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Biomedical subjects

D M Ackerman

Publications and source records attributed to D M Ackerman.

13 recordsLinked to original sources
PubMed1996

Esterified estrogens with and without methyltestosterone decrease arterial LDL metabolism in cynomolgus monkeys.

Although both epidemiological and experimental evidence suggests that estrogen replacement therapy reduces the risk of coronary heart disease, the mechanisms for this beneficial effect are largely unknown. Furthermore, the addition of progestins or androgens to estrogen replacement therapy is of concern. The objective of this study was to examine the effects of esterified estrogens alone or in combination with an androgen on arterial LDL metabolism and early atherogenesis in ovariectomized female cynomolgus monkeys. Arterial LDL metabolism was assessed by using dual-labeled LDL that was injected 24 hours before necropsy. Arterial LDL degradation was reduced by 64% to 84% and cholesteryl ester content was decreased by approximately 50% in the thoracic aorta in both treatment groups compared with controls. In addition, aortic lipid peroxidation products, as assessed by thiobarbituric acid reaction, were significantly lower in animals treated with esterified estrogens, with a similar trend for combined estrogen-androgen treatment. Both treatments also reduced plasma concentrations of apoB-containing lipoproteins, reduced LDL particle size, and increased total-body LDL catabolism. The combination of decreased arterial LDL metabolism, decreased arterial lipid peroxidation, and improved plasma lipoprotein metabolism may explain some of the protective effects of estrogens on coronary heart disease and indicate that beneficial actions extend to a combination of estrogen and androgen.

Animals↗
PubMed1995

Binding of 17-alpha-methyltestosterone in vitro to human sex hormone binding globulin and rat ventral prostate androgen receptors.

We measured the relative binding affinity (RBA) of 17-alpha-methyltestosterone (MET) for the rat prostate androgen receptor and human sex hormone-binding globulin (SHBG) in vitro. The reference compound in both instances was dihydrotestosterone (DHT), the RBA of which was set at 100%. The RBA of methyltestosterone was 44% for the androgen receptor, but 11% for SHBG. The androgen receptor, therefore, would appear to recognize a different part of an androgen compared to the recognition site on SHBG. The difference in RBAs may amplify the biologic action of methyltestosterone.

Animals↗
PubMed1992

The expression of human chorionic gonadotropin/human luteinizing hormone receptors in human gestational trophoblastic neoplasms.

Normal human placental trophoblasts have recently been shown to contain receptors for hCG/hLH. The present studies investigated the expression of these receptors in hyperplastic and anaplastic trophoblasts in gestational trophoblastic neoplasms. The results demonstrated that both hydatidiform moles and choriocarcinomas contained receptor messenger RNA (mRNA) and receptor protein. A variety of nontrophoblast tumors, on the other hand, contained neither receptor mRNA nor receptor protein. Choriocarcinomas contained more receptor mRNA and receptor protein than hydatidiform moles which in turn contained more than normal human placenta. Midluteal phase human corpus luteum contained more receptor mRNA than normal human placenta and about the same as choriocarcinomas. The hyperplastic and anaplastic trophoblasts in hydatidiform moles and choriocarcinomas contained more receptor immunostaining than the normal trophoblasts in the same tissue or those from normal placentas from about the same gestational age. The receptor immunostaining increased as the degree of trophoblast hyperplasia increased in hydatidiform moles. Anaplastic trophoblasts of choriocarcinomas contained a similar amount of receptor immunostaining as severely hyperplastic trophoblasts of hydatidiform moles. Invading anaplastic trophoblasts of choriocarcinoma contained greater amount of receptor immunostaining than the surrounding endometrial stromal and myometrial smooth muscle cells. In summary, this is the first study to our knowledge demonstrating the expression of hCG/hLH receptor gene in gestational trophoblastic neoplasms. The increased receptor expression in these neoplasms suggests that hCG, via its receptors, could play a fundamental and previously unsuspected autocrine role in the regulation of trophoblast transformation, growth, invasion, and high hCG secretion.

Adenocarcinoma↗
PubMed1989

AY-31,906, a novel high ceiling diuretic: characterization of its relative potassium-sparing actions in rats and dogs.

AY-31,906, exo-2-amino-4-[(bicyclo[2.2.1]hept-2-yl)amino-N-[[1- methylethyl)amino]carbonyl]-5-pyrimidinesulfonamide, exhibited potent diuretic and natriuretic activity in rats and dogs. After p.o. administration, AY-31,906 was 1.5- and 12.3-times more potent as a natriuretic than furosemide in rats and dogs, respectively, whereas it was 0.5- and 6.1-times as potent after i.v. administration. The maximum natriuretic effect of AY-31,906 in both species was similar to that observed with furosemide. At equiactive natriuretic p.o. doses in both species, AY-31,906 produced a greater increase in the urinary ratio of Na/K than furosemide, indicating a relative potassium-sparing effect. AY-31,906 produced significant increases in the fractional excretion of sodium and chloride in dogs at a dose that produced no statistically significant changes in the fractional excretion of potassium, glomerular filtration rate or renal plasma flow. After p.o. administration, the onset of activity of AY-31,906 occurred within the 1st hr in both rats and dogs and preliminary data demonstrated that the activity lasted for approximately 2 hr in rats and 4 hr in dogs. Clearance studies in conscious dogs suggest that AY-31,906 inhibited electrolyte reabsorption in the ascending limb of the loop of Henle and, unlike furosemide, AY-31,906 had no activity at the proximal tubule. These results indicate that AY-31,906 is a potent, high ceiling diuretic with relative potassium-sparing properties. The compound is well absorbed after p.o. administration with diuretic activity occurring in the 1st hr.

Animals↗
PubMed1986

Enhancement of epidermal regeneration by biosynthetic epidermal growth factor.

Epidermal regeneration depends on mitosis and migration of keratinocytes. Epidermal growth factor is known to stimulate growth of keratinocytes in vitro, thus it might be expected to promote wound healing. The results of this study show that topical application of biosynthetic human epidermal growth factor accelerates epidermal regeneration in split-thickness wounds and partial-thickness burns. The significant enhancement of epidermal regeneration suggests the potential for clinical use of epidermal growth factor for accelerating healing of burns, wounds from trauma, diabetic ulcers, skin graft donor sites, and others.

Animals↗
PubMed1984

Tri- and tetrapeptide analogues of kinins as potential renal vasodilators.

Tri- and tetrapeptide analogues were synthesized and evaluated as renal vasodilators. These peptides were prepared by standard coupling reactions, which also provided good yields with hindered alpha-methyl amino acid derivatives. Preliminary evidence of renal vasodilator activity was determined in anesthetized dogs by measuring the effects on renal blood flow and calculating the accompanying changes in renal vascular resistance. The most potent compounds contained, in their basic structure, the L-prolyl-DL-alpha-methylphenylalanyl-L-arginine and L-prolyl-DL-alpha-methylphenylalanylglycyl-L-proline arrays. Substitution on the N-terminal proline with 4-phenylbutyryl and 4-(4-hydroxyphenyl)butyryl side chains produced enhanced renal vasodilator activity and, in certain cases, selectivity for the renal vasculature.

Animals↗
PubMed1984

Biochemical interactions and nephrotoxicity.

To understand the nephrotoxicity of xenobiotics, the species, strain, sex, and the presence of other chemicals must be considered. This review has considered the importance of these factors in determining the nephrotoxic liability of a drug. For example, cephaloridine is more nephrotoxic in rabbit than rats and is least nephrotoxic in mice. This species-dependent susceptibility to cephaloridine nephrotoxicity appears to be related to the degree in which cephaloridine depletes renal cortical glutathione. Additionally, only male mice of certain strains are susceptible to chloroform-induced nephrotoxicity. Lastly, the presence of certain ketones or ketogenic substances such as acetone and hexane enhance chloroform-induced nephrotoxicity in male Sprague-Dawley rats. Knowing which factors can enhance or limit nephrotoxicity of drugs will lend to a better understanding of the mechanism of these toxicities as well as to design compounds with lesser toxicities.

Animals↗
PubMed1984

Pharmacological characterization of dopamine-4-O-sulfate.

Dopamine-4-O-sulfate (DA-4-S), a major metabolite of dopamine, was examined for pharmacologic activity both in vivo and in vitro. Intravenous doses of DA-4-S ranging from 1.3-34.3 micrograms/kg had no effect on renal blood flow or blood pressure in the anesthetized dog, demonstrating lack of agonist activity at vascular DA1 receptor sites. These data also suggest that DA-4-S is not metabolically converted to an active dopamine agonist in the dog. No beta-adrenoceptor agonist activity of DA-4-S could be detected in the isolated guinea-pig left atrium, and no alpha 1-agonist activity of DA-4-S could be detected in the perfused rabbit ear artery, although sympathetic neurotransmission was inhibited in this tissue at high concentrations (EC50 = 3.9 X 10(-6) M). This latter response was competitively inhibited by S-sulpiride. This lack of affinity for dopaminergic and adrenergic receptors was confirmed by biochemical assays (striatal adenylate cyclase stimulation; 3H-spiroperidol, 3H-clonidine, and 3H-WB 4101 binding using brain tissue preparations). In all the above tests, the activity of DA-4-S was much weaker than dopamine, showing this metabolite has little intrinsic dopaminergic or adrenergic pharmacological activity.

Adenylyl Cyclase Inhibitors↗
PubMed1983

Potential usefulness of renal vasodilators in hypertension and renal disease: SK&F 82526.

SK&F 82526 and its enantiomers have been shown to increase renal blood flow and decrease renal vascular resistance in the anesthetized dog. The effect of the racemate on lowering systemic blood pressure in the anesthetized dog and the spontaneously hypertensive rat has been shown to be caused by the R-enantiomer with the S-enantiomer being devoid of significant activity on blood pressure. The mechanism by which the R-enantiomer decreases blood pressure is not systemic vasodilatation or prejunctional inhibition of norepinephrine release but appears to result from a unique stimulation of the postjunctional dopamine receptor. Racemic SK&F 82526 also has been shown to increase renal blood flow in an ischemic model of acute renal failure.

Animals↗
PubMed1982

Further studies on the natriuretic activity of p-hydroxytriamterene.

p-Hydroxytriamterene, the phase I metabolite of triamterene, increased sodium excretion without affecting urinary volume or potassium when administered orally to rats on sodium deficient diets at doses of 15 and 30 mg/kg. The urine of these animals also contained p-hydroxytriamterene sulfuric acid ester, the phase II metabolite of triamterene but did not contain p-hydroxytriamterene. This evidence indicates that p-hydroxytriamterene is orally active as a potassium-sparing natriuretic in rats.

Animals↗
PubMedDate not supplied

Prevention of urinary albumin excretion in 6 month streptozocin-diabetic rats with the aldose reductase inhibitor tolrestat.

Recent clinical data strongly suggest that elevated urinary albumin excretion (UAE) identifies diabetic subjects at risk of developing nephropathy. Elevated UAE is attributed to increased transglomerular pressure, which is associated with poor metabolic control in rats. Because excess glucose in diabetes is metabolized via the polyol pathway, we were interested in whether the diabetes-induced elevation in UAE in rats could be prevented by inhibiting aldose reductase (AR), the first enzyme in the polyol pathway, with the AR inhibitor tolrestat. In fact, in rats made diabetic with streptozocin (35 mg/kg IV), treatment for 6 months with tolrestat (25 mg/kg/day in the diet) prevented both sorbitol accumulation in the kidney and the increase in UAE. Sorbitol accumulation and the increased UAE were not associated with statistically significant mesangial expansion, and the thickening of glomerular basement membranes was not affected by tolrestat treatment. The authors conclude that the 4.7-fold elevation in UAE in chronically diabetic rats is linked to the increased flux of glucose through the polyol pathway since it was prevented by inhibiting aldose reductase with tolrestat.

Albuminuria↗
PubMedDate not supplied

Effect of experimental diabetes on drug metabolism in the rat.

The effect of experimental diabetes on hepatic drug metabolism was studied in male Holtzman rats. Treatment of animals with streptozotocin and 6-aminonicotinamide, both agents which produce an insulin-deficient animal, caused prolongation of hexobarbital sleeping times and inhibition of the rate of metabolism of both hexobarbital and, to a lesser extent, aniline in vitro. Treatment of animals with N-methylacetamide, a diabetogen which does not cause insulin deficiency in the animal but rather produces an insulin-resistant state, did not affect the metabolism in vitro of either hexobarbital or aniline. Neither insulin nor any of the diabetogenic agents had any direct effect on drug metabolism in vitro. Furthermore, hepatic microsomal protein and cytochrome P-450 contents were not significantly different in any of the diabetic animals from those of the control animals. Hyperglycemia produced by glucose infusion did not affect the metabolism of hexobarbital in vitro. The effects of streptozotocin and 6-aminonicotinamide appeared to be at least partially due to the presence of an inhibitor in the liver cytosol which correlated with elevated hepatic cyclic AMP concentrations.

6-Aminonicotinamide↗