Methionine transamination—metabolic function and subcellular compartmentation

Enzymatic activities catalysing the inter-conversion of L-methionine and its oxy analogue 4-methylthio-2-oxobutyric acid (2,4-KMB) were detected in the liver, skeletal muscle and heart of the laboratory rat and of sheep. In both species the highest activity of methionine transamination was found in the liver and was located in the cytoplasm and mitochondria. We propose that physiological and nutritional role of the cytoplasmic methionine transamination is amination of 2,4 KMB and formation of L-methionine while in mitochondria the activity is responsible for disposal of excess methionine is oxidised through oxidative decarboxylation of 2,4 KMB.     

Shoulder muscle load and muscle fatigue among industrial sewing-machine operators

Physiological responses to physical work were assessed for 29 female industrial sewing-machine operators during an 8-h working day under ordinary working conditions. During sewing-machine work, the average (left and right) static load in the trapezius muscle was 9% of the maximal electromyogram (EMG) amplitude (% EMG_max), while the average mean load was 15% EMG_max, and the average peak load was 23% EMG_max. The static load level was unrelated to the muscle strength of the sewing-machine operators, which for the group as a whole was within the normal range. The load levels remained unchanged during the working day, while changes in the EMG mean power frequency and zero crossing frequency rate occurred, both indicating the development of muscle fatigue in left and right trapezius muscle during the working day. In line with this, the rating of perceived exertion in the shoulder and neck region increased during. the working day. Dividing the group of sewing-machine operators into two groups, those with the highest frequency and those with the lowest frequency of shoulder/neck troubles showed that the former group had significantly lower muscle strength, despite the fact that no differences in the surface EMG during sewing were found between the two groups. It was concluded that industrial sewing-machine work involves a pattern of shoulder muscle activity which induces fatiguing processes in the shoulder and neck regions. Furthermore, since the static shoulder muscle load was independent of muscle strength, factors other than working posture may be of significance for the static shoulder muscle load.     

Effects of nisin addition on the ethanol fermentation of casein whey permeate

Nisin added at up to 1000 IU ml^-1 did not affect ethanol production or cell growth during fermentation of sulphuric acid casein whey permeate by Kluyveromyces marxianus Y-113. Nisin reduced the bacterial population markedly when added at 100 IU ml^-1 to whey permeate contaminated by addition of incubated cultures derived from milk or whey. The ethanol production rate and yield in the contaminated cultures treated with nisin did not differ from the control values.     

Begomovirus diversity in tomato crops in Costa Rica

Begomoviruses (Geminiviridae family) are characterized by their high recombination rate and a wide range of hosts, making their control difficult. In Costa Rica, various species of bipartite begomoviruses have been reported, which are Pepper golden mosaic virus (PepGMV), Tomato yellow mottle virus (ToYMoV), Tomato leaf curl Sinaloa virus (ToLCSiV) and the monopartite begomovirus Tomato yellow leaf curl virus (TYLCV). Since the TYLCV first report in Costa Rica, neither additional knowledge has been produced on how this begomovirus has spread in the country's territory nor on the distribution of the other bipartite species. A total of 429 tomato samples collected during the years 2015–2016 were used to study these aspects. Each sample was georeferenced and analysed with various techniques such as nucleic acid hybridization, polymerase chain reaction (PCR) and sequencing for the begomoviruses previously reported in Costa Rica. It was found that the presence/absence of the different species can vary, depending on the province. TYLCV is present in the six provinces analysed in this work, with a proportion from 3.7 to 86.6 per cent. Alajuela, Cartago, and Heredia are the provinces most affected by tomato-infecting begomoviruses. Fourteen different haplotypes of TYLCV were detected, but all were identified as TYLCV-IL. The distribution of TYLCV was related to the presence of the whitefly Bemisia tabaci MED, especially in the country's main tomato production areas. This information allows the phytosanitary surveillance services to develop strategies for the integrated management of the disease and to contribute data to the genetic improvement programmes of the crop.     

Distribution of endogenous gibberellins in vegetative and reproductive organs of Brassica

Recognizing the physiological diversity of different plant organs, studies were conducted to investigate the distribution of endogenous gibberellins (GAs) in Brassica (canola or oilseed rape). GA₁ and its biosynthetic precursors, GA₂₀ and GA₁₉, were extracted, chromatographically purified, and quantified by gas-chromatography-selected ion monitoring (GC-SIM), using [²H₂]GAs as internal standards. In young (vegetative) B. napus cv. Westar plants, GA concentrations were lowest in the roots, increased acropetally along the shoot axis, and were highest in the shoot tips. GA concentrations were high but variable in leaves. GA₁ concentrations also increased acropetally along the plant axis in reproductive plants. During early silique filling, GA₁ concentrations were highest in siliques and progressively lower in flowers, inflorescence stalks (peduncles plus pedicels), stem, leaves, and roots. Concentrations of GA₁₉ and GA₂₀ showed similar patterns of distribution except in leaves, in which concentrations were higher, but variable. Immature siliques were qualitatively rich in endogenous GAs and GA₁, GA₃, GA₄, GA₈, GA₉, GA₁₇, GA₁₉, GA₂₀, GA₂₄, GA₂₉, GA₃₄, GA₅₁, and GA₅₃ were identified by GC-SIM. In whole siliques, GA₁₉, GA₂₀, GA₁, and GA₈ concentrations declined during maturation due to declining levels in the maturing seeds; their concentrations in the silique coats remained relatively constant and low. These studies demonstrate that GAs are differentially distributed in _Brassica with a general pattern of acropetally increasing concentration in shoots and high concentration in actively growing and developing organs.     

Mutants in dolichol synthesis: conversion of polyprenol to dolichol appears to be a rate-limiting step in dolichol synthesis

Chinese hamster ovary (CHO) cells of the Lec9 recessive complementationgroup display a distinctive profile of resistance to a varietyof toxic lectins. In addition, they accumulate cis--unsaturatedpolyprenol and use mainly polyprenol rather than dolichol tosynthesize the glycosylated lipids used in asparagine-linkedglycosylation of proteins. The primary defect in these cellsis thought to result from a deficiency in polyprenol reductaseactivity. Three new mutants were isolated and determined tohave qualitatively, although not quantitatively, similar lectinresistance profiles to Lec9 cells. Two of these mutants (Abr^Rand Ric^R) also contained polyprenol rather than dolichol. Thelectin resistance profile of an independent mutant which accumulatespolyprenol, F2A8, was also found to be qualitatively similarto the Lec9 pattern. The relationship among these mutants wasanalysed in more detail by construction of cell—cell hybrids.Lectin resistance profiles of the hybrids demonstrated thatAbr^R, Ric^R and F2A8 fell into the Lec9 complementation group.Analysis of prenols in the hybrids also showed that F2A8 wasa member of the Lec9 group. Surprisingly, a significant fractionof the prenols found in Lec9 Parent hybrids was polyprenol(up to 30% of the neutral fraction), whereas the prenols foundin Parent Parent hybrids were nearly exclusively dolichol(97% of the neutral lipid fraction). Therefore, reduction ofpolyprenol to dolichol appears to be a rate-limiting step inthe synthesis of dolichol since hybrids with differing numbersof wild-type alleles can be biochemically distinguished. CHO cells dolichol lectins mutants polyprenol reductase     

Biosynthesis and function of membrane bound and secreted forms of recombinant CD11b/CD18 (Mac-1)

Full-length (membrane bound) and truncated (secreted) forms of the beta 2 integrin heterodimer, CD11b/CD18 (Mac-1), were expressed in a human kidney cell line (293) that normally does not express leukocyte adhesion molecules (Leu-CAMs). The biosynthesis of recombinant Mac-1 in 293 cells differed from that reported for leukocytes in that heterodimer formation was not required for CD11b to be exported to the cell surface. A stable cell line was constructed that constitutively secreted the recombinant, truncated Mac-1 heterodimer into growth conditioned cell culture medium. A novel monoclonal antibody that enabled an immunoaffinity method for the selective purification of recombinant Mac-1 heterodimers was identified. Sufficient protein was purified to allow the first measurement of the 50% inhibitory concentration (IC₅₀) for CD11b/CD18 and for the direct comparison of the inhibitory activity of recombinant soluble Mac-1 with that of various CD18 and CD11b specific monoclonal antibodies. Purified recombinant soluble Mac-1 inhibited the binding of neutrophils, activated by opsonized zymosan or fMet-Leu-Phe peptide, to human umbilical vein endothelial cells. Similarly, the recombinant integrin was effective in inhibiting the binding of unactivated neutrophils to tumor necrosis factor (TNF-alpha) activated endothelial cells. The availability of an abundant source of purified, biologically active Mac-1 will enable direct physical and chemical investigations into the relationship between the structure and function of this leukocyte adhesion molecule.     

Hatching plasticity in a Southeast Asian tree frog mitigates submergence-induced mortality

Environmentally cued hatching has been well-documented in amphibians in response to a wide range of abiotic and biotic factors. The hatching of terrestrial amphibian eggs in response to flooding may be basal within the group, but amphibian lineages in tropical Asia and sub-Saharan Africa have not received as much attention as their Neotropical counterparts. We investigated submergence-induced hatching in Feihyla hansenae, a Rhacophorid tree frog with terrestrial eggs. We quantified natural rates of clutch submergence at our study site in Thailand. Using submergence experiments, we found that embryos are capable of hatching early to escape flooding, and that failure to hatch results in mortality. Among the embryos that were able to hatch early, only the earliest, youngest hatchlings experienced a trade-off in body size that persisted for 6 days, while later, older hatchlings were not significantly smaller than spontaneous hatchlings under control conditions. By incorporating our natural and experimental data into Monte Carlo methods to simulate and compare survival probabilities with and without hatching plasticity, we found an overall 3.1% increase in submergence survival due to hatching plasticity. Our findings support the idea that flooding-induced hatching is widespread across amphibians with terrestrial eggs and highlight the importance of researching understudied tropical regions. As climate change is projected to affect rainfall patterns, the ability of embryos to escape abiotic egg-stage threats may be an indicator of species' ability to flexibly navigate a changing environment.     

The structure and evolution of the human salivary proline-rich protein gene family

We present the nucleotide sequences of four members of the six-member human salivary prolinerich protein (PRP) gene family. The four genes are PRB1 and PRB2, which encode basic PRPs, and PRB3 and PRB4, which encode glycosylated PRPs. Each PRB gene is approximately 4.0 kb in length and contains four exons, the third of which is entirely composed of 63-bp tandem repeats and encodes the proline-rich portion of the protein products. Exon 3 contains different numbers of tandem repeats in the different PRB genes. Variation in the numbers of these repeats is also responsible for length variations in different alleles of the PRB genes. We have determined a probable evolutionary history of the human PRP gene family by comparing the nucleotide sequences of the six PRP genes. The present-day six PRP loci probably evolved from a single ancestral gene by four sequential gene duplications, leading to six genes that fall into three subsets, each consisting of two genes. During this evolutionary process, multiple rearrangements and gene conversion occurred mainly in the region from the 3 end of IVS2 and the 3 end of exon 3.