Proton Efflux from the Outer Layer of the Peduncle of Tulip in Gravitropism and Circumnutation*

Epidermal plus hypodermal peels from tulip peduncles produced bands of acidity on agar containing bromocresol purple. Peels from horizontally oriented peduncles gave rise to an acidity band which corresponded to the lower side of the peduncle. The band began 3–6 cm beneath the flower and extended basipetally within the region of gravitropic bending. No corresponding band appeared in an agar layer laid on the cortical surface exposed by peeling. Peduncles growing in the normal vertical position showed circumnutations with a period in the range of 4 h. The peels from these stalks produced one or two bands more acid than the remaining part of the peel. Since the acidity band in horizontally positioned stalks corresponds to the zone of faster growth causing gravitropic bending, we infer that the band(s) produced by vertical stalks also correspond to zones of differential growth involved in circumnutation. On the basis of a previous finding that tulip leaves give rise to an oscillating acidity pattern, we infer that vertical stalks also show such a pattern. This inference fits the model proposing the involvement of an internal oscillator in circumnutation. However, the ratio of the circumnutation period to the gravitropic lag phase in tulip peduncles is such as predicted by the gravitropic-feedback model of circumnutation.     

Molybdenum in infancy: Methodical investigation of urinary excretion

PROJECT: The clinical evaluation of trace element metabolism in infancy is based on optimal pre-analytical procedures. Urinary molybdenum excretion, the major determinant of its retention, was investigated to deduce criteria for representative specimen collection. PROCEDURES: 1.) Molybdenum concentration was analyzed in 24-hour urinary specimens (n = 193) to evaluate the range in pediatric patients. 2.) In 20 children aged 0.4 to 9.3 (mean 2.3) years admitted for a micturition cystourethrogram, three urinary collection methods (catheter, spontaneous midstream samples, urinary collection bags) were compared. 3.) Diurnal variations of molybdenum concentration were assessed by fractional urinary colLection in preterm infants fed infant formula or human milk (n = 10). Analysis was performed using atomic absorption spectroscopy. RESULTS: 1.) The molybdenum concentration in 24hour specimens was 4.0 (0-123) microg Mo/l. 2.) Urine gained by catheter collection (n = 20) rendered 7.0 (0.5-60.1) microg Mo/l, midstream samples and the use of urinary collection bags showed a concentration of 21.25 (0-91) microg Mo/l (p > 0.05). 3.) Fractional collection over 72 hours rendered a significant increase in only one participant. Diurnal differences of the urinary molybdenum concentration were significant between 3-6 p.m. and 6-9 p.m.. The molybdenum/creatinine quotient differed between the time intervals 3-6 p.m. and 9-12 p.m., as well as 9-12 a.m. and 6-9 a.m. (p < 0.05). CONCLUSION: Pediatric routine procedures are suitable for the assessment of urinary molybdenum excretion. The diurnal variations assessed are of minor clinical relevance, but should be considered by respective definition of collecting times and reference values.     

Molybdenum metabolism: Stable isotope studies in infancy

The essential trace element molybdenum (Mo) is bound to and required for the function of molybdoenzymes, e.g. sulfite and xanthine oxidase. Dietary recommendations for early infancy are based on limited knowledge about its metabolism. 100Mo was used as an extrinsic tag to study the absorption and kinetics of excretion in infancy. 10 infants with a gestational age of 35 (30-39) weeks, a birth weight of 2.0 (0.9-2.3) kg and a post-natal age of 20 (10-54) days were studied. They received 25 microg 100Mo/kg with a feed of human milk or formula. Fractional urinary and fecal collections were conducted preceding the 100Mo intake and for 48-72 hours afterwards. The materials were analyzed by atomic absorption spectroscopy and inductively coupled plasma mass spectrometry. The median absorption of 100Mo intake was 97.5 (96.3 to 99.1) %. The retention of nutritive Mo intake and 100Mo in the study period was 11.2 (3.8-15.7) microg Mo/kg, equivalent to 35.7 (12.7-55.6) %. The Mo concentration increased to a peak value in urine within 8 (6-13) hours and in feces within 24 (7-48.5) hours. In addition, increases of copper in feces and urine were observed in 8 of 9 infants studied. Mo given orally is well resorbed in premature infants, and predominantly excreted in the urine. Dietary recommendations should prevent excessive intakes in infancy.     

Influence of myocardial isomyosins on cardiac performance and oxygen consumption

There was 21% isomyosin V1 in the 12 month SHR (Spontaneous Hypertensive Rat) and 70% isomyosin V1 in the 6 month WKY (Wystar-Kyoto), nevertheless there was no difference in maximum developed pressure nor maximum dP/dt in the isovolumically beating hearts of the two sets of animals. [Hearts were perfused with hypercalcemic perfusate in the presence of isoproterenol (10(-7)M)]. There was, however, a a 32% reduction in oxygen consumption per gram of dry weight per beat in the 12 month SHR as compared to the 6 mo WKY. Associated with a shift towards isomyosins V2 and V3 in the 6 and 12 month WKY and SHR there was no corresponding change in maximum dP/dt nor developed pressure, but there was a conservation in oxygen consumption.     

Characterization of the microflora of high acid submerged vinegar fermenters by distinct plasmid profiles

Summary Since isolation of the Acetobacter strains responsible for ethanol oxidation in high acid, submerged vinegar fermentations is still extremely difficult, characterization of the vinegar microflora was approached by isolation and gel electrophoresis of plasmids extractable from the harvested microorganisms. Distinct plasmid profiles have been detected in all of 19 investigated fermenters from 5 different locations. Plasmid sizes varied between 1.3 and 133 Megadalton. Between 3 and 11 different plasmids were recognized in particular profiles. Comparison of these profiles from different sources proves that the plasmid profile of a vinegar fermenter is a unique property of the inherent microflora which allows definite conclusions regarding its stability, origin, identity and composition.     

Absolute β-catenin concentrations in Wnt pathway-stimulated and non-stimulated cells

The intracellular level of the proto-oncoprotein β-catenin is a parameter for the activity of the Wnt pathway, which has been linked to carcinogenesis. The paper introduces a novel sandwich-based ELISA for the determination of the β-catenin concentration in lysates from cells or tissues. The advantages of the method were proven by determining β-catenin levels in cell lines and in cells after activation of the Wnt pathway. Analysis revealed high β-catenin concentrations in the cell lines HeLa, KB, HT1080, MCF-7, U-87 and U-373, which had not been described before. β-Catenin concentrations were compared in HEK293 and C57MG cells after activation of the Wnt pathway. The β-catenin concentrations increased by different factors depending on whether the Wnt pathway was activated by incubation with LiCl or with Wnt-3a-conditioned medium. This finding indicated that the β-catenin level depends on the way and level of Wnt pathway activation. The quantitative analysis of β-catenin in colorectal tumours revealed high β-catenin levels in tumours with truncating mutations in the APC gene.     

Weak Mechanical Stimulation Causes Hyperpolarisation in Root Cells of Lepidium

Abstract: In order to study the effect of mechanical stimulation on the membrane potential (E_m) of roots of Lepidium sativum L., the roots were subjected to pulses of perfusion medium expelled from a micropipette positioned 1 mm from the root surface at the level of the elongation zone. On the opposite side of the root, a microelectrode was inserted into rhizodermal or cortical cells of the elongation zone to record the membrane potential during such a pulse. A medium pulse elicited a fast transient hyperpolarisation of up to ?38 mV, reaching a peak approx. 1 min after the start of a pulse. Both degassing the medium and increasing the buffer strength had no effect on the magnitude of the pulse-induced hyperpolarisation. Covering the roots with Parafilm, and thereby preventing an exchange of medium in the vicinity of the root during a pulse, while still providing a mechanical stimulus, also did not abolish the response. We conclude that Lepidium roots are capable of perceiving extremely weak mechanical stimuli (less than 1 mN) which induce rapid transient hyperpolarisations of the plasma membrane.