Relationship of reported clinical features of pre-eclampsia and postpartum haemorrhage to demographic and other variables.

BACKGROUND: Maternal death and disability remain significant problems in developing countries and are predominantly caused by preeclampsia and postpartum haemorrhage. The diagnostic criteria for preeclampsia and postpartum haemorrhage require medical technologies not readily available in underdeveloped areas. OBJECTIVE: To determine the correlates of pre-eclampsia and postpartum haemorrhage using symptoms in a rural setting. METHODS: This was a cross-sectional study in which 577 women from the Kwahu South District of the Eastern Region of Ghana completed questionnaires that sought for signs and symptoms of pre-eclampsia and postpartum haemorrhage in their current or prior pregnancies. The study was conducted over a period of two months, symptoms of pre-eclampsia assessed included headache, visual disturbance, urination, breathing, leg swelling and seizures. For postpartum haemorrhage, the following features were assessed: placenta delivery, length of labour, difficult delivery of placenta, lacerations associated with delivery, size of newborn, headache, visual disturbance and amount of vaginal bleeding. RESULTS: There was a significant association between education and the number of signs and symptoms of preeclampsia, (Χ² =9.059, =0.018; OR no education vs >7 years=6.8). Mothers with no education were about seven times more likely to have all six signs and symptoms of preeclampsia than those with seven or more years of education. There was no significant association between education and postpartum haemorrhage, (Χ² = 1.835, = 0.400). However, the OR of 1.59, indicated an inverse association between the two variables. CONCLUSION: The high number of symptoms associated with preeclampsia among women with no formal education strongly supports the need for educational outreach and basic prenatal care in rural Ghana.

The GLUR2 subunit of AMPA receptors: synaptic role.

Ampa receptors mediate the majority of excitatory synaptic transmission in the brain. Thus, the mechanisms that control the developmental and activity-dependent changes in the functional synaptic expression of AMPA receptors are of fundamental importance. Here we focus on the role of GluR2 subunit in synaptic function and plasticity.

Voltage-operated calcium channel heterogeneity in pancreatic beta cells: physiopathological implications.

Voltage-operated calcium channels play crucial roles in stimulus-secretion coupling in pancreatic beta cells. A growing body of evidence indicates that these channels in beta cells are heterogeneous. In particular, not all the high-threshold calcium channels expressed belong to the best known L-type. In rat insulinoma cells, for example, L, N, and P/Q-type channels are present, while in human beta cells L-type and P/Q-type dominate. Where present, N-type and P/Q-type channels participate, alongside with the dominant L-type, in the control of sugar- or depolarization-induced hormone release. Distinct biophysical properties and selective modulation of the channel subtypes are likely to play important physiological roles. T-type channels are involved in beta cell apoptosis, while calcium channel autoantibodies recognizing high-threshold channels in beta cells, have been described both in neurological and diabetic patients. Subtype-selective calcium channel drugs have the potential for being beneficial in beta cell pathological states.

Subunit-specific temporal and spatial patterns of AMPA receptor exocytosis in hippocampal neurons.

Using a thrombin cleavage assay in cultured hippocampal neurons, we studied the kinetics, regulation and site of AMPA receptor surface delivery. Surface insertion of the GluR1 subunit occurs slowly in basal conditions and is stimulated by NMDA receptor activation and insulin, whereas GluR2 exocytosis is constitutively rapid. Although both subunits ultimately concentrate in synapses, GluR1 and GluR2 show different spatial patterns of surface accumulation, consistent with GluR1 being inserted initially at extrasynaptic sites and GluR2 being inserted more directly at synapses. The spatiotemporal pattern of surface accumulation is determined by the cytoplasmic tails of GluR subunits, and in heteromeric receptors, GluR1 acts dominantly over GluR2. We propose that GluR1 controls the exocytosis and GluR2/3, the recycling and endocytosis of AMPA receptors.

Regulation of dendritic spine morphology and synaptic function by Shank and Homer.

The Shank family of proteins interacts with NMDA receptor and metabotropic glutamate receptor complexes in the postsynaptic density (PSD). Targeted to the PSD by a PDZ-dependent mechanism, Shank promotes the maturation of dendritic spines and the enlargement of spine heads via its ability to recruit Homer to postsynaptic sites. Shank and Homer cooperate to induce accumulation of IP3 receptors in dendritic spines and formation of putative multisynapse spines. In addition, postsynaptic expression of Shank enhances presynaptic function, as measured by increased minifrequency and FM4-64 uptake. These data suggest a central role for the Shank scaffold in the structural and functional organization of the dendritic spine and synaptic junction.

Modulation of N-type calcium channels translocation in RINm5F insulinoma cells.

An intracellular pool of N-type voltage-operated calcium channels has recently been described in both IMR32 human neuroblastoma and PC12 rat pheochromocytoma cells. These channels were found to be accumulated in subcellular fractions where the chromogranin B-containing secretory granules were also enriched. Upon exocytosis N-type calcium channels were reversibly inserted in the plasma membrane. We have now extended this study to RINm5F rat insulinoma cells, and characterized the parallelism between the 'regulated' secretion of serotonin and the recruitment of surface calcium channels. Exocytosis was stimulated by different means, such as depolarization with high KCl, high Ba(2+)alone or protein kinase C activation; on the other hand exocytosis was inhibited with the non-selective calcium channel antagonist Cd(2+)or with noradrenaline. Stimulated release was always accompanied, with parallel kinetics, by calcium channel recruitment, while inhibition of secretion blocked calcium channel recruitment too. During repetitive depolarizations we revealed a potentiation of [Ca(2+)]()i transients in single Fura-2 loaded RINm5F cells, that was accompanied by an increase in surface VOCCs, suggesting a physiological role for the newly recruited channels. 2000 Academic Press@p$hr

Microtubule binding by CRIPT and its potential role in the synaptic clustering of PSD-95.

CRIPT is a postsynaptic protein that binds selectively to the third PDZ domain (PDZ3) of PSD-95. Here we show that CRIPT also binds directly to microtubules, thereby linking PSD-95 to the microtubule cytoskeleton. Disrupting the CRIPT-PSD-95 interaction in cultured hippocampal neurons with a PDZ3-specific peptide prevented the association of PSD-95 with microtubules and inhibited the synaptic clustering of PSD-95, chapsyn-110/PSD-93 and GKAP (a PSD-95-binding protein). However, the number of synapses and the synaptic clustering of NMDA receptors were unaffected, suggesting that PSD-95-family proteins are not essential for the maintenance of synapses and the synaptic localization of NMDA receptors.

Synaptogenesis: The MAP location of GABA receptors.

Microtubule-associated proteins (MAPs) have been identified as binding partners for ionotropic GABAA and GABAC receptors. These interactions suggest a potential role for MAPs in the cytoskeletal anchoring of receptor-ion channels at specific subcellular sites, such as synapses.

Metabolism and trafficking of N-type voltage-operated calcium channels in neurosecretory cells.

The N-type voltage-operated calcium channel has been characterized over the years as a high-threshold channel, with variable inactivation kinetics, and a unique ability to bind with high affinity and specificity omega-conotoxin GVIA and related toxins. This channel is particularly expressed in some neurons and endocrine cells, where it participates in several calcium-dependent processes, including secretion. Omega-conotoxin GVIA was instrumental not only for the biophysical and pharmacological characterization of N-type channels but also for the development of in vitro assays for studying N-type VOCC subcellular localization, biosynthesis, turnover, as well as short-and long-term regulation of its expression. We here summarize our studies on N-type VOCC expression in neurosecretory cells, with a major emphasis on recent data demonstrating the presence of N-type channels in intracellular secretory organelles and their recruitment to the cell surface during regulated exocytosis.

N-type Ca2+ channels are present in secretory granules and are transiently translocated to the plasma membrane during regulated exocytosis.

An intracellular pool of N-type voltage-operated calcium channels has recently been described in different neuronal cell lines. We have now further characterized the intracellular pool of N-type calcium channels in both IMR32 human neuroblastoma and PC12 rat pheochromocytoma cells. Intracellular N-type calcium channels were found to be accumulated in subcellular fractions where the chromogranin B-containing secretory granules were also enriched. 125I-omega-Conotoxin GVIA binding assays on fixed and permeabilized cells revealed that intracellular N-type calcium channels translocate to the plasma membrane in cells exposed to secretagogues (KCl, ionomycin, and phorbol esters). The kinetics, Ca2+ and protein kinase C dependence, and brefeldin A insensitivity of N-type calcium channels translocation were similar to the regulated release of chromogranin B, while no correlation was found with the constitutive secretion of a heparan sulfate proteoglycan. A PC12 subclone deficient in the regulated but not in the constitutive pathway of secretion had a small intracellular pool of N-type calcium channels, and no secretagogue-induced translocation occurred in these cells. Calcium channel translocation was accompanied by a stronger response of Fura-2-loaded cells to depolarizing stimuli, suggesting that the newly inserted channels are functional.

Anti-beta 2 subunit antisense oligonucleotides modulate the surface expression of the alpha 1 subunit of N-type omega-CTX sensitive Ca2+ channels in IMR 32 human neuroblastoma cells.

High voltage activated Ca2+ channels are heteropolymeric complexes in which the alpha 1 subunit forms the channel, while the alpha 2-delta and beta subunits are important for the assembly and regulation of the biophysical properties of the channel. We have tested the role of the beta 2 subunit on the expression and electrophysiological properties of the omega-conotoxin GVIA-sensitive Ca2+ channel expressed in the IMR 32 human neuroblastoma cell line. Anti-beta 2 subunit antisense oligonucleotides supplied to the cells in culture induced a time-dependent increase in the number of [125I]-omega-conotoxin binding sites on the cell surface, which was not paralleled by an increase in current amplitude. We suggest that a reduction in the expression of beta 2 stimulates the transport to the plasma membrane of non-functioning Ca2+ channels and, in particular, of the alpha 1 omega-conotoxin binding subunit.

omega-Conotoxin and Cd2+ stimulate the recruitment to the plasmamembrane of an intracellular pool of voltage-operated Ca2+ channels.

125I-omega-conotoxin binding to neuroblastoma cells at 37 degrees C continuously increased, reaching a plateau after 6-8 hr; this was up to 6 times higher than that observed at lower temperatures. The same effect was induced by short pulses with omega-conotoxin followed by a chase period at 37 degrees C in control medium. Cd2+ also induced up-regulation of surface 125I-omega-conotoxin-binding sites. Fura-2 and patch-clamp experiments showed that the recruited binding sites corresponded to functional voltage-operated Ca2+ channels. Permeabilization experiments revealed a large intracellular pool of 125I-omega-conotoxin-binding sites, whose recruitment to the plasmamembrane was prevented by brefeldin A and nocodazole. These data suggest that specific stimuli might induce voltage-operated Ca2+ channel translocation to plasmamembrane and, in this way, modulate presynaptic events.

Metabolism of omega-conotoxin-sensitive voltage-operated calcium channels in human neuroblastoma cells: modulation by cell differentiation and anti-channel antibodies.

The turnover of voltage-operated calcium channels was studied in two different human neuroblastoma cell lines (IMR32 and SH-SY5Y) using omega-conotoxin. The 125I-omega-conotoxin bound to surface channels was internalized and degraded by the cells in a time- and temperature-dependent manner. The radioactive degradation products released in the medium were all trichloroacetic acid soluble and no longer recognized by anti-omega-conotoxin antibodies. Altering the pH of intracellular organelles with chloroquine and inhibiting lysosomal proteases with leupeptin reduced 125I-omega-conotoxin degradation but had no effect on its internalization. Postlabeling measurements showed that the rates of 125I-omega-conotoxin internalization and degradation were equal to the rate of channel removal from the cell surface after protein synthesis inhibition. The rate of removal of omega-conotoxin binding sites was parallel to the rate of loss of functional channels, as measured by means of the fura-2 technique. Drug-induced differentiation of human neuroblastoma cells slowed down channel internalization and degradation rates, leading to the known increased expression of plasma membrane calcium channels in differentiated cells. On the other hand, both human (from Lambert-Eaton myasthenic patients) and murine (from immunized mice) anti-channel antibodies increased the rates of channel internalization and degradation, leading to channel downregulation. The activity of presynaptic calcium channels is already known to be acutely modulated by a number of different agents (e.g., hormones and neurotransmitters); our studies suggest that a different form of channel modulation (changes in the number of channels due to interference with channel turnover) may be active over a longer time scale in neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Physiopathology of neuronal voltage-operated calcium channels.

Voltage-operated calcium channels are multimeric transmembrane proteins crucially involved in control of calcium homeostasis. Multiple types of voltage-operated calcium channels have been described in both the nervous system and peripheral tissues. Different channels can be classified according to either their biophysical properties or their pharmacology, biochemical and molecular structure, and localization and functional role. Concentrating on neuronal cells, this paper reviews the different properties of low- and high-voltage activated channels, as well as various attempts to subdivide high-voltage activated channels into different subtypes (L, N, omega, P, etc.). The availability of selective drugs (such as dihydropyridines) and natural toxins (such as omega-Conotoxin, omega-agatoxin, and funnel-web spider toxins), which bind to specific channel subtypes, has greatly helped in channel classification. The emerging view is that there are many members of the family of voltage-operated calcium channels, each with its own molecular structure, a different pharmacology, a different localization, and possibly a different physiological role. Different calcium subtypes are selectively affected in human and animal diseases. The use of omega-Conotoxin has led to identification of the channel subtype (omega) specifically affected in Lambert-Eaton myasthenic syndrome (a human disease of neurotransmission), and has permitted development of new diagnostic approaches to the disease.

Presynaptic localization of omega-conotoxin-sensitive calcium channels at the frog neuromuscular junction.

By the use of anti-omega-CTx antibodies in indirect immunofluorescence we demonstrated the presence of omega-CTx binding sites in the presynaptic compartment of frog nerve-muscle preparations. The images we obtained indicate that omega-CTx-sensitive channels are clustered at discrete sites corresponding in distribution to active zones.

Selective vulnerability of hippocampal CA3 neurones after microinfusion of paraquat into the rat substantia nigra or into the ventral tegmental area.

The neuropathological effects of various doses of paraquat, a widely used herbicide, given directly into different areas of the rat brain, were studied. Paraquat, microinfused into the pars compacta of the substantia nigra (3.2, 16, 32 and 160 nmol), i.e. concentrations of 3.2 to 160 mmol l-1 applied at 1 microliter min-1 for 1 min, produced dose-dependent neuropathological lesions culminating in neuronal necrosis. A particular feature of paraquat neurotoxicity after its microinfusion into the substantia nigra (3.2 mmol per 1 at 1 microliter per min for 1 min) or into the ventral tegmental area (1.6 mmol per 1 at 1 microliter per min for 1 min), but not into other areas of the brain, was a selective vulnerability of hippocampal CA3 neurones consisting initially of a significant decrease of dendritic spines and later in neuronal degeneration and cell loss. No damage occurred after microinfusion of paraquat into other areas of the brain near or distant from the infusion sites. In addition, similar neuropathological alterations occurred in other non-dopaminergic areas, such as the locus coeruleus and some raphe nuclei after direct microinfusion of paraquat into these sites. In conclusion, the above neuropathological findings show that paraquat possesses marked neurotoxicity which, despite its chemical similarity to MPTP, is not selective for dopaminergic neurones.

Reabsorption of a saline- or plasma-induced hydrothorax.

In supine rabbits injection of 2 ml of saline into the lower right diaphragmatic region increased pleural liquid pressure at the injection point and, to a minor extent, on the costal and mediastinal side, indicating a redistribution of liquid among the pleural compartments. Over a period of 120 min end-expiratory liquid pressure on the diaphragmatic and costal surfaces approached the control value as a result of local reabsorption. No difference in the time course of liquid pressure was found on injection of either saline or homologous plasma. This was confirmed by measuring the volume of saline or plasma remaining in the cavity 90 min after injection; the net absorption flow amounted to 0.22 ml . kg-1 . h-1. These results suggest that local absorption mechanisms are relatively independent of the Starling pressure gradients acting across the pulmonary-perfused (-10.2 and 6.6 cmH2O with saline and plasma, respectively, the negative sign indicating a reabsorption gradient) and systemically perfused mesothelium (3.3 and 20.1 cmH2O with saline and plasma, respectively).