Biomedical subjects

P Hulin

Publications and source records attributed to P Hulin.

15 recordsLinked to original sources

PubMed2000

Locoregional cancer treatment with magnetic drug targeting.

The specific delivery of chemotherapeutic agents to their desired targets with a minimum of systemic side effects is an important, ongoing challenge of chemotherapy. One approach, developed in the past to address this problem, is the i.v. injection of magnetic particles [ferrofluids (FFs)] bound to anticancer agents that are then concentrated in the desired area (e.g., the tumor) by an external magnetic field. In the present study, we treated squamous cell carcinoma in rabbits with FFs bound to mitoxantrone (FF-MTX) that was concentrated with a magnetic field. Experimental VX-2 squamous cell carcinoma was implanted in the median portion of the hind limb of New Zealand White rabbits (n = 26). When the tumor had reached a volume of approximately 3500 mm3, FF-MTX was injected intraarterially (i.a.; femoral artery) or i.v. (ear vein), whereas an external magnetic field was focused on the tumor. FF-MTX i.a. application with the external magnetic field resulted in a significant (P < 0.05), complete, and permanent remission of the squamous cell carcinoma compared with the control group (no treatment) and the i.v. FF-MTX group, with no signs of toxicity. The intratumoral accumulation of FFs was visualized both histologically and by magnetic resonance imaging. Thus, our data show that i.a. application of FF-MTX is successful in treating experimental squamous cell carcinoma. This "magnetic drug targeting" offers a unique opportunity to treat malignant tumors locoregionally without systemic toxicity. Furthermore, it may be possible to use these magnetic particles as a "carrier system" for a variety of anticancer agents, e.g., radionuclides, cancer-specific antibodies, and genes.

Animals↗

PubMed2000

Optimal L(1)-L(2) primary tone level separation remains independent of test frequency in humans.

Previous studies described a systematic asymmetry of the level of the 2f(1)-f(2) distortion product otoacoustic emission (DP) in the space of the primary tones levels L(1) and L(2) in normal-hearing humans. Optimal primary tone level separations L(1)-L(2), which result in maximum DP levels, were close to L(1)=L(2) at high levels, but continuously increased with decreasing stimulus level towards L(1)>L(2) (Gaskill and Brown, 1990, J. Acoust. Soc. Am. 88, 821-839). At these optimal L(1)-L(2), however, not only DP levels in normal hearing were maximal, but also trauma-induced DP reductions. A linear equation that approximates optimal L(1)-L(2) level separations thus was suggested to be optimum for use in clinical applications (Whitehead et al., 1995, J. Acoust. Soc. Am. 97, 2359-2377). It was the aim of this study to extend the generality of optimal L(1)-L(2) separations to the typical human test frequency range for f(2) frequencies between 1 and 8 kHz. DPs were measured in 22 normal-hearing human ears at 61 primary tone level combinations, with L(2) between 5 and 65 dB SPL and L(1) between 30 and 70 dB SPL (f(2)/f(1)=1.2). It was found that the systematic dependence of the maximum DP level on the L(1)-L(2) separation is independent on frequency. Optimal L(1)-L(2) level separations may well be approximated by a linear equation L(1)=a L(2)+(1-a) b (after Whitehead et al., 1995) with parameters a=0.4 and b=70 dB SPL at f(2) frequencies between 1 and 8 kHz and L(2) levels between 20 and 65 dB SPL. Below L(2)=20 dB SPL, the optimal L(1) was found to be almost constant. Following previous notions (Gaskill and Brown, 1990), an analysis of basilar membrane response data in experimental animals (after Ruggero and Rich, 1991, Hear. Res. 51, 215-230) is further presented that relates optimal L(1)-L(2) separations to frequency-selective compression of the basilar membrane. Based on the assumption that optimal conditions for the DP generation are equal primary tone responses at the f(2) place, a linear increase of the optimal L(1)-L(2) level separation is graphically demonstrated, similar to our results in human ears.

Acoustic Stimulation↗

PubMed2000

Non-invasive measurement of intracranial pressure changes by otoacoustic emissions (OAEs)--a report of preliminary data.

Up to now changes of intracranial pressure can only be objectively assessed by invasive measurement tools e.g. epidural transducers or intraventricular or intraparenchymatous catheters. Changes of intracranial pressure (ICP) are known to influence the inner ear since the subarachnoid space is linked to the perilymphatic space of the inner ear via the cochlear aquaeduct. A new method for assessing cochlear disorders is based on otoacoustic emissions (OAE) which are generated by the outer hair cells (OHCs) of the inner ear. The aim of the present study was to find out whether changes of intracranial pressure can be monitored by spontaneous otoacoustic emissions (SOAEs), transient evoked otoacoustic emissions (TEOAEs) and distortionproduct otoacoustic emissions (DPOAEs). SOAEs, TEOAEs and DPOAEs were measured in 12 young normally hearing subjects (volunteer group) in different body postures (horizontal, -30 degrees and +30 degrees supine position). In 5 patients undergoing continuous intraventricular pressure monitoring for the assessment of normal pressure hydrocephalus (NPH), DPOAEs were measured simultaneously in different body postures as well (patient group). At an increase of ICP the SOAE-level of the volunteer group decreased by -3.3 dB SPL (sound pressure level) and the TEOAE-level by -2.1 dB SPL. The DPOAEs showed a frequency dependent reduction of its level with maximal changes at the lowest frequency tested (f2 = 1 kHz; -7.9 dB SPL). In the patient group the ICP amounted to 19.2 cm H(2)0 and the DPOAE-level also decreased particularly at lower frequencies (-2.0 dB SPL). In conclusion otoacoustic emissions, particularly DPOAEs, may provide a new clinical tool for non-invasive monitoring of ICP.

Environmental Monitoring↗

PubMed2000

Effect of locally applied drugs on the pH of luminal fluid in the endolymphatic sac of guinea pig.

The aim of the present work was to assess the effect of various drugs applied locally on the pH of the luminal fluid (pH(lum)) in guinea pig endolymphatic sac. pH(lum) and transepithelial potential, when measured in vivo by means of double-barrelled pH-sensitive microelectrodes, were 7.06 +/- 0.08 and +6.1 +/- 0.34 mV (mean +/- SE; n = 84), respectively, which is consistent with a net acid secretion in the luminal fluid of the endolymphatic sac. Bafilomycin and acetazolamide increased and decreased, respectively, pH(lum). Amiloride, ethylisopropylamiloride, ouabain, and Schering 28080 had no effect on pH(lum). Results obtained with inhibitors of anionic transport systems were inconclusive; e.g., DIDS reduced pH(lum), whereas neither SITS nor triflocin had any effect. We conclude that bafilomycin-sensitive H(+)-ATPase activity accounts for the transepithelial acid gradient measured in the endolymphatic sac and that intracellular and membrane-bound carbonic anhydrase probably participates in regulating endolymphatic sac pH(lum). The relationship between acid pH, endolymph volume, and Ménière's disease remains to be further investigated.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1999

Structure-function analysis of a double-mutant cystic fibrosis transmembrane conductance regulator protein occurring in disorders related to cystic fibrosis.

A number of disorders related to cystic fibrosis have been described since the cloning of the cystic fibrosis gene, including infertility due to the congenital bilateral absence of the vas deferens. We have identified, in several patients, complex cystic fibrosis transmembrane conductance regulator genotypes like double-mutant alleles. We have now analyzed the structure-function relationships of one of these mutants, R74W-D1270N cystic fibrosis transmembrane conductance regulator, expressed in HeLa cells, to evaluate the contribution of each mutation in the phenotype. We found that R74W cystic fibrosis transmembrane conductance regulator appears to be a polymorphism, while D1270N cystic fibrosis transmembrane conductance regulator could be responsible for the congenital bilateral absence of the vas deferens phenotype. The combination of the two produced a more severe effect on the chloride conductance pathway as well as on the phenotype.

Alleles↗

PubMed1999

Evidence for apical K conductance and Na-K-2Cl cotransport in the endolymphatic sac of guinea pig.

The transepithelial potential in the endolymphatic sac (ESP) was recorded up to 60 min after apical injection of ouabain, bumetanide, quinine, barium, tetraethylammonium, and 4-aminopyridine. After control injection, ESP decreased by 74% and completely recovered at 30 min. After ouabain, barium, or quinine injection, the ESP time course was similar to that in the control group. After bumetanide, tetraethylammonium, or 4-aminopyridine injection, complete recovery was only observed at 60 min. These results suggest that apical K+ conductance and Na-K-2Cl cotransporter could be involved in the genesis of ESP.

Animals↗

PubMed1998

Extracellular ATP raises cytosolic calcium and activates basolateral chloride conductance in Necturus proximal tubule.

1. Extracellular nucleotides modulate ionic transport mechanisms in various epithelia. In the present study, we investigated the effects of extracellular ATP on the intracellular free Ca+2 concentration ([Ca2+]i) and electrophysiological properties of Necturus maculosus proximal convoluted tubule (PCT). 2. ATP raised [Ca2+]i in microdissected fura-2-loaded PCTs (half-maximal effect, approximately mumol 1(-1) ATP). The initial ATP-induced changes in [Ca2+]i were not blunted by the removal of external Ca2+ nor by the presence of Ca2+ channel blockers, but were abolished by thapsigargin and suramin. The sequence for the potency of various agonists on [Ca2+]i was 2-methylthioATP (2MeSATP) = ADP = ATP >> UTP, 2',3',-O-(4-benzoilbenzoil) ATP (BzATP), alpha, beta-methylene ATP (AMPCPP), adenosine. 3. In vivo electrophysiological measurements showed that 100 mumol 1(-1) peritubular ATP added to a Ringer solution reduced the basolateral cell membrane potential (Vm) and increased the cell membrane input conductance. In a low Cl- solution, this ATP-induced depolarization was enhanced. These effects were inhibited by 1 mmol l-1 SITS, consistent with the activation of a basolateral Cl- conductance. 4. The ATP-induced change in Vm was reproduced by ADP but not by UTP or adenosine, and was prevented by suramin. 5. The ATP-induced membrane depolarization was not influenced by thapsigargin, BAPTA AM, or staurosporine and was not reproduced by manoeuvres increasing [Ca2+]i or intracellular cAMP content. 6. We conclude that, in Necturus PCT, a P2y receptor mobilizes Ca2+ mainly from intracellular pools and increases a basolateral Cl- conductance, GCl. The activation of GCl occurs by a mechanism which is not related either to an increase in [Ca2+]i or cAMP content, or to PKC activation.

Adenosine Triphosphate↗

PubMed1997

Symmetric pH dependence of buffering power in giant fused cells from frog kidney proximal tubule.

This study measures the intrinsic buffering power (beta(i)) of giant fused cells from the proximal kidney tubule of the frog (Rana ridibunda) as a function of intracellular pH (pHi). We monitored pHi and transmembrane potential difference during acid or alkaline cell loading, achieved by removal of NH4Cl-containing solutions or CO2-HCO3(-)-equilibrated solutions, respectively, in the absence of extracellular Na+. Data were well fit by the equation for a single, monoprotic buffer with a maximum beta(i) at a pHi of 7.39 +/- 0.06 and a total buffer concentration of 30.7 +/- 1.6 mM (means +/- SD). From pHi measurements obtained during CO2-HCO3- exposure, we also calculated the buffering power afforded by the CO2-HCO3- pair, and we show its increasing contribution to total buffering power at increasing PCO2 and pHi. To our knowledge, this is the first report of a cell type in which intrinsic cell buffers can be adequately approximated as a single monoprotic buffer with a negative logarithm of apparent dissociation constant in the normal physiological range and essentially symmetric dependence on pHi in both acid and alkaline ranges.

Ammonium Chloride↗

PubMed1996

Further investigation of ionic diffusive properties and of NH4+ pathways in Xenopus laevis oocyte cell membrane.

To study the ionic diffusive properties and the NH4+ pathways in the Xenopus laevis oocyte cell membrane, we recorded the effects of various inhibitors on membrane potential (Vm) and membrane resistance (Rm); intracellular acidification was taken as an index of NH4+ influx from the bath to the cytoplasm. The following results were obtained: in the control state, barium and quinine (Q) ions depolarized Vm and raised Rm, consistent with inhibition of K+ conductance(s). Diphenylamine-2-carboxylic acid (DPC), 3',5'-dichlorodiphenylamine-2-carboxylic acid (DCDPC) and gadolinium ions hyperpolarized Vm and increased Rm, suggesting the inhibition of nonselective cationic conductance(s). In the presence of 20 mmol/l NH4Cl, Vm depolarized, Rm fell, and intracellular pH (pHi) decreased, consistent with an NH4+ influx. In the presence of DPC, the same manoeuvre induced a biphasic Vm change (i.e. a spike depolarization followed by a membrane hyperpolarization) and a fall of Rm; in most oocytes, intracellular acidification persisted and was reversible upon adding ouabain (Oua). These results indicate that a DPC-sensitive conductance is not the unique NH4+ pathway and that Na, K-ATPase may also mediate NH4+ influx. However, Oua did not prevent the Rm decrease, suggesting that ouabain-insensitive rheogenic pathway(s) are activated. Thus, we investigated the Vm change induced by NH4Cl addition in the presence of DPC: the spike depolarization followed by secondary hyperpolarization became a plateau depolarization when Q was added, suggesting involvement of Q-sensitive pathway(s) in the above described biphasic Vm change. In the presence of DPC, Q and Oua, intracellular acidification upon adding NH4Cl persisted consistent with further NH4+ influx through quinine-, DPC- and Oua-insensitive pathway(s).

Animals↗

PubMed1995

Differential regulation of membrane potential and conductance via intra- and extracellular pH in fused proximal tubular cells of frog kidney.

Intracellular pH (pHi), membrane potential (Vm) and membrane conductance (Gm) in fused proximal tubular cells of the frog kidney, were determined at three extracellular pH (pHo) values, 7.5, 8.5 and 6.5. Imposed changes of pHo by +/- 1 pH unit induced parallel but smaller shifts of pHi. The alkaline milieu hyperpolarized the cells and increased Gm, whereas the acid milieu depolarized and lowered Gm. We subsequently introduced a weak acid and its conjugate base (acetic acid/acetate), or a weak base and its conjugate acid (NH3/NH4+), at pHo 7.5, 8.5 and 6.5 to shift pHi without altering pHo, or to shift pHi against imposed changes of pHo. From these experiments, we observed that under some circumstances Vm varied with pHo but without Gm or pHi changes, whereas under other circumstances changes of Gm occurred during alterations of pHi while pHo and Vm remained unaltered. At pHi approximately 6.5 associated with Vm approximately -10 mV, Gm dramatically increased to quasi-infinite values. This increase was not an artifact since Gm returned to its control value following recovery to the control solution or in the presence of hyperosmotic solution. In conclusion, we demonstrate a differential regulation whereby Vm and Gm are controlled by pHo and pHi: pHo modulates mainly Vm and pHi modulates chiefly Gm. Furthermore, at pHi approximately 6.5 and Vm approximately -10 mV, our data reveal a large Gm that tends towards infinite values in a reversible fashion.

Animals↗

PubMed1994

Triflocin, a novel inhibitor for the Na-HCO3 symport in the proximal tubule.

1. Triflocin, applied at millimolar concentration hyperpolarizes the basolateral membrane of Necturus proximal convoluted tubular cells, in vivo. 2. Barium, 2.5 x 10(-3) M, ouabain, 10(-3) M, or amiloride 10(-4) M, fail to prevent this hyperpolarization. 3. Triflocin has no effect on the intracellular chloride activity. 4. In physiological acid base conditions, Triflocin increases intracellular pH. 5. Upon an acute isohydric hypercapnia, Triflocin depolarizes the basolateral membrane potential. 6. It is concluded that, Triflocin inhibits the basolateral electrogenic Na-(HCO3)n > 1 cotransport in proximal tubules.

Animals↗

PubMed1992

Millimolar amiloride concentrations block K conductance in proximal tubular cells.

1. Amiloride, applied at millimolar concentrations, results in the blockade of K+ conductance in amphibian proximal convoluted cells (PCT), fused into giant cells. 2. Amiloride results directly in a blockade of K+ conductance that is not related to inhibition of the Na(+)-H+ antiport, which would lower intracellular pH, adversely affecting K+ conductance. On the contrary, high amiloride concentrations promote entry of this lipophilic base in the cell, leading to higher cell pH. 3. Under voltage clamp conditions, control vs. amiloride, current-voltage curves from PCT fused giant cells intersect at -86.2 +/- 3.4 mV, a value close to the equilibrium potential for potassium. 4. Hexamethylene amiloride, 10(-5) M, irreversibly depolarizes the membrane potential. 5. Barium decreased by 50% the initial slope of realkalinization, following removal of a solution containing NH4Cl, as did amiloride. In addition, these blockers reduced membrane conductance by 40%, suggesting that a fraction of the amiloride-suppressible NH4+ efflux may be conductive. 6. Amiloride does not directly inhibit the Na(+)-K+, ATPase in our preparation, contrary to the prevalent belief. 7. In vivo studies show that amiloride interferes with an apical K+ conductance but it does not alter basolateral K+ conductance.

Amiloride↗

PubMed1992

Barium- or quinine-induced depolarization activates K+, Na+ and cationic conductances in frog proximal tubular cells.

1. Frog proximal tubular cells were fused into giant cells. We measured membrane potential (Vm), its changes (delta Vm), and current-induced voltage changes (delta psi) in single cells, during control and experimental states. Each cell served as its own control. 2. In the presence of a physiological Ringer solution, the transference number for potassium (tK) was 0.50. Barium (3 mM) reduced membrane conductance (Gm) by 50%; low-Cl- solutions and low-Na+ solutions also diminished Gm, by 52 and 30%, respectively. The association of barium and low-NaCl solutions decreased Gm to approximately 38% of control, indicating that the impermeant substitute of a physiological ion may interact with other pathways; alternatively, blockade of steady-state conductances may activate physiologically silent processes. 3. In an attempt to enhance the contribution of the partial K+ conductance (GK) to Gm, fused cells were exposed to low-Cl- solutions, containing in addition 0.1 mM-methazolamide, to inhibit the rheogenic Na(+)-HCO3-symport, and 1 microM-amiloride, to block Na+ conductance (GNa). tK went up to 0.83. 4. The high tK preparation was challenged with barium (3 mM) or quinine (Quin, 1 mM). These blockers produced large depolarizations (approximately 60 mV), however, although Gm decreased along early- and mid-depolarization, Gm plateaued and eventually it increased with larger and larger depolarization. 5. Depolarization-associated increase in Gm reflects activation of other conductances. These are Na+, cationic, and K+ conductance(s) poorly sensitive to quinine or barium. In the presence of Ba(2+)- or Quin-induced depolarization, injection of depolarizing current produces delayed increase in conductance. 6. Depolarization-induced activation of cationic conductance (Gcat) and GNa results in enlargement of the K+ electrochemical potential difference, to about 70 mV; this difference allows recycling of K+ ions outwards, since a GK is still detected and may contribute up to 38% of the total conductance.

Amiloride↗

PubMed1982

[Triple juxtacotyloid osteotomy].

The authors have developed a technique of triple innominate osteotomy derived from that describe by Steele. The three osteotomy divisions are made very close to the acetabulum. With this technique the acetabulum can more easily be re-orientated and the pubis and ischium are left intact with their muscle attachments.

Adolescent↗

PubMedDate not supplied

[Slow-release verapamil 240 mg and treatment of mild to moderate hypertension].

The study was carried out in association with medical practitioners who were responsible for observing the patients. Its aim was to determine the effective dosage of slow release verapamil (V) in the treatment of mild to moderate hypertension and to compare plasma concentrations of V with blood pressure effects. The study comprised a 2-week placebo period and a 3-month active treatment period with V, during which patients were examined, 20-24 h after last intake of V, at the end of the first (D30) and of the third (D90) month of treatment. Active treatment started with 240 mg of V (once a day); at D-30 if diastolic blood pressure (DBP) remained above 90 mmHg the dosage of V was increased to 480 mg (t.d.s.). At each examination blood pressure, body weight and heart rate were registered, electrocardiogram and routine biochemical tests were carried out; plasma concentration of V was measured at D30 for every patient and at D90 for those receiving 480 mg. of V. Thirty patients (11 men and 19 women) aged from 29 to 80 years (mean : 61.7) took part in the study. Treatment needed to be stopped in one patient; results are based on the other 29. At D30 systolic blood pressure (SBP) fell from 179.4 +/- 5.9 to 156.2 +/- 5,5 mmHg and DBP from 101.3 +/- 1.8 to 88.3 +/- 3 mmHg; DPB became normal (less than 90 mmHg) in 23 subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗