Paul S. Baur

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.

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.

Bladder reconstruction in rabbits with glutaraldehyde-stablilized 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.

Intracellular crystal formation in bacteria from human urines: A contributing factor in urinary calculi

SummaryUnderstanding of the bacterial contribution to urinary calculi has been limited to those organisms capable of altering the urine through urease activity. Sterilized urines from stone forming and non-stone forming individuals were inoculated with bacteria having either strong, weak, or no urease activity. All organisms grown in unbuffered urines produced crystallization (calcite or apatite) as demonstrated by X-ray diffraction. Bacteria grown in conventional medium (Heart Infusion broth) did not demonstrate crystal formation. Unstained specimens revealed electron-dense deposits within bacteria grown in urine. Deposits were not present in organisms grown in conventional media. Analysis revealed increased levels of calcium within these deposits as compared to extracellular levels. These findings support the hypothesis that both urease producing and non-urease producing organisms may accumulate calcium crystals intracellularly and form nidi for calculus formation.

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.

Late problems in burns

In summary, the commonest late physical complications of the burn injury have been reviewed and an approach to their management described. An understanding of the pathophysiology of the conditions is invaluable in planning ones approach to these problems. The techniques to control and correct chronic wound and hypertrophic scar and contractural deformities have been described. We present only a brief summary of the techniques found most reliable in the management of a large group of burned children over many years.