Solar forcing of drought frequency in the Maya lowlands

We analyzed lake-sediment cores from the Yucatan Peninsula, Mexico, to reconstruct the climate history of the region over the past 2600 years. Time series analysis of sediment proxies, which are sensitive to the changing ratio of evaporation to precipitation (oxygen isotopes and gypsum precipitation), reveal a recurrent pattern of drought with a dominant periodicity of 208 years. This cycle is similar to the documented 206-year period in records of cosmogenic nuclide production (carbon-14 and beryllium-10) that is thought to reflect variations in solar activity. We conclude that a significant component of century-scale variability in Yucatan droughts is explained by solar forcing. Furthermore, some of the maxima in the 208-year drought cycle correspond with discontinuities in Maya cultural evolution, suggesting that the Maya were affected by these bicentennial oscillations in precipitation.

Recall bias in self-reported melanoma risk factors

The evidence implicating sun exposure in the etiology of melanoma derives largely from case-control studies in which the retrospective assessment of sun exposure suggests potential for significant recall bias. Previous attempts at characterizing and quantifying that bias have had significant methodological limitations. In the International Twin Study, a case-control study of melanoma risk factors in twins conducted from 1980 to 1991, the authors asked melanoma cases and their co-twins to quantify their own exposures and asked which twin had the greater exposure. Recall bias was investigated by assuming that, if bias had occurred, the odds ratio based on the case's response would differ significantly from the odds ratio based on the co-twin's response. Case-derived odds ratios were higher than the odds ratios for the controls for sunbathing in childhood and adulthood and for mole frequency and freckling in childhood, suggesting some recall bias. The odds ratios for ease of burning and tanning appeared unbiased. The belief that sunlight was a cause of melanoma appeared related to an increased odds ratio for sunbathing as a child. There is a continuing need to carefully assess recall bias in the study of melanoma risk factors.

Assessment of knowledge of melanoma risk factors, prevention, and detection principles in Texas teenagers

INTRODUCTION

The incidence of melanoma has increased in the past 10 years more rapidly than any other cancer. Exposure to intense solar radiation in youth significantly increases the lifetime risk of developing melanoma. We postulate that teenagers have little awareness of melanoma prevention or detection principles. The purpose of this study was to assess the knowledge of teenagers about melanoma and to identify which age groups are most receptive to altering their sun exposure behaviors.

METHODS

Two hundred and ten examinations testing general knowledge of sun exposure and melanoma were completed and returned by junior high and high school students ages 12 to 18 in Dallas and Houston, Texas. All students completing and returning the examination were provided with the correct answers to the test and a detailed explanation of each of the test items as part of an educational exercise. A second questionnaire was then administered to determine the effect of the educational exercise on future sun exposure practices. Students were divided into two age groups (12 to 15 and >or=16 years old) for comparison of scores on the knowledge examination and responses to behavioral items. Comparison of response rates between age groups was performed using chi(2) analysis.

RESULTS

The return rate was 100%, with 109 students age 12-15 years, and 101 students >or=16 years. Seventy-six percent of all respondents sunbathed outdoors, and 18% had used a tanning bed in the past 6 months. Thirty-three percent of students admitted to at least three blistering sunburns in the past. The average score on the knowledge assessment examination was 65% correct for students >or=16 years old and 54% correct for those 12-15 years old. Students 12 to 15 years old were significantly more likely to indicate they planned to change future behaviors regarding performance of skin self-examinations and limiting sun exposure as compared to the older students.

CONCLUSION

A significant number of teenagers have already enhanced their risk for future melanoma by suffering severe sunburns. Students younger than 16 years of age were significantly more likely to indicate they planned to change future behaviors after receiving information about melanoma. The data from this pilot study support education aimed at younger age groups to most effectively achieve risk reduction and prevent future melanomas.

One-year followup on the impact of a sun awareness curriculum on medical students' knowledge, attitudes, and behavior

BACKGROUND

A one-week sun awareness curriculum was developed at the University of Western Ontario to educate first-year medical students on skin cancer risks and prevention.

OBJECTIVE

To assess the retention of knowledge, attitudes, and behavioral practices one year after receiving education in sun awareness.

METHOD

Three surveys were administered: before, immediately after the sun awareness teaching, and one year later. Actual practiced behavior in the past year was compared with the intended behavior.

RESULTS

Half as many sunburns were reported in the year following the sun awareness curriculum compared with the previous year. Medical students demonstrated a good retention of the knowledge learned a year earlier. However, many students still believed that a tanned appearance looks healthy. While there was intent to adopt more healthy behavior after the curriculum, the actual behavior practiced varied.

CONCLUSIONS

An undergraduate medical curriculum on sun awareness can be effective in improving the knowledge, attitudes, and behaviors of future physicians.

Relationship between season and diagnoses of melanocytic tumours

The frequency of various diagnoses of pigmented lesions, their distribution on various body sites and the seasonal variations in their diagnoses were studied according to the specimen of pigmented lesions sent to a laboratory for histopathological examination. From the total number of 18,402 investigated lesions, 7,682 were excised from males and 10,720 from females. Melanoma was diagnosed in 2.5% of all excised tumours more often during the summer months. Lighter clothing and greater awareness during summer may explain this finding. Additional factors such as a sun-induced melanocytic activation in naevi cannot be ruled out. Dysplastic naevi, which represented 26% of all naevi in this study, were excised less often during summer. Presuming that the majority of the north German population acquires the highest ultraviolet (UV) doses of the year during summer, it seems unlikely that the histological features of dysplasia in naevi are related to short-term UV activation. The localization of dysplastic naevi did not correspond to the body-site distribution of melanoma according to sex. This finding does not indicate the dysplastic naevus as a possible precursor lesion of malignant melanoma.

Surgical management of actinic cheilitis

OBJECTIVE

An analysis is made of the etiologic factors underlying actinic cheilitis and of the results obtained following surgical treatment of the disease in a series of 54 patients (32 males and 22 females).

STUDY DESIGN

The case history was evaluated, along with the triggering factors, histopathological pattern and recurrence of lesions. A cold scalpel vermilionectomy was performed in 41 patients, followed by primary closure of the defect using an oral mucosal flap. The remaining 13 patients were subjected to carbon dioxide laser vermilion ablation.

RESULTS

The history of the patients revealed liver disease associated to alcohol consumption in 35.2% of cases and tobacco smoking in 77.8%. As regards solar exposure, 53.1% of the men referred open-air professional activities, while 100% of the women presented important solar exposure. The most frequent clinical manifestations were bleeding and the presence of leukoplakia patches; pain was reported in only 16% of cases. Over 40% of the patients were asymptomatic. Following treatment, and after a follow-up period of at least 6 months, 90.7% of the subjects showed complete healing. Of the 5 patients reoperated upon, four healed and one evolved towards squamous cell carcinoma.

CONCLUSION

Vermilionectomy is the recommended treatment for actinic cheilitis, using either a cold scalpel or carbon dioxide laser. A histological study of the lesion is indicated in all cases to secure early detection of possible malignization. The control of the possible etiologic factors is also essential.

Stability of attenuated live virus rabies vaccine in baits targeted to wild foxes under operational conditions

The viability of an attenuated live virus rabies vaccine in a bait targeted to red foxes was examined under various operational conditions in a series of experiments in Ontario. The virus was relatively stable over a 28-day period in the field, losing a mean 0.5, s = 0.2 log10 of virus titer. The micro-environment into which the bait was placed (open cultivated field, grassy meadow, wooded grove, sun or shade) did not make an appreciable difference in the viability of the virus. There was no significant difference (P < or = 0.05) between mean ambient temperatures and the temperature of fluids in blister packs of baits placed in sun or shade. Sixty-three percent of foxes fed baits exposed to sun and shade conditions for 21 days (titer 10(6.2) tissue culture infective doses per 1 mL) developed rabies virus-neutralizing antibodies. Storage of vaccine baits at -30 degrees C prior to bait distribution was important in maintaining virus viability.

Intermediate-effect biomarkers in prevention of skin cancer

Skin cancers, both non-melanoma and melanoma, usually progress through sequential steps towards malignant transformation, leading to mutant clones and precancerous lesions. Prevention of skin cancers relies on reduction of exposure to solar radiation and may be evaluated by measuring induction of intermediate-effect biomarkers such as sunburn cells or p53 mutations in the epidermis, actinic (solar) keratoses, UV-induced immunosuppression or naevi. Sunburn cells (apoptotic keratinocytes) and p53 mutations are indicators of UV-induced DNA lesions as early steps of malignant transformation of epidermal keratinocytes. Actinic keratoses are premalignant sun-induced skin lesions, characterized as keratinized patches with aberrant cell differentiation and proliferation; they represent risk factors for basal-cell carcinoma and melanoma and are precursors of squamous-cell carcinoma. Studies in humans have investigated UV-induced immunosuppression and its modulation by topical sunscreen application, focusing on contact hypersensitivity as measured by immunization or response to haptens, or on modulation of stimulation of allogeneic lymphocytes by epidermal cells, or local release of immunomodulatory molecules such as cis-urocanic acid or interleukin-10. Naevi are focal collections of melanocytes, usually found at the junction of the epidermis and dermis or at various depths in the dermis. Common acquired naevi arise after birth both spontaneously and in response to sun exposure. Most acquired naevi are clonal, while most melanocytes in non-naeval areas are not. Although it is not yet certain whether naevi represent premalignant lesions or risk factors, many melanomas arise in acquired naevi, and the number of naevi constitutes the best predictor of individual risk of melanoma. The presence of large (i.e., >5 mm) or atypical naevi (i.e., large naevi with non-uniform colour and irregular borders) is associated with elevated melanoma risk, independently of the number of smaller naevi. Children seem particularly vulnerable to sun-induced biological events involved in the genesis of melanoma, and the greatest increase in naevus numbers per unit of skin surface occurs before adolescence. Therefore, the distribution of naevi and their development in children are relevant to understanding melanoma occurrence in adults.

Does experience predict knowledge and behavior with respect to cutaneous melanoma, moles, and sun exposure? Possible outcome measures

A prospective survey of 3105 adults in 16 randomly selected group practices was conducted to test whether individuals with a personal experience, family history, or other contact with malignant melanoma display more knowledge and appropriate behavior with regard to melanomas and sun exposure than those with no such experience. Although patients with previous contact with the condition were more likely to check for moles, were more aware of the significance of changes in the shape of moles, and were more aware of the necessity for prompt treatment, they were not more knowledgeable about other important signs or more likely to protect themselves from sun exposure. Direct experience or contact with melanoma appeared to have some positive effects on knowledge, but there is no room for complacency for those at increased risk or those treating them. Both primary and secondary prevention for people who are vulnerable could be undertaken in primary care.

[Melanoma in xeroderma pigmentosum: 12 cases]

BACKGROUND

Xeroderma pigmentosum is a rare genodermatosis, with a defect affecting recovery of ultraviolet-induced damages and characterized by a high rate of malignancies of the exposed skin areas. We studied melanoma features of patients with xeroderma pigmentosum.

PATIENTS AND METHODS

A retrospective study of xeroderma pigmentosum patients admitted to the Charles Nicolle Hospital of Tunis between 1973 and 1998.

RESULTS

Two hundred sixteen patients with xeroderma pigmentosum were registered. Melanoma was present in 12 patients, 7 females and 5 males. Two patients were sisters. Cutaneous melanoma was found in 8 patients. Four patients presented with metastatic melanoma. The median age for development of the first melanoma was 17.5 years. All of the cutaneous melanomas were found on the face. Lentigo malignant melanoma was reported in 3 cases. The tumors were treated with surgical excision. Except for a melanoma affecting the orbit, characterized by a fatal outcome, no metastases were detected at the different investigations.

DISCUSSION

Melanoma occurs frequently in patients with xeroderma pigmentosum, it has been reported in 5.5 p. 100 of cases and 11.3 p. 100 of patients with cutaneous carcinoma. The age of onset was low: 17.5 years. It appeared later than the carcinoma. The location of cutaneous melanoma in face in xeroderma pigmentosum patients indicates that they were caused mainly by sunlight exposure. Lentigo malignant melanoma was the most frequent type. Prognosis is difficult to define owing to the large number of other cutaneous malignancies. Apart from one case of rapidly fatal orbital melanoma, we recorded long survivals even in cases of melanoma revealed by metastases.

Late-onset hydroa vacciniforme: two case reports

Hydroa vacciniforme (HV) is a rare blistering photodermatosis that heals with vacciniform scarring, with onset usually in childhood and spontaneous resolution by early adulthood. We report two cases of HV seen at the National Skin Centre, Singapore, both with a late onset at 20 years of age, during compulsory military service, and one with a less typical non-vesicular presentation, that initially caused some diagnostic difficulties.

UVA exposure affects UVB and cis-urocanic acid-induced systemic suppression of immune responses in Listeria monocytogenes-infected Balb/c mice

Ultraviolet radiation can inhibit immune responses locally as well as systemically. Such effects have been measured in animals and humans exposed to ultraviolet B (wavelength 280-315 nm) (UVB) and ultraviolet A (315-400 nm) (UVA). The precise wavelength dependence is important for the identification of possible molecular targets and for assessments of risk of different artificial UV sources and solar UV. In such analyses, it is commonly assumed that radiation energy from each wavelength contributes to the effect independent of the other wavelengths. Here we show that this assumption does not hold good. In the present study, it was investigated whether exposure to broadband UVA or longwave ultraviolet A 1 (340-400 nm) (UVA 1) prior to the standard immunosuppressive UVB protocol might modulate the immunosuppressive effects induced by UVB. Preexposure to broadband UVA or longwave UVA 1, 1 day prior to the standard immunosuppressive UVB protocol, inhibited the UVB-induced suppression of delayed type hypersensitivity (DTH) to Listeria monocytogenes significantly. This effect was not associated with restoring the number of interleukin (IL-12)-positive cells in the spleen. Since isomerization of trans-urocanic acid (UCA) into the immunosuppressive cis-UCA isomer plays a crucial role in UVB-induced immunomodulation, in a second set of experiments it was investigated whether immunosuppression induced by cis-UCA might also be downregulated by preexposure to UVA. Animals were exposed to broad-band UVA or longwave UVA 1 prior to application of an immunosuppressive dose of cis- or trans-UCA as a control. Both UVA and UVA 1 appear to inhibit the cis-UCA-induced systemic immunosuppression (DTH and IL-12) to L. monocytogenes. These studies clearly show that UVA radiation modulates both UVB and cis-UCA-induced immunomodulation. In general, our studies indicate that both broadband UVA and longwave UVA 1 could induce modulation of UVB and cis-UCA-induced immunomodulation. As sunlight contains both UVA and UVB radiation the balance between these two radiations apparently determines the net immunomodulatory effect.

[Sports under the sun]

The outdoor sports during summer and winter are often performed under uncontrolled exposure to ultraviolet irradiation from sunlight. Dangers are not small for the skin, the eyes and the immune system. Adequate sun protection is recommended. Caution is important in young children. The daily UV index represents a standardized assessment having a regional predictive value for the intensity of the ultraviolet irradiation reaching the biosphere.

Eclipse retinopathy

PURPOSE

Solar retinopathy is a well-recognised clinical entity of macular damage caused by viewing the sun, induced by a photochemical process. The term 'eclipse retinopathy' is frequently employed when the condition is sustained as a result of viewing a solar eclipse. Considerable public excitement had been raised in anticipation of the full solar eclipse on 11 August 1999. Whilst experience has shown that visual morbidity is likely to be temporary, current evidence is anecdotal and restricted to isolated case reports and series. This study was conducted to establish the true visual morbidity associated with a solar eclipse, and whether it was temporary or permanent.

METHODS

A 3 month active case ascertainment study was carried out from July to September 1999 to record cases presenting to ophthalmologists with visual symptoms arising from solar viewing. Further information about the cases was sought using a short questionnaire. A follow-up questionnaire requesting outcome data at 6 months was also employed.

RESULTS

There were 70 reported cases of visual loss. The average age was 29.5 +/- 12.9 years. Half the cases presented to an ophthalmologist within 2 days of the eclipse. An abnormal macular appearance was reported in 84% of patients at presentation. There have been no reported cases of continued visual loss or symptoms at 6 months.

CONCLUSIONS

This is the largest nationwide study of the visual effects of a solar eclipse ever undertaken. There were no recorded cases of permanent visual loss, which corroborates the previous evidence that visual morbidity is likely to be temporary. It would appear probable that public health education was most effective in reducing visual morbidity and hence keeping the consequent burden on the NHS to a minimum.

Ultraviolet protection by summer textiles. Ultraviolet transmission measurements verified by determination of the minimal erythema dose with solar-simulated radiation

BACKGROUND

Apart from sunscreen lotions, clothing provides protection from acute and chronic sun damage. Therefore, it is very important to know the ultraviolet (UV) protection factor (UPF) of textiles, in particular of lightweight summer clothing. Usually, the UPF of a textile is determined by spectrophotometric assessment of the UV transmission (in vitro method).

OBJECTIVES

To compare the relationship between in vitro tests and in vivo tests of UPF using solar simulators for determination of the minimal erythema dose (MED), applied to 30 different summer textiles.

METHODS

Thirty summer textiles were spectrophotometrically assessed, and UPFs were calculated with respect to the International Commission on Illumination (CIE) erythemal action spectrum.1 Based on the in vitro UPFs 'on skin' and 'off skin', in vivo testing was performed using a solar simulator for the determination of the MEDunprotected and MEDprotected.

RESULTS

The UPFs obtained from in vivo 'on skin' testing were significantly (r = 0.95; P < 0.001) lower than the predicted in vitro UPFs. This disparity was also confirmed by chromometric assessment of the MED testing; the erythemal responses measured after textile protection were significantly (P < 0.001) higher than those obtained without protection. However, the in vivo 'off skin' UPFs did not significantly (r = 0.98; P > 0.05) differ from the in vitro UPFs; comparison of the chromometrically assessed erythemal responses was also insignificant (P > 0.05).

CONCLUSIONS

The different correlation between in vitro and in vivo measurements of the UPF may be due to the optical-geometrical properties of textiles and the different amount of direct and diffuse radiation passing through the spaces between the yarns. As spectrophotometric measurements of a textile may generally yield lower UPFs than those obtained under average field conditions, the in vitro test method provides 'safe' UPF values representing a 'worst-case scenario'. In contrast to in vitro testing, in vivo methods are much more expensive and time-consuming. Thus, with respect to practicality, spectrophotometric measurements seem to be most suitable for the evaluation of UV protection of textiles.