Stoned B mediates sorting of integral synaptic vesicle proteins.

A continuous supply of fusion-competent synaptic vesicles is essential for sustainable neurotransmission. Drosophila mutations of the dicistronic stoned locus disrupt normal vesicle cycling and cause functional deficits in synaptic transmission. Although both Stoned A and B proteins putatively participate in reconstituting synaptic vesicles, their precise function is still unclear. Here we investigate the effects of progressive depletion of Stoned B protein (STNB) on the release properties of neuromuscular synapses using a novel set of synthetic stnB hypomorphic alleles. Decreasing neuronal STNB expression to < or =35% of wild-type level causes a strong reduction in excitatory junctional current amplitude at low stimulation frequencies and a marked slowing in synaptic depression during high-frequency stimulation, suggesting vesicle depletion is attenuated by decreased release probability. Recovery from synaptic depression after prolonged stimulation is also decelerated in mutants, indicating a delayed recovery of fusion-ready vesicles. These phenotypes appear not to be due to a diminished vesicle population, since the docked vesicle pool is ultrastructurally unaffected, and the total number of vesicles is only slightly reduced in these hypomorphs, unlike lethal stoned mutants. Therefore, we conclude that STNB not only functions as an essential component of the endocytic complex for vesicle reconstitution, as previously proposed, but also regulates the competence of recycled vesicles to undergo fusion. In support of such role of STNB, synaptic levels of the vesicular glutamate transporter (vGLUT) and synaptotagmin-1 are strongly reduced with diminishing STNB function, while other synaptic proteins are largely unaffected. We conclude that STNB organizes the endocytic sorting of a subset of integral synaptic vesicle proteins thereby regulating the fusion-competence of the recycled vesicle.

Developmental maturation of synaptic vesicle cycling as a distinctive feature of central glutamatergic synapses.

The formation of chemical synapses in the mammalian brain involves complex pre- and postsynaptic differentiation processes. Presynaptically, the progressive accumulation of synaptic vesicles is a hallmark of synapse maturation in the neocortex [J Neurocytol 12 (1983b) 697]. In this study, we analyzed the functional consequences of presynaptic vesicle-pool maturation at central glutamatergic and GABAergic synapses. Using (N-(3-triethylammoniumpropyl)-4-(4-(dibutylamino)styryl)pyridinium dibromide (FM1-43) staining of recycling synaptic vesicles, we demonstrate a pronounced developmental increase in presynaptic vesicle accumulation during differentiation of neocortical neurons in culture. Using electrophysiological methods to study functional synaptic maturation, we found an improved recovery from hypertonic solution-induced depletion. As supported by the FM1-43 staining results, this change is most likely caused by a developmental increase in the number of reserve-pool vesicles. In addition, assuming a rapid reuse of freshly recycled vesicles, a developmental maturation of the endocytosis process may also contribute. The observed presynaptic maturation process occurred selectively at glutamatergic synapses, while GABAergic synapses did not show similar developmental alterations. Furthermore, we used high-frequency stimulation (HFS) of glutamatergic and GABAergic synapses to reveal the physiological consequences of reserve-pool maturation. As expected, recovery from HFS-induced depletion was incomplete at immature glutamatergic synapses and strongly improved during synapse maturation. Again, GABAergic synapses did not show similar developmental changes. Taken together, our study characterizes the functional consequences of a pronounced accumulation of reserve-pool vesicles occurring selectively at glutamatergic synapses.

CD20-Positive peripheral T-cell lymphoma: report of a case after nodular sclerosis Hodgkin's disease and review of the literature.

We present a case of peripheral T-cell lymphoma co-expressing CD3 and CD20, as well as demonstrating T-cell receptor gene rearrangement, in a patient who had been diagnosed with nodular sclerosis Hodgkin's disease 5 years previously. Although 15 cases of CD20-positive T-cell neoplasms have been previously reported in the literature, this is the first report of CD20-positive T-cell lymphoma occurring subsequent to treatment of Hodgkin's disease. The current case affords an opportunity to review the rarely reported expression of CD20 in T-cell neoplasms as well as the relationship between Hodgkin's disease and subsequently occurring non-Hodgkin's lymphomas. In addition, the identification of this case supports the suggestion that the use of CD20 antibodies alone in paraffin sections may lead to an incorrect determination of cell lineage in some cases.

Developmental regulation of subunit composition of extrasynaptic NMDA receptors in neocortical neurones.

NMDA receptors undergo drastic changes in their subunit composition during development of the mammalian neocortex. An increase in the expression of the NR2A subunit correlates with developmental changes in the properties of synaptic NMDA receptors. In this study, we investigated whether these developmental alterations are restricted to synaptic NMDA receptors or whether similar developmental changes also occur at extrasynaptic NMDA receptors. To analyse the properties of extrasynaptic receptors, glutamate-evoked ion currents mediated by extrasynaptic NMDA receptors were isolated by irreversibly blocking synaptic NMDA receptors with MK-801. Whole-cell ion currents mediated by extrasynaptic receptors showed developmental changes in their sensitivity against the NR2B subunit-specific antagonist ifenprodil similar to that of synaptic receptors. In summary, our results strongly suggest that NR2A subunit-containing NMDA receptors increasingly contribute also to extrasynaptic NMDA receptors during in vitro differentiation.

Target-specific factors regulate the formation of glutamatergic transmitter release sites in cultured neocortical neurons.

Synapse formation in the mammalian CNS is thought to involve specific target recognition processes between presynaptic and postsynaptic neurons leading to the establishment of defined neuronal circuits. To study the role of target neuron-specific factors in synaptogenesis, we used cocultures of presynaptic explants and dissociated target neurons from rat neocortex, which enabled us to selectively vary the postsynaptic target neurons. Cocultures containing target neurons that were obtained early during development [embryonic day 16 (E16)] were compared to cocultures containing target neurons that were obtained at a later embryonic stage (E19). Postsynaptic currents (PSCs) were evoked in target neurons by maximal extracellular stimulation in the presynaptic explant. The mean amplitudes of AMPA and NMDA receptor-mediated PSCs were sixfold reduced in E16 target neurons, whereas the mean amplitudes of GABA(A) receptor-mediated PSCs did not differ between E16 and E19 target neurons. This reduction was in part caused by an apparently twofold reduction in mean quantal amplitude, as shown by recording AMPA receptor-mediated miniature PSCs. In addition, a reduced number of glutamatergic release sites in E16 target neurons was revealed by synapsin I immunostaining of dendritic presynaptic terminals. No differences in mean release probability were observed between E16 and E19 target neurons. Thus, the formation of glutamatergic transmitter release sites was strongly influenced by target neuron-specific factors. The formation of functional GABAergic synapses, however, was independent of the type of target neurons, suggesting specific retrograde signaling during the establishment of glutamatergic synapses.

Regulation of kinetic and pharmacological properties of synaptic NMDA receptors depends on presynaptic exocytosis in rat hippocampal neurones.

1. Using whole-cell patch-clamp recordings of NMDA EPSCs from co-cultured rat hippocampal (CA region) neurones, developmental changes in the kinetic and pharmacological properties of synaptic NMDA receptors were investigated. During in vitro differentiation a fast decaying component increasingly contributed to NMDA EPSCs. 2. Extracellular Mg2+ (1 mM) strongly blocked NMDA EPSCs at all stages in culture. Using the NR2B subunit-specific NMDA receptor antagonist ifenprodil (3 microM), we observed a developmental decrease in ifenprodil sensitivity of NMDA EPSCs. This suggests developmental changes in the expression of NMDA receptor subtypes. 3. To transiently block presynaptic exocytosis, we incubated presynaptic explants with tetanus toxin (TeTx) prior to cultivation. In TeTx-pretreated cultures the occurrence of fast decaying components of NMDA EPSCs and the developmental decrease in ifenprodil sensitivity was inhibited. Our results indicate a regulatory role of presynaptic exocytosis in the expression of NMDA receptor subtypes.

Monocytoid B-cell lymphomas: an assessment of diagnostic criteria and a perspective on histogenesis.

To determine which morphologic criteria are most useful in distinguishing reactive from malignant monocytoid B cells (MBCs), we compared 16 monoclonal cases (11 nodal, five extranodal) of monocytoid B-cell lymphoma (MBCL) with 12 cases of various reactive diseases in which MBCs were polyclonal. The results of our study showed that in MBCL the MBC component was the predominant architectural finding and that there was confluence of MBCs in all but one case. In contrast, the MBC component did not predominate in the reactive group (P less than .000001) and focal confluence was seen in only one case. A cytologic comparison showed that in MBCL areas there were more large transformed (prominent nucleolated) MBCs (P = .003), a higher mitotic rate (P = .03), and more nuclear irregularities (P = .007) than were present in the reactive group. In addition, evolution to an aggressive histologic type was found in four cases of MBCL. Our results also revealed concomitant multiple, monoclonal, morphologically distinct populations in other compartments (follicular center cells in seven, mantle cells in five, small lymphocytes in five, and plasma cells in 11). These unique findings can be reconciled by postulating (1) that the simultaneous presence of these diverse cytologic types represents morphologic expressions of a B cell whose population is in different phases of its cell cycle and/or its evolution or (2) that the histogenesis of MBCL is possibly from a nodal pluripotent B-stem cell that can differentiate directly into these various cytologic types.

Use of aspiration cytology and frozen section examination for management of benign and malignant thyroid nodules.

Between January 1980 and December 1988, 161 patients underwent thyroidectomy with intraoperative frozen section consultation after fine-needle aspiration (FNA) of a thyroid nodule. The FNA were insufficient in 15 instances (9%) and in error in 39 (24%). In 15 cases, the incorrect aspiration diagnosis could have led to excessive surgery and in ten cases to delayed therapy if it had been the only guide for therapy. The diagnosis was deferred to permanent section analysis in 30 (19%) frozen sections. Twenty-two errors (14% of cases) were made in the interpretation of frozen section material, and in an additional 15 patients (9%), the diagnosis suggested (but deferred at frozen section) was in error. In one patient, this error could have led to more extensive surgery than necessary; in 21 patients, the frozen section error could have led to undertreatment. When frozen section results were combined with those of FNA, no therapeutically important false-positive diagnoses were made. In five patients, the combination of both FNA and frozen section results would not have identified a carcinoma which, in three cases, was a small occult papillary carcinoma not found in the index nodule.

Hodgkin's disease occurring in monocytoid B-cell clusters.

The authors report three cases of Hodgkin's disease (HD) occurring in monocytoid B-cell (MBC) clusters within lymph nodes, a finding heretofore not published. MBC clusters were found mainly in a perisinusoidal and perifollicular distribution in all three cases. Within some of the MBC clusters of each case, small foci of overt necrosis were evident. Sternberg-Reed cells or their variants were found adjacent to all of these foci, as well as within some MBC clusters that were free of necrosis. These findings suggest that the presence of necrosis within MBC clusters has diagnostic utility. In two cases, evidence of HD was detected only within MBC clusters and nowhere else. In the third case, HD was found primarily within MBC clusters. These observations imply that HD arose within MBC clusters. Minimal involvement of lymph node by HD can occur within MBC clusters and should be recognized as such on the basis of morphologic features. The earlier a diagnosis of HD can be made, the better is the patient's outlook for survival.

Isolated noncompaction of left ventricular myocardium. A study of eight cases.

Isolated noncompaction of left ventricular myocardium is a rare disorder of endomyocardial morphogenesis characterized by numerous, excessively prominent ventricular trabeculations and deep intertrabecular recesses. This study comprised eight cases, including three at necropsy. Ages ranged from 11 months to 22.5 years, with follow-up as long as 5 years. Gross morphological severity ranged from moderately abnormal ventricular trabeculations to profoundly abnormal, loosely compacted trabeculations. Echocardiographic images were diagnostic and corresponded to the morphological appearances at necropsy. The depths of the intertrabecular recesses were assessed by a quantitative echocardiographic X-to-Y ratio and were significantly greater than in normal control subjects (p less than 0.001). Clinical manifestations of the disorder included depressed left ventricular systolic function in five patients, ventricular arrhythmias in five, systemic embolization in three, distinctive facial dysmorphism in three, and familial recurrence in four patients. We conclude that isolated noncompaction of left ventricular myocardium is a rare if not unique disorder with characteristic morphological features that can be identified by two-dimensional echocardiography. The incidence of cardiovascular complications is high. The disorder may be associated with facial dysmorphism and familial recurrence.

Neuropathologic findings after bone marrow transplantation: an autopsy study.

Clinicopathologic records and neuropathologic tissues of 109 patients who underwent necropsy after treatment with bone marrow transplantation (BMT) were examined. Underlying disorders included leukemia (70), aplastic anemia (25), solid tumors (7), lymphoma (5), Hodgkin's disease (1) and Wiskott-Aldrich syndrome (1). There were 34 females and 75 males, ranging in age from 2 to 56 years. Survival after transplantation averaged 3.6 months. The most common findings were cerebrovascular lesions (29), including hematomas, hemorrhagic necrosis, and infarcts. Central nervous system infections comprised the next most common finding, including 10 fungal and four bacterial infections. A recurrence of underlying malignancy for which transplant had been performed occurred in five patients. Leukoencephalopathy of varying severity was found in eight patients, half of whom had received intrathecal chemotherapy and/or cranial radiation. Patients with systemic graft-versus-host disease had a variety of nonspecific neuropathologic findings in the nervous system; however, nearly half (44%) showed no detectable changes. Other nonspecific alterations included hypoxic/ischemic changes, vascular siderocalcinosis, and neuroaxonal spheroids (associated with hemorrhage or necrosis). These findings provide a guide as to likely causes of a neurologic syndrome in a patient who has undergone BMT, and can be compared with neuropathologic findings in other forms of immunosuppression.

Clarifying the role of fine-needle aspiration cytologic evaluation and frozen section examination in the operative management of thyroid cancer.

The final histologic diagnoses of 486 patients who underwent thyroidectomy at UCLA Medical Center from March 1975 to August 1988 were reviewed. There were 146 patients with a diagnosis of thyroid malignant neoplasm. All patients who had preoperative fine-needle aspiration cytologic evaluation, intraoperative frozen section analysis, or both were included in the present study. Carcinoma was diagnosed by frozen section in 87 (69%) of 126 cases. Frozen section analysis was incorrect in 39 (31%) of 126 cases. Fine-needle aspiration was performed in 62 patients. A malignant neoplasm was identified by fine-needle preoperative fine-needle aspiration and intraoperative frozen section analysis, and carcinoma was detected by both methods in 32 (57%) of 56 cases. Fine-needle aspiration cytologic evaluation is extremely valuable in the diagnosis of thyroid cancer and is at least as accurate as frozen section analysis with less morbidity and expense. When fine-needle aspiration demonstrates malignant neoplasm, thyroid resection may be planned with confidence.

Evidence for human immunodeficiency virus (HIV) infection of the brain in a patient with aplastic anemia.

A young female patient with a long history of intravenous drug abuse died after a fulminant course of aplastic anemia. At postmortem examination, she was found to have multinucleate giant cells and immunocytochemical evidence of human immunodeficiency virus (HIV) infection of the central nervous system. This case raises the possibility that HIV infection contributed to the patient's aplastic anemia, and suggests that HIV-associated giant cells might be found retrospectively or prospectively within the brains of patients who die of conditions other than those narrowly defined as acquired immune deficiency syndrome (AIDS) or AIDS-related complex (ARC). It furthermore emphasizes that HIV infection of the nervous system is not necessarily accompanied by clinically apparent neurological disease.