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Biomedical subjects

M J Costello

Publications and source records attributed to M J Costello.

At least 19 recordsLinked to original sources
PubMed1997

Light microscopic variation of fiber cell size, shape and ordering in the equatorial plane of bovine and human lenses.

PURPOSE: A rapid means was sought to visualize and quantify the cross-sectional areas of fiber cells, the variations of cell area, and the regularity of packing in the equatorial plane of normal adult bovine and normal aged human lenses. METHODS: Vibratome sections of bovine and human lenses were fixed, embedded in LR White resin, and sectioned for light microscopic observation. Image analysis was performed to determine the cross-sectional areas of fiber cells in selected nuclear regions. RESULTS: Examination of bovine lenses revealed a pattern of cell size and shape in each region that was similar to that recently reported for normal human lenses (1). In the equatorial plane of bovine lenses, average cross-sectional areas were 20 +/- 6 micron2 in the adult nucleus, 43 +/- 19 micron2 in the fetal nucleus, and 63 +/- 61 micron2 in the embryonic nucleus. Light microscopy of human lenses was consistent with our previous electron microscopic observations. Moreover, in both bovine and human lenses, the distribution of cell sizes and the number of cell layers was readily available for each region. Overviews of the equatorial plane demonstrated a gradual improvement in the regular packing of radial cell columns proceeding from the relatively disordered embryonic and fetal nuclei through the well-ordered adult nucleus to the highly regular cortical region. CONCLUSIONS: Light microscopy revealed the highly irregular packing and large average size of cells in the embryonic nucleus and the gradual reduction in size and progressive improvements in regularity of packing in the outer layers. The methods used here have the advantage of rapidly giving a continuous view of the fiber cell structure and arrangement which is not available using electron microscopy.

Aged↗
PubMed1996

Distribution and type of morphological damage in human nuclear age-related cataracts.

The distribution and type of fiber cell damage was evaluated in human age-related nuclear cataracts and in aged normal (non-cataractous) lenses. Ten age-related nuclear cataracts (53 to 89 years old) and four normal lenses (59 to 67 years old) were examined by electron microscopy of fixed Vibratome sections. Images from the adult, juvenile, fetal and embryonic nuclear regions were compared. Each cataractous lens contained a central region of increased light scattering which involved the embryonic and fetal regions with progressively less involvement in the juvenile and adult nuclear regions. Some damaged fiber cells were observed in all specimens, although damage was minor and infrequent in the normal lenses. Degeneration of single or groups of fiber cells was noted in all the adult nuclei of the cataractous lenses, becoming less frequent in the juvenile nuclei. The types of damage included localized voids, multilamellar membrane aggregates, globular bodies, enlarged cells and regions of highly convoluted membranes. The fetal and embryonic nuclei of the cataractous lenses exhibited rare and minor morphological defects, and were virtually identical to the equivalent regions of the normal aged lenses. Examination of cell interfaces in opaque regions of cataractous lenses revealed that the oldest fiber cells sustained apparent membrane loss. Extracellular spaces in the embryonic, fetal and juvenile regions of the cataractous lenses often contained dense deposits, presumably cytoplasmic material lost from adjacent fibers. The results indicate that the region of greatest nuclear opacity, located in the lens center, does not contain any significant cellular damage. This suggests that older fiber cells respond differently to pathological and senescent changes than younger cells made after fetal development. The observed loss of membranes and cytoplasmic material from the oldest fiber cells may be a contributory mechanism in the formation of age-related human nuclear cataracts.

Aged↗
PubMed1996

Fiber cell morphology and cytoplasmic texture in cataractous and normal human lens nuclei.

PURPOSE: The goal of this study was to compare the ultrastructure of the oldest cells in opaque and transparent human lenses. METHODS: Age-related nuclear cataracts, late-onset diabetic nuclear cataracts and normal aged lenses were examined by transmission electron microscopy. Cross-sectional profiles of fiber cells in the embryonic, fetal and juvenile nuclear regions were obtained to facilitate direct comparisons between lens regions and between sample groups. Image analysis was performed to determine cross-sectional areas of fiber cells in each region. RESULTS: The average cross-sectional area increased approximately sixfold from the outer to the inner nuclear regions in all lenses measured. In each nuclear region, fiber cells displayed a characteristic size, shape, arrangement and type of interdigitations which were consistently seen in all the lenses examined. Some lenses had more complex interdigitations than others. Gap junctions were identified as pentalamellar structures having 16 nm width and appeared identical throughout the nuclei of both normal and cataractous lenses. The cytoplasm of all lenses was smooth and free of large density variations. However, the cytoplasm of some cataractous lenses appeared more granular in texture than noncataractous lenses. Cellular degeneration, debris or large cellular defects were not seen in the cores of cataractous lens nuclei. CONCLUSIONS: These results indicate that only minor ultrastructural differences exist between the oldest fiber cells in normal and cataractous lenses, and that the presence of extensive cellular damage and disruptions is not necessary for the generation of nuclear opacities in aged lenses. Our observations suggest that light scattering sufficient for vision impairment may involve structural alterations much smaller than previously proposed.

Aged↗
PubMed1996

Morphology of the normal human lens.

PURPOSE: To provide a quantitative, morphologic description of differentiated lens fiber cells in all regions of aged normal human lenses. METHODS: Transparent normal human lenses (age range, 44 to 71 years) were examined with correlative transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Vibratome sections allowed examination of internal structures, whereas dissected whole lenses revealed surface characteristics. Additionally, image analysis was used to measure cross-sectional areas of fiber cells. RESULTS: Approximate regional dimensions (percentage of diameter and thickness, respectively) were determined for whole lenses: cortex 16%, 17%; adult nucleus 24%, 21%; juvenile nucleus 12%, 9%; fetal nucleus 45%, 49%; and embryonic nucleus 3%, 4%. Cortical cells were irregularly hexagonal, and the average cross-sectional area measured 24 +/- 9 microns2. Adult nuclear cells were flattened with intricate membranous interdigitations and an area of 7 +/- 2 microns2. Juvenile nuclear cells had an area of 14 +/- 5 microns2. Fetal nuclear cells were rounded with an area of 35 +/- 22 microns2. Embryonic nuclear cells also were rounded and had a variable area of 80 +/- 68 microns2. Fiber cell cytoplasm in all lens regions appeared smooth in texture and homogeneous in staining density. CONCLUSIONS: Both TEM and SEM are necessary to obtain a complete description of fiber cells. Cross-sections of fibers give new insights into the lamellar organization of the lens, indicating that each region has characteristic cell shapes and sizes. Furthermore, average dimensions were used to demonstrate that the number of cells and approximate growth rates vary significantly between adjacent regions.

Adult↗
PubMed1993

Morphological changes in human nuclear cataracts of late-onset diabetics.

The ultrastructure of human diabetic lens nuclei is described for the first time. Two cataractous lenses from late-onset diabetics were examined using transmission electron microscopy to determine the type and distribution of cellular disruptions. The diabetic lens nuclei were compared to a transparent nucleus from a normal human lens. Cellular damage to the exterior region of the diabetic lens nuclei was extensive, especially at the cortical-nuclear interface. Areas of lens fiber condensation as well as areas of cytoplasmic loss were observed in the outer nucleus. Morphological defects commonly seen in this region included: multilamellar membrane aggregates, voids where cytoplasmic material was lost, deposits in the extracellular spaces, density variations between adjacent fiber cells, and heterogeneously staining globules. The opaque central regions of the nuclei displayed relatively little cell damage, but fiber cells were very irregular in shape and packing. The ultrastructure of inner nuclear fiber cells was comparable to that seen in the normal lens and in age-related nuclear cataracts in non-diabetics. It appears that the effect of hyperglycemia on lens fiber cells is dependent on their age and stage of differentiation.

Aged↗
PubMed1993

Ultrastructure of fiber cells and multilamellar inclusions in experimental diabetes.

PURPOSE: The goal of this ultrastructural study was to examine fiber cell shape and intercellular junctions during the early stages of fiber cell breakdown and edema in diabetic rabbit lenses. METHODS: Lens abnormalities were recorded with a slit lamp. Between 6-10 mo after drug treatment, diabetic lenses and untreated control lenses were freshly enucleated and sectioned with a vibrating knife microtome. The thick tissue sections were chemically fixed and processed for thin-section electron microscopy. RESULTS: Alloxan-induced diabetes in albino rabbits produced clinically apparent cataracts as soon as 1 mo after the animals became hyperglycemic. The cataracts displayed cortical fluid-filled vacuoles in the equatorial region and at the cortex-nucleus interface, white specks scattered throughout the cortex, and posterior subcapsular cataracts. Fiber cells just deeper than the large cortical vacuoles had oval or spindle-shaped cross sections. Multilamellar inclusions, not reported previously for diabetic lenses, were observed at or near the fiber cell interfaces and were composed of concentric or spiral rings of plasma membrane-bound cytoplasmic processes. Undulating membranes were present throughout most of the multilamellar inclusions. Transparent lenses from untreated controls did not have such multilamellar bodies or extensive membrane undulations in cells at the same distance from the lens surface. CONCLUSIONS: Fiber cells respond to the diabetic insult differently depending on their stage of differentiation and age. The observed changes are consistent with the hypothesis that hyperglycemia accelerates the formation of age-related changes in fiber cells.

Alloxan↗
PubMed1992

Structural characterization of ordered arrays of sn-glycerol-3-phosphate acyltransferase from Escherichia coli.

Overproduction of the sn-glycerol-3-phosphate acyltransferase in Escherichia coli leads to incorporation of this integral membrane protein into ordered tubular arrays within the cell. Freeze-fracture-etch shadowing was performed on suspensions of partially purified tubules and whole bacteria. This procedure revealed the presence of ridges and grooves defining a set of long-pitch left-handed helical ridges. The long-pitch helices represented chains of acyltransferase dimers. Tubules observed within the cell were often closely packed, with an apparent alignment of grooves and ridges in adjacent tubules. Fracture planes passing through the tubules indicated the presence of a bilayer structure, with some portion of the enzyme being associated with the membrane. The major portion of the enzyme extended from the hydrophilic surface, forming a large globular structure that, in favorable views, displayed a central cavity facing the cytoplasm. Computer analysis of shadowed tubules revealed that the left-handed helices were six stranded, with a pitch of 1,050 A (105.0 nm) and a spacing of 75 A (7.5 nm) between acyltransferase dimers along the chains. Analysis of the predicted secondary structure failed to reveal obvious transmembrane segments, suggesting that very little of the protein was inserted into the bilayer.

Cytoplasm↗
PubMed1992

A novel method of sterilizing orthodontic instruments.

A range of orthodontic instruments was artificially inoculated with a mixed culture of representatives of the oral microflora and a marker bacterium and subjected to dry heat sterilization using a glass bead sterilizer. The shortest time which would guarantee total sterilization of the functional parts of the instruments was thirty seconds.

Dental Instruments↗
PubMed1992

Cellular architecture in age-related human nuclear cataracts.

Age-related or senile human nuclear cataracts were examined using electron microscopy of thin sections prepared from thick vibrating-knife microtome sections of nuclei extracted by extracapsular surgery. The use of extended aldehyde-tannic acid fixation of 80-120-microns thick vibrating-knife microtome sections overcame the difficult problem of preserving the hardened nuclear core of aged lenses. Comparisons were made between a typical nuclear cataract, containing a central opacity and a transparent rim, and a more advanced, or mature, completely opaque nuclear cataract. The typical nuclear cataract contained no obvious cell disruption, cellular debris, or objects that readily could explain the central opacity. The fiber cells had intact uniformly stained cytoplasms with well-defined plasma membrane borders and gap junctions. The transparent rim and the nuclear core appeared similar, except that fiber cells in the nucleus were more condensed with more elaborate intercellular interdigitations. The mature cataract showed various types of cell disruption in the perimeter but not in the core of the nucleus. These disruptions were globules, vacuoles, multilamellar membranes, and clusters of highly undulating membranes. Because these potential scattering centers were not found in the nuclear core, they probably were not the sole cause of the observed opacity. Other potential scattering centers found throughout the mature cataract nucleus included variations in staining density between adjacent cells, enlarged extracellular spaces between undulating membrane pairs, and protein-like deposits in the extracellular space. Similar features, although less pronounced, were present in the typical nuclear cataract. It was concluded that massive cell disruption is not essential to the formation of a central nuclear opacity. Subtle structural changes, especially small fluctuations in protein density between adjacent cells and alterations of the membranes and the extracellular space, probably contribute significantly to the central opacities in human nuclear cataracts.

Aged↗
PubMed1991

Immunocompetence as a measure of the biological effects of sewage sludge pollution in fish.

1. Dab, Limanda limanda, exposed to nominal concentrations of 0 (control), 0.0032% (low) and 0.032% (high) sewage sludge in seawater for 12 weeks, were assessed for their immunological competence. 2. No effect upon total blood leucocyte and erythrocyte numbers was found, although significantly fewer thrombocytes were seen in the high-exposure group. 3. A decreased serum protein level was found in the high exposure group, but lysozyme and immunoglobulin levels showed non-significant differences between the groups. 4. Melano-macrophage centres were also affected in the high-exposure dab, which had increased numbers in the spleen and kidney. No effect upon spleen weights or oxygen free radical production by splenocytes was noted. However, oxygen free radical production by kidney leucocytes was inhibited in the low-exposure dab.

Animals↗
PubMed1990

Regional neurotransmitter responses after acute and chronic electroconvulsive shock.

Regional neurotransmitter changes after acute and chronic electroconvulsive shock (ECS) were studied using the technique of repeated microdialysis. Microdialysis was carried out on alternate sides of the brains of anaesthetised rats before and during the first and the eighth ECS or sham (control) treatments. Extracellular fluid release of monoamines and their metabolites was measured in the frontal cortex, striatum and nucleus accumbens using HPLC with electrochemical detection. The first ECS produced selective regional responses, shown by increased concentrations of noradrenaline (NA) and dopamine (DA) in frontal cortex, by unchanged DA content in striatum, and by a small rise in NA and a fall in DA concentrations in nucleus accumbens. Concentrations of metabolites increased after ECS in all regions studied, and for homovanillic acid and dihydroxyphenylacetic acid, the temporal pattern of these changes did not resemble that of DA. Comparison of neurotransmitter responses as per cent of baseline release after the first and eighth ECS treatments showed they were identical. Basal release of monoamines and metabolites before the first ECS or sham treatment was similar in all regions studied. Prior to the eighth treatment, basal release of NA in the frontal cortex and DA in the striatum was elevated in the ECS-treated animals, while basal release of NA in the nucleus accumbens was reduced in both ECS- and sham-treated animals. These data suggest that acute and chronic ECS have different and region-specific effects on neurotransmitter release, although the overall pattern of these responses is not changed by chronic treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1989

Preparation of thin, fine-grained, tantalum metal replicas for freeze-fracture electron microscopy.

Two critical factors in the preparation of metal films on biological specimens are the type of metal used and the potentially damaging effects of radiant energy from the hot metal source. The excessive heating of surfaces is a major limitation to the replication of heat-sensitive aqueous specimens with refractory metals such as tungsten and tantalum, although these metals are known to form smaller grains and thinner films than the more commonly used platinum/carbon deposited under similar conditions. We describe here an electron gun designed for the evaporation of pure tantalum; surface heating is reduced through intermittent deposition controlled by varying the open/closed intervals of a fast shutter that operates in ultra-high vacuum. The effectiveness of the shutter was evaluated with a thin thermocouple in place of the specimen. The composition of the replicas was determined by x-ray microanalysis and by direct observation of the initial melting and subsequent evaporation of the tantalum bead supported on a tungsten rod that remained unchanged during the evaporation. The quality of the tantalum replicas was demonstrated with freeze-fracture replicas of reconstituted proteoliposomes and native membrane vesicles. With shutter intervals of 0.5 sec open and 1.0 sec closed, the surface heating was reduced enough to prevent unintentional etching and to preserve small pits complementary to protein particles in hydrophobic membrane surfaces and in ice.

Cell Membrane↗
PubMed1989

Distribution of gap junctions and square array junctions in the mammalian lens.

The morphology of membrane specializations of the cortex and nucleus of bovine lenses has been analyzed for both isolated membrane fractions and intact tissue fragments. Fractions of fiber cell membranes isolated from the outer cortex and the inner nucleus of lenses have been compared using x-ray diffraction, electron microscopy, SDS polyacrylamide gels and Western blots. Each fraction has distinctive structural characteristics. In x-ray experiments, the cortical fraction gives no sharp equatorial reflections (from the plane of the membrane), whereas the nuclear fraction gives sharp equatorial reflections which index on a square lattice of 6.6 nm. In thin-section electron micrographs, the cortical fraction is composed primarily of closed vesicles and flat membrane sheets, some of which contain pentalamellar structures similar in appearance to the 16-18 nm thick gap junctions found in other tissues. The nuclear fraction contains mostly undulating membrane pairs which often show 11-14 nm pentalamellar profiles and occasionally thicker junctions. In freeze-fracture images the cortical membranes display irregular clusters of intramembrane particles which resemble gap junctions, whereas the nuclear membranes contain numerous large square arrays with a 6.6 nm repeat and few irregular clusters or individual intramembrane particles. Images of fragments of intact lenses used in the membrane isolations give similar results; in the cortex the area covered by gap junctions is over 50 times the area covered by square lattices, whereas nuclear fiber cell membranes contain large square arrays. Thus, cortical and nuclear fiber cell membranes have quite different morphologies. In particular, the size of the square arrays of protein increases as the fiber cells mature. SDS polyacrylamide gels from cortical and nuclear fractions are similar in that they both contain MP26 as the major band. However, Western blot analysis shows increasing quantities of lower molecular weight, 25 kD and 22 kD, cleavage products as one progresses from the cortex to the nucleus. These data indicate that MP26 and/or its cleavage products form square crystalline arrays in nuclear fibers. The morphology of these arrays suggests a role for MP26 in cell-to-cell adhesion.

Animals↗
PubMed1988

Rapid induction of lorazepam dependence and reversal with flumazenil.

Benzodiazepine tolerance, dependence and withdrawal are well established clinical entities although the pharmacological basis for these are still unclear. Recent data suggest that the primary event may be a change in efficacy at the benzodiazepine receptor. The present study demonstrates the rapid development of tolerance and dependence to lorazepam, defines its pharmacology in more detail, and shows that it may be rapidly reversed by treatment with the benzodiazepine antagonist flumazenil. These observations argue in favour of a receptor efficacy change underlying benzodiazepine tolerance and withdrawal and suggest a potential pharmacological treatment for this common and disabling clinical problem.

Animals↗