Unloading Mechanism Research Articles

Stability Analysis of the Abutment Slope in one Hydropower Station Based on Unloading Rock Mass Mechanics

After the excavation of abutment slope, the stress redistributed and the rock mass quality degradation damaged. According to fore-and-aft change of stresses for excavation, the authors divided excavation area and chose suitable mechanical parameters of rock mass for different excavation area. We used theory and methods of unloading rock mass mechanics and used elastic-plastic viscous damage mechanics model to give 2-D finite element analysis of stress and strain for typical profiles. And then we analyzed the changes of stress and deformation of the slope at nature and unloading conditions, analyzed deformation and stability at different reinforcement areas of the slope to choose reasonable reinforcement area. Strengthening plans of rock mass are analyzed and compared to choose reasonable reinforcement plan. The research results herein can offer beneficial reference for the design and the construction engineers.

Factor analysis prediction of effective stress from measurable rock attributes and calibration data

We show how to apply the statistical factor analysis method to effective stress prediction from seismic attributes. Two examples are discussed, one based on a laboratory dataset and relevant to the unloading mechanisms of abnormal pore pressure generation, and the other based on well data and a seismic section, relevant to the compaction disequilibrium mechanism. Arguably, this method of seismic interpretation is superior to the existing deterministic and statistical approaches as it reduces the multitude of available seismic attributes to a small number of factors most relevant to the effective stress and,in addition, provides a mathematically systematic way of arriving at most probable effective stress values as well as the confidence range.

Research on Improving Rock Slope Fuzzy-Precise Evaluation Method

The rock mass quality classification method was introduced for the strength parameters and deformation parameters when carrying out quantitative classification and provided a theoretical basis; Introducing unloading rock mechanics theory, the infiltration conditions of the surface, drainage measures , catchment area as well as the subsequent impact of buildings on the slope were considered in order to increase the coverage of evaluation factors; Considering finite element analysis results of three-dimensional model and reference targets selected , one kind of improved numerical analysis method based on fuzzy - accurate evaluation of slope stability was proposed. The method is based on finite element model of the calculation results and the appropriate references selected, having the calculation analysis of certain factors on the slope stability a quantitative treatment, thus objectively established the weight ratio between these factors, avoiding subjective awareness in expert scoring impacting evaluation results too large. With practical engineering analysis it shows: the method is directed against rock slope analysis , make more factors impacting rock slope stability involved in evaluation, and easy to operate.

Back Analysis about Shear Strength and Deformation Parameters of High Excavated Accumulation Slope in Xiaowan Hydropower Station

Proper mechanical parameters of slope rock mass are the premise which ensures the smooth progress of slope stability calculation. By analyzing the geological information of the yinshuigou accumulation slope on ridge 2 in Xiaowan hydropower station, and according to the deformation and damage in the excavation of the accumulation slope, this paper inverts the shear strength parameters of the accumulation slope by using 2D rigid limit equilibrium method. On base of unloading rock mass mechanics methods, the stress and strain analysis to the accumulation slope is studied by using 3D finite difference method, and by contrast of the monitoring displacement and calculated displacement in slope-direction about the key point of the accumulation slope , the article inverts the deformation parameters of the accumulation slope. Finally, the shear strength parameters in the contact zone are ascertained as: C=0.04MPa, Φ=30°, and the deformation parameter of the accumulation slope is changed from the initial 1.5MPa to 0.95MPa by the damage unloading.

Vasopressin Pituitary Stores Acutely Released in Vasodilatory and Hypovolemic Shock Are Not Immediately Restored With Prolonged Hypotension

Insufficient release of vasopressin (VP) in maintaining elevated circulating VP levels in response to shock is not well understood. Thus, we compared VP responses in anesthetized 8 kg pig models of vasodilatory or hypovolemic shock in the first 4 hours after endotoxin (ETX n=8), hemorrhage (HEMO n=11), or partial cardiopulmonary bypass (ECMO n=9), with that of controls (CON n=9). Mean arterial pressures (MAP) were 88±6, 54±3, 48±8, and 82±4 mmHg, respectively for CON, ETX, HEMO, and ECMO. With ETX, plasma VP levels (pVP) increased with decreased pulmonary arterial and wedge pressures, indicating an intact baroreceptor unloading mechanism for VP stimulation. In hemorrhage, pVP negatively correlated (r=0.97, p<0.01) with decreased MAP indicating VP release in response to hypovolemia. During ECMO, pVP directly correlated (r=0.72, p<0.05) with MAP, unmasking VP influence on maintaining MAP, not normally seen under control conditions. Overall, pVP increased with increased hypothalamic VP mRNA expression. However, pituitary VP content after 4 hours of shock was significantly less (p<0.01) in ETX (257±43 mU) and HEMO (751±92 mU) compared to CON (2139±350 mU) or ECMO (1357±314 mU). Results suggest that while the body responds within the first minutes of a sudden drop in blood pressure with immediate release of VP stores, these stores become depleted, and sustained synthesis does not keep up with prolonged hypotension.

Res-Erection of Viagra as a Heart Drug

In 1998, the world was formally introduced to Viagra (sildenafil), the first oral agent to be approved in the United States for the treatment of erectile dysfunction. Developed by Pfizer chemists, sildenafil inhibited phosphodiesterase type 5 (PDE5), one of the 11-member superfamily of enzymes that hydrolyze cyclic nucleotide monophosphates and among the first discovered that was selective for cGMP. PDE5 had been identified more than 2 decades earlier, first as a protein that bound cGMP and later as one that hydrolyzed it (the binding function turning out to be a mechanism to regulate activity).1 Sildenafil induces vasorelaxation by blocking PDE5-cGMP hydrolysis, raising cGMP levels in smooth muscle to activate protein kinase G (also known as cGK). In platelets, this blunts thrombosis; together, the effects suggested a potential use for coronary vascular disease and hypertension. Pfizer initiated trials targeting coronary ischemia, but, although antianginal effects were disappointing, the study gave a whole new meaning to the term “side effect,” effectively hijacking sildenafil from cardiovascular development to a rather different indication. Article see p 8 There were still some cardiovascular studies performed, but essentially all were limited assessments of volunteer populations, mostly normal and at rest and some with cardiovascular disease; the results were interpreted to support safety for patients taking the drug. In particular, blood pressure changes were slight if present at all, and cardiac function appeared unaltered. Well into the mid 2000s, PDE5 was thought to be expressed in selective vascular beds, lung and corpus cavernosum being dominant, and to have a minor cardiovascular profile elsewhere, with a negligible role in the heart. Sildenafil reemergence as …

Finite element modeling of high-pressure deformation and phase transformation of silicon beneath a sharp indenter

Modeling of the mechanical response of single crystalline silicon to a sharp indenter is an essential step for the optimization of wafer manufacturing processes. In this paper, deformation of silicon during indenter loading and unloading was analyzed by the finite element method, and the changes of stress field and high-pressure phase distribution were dynamically simulated. We found that the deformation of silicon in nanoindentation can be simply characterized by two factors: one is the elastic strain of each high-pressure phase and the other is the equivalent elastic strain of each phase transformation. In loading, indentation energy is absorbed mostly by phase transformation, and accumulated as the elastic strain of the high-pressure phases. The distribution pattern of the high-pressure phases beneath the indenter is independent of the indentation load, and the depth of the phase-transformed region is approximately twice the indentation depth. In unloading, high-pressure phases except the β-Sn phase undergo reverse phase transformations. The β-Sn phase does not transform back to the diamond phase but changes to other non-equilibrium phases, which becomes the dominant reason for residual strain. During unloading, the non-equilibrium phase expands from the diamond phase region toward the indenter tip, while the boundary between the non-equilibrium phase and the diamond phase remains unchanged. The unloading mechanism is independent of the change in the maximum indentation load and the presence/absence of pop-out events.

Coupled effect of size, strain rate, and temperature on the shape memory of a pentagonalCu nanowire

A body-centered pentagonal nanobridge structure with lattice constantsc = 2.35 and a = 2.53 Å has been observed under high strain rate tensile loading on an initially constrained Cu nanowire at various temperatures. Extensive molecular dynamics (MD) simulations have beenperformed using the embedded atom method (EAM) for cross-sectional dimensions ranging from0.723 × 0.723 to2.169 × 2.169 nm2, temperature ranging from 10 to 600 K, and strain rates of109–107 s−1. Formations of such pentagonal nanowire are observed for a temperature range 200–600 Kfor particular cross-sectional dimensions and strain rates. A large inelastic deformation of∼50% is obtained under both isothermal loading and adiabatic loading. With very high degree ofrepeatability of such pentagonal nanowire formation, the present findings indicate that theinteresting stability property and high strength of elongated nanowires have variouspotential applications in nanomechanical and nanoelectronic devices. Further,we demonstrate a novel thermomechanical unloading mechanism by which it ispossible to impart recovery from a pentagonal nanowire following a hysteresisloop: .

Mechanism of buckling development and strain reversal occurrence in elastic–plastic cylindrical shells under axial impact

In order to clarify the mechanism of loading and unloading, buckling growth, and strain-reversal occurrence in elastic–plastic cylindrical shells that are impacted axially, non-linear dynamic equations in incremental form are derived and solved by using the finite difference method. The validity of the developed theory is verified by comparing theoretical and experimental results. From the calculation results, it is found that, at the initial stage of the impact process, the effective stress related to the middle-surface stresses in the part near the impacted end rises with time, and exhibits plastic loading. The radial restraints on the impacted end have obvious influence on the strain reversal occurrence at an early stage of the impact process. The effective modulus controls the post-buckling deformation of the shell, which contrasts with the situation for the bar to be impacted axially.

Shuttles and cycles: transport of proteins into the peroxisome matrix (Review)

Peroxisomes are organelles that carry out diverse biochemical processes in eukaryotic cells, including the core pathways of beta-oxidation of lipid molecules and detoxification of reactive oxygen species. In multicellular organisms defects in peroxisome assembly result in multiple biochemical and developmental abnormalities. As peroxisomes do not contain genetic material, their protein content, and therefore function, is determined by the import of nuclearly encoded proteins from the cytosol and, presumably, removal of damaged or obsolete proteins. Import of matrix proteins can be broken down into four steps: targeting signal recognition by the cycling import receptors; receptor-cargo docking at the peroxisome membrane; translocation and cargo unloading; and receptor recycling. Import is mediated by a set of evolutionarily conserved proteins called peroxins that have been identified primarily via genetic screens, but knowledge of their biochemical activities remains largely unresolved. Recent studies have filled in some of the blanks regarding receptor recycling and the role of ubiquitination but outstanding questions remain concerning the nature of the translocon and its ability to accommodate folded, even oligomeric proteins, and the mechanism of cargo unloading and turnover of peroxisomal proteins. This review seeks to integrate recent findings from yeast, mammalian and plant systems to present an up to date account of how proteins enter the peroxisome matrix.

The developmental and organ specific expression of sucrose cleaving enzymes in sugar beet suggests a transition between apoplasmic and symplasmic phloem unloading in the tap roots

Sucrose utilisation in sink tissues depend on its cleavage and is mediated by two different classes of enzymes, invertase and sucrose synthase, which determine the mechanism of phloem unloading. Cloning of two extracellular (BIN35 and BIN46) and one vacuolar invertase (BIN44) provided the basis for a detailed molecular analysis of the relative contribution of the sucrose cleaving enzymes to the sink metabolism of sugar beets ( Beta vulgaris) during development. The determination of the steady state levels of mRNAs has been complemented by the analysis of the corresponding enzyme activities. The present study demonstrates an inverse regulation of extracellular invertase and sucrose synthase during tap root development indicating a transition between functional unloading pathways. Extracellular cleavage by invertase is the dominating mechanism to supply hexoses via an apoplasmic pathway at early stages of storage root development. Only at later stages sucrose synthase takes over the function of the key sink enzyme to contribute to the sink strength of the tap root via symplasmic phloem unloading. Whereas mRNAs for both extracellular invertase BIN35 and sucrose synthase were shown to be induced by mechanical wounding of mature leaves of adult plants, only sucrose synthase mRNA was metabolically induced by glucose in this source organ supporting the metabolic flexibility of this species.

Analysis of Transport Activity of Arabidopsis Sugar Alcohol Permease Homolog AtPLT5

The transporters responsible for sugar uptake into non-photosynthetic sink tissues in plants, such as roots and flowers, have not been fully identified and analyzed. Plants encode around 100 putative sugar transporters within the major facilitator superfamily, yet only a few have been studied. Here we report the analysis of a sugar alcohol permease homolog (AtPLT5, At3g18830) from Arabidopsis. A wide range of sugars including hexoses, pentoses, tetroses, a sugar acid, and sugar alcohols but not disaccharides induced inward currents in oocytes expressing AtPLT5. AtPLT5 expression also resulted in 14C-labeled substrate uptake in oocytes, indicating that AtPLT5 encodes an ion-coupled uptake transporter. K(0.5) values for glucose and sorbitol were highly dependent on external pH. Expression of AtPLT5 was found primarily in sink tissues: in the elongation zone of roots, in the inflorescence stem, and several floral structures, especially in the floral abscission zone. Expression was induced by mechanical wounding and insect feeding. Analysis of transport properties and expression in Arabidopsis indicate that AtPLT5 functions to transport a wide range of sugars into specific sink tissues in the plant.

Discussion of "Influence of effective parameters of non-orthogonal smeared crack approach in seismic response of concrete arch dams"

Kreuzer 713 The following discussion is not so much on the advanced and interesting approach presented by the authors, Espandar et al., rather than on a general development in seismic analysis of dams. I deeply appreciate the work of Dr. Lotfi, the only author that I know personally. It is this appreciation, which encourages me — a generalist — to take this paper as a hook for the following dialogue. My impression is that the reality in the authors’ minds is the mathematical model. The dam, on which this model is applied, is then a means to an end relating the model to a physical reality. In other words, it is the analyst’s subjective belief that his(her) model is a valid representation for the behavior of the dam. Nothing is wrong with that — but where is the attempt of a proof for this belief, where an engineering judgment about the wide-open outcome of the model? Let me give some examples. Figure 4 shows a 12 s time history of displacements at a crest point of the Shahid Rajaee dam. The variables are the key parameters in the authors’ analysis, namely the “secant and the elastic un/reloading” cases. The authors comment that “extensive cracking of the downstream face [occur] beneath the crest spillway block” and “the drift [of displacements] is more severe in elastic unloading than in secant unloading ...”. Such comments trigger several questions with respect to the anticipated post-earthquake behavior of the dam: • Given the drastic difference in displacements between elastic and secant unloading — which is then, in the authors’ view, the more realistic unloading mechanism for this particular dam? • The radial deformation history in Fig. 4 (upper two diagrams) shows a distinct difference between secant and elastic unloading, i.e., the first seems to indicate a safe behavior (more or less elastic deformations after 12 s), the second not. At 12 s there are about 180 mm irrecoverable radial (downstream?) deformations; this is much compared with the amplitude of the static radial deformation and indicates instability of the central crest section (high tensile strain). much • Cracking will be largely influenced by joint behavior (both behavior of block joints for cross-valley motion and of lift joints for vertical motion). Thus the authors’ cracking criterion (exceeding 1.5 or 3 MPa tensile material strength) might not apply everywhere. • Most laudable is the authors’ use of a fracture energy criterion for tensile strain softening. A value of 600 N/m is assumed, corresponding to a tensile strength of 1.5 MPa, and 2400 N/m for 3 MPa. Which value do the authors consider realistic for Shahid Rajaee dam? Obviously, the four-fold difference in fracture energy is a too wide scatter band for reasonably limiting estimates for postearthquake behavior. (Apparently no fracture energy test results were available.) All of the above relates more or less to the question: How do we value model uncertainties in seismic analysis? In this context, model uncertainty may be taken as the unknown influence of approximations for approaching the true physical behaviour of the dam. It contains two types of impediments: • the innovative part of the model, created in the authors’ imaginations and not yet verified by a sufficient large number of practical applications and test results • the demanding quality–quantity of input parameters, to feed the model Representations of physical phenomena, which cannot be validated empirically, are questionable as they bear the risk of speculative inferences. This requirement complies with a general axiom in scientific methods, where bold conjectures should be verified “by ingenious and severe attempts to refute them ... as a proof that the new theory is a better approximation to truth than the old theory” (Popper 1972). It seems that the strength of modelling seismic phenomena occasionally carries the analyst away to a deductive approach, whereby the main incentive is to create a better algorithm, shunning the inconvenient process of validation. However, validation also signifies to convey complex findings to those, which are finally taking responsibility for dam safety, i.e., the dam owners. The authors’ final statement that

The sucrose transporter StSUT1 localizes to sieve elements in potato tuber phloem and influences tuber physiology and development.

The sucrose (Suc) H(+)-cotransporter StSUT1 from potato (Solanum tuberosum), which is essential for long-distance transport of Suc and assumed to play a role in phloem loading in mature leaves, was found to be expressed in sink tubers. To answer the question of whether SUT1 serves a function in phloem unloading in tubers, the promoter was fused to gusA and expression was analyzed in transgenic potato. SUT1 expression was unexpectedly detected not in tuber parenchyma but in the phloem of sink tubers. Immunolocalization demonstrated that StSUT1 protein was present only in sieve elements of sink tubers, cells normally involved in export of Suc from the phloem to supply developing tubers, raising the question of the role of SUT1 in tubers. SUT1 expression was inhibited by antisense in transgenic potato plants using a class I patatin promoter B33, which is primarily expressed in the phloem of developing tubers. Reduced SUT1 expression in tubers did not affect aboveground organs but led to reduced fresh weight accumulation during early stages of tuber development, indicating that in this phase SUT1 plays an important role for sugar transport. Changes in Suc- and starch-modifying enzyme activities and metabolite profiles are consistent with the developmental switch in unloading mechanisms. Altogether, the findings may suggest a role of SUT1 in retrieval of Suc from the apoplasm, thereby regulating the osmotic potential in the extracellular space, or a direct role in phloem unloading acting as a phloem exporter transferring Suc from the sieve elements into the apoplasm.

Phloem loading and unloading of Cowpea mosaic virus in Vigna unguiculata.

Within their host plants, viruses spread from the initially infected cell through plasmodesmata to neighbouring cells (cell-to-cell movement), until reaching the phloem for rapid invasion of the younger plant parts (long-distance or vascular movement). Cowpea mosaic virus (CPMV) moves from cell-to-cell as mature virions via tubules constructed of the viral movement protein (MP). The mechanism of vascular movement, however, is not well understood. The characteristics of vascular movement of CPMV in Vigna unguiculata (cowpea) were examined using GFP-expressing recombinant viruses. It was established that CPMV was loaded into both major and minor veins of the inoculated primary leaf, but was unloaded exclusively from major veins, preferably class III, in cowpea trifoliate leaves. Phloem loading and unloading of CPMV was scrutinized at the cellular level in sections of loading and unloading veins. At both loading and unloading sites it was shown that the virus established infection in all vascular cell types with the exception of companion cells (CC) and sieve elements (SE). Furthermore tubular structures, indicative of virion movement, were never found in plasmodesmata connecting phloem parenchyma cells and CC or CC and SE. In cowpea, SE are symplasmically connected only to the CC and these results therefore suggest that CPMV employs a mechanism for phloem loading and unloading that is different from the typical tubule-guided cell-to-cell movement in other cell types.

Evidence for symplastic phloem unloading in sink leaves of barley.

The pathway of phloem unloading in sink barley (Hordeum vulgare) leaves was studied using a combination of electron microscopy, carboxyfluorescein transport, and systemic movement of barley stripe mosaic virus expressing the green fluorescent protein. Studies of plasmodesmatal frequencies between the phloem and mesophyll indicated a symplastic sieve element- (SE) unloading pathway involving thick-walled and thin-walled SEs. Phloem-translocated carboxyfluorescein was unloaded rapidly from major longitudinal veins and entered the mesophyll cells of sink leaves. Unloading was "patchy" along the length of a vein, indicating that sieve element unloading may be discontinuous along a single vascular bundle. This pattern was mirrored precisely by the unloading of barley stripe mosaic virus expressing the green fluorescent protein. Transverse veins were not utilized in the unloading process. The data collectively indicate a symplastic mechanism of SE unloading in the sink barley leaf.

Automatic Cabbage Feeding, Piling, and Unloading System for Tractor Implemented Chinese Cabbage Harvester

Since Chinese cabbages weigh 3 to 5kgf and are big in size at the time of harvest, handling operations such as harvesting, loading and unloading including transportation require the highest labor demand among all other cultivation processes. Recently, though several cabbage harvesters were developed in Japan and Europe, those harvesters were not suitable for Chinese cabbages cultivated in Korea because of the size and shape. To compromise system expenses and function, Semi-automatic cabbage piling and pallet unloading mechanism was devised and it required one labor. The foldable mesh pallet with a size of 1050mm × 1050mm × 1000mm and holding capacity of around 70 cabbages was utilized. The prototype for piling and unloading mechanism was composed of three parts such as feeding device, automatic piling device with retractable bellows, and pallet unloading device. Prior to developing the prototype, the geometric properties and the amount of the damage of the cabbage caused during the riling operation were investigated. Considering the height of the pallet, a series of cabbage carrying plates were mounted to the bracket chain to lift and to carry cabbages to the loading device. Indoor laboratory experiments showed that the cabbage carrying chain conveyor worked successfully. Considering the conveying speed 0.46m/sec of the pull up belt from the cabbages on the ground, the speed of cabbage carrying chain conveyor worked property in the range of 0.26m/sec to 0.36m/sec. The system allowed the operator to modify the position of cabbage slightly. Overall system worked successfully resulting into almost same capacity without severe damage to the cabbage as human did.

Regulation of source/sink relations by cytokinins.

Many physiological effects of cytokinins are well established and are known to be involved in various aspects of the plant life cycle. In contrast, little is known about how these effects are evoked at the molecular level. Since cytokinins have been shown to play a major role in the regulation of various processes associated with active growth and thus an enhanced demand for carbohydrates, a link to the regulation of assimilate partitioning has been suggested. This review discusses the current knowledge of the role of cytokinins in the regulation of source-sink relations, based on the finding of the co-ordinated cytokinin induction of an extracellular invertase and a hexose transporter. The induction of these key enzymes of an apoplastic unloading mechanism may be one important molecular prerequisite for different cytokinin-mediated effects.

PHLOEM UNLOADING: Sieve Element Unloading and Post-Sieve Element Transport.

The transport events from the sieve elements to the sites of utilization within the recipient sink cells contribute to phloem unloading. The phenomenon links sink metabolism and/or compartmentation with phloem transport to, and partitioning between, sinks. The nature of the linkage depends upon the cellular pathway and mechanism of unloading. The common unloading pathway is symplasmic, with an apoplasmic step at or beyond the sieve element boundary reserved for specialized situations. Plasmodesmal conductivity exerts the primary control over symplasmic transport that occurs by diffusion with bulk flow anticipated to be of increasing significance as import rate rises. In the case of an apoplasmic step, efflux across the plasma membranes of the vascular cells occurs by simple diffusion, whereas efflux from nonvascular cells of developing seeds is facilitated and, in some cases, energy coupled. Accumulation of sugars from the sink apoplasm universally occurs by a plasma membrane-bound sugar/proton symport mechanism.

Developmental changes of enzymes involved in conversion of sucrose to hexose-phosphate during early tuberisation of potato

A highly synchronised in-vitro tuberisation system, based on single-node cuttings containing an axillary bud, was used to investigate the activity patterns of enzymes involved in the conversion of sucrose to hexose-phosphates during stolon-to-tuber transition of potato (Solanum tuberosum L.). Two different non-tuberising systems were included to distinguish between changes that are or are not tuber-specific. At tuberisation the activity of soluble acid invertase decreased (13-fold) and of sucrose synthase increased (12-fold). The activity of both enzymes remained unchanged in the non-tuberising treatments. Based on the opposite patterns and large difference in activity of these two sucrolytic enzymes, we conclude that sucrose synthase constitutes the predominant route of sucrose breakdown after tuber initiation. During the period before tuberisation, the activity of cell-wall-bound invertase and of hexokinase showed a highly positive correlation (r 2 = 0.96 in all the three treatments, suggesting coordinated coarse control of both enzyme activities. After the onset of tuberisation cell-wall-bound invertase activity decreased to a very low level, a change not observed in the non-tuberising systems, indicating that cell-wall-bound invertase is presumably not involved in the unloading mechanism and/or short-distance transport of sucrose within the perimedulla of growing tubers. The overall activity of fructokinase and of hexokinase both showed a fourfold increase after tuber initiation, but remained unchanged in the non-tuberising systems. The increase of fructokinase suggests that the phosphorylation of fructose by fructokinase down-regulates the cytosolic fructose content in order to maintain a high sucrose-synthase-catalysed net flux of sucrose to phosphorylated hexoses during rapid tuber growth. The increase of total glucose-phosphorylating potential could be a response to the tuberisation-related starch accumulation process. The activity of UDP-glucose pyrophosphorylase showed no developmental change. The level of UDP-glucose pyrophosphorylase activity is very likely the result of metabolic regulation.