Histological estimation of the efficacy of endoscopic laser coagulation therapy for diffuse antral vascular ectasia

We present the case of a 72-year-old woman with successful control of repeated episodes of bleeding from diffuse antral vascular ectasia (DAVE) by laser coagulation therapy. In addition to DAVE, the patient also suffered from severe iron deficiency anaemia (due to recurrent bleeding), liver cirrhosis, and huge tumours of hepatocellular carcinoma (HCC). She was referred from another hospital after failure to stop her bleeding episodes. Endoscopic examination revealed diffuse speckled telangiectasia over most of the stomach (from antrum to the upper portion of the body) and large numbers of blood clots. The patient had received repeated blood transfusions, haemostatic drugs, and H2 receptor antagonists at the other hospital, without improvement of the repeated bleeding. She underwent three sessions of endoscopic laser coagulation therapy for the lesions at our hospital after the final diagnosis of DAVE had been made based on the characteristic histological findings of biopsied specimens. This treatment improved her general condition and stopped the bleeding from the gastrointestinal tract even without fasting. Unfortunately, however, her liver function gradually worsened due to HCC and previous massive bleeding, and she finally died of liver failure three months after the last laser session. Autopsied specimens obtained from the patient's stomach revealed that macroscopic diffuse speckled telangiectasia and microscopic typical vasodilatation in mucosal and submucosal layers of gastric tissue had disappeared in the treated areas but not all portions of the DAVE lesion. These histological findings for the treated areas, in addition to the clinical improvement of bleeding, suggest that endoscopic laser coagulation therapy may be useful and one of the first choices in treatment for DAVE.

Isolation of morphologically and functionally intact gastric mucosal microvessels rapid communication

Gastric mucosal microvessels were isolated after arterial perfusion of the rat stomach with magnetized iron oxide suspension. After homogenization of scrapped gastric mucosa, microvessels were initially separated with a high power magnet and further separated and purified by using a nylon sieve. Aliquots of purified microvessels were assessed for viability, histologic appearance, ultrastructure and generation of prostacyclin. Microvessels were plated on Matrigel and cultured in DMEM with high glucose and 10% FBS for 1, 3 or 5 days. After 1, 3 and 5 days of culturing, endothelial viability was assessed with Fast green exclusion, and the basal and stimulated (with calcium ionophore) generation of prostacyclin was determined by assaying aliquots of the incubating medium for 6-keto PGF(1alpha). At 1 and 3 hrs after isolation, microvessels demonstrated intact morphologic structures as reflected by transmission EM and 92+/-4% of viable endothelial cells. The microvessels plated on Matrigel maintained good viability for at least 5 days and generated prostacyclin at the baseline and following ionophore stimulation. These data demonstrate that isolated microvessels cultured under optimal conditions are fully viable and functional.

Oesophageal cavernous haemangioma diagnosed histologically, not by endoscopic procedures

Haemangioma of the oesophagus is uncommon in patients with benign oesophageal tumours. We present a patient with an oesophageal haemangioma detected during mass screening of the upper gastrointestinal tract. The patient, a 59-year-old man, had neither abdominal complaints nor a history of gastrointestinal diseases. Endoscopic examination revealed a blue-coloured submucosal tumour (approximately 3 cm in diameter) at the middle portion of oesophagus. Endoscopic Doppler ultrasonography showed an homogeneous and hypoechoic mass without blood flow in the submucosal layer of the oesophagus. However, a magnetic resonance imaging scan did not give a typical image for oesophageal haemangioma. Therefore, partial resection of the tumour was performed to obtain a differential diagnosis using the procedures of endoscopic ligation and polypectomy. Histological examination of the resected tissue showed a cavernous haemangioma in the oesophagus. This endoscopic technique may be useful for the differential diagnosis of oesophageal haemangioma.

Effect of culture conditions on morphological changes of Helicobacter pylori

The morphological conversion of Helicobacter pylori from the spiral form to the coccoid form may be the expression of a transitory adaptation to an unsuitable environment. The mechanism(s) of this conversion are not clear. In this study, we examined whether the morphological conversion of H. pylori is affected by various culture conditions, such as oxygen concentration, pH, temperature, or the presence of beta-cyclodextrin. H. pylori (NTCC11916) was cultured on Brucella agar, followed by culture in Brucella broth containing 1% agar under several conditions. Morphological conversion of individual H. pylori on the agar plate was investigated with time after incubation under phase contrast microscopy. When H. pylori was inoculated in Brucella broth containing beta-cyclodextrin, the spiral form of the organism was observed even after 6 days of incubation under standard culture conditions: 37 degrees C, pH 7, and microaerobic atmosphere (5% O2/10% CO2/85% N2) (control). The morphological conversion of H. pylori was completed on day 3 in an aerobic atmosphere (20% O2 supply) and on day 2 in an undermicroaerobic atmosphere (<0.1% O2). Its complete morphological conversion was observed at pH 8 on day 5 and at pH 4 on day 6. All of the H. pylori (100%) incubated at 20 degrees or 42 degrees C had converted from the bacillary to the coccoid form on day 4. Conditioned medium without beta-cyclodextrin caused complete conversion on day 5. These results suggest that oxygen concentration, pH, temperature, and beta-cyclodextrin may be related to the H. pylori morphological conversion from the bacillary to the coccoid form.

HGF triggers activation of the COX-2 gene in rat gastric epithelial cells: action mediated through the ERK2 signaling pathway

Although it is established that growth factors and prostaglandins function in the maintenance of gastric mucosal integrity and in the healing of gastric mucosal injury and ulceration, the regulatory relationship between growth factors and prostaglandins in the gastric mucosa is not well characterized. Therefore, we investigated whether hepatocyte growth factor (HGF) affects expression of COX-2 (the inducible form of the prostaglandin synthesizing enzyme, cyclooxygenase) in gastric epithelial cells and whether this action is mediated through the MAP (ERK) kinase signaling pathway. In RGM1 cells (an epithelial cell line derived from normal rat gastric mucosa), HGF caused an increase in COX-2 mRNA and protein by 236% and 175%, respectively (both P<0.05). This induction of COX-2 expression was abolished by pretreatment with the MAPK kinase (MEK) inhibitor PD98059. HGF also triggered a 13-fold increase in c-Met/HGF receptor phosphorylation (P<0.005) and increased ERK2 activity by 684% (P<0.01). Pretreatment with PD98059 abolished the HGF-induced increase in ERK2 activity, but not c-Met/HGF receptor phosphorylation. The specific inhibitor of p38 MAP kinase, SB203580, had no effect on HGF-induced COX-2 expression. Thus, HGF triggers activation of the COX-2 gene in gastric epithelial cells through phosphorylation of c-Met/HGF receptor and activation of the ERK2 signaling pathway.-Jones, M. K., Sasaki, E., Halter, F., Pai, R., Nakamura, T., Arakawa, T., Kuroki, T., Tarnawski, A. S. HGF triggers activation of the COX-2 gene in rat gastric epithelial cells: action mediated through the ERK2 signaling pathway.

Plasmodium ovale infections detected by PCR assay in Lao PDR

Plasmodium ovate infection was demonstrated in 5 out of 143 inhabitants in a village in Lao PDR by blood microscopy and PCR assay. Although the specimen confirmed to be positive for P. ovale by microscopical examination was only one, the target sequences in the 18S rRNA genes of malaria parasite detected in all of the five cases were consisted with those of P. ovale by the PCR assay. This is the first report concerning the presence of so many cases with P. ovale infection in Lao PDR.

Endoscopic resection of two granular cell tumours of the oesophagus

Granular cell tumour of the oesophagus is rare and usually single. It is diagnosed by endoscopic appearance, results of endosonography, and histological examination of biopsy specimens. Although histological examination is required for diagnosis, it is difficult occasionally to obtain tumour samples by forceps because granular cell tumour is usually located in the submucosal layer. We report the case of a Japanese man with two granular cell tumours of the oesophagus. One lesion was diagnosed as a granular cell tumour by histological examination of a biopsy specimen, but the other was not. Endoscopic resection was performed to obtain the diagnosis and treat the lesions since some granular cell tumours are potentially malignant. Both tumours were completely resected endoscopically, and the diagnosis of granular cell tumour could be established by histological examination of resected tissue. Endoscopic resection is thus useful in the diagnosis and treatment of granular cell tumour of the oesophagus.

Antibacterial and antiandrogen flavonoids from Sophora flavescens

Sixteen flavanones, three flavanonols, and four pterocarpans were isolated from the MeOH extract of the roots of Sophora flavescens. Twelve of these were new compounds, including eight prenylflavanones (1-8), one prenylflavanonol (9) and three novel pterocarpane derivatives (10-12). Their structures were elucidated using NMR and mass spectral methods. Some of these compounds have irregular C10 prenyl moieties at C-8 of the flavanone skeleton. These compounds exhibited significant antibacterial activities against the Gram-positive bacteria Staphylococcus aureus, Bacillus subtilis, S. epidermidis, and Propionibacterium acnes. They also exhibited antiandrogen activities.

Inhibition by 16,16-dimethyl prostaglandin E2 of tumor necrosis factor-alpha and interleukin-1beta production and messenger RNA expression in human monocytes stimulated by Helicobacter pylori

We investigated the effects of 16,16-dimethyl prostaglandin E2 on the production of tumor necrosis factor-alpha and interleukin-1beta in human monocytes stimulated with Helicobacter pylori. Monocytes isolated from human peripheral blood were incubated for 24 hr with the extract of H. pylori diluted 1:100 to 1:100,000 by volume, a combination of the extract and 16,16-dimethyl prostaglandin E2, or a vehicle alone. The extract stimulated the production of tumor necrosis factor-alpha and interleukin-1beta and the expression of their messenger RNA in a dose-dependent manner. 16,16-Dimethyl prostaglandin E2 inhibited the production of these cytokines and their messenger RNA in the presence of H. pylori at doses higher than 10(-6) M, predominantly with tumor necrosis factor-alpha. These data suggest that antiinflammatory effects of prostaglandins on gastric mucosa are in part related to their effects on inhibition of production of proinflammatory cytokines by monocytes.

Down-regulation by bucillamine of lamina propria leucocytes in the rat colitis model

1. The efficacy of bucillamine has been reported in various inflammatory models. 2. In the present study, the effects of 2 weeks administration of bucillamine on hapten-induced experimental rat colitis were analysed. The gross morphological damage score was evaluated and the expression of CD4, CD8, CD11a, CD11b, CD25, CD54 and class II major histocompatibility complex (MHC) antigen was investigated by immunohistochemical methods. 3. Mean bodyweight was significantly increased in colitic rats given 750 micrograms bucillamine compared with colitic rats given vehicle (distilled water). Gross morphological damage was significantly less in colitic rats given 250 or 750 micrograms bucillamine compared with rats given vehicle. 4. Immunohistological studies revealed that CD4, CD11a, CD11b, CD54 and class II MHC antigen expression of infiltrating leucocytes was significantly lower in rat colonic mucosa treated with bucillamine. 5. From these findings, it appears that bucillamine may act through the down-regulation of the activation of lamina propria leucocytes in hapten-induced rat colitis.

Anti- and pro-oxidative effects of flavonoids on metal-induced lipid hydroperoxide-dependent lipid peroxidation in cultured hepatocytes loaded with alpha-linolenic acid

Lipid hydroperoxide (LOOH)-dependent lipid peroxidation was induced in alpha-linolenic acid (LNA)-loaded hepatocytes by adding Fe, Cu, V, or Cd ions at concentrations from 20 to 500 microM. The effects of structurally related flavonoids at concentrations from 10 to 500 microM on the lipid peroxidation were examined. The results with regard to each flavonoid subclass are as follows: (i) Flavonols such as myricetin, quercetin, fisetin, and kaempferol, but not morin, showed dose-dependent antioxidative activity against metal-induced lipid peroxidation at all metal concentrations. Myricetin, quercetin, and fisetin were the most effective antioxidants, although their efficacies depended on the metal ion. Kaempferol and morin had antioxidative activity equal to the other flavonols in the presence of Cu ions, but were much less effective for the other three metal ions. (ii) Flavones, luteolin, apigenin, and chrysin were antioxidative at low Fe concentrations, but were pro-oxidative at high Fe concentrations. Luteolin exhibited antioxidative activity similar to that of catechol-containing flavonols in the presence of the other three metal ions. Apigenin and chrysin also acted as pro-oxidants with V or with all metal ions, respectively. (iii) Taxifolin, a flavanone, also showed both anti- and prooxidative activity, depending on Fe concentrations, but with other metal showed only antioxidative activity ions. (iv) Epigallocatechin, a flavanol, was antioxidative with all metal ions, and its activity was similar to that of catechol-containing flavonols. The various effects of flavonoids on metal-induced lipid peroxidation in LNA-loaded hepatocytes is discussed with regard to the change in redox potential of flavonoid-metal complexes.

Liu-Jun-Zi-Tang, a kampo medicine, promotes adaptive relaxation in isolated guinea pig stomachs

Some patients with dysmotility-like functional dyspepsia present impaired reservoir functions such as gastric adaptive relaxation. A traditional Chinese herbal medicine, Liu-Jun-Zi-Tang, has been identified as an effective drug against dyspeptic symptoms and is widely used for therapy in such patients. In this study, we examined the effects of this drug on the gastric adaptive relaxation in isolated guinea pig stomachs. The changes in intragastric volume and pressure were recorded in the presence of atropine and guanethidine. Gastric adaptive relaxation was induced by luminal distention. Liu-Jun-Zi-Tang (100 mg/ml) induced gastric adaptive relaxation at a lower intragastric pressure and increased the % volume of the gastric adaptive relaxation and the absolute intragastric volume. Metoclopramide (2 mg/ml), trimebutine (6 mg/ml) and cisapride (2 mg/ml) did not affect gastric adaptive relaxation. It was inhibited by means of the incubation of the stomach with NG-nitro-L-arginine (100 microM). Liu-Jun-Zi-Tang (100 mg/ml), but not gastroprokinetics overcame the effect of NG-nitro-L-arginine. These results suggested that Liu-Jun-Zi-Tang promoted gastric adaptive relaxation. This effect might, at least in part, contribute to the symptom relief in patients with functional dyspepsia.

Gastroprotection by Liu-Jun-Zi-Tang (TJ-43): possible mediation of nitric oxide but not prostaglandins or sulfhydryls

Liu-Jun-Zi-Tang (TJ-43), a herbal medicine exerting gastroprotective action, was examined for its mechanism of action in rats. TJ-43 significantly inhibited gastric mucosal damage caused by absolute ethanol at doses over 500 mg/kg in a dose-dependent way. Pretreatment with indomethacin or with N-ethylmaleimide did not affect the gastroprotective effect of TJ-43. However, pretreatment with NG-nitro-L-arginine partially but significantly reversed the protective effect of this drug. These findings suggest that the gastroprotective effect of TJ-43 occurs partly through nitric oxide but not through prostaglandins or sulfhydryls.

Identification and partial purification of DnaK homologue from extremely halophilic archaebacteria, Halobacterium cutirubrum

The levels of synthesis of six proteins were increased at elevated growth temperature of the extremely halophilic archaebacterium Halobacterium cutirubrum. One of these proteins, with an apparent molecular mass of 97 kDa on sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), bound to an ATP-agarose column in the presence of 4 M NaCl, but not in the absence of salt, indicating that this protein retained its ATP-binding activity only at high salt concentration. The NH2-terminal sequence of this protein and the internal sequences of the tryptic peptides covering 1/3 of the total number of residues coincided with that deduced from the nucleotide sequence of the dnaK gene isolated from H. cutirubrum. The results strongly suggest that this apparent 97-kDa protein is the gene product of dnaK, although the molecular mass calculated from the nucleotide sequence is only 68,495, much smaller than the value of this protein determined by SDS-PAGE. Ferguson plot analysis indicated that this protein showed anomalous mobility on SDS-PAGE. We have purified DnaK homologue to greater than 90% homogeneity with stepwise elution from an ATP-agarose column.

Comparison of an antiviral activity of recombinant consensus interferon with recombinant interferon-alpha-2b

To avoid possible uncertainty in comparing biological activities of interferon samples from different sources where interferon concentrations were determined independently, we prepared chromatographically pure preparations of consensus interferon and interferon-alpha-2b (one of the two commercially available recombinant alpha interferons). We revealed that consensus interferon has a stronger antiviral activity than interferon-alpha-2b, although the effects of these two recombinant interferons on the cellular macromolecule synthesis are at similar levels.

Effect of prophylactic administration of hyperimmune plasma to prevent Rhodococcus equi infection on foals from endemically affected farms

The effect on foals of prophylactic administration of hyperimmune plasma to prevent R. equi infection was investigated on three farms at which R. equi infection was endemic. Sixteen foals between 10 and 39 days of age were intravenously given 1-21 of hyperimmune plasma. ELISA antibody titres against R. equi were significantly increased and maintained at high levels for over 30 days in most of the recipient foals. The prevalence of R. equi infection was 6.3% (1/16) in the foals that received the immune plasma, and 26.3% (5/19) in the control foals not given the immune plasma on the three farms. For 2 years before and after this field trial on the three farms, 18 of 64 foals (28.1%) showed clinical signs of respiratory tract infection and four of them died of R. equi pneumonia. Heavy contamination of horses and their environment with virulent R. equi was detected by colony blotting, and plasmid profiles also suggested that foals on the three farms were constantly exposed to virulent R. equi. The results of this field trial support previous observations by some researchers that the administration of hyperimmune plasma to foals in the early days of life promotes prevention of R. equi infection on endemic farms; however, the mechanism of hyperimmune plasma protection remains unclear.

Postmortem findings two weeks after oral treatment for metastatic Candida endophthalmitis with fluconazole

The purpose of this histological study was to present postmortem findings in both eyes of a 53-year-old male with liver dysfunction 2 weeks after short-time oral treatment with 200 mg/day fluconazole for metastatic Candida endophthalmitis due to intravenous hyperalimentation for 18 days. Candida had been demonstrated in the venous blood and on the tip of the intravenous catheter. The bilateral fungal endophthalmitis with hypopyon responded well to fungistatic therapy, but the patient suddenly died from heart failure. Both eyes were obtained at autopsy. Candida was demonstrated only in vitreous puff balls but not in the retina or uvea. Fluconazole administered for a short period had little effect in eliminating fungus from vitreous puff balls, which have no blood supply. Prolonged administration of the antifungal drug or vitrectomy should be considered when treating an eye with vitreous puff balls in the presence of fungal endophthalmitis.

[A case of Churg-Strauss syndrome presented as right thalamic hemorrhage]

Intracerebral hemorrhage is an uncommon sequel of Churg-Strauss syndrome (CSS). We report the first case of CSS accompanied by right thalamic hemorrhage. The patient was 59-year-old male who experienced a sudden onset of left hemiplegia. Magnetic resonance imaging of the brain revealed right thalamic hemorrhage. Although several reports had pointed out a close relationship between hypertension and cerebral hemorrhage in patients with CSS, this patient had no apparent prior history of hypertension. The cause of thalamic hemorrhage in this patient might be probably due to cerebral vasculitis and an effect of abnormal coagulation and fibrinolytic agents.

Type 1 T-helper cell predominance in granulomas of Crohn's disease

OBJECTIVE

The pathogenesis of Crohn's disease (CD) is thought to be associated with production of several cytokines, especially type-1 cytokines. To elucidate the in situ cytokine profiles in CD, cytokine-containing cells were localized by immunohistochemistry, with special attention to noncaseating granulomas. The results were compared with those from studies of ulcerative colitis (UC).

METHODS

We adopted the biotin-streptavidin-peroxidase method on frozen sections obtained at surgery from patients with CD or UC, and we immunohistochemically examined the expression of several cytokines (interferon-gamma, interleukin-2, -4, -10, and -12).

RESULTS

In normal colonic tissue, expression of these cytokines was rare except for interleukin-4. In actively inflamed areas of CD, increased expression of all cytokines by mononuclear cells was observed. In contrast, granulomas in CD involved interferon-gamma+ lymphocytes and interleukin-12+ macrophage-lineage cells (epithelioid cells and multinucleated giant cells) but few interleukin-4+ or -10+ cells. Actively inflamed areas of UC also showed an increase in the number of cytokine-containing cells; however, quantitative analysis revealed that there was more expression of interferon-gamma and interleukin-12, and less of interleukin-10, in CD than in UC, indicating the presence of more type 1 T-helper cells in CD tissue than in UC.

CONCLUSIONS

The findings of the present study suggest that granulomas of CD are coupled with type 1 T-helper responses; these responses may contribute to the pathogenesis of this disease.

[Applications of analytical ultracentrifuge to molecular biology and pharmaceutical science]

Analytical ultracentrifuges, XL-A and XL-I, developed by Beckman Company now find a broad application not only in universities but also in industries. Especially they are utilized conveniently in industries aiming at the development of proteins as a therapeutic drug or in those targeting drugs composed of small molecules developed on the basis of the structures of proteins. Sedimentation techniques can be used 1) to determine the molecular weight of proteins in solution, 2) to examine protein aggregation, 3) to evaluate the molecular shape of proteins, 4) to study the interaction of proteins, e.g. between ligands and receptors, and 5) to obtain insight into biological functions of homologous proteins. Application of this technique to molecular biology and pharmaceutical science will be reviewed with ample examples.

Lansoprazole decreases peripheral blood monocytes and intercellular adhesion molecule-1-positive mononuclear cells

We examined the effects of lansoprazole, a proton-pump inhibitor, on peripheral blood mononuclear cells in healthy subjects in comparison with ranitidine. Ten healthy volunteers were randomly divided into two groups and given either lansoprazole (30 mg daily for 2 days) or ranitidine (150 mg daily for 21 days). Peripheral blood was collected before and 7, 14, and 21 days after the start of treatment. Mononuclear cells were isolated by densitometric centrifugation and were examined for adhesion molecules (ICAM-1, VLA4, SLe(x)), membrane markers of the monocyte/macrophage series, and lymphocyte phenotypes. The number of cells expressing adhesion molecules, the number of monocytes/macrophages, and lymphocyte phenotypes were the same in Helicobacter pylori-positive and -negative subjects. The number of cells expressing ICAM-1 was significantly decreased seven days after the start of lansoprazole treatment, and this change persisted until day 14, while ranitidine had no effect. The number of monocytes (identified by Leu-M3 positivity) was decreased seven days after the start of treatment in both groups, but predominantly in the lansoprazole group. No other changes were observed on administration of either drug. These results suggest that short-term treatment with lansoprazole causes persistent inhibition of inflammatory responses irrespective of the presence of H. pylori infection. This effect may indicate a possible new mechanism of action of proton-pump inhibitors other than inhibition of acid secretion.

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.