Properties of several protein kinases that copurify with rat spinal cord neurofilaments

Several protein kinases that copurify with neurofilaments (NF) were identified and each kinase was assessed for its ability to phosphorylate NF proteins. NFs were isolated using an axonal flotation procedure and the kinases were extracted from NFs with 0.8 M KCl. NF kinases were incubated with peptide substrates for selected protein kinases, [32P]ATP and protein kinase cofactors and inhibitors to characterize the kinases. Using peptide substrates, three types of kinase were identified, and a fourth was identified using NF protein as substrate. The first three kinases were the catalytic subunit of cAMP-dependent protein kinase, calcium-calmodulin dependent protein kinase II and a cofactor-independent kinase that phosphorylated prepro VIP sequence 156-170 and was inhibited by heparin. Using NF proteins as substrate, a fourth kinase was identified which was cofactor-independent and was not inhibited by heparin. Neither cofactor-independent kinase was casein kinase II. NF proteins were phosphorylated in vitro on serine and threonine, primarily by the two cofactor-independent kinases. Using [alpha-32P]8-N3ATP for affinity labeling, one kinase of 43,800 Da was identified. Thus, in addition to cAMP-dependent protein kinase and calcium-calmodulin dependent protein kinase II, two kinases have been found which are primarily responsible for NF phosphorylation in vitro and are cofactor-independent.     

Interactions between Pesticide Genes: Model and Experiment

In response to years of intense selection pressure by organophosphate insecticides, several different insecticide resistance mechanisms have evolved in natural populations of the mosquito Culex pipiens. We examined interactions between two of the most important mechanisms using a four-compartment model of insecticide pharmacokinetics. The joint effect of different mechanisms of resistance can be expressed in terms of epistasis at the physiological level in this model. The type of epistasis predicted by the model depends on the particular physiological mechanisms of resistance involved. Resistance due to a reduced penetration of the insecticide combines multiplicatively with other resistance factors, but resistance due to detoxicative processes and to insensitivity of the target site combines additively. How the pattern of epistasis at the physiological level is translated into fitness epistasis in natural populations of this mosquito depends on the intensity and pattern of insecticide selection in the field.     

Effect of Moniliformis moniliformis density on distribution within the definitive host population (Rattus norvegicus)

The population dynamics of Moniliformis moniliformis was studied in ‘free-ranging’ laboratory rats, Rattus norvegicus, presented with different relative density levels of M. moniliformis in cockroaches, Periplaneta americana. Changes in selected population parameters of the negative binomial distribution were evaluated as indicators of changes in aggregation. A significant increase in the degree of aggregation of parasites occurred as a result of the increase in relative density of infective stages available to the rats. This increase in aggregation was due to the increase in over-dispersion that occurred in female rats only. The degree of aggregation in females was found to be significantly higher than that in males at both treatment levels. The best indicators of the degree of aggregation were found to be the ratio of the variance to the relative density and the ratio of the log-variance to log-relative density. Changes in k were not correlated with changes in over-dispersion or the relative density.     

Evidence for a stem cell-specific repressor of Moloney murine leukemia virus expression in embryonal carcinoma cells.

A negative regulatory element (NRE) spanning the tRNA primer-binding site (PBS) of Moloney murine leukemia virus (M-MuLV) mediates repression of M-MuLV expression specifically in embryonal carcinoma (EC) cells. We precisely defined the element by base-pair mutagenesis to an 18-base-pair segment of the tRNA PBS and showed that the element also restricted expression when moved upstream of the long terminal repeat. A DNA-binding activity specific for the M-MuLV NRE was detected in vitro by using crude EC nuclear extracts in exonuclease III protection assays. Binding was strongly correlated with repression in EC cells. Mutations within the NRE that relieved repression disrupted binding activity. Also, nuclear extracts prepared from permissive, differentiated EC cell cultures showed reduced binding activity for the NRE. These results indicate the presence of a stem cell-specific repressor that extinguishes M-MuLV expression via the NRE at the tRNA PBS.     

Changes in auditory evoked brain potentials during ultra-low frequency whole-body vibration of man or of his visual surround

Auditory evoked brain potentials (AEP) were recorded from nine healthy male subjects during three types of condition: A - subject and visual field stationary; B - subject vibrated (z-axis, 0.6 Hz, 1.85 ms-2 rms), visual field stationary; C - subject stationary, visual field vibrated (as for B). The visual surround was confined to a checkerboard pattern in front of the subject. Auditory stimuli (1000 Hz, 86 dB, interstimulus interval 7 s) were delivered via headphones to evoke AEP. Vibration-synchronous activity in the EEG was eliminated by a subtraction technique. In comparison with condition A, conditions B and C caused an attenuation of P2 and N1P2 components of AEP together with an increased latency of N1. Effects of conditions B and C did not differ. Direct vestibular stimulation and mechanisms specific for whole-body vibration were rejected as modes of action. The AEP-changes and the subjective evaluation of experimental conditions, arousal and performance, as well as symptoms of kinetosis (motion sickness) suggest a sensory mismatch, leading to a "latent kinetosis" with de-arousal, as the dominating mechanism by which the processing of information was affected. This suggestion was supported by an additional pilot study. Under real working conditions a similar effect can be expected during relative motion between the driver and his visual surround, i.e. even with perfect vibro-isolation of the driver's seat.     

Discrimination of jittered sonar echoes by the echolocating bat,Eptesicus fuscus: The shape of target images in echolocation

1. Behavioral experiments with jittering echoes examined acoustic images of sonar targets in the echolocating bat, Eptesicus fuscus, along the echo delay or target range axis. Echo phase, amplitude, bandwidth, and signal-to-noise ratio were manipulated to assess the underlying auditory processes for image formation. 2. Fine delay acuity is about 10 ns. Calibration and control procedures indicate that this represents temporal acuity rather than spectral discrimination. Jitter discrimination curves change in phase when the phase of one jittering echo is shifted by 180 degrees relative to the other, showing that echo phase is involved in delay estimation. At an echo detectability index of about 36 dB, fine acuity is 40 ns, which is approximately as predicted for the delay accuracy of an ideal receiver. 3. Compound performance curves for 0 degrees and 180 degrees phase conditions match the crosscorrelation function of the echoes. The locations of both 0 degrees and 180 degrees phase peaks in the performance curves shift along the time axis by an amount that matches neural amplitude-latency trading in Eptesicus, confirming a temporal basis for jitter discrimination.     

Sequence diversity of pistil S-proteins associated with gametophytic self-incompatibility in Nicotiana alata

Summary In order to study the extent and nature of differences among various S-allele-associated proteins in N. alata, we carried out comparative studies of seven such proteins. We first isolated and sequenced cDNA clones for the S_z-, S_F11-, S₁-, and S_a-alleles, and then we compared the deduced amino acid sequences both of these four S-proteins and of three previously published S₂-, S₃-, and S₆-proteins. This comparison revealed (1) an average homology of 53.8% among the seven proteins and (2) two homology classes, with S_z and S_F11 in one class and S₁, S₂, S₃, and S₆ in the other class. There are 60 conserved residues, including 9 cysteines. Of the 144 variable residues, 50 were identified as hypervariable based on a calculation of their Similarity Indices. Although conserved, variable, and hypervariable residues are dispersed throughout the protein, some are clustered to form five conserved, five hypervariable, and a number of variable regions. Those variable sites which contain residues conserved within one class of S-proteins but different between classes might provide a clue to the evolutionary relationship of these two classes of S-proteins. The hypervariable residues, which account for sequence variability, may contribute to allelic specificity.     

ELISA – Nachweis von Pflanzenviren mit Hilfe unterschiedlicher Reagenzstreifen

Abstract Detection of plant viruses by ELISA using different reagent strips
A simplified immunoassay for detection of plant viruses under field conditions was developed on the basis of the direct double antibody sandwich ELISA using dry reagent carriers immobilized on PVC-supports which are arranged in a fan-like manner. The fan consists of a first reagent carrier with antivirus IgG covalently bound to cyanuric chloride-activated (CCA) paper while the second and third are filter papers impregnated with alkaline phosphatase labelled antivirus IgG and the fluorogenic subsrate, 4-methylumbelliferylphosphate, respectively. Performing the test, the first carrier is contacted with a liquid sample containing the virus to be identified, the second and third carriers is contacted with a liquid sample containing the virus to be identified the second and third carriers are sequentially put one upon the other and the reactions carried out. The virus is detected by the reacted substrate fluorescing under a UV-light. The applicability of the test is demonstrated with cucumber mosaic virus and potato virus X.