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Biomedical subjects

R G Anderson

Publications and source records attributed to R G Anderson.

At least 163 records · Page 9Linked to original sources
PubMed1980

Ménière's disease: results of treatment with the endolymphatic subarachnoid shunt.

Every otolaryngologist confronts the problem of therapy for Ménière's disease. Although the classic triadic symptoms of episodic vertigo, tinnitus and fluctuating sensorineural hearing loss are well known, an effective and permanent method of relief from these disabling attacks is not known. Medical and particularly surgical treatments of Ménière's disease are controversial. This chapter discusses the senior author's experience with surgical treatment of 125 patients with Ménière's disease. In-depth case analyses are presented in an attempt to identify factors that may account for success or failure of the endolymphatic subarachnoid shunt operation.

Adolescent↗
PubMed1979

Coated pits, coated vesicles, and receptor-mediated endocytosis.

Proteins and peptides can enter cells by receptor-mediated endocytosis, a coupled process by which selected extracellular proteins or peptides are first bound to specific cell surface receptors and then rapidly internalised by the cell. Internalisation follows clustering of the receptors in specialised regions of the cell surface called coated pits that invaginate to form intracellular coated vesicles. It is now recognised that receptor-mediated endocytosis has a fundamental role in the growth, nutrition and differentiation of animal cells.

Animals↗
PubMed1979

Reconstituted low density lipoprotein: a vehicle for the delivery of hydrophobic fluorescent probes to cells.

Previous studies have shown that the cholesteryl ester core of plasma low density lipoprotein (LDL) can be extracted with heptane and replaced with a variety of hydrophobic molecules. In the present report we use this reconstitution technique to incorporate two fluorescent probes, 3-pyrenemethyl-23, 24-dinor-5-cholen-22-oate-3 beta-yl oleate (PMCA oleate) and dioleyl fluorescein, into heptane-extracted LDL. Both fluorescent lipoprotein preparations were shown to be useful probes for visualizing the receptor-mediated endocytosis of LDL in cultured human fibroblasts. When normal fibroblasts were incubated at 37 degrees C with either of the fluorescent LDL preparations, fluorescent granules accumulated in the perinuclear region of the cell. In contrast, fibroblasts from patients with the homozygous form of familial hypercholesterolemia (FH) that lack functional LDL receptors did not accumulate visible fluorescent granules when incubated with the fluorescent reconstituted LDL. A fluorescence-activated cell sorter was used to quantify the fluorescence intensity of individual cells that had been incubated with LDL reconstituted with dioleyl fluorescein. With this technique a population of normal fibroblasts could be distinguished from a population of FH fibroblasts. The current studies demonstrate the feasibility of using fluorescent reconstituted LDL in conjunction with the cell sorter to isolate mutant cells lacking functional LDL receptors.

Cells, Cultured↗
PubMed1979

Demonstration of low density lipoprotein receptors in mouse teratocarcinoma stem cells and description of a method for producing receptor-deficient mutant mice.

Familial hypercholesterolemia, a widespread human genetic disorder implicated in vascular and coronary disease, has had no laboratory animal counterpart that would enable the pathogenesis to be analyzed and drugs to be tested in vivo. The primary lesion in some patients is known to occur in the cells' initial handling of the major cholesterol-carrying lipoprotein of plasma. It entails a deficiency in the specific cell surface receptor that binds low density lipoprotein (LDL), with a consequent alteration in the control of cholesterol metabolism. The present study was undertaken to devise a practical scheme for producing, from developmentally versatile mouse teratocarcinoma stem cells, whole-animal models with a comparable genetic lesion. This requires first learning whether the tumor stem cells in culture express LDL receptors, and next establishing a selection or screening procedure to identify receptor-deficient mutants in mutagenized cell cultures. The results show that the teratocarcinoma cells do in fact have specific high-affinity LDL receptors which are similar to those reported for fibroblasts and the parenchymal cells of specialized tissues and different from those of phagocytic cells. Sterols suppressed the otherwise efficient binding, internalization, and degradation of LDL ((125)I-labeled) by the cells. Acetylation of LDL blocked the binding. Only LDL and not high density lipoprotein (HDL) was bound. After LDL uptake and degradation, the liberated cholesterol led, as expected, to increased cholesteryl ester formation; it also suppressed activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase [HMG CoA reductase; mevalonate: NADP(+) oxidoreductase (CoA-acylating), EC 1.1.1.34], the rate-limiting step in cholesterol biosynthesis. Cells with LDL receptors were readily visualized by administering a fluorescent derivative of LDL; in the fluorescence microscope, labeling was seen in all cells. Cells with experimentally depressed receptors, yielding little fluorescence, were separable from those with normal fluorescence in the fluorescence-activated cell sorter. Thus, two methods for isolating receptor-deficient cells from mutagenized cultures are now available, either by visual recognition of low-fluorescing or nonfluorescing colonies in culture plates or by electronic cell sorting. Such mutants in an appropriate line of teratocarcinoma cells can then be passaged into blastocysts for full somatic tissue differentiation and germ-line development into mice.

Animals↗
PubMed1979

Reversible accumulation of cholesteryl esters in macrophages incubated with acetylated lipoproteins.

Mouse peritoneal macrophages accumulate large amounts of cholesteryl ester when incubated with human low-density lipoprotein that has been modified by chemical acetylation (acetyl-LDL). This accumulation is related to a high-affinity cell surface binding site that mediates the uptake of acetyl-LDL by adsorptive endocytosis and its delivery to lysosomes. The current studies demonstrate that the cholesteryl ester accumulation can be considered in terms of a two-compartment model: (a) the incoming cholesteryl esters of acetyl-LDL are hydrolyzed in lysosomes, and (b) the resultant free cholesterol is re-esterified in the cytosol where the newly formed esters are stored as lipid droplets. The following biochemical and morphologic evidence supports the hydrolysis-re-esterification mechanism: (a) Incubation of macrophages with acetyl-LDL markedly increased the rate of cholesteryl ester synthesis from [14C]oleate, and this was accompanied by an increase in the acyl-CoA:cholesteryl acyltransferase activity of cell-free extracts. (b) When macrophages were incubated with reconstituted acetyl-LDL in which the endogenous cholesterol was replaced with [3H]-cholesteryl linoleate, the [3H]cholesteryl linoleate was hydrolyzed, and at least one-half of the resultant [3H]cholesterol was re-esterified to form [3H]cholesteryl oleate, which accumulated within the cell. The lysosomal enzyme inhibitor chloroquine inhibited the hydrolysis of the [3H]cholesteryl linoleate, thus preventing the formation of [3H]cholesteryl oleate and leading to the accumulation of unhydrolyzed [3H]cholesteryl linoleate within the cells. (c) In the electron microscope, macrophages incubated with acetyl-LDL had numerous cytoplasmic lipid droplets that were not surrounded by a limiting membrane. The time course of droplet accumulation was similar to the time course of cholesteryl ester accumulation as measured biochemically. (d) When acetyl-LDL was removed from the incubation medium, biochemical and morphological studies showed that cytoplasmic cholesteryl esters were rapidly hydrolyzed and that the resultant free cholesterol was excreted from the cell.

Acetylation↗
PubMed1978

Immunocytochemical visualization of coated pits and vesicles in human fibroblasts: relation to low density lipoprotein receptor distribution.

The coated pit-coated vesicle system has a key role in the uptake of plasma low density lipoprotein (LDL) and other receptor-bound proteins in human fibroblasts. To study the distribution of coated pits and coated vesicles in fibroblasts by immunochemical techniques at both the light and electron microscopic levels, we immunized rabbits with coat protein extracted from bovine brain-coated vesicles. The resulting anti-coat protein antibody was directed predominantly against clathrin, the 180,ooo dalton protein that constitutes the major component of coat protein. By indirect immunoperoxidase electron microscopy, the anti-coat protein antibody was observed to bind specifically to coated pits on the surface of human fibroblasts and to coated vesicles within the cell. Indirect immunofluorescence and immunoperoxidase staining techniques at the light microscopic level revealed that the coat protein was distributed in fibroblasts in two distinctive patterns: as discrete foci on or near the cell surface that were linearly aligned in association with phase-dense cellular fibers (first pattern), and as intracellular foci that were randomly arranged around the cell nucleus (second pattern). The distribution of coat protein in fibroblasts was compared with the distribution of ferritin-labeled LDL, which was studied with the use of similar electron microscopic and immunofluorescence techniques. As previously reported, electron microscopic studies revealed that the LDL-ferritin binding sites at 4 degrees C were clustered in coated pits. By immunofluorescence microscopy, the LDL-ferritin that was bound to receptors within coated pits was shown to be arranged linearly over the cell surface in a pattern that was similar to the linear arrangement of coat protein (first pattern). Considered together, the current data indicate that coated pits in human fibroblasts contain a protein analogous to clathrin, and that those coated pits which contain receptors for LDL are located over intracellular fibers most likely corresponding to stress fibers. These observationa may have relevance to the mechanisms by which the coated pit-coated vesicle system efficiently delivers recptor-bound ligands to lysosomes.

Cell Membrane↗
PubMed1978

Adenosine triphosphate induced change in light scattering of isolated basal bodies.

Suspensions of isolated basal bodies undergo a characteristic decrease in turbidity following their exposure to 10(-3) M ATP. Typically, turbidity changes range from 8% to 20%, depending on the preparation, with an average change of 12%. Nucleotides other than ATP did not cause a turbidity decrease. The reaction has a pH optimum of pH 8.5 and is inhibited by concentrations of divalent cations greater than 2 X 10(-3) M. These results indicate that ATP induces a conformational change in the basal body that may be related to its activity in the cell.

Adenosine Triphosphate↗
PubMed1978

Polycationic macromolecules inhibit cilia-mediated ovum transport in the rabbit oviduct.

In both in vitro and in vivo experiments, polycationic macromolecules,such as poly(L-lysine), inhibited the transport of either surrogate or freshly ovulated cumulus masses across the oviduct epithelial surface without affecting the ciliary beat. Whereas transport across the fimbria in vivo was completely inhibited, transport down the ampulla was 3 to 7 times slower than normal. The effects of these polycations suggest that cilia-mediated ovum transport may involve the formation of transient adhesive bonds between the tip of the cilium and elements of the cumulus mass during each beat cycle of the cilium.

Animals↗
PubMed1978

Effects of isoprenaline on the time course of the cyclic AMP level in rat uterus.

Isoprenaline markedly relaxed rat uterine muscle and increased its content of cyclic AMP. The cyclic AMP concentration reached its highest value, about ten times the control after 3 min., after which it declined rather quickly at first but later more slowly. After 60 min. the cyclic AMP content reached twice the prestimulation value. The muscle remained relaxed all the time. If the incubation medium from the uterus treated with isoprenaline for 60 min. was added to a fresh muscle, a normal response was elicited. Addition of a new dose of isoprenaline to a muscle previously incubated with isoprenaline for 60 min. only gave a minimal rise in cyclic AMP after 3 min. The presence of catechol or corticosterone, which both decreased the inactivation of isoprenaline, showed no effect on the decrease of the isoprenaline-stimulated cyclic AMP level. Nor could the decrease in the cyclic AMP response be prevented in the presence of GTP,F-, adenosine or in Ca2+-deficient medium. The addition of theophylline and puromycin both lead to a slower decline of cyclic AMP content, but after 60 min. the value returned to near that seen ater only isoprenaline. Our studies on isoprenaline-induced desensitization of rat uterus have led us to the conclusion that the change in the capacity of the preparations to accumulate cyclic AMP may be a result of either changes in the beta-adrenoceptors or in the cyclase-system.

Adenosine↗
PubMed1978

Genetics of the low density lipoprotein receptor. Diminished receptor activity in lymphocytes from heterozygotes with familial hypercholesterolemia.

Using circulating mononuclear cells as a readily available tissue and using the rate of high affinity degradation of 125-I-labeled low density lipoprotein (LDL) as an index of cell surface LDL receptor activity, we have measured receptor activity in cells from 53 individuals. This group includes 32 healthy subjects, 15 subjects with the heterozygous form of familial hypercholesterolemia, and 6 subjects with hyperlipidemic disorders other than familial hypercholesterolemia. 7 of the healthy subjects and 10 of the heterozygotes were members of a single large kindred with five-generation transmission of the mutant familial hypercholesterolemia gene. LDL receptor activity was assayed in blood mononuclear cells under two sets of conditions. First, 125I-LDL degradation was measured in purified lymphocytes that had been incubated for 3 days in the absence of lipoproteins so as to induce a high level of LDL receptor activity. Phase-contrast autoradiograms of cells incubated with 125I-LDL and electron micrographs of cells incubated with ferritin-labeled LDL confirmed the existence of LDL receptors on lymphocytes. Second, 125I-LDL degradation was measured in mixed mononuclear cells (85-90% lymphocytes and 5-15% monocytes) immediately after their isolation from the bloodstream. This assay represented an attempt to assess the number of receptors actually expressed on the cells when they were in the circulation. Under both sets of conditions, cells from the familial hypercholesterolemia heterozygotes expressed an average of about one-half the normal number of LDL receptors. The current findings are consistent with the conclusion that heterozygotes with familial hypercholesterolemia possess only one functional allele at the LDL receptor locus and that the consequent deficiency of LDL receptors produces the clinical syndrome of heterozygous familial hypercholesterolemia.

Adhesiveness↗
PubMed1978

Mental health training and consultation: a model for liaison with clergy.

A chaplain, a psychiatrist, and a social worker developed a program to train clergy in more effective mental health case management, counseling, and referral skills, and to sensitize mental health center professionals to the work of the clergy in mental health. The program consists of 12 two-hour meetings conducted by a clinician and a chaplain once a week. In the first four meetings, clergy are trained to use a self-report personal-data kit with individuals presenting with emotional problems. In the next eight meetings, clergy make case presentations that are used as a basis for consultation and group discussion. The project has established a firm basis for collaboration between clergy and mental health center staff in providing care.

Community Mental Health Services↗
PubMed1977

Mutations affecting the binding, internalization, and lysosomal hydrolysis of low density lipoprotein in cultured human fibroblasts, lymphocytes, and aortic smooth muscle cells.

Studies comparing the metabolism of low density lipoprotein (LDL) in normal cells and in cells cultured from patients with homozygous familial hypercholesterolemia have disclosed the existence of a receptor for plasma LDL. This receptor has been identified on the surface of human fibroblasts, lymphocytes, and aortic smooth muscle cells. An extension of these studies to cell strains derived from patients with other single gene defects in cholesterol metabolism has provided additional insight into the normal mechanisms by which cells regulate their cholesterol content and how alterations in these genetic control mechanisms may predispose to atherosclerosis in man.

Aorta↗