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Biomedical subjects

G Lee

Publications and source records attributed to G Lee.

At least 469 records · Page 26Linked to original sources
PubMed1979

Role of phospholipids in the structure and function of the thyrotropin receptor.

Phosphatidylinositol, phosphatidylserine, and phosphatidylethanolamine interact with 125I-thyrotropin and inhibit its binding to thyroid plasma membranes; phosphatidylcholine is not similarly effective. The interaction has been monitored by column chromatography on Sephadex G-100 which shows, for example, that 125I-labeled thyrotropin forms an adduct with phosphatidylinositol but not with phosphatidylcholine. Formation of the 125I-labeled thyrotropin-phosphatidylinositol adduct is dependent on the phosphatidylinositol concentration but can be reversed by both unlabeled thyrotropin and excess membranes. The efficacy of the phospholipid interaction and the phospholipid inhibition of thyrotropin binding to thyroid membranes is paralleled by changes in fluorescence and fluorescence polarization imposed on the 5-dimethylamino-1-naphthalene sulfonate (dansyl) derivative of thyrotropin. These changes are reversed by unlabeled thyrotropin but not by prolactin, placental lactogen, or growth hormone; similar changes are not observed when phospholipids are incubated with dansylated growth hormone, prolactin, and placental lactogen. Monovalent potassium, sodium, and lithium salts neither prevent nor reverse the formation of the phospholipid-dansyl-thyrotropin adduct; these results contrast with the effects of the same salts on the formation of ganglioside adducts with dansyl-thyrotropin. Despite their ability to interact witw 125I-thyrotropin in solution, neither phosphatidylinositol, phosphatidylserine, nor phosphatidylethanolamine, when incorporated in a liposome, binds the 125I-labeled ligand. These same phospholipids have no effect on ganglioside binding of 125I-labeled thyrotropin when gangliosides are incorporated in a liposome. These phospholipids do, however, modulate the expression of the glycoprotein component of the thyrotropin receptor when it is imbedded in a liposome. The phosphatidylinositol in this case serves as a negative modulator, both by decreasing the incorporation of the glycoprotein component of the receptor into the liposome and by inhibiting the binding activity of the glycoprotein component which is incorporated. Speculation is offered as to a possible role of the phospholipids in the message transmission process which would be consistent with current studies demonstrating a direct interaction of acidic phospholipids with thyrotropin. The effect of phospholipids on liposomes containing the glycoprotein component of the thyrotropin receptor raises the possibility that phospholipids and, in particular, phosphatidylinositol, may also play a role in regulating the insertion and expression of this receptor component in thyroid plasma membranes.

Animals↗
PubMed1979

The fate of fetal and adult B-cell progenitors grafted into immunodeficient CBA/N mice.

The relative ability of various precursors to generate functional B cells in vivo was assessed by transferring normal, chromosomally-marked CBA/H-T6T6 cells to irradiated or unirradiated immunodeficient CBA/N mice. Emergence of donor-derived B cells was monitored by means of a B-cell cloning assay (in which CBA/N cells are inactive), and by karyotpic analysis of lymphoid, myeloid, and stem cell metaphases. Grafts of lymph node, spleen, anti-mu surface immunoglobin suppressed bone marrow, sIg+ cell-depleted marrow, normal marrow, fetal liver, and yolk sac suggest: (a) there is little self-renewal of sIg+ B cells in these models; (b) pre-committed cells have extensive proliferative/differentiative potential and at least initially contribute most of the newly-formed B cells; (c) populations or pre-B cells obtained from various sources differ in their regenerative ability; (d) CBA/N mice are deficient in a category of pre-B cells which are found in fetal liver; and (e) selective B-cell chimerism results from grafting of unirradiated CBA/N mice.

Age Factors↗
PubMed1979

Critical micelle concentrations of gangliosides.

The micellar properties of mixed, bovine gangliosides and purified galactosyl-N-acetylacetylgalactosaminyl (N-acetylneuraminyl) galactosylglucosylceramide were studied by gel filtration, equilibrium dialysis, and band and boundary centrifugation in sucrose gradients. The dissociation of micelles is very slow (days) in water and required us to approach equilibrium by association of monomers rather than by the dissociation of micelles. The gangliosides were therefore first converted into very low molecular weight aggregates (1-3 molecules) by dissolving them in Me2SO. Galactosyl-N-acetylgalactosaminyl(N-acetylneuraminyl)galactosylglucosylceramide was then diluted into aqueous sucrose gradients and sedimented by the boundary centrifugation technique. This gave a sedimenting micelle and a nonsedimenting monomer concentration of (1-2) x 10-10 M (or less) which corresponds to the critical micelle concentration value. The mixed gangliosides revealed two micellar sizes (i.e., 10 and 4.5 S), the slower sedimenting species being formed from the larger one with time (days). The critical micelle concentration of the mixed gangliosides was found to be approximately 10-8 M by a gel filtration, equilibrium dialysis, and band centrifugation.

Animals↗
PubMed1979

Abnormalities in clonable B lymphocytes and myeloid progenitors in autoimmune NZB mice.

Cloning procedures were used to study B lymphocytes and progenitors of granulocytes and macrophages in NZB mice. Numbers of B cells that were detected in sheep erythrocyte-containing semisolid cultures were only slightly elevated in NZB tissues, and these were normally sensitive to inhibition by anti-mu or anti-delta antibodies or prostaglandin E. However, NZB mice rapidly developed large numbers of B cells that could be cloned in the presence of lipopolysaccharide, and these included unusual anti-mu resistant cells. Numbers of myeloid precursors in NZB bone marrow that were responsive to colony-stimulating activity in L-cell conditioned medium or endotoxin serum were at least normal, but at all ages granulocyte-macrophage precursors were poor responders in cultures stimulated by WEHI-3 cell conditioned medium. Almost no colonies were elicited in NZB cultures with a colony-stimulating activity moiety from WEHI-3 cells. Prostaglandin sensitivity of myeloid precursors from NZB and CBA mice was also different. Codominant genetic control of these abnormalities was suggested by their partial expression in F1 hybrid NZB X CBA and NZB X NZW mice. NZB mice expressed an unexpected IgD allotype allele.

Animals↗
PubMed1979

High pressure liquid chromatographic determination of furazolidone in turkey tissue.

A high pressure liquid chromatographic method for determining furazolidone in turkey tissue has been developed. Tissues are ground with methanol and centrifuged. For lower levels of furazolidone, 2--40 ppb, the supernate is evaporated to dryness and redissolved before it is injected onto the liquid chromatographic column. Using a reverse phase column and an ultraviolet absorption detector set at 365 nm, the assay is linear over the concentration range 2--400 ppb with a coefficient of variation of less than 4%. Average recovery from fortified tissues was 96% with a coefficient of variation of 6% at the 50--400 ppb level, and 105% with a coefficient of variation of 11% at the 2--40 ppb level.

Animals↗
PubMed1978

Hemodynamic assessment of the new aortic Carpentier-Edwards bioprosthesis.

Although glutaraldehyde-preserved porcine aortic Hancock heterografts have lower thromboembolism incidence than mechanical aortic valves, Hancock xenografts provide less functional aortic outflow orifices and thereby greater transvalvular gradients than mechanical prostheses. The newly developed aortic Carpentier-Edwards porcine heterografts comprise a thin-walled Elgiloy flexible metal stent covered with Teflon which provides somewhat wider internal orifices than aortic Hancock valves of the same external annulus diameter. Since aortic Carpentier-Edwards xenografts have not been clinically evaluated previously, the present study assessed cardiac function and heterograft performance (1.7 months postoperation) and clinical status (4.2 months postoperation) of 19 patients with severe aortic stenosis and/or regurgitation prior to surgery. Left ventricular end-diastolic pressures decreased (17 to 9 mm Hg), cardiac index remained normal, and clinical symptomatology diminished markedly. Mean peak transxenograft systolic pressure was only 16 mm Hg (valve area 1.73 cm2), without meaningful regurgitation. Thus aortic Carpentier-Edwards bioprostheses provide generally excellent heterograft function which appears more favorable than previous reports of Hancock xenografts.

Adolescent↗
PubMed1978

Relationship of myocardial infarction to presence of angina pectoris in patients with coronary heart disease: lack of abolition of angina by infarction.

To evaluate the relationship between myocardial infarction and angina pectoris, history of symptomatic coronary heart disease was analyzed in 146 patients who had had documented myocardial infarction. There were 126 males and 70 females of mean age 55 years (range 32 to 70 years). Infarction had occurred 6 to 63 months prior to the study (mean: 30 months). Angina pectoris occurred at some time during the clinical course of 75 patients (51%), and 71 patients (49%) had not experienced angina. In the majority of the group with angina (n = 39; 52%) the symptom had not been present before infarction, appearing initially thereafter. Angina was present both before and after infarction in 31 patients (41%). In only 5 patients (7%) was precedent angina lost after infarction. Angina was, therefore, present in 70 of 146 patients (48%) after, compared to 36 patients (25%) before, infarction and in 86% (31/36) of patients with angina before infarction it persisted following the attack. Prior angina following myocardial infarction was not related to increased activity since in the majority of patients activity level was less after than before infarction. Post-infarction cardiac failure, which developed in 9 patients who had prior angina, was not associated with abolition of angina in any of this group. It is concluded that: 1. angina is frequent after myocardial infarction, 2. when present before infarction it usually persists thereafter, 3. angina commonly appears as a new symptom after infarction when not previously present and 4. disappearance of angina after infarction is distinctly uncommon.

Adult↗
PubMed1978

A correlative microscopical analysis of differentiating ovarian follicles of mammals.

The mammalian ovary has been studied by optical microscopy and by scanning and transmission electron microscopy with the purpose of presenting an integrated view of the differentiating mammalian follicle. During follicular development, changes in the granulosa cells are particularly noteworthy and include dramatic modifications in cell shape coincident with antrum formation. The cytoplasmic processes of those granulosa cells immediately surrounding the oocyte, as well as the more peripheral granulosa cells comprising a second and third layer, traverse the zona pellucida, infrequently interdigitate with the microvilli of the egg, and make both desmosomal and gap junction contacts with the oocyte. The zona pellucida is thus distinguished by numerous fenestrations of varying diameters. The membrana limitans (basal lamina) is a bipartite structure composed of (a) a homogenous stratum upon which the peripheral layer of granulosa cells rests, and (b) an outer region of collagen-like fibers. The specific advantages and limitations of the different methodologies utilized to study folliculo-genesis are discussed.

Animals↗
PubMed1978

Membrane alterations following interferon treatment.

Interferon treatment appears to induce a number of changes in the plasma membrane of uninfected cells. Interferon treatment altered the surface exposure of gangliosides of both Ly and KB cell membranes. The differences were found in the amount and pattern of incorporation of tritium after galactose oxidase treatment. In AKR,C- (AKR-2B) mouse cells, not only was there an apparent increase in the number of intramembranous particles in response to treatment with interferon but also the kinetics of the increase followed that of the establishment of the antiviral activity. The buoyant density of plasma membrane was also found to be significantly increased in interferon-treated cells. Moloney murine leukemia virus produced in interferon-treated mouse thymus and bone marrow cells had a high particle to infectivity ration. This virus contained a prominent glycoprotein with a molecular weight of about 85,000. This large glycoprotein was only a very minor component of Moloney leukemia virus produced in control TB cells and might be an uncleaved precursor to gp 69-71.

Cell Membrane↗