A test of the hypothesis that diagnostic ultrasound disrupts myelination in neonatal rats

Neonatal rats were exposed or sham exposed for 30 min to pulsed ultrasound [2.25 MHz carrier frequency, 1 microsecond pulse length, 50 Hz pulse repetition frequency (PRF), 50 W/cm2 Imax, 2 mW/cm2 ITA], euthanised and prepared for electron microscopic analysis of the nodes of Ranvier of the dorsal and ventral roots of the spinal cord. There was also a cage control. All materials were processed and scored blindly, evaluating whether perinodal myelin was normal. Rats from all regimens had areas of disrupted myelination. There was no statistically significant difference among the regimens for absence of myelination. The results did not confirm an earlier report that diagnostic ultrasound disrupts myelination in neonatal rats.     

Microsatellite instability analysis of primary human brain tumors

Microsatellite instability, as shown by the presence of additional alleles or shifts of electrophoretic mobility at simple sequence tandem repeat loci, has been demonstrated in hereditary and sporadic colorectal tumors and many other tumor types. To study microsatellite instability in human brain tumors, we examined a total of 144 sporadic neoplasms. These included 33 astrocytic tumors, 23 oligodendrogliomas, six gangliogliomas, 41 meningiomas, 10 vestibular schwannomas and 31 pituitary adenomas. Di-, tri- and tetranucleotide repeat microsatellite markers localized on chromosome 4 and 9, X, 13 and 22, respectively, were used to assess whether instability was a significant aspect of their abnormal chromosomal pattern. Instability of microsatellite markers was detected in four oligodendrogliomas (17.4%), one pituitary adenoma (3.2%), one meningioma (2.4%), one astrocytic tumor (3.0%) and not at all in gangliogliomas and schwannomas. Therefore, our results suggest that the microsatellite instability which occurs in colorectal cancers with defective mismatch repair is infrequent in many types of human brain tumors and that the lower level of instability observed in brain tumors may be reflective of other mechanisms of genetic instability.     

Molecular interaction of [2,3-14C] acrylonitrile with DNA in gastric tissue of rat

Acrylonitrile (VCN) is used extensively in polymer industries, and is known to induce gastric cancer following oral administration. A paucity of information exists regarding the mechanism(s) by which acrylonitrile induces gastric neoplasia. The time course for uptake of radioactivity by gastric tissue and covalent binding of [2,3-14C] VCN or its metabolites to gastric DNA were determined following a single oral dose of 46.5 mg/kg. The rates of DNA synthesis and repair, as measured by unscheduled DNA synthesis in the gastric tissue of VCN-treated rats, were also studied. Maximum tissue uptake and covalent binding of radioactivity to gastric DNA were observed at 15 minutes following [2,3-14C] VCN administration. At 6 hours following VCN administration, significant inhibition (37% of control) in gastric replicative DNA synthesis was observed. A rebound followed by an increase (211% of control) in replicative DNA synthesis was observed at 24 hours. A three-fold elevation in unscheduled DNA synthesis was observed at 24 hours following treatment with VCN. These results indicate that VCN or its metabolites irreversibly interact with gastric DNA, causing DNA damage. The results also indicate that the delayed VCN-induced DNA repair, determined as unscheduled DNA synthesis, is inefficient for the removal of the resulting DNA lesions.     

Sizing of bovine heart and kidney pyruvate dehydrogenase complex and dihydrolipoyl transacetylase core by quasielastic light scattering

Quasielastic light scattering (QELS) measurements on several preparations of bovine heart and kidney pyruvate dehydrogenase complex yielded hydrodynamic radii (rH values) ranging from 25.7 to 30 nm. Gel filtration chromatography removed stable aggregates and generated preparations that gave essentially the same rH values of 24.3 +/- 0.6 nm for both complexes. The data were characteristic of a monodisperse system and agree with estimates using cryoelectron microscopy [Wagenknecht et al. (1991) J. Biol. Chem. 266, 24650-24656]. The equivalent hydrodynamic sizes for the heart and kidney complex indicate that the larger number of pyruvate dehydrogenase components in the heart complex (M(r) congruent to 9 x 10(6)) than the kidney complex (M(r) congruent to 7.5 x 10(6)) associate without radial expansion of the heart complex. That accommodation of additional mass is consistent with the space available since even in the more massive complex greater than 80% of the volume within the dimensions of the complex must be occupied by solvent. Preparations of the core of the complex are primarily composed of 60 dihydrolipoyl acetyltransferase (E2) subunits whose inner domains associate to form a pentagonal dodecahedron that is readily observed by electron microscopy (particle radius 10.7-11.3 nm). However, the bulk of E2's mass is present in an exterior multidomain structure. These mobile outer structures are very difficult to observe by standard electron microscopy techniques. Preparations of the core formed stable aggregates that were removed by gel filtration chromatography. QELS measurements gave an rH of 20.1 +/- 0.8 nm.(ABSTRACT TRUNCATED AT 250 WORDS)     

Detection and identification of microcystins in the drinking water of Haimen City, China

The main method of classification of chronic viral hepatitis is now by cause, and the old histology-based classification is no longer considered appropriate. However, liver biopsy remains an important part of patient assessment and, in the context of clinical trials, biopsy findings are often scored in a semiquantitative manner. The concepts of grading and staging, borrowed from tumour pathology, have been introduced, representing the severity of the necroinflammatory lesion and the extent of its structural consequences respectively. The pathology of the individual forms of viral hepatitis A to G shows more similarities than differences. However, some pathological features are commonly associated with specific viruses. The combination of portal lymphoid follicles, bile duct damage, lobular activity and steatosis give chronic hepatitis C a characteristic histological profile. Very similar appearances have been noted in the limited number of biopsies so far reported from patients with known combined hepatitis C and G virus infection.     

Specific 3H-imipramine binding in human platelets. Influence of age and sex

Human platelets have been shown to possess high-affinity binding sites for 3H-imipramine. These binding sites have a similar affinity and drug specificity to those already described in rat brain. The platelets from healthy volunteers show no difference in 3H-imipramine binding between the sexes but there is a decrease in maximal 3H-imipramine binding with increasing age of the donor.     

Development and Performance of Boron Carbide‐Based Smoke Compositions

Pyrotechnic smoke compositions for visual obscuration containing boron carbide, potassium nitrate, potassium chloride, and various lubricants are described. Only the waxy lubricants stearic acid and calcium stearate slowed the burning rate into a range suitable for end‐burning smoke grenades. For compositions pressed into steel cans, the addition of just 2 wt‐% calcium stearate was shown to reduce the burning rate from 0.50 cm s⁻¹ to 0.09 cm s⁻¹. In this system, potassium chloride serves as a diluent that reduces incandesence but also increases slag formation. Compositions containing potassium chloride in the 25–30 wt‐% range exhibited both acceptably low incandescense and slag formation upon burning, while also producing copious amounts of white smoke. These experimental compositions were loaded into full‐size grenade cans; field and smoke chamber testing revealed that they outperform the US Army’s in‐service M83 TA grenade both qualitatively and quantitatively. The photopic mass‐based figures of merit for experimental grenades KCl‐25, KCl‐30, and a production‐run M83 TA grenade were 2.51, 2.19, and 1.44 m² g⁻¹, respectively.     

The conserved asparagine and arginine are essential for catalysis of mammalian adenylyl cyclase

Mammalian adenylyl cyclases have two homologous cytoplasmic domains (C1 and C2), and both domains are required for the high enzymatic activity. Mutational and genetic analyses of type I and soluble adenylyl cyclases suggest that the C2 domain is catalytically active and the C1 domain is not; the role of the C1 domain is to promote the catalytic activity of the C2 domain. Two amino acid residues, Asn-1025 and Arg-1029 of type II adenylyl cyclase, are conserved among the C2 domains, but not among the C1 domains, of adenylyl cyclases with 12 putative transmembrane helices. Mutations at each amino acid residue alone result in a 30-100-fold reduction in Kcat of adenylyl cyclase. However, the same mutations do not affect the Km for ATP, the half-maximal concentration (EC50) for the C2 domain of type II adenylyl cyclase to associate with the C1 domain of type I adenylyl cyclase and achieve maximal enzyme activity, or the EC50 for forskolin to maximally activate enzyme activity with or without Gsalpha. This indicates that the mutations at these two residues do not cause gross structural alteration. Thus, these two conserved amino acid residues appear to be crucial for catalysis, and their absence from the C1 domains may account for its lack of catalytic activity. Mutations at both amino acid residues together result in a 3,000-fold reduction in Kcat of adenylyl cyclase, suggesting that these two residues have additive effects in catalysis. A second site suppressor of the Asn-1025 to Ser mutant protein has been isolated. This suppressor has 17-fold higher activity than the mutant and has a Pro-1015 to Ser mutation.     

Effects of the dopamine D3 antagonist PD 58491 and its interaction with the dopamine D3 agonist PD 128907 on brain dopamine synthesis in rat

The dopamine (DA) D3 receptor antagonist PD 58491 [3-[4-[1-[4-[2-[4-(3-diethylaminopropoxy)phenyl]benzoimidazol++ +-1-yl-butyl]-1H-benzoimidazol-2-yl]phenoxy]propyl]diethylamine] bound with high affinity and selectivity to recombinant human DA D3 versus D2L and D4.2 receptors transfected into Chinese hamster ovary cells: Ki values of 19.5 nM versus 2,362 and >3,000 nM, respectively. In contrast, the putative DA D3 receptor antagonist (+)-AJ76 displayed low affinity and selectivity for D3 versus D2L and D4.2 receptors (91 nM vs. 253 and 193 nM, respectively). In vitro, PD 58491 (1 nM-1 microM) exhibited D3 receptor antagonist activity, reversing the quinpirole (10 nM)-induced stimulation of [3H]thymidine uptake in D3 CHOpro-5 cells, but did not have any significant intrinsic activity by itself in this assay. PD 58491 did not decrease the gamma-butyrolactone-induced increase in DA synthesis (L-3,4-dihydroxyphenylalanine accumulation) in rat striatum, indicating that the compound possessed no in vivo DA D2/D3 receptor agonist action at DA autoreceptors. PD 58491 (3-30 mg/kg, i.p.) generally did not alter DA or serotonin synthesis in either the striatum or mesolimbic region of rat brain. The D3-preferring agonist PD 128907 decreased DA synthesis in striatum and mesolimbic regions, and this effect was attenuated by pretreatment with PD 58491. These findings support the hypothesis that DA D3 autoreceptors may in part modulate the synthesis and release of DA in striatum and mesolimbic regions.