Natural Rubber Composites Using Hydrothermally Carbonized Hardwood Waste Biomass as a Partial Reinforcing Filler-Part II: Mechanical, Thermal and Ageing (Chemical) Properties

Natural rubber composites were reinforced by the co-fillers 'hydrochar' (HC), obtained by hydrothermal carbonization of hardwood sawdust and commercial carbon black (CB). The content of the combined fillers was kept constant while their ratio was varied. The aim was to test the suitability of HC as a partial filler in natural rubber. Due to its larger particle size and hence smaller specific surface area, large amounts of HC reduced the crosslinking density in the composites. On the other hand, due to its unsaturated organic character, HC was found to display interesting chemical effects: if it was used as the exclusive filler component, it displayed a very strong anti-oxidizing effect, which greatly stabilized the rubber composite against oxidative crosslinking (and hence embrittlement). HC also affected the vulcanization kinetics in different ways, depending on the HC/CB ratio. Composites with HC/CB ratios 20/30 and 10/40 displayed interesting chemical stabilization in combination with fairly good mechanical properties. The performed analyses included vulcanization kinetics, tensile properties, determination of density of permanent and reversible crosslinking in dry and swollen states, chemical stability tests including TGA, thermo-oxidative aging tests in air at 180 °C, simulated weathering in real use conditions ('Florida test'), and thermo-mechanical analyses of degraded samples. Generally, the results indicate that HC could be a promising filler material due to its specific reactivity.

A Novel Approach for Simulation and Optimization of Rubber Vulcanization

The kinetic model, encompassing the curing and reversion phenomena of the NR/SBR rubber vulcanization process, was developed by means of the finite element method simultaneously with heat transfer equations, including heat generation due to curing reactions. The vulcanization simulation was conducted for three spheres of different diameters (1, 5 and 10 cm) and two rubber wheels, one of which was a commercial product of the rubber industry. The proposed advanced simulation model, based on products’ two-dimensional axisymmetry, includes cooling after vulcanization, during which the crosslinking reactions continue to take place as a result of the products’ heated interiors. As a criterion for removing the product from the mold, an average vulcanization degree of 0.9 was set, whereby, during cooling, the vulcanization degree increases, due to crosslinking reactions. Based on the minimal difference between the maximal and minimal vulcanization degrees, which did not exceed a value of 0.0142, the optimal process parameters for each product were determined, achieving homogeneity and obtaining high-quality rubber products, while simultaneously ensuring a more efficient vulcanization process and enhanced cost effectiveness for the rubber industry.

Kinetics of Microwave-Assisted Extraction Process Applied on Recovery of Peppermint Polyphenols: Experiments and Modeling

The aim of this work was to investigate the microwave-assisted extraction (MAE) kinetics of polyphenolic compounds from organic peppermint leaves. The phytochemicals of peppermint (Mentha piperita L.) are increasingly used in food technology due to their numerous biological activities. The processing of various plant materials by MAE and the production of high-quality extracts is becoming increasingly important. Therefore, the influence of microwave irradiation power (90, 180, 360, 600, and 800 W) on total extraction yield (Y), total polyphenols yield (TP), and flavonoid yield (TF) were investigated. Common empirical models (first-order, Peleg's hyperbolic, Elovich's logarithmic, and power-law model) were applied to the extraction process. The first-order kinetics model provided the best agreement with the experimental results in terms of statistical parameters (SS_er, R², and AARD). Therefore, the influences of irradiation power on the adjustable model parameters (k and C_eq) were investigated. It was found that irradiation power exerted a significant influence on k, while its influence on the asymptotic value of the response was negligible. The highest experimentally determined k (2.28 min^-1) was obtained at an irradiation power of 600 W, while the optimal irradiation power determined by the maximum fitting curve determination predicted the highest k (2.36 min^-1) at 665 W.

Natural Rubber Composites Using Hydrothermally Carbonized Hardwood Waste Biomass as a Partial Reinforcing Filler- Part I: Structure, Morphology, and Rheological Effects during Vulcanization

A new generation biomass-based filler for natural rubber, 'hydrochar' (HC), was obtained by hydrothermal carbonization of hardwood waste (sawdust). It was intended as a potential partial replacement for the traditional carbon black (CB) filler. The HC particles were found (TEM) to be much larger (and less regular) than CB: 0.5-3 µm vs. 30-60 nm, but the specific surface areas were relatively close to each other (HC: 21.4 m²/g vs. CB: 77.8 m²/g), indicating a considerable porosity of HC. The carbon content of HC was 71%, up from 46% in sawdust feed. FTIR and ¹³C-NMR analyses indicated that HC preserved its organic character, but it strongly differs from both lignin and cellulose. Experimental rubber nanocomposites were prepared, in which the content of the combined fillers was set at 50 phr (31 wt.%), while the HC/CB ratios were varied between 40/10 and 0/50. Morphology investigations proved a fairly even distribution of HC and CB, as well as the disappearance of bubbles after vulcanization. Vulcanization rheology tests demonstrated that the HC filler does not hinder the process, but it significantly influences vulcanization chemistry, canceling scorch time on one hand and slowing down the reaction on the other. Generally, the results suggest that rubber composites in which 10-20 phr of CB are replaced by HC might be promising materials. The use of HC in the rubber industry would represent a high-tonnage application for hardwood waste.

Extraction of Peppermint Essential Oils and Lipophilic Compounds: Assessment of Process Kinetics and Environmental Impacts with Multiple Techniques

Consumers are becoming more mindful of their well-being. Increasing awareness of the many beneficial properties of peppermint essential oil (EO) has significantly increased product sales in recent years. Hydrodistillation (HD), a proven conventional method, and a possible alternative in the form of microwave-assisted hydrodistillation (MWHD) have been used to isolate peppermint EO. Standard Soxhlet and alternatively supercritical fluid (SFE), microwave-assisted, and ultrasound-assisted extraction separated the lipid extracts. The distillations employed various power settings, and the EO yield varied from 0.15 to 0.80%. The estimated environmental impact in terms of electricity consumption and CO₂ emissions suggested that MWHD is an energy efficient way to reduce CO₂ emissions. Different extraction methods and solvent properties affected the lipid extract yield, which ranged from 2.55 to 5.36%. According to the corresponding values of statistical parameters, empiric mathematical models were successfully applied to model the kinetics of MWHD and SFE processes.

Modelling and efficiency evaluation of the continuous biosorption of Cu(II) and Cr(VI) from water by agricultural waste materials

As a result of intensive anthropogenic activities, population growth and unplanned urbanization, enormous quantities of organic and inorganic pollutants are discharged into the environment every year. The primary hazardous substances of concern regarding their environmental load and health effects are heavy metals. Heavy metal pollution of aquatic ecosystems, including resources of drinking water and water intended for food processing, has been of increasing interest. Biosorption technology is a promising strategy, as it utilizes industrial or agricultural wastes to remove metals from aqueous media passively, and they represent efficient, cost-effective and environmentally friendly alternatives to traditional adsorbents such as activated carbon. In this paper, the efficiency of biosorption of copper and chromium ions was examined using different agricultural waste biomass - sugar beet shreds, poplar sawdust and wheat straw. The possibility of applying a parallel sigmoidal (PS) model to describe the biosorption process was investigated to confirm its applicability to different types of biomass and various kinds of heavy metal ions. The results showed that the biosorption of copper ions using poplar sawdust and wheat straw consist of two steps. The moiety of one step in the overall process, defined by the parameter p, was determined to be 0.85 for poplar sawdust and 0.86 for wheat straw. These values, being less than 1, clearly indicate that the process consists of two simultaneous, kinetically different steps that shift in their dominance over the process and thus could be successfully modelled by the PS model. These studies also deal with the phenomenological examination of an unusual breakthrough curve obtained for the chromium ions biosorption by sugar beet shreds, by the comparative view of the process flow and changing the pH of the effluent. The clarification of the appearance of a double curve with a negative trend in one part allows adjusting the biosorption conditions to avoid the initial blockage of chromium ion binding to the adsorbent and thus increase the adsorption process efficiency.

The novel modeling approach for the study of thermal degradation of PMMA/nanooxide systems

PMMA (poly(methyl methacrylate)) nanocomposites differing in their nature, size, and surface area were prepared containing one volume percent of silica, alumina or titania. These samples and pure PMMA were prepared in order to analyze how the presence of nanooxides affects the thermal stability and degradation kinetics of the materials. A detailed study of thermal degradation and thermal changes was performed by Simultaneous Thermogravimetry and Differential Scanning Calorimetry (SDT). The proposed mathematical model, including all three heating rates in one minimizing function, well fitted all TGA data obtained with a very high coefficient of correlation. This enabled an assessment of four decomposition steps of the PMMA samples and a calculation of their activation energies and individual contributions to total mass loss. The addition of the largest nanoparticles (titania) caused the highest activation energy for each DTG stage of the PMMA/nanooxide systems. The enhancement of head-to-head H–H bonding strength was achieved by addition of alumina and titania. The influence of the size and nature of nanoparticles on the glass transition temperature of prepared PMMA systems was also determined.

A new approach for modelling and optimization of Cu(II) biosorption from aqueous solutions using sugar beet shreds in a fixed-bed column

The potential use of sugar beet shreds for copper ions removal from aqueous solution in a fixed-bed column was investigated. Experiments were performed using Box-Behnken experimental design on three levels and three variables: concentration of the inlet solution (50-150 mg L^-1), adsorbent dosage (8-12 g) and pH of the inlet solution (4.0-5.0). The obtained breakthrough curves were fitted with two common empirical models, Bohart-Adams and dose-response. Observing the asymmetric shape of the breakthrough curves, the new mathematical model was proposed. The new model proposes the breakthrough curve composed of two parts, sum of which gives the asymmetrical S-shaped curve, accurately matching experimental data. Regarding the lowest SSer (7.8·10^-4) and highest R² (0.9998), new model exhibited the best fit comparing to the commonly used models. RSM and ANN modelling were employed for process variables evaluation and optimization. The most influential parameter exhibiting negative influence on target response (critical time) was concentration of the inlet solution, while the adsorbent dosage exhibited positive influence. Optimization procedure revealed that the highest critical time (341.4 min) was achieved at following conditions: C₀ = 50 mg·L^-1, m_a = 12 g and pH 4.53 by ANN, while RSM considered pH as insignificant factor and obtained 314.8 min as the highest response.

The influence of bentonite and montmorillonite addition on thermal decomposition of novel polyurethane/organoclay nanocomposites

Polycarbonate-based polyurethane (PC-PUs) hybrid materials were obtained by the addition oforganically modified bentonite and montmorillonite (1 w/w %). PC-PUs and their nanocomposites wereprepared using prepolymerization with two polycarbonate diols (both of Mr ca 1000) differing in chainconstitution, hexamethylene-diisocyanate and 1,4-butane diol (chain extender) as starting components. All samples contained the same hard-segment content (30 w/w %). Thermogravimetry coupled with differential scanning calorimetry (TG-DSC) was performed to obtain information about the organoclays addition on the thermal stability of the prepared polyurethane elastomers. The effect of bentonite and montmorillonite nanofillers on the decomposition pattern has been evaluated. By deconvolution of derivative thermogravimetric (DTG) curves, it has been found that the thermal decomposition of polyurethane samples takes place in three overlapping processes. Degradation kinetic parameters (activation energy and reaction order) were calculated on the basis of thermal data obtained at only one heating rate.

The influence of hard segment content on mechanical and thermal properties of polycarbonate-based polyurethane materials

Aliphatic segmented polyurethanes were prepared by one-step procedure in catalytic reaction between polycarbonate diol, hexamethylene-diisocyanate and 1,4-butandiol (as chain extender). The hard segment content TS was varied (17, 24, 30 and 42 wt. %) by changing the ratio of starting compounds. The soft segment is made from flexible aliphatic polycarbonate diol, while hard segments consist of chain extender and diisocyanate component. In order to study the hydrogen bonding formation and phase separation, Fourier transform infrared spectroscopy (FT-IR) was used. Wide angle X-ray scattering (WAXS) was performed to determine a degree of crystallinity and to investigate the phase behavior of prepared elastomers. The effect of TS content on mechanical properties (tensile strength, elongation at break and hardness) was tested. Thermal behavior of prepared novel polycarbonate-based polyurethanes was investigated using differential scanning callorimetry (DSC). It was determined that the elastomer which contains the highest amount of urethane groups in its structure (TS content of 42 wt. %) exhibits the most pronounced phase separation and the highest degree of crystallinity. All prepared polyurethanes exhibit high elongation at break (over 700%). The glass transition temperature Tg of prepared samples was in the temperature region from ?39 to ?36?C, and it was found to be slightly influenced by the soft segment content. The enthalpy of chain segments relaxation in diffused region between hard and soft domains (detected in the temperature range from 35 to 55 ?C) was decreased with the increase of hard segment content. The multiple melting of hard segments (connected with the dissruption of physical crosslinks) appeared above 100 ?C. It was found that the melting enthalpy linearly increases with the increase of urethane group content. Sample with 42 wt. % of TS has the highest value of melting enthalpy (41.5 J/g).

Genetic and functional studies in multiple sclerosis patients from Martinique attest for a specific and direct role of the HLA-DR locus in the syndrome

Among candidate genes involved in multiple sclerosis (MS) genetic susceptibility, MHC genes and particularly HLA-DRB1*1501-DQB1*0602 haplotype play a major role. Based on the strong linkage disequilibrium observed in Caucasians between DRB1*1501 and DQB1*0602 alleles, it is still impossible to draw a firm conclusion about the DRB1 or DQB1 locus involvement. In order to address this issue a strategy associating a genetic and a functional approach was conducted in a population of-non-Caucasian MS patients. We observed that in Martinicans (55 MS and 100 controls), the DRB1*15 and DRB1*07 alleles were positively associated with the disease. However in Martinicans the most common DRB1*15 subtype was *1503 and not *1501. Moreover, in Martinicans, the frequency of DQB1*0602, found in association with other DRB1 alleles than DRB1*15 (42% of DQB1*0602 haplotypes), was not increased in DRB1*15-negative MS patients, suggesting a neutral role of DQB1*0602 in MS genetics. In a second step, we demonstrated the capability of the DRB1*1503 allele associated with MS in Martinicans to present the immunodominant autoantigen MBP 85-99 peptide to a DRB1*1501 restricted MBP specific T cell line. Interestingly, structural features of DRB1*1501 or DRB1*1503 molecules are in good fit with the hypothesis that *1501 and *1503 molecules may act similarly in MS development by presenting the same immunodominant MBP peptide. On the whole, our results show a prominent role of the DRB1 locus (DRB1*1501 and/or DRB1*1503 alleles) in the immunodominant MBP 85-99 peptide presentation to genetically different MS patients and suggest a neutral role of the DQB1 encoded molecule in MS susceptibility.

[The role of yaws in the serologic screening of treponematoses in blood donors in Martinique]

Using TPHA instead of VDRL for syphilis blood-screening since 1995 showed an important increase of positive blood donors in Martinique. Yaws, another treponema disease, has been present on the island until 1975-1980. Usual tests are unable to identify which type--venereal or non venereal--of treponema is involved. Our study, carried out from January 1995 to May 1999, compares actual serological and epidemiological characteristics of TPHA reactive donors to former studies. In our results, the frequency of reactive TPHA is about 1.04% in blood donations. Donors are carrying serological tracks of a past treponema disease with very low rate of antibodies, sometimes linked to yaws. Among donors aged 18 to 30, prevalence is low and is going to become similar to the rate observed in Continental France. This means that this problem will disappear in new donor generations. We suggest the possibility for them to continue blood donation, if their personal preliminary enquiry fits the admission criteria for blood giving.

HLA class I and class II allele and haplotype diversity in Martinicans

The Martinican population is mainly the product of admixture between African people and French Caucasians. The aim of the present study is to investigate at the DNA level the polymorphism of HLA class I (HLA-A, HLA-B) and class II (HLA-DRB1, DQB1 and DPB1) genes in a population of 100 Martinicans. Allelic distributions and interlocus linkage disequilibria were compared to those observed in a French Caucasian population and in African or North American African populations. Our data revealed a higher degree of polymorphism in Martinicans than in Caucasians and showed a prominant contribution of African origin in the admixed genetic feature of this population. African characteristic alleles were significantly represented in Martinicans: A*30, *33 *34, *66, *74, *8001, B*1510, *35, *42, *53, DRB1*0302, *0804, *1202, *1304, *1503, DPB1*0101, *1701, *1801, *3901. Moreover a higher diversity of A*-B* and DRB1*-DQB1* associations was observed in Martinicans compared to Caucasians which also reflects the African genetic background of this population. In the whole, using PCR-based genotyping methods for HLA class I and class II loci, this study allows a preliminary description of HLA allele distribution in this Caribbean island and gives new elements which may be helpful in the anthropologic field as well as in HLA and disease association studies.

MS and neuromyelitis optica in Martinique (French West Indies)

BACKGROUND AND OBJECTIVE

A population-based study is reported of MS in French Afro-Caribbeans (FAC) in Martinique. FAC are descendants of interracial mating that occurred between French Caucasians and black Africans in the 17th and the 18th centuries.

METHODS

The authors surveyed the entire island of Martinique (area 1,128 km(2), population 357,000) between November 1997 and October 1999.

RESULTS

Sixty-two patients (46 females, 16 males, ratio 2.9:1) were identified with definite or probable disease by the Poser criteria. Prevalence for all patients on December 31, 1998, was 17.4/10(5) (95% CI 13.1 to 21.7) and 14.3/10(5) (95% CI 10.4 to 18.2) for clinically definite cases (n = 51). Age range of patients on prevalence day was 17 to 73 years (mean +/- SD 39 +/- 11.3 years). Mean age at onset was 31.2 +/- 11 years. Overall, 9.7% had primary progressive disease and 19.4% had benign MS. A low proportion of definite and probable MS cases had oligoclonal bands in CSF (50.9%). Seventeen patients, 13 of whom were alive on prevalence day, had a relapsing form of neuromyelitis optica.

CONCLUSION

The island of Martinique appears to have a low to medium prevalence of MS. MS was almost unknown in FAC in Martinique until the late 1970s. The apparent recent increase may be explained by improved recognition of patients, increased availability of MRI for diagnosis, increased disease awareness among physicians, increased survival of MS patients, or an actual increase in disease frequency.

Drug resistance mutations among HIV-1 strains from antiretroviral-naive patients in Martinique, French West Indies

We report on the frequency of genetic mutations associated with drug resistance in antiretroviral treatment-naive patients from Martinique (French West Indies), where zidovudine (ZDV) has been available since 1987 and where combination therapy developed simultaneously with its use in continental France. Genotypic resistance was studied in plasma HIV RNA from samples collected between 1988 and 1998 from 70 antiretroviral-naive study subjects, half presenting with either primary infection or documented seroconversion. A line probe assay (LIPA) was used to detect substitutions on the reverse transcriptase (RT) codons 41, 69, 70, 74, 184, and 215. Direct sequencing was used to complete the data for RT codons which were uninterpretable by LIPA. Of these patients, 17 harbored mutated viruses with one or more mutations in the RT gene codons analyzed. ZDV resistance mutations T215Y/F, M41L, and K70R were found in 2, 5, and 12 individuals, respectively. Mutant strains L74V (didanosine [ddI] and dideoxycytidine [ddC]) were detected in 3 patients and M184V (lamivudine/ddI/ddC) in 4 patients. However, pure mutant results at one or more codons of interest were observed in only 5 (7%; 95% confidence interval [CI], 1%-13%) patients, all involving ZDV resistance. One carried both mutations T215Y and M41L known to confer a high degree of phenotypic resistance to ZDV. Among a subgroup of 28 patients with a timepoint of infection after 1995, 24 [86%; approximately 95% CI, 73%-99%) presented with a wild-type pattern. The significance of the high prevalence of mixed patterns observed in drug-naive patients remains unclear. However, the frequency of primary mutant genotypes associated with high levels of drug resistance is low in Martinique and in this study we did not observe any currently increased tendency in this frequency.

Infection with GB virus C/hepatitis G virus among blood donors and hemophiliacs in Martinique, a Caribbean island

GB virus C/hepatitis G virus (GBV-C/HGV) RNA was detected by reverse transcription-polymer- ase chain reaction with primers derived from the nonstructural region 3 (NS3) in 9 (4.1%) of 221 blood donors and 2 of 20 (10%) hemophilia patients in Martinique, French West Indies. Anti-E2 antibodies were found in sera from 33 (14.9%) of the blood donors and 5 (25%) of the hemophiliacs. None of the subjects was positive for both GBV-C/HGV RNA and anti-E2. Among the 20 hemophiliacs, 12 (60%) had anti-HCV antibodies and 7 (35%) were positive for HCV RNA by PCR. All patients positive for HCV markers belonged to the group of 13 patients exposed previously to blood factor concentrates that were not activated virally. Nucleotide sequences of the 5'-untranslated region (5'UTR) of the GBV-C/HGV genome were obtained for the 10 NS3 PCR positive samples. Phylogenetic comparison of these isolates with reference isolates published previously showed a strong homology with European and American GBV-C/HGV strains, 8 isolates belonging to the genotype 2a and 1 isolate to the type 2b. The isolate from 1 blood donor was identified as subtype 1a, indicating the presence of West African type strains.

Seroindeterminate patterns and seroconversions to human T-lymphotropic virus type I positivity in blood donors from Martinique, French West Indies

BACKGROUND

Screening for human T-lymphotropic virus type I (HTLV-I) antibodies in volunteer blood donors has been systematic in the French West Indies since 1989. Western blot-indeterminate results are commonly obtained. The significance of these indeterminate serologic patterns in HTLV-I-endemic areas is still unclear.

STUDY DESIGN AND METHODS

During a 2-year period, 9759 blood donors were tested for HTLV-I antibodies. The epidemiologic features of HTLV-I-seropositive, -seroindeterminate, and -seronegative donors were compared. A lookback investigation was performed for the HTLV-I-seropositive donors, and the HTLV-I-seroindeterminate individuals were followed up.

RESULTS

Thirty-nine donors (0.4%) were HTLV-I seropositive and 49 (0.5%) were seroindeterminate. The age and sex ratio characteristics of the seroindeterminate donors are divergent from those of the HTLV-I-seropositive group and are more like those of the seronegative population. However, during the study period, three cases of seroconversion after an initial seroindeterminate profile were reported. Two cases were detected through follow-up of 38 HTLV-I-seroindeterminate donors over a mean of 8 months (2-24 months). The third seroconverter belonged to the HTLV-I-seropositive group and was identified through lookback investigation. This case is atypical, with p19 reactivity for several months before HTLV-I seropositivity.

CONCLUSION

These findings indicate that, although HTLV-I-seroindeterminate donors mainly are HTLV-I-noninfected, the rate of seroconversion in a repeat blood donor population from an endemic region must be taken into consideration. Moreover, the case of delayed seroconversion observed in this study suggests the difficulty of counseling seroindeterminate blood donors in endemic regions.

Assessment of qualitative functional parameters of stored red blood cells from donors with sickle cell trait (AS) or with heterozygote (AC) status

We have compared the storage quality of three groups of 10 red blood cell concentrates of the AA, AS and AC haemoglobin phenotype. The 30 samples were drawn on CPD on day 0, and were centrifuged 6 hours later. Leukocytes were removed on D1 and the samples were kept at +4 degrees C for 42 days in SAG-mannitol. Viability tests were performed using a series of in vitro tests, including: ATP, 2,3-DPG, K+, glucose, lactic acid, pH, osmotic fragility tests and erythrocytic morphology determination. Results demonstrated a good functional quality for AS and AC haemoglobin RBCs. Higher 2,3-DPG levels were found in Hb AS and Hb AC. A lower osmotic fragility in Hb AC and AS RBCs versus Hb AA was observed; no significant difference was found in terms of ATP levels and other parameters. In addition no variation in S and C haemoglobin levels and no sickling were observed. In conclusion, these results indicate an overall good quality for haemoglobin AS and AC RBCs. Further in vivo studies must now be performed in order to confirm the transfusional quality of haemoglobin AS and AC RBCs.

Immunoradiometric assay of pS2 protein in breast cancer cytosols

We studied the ELSA-pS2 immunoradiometric kit (CIS Bio International) for pS2 protein assay in breast cancer cytosols according to classic validation methods. In addition, we studied correlations between pS2, steroid receptors, and cathepsin-D assays. Repeatability (CV = 1.5% to 4.8%) and reproducibility (CV = 1.6% to 4.9%) were good. The results were linearly related to pS2 concentrations between 205 and 2200 ng/L; the detection limit was 40 ng/L. The accuracy of the assay was measured by assessing recovery; analytical recoveries were near 100% throughout the standard curve. The use of different compounds for cytosol preparation (Tris 10 mmol/L or phosphate 25 mmol/L, KCl 0.4 mol/L, bovine serum albumin 1 g/L) had no effect on pS2 results. pS2 was assayed in breast tumor cytosols from 197 postmenopausal and 92 premenopausal patients. The mean value was 24 micrograms/g of protein; the median and 25th and 75th percentiles were 6, 1, and 23 micrograms/g protein, respectively. We observed a relation between concentrations of pS2 and those of estrogen and progesterone receptors, but there was no relationship between the concentrations of pS2 and cathepsin-D.

Immunoradiometric assay of pS2 protein in breast cancer cytosols

We studied the ELSA-pS2 immunoradiometric kit (CIS Bio International) for pS2 protein assay in breast cancer cytosols according to classic validation methods. In addition, we studied correlations between pS2, steroid receptors, and cathepsin-D assays. Repeatability (CV = 1.5% to 4.8%) and reproducibility (CV = 1.6% to 4.9%) were good. The results were linearly related to pS2 concentrations between 205 and 2200 ng/L; the detection limit was 40 ng/L. The accuracy of the assay was measured by assessing recovery; analytical recoveries were near 100% throughout the standard curve. The use of different compounds for cytosol preparation (Tris 10 mmol/L or phosphate 25 mmol/L, KCl 0.4 mol/L, bovine serum albumin 1 g/L) had no effect on pS2 results. pS2 was assayed in breast tumor cytosols from 197 postmenopausal and 92 premenopausal patients. The mean value was 24 micrograms/g of protein; the median and 25th and 75th percentiles were 6, 1, and 23 micrograms/g protein, respectively. We observed a relation between concentrations of pS2 and those of estrogen and progesterone receptors, but there was no relationship between the concentrations of pS2 and cathepsin-D.