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Variation in temperature (T) is usually accompanied by changes in leaf water potential (Ψleaf ), which may influence mesophyll conductance (gm ). However, the effects of Ψleaf on gm have not yet been considered in models of the gm response to temperature. Temperature responses of gm and Ψleaf and the response of gm to Ψleaf were studied in rice (Oryza sativa) and wheat (Triticum aestivum), and then an empirical model of Ψleaf was incorporated into an existing gm -T model. In wheat, Ψleaf was dramatically decreased with increasing T, whereas in rice Ψleaf was less sensitive or insensitive to T. Without taking Ψleaf into account, gm for wheat showed no response to T. However, at a given Ψleaf , gm was significantly higher at high temperature compared with low. After incorporating the function of Ψleaf into the gm -T model, we suggest that the gm -T relationship can be influenced by the activation and deactivation energy for membrane permeability, Ψleaf gradient between temperatures, and the sensitivity of gm to Ψleaf , below a threshold (Ψleaf,0 ). The data presented here suggest that Ψleaf plays an important role in the gm -T relationship and should be considered in future studies related to the temperature response of gm and photosynthesis.

Replacement of phospholipids with phosphorus (P)-free lipids in cellular membranes has been identified as a mechanism facilitating fast rates of photosynthesis when phosphorus availability is limited. We measured photosynthetic rates, leaf and soil P fractions, and foliar membrane lipid compositions for five species (Geranium antrorsum, Ranunculus graniticola, Poa costiniana, Poa hiemata, and Veronica derwentiana) common to two Australian subalpine ecosystems of contrasting parent material to characterize the extent to which they have adapted to long-term P availability. Our results indicate limited tolerance to reduced P, albeit adaptation strategies differ among species. Under reduced P conditions, phospholipids were replaced in foliage by galactolipids and sulfolipids, but photosynthesis was still impaired owing to reduced stomatal conductance. Accumulation of antioxidants, including carotenoids and alpha-tocopherol, in leaves with limited P supply suggests oxidative stress. Our field study shows that while subalpine Australian plants of a variety of life forms adapt to P availability by replacing phospholipids with P-free lipids in foliar membranes, this adaptation is insufficient to fully mitigate the effects of reduced P on photosynthesis.

BACKGROUND Pyrethroids are one of the most widespread and commonly used classes of insecticide and are used in multiple roles, including protecting potato crops from virus vector aphids. Resistance in some genotypes of a few species is now widespread, but most species remain susceptible. The rate of virus transmission by two genotypes of the peach potato aphid, Myzus persicae, fed on potato virus Y (PVY)-infected leaves of potato treated with the pyrethroid λ-cyhalothrin was evaluated. RESULTS The susceptible genotype, type J, was significantly inhibited from transmitting virus to uninfected seedlings. A genotype containing the M918L super knockdown resistance mutation conferring resistance to pyrethroids, type O, showed no inhibition of transmission. However, when survival of the aphids after exposure was compared, the pyrethroid had not killed the type J aphids. CONCLUSIONS λ-Cyhalothrin in a commercial formulation disrupts PVY transmission by disorienting aphid vectors for a sufficient time for the virus to lose its transmissibility. However, M. persicae genotypes carrying the M918L mutation are not prevented from transmitting. © 2014 Society of Chemical Industry

IN STUDIES of iodine metabolism, particularly those involving the blood and the thyroid, it is becoming important to work with small samples. This is especially true in observations on small animals; but in the clinic, e.g., in pediatric studies, it is also essential that blood “hormonal” iodine (Salter, 1940) be determined without drawing too much human blood. This paper describes a method which will give duplicate analyses on 2 cc. of serum, and is adapted to standard photoelectric colorimeters such as are available in many laboratories at the present time. It is now well established that human thyroid function can be easured satisfactorily by serum iodine analysis, even when the serum is transmitted long distances in simple containers (Salter, Bassett and Sappington, 1941; Riggs, Gildea, Man and Peters, 1941). Normally the concentration of the “hormonal” iodine is approximately 5 micrograms per cent, or 0.05 micrograms per cc. in man.

REPEATED STUDY has shown that the blood iodine in hyperthyroid-ism tends to be abnormally high (Salter, 1944). Furthermore the “organic” or “hormonal” iodine accounts for most of the increase (Bassett, Coons and Salter, 1941). This finding suggests that the cir-culation contains an excess of a physiologically active iodine com-pound. It is the purpose of this communication to show that such blood can increase the respiration of surviving tissues. The time factor looms large in experimental attempts to demon-strate such stimulation of metabolism in vitro. Thus Davis and Has-tings (1936), using the heart of Limulus polyphemus, obtained an elevation of respiration only after 10 to 15 hours’ exposure to thyroxine in vitro. Hopping Scott (1935), however, reported in some instances a prompt increase in oxygen consumption by the nucleated red cells of alligator blood when thyroxine was added in vitro. In the present communication emphasis will be laid upon the prompt respiratory response of mammalian tissues (wh...

The significance of the protein constituents of muscle for the contractile process has long been recognized. The instability of these bodies, however, has rendered difficult their characterization. Danilewsky1 described the extraction of muscle protein with sal ammoniac in 1881. The older method of expression, despite rigid precautions, often led to “denaturation” or “clotting of muscle plasma.” The properties of muscle globulin, as of other globulins, are altered both by too low salinity and by too high acidity.2 Howe3 has employed phosphate buffers as solvents to overcome these difficulties. In the present investigation an ammonium chloride solution, rendered alkaline by excess of ammonia, was used as solvent and yielded solutions of muscle protein which, for several months, retained solubility in neutral salt solutions.A globulin-like fraction of ox muscle protein was studied, which presumably corresponded to the “myosin” of von Furth4 and the “paramyosinogen” of Halliburton.5 The method of preparation...

ACHIEF function of the thyroid gland is to convert inorganic iodine (iodide) to a state of higher oxidation, equivalent to elementary iodine. When various animal proteins, except gelatine which is nearly devoid of tyrosine, are treated with elementary iodine, thyroxine is formed in vitro. In myxedema, the patient's own serum when combined with iodine (1) (2) will restore his health; whereas sodium iodide usually will not. A more striking demonstration is the relief of myxedema by the parenteral administration of elementary iodine (3) (4). The higher state of oxidation allows iodine to form the essential organic iodine complex (5) present in all tissues (“thyrenzyme,” so-called). As this is degraded in the course of metabolism, it reverts to the inorganic form. Therefore, in broad terms, a large section of thyroid physiology may be described as the reciprocal metabolism of organic versus inorganic iodine. It is the purpose of this communication to report observations on the mutual interconversion of organi...

DURING the last fifteen years estimations of the urinary excretion of 17-ketosteroids and androgens have been made in a variety of clinical disturbances with the hope that they might give some indication of the functional status of the testis and the suprarenal cortex (1, 2, 3, 4). The question of the relative significance of biologic assay for androgens and chemical analysis for 17–ketosteroids, when applied to suitably prepared urine extracts, has been raised repeatedly. It is the primary purpose of this paper to compare, in several distinct clinical syndromes, the results obtained by the two methods with the same urine extracts. We were particularly interested to learn whether the decreased urinary 17–ketosteroid excretion in gynecomastia previously observed by Salter, Klatskin and Humm (5) would be reflected in lower excretion of androgens also. EXPERIMENTAL PLAN Three groups were selected among male patients who might be expected to exhibit evidence of androgenic disturbance. In addition, a group of ...

A study by Salter, Meyer, and Aub (1), of the enzyme system in tumors which deals with carbohydrate metabolism, has indicated its high specificity for glucose. Among other characteristics, the inability of intact tumor cells to produce lactic acid from glycogen (derived from the same species) was noteworthy. Barr, Ronzoni, and Glaser (2), likewise using the technic of Warburg for (lactic) acid production, had previously observed the same fact. However, Buxton (3), working twenty-five years ago with various types of malignant tissue, found an amylolytic enzyme uniformly present in hashed tumors which was capable of acting on both starch and glycogen, and whose activity he was able to estimate roughly. It is the purpose of this paper to show the general properties of this enzyme and to suggest a method whereby its activity can be accurately measured. Sourceof Materials Mouse sarcoma 180 was the malignant tissue of choice because of its rapid growth and ready transplantability, and because of the cellular nature of the tumor with comparatively little, and usually localized, necrosis. This transplanted neoplasm, borne by pure strain, tumor-susceptible mice (inbred for nine years) was used throughout. The tumor was studied three to four weeks after transplantation. The mouse was killed by a blow over the head, the throat was cut, and the tumor was removed, its capsule and adherent tissue cleaned off, and the necrotic center discarded. After weighing the tumor to 0.1 gram it was ground in a small mortar with washed sand, and an equal weight of distilled water was added. Grinding and extraction were continued for from two to five minutes, after which the tumor hash was centrifuged for fifteen minutes. The supernatant fluid, designated as concentrated (50 per cent) tumor extract, was decanted. This stock extract, preserved with toluol and kept in the ice box, retains its activity essentially unaltered for several months.

PREVIOUS reports from this laboratory (Salter, Humm and Oesterling, 1948; Humm and Salter, 1948) have suggested that the Kober reaction, slightly modified from Venning’s procedure (Venning, Evelyn, Harkness and Browne, 1937), could be applied to 6-hour samples of urine in the study of physiological and clinical problems. The question has been raised repeatedly how such chemically determined values correlate with biological assays of urinary estrogens. As emphasized by Engel et al. (1950), fluorometric determinations of urinary “estroids” indicate that urine may contain a metabolite which has no estrogenic potency, even though it registers in the fluorometric determination. It is the purpose of the present report to compare the results obtained, colorimetrically and biologically, with the same urine extracts from several distinct groups of individuals. Of special interest is the question whether the low “estroid” excretion in nutritional gynecomastia previously described by Salter, Klatskin and Humm (1947)...

SEVERAL reports (1,2) indicate that thyroid function can be distorted by therapy with I131. In fact, one of the present authors reported with Dr. F. Homburger that both qualitative and quantitative changes in the blood iodine fractions occurred. This tradition has led to a disregard of the orderliness of thyroid physiology, even under conservative therapy. Nevertheless, if preliminary test doses could afford an accurate preview of thyroxine turnover under therapeutic conditions, a more accurate control of therapeutic dosage would be possible. It is the purpose of this communication to demonstrate the orderliness of thyroxine metabolic turnover even under dosage as high as 50 millicuries of radioiodide, I131. The data concern the function of the thyroid during the first week after a single dose of radioiodide. They do not involve the stage of marked inflammation and autolysis which follows. Within this interval a striking result emerges, namely, that the daily production of radioactive hormone is essential...

SEVERAL years ago Callow and Callow (1) demonstrated that the microchemieal determination of 17-ketosteroids could yield valuable information regarding endocrine function in man and other animals. This finding has since been substantiated in many other laboratories (2–6). Nevertheless, considerable opposition to the procedure was raised originally on the grounds that: (a) the urinary 17-ketosteroids constitute a mixture; (b) their value is considerably higher than a biologically equivalent amount of androsterone; and (c) they vary with changes in both testicular and adrenal function. Similar objections can be raised with respect to urinary components related to estradiol. Degradation products of estradiol in urine Like testosterone, estradiol is converted within the human organism into degradation products of lower biological potency. The best known of such degradation compounds in the female are estrone and estriol (6). Smith and Smith (7) have also concentrated from human urine a substance which tentati...

It has been clearly demonstrated that both lead and calcium are retained in the body in the bones and that the chemical behavior of certain lead and calcium salts in vitro are very similar. These facts suggested to one of us (J. C. A.) that perhaps the same physiologic variations which affect the elimination and excretion of calcium would similarly influence the lead stream. As a result of certain observations on animal and man,1it soon became apparent that an analogy existed between the metabolism of lead and of calcium. The administration of various decalcifying agents resulted in an increased excretion of lead. Conversely, forms of therapy promoting calcium retention were found to favor the storage of lead. Consequently in the treatment of lead poisoning a high calcium diet is employed until all the symptoms of intoxication have disappeared. Complete subsidence of symptoms usually occurs within as short a