THERMAL DEPOLARIZATION OF FLUORESCENCE FROM POLYTENE CHROMOSOMES STAINED WITH ACRIDINE ORANGE

The degree of polarization of fluorescence from stretched Chironomus thummi polytene chromosomes, stained with low concentrations of acridine orange (AO), decreases with increasing temperature. The "half temperature" of this decrease (T_½R) is lower than the expected DNA thermal denaturation temperature (T_m) by about 20°C. T_½R is lowered as histone is removed from chromosomes. Balbiani ring regions of the fourth chromosome have T_½R's much lower than other regions, and nearly as low as chromosomes which had been extensively pretreated with trypsin to remove histone and other proteins. Measurements of the thermal change in the rotational diffusion rate of AO in solution with DNA indicate that the temperature at which the DNA-AO bonding changes from a "rigid" to a "loose" mode varies with the GC percentage of the DNA, and in the same fashion as T_m, although 20°C lower.     

THE MECHANISM OF VITAL STAINING WITH BASIC DYES

1. Solutions containing NH₄OH and NaOH, and CO₂ and HCl may be used to produce various combinations of extracellular and intracellular reactions in starfish eggs, Gonionemus, and Nitella cells. 2. Staining by basic dyes is, with a constant intracellular reaction, favored by increased extracellular alkalinity. With a constant extracellular reaction, staining is hindered by increased intracellular alkalinity. 3. These facts are in opposition to the view that staining of cells by basic dyes is chiefly governed by a combination of the dyes with cell proteins. It is more in harmony with the view that the combination is with a substance or substances of acid nature.     

THE RESPONSE OF DIFFERENTCLADONIASPECIES AFTER TREATMENT WITH FERTILIZER OF LIME IN HEATHLAND

The effect of deposition of different fertilizers and of lime on lichens was investigated under field conditions. Three terricolous lichens were tested:Cladonia floerkeanaC. furcataandC. portentosa. The lichens were exposed to three types of powdered fertilizer (NPK-, N-, P-fertilizer) and lime. The applied nutrients were recorded in lichen thalli and soil. the influence on lichen growth rate and vegetation cover was estimated over 2 years. The response was a clear change in vegetation cover with an exceptional stimulating effect of NPK on the mossPolytrichum formosum. A lethal effect was observed onCladonia floerkeanafollowing exposure to lime. NPK and P had the most significant stimulatory effect onC. furcata. Only NPK promoted the growth ofC. portentosaand P, N or Ca had a negative effect.     

ENHANCED BETA-CATENIN EXPRESSION IS ASSOCIATED WITH RECURRENCE OF PAPILLARY THYROID CARCINOMA

Objective: A direct role of β-catenin 1 (β-cat) in the proliferation of human thyroid tumor cells has been identified. This study aimed to determine if there is an association between β-cat gene expression and the staging, recurrence, metastasis, and disease-free survival of papillary thyroid cancer.Methods: A retrospective cohort study was conducted using data from available information in the medical records and paraffin blocks of 81 of 400 patients referred to the endocrine clinic over a 10-year period. Real-time polymerase chain reaction was used to evaluate β-cat gene expression. Disease-free survival was assessed using the Kaplan-Meier method.Results: The 10-year survival rate in these patients was 98.25%, and disease-free survival was 48.1%. Cumulative dose of radioactive iodine that patients received was significantly and positively correlated with β-cat gene expression (r = -0.2; P = .03). Also, in patients with recurrence, β-cat gene expression was higher and statistically significant (5-fold increase; P = .002). Patients in more advanced stage and those with recurrence/distant metastasis had higher β-cat gene expression. We found that the patients had a better survival (lower recurrence) if they had a lower β-cat gene expression (SD, 0.142 to 0.052) (Mantel-Cox test, P = .002).Conclusion: We conclude that β-cat gene expression is positively correlated with recurrence, distant metastasis, and tumor-node-metastasis stage.Abbreviations: β-cat = β-catenin 1; CI = confidence interval; PTC = papillary thyroid carcinoma; ROC = receiver operating characteristic     

CRITICAL INTENSITY AND FLASH DURATION FOR RESPONSE TO FLICKER: WITH ANAX LARVAE

Determinations of the flicker response curve (F – log I_m) with larvae of Anax junius (dragonfly) for various ratios t_L/t_D of light time to dark time in a flash cycle provide relations between t_L/t_D and the parameters of the probability integral fundamentally describing the F – log I function, including the variability of I. These relations are quantitatively of the same form as those found for this function in the sunfish, and are therefore non-specific. Their meaning for the theory of reaction to visual flicker is discussed. The asymmetry of the Anax curve, resulting from mechanical conditions affecting the reception of light by the arthropod eye, is (as predicted) reduced by relative lengthening of the fractional light time in a cycle.     

STUDIES WITH CYANIDIUM CALDARIUM : I. The Fine Structure and Systematic Position of the Organism

The fine structure of Cyanidium caldarium, as seen in thin sections of KMnO₄-fixed cells examined with the electron microscope, is described. This organism, whose taxonomic position among algae is undetermined, contains a single well defined chloroplast, a nucleus, and mitochondria. Studies, with the electron microscope, of Chlorella pyrenoidosa and Nostoc are also reported. Structural differences within cells of Cyanidium, chlorella, and Nostoc are discussed. It is concluded that if Nostoc can be taken as a typical Cyanophyte and Chlorella as a representative Chlorophyte and if the items of fine structure examined are diagnostic, then Cyanidium is certainly not a Cyanophyte and, while it has numerous features in common with Chlorella, is not a green alga similar to Chlorella. Comparisons are also made between Cyanidium and other algae whose fine structure has been described by others.     

THYMIDINE DEGRADATION PRODUCTS IN PLANT TISSUES LABELED WITH TRITIATED THYMIDINE

A study of the metabolic pathways of H³-thymidine utilization in buds of Lilium longiflorum and root tips of Vicia faba was undertaken in order to obtain information that might explain the binding of H³ from H³-thymidine in the cytoplasm of these plants. H³-thymidine was administered for various periods of time, the tissues were fixed and processed in the manner routinely used in preparation for sectioning and autoradiography, and the radioactivity removed in this way from the tissues was determined. It was found that the ethanol/acetic acid fixative contained the major portion of the radioactivity. Analysis of this extract by paper chromatography showed that the radioactivity was distributed among various degradation products of thymidine, principally β-ureidoisobutyric acid and β-aminoisobutyric acid. Time course experiments with Vicia showed that these degradation products rapidly appeared in the tissue during incubation with H³-thymidine, while H³-thymine appeared in the incubation medium. Preliminary studies indicated that Vicia root tips incubated with H³-dihydrothymine for 24 hours would bind a small amount of H³ non-specifically in the cells. It seems unlikely that utilization of degradation products of H³-thymidine is sufficient to explain labeling which is concentrated in the cytoplasm.     

FENESTROCONIDIA CALOPLACAE,A NEW SPORODOCHIAL LICHENICOLOUS FUNGUS WITH CATENATE CONIDIOGENOUS CELLS

The genus Fenestroconidia is described to accommodate the new species Fenestroconidia caloplacae. This lichenicolous fungus produces black sporodochia, has conidiogenous cells arranged in chains, and simple, pale brown conidia with a subhyaline guttule-like zone. It is known only from central Spain (Cuenca province), growing in the apothecia of Caloplaca saxicola s.lat.     

ON PSOROMA SPECIES FROM THE SOUTHERN HEMISPHERE WITH CEPHALODIA PRODUCING VEGETATIVE DISPERSAL UNITS

Abstract: Two new species of Psoroma with unusual cephalodia are described: P. echinaceum with isidiate cephalodia, from southern South America and P. geminatum with fragile phyllidiate cephalodia, from New Zealand and Australia. These are additional to two previously described species producing dispersal units on their cephalodia, P. durietzii P. James & Henssen (with soredia) and P. aphthosum Vain. (syn.nov. P. dimorphum Malme) (with isidia). This is a strategy development that ensures successful establishment of new thalli.     

THE CONCENTRATION EFFECT WITH VALONIA: POTENTIAL DIFFERENCES WITH DILUTED POTASSIUM-RICH SEA WATERS

The concentration effect with sea waters containing more than the normal amount of potassium has been studied in Valonia macrophysa. This was done by comparing the initial changes in P.D. across the protoplasm when natural sea water bathing the cell was replaced by various isotonic dilutions of KCl-rich sea waters. With small dilutions of KCl-rich sea waters, the P.D.-time curves are of the same form as with the undiluted solution, exhibiting the fluctuations characteristic of KCl-rich solutions. This indicates that with these solutions K⁺ enters Valonia protoplasm and plays an important part in the P.D. The value of the initial rise in P.D. decreases with increasing dilution. With high dilutions of KCl-rich sea waters, the P.D.-time curves are of quite different shape, resembling the curves with diluted natural sea water; the P.D. is practically independent of small changes in the concentration of potassium, and increases with increasing dilution. That is, with these higher dilutions, the sign of the concentration effect is reversed, becoming the same as with diluted natural sea water. The greater the concentration of KCl in the undiluted sea water, the higher is the critical dilution at which K⁺ ceases to influence the P.D. For a wide range of sea waters containing both KCl and NaCl, it is shown that the concentration effect above the critical dilution is determined solely by the activity of NaCl in the external solution. It is concluded that with dilute natural sea water and with high dilutions of KCl-rich sea waters we have to do with a diffusion potential, involving only the Na⁺ and Cl^- ions, which are diffusing out from the vacuole. A quantitative relation between the composition of the sea water and the critical dilution has been deduced from the classical theory of the diffusion of electrolytes. It is shown that with dilutions less than this critical value the diffusion of K⁺ in the outer non-aqueous layer of the protoplasm is directed inward; hence K⁺ enters the protoplasm from these solutions. With dilutions greater than the critical value, the diffusion of K⁺ in this layer is directed outward; hence K⁺ does not enter the protoplasm. Since the P.D. shows no evidence of this outward diffusion of K⁺, it is concluded that the amount of K⁺ ordinarily present in the protoplasm is too small to produce any lasting electrical effect, and that the outward diffusion of K⁺ from the vacuole is prevented by the mechanism responsible for the accumulation of KCl in the cell sap.     

THE GROWTH OF DUCKWEEDS IN MINERAL NUTRIENT SOLUTIONS WITH AND WITHOUT ORGANIC EXTRACTS

1. Detmer''s solution and a modified Knop''s solution are unfavorable culture media for the growth of Spirodela polyrhiza. 2. When the modified Knop''s solution was diluted to 10 times its volume, Spirodela polyrhiza and Lemna valdiviana grew and reproduced for periods of 26 months and 21 months, respectively. 3. Growth in the dilute Knop''s solution, which alone can support the growth of Spirodela indefinitely, was considerably stimulated over a period of 23 days by adding to every liter the water-soluble material of 0.4 gm. autolyzed yeast, or the material of 2.5 gm. peat soluble in a 1 per cent solution of NaHCO₃. 4. The nature of the stimulus or of the protection afforded by the organic material is as yet unknown. 5. The necessity of organic accessory foods (auximones) in the nutrition of green plants cannot be accepted as an established fact.     

A THEORY OF INJURY AND RECOVERY : I. EXPERIMENTS WITH PURE SALTS.

In addition to the Correction in Vol. iii, No. 3, January 20, 1921, on page 149, Vol. iii, No. 2, November 20, 1920, line 13, for 92.57 read 89.10; page 154, lines 15, 28, and 32, for O read O+10; page 155, line 3 of the figure legend, for O read O+10.     

Insulin-regulated Glut4 Translocation: MEMBRANE PROTEIN TRAFFICKING WITH SIX DISTINCTIVE STEPS*

The trafficking kinetics of Glut4, the transferrin (Tf) receptor, and LRP1 were quantified in adipocytes and undifferentiated fibroblasts. Six steps were identified that determine steady state cell surface Glut4: (i) endocytosis, (ii) degradation, (iii) sorting, (iv) sequestration, (v) release, and (vi) tethering/docking/fusion. Endocytosis of Glut4 is 3 times slower than the Tf receptor in fibroblasts (k_en = 0.2 min⁻¹ versus 0.6 min⁻¹). Differentiation decreases Glut4 k_en 40% (k_en = 0.12 min⁻¹). Differentiation also decreases Glut4 degradation, increasing total and cell surface Glut4 3-fold. In fibroblasts, Glut4 is recycled from endosomes through a slow constitutive pathway (k_ex = 0.025–0.038 min⁻¹), not through the fast Tf receptor pathway (k_ex = 0.2 min⁻¹). The k_ex measured in adipocytes after insulin stimulation is similar (k_ex = 0.027 min⁻¹). Differentiation decreases the rate constant for sorting into the Glut4 recycling pathway (k_sort) 3-fold. In adipocytes, Glut4 is also sorted from endosomes into a second exocytic pathway through Glut4 storage vesicles (GSVs). Surprisingly, transfer from endosomes into GSVs is highly regulated; insulin increases the rate constant for sequestration (k_seq) 8-fold. Release from sequestration in GSVs is rate-limiting for Glut4 exocytosis in basal adipocytes. AS160 regulates this step. Tethering/docking/fusion of GSVs to the plasma membrane is regulated through an AS160-independent process. Insulin increases the rate of release and fusion of GSVs (k_fuseG) 40-fold. LRP1 cycles with the Tf receptor and Glut4 in fibroblasts but predominantly with Glut4 after differentiation. Surprisingly, AS160 knockdown accelerated LRP1 exocytosis in basal and insulin-stimulated adipocytes. These data indicate that AS160 may regulate trafficking into as well as release from GSVs.     

Trehalose Toxicity in Cuscuta reflexa: CORRELATION WITH LOW TREHALASE ACTIVITY

A toxic effect of α,α-trehalose in an angiospermic plant, Cuscuta reflexa (dodder), is described. This disaccharide and its analogs, 2-aminotrehalose and 4-aminotrehalose, induced a rapid blackening of the terminal region of the vine which is involved in elongation growth. From the results of in vitro growth of several angiospermic plants and determination of trehalase activity in them, it is concluded that the toxic effect of trehalose in Cuscuta is because of the very low trehalase activity in the vine. As a result, trehalose accumulates in the vine and interferes with some process closely associated with growth. The growth potential of Lemna (a duckweed) in a medium containing trehalose as the carbon source was irreversibly lost upon addition of trehalosamine, an inhibitor of trehalase activity. It is concluded that, if allowed to accumulate within the tissue, trehalose may be potentially toxic or inhibitory to higher plants in general. The presence of trehalase activity in plants, where its substrate has not been found to occur, is envisaged to relieve the plant from the toxic effects of trehalose which it may encounter in soil or during association with fungi or insects.     

ACUTE PANCREATITIS IN PATIENTS WITH SEVERE HYPERTRIGLYCERIDEMIA IN A MULTI-ETHNIC MINORITY POPULATION

Objective: To investigate the prevalence and predictors of hypertriglyceridemic acute pancreatitis (HTG-AP) in a multi-ethnic minority population.Methods: A retrospective, cross-sectional study from 2003 to 2013 of 1,157 adults with a serum triglyceride (TG) level =1,000 mg/dL comparing baseline characteristics and risk factors between those with and without HTG-AP.Results: Mean study population age was 49.2 ± 11.5 years; 75.6% were male, 31.6% African American, 38.4% Hispanic, 22.7% Caucasian, 5.7% Asian, and 1.6% Pacific Islander. Prevalence of HTG-AP was 9.2%. Patients with HTG-AP were significantly younger (41.3 years vs. 50.0 years; P<.001) than those without HTG-AP. Excessive alcohol intake (odds ratio [OR], 3.9; 95% confidence interval [CI], 2.5 to 6.0; P<.001), gallstone disease (OR, 3.9; 95% CI, 1.4 to 10.8; P = .008), and TG >2,000 mg/dL (OR, 4.8; 95% CI, 3.1 to 7.4; P<.001) remained significant independent risk factors. TG levels for patients with HTG-AP were higher (median TG, 2,394 mg/dL; interquartile range [IQR], 1,152 to 4,339 mg/dL vs. median TG, 1,406 mg/dL; IQR, 1,180.7 to 1,876.5 mg/dL). TG levels >2,000 mg/dL were associated with higher incidence of AP (22% vs. 5%). Patients with TG levels <2,000 mg/dL and no risk factors had prevalence of 2% compared to 33.6% with one risk factor and TG >2,000 mg/dL. Patients with HTG-AP had higher incidence of diabetic ketoacidosis at admission (7.5% vs. 2.5%; P = .004).Conclusion: TG level =2,000 mg/dL is associated with higher HTG-AP prevalence in ethnic minorities. Presence of excessive alcohol intake and/or gallstones further accentuates risk.Abbreviations: AP = acute pancreatitis; CT = computed tomography; DM = diabetes mellitus; HbA1c = hemoglobin A1c; HIV = human immunodeficiency virus; HTG = hyper-triglyceridemia; HTG-AP = hypertriglyceridemic acute pancreatitis; ROC = receiver operating characteristic; TG = triglyceride     

Structure of Escherichia coli dGTP Triphosphohydrolase: A HEXAMERIC ENZYME WITH DNA EFFECTOR MOLECULES*

The Escherichia coli dgt gene encodes a dGTP triphosphohydrolase whose detailed role still remains to be determined. Deletion of dgt creates a mutator phenotype, indicating that the dGTPase has a fidelity role, possibly by affecting the cellular dNTP pool. In the present study, we have investigated the structure of the Dgt protein at 3.1-Å resolution. One of the obtained structures revealed a protein hexamer that contained two molecules of single-stranded DNA. The presence of DNA caused significant conformational changes in the enzyme, including in the catalytic site of the enzyme. Dgt preparations lacking DNA were able to bind single-stranded DNA with high affinity (K_d ∼ 50 nm). DNA binding positively affected the activity of the enzyme: dGTPase activity displayed sigmoidal (cooperative) behavior without DNA but hyperbolic (Michaelis-Menten) kinetics in its presence, consistent with a specific lowering of the apparent K_m for dGTP. A mutant Dgt enzyme was also created containing residue changes in the DNA binding cleft. This mutant enzyme, whereas still active, was incapable of DNA binding and could no longer be stimulated by addition of DNA. We also created an E. coli strain containing the mutant dgt gene on the chromosome replacing the wild-type gene. The mutant also displayed a mutator phenotype. Our results provide insight into the allosteric regulation of the enzyme and support a physiologically important role of DNA binding.     

Eyespot Disease of Sugarcane : INDUCTION OF HOST-SPECIFIC TOXIN AND ITS INTERACTION WITH LEAF CELLS

Helminthosporium sacchari produces a toxin which is responsible for the symptoms of eyespot disease in Saccharum officinarum. A rapid and highly repeatable bioassay based on increase in conductivity of tissue leachates showed that the interaction of toxin with sugarcane obeys Michaelis-Menten hyperbolic saturation kinetics. There was no evidence for positive or negative cooperation interaction. Resistant and susceptible cultivars of sugar cane had distinctive conductivity characteristics. Co-cultures of H. sacchari and suspension cultures of sugarcane gave up to a 4,000-fold increase in toxin production.