Degree Of Motility Research Articles

Comparative Genomic Analyses of Escherichia coli from a Meat Processing Environment in Relation to Their Biofilm Formation and Persistence.

We investigated the phylogeny of biofilm forming (BF) and nonbiofilm forming (NBF) Escherichia coli (n = 114) from a beef processing environment as well as genetic elements in their BF and persistence via a comparative genomic analysis. Phylogroup B1 made up the largest proportion of both the BF (73.8%) and NBF (50.9%) groups. E. coli from all of the sources that were examined had mixed phylogroups, except for those that were recovered from equipment after cleaning, which were exclusively from phylogroup B1. Both the core genome and gene content trees showed a tree-wide spread of BF strains, with clusters, including both BF and NBF strains. Genome-wide association studies (GWAS) via Scoary or Pyseer did not find any genes or mutations that were overrepresented in the BF group. A retrospective analysis of phenotypes found a significant correlation (P < 0.05) between BF ability and curli production, cellulose synthesis, and/or mobility. However, the BF group also included strains that were negative for curli and cellulose and/or missing encoding genes for the two traits. All curli and cellulose encoding genes were present in most genomes, regardless of their BF status. The degree of motility was correlated with both curli and cellulose production, and 80 common genes were overrepresented in all three of the trait-positive groups. A PTS enzyme II, a subsidiary gluconate catabolism pathway, and an iron-dicitrate transport system were more abundant in the persisting E. coli group. These findings suggest gene function redundancy in E. coli for biofilm formation as well as additional substrate utilization and iron acquisition in its persistence. IMPORTANCE The persistence of potentially hazardous bacteria is a major challenge for meat processing environments, which are conducive for biofilm formation. Marker genes/phenotypes are commonly used to differentiate biofilm forming E. coli strains from their nonbiofilm forming counterparts. We took a comparative genomic analysis approach to analyze E. coli strains that were from the same environment but were differentiated by their biofilm forming ability. A diversification of the genes involved in the biofilm formation of E. coli was observed. Even though there is a correlation on the population level between biofilm formation and the expression of curli and cellulose, uncertainties exist on the individual strain level. Novel substrate utilization and iron acquisition could contribute to the persistence of E. coli. These findings not only advance our understanding of the ecology of E. coli with respect to its persistence but also show that a marker gene/phenotype driven approach for the biofilm control of E. coli may not be prudent.

The interplay between chemo-phoretic interactions and crowding in active colloids.

Many motile microorganisms communicate with each other and their environments via chemical signaling which leads to long-range interactions mediated by self-generated chemical gradients. However, consequences of the interplay between crowding and chemotactic interactions on their collective behavior remain poorly understood. In this work, we use Brownian dynamics simulations to investigate the effect of packing fraction on the formation of non-equilibrium structures in a monolayer of diffusiophoretic self-propelled colloids as a model for chemically active particles. Focusing on the case when a chemical field induces attractive positional and repulsive orientational interactions, we explore dynamical steady-states of active colloids of varying packing fractions and degrees of motility. In addition to collapsed, active gas, and dynamical clustering steady-states reported earlier for low packing fractions, a new phase-separated state emerges. The phase separation results from a competition between long-range diffusiophoretic interactions and motility and is observed at moderate activities and a wide range of packing fractions. Our analysis suggests that the fraction of particles in the largest cluster is a suitable order parameter for capturing the transition from an active gas and dynamical clustering states to a phase-separated state.

A phenotype-structured model to reproduce the avascular growth of a tumor and its interaction with the surrounding environment

We here propose a one-dimensional spatially explicit phenotype-structured model to analyze selected aspects of avascular tumor progression. In particular, our approach distinguishes viable and necrotic cell fractions. The metabolically active part of the disease is, in turn, differentiated according to a continuous trait, that identifies cell variants with different degrees of motility and proliferation potential. A parabolic partial differential equation (PDE) then governs the spatio-temporal evolution of the phenotypic distribution of active cells within the host tissue. In this respect, active tumor agents are allowed to duplicate, move upon haptotactic and pressure stimuli, and eventually undergo necrosis. The mutual influence between the emerging malignancy and its environment (in terms of molecular landscape) is implemented by coupling the evolution law of the viable tumor mass with a parabolic PDE for oxygen kinetics and a differential equation that accounts for local consumption of extracellular matrix (ECM) elements. The resulting numerical realizations reproduce tumor growth and invasion in a number scenarios that differ for cell properties (i.e., individual migratory behavior, duplication, and mutation potential) and environmental conditions (i.e., level of tissue oxygenation and homogeneity in the initial matrix profile). In particular, our simulations show that, in all cases, more mobile cell variants occupy the front edge of the tumor, whereas more proliferative clones are selected at more internal regions. A necrotic core constantly occupies the bulk of the mass due to nutrient deprivation. This work may eventually suggest some biomedical strategies to partially reduce tumor aggressiveness, i.e., to enhance necrosis of malignant tissue and to promote the presence of more proliferative cell phenotypes over more invasive ones.

Locomotion and searching behaviour in the honey bee larva depend on nursing interaction

Although honey bee brood does not need to seek shelter or food and restricts its movements to small wax cells, larvae have some degree of motility. Previously, other studies described how honey bee larvae showed analogous behaviours to the wandering period in holometabolous insects. The current research aimed to measure locomotion of the honey bee brood at different conditions of food supply and larval stadia. Besides, we developed an actometry assay to describe the larval behaviour under laboratory conditions. Our results suggested that the satiety and developmental program of larvae modulated their locomotion. Before they pupated, larval speed increased sharply and then it dropped until quiescence. However, starvation also induced an increase in angular velocity of brood. Starved larvae were between three and five times faster than the satiated ones. Moreover, fifth instars left their wax cells after 2 h of starvation without nurse bees. In the actometry assay, larvae showed behaviours of dispersion and changes in their kinematic parameters after detecting a tactile stimulus like the edge of arenas.

Modeling of kinematics and kinetostatics of planetary-lever mechanism

The article provides analytical formulas for determining the kinematic parameters of a planetary-lever mechanism with one and two degrees of mobility. The obtained formulas were realized on a computer, in the program Math CAD 15. According to the results of calculations on a computer, regularities were established for the change in the kinematic parameters of the links of the mechanisms under consideration. The influence of the direction and magnitude of the angular velocity of the central wheel on the kinematic characteristics of the planetary-lever mechanism with two degrees of mobility has been determined. Formulas are created to determine the reaction in kinematic pairs of a planetary-lever mechanism with one degree of motility. Based on the calculation results and analysis provided, regularities of the reaction change in the kinematic pairs, as well as balancing moments in the carrier, were established during the basic geometric parameters of this mechanism were varied.

High-resolution imaging of living gut mucosa: lymphocyte clusters beneath intestinal M cells are highly dynamic structures

In the Peyer's patches of the small intestine, specialized epithelial cells, the membranous (M) cells, sample antigenic matter from the gut lumen and bring it into contact with cells of the immune system, which are then capable of initiating specific immune reactions. Using autofluorescence 2-photon (A2P) microscopy, we imaged living intestinal mucosa at a 0.5-μm resolution. We identified individual M cells without the aid of a marker and in vivo analyzed their sampling function over hours. Time-lapse recordings revealed that lymphocytes associated with M cells display a remarkable degree of motility with average speed rates of 8.2μm/min, to form new M cell-associated lymphocyte clusters within less than 15min. The lymphocytes drastically deform the M cells' cytoplasm and laterally move from one lymphocyte cluster to the next. This implies that the micro-compartment beneath M cells is a highly efficient container to bring potentially harmful antigens into contact with large numbers of immunocompetent cells. Our setup opens a new window for high-resolution 3D imaging of functional processes occurring in lymphoid and mucosal tissues.

Rapid Accumulation of Motility-Activating Mutations in Resting Liquid Culture of Escherichia coli.

Expression of motility genes is a potentially beneficial but costly process in bacteria. Interestingly, many isolate strains of Escherichia coli possess motility genes but have lost the ability to activate them under conditions in which motility is advantageous, raising the question of how they respond to these situations. Through transcriptome profiling of strains in the E. coli single-gene knockout Keio collection, we noticed drastic upregulation of motility genes in many of the deletion strains compared to levels in their weakly motile parent strain (BW25113). We show that this switch to a motile phenotype is not a direct consequence of the genes deleted but is instead due to a variety of secondary mutations that increase the expression of the major motility regulator, FlhDC. Importantly, we find that this switch can be reproduced by growing poorly motile E. coli strains in nonshaking liquid medium overnight but not in shaking liquid medium. Individual isolates after the nonshaking overnight incubations acquired distinct mutations upstream of the flhDC operon, including different insertion sequence (IS) elements and, to a lesser extent, point mutations. The rapidity with which genetic changes sweep through the populations grown without shaking shows that poorly motile strains can quickly adapt to a motile lifestyle by genetic rewiring.IMPORTANCE The ability to tune gene expression in times of need outside preordained regulatory networks is an essential evolutionary process that allows organisms to survive and compete. Here, we show that upon overnight incubation in liquid medium without shaking, populations of largely nonmotile Escherichia coli bacteria can rapidly accumulate mutants that have constitutive motility. This effect contributes to widespread secondary mutations in the single-gene knockout library, the Keio collection. As a result, 49/71 (69%) of the Keio strains tested exhibited various degrees of motility, whereas their parental strain is poorly motile. These observations highlight the plasticity of gene expression even in the absence of preexisting regulatory programs and should raise awareness of procedures for handling laboratory strains of E. coli.

Induction of focal adhesions and motility inDrosophilaS2 cells

Focal adhesions are dynamic structures that interact with the extracellular matrix on the cell exterior and actin filaments on the cell interior, enabling cells to adhere and crawl along surfaces. We describe a system for inducing the formation of focal adhesions in normally non-ECM-adherent, nonmotile Drosophila S2 cells. These focal adhesions contain the expected molecular markers such as talin, vinculin, and p130Cas, and they require talin for their formation. The S2 cells with induced focal adhesions also display a nonpolarized form of motility on vitronectin-coated substrates. Consistent with findings in mammalian cells, the degree of motility can be tuned by changing the stiffness of the substrate and was increased after the depletion of PAK3, a p21-activated kinase. A subset of nonmotile, nonpolarized cells also exhibited focal adhesions that rapidly assembled and disassembled around the cell perimeter. Such cooperative and dynamic fluctuations of focal adhesions were decreased by RNA interference (RNAi) depletion of myosin II and focal adhesion kinase, suggesting that this behavior requires force and focal adhesion maturation. These results demonstrate that S2 cells, a cell line that is well studied for cytoskeletal dynamics and readily amenable to protein manipulation by RNAi, can be used to study the assembly and dynamics of focal adhesions and mechanosensitive cell motility.

Agentive Motility Meets Structural Viscosity: Australian Families Relocating in Educational Markets

This paper will develop and illustrate a concept of institutional viscosity to balance the more agentive concept of motility with a theoretical account of structural conditions. The argument articulates with two bodies of work: broad social theory of reflexivity as negotiating agency and social structures; and sociology of mobility and mobility systems . It then illustrates the concept of viscosity as a variable (low to high viscosity) through two empirical studies conducted in the sociology of education that help demonstrate how degrees of viscosity interact with degrees of motility, and how this interaction can impact on motility over time. The first study explored how Australian Defence Force families cope with their children’s disrupted education given frequent forced relocations. The other study explored how middle class professionals relate to career and educational opportunities in rural and remote Queensland. These two life conditions have produced very different institutional practices to make relocations thinkable and doable, by variously constraining or enabling mobility. In turn, the degrees of viscosity mobile individuals meet with over time can erode or elevate their motility.

Enucleation versus Evisceration in Ocular Trauma: A Retrospective Review and Study of Current Literature

Purpose: To compare variables and outcomes from ocular trauma leading to either enucleation or evisceration to better inform surgical decision making.Design: Retrospective chart review.Methods: We reviewed 441 patients between 2001 and 2012 presenting with ocular trauma to a Level 1 trauma center in Queens, New York; of these, there were 16 enucleations and 6 eviscerations. Retrospective chart review noted age, gender, mechanism of injury, initial and final visual acuity, time to surgery, length of follow-up, pain, degree of motility, and complications. A review of literature in the context of our study was performed.Results: 20 patients were male and 2 patients were female; average age was 44 (SD: 20.0, range 18–91). 9/16 patients were enucleated to prevent sympathetic ophthalmia, whereas only 1/5 patient was eviscerated for this indication (p = 0.1619). No cases of sympathetic ophthalmia were reported over an average follow-up of 316 days. Average length of follow-up varied significantly between the two groups, with an average of 370.4 days (SD: 566.9, range 0–1870) for enucleated eyes and 172.7 days (SD: 146.3, range 0–422) for eviscerated eyes (p = 0.42). Medpor implants were preferred in eviscerations (5/6 eviscerations), whereas hydroxyapatite implants were preferred in enucleations (10/16 enucleations, p = 0.04).Conclusions: Surgical decision-making in ocular trauma is largely based on surgeon preference and experience, with minimal evidence in the literature to support either enucleation or evisceration. We recommend evisceration over enucleation in cases of reliable patient follow-up due to the low incidence of sympathetic ophthalmia.

Bacterial Attachment and Viscoelasticity: Physicochemical and Motility Effects Analyzed Using Quartz Crystal Microbalance with Dissipation (QCM-D)

This investigation is focused on the combined effect of bacterial physicochemical characteristics and motility on cell adhesion and deposition using a flow-through quartz crystal microbalance with dissipation (QCM-D). Three model flagellated strains with different degrees of motility were selected, including a highly motile Escherichia coli K12 MG1655, an environmental strain Sphingomonas wittichii RW1, and a nonmotile (with paralyzed flagella) Escherichia coli K12 MG1655 ΔmotA that is incapable of encoding the motor torque generator for flagellar movement. Of the three strains, S. wittichii RW1 is highly hydrophobic, while E. coli strains are equally hydrophilic. Consideration of the hydrophobicity provides an alternative explanation for the bacterial adhesion behavior. QCM-D results show that motility is a critical factor in determining bacterial adhesion, as long as the aquatic chemical conditions are conducive for motility and the substratum and bacterial surface are similarly hydrophobic or hydrophilic. Once their properties are not similar, the contribution of hydrophobic interactions becomes more pronounced. QCM-D results suggest that during adhesion of the hydrophobic bacterium, S. wittichii RW1, the initial step of adhesion and maturation of bacteria-substratum interaction on hydrophilic surface includes a dynamic change of the viscoelastic properties of the bond bacterium-surface becoming more viscously oriented.

Abstract 487: Invasion characteristics of tumor cells in a glioblastoma model of genetically modified neural stem cells

Abstract Background: Although several types of cells in the brain are able to migrate during development or even in adulthood, only cells of high grade malignancies exhibit an invasive phenotype. The present study aims to characterize the differences between infiltrating tumor cells and their cells of origin using a model of genetically-induced glioblastoma-initiating cells (GICs) in the syngeneic mouse adult brain. Methods: Neural stem cells/ multipotent progenitor cells (NSCs/NPCs) were isolated from the subventricular zone of adult C57BL/6 mice with a homozygous deletion of the Ink4a/ARF locus and cultured as neurospheres. GICs were established by overexpression of H-RasV12 in the NSCs/NPCs. Tumor cells were isolated from the tumors formed by orthotopic implantation of the GICs into 6-week-old wild type mice and propagated as tumorspheres (TS). The motility of each type of cells and their response to various chemoattractants was assessed using in vitro migration assays. Their preference for anatomical structures and their ability to infiltrate the surrounding normal brain was analyzed by tracking the cells in cultured coronal brain slices established from stereotactically-implanted mice. Results: In vitro, both tumor cells and NSCs exhibited a similar degree of motility, but consistently varied in their response to a panel of chemoattractants. Compared to NSCs, GICs and TS responded only slightly to single growth factors or cytokines, but showed significant responses to combinations of chemoattractants. The most marked increase in migration was triggered by the supernatant of cultured tumor cells. Supernatants obtained from GICs, TS or human glioma cell lines induced migration to a similar degree. Timelapse microscopy confirmed motility of both normal and tumor cells, with all three groups being able to move both within the cortex and within the striatum, and both along blood vessels and fiber tracts. However, NSCs/NPCs did not leave the injection site as single cells, while GICs and TS entered and infiltrated the normal brain as solitary cells. This pattern of migration was greatly reduced by the administration of epithelial-to-mesenchymal transition (EMT) inhibitors, both in vitro and in vivo. Conclusion: Our results show that tumor invasion is multifactorial, with both autocrine secretion of several factors, as well as a mesenchymal phenotype being key regulators. Moreover, the mesenchymal phenotype in itself is a targetable attribute and should be assessed in patient samples in order to adjust anti-invasive therapy when warranted. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 487. doi:1538-7445.AM2012-487

When ONE is the not-so-loneliest number!

When ONE is the not-so-loneliest number!

242 EFFECTS OF TWO COMMERCIAL BOVINE SEMEN EXTENDERS FOR SHORT-TERM STORAGE ON MOTILITY PATTERN OF CHILLED BISON SEMEN

Difficulties of adequate cryopreservation of bison semen has limited the success of artificial insemination and in-vitro embryo production in bison. We evaluated the effects of short-term cooling on motility of bison sperm using two commercial semen extenders (Triladyl® and Andromed®; Minitube, Ingersoll, ON, Canada). Semen was collected by electroejaculation of mature wood bison (n = 3) and plains bison (n = 3) twice a week for 2 wk. Upon collection, the ejaculate was divided into 3 equal aliquots, which were then diluted 1:2 (vol/vol) in Triladyl or Andromed, or were not extended (n = 24 samples per treatment). Samples were maintained at 37°C until transfer to the laboratory (≤2 h). One millilitre of each sample was then placed into a test tube (15 mL, BD Falcon, BD Biosciences, San Jose, CA, USA) and were kept in water bath set at 5°C inside a walk-in refrigerator (4°C). Characteristics of sperm motility were evaluated before cooling (Day 0) and every 24 h after cooling for 5 days using a computer-assisted semen analyzer. Total motility (TM), progressive motility (PM), velocity curved line (VCL), velocity average path (VAP), and velocity straight line (VSL) were compared among treatments by ANOVA for repeated-measures. Values are expressed as mean ± SEM. After collection, the PM of the raw semen and semen extended in Triladyl or Andromed were not significantly different (63.1 ± 4.4%, 63.3 ± 3.1%, and 56.9 ± 4.5%, respectively). Cooling semen for a period of 24 h resulted in a decrease (P &lt; 0.05) in PM in all 3 groups (4.4 ± 2.0%, 22.7 ± 2.9%, and 28.7 ± 4.3%, respectively). The PM of semen extended in Tryladyl or Andromed was greater than that of raw semen on Day 1 (P &lt; 0.05). Semen extended in Triladyl and Andromed maintained PM on Day 2 (24.7 ± 3.3% and 21.8 ± 3.8%, respectively), but PM declined progressively to 1.1 ± 0.6% and 6.3 ± 2.1% by Day 5. A similar pattern was observed for the TM. The VCL, VAP, and VSL parameters for semen extended with Triladyl and Andromed decreased gradually between Day 0 and Day 5 (P &lt; 0.05). From Day 1 to 4 after cooling, these velocity parameters were not significantly different between semen extended with Triladyl or Andromed; however, they were greater than those of raw semen (P &lt; 0.05). All sperm velocity parameters for the raw semen declined by more than 60% between Days 0 and 2 (P &lt; 0.05). On Day 0, VCL for semen extended with Andromed (152.2 ± 4.3) was greater than that of semen extended with Triladyl and raw semen (P &lt; 0.05; 122.5 ± 7.0 and 122.4 ± 6.6, respectively). The VCL then decreased to 98.9 ± 12.9, 100.5 ± 10.8, and 18.6 ± 6.8 in Andromed, Triladyl and raw groups respectively on Day 2 (P &lt; 0.05), followed by a further decline to 51.8 ± 14.3, 19.9 ± 10.0, and 9.0 ± 5.0, respectively, observed on Day 5. In conclusion, both Triladyl and Andromed improved characteristics of sperm motility of chilled bison semen. Despite an initial decrease within the first 24 h, bison sperm extended with Triladyl or Andromed maintained an acceptable degree of motility for up to 2 days after chilling to 5°C. Supported by Agriculture and Agri-Food Canada, Agriculture and Development Fund, and Canadian Animal Genetic Resources program.

Testicular Function after Herniotomy Herniotomy and Fertility

One hundred thirty one men who underwent inguinal herniotomy were included in this study, of these, 19 (14.4%) were found to have changes in their testicular size on the side of the operation. Of the 19 men 9 had been operated on for right inguinal hernia, 6 for left inguinal hernia and 4 for bilateral inguinal hernia. All the men were infertile with decreased sperm quality (as measured by concentration, motility, degree of motility and morphology). Most of the men with damaged testes showed elevated serum FSH and decreased serum testosterone. 112 men who had undergone herniotomy were found to have normal sized testicles. They were referred to this institute because of infertility and their semen quality and blood hormones (FSH, LH and testosterone) were evaluated for comparison with the group of the men possessing damaged testicles.

Intrauterine insemination in male factor subfertility: significance of sperm motility and morphology assessed by strict criteria.

The study was conducted to evaluate the results of IUI treatment in a homogenous group with male factor infertility, and to assess the correlation of sperm variables, including sperm morphology by strict criteria, with pregnancy achievement after IUI. A total of 108 couples with no apparent female aetiology for infertility underwent 264 intrauterine insemination treatment cycles. A comparison was made between the sperm variables in two groups in which the achievement of pregnancy differed. The percentage of motile spermatozoa, degree of motility and normal morphology (by strict criteria) were significantly higher in the pregnant group compared with that of the nonpregnant group. A significant difference in pregnancy rates per couple after intrauterine insemination was demonstrated among three groups according to the percentage of sperm morphology, i.e. poor (< 4%), fair (4-14%) or good (> 14%) (11.1%; 36.1% and 50.0%, respectively). Intrauterine insemination is a valid mode of treatment in cases with male infertility, provided that normal morphology by strict criteria is higher than 4%.

Fine structure of the choroidal coat of the avian eye. Vascularization, supporting tissue and innervation.

To clarify further the functional anatomy of the avian choroid, including its innervation, 12 adult White-Leghorn chickens were studied by standard electron microscopy and immunoelectron microscopy with somatostatin antibody. The endothelial cells of the blood vessels in the choriocapillaris have fenestrations only facing the retina, while the nuclei are situated toward the sclera. In addition to tight junctions and zonulae adherentes, adjoining endothelial cells form gap junctions and dense plaques with attached filaments resembling those of smooth muscle cells. The fine structure of arteries and veins is similar to that of the vasculature described in other organs. The supporting tissue is organized in trabeculae, i.e., bridges of cellular and fibrous elements that surround and sustain blood and lymphatic vessels. This tissue consists primarily of a system of fusiform or star-shaped smooth muscle cells, connected to each other and to those in the vessels' walls through macular junctions of the adherent type, less prominent than desmosomes, and perhaps also punctiform gap junctions. Occasionally, trabecular smooth muscle cells approach the lymphatic vessels, which lack a muscular tunica, and abut their endothelium with spinous appendages. This stromal muscle tissue may act as a pump for moving the lymph. The suprachoroidea consists of large lymphatic lacunae and the multilayered membrana fusca. The elongated fuscal cells form adherent junctions, tight junctions, and perhaps also gap junctions, suggesting that the membrana fusca exerts complex functions. Nerves containing myelinated axons reach the choroid and divide into smaller branches, a few of which innervate the membrana fusca. Numerous, thin nerve branches reach both the walls of arteries and veins and the trabeculae, and synaptic terminals abut the outer muscular layers of the vessel's wall and the smooth muscle cells of the supporting tissue. Immunocytochemistry reveals the presence of numerous somatostatin-positive and somatostatin-negative axons and synaptic terminals within both trabeculae and vascular tunica media. The somatostatin-positive axons are presumed to be cholinergic axons of the choroid neurons residing in the ciliary ganglion. Taken together, these observations indicate that the avian choroid is a highly vascularized muscular sheath that may be endowed with degrees of motility and elasticity higher than those of the mammalian choroid and may therefore play an important role in compensation for experimental defocus.

Active movement of chickpea and bean rhizobia in dry soil

Soil matric potential strongly influenced the movement of three strains of chickpea and bean rhizobia in soil. The strains were able to move (albeit relatively slowly) in soils at matric potentials drier than that believed to be the limit for bacteria movement (−0.1 MPa). The non-motile and non-flagellated strain, 18A str rif moved faster than the flagellated and motile strains in soils at or drier than −1.5 MPa matric potential, but slower than the other strains in wetter soil. The degree of motility and the presence of flagella were important factors influencing the movement of rhizobia in soils that had water-filled pores larger than cell size. The role of flagella and motility became less important as water-pathways became smaller and discontinuous. The movement of rhizobia was less in clay soils than in light-textured soils over the range of matric potentials investigated, possibly due to adsorption to clay particles.

Migration sedimentation technique as a predictive test for the fertilizing capacity of spermatozoa in an in-vitro fertilization programme.

The migration-sedimentation technique (MST) has been proposed as a means of separating high quality motile spermatozoa. The present study was conducted in order to evaluate whether sperm performance following separation by MST predicts their fertilizing capacity in an in-vitro fertilization (IVF) programme. Ninety semen specimens were analysed for use in an IVF-embryo transfer (ET) programme. Each specimens was divided into two parts: one was processed in the IVF programme and was used after sperm swim-up separation for insemination of human ova. The other aliquot (0.2 ml) was separated by MST, and the sperm then characterized by their concentration, motility, degree of motility and morphology. Sperm characteristics after separation by MST were then correlated with the results of the IVF-fertilization rates. In 79 of 90 IVF-ET cycles, at least one oocyte was fertilized. All post-MST sperm characteristics were significantly higher in cycles with fertilizations compared to IVF cycles without fertilization. A larger percentage of the total motile spermatozoa were recovered after MST in semen specimens with fertilization, compared to semen specimens without fertilization (39.9 +/- 3.6 and 20.6 +/- 6.6%, respectively; P < 0.05). This value was correlated with the percentage of fertilized oocytes (r = 0.24; P < 0.02). More IVF cycles with fertilizations were recorded in cases in which the recovery of motile sperm was > 25% (P < 0.005), or when more than 1.5 x 10(6) motile spermatozoa were recovered after MST (P < 0.0001). As sperm characteristics after MST correlated significantly with their fertilizing capacity, the MST test could be used in evaluation of the fertilizing capacity of spermatozoa.

Fertility prognosis for infertile men: results of follow-up study of semen analysis in infertile men from two different populations evaluated by the Cox regression model

Using the Cox proportional hazard regression model on one material (group I = 765, 1950 to 1951) we have identified four variables of semen analysis with significant prognostic information about fertility. The four variables were combined into a model for establishing the probability of the individual male to achieve pregnancy as a function of time. This model is tested first on another material (group II = 321, 1977 to 1985). A Goodness-of-fit test indicates excellent agreement between the expectations from the model and the observed number of pregnancies in group II. Second, the two groups are pooled (= 1,086). Then only three variables give significant prognostic information about the time until pregnancy: (1) the man's age at semen analysis (years); (2) the percentage of morphologically normal spermatozoa (ln %); and (3) the degree of motility (good/poor). These three important variables enter into a new and better prognostic model.