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Biomedical subjects

C Janse

Publications and source records attributed to C Janse.

29 records · Page 2Linked to original sources
PubMed1987

The complete development in vitro of the vertebrate phase of the mammalian malarial parasite Plasmodium berghei.

All three 'vertebrate' stages of the rodent malarial parasite Plasmodium berghei berghei were grown in vitro in the absence of the vertebrate host. The parasite was introduced into culture from infected mosquitoes and 2 in vitro culture methods were used sequentially to complete the 'vertebrate' phases of development in hepatoma and erythrocyte host cells. The resultant blood infection produced mature schizonts and male and female gametocytes. The protocol, which is now being extended to the human pathogen P. falciparum, may assist future studies on this important group of parasites.

Animals↗
PubMed1986

Age-related decrease in electrical coupling of two identified neurons in the mollusc Lymnaea stagnalis.

Electrophysiological characteristics of two identified giant electrotonically coupled neurosecretory cells in the central nervous system of the mollusc Lymnaea stagnalis were studied in mature animals of different age. The coupling coefficient of the neurons decreased considerably with age. The possibility that the decrease is due to an increase in the junctional resistance between the cells is discussed.

Aging↗
PubMed1979

The re-formation of connections in the nervous sytem of Lymnaea stagnalis after nerve injury.

Changes in the tentacle reflex pathway of the pond snail Lymnaea stagnalis induced by peripheral nerve injury were studied with behavioural and electrophysiological techniques. After nerve injury regeneration of sensory axons is obtained in 6-12 days, suggesting an axonal outgrowth at a rate of 1 mm per day. Recovery of the tentacle reflex takes much more time indicating that synaptic efficacy is affected considerably by the period of sensory deprivation following nerve injury.

Action Potentials↗
PubMedDate not supplied

Molluscan ovulation hormone containing neurons and age-related reproductive decline.

Behavioural and neurophysiological experiments were conducted to examine the state of the neurosecretory caudodorsal cells (CDCs) during female reproductive decline in the freshwater snail Lymnaea stagnalis. Old animals that had ceased egg laying do not respond to an oviposition-inducing stimulus. Female reproductive organs in such animals are still intact, though less sensitive to CDC-hormone. The CDC contents of old nonlaying snails are still effective in producing ovulation in young animals. The electrophysiological properties of the CDCs of old nonlaying snails only differ from those of egg-laying snails in one respect; the duration of the afterdischarge is longer. This difference is not directly related to age but to egg-laying activity of the snails since the afterdischarge in old layers did not differ significantly from that in young layers. It is concluded that the CDCs of old nonlaying animals are in principle still intact. Female reproductive decline and subsequent cessation of female reproduction in Lymnaea may result from impairment of input to the CDCs.

Age Factors↗
PubMedDate not supplied

cAMP and excitability in neuroendocrine cells during reproductive senescence.

Excitability changes during reproductive senescence were investigated in the neurosecretory caudodorsal cells (CDCs) that control egg laying in the mollusc Lymnaea stagnalis. CDCs in the isolated central nervous system (CNS) were exposed to different discharge inducing treatments. Senescent CDCs (of animals 8 weeks after laying their last egg mass) and inhibited (I-) state CDCs (of egg-laying (EL) animals) were used. We showed that senescent and I-state CDCs closely resemble each other electrophysiologically. Electrical stimulation did not induce an afterdischarge in either type of CDC but exposure to release products of CDCs from EL animals or to saline with high potassium concentration did induce discharge activity. Also, 8-chlorophenylthio (8-CPT)-cAMP (10(-5) M) induced discharge activity. Exposure to the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) (10(-3) M) or to the adenylate cyclase activator Forskolin (10(-4) M), restored afterdischarge induction by electrical stimulation. Application of IBMX (10(-3) M) and Forskolin (10(-4) M) together induced discharges in the absence of electrical stimulation. Our results suggest that in senescent CDCs changes in the intracellular cAMP pathway may underlie afterdischarge failure.

1-Methyl-3-isobutylxanthine↗
PubMedDate not supplied

Recovery of neuroendocrine cells after injury in the aging brain of a mollusc.

Recovery after crush of neuroendocrine caudodorsal cells (CDCs) in the aging brain of the mollusc Lymnaea stagnalis, was determined as a measure of neuronal plasticity. Neuronal plasticity was determined in differently aged animals containing intact (young: 170 days) or morphologically and physiologically degraded (middle-aged: 305 days and old: 443 days) CDCs. Branching patterns and electrical and chemical connectivity and afterdischarge activity of CDCs were studied. Immediately after crush, electrical coupling and chemical transmission were absent. In all age groups partial recovery occurred within about 20 days. CDCs in old animals exhibited restricted recovery of electrical coupling and enhanced recovery of chemical transmission. In young and middle-aged animals normal afterdischarges occurred from day 8 on. In old animals abnormal afterdischarges occurred starting at day 0, becoming normal by day 12 after crush. Recovery of CDC branching was partial in all age groups. It is concluded that in the aging brain recovery of CDCs after injury does occur but is differentially restricted. Our results suggest that senescent degraded neurons still possess a considerable degree of plasticity.

Aging↗
PubMedDate not supplied

Multiple synaptic connections of a single neuron change differentially with age.

The efficacy of chemical synaptic connections of a single identified interneuron with different types of follower neurons was studied throughout the adult life of the pond snail Lymnaea stagnalis. Simultaneous intracellular recordings were made from the interneuron RPeD1 and its follower neurons in isolated CNS preparations from animals of different age groups (3-18 months of age). The presence of postsynaptic responses to RPeD1 action potentials was tested. With increasing age, the number of A-group neurons that was found with a response to evoked RPeD1 action potentials decreased, yet the number of HIJK-group neurons responding to RPeD1 input increased. The number of G-group neurons and the number of individual neurons VD2/3 and VD4 with RPeD1 input did not differ significantly between age groups. However, there was variability in the presence of responses in these individual neurons. Thus, synaptic connections of the single interneuron RPeD1 change differentially throughout the adult life of L. stagnalis. Within the A-group we found indications that changes in RPeD1 input apply to the entire A-group. In the A-group neurons changes in several electrical properties could not account for the observed age-related changes in the number of neurons responding to RPeD1 action potentials.

Action Potentials↗
PubMedDate not supplied

Excitability and branching of neuroendocrine cells during reproductive senescence.

In the mollusc Lymnaea stagnalis, neuroendocrine caudodorsal cells (CDCs) were studied physiologically and morphologically from egg layers (EL) (aged 154-400), and animals 4 weeks (CEL-4) (342-455 days), and 8 weeks (CEL-8) (477-660 days) after production of their last egg mass. After recording chemical transmission, electrical coupling and stimulation induced afterdischarges (ADs), CDCs then were filled with Lucifer Yellow. Based on the axonal branching revealed by Lucifer Yellow, CDCs were classified as extensively, moderately, or minimally branched. In EL-CDCs, induction of AD activity, which normally (9) precedes egg-laying, only was initiated in the resting state. CEL-4 CDCs exhibited ADs whereas CEL-8 CDCs did not. CEL-8 CDCs exhibited significantly reduced chemical and electrical transmission, and CEL-4 CDCs did not differ from resting state EL-CDCs. CDC branching was significantly reduced with both increasing age and declining egg-laying. Minimally branched CDCs most frequently failed to exhibit an AD and exhibited reduced electrical coupling. We conclude that both physiology and morphology of CDCs are related to age and reproductive state.

Aging↗