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PubMed1996

Stromal fibroblast heparan sulfate is required for cytokine-mediated ex vivo maintenance of human long-term culture-initiating cells.

We have recently demonstrated that 50% of primitive human long-term culture-initiating cells (LTC-IC) are maintained for up to 8 weeks in stroma-dependent cultures in which progenitor-stroma contact is prevented (stroma noncontact), or when progenitors are cultured in medium conditioned by stromal feeders. This indicates that factors responsible for LTC-IC maintenance are present in soluble form in stromal supernatant (SN). Although the picogram concentrations of cytokines present in stromal SN can induce the differentiation of CD34+/HLA-DR- (DR-) cells to clonogenic cells (colony forming cells; CFC), they maintain only 10% of LTC-IC for 5 weeks, suggesting that factors other than these cytokines are required for LTC-IC maintenance. To characterize the factor(s) in stromal SN responsible for LTC-IC maintenance, we purified glycoproteins and proteoglycans (PG) from the SN of the LTC-IC supportive murine marrow stromal fibroblast cell line M2-10B4 by ion exchange high performance liquid chromatography (HPLC). Culture of DR- cells in a combination of M2-10B4-derived PG, but not glycoproteins and picogram concentrations of recombinant human interleukin-6 (IL-6), granulocyte colony-stimulating factor (G-CSF), stem cell factor (SCF), leukemia inhibitory factor (LIF), granulocyte-macrophage colony-stimulating factor (GM-CSF), and macrophage inflammatory protein-1alpha (MIP-1alpha) resulted in the recovery of 96% +/- 8% of LTC-IC maintained in cultures supplemented with unfractionated stromal SN. LTC-IC maintenance was largely retained after digestion of the PG-rich fraction with proteinase K and after dissociative gel filtration chromatography, but was completely abolished following treatment with nitrous acid, which digests heparan sulfate glycosaminoglycans (HS GAG). As for M2-10B4-derived HS GAG, high concentrations of bovine kidney HS GAG, but not bovine tracheal chondroitin sulfate, significantly improved cytokine-mediated LTC-IC maintenance. Maintenance of LTC-IC by these nonmarrow-derived HS GAG was, however, significantly lower than that seen with M2-10B4-derived HS. These studies demonstrate a role for marrow stroma-derived HS GAG in the long-term in vitro maintenance of human LTC-IC. Further structure-function analysis of these HS GAG may have important implications for ex vivo stem cell expansion and gene transfer into hematopoietic progenitors.

Animals↗
PubMed1990

Health maintenance organizations vs indemnity insurance for children with chronic illness. Trading gaps in coverage.

There has been increasing discussion about the potential of health maintenance organizations to provide improved access to and coordination of care for children with complex conditions. This study compares benefits for a sample of health maintenance organizations and traditional indemnity insurers in Connecticut. We conclude that in Connecticut neither health maintenance organizations nor traditional indemnity insurers currently offer comprehensive systems of care to these children. Health maintenance organizations offer preventive care and are easier systems to access. However, for children with chronic conditions, health maintenance organizations have some problematic restrictions, including a lag between start of employment and activation of health care benefits. Both health maintenance organizations and traditional indemnity insurers tend to have restrictions for specific services needed by children with chronic illnesses, such as medical equipment and mental health services. Case managers in both systems tend to control expenditures rather than to coordinate care. Representatives of both systems predict additional restrictions in the future. Our data suggest the need for more extensive evaluation of the generalizability of these findings.

Child↗
PubMed2000

Planning factors for developing an enterprise-wide picture archiving and communication system maintenance program.

Picture archiving and communication system (PACS) maintenance on an individual site basis has historically been a complex and costly challenge. With the advent of enterprise-wide PACS projects such as the Virtual Radiology Environment (VRE) project, the challenge of a maintenance program with even more complexities has presented itself. The approach of the project management team for the VRE project is not one of reactive maintenance, but one of highly proactive planning and negotiations, in hopes of capitalizing on the economies of scale of an enterprise-wide PACS maintenance program. A proactive maintenance program is one aspect of life-cycle management. As with any capital acquisition, life-cycle management may be used to manage the specific project aspects related to PACS. The purpose of an enterprise-wide warranty and maintenance life-cycle management approach is to maintain PACS at its maximum operational efficiency and utilization levels through a flexible, shared, yet symbiotic relationship between local, regional, and vendor resources. These goals include providing maximum operational performance levels on a local, regional, and enterprise basis, while maintaining acceptable costs and resource utilization levels. This goal must be achieved without negatively impacting point of care activities, regardless of changes to the clinical business environment.

Cost-Benefit Analysis↗
PubMed2002

Unsafe acts and unsafe outcomes in aircraft maintenance.

Road safety studies using the Driver Behaviour Questionnaire (DBQ) have provided support for a three-way distinction between violations, skill-based errors and mistakes, and have indicated that a tendency to commit driving violations is associated with an increased risk of accident involvement. The aims of this study were to examine whether the three-way distinction of unsafe acts is applicable in the context of aircraft maintenance, and whether involvement in maintenance safety occurrences can be predicted on the basis of self-reported unsafe acts. A Maintenance Behaviour Questionnaire (MBQ) was developed to explore patterns of unsafe acts committed by aircraft maintenance mechanics. The MBQ was completed anonymously by over 1300 Australian aviation mechanics, who also provided information on their involvement in workplace accidents and incidents. Four factors were identified: routine violations, skill-based errors, mistakes and exceptional violations. Violations and mistakes were related significantly to the occurrence of incidents that jeopardized the quality of aircraft maintenance, but were not related to workplace injuries. Skill-based errors, while not related to work quality incidents, were related to workplace injuries. The results are consistent with the three-way typology of unsafe acts described by Reason et al. (1990) and with the DBQ research indicating an association between self-reported violations and accidents. The current findings suggest that interventions addressed at maintenance quality incidents should take into account the role of violations and mistakes, and the factors that promote them. In contrast, interventions directed at reducing workplace injury are likely to require a focus on skill-based errors.

Accidents, Occupational↗
PubMedDate not supplied

A computer-assisted preventive maintenance system.

With the growing number of hospitals developing in-house preventive maintenance capabilities, and the increasing number of pieces of equipment and instruments needing preventive maintenance, automatic data processing has emerged as a tool to aid the clinical engineer and hospital in planning preventive maintenance programs. Such a system is CAPMS, or Computer Assisted Preventive Maintenance System. Through the use of CAPMS, the department in charge of Preventive Maintenance can keep accurate records of PM history, safety testing, and year-to-year maintenance costs. Some of the special features of CAPMS include: information of availability of equipment for servicing, priorities, and a text file that can be used to print out the procedure form for use during the PM. These additional features make CAPMS a useful tool to the clinical engineer.

Computers↗
PubMedDate not supplied

Classifying medical devices according to their maintenance sensitivity: a practical, risk-based approach to PM program management.

Many medical equipment items need periodic attention to ensure that they continue to operate properly and safely; and most inspecting agencies require healthcare facilities to have a competent equipment maintenance program that is focused on the most critical of those devices. There is however a long-standing lack of consensus on how best to determine which devices should be included in this critical device category, and which can reasonably be excluded. A new methodology is proposed for establishing a logical, fact-based framework for determining which devices should be included. It is based in part on a new FDA-sanctioned definition of what an appropriate regimen of planned maintenance activities for a medical device should include. This new definition addresses the medical device users' concerns about periodic performance verification and safety testing as well as detecting and correcting the wear or progressive deterioration of any non-durable parts, which is the primary focus of the conventional preventive maintenance programs found in less critical industries. The analytical approach proposed utilizes technical information that is either already available or which can be easily developed. It characterizes each different device by means of a 3-letter maintenance sensitivity profile that can be used to analyze the effectiveness of the maintenance procedures as well as quantify the device's sensitivity to planned maintenance. A collaborative effort to assemble and organize this data would provide the industry with a sound, logical platform for narrowing the scope of most PM programs and allow us to redirect a significant amount of scarce technical manpower into more productive activities such as device user training.

Equipment and Supplies↗
PubMed2003

Prevalence of hepatitis C in patients on maintenance haemodialysis.

OBJECTIVE: To find the prevalence of hepatitis C in patients on maintenance haemodialysis. DESIGN: A case control study. PLACE AND DURATION OF STUDY: Haemodialysis unit at Sheikh Zayed Postgraduate Medical Institute, Lahore, Pakistan in December 1999. PATIENTS AND METHODS: Fifty patients who were on maintenance haemodialysis were screened for anti HCV antibody. Fifty normal individuals who did not have any identifiable risk factors were also screened for anti HCV antibody. The relative risk and prevalence was calculated for the patients on maintenance haemodialysis. RESULTS: Sixty-eight percent of the patients on maintenance haemodialysis were found to be positive for anti HCV antibody. Prevalence in normal individuals was 10 percent and relative risk for the patients on maintenance haemodialysis was 6.8. CONCLUSION: Hepatitis-C is endemic among patients on maintenance haemodialysis and prevalence is much higher in developing countries as compared to developed world.

Adolescent↗
PubMed2003

Initial and maintenance naltrexone treatment for alcohol dependence using primary care vs specialty care: a nested sequence of 3 randomized trials.

BACKGROUND: Naltrexone may improve success in primary care treatment of alcohol dependence (AD). This study tests naltrexone and primary care management (PCM) vs naltrexone and cognitive behavior therapy (CBT) and tests naltrexone maintenance among patients who respond to an initial course of naltrexone combined with PCM vs CBT. METHODS: A nested sequence of 3 randomized trials was conducted. In study 1, 197 subjects with AD participated in a 10-week comparison of PCM and naltrexone (50 mg/d) vs CBT and naltrexone (50 mg/d). In study 2, 53 PCM responders from study 1 continued in a 24-week placebo-controlled study of maintenance naltrexone. In study 3, 60 CBT responders from study 1 continued in a 24-week placebo-controlled study of maintenance naltrexone and CBT. RESULTS: Study 1: No difference in the response to treatment; 84.1% (74/88) of the PCM patients and 86.5% (77/89) of the CBT patients avoided persistent heavy drinking. Percentage of days abstinent (PDA) declined over time for PCM vs CBT (P =.03). Study 2: Higher response maintenance for PCM and naltrexone (21/26, 80.8%) vs PCM and placebo (14/27, 51.9%; P =.03) and PDA declined more for the placebo group (P =.02). Study 3: The differences between naltrexone vs placebo on maintenance of response (25/30, 83.3% vs 21/30, 70.0%) or PDA did not reach statistical significance. CONCLUSIONS: Naltrexone yielded comparable results during the initial 10 weeks of treatment when combined with PCM or CBT. Maintenance of improvement was enhanced by continued naltrexone treatment in the PCM but not in the CBT arm.

Adolescent↗
PubMed2001

Methadone maintenance in primary care: a randomized controlled trial.

CONTEXT: Methadone maintenance is an effective treatment for opioid dependence, yet its use is restricted to federally licensed narcotic treatment programs (NTPs). Office-based care of stabilized methadone maintenance patients is a promising alternative but no data are available from controlled trials regarding this type of program. OBJECTIVE: To determine the feasibility and efficacy of office-based methadone maintenance by primary care physicians vs in an NTP for stable opioid-dependent patients. DESIGN: Six-month, randomized controlled open clinical trial conducted February 1999-March 2000. SETTING: Offices of 6 primary care internists and an NTP. PATIENTS: Forty-seven opioid-dependent patients who had been receiving methadone maintenance therapy in an NTP without evidence of illicit drug use for 1 year and without significant untreated psychiatric comorbidity were randomized; 1 patient refused to participate after treatment assignment to NTP. INTERVENTIONS: Patients were randomly assigned to receive office-based methadone maintenance from primary care physicians, who received specialized training in the care of opioid-dependent patients (n = 22), or usual care at an NTP (n = 24). MAIN OUTCOME MEASURES: Illicit drug use, clinical instability (persistent drug use), patient and clinician satisfaction, functional status, and use of health, legal, and social services, compared between the 2 groups. RESULTS: Eleven of 22 (50%; 95% confidence interval [CI], 29%-71%) patients in office-based care compared with 9 of 24 (38%; 95% CI, 21%-57%) of NTP patients had a self-report or urine toxicology test result indicating illicit opiate use (P =.39). Hair toxicology testing detected an additional 2 patients in each treatment group with evidence of illicit drug use, but this did not change the overall findings. Ongoing illicit drug use meeting criteria for clinical instability occurred in 4 of 22 (18%; 95% CI, 7%-39%) patients in office-based care compared with 5 of 24 (21%; 95% CI, 9%-41%) NTP patients (P =.82). Sixteen of the 22 (73%; 95% CI, 54%-92%) office-based patients compared with 3 of the 24 (13%; 95% CI, 0%-26%) NTP patients thought the quality of care was excellent (P =.001). There were no differences over time within or between groups in functional status or use of health, legal, or social services. CONCLUSIONS: Our results support the feasibility and efficacy of transferring stable opioid-dependent patients receiving methadone maintenance to primary care physicians' offices for continuing treatment and suggest guidelines for identifying patients and clinical monitoring.

Adult↗
PubMed2002

Terbutaline pump maintenance therapy after threatened preterm labor for preventing preterm birth.

BACKGROUND: Women with preterm labor that is arrested with tocolytic therapy are at increased risk of recurrent preterm labor. Terbutaline pump maintenance therapy has been given to such women to decrease the risk of recurrent preterm labor, preterm birth, and its consequences. OBJECTIVES: To determine the effectiveness and safety of terbutaline pump maintenance therapy after threatened preterm labor in preventing preterm birth and its complications. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group trials register (searched May 2002) and the Cochrane Controlled Trials Register (Cochrane Library Issue 2, 2002). SELECTION CRITERIA: Randomized trials comparing terbutaline pump maintenance therapy with alternative therapy, placebo, or no therapy after threatened preterm labor. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed the studies for inclusion and then extracted data from eligible studies. MAIN RESULTS: We included two studies. Terbutaline pump maintenance therapy did not appear to offer any advantages over the saline placebo pump or oral terbutaline maintenance therapy in preventing preterm births by prolonging pregnancy or its complications among women with arrested preterm labor. The weighted mean difference (WMD) for gestational age at birth was -0.1 weeks (95% confidence interval (CI) -1.7 to 1.4) for terbutaline pump therapy compared with saline placebo pump for both trials combined and 1.4 weeks (95% CI -1.1 to 3.9) for terbutaline pump versus oral terbutaline therapy for the first trial. The second trial reported a relative risk (RR) of 1.17 (95% CI 0.79 to 1.73) of preterm birth (less than 37 completed weeks) and a RR of 0.97 (95% CI 0.51 to 1.84) of very preterm birth (less than 34 completed weeks) for terbutaline pump compared with saline placebo pump. Terbutaline pump therapy also did not result in a higher rate of therapy continuation or a lower rate of infant complications. No data were reported on long-term infant outcomes, costs, or maternal assessment of therapy. REVIEWER'S CONCLUSIONS: Terbutaline pump maintenance therapy has not been shown to decrease the risk of preterm birth by prolonging pregnancy. Furthermore, the lack of information on the safety of the therapy, as well as its substantial expense, argues against its role in the management of arrested preterm labor. Future use should only be in the context of well-conducted, adequately powered randomized controlled trials.

Drug Administration Schedule↗
PubMed2003

H. pylori eradication therapy vs. antisecretory non-eradication therapy (with or without long-term maintenance antisecretory therapy) for the prevention of recurrent bleeding from peptic ulcer.

BACKGROUND: Peptic ulcer is the main cause for upper gastrointestinal haemorrhage, and Helicobacter pylori infection is the main etiologic factor for peptic ulcer disease. Maintenance antisecretory therapy has been the standard long-term treatment for patients with bleeding ulcers to prevent recurrent bleeding. On the other hand, the precise efficacy of H. pylori eradication for the prevention of rebleeding from peptic ulcer is unknown. OBJECTIVES: To compare the efficacy of H. pylori eradication therapy vs. antisecretory non-eradication therapy (with or without long-term maintenance antisecretory therapy) for the prevention of recurrent bleeding from peptic ulcer. SEARCH STRATEGY: We searched the Cochrane Controlled Trials Register (the Cochrane Library issue 1, 2003), MEDLINE (January 1966 to March 2003), EMBASE (January 1988 to March 2003), CINAHL (January 1982 to March 2003), and reference lists of articles. We also conducted a manual search from several congresses. SELECTION CRITERIA: Controlled clinical trials comparing the efficacy of H. pylori eradication therapy vs. antisecretory non-eradication therapy (with or without long-term maintenance antisecretory therapy) for the prevention of recurrent bleeding from peptic ulcer. DATA COLLECTION AND ANALYSIS: Extraction and quality assessment of studies were done by two reviewers. Study authors were contacted for additional information. MAIN RESULTS: Six studies with a total of 355 patients were included in the first meta-analysis: mean percentage of rebleeding in H. pylori eradication therapy group was 4.5%, and in the non-eradication therapy group without subsequent long-term maintenance antisecretory therapy it was 23.7% (OR 0.18, 95% CI 0.09 to 0.37; there was no statistical evidence of heterogeneity; NNT was 5, 95% CI 4 to 8). Three studies with a total of 470 patients were included in the second meta-analysis: mean percentage of rebleeding in H. pylori eradication therapy group was 1.6%, and in non-eradication therapy group with long-term maintenance antisecretory therapy it was 5.6% (OR 0.25, 95% CI 0.08 to 0.76; heterogeneity was not demonstrated; NNT was 20, 95% CI 12 to 100). Subanalysis. Excluding patients taking non-steroidal anti-inflammatory drugs (NSAIDs) at the time of recurrent bleeding resulted in a rebleeding rate of 4% (first meta-analysis) or 0.78% (second meta-analysis) in the group receiving H. pylori eradication therapy. When only patients with H. pylori eradication success were included, rebleeding rate was 1% in H. pylori eradication therapy group, and NNT decreased from 5 to 4. In some cases, recurrence of H. pylori infection seemed to be responsible for recurrence of bleeding. REVIEWER'S CONCLUSIONS: Treatment of H. pylori infection is more effective than antisecretory non-eradicating therapy (with or without long-term maintenance antisecretory therapy) in preventing recurrent bleeding from peptic ulcer. Consequently, all patients with peptic ulcer bleeding should be tested for H. pylori infection, and eradication therapy should be prescribed to H. pylori-positive patients.

Anti-Ulcer Agents↗
PubMed2004

H. pylori eradication therapy vs. antisecretory non-eradication therapy (with or without long-term maintenance antisecretory therapy) for the prevention of recurrent bleeding from peptic ulcer.

BACKGROUND: Peptic ulcer is the main cause for upper gastrointestinal haemorrhage, and Helicobacter pylori infection is the main etiologic factor for peptic ulcer disease. Maintenance antisecretory therapy has been the standard long-term treatment for patients with bleeding ulcers to prevent recurrent bleeding. On the other hand, the precise efficacy of H. pylori eradication for the prevention of rebleeding from peptic ulcer is unknown. OBJECTIVES: To compare the efficacy of H. pylori eradication therapy vs. antisecretory non-eradication therapy (with or without long-term maintenance antisecretory therapy) for the prevention of recurrent bleeding from peptic ulcer. SEARCH STRATEGY: We searched the Cochrane Controlled Trials Register (the Cochrane Library issue 4, 2003), MEDLINE (January 1966 to January 2004), EMBASE (January 1988 to January 2004), CINAHL (January 1982 to January 2004), and reference lists of articles. We also conducted a manual search from several congresses. SELECTION CRITERIA: Controlled clinical trials comparing the efficacy of H. pylori eradication therapy vs. antisecretory non-eradication therapy (with or without long-term maintenance antisecretory therapy) for the prevention of recurrent bleeding from peptic ulcer. DATA COLLECTION AND ANALYSIS: Extraction and quality assessment of studies were done by two reviewers. Study authors were contacted for additional information. MAIN RESULTS: Seven studies with a total of 578 patients were included in the first meta-analysis: mean percentage of rebleeding in H. pylori eradication therapy group was 2.9%, and in the non-eradication therapy group without subsequent long-term maintenance antisecretory therapy it was 20% (OR 0.17, 95% CI 0.10 to 0.32; there was no statistical evidence of heterogeneity; NNT was 7, 95% CI 5 to 11). Three studies with a total of 470 patients were included in the second meta-analysis: mean percentage of rebleeding in H. pylori eradication therapy group was 1.6%, and in non-eradication therapy group with long-term maintenance antisecretory therapy it was 5.6% (OR 0.25, 95% CI 0.08 to 0.76; heterogeneity was not demonstrated; NNT was 20, 95% CI 12 to 100). SUBANALYSIS: Excluding patients taking non-steroidal anti-inflammatory drugs (NSAIDs) at the time of recurrent bleeding resulted in a rebleeding rate of 2.7% (first meta-analysis) or 0.78% (second meta-analysis) in the group receiving H. pylori eradication therapy. When only patients with H. pylori eradication success were included, rebleeding rate was 1.1% in H. pylori eradication therapy group, and NNT decreased from 7 to 6. In some cases, recurrence of H. pylori infection seemed to be responsible for recurrence of bleeding. REVIEWERS' CONCLUSIONS: Treatment of H. pylori infection is more effective than antisecretory non-eradicating therapy (with or without long-term maintenance antisecretory therapy) in preventing recurrent bleeding from peptic ulcer. Consequently, all patients with peptic ulcer bleeding should be tested for H. pylori infection, and eradication therapy should be prescribed to H. pylori-positive patients.

Anti-Ulcer Agents↗
PubMed2006

Probiotics for maintenance of remission in Crohn's disease.

BACKGROUND: Crohn's disease (CD) is characterised by episodes of disease activity and symptom-free remission. Probiotics are microorganisms that can potentially benefit health, and have been evaluated as an alternate means of preventing relapse in patients with CD. OBJECTIVES: To assess the effectiveness of probiotics for the maintenance of remission in CD. SEARCH STRATEGY: The following databases were searched: the Cochrane Database of Systematic Reviews (2005, Issue 3); the Cochrane Central Register of Controlled Trials (2005, Issue 3); the Cochrane IBD/FBD Group Trials Register (2005), MEDLINE (1966-2005); EMBASE (1980-2005); ISI Web of Knowledge (BIDS) 1981-2005; On-line clinical trials databases (2005); and review articles. Experts in the field were contacted for unpublished data. SELECTION CRITERIA: Randomised controlled trials of probiotic therapy. DATA COLLECTION AND ANALYSIS: Two independent reviewers performed data extraction and assessment of methodological quality. The primary outcome was the relative risk (RR) of relapse after maintenance treatment (and 95% confidence intervals [CI]). MAIN RESULTS: Seven small studies were identified and varied according to probiotics tested, methodological quality and medication regimen. No studies were pooled for statistical analysis. There was no statistically significant benefit of E. coli Nissle for reducing the risk of relapse compared to placebo (RR 0.43, 95% CI 0.15 to 1.20), or Lactobacillus GG after surgically-induced remission (RR 1.58, 95% CI 0.30 to 8.40) or medically-induced remission (RR 0.83, 95% CI 0.25 to 2.80). There was no statistically significant benefit of probiotics for reducing the risk of relapse compared to maintenance therapy employing aminosalicylates or azathioprine (RR 0.67, 95% CI 0.13 to 3.30), and in this study the probiotic Lactobacillus GG was associated with adverse events. In children, there was there was no statistically significant difference between Lactobacillus GG and placebo for reducing the risk of relapse (RR 1.85, 95% CI 0.77 to 4.40). A small study using the yeast Saccharomyces boulardii demonstrated a difference that was not statistically significant in favour of probiotic combined with a reduced level of maintenance therapy over standard maintenance treatment alone (RR 0.17, 95% CI 0.02 to 1.23). AUTHORS' CONCLUSIONS: There is no evidence to suggest that probiotics are beneficial for the maintenance of remission in CD. All of the included studies enrolled small numbers of patients and may have lacked statistical power to show differences should they exist. Larger trials are required to determine if probiotics are of benefit in Crohn's disease.

Adult↗
PubMed2007

On maintenance models in severely and long-term limited membrane bioreactor cultivations.

Membrane bioreactors (MBRs) are combinations of common bioreactors and membrane separation units for biomass retention. Through increased biomass concentration, they allow increased productivity (or smaller reactor volume, respectively). Besides high biomass concentrations, operation at very low growth rates is typical for MBRs. In this regime, maintenance metabolism where substrate uptake only yields energy for cell survival becomes of higher importance than in processes run at higher growth rates. While thermodynamically based correlations for the prediction of maintenance coefficients are available for chemostat or other medium growth rate processes, some authors have mentioned a change in energy demand in MBRs and a dependence of maintenance parameters on operating conditions. Due to the fact that often mixed cultures are used and resulting from the different evaluation methods used by different authors, views on the possible influences on maintenance parameters differ. However, it is accepted that common models describing microbial growth and production of metabolites or degradation of pollutants do not consider the effects caused by severe limitations and therefore cannot sufficiently be applied to MBRs. In this study, maintenance parameters were determined for a model organism (Ustilago maydis) and results from different evaluation methods were compared. A continuous fit of respiration data gave more consistent results than the traditional method of plotting specific uptake versus growth rate. They suggest that below micro = 10% micro(max) the maintenance coefficient drops to a third of the value in short-term limited cultures.

Biomass↗
PubMed1995

Effects of the generation of single-stranded DNA on the maintenance of plasmid pMV158 and derivatives in different Bacillus subtilis strains.

The effects of the single-strand origins (SSOs) of plasmid pMV158 on (i) the conversion of its single-stranded (ss) replication intermediates to double-stranded (ds) plasmid DNA and (ii) its maintenance were analyzed. The rolling-circle plasmid pMV158, which replicates via ssDNA intermediates, contains two single-strand origins (SSOs) of replication, palA and palU. In this paper the results obtained with Bacillus subtilis are described; complementary studies with Lactococcus lactis are presented in the accompanying paper (Meijer et al., 1995). While in L. lactis both SSOs are functional as ssDNA conversion signal, only palU appeared to be active B. subtilis. Similar to the situation in L. lactis, the accumulation of large amounts of ssDNA resulted in a severe decrease in plasmid maintenance in B. subtilis. In the latter bacterium large amounts of ssDNA were only accumulated, however, when plasmids lacking a functional SSO were propagated in RecA mutant strains. In wild-type RecA strains these plasmids accumulated only modest amounts of ssDNA and they were maintained at fairly stable levels. The results suggest that in B. subtilis a RecA-mediated alternative pathway exists for the conversion of ssDNA which can improve plasmid maintenance. In addition to ssDNA accumulation and the antagonizing role of RecA therein, two other plasmid regions were shown to affect pMV158 maintenance in B. subtilis. One was the mob gene region, which had a negative effect on plasmid maintenance, and the other the palA type SSO. Although palA was not functional as an ssDNA conversion signal in B. subtilis, its presence had a positive effect on pMV158 maintenance.

Bacillus subtilis↗
PubMed1991

Preventing relapse in obesity through posttreatment maintenance systems: comparing the relative efficacy of two levels of therapist support.

The present study compared the relative effectiveness of a therapist-supported maintenance condition with a minimal contact maintenance condition in preventing relapse following an obesity treatment program. Thirty-two subjects who completed an initial 12-week cognitive/behavioral plus aerobic exercise treatment program were matched on absolute weight loss and randomly assigned to one of two maintenance conditions. Subjects were assessed at pretreatment, posttreatment, and 3, 6, and 12 months following posttreatment using measures of weight, blood pressure, and depression. Three- and six-month follow-up results indicated that subjects who participated in the therapist-supported maintenance group continued to lose weight and/or maintained therapy-induced weight loss to a greater degree than control subjects. At the 12-month follow-up assessment therapist-supported subjects maintained therapy-induced weight loss better than the control subjects. These findings suggest that maintenance programs which provide continued contact emphasizing relapse prevention training may be an important adjunct in the maintenance of therapy-induced weight loss.

Adult↗
PubMed1975

Effect of alkaline maintenance medium upon the growth of rabies virus in chick embryo cells.

HEP Flury strain of rabies virus was propagated in chick embryo cells under maintenance media of different pH. It was found that viral growth was better and reached a markedly higher maximum titer when the initial pH of maintenance medium was 8.2 to 9.0 than when it was 7.4. The enhancement of viral growth was not ascribable to mere neutralization of acids produced from infected cells, because the different media became almost equally neutral within an early phase of growth curve. Serial passage of the virus in chick embryo cells using pH 8.2 maintenance medium resulted in altered growth characteristics of the progeny virus; first, the virus so passaged could now grow equally well under alkaline and neutral maintenance media, and, secondly, autointerference observable with the parent virus eventually lowered virus yield when neutral maintenance medium was used, but this effect of undiluted passage was eliminated by the use of pH 8.2 maintenance medium.

Animals↗
PubMed1980

Retention of human skin fibroblast fatty acid modifications during maintenance culture.

The fatty acid composition of cultured human skin fibroblasts was modified by adding either oleic or linoleic acid to the growth medium. After the cultures became confluent, they were washed and transferred to different maintenance media in order to determine the stability of the various fatty acyl modifications. Some changes in fatty acid composition occurred under all conditions. When the maintenance medium was supplemented with fatty acid, the cellular neutral lipid and phospholipid fatty acyl composition were altered markedly within 16 to 24 hr. If no supplemental fatty acid was available during the maintenance period, however, the modified fatty acyl compositions were sufficiently retained so that appreciable differences between the cells enriched with oleate and linoleate persisted for at least 48 to 72 hr. This considerable degree of stability occurred when either 10% delipidized fetal bovine serum or 10% fetal bovine serum containing its inherent lipids were present in the maintenance medium. Although the triglyceride content of the fatty acid-modified cells was quite labile, neither the cholesterol nor phospholipid content changed appreciably during culture in any of the maintenance media. Since the fatty acid compositional differences persisted during several days of maintenance under certain conditions, these modified cultures appear to be a useful experimental system for assessing the effect of lipid structure on fairly long-term cellular functions.

Cells, Cultured↗