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Biomedical subjects

M E Anderson

Publications and source records attributed to M E Anderson.

At least 127 records · Page 7Linked to original sources
PubMed1991

An efficient method for the extraction of DNA from formalin-fixed, paraffin-embedded tissue by sonication.

A method was developed for fast and efficient isolation of DNA from formalin-fixed, paraffin-embedded tissue sections for subsequent use in PCRs and DNA hybridization assays. The method relies on the use of a sonicating water bath to disrupt tissue samples to which a small amount of micro-sized glass beads have been added. The sonicating glass beads provide fast and efficient physical shearing of fixed tissue sections, allowing for quick release and solubilization of the DNA. The extraction process from paraffin section to amplifiable target DNA takes 30 minutes. The method eliminates the need for repetitive solvent extractions and exhaustive proteinase K digestion. PCR amplification of human genomic and viral target sequences was successfully carried out on DNA isolated from a number of different types of normal and infected tissues.

Base Sequence↗
PubMed1990

Cellular glutathione as a determinant of sensitivity to mercuric chloride toxicity. Prevention of toxicity by giving glutathione monoester.

Depletion of glutathione (GSH) by treatment of mice with buthionine sulfoximine (BSO), an effective inhibitor of gamma-glutamylcysteine synthetase, markedly enhanced (about 10-fold) the lethal and renal toxicity of mercuric chloride. The lethal toxicity of HgCl2 was prevented by administration of GSH monoester; this was observed in mice pretreated with BSO and given a low dose of HgCl2, and also in untreated mice that were given a much higher dose of HgCl2. In contrast, administration of GSH did not protect. Since administered GSH is not transported effectively into cells, whereas GSH monoester is transported and split intracellularly to GSH, the findings indicate that protection against HgCl2 requires intracellular GSH. The experimental approaches used here suggest that cellular GSH is a major determinant of sensitivity to HgCl2 toxicity, and also that administration of GSH esters may be useful for prevention of HgCl2 toxicity.

Animals↗
PubMed1990

Glutathione regulates activation-dependent DNA synthesis in highly purified normal human T lymphocytes stimulated via the CD2 and CD3 antigens.

Regulation of proliferation of normal human T lymphocytes (T cells) by glutathione (GSH) was explored with T-cell activation models that do not require accessory cell signals. L-Buthionine-(S,R)-sulfoximine (BSO), which inactivates gamma-glutamylcysteine synthetase and therefore inhibits GSH synthesis, inhibited proliferation elicited by monoclonal antibodies directed at cluster designation 2 (CD2) and CD3 antigens, or by sn-1,2-dioctanoylglycerol and ionomycin. L-Buthionine-(R)-sulfoximine, which does not inactivate gamma-glutamylcysteine synthetase, did not affect proliferation. BSO-induced inhibition of accessory cell-independent T-cell proliferation was not reversed by recombinant human interleukin 2, despite activation-dependent expression of interleukin 2 receptor alpha by T cells treated with BSO. However, BSO-associated inhibition of T-cell proliferation was reversed by GSH or GSH ester. These studies, which show that GSH can directly modulate proliferation of highly purified T cells, suggest that GSH is essential for steps close to or at DNA synthesis. The availability of methods for decreasing and for increasing GSH levels suggest therapies to produce (i) immunosuppression (of value in organ transplantation), and (ii) immunopotentiation (of potential value in treatment of immunodeficiency states such as AIDS).

Antibodies, Monoclonal↗
PubMed1990

Protection against cisplatin toxicity by administration of glutathione ester.

The role of cellular glutathione in the prevention of toxicity due to the anti-cancer drug cisplatin (cis-diamminedichloroplatinum) was explored in mice treated with buthionine sulfoximine (BSO), a selective inhibitor of gamma-glutamylcysteine synthetase (and therefore of glutathione synthesis), and with glutathione and glutathione monoisopropyl ester. Pretreatment of mice with BSO enhanced the lethal toxicity of cisplatin by about twofold. Administration of glutathione ester (dose, 2.5-7.5 mmol/kg) protected against lethal cisplatin toxicity; glutathione was also effective, but much less so. Glutathione ester, in contrast to glutathione, is effectively transported into cells and split to glutathione intracellularly. The previous findings that administered glutathione does not protect against lethal toxicity due to cadmium ions and mercuric ions, whereas glutathione ester does, suggest that intracellular glutathione is required for protection against these heavy metal ions. That administration of glutathione has a protective effect on cisplatin toxicity suggests that the toxic effects of cisplatin may be exerted both intracellularly and extracellularly, and that extracellular glutathione (or its degradation products) may form a complex with cisplatin extracellularly. The finding that glutathione ester is more effective than glutathione in protecting against the toxicity of cisplatin suggests that use of glutathione ester may be therapeutically advantageous.

Animals↗
PubMed1990

Three domains in the simian virus 40 core origin orchestrate the binding, melting, and DNA helicase activities of T antigen.

The simian virus 40 (SV40) core origin of replication consists of three functional domains. The sequence 5'-CACTACTTCTGGAATAG-3' with an imperfect inverted repeat (underlined), a palindrome with four 5'-GAGGC-3' pentanucleotide repeats, and a 17-base-pair A + T-rich segment. We have been able to assign primary functions to each domain. Remarkably, SV40 large T antigen melted the inverted repeat domain in the complete absence of other origin sequences. Presumably, this protein-DNA interaction initiates a replication bubble that leads to daughter strand DNA synthesis. The pentanucleotide domain alone docked and arranged T antigen at the origin. The A + T-rich domain had no independent function, but, in the presence of the other two domains, allowed bound T antigen to extend the replication bubble. Thus, three domains of the origin coordinate the binding, melting, and DNA helicase activities of T antigen in an ordered sequence of events to initiate DNA replication.

Antigens, Polyomavirus Transforming↗
PubMed1990

Short-term preoperative smoking abstinence.

Smoking produces some potentially reversible effects that may be relevant to perioperative morbidity. Although the reversal of many effects requires long-term (weeks to months) smoking cessation, a short abstinence period (12 to 72 hours) is sufficient to normalize several important cardiovascular parameters. The physiology of carbon monoxide elimination is the basis for recommending a specific smoke-free interval in the immediate preoperative period.

Carbon Monoxide↗
PubMed1989

Glutathione monoesters.

Glutathione monoesters in which the glycine carboxyl group is esterified are effective cellular glutathione delivery agents because they are readily transported into cells and are deesterified intracellularly. In contrast, glutathione itself is not effectively transported into cells. Detailed procedures are given for the preparation of such esters from glutathione and the corresponding alcohol using hydrogen chloride or sulfuric acid as the catalyst.

Carboxylic Acids↗
PubMed1989

Frequency sensitivity and directional hearing in the gleaning bat, Plecotus auritus (Linnaeus 1758).

1. The neural audiogram of the common long-eared bat, Plecotus auritus was recorded from the inferior colliculus (IC). The most sensitive best frequency (BF) thresholds for single neurones are below 0 dB SPL between 7-20 kHz, reaching a best value of -20 dB SPL between 12-20 kHz. The lower and upper limits of hearing occur at 3 kHz and 63 kHz, respectively, based on BF thresholds at 80 dB SPL. BF threshold sensitivities are about 10 dB SPL between 25-50 kHz, corresponding to the energy band of the sonar pulse (26-78 kHz). The tonotopic organization of the central nucleus of the IC (ICC) reveals that neurones with BFs below 20 kHz are disproportionately represented, occupying about 30% of ICC volume, occurring in the more rostral and lateral regions of the nucleus. 2. The acoustical gain of the external ear reaches a peak of about 20 dB between 8-20 kHz. The gain of the pinna increases rapidly above 4 kHz, to a peak of about 15 dB at 7-12 kHz. The pinna gain curve is similar to that of a simple, finite length acoustic horn; expected horn gain is calculated from the average dimensions of the pinna. 3. The directional properties of the external ear are based on sound diffraction by the pinna mouth, which, to a first approximation, is equivalent to an elliptical opening due to the elongated shape of the pinna. The spatial receptive field properties for IC neurones are related to the directional properties of the pinna. The position of the acoustic axis of the pinna and the best position (BP) of spatial receptive fields are both about 25 degrees from the midline between 8-30 kHz but approach the midline to 8 degrees at 45 kHz. In elevation, the acoustic axis and the BP of receptive fields move upwards by 20 degrees between 9-25 kHz, remaining stationary for frequencies up to 60 kHz. 4. The extremely high auditory sensitivity shown by the audiogram and the directionality of hearing are discussed in terms of the adaptation of the auditory system to low frequencies and the role of a large pinna in P. auritus. The functional significance of low frequency hearing in P. auritus is discussed in relation to hunting for prey by listening and is compared to other gleaning species.

Acoustic Stimulation↗
PubMed1989

Increased capacity for glutathione synthesis enhances resistance to radiation in Escherichia coli: a possible model for mammalian cell protection.

A strain of Escherichia coli, enriched in its content of gamma-glutamylcysteine synthetase and glutathione synthetase activities by recombinant DNA techniques, is more resistant to the lethal effects of gamma-irradiation than is the corresponding wild strain. Although the gene-enriched strain has higher glutathione levels than the wild strain, the observed radioresistance appears to be associated with the increased capacity of the gene-enriched strain to synthesize glutathione when irradiated rather than to the cellular levels of glutathione per se. Thus, resistance was abolished in the presence of buthionine sulfoximine, a selective inactivator of gamma-glutamylcysteine synthetase that decreases glutathione synthesis but that does not act directly to lower cellular glutathione levels. Conclusions drawn from studies on this E. coli model system may have relevance to protection of mammalian cells by glutathione.

Antimetabolites↗
PubMed1989

Glutathione metabolism at the blood-cerebrospinal fluid barrier.

Glutathione metabolism and transport in the choroid plexus were probed by determining the effects of administration to rats of several compounds (buthionine sulfoximine, L-2-oxothiazolidine-4-carboxylate, L-(alpha 5,5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazole acetic acid, gamma-glutamyl alanine, and glutathione monoethyl ester) on the levels of glutathione and cysteine in the cerebrospinal fluid. The findings indicate that glutathione is actively metabolized in the choroid plexus by pathways similar to those in kidney and other tissues. The level of glutathione in the cerebrospinal fluid can be decreased or increased by giving compounds that do not, under similar conditions, appreciably alter total brain levels of glutathione. Glutathione monoethyl ester is effectively transported into the cerebrospinal fluid.

Animals↗
PubMed1989

Marked increase of cysteine levels in many regions of the brain after administration of 2-oxothiazolidine-4-carboxylate.

Although brain cysteine levels can be increased by administration of cysteine, treatment with this amino acid causes toxicity. L-2-Oxothiazolidine-4-carboxylate, a compound in which the thiol group is masked, is effectively transported into the mouse and rat brain. It is converted intracellularly by the action of 5-oxoprolinase into L-cysteine. Study of various regions of the rat brain (cerebellum, hypothalamus, cortex, brain stem, pons, caudate nucleus) showed that the levels of cysteine increased significantly after administration of L-2-oxothiazolidine-4-carboxylate. Glutathione levels were not increased or were only slightly increased under these conditions, reflecting the low rate of glutathione synthesis in many regions of the brain.

Animals↗
PubMed1989

Topoisomerase I sites cluster asymmetrically at the ends of the simian virus 40 core origin of replication.

In vivo, topoisomerase I cleavage sites are located predominantly on the strands of simian virus 40 DNA that are the templates for discontinuous synthesis (S.E. Porter and J.J. Champoux, Mol. Cell. Biol. 9:541-550, 1989). This arrangement of sites suggests that topoisomerase I may associate with replication complexes in unique functional orientations at replication forks. We have mapped topoisomerase I cleavage sites in the simian virus 40 origin of replication in vitro under conditions suitable for DNA replication. Numerous sites cluster in the inverted repeat and AT-rich domains at the ends of the core origin and are arranged on the same strands that are cut most frequently in vivo. We propose that cleavage at these sites would allow bidirectional extension of the replication bubble induced by T antigen within the core origin of replication early in the initiation of DNA synthesis. A mutational analysis of the topoisomerase I sites confirms the importance of positions -4 to -1 and +1 in the consensus sequence 5'-A/T-A/G-A/T-T-break-G/A-3'. Surprisingly, more distant nucleotide positions also influence topoisomerase I sites in the inverted repeat and AT-rich domains of the core origin. The effects of distant sequences could be mediated by direct interactions with topoisomerase I or by the conformation of DNA in the core origin.

Animals↗
PubMed1989

Frog ventricle: participation of SR in excitation-contraction coupling.

Activation of the first beat (B1) following a 60-s pause is diminished in isometrically contracting frog ventricular strips, in contrast to the augmentation documented for sarcoplasmic reticulum (SR)-dependent mammalian myocardium. However, treatment of frog ventricular strips with ouabain, an indirect inhibitor of the sarcolemmal Na+-Ca2+ exchanger, selectively enhanced postpause beats suggesting that in the absence of ouabain significant extrusion of cellular Ca2+ occurred during the pause. Because resting tension did not increase during the pause in ouabain-treated strips, the nonextruded Ca2+ must have been sequestered into a compartment such as SR. Steady-state beats were not affected by ouabain; its actions appeared to be separate from its known positive inotropism. Caffeine, a direct SR stimulus, initially enhanced B1 and subsequently decreased activation of all beats, which was consistent with initial augmentation of SR Ca2+ release and subsequent depletion of SR Ca2+ stores. Ouabain both potentiated the stimulatory effects and blocked the inhibitory effects of caffeine, suggesting that ouabain increased Ca2+ stores in the same intracellular Ca2+ pool as that acted on by caffeine, the SR. Ryanodine, an inhibitor of SR in mammalian myocardium, did not affect activation of frog myocardium. SR may be an important site for activator Ca2+ cycling in frog myocardium under control conditions as well as after long diastolic intervals in the presence of ouabain.

Animals↗
PubMed1989

Effect of fasting and transportation on various physiological parameters and meat quality of slaughter hogs.

Forty-nine slaughter hogs were transported and fasted or fasted with no transport for 0 (no transport), 24, 48 and 72 h. Blood samples were taken before treatments were imposed and again prior to slaughter. Soft tissues of the ham were chemically analyzed and loin samples were evaluated by a sensory panel. Fasting and transportation decreased plasma triiodothyronine and hematocrit and increased plasma osmolality. Preslaughter treatment did not affect juiciness or desirability of cooked chops or percentage of fat in the ham soft tissues. These data suggest that although fasting and transporting of slaughter hogs may disrupt homeostasis of pigs, such physiological changes do not negatively affect meat quality.

Animals↗
PubMed1989

Reduction of visually-induced motion sickness elicited by changes in illumination wavelength.

This experiment was undertaken to assess the degree of stimulus generalization in visually-induced motion sickness. Sixteen subjects participated in six sessions in which they were exposed to a rotating field of vertical stripes for five 4-min trials. This stimulus elicited the perception of self-vection. In the first three sessions, the stripes were illuminated by one monochromatic light (red or green) and in the last three sessions, the stripes were illuminated by the other monochromatic light. Magnitude estimates of motion sickness increased significantly within sessions, but the rate at which this measure increased was significantly diminished across trials in the last three-session block. Magnitude estimates of vection increased within sessions and decreased across sessions, but did not increase with color change. These results can be explained in terms of a model of stimulus generalization and have implications for the reduction of motion sickness in applied settings.

Adolescent↗
PubMed1988

Relationship between intracellular GSH levels and hypoxic cell radiosensitivity.

The present studies show the following: (a) The plating density of cells (V79 and GM3877) affects the experimentally determined OER values. (b) Fibroblasts depleted of cysteine and GSH are more sensitive to radiation under hypoxic conditions (under aerobic conditions the absence of cysteine or GSH has no detectable effect on radiation sensitivity). (c) Addition of GEE to V79 cells (previously depleted of GSH) leads to increased intracellular GSH levels and protects the cells against radiation under hypoxic conditions.

Animals↗
PubMed1987

An analysis of potentially converging inputs to the rostral ventral thalamic nuclei of the cat.

Potentially convergent inputs to cerebellar-receiving and basal ganglia-receiving areas of the thalamus were identified using horseradish peroxidase (HRP) retrograde tracing techniques. HRP was deposited iontophoretically into the ventroanterior (VA), ventromedial (VM), and ventrolateral (VL) thalamic nuclei in the cat. The relative numbers of labeled neurons in the basal ganglia and the cerebellar nuclei were used to assess the extent to which the injection was in cerebellar-receiving or basal ganglia-receiving portions of thalamus. The rostral pole of VA showed reciprocal connections with prefrontal portions of the cerebral cortex. Only the basal ganglia and the hypothalamus provided non-thalamic input to modulate these cortico-thalamo-cortical loops. In VM, there were reciprocal connections with prefrontal, premotor, and insular areas of the cerebral cortex. The basal ganglia (especially the substantia nigra), and to a lesser extent, the posterior and ventral portions of the deep cerebellar nuclei, provided input to VM and may modulate these cortico-thalamo-cortical loops. The premotor cortical areas connected to VM include those associated with eye movements, and afferents from the superior colliculus, a region of documented importance in oculomotor control, also were labeled by injections into VM. The dorsolateral portion of the VA-VL complex primarily showed reciprocal connections with the medial premotor (area 6) cortex. Basal ganglia and cerebellar afferents both may modulate this cortico-thalamo-cortical loop, although they do not necessarily converge on the same thalamic neurons. The cerebellar input to dorsolateral VA-VL was from posterior and ventral portions of the cerebellar nuclei, and the major potential brainstem afferents to this region of thalamus were from the pretectum. Mid- and caudo-lateral portions of VL had reciprocal connections with primary motor cortex (area 4). The dorsal and anterior portions of the cerebellar nuclei had a dominant input to this cortico-thalamo-cortical loop. Potentially converging brainstem afferents to this portion of VL were from the pretectum, especially pretectal areas to which somatosensory afferents project.

Afferent Pathways↗