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Biomedical subjects

M Locke

Publications and source records attributed to M Locke.

At least 55 records · Page 3Linked to original sources
PubMed1990

Golgi complex beads and the transition region.

Secretory proteins and membranes move in transfer vesicles from the rough endoplasmic reticulum through the transition region to the outer saccule of the Golgi complex. In both arthropod and vertebrate cells, the GC beads are a characteristic structural component of the transitional region. The beads are particles about half the size of ribosomes arranged equidistantly from one another and the smooth face of the ER. In an active GC, the beads are in rings through which the ER membrane emerges to form transfer vesicles. The beads may be part of the energy-dependent step required for the movement of proteins along eht secretory pathway, since they lose their ring arrangement under conditions that lower cellular ATP. The beads are organizers for Golgi complexes in the sense that they are the first recognizable components of new GCs as they arise from ER. Arthropod GC beads, but not those of vertebrates, can be visualized through their reaction with bismuth in vivo and in fixed tissue. Useful paradigms for traffic between the ER and the GC need to combine structural and biochemical information. Insect fat body, with its readily resolvable bismuth-strained beads and easily fractionated cell components may have particular value for this problem.

Animals↗
PubMed1990

The psychosocial-cultural aspects of pregnancy and holistic nursing care.

This paper discusses various psychosocial/cultural aspects of pregnancy that may alter the behaviour of the expectant couple. Holistic care plans are more likely to be effective if nurses are cognizant of these influences on the health of the child bearing couple. The quality of life from the moment of conception depends on a vast number of factors not the least being the physical and mental health of the expectant parents. Australian midwives contribute to the quality of maternal and fetal life by providing care throughout the pregnancy. In holistic care the health of the father is also considered therefore the quality of care provided to the growing family in the 1980's is a product of the nurses' knowledge.

Australia↗
PubMed1990

Exercising mammals synthesize stress proteins.

Spleen cells, peripheral lymphocytes, and soleus muscles were removed from male Sprague-Dawley rats that had been run on a treadmill (24 m/min) for either 20, 40, or 60 min or to exhaustion (86 +/- 41 min) and were labeled in vitro with [35S]methionine at 37 degrees C. Similar tissues from nonrunning control rats were labeled in vitro at either 37 or 43 degrees C (heat shock). Fluorographic analyses of one- and two-dimensional polyacrylamide gel electrophoretic separations of the proteins from cells and tissues of exercised rats demonstrate the new or enhanced synthesis of proteins of approximately 65, 72, 90, and 100 kDa. Although synthesis of these proteins is low or not detectable in tissues from control rats labeled at 37 degrees C, they are prominent products of similar tissues labeled under heat-shock conditions (43 degrees C) and, in fact, correspond in Mr and pI with the so-called heat-shock proteins. These results suggest that exercise is a sufficient stimulus to induce or enhance the synthesis of heat shock and/or stress proteins in mammalian cells and tissues.

Animals↗
PubMed1985

Nucleolar cycles during the fifth stadium in Manduca epidermis.

The changing pattern of nucleolar structure in the epidermal cells of Manduca sexta has been correlated with hormonal changes taking place during the fifth stadium. The epidermal nucleoli show three cycles of development, the first and third of which occur at the beginnings of the intermoult and moult phases respectively and are related to larval and pupal syntheses. The second phase occurs in the middle of the stadium but prior to the onset of wandering and commitment to pupation. A phase of mitosis separates the second and third cycles. The three cycles thus correspond in time to those found in Calpodes. The three cycles of nucleolar change are superimposed over nuclear changes relating to the degree of ploidy. Each phase begins with an expansion of the condensed nucleoli to form lobed rings and then necklaces. In the first phase (day 0-3), the rings and necklaces progress to form threaded networks. Both rings and networks have many ribosomal precursor granules that are lacking in condensed nucleoli. The rings and networks are therefore presumed to be more active in rRNA synthesis than the condensed state. The first and third phases of nucleolar change occur after elevated titres of haemolymph ecdysteroid. Post-thoracic ligation of animals at ecdysis blocks nucleolar changes as well as the appearance of polyploid nuclei. Nucleolar changes may be a primary response of the epidermis to stimulation by ecdysone.

Animals↗
PubMed1984

The induction and distribution of an insect ferritin--a new function for the endoplasmic reticulum.

Three insect tissues have particular roles as filters to maintain the fluid composition of the hemolymph. Water and ions enter and leave through the midgut. The pericardial cells filter circulating hemolymph. Malpighian tubules, often with the rectum, allow resorption from a hemolymph filtrate that passes to the hindgut. All three tissues have plasma membrane infolds making a reticulum on their hemolymph surfaces, and all three have RER leading to SER extensions into their reticula. SER is a catch-all description for membranes lacking ribosomes in the pre-Golgi complex set of compartments of the vacuolar system. Some kinds of SER are well known for their role in housing enzymes for steroid metabolism and for detoxification. The SER ramifying within the plasma membrane reticular systems of tissues concerned with hemolymph filtration contains ferritin, suggesting that this SER has another, different function. In contrast to vertebrate cells, where ferritin is confined to the cytosol and lysosomes, we have found that in Calpodes and perhaps in most insects, ferritin occurs in the vacuolar system and not in the cytosol. Ferritin occurs naturally in the RER and SER of cells at the hind end of the midgut, in pericardial cells and in the yellow region of the Malpighian tubules. Additional ferritin is induced by loading the gut or hemolymph with iron. Overloading with iron causes ferritin secretion to the gut lumen. We propose that the SER in these cells functions in iron homeostasis by holding ferritin for loading and unloading as it moves to and from the reticulum at the cell surface where it can be maximally exposed to extracellular fluid flow.

Animals↗
PubMed1984

Lenticles: innervated secretory structures that are expressed at every other larval moult.

Lenticles are dome-shaped circles or ovals of cuticle with a dark rim. They occur with a precise segmental arrangement in the larvae and pupae of lycaenid and hesperiid butterflies. In Calpodes ethlius (Lepidoptera, Hesperiidae) each lenticle is secreted by a pair of large polyploid epidermal cells. The dark rim or annulus is formed from a ring-shaped cell. The dome, which consists of an epicuticle with a perforate intermediate layer like a pepper-pot, is formed by a central goblet cell. Between the perforate intermediate layer and the cell surfaces there is a cavity that contains material presumed to be secretion. Both cells have elaborate basal plasma membrane reticular systems and the apical microvilli associated with an extensive smooth endoplasmic reticulum that is typical of lipid secreting cells. In addition, there is a plasma membrane reticular system in the ring cell and between it and the goblet cell that contains the endings of nerves having neurosecretory vesicles. Lenticles thus have a structure appropriate for an innervated organ of lipid secretion. However, in their development, lenticles arise from bristles that are presumed to be sensory. Lenticles or their precursors are segmentally arranged in the five larval instars and the pupa, but the pattern changes at each moult. The cells that form a lenticle at one moult have a rest period at the next one when they only secrete surface cuticle. Many lenticles are paired in their cycle of development, with only one of the pair making a lenticle at a particular moult. For example, the dorsal and lateral lenticles alternate in position between anterior and posterior. The second and fourth instar segments have anterior and the third and fifth instars have posterior lenticles. In the first instar the cells that will make lenticles for the second and third instars both make bristles. Lenticles are thus formed by cells that not only change their response to ecdysone qualitatively by switching from bristle to lenticle but also alternate in their later responses, switching back and forth at alternate moults between the formation of a lenticle and the secretion of surface cuticle.

Animals↗
PubMed1984

Ankle and subtalar motion during gait in arthritic patients.

The purposes of this study were 1) to document ankle and subtalar motion during gait in 20 healthy subjects and in 25 patients with rheumatoid arthritis (RA) and 2) to determine stride characteristics with and without the use of an extended University of California Biomechanics Laboratory orthosis in RA patients with painful ankle and hindfoot deformity. An insole foot-switch system and ankle and subtalar electrogoniometers measured stride characteristics and dynamic range of motion (ROM). Arthritic patients demonstrated less ROM than healthy subjects except for ROM of hindfoot valgus. Arthritic patients also had slower gait velocity and less single limb support (SLS) time. In five new and five current orthotic wearers, a significant increase (p less than .01) in velocity and SLS time occurred with shoes and a further significant increase (p less than .01) occurred with the orthosis. Nine of 10 patients reported a decrease in ankle and hindfoot pain after using the orthosis. This study demonstrates the value of an orthosis for the treatment of arthritic patients with ankle and hindfoot pain and deformity.

Adult↗
PubMed1983

Tyrosine storage vacuoles in insect fat body.

The watery vacuoles first described from larval insect fat body (Chironomus, Voinov, 1927; Aedes, Wigglesworth, 1942; Rhodnius, Wigglesworth, 1967) have been studied in 4th and 5th stage Calpodes larvae. The vacuoles arise at the beginning (E + 6-24 hr) of the 4th stadium from plasma membrane infolds that separate from the cell surface as provacuoles less than 1 micron in diameter. These provacuoles grow and fuse with one another through the intermolt until about half the volume of each fat body cell is occupied by a single, large vacuole. The vacuoles begin to disappear at molting. Their membrane is either incorporated into the plasma membrane by exocytosis or fragmented into vesicles that fuse to become lamellar bodies where the membranes are presumably digested. All the vacuoles have gone by a few hours after ecdysis. The tyrosine content of the fat body increases and decreases in proportion to the size of the vacuoles. As the vacuoles decrease at molting the titre of tyrosine in the hemolymph is transiently elevated at the time when there is most demand for phenolics for cuticle stabilization. Crystals having the form of tyrosine crystallize out from vacuoles separated from the fat body. In fat body extracts separated by thin layer chromatography, similar crystals occur only in the eluates from spots corresponding to tyrosine. The vacuoles are therefore presumed to be tyrosine stores used in cuticle stabilization at molting. They correspond to a type of aqueous storage compartment that is well known in plants but hitherto little recognized in animal cells.

Adipose Tissue↗
PubMed1983

A function for plasma membrane reticular systems.

The basal surface in transporting epithelia is infolded in a way that encourages the formation of standing gradients. Many insect cells have a similar infolded reticular system (RS) although they are clearly not transporting epithelia. These cells are like one another metabolically in that they sequester lipid from hemolymph lipophorins (lipid transporting proteins). Dietary lipids enter the hemolymph from the midgut RS which may be an adaptation for lipophorin loading. The plasma membrane reticular system of tissues metabolizing lipids (fat body, wax glands, oenocytes, lenticles) may be an adaptation for lipophorin reception and unloading. Cationic ferritin (pI 8.5) shows all RSs are covered by a lamina functioning as a negatively charged sieve. The basal plasma membrane leading to the RS is also negatively charged. The RS is a container with charged entrances that would be expected to affect the composition of the contents. Midgut cells release lipid particles into their RS. The particles are positively charged since in tracer studies they associate with anionic but not cationic ferritin. Lipophorins are anionic. The electrostatic binding of lipid to lipophorin would make it less anionic and more likely to leave the RS when loaded, thus carrying lipid to the hemolymph. Conversely, at the destination RS, loaded lipophorin would penetrate more easily than unloaded. A change in charge with unloading would be expected to alter the equilibrium between entering and leaving lipophorin, causing protein concentration in the RS of lipid receiving tissues as has been observed in the fat body. Reticular systems may thus be reaction vessels for interactions between carrier proteins and their load.

Animals↗
PubMed1983

The mystery of the unstained Golgi complex cisternae.

The Champy-Maillet OsKI reaction has been used upon Golgi complexes to show two kinds of staining. It stains material being processed as it passes along the secretory pathway of the rough endoplasmic reticulum (RER) and Golgi cisternae (GC) up to crystallization in secretory vesicles. It also stains separately the environment within parts of the GC. This GC staining may occur in all compartments (transition vesicles, saccules, condensing vacuoles), but it is characteristically missing from any one of them. The unstained cisternae may be explained if outer saccules are made from either stained or unstained transition vesicles, both of which occur. The presence of empty, unstained transition vesicles is dictated by the surface to volume ratios of microvesicles in relation to saccules. Most transition vesicles must return their membrane to the endoplasmic reticulum, but from time to time it is presumed that they fuse to make a saccule. Saccules, stained and unstained, then mature through the stack. OsKI reactions with tissues and test molecules suggest that in the RER and GC the stain detects labile--S . S--bridges before they lock the tertiary configuration of proteins.

Animals↗
PubMed1982

High resolution microanalysis for phosphorus in Golgi complex beads of insect fat body tissue by electron spectroscopic imaging.

Golgi complex beads are 10 nm particles arranged in rings on the smooth forming face of the Golgi complex that stain specifically with bismuth in arthropod cells. In vitro experiments with biological molecules spotted on to cellulose acetate strips indicated that bismuth bound to the beads through phosphate groups. We could detect a weak phosphorus signal from the beads using a new technique called electron spectroscopic imaging that is capable of very high spatial resolution (0.3-0.5 nm) and sensitivity (50 atoms of phosphorus). Detection was not obscured by tissue staining with bismuth or uranyl acetate of by using an inorganic buffer (Na cacodylate). Localization of phosphorus was greatly improved by using colour-enhanced computer pictures of the electron spectroscopic images and quantitating the images. The results indicate that the phosphorus content of the beads is large enough to account for their bismuth reactivity.

Adipose Tissue↗
PubMed1982

Lead staining in the Golgi complex.

Lead ions at similar concentrations to those used for Gomori type phosphatase localization stain some parts of the vacuolar system, particularly compartments of the Golgi complex (GC) and isolation envelopes (im) in a characteristic way in both vertebrates and invertebrates. After fixation in 2.5% glutaraldehyde, lead citrate in acetate or aspartate buffer (pH 5.5-7.2) leaves the contents of GC cisternal compartments with a fine particulate stippling. In the fat body of Calpodes ethlius and in mouse pancreas the staining is faint but definite without further enhancement of contrast, although it is easily overlooked after section staining. The distribution of lead stain differs from that of the lead phosphate precipitated after Gomori type acid phosphatase reactions. Whereas lead stain may be in all GC and im compartments, acid phosphatase is restricted to the innermost saccules and nearby vacuoles. The compartment specific staining by led also differs from the generalized staining in all compartments given by uranyl. Thus the contents of luminal membrane surfaces of some parts of the vacuolar system can be characterized by their ability to bind lead. In cells where protein synthesis has been blocked by cycloheximide, secretory vesicles are absent and the RER and GC from the generalized staining in all compartments given by uranyl. Thus the contents of luminal membrane surfaces of some parts of the vacuolar system can be characterized by their ability to bind lead. In cells where protein synthesis has been blocked by cycloheximide, secretory vesicles are absent and the RER and GC from the generalized staining in all compartments given by uranyl. Thus the contents of luminal membrane surfaces of some parts of the vacuolar system can be characterized by their ability to bind lead. In cells where protein synthesis has been blocked by cycloheximide, secretory vesicles are absent and the RER and GC cisternae are devoid of uranyl stainable material. However, lead staining and acid phosphatase activity in the GC continue. We presume that they mark the environment within these cisternae rather than the proteins passing through them. This environment is itself not static. Several observations suggest that the function of cisternae that is detectable by lead staining is temporally discontinuous and related to a stage of maturation or development. Only early stage ims stain: the staining ceases by the beginning of autophagy after hydrolytic enzymes are presumed to have been added. Condensing vacuoles cease to stain as the central core crystallizes out. Stain may be absent from one or two GC saccules at any position in the stack as though the phase of lead staining (or lack or it) can move progressively through the system. We conclude that in studies characterizing components of the vacuolar system it is necessary to separate those that mark transient occupants of a compartment from those that mark the compartment itself. Both may vary temporally independently from one another.

Acid Phosphatase↗
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↗