Muscle fluorometry: A determination of the depth of penetration

Summary Fluorometric recordings of NADH (nicotinamide adenine dinucleotide) were made on rabbit papillary muscles. The specimens were placed between the UV light source and a small window of the detection stage. As the muscle was moved over the window in a transverse direction, simultaneous measurement could be taken of transmitted UV light and fluorescent light for various thicknesses of tissue. It is concluded that a muscle thinckness of 0.65 mm, is optimal before absorption of the incident light decreases the fluorescence signal.     

A further proof of polarization vision ofNotonecta glauca and a note on threshold intensity for eliciting the plunge reaction

Summary Polarized UV light from a platform on the ground can attract backswimmers and elicit plunge reactions. Threshold intensity is independent of the overall UV-intensity in the surrounding space. Unpolarized UV light attracts the animals only when the intensity is higher than that of the surroundings. These results show that polarized UV light can be discriminated from unpolarized UV light independently of intensity.     

Alternariol, a dibenzopyrone mycotoxin of Alternaria spp., is a new photosensitizing and DNA cross-linking agent

The mycotoxin alternariol (3,4',5-trihydroxy-6'-methyldibenzo [a] pyrone) but not alternariol monomethyl ether (3,4'-dihydroxy-5-methoxy-6'-methyldibenzo [a] pyrone) is phototoxic to Escherichia coli in the presence of near UV light (320-400 nm). The phototoxicity bioassays with a DNA repair-deficient mutant of E. coli suggested that DNA may be the molecular target for photo-induced toxicity of alternariol. Interactions between alternariol and double-stranded, supercoiled DNA suggest that alternariol interacts with DNA by intercalation. No DNA breakage was detected in this system; however, alternariol forms a complex and cross-links double-stranded DNA in near UV light. These results suggest that alternariol is a new phototoxic, DNA-intercalating agent and is a DNA cross-linking mycotoxin in near UV light.     

Dose-effects of 8-methoxypsoralen and long wave UV-light in 3T3 cells: evaluation of phototoxic index.

3T3 cells were cultured until confluency and treated with various doses of 8-methoxypsoralen followed by long wave UV light irradiation. The inhibition of 3H-thymidine incorporation was dose-dependent for both, psoralen and light. A phototoxic index (PTI) was established demonstrating that a constant correlation between psoralen and UVA light exists for the photoinactivation in living cells.     

Vision in the ultraviolet

Sensitivity to ultraviolet light (UV) is achieved by photoreceptors in the eye that contain a class of visual pigments maximally sensitive to light at wavelengths <400 nm. It is widespread in the animal kingdom where it is used for mate choice, communication and foraging for food. UV sensitivity is not, however, a constant feature of the visual system, and in many vertebrate species, the UV-sensitive (UVS) pigment is replaced by a violet-sensitive (VS) pigment with maximal sensitivity between 410 and 435 nm. The role of protonation of the Schiff base-chromophore linkage and the mechanism for tuning of pigments into the UV is discussed in detail. Amino acid sequence analysis of vertebrate VS/UVS pigments indicates that the ancestral pigment was UVS, with loss of UV sensitivity occurring separately in mammals, amphibia and birds, and subsequently regained by a single amino acid substitution in certain bird species. In contrast, no loss of UV sensitivity has occurred in the UVS pigments of insects.     

A lens-like specialization for photic input in the pineal window of an Indian catfish,Heteropneustes fossilis

Summary An unusual lens-like structure is reported in the pineal window of the Indian nocturnal catfishHeteropneustes fossilis. This is the first report of its kind for the pineal window of fishes. This structure, coupled with a pineal fossa and a pineal window, forms a specialization that apparently serves to concentrate the photic input to the intracranially situated pineal organ. This structure may play a significant role in the photoneuroendocrine function of the photosensitive pineal under conditions of low light intensity, controlling the fish's circadian rhythmic activities.The work was financially supported by CSIR, New Delhi (sanction No. 38(693)/88/EMR-II dated May, 1988) which is thankfully acknowledged.     

Dose-effects of 8-methoxypsoralen and long wave UV-light in 3T3 cells: evaluation of a phototoxic index

Summary 3T3 cells were cultured until confluency and treated with various doses of 8-methoxypsoralen followed by long wave UV light irradiation. The inhibition of³H-thymidine incorporation was dose-dependent for both, psoralen and light. A phototoxic index (PTI) was established demonstrating that a constant correlation between psoralen and UVA light exists for the photoinactivation in living cells.Supported by Deutsche Forschungsgemeinschaft.We thank Miss Anne Schröder for her skillful assistance.     

Conversion of psoralen DNA monoadducts in E. coli to interstrand DNA cross links by near UV light (320-360 nm): inability of angelicin to form cross links, in vivo.

Both angelicin and psoralen monoadducts formed in vivo in E. coli by near UV light produce lethal and mutagenic effects. However psoralen monoadducts are converted to cross links by higher doses of UV; angelicin monoadducts are not. The relevance of these results to psoralen photosensitization is discussed.     

Structure and function of a calmodulin-dependent smooth muscle myosin light chain kinase

In smooth muscle the Mr 20,000 light chain of myosin is phosphorylated by a calmodulin-dependent protein kinase. It consists of 2 subunits: calmodulin, an acidic protein of Mr 17,000 that binds 4 moles of Ca2+; and a larger protein of Mr circa 130,000. Activation of the kinase is dependent upon their association in the presence of Ca2+. Cyclic AMP-dependent protein kinase phosphorylation of the myosin light chain kinase occurs at 2 sites. It decreases the affinity of the kinase for calmodulin and a reduction in the rate of light chain phosphorylation occurs. The kinase has an overall asymmetric shape composed of a globular head and tail region for the skeletal muscle enzyme. Trypsin digestion of this kinase releases a fragment of Mr 36,000 from the globular region that contains the catalytic and calmodulin binding sites. Chymotrypsin digestion of the kinase from smooth muscle generates a fragment of Mr 80,000 that does not contain the calmodulin binding or cyclic AMP-dependent protein kinase phosphorylation sites. It is a Ca2+-independent form of the kinase that phosphorylates the light chain of myosin. These structural features indicate a regulatory role for the kinase in smooth muscle phosphorylation and contraction.     

Intramuscular comparison of myosin isozymes and light chains in rat extensor digitorum longus muscle

Complete muscle cross sections were obtained from the proximal and distal third regions of ten rat extensor digitorum longus muscles. Electrophoretic methods were then used to quantify the various myosin isozymes and light chains in each muscle specimen. The results demonstrated that the relative distribution of the various myosin isozyme and light chain variables do not vary significantly between the two sampling regions.     

Intramuscular comparison of myosin isozymes and light chains in rat extensor digitorum longus muscle

Summary Complete muscle cross sections were obtained from the proximal and distal third regions of ten rat extensor digitorum longus muscles. Electrophoretic methods were then used to quantify the various myosin isozymes and light chains in each muscle specimen. The results demonstrated that the relative distribution of the various myosin isozyme and light chain variables do not vary significantly between the two sampling regions.     

Conversion of psoralen DNA monoadducts in E. coli to interstrand DNA cross links by near UV light (320–360 nm): Inability of angelicin to form cross links,in vivo

Summary Both angelicin and psoralen monoadducts formed in vivo in E. coli by near UV light produce lethal and mutagenic effects. However psoralen monoadducts are converted to cross links by higher doses of UV; angelicin monoadducts are not. The relevance of these results to psoralen photosensitization is discussed.Supported by the National Research Council of Canada.     

Photoreactivation of UV damage in cultured Drosophila cells

Cell survival and photoreactivation of 254 nm ultraviolet (UV) light damage in a wild type Drosophila cell line was assayed by colony formation in liquid medium. Fo, Fq, and extrapolation number for the exponential portion of survival curves are 21 J/m2, 3.6 J/m2, and 1.5 for non-photoreactivated cells and 110 J/m2, 11.2 J/m2, and 1.3 for those exposed to photoreactivating light. Maximal photoreactivation occurs at the 100 J/m2 region of the curve. At 10 and 50% survival, 75-80% of the UV damage was photoreactivable.     

Photolyse ultraviolette et photoréactivation des bactéries — Aspects de dépolymérisation et repolymérisation des acides nucléiques bactériens

Summary Electrophoretic analysis of bacterial substance proves the departure, from UV irradiated microbes screened from light for a certain time, of substances which were responsible for increasing the charge density by surface unit during the first moments which follow the irradiation by UV rays. Spectrophotometric analysis of liquids having contained these bacilli proves concommitantly the diffusion of those substances from the bacterial substance to the aqueous phase and reveals their nature. The photoreactivity which is possible during the first moments following the UV irradiation of bacilli, due to the presence of the fragments of depolymerisation of nucleic acid macromolecule in the bacterial substance, becomes impossible after the departure (diffusion) of those fragments to the aqueous phase. These observations seem to show that the phenomenon of photo-reactivity is connected with the repolymerisation of the macromolecule primitively divided of desoxyribonucleic acid.     

Structure and function of a calmodulin-dependent smooth muscle myosin light chain kinase

Summary In smooth muscle the M_r 20,000 light chain of myosin is phosphorylated by a calmodulin-dependent protein kinase. It consists of 2 subunits: calmodulin, an acidic protein of M_r 17,000 that binds 4 moles of Ca²⁺; and a larger protein of M_r circa 130,000. Activation of the kinase is dependent upon their association in the presence of Ca²⁺. Cyclic AMP-dependent protein kinase phosphorylation of the myosin light chain kinase occurs at 2 sites. It decreases the affinity of the kinase for calmodulin and a reduction in the rate of light chain phosphorylation occurs. The kinase has an overall asymmetric shape composed of a globular head and tail region for the skeletal muscle enzyme. Trypsin digestion of this kinase releases a fragment of M_r 36,000 from the globular region that contains the catalytic and calmodulin binding sites. Chymotrypsin digestion of the kinase from smooth muscle generates a fragment of M_r 80,000 that does not contain the calmodulin binding or cyclic AMP-dependent protein kinase phosphorylation sites. It is a Ca²⁺-independent form of the kinase that phosphorylates the light chain of myosin. These structural features indicate a regulatory role for the kinase in smooth muscle phosphorylation and contraction.     

The ovicidal activity of cis-dehydromatricaria ester: time-dependance of its enhancement by UV light

Freshly laid eggs of Drosophila melanogaster were treated with the polyacetylenic compound cis-dehydromatricaria ester. The toxicity of the chemical was enhanced by treatments with long-wavelength ultraviolet light, and the maximum effect was observed when the UV irradiation was performed 4-5 h after the initial contact of the eggs with the chemical.     

Spektrale Phototaxis von Planktonrotatorien

Summary The spectral sensitivity of 3 species of planktonic Rotatoria (Asplanchna priodonta, Polyarthra remata, Filinia longiseta) were measured by means of the positive phototactic reaction.Asplanchna andPolyarthra both have a broad maximum sensitivity range around 540 nm and a near maximum at 440 nm. In the UV direction (to 360 nm) the spectral sensitivity increases. In contrast,Filinia has only a maximum of 460 nm in the visible spectrum, but behaves similarly to the other species in the UV region. The ecological significance of these results is discussed, as well as their bearing on a possible dermal light sense.     

Photoreactivation of UV damage in culturedDrosophila cells

Summary Cell survival and photoreactivation of 254 nm ultraviolet (UV) light damage in a wild typeDrosophila cell line was assayed by colony formation in liquid medium. F_o, F_q, and extrapolation number for the exponential portion of survival curves are 21 J/m², 3.6 J/m², and 1.5 for non-photoreactivated cells and 110 J/m², 11.2 J/m², and 1.3 for those exposed to photoreactivating light. Maximal photoreactivation occurs at the 100 J/m² region of the curve. At 10 and 50% survival, 75–80% of the UV damage was photoreactivable.     

Alternariol,a dibenzopyrone mycotoxin ofAlternaria spp., is a new photosensitizing and DNA cross-linking agent

Summary The mycotoxin alternariol (3,4,5-trihydroxy-6-methyldibenzo [a] pyrone) but not alternariol monomethyl ether (3,4-dihydroxy-5-methoxy-6-methyldibenzo [a] pyrone) is phototoxic toEscherichia coli in the presence of near UV light (320–400 nm). The phototoxicity bioassays with a DNA repair-deficient mutant ofE. coli suggested that DNA may be the molecular target for photo-induced toxicity of alternariol. Interactions between alternariol and double-stranded, supercoiled DNA suggest that alternariol interacts with DNA by intercalation. No DNA breakage was detected in this system; however, alternariol forms a complex and cross-links double-stranded DNA in near UV light. These results suggest that alternariol is a new phototoxic, DNA-intercalating agent and is a DNA cross-linking mycotoxin in near UV light.Acknowledgment. Dr Albert Stoessl (Agriculture Canada, London, Ontario, Canada) generously provided a mixture of alternariol and alternariol monomethyl ether, and made many helpful suggestions. Dr Ashwood-Smith (University of Victoria, Victoria, British Columbia, Canada) kindly supplied the microorganisms through Dr G.H.N. Towers (University of British Columbia, Vancouver). We gratefully acknowledge the gifts. It is a pleasure to acknowledge the able assistance of Mr S. Tallevi.