Flow Injection Analysis for the Determination of Urea in Cow’s Milk

An inexpensive and easily automated flow injection method for determination of urea in cow’s milk was evaluated. Urea is hydrolysed by urease and in a gas diffusion cell the ammonia formed passes a membrane into an indicator solution. The resulting colour change of the indicator is measured at 590 nm. The repeatability of the analysis, expressed as the coefficient of variation (C.V.), was between 0.5 and 1.2%. Measured (y) and expected (x) milk urea concentrations after addition of known amounts of urea were related according to the equation y = 1.00× – 0.12 with a C.V. for the regression of 1.8%. Recommended amounts (0.02 %) of the preservative bronopol (2-bromo-2-nitropropane-1,3-diol) added to the milk did not affect the results (P > 0.05).     

Difference Spectra of Bovine κ-Casein with Urea

Bovine κ-casein showed a typical CD spectrum for an aperiodic conformation in the far UV region. The comparison of the near UV absorption spectrum of native κ-casein with that of a model compound mixture (Ac-tyr-OEt+Ac-trp-OEt, molar ratio=9: 1) showed a red shift of the former by 2 nm to the longer wavelength. The difference spectra produced by the addition of urea to κ-casein solution showed three peaks at 280, 287, and 292 nm, of which the sign was negative (denaturation blue shift). The magnitude of the blue shift of the trypto- phyl group was found to be ?2,200. It is concluded from these results that some tyrosyl groups are exposed to the solvent, and the other tyrosyl groups and a tryptophyl group are buried in the hydrophobic regions which is very susceptible to the action of a denaturing agent, urea. All the chromophores in κ-casein was exposed to the solvent in the presence of 4 m urea. κ-Casein in the native state was proved to have an aperiodic structure but not a flexible random coil.     

Unfolding and Refolding of Bovine α-Crystallin in Urea and Its Chaperone Activity

We undertook an unfolding and refolding study of α_L-crystallin in presence of urea to explore the breakdown and formation of various levels of structure and to find out whether the breakdown of various levels of structure occurs simultaneously or in a hierarchal manner. We used various techniques such as circular dichroism, fluorescence spectroscopy, light scattering, polarization to determine the changes in secondary, tertiary, and quaternary structure. Unfolding and refolding occurred through a number of intermediates. The results showed that all levels of structure in α_L-crystallin collapsed or reformed simultaneously. The intermediates that occurred in the 2–4 M urea concentration range during unfolding and refolding differed from each other in terms of the polarity of the tryptophan environment. The ANS binding experiments revealed that refolded α_L-crystallin had higher number of hydrophobic pockets compared to native one. On the other hand, polarity of these pockets remained same as that of the native protein. Both light scattering and polarization measurements showed smaller oligomeric size of refolded α_L-crystallin. Thus, although the secondary structural changes were almost reversible, the tertiary and quaternary structural changes were not. The refolded α_L-crystallin had more exposed hydrophobic sites with increased binding affinity. The refolded form also showed higher chaperone activity than native one. Since the refolded form was smaller in oligomeric size, some buried hydrophobic sites were available. The higher chaperone activity of lower sized oligomer of α_L-crystallin again revealed that chaperone activity was dependent on hydrophobicity and not on oligomeric size.     

Escalating Worldwide use of Urea – A Global Change Contributing to Coastal Eutrophication

While the global increase in the use of nitrogen-based fertilizers has been well recognized, another change in fertilizer usage has simultaneously occurred: a shift toward urea-based products. Worldwide use of urea has increased more than 100-fold in the past 4 decades and now constitutes >50% of global nitrogenous fertilizer usage. Global urea usage extends beyond agricultural applications; urea is also used extensively in animal feeds and in manufacturing processes. This change has occurred to satisfy the world’s need for food and more efficient agriculture. Long thought to be retained in soils, new data are suggestive of significant overland transport of urea to sensitive coastal waters. Urea concentrations in coastal and estuarine waters can be substantially elevated and can represent a large fraction of the total dissolved organic nitrogen pool. Urea is used as a nitrogen substrate by many coastal phytoplankton and is increasingly found to be important in the nitrogenous nutrition of some harmful algal bloom (HAB) species. The global increase from 1970 to 2000 in documented incidences of paralytic shellfish poisoning, caused by several HAB species, is similar to the global increase in urea use over the same 3 decades. The trend toward global urea use is expected to continue, with the potential for increasing pollution of sensitive coastal waters around the world.     

Effect of cortisone on the developmental pattern of the neutral and the acid β-galactosidases of the small intestine of the rat

1. The developmental pattern and effect of cortisone on acid beta-galactosidase and neutral beta-galactosidase were studied in postnatal rats by a recently proposed method for their independent determination. 2. After birth the acid beta-galactosidase activity increases in the ileum, whereas it decreases slightly in the jejunum. On day 16 after birth the activity in the ileum decreases and in 20-day-old rats activity in both parts of the intestine decreases to adult values. In suckling animals the activity in the ileum exceeds the jejunal activity severalfold and in adult animals the activity in the jejunum is slightly higher than that in the ileum. 3. Neutral beta-galactosidase activity is high after birth and decreases in both jejunum and ileum after day 20 after birth. In 12-20-day-old rats activity in both parts is essentially the same, but in adult animals jejunal activity exceeds ileal activity four-to five-fold. 4. Cortisone (0.5, 2.0 or 5.0mg/100g body wt. daily for 4 days) does not influence the activity of either enzyme in 60-day-old rats. Acid beta-galactosidase activity is decreased after cortisone treatment in 8-, 12-, 16-and 18-day-old rats, with sensitivity to cortisone increasing with the approach of weaning. No effect of cortisone on acid beta-galactosidase is seen in 8-day-old rats. Neutral beta-galactosidase activity is increased in the ileum of 8-, 12-, 16- and 18-day old rats, but only in the jejunum of 8-and 12-day-old rats.     

Association of the subunits of the calcium-independent receptor of α-latrotoxin

CIRL-1 also called latrophilin 1 or CL belongs to the family of adhesion G protein-coupled receptors (GPCRs). As all members of adhesion GPSR family CIRL-1 consists of two heterologous subunits, extracellular hydrophilic p120 and heptahelical membrane protein p85. Both CIRL-1 subunits are encoded by one gene but as a result of intracellular proteolysis of precursor, mature receptor has two-subunit structure. It was also shown that a minor portion of the CIRL-1 receptor complexes dissociates, producing the soluble receptor ectodomain, and this dissociation is due to the second cleavage at the site between the site of primary proteolysis and the first transmembrane domain. Recently model of independent localization p120 and p85 on the cell surface was proposed. In this article we evaluated the amount of p120-p85 complex still presented on the cellular membrane and confirmed that on cell surface major amount of mature CIRL-1 presented as a p120-p85 subunit complex.     

Phylogeography of the harlequin beetle-riding pseudoscorpion and the rise of the Isthmus of Panamá

Molecular and geological evidence indicates that the emergence of the Isthmus of Panamá influenced the historical biogeography of the Neotropics in a complex, staggered manner dating back at least 9 Myr bp. To assess the influence of Isthmus formation on the biogeography of the harlequin beetle-riding pseudoscorpion, Cordylochernes scorpioides, we analysed mitochondrial COI sequence data from 71 individuals from 13 locations in Panamá and northern South America. Parsimony and likelihood-based phylogenies identified deep divergence between South American and Panamanian clades. In contrast to low haplotype diversity in South America, the Panamanian Cordylochernes clade is comprised of three highly divergent lineages: one clade consisting predominantly of individuals from central Panamá (PAN A), and two sister clades (PAN B1 and PAN B2) of western Panamanian pseudoscorpions. Breeding experiments demonstrated a strictly maternal mode of inheritance, indicating that our analyses were not confounded by nuclear-mitochondrial pseudogenes. Haplotype diversity is striking in western Atlantic Panamá, where all three Panamanian clades can occur in a single host tree. This sympatry points to the existence of a cryptic species hybrid zone in western Panamá, a conclusion supported by interclade crosses and coalescence-based migration rates. Molecular clock estimates yield a divergence time of approximately 3 Myr between the central and western Panamanian clades. Taken together, these results are consistent with a recent model in which a transitory proto-Isthmus enabled an early wave of colonization out of South America at the close of the Miocene, followed by sea level rise, inundation of the terrestrial corridor and then a second wave of colonization that occurred when the Isthmus was completed approximately 3 Myr bp.     

Variations with Breed,Age, Season,Yield, Stage of Lactation and Herd in the Concentration of Urea in Bulk Milk and Individual Cow’s Milk

The concentration of urea in the milk of 510 dairy cows in 10 herds was determined at regular intervals for a year. The herds contained approximately equal numbers of Swedish Red and White, and Swedish Holstein cows. The mean ± sd concentration in the samples from individual cows was 5.32 ± 1.13 mmol/1, and the mean concentration in bulk milk was 5.39 ± 0.96 mmol/1. These values indicated that on average the herds were fed too much protein relative to their intake of energy throughout the year. Herd factors had a strong influence on the milk urea concentration. The concentration was lower during the first month of lactation than later in the lactation, and lower when the cows were housed during the winter than when they were grazing. There was a weak positive relationship between the daily milk yield and urea concentration, particularly during late lactation, but there was no relationship with either breed or age. Bulk milk urea was a reliable guide to the average urea concentration of a herd.     

Did the evolution of the phytoplankton fuel the diversification of the marine biosphere?

We discuss the possible links between the fossil record of marine biodiversity, nutrient availability and primary productivity. The parallelism of the fossil records of marine phytoplankton and faunal biodiversity implicates the quantity (primary productivity) and quality (stoichiometry) of phytoplankton as being critical to the diversification of the marine biosphere through the Phanerozoic. The relatively subdued marine biodiversity of the Palaeozoic corresponds to a time of relatively low macronutrient availability and poor food quality of the phytoplankton as opposed to the diversification of the Modern Fauna through the Mesozoic–Cenozoic. Increasing nutrient runoff to the oceans through the Phanerozoic resulted from orogeny, the emplacement of Large Igneous Provinces (LIPs), the evolution of deep-rooting forests and the appearance of more easily decomposable terrestrial organic matter that enhanced weathering. Positive feedback by bioturbation of an expanding benthos played a critical role in evolving biogeochemical cycles by linking the oxidation of dead organic matter and the recycling of nutrients back to the water column where they could be re-utilized. We assess our conclusions against a recently published biogeochemical model for geological time-scales. Major peaks of marine diversity often occur near rising or peak fluxes of silica, phosphorus and dissolved reactive oceanic phosphorus; either major or minor ⁸⁷Sr/⁸⁶Sr peaks; and frequently in the vicinity of major (Circum-Atlantic Magmatic Province) and minor volcanic events, some of which are associated with Oceanic Anoxic Events. These processes appear to be scale-dependent in that they lie on a continuum between biodiversification on macroevolutionary scales of geological time and mass extinction.     

Imperfect Batesian mimicry—the effects of the frequency and the distastefulness of the model

Batesian mimicry is the resemblance between unpalatable models and palatable mimics. The widely accepted idea is that the frequency and the unprofitability of the model are crucial for the introduction of a Batesian mimic into the prey population. However, experimental evidence is limited and furthermore, previous studies have considered mainly perfect mimicry (automimicry). We investigated imperfect Batesian mimicry by varying the frequency of an aposematic model at two levels of distastefulness. The predator encountered prey in a random order, one prey item at a time. The prey were thus presented realistically in a sequential way. Great tits (Parus major) were used as predators. This experiment, with a novel signal, supports the idea that Batesian mimics gain most when the models outnumber them. The mortalities of the mimics as well as the models were significantly dependent on the frequency of the model. Both prey types survived better the fewer mimics there were confusing the predator. There were also indications that the degree of distastefulness of the model had an effect on the survival of the Batesian mimic: the models survived significantly better the more distasteful they were. The experiment supports the most classical predictions in the theories of the origin and maintenance of Batesian mimicry.     

Review of the fauna of Rotatoria,Cladocera, and Copepoda of the basin of the Anadyr’ River

The zooplankton composition is studied in the thermokarst, glacial and meteorite lakes, channels, former riverbeds, and hollows in the basin of Anadyr’. We found 174 taxa: 78, Rotatoria, 55, Cladocera, and 41, Copepoda. The most diverse is the lake fauna: 51 taxa of Rotatoria, 48, Cladocera, and 37, Copepoda. The thermokarst Lake Maiorskoe hosts 68 taxa: 31, Rotatoria, 14, Cladocera, and 23, Copepoda, wheras the cold ultraoligotrophic Lake El’gygytgyn features only one species of Cyclop of the group scutifer Cyclops neymanae Strel., and Rotatoria and Cladocera are present as allochtonous forms. The Copepoda illustrate the relations of the Anadyr’ fauna with those of Europe, North America, and Japan.