, whatever Vte.

V2-like vasopressin receptor mobilizes intracellular Ca2+ in rat medullary collecting tubules.

Cytosolic free calcium concentration ([Ca2+]i) was measured in single microdissected rat medullary collecting tubules [outer (OMCD) and inner (IMCD)] to identify receptors involved in vasopressin (AVP)-induced [Ca2+]i increases. In both segments, [Phe2,Orn8]vasotocin ([Phe2,Orn8]VT), a specific V1 agonist, as well as the V2 agonist 1-desamino-8-D-AVP (dDAVP) triggered [Ca2+]i variations. In OMCD, the mean response to 10 nM AVP roughly corresponded to the sum of V1 and V2 agonists effects. In IMCD, dDAVP (10 nM) alone reproduced the calcium response to AVP (delta[Ca2+]i = 243 +/- 34 nM, n = 6, and 248 +/- 27 nM, n = 8, with dDAVP and AVP, respectively). Furthermore, in the same experiments V1 and V2 maximal effects were not additive ([Phe2,Orn8]VT = 154 +/- 21 nM, n = 6; dDAVP + [Phe2,Orn8]VT = 233 +/- 23 nM, n = 9). As AVP, dDAVP released intracellular calcium (delta[Ca2+]i in calcium-free medium = 182 +/- 24 nM, n = 8, vs. 182 +/- 14 nM, n = 6 with 10 nM dDAVP and AVP, respectively). Neither 8-(4-chlorophenyl-thio)-adenosine 3',5'-cyclic monophosphate nor forskolin modified [Ca2+]i. A cross-reaction of dDAVP with an oxytocin (OT) receptor can be excluded since 1) the specific OT agonist [Thr4,Gly7]OT (10 nM) increased only slightly [Ca2+]i (delta-[Ca2+]i = 20 +/- 5 nM, n = 11); 2) the dDAVP response was not altered by the specific OT antagonist [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(O-methyl)tyrosine,4-threonine, 8-ornithine,9-tyrosylamide]vasotocin [d(CH2)5(1),O-Me-Tyr2,Thr4,Tyr-NH2(9)]OVT; 3) it was insensitive to V1 antagonists but was totally blocked by the V1/V2 antagonist [d(CH2)5(1),O-Et-Tyr2,Val4]AVP ([delta[Ca2+]i = 18 +/- 4 nM, n = 6). These results indicate that in IMCD AVP increases [Ca2+]i via both V1 and V2 receptors. [Ca2+]i variations due to V2 receptors involve a mechanism independent of adenylate cyclase and coupled to the same intracellular calcium pool as V1 and V2 receptors.

Effects of calcitonin on function of intercalated cells of rat cortical collecting duct.

In the rat cortical collecting duct (CCD), the presence of highly specific receptors to calcitonin (CT) coupled to a sensitive adenylate cyclase system suggests that this segment is a target site for CT. Our aim was to explore the effects of CT on the rat CCD microperfused in vitro. The hormone failed to alter the osmotic water permeability and did not affect net Na+ transport but generated a lumen-positive transepithelial potential difference (PDte), which under control conditions was close to zero. This response was dose dependent and was still observed in the presence of luminal amiloride, despite the luminal positivity generated by the Na+ channel blocker (PDte increased from 4.0 +/- 0.8 to 9.5 +/- 1.1 mV). In contrast, the nominal absence of CO2/HCO3- or the use of a low-Cl- solution totally prevented the PDte changes caused by CT. The CT-induced lumen-positive PDte was reduced by 2.3 +/- 0.8 mV after the basolateral addition of the Cl- channel inhibitor diphenylamine-2-carboxylate. 4-Acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid and acetazolamide, which inhibit Cl-/HCO3- exchangers and carbonic anhydrase activities, respectively, also inhibited the CT-induced PDte by 4.6 +/- 0.5 and 5.0 +/- 0.9 mV. To test whether the acid-base status of the animals influences the response to CT, rats underwent an acid or alkali load. CCD dissected from acid-loaded rats responded to CT to the same extent as control animals, but the hormonal action was significantly attenuated when the CCD was harvested from alkali-loaded rats (PDte increases: acid 4.0 +/- 0.3 vs. alkali 1.6 +/- 0.6 mV, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of osmotic water permeability during differentiation of inner medullary collecting duct.

Urinary osmotic concentration capacity during renal ontogeny is subject to changes of medullary cytoarchitecture and of segmental epithelial transport characteristics. Osmotic equilibrium between interstitial and tubular fluid of the terminal nephron segment in response to vasopressin is an absolute essential of maximal urinary osmotic concentration. The regulation of osmotic water permeability (Pf) in this terminal epithelial segment during ontogenetic differentiation has not been documented. The inner medullary collecting duct (IMCD), the terminal 40% of total segmental length, was dissected at two stages of postnatal ontogenetic differentiation from immature (days 7-15) and from mature (days 33-37) rat kidneys and perfused in vitro. Pf (micron/s) was measured (bath hyperosmotic) in the absence and presence of arginine vasopressin (AVP, 230 pM). Basal Pf was 32.3 +/- 4.03 (n = 26) in the immature IMCD (IMCDi) and 111.5 +/- 20.6 (n = 15) in the mature segment (IMCDm). AVP increased Pf in IMCDi from 46.4 +/- 10.5 to 102 +/- 25.7 micron/s, whereas in IMCDm the AVP-dependent change of Pf was from 104.2 +/- 41.2 to 693 +/- 176 micron/s. AVP (2,300 pM) did not further increase Pf in IMCDi. Forskolin (50 microM) changed Pf in IMCDi from 34.9 +/- 6.3 to 104.1 +/- 16 micron/s; the corresponding change in IMCDm was from 150 +/- 32 to 985.8 +/- 133 micron/s. An analogue of adenosine 3',5'-cyclic monophosphate (cAMP; 10(-3) M) increased Pf in IMCDi from 35.5 +/- 11.4 to 138.5 +/- 32.6 and in IMCDm from 79.6 +/- 32.3 to 702.2 +/- 283 micron/s.(ABSTRACT TRUNCATED AT 250 WORDS)

Voltage dependence and barium sensitivity of colonic K secretion in renal failure.

Net colonic K secretion (JKnet) is increased in rats and humans with chronic renal failure (CRF). To study whether transepithelial potential difference (PD), active transport forces and/or luminal K conductance play a role in this adaptation, experiments were performed in the colon of control, K-adapted, and CRF rats. Under basal conditions the PD in vivo in CRF was greater than in controls and not different from K-adapted rats. JKnet was comparable in vivo in CRF and K-adapted rats and was greater than in controls. Amiloride (10 microM) reduced PD and JKnet in K-adapted and CRF rats to levels comparable to controls. Under in vitro short-circuited conditions serosal-to-mucosal K flux (JKs----m) in distal colon was significantly increased in K-adapted and CRF animals compared with control, whereas barium caused a significant reduction in JKs----m in all groups of animals. The barium-sensitive component of K secretion was greater, however, in the two experimental groups (-0.2 +/- 0.02 and -0.2 +/- 0.07 in K-adapted and CRF animals, respectively, vs. -0.08 +/- 0.02 microeq.h-1.cm-2 in controls, P less than 0.05). However, luminal barium failed to completely inhibit the increase in K secretion observed in the experimental groups. These data suggest that an increase in PD that results in a rise in luminal negativity, stimulation of active transport, and an increase in barium-sensitive K channels and barium-insensitive pathways in apical membrane of distal colon participate in the mechanism by which net K secretion is increased in the large intestine of subjects with CRF.

Mechanism of enhanced transcellular potassium-secretion in man with chronic renal failure.

Previous studies from our laboratory demonstrated that net K secretion in human rectum was 2.5-fold higher in patients with chronic renal failure than in controls. The present study was performed to determine whether K secretion in human large intestine involves an active process and whether an active transport process accounts, at least in part, for the rise in net K secretion in patients with renal insufficiency. Studies were performed under conditions when net water and electrolyte transport approached zero, and the observed distribution of K and Na across the rectal mucosa was compared to expected equilibrium values. In control subjects an active transport of 27.6 +/- 2.6 mV was observed for K and 63 +/- 4.2 mV for Na. Similar values were demonstrated in patients with chronic renal failure. The results of these studies demonstrated that net secretion of K and absorption of Na are governed, at least in part, by active transport processes, and suggest that, since active K secretion is not impaired, the rise in net K secretion in patients with renal insufficiency is caused by active secretion as well as by passive driving forces.