Remangilones A-C, new cytotoxic triterpenes from Physena madagascariensis

Three new 24,28-dinorolean-3-one derivatives, the remangilones A-C (1-3), were isolated from the dried leaves of Physena madagascariensis using a human mammary carcinoma cell line to guide the isolation. The structures of 1-3 were deduced primarily from NMR studies. Compounds 1 and 3, remangilones A and C, respectively, were found to be cytotoxic against two human breast cancer cell lines and induced apoptosis at concentrations of 2.3 microM.

Tolerance of acid-adapted and non-adapted Escherichia coli O157:H7 cells to reduced pH as affected by type of acidulant

A study was carried out to determine if three strains of Escherichia coli O157:H7 grown (18 h) in Tryptic Soy Broth (TSB) and TSB supplemented with 1.25% glucose (TSBG), i.e. unadapted and acid-adapted cells, respectively, exhibited changes in tolerance to reduced pH when plated on Tryptic Soy Agar (TSA) acidified (pH 3.9, 4.2, 4.5, 4.8, 5.1 and 5.4) with acetic, citric or malic acids. All test strains grew well on TSA acidified with acetic acid at pH > or = 5.4 or malic acid at pH > or = 4.5; two strains grew on TSA acidified with citric acid at pH > or = 4.5, while the third strain grew at pH > or = 4.8. Acid-adapted and control (unadapted) cells differed little in their ability to form visible colonies on TSA containing the same acid at the same pH. However, on plates not showing visible colonies, acid-adapted cells retained higher viability than unadapted cells when plated on acidified TSA. Growth of acid-adapted and control cells of E. coli O157:H7 inoculated into TSB containing acetic acid (pH 5.4 and 5.7) and citric or malic acids (pH 4.2 and 4.5) was also studied. There was essentially no difference in growth characteristics of the two types of cells in TSB acidified at the same pH with a given acid. Tolerance of acid-adapted and control cells on subsequent exposure to low pH is influenced by the type of acidulant. The order of sensitivity at a given pH is acetic > citric > malic acid. When performing acid challenge studies to determine survival and growth characteristics of E. coli O157:H7 in foods, consideration should be given to the type of acid to which cells have been exposed previously, the procedure used to achieve acidic environments and possible differences in response among strains. The use of strains less affected by pH than type of acidulant or vice versa could result in an underestimation of the potential for survival and growth of E. coli O157:H7 in acid foods.

Neurotransmitters modulate cytokine-stimulated interleukin 6 secretion in rat intestinal smooth muscle cells

BACKGROUND & AIMS

Cytokine production by resident cells of the richly innervated muscularis externa may contribute to neuromuscular changes observed during intestinal inflammation. This study investigated neurotransmitter modulation of cytokine production by intestinal smooth muscle.

METHODS

We measured interleukin (IL)-6 messenger RNA expression by reverse-transcription polymerase chain reaction, IL-6 by bioassay, and cyclic adenosine monophosphate by enzyme immunoassay in rat cultured intestinal smooth muscle cells exposed to IL-1beta, in the presence or absence of neurotransmitters.

RESULTS

IL-1beta significantly increased IL-6 messenger RNA and protein. This was dose-dependently enhanced by vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), and norepinephrine and inhibited by [LYS1,PRO2,5,ARG3,4,TYR6]VIP and propranolol, respectively. Forskolin mimicked the stimulatory effects of these neurotransmitters on IL-6 secretion, and the protein kinase inhibitor6-22 amide abolished the actions of VIP, CGRP, and norepinephrine, but not that of human recombinant IL-1beta, on IL-6 secretion. These agents each increased cyclic adenosine monophosphate activity in muscle substance P, and the neurokinin 1 agonist Ac-[Arg6,Sar9,Met(O2)11] substance P(6-11) inhibited the IL-1beta-induced IL-6 release.

CONCLUSIONS

This study shows neuropeptide and sympathetic modulation of IL-1beta-induced IL-6 production by intestinal smooth muscle. These interactions may contribute to altered muscle function during intestinal inflammation.

Endothelial function and carotid artery wall thickening in patients with early essential hypertension

To investigate the relationship between endothelial function and carotid artery wall thickening in patients with early mild essential hypertension, the percent dilatation of humerus diameter and intimal-medial thickening (IMT) of common carotid artery was measured by using high-resolution ultrasound in 20 patients with early mild essential hypertension and 18 patients with normotension. The patients with hypertension had not been treated and their history of increased blood pressure was less than 12 months. In essential hypertension group, the percent dilatation of humerus diameter decreased significantly (2.65 +/- 0.98% vs 6.38 +/- 1.61%); IMT of carotid artery increased (0.88 +/- 0.16 mm vs 0.58 +/- 0.08). There was significant negative correlation between IMT and the percent dilatation of humerus diameter (gamma = -0.82, P < 0.05), and no correlation between IMT and 24 h mean systolic, diastolic pressure (gamma = 0.12 and gamma = 0.07, respectively; P > 0.05). Our results suggested that there was endothelial dysfunction in early mild essential hypertension. Endothelial dysfunction may not only contribute to the pathogenesis of hypertension but also serve as the most important inducing factor leading transformation from hypertension to atherosclerosis.

[Middle ear operation of children and juveniles]

OBJECTIVE

To analyse the results and effective factors of middle ear operation in children and juveniles.

METHOD

105 cases (146 ears) were analyzed retrospectively. 49 ears were followed up over 3 months.

RESULT

120 ear had perfect hearing materials. The difference of average air-bone gap between postoperation (21.86 +/- 13.15) dB HL and preoperation (35.20 +/- 13.87) dB HL was significant (P < 0.01).

CONCLUSION

Middle ear operation was a safe, effective operation in children and juveniles, reoperation also was proper option for someone if his first operation didn't success or repeated cases.

Influence of temperature and pH on survival of Escherichia coli O157:H7 in dry foods and growth in reconstituted infant rice cereal

Factors affecting the ability of Escherichia coli O157:H7 to survive in foods with a(w) less than required for growth have not been fully defined. This study was undertaken to determine the ability of E. coli O157:H7 to survive in a commercial dry infant rice cereal as affected by a(w) (0.35+/-0.04, 0.52+/-0.03 and 0.73+/-0.03), pH (4.0 and 6.8), and temperature (5, 25, 35 and 45 degrees C), and in nine other reduced-a(w) foods. Death of E. coli O157:H7 in cereal was enhanced with increased temperature and decreased pH during a 16- to 24-week storage period. Survival was enhanced at pH 6.8 compared to pH 4.0 in cereal at a(w) 0.34+/-0.04 during initial storage at 5 and 25 degrees C. The effect of temperature (8, 15, 21 and 30 degrees C) on survival and growth of acid-adapted cells of E. coli O157:H7 inoculated into cereal reconstituted with milk or apple juice at two inoculum levels (8.2-12.3 cfu/ml and 82-123 cfu/ml of slurry) was also studied. Growth occurred in cereal reconstituted with milk at all test temperatures and in cereal reconstituted with apple juice at 15, 21 and 30 degrees C. Populations increased by >1 log10 cfu/ml within 3-6 h at 21 and 30 degrees C. Acid-adapted and unadapted cells had similar growth patterns. The effects of temperature and acid adaptation on survival of E. coli O157:H7 in nine commercial foods and food ingredients with pH 4.07-6.49 and a(w) 0.17-0.82 were determined. The pathogen survived in these foods for various lengths of time, depending the storage temperature, with an order of survival of 5 degrees C >21 degrees C >37 degrees C. Survival appeared to be enhanced in foods with highest pH, and acid-adapted cells retained higher viability than unadapted cells in only two of the nine test foods. Of particular importance is the ability of E. coli O157:H7 to survive well in dry foods with a wide range in a(w) and pH, particularly at refrigeration temperature.

Deamination of methylamine and aminoacetone increases aldehydes and oxidative stress in rats

Semicarbazide-sensitive amine oxidase (SSAO)-mediated deamination of methylamine and aminoacetone in vitro produces carbonyl compounds, such as formaldehyde and methylglyoxal, which have been proposed to be cytotoxic and may be responsible for some pathological conditions. An HPLC procedure was developed to assess different aldehydes, which were derivatized with 2,4-dinitrophenylhydrazine (DNPH). We have demonstrated in vivo deamination of methylamine and aminoacetone by examining the excretion of formaldehyde and methylglyoxal, respectively, in rats. Following chronic administration of methylamine, the urinary level of malondialdehyde (MDA), an end product of lipid peroxidation, was also found to be substantially increased. A selective SSAO inhibitor blocked the increase of MDA. The results support the idea that increased SSAO-mediated deamination of methylamine and aminoacetone can be a potential cytotoxic risk factor.

[Morphometrical study on inhibitory effect of vitamin B6 and banana-stem extract on calcium crystallization]

OBJECTIVE

To search for the anticrystallization mechanism by vitamin B(6) and banana stem extract.

METHOD

Thirty-six male China-1 mice were divided into 4 groups: normal, crystallization, vitamin B(6) and banana-stem extract groups. Calcium oxalate crystallization was induced by 1% glycol and 1% ammonium chloride in the last 3 groups. Vitamin B(6) was then given to the 3rd group and banana stem extract to the 4th group for 3 weeks. At the end of 3 weeks, all the mice were sacrificed and the kidneys were taken for morphometrical studies using image analysis system and assayed for calcium oxalate.

RESULT

Morphometrical area density and numerical density of crystallization was significantly less in the vitamin B(6) group and the banana-stem extract group as compared with the crystallization group, being the least in the banana-stem extract group. Oxalate in renal tissue was also significantly reduced. Both vitamin B(6) and banana stem extract had no effect on renal tissue calcium.

CONCLUSION

Vitamin B(6) and banana-stem extract may be useful agents in the treatment of patients with hyperocaluric urolithiasis.

Pregnancy-induced changes in central response to atrial distension mimicked by progesterone metabolite

In virgin female rats, atrial distension (an index of blood volume expansion) causes an increase in c-fos expression in the paraventricular nucleus of the lateral hypothalamus. During pregnancy, this response is markedly attenuated. We tested the effects of 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha-OH-DHP) on activation of central pathways following stimulation of the atrial volume receptors. Not only does this progesterone metabolite increase during pregnancy, but it has already been implicated in pregnancy-induced changes in the baroreflex. Female rats were prepared with indwelling venous cannulas and intracardiac balloons that, when inflated, caused a discrete localized stimulation of the atrial volume receptors in the absence of changes in cardiac hemodynamics. Seven days later, the rats were infused with 3alpha-OH-DHP dissolved in cyclodextrin and the intracardiac balloons were inflated. One hour later, the rats were killed and fixed by perfusion and the brains were prepared for visualization of c-fos activity. Infusion with 3alpha-OH-DHP significantly reduced the central response to atrial distension, i.e., it mimicked pregnancy. These results are consistent with the suggestion that this metabolite of progesterone may be an important factor in cardiovascular adaptation to pregnancy.

Modeling and optimization of enantioseparation by capillary electrochromatography

Both electrophoretic and chromatographic transport mechanisms are combined in electrochromatographic separation. In this paper, we developed a model of enantioselectivity in capillary electrochromatography (CEC) which can be applied in the separation of both neutral and ionic compounds. The overall selectivity in enantioseparation is considered to be made up of two contributions: one is the intrinsic difference in formation constants of a pair of enantiomers, and the other is the conversion efficiency of the intrinsic difference into the apparent difference in the migration velocity. The model was illustrated through the chiral separation of (R)- and (S)-salsolinols. Under a positive electric field, enantioseparation of salsolinols was achieved on an ODS column with beta-cyclodextrin as a chiral mobile-phase additive. The experimental results are discussed in relation to the effect of separation parameters, such as the direction and size of electric field and properties of the stationary and mobile phases. It was demonstrated that if both electrophoretic and partitioning mechanisms produce positive effects, high overall selectivity in CEC can be obtained. For pressurized-driven electrochromatography, although the column efficiency is sacrificed due to the introduction of hydrodynamic flow, the increased selectivity significantly reduced the requirement of large column plate numbers for resolution.

[Mechanism of CD44V6 in human colorectal carcinoma metastasis]

OBJECTIVE

To study the mechanism of CD44V6 in human colorectal carcinoma (HCC) matastasis.

METHODS

The effects of CD44V6 on HCC cell adhering to base membrane and vascular endothelium were investigated by human amniotic membrane invasion model and co-culturing HCC cell with vascular endothelium. The influence of CD44V6 variants on cytoskeleton and gap junctional intercellular communication (GJIC) was studied by immunofluorescent confocal 3-dimensional reconstruction and fluorescence recovery after photobleaching technique.

RESULTS

CD44V6 antibody can decrease the ability of HCC cells to adhere to amniotic membrane and vascular endothelium. It also can affect the distribution, polymerization and depolymerization of actin of HCC cells, but does not significantly affect GJIC of HCC cells.

CONCLUSIONS

CD44V6 may play an important role in promoting HCC cells to adhere to vascular endothelium and base membranes and may affect the distribution, polymerization and depolymerization of actin in HCC cells and facilitate HCC cell metastasis.

[Clinical observation and anatomical analysis of middle turbinate and ethmoidal internal wall moved to external side after microsurgery]

OBJECTIVE

To assess the effect of middle turbinate (MT) and ethmoidal internal wall(EIW) moved externally after microsurgery.

METHODS

Twenty-four cases (45 sides) were followed-up endoscopically for (16.3 +/- 9.3) months. Thirteen cases (24 sides) were observed by CT scans. Three cadaver heads were measured for anatomical analysis.

RESULTS

Forty-one (91%) of 45 sides obtained better olfactory function after operation. Twenty-two (91%) of 24 sides were found to have better CT changes in sinus ventilation as compared with preoperative CT scans. The gap between the MT and EIW to the orbital wall was (12.0 +/- 1.0) mm, while that between the ethmoidal bulla and processus uncinatus was only (2.3 +/- 0.6) mm as revealed in the autopsy.

CONCLUSION

MT and EIW moderately moved suitably to externally had no bad effect on sinus ventilation, and it improved olfaction.

Adrenomedullin suppresses atrial natriuretic factor (ANF) secretion from isolated atrium

Atrial natriuretic factor (ANF) secretion was studied using isolated perfused right atria prepared from rats. Adrenomedullin (ADM), a recently identified 52-amino acid peptide whose biological activity has a striking resemblance to that of ANF, was added to the perfusate at a concentration of 1 microg/ml. The concentration of ANF secreted into the perfusate was measured by radioimmunoassay, under basal conditions (atrial wall unstressed), and during atrial distention (intraluminal pressure raised to 4 and to 6 cm water). It was found that basal secretion of ANF was not altered by ADM. However, when intraluminal pressure was raised, there was a significantly smaller increase in ANF secretion in the ADM-infused atria than in the control atria. It is concluded that ADM significantly reduces stretch-induced secretion of ANF, while having only minimal effects on basal secretion. Such an inhibitory mechanism would ensure the necessary negative feedback mechanism to counter the previously-reported stimulatory actions of ANF on ADM secretion. Moreover, these results support the hypothesis that ADM could be responsible for the reduction in stretch-induced ANF release observed during pregnancy.

[The responses of the microvasculature of the periodontal ligament to horizontal force]

OBJECTIVE

The purpose of this study is to examine the responses of the microvasculature in periodontal ligament(PDL) to horizontal force.

METHODS

Using ink injections and celloidin embed, serial sections were cut, then observed by light micrascope, quantitative analysis was conducted by the picture-analysis instrument. Vascular corrosion casts were prepared and examined by scanning electron microscopy. The forth premolars of dogs were pulled by 200 g force in a mesial direction for two hours, and the pressure effects in different positions were demonstrated.

RESULTS

The section area of the microvasculature per unit PDL area is obvious larger on the tension sides than on the pressure sides. There is not an obvious distinction on the pressure sides between the experiment groups and control groups. However, there are clear distinctions in the one-third of cervical, and apical segment on the tension sides between the experiment groups and control groups.

CONCLUSION

The microvascular changes in PDL had importance to the cushioning effect of PDL when a teeth received a kind of force in a short-time.

[The influence of basic fibroblast growth factor on the adherence of endothelial cell to polyurethane]

This study addressed the problem of how to promote the adherence of endothelial cells (EC) to polyurethane (PU). The influence of basic fibroblast growth factor (bFGF) on the adherence of EC to PU was observed by using the fluorescent method. The results showed that the attachment rates for two bFGF groups(PU precoated with fibronectin and PU precoated with collagen IV) were 71% and 68.5%, which were significantly higher than those (62.5% and 55.25%) for two control groups, respectively. These demonstrate that bFGF can promote EC attachment to PU, and suggest that bFGF can be used as a supplement factor in media for achievement of endothelialization on artificial heart and blood vessels.

[Studies on target localization of Parkinson's disease treated with gamma knife]

Ninety cases of Parkinson's disease were treated in our center from Dec. 1993 to Aug. 1997. Based on our work, we have developed a method for the MR localization in the treatment of Parkinson's disease with Gamma knife, including the fixing of stereotactic frame, the selection of target, and the correction of the target's coordinates. In this paper, the effects of fixing of coordinate frame on the localization of target have been analyzed. Also presented are the errors of the coordinates of the selected targets, compared with those corrected. The method reflects a new idea for target localization.

Generation of reactive oxygen species accounts for cytotoxicity of an endogenous dopaminergic neurotoxin, (R)-N-methylsalsolinol, to differentiated dopaminergic SH-SY5Y cells

The mechanism of the cytotoxicity of endogenous dopamine-derived (R)-1,2-dimethyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline [(R)-N-methylsalsolinol] to differentiated human dopaminergic neuroblastoma SH-SY5Y cells was studied using a reduction-oxidation indicator, Alamar Blue. N-Methylsalsolinol and its oxidation product, 1,2-dimethyl-6,7-dihydroxyisoquinolinium ion, were found to inhibit oxidative phosphorylation, as shown by the Redox capacity. Antioxidants, such as reduced glutathione, catalase, Tris and n-propyl gallate, reduced the cytotoxicity of N-methylsalsolinol, suggesting that hydroxyl radical was the major reactive oxygen species for the cytotoxicity. Deprenyl also protected the cells from the decrease of the Redox capavity by N-methylsalsolinol. However, antioxidants did not protect the cells from the cytotoxicity of the catechol isoquinolinium ion. The results suggest that oxidative stress induced by hydroxyl radical may be involved in the cell death of dopaminergic neurons by N-methylsalsolinol.

Assembly of MHC class I molecules with biosynthesized endoplasmic reticulum-targeted peptides is inefficient in insect cells and can be enhanced by protease inhibitors

To study the requirements for assembly of MHC class I molecules with antigenic peptides in the endoplasmic reticulum (ER), we studied Ag processing in insect cells. Insects lack a class I recognition system, and their cells therefore provide a "blank slate" for identifying the proteins that have evolved to facilitate assembly of class I molecules in vertebrate cells. H-2Kb heavy chain, mouse beta 2-microglobulin, and an ER-targeted version of a peptide corresponding to Ova(257-264) were expressed in insect cells using recombinant vaccinia viruses. Cell surface expression of Kb-OVA(257-264) complexes was quantitated using a recently described complex-specific mAb (25-D1.16). Relative to TAP-deficient human cells, insect cells expressed comparable levels of native, peptide-receptive cell surface Kb molecules, but generated cell surface Kb-OVA(257-264) complexes at least 20-fold less efficiently from ER-targeted peptides. The inefficient assembly of Kb-OVA(257-264) complexes in the ER of insect cells cannot be attributed solely to a requirement for human tapasin, since first, human cells lacking tapasin expressed endogenously synthesized Kb-OVA(257-264) complexes at levels comparable to tapasin-expressing cells, and second, vaccinia virus-mediated expression of human tapasin in insect cells did not detectably enhance the expression of Kb-OVA(257-264) complexes. The assembly of Kb-OVA(257-264) complexes could be greatly enhanced in insect but not human cells by a nonproteasomal protease inhibitor. These findings indicate that insect cells lack one or more factors required for the efficient assembly of class I-peptide complexes in vertebrate cells and are consistent with the idea that the missing component acts to protect antigenic peptides or their immediate precursors from degradation.

[Histopathology observations of the facial nerve on dehiscence of the facial nerve canal]

OBJECTIVE

To explore the possible histopathologic changes induced by the seriously defective epinurium on congenital dehiscent facial nerve canal.

METHODS

The facial nerves at the dehiscent facial nerve canal of 885 human temporal bones from otopathology laboratory of the University of Minnesota, USA were observed histopathologically under light microscope.

RESULTS

It showed that the seriously defective epineurium at the dehiscence was found in 48 ears. Of the 48 ears, the facial nerves in forty ears had herniated out from the dehiscence area, in thirteen ears on the outgrowing facial nerve had at the dehiscence areas and facial nerves in three ears with otitis media was obviously infiltrated with inflammatory cells. No similar pathologic change was found in all the 837 ears with the dehiscence covered by epineurium.

CONCLUSION

The seriously defective epineurium at the dehiscencesite is a histological cause for the herniation of facial nerve and formation of outgrowing Schwannomas and inflammatory infiltration of facial nerve.

[The composition and distribution of some kinds of anaerobic microorganisms in Yinqion basin]

Under the strictly anaerobic conditions, the population of Sulfate-reducing bacteria, fermentative bacteria and methanogenic bacteria of serial samples got from erect sections of different Sedimentary of Yingqiong basin (a typical marine sedimentary environment) were measured by MPN method. The morphology of different kinds of bacteria and the metabolic types of methanogen and methanogenic activity were observed. The relation between population of bacteria and some indexes were compared. The results show that SRB present in all of the samples. The distribution of SRB and fermentative bacteria have no interrelation with the depth of samples but SRB has interrelation with the SO(4)2- concentration, and fermentative bacteria has negative interrelation with the contents of organic matter. Two kinds of methanogen present in all of the samples. They belong to Methanobacterium and Methanococcus, respectively. Their types of nutriment are H2/CO2.

[Expression of CD44V6 and its effects on cytoskeleton in human colorectal carcinoma cell lines]

OBJECTIVE

To observe the expression of CD44V6 and its effects on cytoskeleton in human colorectal carcinoma(HCC) HT29 and LoVo cell lines.

METHODS

Expression of CD44V6 variant in HCC HT29 and LoVo cell lines was investigated by in situ hybridization, immunohistochemistry and quantitative immunofluorescence technique. The effects of CD44V6 variants on cytoskeleton was studied by immunofluorescence and confocal 3 dimension reconstruction technique.

RESULTS

CD44V6 was expressed at the mRNA and protein levels in both HT29 and LoVo cell lines, but the expression was higher in LoVo cells than in HT29 cells. When the HT29 cells and LoVo cells were blocked by monoclonal antibodies, it was found that changes developed in the cytoskeleton of these cells.

CONCLUSIONS

The expression of CD44V6 is related to the metastatic potentiality of human colorectal carcinoma cells. CD44V6 may affect the distribution, polymerization and depolymerization of actin of HCC cells and promote HCC cell metastasis.

Cloning, characterization, and the complete 56.8-kilobase DNA sequence of the human NOTCH4 gene

The first complete mammalian genomic sequence reported thus far in the Notch gene family, including a putative promoter region and 30 exons of the human NOTCH4 gene spanning 56.8 kb of DNA, were sequenced. The NOTCH4 locus contains a TATA-less promoter with two putative transcription initiation sites (Inr), three RBP-Jkappa sites, and two GATA recognition sites. Two cDNA isoforms, NOTCH4(L) and NOTCH4(S),were identified. Whereas the NOTCH4(S) isoform contains the entire coding sequence, the NOTCH4(L) isoform has two unspliced intronic sequences between exons 11 and 12 and exons 20 and 21 and a misspliced exon 6. Consistent with these results, two alternatively spliced isoforms of transcripts of approximately 9.3 and 6.7 kb were detected by Northern blot analysis. The predicted amino acid sequence of the NOTCH4 protein based on the NOTCH4(S) cDNA sequence contains 2003 amino acids and includes the predominant motifs of the Notch family: 29 epidermal growth factor (EGF)-like repeats, 3 Notch/lin-12 repeats, a transmembrane region, 6 cdc10/Ankyrin repeats, and a PEST domain.

Identification of unfolding domains in large proteins by their unfolding rates

Three unfolding domains in rabbit muscle aldolase destabilized in 3 M urea have been identified from their unfolding rate constants (0.10, 0.036, and 0.0064 min-1). The populations of folded and various, partially unfolded forms were determined by amide hydrogen exchange and mass spectrometry. Results of this study show that unfolding domains may include multiple, noncontiguous segments of the backbone and that different regions of helices may belong to different unfolding domains. In addition, these results show that the domain unfolding most rapidly is located distant from the subunit binding surfaces and has the greatest access to the denaturant. The bimodal intermolecular distributions of deuterium found in this study show that unfolding of these domains is cooperative. It is proposed that these unfolding domains are correlated with local energy minima in the free-energy folding surface of aldolase. In addition to the three unfolding domains, there are three short segments that do not unfold in 3 M urea. These segments, which are located in the subunit binding surface, identify the most stable regions of aldolase. This study also demonstrates that it is now possible to identify and characterize unfolding domains in relatively large (Mr 158 000) proteins.

Thrombomodulin modulates growth of tumor cells independent of its anticoagulant activity

Thrombomodulin (TM), recognized as an essential vessel wall cofactor of the antithrombotic mechanism, is also expressed by a wide range of tumor cells. Tumor cell lines subcloned from four patients with malignant melanoma displayed a negative correlation between TM expression and cell proliferation in vitro and in vivo. Overexpression of wild-type TM decreased cell proliferation in vitro and tumor growth in vivo. TM mutants with altered protein C activation capacity lead to a similar effect. In contrast, transfection of melanoma cells with mutant TM constructs, in which a portion of the cytoplasmic or lectin domain was deleted, abrogated the antiproliferative effect associated with overexpression of wild-type TM. Experiments performed with either peptide agonists/antagonists of the thrombin receptor, with hirudin, or with inhibitors of thrombin-TM interaction did not alter the growth inhibitory effect of TM overexpression. These data suggest that TM exerts an effect on cell proliferation independent of thrombin and the thrombin receptor, possibly related to the binding of novel ligands to determinants in the lectin domain which might trigger signal transduction pathways dependent on the cytoplasmic domain.