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Biomedical subjects

A Jonas

Publications and source records attributed to A Jonas.

At least 127 records · Page 7Linked to original sources
PubMed1982

Micellar complexes of human apolipoprotein A-I with phosphatidylcholines and cholesterol prepared from cholate-lipid dispersions.

Micellar complexes of human apolipoprotein A-I and phosphatidylcholine, with or without cholesterol, were prepared by adding apolipoprotein A-I (apo A-I) to sodium cholate-lipid mixtures. Cholate was removed by dialysis and the apo A-I.lipid complexes were isolated by gel filtration chromatography or by density gradient ultracentrifugation. The lipid mixtures consisted of dipalmitoylphosphatidylcholine or egg yolk phosphatidylcholine in the presence of various molar ratios of cholesterol. The formation of complexes was examined at different phosphatidylcholine (PC)-to-apo A-I ratios, PC-to-cholate ratios, and cholate concentrations. Yields of complexes were maximal when incubation and dialysis were performed near the transition temperature of the PC. Upon lipid binding and complex formation, apo A-I experienced a significant increase in alpha-helix content, and a blue shift in the intrinsic tryptophan fluorescence. In all lipid-protein incubation mixtures, from 600:1 to 75:1, PC/apo A-I (molar ratios), relatively small, stable complexes were present which gave maximum yields at incubation ratios similar to their isolated stoichiometries of 75:1 to 140:1, PC/apo A-I (molar ratios). For the isolated complexes, molecular weights were determined by sedimentation equilibrium to be in the range from 220,000 to 260,000; fluorescence polarization using the hydrophobic probe 1,6-diphenyl-1,3,5-hexatriene showed a broadened and shifted gel to liquid-crystalline phase transition, characteristic of micellar complexes of apo A-I with PC. Complexes prepared using apo A-I, covalently labeled with 5-dimethylaminonaphthalene-1-sulfonyl chloride, had an overall particle rotational relaxation time of 530 ns. On electron micrographs, the complexes, negatively stained with phosphotungstate, appeared as lamellar, discoidal particles.

Apolipoprotein A-I↗
PubMed1982

Reaction of human lecithin cholesterol acyltransferase with synthetic micellar complexes of apolipoprotein A-I, phosphatidylcholine, and cholesterol.

Micellar, discoidal complexes of human apolipoprotein A-I (apo A-I) with phosphatidylcholines and cholesterol, prepared by the method described in the preceding paper (Matz, C. M., and Jonas, A. (1982) J. Biol. Chem. 257, 4535-4540), were used as substrates for human lecithin cholesterol acyltransferase, purified 10,000-fold. The micellar complexes of apo A-I.egg yolk-phosphatidylcholine.cholesterol were compared to commonly used substrates of lecithin cholesterol acyltransferase, consisting of small unilamellar vesicles of egg yolk-phosphatidylcholine and cholesterol in the presence of apo A-I. Under identical reaction conditions, the micellar complexes had 4- to 5-fold higher initial velocities and 3-fold greater capacities for cholesterol esters than did the corresponding vesicular substrates. Micellar complexes, labeled with 5-dimethylamino-naphthalene-1-sulfonyl fluorescent groups in the apolipoprotein, were isolated by density gradient centrifugation. After reaction with lecithin cholesterol acyltransferase, they had a shorter rotational relaxation time (290 ns) and smaller Stokes radius (47 A) than the unreacted complexes (530 ns and 57 A, respectively). The characteristic stacked, discoidal particles observed on electron micrographs of negatively stained micellar, unreacted complexes disappeared after enzymatic reaction and were replaced by structures with spheroidal shapes.

Apolipoprotein A-I↗
PubMed1982

Clinical features of viral and bacterial gastroenteritis in hospitalized children.

The clinical course of 119 children, hospitalized with acute gastroenteritis of known etiology, was studied. The severity of disease was measured by a scoring system that showed that the disease caused by Escherichia coli was the most severe, followed in decreasing order by Salmonella, human reovirus-like agent (HRLA) and Shigella. The clinical features of salmonella and shigella infections differed from those reported in other countries. Fifty percent of all patients recovered after 5 days of treatment, but 20% of the patients with bacterial infections continued to have symptoms for 10 days or longer. The relationships between etiological agents and various symptoms were measured by odds ratios. These associations may provide a basis for clinical prediction of the etiological agent.

Age Factors↗
PubMed1982

alpha 1-antitrypsin deficiency in Israeli children: a five-year survey.

In order to elucidate the importance of alpha 1-antitrypsin (AAT) deficiency as a cause of liver disease in children in Israel, we conducted a retrospective 5-yr study. The screening of 51 liver biopsies for the presence of AAT inclusion bodies was performed using the immunoperoxidase technique. Serum AAT concentrations of 300 pediatric patients determined during the same period were reviewed. No case of AAT deficiency was detected. We conclude that AAT deficiency is rare in Israel.

Adolescent↗
PubMed1982

Stool output and composition in the chronic non-specific diarrhoea syndrome.

Stool output and composition were studied in 7 children with chronic, non-specific diarrhoea syndrome and the results were compared with those of children with malabsorption due to cystic fibrosis or to bacterial overgrowth syndrome, and with stools from controls. Daily quantities of stool, fat, and total bile acids were normal in patients with chronic, non-specific diarrhoea syndrome. Faecal sodium concentration was high compared with that of controls or patients with cystic fibrosis. The extractable water phase of stools appreciably increased in patients with chronic, non-specific diarrhoea syndrome and contained 50% of the total stool bile acids; this was also the case in patients with bacterial overgrowth syndrome. It is suggested that a secretory state of the large-bowel due to mucosal exposure of large quantities of bile salts in the extractable water phase may be contributory to the diarrhoea of chronic, non-specific diarrhoea syndrome.

Adolescent↗
PubMed1982

Ketamine anesthesia for pediatric gastrointestinal procedures.

Ketamine HCl anesthesia was used for gastrointestinal therapeutic and diagnostic procedures in 26 children aged 3 mo to 16 yr. In addition, atropine was used for the gastroscopies and diazepam for the colonoscopies. Ketamine, 5 to 8 mg/kg body wt administered i.m., produced rapid anesthesia of short duration which allowed easy performance of the procedure. No serious side effects were noted, but care must be taken as ketamine is a general anesthetic with potential side effects during and after the period of anesthesia. This satisfactory initial experience should be confirmed by a controlled study of anesthetic agents for pediatric gastrointestinal procedures.

Adolescent↗
PubMed1981

Interactions of dipalmitoyl- and dimyristoylphosphatidylcholines and their mixtures with apolipoprotein A-I.

Human and bovine A-I apolipoproteins were incubated with multibilayer liposomes of dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC) and several mixtures of these two lipids. The reactions were carried out at temperatures around the transition temperature of the lipids, and the formation of small, micellar complexes of protein with lipid was followed as a function of time. Micellar complexes were isolated by ultracentrifugation and were characterized in terms of stoichiometry, lipid composition by gas chromatography, approximate size by gel filtration, and phase transition behavior by fluorescence polarization measurements. The results indicate a decrease in reaction rates with increasing DPPC contents of the mixtures, consistent with the higher stability of DPPC bilayers. Reactions have optimal rates at the transition temperature and are limited to the temperature range where gel and liquid-crystalline phases coexist. The isolated complexes with DMPC and DPPC have similar molecular weights in the range from 2 X 10(5) to 2.5 X 10(5), but lipid/protein mole ratios differ by about 40%. The lower lipid/protein ratio of DPPC complexes (100:1 mol/mol) is compensated by the longer acyl chains of this lipid, such that the acyl chain area of both complexes stabilized by apolipoprotein is essentially identical.

Animals↗
PubMed1981

Interaction of apolipoprotein A-I with dimyristoylphosphatidylcholine particles of various sizes.

Dimyristoylphosphatidylcholine (DMPC) particles of different sizes were prepared by a short sonication of the lipid followed by fractionation on a Sepharose CL-4B column. Column fractions were pooled to give DMPC multilamellar liposomes, and vesicles ranging in average diameters from 300 to 220 A. These particles were used to prepare complexes with bovine apolipoprotein A-I (apo A-I). Reaction mixtures covering molar ratios from 2000:1 to 100:1 DMPC/apo A-I were equilibrated at 25 degrees C for over 15 h and were fractionated by gel filtration in order to separate vesicular and micellar protein.lipid complexes. The results indicate that under identical reaction conditions, larger particles with a smaller total surface area per mol of lipid give proportionately more micellar complexes. In fact, the multilamellar liposomes give only micellar complexes at all the initial molar ratios. For the smaller DMPC vesicles, the vesicular complexes are saturated when 6 or 7 apo A-I molecules are bound per particle, which corresponds to 2,83 X 10(4) A2 of vesicle surface per apo A-I and an approximate 16% coverage of the surface by apo A-I.

Apolipoprotein A-I↗
PubMed1981

Immunogenetics of childhood celiac disease: the association with HDA DR3 and DR7 in unrelated patients with multiply affected families.

The association between childhood celiac disease and the histocompatibility complex was studied in five multiply affected families and 20 unrelated patients. The diagnosis of celiac disease (CD) was established by three consecutive jejunal biopsies: 1) at the initiation of the diagnosis; 2) following a gluten-free diet; and 3) after gluten provocation. The results of this study indicate that a significant association exists between celiac disease, DR3 (P less than 0.001) and DR7 (P less than 0.001). The relative risks for these antigens were 8.56 and 5.05, respectively. Segregation analysis in the families suggested that the susceptibility genes associated with the histocompatibility antigens are not inherited in either a dominant or a recessive pattern. While an intermediate type fits better into the genetic framework of CD, more than one susceptibility and protecting gene may be involved in the pathogenesis of this disease.

Adult↗
PubMed1980

Bovine apolipoproteins C. I. Isolation and spectroscopic investigations of the phospholipid binding properties.

Seven low-molecular weight proteins of the C class of apolipoproteins have been isolated from bovine serum high density lipoprotein. Amino acid analysis has shown five of these to be equivalent to the apolipoproteins previously described (Lim, C.T. and Scanu, A.M. (1976) Artery 2, 483-496). A spectroscopic examination of these proteins in the presence of increasing amounts of L-alpha-dimyristoyl phosphatidylcholine single-bilayer vesicles indicates that all bovine apolipoproteins C exhibit changes in secondary and tertiary structure as shown by intrinsic fluorescence intensity, wavelength, and polarization changes, and increases in alpha-helical content as seen by circular dichroism. Evidence is presented to show that bovine apolipoproteins C, like all human apolipoproteins of the A and C classes, can cause phospholipid multilamellar liposomes to disrupt and/or rearrange into a smaller complex which scatters less light. This paper details the screening of the bovine apolipoproteins for their phospholipid binding properties, whereas the following paper will examine the nature of their complexes with phospholipid in more detail. Together, these papers represent the first investigation of protein-lipid interactions involving any nonhuman apolipoproteins C.

Animals↗
PubMed1980

Bovine apolipoproteins C. II. Isolation and partial physicochemical characterization of complexes with L-alpha-dimyristoyl phosphatidylcholine.

Complexes were made between L-alpha-dimyristoyl phosphatidylcholine (DMPC) and four of the seven bovine apolipoproteins C described in the preceding paper (Patterson, B.W. and Jonas, A. (1980) Biochim. Biophys, Acta 619, 572-586). Reaction mixtures were fractionated by gel filtration chromatography and isopycnic density gradient ultracentrifugation. Selected complexes were further analyzed by sedimentation equilibrium ultracentrifugation and examined for phospholipid bilayer phase transition properties as reported by the fluorescence polarization of a lipophilic probe. Two bovine apolipoproteins C (D2, D3) were able to form complexes with DMPC of virtually the same size, stoichiometry, and density over a wide range of initial lipid/protein molar ratios (200 : 1 to 10 : 1). At very high initial molar ratios (200 : 1 and 100: 1), an additional lipid-enriched complex was formed with these apolipoproteins. Complexes made with D4 were less discrete, having a size, stoichiometry, and density dependent on the initial lipid : protein ratios used. Isolated complexes were smaller than intact DMPC vesicles, representing a break-down product of vesicular structure. The sizes (molecular weights around 2-3 x 10(5)), hydrated densities (1.06-1.12 g/ml), and weight percentage protein compositions (30-40%) of bovine C apolipoprotein-DMPC complexes are comparable to the corresponding parameters for intact bovine HDL. Isolated bovine C apolipoprotein-DMPC complexes retain some phospholipid bilayer structure as indicated by their phase transition behavior. However, the phase transition is considerably broadened and shifted to a higher temperature in the complexes compared to pure lipid. The results obtained are comparable to the phospholipid binding properties of human C apolipoproteins and are consistent with various oblate ellipsoidal models suggested for apolipoprotein-DMPC complexes.

Animals↗
PubMed1980

Kinetics and mechanism of apolipoprotein A-I interaction with L-alpha-dimyristoylphosphatidylcholine vesicles.

The dynamics of human apolipoprotein A-I (apo A-I) interaction with dimyristoylphosphatidylcholine (DMPC) vesicles were investigated in a 4000:1 DMPC/apo A-I (mol/mol) mixture where all the protein is bound to DMPC in stable vesicular complexes, and in a 100:1 DMPC/apo A-I (mol/mol) mixture which gives micellar complexes at equilibrium. Gel filtration and fluorescence methods (polarization and intensity) were used to follow the reaction kinetics. The binding of apo A-I to DMPC vesicles is a very rapid process which takes only a few minutes, while the formation of micellar complexes takes several hours at 25 degrees C and involves saturated complexes of apo A-I . DMPC and free apo A-I. The rate-limiting step in micellar complex formation is the breakdown of saturated vesicle . apo A-I complexes, a process that exhibits first order kinetics with a rate constant k = 0.22 h-1 and a half-life t 1/2 = 3 h 9 min.

Apolipoproteins↗
PubMed1980

Prevalence of serum antibody to reoviruslike agent in hospital patients in Israel.

The prevalence of antibody to reoviruslike agent was studied in serum from 350 hospitalized patients in the Tel Aviv area by the complement-fixation technique, with calf diarrhea virus as the antigen. There were 217 (62%) serum samples that showed evidence of antibody to reoviruslike agent. The highest prevalence was noted in postpartum women (95%) and in infants under one month of age (93%), the latter probably as the result of placental transfer. The presence of antibody declined rapidly in the first six months of life and rose sharply after this age. These findings accord with the high incidence of reoviruslike agent infection in these age groups, as previously reported. Above the age of three years, the prevalence of detectable antibody remained stable, ranging from 54.5 to 81.0% in various age groups.

Adolescent↗