Biomedical subjects

C Stolinski

Publications and source records attributed to C Stolinski.

At least 19 recordsLinked to original sources

PubMed1998

Structure of chordae tendineae in the left ventricle of the human heart.

The bicuspid (mitral) valve complex of the human heart consists of functional units which include the valve leaflets, chordae tendineae and the papillary muscles. The mechanical properties of these functional units depend to a large extent on the link between the muscle and the valve. This link is usually arranged in a branching network of avascular tendinous chordae composed of collagen and elastic fibres, which transmit contractions of the papillary muscle to the valve leaflets. In order to perform their function efficiently, the chordae have to possess a high degree of elasticity, as well as considerable strength and endurance. Human chordae tendineae originating from the left ventricles were obtained from 7 embalmed cadavers and 6 postmortem subjects of various ages. Samples washed in saline were fixed or postfixed in 9 % formol saline. Observations were made by illuminating the chordae along their axes. The reflected images originating from the superficial collagenous layers of the relaxed chordae showed a striped pattern 11 microm in width. Scanning electron and light microscopy of the chordae confirmed an undulating pattern of collagen fibrils arranged in bundles of planar waves in register and around the entire circumference of the chorda. The dimensions of the waves correlated with those of the striped reflected pattern. The observed undulating arrangement of the collagen fibrils appears to produce an inherent built-in elasticity which is likely to be of considerable advantage for a tissue which is under continuous repetitive stress. The chordae were covered by endocardium composed of a superficial layer of smooth squamous endothelial cells and an underlying dense layer of elastic fibres. It is suggested that the relaxed striped chordae, consisting of undulating collagen fibrils, straighten when the chordae become stretched by papillary muscle contraction, thereby mitigating the peak stress developed during muscle contraction. On relaxation the elastic tissue tends to return the collagen to its wavy configuration. It is also suggested that the regular wavy pattern of collagen seen in young individuals gradually changes with age by elongation of the wave pattern which eventually becomes randomised. In addition, with increasing age, substantial cushions of connective tissue appear below endocardium while the dense collagenous core has a reduced cross-sectional area which may lead to stretching and eventual rupture of the chordae.

Adolescent↗

PubMed1995

Disposition of collagen fibrils in human tendons.

Fixed and unfixed human tendons originating from cadavers and postoperation specimens were examined using inclined parallel beams of light in a reflecting mode. Along the tendon, numerous planes, constantly inclined to the axis, were observed edge-on at the surface and within the interior. Their angle of inclination, with respect to the distal end was very nearly +/- 50 degrees. The planes consisted of individual segments arranged in steps which were on average 190 x 50 microns. Similar configurations were also observed with the scanning electron microscope. Using this technique, the segments were identified with collagen bundles turning at a sharp angle with respect to the axis of the tendon at the level of the inclined plane. Crimped planes were found to be irregularly distributed along the tendons. On longer flatter tendons the average distance between planes was in the range of 1-12 mm. On stretching, the inclined pattern disappeared and was rapidly reestablished in the previously observed position when the strain was released. It is suggested that the observed structure forms a mechanism which is responsible for the appearance of the first part of 'foot' region of the tendon's stress-strain diagram.

Collagen↗

PubMed1995

Structure and composition of the outer connective tissue sheaths of peripheral nerve.

A regular pattern of parallel reflections with a periodicity of approximately 39 microns has been detected on peripheral nerve fascicles. The reflections have been found to originate from a layer of wavy epineurial collagen fibrils arranged in register around the entire circumference of the fascicle. The waves were observed to be disposed in parallel with the plane of the fascicular sheath and along its axis. The pattern was observed in cut or relaxed fascicles in situ as well as in isolated and split layers of the epineurium. The pattern was not observed on nerve fascicles under tension. An additional structural feature consisting of longitudinally disposed elastic fibres was also detected among the epineurial collagen fibrils. The perineurial collagen associated with sheets of cells was found to be disposed in flattened waves as in the inner layer of the epineurium. The period of the waves, however, was much shorter, in the range of 6-9 microns. From the nature of the wavy structure it can be surmised that on stretching or contraction the sheath length may change, thus accommodating displacement and movement of nerve fibres.

Animals↗

PubMed1993

Experimental galactose neuropathy: quantitative changes in intramembranous particles in fracture faces of the perineurium.

Peripheral nerves in rats fed a diet containing 40% galactose develop endoneurial oedema related to the accumulation of interstitial galactitol and sodium. Biochemical studies of the perineurium in galactose neuropathy indicate an increase in membrane bound Na+/K(+)-ATPase activity. The present study has analysed the intramembraneous particles (IMPs) on the P membrane fracture faces of the perineurium in galactose-fed rats and has demonstrated a significant increase in the density of IMPs. This finding may reflect changes in the perineurial cell membranes in galactose neuropathy, such as increased membrane bound Na+/K(+)-ATPase activity.

Animals↗

PubMed1992

A freeze-fracture study of the perineurium in galactose neuropathy: morphological changes associated with endoneurial oedema.

Feeding rats with galactose as 40% of their diet results in peripheral nerve oedema related to the intrafascicular accumulation of galactitol and sodium. In this study, associated changes in the perineurium were examined by the freeze-fracture replication technique. Perineurial cells are linked by tight junctions (zonulae occludentes). In normal animals these are made up of anastomosing strands organized in a belt-like arrangement along the margins of continuous cells. The majority of the tight junctions in the galactose-fed animals displayed structural abnormalities. These ranged from slight separation of the strands to fragmentation and dispersal, with looping of isolated strands. Some of the tight junctions contained large dilated compartments within the junctional network. Short lengths of intramembranous particles, probably representing assembly or disassembly of tight junctional strands, were also observed. The membranes of perineurial cells normally possess numerous openings of caveolae. A quantitative assessment showed that the mean density of these caveolae openings was increased in the galactose-fed rats as compared with controls. The alterations in the tight junctions resemble those that have been produced experimentally in epithelia by subjecting them to abnormal osmotic gradients. They also resemble those seen in human diabetic neuropathy in which osmotic disturbances involving the perineurium have been considered to occur. If the alterations involve the inner layers of the perineurium, they are likely to impair its barrier function. The increased number of caveolae openings in galactose neuropathy may represent a reaction to the endoneurial oedema and indicate that the pinocytotic-like vesicles have a transport function.

Animals↗

PubMed1991

Freeze-fracture observations on normal and abnormal human perineurial tight junctions: alterations in diabetic polyneuropathy.

Perineurial cells in the human sural nerve possess tight junctions which in freeze-fracture replicas are seen to be composed of networks of branching and anastomosing P face strands and E face grooves. Isolated circular tight junctions (maculae occludentes) may represent attachment devices between adjacent perineurial lamellae. At the overlapping margins of the cells, a belt-like tight junction (zonula occludens) encircles the cells and is believed to comprise a paracellular diffusion barrier. As the permeability of the perineurium has been found to be altered in diabetic polyneuropathy, the zonulae occludentes have been studied. In freeze-fracture replicas from cases of diabetic polyneuropathy a mixed population of structurally normal and abnormal junctions was observed. In some, the strands were abnormally curved with reduced numbers of intersections, the intervening plasma membrane displaying prominent P face concavities and E face convexities. At other sites, the junctions were severely disorganized and represented by fragmented and isolated strands with few intersections and numerous free ends. These abnormalities resemble changes that have been produced experimentally in epithelial tight junctions by osmotic damage. The possibility is considered that similar mechanisms could result in the alterations of the perineurial tight junctions in diabetic polyneuropathy and account for its impaired permeability barrier properties.

Adult↗

PubMed1991

A freeze-fracture study of the perineurium in normal and protein-deprived rats.

Observations have been made using the freeze-fracture replication technique on the perineurium of normal and protein-deprived rats in which its permeability barrier function is known to be deficient. The perineurial cells of young normal rats possessed belt-like tight junctions (zonulae occludentes) at the borders and maculae occludentes at sites remote from their borders. In older rats, the zonulae occludentes were more prominent and the maculae occludentes relatively less frequent. No abnormalities were detected in the tight junctions of young rats with early induction of protein deficiency but this may have been related to sampling problems. In older severely protein-deficient animals, although many of the tight junctions were normal, some were abnormal and contained focal regions of dispersed strands. The density of caveolae in the surface membrane of the perineurial cells of older rats with severe protein deficiency was significantly greater than in the control animals. This provides support for the view that the pinocytotic-like vesicles of perineurial cells are involved in transport of substances across the cells. The increased numbers of caveolae in the protein deficient rats may reflect increased transcellular traffic. There were considerable differences in the density of P-face IMPs between the different perineurial lamellae, but the results did not allow a decision to be made as to whether there was a polarization of the cells between their endoneurial and epineurial aspects. No differences were detected in the density of P-face IMPs between the young control and protein-deprived rats. In the perineurium of the older rats with protein deficiency, IMP density was significantly greater in the E face than in the controls but not different in the P face. The delay in the development of enzymatic activity in the perineurium of protein-deficient rats that has been demonstrated histochemically is therefore not paralleled by a reduction in IMPs.

Animals↗

PubMed1990

Ultrastructure of human fetal trachea. A morphological study of the luminal and glandular epithelia at the mid-trimester.

Twenty two mid-trimester human fetal tracheae were processed for light microscopy and scanning, transmission and freeze-fracture replication electron microscopy. The tracheal pseudostratified columnar epithelium was found to be composed of four cell types: ciliated in various stages of development, non-ciliated, basal and degenerating cells. The ratio of ciliated to non-ciliated cells was approximately one-to-one. The non-ciliated cells were of two morphological sub-types. Of these, the vast majority contained characteristic secretory granules, approximately 0.5 microns diameter, found in abundance within the apical region of the cell cytoplasm. The second sub-type of the non-ciliated cell, the well differentiated goblet cell, was observed very infrequently. The relatively large number of non-ciliated cells in the fetal tracheal epithelium suggests a transition stage to the adult where the ratio of ciliated to non-ciliated cells is near 5-to-1. The nature of the first type of the non-ciliated cells, which have not been studied in depth previously, remains obscure. Their probable secretory function is discussed and comparisons are made with previously reported cell types showing similar features, in fetal or adult material from the distal airways of animal and human tissues. Approximately 15 to 20% of the epithelial cells show signs of degeneration. The probable causes of this degenerative process are discussed. Other cell types such as brush cells, endocrine and wandering lymphocytes were not observed. Well-differentiated muco-serous glands were observed within the tela submucosa.

Cilia↗

PubMed1989

Morphometric and freeze-fracture studies on peripheral nerve in shiverer mice.

Observations have been made on the peripheral nerves of shiverer (shi/shi) mice in comparison with control animals. Although this mutant lacks P1 myelin basic protein in peripheral and central myelin, myelin is defective only in the central nervous system. No ultrastructural abnormalities were observed in the shiverer nerves. Myelin spacing was normal. The density and distribution of intramembranous particles on the E and P faces of myelin and in the axolemma of myelinated and unmyelinated axons did not differ between the shiverer and control mice. Morphometric studies showed that external myelinated fiber diameter was significantly less and that myelin thickness was slightly but significantly greater in relation to axon diameter in the shiverer mice, suggesting a minor degree of axonal atrophy. It is concluded that P1 protein is not necessary for the formation and maintenance of the normal structure of peripheral myelin. The failure to detect differences in intramembranous particle density in myelin between shiverer and control mice indicates that P1 protein is not detected in freeze-fracture preparations.

Animals↗

PubMed1986

Peripheral nerve intramembranous particle density and distribution in chronic streptozotocin-induced diabetes in rats.

Freeze-fracture studies have been made on the sciatic nerve of rats with chronic streptozotocin-induced diabetes mellitus. The density of intramembranous particles was reduced in both P and E faces of the axolemma of myelinated and unmyelinated axons, in myelin and in the perineurial cells. This may reflect a general reduction in protein synthesis, or excessive protein degradation, related to the diabetic state. The perineurial cells also showed gap junctions which are not normally present in adult rat peripheral nerve. These may represent a reaction to changes in perineurial activity consequent to alterations in the endoneurial tissue fluid.

Animals↗

PubMed1986

Freeze-fracture observations on human peripheral nerve.

A study has been made on the appearances in normal human sural nerve using freeze-fracture replication techniques. These have included qualitative observations on the major membrane systems and quantitative assessments of the density of intramembranous particles in the perineurial cell membranes, myelin, the nodal and internodal axolemma of myelinated nerve fibres and the axolemma of unmyelinated axons. The results have been compared with those obtained in other species.

Adolescent↗

PubMed1985

Distribution of particle aggregates in the internodal axolemma and adaxonal Schwann cell membrane of rodent peripheral nerve.

Freeze-fracture studies on myelinated fibres from the internodal regions of rat and mouse sciatic nerve show symmetrical particle aggregates within the adaxonal Schwann cell plasmalemma and particle clusters in the axolemma. These are mainly confined to the vicinity of the internal mesaxon and the Schmidt-Lanterman incisures. The Schwann cell particle aggregates are concentrated as bands over the cytoplasmic pockets of Schmidt-Lanterman incisures and the paramesaxonal pockets. In the axolemma there are linear rows of particle aggregates along the groove related to the inner mesaxon and in bands to either side of it. The morphological features suggest the possibility of metabolic coupling between the axoplasm and the Schwann cell cytoplasm via the periaxonal space.

Animals↗

PubMed1984

Design and application of a freeze-fracture stage with a cleaver device for Balzers 'freeze-etching' apparatus.

A fracturing mechanism in the form of a double-wedged cleaver, used previously on other freeze-fracture machines, has been incorporated in the Balzers BAF 400 D apparatus. The design of the stage, with the cleaver, is explained and its performance and advantages are outlined. By minimizing mechanical damage to the exposed surface of the frozen specimen and reducing contamination by effective shrouding, an improvement in the quality of the replicas is achieved. The suitability of this mechanism for the fracturing of tough tissues such as skin is also outlined.

Animals↗

PubMed1983

Reinforcement and protection with polystyrene of freeze-fracture replicas during thawing and digestion of tissue.

An improved method for reinforcing freeze-fracture replicas, which is especially suitable for tough tissues, is described. For this purpose, polystyrene dissolved in chloroform is used to produce a solid protecting layer of plastic on top of the replica, enabling it to withstand the stresses associated with the thawing and digestion of the tissue with strong acids. The method results in production of large clean replicas from tissues such as skin or peripheral nerve which are difficult to process. The method can also be used profitably for reinforcing other softer and more homogeneous tissues.

Axons↗

PubMed1983

Peripheral nerve abnormalities in the diabetic mutant mouse.

Observations were made on the genetically diabetic C57BL/Ks (db/db) mouse. Morphometric observations were performed on the tibial nerve at 6, 9, and 15 mo and compared with those from nondiabetic (m/m) controls. Myelinated fiber size was less in the diabetic animals at all stages and affected cross-sectional axon area and myelin thickness equally. Unmyelinated axons were unaffected. The index of circularity of myelinated axons did not differ between diabetic and control animals. No definite absolute reduction in fiber size occurred and degenerative changes, which were slight, were equally frequent in the diabetic and control nerves. Axonal glycogenosomes, polyglucosan particles, and Schwann cell/axon networks, and Schwann cell Reich granules increased with age in both groups, but only glycogenosomes were consistently more numerous in the diabetic animals. Counts of membrane associated particles in both P and E faces revealed that these were reduced in number in the diabetic animals in myelin and in axolemma of unmyelinated axons, but not in the axolemma of myelinated fibers. Growth in tibial length was also reduced in the diabetic animals and this suggested that the reduced fiber diameter probably represented a maturational deficit. The absence of a selective reduction in axonal size did not favor a primary axonopathy as the cause.

Animals↗

PubMed1981

Cell junctions in explanted tissues from early chick embryos.

Hypoblast and definitive endoblast derived from young chick embryos were explanted and grown for 24 h in culture. The junctional complexes which characterise these tissues were studied on freeze-fracture replicas and thin sections. Cell membranes of the hypoblast displayed tight junctions only, disposed in randomly arranged strands or narrow belts which included many discontinuous strands. The definitive endoblast showed tight and gap junctions as well as desmosomes in close association with the tight junctions. It is suggested that the differences between the two types of tissue may be related to cell cohesiveness, which appears to be relatively low in the hypoblast and high in the definitive endoblast.

Animals↗

PubMed1981

The permeability barrier in the epidermis of the grass snake during the resting stage of the sloughing cycle.

Tracer and freeze-fracture replication techniques show that there are two morphologically and topographically distinct permeability barriers in the epidermis of the grass snake. Tight junctions interconnect the apico-lateral plasma membranes of the uppermost living cells, establishing an ionic or osmotic gradient between the stratum germinativum and alpha layer. The second barrier is formed by intercellular lipid sheets in the overlying mesos layer, which are very similar to the barrier found in the stratum corneum of mammals.

Animals↗

PubMed1981

Associated particle aggregates in juxtaparanodal axolemma and adaxonal Schwann cell membrane of rat peripheral nerve.

Freeze-fracture observations have been made on unfixed cryoprotected, and glutaraldehyde-perfused and cryoprotected rat sciatic nerve. In the juxtaparanodal region of the internode, numerous particle clusters were observed on the axolemmal E face and rings of particles of uniform size on the P face of the adaxonal Schwann cell membrane. Both of these particle aggregates were concentrated in the internodal region immediately adjacent to the paranode (juxtaparanodal). The findings provide evidence for a close association between the two particle formations, suggesting a unitary structure forming links between the axolemma and Schwann cell membrane. Figures are given for the density distribution of these particles at the juxtaparanodal region. They were rarely observed on membrane fracture faces of the general internodal regions. It is possible that these particle formations may represent potassium channels or that they could provide channels for other metabolic communication between the Schwann cell and the axon.

Animals↗