Pregnancy-associated changes in oligomannose oligosaccharides of human and bovine uromodulin (Tamm-Horsfall glycoprotein)

The urinary glycoprotein uromodulin (Tamm-Horsfall glycoprotein) exhibits a pregnancy-associated ability to inhibit antigen-specific T cell proliferation, and the activity is associated with a carbohydrate moiety [Muchmore and Decker (1985) Science 229:479–81; Hessionet al., (1987) Science 237:1479–84; Muchmore, Shifrin and Decker (1987) J Immunol 138:2547–53]. We report here that the Man₆₍₇₎GlcNAc₂-R glycopeptides derived from uromodulin inhibit antigen-specific T cell proliferation by 50% at 0.2–2 M, and further studies, reported elsewhere, confirm that oligomannose glycopeptides from other sources are also inhibitory, with Man₉GlcNAc₂-R the most inhibitory of those tested [Muchmoreet al., J Leukocyte Biol (in press)]. In this work, we have extended the observation of pregnancy-associated inhibitory activity to a second species, and have compared the oligomannose profile of Tamm-Horsfall glycoprotein (nonpregnant) with that of uromodulin (pregnant) derived from both human and bovine sources. Surprisingly, there was a pregnancy-associated decrease in the total content of oligomannose chains due predominantly to a reduction in Man₅GlcNAc₂-R and Man₆GlcNAc₂-R. Man₇GlcNAc₂-R, which did not decrease with pregnancy, comprised a significantly greater proportion of the total oligomannose chains in pregnant vs. nonpregnant samples from both species (human; 34.6% vs. 25.9%: bovine; 14.4% vs. 7.2%).     

Choosing mates: good genes versus genes that are a good fit

Female choice for male ornamental traits is widely accepted as a mechanism by which females maximize their reproductive success and/or offspring quality. However, there is an increasing empirical literature that shows a fitness benefit of genetic diversity and a tendency for females to use genetic dissimilarity as a criterion for mate choice. This genetic compatibility hypothesis for female mate choice presents a paradox. How can females use both an absolute criterion, such as male ornamentation, and a relative criterion, such as genetic dissimilarity, to choose their mates? Here, we present potential solutions for this dilemma and the empirical evidence supporting them. The interplay between these two contrasting forms of female mate choice presents an exciting empirical and theoretical challenge for evolutionary ecologists.     

An Electron Microscope Study of the Salamander Thyroid during Hormonal Stimulation

Cytological changes in thyroid glands following administration of thyroid-stimulating hormone (TSH), were studied in adult salamanders, Ambystoma tigrinum, Triturus torosus, and Triturus viridescens by electron and light microscopy. Thyroids from untreated salamanders contained large follicles, faintly basophilic colloid, low follicle cells with flattened nuclei, and scant, slightly basophilic cytoplasm. After TSH administration the cell height and nuclear volume increased. Cytoplasmic basophilia was markedly increased and follicle lumina were reduced. In electron micrographs, stacks of ergastoplasmic lamellae appeared near the nucleus occasionally in contact with the nuclear membrane. In more advanced stages of stimulation, lamellar arrays were largely replaced by small disoriented vesicles and larger vacuoles containing colloid-like material. Sections of obliquely oriented ergastoplasmic membranes contained rows of extremely fine particles. Microvilli increased in size and number and Golgi structures became more extensive. Homogeneous osmiophilic droplets increased in size and abundance. Some of the smaller droplets were seen associated with the Golgi zone. Droplets similar in size and density frequently contained closely packed, whorled lamellae. Mitochondria showed no structural changes but occurred in aggregates interposed between the nucleus and highly folded portions of the basal cell membrane.     

Role of lysosomal acid lipase in the intracellular metabolism of LDL-transported dehydroepiandrosterone-fatty acyl esters

Dehydroepiandrosterone-fatty acyl esters (DHEA-FAE) belong to a unique family of naturally occurring hydrophobic steroid hormone derivatives that are transported in circulating lipoproteins and may act as a source of dehydroepiendrosterone (DHEA) and other biologically active steroid hormones in cells. Here, we studied the metabolic fate of low-density lipoprotein-associated [(3)H]DHEA-FAE ([(3)H]DHEA-FAE-LDL) and the possible role of lysosomal acid lipase (LAL) in the hydrolysis of DHEA-FAE in cultured human cells. When HeLa cells were incubated with [(3)H]DHEA-FAE-LDL, the accumulation of label in the cellular fraction increased with incubation time and could be inhibited by excess unlabeled LDL, suggesting LDL receptor or LDL receptor-related receptor-dependent uptake. During 48 h of chase, decreasing amounts of [(3)H]DHEA-FAE were found in the cellular fraction, while in the medium increasing amounts of unesterified [(3)H]DHEA and its two metabolites, [(3)H]-5alpha-androstanedione (5alpha-adione) and [(3)H]androstenedione (4-adione), appeared. As LDL-cholesteryl ester hydrolysis is dependent on LAL activity, we depleted LAL from HeLa cells using small interfering RNAs and compared the hydrolysis of [(3)H]DHEA-FAE-LDL and [(3)H]cholesteryl-FAE-LDL. The results demonstrated a more modest but significant reducing effect on the hydrolysis of [(3)H]DHEA-FAE compared with [(3)H]cholesteryl-FAE. Moreover, experiments in LAL-deficient human fibroblasts (Wolman disease patient cells) showed that [(3)H]DHEA-FAE hydrolysis was not completely dependent on LAL activity. In summary, LDL-transported [(3)H]DHEA-FAE entered cells via LDL receptor or LDL receptor-related receptor-mediated uptake, followed by intracellular hydrolysis and further metabolism into 5alpha-adione and 4-adione that were excreted from cells. Although LAL contributed to the deesterification of DHEA-FAE, it was not solely responsible for the hydrolysis.     

Eugenol specialty chemical production in transgenic poplar (Populus tremula × P. alba) field trials

A foundational study assessed effects of biochemical pathway introduction into poplar to produce eugenol, chavicol, p‐anol, isoeugenol and their sequestered storage products, from potentially available substrates, coniferyl and p‐coumaryl alcohols. At the onset, it was unknown whether significant carbon flux to monolignols vs. other phenylpropanoid (acetate) pathway metabolites would be kinetically favoured. Various transgenic poplar lines generated eugenol and chavicol glucosides in ca. 0.45% (~0.35 and ~0.1%, respectively) of dry weight foliage tissue in field trials, as well as their corresponding aglycones in trace amounts. There were only traces of any of these metabolites in branch tissues, even after ~4‐year field trials. Levels of bioproduct accumulation in foliage plateaued, even at the lowest introduced gene expression levels, suggesting limited monolignol substrate availability. Nevertheless, this level still allows foliage collection for platform chemical production, with the remaining (stem) biomass available for wood, pulp/paper and bioenergy product purposes. Several transformed lines displayed unexpected precocious flowering after 4‐year field trial growth. This necessitated terminating (felling) these particular plants, as USDA APHIS prohibits the possibility of their interacting (cross‐pollination, etc.) with wild‐type (native plant) lines. In future, additional biotechnological approaches can be employed (e.g. gene editing) to produce sterile plant lines, to avoid such complications. While increased gene expression did not increase target bioproduct accumulation, the exciting possibility now exists of significantly increasing their amounts (e.g. 10‐ to 40‐fold plus) in foliage and stems via systematic deployment of numerous ‘omics’, systems biology, synthetic biology and metabolic flux modelling approaches.     

The endocrine basis of reproductive inactivity in Monarch butterflies overwintering in central California

Monarch butterflies (Danaus plexippus) collected during winter in central California are reproductively inactive. Oögenesis is stimulated in such animals by environments simulating summer conditions. Allatectomized or neck-ligatured winter animals do not normally undergo oögenesis when placed in summer conditions, but apparently normal oögenesis occurs if they are injected with juvenile hormone isomers. Injections of such isomers into winter animals held in environments simulating winter also promote oögenesis, even though winter conditions typically inhibit ovarian development. Reproductive dormany in winter Monarchs of central California therefore appears to be due (at least partially) to environmentally induced inactivity of the corpora allata.     

Serine racemase and the serine shuttle between neurons and astrocytes

d-Serine is a brain-enriched d-amino acid that works as a transmitter-like molecule by physiologically activating NMDA receptors. Synthesis of d-serine is carried out by serine racemase (SR), a pyridoxal 5'-phosphate-dependent enzyme. In addition to carry out racemization, SR α,β-eliminates water from l- or d-serine, generating pyruvate and NH(4)(+). Here I review the main mechanisms regulating SR activity and d-serine dynamics in the brain. I propose a role for SR in a novel form of astrocyte-neuron communication-the "serine shuttle", whereby astrocytes synthesize and export l-serine required for the synthesis of d-serine by the predominantly neuronal SR. d-Serine synthesized and released by neurons can be further taken up by astrocytes for storage and activity-dependent release. I discuss how SR α,β-elimination with d-serine itself may limit the achievable intracellular d-serine concentration, providing a mechanistic rationale on why neurons do not store as much d-serine as astrocytes. The higher content of d-serine in astrocytes appears to be related to increased d-serine stability, for their low SR expression will prevent substantial d-serine metabolism via α,β-elimination. SR and the serine shuttle pathway are therapeutic targets in neurodegenerative diseases in which NMDA receptor dysfunction plays pathological roles. This article is part of a Special Issue entitled: Pyridoxal Phospate Enzymology.     

Energy requirements for growth and maintenance of Scenedesmus protuberans Fritsch in light-limited continuous cultures

Scenedesmus protuberans Fritsch was grown in light-limited continuous cultures with a light-dark cycle, at temperatures of 20° and 28° C. At 20° irradiances of 12 and 38 W m^–2 were used, at 28° 38 W m^–2.The relationships between growth rate and light uptake rate were of diphasic linear character. With the lower growth rates the relationships were defined with the parameters _e , i.e. the specific maintenance rate constant, and c, the true efficiency of light energy conversion into biomass. The _e -value was dependent on temperature, the c on irradiance.In cultures, incubated in prolonged darkness, decrease rates of biomass were comparable to the derived _e -values.Both diphasic linear relationships between growth rate and light uptake rate and the same order of magnitude of _e -values could be derived from literature data on other green algae.