PCR cloning of a protein-coding part of the thioredoxin gene fromStreptomyces aureofaciens

Summary The method of two-stage half-specific amplification was described and successfully used in the isolation of the protein-coding part of the thioredoxin gene from Streptomyces aureofaciens BMK. The efficiency of a new PCR modification for the specific amplification of the target DNA fragments (genes) with unknown sequences is compared with the used half-specific PCR. The determined target sequence demonstrates the highest homology with the thioredoxin genes from Corynebacterium nephridii C-1 and Anabaena 7119.     

T helper and T suppressor cells are restricted by the A and E molecules,respectively, in the F antigen system

The role of the A and E molecules as restriction elements was examined in the F antigen system. In the mouse the only responder haplotype known to date isk, and blocking studies with a monoclonal antibody show that in vitro T-cell proliferation is restricted by the A^k molecule. The (CBA × DBA/2) F₁ hybrid, which is a responder x nonresponder cross, is itself a nonresponder in terms of E-specific antibody production. Up to 10 days after priming, (CBA × DBA/2) F₁ T cells exhibited an E-specific proliferative response, but this diminished rapidly at later times. This diminution could be blocked with an E-specific monoclonal antibody, suggesting that suppression is restricted by the E molecule.     

Antifolding activity of hsp60 couples protein import into the mitochondrial matrix with export to the intermembrane space.

Cytochrome b2 reaches the intermembrane space of mitochondria by transport into the matrix followed by export across the inner membrane. While in the matrix, the protein interacts with hsp60, which arrests its folding prior to export. The bacterial-type export sequence in pre-cytochrome b2 functions by inhibiting the ATP-dependent release of the protein from hsp60. Release for export apparently requires, in addition to ATP, the interaction of the signal sequence with a component of the export machinery in the inner membrane. Export can occur before import is complete provided that a critical length of the polypeptide chain has been translocated into the matrix. Thus, hsp60 combines two activities: catalysis of folding of proteins destined for the matrix, and maintaining proteins in an unfolded state to facilitate their channeling between the machineries for import and export across the inner membrane. Anti-folding signals such as the hydrophobic export sequence in cytochrome b2 may act as switches between these two activities.     

High-throughput marker assays for <Emphasis Type="Italic">FaRPc2</Emphasis>-mediated resistance to Phytophthora crown rot in octoploid strawberry

Phytophthora crown rot (PhCR) caused by Phytophthora cactorum is a destructive disease of the allo-octoploid cultivated strawberry (Fragaria ×ananassa Duch). Many major strawberry cultivars grown worldwide are susceptible to PhCR. Resistance is conferred by the recently-discovered FaRPc2 locus, but high-throughput markers are not yet available for marker-assisted breeding. In the current study, we developed DNA markers for two haplotypes at the FaRPc2 locus associated with resistance, H2 and H3. Marker validation and marker-assisted selection were performed in University of Florida (UF) breeding population. Seven single nucleotide polymorphism-based high resolution melting (HRM) markers linked to H2 and four HRM markers for H3 were developed. One HRM marker, RPCHRM3 linked to H3, was converted to a Kompetitive Allele Specific PCR (KASP) marker. To further examine the utility of the markers, they were screened in University of California Davis cultivars with known phenotypes as well as in 20 diverse accessions with phenotypes that are reported in the literature and that are preserved at the USDA-ARS National Clonal Germplasm Repository, in Corvallis, Oregon. The most informative markers for FaRPc2 resistance are being implemented in the UF strawberry breeding program to improve PhCR resistance.     

Effect of heavy metals on chromatin supraorganization, nuclear phenotypes, and survival ofTriatoma infestans

The nuclear phenotypes and survival of the hemipteran,Triatoma infestans (Hemiptera, Reduviidae), were studied in specimens treated with copper sulfate and methylmercury. The objective was to determine whether changes in chromatin supraorganization and insect survival similar to those promoted by other stressing agents could also be induced by heavy metals. At the concentrations used, copper sulfate and methylmercury were toxic to the cells, mainly inducing nuclear degenrration in the Malpighian tubules and being lethal to a large part of the insect population. Although some individual resistance was found, especially in fasted specimens, heavy metals were found to be much more lethal than was, for instance, a thermal shock at 0°C for 12 h. The nuclear phenotypes detected after heavy metal treatment were similar to those reported under other stressing conditions. However, the frequency at which nuclei exhibited aspects of heterochromatin unraveling was much higher than that found in fasted and thermal-shocked specimens, and was independent of the heavy metal type used. If this phenotype represents an attempt to improve opportunities for extensive cell and insect survival, it was not sufficiently effective. In 5th instar nymphs, the effect of CuSO₄ on chromatin supraorganization was detected at early steps of spermatogenesis but not in the cells which were at late spermiogenesis when the metal was administered. This is probably due to changes in nuclear protein composition and to the tightly packed state of the DNA-protein complexes occurring at spermiogenesis, which may protect chromatin from damages. However, when CuSO₄ was supplied to 4th instar nymphs, it slowed down the spermiogenesis process, possibly due to several factors including Cu²⁺ binding to DNA phosphates.     

Tissue polarity points from cells that have higher Frizzled levels towards cells that have lower Frizzled levels

Background: The frizzled (fz) gene of Drosophila encodes the founding member of the large family of receptors for the Wnt family of signaling molecules. It was originally studied in the adult epidermis, where it plays a key role in the generation of tissue polarity. Mutations in components of the fz signal transduction pathway disrupt tissue polarity; on the wing, hairs normally point distally but their polarity is altered by these mutations.Results: We devised a method to induce a gradient of fz expression with the highest levels near the distal wing tip. The result was a large area of proximally pointing hairs in this region. This reversal of polarity was seen when fz expression was induced just before the start of hair morphogenesis when polarity is established, suggesting that the gradient of Fz protein acted fairly directly to reverse hair polarity. A similar induction of the dishevelled (dsh) gene, which acts cell autonomously and functions downstream of fz in the generation of tissue polarity, resulted in a distinct tissue polarity phenotype, but no reversal of polarity; this argues that fz signaling was required for polarity reversal. Furthermore, the finding that functional dsh was required for the reversal of polarity argues that the reversal requires normal fz signal transduction.Conclusions: The data suggest that cells sense the level of Fz protein on neighboring cells and use this information in order to polarize themselves. A polarizing signal is transmitted from cells with higher Fz levels to cells with lower levels. Our observations enable us to propose a general mechanism to explain how Wnts polarize target cells.     

Limited Amount of Formula May Facilitate Breastfeeding: Randomized,Controlled Trial to Compare Standard Clinical Practice versus Limited Supplemental Feeding

Objectives

Breastfeeding is known to reduce infant morbidity and improve well-being. Nevertheless, breastfeeding rates remain low despite public health efforts. Our study aims to investigate the effect of controlled limited formula usage during birth hospitalisation on breastfeeding, using the primary hypothesis that early limited formula feeds in infants with early weight loss will not adversely affect the rate of exclusive or any breastfeeding as measured at discharge, 3 and 6 months of age.

Material and Methods

We randomly assigned 104 healthy term infants, 24 to 48 hours old, with ≥ 5% loss of birth weight to controlled limited formula (CLF) intervention (10 ml formula by syringe after each breastfeeding, discontinued at onset of lactation) or control group (standard approach, SA). Groups were compared for demographic data and breastfeeding rates at discharge, 3 months and 6 months of age (p-values adjusted for multiple testing).

Results

Fifty newborns were analysed in CLF and 50 in SA group. There were no differences in demographic data or clinical characteristics between groups. We found no evidence of difference between treatment groups in the rates of exclusive as well as any breastfeeding at discharge (p-value 0.2 and >0.99 respectively), 3 months (p-value 0.12 and 0.10) and 6 months of infants’ age (p-value 0.45 and 0.34 respectively). The percentage weight loss during hospitalisation was significantly higher in the SA group (7.3% in CLF group, 8.4% in SA group, p = 0.002).

Conclusion

The study shows that controlled limited formula use does not have an adverse effect on rates of breastfeeding in the short and long term. Larger studies are needed to confirm a possible potential in controlled limited formula use to support establishing breastfeeding and to help to improve the rates of breastfeeding overall.

Trial Registration

ISRCTN registry ISRCTN61915183