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Biomedical subjects

J M Wehner

Publications and source records attributed to J M Wehner.

At least 109 records · Page 6Linked to original sources
PubMed1986

Differential effects of central nervous system depressants in long-sleep and short-sleep mice.

The relative sleep time response of long-sleep (LS) and short-sleep (SS) mice was determined after the i.p. injection of varying doses of several anesthetic agents that vary in lipid solubility. The LS and SS mice were bred selectively for differences in duration of ethanol-induced sleep time. The drugs tested included: several halogenated ethanol derivatives (trifluoro-, trichloro-, tribromo- and dichloroethanol), chloral hydrate, paraldehyde, urethane and the water soluble barbiturates, barbital and phenobarbital. The LS mice slept for a longer time after the i.p. injection of the majority of these drugs than did the SS. As the lipid solubility of the agents increased, the response differential decreased. These data indicate that the LS and SS mice do not differ only in response to alcohols. Rather, they differ in sensitivity to agents that have lipid solubilities which resemble that of ethanol. Furthermore, these data imply that anesthetic agents with low lipid solubility have different mechanisms of action than do anesthetic agents with high lipid solubility.

Alcohols↗
PubMed1985

Genetically determined differences in acute responses to diisopropylfluorophosphate.

The acute effects of diisopropylfluorophosphate (DFP) were assessed in DBA/2Ibg, C57BL/6Ibg and C3H/2Ibg mice. The DFP was administered by intraperitoneal injection in saline. Brain acetylcholinesterase (AChE) activity was maximally inhibited within 5 min after injection. All mice showed signs of organophosphate intoxication including salivation, lacrimation, diarrhea, respiratory distress, tremor and, at high doses, seizures. The C57BL mice were most susceptible to these effects of DFP. The LD50 values for DFP were 8.0, 7.6, and 6.8 mg/kg for male DBA, C3H, and C57BL mice, respectively. The LD50 values for females were nearly the same. Body temperature and brain AChE activity decreased in a dose-dependent manner following injections of DFP of 3.17, 4.22, 5.28, and 6.33 mg/kg. Maximum temperature depression occurred 2 hours after DFP administration; by 24 hours temperatures had returned to normal except for C57BL mice treated with the highest dose of DFP. The C57BL strain was most susceptible to the DFP-induced hypothermia, the C3H strain was the most resistant, and the DBA strain was intermediate. Maximum temperature depression and residual AChE activity, as measured 24 hours after injection, were linearly related. These strain differences do not seem to be explained easily by a differential inhibition of AChE activity.

Animals↗
PubMed1985

Recovery of acetylcholinesterase activity after acute organophosphate treatment of CNS reaggregate cultures.

The effect of a single dose of diisopropylfluorophosphate on acetylcholinesterase (AChE) activity was examined in mouse CNS reaggregate cultures. At 17-24 days in culture, reaggregates were treated with 0.6 mg/liter DFP for 15 min. The recovery of AChE activity was examined in culture. After treatment, 5.4 +/- 1.19% of control AChE activity remained. By 24 hr, 31.6 +/- 6.4% of control activity had returned and the recovery of activity was essentially complete by 7 days after treatment. Recovery of AChE activity after DFP treatment required protein synthesis, since there was no recovery in the presence of cycloheximide. After treatment with the reversible inhibitor, physostigmine at 0.5 mg/ml, recovery of AChE activity was complete within 24 hr after treatment. These results indicate that CNS reaggregate cultures not only express differentiated functions of the CNS, but also have the capacity to turn over proteins, and thus may provide a good model system in which to examine mechanisms of toxicity.

Acetylcholinesterase↗
PubMed1983

Elution of the regulatory subunit of cAMP-dependent protein kinase Type I isozyme derived from epididymal fat within the type II isozyme chromatographic peak.

No cAMP-dependent protein kinase activity is found upon DEAE-cellulose chromatography of mouse fat extracts at the low salt concentration characteristic of the Type I isozyme. The RI detected in fat extracts by photoincorporation of the analog, 8-N3 [32P]cAMP, elutes within the high salt Type II isozyme peak. The multiple charge variants of this photolabeled RI which can be resolved by two-dimensional gel electrophoresis are similar to those of the histoptypically-related cultured cells, SV3T3 and 3T6, which do contain Type I kinase isozyme activity peaks. This high salt-eluting RI may be part of a Type I holoenzyme whose elution properties are altered by interactions with other substances present in the extract.

Adipose Tissue↗
PubMed1983

Chromosomal assignment of the gene for the human beta 2-adrenergic receptor.

Chinese hamster fibroblasts (CHW) fail to physiologically respond to the beta-adrenergic agonist isoproterenol with an increase in cellular cAMP. This unresponsiveness is due to a lack of beta-adrenergic receptors as indicated by an absence of specific binding of 125I-labeled hydroxybenzylpindolol (125I-HYP) to CHW plasma membranes. Preparation of somatic cell hybrids between CHW and human peripheral blood leukocytes led to the selection of a panel of 15 human-Chinese hamster cell hybrid clones, some of which had beta 2-adrenergic receptors (specifically bound 125I-HYP) and responded to isoproterenol (accumulated cAMP). Biochemical analysis of independent cloned cell hybrids indicated that beta 2-adrenergic receptor density and the intensity of the associated physiological response were closely correlated (r = 0.98). Both of these parameters were concordant in all cell hybrids with the presence of human chromosome 5. All other human chromosomes could be ruled out. These results suggest that the structural gene for the beta 2-adrenergic receptor is found on human chromosome 5.

Adenylyl Cyclases↗
PubMed1983

Enzymatic formation of zinc-protoporphyrin by rat liver and its potential effect on hepatic heme metabolism.

The mitochondrial enzyme heme synthase (ferrochelatase) catalyzes the formation of heme from ferrous iron and protoporphyrin. Using a fluorometric assay, the enzymatic formation of zinc-protoporphyrin in rat liver tissue was compared with heme formation. With sonicated liver homogenate, the rate of zinc-protoporphyrin formation was similar to that of heme when each metal was present alone in the reaction mixture. When combined in the reaction mixture, the two metals competed for the enzyme. With intact mitochondria, zinc was a better substrate, as 90% of the product was zinc-protoporphyrin in the presence of 50 microM zinc and 50 microM iron. The effect of zinc-protoporphyrin on the induction of delta-aminolevulinic acid synthase, the rate-limiting enzyme in hepatic heme biosynthesis, was also examined in the rat. Intraperitoneal injection of allylisopropylacetamide (350 mumol) induced activity of the enzyme fourfold. Concomitant administration of zinc-protoporphyrin (4 mumol) suppressed the induction by 52%, nearly as effectively as the same amount of heme. These findings indicate that the formation of zinc-protoporphyrin in liver may (a) inhibit the synthesis of heme and (b) exert negative feedback regulation on delta-aminolevulinic acid synthase. This combination would reduce the hepatic heme level.

5-Aminolevulinate Synthetase↗
PubMed1982

beta-Adrenergic response in mouse CNS reaggregate cultures.

Primary reaggregate cultures from 17-day embryonic mouse brains were prepared and tested for beta -adrenergic response. Isoproterenol stimulated the production of cAMP 3- to 4-fold over basal levels after 10 days in culture. The response to isoproterenol was rapid, reaching a maximum 1-2 min after stimulation, and was blocked by propranolol. The beta-adrenergic receptor was characterized in membranes prepared from reaggregates by measurement of specific binding of [125I]iodohydroxybenzylpindolol (IHYP). The Kd for IHYP was 100-300 pM and did not change as a function of time in culture. A maximum receptor density of approximately 80-110 fmol/mg membrane protein was found. Both beta-adrenergic receptors and response appeared at times in culture, which were approximately equivalent to birth.

Adrenergic beta-Agonists↗
PubMed1982

The adrenergic responsiveness of Down syndrome cells.

Platelets and cultured fibroblasts were used to examine the hormonal response of normal diploid and Down syndrome (trisomy 21) cells. An enhanced physiological response to catecholamine hormones was found in the trisomy 21 cells. This effect was specific for the adrenergic agonists since other hormones showed equivalent responses in the normal diploid and trisomy 21 cell types. Radioligand analysis of the alpha-adrenergic receptors in trisomy 21 platelets indicated no significant difference in receptor density or ligand affinity. Enzymatic analysis of the platelet adenylate cyclase activity in vitro showed no major changes in catecholamine sensitivity between the normal and Down syndrome preparations. Somatic cell genetic studies using human-hamster hybrids indicated that a gene coding for the beta-adrenergic receptor was not located on chromosome 21 but on human chromosome 5. These receptor, enzymic, and somatic cell genetic studies argue against a gene-dosage effect involving either the adrenergic hormone receptors or a component of the adenylate cyclase enzyme in the trisomy 21 cells. Identifying the gene(s) on chromosome 21 and the molecular mechanism(s) responsible for the exaggerated response of Down syndrome cells to catecholamines are the current objectives of this research program.

Cells, Cultured↗
PubMed1981

Cyclic AMP-dependent protein kinases from Balb 3T3 cells and other 3T3 derived lines.

Cyclic AMP-dependent protein kinase and 3H-cAMP-binding activities were determined in normal Balb 3T3 cells and compared with the same preparations from SV40, chemical, and spontaneous transformants of 3T3 cells. The cytosolic protein kinase activities and protein kinase activity ratios were similar in all cell lines, although when the normal 3T3 cytosol was prepared by homogenization it contained less 3H-cAMP binding activity than the transformed 3T3 cytosols. The Triton X-100 treated particulate fractions from the normal and transformed 3T3 cells contained similar protein kinase and binding activities. The isozymic profile of cAMP-dependent protein kinases was examined by DEAE-chromatography. The 3T3 cells contained only type II isozyme in either cytosolic or membrane fractions. All transformants of the 3T3 cells contained both type I and type II isozymes. Other cell cultures, including chicken embryo fibroblasts, rat kidney cells, and human or calf endothelial cells contained type I and type II isozymes. Binding of the photoaffinity analogue of cAMP, 8-N3 cAMP, to the regulatory subunits of protein kinases in sonicates obtained from Balb 3T3 and SV 3T3 cells followed by separation on SDS polyacrylamide electrophoresis showed that the amount of RII subunit was approximately equal in the two cell lines. RI in Balb 3T3 cells was detectable but in a much lower quantity than in SV 3T3 cells. The cyclic AMP dependent-protein kinases from Balb 3T3 cells appears to be different from SV 3T3 cells by three criteria: 3H-cAMP binding in homogenates, DEAE chromatographic separation of isozymes, and 8-N3 cAMP binding.

Affinity Labels↗
PubMed1978

Brain reaggregate cultures: biochemical evidence for myelin membrane synthesis.

Myelin membrane synthesis was studied using mechanically dissociated fetal rodent CNS which formed spherical reaggregates while being maintained in rotating culture flasks. These reaggregate cultures exhibited myelinogenesis in vitro after precisely the same period of time needed for myelin synthesis to commence in vivo. The myelin membrane related enzymes, 2', 3' cyclic nucleotide phosphohydrolase (CNP) and cerebroside sulfotransferase (CST), appear similar in their specific activities and follow the same developmental patterns that these enzymes exhibit in vivo. In addition, phosphorylation of myelin basic protein occurs by the third week in vitro which agrees with previously published in vivo studies. These experiments indicate that this nerve-cell culture system may be a appropriate model for studying the biological regulation of myelinogenesis as well as a variety of other nervous-system functions.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMedDate not supplied

Effects of aging on spatial learning and hippocampal protein kinase C in mice.

C57BL/6Nia and F1(B6xD2)Nia mice were tested on the Morris water maze task for 5 days followed by 12 days of testing on the place learning-set task (8 trials/day with each task). Mice were tested at 3, 14, and 25 months of age. C57 mice, 25 months of age, were significantly impaired in both the Morris and place learning-set task probe trial performance compared to mice 3 months of age (p < 0.05). These aged C57 mice also demonstrated a significant reduction in membrane-bound hippocampal protein kinase C (PKC) activity (p < 0.05) with no significant change in cytosolic PKC activity. F1 mice, however, showed no effect of age on probe trial performance on the spatial learning tasks. In addition, in a comparison of C57 and F1 mice within each age group, F1 mice demonstrated superior learning performance which was accompanied by a significant elevation in PKC activity (p < 0.05). Spatial learning performance of both strains significantly correlated with membrane-bound PKC activity (p < 0.01). These data provide additional support for our previous hypothesis of an involvement of hippocampal PKC activity in spatial learning and suggest that the amount of membrane-bound PKC activity may be a determinant of age-related decline in spatial learning.

Aging↗
PubMedDate not supplied

Interaction of ethanol and stress with the GABA/BZ receptor in LS and SS mice.

The interaction of stress and ethanol with the GABA/BZ receptor system was evaluated in LS and SS mice. The effects of two separate in vivo treatments, a 2.5 g/kg injection of ethanol or a behavioral stressor, on GABA-enhanced [3H]-FNZ binding were nearly identical in both lines of mice. A 2.5 g/kg ethanol- or stress-pretreatment resulted in increased enhancement in SS cortex, but not LS. In cerebellum, treatment effects were demonstrated in both SS and LS mice. Intraperitoneal injections of increasing doses of ethanol produced biphasic stimulation of GABA-enhanced [3H]-FNZ binding in LS brain regions, but not SS. Adrenalectomies performed one week prior to ethanol administration produced a loss of ethanol enhancement in cerebellum of both lines. However, in cortex, removal of the adrenals had no effect. The in vitro addition of 30 mM ethanol to brain preparations incubated at 37 degrees C from stressed and unstressed animals resulted in greater enhancement of binding in cortex, but not cerebellum of stressed mice. Differences in the degree of enhancement between the lines of mice were lost if the animals were stressed prior to sacrifice or if membrane preparations were incubated at 4 degrees C. The results of this study suggest that the interaction between ethanol and stress is mediated by the GABAergic system, but responses vary dependent on brain region, dose of ethanol, and degree of ethanol sensitivity.

Animals↗
PubMedDate not supplied

The effects of ethanol and Ro 15-4513 on elevated plus-maze and rotarod performance in long-sleep and short-sleep mice.

The effects of ethanol and diazepam were examined in long-sleep (LS) and short-sleep (SS) mice using the elevated plus-maze. Ethanol had more pronounced effects in SS mice than in LS mice. In contrast, LS mice were more sensitive to the effects of diazepam on the elevated plus-maze. The ataxic effects of ethanol were measured by rotarod performance. SS mice were more resistant to the ataxic effects of a 2.0 g/kg dose of ethanol than LS mice. Ro 15-4513 reversed ethanol's ataxic effects when administered after ethanol in both LS mice and SS mice. Pentobarbital-induced ataxia was unaffected by treatment with Ro 15-4513. Studies of competition of Ro 15-4513 on 3H-flunitrazepam binding indicated that LS and SS mice did not differ in this measure in cortex, cerebellum or hippocampus.

Animals↗
PubMedDate not supplied

Chronic intragastric infusion produces tolerance to ethanol in LS and SS mice.

Tolerance to ethanol's effects is seen after chronic injections and after chronic treatment with ethanol-containing liquid diets. However, tolerance associated with injections is often associated with environmental cuing (learned tolerance) and liquid diets do not allow for careful control of dose. The studies reported here demonstrate that chronic (3 g/kg every 6 h for 7 days) intragastric infusion of ethanol produces tolerance to ethanol in both LS and SS mice, as measured by sleep time and effects on open field activity and body temperature. LS mice developed more tolerance for all measures than the SS. The rate of ethanol elimination was increased slightly in both the LS and SS mouse lines following chronic ethanol infusion, which suggests that both lines developed a modest metabolic tolerance to ethanol. In contrast, the waking blood ethanol levels were altered only in the LS mice, which argues that some of the tolerance to ethanol seen in the LS mice is pharmacodynamic tolerance. Thus, chronic intragastric infusion of ethanol is a reliable method for treating animals chronically with ethanol that allows for the precise control of dose and dose interval, oral administration of ethanol, and minimal animal handling that can be associated with drug delivery, thereby reducing the risk of developing learned tolerance to ethanol.

Animals↗