Ionotropic and metabotropic GABA and glutamate receptors in primate basal ganglia

The functions of glutamate and GABA in the CNS are mediated by ionotropic and metabotropic, G protein-coupled, receptors. Both receptor families are widely expressed in basal ganglia structures in primates and nonprimates. The recent development of highly specific antibodies and/or cDNA probes allowed the better characterization of the cellular localization of various GABA and glutamate receptor subtypes in the primate basal ganglia. Furthermore, the use of high resolution immunogold techniques at the electron microscopic level led to major breakthroughs in our understanding of the subsynaptic and subcellular localization of these receptors in primates. In this review, we will provide a detailed account of the current knowledge of the localization of these receptors in the basal ganglia of humans and monkeys.

Differential subcellular localization of mGluR1a and mGluR5 in the rat and monkey Substantia nigra

Neurons in the rat substantia nigra (SN) are enriched in group I metabotropic glutamate receptor (mGluR) subtypes and respond to group I mGluR activation. To better understand the mechanisms by which mGluR1 and mGluR5 mediate these effects, the goal of this study was to elucidate the subsynaptic localization of these two receptor subtypes in the rat and monkey substantia nigra. At the light microscope level, neurons of the SN pars reticulata (SNr) displayed moderate to strong immunoreactivity for both mGluR1a and mGluR5 in rats and monkeys. However, mGluR1a labeling was much stronger in monkey than in rat SN pars compacta (SNc) neurons, whereas a moderate level of mGluR5 immunoreactivity was found in both species. At the electron microscope level, the immunoreactivity for both group I mGluR subtypes was primarily expressed postsynaptically, although light mGluR1a labeling was occasionally seen in axon terminals in the rat SNr. Immunogold studies revealed a striking difference in the subcellular distribution of mGluR1a and mGluR5 immunoreactivity in SNr and SNc neurons. Although the bulk of mGluR1a was attached to the plasma membrane, >80% of mGluR5 immunoreactivity was intracellular. Plasma membrane-bound immunoreactivity for group I mGluRs in both SNc and SNr neurons was mostly extrasynaptic or in the main body of symmetric, putative GABAergic synapses. On the other hand, asymmetric synapses either were nonimmunoreactive or displayed perisynaptic labeling. These data raise important questions about the trafficking, internalization, and potential functions of group I mGluRs at extrasynaptic sites or symmetric synapses in the substantia nigra.

Presynaptic NMDA receptor subunit immunoreactivity in GABAergic terminals in rat brain

N-methyl-D-aspartate (NMDA) receptors are commonly found post-synaptically; they mediate fast excitatory neurotransmission in the central nervous system. In this study, we provide immunocytochemical data supporting the existence of presynaptic NMDA receptors in GABAergic terminals using polyclonal antisera raised against the C-terminus of the NMDAR1 subunit. At the light microscope level, rich plexuses of NMDAR1-positive varicose fibers were found in various nuclei in the basal forebrain (bed nucleus of stria terminalis, septum, parastrial nucleus, vascular organ of the lamina terminalis), thalamus (paraventricular nucleus, midline nuclei), and hypothalamus (parvocellular paraventricular nucleus, arcuate nucleus, preoptic nucleus, suprachiasmatic nucleus). In the brainstem, labeled fibers were much less abundant and were confined to the ventral tegmental area, periaqueductal gray, parabrachial nucleus, and locus coeruleus. At the electron microscope level, NMDAR1-immunoreactive terminals examined in the bed nucleus of stria terminalis, parvocellular paraventricular hypothalamic nucleus, and arcuate nucleus formed symmetric synapses, contained darkly stained large dense-core vesicles, and displayed gamma-aminobutyric acid (GABA) immunoreactivity. Terminals with similar ultrastructural features were found in the paraventricular thalamic nucleus. These findings demonstrate the existence of NMDAR1 subunit immunoreactivity in subsets of GABAergic terminals, which raises questions about the potential roles and mechanisms of activation of presynaptic NMDA heteroreceptors in the rat central nervous system. The pattern of distribution and ultrastructural features of these boutons suggest that they may arise from local GABAergic projections interconnecting a group of brain structures mediating stress responses and/or other endocrine, autonomic, and limbic functions.

GABA(B) and group I metabotropic glutamate receptors in the striatopallidal complex in primates

Glutamate and GABA neurotransmission is mediated through various types of ionotropic and metabotropic receptors. In this review, we summarise some of our recent findings on the subcellular and subsynaptic localisation of GABA(B) and group I metabotropic glutamate receptors in the striatopallidal complex of monkeys. Polyclonal antibodies that specifically recognise GABA(B)R1, mGluR1a and mGluR5 receptor subtypes were used for immunoperoxidase and pre-embedding immunogold techniques at the light and electron microscope levels. Both subtypes of group I mGluRs were expressed postsynaptically in striatal projection neurons and interneurons where they aggregate perisynaptically at asymmetric glutamatergic synapses and symmetric dopaminergic synaptic junctions. Moreover, they are also strongly expressed in the main body of symmetric synapses established by putative intrastriatal GABAergic terminals. In the globus pallidus, both receptor subtypes are found postsynaptically in the core of striatopallidal GABAergic synapses and perisynaptically at subthalamopallidal glutamatergic synapses. Finally, extrasynaptic labelling was commonly seen in the globus pallidus and the striatum. Moderate to intense GABA(B)R1 immunoreactivity was observed in the striatopallidal complex. At the electron microscope level, GABA(B)R1 immunostaining was commonly found in neuronal cell bodies and dendrites. Many striatal dendritic spines also displayed GABA(B)R1 immunoreactivity. Moreover, GABA(B)R1-immunoreactive axons and axon terminals were frequently encountered. In the striatum, GABA(B)R1-immunoreactive boutons resembled terminals of cortical origin, while in the globus pallidus, subthalamic-like terminals were labelled. Pre-embedding immunogold data showed that postsynaptic GABA(B)R1 receptors are concentrated at extrasynaptic sites on dendrites, spines and somata in the striatopallidal complex, perisynaptically at asymmetric synapses and in the main body of symmetric striatopallidal synapses in the GPe and GPi. Consistent with the immunoperoxidase data, immunoparticles were found in the presynaptic grid of asymmetric synapses established by cortical- and subthalamic-like glutamatergic terminals. These findings indicate that both GABA and glutamate metabotropic receptors are located to subserve various modulatory functions of the synaptic transmission in the primate striatopallidal complex. Furthermore, their pattern of localisation raises issues about their roles and mechanisms of activation in normal and pathological conditions. Because of their 'modulatory' functions, these receptors are ideal targets for chronic drug therapies in neurodegenerative diseases such as Parkinson's disease.

Apparent dopamine D1 and D2 receptors in the weaver mutant mouse: receptor binding and coupling to adenylyl cyclase

Weaver mutant mice have a selective degeneration of the nigrostriatal dopamine pathway arising between 7-21 days after birth. The goal of this study was to investigate the effects of this mutation on different parameters of the nigrostriatal and mesolimbic dopamine system: apparent D1 and D2 receptor binding sites as well as their signal transduction pathway. Using quantitative autoradiography of ligands for dopamine D1, D2 receptors and the dopamine uptake site, we found a significant loss in apparent D1 receptor binding sites throughout the neostriatum, significant increase of apparent D2 receptor binding in the dorsal aspect of the neostriatum, and almost complete loss of DA uptake sites in these regions of the weaver mouse. In contrast to the neostriatum, the density of dopamine receptors and uptake sites in the nucleus accumbens of the weaver mouse did not differ from controls. Despite alterations in the binding of apparent D1 and D2 receptors, there was no significant difference in either basal, DA stimulated or GTPgammaS stimulated cAMP production. These findings suggest the down-regulation of apparent D1 receptor binding sites reported in this model, probably does not reflect an important physiological mechanism through which these animals compensate for loss of dopamine innervation.

Cocaine- and amphetamine-regulated transcript (CART) peptide immunoreactivity in myenteric plexus neurons of the rat ileum and co-localization with choline acetyltransferase

Cocaine and amphetamine regulated transcript (CART) encodes a novel brain-enriched protein whose features are reminiscent of a neurotransmitter propeptide. We have now localized CART peptide(s) in the gastrointestinal tract by immunohistochemical methods. Polyclonal antisera raised to CART peptide 106-129 stained neuronal cell bodies and fibers in rat ileum myenteric plexus-longitudinal muscle tissue preparations. Electron microscopic analysis of thin sections showed immunopositive axon terminals in close apposition to CART-labelled and unlabelled neuronal cell bodies as well as to the longitudinal muscle. CART peptide-immunoreactive terminals contained numerous ovoid electron-lucent vesicles and a few dark-stained dense-core vesicles. Light microscopic double labelling studies revealed CART peptide immunoreactivity in a subpopulation of choline acetyltransferase (ChAT)-immunoreactive neurons. This combined light microscopic and ultrastructural examination of CART peptides in the gastrointestinal tract suggests a role of CART peptides as transmitters or neuromodulators in the peripheral nervous system.

[Quality of data acceptable for perinatal epidemiology surveillance: assessment of the health certificate at birth and the national obstetrics medical file. Study in three Seine-Maritime maternal wards]

Data from several sources could be used for perinatal epidemiology surveillance aimed at an assessment of regional programs such as those proposed by the Superior Committee for Public Health. A retrospective study of 561 births was conducted in three maternity wards in the French Seine Maritime department in order to evaluate the reliability of two data sources: the national obstetrics medical file and the health certificate at birth. The delivery room records were used as the gold standard. The sensitivity of the obstetrics file was better than that of the health certificate. With the obstetrics file, it was possible to identify almost all the vaginal route interventions, almost all the premature births and all the cesareans. With the health certificate, 39-58% of the vaginal route interventions, 61% of the premature births and 61-72% of the cesareans performed in the three wards studied were identified. The quality of data in the obstetrics file appears to be better than that in the health certificate but only concerns 40% of births in the geographical area studied. Inversely, the health certificate is theoretically delivered for all births (actually delivered for 93%). Integrating these two information systems could be an optimum solution.

Primary structure and expression of a naturally truncated human P2X ATP receptor subunit from brain and immune system

A novel member of the ionotropic ATP receptor gene family has been identified in human brain. This 422 amino acid long P2X receptor subunit has 62% sequence identity with rat P2X5. Several characteristic motifs of ATP-gated channels are present in its primary structure, but this P2X5-related subunit displays a single transmembrane domain. Heterologous expression of chimeric subunits containing the C-terminal domain of rat P2X5 leads to the formation of desensitizing functional ATP-gated channels in Xenopus oocytes. The developmentally regulated mRNA, found in two splicing variant forms, is expressed at high levels in brain and immune system.

One-stage midline unifocalization and complete repair in infancy versus multiple-stage unifocalization followed by repair for complex heart disease with major aortopulmonary collaterals

BACKGROUND

Patients with pulmonary atresia, ventricular septal defect, and major aortopulmonary collateral arteries have traditionally required multiple unifocalization staging operations before undergoing complete repair. Recently, the feasibility of a single-stage unifocalization and repair was demonstrated by Hanley. In this report, we describe our experience with each approach.

METHODS AND RESULTS

Since 1989, 11 of 12 patients with pulmonary atresia, ventricular septal defect, and major aortopulmonary collateral arteries have undergone complete surgical correction. The first seven patients were subjected to staged bilateral unifocalizations, with repair being achieved in six (group I). The last five patients have undergone a single-stage midline unifocalization and repair via a sternotomy (group II). Four of these were infants (2 weeks to 9 months) and one was 13 years old. All patients in group I had tetralogy of Fallot, whereas in group II three patients had tetralogy of Fallot, one patient had double-outlet right ventricle, and one patient had complete atrioventricular canal and transposition. In group I, the median age at the first operation was 43 weeks. Complete repair was performed at a median age of 3.5 years, with a mean number of 3.3 operations required. In group II, only one operation was required to achieve complete repair at a median age of 28 weeks. The postoperative right ventricular/left ventricular pressure ratio was 0.49 in group I and 0.45 in group II. One intraoperative death and one late death occurred in group I and no early or late deaths in group II. Currently, four patients in group I and all five patients in group II are alive and well.

CONCLUSIONS

Early intervention with both surgical approaches can lead to complete biventricular repair in most patients. Because the single-stage midline unifocalization and repair can achieve a completely repaired heart in infancy with one operation, it is currently our approach of choice.

Identification in the rat neurotensin receptor of amino-acid residues critical for the binding of neurotensin

In order to identify charged amino-acid residues of the cloned rat brain neurotensin (NT) receptor (NTR) that are critical for NT binding, we performed site-directed mutagenesis on the cDNA encoding this protein, followed by transient expression into mammalian COS-7 cells and in Xenopus laevis oocytes. Point substitutions of charged residues in the N-terminal part and in the 2nd and 3rd extracellular loop of the receptor either did not affect (125)I-Tyr3-NT binding or resulted in a decrease in binding affinity by a factor of 2-3. Mutations of amino acids Asp113 in the second transmembrane domain (TM) and of Arg149 or Asp150 in TM III yielded receptors that bound NT as efficiently as the native receptor. By contrast, replacement of the Asp139 residue in the 1st extracellular loop, or of Arg143 or Arg327-Arg328 residues at the top of TM III and in TM VI, respectively, completely abolished ligand binding. Confocal and EM immunocytochemical studies of the expression of these affected receptors, tagged with the C-terminal sequence of the vesicular stomatitis virus glycoprotein (VSV-G), indicated that this loss of binding was not due to altered receptor expression or to their improper insertion into the plasma membrane. When these mutated forms of neurotensin receptor were expressed into Xenopus oocytes, Asp139-Gly- and Arg143-Gly-modified receptors remained functional in spite of a lowered response to NT whereas the Arg327-Arg328 mutant form was totally insensitive to NT at concentrations up to 10 microM. In the case of the Arg327-Arg328 mutation, the observed insensibility to NT could be the result of a drastic conformational alteration of this mutant protein. By contrast, it would appear that Asp139 and Arg143 residues located in the first extracellular loop of the receptor may be directly involved in the interaction of the receptor with neurotensin.

Alterations in the turnover rate of dopamine D1 but not D2 receptors in the adult rat neostriatum after a neonatal dopamine denervation

Adult rats that were treated with intracerebral ventricular injection of 6-hydroxydopamine (6-OHDA) as neonates exhibit a profound loss of nigrostriatal dopamine innervation in addition to a variety of other neurochemical and anatomical changes, including alterations in the number of neostriatal D1 and D2 receptor binding sites. In the present study, the turnover of neostriatal dopamine D1 and D2 receptors was measured in rats previously treated with 6-OHDA or ascorbic acid vehicle as neonates at various time intervals after peripheral N-ethoxycarbonyl-2-ethoxy-1, 2-dihydroquinoline (EEDQ, 10 mg/kg) administration. Dopamine receptors were labelled with [3H]SCH23390 (D1) and [3H]raclopride (D2), while the degree of dopamine denervation was assessed by the measurement of neostriatal dopamine, homovanillic acid and dihydroxyphenylacetic acid content. Two days after acute EEDQ treatment, the maximal binding capacity (Bmax) of [3H]SCH23390 and [3H]raclopride binding was significantly decreased to 58 and 32% of control values, respectively, without any significant alteration in their equilibrium dissociation constants (Kd). A time-dependent increase in the density of [3H]SCH23390 and [3H]raclopride binding was observed in both treatment groups following a single dose of EEDQ. The rate of recovery of D1 receptors was significantly slower in the 6-OHDA-lesioned animals as compared to controls with a half-life of 103 compared to 53 h, respectively. No differences were observed in the rate of recovery of D2 receptors in these two treatment groups. These data are consistent with the findings of decreased expression of D1 receptors in neonatal 6-OHDA-lesioned rats owing to decreased receptor synthesis, and further suggest that in this model the up-regulation of D2 receptors is a result of a post-transcriptional mechanism, such as an increased rate of post-synthetic maturation.

AMPA and NMDA glutamate receptor subunits in midbrain dopaminergic neurons in the squirrel monkey: an immunohistochemical and in situ hybridization study

The objective of the present study was to analyze the cellular and subcellular localization of ionotropic glutamate receptor subunits in midbrain dopaminergic neurons in the squirrel monkey. This was achieved by means of immunohistochemistry at light and electron microscopic levels and in situ hybridization histochemistry. Colocalization studies show that nearly all dopaminergic neurons in both the ventral and dorsal tiers of the substantia nigra compacta (SNc-v, SNc-d) and the ventral tegmental area (VTA) are immunoreactive for AMPA (GluR1, GluR2/3, and GluR4) and NMDAR1 receptor subunits, but not for NMDAR2A/B subunits. The immunoreactivity of the receptor subunits is associated mainly with perikarya and dendritic shafts. Apart from the intensity of immunolabeling for the GluR4 subunit, which is quite similar for the different groups of midbrain dopaminergic neurons, the overall intensity of immunostaining for the other subunits is higher in the SNc-v and SNc-d than in the VTA. In line with these observations, in situ hybridization shows that the average level of labeling for the GluR2 and NMDAR1 subunit mRNAs is significantly higher in the SNc-v than in the VTA, and for the NMDAR1 subunit, higher in the SNc-v than in the SNc-d. In contrast, no significant difference was found for the level of GluR1 mRNA labeling among the three groups of midbrain dopaminergic neurons. At the subcellular level in the SNc-v, AMPA (GluR1 and GluR2/3) and NMDAR1 receptor subunit immunoreactivity is preferentially associated with the postsynaptic densities of asymmetric synapses, but occasionally some immunoreactivity is found along nonsynaptic portions of plasma membranes of dendrites. A small number of preterminal axons, axon terminals, and glial cell processes are also immunoreactive. Our observations indicate that the different groups of midbrain dopaminergic neurons in primates exhibit a certain degree of heterogeneity with regard to the level of expression of some ionotropic glutamate receptor subunits. The widespread neuronal and glial localization of glutamate receptor subunits suggests that excitatory amino acids may act at different levels to control the basal activity and, possibly, to participate in the degeneration of midbrain dopaminergic neurons in Parkinson's disease.

Differential localization of AMPA glutamate receptor subunits in the two segments of the globus pallidus and the substantia nigra pars reticulata in the squirrel monkey

The subthalamic nucleus has long been known as the main source of glutamatergic afferents to the pallidum and the substantia nigra in primates. Recent findings showed that the excitatory effects induced by the subthalamic nucleus in pallidal cells are mediated through the activation of non-NMDA receptors in the rat. The objective of the present study was to analyse the distribution of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) glutamate receptor subunits in the external pallidum (GPe), the internal pallidum (GPi) and the substantia nigra pars reticulata (SNr) in squirrel monkeys (Saimiri sciureus). This was achieved by means of immunohistochemistry using antibodies raised against the GluR1 and the GluR2/3 subunits of the AMPA receptor. Our results show that all neuronal perikarya in GPe and GPi display immunoreactivity for GluR2/3 subunits whereas GluR1 is confined exclusively to cells in the GPe. The proportion of GluR1-immunoreactive neurons is not uniform throughout the rostrocaudal extent of GPe; in the rostral third all GPe cells display GluR1 immunoreactivity, whereas in the caudal third the proportion of GluR1-positive cells decreases to 50%. The intensity of GluR1 immunostaining associated with GPe cells is lower than that associated with neighbouring large-sized neurons in the nucleus basalis of Meynert. In contrast to GPi cells, the neurons in the SNr display immunoreactivity for both GluR1 and GluR2/3 subunits. In conclusion, our results provide the first evidence for a different distribution of the GluR1 subunit of the AMPA receptors in the two segments of the globus pallidus in monkeys. These findings imply that the control of the basal activity of GPe and GPi cells by the subthalamic nucleus is exerted via the activation of AMPA receptors composed of different subunits. These data reinforce the view that the two segments of the globus pallidus are different entities that possess their own functional characteristics in primates.

Institutional experience with a protocol of early primary repair of double-outlet right ventricle

BACKGROUND

Our institution has adopted a protocol of primary repair for all patients with double-outlet right ventricle.

METHODS

Since May 1989, 24 consecutive neonates and infants with double-outlet right ventricle and atrioventricular concordance (median age, 4 months) underwent anatomic biventricular repair. One patient (4%) received prior pulmonary artery banding but was still repaired as a neonate at 22 days of age. Twelve patients had a subaortic ventricular septal defect (VSD), 5 patients a subpulmonary VSD, 3 patients doubly committed VSD, and 4 patients a noncommitted VSD. Sixty-nine of 72 associated lesions were repaired simultaneously. Four types of repairs were used: intraventricular rerouting in 16 patients, arterial switch operation with VSD closure into the pulmonary artery in 4 patients, Rastelli-type repair with extracardiac conduit in 3 patients, and the Damus-Kaye-Stansel repair with concomitant repair of aortic arch obstruction in 1 patient. Ventricular septal defect enlargement was necessary in 15 patients. Repair of subpulmonary stenosis and of subaortic stenosis was carried out in 13 and 4 patients, respectively. Three patients underwent simultaneous repair of aortic arch obstruction with no mortality. Two of the patients with noncommitted VSD had simultaneous repair of complete atrioventricular canal and repair of severe pulmonary venous obstruction.

RESULTS

The perioperative mortality was 8% (2 patients, and there was one late death (4%). Two patients (9%) underwent early successful reoperations (5 and 8 weeks postoperatively). The two reoperations were for residual VSD (1 patient) and severe mitral regurgitation (1 patient). All 21 survivors are alive at a mean follow-up of 40 months (range, 7 months to 6 years). The estimated 5-year actuarial survival is 88%, with no deaths after 2 months postoperatively. Ninety-five percent of long-term survivors have no restriction of physical activities because of cardiac status and are receiving no cardiac medications.

CONCLUSIONS

An institutional protocol of early anatomic biventricular repair of double-outlet right ventricle in infants and neonates achieves excellent survival, making palliative operations unnecessary. Associated lesions should be repaired simultaneously. The complexity of these malformations requires a highly individualized and flexible surgical approach.

Origin of the right subclavian artery from the right pulmonary artery in a newborn with complete transposition of the great arteries

The clinical and angiographic features of a newborn with differential cyanosis between the right arm and the rest of the body are described. The embryology of the vascular anomalies and the hemodynamic mechanisms are discussed.

Cardiac fibroma presenting with clinically significant arrhythmias in infancy

Supraventricular or ventricular ectopy has been reported in association with cardiac fibroma. We report two patients, one with acquired complete heart block and one with mixed ventricular and supraventricular arrhythmias associated with this rare tumor of the heart.

[Transfemoral vein catheter occlusion of patent ductus arteriosus]

Between February 1988 and September 1989, 15 patients underwent closure of patent ductus arteriosus by the Rashkind technique modified by Mullins. The insertion of the occluder was achieved in all cases; however, in one patient, the prosthesis migrated to the abdominal aorta several hours after implantation. No other complications were observed. All patients were discharged from hospital under 24 hours after the procedure. The follow-up period ranges from 3 to 12 months. The rate of complete closure of the ductus was 50% 24 hours after implantation, 57% at 3 months, 66% at 6 months and 82% 12 months after the procedure. Our results suggest that the Rashkind technique for the closure of patent ductus arteriosus by the transvenous femoral approach is an effective and low risk procedure.

Pericardial effusion after cardiac surgery in children and effects of aspirin for prevention

Seventy-four children aged 0.3 to 21.4 years (median 4.0) were followed echocardiographically on days 4, 7, 14 and 28 (+/- 2 days) after cardiac surgery to evaluate the incidence of postoperative pericardial effusion, to identify the patients at greatest risk of developing an effusion and to evaluate the use of aspirin as prophylaxis against pericardial effusion. Pericardial effusion was graded relative to the size of the aortic root from grade 0 (no effusion) to grade 5 (larger than the aortic root dimension). Patients were randomly divided into 2 groups: group 1 (32 patients) received aspirin 60 mg/kg/day for 7 days starting on the third postoperative day; group 2 (42 patients) received no aspirin. Forty-eight patients (65%) developed an effusion during the study period, 3 required pericardiocentesis and 1 died of tamponade. All patients with tamponade had a grade 4 effusion. Age or type of operation did not alter the cumulative incidence of significant effusion. No patient with a grade 0 effusion on the first echocardiogram developed a grade 4 or 5 effusion. Results in groups 1 and 2 were similar. Pericardial effusions are common in the first month after cardiac surgery. Patients with no effusion in the immediate postoperative period appear to be at lesser risk of developing a grade 4 effusion in the first month after operation. Finally, aspirin prophylaxis against postoperative pericardial effusions did not significantly alter the outcome in this small series of patients.

Transseptal catheterization of the left heart in infants and children: experience in a small volume catheterization laboratory

During a five-and-one-half year period, the transseptal technique was used for left heart catheterization in 37 patients with a variety of congenital heart disease. The age of the patients ranged from four months to 21 years and weights ranged from 6.6 to 65 kg. Access to the left heart cavities and ascending aorta was achieved in all but two patients. There were no complications. Even when used infrequently, the transseptal technique allows rapid and safe entry to the left heart cavities in infants and children.

Success in NCLEX-RN: Identifying Predictors and Optimal Timing for Intervention

This ex post facto study was designed to identify predictors of success in the NCLEX-RN and determine the optimal point in time for identifying students at risk. The convenience sample consisted of 407 graduates of an integrated, upper division, baccalaureate nursing program, 1984-1987. Prematriculation (total lower division GPA, science GPA, type of lower division College, age, and sex), junior year (three Nursing theory course grades) and pre graduation variables (three senior year nursing theory course grades and Mosby ASSESSTEST) were analyzed for predictive value. Nursing theory courses at the junior and senior year and the Mosby ASSESSTEST strongly correlated (p less than .0001) with NCLEX performance. Discriminant analysis enabled successful classification of 62% of the sample at prematriculation, 81% at the end of the junior year, and 86% at the end of the senior year. The study indicates that students at high risk can be identified at the end of the junior year so that enrichment and support programs can be introduced at that time.