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Biomedical subjects

J J McCann

Publications and source records attributed to J J McCann.

36 records · Page 2Linked to original sources
PubMed1988

The fillet foot for endweight-bearing cover of below knee amputations.

Four patients with five severely traumatized lower legs but preserved feet were treated with fillet flaps from the foot to cover an elective, below knee amputation stump. The posterior tibial neurovascular bundle nourished and innervated this flap. While the posterior tibial artery and vein may be cut and re-anastomosed to prevent kinking and occlusion, the posterior tibial nerve should always be kept in continuity to maintain the quality of sensation to this flap. Four flaps survived and one necrosed secondary to venous insufficiency. Due to its innervation and the unique qualities of heel skin, the flap is very durable and has endweight-bearing capabilities. This has permitted the fitting of an endweight-bearing, total contact, fully extended, below knee prosthesis that appears to offer significant improvement in ease of use and normality of gait pattern over standard patellar tendon-bearing prostheses.

Adult↗
PubMed1987

The free radial forearm flap with and without bone for closure of large palatal fistulae.

Three cases of palatal fistulae closed by microvascular transfer of radial forearm flaps are presented. Vascularised bone was included in one flap and all operations were free of complications. Facial scarring is minimal and the secondary deformity in the arm has not been significant. It is suggested that this procedure presents fewer difficulties than other techniques for treating the large palatal fistula and may prevent the collapse of the alveolar arch which follows the scarring associated with closure by local tissue.

Adolescent↗
PubMed1987

Protein metabolism and fibrosis in experimental canine obstructive lymphedema.

Obstructive lymphedema is a pathologic condition resulting in the accumulation and stagnation of serum proteins in the lymphatics and interstitial spaces. In a canine model of obstructive lymphedema, one limb was rendered lymphedematous, and various biochemical parameters were determined in this and an unaffected control limb. Both lymph and interstitial fluid had significantly decreased acid proteinase activity (comprising mostly cathepsin D-like enzymes) and neutral proteinase activity (comprising metallo, sulfhydryl, and serine proteinases, and collagenase). Possible reasons for these decreases could be: (1) saturation of macrophages and their surrounding environment with whole or partially digested proteins, or (2) elevation in the levels of circulating inhibitors like alpha 2-macroglobulin. The lymphedematous skin was significantly thicker than control skin and had elevated levels of collagen. However, unlike some fibrotic conditions, the relative proportions of types I, III, and V collagen, as determined by pepsin solubilization and neutral salt fractionation of the collagen fibrils, were similar to those found in normal skin. It is speculated that a decrease in the breakdown of collagen by collagenase and a continuing synthesis of collagen by fibroblasts led to an imbalance in favor of collagen deposition in the skin.

Animals↗
PubMed1987

Some further characteristics of expanded tissue.

It has been shown that during expansion there is a component of migration of surrounding tissue that probably contributes to the available tissue in local reconstructive procedures. Although there is a 63 per cent increase through expansion of a given flap with a particular expander, this results in only a 30 per cent increase after elevation and inset. This increase is basically maintained for a 3- or 4-month period. The 56 per cent decrease in area probably results from contraction of the extensible skin. The 30 per cent that remains probably results from a combination of stretch evidenced by reorientation, along with an increase in the cellular and extracellular components of expanded tissue. Therefore, there are components of both loan and dividend in tissue expansion. This further understanding should be helpful in the planning of tissue expansion. (Editors' note: Although there may be some element of "loan" initially, from peripheral regions, no thinning of the periphery has been observed. To the contrary, the periphery appears normal. It is likely that transient thinning of the periphery causes increased mitotic activity, and that this area is also made to produce a "dividend" ultimately. Unless permanent thinning can be documented, the "dividend hypothesis" remains valid.

Animals↗
PubMed1983

Influence of intraocular scattered light on lightness-scaling experiments.

Following Munsell's bisection procedure [J. Opt. Soc. Am. 23, 394 (1933)], we established a nine-step gray scale in which each step is an equal increment in lightness. We calculated retinal illuminances after intraocular scatter by using the point-spread function of Vos et al. [Vision Res. 16, 215-219 (1976)]. After this correction for intraocular scatter, we find a logarithmic relationship between retinal illuminance and achromatic lightness scales that are determined by the bisection method. Additional bisection experiments with a series of different backgrounds corroborate this result. We find that lightness depends linearly on the logarithm of scatter-corrected retinal illuminance, with different slopes for backgrounds of different lightness. This study also highlights the importance of using scatter-corrected illuminance in any quantitative model of lightness.

Adult↗
PubMed1977

Variegated color sensations from rod-cone interactions: flicker-fusion experiments.

Multicolored images were produced by the combination of two different color-separation images, one illuminated with 656 nm light and the other illuminated with 500 nm light. Flicker-fusion frequency measurements were used to identify the conditions in which the 500 nm light was below cone threshold. Under those conditions the multicolored images were shown to be generated by rod and long-wave cone interactions.

Color Perception↗
PubMed1976

Shifting linear growth during infancy: illustration of genetic factors in growth from fetal life through infancy.

A percentile linear growth chart, from the third to ninety-seven percentiles, was derived from longitudinal data on 90 normal full-term infants of middle class suburban families, and the individual growth curves of each infant was contrasted to the growth chart for the entire group. Individual shifting in growth rate was noted in two thirds of the infants. To better determine the timing and nature of these shifts in linear growth, a search was made for otherwise normal full-term infants who were at or below the tenth percentile for length at birth and who moved up to the fiftieth percentile or better by age 2 years and those who were at or above the ninetieth percentile at birth and moved down to the fiftieth percentile or less by 2 years of age. Those shifting upward had accelerated linear growth soon after birth; they achieved a new "channel" at a mean age of 11.5 months. Those shifting downward did not decelerate until after the first three to six months; they achieved a new channel by the mean age of 13 months. These findings plus the correlation coefficients relating parental size to the length of the infant at birth, one year, and two years of age are compatible with the following statements: Birth length relates predominantly to maternal size whereas by 2 years of age the length correlates best to mean parental height, reflecting the genetic growth factors of both parents. Those infants "catching-up" after birth usually do so in early infancy, whereas those "lagging-down" tend to do so in midinfancy.

Birth Weight↗
PubMed1975

Visibility of low-spatial-frequency sine-wave targets: Dependence on number of cycles.

The number of cycles in a low-frequency sinusoidal display is a crucial variable in determining the visibility of the display. In particular, the threshold contrast is essentially independent of spatial frequency for these displays. We have extended the above experiments, using more cycles and a variety of targets and observer tasks. The results confirm previous findings; they also show that the type of target or task has little influence. For low-frequency sinusoids that contain up to about 3 cycles, the threshold contrast is determined by the number of cycles. For high-number-of-cycles targets with spatial frequencies above 6-10 cycles per degree, visibility is predominantly dependent on the spatial frequency. The results suggest that the low-frequency decrease in reported MTF's is due to the decrease of the number of cycles used in determining them.

Fourier Analysis↗