Adam Anthony

Protective effect of diazepam pretreatment on soman-induced brain lesion formation.

Histopathological analyses of brains of rats receiving a single 0.9 LD50 injection of soman, a potent anticholinesterase neurotoxin, revealed massive widespread lesions in the cerebral cortex and thalamus 4 weeks post-injection. Such lesions were not evidenced in rats receiving diazepam (2.2 mg/kg, i.m.) 10 min prior to soman treatment. Thus, anticonvulsant antidotes may aid in preventing extensive or permanent brain damage in rats surviving near-lethal soman dosages.

Neuronal RNA in relation to neuronal loss and neurofibrillary pathology in the hippocampus in Alzheimer's disease.

Topographic analyses were performed on the distribution of neuronal RNA loss in relation to local neuronal loss and neurofibrillary degeneration in the hippocampal region of brains of patients with Alzheimers disease (AD). Compared to age-matched controls, pyramidal neuronal RNA was depressed (p < 0.0001) in all areas of the hippocampus examined in AD, viz., the endplate (33%), Roses H2 field (30%), Roses H1 field (37%) and the subiculum (46%). Significant neuronal loss was observed in Roses H1 field and the subiculum but not in the endplate or Roses H2 field. The frequency of neurofibrillary tangle-bearing neurons was enhanced in all four regions of AD brains, the number of involved neurons being markedly greater in Roses H1 field and the subiculum than in the endplate and Roses H2 field. Overall, the data indicate the existence of a generalized disturbance in RNA metabolism within pyramidal neurons in the hippocampus in AD, occurring in regions of minimal (endplate, Roses H2 field) as well as those of extensive (Roses H1 field, subiculum) pathological alterations. Although there is focal accentuation of RNA depletion in the latter, the marked RNA depletion in regions of minimal pathologic change suggests that this effect is largely unrelated to local neuronal loss or neurofibrillary degeneration.

Blood PO2, PCO2 and pH changes in brook trout (Salvelinus fontinalis) exposed to sublethal levels of acidity

Abstract 1. 1. Acute exposure of winter and summer collected brook trout, Salvelinus fontinalis, to near toxic levels of acidity caused an elevation in PCO2, hematocrit, and rate of ventilation. 2. 2. Other than a transient drop in PO2 in June exposed fish, neither hypoxemia nor blood acidosis was evidenced. 3. 3. Summer exposed trout which showed severe behavioral responses to acid toxication actually exhibited a moderate alkalosis.

Interferometric analysis of intrasection and intersection thickness variability associated with cryostat microtomy

SummaryMach-Zehnder interferometric measurements were used to assess the extent of section thickness variability (inter- and intrasection) associated with cryostat microtomy of adrenal sections over a typical working range of 10–20 μm. Sections were obtained using a Brights Cambridge rocking type and a Damon rotary type cryostat microtome to allow comparative analyses. The effective thickness of tissue sections after being mounted onto slides by flash drying was reduced by 90% relative to microtome section thickness setting. A linear relationship between measured thickness and microtome setting was obtained with both instruments. Thickness variability between replicate sections over the range of microtome settings approximated 11% for the rocking microtome and 5% with the rotary microtome. Average intrasection variability was found to be 7% for rocking microtome sections and 4% for sections obtained with the rotary microtome. However, this variability is a negligible source of error in cytophotometric analyses, providing replicate sections are used and an adequate number of measurements are made on mask-delimited individual cells or tissue specimen areas.

Brain neuronal RNA metabolism during acute soman toxication: Effects of antidotal pretreatments

Effects of various antidotal treatments on neuronal RNA contents and on soman induced RNA and acetylcholinesterase (AChE) depletion were monitored using quantitative cytochemical techniques. In rats treated only with antidotes, atropine depressed whereas pralidoxime (2-PAM) elevated RNA contents of both caudate and cerebrocortical (Layer V) neurons. Soman produced a virtually complete inhibition of AChE activity and a moderate decline in neuronal RNA contents. Atropine pretreatment partially restored neuronal RNA levels. Atropine+2-PAM prophylaxis eventuated in a complete restoration of RNA levels but no reactivation of AChE. Addition of physostigmine to the atropine +2-PAM treatment regimen resulted in appreciable AChE reactivation but reduced RNA levels. The overall data indicate that: (1) soman-induced neuronal RNA depletion can be completely reversed by antidotal pretreatment; (2) no precise relationship exists between the extents of antidote-induced restoration of RNA and AChE levels; and (3) 2-PAM exerts marked effects on the brain neuronal network which are unrelated to AChE reactivation. It is postulated that effects of soman and antidotes on neuronal RNA metabolism may signify alterations in acetylcholine (ACh) sensitivity and that pharmacologic manipulation of ACh responsiveness during organophosphate cholinesterase poisoning may be a mechanism for additional therapeutic intervention.

Interrenal histochemistry of acid-exposed brook trout, Salvelinus fontinalis (mitchill) ☆

Abstract Acute exposure of brook trout to acid water (pH 4.0) caused a significant decrease in interrenal (adrenocortical cell) nuclear diameter, concomitant with an increase in the intensity of nuclear staining. Cytochemical analyses of Feulgen-DNA (F-DNA) of interrenal cell nuclei revealed these cells to be diploid (2C) and nonreplicating. There was no loss in DNA evidenced in interrenal nuclei of acid-stressed trout. In the same fish, there appeared to be a progressive decrease in azure B-RNA levels measured cytophotometrically over a 3- to 24-hr-exposure interval. A marked but transient elevation in circulating cortisol levels occurred at 1–3 hr of exposure with a return to control levels after 24 hr of exposure. No visually discernible changes in Sudan black B staining for lipids were evidenced after acute acid exposure. The findings support the conclusion that there is a marked inhibition of RNA synthesis and presumably of steroidogenesis in interrenal tissue following acute exposure of trout to low pH.

Scanning cytophotometric analysis of brain neuronal nuclear chromatin changes in acute T-2 toxin-treated rats.

Male Sprague-Dawley rats (200 g) were injected intraperitoneally with T-2 toxin, a trichothecene mycotoxin protein synthesis inhibitor, at dosages of 0.75, 1.0, 1.5, and 6.0 mg/kg (1 LD50 = 0.9 mg/kg) before decapitation at 8-hr postexposure. Correlative data were obtained on changes in physicochemical properties of nuclear chromatin, chromatin dispersion, and nuclear volume of cerebrocortical (layer III) and striatal neurons using Feulgen-DNA (F-DNA) cytophotometry and ocular filar micrometry. Decreased lability of neurons to F-DNA acid hydrolysis (reduced F-DNA yield), nuclear shrinkage, and chromatin aggregation (decreased chromophore area) were used as indices of suppression of genomic template activity, i.e., neuronal nuclear functioning. Conversely, increased F-DNA yield, chromophore area, and nuclear volume signify enhanced neuronal activation. At 8 hr following T-2 toxin exposure, cerebrocortical and striatal neurons exhibited a dose-dependent decrease in F-DNA hydrolyzability, i.e., impaired chromatin activity, and increases in both chromatin dispersion and nuclear volume. Microscopic observation revealed no gross evidence of T-2 induced neurotoxicity. These data indicate that T-2 toxin elicits both neurochemical injury and adaptive or compensatory processes simultaneously. The toxicological importance of observed nuclear alterations and the role of impairments in central nervous system metabolism in acute T-2 toxicity remain to be ascertained.

Cytophotometric analysis of RNA changes in prolactin and Stannius corpuscle cells of acid-stressed brook trout.

Abstract Analytical histochemical analyses of prolactin (PC) and Stannius corpuscle (SC) cells of brook trout exposed to acidified water (pH 4.5) for 2, 3, and 5 days were undertaken to ascertain the secretory response pattern of these endocrine glands to acid stress. A 2-day acid exposure caused a transient decrease in RNA synthesis and depletion of secretory material in prolactin cells as indicated by cellular shrinkage, decreased pituitary acid proteins, lower nuclear and cytoplasmic RNA levels, and decreased incorporation of [3H]uridine. A compensatory increase of RNA and an increase in protein occurred in the 3- and 5-day exposed groups which also exhibited increased skin mucification. Activation of Stannius corpuscle secretory processes was observed in 2-, 3-, and 5-day exposed trout using cell hypertrophy, increased RNA, and protein as indices of augmented synthesis and secretion by SC cells. It was established that bovine prolactin injections caused cytomorphological changes in PC but not in SC cells. The overall findings are in accord with the concept that these two tissues have independent but synergistic roles in osmoregulation during acclimation to acid stress.

Nuclear chromatin changes in hepatocytes of soman treated rats.

Cytochemical and morphometric indices of DNA metabolism and nuclear transcriptional-translational capabilities were used to monitor liver responses in Sprague-Dawley X Wistar rats subcutaneously injected with 0.9 LD50 soman, a highly toxic acetylcholinesterase-inhibiting organophosphate. Thirty minutes post-soman the following were evident: (1) increased polyploidization; (2) expansion of the nuclear envelope; and (3) elevated deoxyribonucleoprotein (DNP) complex lability to acid hydrolysis. Nuclear changes were accompanied by cytoplasmic correlates of impaired hepatocyte function, i.e., vacuolation and depressed basophilia. The overall data suggest that with acute soman toxication there are concomitant adaptive and maladaptive responses occurring within liver parenchymal elements. It is postulated that nuclear changes represent an early proliferative response and DNP activation to enhance detoxification capabilities, whereas cytoplasmic changes reflect the disruption of normal function and hepatotoxic injury.

Feulgen-deoxyribonucleic acid analysis of rabbit aortic smooth muscle cells using scanning- integrating microdensitometry.

A procedure entailing the use of the Feulgen reaction is described for precise quantification of nuclear DNA levels in smooth muscle cells (SMC) of paraffin-processed microtome sections of the rabbit aorta. It was established that maximal, stable, and reproducible Feulgen-DNA (F-DNA) staining of SMC nuclei is achieved using 3.5 N HCl hydrolysis of 30-50 min prior to staining of aortic sections in Schiff reagent for 60 min at 22 degrees C. Scanning-integrating microdensitometry of Feulgen-stained SMC revealed that the tunica media is comprised of a relatively homogeneous population of cells with between 0.3 and 1% of the SMC nuclei yielding 3C or 4C (tetraploid) F-DNA levels, depending on location within the aortic wall. The nuclear chromatin in inner medial SMC was found to be in a more dispersed state than that of outer SMC (using nuclear area and nuclear susceptibility to acid hydrolysis as indices of chromatin dispersion). A linear correspondence was evidenced between nuclear area and nuclear F-DNA stainability throughout the tunica media. The observation that the lumenal portion of the tunica media contains a greater abundance of SMC with large, vesicular nuclei is interpreted as reflecting a greater metabolic reactivity of this compartment relative to that of SMC bordering the tunica adventitia.