Carryover effects from environmental change in early life: An overlooked driver of the amphibian extinction crisis?

Ecological carryover effects, or delayed effects of the environment on an organism's phenotype, are central predictors of individual fitness and a key issue in conservation biology. Climate change imposes increasingly variable environmental conditions that may be challenging to early life-history stages in animals with complex life histories, leading to detrimental physiological and fitness effects in later life. Yet, the latent nature of carryover effects, combined with the long temporal scales over which they can manifest, means that this phenomenon remains understudied and is often overlooked in short-term studies limited to single life-history stages. Herein, we review evidence for the physiological carryover effects induced by elevated ultraviolet radiation (UVR; 280–400 nm) as a potential contributor to recent amphibian population declines. UVR exposure causes a suite of molecular, cellular and physiological consequences known to underpin carryover effects in other taxa, but there is a lack of research linking embryonic and larval UVR exposures to fitness consequences post-metamorphosis in amphibians. We propose that the key impacts of UVR on disease-related amphibian declines are facilitated through carryover effects that bridge embryonic and larval UVR exposure with potential increased disease susceptibility post-metamorphosis. We conclude by identifying a practical direction for the study of ecological carryover effects in amphibians that could guide future ecological research in the broader field of conservation physiology. Only by addressing carryover effects can many of the mechanistic links between environmental change and population declines be elucidated.     

The Economics of Dementia-Care Mapping in Nursing Homes: A Cluster-Randomised Controlled Trial

Background

Dementia-care mapping (DCM) is a cyclic intervention aiming at reducing neuropsychiatric symptoms in people with dementia in nursing homes. Alongside an 18-month cluster-randomized controlled trial in which we studied the effectiveness of DCM on residents and staff outcomes, we investigated differences in costs of care between DCM and usual care in nursing homes.

Methods

Dementia special care units were randomly assigned to DCM or usual care. Nurses from the intervention care homes received DCM training, a DCM organizational briefing day and conducted the 4-months DCM-intervention twice during the study. A single DCM cycle consists of observation, feedback to the staff, and action plans for the residents. We measured costs related to health care consumption, falls and psychotropic drug use at the resident level and absenteeism at the staff level. Data were extracted from resident files and the nursing home records. Prizes were determined using the Dutch manual of health care cost and the cost prices delivered by a pharmacy and a nursing home. Total costs were evaluated by means of linear mixed-effect models for longitudinal data, with the unit as a random effect to correct for dependencies within units.

Results

34 units from 11 nursing homes, including 318 residents and 376 nursing staff members participated in the cost analyses. Analyses showed no difference in total costs. However certain changes within costs could be noticed. The intervention group showed lower costs associated with outpatient hospital appointments over time (p = 0^.05) than the control group. In both groups, the number of falls, costs associated with the elderly-care physician and nurse practitioner increased equally during the study (p<0^.02).

Conclusions

DCM is a cost-neutral intervention. It effectively reduces outpatient hospital appointments compared to usual care. Other considerations than costs, such as nursing homes’ preferences, may determine whether they adopt the DCM method.

Trial Registration

Dutch Trials Registry NTR2314     

Prenatal treatment of congenital human cytomegalovirus infection by fetal intravascular administration of ganciclovir

Ganciclovir was administered 'in utero' for 12 days in a 29-week-old fetus with ascertained congenital human cytomegalovirus (HCMV) infection, thrombocytopenia and elevated gamma-glutamyl transferase (gammaGT) value. Efficacy of therapy was shown by reduction in virus titer of amniotic fluid and fetal urine, disappearance of viral DNA in fetal blood, and normalization of platelet count and gammaGT value. However, stillbirth occurred at 32 weeks of gestation and HCMV inclusion bodies were detected in kidneys, lungs, heart and pancreas at autopsy. During therapy, side-effects,possibly related to ganciclovir administration, were observed.     

Mutation of the cyclin-dependent kinase phosphorylation site in simian virus 40 (SV40) large T antigen specifically blocks SV40 origin DNA unwinding.

A mutant simian virus 40 (SV40) large tumor (T) antigen bearing alanine instead of threonine at residue 124 (T124A) failed to replicate SV40 DNA in infected monkey cells (J. Schneider and E. Fanning, J. Virol. 62:1598-1605, 1988). We investigated the biochemical properties of T124A T antigen in greater detail by using purified protein from a baculovirus expression system. Purified T124A is defective in SV40 DNA replication in vitro, but does bind specifically to the viral origin under the conditions normally used for DNA replication. The mutant protein forms double-hexamer complexes at the origin in an ATP-dependent fashion, although the binding reaction requires somewhat higher protein concentrations than the wild-type protein. Binding of T124A protein results in local distortion of the origin DNA similar to that observed with the wild-type protein. These findings indicate that the replication defect of T124A protein is not due to failure to recognize and occupy the origin. Under some conditions T124A is capable of unwinding short origin DNA fragments. However, the mutant protein is almost completely defective in unwinding of circular plasmid DNA molecules containing the SV40 origin. Since the helicase activity of T124A is essentially identical to that of the wild-type protein, we conclude that the mutant is defective in the initial opening of the duplex at the origin, possibly as a result of altered hexamer-hexamer interactions. The phenotype of T124A suggests a possible role for phosphorylation of threonine 124 by cyclin-dependent kinases in controlling the origin unwinding activity of T antigen in infected cells.     

Recognition of pathogenic Yersinia enterocolitica by crystal violet binding and polymerase chain reaction

Cefsulodin-Irgasan-Novobiocin (CIN) agar is used for the selective isolation and enumeration of Yersinia enterocolitica from clinical specimens and food. The medium contains crystal violet and about 1 mmol l^-1 calcium and can be used for the phenotypic characterization of strains that carry a virulence plasmid. At 32°C, irrespective of pathogenicity, colonies are translucent with a pale pink centre surrounded by a transparent border ('bullseye'), while at 37°C pathogenic strains grow as calcium-dependent microcolonies which, because of crystal violet binding, are intensely coloured. These results were confirmed by the polymerase chain reaction with primers directed at the vir F gene, which is present only in pathogenic strains of Y. enterocolitica. Pathogenic strains of Y. enterocolitica can be recognized by growth at 37°C on Yersinia selective agar.     

An investigation into the membrane-interactive potential of the Escherichia coli KpsE C-terminus

Membrane binding via C-terminal amphiphilic alpha-helical structure is a novel anchoring mechanism, which has been characterised in a number of prokaryotic carboxypeptidases. Here, we have used graphical and DWIH analyses to ascertain if a similar anchoring mechanism may be utilised by the Escherichia coli KpsE protein in its binding to the periplasmic face of the inner membrane. The results of these analyses have been compared to those obtained for similar analyses of the C-terminal sequences of E. coli penicillin-binding proteins (PBPs) PBP5 and PBP6 which, are known to function as amphiphilic alpha-helical membrane anchors, and of melittin, a known membrane-interactive toxin. We have also used FTIR spectroscopy and lipid phase transition temperature analysis to investigate the interaction of a peptide homologue of KpsE C-terminal region with membrane lipid. Our results suggest that the KpsE C-terminal sequence has the potential to form an amphiphilic alpha-helix and that this alpha-helix could feature in the membrane binding of the protein.     

Phenylalanine kinetics in healthy volunteers and liver cirrhotics: implications for the phenylalanine breath test

Expired 13CO2 recovery from an oral l-[1-13C]phenylalanine ([13C]Phe) dose has been used to quantify liver function. This parameter, however, does not depend solely on liver function but also on total CO2 production, Phe turnover, and initial tracer distribution. Therefore, we evaluated the impact of these factors on breath test values. Nine ethyl-toxic cirrhotic patients and nine control subjects received intravenously 2 mg/kg of [13C]Phe, and breath and blood samples were collected over 4 h. CO2 production was measured by indirect calorimetry. The exhaled 13CO2 enrichments were analyzed by isotope ratio mass spectrometry and the [13C]Phe and l-[1-13C]tyrosine enrichments by gas chromatography-mass spectrometry. The cumulative 13CO2 recovery was significantly lower in cirrhotic patients (7 vs. 12%; P < 0.01), in part due to lower total CO2 production rates. Phe turnover in cirrhotic patients was significantly lower (33 vs. 44 micro mol. kg(-1). h(-1); P < 0.05). When these extrahepatic factors were considered in the calculation of the Phe oxidation rate, the intergroup differences were even more pronounced (3 vs. 7 micro mol. kg(-1). h(-1)) than those for 13CO2 recovery data. Also, the Phe-to-Tyr conversion rate, another indicator of Phe oxidation, was significantly reduced (0.7 vs. 3.0 micro mol. kg(-1). h(-1)).     

Restriction enzyme analysis of DNA methylation in "condensed" chromatin of Ha-ras-transformed NIH 3T3 cells.

Increased amounts of chromatin condensation (i.e., localized areas of high DNA density, or chromatin higher order packing state) have been described in NIH 3T3 cells transformed with the Ha-ras oncogene. The structural basis for this oncogene-mediated alteration in nuclear organization is unknown. Since DNA methylation is likely to be involved in regulating the nucleosomal level of DNA packaging, we studied the role of DNA methylation in higher-order chromatin organization induced by Ha-ras. CpG-methylated DNA content was estimated in "condensed" chromatin of Ha-ras-transformed NIH 3T3 cell lines which differ in ras expression and ras-induced metastatic ability but present approximately the same values of "condensed" chromatin areas. The question posed was that if DNA methylation were involved with the chromatin higher-order organization induced by Ha-ras in these cell lines, the methylated DNA density in the "condensed" chromatin would also be the same. The DNA evaluation was performed by video image analysis in Feulgen-stained cells previously subjected to treatment with Msp I and Hpa II restriction enzymes, which distinguish between methylated and non-methylated DNA. The amount of methylated CpG sequences not digested by Hpa II in "condensed" chromatin regions was found to vary in the studied ras-transformed cell lines. DNA CpG methylation status is thus suggested not to be involved with the higher order chromatin condensation induced by ras transformation in the mentioned NIH 3T3 cell lines.