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At least 163 records · Page 9Linked to original sources

PubMed1994

In vitro exposure of a novel polyesterurethane graft to enzymes: a study of the biostability of the Vascugraft arterial prosthesis.

The biostability of the Vascugraft arterial prosthesis, a porous synthetic graft made by a novel spinning process from a unique poly(ester urethane) polymer, has been studied by means of an in vitro enzyme incubation technique. Samples of the Vascugraft were exposed to buffered solutions of collagenase and pancreatin, as well as the buffer solutions alone, for periods of up to 100 days at 37 +/- 1 degrees C. On removal and after cleaning, a number of different analytic methods, including X-ray photoelectron spectroscopy for chemical analysis (ESCA), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), size exclusion chromatography (SEC), scanning electron microscopy (SEM), interference microscopy, moisture content and contact angle measurements, were used to examine the changes in chemical structure and surface morphology of the samples. During incubation in both enzymes the molecular weight of the polyurethane appeared to decrease in the presence of enzyme but increase in the presence of buffer. Further microphase separation in the polyurethane material developed during incubation in buffer solutions. Such changes in microstructure were associated with increased surface hydrophilicity, increased moisture content and a significant improvement in the extent of order and preferred orientation of the hard segment domains within the fibres. In the sampling depth of about 5 nm, both enzymes decreased the carbonate group content at the surface of the prosthesis to as little as 40% of their original values. The results from ATR-FTIR and DSC demonstrated that this phenomenon was limited primarily to the soft segment phase. While the Vascugraft prosthesis did exhibit some limited chemical modifications on exposure to concentrated enzyme solutions, nevertheless such changes were confined to the surface layer of the polyurethane microfibres. The importance and significance of those results will be more adequately determined by in vivo investigation.

Blood Vessel Prosthesis↗

PubMed1983

Interference microscopic determination of the section thickness of different paraffin-embedded organ tissues.

With respect to the significance of the section thickness in quantitative-morphological studies the thickness of different paraffin-embedded tissue sections was determined by interference microscopy. Within the range of 3-5 microns the measurements revealed accordance of the measured section thickness with that adjusted on the sliding microtome. In the range surpassing 5 microns the section thickness obtained was in all cases lower than that adjusted on the microtome. The deviations were up to 40%.

Histological Techniques↗

PubMed1992

The direct effects of graded axonal compression on axoplasm and fast axoplasmic transport.

The direct effects of mechanical compression on axoplasm and fast axoplasmic transport were studied by video-enhanced differential interference microscopy. Single axons, isolated from the squid, were compressed with 0.5, 5, 20, or 100 gram (g) weights placed over a 1 millimeter (mm) length of axon. Brief compressions (10 seconds) at low pressures (0.5 g/mm) momentarily deformed the axon, but the axoplasm and axon returned to their normal shape and position after the pressure was removed, and no residual changes in axoplasmic structures, fast axoplasmic transport or membrane function were seen. Compressing the axon with 5-20 g/mm, however, broke the axoplasm at the site of the crush and squeezed the axoplasm out from under the compression site. Though the axoplasm usually returned to the crush site after the weight was removed and organelles continued to move in the axoplasm under the crush, the organelles failed to cross a dense line that marked the site of the rejoined axoplasm, instead they accumulated over time at the crush site. This results suggests that the blockage of fast transport at moderate compressions was due to a mechanical breakage of the axoplasm at the compression site. The plasma membrane was apparently not transected after moderate compressions (5-20 g/mm) since the resting membrane potential returned to nearly control levels after the weight was removed. Compressions with 100 g/mm, however, did break the plasma membrane as evidenced by the rapid and irreversible loss of the action potential and resting potential and the ion-dependent liquefaction of axoplasm and loss of all organelle transport at the 100 g/mm compression site. Thus, small mechanical pressure elastically deformed the axoplasm, moderate pressures mechanically broke the axoplasm, and high pressures broke the axoplasm and the plasma membrane.

Action Potentials↗

PubMed1969

The response of motor neurones to intramuscular injection of botulinum toxin.

1. The dry mass and nucleic acid content of both nerve cell bodies and their nucleoli were measured by interference microscopy and ultra-violet absorption microspectrography respectively: succinoxidase and acetylcholine hydrolase activities were also determined. Autoradiography was used to follow synthesis of deoxyribonucleic acid (DNA) by glial cells, and to follow nucleic acid and protein metabolism in muscle fibres.2. After injection of botulinum toxin the synthesis of ribosomal RNA by the neurone followed closely the pattern found after axotomy.3. After injection of toxin neuronal dry mass increased before the rate of ribosomal RNA synthesis was raised. This early increase, which was not due to increased protein synthesis, probably represents a ;damming back' of proteins within the nerve cell body.4. After injection of toxin no local accumulation of microglial cells synthesizing DNA was found around the affected neurones: it is suggested that this reflects the intact system for intra-axonal transport under these conditions.5. The affected muscles show increased nucleic acid and protein synthesis.6. It is suggested that the results obtained indicate that membrane expansion or synthesis which occurs both in muscle and in neurone under these circumstances is the factor responsible for inducing directly or indirectly the changes found in nucleic acid metabolism after injection of botulinum toxin and after axotomy.

Animals↗

PubMed1972

Some quantitative observations upon the responses of neuroglial cells which follow axotomy of adjacent neurones.

1. The dry mass and nucleic acid content of freshly isolated neuroglial cells and of their nucleoli were measured by interference microscopy and ultraviolet absorption microspectrography. The incorporation of tritiated nucleosides and of an amino acid was followed autoradiographically.2. After hypoglossal axotomy in the adult rat hypertrophy of astrocytes of the hypoglossal nucleus occurred in a biphasic manner. The first phase lasted from days 1-10 and was accompanied by a small degree of astrocytic hyperplasia, and the second from days 20-80. Hypertrophy of oligodendrocytes accompanied the second phase of the astrocytic response.3. When severed axons failed to reinnervate denervated muscle, the second phase of the astrocytic response was markedly reduced and the hypertrophy of oligodendrocytes did not occur.4. If the severed axons re-innervated denervated muscle after a controlled delay, the second phase of the astrocytic response and the oligodendroglial hypertrophy was also delayed.5. Injection of botulinum toxin into the tongue caused changes in astrocytes and oligondendrocytes closely resembling those found after axotomy.6. Transient astrocytic hypertrophy occurred in the uninjured right hypoglossal nucleus, and had a different time course to the changes occurring on the injured side.7. The results are discussed in relation to changes in the metabolism and to alterations in the dendritic fields of injured neurones, previously measured in these circumstances.

Animals↗

PubMed2001

Controlled cell deformation produces defined areas of contact between cells and ligand-coated surfaces.

A method which allows precise control of the time of initiation and the area of contact of T cells with immobilized ligands has been developed. Cells are trapped in an asymmetric film that can be quantitatively thinned by reducing the film's capillary pressure. Ligands adsorbed to the base of the apparatus are forced into close contact with the cells as the air-liquid interface is drawn down. Using interference microscopy and microbeads to indicate the film height, the amount of thinning can be controlled to within 1 microm. In this study, this system was used to produce contact areas of 182 and 356 microm2 between T cells and anti-CD3 coated surfaces. These contact areas were measured using fluorescent dye exclusion microscopy. This apparatus can be used for quantitative studies of T cell activation, as is reported in Patrick et al., J. Immunol. Method. 24:97-108, 2000.

Animals↗

PubMed1966

Structure and organization of the living mitotic spindle of Haemanthus endosperm.

New details of mitotic spindle structures in the endosperm of Haemanthus katherinae (Bak) have been demonstrated by differential interference microscopy. Spindle fibers are clearly seen in the living spindle extending from the kinetochores to the polar region. Individual spindle fibers consist of a bundle of smaller filaments which diverge slightly from the kinetochore and intermingle with filaments from other spindle fibers as they approach the polar region. The degree of intermingling increases during metaphase and anaphase. The chromosomes stop moving when the spindle fibers are still 5 to 10microns long; then the fibers disappear. These observations explain some aspects of spindle movements which were difficult to reconcile with earlier concepts of spindle organization.

Cell Division↗

PubMed1982

Refractive index of the fly rhabdomere.

The refractive index and the diameter of the fly rhabdomere were determined by comparing the experimental results derived from interference microscopy with the results of theoretical study on the scattering of plane waves by a homogeneous, isotropic cylindrical dielectric rod. It was found that the refractive index of the isolated rhabdomere of Calliphora erythrocephala is 1.363 +/- 0.003 in an area of the rhabdomere where its diameter is calculated to be 1.32 +/- 0.04 micrometers.

Animals↗

PubMed1980

Fibrous waveforms or crimp in surface and subsurface layers of hyaline cartilage maintained in its wet functional condition.

The structural features of hyaline cartilage maintained in its wet functional condition have been examined using the technique of Nomarski interference microscopy. The collagenous arrays and associated chondrocytes in both the extreme superficial layers and in the deeper subsurface zones were satisfactorily imaged with this technique. Most significantly the collagen fibers were observed to possess a geometric waveform or "crimp" of varying acuteness and the role of this crimp is discussed in relation to the mechanical and biological function of the tissue. It is clear from these wet tissue studies that the fibrous layout in hyaline cartilage is considerably more "disciplined" than has been previously recognized from morphological data obtained using more indirect experimental techniques involving prepared histological sections or scanning and transmission electron microscopy.

Animals↗

PubMed1991

The density of the cell sap and endoplasm of Nitellopsis and Chara.

We measured the densities of the cell sap, endoplasm and cell wall of Nitellopsis obtusa and Chara corallina using interference microscopy, refractometry, immersion refractometry, equilibrium sedimentation and chemical microanalysis techniques. These values are important for the determination of many rheological properties of the cytoplasm as well as for understanding buoyancy regulation, dispersal mechanisms and how cells respond to gravity. The average densities of the cell sap, endoplasm and cell wall are 1,006.9, 1,016.7 and 1,371 kg m-3 for Nitellopsis and 1,005.0, 1,013.9, and 1,355.3 kg m-3 for Chara.

Cell Wall↗

PubMed1992

A new morphological classification of urinary erythrocytes for differential diagnosis of glomerular hematuria.

A new morphological classification of urinary erythrocytes was instituted in order to differentiate glomerular from urological hematuria. One hundred and thirteen hematuric patients including 73 glomerular and 40 urological disease patients were examined. The former group consisted of IgA nephropathy (n = 45), lupus nephritis (6), membrano-proliferative glomerulonephritis (5), non-IgA mesangial proliferative glomerulonephritis (4), Henoch-Schoenlein purpura nephritis (4), membranous nephropathy (4), endocapillary proliferative glomerulonephritis (3), and minimal change nephrotic syndrome (2). The latter group included bladder cancer (n = 15), renal calculi (15), prostate cancer (3), urethral cancer (1) and post-transurethral resection (6). In each urine sample, 100 urinary erythrocytes were observed under differential interference microscopy and classified into 10 concretely defined shapes (5 "glomerular" and 5 "urological" shapes) and unclassified shapes. Using percentage of "glomerular" shape erythrocytes and setting the cut-off at 15%, 90.4% of sensitivity and 97.5% of specificity for the diagnosis of glomerular disease were obtained. When percentage of one specific shape (G1), [i.e. doughnut-like cell with one or more blebs] was used at a cut-off of 1%, sensitivity and specificity were 89.0% and 95.0% respectively. These results were satisfactory as compared with most previous reports. Moreover, our classification is so concrete that it is more objective, accurate, and easily understandable, even for beginners. Distinct shape "G1" is particularly important for morphological investigation of hematuria.

Diagnosis, Differential↗

PubMed1975

Encephalitis in suckling rats induced with rat cytomegalovirus.

Encephalitis has been induced in suckling rats by intracerebral inoculation of rat cytomegalovirus. This agent has been carried through five animal passages without changes in virulence. Principal sites of viral attack were the meninges and ependyma with limited parenchymal invasion from these sites. Characteristic features of cytomegalovirus disease observed included cytomegaly, formation of nuclear and cytoplasmic inclusions, and polykaryocytosis. Fundamental tinctorial and optical differences were noted between nuclear and cytoplasmic inclusions, the latter being characterized by their phloxinophilia which contrasts with the hematoxylinophilia of nuclear inclusions. Differential interference microscopy improved visualization and photography of cytoplasmic inclusions. Hydrocephalus developed in a few of the animals and was studied in late phases of the disease.

Animals↗

PubMed1989

Cytophotometric and interference microscopic investigations in carcinomas of the oral cavity.

The DNA content and the nuclear dry mass of 18 keratinized squamous cell carcinomas and their metastases, of one adamantinoma recurrence and two adenoid cystic carcinomas of the oral cavity were determined in comparison to the normal buccal mucosa using Feulgen scanning cytophotometry and interference microscopy. The squamous cell carcinomas could be classified into five groups based on their DNA distribution pattern. The nuclear dry mass and its variation were found to be different from the normal mucosal epithelial cells in all cases. No differences could be found between diploid cells and cells of a higher degree of ploidy. Therefore the relation of nuclear dry mass and DNA content appeared to be lower in cells of higher DNA ploidy. This fact is discussed in relation to the underlying molecular biological processes. This leads to the conclusion that the increase of the nuclear dry mass (mainly protein) precedes the increase of the DNA content. The combined measurement of DNA content and nuclear dry mass allows a better characterization of malignancy than each of the nuclear components measured alone. The difference of nuclear dry mass between malignant cells and normal mucosal epithelial cells is more sensitive than the deviation of the DNA content owing to the fact that malignant tumours with normal DNA content exist.

Carcinoma, Squamous Cell↗

PubMed1984

Microfilament distribution and adhesion patterns in cultured cells after glutaraldehyde-formaldehyde fixation.

To study the relationship between microfilament distribution and adhesion patterns in the same cultured cell, we have employed a simple glutaraldehyde-formaldehyde fixation technique followed by permeabilization of the cells in buffered Triton X-100. This method gives an excellent preservation of cellular morphology in general and of adhesion patterns in particular for examination with surface reflection interference microscopy. It also permits the concomitant use of the actin-specific fluorescent probe NBD-phallacidin to visualize the distribution of microfilaments.

Cell Adhesion↗

PubMedDate not supplied

[Changes in the dry weight of retinal pigment epithelium cells in the postnatal ontogeny of rats].

The dry weight of cytoplasm of individual cells of the retinal pigment epithelium was determined by interference microscopy in the rats (both in mononuclear and binuclear cells). During postnatal development the dry weight of cell cytoplasm is subject to fluctuations: it increases from the 1st till the 5th day, decreases between the 5th and 15th days and increases again between the 15th and 18th days. It is suggested that the decrease in dry weight of cytoplasm of the retinal pigment epithelium cells precedes the onset of phagocytizing by these cells of shed discs of the external rod segments.

Animals↗

PubMed1982

[Action of hypothyroidism on the metabolic maturation of the pyramidal neurons of the rat hippocampus].

Interference microscopy was used to measure dry mass of pyramidal neurones of hippocampal CA1 and CA3 areas in control and hypothyroid rats aged 14 and 21 days and 2 months. Hypothyrosis was induced in the newborn by intraperitoneal injection of methylthiouracil to the lactating female during the lactation period (for 1 month). Hypothyrosis caused a considerable retardation of the animals' growth. A significant decrease in he concentration of dry substances was detected only in the cytoplasm of Ca1 area neurones in the group of 2-month-old hypothyroid animals. The measurements have demonstrated that hypothyrosis gives rise to pronounced retardation of the neuronal build-up and accumulation of protein products in the cytoplasma of hippocampal pyramidal cells in all the animal groups examined. The size and dry weight of neuronal nuclei of both the hyppocampal areas substantially diminish in the group of 2-month-old hypothyroid animals.

Aging↗

PubMed1994

An indirect comparison of third-body wear in retrieved hydroxyapatite-coated, porous, and cemented femoral components.

The osteoconductive properties of hydroxyapatite (HA)-coated titanium implants are well documented, but eventual coating degradation may result in HA particles adjacent to the substrate, and if the particles were to migrate into the joint space then accelerated polyethylene wear might be expected. As an indirect indication of third-body wear, the authors used laser interference microscopy to measure and compare surface roughness on modular heads from 15 clinically retrieved HA-coated femoral components, with heads from 15 retrieved uncemented (porous) and 15 cemented implants. The results showed increased median surface roughness over initial manufacturer specifications in all groups, but the cobalt-chrome heads from the HA-coated group showed significantly less surface roughness and less deep scratches than the heads from either the porous or uncemented group. Three-body wear appears to be a common problem, but evidence available suggests that it is no more of a problem with HA-coated devices than porous or cemented.

Cementation↗

PubMed1995

Histologic observations of bone remodeling adjacent to endosteal dental implants.

To examine bone morphology associated with endosteal dental implants at various time intervals, we inserted 20 one-stage and 20 two-stage titanium blade implants and 20 one-stage and 20 two-stage titanium root-form implants into 30 dog mandibles. Sixteen implants in 6 control (c) dogs (in situ five months) did not receive bridgework. Sixty-four implants in 24 dogs supported bridges for six, 12, 18, or 24 months. The entire area of the mandible containing the implants was examined by routine light and Nomarski differential interference microscopy (NM) for bone morphology (including osteon orientation) at the implant surface and at regions away from the implant. Control root-form implants were apposed by woven bone, with homogenous compact bone in the cortical plate distant to the implant. After 6 mo of load, immature bone was predominant apposing the implant, but initial osteonal maturation was apparent. NM clearly demonstrated the interstitial and concentric lamellae of the bone. Surprisingly, compact bone formed internal to the cortical plate, an area where trabecular bone is expected. At later periods of load, more mature osteons were seen apposing the implants; however remodeling events were still apparent. These remodeling events extend further away from the implant than was expected if the events resulted only from surgical repair. Also, when the implant inclined so that half was totally in the cortical plate and half in the marrow (in trabecular patterns), osteonal bone appeared to remodel in both areas. Control blade implants and blades loaded for six months were apposed by immature osteons when the implant was placed into the cortical plate. A trabecular meshwork was inferior to the osteonal bone. At 12 mo of load, the bone internal to the cortical plate appeared similar to the lamina dura supporting teeth; however, no PDL existed; the lamina-dura-like pattern directly apposed the implant. Even after 24 mo of load, extensive bone remodeling was apparent adjacent to the implant, markedly different from the bone making up the existing cortical plate. From these data, remodeling activities to blade implants may involve the development of a lamina-dura-like bone morphology after longer periods of load. Osteonal bone was apparent, but only at regions where the implant was inserted into the cortical plate. Further, bone remodeling was apparent even after long periods of load.

Alveolar Process↗