Cardiopulmonary Exercise Testing Provides Prognostic Information in Advanced Cystic Fibrosis Lung Disease

Rationale: Cardiopulmonary exercise testing (CPET) provides prognostic information in cystic fibrosis (CF); however, its prognostic value for patients with advanced CF lung disease is unknown. Objectives: To determine the prognostic value of CPET on the risk of death or lung transplant (LTX) within 2 years. Methods: We retrospectively collected data from 20 CF centers in Asia, Australia, Europe, and North America on patients with a forced expiratory volume in 1 second (FEV1) ⩽ 40% predicted who performed a cycle ergometer CPET between January 2008 and December 2017. Time to death/LTX was analyzed using mixed Cox proportional hazards regression. Conditional inference trees were modeled to identify subgroups with increased risk of death/LTX. Results: In total, 174 patients (FEV1, 30.9% ± 5.8% predicted) were included. Forty-four patients (25.5%) died or underwent LTX. Cox regression analysis adjusted for age, sex, and FEV1 revealed percentage predicted peak oxygen uptake ([Formula: see text]o2peak) and peak work rate (Wpeak) as significant predictors of death/LTX: adjusted hazard ratios per each additional 10% predicted were 0.60 (95% confidence interval, 0.43-0.90; P = 0.008) and 0.60 (0.48-0.82; P < 0.001). Tree-structured regression models, including a set of 11 prognostic factors for survival, identified Wpeak to be most strongly associated with 2-year risk of death/LTX. Probability of death/LTX was 45.2% for those with a Wpeak ⩽ 49.2% predicted versus 10.9% for those with a Wpeak > 49.2% predicted (P < 0.001). Conclusions: CPET provides prognostic information in advanced CF lung disease, and Wpeak appears to be a promising marker for LTX referral and candidate selection.

Sociotechnical Factors Contributing to Burnout among Radiation Oncology Medical Physicists: Survey and Focus Group Results from a Systems-Analysis Approach

PURPOSE/OBJECTIVE(S)

While burnout and contributing factors have been studied among physicians and surgeons, there is limited understanding of the factors contributing to radiation oncology medical physicists' (MPs) burnout. Therefore, this study aims to i) explore factors associated with burnout among MPs using a systems-analysis approach, and ii) identify and prioritize key improvement efforts.

MATERIALS/METHODS

We administered a survey to MPs at a US academic medical center between May 19-June 2, 2022. The survey included a 2-item Connor-Davidson Resilience Scale, a 2- item abbreviated Maslach Burnout Inventory (MBI) measuring emotional exhaustion (EE) and depersonalization (DP), and 21 general workplace stressors based on the National Academy of Medicine's systems approach to clinicians' burnout. Participants rated workplace stressor severity on a 5-item Likert scale and priorities for improvement on a 4-item Likert scale. Burnout was categorized using a 2-Question Summative Score totaling >3 for EE and DP. Focus groups were held with ∼3 participants per group via a video conferencing platform on June 8-9, 2022. Survey results from top-rated workplace stressors and priorities were summarized and presented to focus groups. Participants were asked open-ended questions to promote discussion and elicit more contextual information about workplace stressors and to rank their highest priority stressors at the end of the focus group.

RESULTS

Of the 12 MPs the survey was sent to, 8 responses (67%) were received. Table 1 summarizes the results. The mean resilience score was 6.88, with a standard deviation (SD) of 0.63. 87.5% (n = 7) of MPs identified themselves as burned out. The key workplace stressors contributing most to MPs' burnout were inadequate staffing (mean [SD] 3.1 [1.2]), work-life integration (3.1 [1.2]), excessive workload (2.8 [1.1]), and time pressure (2.6 [1.2]). Specifically, MPs suggested following improvements: i) hire additional physicists to cover clinic responsibilities, ii) limit or compensate for work done post-work hours, iii) improve scheduling workflow, and iv) retain hybrid work model.

CONCLUSION

Survey data demonstrated moderate resilience but high levels of burnout among MPs. Results indicate inadequate staffing as the most severe workplace stressor and highest priority for improvement efforts and remained the top priority even after focus groups. These results warrant further studies with larger sample sizes, assessing factors contributing to burnout among MPs and systems-focused interventions.

Factors influencing clinical trial participation for adult and pediatric patients with cystic fibrosis

There remains a limited understanding of the factors influencing clinical trial participation for individuals with Cystic Fibrosis (CF). A comprehensive survey was developed to examine the interests, preferences, and barriers/facilitators to research and clinical trial participation for CF patients. A consecutive sample of 198 CF adults attending the St. Paul's Hospital CF Clinic and parents of children with CF attending the BC Children's Hospital CF Clinic from Vancouver, Canada were surveyed. Parents of pediatric patients were less comfortable with blood collection, required more safety data prior to participating, and were more concerned about potential side effects. Very few respondents (<10%) appeared able/willing to fulfill the typical requirements to participate in a phase 1 clinical trial. Overall, there were more similarities than differences between the responses of adult and parents of pediatric CF patients. The patient-centered information can be used to inform the design of future clinical trials to enhance feasibility.

Frailty, pain and psychological variables among older adults living in Hong Kong nursing homes: can we do better to address multimorbidities?

WHAT IS KNOWN ON THE SUBJECT?: Frailty and multimorbidity are common in later life. A higher level of frailty is associated with a higher risk of adverse physical and psychological health situations. Older adults with pain have been reported to be lonelier and more depressed, as well as less happy and less satisfied with their life as compared to those without pain. In view of the high prevalence of pain among older adults and the reversibility of frailty, it is important to explore the relationship between pain, frailty and psychological parameters in order to devise patient-centred interventions. WHAT THIS PAPER ADDS TO EXISTING KNOWLEDGE?: Frailty index is positively correlated with the presence of pain, and associated with gender, functional mobility and loneliness. Among these significant variables, loneliness was the factor that contributed the most to the frailty index. WHAT ARE THE IMPLICATIONS FOR PRACTICE?: It is essential to put the focus of healthcare on both the physical and psychological aspects of well-being. All nurses are advised to improve the management of pain in older people in order to lower the levels of pain, frailty and psychological distress among this population. Nursing care should address the loneliness level especially the problem of social loneliness among older adults particularly those living in nursing homes.

ABSTRACT

Introduction In view of the high prevalence of pain among older adults and the reversibility of frailty, it is important to explore the relationship between pain, frailty and psychological parameters in order to devise patient-centred interventions. Aim To examine the levels of frailty, pain and psychological parameters among older adults living in Hong Kong nursing homes, and the cross-sectional relationships among these items. Methods A cross-sectional study was conducted among 178 residents from six nursing homes. Frailty, pain, mobility, happiness, loneliness and life satisfaction of participants were assessed using validated questionnaires. Results A multiple linear regression (R(2)  = 0.338, P < 0.05) showed that the frailty index was associated with loneliness, functional mobility and gender. Among these significant variables, loneliness was the factor that contributed the most to the frailty index. Discussion It is essential to put the focus of healthcare on both the physical and psychological aspects of well-being. Findings suggest that apart from improving mobility and reducing pain, loneliness could be a target of psychosocial interventions to reduce frailty and improve quality of life. Implications for practice It is advised that nursing care should address loneliness, especially the problem of social loneliness among older adults particularly those living in nursing homes.

Microwave-assisted extraction of active pharmaceutical ingredient from solid dosage forms

The microwave assisted extraction (MAE) technique has been evaluated for the extraction of active pharmaceutical ingredients (API) from various solid dosage forms. Using immediate release tablets of Compound A as a model, optimization of the extraction method with regards to extraction solvent composition, extraction time and temperature was briefly discussed. Complete recovery of Compound A was achieved when samples were extracted using acetonitrile as the extraction solvent under microwave heating at a constant cell temperature of 50 degrees C for 5 min. The optimized MAE method was applied for content uniformity (single tablet extraction) and potency (multiple tablets extraction) assays of release and stability samples of two products of Compound A (5 and 25mg dose strength) stored at various conditions. To further demonstrate the applicability of MAE, the instrumental extraction conditions (50 degrees C for 5 min) were adopted for the extraction of montelukast sodium (Singulair) from various solid dosage forms using methanol-water (75:25, v/v) as the extraction solvent. The MAE procedure demonstrated an extraction efficiency of 97.4-101.9% label claim with the greatest RSD at 1.4%. The results compare favorably with 97.6-102.3% label claim with the greatest RSD at 2.9% obtained with validated mechanical extraction procedures. The system is affordable, user-friendly and simple to operate and troubleshoot. Rapid extraction process (7 min/run) along with high throughput capacity (up to 23 samples simultaneously) would lead to reduced cycle time and thus increased productivity.

Suppression of intestinal polyps in Msh2-deficient and non-Msh2-deficient multiple intestinal neoplasia mice by a specific cyclooxygenase-2 inhibitor and by a dual cyclooxygenase-1/2 inhibitor

Epidemiological studies suggest that nonsteroidal anti-inflammatory agents decrease the risk of colorectal cancer. This is believed to be mediated, at least in part, by inhibition of cyclooxygenase (COX) activity. There are two COX isoenzymes, namely the constitutively expressed COX-1 and the inducible COX-2. COX-2 is overexpressed in adenomas and colorectal cancers, and COX-2-specific inhibitors have been shown to inhibit intestinal polyps in Apc(Delta716) mice more effectively than dual COX-1/COX-2 inhibitors such as sulindac. Various Apc knockout mice, including the multiple intestinal neoplasia (Min) mouse and the Apc(Delta716) mouse, are limited by their lack of large numbers of colonic adenomas and aberrant crypt foci, the putative precursors of large-bowel polyps and cancers. Our DNA mismatch-repair-deficient Min mouse model (Apc+/-Msh2-/-) has genetic features of both familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, and most importantly, rapidly develops numerous small- and large-bowel adenomas, as well as colonic aberrant crypt foci. The purpose of this study was to determine the effects of COX inhibitors on intestinal adenomas and colonic aberrant crypt foci in this accelerated polyposis, mismatch-repair-deficient Min mouse model, in addition to a standard Min mouse model. Weanling Apc+/-Msh2-/- and Min mice were fed diets containing no drug, sulindac, or a specific COX-2 inhibitor (MF-tricyclic). Apc+/-Msh2-/- and Min mice were sacrificed after 4 weeks and 5 months on diet, respectively. Apc+/-Msh2-/- mice treated with MF-tricyclic had significantly fewer small-bowel polyps (mean +/- SD, 178 +/- 29) compared with mice on sulindac (278 +/- 80), or control diet (341 +/- 43; P < 0.001). There was no difference in numbers of large-bowel polyps or aberrant crypt foci in mice in the three groups. MF-tricyclic was also effective in reducing both small- and large-bowel polyps in Min mice. Western analysis demonstrated COX-2 expression in both large- and small-bowel polyps from mice of both genotypes. This study demonstrates that a specific COX-2 inhibitor is effective in preventing small-bowel polyps in mismatch-repair-deficient Min mice and both small- and large-bowel polyps in standard Min mice. Therefore, specific COX-2 inhibitors may be useful as chemopreventive and therapeutic agents in humans at risk for colorectal neoplasia.

Permeability of the peptidic GH secretagogues hexarelin and EP 51389, across rat jejunum

The intestinal permeability of hexarelin and EP 51389, two growth hormone releasing hexa- and tri- peptide analogues, was assessed in vitro with side-by-side diffusion chambers in the apical-to-basolateral (AP-to-BL) and in the basolateral-to-apical (BL-to-AP) direction using excised rat jejunal segments. The effect of EP 51389 on P-glycoprotein (P-gp) was evaluated by rhodamine 123 accumulation on monolayers of CH(R)C5 cells with increasing concentrations of EP 51389. Hexarelin and EP 51389 permeability were found to be < 1%. Permeability coefficients (P(app)) were 18.87 +/- 2.86 (x10(-7) cm/s) and 5.87 +/- 0.45 (x10(-7) cm/s) for hexarelin and EP 51389, respectively. Bidirectional studies revealed that hexarelin transport was similar in both directions. EDTA did not influence hexarelin permeability. Permeability was predominantly secretory for EP 51389 as P(app) in the BL-to-AP direction [32.56 +/- 6.11 (x10(-7) cm/s)] was greater than AP-to-BL. Confirming involvement of a secretory transport system, chlorpromazine inhibited EP 51389 transport across the jejunum. EP 51389 inhibited P-gp in a dose dependent manner resulting in the intracellular accumulation of rhodamine in CH(R)C5 cells. These results suggest that: 1) the intestinal permeability of hexarelin and EP 51389 is poor; 2) the passage of hexarelin is mainly via a transcellular passive pathway since the contribution of paracellular permeability to the overall permeability is rather low; 3) P-gp may act as a potential barrier for the intestinal absorption of EP 51389.

Chemoprevention of intestinal polyposis in the Apcdelta716 mouse by rofecoxib, a specific cyclooxygenase-2 inhibitor

Mutations in the human adenomatous polyposis (APC) gene are causative for familial adenomatous polyposis (FAP), a rare condition in which numerous colonic polyps arise during puberty and, if left untreated, lead to colon cancer. The APC gene is a tumor suppressor that has been termed the "gatekeeper gene" for colon cancer. In addition to the 100% mutation rate in FAP patients, the APC gene is mutated in >80% of sporadic colon and intestinal cancers. The Apc gene in mice has been mutated either by chemical carcinogenesis, resulting in the Min mouse Apcdelta850, or by heterologous recombination, resulting in the Apcdelta716 or Apedelta1368 mice (M. Oshima et al., Proc. Natl. Acad. Sci. USA, 92: 4482-4486, 1995). Although homozygote Apc-/- mice are embryonically lethal, the heterozygotes are viable but develop numerous intestinal polyps with loss of Apc heterozygosity within the polyps (M. Oshima et al., Proc. Natl. Acad. Sci. USA, 92: 4482-4486, 1995). The proinflammatory, prooncogenic protein cyclooxygenase (COX)-2 has been shown to be markedly induced in the Apcdelta716 polyps at an early stage of polyp development (M. Oshima et al., Cell, 87: 803-809, 1996). We demonstrate here that treatment with the specific COX-2 inhibitor rofecoxib results in a dose-dependent reduction in the number and size of intestinal and colonic polyps in the Apcdelta716 mouse. The plasma concentration of rofecoxib that resulted in a 55% inhibition of polyp number and an 80% inhibition of polyps > 1 mm in size is comparable with the human clinical steady-state concentration of 25 mg rofecoxib (Vioxx) taken once daily (A. Porras et al., Clin. Pharm. Ther., 67: 137, 2000). Polyps from both untreated and rofecoxib- or sulindac-treated Apcdelta716 mice expressed COX-1 and -2, whereas normal epithelium from all mice expressed COX-1 but minimal amounts of COX-2. Polyps from either rofecoxib- or sulindac-treated mice had lower rates of DNA replication, expressed less proangiogenic vascular endothelial-derived growth factor and more membrane-bound beta-catenin, but showed unchanged nuclear localization of this transcription factor. This study showing the inhibition of polyposis in the Apcdelta716 mouse suggests that the specific COX-2 inhibitor rofecoxib (Vioxx) has potential as a chemopreventive agent in human intestinal and colon cancer.

Activity-dependent and use-dependent regulation of dopamine-receptor clustering

In this study, fluorescence-conjugated ligands were employed to label dopaminergic D1-like and D2-like receptors, respectively, in neurons derived from the frontal cortex of embryonic rats. The receptor binding sites were visualized and analyzed using confocal microscopy. Our results showed that fluorescently labeled receptors tended to form clusters with a diameter of about one micrometer and were distributed on both somata and dendrites. Chronic treatment with tetrodotoxin reduced the number of fluorescent clusters of both D1-like and D2-like receptors, while chronic treatment with a high concentration of potassium increased the number of fluorescent clusters of both D1-like and D2-like receptors. Further, chronic treatment with SCH23390 up-regulated the number of D1-like receptor clusters, whereas chronic treatment with bromocriptine down-regulated the number of D2-like receptor clusters. In addition, chronic treatment with spiperone down-regulated the number of D1-like receptor clusters. These results suggest that both neuronal activity and dopaminergic receptor occupancy are important factors that determine dopaminergic receptor clustering which is an essential step toward synaptogenesis during neuronal maturation process.

Human NELL-1 expressed in unilateral coronal synostosis

Surgical correction of unilateral coronal synostosis offers a unique opportunity to examine the molecular differences between an abnormal and a normal cranial suture. We isolated and identified a cDNA fragment whose expression was up-regulated in the premature fusing and fused coronal sutures, as compared with normal coronal sutures. The nucleotide sequence of the full-length cDNA of this gene, human NELL-1, has approximately 61% homology with the chicken Nel gene. Both chicken Nel and human NELL-1 are comprised of six epidermal growth factor-like repeats. The human NELL-1 messages were localized primarily in the mesenchymal cells and osteoblasts at the osteogenic front, along the parasutural bone margins, and within the condensing mesenchymal cells of newly formed bone in sites of premature sutural fusion. Human multiorgan tissue mRNA blot showed that NELL-1 was specifically expressed in fetal brain but not in fetal kidney, liver, or lung. We also showed that Nell-1 was expressed in rat calvarial osteoprogenitor cells and was largely absent in rat tibiae and fibroblast cell cultures. In conclusion, our data suggest that the NELL-1 gene is preferentially expressed in cranial intramembranous bone and neural tissue (both of neural crest cell origin) and is up-regulated during unilateral premature closure of the coronal suture. The precise role of this gene is unknown.

Karaoke therapy in the rehabilitation of mental patients

OBJECTIVES

To study the efficacy of karaoke singing and its implications in the rehabilitation of mental patients in Hong Kong Chinese.

METHODS

A double blind controlled trial was conducted over six weeks in a small sample of chronic schizophrenic patients matched in age, sex and duration of illness. The index group practised karaoke and the controlled group practised simple singing. Subjects were assessed in changes in mood and social interaction.

RESULTS

No significant difference was detectable within the 2 groups. However, significant differences of anxiety and social interaction at the end of the third and sixth weeks respectively, were detectable between the 2 groups.

CONCLUSION

Karaoke therapy may be more effective than simple singing in improving social interaction. There is preliminary evidence that it may be anxiety-provoking for unstable schizophrenic patients. More research is required for further elucidation of the characteristics of favourable candidates, optimal schedule and active components of the therapy.

Substituted (pyridylmethoxy)naphthalenes as potent and orally active 5-lipoxygenase inhibitors; synthesis, biological profile, and pharmacokinetics of L-739,010

Dioxabicyclooctanyl naphthalenenitriles have been reported as a class of potent and nonredox 5-lipoxygenase (5-LO) inhibitors. These bicyclo derivatives were shown to be metabolically more stable than their tetrahydropyranyl counterparts but were not well orally absorbed. Replacement of the phenyl ring in the naphthalenenitrile 1 by a pyridine ring leads to the potent and orally absorbed inhibitor 3g (L-739,010, 2-cyano-4-(3-furyl)-7-[[6-[3-(3-hydroxy-6,8-dioxabicyclo[3.2.1] octanyl)]-2-pyridyl]methoxy]naphthalene). Compound 3g inhibits 5-HPETE production by human 5-LO and LTB4 biosynthesis by human PMN leukocytes and human whole blood (IC50S of 20, 1.6, and 42 nM, respectively). Derivative 3g is orally active in the rat pleurisy model (inhibition of LTB4, ED50 = 0.3 mg/kg) and in the anesthetized dog model (inhibition of ex vivo whole blood LTB4 and urinary LTE4, ED50 = 0.45 and 0.23 microgram/kg/min, respectively, i.v. infusion). In addition, 3g shows excellent functional activity against ovalbumin-induced dyspnea in rats (60% inhibition at 0.5 mg/kg, 4 h pretreatment) and Ascaris-induced bronchoconstriction in conscious sheep (50% and > 85% inhibition in early and late phases, respectively at 2.5 micrograms/kg/min, i.v. infusion) and, more particularly in the conscious antigen sensitive squirrel monkey model (53% inhibition of the increase in RL and 76% in the decrease of Cdyn, at 0.1 mg/kg, po). In rats and dogs, 3g presents excellent pharmacokinetics (estimated half-lives of 5 and 16 h, respectively) and bioavailabilities (26% and 73% when dosed as its hydrochloride salt at doses of 20 and 10 mg/kg, respectively, in methocel suspension). Based on its overall biological profile, compound 3g has been selected for preclinical animal toxicity studies.

Suppression of intestinal polyposis in Apc delta716 knockout mice by inhibition of cyclooxygenase 2 (COX-2)

Two cyclooxygenase isozymes catalyze conversion of arachidonic acid to prostaglandin H2: constitutive COX-1 and inducible COX-2. To assess the role of COX-2 in colorectal tumorigenisis, we determined the effects of COX-2 gene (Ptgs2) knockouts and a novel COX-2 inhibitor on Apc delta716 knockout mice, a model of human familial adenomatous polyposis. A Ptgs2 null mutation reduced the number and size of the intestinal polyps dramatically. Furthermore, treating Apc delta716 mice with a novel COX-2 inhibitor reduced the polyp number more significantly than with sulindac, which inhibits both isoenzymes. These results provide direct genetic evidence that COX-2 plays a key role in tumorigenesis and indicate that COX-2-selective inhibitors can be a novel class of therapeutic agents for colorectal polyposis and cancer.

Recognition of tetrahedral 1,10-phenanthroline-cuprous chelates by transcriptionally active complexes does not depend on the sequence of the promoter

BACKGROUND

The open complex formed at the initiation site of transcription within the active site of RNA polymerase is unique to actively transcribing genes and is thus an ideal target for the design of transcription inhibitors. Many redoxactive tetrahedral cuprous chelates of 1,10-phenanthroline (OP) or derivatives cleave the single-stranded template, principally at sequence positions -7 to -3, whereas the redox-inactive tetrahedral cuprous chelate of 2, 9-dimethyl-OP (neocuproine) blocks transcription, but does not cleave. The octahedral (OP)3-Fe2+ chelate has no effect. Different promoters can give different cleavage patterns. We therefore searched for structural determinants of the open complex that are important in the cleavage reaction.

RESULTS

Using site-directed mutagenesis, we systematically altered the nucleotides at the cleavage sites of the Escherichia coli lac UV-5-RNA polymerase open complex (positions -6 to -4), which are highly variable in E. coli promoters. Surprisingly, these changes had little effect on catalytic activity, on transcription inhibition by the cuprous complex of neocuproine and on the cleavage patterns generated by the cuprous chelates of OP derivatives. The scission pattern of a lac UV-5 promoter mutant in which the cleavage sites have the sequence of the trp EDCBA promoter is that of the lac UV-5 promoter, not the trp EDCBA promoter.

CONCLUSIONS

Nucleotide-specific interactions are not responsible for the observed cleavage patterns. The recognition of the tetrahedral OP chelate must be due to a specific structure of the single-stranded regions, determined by RNA polymerase-DNA interactions in the upstream regulatory region.

Determination of procaine in equine plasma and urine by high-performance liquid chromatography

The variability in plasma and urine equine procaine measurement between three independent laboratories using current methods led to the development of a sensitive, reliable, and reproducible high-performance liquid chromatographic method. Standardbred mares were administered either a penicillin G procaine preparation intramuscularly or procaine hydrochloride subcutaneously, and blood and urine were collected at defined time intervals. By HPLC the detection limits for procaine in plasma and urine were 1 and 10 ng/mL, respectively. In contrast procaine in plasma could not be detected by GC-NPD, while the urinary detection limit was 50 ng/mL. The concentration of fluoride in the collection tubes and repetitive freeze-thawing modified plasma procaine measurement. Urinary pH was a factor in estimation of urine procaine levels with greater recovery and reproducibility of results at pH 5 as compared to pH 7. This HPLC method provides a simple, sensitive, and reliable quantitation of procaine in equine plasma and urine.

HPLC analysis of an amino bisphosphonate in pharmaceutical formulations using postcolumn derivatization and fluorescence detection

Monosodium 4-amino-1-hydroxybutane-1, 1-diphosphonic acid (MK-217) is a bone resorption inhibitor implicated in the treatment of malignant hypercalcemia. This compound is very water soluble and has five ionizable groups with pKa values over the entire pH range. As a result, it is difficult to maintain a single species in solution for chromatographic separation. Since there is no chromophore in the molecular structure, UV detection is ineffective. The compound and its potential degradation products are separated by ion-pair chromatography using 0.01 M cetyltrimethylammonium bromide as the ion-pairing agent and a polymeric stationary phase. Detection is by fluorescence detection after postcolumn derivatization of the primary amine with ophthalaldehyde and mercaptoethanol (OPA-MERC). Optimization of the chromatographic separation and the postcolumn reaction has been carried out, and the method has been applied to the analysis of MK-217 in intravenous solutions and tablet formulations.

Comparison of analysis of digoxin in cardiac patients by HPLC and RIA

A sensitive and selective high-performance liquid chromatographic-post column derivatization (HPLC-PC) method was used to determine the digoxin levels in the sera of cardiac patients and was compared to the values obtained from analysis of the same samples by conventional radioimmunoassay (RIA) procedures. A statistical comparison of the results obtained by the RIA and HPLC-PC methods showed an overall lower assay value for the samples determined by the HPLC-PC method. High cross-reactivity values for the metabolites of digoxin were determined using RIA kits currently available for digoxin measurements.

The influence of furosemide on plasma elimination and urinary excretion of drugs in standardbred horses

A study of the effects of intravenous administration of either 150 mg or 250 mg of furosemide to standardbred mares pre-treated with other drugs was undertaken to determine whether a unique pattern of drug elimination into urine and from plasma for each compound occurred. Furosemide significantly reduced the plasma concentrations of codeine compared to control 2-6 h after furosemide administration. In contrast, the plasma concentrations of theophylline, phenylbutazone, pentazocine, guaifenesin and flunixin were not markedly altered by furosemide. In the case of acepromazine, clenbuterol and fentanyl, the data generated were insufficient to state with certainty whether or not furosemide affected the plasma concentrations of these three drugs. A significant reduction was noted in the urinary concentrations of guaifenesin, acepromazine, clenbuterol, phenylbutazone, flunixin, fentanyl and pentazocine within 1-4 h of furosemide administration. The urinary concentrations of theophylline remained reduced as long as 8 h after furosemide injection. Furosemide administration to horses pre-treated with codeine resulted in depression of urinary morphine concentrations 2-4 h and 9-12 h after furosemide injection. A lower furosemide dose (150 mg) produced changes in drug urinary excretion and plasma elimination equivalent to the higher dose (250 mg). It is evident that furosemide affects the urinary and plasma concentrations of other co-administered drugs but not in a predictable fashion, which limits the extrapolation of these results to as yet untested drugs.

Stereoselective high-performance liquid chromatographic assay for propranolol enantiomers in serum

A simple and sensitive stereoselective high-performance liquid chromatographic assay for the quantitation of propranolol enantiomers in serum is described. The method involves conversion of the propranolol enantiomers to diastereomeric urea derivatives by reaction with the clinical reagent (+)-phenylethylisocyanate, followed by chromatographic separation of the diastereomeric products. Conditions of the derivatization reaction were optimized to achieve rapid and quantitative yield with either of the enantiomers. Baseline resolution of the diastereomers was achieved on a reversed phase C8 column with an isocratic mobile phase. Fluorescence detection afforded an absolute on-column detection limit of 100 pg. The assay has been applied to pharmacokinetic studies in humans and small laboratory animals.

Analysis of digoxin at therapeutic concentrations using high-performance liquid chromatography with post-column derivatization

A high-performance liquid chromatographic (HPLC) procedure has been developed for the analysis of digoxin in plasma at therapeutic concentrations. The assay method provides resolution of digoxin from its metabolites using a 15 cm X 4.6 mm HPLC column containing 3-micron octadecylsilane-bonded stationary phase. The effluent of the column is passed through a post-column reactor in which a fluorescent derivative is formed by the co-addition of hydrochloric acid and dehydroascorbic acid. Detection of the derivative is accomplished in a fluorometer with excitation at 336 nm and emission at 425 nm. The extraction efficiency for recovery of digoxin from plasma samples was 70% using chloroform-isopropanol (9:1) following a pre-wash with isooctane to remove endogenous substances. The calibration curve was linear (r = 0.9999) over the range 0.5-4 ng/ml digoxin in plasma using digitoxigenin as internal standard. The minimum detectable quantity of digoxin in plasma was 0.5 ng/ml at a signal-to-noise ratio of 4:1. Split-samples of digoxin control sera were assayed by the HPLC procedure and by the prescribed radioimmunoassay procedure. Excellent correlation was observed between the two methods (r = 0.999). No interference was noted when a selection of commonly co-prescribed drugs were evaluated for chromatographic co-elution or interference in detection with that of digoxin or the internal standard.

Fluorometric determination of nanogram quantities of protein in small samples: application to calcium-transport adenosine triphosphatase

A fluorometric micro protein assay based on fluorescamine-labelling of homogeneous proteins in solution has been developed which is capable of accurately quantitating as little as 25 ng protein at a concentration of 1.25 micrograms/ml. This micro assay uses a flow-through HPLC fluorescence detector. Typical micro assays measuring bovine serum albumin standards (0-25 mg/l) yielded linear regression coefficients of r = 0.999. Assays of purified Ca2+-ATPase solutions determined by the micro fluorescamine procedure correlated well with measurements made using the deoxycholate-TCA-precipitation modification of the Lowry assay: 1.0 microgram ATPase by Lowry method = 1.1 microgram protein by fluorescamine microassay (when both procedures were standardized with bovine serum albumin) (r = 0.995). The assay proposed offers a 100-fold increase in sensitivity, compared to the Lowry procedure.

Development of a high-performance liquid chromatographic assay for digoxin using post-column fluorogenic derivatization

An efficient high-performance liquid chromatographic (HPLC) separation for digoxin and its metabolites has been developed. Quantitation of digoxin at plasma levels was possible after the column effluent was passed through a fluorogenic post-column reactor. A study of the optimum post-column conditions was undertaken using a combination of ascorbic acid, hydrogen peroxide and hydrochloric acid, which was known to induce fluorescence in the digoxin molecule. Digoxin and its metabolites were separated on a 15 cm X 4.6 mm I.D., 3-microns reversed-phase (C18) HPLC column using methanol--ethanol--isopropanol--water (52:3:1:45) as the mobile phase at a flow-rate of 0.3 ml/min. A solution of 1.1 X 10(-3) M hydrogen peroxide in a 0.1% ascorbic acid solution and concentrated hydrochloric acid were added into the post-column reactor through a peristaltic pump at a combined flow with a flow-rate of 0.23 ml/min. The mixture was passed into the 20-m reaction coil maintained at 79 +/- 1 degrees C. The resulting digoxin fluorophore was monitored with a fluorescence detector. Detector responses were linear from 1.5 to 10 ng injected on-column. The overall performance demonstrated that this system has the sensitivity, linearity and stability desired in a digoxin plasma level determination. The total chromatographic time including the postcolumn derivatization step was about 40 min.

Carbon isotopic fractionation in heterotrophic microbial metabolism

Differences in the natural-abundance carbon stable isotopic compositions between products from aerobic cultures of Escherichia coli K-12 were measured. Respired CO2 was 3.4% depleted in 13C relative to the glucose used as the carbon source, whereas the acetate was 12.3% enriched in 13C. The acetate 13C enrichment was solely in the carboxyl group. Even though the total cellular carbon was only 0.6% depleted in 13C, intracellular components exhibited a significant isotopic heterogeneity. The protein and lipid fractions were -1.1 and -2.7%, respectively. Aspartic and glutamic acids were -1.6 and +2.7%, respectively, yet citrate was isotopically identical to the glucose. Probable sites of carbon isotopic fractionation include the enzyme, phosphotransacetylase, and the Krebs cycle.

The influence of diet on the regression of the Walker carcinosarcoma 256 in rats

Regression of the Walker carcinosarcoma 256 has been observed in rats inoculated with 10(4) viable tumor cells. The regression was found to be affected by dietary composition. Tumors in rats fed a commercial laboratory diet (CLD) regressed after a 9-day initial growth period while tumors in rats fed a purified diet high in free fatty acids continued to grow. Diets with 20% corn oil promoted tumor regression, but rats fed diets containing 20% free fatty acids from corn oil had tumors that continued to grow. The nonsaponifiable fraction (NSF) of corn oil appeared to promote tumor regression when this fraction was added to diets containing corn oil fatty acids. At the end of the experiment (14 days), the tumors of rats fed a free fatty acid diet weighed 13-17 g. The tumors of rats fed CLD, corn oil diet and the corn oil free fatty acid diet plus the NSF of corn oil weighed 1-5 g. These results indicate that something in the NSF of corn oil was associated with the regression of the tumor. However, the nature of the dietary components promoting tumor regression, and the host response to those components, have not been determined.

Effects of diets deficient in glucose and glucose precursors on the growth of the Walker carcinosarcoma 256 in rats

The effects of carbohydrate-deficient diets on the growth of the Walker carcinosarcoma 256 in rats and on the carcinostatic action of the glucose analogue 2-deoxyglucose were studied. All diets contained 13.0% casein with glucose levels as indicated and the balance of calories present as corn oil free fatty acids. The growth of the tumor was directly related to the glucose level in such diets; after 16 days rats fed 0.0, 1.5 and 4.5% glucose had tumors weighing 7.0, 11.1 and 13.3 g, respectively. The decrease in tumor weight was related to dietary glucose level rather than the anorexia produced by the diets low in glucose, as shown by the fact that tumors in rats fed 4.5% glucose were larger than rats fed 1.5% glucose even when the rats fed 4.5% glucose were pair-fed to the levels consumed by those fed 1.5% glucose. 2-Deoxyglucose (0.2%) also caused a reduction in tumor growth in a manner independent from the anorexia produced by its presence in the diet. This carcinostatic effect was potentiated by low glucose levels in the diets in the rats fed 4.5% glucose plus 0.2% 2-deoxyglucose had proportionally greater reductions in tumor weights due to the glucose analogue than did rats fed 20% glucose plus 0.2% 2-deoxyglucose.

Pleurectomy and intraoperative brachytherapy and postoperative radiation in the treatment of malignant pleural mesothelioma

Forty-one patients with diffuse, pleural mesothelioma limited to one hemi-thorax underwent a thoracotomy at Memorial Sloan-Kettering Cancer Center from January 1976 to July 1982. Treatment at thoracotomy consisted of as complete a parietal pleurectomy as was possible to remove the bulk of the tumor. Measurable gross residual disease was treated whenever feasible, with permanent 125I implantation; residual diffuse disease was treated by a temporary 192Ir implantation or by postoperative instillation of 32P. External radiation therapy was given 4-6 weeks postoperatively to the involved hemi-thorax, shielding the lung and utilizing a combination of electron and a photon beam. A dose of 4500 rad in 4.5 weeks was given to the pleural surface by the mixed beam. There was no postoperative mortality in this group of 41 patients. Complications developed in 6 patients (15%). The median survival was 21 months; the one year survival was 65% and the two year survival was 40%. The median disease-free survival was 11 months and the one and two year disease-free survival 44 and 13% respectively. This study suggests that the combination of pleurectomy, intraoperative brachytherapy and postoperative external radiation increased the local control of the tumor and prolonged the survival.

Arginine uptake by chick kidney mitochondria

Arginine uptake by kidney mitochondria in two strains of chicks of high (HA) and low (LA) requirement of dietary arginine was studied by using an ion-exchange method. Dietary factors influencing uptake of arginine were also investigated. The results indicate that arginine uptake by kidney mitochondria of HA chicks was significantly higher than the LA chicks when arginine-deficient diet or diet with excess lysine was fed. The arginine uptake by kidney mitochondria reflects the kidney arginase activity. Both arginase activity and arginine uptake inversely correlated with growth rate of the two strains of chicks. However, the dietary factors that affect kidney mitochondria arginase activity are not completely parallel to the uptake of arginine by kidney mitochondria. A system that facilitates entry of arginine into kidney mitochondrial membrane is suggested.

HPLC analysis of indomethacin and its impurities in capsule and suppository formulations

Indomethacin and its impurities in suppository and capsule formulations were quantitatively determined by HPLC using a reversed-phase, octadecyl column and a mobile phase of methanol-water-acetonitrile-acetic acid (55:35:10:1). Analysis of the suppository formulations provided a mean potency for indomethacin of 103.8%. The same formulation was found to contain 4-chlorobenzoic acid (0.02%), 5-methoxy-2-methyl-3-indoleacetic acid (0.07%), 4-chlorobenzoic acid-alpha-monoglyceride (0.39%), and indomethacin-alpha-monoglyceride (0.9%) as impurities. The latter two impurities were a result of the interaction of indomethacin and 4-chlorobenzoic acid with glycerin used in the suppository base. Capsule formulations were likewise assayed with an average potency of 99.9 and 101.5% for 25- and 50-mg dosage forms, respectively. Only one of the two capsule formulations examined contained detectable quantities of 4-chlorobenzoic acid (0.05%).

Separation of digoxin, digitoxin and their potential metabolites, impurities or degradation products by high-performance liquid chromatography

A rapid and versatile series of high-performance liquid chromatographic systems are described for the resolution of digoxin, digitoxin and their potential metabolites or degradation products and impurities. These systems consist of isocratic, single-step gradient and linear gradient modes that provide resolution of the glycosides in 25, 17 and 14 min respectively. Digoxin, its mono- and bisdigitoxosides, digoxigenin and gitoxin, a potential impurity, may be isocratically separated in 11 min. The two semi-synthetic glycosides alpha- and beta-acetyldigoxin are resolved and separated from digoxin and its metabolites in a chromatographic time of 23 min. Digitoxin and its metabolites or degradation products may be separated in as little as 9 min using an isocratic system. The solvent systems employ varying proportions of methanol, water, isopropanol and dichloromethane and a conventional 5 micrometers bonded, octadecyl phase. Detection was accompanied using a variable wavelength detector set at 220 nm.

Comparative contributions of dietary protein quality and quantity to growth during gestation, lactation and postweaning in the rat

The growth promotion by feeding purified diets containing 25%, 12% or 7% of either casein or wheat gluten (W.G.) and the supplementation value of adding cystine to the low casein diets, and lysine or lysine plus threonine to the wheat gluten diets ascertained in rats by comparing the weight achieved at birth, after 3 weeks suckling or 4 weeks postweaning. Birth weight was depressed by 30% with 7% casein; by 20% with 7% W.G.; by 15% with 25% W.G. compared to controls and there was no change when lysine alone was added to 7% W.G. Addition of lysine plus threonine to 7% W.G., lysine to 25% W.G. and cystine to 7% casein increased birth weight. The weight gain of dams reflected birth weight of pups in most cases. Weaning weight was depressed by 60% with either 12% casein or 12% W.G., and by 40% with 25% W.G. compared to controls. Addition of cystine to 12% casein and lysine to 25% W.G. increased the weaning weight slightly. Addition of lysine, lysine plus threonine or lysine plus glutamic acid (G.A.) to 12% W.G. had no effect on weaning weight. Maternal weight loss was decreased by amino acid supplementation of the diet. Four-week postweaning body weight was equal to the control when cystine was added to 12% casein and lysine was added to 25% W.G. Addition of lysine to 12% W.G. improved the growth rate, and addition of lysine plus threonine further improved the growth rate. Food intake was not decreased by protein deficiency during gestation. Food intake was significantly lowered by protein deficiency during both lactation and postweaning, however, supplementation of amino acid partially restored food intake to normal levels.

Effect of different postnatal periods of protein-energy malnutrition in young rats upon subsequent protein utilization

Previously it had been shown that rat pups, malnourished during the 3-week suckling period and the nutritionally rehabilitated for about 30 weeks, showed an increase in the efficiency of dietary protein utilization of the protein was fed at a less than optimal level and if the protein was of poor nutritional quality (J. Nutr. 103, 273, 1973). The present study extends this observation to growing rats malnourished during the first 3 weeks of life and then rehabilitated with a 25% casein diet for 4 weeks. The test proteins were casein, fed at a level of 12%, and wheat gluten, at a level of 25%. Efficiency of nitrogen retention was greater for both proteins in rats previously malnourished than for control, non-malnourished rats. Malnutrition was then imposed on rats malnourished by feeding a low protein diet either during the first 4 weeks postweaning or from the 7th to 11th week of life. After these periods of malnourishment, the rats were rehabilitated for 4 weeks and efficiency of utilization measured for both casein and wheat gluten fed at 10% of the diet. No change in utilization was found for either protein fed to rats rehabilitated from either of these periods of malnutrition.

Role of coprophagy in masking dietary deficiencies of cystine in the rat

When a diet containing raw soybean was fed to rats, there was an increase in the synthesis of pancreatic protein, presumably exocrine protein, as evidenced by an increased uptake of [35S]cystine. There was also an increased transsulfuration of methionine sulfur as indicated by labeled sulfur transformation from methionine to cystine. This same pattern of events was produced in rats receiving a casein-containing diet when 50 mg of crystalline trypsin inhibitor was administered by gavage. However, if coprophagy was prevented, the increased uptake of [35S]cystine and [35S]methionine transsulfuration under both dietary conditions was blocked. It was found that prevention of coprophagy was without effect upon these two processes if supplementary dietary cystine was provided or if a dietary protein source with adequate cystine, i.e., heat-treated soybean, was provided. It was concluded that by practicing coprophagy, sufficient fecal cystine was being returned to the upper intestinal tract to permit some synthesis of pancreatic exocrine protein and with this stimulation of synthesis, transulfuration could proceed. This assumes that the biosynthesis of cystine is dependent upon the availability of sufficient cystine to permit active protein synthesis. In another situation where cystine requirement is high, namely, the rapidly growing rat, a limited amount of cystine was fed by providing a 12% casein diet. Either supplementary cystine or methionine was provided and it was found that both amino acids gave optimal growth in conventional rats, but when coprophagy was prevented, optimal growth was achieved only with the cystine-supplemented diet.