Biochemical Studies on Amphibian Metamorphosis : I. The effect of thyroxine on protein synthesis in the tadpole

Thyroxine has been shown to accelerate the synthesis of carbamyl phosphate synthetase in the liver of Rana catesbeiana. Stimulation of carbamyl phosphate synthetase synthesis by thyroxine appears to be relatively specific because of the following observations: (1) succinoxidase activity decreased during the time that carbamyl phosphate synthetase increased; (2) liver catalase responded more slowly than carbamyl phosphate synthetase to thyroxine; (3) the ratio of biochemical changes/morphological changes was greatly altered during thyroxine-induced metamorphosis. The relationships between the concentration of thyroxine and (1) temperature; (2) duration of exposure of the tadpole to thyroxine; and (3) the activity of carbamyl phosphate synthetase during the induced synthesis of carbamyl phosphate synthetase by thyroxine are discussed. Chloramphenicol and thiouracil partly counteracted the effect of thyroxine on the synthesis of carbamyl phosphate synthetase.     

Active Ion Transport Across Canine Blood Vessel Walls

Experiments giving evidence of active Na and Cl ion fluxes across large canine blood vessel walls (aorta, vena cava) in vitro have been presented. The information has been obtained using ion tracer techniques after Ussing and with diffusion cells of the Hogben type. The available data suggest that the membranes are satisfactorily oxygenated by the bathing solutions saturated with oxygen at atmospheric pressure. Evidence is offered which indicates that active ion transport does occur across the aorta and vena cava in in vitro experiments. Under the conditions of the experiment net Na and Cl flux takes place from intima to adventitia across the aorta, and from adventitia to intima across the vena cava at low measured potential differences. The possible relationships of derangement of active ion transport mechanisms, produced by electric currents and tissue injury potential differences, to intravascular thrombosis are alluded to. It would appear that sodium and chloride fluxes across large blood vessel walls in vitro occur at least in part as the result of metabolic processes and cannot be explained simply on the basis of diffusion across a semipermeable membrane.     

Teak in Trinidad

Teak plantations have been established in Trinidad to provide first quality timber for the future. Thinnings from the teak plantations are being utilized by the “Brickfield Forest Industries” which produces fences, building and construction lumber, and creosoted posts and poles.     

Characterization of human mammary cell types in primary culture: Immunofluorescent and immunocytochemical indicators of cellular heterogeneity

Summary Parenchymal organoidal structures that were obtained from collagenase digestion of reduction mammoplasty specimens of apparently normal human breasts have been grown in short-term primary cultures, either on plastic or on floating gels of polymerized rat-tail collagen. Three morphologically distinct major cell types are readily observed in both systems: cuboidal cells, which occupy apical positions on collagen gels; larger, epithelioid, or basal cells on gels; and elongated cells which penetrate into the gel. In addition, a fourth cell type, that of a large, flat cell, is observed less readily by phase contrast microscopy on the surface of cultures grown on plastic. Immunofluorescent and immunocytochemical staining of cultures on plastic or histologic sections of cultures on gels have been undertaken with antisera and other histochemical reagents that stain the different parenchymal cell types in vivo. Thus antisera to epithelial membrane antigen(s), monoclonal antibodies (MABs) to the defatted mammary milk fat globule membrane, peanut lectin, and keratin MAB LE61, which preferentially stain the epithelial cells of ducts in vivo, also stain the cuboidal/apical cells in vitro. The large, flat cells are stained intensely by the first three reagents but not by the last one. Antisera to collagen IV, laminin, fibronectin, actin, keratin MAB LP34, MABs to the common acute lymphoblastic leukemia antigen, and MAB LICR-LON-23.10, which showed enhanced staining for the ductal myoepithelial cells in vivo, also stain the epithelioid/elongated cells in vitro. However, the effect of the last four reagents is reduced considerably in most elongated cells, and MAB LP34 stains the large, flat cells intensely. Heterogeneous cells of intermediate morphologies and staining patterns between the cuboidal/flat cells and large epithelioid cells have also been identified. The results suggest that the cuboidal cells and large, flat cells are related to mammary epithelial cells, whereas the large epithelioid/elongated cells have some characteristics of myoepithelial cells, and that intermediate forms may exist in culture between the two parenchymal cell types. This work was supported in part by the Ludwig Institute for Cancer Research and the Cancer and Polio Research Fund. Dr. M. J. Warburton is supported by the Cancer Research Campaign.     

Differential responses of expiratory muscles to chemical stimuli in awake dogs

We assessed respiratory muscle response patterns to chemoreceptor stimuli (hypercapnia, hypoxia, normocapnic hypoxia, almitrine, and almitrine + CO2) in six awake dogs. Mean electromyogram (EMG) activities were measured in the crural (CR) diaphragm, triangularis sterni (TS), and transversus abdominis (TA). Hypercapnia and normocapnic hypoxia caused mild to marked hyperpnea [2-5 times control inspiratory flow (VI)] and increased activity in CR diaphragm, TS, and TA. When hypocapnia was permitted to develop during hypoxia and almitrine-induced moderate hyperpnea, CR diaphragm activity increased, whereas TS and TA activities usually did not change or were reduced below control. Over time in hypercapnia, CR diaphragm, TS, and TA were augmented and maintained at these levels over many minutes; with hypoxic hyperventilation CR diaphragm, TS, and TA were first augmented but then CR diaphragm remained augmented while TS and, less consistently, TA were inhibited over time. Marked hyperpnea (4-5 times control) due to carotid body stimulation increased TA and TS EMG activity despite an accompanying hypocapnia. We conclude that in the intact awake dog 1) carotid body stimulation augments the activity of both inspiratory and expiratory muscles; 2) hypocapnia overrides the augmenting effect of carotid body stimulation on expiratory muscles during moderate hyperpnea, usually resulting in either no change or inhibition; 3) at higher levels of hyperpnea both chemoreceptor stimulation and stimulatory effects secondary to a high ventilatory output favor expiratory muscle activation; these effects override any inhibitory effects of a coincident hypocapnia; and 4) expiratory muscles of the rib cage/abdomen may be augmented/inhibited independently of one another.     

A phase I trial of recombinant tumor necrosis factor (rTNF) administered by continuous intravenous infusion in patients with disseminated malignancy

rTNF was administered to 28 patients with advanced metastatic cancers by continuous intra venous infusion for 5 consecutive days every 2 weeks. The dose levels were 30, 40, 70, 110, 180 and 290 µg/M²/day. Groups of 3 patients were started at each successive dose level and then on subsequent courses treated with the next dose level through 4 escalations as tolerated. Tumor types were: colon cancer 14; adenocarcinoma of unknown primary, 2; renal cancer, 2; leiomyosarcoma, 2; lung cancer, 1; prostate cancer, 1; thymona, 1; bladder cancer; 1; parotid, 1; Kaposi's sarcoma 2; ovarian 1. Toxicities included fever and chills (usually within the first 8 hours of infusion), fatigue, headache, decreased performance status, hypotension and CNS. All patients experienced leukopenia and thrombocytopenia within 24 hours or less after start of infusion with return of baseline by 72 hours after rTNF was stopped. The fall in these counts averaged 50% and was not dose related. No major changes in liver or renal function, coagulation or blood lipids were seen. Major dose limiting toxicities were fatigue, confusion, thrombocytopenia, seizures, hypotension and decreased performance status. NK cell activity measured against K562 target cells was augmented from about 30% target cell lysis to about 70% target cell lysis over the first 7 days of treatment. Two patients, both with metastatic colon cancer showed transient, objective tumor regression which did not qualify as a partial response. One patient with ovarian cancer had a stable partial response but progressed after 13 courses of treatment. Continuous infusion of TNF can be safely administered to patients with a maximum tolerated dose of only between 30 and 40 µg/M²/day. In addition, the MTD with continuous infusion seems to be highly variable and unpredictable from patient to patient. These data suggest that continuous infusion will not be an optimal way to administer TNF.     

Postnatal Development of a Granule Cell-Enriched, Neurone-Specific Glycoprotein, gp50, in Normal and Thyroid-Deficient Rats

Glycoprotein gp50 is a neurone-specific, granule cell-enriched glycoprotein that is also a major component of isolated synaptic membranes. Here, we describe the use of a monoclonal antibody, mab SM gp50, to study the postnatal development of gp50 in the brain of normal and thyroid-deficient rats. Radioimmunoassay, enzyme-linked immunosorbent assay, and Western blotting show that gp50 is not detectable in brain until postnatal day 4 (P4) in both forebrain and cerebellum. In forebrain, the rate of increase of gp50 levels is maximal between P12 and P20. It is somewhat later in cerebellum, where peak levels are attained between P30 and P35. Immunocytochemical studies show little detectable gp50-like immunoreactivity before P16, and the staining is still weak, relative to adult tissue, at P25. The intense staining of the granule cell layer characteristic of adult cerebellum predominantly appears after P25. Development of gp50 is severely retarded in the cerebellum of thyroid-deficient rats, particularly during the second and third postnatal weeks. However, by the fourth postnatal week, gp50 levels in normal and hypothyroid animals are comparable. The results indicate that significant alterations in the pattern of gp50 expression continue to occur at a late stage of cerebellar development. In particular, the increase in immunocytochemical staining of the granule cells after P25 is striking in that by this time most major events associated with cerebellar development are essentially complete.     

Subacute and Chronic In Vivo Lithium Treatment Inhibits Agonist- and Sodium Fluoride-Stimulated Inositol Phosphate Production in Rat Cortex

We have investigated the effects of in vivo lithium treatment on cerebral inositol phospholipid metabolism. Twice-daily treatment of rats with LiCl (3 mEq/kg) for 3 or 16 days resulted in a 25-40% reduction in agonist-stimulated inositol phosphate production, compared with NaCl-treated controls, in cortical slices prelabelled with [3H]inositol. A small effect was also seen with 5-hydroxytryptamine (5-HT) 24 h after a single dose of LiCl (10 mEq/kg). Dose-response curves to carbachol and 5-HT showed that lithium treatment reduced the maximal agonist response without altering the EC50 value. This inhibition was not affected by the concentration of LiCl in the assay buffer. Stimulation of inositol phosphate formation by 10 mM NaF in membranes prepared from cortex of 3-day lithium-treated rats was also inhibited, by 35% compared with NaCl-treated controls. Lithium treatment did not alter the kinetic profile of inositol polyphosphate formation in cortical slices stimulated with carbachol. Muscarinic cholinergic and 5-HT2 bindings were unaltered by lithium, as was cortical phospholipase C activity and isoproterenol-stimulated cyclic AMP formation. [3H]Inositol labelling of phosphatidylinositol 4,5-bisphosphate was significantly enhanced by 3-day lithium treatment. The results, therefore, indicate that subacute or chronic in vivo lithium treatment reduces agonist-stimulated inositol phospholipid metabolism in cerebral cortex; this persistent inhibition appears to be at the level of G-protein-phospholipase C coupling.