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Biomedical subjects

P S Baur

Publications and source records attributed to P S Baur.

At least 19 recordsLinked to original sources
PubMed1984

Epithelial mediated wound contraction in experimental wounds--the purse-string effect.

Wound contraction, a process whereby wound edges are drawn together, is thought to be mediated by the myofibroblast cell population. However, experimental wounds may close as much as 25% (surface area) before the onset of fibroplasia which is marked by the migration of fibroblasts and myofibroblasts into the wound bed 2 to 3 days after injury. This early phase of wound closure appears to be mediated by a contractile force produced by a circumferentially arranged band of fusiform-shaped epidermal cells situated in the wound margin. Cytoplasmic microfilaments in the epidermal cells, similar in size and configuration to actin filaments and/or tonofilaments, are found to be aligned with the long axis of the constitutive cells comprising the contractile band. The data suggest that contraction in experimental wounds is promoted by at least two distinct cell-mediated contractile events: an initial although brief phase effected by cells of the epidermis followed by an extended phase of soft connective tissue contraction produced vis à vis the myofibroblasts in the dermis.

Animals↗
PubMed1983

The myofibroblast anchoring strand--the fibronectin connection in wound healing and the possible loci of collagen fibril assembly.

Myofibroblast anchoring strands (MAS) are extracellular structures that connect the termini of actin bundles within myofibroblasts to collagen fascicles in the extracellular space of wound healing tissues. The strands appear to be primarily comprised of microfibrils of fibronectin 2-5 nm in diameter. They also embody parallel arrays of intermediary sized filaments (ISF) and an amorphous matrix of collagen. The MAS effectively translate the cellular contractile forces required for cell motility into the collagen filament/fiber deformations required for wound contraction. However, the primary function of the strands appears to be the assembly of ISF into collagen fibrils.

Collagen↗
PubMed1983

Effect of tunicamycin, an inhibitor of protein glycosylation, on division of tumour cells in vitro.

We determined the effect tunicamycin (TM), an inhibitor of protein glycosylation, had on cells in vitro that were derived from solid and ascites variants of a chemically induced rat hepatoma. Using flow microfluorometry (FMF), labelling index (LI), and population-doubling time assays, we monitored the progression of cells through the cell cycle after treatment with TM. Cells in monolayer culture were first incubated in 0.05 or 0.10 micrograms TM/ml medium for 24 h then analysed or given fresh medium without TM and allowed to recover for 6-24 h. Exposing cells to 0.05-0.50 micrograms TM/ml medium did not affect the percentage of viable cells as determined using the Trypan Blue exclusion procedure. However, continuous exposure to 0.05 micrograms TM/ml medium did affect the population-doubling times of both the ascites and solid variants, and the ascites tumour cells were more sensitive than the solid tumour cells. TM reversibly inhibited hepatoma cells from entering S phase of the cell cycle. After exposure to TM for 24 h, the percentage of solid tumour cells in vitro in S phase decreased to 19%, as determined by autoradiography of tritiated-thymidine-labelled cells, and to 21% as determined by FMF; 49% of untreated solid tumour cells were in S phase. The percentage of ascites tumour cells in vitro decreased to 12% after exposure to TM for 24 h; 37% of untreated cells were in S phase. We concluded that TM can inhibit division of rat hepatoma cells in vitro by blocking them in G1 phase of the cell cycle.

Animals↗
PubMed1983

A sample-grouping technique for paraffin embedments.

A technique is described which facilitates histological preparation of multiple tissue specimens for light microscopy. The procedure enables the investigator to separate and label identifiable subgroups from a larger number of specimens in one histological section. After standard fixation, murine esophagi were arranged longitudinally and secured within segments of murine intestine. Markers such as plant fibers and human hairs were threaded alongside the esophagi within each intestinal casing. After standard dehydration and infiltration, several segments of intestine were arranged parallel to each other and at right angles to the intended plane of sectioning and were embedded together in one paraffin block. This method made it possible to assemble onto one microscope slide cross sections of 42 individual esophagi in 6 identifiable subgroups, each containing 7 esophagi.

Animals↗
PubMed1982

Bladder reconstruction in rabbits with glutaraldehyde-stabilized amniotic membranes.

Glutaraldehyde-treated human amniotic membranes were used to repair rabbit bladders after supratrigonal cystectomies. The membranes maintained the integrity of the bladders until healing and reepithelialization occurred. There was no significant loss of bladder capacity or decreased renal function postoperatively. Calcification did not occur on the membranes but was noted on chromic sutures retaining the membranes in 7 of 27 bladders. These findings suggest that glutaraldehyde-stabilized amnion is well tolerated by the urothelium and may serve as a suitable material for replacement of genitourinary tissues.

Amnion↗
PubMed1981

SEM of epithelial mediated wound in mice.

Wound edges are drawn together by a process known as wound contraction. Myofibroblasts are thought to mediate this contractile force. However, up to 25% of the surface area of a wound may close in the first few days, long before significant numbers of myofibroblasts appear in the wound bed. This suggests that another contractile force exists in the margins of the wound tissue. This force appears to be mediated by a band comprised of fusiform shaped epidermal cells. These cells are circumferentially distributed with respect to the wound margin. Microfilaments, similar in size to actin filaments and/or tonofilaments, can be observed in these cells. The filaments are aligned with the long axis of the epithelial cells that comprise the contractile band. Thus, wound contraction may in all likelihood be a biphasic phenomenon initially involving epidermal cells followed by the myofibroblasts.

Animals↗
PubMed1981

Papillary necrosis in vitro: a scanning electron microscopic comparison of escherichia coli and Proteus mirabilis infection.

The effect of bacterial infection on excised renal papillae as a model for papillary necrosis and subsequent calcification was investigated. Sterile rat renal papillae were placed in 25 ml aliquots of filter sterilized human urine and then inoculated with one ml suspensions of sterilized human urine and then inoculated with one ml suspensions of sterile saline as a control, or 1 x 108/ml Escherichia coli or proteus mirabilis. After incubation at 37 degrees C for periods of 8 hr, 24 hr, 48 hr, 72 hr, 1 wk, 2 wk and 3 wk, urinary pH was measured, bacterial culture performed and the renal papillae were recovered and examined by scanning electron microscopy (SEM) and energy dispersive spectrophotometry (EDS). In the case of Proteus mirabilis, the sequence of events noted included bacterial-papillary interactions consisting of cell desquamation and strand formation, despite infrequent bacterial attachment. After 10 hr, a rapid, urease induced pH rise resulted in calcium salt deposition on the papillae surface. Organism death was apparent after 72 hr. Escherichia coli infected papillae demonstrated similar cell surface changes after a 8 hr as seen in P. mirabilis; however, frequent evidence of bacterial attachment and penetration was apparent. Bacterial attachment was a prominent feature throughout the incubation period with E. coli. After one week, rare areas of degenerating cells and bacteria with increased calcium levels as compared to surrounding areas were noted by EDS analysis. Urinary pH was stable throughout the incubation period. This study suggests varied roles for the organisms most associated with infection induced papillary necrosis (E coli) and papillary necrosis with subsequent stone formation (P. mirabilis). A role for bacterial calcification in the absence of bacterial urease activity by E. coli is also suggested.

Animals↗
PubMed1981

Morphological studies of experimental wound healing cells in a murine model.

Integument wounds are primarily healed by fibroblasts. These multifunctional cells synthesize collagen and ground substances (acid mucopolysaccharides) from which they fashion fibers and/or laminae. The fibers are formed in the upper layers of the wound by spindle shaped cells which initially grow along fibrin strands. This area of repair eventually becomes the papillary dermis of the scar. Flattened fibroblasts produce stacks of collagen laminae in the deep part of the wound. The laminae are initiated in the subpannicular region several mm behind the wound margin. The laminae grow centripetally and mature (thicken by collagen and ground substance deposition which is effected by subsequent fibroblast activity). The laminae become the reticular layer of the scar dermis. Thus, the collagenous architecture of a scar's connective tissue appears to be related to the shape of the cells involved in assembly.

Animals↗
PubMed1979

Ultrastructure of Aplysia neurons having different degrees of light sensitivity.

The relationship between ultrastructure and photosensitivity of pigmented neurons of the abdominal ganglion of Aplysia californica was investigated using electron microscopy and electrophysiological methods. Four identified neurons of similar light microscopic appearance were examined; two are photoresponsive and two are not. Illumination hyperpolarizes both responsive neurons. One of them, R2, requires roughly 100 times greater light intensities than does the other, the ventral photoresponsive neuron (VPN), for similar responses. Two neurons lying adjacent to VPN and similar in appearance to VPN do not have measurable electrophysiological responses to even the highest light intensities. All four neurons contained lipochondria, pigmented organelles associated with the light response. Therefore the presence of these organelles is not the only requirement for light sensitivity in these neurons. Illumination appeared to increase the number of membranous lipochondria in both R2 and the ventral neurons, but only in R2 was this increase significant. Factors such as the concentration of lipochondria near the plasma membrane may affect quantitative aspects of the light response, but in the insensitive cells the lipochondria are apparently uncoupled from other factors required for the light response.

Animals↗
PubMed1979

Ultrastructural evidence for the presence of "fibroclasts" and "myofibroclasts" in wound healing tissues.

We have observed, by light and electron microscopy, fibroblast-like cells which appear to be involved in collagen fiber and filament degradation. These cells are most prominent in the dermis of mature hypertrophic scars which were clinically observed to be in the remodeling phase of wound repair. Total incorporation of collagen filaments within cellular vacuoles, as seen by TEM, appears to precede the enzymatic degradation of the collagen. Cytoplasmic contractile bundles and/or collagen filament remnants found within residual lysosomes were also seen in many of these cells. Evidence of structural reorganization within the tissue was observed by means of SEM. These cells appear to be similar to osteoclasts in function: thus we propose to name them "fibroclasts" and "myofibroclasts."

Adolescent↗
PubMed1978

Observations of globular membranes and apparent elementary particles in rat mitochondria, in situ.

Ultrastructural details of rat skeletal muscle, fixed in a PIPES-buffered glutaraldehyde solution, included the globular configuration of the outer and inner mitochondrial membranes as well as small transparent particles (80--100A diameter) distributed throughout the matrix of these organelles. The size of these particles and their intimate relationship with the innermost surface of the cristae suggests that they may represent an in situ visualization of the elementary particles once reported in intact cells and frequently observed in negatively stained mitochondrial preparations. The membrane configurations and particles were not discernable in these tissues when a phosphate buffer system was used in the fixation regimen.

Animals↗
PubMed1977

Lipochondria and the light response of Aplysia giant neurons,.

The ultrastructure, absorbance, and elemental content of lipochondria present in the cytoplasm of Aplysia giant neurons have been investigated before and after 30-1,200 sec doses of white light at intensities which produce saturated light responses. The effects of exposure to the calcium ionophore A-23187 and to EGTA were also examined. The lipochondria of nonilluminated neurons are membrane-bound, and contain lipids, protein, Na, K, Mg Ca, Si, Cl, Br, P, and a pigment which is probably beta-carotene. The cytoplasm appeared to have little pigment. When neurons were illuminated for 20 min, 60-70% of the lipochondria showed marked ultrastructural alterations, the most notable being the appearance of membranous material. Earlier changes which occur after 30 sec of illumination include the appearance of paracrystalline arrays and mottling. Less than 10% of lipochondria in nonilluminated neurons have a similar appearance. These effects were greatly enhanced in illuminated neurons exposed to the calcium ionophore or EGTA. In nonilluminated neurons, the ionophore also produced ultrastructural changes. In frozen specimens, the calcium content of the most electron dense lipochondria of illuminated neurons was reduced. Other elements which were counted were also reduced. The lipochondria are the main intracellular site of photopigment. They may also act as an intracellular source for calcium which, as the accompanying paper indicated, may mediate phototransduction in Aplysia neurons.

Animals↗
PubMed1977

An in situ procedure for the biopsy of pressure-wrapped hypertrophic scars.

A plexiglass device can be incorporated in the therapeutic elastic wrapping of hypertrophic scars. The removal of a small access port on this device permits the exposure of the underlying tissue for full-thickness biopsy without the necessity of first removing the pressure wrapping. The ultrastructural detail of tissues biopsied in this manner more readily reflects the in situ microarchitecture of the pressure-wrapped skin and/or scars.

Bandages↗
PubMed1977

The use of PIPES buffer in the fixation of mammalian and marine tissues for electron microscopy.

PIPES, an organic based buffer, was used in the preparation of a variety of marine and mammalian tissues for electron microscopic study. The ultrastructural results demonstrate that this buffer renders superior ultrastructural details to those obtained with some of the more common inorganic buffers especially when long fixation times are required. Furthermore, this buffer system does not appear to contribute extraneous anions or cations to the tissues and thus permits accurate elemental determinations to be performed on thin sections of the plastic embedded specimens by means of energy dispersive X-ray analysis.

Animals↗
PubMed1977

Retention of the glycocalyx after cell detachment by EGTA.

Chinese hamster ovary cells were examined ultrastructurally following several detachment procedures. Alterations in the surface glycoproteins were observed by using ruthenium red in the fixation procedure. Trypsin removed a major portion of the cells glycocalyx and formed spherical cellular configurations. EGTA detached cells were also spherical, however, their glycocalyx appeared to remain although redistributed over the cell surface. Kinetic studies showed no alterations in subsequent population doubling times following either detachment procedure. EGTA may thus represent the current method of choice for cell detachment if preservation of the surface glycoproteins is of interest.

Animals↗