Professional Jurisdictions and Intraprofessional Identity Dynamics: Doctors of Osteopathic Medicine and the Doctors of General Medicine

Professional jurisdictional boundaries change throughout time due to a myriad of factors such as scientific advances, social changes, or governmental requirements. Research on the negotiation of these jurisdictional changes has primarily focused on the relational dynamics between professions that affect these boundaries. We examine two physician groups that considered jurisdictional changes which were initially antithetical to their core professional identity. The DOs grappled with whether or not to incorporate drug therapy into their practice, and generalist MDs had to decide whether or not to become a specialty. We find that jurisdictional negotiations also occur within a profession, not just between them. We argue that for a profession to pursue a change in scope, members must settle on an interpretation of their professional identity congruent with the potential jurisdictional change.

Advance care planning in Medicare: an early look at the impact of new reimbursement on billing and clinical practice

OBJECTIVE

In this study, we examined the US Medicare programme's (government-funded social insurance for the elderly or disabled) new reimbursement for advance care planning (ACP) that began on 1 January 2016. This single-centre study addressed whether clinicians who have ACP conversations with patients will use the new reimbursement code and if the new reimbursement is successful at motivating clinicians to have more ACP conversations with patients.

METHODS

This is a multimethod study. To gain a general sense of ACP practice and code visibility, we first surveyed 493 clinicians in a large academic medical centre (20% response rate). Then, for more in-depth answers and to illuminate the reasons behind survey findings, we conducted semistructured interviews with 28 physicians.

RESULTS

We found that while clinicians are open to using the reimbursement codes, organisational barriers such as low visibility and documentation make it difficult for clinicians to bill for ACP. Moreover, structural and professional factors have rendered Medicare's ACP reimbursement largely ineffective at motivating healthcare providers to perform more ACP conversations during the first 3 months of this policy.

CONCLUSIONS

It does not appear that Medicare's reimbursement of ACP has made a significant, direct impact on ACP billing or practice during the policy's first 90 days. However, there is a symbolic role that this change can serve, and the policy could have more impact as its existence becomes more widely known. Barriers to ACP that we identify should be addressed directly to expand the use of ACP.

Early embryonic death of glutamate carboxypeptidase II (NAALADase) homozygous mutants

Glutamate carboxypeptidase II (EC 3.4.17.21) catalyzes the hydrolysis (Km = 0.2 microM) of the neuropeptide N-acetylaspartylglutamate to yield N-acetylaspartate and glutamate and also serves as a high-affinity folate hydrolase in the gut, cleaving the polyglutamate chain to permit the absorption of folate. N-acetylaspartylglutamate is an agonist at the mGluR3 metabotropic receptor and a source of extracellular glutamate through hydrolysis by glutamate carboxypeptidase II. Given the important role of glutamate in brain development and function, we were interested in the effects of a null mutation of glutamate carboxypeptidase II that would potentiate the effects of N-acetylaspartylglutamate. The PGK-Neomycin cassette was inserted to delete exons 9 and 10, which we previously demonstrated encode for the zinc ligand domain essential for enzyme activity. Successful germline transmission was obtained from chimeras derived from embryonic stem cells with the targeted mutation of glutamate carboxypeptidase II. Homozygous null mutants did not survive beyond embryonic day 8. Folate supplementation of the heterozygous mothers did not rescue the homozygous embryos. Mice heterozygous for the null mutation appeared grossly normal and expressed both mutated and wild-type mRNA but the activity of glutamate carboxypeptidase II is comparable to the wild-type mice. The results indicate that the expression of glutamate carboxypeptidase II is upregulated when one allele is inactivated and that its activity is essential for early embryogenesis.

The development and validation of the Taiwanese Ethnic Identity Scale (TEIS): a "derived etic" approach

The purpose of this study was to design a multidimensional measure of ethnic identity (EI) that would be appropriate for research on acculturating and modernizing cultural groups. Four qualitative approaches were utilized: in-depth interviews, free-listing exercise, card-sorting technique, and cognitive interviews. Qualitative interviews conducted with Taiwanese American subjects identified ten major domains related to EI. Fifty items were generated from the four qualitative approaches and the psychometric properties of the Taiwanese Ethnic Identity Scale (TEIS) were tested with two samples: 305 Taiwanese American (TA) and 354 Taiwanese (T) women. Factor analysis yielded a 26-item TEIS with six factors. The six factors and the percentage of variance accounted for by each factor were: rituals and traditions (22.8%), language (10.3%), family dynamics/good child (7.1%), parental opinion (6.0%), individualism (4.5%), and collectivism (4.5%). Components of content, construct, and known groups validity were assessed, as well as reliability.

Mapping of brain stem neuronal circuitry active during swallowing

A poorly understood neural circuit in the brain stem controls swallowing. This experiment studied the swallowing circuit in the rat brain stem by means of fos immunocytochemistry. The fos protein is a marker of activated neurons, and under experimental conditions, repetition of a behavior causes the fos protein to be produced in the neurons involved in that behavior. The fos technique has been successfully used to delineate neural circuits involved in reflex glottic closure, cough, and vocalization; however, the technique has not been used to map the swallowing circuit. Nine rats were used in this study. Swallows were evoked in anesthetized rats for 1 hour, then, after a 4-hour delay to allow maximum fos production, the rats were painlessly sacrificed by perfusion. The brain stems were removed and sectioned in the frontal plane, and every fourth section was immunoreacted for fos protein. All sections were examined by light microscopy, and cells positive for fos were marked on drawings of brain stem structures for different levels throughout the brain stem. Control animals underwent sham experiments. After subtraction of the areas of fos labeling seen in controls, all experimental rats showed fos-labeled neurons in very discrete and localized areas, including practically all regions implicated by prior neurophysiology studies of swallowing. The distribution of labeled neurons was more dispersed through the brain stem than current theories of swallowing would suggest. Specifically, recent studies of swallowing control have focused on the nucleus of the solitary tract (NST) and the region surrounding the nucleus ambiguus (periambigual area) just rostral to the obex. These areas contained fos-labeled neurons, but unexpectedly, heavy labeling was found in the same areas caudal to the obex. Areas containing the heaviest labeling were specific subnuclei of the NST and surrounding reticular formation; the periambigual area; and the intermediate reticular zone in the pons and caudal medulla. Interestingly, none of these anatomic structures had uniform fos labeling; this finding suggests that the unlabeled areas are involved in other oromotor behaviors, or that the specific protocol did not activate the full population of swallowing-related neurons. A notable finding of this study is a candidate for the central pattern generator (CPG) of swallowing. Careful lesioning studies in cats strongly suggest that a region in the rostral-medial medulla contains the CPG for swallowing, although the exact location of the CPG was never pinpointed. In the homologous region of the rat brain stem, fos labeling was only found in a small group of neurons within the gigantocellular reticular formation that may be a candidate for the CPG. In summary, correlation with prior physiology experiments suggests that this experiment appears to have delineated many, if not all, of the components of the swallowing circuit for the first time in any mammal. In addition, other areas were found that might also be swallowing-related. One notable example is a small group of fos-labeled cells that may be the CPG for swallowing. Further studies are required to clarify the specific roles of the fos-labeled neurons seen in this study.

Eating disorders in the Far East

OBJECTIVE

To investigate eating disorders (EDs) prevalence rates among Asian populations and identify characteristics that distinguish them from their Western counterparts.

METHOD

Potential references were identified through an English-language literature search using Medline, Psychinfo, Dissertation Abstracts (1966 to 1999) and through extensive manual searching of textbooks, reviews and reference lists.

RESULTS

The majority of studies related to EDs were conducted in Japan and China and a few were conducted in Singapore, Malaysia, Taiwan, and Korea whereas there was none in the Philippines, Laos, Vietnam, Cambodia, Myanmar, Indonesia and Thailand. Prevalence rates in Japan range from 0.025 to 0.030% for anorexia nervosa (AN) and from 1.9 to 2.9% for bulimia nervosa (BN). Community studies in China have found the AN prevalence to be 0.01% and BN rates ranging from 0.5% to 1.3%. These rates are lower than ED rates in the West (particularly the U.S. and Britain). Body dissatisfaction (BD) and dieting rates, however, were similar to those in the West. BD rates ranged from 68% (Taiwan) to 81% (Korea) and dieting rates ranged from 34% (Taiwan) to 68% (Japan). Sociocultural and developmental risk factors were relevant to this population.

CONCLUSIONS

EDs in Asian populations have received little attention because they have been predominantly viewed as associated with Western culture. Classified by many as a "culture-bound syndrome" of the West, they may really be a culture-change syndrome.

Entanglement of guide wires by vena cava filters during central venous catheter insertion: report of three cases and a review of the literature

Since 1993, 14 cases of central line guide wires becoming entangled with vena cava filters have been reported. We present three additional cases and review the 14 cases in the literature. Obtaining a detailed patient history is important in identifying patients with a vena cava filter. A low threshold of suspicion is needed and immediate radiograph obtained. Entangled guide wires required fluoroscopic manipulation and or retrieval of the dislodged filter. Of all reported cases, only one sustained an arrhythmia. With no signs and symptoms, conservative management of the dislodged filter is a viable option.

Central nervous pathway for acupuncture stimulation: localization of processing with functional MR imaging of the brain--preliminary experience

PURPOSE

To characterize the central nervous system (CNS) pathway for acupuncture stimulation in the human brain by using functional magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Functional MR imaging of the whole brain was performed in two groups of nine healthy subjects during four stimulation paradigms: real acupuncture at acupoints ST.36 (on the leg) and LI.4 (on the hand) and control stimulations (minimal acupuncture and superficial pricking on the leg). Stimulations were performed in semirandomized, balanced order nested within two experiments. Psychophysical responses (pain, De-Qi effect [characteristic acupuncture effect of needle-manipulation sensation], anxiety, and unpleasantness) and autonomic responses were assessed. Talairach coordinates-transformed imaging data were averaged for a group analysis.

RESULTS

Acupuncture at LI.4 and ST.36 resulted in significantly higher scores for De-Qi and in substantial bradycardia. Acupuncture at both acupoints resulted in activation of the hypothalamus and nucleus accumbens and deactivation of the rostral part of the anterior cingulate cortex, amygdala formation, and hippocampal complex; control stimulations did not result in such activations and deactivations.

CONCLUSION

Functional MR imaging can demonstrate the CNS pathway for acupuncture stimulation. Acupuncture at ST.36 and LI.4 activates structures of descending antinociceptive pathway and deactivates multiple limbic areas subserving pain association. These findings may shed light on the CNS mechanism of acupuncture analgesia and form a basis for future investigations of endogenous pain modulation circuits in the human brain.

Ca2+-independent myosin II phosphorylation and contraction in chicken embryo fibroblasts

1. Non-muscle contraction is widely believed to be mediated through Ca2+-stimulated myosin II regulatory light chain (LC20) phosphorylation, similar to the contractile regulation of smooth muscle. However, this hypothesis lacks conclusive experimental support. 2. By modulating chicken embryo fibroblast cytosolic Ca2+ concentration ([Ca2+]i), we investigated the putative role of [Ca2+]i in fetal bovine serum (FBS)-stimulated LC20 phosphorylation and force development in these cells. 3. Eliminating the FBS-stimulated rise in [Ca2+]i with the Ca2+ chelator BAPTA only partially inhibited FBS-stimulated LC20 phosphorylation and did not significantly alter the magnitude of FBS-stimulated isometric contraction. 4. Ionomycin (1 microM) produced a larger but shorter lasting rise in [Ca2+]i relative to FBS. However, ionomycin only stimulated a small and transient increase in LC20 phosphorylation and did not cause contraction. 5. We conclude that fibroblasts differ from smooth muscle in that LC20 phosphorylation and contraction are predominantly regulated independently of [Ca2+]i.

A placebo-controlled trial of D-cycloserine added to conventional neuroleptics in patients with schizophrenia

BACKGROUND

In a preliminary dose-finding study, D-cycloserine, a partial agonist at the glycine modulatory site of the glutamatergic N-methyl-D-aspartate (NMDA) receptor, improved negative symptoms and cognitive function when added to conventional neuroleptics at a dose of 50 mg/d.

METHODS

Forty-seven patients with schizophrenia meeting criteria for deficit syndrome were randomized to D-cycloserine, 50 mg/d (n=23) or placebo (n=24) added to their conventional neuroleptic for an 8-week, double-blind trial. Clinical assessments were performed at baseline and at weeks 1, 2, 4, 6, and 8. Serum concentrations of D-cycloserine, relevant amino acids, and homovanillic acid were assayed at baseline and at weeks 4 and 8. A cognitive battery was performed at baseline and at week 8.

RESULTS

Thirty-nine patients completed the 8-week trial. Seven dropouts occurred in the D-cycloserine group and 1 in the placebo group. The mean reduction in negative symptoms with D-cycloserine (23%) was significantly greater than with placebo (7%) as calculated by slopes representing Scale for the Assessment of Negative Symptoms (SANS) total scores. Improvement of negative symptoms was predicted by low neuroleptic dose and low baseline SANS total score. No differences were found in performance on any cognitive test between groups or in changes in any other clinical measure. Clinical response did not correlate significantly with serum amino acid concentrations at baseline or with concentrations of D-cycloserine at weeks 4 and 8.

CONCLUSION

These results support the hypothesis that agents acting at the glycine modulatory site of the NMDA receptor improve primary negative symptoms.

D-serine added to antipsychotics for the treatment of schizophrenia

BACKGROUND

Hypofunction of N-methyl-D-aspartate (NMDA) subtype glutamate receptor has been implicated in the pathophysiology of schizophrenia. D-serine is a full agonist of the glycine site of NMDA receptor, an endogenous cotransmitter enriched in corticolimbic regions and distributed in parallel with NMDA receptor. Supplementation of D-serine may improve the symptoms of schizophrenia.

METHODS

Thirty-one Taiwanese schizophrenic patients enrolled in a 6-week double-blind, placebo-controlled trial of D-serine (30 mg/kg/day), which was added to their stable antipsychotic regimens. Of these, 28 completed the trial. Measures of clinical efficacy, side effects, and serum levels of amino acids and D-serine were determined every other week. Wisconsin Card Sorting Test (WCST) was performed at the beginning and end of the trial.

RESULTS

Patients who received D-serine treatment revealed significant improvements in their positive, negative, and cognitive symptoms as well as some performance in WCST. D-serine levels at week 4 and 6 significantly predicted the improvements. D-serine was well tolerated and no significant side effects were noted.

CONCLUSIONS

The significant improvement with the D-serine further supports the hypothesis of NMDA receptor hypofunction in schizophrenia. Given the effects of D-serine on positive symptoms, a trial of D-serine alone in schizophrenia should be considered.

Glutamatergic neurotransmission involves structural and clinical deficits of schizophrenia

BACKGROUND

Phencyclidine and ketamine induce a syndrome closely resembling schizophrenia due to their blockade of N-methyl-D-aspartate (NMDA) receptor. These findings suggested that some aspects of schizophrenia are associated with decreased NMDA--glutamatergic function. We hypothesized that structural and symptomatic deficits in schizophrenia are related to glutamatergic neurotransmission.

METHODS

We studied the relationships among cerebrospinal fluid (CSF) glutamatergic markers, clinical presentation of schizophrenia, and CT parameters of brain structure in drug-free schizophrenics.

RESULTS

We found no significant differences between patients with schizophrenia and controls in CSF glutamatergic markers. When patients with schizophrenia were considered as a group, significant negative correlations between glutamatergic markers and brain structural measures as well as clinical measures were observed. Cluster analysis reveals a group of lower indices of glutamatergic neurotransmission, and more prominent thought disorder as well as ventricular enlargement, and a group with increased glutamate level.

CONCLUSIONS

The findings support the hypothesis that altered glutamatergic neurotransmission plays a role in the brain structure and the clinical symptoms of schizophrenia.

Markers of glutamatergic neurotransmission and oxidative stress associated with tardive dyskinesia

OBJECTIVE

Tardive dyskinesia is a movement disorder affecting 20%-40% of patients treated chronically with neuroleptic drugs. The dopamine supersensitivity hypothesis cannot account for the time course of tardive dyskinesia or for the persistence of tardive dyskinesia and the associated structural changes after neuroleptics are discontinued. The authors hypothesized that neuroleptics enhance striatal glutamatergic neurotransmission by blocking presynaptic dopamine receptors, which causes neuronal damage as a consequence of oxidative stress.

METHOD

CSF was obtained from 20 patients with schizophrenia, 11 of whom had tardive dyskinesia. Markers for oxidative stress, including superoxide dismutase, lipid hydroperoxide, and protein carbonyl groups, and markers for excitatory neurotransmission, including N-acetylaspartate, N-acetylaspartylglutamate, aspartate, and glutamate, were measured in the CSF specimens. Patients were also rated for tardive dyskinesia symptoms with the Abnormal Involuntary Movement Scale.

RESULTS

Tardive dyskinesia patients had significantly higher concentrations of N-acetylaspartate, N-acetylaspartylglutamate, and aspartate in their CSF than patients without tardive dyskinesia when age and neuroleptic dose were controlled for. The significance of the higher levels of protein-oxidized products associated with tardive dyskinesia did not pass Bonferroni correction, however. Tardive dyskinesia symptoms correlated positively with markers of excitatory neurotransmission and protein carbonyl group and negatively with CSF superoxide dismutase activity.

CONCLUSIONS

These findings suggest that there are elevated levels of oxidative stress and glutamatergic neurotransmission in tardive dyskinesia, both of which may be relevant to the pathophysiology of tardive dyskinesia.

The role of glutamatergic neurotransmission in the pathophysiology of alcoholism

Recent evidence suggests that ethanol abuse produces its diverse effects on the brain to a substantial degree by disrupting the function of the major excitatory neurotransmitter, glutamate. Ethanol, at concentrations associated with behavioral effects in humans, inhibits the N-methyl-D-aspartate (NMDA) receptor, which mediates the post-synaptic excitatory effects of glutamate. Tolerance to ethanol results in up-regulation of the NMDA receptor so that abrupt withdrawal produces a hyperexcitable state that leads to seizures, delerium tremens, and excitotoxic neuronal death. Ethanol's inhibition of the NMDA receptor in the fetal brain likely contributes to the CNS manifestations of fetal alcohol syndrome. Therapeutic strategies aimed at correcting glutamatergic dysregulation in alcoholism need to be explored.

D-cycloserine added to clozapine for patients with schizophrenia

OBJECTIVE

The effects of D-cycloserine added to clozapine were assessed and compared with previous results for D-cycloserine plus conventional neuroleptics.

METHOD

Ten schizophrenic outpatients receiving clozapine entered consecutive 2-week trials of placebo and D-cycloserine at 5, 15, 50, and 250 mg/day. Clinical evaluations were videotaped and scored by a rater blind to the sequence of assessments.

RESULTS

There was a significant dose effect of D-cycloserine on scores on the Scale for the Assessment of Negative Symptoms (SANS); the 50-mg dose produced a mean 21% increase in SANS score. The patients had significantly higher baseline serum glutamate concentrations than the patients receiving typical neuroleptics in the previous trial. Baseline glutamate level and change in glycine level significantly correlated with response of negative symptoms to 50-mg D-cycloserine.

CONCLUSIONS

The improvement of negative symptoms with D-cycloserine previously observed in patients receiving typical neuroleptics did not occur in patients treated with clozapine.

Circulating soluble intercellular adhesion molecule-1 in type C viral hepatitis

BACKGROUND/AIMS

Intercellular adhesion molecule-1 (ICAM-1) is one of the members of the immunoglobulin supergene family; it expresses in response to inflammatory mediators and activation. Circulating soluble ICAM-1 (sICAM-1) levels in acute and chronic viral hepatitis C virus infection were studied.

MATERIALS AND METHODS

Thirty blood samples from 10 patients with acute hepatitis C, and 36 blood samples from 25 patients with chronic hepatitis C were compared with those from 10 healthy volunteers, using the enzyme immunoassay method.

RESULTS

The mean circulating sICAM-1 activities in healthy volunteers was 339 +/- 93 ng/ml. Maximum values of sICAM-1 activities in acute (1394 +/- 502 ng/ml, P = 0.004) and chronic (662 +/- 477 ng/ml, P = 0.047) hepatitis C were increased. Acute hepatitis had a higher maximum circulating sICAM-1 activity than chronic hepatitis (P = 0.009). Longitudinal circulating sICAM-1 activities roughly correlated with the serum aminotransferase (ALT) activities. In acute viral hepatitis C, three patients developed an increase in circulating sICAM-1 activities before the manifestation of abnormal ALT activity. Circulating sICAM-1 activities showed a positive correlation with serum ALT activities (P < 0.001) and serum total bilirubin levels (P = 0.001) and a negative correlation with serum albumin levels (P = 0.01).

CONCLUSIONS

The present study suggested that ICAM-1 plays a role in the hepatocellular injury during viral hepatitis C infection.

Tardive dyskinesia and substrates of energy metabolism in CSF

OBJECTIVE

This study was undertaken to assess the relationships among CSF concentrations of substrates of mitochondrial energy metabolism, neuroleptic medication, and neurological side effects.

METHOD

CSF was obtained from 25 patients with schizophrenia; seven were unmedicated and 11 had tardive dyskinesia. CSF concentrations of four substrates of mitochondrial energy metabolism (Krebs cycle)--alanine, aspartate, lactate, and pyruvate--were determined. Tardive dyskinesia was measured with the Abnormal Involuntary Movement Scale (AIMS), and parkinsonism was measured with the Simpson-Angus Rating Scale.

RESULTS

CSF concentrations of alanine were significantly elevated in the medicated patients when tardive dyskinesia status was controlled for. CSF aspartate concentrations were significantly elevated in patients with tardive dyskinesia when medication status was controlled for and were significantly correlated with total scores on the AIMS.

CONCLUSIONS

These results are consistent with a model linking neuroleptic-induced neurological side effects with impairment of mitochondrial energy metabolism, possibly mediated by inhibition of complex 1 of the electron transport chain.

Abnormal excitatory neurotransmitter metabolism in schizophrenic brains

BACKGROUND

Schizophrenia has been hypothesized to be caused by a hypofunction of glutamatergic neurons. Findings of reduced concentrations of glutamate in the cerebrospinal fluid of patients with schizophrenia and the ability of glutamate-receptor antagonists to cause psychotic symptoms lend support to this hypothesis. N-acetylaspartylglutamate (NAAG), a neuropeptide that is highly concentrated in glutamatergic neurons, antagonizes the effects of glutamate at N-methyl-D-aspartate receptors. Moreover, NAAG is cleaved to glutamate and N-acetylaspartate by a specific peptidase, N-acetyl-alpha-linked acidic dipeptidase (NAALADase). To test the glutamatergic hypothesis of schizophrenia, we studied the NAAG-related glutamatergic variables in postmortem brains from patients with schizophrenia, neuroleptic-treated controls, and normal individuals, with particular emphasis on the prefrontal cortex and hippocampus.

METHOD

Different regions of frozen brain tissue from three different groups (patients with schizophrenia, neuroleptic-treated controls, and normal controls) were assayed to determine levels of NAAG, N-acetylaspartate, NAALADase, and several amino acids, including aspartate and glutamate.

RESULTS

Our study demonstrates alterations in brain levels of aspartate, glutamate, and NAAG and in NAALADase activity. Levels of NAAG were increased and NAALADase activity and glutamate levels were decreased in the schizophrenic brains. Notably, the changes in NAAG level and NAALADase activity in schizophrenic brains were more selective than those for aspartate and glutamate. In neuroleptic-treated control brains, levels of aspartate, glutamate, and glycine were found to be increased.

CONCLUSIONS

The changes in levels of aspartate, glutamate, NAAG, and NAALADase are prominent in the prefrontal and hippocampal regions, where previous neuropathological studies of schizophrenic brains demonstrate consistent changes. These findings support the hypothesis that schizophrenia results from a hypofunction of certain glutamatergic neuronal systems. They also suggest that the therapeutic efficacy of neuroleptics may be related to increased glutamatergic activity.

N-acetylaspartate in neuropsychiatric disorders

N-Acetyl aspartate (NAA) is the second most abundant amino acid in the human brain. NAA is synthesized by L-aspartate N-acetyl transferase or by cleavage from N-acetyl aspartyl glutamate by N-acylated alpha-linked L-amino dipeptidase (NAALADase); and it is catabolized to acetate and aspartate by N-acetyl aspartate amino hydrolase (amino acylase II). NAA is localized primarily to neurons, where it is concentrated in the cytosol. Although NAA is devoid of neurophysiological effects, it serves as an acetyl donor, an initiator of protein synthesis or a carbon transfer source across the mitochondrial membrane. The concentration of NAA in human brain increases 3-fold between midgestation and adulthood. In Canavan's Disease, an autosomal recessive disorder due to a null mutation in amino acylase II, NAA levels in brain are markedly increased and disrupt myelination. NAA levels have been found to be reduced in neurodegenerative disorders, including Alzheimer's Disease and Huntington's Disease. Since endogenous NAA can be readily detected in human brain by magnetic resonance spectroscopy, it is increasingly being exploited as a marker for functional and structural integrity of neurons in an expanding number of disorders.

Dose-finding trial of D-cycloserine added to neuroleptics for negative symptoms in schizophrenia

OBJECTIVE

The authors conducted a dose-finding study of D-cycloserine, a partial agonist at the glycine site of the N-methyl-D-aspartate subtype of the glutamate receptor, added to conventional neuroleptics for schizophrenic patients with prominent negative symptoms.

METHOD

Nine patients with schizophrenia completed consecutive 2-week trials of placebo and four doses of D-cycloserine. Clinical assessments were videotaped and were scored by a rater who was blind to temporal sequence.

RESULTS

D-Cycloserine at a dose of 50 mg/day produced a significant reduction (mean = 21%, SD = 28%) in negative symptoms and significantly improved reaction time as measured by Sternberg's Item Recognition Paradigm, a test mediated in part by prefrontal cortex.

CONCLUSIONS

This preliminary evidence suggests that D-cycloserine may improve negative symptoms and cognitive deficits over a narrow dose range when added to conventional antipsychotic agents.

Neuroleptic malignant syndrome associated with clozapine treatment

Although not universally accepted, evidence exists that clozapine treatment may be associated with neuroleptic malignant syndrome (NMS). To date, 10 cases of NMS associated with the use of clozapine have been reported in the literature. We report two more cases of NMS in patients on clozapine treatment and review the clinical presentations, biochemical features, risk factors, treatment, and rechallenge with neuroleptics in all reported patients who developed NMS while receiving clozapine treatment. An update and critical review of clozapine-induced NMS are also presented. Clozapine treatment can cause NMS similar to that induced by conventional neuroleptics. A history of NMS, existing brain insults, low serum iron concentrations, and being a young male may be risk factors for the development of NMS associated with clozapine treatment. NMS most commonly occurs when clozapine is being used along with other psychotropics. Early recognition of the syndrome and cessation of clozapine when NMS occurs are advised. Supportive care and use of dopamine agonists and dantrolene may be helpful in treating clozapine-associated NMS. These results support the notion that clozapine can cause NMS. However, NMS associated with clozapine treatment is a rare event. When it happens, the clinical presentation, risk factors, and management appear to be similar to those of NMS associated with conventional neuroleptics.

The glutamatergic basis of human alcoholism

OBJECTIVE

Although alcoholism is one of the most common psychiatric diagnoses, understanding of its pathophysiology remains poor. Accumulating evidence suggests that neurophysiological and pathological effects of ethanol are mediated to a considerable extent through the glutamatergic system. This article reviews the evidence of ethanol's effects on glutamatergic transmission and proposes a glutamatergic basis for alcoholism.

METHOD

The information was derived from original research. The authors located more than 100 articles from psychiatry and neuroscience journals that related ethanol to glutamatergic transmission. They critically reviewed the neurobiology of the glutamatergic system in alcoholism and synthesized a unifying glutamatergic theory.

RESULTS

Acute effects of ethanol disrupt glutamatergic neurotransmission by inhibiting the response of the N-methyl-D-aspartate (NMDA) receptor. Prolonged inhibition of the NMDA receptor by ethanol results in development of supersensitivity; acute removal of ethanol causes marked augmentation of activity of postsynaptic neurons, such as those in the noradrenergic system, and, in the extreme, glutamate-induced excitotoxicity. Neurobiological effects of alcoholism, such as intoxication, withdrawal seizures, delirium tremens, Wernicke-Korsakoff syndrome, and fetal alcohol syndrome, can be understood as a spectrum of consequences of ethanol's effect on the glutamatergic system.

CONCLUSIONS

A host of findings support the hypothesis that the unifying mechanism of action of ethanol in interference with glutamatergic neurotransmission, especially through the NMDA receptor. Alcoholism may be considered another member of the expanding family of glutamate-related neuropsychiatric disorders. These insights should increase understanding of the biologic vulnerabilities leading to ethanol abuse and dependence and aid development of more effective pharmacologic interventions.

Abnormal acidic amino acids and N-acetylaspartylglutamate in hereditary canine motoneuron disease

Hereditary canine spinal muscular atrophy (HCSMA) is a lower motor neuron disease found in Brittany Spaniels that shares clinical and pathological features with human amyotrophic lateral sclerosis (ALS). Since acidic excitatory amino acids and the neuropeptide N-acetyl-aspartyl-glutamate (NAAG) are reduced in spinal cord and cerebral cortex in ALS, the levels of these substances were measured in nervous tissue in Brittany Spaniels heterozygous and homozygous for HCSMA. Significant reductions in the levels of endogenous aspartate, glutamate, N-acetylaspartate (NAA), and NAAG were found in the spinal cord in homozygous but not heterozygous HCSMA. In contrast, the activity of N-acetylated-alpha-linked-amino dipeptidase (NAALADase), an enzyme that cleaves NAAG into NAA and Glu, was significantly increased. None of these parameters was affected in the motor cortex or occipital cortex. Since NAA and NAAG are highly concentrated in motoneurons, they may play a role in the pathogenesis of motor neuron disease.

Immunocytochemical distribution of N-acetylaspartylglutamate in the rat forebrain and glutamatergic pathways

N-acetylaspartylglutamate (NAAG) is an acidic dipeptide found in high concentration throughout the rat central nervous system. NAAG has been proposed as a neurotransmitter/modulator in some excitatory glutamatergic pathways where it is released by a Ca(2+)-dependent process with neuronal activity. Previous immunocytochemical studies have revealed few neurons exhibiting NAAG-like immunoreactivity (LI) in the forebrain, especially in putative glutamatergic neurons. In this study, we present a detailed map of NAAG-LI in rat forebrain utilizing a modified fixation technique that markedly enhances sensitivity. NAAG-LI is located in most of the putative glutamatergic pathways in the forebrain including pyramidal neurons in motor and sensory cortices and the hippocampal formation. Co-localization of NAAG-LI to cholinergic systems of the forebrain was quite extensive with the exception of the striatal local circuit neurons. A noteworthy feature of NAAG-LI-positive neuronal groups is that they were often configured in hierarchical relationships. For example, the pyramidal neurons of the motor cortex and the motor neurons of the brainstem and and spinal cord expressed NAAG-LI; also, several inter-related components of the limbic system stained for NAAG-LI. Taken together, these findings indicate that NAAG is a neuropeptide localized to subpopulations of neurons throughout forebrain as well as in brainstem and spinal cord.

Immunocytochemical localization of the N-acetyl-aspartyl-glutamate (NAAG) hydrolyzing enzyme N-acetylated alpha-linked acidic dipeptidase (NAALADase)

N-acetylated alpha-linked acidic dipeptidase (NAALADase) is a membrane bound enzyme that cleaves glutamate from the endogenous neuropeptide N-acetyl-aspartyl-glutamate (NAAG). We report the immunocytochemical localization of NAALADase in rat brain and kidney by using specific anti-NAALADase antiserum. NAALADase-immunoreactivity (NAALADase-IR) was widely distributed, abundant in neuropil, absent from neuronal cytoplasm, and displayed regional heterogeneity. Staining was selectively enriched in several structures previously reported to contain NAAG-immunoreactivity (NAAG-IR) including the amygdala, caudate-putamen, central gray, dorsal raphe, globus pallidus, hippocampus, hypothalamus, locus coerulus, medial and lateral geniculate, olfactory bulb, periaqueductal gray, solitary nucleus, spinal trigeminal nucleus, substantia nigra, superior colliculus, and thalamus. Staining within these structures was enriched in neuropil; no intracellular staining was detected, even after colchicine treatment. In addition, NAALADase-IR was observed in some NAAG-containing fiber tracts including the corpus callosum, fornix, habenular commissure, solitary tract, stria medularis, and stria terminalis. The co-localization of NAALADase-IR and NAAG-IR support the hypothesis that NAALADase is responsible for the catabolism of NAAG in vivo. NAALADase-IR was also detected in brain regions that, to date, have not revealed NAAG-IR, including the bed nucleus of the stria terminalis and the median eminence. In addition, NAALADase-IR was detected in the rat kidney cortex, specifically in the brush border of the proximal convoluted tubules. The observation that NAALADase-IR was more widespread than NAAG-IR suggests that NAALADase may also be involved in the catabolism of other structurally related neural and renal peptides.

Rat brain N-acetylated alpha-linked acidic dipeptidase activity. Purification and immunologic characterization

N-Acetylated alpha-linked acidic dipeptidase (NAALA dipeptidase) is a membrane-bound metallopeptidase that cleaves glutamate from the endogenous neuropeptide N-acetyl-L-aspartyl-L-glutamate. In this report, we have solubilized NAALA dipeptidase activity from synaptosomal membranes with Triton X-100 and purified it to apparent homogeneity by sequential column chromatography on DEAE-Sepharose, CM-Sepharose, and lentil lectin-Sepharose. This procedure resulted in a 720-fold purification with 1.6% yield. The purified ezyme migrated as a single silver-stained band on a sodium dodecyl sulfate gel with an apparent molecular weight of 94 kDa. Using an enzymatic stain to visualize NAALA dipeptidase activity within a gel matrix, we have confirmed that the 94-kDa band is, indeed, NAALA dipeptidase. The purified enzyme was characterized and found to be pharmacologically similar to NAALA dipeptidase activity described previously in synaptosomal membrane extracts. Using the purified NAALA dipeptidase as antigen, we have raised specific and high titer polyclonal antibodies in guinea pig. Immunocytochemical studies show intense NAALA dipeptidase immunoreactivity in the cerebellar and renal cortices.

Abnormal excitatory amino acid metabolism in amyotrophic lateral sclerosis

Recently, the excitatory amino acid neurotransmitter glutamate was implicated in the pathogenesis of a variety of chronic degenerative neurological diseases in humans and animals. This report describes abnormalities in excitatory amino acids in the central nervous system of 18 patients with amyotrophic lateral sclerosis (ALS). The concentration of the excitatory amino acids glutamate and aspartate in the cerebrospinal fluid were increased significantly (p less than 0.01) by 100 to 200% in patients with ALS. Similarly, the concentrations of the excitatory neuropeptide N-acetyl-aspartyl glutamate and its metabolite, N-acetyl-aspartate, were elevated twofold to threefold in the cerebrospinal fluid from the patients. There was no relationship between amino acid concentrations and duration of disease, clinical impairment, or patient age. In the ventral horns of the cervical region of the spinal cord, the level of N-acetyl-aspartyl glutamate and N-acetyl-aspartate was decreased by 60% (p less than 0.05) and 40% (p less than 0.05), respectively, in 8 patients with ALS. Choline acetyltransferase activity was also diminished by 35% in the ventral horn consistent with motor neuron loss. We conclude that excitatory amino acid metabolism is altered in patients with ALS. Based on neurodegenerative disease models, these changes may play a role in motor neuron loss in ALS.

Selective release of N-acetylaspartylglutamate from rat optic nerve terminals in vivo

Glutamate (Glu) and aspartate (Asp) are considered to be the neurotransmitters of the optic pathway in submammalian species, but their roles in mammals is uncertain. Recently, N-acetylaspartylglutamate (NAAG) has been proposed as a neurotransmitter in mammalian optic pathway; however, the release of endogenous NAAG on stimulation of the optic pathway has not been demonstrated. Using an in vivo microdialysis technique, we now report that electrical stimulation of rat optic nerve markedly increased the extracellular concentration of NAAG but not Glu/Asp in superficial superior colliculus where retinal afferents terminate, whereas non-specific stimulation of neurotransmitter release by high potassium or veratridine increased both extracellular Glu/Asp and NAAG concentration in the perfusate. The release of NAAG was dependent on Ca2+ and the presence of optic terminals. We conclude that NAAG is a better candidate as a neurotransmitter of rat optic nerve terminals than Glu/Asp.

The effects of N-acetylated alpha-linked acidic dipeptidase (NAALADase) inhibitors on [3H]NAAG catabolism in vivo

N-Acetylated, alpha-linked acidic dipeptidase (NAALADase) is a chloride-activated, membrane bound, metallopeptidase that cleaves the endogenous neuropeptide N-acetyl-aspartyl-glutamate (NAAG) in vitro. To determine whether NAALADase is the catabolic enzyme of NAAG in vivo, we have examined the effects on [3H]NAAG metabolism of intrastriatal co-injections of agents that affect NAALADase activity in vitro. Co-injections of NAALADase inhibitors, such as quisqualate (Quis), phosphate, dithiothreitol and EGTA were found to prolong the t1/2 of [3H]NAAG, whereas cobalt, a NAALADase activity stimulator, accelerated [3H]NAAG catabolism. These results are consistent with a role for NAALADase in the extracellular disposition of endogenous NAAG.

[The influence of truncal vagotomy or surgical sympathectomy on the pancreatic trophic effect of trypsin inhibitor upon normal rats and major pancreatectomized rats]

The influences of truncal vagotomy or surgical sympathectomy on the pancreatic trophic effect of oral administration of synthetic trypsin inhibitor (FOY-305) were examined upon normal rats and 85% major pancreatectomized rats. On normal rats, oral administration of trypsin inhibitor increased pancreatic weight, DNA content RNA content, protein content, pancreatic weight/DNA, RNA/DNA and protein/DNA. This pancreatic trophic effect seemed to be consisted of hyperplasia and hypertrophy of pancreatic acinar cell. Under truncal vagotomy or surgical sympathectomy, this trophic effect was not diminished. On major pancreatectomized rats, oral administration of trypsin inhibitor also caused pancreatic trophic action, consisted of hyperplasia mainly. And truncal vagotomy or surgical sympathectomy did not decrease this action. These results suggested that oral administration of trypsin inhibitor might be a beneficial method for functional recovery of remnant pancreas after major pancreatectomy even under the denervated state.

Calcium-dependent evoked release of N-[3H]acetylaspartylglutamate from the optic pathway

N-Acetylaspartylglutamate (NAAG) is a neuropeptide localized to several putative glutamatergic neuronal systems, including the rodent optic pathway. To determine whether the peptide is released by depolarization, the superior colliculus of the rat was perfused with 2 microCi of [3H]NAAG, then with Krebs-bicarbonate buffer for 1 h, using a microdialysis system. Subsequently, 10-min fractions were collected and analyzed by HPLC for [3H]NAAG. Addition of 100 microM veratridine resulted in a several-fold increase in the evoked release of [3H]NAAG that was virtually abolished by coperfusion with Ca2+-free Krebs buffer containing 1 mM EGTA. When [3H]glutamate was used as the precursor, veratridine depolarization resulted in only an 80% increase in the release of [3H]NAAG. Prior enucleation of the right eye reduced the spontaneous release of [3H]NAAG by 50%, and the veratridine-evoked release by greater than 85%, from the left superior colliculus. These results suggest that NAAG is released upon depolarization and may serve as a neurotransmitter/neuromodulator in the optic tract.