Long-term survival, prevalence, and cure of cancer: a population-based estimation for 818 902 Italian patients and 26 cancer types

Original, population-based estimates of indicators of long-term survival and cure in cancer patients are provided. More than a quarter of cancer patients in Italy have reached death rates similar to those of the general population. Nearly three quarters of them will not die as a result of cancer. These estimates are potentially helpful to health-care planners, clinicians, and patients.

Background

Persons living after a cancer diagnosis represent 4% of the whole population in high-income countries. The aim of the study was to provide estimates of indicators of long-term survival and cure for 26 cancer types, presently lacking.

Patients and methods

Data on 818 902 Italian cancer patients diagnosed at age 15–74 years in 1985–2005 were included. Proportions of patients with the same death rates of the general population (cure fractions) and those of prevalent patients who were not at risk of dying as a result of cancer (cure prevalence) were calculated, using validated mixture cure models, by cancer type, sex, and age group. We also estimated complete prevalence, conditional relative survival (CRS), time to reach 5- and 10-year CRS >95%, and proportion of patients living longer than those thresholds.

Results

The cure fractions ranged from >90% for patients aged <45 years with thyroid and testis cancers to <10% for liver and pancreatic cancers of all ages. Five- or 10-year CRS >95% were both reached in <10 years by patients with cancers of the stomach, colon–rectum, pancreas, corpus and cervix uteri, brain, and Hodgkin lymphoma. For breast cancer patients, 5- and 10-year CRSs reached >95% after 19 and 25 years, respectively, and in 15 and 18 years for prostate cancer patients. Five-year CRS remained <95% for >25 years after cancer diagnosis in patients with liver and larynx cancers, non-Hodgkin lymphoma, myeloma, and leukaemia. Overall, the cure prevalence was 67% for men and 77% for women. Therefore, 21% of male and 31% of female patients had already reached 5-year CRS >95%, whereas 18% and 25% had reached 10-year CRS >95%.

Conclusions

A quarter of Italian cancer patients can be considered cured. This observation has a high potential impact on health planning, clinical practice, and patients' perspective.

Prognostic value of EGFR expression in de novo and progressed atypical and anaplastic meningiomas: an immunohistochemical and fluorescence in situ hybridization pilot study

AIM

The aim of this study was to assess both the epidermal growth factor receptor (EGFR) protein expression by immunohistochemistry and the EGFR gene amplification by fluorescence in situ hybridization in meningiomas of different grade, in order to evaluate their possible role in the development of the disease. EGFR protein belongs to the family of tyrosine kinase growth factor receptors, which also includes HER2, HER3 and HER4. Elevated expression or activity of EGFR has been reported in several cancers, including brain tumours. EGFR activation can enhance the malignant potential of epithelial tissues.

METHODS

We investigated whether there was a difference in the EGFR protein expression and the EGFR gene amplification between the so called de novo malignant meningiomas and recurrent meningiomas with or without malignant progression from a previously lower grade tumor. Our goal was to evaluate if EGFR expression was a useful marker to select patients affected by meningioma with a major risk of recurrences. We also assessed the prognostic value of the EGFR expression on overall survival.

RESULTS

Progression from benign meningiomas to atypical or anaplastic meningiomas correlated with an increase in the expression of EGFR protein. Our study shows that EGFR immunostaining in meningiomas directly correlates to the tumor's grade. The EGFR expression did not correlate with the overall survival and the recurrence-free survival of the patients affected by meningioma (de novo, recurrent and progressed).

CONCLUSION

We submit that the EGFR expression is not a useful prognostic element to identify patients with a major risk of meningioma recurrence.

Role of ALK activation in the development and maintenance of the neoplastic phenotype in neuroblastoma

10008

Background: Activating mutations of the Anaplastic Lymphoma Kinase (ALK) receptor could be responsible for most familial neuroblastoma cases and for up to 15% of somatic cases. The objective of the present study was to further investigate the role of ALK activation in neuroblastoma. Methods: Tissue microarrays were constructed containing 101 primary tumors and 56 paired normal tissues. Sections were immunostained with anti-ALK or anti-P-ALK antibodies, and with antibodies directed against the ALK ligands: PTN (Pleiotrophin) or MDK (Midkine). The Wilcoxon signed rank test was applied for comparison of paired data. Associations with prognostic factors were analyzed using t-tests. Effects of the ALK inhibitor TAE684 (Novartis) on cell proliferation and signaling was evaluated in wild-type or mutated ALK neuroblastoma cell lines and xenografts. Results: ALK was expressed in about 100% of tumors and normal tissues, while phospho-ALK was detected in 5% of normal tissues and 50% of tumors. Sequencing of the kinase domain of ALK showed that its phosphorylation was largely independent of mutations and we found that MDK and PTN ligands were expressed in 66% and 50% of tumors, respectively. Interestingly, ALK, P-ALK, and MDK were expressed at higher levels in tumors as compared with paired normal tissues (p < 0.0001), while PTN showed an inverse tendency, being more expressed in normal tissues (p = 0.07). In tumors, P-ALK was associated with good-prognosis factors, including favorable stages (p = 0.01), absence of MYCN amplification (p = 0.05) and a younger age at diagnosis (p = 0.03). Inhibition of cell proliferation by TAE684 was detectible in all neuroblastoma cell lines, regardless of ALK status. However, TAE684 failed to demonstrate antitumor activity in advanced stage neuroblastoma xenografts expressing either a wild-type or a mutated ALK. Interestingly, ALK pathway activation (P-STAT3, P-AKT) was weak or barely detectible in these xenografts. Conclusions: ALK activation occurs during neuroblastoma oncogenesis, along with a concomitant switch between the expressions of PTN and MDK. However, ALK may not be a relevant therapeutic target since in vivo inhibition showed no antitumor activity.

[Table: see text]

Pharmacogenetic analysis of toxicity after 5-fluorouracil (5FU) or 5FU/oxaliplatin therapy for metastatic colorectal cancer: Preliminary results in FFCD 2000–05 trial

2508

Background: The FFCD 2000–05 randomized trial compared simplified LV5FU2 followed by FOLFOX6 (arm 1) to FOLFOX6 followed by FOLFIRI (arm 2) in the treatment of metastatic colorectal cancer. The aim was predicting the toxicity profile of oxaliplatin after the first line treatment using pharmacogenetic data. Methods: Patients (pts) with available blood samples were compared to the other pts for clinical prognostic factors (chi2 test). A logistic model was computed to test the association between polymorphisms and toxicity in each arm. An interaction test was used to assess a differential effect according to treatment (predictive effect), in order to identify a predictive effect of oxaliplatin. Grade 3–4 hematological and non-hematological toxicities (H-tox and NH-tox) at 4 months and grade 2–4 neurological at 6 months were the endpoints of the study. Thirteen genetic variants in 10 candidate genes were selected for pharmacogenetic analysis: ERCC1_04 (rs3212961), ERCC1_05 (rs11615), ERCC1_06 (rs3212948), ERCC1_24 (rs3212955), ERCC2_02 (rs1799793), ERCC2_03 (rs13181), ERCC2_06 ( rs238406 ), ERCC2_09 (rs1799787), GSTM1 (null/present), GSTT1 (null/present), TS (TSER, Ins/del6bp) and UGT1A1 (rs8175347). Genotyping was performed using Taqman probes, QMPSF and fragment analysis. Results: 327 pts (156/171) out of 410 were included (61 had no blood samples, 16 had less than 2 cycles, 3 had incomplete data on toxicity, 3 had insufficient DNA). No difference was found between included and excluded pts in the analysis for gender, age, OMS, number of metastatic organs and adjuvant chemotherapy. Pts received similar 5FU doses in both arms. Number of patients with at least one toxicity in arms 1/2 were as followed: 5/54 grade 3–4 H-tox, 28/47 grade 3–4 NH-tox, and 0/103 grade 2–4 neurological. The genotype CC of ERCC2_02 correlated with higher NH-tox at 4 months in arm 2 (p=0.0008, OR=0.31, 95%CI=[0.15–0.62] versus p=0.87, OR=0.93, CI=[0.39–2.21] in arm 1) compared to genotypes CT and TT, with borderline interaction (p=0.05). Conclusions: These preliminary results on early toxicity in first-line are in favour of an effect of ERCC2_02 on NH-tox of FOLFOX6 and a predictive effect on NH-tox of oxaliplatin.

[Table: see text]

Randomized strategical trial of chemotherapy in metastatic colorectal cancer (FFCD 2000–05): Preliminary results

4069

Background: The survival benefit of using a combination therapy instead of keeping it for a second line (L2) has not been demonstrated in metastatic colorectal cancer. The purpose of this trial was to compare the efficacy of simplified LV5FU2 (s) followed by FOLFOX6 (arm A) to FOLFOX6 followed by FOLFIRI (arm B) on progression-free survival after two lines of chemotherapy. We present here preliminary results relating to toxicity, observance and overall survival. Methods: Inclusion criteria: a) non resectable metastases of histologically proven colorectal adenocarcinoma , b) evaluable disease (WHO criteria), c) absence of previous chemotherapy other than adjuvant. Treatment was as follows: LV5FU2s = at day 1, folinic acid 400 mg/m2, 5-FU bolus 400 mg/m2 and continuous infusion over 46 hours 2,400 mg/m2/2 weeks; FOLFOX6 = LV5FU2s + oxaliplatin 100 mg/m2 at day 1; FOLFIRI = LV5FU2s + irinotecan 180 mg/m2 at day 1. Results: 410 pts out of 570 initially planned (early stopping due to slow accrual and new treatments) were included from 02/2002 to 02/2006 (205 in each arm). Median follow-up was 25 months. The median number (range) of cycles (28 days) in first line (L1) was respectively 5 (1–24) and 6 (1–24) in the arms A and B (p=0.01), and for L2 (152 and 144 pts in the arms A/B): 5 (1–17) and 3 (1–33) (NS). In the arms A and B, 74% and 70% of pts had L2. L1 was stopped for toxicity for 1% and 16% of the pts in arms A and B (p<0.0001); L2 respectively for 15% and 2% pts (p<0.0001). The percentages of pts presenting at least a grade 3–4 hematologic toxicity (mainly neutropenia) by arm were: 6% versus 37% (p<0.0001) for L1 and 30% versus 27% (NS) for L2; grade 3–4 non hematological toxicity (grade 2–4 neurotoxicity): 26% (1%) versus 56% (64%)(p<0.0001; p<0.0001) for L1 and 54% (60%) versus 46% (40%) of the pts for L2 (NS; p<0.01). No toxic death was observed in the arm A against 5 in the arm B: 3 in L1 and 2 in L2. Overall survival medians were 17 and 16 months in arms A/B (logrank p=0.64) (preliminary results, 291 observed deaths). Conclusions: This trial does not show any substantial difference in treatment duration and overall survival between both arms and shows a more important toxicity in the arm with first line combined chemotherapy.

No significant financial relationships to disclose.

Localized myxoid/round cell liposarcoma in adult patients. IL6 protein expression analysis

10075

Background: Myxoid/round cell liposarcoma (MLPS) is an uncommon soft tissue sarcoma with a relatively favorable prognosis and is considered a low grade malignancy. Methods: Retrospective analysis of 123 localized MLPS adult patients (pts) treated at our institution from 1987 to 2005 was performed. Paraffin embedded tissue was analyzed for IL6, IL6 receptor, NFkB and bcl-2 protein expression (positive (+) or negative) by tissue microarray immunostaining. Results: The median age of the 77 males and 46 females was 42 years (yr) (range 15–70). Lower extremity (LE) was the site more affected (77 pts). Median tumor size was 11 cm (range 2.5–40 cm), 87 were deep tumors and 63 were grade 1 tumors. Preoperative biopsy was carried on 38 pts. All but 2 pts underwent surgery (R0 24%, R1/R2 76%); 44 pts had a second surgery. Chemotherapy (CT) and radiation therapy were given to 30% and 52% of pts respectively. Complete remission was achieved in 98% of pts. After a median follow up of 6 yr (range 0.1–19 yr) 53 pts relapsed (43%); 37 locally, 11 distant and 5 both. Metastases occurred in 26 pts, 17 solitary and 9 multiple. The 5-yr, 10-yr and 15-yr DFS were 56%, 48% and 44% respectively. Median time to first relapse was 6.5 yr (range 0.1–16 yr). The 5-yr, 10-yr and 15-yr OS are 90%, 79% and 64% respectively. Tumor site, pre-surgical biopsy, R0 surgery and second surgery correlates with a better DFS in the multivariate analysis. So far 19 tumors have been studied for, NFkB (+) 57%, IL6 (+) 47% and Bcl2 (+) 30%, positivity. All tumors (+) for IL6 were also (+) for IL6 receptor. None of the proteins correlated to DFS and/or OS. Conclusions: Pts with localized resected MLPS require a prolonged follow-up since relapses occur after 10 yrs. PFS and OS correlate with an optimal loco-regional treatment. Half of MLPS expressed IL6, probably involving an autocrine phenomenon; whether this cytokine is involved in tumor aggressiveness, remains to be established.

No significant financial relationships to disclose.

Can ERCC1 and topoisomerase II-alpha predict histological response and outcome after induction chemotherapy in locally advanced soft tissue sarcomas (LASTS)?

10074

Background: The impact of histological response (± 95% of necrosis) on patients (pts) outcome with LASTS treated by induction chemotherapy (CT) is still debated. Methods: From 1995 to 2005, 79 LASTS pts received induction CT consisting in two cycles of API-AI regimen and results were already reported (Gomez-Abuin, ASCO 2004). ERCC1, HER2 and Topoisomerase IIa (TopoII) was assessed by IHC on initial biopsies after paraffin embedding and correlated to histological response and pts outcome. Results: The median age of the 43 males and 36 females was 43 years (yr) (range 18–68) and the median tumor size at diagnosis was 109 mm (range 10–250 mm). CR was achieved in 4 pts, PR in 25 pts, SD in 45 pts and PD in 5 pts. R0 surgery was possible in 82% of pts; histological necrosis (HN) after chemotherapy was >95% in 25 pts, between 50–95% in 28 pts and <50% in 25 pts (median HN was 70%). All pts but one received postoperative radiotherapy. Relapse occurred in 37 pts; local in 3, distant in 33 and both in 1. After a median follow-up of 48 months (9–118 months) 51 pts are alive. The 5 yr DFS and OS were 45% and 60% respectively. Multivariate analysis correlated median HN to a better EFS and a non grade 3 to a better OS. Regarding protein expression (54 pts analyzed), a higher protein expression of TopoII was correlated to a better EFS (p=0.032) by univariate analysis and to OS by multivariate analysis (p=0.025). ERCC1 protein expression was not related to EFS and/or OS. There is no correlation between over expression of both proteins and any percentage of HN. Conclusions: A high rate of HN (> 70%) after induction chemotherapy treatment is predictive for a better EFS. TopoII expression seems to be a relevant early predictive marker for outcome of pts with LASTS treated with doxorubicine-containing induction CT.

No significant financial relationships to disclose.

A multivariate analysis of a series of 382 primary retroperitoneal sarcomas (RPS)

10065

Background: A national retrospective study was conducted by the French Association of Surgery on primary RPS in order to define the best type of surgery and determine prognostic factors for abdominal recurrence and patient survival. There is still no consensus concerning the precise value of the extent of surgery and additional treatment modalities. Methods: Types of surgery were classified as: “systematic complete resection”, which is a systematic or partial resection of non-involved contiguous organs to achieve wide margins, “contiguously involved organ resection” and “simple complete resection”, a resection of the tumor with grossly negative margins. Survival was determined with the Kaplan-Meier method. Univariate and multivariate prognostic analyses were performed using logrank test and Cox model. Results: Data of 382 pts operated between 1985 and 2005 were retrospectively reviewed. Median age was 57 years (range 14–87). Median tumor size was 18 cm. Systematic complete resection, contiguously involved organ resection and simple complete resection were performed for 134 (35%), 153 (40%) and 87 (23%) pts, respectively. Eight pts (2%) had a biopsy without resection and 45 pts (12%) had macroscopic residual disease. Tumor was spilled during surgery for 76 pts (20%). Systematic complete resection and no spilling of the tumor were highly correlated with the number of pts operated by center (p-values <10-4). Histologic negative margins (136 pts, 36%) were highly correlated with systematic complete resection (p-value <10-4). Chemotherapy and radiotherapy were given to 135 (35%) and 122 pts (32%). Median survival was 6 years whereas median time to abdominal recurrence and metastasis were 4 and 15 years, respectively. On multivariate analysis, pre op biopsy, low grade, no spilling of the tumor, negative margins and number of pts operated by center were the significant factors predicting abdominal recurrence control whereas low grade, no spilling of the tumor and no macroscopic residual disease significantly predicted better overall survival. Conclusions: Tumor grade and quality of surgery were the two main prognostic factors for abdominal recurrence and overall survival. Surgical experience of these rare tumors and systematic complete resection decreased abdominal recurrence rate.

No significant financial relationships to disclose.

Phased-array grating compression for high-energy chirped pulse amplification lasers

The development of phased-array grating compressor is a crucial issue for high-energy, ultra-short pulse petawatt-class lasers. We present a theoretical and experimental analysis of two-grating phasing in a broadband pulse mosaic compressor. The phase defaults induced by misaligned gratings are studied. Monochromatic grating phasing is experimentally achieved with an interferometric technique and pulse compression is demonstrated with a two-phased-array grating system.

Re-irradiation combined with chemotherapy after salvage surgery in head and neck carcinoma: A randomized trial from the GETTEC and GORTEC groups

5508

Background: Full dose re-irradiation combined with chemotherapy has been shown to be feasible after salvage surgery with an “acceptable” toxicity (Cancer 2001; 91:2071–6). We performed a prospective, multicentric, randomized study to assess its carcinologic value. Methods: Between 1999 and 2005, 130 head and neck cancer patients were treated with salvage surgery and then randomly assigned either to full dose re-irradiation combined with chemotherapy (arm A) or absence of post-operative treatment (arm B). Patients eligibility criteria were: recurrence or second primary in a previously irradiated area to at least 45 Gy, absence of distant metastasis, salvage surgery with macroscopic complete resection; possibility of starting adjuvant treatment within 6 weeks after salvage surgery. Patients in arm A received 60 Gy in 12 weeks combined with concomitant 5FU, Hydroxyurea, as previously described (Ann Oncol 1996;7:913–8). Cox model was adjusted with stratification factors: tumor site, center, type of event (recurrence vs second primary). Results: 65 patients were randomized in each arm, including 71% of local and/or regional relapse and 29% of second primary. There was no imbalance in the distribution of age, sex, tumor site, T and N re-staging, and histological gravity signs (N+ with ECE and/or positive margin). The most important acute toxicity related to re-irradiation and chemotherapy was mucositis with ≥ grade 3 in 29% of patients. A moderate and acceptable increase in ≥ grade 3 RTOG late toxicity was observed in arm A (trismus, mucosa, fibrosis). Progression-free survival was significantly improved in Arm A with a hazard ratio of 1.6 (CI 95%, 1.1–2.4, p = 0.01), but overall survival was not statistically different. Conclusions: This is the first randomized trial to evaluate the effect of full dose re-irradiation combined with chemotherapy after salvage surgery. The results showed that re-irradiation and chemotherapy were able to significantly improve progression-free survival, with no significant impact on survival and acceptable toxicity. Supported by ARC.

No significant financial relationships to disclose.

Expression of erythropoietin and its receptor in neuroblastomas

9054

Background: Children with neuroblastomas (NB) may potentially benefit from treatment with recombinant human erythropoietin (Epo). Epo is a specific stimulator of erythropoiesis, acting via its specific receptor (EpoR). The aim of this study was to evaluate the expression of Epo and EpoR in NB and in normal tissues and their action in the proliferation of tumor cells. Methods: A tissue microarrays study was performed on 101 patients with NB from 3 hospitals (16 stage I; 7, II; 22, III; 48, IV and 8, IVS). Four blocks were constructed and contained 101 primary tumors, 39 paired metastases (35 lymph nodes), 56 paired control normal tissues and 6 cell lines of NB. Immunohistochemical staining was performed on sections using antibodies against Epo and EpoR. Immunostaining intensity was evaluated by a semi-quantitative score based on the percentage of positive cells. The wilcoxon signed rank test was applied for the comparison of paired data. For overall survival analysis, the expression was dichotomized at the median value and cox regression models were used stratified by hospital. An in vitro study of cell proliferation in presence of recombinant Epo was carried out with two of the 6 cell lines, one expressing EpoR, the other not. Results: Median follow-up was 64 months. The expression of EpoR was significantly higher in tumors than in paired control tissues (p<0.0001) but not for Epo (p=0.06). When restricted to the lymph nodes metastases, the level of expression of EpoR was significantly more expressed in the metastases than in primary tumors (p=0.02), contrary to Epo (p=0.99). Survival analysis showed that patients who expressed more EpoR had a statistically significant better overall survival than those who did not (p=0.03). Furthermore, the expression of EpoR was an independent prognostic factor from induction chemotherapy, tumor stage and age (p=0.02). No significant differences were found in Epo analyses. EpoR was expressed in only three cell lines and Epo not in any of them. In the in vitro study, recombinant Epo did not modify the proliferation of both cell lines. Conclusions: Epo and EpoR were expressed in NB but did not modify cells proliferation. The use of Epo in children with NB could be proposed but its benefit should be confirmed in a clinical trials.

No significant financial relationships to disclose.

Efficient restricted gene expression in beta cells by lentivirus-mediated gene transfer into pancreatic stem/progenitor cells

AIMS/HYPOTHESIS

Gene transfer into pancreatic beta cells, which produce and secrete insulin, is a promising strategy to protect such cells against autoimmune destruction and also to generate beta cells in mass, thereby providing a novel therapeutic approach to treat diabetic patients. Until recently, exogenous DNA has been directly transferred into mature beta cells with various levels of success. We investigated whether exogenous DNA could be stably transferred into pancreatic stem/progenitor cells, which would subsequently differentiate into mature beta cells expressing the transgene.

METHODS

We designed transplantation and tissue culture procedures to obtain ex vivo models of pancreatic development. We next constructed recombinant lentiviruses expressing enhanced green fluorescent protein (eGFP) under the control of either the rat insulin promoter or a ubiquitous promoter, and performed viral infection of rat embryonic pancreatic tissue.

RESULTS

Embryonic pancreas infected with recombinant lentiviruses resulted in endocrine cell differentiation and restricted cell type expression of the transgene according to the specificity of the promoter used in the viral construct. We next demonstrated that the efficiency of infection could be further improved upon infection of embryonic pancreatic epithelia, followed by their in vitro culture, using conditions that favour endocrine cell differentiation. Under these conditions, endocrine stem/progenitor cells expressing neurogenin 3 are efficiently transduced by recombinant lentiviral vectors. Moreover, when eGFP was placed under the control of the insulin promoter, 70.4% of the developed beta cells were eGFP-expressing cells. All of the eGFP-positive cells were insulin-producing cells.

CONCLUSIONS/INTERPRETATION

We have demonstrated that mature rat pancreatic beta cells can be stably modified by infecting pancreatic stem/progenitor cells that undergo endocrine differentiation.

Interactions between verapamil and neutral and acidic liposomes: effects of the ionic strength

Patients with cancer often develop major electrolyte disorders, which are aggravated by radiation therapy and chemotherapy and by the concomitant impairment of the renal function and the development of drug resistance. In addition, tumour cells have membranes with more negative charges than normal eukaryotic cells. This study was designed to test the hypothesis that the ability of the Ca(2+) blocker verapamil to mediate the reversal of multidrug resistance (MDR) by interacting with the membrane phospholipids may be correlated with the ionic strength and membrane surface potential in resistant tumours. The permeation properties of verapamil, which is the best-known MDR-modulator, were therefore studied by quantifying its ability to induce the leakage of carboxyfluorescein through unilamellar liposomes containing various mole fractions of phosphatidic acid (x(EPA)=0, 0.1 and 0.3), at four different ionic strengths (I=0.052, 0.124, 0.204 and 0.318 M). The dye leakage induced by verapamil varied greatly with I, depending on x(EPA). The permeation process was a co-operative one (1.3<Hill coefficient<3.5) and the permeation doses inducing 50% dye leakage (PD(50)) ranged between 0.2 and 1.8 mM. A highly significant multiple correlation was found to exist between the variations of log(1/PD(50)) with those of 1/ radical I and x(EPA) (dlog(1/PD(50))/d(1/ radical I)=0.15+/-0.01, dlog(1/PD(50))/dx(EPA)=2.07+/-0.08, y-intercept=2.46+/-0.03, P<0.000001). Kinetic studies on the permeation process showed that it involved two steps. The apparent rate constants of the slow and fast kinetic steps, which were driven by electrostatic and hydrophobic interactions, respectively, increased with the verapamil concentrations, depending on x(EPA). The results provide evidence that in resistant tumours (high negative membrane surface potential), the MDR reversal by verapamil might be enhanced by favourable drug-membrane interactions in patients with severe hypo-electrolytic (Na(+) and K(+)) disorders, whereas the MDR reversal might be reduced by unfavourable drug-membrane interactions in patients with severe hyper-electrolytic (Ca(2+), Na(+) and K(+)) disorders.

Blood glucose normalization upon transplantation of human embryonic pancreas into beta-cell-deficient SCID mice

AIMS/HYPOTHESIS

Transplanting human pancreatic islet beta cells could represent a radical new treatment of Type I (insulin-dependent) diabetes mellitus. However, beta cells available for grafting are scarce and finding new sources of such cells would be crucial for any cell therapy for diabetes. Undifferentiated precursor cells present in the human embryonic pancreas could represent such a source.

METHODS

We grafted human embryonic pancreases (6-9 weeks of development) that contain very few beta cells onto NOD/scid mice.

RESULTS

The human pancreatic tissue grew, increasing in weight 200 times within six months and endocrine cells differentiated, the number of human beta cells being increased by a factor 5000. Finally, the developed human endocrine tissue was mature enough to control the glycaemia of mice deficient in endogenous beta cells.

CONCLUSION/INTERPRETATION

Human embryonic pancreas represent a source of immature cells that can proliferate and differentiate into mass beta cells after transplantation. Transplantation of human embryonic pancreas into NOD/scid mice is a useful model for understanding the development of the human pancreas during prenatal life.

Designing multidrug-resistance modulators circumventing the reverse pH gradient in tumours

Multidrug-resistant tumours often exhibit a reverse pH gradient (acid outside), as they have an acid extracellular pH (pHe) and a neutral alkaline intracellular pH (pHi). This study was designed to test the hypothesis that the ability of lipophilic drugs to mediate multidrug resistance (MDR) reversal by interacting with the membrane phospholipids may be correlated with pH in resistant tumours. The permeation properties of five MDR modulators were therefore studied at 37 degrees C by quantifying their ability to induce the leakage of Sulfan blue through unilamellar anionic liposomes, over the range pH 6.5-7.7, and in the absence of any membrane potential (pHe = pHi). The dye leakage induced by two calcium blockers (diltiazem and verapamil) and two antiparasitic agents (thioacridine derivative and mepacrine) was found to significantly increase with the pH of the medium (P < 0.001), whereas that induced by a non-ionic detergent (Triton X-100) showed almost no pH-dependent variations. This process was a cooperative one (0.8 < Hill coefficient < 8.5) and the permeation doses inducing 50% dye leakage (PD50) ranged from 1.6 to 36.0 mM. The permeation ability of the MDR modulators (log(1/PD50)) significantly increased with their octanol-buffer distributions (logD) (slope = 0.35+/-0.06; y intercept = 1.65 +/- 0.14; P < 0.0001) and significantly decreased with their net electric charge (z) (slope = -0.48+/-0.07; y intercept = 2.85+/-0.08; P < 0.0001). A highly significant multiple correlation was found to exist between the variations of log(1/PD50) with those of logD and z (dlog(1/PD50)/dlogD = 0.21 +/- 0.05; dlog(1/PD50)/dz = -0.34+/-0.07; y intercept = 2.27+/-0.17; P < 0.000001). The results provide evidence that in resistant tumours (acid pHe and neutral alkaline pHi), the MDR reversal might be enhanced by favourable drug-membrane interactions if the modulators are designed in the form of highly lipophilic (logP approximately equals 4) mono-basic drugs with a near neutral pKa (pKa approximately equals 7-8).

Thermal dependence of multidrug-resistant-modulator efficiency: a study in anionic liposomes

This study was designed to test the hypothesis that there exists a correlation between the ability of lipophilic drugs to mediate the reversal of multidrug-resistance (MDR) by interacting with the membrane phospholipids and the metabolic level in tissues. The permeation properties of five MDR-modulators were studied by quantifying their ability to induce the leakage of Sulphan blue through unilamellar liposomes, over the temperature range 27-42 degrees C. The dye leakage induced by a non-ionic detergent (Triton X-100), two calcium blockers (diltiazem and verapamil) and two antiparasitic agents (thioacridine derivative and mepacrine) was temperature-dependent. The permeation process was a co-operative one (1.1 < Hill coefficient < 7.5) and the permeation doses inducing 50% dye leakage (PD50) were 1.5 - 14.9 mM. The permeation ability of the MDR-modulators (log(1/PD50)) decreased significantly as the net electric charge (z) increased. The passive dye leakage (deltaG < 0) was found to be an endothermic process (deltaH > 0), favoured by an increase in the membrane disorder (deltaS > 0). The apparent enthalpy factor (deltaH50) associated with 50% dye leakage increased with the net electric charge of the compound, and this energetically non-favoured event was entirely offset by the concomitant increase in the entropy factor (deltaS50). The apparent permeation enthalpy (deltaH50) and entropy (deltaS50) showed the lowest values for Triton X-100 (deltaH50 = 7.1 +/- 0.53 kJ mol(-1), deltaS50 = 76.9 +/- 1.86 Jmol(-1) K(-1)), and the highest values for mepacrine (deltaH50 = 79.5 +/- 3.80 kJmol(-1), deltaS50 = 306.7 +/- 5-97 J mol(-1) K(-1)). When the temperature was increased from 27 to 42 degrees C, the apparent Gibbs free energy (deltaG50) of the dye leakage induced by Triton X-100 decreased by less than 10% of the initial value, and that induced by mepacrine decreased by nearly 40%. The results provide evidence that in tissues with high metabolic levels and therefore high temperatures, MDR-reversal is likely to be enhanced via favourable drug-membrane interactions controlled by the electric charge of the modulators.

Membrane permeation by multidrug-resistance-modulators and non-modulators: effects of hydrophobicity and electric charge

This study was designed to test the hypothesis that lipophilic cationic drugs with only roughly similar structures mediate the reversal of multidrug-resistance (MDR) by interacting with membrane phospholipids. The permeation properties of MDR-modulators and non-modulators were studied by quantifying their ability to induce the leakage of Sulphan blue through the membrane of negatively charged unilamellar liposomes. Of the 22 compounds under investigation, only those bearing a net positive electric charge per molecule (z) > or = 0.2 induced dye leakage. All these efficient drugs are well-known MDR-modulators: calcium-channel blockers (propranolol, verapamil, diltiazem and dipyridamole), calmodulin antagonists (clomipramine and thioridazine) and antiparasitic agents (mepacrine, thioacridine derivatives and quinine). The non-modulators tested, including antineoplastic agents and steroids, did not induce any membrane permeation. The permeation process was a co-operative one (1.1 < Hill coefficient < 4.1) and the permeation doses inducing 50% dye leakage (PD50) were 1.9-11.2 mM. The permeation ability of the MDR-modulators (log(1/PD50)) increased significantly with octanol-buffer distributions per unit net electric charge ((logD)/z). The results provide evidence that a complex interplay occurs between the electric charge and the lipophilicity of the MDR-modulators when a dye leakage is induced through model membranes, and probably also when the MDR is reversed in leukaemic cells.

Potassium transport in opossum kidney cells: effects of Na-selective and K-selective ionizable cryptands, and of valinomycin, FCCP and nystatin

The effects of two ionizable cryptands, the Na-selective (221)C10 and the K-selective (222)C10, and of valinomycin, FCCP and nystatin on K+ fluxes in opossum kidney (OK) cells have been quantified. The Na,K-ATPase (ouabain-sensitive 86Rb influx) was stimulated by nystatin (> or = 20%), and inhibited by the other ionophores (50-80%), by barium (K-channel blocker) (61%) and by amiloride (Na entry blocker) (34%). The Vmax of the Na,K-ATPase phosphatase activity was unmodified by the ionophores, indicating the absence of direct interaction with the enzyme. The ATPi content was unmodified by the inhibitors and nystatin, but was lowered by (221)C10 (47%), (222)C10 (75%), valinomycin (72%) and FCCP (88%). Amiloride was found to partially remove the inhibition caused by (222)C10 (51%) and valinomycin (49%). Rb efflux was stimulated by nystatin (32%), unmodified by valinomycin, and was inhibited by (221)C10 (19%), (222)C10 (19%) and FCCP (10%). Barium (39%) and amiloride (32%) inhibited this efflux and, in their presence, the nystatin effect persisted, whereas that of the other ionophores vanished. At pH 6.4, the Rb efflux decreased by 14% of its value at pH 7.4, with no additional inhibition by cryptands. Cryptands are shown to inhibit the pH-sensitive K+-conductance, probably by inducing a K+-H+ exchange at the plasma membrane, and by uncoupling oxidative phosphorylation by inducing the entry of K+ and H+ (and possibly Ca2+) ions into the mitochondria.

Transport of competing Na and K ions by (222) C10-cryptand, an ionizable mobile carrier: effects of pH and temperature

The kinetics of the electroneutral exchange of competing sodium and potassium with protons across the membrane of large unilamellar vesicles (LUV) were determined at two pH values when transport was induced by the simultaneous presence of (222)C10-cryptand and FCCP (proton carrier) at various temperatures. The aim of the present work was to quantify the pH-dependent enthalpies of an ionizable mobile carrier affinities for competing alkali cations, and to focus on the effects of pH and temperature on the competitive transport selectivity of the carrier for K+ over Na+ ions. At any given temperature and pH, the apparent pH-dependent affinity of (222)C10 was higher for K+ than for Na+. The enthalpy of this affinity for K+ was significantly lower than that for Na+, whereas it varied similarly with the pH (delta H(KpHmK) = 32.8 and 37.0 kJ/mol, and delta H(KpHmNa) = 47.9 and 52.9 kJ/mol at pH 7.8 and 8.8, respectively). When using a kinetic model, the pH effect on these parameters was discriminated (delta H(KmK) = 37.9 kJ/mol and delta H(KmNa) = 53.9 kJ/mol). The pH-dependence of the delta H(KpHm) of the cations could therefore theoretically be shown to arise from the temperature-induced changes in the ionization of the buffer dissolved in the aqueous phases and of the amine groups of the binding cavity of the carrier. The K/Na competitive transport selectivity (Sc(K/Na)) of (222)C10 increased linearly with the K+ concentration. It decreased hyperbolically with increasing concentration of Na+ while being independent of pH at any given temperature. In equimolecular ionic mixtures, Sc(K/Na) varied from 2.2 to 3.0 when temperature rose from 20 degrees C to 35 degrees C (delta H(Sc(K/Na)) = 15.6 +/- 0.5 kJ/mol). The results are discussed in terms of the structural, physico-chemical and electrical characteristics of carriers and complexes.

Na/K competitive transport selectivity of (221)C10-cryptand: effects of pH and carrier concentration

The kinetics of the competitive transport of Na+ and K+ ions across the membrane of large unilamellar vesicles (LUV) were determined when transport was induced by (221)C10-cryptand, an ionizable mobile carrier. The experiments were performed at various pH values (7.7 and 8.7) and carrier concentrations (0.1, 0.5 and 1.0 microM) in order to quantify the effects of these parameters on the Na/K competitive transport selectivity of this mobile carrier. At any given pH and carrier concentration, the apparent affinity of (221)C10 for Na+ was higher and less dependent on the concentration of the other competing ion than that for K+. The Na/K competitive transport selectivity (SC(Na/K)) of (221)C10 increased linearly with the Na+ concentrations, decreased hyperbolically with increasing those of K+ and was independent of the pH and of the carrier concentration. In equimolecular ionic mixtures, this competitive selectivity amounted to about 1.5 and when the pH rose, the carrier selectivity for Na+ over K+ ions was enhanced by cation competition compared to transport of cations as unique substrates. Equations were established to describe the variations of the competitive transport selectivity (SC) of cryptands, and for comparison of their noncompetitive selectivity (SNC), with the ionic concentrations, the Michaelis parameters of the cations and the pH. The reaction order in Na+ (n(Na)) increased significantly with decreasing the pH and the K+ concentration. The results are discussed in terms of the structural, physico-chemical and electrical characteristics of carriers and complexes.

Na/K competitive transport selectivity of (221) C10-cryptand: effect of temperature

The kinetics of the competitive transport of Na+ and K+ ions across the membrane of large unilamellar vesicles (LUV) were determined when transport was induced by (221)C10-cryptand at various temperatures in order to quantify the temperature-dependence of the Na/K competitive transport selectivity of this ionizable mobile carrier. At any given temperature, the apparent affinity of (221)C10 for Na+ was higher and less dependent on the concentration of the other competing ion than that for K+. Its enthalpy for Na+ (delta H(KmNa) = 50.6 kJ/mol) was not significantly different from that for K+ (delta H(KmK) = 52.7 kJ/mol). The Na/K competitive transport selectivity (SC(Na/K)) of (221)C10 increased linearly with the Na+ concentrations and decreased hyperbolically with increasing those of K+. When the cation concentrations were equal, this competitive selectivity amounted to about 2 at any given temperature. Equations were established to describe the variations of the competitive transport selectivity (SC) of cryptands, and for comparison of their noncompetitive selectivity (SNC), with the ionic concentrations and the Michaelis parameters of the cations. It is theoretically demonstrated that the ratio between the competitive and noncompetitive transport selectivities, i.e., SC/SNC, of mobile carriers does not depend on the Jmax of the competing ions and that its value amounts to 1 when the specific concentrations (C'S/Km) of the ions are equal. Under these conditions, the transport selectivity of any given mobile carrier has the same value whether determined from competition or separated experiments. The reaction order in Na+ (n(Na)) increased significantly as the temperature rose and decreased significantly as the K+ concentration increased. The results are discussed in terms of the structural, physicochemical and electrical characteristics of carriers and complexes.

Structural requirements for unsaturated fatty acids and fatty alcohols to induce optimal biological responses: an approach using model membranes

The permeation induced by unsaturated fatty acids and fatty alcohols through the membrane of dihexadecyl phosphate vesicles was quantified, using [Ru(bpy)3(2+)] ions as a permeant probe. In both the free fatty acid and the free fatty alcohol series, the permeation induced by the unsaturated isomers is higher than that of the corresponding saturated analogues. Moreover the permeant effect associated with free fatty acids or free fatty alcohols is under the control of structural and conformational parameters: carbon chain length, number and position of the double bonds, and the geometry Z or E of the double bond. Optimal membrane perturbing effects are observed for compounds having a carbon chain length ranging from 18 to 20 carbon atoms, incorporating two or four Z double bonds in the center of the carbon chain. Good correlation has been found between the membrane perturbing effect quantified as PD50 values and some of the biological properties associated with these fatty lipids. The PD50 values obtained for free fatty alcohols are in fair agreement with anesthetic properties reported by different authors, (Pringle et al., 1981) while PD50 values obtained for free fatty acids show a good correlation with their activity on the superoxide respiratory burst induced by chemotactic peptides. These preliminary results led to the conclusion that as far as a biological activity directly associated with unsaturated fatty acids or alcohols, involved a membrane barrier passage, the measure of their permeant properties using a DHP vesicle model appears to be an excellent criterion for the quantification of optimal biological effects.

Sodium transport by an ionizable and a neutral mobile carrier: effects of membrane structure on the apparent activation energy

Temperature-jump relaxation experiments on Na+ transport by (221)C10-cryptand (ionizable mobile carrier) and nonactin (neutral mobile carrier) were carried out in order to study the effects of cholesterol and the degree of acyl chain unsaturation, and their temperature-dependence on ion transport through thin lipid membranes. The experiments were performed on large, negatively charged unilamellar vesicles (LUV) prepared from mixtures of phosphatidylcholine (egg phosphatidylcholine, dioleoylphosphatidylcholine and dilinoleolylphosphatidylcholine), phosphatidic acid and cholesterol (mole fractions 0-0.43), at various temperatures and carrier concentrations. The apparent rate constants of Na+ translocation by (221)C10 and nonactin increased with the carrier concentration, the degree of acyl chain unsaturation and the temperature. The incorporation of cholesterol into the membranes significantly reduced the carrier concentration-, acyl chain unsaturation- and temperature-dependence of this parameter. The apparent energy required to activate the transport decreased significantly with increasing (221)C10 concentrations and remained constant with increasing those of nonactin at any given cholesterol molar fraction and degree of acyl chain unsaturation. It increased significantly with increasing the cholesterol molar fraction at any given carrier concentration to an extent depending on the degree of acyl chain unsaturation. Our interpretation of the action of cholesterol on these transport systems is based on the assumption that the adsorption plane of Na(+)-(221)C10 and Na(+)-nonactin complexes is likely to be located towards the aqueous and the hydrocarbon side of the dipole layer, respectively. The results are discussed in terms of the structural, physico-chemical and electrical characteristics of carriers and complexes, and of the interactions occurring between an ionizable or a neutral mobile carrier and the membrane.

Temperature-dependent effects of cholesterol on sodium transport through lipid membranes by an ionizable mobile carrier

Temperature-jump relaxation experiments on Na+ transport by (221)C10-cryptand were carried out in order to study the influence of cholesterol and its temperature-dependence on ion transport through thin lipid membranes. The experiments were performed on large, negatively charged unilamellar vesicles (LUV) prepared from mixtures of dioleoylphosphatidylcholine, phosphatidic acid and cholesterol (mole fractions 0-0.43), at various temperatures and carrier concentrations. The initial rates of Na+ transport and the apparent rate constants of its translocation by (221)C10 increased with the carrier concentration and the temperature. The incorporation of cholesterol into the membranes significantly reduced the carrier concentration- and temperature-dependence of these two parameters. The apparent energy required to activate the transport decreased significantly with increasing carrier concentrations at any given cholesterol molar fraction, and increased significantly with the cholesterol molar fraction at any given carrier concentration. Our interpretation of the action of cholesterol on this transport system is based on the assumption that the binding cavity of cryptands is likely to be located towards the aqueous side of the dipole layer. The results are discussed in terms of the structural, physico-chemical and electrical characteristics of carriers and complexes, and of the interactions occurring between an ionizable mobile carrier and the membrane.

Passive permeability of dihexadecylphosphate vesicles altered by aliphatic alcohols and omega-diols

Alcohols act as anaesthetics only up to a certain chain length, beyond which their biological activity disappears. Although the molecular nature of general target sites remains unknown, presently available data support the hypothesis that this 'cut-off' in anaesthetic activity could be due to a corresponding cut-off in the absorption of long-chain alcohols into lipid-bilayer portions of nerve membranes. To test this hypothesis, we developed a method based on leakage of Ru(bpy)3(2+) ions across the membrane of dihexadecylphosphate (DHP) vesicles induced by aliphatic alcohols (C1 to C18) and some of their omega-diol. The permeant effects of aliphatic linear alcohols expressed as PD50 values rise to a maximum for n-dodecanol (PD50 = 2 x 10(-3) M 1(-1]. Dodecanol was found to be the alcohol which presents the greatest anaesthetic potency among the series of linear aliphatic alcohols (cut-off anaesthetic effect). The results are discussed in terms of the structural physicochemical and geometrical characteristics of the permeating alcohols.

Temperature-jump method for studying the fast transport of Na+ by (221) C10-cryptand across lipid membranes

The kinetics of Na+ transport by (221)C10-cryptand through thin lipid membranes were determined by performing temperature-jump relaxation experiments on large unilamellar vesicles (L.U.V.) loaded with a fluorescent pH indicator. Applying temperature jumps of 4 to 7 degrees C to liposomes having phosphate as internal buffer and Tris as external buffer resulted in transmembrane delta pH's of about 0.104 to 0.182. After a temperature-jump, a decay in the delta pH was observed which corresponded to a Na+/H+ exchange occurring through membranes in the simultaneous presence of the cryptand and a proton carrier. The transport of Na+ ions by (221)C10 was found to be a fast kinetic process. Its initial rate increased with both the temperature and the cryptand concentrations. In addition, the temperature-induced changes in the apparent rate constants of the translocation of Na+ by (221)C10 were carrier concentration-dependent, and the apparent activation energy required to activate the transport decreased significantly with increasing cryptand concentrations. The results are discussed in terms of the structural, physico-chemical and electrical characteristics of carriers and complexes.

Permeability of cryptands through dihexadecyl phosphate bilayer membranes

The leakage of Ru(bpy)3(2+) across a membrane of dihexadecyl phosphate (DHP) vesicles was compared when induced by (2.1.1), (2.2.1), (2.2.2.), (2.2.1.)C10 and (2.2.2.)C10-cryptands, and by (2.2.) and (2.2.)-bishydroxyethyl, i.e., ionizable macrobicyclic and monocyclic amino polyethers. Ru(bpy)3(2+) leakage increased as the permeant concentrations rose and was much higher for the very lipophilic cryptands. It also increased as the pH fell, and was lower and less dependent on the permeant concentration when induced by addition of partially titrated than by non-pretitrated cryptand. The efficiency of the permeant decreased as the alkali cation concentration rose and was independent of the cation type. It also varied with the membrane type: the efficiency of the (2.2.2.)C10-cryptand was higher on permeation of the membrane of DHP vesicles made from dihexadecyl phosphate than that of large unilamellar vesicles (LUV) composed of alpha-phosphatidylcholine, alpha-phosphatidic acid and cholesterol in an 8:1:1 molar ratio. The results are discussed in terms of the structural, physico-chemical and electrical characteristics of the permeating agents and of the membranes.

Synthesis and biological activity of a new squaric acid-formylmethionine peptide conjugate

A new squaric acid-formylmethionine peptide has been synthesized. In view of its biological properties to induce lysosome release and to inhibit glyoxalase, this compound may be of pharmacologic value.

Inhibition of yeast glyoxalase I by biologically active peptides

The antiglyoxylase activity of biologically active peptides f-Met-Leu-Phe-OCH3 and Boc-Phe-Leu-Phe-OCH3 has been evaluated and compared with those of standard inhibitors s-octylglutathione and squaric acid. The inhibitory properties of these peptides are discussed in terms of biological and pharmacological aspects.

Inhibition of glyoxalase I by new squaric acid derivatives

Synthesis and antiglyoxalase activity of new squaric acid derivatives have been studied. It has been established that the substitution of one hydroxyl group of the squaric acid (1,2-dihydroxy cyclobutene 3,4-dione) by an N-substituted group decreased the antiglyoxalase activity while the corresponding - 2 methoxy substituted derivatives were comparatively equipotent.

A comparative study of the permeation of dihexadecyl phosphate vesicles by various carboxylic acids and some of their tetrazole analogues

The evaluation of the effect that perturbers may have on a membrane model is described. The model was made from dihexadecyl phosphate bilayers. The perturbers used were carboxylic acids and some of their tetrazole analogues. The results show a good correlation between the permeation properties of the carboxylic acids and tetrazole analogues. Moreover, this study reveals that membrane-perturbing effects are mainly under the control of conformational parameters and dependent on the carbon chain length of the permeants.

Efficiency, Na+/K+ selectivity and temperature dependence of ion transport through lipid membranes by (221)C10-cryptand, an ionizable mobile carrier

The kinetics of Na+ and K+ transport across the membrane of large unilamellar vesicles (LUV) were determined at two pH's when transport was induced by (221)C10-cryptand (diaza-1,10-decyl-5-pentaoxa-4,7,13,16,21-bicyclo [8.8.5.] tricosane) at various temperatures, and by nonactin at 25 degrees C and (222)C10-cryptand at 20 and 25 degrees C. The rate of Na+ and K+ transport by (221)C10 saturated with the cation and carrier concentrations. Transport was noncooperative and exhibited selectivity for Na+ with respect to K+. The apparent affinity of (221)C10 for Na+ was higher and less pH-dependent than that for K+, and seven times higher than the affinity for Na+ of nonactin. Its enthalpy was higher than that of (222)C10 for K+ ions (20.5 vs. 1.7 kcal . mole-1). The efficiency of (221)C10 transport of Na+ was pH- and carrier concentration-dependent, and was similar to that of nonactin; its activation energy was similar to that for (222)C10 transport of K+ (35.5 and 29.7 kcal . mole-1, respectively). The reaction orders in cation n(S) and in carrier m(M), respectively, increased and decreased as the temperature rose, and were both independent of carrier or cation concentrations; in most cases, they varied slightly with the pH. n(S) varied with the cation at pH 8.7 and with the carrier for Na+ transport only, while m(M) always depended on the type of cation and carrier. Results are discussed in terms of the structural, physico-chemical and electrical characteristics of carriers and complexes.

Transport of alkali cations through thin lipid membranes by (222)C10-cryptand, an ionizable mobile carrier

The kinetics of K+ and Na+ transport across the membrane of large unilamellar vesicles (L.U.V.) were compared at two pH's, with two carriers: (222)C10-cryptand (diaza-1,10-decyl-5-hexaoxa-4,7,13,16,21,24-bicyclo[8.8.8.]+ ++hexacosane) and valinomcyin, i.e. an ionizable macrobicyclic amino polyether and a neutral macrocyclic antibiotic. The rate of cation transport by (222)C10 saturated as cation and carrier concentrations rose. The apparent affinity of (222)C10 for K+ was higher and less pH dependent than that for Na+ but resembled the affinity of valinomycin for K+. The efficiency of (222)C10 transport of K+ decreased as the pH fell and the carrier concentration rose, and was about ten times lower than that of valinomycin. Noncompetitive K+/Na+ transport selectivity of (222)C10 decreased as pH, and cation and carrier concentrations rose, and was lower than that of valinomycin. Transport of alkali cations by (222)C10 and valinomycin was noncooperative. Reaction orders in cation n(S) and carrier m(M) varied with the type of cation and carrier and were almost independent of pH; n(S) and m(M) were not respectively dependent on carrier or cation concentrations. The apparent estimated constants for cation translocation by (222)C10 were higher in the presence of Na+ than of K+ due to higher carrier saturation by K+, and decreased as pH and carrier concentration increased. Equilibrium potential was independent of the nature of carrier and transported cation. Results are discussed in terms of the structural, physiocochemical and electrical characteristics of carriers and complexes.

Cation permeability induced by two 15-O5 macrocyclic polyether carriers in phospholipidic large unilamellar vesicles

Sodium permeability in phospholipidic large unilamellar vesicles induced by two 15-O5 macrocyclic polyether derivatives, a carboxylic one 1a and a neutral one 1b, has been studied. The neutral derivative, 1b, appears to behave as a classical mobile carrier such as valinomycin and the carboxylic carrier, 1a, as an ionophore of the nigericin group.

Tissue acid-base balance and oxygen metabolism in human cerebral infarction studied with positron emission tomography

Nine patients who had suffered strokes were examined between 10 and 34 days after onset using positron emission tomography. DMO labeled with carbon 11 was used to evaluate brain acid-base balance, and the oxygen-15 inhalation technique was used to measure regional cerebral blood flow, the oxygen extraction fraction, and cerebral metabolic rate for oxygen. [11C]DMO concentration and oxygen metabolism variables were measured in the infarcted area and in the symmetrical region in the contralateral cerebral hemisphere. [11C]DMO concentration was found to be unchanged or slightly increased in five cases and markedly increased in four cases. The apparent increase in tissue pH can be explained by the presence of a large extracellular fluid space with a pH nearly identical to that of brain plasma, or by an increase in intracellular pH, or by both phenomena. The change in [11C]DMO concentration in the infarcted area relative to that in the normal tissue was independent of the change in blood flow. Cerebral metabolic rate for oxygen was decreased in all cases. The increase in [11C]DMO concentration in the infarcted area was linearly correlated with the decrease in the oxygen extraction fraction in the same region; that is, it was correlated with the occurrence of perfusion in excess of metabolic demand. The overabundant local perfusion could play a role in the decreased H+ content.

[Relations between acid-base equilibrium and body temperature. Physiological concepts and practical applications]

In 1975 H. Rahn put forward a new concept of hydrogen ions regulation which explains acid-base regulation in relation to body temperature and applies to all animal species. At the root of this concept is the finding that maintenance of intracellular neutrality is governed by water dissociation and regulated by imidazole-rich protein buffers. The pH of the extracellular fluid, which receives acid by-products of cell activity, is kept higher than that of the intracellular fluid (relative alkalinity). The difference between extracellular pH and neutrality is constant for each species and ranges from 0.6 to 0.8 pH units. It is unaffected by changes in temperature, and the total CO2 content of extracellular fluid remains constant. The authors were able to confirm the value of this new concept in man by experimental studies of in vitro and in vivo blood of patients undergoing aorto-coronary bypass under controlled hypothermia. They draw the following practical conclusions: (1) in subjects under moderate or deep hypothermia for surgical purposes, the acid-base status can be controlled and the extracellular pH adjusted by ensuring intracellular neutrality; this is done by keeping PCO 2 at such a level that the arterial blood pH measured at 37 degrees C remains around 7.40; (2) the problem of correcting acid-base values (pH-PCO 2) according to body temperature is solved simply by using pH and PCO 2 values measured at 37 degrees C and interpreting them, as usual, in terms of metabolic or respiratory acidosis or alkalosis.

The apparent buffer value of human blood for CO2 as a function of temperature

The influence of temperature on the acid-base status of normal human deoxygenated whole blood was studied in open systems (variable total CO2 content). (1) When the temperature was raised from 26 degrees C to 42 degrees C, the apparent buffering value of deoxygenated whole blood for CO2 increased by 7% of its value at 26 degrees C; this increase was not statistically significant. (2) Comparing the present data with those obtained previously from oxygenated whole blood in the same temperature range (Castaing & Pocidalo, 1979) indicates that arterial and venous blood have slightly different buffering capacities for CO2 in the 26 to 42 degrees C temperature range. It also suggests that, at physiological SO2 levels (SO2 greater than or equal to 30%), the apparent buffering value of venous blood for CO2 would be increased by at least 10% of its value at 26 degrees C when the temperature is raised to 42 degrees C. (3) It is concluded that pH stability would be reduced upon CO2 uptake within tissues with a high metabolism and therefore a high temperature.

Effect of carbamination on the buffering power of purified human hemoglobin A solutions at two temperatures

The effect of CO2 on hemoglobin buffering power was studied in purified human hemoglobin A solutions, native and specifically carbamoylated on N-terminal valines, at 26 degrees C and 42 degrees C, in the oxy and deoxy states. Titrations were performed by varying Pco2 and by strong acid or base in the absence of CO2. The participation of N-terminal valines to the total buffering power was estimated by subtracting the buffering value measured on carbamoylated hemoglobin solutions from that measured on native hemoglobin solutions. In the absence of CO2 the buffering value of native and modified hemoglobin increased slightly (less than 10%) (a) on going from the deoxy to the oxy state, and (b) on raising the temperature from 26 degrees C to 42 degrees C. In the presence of CO2 the buffering value of Hb increased from 9.1 to 16.6 mol mol Hb4-1 pH-1 and that of HbO2 from 10.1 to 19.6 mol mol Hb4-1 pH-1 when the temperature was raised from 26 degrees C to 42 degrees C. These figures correspond to a rise in the fraction of the total buffering value attributable to N-terminal valines from 11% to 25% for Hb and from 3% to 33% for HbO2. The present results point to a non-specific effect of CO2 within the hemoglobin molecule independent of that of N-terminal valines. This effect nearly doubles the buffering value for CO2 when the temperature is raised, and contributes to pH regulation and CO2 removal in tissues with a high metabolic rate.

Temperature and oxygenation of human blood at constant total CO2 content

The influence of temperature on the oxygeneration of normal and 2,3-diphosphoglycerate-depleted human blood suspensions (final hemoglobin concentration: 0.75%) was studied under closed-system conditions (constant total CO2 content) beginning with standard values:pH 7.40, Pco2 40 torr, at 37 degrees C. The present results quantify the temperature-induced changes in Po2 occuring in association with the concomitant acid-base variations prevailing in a closed system. When the temperature was raised from 25 to 42 degrees C, P50 varied from 13.9 +/- 1.1 to 40.7 +/- 1.9 torr in the presence of 2,3-DPG and from 7.6 +/- 0.4 to 24.8 +/- 1.2 torr in the absence of the cofactor. The derived equations correlate Po2 variations with those of temperature (T: 25--42 degrees C) and oxygen saturation (So2:10--90%). The temperature coefficient of oxygenation and the DPG-induced decrease in the heat of hemoglobin oxygenation were shown to be saturation dependent. DPG lowered dlog Po2/dT from 0.0299 to 0.0275 and delta H from --12.9 to --11.8 kcal/mole O2 bound at 50% So2 but had no significant influence on these parameters for So2 less than or equal to 20%. The results suggest that the release of carbamate at the beginning of oxygenation is virtually unaffected by presence of 2,3-DPG in the 25--42 degree C temperature range.