Cutting edge: CD47 controls the in vivo proliferation and homeostasis of peripheral CD4+ CD25+ Foxp3+ regulatory T cells that express CD103

Peripheral CD103(+)Foxp3(+) regulatory T cells (Tregs) can develop both from conventional naive T cells upon cognate Ag delivery under tolerogenic conditions and from thymic-derived, expanded/differentiated natural Tregs. We here show that CD47 expression, a marker of self on hematopoietic cells, selectively regulated CD103(+)Foxp3(+) Treg homeostasis at the steady state. First, the proportion of effector/memory-like (CD44(high)CD62L(low)) CD103(+)Foxp3(+) Tregs rapidly augmented with age in CD47-deficient mice (CD47(-/-)) as compared with age-matched control littermates. Yet, the percentage of quiescent (CD44(low)CD62L(high)) CD103(-)Foxp3(+) Tregs remained stable. Second, the increased proliferation rate (BrdU incorporation) observed within the CD47(-/-)Foxp3(+) Treg subpopulation was restricted to those Tregs expressing CD103. Third, CD47(-/-) Tregs maintained a normal suppressive function in vitro and in vivo and their increased proportion in old mice led to a decline of Ag-specific T cell responses. Thus, sustained CD47 expression throughout life is critical to avoid an excessive expansion of CD103(+) Tregs that may overwhelmingly inhibit Ag-specific T cell responses.     

A bistable gene switch for antibiotic biosynthesis: the butyrolactone regulon in Streptomyces coelicolor

Many microorganisms, including bacteria of the class Streptomycetes, produce various secondary metabolites including antibiotics to gain a competitive advantage in their natural habitat. The production of these compounds is highly coordinated in a population to expedite accumulation to an effective concentration. Furthermore, as antibiotics are often toxic even to their producers, a coordinated production allows microbes to first arm themselves with a defense mechanism to resist their own antibiotics before production commences. One possible mechanism of coordination among individuals is through the production of signaling molecules. The gamma-butyrolactone system in Streptomyces coelicolor is a model of such a signaling system for secondary metabolite production. The accumulation of these signaling molecules triggers antibiotic production in the population. A pair of repressor-amplifier proteins encoded by scbA and scbR mediates the production and action of one particular gamma-butyrolactone, SCB1. Based on the proposed interactions of scbA and scbR, a mathematical model was constructed and used to explore the ability of this system to act as a robust genetic switch. Stability analysis shows that the butyrolactone system exhibits bistability and, in response to a threshold SCB1 concentration, can switch from an OFF state to an ON state corresponding to the activation of genes in the cryptic type I polyketide synthase gene cluster, which are responsible for production of the hypothetical polyketide. The switching time is inversely related to the inducer concentration above the threshold, such that short pulses of low inducer concentration cannot switch on the system, suggesting its possible role in noise filtering. In contrast, secondary metabolite production can be triggered rapidly in a population of cells producing the butyrolactone signal due to the presence of an amplification loop in the system. S. coelicolor was perturbed experimentally by varying concentrations of SCB1, and the model simulations match the experimental data well. Deciphering the complexity of this butyrolactone switch will provide valuable insights into how robust and efficient systems can be designed using "simple" two-protein networks.     

Regulation of neurocoel morphogenesis by Pard6 gamma b

The Par3/Par6/aPKC protein complex plays a key role in the establishment and maintenance of apicobasal polarity, a cellular characteristic essential for tissue and organ morphogenesis, differentiation and homeostasis. During a forward genetic screen for liver and pancreas mutants, we identified a pard6γb mutant, representing the first known pard6 mutant in a vertebrate organism. pard6γb mutants exhibit defects in epithelial tissue development as well as multiple lumens in the neural tube. Analyses of the cells lining the neural tube cavity, or neurocoel, in wildtype and pard6γb mutant embryos show that lack of Pard6γb function leads to defects in mitotic spindle orientation during neurulation. We also found that the PB1 (aPKC-binding) and CRIB (Cdc-42-binding) domains and the KPLG amino acid sequence within the PDZ domain (Pals1-and Crumbs binding) are not required for Pard6γb localization but are essential for its function in neurocoel morphogenesis. Apical membranes are reduced, but not completely absent, in mutants lacking the zygotic, or both the maternal and zygotic, function of pard6γb, leading us to examine the localization and function of the three additional zebrafish Pard6 proteins. We found that Pard6α, but not Pard6β or Pard6γa, could partially rescue the pard6γb^s441 mutant phenotypes. Altogether, these data indicate a previously unappreciated functional diversity and complexity within the vertebrate pard6 gene family.     

The ylo-1 gene encodes an aldehyde dehydrogenase responsible for the last reaction in the Neurospora carotenoid pathway

The accumulation of the apocarotenoid neurosporaxanthin and its carotene precursors explains the orange pigmentation of the Neurospora surface cultures. Neurosporaxanthin biosynthesis requires the activity of the albino gene products (AL-1, AL-2 and AL-3), which yield the precursor torulene. Recently, we identified the carotenoid oxygenase CAO-2, which cleaves torulene to produce the aldehyde β-apo-4'-carotenal. This revealed a last missing step in Neurospora carotenogenesis, namely the oxidation of the CAO-2 product to the corresponding acid neurosporaxanthin. The mutant ylo-1 , which exhibits a yellow colour, lacks neurosporaxanthin and accumulates several carotenes, but its biochemical basis is unknown. Based on available genetic data, we identified ylo-1 in the Neurospora genome, which encodes an enzyme representing a novel subfamily of aldehyde dehydrogenases, and demonstrated that it is responsible for the yellow phenotype, by sequencing and complementation of mutant alleles. In contrast to the precedent structural genes in the carotenoid pathway, light does not induce the synthesis of ylo-1 mRNA. In vitro incubation of purified YLO-1 protein with β-apo-4'-carotenal produced neurosporaxanthin through the oxidation of the terminal aldehyde into a carboxyl group. We conclude that YLO-1 completes the set of enzymes needed for the synthesis of this major Neurospora pigment.     

Hypoxemia and low Crs in vagally denervated lambs result from reduced lung volume and not pulmonary edema.

Vagal denervation performed in the intrathoracic region in newborn lambs leads to hypoxemia and decreased respiratory system compliance (Crs), which could result from atelectasis and/or pulmonary edema. The objective of the present study was to quantify the relative roles of alveolar derecruitment and pulmonary edema as underlying cause(s) of respiratory failure. Vagal denervation was performed in the intrathoracic region and below the recurrent laryngeal nerves in six newborn lambs within 24 h of birth, whereas six were sham operated. Pre- and postinflation Crs was measured to investigate the presence of alveolar derecruitment. Pulmonary edema was assessed with lung wet-dry-to-wet and lung tissue wet-to-dry ratios, total protein, and FITC-BSA recovery in lung tissue and bronchoalveolar lavage. Compared with that in the sham-operated animals, Crs was significantly lower in vagally denervated animals. However, postinflation, pulmonary system compliance obtained by quasi-static lung inflation and deflation to 30 cmH2O showed no significant difference between the sham-operated and denervated lambs. The lung wet-dry-to-wet and lung tissue wet-to-dry ratios, total protein, and FITC-BSA recovery in lung tissue and bronchoalveolar lavage were similar in denervated and sham-operated groups. We provide evidence that reduced lung volume and not pulmonary edema is associated with intrathoracic vagal denervation and is the likely underlying mechanism for hypoxemia and low Crs.     

Treatment of tetanus: an open study to compare the efficacy of procaine penicillin and metronidazole.

A prospective, open, non-randomised clinical trial was carried out to compare the efficacy of procaine penicillin with metronidazole in the treatment of moderate tetanus among 173 patients. Patients in the metronidazole group had a significantly lower mortality rate, a shorter stay in hospital, and an improved response to treatment. These results establish the value of antimicrobial treatment in the management of tetanus and show that metronidazole is more efficacious than penicillin in this respect.     

Historical demographic profiles and genetic variation of the East African Butana and Kenana indigenous dairy zebu cattle

Butana and Kenana breeds from Sudan are part of the East African zebu Bos indicus type of cattle. Unlike other indigenous zebu cattle in Africa, they are unique due to their reputation for high milk production and are regarded as dairy cattle, the only ones of their kind on the African continent. In this study, we sequenced the complete mitochondrial DNA (mtDNA) D‐loop of 70 animals to understand the maternal genetic variation, demographic profiles and history of the two breeds in relation to the history of cattle pastoralism on the African continent. Only taurine mtDNA sequences were identified. We found very high mtDNA diversity but low level of maternal genetic structure within and between the two breeds. Bayesian coalescent‐based analysis revealed different historical and demographic profiles for the two breeds, with an earlier population expansion in the Butana vis a vis the Kenana. The maternal ancestral populations of the two breeds may have diverged prior to their introduction into the African continent, with first the arrival of the ancestral Butana population. We also reveal distinct demographic history between the two breeds with the Butana showing a decline in its effective population size (N_e) in the recent past ~590 years. Our results provide new insights on the early history of cattle pastoralism in Sudan indicative of a large ancient effective population size.     

Rapid plant regeneration,validation of genetic integrity by ISSR markers and conservation of Reseda pentagyna an endemic plant growing in Saudi Arabia

Reseda pentagyna is the only endemic species among the seven species of the genera Reseda found in Saudi Arabia. Probably no information is available on regeneration by conventional method of regeneration through seeds or cuttings. Therefore, alternative method of tissue culture was attempted to regenerate and multiply the plant. High shoot regeneration (14.44 shoots/explant) was obtained after four weeks, when shoot cuttings cultured on MS containing BA at 1.0 µM. Other cytokinins e.g., Kn, 2iP and TDZ found to be less effective in bud induction and shoot multiplication. Individual shoots were rooted on MS medium supplemented with various auxins at 0.5–5.0 µM concentrations. The IBA (1.5 µM) supplemented MS media induced maximum (83.3%) rooting. The plantlets were acclimatized and hardened under greenhouse conditions in plastic pots containing soil and farm yard manure with 95.0% success. The protocol developed would help to multiply the plant as well as conserve them in natural habitat. This can also be utilized to obtain active constituents for pharmaceutics and genetic manipulations.     

Human Papillomavirus Type 16 Integration Analysis by Real-time PCR Assay in Associated Cancers

Human papillomavirus (HPV) is a common viral infection worldwide associated with a variety of cancers. The integration of the HPV genome in these patients causes chromosomal instability and triggers carcinogenesis. The aim of this study was to investigate the HPV-16 genome physical status in four major cancers related to HPV infection. Formalin-fixed paraffin-embedded blocks from our previous projects on head and neck, colorectal, penile, and cervical cancers were collected, and HPV-16–positive specimens were used for further analysis. The DNA extraction copy number of E2 and E7 genes was calculated by qualitative real-time PCR method. Serially diluted standards that were cloned in PUC57 plasmid were used. Standard curve and melting curve analysis was used for quantification. Of the 672 specimens studied, 76 (11.3%) were HPV-16 positive. We found that 35.6% (16/45) were integrated. Statistical analysis showed that there were significant correlations between integration of HPV-16 and cervical cancer end-stage carcinogenesis (P < .0001), episomal form, and ASCUS lesions (P = .045). Significant correlation in penile cancer patients was seen between the episomal form and high-grade cancer stage (P = .037). Integration is a major factor in the carcinogenesis mechanism of HPV and has different prevalence in various cancers with a higher rate in progression except in penile cancer.     

Porewater nutrient profiles and nutrient sediment–water exchange in a tropical mangrove waterway, Mapopwe Creek, Chwaka Bay, Zanzibar

Sediments were examined in the Mapopwe Creek, a tidally dominated mangrove waterway in the Chwaka Bay mangrove forest, Zanzibar, to assess their significance in the nutrient dynamics of the mangrove forest and the adjacent bay. Porewater concentrations of dissolved ammonium and that of soluble reactive phosphorus (SRP) were generally higher during the dry season than during the wet season. NO₃^? plus NO₂^? concentration averaged 1 µm and did not vary much between the two periods. Fluxes of ammonium ranged from ?575 to 523 µm m^?2 h^?1 and those of SRP from ?55.7 to 69.5 µm m^?2 h^?1. Measurements of NO_x did not show any consistent fluxes of this dissolved nitrogen species. Variations of flux rates between the two seasons were not significant even though there were small variations in the flux direction in both nutrients. Results imply that Mapopwe sediments are a source of NH₄⁺ but act as a sink for SRP.