Showing papers by "University of Texas Southwestern Medical Center published in 1979"

Binding Site on Macrophages that Mediates Uptake and Degradation of Acetylated Low Density Lipoprotein, Producing Massive Cholesterol Deposition

Abstract: Resident mouse peritoneal macrophages were shown to take up and degrade acetylated 125I-labeled low density lipoprotein (125I-acetyl-LDL) in vitro at rates that were 20-fold greater than those for the uptake and degradation of 125I-LDL. The uptake of 125I-acetyl-LDL and its subsequent degradation in lysosomes were attributable to a high-affinity, trypsin-sensitive, surface binding site that recognized acetyl-LDL but not native LDL. When 125I-acetyl-LDL was bound to this site at 4°C and the macrophages were subsequently warmed to 37°C, 75% of the cell-bound radioactivity was degraded to mono[125I]iodotyrosine within 1 hr. The macrophage binding site also recognized maleylated LDL, maleylated albumin, and two sulfated polysaccharides (fucoidin and dextran sulfate) indicating that negative charges were important in the binding reaction. A similar binding site was present on rat peritoneal macrophages, guinea pig Kupffer cells, and cultured human monocytes but not on human lymphocytes or fibroblasts, mouse L cells or Y-1 adrenal cells, or Chinese hamster ovary cells. Uptake and degradation of acetyl-LDL via this binding site stimulated cholesterol esterification 100-fold and produced a 38-fold increase in the cellular content of cholesterol in mouse peritoneal macrophages. Although the physiologic significance, if any, of this macrophage uptake mechanism is not yet known, we hypothesize that it may mediate the degradation of denatured LDL in the body and thus serve as a “backup” mechanism for the previously described receptor-mediated degradation of native LDL that occurs in parenchymal cells. Such a scavenger pathway might account for the widespread deposition of LDL-derived cholesteryl esters in macrophages of patients with familial hypercholesterolemia in whom the parenchymal cell pathway for LDL degradation is blocked, owing to a genetic deficiency of receptors for native LDL.

Coated pits, coated vesicles, and receptor-mediated endocytosis

Abstract: Proteins and peptides can enter cells by receptor-mediated endocytosis, a coupled process by which selected extracellular proteins or peptides are first bound to specific cell surface receptors and then rapidly internalised by the cell. Internalisation follows clustering of the receptors in specialised regions of the cell surface called coated pits that invaginate to form intracellular coated vesicles. It is now recognised that receptor-mediated endocytosis has a fundamental role in the growth, nutrition and differentiation of animal cells.

Dominant Language Functions of the Right Hemisphere?: Prosody and Emotional Gesturing

Abstract: • Two patients lost the ability to impart affective qualities to their speech following lesions in the right hemisphere. Arguments are given to support the idea that the right or "minor" hemisphere has a dominant role in modulating the affective components of speech. The anatomical organization of the cortical areas subserving affective speech in the right hemisphere seem to be similar to the organization of cortical areas subserving propositional speech in the left or "major" hemisphere.

Reversible accumulation of cholesteryl esters in macrophages incubated with acetylated lipoproteins

Abstract: Mouse peritoneal macrophages accumulate large amounts of cholesteryl ester when incubated with human low-density lipoprotein that has been modified by chemical acetylation (acetyl-LDL). This accumulation is related to a high-affinity cell surface binding site that mediates the uptake of acetyl-LDL by adsorptive endocytosis and its delivery to lysosomes. The current studies demonstrate that the cholesteryl ester accumulation can be considered in terms of a two-compartment model: (a) the incoming cholesteryl esters of acetyl-LDL are hydrolyzed in lysosomes, and (b) the resultant free cholesterol is re-esterified in the cytosol where the newly formed esters are stored as lipid droplets. The following biochemical and morphologic evidence supports the hydrolysis-re-esterification mechanism: (a) Incubation of macrophages with acetyl-LDL markedly increased the rate of cholesteryl ester synthesis from [14C]oleate, and this was accompanied by an increase in the acyl-CoA:cholesteryl acyltransferase activity of cell-free extracts. (b) When macrophages were incubated with reconstituted acetyl-LDL in which the endogenous cholesterol was replaced with [3H]-cholesteryl linoleate, the [3H]cholesteryl linoleate was hydrolyzed, and at least one-half of the resultant [3H]cholesterol was re-esterified to form [3H]cholesteryl oleate, which accumulated within the cell. The lysosomal enzyme inhibitor chloroquine inhibited the hydrolysis of the [3H]cholesteryl linoleate, thus preventing the formation of [3H]cholesteryl oleate and leading to the accumulation of unhydrolyzed [3H]cholesteryl linoleate within the cells. (c) In the electron microscope, macrophages incubated with acetyl-LDL had numerous cytoplasmic lipid droplets that were not surrounded by a limiting membrane. The time course of droplet accumulation was similar to the time course of cholesteryl ester accumulation as measured biochemically. (d) When acetyl-LDL was removed from the incubation medium, biochemical and morphological studies showed that cytoplasmic cholesteryl esters were rapidly hydrolyzed and that the resultant free cholesterol was excreted from the cell.

Somatostatinoma syndrome. Biochemical, morphologic and clinical features.

Abstract: Diabetes mellitus, steatorrhea, cholelithiasis and a tumor distorting the duodenum prompted a work-up for somatostatinoma in a 52-year-old man. The responses of pancreatic B-cells but not of A-cells to nutrient stimuli were inhibited, and growth-hormone release was suppressed, suggesting somatostatin resistance in some target tissues. Plasma somatostatin-like immunoreactivity ranged from 9000 to 13,000 pg per milliliter (normal: 88+/-8, mean +/- S.E.M.) and was distributed in four molecular forms, including free somatostatin. The primary tumor contained 5 microgram of somatostatin-like immunoreactivity per milligram of wet tissue, distributed in three of the molecular forms noted in plasma. Plasma calcitonin was also elevated (4650 pg per milliliter; normal: less than 120). Immunocytochemical studies showed that cells of the primary tumor contained somatostatin and calcitonin but no other peptide hormones. Only somatostatin was present in the metastases. Somatostatin was localized electron microscopically in all secretory granules, irrespective of size and shape, whereas calcitonin was present only within a single subpopulation of small granules in the same cells.

Origin of Estrogen in Normal Men and in Women with Testicular Feminization

Abstract: The purpose of this study was to quantify the various sources of estrone (E1) and 17 beta-estradiol (E2) production in normal men and in women with testicular feminization. The mean production rate of E1 in four young adult men was 58 micrograms/24 h, while that of E2 was 44 micrograms/24 h. In these men, E1 production could be accounted for totally by extraglandular formation through 1) aromatization of plasma androstenedione, 2) conversion of E2 which was formed from the aromatization of plasma testosterone, and 3) conversion of secreted E2. In these men, only 12 micrograms or less of E2 production could not be accounted for by extraglandular formation from plasma C19 precursors, and is presumed to have arisen by testicular secretion. In six women with testicular feminization, the mean production rate of E1 was 99 micrograms/24 h, while that of E2 was 77 micrograms/24 h. THe amount of E2 production that arose by glandular secretion could be computed in four of these women and was considerably greater than that found in the young adult men. In these women with testicular feminization, an average of 44 micrograms/24 h E2 could not be accounted for by extraglandular formation and is presumed to have arisen by testicular secretion. The mean plasma production rate of testosterone in the normal men was 5.7 mg/24 h, while that in the women with testicular feminization was 8.3 mg/24 h. However, the range of plasma production rates of testosterone in the women with testicular feminization was large (1.3--17.0 mg/24 h).

Receptor-mediated uptake of lipoprotein-cholesterol and its utilization for steroid synthesis in the adrenal cortex

Abstract: Publisher Summary This chapter discusses the receptor-mediated uptake of lipoprotein cholesterol and its utilization for steroid synthesis in the adrenal cortex. It discusses the four model system (1)mouse adrenal tumor cells in culture (Y-1 clone) ,(2) rats treated in vivo with 4-aminopyrazolopyrimidine (4-APP), (3) bovine adrenal cortex ,and (4) Human fetal adrenal membranes to demonstrate the presence and physiological significance of low-density lipoprotein. The studies in the four model systems allow the formulation of a hypothetical working model to explain some aspects of cholesterol metabolism in the adrenal cortex. In this model, the adrenal is considered to have a small pool of metabolically active free cholesterol that is rapidly turning over. In the steady state, the input and output of cholesterol from this metabolically active cholesterol pool must be balanced. The net output of cholesterol from this pool occurs when cholesterol is converted to steroid hormones that are secreted from the gland and when cholesterol is esterified to form cholesteryl ester droplets. The adrenal gland contains at least two pools of cholesterol in addition to the metabolically active pool. One of these is a fixed pool of free cholesterol in cell membranes. The second pool of cholesterol is contained in storage droplets, where the cholesterol is esterified with fatty acids. These cholesteryl esters exert a buffer function that tends to stabilize the free cholesterol content of the adrenal gland during transient fluctuations in steroid demand. In the model systems, the endogenous synthesis of cholesterol in the adrenal is important in several situations: (1) when insufficient plasma lipoproteins are available, a situation that is probably never encountered in normal physiology, (2) transiently, when there is a sudden stimulus to steroid secretion and sufficient time has not elapsed for the full induction of lipoprotein receptor activity, and (3) when the rate of steroid synthesis is so great that maximal lipoprotein receptor activity cannot supply sufficient cholesterol and supplementary cholesterol synthesis within the gland is required.

The pathological anatomy of fatal atlanto-occipital dislocations

Abstract: Nine atlanto-occipital dislocations were found in postmortem examinations of 112 victims of multiple trauma Axial traction facilitated roentgenographic identification of the injury A hyperextension mechanism of injury was suggested by the associated injuries, including submental lacerations and mandibular fractures Atlanto-occipital dislocations were more frequent in children than in adults A pure dislocation injury without fracture was identified

Corneal allografts fail to express ia antigens.

Abstract: Although the surface determinants encoded by class I genes of the major histocompatibility complex (murine K/D; human HLA-A/B/C) are expressed on virtually all nucleated cells, the molecular products of class II genes (murine I, human HLA-D/DR) are expressed only on B lymphocytes, macrophages, sperm and certain subsets of T lymphocytes, especially suppressor cells1,2. Controversy exists concerning the expression of class II antigens on cells of the epidermis. On the one hand, Hammerling et al.3 and Frelinger et al.4 have used serological methods to detect Ia antigens on epidermal cells. On the other hand, fluorescein isothiocyanate-conjugated antisera have been used to show that human and guinea pig class II alloantigens are only expressed on Langerhans cells in the epidermis5–7. Recently, Rowden et al.8 have convincingly demonstrated that Ia antigens are expressed exclusively on Langerhans cells within murine epidermis. We have now shown that cornea, which is an epidermal tissue devoid of Langerhans cells, does not express Ia antigens.

Metabolic Studies in Familial Hypercholesterolemia: EVIDENCE FOR A GENE-DOSAGE EFFECT IN VIVO

Abstract: To investigate the gene-dosage effect in familial hypercholesterolemia (FH), metabolic studies were conducted in a group of well-characterized patients with either heterozygous (n = 7) or homozygous (n = 7) FH and the results were compared to those obtained in normal subjects (n = 6). The turnover of 125I-labeled low-density lipoprotein (LDL) was measured in all of the normals, all but one of the FH heterozygotes, and in all of the homozygotes. Chemical cholesterol balance was performed simultaneously with the 125I-LDL turnover in all seven of the homozygotes. With regard to 125I-LDL turnover, FH homozygotes, who possess two doses of the mutant FH gene, exhibited a threefold increase in the rate of apoLDL synthesis while the fractional catabolic rate (FCR) for the apoprotein was only about one-third of normal. Heterozygotes, who have only one dose of the mutant FH gene, exhibited intermediate values for both parameters; that is, the FCR was two-thirds of normal and the apoLDL synthetic rate was 1.7-fold greater than normal. The data indicate that the single gene defect in FH produces two distinct abnormalities of LDL metabolism: (a) an increase in the synthetic rate for apoLDL and (b) a decrease in the efficiency of apoLDL catabolism. Both defects are more severe in FH homozygotes than in heterozygotes. The FCR for apoLDL in the homozygotes appeared to be fixed at 17%/d whereas the plasma LDL level varied about twofold. These findings suggest that the twofold variation in plasma LDL levels observed in these seven patients is caused by variation in the plasma apoLDL synthetic rates. Consistent with this conclusion was the finding that the correlation between the plasma LDL level and the apoLDL synthetic rates in the seven FH homozygotes was 0.943. The rate of total body cholesterol synthesis determined by chemical cholesterol balance did not appear to clearly differ between normals and patients with either one or two mutant FH genes. Two of the youngest FH homozygotes exhibited cholesterol overproduction but the other five did not. No consistent abnormality of bile acid metabolism was observed in these patients. Because the daily plasma flux of cholesterol on LDL is about threefold greater than the amount of cholesterol produced per day, a significant amount of the cholesterol liberated from LDL degradation must be reused.

Androgen insensitivity as a cause of infertility in otherwise normal men.

Abstract: To ascertain if androgen insensitivity causes severe oligospermia or azoospermia we studied three unrelated, phenotypically normal men with long histories of infertility. The mean plasma concentrations and production rates of testosterone were 14.3 ng per milliliter and 10.1 mg per day, respectively, values approximately twice the average found in normal men. Serum luteinizing hormone concentrations were elevated in two of the three subjects. The specific high-affinity dihydrotestosterone binding capacity of cultured genital-skin fibroblasts was 8, 0 and 10 fmol per milligram of cellular protein, values half (or less) of those from normal men and women but similar to values in subjects with partial androgen insensitivity manifested by incomplete testicular feminization or Reifenstein syndrome. The low amount of androgen receptor and the combination of high serum gonadotropins and plasma testosterone production rates suggest that the defective spermatogenesis in these infertile men was the consequence of androgen insensitivity.

Early cardiovascular adaptation to simulated zero gravity.

Abstract: A study was conducted on five normal male volunteers (23-29 yr), under controlled conditions, to evaluate early adaptive responses to zero gravity. Specific objectives are (1) to characterize the hemodynamic, renal and hormonal responses to a central fluid shift, and (2) to compare data obtained during and after head-down tilt with corresponding data from actual space flight to validate tilt as a physiological model for simulation of zero gravity. Zero gravity is simulated by a 24-hr period of head-down tilt at 5 deg. The results suggest that hemodynamic adaptation occurs rapidly and is essentially accomplished by 6 hr, and that adaptation includes diuresis and reduction in blood volume. The validity of head-down tilt at 5 deg as an experimental model is established by comparing the results obtained with data from Apollo and Skylab astronauts on body fluid distributions and postflight responses to orthostatic and exercise stress.

Monocyte Dependence of Pokeweed Mitogen-Induced Differentiation of Immunoglobulin-Secreting Cells from Human Peripheral Blood Mononuclear Cells

Abstract: Human peripheral blood mononuclear cells (PBM) lost the capacity to generate immunoglobulin-secreting cells (ISC) in response to pokeweed mitogen (PWM) when depleted of adherent cells (AC). The diminished responsiveness of the nonadherent cells (NAC) could not be ascribed to cell death, altered PWM dose response characteristics, or a change in the length of incubation required to generate a response. Supplementation with autologous or homologous AC, but not 2-mercaptoethanol, restored the capacity of NAC to generate ISC after PWM stimulation. By standard criteria AC were found to contain 85 to 90% monocytes. Furthermore, the monocytes and not the few lymphocytes contaminating the AC were responsible for restoring PWM responsiveness to the NAC. PWM-induced DNA synthesis of NAC also was markedly reduced compared to PBM. Again, supplementation with monocytes restored responsiveness to NAC. The monocyte dependence of PWM-induced proliferation and generation of ISC was most apparent when cultural conditions were employed that limited cell-to-cell interaction.

Enhancement of experimental cerebral edema after decompressive craniectomy: implications for the management of severe head injuries.

Abstract: Decompressive craniectomy has been advocated as a treatment for the cerebral edema associated with massive head injury. Although craniectomy has been successful in lowering intracranial pressure after head injury, a comparison of computerized tomographic scans of comparable patients with traumatic brain edema treated by medical means or decompressive craniectomy showed that bony decompression resulted in apparent exacerbation of edema. To investigate the possibility of enhancement of brain edema by craniectomy, we produced standardized cold lesions in the brains of 10 dogs. Five animals served as controls. In the other 5 animals we performed large decompressive craniectomies after lesioning. Physiological parameters were comparable in both groups. The dogs were killed 8 hours after lesioning. After fixation, their brains were cut into 1-mm-thick slices. We used an image analysis facility built around a PDP 11/105 computer to measure the volume of edema as outlined by Evans blue staining. The mean volume of the brain edema in the control animals was 0.27 +/- 0.19 ml. Mean edema volume was over 7 times greater in craniectomized animals (1.96 +/- 1.89 ml). This difference is statistically significant (p less than 0.05). The driving force for the formation of edema fluid is the difference between intravascular and interstitial presssure. Decompression of the brain by bone removal probably results in a reduction of interstitial fluid pressure and edema enhancement. The clinical literature contains no evidence that craniectomy decreases the morbidity or mortality of human head injury. In view of our experimental findings, this is not surprising. Indeed, pathological evidence indicates that severe edema (such as that accentuated by craniectomy) may produce permanent changes in the neuropil.

Low density lipoprotein receptors in bovine adrenal cortex. II. Low density lipoprotein binding to membranes prepared from fresh tissue.

Abstract: Low density lipoprotein (LDL)-binding activity was measured in whole homogenates and membranes prepared from fresh bovine adrenal cortex by an ultracentrifugation assay. The binding site for 125I-labeled LDL in isolated membranes shared the properties of the LDL receptor previously demonstrated in intact monolayers of cultured bovine adrenocortical cells. The amount of high affinity [125I]iodo-LDL-binding activity in the adrenal cortex was 6- to 12-fold higher than in the medulla of the same glands. Large amounts of high affinity [125I]iodo-LDL-binding activity were also present in the ovarian corpus luteum but not in the ovarian interstitium. Lesser amounts of high affinity binding activity were observed in 14 other bovine tissues. These results lend support to the concept that cells in the bovine adrenal cortex can obtain cholesterol for steroid hormone synthesis through the receptor-mediated uptake of plasma LDL.

Low Density Lipoprotein Receptors in Bovine Adrenal Cortex. I. Receptor-Mediated Uptake of Low Density Lipoprotein and Utilization of Its Cholesterol for Steroid Synthesis in Cultured Adrenocortical Cells*

Abstract: . Functioning bovine adrenocortical cells in monolayer culture were shown to obtain cholesterol for steroid synthesis from plasma low density lipoprotein (LDL). When grown in medium devoid of lipoproteins, the cells developed a minimal enhancement in steroid secretion in response to ACTH or cholera toxin. However, when LDL was available, steroid secretion was stimulated 4- to 9-fold. To determine the mechanism for this effect, we used LDL in which the protein component was labeled with 125I and the cholesteryl ester component was labeled with [3H]cholesteryl linoleate. These studies demonstrated that the cells derived cholesterol from LDL by binding the lipoprotein at a high affinity receptor site, internalizing it, and hydrolyzing its cholesteryl esters within lysosomes. The resultant free cholesterol was used for steroid synthesis and also acted to suppress the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase and cholesterol synthesis within the cell. LDL receptor activity was enhance...

Malignant pineal region tumors: A clinico-pathological study

Abstract: Eight patients with primary malignant pineal tumors have been seen at this institution over the past 6 years; six of them underwent definitive surgical exploration. Complete gross microsurgical excision of well encapsulated tumors was possible in four of these patients. In two cases of pineal germinomas, a biopsy and a subtotal resection were carried out because of the known radiosensitivity of this tumor. These six surgical patients all received postoperative craniospinal radiation and continue to do well up to 6 years postoperatively. Two nonoperative patients were initially treated at other institutions by ventriculoperitoneal shunt and radiation and were the only ones to develop metastatic disease. One patient had metastasis of her pineoblastoma to her unirradiated spinal canal and the other patient had metastasis of his germinoma to the peritoneum. The former patient was quadriplegic on admission, although her pineal tumor was no longer visible on computerized tomography (CT), and she died of pneumonia. The latter patient's tumor secreted the beta chain of human chorionic gonadotropin (HCG). This patient's massive metastatic tumor burden completely regressed as determined by body CT scan and HCG levels after four courses of chemotherapy with bleomycin, vinblastine, and cis-platinum. In 20 patients with lesions of the pineal region, craniotomy was associated with only one death (a patient with metastatic adenocarcinoma). Thus, microsurgery for pineal tumors provides either a reasonably safe potential for complete tumor extirpation and possible cure, or a tissue diagnosis which is necessary for appropriate therapeutic planning for radiotherapy and/or chemotherapy. The traditional therapeutic approach of empiric radiotherapy without a tissue diagnosis for pineal lesions may no longer be warranted.

Occult cervical spine injuries in fatal traffic accidents

Abstract: Post-mortem radiographs as well as careful inspection at autopsy of 100 consecutive traffic accident victims revealed an incidence of cervical spine injury of 24%. All but four of the 24 fractures and/or dislocations were localized to the level between the occiput and the axis. One half of the cases were not clinically suspected of having spine injuries before the detailed postmortem search. Seventeen of the 24 cervical spines were resected en bloc and the pathologic anatomy of the injuries was determined. The high incidence of cervical spine injuries and the anatomic findings at dissection have clinical implications for physicians who manage multiply traumatized patients. The need for immobilization and early radiographic evaluation of patients with cervical spine injuries is emphasized.

Regulation of cytoplasmic dihydrotestosterone binding in dog prostate by 17 beta-estradiol.

Abstract: 17 beta-estradiol enchances androgen-induced prostate growth in the castrate dog to a degree comparable to that seen in spontaneous prostatic hypertrophy. To investigate the mechanism of this synergism, cytosol androgen binding was measured by a density gradient technique in prostates of control and 17 beta-estradiol-treated castrate dogs. [3H]Dihydrotestosterone was bound principally to a moiety that averaged 8.6S in size. Approximately twofold enhancement of this binding by 17 beta-estradiol was demonstrable after 1 wk of treatment with 750 microgram/wk and after 3 wk with 75 microgram/wk. Under conditions in which binding in the 8S region was demonstrable with dihydrotestosterone and testosterone no binding of 3 alpha-androstanediol or progesterone was detectable. Thus, enhancement by 17 beta-estradiol of a prostate cytosol androgen-binding protein occurs under circumstances in which 17 beta-estradiol enhances androgen-mediated prostatic growth.