Martino Rizzotti

Ricerche Elettroforetiche Sulla Variabilita Genetica Di Anguilla Anguilla

Abstract This note refers to a preliminary research intended to verify the possible presence of different populations of eels (Anguilla anguilla L.) in the Mediterranean sea. Eel tissue samples have been analyzed by means of electrophoresis on starch gel. Five enzyme systems present in tissue extracts from glass-eels (elvers) have been studies: MDH I and II, PHI I and II, SHD; four of which are variable and useful as genetic markers. The genetic and molecular interpretations of the complex electrophoretic patterns and the gene frequencies observed on three different samples of elvers from the Tyrrhenian sea are also reported.

The hemoglobins of Anguilla anguilla (L.) ontogenetic variations

Abstract 1. 1. The electrophoretic pattern of the hemoglobin of adult European eels shows two bands. The pattern of the elvers is composed of nine bands, divided into three groups with three bands in each. This pattern undergoes gradual modifications till it changes, after a few months of aquarium rearing, into the two band pattern typical of the adult eels. 2. 2. The ontogenetic variation of the hemoglobin pattern of the eel, a catadromous fish, was postulated by some Authors to be functionally similar to that of an anadromous salmon. Our results do not support this hypothesis, while being in agreement with the habits and physiological requirements of elvers and eels.

CILIUM : ORIGIN AND 9-FOLD SYMMETRY

How the cilium appeared is still such a poorly defined question that current hypotheses range from a symbiotic spirochaete to a cellular eye. In this paper, the whole question is subdivided into a list of problems which are morphological, physiological and temporal. These problems are examined one by one, in order to analyse the most popular exogenous hypothesis of Margulis as well as other recent exogenous and endogenous hypotheses. To overcome fundamental topological and temporal difficulties, a new endogenous hypothesis is expounded, according to which the cilium derives from a cellular peduncle reinforced with microtubules. This hypothesis implies a geometrical rationale for the ninefold symmetry. In the last paragraph the consequences of the various hypotheses are compared.

Fish haemoglobins: the order Clupeiformes

The haemoglobin systems of the order Clupeiformes have been studied by several researchers in 41 species belonging to three out of its five families. Most of them were investigated in the native form using electrophoretic methods, and a few were also examined from the functional point of view. Both approaches corroborate the widespread view that acidic and basic haemoglobin components, which are structurally and functionally distinct, may be present in teleost fish. However, the former are always present, whereas the latter are often lacking, depending on the taxonomic group. Both kinds of components are found in families Clupeidae and Pristigasteridae, but only acidic ones in Engraulidae.Most electrophoretic patterns show high multiplicity, and chiefly concern the acidic components. Ontogenetic variation was described in three species. Individual variants were also observed in other species, although some of these might be due to ontogenetic variations rather than genetic polymorphism.

Note on amino acid composition of eel hemoglobin

Abstract All hemoglobin sequences of Osteichthyes determined so far have been limited to the division Euteleostei, while the European eel, Anguilla anguilla (L.), belongs to the division Taeniopaedia; its sequences are thus phylogenetically important. As a preliminary to sequence determination, the amino acid composition of the two hemoglobin components of A. anguilla was determined. As expected, the data were similar to those of the American eel, while more differences were found with respect to the Japanese species.

The hemoglobins of Anguilla anguilla (L.). II: Polypeptide constitution

Abstract 1. 1. The over 300 adult individuals of the European eel, Anguilla anguilla (L.), examined showed the same electrophoretic pattern of the hemoglobins; the 293 juvenile individuals were found to be monomorphic too. 2. 2. The hemoglobin system of the adult individuals includes an acidic (anodic) component and two basic (cathodic) components, a major one and a minor one. 3. 3. Both the acidic component and the major basic component, separated by electrophoresis or by ion-exchange chromatography and analyzed by 8 M urea electrophoresis, were found to be symmetrical heterotetramers. 4. 4. By means of isoelectric focusing a higher multiplicity is obtained, but the polypeptide constitution of the focused fractions is the same we found with the previous methods: the higher multiplicity should depend on associations with the polyampholytes. 5. 5. The molecular weights of the polypeptides have been compared by means of SDS—urea electrophoresis, while the acidic component seems almost normal, in the basic component the β polypeptide were found to be lighter than the α polypeptide. 6. 6. These polypeptides have been attributed to the classes α and β by digestion with carboxypeptidases A and B.

Toward Creating Life in a Test-Tube

Attempts to dominate minimal life from the conceptual as well as the experimental viewpoints would take advantage of better understanding of the properties of life in general. Reproduction is usually considered as its most basic property, but detailed examination leads us to the conclusion that this property derives from two more basic ones, namely, overproduction and modularity. From the experimental viewpoint, the requirements of a minimal cell are being currently investigated both from subtracting components from the simplest known organism and from adding components to a fully synthetic cell-like object. However, even the concept of a minimal cell is poorly defined.

Prokaryotes: The Flagellum

To avoid any misunderstanding, it is worth noting here the definite distinction between flagellum (prokaryotic) and cilium (eukaryotic). The two structures only have in common the fact that they are thin mobile protrusions with a precise and stable organization, and also a definite position in the cell (unlike, for example, the pseudopods of eukaryotic cells which may change, be reabsorbed and sent out again in different positions). Apart from these common characteristics, the two structures differ in every particular aspect. The flagellum is much thinner and extracellular, as at the level of the plasma membrane it only has its basal body, whereas the cilium is intracellular, and is therefore covered by the plasma membrane for the whole of its extended portion (Fig. 4.1). Furthermore, the former is passive and only rotates at its base, whereas the latter bends laterally along its full length or part of it and is immobile at its base; the former exploits the inflow of hydrogen ions41(or sodium ions in rare cases42) as its source of energy for motion at the level of its rotary motor, whereas the latter exploits energy delivered by ATP hydrolysis, according to the usual scheme: that energy produces bending at the point at which it is delivered. In addition, the constituent proteins differ completely: they are flagellin, virtually alone, for the extended portion of the flagellum, i.e. its filament, whereas the cilium has many proteins, a few of which give rise to a contractile system (Section 11.1). All these differences also imply radically different morphogenesis.

The First Cell

The properties attributed to the first cell coincide with the minimal properties which are attributed to an object in order to define it as a cell. Although their identification may seem to be a simple task at first sight, the list itself continues to arouse debate. Some agreement has been reached on just one point: defining a cell is the same as defining life1. Therefore, the properties of the first cell coincide with the minimal properties of life.

Eukaryotes: Plastidial Symbioses

The origin of plastids treads in the footsteps of the origin of mitochondria, to a large extent. It is thought to have occurred later, as plastids are only present in organisms endowed with mitochondria, apart from secondary loss (Section 10.4, middle). It means that these are either essential for the survival of a photosynthetic eukaryotic cell or so widespread that it is very difficult for a cell without them to have the chance to engulf a photosynthetic Prokaryote. Perhaps the second reason has not only a probabilistic basis, but also an ecological one, in the sense that the almost anaerobic lifestyle carried out by Eukaryotes without mitochondria keeps them far from Prokaryotes with oxygenic photosynthesis. The ecological explanation is in accordance with the functional one, because plastids deliver oxygen, and this has dangerous effects on many cellular components, but the damage is precisely reduced thanks to its prompt removal by mitochondria. Moreover, its energetic exploitment by mitochondria confers to the cell with plastids a further advantage with respect to its simple dispersion in the environment or chemical inactivation which would occur in a hypothetical cell with plastids, but without mitochondria.