Effects of aging on intracellular transport of vitamin B12(B12) in rat enterocytes.

Masanori TOYOSHIMA; Masami INADA; Masakuni KAMEYAMA

doi:10.3177/jnsv.29.1

Cytoplasmic transport of fatty acids in rat enterocytes: role of binding to fatty acid-binding protein

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1999.277.2.g361 ◽

1999 ◽

Vol 277 (2) ◽

pp. G361-G366 ◽

Cited By ~ 3

Author(s):

Bruce A. Luxon ◽

Michael T. Milliano

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Intracellular Transport ◽

Fatty Acid Binding Protein ◽

Binding Capacity ◽

Binding Protein ◽

Fatty Acid Binding ◽

Acid Binding Protein ◽

Cytoplasmic Transport ◽

Rat Enterocytes

The intracellular movement of fatty acids is thought to be facilitated through codiffusion with fatty acid-binding protein (FABP). This facilitation may occur by decreasing binding to immobile membranes, leading to faster cytoplasmic diffusion. The aims of this study were to measure the intracellular transport of 12- N-methyl-(7-nitrobenzo-2-oxa-1,3-diazol)aminostearate (NBD-stearate) in villus rat enterocytes and to determine 1) the mechanism of its cytoplasmic transport and 2) if its transport rate correlated with the known variation of FABP binding capacity along the length of the small intestine. Two-dimensional laser photobleaching was used to measure the movement of a fluorescent fatty acid NBD-stearate in enterocytes isolated from different segments of rat intestine. The fraction of NBD-stearate found in the cytostol of enterocytes was determined by differential centrifugation. Cytoplasmic transport of NBD-stearate occurred solely by diffusion and not by convection. Diffusion was homogeneous (nondirectional), consistent with isotropic diffusion. The diffusion rate varied with location along the intestine, correlating with the local FABP concentration and measured cytosolic binding. We conclude that cytoplasmic proteins like FABP promote the intracellular transport of fatty acids by enhancing their diffusive flux. We suggest that facilitation is not specific for a particular cell type but occurs in a variety of cells that transport fatty acids and may contain different types of FABP.

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Changes Occur in Plasma Membrane Turnover when K562 Leukemia Cells are Induced to Differentiate

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100054042 ◽

1982 ◽

Vol 40 ◽

pp. 286-287

Author(s):

L. M. Marshall

Keyword(s):

Plasma Membrane ◽

Membrane Proteins ◽

Intracellular Transport ◽

Parent Cell ◽

Membrane Turnover ◽

Coated Pits ◽

Surface Distribution ◽

Specific Proteins ◽

Erythroleukemic Cell ◽

Specific Membrane

A human erythroleukemic cell line, metabolically blocked in a late stage of erythropoiesis, becomes capable of differentiation along the normal pathway when grown in the presence of hemin. This process is characterized by hemoglobin synthesis followed by rearrangement of the plasma membrane proteins and culminates in asymmetrical cytokinesis in the absence of nuclear division. A reticulocyte-like cell buds from the nucleus-containing parent cell after erythrocyte specific membrane proteins have been sequestered into its membrane. In this process the parent cell faces two obstacles. First, to organize its erythrocyte specific proteins at one pole of the cell for inclusion in the reticulocyte; second, to reduce or abolish membrane protein turnover since hemoglobin is virtually the only protein being synthesized at this stage. A means of achieving redistribution and cessation of turnover could involve movement of membrane proteins by a directional lipid flow. Generation of a lipid flow towards one pole and accumulation of erythrocyte-specific membrane proteins could be achieved by clathrin coated pits which are implicated in membrane endocytosis, intracellular transport and turnover. In non-differentiating cells, membrane proteins are turned over and are random in surface distribution. If, however, the erythrocyte specific proteins in differentiating cells were excluded from endocytosing coated pits, not only would their turnover cease, but they would also tend to drift towards and collect at the site of endocytosis. This hypothesis requires that different protein species are endocytosed by the coated vesicles in non-differentiating than by differentiating cells.

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Effects of aging on axon terminals in the dentate molecular layer

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100128924 ◽

1987 ◽

Vol 45 ◽

pp. 928-929

Author(s):

K. Cullen-Dockstader ◽

E. Fifkova

Keyword(s):

Granule Cells ◽

Molecular Layer ◽

Age Groups ◽

Long Term Potentiation ◽

Male Rats ◽

Perforant Path ◽

Axon Terminals ◽

Fischer 344 ◽

Spatial Memory Deficit ◽

Effects Of Aging

Normal aging results in a pronounced spatial memory deficit associated with a rapid decay of long-term potentiation at the synapses between the perforant path and spines in the medial and distal thirds of the dentate molecular layer (DML), suggesting the alteration of synaptic transmission in the dentate fascia. While the number of dentate granule cells remains unchanged, and there are no obvious pathological changes in these cells associated with increasing age, the density of their axospinous contacts has been shown to decrease. There are indications that the presynaptic element is affected by senescence before the postsynaptic element, yet little attention has been given to the fine structure of the remaining axon terminals. Therefore, we studied the axon terminals of the perforant path in the DML across three age groups.5 Male rats (Fischer 344) of each age group (3, 24 and 30 months), were perfused through the aorta.

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Confocal microscopy of the cytoskeleton in living plant cells following microinjection of fluorescent probes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100146497 ◽

1993 ◽

Vol 51 ◽

pp. 130-131

Author(s):

Ann Cleary

Keyword(s):

Cell Division ◽

Fluorescent Probes ◽

Actin Filaments ◽

Intracellular Transport ◽

Cell Structure ◽

Plant Cells ◽

Cell Plate ◽

Cell Cortex ◽

Living Plant ◽

Rhodamine Phalloidin

Microinjection of fluorescent probes into living plant cells reveals new aspects of cell structure and function. Microtubules and actin filaments are dynamic components of the cytoskeleton and are involved in cell growth, division and intracellular transport. To date, cytoskeletal probes used in microinjection studies have included rhodamine-phalloidin for labelling actin filaments and fluorescently labelled animal tubulin for incorporation into microtubules. From a recent study of Tradescantia stamen hair cells it appears that actin may have a role in defining the plane of cell division. Unlike microtubules, actin is present in the cell cortex and delimits the division site throughout mitosis. Herein, I shall describe actin, its arrangement and putative role in cell plate placement, in another material, living cells of Tradescantia leaf epidermis.The epidermis is peeled from the abaxial surface of young leaves usually without disruption to cytoplasmic streaming or cell division. The peel is stuck to the base of a well slide using 0.1% polyethylenimine and bathed in a solution of 1% mannitol +/− 1 mM probenecid.

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Effects of Aging on the Subcortical Encoding of Stop Consonants

American Journal of Audiology ◽

10.1044/2020_aja-19-00044 ◽

2020 ◽

Vol 29 (3) ◽

pp. 391-403

Author(s):

Dania Rishiq ◽

Ashley Harkrider ◽

Cary Springer ◽

Mark Hedrick

Keyword(s):

Older Adults ◽

Repeated Measures ◽

Mixed Model ◽

Auditory Brainstem ◽

Auditory Brainstem Responses ◽

Aging Effects ◽

Formant Frequency ◽

Place Of Articulation ◽

Second Formant ◽

Effects Of Aging

Purpose The main purpose of this study was to evaluate aging effects on the predominantly subcortical (brainstem) encoding of the second-formant frequency transition, an essential acoustic cue for perceiving place of articulation. Method Synthetic consonant–vowel syllables varying in second-formant onset frequency (i.e., /ba/, /da/, and /ga/ stimuli) were used to elicit speech-evoked auditory brainstem responses (speech-ABRs) in 16 young adults ( M age = 21 years) and 11 older adults ( M age = 59 years). Repeated-measures mixed-model analyses of variance were performed on the latencies and amplitudes of the speech-ABR peaks. Fixed factors were phoneme (repeated measures on three levels: /b/ vs. /d/ vs. /g/) and age (two levels: young vs. older). Results Speech-ABR differences were observed between the two groups (young vs. older adults). Specifically, older listeners showed generalized amplitude reductions for onset and major peaks. Significant Phoneme × Group interactions were not observed. Conclusions Results showed aging effects in speech-ABR amplitudes that may reflect diminished subcortical encoding of consonants in older listeners. These aging effects were not phoneme dependent as observed using the statistical methods of this study.

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