Spectral tuning and deactivation kinetics of marine mammal melanopsins.

In mammals, the photopigment melanopsin (Opn4) is found in a subset of retinal ganglion cells that serve light detection for circadian photoentrainment and pupil constriction (i.e., mydriasis). For a given species, the efficiency of photoentrainment and length of time that mydriasis occurs is determined by the spectral sensitivity and deactivation kinetics of melanopsin, respectively, and to date, neither of these properties have been described in marine mammals. Previous work has indicated that the absorbance maxima (λmax) of marine mammal rhodopsins (Rh1) have diversified to match the available light spectra at foraging depths. However, similar to the melanopsin λmax of terrestrial mammals (~480 nm), the melanopsins of marine mammals may be conserved, with λmax values tuned to the spectrum of solar irradiance at the water's surface. Here, we investigated the Opn4 pigments of 17 marine mammal species inhabiting diverse photic environments including the Infraorder Cetacea, as well as the Orders Sirenia and Carnivora. Both genomic and cDNA sequences were used to deduce amino acid sequences to identify substitutions most likely involved in spectral tuning and deactivation kinetics of the Opn4 pigments. Our results show that there appears to be no amino acid substitutions in marine mammal Opn4 opsins that would result in any significant change in λmax values relative to their terrestrial counterparts. We also found some marine mammal species to lack several phosphorylation sites in the carboxyl terminal domain of their Opn4 pigments that result in significantly slower deactivation kinetics, and thus longer mydriasis, compared to terrestrial controls. This finding was restricted to cetacean species previously found to lack cone photoreceptor opsins, a condition known as rod monochromacy. These results suggest that the rod monochromat whales rely on extended pupillary constriction to prevent photobleaching of the highly photosensitive all-rod retina when moving between photopic and scotopic conditions.

Neurological Disorders Associated with Glutamic Acid Decarboxylase Antibodies.

Anti-glutamic acid decarboxylase (GAD) antibodies have been discovered in a variety of neurological syndromes with unique presentations. These syndromes include limbic encephalitis (LE), stiff person syndrome (SPS), opsoclonus-myoclonus-ataxia syndrome, cerebellar ataxia, status epilepticus, and palatal myoclonus among others. We present two patients who presented with Guillain-Barré (GBS) and myasthenia gravis (MG) like syndromes, who were found to have anti-GAD antibodies. These case reports highlight the complex presentation of patients with neurological disorders associated with anti-GAD antibodies. The proper identification of anti-GAD antibody's presence has proven to be beneficial in treatment and provide enhanced quality of life.

Case Report: An Incidental Finding of Fahr's Disease in a Patient with Hypochondria.

Idiopathic basal ganglia calcification (IBGC), commonly referred to as Fahr's disease, is a rare neurological disorder characterized by the abnormal, symmetrical, and bilateral calcification of the basal ganglia and other brain regions. Patients typically present in their forties and fifties with various neurologic and/or psychiatric symptoms, including movement disorders, Parkinsonism, psychosis, and depression. The pathophysiology of this disease is not completely understood; however, several gene mutations have been identified in the pathogenesis of Fahr's disease. These mutations display an autosomal dominant inheritance pattern. Furthermore, the regional phenotypic expression of calcifications differs greatly from patient to patient, as do their clinical presentations. Here, we describe a patient who presented with psychiatric manifestations and imaging consistent with Fahr's disease.