Low prevalence of p53, p16(INK4a) and Ha-ras tumour-specific mutations in low-graded actinic keratosis

BACKGROUND

Ultraviolet radiation induces DNA damage and is the major risk factor for the development of non-melanoma skin cancer (NMSC). Different mutation rates of p53, p16(INK4a) and Ha-ras in cutaneous squamous cell carcinoma (SCC) and the earlier stage actinic keratosis (AK) have been reported.

OBJECTIVES

To assess the presence of missense mutations in hotspot exons of p53, p16(INK4a) and Ha-ras in low-graded AK.

PATIENTS/METHODS

Cryo-biopsies of 75 sun-exposed AK lesions and 75 sun-shielded areas of normal skin from 75 AK patients were analysed to identify mutations in p53 (exons 7 and 8), p16(INK4a) (exon 2) and Ha-ras (exon 1) using polymerase chain reaction (PCR) followed by direct sequencing. As a representative subset of the specimens, ten mutation-negative AK were also micro-dissected in order to exclude the possibility that additional mutations were undetected.

RESULTS

Eight missense and one nonsense point mutations were found in the 75 AK lesions examined (12%), of which seven (9%) were tumour-specific (i.e. present in AK lesions only) and two (3%) were p16(INK4a) mutations (i.e. also detected in normal skin). Three of the tumour-specific mutations (42%) were cytosine (C) to thymine (T) transitions at pyrimidine-rich sequences. Tumour-specific mutations were identified in 1% of p16(INK4a) (exon 2), 1% of Ha-ras (exon 1) and at a higher rate of 7% in p53 (exons 7 and 8), including one nonsense mutation.

CONCLUSIONS

The evaluation of a large number of AK specimens in this study have found a low gene mutation rate in low-graded AK lesions. p53 mutations rather than p16(INK4a) and/or Ha-ras mutations may be an early event in the development of AK to cutaneous SCC.

Identification of cold shock gene loci in Sinorhizobium meliloti by using a luxAB reporter transposon

Using a luxAB reporter transposon, seven mutants of Sinorhizobium meliloti were identified as containing insertions in four cold shock loci. LuxAB activity was strongly induced (25- to 160-fold) after a temperature shift from 30 to 15 degrees C. The transposon and flanking host DNA from each mutant was cloned, and the nucleic acid sequence of the insertion site was determined. Unexpectedly, five of the seven luxAB mutants contained transposon insertions in the 16S and 23S rRNA genes of two of the three rrn operons of S. meliloti. Directed insertion of luxAB genes into each of the three rrn operons revealed that all three operons were similarly affected by cold shock. Two other insertions were found to be located downstream of a homolog of the major Escherichia coli cold shock gene, cspA. Although the cold shock loci were highly induced in response to a shift to low temperature, none of the insertions resulted in a statistically significant decrease in growth rate at 15 degrees C.

The effects of chronic middle ear effusion on speech and language development -- a descriptive study

In this study, the speech and language skills of children with histories of chronic middle ear effusion were analyzed. Forty-seven children between the ages of one year eleven months and five years five months were given a battery of speech and language tests in the course of a diagnostic evaluation. All the children had been referred to speech pathology by a physician because of a suspected communication disorder. All subjects had histories of three or more episodes of middle era effusion, with the first episode occurring prior to 18 months of age. All medical records were checked and in-depth case histories were obtained in order to rule out other possible complicating factors that might have contributed to a speech and language delay. The results of this study revealed essentially age-appropriate receptive language skills in this group of children. Expressive language and articulatory skills were significantly below chronological age level expectation, indicating the possible serious effects of chronic middle ear effusion on speech and language development.

Hearing impaired clinic--a one-year survey

The Hearing Impaired Clinic was established at Children's Hospital Medical Center in Cincinnati for the purpose of integrating a multifaceted effort of habilitation of the child with a hearing impairment. This article discusses the rationale for such a clinic and presents the data obtained from the first year that the clinic was functioning. Details of audiological and otological evaluations indicate that there is still a significant delay in the habilitation of these children that could be countered by a greater awareness of the significance of hearing loss in the young child.