Flower-Inducing Activity of Water Extract of Lemna

Flowering of Lemna paucicostata 441 (P441), a sensitive short-dayplant (SDP), was promoted under a near critical photoperiodby the crude water extract of the same plant added to the medium.The extract induced flowering in L. paucicostata 151 (P151),a weakly responsive SDP, under continuous light. The activityfor P151 was greatly promoted by simultaneous application ofbenzyladenine, and the extract of only 0.3 mg fr wt plant addedto 10 ml of assay medium with 1 µM benzyladenine was active.Active substance(s) was similarly obtained from both flower-inducedand non-induced plants, and more or less from all species andstrains of Lemna tested, including P151. However, the extractof short-day strains was more active than that of L. gibba G3(G3), a long-day strain. G3 responded only slightly to the extractof either P441 or G3, whereas P151 responded far more stronglyto the extract of P441 than to that of G3. (Received April 17, 1989; Accepted August 10, 1989)     

ADIPOR1 deficiency-induced suppression of retinal ELOVL2 and docosahexaenoic acid levels during photoreceptor degeneration and visual loss

Lipid metabolism-related gene mutations can cause retinitis pigmentosa, a currently untreatable blinding disease resulting from progressive neurodegeneration of the retina. Here, we demonstrated the influence of adiponectin receptor 1 (ADIPOR1) deficiency in retinal neurodegeneration using Adipor1 knockout (KO) mice. Adipor1 mRNA was observed to be expressed in photoreceptors, predominately within the photoreceptor inner segment (PIS), and increased after birth during the development of the photoreceptor outer segments (POSs) where photons are received by the visual pigment, rhodopsin. At 3 weeks of age, visual function impairment, specifically photoreceptor dysfunction, as recorded by electroretinography (ERG), was evident in homozygous, but not heterozygous, Adipor1 KO mice. However, although photoreceptor loss was evident at 3 weeks of age and progressed until 10 weeks, the level of visual dysfunction was already substantial by 3 weeks, after which it was retained until 10 weeks of age. The rhodopsin mRNA levels had already decreased at 3 weeks, suggesting that reduced rhodopsin may have contributed to early visual loss. Moreover, inflammation and oxidative stress were induced in homozygous KO retinas. Prior to observation of photoreceptor loss via optical microscopy, electron microscopy revealed that POSs were present; however, they were misaligned and their lipid composition, including docosahexaenoic acid (DHA), which is critical in forming POSs, was impaired in the retina. Importantly, the expression of Elovl2, an elongase of very long chain fatty acids expressed in the PIS, was significantly reduced, and lipogenic genes, which are induced under conditions of reduced endogenous DHA synthesis, were increased in homozygous KO mice. The causal relationship between ADIPOR1 deficiency and Elovl2 repression, together with upregulation of lipogenic genes, was confirmed in vitro. Therefore, ADIPOR1 in the retina appears to be indispensable for ELOVL2 induction, which is likely required to supply sufficient DHA for appropriate photoreceptor function and survival.Subject terms: Mechanisms of disease, Developmental neurogenesis     

Integrated model incorporating circadian phase dynamics and the thermoregulatory mechanism of sleep

Sleep and Biological Rhythms - Recently, physiological findings have suggested the existence of an integrated regulatory mechanism for sleep-wake rhythms, as follows. Homeostatic regulation of the...     

Fast trigonal/tetragonal interconversion followed by slow chelate-ring closure in the complexation of boronic acids

Which of the step is rate determining in the complexation of boronic acid with bidentate ligands, the first trigonal/tetragonal interconversion step or the following chelate-ring closure step ? No one could have ever answered this simple question clearly. In this study, we for the first time gave an explicit answer to this question. Reaction systems were devised for kinetic measurements to answer this simple question. At first, pK_a values of 15 boronic acids were determined spectrophotometrically at I = 1.0 M and 25 °C: pK_a = 6.40 ± 0.06 for 3,5-Cl₂PhB(OH)₂, 6.62 ± 0.03 for 3,5-(CF₃)₂PhB(OH)₂, 6.95 ± 0.09 for 3,5-Br₂PhB(OH)₂, 7.04 ± 0.03 for 3-NO₂PhB(OH)₂, 7.08 ± 0.03 for 3,5-F₂PhB(OH)₂, 7.12 ± 0.02 for 2,4-F₂PhB(OH)₂, 7.39 ± 0.02 for 4-CF₃PhB(OH)₂, 7.50 ± 0.02 for 3-FPhB(OH)₂, 7.83 ± 0.02 for 2-FPhB(OH)₂, 7.87 ± 0.01 for 3-CF₃PhB(OH)₂, 8.11 ± 0.01 for 2-ClPhB(OH)₂, 8.14 ± 0.03 for 3-(COOH)PhB(OH)₂, 8.15 ± 0.03 for 3-(CH₃CO)Ph(OH)₂, 8.20 ± 0.01 for 3-ClPhB(OH)₂, and 8.66 ± 0.05 for 4-FPhB(OH)₂. The kinetic results for the reactions of some of these boronic acids with 4-isopropyltropolone clearly show that the rate-determining step is not the interconversion step but the chelate-ring closure step.     

Effect of time-varying load on degree of bronchoconstriction in the dog

It is wellestablished that the degree of airway smooth muscle shortening producedby a given dose of bronchial agonist is greatly affected by lungvolume. The airways are tethered by parenchymal attachments, thetension of which increases progressively with lung volume, therebypresenting a commensurately increasing hindrance to smooth musclecontraction. Earlier studies (P. F. Dillon, M. O. Aksoy, S. P. Driska,and R. A. Murphy. Science 211:495-497, 1981) presented evidence that smooth muscle contractioninitially involves rapidly cycling cross bridges, whichthen change to noncycling (latch) bridges. They also suggested thatmost of the muscle shortening occurs during the early rapidcross-bridge phase. This implies that smooth muscle subject to a givenload early in contraction should shorten less than when it is subjectto the same load later on. An in vitro study (W. Li and N. L. Stephens.Can. J. Physiol. Pharmacol. 72:1458-1463, 1994) obtained support for this notion. To test thishypothesis in vivo, we measured the changes in lung impedance at 1 and6 Hz produced in dogs by a bolus intravenous injection of methacholinewhen lung volume was increased for 10 s at different times afterinjection. We found that the changes in mechanics were greatlyinhibited, whereas lung volume was elevated. However, when lung volumewas returned to its initial level, the lung mechanics continued tochange at a rate unaffected by the preceding volume change. We concludethat temporary mechanical inhibition of airway smooth muscle shorteningin the normal dog in vivo merely delays an otherwise normal course ofcontraction.