Temporal Evolution of Ischemic Lesions in Nonhuman Primates: A Diffusion and Perfusion MRI Study

MethodsPermanent MCA occlusion was induced with silk sutures through an interventional approach via the femoral artery in adult rhesus monkeys (n = 8, 10–21 years old). The stroke lesions were examined with high-resolution DWI and perfusion MRI, and T2-weighted imaging (T2W) on a clinical 3T scanner at 1–6, 48, and 96 hours post occlusion and validated with H&E staining.ResultsThe stroke infarct evolved via a natural logarithmic pattern with the mean infarct growth rate = 1.38 ± 1.32 ml per logarithmic time scale (hours) (n = 7) in the hyperacute phase (1–6 hours). The mean infarct volume after 6 hours post occlusion was 3.6±2.8 ml (n = 7, by DWI) and increased to 3.9±2.9 ml (n = 5, by T2W) after 48 hours, and to 4.7±2.2ml (n = 3, by T2W) after 96 hours post occlusion. The infarct volumes predicted by the natural logarithmic function were correlated significantly with the T2W-derived lesion volumes (n = 5, r = 0.92, p = 0.01) at 48 hours post occlusion. The final infarct volumes derived from T2W were correlated significantly with those from H&E staining (r = 0.999, p < 0.0001, n = 4). In addition, the diffusion-perfusion mismatch was visible generally at 6 hours but nearly diminished at 48 hours post occlusion.ConclusionThe infarct evolution follows a natural logarithmic pattern in the hyperacute phase of stroke. The logarithmic pattern of evolution could last up to 48 hours after stroke onset and may be used to predict the infarct volume growth during the acute phase of ischemic stroke. The nonhuman primate model, MRI protocols, and post data processing strategy may provide an excellent platform for characterizing the evolution of acute stroke lesion in mechanistic studies and therapeutic interventions of stroke disease.     

HH Domain of Alzheimer’s Disease Aβ Provides Structural Basis for Neuronal Binding in PC12 and Mouse Cortical/Hippocampal Neurons

A key question in understanding AD is whether extracellular Aβ deposition of parenchymal amyloid plaques or intraneuronal Aβ accumulation initiates the AD process. Amyloid precursor protein (APP) is endocytosed from the cell surface into endosomes where it is cleaved to produce soluble Aβ which is then released into the brain interstitial fluid. Intraneuronal Aβ accumulation is hypothesized to predominate from the neuronal uptake of this soluble extracellular Aβ rather than from ER/Golgi processing of APP. We demonstrate that substitution of the two adjacent histidine residues of Aβ40 results in a significant decrease in its binding with PC12 cells and mouse cortical/hippocampal neurons. These substitutions also result in a dramatic enhancement of both thioflavin-T positive fibril formation and binding to preformed Aβ fibrils while maintaining its plaque-binding ability in AD transgenic mice. Hence, alteration of the histidine domain of Aβ prevented neuronal binding and drove Aβ to enhanced fibril formation and subsequent amyloid plaque deposition - a potential mechanism for removing toxic species of Aβ. Substitution or even masking of these Aβ histidine residues might provide a new therapeutic direction for minimizing neuronal uptake and subsequent neuronal degeneration and maximizing targeting to amyloid plaques.     

Pathology: Cervical Pathology—The Bethesda System and the `Atypical Squamous Cells of Undetermined Significance' Controversy

The Council on Scientific Affairs of the California Medical Association presents the following epitomes of progress in pathology. Each item, in the judgment of a knowledgeable physicians, has recently become reasonably firmly established, both as to scientific fact and clinical importance. The items are presented in simple epitome, and an authoritative reference, both to the item itself and to the subject as a whole, is generally given for those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, researchers, and scholars to stay abreast of progress in medicine, whether in their own field of special interest or another.The epitomes included here were selected by the Advisory Panel to the Section on Pathology of the California Medical Association, and the summaries were prepared under the direction of Yutaka Kikkawa, MD, and the panel.     

Mechanism for the emetic side effect of xanthine bronchodilators.

The usefulness of xanthine bronchodilators in the treatment of asthma is often limited by the side effects of nausea and vomiting. We investigated the mechanism of emesis induced by xanthines, by examining the roles of phosphodiesterase (PDE) inhibition and adenosine antagonism. Theophylline, enprofylline, 8-phenyltheophylline and isobutylmethylxanthine (IBMX), as well as vehicle, were given to ferrets at doses ranging from 0.1 to 150 mg/kg i.p. The potencies of these compounds in producing emetic responses were ranked IBMX greater than enprofylline greater than theophylline greater than 8-phenyltheophylline. These results correlate well with the relative potencies of the compounds as nonselective PDE inhibitors but do not correlate with their relative potencies as adenosine A1 or A2 receptor antagonists. The emetic responses also correlate well with the previously reported potencies of these xanthines as bronchodilators in guinea pigs. We conclude that the emetic side effect of xanthine bronchodilators results from the inhibition of one or more forms of PDE rather than from adenosine antagonism.     

Variation in the molecular size of the DNA from closely related strains of type I herpes simplex virus.

We have investigated the comparative genome size of five strains of HSV type 1 (HSV-1). Two of these strains have a common origin and differ in their plaque morphology on HeLa cells, one strain is a wild type isolate, and two others are established laboratory strains. All strains show high sequence homology based on the melting behavior of heteroduplexes. The greatest sequence divergence between any two strains was found to be no more than 10%. There are real differences in the size of the genomes of these strains of HSV-1 as measured by electron microscopy. The shortest and largest genomes measured differ in size by 10%, however, the size of the genomes of all strains are within 5% of a median valve of 87-88X106.     

TGF-β Isoform Specific Regulation of Airway Inflammation and Remodelling in a Murine Model of Asthma

The TGF-β family of mediators are thought to play important roles in the regulation of inflammation and airway remodelling in asthma. All three mammalian isoforms of TGF-β, TGF-β_1–3, are expressed in the airways and TGF-β₁ and -β₂ are increased in asthma. However, there is little information on the specific roles of individual TGF-β isoforms. In this study we assess the roles of TGF-β₁ and TGF-β₂ in the regulation of allergen-induced airway inflammation and remodelling associated with asthma, using a validated murine model of ovalbumin sensitization and challenge, and isoform specific TGF-β neutralising antibodies. Antibodies to both isoforms inhibited TGF-β mediated Smad signalling. Anti-TGF-β₁ and anti-TGF-β₂ inhibited ovalbumin-induced sub-epithelial collagen deposition but anti-TGF-β₁ also specifically regulated airway and fibroblast decorin deposition by TGF-β₁. Neither antibody affected the allergen-induced increase in sub-epithelial fibroblast-like cells. Anti- TGF-β₁ also specifically inhibited ovalbumin-induced increases in monocyte/macrophage recruitment. Whereas, both TGF-β₁ and TGF-β₂ were involved in regulating allergen-induced increases in eosinophil and lymphocyte numbers. These data show that TGF-β₁ and TGF-β₂ exhibit a combination of specific and shared roles in the regulation of allergen-induced airway inflammation and remodelling. They also provide evidence in support of the potential for therapeutic regulation of specific subsets of cells and extracellular matrix proteins associated with inflammation and remodelling in airway diseases such as asthma and COPD, as well as other fibroproliferative diseases.     

A rapid technique for producing silver-stained nucleolus organizer regions and trypsin-Giemsa bands on human chromosomes

Summary A simple and rapid technique is described whereby the nucleolus organizer regions (NORs) of human chromosomes can be differentially stained with silver. This staining is followed by trypsin-Giemsa banding on the same metaphase chromosomes. The metaphases simultaneously exhibit silverstained NORs and G bands, allowing for the unequivocal identification of all chromosomes and greatly facilitating studies involving the NOR-bearing acrocentrics.