Utilization of milk energy by suckling mink kits

A total of 36 mink dams and their litters of 3, 6 or 9 kits were used for determination of milk intake of the suckling young by means of deuterium dilution technique, and chemical composition of milk and of kit bodies. Measurements were performed during lactation weeks 1?–?4, each week with 3 dams with each litter size. Milk intake was determined over a 48?h measurement period, and by the end of this milk samples were collected and 2 kits (litters of 6 and 9) or 1 kit per litter (litters of 3) were killed for body chemical composition. Based on the results, different models were applied for calculation of the energetic efficiency of milk. Dam milk yield increased steadily from week 1 until week 3 but only slightly from week 3 to 4. The increase declined with increasing litter size, and for dams suckling 9 kits the increment from week 3 to week 4 was only 2?g. The dry matter content of milk increased significantly as lactation progressed, being reflected in crude protein increasing from 6.9% in lactation week 1 to 8.1% in week 4. Milk fat increased concomitantly from 5.6% to 8.0%. In kit bodies, crude protein content increased from 9.4% in week 1 to about 12% in weeks 3 and 4. Body fat content increased from week 1 (4.1%) to week 3 (8.4%) and then declined in week 4 (7.1%). Animals suckled in litters of 3 kits had the highest milk intake and live weight and kits suckled in litters of 9 had the lowest milk intake, live weight and daily gain. In terms of milk intake per g gain kits in litters of 6 were the most efficient, with 4.1?g milk per g body gain. The metabolizable energy requirement for maintenance (MEm) was estimated to 448 kJ/kg^0.75 and the efficiency of utilization of ME for body gain (k_g) to 0.67, the estimates being higher (MEm) or in good agreement with previous findings (k_g) in suckling mink kits.     

Reduced toxicity and broad spectrum resistance to viral and fungal infection in transgenic plants expressing pokeweed antiviral protein II

Pokeweed antiviral protein II (PAPII), a 30 kDa protein isolated from leaves of Phytolacca americana, inhibits translation by catalytically removing a specific adenine residue from the large rRNA of the 60S subunit of eukaryotic ribosomes. The protein sequence of PAPII shows only 41% identity to PAP and PAP-S, two other antiviral proteins isolated from pokeweed. We isolated a cDNA corresponding to PAPII and introduced it into tobacco plants. PAPII expressed in transgenic tobacco was correctly processed to the mature form as in pokeweed and accumulated to at least 10-fold higher levels than wild-type PAP. We had previously observed a significant decrease in transformation frequency with PAP and recovered only two transgenic lines expressing 1–2 ng per mg protein. In contrast, eight different transgenic lines expressing up to 250 ng/mg PAPII were recovered, indicating that PAPII is less toxic than PAP. Two symptomless transgenic lines expressing PAPII were resistant to tobacco mosaic virus, potato virus X and the fungal pathogen Rhizoctonia solani. The level of viral and fungal resistance observed correlated well with the amount of PAPII protein accumulated. Pathogenesis-related protein PR1 was constitutively expressed in transgenic lines expressing PAPII. Although PR1 was constitutively expressed, no increase in salicylic acid levels was detected, indicating that PAPII may elicit a salicylic acid-independent signal transduction pathway.     

The variant inv(2)(p11.2q13) is a genuinely recurrent rearrangement but displays some breakpoint heterogeneity

Human chromosome 2 contains large blocks of segmental duplications (SDs), both within and between proximal 2p and proximal 2q, and these may contribute to the frequency of the common variant inversion inv(2)(p11.2q13). Despite their being cytogenetically homogeneous, we have identified four different breakpoint combinations by fluorescence in situ hybridization mapping of 40 cases of inv(2)(p11.2q13) of European origin. For the vast majority of inversions (35/40), the breakpoints fell within the same spanning BACs, which hybridized to both 2p11.2 and 2q13 on the normal and inverted homologues. Sequence analysis revealed that these BACs contain a significant proportion of intrachromosomal SDs with sequence homology to the reciprocal breakpoint region. In contrast, BACs spanning the rare breakpoint combinations contain fewer SDs and with sequence homology only to the same chromosome arm. Using haplotype analysis, we identified a number of related family subgroups with identical or very closely related haplotypes. However, the majority of cases were not related, demonstrating for the first time that the inv(2)(p11.2q13) is a truly recurrent rearrangement. Therefore, there are three explanations to account for the frequent observation of the inv(2)(p11.2q13): the majority have arisen independently in different ancestors, while a minority either have been transmitted from a common founder or have different breakpoints at the molecular cytogenetic level.     

An infantile case of Zellweger syndrome presented with Kabuki-like phenotype

Zellweger syndrome is a peroxisomal disorder resulting from the mutations in PEX genes generally presenting in the neonatal period with profound hypotonia seizures, inability to feed, liver cysts with hepatic dysfunction, chondrodysplasia punctata. Kabuki make-up syndrome is a multiple congenital anomalies and mental retardation syndrome with characteristic facial appearance, skeletal abnormalities, dermatoglyphic abnormalities, mental retardation and short stature. Abnormal liver functions and some atypical findings were also reported in some patients with Kabuki syndrome. In this report a case with late onset Zellweger syndrome who had some phenotypical findings which are also seen in Kabuki Syndrome will be presented. The inclusion of Zellweger syndrome into the differential diagnosis of the patients with Kabuki-like phenotype in addition to abnormal liver functions is emphasized.     

Evidence for retro-translocation of pokeweed antiviral protein from endoplasmic reticulum into cytosol and separation of its activity on ribosomes from its activity on capped RNA

Pokeweed antiviral protein (PAP) is a single-chain ribosome inactivating protein (RIP) that binds to ribosomes and depurinates the highly conserved alpha-sarcin/ricin loop (SRL) of the large subunit rRNA. Catalytic depurination of a specific adenine has been proposed to result in translation arrest and cytotoxicity. Here, we show that both precursor and mature forms of PAP are localized in the endoplasmic reticulum (ER) in yeast. The mature form is retro-translocated from the ER into the cytosol where it escapes degradation unlike the other substrates of the retro-translocation pathway. A mutation of a highly conserved asparagine residue at position 70 (N70A) delays ribosome depurination and the onset of translation arrest. The ribosomes are eventually depurinated, yet cytotoxicity and loss of viability are markedly absent. Analysis of the variant protein, N70A, does not reveal any decrease in the rate of synthesis, subcellular localization, or the rate of transport into the cytosol. N70A destabilizes its own mRNA, binds to cap, and blocks cap dependent translation, as previously reported for the wild-type PAP. However, it cannot depurinate ribosomes in a translation-independent manner. These results demonstrate that N70 near the active-site pocket is required for depurination of cytosolic ribosomes but not for cap binding or mRNA destabilization, indicating that the activity of PAP on capped RNA can be uncoupled from its activity on rRNA. These findings suggest that the altered active site of PAP might accommodate a narrower range of substrates, thus reducing ribotoxicity while maintaining potential therapeutic benefits.     

A relatively low level of ribosome depurination by mutant forms of ricin toxin A chain can trigger protein synthesis inhibition,cell signaling and apoptosis in mammalian cells

The A chain of the plant toxin ricin (RTA) is an N-glycosidase that inhibits protein synthesis by removing a specific adenine from the 28S rRNA. RTA also induces ribotoxic stress, which activates stress-induced cell signaling cascades and apoptosis. However, the mechanistic relationship between depurination, protein synthesis inhibition and apoptosis remains an open question. We previously identified two RTA mutants that suggested partial independence of these processes in a yeast model. The goals of this study were to establish an endogenous RTA expression system in mammalian cells and utilize RTA mutants to examine the relationship between depurination, protein synthesis inhibition, cell signaling and apoptosis in mammalian cells. The non-transformed epithelial cell line MAC-T was transiently transfected with plasmid vectors encoding precursor (pre) or mature forms of wild-type (WT) RTA or mutants. PreRTA was glycosylated indicating that the native signal peptide targeted RTA to the ER in mammalian cells. Mature RTA was not glycosylated and thus served as a control to detect changes in catalytic activity. Both pre- and mature WT RTA induced ribosome depurination, protein synthesis inhibition, activation of cell signaling and apoptosis. Analysis of RTA mutants showed for the first time that depurination can be reduced by 40% in mammalian cells with minimal effects on inhibition of protein synthesis, activation of cell signaling and apoptosis. We further show that protein synthesis inhibition by RTA correlates more linearly with apoptosis than ribosome depurination.     

Fluctuating asymmetry in bank vole populations (Rodentia, Arvicolinae) reflects stress caused by landscape fragmentation in the Mont-Saint-Michel Bay

In intensively farmed, reclaimed areas (polders) of Mont-St-Michel Bay, France, bank voles ( Clethrionomys glareolus ) live in fragmented hedgerows, where populations are small and dispersal rates and genetic diversity are low. These small populations are likely to have been exposed to potential environmental and/or genetic stress. The sensitivity of development to stress can be measured by fluctuating asymmetry (FA). FA was calculated for three samples from a disturbed area and one sample from an adjacent, more connected and undisturbed landscape. Size FA was estimated from 16 measurements of the skull and teeth whilst shape asymmetry was estimated from the skull alone. Bank voles in fragmented hedgerows of the disturbed area had a higher degree of FA than bank voles from the more extensive and more connected hedges of the undisturbed area. These results were confirmed by the study of shape asymmetry, body mass and centroid size of the skull. There were no differences in FA between the three disturbed area samples. We conclude that FA does not reveal differences in the development of bank voles living in isolation under different local conditions in the various parts of the disturbed area. However, FA may allow differentiation between populations from greatly contrasting landscapes.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80, 37–44.     

The effect of intracerebroventricular D-ALA2 methionine enkephalinamide and naloxone on cardiovascular parameters in the cat

Lathers and Schraeder (1) have shown that autonomic dysfunction is associated with epileptogenic activity induced by pentylenetetrazol while Vindrola et al (2) found increased D-ALA2 methionine-enkephalinamide (DAME) levels in the rat brain after pentylenetetrazol-induced epileptogenic activity. Thus, this study was designed to determine whether DAME could have contributed, at least in part, to the autonomic dysfunction associated with pentylenetetrazol-induced epileptogenic activity in the study of Lathers and Schraeder (1). DAME (500 micrograms/kg, icv) was given to 9 cats anesthetized with alpha chloralose. Epileptogenic activity and hypotension occurred in all cats (maximum fall ranging from 6 to 46 mmHg; duration of 6 to 35 min). In 6 cats the heart rate decreased, in 2 it increased, and in 1 it showed little or no change. The duration of heart rate changes varied from 18 to 76 min. Naloxone (100 micrograms/kg, iv) was given to 6 cats after DAME. Naloxone suppressed or abolished the epileptogenic activity in all 6 cats, reversed the DAME-induced hypotension and increased the heart rate in 3 cats, decreased it in 2, and produced no change in 1. These results indicate that DAME may produce epileptogenic activity and cardiovascular changes through an action on central opiate receptors. It is hypothesized that: 1) increased levels of DAME inhibit the release of gamma aminobutyric acid; 2) this then increases vagal bradycardia and hypotension; and 3) step 2 causes an imbalance in peripheral autonomic cardiac neural discharge which may cause arrhythmias and/or sudden unexplained death in the epileptic person.     

Plant palatability and disturbance level in aquatic habitats: an experimental approach using the snail Lymnaea stagnalis (L.)

1. The palatability of aquatic macrophytes to the snail Lymnaea stagnalis was investigated in the laboratory. Eight species of macrophyte were selected from habitats that differed in either flood disturbance regime or nutrient status.
2. In a non-choice test, single macrophyte species were offered to individual snails. The average amount of plant dry mass consumed per Lymnaea dry mass ranged from 3.6 ± 1.4 (±SE) to 63.6 ± 13.9 mg g^–1 day^–1 across plant species. In a choice test, all eight plant species were presented simultaneously to sets of five snails. The average total consumption was 66.1 ± 3.8 mg g^–1 day^–1 and the maximum average consumption for a single plant was 26.2 ± 3.6 mg g^–1 day^–1.
3. In both tests, the amount consumed by snails differed significantly between the plant species. The species growing in undisturbed habitats were the least consumed. Habitat nutrient status was unrelated to plant palatability.
4. These results suggest that macrophyte species growing in habitats that are rarely disturbed by floods allocate a greater proportion of their resources to resisting herbivory.