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Biomedical subjects

B Sun

Publications and source records attributed to B Sun.

At least 109 records · Page 6Linked to original sources
PubMed2000

[Effects of hypoxia on the proliferation and differentiation of CD34(+) hematopoietic stem/progenitor cells and their response to cytokines].

To elucidate the effects of hypoxia on the proliferation and differentiation of CD34(+) hematopoietic stem/progenitor cells and their response to cytokines, the cells were isolated from umbilical cord blood by using a high-gradient magnetic cell sorting system (MACS). Mononuclear cells (MNC) and CD34(+) cells were incubated in severe hypoxia (1% oxygen) culture system, and the colony forming cells and antigen expression were studied by colony forming assays and FACS analysis. The results showed that incubation in severe hypoxia increased the number of erythroid bursts (BFU-E) (324.8+/-41.4/10(4) cells) generated from CD34(+) cells (191.2+/-34.5/10(4) cells in the control group, P<0.01). Severe hypoxia also enhanced the maintenance and cloning efficiency of BFU-E in a liquid culture system without growth factors, the number of BFU-E (152.4+/-22.6/10(4)cells) was much bigger than that in the control group (74.2+/-9.3/10(4) cells, P<0.01). In cultures incubated in hypoxia, the percentage of CD34(+) cells was significantly higher (2.5+/-1.2-fold, P<0.05) than in those incubated in air. BFU-E cloning efficiency of MNC was not significantly affected by hypoxia. The above results show that hypoxia enhances the maintenance of erythroid progenitor cells generated from CD34(+) hematopoietic stem/progenitor cells, no matter growth factors are present or not. These positive effects of hypoxia did not occur for the other progenitors.

Antigens, CD34↗
PubMed2000

Study on modified cold storage method of rat livers with self-made hyd solution.

OBJECTIVE: To investigate the cold preservation effect of rat livers by modified storage method with self-made HYD solution. METHODS: The modified method was that the vascular bed of rat livers was expanded with an additional 20 to 40ml self-made HYD solution/100g liver. After removing the liver, the extra HYD solution expressed as % liver weight was entrapped via portal infusion by tying off the supra-and infra hepatic inferior vena cava. According to the amount of extra HYD solution, 40 rats were randomly divided into four groups including: control group with conventional storage method, 20% group, 30% group and 40% group. The preservation effect of modified storage method with that of conventional storage method by using isolated perfused rat liver model was compared. RESULTS: Bile production and all the indices of hepatic microcirculation including portal perfusion pressure, endothelin-1 in the effluent, trypan blue distribution time and histology in modified method groups were significantly superior to those in control group (P < 0.05). The liver enzymes in 30% group were markedly lower than those in control group (P < 0.05). The preservation effect of rat liver in 30% group was the best among the modified method groups. CONCLUSION: The modified cold stage method is effective and may have potential for clinical application for liver preservation.

Alanine Transaminase↗
PubMed1999

Interaction between GPIbalpha and FcgammaIIA receptor in human platelets.

Glycoprotein (GP) Ib (alpha and beta) in platelets forms a noncovalent hetero-oligomeric complex with GPIX and GPV and serves as a receptor for von Willebrand factor (vWF), which mediates the initial adhesion of platelets to the subendothelium after vascular damage and also plays a role in thrombin-induced platelet activation. We investigated the interaction between GPIbalpha and FcgammaIIA receptor using a yeast two-hybrid system and mutagenesis, and we identified residues R542G543R544 in GPIbalpha and D298D299D300 in FcgammaIIA receptor as the primary interaction sites. These results further confirmed the interaction between GPIbalpha and FcgammaIIA receptor and support the hypothesis that the signal transduction of GPIb-IX-V that leads to platelet activation may be partially mediated through FcgammaIIA receptor.

Antigens, CD↗
PubMed1999

Inhibition of growth of human malignant glioblastoma in nude mice by antagonists of bombesin/gastrin-releasing peptide.

The effects of antagonists of bombesin/gastrin-releasing peptide (GRP) on the growth of human malignant glioblastoma cell line U-87MG xenografted into nude mice were evaluated. Nude mice bearing s.c. implanted U-87MG tumors were treated with bombesin/GRP antagonists RC-3095 and RC-3940-II. RC-3095 and RC-3940-II administered s.c. at a dose of 20 micrograms/day for 4 weeks decreased the volume of U-87MG xenografts by 60 and 74%, respectively, compared with controls. RT-PCR analysis showed that U-87MG xenografts expressed mRNA for bombesin receptor subtype (BRS)-1 (GRP receptor) and BRS-2 (neuromedin-B receptor), but the mRNA for GRP ligand was not detected in U-87MG cells suggesting that GRP may stimulate the growth of U-87MG glioblastomas by a paracrine mechanism. The levels of mRNA for c-fos oncogene were decreased by 30-40% in U-87MG tumors treated with RC-3095 or RC-3940-II. In U-373MG glioblastoma cells, which also express BRS-1, and U-87MG cells, cultured in vitro, GRP(14-27) induced the expression of c-fos mRNA, and some c-jun mRNA, in a time-dependent manner with the maximal effect occurring 2 h after the stimulation and a return to basal levels after 8 h. Antagonist RC-3940-II inhibited the stimulation of c-fos by GRP(14-27). Our results indicate that antagonists of bombesin/GRP inhibit the growth of U-87MG glioblastomas by a mechanism that may involve the downregulation of c-fos oncogene.

Animals↗
PubMed1999

Cytochrome P450 isoforms catalyzing benzo[a]pyrene metabolism in the Chinese hamster liver.

Cytochrome P450 isoforms involved in the benzo[a]pyrene metabolism in the Chinese hamster liver were characterized. The activity of benzo[a]pyrene hydroxylase in male hamster livers increased markedly by treatment with 3-methylcholanthrene (25 mg/kg per day, i.p., 3 days) and moderately with phenobarbital (60 mg/kg per day) and dexamethasone (100 mg/kg per day). In contrast, the ability for the mutagenic activation of benzo[a]pyrene determined by the mutagenicity test was increased most markedly by treatment with phenobarbital and significantly with 3-methylcholanthrene, but not with dexamethasone. These observations are similar to those in the rat rather than in the Syrian hamster. Western blot analysis and assay of the enzymes associated with cytochrome P450 isoforms showed that the 3-methylcholanthrene treatment elevated markedly the level of CYP1A2, but not that of CYP1A1, while the phenobarbital treatment elevated markedly the level of CYP2A and CYP3A, but not that of CYP2B. Further, immunoinhibition study demonstrated that, in Chinese hamster livers, CYP2A and CYP1A2 were mainly involved in the mutagenic activation of benzo[a]pyrene and CYP3A in the benzo[a]pyrene hydroxylase activity, respectively.

Animals↗
PubMed1999

Dynamic visualization of nervous system in live Drosophila.

We have constructed transgenic Drosophila melanogaster lines that express green fluorescent protein (GFP) exclusively in the nervous system. Expression is controlled with transcriptional regulatory elements present in the 5' flanking DNA of the Drosophila Na(+), K(+)-ATPase beta-subunit gene Nervana2 (Nrv2). This regulatory DNA is fused to the yeast transcriptional activator GAL4, which binds specifically to a sequence motif termed the UAS (upstream activating sequence). Drosophila lines carrying Nrv2-GAL4 transgenes have been genetically recombined with UAS-GFP (S65T) transgenes (Nrv2-GAL4+UAS-GFP) inserted on the same chromosomes. We observe strong nervous system-specific fluorescence in embryos, larvae, pupae, and adults. The GFP fluorescence is sufficiently bright to allow dynamic imaging of the nervous system at all of these developmental stages directly through the cuticle of live Drosophila. These lines provide an unprecedented view of the nervous system in living animals and will be valuable tools for investigating a number of developmental, physiological, and genetic neurobiological problems.

Animals↗
PubMed1999

Organization and transcriptional regulation of Drosophila Na(+), K(+)-ATPase beta subunit genes: Nrv1 and Nrv2.

Drosophila melanogaster has two Na(+),K(+)-ATPase beta subunit genes (Nervana 1 and 2; Nrv), with tissue-specific expression patterns. Nrv1 produces a single beta subunit isoform expressed primarily in muscle tissue, whereas Nrv2 codes for two different isoforms (2.1 and 2.2) expressed in the nervous system. We have determined the complete molecular genomic organization for both Nrv genes. Only 3kb of DNA separate the 3' end of Nrv2 from Nrv1. The cDNAs from all three forms of Nrv have been mapped onto the genomic structure and all intron-exon junctions have been confirmed by direct sequencing. The genomic DNA positioned in the 5' flanking region of each Nrv gene has also been tested for tissue-specific transcriptional regulatory activity. P-element transformation vectors were constructed, which contained either 7.7kb of Nrv2 or 3.5kb Nrv1 5' flanking DNA driving expression of a lacZ reporter gene. Multiple transgenic Drosophila lines were established for each construct and analyzed for their beta-galactosidase expression pattern. The tissue-specific expression of each Nrv gene is independently regulated by the cis-element(s) present in the 5' flanking region. The Nrv2 5' flanking DNA directs expression exclusively to the nervous system, whereas Nrv1 5' flanking DNA directs expression primarily in muscle tissue.

Animals↗
PubMed1999

Inhibition of growth of MX-1, MCF-7-MIII and MDA-MB-231 human breast cancer xenografts after administration of a targeted cytotoxic analog of somatostatin, AN-238.

Since somatostatin (sst) receptors are expressed in a high percentage of human breast cancers, we studied the effects of a targeted cytotoxic somatostatin analog (AN-238) formed by linking the highly active doxorubicin (DOX) derivative 2-pyrrolino-DOX (AN-201) to octapeptide RC-121 (D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH(2)) in 3 human breast cancer models. The models included estrogen-independent MDA-MB-231 and MX-1 and estrogen-sensitive MCF-7-MIII tumors. Nude mice bearing xenografts of these cancers were injected i.v. with 250 nmol/kg doses of cytotoxic radical AN-201, cytotoxic analog AN-238 or the unconjugated mixture of AN-201 and sst analog RC-121. Significant inhibition of growth of MDA-MB-231, MX-1 and MCF-7-MIII tumors was observed 1 week after injection of a single dose of cytotoxic analog AN-238. The volume of MDA-MB-231 tumors remained significantly decreased 3 weeks after treatment. The volumes and weights of MCF-7-MIII tumors continued to be significantly reduced 60 days after therapy with AN-238. AN-238 also caused complete regression of MX-1 tumors in 5 of 10 animals, which remained tumor-free 60 days after treatment. In contrast, after treatment with cytotoxic radical AN-201, MDA-MB-231 and MCF-7-MIII tumors grew steadily and the regression of MX-1 tumors was only transitory in most animals. Toxicity of AN-201 was much greater than that of AN-238, as measured by animal deaths, loss of body weight and leukopenia. High-affinity sst receptors and mRNA for both sst(2) and sst(5) subtypes were found in all 3 tumor lines. Expression of sst receptors was not significantly affected by treatment with AN-238. Our results indicate that the cytotoxic somatostatin analog AN-238 efficaciously inhibits growth of human breast cancers expressing sst receptor subtypes 2 and 5.

Animals↗
PubMed1999

Age-dependent paraparesis in WKA rats: evaluation of MHC k-haplotype and HTLV-1 infection.

Human T-cell leukemia virus type 1 (HTLV-1) infection is shown to be closely associated with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Although the occurrence of HAM/TSP was reported to be associated with MHC class II, the mechanism is still unclear. The WKA(RT1k) strain of rats was reported to develop HAM/TSP-like paraparesis after HTLV-1 infection, and was suggested to be an animal model of HAM/TSP. We asked whether MHC k-haplotype is specifically involved in the pathogenesis of paraparesis of WKA(RT1k) rats. We injected the HTLV-1 producing human T cells (MT-2 cells) intravenously into WKA(RT1k) rats and MHC congenic WKA.1L(RT1l) rats which have MHC l-haplotype of LEW rats on the WKA background. Positive antibody response to HTLV-1 antigens and presence of provirus in peripheral blood mononuclear cells confirmed that MT-2 cell-injected rats were infected with HTLV-1. Two of 13 MT-2 cell-injected WKA(RT1k) rats and five of 13 MT-2 cell-injected WKA.1L(RT1l) rats developed HAM/TSP-like hindlimb paraparesis between 16 and 26 months old. Interestingly, three of 14 MT-2 cell-uninjected WKA(RT1k) rats and four of 13 MT-2 cell-uninjected WKA.1L(RT1l) rats showed similar paraparesis between 15 and 26 months old. MHC k-haplotype is not specific to the development of paraparesis in WKA(RT1k) rats. The role of aging, genetic background, HTLV-1 infection and other factors on the development of HAM/TSP-like paraparesis in rats are discussed.

Age Factors↗
PubMed1999

Somatic mutation in the mammary gland: influence of time and estrus.

A critical factor in the quantitation of mutation induction in vivo is the time interval between treatment and sampling. In order to study mutagenesis in the mammary epithelium, the cell type in which breast cancer arises, we have measured the manifestation time, the minimum time required for the maximum mutant frequency to be achieved, in this tissue. The F1 LacZ transgenic mice (Muta MousexSWR) were treated with N-ethyl-N-nitrosourea (ENU) at 50 mg/kg for five consecutive days and then sampled at 1, 2, 4, 6, 9, or 12 weeks after the last treatment. The LacZ- mutant frequency reached a maximum at 4 weeks post-treatment and did not vary significantly thereafter. Dlb-1- mutations in the small intestine reached a maximum at 2 weeks after treatment and did not vary significantly thereafter. Since the stage of estrus cycle during carcinogen exposure influences the mammary tumor incidence and latency, it was expected that it would also affect mutation induction. To test this, F1 LacZ mice in the estrus or di-estrus stage were treated with an acute dose of 250 mg/kg ENU and sampled 10-13 weeks post-treatment. No statistical difference between the two groups was found, indicating that the effect of estrus on carcinogenesis is not due to variation in the sensitivity of the stage of the mammary gland to mutation.

Animals↗
PubMed1999

Inhibition of PC-3 human androgen-independent prostate cancer and its metastases by cytotoxic somatostatin analogue AN-238.

We evaluated whether AN-238, the cytotoxic analogue of somatostatin (SST) consisting of the radical 2-pyrrolinodoxorubicin (AN-201) linked covalently to the SST octapeptide carrier RC-121 (D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH2), could be used for targeting human primary and metastatic prostate carcinomas that express SST receptors (SSTRs). The antitumor activity and toxicity of AN-238 and its components were first characterized in nude mice bearing s.c. xenografts of PC-3 human androgen-independent prostate cancer. In experiment 1, AN-238 was injected once i.v. at 200 nmol/kg when the mean volume of s.c. tumors was about 30 mm3. Administration of AN-238 inhibited tumor growth, as shown by a 74% decrease in tumor volume and by a 71% reduction in tumor weight after 7 weeks as compared with the control group. AN-201 at an equimolar dose did not show any antitumor activity. The mortality was 14.3% (one of seven mice) in the AN-238-treated group and 47% (three of seven mice) in mice that received AN-201. In experiment 2, two i.v. injections of AN-238 at 150 nmol/kg were given 10 days apart when the tumors measured 65-70 mm3. A significant inhibition of tumor volume (62.3%; P < 0.001) and tumor weight (61.1%; P < 0.01) was observed after 4 weeks of treatment. AN-201, given alone at the same dose or coadministered with RC-121, had no significant effect on PC-3 tumors. The suppression of tumor growth induced by AN-238 was accompanied by a significant enhancement of apoptosis (P < 0.01). There were similar side effects in all treated groups, which included a transient loss of body weight and leukopenia. The effectiveness of AN-238 in a metastatic model was then investigated in animals implanted orthotopically with 2 x 10(6) PC-3 cells. Two i.v. injections of AN-238 or AN-201 at 150 nmol/kg were administered 10 days apart at 10 weeks after intraprostatic inoculation of PC-3 cells. After 4 weeks of treatment, the mean weight of primary tumors in animals receiving AN-238 was 77% lower (P < 0.01) than that in controls. This reduction was also significantly greater (P < 0.05) than that in animals given AN-201, which showed only a 34% inhibition (nonsignificant versus controls). All control animals and four of six (67%) mice treated with AN-201 developed metastases in the lymph nodes; however, no lymphatic spread of cancer was found in the AN-238-treated group. Using reverse transcription-PCR analysis, we demonstrated the expression of SSTR2 and SSTR5 in intraprostatic tumors and their metastases in lymph nodes as well as in s.c. tumors. The present study demonstrates the high efficacy of SSTR-targeted chemotherapy in a model of advanced human androgen-independent prostatic carcinoma, as shown by the inhibition of primary tumors and their metastases by the cytotoxic SST analogue AN-238.

Androgens↗
PubMed1999

The plasminogen-plasminogen activator (PA) system in neuroblastoma: role of PA inhibitor-1 in metastasis.

Proteases of the plasminogen-plasminogen activator (PA) system play an important role in cancer metastasis. We have examined the expression of these proteases and their cell surface receptors and inhibitors in neuroblastoma, a tumor that originates in cells of the neural crest and is the second most common solid tumor in children. This analysis was performed in seven established human cell lines and 20 primary tumor specimens. Urokinase PA and, in particular, tissue-type PA were expressed in cell lines and in tumor tissues; however, their levels of expression did not correlate with clinical stage. There was little evidence suggesting that neuroblastoma cells concentrate PA activity at their cell surface because urokinase-type PA receptor mRNA was detected in two cell lines and in 5 of 20 tumor samples by reverse transcription-PCR only. PA inhibitor (PAI)-2 was absent in all cell lines and tumor tissue samples examined. However, PAI-1, which was not expressed by the cell lines, was expressed by stromal cells and, specifically, endothelial cells in tumor tissue. By extending the analysis of PAI-1 expression in 64 primary tumor specimens, we found that high PAI-1 expression paradoxically correlated with metastatic stage and tumor recurrence. In vitro experiments indicated that the expression of PAI-1 by human microvascular endothelial cells was stimulated in the presence of SK-N-BE(2) human neuroblastoma cells and neuroblastoma culture medium. Recombinant PAI-1 also promoted SK-N-BE(2) cell detachment from vitronectin and migration from vitronectin toward fibronectin. From these data, we conclude that the up-regulation of PAI-1 expression in endothelial cells may promote rather than inhibit metastasis in neuroblastoma.

Cell Adhesion↗
PubMed1999

P21WAF1/Cip1 gene expression in primary human hepatocellular carcinoma and its relationship with P53 gene mutation.

P21WAF1/Cip1, an inhibitor of cyclin-dependent kinases, is a critical downstream effector in the P53-specific pathway of growth control. Increased expression of P21WAF1/Cip1 has been found to reflect the status of the P53 tumor-suppressor pathway. We investigated the expression of P21WAF1/Cip1 in a relatively small, but well-characterized group consisting of 28 hepatocellular carcinomas. The samples were previously studied for P53 gene mutation. P21WAF1/Cip1 expression were identified by in situ hybridization and immunohistochemistry. Positive ISH for P21WAF1/Cip1 transcripts was found in 18 of 28 cases (64.3%). All positive cases by ISH showed detectable P21WAF1/Cip1 protein reactivity by IHC. No relationship was found between P21WAF1/Cip1 staining and P53 mutational status. No associations were seen with tumor metastasis, size and tumor grade, except for tumor differentiation status which showed higher frequency of P21WAF1/Cip1 expression in moderate-well differentiated HCCs than poorly differentiated tumors (P < 0.05). It is concluded that expression of P21WAF1/Cip1 is common in HCCs, but does not correlate with P53 mutational status or pathological parameters investigated except for tumor differentiation. Also, there may be other factors beside P53 that regulate P21WAF1/Cip1 gene expression in HCCs.

Adult↗
PubMed1999

MRI characteristics of midbrain tumours.

We diagnosed 60 cases of midbrain tumours by MRI between 1993 to 1997. There were 39 males and 21 females, aged 2-64 years, mean 25.6 years. We found 38 patients with true intramedullary mid-brain tumours, 11 predominantly in the tectum, 20 in the tegmentum and 7 with a downward extension to the pons; there were 7 within the cerebral aqueduct. There were 22 patients with infiltrating midbrain tumours extending from adjacent structures, 11 cases each from the thalamus and pineal region. All patients received surgical treatment. Gross total resection was achieved in 42 cases, subtotal (> 75 %) resection in 18. Pathological diagnoses included 16 low-grade and 15 high-grade astrocytomas; 5 oligodendroastrocytomas; 2 ependymomas; 11 glioblastomas; and 11 pineal parenchymal or germ-cell tumours. Midbrain tumours are a heterogeneous group of neoplasms, with wide variation in clinical and MRI features, related to the site and type of tumour. MRI not only allows precise analysis of their growth pattern, but also can lead to a correct preoperative diagnosis in the majority of cases.

Adolescent↗
PubMed1999

Improved postprandial blood glucose control and reduced nocturnal hypoglycemia during treatment with two novel insulin lispro-protamine formulations, insulin lispro mix25 and insulin lispro mix50. Mix50 Study Group.

The objective of this 6-month, open-label, randomized, two-period crossover study was to compare glycemic control when patients were treated with (1) 2 manufactured premixed insulin formulations containing insulin lispro and a novel insulin lispro-protamine formulation, neutral protamine lispro (NPL), and (2) 2 manufactured premixed human insulin formulations, human insulin 50/50 and human insulin 30/70. One hundred individuals, 37 with type 1 diabetes mellitus (12 females, 25 males; mean age, 39.4 years; mean body mass index [BMI], 24.8; mean duration of diabetes, 12.9 years) and 63 with type 2 diabetes mellitus (33 females, 30 males; mean age, 59.0 years; mean BMI, 28.4; mean duration of diabetes, 12.6 years), were treated with insulin lispro mixtures. Insulin lispro Mix50 (50% insulin lispro/50% NPL) and human insulin 50/50 (50% regular insulin/50% neutral protamine Hagedorn [NPH] insulin) were administered before breakfast; insulin lispro Mix25 (25% insulin lispro/75% NPL) and human insulin 30/70 (30% regular insulin/70% NPH) were administered before dinner. Blood glucose (BG), hypoglycemic episodes (hypoglycemic signs or symptoms or BG <3.0 mmol/L), insulin dose and timing of dose before meals, and hemoglobin A1c were measured. Mean doses of insulin lispro and human insulin mixtures were similar overall and for both diabetes subgroups. However, compared with human insulin mixtures, twice-daily administration of insulin lispro mixtures resulted in improved postprandial glycemic control, similar overall glycemic control, and less nocturnal hypoglycemia, as well as offering the convenience of dosing closer to meals.

Adult↗
PubMed1999

Reversibility of heat-induced denaturation of the recombinant human megakaryocyte growth and development factor.

PURPOSE: The present study was performed to examine the effect of solution conditions on the reversibility of the thermal denaturation of megakaryocyte growth and development factor (rHuMGDF). METHODS: Changes in the far UV CD spectra of rHuMGDF with temperature were used to monitor the thermal denaturation of the protein, and the recovery of folded protein following a return to room temperature. The effect of protein concentration, scan rate, and buffer composition on thermal denaturation and on the reversibility were determined. Surface tension measurements were used to determine the effect of this unfolding reaction on the surface adsorption of the protein. Sedimentation velocity was used to assess recovery of native monomer and the size of soluble aggregates. In addition, monomeric protein remaining in solution after incubation at 37 degrees C for 2 weeks in either 10 mM imidazole of 10 mM phosphate was determined. RESULTS: In phosphate buffer the rHuMGDF irreversibly precipitates upon unfolding under all the conditions examined. In imidazole the unfolding is at least partially reversible, with no visible precipitate seen; the degree of reversibility increased by lowering both protein and salt concentrations, and the amount of time spent at elevated temperature. In order to compare thermal unfolding occuring with different degrees of reversibility, the melting temperature was defined as the temperature at which melting begins. The melting temperature itself is relatively independent of the buffer composition, or experimental conditions. At low protein concentrations the protein stabilizer sucrose had a marginal effect on the thermal transition of rHuMGDF, while at protein concentrations of about 2 mg/ml the inclusion of sucrose increased the apparent melting temperature by about 4 degrees C, to that seen at low protein concentrations, but had little effect on the reversibility of denaturation. Inclusion of 1 or 2 M urea did not affect the reaction. Surface tension measurements of rHuMGDF solutions showed little difference before and after melting, and in the presence or absence of sucrose. When unfolding is irreversible, the MGDF appears to form soluble aggregates of tetramers to 14-mers, while under reversible conditions native monomer is recovered. More monomeric MGDF remained in solution following storage for 2 weeks at 37 degrees C in imidazole than in phosphate, in both the presence and absence of sucrose. CONCLUSIONS: These results can be explained by assuming that thermal denaturation proceeds as a two-step reaction, the first step being the equilibrium between folded and unfolded states, while the second step is a slow irreversible aggregation. The different buffer systems affect the rate of the aggregation step, but not the intrinsic thermal stability nor the rate of the unfolding step.

Buffers↗