Search

The hereditary spastic paraplegias (HSP) are characterized by spastic gait with weakness in the legs and additional neurological or extra-neurological signs in "complicated" forms. The past two decades have witnessed major advances in our understanding of their molecular bases with the identification of a plethora of loci and the cloning of several SPG genes. Combined genetic and clinical information has permitted a modern, molecularly-driven classification and an improved diagnosis, with several new data on the possible disease mechanisms. Further heterogeneity will rapidly emerge with the diffusion of next-generation sequencing platforms and, under the shadow of common themes in the pathogenesis, new therapeutic options will likely emerge for a great number of patients.

With the aim of dissecting host-parasite interaction processes in the system Lycopersicon aesculentum-Fusarium oxysporum f. sp. lycopersici we have isolated plant cell mutants having single-step alterations in their defense response. A previous analysis of the physiological phenotypes of mutant cell clones suggested that recognition is the crucial event for active defence, and that polysaccharide content, fungal growth inhibition, peroxidase induction in in vitro dual culture and ion leakage induced by cultural filtrates of the pathogen can be markers of resistance. In this paper we present the results of a similar analysis carried out on cell cultures from one susceptible (‘Red River’), one tolerant (‘UC 105’) and three resistant (‘Davis UC 82’, ‘Heinz’, ‘UC 90’) tomato cultivars. Our data confirm that the differences in the parameters considered are correlated with resistance versus susceptibility in vivo. Therefore, these parameters can be used for early screening in selection programmes. These data, together with those obtained on isolated cell mutants, suggest that the selection in vitro for altered fungal recognition and/or polysaccharide or callose content may lead to in vivo — resistant genotypes. The data are thoroughly discussed with particular attention paid to the importance of polysaccharides in active defense initiation.

Platelets, lymphocytes, and megakaryocytes, specifically processed for the intracellular detection of antigens, were studied by indirect immunofluorescence techniques using monospecific antibodies directed against factor VIII-related antigen (F-VIII-RA). Specific staining was observed in platelets of the peripheral blood from normal individuals and from patients with haemophilia A, and in megakaryocytes and platelets of bone marrow from normal subjects. The same cells studied in patients with von Willebrand’s disease were negative. No bone marrow biopsies were performed on patients with haemophilia A. Our results indicate that F-VIII-RA is localized in megakaryocytes and platelets of normal subjects; the possible role of this F-VIII-RA in platelet function is discussed.

We have studied the effect of a change in the endogenous hormone equilibria on the competence of tomato (Lycopersicon esculentum) cells to defend themselves against the fungal pathogen Fusarium oxysporum f. sp. lycopersici. Calluses from cvs ‘Davis’ and ‘Red River’, respectively resistant and susceptible to Fusarium and transgenic for an auxin- or cytokinin-synthesizing gene from Agrobacterium tumefaciens, were used. The integration of Agrobacterium hormone-related genes into susceptible cv ‘Red River’ can bring the activation of defense processes to a stable competence as assessed by the inhibition of mycelial growth in dual culture and gem-tube elongation of Fusarium conidia, the determination of callose contents, peroxidase induction and ion leakage in the presence of fusaric acid. This is particularly true when the transformation results in a change of phytohormone equilibria towards an higher cytokin in concentration. On the contrary, in resistant cv ‘Davis’ the inhibition of both fungal growth in dual culture and conidia germination is higher when the hormone balance is modified in favour of the auxins. No significant effect was observed for ion leakage and peroxidase induction, probably because of a constitutive overproduction of cytokinins in ‘Davis’ cells.

Plant cell walls play a major role in the outcome of host-parasite interactions. Wall fragments released from the plant, and/or the fungal pathogen, can act respectively as endogenous and exogenous elicitors of the defence response, and other wall components, such as callose, lignin, or hydroxyproline-rich glycoproteins, can inhibit pathogen penetration and/or spreading. We have previously demonstrated that calli from tomato cultivars resistant in vivo to Fusarium oxysporum f.sp. lycopersici show a high amount of polysaccharides in vitro. The aim of the present work was to assess the possible role of polysaccharide content and/or synthetic capacity in determining the competence of plant cells for active defence. For this purpose, tomato cell clones with increased and decreased polysaccharide (FL+, FL-) and callose (A+, A-) content have been selected by means of specific stains as visual markers and tested for the effect of these changes on the extent of response to Fusarium. The analysis of several parameters known to be indicative of active defence (cell browning after elicitor treatment, peroxidase and ß-glucanase induction and inhibition of fungal growth in dual culture) clearly shows that FL+ and A+ clones have acquired an increased competence for the activation of defence response. The results are thoroughly discussed in terms of an evaluation of the relative importance of constitutive and/or inducible polysaccharide synthetic capacity for plant response to pathogens, and their possible regulation by plant physiological backgrounds.

With the aim of better understanding in vitro host-parasite interactions, tomato cell lines selected for altered response to Fusarium oxysporum f. sp. lycopersici cell wall components were further characterized. Particularly, their behaviour in dual culture in regard to both fungal inhibition and peroxidase activation was analysed and selected, and control cell clones were screened for esopolysaccharide content and toxin tolerance. Interclonal differences in growth response to 2,4-D and DMSO and the capacity to grow on a medium devoid of hormones (habituation) were taken as parameters representative of physiological variability not directly correlated with the response to pathogens. Significant differences between clones selected for increased (F+) and decreased (F-) response to fungal elicitors were found for pathogen inhibition, peroxidase and esopolysaccharide content, toxin tolerance being reduced in F but not significantly different from the control in F+. As expected, clonal variability for the response to 2,4-D and DMSO, although significant, was not connected with hostparasite interactions. The data reported thus show that selection for a character (response to elicitors), probably critical for the response to pathogens, may lead to the recovery of genotypes showing a set of modifications suggestive of a cascade of events leading to active defense.

Summary A new test of the functional capacity of platelets is described. It is founded on their resistance to a continued mechanical traumatism. The results obtained show that in the normal persons the mechanical resistance of platelets is a biological constant. Preliminary results of a comparison with pathologic cases are also reported.

Summary 29 cases of idiopathic thrombocytopenic purpure were studied by the test of mechanical resistance of platelets. Under these conditions platelets are much more fragile than normal. Furthermore, their resistance increases to normal values in cases showing favourable response to splenectomy.

By studying the behavior of the resistance of leukocytes to hypotonic saline solution we have found that leukocytes leaving the spleen are much less resistant than those entering it. It is felt that the change in resistance affecting leukocytes on their passage through the spleen is in all probability the manifestation of one of the mechanisms by which the spleen regulates the life span of leukocytes.

Zusammenfassung Bei Kaninchen wurde das Verhalten der Resistenz der Leukozyten gegen eine hypotonische Kochsalzlösung im rechten Herzen, im linken Herzen und im Körperkreislauf untersucht. Es konnte festgestellt werden, daß die Leukozyten, die aus der Lunge kommen, resistenter sind als die, die in die Lunge eintreten.

Zusammenfassung: Der Verfasser nimmt eine Reihe von experimentellen Versuchen an Kaninchen vor, in der Absicht, zu unseren Kenntnissen �ber den pathogenetischen Mechanismus der Hypocalc�mie bei Nephritikern und Ur�miker beizutragen, und um festzustellen, bis zu welchem Punkt die Oxals�ureretention (vonBecher festgestellt) die Hypocalc�mie erkl�ren kann. Diesen Kaninchen wurden wechselnde Mengen von Natriumoxalat intraven�s zugef�hrt und daraufhin die entsprechenden quantitativen Ver�nderungen des Blutkalkspiegels festgestellt. Der Verfasser stellt eine deutliche und regelm��ige Erniedrigung des Blutkalkspiegels fest, welche in enger zeitlicher Beziehung zu der eingef�hrten Oxalatmenge steht und bis 50% des Ausgangswertes erreichen kann. Der Blutkalkspiegel kann mit dem Aufh�ren der Oxalatzufuhr wieder steigen. Die tetanischen Kr�mpfe stehen in enger zeitlicher Beziehung zu der Erniedrigung des Blutkalkspiegels und treten mit dem Sinken des Calciums unter einen bestimmten Wert (8 mg-%) auf. Der Verfasser kommt zu der Ansicht, da� die Oxals�ureretention in der menschlichen Pathologie bei der Erzeugung der Hypocalc�mie mit die wichtigste Rolle spielt, und da� die neuromuskul�re Hyperregbarkeit solcher Patienten auf den Ca-Entzug zur�ckzuf�hren ist.