Freeze-dried sperm fertilization leads to full-term development in rabbits

To date, the laboratory mouse is the only mammal in which freeze-dried spermatozoa have been shown to support full-term development after microinjection into oocytes. Because spermatozoa in mice, unlike in most other mammals, do not contribute centrosomes to zygotes, it is still unknown whether freeze-dried spermatozoa in other mammals are fertile. Rabbit sperm was selected as a model because of its similarity to human sperm (considering the centrosome inheritance pattern). Freeze- drying induces rabbit spermatozoa to undergo dramatic changes, such as immobilization, membrane breaking, and tail fragmentation. Even when considered to be "dead" in the conventional sense, rabbit spermatozoa freeze-dried and stored at ambient temperature for more than 2 yr still have capability comparable to that of fresh spermatozoa to support preimplantation development after injection into oocytes followed by activation. A rabbit kit derived from a freeze-dried spermatozoon was born after transferring 230 sperm-injected oocytes into eight recipients. The results suggest that freeze-drying could be applied to preserve the spermatozoa from most other species, including human. The present study also raises the question of whether rabbit sperm centrosomes survive freeze-drying or are not essential for embryonic development.     

Ontogenesis of epithelial phosphate transport systems in goats

The rapid development of precocial goats in the first weeks after birth requires an adequate adaptation of phosphate transport systems to maintain the P homeostasis at each developmental stage. Here we examined the age-related development of Na+-Pi transport systems in small intestines, kidneys, and parotid glands of goats. Kinetic parameters were determined by brush-border membrane vesicle uptake studies, and relative expression of NaPi type II mRNA and protein was recorded by molecular biological methods. High intestinal Pi transport capacity was already present on the first day of life. Within the first 3 wk of life there seemed to be a change in the type of Na+-dependent Pi transporter, and NaPi IIb was expressed increasingly up to the fifth month of life. Renal Na+-Pi transport capacity was also high at birth, and this was associated with high expression levels of NaPi IIa mRNA, indicating the important role of this transporter for renal Pi reabsorption. At weaning an increase in both intestinal and renal Na+-Pi transport balanced the increasing requirements for Pi to establish the endogenous Pi cycle. Salivary Pi concentration and parotid NaPi II mRNA rose markedly to guarantee an adequate Pi supply for rumen microbes. We concluded that the high demand for Pi in young goats was assured by high basal Na+-Pi transport capacity of small intestines and kidney expressed continuously during ontogenesis.     

Antiangiogenic activity of chemopreventive drugs

Tumors growing within the host form dynamic aberrant tissue that consists of host components, including the stroma, an expanding vasculature and often chronic inflammation, in addition to the tumor cells themselves. These host components can contribute to, rather than limit, tumor expansion, whereas deprivation of vessel formation has the potential to confine tumors in small, clinically silent foci. Therapeutic inhibition of vessel formation could be best suited to preventive strategies aimed at the suppression of angiogenesis in primary tumors in subjects at risk, or of micrometastases after surgical removal of a primary tumor. Our analysis of potential cancer chemopreventive molecules including N-acetylcysteine, green tea flavonoids and 4-hydroxyphenyl-retinamide has identified antiangiogenic activities that could account--at least in part--for the tumor prevention effects observed with these compounds. These drugs appear to target common mechanisms of tumor angiogenesis that may permit identification of critical targets for antiangiogenic therapy and antiangiogenic chemoprevention.     

Membrane domains in the secretory and endocytic pathways

Progress in identifying, characterizing, and localizing the constituents of distinct membrane bound compartments has revealed a new level of intracellular subcompartmentation. Proteins and lipids are not uniformly distributed in a given organelle, and subdomains are formed by a combination of hierarchical assembly processes and protein exclusion. Thus, functionally distinct specializations of a given organelle are physically segregated to a greater extent than previously believed.     

Salmonella typhimurium strains carrying independent mutations display similar virulence phenotypes yet are controlled by distinct host defense mechanisms

The outcome of Salmonella infection in the mammalian host favors whoever succeeds best in disturbing the equilibrium between coordinate expression of bacterial (virulence) genes and host defense mechanisms. Intracellular persistence in host cells is critical for pathogenesis and disease, because Salmonella typhimurium strains defective in this property are avirulent. We examined whether similar host defense mechanisms are required for growth control of two S. typhimurium mutant strains. Salmonella pathogenicity island 2 (SPI2) and virulence plasmid-cured Salmonella mutants display similar virulence phenotypes in immunocompetent mice, yet their gene loci participate in independent virulence strategies. We determined the role of TNF-alpha and IFN-gamma as well as different T cell populations in infection with these Salmonella strains. After systemic infection, IFN-gamma was essential for growth restriction of plasmid-cured S. typhimurium, while SPI2 mutant infections were controlled in the absence of IFN-gamma. TNFRp55-deficiency restored systemic virulence to both Salmonella mutants. After oral inoculation, control of plasmid-cured bacteria substantially relied on both IFN-gamma and TNF-alpha signaling while control of SPI2 mutants did not. However, for both mutants, ultimate clearance of bacteria from infected mice depended on alphabeta T cells.     

Boron in Plant Biology

Abstract: The interest of biologists in boron (B) has largely been focused on its role in plants for which B was established as essential in 1923 (Warington, 1923^[296]). Evidence that B has a biological role in other organisms was first indicated by the establishment of essentiality of B for diatoms (Smyth and Dugger, 1981^[296]) and cyanobacteria (Bonilla et al., 1990^[296]; Garcia‐Gonzalez et al., 1991^[296]; Bonilla et al., 1997^[296]). Recently, B was shown to stimulate growth in yeast (Bennett et al., 1999^[296]) and to be essential for zebrafish (Danio rerio) (Eckhert and Rowe, 1999^[296]; Rowe and Eckhert, 1999^[296]) and possibly for trout (Oncorhynchus mykiss) (Eckhert, 1998^[296]; Rowe et al., 1998^[296]), frogs (Xenopus laevis) (Fort et al., 1998^[296]) and mouse (Lanoue et al., 2000^[296]). There is also preliminary evidence to suggest that B has at least a beneficial role in humans (Nielsen, 2000^[296]). While research into the role of B in plants has been ongoing for 80 years it has only been in the past 5 years that the first function of B in plants has been defined. Boron is now known to be essential for cell wall structure and function, likely through its role as a stabilizer of the cell wall pectic network and subsequent regulation of cell wall pore size. A role for B in plant cell walls, however, is inadequate to explain all of the effects of B deficiency seen in plants. The suggestion that B plays a broader role in biology is supported by the discovery that B is essential for animals where a cellulose‐rich cell wall is not present. Careful consideration of the physical and chemical properties of B in biological systems, and of the experimental data from both plants and animals suggests that B plays a critical role in membrane structure and hence function. Verification of B association with membranes would represent an important advance in modern biology. For several decades there has been uncertainty as to the mechanisms of B uptake and transport within plants. This uncertainty has been driven by a lack of adequate methodology to measure membrane fluxes of B at physiologically relevant concentrations. Recent experimentation provides the first direct measurement of membrane permeability of B and illustrates that passive B permeation contributes sufficient B at adequate levels of B supply, but would be inadequate at conditions of marginal B supply. The hypothesis that an active, carrier mediated process is involved in B uptake at low B supply is supported by research demonstrating that B uptake can be stimulated by B deprivation, that uptake rates follow a Michaelis‐Menton kinetics, and can be inhibited by application of metabolic inhibitors. Since the mechanisms of element uptake are generally conserved between species, an understanding of the processes of B uptake is relevant to studies in both plants and animals. The study of B in plant biology has progressed markedly in the last decade and we are clearly on the cusp of additional, significant discoveries. Research in this field will be greatly stimulated by the discovery that B is essential for animals, a discovery that will not only encourage the participation of a wider cadre of scientists but will refocus the efforts of plant biologists toward a determination of roles for B outside the plant cell wall. Determination of the function of B in biology and of the mechanisms of B uptake in biological systems, is essential to our understanding and management of B deficiency and toxicity in plants and animals in both agricultural and natural environments. Through an analysis of existing data and the development of new hypotheses, this review aims to provide a vision of the future of research into the biology of boron.     

3-Nitropropanoyl-d-glucopyranoses of Corynocarpus laevigatus

A new nitropropanoyl glucopyranose, 1,4,6-tri-(3-nitropropanoyl)-β-d-glucopyranose (corynocarpin), and three known compounds, 1,6-di-(3-nitropropanoyl)-β-d-glucopyranose (cibarian), 2,6-di-(3-nitropropanoyl)-α-d-glucopyranose (coronarian) and 2,3,6-tri-(3-nitropropanoyl)-α-d-glucopyranose (corollin), were isolated from seeds and plants of Corynocarpus laevigatus. Structural assignments were made on the basis of 220 MHz PMR spectra.