On the cytotaxonomy of phasmids (Phasmatodea)

Summary A wide diversity in chromosome complement is found in two species of phasmids of the primitive group Prisopini—Prisopus ariadne Hebard and Prisopus berosus Westwood. P. ariadne has a diploid male complement of 28, comprising 13 pairs of relatively large mediokinetic autosomes and Neo XY sex chromosomes. P. berosus, 2n =49, has relatively small autosomes most of which are mediokinetic, and retains the XO—XX sex mechanism. Chromosomal polymorphism in this species is suggested by the presence of an unequal pair of autosomes and a structural differentiation in the X in one of two males studied.The relative amount of DNA per nucleus in male germ cells (Peulgen cytophotometry) shows a significant difference in total chromosomal content between the complements of the two species.These data are discussed with reference to the cytotaxonomy of phasmids.Supported in part by research grant G-4370 from the National Institutes of Health, Public Health Service.     

Free mycolic acid accumulation in the cell wall of the mce1 operon mutant strain of Mycobacterium tuberculosis

The lipid-rich cell wall of Mycobacterium tuberculosis, the agent of tuberculosis, serves as an effective barrier against many chemotherapeutic agents and toxic host cell effector molecules, and it may contribute to the mechanism of persistence. Mycobacterium tuberculosis strains mutated in a 13-gene operon called mce1, which encodes a putative ABC lipid transporter, induce aberrant granulomatous response in mouse lungs. Because of the postulated role of the mce1 operon in lipid importation, we compared the cell wall lipid composition of wild type and mce1 operon mutant M. tuberculosis H37Rv strains. High resolution mass spectrometric analyses of the mce1 mutant lipid extracts showed unbound mycolic acids to accumulate in the cell wall. Quantitative analysis revealed a 10.7 fold greater amount of free mycolates in the mutant compared to that of the wild type strain. The free mycolates were comprised of alpha, methoxy and keto mycolates in the ratio 1:0.9:0.6, respectively. Since the mce1 operon is regulated in vivo, the free mycolates that accumulate during infection may serve as a barrier for M. tuberculosis against toxic products and contribute to the pathogen’s persistence.     

Mutualism can mediate competition and promote coexistence

Mutualistic interactions are not believed to promote coexistence of competitors because mutualisms produce positive feedbacks on abundances whereas coexistence requires negative feedbacks. Here we show that a mutualism between an anemonefish (Amphiprion) and its sea anemone host mediates the effect of asymmetrical competition for space between the anemonefish and another damselfish (Dascyllus) in a manner that fosters their coexistence. Amphiprion stimulates increases in host area, the shared resource, but social interactions cap the number of anemonefish to two adults per host. Space generated by the mutualism becomes differentially available to Dascyllus because the effectiveness of an anemonefish in excluding its competitor declines with increases in the area it defends. This alters Amphiprion's ratio of per capita intra‐ to interspecific effects and thus facilitates coexistence of the fishes. This mechanism may be prevalent in nature, adding another major pathway by which mutualism can enhance diversity.     

Elimination of the non-specific binding of avidin to tissue sections

Summary A simple procedure is described for eliminating non-specific staining with avidin—peroxidase conjugates. Murine ovaries were embedded in either paraffin wax or epoxy resin and, after blocking endogenous peroxidase activity, were treated with 10 µg/ml biotinylatedPisum sativum agglutinin. Avidin—peroxidase conjugates (5 µg/ml), diluted in standard 0.05m tris-buffered saline, pH 7.6, containing 0.139m NaCl, produced considerable background coloration and intense mast cell staining in controls without the lectin. This background diminished as the ionic strength of the buffer was raised. At 0.125m Tris-buffered saline (containing 0.347m NaCl) the background was completely unstained, with elimination of all binding to mast cells and only minimal loss of specific lectin binding.     

Diversity of fungi on rainforest litter in North Queensland, Australia

Ten leaves from each of 13 different tree types from two differentrainforest sites in North Queensland, Australia were examined in order toestablish the fungal diversity developing on these leaves. A total of 57microfungi were identified, most of which were mitosporic fungi. Speciesdiversity in terms of richness and evenness were compared and the Mt Lewis sitewas found to be richer as compared to the Butchers Creek site. Statisticalmeasurements of diversity indices, however, showed that the two forest siteswere of similar diversity. Thirty-six of the fungi identified occurred only onone leaf type, indicating possible host specificities or recurrences. The samplesize, however, is deemed to be insufficient, as a larger sample size may haveresulted in less of the fungi appearing to be host specific. It is recommendedthat future studies should include more leaf samples and less tree types. It isparticularly important that the same leaf species are collected within the samesite and at different sites in order to establish the effects of host on fungalcomposition.     

A behavioral comparison of male and female adults with high functioning autism spectrum conditions

Autism spectrum conditions (ASC) affect more males than females in the general population. However, within ASC it is unclear if there are phenotypic sex differences. Testing for similarities and differences between the sexes is important not only for clinical assessment but also has implications for theories of typical sex differences and of autism. Using cognitive and behavioral measures, we investigated similarities and differences between the sexes in age- and IQ-matched adults with ASC (high-functioning autism or Asperger syndrome). Of the 83 (45 males and 38 females) participants, 62 (33 males and 29 females) met Autism Diagnostic Interview-Revised (ADI-R) cut-off criteria for autism in childhood and were included in all subsequent analyses. The severity of childhood core autism symptoms did not differ between the sexes. Males and females also did not differ in self-reported empathy, systemizing, anxiety, depression, and obsessive-compulsive traits/symptoms or mentalizing performance. However, adult females with ASC showed more lifetime sensory symptoms (p = 0.036), fewer current socio-communication difficulties (p = 0.001), and more self-reported autistic traits (p = 0.012) than males. In addition, females with ASC who also had developmental language delay had lower current performance IQ than those without developmental language delay (p<0.001), a pattern not seen in males. The absence of typical sex differences in empathizing-systemizing profiles within the autism spectrum confirms a prediction from the extreme male brain theory. Behavioral sex differences within ASC may also reflect different developmental mechanisms between males and females with ASC. We discuss the importance of the superficially better socio-communication ability in adult females with ASC in terms of why females with ASC may more often go under-recognized, and receive their diagnosis later, than males.     

Short-term succession dynamics of macrobenthos in a salinity-stressed estuary

It is postulated that early succession is influenced by environmental conditions directly after a disturbance event and the temporal scale of succeeding disturbances. For example, Rincon Bayou, Texas, U.S.A. is an estuary stressed by large fluctuations in salinity ranging from oligohaline to hypersaline conditions; leading to the question: are benthic succession dynamics interrupted or affected by the temporal scale of salinity fluctuations? To answer this question, succession dynamics were investigated by manipulation of 1) initial environmental conditions, and 2) time between severe disturbances. The influence of environmental conditions and time course of succession were investigated by comparing two experiments. A synoptic-deployment experiment where samples were deployed at the same environmental conditions and a synoptic-retrieval experiment where samples were collected from deployments under different environmental conditions. Both experiments were conducted at varying time courses of 2-, 4- and 8-week durations between severe disturbances. Severe disturbances were simulated with defaunated sediment. Ambient conditions were simultaneously sampled as a reference. Environmental conditions directly affected succession. In the ambient study, succession occurred in conjunction with changes in environmental conditions. In the synoptic-deployment and synoptic-retrieval studies, environmental conditions at the time of retrieval were more important in determining community structure than deployment duration or initial environmental conditions at time of deployment. Initial environmental conditions were not the primary mechanism in regulation of succession because succession is likely interrupted by frequent salinity disturbances. The salinity-stressed estuary of Rincon Bayou appears to be in a constant state of early and intermediate succession because of frequent salinity-related disturbances.     

Preclinical Assessment of Adjunctive tPA and DNase for Peritoneal Dialysis Associated Peritonitis

A major complication of peritoneal dialysis is the development of peritonitis, which is associated with reduced technique and patient survival. The inflammatory response elicited by infection results in a fibrin and debris-rich environment within the peritoneal cavity, which may reduce the effectiveness of antimicrobial agents and predispose to recurrence or relapse of infection. Strategies to enhance responses to antimicrobial agents therefore have the potential to improve patient outcomes. This study presents pre-clinical data describing the compatibility of tPA and DNase in combination with antimicrobial agents used for the treatment of PD peritonitis. tPA and DNase were stable in standard dialysate solution and in the presence of antimicrobial agents, and were safe when given intraperitoneally in a mouse model with no evidence of local or systemic toxicity. Adjunctive tPA and DNase may have a role in the management of patients presenting with PD peritonitis.