Showing papers by "University of Texas Southwestern Medical Center published in 1987"

Redesigning nature's poisons to create anti-tumor reagents.

Abstract: Immunotoxins are conjugates of cell-reactive antibodies and toxins or their subunits. In this report, the chemistry, biology, pharmacokinetics, and anti-tumor effects of first generation immunotoxins; the preparation of improved second generation immunotoxins that display greater anti-tumor efficacy; and the role of genetic engineering in creating third-generation immunotoxins are discussed.

A prospective two-year study of functional restoration in industrial low back injury. An objective assessment procedure

Abstract: One hundred sixteen consecutive patients entered a functional restoration treatment program for chronic low back pain and were compared with 72 patients not treated. A two-year follow-up survey reached more than 85% of both groups; its findings were compared with earlier results of a five-month and one-year follow-up. Analysis demonstrated that 87% of the treatment group was actively working after two years, as compared with only 41% of the nontreatment comparison group. Moreover, about twice as many of the comparison group patients had additional spine surgery relative to the treatment group. The comparison group continued with an approximately five times higher rate of patient visits to health professionals in the second year as the treatment group. Also, treatment group reinjury rates were no higher than those expected in the general population, while nontreatment subjects had a higher incidence of reinjury. Finally, a small treatment "dropout" group did poorest of all, with results in almost all areas even worse than those of the comparison group patients.

Acid-dependent ligand dissociation and recycling of LDL receptor mediated by growth factor homology region.

Abstract: A domain in the low-density lipoprotein receptor contains three cysteine-rich 'growth factor' repeats like those that occur in many proteins. When this domain is deleted, the receptor no longer releases its ligand at acid pH, it is no longer recycled efficiently and it is rapidly degraded after ligand binding.

Diversity of alpha-fetoprotein gene expression in mice is generated by a combination of separate enhancer elements

Abstract: The 59 flanking region of the mouse alpha-fetoprotein (AFP) gene contains a tissue-specific promoter and three upstream regulatory elements that behave as classical enhancers. At least one of these enhancers is now shown to be required for the tissue-specific expression of the AFP gene when it is introduced into the mouse genome by microinjection of cloned DNA fragments into fertilized eggs. Each enhancer can direct expression in the appropriate tissues, the visceral endoderm of the yolk sac, the fetal liver, and the gastrointestinal tract, but each exerts different influence in these three tissues. These differences may explain the tissue-specific diversity in the levels of expression characteristic of the AFP gene. The postnatal repression of transcription of the AFP gene in both liver and gut, as well as the reinitiation of its transcription during liver regeneration, is mimicked by the introduced gene when it is linked to the enhancer domains together or singly. Thus, the DNA sequence elements responsible for directing the activation of AFP transcription, its repression, and reinduction are contained in a limited segment of DNA within or 59 to the gene (or both) and are operative in the absence of the closely linked albumin gene.

Rejection of bone marrow allografts by mice with severe combined immune deficiency (SCID). Evidence that natural killer cells can mediate the specificity of marrow graft rejection

Abstract: C.B-17 scid (H-2d) mice are homozygous for the gene that causes severe combined immune deficiency (SCID). These mice have no T or B cell function, yet display normal natural killer (NK) activity. Irradiated SCID mice were challenged with marrow grafts to determine if antibodies are necessary for marrow allograft rejection. SCID mice rejected H-2/Hh-1 allogeneic marrow grafts. Moreover, this rejection capability could be adoptively transferred using SCID marrow as a source of NK progenitors infused into irradiated B6 (H-2b) hosts. We conclude that NK cells can mediate marrow allograft reactivity in the absence of immunoglobulin. It follows that NK cells probably have specific receptors for Hh antigens.

Anatomy of the subcutaneous tissue of the trunk and lower extremity.

Abstract: Dissections on 8 fresh and 10 embalmed cadavers were used to determine the anatomy of the subcutaneous adipose tissue in the trunk and extremities These dissections, along with CT scans, confirmed Gray's original description of the subcutaneous tissue consisting of a superficial and deep adipose layer The superficial adipose layer is contained within organized, compact fascial septa The deep adipose layer demonstrated regional variations with respect to its fascial framework, but was contained within a relatively loose, less organized, and more widely spaced fascial septa We observed that the adipose layers are partitioned by a discrete subcutaneous fascia which fuses with the underlying muscle fascia at particular anatomic locations The deep layer is thus contained by the subcutaneous fascia above and the muscle fascia below to form what we termed the deep adipose compartments The deep adipose compartments contributed significantly to overall adipose thickness, are bilateral, and are found in the abdomen and paralumbar and gluteal-thigh regions

Tumor necrosis factor-alpha enhances cytolytic activity of human natural killer cells.

Abstract: The effect of recombinant tumor necrosis factor-alpha (rTNF alpha) on human natural killer (NK) function was examined. Lysis of both the NK-sensitive K562 erythroleukemia line and the relatively insensitive renal carcinoma line Cur by nonadherent peripheral blood lymphocytes was significantly enhanced as a result of an 18-hr preincubation with either rTNF alpha or recombinant interleukin 2 (rIL 2). When cells were preincubated with rTNF alpha and low doses of rIL 2 (1 to 10 U/ml), marked additional augmentation of lysis of both targets was noted which was greater than that caused by either cytokine alone. Similar results were observed when responses of CD16+ large granular lymphocytes selected with the fluorescence-activated cell sorter after staining with the NK-specific monoclonal antibody Leu-11 were examined, indicating that the action of the cytokines was directly on the cytotoxic cells. Augmentation of tumor cell lysis could not be ascribed to a cytolytic activity of rTNF alpha on the targets, because no combination of rIL 2, rTNF alpha, or interferon-gamma caused lysis of K562 or Cur. By flow cytometric analysis, it was found that expression of IL 2 receptors was induced on purified CD16+ large granular lymphocytes by rTNF alpha alone and to an even greater degree by the combination of rTNF alpha and rIL 2. Additional analysis of the expression of surface antigens and blocking studies with monoclonal antibodies showed that enhanced tumor cell lysis was not caused by the augmentation of leukocyte function-associated antigen-1-mediated effector/target interactions. These data indicate that rTNF alpha alone, or in combination with rIL 2, directly augments NK cytotoxic activity.

Enhancement of human B cell proliferation and differentiation by tumor necrosis factor-alpha and interleukin 1.

Abstract: The role of tumor necrosis factor-alpha (TNF-alpha) in human B cell responses was examined and compared with that of interleukin (IL) 1 by assessing the ability of each cytokine to support proliferation and differentiation Recombinant TNF-alpha (rTNF-alpha) and recombinant IL-1 (rIL-1) each enhanced the generation of immunoglobulin-secreting cells (ISC) in cultures of pokeweed mitogen-stimulated B cells incubated with T cells To examine the direct effect of rTNF-alpha and rIL-1 on the responding B cell, highly purified peripheral blood B cells were stimulated with Cowan I Staphylococcus aureus (SA) In the absence of T cell factors, proliferation was minimal and there was no generation of ISC Recombinant IL-2 (rIL-2) supported both responses Although rTNF-alpha alone did not support SA-stimulated generation of ISC, it did increase SA-stimulated B cell DNA synthesis by two- to eightfold In addition, rTNF-alpha augmented B cell proliferation in rIL-2 supported SA-stimulated cultures Moreover, rTNF-alpha enhanced the generation of ISC stimulated by rIL-2 alone or rIL-2 and SA rIL-1 also augmented DNA synthesis and generation of ISC by B cells stimulated with SA and rIL-2 However, rTNF-alpha enhanced proliferation and ISC generation in SA + rIL-2-stimulated cultures even when they were supplemented with saturating concentrations of rIL-1 Utilizing a two-stage culture system, it was found that the major effect of rTNF-alpha was to enhance responsiveness of SA-activated B cells to rIL-2, whereas it exerted only a minimal effect during initial stimulation These results indicate that TNF-alpha as well as IL-1 augment B cell responsiveness Moreover, the ability of rTNF-alpha to enhance B cell responsiveness was not an indirect effect resulting from the induction of Il-1 production by contaminating monocytes, but rather resulted from the delivery of a signal by rTNF-alpha directly to the responding B cell that promoted both proliferation and differentiation after initial activation The data therefore indicate that human B cell responsiveness can be independently regulated by the action of two separate monocyte-derived cytokines

Discharge properties of group III and IV muscle afferents: their responses to mechanical and metabolic stimuli.

Abstract: Static contraction of the hind limb muscles induced by electrical stimulation of the ventral roots has been firmly established to reflexly increase cardiovascular and ventilatory function. Moreover, Group III and IV afferents are known to compose the afferent arm of this reflex arc. The present experiments investigated the discharge properties of Group III and IV afferents whose activation is responsible for the pressor reflex response to static contraction. In general, we found that Group III afferents were more responsive to mechanical stimuli, such as distortion of their receptive fields and tendon stretch, than were Group IV afferents. In contrast, Group IV afferents were more responsive to ischemic contraction than were Group III afferents. In addition, equal percents of Group III and IV afferents were found to be stimulated by increasing interstitial potassium to levels that were similar to those found during muscular contraction. The afferents' response to potassium adapted within seconds, while the interstitial concentration of this ion remained elevated for several minutes. This rapidly adapting response casts doubt on the effectiveness of potassium as the metabolite that signals blood supply and demand in a working muscle are improperly matched.

Regulation of T-cell receptor γ-chain RNA expression in murine Thy-1+ dendritic epidermal cells

Abstract: The epidermis of normal mice contains two distinct populations of dendritic cells derived from the bone marrow, Ia+ Langerhans cells and Ia- cells that express the Thy-1 alloantigen. The Thy-1-bearing dendritic epidermal cells (Thy-1+ dEC) have a surface phenotype similar to that of very early T-lineage cells, produce IL-2-like growth factors and exhibit cytotoxicity which is not restricted by the major histocompatibility complex (MHC). The relationship of Thy-1+ dEC to the T-cell lineage is unclear. Most T lymphocytes bear a receptor for antigen composed of an alpha chain and a beta chain associated with a nonpolymorphic complex termed CD3 (T3). A minor population carries a receptor in which CD3 is associated with a gamma/delta complex. We have analysed clones of Thy-1+ dEC for rearrangement and expression of the genes for the alpha-, beta- and gamma-chains of the T-cell receptor (TCR). They do not express alpha or beta but do carry a gamma/delta complex. Activation of the cells with Con A is associated with a rapid decrease in the steady-state level of gamma-chain RNA. Because Thy-1+ dEC resemble early stage T lymphocytes, down-regulation of TCR expression may reflect a necessary event during T cell differentiation.

Action spectra for the induction of pyrimidine(6‐4)pyrimidone photoproducts and cyclobutane pyrimidine dimers in normal human skin fibroblasts

Abstract: . Normal human skin fibroblasts were exposed to 265–313-nm monochromatic UV wavelengths and the yield of pyrimidine(6-4)pyrimidone photoproducts [(6-4) photoproducts] and cyclobutane pyrimidine dimers (dimers) measured by radioimmunoassay. The action spectra for the induction of these two types of DNA damage were very similar for wavelengths from 254 to 302 nm. However, the action spectrum value for (6-4) photoproduct production was less than half the value obtained for dimer induction by 313-nm UV. Cells were also exposed to the UV produced by a broad-spectrum fluorescent sunlamp (280–360 nm, peak at 313 nm) under conditions in which various wavelength components were removed from the spectrum. For exposures in which the (6-4) photoproducts and dimers were induced primarily by wavelengths shorter than 310 nm, their rates of induction, relative to 254-nm-irradiated cells, were similar. However, the level of (6-4) photoproduct production was about three-fold lower than dimer induction for sunlamp irradiations in which the 315–330-nm component of this source was primarily responsible for the formation of this damage. These results are consistent with the conclusion that for treatments in which (6-4) photoproducts are produced by wavelengths in the 310–320-nm range, which represent the region of absorption peaks for these photoproducts, both the induction and photolysis of (6-4) photoproducts occur simultaneously during irradiation.

Maximal vascular leg conductance in trained and untrained men.

Abstract: Lower leg blood flow and vascular conductance were studied and related to maximal oxygen uptake in 15 sedentary men (28.5 +/- 1.2 yr, mean +/- SE) and 11 endurance-trained men (30.5 +/- 2.0 yr). Blood flows were obtained at rest and during reactive hyperemia produced by ischemic exercise to fatigue. Vascular conductance was computed from blood flow measured by venous occlusion plethysmography, and mean arterial blood pressure was determined by auscultation of the brachial artery. Resting blood flow and mean arterial pressure were similar in both groups (combined mean, 3.0 ml X min-1 X 100 ml-1 and 88.2 mmHg). After ischemic exercise, blood flows were 29- and 19-fold higher (P less than 0.001) than rest in trained (83.3 +/- 3.8 ml X min-1 X 100 ml-1) and sedentary subjects (61.5 +/- 2.3 ml X min-1 X 100 ml-1), respectively. Blood pressure and heart rate were only slightly elevated in both groups. Maximal vascular conductance was significantly higher (P less than 0.001) in the trained compared with the sedentary subjects. The correlation coefficients for maximal oxygen uptake vs. vascular conductance were 0.81 (trained) and 0.45 (sedentary). These data suggest that physical training increases the capacity for vasodilation in active limbs and also enables the trained individual to utilize a larger fraction of maximal vascular conductance than the sedentary subject.

Acute rejection of murine bone marrow allografts by natural killer cells and T cells. Differences in kinetics and target antigens recognized.

Abstract: Lethally irradiated C.B-17 +/+, C.B-17 scid/scid (severe combined immunodeficiency, SCID), BALB/c-nu/nu (nude), and C57BL/6 (B6) mice were challenged with H-2-homozygous or H-2-heterozygous totally allogeneic bone marrow cell (BMC) grafts. Some of the irradiated mice were immunized simultaneously with large numbers of irradiated marrow and spleen cells syngeneic with the viable BMC transferred. Irradiated SCID and nude mice, devoid of T cells but with normal NK cell function, were able to reject H-2-homozygous BMC grafts within 4 d. However, they were unable to reject H-2-heterozygous BMC allografts by 7 d even if they were immunized. B6 and C.B-17 +/+ mice were able to reject H-2 heterozygous BMC allografts by 7-8 d, but not as early as 4 d, if they were immunized. The rejection of H-2-homozygous BMC on day 4 was inhibited by administration of anti-NK-1.1 antibodies, but not by anti-Lyt-2 antibodies. Conversely, the rejection of H-2-heterozygous allogeneic BMC on day 8 was prevented by anti-Lyt-2 but not by anti-NK-1.1 antibodies. The data indicate that both NK cells and Lyt-2+ T cells can mediate rejection of allogeneic BMC acutely, even after exposure of mice to lethal doses of ionizing irradiation. NK cells appear to recognize Hemopoietic histocompatibility (Hh) antigens on H-2 homozygous stem cells. The inability of SCID and nude mice to reject H-2 heterozygous totally allogeneic BMC indicate that NK cells do not survey donor marrow cells for self H-2 antigens and reject those cells that express nonself H-2 antigens. The T cells presumably recognize conventional H-2 antigens (probably class I) under these conditions.

Contraction of hydrated collagen gels by fibroblasts: evidence for two mechanisms by which collagen fibrils are stabilized.

Abstract: Studies were conducted to learn more about the mechanism by which fibroblasts contract hydrated collagen gels, a process that may be important in the supramolecular organization of the extracellular matrix. Removal of cells from contracted gels by two different methods, treatment with detergent or treatment with trypsin/EDTA solution, had no visible effect on the bundles of collagen fibrils that had been organized in frameworks around and in between the cells. There was, however, a portion of the collagen gels that expanded after the cells were removed. We conclude that during concentration of collagen gels by fibroblasts, rearranged collagen fibrils were stabilized in place by two different mechanisms. At first, the fibrils were mechanically held in place by the cells. Subsequently, the fibrils were stabilized by non-covalent chemical interactions that are independent of cells. A model system for studying collagen gel reorganization in the absence of cells was developed based on centrifugation of the gels. The overall features of collagen gel reorganization by centrifugation were similar to the features of collagen gel contraction by cells. The collagen fibrils of gels reorganized by centrifugation were at first stabilized mechanically and the gels expanded after centrifugation was stopped. With additional time, the collagen fibrils were stabilized by non-covalent chemical interactions, and then the gels no longer expanded after centrifugation was stopped.

Heparin Modulates the Organization of Hydrated Collagen Gels and Inhibits Gel Contraction by Fibroblasts

Abstract: We studied the effects of extracellular matrix components on fibroblast contraction of hydrated collagen gels. After 4-h incubations, heparin-containing collagen gels contracted only 10% compared with 50% contraction of control gels. Contraction was not affected by hyaluronic acid, dermatan sulfate, or fibronectin, implying that the activity of heparin was specific. The possibility that heparin inhibited attachment of the cells to the gels was ruled out. Also, addition of heparin to the incubation medium had no effect on contraction. Microscopic examination showed that control collagen gels were composed of a uniform network of interlocking fibrils of similar sizes. Heparin-containing gels, on the other hand, were highly variable with some collagen bundles containing 5-6 collagen fibrils and other regions containing amorphous material. Unlike the control gels, the fibrils of heparin-containing gels were not continuously interconnected. Based on the results, we propose that fibroblasts attach normally to the collagen fibrils of heparin-containing gels and attempt to contract the gels, but the mechanical forces exerted by fibroblasts on individual collagen fibrils cannot be propagated throughout the gels.

Effect of burn trauma on adrenal and testicular steroid hormone production.

Abstract: The effects of burn trauma in men on the production of adrenal and testicular steroids was investigated. Whereas there were significant increases in serum cortisol levels and urinary 17-hydroxycorticosteroid excretion soon after thermal injury, there were significant decreases in serum dehydroepiandrosterone sulfate, dehydroepiandrosterone, androstenedione, and testosterone concentrations during the first 4 weeks following burn trauma. Serum androstenediol and androstenediol sulfate levels also were reduced, though insignificantly, 10-23 days postburn. Serum LH levels were unchanged during the postburn interval. Since urinary 17-ketosteroid excretion was normal or below normal rather than increased, the decline in serum C19-steroid levels probably resulted from decreased glandular secretion rather than increased rates of metabolism and excretion. Low dehydroepiandrosterone sulfate and/or testosterone levels were found in some men several months after recovery from their burns. These data suggest that thermal injury leads to acute inhibition of adrenal and testicular C19-steroid secretion, but stimulation of adrenal glucocorticosteroid production, and that endocrine function in many instances is not normalized after complete healing of the burned surfaces. The mechanisms and physiological consequences of such changes in the steroid milieu of men after burn trauma are unknown.

External approach for secondary rhinoplasty.

Abstract: A systematic approach, using the external rhinoplasty technique, is presented to aid the plastic surgeon in obtaining improved aesthetic and functional results in patients with postoperative nasal deformities. In over 100 external rhinoplasties, there were no problems with the stairstep transcolumel

Fatigue fracture of the interlocking nail in the treatment of fractures of the distal part of the femoral shaft.

Abstract: The clinical and mechanical factors predisposing to a fatigue fracture of an interlocking nail were studied in seven patients who were treated for a fracture of the distal part of the femur. In all patients, the fracture of the femur was five centimeters or less from the more proximal of the two distal screw-holes. Finite-element analysis revealed that the stress on the nail exceeded its fatigue endurance limit and that the femur had to regain 50 per cent of its original stiffness through healing to accommodate weight-bearing without the risk of fatigue failure of the nail. The risk of fatigue failure may be minimized by using nails that have a larger diameter and by avoiding early weight-bearing.

Regulation by follicle-stimulating hormone of the synthesis of aromatase cytochrome p-450 in human granulosa cells

Abstract: The effects of FSH to increase the activity of aromatase, as well as the synthesis of the components of the aromatase enzyme complex, have been studied in human ovarian granulosa cells obtained from women undergoing oocyte retrieval. FSH increased aromatase activity, as well as the synthesis of aromatase cytochrome P-450 (P-450AROM) in a time-dependent fashion, whereas in the absence of FSH, both activity and synthesis declined with duration of culture. The effect of FSH was mimicked by forskolin, an activator of adenylate cyclase. FSH also increased the synthesis of NADPH-cytochrome P-450 reductase, butto a relatively modest extent. The levels of hybridizable mRNA species encoding cytochrome P-450AROM of lengths 3.0, 2.4, and 1.6 kilobases were also increased with FSH treatment. It is concluded that the regulation of aromatase activity by FSH in human granulosa cells is mediated primarily by changes in the synthesis of cytochrome P-450AROM, that this action of FSH is mediated by cAMP, and that the change...

The financial incentive for hospitals to prevent nosocomial infections under the prospective payment system. An empirical determination from a nationally representative sample

Abstract: To clarify the financial incentives for hospitals to prevent nosocomial infections, we analyzed 9423 nosocomial infections identified in 169526 admissions selected randomly from the adult admissions to a random sample of US hospitals. By classifying each admission into a baseline diagnosis related group (DRG) (after first excluding all diagnoses of nosocomial infection) and a final DRG (after including these diagnoses), we found that only 5% to 18% of nosocomial infections would have caused the admission to be reclassified to a higher-paying DRG, depending on the extent to which physicians recorded nosocomial infection diagnoses in patients' medical records. The extra payment from the reclassification, averaged over all nosocomial infections, would have been no more than $93 per infection (in 1985 reimbursement rates), constituting only 5% of the hospitals' costs for treating these infections. Thus, at least 95% of the cost savings obtained from preventing nosocomial infections represents financial gains to the hospital. ( JAMA 1987;257:1611-1614)