Testosterone regulates the density of dendritic spines in the male preoptic area

Male-typical behavior is dependent on testosterone. Castrated males gradually stop mating and engaging in sexual behaviors. Castrates treated with testosterone regain motivation and sex behaviors over time. Although this effect is well characterized, the specific mechanisms by which testosterone treatment recovers sexual behaviors remain unknown. The medial preoptic area (MPOA) is a likely site for testosterone's action on copulation. The integrity of the area is essential for the expression of male sex behavior; and the MPOA is densely populated with receptors for gonadal steroids. Moreover testosterone appears to regulate synaptic efficacy in the MPOA. Exposure to sexually relevant stimuli stimulates the MPOA but only in the presence of circulating testosterone. Sites afferent to the area respond to similar exposure independent of the hormonal milieu suggesting that testosterone mediates communication between the MPOA and its afferents. The protracted time course suggests that the effects of steroidal manipulation are mediated by structural changes. The present experiment evaluated this hypothesis by comparing dendritic spine density among Syrian hamsters that were castrated, castrated and treated with testosterone, or were left gonadally intact. Brains were sectioned and stained using the rapid Golgi stain protocol (FD Neurotechnologies, Baltimore), and the spine density, dendrite length, and the number of branches were compared among groups. Intact and testosterone replaced animals had more spines and greater spine density but did not differ in dendrite length and branching from castrated animals. These results suggest that existing dendrites increase the number of spines available for synapse formation but do not extend their dendrites in response to testosterone treatment.     

Chemosensory and hormone information are relayed directly between the medial amygdala, posterior bed nucleus of the stria terminalis, and medial preoptic area in male Syrian hamsters

In many rodent species, including Syrian hamsters, the expression of appropriate social behavior depends critically on the perception and identification of conspecific odors. The behavioral response to these odors is mediated by a network of steroid-sensitive ventral forebrain nuclei including the medial amygdala (Me), posterior bed nucleus of the stria terminalis (BNST), and medial preoptic area (MPOA). Although it is well-known that Me, BNST, and MPOA are densely interconnected and each uniquely modulates odor-guided social behaviors, the degree to which conspecific odor information and steroid hormone cues are directly relayed between these nuclei is unknown. To answer this question, we injected the retrograde tracer, cholera toxin B (CTB), into the BNST or MPOA of male subjects and identified whether retrogradely-labeled cells in Me and BNST 1) expressed immediate early genes (IEGs) following exposure to male and/or female odors or 2) expressed androgen receptor (AR). Although few retrogradely-labeled cells co-localized with IEGs, a higher percentage of BNST- and MPOA-projecting cells in the posterior Me (MeP) expressed IEGs in response to female odors than to male odors. The percentage of retrogradely-labeled cells that expressed IEGs did not, however, differ between and female and male odor-exposed groups in the anterior Me (MeA), posterointermediate BNST (BNSTpi), or posteromedial BNST (BNSTpm). Many retrogradely-labeled cells co-localized with AR, and a higher percentage of retrogradely-labeled MeP and BNSTpm cells expressed AR than retrogradely-labeled MeA and BNSTpi cells, respectively. Together, these data demonstrate that Me, BNST, and MPOA interact as a functional circuit to process sex-specific odor cues and hormone information in male Syrian hamsters.     

Nitrogen fixation associated with roots of Kallar grass (Leptochloa fusca L. Kunth)

Summary An ecological survey was made to measure the N₂-fixing activity in the rhizosphere of a salt-tolerant grass,Leptochloa fusca (L.) Kunth. Samples were obtained every month at two sites over a period of one year. Soil cores, unwashed, washed and surface-sterilized roots were subjected to acetylene reduction assay (ARA). ARA values up to 50 nmoles h^–1 for soil cores, 1095 nmoles g dry root^–1 h^–1 for unwashed roots, 4929 nmoles g dry root^–1 h^–1 for washed roots and 2494 nmoles g dry root^–1 h^–1 for surface-sterilized roots were observed but for most samples the range was 1–200 nmoles g dry root^–1 h^–1. A lag period of 5–7 h was observed before the onset of N₂-fixing activity by excised roots and O₂ levels had no effect on this lag. Values for roots incubated without preincubation were similar to those for unwashed preincubated roots. Activity was highest in September, October and November when the temperature is not very high and photosynthetic activity is reasonably good. N₂-fixing-bacteria were counted on the same samples by plate count and MPN methods, the latter being estimated on the basis of ARA and pellicle formation. Fairly high numbers of bacteria (10⁴–10⁷) were recorded in the histoplane fraction which indicates the presence of diazotrophs in the inner cells of grass roots.     

Temperature-dependent enumeration and characterization of anaerobic, thermophilic xylan-degrading bacteria present in two Icelandic hot springs

Abstract Anaerobic thermophilic xylan-degrading bacteria present in unenriched and enriched 70°C samples from two Icelandic hot springs were enumerated at 68, 78, 90 and 99°C by the use of the Most-Probable-Number method. Xylan was used as substrate. From the samples taken at 70°C and incubated at the temperatures previously described no growth was observed above 78°C. A total of ten strains were isolated and characterized from the positive MPN enrichment cultures from the MPN experiments. A higher number of different strains could be isolated in the enriched samples compared with the unenriched, control samples from the same hot spring. Introduction of xylan, i.e., in situ enrichment, into one of the hot springs changed the bacterial population, as none of the bacteria isolated from the unenriched samples were isolated from the enriched samples. All the isolated bacteria were asporogenous, non-motile and gram-negative rods. One long thin rod had morphological similarities to members of the genus Dictyoglomus and was found in both hot spring samples.     

Evaluation of a new medium for the enumeration of total coliforms and Escherichia coli in Japanese surface waters

Aim: A new medium, EC‐Blue‐10, containing chromogenic and fluorogenic substrates, KNO₃ and sodium pyruvate has been developed for the rapid simultaneous detection and enumeration of total coliforms and Escherichia coli in water. Methods and Results:  Two evaluations of EC‐Blue‐10 were carried out. Firstly, EC‐Blue‐10 was compared with Colilert‐MPN for 96 water samples using MPN for total coliforms and E. coli. Secondly, the detection of coliforms and E. coli were compared using 2400 tubes of EC‐Blue‐10 and Colilert‐MPN. The regression coefficients between EC‐Blue‐10 and Colilert‐MPN for total coliforms and E. coli were 0·91 and 0·89, respectively. For the detection results, the Cohen’s kappa values between the two media were 0·79 for coliforms and 0·72 for E. coli. Conclusions: EC‐Blue‐10 is almost same as Colilert‐MPN for the detection of coliforms and E. coli in surface waters. Further evaluation for EC‐Blue‐10 is needed to verify in different geographical areas. Significance and Impact of the Study: EC‐Blue‐10 is useful method for the rapid and simultaneous detection of total coliforms and E. coli in water sample.     

Inhibition of Acetoclastic Methanogenesis in Crude Oil- and Creosote-Contaminated Groundwater

Results from a series of studies of methanogenic processes in crude oil- and creosote-contaminated aquifers indicate that acetoclastic methanogenesis is inhibited near non-aqueous sources. At a crude oil-contaminated site, numbers of acetoclastic methanogens found close to crude oil were one hundred times fewer than those of hydrogen- and formate-utilizing methanogens. In laboratory toxicity assays, crude oil collected from the site inhibited methane production from acetate but not from formate or hydrogen. Toxicity assays with aqueous creosote extract completely inhibited acetate utilization over the range of tested dilutions but only mildly affected formate and hydrogen utilization. The combined results from the laboratory and field studies suggest that in methanogenic contaminated aquifers, inhibition of acetoclastic methanogenesis may lead to a buildup of acetate relative to dissolved organic carbon.     

Molecular analysis of ammonia-oxidising bacteria in soil of successional grasslands of the Drentsche A (The Netherlands)

Changes in the community structure of chemolitho-autotrophic ammonia-oxidising bacteria of the beta-subgroup Proteobacteria were monitored during nutrient-impoverishment management of slightly acidic, peaty grassland soils, which decreased in pH with succession. Specific PCR, cloning and sequence analysis, denaturing gradient gel electrophoresis (DGGE) and probe hybridisation were used to analyse rDNA sequences directly recovered from successional soils. Four previously characterised ammonia oxidiser sequence clusters were recovered from each soil, three associated with the genus Nitrosospira and one with the genus Nitrosomonas. All samples were dominated by Nitrosospira-like sequences. Nitrosospira cluster 3 was the most commonly recovered ammonia oxidiser group in all fields, but a greater representation of Nitrosospira clusters 2 and 4 was observed in older fields. Most probable number (MPN) counts were conducted using neutral and slightly acid conditions. Neutral pH (7.5) MPNs suggested a decrease in ammonia oxidiser numbers in later successional fields, but this trend was not observed using slightly acid (pH 5.8) conditions. Analysis of terminal MPN dilutions revealed a distribution of sequence clusters similar to direct soil DNA extractions. However, an increased relative recovery of Nitrosospira cluster 2 was observed for acid pH MPNs compared to neutral pH MPNs from the most acidic soil tested, in agreement with current hypotheses on the relative acid tolerance of this group.     

The Organization of a CSN5-containing Subcomplex of the COP9 Signalosome

The COP9 signalosome (CSN) is an evolutionarily conserved multi-protein complex that interfaces with the ubiquitin-proteasome pathway and plays critical developmental roles in both animals and plants. Although some subunits are present only in an ∼320-kDa complex-dependent form, other subunits are also detected in configurations distinct from the 8-subunit holocomplex. To date, the only known biochemical activity intrinsic to the complex, deneddylation of the Cullin subunits from Cullin-RING ubiquitin ligases, is assigned to CSN5. As an essential step to understanding the structure and assembly of a CSN5-containing subcomplex of the CSN, we reconstituted a CSN4-5-6-7 subcomplex. The core of the subcomplex is based on a stable heterotrimeric association of CSN7, CSN4, and CSN6, requiring coexpression in a bacterial reconstitution system. To this heterotrimer, we could then add CSN5 in vitro to reconstitute a quaternary complex. Using biochemical and biophysical methods, we identified pairwise and combinatorial interactions necessary for the formation of the CSN4-5-6-7 subcomplex. The subcomplex is stabilized by three types of interactions: MPN-MPN between CSN5 and CSN6, PCI-PCI between CSN4 and CSN7, and interactions mediated through the CSN6 C terminus with CSN4 and CSN7. CSN8 was also found to interact with the CSN4-6-7 core. These data provide a strong framework for further investigation of the organization and assembly of this pivotal regulatory complex.