The pineal body: Site of extraocular perception of celestial cues for orientation in the tiger salamander (Ambystoma tigrinum)

Summary Tiger salamanders (Ambystoma tigrinum) trained to orient in a particular compass direction under the sun fail to orient in the trained direction if they are (i) eyeless and simultaneously have the brain covered with opaque plastic or are (ii) eyeless and pinealectomized (Fig. 1–2, Table 1). Salamanders with either the eyes or the pineal intact and unobstructed continue to orient in the trained direction. These data strongly support the hypothesis that the pineal body is an effective extraocular photoreceptor (EOP) for compass orientation in tiger salamanders.We thank M.P. Farrell for developing computer programs for data analysis. B. Bailey and R. Walton helped conduct tests. Financial support was provided for separate phases of this research by a Biomedical Science Support Grant (NIH FR 07033-05) and NSFgrants GB-30647 and BMS 75-18693 to K. Adler and an Indiana Academy of Science Research Grant, a postdoctoral fellowship (NSF GU-2058), a Miami University Research Grant and an NSF grant (GB-41102) to D.H. Taylor.     

What chance did Mendel's experiments give him of noticing linkage?

The a priori probability of noticeable linkage among all conceivable experiments of the size reported by Mendel cannot reasonably be taken as greater than 24-36 per cent; and therefore, the frequently heard opinion that his chances of encountering linkage were high, approaching 99-4 per cent, appears to be mistaken.     

Mass spectra of underivatized peptide amides related to substance P

Mass spectra of underivatized hexa- and heptapeptide amides related to Substance P have been obtained with a conventional electron ionization mass spectrometer using sample vaporization from a tungsten wire by the technique of rapid heating, proton transfer ionization using ammonia, and photoplate recording of spectra. These spectra exhibit little evidence of sample pyrolysis and are readily interpreted to yield amino acid sequences.     

Variation in satellite DNA from some higher plants

Pure satellite DNAs were prepared as minor components after centrifugation to equilibrium on CsCl gradients. A single satellite DNA band was isolated from flax (Linum usitatissimum) DNA and two bands were resolved in cucumber (Cucumis sativus) DNA. These apparently homogeneous components of the plant genomes were further analyzed by thermal denaturation and renaturation. The flax satellite DNA appeared homogeneous on thermal denaturation but was shown to contain several components of renaturation. The two cucumber satellite DNAs were different from each other, but both showed at least two components in denaturation and renaturation analyses. Renaturation in the three satellites, particularly in flax, was inaccurate, indicating a considerable degree of sequence divergence. Although each satellite contained quite large amounts of simple repetitious sequences, a residual heterogeneous DNA fraction was always present. It is considered that this was too large a portion of the satellite DNA to be due to organelle or ribosomal DNA in cucumber. The latter possibility is precluded in flax, where the satellite is completely resolved in buoyant density from both organelle and ribosomal DNA.     

An evaluation of sodium dodecyl sulfate-polyacrylamide gel electrophoresis for the identification of microsporidia

Microsporidian spore polypeptides separated with sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) can be used to identify isolates of microsporidia. The spore polypeptides separated with SDS/PAGE provided unique, reproducible electrophoretic profiles which were not influenced by host species or the temperature at which the host larvae were maintained for development. Furthermore, host proteins were not detected in electrophoretic profiles of the spore polypeptides. Spore mixtures of two microsporidian species can be detected when the spore polypeptides of either or both species have been previously separated with SDS/PAGE.     

Analysing the patterning of a sequence of discrete behavioural events

Existing techniques for analysing the organization of behavioural events are discussed. Cluster analysis, mutual replaceability, ‘melody’ detection and Markov analyses are examined in order to discover the validity and usefulness of the concepts searched for by each technique, and the mathematical and statistical background of the techniques is scrutinized. Some new techniques, designed to search for and detect possible important sequential organization patterns, are described in the light of the previous criticisms. Of these techniques, the Pre-post-state Histogram (PPSH)—a multi-order Markov graphical analysis—would appear to be the most important for future work, especially when used in conjunction with the other techniques described.     

Secretion of lysosomal enzymes by human placental villi in vitro

Summary Chorionic villi from first trimester and term human placentas have been incubated in vitro and shown to release the lysosomal enzymes, -hexosaminidase, -glucosidase and -gluctlronidase. There was negligible release of the cytoplasmic enzyme, lactate dehydrogenase, under the same conditions. The first trimester villi released proportionally more of their lysosomal enzyme content than did the term villi. Extracellular levels of -hexosaminidase were raised and those of -glucosidase and, -glucuronidase were lowered when tissue was incubated with 1 M colchicine, suggesting that microtubules are involved in the control of lysosomal enzyme release from placental villi.