The effect of humic substances on the toxicity of aluminium to adult rainbow trout, Oncorhynchus mykiss (Walbaum)

Some physiological parameters were measured in adult rainbow trout during a 10-day exposure to 180 μg Al_total l⁻¹ in acid water (pH 4.7) with or without humic substances (10 mg l⁻). The fish were acclimatized to pH 5.0 for 7 days prior to the experimental treatments.
Chemical analyses revealed that, in the presence of human substances, 74–80% of the A1 was organic bound, while in the absence of humic substances most of the Al(987percnt;) occurred in the inorganic form.
Al bound to humic substances (13–150 μg l⁻¹) did not alter the plasma NaCl-concentration, nor the haematocrit value, of rainbow trout during an exposure period of 10 days. This contrasts with the high death rate obtained within 2–3 days when most of the A1 (175 μg l⁻¹) was in the inorganic form. The lethality was accompanied by a 25% decrease in the plasmaconcentration of NaCl and a doubling of the haematocrit value. Bulk analysis revealed that when the metal was present in inorganic forms the total Al content of the gills (75 μg A1 g⁻¹ wet weight) was 15 times higher than when it was present as bound to the humic substances. These experiments showed that the accumulation of A1 at the gills was accompanied by physiological disturbances, both being a function of the chemical speciation of Al.     

Dimethylarginine Levels in Cerebrospinal Fluid of Hyperacute Ischemic Stroke Patients are Associated with Stroke Severity

We hypothesise that asymmetric and symmetric dimethylarginine (ADMA, SDMA) are released in cerebrospinal fluid (CSF) due to ischemia-induced proteolysis and that CSF dimethylarginines are related to stroke severity. ADMA and SDMA were measured in CSF of 88 patients with ischemic stroke or TIA within 24 h after stroke onset (mean 8.6 h) and in 24 controls. Stroke severity was assessed by the National Institutes of Health Stroke Scale (NIHSS) score at admission. Outcome was evaluated by institutionalization due to stroke and the modified Rankin scale. Dimethylarginine levels were higher in patients with stroke than in TIA patients, who had higher levels than controls and correlated with the NIHSS. Logistic regression analysis confirmed that dimethylarginines were independently associated with stroke severity. The SDMA/ADMA ratio did not differ significantly between controls and stroke patients. CSF dimethylarginine levels are increased in hyperacute ischemic stroke and are associated with stroke severity. R. Brouns is a research assistant of the Fund for Scientific research Flanders (FWO-Vlaanderen).     

Assay of protein kinase C with an N-bromosuccinimide-cleavage fragment of histone H1.

N-Bromosuccinimide cleavage of a lysine-rich histone fraction (histone III-S) yields a peptide substrate, purified by reverse-phase h.p.l.c., for the Ca2+ + phospholipid-dependent protein kinase (protein kinase C). This substrate displays no reactivity with the cyclic AMP-dependent protein kinase, and may prove useful for the detection of protein kinase C activity in crude tissue extracts.     

Quantitation by immunoblotting of the in vivo induction and subcellular distribution of hepatic acetyl-CoA carboxylase

The in vivo induction of rat liver acetyl-CoA carboxylase (ACC) the rate-limiting enzyme of fatty acid biosynthesis, has been examined by immunoblotting, avidin blotting, and enzyme isolation. Three high-molecular-weight immunoreactive bands (Mr 220,000-260,000) were recognized in liver extracts by an anti-carboxylase polyclonal antiserum. Two bands, A and B, comigrated on sodium dodecyl sulfate polyacrylamide gels with purified acetyl-CoA carboxylase, were avidin binding, and were dramatically induced following high carbohydrate refeeding. Only band A was recognized on immunoblots using a monoclonal antibody directed against acetyl-CoA carboxylase, suggesting that band B is a proteolytic fragment in which the epitope recognized by the monoclonal antibody is absent. Following refeeding, approximately 57% of acetyl-CoA carboxylase mass (band A + band B) was present in the high-speed supernatant fraction, while 34 and 9% were in the high-speed (microsomal) and low-speed pellet fractions, respectively. Refeeding caused a large increase in total acetyl-CoA carboxylase mass, the magnitude of which differed in the various fractions. In the low-speed supernatant, a 20-fold increase in ACC mass was observed, while a 12-fold increase was seen in the high-speed supernatant. The fold increase in the high-speed pellet was even greater (greater than 27-fold). Acetyl-CoA carboxylase purified by avidin-Sepharose chromatography from fasted/refed rats had an approximate 4-fold higher Vmax and a significantly lower Ka for citrate than enzyme purified from fasted animals. The results of this study indicate that the induction of hepatic ACC that occurs during high carbohydrate refeeding of the fasted rat predominantly involves increases in enzyme content in both cytosol and microsomes, but is also accompanied by an increase in enzyme specific activity.