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C Janse

Publications and source records attributed to C Janse.

At least 19 recordsLinked to original sources
PubMed2005

Effects of age on feeding behavior and chemosensory processing in the pond snail, Lymnaea stagnalis.

This study used behavioral and electrophysiological techniques to examine age-related changes in the feeding behavior and chemosensory processing in the pond snail, Lymnaea stagnalis. Increasing age was associated with a 50% decrease in long-term food consumption. Analysis of short-term sucrose-evoked feeding bouts showed an age-related increase in the number of animals that failed to respond to the stimulus. Of the animals that did respond increasing age was associated with a decrease in the number of sucrose-evoked bites and a increase in the duration of the swallow phase. These changes were observed with both 0.01 and 0.05M sucrose stimuli but were not seen when 0.1M sucrose was used as the stimulus. Electrophysiological analysis of the chemosensory pathway in semi-intact lip-CNS preparations failed to demonstrate a significant change in the neuronal information entering the cerebral ganglia from the lips via the median lip nerve, but did demonstrate an age-related deficit in the neuronal output from the cerebral ganglia. This deficit was also dependent on the sucrose concentration and mirrored the concentration-dependent changes in feeding behavior. In summary, aging appeared to affect central but not peripheral processing of chemosensory information and suggests that this deficit contributes to the age-related changes in feeding behavior.

Aging↗
PubMed2005

Auto-inhibitory control of peptidergic molluscan neurons and reproductive senescence.

We recently, characterized a novel peptide of the egg-laying controlling caudodorsal cells (CDC) of Lymnaea stagnalis. Here, we show that the novel peptide has autoinhibitory actions and its expression is significantly up-regulated in reproductively senescent animals. Intracellular recordings show that when bath-applied to the central nervous system in vitro, the peptide reduces the depolarizing after potential (DAP) in CDCs without affecting the action potential-threshold and -amplitude and the resting membrane potential. Moreover, peptide application can terminate an ongoing after discharge in the CDCs or, when electrical stimulation fails to induce an after discharge, can terminate the long-lasting depolarization. Semiquantitative peptide profiling by mass spectrometry demonstrated correct processing and targeting of peptides in the CDC somata and axon terminals of reproductively senescent animals. Interestingly, the level of the autoinhibitory peptide was selectively increased in the CDCs of reproductively senescent animals. Our results indicate that a shift in balance between excitatory and inhibitory auto-transmitter peptides in the CDC system of old non-egg-laying animals, plays a role in after discharge failure in CDCs of reproductively senescent Lymnaea.

Action Potentials↗
PubMed2004

Survival of egg-laying controlling neuroendocrine cells during reproductive senescence of a mollusc.

During brain aging neuronal degradation occurs. In some neurons this may result in degeneration and cell death, still other neurons may survive and maintain their basic properties. The present study deals with survival of the egg-laying controlling neuroendocrine caudodorsal cells (CDCs) during reproductive senescence of the pond snail Lymnaea stagnalis. In senescent animals CDCs exhibited reduced branching patterns but still maintained their electrophysiological characteristics. In the isolated CNS the cells could still respond with an afterdischarge upon electrical stimulation. After an extended period of no egg laying of Lymnaea CDCs failed to exhibit an afterdischarge. In senescent CDCs that failed an afterdischarge, discharge activity could be restored by exposure to peptides released by CDCs from reproductive animals. Moreover, raising the intracellular cAMP level could induce discharge activity in CDCs with afterdischarge failure. Discharge activity also occurred during depolarization of senescent CDCs by exposure of the cells to saline with a high potassium concentration. These results indicate that in senescent CDCs the pacemaking mechanism of the afterdischarge is still intact but that the initial activation fails. Chemical (auto)transmission of CDCs in such animals was indeed reduced as indicated by the small amplitude of the depolarizing afterpotential (DAP) induced by electrical stimulation. Interestingly, CDCs of senescent animals contained a relative large amount of a particular small peptide. The artificially synthesized peptide appeared to suppress DAP induction in CDCs. Possibly, release of the peptide contributes to the prevention of afterdischarge induction in senescent CDCs. The results so far indicate that in senescent Lymnaea neurons electrophysiological functions persist even after long periods of inactivity and severe morphological reduction.

Aging↗
PubMed2000

Changes in molluscan neurosecretory cells during reproductive cessation: cause or effect?

The pond snail Lymnaea stagnalis has a maximum life span of about 22 months. At the age of about 250 days animals start to decrease egg laying activity and at about 500 days most animals ceased egg laying activity. At the age of cessation of egg laying the neurosecretory caudodorsal cells (CDCs) which control egg laying in Lymnaea exhibit reduced branching patterns. At this stage the cells still exhibit their physiological properties. CDCs still contain biologically active peptides and in the isolated CNS they still exhibit an afterdischarge upon electrical stimulation. Probably in the intact animal cessation of egg laying occurs because the CDCs are not activated anymore by natural egg laying inducing stimuli. In very old animals CDCs exhibit signs of degeneration indicating that cell death occur. After an extended period of no egg laying of Lymnaea physiological changes occur in the CDCs. CDCs from animals after an extended period of no egg laying failed to exhibit an afterdischarge. In such CDCs chemical and electrical coupling among the CDCs are reduced. Morphologically reduced CDCs predominantly fail to exhibit an afterdischarge. However, there are minimally branched CDCs that still could give an afterdischarge. Probably morphological reduction is not the only factor that defines afterdischarge failure. At present we suggest the following sequence of changes. 1. Morphological reduction of CDC branching patterns. 2. Cessation of egg laying. 3. Physiological changes in the CDCs resulting in afterdischarge failure. 4. Further morphological and physiological deterioration of CDCs.

Aging↗
PubMed1998

Precise timing of expression of a Plasmodium falciparum-derived transgene in Plasmodium berghei is a critical determinant of subsequent subcellular localization.

The development of transfection technology for malaria parasites holds significant promise for a more detailed characterization of molecules targeted by vaccines or drugs. One asexual blood stage vaccine candidate, apical membrane antigen-1 (AMA-1) of merozoite rhoptries has been shown to be the target of inhibitory, protective antibodies in both in vitro and in vivo studies. We have investigated heterologous (trans-species) expression of the human malaria Plasmodium falciparum AMA-1 (PF83/AMA-1) in the rodent parasite Plasmodium berghei. Transfected P. berghei expressed correctly folded and processed PF83/AMA-1 under control of both pb66/ama-1 and dhfr-ts promoters. Timing of expression was highly promoter-dependent and was critical for subsequent subcellular localization. Under control of pb66/ama-1, PF83/AMA-1 expression and localization in P. berghei was limited to the rhoptries of mature schizonts, similar to that observed for PF83/AMA-1 in P. falciparum. In contrast the dhfr-ts promoter permitted PF83/AMA-1 expression throughout schizogony as well as in gametocytes and gametes. Localization was aberrant and included direct expression at the merozoite and gamete surface. Processing from the full-length 83-kDa protein to a 66-kDa protein was observed not only in schizonts but also in gametocytes, indicating that processing could be mediated outside of rhoptries by a common protease. Trans-species expressed PF83/AMA-1 was highly immunogenic in mice, resulting in a response against a functionally critical domain of the molecule.

Animals↗
PubMed1997

Gene targeting in malaria parasites.

Gene targeting, which permits alteration of a chosen gene in a predetermined way by homologous recombination, is an emerging technology in malaria research. Soon after the development of techniques for stable transformation of red blood cell stages of Plasmodium falciparum and Plasmodium berghei, genes of interest were disrupted in the two species. The main limitations of gene targeting in malaria parasites result from the intracellular growth and slow replication of these parasites. On the other hand, the technology is facilitated by the very high rate of homologous recombination following transformation with targeting constructs (approximately 100%). Here, we describe (i) the vector design and the type of mutation that may be generated in a target locus, (ii) the selection and screening strategies that can be used to identify clones with the desired modification, and (iii) the protocol that was used for disrupting the circumsporozoite protein (CS) and thrombospondin-related anonymous protein (TRAP) genes of P. berghei.

Animals↗
PubMed1996

Atrophy and degeneration of peptidergic neurons and cessation of egg laying in the aging pond snail Lymnaea stagnalis.

The morphology of the neuroendocrine caudodorsal cells (CDCs), which are involved in the regulation of female reproduction in the pond snail Lymnaea stagnalis, was studied in young (200 to 234 days of age) and old (400 to 500 days) animals. Lucifer Yellow fills of ventral CDCs showed that in young animals ventral CDCs branch ipsilaterally as well as contralaterally in the cerebral commissure. In old animals these branches were reduced at different degrees and in some cases even lacking completely, leaving only an axon crossing the commissure. Immunocytochemical stainings with antibodies against CDC peptides (CDCH-I and alpha CDCP) corroborated the finding that ventral CDCs degenerate. Among the other types of CDCs (dorsal, lateral), degeneration was found as well. The immunocytochemical findings showed that in old animals the axon terminals of the CDCs were strongly stained, indicating that they are packed with secretory vesicles containing peptides. It was also found that these darkly stained, peptide-containing axon terminals protruded into the perineurium. These findings suggest that accumulation of peptides in the terminals of the CDCs of old animals may be due to the impaired release. The relationship between atrophy and degeneration of CDCs and cessation of egg-laying activity in Lymnaea is discussed.

Aging↗
PubMed1995

Comparison of introns in a cdc2-homologous gene within a number of Plasmodium species.

The first three introns of CRK2, a cdc2-homologous gene, have been compared in a total of seven Plasmodium species. The introns were located at conserved sites, suggesting an ancestral origin. Interspecific comparison of intron sequences agreed with the previously inferred evolutionary relationships of the malaria parasites. Unlike the introns in the rodent malaria species, the similarity of the CRK2 introns was regionalized between the human parasite P. vivax and the simian parasite P. knowlesi: the central region of all three introns showed markedly less interspecific similarity than the 5' and 3' regions. This was also in contrast with the organisation and composition of homologous intron pairs from other genes of the same two species. No conservation at the level of secondary structure could be detected, even between highly similar introns. A database search for intron-containing Plasmodium genes was performed. All introns obtained in this way plus the additional CRK2 introns were scanned for the presence of putative branching site consensus sequences. For P. falciparum, we present an update of the 5' and 3' splice-site consensus.

Amino Acid Sequence↗
PubMed1995

Degeneration of CDCs and egg laying in the pond snail Lymnaea stagnalis.

In the pond snail Lymnaea stagnalis egg laying is induced by multiple peptides, which are released by the neuroendocrine caudo-dorsal cells (CDCs). Egg laying in Lymnaea starts at about 50 days and increases initially with age to decreases again at an age of about 250 days. From that age on, the total number of animals that stop egg laying increases with age. The maximum age of Lymnaea is about 660 days. Lucifer Yellow fills of individual ventral CDCs showed reduced branching patterns in old animals. Immunocytochemical stainings demonstrated degeneration in ventral, dorsal and lateral CDCs. In animals that had stopped egg laying, CDCs could still be electrically activated. Regeneration studies after crushing the cerebral commissure showed that in old animals CDCs still can regenerate connections in the cerebral commissure. The properties of CDCs in old animals are discussed in relationship with possible mechanisms of cessation of egg laying in Lymnaea.

Aging↗
PubMed1992

The role of membrane properties, synaptic input and electrical junction in determination of spike output of a pair of peptidergic neurons in the mollusc Lymnaea stagnalis.

The two electrotonically coupled peptidergic neurons, VD1 and RPD2 show in the isolated central nervous system (CNS) a patterned activity. The cells fire in almost perfect synchrony in CNS's derived from animals of moderate age, while in old animals disturbances in synchrony are observed. The firing pattern varies from beating to bursting. Isolated VD1's show a beating firing pattern, indicating that the cell possesses pacemaker properties, while the isolated RPD2 is almost always silent. Hybrid current/voltage clamp experiments show that in the intact CNS spike generation in the two cells is due to VD1, indicating that the pacemaker properties of VD1 constitute the main driving force for the firing rhythm of the two cell system. In low calcium/high magnesium solutions the rhythm is a beating one, while in solutions which do not suppress synaptic input, sometimes a bursting pattern is observed. The idea that the bursting pattern is due to synaptic modulation of these cells is corroborated by the observation that application of certain transmitters induces a very prominent burst of activity in these neurons. These bursts are very reminiscent of the bursts, observed in semi-intact preparations, which are accompanied by penumostome movements. Increase in coupling resistance, which occurs at older age, is accompanied by irregularities in firing rhythm. Apparently the electrotonic junction is essential for the patterned output of the two cell system.

Action Potentials↗
PubMed1991

The role of pacemaker properties and synaptic input in generation and modulation of spiking activity in a pair of electrically coupled peptidergic neurons.

The origin of patterned electrical activity in two electronically coupled peptidergic neurons, VD1 and RPD2, in the CNS of Lymnaea stagnalis was investigated. VD1 proved to have intrinsic beating pacemaker properties. Hybrid current/voltage clamp experiments demonstrated that in the intact CNS generation of spike activity in the coupled cell system is dominated by VD1. Modulation of spiking activity of VD1/RPD2 appears to originate mainly from chemical synaptic input. The electrical coupling of VD1 and RPD2 proved essential for spike synchronization between the cells.

Action Potentials↗
PubMed1991

Age-related changes in junctional and non-junctional conductances in two electrically coupled peptidergic neurons of the mollusc Lymnaea stagnalis.

Age-related changes in electrotonic coupling ratio of two identified neurons in Lymnaea stagnalis were studied together with the underlying changes in the steady-state conductance properties of the network. Two phases were distinguished in the development of coupling ratio across lifespan. During the first phase (age of 3-13 months), coupling ratio decreased from decreased from 60% to 30%. The second phase (age 13-20 months) was characterized by an increase in coupling ratio. Values of up to 60% were reached again in the oldest animals. Voltage clamp measurements showed that the biphasic trend of the age-related changes in coupling ratio is paralleled by changes in conductance properties of the junction between VD1 and RPD2. During the first phase junctional conductance decreased, whereas during the second phase junctional conductance increased. In addition to the decrease in junctional conductance, a growth-related increase in non-junctional conductance of VD1 and RPD2 contributed to the decrease in coupling ratio observed during the first phase. Thus our results indicate that in Lymnaea junctional connections between neurons may undergo considerable and discontinuous changes after sexual maturation. In addition to these changes in steady-state electrical properties, indications were obtained that age-related changes of kinetically slower conductance(s) may occur in the non-junctional membrane of VD1 and RPD2.

Aging↗
PubMed1990

Long insertions within telomeres contribute to chromosome size polymorphism in Plasmodium berghei.

During prolonged in vivo mitotic multiplication of a Plasmodium berghei ANKA clone (8417HP), parasites that contained an enlarged version of chromosome 4 were observed. Restriction mapping and hybridization results demonstrated that the extra DNA present in the enlarged chromosome consists of 2.3-kb tandem repeats, known to be normally located in subtelomeric position at several chromosomal ends but absent in the original chromosome. The inserted 2.3-kb units appeared to interrupt one of the original telomeres and to create an internal (approximately 1-kb-long) telomeric sequence.

Animals↗
PubMed1989

Age-related changes in female reproductive activity and growth in the mollusc Lymnaea stagnalis.

Age-related changes in reproduction and growth of the pulmonate snail Lymnaea stagnalis were studied in animals under standard culture conditions. Longitudinal studies as well as cross-sectional studies were done. Egg-laying activity starts in Lymnaea at an age of about 2 months. Up to an age of about 250 days it increases, and in older snails it decreases with age. Cross-sectional studies showed that the increase in egg-laying activity is due to an increase in the number of animals that lay eggs and to an increase in the egg-laying frequency of individuals. The decrease in egg-laying activity is due to a decrease in the egg-laying frequency of individual animals and to an increase in the number of animals that stop egg laying. Growth (shell length and body weight) ceases at about the same age at which egg laying begins to decrease. The results are discussed in relation to the organization of the neuroendocrine system in Lymnaea and to results of earlier studies on age-related changes in peptidergic neurons in the CNS of Lymnaea.

Aging↗
PubMed1988

Survival characteristics of the mollusc Lymnaea stagnalis under constant culture conditions: effects of aging and disease.

Survival characteristics of seven different populations of the mollusc Lymnaea stagnalis were studied under constant culture conditions. On the basis of these characteristics four populations were considered as healthy and three as infected. In the healthy populations senescence started at an age of about 200 days, 50% survival age varied from 282 to 372 days, 10% survival age from 417 to 508 days and the maximum age from 528 to 673 days. Infected populations differed from healthy ones: (1) in behaviour of the animals; and (2) in shape of survival curve and age-specific death rate. It is concluded that in aging studies in addition to the absolute age of the animals, the following information should be given: the percentage of survival of the population at the time of sampling and a quantitative estimate of the quality of the cultures from which the animals were sampled. The parameters of the Weibull function seem to be suitable for such estimations.

Aging↗
PubMed1988

A quantitative method to evaluate the quality of interrupted animal cultures in aging studies.

A method is described for a quantitative estimation of the quality of interrupted animal cultures. It is applicable when survival can be described by a Weibull or by a Gompertz function. Application to four healthy and three infected cultures of Lymnaea stagnalis shows that survival curves can be successfully predicted from cultures censored at 25%, 50%, and 75% survival. The parameters of these predicted survival curves can be used to evaluate experimental results from single (longitudinal or cross-sectional) aging studies, and to evaluate comparisons among different aging studies.

Aging↗