GAD1 (2q31.1), which encodes glutamic acid decarboxylase (GAD67), is associated with childhood-onset schizophrenia and cortical gray matter volume loss

Postmortem brain studies have shown deficits in the cortical gamma-aminobutyric acid (GABA) system in schizophrenic individuals. Expression studies have shown a decrease in the major GABA-synthesizing enzyme (glutamic acid decarboxylase (GAD67) mRNA levels in neurons in dorsolateral prefrontal cortex in schizophrenics relative to controls. In the present study, SNPs in and around the GAD1 gene, which encodes the protein GAD67, were tested on a rare, severely ill group of children and adolescents with childhood-onset schizophrenia (COS) (n=72), in a family-based association analysis. Compared to adult-onset samples, the COS sample has evidence for more salient familial, and perhaps genetic, risk factors for schizophrenia, as well as evidence for frontal cortical hypofunction, and greater decline in cortical gray matter volume on anatomic brain MRI scans during adolescence. We performed family-based TDT and haplotype association analyses of the clinical phenotype, as well as association analyses with endophenotypes using the QTDT program. Three adjacent SNPs in the 5' upstream region of GAD1 showed a positive pairwise association with illness in these families (P=0.022-0.057). Significant transmission distortion of 4-SNP haplotypes was also observed (P=0.003-0.008). Quantitative trait TDT analyses showed an intriguing association between several SNPs and increased rate of frontal gray matter loss. These observations, when taken together with the positive results reported recently in two independent adult-onset schizophrenia pedigree samples, suggest that the gene encoding GAD67 may be a common risk factor for schizophrenia.

The osteodystrophy of mucolipidosis type III and the effects of intravenous pamidronate treatment

Mucolipidosis type III (ML III; McKusick 252600) is a rare lysosomal storage disease in which skeletal involvement is prominent, in particular the destruction of vertebral bodies and the femoral heads. We describe studies in two siblings with ML III that suggest the presence of a distinct metabolic bone disorder. Biochemical indices of bone turnover were increased, and transiliac bone biopsy demonstrated both trabecular osteopenia and marked subperiosteal bone resorption. Intravenous pamidronate treatment given monthly for a year was well tolerated and produced dramatic clinical effects, with reduction in bone pain and improvements in mobility, despite incomplete suppression of bone resorption as assessed by biochemical, radiographic and histological criteria. Bisphosphonate therapy may have an important role in the management of bone pain in ML III, as it does in the related lysosomal disorder of Gaucher disease.

Eikenella corrodens infective endocarditis in a previously healthy non-drug user

Reported here is a case of Eikenella corrodens aortic valve infective endocarditis presenting as a stroke in a previously healthy 31-year-old man. The patient had no evidence of structural heart disease and reported no history of intravenous drug use or recent dental treatment. There are no other cases reported in the available literature in which this microorganism has caused endocarditis in the absence of recognised risk factors.

Socio-demographic and health system factors in relation to exclusive breast-feeding in Tobago

To determine the prevalence and significant correlates of exclusive breast-feeding among nursing mothers, we conducted a survey among nursing mothers attending the Wellness Baby Clinic in Tobago from July 1 to December 1, 1998. A random sample of 151 mothers had face-to-face interviews with a standardized pretested questionnaire. Our results suggest that 48.3% and 20.8% of infants were exclusively breast-fed at two and four months respectively. Univariate logistic regression analyses showed that exclusive breast-feeding at two months was significantly positively associated with years of schooling completed by the mother, frequency of prenatal visits, mode of breast-feeding, mother's knowledge of the recommended duration of breast-feeding, and occupation of the child's father. Exclusive breast-feeding at four months was significantly positively associated with mother's age, years of schooling completed by the mother, frequency of prenatal visits, mother's knowledge of the recommended duration of breast-feeding, years of schooling completed by the child's father and occupation of the child's father. In multivariate logistic analyses, adjusting simultaneously for all relevant explanatory variables, exclusive breast-feeding at two months was significantly positively associated with frequency of prenatal clinic visits, mode of breast-feeding, mother's knowledge of the recommended duration of breast-feeding and occupation of the child's father. In addition, exclusive breast-feeding at four months was significantly positively associated with frequency of prenatal clinic visits, length of hospital stay, mother's knowledge of recommended duration of breast-feeding, years of schooling completed by the child's father, family structure and inversely associated with mother's age. In this sample, parental socio-demographic characteristics and health system factors were associated with subsequent infant feeding practices.

An open-label trial of tomoxetine in pediatric attention deficit hyperactivity disorder

OBJECTIVE

To collect pilot data assessing the safety, tolerability, and efficacy of tomoxetine, a nonstimulant norepinephrine enhancer, in pediatric attention deficit hyperactivity disorder (ADHD).

METHODS

An open-label trial of tomoxetine in pediatric ADHD was conducted as part of a multisite clinical trial. Following a baseline assessment, an ascending dose titration was completed during 10 weekly visits.

RESULTS

Ten subjects were enrolled at baseline, with eight completing the study. Seven of the eight remaining subjects met efficacy criteria. Significant decreases in symptom severity ratings by parents and study investigators were found. The medication was well tolerated, with transient appetite suppression the most frequently reported side effect. However, subjects' weights remained stable across study visits.

DISCUSSION

These preliminary findings suggest that tomoxetine may hold promise as a treatment for pediatric ADHD.

Further modification to soft drinks to minimise erosion. A study in situ

Soft drinks have been successfully modified to reduce enamel erosion. The aim of this study was to further modify an original low erosive blackcurrant drink product by the addition of a gum, to manipulate more favourably other drink parameters. The study was a single-blind, randomised four treatment crossover design involving 12 healthy volunteers. During 10 working-day study periods, subjects wore enamel samples in the mid palatal region of a removable appliance. Specimens were taped to expose a 2-mm enamel window. The drinks under test were: (1) Orange juice, (2) Original blackcurrant drink, (3) Water, and (4) Experimental blackcurrant drink. Drinks were imbibed at 250-ml volumes 4 times a day during appliance wearing from 09.00 to 17.00. Appliances were removed at lunchtime. Measurements of specimens were made at baseline, 2, 5 and 10 days using a profilometer. One 5-day and one 10-day specimen from each subject during each treatment were ultrasonicated. Significant differences, in erosion between drinks, were seen at days 5 and 10. Comparisons of preselected pairs of drinks of interest showed significantly reduced erosion by the two blackcurrant drinks compared to orange juice with no significant differences from water. The original blackcurrant drink produced significantly less erosion than the experimental drink. Ultrasonication removed enamel from the Orange juice specimens but very little from those exposed to water and the two blackcurrant drinks. Extrapolating the effects of both blackcurrant drinks suggested that alone they should not cause significant clinical erosion in a lifetime's intake of 1 litre per day.

Dimensional perspective on the recognition of depressive symptoms in primary care: The Hampshire Depression Project 3

BACKGROUND

Most studies of the recognition of depression in primary care have used a categorical definition of depression. This may overstate the extent of the problem.

AIMS

Our objective was to investigate the relationship between severity and recognition of depression, and its modification by patient and practitioner characteristics.

METHOD

An association study in multiple consecutive adult cohorts of 18 414 primary care consultations drawn from a representative sample of 156 general practitioners in Hampshire, UK.

RESULTS

There was a curvilinear relationship between the severity of depression and practitioners' ratings of depression. One case of probable depression was missed in every 28.6 consultations. Anxiety and unemployment altered the chances of recognition, but age, gender and deprivation scores did not.

CONCLUSIONS

A dimensional approach to severity of depression shows that general practitioners may be better able to recognise depression than previous categorical studies have suggested. Efforts to improve the care of depression should therefore focus on doctors who have been shown to have difficulty making the diagnosis and on improving the treatment of identified patients.

Exploring the use of an alginate dressing for diabetic foot ulcers

Few studies have investigated the use of dressings on patients with diabetic foot ulceration. This paper reports the results of a non-comparative, two-centre study investigating the performance characteristics of SeaSorb dressing in patients with this condition. This was an exploratory study to determine the potential use of this dressing, and not a large randomised control trial. All patients had diabetic foot ulceration of 1 cm or more in diameter, classified as Wagner grade I or II, with an ankle brachial pressure index of > 0.4. The investigators carried out objective assessments including photography and ulcer tracing as well as subjective assessments of exudate levels, wound bed condition, peri-ulcer skin condition, ease of application and removal of the dressing, dressing conformability, discomfort during dressing application and removal, and clinical signs of infection. Investigators recruited 41 patients in two sites (31 in site one and 10 in site two). Of these, the findings relating to 39 patients could be evaluated. The patients were treated for a maximum of six weeks or until the ulcer healed. The study found that 28.2% (11/39) of the ulcers healed within the six-week period. Overall, there was a significant reduction in mean ulcer area from 2.8 cm 2 to 1.02 cm 2 from week 0 to week six. The relative ulcer area showed a significant decrease from 100% to 33%. For patients who experienced ulcer pain (11 patients), its intensity decreased over the six weeks. Severe maceration was not reported for any patient throughout the study. Six patients required treatment for infection. A total of 12 adverse events were reported: seven mild to moderate and five severe. None were directly attributed to the study dressing.

The role of the insulin-like growth factor system in the developing brain

Insulin-like growth factors (IGFs) play a central role in brain growth and development, with IGF-1, its receptors and binding proteins (IGFBPs) being highly expressed, particularly in the olfactory bulb (OB), representing a local paracrine system. A potential role of IGFBPs in transporting and targeting IGFs to their receptors is supported by the finding that abundant IGFBP-2 is associated with cell surface proteoglycans. An OB organ culture system expressing IGF-1 and IGFBPs represents an in vitro injury model. Although IGF-1 is potently antiapoptotic for neurons and oligodendrocytes, marked gliosis and IGFBP-3 expression are seen, similar to in vivo injury responses, where intraventricular injection of IGF-1 postinjury enhances neuronal survival by blocking apoptosis. In contrast, des (1-3) IGF-1, which has low affinity for IGFBPs, is ineffective, supporting a transport or receptor targeting role for local IGFBPs. We conclude that the IGF system plays a crucial cell survival and growth role in the developing and injured brain and that IGFs have significant therapeutic potential.

Council tax valuation band as marker of deprivation and of general practice workload

This study tests the hypothesis that Council Tax Valuation Banding (CTVB) is a measure both of UK socioeconomic status and of general practice workload. It is a retrospective cohort study based in a UK semi-rural general practice, North Wiltshire. The study group is a randomised selection of UK general practice patients. The outcome measures are socio-demographic and primary care workload parameters versus CTVBs by logistic regression analyses in a sample of 378 patients (90% participation rate). People who pay little or no council tax are significantly less likely to live in owner-occupied homes or to have access to a car than their counterparts. There is also a significant inverse association between CTVB and demand for general practitioner services. CTVB could be an accessible, universal, non-census marker of UK socioeconomic status and of general practice workload that would have validity in the context of primary care resource allocation and is a concept worthy of further investigation.

A look to the past, directions for the future

This article represents the history of primary care and behavioral health integration at Group Health Cooperative (GHC) over the last decade, and foreshadows probable futures for this work into the next decade. To build from a logical progression, the article responds to a series of questions: 1. Why integrate primary care and behavioral health? 2. What has been done so far and how well has it worked? 3. Keeping the end in mind, what's the idealized picture of integration for the future? 4. How to get from here to there? What will help or hinder the effort? and 5. Again, why make these efforts to integrate?

Fasting hyperinsulinemia and increased waist-to-hip ratios in non-wasting individuals with AIDS

OBJECTIVE

To identify metabolic and body composition changes associated with HIV-1 infection in a cross-sectional study of individuals stratified by immunologic status and body mass.

DESIGN

Metabolic abnormalities including glucose intolerance and changes in body morphology have recently been described in HIV-1-infected individuals following therapy with protease inhibitor-containing highly active anti-retroviral therapy. Although this is suggestive of a direct drug effect, the possibility that HIV infection may induce a tendency towards such underlying derangements should be considered. HIV-infected patients are heterogeneous with respect to immunologic status and body mass. In examining the underlying effect of HIV-1 on metabolic and body composition parameters, stratification by various immunologic and body mass categories may give divergent results that would not be detected otherwise.

METHODS

Thirty male participants were categorized into four cohorts: non-wasting HIV-seronegative controls, non-wasting HIV-infected patients with relatively intact immune function (CD4 cell count > 500 x 10(6)/l); non-wasting individuals with AIDS (CD4 cell count < 200 x 10(6)/l); and individuals with AIDS wasting.

RESULTS

Increased fasting plasma insulin and waist-to-hip ratios were found specifically in non-wasting individuals with AIDS compared with HIV-negative controls.

CONCLUSIONS

Our study emphasises the importance of both body mass and immune function in studying metabolic and body composition abnormalities associated with HIV-1 infection. The association of increased waist-to-hip ratios and hyperinsulinemia suggestive of insulin resistance in non-wasting individuals with AIDS suggest that the tendency towards these metabolic abnormalities may be related to the HIV infectious process or to factors associated with immunologic dysfunction.

Elevated glutathione biosynthetic capacity in the chloroplasts of transgenic tobacco plants paradoxically causes increased oxidative stress

Glutathione (GSH), a major antioxidant in most aerobic organisms, is perceived to be particularly important in plant chloroplasts because it helps to protect the photosynthetic apparatus from oxidative damage. In transgenic tobacco plants overexpressing a chloroplast-targeted gamma-glutamylcysteine synthetase (gamma-ECS), foliar levels of GSH were raised threefold. Paradoxically, increased GSH biosynthetic capacity in the chloroplast resulted in greatly enhanced oxidative stress, which was manifested as light intensity-dependent chlorosis or necrosis. This phenotype was associated with foliar pools of both GSH and gamma-glutamylcysteine (the immediate precursor to GSH) being in a more oxidized state. Further manipulations of both the content and redox state of the foliar thiol pools were achieved using hybrid transgenic plants with enhanced glutathione synthetase or glutathione reductase activity in addition to elevated levels of gamma-ECS. Given the results of these experiments, we suggest that gamma-ECS-transformed plants suffered continuous oxidative damage caused by a failure of the redox-sensing process in the chloroplast.

Theoretical and experimental investigations of electrostatic effects on acetylcholinesterase catalysis and inhibition

The role of electrostatics in the function of acetylcholinesterase (AChE) has been investigated by both theoretical and experimental approaches. Second-order rate constants (kE = k(cat)/Km) for acetylthiocholine (ATCh) turnover have been measured as a function of ionic strength of the reaction medium for wild-type and mutant AChEs. Also, binding and dissociation rate constants have been measured as a function of ionic strength for the respective charged and neutral transition state analog inhibitors m-(N,N,N-trimethylammonio)trifluoroacetophenone (TMTFA) and m-(t-butyl)trifluoroacetophenone (TBTFA). Linear free-energy correlations between catalytic rate constants and inhibition constants indicate that kE for ATCh turnover is rate limited by terminal binding events. Comparison of binding rate constants for TMTFA and TBTFA attests to the sizable electrostatic discrimination of AChE. Free energy profiles for cationic ligand release from the active sites of wild-type and mutant AChEs have been calculated via a model that utilizes the structure of T. californica AChE, a spherical ligand, and energy terms that account for electrostatic and van der Waals interactions and chemical potential. These calculations indicate that EA and EI complexes are not bound with respect to electrostatic interactions, which obviates the need for a 'back door' for cationic ligand release. Moreover, the computed energy barriers for ligand release give linear free-energy correlations with log(kE) for substrate turnover, which supports the general correctness of the computational model.

Symptom control in patients with hay fever in UK general practice: how well are we doing and is there a need for allergen immunotherapy?

BACKGROUND

Seasonal allergic rhinitis is often regarded as a trivial condition which patients should treat themselves. However, a significant proportion of sufferers are not fully controlled on standard hay fever medication, either because they do not use it properly or because their symptoms are resistant to standard therapy. The latter group may be suitable for allergen immunotherapy, which was once widely available in UK general practice but is now only available through specialist centres.

AIMS

To describe the symptom control of patients with hay fever, to assess concordance with prescribed medication, and to estimate the number of patients who may benefit from referral for allergen immunotherapy.

SETTING

General practices in Hampshire and Dorset, UK.

METHOD

Survey of adult hay fever sufferers prescribed a non-sedating antihistamine and nasal steroid spray by their general practitioner. A postal questionnaire was sent to all eligible patients aged 16-64 registered with 16 general practices. Self-assessment of symptom control and reported compliance with medication were used to identify those patients who were suboptimally controlled and might therefore benefit from immunotherapy.

RESULTS

Eight hundred and forty-six out of 62500 registered patients aged 16-64 (1.4%) were receiving both drugs, and responses were received from 627 (74.1%); 526 of these met the full entry criteria. One hundred and forty-two patients (27.0%) were using both types of drug regularly. Of the 142 patients using optimum pharmacotherapy, 54 (38.0%) reported good control of their hay fever symptoms. The remaining 62.0% experienced troublesome residual symptoms and described symptom control as partial or poor. Among those using suboptimal pharmacotherapy, 181/376 (48.1%) reported good control.

CONCLUSION

Many patients are using treatment inappropriately. Current guidelines need to be applied better but there is also a significant burden of residual symptoms, even among those receiving current optimal therapy. This indicates a need for patients with severe summer hay fever to receive specialist assessment.

Andersen's syndrome: a distinct periodic paralysis

A previous study of 4 patients defined Andersen's syndrome (AS) as a triad of potassium-sensitive periodic paralysis, ventricular dysrhythmias, and dysmorphic features. AS appears to be distinct in terms of its genetic defect from the alpha-subunit of skeletal muscle sodium channel and the cardiac potassium channel responsible for most long QT syndromes (LQT1). We studied 11 additional patients with AS from 5 kindreds. Spontaneous attacks of paralysis were associated with hypokalemia, normokalemia, or hyperkalemia. All 11 patients had similar dysmorphic features. The QT interval was prolonged in all patients although only 4 were symptomatic. Genetic linkage studies excluded linkage to the alpha-subunit of the skeletal muscle sodium channel and to four distinct LQT loci. In addition, none of the common dihydropyridine receptor mutations responsible for hypokalemic periodic paralysis were present. We conclude that (1) AS is a genetically unique channelopathy affecting both cardiac and skeletal membrane excitability, (2) attacks of paralysis may be either hypokalemic or hyperkalemic, (3) a prolonged QT interval is an integral feature of this syndrome, and (4) a prolonged QT interval may be the only sign in an individual from an otherwise typical AS kindred. This may be confused with more common, potentially lethal LQT syndromes.

MR imaging of dedifferentiated chondrosarcoma

MR imaging of a dedifferentiated chondrosarcoma of the humerus is presented and correlated with gross and microscopic histology from the surgical specimen. The classification of chondrosarcoma and specific MR signal characteristics that suggest dedifferentiation are discussed.

Molecular recognition by cholesterol esterase of active site ligands: structure-reactivity effects for inhibition by aryl carbamates and subsequent carbamylenzyme turnover

Interactions of mammalian pancreatic cholesterol esterases from pig and rat with a family of aryl carbamates CnH2n+1NHCOOAr [n = 4-9; Ar = phenyl, p-X-phenyl (X = acetamido, bromo, fluoro, nitro, trifluoromethyl), 2-naphthyl, 2-tetrahydronaphthyl, estronyl] have been investigated, with an aim of delineating the ligand structural features which lead to effective molecular recognition by the active site of the enzyme. These carbamates inhibit the catalytic activity of CEase by rapid carbamylation of the active site, a process that shows saturation kinetics. Subsequent slow decarbamylation usually leads to full restoration of activity, and therefore aryl carbamates are transient inhibitors, or pseudo-substrates, of CEase. Structural variation of carbamate inhibitors allowed molecular recognition in the fatty acid binding and steroid binding loci of the extended active site to be probed, and the electronic nature of the carbamylation transition state to be characterized. Optimal inhibitory activity is observed when the length of the carbamyl function is n = 6 and n = 7 for porcine and rat cholesterol esterases, respectively, equivalent to eight- and nine-carbon fatty acyl chains. In contrast, inhibitory activity increases progressively as the partial molecular volume of the aromatic fragment increases. Hammett plots for p-substituted phenyl-N-hexyl carbamates indicate that the rate-determining step for carbamate inhibition is phenolate anion expulsion. Effects of the bile salt activator taurocholate on the kinetically resolved phases of the pseudo-substrate turnover of aryl carbamates were also studied. Taurocholate increases the affinity of the carbamate for the active site of cholesterol esterase in the reversible, noncovalent complex that precedes carbamylation and increases the rate constants of the serial carbamylation and decarbamylation steps. Structural variation of the N-alkyl chain and of the aryl fused-ring system provides an accounting of bile salt modulation of the fatty acid and steroid binding sites, respectively. In that pseudo-substrate turnover of aryl carbamates proceeds by a three-step mechanism that is analogous to that for rapid turnover of lipid ester substrates, these investigations illuminate details of ligand recognition by the extended active site of cholesterol esterase that are prominent determinants of the substrate specificity and catalytic power of the enzyme.

Resolution of the neutropenia of Felty's syndrome by longterm administration of recombinant granulocyte colony stimulating factor

Felty's syndrome is characterized by neutropenia, splenomegaly, and recurrent infection in patients with rheumatoid arthritis. We used recombinant granulocyte colony stimulating factor (rGCSF) in a patient with Felty's syndrome and recurrent sepsis. rGCSF induced a statistically significant increase in the patient's absolute neutrophil and total white blood cell counts. During 14 months of followup taking rGCSF, disseminated varicella zoster was the only infectious complication. Except mild thrombocytopenia and a transient flare of arthritis, no serious adverse effects occurred. rGCSF may be a safe and effective therapy for Felty's syndrome in selected patients.

Auditory sensory gating, hippocampal volume, and catecholamine metabolism in schizophrenics and their siblings

Schizophrenia may result from the concerted action of several pathophysiological factors. This pilot study compared the distribution of measurements of three such putative factors in 11 schizophrenics and their siblings: a neurophysiological deficit in auditory sensory gating, diminished hippocampal volume, and increased catecholamine metabolism. Abnormal auditory sensory gating was found in all schizophrenics in the 11 families studied and in 8 of their 20 siblings. Compared with the schizophrenics, the clinically unaffected siblings with abnormal auditory gating had larger hippocampal volume. There was no similar difference for the siblings with normal gating. The siblings with abnormal auditory gating also had lower homovanillic acid levels than the other siblings. The data suggest that a familial neuronal deficit, identified by diminished sensory gating, may be a necessary, but not sufficient factor in the pathogenesis of schizophrenia. Individuals with this deficit are generally clinically unaffected, except for schizophrenics, who also have other abnormalities, such as diminished hippocampal volume and increased catecholamine metabolism.

The effects of drug therapy on radiographic progression of rheumatoid arthritis. Results of a 36-week randomized trial comparing methotrexate and auranofin

OBJECTIVE

To determine the effects of drug therapy (methotrexate [MTX] versus auranofin [AUR]) on radiographic progression in patients with active rheumatoid arthritis (RA).

METHODS

We conducted a 9-month randomized, multicenter, double-blind trial comparing MTX and AUR. Standardized radiographs of the hands and wrists were obtained at baseline and at completion of the study. Four experienced bone radiologists graded the radiographs for erosions, joint space narrowing, erosion healing, and reparative bone formation.

RESULTS

Two hundred eighty-one patients were enrolled in the study. Radiographs were available on 167 of the 183 who completed the trial. After 9 months of therapy, there was a significantly greater worsening of the erosion score in the AUR group (mean +/- SEM change of 1.67 +/- 0.4) compared with the change in the MTX group (0.60 +/- 0.3) (P = 0.040). There was also a significantly greater worsening of the joint space narrowing score in the AUR group compared with the MTX group (1.36 +/- 0.3 versus 0.42 +/- 0.2) (P = 0.007). There was no difference demonstrated between groups in healing of erosions or in reparative bone formation.

CONCLUSION

The rate of radiographic progression in patients with RA, as measured by erosion score and joint space narrowing score, was demonstrated to be lower in those treated with MTX, as compared with AUR, over a 36-week period.

Auditory sensory gating and catecholamine metabolism in schizophrenic and normal subjects

Diminished neuronal response to repeated sensory input is a sensory-gating phenomenon that has been found to be deficient in schizophrenic patients. For example, schizophrenic patients fail to decrease the amplitude of the P50 wave of the auditory evoked potential to the second of paired click stimuli. In some studies, however, normal subjects have also failed to decrease their P50 responses. The aim of this study was to determine if accommodation to the recording situation over time would affect the gating of the P50 response. The gating of the P50 wave is measured as the ratio of the amplitude of the second response to the amplitude of the first. Three successive auditory evoked potentials were compiled, each from trains of 32 pairs of stimuli. Twelve normal subjects and 12 schizophrenic patients were studied. Unconjugated catecholamine metabolites were measured from venous samples drawn before and after the electrophysiological recording. Between the first and third trials, the normal subjects significantly increased their gating of P50. This increase in gating of P50 was related to decreased levels of the noradrenergic metabolite 3-methoxy-4-hydroxyphenylglycol. No similar phenomenon was observed in the schizophrenic patients, a number of whom had a further decrease in P50 gating over the three trials. Transient failure to observe gating of P50 in normal subjects may be related to increased state-dependent noradrenergic activity, which is known to disrupt sensory gating. This mechanism does not seem to account for the more persistent failure of sensory gating in schizophrenia.

Musculoskeletal manifestations in beta 2-microglobulin amyloidosis. Case discussion

The cases presented illustrate some of the typical (case 1) and less common (case 2) clinical features of beta 2m amyloidosis. The accumulation of beta 2m amyloid in tissues is a potentially severe complication of dialysis-treated chronic renal failure. Beta 2m amyloidosis has been shown to have distinct clinical, radiologic, and pathologic features. The pathogenesis of this condition is not yet clearly understood, and recommendations for the clinical management of these patients at present are limited to recognition of the disease and symptomatic treatment. Further insights into the biology of this disease should lead to new strategies for prevention and treatment.

Anorexic contribution to increased linoleate mobilization and oxidation in lymphoma-bearing mice

To test for a regulatory defect in adipose triacylglycerol (essential) fatty acid mobilization in lymphoma-bearing mice, free [1-14C]linoleic acid/mouse serum albumin was injected iv into lymphoma-bearing and control mice, adapted to a reversed light cycle, and studied in three dietary states in the dark period. Mean daily food intake decreased in mice with small and large tumor burdens. Plasma free fatty acid (FFA) oxidation rates, which approximate FFA mobilization rates, were estimated by multicompartmental analysis (CONSAM). Oxidation of linoleate to CO2 was reduced significantly (85%) in ad libitum fed as compared to briefly fasted control mice but not in fed vs. fasted mice with large or small tumor burdens. However, plasma FFA oxidation rates to CO2 did not differ in briefly fasted tumor-bearing and pair-fed control mice. When re-fed a 250-mg test meal, briefly fasted mice with small tumors suppressed plasma free linoleic acid oxidation, as did controls. During simulated night, mildly anorexic, tumor-bearing mice with small tumor burdens mobilized essential fatty acids much faster than controls. This could explain body fat loss. The abnormally rapid rates of FFA (free linoleic acid) mobilization at night probably result from anorexia rather than from inability of food to suppress fat mobilization.

Effect of human mammary MX-1 tumor on plasma free fatty acids in fasted and fasted-refed nude mice

We hypothesized that tumor-bearing (TB) nude mice, because they are reported to have no detectable, circulating tumor necrosis factor (TNF)/cachectin, would regulate their plasma free fatty acid (FFA) levels normally when fasted and refed. We compared levels of individual plasma FFA in response to fasting (24 hr) and to refeeding (for 20 hr after fasting) a fat-free, 65% sucrose diet in control, nude mice and in mice bearing 1.3 +/- 0.4 g MX-1 tumors. Total plasma FFA levels were typically high in 24-hr fasted mice [mean concentrations in microM +/- SE (n); controls 515 +/- 63 (6); TB, 625 +/- 63 (6)]. FFA levels were reduced by 65% in each group in response to refeeding. Each major plasma FFA species fell in response to refeeding, except arachidonate, which did not change significantly (fasted vs. fasted-refed concentrations) in either controls or TB mice. In refed mice, the molar FFA ratio of oleate to linoleate rose; however, that of oleate to arachidonate fell markedly. TB nude mice had normal appetites. We conclude that all species of FFA were mobilized from adipose tissue in a normal manner in TB nude mice; therefore, regulation of adipose triacylglycerol fatty acid mobilization (as plasma FFA) by dietary sugar is probably not affected by MX-1 tumor growth in these mice. Our findings are consistent with the hypothesis that nude mice may be unable to secrete TNF/cachectin in response to tumor growth, but they do not establish whether or not endogenous, circulating TNF/cachectin increases FFA mobilization in any TB animal.

Renal epithelium: reversal of cytotoxic damage by addition of anti-thymocyte globulin

A novel in vitro assay of renal epithelium tight junction function was used to assess the efficacy with which rabbit anti-thymocyte globulin (ATG) blocks epithelium damage mediated by lymphokine-activated killer (LAK) cells. It was found that LAK cells lysed renal epithelial cells poorly in standard chromium-release assays but that they caused a rapid, and almost total, reduction in trans-epithelium monolayer resistance, indicating tight junction failure and, hence, loss of tissue function. LAK cell-mediated cytolysis of the sensitive K562 cell line was completely blocked in the presence of ATG at a concentration of 200 micrograms/ml. Addition of ATG at this concentration to damaged renal cell monolayers in the presence of LAK cells allowed the trans-monolayer resistance to recover rapidly to levels approaching the values recorded before initial addition of LAK cells. On this basis it seems likely that the rapid restoration of renal function frequently observed after appropriate "rescue" therapy during episodes of acute rejection may reflect subtle changes in tissue function rather than recovery from widespread graft cell cytolysis.

Evidence of extensive phospholipid fatty acid methylation during the assumed selective methylation of plasma free fatty acids by diazomethane

We compared a conventional method (Method I) for measuring plasma free fatty acid (FFA) concentrations with two more rapid procedures (Method II and Method III). Method I required total lipid extraction, separation of FFA by thin-layer chromatography, methylation, and gas-liquid chromatographic analysis of the fatty acid (FA) methyl esters. Method II was a colorimetric procedure. Method III relied upon diazomethane's presumed ability to selectively methylate FFA even in the presence of FA esters. The three methods were compared using plasma from fasted and from fed nude mice, tumor-bearing mice (MX-1 and ZR-75-1 human mammary carcinomas), and controls. Method II, was less reliable than Method I, but both gave similar mean values for plasma FFA levels in fasted mice. Both Methods I and II also showed similar lowering of plasma FFA levels after feeding previously fasted mice. Method III consistently gave values that were far greater than those obtained using Methods I and II. Moreover, highly significant differences between fasted and fed mice were obscured by direct methylation of plasma FFA with diazomethane (Method III). The excess FA methyl esters formed in Method III were derived from plasma phospholipids, but not from plasma triacylglycerols. After feeding fasted mice, plasma free palmitic acid and oleic acid levels fell (Method I); by contrast, the excess "FFA" formed by methylation of plasma phospholipid FA increased two-fold and fourteen-fold, respectively. Caution is therefore advised in the use of direct methylating agents when measuring total and individual plasma FFA levels.