Claudia Kusmic

Natural vitamin E enrichment of Artemia salina fed freshwater and marine microalgae

Three species of microalga, the freshwater Euglena gracilis and the marine Dunaliella salina and Tetraselmis suecica, were compared in terms of vitamin E enrichment and survival and growth of the brine shrimp Artemia salina. The tocopherol content was investigated using HPLC for the post-larval and pre-adult stages of Artemia fed the microalgae and the results compared to the initial content of unfed newly hatched nauplii. There was a markedly higher content of tocopherols (about two-fold) in Artemia fed Euglena. Since this microalga contains other antioxidants such as β-carotene, vitamin C and glutathione, bioactive molecules such as PUFA, and the immunostimulant polysaccharide β-glucan, it represents a valuable alternative for enriching the diets of Artemia and increase its nutritional value as a food item.

Euglena gracilis as source of the antioxidant vitamin E. Effects of culture conditions in the wild strain and in the natural mutant WZSL

The photosynthetic wild type and the spontaneous non-photosynthetic WZSL mutant of the unicellular flagellate Euglena gracilis were grown to investigate the influence of photoheterotrophic and heterotrophic conditions on α-tocopherol (vitamin E) content. HPLC analysis demonstrated a marked enhancement (almost 100%) of tocopherol content in the light in both strains, independent of the presence of chloroplasts. These findings indicate that the formation of vitamin E occurs inside both the mitochondrial and chloroplastic compartment, and that the correlation between light and vitamin E production is not linked to the existence of chlorophyll.

A new technique for total hepatectomy in the pig for testing liver support devices

BACKGROUND A large animal model of total hepatectomy is suitable to test the efficacy of any system designed to support patients in hepatic coma. The models previously described in the pig entail a significant degree of surgical trauma, which might alter the evolution of the ensuring hepatic failure and compromise the reproducibility of the model. METHODS Twenty-eight pigs underwent a total hepatectomy according to a new technique. A model was considered satisfactory when it required no blood transfusions and when hematologic and hemodynamic parameters determined before, during, and until 4 hours after hepatectomy showed no significant variations. Moreover, to revive the pattern of hepatic coma produced in the anhepatic model, 7 pigs were monitored until brain death occurred. RESULTS Twenty-five pigs (89%) underwent a smooth total hepatectomy with minimal variations of the selected parameters. They constituted a highly homogeneous group. Survival of the 7 pigs, followed up until brain death occurred, ranged from 625 to 1595 minutes (mean 1013.57 minutes). The animals remained stable until a few hours before brain death, an event heralded by a final sharp increase of the serum ammonia level and by a well-evident decline of both arterial pressure and liver-dependent clotting factors. CONCLUSIONS This technique of total hepatectomy allows the construction of a reproducible model of anhepaty suitable to test the efficacy of any system conceived to temporarily replace hepatic functions.

Photoreceptor morphology and visual pigment content in the pineal organ and in the retina of juvenile and adult trout, Salmo irideus

Abstract We performed microspectrophotometric measurements on isolated retinal and pineal photoreceptors of the trout Salmo irideus. Retinal rods contain a visual pigment with λmax at 512 nm. In adult trout the retinal cone system consists of single and double cones with pigments having peaks at 453 nm (single cones and one member of double cones), 530 nm (single cones and one member of double cones) and 598 nm (one member of double cones). Juvenile fish possess an additional type of single cone absorbing maximally at 400 nm. Scanning electron microscopy analysis of the cone mosaic shows a square pattern of double cones with a central single cone and corner single cones in yearling trout, and a similar pattern without corner single cones in two-year-old trout. Our data on the pineal organ reveal two different kinds of cells showing two distinct types of pigments, the former having its λmax at 463 nm and the latter with its maximum at 561 nm.

Chapter 1 The electrical responses of the trout pineal photoreceptors to brief and prolonged illumination

Intracellular recordings from 103 photoreceptors in the excised pineal body of adult trouts were obtained by using single electrode current- and voltage-clamp techniques. The photoresponses to brief flashes showed the same polarity but a slower time course than those previously recorded from retinal photoreceptors of lower vertebrates. Pineal photoreceptors showed spectral sensitivity peaks at about 495 and 521 nm and absolute sensitivity comparable to retinal cone cells of the same species. The photoreceptor membrane conductance, measured under voltage clamp during moderate illumination was about 10% lower than in the dark, and the extrapolated reversal potential of the response was at 60 mV above the dark membrane potential. The addition of 3-isobutyl-1-methylxanthine (IBMX) to the perfusate was followed by a receptor depolarization in the dark and by a slow-down of the response kinetic. Pineal receptor cells produce constant amplitude responses during steady illumination, without displaying the delayed slow depolarization typically associated with light adaptation of retinal photoreceptors. Photoresponses to brief flashes superimposed on a steady illumination are decreased in amplitude by an amount directly related to the background intensity. Increase of the background intensity leads to threshold increments without significant changes of the saturation intensity, resulting in a gradual compression of the cell dynamic range. These results were discussed relative to light adaptation in retinal photoreceptors. The conclusion can be drawn that the response properties of pineal photoreceptors during steady illumination are part of an unknown, self-regulating mechanism to lock the rate of metabolism and secretion of indolamines to the absolute level of diurnal light.

Binocular interactions measured by choice reaction times in pigeons

In 7 pigeons binocular interactions were studied by recording monocular and binocular choice reaction times (RTs) to a pattern discrimination task. In all the animals binocular responses were found to be significantly faster than monocular RTs. In order to assess whether binocular advantage might be ascribed to a neural interaction between the two eyes, monocular and binocular performances were evaluated according to a probability summation model. The results indicate that in the great majority of animals, probability summation alone can account for binocular superiority.

Visuomotor Coordination in Behaviour of Pigeons Following Post-Hatching Monocular Experience: An Image Analysis Study

We investigated the role of visual binocular inputs during the development on visuo-motor coordination in conditioned key-pecking responses to differently sized spots. Five groups of pigeons were used: monocular control group; two early groups (retinal ablated -ERA-, and eyeball enucleated -EEE) operated in two days post-hatching; two late groups (adult pigeons, retinal ablated — LRA-, and eyeball enucleated -LEE). The most substantial results occurred in early groups: the impairment of visual performance at small size spot, the loss of bill gape/spot size coordination and the permanent inaccurate reaching trajectory, particularly in the EEE group. On the contrary, late groups did not show any significant difference compared with the control group. The present data indicate that binocular interactions are crucial during the development of the visual system and, in addition, prove the differential role played by retinal and extraretinal inputs on the development of the visuomotor coordination. Once the maturation stage is accomplished (late groups) the eyes can work independently one from the other in conditioned key-pecking responses.

An algorithm comparing the two mononuclear curves of choice reaction times in pigeons

A simple and fast algorithm allowing the matching between frequency distributions is developed. The procedure consists in a class by class mapping of two distributional curves in order to derive a class transformation function that specifies how a class from one distribution is modified to produce a class in another distribution. Being interested in investigating the equivalence between the eyes, we have compared left and right monocular curves of choice reaction times to three different visual discrimination tasks in intact and surgically manipulated pigeons by means of the present technique of analysis. The results indicate that RTs distributions of the eyes belong to the same family of functions. It is possible, however, to demonstrate a difference in the range of time responses between the two monocular curves during one of the three visual discriminations used, particularly in the lesioned group.