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.     

Characterization and molecular cloning of Bifidobacterium longum cryptic plasmid pMB1

The small cryptic plasmid pMB1 (1.9 kb), previously isolated from Bifidobacterium longum, has been characterized by physical mapping. Two cloning vectors, pMR3 and pDG7, carrying chloramphenicol and ampicillin resistances derived from pJH101, have been electroporated in Escherichia coli.     

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.     

Cytogenetic analysis of 400 sperm from three translocation heterozygotes

Summary Sperm chromosome complements were studied in three men who carried reciprocal translocations. A total of 400 sperm were karyotyped after in vitro penetration of hamster eggs: 217 sperm from t(2;9) (q21;p22), 164 from t(4;6) (q28;p23) and 19 from t(7;14) (q21;q13). All possible 22 and 31 meiotic segregations were observed for t(2;9) and t(4;6); for t(7;14) only 22 segregations were observed. For alternate segregations, the number of normal sperm was not significantly different from the number of sperm carrying a balanced form of the translocation in any of the translocations, as theoretically expected. The percentage of sperm with an unbalanced form of the translocation was 57% for t(2;9), 54% for t(4;6) and 47% for t(7;14). There was no evidence for an interchromosomal effect in any of the translocations since the frequencies of numerical abnormalities (unrelated to the translocation) were within the normal range of control donors. The frequencies of X- and Y-bearing sperm did not differ significantly from 50%. Results from a total of 17 reciprocal translocations studied by sperm chromosomal analysis were reviewed.     

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.     

Anatomy of antenno-cerebral pathways in the brain of the sphinx moth Manduca sexta

Summary In the moth Manduca sexta, the number and morphology of neuronal connections between the antennal lobes and the protocerebrum were examined. Cobalt injections revealed eight morphological types of neurons with somata adjacent to the AL neuropil that project in the inner, middle, and outer antenno-cerebral tracts to the protocerebrum. Neurons innervating the macroglomerular complex and many neurons with fibers in the inner antennocerebral tract have uniglomerular antennal-lobe arborizations. Most neurons in the middle and outer antenno-cerebral tracts, on the other hand, seem to innervate more than one glomerulus. Protocerebral areas receiving direct input from the antennal lobe include the calyces of the mushroom bodies, and circumscribed areas termed olfactory foci in the lateral horn of the protocerebrum and several other regions, especially areas in close proximity to the mushroom bodies. Fibers in the inner antenno-cerebral tract that innervate the male-specific macroglomerular complex have arborizations in the protocerebrum that are distinct from the projections of sexually non-specific neurons. Protocerebral neurons projecting into the antennal lobe are much less numerous than antennal-lobe output cells. Most of these protocerebral fibers enter the antennal lobe in small fiber tracts that are different from those described above. In the protocerebrum, these centrifugal cells arborize in olfactory foci and also in the inferior median protocerebrum and the lateral accessory lobes. The morphological diversity of connections between the antennal lobes and the protocerebrum, described here for the first time on a single-cell level, suggests a much greater physiological complexity of the olfactory system than has been assumed so far.     

Alteration of the synthesis of lipoxygenase in the early stages of soybean cotyledon culture

A detailed study of lipoxygenase (EC 1.13.11.12) synthesis in cotyledons of soybean [ Glycine max (L.) Merr. cv. Century] cultured in vitro for up to 40 h showed that synthesis of this protein, measured by in vivo [35S]-methionine labelling in connection with immunological methods and cell-free translation of mRNA, underwent a large transient reduction in the first 4 h of culturing and gradually increased in the following 36 h. Northern blot hybridizations with lipoxygenase cDNA clones showed that the decrease in translational activity was the consequence of a considerable reduction in lipoxygenase mRNA in the cotyledons. From these results we conclude that the transient decline in lipoxygenase synthesis in excised soybean cotyledons is regulated at the RNA level. Similarly judged from the analysis of patterns of uni-dimensional gel electrophoresis, the synthesis of a few other polypeptides decreased during the first 4 h of culture as well, while several others increased; in cotyledons cultured for 20 to 40 h the protein-synthesis pattern had returned to that in freshly excised cotyledons. An acclimation period of ca 1 day seems to be needed for isolated soybean cotyledons to stabilize and to resume regular RNA and protein synthesis.     

Deglycosylation of a lectin intermediate during assembly of ConA

Summary Metabolic labelling of immature jackbeans (Canavalia ensiformis) has been used in a pulse-chase study to determine changes in the glycosylation pattern of polypeptides during the assembly of Concanavalin A. In an analysis that allowed the identification of 7 intermediates, only the first precursor form of the lectin was labelled with D-[U-¹⁴C]-glucosamine. These results indicate that processing of the lectin involves a novel deglycosylation event in which an N-linked oligosaccharide is removed from a protein in the absence of proteolysis.Abbreviations endo H endo -N-acetylglucosaminidase H - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis - ConA Concanavalin A     

Chromosome aberrations (CA), sister-chromatid exchanges (SCE) and mitogen-induced blastogenesis in cultured peripheral lymphocytes from 48 control individuals sampled 8 times over 2 years

Confidence in the measurement of positive effects determined by monitoring of environmentally or occupationally exposed individuals can be enhanced by a knowledge of the normal variability in these endpoints in the general population. Confounding effects can be determined and study interpretation improved by correlation of this variability with various lifestyle factors such as sex and age of donor, smoking and drinking habits, viral infections, exposure to diagnostic X-rays, etc.

8 blood samples were taken from each of 24 male and 24 female volunteers over a period of 2 years. Questionnaires pertaining to lifestyle were completed at the time of each sampling. Whole blood was cultured and slides prepared for CA or SCE analysis. Separated mononuclear cells were cultured with a range of phytohaemagglutinin concentrations and the maximum level of mitogen-induced blastogenesis was determined by measurement of [³H]thymidine uptake.

There was a significant effect of both year and season of sampling for all 3 endpoints. No significant effects in any of the 3 endpoints were found with respect to sex or age of donor nor any of the other lifestyle factors, although SCE frequency and mitogen-induced blastogenesis were nearly always higher in females than males. These results point to the need for concurrent sampling of controls with exposed populations.