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D Rubinstein

Publications and source records attributed to D Rubinstein.

At least 55 records · Page 3Linked to original sources
PubMed1981

Fate of apolipoproteins C-1, C-iii, and E during lipolysis of human very low density lipoproteins in vitro.

The apoprotein and lipid composition of HDL-like products arising from lipolysis of human VLDL was studied. The VLDL was perfused through beating rat hearts in the absence of serum to avoid possible alteration of the primary products of lipolysis due to apoprotein exchange with serum lipoproteins. The lipolytic products were separated by gel filtration to obviate possible losses of apoproteins from the lipoproteins during ultracentrifugation. Apoprotein B, E, C-II, and C-III were quantitated by electroimmunoassay and lipids were determined by chemical methods. During perfusion, a 50% hydrolysis of the VLDL triacylglycerols was associated with the appearance of 11% of the apoC-II, 30% of the apoC-III, and 20% of apoE of the VLDL in HDL-like particles as isolated by agarose gel filtration. The shift of the apoproteins to these particles was associated with a similar redistribution of cholesterol, phospholipid, and cholesteryl ester. The lipid composition of the HDL-like particles was cholesterol (15.1 +/- 4.0%), phospholipid (37.8 +/- 3.2%), cholesteryl ester (34.2 +/- 2.6%), and triglyceride (12.9 +/- 3.2%). The particles possessed a hydrated density of 1.063-1.21 g/ml and were spherical, with particle diameters (mean 124 +/- 36 A, range 50-160 A) that were comparable to the diameter (140 A) estimated from calculations of the surface to volume ratio, assuming a spherical particle consisting of a neutral lipid core surrounded by cholesterol, phospholipid, and protein. No discoidal forms or rouleau structures were observed in the HDL-sized fraction isolated by gel filtration. The HDL-like fraction could be resolved further by heparin-Sepharose chromatography into an unretained fraction containing predominantly apoC-III with apoE and apoC-II, and a retained fraction containing apoC-III and apoE. Small amounts of apoE were also recovered in extremely small particles that are normally observed in the d > 1.21 g/ml fraction after ultracentrifugation. No apoC-II or C-III was observed in this fraction. Incubation of VLDL with lipoprotein lipase, mobilized from hearts by heparin perfusion, yielded results that were similar to those with the perfused heart. Hearts perfused with VLDL removed apoB but not apoC-II, C-III, E, or phospholipids from the perfusate. It is concluded that the initial products of VLDL catabolism include spherical particles, similar in size to HDL, that contain apoC-II, C-III, E, cholesterol, cholesteryl esters, and phospholipids. ApoE is also released as a small extensively delipidated particle.-Tam, S. P., L. Dory, and D. Rubinstein. Fate of apolipoproteins C-II, C-III, and E during lipolysis of human very low density lipoproteins in vitro.

Animals↗
PubMed1980

Family psychiatry in psychosomatics: problems of adolescence.

Adolescents are frequently entangled in a web of transitions during their developmental journey from child to adult. These modulations include physiological and psychological changes: individual, familial and social readjustments, and alterations in the evolving family group. Psychosomatic manifestations are often target dysfunctions in the shift among various systems pivoted on the adolescent's life cycle. The family psychiatrist, acquainted with evolving systems, has been demonstrated to be in an advantageous position to design therapeutic programs for these clinical problems.

Adolescent↗
PubMed1979

Changes in weight during treatment for depression.

Changes in appetite and weight were examined in a group of 47 carefully diagnosed primary depressives who were treated in a random design with either placebo (N = 17) or amitryptyline (N = 30) over a 35-day protocol. While the amitriptyline treated group as a whole showed a greater gain in weight than did the placebo group (4.5 vs. 0.5 lb, p less than 0.05), no differential effects could be demonstrated between drug responders and nonresponders. Likewise, while a consistent relationship between the self-report of decreased appetite and final weight change was noted in the placebo group, no simple relationship between final weight change and self-reported changes in appetite were apparent in the drug-treated patients. There was, however, a relationship between the report of decreased appetite and clinical severity of depression in the drug nonresponder subgroup despite significant weight gain during the protocol. Thus, weight change during this study period did not appear to show a simple relationship to corresponding clinical change. The clinical lore that has supported the notion that increased appetite and weight gain in patients being treated with tricyclic antidepressants are "good" signs cannot be confirmed by our findings.

Adult↗
PubMed1979

Turnover of apoE in normal and hypercholesterolemic rats.

The turnover of apoE in the total lipoprotein fraction (p less than 1.21 g/ml) of normolipemic and hypercholesterolemic rats was compared. The specific activity of 125I-labelled apoE in the lipoproteins was determined after isolation of the apoprotein by immunoaffinity chromatography. The serum apoE decay curves showed rapid first and slower second phases. The first phase of the curve of hypercholesterolemic animals suggests some sequestration of the apoprotein. The half-lives of apoE in the second phase were approximately 7 and 23 h in the normal and hypercholesterolemic sera, respectively. Elevated apoE levels and moderate hypercholesterolemia persisted one week after restoration of the normal diet, indicating that the increased apoprotein level seen in hypercholesterolemic rats was not solely to VLDL or chylomicron remnants. However, due to the elevated apoE levels in the hypercholesterolemic rats, the total replacement rates of the apoprotein appeared to be greater than that in normolipemic animals, consistent with the concept that in the steady state there is an increase in apoE secretion in hypercholesterolemic animals rather than a decrease in catabolism.

Animals↗
PubMed1978

Frequency of sexual dysfunction in "normal" couples.

In analyzing the responses of 100 predominantly white, well educated and happily married couples to a self-report questionnaire, this study examined the frequency of sexual problems experienced and the relations of those problems to sexual satisfaction. Although over 80 per cent of the couples reported that their marital and sexual relations were happy and satisfying, 40 per cent of the men reported erectile or ejaculatory dysfunction, and 63 per cent of the women reported arousal or orgasmic dysfunction. In addition, 50 per cent of the men and 77 per cent of the women reported difficulty that was not dysfunctional in nature (e.g., lack of interest or inability to relax). The number of "difficulties" reported was more strongly and consistently related to overall sexual dissatisfaction than the number of "dysfunctions."

Adult↗
PubMed1978

The catabolism of human and rat very low density lipoproteins by perfused rat hearts.

The catabolism of human and rat 125I-labelled very low density lipoproteins (VLDL) was compared by perfusing the lipoproteins through beating rat hearts. Triacylglycerol was removed from the VLDL to a greater extent than the protein moiety, leaving remnants containing relatively more apo-B and less apo-C. The change in apo-C content of the remnants correlated with the loss of triacylglycerol. The extent of removal of triacylglycerol from the rat and human VLDL was similar and in most cases appeared to saturate the heart lipoprotein lipase. The remnants were slightly smaller in size than the VLDL, and included particles which appeared to be partially emptied. In addition to remnants of d less than 1.019 g/ml, iodinated lipoproteins derived from rat and human VLDL were recovered at d 1.019-1.063 and 1.063-1.21 g/ml. The former contained largely cholesterol and cholesteryl esters, while phospholipids were the dominant lipid in the latter. An average of 40% of the 125I-labelled apoprotein lost from the VLDL was associated with the perfused hearts. Very little d 1.019-1.063 g/ml lipoprotein was produced from low (physiological) concentrations of rat VLDL, most of the lipoprotein being removed by the heart. However, lipoproteins of density 1.019-1.063 g/ml were formed from human VLDL at all concentrations in the perfusate, as well as from higher concentrations of the rat VLDL. Agarose gel filtration of lipoproteins following heart perfusion with human VLDL revealed large aggregates containing particles which resemble low density lipoproteins (LDL) in electron microscopic appearance and apoprotein composition, since they contain largely apo-B. These data suggest that at normal concentrations rat VLDL are almost completely catabolised and taken up by the heart without the formation of LDL, while LDL is produced from human VLDL at all concentrations.

Animals↗
PubMed1978

Love and work.

Explore the source record for details and available documents.

Humans↗
PubMed1978

The levels of apolipoprotein-E in hypercholesterolemic rat serum.

The levels of apolipoprotein-C (apo-E) in serum and isolated liproproteins from diet-induced hypercholesterolemic, and to some extent hypertriglycerdemic rats were measured by electroimmunoassay. The hypocholesterolemia was accompanied by a mild hypertriglyceridemia. The apo-E was increased by 60% in the hypercholesterolemic serum with a 5- and 50-fold increase in very low density lipoproteins (VLDL) and low density lipoproteins (LDL) respectively. However, the proportion of apo-E in nascent VLDL isolated from the hepatic Golgi apparatus of hypercholesterolemic rats was significantly decreased. In control serum, 40--50% of the apo-E is found in the density greater than 1.21 g/ml fraction, although this is at least partially due to ultracentrifugation. The aproprotein is absent from the density greater than 1.21 g/ml fraction from hypercholesterolemic serum, suggesting that it is bound more firmly to the lipoprotein complex. It is concluded that the large increases in apo-E in the VLDL and LDL density ranges of serum from hypercholesterolemic rats may in part be accounted for by the utilization of apo-E normally found at higher densities.

Amino Acids↗
PubMed1978

A comparison of some immunological characteristics of very low density lipoproteins of normal and hypercholesterolemic rat sera.

The immunological characteristics of a very low density lipoproteins (VLDL) from normal and hypercholesterolemic rat sera were compared using polyspecific antisera to VLDL and high density lipoproteins (HDL) and monospecific antisera to apo-B, apo-C, apo-A-I, and apo-E. Ultracentrifugally isolated VLDL from normal serum were studied by immunodiffusion and found to contain both discrete and associated (with apo-B) apo-C and apo-E, probably in the form of lipid-containing lipoproteins. However, immunoelectrophoresis of whole serum revealed only an associated form of the liporpotein having pre-beta mobility (i.e., VLDL), suggesting that the presence of discrete lipoproteins in isolated VLDL, each containing a single apoprotein family, may represent ultracentrifugal artifacts. Ultracentrifugally isolated VLDL from diet-induced hypercholesterolemic rat serum contained only trace amounts of apo-C and large quantities of apo-E, both of which were totally associated with apo-B. VLDL isolated by ultracentrifugation from perfusate of normal and hypercholesterolemic livers contained only associated lipoprotein complexes made up of apo-B, apo-C, and apo-E in the former but only apo-B and apo-E in the latter. These data suggest that normal VLDL are secreted as lipoprotein complexes containing apo-B, apo-C, and apo-E, which may become destabilized in the circulation. However, VLDL from hypercholesterolemic serum shows a marked diminution in the quantity of apo-C as indicated by the relative incorporation of [3H]leucine in vivo and by polyacrylamide gel electrophoresis of apo-VLDL.

Animals↗
PubMed1977

Glycosylation of apoproteins of rat very low density lipoproteins during transit through the hepatic Golgi apparatus.

The glycosylation of apo very low density lipoproteins (apo-VLDL) in vivo was studied by following the incorporation of [14C]glucosamine into several groups of apoproteins of VLDL isolated from hepatic Golgi fractions and from serum of sucrose-fed, colchicine-treated rats. Simultaneous incorporation of [3H]leucine was used to quantitate the apoproteins following separation by polyacrylamide gel electrophoresis. Experimental conditions were selected so that the 14C:3H ratio in the apoproteins permitted estimations of the extent of glycosylation by glucosamine and its metabolites. A rapidly decreasing 14C:3H ratio was noted in serum apo-VLDL for the first 30 min after administration of the isotopically labelled precursors, followed by stabilization of the ratio. These data are consistent with the glycosylation of a preformed pool of apo-VLDL, probably apo-B. Glucosamine was progressively incorporated into apo-VLDL during transition from the forming face of the Golgi apparatus to the secretory vesicles, as indicated by an increasing 14C:3H ratio. On the other hand, the ratio of the rapidly migrating apoproteins of VLDL, corresponding to the apo-C-II and apo-C-III, showed the opposite trend, as did total apo high density lipoprotein (apo-HDL) and the rapidly migrating bands of apo-HDL. Division of the rapidly migrating apoproteins of VLDL into upper bands (probably apo-C-II and apo-C-III-0) and lower bands (probably apo-C-III-3) resulted in a 14C:3H ratio near zero in the upper band apoproteins, consistent with the absence of carbohydrates. The lower band showed a rising 14C:3H ratio during transition through the Golgi apparatus, suggesting increased glycosylation, The decreasing 14C:3H ratio in the rapidly migrating proteins is therefore due to the acquisition of apo-C-II and apo-C-III-0 by VLDL during passage from the forming face to the secretory vesicles of the Golgi apparatus.

Animals↗
PubMed1976

The nature of pituitary large growth hormone as studied by immunoabsorption.

Porcine pituitaries were homogenized in neutral pH buffer and the supernatant layer after centrifugation was fractionated by gel filtration on Sephadex G-200. The void volume peak contained 0.2-0.5% of the immunoreactive growth hormone (large GH), the remainder (small GH) eluted at Kd 0.6. The isolation of large GH was attempted with anti-GH coupled to Sepharose 2B: of the immunoreactive large GH 50-60% was absorbed to a large excess of anti-GH Sepharose during an 18 h incubation at 4 degrees C. Over 80% of the absorbed immunoreactivity could be eluted with neutral 6M-sodium thiocyanate at 4 degrees C. The eluate, when rechromatographed, contained small GH, RNA which had absorbed to anti-GH Sepharose remained in the void volume on rechromatography. RNA was also absorbed when Sepharose-coupled bovine serum gamma-globulin was substituted for anti-GH Sepharose or when rat liver was substituted for porcine pituitaries. No RNA was absorbed when large GH was converted into small GH with 6M-NaSCN and rechromatographed before immunoabsorption. However, significant absorption of prolactin was found. After a two-hour incubation of porcine pituitary slices with [3H]leucine, GH dissociated from large GH had a specific activity 10-100 times that of small GH but appeared similar to it by gel chromatography and polyacrylamide gel electrophoresis. We conclude that pituitary large GH represents a different metabolic pool from pituitary small GH and may be newly synthesized small GH not yet incorporated into granules, thus being susceptible to non-specific binding to RNA during the extraction procedure.

Animals↗
PubMed1976

Inhibition of actions of glucagon in adipocytes by gastric inhibitory polypeptide.

Possible interactions between gastric inhibitory polypeptide (GIP) and glucagon were investigated in rat adipocytes. GIP was nonlipolytic and inhibited lipolysis stimulated by glucagon but not that stimulated by secretin or vasoactive intestinal polypeptide (VIP). GIP competed with 125I-glucagon for binding to adipocyte receptors, and at physiologic concentrations inhibited the stimulation of AMP produced by glucagon. Thus GIP acts as an inhibitor of actions of glucagon on adipocytes and may be a physiologic modulator of effects of glucagon.

Adipose Tissue↗
PubMed1976

The synthesis of apoproteins of very low density lipoproteins isolated from the Golgi apparatus of rat liver.

The incorporation of [3H]leucine in vivo into very low density lipoproteins (VLDL) from the rat hepatic Golgi apparatus and serum was studied. A Golgi-rich fraction isolated on a discontinuous sucrose gradient between 0.5 and 1.1 M was found to contain VLDL having common antigenic determinants with serum VLDL. The incorporation of the [3H]leucine into the Golgi VLDL and serum VLDL suggested a precursor-product relationship. Analysis of the apoproteins of the Golgi VLDL by polacrylamide gel electrophoresis revealed protein bands with similar mobility to those of serum VLDL, except that the former contained virtually no rapidly migrating peptides with the mobility of serum apo-C-II and apo-C-III. The pattern of incorporation of the [3H]leucine into the apoproteins was similar in VLDL from Golgi apparatus and serum, except for the absence of radioactivity in the area of the gel of Golgi apo-VLDL corresponding to apo-C-II and apo-C-III. The radioactive amino acid was incorporated predominantly into the Golgi apo-VLDL bands with similar mobility to apo-B and an apoprotein or group of apoproteins containing the arginine-rich peptide of serum VLDL. In vitro incubation of the Golgi VLDL with [3H]leucine-labeled HDL resulted in the acquisition of a number of proteins, including the rapidly migrating proteins. Administration of colchicine prior to the injection of [3H]leucine resulted in the appearance of gel bands and radioactivity in the apo-C-II and apo-C-III areas of Golgi apo-VLDL, suggesting that these can be acquired if secretion of VLDL is slowed or inhibited. The hepatic Golgi apparatus was then divided into fractions of predominantly forming face (GF3) or secretory granules (GF1). After polyacrylamide gel electrophoresis of the apo-VLDL from GF, no visible bands or incorporation of [3H]leucine was found in the region of apo-C-II or apo-C-III. However VLDL from GF1, showed visible and radioactive bands in the apo-C-II and apo-C-III area although they represented a much smaller proportion of the total apoprotein than was found in the corresponding serum apo-VLDL. In the isolated perfused liver the percentage incorporation of [3H]leucine into the rapidly migrating apoproteins of Golgi VLDL was considerably less than that found in the corresponding apoproteins of perfusate VLDL, where circulating C lipoproteins are virtually absent. The data indicate that nascent VLDL begins to acquire the C-II and C-III apoproteins during its passage through the Golgi apparatus but that the main acquisition occurs during or after secretion into the space of Disse.

Animals↗