Single Sigmoid Research Articles

FRUIT GROWTH AND DESWEETING AMONG LONGAN (Euphoria longana Lam.) VARIETIES

Fruit growth curves of three longan varieties showed single sigmoid. Seed was the major sink in longan at early fruit development. Aril grew only after seed had approached full development. Early `Yangtaoyeh' grew more rapidly than two later varieties. Desweeting, levels of aril total soluble solids (TSS) increased to maximum and then declined gradually at later fruit development, occurs often in longan. Variation of desweeting rate among varieties was significant. Increases of fruit weight during desweeting (from dates of maximum TSS to end of experiment) were 55.4%, 50.9%, and 7.3% for `Yangtaoyeh', `Fenko', and `Shihyueh', respectively. Periods of water contents increase in aril coincided with the changes of fruit weight of three varieties. Dilution of TSS by water inflow was one of major factor of desweeting in longan fruit. Girdling did not slow down decline of aril total soluble solids.

Growth and compositional changes during the development of prickly pear fruit

Growth and compositional changes in prickly pear (Opuntia spp.) fruit during the development of four species (O. ficus-indica, O. inermis, O. hyptiacantha and O. lind- heimeri) were studied. The weight and size of fruits belonging to O. ficus-indica, O. hyptiacantha and O. lindheimeri generally followed a single sigmoid growth pattern while fruits belonging to O. inermis followed a double sigmoid growth pattern. In all species, soluble solids and ascorbic acid contents increased with a concomitant decrease in titrat- able acidity as fruits matured. O. hyptiacantha consistently had the highest soluble solids and ascorbic acid contents and the lowest titratable acidity while O. lindeimeri consistently had the lowest soluble solids and ascorbic acid contents and highest titratable acidity throughout ontogeny. Although significant differences in soluble solids and ascorbic acid contents were observed, all four prickly pear species exhibited similar trends in compositional changes with growth. Attributes that ...

INTERPRETING FRUIT GROWTH: PROBLEMS AND POSSIBLE SOLUTIONS

Fruits of different species grow in different patterns (such as the “double sigmoid” of stone fruits and grapes or the apparent single sigmoid of apples), and each has periods of cell division followed by periods of only cell expansion. It should not be expected that one mathematical growth description would hold for all species, or even at all times of the season for one species. Perhaps hybrid growth models need to be developed, although specific questions asked about fruit growth may be satisfactorily answered with models of only parts of the fruit growth period of interest.

THE SINGLE ROOTS SIGMOID MODEL IN ENZYME KINETICS

The single roots sigmoid model of population dynamics is proposed as a mechanism for enzyme kinetics. Within this paradigm enzyme co‐operativity is analyzed, deriving an alternate formulation for the Hill coefficient and the binding polynomials.

Effect of Stage of Development on Postharvest Behavior of Cucumber Fruit

Abstract Parthenocarpic cucumber fruit (Cucumis sativus L. cv. Deliva) were harvested from 3 to 30 days after an thesis. Fresh weight increase followed a single sigmoid curve. Commercial maturity was attained 10 to 11 days after anthesis, and these mature fruit had a 20- to 30-day shelf life and good color retention at 20°C. Chlorophyll content at harvest decreased with fruit age. Fruit harvested before commercial maturity showed declining rates of CO2 and C2H4 production at 20°, while commercially mature fruit maintained relatively constant rates throughout their holding period. Fruit harvested after commercial maturity showed increased respiration during holding; this increase was greatest for 30-day-old fruit. Fruit harvested 20, 25, and 30 days after anthesis showed peaks of C2H4 production during holding; this production was most pronounced for mature fruit.

The characteristics and distribution of monoamine oxidase (mao) activity in different tissues of the rainbow trout, salmo gairdneri

1. Monoamine oxidase (MAO) activity was determined fluorometrically in brain, intestine, kidney and liver tissues of the rainbow trout, Salmo gairdneri. 2. MAO activity was inhibited by various drugs in a concentration-related manner, with single sigmoid inhibition curves, the inhibitors of type A MAO, harmaline and clorgyline being more effective than deprenyl, an inhibitor of type B MAO. 3. Intestine exhibited greatest MAO activity followed by liver and brain with kidney showing least activity. The Michaelis constants ( K m) also showed variability between tissues. 4. Inhibition of MAO by harmaline was non-competitive and dependent on the concentration of substrate present.

Pomegranate fruit development and maturation

SummaryThe development of pomegranate fruit was studied under continental (Bet Shean Valley) and moderate maritime (coastal plain) climatic conditions. Fertile flowers were vase-shaped and developed into fruits. Bell-shaped flowers with few egg cells were sterile and did not produce fruits. Gibberellic acid induced the sterile flowers to develop into small fruits; however, these were devoid of juicy seeds. The growth curve of pomegranate fruits from both climatic regions showed a single sigmoid pattern. The seeds accounted for about half of the fruit weight. The edible juicy tissue of the seeds grew continuously from June to October whereas the internal stone tissue stopped growing and hardened by the end of June. Juice, total soluble solids (TSS) and anthocyanin content increased continuously during maturation while acidity decreased. Fruit of cv Mule’s Head ripens early and has a low acid content, whereas fruit of the late-ripening cv Wonderful has high juice contents, TSS, acids and anthocyanins, and i...

English walnut fruit growth and development

Samples of the ‘Ashley’, ‘Hartley’ and ‘Franquette’ cultivars of English walnut ( Juglans regia L.) were collected at weekly intervals from bloom to harvest, and development of the fruit, embryo and surrounding tissue was followed. The first division of the zygote occurred approximately one week after pollination, by which time the endosperm, nucellus and integument had shown considerable growth. The endosperm first formed cell walls at the 8-celled embryo stage and was completely cellular by the time the embryo contained approximately 64 cells. Rapid growth of the cotyledons started as the shell began to harden at Week 7. Measurement of fruit growth indicated that fresh weight gain in ‘Ashley’ and ‘Hartley’ fruits followed a double sigmoid pattern, characterized by a 3-week period of slowed growth that began approximately 7 weeks after bloom. Rate of increase in total length and diameter also slowed greatly at Week 7. Fresh weight gain in ‘Franquette’ appeared to follow a single sigmoid curve, with no prolonged period of slowed growth corresponding to that in the other cultivars. Kernel growth also described a double sigmoid curve, with its initial, rapid phase nearly coincident with the beginning of Stage III of the whole-fruit, fresh-weight curve at Week 10.

Effects of inhibitors on monoamine oxidase activity in perch (Perca flavescens) brain in vitro

1. Perch brain homogenates were incubated in vitro and monoamine oxidase (MAO) activity was determined fluorometrically, using a kynuramine substrate. 2. Clorgyline, harmaline and deprenyl inhibited MAO activity in a concentration-related manner, with single sigmoid inhibition curves, and the type A inhibitors harmaline and clorgyline were more effective than the type B inhibitor deprenyl. 3. Two types of inhibition were recognized in vitro; a fast-onsetting inhibition, similar to that produced by a reversible inhibitor, and a slow-onsetting inhibition, which is time- and concentration-dependent and presumably represents inactivation of the enzyme.

Monoamine oxidase types A and B in the vertebrate brain

1. Monoamine oxidase (MAO) activity was measured in brains of teleosts, amphibians, a reptile, birds and mammals. Selective inhibitors were used to determine the relative proportion of MAO type A and MAO type B. 2. Brain homogenates of all tetrapods showed double sigmoid inhibition curves, indicating the presence of both forms of MAO. 3. Brain homogenates of all teleosts showed single sigmoid inhibition curves, with greater sensitivity to type A inhibitors. 4. These results indicate that tetrapod brains contain both type A and type B MAO activity, whereas teleost brains contain only a type A-like enzyme. 5. It is possible that the presence of two forms of MAO in brain may confer an advantage to a terrestrial lifestyle.

Phenylethanolamine is a specific substrate for type B monoamine oxidase

The characteristics of phenylethanolamine as both a competitive inhibitor and as a substrate for monoamine oxidase (MAO) were studied using rat brain and liver homogenates. Although phenylethanolamine, even at high concentrations (1 mM), produced minimal inhibition of MAO when serotonin (a substrate for type A MAO) was used as the substrate, it was a potent competitive inhibitor (K i =11 μM) of the deamination of phenylethylamine (a substrate for type B MAO). When phenylethanolamine was used as a substrate, deprenyl, a selective inhibitor of type B MAO, was found to produce a single sigmoid inhibition curve at low concentrations of the inhibitor (pI 50=7.5). These results indicate that phenylethanolamine is a specific substrate for type B MAO. Identification of the products formed under the assay conditions show that phenylethanolamine is converted to both mandelic acid and phenylethylene glycol by liver homogenates but only to the latter, neutral metabolite by brain homogenates.

Studies of monoamine oxidases: Inhibition of bovine brain MAO in intact mitochondria by selective inhibitors

The inhibition of mitochondrial monoamine oxidase (MAO) from beef brain cortex by the selective inhibitors, clorgyline, harmaline, Deprenyl and pargyline, was compared using five substrates: serotonin (5-HT), β-phenylethylamine (PEA), tyramine, tryptamine and dopamine. Dose-response studies, consistent with the classification of MAO, types A and B, indicated that serotonin deamination was more sensitive to clorgyline and harmaline inhibition than was phenylethylamine. However, the curves for all substrates were double-sigmoidal, rather than being a single sigmoid curve for 5-HT and PEA. Deprenyl and pargyline did not exhibit any marked selectivity for inhibiting PEA deamination without prior preincubation of enzyme and inhibitor. The rate of inhibition was variable and was dependent upon the substrate, the nature of the inhibitor and the inhibitor concentration. Dual inhibitor studies, using the “type A” inhibitor, clorgyline, and the “type B” inhibitor, Deprenyl, together, resulted in almost complete MAO inhibition, regardless of substrate. Combining the two type A inhibitors, clorgyline and harmaline, or the two type B inhibitors, deprenyl and pargyline, resulted in inhibitions that were equal to or only slightly greater than the inhibition produced by a single inhibitor. These results suggested that there are at least two distinct sites in beef brain MAO from cortical mitochondria which may be interacting. The deamination of all substrates occurs at both sites.

The tamarillo: Fruit growth and maturation, ripening, respiration, and the role of ethylene

AbstractThe tamarillo (tree tomato, Cyphomandra betacea Sendt.) flowers and sets fruit over an extended period. Many blossoms and young fruits abscise; survival of tagged fruitlets ranged from 0 to 32%. Tagged fruits were harvested at known ages for measurement of size and shape, respiration rate, ethylene production, and response to ethylene treatment. Fruit growth followed a single sigmoid pattern, and fruits were commercially mature at 21–24 weeks after anthesis. The amount of red skin pigment increased with age from 15 weeks, but harvesting of immature fruits appeared to stop red pigment development. Fruits harvested at 12–19 weeks or younger shrivelled in storage. Respiration studies showed tamarillo fruits to be non‐climacteric, and only traces of ethylene were produced until final senescence. Ethylene treatment increased the respiration rate and hastened senescence of harvested fruits of all ages. The yellow strain behaved similarly to the red and had a somewhat longer storage life.

Inhibition of mitochondrial monoamine oxidase of the rat uterus and liver by clorgyline, pargyline and harmine

The inhibition of mitochondrial monoamine oxidase (MAO) activity in rat uterus and liver by clorgyline, harmine and pargyline is reported. MAO activity is shown to be present in mitochondria of the rat uterus by rate-zonal centrifugation on a sucrose gradient. Each inhibitor was tested for its ability to inhibit the oxidation of tyramine (TYN). 5-hydroxytryptamine (5HT) and β-phenylethylamine (PEA). TYN deamination by uterine organelles was inhibited in two distinct steps by clorgyline and harmine, whereas in liver mitochondria only clorgyline manifested the two-step inhibition pattern. Elimination of TYN oxidation by pargyline occurred as a single sigmoid curve. Single sigmoid inhibition curves with all three inhibitors were also observed for 5HT and PEA in both tissues. For uterine and liver mitochondria the relative effectiveness of each inhibitor toward the oxidation of the three substrates was as follows: (a) clorgyline and harmine. 5HT > TYN > PEA; (b) pargyline. PEA > TYN > 5HT. It was concluded that, as has been previously demonstrated in liver, two forms of MAO exist in mitochondria isolated from the rat uterus. This conclusion is based upon (1) the biphasic inhibition of TYN deamination by clorgyline and harmine and (2) the reversal of the relative inhibitory effectiveness of the two classes of MAO inhibitors, (a) clorgyline and harmine and (b) pargyline, toward the three substrates. Semicarbazide did not inhibit the oxidation of any of the substrates. This indicates that the mitochondrial enzyme activity from the uterus, as in the liver, is a true monoamine oxidase.

Development of Seeded and Parthenocarpic Fruits in Mulberry (Morus RubraL.)

SummaryOpen-pollinated fruits of the ‘Tufts’ mulberry (Morus rubra L.) were studied throughout the 1969 growing season. Growth of the multiple fruit followed the double sigmoid pattern characteristic of drupaceous fruits. Growth of the accessory fruitlet (pistil plus persistent calyx), the sepals, which become succulent as the fruitlet ripens, and the ovary also followed the double sigmoid curve. Since the mulberry ovary is similar to that of fleshy drupaceous fruits both morphologically and in growth pattern, it should be classified as a drupelet rather than as an achene or nutlet. The growth pattern for seeds is a single sigmoid curve, but growth continues during the plateau (period 2) of the ovary growth curve. In typical drupes the integuments attain their ultimate size during period 1 of the curve.About 45% of the open-pollinated fruitlets examined in 1969 were seedless, but had growth curves similar to those of their seeded counterparts. ‘Tufts’ and ‘Hicks’ inflorescences bagged in 1970 to prevent p...

Studies on fruiting, bearing habit and fruit growth of jackfruit germplasm

Studies on fruiting, bearing habit and fruit growth of jackfruit was carried out at orchard of Jackfruit Research Project, Department of Horticulture, Bangladesh Agricultural University (BAU), Mymensingh during the period from November 2000 to October 2001. Ten jackfruit germplasm of 13 years of age were selected for this study. Fruit bearing habit of jackfruit was cauliflorous i.e., fruits are borne on trunk and branches. The germplasm under study bore fruits on trunk, primary, secondary, tertiary, fourth, fifth and sixth branches of jackfruit trees. On an average, the maximum fruits were borne on primary branches (33.0%) followed by those on trunk (31.5%), secondary (12.3%), and fourth branch (8.4%), while it was the lowest on sixth branch (2.0%). The growth pattern of fruit of jackfruit is characterized by single sigmoid curve. This is true when all aspects of measurements viz, length, diameter, circumference, weight, and volume of fruits; length, breadth, weight of bulb as well as seed were plotted against time from fruit set to haiwesting maturity. Key Words: Bearing habit, fruit growth, jackfruit germplasm. doi:10.3329/bjar.v33i3.1598 Bangladesh J. Agril. Res. 33(3) : 391-397, September 2008

Growth and Development of the Green Frog, Rana clamitans, Under Natural Conditions

Compared to other vertebrates, relatively little is known concerning the rate of growth and development (other than embryonic) of amphibians in nature. In the laboratory, on the other hand, many physiological experiments, most of which concern the influence of endocrine secretions on the rate of growth and development of amphibians, have been reported. Noteworthy among these is the work of Swingle (1919, 1922) who studied the accelerating effect of thyroid extracts on metamorphosis. He found also that iodine or its inorganic compounds induced early transformation of amphibians. Many laboratory studies have been macie of the rate of growth of amphibian larvae. In general, most of these studies, especially the more critical ones, deal with salamanders. Wilder (1924) pointed out that the curve representing the larval growth of Eurycea bislinedta is sigmoid and Patch (1927) showed that two sigmoid curves are produced by Ambystoma maculatum and A. tigrinum as they increase in length, one curve being embryonic and the other larval. Later, Dempster (1930) found that the growth in weight of embryonic and larval A4. maculatum under natural conditions may be expressed as a single sigmoid curve. Among the reports dealing with the growth of frog larvae are those of Davenport (1899) and Schaper (1902). They presented rather complete data on the larval growth in weight and volume of European species of Rana resulting from the acquisition of water, organic matter and ash. More recently, Burgess (1950) made a comparative study of the increase in body dimensions of larval Scaphiopus hammondi'i, some of which were reared in tap, water and others in field-collected water. With regard to the growth of transformed amphibians, only a few cobser. vations have been made. These are limited to the frogs and toads. Some data on the growth of Rana pipiens determined by study of length-frequency curves based on large numbers of individuals taken at the same timne, have been presented by Force (1933). From recapture data obtained from 20 marked Bufo lerrestris, Hamilton (1934) concluded that young toads double their length and are sexually mature by the time they are two years of age. Raney and Ingram (1941) found considerable variation in the rate of growth of Rana catesbeiana, reporting that the average bullfrog reaches sexual maturity in about a year following transformation and attains a size near the maximum during the subsequent year. Raney and Lachner (1947) reported that adult Bufo terrestris grow slowly and probably reach their maximum letfgth in three or four years.

The Relation between the Intensity of Light and the Electrical Excitability of the Human Retina

The electrical excitability of the human retina becomes supernormal after an illumination of the eye. The maximum increase ζ in electrical excitability expressed in percentage of the excitability in the dark varies with intensities of illumination. The relation between ζ and log intensity is represented by a single sigmoid curve at the fovea, but consists of two different sections outside the fovea. The double nature of the peripheral measurements very likely represents. rod function for the low intensity section and cone function for the high intensity section. The data for both cones and rods are adequately described by Hecht's equation KI=ζ2/(α-ζ)2.

INTERMITTENT STIMULATION BY LIGHT

When measurements of the critical fusion frequency for white light over a large range of intensities are made with the rod-free area of the fovea, the relation between critical frequency and log I is given by a single sigmoid curve, the middle portion of which approximates a straight line whose slope is 11.0. This single relation must be a function of the foveal cones. When the measurements are made with a retinal area placed 5 degrees from the fovea, and therefore containing both rods and cones, the relation between critical frequency and log I shows two clearly separated sections. At the lower intensities the relation is sigmoid and reaches an upper level at about 10 cycles per second, which is maintained for 1.25 log units, and is followed by another sigmoid relationship at the higher intensities similar to the one given by the rod-free area alone. These two parts of the data are obviously separate functions of the rods at low intensities and of the cones at high intensities. This is further borne out by similar measurements made with retinal areas 15 degrees and 20 degrees from the fovea where the ratio of rods to cones is anatomically greater than at 5 degrees . The two sections of the data come out farther apart on the intensity scale, the rod portion being at lower intensities and the cone portion at higher intensities than at 5 degrees . The general form of the relation between critical frequency and intensity is therefore determined by the relative predominance of the cones and the rods in the retinal area used for the measurements.

THE GROWTH OF LARVIÆ OF AMBYSTOMA MACULATUM UNDER NATURAL CONDITIONS

1. Growth in weight of embryonic and larval Ambystoma maculatum from the time that eggs are deposited to the period of metamorphosis may be expressed as a single sigmoid curve.2. The length curve, except for a short period before hatching when the embryonic axis is curved, is likewise sigmoid.3. The Ambystoma population of a pond is quite homogeneous, the specimens metamorphosing at approximately the same time.4. Under natural conditions the relation between weight and length from year to year seems to be constant during the stages before feeding. Later the relationships are variable because of feeding differences.5. Growth to the time of food ingestion is associated with imbibition of water. Later growth to the time of emergence of the salamanders is correlated with a process in which the percentage of water content decreases. During this period the inorganic constituents gradually increase.