Chromosomal aberration induction in CHO cells by combined exposure to restriction enzymes and X-rays.

The potential interaction between restriction enzyme-induced double-strand breaks (dsb) and X-ray-induced lesions in the formation of chromosomal aberrations was investigated in Chinese hamster ovary cells. Either Alu I, which induces blunt-end dsb, or Sau 3AI, which induces cohesive-end dsb, was electroporated into cells, which were irradiated with 2 Gy of X-rays immediately or 15, 30, 60, 120, or 180 min after electroporation. A significant increase in Alu I-induced chromosomal aberrations was observed when cells were irradiated with 0, 15, 30, or 60 min after enzyme exposure, but only additive effects were found when cells were irradiated 120 or 180 min after enzyme exposure. In one of three experiments, cells exposed to Sau 3AI showed a large increase in aberrations when X-irradiated 0 or 15 min after Sau 3AI exposure, and no increase at any time-points thereafter. These results indicate that restriction enzyme-induced dsb can interact with X-ray-induced lesions, resulting in a synergistic increase in chromosomal aberration formation. Furthermore, this interaction depends on both the type of dsb and the time between enzyme and X-ray exposure.     

Inhibition of thromboxane synthesis ameliorates the progressive kidney disease of rats with subtotal renal ablation.

Ablation of greater than 70% of renal mass in the rat results in hypertension, proteinuria, and glomerular sclerosis of the remnant kidney. Rats with a remnant kidney have increased excretion of thromboxane in the urine when compared with normal rats. Chronic oral administration of OKY 1581, an inhibitor of thromboxane synthesis, in rats with a remnant kidney increases renal blood flow and glomerular filtration rate (GFR), decreases protein and thromboxane excretion in the urine, lowers blood pressure and cardiac index, and improves renal histology. The degree of hypertrophy of the remnant kidney was unaffected by administration of OKY 1581. Calculated values for single nephron plasma flow and GFR were significantly greater in rats with remnant kidneys given OKY 1581 than in rats given saline. Acute i.v. administration of OKY 1581 increased renal plasma flow and GFR in rats with a remnant kidney but not in normal rats or rats with a remnant kidney previously treated with acetylsalicyclic acid. OKY 1581 markedly inhibited platelet aggregation. We suggest that in this model of renal disease platelet aggregation and intraglomerular thrombosis play a key role in the development of glomerulosclerosis. Inhibition of platelet aggregation prevents development of glomerulosclerosis, hypertension, and cardiac hypertrophy. We suggest that hyperperfusion and hyperfiltration per se occurring in remnant glomeruli are not directly responsible for the development of glomerulosclerosis.     

Activation of spinal cord interneurons which process inputs from the femoral-saphenous vein

Recordings were made from single spinal cord interneurons which could be activated by electrical stimulation of afferents terminating in the wall of the femoral-saphenous vein. Interneurons were either excited or both excited and inhibited by venous afferent stimulation. Most of the venous afferent-driven interneurons could also be driven by electrical activation of A-alpha beta muscle and cutaneous afferents. Stimulation of several different muscle nerves drove single interneurons.     

Gangliosides in the nervous system during development and regeneration

Gangliosides are present in nervous tissues of echinoderms and chordates, but the amounts and patterns differ widely. There are changes in the ganglioside contents of nervous tissues during development in most animals studied. To a large extent, regional differences and changes with development and degeneration in ganglioside composition reflect changing and different proportions of cellular types and subcellular organelles within the tissue. G_M1 and G_M4 are enriched in myelin; G_D1a may be a marker for dendritic arborization. During regeneration of fish optic nerve and rat sciatic nerve there is an increased amount of ganglioside proximal to the regenerating axon tips, which may largely be a result of accumulation. This could provide a relatively large reservoir of ganglioside to become incorporated into the sprouting axolemma. Gangliosides added exogenously to growth medium can induce neuritogenesis of several types of neurons. The mechanisms of this action are unknown but may be related to nerve growth factor, microskeletal organization, membrane fluidity, and other factors. Gangliosides injected into young animals affect brain development, but further studies are required to determine these effects more specifically. Ganglioside administration increases the number of sprouts in regenerating peripheral nerves, but does not seem to accelerate axonal elongation. Parenterally administered gangliosides alter the recovery of brain tissue from a variety of types of lesions, and clinical trials are in progress to determine if they are of benefit in human neurological disorders. The biochemical mechanisms of these in vivo ganglioside effects are poorly understood, but may involve modulation of several enzyme systems as well as other properties of neural membranes, such as fluidity. It is possible that gangliosides may play similar roles and operate through some of the same mechanisms in developing and regenerating nervous tissues.     

The emergency department and the community: a model for improved cooperation.

Improved emergency care may be achieved by closer integration of hospital and community management. This has been promoted in Salford by the appointment of an Emergency Services Practice Manager jointly funded by the Family Health Services Authority and Salford Health Authority. Communication has improved, complementary working relationships developed and health promotion initiatives established.     

Alzheimer''s disease: a correlative study.

In a study of 17 patients with histologically proven Alzheimer's disease the relationship between psychological, pathological and chemical measures of disorder was examined. Severity of dementia, determined by mental test performance, correlated highly with pathological change in large cortical neurons (cell loss and reduction in nuclear and nucleolar volume and cytoplasmic RNA content), to a lesser extent with cortical senile plaque and neurofibrillary tangle frequency and reduction in acetylcholine (ACh) synthesis, and not with reduction in choline acetyltransferase (CAT) activity. A strongly significant relationship was demonstrated between cell loss and reductions in nuclear and nucleolar volume and cytoplasmic RNA content. Reduction in CAT activity and senile plaque frequency were significantly correlated, thereby linking changes in the sub-cortical projection system of the nucleus basalis with the cortical pathology. The pattern of correlations suggests that the dementia of Alzheimer's disease is largely a reflection of the state of large cortical neurons, and it is argued that abnormalities in the latter may not be directly related to primary loss of cholinergic neurons in the subcortex.     

Aspartylglycosaminuria in the Finnish population: identification of two point mutations in the heavy chain of glycoasparaginase.

Aspartylglycosaminuria is an inherited lysosomal storage disease caused by deficiency of glycoasparaginase (EC 3.5.1.26) and occurs with higher frequency among Finns than other populations. We have purified human glycoasparaginase and determined about 90% of the amino acid sequence of its light subunit and greater than 70% of that of its heavy subunit by Edman degradation and mass spectrometry. Additional sequence data were obtained from the cloning and subsequent nucleotide analysis of a cDNA corresponding to the normal human glycoasparaginase gene. The enzyme is encoded by a single mRNA as a single polypeptide that is posttranslationally processed to generate the subunits and is glycosylated. After preparing first-strand cDNA from leukocyte and fibroblast total RNA, we used the polymerase chain reaction to amplify the glycoasparaginase cDNA of eight Finnish aspartylglycosaminuria patients. We demonstrate that the Finnish patients' mRNA sequence differed from the normal sequence by two single-base changes six nucleotides apart from one another in the heavy chain of glycoasparaginase. The first change resulted in the replacement of arginine by glutamine (R161Q), whereas the second change resulted in a cysteine to serine substitution (C163S). Both mutations resulted in novel restriction endonuclease sites and were present in all eight Finnish aspartylglycosaminuria patients originating from different pedigrees, but they were absent from Finnish and non-Finnish controls and a non-Finnish case of aspartylglycosaminuria. These results indicate molecular homogeneity in aspartylglycosaminuria alleles in the Finnish population.     

Genetic analysis in a female manifesting haemophilia B.

A 5 year old female child presented with a psoas haematoma as the first manifestation of haemophilia B. Molecular genetic studies were performed to investigate the inheritance of the disorder and the mechanisms by which females may express the haemophilia B phenotype are discussed.