Periodicity and chaos in the response of Halobacterium to temporal light gradients

Halobacteria spontaneously reverse their swimming direction about every 10 s. This periodicity can be altered by light stimuli. We found that temporal exponential changes in light intensity, depending on wavelength and sign, lengthened or shortened the intervals between reversals. Within a limited range of steepness, light gradients enforced a new stable periodicity upon the system. Outside this range, they caused period doubling or induced a sequence of reversal events without any obvious regularity. An analysis of a functional relationship between apparently irregular periods by plotting each period as a function on the preceding one yielded a clearly discernible non-random structure, which shows some similarities to the one obtained by a model calculation for a periodically perturbed limit cycle oscillator. These results indicate that external forcing of the system may generate chaos. When the decay of intracellular sensory signals is delayed by inhibition of protein methylation the transition from periodic to aperiodic behavior occurs at a lower steepness of the gradient. We therefore assume that the generation of either periodic or deterministic chaotic behavior is determined by the relation between the signal lifetime and the frequency of stimulus inputs. The strong indications for transitions from periodic to chaotic behavior can be regarded as a further support of our hypothesis that the behavioral pattern of Halobacterium is controlled by an endogeneous oscillator.     

Acetylcholinesterase activity in antennal receptor neurons of the sphinx moth Manduca sexta

Summary We have used a cytochemical technique to investigate the distribution of acetylcholinesterase (AChE) activity in the antenna of the sphinx moth Manduca sexta. High levels of echothiophate-insensitive (presumably intracellular) AChE activity were found in six different types of antennal receptors localized in specific regions of the three antennal segments of the adult moth. Mechanosensory organs in the scape and pedicel, the Böhm bristles and Johnston's organ, are innervated by AChE-positive neurons. In each annulus of the antennal flagellum, AChE-positive neurons are associated with six sensilla chaetica and a peg organ, probably a sensillum styloconicum. At least 112 receptor neurons (8–10 per annulus) innervating the intersegmental membranes between the 14 distalmost annuli also exhibit high levels of echothiophate-resistant AChE. In addition, each annulus has more than 30 AChE-positive somata in the epidermis of the scale-covered (back) side of the flagellum, and 4 AChE-positive somata reside within the first annulus of the flagellum. Since none of the olfactory receptor neurons show a high level of echothiophateresistant AChE activity, and all known mechanoreceptors are AChE-positive, apparently intracellular AChE activity in the antenna correlates well with mechanosensory functions and is consistent with the idea that these cells employ acetylcholine as a neurotransmitter.     

Human metallothionein genes: structure of the functional locus at 16q13

The functional human metallothionein (MT) genes are located on chromosome 16q13. We have physically mapped the functional human MT locus by isolation and restriction digest mapping of cloned DNA. The mapped region contains all sequences on chromosome 16 that hybridize to metallothionein gene probes and comprises 14 tightly linked MT genes, 6 of which have not been previously described. This analysis defines the genetic limits of metallothionein functional diversity in the human genome.     

Entrainment and temperature dependence of the response oscillator in Halobacterium halobium.

Halobacterium halobium spontaneously reverses its swimming direction with a frequency of about 0.1 s-1. The self-sustained periodicity can be entrained by rhythmic light stimuli within a limited range between 0.13 and 0.3 s-1. Increase of temperature increases the reversal frequency and shortens the time to reach maximal responsiveness to attractant stimuli during a cycle. Also, the period of absolute refractoriness to repellent stimuli is shortened. The results illustrate characteristic properties of biological oscillators.     

Studies on the pharmacokinetics of ZK 96 480, a novel PGI2-mimetic, in rat and cynomolgus monkey

ZK 96 480 (5- [(E)-(1S,5S,6S,7R)-7-Hydroxy-6-[(3S,4S)-3-hydroxy-4- methylnona-1,6-diinyl]-bicyclo [3.3.0] octan-3-yliden]-3-oxapentanoic acid) is a novel PGI2-derivative. The pharmacokinetics and biodegradation of the new drug were studied in rat and cynomolgus monkey after i.v. and i.g. administration of 3H-labelled ZK 96 480. In a rat liver perfusion experiment ZK 96 480 remained unchanged over 90 min. Following i.v. and i.g. dosing, the metabolic pattern in the urine and the methanolic extracts of homogenized, freeze-dried feces samples revealed almost exclusively unchanged compound in both animal species. After i.v. treatment, drug disposition in the plasma exhibited half-lives of 0.14 h and 4.3 h in rat and 0.07 h, 0.4 h and 2.5 h in monkey. Total clearance was 14 ml/min/kg in the latter species. Excretion of 3H-label was mainly fecal in rat, but exhibited no preferred route in monkey. On the basis of the urinary excretion of 3H-label and unchanged drug both gastro-intestinal absorption and bioavailability were complete. Whole body autoradiographs in rat demonstrated that there was no specific enrichment of radiolabel in any tissue or organ. The present results demonstrate that ZK 96 480 is an orally available and metabolically stable carbacyclin derivative in female rats and monkeys.     

Localization of Arbutin in Pyrvs by Means of Alkaline P-Phenylenediamine

A reagent composed of 0.2% p-phenylenediamine in 2 N NH₄OH was used for the cytochemical demonstration of arbutin in plant tissue. Sections of fresh tissue were cut at 25-50 μ, mounted in a drop of the reagent, and allowed to stand uncovered 15-20 min before applying a coverslip. Arbutin stained dark blue to dark purple and was easily distinguished from other constituents of the cell, such as chlorogenic acid, isochlorogenic acid, caffeic acid, and quinic acid, which stained yellow, yellow-green, red or brown in color. The limit of sensitivity of the p-phenylenediamine-arbutin reaction was 1:100,000, as determined by spot-plate tests.     

A new peptide in the FMRFamide family isolated from the CNS of the hawkmoth, Manduca sexta

We have purified a FMRFamide-like peptide from extracts of brain-subesophageal ganglion of the moth, Manduca sexta. The purification was monitored with a new, competitive ELISA, and accomplished with ion exchange and reverse-phase HPLC. The peptide structure was determined by a combination of tandem mass spectrometry and automated Edman degradation. The amino acid sequence of the peptide is less than Glu-Asp-Val-Val-His-Ser-Phe-Leu-Arg-Phe-amide (pEDVVHSFLRF-NH2). In a separate purification, an identical peptide was isolated from extracts of brain-associated neurohemal structures. We have named this peptide ManducaFLRFamide, to indicate its homology with other members of the "FMRFamide" family. In bioassays, chemically synthesized peptide increased the force of neurally evoked contractions in the major power-producing flight muscles, the dorsal longitudinal muscles. This observation suggests that hormonally released ManducaFLRFamide may play a role in sustaining or promoting the flight behavior necessary for mate-seeking (in males) or oviposition (in females) in sphingid moths.