Untreated Pairs Research Articles

Influence of the microstructure on the rolling contact fatigue of rail steel: Spheroidized pearlite and fully pearlitic microstructure analysis

Twin-disc tests were carried out between two discs of rail steel (fully pearlitic and spheroidized microstructures) to investigate the effect of the flash-butt welded rail HAZ microstructure. The spheroidized cementite microstructure was obtained by heat-treating simulating the HAZ softer region. Ten tests were performed for each condition, considering maximum Hertz pressure of 1100 MPa, rotation speed of 400 rpm and slip of 0% and 1%. The results showed that the spheroidized cementite discs (with less hardness) presented more significant surface hardness due to deformation, more clearly for the tests carried out with 1% slip. This factor led to a cracking process for both heat-treated discs and counter-discs with a completely pearlitic microstructure. The number of cycles for the beginning of contact fatigue between the specimens compared to the untreated pairs proved to be statistically equal in the tests carried out with 1% slip. In tests without slip, however, this phenomenon did not occur, as the spheroidized discs showed a significant decrease in the number of cycles before the beginning of contact fatigue. Plastic deformation was observed around the fatigue cracks (even in the spheroidized microstructure’s discs), and the presence of inclusions influenced the cracking process.

Impact of contraceptive hormones on the reproductive potential of male and female commensal black rats (Rattus rattus).

The black rat is considered one of the world's top pests. With increased restrictions on rodenticides, new alternatives to manage rats are urgently needed. Research on the use of contraceptive hormones, levonorgestrel (LE), and quinestrol (QU), have been evaluated against some rodent species, and this research is the first study to assess these on black rats. Hormones were incorporated into rodent bait at 10 and 50 ppm concentrations singly and in combination (EP-1). Groups of 10 animals of each sex were fed the baits over 7days. Lower bait consumption was observed with slight body mass reductions. On dissection, it was observed that the uterus was in a state of edema and male reproductive organs weighed less with reduced sperm counts/motility. The 2 most promising baits, 50 ppm QU and EP-1, were used to assess impact on pregnancy and litter size. Pregnancy was reduced from 70% success when both males and females consumed untreated bait, down to 30% when males had consumed contraceptive bait but females had not, and down to 0% when females had consumed contraceptive bait, regardless of whether they had paired with a treated or untreated male. Litter size in the untreated pairs was 8 pups, but only 4 pups in those cases where the male only had consumed the contraceptive. Further studies should investigate how long the effect lasts and its reversibility. Field studies at the population level may also shed light on the practicality of using contraceptive baits for black rats in different habitats.

Inductions of reproduction and population growth in the generalist predator Cyrtorhinus lividipennis (Hemiptera: Miridae) exposed to sub-lethal concentrations of insecticides.

The miridbug, Cyrtorhinus lividipennis, is a significant predacious enemy of rice planthoppers. The effects of sub-lethal concentrations of triazophos, deltamethrin and imidacloprid on fecundity, egg hatchability, expression levels of genes associated with reproduction, and population growth in C. lividipennis were investigated. The fecundities for three pair combinations (♀c × ♂t , ♀t × ♂c and ♀t × ♂t ) treated with sub-lethal concentrations of the insecticides triazophos, deltamethrin and imidacloprid (LC10 and LC20 ) showed a significant increase compared to the untreated pairs (♀c × ♂c ). However, sub-lethal concentration treatments did not affect the egg hatchability. The ClVg expression levels of female adults exposed to triazophos, deltamethrin and imidacloprid (LC20 ) increased by 52.6, 48.9 and 91.2%, respectively. The ClSPATA13 expression level of adult males exposed to triazophos, deltamethrim and imidacloprid (LC20 ) increased by 80.7, 41.3 and 48.3%, respectively. Furthermore, sub-lethal concentrations of insecticides (LC20 ) caused increased population numbers in C. lividipennis. Sub-lethal concentrations of triazophos, deltamethrin and imidacloprid stimulated reproduction and enhanced population growth of C. lividipennis. The reproductive stimulation might result from the up-regulation of ClVg or ClSPATA13. These findings may be useful in mediating populations of planthoppers. © 2017 Society of Chemical Industry.

Abstract 5017: T-cell repertoire turnover induced by anti-CTLA-4 antibody treatment in cancer patients

Abstract While treatment with anti-CTLA-4 antibody can induce clinical responses in advanced cancer patients, its effects on the breadth of the T cell response is unknown. We used a next-generation sequencing-based method to assess T cell repertoire diversity in 46 patients with metastatic castration resistant prostate cancer or metastatic melanoma. Peripheral blood mononuclear cells were obtained from patients prior to and during treatment with anti-CTLA-4 antibody. mRNA was amplified using locus-specific primer sets for T cell receptor (TCR) beta, and the amplified product was sequenced. Sequence reads were used to quantitate absolute TCR frequencies using standardized clonotype determination algorithms with normalization by spiked reference TCR sequences. Following clonotype quantitation, repertoire differences between serial samples were assessed by the Morisita index, a statistical measure of population dispersion. 97 paired samples were assessed, of which 46 (47%) had increases and 22 (23%) had decreases in TCR diversity by more than 2-fold. By comparison, none of 9 untreated sample pairs underwent more than a 2-fold change in diversity (P = 0.005, Fisher's exact test, two tailed). TCR repertoire differences between monthly samples were markedly higher than for time-matched controls. After the first treatment, median Morisita index between samples was 0.197 for treated samples versus 0.039 for untreated (P = 0.0005, Mann-Whitney U test). The median number of clones that significantly changed in abundance was 421 for treated versus 45 for controls. In patients with multiple time points, this rapid clonotype evolution continued through treatment. Whereas the number of clonotypes that increased with treatment was not associated with clinical outcome, improved overall survival was associated with maintenance of high frequency clones present at baseline. In contrast the highest frequency clonotypes fell with treatment in patients with shorter overall survival. Stably maintained clonotypes included T cells possessing high avidity TCR such as CMV-reactive T cells. Together, these results suggest that CTLA-4 blockade induces T-cell repertoire evolution and diversification. Moreover, improved clinical outcomes are associated with less clonotype loss, consistent with the maintenance of high frequency TCR clonotypes during treatment. These clones may represent the presence of pre-existing high avidity T cells that may be relevant in the anti-tumor response. Citation Format: Lawrence H. Fong, Edward Cha, Mark Klinger, Yafei Hou, Craig Cummings, Antoni Ribas, Malek Faham. T-cell repertoire turnover induced by anti-CTLA-4 antibody treatment in cancer patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5017. doi:10.1158/1538-7445.AM2014-5017

Let us go back to basics

Let us go back to basics

Restoration Practices Have Positive Effects on Breeding Bird Species of Concern in the Chihuahuan Desert.

Woody plant encroachment into grasslands is a global concern. Efforts to restore grasslands often assume that removal of woody plants benefits biodiversity but assumptions are rarely tested. In the Chihuahuan Desert of the Southwestern United States, we tested whether abundances of grassland specialist bird species would be greater in plant communities resulting from treatment with herbicides to remove encroaching shrubs compared with untreated shrub‐dominated areas that represented pre‐treatment conditions. In 2010, we surveyed breeding birds and vegetation at 16 treated–untreated pairs. In 2011, we expanded the survey effort to 21 treated–untreated pairs, seven unpaired treatment areas, and five reference grassland areas. Vegetation in treatment areas had higher perennial grass foliar and basal cover and lower shrub foliar cover compared with untreated areas. Several regionally declining grassland specialists exhibited higher occurrence and relative abundance in treated areas. A shrubland specialist, however, was associated with untreated areas and may be negatively impacted by shrub removal. Bird community composition differed between treated and untreated areas in both years. Our results indicate that shrub removal can have positive effects on grassland specialist bird species, but that a mosaic of treated and untreated areas might be most beneficial for regional biodiversity.

Effect of anti-CTLA-4 antibody treatment on T-cell repertoire evolution in treated cancer patients.

3020 Background: CTL-associated antigen 4 (CTLA-4) is an immune checkpoint expressed by T cells. While treatment with anti-CTLA-4 antibody can induce clinical responses in advanced cancer patients, its effects on the breadth of the T cell response is unknown. Methods: We used a sequencing-based method, LymphoSIGHT, to assess T cell repertoire diversity in 46 patients with metastatic castration resistant prostate cancer or metastatic melanoma. Peripheral blood mononuclear cells were obtained from patients prior to and during treatment with anti-CTLA-4 antibody. mRNA was amplified using locus-specific primer sets for T cell receptor (TCR) beta, and the amplified product was sequenced. Sequence reads were used to quantitate absolute TCR frequencies using standardized clonotype determination algorithms with normalization by spiked reference TCR sequences. Following clonotype quantitation, repertoire differences between serial samples were assessed by the Morisita index, a statistical measure of population dispersion. Results: 97 paired samples were assessed, of which 46 (47%) had increases and 22 (23%) had decreases in TCR diversity by more than 2-fold. By comparison, none of 9 untreated sample pairs underwent more than a 2-fold change in diversity (P = 0.005, Fisher’s exact test, two tailed). TCR repertoire differences between monthly samples were markedly higher than for time-matched controls. After the first treatment, median Morisita index between samples was 0.197 for treated samples versus 0.039 for untreated (P = 0.0005, Mann-Whitney U test). The median number of clones that significantly changed in abundance was 421 for treated versus 45 for controls. In patients with multiple time points, this rapid clonotype evolution continued through treatment. Despite this global turnover in repertoire, a subset of high frequency clones, including CMV-specific T cells, remained relatively constant over the course of the study. Conclusions: CTLA-4 blockade increases the global rate of T cell clonotype turnover and influences TCR diversity. This evolution of the TCR repertoire may reflect a mechanism by which CTLA-4 blockade enhances tumor-specific T cells over time.

Abstract 1885: A comprehensive untargeted UPLC-MS based metabolomic analysis of ASS1-deficient solid tumor cell lines treated with arginine deiminase.

Abstract Background Arginine is an important amino acid for tumor cell growth and development. Argininosuccinate synthetase 1 (ASS1) is a key enzyme required for biosynthesis of arginine. Preclinically, ASS1-deficient tumor cells are particularly sensitive to arginine depletion, and randomised trials exploring this strategy are in progress in hepatocellular carcinoma and mesothelioma using the drug pegylated arginine deiminase (ADI-PEG20). In this study, we determined the metabolic changes induced by ADI-PEG20 treatment in a panel of bladder cancer and mesothelioma cell lines with promoter methylation-dependent silencing of ASS1. We used two cancer cell lines expressing ASS1 as a control. Methods Malignant mesothelioma, ASS1-negative (H2591, MSTO and JU77) and ASS1- positive (H28) cell lines were used. For bladder cancer, ASS1-negative (T24, 253J, UMUC-3) and ASS1-positive (RT112) cell lines were also used. All cells were treated with 750 ng/ml of ADI-PEG20 for 24 hours which induces up to 90% killing of arginine-dependent cell lines. Then, ultra performance liquid chromatography-mass spectrometry (UPLC-MS) technique was employed for untargeted quantitation of the metabolomic changes induced by ADI-PEG20. Results: All cell lines treated with ADI-PEG20 could be clearly discriminated from their untreated control pair when using PCA multivariate analysis. Arginine depletion was noted in all treated cell lines irrespective of ASS1 expression, however the reduction was at least one-log-fold greater in the ASS1-negative tumor cells. Citrulline, n-a-acetylcitrulline, and glutamine were upregulated specifically in ASS1-negative tumor cell lines. The main impact of ADI-PEG20 treatment was on pyrimidine metabolism in the ASS1-deficient tumor cells with upregulation of thymine and downregulation of thymidine, ureidosuccinic acid, uridine monophosphate and 5-hydroxymethyluracil. Notably, we identified that the reduction of the thymidine nucleotide pool was linked to suppression of thymidylate synthetase and dihydrofolate reductase, and paradoxically, reduced uptake of 3H-FLT. Finally, ADI-PEG20 caused variable effects on cytidine, uridine and ornithine levels in different cancer cell lines. Conclusion This study provides an insight into possible metabolic pathways affected by ADI-PEG20. The impact of ADI-PEG20 on thymidine metabolism, in particular, may be employed as a potential biomarker for optimizing the efficacy of ADI-PEG20 in the treatment of arginine auxotophic cancers. Citation Format: Essam A. Ghazaly, Phuong Luong, Malgorzata Chmielewska-Kassasir, Chantelle Hudson, John S. Bomalaski, L Wozniak, Norbert E. Avril, Simon P. Joel, Peter W. Szlosarek. A comprehensive untargeted UPLC-MS based metabolomic analysis of ASS1-deficient solid tumor cell lines treated with arginine deiminase. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1885. doi:10.1158/1538-7445.AM2013-1885

Response of lizard community structure to desert grassland restoration mediated by a keystone rodent

Many grasslands in the Chihuahuan Desert have transformed to shrublands dominated by creosotebush (Larrea tridentata). Grassland restoration efforts have been directed at controlling creosotebush by applying herbicide over large spatial scales. However, we have a limited understanding of how landscape-scale restoration affects biodiversity. We examined whether restoration treatments in southern New Mexico, USA have influenced the community structure of lizards, which are sensitive to shrub encroachment. We compared lizard community structure on 21 areas treated with herbicide from 7 to 29 years ago with paired untreated areas that were dominated by shrubs and matched by geomorphology, soils, and elevation. To examine mechanisms underlying responses to restoration, we tested whether the abundance of a grassland specialist, Aspidoscelis uniparens, depended on time since treatment, treatment area and isolation, and local habitat quality. Because lizards use rodent burrows as habitat, we tested whether community structure and A. uniparens abundance depended on the abundance of the keystone rodent, Dipodomys spectabilis. Treated areas had reduced shrub cover and increased grass cover compared to untreated areas. Lizard community composition differed strongly between areas, with four species responding to treatments. Divergence in community composition between treated–untreated pairs was greatest for old treatments (≥22 years), and community composition was influenced by D. spectabilis. In particular, the abundance of A. uniparens was greatest on old treatments with a high density of D. spectabilis. Overall, our results demonstrate lizard community structure responds to grassland restoration efforts, and keystone species can shape restoration outcomes. Reestablishment of keystone species may be a critical constraint on the recovery of animal biodiversity after habitat restoration.

Communication disruption of light brown apple moth (Epiphyas postvittana) using a four-component sex pheromone blend

A new four-component sex pheromone blend for light brown apple moth (Epiphyas postvittana) was examined for efficacy of communication disruption in laboratory and field trials. Vineyard trials using SPLAT LBAM™ examined disruption of traps in the presence of: a) the current two-component ((E)-11-tetradecenyl acetate and (E,E)-9,11-tetradecadienyl acetate, 95:5), b) a new four-component blend ((E)-11-tetradecenyl acetate and (E,E)-9,11-tetradecadienyl acetate plus (E)-11-tetradecen-1-ol and (E)-11-hexadecenyl acetate (10:0.5:0.1:0.05)), c) higher ratio of the two new compounds (10:0.5:10:10), d) four compounds with an antagonist ((Z)-11-tetradecenyl acetate) added, e) three compounds with antagonist minus the most expensive component ((E,E)-9,11-tetradecadienyl acetate), compared to f) untreated controls. In the laboratory, 69.0% of untreated pairs mated, and communication was suppressed by both attractive blends (41.1% communication (P = 0.024, two-component blend), and 18.4% communication (P = 0.003, four-component blend)). In vineyards, totals of 24,776 and 41,053 male moths were caught in the two trials, respectively, to delta traps baited with four-component lures and virgin females. Communication disruption was achieved at a higher level with a four-component blend for 13/14 weeks in disruption trial one and for 10/10 weeks in disruption trial two, compared with the two-component blend. Disruption was on average improved by 12% with the four-component blend compared to the two-component blend (P = 0.091). Other blends were less effective at communication disruption. The best formulation released from SPLAT™ was only weakly attractive compared to rubber septa, so false trail following to point sources was unlikely to be as important as other mechanisms.

Influence of sterilization on the retention properties of magnetic attachments for dental implants

When used with dental implants advantages of the magnetic attachments include control of load transmitted to implants, improvements in stability, support and retention for the prosthesis, and the relative ease of prostheses fabrication. Clinically, the use of sterilized components is required, and this may be problematic as magnetic alloys are sensitive to temperature. The purpose of this study was to evaluate the influence of autoclave sterilization on the maximum retentive forces and characteristic curves for magnetic attachments recommended for use with dental implants. Eleven SmCo and NeFeB implant magnetic attachments were evaluated as provided by the respective manufacturers. Implant magnetic abutment and the corresponding denture magnet (n=5 magnet pairs) were tested before and after standardized autoclave sterilization (10 min at 134 degrees C). Each magnet pair was tested 10 times in a calibrated universal testing machine using a non-magnetic test device (s=40 mm, v=20 mm/min). Results were recorded electronically and statistically analyzed using t-test and ANOVA (Welch and Brown-Forsythe test; P<0.05). After autoclave sterilization all magnetic pairs produced lower (though statistically insignificant) overall retention forces compared with the untreated pairs. After sterilization mean maximum retentive forces (SD) ranged from 5.65 (0.33) to 1.41 (0.07) N. The characteristic force-displacement curves of the tested magnetic systems showed differences among the single products. Autoclave sterilization caused a non-significant reduction in retentive force of 0.04-14.6% when compared with the unsterilized magnet pairs. There were differences between the tested magnetic pairs for both the initial breakaway forces and the characteristic force-displacement curves. Within the limitations of this study all tested magnetic attachments were sterilized in an autoclave without significant change of retention properties. Nevertheless magnetic implant abutments should be sterilized with caution to reduce the risk of alterations of the retention properties.

A Radiolabeled Oligonucleotide Ligation Assay Demonstrates the High Frequency of Nevirapine Resistance Mutations in HIV Type 1 Quasispecies of NVP-Treated and Untreated Mother–Infant Pairs from Uganda

This study explores the levels of NVP and AZT resistance mutations in untreated, NVP- or AZT-treated mother-infant pairs in Uganda. PCR-amplified reverse transcriptase (RT) gene fragments derived from PBMC samples of 85 mothers (10 AZT treated, 35 NVP treated, and 40 untreated) and their 52 infected infants (5 AZT, 9 NVP, and 38 untreated) were classified as subtype A (59%), D (29%), C (3%), and recombinant forms (9%) by population sequencing. Only 16% of the NVP-treated infected mothers and infants harbored either the K103N or the Y181C at 6 weeks postdelivery. The majority of these samples (n = 107) were then analyzed using a radiolabeled oligonucleotide ligation assay (OLA) specific for K70R, K103N, and Y181C, using nonstandard bases to accommodate sequence heterogeneity. By OLA, 43% of the NVP-treated group had K103N and/or Y181C mutations in their HIV-1 population, using >0.6% cutoff based on a comparative clonal analysis of clinical isolates. Surprisingly, an equal fraction of the untreated and NVP-treated mother-infant group had the K103N mutation in their HIV-1 population in the range of 0.6-5%. These findings suggest a relatively high frequency of K103N mutation in the drug-naive, subtype A and D infected Ugandan population as compared to the very low frequency of the Y181C and K70R mutation (<0.6%). The prevalence of the K103N mutations may be related to its low fitness cost and high genetic stability. The persistence of these mutations may reduce the effectiveness of subsequent NVP use in treatment or prevention of perinatal transmission.

Identification and Characterization of HIV‐1 CD8+T Cell Escape Variants with Impaired Fitness

In this study, amino acid sequence variation in human immunodeficiency virus (HIV)-1 Gag CD8(+) T cell epitopes was examined in untreated mother-infant pairs. Several HIV-1 CD8(+) T cell escape variants were identified within maternal plasma viral p17 and p24 sequences that were either not detected or did not persist in the plasma of their non-HLA-matched HIV-1-infected infants. Viruses constructed with each of these mutations demonstrated reduced viral replication in vitro and reduced expression of p17 and p24 proteins compared with wild type. Reduced recognition of the variant sequences compared with wild-type sequence was also demonstrated by enzyme-linked immunospot assays. Nontransmission or reversion after transmission was thus associated with reduced viral fitness cost in vivo. Better understanding of the balance between CD8(+) T cell selective pressures and viral fitness cost may facilitate the identification of optimal viral sequences for inclusion in HIV-1 vaccines.

In vitro-activated charcoal binding of staphylococcal enterotoxin B

Objective. Staphylococcal enterotoxin B (SEB) is a CDC category B bioterror agent that may cause significant morbidity. We assessed the in vitro binding of SEB by activated charcoal (AC). Methods. Aqueous solutions of SEB at three concentrations (0.4, 2 and 10 mcg/mL) were combined in volume rations of 3:1, 6:1, and 12:1 with AC at three concentrations (62.5, 125, and 250 mg/mL) or left untreated as control samples. Subsequently, each sample was tested with a qualitative SEB immunoassay to detect the presence of SEB at concentrations of >12.5 ng/mL. Results. SEB was detectable in each untreated control solution. SEB was undetectable in the 2 mcg/mL and 0.4 mcg/mL solutions after treatment with AC in all quantities. SEB was detected in the 10 mcg/mL solution after combination with all three concentrations of AC. The difference in assay results between charcoal treated and untreated pairs was statistically significant. Conclusion. At ratios of 3:1 and above, SEB was adsorbed by AC when combined in the manner described in concentrations of 2 mcg/mL and 0.4 mg/mL. In a quantity of 10 mcg/mL complete charcoal binding of SEB did not occur with any ratio of AC used. These results support a role for AC in treating patients exposed to SEB or purifying liquids or gases containing SEB.

Quantification of optic nerve axon loss associated with a relative afferent pupillary defect in the monkey.

To quantify the amount of optic nerve axonal loss associated with the presence of a mild relative afferent pupillary defect (RAPD) in an experimental monkey model. The right macula of 5 rhesus monkeys (Macaca mulatta) was treated with concentrically enlarging diode laser burns until an RAPD was detected using a transilluminator light and measured with neutral density filters. Intervals between treatments were 3 to 7 days over a period of 2 months. Pupillary responses to light stimulation were recorded with a monocular infrared television pupillometer. Two months after detection of an RAPD, 5 treated and 4 control monkeys underwent euthanasia and enucleation. Histopathologic analysis and quantification of optic nerve axon counts using an image analysis system were performed. No RAPD was observed despite an estimated ganglion cell loss of up to 26%. A 0.6 log unit RAPD was present in 5 monkeys when the laser scar incorporated the entire macula within the temporal vascular arcades. One eye had progressive vitreomacular traction with worsening of the RAPD to 1.8 log units without further laser treatment. Histopathologic evaluation disclosed complete loss of the normal retinal architecture within the macula. The average fiber loss for the 4 treated eyes with 0.6 log unit RAPDs compared with fellow eyes was 53.3% (95% confidence interval [CI], 45.0%-61.6%). The average difference in axon counts between untreated pairs of optic nerves was 12.8% (95% CI, 10.0%-15.6%). Optic nerve axon loss between pairs of experimental and control eyes was statistically significant (P<.001). In rhesus monkeys, an RAPD develops after an approximate unilateral loss between 25% and 50% of retinal ganglion cells. Owing to redundancy in the anterior visual pathways, unilateral retinal ganglion cell loss may occur prior to the observation of an RAPD. The presence of an RAPD measuring 0.6 log units implies that significant retinal ganglion cell injury has occurred.

Testosterone and the allocation of reproductive effort in male house finches ( Carpodacus mexicanus )

Testosterone has been proposed to serve as the mediator that controls the relative effort that an individual male bird will devote to mating effort versus parental effort. Here, we demonstrate a testosterone-influenced trade-off between parental and mating efforts in male house finches. Male house finches with experimentally elevated testosterone fed nestlings at a significantly lower rate, but sang at a higher rate than males without manipulated testosterone levels. Females mated to testosterone-implanted males fed nestlings at a significantly higher rate than females mated to males without testosterone implants, resulting in similar feeding rates for both treated and untreated pairs. The effects of testosterone on male house finches, however, were not as dramatic as the effects of testosterone observed in some other socially monogamous species of birds. Because extra-pair copulations are uncommon in house finches and males provide substantial amounts of parental care, these more modest effects may be due to differences in how the allocation of reproductive effort affects the costs and benefits of different reproductive behaviors.

A highly specific microtubule depolymerizing agent (nocodazole) affecting meiosis activation in the protozoan Blepharisma japonicum (Ciliata, Heterotrichida)

The aim of the research presented here was to determine whether low concentrations (1 μg/ml) of a highly specific microtubule depolymerizing agent, nocodazole (NOC), affects the meiosis ac tivation process in conjugating pairs of the ciliated protozoan Blepharisma japonicum. In order to identify and quantify differen ces in meiosis, both NOC treated and untreated coeval pairs were stained and examined for their meiotic phases. A clear‐cut delay in the progression of meiosis in treated pairs was found. The findings indicate that NOC reversibly inhibits meiosis induction and that treated pairs need both continuous cell union and a period of recovery in order to progress through meiosis after NOC is with drawn. These results suggest that cytoplasmic microtubule dynamics may be involved in the meiotic activation processs of Blepharisma conjugating pairs.

Effectiveness of Sofscale™ Calculus Scaling Gel as an AID during Dental Scaling of Teeth of Dogs

The effect of pre-scaling application of SofScale Calculus Scaling Gel was studied on teeth of cadaver dogs, comparing scaling time and effort among pre-treated and untreated pairs of teeth. Teeth with light, moderate and heavy calculus were studied, treated by either hand-scaling only or hand and ultrasonic scaling. No significant difference was found in overall mean time required, comparing SofScale treated and untreated teeth. Scaling time was faster for SofScale treated teeth with light calculus, and slower for SofScale treated teeth with heavy calculus. There were no differences observed in the effort required for scaling, comparing SofScale treated and untreated teeth.

Contact-mediated loss of the nonsynaptic response to transmitter during reinnervation of an identified leech neuron in culture

We have examined the modification of responses to transmitter during the reformation of a specific synapse by identified leech neurons in culture. Single pressure-sensitive mechanosensory (P) neurons in culture and the soma of this cell in vivo have 2 conductances that are activated by application of 5-HT: a Cl conductance and a monovalent cation conductance (gCations); synaptic release of 5-HT by a serotoninergic Retzius cell in vivo and in culture activates only the Cl conductance and not gCations in the P cell. We have characterized the loss of gCations in P cells by manipulating the culture conditions. When 5-HT was applied from a pipette, innervated P cells and P cells paired with Retzius cells that had not formed synapses had a gCations that was markedly reduced compared with gCations in the single P cell. When 5-HT was included in the culture medium in which single P cells were grown, gCations was not reduced. When Retzius-P cell pairs were treated with reserpine, which was shown to deplete the presynaptic neuron of 5-HT, gCations in the P cell was as low as in untreated pairs. Pairing aldehyde-fixed Retzius cells with untreated P cells also resulted in the loss of gCations. The Retzius cell had both types of receptors, but synapse formation did not affect gCations in the presynaptic neuron. The results demonstrate that the loss of the nonsynaptic response of the P cell to transmitter is due to contact between the neurons rather than to the release of transmitter or trophic factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Gamma irradiation effects on mating competitiveness of Tribolium castaneum (Herbst)

When males of Tribolium castaneum (Herbst) substerilized with 35, 40 or 50 Gy of gamma irradiation (I) were added to untreated (U) pairs of adults at I : U ratios of 1:1, 2:1 and 5:1, the percentage of hatched eggs was increased by increasing the dose administered to males, as not expected, at equal flooding ratio. The calculated degree of competitiveness showed that males irradiated with the lowest dose (35Gy) were more competitive than males irradiated with the highest dose (50 Gy). However, increasing the ratio of irradiated males with 50 Gy to 10 or 20 increased, accordingly, the competitiveness value. The results also indicate that if an equal number of irradiated males and females with 50 Gy, which had given 99.16 % sterility, were placed with untreated pairs of adults at different ratios (1:1, 5:1, 10:1, and 20:1), the effectiveness was more promising. Moreover, the data further suggest that the effectiveness was enhanced when the ratio of irradiated males and females was increased. Thus, the presence of sterile females along with sterile males in the stored products appears to dilute the effectiveness of normal males, which otherwise would mate with normal females.