An application of cineradiography to the study of locomotion in primates

The cineradiographic technique, whereby, at 64 frames/second, the successive positions of every bone segment of animals in motion can be accurately analyzed, was used to study the vertical leap of a Galago alleni from the ground position. This jump, 13 to 14 times the body length of the animal excluding the tail, is a record among primates challenged only by the tarsier. Such vertical leaps from the ground are a common mode of locomotion for the galago. Two different patterns were observed, a symmetrical and an asymmetrical jump. In the former, the two hind limbs move in the same manner and simultaneously; and the propulsive force is equally distributed in both limbs. In the latter (more frequent in our records), the animal shifts its weight onto one foot during the preparatory phase and lifts the other; thus, only one of the hind limbs is responsible for the launching. The angular variations of every knee and ankle articulation and the successive positions of the hind limb bones were measured and diagrammatically analyzed frame by frame. A short film was made to illustrate the cineradiographic technique; it cinematographically and cineradiographically records in successive sequence the galago's leap from the ground. The symmetrical and asymmetrical jumps are also schematically presented.     

The marine toxin okadaic acid is a potent neurotoxin for cultured cerebellar neurons.

The tumor promoter okadaic acid (OKA), is a marine toxin of algal origin, identified as a potent inhibitor of protein phosphatases 1 and 2A, and possibly enhancing calcium influx through voltage dependent calcium channels (VSSC). We now report that OKA at concentrations as low as 0.5 nM produced neurotoxicity, characterized first by the desintegration of the neurites and swelling of cell bodies, and later by cellular death. Non-neuronal cells viability and morphology were unaffected up to at least 5 nM OKA. Neurons sensitivity to the toxin changed with age in culture. Maximum neurotoxicity was observed in neurons at 9 DIC, when the OKA concentration producing half of the maximum reduction in neuronal survival (EC50) was approximately 0.65 nM. At 5 DIC or 19 DIC (EC50 approximately 2.5 nM and approximately 4.5 nM respectively), neurons appeared to be less sensitive to OKA. Neurotoxicity by OKA was not reduced by VSCC antagonists such as nifedipine and verapamil, nor by antagonists of excitatory aminoacid (EAA) receptors including APV, MK801 or CNQX. VSCC antagonists and EAA receptors antagonists fully protected from neurotoxicity induced by depolarization with KCl. These results suggest that OKA mechanism of neurotoxicity may not directly involve VSCC, endogenous EAA release and EAA receptors, but may depend upon other neurochemical events.     

The amnesic shellfish poison domoic acid enhances neurotoxicity by excitatory amino acids in cultured neurons

Summary A recent episode of human intoxication by cultured mussels containing a rare excitatory amino acid named domoic acid, received particular attention for its neurological implications. The intoxication produced neurological problems, such as headache, confusion, and loss of memory, particularly severe at times. Neuronal damage was found in the hippocampus and amygdala of four patients. We now report that in neuronal cultures the neurotoxicity of a domoic acid-containing mussel extract is the result of domoic acid potentiation of the excitotoxic effect of glutamic acid and aspartic acid present in high amounts in mussel tissue. Moreover, we show that subtoxic concentrations of domoic acid are sufficient to potentiate glutamic acid and aspartic acid neurotoxicity. We present evidence suggesting that the neurotoxic synergism may be due to a reduction of Mg^{+ +} block at the NMDA receptor-associated channel, following activation of NON-NMDA receptors by domoic acid.     

Protein kinase C from small intestine epithelial cells

Protein kinase C activity has been identified in cytosolic and membrane fractions from rat and rabbit small intestine epithelial cells. The cytosolic fraction comprised about the 75% of total activity. Protein kinase C activity was resolved from other protein kinase activities by ion exchange chromatography. Phosphatidylserine or phosphatidylinositol were required for protein kinase C to be active. In addition, the activity was enhanced by the presence of a diacylglycerol. Diolein and dimyristin were the most effective (13-14 fold activation). In the presence of phosphatidylserine and diolein, the Ka for activation by Ca2+ was 10(-7)M. The phorbol ester TPA substituted for diacylglycerol in activating protein kinase C. Brush border and basolateral membranes contained protein kinase C activity, although the specific activity of the basal lateral membranes was four-fold higher than the specific activity of the brush border membranes. The presence of PKC in small intestine epithelial cells might have important implications in the Ca2+ mediated control of ionic transport in this tissue.     

Combined technique of immunohistochemistry and autoradiography for the simultaneous detection of steroid hormone receptors and their ligand

A combined technique of immunohistochemistry and autoradiography was applied to detect progesterone target cells in tissue sections. The radioactively labeled progestin [3H]-Organon 2058 and the progesterone receptor, revealed by antibodies to the receptor molecule, were localized simultaneously in identical cells on the same tissue section. Technical details that make possible combined detection of the nuclear antigen, present in very small amounts, simultaneously with its steroid ligand are described.     

Morphofunctional study of the digging system of the Namib Desert Golden mole (Eremitalpa granti namibensis): cinefluorographical and anatomical analysis

Digging locomotion of Namib Golden moles has been studied by making X–ray cinematograph films, and the morphology of their locomotor system investigated by means of radiographs and dissections. Biomechanical interpretations of the data so obtained show that moving forwards results from a cyclical compacting and decompacting of the surrounding sand. The whole step–cycle IS made up of a buttressing phase followed by several digging propulsion phases.     

A two-component signal-transducing system is involved in competence and penicillin susceptibility in laboratory mutants of Streptococcus pneumoniae

Penicillin resistance in Streptococcus pneumoniae has been attributed so far to the production of penicillin-binding protein (PBP) variants with decreased affinities for β-lactam antibiotics. Cefotaxime-resistant laboratory mutants, selected after several steps on increasing concentrations of this β-lactam, become deficient in transformation as well. A DNA fragment conferring both cefotaxime resistance and transformation deficiency was isolated and cloned from the mutant C306. The cefotaxime resistance associated with this resistance determinant was not accompanied with apparent changes in PBP properties, and it mapped on the chromosome distinct from the known resistance determinants, genes encoding PBP2x, PBP1a or PBP2b. Determination of a 2265 bp DNA sequence of the resistance determinant revealed two open reading frames, claR and claH, whose deduced amino acid sequence identified the corresponding proteins as the response regulator and histidine kinase receptor, respectively (members of the two families of bacterial signal-transducing proteins). Two hydrophobic peptide regions divided the histidine kinase ClaH into two putative domains: an N-terminal extracelluiar sensor part, and an intracelluiar C-terminal domain with the conserved His-226 residue, the presumed phosphorylation site. The single point mutations responsible for cefotaxime-resistance and transformation deficiency of C306 and of another two independently isolated cefotaxime-resistant mutants were each located in the C-terminal half of ClaH. A small extracellular protein, the competence factor, is required for induction of competence. Neither C306 nor the transformants obtained with the mutated claH gene produced competence factor, and exogenous competence factor could not complement the transformation deficiency, indicating that the signal-transducing system cia is involved in early steps of competence regulation.     

Nuclear localization of two steroid receptor-associated proteins, hsp90 and p59

It has been proposed that the unliganded nontransformed form of steroid hormone receptor is a heterooligomer comprising, in addition to the hormone-binding subunit, two associated proteins: a heat shock protein of MW 90,000 (hsp90) and another protein of MW 59,000 (p59). Using monoclonal antibodies, we demonstrate immunocytochemically the presence of both hsp90 and p59 in cell nuclei of progesterone target cells of the rabbit uterus. While steroid receptors (e.g., progesterone receptors) appear to be exclusively nuclear, we find p59 predominantly in the cell nuclei and hsp90 in both the nucleus and the cytoplasm. In addition, Western blotting of high-salt extracts of nuclear proteins detects the presence of hsp90 and p59 in the nuclei of rabbit uterus. These observations are consistent with the presence of the untransformed heterooligomeric form of steroid hormone receptors in the nuclei of target cells.