Quantum Size Effect on Surface Photovoltage Spectra: Alpha-Fe2O3 Nanocrystals on the Surface of Monodispersed Silica Microsphere

A new method for the preparation of Fe(2)O(3) nanoparticle/SiO(2) microsphere composites is described, in which fine alpha-Fe(2)O(3) nanocrystals were prepared by forced hydrolysis of FeCl(3) aqueous solution. The structure and optical spectra of these alpha-Fe(2)O(3) nanocrystals have been studied. Their visible optical absorption can be enhanced by their adsorptions on the surface of SiO(2) microspheres and thereafter simple packing of these microspheres to the aggregated structures. The size-dependent photogenerated surface photovoltage spectra (SPS) of these composites were studied, and quantum confinement effects of the SPS properties were observed. The transport of photoinduced charges between nanocrystals with intrinsic electronic nature of confined states accounts for this phenomenon. These results are helpful in understanding the relationship among d-d transition and charge-transfer transition in transition metal oxides and find applications in photovoltaic devices.

Ultrasound and magnetic resonance imaging assessmentof active bowel segments in Crohn's disease

AIM

Determining bowel disease activity in Crohn's patients can be difficult on clinical and laboratory assessment. Endoscopy is invasive and barium studies use ionising radiation. The aim of this study was to compare ultrasound and magnetic resonance imaging (MRI) in detecting Crohn's disease activity in the small or large bowel.

MATERIALS AND METHODS

Thirty patients, previously diagnosed with Crohn's disease, had bowel ultrasound and MR imaging, and were deemed active or inactive on each test. The 'gold standard' was based on clinical assessment and one or more of the following: endoscopy, barium studies or surgery.

RESULTS

For determining Crohn's disease activity, the sensitivities and specificities of bowel ultrasound and MRI were 87 percent and 100 percent, and 87 percent and 71 percent, respectively. Significant parameters that defined disease activity were bowel wall thickening on ultrasound and MRI, and contrast enhancement of the bowel wall and mesenteric vascularity/stranding on MRI.

CONCLUSION

Ultrasound and MRI were both sensitive for determining Crohn's disease activity in the bowel, but MRI with gadolinium enhancement was less specific.

A prospective single centre study comparing computed tomography pneumocolon against colonoscopy in the detection of colorectal neoplasms

BACKGROUND AND AIMS

To determine the sensitivity and specificity of computed tomography (CT) pneumocolon in the detection of colorectal neoplasms.

METHODS

A total of 201 consecutive patients with colorectal symptoms or requiring surveillance for colorectal neoplasms underwent both conventional colonoscopy and CT pneumocolon.

RESULTS

On conventional colonoscopy 13 invasive colorectal carcinomas were detected in 13 patients, and 118 polyps in 63 patients (14 polyps were > or =1 cm in diameter, 25 were 6-9 mm, and 79 were < or =5 mm). CT pneumocolon detected all 13 cancers, two false positive cancers, but only 20 polyps (seven were > or =1 cm). This resulted in a sensitivity of 100% (95% confidence interval (CI) 87-100%) and specificity of 99% (95% CI 97-100%) for detection of invasive carcinoma, and a sensitivity of 73% (95% CI 56-90%) and specificity of 94% (95% CI 91-98%) for detection of invasive carcinoma and/or > or =1 cm polyps. CT pneumocolon also identified invasive carcinoma not seen at colonoscopy because of incomplete examination in three patients, and detected metastases in six colorectal carcinoma patients and extracolonic carcinoma in a further seven patients.

CONCLUSIONS

CT pneumocolon had a high sensitivity and specificity for detection of invasive colorectal carcinoma but not colorectal polyps. CT pneumocolon may be suitable for initial investigation of patients with symptoms of colorectal malignancy.

Eradication of cryptosporidia and microsporidia following successful antiretroviral therapy

OBJECTIVES

Incidence of opportunistic protozoal infections causing diarrheal illnesses in patients with HIV has decreased since the introduction of highly active antiretroviral therapy (HAART). The objective of this study was to determine whether the parasites, cryptosporidia, and microsporidia were effectively eradicated or only suppressed following treatment.

DESIGN

Six HIV-positive patients with diarrheal symptoms caused by cryptosporidia or microsporidia were prospectively followed up with stool samples and duodenal biopsies. Samples were taken before HAART, between 1 to 3 months, and 6 months post-HAART.

METHODS

Duodenal samples were analyzed using routine histology and transmission electron microscopy. Stool samples were analyzed by both light microscopy and polymerase chain reaction (PCR) techniques.

RESULTS

Patients who responded successfully to HAART eradicated both cryptosporidial and microsporidial organisms. Symptoms improved within 1 month of therapy but complete eradication of the organisms was only observed after 6 months of treatment.

CONCLUSIONS

AIDs-related cryptosporidiosis and microsporidiosis can be cured following successful antiretroviral therapy.

Management of protozoal diarrhoea in HIV disease

Since the first reported case of HIV infection in 1981, many HIV-seropositive patients have died as a result of diarrhoea induced by opportunistic protozoal infections: pathogens that would normally cause only a transient illness in immunocompetent individuals. The introduction of highly active antiretroviral therapy (HAART) in 1996 has been associated with a significant decline in incidence and mortality arising from infections such as cryptosporidia and microsporidia. Previously, there were no chemotherapeutic agents known to be effective in eradicating these parasites, but since the availability of HAART, the memory of the emaciated terminally ill patient with advanced AIDS suffering from refractory diarrhoea will hopefully be a thing of the past. Significant advances in the knowledge of the pathogenesis of HIV disease, earlier detection and thus treatment of the virus, and availability of improved diagnostic techniques and HAART have transformed the way HIV-associated diarrhoea is managed. In this review, we look specifically at the management of protozoa-induced diarrhoea.

Alterations in blood leucocyte adhesion molecule profiles in HIV-1 infection

CD4 and CD8 lymphocyte numbers in the gut lamina propria are grossly altered in HIV-1 infection, out of proportion to alterations in the circulation. Such alterations in lymphocyte counts in the tissues may be due to altered leucocyte migration from the blood. One factor affecting leucocyte migration is adhesion molecule expression. Levels of adhesion molecule expression on peripheral CD4 and CD8 lymphocytes, monocytes and neutrophils from HIV-1-infected (AIDS and non-AIDS) and low-risk control individuals were compared. CD11a, CD62L, CD44, CD49d and beta7 integrin expression were examined by FACS analysis of fresh whole blood. Significant alterations in adhesion molecule expression were detected in HIV infection. The most striking alterations were observed in the CD8 lymphocyte population. CD11a expression was increased and CD62L and CD44 decreased. The CD4 lymphocyte population followed a similar, though less striking, pattern of alteration in adhesion molecule expression. Neutrophils displayed significantly reduced expression of both CD11a and CD62L, but only after onset of AIDS. Monocytes from infected individuals without AIDS displayed a different pattern of altered adhesion molecule expression compared with individuals with AIDS. These findings suggest that in HIV infection, leucocyte functions, such as migration, which require adhesion molecules are abnormal.

Colonic variceal bleeding in a patient with mesenteric venous obstruction due to an ileal carcinoid tumour

Colonic varices are a recognized cause of rectal bleeding in portal hypertension. We report here a patient who presented with melaena several months after resection of an ileal carcinoid tumour. Subsequent colonoscopy for continued episodes of rectal bleeding demonstrated extensive colonic varices. In the absence of portal hypertension, the varices appeared to be related to mesenteric venous obstruction. The management of bleeding colonic varices, in these circumstances, is discussed.