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Biomedical subjects

A Tietz

Publications and source records attributed to A Tietz.

At least 37 records · Page 2Linked to original sources
PubMed1996

The effects of dietary phospholipids enriched with phosphatidylethanolamine on bile and red cell membrane lipids in humans.

The role of phospholipids in biliary cholesterol solubilization and crystallization has only recently begun to be appreciated. Phospholipid vesicles are believed to be the metastable carrier from which cholesterol nucleates. Cholesterol crystallization is influenced by the phospholipid species in bile. Feeding rats and hamsters with diets enriched in phospholipids or their precursors, especially ethanolamine, resulted in reduced cholesterol saturation of bile. Although whole phospholipids are normal dietary constituents, the effects and safety of phospholipid components have not been tested in humans. In the present study, we have evaluated the effects of a dietary phospholipid mixture, enriched with phosphatidylethanolamine, on human bile and red blood cell membrane lipid composition. Five ambulatory volunteers having a chronic indwelling T-tube, with an intact enterohepatic circulation, were investigated. Thirty-six grams of phospholipids (54% phosphatidylethanolamine, 54% linoleyl acyl chains) were added to their daily diet for fourteen days. Biliary nucleation time, cholesterol carriers, as well as plasma, red blood cell membrane, and bile lipid compositions, were monitored. Following phospholipid supplementation, the proportion of linoleyl chains (18:2) in biliary phospholipids increased significantly from 31.1 +/- 1.2 to 37.7 +/- 5.3%, while that of oleyl chains (18:1) decreased from 11.4 +/- 1.6 to 9.6 +/- 1.1%. These changes were accompanied by an increase of linoleate and its metabolite, arachidonate, in red cell membranes. Phospholipid feeding did not cause any side effects, and no significant changes in biliary nucleation time, cholesterol, phospholipid, or bile salt concentrations, or in the distribution of cholesterol within micelles or vesicles. We conclude that phospholipid feeding is safe, and can be effective as a vehicle for lecithin fatty acyl chain modulation of bile and lipid membranes. These findings may provide a basis for a controlled modulation of biliary phospholipids to increase cholesterol solubility in bile.

Adult↗
PubMed1996

Cerebrospinal fluid shunting in idiopathic normal-pressure hydrocephalus of the elderly: effect of periventricular and deep white matter lesions.

OBJECTIVE: We investigated the effect of periventricular and deep white matter lesions (DWMLs) on outcome after cerebrospinal fluid shunting in a prospective series of elderly patients with idiopathic normal-pressure hydrocephalus. METHODS: White matter lesions were assessed with T2-weighted magnetic resonance scans according to a standard protocol in 41 patients with idiopathic normal-pressure hydrocephalus of the elderly who underwent subsequent shunting. In all patients, the diagnosis of idiopathic normal-pressure hydrocephalus had been established preoperatively by clinical and diagnostic investigations. RESULTS: At a mean follow-up of 16 months, clinical improvement was observed in 37 of 41 patients (90%). There was no persistent morbidity related to surgery. The degree of overall clinical improvement was negatively correlated with the extension of periventricular lesions (correlation coefficient r = -0.324 [P = 0.04]) and DWMLs (correlation coefficient r = -0.373 [P = 0.02]). This negative correlation was also noted when the analysis was conducted separately for each of the cardinal symptoms (gait disturbance, cognitive impairment, and urinary incontinence). There was no consistent pattern of periventricular and DWMLs in the four patients who failed to respond to shunting. CONCLUSION: Periventricular and DWMLs of varying degrees are common findings on magnetic resonance scans of patients with idiopathic normal-pressure hydrocephalus of the elderly. After careful preoperative selection of patients with idiopathic normal-pressure hydrocephalus, individuals with DWMLs suggestive of concomitant vascular encephalopathy may also benefit from cerebrospinal fluid diversion. Although, in general, the degree of improvement depends on the severity of periventricular and DWMLs, patients with more extensive WMLs still may derive clinical benefit from the operation.

Aged↗
PubMed1994

Cell-free synthesis of vitellin in the shrimp Penaeus semisulcatus (de Haan).

The vitellogenic ovary of Penaeus semisulcatus contains mRNA specific for vitellin (Vt), low levels of which are found in nonvitellogenic ovaries, and is absent from testes. Immunoisolation from cell-free translation of poly(A)+ RNA using antiserum against purified Vt produced a 35-kDa polypeptide. No differences were found between Vt precipitated from the translation products of the rabbit reticulocyte system and that from the wheat germ extract. The specificity of the immunoprecipitation reaction was demonstrated by the absence of precipitation with nonimmunized rabbit serum and with antibodies prepared against purified hemocyanin or lipoprotein I (LPI), which are crustacean hemolymph proteins. In addition, competition with the radioactively labeled translation product occurred only in the presence of purified Vt, but not BSA or LPI. Vt synthesized in the translation system had a significantly lower molecular weight than that of the purified Vt or that synthesized by ovaries incubated in vitro. The possibility that this difference may be because of the non-glycosylated nature of a cell-free translation product was tested. The removal of oligosaccharides from purified Vt by enzymatic digestion with N-glycosidase F resulted in the appearance of a smaller polypeptide of 36 kDa, which reacted immunologically with Vt antiserum in a Western blot. The size of this fragment is very close to the molecular weight of the translation product.

Animals↗
PubMed1994

Are vitellin and vitellogenin coded by one gene in the marine shrimp Penaeus semisulcatus?

A cDNA clone encoding a female-specific ovarian protein (presumably vitellin, Vt) has been isolated from a cDNA library prepared from poly (A)+ RNA extracted from vitellogenic ovaries of the shrimp Penaeus semisulcatus. The cDNA library was constructed and screened using a major cDNA band which was observed following analysis of total cDNA products by gel electrophoresis. This band, as well as the cDNA insert purified from the library, was estimated to have 1.1 kb. Both hybridized to mRNA prepared from ovaries or hepatopancreas (HEP) of vitellogenic females and showed a faint signal with ovaries from non-vitellogenic females, but did not hybridize to HEP from non-vitellogenic females or to HEP from males or testes. The size of the transcripts from the ovary and HEP was estimated to be 1.1 kb, similar to that of the cDNA insert, suggesting that a full length cDNA had been synthesized. Furthermore, the identical sizes of the transcripts from ovary and HEP and the ability of the ovarian cDNA to detect a transcript in HEP mRNA suggest that Vt from the ovary and vitellogenin (Vg) from HEP are the gene products of one gene. Alternatively, the homology between Vt and Vg is very high.

Animals↗
PubMed1994

[Multiple diverticula of the jejunum as a cause of recurrent sub-ileus conditions].

The authors describe the case of a 72-year-old man who suffered from marked digestive complaints for almost 50 years. They depended on the amount of food and the composition of the diet and during the last six years they led to attacks of severe epigastrial pain and backache associated with subileous conditions. Only enteroclysis led to a diagnostic solution. It revealed a parapapillary diverticulum of the duodenum and multiple diverticulosis of the upper jejunum. CT and scintigraphy, using autologous leucocytes labelled with 99mTc indicated the possible diverticulitis. Simple dietetic and therapeutic provisions eliminated completely the painful attacks and the patient's complaints were reduced to occasional slight flatulence.

Aged↗
PubMed1993

Octadecatetraenoate synthesis in the unicellular alga Isochrysis galbana: studies with intact and broken chloroplasts.

(1) Monogalactosyldiacylglycerol (MGD) is the major lipid component of Isochrysis galbana. In cells incubated for 3 h with [1-14C]]acetate or [1-14C]oleate. MGD contained 35.9% and 52.8%, respectively, of the label incorporated into cellular lipids. (2) 18:4 amounted to 50-60% of the total FA of MGD. Separation of MGD species of cells grown with [1-14C]oleate on AgNO3 impregnated plates revealed 20 distinct spots. The slowest spot was identified as dioctadecatetraenoyl MGD. Fast moving species were enriched with 18:1. (3) In cells incubated for 3 h with [1-14C]oleate, approx. 60% of the radioactivity was associated with 18:1. Subsequent chase resulted in a gradual shift of label and after 48 h [14C]18:1 declined to 10% and [14C]18:4 reached 52%. This shift was also reflected in the labeling pattern of the MGD-species. Dioctadecatetraenoyl-MGD became labelled only after 24 h. (4) Addition of the substituted pyridazinone herbicide (SAN 9785) during the chase period inhibited [14C]18:4 formation; [14C]18:2 and [14C]18:3 accumulated instead. (5) Isolated chloroplast readily incorporated [14C]oleate into MGD and PA. Considerable amounts of [14C]18:1 were desaturated to 18:2 and 18:3. Only very small amounts of 18:4 were formed. O2 was required for desaturation. Cofactor requirement could not be shown. (6) Membranes isolated from broken chloroplasts retained the ability to incorporate [14C]oleate into MGD and PA and desaturate 18:1 to 18:2 and 18:3.

Chloroplasts↗
PubMed1992

The effect of short-term lipid infusion on liver function and biliary secretion in rats.

This study was undertaken to determine the effect of various lipid emulsions on the hepato-biliary system in rats. Rats were randomly divided into six groups and infused continuously for 48 hr with either long-chain triglycerides (LCT), medium-chain triglycerides (MCT) or a mixture of MCT and LCT. One group infused with physiological saline solution served as controls. Throughout this period the rats received a fat free diet ad libitum. During the last hour of lipid infusion bile was collected for determination of bile flow and composition. Subsequently, the rats were sacrificed and the morphology and lipid content of the liver determined. Only LCT lipid emulsions induced morphological changes and increased liver cholesterol content. In two rats infused with radiolabeled LCT, no labeled cholesterol was found in the liver, indicating that the excess hepatic cholesterol level may originate from enhanced cholesterol mobilization to the liver. Biliary cholesterol and phospholipid concentrations in LCT-treated rats were also elevated, as was the lithogenic index, whereas the other emulsions had no such effects. None of the emulsions affected the plasma liver function tests or bile flow. We therefore conclude that the lithogenicity of the bile in rats is directly related to the lipid components of the total parenteral nutrition and the type of triglyceride infused.

Animals↗
PubMed1987

The biochemical composition of tympanosclerotic deposits.

We have studied the quantitative analysis of calcium, phosphate and cholesterol in the tympanosclerotic plaques removed from 25 patients. Our findings confirm that tympanosclerosis has a partly calcified organic matrix, in which the calcification process is probably similar in its qualitative chemical structure to that occurring in other calcified pathological tissues. The degree of calcification varies from one case to another and is even different in various locations of the same sampling. However, calcium levels are usually lower than in other pathological tissues which are calcified. The average quantity of calcium in our studies was 2 mg in 100 mg tissue or 12 mg in 100 mg protein. The average molar ratio between calcium and phosphate was 3, corresponding to the hydroxyapatite ratio. The average total quantity of cholesterol present was only 15 micrograms in 100 mg protein.

Calcinosis↗
PubMed1986

Bile acid synthesis from HDL cholesterol and cholesterol ester by cultured chick embryo hepatocytes.

A comparison of the uptake and conversion of HDL cholesterol and cholesterol ester to bile acids by chick embryo hepatocytes showed the following. Considerable amounts of cholesterol but not cholesterol ester accumulated in the cells. Cholesterol ester was hydrolyzed to cholesterol, 60% of which was converted to bile acids. Approximately 3-5-times more cholesterol ester than cholesterol were converted to bile acids. The degradation of 125I-labelled HDL by the hepatocytes was negligible. Chloroquine did not inhibit the conversion of HDL cholesterol and cholesterol ester to bile acids. HDL stimulated the conversion of [14C]mevalonolactone to cholesterol, the greater part of which was found in the medium. Its conversion to bile acids was not affected. The cholesterol pool of hepatocytes was labelled by preincubation with [14C]mevalonolactone. Upon addition of 3H-labelled HDL cholesterol, cholesterol efflux and influx were measured simultaneously. Both processes were dependent on HDL concentration and time of incubation. Efflux exceeded influx, drawing upon the cholesterol and cholesterol ester reserves of the cell. Bile acids were formed simultaneously from the prelabelled [14C]cholesterol pool and the exogenously added 3H-labelled HDL cholesterol.

Animals↗
PubMed1986

The catabolism of lung surfactant by alveolar macrophages.

Surfactant was isolated from lung tissue of normal and chlorocyclizine-fed rats. Chlorocyclizine surfactant contained 2.5-3.4 times more phospholipids per mg protein than normal surfactant. Alveolar macrophages, incubated in vitro with normal and chlorocyclizine surfactants hydrolyzed the surfactant phospholipids and incorporated the fatty acids into cellular triacylglycerol. Employing [3H]palmitate-labeled surfactant, it was shown that cells incubated with chlorocyclizine surfactant incorporated 46.2-73.0 nmol of fatty acids per mg protein and were transformed into foam cells. Employing fluorescein or 125I-labeled surfactant, the uptake of surfactant protein by macrophages was shown. No significant differences between protein uptake from normal and chlorocyclizine surfactants were observed. These results suggest that the surfactant phospholipids and protein were catabolized independently.

Animals↗
PubMed1986

Myxococcus xanthus autocide AMI.

Autocide AMI of Myxococcus xanthus was purified and shown to be a mixture of fatty acids: 46.4% saturated, 49.3% monounsaturated, and 4.3% diunsaturated. The specific autocidal activities (units per milligram) were as follows: purified AMI, 1,000; saturated fraction, 100; monounsaturated fraction, 800; diunsaturated fraction, 2,200. Model fatty acids mimicked to some extent the activity of AMI, although none of the fatty acids tested were as active as purified AMI. Spontaneous and induced mutants of M. xanthus were selected for resistance to AMI and to fatty acids. The AMI-resistant mutants were also resistant to the model fatty acids, whereas resistance to fatty acids was specific to the compound used for mutant selection. All AMI- and fatty acid-resistant mutants examined were found to be blocked in fruiting body formation. Some of these mutants were able to form normal fruiting bodies when mixed with the extracellular fluid of the parental strain. The data suggest that AMI plays a role in developmental lysis of M. xanthus.

Bacteriolysis↗
PubMed1985

The availability of different sources of cholesterol for bile acid synthesis by cultured chick embryo hepatocytes.

The availability of different sources of cholesterol for bile acid synthesis by cultured chick embryo hepatocytes was studied. Mevalonolactone was taken up by the cells and converted to cholesterol, cholesterol ester and tauroconjugates of bile acids. The addition of mevalonolactone had little effect on the conversion of endogenous cholesterol to taurocholic acid; however, taurochenodeoxycholic acid synthesis was stimulated. 25-30% of the cholesterol synthesized from mevalonolactone was converted to taurochenodeoxycholic, taurocholic and two so-far unidentified bile acids. All bile acids were secreted into the incubation medium. When cholesterol was added as mixed liposomes with phosphatidylcholine, it was taken up by the cells and converted to bile acids. At low concentrations of liposomes, the greater part of the cholesterol which was taken up by the cells was converted to bile acids. At higher concentrations, considerable amounts of cholesterol and cholesterol ester accumulated inside the cells. When mevalonolactone and cholesterol liposomes was added together, both substrates were used simultaneously for bile acids synthesis. HDL cholesterol was the best substrate tested, yielding large amounts of two, so-far, unidentified bile acids (possibly allo-bile acids) and smaller amounts of taurocholic and taurochenodeoxycholic acid. Addition of HDL suppressed the conversion of endogenous cholesterol to taurocholic acid; taurochenodeoxycholic acid synthesis, however, was stimulated.

Acetates↗
PubMed1983

Effects of chlorocyclizine on pulmonary lipid metabolism in rats.

Pulmonary lipidosis was induced in rats by including 0.36 and 0.54% chlorocyclizine in their diet. Chemical analyses of the lung tissue revealed a very marked increase in phosphatidylcholine concentration. Phosphatidylglycerol and phosphatidylinositol concentrations were also markedly increased. An increase in the phosphatidylcholine content was also observed in lavage fluid and macrophages. Microscopic examination of the cell fraction showed that almost all the cells of the lavage fluid were macrophages and that histochemically demonstrable acid esterase activity was mostly inversely related to storage of lipids in the cells. Sonication of macrophages isolated from normal or chlorocyclizine-treated rats yielded a soluble acid phospholipase (pH optimum, 4.0) and a neutral (pH optimum, 8.2) membrane-bound, CaCl2-dependent enzyme. An inhibitory effect of chlorocyclizine in vitro on the activity of the soluble phospholipase was shown.

Animals↗
PubMed1980

Effects of salts and ionophores on proline transport in a moderately halopholic halotolerant bacterium.

The effect of salt on proline uptake in a moderately halophilic halotolerant bacterium was studied. Cells were grown either on low salt or high salt media. A correlation was found between the salt concentrations in the growth media and the optimal concentration for uptake. The uptake rate was stimulated 2--3-fold by NaCl, as compared to KCl. The Km, V and activation energies values for proline uptake, as well as the external pH effect, were similar in low-salt-grown cells and high-salt-grown cells. This suggests that the halotolerance of the transport system is not due to alterations of the system during growth at various conditions, but rather to its intrinsic ability to function under extreme environmental conditions. The uptake was inhibited by cyanide and carbonyl cyanide m-chlorophenylhydrazone, but not by arsenate, indicating that the electrochemical proton gradient (delta mu- H+), generated by respiration, is the main driving force for proline transport. In low-salt-grown cells, at pH 6.0, partial inhibition was exerted by nigericin or valinomycin, whereas at pH 8.0 the uptake was inhibited by valinomycin only. Similar, although less pronounced effects were found in high-salt-grown cells. The data suggest that at pH 6.0 proline transport is driven by delta mu- H+ (composed of electrical potential (delta psi) and pH gradient), whereas at pH 8.0 delta psi is the main driving force. Procedures of pretreatment with EDTA were developed to enable the penetration of the ionophores into the cells.

Arsenates↗
PubMed1978

Glycolipids of a halotolerant, moderately halophilic bacterium.

A 247 000 x g particulate fraction from a moderately halophilic halotolerant bacterium incorporated [14C] glucose added as UDP[14C]glucose and 32P-labeled phosphatidylglycerol into glucosylphosphatidylglycerol. Exogenously added phosphatidylglycerol was available to the enzyme only when dispersed in a detergent, preferably Triton X-405, by sonication. The 14C- or 32P-labeled glucosylphosphatidylglycerol was degraded with phospholipase C. The water soluble product formed was isolated and identified by paper chromatography as glucosylglycerolphosphate. The system required Mg2+ or Ca2+ for activity. KCl and NaCl were inhibitory even when added at low concentrations.

Bacteria↗