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Biomedical subjects

M M Mathews-Roth

Publications and source records attributed to M M Mathews-Roth.

At least 37 records · Page 2Linked to original sources
PubMed1986

Preferential light absorption in atheromas in vitro. Implications for laser angioplasty.

Laser angioplasty, the in situ ablation of arterial obstructions with laser radiation, has been demonstrated in animal models and early clinical trials. A problem with this technique, however, is the possibility of thermal damage to adjacent or underlying normal tissues that also absorb the radiation. Using a spectrophotometer with an integrating sphere and a specially constructed tunable-dye laser-based spectrophotometer, we evaluated the transmittance and remittance of human cadaveric atheromas and adjacent normal aorta from 250 to 1,300 nm to identify wavebands where there is preferential light absorption by atheromas. Data were analyzed by both the Kubelka-Munk formalism and a Beer's law model. Both methods indicate that atheromas absorb more than normal aorta between 420 and 530 nm. At 470 nm the average Kubelka-Munk absorption coefficient of atheromas from 10 cadavers was 54 +/- 9 cm-1 compared with 26 +/- 6 cm-1 for normal aortic specimens from seven cadavers. Yellow chromophores responsible for the atheroma absorbance were extractable with xylenes. Thin-layer chromatography and absorption spectra identified the extracted chromophores as predominantly consisting of a mix of carotenoids, which are known constituents of atheromatous lesions. Preferential absorption of blue light by carotenoids in atheromas may permit selective ablation of atheromatous obstructions with appropriate pulses of laser radiation.

Absorption↗
PubMed1986

Systemic photoprotection.

At present, three classes of compounds are used as systemic photoprotective agents, but only for specific indications, not for general use in healthy individuals. Beta-carotene prevents or lessens photosensitivity in most patients with erythropoietic protoporphyria and in some patients with other photosensitivity diseases. The antimalarial drugs can clear up skin lesions in patients with polymorphous light eruption and solar urticaria who cannot obtain relief with topical sunscreens and in some patients with porphyria cutanea tarda. Oral psoralens and controlled exposure to sunlight or artificial sources of UVA radiation can increase tolerance to sunlight in fair-skinned individuals and in certain patients with vitiligo or polymorphous light eruption.

Administration, Oral↗
PubMed1984

Treatment of erythropoietic protoporphyria with beta-carotene.

We have found that beta-carotene, when administered in sufficiently high doses, can be an effective therapy for ameliorating the photosensitivity associated with EPP. Other workers have confirmed our findings, using either beta-carotene, canthaxanthin or combinations of these two carotenoids. Carotenoids may be of some use in congenital porphyria, if given in high doses and started when the patient is very young. Carotenoid treatment seems of limited use in polymorphous light eruption, solar urticaria, hydroa aestivale and hydroa vacciniforme: we would recommend their use in these conditions only after the more standard treatments for these diseases have proven ineffective for a given patient. Carotenoid treatment seems to be of no use in porphyria cutanea tarda and actinic reticuloid.

Age Factors↗
PubMed1984

Some factors affecting determination of carotenoids in serum.

Because of increasing interest in carotenoid pigments, we conducted a study of the methods of determining carotenoids in serum. We found 1 mol of KOH per liter of absolute methanol to be the most effective saponifying solution. The absorbance of beta-carotene in petroleum ether, the extraction solvent, is proportional to dilution up to an absorbance of 0.85 at 450 nm. Beta-carotene in petroleum ether solution is not impracticably sensitive to ambient light at room temperature. However, if vitamin A is also to be measured in these serum specimens or petroleum ether extracts, exposure to light should be minimized. We found that serum may be shipped either in cold packs or at ambient temperature (tested up to five days) without significant change in carotenoid concentration. Serum samples for carotenoid determination are best stored at -70 degrees C: samples stored at -20 degrees C deteriorate substantially over several months.

Carotenoids↗
PubMed1982

Antitumor activity of beta-carotene, canthaxanthin and phytoene.

Mice were given either beta-carotene or either of two carotenoids with no vitamin A activity--canthaxanthin or phytoene--or placebo. Skin tumors were induced in each group by each of three methods: (1) UV-B (290--320 nm); (2) dimethylbenz(a)anthracene (DMBA)/croton oil applications; (3) DMBA followed by low-dose UV-B. For tumors induced by UV-B alone, beta-carotene-phytoene- and canthaxanthin-treated mice developed fewer tumors per mouse, with a delay in tumor appearance, than did control mice. For tumors induced by DMBA/croton oil or DMBA/UV-B, mice receiving beta-carotene showed a significant difference in tumor numbers and appearance time from placebo mice; phytoene and canthaxanthin treatment had no effect.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1982

Effect of crocetin on experimental skin tumors in hairless mice.

Crocetin seems to have a small effect in slowing the development of skin tumors induced in hairless mice by the application of dimethyl-benz-a-anthracene and croton oil. No definite effect is shown on preventing the development of tumors induced by UV-B radiation.

9,10-Dimethyl-1,2-benzanthracene↗