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E Baldi

Publications and source records attributed to E Baldi.

At least 37 records · Page 2Linked to original sources
PubMed2000

Intracellular events and signaling pathways involved in sperm acquisition of fertilizing capacity and acrosome reaction.

Two processes, namely capacitation and acrosome reaction, are of fundamental importance in the fertilization of oocyte by spermatozoon. Physiologically occurring in the female genital tract, capacitation is a complex process, which renders the sperm cell capable for specific interaction with the oocyte. During capacitation, modification of membrane characteristics, enzyme activity and motility properties of spermatozoa render these cells able to penetrate oocyte investments and responsive to stimuli that induce acrosome reaction prior to fertilization. Physiological acrosome reaction occurs upon interaction of the spermatozoon with the zona pellucida protein ZP3. This is followed by liberation of several acrosomal enzymes and other constituents that facilitate penetration of the zona and expose molecules on the sperm equatorial segment that allows fusion of sperm membrane with the oolemma. The molecular mechanisms and the signal transduction pathways mediating the processes of capacitation and acrosome reaction have been partially defined, and appear to involve modifications of intracellular calcium and other ions, lipid transfer and phospholipid remodeling in sperm plasma membrane as well as changes in protein phosphorylation. Some of the kinases and phosphorylated proteins that are involved in the processes of capacitation and acrosome reaction have been now characterized. Characterization of sperm receptors to physiological inducers of acrosome reaction is in progress. This review summarizes the main signal transduction pathways involved in capacitation and acrosome reaction.Furthermore, the mechanisms underlying sperm DNA fragmentation are also briefly reviewed.

Acrosome Reaction↗
PubMed2000

A novel functional estrogen receptor on human sperm membrane interferes with progesterone effects.

We have identified an estrogen receptor of approximately 29 kDa apparent molecular weight in human sperm membranes by ligand and Western blot analysis, respectively, using peroxidase-conjugated E(2) and an antibody directed against the ligand binding region of the genomic receptor (alphaH222). Such receptor is functional since 17betaE(2) induces a rapid and sustained increase of intracellular calcium concentrations ([Ca(2+)](i)) which is completely eliminated by preincubation with alphaH222. 17betaE(2) effects on calcium are clearly mediated by a membrane receptor, as they are reproduced by the membrane-impermeable conjugate of the hormone BSA-E(2). Dose-response curve for this effect is biphasic with EC(50)s in the nanomolar and micromolar range. In addition to calcium increase, 17betaE(2) stimulates tyrosine phosphorylation of several sperm proteins including the 29-kDa protein band. Preincubation of human sperm with 17betaE(2) inhibits calcium and acrosome reaction increases in response to progesterone. We conclude that estrogens may play a role in the modulation of non-genomic action of progesterone (P) in human sperm during the process of fertilization.

Acrosome Reaction↗
PubMed2000

Effects of coupled perirhinal cortex and medial septal area, fimbria-fornix, entorhinal cortex tetrodotoxin inactivations on passive avoidance consolidation in the rat.

In order to ascertain the rat perirhinal cortex (PC) function during early consolidation of a passive avoidance response (PAR), and to ascertain whether there are some functional interactions with the medial septal area (MSA), the fimbria-fornix complex (FF) and the entorhinal cortex (EC), PC-MSA, PC-FF, and PC-EC coupled inactivations were performed immediately after the PAR acquisition session. Anesthetized male adult Wistar rats aged 60 days were treated with stereotaxical bilateral injections of TTX (5 ng in 0.5 microl saline) in the appropriate sites. Retrieval testing was performed 48 h later. It was shown that all three coupled inactivations were followed by significant PAR disruption. It may be concluded that PC is somehow active even during the first mnemonic phase following the acquisition session, thus better defining PC mnemonic involvement chronology. These results may be taken as indicating that during initial consolidation the engram is concurrently processed in more than one septal and parahippocampal site, each of which by itself is not absolutely necessary for the final engram formation.

Analysis of Variance↗
PubMed2000

Progesterone action in a murine Leydig tumor cell line (mLTC-1), possibly through a nonclassical receptor type.

In a recent report we demonstrated that a high (micromolar) concentration of progesterone (P) specifically down-regulates LH receptor (R) expression and function in murine Leydig tumor cells. The aim of the present study was to characterize further the putative novel R, mediating these P effects in the murine Leydig tumor cell line, mLTC-1. The binding of [3H]P to these cells revealed a high (Kd, approximately 9.3 nmol/liter) and a low affinity (Kd, approximately 284 nmol/liter) component, and the binding displayed with specificity (P > dehydroepiandrosterone > 17-OHP). The binding was apparently different from that of the classical nuclear PR in the following ways. 1) The P/glucocorticoid antagonist RU 486 did not compete with [3H]P binding to the mLTC-1 cells. 2) No expression of the classical PR messenger RNA was detected, despite clear P binding to these cells, by Northern hybridization or RT-PCR. 3) An antibody against the C-terminal end of the classical PR (alpha c-262) revealed in mLTC-1 cells several molecular size protein bands between 45-57 kDa on Western hybridization, whereas these immunoreactive proteins were faintly recognized by another antibody (alpha-PR) directed toward the NH2-terminal region of the classical PR. The sizes of the immunoreactive molecules were relatively similar to those detected using the same antibodies in human sperm lysates, but were at variance with the classical PR (120, 94, and 60 kDa), detected with these antibodies in human uterus. The immunoreactive proteins bound peroxidase-labeled-P, which could be displaced in the presence of a 10-fold excess of free P. 4) An immediate increase in the intracellular free calcium level was observed after P treatment in cultured mLTC-1 cells, whereas it also increased the 45Ca2+ entry within 15 min in these cells. 5) Increasing doses of P (0.1-10 micromol/liter) demonstrated significant inhibition of LH receptor messenger RNA levels in a dose-dependent manner in mLTC-1 cells. In conclusion, a nonclassical PR is expressed and functional in these cells, and it is clearly distinct from the classical nuclear PR. It is apparent that recently reported inhibitory effects of P on LH receptor gene expression and function are mediated through this novel type PR in mouse Leydig cells.

Animals↗
PubMed2000

Androgen receptor expression in prostate carcinoma cells suppresses alpha6beta4 integrin-mediated invasive phenotype.

Prostate cancer cells may lose androgen-sensitivity after androgen ablation therapy, becoming highly invasive and metastatic. The biological mechanisms responsible for higher tumurogenicity of androgen-independent prostate carcinomas are not entirely known. We demonstrate that androgen receptor regulation of adhesion and invasion of prostate cancer cells through modulation of alpha6beta4 integrin expression may be one of the molecular mechanisms responsible of this phenomenon. We found that protein and gene expressions of alpha6 and beta4 subunits were strongly reduced in the androgen-sensitive cell line LNCaP respect to the androgen-independent PC3 and that transfection of PC3 cells with a full-length androgen receptor expression vector resulted in a decreased expression of alpha6beta4 integrin, reduced adhesion on laminin, and suppressed Matrigel invasion. Growth in soft agar was also suppressed in androgen receptor-positive PC3 clones. Treatment of androgen receptor positive clones with the synthetic androgen R1881 further reduced alpha6 and beta4 messenger RNA expression as well as adhesion on laminin and Matrigel invasion. Our results indicate that androgens regulate cell-extracellular matrix adhesion and invasion by modulation of integrin expression and function, thus keeping a low invasive phenotype of prostate cancer cells.

Antigens, Surface↗
PubMed2000

[Richter's hernia: a clinical case and the clinico-therapeutic considerations].

The authors report a case of Richter's hernia. They underline main clinical and therapeutic patterns, emphasizing the need of an early diagnosis and surgery. This is a hernia of abdominal wall with partial entrapment of bowel wall (antimesenteric site) through a small ring. The incidence increased in the last years because of diffusion of laparoscopic techniques. Richter's hernia could be asymptomatic for a long time or show vanish sign. Sometimes this hernia can be diagnosed during surgery. The clinical signs are conclamated if hernia is complicated by strangulation. High mortality is justified by performing too late diagnosis and operation.

Aged↗
PubMed2000

Role of the perirhinal cortex in rats' conditioned taste aversion response memorization.

The role of the perirhinal cortex (PC) in conditioned taste aversion (CTA) learning was investigated in Long Evans rats. CTA was induced by the intraperitoneal administration of LiCl 60 min after saccharin-sweetened water drinking. The PC was reversibly inactivated by the stereotaxic administration of tetrodotoxin (TTX) 60 min before saccharin drinking, immediately after saccharin drinking (Experiment 1), 6 or 24 hr after LiCl administration (Experiment 2), and 60 min before CTA retrieval testing (Experiment 3). Only pre-saccharin drinking PC inactivation disrupted CTA. Thus, PC integrity is necessary only during the earliest phases of CTA mnemonic processing, that is, taste information acquisition and early gustatory memory elaboration. The results are discussed in relation to PC connectivity and PC temporal involvement in the memorization process of other aversive responses.

Animals↗
PubMed1999

Auditory thalamus, dorsal hippocampus, basolateral amygdala, and perirhinal cortex role in the consolidation of conditioned freezing to context and to acoustic conditioned stimulus in the rat.

On the basis of previous experimental evidence, it is known that the auditory thalamus (AT), the dorsal hippocampus (DH), the basolateral amygdala (BLA), and the perirhinal cortex (PC) are involved in the mnemonic processing of conditioned freezing. In particular, BLA and PC appear to be involved both in conditioned stimulus (CS) and context conditioned freezing. Through AT, the auditory CS is sent to other sites, whereas DH is involved in context conditioning. Nevertheless, the existing evidence does not make it possible to assess AT, DH, BLA, and PC involvement during the consolidation phase of conditioned freezing. To address this question, fully reversible tetrodotoxin (TTX) inactivation was performed on adult male Wistar rats having undergone CS and context fear training. Anesthetized animals were injected stereotaxically with TTX (either 5 or 10 ng in 0.5 or 1.0 microliter of saline, according to site dimensions) at increasing post-acquisition delays. Context and CS freezing durations were measured during retention testing, always performed 48 and 72 hr after TTX administration. The results showed that AT inactivation does not disrupt consolidation of either contextual or auditory fear memories. In contrast, inactivation of the other three structures disrupted consolidation. For the DH, this disruption was specific to contextual cues and only occurred when inactivation was performed early (up to 1.5 hr) after training. The BLA and PC were shown to be involved in the consolidation of both contextual and auditory fear. Their involvement persisted for longer periods of time (2d for BLA and 8 d for PC). These findings provide information to build a temporal profile for the post-training processing of fear memories in structures known to be important for this form of learning. The results are discussed in relation to previous studies on conditioned freezing and other aversive conditioned response neural correlates.

Acoustic Stimulation↗
PubMed1999

Effects of combined medial septal area, fimbria-fornix and entorhinal cortex tetrodotoxin inactivations on passive avoidance response consolidation in the rat.

On the basis of previous experimental evidence, it has been concluded that the entorhinal cortex (EC), the fimbria-fornix (FF) complex and medial septal area (MSA) do not take part in the consolidation phase of passive avoidance response (PAR) memorization. On the other hand, a mnemonic role during consolidation of at least two of these structures has been argued, based on several considerations. In order to ascertain whether the EC and FF are still involved in PAR memorization during consolidation, the coupled fully reversible functional tetrodotoxin (TTX) inactivation of MSA, FF and EC was performed in rats having undergone a PAR training. In Experiment 1 MSA, FF and EC were inactivated pair-wise (FF and EC always bilaterally). Permanently cannulated animals were injected stereotaxically with TTX (5 ng in 0.5 microliter saline) or saline (0.5 microliter) immediately following PAR acquisition. It was shown that combined FF-EC inactivation induced PAR retention impairment, whereas FF-MSA and EC-MSA inactivation was not followed by amnesic effects. Having obtained a positive result, in Experiment 2 the combined FF-EC inactivation was performed at different post-acquisition delays (0.25 h, 1.5 h, 6 h), so as to assess the duration of their involvement in PAR consolidation. It was shown that only the coupled inactivation performed at the shortest post-acquisition delay was followed by amnesic effects. Thus EC and FF play a definite role during early consolidation. The results are discussed in relation to EC, FF, MSA, and hippocampal involvement in PAR memorization, as reported in previous studies, and to their connectivity.

Animals↗
PubMed1999

Neural topography and chronology of memory consolidation: a review of functional inactivation findings.

Findings on the role of subcortical and cortical structures in mnemonic processes, obtained by means of the reversible functional inactivation technique, are reviewed. The main advantage of this method (subcortical or cortical administration of local anesthetics or tetrodotoxin) is that it provides information not only on "where" but also "when" and for "how long" these processes take place, thus adding to the topographical dimension the chronological one. The review covers several types of memory (e.g., passive avoidance and spatial memory) studies examining the neural substrates of memory consolidation on the basis of the functional inactivation of the nucleus of the solitary tract, parabrachial nuclei, substantia nigra, hippocampus (dorsal and ventral), nucleus basalis magnocellularis, amygdala, medial septal area, striatum, olfactory bulb, and neocortex. The data are discussed in relation to earlier research and with respect to the anatomical and functional connectivity of the examined centers.

Anesthetics, Local↗
PubMed1999

A peculiar pattern of temporal involvement of rat perirhinal cortex in memory processing.

By means of the fully reversible tetrodotoxin inactivation technique, perirhinal cortex (PC) mnemonic function was investigated in rats trained to a passive avoidance response (PAR). It was shown that PC functional integrity is necessary during PAR acquisition, during late and very late consolidation (from 24 hr up to 192 hr after the training session), and during retrieval. An unexpected finding was that the PC was not involved in the early consolidation period. Thus the PC may play a relatively simple relay or connective role during acquisition, but its very late and very long consolidative involvement may indicate a peculiar function in consolidation and possibly in the storage of the PAR engram. The results are discussed in terms of the mnemonic characteristics of other neural sites (amygdala, hippocampus, and entorhinal cortex) involved in the same learning process.

Analysis of Variance↗
PubMed1999

Local control after curative surgery for cancer of the extraperitoneal rectum. Twenty years of experience.

A retrospective study was carried out in 264 patients with low rectal cancer surgically treated with curative intent from January 1975 to December 1995 to analyze the influence of stapling devices on surgical and disease outcome. Patients were classified as follows: group 1 underwent surgery from 1975 to 1980, when staplers were not employed, and group 2 from 1981 to 1995, when stapling devices were routinely used. The use of stapling devices determined a corresponding increase in low anterior resection (LAR) and a decrease in postoperative mortality. A statistically significant difference in local recurrence rate between abdominoperineal resection (APR) patients and LAR sutured cases of group 1 was observed. In T3, N+ cases local recurrence rate was comparable in APR patients and LAR cases with stapled anastomosis. Improved local control occurred in stapled group 2 patients which was independent of the distal clearance. Although APR still plays an important role in treatment of lower rectal cancer, results indicated that a similar outcome after stapled LAR can also be expected in locally advanced carcinoma of the distal rectum, if accurate excision of perirectal tissue is carried out.

Aged↗
PubMed1999

Identification and characterization of a novel functional estrogen receptor on human sperm membrane that interferes with progesterone effects.

The presence of a novel functional estrogen receptor on the human sperm surface has been demonstrated by using different experimental approaches. Ligand blot analysis of sperm lysates, using peroxidase-conjugated estradiol as probe, identified a specific estradiol-binding protein of approximately 29-kDa apparent molecular mass. The same protein band was also revealed by using alphaH222 antibody, which is directed against the steroid binding domain of the genomic estrogen receptor. The biological effects of estrogen receptor were investigated by analyzing calcium fluxes, tyrosine phosphorylation, and acrosome reaction (AR) in response to 17beta-estradiol (17betaE2) and by measuring the steroid influence on calcium and AR in responses to progesterone (P), a well-known physiological stimulus for human spermatozoa. Our results demonstrate that 17betaE2 induces a rapid and sustained increase of intracellular calcium concentrations ([Ca2+]i). This effect is totally dependent on the presence of extracellular calcium, because it is completely abolished in a calcium-depleted medium. The dose-response curve for calcium increase to 17betaE2 is biphasic with a first component in the nanomolar range (effective concentration 50 = 0.60 +/- 0.12 nmol/L) and a second component in the micromolar range (EC50 = 3.80 +/- 0.26 micromol/L). 17BetaE2 stimulates tyrosine phosphorylation of several sperm proteins, including the 29-kDa protein band, and determines a reduction of calcium response to P, finally resulting in inhibition of P-stimulated sperm AR. Conversely, no direct effect of 17betaE2 is observed on AR. 17BetaE2 effects on calcium are clearly mediated by a membrane receptor, because they are reproduced by the membrane-impermeable conjugate of the hormone BSA-E2 and reduced by sperm preincubation with alphaH222 antibody. Taken together, our results clearly show the presence of a functional surface estrogen receptor, of 29 kDa, on human spermatozoa. This receptor may play a role in the modulation of nongenomic action of P in these cells during the process of fertilization.

Acrosome Reaction↗
PubMed1999

Memorization of contextual and CS conditioned fear response (freezing) in a one-trial acquisition paradigm.

In fear-conditioned Wistar rats freezing was induced by the delivery of a series of footshocks paired to tones (CS) in a specific conditioning chamber (context). CS and contextual fear were acquired in the same single conditioning session without preexposition to the conditioning chamber (day 1). Different groups of animals were conditioned employing three increasing US (footshock) intensities (0.25, 0.5, 0.75 mA). During the retention sessions context and CS conditioned freezing (fear response) were measured using a paradigm that fulfilled the following conditions: i) CS freezing retention was measured in a context different from the conditioning one; ii) CS and context freezing were measured at increased delays after the training session (days 3 and 4, 14 and 15, 28 and 29). The results show that there are significant differences between CS and context freezing retention, which are clearly related to delay after the initial session and to US intensity. In particular: 1) conditioned freezing to a discrete tone is better retained than conditioned freezing to context (irrespective of US intensity); 2) context freezing is directly related to US intensity much more than to tone freezing; 3) context freezing is easier to extinguish than tone freezing. The results are discussed in relation to previous ones and to their relevance to freezing genesis neural correlates.

Acoustic Stimulation↗
PubMed1999

Effects of progesterone on human spermatozoa: clinical implications.

Progesterone is a physiological stimulus of human sperm acrosome reaction. The effects of the steroid, which is present in high levels in the cumulus matrix that surrounds the oocyte, are mediated by an increase of intracellular calcium concentrations, tyrosine phosphorylation of proteins, efflux of chloride and stimulation of activity of phospholipases. These effects are due to activation of a nongenomic pathway. Two different types of receptors for progesterone, distinct from the genomic ones, have been identified on the surface of human spermatozoa. We demonstrated that sperm responsiveness to progesterone is impaired in subfertile patients and that is strictly correlated to the ability of fertilize the oocyte. In addition, the determination of sperm responsiveness is predictive of fertilizing ability with a positive predictive value of 90% and can be clinically useful for the preliminary assessment of the male partner to select the appropriate assisted reproductive technique.

Acrosome Reaction↗
PubMed1998

Nongenomic effects of progesterone on spermatozoa: mechanisms of signal transduction and clinical implications.

Progesterone (P) is one of the physiological stimuli of human sperm acrosome reaction. It is present in high levels at the site of fertilization (cumulus oophorus) and has been describe to affect several sperm functions including motility, capacitation and acrosome reaction. The effects of the steroid, which is present in high levels in the cumulus matrix that surrounds the oocyte, are mediated by an increase of intracellular calcium concentrations, efflux of chloride, stimulation of activity of phospholipases and phosphorylation of proteins. These effects are due to activation of a rapid/nongenomic pathway. Two different types of receptors for P, distinct from the genomic ones, have been recently identified on the surface of human spermatozoa. The affinities of P for these receptors are respectively in the nano- and in the micromolar range. Sperm responsiveness to progesterone is impaired in subfertile patients and is strictly correlated to the ability of fertilize the oocyte. In addition, the determination of sperm responsiveness is predictive of fertilizing ability with a positive predictive value of 90% and can be clinically useful for the preliminary assessment of the male partner to select the appropriate assisted reproductive technique.

Calcium↗
PubMed1998

Entorhinal cortex and fimbria-fornix role in rat's passive avoidance response memorization.

The stereotaxic administration of tetrodotoxin (TTX) was employed to induce the fully reversible inactivation of the fimbria-fornix complex (FF) and of the entorhinal cortex (EC), in order to ascertain the role of these structures in the memorization of a passive avoidance response (PAR). On permanently cannulated rats TTX (5 ng in 0.5 microliter saline) or saline (0.5 microliter) was injected uni- or bilaterally, respectively, in the FF and in the EC, 60 min before PAR acquisition, immediately after PAR acquisition and 60 min before PAR retrieval, always performed 48 h after the acquisition trial. It was shown that EC unilateral or bilateral pre-acquisition inactivation was followed by amnesia, while TTX inactivation in post-acquisition and pre-retrieval had no effects. Identical results were obtained by TTX administration in FF. The experimental evidence indicates that both EC and FF play a role during acquisition of PAR engram. The results are discussed in comparison with previous ones concerning dorsal and ventral hippocampus TTX inactivation effects on rat's PAR, and in relation to hippocampal and medial septal area connectivity.

Animals↗