BioVision: an application for the automated image analysis of histological sections

We describe a computer application, "BioVision", that can be trained to quickly and effectively classify and quantify user definable histological objects (e.g., senile plaques, neurofibrillary tangles) within single or double-labeled immunocytochemically stained sections. For a given image population, BioVision is interactively trained (in Independent User Mode) by an investigator to perform the desired classifications. This training yields a statistical model of the different types of objects occurring in the target image population. The resulting model can then be used (in Automated User Mode) to classify all objects in any image or images from the target population. BioVision simplifies the quantification of complex visual objects and improves inter-rater reliability. The program accomplishes classification in two major stages: pixel classification and blob classification. In pixel classification, each pixel is assigned to one of some number of substance classes, based on its chromatic properties and local context, reflecting basic histological distinctions of interest. In the blob classification phase, the image's pixels are first partitioned into "blobs": maximal connected sets of pixels assigned to the same substance class. Then, based on its size, shape, textural and contextual properties, each blob is assigned to a histological object class. A Bayesian classifier is used in each of the pixel and blob classification stages. We report several tests of BioVision. First, we applied BioVision to classify senile plaques and neurofibrillary tangles in several test cases of Alzheimer's brain immunostained for beta-amyloid and PHF-tau and compared the results to those produced by experienced investigators. BioVision was trained to classify Plaque-type blobs as either plaques or plaque-type nonentities, and tangle-type blobs as either tangles or tangle-type nonentities. BioVision classified the objects with an accuracy comparable to the trained investigator. Next, we applied BioVision to the task of counting all the tangles in hippocampal images from 22 Alzheimer's disease (AD) cases selected to span a broad range of dementia levels from the tissue repository of UC Irvine's Center for the study of Brain Aging and Dementia. The tangle counts produced by BioVision proved to be significantly better predictors of the cases' adjusted MMSE scores than any of tangle load, age at death, post mortem interval or the interval between the last MMSE score and death.     

Some observations on the measurement of haemoglobin A2 and S percentages by high performance liquid chromatography in the presence and absence of alpha thalassaemia

AIMS: To assess the accuracy and precision of measuring haemoglobin A(2) by high performance liquid chromatography (HPLC) in the presence and absence of sickle cell trait, with or without alpha thalassaemia trait. METHODS: The haemoglobin A(2) percentage and the haemoglobin A(2) plus S percentages were determined by HPLC on 82 normal controls and 78 patients with sickle cell trait, respectively; the alpha thalassaemia status of each patient was determined by polymerase chain reaction. Red cell indices and haemoglobin A(2) and S percentages were compared in patients with two, three, or four alpha genes. RESULTS: Of the 78 patients with sickle cell trait, 17 were heterozygous for alpha(+) thalassaemia (-alpha(3.7)/alphaalpha) and 13 were homozygous (-alpha(3.7)/-alpha(3.7)). Microcolumn chromatography showed that the haemoglobin A(2) percentage was slightly, but significantly, higher than normal in sickle cell trait. HPLC determinations of haemoglobin A(2) percentage in patients with sickle cell trait are precise but inaccurate, the percentage being appreciably overestimated. The measured haemoglobin A(2) percentage is stable for one week, but inaccuracy increases by two weeks in most samples. Despite this inaccuracy, there are significant differences in the HPLC "haemoglobin A(2) percentage" between groups of individuals with two, three, and four alpha genes. CONCLUSIONS: Haemoglobin A(2) determinations by HPLC are precise but inaccurate. Nevertheless, there are significant differences in the haemoglobin A(2) percentage in subjects with two, three, and four alpha genes. Although there is some overlap between groups, this can be useful, together with the red cell indices, in predicting the likelihood of coexisting alpha thalassaemia.     

EDL and soleus muscles of the C57BL6J/dy2j laminin-alpha 2-deficient dystrophic mouse are not vulnerable to eccentric contractions

Many muscular dystrophies arise as a consequence of mutations in a series of interconnected proteins associated with the sarcolemma. This group of proteins is collectively referred to as the 'dystrophin-associated complex'. We used the C57BL6J/dy(2j), dystrophia muscularis, dystrophic mouse, in which the laminin-alpha(2) component of the dystrophin-associated complex is mutated, to test the hypothesis that the disruption of this complex will destabilize the lipid bilayer, rendering it more susceptible to damage during eccentric contractions. We demonstrated that neither slow- nor fast-twitch dystrophic muscles were more susceptible to eccentric contractions when compared with controls. Only fast-twitch extensor digitorum longus (EDL) muscles (from both dystrophic and control mice) showed an irreversible loss of force with our eccentric contraction protocol, suggesting that it is the fast 11b fibres (not present in slow-twitch soleus) which are most susceptible to eccentric damage. We used the general anaesthetic halothane to increase the fluidity of the lipid bilayer to see if this would uncover any greater susceptibility of the dystrophic muscle to eccentric damage. This also did not reveal any greater fragility of fast- and slow-twitch dystrophic muscles. We did, however, demonstrate that halothane made both control and dystrophic fast- and slow-twitch muscles more susceptible to eccentric contraction damage. The C57BL6J/dy(2j) dystrophic laminopathy produced the pathophysiological and pathohistological characteristics associated with muscular dystrophy: the fast- and slow-twitch dystophic muscles produced only 55 and 53%, respectively, of the force of control muscles and 34 and 40%, respectively, of the dystrophic muscle fibres were branched. The presence of the branched fibres in the dystrophic muscles did not make them more susceptible to eccentric damage but may have contributed to the reduction in maximal force in the dystrophic muscles. We conclude that our data do not support the structural hypothesis that the dystrophin-associated complex acts as a scaffolding to support the lipid bilayer, but are consistent with channel-based hypotheses put forward to explain the dystrophic process.     

Prion protein accumulation and neuroprotection in hypoxic brain damage

The function of the normal conformational isoform of prion protein, PrP(C), remains unclear although lines of research have suggested a role in the cellular response to oxidative stress. Here we investigate the expression of PrP(C) in hypoxic brain tissues to examine whether PrP(C) is in part regulated by neuronal stress. Cases of adult cerebral ischemia and perinatal hypoxic-ischemic injury in humans were compared with control tissues. PrP(C) immunoreactivity accumulates within neuronal processes in the penumbra of hypoxic damage in adult brain, and within neuronal soma in cases of perinatal hypoxic-ischemic injury, and in situ hybridization analysis suggests an up-regulation of PrP mRNA during hypoxia. Rodents also showed an accumulation of PrP(C) in neuronal soma within the penumbra of ischemic lesions. Furthermore, the infarct size in PrP-null mice was significantly greater than in the wild type, supporting the proposed role for PrP(C) in the neuroprotective adaptive cellular response to hypoxic injury.     

Visuospatial impairments in aged canines (Canis familiaris): the role of cognitive-behavioral flexibility

This study used a novel delayed nonmatching-to-position task to compare visuospatial learning and memory in young and aged beagle dogs (Canis familiaris). The task used 3, rather than 2, spatial locations, which markedly increased difficulty. There were striking age differences in acquisition. Most of the aged canines did not learn the task, and those that did showed impaired learning when compared with the young canines. The aged canines also showed reduced maximal working memory capacity compared with the young canines. Analysis of the response patterns of individual canines indicated that the deficits were related to the use of ineffective strategies and inflexibility in strategy modification.     

What evidence is there that adjustment for adult height influences the relationship between birth weight and blood pressure?

Background: The inverse association between birth weight and blood pressure may partly be the result of inappropriate adjustment for adult body size, but it remains unclear whether adjustment for adult height elicits this effect.

Aim: The study investigated the impact of adjustment for adult height on the relationship between birth weight and blood pressure.

Methods: A systematic search of Medline® from 1996 to 2006 was conducted using the terms ‘birth weight’, ‘blood pressure’ and ‘hypertension’, and any papers containing linear regression analyses of blood pressure on birth weight for populations with an average age of 25+ were eligible for inclusion in comparative meta-analyses.

Results: None of the 30 studies identified had published regression coefficients for blood pressure on birth weight before and after adjustment for adult height, and only two studies were found to adjust for adult height at all. Data from these studies were obtained, and it was found that adjustment for height made the association between birth weight and systolic blood pressure (SBP) more negative in one study but less negative in the other. When compared with meta-analyses of comparable models, it was found that both studies were substantially different from the combined estimate of the relationship between birth weight and SBP.

Conclusions: Both the differences between the two selected studies and their differences from the combined estimates obtained by meta-analysis are likely to be due to differences in the age of the participants. The relationship between birth weight and SBP tended to become more strongly inverse in studies with older participants. Additionally, the correlations between height and SBP were found to change from positive to negative with increasing age, which explained the differential impact of adjustment for height in the two selected studies. It therefore appears that adjustment for height may have little effect for older participants, but more so for younger participants.     

Caspases as Therapeutic Targets in Alzheimer’s Disease: Is It Time to “Cut” to the Chase?

Mounting evidence suggests the involvement of caspases in the disease process associated with Alzheimer’s disease (AD). The activation of caspases may be responsible for the neurodegeneration associated with AD and several recent studies have suggested that caspases may also play a role in promoting pathogenic mechanisms underlying this disease. Thus, caspase activation and cleavage of the amyloid precursor protein (APP) and tau may facilitate both the production of beta-amyloid (Aβ) as well as the formation of neurofibrillary tangles (NFTs). Because the activation of caspases in AD may be a proximal event that is not just associated with neurodegeneration, caspases are potential therapeutic targets for the treatment of this disorder. In this review, studies documenting the role of caspases in the AD brain will be discussed. In this context, a discussion of the therapeutic value of targeting caspase inhibition in the treatment of AD will be evaluated including drug targets, delivery and selectivity.     

In vitro amplification and detection of variant Creutzfeldt-Jakob disease PrPSc

Variant Creutzfeldt-Jakob disease (vCJD) poses a serious risk of secondary transmission and the need to detect infectivity in asymptomatic individuals is therefore of major importance. Following infection, it is assumed that minute amounts of disease-associated prion protein (PrP(Sc)) replicate by conversion of the host cellular prion protein (PrP(C)). Therefore, methods of rapidly reproducing this conversion process in vitro would be valuable tools in the development of such tests. We show that one such technique, protein misfolding cyclic amplification (PMCA), can amplify vCJD PrP(Sc) from human brain tissue, and that the degree of amplification is dependent upon the substrate PRNP codon 129 polymorphism. Both human platelets and transgenic mouse brain are shown to be suitable alternative substrate sources, and amplified PrP(Sc) can be detected using a conformation-dependent immunoassay (CDI), allowing the detection of putative proteinase K sensitive forms of PrP(Sc).