PubMed Health⌕ Search

Biomedical subjects

A Pentland

Publications and source records attributed to A Pentland.

5 recordsLinked to original sources
PubMed1989

Heterogeneity of cellular expression of arachidonate 15-lipoxygenase: implications for biological activity.

Comparison of relative arachidonate 15-lipoxygenase activities in different types of human cell reveals striking differences in levels of product generation. Among available human cell types, the tracheal epithelial cell and the eosinophil have markedly higher levels of activity than other cell types with reported activity. Theories of functional significance for this enzymatic pathway will need to account for the selective expression of high levels of activity in a highly limited number of cell types.

Arachidonate 15-Lipoxygenase↗
PubMed1989

Use of injectable cultured human fibroblasts for percutaneous tissue implantation. An experimental study.

Large quantities of cultured human facial dermal fibroblasts were propagated from randomly selected patients to determine their relative suitability as percutaneously injectable living implants. Volumetric and histologic comparisons were made between the following implants that were injected subcutaneously into athymic nude mice: (1) cultured human fibroblasts (HFb); (2) cultured human fibroblasts dispersed in Zyderm II collagen (HFb + Zyd); (3) Zyderm II collagen (Zyd); and (4) Zyplast collagen (Zyp). Both the HFb and HFb + Zyd implants were accepted as primary takes but regressed volumetrically at significantly greater rates than either the Zyd or Zyp implants. Correlative immunohistochemical staining revealed that, by 10 days, 90% of the cells within the HFb implants and 80% within the HFb + Zyd implants were of human origin; however, by 9 weeks, approximately 25% of the cells were of human origin in both types of implants. These results indicated that cultured human fibroblasts can be successfully injected as living grafts; however, the subsequent gradual attrition in the numbers of implanted cells, as noted in this model system, limits the long-term retention of the implants.

Animals↗
PubMed1989

Shape information from shading: a theory about human perception.

I present evidence that people assume a simple, linear reflectance function when interpreting shading information. Using this reflectance function I derive a closed-form solution to the problem of extracting shape information from image shading. The solution does not employ an assumption about surface smoothness and so is directly applicable to complex natural surfaces such as hair or cloth. A simple biological mechanism is proposed to implement this recovery of shape. It is shown that this simple mechanism can also extract significant shape information from line drawings.

Form Perception↗
PubMed1989

A regiospecific monooxygenase with novel stereopreference is the major pathway for arachidonic acid oxygenation in isolated epidermal cells.

We investigated the enzymatic mechanisms responsible for AA oxygenation in homogenous cell suspensions obtained by trypsinization of epidermis from healthy subjects. Cell incubation with AA (0.3-150 microM) invariably resulted in the predominant generation of a compound identified as 12-hydroxyeicosatetraenoic acid (12-HETE) by HPLC and by both negative-ion chemical ionization and electron-impact mass spectrometry. Maximal amounts of 12-HETE were 126 +/- 21 pmol/10(6) cells (+/- SE), and concentration-response curves yielded half-maximal levels for 12-HETE similar to PGE2 at 2 microM AA. Two epoxyeicosatrienoic acids derived from AA were also identified. Stereochemical analysis by chiral-phase chromatography demonstrated that the epidermal cell 12-HETE was a mixture of the 12S- and 12R-hydroxy isomers in a molar ratio varying from 2:1 to 8:1 among subjects. Subcellular fractionation into 12,000 g pellet (containing mitochondria) and 100,000 g supernatant (cytosol) and pellet (microsome) demonstrated that greater than 99% of the 12-HETE was generated by enzymatic activity distributed equally in the two pellets. Both mitochondrial and microsomal activities were increased upon addition of NADPH and were inhibited by carbon monoxide, but the molar ratio of 12S/12R-HETE was threefold greater in microsomal than in mitochondrial fractions. The results demonstrate that human epidermis contains active membrane-bound monooxygenase(s) which preferentially generates 12-HETE from AA, exhibits a 12S stereopreference of hydroxylation, and suggests the presence of distinct mitochondrial and microsomal enzyme systems in epidermal cells.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗