Facilitatory and inhibitory effects of supplementary estradiol benzoate given to ovariectomized,estrogen-primed guinea pigs

Ovariectomized guinea pigs were given a priming dose of estradiol benzoate followed 18, 36, or 96 hr later by concurrent injections of supplementary estradiol benzoate plus progesterone. The 36-hr group showed a prolongation of duration of estrus while the 18- and 96-hr groups showed an increased latency to response. These results show that the effect of supplementary estradiol is dependent upon the time interval permitted for priming. An additional study (using the 36-hr group) in which the supplementary estradiol was given at various times in relation to progesterone indicated that the estrogenic mechanisms regulating latency and duration of heat are experimentally separable. Latency seems primarily dependent on the amount of estrogen given as a priming dose. Duration, on the other hand, seems primarily dependent on the amount of estrogen available at the time of progesterone injection providing that the priming interval is optimal (i.e. 36 hr).     

Induction of sexual receptivity in the female lizard, Anolis carolinensis: Effects of estrogen and the antiestrogen CI-628

Daily behavioral testing revealed that there is a latency period of at least 48 hr from the administration of a single injection of estradiol benzoate (EB) to the first significant increase in female sexual receptivity in the ovariectomized female lizard, Anolis carolinensis. This latency period did not vary with dosage of EB used in these experiments (i.e., 0.8, 1.4, and 4.0 μg) nor with method of injection (subcutaneous vs intraperitoneal for dose of 1.4 μg EB). Following a single EB injection, female sexual receptivity increased after the 48-hr latency period, reached an observed peak from Day 3 to Day 6, and thereafter declined to pretreatment levels by Day 19. Although both 1.4 and 4.0 μg of EB produced higher levels of female sexual receptivity than did treatment with 0.8 μg of EB, results obtained with 4.0 μg EB did not differ from those obtained with 1.4 μg EB. Administration of the nonsteroidal antiestrogen CI-628 (80 μg) at either 4 or 24 hr following a single subcutaneous injection of 1.4 μg EB significantly reduced subsequent female sexual receptivity. These results suggest that there is a critical length of time during which estrogen must act on the brain and support the concept of an estrogen “maintenance” effect during this priming period.     

Evidence of odor priming: edibility judgements are primed differently between the hemispheres

In olfaction, there is only weak evidence of repetition priming. Repetition priming was therefore investigated in two experiments using birhinal presentation of odors at study and monorhinal at test. Experiment 1 demonstrated repetition priming for repeated judgements of edibility in terms of response latency, but not in terms of correctness. No differences were found between the hemispheres (nostrils). Experiment 2 utilized a slightly different design, in which identity of odors was studied and judgement of edibility was tested. This time, only the right hemisphere (RH) was associated with priming. This persistence of RH priming should be seen in the light of a general tendency for superiority of the left hemisphere for correctly judging edibility. It is concluded that the olfactory system benefits from previous exposure/processing just as do vision, audition and touch. In line with previous research in vision, it is suggested that RH priming may be more associated with perceptual priming and left-hemisphere (LH) priming with conceptual priming.     

Priming of inducible defenses protects Norway spruce against tree-killing bark beetles

Plants can form an immunological memory known as defense priming, whereby exposure to a priming stimulus enables quicker or stronger response to subsequent attack by pests and pathogens. Such priming of inducible defenses provides increased protection and reduces allocation costs of defense. Defense priming has been widely studied for short-lived model plants such as Arabidopsis, but little is known about this phenomenon in long-lived plants like spruce. We compared the effects of pretreatment with sublethal fungal inoculations or application of the phytohormone methyl jasmonate (MeJA) on the resistance of 48-year-old Norway spruce (Picea abies) trees to mass attack by a tree-killing bark beetle beginning 35 days later. Bark beetles heavily infested and killed untreated trees but largely avoided fungus-inoculated trees and MeJA-treated trees. Quantification of defensive terpenes at the time of bark beetle attack showed fungal inoculation induced 91-fold higher terpene concentrations compared with untreated trees, whereas application of MeJA did not significantly increase terpenes. These results indicate that resistance in fungus-inoculated trees is a result of direct induction of defenses, whereas resistance in MeJA-treated trees is due to defense priming. This work extends our knowledge of defense priming from model plants to an ecologically important tree species.     

Effects of the antiestrogens,MER-25 and CI 628, on rat and hamster lordosis

Antiestrogens were used to test the hypothesis that estrogen exerts a “maintenance,” as well as a “priming,” effect on rat and hamster sexual receptivity as it apparently does for guinea pigs. MER-25 (75 or 150 mg/kg) significantly reduced rat LQ when given ?2 hr or 8 hr after EB injection. MER-25 given at 34 hr (2 hr prior to P) failed to diminish rat LQ. With hamsters, MER-25 in large doses (750 mg/kg) given either at ?2 hr or 34 hr reduced lordosis duration to 40% of controls, but this effect was confounded by severe illness among the MER-25 injected animals. Lower doses failed to block behavior, but still produced some toxicity. CI 628 (50 mg/kg) greatly reduced hamster lordosis duration and increased lordosis latency when given 0 hr, but not 34 hr, after EB. The results are consistent with similar previous work on rats and do not support the concept of estrogen “maintenance” in either rats or hamsters.     

Social Experience During Development and Female Offspring Aggression in Peromyscus Mice

Cross‐fostering between the highly aggressive, biparental California mouse (Peromyscus californicus) and the less aggressive, less parental white‐footed mouse (P. leucopus) influences female offspring attack latency in California mice, but not in white‐footed mice. Adult female California mice raised by white‐footed mice expressed longer attack latencies in a neutral‐arena test but not in a resident‐intruder test. One social cue that may be used by offspring to develop environmentally appropriate levels of aggression is the type of parental care during development. In California mice, a composite score of maternal behavior was positively associated with neutral‐arena aggression as indicated by decreased attack latency. In both species, paternal nest‐building was positively associated with neutral‐arena aggression and higher maternal retrieval behavior predicted higher offspring resident‐intruder aggression as indicated by decreased attack latency. Together, these results indicate that parental behavior has the potential to shape the development of attack latency in female offspring.     

The comparative potency of various steroids to complete the priming process for lordosis in guinea pigs

Ovariectomized adult guinea pigs were treated with a regimen of estradiol benzoate (0.2 μg/animal estradiol benzoate at hr 0 and 19) that was shown to be minimally effective for the induction of lordosis. They were then treated with 10, 20, or 80 mg of enclomiphene, 5, 20, 40, or 100 μg of estradiol, or testosterone, cortisol, estrone, estriol, diethylstilbestrol, catechol estradiol, or catechol estrone (all at a dose equivalent to 5 μg of estradiol) at hr 28. At hr 39 all females were given 0.5 mg progesterone, and subsequently tested for lordosis behavior. Of the various agents injected at hr 28 only estradiol (at all doses given), estrone, estriol, and diethylstilbestrol were effective in supporting display of lordosis behavior. The results indicate that the antiestrogen enclomiphene, the catechol estrogens, and at least some C₁₉ and C₂₁ steroids are weaker than E₂ or ineffective in facilitating lordosis behavior when given late in the priming period. Because previous work had shown that enclomiphene has partial estrogenic effects on lordosis behavior when administered early in the priming period (i.e., at hr 0, 19), it is suggested the early and late phases of the priming process induced by E₂ entail qualitatively different neural processes.     

Cumulus cells secrete a meiosi-inducing substance by stimulation with forskolin and dibutyric cyclic adenosine monophosphate

The role of the cumulus cells in initiating the resumption of meiosis after exposure to forskolin and dbcAMP was studied in the mouse. The resumption of meiosis was monitored by the percentage of germinal vesicle breakdown (GVBD) and polar body formation (PB). The cumulus-enclosed oocytes (CEO) and denuded oocytes (DO) were cultured with and without hypoxanthine (HX) in the culture medium. Three types of experiments were performed: (1) Effect of forskolin on spontaneous resumption of meiosis, i.e. cultures without HX, and two experiments in which HX is present throughout the culture: (2) Effect of transient exposure to forskolin or dibutyric-cyclic adenosinemonophosphate (dbcAMP) on GVBD prior to continued culture without forskolin or dbcAMP (oocyte priming). (3) Priming of CEO with forskolin for 2 hr, separation of cumulus cells and oocytes, followed by coculture of rejoined cumulus cells and oocytes, or coculture of the cumulus cells and new, unprimed DO. (1) Forskolin inhibited a spontaneous resumption of meiosis in a dose-dependent manner during the first 5 hr of culturing. After 22 hr all controls and CEO resumed meiosis, whereas only half of the DO did. (2) At least 1 hr of priming the CEO with forskolin is needed to induce GVBD and PB formation, but forskolin inhibited the resumption of meiosis when present for 24 hr. Similar results were obtained with a high concentration of dbcAMP. (3) A separation and rejoining of oocytes and cumulus cells after priming induced the resumption of meiosis in a significantly greater number of oocytes than in the control oocytes which were not primed. The GVBD of unstimulated DO also increased significantly when cocultured with cumulus cells from primed CEO. The percentage of GVBD in unprimed DO and in DO isolated from primed CEO was the same. We suggest that within 1–2 hr, forskolin and cAMP stimulate cumulus cells to produce a diffusible meiosis-inducing substance which overcomes HX-inhibition and induces oocyte maturation, including both GVBD and PB formation. The CEO must be primed for more than 2 hr before the resumption of meiosis in DO isolated from such CEO is induced. Oocyte-cumulus connections are crucial as far as initiating the production of a meiosis-inducing substance is concerned. Oocyte-cumulus connections are not needed for transferring this substance to the oocyte. © 1994 Wiley-Liss, Inc.     

Priming Intelligent Behavior: An Elusive Phenomenon

Can behavior be unconsciously primed via the activation of attitudes, stereotypes, or other concepts? A number of studies have suggested that such priming effects can occur, and a prominent illustration is the claim that individuals'' accuracy in answering general knowledge questions can be influenced by activating intelligence-related concepts such as professor or soccer hooligan. In 9 experiments with 475 participants we employed the procedures used in these studies, as well as a number of variants of those procedures, in an attempt to obtain this intelligence priming effect. None of the experiments obtained the effect, although financial incentives did boost performance. A Bayesian analysis reveals considerable evidential support for the null hypothesis. The results conform to the pattern typically obtained in word priming experiments in which priming is very narrow in its generalization and unconscious (subliminal) influences, if they occur at all, are extremely short-lived. We encourage others to explore the circumstances in which this phenomenon might be obtained.     

Studies in wild house mice. II. Testosterone and aggression

The relationship between testosterone level and attack latency was studied in genetically different wild house mice by means of castration and subsequent testosterone therapy. This was done to provide adequate physiological knowledge for further research on the genetic basis of individual differences in these mice. The findings show that individual variation in attack latency is related not only to variation in baseline plasma testosterone level (via a dose-response relation), but also to variation in responsiveness to testosterone that is induced before puberty. In addition it is shown that in fast-attacking mice the maintenance of the attack latency level reached by maturation is independent of testosterone, whereas this is not the case in mice that are reluctant to attack.     

Short-term tolerance to morphine: Effects of indomethacin

Short-term tolerance to opiates has been demonstrated in as little as three hours after priming with a single dose of morphine in naive animals. Tail-flick latency in mice and changes in plasma corticosterone in rats were the indicators tested in these experiments. Rats primed with either saline or morphine, 10 mg/kg, were injected 3 hrs. subsequently with morphine, 5 mg/kg. Those primed with saline showed the characteristic plasma corticosterone elevation following morphine, when serial blood samples were examined, whereas those previously treated with morphine did not. Mice were primed with saline or either of two doses of morphine, 30 or 100 mg/kg, 3.5 hrs. prior to estimation of tail-flick latency and ED 50 determinations. Mice primed with either dose of morphine had significantly higher ED50's than those primed with saline. The effects of indomethacin, 5 or 10 mg/kg, were examined on both systems. Rats and mice were pretreated with indomethacin at 2.25 or 3 hrs., respectively, before morphine-priming. In all cases, indomethacin did not produce alterations in responses previously observed in correspondently treated controls.     

Cumulus cells of oocyte-cumulus complexes secrete a meiosis-activating substance when stimulated with FSH

The effect of the different follicular cell types on resumption of meiosis was studied during stimulation with FSH. Cumulus enclosed oocytes (CEO), denuded oocytes (DO), and cumulus and mural granulosa cells were used. The resumption of meiosis and oocyte maturation were assessed by the determination of the germinal vesicle breakdown (GVBD) and polar body formation (PB) at the end of a 24 hr culture period in the presence of 4 mM hypoxanthine (HX). The effects of recombinant LH (r-LH) and hCG were also evaluated. Oocyte exposure to the gonadotrophins varied from 5 min to 24 hr (i.e., priming time). Oocytes were obtained from immature gonadotrophin-stimulated and -unstimulated mice. 1. FSH (1 IU/L-75 IU/L) provoked a dose-dependent increase in GVBD and PB in CEO, but not in DO, in stimulated and unstimulated mice. Eight IU/L was sufficient for inducing resumption of meiosis. In contrast, LH and hCG (both 1 IU/L-1500 IU/L) were without effect on GVBD and PB in CEO and DO of oocytes from stimulated and unstimulated mice. A combination of 8IU/L FSH and 4–8 IU/L hCG produced an additive effect, whereas combinations with LH and higher concentrations of hCG had no such effect. 2. A 2 hr priming with FSH (8 IU/L-75 IU/L) induced a dose-dependent oocyte maturation in CEO. Thirty minutes of priming with FSH (75 IU/L) was sufficient for induction of meiotic resumption in CEO. 3. Priming CEO with FSH for 2 hr followed by the separation and repooling of oocytes and cumulus cells induced oocyte maturation. GVBD of new, unprimed DO added to cumulus cells of primed CEO increased slightly but was significant, whereas GVBD in DO isolated from the primed CEO only increased marginally. DO cocultured with FSH-primed cumulus masses seem to be prevented from resuming meiosis. 4. Priming a coculture of granulosa cells and DO with FSH for 2 hr caused a significant increase in GVBD compared to the control, evaluated after 24 hr. In contrast, a 24 hr FSH-priming of a coculture of granulosa cells and DO was without effect on GVBD. 5. A spent medium in which unstimulated cumulus cells or mural granulosa cells had grown was without effect on GVBD in DO. However, a small fraction of the DO resumed meiosis after culture in a spent medium derived from a 2 hr priming of CEO and spent media from 24 hr priming of CEO induced a 2–3 times higher GVBD frequency in the DO compared to the controls. Heat treatment of spent media (70°C, 30 min) from a 24 hr FSH-priming of CEO still induced GVBD in naive DO. The results showed that FSH, in a concentration of as little as 8 IU/L, but not r-LH and hCG, induced within 30 minutes the cumulus cells to produce and after 2 hr to secrete a diffusible heat stable meiosis activating substance. This substance overcame, in a paracrine fashion, the inhibiting effect of HX and induced oocyte maturation directly in DO. The production of this substance, however, was dependent on the initial connection between the cumulus cells and the oocyte, indicating an important 2-way communication between these 2 cell types. The mural granulosa cells did not produce a meiosis inducing activity by stimulation with FSH, but significantly, more DO matured after coculture with the nonstimulated granulosa cells for 24 hr than for 2 hr. It is proposed that the heat stable meiosis activating component of the spent media from the FSH-stimulated CEO belongs to the meiosis activating sterols, MAS, previously isolated from human follicular fluid and from adult bull testes. Mol. Reprod. Dev. 46:296–305, 1997. © 1997 Wiley-Liss, Inc.     

Identity Negative Priming: A Phenomenon of Perception,Recognition or Selection?

The present study addresses the problem whether negative priming (NP) is due to information processing in perception, recognition or selection. We argue that most NP studies confound priming and perceptual similarity of prime-probe episodes and implement a color-switch paradigm in order to resolve the issue. In a series of three identity negative priming experiments with verbal naming response, we determined when NP and positive priming (PP) occur during a trial. The first experiment assessed the impact of target color on priming effects. It consisted of two blocks, each with a different fixed target color. With respect to target color no differential priming effects were found. In Experiment 2 the target color was indicated by a cue for each trial. Here we resolved the confounding of perceptual similarity and priming condition. In trials with coinciding colors for prime and probe, we found priming effects similar to Experiment 1. However, trials with a target color switch showed such effects only in trials with role-reversal (distractor-to-target or target-to-distractor), whereas the positive priming (PP) effect in the target-repetition trials disappeared. Finally, Experiment 3 split trial processing into two phases by presenting the trial-wise color cue only after the stimulus objects had been recognized. We found recognition in every priming condition to be faster than in control trials. We were hence led to the conclusion that PP is strongly affected by perception, in contrast to NP which emerges during selection, i.e., the two effects cannot be explained by a single mechanism.     

The latent membrane protein 1 of Epstein-Barr virus (EBV) primes EBV latency cells for type I interferon production

Epstein-Barr virus (EBV) latency has been associated with a variety of human cancers. Latent membrane protein 1 (LMP-1) is one of the key viral proteins required for transformation of primary B cells in vitro and establishment of EBV latency. We have previously shown that LMP-1 induces the expression of several interferon (IFN)-stimulated genes and has antiviral effect (Zhang, J., Das, S. C., Kotalik, C., Pattnaik, A. K., and Zhang, L. (2004) J. Biol. Chem. 279, 46335-46342). In this report, a novel mechanism related to the antiviral effect of LMP-1 is identified. We show that EBV type III latency cells, in which LMP-1 is expressed, are primed to produce robust levels of endogenous IFNs upon infection of Sendai virus. The priming action is due to the expression of LMP-1 but not EBV nuclear antigen 2 (EBNA-2). The signaling events from the C-terminal activator regions of LMP-1 are essential to prime cells for high IFN production. LMP-1-mediated activation of NF-kappaB is apparently necessary and sufficient for LMP-1-mediated priming effect in DG75 cells, a human B cell line. IFN regulatory factor 7 (IRF-7) that can be activated by LMP-1 is also implicated in the priming action. Taken together, these data strongly suggest that LMP-1 may prime EBV latency cells for IFN production and that the antiviral property of LMP-1 may be an intrinsic part of EBV latency program, which may assist the establishment and/or maintenance of viral latency.     

Induced facilitation in the ventral tegmentum area on the latency of biting evoked by hypothalamic stimulation in the cat

The effects of VTA stimulation on the quiet biting attack evoked by hypothalamic activation in the cat, were studied. The reference value of the aggressive behaviour was the latency of the biting. Concurrent activation of both the hypothalamus and VTA determined a decrease of the biting latency, which depended on the parameters of VTA stimuli. The facilitatory effect of the dopaminergic mesolimbic system on the attack behaviour is emphasized.     

Immune responses to weakly immunogenic virally induced tumors. V. Short in vitro cultivation of YAC changes its antigenic properties.

YAC tumor, a Moloney virus-induced lymphoma of A mice, considerably changes its immunogenic properties following cultivation for 12 to 14 hr in vitro. The cultivated tumor, designated YAC-1, generates anti-YAC and anti-YAC-1 reactive cells, while the original YAC tumor generates suppressor cells with abrogate anti-YAC and anti-YAC-1 cytotoxic responses. In this report, we demonstrate by cold target competition experiments that YAC-1 and YAC tumors have distinctive antigenic structures on their surfaces. We have also found that RBL5, a Rauscher virus-induced lymphoma of C57BL/6 mice, generates anti-YAC, anti-YAC-1, and anti-RBL5 reactive cells in A mice. YAC-1 also generates reactive cells against the allogeneic RBL5 tumor. The total population of antitumor reactive cells was found to contain separate subpopulations directed maximally toward each of the three target tumors. The subpopulation directed toward each tumor was shown to be partially, but not completely, cross-reactive with the other tumors. Further, RBL5 priming and YAC-1 priming were shown to stimulate separate populations of antitumor reactive cells.     

Shifts in priming partly explain impacts of long‐term nitrogen input in different chemical forms on soil organic carbon storage

Input of labile organic carbon can enhance decomposition of extant soil organic carbon (SOC) through priming. We hypothesized that long‐term nitrogen (N) input in different chemical forms alters SOC pools by altering priming effects associated with N‐mediated changes in plants and soil microbes. The hypothesis was tested by integrating field experimental data of plants, soil microbes and two incubation experiments with soils that had experienced 10 years of N enrichment with three chemical forms (ammonium, nitrate and both ammonium and nitrate) in an alpine meadow on the Tibetan Plateau. Incubations with glucose–¹³C addition at three rates were used to quantify effects of exogenous organic carbon input on the priming of SOC. Incubations with microbial inocula extracted from soils that had experienced different long‐term N treatments were conducted to detect effects of N‐mediated changes in soil microbes on priming effects. We found strong evidence and a mechanistic explanation for alteration of SOC pools following 10 years of N enrichment with different chemical forms. We detected significant negative priming effects both in soils collected from ammonium‐addition plots and in sterilized soils inoculated with soil microbes extracted from ammonium‐addition plots. In contrast, significant positive priming effects were found both in soils collected from nitrate‐addition plots and in sterilized soils inoculated with soil microbes extracted from nitrate‐addition plots. Meanwhile, the abundance and richness of graminoids were higher and the abundance of soil microbes was lower in ammonium‐addition than in nitrate‐addition plots. Our findings provide evidence that shifts toward higher graminoid abundance and changes in soil microbial abundance mediated by N chemical forms are key drivers for priming effects and SOC pool changes, thereby linking human interference with the N cycle to climate change.     

The Mode of Production of Endotoxin-Induced Interferon in Rabbit Tissue Cells

In vitro production of endotoxin-induced interferon in rabbit tissue cell cultures could be enhanced by pretreatment with interferon. The enhancible state developed from the first hr of incubation at 37 C and a maximal priming effect was attained at 6 hr of incubation. Yields of interferon from unprimed cultures were usually 20–200 units/ml. In contrast, the primed cultures constantly yielded 1,000–2,500 units/ml of interferon. The pretreatment with interferon seemed to cause an earlier appearance of detectable interferon and the primed cells became more sensitive to endotoxin. It turned out that 10–30 units/ml of rabbit interferon were enough to develop the maximal priming. Even when cells were pretreated with higher doses of rabbit interferon such as 1.0 × 10⁴–1.0 × 10⁵ units/ml, the same level of priming effect was always observed without diminution. Various types of homologous (rabbit) and heterologous (human and mouse) interferon preparations showed similar dose-dependent enhancement of interferon production in proportion to the antiviral titers of these preparations as tested with RK-13 cells of rabbit origin.     

Induction of lordosis in female rats: two modes of estrogen action and the effect of adrenalectomy.

In ovariectomized female rats, progesterone treatment alone does not induce lordosis, but following estrogen treatment by an appropriate interval it greatly enhances the performance of lordosis compared to that with estrogen alone. This “facilitating” effect of progesterone is thought to act synergistically with the initial “priming” effect of estrogen. In the present experiments a second estrogen treatment given to estrogen-primed ovariectomized rats in place of progesterone was found to facilitate lordosis. Latency of the facilitation of lordosis following this second estrogen treatment was similar to that of progesterone and was much shorter than that required for the usual “priming” effect, but higher doses were needed for the “facilitatory” effect. Experiments with adrenalectomized-ovariectomized female rats showed that this short latency effect of second estrogen treatment need not be mediated by the adrenals. These results raise the possibility that estrogen acts on the central nervous system in more than one way to induce lordosis.     

Antigen-specific suppressor cell activity in man: I. Temporal, antigenic, and proliferative requirements

The temporal, antigenic, and proliferative requirements of antigen-specific suppression of the in vitro plaque-forming cell (PFC) response of human peripheral blood mononuclear cells (PBM) were studied. Suppressor cell activity (SCA) was generated by priming PBM with high doses of the T-cell-dependent antigen ovalbumin (OA) and measured by adding washed primed cells to target PFC cultures. Priming with high doses of OA was shown to induce a population of antigen-specific T lymphocytes which interfered with the anti-OA PFC response of optimally stimulated target cultures. The generation of SCA was demonstrated following as little as 24 hr of high-dose OA priming and could be abrogated by prolonged priming (72 hr) or by pretreatment with mitomycin prior to priming. The expression of optimal SCA required the addition of primed PBM at the initiation of the target culture and could be directly correlated to both the OA concentration used for priming and the number of primed cells added. Higher priming doses of OA (up to 100 μg) generated increasing numbers of cells capable of antigen-specific SCA as measured via a cell dilution protocol. Our data suggest that an antigen-driven and dose-dependent expansion of an antigen-specific T-suppressor cell pool is an early regulative event limiting the in vitro PFC response of human lymphocytes to OA.