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L A Paul

Publications and source records attributed to L A Paul.

10 recordsLinked to original sources
PubMed1993

Chloroisothiocyanatoquinolines as fluorogenic derivatizing agents for primary and secondary amines.

Two new prechromatographic LC fluorogenic derivatizing agents, 2- and 4-chloro-3-isothiocyanatoquinoline (4 and 5) have been synthesized and shown to react smoothly with primary and secondary amines to produce fluorescent thiazoloquinolines. Compounds 4 and 5 hydrolyse in aqueous base and the rates of this reaction compared with the rates of derivatizations with amino acids indicate that the hydrolysis reaction interferes with derivatization when UV detection is used. The kinetics of derivatization with ordinary amines indicate that this reaction is quite facile, although less nucleophilic amines, e.g. aniline, react slowly. The pKas for first protonations indicate that derivatives of 4 would be unprotonated and those of 5 would be protonated with typical RP-LC mobile phases. The Stokes shift for protonated derivatives of 5 is nearly 200 nm. The excess of unreacted derivatizing reagent interferes with UV detection of some analytes; but when fluorescence detection is used this excess produces only a small negative peak. With fluorescence detection the sensitivity of this method is about 0.8 microM at S/N of 2, and the response of peak height to concentration is linear over at least two decades of concentration.

Amines↗
PubMed1989

Macrophage-mediated induction of DNA strand breaks in target tumor cells.

We have shown previously that macrophages are mutagenic to bacteria (A. M. Fulton et al., Cancer Res., 44: 4308-4311, 1984) and can induce the appearance of drug-resistant variants of murine mammary tumor cells (K. Yamashina et al., Cancer Res., 46: 2396-2401, 1986). The present study asks whether inflammatory macrophages can induce lesions in the DNA of cocultured tumor cells and seeks to determine the mediators of this damage. We quantitated the induction of DNA strand breaks using the technique of fluorometric analysis of DNA unwinding. We report that inflammatory macrophages coincubated with a mammary tumor cell line for 60 min at a 1:1 ratio result in significant numbers of strand breaks in the tumor cell DNA. The degree of damage is equivalent to 300 to 1200 rads of gamma-irradiation. Resident (unstimulated) peritoneal macrophages also induce tumor cell DNA strand breaks. However, inhibitor studies reveal quantitative and qualitative differences in strand breaks induced by inflammatory (elicited) versus resident peritoneal macrophages. Resident macrophages require a longer induction period (60 min) before significant breaks are detected, but induce more breaks than do elicited macrophages, which require only a 5-min coincubation period to induce significant damage. The enzyme catalase, which removes H2O2, protects tumor cells from both macrophage effector populations as does the prostaglandin synthase inhibitor, indomethacin. The superoxide anion scavenger, superoxide dismutase, and the lipoxygenase inhibitor, nordihydroguaiaretic acid, are protective against resident macrophage effects only. The metal chelator, o-phenanthroline, provides limited protection for elicited macrophages but induces total DNA breakage in the presence of resident macrophages. Taken together, our data indicate that the degree of strand breakage is greater for the macrophage population with high arachidonate metabolism and low oxidative metabolism (resident macrophages) and less for the macrophage population with high oxidative and low arachidonate metabolism (MVE-2 elicited macrophages). Inhibitor studies implicate both metabolites of reactive oxygen and arachidonate as mediators of this tumor cell DNA damage, with the relevant mediator dependent upon the particular macrophage population under study.

Animals↗
PubMed1989

Selective loss of hippocampal granule cells in the mature rat brain after adrenalectomy.

Adrenalectomy of adult male rats resulted in a nearly complete loss of hippocampal granule cells 3 to 4 months after surgery. Nissl and immunocytochemical staining of hippocampal neurons revealed that the granule cell loss was selective; there was no apparent loss of hippocampal pyramidal cells or of gamma-amino butyric acid (GABA)-, somatostatin-, neuropeptide Y-, calcium binding protein-, or parvalbumin-containing hippocampal interneurons. The hippocampal CA1 pyramidal cells of adrenalectomized animals exhibited normal electrophysiological responses to afferent stimulation, whereas responses evoked in the dentate gyrus were severely attenuated. Corticosterone replacement prevented both the adrenalectomy-induced granule cell loss and the attenuated physiological response. Thus, the adrenal glands play a role in maintaining the structural integrity of the normal adult brain.

Adrenalectomy↗
PubMed1989

Reactive oxygen-mediated damage to murine mammary tumor cells.

We have shown, in a preliminary report, that macrophages can induce strand breaks in the DNA of co-cultured tumor cells (Chong et al., 1988). The present study is designed to determine if oxygen-centered species generated by the cell-free enzyme-substrate combination of hypoxanthine and xanthine oxidase can induce similar lesions and to identify the specific mediator(s). We report that co-incubation of murine mammary tumor cell lines with hypoxanthine and xanthine oxidase leads to the induction of DNA-strand breaks as determined by fluorescence analysis of DNA unwinding (FADU) assay or alkaline elution techniques. This damage is preventable by catalase which removes hydrogen peroxide but no protection is provided by agents to remove or prevent the formation of superoxide anion (superoxide dismutase), or hydroxyl radical (mannitol or the iron chelator o-phenanthroline). Likewise, cyclooxygenase or lipoxygenase inhibitors of arachidonate metabolism (indomethacin, nordihydroguaiaretic acid, caffeic acid) or bromophenacyl bromide do not alter the degree of DNA scission. Treatment with higher doses of oxygen species leads to significant toxicity as determined by evaluation of cell growth potential or colony-forming ability. Again, toxicity is prevented only by the presence of catalase. Tumor cells are able to rejoin strand breaks at lower, less toxic doses. When comparing different tumor cell subpopulations at various stages of progression, i.e., metastatic vs. nonmetastatic, for sensitivity to hydrogen peroxide-induced strand breakage, we found that at lower concentrations (less than 5 microM) metastatic populations are sensitive whereas nonmetastatic populations exhibit no significant breakage. At higher concentrations of hydrogen peroxide, all lines were sensitive, suggesting that a lower threshold of sensitivity may exist for more progressed tumor cell lines.

Animals↗
PubMed1987

Diet-induced changes in rabbit serum potassium do not alter size or number of brain capillary endothelial cell mitochondria.

Previous studies have shown brain extracellular (EC) [K+] to remain constant during wide variations of the plasma-brain [K+] gradient. High serum [K+] is hypothesized to increase K+ pumping by the blood-brain barrier (BBB) to maintain normal EC levels. This changing metabolic work could be reflected in endothelial cell mitochondria which have been shown to be three to four times more numerous in the BBB than in other capillary endothelial cells. We measured several morphologic parameters of brain capillary endothelial cells in white male New Zealand rabbits following dietary manipulation of their serum [K+] levels. Four groups, based on serum [K+] levels, were formed: Deficient, Low, Normal, and High. Following the final day's weight and blood samples, rabbits were anesthetized and perfused for transmission electron microscopic planimetry. Variables included number and area of mitochondria, areas of capillary lumen and capillary diameter, area of endothelial cell, and proportion of endothelial cell taken up by mitochondria. With the exception of the area of the endothelial cell (P less than 0.01), which decreased with increasing serum [K+] levels, no differences appeared among the variables in any of the four groups. Lack of anticipated differences in mitochondrial number or proportional area indicates either that pumping K+ occupies a minor fraction of cell energy, or changes in mitochondrial size or number are not sufficiently sensitive indicators of metabolic workload in this model.

Animals↗
PubMed1986

Structural substrates of epilepsy.

Although interest in possible structural substrates of epilepsy has been high since anatomical abnormalities in autopsy material were first noted, a clear pathognomic picture has yet to emerge for subtypes other than temporal lobe epilepsy. While identification of anatomical features unique to the diseased brain does not ensure that a cure will be found (viz. Alzheimer's disease), such knowledge can certainly guide researchers who must search out both the necessary and sufficient etiologic agent. Such investigation is hampered by the difficulty of separating cause from effect in clinical material, where the patient may have a history of drug use or of poorly controlled seizures. For instance, the cell-density depletion noted in temporal-lobe epileptics could follow from, or be a cause of, seizures. An experimental approach to isolating the structural substrates of epilepsy requires establishing several "levels" of epilepsy of varying duration, and observing the evolution of anatomical change. Such manipulation is, of course, possible only when an animal model is used, and it is for this reason, among others, that researchers have developed several of these. In general, there are two types of animal model: one where an exogenous agent (for example, a neurotoxin) or treatment (kindling) is applied, and another that relies on a strain of animal bred to exhibit seizures. Anatomical findings in this latter case have been reported infrequently, although the approach, which is not confounded by central nervous system (CNS) damage, seems promising as a model for certain types of epilepsy. Rodents have been among the best-researched genetic preparations, and several such reports appear in this volume. We have investigated one such strain, the Mongolian gerbil, which has been bred in UCLA's animal colony to exhibit seizures (the SS strain). Another strain (SR) has been bred to be seizure-free. Our initial study compared adult SS and SR animals with respect to two morphometric parameters in hippocampal region CA3. We found that the SS adult gerbil had fewer dendritic spines than its nonseizuring counterpart. Dendritic spines are considered the locus of excitatory synapses, and their density has been correlated with a variety of functional states in other paradigms. Our next set of questions concerned the development of these strain differences, and we accordingly set up four different age groups, bracketing the age at which seizures first appear in the gerbil. Again, spine-density differences appeared between SS and SR animals, but in the opposite direction from the adult case.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1985

Dendritic organization of the anterior speech area.

Golgi studies revealed significant differences in dendritic patterns between neurons of the left and right opercular regions of the frontal lobe (Broca's speech area on the dominant side) and between cells of the left and right precentral areas (the orofacial motor zones) just behind. Although total dendritic length of the basilar dendritic array seemed characteristic of an area independent of side, a larger proportion of the length on the left (dominant) side was made up of higher order (4, 5, 6) dendrite branches, and lower order (1, 2, 3) segments predominated on the right. The pattern was partially reversed in non-right-handed patients. These findings can be interpreted as indicating an early preponderance of dendrite growth in the non-speech-gifted hemisphere followed by enhanced dendrite growth in the dominant hemisphere coincident with the beginning of conceptualization and speech function.

Aged↗
PubMed1984

Scanning electron microscopy of the central nervous system. II. The hippocampus.

This study has presented cells, fibers and non-neuronal elements as seen in 3 dimensions using the SEM. Our discussion on possible artifacts which can occur with this method is offered in the hope that others will develop better techniques of dissection and specimen preparation. With the picture of normal tissue in mind, the investigator can undertake studies to determine the effects of various interventions on the structures of interest. Such treatments could include deafferentation or the use of macromolecular probes bound to cell surfaces. We anticipate that improvements in tissue preparation techniques by ourselves and others will open the way to intensive investigation of the nervous system using this powerful tool.

Animals↗
PubMed1981

Structural correlates of seizure behavior in the mongolian gerbil.

Hippocampi of seizure-sensitive and seizure-resistant Mongolian gerbils were examined in search of structural correlates of seizure behavior. In animals with well-established seizure histories, differences were found in both presynaptic and postsynaptic structures. Seizing animals had less dense dendritic spines, a greater proportion of mossy tuft area devoted to presynaptic vesicles, and a smaller proportion devoted to spines. The possible relationship of these findings to epilepsy is discussed.

Animals↗