Lack of Melanopsin Is Associated with Extreme Weight Loss in Mice upon Dietary Challenge

Metabolic disorders have been established as major risk factors for ocular complications and poor vision. However, little is known about the inverse possibility that ocular disease may cause metabolic dysfunction. To test this hypothesis, we assessed the metabolic consequences of a robust dietary challenge in several mouse models suffering from retinal mutations. To this end, mice null for melanopsin (Opn4^-/-), the photopigment of intrinsically photosensitive retinal ganglion cells (ipRGCs), were subjected to five weeks of a ketogenic diet. These mice lost significantly more weight than wild-type controls or mice lacking rod and cone photoreceptors (Pde6b^rd1/rd1). Although ipRGCs are critical for proper circadian entrainment, and circadian misalignment has been implicated in metabolic pathology, we observed no differences in entrainment between Opn4^-/- and control mice. Additionally, we observed no differences in any tested metabolic parameter between these mouse strains. Further studies are required to establish the mechanism giving rise to this dramatic phenotype observed in melanopsin-null mice. We conclude that the causality between ocular disease and metabolic disorders merits further investigation due to the popularity of diets that rely on the induction of a ketogenic state. Our study is a first step toward understanding retinal pathology as a potential cause of metabolic dysfunction.     

Amino acid sulfur as a source of sulfate for sulfated proteoglycans produced by Swiss mouse 3T3 cells

The uptake of sulfate by Swiss mouse 3T3 cells is blocked in the presence of 1 mM 4-isothiocyano-4'-acetamido-stilbene-2,2-disulfonic acid (SITS). In the absence of an exogenous source of sulfate, glycosaminoglycans produced by cells in the presence of the inhibitor are sulfated to the same extent as those produced by cells grown in its absence. The sulfate utilized in the absence of medium sulfate has been identified as that produced by the oxidation of the sulfur present in the amino acids cysteine and methionine. This finding indicates that, under conditions of restricted exogenous sulfate, caution is needed in the interpretation of data obtained with the use of [35S]methionine and/or [35S]cysteine as a general protein label, since both tyrosine and a variety of types of protein-linked carbohydrate chains may be modified by sulfation.     

Distribution of a novel cardioactive neuropeptide (CCAP) in the nervous system of the shore crab Carcinus maenas

A radioimmunoassay (RIA) for the recently discovered crustacean cardioactive peptide (CCAP) has been developed and used to determine contents of CCAP in different parts of the nervous system of the shore crab Carcinus maenas. Immunoreactive material was detected throughout the nervous system. In contrast to the main ganglia which contained low levels of approximately 1.4 pmol CCAP/mg protein (brain and thoracic ganglion), a high concentration was found in a neurohemal structure, the pericardial organs (PO) (868 pmol/mg protein). A predominantly neurohormonal role of CCAP thus suggested is further supported by in vitro release studies. Incubation of POs in high (K+) saline showed that CCAP is secretable in considerable amounts by a Ca++-dependent release mechanism.     

High frequency plant regeneration from thin cell layer explants of Brassica napus

Explants composed of the epidermis and 4–9 layers of subepidermal cells were excised from internodes of Brassica napus L. ssp. oleifera cv. Westar and cultured on modified Murashige and Skoog (MS) medium. The three or four terminal internodes excised from plants at an early stage (before any flower buds had opened) were shown to be the best explant source. Both cytokinin and auxin were required for induction of shoot organogenesis. Of six auxins tested, only naphthaleneacetic acid (NAA) was effective in shoot bud initiation. All four cytokinins tested (when associated with 0.5 mgl^-1 NAA) promoted organogenesis, but at differing frequencies. The highest shoot induction frequency was obtained at 10–15 mgl^-1 benzyladenine (BA). The organogenic response was strongly affected by the nitrogen content of the medium. The best response was observed when NO₃ ^- was the sole nitrogen source (supplied as KNO₃) in the range 30–90 mM. Sucrose and glucose were equally supportive in shoot regeneration with the optimal levels at 0.12 M and 0.15 M, respectively. Shoots were rooted on medium free of growth regulators and mature plants were grown in the greenhouse. Plants were also recovered from leafy structures which differed morphologically and histologically from shoot buds.     

Purification of arogenate dehydrogenase from Phenylobacterium immobile

Phenylobacterium immobile, a bacterium which is able to degrade the herbicide chloridazon, utilizes for L-tyrosine synthesis arogenate as an obligatory intermediate which is converted in the final biosynthetic step by a dehydrogenase to tyrosine. This enzyme, the arogenate dehydrogenase, has been purified for the first time in a 5-step procedure to homogeneity as confirmed by electrophoresis. The Mr of the enzyme that consists of two identical subunits amounts to 69000 as established by gel electrophoresis after cross-linking the enzyme with dimethylsuberimidate. The Km values were 0.09 mM for arogenate and 0.02 mM for NAD+. The enzyme has a high specificity with respect to its substrate arogenate.     

Cortinarius sarcoflammeus sp. nov, a new species of subgenus Dermocybe (Agaricales) growing in Sphagnum bogs

 Cortinarius sarcoflammeus is proposed as a new species belonging to subgenus Dermocybe, on the basis of its morphological, chemical and ecological characters. The strong red-orange colour of the context and stipe base, large spores, sphagnicolous habitat and high dermorubin content are characteristic for the new species. Holotypes of C. huronensis and C. huronensis var. olivaceus have been examined for comparison, and their differences discussed. Photographs and line drawings of C. sarcoflammeus are added. Received February 13, 2001 Accepted March 23, 2001