Biomedical subjects

S J McKnight

Publications and source records attributed to S J McKnight.

4 recordsLinked to original sources

PubMed1998

The role of alcohol dehydrogenase in the metabolism of the colon carcinogen methylazoxymethanol.

The aim of this study was to determine whether the cytosolic enzyme alcohol dehydrogenase (ADH) activates methylazoxymethanol (MAM) in the mouse colon and whether differential tumor susceptibility in the mouse is dependent, in part, on strain-related differences in MAM metabolism by ADH. Liver and colon cytosols were isolated from 7-week-old male tumor-susceptible (SWR/J) and -resistant (AKR/J) mice. Minimal reduction of NAD+ was found in colon cytosols from AKR/J mice at the highest concentration (2 mM) of MAM tested. In liver cytosols, only SWR was capable of sustaining NAD+ reduction with MAM, although at very low levels. Despite minimal reactivity with MAM, however, mouse cytosols did effectively reduce NAD+ in the presence of the common ADH subrates ethanol and benzyl alcohol. NAD(+)-coupled oxidation of benzyl alcohol was significantly higher (two- to three-fold, p < 0.05) in mouse colon cytosols compared to activity present within corresponding rat tissues. Incubation of colon and liver cytosols with the ADH-3 inhibitor 4-methylpyrazole markedly (95-100% of controls) reduced ethanol oxidation in both strains. However, 4-methylpyrazole was a less effective inhibitor of benzyl alcohol oxidation in AKR/J colons, suggesting a different ADH isoform complement. An opposite inhibition pattern of benzyl alcohol oxidation was seen in the liver, where 4-methylpyrazole produced a greater inhibition in SWR/J mice. These studies suggest that the metabolism of the proximate mutagen MAM occurs by processes in the mouse that are independent of ADH.

Alcohol Dehydrogenase↗

PubMed1988

Corneal rupture following radial keratotomy in cats subjected to BB gun injury.

We performed this investigation to determine if radial keratotomy (RK) predisposes an eye to rupture when exposed to projectile trauma. Radial keratotomy was performed on 22 cat eyes; 17 eyes were used as controls. Incision depth was set at 90% by averaging ten corneal thickness readings by ultrasonic pachymetry of each cornea. An optical zone of 4.0 mm was used and eight incisions were made. Eight weeks after RK the cats were divided into three groups, subjected respectively to BB velocities of 148.5 ft/sec (N = 4), 190 ft/sec (N = 5), and 240 ft/sec (N = 13). In groups 1 and 2, all nine eyes had hyphemas and no eyes perforated. In group 3, four of 13 RK eyes had corneal rupture. All control eyes had hyphemas and none ruptured. The study suggests that RK can predispose to rupture eyes exposed to projectile trauma sufficient to produce hyphema.

Animals↗

PubMed1987

Inflammatory response to viscoelastic materials.

Healon, Amvisc, or Viscoat was injected into the corneal stroma of 36 normal rabbit eyes. Twelve additional rabbit eyes were used as controls by performing a sham procedure. Twelve rabbits were euthanized at one day and the remainder seven days after injection. The eyes were enucleated and examined by light microscopy. No control eyes had detectable inflammation. Only Viscoat produced mild inflammation at seven days, but this was statistically significant only at p = 0.182. There appears to be little difference in the inflammatory response of these three viscoelastic substances.

Animals↗

PubMed1984

Metastasis of a very small choroidal melanoma without apparent clinical change.

An unusual case occurred of a very small choroidal melanoma which was clinically inactive for 5 1/2 years, yet developed metastasis. This case appears to be the smallest reported choroidal melanoma with metastatic disease and the first reported metastasis to the anus. The very small size of this choroidal melanoma and its quiescent clinical behavior at the time of the discovery of metastasis, emphasizes the possible danger of observing of small choroidal melanomas.

Aged↗