Macromolecular Physiology of Plastids

1969 ◽  
Vol 5 (3) ◽  
pp. 757-793
Author(s):  
K. W. HENNINGSEN ◽  
J. E. BOYNTON
Keyword(s):  
Structural Changes ◽  
Spectral Shift ◽  
Primary Leaf ◽  
Prolamellar Body ◽  
Time Interval ◽  
Intermediate Step ◽  
Thin Sections ◽  
Prolamellar Bodies ◽  
Rapid Transformation

Barley seedlings developing at 23 °C in darkness have been studied at various ages for changes in fresh weight, height of shoot, protochlorophyll content and structure of the etioplasts in the primary leaf. Changes of the pigments in vivo, such as the spectral shift of the newly formed chlorophyll and the resynthesis of protochlorophyll, were studied spectrophotometrically prior to and following a 1-min illumination. Concomitantly, leaf tissue was fixed with glutaraldehyde-OsO4 and later analysed in thin sections using the electron microscope. In darkness, protochlorophyll content in the primary leaf, size of the etioplasts, size of the crystalline prolamellar bodies and area of the primary lamellar layers reach their maximum values on the 7th day. Thereafter all the aforementioned parameters decrease, particularly the protochlorophyll content. The structural changes of the prolamellar-body material, rate of the spectral shift of the newly formed chlorophyll and rate of the resynthesis of protochlorophyll in darkness after photoconversion of the original protochlorophyll depend on seedling age. In both 5- and 7-day-old seedlings with high protochlorophyll content, the illumination causes a rapid transformation of the prolamellar bodies. Subsequently in 5-day-old seedlings, a rapid resynthesis of protochlorophyll takes place and the prolamellar bodies recrystallize before dispersal is completed. In the 7-day-old seedlings, resynthesis of protochlorophyll is slower and the prolamellar bodies are largely dispersed into primary lamellar layers before resynthesis of protochlorophyll and reformation of crystalline prolamellar bodies ensue. In 5-day-old seedlings, in which resynthesis of protochlorophyll and recrystallization of the prolamellar bodies are completed within less than 1 h in darkness following illumination, a second illumination effects a more rapid transformation and dispersal of the prolamellar bodies than is observed after the first illumination. In 9- and 11-day-old seedlings, in which the content of protochlorophyll is low, transformation of the prolamellar bodies occurs slowly in darkness following the initial illumination and is not completed within 60 min. No significant protochlorophyll resynthesis and no dispersal of the prolamellar bodies were observed during this time interval. Dispersal of the prolamellar bodies results in an increase in the area of the primary lamellar layers. During reformation of protochlorophyll, a decrease in area of the primary lamellar layers is correlated with an increase in volume and number of the prolamellar bodies. These quantitative relationships between the parameters for prolamellar bodies and primary lamellar layers indicate that, for dispersal and recrystallization of the prolamellar bodies, no significant amount of membrane synthesis is required. Different configurations of the prolamellar bodies can occur: protochlorophyll is associated with the crystalline configurations where the spacing of the tubules is either narrow or wide; chlorophyll is associated with the transformed prolamellar-body configuration. The narrow and wide crystalline configurations appear to be interconvertible, and re-organization does not necessarily involve the primary lamellar layers as an intermediate step. Wide spacing of the tubules coincides with the highest pigment content.

scholarly journals EARLY STAGES IN THE DEVELOPMENT OF PLASTID FINE STRUCTURE IN RED AND FAR-RED LIGHT

1964 ◽  
Vol 22 (2) ◽  
pp. 433-442 ◽  
Author(s):  
Shimon Klein ◽  
G. Bryan ◽  
Lawrence Bogorad
Keyword(s):  
Fine Structure ◽  
Stages Of Change ◽  
Structural Changes ◽  
Red Light ◽  
Prolamellar Body ◽  
Lag Phase ◽  
Prolamellar Bodies ◽  
Chlorophyll Accumulation ◽  
Time Required ◽  
Bean Leaves

Developmental changes in fine structure were studied in plastids of etiolated bean leaves during the time required for the protochlorophyllide-chlorophyllide transformation and the following lag phase prior to chlorophyll accumulation. In agreement with some other workers, two distinct stages of change in the fine structure of proplastids were found to occur upon illumination during this period. The first involves a dissociation of the previously fused units in the prolamellar bodies of the proplastids and occurs simultaneously with the protochlorophyllide-chlorophyllide conversion in light of 655 mµ, but not of 682, 700, or 730 mµ. The effect of the red light could not be reversed by a simultaneously supplied stronger far-red irradiation. The energy requirements for these structural changes parallel those for the pigment conversion. During the following step the vesicles which arose from the fused units of the prolamellar body were dispersed in rows through the stroma, and the prolamellar bodies themselves disappeared. For these changes to occur, higher light energies were required and the leaves had to be illuminated for longer periods. A red preillumination seemed to accelerate the development somewhat. The structural changes could be induced by light of 655 mµ, but also, to a lesser degree, of 730 mµ. No measurable additional chlorophyll accumulated during this period. Thus, the structural changes observed were independent of major changes in pigment content.

Macromolecular Physiology of Plastids

1970 ◽  
Vol 7 (3) ◽  
pp. 587-621
Author(s):  
K. W. HENNINGSEN
Keyword(s):  
Absorption Maximum ◽  
Time Course ◽  
Spectral Shift ◽  
Prolamellar Body ◽  
Phaseolus Vulgaris L ◽  
Freezing And Thawing ◽  
Temperature Dependent ◽  
In Vivo Absorption ◽  
Tubular Membranes

Dispersal of the prolamellar body tubules into primary lamellar layers has been studied in leaves of dark-grown bean seedlings (Phaseolus vulgaris L.). Following complete photoconversion of protochlorophyllide the dispersal process can proceed in either light or darkness. The dispersal is reversibly inhibited in leaves at o °C. Above o °C the time course for the dispersal is temperature dependent. The spectral shift of the in vivo absorption maximum of newly formed chlorophyllide from 684 to 672 nm is also inhibited at o °C and the time course is temperature-dependent in a manner similar to that of the membrane dispersal. A causal connexion between the 2 phenomena can thus be suggested. Derangement of the tubular membranes produced by heat treatment or by freezing and thawing in darkness causes the appearance of photoactive protochlorophyllide absorbing at 635 nm. Photoconversion of protochlorophyllide 635 nm results in chlorophyllide absorbing at 672 nm and further dissociation of the membranes. Denaturation of the prolamellar body membranes by heating or by slow thawing results in the formation of photoinactive protochlorophyllide absorbing at 632 nm.

Fine Structural Changes in the Microvasculature of the Mouse Pinna: Aging and Radiation Injury

1974 ◽  
Vol 32 ◽  
pp. 54-55
Author(s):  
S. Phyllis Steamer ◽  
Rosemarie L. Devine
Keyword(s):  
Structural Changes ◽  
Radiation Treatment ◽  
Arterial Stenosis ◽  
Ultrastructural Changes ◽  
Vascular Effects ◽  
Microvascular Changes ◽  
Surrounding Connective Tissue ◽  
Fission Neutrons ◽  
Total Body

The importance of radiation damage to the skin and its vasculature was recognized by the early radiologists. In more recent studies, vascular effects were shown to involve the endothelium as well as the surrounding connective tissue. Microvascular changes in the mouse pinna were studied in vivo and recorded photographically over a period of 12-18 months. Radiation treatment at 110 days of age was total body exposure to either 240 rad fission neutrons or 855 rad 60Co gamma rays. After in vivo observations in control and irradiated mice, animals were sacrificed for examination of changes in vascular fine structure. Vessels were selected from regions of specific interest that had been identified on photomicrographs. Prominent ultrastructural changes can be attributed to aging as well as to radiation treatment. Of principal concern were determinations of ultrastructural changes associated with venous dilatations, segmental arterial stenosis and tortuosities of both veins and arteries, effects that had been identified on the basis of light microscopic observations. Tortuosities and irregularly dilated vein segments were related to both aging and radiation changes but arterial stenosis was observed only in irradiated animals.

Probing the ultrastructure of the mitotic and meiotic spindle in eggs: An expeditious approach based on semi-thin (0.25 μm) serial sections

1983 ◽  
Vol 41 ◽  
pp. 552-555
Author(s):  
Conly L. Rieder ◽  
S. Bowser ◽  
R. Nowogrodzki ◽  
K. Ross ◽  
G. Sluder
Keyword(s):  
Small Sample Size ◽  
Small Sample ◽  
Meiotic Spindle ◽  
Serial Sections ◽  
Mitotic Apparatus ◽  
Thin Sections ◽  
Cell Cycles ◽  
Ultrastructural Studies

Eggs have long been a favorite material for studying the mechanism of karyokinesis in-vivo and in-vitro. They can be obtained in great numbers and, when fertilized, divide synchronously over many cell cycles. However, they are not considered to be a practical system for ultrastructural studies on the mitotic apparatus (MA) for several reasons, the most obvious of which is that sectioning them is a formidable task: over 1000 ultra-thin sections need to be cut from a single 80-100 μm diameter egg and of these sections only a small percentage will contain the area or structure of interest. Thus it is difficult and time consuming to obtain reliable ultrastructural data concerning the MA of eggs; and when it is obtained it is necessarily based on a small sample size.We have recently developed a procedure which will facilitate many studies concerned with the ultrastructure of the MA in eggs. It is based on the availability of biological HVEM's and on the observation that 0.25 μm thick serial sections can be screened at high resolution for content (after mounting on slot grids and staining with uranyl and lead) by phase contrast light microscopy (LM; Figs 1-2).

Facilitated migration of cells from a transected peripheral nerve over collagen fibers: in vivo observations

1989 ◽  
Vol 47 ◽  
pp. 888-889
Author(s):  
Arthur J. Wasserman ◽  
Azam Rizvi ◽  
George Zazanis ◽  
Frederick H. Silver
Keyword(s):  
Sciatic Nerve ◽  
Peripheral Nerve ◽  
Collagen Gel ◽  
Collagen Fibers ◽  
Control Group ◽  
Guide Tube ◽  
Sprague Dawley ◽  
Silicone Tube ◽  
Thin Sections

In cases of peripheral nerve damage the gap between proximal and distal stumps can be closed by suturing the ends together, using a nerve graft, or by nerve tubulization. Suturing allows regeneration but does not prevent formation of painful neuromas which adhere to adjacent tissues. Autografts are not reported to be as good as tubulization and require a second surgical site with additional risks and complications. Tubulization involves implanting a nerve guide tube that will provide a stable environment for axon proliferation while simultaneously preventing formation of fibrous scar tissue. Supplementing tubes with a collagen gel or collagen plus extracellular matrix factors is reported to increase axon proliferation when compared to controls. But there is no information regarding the use of collagen fibers to guide nerve cell migration through a tube. This communication reports ultrastructural observations on rat sciatic nerve regeneration through a silicone nerve stent containing crosslinked collagen fibers.Collagen fibers were prepared as described previously. The fibers were threaded through a silicone tube to form a central plug. One cm segments of sciatic nerve were excised from Sprague Dawley rats. A control group of rats received a silicone tube implant without collagen while an experimental group received the silicone tube containing a collagen fiber plug. At 4 and 6 weeks postoperatively, the implants were removed and fixed in 2.5% glutaraldehyde buffered by 0.1 M cacodylate containing 1.5 mM CaCl2 and balanced by 0.1 M sucrose. The explants were post-fixed in 1% OSO4, block stained in 1% uranyl acetate, dehydrated and embedded in Epon. Axons were counted on montages prepared at a total magnification of 1700x. Montages were viewed through a dissecting microscope. Thin sections were sampled from the proximal, middle and distal regions of regenerating sciatic plugs.

scholarly journals Interaction of Lactoferrin with Unsaturated Fatty Acids: In Vitro and In Vivo Study of Human Lactoferrin/Oleic Acid Complex Cytotoxicity

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1602
Author(s):  
Anna Elizarova ◽  
Alexey Sokolov ◽  
Valeria Kostevich ◽  
Ekaterina Kisseleva ◽  
Evgeny Zelenskiy ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Structural Changes ◽  
Unsaturated Fatty Acids ◽  
Structural Features ◽  
Control Group ◽  
Acid Complex ◽  
Hepatoma 22A ◽  
Constitutive Parameters

As shown recently, oleic acid (OA) in complex with lactoferrin (LF) causes the death of cancer cells, but no mechanism(s) of that toxicity have been disclosed. In this study, constitutive parameters of the antitumor effect of LF/OA complex were explored. Complex LF/OA was prepared by titrating recombinant human LF with OA. Spectral analysis was used to assess possible structural changes of LF within its complex with OA. Structural features of apo-LF did not change within the complex LF:OA = 1:8, which was toxic for hepatoma 22a cells. Cytotoxicity of the complex LF:OA = 1:8 was tested in cultured hepatoma 22a cells and in fresh erythrocytes. Its anticancer activity was tested in mice carrying hepatoma 22a. In mice injected daily with LF-8OA, the same tumor grew significantly slower. In 20% of animals, the tumors completely resolved. LF alone was less efficient, i.e., the tumor growth index was 0.14 for LF-8OA and 0.63 for LF as compared with 1.0 in the control animals. The results of testing from 48 days after the tumor inoculation showed that the survival rate among LF-8OA-treated animals was 70%, contrary to 0% rate in the control group and among the LF-treated mice. Our data allow us to regard the complex of LF and OA as a promising tool for cancer treatment.

scholarly journals Brown Spiders’ Phospholipases-D with Potential Therapeutic Applications: Functional Assessment of Mutant Isoforms

Biomedicines ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 320
Author(s):  
Thaís Pereira da Silva ◽  
Fernando Jacomini de Castro ◽  
Larissa Vuitika ◽  
Nayanne Louise Costacurta Polli ◽  
Bruno César Antunes ◽  
...  
Keyword(s):  
Structural Changes ◽  
Capillary Permeability ◽  
Structural Data ◽  
Histopathological Analysis ◽  
Amino Acid Residues ◽  
Wild Type ◽  
Antigenic Properties ◽  
Harmful Effects

Phospholipases-D (PLDs) found in Loxosceles spiders’ venoms are responsible for the dermonecrosis triggered by envenomation. PLDs can also induce other local and systemic effects, such as massive inflammatory response, edema, and hemolysis. Recombinant PLDs reproduce all of the deleterious effects induced by Loxosceles whole venoms. Herein, wild type and mutant PLDs of two species involved in accidents—L. gaucho and L. laeta—were recombinantly expressed and characterized. The mutations are related to amino acid residues relevant for catalysis (H12-H47), magnesium ion coordination (E32-D34) and binding to phospholipid substrates (Y228 and Y228-Y229-W230). Circular dichroism and structural data demonstrated that the mutant isoforms did not undergo significant structural changes. Immunoassays showed that mutant PLDs exhibit conserved epitopes and kept their antigenic properties despite the mutations. Both in vitro (sphingomyelinase activity and hemolysis) and in vivo (capillary permeability, dermonecrotic activity, and histopathological analysis) assays showed that the PLDs with mutations H12-H47, E32-D34, and Y228-Y229-W230 displayed only residual activities. Results indicate that these mutant toxins are suitable for use as antigens to obtain neutralizing antisera with enhanced properties since they will be based on the most deleterious toxins in the venom and without causing severe harmful effects to the animals in which these sera are produced.

scholarly journals Structural basis for a complex I mutation that blocks pathological ROS production

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Zhan Yin ◽  
Nils Burger ◽  
Duvaraka Kula-Alwar ◽  
Dunja Aksentijević ◽  
Hannah R. Bridges ◽  
...  
Keyword(s):  
Point Mutation ◽  
Complex I ◽  
Structural Changes ◽  
Ischemia Reperfusion ◽  
Single Point ◽  
Structural Basis ◽  
Single Point Mutation ◽  
Ros Production

AbstractMitochondrial complex I is central to the pathological reactive oxygen species (ROS) production that underlies cardiac ischemia–reperfusion (IR) injury. ND6-P25L mice are homoplasmic for a disease-causing mtDNA point mutation encoding the P25L substitution in the ND6 subunit of complex I. The cryo-EM structure of ND6-P25L complex I revealed subtle structural changes that facilitate rapid conversion to the “deactive” state, usually formed only after prolonged inactivity. Despite its tendency to adopt the “deactive” state, the mutant complex is fully active for NADH oxidation, but cannot generate ROS by reverse electron transfer (RET). ND6-P25L mitochondria function normally, except for their lack of RET ROS production, and ND6-P25L mice are protected against cardiac IR injury in vivo. Thus, this single point mutation in complex I, which does not affect oxidative phosphorylation but renders the complex unable to catalyse RET, demonstrates the pathological role of ROS production by RET during IR injury.

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