Search PubMed⌕ Search

Biomedical subjects

C G Jones

Publications and source records attributed to C G Jones.

At least 19 recordsLinked to original sources
PubMed2007

Avian blood parasites in an endangered columbid: Leucocytozoon marchouxi in the Mauritian Pink Pigeon Columba mayeri.

There is increasing evidence that pathogens can play a significant role in species decline. This study of a complete free-living species reveals a cost of blood parasitism to an endangered host, the Pink Pigeon Columba mayeri, endemic to Mauritius. We investigated the prevalence and effect of infection of the blood parasite, Leucocytozoon marchouxi, in the free-living Pink Pigeon population. Overall, L. marchouxi infection prevalence detected was 18.3%. Juveniles were more likely to be infected than older birds and there was geographical variation in infection prevalence. Survival of birds infected with L. marchouxi was lower than that of uninfected birds to 90 days post-sampling. This study suggests that while common haematozoa are well tolerated in healthy adults, these parasites may have greater pathogenic potential in susceptible juveniles. The study is unusual given its completeness of species sampling (96%) within a short time-period, the accurate host age data, and its focus on blood parasites in a threatened bird species. Species for which long-term life-history data are available for every individual serve as valuable models for dissecting the contribution of particular pathogens to species decline.

Animals↗
PubMed2004

Reconstructing an island radiation using ancient and recent DNA: the extinct and living day geckos (Phelsuma) of the Mascarene islands.

Mitochondrial (12SrRNA and cyt b, 1086 bp) and nuclear (c-mos, 374 bp) DNA sequences were used to investigate relationships and biogeography of 24 living and extinct taxa of Phelsuma geckos. Monophyly of Phelsuma and sister relationship to the SW African Rhoptropella is corroborated. Phelsuma originated on Madagascar and made multiple long-distance invasions of oceanic islands including the Mascarenes, Aldabra, Comores, Seychelles, Andamans, and perhaps Pemba. The Mascarenes were probably colonised once, about 4.2-5.1Ma, and here Phelsuma rosagularis and Phelsuma inexpectata are newly recognised as species, as are three lineages of Phelsuma cepediana. Mascarene relationships are: Phelsuma edwardnewtoni, Phelsuma gigas (Phelsuma guentheri ((((P. cepediana A (P. cepediana B, C)) P. rosagularis) Phelsuma borbonica) ((Phelsuma ornata, P. inexpectata) Phelsuma guimbeaui))). The two recently extinct species, P. edwardnewtoni and the giant secondarily nocturnal Phelsuma gigas, differentiated on Rodrigues while on Mauritius the large nocturnal P. guentheri separated from a small diurnal form that radiated into six species, a likely result of volcanic activity. Two small-bodied lineages from Mauritius invaded the more recent island of Réunion producing two more species. Outside the Mascarenes, two mainly Madagascan assemblages are substantiated: Phelsuma serraticauda (Phelsuma lineata, Phelsuma laticauda, Phelsuma quadriocellata); (Phelsuma m. kochi (Phelsuma m. grandis, Phelsuma abboti)) (Phelsuma astriata, Phelsuma sundbergi). Their relationships to the Mascarene clade, and to Phelsuma mutabilis, Phelsuma standingi and Phelsuma andamanensis are unresolved.

Animals↗
PubMed2001

Effects of acorn production and mouse abundance on abundance and Borrelia burgdorferi infection prevalence of nymphal Ixodes scapularis ticks.

Risk of exposure to Lyme disease is a function of the local abundance of nymphal Ixodes ticks that are infected with the etiological agent, the spirochete Borrelia burgdorferi. We monitored abundance of white-footed mice (the principal B. burgdorferi reservoir in the eastern and central United States) and acorns (a critical food resource for mice), and Ixodes scapularis ticks, as well as ambient temperature (cumulative growing degree days) and growing season precipitation, in a forested landscape of southeastern New York State from 1994 to 2000. We found that acorn production in autumn strongly influenced abundance of white-footed mice the following summer and that abundance of mice in summer, when larval ticks are active, influenced the abundance of infected nymphs the following year. Consequently, the abundance of infected nymphal ticks can be predicted from acorn production 1.75 years earlier. Monitoring of natural fluctuations in acorn production thus supports results of prior acorn addition experiments that were conducted at small spatial scales. Growing degree days and precipitation either had no significant effect on density of nymphs or marginally increased the explanatory power of models that included acorns or mouse density as independent variables. We conclude that, at our study site in New York, the risk of human exposure to Lyme disease is affected by mouse density in the prior year and by acorn production 2 years previously.

Animal Feed↗
PubMed2000

The evolution of secondary metabolism - a unifying model.

Why do microbes make secondary products? That question has been the subject of intense debate for many decades. There are two extreme opinions. Some argue that most secondary metabolites play no role in increasing the fitness of an organism. The opposite view, now widely held, is that every secondary metabolite is made because it possesses (or did possess at some stage in evolution) a biological activity that endows the producer with increased fitness. These opposing views can be reconciled by recognizing that, because of the principles governing molecular interactions, potent biological activity is a rare property for any molecule to possess. Consequently, in order for an organism to evolve the rare potent, biologically active molecule, a great many chemical structures have to be generated, most of which will possess no useful biological activity. Thus, the two sides of the debate about the role and evolution of secondary metabolism can be accommodated within the view that the possession of secondary metabolism can enhance fitness, but that many products of secondary metabolism will not enhance the fitness of the producer. It is proposed that secondary metabolism will have evolved such that traits that optimize the production and retention of chemical diversity at minimum cost will have been selected. Evidence exists for some of these predicted traits. Opportunities now exist to exploit these unique properties of secondary metabolism to enhance secondary product diversity and to devise new strategies for biotransformation and bioremediation.

Bacteria↗
PubMed1998

Minimal residual disease status before allogeneic bone marrow transplantation is an important determinant of successful outcome for children and adolescents with acute lymphoblastic leukemia.

The efficacy of allografting in acute lymphoblastic leukemia (ALL) is heavily influenced by remission status at the time of transplant. Using polymerase chain reaction (PCR)-based minimal residual disease (MRD) analysis, we have investigated retrospectively the impact of submicroscopic leukemia on outcome in 64 patients receiving allogeneic bone marrow transplantation (BMT) for childhood ALL. Remission BM specimens were taken 6 to 81 days (median, 23) before transplant. All patients received similar conditioning therapy; 50 received grafts from unrelated donors and 14 from related donors. Nineteen patients were transplanted in first complete remission (CR1) and 45 in second or subsequent CR. MRD was analyzed by PCR of Ig or T-cell receptor delta or gamma rearrangements, electrophoresis, and allele-specific oligoprobing. Samples were rated high-level positive (clonal band evident after electrophoresis; sensitivity 10(-2) to 10(-3)), low-level positive (MRD detected only after oligoprobing; sensitivity 10(-3) to 10(-5)), or negative. Excluding 8 patients transplanted in CR2 for isolated extramedullary relapse (all MRD-), MRD was detected at high level in 12 patients, low level in 11, and was undetectable in 33. Two-year event-free survival for these groups was 0%, 36%, and 73%, respectively (P <.001). Follow-up in patients remaining in continuing remission is 20 to 96 months (median, 35). These results suggest that MRD analysis could be used routinely in this setting. This would allow identification of patients with resistant leukemia (who may benefit from innovative BMT protocols) and of those with more responsive disease (who may be candidates for randomized trials of BMT versus modern intensive relapse chemotherapy).

Adolescent↗
PubMed1998

Chain reactions linking acorns to gypsy moth outbreaks and Lyme disease risk.

In eastern U.S. oak forests, defoliation by gypsy moths and the risk of Lyme disease are determined by interactions among acorns, white-footed mice, moths, deer, and ticks. Experimental removal of mice, which eat moth pupae, demonstrated that moth outbreaks are caused by reductions in mouse density that occur when there are no acorns. Experimental acorn addition increased mouse density. Acorn addition also increased densities of black-legged ticks, evidently by attracting deer, which are key tick hosts. Mice are primarily responsible for infecting ticks with the Lyme disease agent. The results have important implications for predicting and managing forest health and human health.

Animals↗
PubMed1998

Minimal residual disease status as a predictor of relapse after allogeneic bone marrow transplantation for children with acute lymphoblastic leukaemia.

We have analysed the behaviour of minimal residual disease (MRD) after allogeneic bone marrow transplantation (allo-BMT) in 71 children with acute lymphoblastic leukaemia (ALL). The method relied on PCR of IgH, TCRdelta and/or TCRgamma gene rearrangements followed by electrophoretic size resolution and allele-specific oligoprobing. Patients were similarly conditioned; 55 received marrow from unrelated donors and 16 from related donors. MRD was assessed at various time-points up to 24 months after BMT. Three children were not evaluable due to transplant-related mortality. MRD was detected in 28/32 patients (88%) who relapsed post-BMT; 16 were positive at all times and 12 were initially negative but became positive at a median of 3 months (range 1.5-11) prior to relapse. In contrast, only eight of 36 (22%) patients who remained in continuing complete remission (CCR) (median follow-up 43 months, range 20-94) showed MRD at any time after BMT (P<0.0001). In these eight patients MRD was found up to 9 months after transplant and at low levels (0.01-0.001%). All eight (median follow-up 39 months, range 24-87) had at least two MRD-negative samples tested subsequently and five of the eight had evidence of grade I-II acute graft-versus-host disease (GvHD), raising the possibility of a graft-versus-leukaemia effect. In general, any evidence of MRD after allo-BMT is a poor prognostic sign. However, if immunotherapy were to be targeted towards patients with evidence of persisting MRD after BMT, the method described would expose only a small proportion of patients to unnecessary additional toxicity.

Adolescent↗
PubMed1998

Unrelated donor bone marrow transplantation for children and adolescents with Philadelphia-positive acute lymphoblastic leukemia.

PURPOSE: Few patients with Philadelphia-positive acute lymphoblastic leukemia (Ph-positive ALL) have been cured by chemotherapy alone. Registry figures show that 38% of patients who have a matched-sibling bone marrow transplant (BMT) are disease-free 2 years after transplant, but the majority of patients lack a sibling donor. Most modern ALL protocols recommend unrelated donor (UD) BMT for patients with Ph-positive ALL in first complete remission (CR1), but the outcome of this is unknown. PATIENTS AND METHODS: We report the results of 15 children and adolescents who had a T-cell depleted UD-BMT for Ph-positive ALL. Thirteen of 15 had been previously treated on United Kingdom ALL protocols. Nine were in CR1 and six had more advanced disease. Eleven donor recipient pairs were matched at HLA-A, HLA-B, HLA-DR, and HLA-DQ, and four were mismatched at one or two HLA loci. RESULTS: The incidence of greater than grade I acute and chronic graft-versus-host disease (GVHD) was low (13% and 8%, respectively). Six patients have relapsed and seven patients survive at a median of 21 months post-BMT; six of seven are disease free. All seven survivors are in full-time education or work. The 2-year overall and disease-free survivals are 44% +/- 13% and 37% +/- 13% (+/- SE). None of four patients who had mismatched donors survived, but seven of 11 matched recipients survive (P < .05). CONCLUSION: UD-BMT can produce prolonged disease-free survival in young patients with Ph-positive ALL who otherwise would have an extremely poor outlook.

Adolescent↗
PubMed1997

Colorimetric detection of immobilised PCR products generated on a solid support.

By extending functional primers attached to a solid phase and incorporating a digoxigenin label, it is possible to visualise PCR products as discrete spots on specific regions of a solid support after colorimetric detection. The technique has been used for the detection of the point mutation associated with porcine malignant hyperthermia.

Alleles↗
PubMed1997

Chlorhexidine: is it still the gold standard?

After 20 years of use by the dental profession, chlorhexidine is recognized as the gold standard against which other antiplaque and gingivitis agents are measured. Chlorhexidine's antiplaque effect is a result of the dicationic nature of the chlorhexidine molecule, which affords the agent the property of persistence of antimicrobial effect at the tooth surface, through both bactericidal and bacteriostatic effects. Although other antiplaque agents may show either purely immediate effect, or limited persistence, the degree of chlorhexidine's persistence of effect at the tooth surface is the basis of its clinical efficacy. Similarly, the cationic nature of the chlorhexidine molecule is the basis of the most common side effect associated with the use of the agent--extrinsic tooth staining. Such tooth staining seems to be the result of a local precipitation reaction between tooth-bound chlorhexidine and chromogens found within foodstuffs and beverages. The cationic nature of the chlorhexidine molecule also means that the activity of the agent is rapidly reduced in the presence of anionic agents, specifically those found within certain types of toothpaste; thus care is required when using normal toothbrushing alongside chlorhexidine. By understanding how the chemical properties of the chlorhexidine molecule can explain the plethora of clinical efficacy and safety data, the use of chlorhexidine can be optimally aimed towards the patient groups who would most benefit from the superior therapeutic effect of the agent. Specifically, chlorhexidine would seem to be of most value to patients in whom the ability to perform adequate oral hygiene procedures has been compromised. In these individuals the delivery of the correct dose of chlorhexidine to the tooth surface can be optimized through the judicial use of the several different chlorhexidine formulations now available. Thus, by understanding the properties and limitations of the chlorhexidine molecule, the dental profession can ensure that the efficacy of the agent is maximized, and the side effects associated with the agent are minimized, allowing chlorhexidine to rightly remain the gold standard against which other antiplaque agents are measured.

Anti-Infective Agents, Local↗
PubMed1996

Measurement of metabolic fluxes through pyruvate kinase, phosphoenolpyruvate carboxykinase, pyruvate dehydrogenase, and pyruvate carboxylate in hepatocytes of different acinar origin.

Isolated hepatocytes were prepared from the periportal and perivenous regions of the liver of 18-h-starved rats. These showed characteristics enzyme patterns and an enhanced rate of ureagenesis in the periportal cells; however, total cellular ATP content was unchanged in the two cell types. Measurements of pyruvate kinase flux showed no significant difference in the overall rate in the two cell types; however, the flux through phosphoenolpyruvate (PEP) carboxykinase was significantly higher in the periportal cells, such that the percentage of PEP being metabolized by pyruvate kinase was enhanced in the perivenous cells. The increase in partitioning of PEP through pyruvate kinase could account for only a small percentage of the difference in gluconeogenic flux in the two cell types, suggesting that the rate of provision of PEP was the principal limiting factor for glucose synthesis. The flux through pyruvate dehydrogenase showed no significant metabolic zonation, whereas pyruvate carboxylase flux was enhanced in the periportal zone. The partitioning of pyruvate between pyruvate carboxylase and pyruvate dehydrogenase was increase 2.8-fold in the periportal cells compared to that in the perivenous cells and it is suggested that this, together with possible alterations in phosphoenolpyruvate carboxykinase, is primarily responsible for the different gluconeogenic rates in the two zones of the liver.

Animals↗
PubMed1996

Protease inhibitor studies and cloning of a serine carboxypeptidase cDNA from germinating seeds of pea (Pisum sativum L.).

The nature of the proteolytic activity found within the germinating pea (Pisum sativum) seed, 4 days from the initiation of imbibition, was determined by the use of specific protease inhibitors. These studies have shown most of the activity to belong to metallo or metal-activated and serine proteases. In order to investigate further the serine protease activity, a pea cotyledon germination cDNA library was, therefore, screened with a wheat cDNA (2437) [Baulcombe, D.C., Barker, R.F. & Jarvis, M.G. (1987) J. Biol. Chem. 262, 13726-13735] which had extensive similarity to the yeast serine carboxypeptidase Y gene. A positive cDNA clone (pNY551) was obtained which had extensive similarity to the four carboxypeptidases, Arabidopsis thaliana carboxypeptidase Y-like protein, rice serine carboxypeptidase III, barley serine carboxypeptidase III and wheat serine carboxypeptidase III precursor. Northern-blot analysis showed mRNA homologous to pNY551 to be expressed in late developmental pea seed and again during germination.

Amino Acid Sequence↗
PubMed1996

Controlling growth and chemical composition of saplings by iteratively matching nutrient supply to demand: a bootstrap fertilization technique.

We developed a fertilization technique that results in the control, and maintenance at defined rates and levels, of growth and tissue composition of plants of different sizes and developmental stages growing at exponential and nonexponential rates in solid media under naturally fluctuating light and temperature regimes. Clonal cottonwood (Populus deltoides Bartr.) saplings were grown in sand. Low concentrations of nutrient solution were added daily at different constant exponentially increasing rates for 20-30 days to produce plants with different growth rates and tissue nutrient composition. Matching nutrient supply to measured growth demand by bootstrapping, where bootstrapping is the use of an iterative equation that calculates demand from either actual or desired growth rates, maintained these differences for 20-40 days. Nutrient additions controlled growth of saplings with growth rates between 2.0 and 4.0% day(-1), heights between 13.9 and 37.5 cm, dry weights between 0.70 and 3.90 g, leaf nitrogen contents between 1.2 and 3.9%, and leaf carbon/nitrogen ratios between 42.1 and 12.5. The technique was reproducible in a greenhouse without temperature, humidity, or light control, and is easily modified to suit different plant species, plants of various sizes, and various growing conditions.

Journal Article↗