Alberto Lanfranchi

Influence of long-term diabetes on liver glycogen metabolism in the rat.

Diabetes acutely impairs the ability of the liver to synthesize glycogen. However, the effect of chronic diabetes on the glycogenic function of the liver is not known. We measured hepatic glycogen contents in streptozotocin (STZ)-diabetic rats 3 weeks or 9 months after the induction of diabetes, in the fed state and following a 24-hour fast. In the fed state, liver glycogen levels were markedly decreased in short-term diabetic animals (5.8 +/- 2.0 v 33.9 +/- 2.3 mg/g, P less than .001), but not in long-term diabetic rats (18.3 +/- 4.4 v 20.7 +/- 1.3 mg/g, P = NS) as compared with age-matched nondiabetic animals, despite comparable hyperglycemia (portal plasma glucose levels of 424 +/- 21 and 449 +/- 24 mg/100 mL, short- and long-term diabetics, respectively). In the fasted state, on the other hand, liver glycogen was depleted in acute diabetes (4.5 +/- 2.2 mg/g v 1.9 +/- 0.5 of control rats), but significantly increased in chronic diabetes (10.1 +/- 3.1 v 0.2 +/- 0.03 mg/g, P less than .001). The latter finding was confirmed by electron-microscopical examination of liver cells. Furthermore, the percentage of hepatic glycogen synthase in the active form (synthase a) was lower than normal in short-term diabetic rats and in old nondiabetic rats. In long-term diabetic animals, on the other hand, synthase a was significantly higher than in old controls (P less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

The ultrastructure of ciliary sensory cells in two turbellaria acoela

Abstract. In Convoluta psammophila and Mecynostomum sp. it has been possible to distinguish two types of epithelial receptors. The first type possesses a dendrite protruding from the epithelial surface and is supplied with a long cilium and a large rootlet. The second type has a dendrite supplied with a central kinocilium surrounded by a crown of stereocilia. One particular structure, situated under the kinocilium and interpreted as a transformed rootlet, is connected to two or three stereocilia located inside the crown. The orientation of the inner stereocilia is similar to that of the pair of central tubules of the kinocilium. Morphological analogies and the functional role of these findings are discussed.

Fine structural observations on the ciliary receptors in the epidermis of three otoplanid species (Turbellaria proseriata)

In Notocaryoturbella bigermaria, Otoplana truncaspina and Paroto-planella heterorhabditica three types of epidermal receptors are recognized. Type I: with a single cilium running in a duct, piercing the distal dendrite process of the receptor. The internal wall of the dendrite process has eight ridges with longitudinal filaments lying inside them. The ciliary basal body lacks a longitudinal rootlet but is encircled by a thin annular formation. Type II: with a single (A) or several (B) cilia which protrude from the outer epithelial surface and are provided with a large and striped rootlet. Both types are considered as mechanoreceptors. Type III: with two or more short and stumpy cilia devoid of rootlets and displaying the usual 9 + 2 pattern in the proximal part only. They are considered as chemoreceptors.

The ultrastructure of the eyes in larval and adult polyclads (Turbellaria)

Examination of the larvae of Thysanozoon brocchii and Stylochus mediterraneus shows that they have both epidermal and cerebral eyes, while the young worms of Notoplana alcinoi have only cerebral eyes. A description is given of the ultrastructure of both kinds of eyes. The epidermal eye consists of one cup-shaped pigmented cell, whose cavity is filled with lamellae of ciliary origin. A small covering cell is located over the cup-opening. The cerebral eye is made up of three cells: one pigmented cell with ciliary projections and two rhabdomeric-type photoreceptor cells. The cerebral eye in the adult is formed of a pigmented cup without cilia and at least three rhabdomeric-type photoreceptors. A number of remarks of a morpho-onthological nature are presented.

Fine structural changes induced by circadian light—dark cycles in photoreceptors of Dalyelliidae (Turbellaria: Rhabdocoela)

The circadian light—dark cycles in the dalyelliid flatworm eyes induce two changes of particular interest. One involves the metabolic membrane system, its turnover, and the localization and appearance of mitochondria and glycogen; the other is connected with retinomotor response. In the second process the dark-adapted eye presents an empty eye cup. The microvillar border of the photoreceptors and the “lens” projections come out of the cup and the cell bodies are displaced laterally with respect to that cup. An attempt was made to elucidate the development within time of the retinomotor response. The plot of the ratio of empty area/microvillar area in median sections of several eyes shows a long-lasting dark-adaptation, completed in 6–9 hr and a short-term light-adaptation completed 5–10 min after light onset. Some hypotheses on the regulation of this response are discussed.

Influence of Long-Term Diabetes on Renal Glycogen Metabolism in the Rat

Background/Aims: The effects of acute insulin deficiency on the kidney have been investigated in animal models of experimental diabetes; however, the impact of long-term diabetes has not been determined. Methods: We measured renal glycogen contents in streptozotocin (STZ)-diabetic rats 3 weeks (n = 12) or 9 months (n = 12) after the induction of diabetes, and in 2 groups of control rats of similar age (n = 16 and n = 12, respectively), in the fed state and after a 24-hour fast. Results: Diabetic rats had high glucose levels, low insulin but normal glucagon concentrations in portal blood. In the fasting state, kidney glycogen content was very low in both young control and young diabetic rats (54 ± 15 and 189 ± 26 µg/g, respectively, mean ± SD); in contrast, glycogen levels were markedly elevated in rats with long-standing diabetes as compared to old nondiabetic animals (2,628 ± 1,023 ± and 1,968 ± 989 µg/g of diabetic rat, fasting and fed, respectively, p < 0.001 vs. 0 ± 0 and 4 ± 6 µg/g of control rats). On electron microscopy, large glycogen clusters were localized to the renal tubules. Kidney phosphorylase activity was higher, and synthase activity lower in diabetic than control rats (p < 0.05 for both), whereas kidney glycogen was strongly related to plasma glucose levels, suggesting that the enzyme changes were secondary to glycogen accumulation itself. Renal hexosephosphates and fructose-2,6-bisphosphate contents were both increased in long-term diabetic rats (p < 0.05), implying enhanced fluxes through both glycolysis and gluconeogenesis. Conclusion: In chronic, untreated diabetes glycogen accumulates in the renal tubules; prolonged hyperglycemia is the sole driving force for this phenomenon.

Morphology and Taxonomy of Two New Otoplanids (Turbellaria, Proseriata) from the Ligurian Sea

Two new species of Otoplanidae belonging to the subfamily Parotoplaninae are described: Parotoplana macrostyla sp.n. and P. uncinate sp.n. In both species the anterior body end bears a swelling. The rhabdites are grouped into bundles of several elements (up to 20 or more). The caudal plate is fan‐shaped. The cuticular apparatus has a stylet and two types of spines. The germovitelloducts do not form the common duct and the bursa stalk has a peculiar structural pattern.

Electron microscopic study of larval eye development in Turbellaria Polycladida

The appearance and development of the embryonic and larval eyes of the polyclad turbellarian Stylochus mediterraneus were studied. In the embryo, the left epidermal eye appears first. Subsequently, the right epidermal eye appears, and within hours it sinks into the parenchyma and turns into a cerebral eye. Newly hatched Gottes larvae possess both the left epidermal and the right cerebral eye. Three days after hatching, an incomplete eye appears adjacent to the left epidermal eye. The left cerebral eye then originates from this incomplete eye as it sinks into the parenchyma. This third eye is believed to originate through a process of induction.

The ultrastructure of the sense organs of some turbellaria rhabdocoela. I. The eyes of Polycystis naegelii Klliker (Eukalyptorhynchia Polycystididae)

SummaryEach pigment-cup eye of Polycystis naegelii consists of two retinal clubs and a single pigmented cell. The latter is divided into two cavities by a septum. Under bright illumination the photoreceptor process appears as a disk containing membranous laminar whorls; under faint illumination the latter are replaced by numerous straight, closely packed, microvilli. This morphological variation is correlated with the intensity of the photoreceptors exposure to light. The lenticular structures described by previous light microscopists have not been observed.

Abscisic acid levels and cell structure in single seed tissues of shedding affected fruits of Malus domestica Borkh

Summary To improve knowledge of the processes involved in fruit abscission, the abscisic acid levels and the structure of both whole seed and single seed tissues were investigated in control (sample A) and shedding affected fruits (sample B) of Malus domestica . ABA content was measured in crude extracts by radioimmunoassay and the results were validated by physicochemical methods. Whole seeds were embedded and sectioned for light and electron microscopy studies. The ABA level in whole seeds was almost three times higher in the affected fruits than in the control. No difference in ABA content was observed between the embryos of the two samples, while in the endosperm, the nucellus and especially in the integuments, the ABA level was clearly higher in sample B than in sample A. Delayed development and precocious cell differentiation as well as certain aspects of whole system degeneration were observed. The authors conclude that ABA levels seem to be one of the factors involved in fruit abscission in an early period of development.