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At least 487 records · Page 27Linked to original sources
PubMed1990

Fine structure of the organic matrix remaining in the mature cap enameloid in Halichoeres poecilopterus, teleost.

Crystals and the organic matrix in both the enameloid and the maturation stage in this teleost fish were viewed by scanning and transmission electron microscopy. For transmission electron microscopy, specimens were demineralized by basic chromium (III) sulphate or phosphotungstic acid. Large numbers of defined compartments, thought to represent the outline of enameloid crystals, were seen in the outer layer of mature cap enameloid after this demineralization. However, the compartments were both less numerous and less well defined in the inner layer. These compartments suggest the existence of an organic enameloid matrix, which may correspond to the enamelins in mammalian enamel. As these defined compartments occurred in the areas of the tooth where large enameloid crystals were present, it is possible that the organic matrix constituting these compartments is involved in the production of large crystals.

Animals↗
PubMed1996

Binding of lipoprotein lipase to apolipoprotein B-containing lipoproteins.

The binding of lipoprotein lipase (LPL) to different lipoproteins and to a lipid emulsion was studied. After incubating the same amount of 125I-labelled LPL with VLDL, LDL or a lipid emulsion containing no apolipoproteins, we separated the free enzyme from the lipoprotein-bound LPL by gel filtration and by lipoprotein precipitation with phosphotungstic acid. By the former method we observed that all these types of lipid particles bound LPL indicating that the lipid moiety accounts for the LPL-lipoprotein interaction. This binding of LPL to lipoproteins was disrupted by high salt concentrations. When balanced by the apolipoprotein B content, it was observed that a significantly higher amount of 125I-labelled LPL co-eluted with VLDL than with LDL in gel permeation. The Kd values for binding of LPL to lipoproteins were estimated by use of lipoprotein precipitation. The obtained Kd values, both in the absence and in the presence of human lipoprotein deficient serum, were lower for VLDL than for LDL indicating a higher affinity of LPL for VLDL than for LDL. We finally compared binding capacity of LPL to VLDL subfractions with different apo E content. For this, we used apo E-poor (VLDL-B) and apo E-rich (VLDL-D) subfractions separated by heparin-Sepharose chromatography. We found that 125I-labelled LPL co-eluted to a similar extent with both subfractions on gel filtration, and the estimated Kd values from lipoprotein precipitation were not statistically different. Taken together, our results indicate that the lipid moiety, probably the phospholipids, accounts for the LPL-lipoprotein interaction; differences in size, the presence of C apolipoproteins or the conformation of apo B may be responsible for the higher affinity of LPL for VLDL than for LDL herein observed.

Apolipoproteins B↗
PubMed1976

Some effects of undernutrition on synaptic development -- a quantitative ultrastructural study.

The development of synaptic junctions in rat occipital cortex has been studied at 7 and 20 days postnatal in control and undernourished animals. In addition, adult control cortex has been compared with cortex derived from animals undernourished until 35 days postnatal and then nutritionally rehabilitated. Emphasis has been placed on material stained with phosphotungstic acid (E-PTA technique) although osmicated material has been examined. The body weights of the undernourished animals were lower than those of their age-matched controls, the deficit at 20 days being 55%. The number of synaptic junctions per unit area of the molecular layer was lower in the undernourished animals at 7 and 20 days, the most prominent deficit being at 20 days. In an attempt to detect ultrastructural correlates of undernutrition, E-PTA stained synaptic junctions were divided into 5 types (A-E), based upon their presynaptic characteristics are reflecting varying degrees of maturity. During normal development the immature synaptic types, particularly type E, are predominant, giving way to the more mature types (A-C) as development proceeds. Undernutrition however, appears to disrupt this developmental sequence, with a higher than normal percentage of immature synaptic types present at the age studied. Nutritional rehabilitation rectifies the imbalance to a degree, the adult rehabilitated pattern resembling the 20-day control pattern. Preliminary examination of the 20-day osmicated material confirmed the deficit of synapses per area of tissue in the undernourished cortex. It also revealed decreases in the number of vesicles per terminal unit area and in the internal area of the synaptic vesicles in the undernourished tissue.

Age Factors↗
PubMed1978

An ultrastructural study into the effects of pentobarbitone on synaptic organization.

A series of adult male rats was analyzed to test the effects of varying doses of pentobarbitone sodium on the ultrastructure of synapses in the molecular layer of the parietal cortex. The rats were divided into the following categories: unanaesthetized stunned, unanaesthetized cannulated and those subjected to 40, 80, 160, 300, or 400 mg/kg pentobarbitone. All material was examined both qualitatively and quantitatively after aldehyde-OsO4 or ethanolic phosphotungstic acid (E-PTA) treatment. The principal qualitative observations were: the preponderance in the unanaesthetized stunned and 160-400 mg/kg material of a variety of intraterminal profiles including synaptic vesicles, mitochondria, coated vesicles, tubular profiles, vacuoles, cisterns and double membrane profiles; the presence of exocytotic sites along the presynaptic membrane in the unanaesthetized stunned and cannulated material; the presence of endocytotic sites over the limiting membrane of the terminal away from the cleft in the unanaesthetized stunned and 160-400 mg/kg material; the prominence of the presynaptic network in the unanaesthetized and 40 mg/kg E-PTA material; discontinuity of the cleft material in the 40-160 mg/kg material. Findings to emerge from the quantitative aspect of the study show that pentobarbitone influences synaptic curvature, with a marked increase in curvature negativity over the 0-80 mg/kg dose range and a decrease in negativity at higher dose levels. The increase in curvature negativity is accompanied by an increase in synaptic length and dense projection numbers, with a consonant increase in the perimeter and area of the presynaptic terminal. Reversal of the negativity trend at higher dose levels is parallelled by reversal of these accompanying trends. Both sets of findings can be accounted for by membrane recycling within the terminal, supporting a membrane redistribution hypothesis.

Animals↗
PubMed1979

Synaptic density in human frontal cortex - developmental changes and effects of aging.

Density of synaptic profiles in layer 3 of middle frontal gyrus was quantitated in 21 normal human brains ranging from newborn to age 90 years. Synaptic profiles could be reliably demonstrated by the phosphotungstic acid method (Bloom and Aghajanian) in tissue fixed up to 36 h postmortem. Synaptic density was constant throughout adult life (ages 16--72 years) with a mean of 11.05 X 10(8) synapses/cu.mm +/- 0.41 S.E.M. There was a slight decline in synaptic density in brains of the aged (ages 74--90 years) with a mean of 9.56 X 10(8) synapses/cu.mm +/- 0.28 S.E.M. in 4 samples (P less than 0.05). Synaptic density in neonatal brains was already high--in the range seen in adults. However, synaptic morphology differed; immature profiles had an irregular presynaptic dense band instead of the separate presynaptic projections seen in mature synapses. Synaptic density increased during infancy, reaching a maximum at age 1--2 years which was about 50% above the adult mean. The decline in synaptic density observed between ages 2--16 years was accompanied by a slight decrease in neuronal density. Human cerebral cortex is one of a number of neuronal systems in which loss of neurons and synapses appears to occur as a late developmental event.

Adolescent↗
PubMed1984

Variations in presynaptic grid size in the granular and molecular layer of the cerebellar cortex of the cat. I. A quantitative ultrastructural study on semithin E-PTA sections.

The size distribution of synapses in the cerebellar cortex of the cat was defined on 0.5-micron semithin sections stained with ethanolic phosphotungstic acid (E-PTA). The surface area (SA) of synaptic grids was measured and the number of dense projections per grid (NDP) was counted. The results show large differences in mean values between molecular and granular layer. Within the molecular layer the differences in mean values at different levels below the pial surface were small; however, the frequency distributions differed significantly. In the granular layer a confined unimodal frequency distribution of SA and NDP was observed (mean NDP, 7.02 +/- 0.10), in the molecular layer a considerable variation in the size of the synaptic discs was observed (mean NDP, 20.40 +/- 0.43). Only a small percentage of the synaptic discs have less than 5 or more than 47 DPs. The sharply defined differences in synaptic size between the granular and molecular layer and the smaller differences within the granular and molecular layer are discussed in the context of the congruity hypothesis of Chan-Palay.

Animals↗
PubMed1990

Morphological adaptive response of the synaptic junctional zones in the human dentate gyrus during aging and Alzheimer's disease.

A computer-assisted morphometric study has been carried out on ethanol phosphotungstic acid (E-PTA) stained synaptic junctions in the human dentate gyrus supragranular layer from adult, old and Alzheimer's disease (AD)-affected patients. The number of synapses per unit volume of tissue (Nv = numerical density), the average area of the single junction (S) and the total area of the synaptic contact zones in a unit volume of tissue (Sv = surface density) were the 3 parameters taken into account. The synapse to neurone ratio was also calculated for each patient. During physiological aging, Nv and Sv significantly decreased and S increased, respectively. In the AD hippocampi, Nv and Sv underwent a further decrease which was in the range of more than 40% with reference to the adult values. S was the same as the old control group. In comparison with the adult values, the number of synapse/neurone decreased by 15.6 and 48% in old and AD patients, respectively. Nv, S and Sv, while reporting on discrete ultrastructural features of the synaptic junctional zones, are closely related to each other and, taken together per group of patients, may represent a reliable index of the morphological adaptive changes taking place at the synapses. Thus, the significant increase of S both in old and AD hippocampi may be regarded as a CNS plastic response to aging and disease, although the marked decrease of Nv and Sv supports that in AD synaptic ultrastructural alterations proceed beyond a critical threshold for functional recovery.

Aged↗
PubMed1993

Ultrastructural localization of neuropeptide Y-immunoreactivity in the axonal reticulum elements, accumulating anterogradely in transected rat sciatic nerve.

The detection of dopamine-beta-hydroxylase and cytochrome B561 on the membranes of the axonal reticulum demonstrated that in sympathetic neurons the different compartments of the axonal reticulum participate in the formation of neurosecretory vesicles. In the present study we tried to reveal that the components of the vesicular content are also channeled along the axonal reticulum, by examining whether neuropeptide Y could be localized in elements of the axonal reticulum. Therefore 6 h transected rat sciatic nerve was embedded in glycolmethacrylate and an immunogold labeling was performed. Counterstaining with phosphotungstic acid at low pH selectively contrasted the accumulated axonal reticulum elements and associated granules. In the non-myelinated axons gold labeling was localized on granules and on tubular and granular profiles, demonstrating the presence of neuropeptide Y in the accumulated axonal reticulum elements. This indicates that neuropeptides are indeed transported via the axonal reticulum to the nerve ending and suggests that the accumulation of large dense-cored vesicles at a block is mainly due to local new formation rather than down transport.

Animals↗
PubMed1994

Dynamic morphology of the synaptic junctional areas during aging: the effect of chronic acetyl-L-carnitine administration.

The ultrastructural features of hippocampal synaptic contact zones have been investigated by means of computer-assisted morphometry in rats of 6, 12 and 22 months of age and in age-matched animals chronically treated with ALCAR at a daily dose of 50 mg/100 g body weight from the age of 1 month up to the day of sacrifice. The number of synapses/microns 3 (Nv), the average size of the junctional areas (S) and the total area of the synaptic contact zones/microns 3 (Sv) were measured in tissue samples stained by means of the ethanol phosphotungstic acid (E-PTA) preferential technique for synaptic membranes. In control animals Nv was constant between 6 and 12 months of age, but significantly decreased in 22-month-old rats; S did not show significant differences due to age; Sv was unchanged between 6 and 12 months, but it decreased significantly in the old animals. In ALCAR treated rats Nv increased and S decreased significantly vs. Age-matched controls. Sv showed a lifespan constancy among the groups of age analysed. In ALCAR treated rats the number of contact areas smaller than 0.08 micron 2 increased by 18, 9 and 10% at 6, 12 and 22 months of age, respectively. ALCAR administration resulted in a lifespan modulation of synaptic structural dynamics. A proper metabolism at nerve terminals is accounted to play a crucial role in synaptic remodelling potential: on the basis of current research data, it is suggested that ALCAR may improve neuronal bioenergetic mechanisms.

Acetylcarnitine↗
PubMed1995

The organisation of the axonal reticulum at a ligation, in in vitro incubated bovine splenic nerves.

From previous studies we concluded that in noradrenergic neurons the axonal reticulum can be considered to be an extension of the Golgi apparatus, directly involved in the condensation and packaging of neurosecretion. But the precise ultrastructure of the organisation of the axonal reticulum in relation to neurosecretory granule formation remained to be elucidaded. This conversion was studied in ligated bovine splenic nerve incubated in vitro for three hours. The ultrastructure of the material accumulating proximally and distally was examined and its nature was determined by phosphotungstic acid staining and immunocytochemistry on glycolmethacrylate sections. Proximal to the ligation predominantly electron-lucent vesicles and tubules were found. Tubules of intermediate electron density appeared in between. The latter, especially in thicker sections, were seen to form complexes with tubules and granules of high electron density. All those elements were shown to be positive for dopamine-beta-hydroxylase and cytochrome b561. In the distal part multivesicular bodies accumulated and they were also positive for both enzymes. From these findings it is concluded that the different types of structures accumulating proximally belong to a neurosecretory axonal reticulum. At a block the axonal reticulum is triggered to generate a reticular differentiation, in which granular densities of different size are found. This configuration compares well with that in nerve terminals and strongly suggests that granule formation is basically a local process.

Animals↗
PubMed1988

A specific method for the direct determination of lipoprotein cholesterol in electrophoretic patterns.

Lipoproteins are separated electrophoretically and cholesterol is visualised with an enzymic reagent specific for cholesterol in which the gels are incubated. Quantitation of the individual fractions is accomplished by scanning densitometry. No sample pretreatment is necessary. All major fractions are detected readily. Accuracy agrees favorably with results from the ultracentrifugation. On the average, imprecision is 3.1% for beta-, 6.9% for prebeta-, and 5.2% for alpha-lipoprotein cholesterol. Concentration and color development are linear up to 8 mmol/l cholesterol in a given lipoprotein fraction. The results of the direct enzymic procedure for beta-, prebeta- and alpha-lipoprotein cholesterol are compared to the quantitative lipoprotein electrophoresis after precipitation with phosphotungstic acid and bivalent cations.

Cholesterol↗
PubMed1986

Isolation and properties of rat cell lines morphologically intermediate between cultured mammary epithelial and myoepithelial-like cells.

The cloned cuboidal epithelial cell line Rat Mammary (Rama) 25 converts at low frequency in culture to elongated cells that possess some of the properties of myoepithelial cells; one such clonal cell line is termed Rama 29. Three morphologically intermediate clonal cell lines have been isolated from Rama 25 which form a morphological series in the order: Rama 25 cuboidal cells, Rama 25-Intermediate 2(I2), Rama 25-I1, Rama 25-I4, and Rama 29 elongated cells. This same order is largely maintained for increasing percentages of elongated cells, decreasing percentages of cuboidal cells, decreasing tubular structures on collagen gels, and increasing times of appearance of tumors in nude mice. The fully elongated cells fail to revert to cuboidal cells and to form tumors. Binding of antisera to epithelial-specific milk fat globule membranes and human keratin declines whereas binding of antisera to myoepithelial-associated laminin, vimentin, and Thy-1 increases in the cell lines in the same order. Similarly 7 polypeptides characteristic of elongated cells increase and 4 polypeptides characteristic of cuboidal cells decrease in the cell lines in the same way. Anti-actin serum binds equally to all cell lines grown on plastic, except for Rama 25-I4, where its binding is increased. Rama 25-I1 and Rama 25-I4 cells also give rise to anti-actin, anti-myoglobin, and phosphotungstic acid hematoxylin-staining giant, striated cells on collagen gels and in tumors that also have ultrastructural characteristics of skeletal muscle. Fresh elongated converts of Rama 25 bind appreciably more anti-actin serum than many of the clonal elongated cell lines such as Rama 29. Ultrastructural analysis confirms the gradual loss of epithelial characteristics and the acquisition of immature myoepithelial characteristics in the same sequence of cell lines. It is suggested that such a linear sequence of intermediate morphological states occurs between the Rama 25 cuboidal cells and the elongated myoepithelial-like cells in vitro, and that a similar morphological sequence may exist in terminal ductal structures in vivo.

Actins↗
PubMed1985

Improved negative staining of microfilament arrangements in detergent-extracted Physarum amoeboflagellates.

A motile, lamellipodium-like structure, the ridge, forms as amoeboflagellate cells of Physarum polycephalum release from a substratum and begin swimming in fluid. Actin microfilaments form a distinct laminar core within the ridge; they are seen as a sparse, disordered meshwork in cytoskeletons prepared by conventional methods using uranyl acetate negative staining [10]. Preservation and visualization of these filaments and their arrangements improved considerably when cytoskeletons were imaged with phosphotungstic acid buffered with ammonium hydroxide (PTA(NH4]. Microfilaments within ridge cytoskeletons were found to form loose bundles and criss-crossing, 'meshwork' arrays several layers deep. Differences could be detected in morphology and detailed arrangement of microfilaments within cytoskeletons prepared in the presence of phalloidin. PTA(NH4) may be useful for studies of cytoskeletal elements and their rearrangements in dynamic, motile regions of cells.

Cell Cycle↗
PubMed1984

Synaptic density in chronic animals with experimental neurofibrillary changes.

Synaptic density was quantitated in the cerebral cortex and subiculum of rabbits with experimental neurofibrillary changes. Animals were subjected to subcutaneous injection of aluminum tartrate for 90 days, and synapses stained with ethanolic phosphotungstic acid were analyzed in animals killed 100, 200, or 300 days postinjection with aluminum tartrate. A significant difference was found in synaptic density between animals injected with aluminum tartrate and their age-matched controls. This difference was a result of a low synaptic density present in animals killed 200 or 300 days postinjection of aluminum tartrate. In contrast, animals killed 100 days postinjection revealed the same synaptic density as their control. The data suggest that the synaptic depopulation associated with experimental neurofibrillary changes is a gradual process, and such changes are demonstrable only long after the initial appearance of neurofibrillary changes.

Aluminum↗
PubMed1985

Age-related changes in the subiculum of Macaca mulatta: synaptic density.

Dendritic spines and synapses were quantitated in the subiculum of 12 Macaca mulatta from 7 to 29 years of age. Dendritic spines were analyzed in six dendritic foci of pyramidal neurons impregnated by the Golgi-Cox method. The dendritic foci examined were the apical shaft, apical oblique, apical tuft, apical terminal, basal terminal, and basal dendrites. Electron microscopic observations were made on synapses stained with ethanolic phosphotungstic acid. There was no difference in spine density between a group of young (7 to 12 years of age) and middle-aged (18 to 21 years) animals. The mean spine density was 1.09/microns for the young and 1.15/microns for the middle-aged animals. In contrast, the spine density of the old animals was 0.87/microns, which was significantly lower than the spine density found in the young and middle-aged animals. A loss of dendritic spines in the old animals occurred equally in all six dendritic foci. A decline in synaptic density in the aged animals were further evidenced by an ultrastructural analysis. The synaptic density of the old animals was 8.3 X 10(8)/mm3, significantly lower than 9.5 X 10(8)/mm3 and 10.2 X 10(8)/mm3 found in the young and middle-aged animals, respectively. This study on synaptic density demonstrated the decline in synaptic number as a function of age in M. mulatta.

Aging↗
PubMed1987

Neocortical synaptogenesis, aging, and behavior: lifespan development in the motor-sensory system of the rat.

Little evidence presently exists on the development and aging of synaptic contacts and their relationship to behavior, particularly in nonvisual brain areas. To investigate this interrelationship, rats at a series of developmental ages [postnatal day 1 (P1) to P90] were initially examined on a battery of motor tasks. The battery, ranging from simple reflexive tests to tests of complex locomotor capacities, consisted of tactile-induced forelimb placing, chin-induced placing, body righting, climbing an inclined plane, traversing a narrow beam, and keeping up with a revolving wheel. Following completion of the behavioral testing, the animals, together with an additional group of aged (28- to 29-month-old) rats, were killed and their motor-sensory cortex was removed, stained with osmium tetroxide or ethanol phosphotungstic acid (EPTA), and examined under electron microscopy for density of synaptic contacts. Simple motor abilities such as tactile-induced placing was present by the end of the first postnatal week, with locomotor performance reaching a mature level by the end of the third postnatal week, and intermediate task abilities maturing within this range. Paralleling the development of complex locomotor skills was a sharp increase in synaptic density in the molecular layer of the motor-sensory cortex, commencing in the second postnatal week and peaking at P30. After P30 there was a sharp decline in synaptic density as well as a decline in performance on some motor tasks, although these two functions seemed to be occurring independently. There was a continued, but less dramatic synaptic loss evident in the aged rats.

Aging↗
PubMed1992

Schistosoma mansoni: the chemical nature of the secretions produced by the Mehlis' gland and ootype as revealed by cytochemical studies.

The 'secretory pathway' of the Mehlis' gland secretion as well as the maturation of the secretory granules are described. The secretions produced by the Mehlis' gland and the distal ootype in Schistosoma mansoni were identified as neutral glycoproteins. They were both periodate reactive, stained with phosphotungstic acid at low pH, and sensitive to the proteolytic action of papain. The secretions did not strain with both the low-iron diamine and the high-iron diamine methods for the presence of acidic glycoconjugates, and they did not contain a detectable level of sulphydryl groups. The possible role of the secretion from the Mehlis' gland in egg-shell formation is discussed.

Animals↗