The spatial pattern of the synaptic vesicular apparatus as a correlate of transmitter storage models.

A statistical stereological approach which allows one to derive a three-dimensional pattern of synaptic vesicle accumulation in relation to the active zone from an analysis of electron micrograms (random sections) of synapses is described. This approach is illustrated with a study of presynaptic terminals from the dorsal horn of the cat spinal cord, based on the morphometrical treatment of 105 micrographs containing 5190 synaptic vesicles. The spatial pattern obtained was found to have a bimodal shape, which can be considered a possible structural correlate of the two-pool model of transmitter storage. The connection of similar quantitative estimates with physiological data is discussed.     

Gene conversion is a likely cause of mutation in PKD1

Approximately 70% of the gene responsible for the most common form of autosomal dominant polycystic kidney disease ( PKD1 ) is replicated in several highly homologous copies located more proximally on chromosome 16. We recently have described a novel technique for mutation detection in the duplicated region of PKD1 that circumvents the difficulties posed by these homologs. We have used this method to identify two patients with a nearly identical cluster of base pair substitutions in exon 23. Since pseudogenes are known to be reservoirs for mutation via gene conversion events for a number of other diseases, we decided to test whether these sequence differences in PKD1 could have arisen as a result of this mechanism. Using changes in restriction digest patterns, we were able to show that these sequence substitutions are also present in N23HA, a rodent-human somatic cell hybrid that contains only the PKD1 homologs. Moreover, these changes were also detected in total DNA from several affected and unaffected individuals that did not harbor this mutation in their PKD1 gene copy. This is the first example of gene conversion in PKD1 , and our findings highlight the importance of using gene-specific reagents in defining PKD1 mutations.      

Quantitative characteristics and reconstruction of the surface topography of histochemical markers on the nerve cell plasmalemma]

An electron microscopic study of topography of colloidal gold-bound lectins conjugating to glycocalix carbohydrate residues on the somatic membrane surface of the cultivated spinal neurons has been carried out. The quantitative procedures are suggested for analyzing the surface pattern of the markers: two stochastic functions are considered to correspond properly to the particle distribution observed in the electron micrograms. The analysis of these functions permits obtaining required numerical characteristics. The Monte Carlo reconstructing model is described, and results of its work (on the basis of the above experimental data) are demonstrated in the form of "averaged" surface topography of the studied markers within the membrane fragments bordered. Possible connection of the obtained data with cooperative properties of the membrane is discussed.     

Shwachman syndrome: Exocrine pancreatic dysfunction and variable phenotypic expression

BACKGROUND & AIMS: Shwachman syndrome is an inherited condition with multisystemic abnormalities, including exocrine pancreatic dysfunction. The aim of this study was to evaluate the occurrence and progression of features in a large cohort of patients. METHODS: Clinical records of 25 patients with Shwachman syndrome were reviewed. RESULTS: Mean birth weight (2.92 +/- 0.51 kg) was at the 25th percentile. However, by 6 months of age, mean heights and weights were less than the 5th percentile. After 6 months of age, growth velocity was normal. Severe fat maldigestion due to pancreatic insufficiency was present in early life (fecal fat, 26% +/- 17% of fat intake; age, < 2 years). Serial assessment of exocrine pancreatic function showed persistent deficits of enzyme secretion, but 45% of patients showed moderate age-related improvements leading to pancreatic sufficiency. Neutropenia was the most common hematologic abnormality (88%), but leukopenia, thrombocytopenia, and anemia were also frequently encountered. Patients with hypoplasia of all three bone marrow cellular lines (n = 11) had the worst prognosis; 5 patients died, 2 of sepsis and 3 of acute myelogenous leukemia. Other findings included hepatomegaly and/or abnormal liver function test results and skeletal abnormalities. CONCLUSIONS: A wide and varied spectrum of phenotypic abnormalities among patients with Shwachman syndrome is described. Pancreatic acinar dysfunction is an invariable abnormality. Patients with severe bone marrow involvement may have a guarded prognosis. (Gastroenterology 1996 Dec;111(6):1593-602)     

Prostaglandin E2 potentiates platelet aggregation by priming protein kinase C

Prostaglandin E2 (PGE2) is produced by activated platelets and by several other cells, including capillary endothelial cells. PGE2 exerts a dual effect on platelet aggregation: inhibitory, at high, supraphysiologic concentrations, and potentiating, at low concentrations. No information exists on the biochemical mechanisms through which PGE2 exerts its proaggregatory effect on human platelets. We have evaluated the activity of PGE2 on human platelets and have analyzed the second messenger pathways involved. PGE2 (5 to 500 nmol/L) significantly enhanced aggregation induced by subthreshold concentrations of U46619, thrombin, adenosine diphosphate (ADP), and phorbol 12-myristate 13-acetate (PMA) without simultaneously increasing calcium transients. At a high concentration (50 mumol/L), PGE2 inhibited both aggregation and calcium movements. PGE2 (5 to 500 nmol/L) significantly enhanced secretion of beta-thromboglobulin (beta TG) and adenosine triphosphate from U46619- and ADP-stimulated platelets, but it did not affect platelet shape change. PGE2 also increased the binding of radiolabeled fibrinogen to the platelet surface and increased the phosphorylation of the 47-kD protein in 32P- labeled platelets stimulated with subthreshold doses of U46619. Finally, the amplification of U46619-induced aggregation by PGE2 (500 nmol/L) was abolished by four different protein kinase C (PKC) inhibitors (calphostin C, staurosporine, H7, and TMB8). Our results suggest that PGE2 exerts its facilitating activity on agonist-induced platelet activation by priming PKC to activation by other agonists. PGE2 potentiates platelet activation at concentrations produced by activated platelets and may thus be of pathophysiologic relevance.     

Interleukin-6 enhances growth factor-dependent proliferation of the blast cells of acute myeloblastic leukemia

The effects of recombinant interleukin-6 (IL-6) on the proliferation of blast precursors present in the peripheral blood of patients with acute myeloblastic leukemia (AML) was investigated. IL-6 had little effect by itself; however, it synergized with granulocyte macrophage colony- stimulating factor (GM-CSF) and interleukin-3 (IL-3) in the stimulation of AML blast colony formation. Responsiveness of blast progenitors to IL-6 was heterogeneous. On normal bone marrow cells the same synergy was observed on granulocyte and monocyte precursors (GM-CFC), while there was no significant effect on erythroid and multipotential precursors.     

Anesthesia systems. Part 1: Operating principles of fundamental components

This article is the first in a two-part series on the operation of principal components within Narkomed anesthesia systems. Part 1 illustrates the structure and function of various sections of the machine's internal piping, including components of the pneumatic circuit and the oxygen flush valve, and several safety features, such as the oxygen supply pressure alarm, oxygen failure protection device, and oxygen ratio monitor controller. The article progresses to other basic components of the anesthesia system. Topics include the function of the absorber unit and the flow of gas through it, the principle of operation of the positive end-expiratory pressure valve, the function and mechanics of the adjustable pressure limiter valve, and the open reservoir scavenger system. Part 1 is a valuable tool in understanding the function and pneumatics of the primary components of the anesthesia system.All figures are compliments of the Department of Education at North American Dräger, Telford, PA.     

Synthesis of fused [1,2,6]thiadiazine 1,1-dioxides as potential transition-state analogue inhibitors of xanthine oxidase and guanase.

Ring closure of ethyl 3-aminopyrazole-4-carboxylate with sulfamoyl chloride gave 1,7-dihydropyrazolo[3,4-c][1,2,6]thiadiazine-4(3H)-one 2,2-dioxide. The corresponding 4-amino analogue of this new heterocyclic ring system was similarly prepared from 3-aminopyrazole-4-carbonitrile. Treatment of 4,5,6-triamino-2H-1,2,6-thiadiazine 1,1-dioxide with N-thionylaniline gave a derivative of another new ring system, 7-amino-4H-[1,2,5]thiadiazolo[3,4-c][1,2,6]thiadiazine 5,5-dioxide. These compounds and the corresponding 4-amino- and 4-hydroxyimidazol[4,5-c][1,2,6]thiadiazine 2,2-dioxides were examined as potential transition-state analogue inhibitors of xanthine oxidase and guanine aminohydrolase. Two of the compounds possessed Ki values of about 2x 10(-4) M with guanine aminohydrolase, but no inhibition of xanthine oxidase was observed by any at 5 x 10(-4) M.     

Microglia and astrocytes in the adult rat brain: comparative immunocytochemical analysis demonstrates the efficacy of lipocortin 1 immunoreactivity

The distribution of glial cells (microglia and astrocytes) in different regions of normal adult rat brain was studied using immunohistochemical techniques and computer analysis. Lipocortin 1, phosphotyrosine, and lectin GSA B(4), were used for identification of microglia, while S100beta and glial fibrillary acidic protein identified astrocytes. Bioquant computerized image analysis was used to quantify and map the immunostained cells in sections from adult rat brain. If lipocortin 1 was used as a marker, more microglial cells were detected than with phosphotyrosine or lectin. The lipocortin 1-positive microglial population was most numerous (on average, 130+/-5 cells/mm(2) of the brain section area) in neostriatum, and least (51+/-4 cells/mm(2)) in cerebellum and medulla oblongata. In general, the density of lipocortin 1 microglia was higher in the forebrain, and lower in the midbrain, and the least in the brainstem and cerebellum. The number of S100beta astrocytes was two to three times larger than the number of microglial cells, and approximately two times greater than glial fibrillary acidic protein cells. A high density of astrocytes was found in the hypothalamus and hippocampus (more than 260 cells/mm(2)); they were more numerous in the white matter than in the gray matter. Fewer astrocytes were observed in the cerebral cortex, neostriatum, midbrain, medulla oblongata and cerebellum (less than 200 cells/mm(2)). Thus lipocortin 1 and S100beta were shown to be the most specific and reliable markers for microglia and astrocytes, respectively.The regional population differences demonstrated for lipocortin 1 microglia and S100beta astrocytes presumably reflect structural and functional specializations of the certain brain regions.