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M Locke

Publications and source records attributed to M Locke.

At least 73 records · Page 4Linked to original sources
PubMed1982

The correlation between bismuth and uranyl staining and phosphorus content of intracellular structures as determined by electron spectroscopic imaging.

Four groups of intracellular structures can be recognized according to bismuth and uranyl staining and phosphorus content. (1) Those which contain phosphorus and stain strongly with uranyl acetate but not with bismuth (ribosomes, heterochromatin and mature ribosomal precursor granules), presumably because of their nucleic acid content. (2) Those which contain phosphorus and stain with uranyl acetate and bismuth (interchromatin granules, immature ribosomal precursor granules and mitochondrial granules), presumably because at least some of their phosphate is available to react with bismuth. (3) Those which contain little phosphorus but which stain strongly with bismuth and weakly with uranyl acetate (Golgi complex beads), perhaps because some ligand in addition to phosphate reacts with bismuth, and (4) those which do not contain phosphorus and stain with neither uranyl acetate nor bismuth (portasomes). Uranyl staining correlates strongly with the phosphorus content of nucleic acids, proteins and inorganic deposits. Bismuth will stain some phosphorylated molecules but not all. Thus only some phosphates stain with bismuth.

Animals↗
PubMed1981

Epidermal feet in pupal segment morphogenesis.

Epidermal cells in insect integumental epithelia develop branched cytoskeletal extensions or feet at their base that are similar in appearance to the processes put out by cells in tissue culture. We have developed a procedure to show the feet that gives an effect as if thousands of cells randomly arranged in the epithelium had each been injected with lead salt visualized as black lead sulphide. The procedure depends upon the fact that after brief glutaraldehyde fixation, tannic acid only penetrates some cells where it mordants lead ions and binds osmium. Individual cells visualized in this manner show their outlines as if they are separate in a tissue culture although they are part of a closely packed epithelium. The feet are metamorphic structures formed after pupal commitment and are necessary for metamorphic changes in segment shape. In Calpodes larvae the feet are orientated axially in the direction of the segmentally repeating gradient and may extend for several cell diameters. They extend under the influence of low titres of 20-hydroxyecdysone such as those occurring in the intermoult. When stimulated by high titres like those in pre-pupae, the feet contract at the same time as the segments shorten to pupal proportions. We believe that cell processes like the epidermal feet are ubiquitous but that they have often been overlooked because of the difficulty of demonstrating the outlines of single cells that are united in epithelia.

Animals↗
PubMed1980

The nucleolus during epidermal development in an insect.

The fifth stadium of Calpodes has two phases of epidermal cell development corresponding to preparation for intermoult and for moult syntheses. Both phases begin with a period of elevated RNA synthesis and the elaboration of a multilobed nucleolus. The apparent number of nucleoli changes from about two to eight and back to two again within the few hours of elevated RNA synthesis. The nucleolar changes are preceded by elevated titres of haemolymph ecdysteroid. During the two periods of activity, alveoli in the matrix of the nucleoli contain particles believed to be ribosomal precursors. The staining properties of these granules differ according to size in a way that suggests a developmental sequence. Mature granules are about 20 nm in diameter and do not stain with bismuth. They are found at the periphery of the nucleolus, in the nucleoplasm, at the approaches to and within the nucleopores. Perichromatin granules, believed to be m-RNA precursor packages, are up to 60 nm in diameter, do stain with bismuth and are found at the periphery of chromatin, in nucleoplasm and distorted at the approaches to the nuclear pores to fit within the central channel. During these periods of heightened activity the nuclear envelope contains microvesicles that may be free or attached to either nuclear or cytoplasmic surfaces. The structure is appropriate for the microvesicular transnuclear envelope movement of molecules such as the ecdysteroid believed to initiate the nuclear changes.

Animals↗
PubMed1979

Apolysis and the turnover of plasma membrane plaques during cuticle formation in an insect.

The apical plasma membranes of Calpodes epidermal cells have small fattened areas or plaques with an extra density upon their cytoplasmic face. The plaques are typically at the tips of microvilli. The are present during the deposition of fibrous cuticle and the cuticulin layer. Since the plaques are close (less than 15nm) to the sites where these kinds of cuticle first appear, they are presumed to have a role in their synthesis and/or deposition and orientation. When fifth stage larval cuticle deposition ceases prior to pupation, the plaques are lost as the area of the apical plasma membrane is reduced. The plaques pass from the surface into pinocytosis vesicles and multivesicular bodies where they are presumably digested. The loss of plaques occurs as the blood level of moulting hormone reaches a peak at the critical period after which the prothoracic glands are no longer needed for pupation. Apolysis or separation of the epidermis from the old cuticle is the stage when plaques are absent, the old ones have been lost but the new ones have yet to form. After the critical period, the epidermis prepared for pupation with a phase of elevated RNA synthesis at the end of which plaques and microvilli reform in time to secrete the new cuticulin layer and later the fibrous cuticle of the pharate pupa. There is a new generation of plaques for each moult and succeeding intermoult and each generation is involved in two kinds of cuticle deposition before involution and redifferentiation.

Animals↗
PubMed1978

Nucleoprotein localization by bismuth staining.

Experiments on isolated mouse liver muclei involving enzyme digestion, the crosslinking of amino groups and alkaline hydrolysis demonstrate that bismuth binds to nucleoproteins through amino and phosphate groups. Analysis of the nucleoproteins extracted with salt and acid solutions in conjunction with bismuth staining after these treatments suggests that: (1) a bismuth amino group interaction occurs on ribonucleo-protein particles, histones and perhaps some non-histone chromosomal proteins, and (2) bismuth phosphate binding is specific for one, or all, of three distinct species of non-histone proteins. These results suggest that histones not tightly bound to DNA through their amino groups are present on interchromatin granules, the presumed transcriptionally active regions of chromatin. Phosphorylated non-histone proteins are also localized at these sites. Staining with heavy metals such as bismuth may be the best method for high resolution localization of nucleoproteins involved with regulating gene activity and maintaining chromatin structure.

Animals↗
PubMed1976

Vertebrate Golgi complexes have beads in a similar position to those found in arthropods.

Insects and other arthropods have bead-like structures in Golgi complexes from all cell types. They are arranged in rings at the base of transition vesicles located near the smooth surface of the rough endoplasmic reticulum making the forming face of the Golgi complex and are only seen easily after staining in bismuth salts. Procedures used to demonstrate the beads in arthropod Golgi complexes do not selectively stain any structures where they would be expected to occur in several mouse and tadpole tissues. However, a faint pattern similar to the arthropod GC beads can be made out in the large GCs concerned in the formation of acrosomes during mouse spermatogenesis. Uranyl staining shows particles of about the same size and spacing as the beads of arthropod GCs. We conclude that vertebrate GCs may have beads that differ from arthropods in their staining properties.

Acrosome↗
PubMed1976

The beads in the Golgi complex-endoplasmic reticulum region.

The region between the rough endoplasmic reticulum (ER) and the Golgi complex has been studied in a variety of insect cell types in an attempt to find a marker for the exit gate or gates from the ER. We have found that the smooth surface of the rough endoplasmic reticulum near Golgi complex transitional elements has beadlike structures arranged in rings at the base of transition vesicles. They occur in all insect cell types and a variety of other organisms. The beads can be seen only after staining in bismuth salts. They are 10-12 nm in diameter and are separated from the membrane and one another by a clear halo giving them a center to center spacing of about 27 nm. The beads are not sensitive to nucleases under conditions which disrupt ribosomes or remove all Feulgen staining material from the nucleus. Under conditions similar to those used to stain tissue, bismuth does not react in vitro with nucleic acids. The component of the beads that stains preferentially with bismuth is therefore probably not nucleic acid.

Bismuth↗
PubMed1975

Golgi complex--endoplasmic reticulum transition region has rings of beads.

The smooth surface of the rough endoplasmic reticulum that makes the forming face of the Golgi complex has beadlike structures arranged in rings at the base of transition vesicles. The beads can only be seen easily after staining in bismuth salts. They are 10 to 12 nanometers in diameter and occur in a variety of cell types and organisms.

Animals↗
PubMed1975

The role of the Golgi complex in the isolation and digestion of organelles.

The origin of the membranes and lytic enzymes involved in autophagy has been studied in metamorphosing insect fat body. The Golgi complex has two functions in the organelle destruction which takes place when fat body cells change their activities. (1) It gives rise to envelopes which extermalize organelles scheduled for destruction. Microbodies, mitochodria and rough endoplasmic reticulum are sequentially removed from the cytoplasm by investment in isolation membranes. During the isolating phase, isolation membranes have the same osmiophilia as the outer saccular and microvesicular components of the Golgi complex, they do not contain lytic enzymes and they are specific in their adhesion to organelles scheduled for destruction. (2) The Golgi complex gives rist to lytic enzymes. Primary lysosomes which contain acid phosphatase fuse with the isolation bodies formed from invested organelles to become autophagic vacuoles. During this lytic phase, acid phosphatase is present in the inner saccules and microvesicular components of the Golgi complex, in the primary lysosomes seen fusing with isolation bodies and in autophagic vacuoles.

Acid Phosphatase↗
PubMed1971

The origin and fate of microbodies in the fat body of an insect.

The structure and life history of insect microbodies are described during the development of the fat body from the 4th to 5th larval molt through the 5th to pupal molt. The mature microbodies are flattened spheres about 1.1 x 0.9 micro, with a depression on one side where a dense mass connects the limiting membrane to the core of coiled tubules. They contain catalase and urate oxidase. The precise synchrony of development of insect cells during the molt/intermolt cycle makes it easy to study the life history of particular organelles. Phases of growth are correlated with the hormonal milieu. Mature 4th stage microbodies decrease in size before ecdysis to the 5th stage when they atrophy at the same time as the new 5th stage generation arises. The 5th stage microbodies form as diverticula of the RER and, grow while confronted by RER cisternae. The mature microbodies decrease in size when the fat body engages in massive larval syntheses. At the end of the 5th larval stage, the microbodies are invested by isolation membranes and destroyed before pupation. There are thus two mechanisms for microbody destruction: atrophy of the 4th stage organelles and isolation with autophagy at the end of the 5th stage.

Animals↗