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Biomedical subjects

M L Berger

Publications and source records attributed to M L Berger.

At least 55 records · Page 3Linked to original sources
PubMed1989

Induction of stress protein HSP70 in nerve cells after status epilepticus in the rat.

The accumulation of the stress protein HSP70 was found to be an excellent marker for prolonged seizure related metabolic activity of neurons. After kainic acid (KA) induced status epilepticus we observed HSP70 immunoreactivity in the hippocampal CA4 and CA1 sectors, the subiculum, the basolateral and the lateral nuclei of the amygdala, the mediodorsal nucleus of the thalamus, the caudal part of the striatum, the claustrum and in neurons of certain neocortical areas. HSP70-positive nerve cells appeared normal in conventional histological stains. Conversely, degenerating neurons (e.g. in the hippocampal CA3 sector) remained unlabeled.

Animals↗
PubMed1989

Anoxic hepatocyte injury: role of reversible changes in elemental content and distribution.

Examination of anoxic isolated hepatocytes by light and electron microscopy indicated that initial morphologic changes were largely localized to the periphery of the cells. This early phase consisted of surface bleb formation but was not accompanied by alterations in parameters of plasma membrane integrity (leakage of cellular enzymes, exclusion of trypan blue). The time course of changes in structure was temporally related to alterations in the elemental distribution and content of various subcellular compartments. These studies, which employed electron probe X-ray microanalysis, demonstrated that rapid increases in the sodium and chlorine content and decreases in the potassium content of the cytoplasm, mitochondria and nucleus occurred, whereas no change in the calcium content of any subcellular compartment was detected. Concurrently, two cellular functions known to be dependent upon ion homeostasis, sodium-dependent taurocholate uptake and mitochondrial respiratory control, became markedly impaired. Reoxygenation within 30 min resulted in the restoration of both elemental distribution and the latter two functions to baseline. These data are consistent with the hypothesis that some early functional changes may be mediated by altered ion homeostasis. In contrast, additional studies indicated that sodium and water fluxes could be dissociated from the appearance of plasma membrane blebs. Thus, this study provides direct evidence that the structural and functional changes of early anoxic hepatocyte injury cannot be explained by a single mechanistic cascade, but apparently involve multiple mechanisms which may not be directly linked.

Animals↗
PubMed1989

Manufacture and use of fused silica cannulas for intracerebral injections in freely moving rats.

This report describes in detail the assembly and use of miniature cannulas for intracerebral injections in freely moving rats. Guide and injection cannulas were prepared from polyimid-coated fused silica capillaries as routinely in use for gas chromatography, in this way avoiding the permanent contact of stainless-steel with brain tissue. The outer diameter of the guide capillary measured 300 microns, that of the injection capillary 170 microns. In spite of their fragile appearance, the capillaries were robust and easy to handle. In the same animal, up to 20 consecutive injections were possible. In the course of 2 years 204 cannulas directed to the amygdala or the lateral ventricle were implanted, and only in 8 rats (4%) the inner capillary broke and plugged the guide cannula, making injections impossible. Histological examination of brains implanted for up to 2 months demonstrated only blunt scar formation along the cannula's track. No changes in transmitter levels (biogenic amines, amino acids) could be detected in chronically implanted rat brains except for a slight increase in serotonergic activity in the contralateral piriform cortex. Intra-amygdaloid injection of 0.32 microliters 0.9% saline resulted in a mild and transient reduction of GABA levels in both piriform cortices, without any detectable persistent histopathological consequences.

Animals↗
PubMed1988

Toxicity of methylating agents in isolated hepatocytes.

To investigate the pathogenesis of hepatotoxicity by methylating agents, we exposed isolated hepatocytes to N-nitrosodimethylamine (NDMA), N-methyl-N'-nitro-N nitrosoguanidine (MNNG), N-methyl-N-nitrosourea (MNU), or methyl methanesulfonate (MMS). Although NDMA is a potent in vivo hepatotoxicant in rats, no evidence of hepatocyte injury, measured by the leakage of lactate dehydrogenase (LDH) activity into the medium, was observed following exposure to a 1-100 mM concentration of either NDMA or MNU. In contrast, exposure of hepatocytes to MMS or MNNG resulted in greater than or equal to 90% LDH release. These differences in toxicity were not related to the extent of covalent binding to hepatocytes. Following MMS or MNNG, but not MNU or NDMA exposure, a significant rise in the generation of thiobarbiturate (TBA)-reactive species was observed. When hepatocytes were exposed to the antioxidant promethazine prior to the addition of MMS or MNNG, the formation of TBA-reactive species was inhibited completely. Although promethazine blocked MNNG-mediated cell injury, the antioxidant had no effect on MMS intoxication. These data suggest that methylating agents can cause hepatotoxicity by more than a single mechanism. For MNNG, lipid peroxidation may be involved in the pathogenesis of acute hepatotoxicity.

Animals↗
PubMed1988

Intervention in free radical mediated hepatotoxicity and lipid peroxidation by indole-3-carbinol.

The cytoprotective effect of the natural dietary constituent indole-3-carbinol (I-3-C) on carbon tetrachloride (CCl4) mediated hepatotoxicity in mice was examined. I-3-C pretreatment by gavage 1 hr prior to intraperitoneal injection of CCl4 produced a 63% decrease in CCl4-mediated centrolobular necrosis and a related 60% decrease in plasma alanine aminotransferase activity (a marker of liver necrosis). Since the toxicological effects of CCl4 are mediated by radical species generated during reductive metabolism by cytochrome P-450, we examined the potential ability of I-3-C to scavenge reactive radicals. Three systems were used to evaluate the ability of I-3-C to intervene in free radical mediated lipid peroxidation. These systems consisted of the following: (1) phospholipid dissolved in chlorobenzene, with peroxidation initiated by the thermal and photo decomposition of azobisisobutyronitrile (AIBN); (2) sonicated phospholipid vesicles in phosphate buffer (pH 7.4), with peroxidation initiated by ferrous/ascorbate; and (3) mouse liver microsomes containing an NADPH-regenerating system, with peroxidation initiated with CCl4. Lipid peroxidation was measured in these three systems as thiobarbiturate-reacting material. In the AIBN and ferrous/ascorbate systems, I-3-C inhibited lipid peroxidation, with greater inhibition under conditions of low rates of free radical generation. I-3-C was not as effective an antioxidant as butylated hydroxytoluene (BHT) or tocopherol, but it inhibited peroxidation in a dose-response manner. I-3-C was most effective as a radical scavenger in the microsomal CCl4-initiated system by inhibiting lipid peroxidation in a dose-dependent fashion, with 50% inhibition at 35-40 microM I-3-C. This concentration is about one-third of the concentration of I-3-C achieved in liver after treatment of mice by gavage with 50 mg I-3-C/kg body weight. These data suggest that I-3-C may be a natural antioxidant in the human diet and, as such, may intervene in toxicological or carcinogenic processes that are mediated by radical mechanisms.

Animals↗
PubMed1988

Calcium transport, thiol status, and hepatotoxicity following N-nitrosodimethylamine exposure in mice.

The hepatotoxicant N-nitrosodimethylamine (NDMA) is presumed to exert toxicity through reactive metabolites. NDMA is similar in this respect to numerous other hepatotoxicants, for which hepatotoxicity is also associated with a rapid depletion of soluble and/or protein thiols, and an inhibition of calcium transport systems. We examined the hypothesis that hepatotoxicity for NDMA is preceded by thiol depletion and/or inhibition of calcium transport in isolated liver subcellular fractions. Centrizonal liver necrosis in mice was evident at 24 but not at 12 h subsequent to intraperitoneal administration of 40 mg NDMA/kg. Hepatotoxicity was not preceded by depletion of liver protein-free sulfhydryls, nor by protein sulfhydryl depletion in liver whole homogenate, microsomal, or plasma membrane fractions. NDMA-mediated toxicity was also not preceded by inhibition of calcium uptake capability by microsomal, mitochondrial, or plasma membrane fractions. In contrast, carbon tetrachloride produced the expected rapid decrease in microsomal calcium uptake capability, followed by a centrizonal necrosis that was maximal at about 24 h. These studies suggest that the mechanism of NDMA hepatotoxicity may differ from that of a number of other hepatotoxicants (e.g., carbon tetrachloride, acetaminophen, bromobenzene) for which toxicity is also mediated through reactive metabolites.

Animals↗
PubMed1988

Diagnosis of nontraumatic hematobilia by computerized tomography of the abdomen.

Hematobilia was diagnosed by computerized tomography as the cause of gastrointestinal bleeding in a 73-yr-old man. The patient suffered from recurrent abdominal pain for 4 yr and presented with a history of episodic hematochezia over the previous 24 h, suggestive of significant lower gastrointestinal bleeding. Endoscopic evaluation of the lower and upper gastrointestinal tract revealed only blood in the region of a normal ampulla. Computerized tomography demonstrated a thickened gallbladder filled with material the density of blood. A blood-filled gallbladder was removed at cholecystectomy and pathological examination of the excised gallbladder demonstrated ulceration and inflammation of the mucosa. The diagnostic evaluation of hematobilia is discussed.

Aged↗
PubMed1987

Carbon tetrachloride-induced morphologic alterations in isolated rat hepatocytes.

Isolated rat hepatocytes were exposed to CCl4 in doses commonly used in in vitro studies and for which we have provided biochemical evidence would induce solvent injury. Rapidly evolving morphologic alterations were observed in the plasma membrane, endoplasmic reticulum, and mitochondria. Swelling and fusion of surface microvilli with formation of blebs were particularly prominent and occurred within 2 min of exposure. Blebs regressed in some hepatocytes without evidence of cell death, when these cells were exposed to CCl4 under conditions promoting its evaporation. Disorganization of endoplasmic reticulum and mitochondrial injury were also prominent early findings. Rapid appearance of diffuse ultrastructural alterations in isolated hepatocytes exposed to CCl4 is consistent with nonspecific membrane injury induced by solvent effects.

Animals↗
PubMed1987

Protection against carbon tetrachloride hepatotoxicity by pretreatment with indole-3-carbinol.

The effects of administering indole-3-carbinol (I-3-C) on carbon tetrachloride (CCl4)-induced hepatotoxicity were examined. Mice received by gavage 0-150 mg I-3-C/kg body wt in methanol-extracted corn oil, followed 1 h later by 15 microliters CCl4/kg body wt in corn oil. Animals were sacrificed 24 h after receiving CCl4. Pretreatment with I-3-C reduced the degree of centrolobular necrosis, as observed histologically. Additionally, CCl4-mediated elevated serum enzymes were reduced by I-3-C. Although I-3-C induced elevated levels of cytochrome P-450 and associated mixed-function oxidase activity, the CCl4 depression of these parameters was not clearly reversed by I-3-C. However, CCl4 produced decreases in hepatic levels of glutathione (GSH), total reducing equivalents, and protein sulfhydryls, all of which were restored to control levels by I-3-C. Using mouse liver microsomes in an NADPH-fortified reaction mixture, I-3-C inhibited, in a concentration-dependent manner, CCl4-initiated lipid peroxidation, with 50% inhibition at 35-40 microM I-3-C. When mice were treated by gavage with 50 mg [14C]I-3-C/kg body wt, concentrations of radiolabel in the liver were greater than 100 microM after 1 hr. This was five times the level of radioactivity measured in blood and three times the concentration of I-3-C necessary for 50% inhibition of CCl4-mediated lipid peroxidation in vitro. The data are consistent with the hypothesis that I-3-C intervenes in CCl4-mediated hepatic necrosis by combining with reactive free radical metabolites of CCl4, thereby protecting critical cellular target sites.

Alanine Transaminase↗
PubMed1987

Protection from N-nitrosodimethylamine-mediated liver damage by indole-3-carbinol.

Indole-3-carbinol (I-3-C) was examined for its ability to protect mice against 24-hr N-nitrosodimethylamine (NDMA)-mediated hepatotoxicity. NDMA (20 mg/kg body weight) alone produced extensive hemorrhagic and centrolobular necrotic lesions, with a necrotic severity index of 3.0 +/- 0.4 (scale of 0-5). Treatment with 50 mg/kg body weight of I-3-C by gavage, 1 hr prior to NDMA, substantially protected against hemorrhagic lesions. Furthermore, I-3-C lowered the NDMA-mediated tissue necrotic index to 1.5 +/- 0.3, by reducing the extent of tissue necrosis rather than the severity in the necrotic region. Release of liver enzymes into the blood correlated with the histopathology; I-3-C reduced NDMA-mediated elevated activities of plasma alanine transaminase and ornithine transcarbamylase by 84 and 51.3%, respectively. Although no changes in nonprotein sulfhydryls were evident at 24-hr after NDMA, ascorbate levels were reduced to 40% of control values. However, treatment with I-3-C prior to NDMA prevented the decline in tissue ascorbate concentrations. In vitro, I-3-C was found to be a type II ligand for cytochrome P-450, with a Ks value of 237 microM. However, if such binding occurs in vivo, it does not protect against the approximately 60% decrease in hepatic cytochrome P-450 or the 80% decrease in NDMA demethylase I activity produced by NDMA. Since I-3-C slightly enhances cytochrome P-450 content and NDMA demethylase activity, the histopathologic protection by I-3-C must be due to factors other than inhibiting metabolic activation of NDMA.

Alanine Transaminase↗
PubMed1987

Rapid halogenated hydrocarbon toxicity in isolated hepatocytes is mediated by direct solvent effects.

The toxicity of several halogenated and non-halogenated hydrocarbons (CH2Cl2, CHCl3, CCl4, C6H14, C8H10) in isolated rat hepatocytes were compared. Release of aspartate aminotransferase (AST) activity was rapid and concentration-dependent. Fractional AST release plateaued at 10-60 min following hydrocarbon exposure. Enzyme leakage at 60 min correlated with the oil/water partition coefficient (pi) of the compounds. All compounds, except n-hexane, also caused an immediate inhibition of the rate of cellular respiration. Inhibition of cell respiration also correlated with pi and was reversible. The recovery of cellular oxygen consumption was examined in detail for CCl4 and correlated with evaporation of the compound. These data suggest that acute hydrocarbon-induced injury in isolated hepatocytes is mediated by concentration-dependent direct solvent effects. Since halogenated hydrocarbons are widely used to induce general anesthesia, the clinical implications of possible direct effects by halocarbons on liver function in vivo and the potential relationship to liver injury are discussed.

Animals↗
PubMed1986

Effect of seizures induced by intra-amygdaloid kainic acid on kainic acid binding sites in rat hippocampus and amygdala.

[3H]Kainic acid binding sites with a slow dissociation rate in the rat limbic system were investigated in detail. Extensively washed membranes prepared from the hippocampal formation and from the region comprising the amygdala and the piriform cortex yielded non-linear Scatchard plots. Microdissection showed that the high-affinity component (affinity constant around 1 nM) was present in the hippocampal CA3 region (4.2 fmol/mg wet tissue) and the amygdaloid complex (4.6 fmol/mg wet tissue), whereas the remaining part of the hippocampal formation and the piriform lobe contained the low-affinity component (affinity constant 5-20 nM; 11.6 and 11.3 fmol/mg wet tissue, respectively). In the lateral + medial septum we detected only the low-affinity component. Severe limbic seizures, induced by unilateral injection of 0.7 or 0.8 microgram kainic acid in 0.3 microliter of phosphate-buffered saline into the amygdala, reduced kainic acid binding sites in the ipsilateral amygdala and CA3 region. The decline of kainic acid binding sites in the injected amygdala was followed by a similar effect in the contralateral amygdala ("mirror focus") and later by a moderate loss also in the contralateral CA3 region. Kainic acid receptor autoradiography demonstrated that binding sites were lost from the stratum lucidum in hippocampus. Septal lesion had no effect on kainic acid binding sites in the hippocampus. Comparison with previous results on the histopathological changes after this lesion shows that high-affinity kainic acid binding sites are preferentially located on neurons that undergo selective degenerations after severe kainic acid-induced seizures.

Amygdala↗
PubMed1984

Maturation of kainic acid seizure-brain damage syndrome in the rat. I. Clinical, electrographic and metabolic observations.

The maturation of the seizure/brain damage syndrome produced by parenteral administration of kainate was studied in the rat. The motor, electrographic and metabolic alterations are described in the present report, the maturation of the pathological abnormalities and of the specific kainate binding sites are described in the two following companion papers. Parenteral kainate produces tonico-clonic seizures until the end of the third week of age when limbic motor signs (wet-dog shakes, facial myoclonia, paw tremor etc.) were first produced. Using the 2-deoxyglucose autoradiographic method, we found that in animals of 3 days of age and until the third week of age, kainate produced a rise in metabolism restricted to the hippocampus and lateral septum. This was paralleled by paroxysmal discharges which were recorded in the hippocampus. Starting from the end of the third week of age approximately--i.e. when the toxin produced limbic motor seizures--there was a rise of labelling in other structures which are part of or closely associated to the limbic system i.e. the amygdaloid complex, the mediodorsal and adjacent thalamic nuclei, piriform, entorhinal and rostral limbic cortices and areas of projection of the fornix. These metabolic maps are thus similar to those seen in adults. Two main conclusions can be drawn from these experiments: kainate activates the hippocampus from a very early age probably by means of specific receptors present in this structure and the limbic syndrome will only be produced by the toxin once the limbic circuitry--including in particular the amygdaloid complex--is activated by the procedure i.e. after the third week of age.

Animals↗
PubMed1984

Maturation of kainic acid seizure-brain damage syndrome in the rat. II. Histopathological sequelae.

The histopathological sequelae of parenteral administration of kainic acid were investigated in immature rats (3-35 days of age). The brains were fixed 1-14 days after the administration of kainate and the damage evaluated by means of argyrophylic (Fink-Heimer, Gallyas or Nauta-Gygax) and Nissl stains. In animals of less than 18 days of age there was no sign of damage even after 1-2 h of severe tonico-clonic convulsions. Between 18 and 35 days after birth, there was a progressive increase in the severity of the damage, the adult pattern being reached at the latter age. As in adult animals, brain damage was most severe in structures which are part of the limbic system, i.e. the hippocampal formation, lateral septum, amygdaloid complex, claustrum, piriform cortex, etc. In addition to neuronal abnormalities, the following reactions were observed: hypertrophy and swelling of satellite oligodendroglia, proliferation of hypertrophic microglia, proliferation of astroglia and hypertrophy of endothelial cells in the capillary wall. The latter type of change, together with local coagulative necrosis, was almost exclusively restricted to the granular and molecular layers of the fascia dentata. In the hippocampal formation we found a temporal gradient of vulnerability. The earliest and most consistent neuronal alterations were largely restricted to interneurons of the hilar region and to a lesser extent to non-pyramidal neurons of strata oriens and radiatum. The severe necrotic destruction of the pyramidal layer of CA3 is conspicuous at a later age (postnatal day 30-35) and with longer survival times. Our results suggest that: (1) the neurotoxin only induces brain damage once it also causes limbic motor seizures and its associated metabolic activations, notably in the amygdala; (2) the earliest pathological sequelae occur in interneurons of the hilar region and (3) sclerosis of the vulnerable region of the Ammon's horn--the CA3 region--is only obtained once the dentate granules and their mossy fibres are fully operational, thereby reflecting the crucial role of this axonal connection in eliciting hippocampal damage.

Age Factors↗
PubMed1984

Maturation of kainic acid seizure-brain damage syndrome in the rat. III. Postnatal development of kainic acid binding sites in the limbic system.

The progressive appearance of [3H]kainic acid binding sites with age has been studied in membrane suspensions prepared from various regions of the rat limbic system, and by autoradiography. Binding sites with fast dissociation rate appeared earlier than binding sites with slow dissociation rate. Scatchard analysis demonstrated apparent receptor heterogeneity for both subclasses. High affinity components were detected in the hippocampus as early as 10 days after birth, but in the amygdala + piriform lobe were found only towards the end of the third week, when animals also respond to parenteral kainic acid, for the first time, with limbic seizures accompanied by metabolic activation of the amygdala. Slice autoradiography revealed distinct labelling of the hippocampal CA3 region by postnatal day 10. A comparison with the ontogenesis of the kainic acid-induced seizure-brain damage syndrome suggests a role of high affinity receptors as mediators of metabolic nerve cell activation by kainic acid. However, this receptor interaction per se does not result in neuronal damage to the vulnerable region of the Ammon's horn, which will only occur at an age when also the amygdala is activated by the neurotoxin.

Age Factors↗