Polarized pigment granule transport occurs in the absence of microtubules in squirrelfish erythrophores: studies of the effects of estramustine

1987 ◽  
Vol 87 (4) ◽  
pp. 565-580
Author(s):  
M.E. Stearns ◽  
M. Wang
Keyword(s):  
Pigment Granule ◽  
Electron Microscopic ◽  
Microtubule Associated Proteins ◽  
Voltage Electron ◽  
Associated Proteins ◽  
Drug Inhibition ◽  
Microscopic Studies ◽  
10 Nm Filaments ◽  
Inhibition Studies

We have re-examined the involvement of microtubules in the process of pigment granule transport in squirrelfish erythrophores in situ (i.e. on scales). Light-microscopic studies revealed that following exposure to 5 microM-nocodazole for 1 h at 4 degrees C erythrophores retained an ability to aggregate and disperse their pigment uniformly, though at reduced rates. Serial thick-section stereo high-voltage electron-microscopic studies showed that the entire microtubule population was removed by drug treatment and that the microtubules were not reassembled as a result of pigment translocation processes in the presence of reduced levels of nocodazole (0.4 microM). Immunofluorescence microscopic studies confirmed that nocodazole (0.5-1 microM) produced rapid disassembly of the microtubules. Whole-mount electron-microscopic studies showed that the pigment granules were suspended in a cross-linking network of 3–10 nm filaments, which appeared to support ordered pigment transport in situ in the absence of microtubules. Drug inhibition studies showed that micromolar levels of estramustine, a novel anti-MAPs (microtubule-associated proteins) drug, reversibly inhibited pigment transport. The results suggest that an estramustine-sensitive cytomatrix component might produce polarized pigment transport in intact erythrophores.

mRNA localization by Electron microscopic in situ hybridization

1991 ◽  
Vol 49 ◽  
pp. 430-431
Author(s):  
J. A. Pollock ◽  
M. Martone ◽  
T. Deerinck ◽  
M. H. Ellisman
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Nucleic Acids ◽  
Recombinant Dna ◽  
Light And Electron Microscopy ◽  
Electron Microscopic ◽  
High Voltage Electron Microscopy ◽  
Functional Sites ◽  
Voltage Electron

Localization of specific proteins in cells by both light and electron microscopy has been facilitate by the availability of antibodies that recognize unique features of these proteins. High resolution localization studies conducted over the last 25 years have allowed biologists to study the synthesis, translocation and ultimate functional sites for many important classes of proteins. Recently, recombinant DNA techniques in molecular biology have allowed the production of specific probes for localization of nucleic acids by “in situ” hybridization. The availability of these probes potentially opens a new set of questions to experimental investigation regarding the subcellular distribution of specific DNA's and RNA's. Nucleic acids have a much lower “copy number” per cell than a typical protein, ranging from one copy to perhaps several thousand. Therefore, sensitive, high resolution techniques are required. There are several reasons why Intermediate Voltage Electron Microscopy (IVEM) and High Voltage Electron Microscopy (HVEM) are most useful for localization of nucleic acids in situ.

Scanning electron microscopic study of collagen fibrillogenesis and extracellular compartmentalization in the chick embryo tendon

1986 ◽  
Vol 44 ◽  
pp. 208-209
Author(s):  
Grace C.H. Yang
Keyword(s):  
Chick Embryo ◽  
Extracellular Space ◽  
Fibroblast Cell ◽  
Collagen Fibrils ◽  
Electron Microscopic ◽  
Voltage Electron ◽  
Scanning Electron Microscopic Study ◽  
Microscopic Studies ◽  
And Function

The size and organization of collagen fibrils in the extracellular matrix is an important determinant of tissue structure and function. The synthesis and deposition of collagen involves multiple steps which begin within the cell and continue in the extracellular space. High-voltage electron microscopic studies of the chick embryo cornea and tendon suggested that the extracellular space is compartmentalized by the fibroblasts for the regulation of collagen fibril, bundle, and tissue specific macroaggregate formation. The purpose of this study is to gather direct evidence regarding the association of the fibroblast cell surface with newly formed collagen fibrils, and to define the role of the fibroblast in the control and the precise positioning of collagen fibrils, bundles, and macroaggregates during chick tendon development.

The lurcher gene induces apoptotic death in cerebellar Purkinje cells

Development ◽  
1995 ◽  
Vol 121 (4) ◽  
pp. 1183-1193 ◽  
Author(s):  
D.J. Norman ◽  
L. Feng ◽  
S.S. Cheng ◽  
J. Gubbay ◽  
E. Chan ◽  
...  
Keyword(s):  
Purkinje Cells ◽  
Nuclear Dna ◽  
Neuronal Loss ◽  
Terminal Phase ◽  
Nuclear Condensation ◽  
Electron Microscopic ◽  
Apoptotic Death ◽  
Microscopic Studies ◽  
Cerebellar Purkinje Cells

In the neurologically mutant mouse strain lurcher (Lc), heterozygous animals display cell autonomous degeneration of cerebellar Purkinje cells beginning in the second postnatal week. During the course of our studies to identify the genetic lesion responsible for this disease (Norman et al., 1991), we have formulated an hypothesis suggesting that in Lc Purkinje cells homeostasis is sufficiently perturbed to lead to the activation of programmed cell death, thus resulting in neuronal loss and the consequent neurologic disease (Heintz, 1993). To address this possibility, we have examined the properties of Lc Purkinje cells as they die during the second postnatal week. Our light and electron microscopic studies demonstrate that dying Lc Purkinje cells exhibit the characteristic morphologic features of apoptosis, including nuclear condensation, axon beading and membrane blebbing. Using an in situ end-labeling method, we have also detected nicked nuclear DNA in these cells. Furthermore, we have examined the expression of the sulfated glycoprotein 2 (SGP2), whose mRNA is induced in both T-cells and prostate epithelial cells undergoing apoptotic death. We show by in situ hybridization that SGP2 is not expressed at detectable levels in normal Purkinje cells, but that its mRNA is present in Lc Purkinje cells prior to their death. Also expression of the Kv3.3b potassium channel, which marks the terminal phase of Purkinje cell differentiation, is evident in Lc Purkinje cells prior to their death. These data demonstrate that the Lc mutation induces apoptosis in cerebellar Purkinje cells following their maturation in postnatal cerebellum. Isolation of the Lc mutation and further analysis of its action in eliciting apoptosis can provide an important opportunity for understanding the etiology of neurodegenerative disease.

Estramustine binds MAP-2 to inhibit microtubule assembly in vitro

1988 ◽  
Vol 89 (3) ◽  
pp. 331-342
Author(s):  
M.E. Stearns ◽  
K.D. Tew
Keyword(s):  
Linear Regression Analysis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Gel Filtration ◽  
Microtubule Assembly ◽  
Scatchard Analysis ◽  
Binding Assays ◽  
Electron Microscopic ◽  
Associated Proteins ◽  
Microscopic Studies

We have investigated the ability of estramustine to bind to rat brain microtubule-associated proteins (MAPs) and purified MAP-2 in vitro. [3H]estramustine's relative affinity for tubulin and MAPs was assessed by gel filtration chromatography, immunoprecipitation and binding assays. Scatchard analysis demonstrated a specific affinity of the drug for MAP-2. Calculations from kinetic parameters and non-linear regression analysis gave a Kd of 15 microM, and a Bmax of 3.4 × 10(−7)M ml-1. Extrapolation of this value suggested that each MAP-2 molecule binds approximately 20 molecules of estramustine. Microtubule assembly studies and SDS-polyacrylamide gel electrophoresis revealed that at 20–60 microM levels, estramustine inhibited the association of MAPs with taxol microtubules. Turbidity (A350) studies further demonstrated that 20–60 microM-estramustine inhibited MAP-2-driven tubulin assembly and produced microtubule disassembly. Electron-microscopic studies confirmed the centrifugation and turbidity results. The data demonstrated that estramustine can bind MAPs and MAP-2 specifically, thereby inhibiting microtubule assembly.

Sodium channels in astrocytes of rat optic nerve in situ: immuno-electron microscopic studies.

Glia ◽  
1999 ◽  
Vol 28 (1) ◽  
pp. 84-84
Author(s):  
J.A. Black ◽  
B. Friedman ◽  
L.W. Elmer ◽  
S.G. Waxman
Keyword(s):  
Optic Nerve ◽  
Sodium Channels ◽  
Electron Microscopic ◽  
Microscopic Studies

In Situ Nitride Growth Studies by Low Energy Electron Microscopy (LEEM) and Low Energy Electron Diffraction (LEED)

1997 ◽  
Vol 3 (S2) ◽  
pp. 611-612
Author(s):  
E. Bauer ◽  
A. Pavlovska ◽  
I.S.T. Tsong
Keyword(s):  
Low Energy ◽  
Energy Electron ◽  
Ex Situ ◽  
Electron Microscopic ◽  
Insulating Layer ◽  
Light Emitting ◽  
Surface Sensitivity ◽  
Microscopic Studies ◽  
Low Energy Electron

Nitride films play an increasing role in modern electronics, for example silicon nitride as insulating layer in Si-based devices or GaN in blue light emitting diodes and lasers. For this reason they have been the subject of many ex situ electron microscopic studies. A much deeper understanding of the growth of these important materials can be obtained by in situ studies. Although these could be done by SEM, LEEM combined with LEED is much better suited because of its excellent surface sensitivity and diffraction contrast. We have in the past studied the high temperture nitridation of Si(l11) by ammonia (NH3)and the growth of GaN and A1N films on Si(l11) and 6H-SiC(0001) by depositing Ga and Al in the presence of NH3 and will report some of the results of this work for comparison with more recent work using atomic nitrogen instead of NH3.

LIGHT AND ELECTRON MICROSCOPIC STUDIES OF THYROTROPHIN RELEASING HORMONE-INDUCED GROWTH HORMONE AND PROLACTIN RELEASE IN HYPOPHYSECTOMIZED RATS BEARING AN ECTOPIC PITUITARY GLAND

1977 ◽  
Vol 72 (3) ◽  
pp. 313-319 ◽  
Author(s):  
G. L. ROSSI ◽  
DOROTHEA PROBST ◽  
A. E. PANERAI ◽  
IRIT GIL-AD ◽  
DANIELA COCCHI ◽  
...  
Keyword(s):  
Prolactin Cells ◽  
Electron Microscopic ◽  
Time Intervals ◽  
Thyrotrophin Releasing Hormone ◽  
Releasing Hormone ◽  
Highly Active ◽  
Microscopic Studies ◽  
Pituitary Glands ◽  
Hypophysectomized Rats

SUMMARY A light microscopic and ultrastructural study of anterior pituitary glands transplanted under the kidney capsule of hypophysectomized rats was performed, in basal conditions and after stimulation with thyrotrophin releasing hormone, at various intervals (24 h–2 months) after transplantation. Confirming previous biochemical findings, the results suggest that with time, somatotrophs acquire sensitivity to thyrotrophin releasing hormone and respond with increased exocytosis at doses that were found ineffective in pituitary glands in situ. Thryotrophin releasing hormone stimulation did not seem to influence the morphology of prolactin cells, which were already highly active under basal conditions at all time intervals.

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