Estimating the cost and epidemiology of mild to severe chronic pain associated with osteoarthritis in England: a retrospective analysis of linked primary and secondary care data

OBJECTIVE

Osteoarthritis (OA) affects 10% of adults in the UK. Despite over one-third of people with OA experiencing chronic pain, few studies have examined the population-level impact of chronic pain associated with OA. We compared resource-use and epidemiological outcomes in patients with mild, moderate and severe chronic OA-associated pain and matched controls without known OA.

DESIGN

Retrospective, longitudinal, observational cohort study (July 2008 to June 2019).

SETTING

Electronic records extracted from Clinical Practice Research Datalink GOLD primary care linked to Hospital Episode Statistics (HES).

PARTICIPANTS

Patients (cases; n=23 016) aged ≥18 years with chronic OA-associated pain. Controls (n=23 016) without OA or chronic pain matched on age, sex, comorbidity burden, general practitioner practice and available HES data.

INTERVENTIONS

None.

PRIMARY AND SECONDARY OUTCOME MEASURES

Total healthcare resource use (HCRU), direct healthcare costs in 0-12, 12-24 and 24-36 months postindex. Secondary outcomes included incidence and prevalence of chronic OA-associated pain and pharmacological management.

RESULTS

HCRU was consistently greater in cases versus controls for all resource categories during preindex and postindex periods. Across follow-up periods, resource use was greatest in patients with severe pain. In the first 12 months postindexing, mean total costs incurred by cases were four times higher versus matched controls (£256 vs £62); costs were approximately twice as high in cases vs controls for months 12-24 (£166 vs £86) and 24-36 (£150 vs £81; all p<0.0001). The incidence of new cases of chronic pain associated with OA was 2.64 per 1000 person-years; the prevalence was 1.4%.

CONCLUSIONS

This study highlights the real-world cost of chronic pain associated with OA in cases versus matched controls. We included patients with mild, moderate and severe pain associated with OA, and showed HCRU in discrete 1-year time frames. The true economic burden of pain associated with OA is likely to be considerably higher when indirect costs are considered.

Chronic Low Back Pain with and without Concomitant Osteoarthritis: A Retrospective, Longitudinal Cohort Study of Patients in England

Objective

Despite the high prevalence of chronic low back pain (CLBP) and osteoarthritis (OA), few estimates of the economic cost of these conditions in England have been published. The aim of the present analysis was to characterise the economic burden of moderate-to-severe pain associated with CLBP + OA and CLBP alone compared with general population-matched controls without CLBP or OA. The primary objective was to describe the total healthcare resource use (HCRU) and direct healthcare costs associated with the target patient populations. Secondary objectives were to describe treatment patterns and surgical procedures.

Methods

This was a retrospective, observational cohort study of patients receiving healthcare indicative of moderate-to-severe chronic pain associated with CLBP, with or without OA. We used linked longitudinal data from the Clinical Practice Research Datalink GOLD and Hospital Episode Statistics (HES). Patients (cases) were matched 1 : 1 with controls on age, sex, comorbidity burden, GP practice, and HES data availability.

Results

The CLBP-alone cohort comprised 13 554 cases with CLBP and 13 554 matched controls; the CLBP + OA cohort comprised 7803 cases with both OA and CLBP and 7803 matched controls. Across all follow-up periods, patients with CLBP alone and those with CLBP + OA had significantly more GP consultations, outpatient attendances, emergency department visits, and inpatient stays than controls (all p < 0.0001). By 36 months after indexing, the mean (SD) per-patient total direct healthcare cost in the CLBP-alone cohort was £5081 (£5905) for cases and £1809 (£4451) for controls (p < 0.0001); in the CLBP + OA cohort, the mean (SD) per-patient total direct healthcare cost was £8819 (£7143) for cases and £2428 (£4280) for controls (p < 0.0001).

Conclusion

Moderate-to-severe chronic pain associated with CLBP-with or without OA-has a substantial impact on patients and healthcare providers, leading to higher HCRU and costs versus controls among people with CLBP alone or together with OA.

Health economic impact of moderate-to-severe chronic pain associated with osteoarthritis in England: a retrospective analysis of linked primary and secondary care data

OBJECTIVE

Despite the prevalence of osteoarthritis (OA) in England, few studies have examined the health economic impact of chronic pain associated with OA. The aim of this study was to compare outcomes in patients with moderate-to-severe chronic pain associated with OA and matched controls without known OA.

DESIGN

Retrospective, longitudinal, observational cohort study.

SETTING

Electronic records extracted from the Clinical Practice Research Datalink GOLD primary care database linked to Hospital Episode Statistics (HES) data set.

PARTICIPANTS

Patients (cases; n=5931) ≥18 years and with existing diagnosis of OA and moderate-to-severe pain associated with their OA, and controls matched on age, sex, comorbidity burden, general practitioner (GP) practice and availability of HES data.

INTERVENTIONS

None.

PRIMARY AND SECONDARY OUTCOME MEASURES

Total healthcare resource use (HCRU) and direct healthcare costs during 0-6, 0-12, 0-24 and 0-36 months of follow-up. Secondary outcomes measures included pharmacological management and time to total joint replacement.

RESULTS

Patients with moderate-to-severe chronic pain associated with OA used significantly more healthcare services versus matched controls, reflected by higher HCRU and significantly higher direct costs. During the first 12 months' follow-up, cases had significantly more GP consultations, outpatient attendances, emergency department visits and inpatient stays than matched controls (all p<0.0001). Total mean costs incurred by cases during 0-12 months' follow-up were five times higher in cases versus controls (mean (SD): £4199 (£3966) vs £781 (£2073), respectively). Extensive cycling through pharmacological therapies was observed; among cases, 2040 (34.4%), 1340 (22.6%), 841 (14.2%), 459 (7.7%) and 706 (11.9%) received 1-5, 6-10, 11-15, 16-20 and >20 lines of therapy, respectively.

CONCLUSIONS

This wide-ranging, longitudinal, observational study of real-world primary and secondary care data demonstrates the impact of moderate-to-severe chronic pain associated with OA in patients compared with matched controls. Further studies are required to fully quantify the health economic burden of moderate-to-severe pain associated with OA.

Long-term improvements following a residential combined physical and psychological programme for chronic low back pain

OBJECTIVES

Evaluate the outcomes and explore experiences of patients undergoing a residential combined physical and psychological programme (CPPP) for chronic low back pain.

DESIGN

A longitudinal observational cohort design, with a parallel qualitative design using semistructured interviews.

SETTING

Residential, multimodal rehabilitation.

PARTICIPANTS

136 adults (62 male/74 female) referred to the CPPP, 100 (44 male/56 female) of whom completed the programme, during the term of the study. Ten (2 male/8 female) participated in the qualitative evaluation.

INTERVENTION

A 3-week residential CPPP.

OUTCOME MEASURES

Primary outcome measures were the STarT Back screening tool score; pain intensity-11-point Numerical Rating Scale; function-Oswestry Disability Index (ODI); health status/quality of life-EQ-5D-5L EuroQol five-Dimension-five level; anxiety-Generalised Anxiety Disorder-7; depression-Patient Health Questionnaire-9. Secondary outcome measures were the Global Subjective Outcome Scale; National Health Service Friends and Family Test;.

RESULTS

At discharge, 6 and 12 months follow ups, there were improvements from baseline that were greater than minimum clinically important differences in each of the outcomes (with the sole exception of ODI at discharge). At 12 months, the majority of people considered themselves a lot better (57%) and were extremely likely (86%) to recommend the programme to a friend. The qualitative data showed praise for the residential nature of the intervention and the opportunities for interaction with peers and peer support. There were testimonies of improvements in understanding of pain and how to manage it better. Some participants said they had reduced, or stopped, medication they had been taking to manage their pain.

CONCLUSIONS

Participants improved, and maintained long term, beyond minimum clinically important differences on a wide range of outcomes. Participants reported an enhanced ability to self-manage their back pain and support for the residential setting.

Changes in Factor VIII Complex Activities During the Production of a Clinical Intermediate Purity Factor VIII Concentrate

Samples taken at various stages of preparation of intermediate purity factor VIII concentrate were assayed for factor VIII coagulant activity (VIII:C), factor VIII coagulant antigen (VIIIC: Ag) and factor VIII related antigen (VIIIR: Ag). The antigen results were used to assess mechanical loss during fractionation as these markers are relatively stable. In contrast VIII:C is sensitive to both mechanical and inactivation losses.

The major loss of factor VIII occurred during the cryoprecipitation and extraction step and was due to both mechanical loss and inactivation. Losses before and after this step were largely due to inactivation of the factor VIII.

Assay of VIIIR: Ag in concentrates presented problems and a modified technique is suggested.

Expression of CCAAT/enhancer binding protein family genes in monolayer and sandwich culture of hepatocytes: induction of stress-inducible GADD153

Removal of hepatocytes from their physiological environment for experimentation in vitro activates loss of liver-specific phenotype. Hepatocytes cultured in a sandwich configuration reportedly maintain greater expression of certain liver-specific genes than hepatocytes in monolayer cultures. We show that sandwich culture of rat hepatocytes improves retention of expression of a liver-enriched transcription factor, C/EBPalpha (CCAAT/enhancer binding protein alpha), which regulates many liver-specific genes. However, we also demonstrate increased expression of a stress-responsive C/EBP homologue, GADD153 (growth arrest and DNA damage gene 153), during monolayer culture, which may promote dedifferentiation. Induction of GADD153 was not prevented in sandwich cultured hepatocytes. Activation of a homologue of the mouse GADD153 target gene, doc1, was observed in monolayer and sandwich culture, suggesting that GADD153 was transcriptionally active. We suggest that the capability of sandwich cultures to maintain hepatocyte phenotype may be limited by the altered profile of transcription factor activity.

Expression of the transcription factor GADD153 is an indicator of apoptosis for recombinant chinese hamster ovary (CHO) cells

Loss of cell viability, through engagement of apoptotic cell death, represents a limitation to maintenance of high levels of productivity of recombinant animal cells in culture. The ability to monitor the status of recombinant cells, and to define indicators of their "well-being," would present a valuable approach to permit a rational intervention at appropriate times during culture. Growth arrest and DNA damage gene 153 (GADD153) is a member of the CCAAT/enhancer-binding protein (C/EBP) family of transcription factors and has been associated with apoptosis. We have examined the expression of GADD153 in conditions associated with apoptosis of recombinant CHO cells in batch culture. GADD153 expression is very low in CHO cells growing in the exponential phase of batch culture but is activated as cells enter the decline phase. Depletion of nutrients (glucose or glutamine) causes activation of GADD153 expression as does the imposition of endoplasmic reticulum stress. In all cases, there is a good relationship between the extent of apoptosis that occurs in response to each stress and the degree of GADD153 expression. In addition, nutrient refeeding or reversal of stress produces a concomitant decrease in expression of GADD153 and the susceptibility to apoptosis. Thus, GADD153 appears to offer a valid indicator of apoptosis and illustrates the potential for definition of monitors of cellular status related to the likelihood of apoptosis of cell populations.

Characterization of the stability of recombinant protein production in the GS-NS0 expression system

The GS-NS0 system is an important mammalian expression system used largely within industry for the high-level expression of recombinant proteins for therapeutic use. It is essential that the productivity of this system remains stable throughout culture expansion for the successful long-term production of recombinant proteins. Here we present a study of the stability of recombinant protein production from unamplified GS-NS0 cell lines over extended period of continuous culture. The cell lines used in this study were generated by the transfection of NS0 cells with DNA encoding for a secreted recombinant protein and by two subsequent rounds of limiting dilution cloning prior to analysis of stability. The stability of recombinant protein production was assessed at intervals over a period of 134 days using repeated batch culture in shake flasks. Heterogeneous stability was identified. The productivity of some clones remained consistent throughout 134 days of continuous culture. Others exhibit rapid and progressive loss of productivity. Analysis of the causal relationships underlying stability indicates that the initial transfectant determines the susceptibility to loss or retention of productivity. Selection of production clones on the basis of growth and productivity alone will not predict stability during long-term culture. Our research indicates that stable high-producing clones can readily be obtained from use of the GS-NS0 system in the absence of amplification but there may be molecular features of the original transfectants that could serve as very important predictive indicators of the stability of recombinant protein production.

Protein kinase C isoenzyme expression in retinal cells

Protein kinase C (PKC) is involved in both the physiological and pathophysiological processes in the retina and plays an important role in signal transduction. The aim of this study was to determine the PKC isoenzyme profile in three retinal cell types in culture, namely RPE cells, pericytes and retinal microvascular endothelial cells. Confluent cultures were lysed and isoenzyme expression detected by Western blotting. PKC isoenzymes alpha, beta(2) and delta were observed for all three cell types while beta(1) was specific for RPE cells. This study has characterised the PKC isoenzyme profile in three retinal cell types and suggests that defining the cell-specific isoenzyme pattern is an important step in understanding their precise physiological role and regulation in the retina.

Advances in animal cell recombinant protein production: GS-NS0 expression system

The production of recombinant proteins using mammalian cell expression systems is of growing importance within biotechnology, largely due to the ability of specific mammalian cells to carry out post-translational modifications of the correct fidelity. The Glutamine Synthetase-NS0 system is now one such industrially important expression system.Glutamine synthetase catalyses the formation ofglutamine from glutamate and ammonia. NS0 cellscontain extremely low levels of endogenous glutaminesynthetase activity, therefore exogenous glutaminesynthetase can be used efficiently as a selectablemarker to identify successful transfectants in theabsence of glutamine in the media. In addition, theinclusion of methionine sulphoximine, an inhibitor ofglutamine synthetase activity, enables furtherselection of those clones producing relatively highlevels of transfected glutamine synthetase and henceany heterologous gene which is coupled to it. Theglutamine synthetase system technology has been usedfor research and development purposes during thisdecade and its importance is clearly demonstrated nowthat two therapeutic products produced using thissystem have reached the market place.

Hepatocyte isolation stimulates formation of interferon stimulatory response element DNA-protein complexes

We have examined the relationship between intracellular signalling pathways and loss of differentiated function during hepatocyte isolation and culture. We have shown that isolation induces the activation of the interferon stimulatory response element (ISRE). This activation was transient and peaked at 3 h before it returned to basal by 24 h of culture. Interferon regulatory factor-1 (IRF-1) was shown to be important for generation of ISRE complexes by electromobility shift assays and supershift intervention. IRF-1 was translocated to the nucleus in parallel with changes to ISRE complex formation. The p38 kinase inhibitor, SB 203580, diminished the formation of ISRE binding complexes. Hence p38 kinase may be involved in the activation and binding of IRF-1 or related proteins to the ISRE motif. Changes in ISRE activation levels in cultured hepatocytes may have important implications in primary hepatocyte differentiation and loss of function.

Activation of stress-activated protein kinases by hepatocyte isolation induces gene 33 expression

Gene 33 is a putative immediate early gene and we have shown that mRNA encoding for gene 33 exhibits a transient increase as a result of the procedures used for hepatocyte isolation. The stress-activated protein kinases p46 JNK, p54 JNK, and p38 SAPK are activated by hepatocyte isolation and precede changes in gene 33 mRNA content. Although each SAPK isoform shows a distinctive profile of activity during isolation and subsequent hepatocyte culture, in each case the activation is transient and is largely reversed within 3 h of hepatocyte isolation. SB 203580, a p38 SAPK inhibitor, prevents the change to gene 33 expression in response to hepatocyte isolation. Given the possible role of gene 33 as an immediate early gene, the data presented here have general implications for control of hepatocyte proliferation and differentiation.

Rat primary hepatocytes and H4 hepatoma cells display differential sensitivity to cyclic AMP at the level of expression of tyrosine aminotransferase

We have shown that the sensitivity of isolated hepatocytes and H4 hepatoma cells to cyclic AMP is different. In terms of activation of tyrosine aminotransferase at mRNA and activity level in response to cyclic AMP, isolated hepatocytes are 10-fold more sensitive. Hepatocytes and H4 hepatoma cells show similar sensitivities to cyclic AMP at the level of protein kinase A activation and phosphorylation of cyclic AMP response element binding protein (CREB) and the differential sensitivity must reside at other sites. The consequences of these findings to studies of control phenomena at the transcriptional level is discussed.

Apoptosis regulation and its applications to biotechnology

Increased knowledge of the molecular interactions that characterize the control of apoptosis is identifying possible novel approaches to inhibit cell death and generate enhanced viable cell biomass. The application of such approaches to recombinant mammalian cells promises to improve the cost-effectiveness of industrial-scale protein expression.

Dichloroacetate inhibits glutamine oxidation by decreasing pyruvate availability for transamination

We have shown that dichloroacetate (DCA) inhibits growth, glutamine oxidation, and pyruvate and alanine production in a concentration-dependent manner in PQXB 1/2 hybridoma cells. The use of inhibitors indicates that glutamine oxidation proceeds by an aminooxyacetate-sensitive transamination reaction in this cell line. Addition of pyruvate to DCA-treated cells restored glutamine oxidation to control values. Our data suggest that DCA inhibits glutamine oxidation by decreasing the availability of pyruvate for transamination, which in turn results in glutamate accumulation and a consequent inhibition of glutaminase activity. Impaired glutamine catabolism in the presence of DCA has subsequent effects on overall metabolic balance and cell maintenance and growth.

Inhibitors of signalling identify differential control processes responsible for selective effects of insulin on the expression of phosphoenolpyruvate carboxykinase and gene 33 in rat H4 hepatoma cells

Gene 33 and phosphoenolpyruvate carboxykinase (PEPCK) present excellent model systems for the analysis of the differential control of hepatic gene expression by the insulin-regulated signal-transduction pathway(s). We have analysed the importance of specific components in the insulin-regulated transduction pathway(s) towards enhanced gene expression (gene 33) and inhibited gene expression (PEPCK) by examination of the influence of selective inhibitors. Rapamycin, which inhibits the 70 kDa S6 kinase (p70rsk) does not influence the actions of insulin on gene 33 or PEPCK; thus the kinase p70rsk appears to play no direct role in the regulation of expression of these two hepatic genes. Wortmannin, an inhibitor of phosphatidylinositol 3-kinase, differentiates between processes involved in insulin regulation of gene 33 and PEPCK mRNA expression. Although the actions of insulin on gene 33 expression are abolished by wortmannin, the actions of insulin on PEPCK expression are insensitive to wortmannin. The existence of wortmannin-sensitive and rapamycin/wortmannin-insensitive pathways for transducing insulin signals to factors controlling gene expression, and the differential actions on specific genes, presents an initial step towards deciphering the linkage between signalling components and selective control of gene expression.

Regulation of tyrosine aminotransferase activity by glucagon and cAMP analogues in chick embryos in ovo

Glucagon, dibutyryl cAMP (Bt2cAMP) and 8-(4-chlorophenylthio) cAMP (CptcAMP), singly or when combined, stimulated tyrosine aminotransferase (TAT) activity in 17-day-old chick embryos in ovo. Maximal induction was produced within 4 hr of injection of the inducers. The effects of glucagon and the cAMP analogues were not additive. Glucagon administration was accompanied by a rapid increase in hepatic cAMP concentration which remained elevated for at least 4 hr. The stimulated increase in TAT activity elicited by the hormone or cyclic nucleotide was prevented by injection of cycloheximide or cordycepin. These results are discussed vis-à-vis the possible regulation of TAT in ovo by physiological concentrations of glucagon and the likely role of cAMP as a second messenger in this process during chick embryogenesis.

Establishment of a murine leukaemia cell line resistant to the growth-inhibitory effect of bryostatin 1

Bryostatin 1 is a novel macrocyclic lactone activator of protein kinase C (PKC) which has clinical potential as an anti-cancer agent. The mechanism of action of this agent is unknown, but protein kinase C has been implicated. In order to investigate this possibility, we have developed P388 sublines resistant to bryostatin 1, by continuous challenge of the parent cell line with increasing incremental concentrations of the drug over 4 months. Cell lines were established at monthly intervals yielding four sublines: P388/BR/A, which were removed at 1 month; P388/BR/B, obtained after 2 months; P388/BR/C, obtained after 3 months; and P388/BR/D, which were established after 4 months. All four P388/BR sublines show an equal degree of resistance to the growth inhibitory effects of bryostatin 1, with a relative resistance ratio (RR) IC50 of approximately 4,000. The ability of the cytosol of cells to phosphorylate PKC-specific substrate is decreased by 41% for BR/A, 57% for BR/B 80% for BR/C and 94% for BR/D compared with the parental cell line, even when grown in the absence of bryostatin 1 for up to 4 weeks. Similar decreases are seen for cytosolic phorbol ester binding and whole-cell PKC isoenzyme expression. All four P388/BR sublines show high and equal levels of cross-resistance to the PKC activatory phorbol ester, phorbol 12-myristate 13-acetate (PMA). There is no loss of resistance to either bryostatin 1 or PMA up to 3 months after termination of exposure of the sublines to bryostatin 1. There was no significant degree of cross-resistance to daunorubicin in the bryosatin 1-resistant cell lines, P388/BR/A, B, C or D, when compared with the parent cell line, P388.

A career in nursing for the physically disabled individual?

This paper highlights the small percentage of nurses who are disabled, and seeks to give some explanations for this phenomenon by reference to theories of stigma and labelling. Having acknowledged that one of the main barriers to disabled people entering nursing may be an attitudinal one on the part of health care staff, some recommendations are made in relation to nursing curricula, which may facilitate the recruitment and education of people with physical disabilities.

Effects of okadaic acid on expression of phosphoenolpyruvate carboxykinase in cultured rat hepatocytes

In normal rat hepatocytes in primary culture the level of mRNA encoding the key gluconeogenic enzyme phospho enol pyruvate carboxykinase (PEPCK) is increased by the cyclic AMP analogue, chlorophenylthio cyclic AMP (cpt cAMP), and this response is reversed by insulin. The protein-phosphatase inhibitor okadaic acid diminished the stimulatory effects of cpt cAMP on PEPCK mRNA. Protein kinase A remained fully active in the presence of okadaic acid, therefore, the insulin-mimetic actions of okadaic acid were localised to a site subsequent to initial protein kinase A activation. Insulin produced a decrease in PEPCK mRNA expression which was similar to that of okadaic acid both in extent and mechanism (i.e., lack of change in protein kinase A activation). The effects of okadaic acid on PEPCK mRNA amount were not additive with those of insulin and the effects of insulin were not abolished by okadaic acid. These data suggest that okadaic acid and insulin may interact with the cAMP regulation of the PEPCK gene expression at a common site. The mechanisms by which this may be attained are discussed in relation to what is known about the control of specific protein kinases and protein phosphatases by insulin and okadaic acid and of the importance of protein phosphorylation state to regulation of gene-transcriptional processes.

Glycolipids isolated from cultured rat hepatocytes: analysis of their role in insulin signal transduction

The precise mechanism by which insulin elicits its effects remains to be fully determined. A glycophospholipid, isolated from H35 cells, has been proposed as a possible precursor for an insulin-generated second messenger that mediates the intracellular effects of insulin. This glycolipid contains a hexosamine moiety, inositol, galactose and palmitate. We have isolated a glycolipid from cultured rat hepatocytes that exhibits chromatographic and radiolabelling characteristics similar to this proposed precursor. The glycolipid can be radiolabelled with glucosamine, galactosamine, galactose and palmitate, but not myristate or myoinositol. Incorporation of radiolabel into this glycolipid was insensitive to the presence of either insulin (10(-7) M) or phosphatidylinositol-specific phospholipase C (PI-PLC) in the culture medium. The cultured hepatocytes used exhibited normal insulin responses with respect to glycogen turnover and gene expression. Treatment of partially purified glycolipid with either PI-PLC or nitrous acid did not result in the generation of an aqueous soluble phosphooligosaccharide indicating that the glycolipid was not cleaved by either agent. This is in contrast to the reported cleavage of the glycolipids found in H35 hepatoma and lymphocytes. These results question the role of the putative phosphooligosaccharide mediator in the intracellular transduction system activated by insulin.

Effects of glucagon and an analogue of cAMP on tyrosine aminotransferase in isolated chick embryo hepatocytes

Hepatocytes were isolated from 17-day-old chick embryos by the use of collagenase. Glucagon and dibutyryl cAMP (bt2cAMP), individually or in combination, stimulated tyrosine aminotransferase (TAT) activity and synthesis in the isolated hepatocytes; maximal stimulation occurred 4 h after exposure of hepatocytes to the inducers. The stimulatory effects produced by glucagon and bt2cAMP were abolished by treatment of hepatocytes with cordycepin or cycloheximide. The effects of the hormone and the cyclic nucleotide were not additive. The induction of the enzyme by glucagon suggests a physiological role for the hormone in the expression of TAT activity during chick embryonic development.

Characterization of glutamine metabolism in two related murine hybridomas

Aspects of glutamine metabolism were examined in two related hybridomas, a high-producing line (PQX B1/2) and a low-producing line (PQX B2/2). The growth and metabolic characteristics of both cell lines were identical or very similar. During batch growth glutamine was completely exhausted from the medium and an examination of the fate of [14C]glutamine highlighted the importance of this amino acid as an energy source. The relative enzyme activities and the amount of ammonia produced during growth indicated that glutamine is oxidized preferentially via the transamination pathway. The overall rate of glutamine utilization from the growth medium was similar to the rate of [14C]glutamine uptake which suggests that transport may regulate glutamine metabolism.

Control of glycolysis in cultured chick embryo hepatocytes. Fructose 2,6-bisphosphate content and phosphofructokinase-1 activity are stimulated by insulin and epidermal growth factor

Chick embryo hepatocytes were maintained in monolayer culture in a serum-free chemically defined medium for periods of up to 2 days. Over this time period, insulin provoked selective increases (up to 5-fold) in factors relevant to the control of glycolysis: the activities of phosphofructokinase-1 (PFK-1), phosphofructokinase-2 (PFK-2) and hexokinase isoenzymes and the content of fructose 2,6-bisphosphate (F26BP). Half-maximal effects of insulin on pFK-1 activity were in the physiological range (0.1 nM). Changes in enzyme activities and F26BP content in response to insulin were correlated with stimulation of glycolytic flux as estimated by radioisotopic flux. These data are discussed in relation to known changes which occur in hepatic glycolytic activity and PFK-1 activity in the intact chick around hatching. The effects of insulin on F26BP content, PFK-1 activity and glycolytic flux were mimicked by epidermal growth factor (EGF). In contrast, phorbol esters produced minimal actions on any of the above parameters. Our data indicate that protein kinase C is not involved in the actions of insulin or EGF in control of F26BP content or PFK-1 activity. This work indicates that the related tyrosyl kinase receptors of insulin and EGF may provoke identical responses within hepatocytes, but through the utilization of different transduction systems which merge to common control points.

Phenylalanine hydroxylation in isolated rat kidney tubules

1. Phenylalanine hydroxylation has been demonstrated to occur in isolated rat kidney tubules under physiological conditions. 2. The hydroxylation flux response is hyperbolic with apparent Km and Vmax values of ca 85 microM phenylalanine and 49 nmol tyrosine formed/mg dry wt per hr respectively. 3. Hydroxylation in kidney tubules is substantially less sensitive to effectors of cyclic AMP turnover and Ca2+ mobilization than phenylalanine hydroxylation in isolated liver cells.

Developmental changes in hepatic fructose 2,6-bisphosphate content and phosphofructokinase-1 activity in the transition of chicks from embryonic to neonatal nutritional environment

Within 2 days of hatching in chicks, there are parallel increases in hepatic fructose 2,6-bisphosphate content and phosphofructokinase-1 activity. The changes observed are a consequence of feeding on the carbohydrate-rich diet of neonatal life: lack of access to food after hatching prevents changes for either parameter. The results are discussed in relation to changes in the activities of hepatic lipogenic enzymes during the embryonic/neonatal transition of chicks and the role of insulin in co-ordination of developmental processes.

Relative importance of physiological precursors for ketogenesis in the nutritional homeostasis of the development of the embryonic chick

This paper investigates the relative importances of specific amino acids, and, in particular, branched chain amino acids and their keto derivatives as possible ketogenic precursors in suspensions of liver cells isolated from chick embryos. Addition of the branched chain keto acids stimulated ketogenesis. The order of potency was alpha-ketoisocaproic acid greater than alpha-ketoisovaleric acid greater than DL-alpha-keto-beta-methyl-n-valeric acid. The relative order of effectiveness for branched chain keto acids was maintained at all comparable concentrations, and in each case maximum rates were observed with concentrations of 1-2 mM. In contrast to the stimulation of ketogenesis by their keto derivatives, branched chain amino acids were ineffective as precursors for ketogenesis. Of the other amino acids (utilised at concentrations present in chick embryo plasma) only Tyr, Lys, Phe and Arg produced significant increases in ketone body formation above the endogenous rate. At these physiological concentrations, the effectiveness of the amino acids were in the order of Tyr greater than Lys = Phe greater than Arg. The interactions between three groups of ketogenic precursor (fatty acids, amino acids and keto amino acids, all at physiological concentrations), produced rates of ketogenesis that were purely additive. These results indicate that high concentrations of hydroxybutyrate and acetoacetate found in plasma of developing chick embryos may arise from hepatic metabolism of several distinct precursors. The relative importance of each category of precursor may vary with the precise developmental status of animals.

The role of insulin in the modulation of glucagon-dependent control of phenylalanine hydroxylation in isolated liver cells

The stimulation of phenylalanine hydroxylation in isolated liver cells by sub-maximally effective concentrations of glucagon (less than 0.1 microM) is antagonized by insulin (0.1 nM-0.1 microM). This phenomenon is a consequence of a decrease in the glucagon-stimulated phosphorylation of phenylalanine hydroxylase from liver cells incubated in the presence of insulin. The impact of insulin on the phosphorylation state and activity of the hydroxylase is mimicked by incubation of liver cells in the presence of orthovanadate (10 microM). A series of cyclic AMP and cyclic GMP analogues enhanced phenylalanine hydroxylation: in each case insulin diminished the stimulation of flux. These results are discussed in the light of the characteristics of insulin action on other metabolic processes.

Kidney gluconeogenesis: its importance to net glucose synthesis during the development of chick embryos

A technique is described for the preparation of viable isolated kidney tubules from chick embryos. Assessment of the potencies of various possible gluconeogenic precursors indicates that kidney is the site of net glucose synthesis from physiologically relevant precursors during embryonic life. The plasma concentrations of physiological gluconeogenic precursors was determined and the rates of glucose synthesis by tubules was measured from a precursor mixture which stimulated plasma contents.

The polyamine-dependent modulation of phenylalanine hydroxylase phosphorylation state and enzymic activity in isolated liver cells

The role of polyamines in the control of phenylalanine hydroxylase phosphorylation state and enzymic activity was investigated. Pre-treatment of liver cells with spermine (1 mM) abolishes the glucagon (1 nM)-stimulated increase in hydroxylase phosphorylation. Concurrently there is a decrease in phenylalanine hydroxylation flux, reflecting decreased enzyme activity; 50% inhibition occurs at approx. 10 microM-spermine. These results are discussed in the context of reports concerning the properties of protein phosphatase 2A.

Phosphopeptide analysis of phenylalanine hydroxylase isolated from liver cells exposed to hormonal stimuli

Hormonal control of the phosphorylation of phenylalanine hydroxylase was studied by using rat liver cells incubated with [32P]Pi. After immunoprecipitation from cell extracts, the hydroxylase was subjected to proteinase digestion and subsequent sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. V8-proteinase digestion yielded one major 32P-labelled fragment, of approx. 9 kDa. Chymotrypsin digestion gave five 32P-labelled fragments ranging from approx. 39 kDa to approx. 10 kDa. Noradrenaline (10 microM) and glucagon (0.1 microM) enhanced the 32P content of all peptide fragments uniformly. Phorbol ester, in contrast with ionophore A23187, did not stimulate enzyme phosphorylation or enhance phenylalanine metabolism in liver cells. These results are discussed in relation to the nature of the protein kinase(s) that mediate phosphorylation of phenylalanine hydroxylase in liver cells.

Control of phenylalanine and tyrosine metabolism by phosphorylation mechanisms

A system for the parallel determination of enzyme phosphorylation and expressed activity in rat liver cells, and its application to studies of phenylalanine hydroxylase and tyrosine aminotransferase, is described. Phenylalanine hydroxylase is phosphorylated by agents which stimulate cyclic AMP- and Ca2+-dependent protein kinase activity. The phosphorylation site(s) appear to be the same for both kinases. Phosphorylation is accompanied by increased metabolic flux at low, physiologically relevant, substrate concentrations. Insulin and spermine both inhibit the phosphorylation of the enzyme, possibly by increasing dephosphorylation. Tyrosine aminotransferase is phosphorylated in liver cell incubations but the rate is slow and insensitive to additions to the medium. No parallel changes in flux could be detected. Both enzymes are subject to complex regulatory mechanisms, short- and long-term. Their activities may be coordinated in vivo by control exerted at the level of the plasma membrane where both amino acids share the same transport processes. Determination of the control coefficients for the several components indicates that membrane transport may be a major limitation on flux.

Tryptophan aminotransferase activity in rat liver

By using an antiserum raised against rat liver tyrosine aminotransferase, it was shown that about 60% of tryptophan aminotransferase activity in rat liver extracts is catalysed by this enzyme. Induction of tryptophan aminotransferase activity by intraperitoneal injections of tryptophan or triamcinolone can be entirely attributed to the effects of these agents on tyrosine aminotransferase. The origin of the other 40% of tryptophan aminotransferase activity remains to be established. This activity increases after starvation for 48 h. It is unlikely that tryptophan transamination plays a quantitatively important role in the metabolism of tryptophan by the liver.

Ketogenesis in chick embryo isolated hepatocytes

Isolated hepatocytes from 17-day chick embryos exhibit high endogenous rates of ketogenesis. The addition of long-chain fatty acids stimulated ketogenesis with potency ordered as follows: palmitate greater than oleate greater than stearate. Octanoate produced a slight stimulation of ketogenesis when added at low concentrations (less than 0.25 mM). At higher concentrations the effect of octanoate was inhibitory. The addition of glucose to incubations failed to lessen endogenous ketogenesis whereas propionate, pyruvate and lactate produced inhibition. Ketogenesis from both endogenous sources and added fatty acids was not altered by the addition of glucagon, insulin, adrenalin or vasopresin.

Gluconeogenesis in chick embryo isolated hepatocytes

1. The effectiveness of gluconeogenic precursors in hepatocytes isolated from 18 day old chick embryos is:Lactate much much greater than pyruvate greater than alanine = glutamine greater than glycerol and other amino acids. This result is qualitatively and quantitatively similar to hepatocytes isolated after hatching. 2. In the presence of endogenous glycogenolysis, conversion of [U-14C]lactate to glucose was used to estimate gluconeogenic flux and its control by hormones. 3. Glucagon failed to stimulate lactate gluconeogenesis although simultaneously increasing glycogenolysis. Insulin had no effects on gluconeogenesis.

Control of large-scale plasma thawing for recovery of cryoprecipitate factor VIII

Cryoprecipitation is commonly used as the primary step in the preparation of clinical factor VIII concentrates; yet recovery is usually very low. Much of this loss is due to poor temperature control and a process of continuous plasma thawing has been designed to overcome this. A substantial improvement has resulted, with an increase in both yield and purity of factor VIII:C of over 50% in comparison to a conventional batch thaw process.

Hormonal regulation of glycogen metabolism in hepatocyte suspensions isolated from chicken embryos

1. A method is described for efficient and rapid isolation of viable hepatocyte suspensions from chick embryos in the last few days of incubation. 2. Although qualitatively similar, quantitative differences exist in the hormonal control of glycogen metabolism between embryonic and hatched chicks. 3. Glucagon and adrenaline activate glycogenolysis. 4. Insulin did not inhibit basal or glucagon-stimulated glycogenolysis. 5. Phenylephrine (an alpha-adrenergic agonist), angiotensin and vasopressin, all of which activate glycogen breakdown in rat liver through a Ca2+-dependent mechanism, were without effect on chick embryo hepatocytes.

Changes in factor VIII complex activities during the production of a clinical intermediate purity factor VIII concentrate

Samples taken at various stages of preparation of intermediate purity factor VIII concentrate were assayed for factor VIII coagulant activity (VIII:C), factor VIII coagulant antigen (VIIIC:Ag) and factor VIII related antigen (VIIIR:Ag). The antigen results were used to assess mechanical loss during fractionation as these markers are relatively stable. In contrast VIII:C is sensitive to both mechanical and inactivation losses. The major loss of factor VIII occurred during the cryoprecipitation and extraction step and was due to both mechanical loss and inactivation. Losses before and after this step were largely due to inactivation of the factor VIII. Assay of VIIIR:Ag in concentrates presented problems and a modified technique is suggested.