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Biomedical subjects

R E Ecklund

Publications and source records attributed to R E Ecklund.

At least 19 recordsLinked to original sources
PubMed1996

Effects of the novel thyroid hormone analogues, SKF L-94901, DIBIT, and 3'-AC-T2 on mitochondrial function.

The effects of L-T3 (3,3',5-triiodo-L-thyronine) and three novel analogues, SKF L-94901 (3,5-Dibromo-3'-pyridazinone-L-thyronine), Dibit (3,5-Dibromo-3'-isopropyl-L-thyronine), and 3'-Ac-T2(3'-Acetyl-3,5,-Diiodo-L-thyronine), on mitochondrial parameters were determined in hypothyroid rats. The parameters include the 24 hour hormone-induced changes in the bc1 complex and in the proton permeability of the mitochondrial inner membrane. The cardiac sparing analogue, SKF L-94901, had no effect on mitochondrial respiration or proton permeability; but the analogue did increase a-glycerophosphate dehydrogenase activity, mitochondrial ubiquinone content, and altered the bypass respiration in the bc1 complex. Dibit also did not increase respiration significantly but did change the other parameters. 3'-Ac-T2 increased respiration, mitochondrial ubiquinone content, proton permeability, enzyme activity and altered the bypass of the Antimycin A blockage in the bc1 complex.

Animals↗
PubMed1995

Effects of 3,3',5-triiodo-L-thyronine (L-T3) and T3 analogues on mitochondrial function.

The effects of L-T3 and several analogues on mitochondrial parameters were determined in hypothyroid rats. These parameters include the 24 hour hormone-induced changes in the bc1 complex and in the inner membrane's proton permeability. L-T3, and all analogues except rT3, increased mitochondrial ubiquinone to euthyroid levels. L-T3, D-T3 and 3'IpT2 but not rT3, Triac, Triprop, or Dimit, altered the bypass respiration in the bc1 complex. L-T3, D-T3, Triac, 3'IpT2, and Triprop, but not rT3 or Dimit, increased the membrane's proton permeability. Actinomycin D did not prevent the increase in mitochondrial ubiquinone or the permeability change. The results show the selective thyromimetic properties of the analogues and that some of the mitochondrial changes do not require protein synthesis.

Animals↗
PubMed1995

Somatostatinoma: atypical presentation of a rare pancreatic tumor.

Somatostatinomas are rare neuroendocrine tumors that can result in a variety of symptoms depending on the secretion of other peptides in association with or in response to somatostatin. The rarity and variable clinical presentation of these tumors present problems in diagnosis and management. This report details the treatment of a 66-yr-old male who had a somatostatinoma with an atypical location and presentation. His clinical course was one of recurrent disease treated surgically and the interval development of cholelithiasis. He has survived 5 yr with his tumor, illustrating that monitoring peptide levels and an aggressive surgical approach are warranted for this condition. Prophylactic cholecystectomy should be considered at the time of exploration.

Aged↗
PubMed1992

The early triiodothyronine-induced changes in state IV respiration is not regulated by the proton permeability of the mitochondrial inner membrane.

The time course of changes in mitochondrial respiration, alpha-glycerophosphate dehydrogenase activity, and inner membrane proton permeability and the effects of protein synthesis inhibition was determined in hypothyroid rats treated with triiodothyronine. Respiratory rates, alpha-glycerophosphate dehydrogenase activity and proton permeability were decreased in hypothyroid rats and rose to euthyroid levels 9-12 hours after triiodothyronine treatment. Some rats received actinomycin D with the hormone to inhibit protein synthesis. Sixteen hours after actinomycin D and hormone treatment, the increases in respiratory rates and in alpha-glycerophosphate dehydrogenase activity, were completely inhibited. However, actinomycin D did not inhibit the increase in the membrane's permeability.

Animals↗
PubMed1991

Effects of thyroid hormones on the bypasses of the antimycin A block in the bc1 complex of rat liver mitochondria.

The effect of thyroid hormones on the electron flow through the bc1 complex of rat liver mitochondria was studied using two dye bypasses of the Antimycin A block of the bc1 complex by the method of Alexandre and Lehninger (Biochim. Biophys. Acta 767:120; 1984). Bypass respiration rates with both DCIP (2,6-dichlorophenolindophenol) and TMPD (N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride) were elevated in the hyperthyroid rats and depressed in the hypothyroid groups compared to the euthyroid controls. T3 treatment of hypothyroid rats returned the bypass rates to control levels in 24 hours with the TMPD dye but not for the DCIP. This further demonstrates that different portions of the bc1 complex respond individually to the thyroid state.

2,6-Dichloroindophenol↗
PubMed1991

Thyroid hormone effects on the State IV proton motive force in rat liver mitochondria.

In order to further investigate the mechanisms regulating the control of mitochondrial respiration by thyroid hormone, the proton motive force was measured during State IV respiration in liver mitochondria isolated from euthyroid, hyperthyroid, hypothyroid and T3-treated hypothyroid rats. The proton motive force was significantly higher in the hyperthyroid group due to an increased delta pH. The proton motive force of hypothyroid mitochondria was lower than controls due to a decreased membrane potential. The proton motive force for the T3-treated hypothyroid group did not differ from the euthyroid group due to negating changes in the pH gradient and the membrane potential. The intramitochondrial volume was decreased in the hyperthyroid group and unchanged in the other groups. The results indicate that the thyroid status alters the proton motive force in State IV through individual changes in the pH and membrane potential components of the force. The component that changes in hyperthyroid mitochondria is different from that changing in hypothyroid mitochondria.

Animals↗
PubMed1990

Thyroid hormone effects on the proton permeability of rat liver mitochondria.

The effect of thyroid status on passive permeability of liver mitochondrial inner membrane was studied in euthyroid (EU), hyperthyroid (HYPER), hypothyroid (HYPO) rats and hypothyroid rats treated with a single dose of 3,3',5-triiodothyronine (HYPO + T3). Respiration was titrated with uncoupler and plotted against uncoupler concentration to calculate proton permeability. The passive permeability was the same in EU, HYPER, and HYPO + T3 rats, but was significantly lower in HYPO mitochondria. The State IV respiration rates were the same as the oligomycin-inhibited rats for EU, HYPO and HYPO + T3 rats, but in HYPER rats the oligomycin rate was less than the State IV rate. The data show that hypothyroid mitochondria have decreased permeability of the inner membrane which can be normalized by a single dose of T3. Hyperthyroid mitochondria show increased oligomycin-sensitive ATPase activity in State IV, a possible mechanism of the enhanced respiratory rate.

Animals↗
PubMed1986

Thyroxine-induced changes in rat liver mitochondrial ubiquinone.

Ubiquinone was extracted from liver mitochondria isolated from euthyroid and hyperthyroid rats. The redox state of ubiquinone was determined during States III and IV respiration with succinate or glutamate-malate substrates. Ubiquinone was more reduced during State III or IV in the hyperthyroid mitochondria with either substrate. Furthermore, the concentration of ubiquinone increased in the hyperthyroid rats.

Animals↗
PubMed1986

Inhibition of respiration in mitochondria and in digitonin-treated rat hepatocytes by podophyllotoxin.

The effects of the microtubular inhibitor, podophyllotoxin, on mitochondrial respiration were determined using isolated, digitonin-permeabilized hepatocytes and isolated mitochondria. In hepatocytes, podophyllotoxin (1.5 mM) inhibited coupled and uncoupled respiration of both FAD and NAD-linked substrates. In mitochondria, podophyllotoxin inhibited State III respiration, prevented the return to State IV respiration, and inhibited uncoupled respiration. There was no inhibition of ascorbate/TMPD oxidation in either the hepatocytes or the mitochondria. Podophyllotoxin had no effect upon oligomycin inhibition of coupled respiration. Oligomycin had no effect on the podophyllotoxin-inhibition of uncoupled respiration in either hepatocytes or mitochondria. The results indicate that podophyllotoxin alters electron flow at a site early in the electron transport chain.

Animals↗
PubMed1986

Altered tissue oxygen tension responsiveness in diabetes.

Subcutaneous oxygen tension (tissue PO2) was measured by a polarographic method in the legs of insulin-dependent diabetics (IDDM) and controls. Current flow was measured continuously using a five-stage protocol: baseline; 4 min of complete arterial occlusion; during recovery from ischemia; baseline approximately re-established; induction of hyperemia by local application of heat. Eleven patients with IDDM of 4-32 years of duration, without peripheral arterial disease, were studied and compared with 10 controls. The mean baseline subcutaneous PO2 in diabetics was less than controls; however, the difference was not statistically significant. At the end of arterial occlusion the mean decrease in tissue PO2 was less (P less than 0.025) in diabetics (4.7 +/- 0.9 mm Hg, SEM) compared to controls (10.2 +/- 1.6 mm Hg). With induction of hyperemia the increase in tissue PO2 was lower (P less than 0.001) in diabetics (7.4 +/- 0.4 mm Hg) than in controls (18.6 +/- 1.7 mm Hg). The observed differences provide for the first time direct evidence of altered tissue PO2 responses in diabetes.

Adolescent↗
PubMed1985

Thyroxine-induced changes in rat liver mitochondrial cytochromes.

The effects of 10 days of thyroxine injection (15 micrograms/100 g body weight) on rat liver mitochondrial cytochrome concentration and on the percent reduction of the individual cytochromes during succinate-driven state III and IV respiration was spectrophotometrically determined at cytochrome-specific wave-length pairs. The concentrations of cytochromes b, c, total c (c + c1) and a a3 increased in hyperthyroid rats. The concentration of cytochrome c1 remained constant in euthyroid and hyperthyroid rats. Changes in the concentration of the membrane-bound cytochromes were also determined by difference spectra in cytochrome c-depleted mitochondrial membranes. Cytochromes b and a a3 showed increased concentrations in hyperthyroid rats while the concentration of cytochrome c1 remained unchanged. Hyperthyroid mitochondria showed increased reduction of cytochromes b, c1, c and total c during state III respiration and cytochromes c1, c, and total c during state IV respiration. The percent reduction of cytochrome b decreased during state IV respiration in the hyperthyroid mitochondria. These results suggest that the increase in respiration observed in the hyperthyroid state may be related to changes both in the mitochondrial cytochrome concentration and in the cytochrome reduction level.

Animals↗
PubMed1979

Effect of thyroidectomy upon the activity of three mitochondrial shuttles in rats.

The activities of mitochondrial alpha-glycerophosphate, malate-asparte, and malate-citrate shuttles which oxidize NADH were determined in liver and kidney cortex mitochondria isolated from Tx and control rats. Weight gain, relative liver and kidney size, oxygen consumption, and serum thyroxine were also determined. Tx animals weighed less, had smaller livers and kidneys, and showed significantly lower oxygen consumption of the resting animal and a marked decrease in serum thyroxine levels. The activity of the three shuttles studies was significantly less in liver mitochondria from Tx animals, particularly when studied in the absence of added ADP. Thyroidectomy had less effect upon shuttle activity of mitochondria from the kidney cortex, with significant decrease in activity found only in the complete alpha-glycerophosphate shuttle and in the endogenous malate-aspartate and malate-citrate shuttles studied in the absence of ADP. Changes in shuttle activity caused by thyroid hormone are discussed in relation to other known metabolic effects of thyroxine, and the possible primary role of adenine nucleotide translocase activity in mediating other thyroxine-dependent metabolic changes is considered.

Adenosine Diphosphate↗
PubMedDate not supplied

Diabetic thoracic radiculopathy: electrodiagnostic study.

We investigated the diagnostic value of electromyographic (EMG) examination of the anterior abdominal wall muscles (AWMS) in thoracic radiculopathy and compared it with examination of thoracic paraspinal muscles (TPSM). Technically, examination of AWMS was much easier compared to TPSM. In eight patients with thoracic diabetic radiculopathy at the level of T7-T12, AWMS was abnormal in all and was considered to be diagnostic, whereas AWMS was normal in diabetic lumbar radiculopathy, patients with diabetes mellitus without radiculopathy, patients with unspecified gastrointestinal pain, and patients with musculoskeletal-type back pain. We conclude that EMG evaluation for possible thoracic radiculopathy should include examination of AWMS, and if abnormal, would be of great diagnostic help in patients with unspecified gastrointestinal symptoms.

Abdominal Muscles↗
PubMedDate not supplied

L-Thyroxine effects upon ATPase activities of several subcellular fractions of liver of the rat and the guinea pig.

The effect of thyroxine administration upon ATPase activity of several subcellular fractions of livers from rats and guinea pigs has been studied. To determine a patho-physiological dose of levo thyroxine [T4] for guinea pigs, a dose-response curve was examined of T4 effect upon oxidative phosphorylatin of guinea pig liver mitochondria. Maximum stimulation of mitochondrial respiration without uncoupling of oxidative phosphorylation was found with 15 microgram of T4 per 100 g body weight per day. This dose of T4 stimulated Mg++ activated ATPase of plasma membranes of guinea pigs and slightly stimulated Mg++ activated ATPase of guinea pig liver nuclear membranes. Rat liver nuclear membrane ATPase was not responsive to thyroxine at doses from 5 to 150 microgram per 100 g body weight. T4 significantly stimulated Ca++ or Mg++ ATPase of mitochondria and microsomes from both rat and guinea pig liver. Microsomes from both species were maximally activated by Mg++ and no significant additional stimulation with Ca++ was found. Mitochondrial ATPase from both species showed significantly greater Ca++ plus Mg++ ATPase activity than did Mg++ alone. Ca++ activated ATPase was approximately equal to dinitrophenol stimulated mitochondrial ATPase. Maximum activation of microsomal ATPase in both species was found with 1 mM calcium. We conclude that at physiological-intracellular concentrations of Ca++ and Mg++, thyroxine probably stimulates Mg++ activated microsomal ATPase and Ca++ activated mitochondrial ATPase. A potential role of Ca++ as a moderator of thyroxine stimulated activity in mitochondria and the relation of calcium to other metabolic reactions that are thyroxine sensitive is discussed.

Adenosine Triphosphatases↗
PubMedDate not supplied

Effects of thyroxine treatment on the hepatic plasma membrane ATPase activity in rats.

The effects of T4 and T3 upon ATPase activity of plasma membrane preparations produced by different methods has been studied. Media without Na+ or K+ was used to identify Mg++ activated ATPase, and media containing 100-120 mM Na+ and 20-30 mM K+ in addition to Mg++ was used to identify the augmented activity of Na-K ATPase. We also utilized media containing Na+, K+, and Mg++ in the presence and absence of ouabain to identify the Na+-K+ activation. We found no effect of doses of thyroxine in the physiologic range upon the Na+-K+ ATPase activity. A dose-response study indicated that high doses of T4 may stimulate Mg++ activated ATPase. In the P2 preparation of the Touster method we found minimally enhanced Na+-K+ ATPase activity. The quantity of T4 needed to cause such enhancement is approximately 50 times the physiologic replacement dose needed to restore thyroidectomized animals to a euthyroid state. We conclude that thyroid hormones do not stimulate Na+-K+ ATPase of plasma membranes when administered in a physiologic quantity, but may enhance Mg++ atpase activity when administered in a pharmacologic or toxic quantity.

Adenosine Triphosphatases↗