Multi-subject Stochastic Blockmodels for adaptive analysis of individual differences in human brain network cluster structure.

There is considerable interest in elucidating the cluster structure of brain networks in terms of modules, blocks or clusters of similar nodes. However, it is currently challenging to handle data on multiple subjects since most of the existing methods are applicable only on a subject-by-subject basis or for analysis of an average group network. The main limitation of per-subject models is that there is no obvious way to combine the results for group comparisons, and of group-averaged models that they do not reflect the variability between subjects. Here, we propose two new extensions of the classical Stochastic Blockmodel (SBM) that use a mixture model to estimate blocks or clusters of connected nodes, combined with a regression model to capture the effects of subject-level covariates on individual differences in cluster structure. The proposed Multi-Subject Stochastic Blockmodels (MS-SBMs) can flexibly account for between-subject variability in terms of homogeneous or heterogeneous covariate effects on connectivity using subject demographics such as age or diagnostic status. Using synthetic data, representing a range of block sizes and cluster structures, we investigate the accuracy of the estimated MS-SBM parameters as well as the validity of inference procedures based on the Wald, likelihood ratio and permutation tests. We show that the proposed multi-subject SBMs recover the true cluster structure of synthetic networks more accurately and adaptively than standard methods for modular decomposition (i.e. the Fast Louvain and Newman Spectral algorithms). Permutation tests of MS-SBM parameters were more robustly valid for statistical inference and Type I error control than tests based on standard asymptotic assumptions. Applied to analysis of multi-subject resting-state fMRI networks (13 healthy volunteers; 12 people with schizophrenia; n=268 brain regions), we show that Heterogeneous Stochastic Blockmodel (Het-SBM) identifies a range of network topologies simultaneously, including modular and core structures.

The expression of xenobiotic-metabolizing enzymes in human prostate and in prostate epithelial cells (PECs) derived from primary cultures.

BACKGROUND: Dietary heterocyclic amines (HCAs) are carcinogenic in rodent prostate requiring activation by enzymes such as cytochrome P450 (CYP) and N-acetyltransferase (NAT). METHODS: We investigated by Western blotting and immunohistochemistry the expression of CYP1A1, CYP1A2, and NAT1 in human prostate and in prostate epithelial cells (PECs) derived from primary cultures and tested their ability to activate the dietary carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and its N-hydroxy metabolite (N-OH-IQ) to DNA-damaging moieties. RESULTS: Western blotting identified CYP1A1, CYP1A2, and NAT1. Immunohistochemistry localized NAT1 to the cytoplasm of PECs. Inter-individual variation was observed in the expression levels of CYP1A1, 1A2, and NAT1 (11, 75, and 35-fold, respectively). PECs expressed CYP1A1 and NAT1 but not CYP1A2. When incubated with IQ or N-OH-IQ, PECs formed DNA adducts indicating their ability to metabolically activate these compounds. CONCLUSIONS: Prostate cells possess the capacity to activate dietary carcinogens. PECs may provide a useful model system to study their role in prostate carcinogenesis.

Misplacement of dysplastic epithelium in Peutz-Jeghers Polyps: the ultimate diagnostic pitfall?

Peutz-Jeghers syndrome is characterized by multiple polyps throughout the gastrointestinal tract in association with mucocutaneous pigmentation. Small bowel polyps in the syndrome may exhibit epithelial misplacement, into the submucosa, the muscularis propria, and even the subserosa. The authors demonstrate two patients in whom there is also misplacement of dysplastic epithelium into the submucosa and muscularis propria of the small bowel. Epithelial misplacement is recognized to mimic invasive malignancy. Such mimicry is heightened substantially when the misplaced epithelium is dysplastic. Correct interpretation of the histologic changes is aided by the use of special stains, which demonstrate the associated lamina propria and the lack of a desmoplastic response, and immunohistochemistry, which shows that the misplaced dysplastic epithelium is accompanied by non-neoplastic mucosa. There is an increased prevalence of gastrointestinal malignancy in Peutz-Jeghers syndrome. However, the presence of perplexing histologic features, caused by epithelial misplacement, especially when some of that epithelium is dysplastic, in small bowel polyps at least has the potential for the overdiagnosis of malignancy in the syndrome.

Penicillamine-induced changes in elastic tissue of the upper respiratory tract.

We describe a patient who developed upper respiratory tract symptoms following long-term treatment of Wilson's disease with penicillamine. These symptoms were attributed to areas of pharyngeal thickening and were treated with a laser. Histological examination of the lesions showed proliferations of abnormal elastic fibres similar to those previously described at other sites, especially the skin, in patients receiving penicillamine. This drug impairs the maturation and reduces the stability of elastic fibres and although elastic tissue throughout the body is affected, we are aware of no previous reports of penicillamine-induced changes presenting with upper respiratory tract symptoms.

Arteries and veins formed within renal vessels: a previously neglected observation.

An abnormality of blood vessels was noted in a biopsy of a renal transplant. This took the form of apparent development of a new artery inside and concentric with the old, with elastic laminae and a muscular media, separated from the old internal elastic lamina by poorly cellular tissue. In a systematic study of material from another 119 renal transplants, 13 nephrectomy specimens for chronic pyelonephritis and hydronephrosis, 28 renal biopsies showing interstitial nephritis, and 18 renal biopsies showing small vessel vasculopathy of accelerated hypertensive type, similar arterial changes were seen in another 10 renal transplants that showed chronic vascular rejection, 1 case of chronic interstitial nephritis, and 3 cases of vasculopathy, 2 with accelerated hypertension and 1 with systemic sclerosis. One renal transplant also showed apparent development of new muscular veins inside old veins. Immunohistological study for smooth muscle actin confirmed that the apparently new arterial and venous structures contained smooth muscle cells. The arterial abnormality may be called arterialisation of intrarenal arteries. This change appears to be not rare, is distinctive, and has scarcely been previously recognised or reported as a response of intrarenal blood vessels to damage.

Granulomatous prostatitis: a clinicopathological study.

In a clinicopathological study of granulomatous prostatitis, we have found two distinct histological patterns. Approximately one third of cases consisted of localized, often elongated or stellate lesions, resembling rheumatoid nodules. Where clinical details were available, most of these cases had a history of previous transurethral resection. The remaining cases showed more diffuse involvement of the prostate, with lesions centred on ducts and glands, and were not associated with previous prostatic surgery or systemic illness. Immunohistochemical studies of the associated inflammatory infiltrate showed an apparently random distribution of T- and B-lymphocytes in the former group, while in the latter group there was a concentration of T-cells in and around damaged ducts and glands, suggesting a possible immune-mediated destruction of these structures.

Intestinal graft versus host disease.

An ileocolectomy specimen was examined from a patient with graft versus host disease (GvHD). In addition to the characteristic histological features of this condition, both the small and the large intestine showed extensive destruction of mucosal tissue with survival of clusters of enterochromaffin cells. This appearance has previously been described only in the large bowel. Endocrine cells seem to be less vulnerable to the effects of GvHD than epithelial cells, resulting in their being spared, which is not seen in other types of crypt destruction.

A predominantly adrenaline-secreting phaeochromocytoma.

A 61-year-old woman who presented with diabetes, nausea, weight loss and sweating was found to have a phaeochromocytoma secreting adrenaline, with a small amount of N-methyladrenaline. There was no significant increase in noradrenaline secretion. She was normotensive, and developed profound hypotension in response to the alpha-adrenergic antagonist phenoxybenzamine. These features are unusual in phaeochromocytoma, but similar features occurred in the very few previous reported cases of pure adrenaline-secreting phaeochromocytoma. We conclude that it is important to identify such patients, so that they should not be given alpha-adrenergic antagonist drugs.

Detection of HPV 6 and 11 in tumours of the upper respiratory tract using the polymerase chain reaction.

We have applied the polymerase chain-reaction (PCR) technique to benign and malignant squamous tumours of the pharynx and larynx and to nasal inverted papillomas to detect evidence of infection with human papillomavirus (HPV) 6 and 11. Each of these lesions tended to be infected with either or both of these but the prevalence of infection when compared with that of histologically normal biopsies from the nasopharynx was not significantly increased.

Nucleolar organiser regions in kidney tumours and xanthogranulomatous pyelonephritis.

The AgNOR argyrophil technique was applied to clear cut examples of renal adenoma (n = 7), clear cell carcinoma (n = 9), and xanthogranulomatous pyelonephritis (n = 5). There was no significant difference between mean AgNOR counts per cell in adenomas and carcinomas, supporting the idea that there is a continuous spectrum of kidney tumours. Xanthogranulomatous pyelonephritis and clear cell carcinoma showed significant differences in mean AgNOR counts per cell, suggesting that the technique may be of use in distinguishing between these conditions, although further cases may need to be examined to confirm this.

A simple method for assessment of glomerular size and its use in the study of kidneys in acromegaly and compensatory renal enlargement.

As measurement of absolute glomerular size is difficult we developed a method of assessing glomerular size that was simple and practical and could be used to compare the kidneys in different groups of patients. Using a semi-automatic image analyser, the cross-sectional area of 100 randomly-selected glomeruli, outlined by Bowman's capsule, was measured on sections of kidneys taken at necropsy. The mean of the logarithms of the largest 25 areas was calculated. The method was applied to compare control kidneys (53) with the kidneys in acromegalics (20), in patients with one kidney (10) and in patients with asymmetrical kidneys (12). Kidneys were heavier in the three test groups than in controls. Glomerular sizes were similar in controls and in acromegalics but were larger in single and disparate kidneys. There was a relationship between glomerular size and kidney weight within the control group and across the four groups taken together. This only partly accounted for the observed differences in glomerular size between the groups. Histological comparison of the acromegalic and single kidneys showed more global glomerulosclerosis in single kidneys and also segmental lesions, mainly at the glomerular hilum, only in the single kidneys. These findings show that renal enlargement occurs in acromegaly and in single and disparate kidneys but is accompanied by markedly different glomerular features. This implies different mechanisms for the renal enlargement. The method of assessing glomerular size is useful in the study of these and other conditions affecting the kidney.

Malignant coarctation of the aorta.

A case of primary malignant fibrous histiocytoma of the aorta is described.