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Showing papers by "University of Texas Southwestern Medical Center published in 1981"


Journal ArticleDOI
TL;DR: The data suggest that local thromboxane release is associated with recent episodes of angina in patients with unstable angina pectoris, but whether this release is a cause or an effect is not yet known.
Abstract: Endogenous modulators of platelet aggregability and vascular tone may play a part in coronary-artery disease. We therefore measured the release of prostaglandins and thromboxane into the coronary circulation in patients with various kinds of cardiac disease. Simultaneous coronary-sinus (CS) and ascending-aortic (AO) blood samples were obtained from 60 patients for measurement of 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha, a prostaglandin I2 metabolite) and of thromboxane B2 (TxB2). Samples from 45 of these patients were also tested for prostaglandin E2 (PGE2) and lactate. Patients with unstable angina pectoris who reported chest pain within 24 hours of study had higher TxB2 CS/AO ratios (5.8 +/- 2.8, mean +/- S.D.) than patients whose most recent anginal pain was more than 96 hours before study (1.3 +/- 0.6; P less than 0.05), than those with nonischemic chest pain (1.2 +/- 0.4; P less than 0.05), or with valvular or congenital nonischemic heart disease (1.2 +/- 0.6; P less than 0.05). Those whose most recent anginal pain occurred 24 to 96 hours before study were distributed bimodally: the majority had low TxB2 CS/AO ratios (range, 0.5 to 2.1) like the patients in the three aforementioned groups, whereas a few had markedly elevated values (range, 10.5 to 46.6). The 6-keto-PGF1 alpha and PGE2 CS/AO ratios and myocardial lactate extraction were not significantly different among the five groups. These data suggest that local thromboxane release is associated with recent episodes of angina in patients with unstable angina pectoris, but whether this release is a cause or an effect is not yet known.

592 citations


Journal ArticleDOI
TL;DR: The results indicate that fibronectin is a major component present during wound healing, and appears to be type I collagen in the reticular dermis adjacent to the wound area.

465 citations


Journal ArticleDOI
TL;DR: The ability of human adipose tissue to form estrogen is not a function primarily of the adipocytes but rather resides principally in the cells of the stroma.
Abstract: Stromal cells and adipocytes were separated after collagenase treatment of adipose tissue obtained from women undergoing elective surgery, and these cells were used to study aromatization of [3H]androstenedione in vitro. Aromatization activity was estimated either 1) by determining the incorporation of tritium from [1-3H]androstenedione into [3H]water or else 2) by determining the formation of [3H]estrone (E1) and [3H]estradiol (E2) from [1,2,6,7-3H]androstenedione. It was established that only 13% of the aromatase activity of adipose tissue resided in the adipocyte fraction, whereas 87% of the aromatase activity was in the stromal/vascular fraction. Subsequent studies of aromatization were conducted utilizing stromal/vascular cells grown to confluence in monolayer culture. In such cells, the formation of [3H]E2 was slower initially but increased with time, and after 48 h of incubation, the amount of [3H]E2 produced exceeded that of [3H]E1. The rate of [3H]E1 formation, as a function of [3H]androstenedione concentration, followed Michaelis-Menten kinetics. The Vmax ranged from 0.8-3.0 pmol and ranged from 0.16-0.67 pmol mg-1 cell protein 6 h-1 in cells from omental adipose tissue. The apparent Km for [3H]androstenedione in stromal cells derived from both omental and sc tissue was the same, i.e. about 25 nM. We conclude that the ability of human adipose tissue to form estrogen is not a function primarily of the adipocytes but rather resides principally in the cells of the stroma.

392 citations


Journal ArticleDOI
TL;DR: In this paper, the liver membranes from young beagle dogs were found to possess binding sites that resemble the low density lipoprotein (LDL) receptors originally described in cultured human fibroblasts.
Abstract: Liver membranes from young beagle dogs were found to possess binding sites that resemble the low density lipoprotein (LDL) receptors originally described in cultured human fibroblasts. Treatment of the dogs with colestipol (a bile acid sequestrant) and mevinolin (a cholesterol synthesis inhibitor) produced a 3-fold increase in LDL binding activity. This increase correlated with a 2-fold increase in the fractional catabolic rate for intravenously administered human or canine 125I-labeled LDL, suggesting that the increased hepatic receptors were responsible for the enhanced clearance of LDL from plasma. The hepatic lipoprotein receptors of control and drug-treated dogs resembled human fibroblast LDL receptors in that they bound apoprotein E-containing lipoproteins, such as very low density lipoproteins and a subfraction of high density lipoproteins (HDL1), with 10-fold higher affinity than the apoprotein B-containing lipoprotein LDL; failed to bind canine HDL2 and human HDL3, which are devoid of apoproteins B and E; failed to bind methylated LDL; required calcium; and were destroyed by Pronase. Treatment of dogs with mevinolin not only increased the fractional catabolic rate for LDL but also reduced the synthetic rate for the lipoprotein. The current data suggest that the liver of dogs contains functional LDL receptors that are susceptible to metabolic regulation and that a drug-induced increase in the activity of these receptors can contribute to a lowering of plasma levels of LDL-cholesterol.

379 citations


Journal ArticleDOI
TL;DR: It was found that pFN has a much higher affinity for BAC-T or TC dish surfaces than albumin or fibrinogen, and mild heat denaturation of albumin increased its affinity for the surface by an order of magnitude.
Abstract: We studied the adsorption properties of plasma fibronectin (pFN) on wettable tissue culture (TC) dishes and nonwettable bacteriological (BAC-T) dishes in relationship to its biological activity of promoting fibroblast spreading. The binding of pFN to the dish surfaces was found to be very tight and partially resistant to treatments with 1M NaOH, 2% SDS, 8M urea, or 6M guanidine HCl. Only the combination of trypsin (1 mg/ml) followed by 1M NaOH resulted in complete recovery of surface bound material. The amount of surface bound pFN did not directly correlate with its activity when comparing TC and BAC-T dishes. At low concentrations, more pFN adsorbed onto the surfaces of BAC-T dishes than TC dishes, but the adsorbed material was biologically less active on BAC-T dishes. At high concentrations, pFN adsorbed similarly on both dish surfaces reaching a maximum level of 320 ng/cm2 or 4.4 x 10(11) molecules/cm2. The possibility was considered that pFN unfolded into an inactive conformation when adsorbed on BAC-T dishes at a low concentration but that at high concentrations, molecular packing requirements prevented unfolding. Evidence in favor of this hypothesis was the observation that addition of 50 micrograms/ml of serum albumin simultaneously with low pFN concentrations resulted in adsorption of pFN on BAC-T dishes in an active conformation even though the amount of adsorbed pFN decreased. Competition experiments between pFN and other proteins were carried out, and it was found that pFN has a much higher affinity for BAC-T or TC dish surfaces than albumin or fibrinogen. It was also found that mild heat denaturation of albumin increased its affinity for the surface by an order of magnitude.

345 citations


Journal ArticleDOI
TL;DR: The rise in plasma ACTH concentrations, asregnancy advances, is suggestive of the possibility that a source of ACTH exists that is not subject to negative feedback control, that the clearance of free cortisol increases as pregnancy advances, or that there is an alteration in the metabolism of the ACTH precursor protein produced by the pituitary and/or placenta.

332 citations


Journal ArticleDOI
TL;DR: It is shown that the abnormal protein specified by the Ed allele (apo E-D) from some, but not all, patients with F. Dys.
Abstract: Patients with familial dysbetalipoproteinemia (F. Dys.), also called familial type 3 hyperlipoproteinemia, are homozygous for a mutant allele, Ed, that specifies an abnormal form of apoprotein (apo) E, a prominent constituent of remnant lipoproteins derived from very low density lipoproteins (VLDL) and chylomicrons. Apo E is thought to mediate the removal of remnant lipoproteins from the plasma by virtue of its ability to bind to hepatic lipoprotein receptors. In F. Dys. patients, remnant-like lipoproteins accumulate, apparently because of delayed clearance by the liver. In the current studies, we show that the abnormal protein specified by the Ed allele (apo E-D) from some, but not all, patients with F. Dys. has a markedly deficient ability to bind to low density lipoprotein (LDL) receptors. Apo E was isolated from eight control subjects and nine patients with F. Dys. and incorporated into phospholipid complexes. The complexes were tested for their ability to compete with human 125I-LDL or rabbit 125I-beta-VLDL fo binding to LDL receptors in four assay systems: cultured human fibroblasts, solubilized receptors from bovine adrenal cortex, liver membranes from rats treated with 17 alpha-ethinyl estradiol, and liver membranes from normal rabbits. The apo E-D from six of the nine patients with F. Dys. showed binding affinities for LDL receptors that were reduced by greater than 98% in all receptor assays (group 1 patients). All of these group 1 patients were unequivocally of phenotype apo E-D/D by the criterion of isoelectric focussing. The apo E from the three other F. Dys. patients showed a near normal binding ability in all four of the receptor assays (group 2 patients). One of these group 2 patients appeared to have the apo E-D/D phenotype by isoelectric focussing. In the other two patients in group 2, apo E-D was the predominant protein (phenotype, apo E-D/D), but traces of protein in the region corresponding to normal apo E (apo E-N) were also present. The difference between group 1 and group 2 patients was also apparent when the apo E was iodinated and tested directly for binding to liver membranes from rats treated with 17 alpha-ethinyl estradiol. The 125I-labeled apo E from a group 2 patient, but not a group 1 patient, showed enhanced uptake when perfused through the liver of an estradiol-treated rate, indicating that the receptor binding ability of apo E correlated with uptake in the intact liver. The current studies allow the subdivision of patients with F. Dys. into two groups. In group 1, the elevated plasma level of remnants appears to be due to a diminished receptor binding activity of the abnormal protein specified by the Ed allele; in group 2 patients, the cause of the elevated plasma level of remnants remains to be explained.

313 citations


Journal ArticleDOI
TL;DR: A role for apoE in the plasma transport of cholesterol excreted from cholesterol-loaded macrophages is suggested.
Abstract: Monolayers of mouse peritoneal macrophages were shown to synthesize and secrete a protein that resembles apoprotein E (apoE), a normal constituent of plasma lipoproteins. Synthesis and secretion were studied by incubation of macrophages with L-[35S]methionine and analysis of the 35S-labeled proteins secreted into the culture medium. The 35S-labeled protein resembling apoE showed the following properties: (i) it floated in the ultracentrifuge at a density less than 1.215 g/ml, indicating that it was associated with lipid; (ii) by NaDodSO4/polyacrylamide gel electrophoresis, its Mr of 35,000 was identical to that of authentic apoE obtained from mouse plasma very low density lipoprotein; (iii) its isoelectric point of 5.4 was the same as that of authentic mouse apoE; (iv) it comigrated with authentic mouse apoE after two-dimensional isoelectric focusing/NaDodSO4/polyacrylamide gel electrophoresis; and (v) it was quantitatively precipitated by a monospecific antibody directed against rat apoE. Synthesis and secretion of the apoE-like protein was stimulated 3- to 8-fold when the macrophages were loaded with cholesterol by incubation with either acetylated low density lipoprotein (acetyl-LDL) or beta-migrating very low density lipoprotein from cholesterol-fed rabbits. When the cells were incubated with acetyl-LDL, the apoE-like protein composed approximately 2% of the total 35S-labeled protein synthesized by the cells and approximately 10% of the total 35S-labeled protein secreted into the medium. The current findings suggest a role for apoE in the plasma transport of cholesterol excreted from cholesterol-loaded macrophages.

290 citations


Journal ArticleDOI
TL;DR: Prostaglandin synthetase activity was assayed in homogenates prepared from human fetal membranes and uterine decidua tissues with [14C] arachidonic acid used as substrate and the specific activities of this enzyme in chorion laeve andDecidua vera tissues obtained before and after labor were high, whereas 15-hydroxyprostaglandsin dehydrogenase activity in amnion was low.

281 citations


Journal ArticleDOI
TL;DR: The data hold promise that therapeutic protocols using appropriately timed splenectomy and specific immunization can be devised to induce hosts bearing intraocular tumors to mount an immune response sufficiently vigorous to destroy the tumor within the eye, and sufficiently precise to preserve the functional and anatomic integrity of the eye.
Abstract: Anterior chamber-associated immune deviation (ACAID) expresses itself in BALB/c mice inoculated intracamerally with P815 cells in three ways: progressive growth of the tumor within the eye, transient growth of P815 cells injected subcutaneously, and prolonged acceptance of DBA/2 skin allografts. The spleen was found to play a crucial role in the development of ACAID. Splenectomized animals bearing intracameral P815 tumors reject DBA/2 skin grafts in an accelerated manner. A functioning spleen was required during the first 10 d after intracameral inoculation of P815 cells, but not thereafter. Reconstitution experiments revealed that the spleen's ability to support the induction of ACAID depends partly upon its constituent lymphoid cells, but also upon either a stromal component or a unique architectural arrangement that can only be restored with splenic fragments. The data hold promise that therapeutic protocols using appropriately timed splenectomy and specific immunization can be devised to induce hosts bearing intraocular tumors to mount an immune response sufficiently vigorous to destroy the tumor within the eye, and sufficiently precise to preserve the functional and anatomic integrity of the eye.

250 citations


Journal ArticleDOI
TL;DR: It is concluded that a deficiency of hepatic and adrenal LDL receptors contributes to the hypercholesterolemia of the WHHL rabbits.
Abstract: The WHHL (Watanabe heritable hyperlipidemic) rabbit has been proposed as an animal model for human familial hypercholesterolemia. Homozygous WHHL rabbits have marked increases in the plasma level of low density lipoprotein (LDL), removal of LDL from their plasma is delayed, and LDL receptors are absent from their cultured fibroblasts [Tanzawa, K., Shimada, Y., Kuroda, M., Tsujita, Y., Arai, M. & Watanabe, Y. (1980) FEBS Lett. 118, 81--84]. We here report that membranes from the liver and adrenal gland of WHHL rabbits lack high-affinity LDL receptors. In normal rabbit membranes, binding of LDL to this receptor required calcium and is inhibited by EDTA. The LDL receptor binds rabbit 125I-labeled beta-migrating very low density lipoprotein (beta-VLDL), which contains apoproteins B and E, as well as rabbit 125I-labeled LDL, which contains only apoprotein B. It does not bind high density lipoprotein or methyl-LDL. All of these properties are identical with those of the LDL receptor of cultured fibroblasts. We conclude that a deficiency of hepatic and adrenal LDL receptors contributes to the hypercholesterolemia of the WHHL rabbits.

Journal ArticleDOI
TL;DR: Fructose-2,6-P2 may be the most important allosteric effector in regulation of phosphofructokinase in liver as well as in other tissues and protects phosphofStructokinase against inactivation by heat.

Journal Article
TL;DR: The apparent capacity of the immune system to prevent or enhance the growth of tumors can be successfully manipulated in ways that suggest the possibility of therapeutic benefit in ophthalmologic disease.
Abstract: The ability to introduce carefully controlled numbers of viable cells into the anterior chamber of mouse eyes made it possible to examine the interrelationship between presentation of antigens intracamerally and into conventional body sites and their synergistic/antagonistic effects on the immune system. P815 mastocytoma (DBA/2; H-2d) cells are syngeneic with BALB/c hosts at the major histocompatibility complex but differ at numerous minor histocompatibility loci. When these cells are injected intracamerally into BALB/c mice, they subvert the host's immune response; that is, tumor cells injected subcutaneously developed into tumors. The dynamics of this anterior chamber-associated immune deviation was manipulable. When subcutaneous (SC) inoculations preceded intracameral (IC) inoculations by 5 days or more, systemic anti-DBA/2 immunity elicited by SC inoculation prevented successful engraftment of P815 tumors in the anterior chamber. As the time interval between SC and IC inoculations of P815 cells decreased, the balance between destruction or survival or intraocular tumors was tipped in favor of tumor growth. Intraocular tumor growth increased when IC inoculations preceded SC inoculations and was most impressive when this interval was 7 days. In these mice the tumors grew briskly and aggressively in a fashion comparable to that seen in hosts not receiving prior SC inoculations. The apparent capacity of the immune system to prevent or enhance the growth of tumors can be successfully manipulated in ways that suggest the possibility of therapeutic benefit in ophthalmologic disease.

Journal ArticleDOI
TL;DR: It is suggestive that glucocorticosteroids act to increase aromatase activity in stromal cells by inducing the synthesis of new enzyme protein.
Abstract: Stromal cells prepared from adipose tissue of women were maintained in monolayer culture to study the regulation of aromatase activity by hormones. Aromatase activity was stimulated 20- to 100-fold by dexamethasone at a concentration of 250 nM. Half-maximal stimulation of aromatase activity was attained at a dexamethasone concentration of 2.7 nM. The stimulatory effect of dexamethasone was apparent after a preincubation time of 4 hr, and stimulation was maximal after 24 hr of preincubation. The stimulatory effect of dexamethasone was observed only when fetal calf serum also was present in the culture medium. Of the various steroids tested, dexamethasone was the most potent in stimulating aromatase activity. Cortisol was less effective than dexamethasone, whereas corticosterone, at a concentration of 250 nM, caused only a small stimulation of aromatase activity. Progesterone and deoxycorticosterone (250 nM) did not affect aromatase activity. Cytosolic fractions prepared from stromal cells that had been maintained in monolayer culture were found to contain a homogenous population of sites that specifically bound [3H]dexamethasone with relatively high affinity (Kd = 2.9 nM) and low capacity (38 fmol per mg of protein). The stimulatory effect of dexamethasone on aromatase activity was prevented by simultaneous incubation with cortisol 21-mesylate (0.1-10 microM), a compound known to block the binding of glucocorticosteroids to cytoplasmic receptors. The stimulatory effect of dexamethasone also was prevented by incubation of the cells with cycloheximide or actinomycin D. These findings are suggestive that glucocorticosteroids act to increase aromatase activity in stromal cells by inducing the synthesis of new enzyme protein.

Journal ArticleDOI
TL;DR: It is concluded that verapamil is safe and effective in the therapy of variant angina pectoris and caused no side effects forcing a reduction in dosage or a discontinuation.
Abstract: To assess the efficacy and safety of verapamil in variant angina pectoris, we entered 16 patients in a double-blind, randomized trial of nine months, duration. During treatment with verapamil, the frequency of angina fell substantially (12.6 +/- 25.9 chest pains per week with placebo, 1.7 +/- 2.8 pains per week with verapamil, mean +/- S.D.; P less than 0.01), as did the use of nitroglycerin tablets (14.4 +/- 34.4 tablets per week with placebo, 2.1 +/- 3.3 tablets per week with verapamil; P less than 0.05). The number of hospitalizations for clinical instability was significantly lower with verapamil (P less than 0.01). The number of episodes of transient ST-segment deviation during treatment with verapamil was reduced (33.1 +/- 39.3 ST-segment deviations per week with placebo, 7.7 +/- 11.7 deviations per week with verapamil; P less than 0.01). Verapamil caused no side effects forcing a reduction in dosage or a discontinuation. We conclude that verapamil is safe and effective in the therapy of variant angina pectoris.

Journal ArticleDOI
TL;DR: In rabbit CSF, moxalactam had the greatest concentration and penetration, but rocephin had the longest half-life and duration of bactericidal activity, and the four drugs were comparable to ampicillin in reducing counts of group B Streptococcus type III in CSF.
Abstract: The pharmacokinetics and bacteriologic efficacy of four beta-lactam antibiotics were studied in the serum and cerebrospinal fluid (CSF) of rabbits using two test strains, Escherichia coli type K1 and group B Streptococcus type III, and 24 gram-positive isolates. Although moxalactam, cefotaxime, cefoperazone, and rocephin are active in vitro against gram-negative bacilli, the gram-positive bacteria Listeria monocytogenes and Streptococcus faecalis were resistant to all four drugs; group B streptococci were resistant to moxalactam. In rabbit CSF, moxalactam had the greatest concentration and penetration, but rocephin had the longest half-life and duration of bactericidal activity. These two drugs were most effective in the CSF of E. coli K1-infected rabbits. Except for moxalatam, the four drugs were comparable to ampicillin in reducing counts of group B Streptococcus type III in CSF. Drug accumulation in CSF and appreciable bacterial killing were observed in E. coli K1-infected animals give moxalactam either periodically or by constant infusion.

Journal Article
TL;DR: Study of binding sites in rat renal membranes suggest that rat renal plasma membranes contain binding sites with both alpha-1 and alpha-2 adrenergic receptor specificity, in a ratio of approximately 1:3.
Abstract: [3H]Dihydroergocryptine, a nonselective alpha adrenergic antagonist, the alpha-1 selective antagonist, [3H]prazosin and the alpha-2 selective antagonist, [3H]yohimbine, were used to study binding sites in rat renal membranes. To establish a correlation between binding and a biological function, the ability of alpha adrenergic agents to stimulate or inhibit vasoconstriction was quantified in vitro using an isolated perfused kidney preparation. Binding with each radioligand was rapid, saturable and specific. Moreover, the order of potencies of a variety of adrenergic agents, determined by competitive inhibition studies, suggested that the binding of each radioligand was to sites with alpha adrenergic specificity. The total number of binding sites in these rat renal membranes. determined with [3H]dihydroergocryptine (Bmax, 212 fmol/mg of protein; KD, 12.8 nM) was approximately equal to the sum of binding site concentrations determined with the alpha-1 and alpha-2 selective radioligands (Bmax, 57 and 170 fmol/mg of protein; KD, 0.85 and 20 nM, respectively). However, the alpha receptor mediating renal arteriolar vasoconstriction appeared to be of the alpha-1 subtype as there was a close correlation between the in vitro results and the binding data determined with [3H]prazosin (r = 0.93). In addition, in both the functional and [3H]prazosin binding studies, unlabeled prazosin ws 5 to 40-fold more potent than the nonselective antagonist, phentolamine, and 400- to 1500-fold more potent than the alpha-2 antagonist, yohimbine. These studies suggest that rat renal plasma membranes contain binding sites with both alpha-1 and alpha-2 adrenergic receptor specificity, in a ratio of approximately 1:3. Despite the preponderance of alpha-2 receptors, the alpha receptor mediating renal vasoconstriction appears to be of the alpha-1 type.

Journal ArticleDOI
09 Jan 1981-Science
TL;DR: Phosphorus-31 nuclear magnetic resonance measurements with small surface coils have been used to observe phosphorus metabolism of perfused hearts within localized regions for direct, noninvasive, sequential assessment of the altered regional metabolism resulting from myocardial infarction and its response to drug treatment.
Abstract: Phosphorus-31 nuclear magnetic resonance (NMR) measurements with small surface coils have been used to observe phosphorus metabolism of perfused hearts within localized regions. The method allows for direct, noninvasive, sequential assessment of the altered regional metabolism resulting from myocardial infarction and its response to drug treatment, which cannot be observed by conventional techniques.

Journal ArticleDOI
TL;DR: Reversibility of brainstem abnormalities (excluding multiple sclerosis) and sensitivity to toxic-metabolic disorders are features of the response not previously described in adults with neurologic disorders.
Abstract: Brainstem auditory evoked responses (BAERs) were measured in pediatric patients with neurologic diseases Abnormalities of interwave intervals, amplitude ratios, and response to changing rate of stimulation were found in patients with tumors, myelin disorders, anoxic-ischemic encephalopathy, trauma, and neurodegenerative disorders Reversibility of brainstem abnormalities (excluding multiple sclerosis) and sensitivity to toxic-metabolic disorders are features of the response not previously described in adults with neurologic disorders The BAER is a promising new tool for the investigation of pediatric neurologic disease

Journal ArticleDOI
TL;DR: It is suggested that once the mitochondrial cholesterol side-chain cleavage system is fully activated by ACTH, the supply of cholesterol to the mitochondria becomes rate-limiting for steroidogenesis, and sufficient cholesterol is obtained to provide for precursor cholesterol to maintain the high rate of steroid synthesis by the HFA.
Abstract: A model proposed for regulation of steroidogenesis, lipoprotein utilization and cholesterol metabolism in HFA tissue is presented in Fig 17. We envision that the role of ACTH and cAMP in steroidogenesis and cholesterol metabolism is as follows. ACTH binds to specific receptors on the surface of the cells of the HFA gland and as a consequence, adenylate cyclase is activated, leading to increased formation of cAMP. cAMP causes activation of protein kinase that leads, presumably, to phosphorylation of specific proteins. This leads to the initiation of reactions that give rise to increased activity of key enzymes and levels of proteins involved in adrenal cholesterol metabolism. Presumably, the action of ACTH causes an increase in the activity of cholesterol side chain cleavage, the rate-limiting step in the conversion of cholesterol to steroid hormones. We suggest that once the mitochondrial cholesterol side-chain cleavage system is fully activated by ACTH, the supply of cholesterol to the mitochondria becomes rate-limiting for steroidogenesis. To meet this demand for cholesterol, a further action of ACTH results in an increase in the number of LDL receptors. LDL binds to specific receptors on the cell surface that are localized in coated pits. LDL is internalized by a process of adsorptive endocytosis and the internalized vesicles fuse with lysosomes and the protein component of LDL is hydrolyzed by lysosomal proteolytic enzymes to amino acids. The cholesteryl esters of LDL also are hydrolyzed to give rise to fatty acids and cholesterol. The liberated cholesterol is available for utilization in the biosynthesis of steroid hormones and other cellular processes. In addition, ACTH stimulates the activity of HMG CoA reductase and, thus, the rate of de novo cholesterol biosynthesis. In this way sufficient cholesterol is obtained to provide for precursor cholesterol to maintain the high rate of steroid synthesis by the HFA. HDL is not utilized as a source of cholesterol by the HFA. Because of the rapid rate of utilization of LDL by the HFA, fetal plasma levels of LDL are low and the activity of the HFA is a primary determinant of these levels. Thus, in the case of anencephaly, in which the activity of the adrenal is very low, plasma levels of LDL are 2--3 times higher than in normal fetuses, whereas plasma HDL levels are similar. In addition, in the normal neonate plasma LDL levels rise rapidly after birth, and this event is coincident with the involution of the fetal zone of the adrenal. The fetal liver is likely to be the major source ultimately of the LDL-cholesterol utilized by the HFA. Consequently, factors that regulate cholesterol and lipoprotein synthesis in the fetal liver may, in turn, affect the steroidogenic activity of the HFA through regulation of the supply of cholesterol precursor. Thus, if trophic factors for the HFA other than ACTH exist, an important site of their action might be the fetal liver, rather than a direct action to influence the rate of synthesis of steroids by the fetal adrenal.

Journal ArticleDOI
TL;DR: If a high rate of LDL metabolism proves to be a general property of cancer cells, such a property could prove useful for tumor chemotherapy, providing cytotoxic chemicals could be incorporated within the LDL molecule.
Abstract: The metabolism of low-density lipoprotein (LDL) was studied in neoplastic and non-neoplastic cells of human gynecological origin, in monolayer cultures. The neoplastic cells were derived from epidermoid vaginal carcinoma, epidermoid cervical carcinoma and endometrial adenocarcinoma, in various degrees of differentiation. The non-neoplastic cells were cervical fibroblasts and epithelial cells from proliferative endometrial glands. Both neoplastic and non-neoplastic cells assimilated and degraded LDL in a similar fashion to other human cells (e.g. skin fibroblasts). However, the neoplastic cells metabolized LDL at a higher rate than the non-neoplastic cell (e.g. epidermoid cervical cancer cells metabolized LDL at a 20 times higher rate than did cervical fibroblasts). Such a high rate of LDL metabolism probably enables continuously replicating cancer cells to obtain the large amounts of cholesterol required for cell membrane synthesis. If a high rate of LDL metabolism proves to be a general property of cancer cells, such a property could prove useful for tumor chemotherapy, providing cytotoxic chemicals could be incorporated within the LDL molecule.

Journal ArticleDOI
TL;DR: To explore the relationship between extraglandular estrogen formation and the clinical parameters of age, weight, and endometrial neoplasia, an assay was developed to measure the rate of estrogen formation from androgen precursors in human adipose tissue.
Abstract: To explore the relationship between extraglandular estrogen formation and the clinical parameters of age, weight, and endometrial neoplasia, an assay was developed to measure the rate of estrogen formation from androgen precursors in human adipose tissue. The substrate, [3H]androstenedione, was more efficient than [3H]testosterone for the aromatase system in this tissue. The highest rate of conversion of androgen to estrogen occurred in tissue slices rather than in minces or microsomal preparations. The addition of cofactor NADPH was not required for aromatization in slices or minces, probably as a consequence of endogenous production of NADPH by the tissue. [3H]Estrone was the sole estrogenic product identified in incubations when [3H]androstenedione was used as the substrate, whereas [3H]estradiol-17/β was the exclusive estrogen detected when using [3H]testosterone. The rate of [3H]estrone formation from [3H]androstenedione in tissue slices was linear with time of incubation up to 2 h and with tissue ma...

Journal Article
TL;DR: During a 4.5-year period, over 2% of 24,000 obstetric patients at Parkland Memorial Hospital were admitted for acute pyelonephritis; chills accompanying back pain was the most common presenting complaint in 656 women; lower urinary tract symptoms and nausea and vomiting were also common.

Journal ArticleDOI
TL;DR: The MAST garment acts as a local, effective, nonpharmacologic vasoconstrictor and should be used when such an effect is clinically appropriate and why the trousers should not be used if one wishes to avoid increasing afterload.
Abstract: Despite widespread use of the Medical Anti-Shock Trousers (MAST) little is known about the exact mechanism by which they increase arterial pressure. It is assumed that an autotransfusion occurs. To examine this question, blood pressure, heart rate, forearm blood flow, cardiac output, and stroke volume were measured in ten healthy adults, supine and during 60 degree headup tilt with MAST garment pressures of 409 and 100 mm Hg. Supine, the garment produced no net 'autotransfusion,' but raised blood pressure (27%) by increasing peripheral resistance (48%) with decreased stroke volume and cardiac output (18%). During headup tilt without the MAST device, venous pooling in the legs decreased stroke volume (52%), cardiac output (30%), and increased total peripheral resistance (40%). Application of the garment during tilt shifted this blood centrally, producing increased stroke volume (52%), cardiac output (30%), and increased total peripheral resistance (40%). Application of the garment during tilt shifted this blood centrally, producing increased stroke volume (14%). In supine normovolemic subjects, the garment raised pressure almost exclusively by increased systemic afterload. Forearm vascular resistance did not change and the increased pressure augmented flow to the arm, i.e., to noncompressed tissue. With increased venous pooling during tilt, the MAST garment acted as a 'G-suit' and caused a central shift of blood volume. These findings could explain: 1) why fluid replacement is not always adequate to maintain pressure when deflating the trousers; 2) why the trousers should not be used if one wishes to avoid increasing afterload (e.g., certain patients with acute myocardial infarction). We conclude that the MAST garment acts as a local, effective, nonpharmacologic vasoconstrictor and should be used when such an effect is clinically appropriate.

Journal ArticleDOI
TL;DR: The procedure takes advantage of the unique structure of low density lipoprotein, a plasma cholesterol transport protein that enters cells by receptor-mediated endocytosis, and may have general utility in isolating cells with mutations affecting other receptor systems.

Journal ArticleDOI
TL;DR: The results of these studies are suggestive that certain tumor cells might have a higher affinity for LDL than normal tissues and cytotoxic drugs or radionucleotides ligated to the LDL macromolecule may be utilized for the specific delivery of these agents.

Journal ArticleDOI
TL;DR: The fasted-to-fed transition of hepatic carbohydrate and lipid metabolism can be accomplished in vitro over a time frame similar to that operative in vivo, and the requirement for insulin in the reversal of the fasting state of liver metabolism in vivo can best be explained by its ability to offset the catabolic actions of glucagon.
Abstract: Studies were conducted to determine whether the direction of hepatic carbohydrate and lipid metabolism in the rat could be switched simultaneously from a "fasted" to a "fed" profile in vitro. When incubated for 2 h under appropriate conditions hepatocytes from fasted animals could be induced to synthesize glycogen at in vivo rates. There was concomitant marked elevation of the tissue malonyl-coenzyme A level, acceleration of fatty acid synthesis, and suppression of fatty acid oxidation and ketogenesis. In agreement with reports from some laboratories, but contrary to popular belief, glucose was not taken up efficiently by the cells and was thus a poor substrate for eigher glycogen synthesis or lipogenesis. The best precursor for glycogen formation was fructose, whereas lactate (pyruvate) was most efficient in lipogenesis. In both case the addition of glucose to the gluconeogenic substrates was stimulatory, the highest rates being obtained with the further inclusion of glutamine. Insulin was neither necessary for, nor did it stimulate, glycogen deposition or fatty acid synthesis under favorable substrate conditions. Glucagon at physiological concentrations inhibited both glycogen formation and fatty acid synthesis. Insulin readily reversed the effects of glucagon in the submaximal range of its concentration curve. The following conclusions were drawn. First, the fasted-to-fed transition of hepatic carbohydrate and lipid metabolism can be accomplished in vitro over a time frame similar to that operative in vivo. Second, reversal appears to be a substrate-driven phenomenon, in that insulin is not required. Third, unless an unidentified factor (present in protal blood during feeding) facilitates the uptake of glucose by liver it seems unlikely that glucose is the immediate precursor for liver glycogen or fat synthesis in vivo. A likely candidate for the primary substrate in both processes is lactate, which is rapidly formed from glucose by the small intestine and peripheral tissues. Fructose and amino acids may also contribute. Fourth, the requirement for insulin in the reversal of the fasting state of liver metabolism in vivo can best be explained by its ability to offset the catabolic actions of glucagon.

Journal ArticleDOI
TL;DR: Results are supportive of the hypothesis that the ability of estrogen to antagonize the inhibitory action of dopamine on PRL secretion is mediated through an estrogen-induced reduction in the capacity of the PRL cell to incorporate dopamine into PRL secretory granules.
Abstract: The effect of estrogen on the dopaminergic control of PRL secretion was investigated. Treatment of ovariectomized rats with estradiol benzoate (25 microgram/kg, sc) daily for 5 days resulted in a marked elevation of the serum PRL concentration. This estrogen-induced increase in serum PRL levels was apparently not the result of a suppressed release of dopamine into hypophysial portal blood, since the mean dopamine concentration in hypophysial portal plasma in estrogen-treated rats was 2.5 times that in vehicle-treated animals. It was found that under in vitro conditions, dopamine was much less effective in inhibiting the release of PRL from pituitary glands of estrogen-treated rats than from glands of vehicle-treated controls. The capacity of PRL cells to internalize dopamine and incorporate it into PRL secretory granules was evaluated in anterior pituitary tissue obtained from estrogen- or vehicle-treated animals. When tissue fragments of the anterior pituitary gland were incubated in the presence of dopamine (10(-5) M) for 30 min at 37 C and then homogenized and fractionated by means of continuous sucrose density gradient centrifugation, it was found that the amount of dopamine associated with PRL granules from anterior lobe tissue of estrogen-treated rats was only 40% of that from the tissue of vehicle-treated controls. These results are supportive of the hypothesis that the ability of estrogen to antagonize the inhibitory action of dopamine on PRL secretion is mediated through an estrogen-induced reduction in the capacity of the PRL cell to incorporate dopamine into PRL secretory granules. (Endocrinology 108: 440, 1981)

Journal ArticleDOI
TL;DR: It is suggested that human fetal lung development is under multihormonal control and that PRL and cortisol serve to increase surfactant synthesis and secretion.
Abstract: Explants prepared from the lung tissue of human abortuses of 20-22 weeks gestational age were incubated in defined medium without serum. These tissues developed the capacity for surfactant synthesis within 4 days. The ductular epithelium differentiated into type II pneumonocytes that contained numerous lamellar bodies. These morphological changes were accompanied by an increase in the rate of choline incorporation into phosphatidylcholine as well as an increase in the phosphatidylcholine content of the explants. Cortisol (0.2 micrograms/ml) plus PRL (2.5 micrograms/ml), when added to the medium from the beginning of the culture period, caused a 2- to 3-fold increase in the rate of choline incorporation into phosphatidylcholine, as measured on the second, fourth, sixth, and eighth days of incubation, as well as an increase in the phosphatidylcholine content of the explants. However, when administered alone, neither cortisol nor PRL affected phosphatidylcholine synthesis. In explants incubated with cortisol plus PRL there also was a stimulation of lamellar body secretion into the prealveolar ducts. The lamellar bodies in epithelial cells were larger in cortisol- plus PRL-treated tissue than those in nontreated tissues. Increases in phosphatidylcholine synthesis and lamellar body secretion also were observed in tissues incubated with insulin (2.5 micrograms/ml), cortisol, and PRL in combination or with insulin and cortisol in combination. The stimulatory effect of cortisol plus insulin on phosphatidylcholine synthesis, however, was significantly less than that of cortisol plus PRL or cortisol plus insulin plus PRL. It is suggested that human fetal lung development is under multihormonal control and that PRL and cortisol serve to increase surfactant synthesis and secretion.

Journal ArticleDOI
TL;DR: Bovine adrenocortical cell preparation and culture were carried out in a manner previously described and the cells were harvested and washed by centrifugation and placed in 60-mm or 100-mm dishes.