[Total Arch Replacement Using Bilateral Axillary Artery Perfusion]

OBJECTIVES

The selection of arterial cannulation site is an important decision to avoid cerebral complication for total arch replacement(TAR). We report the surgical outcome of TAR using bilateral axillary artery perfusion in our hospital.

METHODS

Between January 2012 and June 2020, 97 patients who underwent elective TAR for atherosclerotic aneurysms were enrolled in this study. Among them, bilateral axillary artery perfusion was used for 81 patients, and frozen elephant trunk( FET) procedure were used for 34 patients. In the case of FET procedure, translocated TAR was performed with distal anastomosis between the left common carotid artery and the left subclavian artery. The left subclavian artery was reconstructed by rerouting the graft used for the left axillary artery perfusion.

RESULTS

There were no perioperative cerebral infarction and no hospital deaths. The mean operation time was 420 minutes. Compared to the conventional elephant trunk method, the FET method significantly reduced the operation time to 381 minutes.

CONCLUSIONS

Bilateral axillary artery perfusion could contribute to reduce the cerebral infarction in TAR and facilitate the FET procedure.

A biodegradable microneedle sheet for intracorporeal topical hemostasis

Management of bleeding is critical for improving patient outcomes. While various hemostatic products are used in daily practice, technical improvement is still needed. To addresses this problem, we newly developed a microneedle hemostatic sheet based on microneedle technology. We demonstrated the unique features of this microneedle hemostatic sheet, including reduced hemostatic time, biodegradable polymer composition that allows intracorporeal use without increasing infectious risk incorporation of microneedles to fix the sheet to the wound even on the left ventricular wall of a swine while beating, and a mesh structure with flexibility comparable to that of bonding surgical tape and sufficient rigidity to penetrate human aorta tissue and swine left ventricular wall. One potential application of the microneedle hemostatic sheet is intracorporeal topical hemostasis for parenchymatous organs, large vessels, and heart wall during trauma or surgery, in addition to new, widespread applications.

Impact of instantaneous wave-free ratio on graft failure after coronary artery bypass graft surgery

BACKGROUND

We aimed to assess an impact of instantaneous wave-free ratio (iFR) on a graft failure after coronary artery bypass grafting (CABG).

METHODS AND RESULTS

A total of 131 coronary arteries from 88 patients who underwent invasive coronary angiography, intracoronary pressure measurements, CABG, and scheduled follow-up coronary computed tomography angiography within one year were investigated. All studied arteries had FFR <0.80. The rate of graft failure was significantly higher in vessels with negative iFR (>0.89) than in those with positive iFR (<0.89) (25.7% vs. 7.3%, p = 0.012). The graft failure rates increased as the preoperative iFR values rose (iFR <0.80, 3.3%; iFR: 0.80-0.84, 5.6%; iFR: 0.85-0.89, 16.0%; iFR: 0.90-0.94, 28.0%; and iFR: 0.95-1.00, 50.0%; p = 0.002). A cut-off value of iFR to predict graft failures was determined as 0.84 by receiver-operating characteristic curve analysis with sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 88%, 62%, 25%, 97%, and 66%, respectively.

CONCLUSIONS

The risk of graft failure becomes higher, as the preoperative iFR increases. The graft failure is significantly more frequent when a bypass graft is anastomosed on vessels with negative iFR than those with positive iFR.

Serum Cystatin C Level as a Biomarker of Aortic Plaque in Patients with an Aortic Arch Aneurysm

Aim: During surgery for an aortic arch aneurysm, aortic plaque in the descending aorta should be evaluated, but there are currently no suitable biomarkers for it. Surgeons should be especially aware of cerebral embolism from femoral perfusion and of peripheral embolism from stent graft deployment. Cystatin C is a known useful marker of renal dysfunction with a role as a biomarker for severity of coronary artery disease. In the absence of a suitable biomarker for aortic plaque in the descending aorta, we examine cystatin C as a candidate.

Methods: In all, 75 patients who underwent surgery for an aortic arch aneurysm were enrolled. They were divided into two groups, depending on whether they had chronic kidney disease or not. The serum cystatin C value and creatinine value were evaluated preoperatively. The aortic plaque volume ratio and components in the descending aorta were calculated from preoperative enhanced computed tomography.

Results: The soft plaque volume ratio was higher in patients with chronic kidney disease than in patients without it. Cystatin C positively correlated with the total aortic plaque volume ratio in all cases, and it positively correlated with the soft plaque volume ratio in both groups. Creatinine had no correlation with any type of plaque volume ratio in either group. In patients without chronic kidney disease, the soft plaque volume ratio was higher in patients with higher cystatin C levels than in patients with normal levels.

Conclusion: The preoperative serum cystatin C level could be a biomarker of aortic plaque in the descending aorta in patients with an aortic arch aneurysm.

Severe aortic regurgitation with intimal intussusception secondary to Debakey type I aortic dissection

Aortic regurgitation (AR) with intimal intussusception, secondary to aortic dissection, is relatively rare and the images are interesting findings. We report a typical case of severe AR with intimal intussusception, secondary to DeBakey type I aortic dissection, detected by contrast-enhanced computed tomography (CECT) and transesophageal echocardiography (TEE). Since there are three types of aortic regurgitation with aortic dissection, it is imperative to consider the most appropriate intervention for AR. The combination of CECT, TEE, and surgical findings may play an important role in determining the optimum surgical procedure for AR with aortic dissection.

Effect of coronary artery bypass grafting on blood pressure response to head-up tilting

Blood pressure response to head-up tilt (HUT) in 7 healthy subjects and 9 patients before and after coronary artery bypass grafting (CABG) was measured during supine and 15-min 60° HUT. Stroke volume (SV) and ejection fraction (EF) were assessed by echocardiography. Baseline mean arterial pressure (MAP) and heart rate (HR) in patients before CABG were similar to healthy subjects. MAP in patients decreased by 6 (4-9) mmHg [median (1st-3rd quartiles)] during 7-12 mmHg of HUT with decreased cardiac output (CO = SV × HR) while HR remained unchanged. MAP in healthy subjects remained unchanged during HUT with increased HR. Body weight decreased by 3.5 (2.5-3.7) kg and MAP decreased by 6 (2-13) mmHg during the last 3-min HUT while HR increased after CABG. Decreases in SV and CO during HUT disappeared after CABG. Blood pressure decreased during HUT in patients before and after CABG regardless of HR response.

Staged hybrid aortic procedure for chronic type B aortic dissection in two patients with Marfan syndrome

We here report two patients with Marfan syndrome treated by a combination of surgical grafting and endovascular repair in our hospital. One was a 32-year-old woman who underwent thoracoabdominal aortic replacement for a Crawford type III dissected aortic aneurysm. Subsequently, the Bentall procedure and total arch replacement was performed for an aortic root and arch aneurysm. Finally, thoracic endovascular aortic repair bridging implanted grafts was performed. The second was a 67-year-old woman with Stanford type A acute aortic dissection who underwent the Bentall procedure and total arch replacement at the age of 64. Subsequently, she underwent thoracoabdominal replacement for a dilated dissected aortic aneurysm and finally, bridging endovascular aortic repair was performed. This procedure is less invasive than open repair for patients with Marfan syndrome.

Usefulness of routine use of bilateral axillary artery perfusion in total arch replacement

OBJECTIVES

To avoid cerebral infarction for aortic arch aneurysm and malperfusion for acute aortic dissection, the site of cannulation during total arch replacement remains important. Recently, we have used bilateral axillary artery perfusion in total arch replacement and in acute aortic dissection. Herein, we report the surgical outcomes.

METHODS

Seventy-eight patients with aortic arch aneurysm and 45 patients with acute aortic dissection were enrolled in this study. During surgery, translocation of the total arch was performed on 67 patients using a 'frozen elephant trunk technique'.

RESULTS

In patients with aortic arch aneurysm, there was no postoperative cerebral infarction. New postoperative cerebral infarction was observed in only one patient who underwent acute aortic dissection. Two patients who had aortic arch aneurysm and 2 patients who had acute aortic dissection died at the hospital. Complications related to bilateral axillary perfusion were not observed.

CONCLUSIONS

The routine use of bilateral axillary artery perfusion in total arch replacement for aortic arch aneurysm to avoid cerebral infarction has the potential to be a useful procedure. It can facilitate the frozen elephant trunk procedure in acute aortic dissection.

Repair of an adult aorto-pulmonary artery fistula associated with a ruptured aortic arch aneurysm using a frozen elephant trunk technique

We describe the repair of an acute aorto-pulmonary artery fistula in a 82-year-old patient with a ruptured aortic arch aneurysm using a frozen elephant trunk technique.

Aortic valve replacement with essential thrombocythemia

Cardiac surgery in patients with essential thrombocythemia carries the risks of both thrombotic events and a bleeding tendency. We report the case of a 75-year-old man with essential thrombocythemia who underwent successful surgical aortic valve replacement after his platelet count was controlled with plateletpheresis 3 times before surgery.

Congenital mitral regurgitation with Down syndrome

A 19-year-old man with Down syndrome had congenital mitral regurgitation. He had slight mental retardation and difficulty in performing independent oral drug administration. We planned mitral valve plasty to avoid postoperative anticoagulant therapy. The mitral valve lesions were complicated. A prolapsed anterior mitral leaflet, shortened posterior leaflet, abnormal cleft, abnormal papillary muscle, and enlarged annulus were observed. Successful mitral valve plasty was performed using several techniques. The postoperative course was uneventful, and no significant mitral regurgitation was found.

Efficacy of Paclitaxel in a Patient with Inoperable Pulmonary Vein Leiomyosarcoma

Pulmonary vein leiomyosarcoma is extremely rare and has a poor prognosis. Surgical resection with a wide margin seems to offer the only chance of cure. The role of adjuvant therapy is controversial, and the exact efficacy of chemotherapy has not been observed. In this report, we present an 18-year-old male patient with pulmonary vein leiomyosarcoma in whom the use of paclitaxel (PAX) proved to be effective. Because the tumor originated from the left superior pulmonary vein and diffused into the left atrial wall and the junction of the right superior pulmonary vein and left atrium, the en bloc excision of the tumor was impossible. The first-line chemotherapy, including ifosfamide, doxorubicin, and dacarbazine, in conjugation with radiation therapy could not demonstrate any effect on the tumor size. However, the following PAX-containing regimen provided complete regression of the tumor. After PAX-based high-dose chemotherapy with autologous peripheral blood stem cell transplantation, the patient showed complete remission for 2 years. Although he suffered metastatic recurrences and died 4 years after the onset of symptoms, our patient's clinical course clearly reveals the efficacy of PAX.

[Outcomes after total arch replacement using antegrade selective cerebral perfusion under right axillary artery perfusion]

Although the outcomes of total arch replacement have been improving, the prevention of cerebral infarction is still an important consideration in aortic arch surgery. Herein, we reviewed our experience with total arch replacement using antegrade selective cerebral perfusion under right axillary artery perfusion. Between January 2002 and March 2013, total arch replacement was performed for 125 patients including 31 patients with acute aortic dissection. An 8 mm polyester grafts was sutured to the axillary artery through the right subclavicular incision and was connected to cardiopulmonary bypass circuit. Antegrade selective cerebral perfusion under hypothermic circulatory arrest was initiated using right axillary artery perfusion. Postoperative cerebral infarction occurred in 5.6% of patients. Hospital mortality rate was 3.2%. The 5-year rate of freedom from aortic event was 83%. The 5-year survival rate was 75%. We consider that right axillary artery perfusion is advantageous for preventing cerebral infarction in total arch replacement.

Clinical outcomes of redo valvular operations: a 20-year experience

BACKGROUND

A higher operative mortality rate has been reported after redo valvular procedures than after the primary operation.

METHODS

Outcomes of 330 consecutive patients undergoing 433 redo valvular operations at our institute during a 20-year period (January 1990 to December 2010) were reviewed retrospectively. The mean follow-up was 6.4 years (range, 0.05 to 1.3 years). Logistic regression analysis was used to identify factors associated with hospital death.

RESULTS

The overall hospital mortality rate was 6.7% (29 of 433 procedures). Logistic regression analysis identified only advanced New York Heart Association (NYHA) class as an independent predictor of hospital death. Overall survival at 5, 10, and 15 years was 83.6%±2.2%, 70.7%±3.4%, and 61.5%±4.5%, respectively. The 5-, 10-, and 15-year survivals for the first redo vs more than second redo groups were 86.5%±2.4% vs 74.7%±5.5%, 71.8%±3.9% vs 66.8%±6.6%, and 60.2%±5.7% vs 63.1%±7.2%, respectively (log-rank P=0.505). The 5- and 10-year survivals for NYHA class I/II vs III/IV patients were 91.5%±2.1% vs 70.4%±4.5% and 77.8%±4.1% vs 58.5%±5.6%, respectively (log-rank p<0.005).

CONCLUSIONS

Redo valvular operation in NYHA class III/IV patients is associated with high hospital death and poor long-term survival. To achieve low hospital death and good long-term survival, redo operations, including more than third redo operations, should be performed in patients with lower NYHA class.

Aortic valve replacement after esophagectomy with substernal gastric tube and total laryngectomy with tracheostoma

A 77-year-old man successfully underwent aortic valve replacement with a bioprosthesis through a right thoracotomy. Right thoracotomy was utilized because the patient had previously undergone esophagectomy with reconstruction of a substernal gastric tube for esophageal cancer as well as total laryngectomy with tracheostoma formation for laryngeal cancer. Thus, even in a situation in which conventional median sternotomy was difficult, a good outcome for aortic valve replacement was achieved through an alternate approach. This case highlights the need to consider patient history when selecting a surgical approach.

Dissecting aneurysm in a patient with autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is primarily associated with renal failure, but it also causes systemic diseases, including cysts of other systemic organs and cerebral or visceral aneurysm. To make matters worse, life-threatening aortic diseases are associated with ADPKD in some cases. However, only a few reports of ADPKD-associated with thoracic aortic dissection have been published. Herein, we present a case of dissecting aneurysm in a patient with hypertension and ADPKD. He had been followed up for type B aortic dissection for six years. Preoperative creatinine level ranged from 2.1 to 2.4 mg/dl. We performed replacement of the thoracic aorta with prosthetic graft successfully, and postoperatively, dialysis was not required.It is very important for us to recognize the relationship between ADPKD and thoracic aortic dissection, which can cause high mortality and morbidity rates.

New (but old) molecules regulating synapse integrity and plasticity: Cbln1 and the delta2 glutamate receptor

The delta2 glutamate receptor (GluRdelta2) is predominantly expressed in cerebellar Purkinje cells and plays crucial roles in cerebellar functions: GluRdelta2-null mice display ataxia and impaired motor learning. Interestingly, the contact state of synapses between parallel fibers (PFs) and Purkinje cells is specifically and severely affected, and the number of normal PF synapses is markedly reduced in GluRdelta2-null Purkinje cells. Furthermore, long-term depression at PF-Purkinje cell synapses is abrogated. Cbln1, a member of the C1q/tumor necrosis factor (TNF) superfamily, is predominantly expressed and released from cerebellar granule cells. Unexpectedly, the behavioral, physiological and anatomical phenotypes of cbln1-null mice precisely mimic those of GluRdelta2-null mice. Thus, we propose that Cbln1, which is released from granule cells, and GluRdelta2, which is predominantly expressed in Purkinje cells, are involved in a common signaling pathway crucial for synapse formation/maintenance and plasticity in the cerebellum. Since molecules related to Cbln1 are expressed in various brain regions other than the cerebellum, other C1q/TNF superfamily proteins may also regulate various aspects of synapses in the CNS. Therefore, an understanding of the signaling mechanisms underlying Cbln1 and GluRdelta2 in the cerebellum will provide new insights into the roles of C1q/TNF superfamily proteins as new cytokines that regulate normal and abnormal brain functions.

[Effects of octreotide acetate on intractable chylothorax after surgery for congenital heart diseases]

We experienced 2 infants in whom octreotide acetate was effective on intractable chylothorax after surgery for congenital heart diseases. They were 8- and 5-month-old. They were diagnosed as having corrected transposition of the great arteries (TGA) and tetralogy of Fallot respectively, and underwent bidirectional Glenn anastomosis and right modified Blalock Taussig shunt. Chylothorax was revealed on the 11th and the 1st postoperative day, and was not improved by any conventional therapy in either case. Then octreotide acetate was infused continuously with 0.1-0.6 micorg/kg/hour for 24 and 7 days. Chylothorax disappeared completely without any complications such as disturbance of blood sugar level or growth retardation. Octreotide acetate was effective and safe even in infants in intractable chylothorax after surgery for congenital heart diseases, as long as used for short period.

[Effects of additional pulmonary blood flow after bidirectional Glenn procedure]

Thirteen cases of functional single ventricle who had undergone bidirectional Glenn procedure were divided into 2 groups according to presence (5) or absence (8) of additional pulmonary blood flow. Additional flow was preserved in cases with relatively small pulmonary artery index (PA index), and their sources were antegrade pulmonary blood flow (2), and Blalock-Taussig (BT) shunt (3). In the control group, PA index was reduced to about 70% of the preoperative value, while in the additional group, pulmonary artery growth was recognized without significant elevation of mean pulmonary artery pressure. However, atrioventricular valve regurgitation progressed and systemic ventricular volume did not decrease after Glenn in the additional group. Therefore special consideration for the timing of Fontan procedure is mandatory.

[Evaluation of aortic valve replacement involving small severely calcified aortic annulus in elderly patients]

We performed aortic valve replacement in 24 patients aged over 70 with small calcified valves. The surgical management of such patients remains controversial as the extensive calcification compromises implantation. Hence, we used an ultrasonic debridement instrument to remove calcium and selected a small prosthesis with the largest possible orifice without enlargement of the aortic annulus. Echocardiography showed significant reductions in left ventricular mass index compared with preoperative values. Early and mid-term prognosis has been relatively good.

[Histoculture drug response assay for solitary fibrous tumor--a case report]

A 49-year-old male was referred to our hospital because of an abnormal shadow in his left lower lung field on chest X-ray. Magnetic resonance imaging scans revealed a large mass on the left diaphragm. The tumor was surgically extirpated. The tumor, encapsulated and growing from the center of the left diaphragm, measured 18 x 8 x 4 cm and weighed 440 g. Microscopic examination revealed a solitary fibrous tumor with mitotic activity of 7/ 50 hpf. Immunohistochemically, the tumor was negative for cytokeratin, s-100 protein, desmin, and alpha-smooth muscle actin, while positive for vimentin and CD34. On a histoculture drug response assay using the resected tissue, the tumor was sensitive to 5-FU, adriamycin, mitomycin C and docetaxel, and resistant to cisplatin, irinotecan, and gemcitabine.

Purification of Purkinje cells by fluorescence-activated cell sorting from transgenic mice that express green fluorescent protein

The cerebellar Purkinje cell has been the focus of numerous studies involving the analysis of development and information processing in the nervous system. Purkinje cells represent less than 0.1% of the total cell content of the cerebellum. To facilitate studies of molecules that are expressed in such a small proportion of neurons, we have established procedures for the purification of these cells. Transgenic mice were developed in which the expression of green fluorescent protein (GFP) was controlled by the L7 promoter. In adult cerebellum, GFP fluorescence was only detected in Purkinje cells, where it filled dendrites, soma and axons. GFP fluorescence was detected in Purkinje cells as early as embryonic day 17 and increased during development in vivo and in dissociated cerebellar culture. Mirroring endogenous L7 expression, high levels of GFP were observed in retinal rod bipolar cells. Lower levels of GFP were seen in olfactory periglomerular cells, neurons in the interpeduncular nucleus, and superior colliculus neurons. Cerebella from transgenic mice were dissociated by mild enzymatic treatment and Purkinje cells were isolated by fluorescence-activated cell sorting (FACS). By selecting optimal parameters, a fraction of viable Purkinje cells that was 94% pure was obtained. These results indicate that FACS is a powerful tool for isolating Purkinje cells from postnatal L7-GFP transgenic mice. GFP-positive neurons will also be useful in the real-time observation of dendritic morphogenesis and axonal outgrowth during development, or after neuronal activity in vitro.

Characterization of the apoptosis-associated tyrosine kinase (AATYK) expressed in the CNS

We isolated three related cDNA clones from a mouse cerebellar library; the type I cDNA was identical to the gene encoding the apoptosis-associated tyrosine kinase (AATYK), whose expression in myeloid precursor cells is increased during growth arrest or apoptosis. Low levels of AATYK mRNA expression were seen in adult mouse brains but not in embryos. In situ hybridization confirmed the widespread expression of AATYK mRNA in neurons throughout the adult brain. AATYK possessed tyrosine kinase activity and was autophosphorylated when expressed in 293 cells. AATYK mRNA expression was rapidly induced in cultured cerebellar granule cells during apoptosis induced by a low concentration of KCl (5 mM). Levels of endogenous AATYK protein were increased only slightly, but they were accompanied by an increase in molecular weight during apoptosis. Results of the tyrosine phosphatase treatments indicated that the increase in molecular weight was partly caused by tyrosine phosphorylation. The number of apoptotic granule cells overexpressing wild-type AATYK protein was significantly greater than the number of apoptotic granule cells overexpressing a mutant AATYK that lacked tyrosine kinase activity in low concentrations of KCl. These findings suggest that through its tyrosine kinase activity, AATYK is involved in the apoptosis of mature neurons.

Mutation of a glutamate receptor motif reveals its role in gating and delta2 receptor channel properties

Despite its importance in the cerebellum, the functions of the orphan glutamate receptor delta2 are unknown. We examined a mutant delta2 receptor channel in lurcher mice that was constitutively active in the absence of ligand. Because this mutation was within a highly conserved motif (YTANLAAF), we tested its effect on several glutamate receptors. Mutant delta2 receptors showed distinct channel properties, including double rectification of the current-voltage relationship, sensitivity to a polyamine antagonist and moderate Ca 2+ permeability, whereas other constitutively active mutant glutamate channels resembled wild-type channels in these respects. Moreover, the kinetics of ligand-activated currents were strikingly altered. We conclude that the delta2 receptor has a functional ion channel pore similar to that of glutamate receptors. The motif may have a role in the channel gating of glutamate receptors.

Characterization of L-homocysteate-induced currents in Purkinje cells from wild-type and NMDA receptor knockout mice

L-Homocysteic acid (HCA), an endogenous excitatory amino acid in the mammalian CNS, potently activates N-methyl-D-aspartate (NMDA) receptors in hippocampal neurons. However, the responses to HCA in Purkinje cells, which lack functional NMDA receptors, have been largely unexplored: HCA may activate conventional non-NMDA receptors by its mixed agonistic action on both NMDA and non-NMDA receptors, or it may activate a novel non-NMDA receptor that has high affinity for HCA. To test these possibilities, we compared the responses to HCA in cultured Purkinje cells with those in hippocampal neurons by using the whole cell patch-clamp technique. To clearly isolate HCA responses mediated by non-NMDA receptors, we complemented pharmacological methods by using neurons from mutant mice (NR(-/-)) that lack functional NMDA receptors. A moderate dose of HCA (100 microM) induced substantial responses in Purkinje cells. These responses were blocked by non-NMDA receptor antagonists but were insensitive to NMDA receptor antagonists. HCA also activated responses mediated by non-NMDA receptors in both wild-type and NR1(-/-) hippocampal neurons. HCA responses in Purkinje cells had a pharmacological profile (EC(50) and Hill coefficient) very similar to that of non-NMDA receptor components of HCA responses in hippocampal neurons. Moreover, the amplitude of the non-NMDA receptor component of HCA responses was directly correlated with that of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)- and kainate-induced responses in both types of neurons. Finally, in both types of neurons, HCA currents mediated by non-NMDA receptors were potently blocked by the AMPA receptor antagonist GYKI52466. These findings indicate that HCA-activated AMPA receptors in Purkinje cells are similar to those in hippocampal neurons and that there is no distinct HCA-preferring receptor in Purkinje cells. We also found that in hippocampal neurons, the EC(50)s of HCA for non-NMDA receptors and for NMDA receptors were more similar than originally reported; this finding indicates that HCA is similar to other mixed agonists, such as glutamate. HCA responses may appear to be selective at NMDA receptors in cells that express these receptors, such as hippocampal neurons; in cells that express few functional NMDA receptors, such as Purkinje cells, HCA may appear to be selective at non-NMDA receptors.

Neuronal interleukin-16 (NIL-16): a dual function PDZ domain protein

Interleukin (IL)-16 is a proinflammatory cytokine that has attracted widespread attention because of its ability to block HIV replication. We describe the identification and characterization of a large neuronal IL-16 precursor, NIL-16. The N-terminal half of NIL-16 constitutes a novel PDZ domain protein sequence, whereas the C terminus is identical with splenocyte-derived mouse pro-IL-16. IL-16 has been characterized only in the immune system, and the identification of NIL-16 marks a previously unsuspected connection between the immune and the nervous systems. NIL-16 is a cytosolic protein that is detected only in neurons of the cerebellum and the hippocampus. The N-terminal portion of NIL-16 interacts selectively with a variety of neuronal ion channels, which is similar to the function of many other PDZ domain proteins that serve as intracellular scaffolding proteins. Among the NIL-16-interacting proteins is the class C alpha1 subunit of a mouse brain calcium channel (mbC alpha1). The C terminus of NIL-16 can be processed by caspase-3, resulting in the release of secreted IL-16. Furthermore, in cultured cerebellar granule neurons undergoing apoptosis, NIL-16 proteolysis parallels caspase-3 activation. Cerebellar granule neurons express the IL-16 receptor CD4. Exposure of these cells to IL-16 induces expression of the immediate-early gene, c-fos, via a signaling pathway that involves tyrosine phosphorylation. This suggests that IL-16 provides an autocrine function in the brain. Therefore, we hypothesize that NIL-16 is a dual function protein in the nervous system that serves as a secreted signaling molecule as well as a scaffolding protein.

Selective activation of calcium permeability by aspartate in Purkinje cells

Glutamate and aspartate are endogenous excitatory amino acid neurotransmitters widely distributed in the mammalian central nervous system. Aspartate was shown to induce a large membrane current sensitive to N-methyl-D-aspartate (NMDA) and non-NMDA receptor antagonists in Purkinje cells from mice lacking functional NMDA receptors (NR1(-/-)). This response was accompanied by high permeability to calcium. In contrast, no current was induced by aspartate in hippocampal neurons and cerebellar granule cells from NR1(-/-) mice. Several other glutamate receptor agonists failed to evoke this response. Thus, in Purkinje cells, aspartate activates a distinct response capable of contributing to synaptic plasticity through calcium permeability.

Functional NMDA receptors are transiently active and support the survival of Purkinje cells in culture

Conflicting evidence exists concerning the activity of NMDA receptors (NMDARs) in cerebellar Purkinje cells and their possible functions. To investigate the activity of NMDARS, we used whole-cell recording on immunocytochemically identified Purkinje cells in primary culture. In addition, we used mice with a disrupted NMDAR1 gene that lack functional NMDARs (NR1-/-) to assess the physiological role of NMDARs. In cultures from normal mice, NMDA-medicated currents were detected in all identified Purkinje cells at 4 d in vitro (div). After 14 d, however, NMDA responses were reduced in amplitude, whereas the responses to kainate and glutamate increased steadily in amplitude. In addition, the NMDA-induced current displayed a pronounced desensitization at these later stages; peak current declined to zero during steady application of NMDA. At 7 div, the number of surviving Purkinje cells was less in cultures treated with NMDA antagonists, and their survival was dose-dependent. Purkinje cell survival was correspondingly poorer in cultures from the NR1-/- mice than in wild-type controls, suggesting that NMDAR activity enhances the survival of Purkinje cells in vitro. The addition of moderate doses of NMDA promoted the survival of wild-type Purkinje cells in the presence of tetrodotoxin. Feeder layers of cerebellar granule cells derived from wild-type or NR1-/- mice promoted survival of Purkinje cells to a similar degree, suggesting that the NMDAR in Purkinje cells, but not in other cells, is directly involved in Purkinje cell viability. The results demonstrate that NMDARs transiently produce membrane current in Purkinje cells and may serve as one of the epigenetic factors that support the survival of Purkinje cells in vitro.

An additional form of rat Bcl-x, Bcl-xbeta, generated by an unspliced RNA, promotes apoptosis in promyeloid cells

The bcl-2 oncogene product delays apoptotic cell death and prolongs the cell survival. We cloned two bcl-2-related cDNAs from a rat thymus cDNA library by low stringency hybridization with a rat bcl-2 fragment as a probe. One of these, designated bcl-xalpha, was a counterpart of the human bcl-xL reported previously as a bcl-2-related gene (Boise, L. H., Gonzalez-Garcia, M., Postema, C. E. , Ding, L., Lindsten, T., Turka, L. A., Mao, M., Nunez, G., and Thompson, C. B. (1993) Cell 74, 597-608). The other, designated bcl-xbeta, was novel and found to be generated by an unspliced mRNA, whereas bcl-xalpha was generated from a spliced transcript. The splice junction exactly corresponded to that found in the bcl-2 gene. bcl-xbeta was specifically expressed in cerebellum, heart, and thymus. When bcl-xbeta directed by a strong promoter was introduced into an interleukin-3-dependent promyeloid cell line, FDC-P1, DNA fragmentation was observed even in the growing state in the presence of interleukin-3 although not in the control transfectants. This finding suggests that the rat bcl-xbeta gene product promotes apoptosis in the promyeloid cells.

A stimulus paradigm inducing long-term desensitization of AMPA receptors evokes a specific increase in BDNF mRNA in cerebellar slices

Long-term desensitization of AMPA receptors (LTDA) is a core mechanism of long-term depression, a model of motor learning in the cerebellum. In this study we investigated the expression of neurotrophic factor genes after induction of LTDA in cultured cerebellar slices. LTDA was induced by application of quisqualate and monitored as a population response with a wedge recording technique. The levels of mRNA were quantified by reverse transcription followed by polymerase chain reaction. Quisqualate, at a dose and duration that reliably induced LTDA, elicited a significant and specific increase in BDNF mRNA with a peak at four hours after the application. By cell fractionation, the major source of BDNF mRNA increase was found to be in granule cells. In addition, a small but significant increase of transcripts with specific exon usage was observed in a Purkinje cell fraction. These results indicate that BDNF may be coinduced with LTDA and suggest that the slow and sustained increase of BDNF mRNA might play a role in later phases of synaptic plasticity in the cerebellum.

Targeted disruption of NMDA receptor 1 gene abolishes NMDA response and results in neonatal death

In vitro studies have suggested that the NMDA receptor consists of an essential subunit, NR1, and various modulatory NR2 subunits. To test this hypothesis directly in vivo, we generated mice carrying a disrupted NR1 allele. NMDA-inducible increases in intracellular calcium and membrane currents were abolished in neurons from homozygous null mutants (NR1-/-). Thus, NR1 has a unique role, which cannot be substituted by any other subunit, in determining the activity of the endogenous NMDA receptor. A concomitant reduction in levels of NR2B but not NR2A occurred in NR1-/- mice, demonstrating that there is an interdependence of subunit expression. NR1-/- mice died 8-15 hr after birth, indicating a vital neonatal function for the NMDA receptor. Although the NMDA receptor has been implicated in several aspects of neurodevelopment, overall neuroanatomy of NR1-/- mice appeared normal. Pathological evidence suggested that respiratory failure was the ultimate cause of death.

A stimulus paradigm inducing long-term desensitization of AMPA receptors evokes a specific increase in BDNF mRNA in cerebellar slices

Long-term desensitization of AMPA receptors (LTDA) is a core mechanism of long-term depression, a model of motor learning in the cerebellum. In this study we investigated the expression of neurotrophic factor genes after induction of LTDA in cultured cerebellar slices. LTDA was induced by application of quisqualate and monitored as a population response with a wedge recording technique. The levels of mRNA were quantified by reverse transcription followed by polymerase chain reaction. Quisqualate, at a dose and duration that reliably induced LTDA, elicited a significant and specific increase in BDNF mRNA with a peak at four hours after the application. By cell fractionation, the major source of BDNF mRNA increase was found to be in granule cells. In addition, a small but significant increase of transcripts with specific exon usage was observed in a Purkinje cell fraction. These results indicate that BDNF may be coinduced with LTDA and suggest that the slow and sustained increase of BDNF mRNA might play a role in later phases of synaptic plasticity in the cerebellum.

Cerebellar astrocytes specifically support the survival of Purkinje cells in culture

As a first step toward identifying the factor(s) that is/are produced by astrocytes and support(s) the survival of cerebellar Purkinje cells in dissociated culture, we compared the effect of astrocytes of cerebellar, hippocampal, and cerebral origin. A feeder coverslip of cerebellar astrocytes, which did not have cell-to-cell contact to neuronal culture, increased the percentage of Purkinje cells to about 8-9 fold with no change in the percentage of astrocytes. On the other hand, astrocytes of hippocampal or cerebral origin did not increase the percentage of Purkinje cells at low plating density, whereas they increased the number of astrocytes in neuronal culture. These results indicate that the factor(s), tentatively named as Purkinje-cell survival factor was/were specifically produced by cerebellar astrocytes and affected directly on Purkinje cells.