Ultraviolet radiation-induced skin tumors in a South American opossum (Monodelphis domestica).

A total of 19 male and 21 female South American opossums (Monodelphis domestica) were exposed to 250 J/m2 ultraviolet radiation from FS-40 sunlamps (280-400 nm) three times weekly for 70 weeks. The backs of the opossums were shaved as necessary to remove hair. In order to prevent photoreactivation of ultraviolet radiation-induced pyrimidine dimers by the light-dependent photolyase enzyme of the opossum, ultraviolet radiation-exposed opossums were housed under red lights (600-800 nm).

The efficacy of breathing retraining and the centrality of hyperventilation in panic disorder: a reinterpretation of experimental findings.

The present paper addresses de Ruiter, Rijken, Garssen, and Kraaimaat's (Behaviour Research and Therapy, 27, 647-655, 1989) interpretation of data pertaining to the efficacy of breathing retraining in the treatment of panic disorder. The proffered reinterpretation of these data makes it clear that breathing retraining led to a significant reduction in the frequency of panic attacks. These findings thus lend additional support to the central role of hyperventilation in primary panic attacks.

Production of interleukin-1 in a South American opossum (Monodelphis domestica).

A homologous thymocyte costimulatory assay using thymocytes from a South American opossum (Monodelphis domestica) detected and measured interleukin-1 (IL-1). Opossum IL-1 was obtained from lipopolysaccharide-stimulated macrophage and skin cultures and its molecular weight was determined to be 15,000 to 17,000. Opossum IL-1 did not stimulate proliferation of murine thymocytes; conversely, neither human nor murine IL-1 stimulated opossum thymocytes.

Spectral comparison of solar simulators and sunlight.

In evaluating sunscreen efficacy, spectral distribution of the irradiation sources can influence the sun protection factor (SPF). The purpose of this investigation was to examine the uniformity of ultraviolet (UV) spectral irradiance of solar simulators used in various SPF testing laboratories, compare them with natural sunlight UV radiation (UVR), and recommend performance limits to ensure that the variability of radiation sources in the UVB region minimally affects SPF estimates. The critical portion of the solar erythemogenic spectrum was identified as the UVB portion, defined as the region between 280 and 320 nm.

Photoreactivation of cyclobutane dimers and (6-4) photoproducts in the epidermis of the marsupial, Monodelphis domestica.

Radioimmunoassays were used to investigate the repair of cyclobutane pyrimidine dimers and pyrimidine (6-4)pyrimidone photoproducts ((6-4] photoproducts) in the epidermis of the South American opossum, Monodelphis domestica. In the absence of photoreactivating light, both types of photodamage were excised with similar kinetics, 50% of the damage remaining 8 h after UV irradiation in vivo. Exposure of UV-irradiated skin to photoreactivating light resulted in removal of most of the cyclobutane dimers and an enhanced rate of (6-4) photoproduct repair.

Hypersensitivity of skin fibroblasts from basal cell nevus syndrome patients to killing by ultraviolet B but not by ultraviolet C radiation.

Basal cell nevus syndrome (BCNS) is an autosomal dominant genetic disorder in which the afflicted individuals are extremely susceptible to sunlight-induced skin cancers, particularly basal cell carcinomas. However, the cellular and molecular basis for BCNS is unknown. To ascertain whether there is any relationship between genetic predisposition to skin cancer and increased sensitivity of somatic cells from BCNS patients to killing by UV radiation, we exposed skin fibroblasts established from unexposed skin biopsies of several BCNS and age- and sex-matched normal individuals to either UV-B (280-320 nm) or UV-C (254 nm) radiation and determined their survival.

Identification of the molecular target for the suppression of contact hypersensitivity by ultraviolet radiation.

This study was conducted to explore the involvement of DNA damage in the suppression of contact hypersensitivity (CHS) by UV irradiation. The opossum, Monodelphis domestica, was used because cells of these marsupials have an enzyme that is activated by visible light (photoreactivating enzyme) and repairs ultraviolet radiation (UVR)-induced pyrimidine dimers in DNA. A single dose of 1,500 J/m2 of UVB (280-320 nm) radiation, representing 2 minimal erythema doses, was administered to the dorsal skin of opossums.

Ultraviolet radiation--induced malignant melanoma in Monodelphis domestica.

Several lines of evidence support the hypothesis that ultraviolet radiation (UVR) is involved in the etiology of cutaneous melanoma in humans. However, progress in understanding the mechanisms involved in induction of melanotic tumors by UVR has been hindered by lack of a suitable animal model. During the course of multiple exposures (3 times/wk for 70 wk) of the South American opossum, Monodelphis domestica, to UVR, we first observed the appearance of areas of dermal melanocytic hyperplasia (MH) on the exposed skin.

Excision repair characteristics of denV-transformed xeroderma pigmentosum cells.

Introduction of the denV gene of phage T4, encoding the pyrimidine dimer-specific endonuclease V, into xeroderma pigmentosum cells XP12RO(M1) was reported to result in partial restoration of colony-forming ability and excision repair synthesis. We have further characterized 3 denV-transformed XP clones in terms of rates of excision of pyrimidine dimers and size of the resulting resynthesized regions following exposure to 100 J/m2 from an FS-40 sunlamp. In the denV-transformed XP cells we observed 50% dimer removal within 3-6 h after UV exposure as compared to no measurable removal in the XP12RO(M1) line and 50% dimer excision after 18 h in the GM637A human, control cells.

Dyspneic-fear and catastrophic cognitions in hyperventilatory panic attacks.

The tenability of cognitive explanations of the experience of fear during panic attacks (viz. Ley's misattribution-of-symptoms hypothesis and Beck's and Clark's catastrophic-misinterpretation-of-symptoms hypotheses) is seriously questioned by findings from three independent lines of research: (a) Wolpe and Rowan's observation that catastrophic cognitions follow fear, (b) Rachman, Levitt and Lopatka's reports of panic attacks without fearful cognitions, and (c) reports of panic attacks during sleep occurring predominately during non-dreaming stages of sleep. Recognition of these findings led Ley to reject his misattribution-of-symptoms hypothesis in favor of an innate emotional-respiratory-response explanation.

Panic attacks during relaxation and relaxation-induced anxiety: a hyperventilation interpretation.

This paper explains how a hyperventilation theory of panic disorder accounts for panic attacks during relaxation and relaxation-induced anxiety. The explanation is based on the observation that chronic hyperventilators maintain a steady state of low pCO2 (arterial carbon dioxide tension) and are, therefore, sensitive to relatively small increases in ventilation when metabolism is low and to relatively sudden reductions in metabolism when ventilation is relatively constant. Thus, if minute volume of air breathed remains constant while the metabolic production of CO2 decreases, as in the case of one who sits down or lies down to relax, respiratory hypocapnea may increase in intensity until it produces the familiar sensations which mark the panic attack.

Photoreversal of the ultraviolet radiation-induced disappearance of ATPase-positive Langerhans cells in the epidermis of Monodelphis domestica.

The present study was undertaken to explore the possible causes of ultraviolet radiation (UVR)-induced disappearance of ATPase-positive, epidermal Langerhans cells (LC). Monodelphis domestica was used because it has the capacity for photoreactivation of UVR-induced pyrimidine dimers in epidermal DNA. Single, 330 J/m2 (ears) or 500 J/m2 (back) UVR exposures (FS-40 sunlamps) reduced the numbers of ATPase-positive epidermal LC in M.

Sunscreen protection against UV-induced pyrimidine dimers in DNA of human skin in situ.

We have determined the ability of a chemical sunscreen with a sun protection factor (SPF) of 15 to protect human skin from ultraviolet (UV) radiation-induced DNA damage. The DNA damage was susceptible to cleavage by Micrococcus luteus UV endonuclease, which recognizes pyrimidine dimers in DNA. An alkaline agarose gel electrophoresis method was used to quantify the number of pyrimidine dimers in nonradioactive DNA from skin biopsies of 5 individuals irradiated with UV from a solar simulator.

Panic attacks during sleep: a hyperventilation-probability model.

Panic attacks during sleep are analysed in terms of a hyperventilation theory of panic disorder. The theory assumes that panic attacks during sleep are a manifestation of severe chronic hyperventilation, a dysfunctional state in which renal compensation has led to a relatively steady state of diminished bicarbonate. Reductions in respiration during deep non-REM sleep lead to respiratory acidosis which triggers hyperventilatory hypocapnea and subsequent panic.

Photorepair of ultraviolet radiation-induced pyrimidine dimers in corneal DNA.

The induction and photorepair of pyrimidine dimers in DNA have been measured in the ultraviolet-irradiated, corneal epithelium of the marsupial, Monodelphis domestica, using damage-specific nucleases from Micrococcus luteus in conjunction with agarose gel electrophoresis. We observed that FS-40 sunlamps (280-400 nm) induced 7.2 +/- 1.

Ultraviolet radiation-induced lethality and repair of pyrimidine dimers in fish embryos.

Pimephales promelas (fathead minnow) embryos were used to show a correlation between induction of pyrimidine dimers in DNA and embryo death. Embryo killing was measured by a lack of heart-beat and blood circulation at 48 h post-ultraviolet radiation (UVR). When the embryos were exposed to various doses of UVR from a FS-40 sunlamp followed by exposure to photoreactivating light (PRL) (320-400 nm), the number of pyrimidine dimers decreased significantly.

Panic disorder and agoraphobia: fear of fear or fear of the symptoms produced by hyperventilation?

Two versions of the fear-of-fear hypothesis of panic disorder are discussed. The fear-of-the-somatic-effects-of-fear version, which is distinguished from the classical conditioning version, is compared with the hyperventilation theory of panic disorder and agoraphobia. The fear-of-the-somatic-effects-of-fear hypothesis is criticized on the basis of its inability to explain adequately (a) the initiation of panic attacks, (b) the growth in intensity of panic attacks, and (c) the termination of panic attacks.

Hair growth induction by ultraviolet radiation in the marsupial Monodelphis domestica.

Hair follicles in the telogen stage of the hair cycle were induced into anagen phase after the skin of the South American opossum, Monodelphis domestica, was exposed to levels of ultraviolet B radiation (280 to 320 nm), which induced desquamation. Post-ultraviolet B exposure to long-wavelength radiation (320 to 400 nm, ultraviolet A) suppressed the induction of edema and desquamation and the induction of hair growth. Hair growth induction was also observed in skin damaged either by mechanical abrasion or by exposure to methoxsalen and ultraviolet A.