Pretreatment of astrocytes with interferon-alpha/beta impairs interferon-gamma induction of nitric oxide synthase

Excessive nitric oxide/peroxynitrite generation has been implicated in the pathogenesis of multiple sclerosis, and the demonstration of increased astrocytic nitric oxide synthase activity in the postmortem brain of multiple sclerosis patients supports this hypothesis. Exposure of astrocytes, in primary culture, to interferon-gamma results in stimulation of nitric oxide synthase activity and increased nitric oxide release. In contrast to interferon-gamma, interferon-alpha/beta had a minimal effect on astrocytic nitric oxide formation. Furthermore, pretreatment of astrocytes with interferon-alpha/beta inhibited (approximately 65%) stimulation by interferon-gamma of nitric oxide synthase activity and nitric oxide release. Treatment with interferon-alpha/beta at a concentration as low as 10 U/ml caused inhibition of mitochondrial cytochrome c oxidase. Furthermore, the damage to cytochrome c oxidase was prevented by the putative interferon-alpha/beta receptor antagonist oxyphenylbutazone. In view of these observations, our current hypothesis is that the mitochondrial damage caused by exposure to interferon-alpha/beta may impair the ability of astrocytes to induce nitric oxide synthase activity on subsequent interferon-gamma exposure. These results may have implications for our understanding of the mechanisms responsible for the therapeutic effects of interferon-alpha/beta preparations in multiple sclerosis.     

Topoisomerase function during replication-independent chromatin assembly in yeast

DNA topoisomerases I and II are the two major nuclear enzymes capable of relieving torsional strain in DNA. Of these enzymes, topoisomerase I plays the dominant role in relieving torsional strain during chromatin assembly in cell extracts from oocytes, eggs, and early embryos. We tested if the topoisomerases are used differentially during chromatin assembly in Saccharomyces cerevisiae by a combined biochemical and pharmacological approach. As measured by plasmid supercoiling, nucleosome deposition is severely impaired in assembly extracts from a yeast mutant with no topoisomerase I and a temperature-sensitive form of topoisomerase II (strain top1-top2). Expression of wild-type topoisomerase II in strain top1-top2 fully restored assembly-driven supercoiling, and assembly was equally efficient in extracts from strains expressing either topoisomerase I or II alone. Supercoiling in top1-top2 extract was rescued by adding back either purified topoisomerase I or II. Using the topoisomerase II poison VP-16, we show that topoisomerase II activity during chromatin assembly is the same in the presence and absence of topoisomerase I. We conclude that both topoisomerases I and II can provide the DNA relaxation activity required for efficient chromatin assembly in mitotically cycling yeast cells.     

Some morphological, physiological and behavioral specializations in North American beavers (Castor canadensis)

In order to gain insight into the functional properties of the tail in North American beavers (Castor canadensis) we (1) examined morphological features of skeletal, muscular, vascular, cutaneous and neural structures; (2) determined the segmental organization of spinal roots and certain stimulus-response features of receptive fields of single dorsal root fibers; (3) mapped the main somatic sensory area (SI) of the cerebral neocortex, and (4) attempted to relate these findings to observations of tail behavior in living beavers. The behavioral observations revealed the beaver capable of forceful yet discrete movements of the tail in water. A morphological correlate of these motor skills was the distinct segmentally organized pattern of serial muscle tendon arrangements and spinal sensory and motor innervation. Neither the receptors innervating the scales or hairs of the tail, the stimulus-response properties of single dorsal root afferents, nor the representation of the tail in SI suggested unusual cutaneous sensory capabilities associated with the morphological and behavioral specializations exhibited by the beaver's tail.     

Rupture of a previously documented small asymptomatic intracranial aneurysm in a patient with autosomal dominant polycystic kidney disease. Case report

Intracranial aneurysms are common extrarenal manifestations of autosomal dominant polycystic kidney disease (ADPKD). Although their natural history is not completely understood, small asymptomatic intracranial aneurysms in patients with ADPKD often are not treated but are followed with serial magnetic resonance (MR) angiography. The authors report the unique case of a patient with ADPKD who bled from a previously documented asymptomatic 3-mm intracranial aneurysm. This 42-year-old man with ADPKD suffered a subarachnoid hemorrhage (SAH) from a 7-mm left pericallosal artery aneurysm. This aneurysm was clipped and the patient made an excellent recovery. An irregular asymptomatic 3-mm right middle cerebral artery (MCA) aneurysm had also been demonstrated on angiography. While the patient was considering elective surgery for the MCA aneurysm, he suffered a hemorrhage from this lesion 10 weeks after the initial SAH. The aneurysm was clipped and the patient made a satisfactory recovery (he was moderately disabled). In this report the authors indicate that small asymptomatic intracranial aneurysms are not always innocuous in patients with ADPKD, and they suggest that treatment should be strongly considered for these lesions in this group of patients when there is a history of SAH or the aneurysm is irregular in appearance. Because MR angiography studies may not adequately define the configuration of small aneurysms and irregularity may easily be missed, conventional angiography is recommended for patients with ADPKD who are found to have an intracranial aneurysm on screening with MR angiography.     

Chronic obstructive pulmonary disease: role of bronchiolar mast cells and macrophages

Chronic obstructive pulmonary disease (COPD) is considered to be caused in part by smoking-induced inflammation, but it is unknown which inflammatory cells within the small airways are associated with the obstruction. We investigated the inflammatory infiltrate in the small airways of 16 current or ex-smokers with COPD (FEV1 < or = 75% predicted) and 15 without COPD (FEV1 > or = 85% predicted) in pneumectomy specimens that were removed for lung cancer. Mast cells, macrophages, neutrophils, eosinophils, T cells, and B cells were identified using immunohistochemistry on formalin-fixed, paraffin-embedded specimens. These cells were quantified in the epithelium and the remainder of the airway wall. The number of mast cells and macrophages in the epithelium, but not in the remainder of the airway wall, was significantly increased in patients with COPD. Neutrophil and T cell numbers did not differ between the groups. Only few B cells and eosinophils were present in both groups. Smoking history, perioperative steroid usage, tumor localization, or reversibility in the FEV1 to salbutamol could not account for the observed differences. We conclude that the number of epithelial mast cells and macrophages is increased in the bronchioli in smokers with airflow limitation, suggesting a role in development of COPD.     

Metastatic basal-cell carcinoma

Three cases of metastatic basal-cell carcinoma are reported. All of the cases were relatively small when compared with other lesions reported in the literature. With early chemosurgical treatment of small recurrent carcinomas, metastasizing basal-cell carcinoma will be a condition of the past.     

A genetic screen for aminophospholipid transport mutants identifies the phosphatidylinositol 4-kinase, STT4p, as an essential component in phosphatidylserine metabolism

In an effort to understand molecular mechanisms of intracellular lipid transport, we have focused upon specific events required for de novo aminophospholipid synthesis in the yeast Saccharomyces cerevisiae. A genetic system for examining the steps between phosphatidylserine (PtdSer) synthesis in the endoplasmic reticulum and its transport to and decarboxylation by PtdSer decarboxylase 2 in the Golgi/vacuole has been developed. We have isolated a mutant, denoted pstB1, that accumulates PtdSer and has diminished phosphatidylethanolamine formation despite normal PtdSer decarboxylase 2 activity. The lesion in PtdSer metabolism is consistent with a defect in interorganelle lipid transport. A genomic DNA clone that complements the mutation was isolated, and sequencing revealed that the clone contains the STT4 gene, encoding a phosphatidylinositol 4-kinase. The pstB1 mutant exhibits a defect in Stt4p-type phosphatidylinositol 4-kinase activity, and direct gene replacement indicates that STT4 is the defective gene in the mutant. Creation of an STT4 null allele (stt4Delta::HIS3) demonstrates the gene is essential. These results provide evidence that implicates phosphoinositides in the regulation of intracellular aminophospholipid transport.