Nuclear factor kappa B is required for the development of marginal zone B lymphocytes.

Although immunoglobulin (Ig)M(hi)IgD(lo/-)CD21(hi) marginal zone B cells represent a significant proportion of naive peripheral splenic B lymphocytes, few of the genes that regulate their development have been identified. This subset of peripheral B cells fails to emerge in mice that lack nuclear factor (NF)-kappa Bp50. Less drastic reductions in marginal zone B cell numbers are also seen in the spleens of recombination activating gene (Rag)-2(-/-) mice reconstituted with NF-kappa Bp65(-/-) fetal liver cells and in c-Rel(-/-) mice. In contrast, steady-state levels of IgD(hi) splenic follicular B cells are not significantly reduced in the absence of NF-kappa Bp50, NF-kappa Bp65, or c-Rel. Reconstitution of B cells in Rag-2(-/-) mice with a mixture of p50(-/-)/p65(-/-) fetal liver cells and Rag-2(-/-) bone marrow cells revealed that the generation of marginal zone B cells requires the expression of NF-kappa B in developing B cells, as opposed to supporting cells.

Large-scale neural model validation of partial correlation analysis for effective connectivity investigation in functional MRI.

Recent studies of functional connectivity based upon blood oxygen level dependent functional magnetic resonance imaging have shown that this technique allows one to investigate large-scale functional brain networks. In a previous study, we advocated that data-driven measures of effective connectivity should be developed to bridge the gap between functional and effective connectivity. To attain this goal, we proposed a novel approach based on the partial correlation matrix. In this study, we further validate the use of partial correlation analysis by employing a large-scale, neurobiologically realistic neural network model to generate simulated data that we analyze with both structural equation modeling (SEM) and the partial correlation approach. Unlike real experimental data, where the interregional anatomical links are not necessarily known, the links between the nodes of the network model are fully specified, and thus provide a standard against which to judge the results of SEM and partial correlation analyses. Our results show that partial correlation analysis from the data alone exhibits patterns of effective connectivity that are similar to those found using SEM, and both are in agreement with respect to the underlying neuroarchitecture. Our findings thus provide a strong validation for the partial correlation method.

pH-sensitive liposomes: possible clinical implications.

When pH-sensitive molecules are incorporated into liposomes, drugs can be specifically released from these vesicles by a change of pH in the ambient serum. Liposomes containing the pH-sensitive lipid palmitoyl homocysteine (PHC) were constructed so that the greatest pH differential (6.0 to 7.4) of drug release was obtained near physiological temperature. Such liposomes could be useful clinically if they enable drugs to be targeted to areas of the body in which pH is less than physiological, such as primary tumors and metastases or sites of inflammation and infection.

Age-related reductions in human recognition memory due to impaired encoding.

The participation of the medial temporal cortex and other cerebral structures in the memory impairment that accompanies aging was examined by means of positron emission tomography. Cerebral blood flow (rCBF) was measured during encoding and recognition of faces. Young people showed increased rCBF in the right hippocampus and the left prefrontal and temporal cortices during encoding and in the right prefrontal and parietal cortex during recognition. Old people showed no significant activation in areas activated during encoding in young people but did show right prefrontal activation during recognition. Age-related impairments of memory may be due to a failure to encode the stimuli adequately, which is reflected in the lack of cortical and hippocampal activation during encoding.

Functional interactions of the inferior frontal cortex during the processing of words and word-like stimuli.

The hypothesis that ventral/anterior left inferior frontal gyrus (LIFG) subserves semantic processing and dorsal/posterior LIFG subserves phonological processing was tested by determining the pattern of functional connectivity of these regions with regions in left occipital and temporal cortex during the processing of words and word-like stimuli. In accordance with the hypothesis, we found strong functional connectivity between activity in ventral LIFG and activity in occipital and temporal cortex only for words, and strong functional connectivity between activity in dorsal LIFG and activity in occipital and temporal cortex for words, pseudowords, and letter strings, but not for false font strings. These results demonstrate a task-dependent functional fractionation of the LIFG in terms of its functional links with posterior brain areas.

44-amino-acid E5 transforming protein of bovine papillomavirus requires a hydrophobic core and specific carboxyl-terminal amino acids.

The 44-amino-acid E5 protein of bovine papillomavirus type 1 is the shortest known protein with transforming activity. To identify the specific amino acids required for in vitro focus formation in mouse C127 cells, we used oligonucleotide-directed saturation mutagenesis to construct an extensive collection of mutants with missense mutations in the E5 gene. Characterization of mutants with amino acid substitutions in the hydrophobic middle third of the E5 protein indicated that efficient transformation requires a stretch of hydrophobic amino acids but not a specific amino acid sequence in this portion of the protein. Many amino acids in the carboxyl-terminal third of the protein can also undergo substitution without impairment of focus-forming activity, but the amino acids at seven positions, including two cysteine residues that mediate dimer formation, appear essential for efficient transforming activity. These essential amino acids are the most well conserved among related fibropapillomaviruses. The small size of the E5 protein, its lack of similarity to other transforming proteins, and its ability to tolerate many amino acid substitutions implies that it transforms cells via a novel mechanism.

Genetic evidence that acute morphologic transformation, induction of cellular DNA synthesis, and focus formation are mediated by a single activity of the bovine papillomavirus E5 protein.

The bovine papillomavirus (BPV) type 1 E5 gene encodes a 44-amino-acid protein that can stably transform cultured rodent cells when expressed in the absence of all other viral genes. We have previously constructed a BPV-simian virus 40 recombinant virus (Pava-1) which efficiently expresses the BPV type 1 E5 gene in infected cells (J. Settleman and D. DiMaio, Proc. Natl. Acad. Sci. USA 85:9007-9011, 1988). Within 48 h of Pava-1 infection, the vast majority of mouse C127 cells underwent a dramatic morphologic transformation which was accompanied by cell proliferation. Infection of C127 cells made quiescent by contact inhibition and serum starvation caused a great induction of cellular DNA synthesis. These morphologic and mitogenic responses were proportional to the virus multiplicity of infection. Mutational analysis indicated that the E5 gene is both necessary and sufficient for these activities. Analysis of a variety of E5 missense mutants revealed a strong correlation between their phenotypes in the acute transformation assays following infection and in the stable focus-forming assay following transfection. Most of the defective mutants expressed normal levels of E5 protein following infection, indicating that their defective phenotypes are not due to the synthesis of an unstable protein. The failure to genetically resolve these E5 activities suggests that the ability of the E5 protein to cause acute morphologic transformation and reentry into the cell cycle may be intimately related to its ability to cause stable cell transformation and that these functions are probably mediated by a single biochemical activity of the E5 protein.

Interleukin-22 drives nitric oxide-dependent DNA damage and dysplasia in a murine model of colitis-associated cancer.

The risk of colon cancer is increased in patients with Crohn's disease and ulcerative colitis. Inflammation-induced DNA damage could be an important link between inflammation and cancer, although the pathways that link inflammation and DNA damage are incompletely defined. RAG2-deficient mice infected with Helicobacter hepaticus (Hh) develop colitis that progresses to lower bowel cancer. This process depends on nitric oxide (NO), a molecule with known mutagenic potential. We have previously hypothesized that production of NO by macrophages could be essential for Hh-driven carcinogenesis, however, whether Hh infection induces DNA damage in this model and whether this depends on NO has not been determined. Here we demonstrate that Hh infection of RAG2-deficient mice rapidly induces expression of iNOS and the development of DNA double-stranded breaks (DSBs) specifically in proliferating crypt epithelial cells. Generation of DSBs depended on iNOS activity, and further, induction of iNOS, the generation of DSBs, and the subsequent development of dysplasia were inhibited by depletion of the Hh-induced cytokine IL-22. These results demonstrate a strong association between Hh-induced DNA damage and the development of dysplasia, and further suggest that IL-22-dependent induction of iNOS within crypt epithelial cells rather than macrophages is a driving force in this process.

A positron emission tomographic study of auditory localization in the congenitally blind.

We have used positron emission tomography (PET) to measure regional cerebral blood flow (rCBF) in sighted and congenitally blind subjects performing auditory localization tasks. During scanning, the spectral and binaural cues of localized sound were reproduced by a sound system and delivered via headphones. During tasks that required auditory localization both the sighted and blind subjects strongly activated posterior parietal areas. In addition, the blind subjects activated association areas in the right occipital cortex, the foci of which were similar to areas previously identified in visual location and motion detection experiments in sighted subjects. The blind subjects, therefore, demonstrated visual to auditory cross-modal plasticity with auditory localization activating occipital association areas originally intended for dorsal-stream visual processing. To determine the functional connectivity of pre-selected brain regions in primary and non-primary auditory and posterior parietal cortex in the two cohorts, we performed an inter-regional correlation analysis on the rCBF data set. During auditory localization in the blind subjects, rCBF activity in the right posterior parietal cortex was positively correlated with that in the right occipital region, whereas in sighted subjects correlations were generally negative. There were no significant positive occipital correlations in either cohort when reference regions in temporal or left parietal cortex were chosen. This indicates that in congenitally blind subjects the right occipital cortex participates in a functional network for auditory localization and that occipital activity is more likely to arise from connections with posterior parietal cortex.

Nucleotide effects on liver and muscle mitochondrial non-phosphorylating respiration and membrane potential.

Uncoupling protein-1 homologs are hypothesized to mediate mitochondrial proton leak. To test this hypothesis, we determined the effects of ATP and other nucleotides on liver and skeletal muscle mitochondrial non-phosphorylating respiration (VO(2)), membrane potential, FCCP-stimulated respiratory control ratios, and swelling. Neither ATP nor CTP affected liver or muscle proton leak, but both inhibited the respiratory chain. Unexpectedly, CMP stimulated liver proton leak (EC(50) approximately 4.4+/-0.5 mM). Using CMP chromatography, we identified two proteins (M(r)=31.2 and 32.6 kDa) from liver mitochondria that are similar in size to members of the mitochondrial carrier protein family. We conclude (a) liver and muscle mitochondrial proton leak is insensitive to ATP and CTP, and (b) CMP activates a leak in liver mitochondria. The CMP-inducible leak may be mediated by a 30-32 kDa protein. Based on the high concentrations required, CMP is unlikely to be a physiologically important leak regulator. Nonetheless, our results show that tissues other than brown fat have inducible leaks that may be protein-mediated.

Individual Members of the Cab Gene Family Differ Widely in Fluence Response.

Chlorophyll a/b-binding protein genes (Cab genes) can be extremely sensitive to light. Transcript accumulation following a red light pulse increases with fluence over 8 orders of magnitude (L.S. Kaufman, W.F. Thompson, W.R. Briggs [1984] Science 226: 1447-1449). We have constructed fluence-response curves for individual Cab genes. At least two Cab genes (Cab-8 and AB96) show a very low fluence response to a single red light pulse. In contrast, two other Cab genes (AB80 and AB66) fail to produce detectable transcript following a single pulse of either red or blue light but are expressed in continuous red light. Thus, very low fluence responses and high irradiance responses occur in the same gene family.

The impact of past alcohol use on treatment response rates in patients with chronic hepatitis C.

BACKGROUND: Studies have shown that past alcohol consumption reduces response rates in patients with chronic hepatitis C treated with interferon monotherapy. AIM: To clarify the importance of alcohol consumption on response rates in patients undergoing treatment with pegylated interferon and ribavirin. METHODS: In a single centre, prospective study, median daily alcohol consumption (determined by previously validated method) and quartiles of alcohol consumption were calculated. Univariate and binary logistic regression analyses were performed using treatment response status as the dependent variable. RESULTS: Overall, in an intention-to-treat analysis, 34 of 115 patients (30%) responded to treatment. In univariate analysis, black patients, especially those with hepatitis C virus genotype 1, high viral load and low alanine aminotransferase were significantly less likely to respond. Predictors of response by regression analysis included alcohol <30 g/day (OR=3.02, 95% CI: 1.02-8.93; P=0.04), non-genotype 1 status (OR=1.98, 95% CI: 1.03-3.80; P=0.04) and non-black race (OR=2.79, 95% CI: 1.33-5.85; P=0.006). CONCLUSIONS: Median daily alcohol use >30 g/day is associated with failure to respond to pegylated interferon and ribavirin for treatment of hepatitis C. Past alcohol use should be evaluated when considering treatment for hepatitis C.

Sex differences in human brain morphometry and metabolism: an in vivo quantitative magnetic resonance imaging and positron emission tomography study on the effect of aging.

BACKGROUND: There are significant age and sex effects in cognitive ability and brain disease. However, sex differences in aging of human brain areas associated with nonreproductive behavior have not been extensively studied. We hypothesized that there would be significant sex differences in aging of brain areas that subserve speech, visuospatial, and memory function. METHODS: We investigated sex differences in the effect of aging on human brain morphometry by means of volumetric magnetic resonance imaging and on regional cerebral metabolism for glucose by positron emission tomography. In the magnetic resonance imaging study, we examined 69 healthy right-handed subjects (34 women and 35 men), divided into young (age range, 20 to 35 years) and old (60 to 85 years) groups. In the positron emission tomography study, we investigated 120 healthy right-handed subjects (65 women and 55 men) aged 21 to 91 years. RESULTS: In the magnetic resonance imaging study, age-related volume loss was significantly greater in men than women in whole brain and frontal and temporal lobes, whereas it was greater in women than men in hippocampus and parietal lobes. In the positron emission tomography study, significant sex differences existed in the effect of age on regional brain metabolism, and asymmetry of metabolism, in the temporal and parietal lobes, Broca's area, thalamus, and hippocampus. CONCLUSIONS: We found significant sex differences in aging of brain areas that are essential to higher cognitive functioning. Thus, our findings may explain some of the age-sex differences in human cognition and response to brain injury and disease.

Brain atrophy in hypertension. A volumetric magnetic resonance imaging study.

To determine whether hypertension, the predominant risk factor for stroke and vascular dementia, is associated with brain atrophy, magnetic resonance imaging (MRI) scans were performed to quantify brain volumes and cerebrospinal fluid spaces. Eighteen otherwise healthy, cognitively normal older hypertensive men (mean +/- SD age, 69 +/- 8 years, duration of hypertension 10-35 years) and 17 age-matched healthy, normotensive male control subjects were studied in a cross-sectional design. Axial proton-density image slices were analyzed using region-of-interest and segmentation analyses. The hypertensive subjects had significantly larger mean volumes of the right and left lateral ventricles (p less than 0.05, both absolute volume and volume normalized to intracranial volume) and a significantly smaller normalized mean left hemisphere brain volume (p less than 0.05) with a trend toward significance for a smaller normalized mean right hemisphere volume (p less than 0.09). Four hypertensive subjects and one healthy control subject were found to have severe periventricular hyperintensities on T2-weighted MRI images. When data for these subjects were removed from the analyses, the normalized lateral ventricle volumes remained significantly larger in the hypertensive group. Lateral ventricle enlargement was not related to age or use of diuretics in the hypertensive group nor to duration of hypertension between 10 and 24 years. Our findings suggest that long-standing hypertension results in structural changes in the brain. Longitudinal studies will determine whether MRI-associated changes are progressive and if such changes identify hypertensive subjects at increased risk for clinically apparent brain dysfunction.

Individual differences in cerebral metabolic patterns during pharmacotherapy in obsessive-compulsive disorder: a multiple regression/discriminant analysis of positron emission tomographic data.

A multiple regression/discriminant analysis of positron emission tomographic cerebral metabolic (rCMRglc) data in 10 obsessive-compulsive disorder (OCD) patients before and during pharmacotherapy was carried out to see if rCMRglc interdependencies distinguished OCD patients from controls. Before therapy, a discriminant function reflecting parietal, sensorimotor, and midbrain rCMRglc interdependencies correctly classified eight (80%) of the 10 patients as OCD; after therapy, six (70%) were classified as controls, most of whom were responders. Before therapy, rCMRglc interdependencies involving basal ganglia, thalamus, limbic, and sensory and association cortical regions distinguished 67% of patients who clinically responded to drug (RESP, n = 6) and 75% of patients who did not (NRESP, n = 4) from controls. After therapy, all RESP were classified as controls; classification of NRESP remained unchanged. The results suggest the conjunctive utility of this method to assess individual differences in rCMRglc during pharmacotherapy, and to explore the neurobiology of OCD.

Abnormal brain glucose metabolism in the delusional misidentification syndromes: a positron emission tomography study in Alzheimer disease.

Brain lesions have been reported with increasing frequency in the delusional misidentification syndromes (DMS). This is the first controlled study to describe DMS regional cerebral metabolic rates of glucose (rCMRglc). We compared rCMRglc (using positron emission tomography) and neuropsychological data in 9 patients with DMS and Alzheimer dementia (AD), 15 AD patients without DMS, and 17 healthy controls. The DMS group differed from the AD group without DMS in having significant hypometabolism in paralimbic (orbitofrontal and cingulate areas bilaterally) and left medial temporal areas, and significant bilateral normalized hypermetabolism in sensory association cortices (superior temporal and inferior parietal) without right left asymmetry. Compared to healthy controls, both AD groups had significant dorso lateral frontal hypometabolism bilaterally. No specific DMS neuropsychological profile was identified. Dysfunctional connections among multimodal association areas, paralimbic structures, and dorsolateral frontal cortex are proposed as the predisposing neural deficit underlying DMS, causing cognitive-perceptual-affective dissonance, which under specific conditions results in "positive" delusion formation.

Volumes of medial temporal lobe structures in patients with Alzheimer's disease and mild cognitive impairment (and in healthy controls).

BACKGROUND: The clinical diagnosis of Alzheimer's disease (AD) can be difficult to make in early stages of disease. Structural neuroimaging offers a potential tool in the clinical diagnosis of AD with mild cognitive impairment. Postmortem studies indicate that early neuropathology in AD occurs in medial temporal lobe limbic structures. Magnetic resonance imaging (MRI) studies that assessed these volumes in mildly impaired AD patients remain inconclusive. METHODS: Using MRI, we measured volumes of left and right hippocampus, amygdala, and anterior and posterior parahippocampal gyrus (PHG) in 13 AD patients with mild cognitive impairment, defined as > or = 20 on the Mini-Mental State Exam, and in 21 healthy age- and sex-matched controls. RESULTS: The AD patients had smaller medial temporal lobe volumes, except for the right anterior PHG. Discriminant function analysis using MRI volumes produced 94% correct group classification. CONCLUSIONS: These results show that in mildly impaired AD patients atrophy is present in medial temporal lobe structures; that MRI volumes of the anterior PHG, which contains entorhinal cortex, are reduced, but the amygdala and hippocampal volumes show greater reduction; and that discriminant function analysis using all volumes as predictors can correctly classify a high proportion of individuals.

Volumetric magnetic resonance imaging in men with dementia of the Alzheimer type: correlations with disease severity.

Using magnetic resonance imaging (MRI), we measured the volumes of various brain structures and cerebrospinal fluid (CSF) in 19 men with dementia of the Alzheimer type (DAT) and 18 healthy age-matched control men. The mean (+/- S.D) Mini-Mental State exam score (MMSE) of the DAT men was 16 +/- 7; 9 were mildly (MMSE > 20), 5 moderately (MMSE 10-20), and 5 severely (MMSE < 10) demented. Brain and CSF volumes were normalized as a percent of the traced intracranial volume to control for the relation of volumes of cerebral structures to head size, and analyzed statistically. The whole group of DAT subjects had significantly smaller mean cerebral brain matter and temporal lobe volumes (p < 0.05), and significantly larger mean ventricular and temporal lobe peripheral CSF volumes than did controls. Mean volumes of the subcortical nuclei did not differ significantly between groups, and mean volume of temporal lobe brain matter decreased significantly more than whole brain, suggesting regional loss of brain matter in DAT. Mildly demented DAT patients had significantly smaller mean cerebral brain matter and temporal lobe volumes and significantly larger volumes of lateral ventricles, and of temporal lobe peripheral CSF, than did controls. Neuropsychological measures of disease severity in DAT patients were significantly (p < 0.05) and appropriately correlated to volumes of cerebral brain matter and right lateral ventricle. These results suggest that in DAT: (i) significant brain atrophy is present early in the disease process, (ii) brain atrophy correlates with severity of cognitive impairment, and (iii) there is greater involvement of the telencephalic association system than whole brain, and there is relative sparing of the caudate, lenticular and thalamic nuclei.

A PET study of Turner's syndrome: effects of sex steroids and the X chromosome on brain.

Women with Turner's syndrome (TS) allow us to study the neurobiological associates of cognitive and behavioral abnormalities because they lack one/part of one X chromosome, and endogenous estrogen. We studied 13 healthy controls (mean age +/- SD, 28 +/- 6 years) and 16 TS subjects (mean age +/- SD, 26 +/- 6 years). We measured cognitive abilities using neuropsychological tests, and cerebral metabolic rates for glucose with positron emission tomography. Compared to controls, TS subjects had significant absolute hypermetabolism in most brain areas; however, normalized metabolism was significantly lower in TS subjects than controls in the insula and association neocortices bilaterally, and there were significant differences in functional metabolic associations of brain region pairs originating in occipital cortex bilaterally, and within the right hemisphere. There were significant correlations between right-left cognitive and metabolic asymmetries in the TS group. Also, within TS a preliminary analysis demonstrated "X chromosome dosage" effects in language ability and left temporal metabolism, asymmetry of right-left test scores, and parietal metabolism. We hypothesize that within TS: i) generalized brain hypermetabolism reflects global abnormalities in neuron packing; ii) neuronal abnormalities occur in association neocortex that differ in nature or extent from whole brain and are associated with significant differences in normalized metabolism; iii) cognitive deficits are related to brain metabolic abnormalities; and iv) social-behavioral problems may be related to abnormalities of brain metabolism. Moreover, in human brain the X chromosome involved in development of the association neocortices.

Functional interactions in the brain: use of correlations between regional metabolic rates.

Correlation coefficients between pairs of regional metabolic rates have been used to study patterns of functional associations among brain regions in humans and animals. An overview is provided concerning the additional information about brain functioning this type of analysis yields. A computer simulation model is presented for the purpose of giving a partial validation for correlational analysis. The model generates a set of simulated metabolic data upon which correlational analysis is performed. Because the underlying pattern of functional couplings in the model is known, these simulations demonstrate that the correlation coefficient between normalized metabolic rates is proportional to the strength of the functional coupling constant and that correlational analysis yields information on regional involvement in neural systems not evident in the pattern of absolute metabolic values.