Restriction mapping of the rRNA genes from Artemia larvae

A restriction endonuclease analysis of the genes coding for the ribosomal RNA from Artemia larvae has shown that these genes consist of a repeat unit of 16.2 kilobase pairs (10.7 Mdaltons) and that the repeat unit seems to be homogeneous in size.     

On the purification of beta-bungarotoxin

It has recently been claimed that our beta-bungarotoxin preparation contained three contaminants, including a postsynaptic toxin. We have extended our purification procedure and found no evidence of such contaminants.     

Modulation by polyelectrolytes of canine cardiac microsomal calcium uptake and the possible relationship to phospholamban

Calcium uptake and (Ca2+ + Mg2+)-ATPase activity in canine cardiac microsomes were found to be stimulated by heparin and various other polyanions. Prior treatment of the microsomes with the ionophores alamethicin or A23187 produced no change in the extent of stimulation of the ATPase activity by heparin yet eliminated net calcium uptake. This finding and a lack of change in the stoichiometric ratio of mol of calcium transported/mol of ATP hydrolyzed (calcium:ATP) suggest that the effect of heparin is on the calcium pump rather than on a parallel calcium efflux pathway. Certain polycationic compounds including poly-L-arginine and histone inhibited both cardiac and fast skeletal muscle microsomal calcium uptake and also produced no change in the stoichiometric ratio of calcium to ATP. Several lines of evidence indicate that the polyanionic compounds tested stimulate calcium uptake by interacting with phospholamban, the putative phosphorylatable regulator of the cardiac sarcoplasmic reticulum calcium pump, whereas polycationic compounds appear to interact with the pump. (i) Heparin stimulated calcium uptake to the same extent as protein kinase A or trypsin, whereas prior phosphorylation or tryptic cleavage of phospholamban from the membrane abolished the stimulatory effect of heparin. (ii) Calcium uptake and (Ca2+ + Mg2+)-ATPase activity in fast skeletal muscle microsomes, which lack phospholamban, were unaffected by heparin. (iii) Purified cardiac (Ca2+ + Mg2+)-ATPase activity was no longer stimulated by heparin yet was still inhibited by polycationic compounds. The heparin-induced stimulation of calcium uptake was dependent on the pH and ionic strength of the heparin-containing preincubation medium, hence electrostatic interactions appear to play a significant role in heparin's stimulatory action. The data are consistent with an inhibitory role of the positively charged cytoplasmic domain of phospholamban with respect to calcium pump activity and the relief of the inhibition upon reduction in phospholamban's positive charge by phosphorylation or binding of polyanions.     

Cyclic AMP-like effects of polyamines on phosphatidylcholine synthesis and protein phosphorylation in human promyelocytic leukemia HL60 cells. Comparison with the effects of phorbol ester

Spermine or putrescine increased cAMP levels through a catalase-sensitive mechanism, resulting in, most notably, a dephosphorylation of protein A (Mr 45,000, pI 5.15) and protein B (Mr 45,000, pI 4.9) and slightly increased phosphatidylcholine (PC) synthesis in HL60 cells. Exogenous dibutyryl cAMP mimicked the polyamine effects. 12-O-Tetradecanoyl phorbol-13-acetate (TPA) also promoted the protein dephosphorylation and PC synthesis, the effects augmented by R59022 and mimicked by exogenous 1-oleoyl-2-acetylglycerol. The effects of spermine (or dibutyryl cAMP) and TPA on PC synthesis were synergistic. It was suggested that cAMP-dependent protein kinase and protein kinase C might mediate, in an independent but inter-related manner, the effects of polyamines and TPA.     

Rectus abdominis myocutaneous free-flap reconstruction following a cranio-orbital-maxillary resection for neurofibrosarcoma

An unusual case of neurofibrosarcoma of the cranio-orbital-maxillary region was resected by a combined neurosurgical and plastic surgical team. The resulting defect was reconstructed in one stage with a free rectus abdominis myocutaneous flap, obviating the need for subsequent prosthetic obturation of the maxillary defect. This reconstructive technique expedited the patient's convalescent period, allowing him to return to work 3 weeks following surgery. Wound healing was uneventful, and the cosmetic result was acceptable to the patient.     

Astrocyte Resilience to Oxidative Stress Induced by Insulin-like Growth Factor I (IGF-I) Involves Preserved AKT (Protein Kinase B) Activity

Disruption of insulin-like growth factor I (IGF-I) signaling is a key step in the development of cancer or neurodegeneration. For example, interference of the prosurvival IGF-I/AKT/FOXO3 pathway by redox activation of the stress kinases p38 and JNK is instrumental in neuronal death by oxidative stress. However, in astrocytes, IGF-I retains its protective action against oxidative stress. The molecular mechanisms underlying this cell-specific protection remain obscure but may be relevant to unveil new ways to combat IGF-I/insulin resistance. Here, we describe that, in astrocytes exposed to oxidative stress by hydrogen peroxide (H₂O₂), p38 activation did not inhibit AKT (protein kinase B) activation by IGF-I, which is in contrast to our previous observations in neurons. Rather, stimulation of AKT by IGF-I was significantly higher and more sustained in astrocytes than in neurons either under normal or oxidative conditions. This may be explained by phosphorylation of the phosphatase PTEN at the plasma membrane in response to IGF-I, inducing its cytosolic translocation and preserving in this way AKT activity. Stimulation of AKT by IGF-I, mimicked also by a constitutively active AKT mutant, reduced oxidative stress levels and cell death in H₂O₂-exposed astrocytes, boosting their neuroprotective action in co-cultured neurons. These results indicate that armoring of AKT activation by IGF-I is crucial to preserve its cytoprotective effect in astrocytes and may form part of the brain defense mechanism against oxidative stress injury.