Metabolic pathways of glucose during germination of Bacillus megaterium QM B1551 spores were studied by using specifically labeled glucose and gluconate. The Embden-Meyerhof pathway, the pentose cycle, and the direct oxidation route of glucose to gluconate (the gluconate pathway) were all operative at this stage; among those, gluconate accumulation was most predominant, especially in the early stage. Potassium fluoride, an enolase inhibitor, abolished the catabolism by the Embden-Meyerhof pathway totally without affecting gluconate accumulation. Under these conditions glucose was exclusively oxidized to gluconate. Gluconate thus accumulated could be metabolized further via phosphorylation by gluconate kinase. Remarkable gluconate accumulation was also demonstrated in several other spores requiring alanine as an effective germinant. NADH formed by the direct glucose oxidation may serve as a initial ATP source to phosphorylate glucose in germinating spores.Although glucose catabolism is not a prerequisite for triggering spore germination (4, 15, 22), it becomes detectable immediately after the initiation of germination (10,15,21,22). Oxygen consumption (4,7,8), ATP production (4, 12, 21), and other activities involved in energy metabolism (18,19) are also greatly enhanced by glucose catabolism in germinated (or germinating) spores. Previous studies (5-8, 12, 14, 21) suggest that three possible pathways are operative during germination, (i) the Embden-Meyerhof (EM) pathway, (ii) the pentose cycle, and (iii) a pathway which can oxidize glucose to gluconate without prior phosphorylation. The last pathway, which is catalyzed by glucose dehydrogenase (GDH, EC 1.1.1.47) coupling with NAD(P) reduction, is unique to spores; gluconate thus formed may be metabolized further, presumably by the pentose cycle or the EntnerDoudoroff pathway. This pathway is designated as the gluconate pathway in this study.Generally, to investigate metabolic pathways, the use of specifically labeled glucose seems to be of primary importance; nonetheless only a few attempts have been made in bacterial spores. As far as we know, a plausible determination was made only in Bacillus cereus T spores (6); Goldman and Blumenthal concluded the predominance of the EM pathway by using [1-14C]glucose and [6-14C]glucose. In Bacillus megaterium QM B1551 spores, the primary role of the EM pathway was also stressed by Komberg and his coworkers (12, 21), mainly based on the indirect findings. Contrary to this, we found a remarkable accumulation of gluconate in B. megaterium QM B1551 (10), which led us to make more extensive studies before drawing any definite conclusion.In this study we attempted to determine the possible pathways of glucose catabolism more directly, especially to evaluate the most predominant pathway during germination of B. megaterium QM B1551 spores. A possible role of the gluconate pathway in ATP production is also discussed. * Corresponding author. MATERIALS AND METHODSBacterial strains and spore production. Unless indicated otherwise, s...
A new rat strain has been developed, in which a spontaneous cataract occurs without exception at 3-4 months after birth and matures completely at 4-6 months of age, indicating that this rare strain possesses a maturity-onset cataract. In the present report, histological data are presented and discussed.
The Ihara epileptic rat (IER) is a mutant model with limbic-like seizures whose pathology and causative gene remain elusive. In this report, via linkage analysis, we identified Down syndrome cell adhesion molecule-like 1(Dscaml1) as the responsible gene for IER. A single base mutation in Dscaml1 causes abnormal splicing, leading to lack of DSCAML1. IERs have enhanced seizure susceptibility and accelerated kindling establishment. Furthermore, GABAergic neurons are severely reduced in the entorhinal cortex (ECx) of these animals. Voltage-sensitive dye imaging that directly presents the excitation status of brain slices revealed abnormally persistent excitability in IER ECx. This suggests that reduced GABAergic neurons may cause weak sustained entorhinal cortex activations, leading to natural kindling via the perforant path that could cause dentate gyrus hypertrophy and epileptogenesis. Furthermore, we identified a single nucleotide substitution in a human epilepsy that would result in one amino acid change in DSCAML1 (A2105T mutation). The mutant DSCAML1A2105T protein is not presented on the cell surface, losing its homophilic cell adhesion ability. We generated knock-in mice (Dscaml1A2105T) carrying the corresponding mutation and observed reduced GABAergic neurons in the ECx as well as spike-and-wave electrocorticogram. We conclude that DSCAML1 is required for GABAergic neuron placement in the ECx and suppression of seizure susceptibility in rodents. Our findings suggest that mutations in DSCAML1 may affect seizure susceptibility in humans.
We analyzed the mode of inheritance of cataract in the Ihara epileptic rat (IER) by crossing experiments, and mapped cataract-related genes by linkage analysis. Cataract did not develop in the F1 animals, but it developed in both male and female animals of backcross and F2. The occurrence rate of cataract was 48.5% in the backcross progeny and 19.4% in the F2 progeny. Thus, the character was considered to be inherited by the autosomal recessive mode. We found two groups that differed according to the time of onset among the backcross and F2 progeny: an early-onset group (EOG), in which cataracts developed by about 4 months after birth, and a late-onset group (LOG), in which cataracts developed 8 months or more after birth. Linkage analysis indicated the presence of one cataract gene each on Chromosome (Chr) 8 and Chr 15, and the cataract was demonstrated to be governed by more than one gene. The gene on Chr 8 was named Catil, and that on Chr 15. Cati2. Catil was involved in the occurrence of cataract, and the conditions required for cataract to develop were Cati1i/Cati1i or Cati1i/Cati1w. However, in the cataract rats with Cati1i/ Cati1w, the allele of Cati2 was always Cati2i/Cati2i. Cati2 was involved in the timing of onset of the cataract, and the precondition for early onset was Cati2i/Cati2i.
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