The extracellular matrix macromolecule, hyaluronan, is thought to modulate wound healing. However, the molecular size of hyaluronan and contaminating associated proteins may be important determinants of these effects. We have examined the results of seven daily topical treatments of full-thickness skin wounds in pigs with ultrapure hyaluronan of defined molecular size. High molecular weight hyaluronan (>1000 kd) enhanced, whereas low molecular weight hyaluronan decreased, the rate of early wound contraction as compared with intermediate hyaluronan (molecular weight = 100 kd) and saline solution controls. Fracture strength at 21 days was reduced by high and intermediate molecular weight hyaluronan but not by low molecular weight hyaluronan. Wound perfusion, measured by means of a scanning laser-Doppler technique as a noninvasive indicator of angiogenesis, showed depression by high and intermediate molecular weight hyaluronan on day 3, but all forms of hyaluronan caused elevated blood flow on day 7. The architecture of granulation tissue in this wet healing model was highly organized, but no gross histologic differences were seen because of treatment. Different molecular species of hyaluronan have differential effects on contraction, angiogenesis, and the evolution of wound strength. Where hyaluronan is used as a treatment or vehicle for wounds, its precise composition should be specified.

Journal Article↗

PubMedDate not supplied

Effects of chronic wound fluid on the bioactivity of platelet-derived growth factor in serum-free medium and its direct effect on fibroblast growth.

The fate of biologically active proteins applied to chronic wounds is almost totally unknown. Growth factors may be degraded by proteases, which are produced by both inflammatory and skin cells and by resident bacteria. However, there has been little work on the effect of chronic wound fluid on the activity of growth factors. A bioassay method has been chosen to examine the effect of incubation of platelet-derived growth factor with chronic wound fluid from leg ulcers on the in vitro growth of human dermal fibroblasts. Human dermal fibroblasts were cultured in serum-free medium, and a dose-response curve for proliferation in response to platelet-derived growth factor was obtained. Wound fluid was collected under occlusive dressings from five patients with chronic leg ulcers. Platelet-derived growth factor was incubated with chronic wound fluid at 37 degrees C for 4 hours, and the reactions arrested by snap freezing. The resultant solutions were tested for their ability to promote fibroblast proliferation. A colorimetric assay was used to monitor changes in the platelet-derived growth factor mitogenicity. The results showed that, in our standard culture conditions, chronic wound fluid always stimulated fibroblast proliferation, and, in most cases, incubation of platelet-derived growth factor with chronic wound fluid increased the stimulation compared with that produced by platelet-derived growth factor or chronic wound fluid alone.

Aged↗

PubMedDate not supplied

The mechanism of physiological height vertigo. I. Theoretical approach and psychophysics.

A theory is presented supporting a geometrical explanation of physiological height vertigo as a 'distance vertigo' created by visual destabilization of posture when the distance between the observer and visible stationary contrasts becomes critically large. Though height vertigo is generally regarded as a psychopathological process, we hypothesize that it might instead result from an intersensory mismatch when visual information is at variance with vestibular and proprioceptive inputs. Psychophysical experiments confirming the hypothesis revealed that: 1) height vertigo is clearly related to body position, being the greatest in the upright stance; 2) it is the eye-object distance rather than the direction of gaze which is critical; 3) there is a saturation of height vertigo magnitude. Subjective vertigo increases with increasing altitude only below 20 metres. Physiological 'distance vertigo' must be distinguished from psychological 'acrophobia'. Its postural consequences may be ameliorated by strategies gleaned from knowledge of its mechanism such as providing nearby stationary contrasts in the peripheral visual field.

Adult↗

PubMedDate not supplied

The mechanism of physiological height vertigo. II. Posturography.

In order to validate the hypothesis that height vertigo is based on visual destabilization of free stance when the distance between eye and object becomes critically large, several of its consequences were demonstrated in posturographic experiments: (1) Visual signals conflicting with simultaneous vestibular and somatosensory inputs provided by sinusoidally tilting rooms may destabilize postural sway in the fore-aft as well as in the lateral direction. (2) In natural surrounding sway amplitudes increase with increasing eye-object distance up to 5 meters. Thus, teleologically, subjective height vertigo serves as an appropriate warning signal to withdraw the body from a stimulus situation inducing postural imbalance. (3) Postural height vertigo problems can be alleviated (a) by adjusting the head relative to the gravitational vector, and (b) by the presence of nearby stationary contrasts in the visual periphery according to the dominance of retinal periphery for dynamic spatial orientation.

Adult↗

PubMedDate not supplied

Utilization of diagnostic resources for meningoencephalitis in the pediatric ICU.

To determine whether a Pediatric Critical Care team has an evolution of medical practice that decreases the utilization of diagnostic tests and consults, we examined the records of 69 patients admitted for meningitis or meningoencephalitis at Women and Children's Hospital in Charleston, W.Va., a university-affiliated, teaching hospital. The study was conducted from August 1990 to August 1994. We found that utilization of diagnostic resources (UDR) decreased over the four years, and there was a direct relationship between an increase in severity of illness and an increase in UDR. When adjusted per severity of illness, UDR decreased by $423 per year. The presence of a consult was a factor leading to an increase in resources, which were associated with an increased utilization of diagnostic tests and length of stay. The consultation rate was independent of the severity of illness and experienced a decrease over the years.

Analysis of Variance↗