Effect of monensin and diabetes on asialoglycoprotein degradation in rat hepatocytes

We have studied the effects of two modulations — streptozotocin-induced diabetes in vivo, and the presence of the carboxylic proton ionophore monensin in vitro — on the degradation of³H-asialoorosomucoid ligand in isolated rat hepatocytes.The ligand was internalized by means of a synchronous wave procedure. Diabetes was associated with a marked decrease in the amount of total degraded radioactive ligand compared to that in normal cells (3.6% and 37.3% of internalized ligand respectively, at 60 min), together with increased secretion of degradation products into the incubation medium (87% and 46.3% of the total degraded ligand was secreted by diabetic and normal cells, respectively). Monensin induced similar effects in normal cells, but had no apparent effect in diabetic cells.     

Evaluation of the hepatotoxicological effects of a drug in an in vivo/in vitro model.

Both in vivo and in vitro models have certain disadvantages for the study of the chronic hepatotoxicity of drugs. The aim of this work was to evaluate a new approach based on an in vivo/in vitro model. After chronic in vivo treatment of rats with Vincamine and Vindeburnol (an eburnamenine derivative which exhibits hepatotoxic properties in man) liver cells were isolated, and functional and metabolic disorders (metabolic utilization of fructose and protein biosynthesis) were studied to determine injury. The results showed no modification of blood parameters, but a direct relationship between the dose of Vindeburnol administered in vivo and the metabolic disorders observed in vitro, evidencing the high sensitivity and reliability of this model.     

Close linkage of glucokinase locus on chromosome 7p to early-onset non-insulin-dependent diabetes mellitus.

Non-insulin-dependent diabetes mellitus (NIDDM) is a major health problem, affecting 5% of the world population. Genetic factors are important in NIDDM, but the mechanisms leading to glucose intolerance are unknown. Genetic linkage has been investigated in multigeneration families to localize, and ultimately identify, the gene(s) predisposing to NIDDM. Here we report linkage between the glucokinase locus on chromosome 7p and diabetes in 16 French families with maturity-onset diabetes of the young, a form of NIDDM characterized by monogenic autosomal dominant transmission and early age of onset. Statistical evidence of genetic heterogeneity was significant, with an estimated 45-95% of the 16 families showing linkage to glucokinase. Because glucokinase is a key enzyme of blood glucose homeostasis, these results are evidence that a gene involved in glucose metabolism could be implicated in the pathogenesis of NIDDM.     

Central inputs mask multiple adult neural networks within a single embryonic network

It is usually assumed that, after construction of basic network architecture in embryos, immature networks undergo progressive maturation to acquire their adult properties. We examine this assumption in the context of the lobster stomatogastric nervous system. In the lobster, the neuronal population that will form this system is at first orgnanized into a single embryonic network that generates a single rhythmic pattern. The system then splits into different functional adult networks controlled by central descending systems; these adult networks produce multiple motor programmes, distinctively different from the single output of the embryonic network. We show here that the single embryonic network can produce multiple adult-like programmes. This occurs after the embryonic network is silenced by removal of central inputs, then pharmacologically stimulated to restore rhythmicity. Furthermore, restoration of the flow of descending information reversed the adult-like pattern to an embryonic pattern. This indicates that the embryonic network possesses the ability to express adult-like network characteristics, but descending information prevents it from doing so. Functional adult networks may therefore not necessarily be derived from progressive ontogenetic changes in networks themselves, but may result from maturation of descending systems that unmask preexisting adult networks in an embryonic system.     

pHi regulatory ion transporters: an update on structure, regulation and cell function

Intracellular pH (pH_i) is a major regulator of various and critical cellular functions. A close regulation of pH_i is thus mandatory to maintain normal cellular activity. To this end, all cells express ion transporters that carry across their plasma membrane H⁺ or equivalent H⁺ into and out of the cell. Besides pH_i, these ion transporters are under the regulation of neurohormonal stimuli. This review summarises the molecular identity, regulation and function of the main membrane pH-regulatory ion transporters. Received 30 December 1998; received after revision 4 February 1999; accepted 9 February 1999     

Action Research on Land Management in the Western Amazon, Peru – A Research Process, Its Outcomes and the Researcher’s Role

The article explores the action research process throughout a land management research project, with the ambition to reflect upon action research as a working approach. It is shown how this process is experienced from a researcher’s point of view and it critically analyses its methodology and process, outcome and the role of the action researcher.The learning environment known to farmers and framed by local institutions and practical experimentation, embedded in the local worldview, constituted a necessary starting point for achieving motivation and practical outcomes. Tight feedback loops between practice and reflection enabled joint learning and innovation and rapid implementation of measures suggested by the farmers. The approach could be particularly useful for local NGOs and local universities.     

Microorganism-associated variation in host infestation efficiency in a parasitoid wasp,Trichogramma bourarachae (Hymenoptera: Trichogrammatidae)

InTrichogramma bourarachae (Hymenoptera: Trichogrammatidae), the infestation efficiency presents important variation among strains: 60 eggs/5 days/female in the High (H) strain and 25 eggs/5 days/female in the Low (L) strain. Crosses show that between-strains variation is inherited by the matrocline route. Antibiotic and heat treatments reduce infestation efficiency in the H strain and have no effect on the L strain. The hypothesis of cytoplasmic-symbiotic microorganisms accounting for the higher infestation efficiency in the H strain is supported by microscopic observations. The origin and the significance of this between-strains variation are discussed.     

Experimentelle Reversion von Tumorzellen in vivo

Summary European eels with fast growing epidermal papillomas (cauliflower disease) were treated with quinine-sulphate. At concentrations of 15 to 60 mg/l and after 8 weeks of treatment, there occurred newly formed mucous cells and club cells in the tumor tissue. Tight contact between all cells was reestablished. The nucleus-plasma-relation had evidently decreased. Electron microscopical studies showed a restauration of degenerated cell organelles, especially of the outer membrane. Growth rate of the tumors was reduced, and at a concentration of 60 mg/l the tumor tissue ceased growing from the beginning of treatment.