Lymphoma Ascites Cells Research Articles

Surface modification of titania nanoparticles with BSA engineered coating: Investigation of antimicrobial and anticancer activities

Intensive investigate in the scientific community focuses on designing and altering nanosystem surfaces with biomolecules to create more biocompatible and stable systems, leveraging their unique structure. The current work reports the synthesis of an ultrafine titania nano-bio-corona system (TNPs-BSA-PyBA) by surface functionalization of titania nanoparticles (TNPs) with 1-pyrene butyric acid (PyBA) coupled with bovine serum albumin (BSA). This biocompatible photocatalytic system was studied using Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–Visible), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal analysis, zeta potential and fluorescence emission studies. The photocatalytic antimicrobial properties of synthesized TNPs and TNPs-BSA-PyBA system were evaluated against various antibiotic-resistant microbial strains via the well diffusion method, and the result showed that the surface-modified titania nanoparticles showed an enhanced bacteriostatic effect against various bacterial and fungal strains. Also, in vitro cytotoxic studies and cell viability of the TNPs-BSA-PyBA nanocomposite system were studied by the trypan blue exclusion method on Dalton’s Lymphoma Ascites cells as well as normal cells. The cytotoxicity investigations demonstrated that the TNPs-BSA-PyBA system selectively targeted and destroyed cancer cells, with the effectiveness varying depending on the dosage.

Low-temperature Co-precipitation Synthesis of ZnAl2O4 Nanophosphors Probing its Luminescent, Antibacterial and Anticancer Potentials.

Metal nanoparticles and their binary oxides are well-known for their interactions with biomolecules and their applications in the biomedical field. However, the potential of ternary oxide nanophosphors remains underexplored in these fields due to challenges associated with high-temperature synthesis procedures and the use of toxic chemicals. ZnAl2O4, a ternary oxide matrix, being recognized for its adjustable wide bandgap, impressive surface properties, mechanical strength, thermal stability, and high quantum yield, is chosen for the present work. This study aims to comprehensively investigate the structural, morphological, optical, and cytotoxic properties of zinc aluminate nano phosphors synthesized through a co-precipitation method followed by low-temperature calcination. Analysis using X-ray diffraction spectroscopy (XRD) and Fourier-transform infrared spectroscopy (FTIR) revealed that the formation of the ZnAl2O4 spinel phase initiates at 300°C and completes at 750°C.SEM-EDAX measurements provided further confirmation of the compositional integrity of the synthesized sample. The average crystallite size, determined to be 11.47nm through a W-H plot, along with a higher bandgap value of 4.49eV compared to bulk ZnAl2O4 from the diffuse reflectance spectra (DRS), attests to the success of the nanophosphor synthesis. The self-activated blue luminescent centers of ZnAl2O4 can be fine-tuned to emit light in the green and red regions of the electromagnetic spectrum through appropriate rare earth (RE) doping, utilizing Tb3+ and Eu3+ respectively. Furthermore, the particles underwent short-term in-vitro cytotoxicity testing using Dalton's Lymphoma Ascites cells (DLA) and normal cells, demonstrating high activity against DLA cells while maintaining compatibility with normal cells.

Anticancer potential of Mimosa Pudica Linn. Lajwanti in cultured dalton’s ascites lymphoma cells

Anticancer potential of Mimosa Pudica Linn. Lajwanti in cultured dalton’s ascites lymphoma cells

Reduced graphene oxide/silver nanohybrid as a multifunctional material for antibacterial, anticancer, and SERS applications

Development of multipurpose materials like graphene–silver hybrid nanocomposite has attracted much appreciation in recent years because of their improved synergistic properties like higher effective surface area, high electron mobility, stability, and biocompatibility. Here, we report the synthesis, characterization, and multifunctional properties of reduced graphene oxide/silver (rGO/Ag) nanohybrid. This novel material shows promising results against two antibiotic resistant bacteria—Escherichia coli and Bacillus subtilis. The toxicity study on Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Bacillus subtilis) was done by the evaluation of cell viability through Resazurin-based Microtitre Dilution Assay (RMDA). We have observed that this nanohybrid is more effective against Bacillus subtilis than Escherichia coli which is different from the conventional observations. With Dalton’s Lymphoma Ascites cells (DLA), we have examined short-term in vitro cytotoxicity of this nanohybrid by trypan blue dye exclusion technique. The anticancer response of this nanohybrid was recorded with Human Colon epithelial carcinoma cells (HCT-15) as well by MTT assay. We also report SERS effect of (rGO/Ag) substrate in detecting very small amounts of Rhodamine B molecules by estimating the analytical enhancement factor.

Half‐sandwich ruthenium, rhodium and iridium complexes featuring oxime ligands: Structural studies and preliminary investigation of in vitro and in vivo anti‐tumour activities

Half‐sandwich ruthenium, rhodium and iridium complexes (1–12) were synthesized with aldoxime (L1), ketoxime (L2) and amidoxime (L3) ligands. Ligands have the general formula [PyC(R)NOH], where R = H (L1), R = CH3 (L2) and R = NH2 (L3). Reaction of [{(arene)MCl2}2] (arene = p‐cymene, benzene, Cp*; M = Ru, Rh, Ir) with ligands L1–L3 in 1:2 metal precursor‐to‐ligand ratio yielded complexes such as [{(arene)MLκ2(N∩N)Cl}]PF6. All the ligands act as bidentate chelating nitrogen donors in κ2(N∩N) fashion while forming complexes. In vitro anti‐tumour activity of complexes 2 and 10 against HT‐29 (human colorectal cancer), BE (human colorectal cancer) and MIA PaCa‐2 (human pancreatic cancer) cell lines and non‐cancer cell line ARPE‐19 (human retinal epithelial cells) revealed a comparable activity although complex 2 demonstrated greater selectivity for MIA PaCa‐2 cells than cisplatin. Further studies demonstrated that complexes 3, 6, 9 and 12 induced significant apoptosis in Dalton's ascites lymphoma (DL) cells. In vivo anti‐tumour activity of complex 2 on DL‐bearing mice revealed a statistically significant anti‐tumour activity (P = 0.0052). Complexes 1–12 exhibit HOMO–LUMO energy gaps from 3.31 to 3.68 eV. Time‐dependent density functional theory calculations explain the nature of electronic transitions and were in good agreement with experiments.

Antiproliferative Activity and Apoptosis Inducing Mechanism of Anthocephalus cadamba on Dalton's Lymphoma Ascites Cells.

The purpose of this investigation was to evaluate the antiproliferative and apoptogenic mechanistic studies of methanol extract of Anthocephalus cadamba (MEAC) on Dalton's lymphoma ascites (DLA) cells treated mice. Determination of antiproliferative activity was performed by using different DLA cells (2×106 cells, i.p.) inoculated mice groups (n = 12). Groups were treated for 14 consecutive days with MEAC at the doses of 200 and 400 mg/Kg b.w. respectively. The mechanism of antiproliferation activity of MEAC was investigated through morphological studies by acridine orange (AO)/ethidium bromide (EB) double staining method. Comet assay was estimated to check the DNA damage induced apoptosis property. Furthermore, flow cytometry (FACS) was used to quantitatively detect the apoptotic rate by double labeling techniques using Annexin-V FITC/propidium iodide staining analysis and apoptotic proteins expression done by western blotting assay method. MEAC exhibited significant (p<0.01) decrease the tumor volume, viable cell count, tumor weight and elevated the life span of DLA tumor bearing mice. Analysis of AO/EB staining and flow cytometry showed that MEAC possessed apoptosis induced antitumor activity on DLA cells in a dose dependant manner. Dose dependent induction of DNA damage on DLA cells were observed after MEAC treatment, which was evident from the appearance of comet tail length. Pro-apoptotic gene, Bax was up-regulated and down-regulation of the Bcl-2/Bax ratio, suggesting that Bcl-2 family involved in the control of apoptosis. Experimental results revealed that MEAC possess potent antitumor activity via induction of cancer cell apoptosis mechanism.

Silver nanoparticles provoke apoptosis of Dalton’s ascites lymphoma in vivo by mitochondria dependent and independent pathways

The aim of this report was to investigate the antitumor and apoptotic effects of silver nanoparticles (AgNPs) on the Dalton’s ascites lymphoma cells in vivo. Thirty Swiss albino male mice were assigned into five groups of six each. Group I were intact animals. Group II animals served as tumor control injected with DAL cells intraperitonially. Group III induced animals received plant extract (17mg/kg BW) and Group IV induced animals received AgNPs (35μg/kg BW). Group V induced animals received standard anticancer drug 5-Fluorouracil (5-FU, 20μg/kg BW). The treatment period was 10 days excluding the day of tumor injection. Tumor cells were collected after euthanizing the animals and real-time PCR was used to analyze p53, caspase-3, 8, 9, 12 and cytochrome C expressions. Results indicate that the AgNPs were efficient in prolongation of life span, reduction of tumor volume and body weight in tumor animals. All the apoptotic genes were upregulated by treatment with AgNPs. To conclude, the present study elicits that AgNPs are potent in antitumor activity and the molecular mechanism is by the induction of apoptosis through the mitochondrial dependent and independent pathways.

IN VITRO ANTIOXIDANT AND ANTICANCER ACTIVITIES OF SEED EXTRACT OF SOLANUM VIRGINIANUM

The aim of the present study is to evaluate the antioxidant and anticancer activities of seed extract of Solanum Virginianum . The antioxidant activity was assessed using DPPH scavenging assay while the anticancer property of the Solanum virginanum in swiss albino mice against Dalton Ascites Lymphoma (DAL).Tumor was induced in mice by intraperitoneal inoculation of Dalton Ascites Lymphoma cells (1 x 10 5 cells / mouse).The seed extract was found to possess significant antioxidant and anticancer activities.

Synthesis and evaluation of new salicylaldehyde-2-picolinylhydrazone Schiff base compounds of Ru(II), Rh(III) and Ir(III) as in vitro antitumor, antibacterial and fluorescence imaging agents.

Reaction of salicylaldehyde-2-picolinylhydrazone (HL) Schiff base ligand with precursor compounds [{(p-cymene)RuCl2}2] 1, [{(C6H6)RuCl2}2] 2, [{Cp*RhCl2}2] 3 and [{Cp*IrCl2}2] 4 yielded the corresponding neutral mononuclear compounds 5-8, respectively. The in vitro antitumor evaluation of the compounds 1-8 against Dalton's ascites lymphoma (DL) cells by fluorescence-based apoptosis study and by their half-maximal inhibitory concentration (IC50) values revealed the high antitumor activity of compounds 3, 4, 5 and 6. Compounds 1-8 render comparatively lower apoptotic effect than that of cisplatin on model non-tumor cells, i.e., peripheral blood mononuclear cells (PBMC). The antibacterial evaluation of compounds 5-8 by agar well-diffusion method revealed that compound 6 is significantly effective against all the eight bacterial species considered with zone of inhibition up to 35 mm. Fluorescence imaging study of compounds 5-8 with plasmid circular DNA (pcDNA) and HeLa RNA demonstrated their fluorescence imaging property upon binding with nucleic acids. The docking study with some key enzymes associated with the propagation of cancer such as ribonucleotide reductase, thymidylate synthase, thymidylate phosphorylase and topoisomerase II revealed strong interactions between proteins and compounds 5-8. Conformational analysis by density functional theory (DFT) study has corroborated our experimental observation of the N, N binding mode of ligand. Compounds 5-8 exhibited a HOMO (highest occupied molecular orbital)-LUMO (lowest unoccupied molecular orbital) energy gap 2.99-3.04 eV. Half-sandwich ruthenium, rhodium and iridium compounds were obtained by treatment of metal precursors with salicylaldehyde-2-picolinylhydrazone (HL) by in situ metal-mediated deprotonation of the ligand. Compounds under investigation have shown potential antitumor, antibacterial and fluorescence imaging properties. Arene ruthenium compounds exhibited higher activity compared to that of Cp*Rh/Cp*Ir in inhibiting the cancer cells growth and pathogenic bacteria. At a concentration 100 µg/mL, the apoptosis activity of arene ruthenium compounds, 5 and 6 (~30 %) is double to that of Cp*Rh/Cp*Ir compounds, 7 and 8 (~12 %). Among the four new compounds 5-8, the benzene ruthenium compound, i.e., compound 6 is significantly effective against the pathogenic bacteria under investigation.

Preliminary Evaluation of In Vitro Cytotoxicity and In Vivo Antitumor Activity of Xanthium strumarium in Transplantable Tumors in Mice

In the present study, active fractions of the methanolic extract of Xanthium strumarium (XS) showing potent cytotoxicity were determined using microculture tetrazolium (MTT) and sulforhodamine B (SRB) assays in selected cancer cell lines. The active fractions viz., chloroform soluble fraction of root (CEXSR), hexane soluble fraction of leaf (HEXSL), hexane soluble fraction of fruits (HEXSF) and chloroform soluble fraction of fruits (CEXSF) of XS were tested in transplantable animal tumor models for their antitumor potential. Dalton's ascitic lymphoma (DLA) cells were used to induce solid and liquid (ascites) tumor in mice. The tumor bearing animals were treated with active fractions at two dose levels (100 and 200 mg/kg). The antitumor activities of the active fractions in tumor bearing animals were monitored with parameters such as body weight and increase in life-span as well as biochemical and hematological modalities (in the case of liquid tumor). Tumor incidence and tumor volume were the parameters monitored in the case of the solid tumor model. The results were analyzed by one-way ANOVA followed by Tukey's post hoc test. The extracts were found to increase the life-span of tumor bearing animals and restore the altered hematological and biochemical parameters significantly.

IRL-1620, an Endothelin-B Receptor Agonist, Enhanced Radiation Induced Reduction in Tumor Volume in Dalton’s Lymphoma Ascites Tumor Model

ETB receptor agonist, IRL-1620 (or SPI-1620) presently in US Phase 1 clinical trial, has been demonstrated to selectively and transiently increase tumor blood flow. The present study was conducted to determine the effect of IRL-1620 on radiation therapy in tumor bearing mice inoculated with Dalton's Lymphoma Ascites cells. Tumors were allowed to grow for 30 days to a size of 1.10-1.29 cm3 before starting the treatment. The animals with or without IRL-1620 treatment were exposed to radiation (4 Gy/dose) on every alternate day for a total of 5 doses. Tumor volume was determined twice every week till the end of study. Radiation alone did not affect the tumor volume; however, animals treated with IRL-1620 followed by radiation produced a significant (64%) reduction in tumor volume. Survival of mice improved from 0/10 at 56 days after tumor inoculation in vehicle plus radiation group to 6/10 at 70 days in IRL-1620 (9 nmol/kg) plus radiation group. It is concluded that IRL-1620 improves the efficacy of radiation treatment in tumor bearing mice. (These findings have been earlier presented as an abstract ).

Phyllanthus amarus Inhibits Cell Growth and Induces Apoptosis in Dalton's Lymphoma Ascites Cells Through Activation of Caspase-3 and Downregulation of Bcl-2

The authors found in an earlier study that Phyllanthus amarus extract could significantly inhibit the solid and ascites tumor development in mice induced by Dalton's lymphoma ascites (DLA) cells. In the present study, the apoptotic effects of P. amarus against DLA cells in culture was evaluated. P. amarus produced significant reduction in cell viability as determined by the MTT assay. It also induces the formation of apoptotic bodies with characteristic features like plasma membrane invagination, elongation, fragmentation, and chromatin condensation. P. amarus at concentrations of 100 and 200 microg/mL is shown to induce DNA fragmentation. Gene expression analysis reveals that P. amarus induces the expression of caspase-3 and inhibits the expression of Bcl-2, which is an antiapoptotic protein. So the present study provides some insights into the possible mechanism by which P. amarus brings about apoptosis and growth inhibition in DLA cells.

Regulation of Caspase‐3 and Bcl‐2 Expression in Dalton′s Lymphoma Ascites Cells by Abrin

The role of abrin, a toxic lectin isolated from seeds of Abrus precatorius Linn in inducing apoptosis in murine Dalton's Lymphoma Ascites (DLA) cells was evaluated. Abrin when incubated at the concentration of 10 ng per million DLA cells could bring about cell death as typical morphological changes with apoptosis. However, necrotic cell death dominated when a higher dose of abrin was used. DNA samples, isolated from DLA cells treated with abrin showed fragmentation. Abrin brought about induction of apoptosis by stimulating the expression of pro-apoptotic Caspase-3, at the same time blocking the expression of Bcl-2, which is an anti apoptotic gene. However, the expression of tumor suppressor gene p53 has not been observed in control and abrin-treated DLA cells. Results suggested that abrin effectively induced apoptotic changes in the tumor cells that led to cellular death.

Cytotoxicity, Anti-tumor Activity, Cumulative Skin Irritation and Sensitization Study of 5-Fluorouracil from a Transdermal Patch for Dalton's Lymphoma Ascites Cells

Dalton’s lymphoma ascites (DLA) cells were used as a model cell line to evaluate the cytotoxic concentration and anti-tumor activity of 5-fluorouracil (5-FU) through transdermal drug delivery (TDD) for solid tumors. Cytotoxicity was measured by exposing cell suspensions to increased concentrations of drug from 10–50µg/ml and then th ev iable cells count was measured by the tryphan blue exclusion method. The results confirmed that 50µg/ml of 5-FU was cytotoxic to DLA cells. The tumor volume was 0.23 cm 2 and the increase in life span (ILS) was 81.8% with a maximum survival time of 39.5±1.87 days fo r5 -F Um onolithic matrix transdermal patch in mice with solid tumors induced by DLA. The results were significantly different (p 500 foldings), elegance, smoothness, transparency, and flexibility. The Velcro protection jackets were suitable for the study and prevented the mice from licking, scratching, and rubbing the patches.

Long distance polymerase chain reaction of ascites lymphoma cells aids diagnosis establishment of abdominal Burkitt's lymphoma and Burkitt-like lymphoma

Burkitt's lymphoma (BL) and its variants, including Burkitt-like lymphoma (BLL), can be difficult to distinguish morphologically and immunophenotypically from diffuse large B-cell lymphoma (DLBCL). Because the treatment of BL differs markedly from that of other types of non-Hodgkin's lymphoma (NHL), exact pathological diagnosis is crucial. We report 2 cases of patients with BL initially diagnosed as DLBCL. Due to clinical features typical of BL, long distance polymerase chain reaction (PCR) for detecting the t(8;14) translocation involving the c-myc proto-oncogene was performed on ascites lymphoma cells. Re-evaluation by a reference hematopathologist, together with long distance PCR in both patients revealing the t(8;14) translocation, resulted in diagnosis modification to BL and BLL. Consequently, the patients were treated with intense high-dose chemotherapy regimens including central nervous system (CNS) prophylaxis, and complete remission was initially achieved in both patients. Both BL and BLL should be considered in the differential diagnosis of DLBCL if abdominal spread with ascites and metabolic disorders are present. Long distance PCR analysis of ascites lymphoma cells for the detection of the BL-typical c-myc rearrangement offers a convenient and rapid possibility of diagnosis verification in atypical or borderline cases of BL.

Formulation and In Vivo Evaluation of Niosome-Encapsulated Daunorubicin Hydrochloride

ABSTRACTThe central aim of this present study was to modify the reverse evaporation process, such that an enhanced entrapment, with increased storage stability and prolonged release, could be achieved, and to translate these advantages to increased therapeutic efficacy of daunorubicin hydrochloride on Dalton's ascitic lymphoma. Niosomes prepared exhibited entrapment efficiency 20% higher than theoretically possible by the reverse evaporation process. The niosomes were found to be very stable at a storage temperature of 4°C for a duration of three months. Even the drug leakage was restricted to just 10%. The in vivo studies suggested a prolonged release of 20 hr. Niosomal daunorubicin hydrochloride exhibited an enhanced anti-tumor efficacy when compared to free drug. The niosomal formulation was able to destroy the Dalton's ascitic lymphoma cells in the peritoneum within the third day of treatment, while free drug took around six days and the process was incomplete. The hematological studies also prove that the niosomal formulation was superior to free drug treatment. An enhanced mean survival time was achieved by the niosomal formulation that finally substantiates the overall efficacy of the niosomal formulation. This study suggests that the multilamellar vesicles obtained by the presently utilized reverse evaporation process resulted in vesicles that resisted the immediate lysis in the Kupffer cells, whereby a prolonged drug concentration was achieved which enhanced the cell lysis. But the major factor responsible for the quicker onset of action could be the increased permeability of the niosomes into the cell membrane and the cytoplasm of the Dalton's ascitic lymphoma cells.

Comparison of glycine metabolism in mouse lymphoma cells either sensitive or resistant to L-asparaginase

Previous work suggested a relationship between glycine metabolism and the effect of l-asparaginase upon tumor cells. Therefore, L5178Y (sensitive) or L5178Y/L-ASE (resistant) ascites lymphoma cells were incubated with 14C-labeled glyoxylate, glycine, serine, or asparagine, and the metabolism to other amino acids was measured by high performance liquid chromatography. Metabolic differences between the two cells lines were found. Under control conditions, the interconversion rate of glycine and serine via serine hydroxymethyltransferase (SHMT) was higher in sensitive than in resistant cells. The transformation rate of glyoxylate to serine was also higher in sensitive cells. These results may indicate a difference in the activity of SHMT. An alternate explanation would be that transport or diffusion of serine and glycine into sensitive cells is greater than into resistant cells. Several crucial metabolic differences were observed between the two cell types when l-asparaginase was added. A key difference is the decrease of glycine synthesis from glyoxylate observed in the sensitive cells compared to resistant cells which show no change. This suggests that asparagine is used for transamination of glyoxylate. Also, only sensitive cells appear to compensate for l-asparaginaseinduced loss of glycine formation from glyoxylate by increasing glycine synthesis from serine. Alterations in sensitive tumor glycine metabolism may be an important function of l-asparaginase anticancer activity.

Two novel cultured cell lines, A3/Kawakami and A4/Fukuda, derived from malignant lymphoma of B(non-T)-cell nature of the gastrointestinal tract.

A3/Kawakami was derived from ascitic lymphoma cells of a 68-year-old female patient with malignant lymphoma (non-Hodgkin's lymphoma, diffuse, large cell type) of the stomach and A4/Fukuda was derived from ascitic lymphoma cells of a 52-year-old female patient with double cancer of the colon (well-differentiated papillary adenocarcinoma and non-Hodgkin's lymphoma, diffuse, large cell type). The fresh ascitic lymphoma cells in the case of A3/Kawakami were surface immunoglobulin-positive, but the cultured A3/Kawakami cells no longer expressed any distinct markers. In the case of A4/Fukuda, the fresh ascitic lymphoma cells and cultured cells did not express any specific surface markers. Only 20% of A4/Fukuda cells were reactive with OKI1. However, a small amount of IgM could be detected in the cell extract and concentrated culture supernate of A4/Fukuda. In addition, A4/Fukuda cells heterotransplanted into anti-thymocyte sera-treated newborn hamster or athymic nude mice with a BALB/c genetic background were found to have weak surface immunoglobulin and distinct cytoplasmic immunoglobulin (gamma, mu). These data suggest that A4/Fukuda cells share the characteristics of the late differentiation stage of B-cell lineage (intermediate between mature B-cells and plasma cells). It was found that monoclonal antibodies, OKT4 and anti-Leu 3a, which are known to react specifically with inducer/helper T-cells, reacted to both A3/Kawakami and A4/Fukuda cells. The karyotypes of both A3/Kawakami and A4/Fukuda cells were very complicated but included some marker chromosomes such as 14q+.

The Ratio of Cytochromes in Radiation-Induced Leukemia Cells of Mice

The content of cytochromes in various leukemia cells and normal thymocytes of mice was determined spectrophotometrically at room temperature and at the temperature of liquid nitrogen. The ratio of cytochrome c + c/sub 1/ to cytochrome aa/sub 3/ of primary thymic lymphomas, whether arising spontaneously in AKR mice or induced by x-irradiation in NIH Swiss mice, was similar to that of normal thymocytes. In contrast, three lines of transplantable ascites lymphoma cells, originally derived from radiation-induced lymphoma, showed a definitely higher ratio than that of normal thymocytes. The results revealed that the c + c/sub 1//aa/sub 3/ ratio of the lymphoma cells increased in successive generations during serial passage of the cells in vivo.

The spontaneous release of 51Cr from labeled EL-4 ascitic lymphoma cells as dependent upon the composition of the cell population.

Investigations on the spontaneous release of 51Cr from the EL-4 ascitic lymphoma showed that daily rhythmic changes can be correlated with the dominance of certain cell types in the population. A generation time of 9.8 h, an average doubling time of 32 h, and an 'appearance cycle' of 96 h were established for the population. Earlier observed variations in the values for spontaneous 51Cr release can be explained in terms of the cellular composition of the population.