The wiring-in of neural nets revisited

Earlier and some recent ideas about the possible modes of specification of the wiring-in of nervous systems are reviewed in the light of older and several recent experiments, and some new ideas are suggested. It is argued that certain general principles, notably the postulated ‘principle of alternative matching’ (PALMA) and a suggested and related ‘kaleidoscopic effect’ (KALEF), as well as the notion of an ‘extracellular guidance network’ (ECGN), are in good agreement with recent and older findings concerning axonal guidance during neural wiring-in. It seems possible that by means of genetically programmed processes, neurons become systematically combinatorially labelled to such a degree that possibly all neurons areuniquely specified, as regards the combination oftypes of cell labels they make. Yet, there remains considerable freedom as regards the modes of arrangements of cell labels within cell surface membranes and the KALEF permits to overcome apparent difficulties that confronted earlier versions of the cell labelling hypotheses (cf. Edelman,Science 219, 450–457, 1983, for mention of such difficulties). Apart from label specification, neural development seems to depend on trophic factors, which are also essential for the maintenance of the developed nervous system. The systematic programmes for cell labelling, apart from generating all the required neurons, also produces inappropriate neurons and synaptic connections. These are got rid of by systematic cell death and/or atrophy of inappropriate synapses and/or elimination of inappropriate axon collaterals. The resulting neural net seems then very specifically wired-in for each species, apparently without redundant neurons.     

A possible role for altered poly(adenosine diphosphoribose)-synthesis in the sensitivity of human head and neck squamous carcinoma cells to ionizing radiation

Cytotoxicity, extent of DNA double-strand breaks, and stimulation of poly(adenosine diphosphoribose)-synthesis were measured in two established human head and neck squamous carcinoma cell lines (183A and 1483) following x-irradiation. The 1483 cell line was 15-fold more resistant to x-ray-mediated cytotoxicity than was the 183A cell line. X-ray-mediated DNA strand cleavage also differed in these two cell lines with the absolute frequency of DNA double-strand breaks in the sensitive cells 183A cells being twice that in the resistant 1483 cell line. No detectable stimulation of poly(adenosine diphosphoribose)-synthesis was measured in the sensitive 183A cells whereas a marked increase in incorporation of [3H]-nicotinamide adenine dinucleotide was readily detected following x-irradiation of the resistant 1483 cells. These findings suggest a possible role of altered poly(adenosine diphosphoribose)-synthesis in the sensitivity of human head and neck squamous carcinoma cells to ionizing radiation.     

Phenothiazine-N-carbonyl chloride, a specific inactivator of chymotrypsin

Phenothiazine-N-carbonyl chloride inactivated chymotrypsin and trypsin by means of a 1:1 stoicheiometric reaction. Its reaction with chymotrypsin was 29 times as fast as that with trypsin and was inhibited by indole. The reaction of phenothiazine-N-carbonyl chloride with chymotrypsin resembled an enzyme-substrate reaction in which the deacylation step is rate-limiting. Slow deacylation occurred, resulting in complete regeneration of active enzyme in 15h. The pH-rate profile of the inactivation process had a maximum at pH7.8. These data and other evidence indicate that the reaction of phenothiazine-N-carbonyl chloride with chymotrypsin exhibits ;kinetic specificity'. Therefore any hypothesis that attempts to describe the topography of the active site of chymotrypsin should take into account the reactivity of phenothiazine-N-carbonyl chloride. The above findings, as well as recent reports of others, are examined within the context of a hypothesis given in an earlier paper (Erlanger, 1967).     

Testicular glycoprotein biosynthesis stimulated byin vivo administration of follicle stimulating hormone

Summary In vivo administration of follicle-stimulating hormone causes the increase of the in vitro incorporation of D-[1-³H] glucose, D-[¹⁴C-(U)] glucosamine or D-[2-³H] mannose into glycoproteins of normal or Sertoli cell enriched testes of immature rats. This effect is blocked by preincubation of the testes with tunicamycin.Abbreviations FSH follicle stimulating hormone - KRB Krebs Ringer bicarbonate buffer - TCA trichloroacetic acid - SCE testes Sertoli cell enriched testes     

Changes in protein kinase activity in rat testes during development.

Protein kinase activity in rat testes remained fairly constant from day 16 1/2 of embryonic life up to 10 days after birth. At the 21st postnatal day a nadir of activity was observed, and after an increase at 35 days of age a decrease in activity at 60 days was seen. The enzyme reached maximal specific activity in the testes of 90-day-old rats.     

The Brassica napus seed microbiota is cultivar-specific and transmitted via paternal breeding lines

Seed microbiota influence germination and plant health and have the potential to improve crop performance, but the factors that determine their structure and functions are still not fully understood. Here, we analysed the impact of plant-related and external factors on seed endophyte communities of 10 different oilseed rape (Brassica napus L.) cultivars from 26 field sites across Europe. All seed lots harboured a high abundance and diversity of endophytes, which were dominated by six genera: Ralstonia, Serratia, Enterobacter, Pseudomonas, Pantoea, and Sphingomonas. The cultivar was the main factor explaining the variations in bacterial diversity, abundance and composition. In addition, the latter was significantly influenced by diverse biotic and abiotic factors, for example host germination rates and disease resistance against Plasmodiophora brassicae. A set of bacterial biomarkers was identified to discriminate between characteristics of the seeds, for example Sphingomonas for improved germination and Brevundimonas for disease resistance. Application of a Bayesian community approach suggested vertical transmission of seed endophytes, where the paternal parent plays a major role and might even determine the germination performance of the offspring. This study contributes to the understanding of seed microbiome assembly and underlines the potential of the microbiome to be implemented in crop breeding and biocontrol programmes.     

Multiple rough endoplasmic cisternae in the endocrine pancreas of the adult rat

Multiple rough endoplasmic cisternae were found in the parenchymatous cells of the endocrine pancreas of the adult rat (alpha, beta, D and intermediary cells) and were especially developed in beta cells. They are considered to be normal constituents of the parenchymatous cells of the endocrine pancreas. Their close proximity to Golgi dictyosomes and the accumulation of secretory material sometimes seen at the extremities of such cisternae, suggest that they may have a role in the secretory activity of these endocrine cells.