An unexpected spectrum of p53 mutations from squamous cell carcinomas in psoriasis patients treated with PUVA

Photochemotherapy employing 8-methoxypsoralen and long-wavelength ultraviolet radiation (UVA, 320-400 nm) is widely used in the treatment of psoriasis. The photoactivation of psoralens in skin cells leads to formation of DNA photoadducts which may be responsible, at least in part, for the efficacy of these photochemotherapies. However, mutations arising from these adducts may also lead to the well-characterized increased incidence of squamous cell carcinoma. Mutations in the p53 tumor suppressor gene have been detected in many human cancers. To determine whether p53 mutations occur in squamous cell carcinomas in PUVA patients, PCR was used to amplify the exons (5-9) in which other studies have found a high frequency of point mutations. Gel electrophoresis was used to detect single-strand conformational polymorphisms. Aberrantly migrating bands were excised, reamplified and sequenced. Thirty-four specimens from 10 patients were examined. Specimens from one patient who had received no phototherapy as well as from normal controls were also analyzed. Five of the 10 patients showed at least one p53 mutation. In contrast to previously reported psoralen-induced p53 mutations in mice, the expected psoralen type mutations at alternating AT sites were not detected. All but two of the altered sequences occurred at dipyrimidine sites which is typical of solar type mutations. Two C-->T mutations and two dipyrimidine mutations (CC-->TT) were found. Other mutations included: C-->G, G-->T, C-->A and an 18 bp deletion. A review of therapeutic history of these patients showed that some had also received UVB phototherapy. Furthermore, because sunlight is thought to be beneficial for psoriasis, nontherapeutic, casual UVB exposure cannot be excluded. Our observations suggest that the SCC may have arisen from the solar mutations and that PUVA may enhance tumor progression or immune suppression.

Differential sensitivity of human visual cortex to faces, letterstrings, and textures: a functional magnetic resonance imaging study

Twelve normal subjects viewed alternating sequences of unfamiliar faces, unpronounceable nonword letterstrings, and textures while echoplanar functional magnetic resonance images were acquired in seven slices extending from the posterior margin of the splenium to near the occipital pole. These stimuli were chosen to elicit initial category-specific processing in extrastriate cortex while minimizing semantic processing. Overall, faces evoked more activation than did letterstrings. Comparing hemispheres, faces evoked greater activation in the right than the left hemisphere, whereas letterstrings evoked greater activation in the left than the right hemisphere. Faces primarily activated the fusiform gyrus bilaterally, and also activated the right occipitotemporal and inferior occipital sulci and a region of lateral cortex centered in the middle temporal gyrus. Letterstrings primarily activated the left occipitotemporal and inferior occipital sulci. Textures primarily activated portions of the collateral sulcus. In the left hemisphere, 9 of the 12 subjects showed a characteristic pattern in which faces activated a discrete region of the lateral fusiform gyrus, whereas letterstrings activated a nearby region of cortex within the occipitotemporal and inferior occipital sulci. These results suggest that different regions of ventral extrastriate cortex are specialized for processing the perceptual features of faces and letterstrings, and that these regions are intermediate between earlier processing in striate and peristriate cortex, and later lexical, semantic, and associative processing in downstream cortical regions.

Non-radioactive DNA probe and polymerase chain reaction procedures for the specific detection of Acanthamoeba

Acanthamoebae are potential pathogens which can cause serious infections of humans. A non-radioactive rDNA probe and polymerase chain reaction (PCR) amplification procedures which are specific, rapid, sensitive and safe for the detection of Acanthamoeba have been developed. A restriction fragment (126 bp; ArDNA-a) from a variable region of the cloned 26S rDNA unit of Acanthamoeba castellanii (from plasmid pAR2) was labelled by biotinylation. Cells and DNAs were incubated with the labelled rDNA probe to define conditions providing the highest hybridization specificity for Acanthamoeba by both colorimetric and chemiluminescent assays. Four recent isolates of Acanthamoeba, Acanthamoeba polyphaga, various bacteria, Herpes simplex virus, other eukaryotic amoebae and human cell lines, were sources of DNA for testing. The rDNA probe was found to be highly specific for Acanthamoeba and is capable of directly detecting about 250 cells without prior DNA purification. PCR primers for this unique ArDNA-a fragment have also been designed. Amplification of the targeted sequence by PCR using those primers yielded a single product which was specifically generated for Acanthamoeba template DNA and not DNA from the other control cells. This PCR procedure provided increased sensitivity with the direct detection of as few as 10 Acanthamoeba cells.

The function of slime from Physarum flavicomum in the control of cell division

A haploid cell of the myxomycete Physarum flavicomum undergoes cytokinesis, producing a large population of cells. However, after syngamy, cytokinesis no longer occurs but karyokinesis does and subsequent growth results in the formation of a diploid syncytial plasmodium. Slime, which is produced by the plasmodium but not the haploid cells, was aseptically isolated and purified, and tested for its effect as a cytokinetic regulator. Slime (a viscous, high molecular weight, acidic glycoprotein) affected cytokinesis of the haploid myxamoebae growing in pure culture in soluble media, and the effect was concentration dependent. In simple media, a slime concentration of about 6 10(-5) mug protein per cell suppressed cytokinesis about 50%, unequally inhibited the synthesis of protein, RNA, and DNA, but stimulated respiration. The biological activity of slime was not species specific and it also affected the bacterium Bacillus subtilis by inhibiting cytokinesis, stimulating oxygen uptake, and producing an aberrant cell morphology. Slime was inactivated by heat, fragmentation, and incubation with dithiothreitol, mercaptoethanol, and the proteolytic enzyme papain (EC 3.4.22.2). The inhibitory effect of slime on cell division of haploid cells could not be achieved using mucin or various polyanions. The possible role of slime in the production of the diploid syncytium is discussed.

Growth of the haploid phase of the myxomycete Physarum flavicomum in defined minimal medium

The haploid phase (myxamoebae-swarm cells) of the myxomycete Physarum flavicomum grew readily in chemical defined liquid media. The minimal medium contained salts, glucose, biotin, thiamine, hematin, glycine, L-arginine and L-methionine. Cell yields of 1.4 times 10(7) cells/ml were obtained in this medium in aerobic shake culture. These cells consumed about 35 muliters of oxygen/mg protein-hr in the minimal medium. The morphology of cells maintained in this medium appeared to be "normal". L-valine replaced either glycine or L-methionine in the minimal medium but the growth rates and cell yields were reduced. Growth rates increased in media containing four, seven, or fourteen amino acids.

Growth of the haploid and diploid phases of Physarum flavicomum in the same partially defined media

The haploid phase (myxamoebae-swarm cells) of the myxomycete Physarum flavicomum variety 1 grows readily in partially defined liquid media, which were developed for the culture of the diploid plasmodial phase. Cell yields of between 2 × 107 and 4 × 107 cells/ml are obtained in these media in aerobic shake culture. Growth rates are more rapid in shake culture than in stationary culture but growth does not occur in anaerobic conditions. The simpler of the two media contains salts, glucose, biotin, thiamine, hematin, and casein hydrolysate. Haploid cells consume about half as much oxygen per milligram protein per hour as the diploid microplasmodia growing in the same medium.