Experimental alteration of sex ratios in populations of Microtus townsendii, a field vole

1978 ◽  
Vol 56 (1) ◽  
pp. 17-27 ◽  
Author(s):  
J. A. Redfield ◽  
M. J. Taitt ◽  
C. J. Krebs
Keyword(s):  
Population Regulation ◽  
Sex Ratios ◽  
Field Vole ◽  
Vole Population ◽  
Partial Removal ◽  
Male Density ◽  
Experimental Alteration ◽  
Two Populations ◽  
Microtus Townsendii

Sex ratios in two populations of Microtus townsendii were experimentally manipulated toward 80% males and 20% males over a 2-year period. The demography of these manipulated populations was changed very little in comparison with a control population with 50% males. Neither survival, breeding, nor growth were related to the density of voles of the same sex. All populations had restricted immigration and the recruitment of females was more tightly regulated than recruitment of males. The number of young voles recruited per pregnancy is inversely related to female density on all areas, and not related to male density. The survival rate of juveniles was influenced more by the females than by the males.Microtus townsendii seems to fit the model of a species in which spacing behavior is sex specific, so that the partial removal of one sex has virtually no effect on the other sex. We need to determine the factors that restrict the entrance of recruits into a vole population. These experiments suggest that the role of females in the restriction on juvenile survival and female recruitment could be critical for vole population regulation.

scholarly journals A fencing experiment on a high-density population of Microtus townsendii

1977 ◽  
Vol 55 (7) ◽  
pp. 1166-1175 ◽  
Author(s):  
Rudy Boonstra ◽  
Charles J. Krebs
Keyword(s):  
Survival Rate ◽  
Breeding Season ◽  
Population Regulation ◽  
Control Area ◽  
High Density ◽  
Low Density ◽  
Vole Population ◽  
Sharp Decline ◽  
Density Population ◽  
Microtus Townsendii

If dispersal is prevented, a low-density vole population will increase to unusually high densities. A mouse-proof fence was constructed around a vole population that had already reached high density and both this population and one on a control area were live-trapped from January 1975 to November 1975. The population on the control remained at peak densities. The enclosed population increased to even higher density once the breeding season had started and had a higher survival rate than the control population. By midsummer the enclosed population had severely overgrazed the vegetation and went into a sharp decline. Dispersal losses from the control were estimated at 32% for males and 31% for females in these high-density populations. Microtus townsendii populations thus responded to a fence in a manner similar to that of other species that have been studied. This experiment indicates the importance of dispersal to population regulation in voles even at peak densities.

scholarly journals Microtubule–microtubule sliding by kinesin-1 is essential for normal cytoplasmic streaming in Drosophila oocytes

2016 ◽  
Vol 113 (34) ◽  
pp. E4995-E5004 ◽  
Author(s):  
Wen Lu ◽  
Michael Winding ◽  
Margot Lakonishok ◽  
Jill Wildonger ◽  
Vladimir I. Gelfand
Keyword(s):  
Cytoplasmic Streaming ◽  
Cell Types ◽  
Nurse Cells ◽  
Wild Type ◽  
Actin Cortex ◽  
Microtubule Motor ◽  
Multiple Cell ◽  
Cytoplasmic Microtubules ◽  
Two Populations

Cytoplasmic streaming in Drosophila oocytes is a microtubule-based bulk cytoplasmic movement. Streaming efficiently circulates and localizes mRNAs and proteins deposited by the nurse cells across the oocyte. This movement is driven by kinesin-1, a major microtubule motor. Recently, we have shown that kinesin-1 heavy chain (KHC) can transport one microtubule on another microtubule, thus driving microtubule–microtubule sliding in multiple cell types. To study the role of microtubule sliding in oocyte cytoplasmic streaming, we used a Khc mutant that is deficient in microtubule sliding but able to transport a majority of cargoes. We demonstrated that streaming is reduced by genomic replacement of wild-type Khc with this sliding-deficient mutant. Streaming can be fully rescued by wild-type KHC and partially rescued by a chimeric motor that cannot move organelles but is active in microtubule sliding. Consistent with these data, we identified two populations of microtubules in fast-streaming oocytes: a network of stable microtubules anchored to the actin cortex and free cytoplasmic microtubules that moved in the ooplasm. We further demonstrated that the reduced streaming in sliding-deficient oocytes resulted in posterior determination defects. Together, we propose that kinesin-1 slides free cytoplasmic microtubules against cortically immobilized microtubules, generating forces that contribute to cytoplasmic streaming and are essential for the refinement of posterior determinants.

scholarly journals Private specificities of H-2K and H-2D loci as possible selective targets for effector lymphocytes in cell-mediated immunity.

1975 ◽  
Vol 141 (1) ◽  
pp. 11-26 ◽  
Author(s):  
B D Brondz ◽  
I K Egorov ◽  
G I Drizlikh
Keyword(s):  
T Lymphocytes ◽  
Target Cells ◽  
Cell Mediated Immunity ◽  
Skin Grafts ◽  
Immune Lymphocytes ◽  
Direct Cytotoxicity ◽  
Cross Absorption ◽  
Private Specificity ◽  
Two Populations

Receptors of effector T lymphocytes of congeneic strains of mice do not recognize public H-2 specificities and react to private H-2 specificities only. This has been established with the use of three tests: direct cytotoxicity assay of immune lymphocytes upon target cells, specific absorption of the lymphocytes on the target cells, and rejection of skin grafts at an accelerated fashion. Immunization with two private H-2 specificities in the system C57BL/10ScSn leads to B10.D2 induces formation of two corresponding populations of effector lymphocytes in unequal proportion: a greater part of them is directed against the private specificity H-2.33 (Kb), while the smaller part is towards H-2.2 (Db) private specificity. These two populations of effector lymphocytes do not overlap, as demonstrated by experiments on their cross-absorption on B10.D2 (R107), B10.D2 (R101), B10.A(2R), and B10.A(5R) target cells, as well as on mixtures of R107 and R101 targets. Following removal of lymphocytes reacting with one of the private H-2 specificities, lymphocytes specific to the other specificity are fully maintained. A mixture of target cells, each bearing one of the two immunizing private specificities, absorbs 100% of the immune lymphocytes and is totally destroyed by them. It is suggested that H-2 antigens are natural complexes of hapten-carrier type, in which the role of hapten is played by public H-2 specifities and that of the carrier determinant by either private H-2 specificities or structures closely linked to them. Various models of steric arrangement of MHC determinants recognized by receptors of effector T lymphocytes are discussed.

scholarly journals Estrogen binding by leukocytes during phagocytosis,.

1977 ◽  
Vol 145 (4) ◽  
pp. 983-998 ◽  
Author(s):  
S J Klebanoff
Keyword(s):  
Chronic Granulomatous Disease ◽  
Reaction Mechanisms ◽  
Dehydrogenase Deficiency ◽  
Cell Types ◽  
Neutrophil Function ◽  
Granulomatous Disease ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Estrogen Binding ◽  
Two Populations

Estradiol binds covalently to normal leukocytes during phagocytosis. The binding involves three cell types, neutrophils, eosinophils, and monocytes and at least two reaction mechanisms, one involving the peroxidase of neutrophils and monocytes (myeloperoxidase [MPO]) and possibly the eosinophil peroxidase, and the second involving catalase. Binding is markedly reduced when leukocytes from patients with chronic granulomatous disease (CGD), severe leukocytic glucose 6-phosphate dehydrogenase deficiency, and familial lipochrome histiocytosis are employed and two populations of neutrophils, one which binds estradiol and one which does not, can be demonstrated in the blood of a CGD carrier. Leukocytes from patients with hereditary MPO deficiency also bind estradiol poorly although the defect is not as severe as in CGD. These findings are discussed in relation to the inactivation of estrogens during infection and the possible role of estrogens in neutrophil function.

Role of Jasmonic and Salicylic Acid on Enzymatic Changes in the Root of Two Alyssum Inflatum Náyr. Populations Exposed to Nickel Toxicity

2021 ◽  
Author(s):  
Shiva - Najafi Kakavand ◽  
Naser - Karimi ◽  
Hamid-Reza - Ghasempour ◽  
Ali - Raza ◽  
Mehrdad - Chaichi ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Interactive Effect ◽  
Plant Tolerance ◽  
Nickel Toxicity ◽  
Defense Systems ◽  
Antioxidant Defense Systems ◽  
Enzymatic Changes ◽  
Two Populations ◽  
Ni Accumulation

Abstract Salicylic acid (SA) and jasmonic acid (JA) as plant growth regulators (PGRs) have the potential to ameliorate plant development and tolerance to deleterious effects of toxic metals like nickel (Ni). Therefore, the current study was carried out to evaluate SA and JA's interactive effect on the root antioxidative response of two Alyssum inflatum Nyár. populations against Ni-toxicity. Two A. inflatum species under Ni-stress conditions (0, 100, 200, and 400 µM) were exposed to alone or combined levels of SA (0, 50, and 200 µM) and JA (0, 5, and 10 µM) treatments. Results showed that high Ni doses reduced the roots fresh weight (FW) in two populations than control; however, the use of external PGRs had ameliorated roots biomass by mitigated Ni-toxicity. Under Ni toxicity, SA and JA, especially their combination, induced high Ni accumulation in plants' roots. Moreover, the application of SA and JA alone, as well as combined SA + JA, was found to be effective in the scavenging of hydrogen peroxide (H2O2) by improving the activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in both populations under Ni-toxicity. Overall, our results manifest that SA and JA's external use, especially combined SA + JA treatments, ameliorate root biomass and plant tolerance by restricting translocation Ni to the shoot, accumulating in roots, and also enhancing antioxidant defense systems.

Interactions between compound and normal eye projections in dually innervated tectum: a study of optic nerve regeneration in Xenopus

Development ◽  
1981 ◽  
Vol 66 (1) ◽  
pp. 159-174
Author(s):  
Charles Straznicky ◽  
David Tay
Keyword(s):  
Optic Nerve ◽  
Nerve Regeneration ◽  
Compound Eye ◽  
Compound Eyes ◽  
Lateral Region ◽  
Optic Nerve Regeneration ◽  
Xenopus Embryos ◽  
Retinotectal Projections ◽  
Two Populations

Right compound eyes were formed in Xenopus embryos at tailbud stages by the fusion of two nasal (NN), two temporal (TT) or two ventral (VV) halves. The left eye was kept intact. Two to four weeks after metamorphosis the optic nerve from the intact eye was severed to induce bilateral optic nerve regeneration. The contralateral retinotectal projections from the compound eye and the induced ipsilateral projections from the intact eye to the same (dually innervated) tectum were studied by [3H]proline autoradiography and visuotectal mapping from 3 to 6 months after the postmetamorphic surgery. The results showed that the NN, TT and VV projections, in the presence of optic fibres from the intact eye failed to spread across the whole extent of the dually innervated tectum. Unexpectedly the bulk of the regenerating projection from the intact eye was confined to the previously uninnervated parts of the dually innervated tecta, the caudomedial region in TT, the rostrolateral region in NN and the lateral region in VV eye animals. The partial segregation of the two populations of optic fibres in the dually innervated tectum has been taken as a further indication of the role of fibre-fibre and fibre-tectum interactions in retinotectal map formation.

scholarly journals Kin-Mediated Male Choice and Alternative Reproductive Tactics in Spider Mites

Biology ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 360
Author(s):  
Peter Schausberger ◽  
Yukie Sato
Keyword(s):  
Random Mating ◽  
Reproductive Potential ◽  
Spider Mites ◽  
Alternative Reproductive Tactics ◽  
Male Choice ◽  
Reproductive Tactics ◽  
Kin Competition ◽  
Context Specific ◽  
Two Populations

Optimal outbreeding and kin selection theories state that the degree of kinship is a fundamental determinant in any mating system. However, the role of kinship in male choice and alternative reproductive tactics (ARTs) is poorly known. We assessed the influence of kinship on male choice and expression of ARTs in two populations of two-spotted spider mites Tetranychus urticae. Male spider mites guard premature females, which is an indicator of mate choice, and may conditionally adopt fighting or sneaking tactics to secure access to females. Males competing with kin or non-kin were offered one kin or non-kin female (experiment 1) and single males were presented a choice of kin and non-kin females (experiment 2). Under kin competition, males of both populations were more prone to guard non-kin than kin females at a 3:1 fighter:sneaker ratio. Under non-kin competition, all males were fighters. Under no-choice, males used novelty as indicator of genetic dissimilarity, serving as absolute decision rule for outbreeding. Under choice, comparative evaluation allowed males to preferentially guard females with higher reproductive potential. Overall, our study suggests that male spider mites can assess kinship of rivals and prospective mates. Kin discrimination allows adaptive, context-specific non-random mating preference and adjustment of ARTs.

RNA dynamics of fertile and infertile spermatozoa

2007 ◽  
Vol 35 (3) ◽  
pp. 634-636 ◽  
Author(s):  
S. Carreau ◽  
S. Lambard ◽  
L. Said ◽  
A. Saad ◽  
I. Galeraud-Denis
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Complete Disappearance ◽  
Motile Sperm ◽  
Nuclear Condensation ◽  
Complex Population ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide ◽  
Two Populations

The presence of a complex population of mRNAs in human mature spermatozoa is well documented; among them, transcripts of aromatase and ERs (oestrogen receptors) have been described but their significance is not clear. Therefore, to clarify the role of this complex population of mRNAs in human ejaculated sperm, we have isolated on discontinuous density gradients two main fractions from the same sample: high- and low-motile spermatozoa. The levels of different transcripts coding for molecules involved in nuclear condensation [Prm-1 (protamine 1) and Prm-2], capacitation [eNOS (endothelial nitric oxide synthase), nNOS (neuronal nitric oxide synthase), c-myc], motility and sperm survival (aromatase) have been assessed using semi-quantitative RT (reverse transcriptase)–PCR. The viability of sperm as well as the percentage of apoptosis were identical in high- and low-motile fractions. No significant change in the c-myc/Prm-2 ratio between the two populations of spermatozoa was observed. Conversely the amount of Prm-1 mRNA was significantly higher in low-motile than in high-motile fraction; in most of the high-motile sperm samples analysed, eNOS and nNOS transcripts were undetectable, whereas they were observed in low-motile sperm. Moreover, a partial or complete disappearance of c-myc transcripts was observed after capacitation. As to the aromatase expression, a significant decrease in the amount of transcripts in immotile sperm fraction was recorded in all samples studied. To conclude, analysing mRNA profiles in humans could be helpful either as a diagnostic tool to evaluate male fertility, since they reflect spermatogenesis gene expression, and/or a prognosis value for fertilization, since these RNAs are delivered to oocytes.

scholarly journals Kisspeptin Neurons from Mice to Men: Similarities and Differences

Endocrinology ◽  
2012 ◽  
Vol 153 (11) ◽  
pp. 5105-5118 ◽  
Author(s):  
Robert L. Goodman ◽  
Michael N. Lehman
Keyword(s):  
Strong Evidence ◽  
Species Differences ◽  
Mammalian Species ◽  
Limited Area ◽  
Sexually Dimorphic ◽  
Functional Consequences ◽  
Similarities And Differences ◽  
Reproductive Neuroendocrinology ◽  
Two Populations

Abstract The discovery that kisspeptin was critical for normal fertility in humans ushered in a new chapter in our understanding of the control of GnRH secretion. In this paper, we will review recent data on the similarities and differences across several mammalian species in the role of kisspeptin in reproductive neuroendocrinology. In all mammals examined to date, there is strong evidence that kisspeptin plays a key role in the onset of puberty and is necessary for both tonic and surge secretion of GnRH in adults, although kisspeptin-independent systems are also apparent in these studies. Similarly, two groups of kisspeptin neurons, one in the arcuate nucleus (ARC) and the other more rostrally, have been identified in all mammals, although the latter is concentrated in a limited area in rodents and more scattered in other species. Estrogen has divergent actions on kisspeptin expression in these two regions across these species, stimulating it the latter and inhibiting expression in the former. There is also strong evidence that the rostral population participates in the GnRH surge, whereas the ARC population contributes to steroid-negative feedback. There may be species differences in the role of these two populations in puberty, with the ARC cells important in rats, sheep, and monkeys, whereas both have been implicated in mice. ARC kisspeptin neurons also appear to participate in the GnRH surge in sheep and guinea pigs, whereas the data on this possibility in rodents are contradictory. Similarly, both populations are sexually dimorphic in sheep and humans, whereas most data in rodents indicate that this occurs only in the rostral population. The functional consequences of these species differences remain to be fully elucidated but are likely to have significance for understanding normal neuroendocrine control of reproduction as well as for use of kisspeptin agonists/antagonists as a therapeutic tool.

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