[The survival rate of impaired glucose tolerance groups in the elderly]

We analyzed a total of 468 cases, all inmates of the Yokufukai Home for the Aged who had undergone a 50-gram oral glucose tolerance test (OGTT) from January 1980 to December 1981 and who were followed up to the end of March 1994. All cases were divided into different normal, borderline and diabetic categories according to glucose tolerance. 1) Normal cases accounted for 39.6% of males and 39.2% of females, 50% and 52.5% were borderline cases in males and female and these were 10.4% and 8.3% diabetic cases, respectively. 2) The overall survival rate of females was significantly higher than that of males groups (p < 0.05). 3) There was no significant difference in survival rate of males and females in the normal and impaired glucose tolerance groups (border and diabetic). CONCLUSION. Mildly impaired glucose tolerance could be considered as part of the normal aging process.

Presence of activated eosinophils, high IgE and sCD23 titers in gingival crevicular fluid of patients with adult periodontitis

Our previous studies showed that the expression of CD23 on polymorphonuclear leukocytes (PMNLs) in gingival crevicular fluid (GCF) from adult periodontitis (AP) patients was higher than in autologous peripheral blood (PB). Percentages of eosinophils in GCF PMNLs ranged between 6 and 14%. The purpose of the present studies was to increase understanding of the potential role of eosinophils and their products, including CD23, in periodontal disease. We analysed the eosinophil fraction in GCF and PB by flow cytometry using monoclonal antibodies to CD23b (BB10), eosinophil cationic protein (ECP) in stored and secretory forms (EG1 and EG2), and CD67 (80H3). Simultaneously, we measured IgE and soluble CD23 titer and GCF and serum by ELISA. Flow cytometric analysis of BB10, EG2 and 80H3 binding showed that GCF eosinophils from AP were activated. A large BB10+ EG2+ cellular fraction was detected in GCF from AP whereas it was very low in autologous serum (9.30 +/- 2.460 vs 0.16 +/- 0.10, p < 0.001). GCF from gingivitis patients exhibited no flow cytometric evidence for the presence of BB10+ EG2+ cells. BB10+ EG1+ cells, or inactivated eosinophils rated lower in GCF than in PB both in gingivitis and periodontitis patients (0.45 +/- 0.63 vs 1.83 +/- 0.96 and 0.15 +/- 0.30 vs 1.30 +/- 0.20, p < 0.05, respectively). IgE titer in AP patients reached 1208.1 +/- 421.2 IU/ml in GCF while only 49.1 +/- 50.4 in sera. Soluble CD23 in GCF reached 236.1 +/- 81.3 ng/ml in GCF and 5.6 +/- 1.8 ng/ml in sera. GCF of gingivitis patients, however, contained no detectable sCD23.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation of elastin expression by minoxidil in chick skin fibroblasts

Minoxidil inhibited the proliferation of embryonic skin fibroblasts during the growth phase but not during the stationary phase. Minoxidil stimulated elastin synthesis two-fold in a dose-dependent manner at a concentration of 1 mM during the stationary phase. The stimulation of elastin synthesis paralleled a comparable increase in elastin mRNA level. These results suggest that the stimulation of elastin expression by minoxidil in skin fibroblasts was controlled at the elastin mRNA level and also suggest that its elastin-stimulating effect is not related to the suppressive effect on cell proliferation. Minoxidil appears to be a potent stimulator for elastin expression in skin fibroblasts.

Metallothionein binding zinc inhibits nuclear chromatin decondensation of human spermatozoa

Nuclear chromatin decondensation (NCD) of the human spermatozoa was induced by 1% sodium dodecyl sulphate (SDS). NCD of the spermatozoa induced in healthy and fertile men was significantly stronger and at higher rates than that in infertile men. In 1% SDS with 6 mM zinc chelating EDTA, metallothionein (MT) significantly enhanced NCD in a healthy man. In contrast MT alone significantly inhibited sperm NCD. Sperm NCD rate induced by 1% SDS in 10 infertile men was significantly inhibited by adding 75 or 750 micrograms ml-1 of MT. By adding 1.5 mM zinc, MT at concentrations of 0.75, 7.5, 75, or 750 micrograms ml-1, enhanced the inhibitory effect of 1.5 mM zinc. This suggested that thiols in the MT could, when liberated from zinc by zinc-chelating EDTA, induce sperm decondensation by cleaving stabilizing S-S bridges and that zinc bound to MT could exert a chromatin stabilizing effect mediated by the zinc dependent type of chromatin stability. The present study suggested that zinc bound to MT, which is secreted mainly from the prostate gland, is one factor that contributes to the chromatin stabilizing effect of human prostatic fluid.

Characterization of an established human hepatoma cell line constitutively expressing non-structural proteins of hepatitis C virus by transfection of viral cDNA

A human hepatoma cell line constitutively expressing proteins of hepatitis C virus (HCV) was established by transfection with cDNA encoding part of the virus nonstructural (NS) genome region. Proteins consistent with authentic processing at NS3/NS4A, NS4A/NS4B and NS4B/NS5A were identified. Pulse-chase experiments indicated that the cleavage between NS3 and NS4A occurred first and cleavage at other sites followed. Expression of specific surface antigens in response to the presence of HCV proteins was analysed by flow cytometry. A significant increase in CD26 expression was observed in cells expressing the HCV proteins. CD26 plays an important role in cellular signal transduction. Its upregulation in response to the presence of HCV proteins may play a role in viral pathology.

[Clinical analysis of ureteral injuries]

Six cases of ureteral injuries were analyzed. Two cases were male and 4 cases were female. The right side was affected in 1 case and the left in 5 cases. The affected portion was the uretero-pelvic junction in 1 case and lower iliac vessels in the other cases. Five cases were iatrogenic injuries in surgical or gynecological pelvic operation, and the other was due to blunt trauma. Intraoperative diagnosis was made in 4 cases. Drain leakage led to diagnosis in one case and pyelonephritis in another. Ureteroureterostomy was performed in 2 cases, pyeloureterostomy in 1 case, ureteroneocystostomy with psoas hitch in 1 case, Boari bladder flap in 1 case and simple suture in 1 case. 4-0 or 5-0 Dexon with an atraumatic needle was used for all anastomoses. Except for case 1, who died of the recurrence of carcinosarcoma, renal functions were preserved in all patients during the follow-up period ranging from 5 months to 7 years 8 months.

Characterization of enriched CD34+ cells from healthy volunteers and those from patients treated with chemotherapy plus granulocyte colony-stimulating factor (G-CSF)

CD34+ cells were enriched, using a panning method, from peripheral blood (PB) and bone marrow (BM) of healthy volunteers and of patients treated with chemotherapy plus granulocyte colony-stimulating factor (G-CSF). In healthy volunteers, PB CD34+ cells expressed CD33 and CD13 at a higher frequency than BM CD34+ cells, and PB CD34+ cells contained a greater number of burst-forming units-erythroid (BFU-E) than colony-forming units granulocyte-macrophage (CFU-GM). Administration of G-CSF to healthy volunteers induced a marked increase in the number of PB CD34+ cells, although the proportions of those expressing CD33, CD13, and c-kit among these cells as well as colony-forming ability were not changed before and after G-CSF administration. There were no significant differences in surface antigens on PB CD34+ cells between healthy volunteers and patients after chemotherapy plus G-CSF, except for low expression of c-kit in the PB of patients. However, PB CD34+ cells from patients contained almost the same number of CFU-GM as BFU-E. These results indicate that there were clear differences in the features of CD34+ cells from BM and from PB, and between healthy volunteers and patients after chemotherapy plus G-CSF. Enriched CD34+ cells are useful for analyzing the characteristics of hematopoietic progenitor cells, and such analysis may predict the usefulness of autologous or allogeneic peripheral blood stem cell transplantation.

Regulatory role of gamma delta T cells in uterine intraepithelial lymphocytes in maternal antifetal immune response

To elucidate the potential roles of the gamma delta T cells in uterine intraepithelial lymphocytes (IEL) in the regulation of maternal antifetal immune response during pregnancy, we examined the kinetics and function of gamma delta T cells in uterine IEL obtained from (C3H/He x AKR/J) pregnancy. The number of gamma delta T cells increased in the uterine IEL in (C3H/HexAKR/J) pregnancy more than those in (C3H/HexC3H/He) pregnancy and much more than in nonpregnant C3H/He mice. The uterine IEL in (C3H/HexC3H/He) pregnancy significantly proliferated in response to AKR/J stimulator cells. In contrast, the uterine IEL in (C3H/HexAKR/J) pregnancy showed little, if any, proliferation in response to the same stimulator cells. gamma delta T cell depletion from the uterine IEL in (C3H/HexAKR/J) pregnancy restored their responsiveness against AKR/J stimulator cells. Both gamma delta T cell-enriched fraction and alpha beta T cell-depleted fraction, but neither gamma delta T cell-depleted fraction nor alpha beta T cell-enriched fraction in the uterine IEL exhibited suppressive activity against allogeneic responses of nonpregnant C3H/He LN cells. This suppressive activity was shown by transferring the supernatant of culture medium in the uterine IEL stimulated with AKR/J cells that contained a large amount of TGF-beta, and the suppressive activity was significantly blocked by addition of anti-TGF-beta mAb to the culture. Taken together, our results suggest that gamma delta T cells in the uterine IEL suppress the maternal antifetal immune response at the maternal-fetal interface at least in part through TGF-beta production to prevent a rejection of the fetus.

The effects of delta-opioid receptor agonists on synaptic transmission in hamster submandibular ganglion

The effects of agonists for delta-opioid receptors on synaptic transmission in hamster submandibular ganglion were studied in vitro, using an intracellular recording technique. [Met5]enkephalinamide (17 microM), [D-Ser2¿Leu-enkephalin-Thr (14 microM) and [D-Pen2, D-Pen5]enkephalin (10 microM), delta selective agonists caused reversible depression of the fast EPSP amplitude in 10 of 30 cells tested. The inhibitory actions of [D-Pen2, D-Pen5]enkephalin were antagonized by ICI 174,864, a delta selective antagonist. Naloxon a non-selective antagonist and ICI 174,864 both also potentiated the fast EPSP amplitude in 5 of 11 cells tested.

1H-NMR and EPR studies on met-azido and met-imidazole Dolabella auricularia myoglobin

Met-azido and met-imidazole forms of the myoglobin from the mollusc Dolabella auricularia have been studied by 1H-NMR and EPR spectroscopy. In the mollusc myoglobin, in which His-E7 is replaced by Val, the guanidino group of Arg-E10 serves as an alternative hydrogen-bond donor to the bound ligand. Therefore, the guanidino group of Arg-E10 plays similar roles in ligand stabilization to that the His-E7 imidazole does in most vertebrate myoglobins. Differences in both the structural and electronic properties between Arg and His side chains largely affect the stability of met-azido and met-imidazole forms of the protein. Due to a weak stabilization by Arg-E10, the bound-N3- ligand is replaced by OH- at higher pH, although it is stable at neutral and acidic pH. In the absence of the hydrogen-bonding interaction, Fe-bound imidazole in met-imidazole Dolabella myoglobin is only stable at neutral pH and is removed at acidic pH and replaced by OH- at basic pH. The temperature study also revealed that the bound imidazole is replaced by OH- at higher temperature. These results confirm that the presence of steric hindrance between these bulky ligands and the long and bulky side chain of Arg-E10 in the distal pocket of the mollusc myoglobin. Thus steric effects contribute significantly to the stability of exogenous ligand in the distal pocket of myoglobin.

Interaction between discriminative stimulus effects of cocaine and morphine

We recently demonstrated that combining cocaine and morphine could enhance their reinforcing effects which may be mediated by the dopaminergic system. In the present study, the effects of cocaine and morphine on the discriminative stimulus effects of morphine and cocaine, respectively, were examined. Furthermore, dopaminergic mediation in the discriminative stimulus effects of morphine was also examined. Pretreatment with 1.0 or 3.0 mg/kg morphine shifted the dose-response curve for cocaine to the left, and 3.0 mg/kg morphine significantly potentiated the discriminative stimulus effects of cocaine. On the other hand, neither 1.25 nor 2.5 mg/kg cocaine affected the discriminative stimulus effects of morphine. These results suggest that potentiation of the discriminative stimulus effects of cocaine by morphine may reflect the enhancement of reinforcing effects in the combination of cocaine and morphine. Furthermore, neither SCH23390 (D1-receptor antagonist) nor haloperidol (D2-receptor antagonist) affects the discriminative stimulus effects of morphine, while combining these drugs slightly attenuated the effects of morphine. Thus, another neurotransmitter rather than dopamine may play an important role in the discriminative stimulus effects of morphine. Therefore, the discriminative stimulus effects of morphine are apparently not potentiated by cocaine, unlike those of reinforcing effects.

Mechanism of chromium(VI) toxicity in Escherichia coli: is hydrogen peroxide essential in Cr(VI) toxicity?

To investigate the role of hydrogen peroxide in Cr(VI) toxicity in vivo toward bacterial cells, we examined the effect of Cr(VI), hydrogen peroxide, sodium azide, and mannitol on the viability of Escherichia coli. Bacterial cells were incubated for 1 h with shaking in the presence of Cr(VI), hydrogen peroxide, sodium azide as catalase inhibitor, and/or mannitol as radical scavenger. The colony-forming ability and double-strand DNA degradation were examined. The viability assays revealed that Cr(VI) toxicity depended on hydroxyl radicals generated in the reaction involving hydrogen peroxide and chromium. Moreover, incubation of E. coli cells with 10 mM Cr(VI) and 3 mM hydrogen peroxide caused the degradation of double-strand DNA in vivo, which was suppressed by the addition of mannitol. These results indicated that hydroxyl radicals generated in the incubation degraded DNA of E. coli cells, resulting in cell death. In the absence of added hydrogen peroxide, the intracellular concentration of hydrogen peroxide in E. coli was low (below 1 microM). A catalase-defective strain incubated in the absence of added hydrogen peroxide remained fully viable after 1 h but showed decreased viability after prolonged incubation (4-8 h). The addition of mannitol suppressed this decrease, suggesting that hydroxyl radicals may be involved in the expression of Cr(VI) toxicity even without added hydrogen peroxide.

[Arterial oxygen saturation monitoring of sleeping infants by pulse-oximeter--effect of sleeping position on arterial oxygen saturation in infants]

Monitoring of the arterial oxygen saturation (SaO2) in two sleeping infants was reported. They were a couple of female twins and had grown up normally after admission to NICU (Neonatal Intensive Care Unit) for a month. We investigated their SaO2 with the puls-oximeter at the terms between the 2nd and the 10th month. There was no significant difference between SaO2 in prone positions (n = 29) and that in supine positions (n = 30). In the infant with the sniffing conditions, however, SaO2 in prone positions seemed to be slightly lower than that in the healthy conditions. The slightly low SaO2 would give no effects on the healthy infants, but it may cause ALTE (Apparent Life Threatening Event) or death from SIDS (Sudden Infant Death Syndrome) to some infants who are not in good health and/or who are prone to get into ALTEA or SIDS. Especially, in the sniffing condition with hyperthermia, as the oxygen dissociation curve sifts to right and SaO2 degradation appears easily, sudden infant death may be possible to happen in prone position.

Phosphatidyl inositol-phospholipase C in squid photoreceptor membrane is activated by stable metarhodopsin via GTP-binding protein, Gq

Phosphatidyl inositol-phospholipase C (PI-PLC) in squid retina was studied by immunoblotting and its activities were determined using [3H]phosphatidyl inositol bisphosphate ([3H]PIP2) as substrate. PI-PLC activity was found mostly in soluble fraction when the retina homogenate was treated with 400 mM KCl, but was associated with rhabdomal membranes under low salt conditions (20 mM Hepes). A protein with apparent molecular mass of 130kD was recognized by an antibody against PLC beta 4/norp A in both 400 mM KCl soluble and rhabdomal membrane fractions. A 42 kD protein recognized by antibody against the C-terminus of Gq alpha was also present in these two fractions. GTP gamma S stimulated only the PI-PLC activity associated with membrane and was magnesium dependent. PI-PLC activity was found to be (i) highly dependent upon calcium concentrations, (ii) enhanced by GTP but not by other nucleotides, and (iii) significantly stimulated by light at lower concentrations of GTP gamma S. The stimulation by light was still observed when irradiated membrane was incubated at 10 degrees C for 10 min and then mixed with GTP gamma S. These results suggest that stable metarhodopsin stimulates a PLC beta 4/norp A-like enzyme via a G-protein, Gq.

[A case report of dural sinus thrombosis: direct thrombolytic therapy using endovascular surgery]

Dural sinus thrombosis, a relatively rare disease, is difficult to diagnose because of variable symptomatic manifestations. We successfully treated a case of dural sinus thrombosis by direct thrombolysis using an endovascular technique in combination with postoperative anticoagulant therapy. The patient, a 19-year-old female, developed a headache affecting her whole head on December 13, 1993. She was admitted to our hospital the next day. Neurological examination upon admission revealed no neurological abnormalities, nor was there any abnormality in CT scan, either plain or enhanced, taken on the day of admission. The patient's consciousness deteriorated in the early morning of December 22. MRI and cerebral angiography revealed thrombi from the confluence of the sinuses to the right transverse and sigmoid sinus, with disturbed circulation through deep cerebral veins. Systemic thrombolytics, steroid and mannitol were started, but, on the next day, the third ventricle was compressed by bilateral swelling of the basal ganglia, with hydrocephalus. Since her consciousness deteriorated further despite ventricular drainage and barbiturate therapy, direct thrombolytic therapy was performed on December 25. A catheter was placed in the superior sagittal sinus, and 600,000 units of urokinase was locally injected, followed by postoperative anticoagulant therapy. The patient's condition improved rapidly. On CT scan, the bilateral swelling of the basal ganglia disappeared along with the hydrocephalus. At about 1 month after endovascular surgery, MRI and cerebral angiography revealed recanalization of the deep cerebral veins, straight sinus and confluence of sinuses with improved opacification of the left transverse sinus, although the right transverse sinus was found to be re-occluded.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of losartan, an AT1 selective angiotensin II receptor antagonist, on isoproterenol-induced cardiac ornithine decarboxylase activity

Ornithine decarboxylase (ODC,EC 4.1.1.7), a rate-limiting enzyme in polyamine biosynthesis, is known to be induced by a beta-adrenoceptor agonist, isoproterenol (ISO). ODC activity and cardiac polyamine content are considered to be correlated with ISO-induced cardiac hypertrophy in rat hearts. To determine whether ISO-induced cardiac ODC activity is mediated through the renin-angiotensin system, especially at the AT1-receptor, we used a nonpeptide AT1 receptor antagonist, losartan, in this study. Losartan (10 mg/kg) suppressed both heart ODC and polyamine contents in ISO-treated rats. Although metoprolol (a selective beta-adrenoceptor antagonist) totally suppressed ODC activity, these results suggest that ISO-stimulated cardiac ODC activity may be regulated through beta 2-adrenoceptors coupled with AT1 receptors in rats.

Sialidase of swine influenza A viruses: variation of the recognition specificities for sialyl linkages and for the molecular species of sialic acid with the year of isolation

The sialidase of swine influenza A viruses of N1 and N2 subtypes, isolated from 1930 to 1992, was studied for substrate specificity with ganglio-series, lacto-series type II and GM3 gangliosides containing Neu5Ac alpha 2-3Gal, Neu5Gc alpha 2-3Gal and Neu5Ac alpha 2-6Gal linkages. All viral sialidases tested showed that the activity for hydrolysing substrates with Neu5Ac alpha 2-3Gal was higher than the activities with Neu5Gc alpha 2-3Gal and Neu5Ac alpha 2-6Gal linkages. When GM1b, GM3 and sialylparagloboside were used as substrates, the earliest strain (A/Wisconsin/15/30 H1N1, isolated in 1930) showed the activity ratio of Neu5Ac alpha 2-6Gal to Neu5Ac alpha 2-3Gal to be 0.13:0.2, and the ratio Neu5Gc alpha 2-3Gal/Neu5Ac alpha 2-3Gal to be 0.19:0.37, while those strains isolated from 1978 to 1992 exhibited ratios of 0.29:0.58 for Neu5Ac alpha 2-6Gal/Neu5Ac alpha 2-3Gal and 0.51:0.76 for Neu5Gc alpha 2-3Gal/Neu5Ac alpha 2-3Gal. The above results indicate that the substrate specificities of sialidases from swine influenza A viruses towards sialyl linkages and the molecular species of sialic acid are related to the year of isolation, i.e. strains isolated after 1978 exhibited higher activity towards Neu5Ac alpha 2-6Gal and Neu5Gc alpha 2-3Gal linkages when compared with strains isolated in an earlier year, 1930.

Xylanase IV, an Exoxylanase of Aeromonas caviae ME-1 Which Produces Xylotetraose as the Only Low-Molecular-Weight Oligosaccharide from Xylan

A novel xylanase (xylanase IV) which produces xylotetraose as the only low-molecular-weight oligosaccharide from oat spelt xylan was isolated from the culture medium of Aeromonas caviae ME-1. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the xylanase IV molecular weight was 41,000. Xylanase IV catalyzed the hydrolysis of oat spelt xylan, producing exclusively xylotetraose. The acid hydrolysate of the product gave d-xylose. The enzyme did not hydrolyze either p-nitrophenyl-(beta)-d-xyloside, small oligosaccharides (xylobiose and xylotetraose), or polysaccharides, such as starch, cellulose, carboxymethyl cellulose, laminarin, and (beta)-1,3-xylan.

Young female patient with testosterone-producing adrenocortical adenoma also showing signs of subclinical Cushing's syndrome

A 28-year old female patient with virilization due to left adrenocortical adenoma was studied. The patient had clinical features of hyperandrogenism such as hirsutism and a low pitched voice, but not of hypercorticoidism. Plasma testosterone and dehydroepiandrosterone-sulfate (DHEA-S) were high. Although the basal plasma cortisol concentration and urinary excretion of 17-hydroxycorticosteroids (17-OHCS) were within the normal range, the absence of diurnal variation in plasma cortisol and loss of suppressibility by dexamethasone suggested constitutive secretion of cortisol by the tumor. Inappropriate cortisol secretion was also supported by blunted ACTH response to provocative stimuli. After successful removal of the left adrenal tumor, such endocrinological abnormalities were all normalized. Immunohistochemical analysis revealed that tumor cells were positively stained for C21 hydroxylase cytochrome P-450 (P-450C21) and P-450(11) beta which convert 17-hydroxy (OH) progesterone to cortisol as well as P-450SCC, 3 beta-hydroxysteroid dehydrogenase and P-450(17) alpha which are involved in testosterone biosynthesis. These findings suggest that adrenocortical adenoma secretes predominantly testosterone and constitutively cortisol in a young woman patient with virilization.

Evaluation of gallbladder function before and after gastrectomy using a double-isotope method

The motor function of the gallbladder after partial distal gastrectomy for gastric carcinoma (Billroth-I reconstruction) and its relationship to the motor function of the stomach was investigated using a double-isotope method. In this method, [99mTc]N-54-pyridoxyl-5-methyltryptophan ([99mTc]PMT) was utilized as a tracer for the biliary tract and [111In]diethyl-triaminopontacetic acid ([111In]DTPA) mixed with a liquid test meal was used as a tracer for the digestive tract. Gastric emptying half-time (GET1/2) was measured, since this was used historically as the physiologic indicator of gallbladder contractile stimulus. The volume of test meal that emptied from the stomach into the duodenum per minute (VOL/MIN) was measured, as was the gastric emptying duration (GED). A series of gallbladder emptying phenomena were analyzed using three different criteria: gallbladder emptying half-time (GBET1/2), retention rate of bile in the gallbladder (RR), and the start of gallbladder bile ejection into the duodenum after ingestion (TL: time lag). While GET1/2 was reduced (P < 0.01) and VOL/MIN was increased (P < 0.01) after gastrectomy, GED was shortened remarkably (P < 0.01). GBET1/2 showed no significant change, RR increased (P < 0.05), and TL was prolonged (P < 0.01). The postoperative dysfunction of the gallbladder was caused by the short and intense stimulus on the biliary tract during the duodenal phase and by intraoperative injury to the innervation of the gallbladder. In particular, the hepatic branch of the left vagus nerve was injured during the right paracardiac lymph node dissection performed as a component of the radical gastrectomy.

Thermotropic behavior of stratum corneum lipids containing a pseudo-ceramide

The mechanism of the self-assembly of the lamellar structure of natural stratum corneum lipids (SCL) has been a subject of considerable interest. We have examined this question by using a synthetic pseudo-ceramide (sphingolipid E, SLE) which was analogous to the naturally occurring ceramide type 2. The thermotropic properties and the structural characteristics of SLE, together with other main components of SCL, fatty acids, and cholesterol, were investigated by differential scanning calorimetry and X-ray analysis. A mixture of SLE and stearic acid was in a stable alpha-form having a lamellar structure, which is very similar to that of natural SCL. However, lipid mixtures in which stearic acid were replaced by oleic acid did not form lamellar structures, and existed in the crystalline states. This indicates that the stable bilayer formation of the natural SCL is strongly dependent on the molecular fatty acid structure. Moreover, incorporation of cholesterol (0-50%) into equimolar mixtures of SLE/stearic acid and of SLE/oleic acid caused a marked decrease of melting entropies, while the aggregation states of both systems were not changed. This effect of cholesterol can be attributed to the disorder of the molecular packing. These results suggest that the hydrophobic interactions between the SCL are important for bilayer formation as are the hydrophilic interactions between the polar groups.