Control of echolocation pulses by neurons of the nucleus ambiguus in the rufous horseshoe bat,Rhinolophus rouxi

Horseradish peroxidase was applied by inotophoretic injections to physiologically identified regions of the laryngeal motor nucleus, the nucleus ambiguus in the CF/FM bat Rhinolophus rouxi. The connections of the nucleus ambiguus were analysed with regards to their possible functional significance in the vocal control system, in the respiration control system, and in mediating information from the central auditory system. The nucleus ambiguus is reciprocally interconnected with nuclei involved in the generation of the vocal motor pattern, i.e., the homonomous contralateral nucleus and the area of the lateral reticular formation. Similarly, reciprocal connections are found with the nuclei controlling the rhythm of respiration, i.e., medial parts of the medulla oblongata and the parabrachial nuclei. Afferents to the nucleus ambiguus derive from nuclei of the 'descending vocalization system' (periaqueductal gray and cuneiform nuclei) and from motor control centers (red nucleus and frontal cortex). Afferents to the nucleus ambiguus, possibly mediating auditory influence to the motor control of vocalization, come from the superior colliculus and from the pontine nuclei. The efferents from the pontine nuclei are restricted to rostral parts of the nucleus ambiguus, which hosts the motoneurons of the cricothyroid muscle controlling the call frequency.     

Processing of yeast mitochondrial RNA: involvement of intramolecular hybrids in splicing of cob intron 4 RNA by mutation and reversion

Revertants have been obtained from six mutants of the box9 cluster, which are supposed to be defective in RNA splicing as a result of alterations in a splice signal sequence. This sequence is in the 5' part of intron 4 of the cob gene, 330 to 340 bp downstream from the 5' splice site. Sequencing reveals that reversion to splicing competence is achieved by restoration of the wild-type box9 sequence; by creation of novel box9 sequences; and by introduction of a second site or suppressor mutation (sup-) compensating for the effect of the primary box9- mutation. The sup- mutation alters a sequence in intron 4,293 bp upstream from the box9- primary mutation. The box9 sequence and this upstream sequence can base pair to form an intramolecular hybrid in intron RNA in which box9- and sup- are compensatory base pair exchanges (G----A and C----U, respectively). Thus intramolecular hybrid structures of intron RNA are essential for RNA splicing.     

Germline integration of moloney murine leukemia virus at the Mov13 locus leads to recessive lethal mutation and early embryonic death

Thirteen mouse substrains genetically transmitting the exogenous Moloney murine leukemia virus (M-MuLV) at a single locus (Mov locus) have been derived previously. Experiments were performed to investigate whether homozygosity at the Mov loci would be compatible with normal development. Animals heterozygous at an Mov locus were mated, and the genotype of the offspring was analyzed. From parents heterozygous at the loci Mov1 to Mov12, respectively, homozygous offspring were obtained with the expected Mendelian frequency. In contrast, no homozygous offspring or embryos older than day 15 of gestation were obtained from parents heterozygous at the Mov13 locus. When pregnant Mov13 females at day 13 and day 14 of gestation were analyzed, approximately 25% of the embryos were degenerated. Genotyping revealed that these degenerated embryos were invariably homozygous and the normal appearing embryos were either heterozygous or negative for M-MuLV. These results suggest that integration of M-MuLV at the Mov13 locus leads to insertion mutagenesis, resulting in embryonic arrest between day 12 and day 13 of gestation. It is possible that the Mov13 locus represents a gene or gene complex involved in the early embryonic development of the mouse.     

The influence of spermine on the structural dynamics of yeast tRNA

A tRNA^Phe derivative carrying ethidium at position 37 in the anticodon loop has been used to study the effect of spermine on conformational transitions of the tRNA. As previously reported (Ehrenberg, M., Rigler, R. and Wintermeyer, W. (1979) Biochemistry 18, 4588–4599) in the tRNA derivative the ethidium is present in three states (T₁–T₃) characterized by different fluorescence decay rates. T-jump experiments show two transitions between the states, a fast one (relaxation time 10–100 ms) between T₁ and T₂, and a slow one (100–1000 ms) between T₂ and T₃. In the presence of spermine the fast transition shows a negative temperature coefficient indicating the existence of a preequilibrium with a negative reaction enthalpy. Spermine shifts the distribution of states towards T₃, as does Mg²⁺, but the final ratio obtained with spermine is higher than with Mg²⁺, which we tentatively interpret to mean that spermine stabilizes one particular conformation of the anticodon loop.     

The influence of spermine on the structural dynamics of yeast tRNAPhe

A tRNA^Phe derivative carrying ethidium at position 37 in the anticodon loop has been used to study the effect of spermine on conformational transitions of the tRNA. As previously reported (Ehrenberg, M., Rigler, R. and Wintermeyer, W. (1979) Biochemistry 18, 4588–4599) in the tRNA derivative the ethidium is present in three states (T₁–T₃) characterized by different fluorescence decay rates. T-jump experiments show two transitions between the states, a fast one (relaxation time 10–100 ms) between T₁ and T₂, and a slow one (100–1000 ms) between T₂ and T₃. In the presence of spermine the fast transition shows a negative temperature coefficient indicating the existence of a preequilibrium with a negative reaction enthalpy. Spermine shifts the distribution of states towards T₃, as does Mg²⁺, but the final ratio $\text{[}\text{T}{}_2\text{]}\text{[}\text{T}{}_1\text{]}$ obtained with spermine is higher than with Mg²⁺, which we tentatively interpret to mean that spermine stabilizes one particular conformation of the anticodon loop.     

Beiträge zur funktionellen Morphologie der Neurohypophyse

Zusammenfassung Beidseitige Adrenalektomie und Hypophysektomie führen bei der Ratte zu gleichartigen histologischen Veränderungen in der Zona externa infundibuli. In beiden Fällen treten in der normalerweise weitgehend goniorinegativen Zona externa infundibuli große Mengen gomoripositiver Granula auf. Sie scheinen Fasern anzugehören, die senkrecht zur Längsachse des Infundibulum verlaufen.Die Befunde werden als weiterer Hinweis dafür betrachtet, daß die gomoripositiven Substanzen der Zona externa infundibuli eine Bedeutung für die Steuerung der Nebennierenrindenfunktion haben.

---

Studies on the functional morphology of the neurohypophysisII. Comparison of histological changes in the median eminence of the rat after bilateral adrenalectomy and hypophysectomy

Summary Bilateral adrenalectomy and hypophysectomy in the rat produce similar histological changes in the outer layer of the median eminence. In both cases, abundant gomoripositive granules are observed in the outer layer, which normally reacts gomorinegative. The gomoripositive granules seem to belong to fibres running vertically through the infundibulum.These findings are regarded as a further indication, that the gomoripositive substances of the outer layer of the median eminence play a significant role in controlling adrenocortical function.

     

MECHANISM OF TOXICITY AND RESISTANCE TO D-MANNOSE AND CERTAIN DERIVATIVES IN SPECIES OF THE GENUS CHLORELLA BEIJ.12

d -Mannose and related derivatives, e.g., d -glucosa-mine and 2-deoxy-<d -glucose, blocked autotrophic and heterotrophic growth of several species of the genus Chlorella. Manometric studies showed differences in the effects of these compounds on substrate-induced O₂ uptake, indicating different modes of action. In a clonal culture, shaken in the light, mannose produced a lag phase of 7 days during which only ca. 0.05% of the cells continued to grow. From, these cells a resistant strain was isolated. Prolonged incubation in glucose media in darkness brought about a reversion to the sensitive condition. These metabolic shifts could not be explained on the basis of adaptation or nuclear gene mutation because of the permanency and high frequency of the resistant cells. The mechanism was suggested to be cytoplasmically controlled. The shift in sensitivity to the inhibitors was considered a reproducible characteristic of certain species. In contrast to the normal, rnannose-sensitive strain of C. infusionum var. acetophila, cells of a resistant strain carried a gelatinous envelope. The resistant strain utilized glucosamine as a source of nitrogen, but lost the capacity to use sugars for dark growth. This was reflected in drastic reductions in glucose and mannose uptake. The hexokinase activities in cell extracts were equivalent for both strains. The resistant strain did not accumulate hexose-6-phos-phates and showed an increased phosphatase activity at an alkaline pH.