Metabolic engineering of Arabidopsis and Brassica for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer production

Poly(hydroxyalkanoates) are natural polymers with thermoplastic properties. One polymer of this class with commercial applicability, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) can be produced by bacterial fermentation, but the process is not economically competitive with polymer production from petrochemicals. Poly(hydroxyalkanoate) production in green plants promises much lower costs, but producing copolymer with the appropriate monomer composition is problematic. In this study, we have engineered Arabidopsis and Brassica to produce PHBV in leaves and seeds, respectively, by redirecting the metabolic flow of intermediates from fatty acid and amino acid biosynthesis. We present a pathway for the biosynthesis of PHBV in plant plastids, and also report copolymer production, metabolic intermediate analyses, and pathway dynamics.

Management of diabetes mellitus in the Lovelace Health Systems' EPISODES OF CARE program

OBJECTIVE

To design and implement the Lovelace Diabetes EPISODES OF CARE program in a managed care setting. This program is intended to address the complex needs of patients with type 2 diabetes mellitus by using specific physician-provider and patient interventions.

DESIGN

Observational study.

SETTING

Lovelace Health Systems, the second-largest and most fully integrated health care delivery system in New Mexico. The main facility is located in Albuquerque.

PARTICIPANTS

Lovelace Health Plan members with type 2 diabetes.

INTERVENTIONS

Physician-provider interventions included practice guidelines medical profile screens, and provider support reports. Patients interventions included diabetes education; improved access to care, with focused diabetes clinic visits and "Diabetes Days"; and reminder systems.

MAIN OUTCOME MEASURES

Glycohemoglobin values, dilated eye examination rates, and access to education.

RESULTS

Significant lowering of glycohemoglobin values, dilated eye examination rates exceeding benchmark measures, and increases in educational access rates have occurred since the Lovelace Diabetes EPISODES OF CARE program was implemented.

CONCLUSIONS

An integrated health care delivery system with a comprehensive, diabetes disease management program can substantially improve outcomes.

Time delays in density dependence are often not destabilizing

Time delays in density dependence have been associated with regular and sustained fluctuations in population size. Mathematical models have found that delays that are long enough can produce limit cycles. In experimental populations with preadult and adult phases in the life cycle and density regulation in any of the phases, it has been found that the time delay represented by maturation time can produce fluctuations in adult size. This has been corroborated by mathematical models. The present study develops mathematical models of growth in this type of population. The analysis of these models indicate that when preadult cohorts do not overlap in space, and preadult mortality is affected by the density of preadults at the present moment, the time delay does not destabilize the population. However, with spatial overlap of preadult cohorts and the same mechanism of density dependence, time delays can be destabilizing. It is concluded that time delays in density effects during preadulthood are not necessarily destabilizing, and that fluctuations in population size can also be due to delays with density effects in preadulthood and adulthood, or exogenous agents. Copyright 1998 Academic Press Limited

The metabolic response to spinal cord injury

The metabolic response to trauma, including neurotrauma in general, has been studied extensively, but the acute metabolic response to spinal cord injury (SCI) has not. Therefore, 12 patients with SCI are presented in whom intensive nutrition assessment and management were instituted immediately after injury. Nitrogen balance (NB), predicted energy expenditure (PEE), and actual energy expenditure (MEE) were calculated or measured in each patient. A persistent negative NB was observed in all but one of the 12 patients. The single patient who did not exhibit persistent negative NB (no positive NB from week 2 to week 4 in the face of appropriate feeding) had an incomplete myelopathy, thus implying that the degree of motor dysfunction correlates with the obligatory nature of the negative NB. The negative NB observed in several of the patients did not occur until the second or third post-injury week. In addition, calculations of PEE by successively multiplying the Harris-Benedict equation by an activity factor of 1.2 and then by a stress factor of 1.6, resulted in excessive feeding (as assessed by metabolic cart measurements; ie indirect calorimetry) in the majority of the patients. In all of the 11 patients with persistent negative NBs, protein administration in the amount of 2 g/k of ideal body weight and aggressive caloric delivery did not alter the negative pattern of the NBs. Therefore, it is concluded that the negative NB following SCI is obligatory. Furthermore, the extent of SCI (extent of myelopathy or of neurological injury) correlates with the obligatory nature of the negative NB. In addition, the results from using the above method for estimating caloric requirements and the delayed manifestation of the negative NB may cause an additional tendency to acutely overfeed SCI patients. Therefore, eliminating the activity factor of 1.2 (due to the diminished activity arising from paralysis) and a diminution of the stress factor is recommended for initial PEE calculations. Serial metabolic cart (indirect calorimetry) measurements are recommended to accurately assess the patient's subsequent metabolic requirements.

Nutrition in patients with severe burns: state of the art

Postburn hypermetabolism can lead rapidly to deleterious consequences if adequate nutrition support is not provided. Several predictive formulas are used currently for estimation of the nutrition needs of both adult and pediatric patients with burn injuries. Adequacy of enteral or parenteral or both deliveries of nutrients must be interpreted in light of injury-induced effects on nutrition parameters.

Is measured energy expenditure correlated to injury severity score in major trauma patients?

A common method for calculating energy needs (PEE) in acute trauma patients is multiplying the Harris-Benedict equation (BEE) by activity factors (AF) and variable stress factors (SF) depending on the injury severity. Selection of the SF can be an arbitrary and potentially inaccurate decision. The purposes of this study were: (1) to investigate the relationship between injury severity score (ISS) to postinjury energy expenditure (MEE), and (2) to compare the MEE to PEE when using the SF of 1.75. Thirty-five severely injured patients (mean ISS = 27.5 +/- 10.7 SD) admitted to our Level I Trauma Center of the University of New Mexico were prospectively assessed for energy needs [PEE = BEE x 1.2(AF) x 1.75(SF)] and ISS. Total nutritional support delivered estimated needs. Indirect calorimetry measurements were obtained on all of the patients within the first 7-10 days following injury. No correlation (r = -0.042) existed between the MEE and ISS. There was a significant correlation (r = 0.772, P < 0.05) between PEE and MEE when using the SF of 1.75 for all of the patients. These results suggest that there is not a correlation between ISS and subsequent MEE in major trauma patients. In addition, using the SF of 1.75 will closely estimate energy needs in acute trauma patients.

Decision-making for enteral feeding administration: the why behind where and how

Enteral nutrition has become the preferred route of nutrient administration. Because of vigorous attempts to deliver nutrient enterally in expanded patient groups, many different locations for enteral access have been advocated along with a variety of methods related to rate and pattern of delivery. Because all modes of delivery are not compatible with all sites of access and both need to be tailored to specific subsets of patients, confusion can develop regarding where and how enteral nutrients are best delivered and why. In an era when such a high priority has been placed on feeding through the enteral route, a review of the methods and rationale behind the ever-expanding choices of enteral access is timely.

Effectiveness and tolerance to highly concentrated vs conventional TPN formulas

Conventional total parenteral nutrition regimens (TPN-C) involve concentrations of dextrose/protein which necessitate administration of 2.5-4 liters/day to meet target nutritional needs. Although this is frequently acceptable, certain clinical settings mandate a volume-restricted (VR) approach. This study compares a VR TPN regimen (TPN-VR) involving the use of 25% dextrose and 9.5% amino acid with D17.5 AA 5.0 (TPN-C). The two groups were compared for adequacy of nutritional delivery, balance, and tolerance. Twenty patients received the TPN-VR (Group 1) and 20 patients received TPN-C (Group 2). The groups were comparable in age, sex, injury severity, and APACHE 2 scores. Harris-Benedict (BEE) x 2 and 2 g/protein/kg of ideal body weight were delivered by the second day of TPN. A 27% reduction in administered fluid was achieved in Group 1 (P < 0.001). Metabolic cart data in both groups demonstrated that delivered calories exceeded REE. The average RQ in Group 1 was 0.84 and in Group 2 was 0.90 (P > 0.1). There was no significant difference between the two groups in nitrogen balance, mean serum bilirubin levels, PT and PTT, serum albumin levels, and triglycerides (P > 0.20). SGPT and alkaline phosphatase levels were significantly higher in Group 2 (P < 0.001). Group 2 received an average of 22% more carbohydrate than Group 1 and 45% required insulin compared to 25% in Group 1 (P < 0.01). In summary, TPN-VR is comparable to TPN-C in terms of effectiveness of delivery, nutritional balance, and tolerance.

Successful enteral refeeding after massive small bowel resection

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Protein and energy tolerance by stressed geriatric patients

Nutritional support of stressed geriatric patients remains empiric and has classically been limited by tolerance. Although the hypermetabolic response is known to increase protein and calorie demands, tolerance to increased loads of delivered nutrients in older patients has been questioned. We compared tolerance to nutrient delivery and nitrogen metabolism in 38 stressed surgical patients over age 65 to 38 Injury Severity Score or disease matched younger controls. Twenty-seven of the 31 geriatric patients (87%) who maintained normal renal function (serum creatinine less than 2.0 mg/dl) became azotemic (BUN greater than 30) while receiving 1.5 to 2.0 g of protein per kilogram of ideal body weight compared to only 21% of controls. This phenomenon led to inaccuracies in 17% of geriatric nitrogen balance studies because of unaccounted for serum accumulation of urea nitrogen (compared to only 6% in the control group). When calculated protein requirements were administered to the geriatric group, the mean nitrogen balance was -1.6. Resting energy expenditure as measured by indirect calorimetry demonstrated a strong correlation between actual calorie expenditures and calculated needs based on the Harris-Benedict basal energy expenditure (BEE) multiplied by an activity factor of 1.2 and a stress factor of 1.75 for trauma (r = 0.86, P less than 0.05) or 1.5 for general surgery patients (r = 0.72, P less than 0.05). In summary, energy requirements by stressed geriatric patients can be closely defined by calculation of the Harris-Benedict BEE in conjunction with appropriate activity and stress factors. However, attempts to deliver traditional levels of protein lead to azotemia and are frequently unsuccessful in achieving positive nitrogen balance.(ABSTRACT TRUNCATED AT 250 WORDS)

Obligatory negative nitrogen balance following spinal cord injury

Obligatory nitrogen losses due to paralysis in the spinal cord-injured (SCI) patient prevent positive nitrogen balance (NB) regardless of the calorie and protein intakes. Ten patients with SCI and 20 controls with nonspinal cord injury (NSCI) matched for time, sex, age, and injury severity score (ISS) were admitted to our Level I trauma center. In both groups, total nutritional support was delivered within 72 hours of admission based on predicted energy expenditures (PEE = Harris-Benedict equation x 1.2 x 1.6) and 2 g of protein/kg of ideal body weight (IBW). Subsequent changes in nutrient delivery were based on NB. No SCI patient established positive NB during the 7-week period following injury despite an average delivery of 2.4 g of protein/kg IBW and 120% of the PEE at the time of peak negative NB (-10.5). In six SCI patients, an average increase of 25% in delivered protein and 12% in delivered calories over a 1-week period effected no change in average NB (-7.4 vs -6.8). Indirect calorimetry in five SCI patients showed that calorie intakes were 110% more than average measured energy expenditures. In contrast, 17 of 20 NCSI patients achieved positive NB within 3 weeks of admission. They required an average delivery of 2.3 g of protein/kg IBW and 110% of PEE to reach positive NB. These data demonstrate the phenomenon of obligatory negative NB acutely following SCI. Aggressive attempts to achieve positive NB in these patients will fail and result in overfeeding.

Models of growth with density regulation in more than one life stage

Discrete-time models of growth of populations with nonoverlapping generations and density regulation in two life stages are studied. It is assumed that there is no delay in the effects of density. Assigning exponential, linear, or hyperbolic functions to describe the dependence of preadult survival and fecundity on density, nine models are obtained. The dynamics of the model resulting from using the exponential function to describe the density dependence of both preadult survival and fecundity is analyzed: for large values of the intrinsic rate of increase there may exist up to three equilibrium population sizes, two stable. This indicates that a life history with two episodes of density regulation can give origin to alternative stable states. The models are fitted to recruitment data from growth experiments of Drosophila laboratory populations obtained with the Serial Transfer System Type 2 (Ayala et al., 1973. Theor. Pop. Biol. 4, 331-356) and collected by other authors. The results of the fittings suggest that this recruitment data can be adequately described with the models.

Synthesis of prostaglandins by the ductus arteriosus of the bovine fetus

Previous studies demonstrated that prostaglandins are local or tissue hormones which can be released from blood vessel walls. In the present study, we investigated the capacity of bovine ductus arteriosus to synthetize prostaglandins in vitro. After incubation of slices of ductus arteriosus in Krebs' solution with (1-14C) arachidonic acid for 3 hours, more than 40% of the radiolabeled material recovered from the incubating medium were metabolites of arachidonic acid. The major product was indistinguishable from 6 keto-PGF1alpha as determined by its chromatographic motility and resistance to alkaline conversion to PGB. The PGI2 synthetic capacity of the ductus arteriosus, as revealed by the predominance of its major metabolite 6 keto-PGF1alpha, suggests that this metabolic pathway of arachidonic acid may contribute to the hemodynamic changes occurring during fetal life and at birth.