Effects of ursodeoxycholate and other bile salts on levels of rat intestinal alkaline sphingomyelinase: a potential implication in tumorigenesis

Previous studies showed that bile salts had a promoting effect on colon cancer development and this effect was inhibited by ursodeoxycholate (UDC). We recently found that both human colorectal adenomas and carcinomas were associated with a specific decrease in alkaline sphingomyelinase activity. In this work, we compared the effects of ursodeoxycholate and other bile salts on the levels of rat intestinal alkaline sphingomyelinase both in the intestinal loops and after oral administration. Bile salts at different concentrations were injected into intestinal loops and the dissociation of alkaline sphingomyelinase from the mucosa was assayed. We found that bile salts, including taurocholate, taurodeoxycholate, glycocholate, glycochenodeoxycholate, and 3-(3-cholamidopropyl dimethylammonio)-1-propanesulonate (CHAPS), dose dependently dissociated alkaline sphingomyelinase from the intestinal mucosa. UDC alone did not dissociate the enzyme but significantly inhibited the dissociation caused by other bile salts and CHAPS. Feeding rats with 0.3% (w/w) taurocholate for four days decreased peak activity of intestinal alkaline sphingomyelinase by 39% and total activity in the intestine by 20% and increased the output of the enzyme in the feces. In contrast, feeding 0.3% (w/w) UDC for four days increased the peak activity of alkaline sphingomyelinase in the small intestine by 87% and the activity in the colon by 187%. The total activity of alkaline sphingomyelinase was increased by 80% and the output of the enzyme in the feces was only slightly increased by UDC administration. The changes in alkaline phosphatase after feeding taurocholate and UDC were much smaller. Our results indicate that UDC and other bile salts have different effects on the levels of alkaline sphingomyelinase, which may be implicated in their different influences on cancer development reported previously.

Glycolytic flux is conditionally correlated with ATP concentration in Saccharomyces cerevisiae: a chemostat study under carbon- or nitrogen-limiting conditions

Anaerobic and aerobic chemostat cultures of Saccharomyces cerevisiae were performed at a constant dilution rate of 0.10 h(-1). The glucose concentration was kept constant, whereas the nitrogen concentration was gradually decreasing; i.e., the conditions were changed from glucose and energy limitation to nitrogen limitation and energy excess. This experimental setup enabled the glycolytic rate to be separated from the growth rate. There was an extensive uncoupling between anabolic energy requirements and catabolic energy production when the energy source was present in excess both aerobically and anaerobically. To increase the catabolic activity even further, experiments were carried out in the presence of 5 mM acetic acid or benzoic acid. However, there was almost no effect with acetate addition, whereas both respiratory (aerobically) and fermentative activities were elevated in the presence of benzoic acid. There was a strong negative correlation between glycolytic flux and intracellular ATP content; i.e., the higher the ATP content, the lower the rate of glycolysis. No correlation could be found with the other nucleotides tested (ADP, GTP, and UTP) or with the ATP/ADP ratio. Furthermore, a higher rate of glycolysis was not accompanied by an increasing level of glycolytic enzymes. On the contrary, the glycolytic enzymes decreased with increasing flux. The most pronounced reduction was obtained for HXK2 and ENO1. There was also a correlation between the extent of carbohydrate accumulation and glycolytic flux. A high accumulation was obtained at low glycolytic rates under glucose limitation, whereas nitrogen limitation during conditions of excess carbon and energy resulted in more or less complete depletion of intracellular storage carbohydrates irrespective of anaerobic or aerobic conditions. However, there was one difference in that glycogen dominated anaerobically whereas under aerobic conditions, trehalose was the major carbohydrate accumulated. Possible mechanisms which may explain the strong correlation between glycolytic flux, storage carbohydrate accumulation, and ATP concentrations are discussed.

Tissue uptake and interconversion of plasma unesterified 14C linoleic acid in the guinea pig

Part of the arachidonic acid (20:4, n - 6) pools in the gastrointestinal tract and blood forming tissues may be formed by local interconversion of linoleic acid (18:2, n - 6) taken up as a free fatty acid from blood. This study examined the rate of uptake and interconversion of unesterified 14C-18:2 by different tissues in young guinea pigs. The clearance rate of 14C-18:2 was fast, and the initial half-life was 6.3 s. The retention of 14C in tissue lipids was 1.6-1.8% g-1 in the liver, 0.4% g-1 in stomach, 0.7% g-1 in small intestine, 0.2% g-1 in colon, 0.4% g-1 in bone marrow and 0.7% g-1 in spleen. Autoradiographic localization of 3H-18:2 under light microscope demonstrated that most of the 3H radioactivity of the gastrointestinal tract was in the mucosa, in both villus and crypt cells. In bone marrow smears, a high density of silver grains was found in megakaryocytes. The percent of 14C in delta6 desaturase products was higher in gastrointestinal tract, heart, lung, bone marrow and spleen than in liver. The ratio of 14C-20:3/14C-20:4 formation in most tissues was high, and a notable finding being a lower rate of 20:4 formation from plasma free 18:2 in the liver, (170 pmol min-1) than in the gastrointestinal tract (428 pmol min-1) and bone marrow (1203 pmol min-1). The local interconversion of 18:2 into delta6 desaturase products is thus an important source of 20:4 in these organs in guinea pigs.

Renal adaptation to dietary sodium restriction and loading in rats treated neonatally with enalapril

Neonatal treatment of rats with angiotensin-converting enzyme inhibitors or the angiotensin II type 1 receptor antagonist losartan induces irreversible renal histological abnormalities, mainly papillary atrophy, in association with an impairment in urinary concentrating ability. In the present study, sodium and potassium balance were assessed during high and low sodium intake and dietary potassium restriction in adult Wistar rats treated neonatally with enalapril (10 mg x kg(-1) x day(-1)) from 3 to 24 days of age. During balance studies, neonatally enalapril-treated rats showed 1) normal adaptation to dietary sodium restriction, 2) sodium retention during dietary sodium loading, and 3) a transient, modest, renal potassium wastage during dietary potassium restriction. Renal clearance determinations under pentobarbital anesthesia showed elevated fractional excretions of sodium and potassium and osmolar clearance without changes in glomerular filtration rate or effective renal plasma flow in enalapril-treated compared with vehicle-treated rats. Thus, in addition to the impaired urinary concentrating ability, adult rats treated neonatally with enalapril demonstrated alterations in renal sodium and potassium handling, which may be related to the prevailing papillary atrophy.

Color Doppler energy: computer analysis for detection of volume flow variations

The aims of this study were to (1) determine whether analysis of a color Doppler energy image can show small differences in volume flow and (2) determine the performance characteristics of color Doppler energy to aid future analyses. Flow through a silicone tube in a waterbath was insonated, and the images were analyzed by computer producing arbitrary values for the different flow volumes at different machine settings. A significant difference in the derived values was found at volume low changes of 10 ml/min. The differences are most pronounced when small amounts of color are shown in the vessel. This region of high sensitivity can be altered by changing the machine settings of filter, scale, or level. The angle of insonation must be taken into account. In conclusion, computer analysis of color Doppler energy can monitor changes in blood flow volume with a high sensitivity.

Purification of a newly identified alkaline sphingomyelinase in human bile and effects of bile salts and phosphatidylcholine on enzyme activity

The hydrolysis of sphingomyelin (SM) generates important signals regulating cell proliferation and apoptosis. Acid and neutral sphingomyelinases (SMase) have been identified and their biological effects intensively studied. We recently found in human bile a novel alkaline SMase that may have important roles in hepatobiliary diseases. In this work, we purified the enzyme and studied the factors influencing enzyme activity. Purification steps included Sephadex G25, diethylaminoethyl (DEAE)-Sepharose, Sephacryl S-200, and sphingosylphosphorylcholine (SPC) affinity chromatographies. A single protein of 92 kd was obtained with the specific enzyme activity increased 1,154-fold. The enzyme specifically hydrolyzed SM to ceramide, had a weaker activity against phosphatidylcholine (PC), and no activity against either phosphatidylethanolamine (PE) or p-nitrophenyl phosphate. Its optimum pH was 9.0 and its Vmax and Km were 45 micromol/h/mg and 2.5 x 10(-5) mol/L, respectively. The enzyme activity was dependent on concentration and structure of bile salts. Both trihydroxy and dihydroxy bile salts at concentrations up to their critical micellar concentrations activated the alkaline SMase, trihydroxy bile salts being more potent than dihydroxy ones. The side chain of trihydroxy bile salts was also important. Taurocholate (TC) was most effective in activating SMase, followed by glycocholate (GC), and cholate. 3-((3-cholamidopropyl)dimethylammonio)-propanesulfonate (CHAPS) alone had no effect on SMase activity but inhibited TC-induced activation of SMase. PC competitively inhibited bile alkaline SMase activity, with the 50% inhibition occurring at a PC/SM ratio of approximately 28. In conclusion, we purified a novel alkaline SMase from human bile and found that its activity is dependent on the levels of two major biliary components: PC and bile salts.

Characterisation of the G1/S cell cycle checkpoint defect in lung carcinoma cells with different intrinsic radiosensitivities

Cell cycle perturbations in three lung carcinoma cell lines (U-1285,U1906 and U-1810) with different intrinsic radiosensitivities (SF2 U-1285 = 0.25, SF2 U-1906 = 0.45, SF2 U-1810 = 0.88) were investigated following x-irradiation. Cell cycle flow calculations showed that the G1-->S-phase transit was accelerated in irradiated compared with untreated U-1285 cells, up to 24 hours postirradiation. In U-1810 cells and U-1906 cells the postirradiation G1-->S transit decreased compared with controls. All three cell lines showed no postirradiation induction of p53 and p21CIP1 proteins. Cyclin E was overexpressed and cyclin E-dependent kinase activity was substantially induced by irradiation in U-1285 cells compared with U-1906 and U1810 cells while p27KIP1 was detected at the highest intensity in U-1810 cells and lowest in U-1285 cells. We hypothesise that the accelerated postirradiation G1-->S transit in U-1285 cells is associated with induction of cyclin E-dependent kinase activity and may account for increased radiosensitivity in these cells.

Phosphorylation controls the three-dimensional structure of plant light harvesting complex II

The most abundant chlorophyll-binding complex in plants is the intrinsic membrane protein light-harvesting complex II (LHC II). LHC II acts as a light-harvesting antenna and has an important role in the distribution of absorbed energy between the two photosystems of photosynthesis. We used spectroscopic techniques to study a synthetic peptide with identical sequence to the LHC IIb N terminus found in pea, with and without the phosphorylated Thr at the 5th amino acid residue, and to study both forms of the native full-length protein. Our results show that the N terminus of LHC II changes structure upon phosphorylation and that the structural change resembles that of rabbit glycogen phosphorylase, one of the few phosphoproteins where both phosphorylated and non-phosphorylated structures have been solved. Our results indicate that phosphorylation of membrane proteins may regulate their function through structural protein-protein interactions in surface-exposed domains.

Serotonin as a regulator of hypothalamic-pituitary-interrenal activity in teleost fish

Evidence for the presence of a serotonin1A (5-HT1A) receptor subtype in the salmonid fish brain has recently been presented. In the present study the potent 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) was tested for its effect on plasma cortisol concentrations in rainbow trout (Oncorhynchus mykiss). Blood was sampled and 8-OH-DPAT administered through a catheter in the dorsal aorta. Thirty minutes after the injection of 40 microg of 8-OH-DPAT/kg, plasma cortisol levels had increased from 12 to 149 ng/ml, whereupon they fell, reaching baseline levels after 4 h. The effect of 1-40 microg 8-OH-DPAT/kg on plasma cortisol concentrations was dose-dependent. The results lends further support to the hypothesis that the brain serotonergic system plays a key role in integrating autonomic, behavioral and neuroendocrine stress-responses in fish as well as mammals, suggesting that not only the structural and biochemical organization, but also the function of the serotonergic system has been conserved during vertebrate evolution.

Mortality in diabetic patients participating in an ophthalmological control and screening programme

The aim of this follow-up study has been to assess retinopathy and change of treatment to insulin therapy as risk factors for mortality in diabetic patients participating in a control and screening programme for retinopathy. A total of 3220 diabetic patients, 483 with an age at diagnosis <30 years, and 2737 with an age at diagnosis > or = 30 years, were included. Retinopathy was graded on fundus photographs using the Wisconsin Scale, and the visual acuity was assessed. The average HbA1c value was calculated for each patient for the previous 8 years to estimate long-term glycaemic control. Mortality data were obtained from death certificates. Two hundred and sixty-three diabetic patients (8.2%) died during the mean follow-up time of 3.4 years, 13 (2.7%) of those with younger-onset (<30 years) and 250 (9.1%) of those with older-onset (> or = 30 years) diabetes. Of them, 148 (56.3%) died from cardiovascular and 23 (8.7%) from cerebrovascular disorders. After adjusting for differences in age and sex, more severe retinopathy and the use of antihypertensive drugs were associated with a decreased overall survival rate as well as an increased mortality from cardiovascular and cerebrovascular diseases. A statistically significant association between HbA1c values in the highest quartile, i.e. > or =8.4%, and cardiovascular and all cause mortality did not remain when retinopathy was entered into the multivariate analyses. Duration of diabetes, but not change of treatment to insulin therapy, was associated with higher cardiovascular mortality in patients whose diabetes was diagnosed after the age of 30 years. We conclude that severe retinopathy, use of antihypertensive drugs, and poor glycaemic control predicted death from cardiovascular disease in diabetic patients participating in an ophthalmological screening programme.

Cardiac output and ethanol monitoring of fluid absorption

The purpose of this experimental study was to find out whether central haemodynamic activity influences the precision of the ethanol method used to monitor fluid absorption during endoscopic surgery. Today, the nomograms used together with this monitoring method indicate that increasing breath ethanol values reflect progressively larger absorption volumes regardless of the haemodynamic situation. Cardiac output was measured by ultrasound-Doppler and compared with the concentrations and pharmacokinetics of ethanol in the breath during and after 13 intravenous (i.v.) infusions of 15 mL kg-1 of irrigating fluid containing 1% of ethanol in nine healthy male volunteers. The results show that the peak ethanol concentration increases with cardiac output. This can probably be explained by the shorter time needed for the blood to reach and to return from well perfused tissues, thereby prolonging the apparent rate of distribution to poorly perfused tissues. It is concluded that a hyperkinetic circulation causes the ethanol monitoring method to indicate larger absorption volumes.

Threonine-89 participates in the active site of bacteriorhodopsin: evidence for a role in color regulation and Schiff base proton transfer

Bacteriorhodopsin (bR) functions as a light-driven proton pump in the purple membrane of Halobacterium salinarium. A major feature of bR is the existence of an active site which includes a retinylidene Schiff base and amino acid residues Asp-85, Asp-212, and Arg-82. This active site participates in proton transfers and regulates the visible absorption of bacteriorhodopsin and its photointermediates. In this work we find evidence that Thr-89 also participates in this active site. The substitution Thr-89 --> Asn (T89N) results in changes in the properties of the all-trans retinylidene chromophore of light-adapted bR including a redshift of the visible lambda(max) and a downshift in C=N and C=C stretch frequencies. Changes are also found in the M and N intermediates of the T89N photocycle including shifts in lambda(max), a downshift of the Asp-85 carboxylic acid C=O stretch frequency by 10 cm(-1), and a 3-5-fold decrease in the rate of formation of the M intermediate. In contrast, the properties of the 13-cis retinylidene chromophore of dark-adapted T89N as well as the K and L intermediates of the T89N photocycle are similar to the wild-type bacteriorhodopsin. These results are consistent with an interaction of the hydroxyl group of Thr-89 with the protonated Schiff base of light-adapted bR and possibly the N intermediate but not the 13-cis chromophore of dark-adapted bR or the K and L intermediates. Thr-89 also appears to influence the rate of Schiff base proton transfer to Asp-85 during formation of the M intermediate, possibly through an interaction with Asp-85. In contrast, the hydroxyl group of Thr-89 is not obligatory for proton transfer from Asp-96 to the Schiff base during formation of the N intermediate.

Delta-6-desaturase and delta-5-desaturase in human Hep G2 cells are both fatty acid interconversion rate limiting and are upregulated under essential fatty acid deficient conditions

Essential fatty acids are interconverted by desaturases and elongases to eicosanoid precursors. In essential fatty acid deficiency (EFAD) an increased hepatic interconversion of linoleic acid (18:2) to arachidonic acid (20:4n-6) has been demonstrated in vivo. We now cultured Hep G2 cells under EFAD conditions. 20:3n-6 appeared in EFAD cells, but also in controls. After adding 14C-18:2 to the medium, interconversion products and their distribution in different lipids were studied by HPLC. When trace amounts 18:2 were incubated, 38% were converted by the EFAD cells after 21 h, vs 6% by controls. 20% was converted to 20:4 by EFAD cells vs 14% by controls. EFAD cells preferentially distributed more 18:2 and conversion products to neutral fats and to phosphatidyl ethanolamine, but less to cardiolipin than controls did, when incubated with trace amount 18:2, but not with 1 mM 18:2. A relative accumulation of radioactivity in 20:3 was observed. In conclusion; in EFAD Hep G2 cells delta-6- and delta-5-desaturase both were found to be upregulated and eicosanoid precursors were distributed more into phosphatidyl ethanolamine. Delta-5-desaturase had a rate limiting property as well as delta-6-desaturase.

Color Doppler energy: computer analysis of color to assess angle dependency and detection of volume flow differences

The aims of this study were to assess (1) any angle dependency of color Doppler energy and (2) if computer analysis of the color can distinguish variations in volume flow. Fluid flowing through a silicon tube in a waterbath was insonated and the color in the images analyzed by a computer. The color presentation on the screen decreases rapidly as the angle approaches 90 degrees. At angles that did not produce a saturation of the color in the tube, the computer analysis detected significant differences between different flow volumes. We have concluded that monitoring of volume flow changes by analysis of color Doppler energy is possible, but the angle of insonation must be taken into account.

Cigarette smoking is associated with abnormal involuntary movements in the general male population--a study of men born in 1933

Abnormal involuntary movements, i.e., spontaneous and tardive dyskinesias, were studied in a random population sample of 559 men, aged 59 years, who were participating in an epidemiological study focused on cardiovascular health. The research diagnostic criteria for tardive dyskinesia were fulfilled by 8.2% (n = 46), discounting the fact that all had not been exposed to neuroleptics. The mean Abnormal Involuntary Movements Scale score in the dyskinetic group was 5.0 (SD = 1.8), indicating mild to moderate symptoms. Dyskinetic men had higher daily cigarette consumption and higher scores for parkinsonian symptoms. They also had higher frequencies of psychiatric morbidity, exposure to neuroleptics, and alcohol dependence than the men without dyskinesia. In a logistic regression model, exposure to neuroleptics (p < .05) and daily cigarette consumption (p < .0005) were independently associated with dyskinesia. The probability of dyskinesia in a person smoking 20 or more cigarettes per day was 19%, whereas the probability associated with exposure to neuroleptics was 30%.

Design, synthesis, and biological activities of four angiotensin II receptor ligands with gamma-turn mimetics replacing amino acid residues 3-5

Disulfide cyclization is a powerful method for reducing the conformational space of a peptide. This in turn may enable the study of its bioactive conformation. Several analogues of angiotensin II (Ang II) containing a disulfide bridge between amino acids 3 and 5 have been reported. Among these the cyclic octapeptides c[Hcy3,5]-Ang II, c[Cys3,5]-Ang II, and c[Pen 3,5]-Ang II showed significant activity at Ang II receptors. We have performed conformational analysis studies using theoretical calculations and 1H-NMR spectroscopy on tripeptide model compounds of these cyclic octapeptides which show that the cyclic moieties of c[Cys3,5]-Ang II and c[Pen3,5]-Ang II preferentially assume an inverse gamma-turn conformation. On the basis of these results, we substituted amino acid residues 3-5 in Ang II with two different gamma-turn mimetics giving four diastereomeric Ang II analogues. Interestingly, two of these are equipotent to Ang II in binding to AT1 receptors. In the contractile test using rabbit aorta rings, one of the analogues is an agonist with full contractile activity approximately equipotent to c[Pen3,5]-Ang II but 300-fold less potent than Ang II. This low potency may suggest that Ang II does not adopt a gamma-turn in the 3-5 region when interacting with the receptor.

Alkaline sphingomyelinase activity is decreased in human colorectal carcinoma

BACKGROUND

The metabolism of sphingomyelin generates important signals regulating cell proliferation and apoptosis. Previous studies found that the administration of colon carcinoma carcinogen was associated with an accumulation of membrane sphingomyelin, and that dietary sphingomyelin inhibited promotion of experimental colon carcinoma in mice, indicating that the abnormal metabolism of sphingomyelin is linked to colon carcinoma development. However, the changes in sphingomyelinase (SMase) activity in colon carcinoma have not been directly studied. The authors identified, specifically in the intestine, a distinctive alkaline SMase that differs from the known acidic and neutral SMases. The functions and clinical implications of the enzyme are unknown. This study examined the changes in all three SMase activities in human colorectal carcinoma.

METHODS

Tissue samples were taken from colorectal carcinoma and normal mucosa from 18 patients. After homogenization, the activities of acidic, neutral, and alkaline SMase, as well as ceramidase and alkaline phosphatase, were determined. The enzyme activities in cancer tissue were compared with normal tissue from the same patients.

RESULTS

In the normal tissue, there is an activity gradient from the ascending colon to the rectum for neutral and alkaline SMases but not for acidic SMase. In colorectal carcinoma, alkaline SMase activity was preferentially decreased by 75%, whereas acidic and neutral SMase activity decreased by 30% and 50%, respectively. No changes could be found for either ceramidase or alkaline phosphatase activity.

CONCLUSIONS

Alkaline SMase activity preferentially decreases in human colorectal carcinoma, suggesting a regulatory role of the enzyme in colon mucosa cell proliferation.