Expression of GABAA α2-, β1- and ε-receptors are altered significantly in the lateral cerebellum of subjects with schizophrenia, major depression and bipolar disorder

There is abundant evidence that dysfunction of the γ-aminobutyric acid (GABA)ergic signaling system is implicated in the pathology of schizophrenia and mood disorders. Less is known about the alterations in protein expression of GABA receptor subunits in brains of subjects with schizophrenia and mood disorders. We have previously demonstrated reduced expression of GABA(B) receptor subunits 1 and 2 (GABBR1 and GABBR2) in the lateral cerebella of subjects with schizophrenia, bipolar disorder and major depressive disorder. In the current study, we have expanded these studies to examine the mRNA and protein expression of 12 GABA(A) subunit proteins (α1, α2, α3, α5, α6, β1, β2, β3, δ, ε, γ2 and γ3) in the lateral cerebella from the same set of subjects with schizophrenia (N=9-15), bipolar disorder (N=10-15) and major depression (N=12-15) versus healthy controls (N=10-15). We found significant group effects for protein levels of the α2-, β1- and ε-subunits across treatment groups. We also found a significant group effect for mRNA levels of the α1-subunit across treatment groups. New avenues for treatment, such as the use of neurosteroids to promote GABA modulation, could potentially ameliorate GABAergic dysfunction in these disorders.

Glial fibrillary acidic protein is elevated in superior frontal, parietal and cerebellar cortices of autistic subjects

Autism is a debilitating neurodevelopmental disorder of early childhood with both genetic and environmental origins. Immune system dysregulation has been hypothesized to be involved in this disorder. We quantified levels of glial fibrillary acidic protein (GFAP) and ss-actin in three areas of the brain, namely, area 9, area 40 and cerebellum, in age matched autistic and control postmortem specimen using SDS-PAGE and western blotting techniques. Significant elevations in levels of GFAP were observed in all three brain areas in autism. This report confirms a recent report showing microglial and astroglial activation in autism. Increased GFAP levels in autistic brains signify gliosis, reactive injury, and perturbed neuronal migration processes.

Prenatal viral infection in mouse causes differential expression of genes in brains of mouse progeny: a potential animal model for schizophrenia and autism

Schizophrenia and autism are neurodevelopmental disorders with genetic and environmental etiologies. Prenatal viral infection has been associated with both disorders. We investigated the effects of prenatal viral infection on gene regulation in offspring of Balb-c mice using microarray technology. The results showed significant upregulation of 21 genes and downregulation of 18 genes in the affected neonatal brain homogenates spanning gene families affecting cell structure and function, namely, cytosolic chaperone system, HSC70, Bicaudal D, aquaporin 4, carbonic anhydrase 3, glycine receptor, norepinephrine transporter, and myelin basic protein. We also verified the results using QPCR measurements of selected mRNA species. These results show for the first time that prenatal human influenza viral infection on day 9 of pregnancy leads to alterations in a subset of genes in brains of exposed offspring, potentially leading to permanent changes in brain structure and function.

Reelin glycoprotein: structure, biology and roles in health and disease

Reelin glycoprotein is a secretory serine protease with dual roles in mammalian brain: embryologically, it guides neurons and radial glial cells to their corrected positions in the developing brain; in adult brain, Reelin is involved in a signaling pathway which underlies neurotransmission, memory formation and synaptic plasticity. Disruption of Reelin signaling pathway by mutations and selective hypermethylation of the Reln gene promoter or following various pre- or postnatal insults may lead to cognitive deficits present in neuropsychiatric disorders like autism or schizophrenia.

Human influenza viral infection in utero alters glial fibrillary acidic protein immunoreactivity in the developing brains of neonatal mice

Epidemiological reports describe a strong association between prenatal human influenza viral infection and later development of schizophrenia. Postmodern human brain studies, however, indicate a lack of gliosis in schizophrenic brains presumably secondary to absence of glial cells during the second trimester viral infection in utero. We hypothesized that human influenza infection in day 9 pregnant mice would alter the expression of glial fibrillary acidic protein (GFAP, an important marker of gliosis, neuron migration, and reactive injury) in developing brains of postnatal days 0, 14 and 35 mice. Determination of cellular GFAP immunoreactivity (IR) expressed as cell density in cortex and hippocampus of control and experimental brains showed increases in GFAP-positive density in exposed cortical (P = 0.03 day 14 vs control) and hippocampal cells (P = 0.035 day 14, P = 0.034 day 35). Similarly, ependymal cell layer GFAP-IR cell counts showed increases with increasing brain age from day 0, to days 14 and 35 in infected groups (P = 0.037, day 14) vs controls. The GFAP-positive cells in prenatally exposed brains showed 'hypertrophy' and more stellate morphology. These results implicate a significant role of prenatal human influenza viral infection on subsequent gliosis, which persists throughout brain development in mice from birth to adolescence.

Dysregulation of Reelin and Bcl-2 proteins in autistic cerebellum

Autism is a severe neurodevelopmental disorder with potential genetic and environmental causes. Cerebellar pathology including Purkinje cell atrophy has been demonstrated previously. We hypothesized that cell migration and apoptotic mechanisms may account for observed Purkinje cell abnormalities. Reelin is an important secretory glycoprotein responsible for normal layering of the brain. Bcl-2 is a regulatory protein responsible for control of programmed cell death in the brain. Autistic and normal control cerebellar corteces matched for age, sex, and post-mortem interval (PMI) were prepared for SDS-gel electrophoresis and Western blotting using specific anti-Reelin and anti-Bcl-2 antibodies. Quantification of Reelin bands showed 43%, 44%, and 44% reductions in autistic cerebellum (mean optical density +/- SD per 30 microg protein 4.05 +/- 4.0, 1.98 +/- 2.0, 13.88 +/- 11.9 for 410 kDa, 330 kDa, and 180 kDa bands, respectively; N = 5) compared with controls (mean optical density +/- SD per 30 microg protein, 7.1 +/- 1.6, 3.5 +/- 1.0, 24.7 +/- 5.0; N = 8, p < 0.0402 for 180 kDa band). Quantification of Bcl-2 levels showed a 34% to 51% reduction in autistic cerebellum (M +/- SD per 75 microg protein 0.29 +/- 0.08; N = 5) compared with controls (M +/- SD per 75 microg protein 0.59 +/- 0.31; N = 8, p < 0.0451). Measurement of beta-actin (M +/- SD for controls 7.3 +/- 2.9; for autistics 6.77 +/- 0.66) in the same homogenates did not differ significantly between groups. These results demonstrate for the first time that dysregulation of Reelin and Bcl-2 may be responsible for some of the brain structural and behavioral abnormalities observed in autism.

Altered levels of Reelin and its isoforms in schizophrenia and mood disorders

Reelin is a secreted extracellular matrix protein approximately 410 kDa mol. wt that is reduced in brains of patients with schizophrenia, autism, bipolar disorder and major depression. Recent reports also indicate its near absence in sera of some patients with an autosomal recessive form of lissencephaly. Moreover, Reelin is involved not only in normal cortical lamination of the brain during mammalian embryogenesis but is also implicated in cell signaling systems subserving cognition in adult brain. Here, we show that blood levels of Reelin and its isoforms are altered in three psychiatric disorders, namely, schizophrenia, bipolar disorder and major depression. The changes include significant increases in 410 kDa Reelin moiety of 49% in schizophrenic patients (p < 0.022) of four ethnic compositions (Caucasian, Vietnamese, Hmong and Laotian) and non-significant increases in depressed patients by 34% vs control blood. In contrast, 410 kDa Reelin levels decreased by 33% in bipolar blood, albeit non-signficantly, vs. controls. There was a significant increase of 90% (p < 0.0061) in 330 kDa Reelin in Caucasian schizophrenics; the depressed value was elevated by 30% vs. control but non-significantly. Again, in contrast, bipolar 330 kDa value decreased by 31% vs control (p < 0.0480). Finally, all 180 kDa Reelin values varied minimally in schizophrenics vs controls. In contrast, the 180 kDa Reelin values dropped significantly by 49% (p < 0.0117) and 29% (p < 0.0424) in bipolar and depressed patients, respectively, compared with controls. The alterations in blood Reelin values appear to be specific since levels of two other blood proteins, ceruloplasmin and albumin did not vary significantly between all psychiatric subjects and controls. These findings suggest that blood Reelin levels and its isoforms may be used as potential peripheral markers to diagnose presence of several psychiatric disorders and may also serve as targets for future therapeutic interventions.

Altered levels of the synaptosomal associated protein SNAP-25 in hippocampus of subjects with mood disorders and schizophrenia

SNAP-25 levels were measured in ventral hippocampus in subjects with unipolar depression (n = 12), bipolar disorder (n = 13), schizophrenia (n = 15) and controls (n = 15) using quantitative immunocytochemistry. SNAP-25 levels were reduced significantly in stratum oriens of bipolar patients compared with controls (p < 0.05); they were also reduced significantly in st. oriens (p < 0.01 vs schizophrenia), in alveous (p < 0.01 vs schizophrenia) and in presubiculum (p < 0.05 vs depressed). SNAP-25 levels were also reduced in several layers of schizophrenics, only significantly so in st. granulosum (p < 0.05 vs controls). In contrast, depressed SNAP-25 levels increased in st. moleculare (p < 0.01 vs schizophrenics) and presubiculum (p < 0.05 vs controls and bipolars; p < 0.01 vs schizophrenics). SNAP-25 values were not affected by age, sex, race, post-mortem interval, brain pH, side of brain, age of onset of disease, family history of psychiatric disease, drug or alcohol use, antipsychotic drug treatment, or mode of death. The reported changes in SNAP-25 levels appear to be disease specific, separating synaptic pathology in unipolar depression from that observed in schizophrenia and bipolar disorders.

Reduction in anti-apoptotic protein Bcl-2 in autistic cerebellum

Autism is a neurodevelopmental disorder with genetic and environmental etiologies. Neurohistologic findings have shown Purkinje cell depletion and atrophy in the cerebellum of autistic subjects. We hypothesized that apoptotic mechanisms might explain these Purkinje cell findings. Bcl-2 is a potent anti-apoptotic regulatory protein, which is reduced in schizophrenic brains. Autistic and normal control cerebellar cortices matched for age, sex and PMI were prepared for SDS-gel electrophoresis and Western blotting using specific anti-Bcl-2 antibodies. Quantification of Bcl-2 showed a significant 34-51% reduction in autistic cerebellum (mean (+/- s.d.) optical density/75 microg protein 0.290 +/- 0.08, n = 5) compared with controls (0.595 +/- 0.31, n = 8; p < 0.04); levels of neuronal-specific class III beta-tubulin (controls 49.8 +/- 6.7; autistics 36.2 +/- 18.2), or beta-actin (controls 7.3 +/- 2.7; autistics 6.77 +/- 0.66) in the same homogenates did not differ significantly between groups. These results indicate for the first time that autistic cerebellum may be vulnerable to pro-apoptotic stimuli and to neuronal atrophy as a consequence of decreased Bcl-2 levels.

Reduction in Reelin immunoreactivity in hippocampus of subjects with schizophrenia, bipolar disorder and major depression

Accumulation of neurobiological knowledge points to neurodevelopmental origins for certain psychotic and mood disorders. Recent landmark postmortem reports implicate Reelin, a secretory glycoprotein responsible for normal lamination of brain, in the pathology of schizophrenia and bipolar disorders. We employed quantitative immunocytochemistry to measure levels of Reelin protein in various compartments of hippocampal formation in subjects diagnosed with schizophrenia, bipolar disorder and major depression compared to normal controls. Significant reductions were observed in Reelin-positive adjusted cell densities in the dentate molecular layer (ANOVA, P < 0.001), CA4 area (ANOVA, P < 0.001), total hippocampal area (ANOVA, P < 0.038) and in Reelin-positive cell counts in CA4 (ANOVA, P < 0.042) of schizophrenics vs controls. Adjusted Reelin-positive cell densities were also reduced in CA4 areas of subjects with bipolar disorder (ANOVA, P < 0.001) and nonsignificantly in those with major depression. CA4 areas were also significantly reduced in schizophrenic (ANOVA, P < 0.009) patients. No significant effects of confounding variables were found. The exception was that family history of psychiatric illness correlated strongly with Reelin reductions in several areas of hippocampus (CA4, adjusted cell density, F = 13.77, P = 0.001). We present new immunocytochemical evidence showing reductions in Reelin expression in hippocampus of subjects with schizophrenia, bipolar disorder and major depression and confirm recent reports documenting a similar deficit involving Reelin expression in brains of subjects with schizophrenia and bipolar disorder.

Prenatal viral infection causes alterations in nNOS expression in developing mouse brains

Epidemiological evidence points to prenatal viral infection being responsible for some forms of schizophrenia and autism. We hypothesized that prenatal human influenza viral infection in day 9 pregnant mice may cause changes in the levels of neuronal nitric oxide synthase (nNOS), an important molecule involved in synaptogenesis and excitotoxicity, in neonatal brains. Brains from 35- and 56-day-old mice were prepared for SDS-gel electrophoresis and Western blotting using polyclonal anti nNOS antibody. Quantification of nNOS showed time and region-dependent changes in the levels of nNOS protein. Mean rostral brain area value from prenatally infected animals showed a significant (p=0.067) increase of 147% in nNOS levels at 35 days postnatally, with an eventual 29% decrease on day 56. Middle and caudal brain areas showed reductions in nNOS in experimental mice at 35 and 56 days, with a significant 27% decrease in nNOS in the middle segment of day 56 brains (p=0.016). Significant interactions were found between group membership and brain area (Wilks lambda=0.440, F(2.9)=5.72, p=0.025); there was also a significant interaction between brain area, group and age (Wilks lambda=0.437, F(2.9)=5.79, p=0.024). These results provide further support for the notion that prenatal viral infection affects brain development adversely via the pathological involvement of nNOS expression.

Venlafaxine and bupropion combination therapy in a case of treatment-resistant depression

OBJECTIVE

To report the therapeutic efficacy of venlafaxine and bupropion in a patient with treatment-refractory major depression.

CASE SUMMARY

A 21-year-old white woman with chronic and recurrent major depression presented with lack of response to several antidepressants. On examination, the patient exhibited neurovegetative signs of depression, guilt feelings, and suicidal ideation. The patient was administered venlafaxine 75 mg three times daily. The dose was titrated to 150 mg three times daily over the next month. Later bupropion was instituted up to 100 mg three times daily over a four-month period. The patient responded favorably to combination therapy and has remained free of depression for approximately 23 months.

DISCUSSION

Venlafaxine and bupropion are antidepressant agents with unique pharmacologic profiles, each effective in the treatment of depression. Recent data indicate that combinations of selective serotonin-reuptake inhibitors and bupropion can convert partial response to full response in patients with treatment-resistant depression. We considered whether a combination of venlafaxine and bupropion would reduce the depressive symptoms of a patient who was unresponsive to various classes of psychotropic agents. Gradual administration of venlafaxine and bupropion acted synergistically to significantly reduce depressive symptoms (p < 0.002) and significantly increase social function (p < 0.002) over a period of eight months.

CONCLUSIONS

To our knowledge this is the first report of successful combination therapy with venlafaxine and bupropion in treatment of chronic recurrent and refractory major depression.

Defective corticogenesis and reduction in Reelin immunoreactivity in cortex and hippocampus of prenatally infected neonatal mice

Recent reports indicate an association between second trimester human influenza viral infection and later development of schizophrenia. Postmortem human brain studies also provide evidence for reduction in Reelin mRNA (an important secretory protein responsible for normal lamination of the brain) in schizophrenic brains. We hypothesized that human influenza infection in day 9 pregnant mice would alter the expression of reelin in day 0 neonatal brains. Prenatally-infected murine brains from postnatal day 0 showed significant reductions in reelin-positive cell counts in layer I of neocortex and other cortical and hippocampal layers when compared to controls. Whereas layer I Cajal-Retzius cells produced significantly less Reelin in infected animals, the same cells showed normal production of calretinin and nNOS when compared to control brains. Moreover, prenatal viral infection caused decreases in neocortical and hippocampal thickness. These results implicate a potential role of prenatal viral infection in causation of neuronal migration abnormalities via reduction in Reelin production in neonatal brains.

Fluoxetine in treatment of adolescent patients with autism: a longitudinal open trial

Retrospective chart reviews of seven adolescent and young adults with autistic disorder treated with fluoxetine alone or in combination with other medications were performed. Patient's ages varied from 9-20 years (M +/- SD, = 16 +/- 3.87). Fluoxetine doses ranged from 20-80 mg per day (M +/- SD of final doses 37.14 +/- 21). Duration of treatment ranged from 1.3-32 months (M 18.04 +/- 10.39). Patients' symptoms were monitored using the Aberrant Behavior Checklist (ABC) rating scale during every visit. Side effects included initial appetite suppression, vivid dreams, and hyperactivity. Improvement from baseline was seen in four subscales: irritability (21%), lethargy (37%), stereotype (27%), and inappropriate speech (21%). Lethargy subscales improved significantly during treatment (p < .029). Hyperactivity subscale increased by 14% but did not attain statistical significance. Fluoxetine appears to have important behavioral effects in treatment of clinic-referred autistic children. Future double-blind placebo controlled studies evaluating core and associated symptom response with fluoxetine are warranted.

Differential expression of synaptosome-associated protein 25 kDa [SNAP-25] in hippocampi of neonatal mice following exposure to human influenza virus in utero

We investigated the role of maternal exposure to human influenza virus [HI] in C57BL/6 mice on day 9 of pregnancy on the hippocampal expression of SNAP-25 in postnatal day 0 neonates, and compared them to sham-infected pups. The expression of SNAP-25 in infected neonates varied along the septotemporal axis of hippocampus and in various anatomic layers. Quantitative densitometric analysis of specific immunogold silver-enhanced SNAP-25 immunoreactivity [IR] showed increases of 40-347% over control in all septal-dorsal hippocampal layers except for the subplate layer. In mid septo-temporal hippocampus, SNAP-25 IR increased by 10-114% over control in all layers, except for the hippocampal plate, but the extent of this increase was smaller than in the dorsal-septal area. Finally,in temporal-ventral levels, SNAP-25 expression was reduced in all infected layers by 21-33% below control except for mild increases of 8.8 and 10% in subplate and hippocampal plate layers. Additionally, the infected SNAP-25 maximal density bin shifted to lower values dorsally and to higher values medially, with ventral maximal bins remaining unchanged when compared to controls. The differential expression of SNAP-25 in the hippocampi of infected neonates indicates a variable degree of vulnerability across the septo-temporal axis of hippocampus. It is surmised that while viral infection may induce excitotoxicity in the ventral hippocampus, it may cause reactive synapto-genesis in the medial and dorsal sectors of the developing brains of postnatal day 0 neonates.

Human influenza viral infection in utero increases nNOS expression in hippocampi of neonatal mice

We investigated the role of maternal exposure to human influenza virus (HI) in C57BL/6 mice on day 9 of pregnancy on hippocampal expression of nNOS in day 0 neonates and compared that to sham-infected pups. Qualitative analysis using polyclonal antibody to nNOS showed overall increases in immunoreactivity (IR) in hippocampal and dentate layers of day 0 infected neonates when compared to sham-infected animals. These increases in nNOS immunoreactivity were pronounced in hippocampal plate, intermediate, molecular, subplate, and dentate areas. Quantitative analysis of specific immunogold silver-enhanced nNOS IR via densitometry showed nNOS IR increases of 26-71.6% in all layers, i.e., hippocampal plate (35.1%), dentate area (71.6%), molecular area (43.75%), subplate (45.7%), and intermediate zone (26%) in infected neonatal brains vs. controls. The changes in levels of nNOS expression in hippocampi of neonates born to mothers exposed to HI virus during the second trimester of pregnancy may reflect the potential for glutamatergic excitotoxicity via activation of NMDA receptors in the developing brains of these neonatal mice.

Lamotrigine in rapid-cycling bipolar disorder

BACKGROUND

We evaluated the antidepressant and mood-stabilizing effects of lamotrigine, a novel anticonvulsant, in a group of rapid-cycling bipolar patients. Most were already nonresponders or poor partial responders to other conventional mood-stabilizing agents.

METHODS

This open, naturalistic, and prospective study was conducted with five rapid-cycling bipolar patients (DSM-IV). Each received lamotrigine titrated to a minimum dose of 150 mg/day as monotherapy or in combination with other psychotropic agents. Patients were assessed with the Global Assessment Scale (GAS), Beck Depression Inventory (BDI), and Young Mania Rating Scale (YMRS) for evidence of cycling mood.

RESULTS

Lamotrigine was used at a mean +/- SD dose of 185.0 +/- 33.5 mg/day for 225.8 +/- 28.0 days. Random regression modeling of data showed significant dose- and time-dependent improvements in depressive symptoms and social function of patients taking lamotrigine (Dose: z = 2.17, p < .03 for BDI, z = 4.44, p < .001 for GAS; Time: z = -3.79, p < .001 for BDI, z = 2.16, p < .03 for GAS). Further random regression modeling analysis of change over time in symptoms prior to lamotrigine compared with symptoms during lamotrigine treatment showed a significant treatment by time effect for GAS (z = 2.40, p < .016) and a trend for BDI scores (z = -1.79, p < .073). No significant time or dosage effect or time by treatment effect was observed for YMRS. Finally, t statistics showed a significant reduction in mean BDI scores following treatment with lamotrigine (t = -5.26, p < .006). Lamotrigine was well tolerated by all patients; only one patient experienced several side effects, which were probably due to interaction between several psychotropic medications.

CONCLUSION

Lamotrigine augmentation therapy and monotherapy appeared to have mood-stabilizing and antidepressant efficacy in the treatment of five rapid-cycling bipolar patients. The effect persisted for an average of 7.5 months.

Predictors of response to mood stabilizers

Although lithium remains the preferred treatment of bipolar disorder, only 60 to 80% of patients with the classic presentation have an adequate response to this drug. When the response rate to lithium is considered across the entire spectrum of bipolar disorders, this rate probably decreases to 50%. Natural history, illness subtype, and comorbidity are all important general predictors of response to treatment. At present, the only predictors that seem to differentially favor divalproex, and possible, carbamazepine over lithium are mixed states and rapid cycling. An overview of clinical presentations that predict general and differential response to mood stabilizers is provided.

Occurrence of respiratory syncytial virus subtypes in hospitalized children in Cleveland, Ohio from 1985 to 1988

In order to determine the frequency of occurrence of the two respiratory syncytial virus (RSV) subtypes in hospitalized children in Cleveland, Ohio, we analyzed clinical isolates obtained during three consecutive winter epidemic seasons between 1985 and 1988. RSV was recovered from the frozen clinical specimens of 197 patients: 176 subtype A, and 21 subtype B. Subtype A predominated during all three epidemic seasons, ranging from 83 to 94% of isolates. We surveyed the clinical records of 16 children with subtype B, and 101 children with subtype A infections, hospitalized at the University Hospitals of Cleveland during these winter epidemics and found no differences in age, sex, race, or clinical spectrum of severity of disease caused by the two subtypes. In contrast to previously reported data, subtype A predominated in each of the winter seasons studied within this community. We conclude that both subtypes circulate concurrently within the community during the winter. In hospitalized children both subtypes appear to cause a similar spectrum of disease. Both the concurrent circulation of RSV subtypes and the similar spectrum of illness pose for important considerations in the development of effective vaccines against this common respiratory agent in children.

Dynamics and longevity of the glycolipid-anchored membrane protein, Thy-1

Thy-1 and a number of other proteins are anchored to the outer hemi-leaflet of membranes by a glycolipid moiety containing ethanolamine phosphate, mannose, glucosamine, and phosphatidylinositol. They nevertheless have the striking property of being able to transduce signals across the plasma membrane. We here demonstrate, for the BW5147 murine T lymphoma, that (a) greater than 90% of Thy-1 is at the cell surface, (b) Thy-1 is about one order of magnitude less concentrated in coated pits than the transferrin receptor or H-2 antigens, (c) Thy-1 undergoes at most very limited endocytosis or diacytosis, and (d) Thy-1 has an unusually slow turnover rate. Several similar observations have also been made for a second glycolipid-anchored protein, the T cell activating protein. Thus, the absence of cytoplasmic and trans-membrane domains may result in lipid-anchored proteins being confined to the cell surface and being free from constraints which affect the turnover of transmembrane proteins.

The phenotype of five classes of T lymphoma mutants. Defective glycophospholipid anchoring, rapid degradation, and secretion of Thy-1 glycoprotein

Thy-1 glycoprotein is a member of a class of proteins which are anchored to the plasma membrane via a covalently bound glycophospholipid. The biosynthesis and anchoring of Thy-1 were investigated in a family of wild-type and mutant (complementation groups A, B, C, E, and F) T lymphomas. The mutants all synthesize Thy-1 but fail to express it on the cell surface. Analysis of the size of D-[2-3H]mannose-labeled dolichol-linked oligosaccharides showed that the class E mutant is the only cell line which does not synthesize dolichol-P-P-Glc3Man9GlcNAc2. Turnover and possible secretion of Thy-1 by mutant T lymphoma cells were documented in D-[2-3H]mannose pulse-chase experiments. The turnover of [3H]Thy-1 for all wild-type cells is considerably slower than for the mutant cells. Class B and E cells release appreciably more [3H]Thy-1 than wild-type cells. Additional experiments were performed to determine the electrophoretic mobility and hydrophobicity of cell-associated and released forms of Thy-1 labeled overnight with [3H]mannose. All wild-type and class A, C, E, and F mutant cells contain a major Triton X-114 binding species of cell-associated [3H]Thy-1. All extracellular [3H]Thy-1 was almost exclusively hydrophilic. The presence of two Thy-1 anchor components, ethanolamine and palmitate, was investigated. Biosynthetic labeling with [3H]palmitic acid showed that all of the wild-type cells but none of the mutants incorporated this anchor precursor into Thy-1. In [3H]ethanolamine-labeling experiments, incorporation was detected in the Thy-1 of all wild-type cells and in two mutants, S1A-b and T1M1-c. Based on the above studies, the phenotype of Thy-1 negative T lymphoma mutants can be re-evaluated. In classes A and F, dolichol-linked oligosaccharides appear normal and no anchor is detected. In class B, dolichol-linked oligosaccharides appear normal, a partial anchor may be present, and a substantial amount of Thy-1 is released. In class C, dolichol-linked oligosaccharides appear normal and a partial anchor may be present. In class E, truncated dolichol-linked oligosaccharides are formed, no anchor is detected, but a substantial amount of newly synthesized Thy-1 is released. These observations are discussed with reference to the possibility that the lesions which characterize the mutants pertain to the biosynthesis of the glycophospholipid moiety of Thy-1.

The glycophospholipid anchor of Thy-1. Biosynthetic labeling experiments with wild-type and class E Thy-1 negative lymphomas

The Thy-1 antigen of the surface of lymphocytes and neurons is anchored to the plasma membrane via a glycophospholipid moiety. In contrast, the Thy-1 synthesized by the class E Thy-1 negative mutant lymphoma is secreted as a hydrophilic species. The present investigation uses the approach of biosynthetic labeling to investigate further the structure of the intracellular Thy-1 of wild-type cells and the secreted Thy-1 of these mutant cells. In the wild-type cells, Thy-1 can be labeled with [3H] mannose, [3H]galactose, [3H]fucose, [3H]ethanolamine, and [3H]palmitic acid. In the latter two cases the label is recovered almost exclusively in a detergent-binding Pronase fragment of the protein. The incorporated label is in the form of [3H]ethanolamine, or [3H]palmitate and stearate, respectively. Reductive methylation of biosynthetically labeled Thy-1 and a nonradioactive sample of Thy-1 shows that [3H]ethanolamine is incorporated equally into two residues of ethanolamine, only one of which has a free amino group. A single residue of glucosamine with a free amino group is also detected. Each of the sugar precursors is incorporated with extensive conservation of chemical identity. In the class E cells, each of the labeled sugars but neither [3H]ethanolamine nor [3H]palmitate is incorporated into Thy-1. The anchor moiety therefore appears to be entirely missing, although N-linked oligosaccharide processing is essentially normal. We postulate that the anchor deficiency in the mutant cells results from a biosynthetic lesion.

The role of secretory granules in the transport of basement membrane components: radioautographic studies of rat parietal yolk sac employing 3H-proline as a precursor of type IV collagen

Biosynthesis of type IV collagen in the parietal endodermal cells of 12 day gestant Sherman rats was examined following intraconceptal injection of 3H-proline. The concepti were removed at times varying from 2 minutes to 24 hours after the injection. The parietal wall of the yolk sac, including endodermal cells and the associated basement membrane known as Reichert's membrane were processed for electron microscopic radioautography. Silver grains were counted over the organelles of endodermal cells as well as over Reichert's membrane. Radioactivity was high in endodermal cells during the first 2 hr after 3H-proline injection and later dropped to some extent, while radioactivity rose in Reichert's membrane. Examination of endodermal cell organelles showed some early labeling over rER and Golgi apparatus without a clear-cut trend, except for a drop in Golgi label at late times after 3H-proline injection. The density of silver grains over secretory granules rose significantly by 40 min, reached a high peak by 4 hr and then declined at the time when radioactivity increased over Reichert's membrane. Furthermore, the radioactively-labeled secretory granules were localized mainly at the trans Golgi face soon after injection and near the cell surface adjacent to Reichert's membrane at later times. Biochemical reports indicate that a substantial amount of the proline taken up by the 12-14.5 day rat embryo endodermal cells is incorporated into type IV collagen. Since there is high labeling of the secretory granules from 40 min to 4 hr and the labeled granules are associated with the Golgi apparatus at early times, it is proposed that collagen precursors are processed through rER and Golgi apparatus, packaged into secretory granules and then transported to the cell surface where type IV collagen or its precursors are released and subsequently deposited into Reichert's membrane.

Hydrophilic anchor-deficient Thy-1 is secreted by a class E mutant T lymphoma

To investigate the mechanism of glycophospholipid anchoring of the surface antigen Thy-1, we have undertaken a comparative biosynthetic study using a wild-type Thy-1+ murine T lymphoma (BW5147) and a mutant T lymphoma (class E) that synthesizes Thy-1 but fails to express it on the plasma membrane. Labelling experiments with D-[2-3H]mannose demonstrate that, unlike the wild type, the mutant cells are secreting large amounts of Thy-1 and that the secreted molecules are hydrophilic. Moreover, unlike the wild type, they fail to incorporate [3H]palmitic acid into Thy-1. Both wild-type and mutant cells do incorporate labeled galactose and fucose into Thy-1. We conclude that the lack of surface expression of Thy-1 by this mutant results from the failure to add anchor components to Thy-1.

Comparison of the intravenous and intraperitoneal routes of administration of tritiated thymidine in studies of cell production in the gastrointestinal tract of the rat

Incorporation of 3H-Thymidine into DNA-synthesizing cells of the gastrointestinal tract of the rat was examined following administration of the isotope by intraperitoneal and intravenous routes. Estimates of whole tissue incorporation expressed as DPM/mg dry weight and of proliferating cells expressed as DPM/crypt or gland in the different segments of the gut indicated no differences in the degree of 3H-TdR uptake into DNA following intraperitoneal or intravenous routes of administration. The possibility of misdirected I.P. injections was examined following injection of 3H-TdR into the cecum or bladder. DPM/mg wet weight of gastrointestinal tissues indicated reduction in the uptake of 3H-TdR into DNA of intestinal tissues following intracecal and intrabladder administration of 3H-Tdr. The intraperitoneal route of administration of 3H-TdR appears to be equally effective in the distribution of the isotope into different segments of the gut when compared to the intravenous route and is a more convenient method in studies of cell production in the gastrointestinal tract of the rat.

Late ultrastructural effects of heavy ions and gamma irradiation in the gastrointestinal tract of the mouse

The irradiated gastrointestinal tract of LAF1 mice was examined one year following a single dose (1000 rad) of either 12C heavy ions or 60Co gamma rays. Qualitative ultrastructural analysis of the gastrointestinal tract of mice exposed to heavy ions or gamma irradiation did not show any discernible differences. In the stomach of irradiated mice, parietal cells contained numerous lysosomes; the gastric chief cells occasionally contained myelin figures. The epithelial cells of the small intestine, especially jejunum and ileum, showed several changes: (1) increased vacuolation was seen both inter- and intra-cellularly, (2) epithelial cell projections penetrated the basal lamina and were in contact with underlying mesenchymal cells, (3) occasional Paneth cells contained intracellular vacuoles consisting of fibrillar and granular material. In the large intestine occasional signs of degeneration were observed. Qualitative analysis of stromal elements of the gut in irradiated mice indicated the presence of damage to capillary endothelial cells, smooth muscle cells and some nerve processes. The amount of basement membrane (BM) around capillaries and small vessels was increased; the same phenomenon was observed to affect the nerve processes, but with less severity. Quantitative analysis of the basement membrane thickness around capillaries in irradiated vs. control mice showed significant differences. Basement membrane thickness around capillaries in the gastric mucosa and duodenum did not differ significantly in any of the treatment groups. In jejunum, the gamma treated animals exhibited significantly higher BM thickness when compared to unirradiated controls. In ileum, only 12C-heavy ion treated animals showed thicker BM when compared to their respective controls. In colon, both 12C- and 60Co-treated animals showed increased BM thickness when compared to controls.

Evaluation of the effects of pentagastrin, gastrin and pancreatic glucagon on cell proliferation in the rat gastrointestinal tract

The effects of six injections of a range of doses (100-1000 micrograms/kg bodyweight) of pentagrastrin and single injection of a range of doses of porcine gastrin (10-40 micrograms/kg bodyweight) and pancreatic glucagon (25-100 micrograms/kg bodyweight) on cell proliferation in the intestine of fasted rats has been investigated. The end-point employed included the measurement of 14C leucine incorporation and thymidine-derived tritium content of the body of the stomach, duodenum, jejunum, ileum and colon. The carbon 14 and tritium content per microgram of tissue in triplicate samples of fifty individually dissected crypts of glands were determined. From these data and the wet weight of the washed, blotted, intestinal segments, values for crypts/micrograms tissue and crypts/segment were calculated. The results demonstrated that pentagastrin at physiological doses decreased cell proliferation slightly in stomach, while gastrin and glucagon were without effect. In the small intestine, pentagastrin and gastrin were without significant effect with the exception that they increased the weight of the duodenum. In contrast, a high physiological dose of glucagon increased DNA and protein synthesis throughout the small bowel, but particularly in the ileum. Pharmacological doses of pentagastrin and all doses of gastrin appeared to increase cell proliferation in the colon although the possibility could not be excluded that this was due to stimulation of precursor uptake. Gastrin also increased colonic weight. Glucagon had no effects in the colon. These observations are compatible with the hypothesis that (i) the primary effects of gastrin and pentagastrin on the proximal intestine are as secretogogues and effects on cell proliferation may be secondary, (ii) gastrin and pentagastrin at physiological levels do not stimulate small intestinal cell proliferation, however glucagon does, and (iii) gastrin at physiological levels and pentagastrin at pharmacological levels may stimulate cell proliferation in the colon.

Isolation and enrichment of the gastric chief cells of the rat

The isolation and enrichment of the gastric chief cells of the rat are described. Ultrastructural examination showed 85% enrichment from a mixed population of mucosal cells following their centrifugation through a discontinuous Percoll gradient. When compared to homogenates of the initial mixed cell population, the enriched chief cell population showed over a three-fold increase in pepsin(ogen) content. Preliminary experiments showed that a combination of the secretagogues histamine and carbamylcholine caused a significant increase in pepsin release from enriched chief cell preparations and a concomitant decrease in their pepsin content as compared to untreated cells. The results obtained in this study indicate the feasibility of employing this procedure for the isolation of gastric chief cells for the in vitro study of secretagogue regulation of pepsin secretion.

Re-evaluation of the surgical anatomy of the mesocaval shunt

On the basis of these findings, we have concluded that the surgeon contemplating the construction of a mesocaval shunt can expect to find ideal or nearly ideal conditions in approximately one third of the population. Another two thirds can be expected to present anatomical variations which may complicate the procedure in varying degrees. In approximately one tenth of the cases, the construction of a shunt would probably prove impossible.