Virulence and pathogenicity of human and environmental isolates of Cladosporium carrionii in new born ddY mice

Three strains of Cladosporium carrionii, two human isolates and one from a xerophilous plant, were used to study the effect of culture conditions in 106 newborn ddY mice. Growth in a complex medium (YPG) and a basal synthetic medium (BSM) was compared. Filamentous forms developed during static incubation while conidia were readily formed with shaking. Mice inoculated intraperitoneally were sacrified and autopsied after 4 weeks. Mortality was related only to sporulated exponential phase growing cells. Invasiveness ability was preserved in all experimental conditions. BSM medium that inhibited exopigment formation appeared more suitable than YPG to obtain intact cells for further studies.Biochemical and physiological alteration associated with shape changes during differentiation of vegetative cells into spores could play an important role in virulence of C. carrionii     

Calcium-sensitive cls4 mutant of Saccharomyces cerevisiae with a defect in bud formation.

A calcium-sensitive cls4 mutant of Saccharomyces cerevisiae ceased dividing in the presence of 100 mM CaCl2, producing large, round, unbudded cells. Since its DNA replication and nuclear division still continued after interruption of normal budding, the cls4 mutant had a defect in bud formation in Ca2+-rich medium. Its calcium content and calcium uptake activity were the same as those of the wild-type strain, suggesting that the primary defect of the mutation was not in a Ca2+ transport system. Genetic analysis showed that the cls4 mutation did not complement the cdc24-1 mutation, which is known to be a temperature-sensitive mutation affecting bud formation and localized cell surface growth at a restrictive temperature. Moreover, cls4 was tightly linked to cdc24, and a yeast 3.4-kilobase-pair DNA fragment carrying both the CLS4 and CDC24 genes was obtained. These results suggest that the cls4 mutation is allelic to the cdc24 mutation. Thus, Ca2+ ion seems to control bud formation and bud-localized cell surface growth.     

A New Myelin-Deficient Mutant Hamster: Biochemical and Morphological Studies

Biochemical and morphological studies were done on a new trembling mutant hamster CBB. The yield of myelin from the mutant was 30 and 40% of the control at 46 and 140 days of age, respectively, but myelin composition and 2',3'-cyclic nucleotide-3'-phosphohydrolase (CNPase) activity were normal. Morphologically, about 18% of the axons were myelinated in the mutant optic nerve at 46 days of age, in which the myelinated fibers were those with larger diameters (more than 0.6 micron), while the control had a peak at 0.4 micron in diameter. The ultrastructure and thickness of compact myelin lamellae in the mutant were normal. Myelination and the structure of peripheral nerve myelin appeared normal. The results indicate that the essential defect is the delay and arrest of myelination in the CNS, which is probably caused by either a decreased rate of synthesis of myelin components in oligodendrocytes or a defect in the oligodendrocyte-axon recognition in smaller axons.     

(6R)-Tetrahydrobiopterin Increases the Activity of Tryptophan Hydroxylase in Rat Raphe Slices

The effects of (6R)- and (6S)-tetrahydrobiopterin (BPH4), tetrahydroneopterin, and 6-methyltetrahydropterin on the activity of tryptophan hydroxylase were investigated in rat raphe slices. The activity of tryptophan hydroxylase was estimated by measurement of 5-hydroxytryptophan (5-HTP) formation under inhibition of aromatic L-amino acid decarboxylase with use of HPLC-fluorometric detection. (6R)-BPH4 (the naturally occurring form) at 42 microM, tetrahydroneopterin at 50 microM, and 6-methyltetrahydropterin at 100 microM increased tryptophan hydroxylase activity to 350, 145, and 146% of control values, respectively. (6S)-BPH4, however, had no significant effects on tryptophan hydroxylase activity. These results suggest that tryptophan hydroxylase is subsaturating in vivo for the naturally occurring cofactor, (6R)-BPH4, and that the concentration of (6R)-BPH4 may play an important role for the regulation of tryptophan hydroxylase activity in vivo.     

Determination of membrane potential with lipophilic cations: correction of probe binding

The binding of lipophilic ions to the membrane of envelope vesicles from Halobacterium halobium was examined in the absence and presence of membrane potential. The lipophilic ions used constitute a homologous series of (Phe)₃-P⁺-(CH₂)_n-CH₃ (n = 0–4) and tetraphenylphosphonium (TPP⁺). In the absence of membrane potential, the amounts of binding were proportional to the probe concentration in the medium when the concentration is dilute. Upon illumination, interior negative membrane potential is generated which induces the uptake of phosphonium cation probe. 2 μM were employed as the initial probe concentration. The real membrane potential was evaluated by means of extrapolation to the state of no binding: The values of for various probes are plotted against the binding coefficient. Here, C_i^app is the apparent intra-vesicular concentration of the probes which is calculated without consideration of bound probes. The ordinate intercept of the plot gives the true concentration ratio, and from this the membrane potential is evaluated. The membrane potential-dependent binding was analysed with a model: the membrane is split into two halves, outer and inner half, and the amounts of bound probes in each region are governed by the concentration in the contiguous solution. We obtained a formula which describes amounts of binding as a function of the membrane potential.     

Resonance Raman study of cytochrome b562-o complex, a terminal oxidase of Escherichia coli in its ferric, ferrous, and CO-ligated states

Cytochrome b562-o complex, a terminal oxidase in the respiratory chain of aerobically grown Escherichia coli, has been studied by resonance Raman spectroscopy in its air-oxidized, dithionite-reduced, and reduced and CO-ligated states. In the reduced state, with a 406.7-nm excitation, there appeared 1494 and 1473 cm-1 lines, indicating that low spin and high spin components are included in the cytochrome b562-o complex. For the air-oxidized protein, resonance Raman lines were observed at 1372, 1503, and 1580 cm-1 with a 413.1-nm excitation, indicating that there is a ferric low spin heme. In addition, a weak but appreciable Raman line was observed at 1480 cm-1 assignable to a ferric high spin heme. Accordingly, it was concluded that low spin and high spin components are included in the cytochrome b562-o complex in the reduced and the air-oxidized states. In the CO-ligated state, with a defocused laser beam of 413.1 nm, two Raman bands assignable to the Fe-CO stretching mode have been observed at 489 and 523 cm-1, as a major and a minor component, respectively. When the laser beam was focused upon the sample to cause a photodissociation of CO from the heme moiety, the intensity of the major band at 489 cm-1 was reduced as expected. On the other hand, the minor band at 523 cm-1 remained still obvious. It was suggested that the cytochrome b562-o complex may have an additional anomalous site for CO that is resistant to photodissociation.     

Effect of DN-1417, a thyrotropin releasing hormone analog, on dopaminergic neurons in rat brain

Acute and chronic effects of γ-butyrolactone-γ-carbonyl-histidyl-prolinamide (DN-1417) were investigated on motor activity, dopamine (DA) metabolites and DA receptors in various brain regions of rats. The motor activity, as measured with Automex recorder, was enhanced after a single injection with DN-1417 (20 mg/kg, IP), and the motor stimulating action persisted during 21 daily injections. Acute DN-1417 elevated both homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) levels in 7 brain regions, prefrontal cortex polar, medial and lateral fields, nucleus accumbens, olfactory tubercles, amygdala and striatum. After chronic treatment for 7 days, the acute effect of DN-1417 on DA metabolites disappeared in all regions except for the striatum in which DN-1417 still increased HVA and DOPAC. The response of striatal DA metabolites was also observed after chronic treatment for 21 days. Chronic DN-1417 produced no significant change in ³H-spiperone binding in the prefrontal cortex, nucleus accumbens, olfactory tubercles and striatum, while striatal ³H-DA binding displaced by 30 nM spiperone was enhanced after chronic treatment. These results indicate that DN-1417 interacts with mesocortical, mesolimbic and nigrostriatal DA systems in the different modes of action. The lack of tolerance to motor hyperactivity, however, raises the question as to whether DN-1417-induced hyperactivity may be mediated by the activation of mesolimbic DA neurons. The involvement of nigrostriatal neurons in DN-1417-induced motor hyperactivity is suggested.     

The Escherichia coli cytochrome b556 gene, cybA, is assignable as sdhC in the succinate dehydrogenase gene cluster

Abstract The cytochrome b556 -deficient mutant Escherichia coli K12 strain TK3D11 [7] could not grow with succinate as the sole carbon source, but could grow well on dl -lactate. This finding suggested that cytochrome b556 is primarily responsible for oxidative metabolism and utilization of succinate. 24 Amino acid residues at the amino-terminal of purified cytochrome b556 were determined. This sequence coincided completely with amino acid residues 4 to 27, predicted from the DNA sequence of the sdhC gene, one of the unassigned open reading frames of the sdh gene cluster recently reported by Wood et al. [16]. Based on these and other results, we concluded that cybA , the gene for cytochrome b556 , is assignable as sdhC .