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Biomedical subjects

J Tannenbaum

Publications and source records attributed to J Tannenbaum.

At least 37 records · Page 2Linked to original sources
PubMed1985

Evidence for regulation of actin synthesis in cytochalasin D-treated HEp-2 cells.

In HEp-2 cells treated with 0.2 or 2.0 microM cytochalasin D (CD), the relative rate of actin synthesis increased for about 12 h and then reached a plateau; this increase was suppressed by actinomycin D (AD). When CD was washed from cells which had been treated for 20 h, the elevated rate of actin synthesis declined to the control value within ca 4 h, as the actin-containing cytoskeletal components rearranged by CD recovered their normal morphology. Subsequently, actin synthesis was depressed below control values for a prolonged period; during recovery from 2 h treatment with CD, this depression was of much shorter duration. Re-addition of CD to cells after a 3 h recovery period again induced the cytoskeletal alterations characteristic of CD treatment but did not reverse the prior decline in the rate of actin synthesis. In HEp-2 cells treated with cycloheximide during exposure to CD for 20 h, the relative rate of actin synthesis measured after removal of cycloheximide was twofold higher than with CD alone and such cells exhibited a twofold slower decline in the rate of actin synthesis during recovery from CD in the continued presence of cycloheximide. These effects of cycloheximide, which resemble observations on "super-induction", suggest that actin synthesis in CD-treated and recovering HEp-2 cells may be regulated by a repressor protein. The possibility that the proposed repressor protein is actin and that actin may thus be a feedback inhibitor of its own synthesis is discussed.

Actins↗
PubMed1985

Cytochalasin D-induced increase in actin synthesis and content in a variety of cell types.

Treatment of a variety of mesenchymal cells (normal and transformed rat fibroblasts, bovine aortic endothelial cells, rabbit smooth muscle cells), exhibiting different cytoskeletal organizations and derived from several species, with doses of cytochalasin D (CD, 2-6 microM for 20 h) sufficient to induce cytoskeletal rearrangement and altered cellular morphology results in an increase in the relative content and rate of synthesis of actin. These data extend our previous findings for HEp-2 cells to other cell types and provide further evidence for our hypothesis that the CD-induced cytoskeletal reorganization triggers stimulation of actin synthesis and the resulting increase in actin content.

Actins↗
PubMed1985

Ethics and human-companion animal interaction. A plea for a veterinary ethics of the human-companion animal bond.

For both moral and practical reasons, the veterinary profession must begin to nurture a serious veterinary ethics of human-companion animal interaction. Among the central concerns of such a discipline will be the moral value of the veterinary patient: the moral significance of human-animal companionship; the proper response of the practitioner to conflicts of interests between the patient, its owner, and himself; and the proper role of the practitioner in the client's decisions. Approaches that urge moral equality of man and animal or encourage the veterinarian to control the client's decision undervalue the moral status of the animal owner in the human-companion animal bond.

Animals↗
PubMed1983

Cytochalasin D induces increased actin synthesis in HEp-2 cells.

In HEp-2 cells treated with 0.2 to 2.0 microM cytochalasin D (CD) for 7.5 to 24 h there was a 20 to 50% relative increase in actin content (units of actin per microgram of total cell protein). This augmentation, which was concentration and time dependent, was prevented by treatment with cycloheximide during exposure to CD. A 15 to 20% increase in the relative rate of actin synthesis in CD-treated HEp-2 cells (0.2 to 2.0 microM CD) was detectable after 1 h of treatment and increased to 30 to 50% by 24 h. This increased rate of actin synthesis was apparently responsible for the higher actin content of CD-treated HEp-2 cells. The concentration dependence of these effects of CD on actin metabolism correlated with the pattern seen for CD-triggered changes in cellular morphology and the underlying rearrangements of the actin-containing cytoskeletal structures, suggesting that the effects on metabolism and morphology were interrelated. Since the rapidly occurring cytoskeletal reorganization preceded the effects of CD on actin metabolism, it is proposed that actin synthesis is induced by the cytoskeletal rearrangement resulting from exposure to CD.

Actins↗
PubMed1983

Effect of unilateral ureteral obstruction on metabolism of renal lipids in the rat.

The metabolism of lipids in the cortex and inner medulla of control and experimental kidneys of rats with unilateral ureteral obstruction (UUO) was studied in vitro. A marked increase in the tissue triglyceride content was noted after 24 h of obstruction in the experimental kidney compared with the contralateral kidney of rats with UUO and normal kidneys from sham-operated rats. A decrease in total phospholipid content was seen in the experimental kidney after 24 h of obstruction. The incorporation of [1-14C]oleic acid or [14C]arachidonic acid into tissue triglycerides was significantly increased in the cortex and medulla of the experimental kidney of rats with UUO compared with either the contralateral kidney of the same animals or kidneys from sham-operated rats. The oxidation of [1-14C]oleic acid to 14CO2 and the incorporation of [14C]arachidonic acid into tissue phospholipids or free fatty acids were significantly lower in the experimental kidney of rats with UUO. The results strongly suggest an increase in the net synthetic rate of triglycerides in the experimental kidney of UUO rats. This increase may be related to both a decrease in fatty acid oxidation and an increased release of fatty acids from phospholipids presumably due to increased phospholipase activity.

Animals↗
PubMed1980

Cytochalasin D does not produce net depolymerization of actin filaments in HEp-2 cells.

The altered morphology, disappearance or 'disruption' of actin filaments (microfilaments) in cells treated with cytochalasin has sometimes been attributed to depolymerization of filamentous actin (F-actin) to its globular subunit (G-actin), but attempts to confirm that mechanism have been inconclusive. Treatment of purified actin filaments with cytochalasin B (CB) decreased their viscosity, consistent with depolymerization, which was not, however, revealed by electron microscopy, although the filaments appeared abnormal. CB also increased the ATP-ase activity of F-actin, suggesting that it had been destabilized, while actin filaments in the acrosomal process were not depolymerized. CB or cytochalasin D (CD) can dissolve actin gels (reviewed in ref. 7, see also refs 8 and 9) without depolymerizing their filaments. The 'disrupted' actin structures in CD-treated cells bound heavy meromysin, indicating that at least some of the cellular actin was filamentous. Using a rapid assay for G- and F-actin in cell extracts, based on the inhibition of DNase I, we have found that neither short-nor long-term exposure of HEp-2 cells to CD produce net depolymerization of actin filaments.

Actins↗
PubMed1979

The effect of glucose on the synthesis of prostaglandins by the renal papilla of the rat in vitro.

Renal pappillae from rats were incubated in vitro. The release of prostaglandin by this tissue was found to be inversely related to the glucose concentration of the buffer. Estimates of prostaglandin release were determined by a rat stomach strip bioassay, and in some instances, gas-chromatography and mass spectrometry. When incubated in the presence of C14-arachidonic acid, the specific activity of prostaglandins E2 and F2 alpha released by the tissue was lower at the lower glucose concentration. Provision of 625 micrograms/ml of exogenous arachidonic acid in the buffer obliterated the effect of glucose on prostalglandin release. These data indicate that increasing amounts of glucose suppresses prostaglandin synthesis in the renal papilla of the rat, and that the mechanism of this phenomenon is related to the release of arachidonic acid from its storage pools in tissue lipids.

Animals↗
PubMed1979

Studies of the cognitive representation of spatial relations: II. A familiar environment.

This experiment tested the ability of people to recall the locations of buildings in a familiar campus setting. Ten graduate students represented the relative locations of buildings by pairwise distance judgments (on a 100-point scale) and by direct mapping of locations on a Tektronix cathode ray terminal. As evaluated by Stevens's power law, both methods led to accurate judgments of relative distance (the average exponent was close to 1). In addition, the pairwise judgments were analyzed by multidimensional scaling (MDS) and the buildings were located in a two-dimensional map. When asked to choose between the MDS representation and the map created directly on the Tektronix, all 10 subjects chose the latter as the more accurate. Moreover, 6 out of 10 subjects thought the direct map was more accurate than the actual map of the building locations. These results suggest that either pairwise judgment or direct mapping yield accurative representations of spatial relations in a familial environment, but that subjects favor the direct map.

Cognition↗
PubMed1978

Treatment of pain by transcutaneous electrical stimulation.

Two hundred and ninety-two patients suffering from a wide range of pain syndromes were treated with transcutaneous electrical stimulation (TES). Electrical stimulation of the painful area was administered on the skin by externally applied electrodes, attached to a portable battery-operated apparatus. The results, determined according to a subjective scoring system, were good in 50.7%, moderate in 24.3% and poor in 25% of the patients. TES is a non-invasive technique, has no side effects and may easily be self-administered. It is concluded that it should be tried in pain syndromes for which no specific therapy is available.

Adolescent↗
PubMed1977

The binding sites of cytochalasin D. I. Evidence that they may be peripheral membrane proteins.

Binding sites for tritiated cytochalasin D (3H-CD) on the isolated plasma membrane from HEp-2 cells were reversibly inactivated, but not dissociated from the membrane, by dialysis in 0.6 M KCl. Activity was restored by subsequent dialysis in 0.06 M KCl. Treatment with 0.2 mM ATP at low ionic strength also inactivated these sites, apparently irreversibly. Extraction of the membrane with 6% Triton X-100 removed 75% of its protein, resulting in a two-fold increase in specific binding activity for 3H-CD. Both high and low affinity binding sites were retained by the detergent-extracted membrane; at least 60% of the high affinity sites were resistant to this treatment. Evidence is presented for the attachment to the HEp-2 plasma membrane of both actin and myosin. The results support the tentative conclusion that plasma membrane binding sites for 3H-CD are peripheral proteins on the cytoplasmic face of the membrane. They are consistent with the hypothesis that myosin may be the location of the high affinity binding site and actomyosin may be the low affinity site. Comparison of these observations with those reported for the congeneric drug, cytochalasin B, suggests that CD binding sites differ from the high affinity site for cytochalasin B.

Actomyosin↗
PubMed1977

The binding sites of cytochalasin D. II. Their relationship to hexose transport and to cytochalasin B.

Cytochalasin B (CB) was able to compete with tritiated cytochalasin D (3H-CD) for binding sites in HEp-2 cells. The pattern of inhibition suggested that CB associates with a low affinity class of CD binding sites. Glucose and maltose did not inhibit binding of 3H-CD to isolated HEp-2 plasma membrane. Inhibition of hexose transport by CD was negligible, but CD did not block the potent inhibition of this transport by CB. These results indicate that CD does not bind to the high affinity CB receptor reportedly associated with the hexose transport system, and that this receptor cannot mediate the morphological effects of CD. Both CD and CB induced contraction-zeoisis in HEp-2 cells; CB was less potent than CD, and their effects appeared to be additive. It was concluded that the high affinity binding sites for CD and CB are different, but that these congeners share a low affinity site. Both high and low affinity sites for CD appear to mediate its morphological effects; only the low affinity class appears to be involved for CB. Possible identification of the common low affinity binding site as actomyosin (detailed in Tannenbaum et al., '77) is further discussed.

Binding Sites↗