Biomedical subjects

B Fischer

Publications and source records attributed to B Fischer.

At least 73 records · Page 4Linked to original sources

PubMed2000

Delayed and blunted induction of mRNA for tissue plasminogen activator in the brain of old rats following pentylenetetrazole-induced seizure activity.

The ability of the rodent brain to support plasticity-related phenomena declines with increasing age. Here we investigated the extent to which old rats retain the capacity to initiate transcription for immediate early genes, particularly as it relates to brain plasticity, in response to a strong stimulus. The intraperitoneal administration of pentylenetetrazole (PTZ) to rats of various ages evoked tonic-clonic seizures. Using an RNA gel-blot and in situ hybridization analysis, we found that 1 hour after the onset of seizure, messenger RNA (mRNA) for tissue plasminogen activator (TPA) was increased approximately 3.7-fold in the hippocampi of 3-month-old rats. The levels of TPA mRNA in the hippocampi and cortices of 3-month-old rats returned to control levels by 3 hours after PTZ administration. The levels of TPA mRNA increased 2.5-fold in the hippocampi of 18-month-old rats and 1.8-fold in the brains of the 28-month-old-rats at 3 hours and returned to basal levels by 15 hours following PTZ treatment. Quantitatively similar increases were calculated for the cortex. At peak induction the transcripts were localized throughout the cortical layers of the 3-month-old rats, whereas the TPA mRNA expression was restricted to cortical layer V of the older rats. Our results suggest that although the aging brain retains the capacity to respond to chemically induced seizures, the induction of TPA mRNA is temporarily delayed and the levels are diminished with increasing age. Because TPA has been implicated in neuronal plasticity, this finding suggests that immediate early genes are important factors in the limited plasticity of the aging brain.

Aging↗

PubMed2000

Oxygen stress increases prolyl cis/trans isomerase activity and expression of cyclophilin 18 in rabbit blastocysts.

The peptidyl-prolyl cis/trans isomerase (PPIase) activity and the expression of cyclophilins were studied in 6-day-old rabbit preimplantation embryos cultured under physiological and increased oxygen concentrations of 5% and 20% O(2), respectively. The PPIase activity was completely inhibited by cyclosporin A (CsA). The inhibitor of FK506-binding proteins, rapamycin, had no effect on the PPIase activity, indicating that the PPIase activity in rabbit blastocysts originates from cyclophilins. Using CsA affinity chromatography, only one cyclophilin with a molecular mass of about 17.8 kDa was separated. The cDNA of rabbit cyclophilin was cloned and sequenced. Analysis of the 682-base pair cDNA revealed an open reading frame coding for a polypeptide of 164 amino acid residues with a molecular weight of 17.83 kDa. Homologies of 90% and 96% for the cDNA and amino acid sequence, respectively, to the human CyP18 were found, suggesting that the novel rabbit cyclophilin is a member of the CyP18 family (rabCyP18). The transcription level of rabCyP18 mRNA was 8.3 +/- 0.6 pg in 100 ng total RNA in noncultured blastocysts. In vitro culture with moderate oxygen stress (20% O(2)) resulted in a 1.5-fold increase in rabCyP18 transcription and an increased PPIase activity compared to that of blastocysts cultured with 5% O(2). Increase in transcription rate and PPIase activity by oxygen stress suggests an involvement of CyP18 in oxygen defense in rabbit preimplantation embryos.

Amino Acid Sequence↗

PubMed2000

Ruminant relaxin in the pregnant one-humped camel (Camelus dromedarius).

We have determined the cDNA sequence of preprorelaxin in the pregnant one-humped camel by employing reverse transcription- and rapid amplification of cDNA ends-polymerase chain reaction. Camel preprorelaxin consisted of 600 base pairs (bp) encoding a protein of 199 amino acids (aa) with a signal peptide of 25 aa (75 bp), a B domain of 28 aa (84 bp), a C domain of 121 aa (366 bp), and an A domain of 24 aa (72 bp). The N terminus of the C domain of camel prorelaxin contained the unique proline-rich repetitive sequence (-RPAP)(3)-(-K/RPAL-)(2), and within the B domain the classical -GRELVR- receptor binding motif was found. Camel preprorelaxin showed highest homology with porcine (74.6%) and equine (65.4%) relaxin. The ovary and the uteroplacental unit were a dual source of relaxin in the pregnant dromedary. Within the ovary, weak expression of relaxin was detected in large luteal cells of the mature corpus luteum. In the ovarian follicles, immunoreactive relaxin, but not relaxin mRNA, was detected in the granulosa and theca interna cell layer. Beginning at around Day 93 of gestation and coinciding with increasing interdigitation of the fetal villus with the underlying maternal endometrium, uterine luminal epithelial cells in the uteroplacental tissue expressed relaxin. Weak expression of immunoreactive relaxin, but not relaxin mRNA, was observed in villous trophoblast cells. Pseudostratified trophoblast cells at the base of the placental villi and multinucleate giant cells did not express relaxin.

Amino Acid Sequence↗

PubMed2000

Experimental observation of localization in the spatial frequency domain of a kicked optical system

An experimental realization of an optical "kicked" system is presented. It exhibits localization analogous to that of the quantum "kicked-rotor." In the experiment, free space propagating light is periodically kicked by thin sinusoidal phase gratings, which produce high order diffractions and tend to increase the spatial frequency band. The wave property suppresses this diffusive spread. The localization is realized in a regime near anti-resonance of the system, which is also studied theoretically. The behavior in this regime is similar to that of electronic motion in incommensurate potentials. A crucial part of the experimental system is the grating in-phase positioning, which is done by using the Talbot effect.

Journal Article↗

PubMed2000

Trophoblast cell-specific carcinoembryonic antigen cell adhesion molecule 9 is not required for placental development or a positive outcome of allotypic pregnancies.

The carcinoembryonic antigen (CEA) family consists of a large group of evolutionarily divergent glycoproteins. The secreted pregnancy-specific glycoproteins constitute a subgroup within the CEA family. They are predominantly expressed in trophoblast cells throughout placental development and are essential for a positive outcome of pregnancy, possibly by protecting the semiallotypic fetus from the maternal immune system. The murine CEA gene family member CEA cell adhesion molecule 9 (Ceacam9) also exhibits a trophoblast-specific expression pattern. However, its mRNA is found only in certain populations of trophoblast giant cells during early stages of placental development. It is exceptionally well conserved in the rat (over 90% identity on the amino acid level) but is absent from humans. To determine its role during murine development, Ceacam9 was inactivated by homologous recombination. Ceacam9(-/-) mice on both BALB/c and 129/Sv backgrounds developed indistinguishably from heterozygous or wild-type littermates with respect to sex ratio, weight gain, and fertility. Furthermore, the placental morphology and the expression pattern of trophoblast marker genes in the placentae of Ceacam9(-/-) females exhibited no differences. Both backcross analyses and transfer of BALB/c Ceacam9(-/-) blastocysts into pseudopregnant C57BL/6 foster mothers indicated that Ceacam9 is not needed for the protection of the embryo in a semiallogeneic or allogeneic situation. Taken together, Ceacam9 is dispensable for murine placental and embryonic development despite being highly conserved within rodents.

Animals↗

PubMed2000

Neutrophil elastase induces MUC5AC messenger RNA expression by an oxidant-dependent mechanism.

Airway diseases such as cystic fibrosis, chronic bronchitis, and viral- or pollution-triggered asthma have two common pathologic features: mucus obstruction of the airways, and neutrophil-predominant airway inflammation. Neutrophils release high concentrations of elastase (neutrophil elastase [NE]), a serine protease, into the airways; exposure to elastase results in secretory metaplasia and increased production/secretion of mucin glycoproteins. We have previously shown that NE increases gene expression of a respiratory mucin, MUC5AC, in both A549, a lung adenocarcinoma cell line, and cultured normal human bronchial epithelial cells. In this study, we explored the intracellular signaling mechanisms required for NE-regulated MUC5AC gene expression. A549 cells were treated with dimethylthiourea (DMTU; 4 mM and 40 mM), a scavenger of hydroxyl radical, peroxynitrite, and other hydroxylated products, prior to and during NE stimulation. DMTU inhibited NE-induced MUC5AC expression. Furthermore, using dichlorodihydrofluorescein, an intracellular redox indicator, we showed that in both A549 cells and cultured normal human bronchial epithelial cells, NE treatment induced oxidative stress. These results support the role of reactive oxygen species mediating NE-induced MUC5AC gene expression.

Blotting, Northern↗

PubMed2000

Prescriptions, power and politics: the turbulent history of methadone maintenance in Canada.

Illicit opiate addiction has emerged as a major problem in many Western countries in the second half of this century, and its social harm implications have become much exacerbated with the onset of the HIV epidemic in the 1980s. By now, most Western jurisdictions have resorted to methadone treatment as the most effective and best researched intervention against the negative consequences of opiate addiction including mortality, morbidity, crime, and loss of social functioning. Methadone treatment in Canada features a long, turbulent, and instructive history as an exemplary case study in public policy. While both Britain and the U.S. experimented with opiate prescription treatment in the first half of the century, Canadian proposals for such programs initially never made it beyond the discussion stage, largely due to the influential resistance from the law enforcement sector. However, in light of growing influence from an emerging addictions treatment sector, Canada became the first Western jurisdiction to experiment with methadone prescription for the treatment of opiate addiction forty years ago. Methadone treatment became quickly and widely established as an effective treatment modality through the 1960s. But in the early 1970s, resistance from the law and health sectors evolved, and triggered the government to establish a set of comprehensive and restrictive federal methadone treatment regulations, which have dominated its realities until today. Almost completely regulated out of existence by the end of the 1970s, methadone treatment's prevalence gradually increased again through the 1980s, and recent decentralization efforts to provincial levels earlier this decade have had dramatic effects on treatment availability. Significant events in the Canadian history of methadone treatment and its regulation reflect developments in the U.S., and substantial recent domestic treatment expansion developments--as well as renewed sparks of resistance--are reminiscent of methadone treatment's patterns of history as they developed in the late 1960s. This paper traces the turbulent history of methadone treatment, regulation and policy in Canada with particular attention to institutional, professional and political determinants at the complex intersection of health, law, and addiction.

Canada↗

PubMed2000

2-Thioether-5'-O-(1-thiotriphosphate)-adenosine derivatives: new insulin secretagogues acting through P2Y-receptors.

P2-receptors (P2-Rs) represent significant targets for novel drug development. P2-Rs were identified also on pancreatic B cells and are involved in insulin secretion. The aim of our study was to synthesize and evaluate pharmacologically the novel P2Y-R ligands, 2-thioether-5'-O-phosphorothioate adenosine derivatives, as potential insulin secretagogues. An efficient synthesis of these nucleosides and a facile method for separation of the chiral products is described. The enzymatic stability of the compounds towards pig-pancreas NTPDase was evaluated. The rate of hydrolysis of 2-hexylthio-5'-O-(1-thiotriphosphate)-adenosine (2-hexylthio-ATP-alpha-S) isomers by NTPDase was 28% that of ATP. The apparent affinity of the compounds to P2Y1-R was determined by measurement of P2Y-receptor-promoted phospholipase C activity in turkey erythrocyte membranes. 2-RS-ATP-alpha-S derivatives were agonists, stimulating the production of inositol phosphates with K0.5 values in the nM range. 2-RS-AMP-S derivatives were full agonists although 2 orders of magnitude less potent. All the compounds were more potent than ATP. The effect on insulin secretion and pancreatic flow rate was evaluated on isolated and perfused rat pancreas. A high increase, up to 500%, in glucose-induced insulin secretion was due to addition of 2-hexylthio-ATP-alpha-S in the nM concentration range, which represents 100-fold enhancement of activity relative to ATP. 2-Hexylthio-AMP-S was 2.5 orders of magnitude less effective. A high chemical hydrolytic stability was observed for 2-hexylthio-ATP-alpha-S. Hydrolysis of the phosphoester bond, which was the only detectable degrading reaction under the investigation conditions (pH 7.4, 37 degrees C), was slow, with a half-life of 264 hours. Moreover, even at gastric juice conditions (pH 1.4, 37 degrees C), hydrolysis of the terminal phosphate was the only detectable reaction, with a half-life of 17.5 hours. 2-Hexylthio-ATP-alpha-S isomers are enzymatically and chemically stable. These isomers are highly potent and effective insulin secretagogues, increasing, however, pancreatic vascular resistance.

Acid Anhydride Hydrolases↗

PubMed2000

Stability of gaze control in dyslexia.

The neurobiological basis of saccade control has at least three components: fixation, reflexes, voluntary control. It was found in earlier studies that the voluntary component of saccade is specifically impaired in dyslexics as compared with controls of the same age. In this study, we searched for evidence of fixation instability by analyzing the eye movements of 99 control subjects and 262 dyslexics (age 7-17 years) performing an overlap prosaccade and a gap antisaccade task. The percentage of intrusive saccades was counted for each subject during a period of the trial where stationary fixation was required. Both groups showed improvements of fixation stability with age, but the dyslexic group exhibited developmental deficits. It is discussed whether these deficits could be interpreted as consequences of deficits in the magnocellular pathway.

Adolescent↗

PubMed1999

Molecular recognition of modified adenine nucleotides by the P2Y(1)-receptor. 1. A synthetic, biochemical, and NMR approach.

The remarkably high potencies of 2-thioether-adenine nucleotides regarding the activation of the P2Y(1)-receptor (P2Y(1)-R) in turkey erythrocyte membranes represent some of the largest substitution-promoted increases in potencies over that of a natural receptor ligand. This paper describes the investigation regarding the origin of the high potency of these P2Y(1)-R ligands over that of ATP. For this study, an integrated approach was employed combining the synthesis of new ATP analogues, their biochemical evaluation, and their SAR analysis involving NMR experiments and theoretical calculations. These experiments and calculations were performed to elucidate the conformation and to evaluate the electronic nature of the investigated P2Y(1)-R ligands. ATP analogues synthesized included derivatives where C2 or C8 positions were substituted with electron-donating groups such as ethers, thioethers, or amines. The compounds were tested for their potency to induce P2Y(1)-R-mediated activation of phospholipase C in turkey erythrocytes and Ca(2+) response in rat astrocytes. 8-Substituted ATP and AMP derivatives had little or no effect on phospholipase C or on calcium levels, whereas the corresponding 2-substituted ATP analogues potently increased the levels of inositol phosphates and ¿Ca(2+)(i). AMP analogues were ineffective except for 2-butylthio-AMP which induced a small Ca(2+) response. P2Y(1)-R activity of these compounds was demonstrated by testing these ligands also on NG108-15 neuroblastoma x glioma hybrid cells. NMR data together with theoretical calculations imply that steric, rather than electronic, effects play a major role in ligand binding to the P2Y(1)-R. Hydrophobic interactions and H-bonds of the C2 substituent appear to be important determinants of a P2Y(1)-R ligand affinity.

Adenine Nucleotides↗

PubMed1999

Molecular recognition of modified adenine nucleotides by the P2Y(1)-receptor. 2. A computational approach.

The molecular recognition of C2- or C8-substituted ATP derivatives by the P2Y(1)-receptor (P2Y(1)-R) is analyzed using ab initio quantum mechanical calculations. Parameters that may determine ligand specificity toward P2Y(1)-R were examined on reduced models and correlated with the biochemical data for the parent compounds. These include tautomerism and protonation energy in the gas and aqueous phases, as well as molecular electrostatic potential (MEP) and dipole moment vector. The calculated electronic parameters cannot explain the inactivity of the C8-substituted ATP derivatives, nor the difference in activity among the C2-substituted ATP analogues. These results indicate that neither tautomerism nor changes in the electronic distribution of the adenine ring play a major role in determining binding specificity of adenine nucleotides to the receptor. It is suggested that the higher potency of the C2-substituted ATP derivatives, compared to ATP, might be due to interaction between the C2 side chain heteroatom and the receptor. Furthermore, the interaction of the C2 alkyl side chain with a hydrophobic pocket at the receptor binding site is suggested. In addition, NMR data in the companion paper indicate that the inactivity of the C8-substituted ATP analogues may be due to steric and conformational, rather than electronic, effects.

Adenine Nucleotides↗

PubMed1999

Expression of the arylhydrocarbon receptor and the arylhydrocarbon receptor nuclear translocator during early gestation in the rabbit uterus.

The arylhydrocarbon receptor (AhR) and the arylhydrocarbon receptor nuclear translocator (ARNT) are members of the PAS gene family mediating toxic effects of xenobiotics such as dioxin and polychlorinated biphenyls. We have analyzed the expression and cellular distribution of rabbit AhR and ARNT mRNA and protein level in the nonpregnant uterus and the pregnant and pseudopregnant uterus at Days 6 to 12 of gestation. In the preimplantation uterus at Day 6 of gestation and in the interimplantation and pseudopregnant uterus at Days 7, 8, 9, and 12 of gestation, low levels of AhR transcripts were detected in the glandular uterine epithelium. Upon attachment of the blastocyst at Day 7 of gestation, a strong expression of AhR and ARNT mRNA was observed in the luminal and glandular epithelium of the antimesometrial uterine compartment. In contrast, AhR and ARNT expression was low in the luminal epithelium of the paraplacental and the mesometrial placental fold. AhR mRNA was also detected in the trophoblast cells. During early placentation at Day 9 of gestation, expression of AhR and ARNT was first observed in the perivascular decidualized stromal cells and, at Day 12, extended to the decidualized stromal cells of the placental bed. Within the placenta, the syncytiotrophoblast expressed only low levels of AhR and ARNT mRNA and no protein. The specific expression patterns of AhR and ARNT during early gestation suggest functional roles for both transcription factors during feto-maternal interactions in the rabbit.

Animals↗

PubMed1999

2-thioether 5'-O-(1-thiotriphosphate)adenosine derivatives as new insulin secretagogues acting through P2Y-Receptors.

P2-Receptors (P2-Rs) represent significant targets for novel drug development. P2-Rs were identified also on pancreatic B cells and are involved in insulin secretion. Therefore, novel P2Y-R ligands, 2-thioether 5'-O-phosphorothioate adenosine derivatives (2-RS-ATP-alpha-S), were synthesized as potential insulin secretagogues. An efficient synthesis of these nucleotides and a facile method for separation of the chiral products are described. The enzymatic stability of the compounds toward pig pancreas type I ATPDase was evaluated. The rate of hydrolysis of 2-hexylthio-5'-O-(1-thiotriphosphate)adenosine (2-hexylthio-ATP-alpha-S) isomers by ATPDase was 28% of that of ATP. Some 2-thioether 5'-(monophosphorothioate)adenosine derivatives (2-RS-AMP-S) exerted an inhibitory effect on ATPDase. The apparent affinity of the compounds to P2Y(1)-R was determined by measurement of P2Y-R-promoted phospholipase C activity in turkey erythrocyte membranes. 2-RS-ATP-alpha-S derivatives were agonists, stimulating the production of inositol phosphates with K(0.5) values in the nanomolar range. 2-RS-AMP-S derivatives were full agonists, although 2 orders of magnitude less potent. All the compounds were more potent than ATP. The effect on insulin secretion and pancreatic flow rate was evaluated on isolated and perfused rat pancreas. A high increase, up to 500%, in glucose-induced insulin secretion was due to addition of 2-hexylthio-ATP-alpha-S in the nanomolar concentration range, which represents 100-fold enhancement of activity relative to ATP. 2-Hexylthio-AMP-S was 2.5 orders of magnitude less effective.

Adenosine↗

PubMed1999

Characterization of "mini-nucleotides" as P2X receptor agonists in rat cardiomyocyte cultures. An integrated synthetic, biochemical, and theoretical study.

The design and synthesis of "mini-nucleotides", based on a xanthine-alkyl phosphate scaffold, are described. The physiological effects of the new compounds were evaluated in rat cardiac cell culture regarding Ca(2+) elevation and contractility. The results indicate biochemical and physiological profiles similar to those of ATP, although at higher concentrations. The biological target molecules of these "mini-nucleotides" were identified by using selective P2-R and A(1)-R antagonists and P2-R subtype selective agonists. On the basis of these results and of experiments in Ca(2+) free medium, in which [Ca(2+)](i) elevation was not observed, we concluded that interaction of the analogues is likely with P2X receptor subtypes, which causes Ca(2+) influx. Theoretical calculations analyzing electronic effects within the series of xanthine-alkyl phosphates were performed on reduced models at quantum mechanical levels. Calculated dipole moment vectors, electrostatic potential maps, and volume parameters suggest an explanation for the activity or inactivity of the synthesized derivatives and predict a putative binding site environment for the active agonists. Xanthine-alkyl phosphate analogues proved to be selective agents for activation of P2X-R subtypes, whereas ATP activated all P2-R subtypes in cardiac cells. Therefore, these analogues may serve as prototypes of selective drugs aiming at cardiac disorders mediated through P2X receptors.

Animals↗

PubMed1999

Induction of arylhydrocarbon receptor expression in embryoblast cells of rabbit preimplantation blastocysts upon degeneration of Rauber's polar trophoblast.

The arylhydrocarbon receptor (AhR) is a ligand-activated transcription factor and mediates carcinogenic, teratogenic, and toxic effects of xenobiotics such as dioxin and coplanar polychlorinated biphenyls. The AhR nuclear translocator (ARNT) is involved in AhR signal transduction. We have analyzed the expression of AhR and ARNT mRNA and AhR protein in Day 3 pc (postcoitum) rabbit morulae and Days 4 and 6 pc blastocysts using RT-PCR, nested PCR, whole mount in situ hybridization, and whole mount immunohistochemistry with subsequent confocal laser scanning analysis. AhR and ARNT transcripts were detected in all stages investigated, indicating coexpression of both transcription factors. AhR protein was localized in the cytoplasm. It was detected in Day 3 pc morulae and in blastocysts. In Day 4 pc blastocysts, only trophoblast cells but not embryoblast cells were immunopositive. However, at Day 6 pc, the embryoblast cells also expressed AhR protein and this expression was correlated with the degeneration of Rauber's trophoblast layer.

Animals↗

PubMed1999

Molecular cloning and localization of caprine relaxin-like factor (RLF) mRNA within the goat testis.

The relaxin-like factor (RLF) is one of the insulin-like molecules, which also includes insulin, insulin-like growth factor I and II, placentin, and relaxin. Employing RT- and RACE-PCR on RNA isolated from goat testicular tissue, we report the cloning and nucleic acid sequence of goat RLF. The caprine RLF cDNA coding sequence consisted of 396 base pairs encoding a peptide of 131 amino acids. Caprine RLF showed the highest homology in nucleic acid and amino acid sequence with bovine and sheep RLF, suggesting conservation of the RLF gene among ruminants. Northern blot analysis revealed a single 0.9 kb RLF transcript expressed in the goat testis but not in the epididymis, liver, or muscle tissue. Only a single goat RLF gene is present in the goat genome as determined by Southern blot analysis. Employing nonradioactive in situ hybridization for goat RLF mRNA and immunohistochemistry for 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and 17alpha-hydroxylase, we identified the Leydig cells as the sole source of RLF mRNA in the goat testis.

Amino Acid Sequence↗

PubMed1999

Stage-specific effects of defined mixtures of polychlorinated biphenyls on in vitro development of rabbit preimplantation embryos.

PCBs adversely affect various reproductive functions. Little is known about the embryo- toxic effects during the preimplantation period in mammals. In the present study the effects of various mixtures of highly purified PCB-congeners on embryo morphology, blastocyst formation, embryo size and cell proliferation were investigated. For 24 hr, day 3 morulae and day 4 blastocysts were cultured in the presence/absence of coplanar congeners (PCB77, PCB126, and PCB169), non-coplanar congeners (PCB28, PCB52, PCB101, PCB118, PCB138, PCB153, PCB180) or both mixtures in concentrations ranging from 0.3 ng/mL to 60 microg/mL total PCB. The main effects were (1) degeneration of all embryos at 60 microg/mL, (2) reduction of cell proliferation in day 4 embryos only by coplanar PCB; in day 3 embryos, however, by all PCB-mixtures, and (3) reduction of cell proliferation in a non-linear dose response with the strongest impairment caused by the lowest concentration. Cell proliferation was decreased by 0.3 ng/mL coplanar PCB to 50% of the level in control blastocysts. Our results show that purified PCB congeners in the range of 0.3 ng/mL to 30 microg/mL affect the development of preimplantation embryos in a stage-specific and congener-specific manner. This study provides first evidence for an embryotoxic potential of coplanar PCB congeners.

Animals↗

PubMed1999

The recognition and correction of involuntary prosaccades in an antisaccade task.

This paper reports a striking misperception associated with involuntary saccadic eye movements: when subjects are instructed to look to the opposite side of a suddenly presented stimulus (antisaccade), they produce a certain number of involuntary prosaccades to the stimulus before they move their eyes to the other side by a corrective saccade of approximately twice the size. When asked to indicate at the end of each trial whether they believed that they made such a detour sequence of two saccades, one finds that, on average, 50+/-25% of these involuntary movements are not recognized. The average size and correction time for recognized prosaccades is larger than unrecognized prosaccades, while their mean reaction times are the same. The corrective saccades compensate for the size of both the recognized and unrecognized errors. When similar sequences of saccades are made voluntarily, the time spent at the stimulus side was 222 ms compared with 95 ms for unrecognized and 145 ms for recognized errors. The distributions of the corresponding correction times differ in their multimodal composition. Whether voluntary and involuntary saccades and their corrections are associated with different effects on the updating of the perceptual spatial frame and attention allocation is discussed.

Attention↗