Agents intervening against delirium in the intensive care unit trial-Protocol for a secondary Bayesian analysis

Background

Delirium is highly prevalent in the intensive care unit (ICU) and is associated with high morbidity and mortality. The antipsychotic haloperidol is the most frequently used agent to treat delirium although this is not supported by solid evidence. The agents intervening against delirium in the intensive care unit (AID‐ICU) trial investigates the effects of haloperidol versus placebo for the treatment of delirium in adult ICU patients.

Methods

This protocol describes the secondary, pre‐planned Bayesian analyses of the primary and secondary outcomes up to day 90 of the AID‐ICU trial. We will use Bayesian linear regression models for all count outcomes and Bayesian logistic regression models for all dichotomous outcomes. We will adjust for stratification variables (site and delirium subtype) and use weakly informative priors supplemented with sensitivity analyses using sceptical priors. We will present results as absolute differences (mean differences and risk differences) and relative differences (ratios of means and relative risks). Posteriors will be summarised using median values as point estimates and percentile‐based 95% credibility intervals. Probabilities of any benefit/harm, clinically important benefit/harm and clinically unimportant differences will be presented for all outcomes.

Discussion

The results of this secondary, pre‐planned Bayesian analysis will complement the primary frequentist analysis of the AID‐ICU trial and facilitate a nuanced and probabilistic interpretation of the trial results.

The Agents Intervening against Delirium in the Intensive Care Unit Trial (AID-ICU trial): A detailed statistical analysis plan

BACKGROUND

The AID-ICU trial aims to assess the benefits and harms of haloperidol for the treatment of delirium in acutely admitted, adult intensive care unit (ICU) patients. This paper describes the detailed statistical analysis plan for the primary publication of results from the AID-ICU trial.

METHODS

The AID-ICU trial is an investigator-initiated, pragmatic, international, multicentre, randomized, blinded, parallel-group trial allocating 1000 adult ICU patients with manifest delirium 1:1 to haloperidol or placebo. The primary outcome measure is days alive and out of hospital within 90 days post-randomization. Secondary outcome measures are days alive without delirium or coma, serious adverse reactions (SARs) to haloperidol, use of escape medicine, days alive without mechanical ventilation, and mortality, health-related quality-of-life measures and cognitive function 1-year post-randomization. Statistical analysis will be conducted in accordance with the current pre-specified statistical analysis plan. One formal interim analysis will be performed. The primary outcome will be adjusted for stratification variables (site and delirium motor subtype) and compared between treatment groups using a likelihood ratio test described by Jensen et al A secondary analysis will be conducted with additional adjustment of the primary outcome for prognostic variables at baseline. The primary conclusion of the trial will be based on the intention-to-treat analysis of the primary outcome adjusted for stratification variables.

CONCLUSION

The AID-ICU trial will provide important, high-quality data on the benefits and harms of treatment with haloperidol in acutely admitted, adult patients with manifest delirium in the ICU.

Agents intervening against delirium in the intensive care unit (AID-ICU) - Protocol for a randomised placebo-controlled trial of haloperidol in patients with delirium in the ICU

BACKGROUND

Delirium among patients in the intensive care unit (ICU) is a common condition associated with increased morbidity and mortality. Haloperidol is the most frequently used pharmacologic intervention, but its use is not supported by firm evidence. Therefore, we are conducting Agents Intervening against Delirium in the Intensive Care Unit (AID-ICU) trial to assess the benefits and harms of haloperidol for the treatment of ICU-acquired delirium.

METHODS

AID-ICU is an investigator-initiated, pragmatic, international, randomised, blinded, parallel-group, trial allocating adult ICU patients with manifest delirium 1:1 to haloperidol or placebo. Trial participants will receive intravenous 2.5 mg haloperidol three times daily or matching placebo (isotonic saline 0.9%) if they are delirious. If needed, a maximum of 20 mg/daily haloperidol/placebo is given. An escape protocol, not including haloperidol, is part of the trial protocol. The primary outcome is days alive out of the hospital within 90 days post-randomisation. Secondary outcomes are number of days without delirium or coma, serious adverse reactions to haloperidol, usage of escape medication, number of days alive without mechanical ventilation; mortality, health-related quality-of-life and cognitive function at 1-year follow-up. A sample size of 1000 patients is required to detect a 7-day improvement or worsening of the mean days alive out of the hospital, type 1 error risk of 5% and power 90%.

PERSPECTIVE

The AID-ICU trial is based on gold standard methodology applied to a large sample of clinically representative patients and will provide pivotal high-quality data on the benefits and harms of haloperidol for the treatment ICU-acquired delirium.

Remote real-time supervision via tele-ultrasound in focused cardiac ultrasound: A single-blinded cluster randomized controlled trial

BACKGROUND

Supervision via tele-ultrasound presents a remedy for lacking on-site supervision in focused cardiac ultrasound, but knowledge of its impact is largely absent. We aimed to investigate tele-supervised physicians' cine-loop quality compared to that of non-supervised physicians and compared to that of experts.

METHODS

We conducted a single-blinded cluster randomized controlled trial in an emergency department in western Denmark. Physicians with basic ultrasound competence scanned admitted patients twice. The first scan was non-supervised, and the second was non-supervised (control) or tele-supervised (intervention). Finally, experts in focused cardiac ultrasound scanned the same patient. Two blinded observers graded cine-loops recorded from all scans on a 1-5 scale. The outcome was the mean summarized scan gradings compared with a linear mixed-effects model.

RESULTS

In each group, 10 physicians scanned 44 patients. From the mean summarized gradings, on a scale from 4 to 20, the second non-supervised scan grading was 10.9 (95% CI 10.2-11.7), whereas the tele-supervised grading was 12.6 (95% CI: 11.8-13.3). From the first to the second scan, tele-supervised physicians moved 9% (1.09; 95% CI: 1.00-1.19; P = 0.041) closer to the experts' quality than the non-supervised physicians.

CONCLUSION

Tele-supervised physicians performed scans of better quality than non-supervised physicians. The present study supports the use of tele-supervision for physicians with basic focused ultrasound competence in a setting where on-site supervision is unavailable.

Impact of metabolic disorders on the relation between overweight/obesity and incident myocardial infarction and ischaemic stroke in fertile women: a nationwide cohort study

AIMS

Whether overweight is a risk factor for cardiovascular disease in the absence of metabolic disorders remains under debate and is largely unexamined in young women. We evaluated the risk of myocardial infarction and ischaemic stroke in fertile women conditional on time-dependent presence of metabolic disorders.

MATERIALS AND METHODS

From nationwide registers we identified all normal weight (body mass index [BMI] ≥ 18.5 to <25 kg m(-2) and overweight (BMI ≥ 25 kg m(-2)) Danish women giving birth from 2004 to 2009. Using multivariable Poisson regression models adjusted for age, calendar year and smoking, the risk of the composite outcome of myocardial infarction and ischaemic stroke was assessed with metabolic disorders (i.e. hypertensive conditions, abnormal glucose metabolism and/or dyslipidaemia) included as time-dependent variables.

RESULTS

The population comprised 261,489 women with median age of 30.5 years (interquartile range = [27.3, 33.8]). Median follow-up was 5.6 years (interquartile range = [4.0, 6.8]). Compared with normal weight women without metabolic disorders (with an incidence rate [IR] of 17.0 [95% confidence interval {CI} = 14.5-20.0] events per 100,000 person-years), overweight women without metabolic disorders had no significantly increased risk, IR 22.6 (CI = 18.3-27.8), adjusted incidence rate ratio (IRR), 1.26 (CI = 0.97-1.65). For women with metabolic disorders, IR was 30.2 (CI = 18.8-48.6) and adjusted IRR 1.77 (CI = 1.07-2.93) in normal weight, while IR was 87.1 (CI = 67.6-112.2) and IRR 4.24 (CI = 5 3.11-5.79) in overweight.

CONCLUSIONS

The risk of myocardial infarction and ischaemic stroke was more strongly associated with the presence of metabolic disorders than with overweight per se in fertile women. Targeting prevention of metabolic disorders might be beneficial to reduce cardiovascular disease in overweight/obese young women.

High-affinity DNA targeting using readily accessible mimics of N2'-functionalized 2'-amino-α-L-LNA

N2'-Pyrene-functionalized 2'-amino-α-L-LNAs (locked nucleic acids) display extraordinary affinity toward complementary DNA targets due to favorable preorganization of the pyrene moieties for hybridization-induced intercalation. Unfortunately, the synthesis of these monomers is challenging (~20 steps, <3% overall yield), which has precluded full characterization of DNA-targeting applications based on these materials. Access to more readily accessible functional mimics would be highly desirable. Here we describe short synthetic routes to a series of O2'-intercalator-functionalized uridine and N2'-intercalator-functionalized 2'-N-methyl-2'-aminouridine monomers and demonstrate, via thermal denaturation, UV-vis absorption and fluorescence spectroscopy experiments, that several of them mimic the DNA-hybridization properties of N2'-pyrene-functionalized 2'-amino-α-L-LNAs. For example, oligodeoxyribonucleotides (ONs) modified with 2'-O-(coronen-1-yl)methyluridine monomer Z, 2'-O-(pyren-1-yl)methyluridine monomer Y, or 2'-N-(pyren-1-ylmethyl)-2'-N-methylaminouridine monomer Q display prominent increases in thermal affinity toward complementary DNA relative to reference strands (average ΔT(m)/mod up to +12 °C), pronounced DNA-selectivity, and higher target specificity than 2'-amino-α-L-LNA benchmark probes. In contrast, ONs modified with 2'-O-(2-napthyl)uridine monomer W, 2'-O-(pyren-1-yl)uridine monomer X or 2'-N-(pyren-1-ylcarbonyl)-2'-N-methylaminouridine monomer S display very low affinity toward DNA targets. This demonstrates that even conservative alterations in linker chemistry, linker length, and surface area of the appended intercalators have marked impact on DNA-hybridization characteristics. Straightforward access to high-affinity building blocks such as Q, Y, and Z is likely to accelerate their use in DNA-targeting applications within nucleic acid based diagnostics, therapeutics, and material science.

Thermodynamic and biological evaluation of a thrombin binding aptamer modified with several unlocked nucleic acid (UNA) monomers and a 2'-C-piperazino-UNA monomer

Thrombin binding aptamer is a DNA 15-mer which forms a G-quadruplex structure and possess promising anticoagulant properties due to specific interactions with thrombin. Herein we present the influence of a single 2'-C-piperazino-UNA residue and UNA residues incorporated in several positions on thermodynamics, kinetics and biological properties of the aptamer. 2'-C-Piperazino-UNA is characterized by more efficient stabilization of quadruplex structure in comparison to regular UNA and increases thermodynamic stability of TBA by 0.28-0.44 kcal/mol in a position depending manner with retained quadruplex topology and molecularity. The presence of UNA-U in positions U3, U7, and U12 results in the highest stabilization of G-quadruplex structure (ΔΔG(37)(°)=-1.03kcal/mol). On the contrary, the largest destabilization mounting to 1.79 kcal/mol was observed when UNA residues were placed in positions U7, G8, and U9. Kinetic studies indicate no strict correlation between thermodynamic stability of modified variants and their binding affinity to thrombin. Most of the studied variants bind thrombin, albeit with decreased affinity in reference to unmodified TBA. Thrombin time assay studies indicate three variants as being as potent as TBA in fibrin clotting inhibition.

Synthesis of an unlocked nucleic acid terpyridine monomer and binding of divalent metal ion in nucleic acid duplexes

Herein we present the synthesis and thermal stability studies of modified oligonucleotides containing an unlocked nucleic acid (UNA) terpyridine monomer. Incorporation of this monomer into both strands of a DNA duplex allowed reversible thermal stability modulation upon addition or withdrawal of divalent metal ions. A likely explanation of this phenomenon is interstrand complexation between two terpyridine units and a metal ion. This system could be useful in the development of nanoscale devices based on DNA hybridization.

Osteogenic protein-1 increases the fixation of implants grafted with morcellised bone allograft and ProOsteon bone substitute: an experimental study in dogs

Impacted bone allograft is often used in revision joint replacement. Hydroxyapatite granules have been suggested as a substitute or to enhance morcellised bone allograft. We hypothesised that adding osteogenic protein-1 to a composite of bone allograft and non-resorbable hydroxyapatite granules (ProOsteon) would improve the incorporation of bone and implant fixation. We also compared the response to using ProOsteon alone against bone allograft used in isolation. We implanted two non-weight-bearing hydroxyapatite-coated implants into each proximal humerus of six dogs, with each implant surrounded by a concentric 3 mm gap. These gaps were randomly allocated to four different procedures in each dog: 1) bone allograft used on its own; 2) ProOsteon used on its own; 3) allograft and ProOsteon used together; or 4) allograft and ProOsteon with the addition of osteogenic protein-1. After three weeks osteogenic protein-1 increased bone formation and the energy absorption of implants grafted with allograft and ProOsteon. A composite of allograft, ProOsteon and osteogenic protein-1 was comparable, but not superior to, allograft used on its own. ProOsteon alone cannot be recommended as a substitute for allograft around non-cemented implants, but should be used to extend the volume of the graft, preferably with the addition of a growth factor.

No effect of platelet-rich plasma with frozen or processed bone allograft around noncemented implants

We compared processed morselized bone allograft with fresh-frozen bone graft around noncemented titanium implants. Also, the influence of platelet-rich plasma (PRP) in combination with bone allograft was evaluated. Analysis was based on implant fixation and histomorphometry. PRP was prepared by isolating the buffy coat from autologous blood samples. Bone allograft was used fresh-frozen or processed by defatting, freeze drying, and irradiation. Cylindrical hydroxyapatite-coated titanium implants were inserted bilaterally in the femoral condyles of eight dogs. Each implant was surrounded by a 2.5-mm concentric gap, which was filled randomly according to the four treatment groups--group 1: fresh-frozen bone allograft; group 2: processed bone allograft; group 3: fresh-frozen bone allograft + PRP; group 4: processed bone allograft + PRP. Histological and mechanical evaluation demonstrated no influence of bone allograft processing. Even though the level of platelet in PRP was 7.7 times that found in whole blood, we found no improvement of bone formation or implant fixation by adding PRP.

Platelet rich plasma and fresh frozen bone allograft as enhancement of implant fixation. An experimental study in dogs

Platelet rich plasma (PRP) is an autologous source of growth factors. By application of PRP around cementless implants alone or in combination with bone allograft chips, early implant fixation and gap healing could be improved. We inserted two porous HA coated titanium implants extraarticularly in each proximal humerus of eight dogs. Each implant was surrounded by a 2.5 mm gap. Four treatments were block randomized to the four gaps in each dog: Treatment 1: empty gap, treatment 2: PRP, treatment 3: fresh frozen bone allograft, treatment 4: fresh frozen bone allograft+PRP. PRP was prepared from each dog prior to operation by isolating the buffycoat from centrifuged blood samples. Platelet count in PRP was increased 670% compared to baseline level. Calcium/thrombin was added to degranulate platelets and form a gel. Three weeks after surgery, push-out test and histomorphometri was performed. After three weeks, the non-allografted implants had poor mechanical properties. Bone grafting significantly increased implant fixation, bone formation in the gap and bone growth on the implant surface. We found no significant effect of PRP alone or mixed with bone allograft on implant fixation or bone formation. In conclusion, we showed the importance of bone allografting on early implant fixation and bone incorporation but we found no effect of PRP. More studies are needed to investigate the effect and possible clinical applications of platelet concentrates which are now being commercialised.

Autologous growth factor (agf) mixed with allograft increases fixation of cementless implants: an experimental dog study

None.

Effect of osteogenic protein 1/collagen composite combined with impacted allograft around hydroxyapatite-coated titanium alloy implants is moderate

This study evaluated the effects of osteogenic protein 1/collagen composite (OP-1/col) mixed with impacted allograft around hydroxyapatite (HA)-coated titanium alloy implants in a canine model. The aim of the study was to test different doses of OP-1 growth factor in a collagen composite for stimulatory effect on allograft incorporation around an implant. Unloaded implants were inserted in each proximal humerus of 16 skeletally mature dogs. The cylindrical implants (4 x 9 mm) coated with HA were initially surrounded by a 3-mm gap into which allograft mixed with OP-1/col was impacted. Two different doses of OP-1 were investigated. In eight animals 325 mg OP-1 protein and 130 mg bovine collagen type I as carrier were mixed with the allograft chips. This composite is identical to the clinically used OP-1 device called Novus. In another eight animals a lower dose of 65 mg OP-1 protein and 130 mg bovine collagen type I was used. Control implants placed in the contralateral humerus were surrounded by allograft mixed with collagen carrier only. The dogs were euthanized at 6 weeks. Implant fixation was determined by push-out testing. Bone ingrowth and bone formation were evaluated by quantitative histomorphometry on serial sections of the bone-implant interface. Impacted allograft together with low-dose OP-1 enhanced bone volume in a zone adjacent to HA-coated titanium alloy implants. The high dose had no effect on bone formation. Mechanical fixation, bone ingrowth, and bone volume in the gap near the original trabecular bone were unaffected by both low and high OP-1/col composite. In this model and observation period, the low dose of OP-1/col composite mixed with impacted allograft has a moderate effect on bone healing around HA-coated implants and no effect on implant fixation.

Sealing effect of hydroxyapatite coating: a 12-month study in canines

This study addresses the clinical problems regarding access of wear debris to the bone-implant interface and the possible dissemination of polyethylene (PE) particles to distant organs. We inserted two implants into each knee of 7 dogs allowing access of joint fluid to the bone-implant interface with a 0.75 mm initial gap around the implant. Hydroxyapatite (HA)-coated and non-coated (Ti) titanium alloy implants were randomly allocated to each distal femoral condyle. PE particles were repeatedly injected into the right knee joint 3 weeks after surgery for a period of 49 weeks, while only vehicle was injected into the left knee joint. We found huge amounts of PE particles mainly in the bone-implant interface around Ti implants. Infiltration of mononuclear inflammatory cells was present around 3 of 7 Ti implants in relation to PE particles. HA implants had approximately 70% bone ongrowth. In contrast, no bone ongrowth was seen on any Ti implants, all being surrounded by a fibrous membrane. The number of PE particles was evaluated semi-quantitatively. More PE particles were found around Ti implants than with HA implants (p < 0.002). Specimens from iliac lymph nodes, liver, spleen and lung were examined and showed dissemination of PE particles only in regional lymph nodes.

PACAP-(1-38) as neurotransmitter in the porcine adrenal glands

The concentration of pituitary adenylyl cyclase-activating polypeptide [PACAP-(1-38)] in porcine adrenal glands amounted to 14 +/- 3 pmol/g tissue. PACAP immunoreactive (PACAP-IR) fibers innervated adrenal chromaffin cells (often co-localized with choline acetyltransferase). Subcapsular fibers traversed the cortex-innervating endocrine cells and blood vessels [some co-storing mainly calcitonin gene-related peptide but also vasoactive intestinal polypeptide (VIP)]. PACAP-IR fibers were demonstrated in the splanchnic nerves, whereas IR adrenal nerve cell bodies were absent. In isolated, vascularly perfused adrenal gland, splanchnic nerve stimulation (16 Hz) and capsaicin (10(-5) M) increased PACAP-(1-38) release (1.6-fold and 6-fold respectively, P = 0.02). PACAP-(1-38) dose-dependently stimulated cortisol (2 x 10(-10) M; 24-fold increase, P = 0.02) and chromogranin A fragment (2 x 10(-9) M; 15-fold increase, P = 0.05) secretion. Both were strongly inhibited by the PAC(1)/VPAC(2) receptor antagonist PACAP-(6-38) (10(-7) M). PACAP-(6-38) also inhibited splanchnic nerve (10 Hz)-induced cortisol secretion but lacked any effect on splanchnic nerve-induced pancreastatin secretion. PACAP-(1-38) (2 x 10(-10) M) decreased vascular resistance from 5.5 +/- 0.6 to 4.6 +/- 0.4 mmHg. min. ml(-1). PACAP-(6-38) had no effect on this response. We conclude that PACAP-(1-38) may play a role in splanchnic nerve-induced adrenal secretion and in afferent reflex pathways.

Pancreastatin plasma levels in patients with primary hyperparathyroidism

Pancreastatin, a C-terminally amidated peptide derived from chromogranin A, is known to inhibit insulin secretion, pancreatic enzyme release, and gastric acid secretion. It also inhibits parathyroid hormone (PTH) secretion in animals. The physiologic and clinical relevance of pancreastatin in humans, however, is not known. Because pancreastatin has been found in parathyroid adenomas, we investigated the plasma levels in patients with primary hyperparathyroidism (pHPT). Thirteen patients operated on for solitary parathyroid adenoma were investigated. Plasma levels of pancreastatin and serum levels of ionized calcium and intact PTH were measured before and 6 weeks after operation. In 10 patients the levels were also monitored before and 60 minutes after adenoma excision. The adenomas were investigated for pancreastatin immunoreactivity by immunocytochemistry. The median weight of the excised parathyroid adenoma was 0.64 g (range 0.07-2.00 g). Cells displaying pancreastatin immunoreactivity were present in all adenomas examined and varied in number and immunostaining intensity among and within the adenomas. Intraoperatively, after adenoma excision the levels of PTH and pancreastatin declined (p < 0.01), whereas the levels of ionized calcium did not change (p = 0.96). At the 6-week follow-up the levels of ionized calcium and PTH had decreased compared to the preoperative levels (p < 0.01), and all patients were normocalcemic. In contrast, the pancreastatin levels were not changed (14.5 +/- 6.1 pmol/L preoperatively vs. 12.8 +/- 11.2 pmol/L 6 weeks postoperatively; p = 0.12). In patients with pHPT, pancreastatin is likely to be produced by the parathyroid adenoma. The changes in pancreastatin levels immediately after surgery warrant further investigation.

[Stimulation of bone healing with growth factors in orthopedic surgery]

Growth factors with specific effects on bone cells have been known of for more than a decade. Clinical usage of growth factors has recently become possible due to recombinant gene technology. In vivo studies over the last five years have demonstrated that growth factors can stimulate bone formation and bone healing and these results have made growth factors candidates for future clinical use in orthopaedic surgery. Growth factors for clinical use will become commercially available in the near future. The aim of this review paper is to describe the most important growth factors with effect on bone tissue and to give an updated review on experimental and clinical data on growth factor mediated bone healing in situations related to orthopaedic surgery. Possible areas for future clinical usage of growth factors are also discussed.

Novel simulated moving-bed method for reduced solvent consumption

Simulated moving-bed (SMB) chromatography is attractive for reducing sorbent and solvent consumption relative to fixed-bed systems. In this contribution, we describe a novel and versatile method for further reducing solvent consumption in the case of reversed-phase chromatography. The method is based on the variation of the distribution coefficients of solutes to be separated upon varying the composition of a multi-component mobile phase. If the solvent strength of the desorbent is set higher than the solvent strength of the feed, the components will have smaller distribution coefficients in the extraction section of the SMB and hence will be more easily eluted. This will result in a lower desorbent flow and possibly also in a shorter desorbent zone, and, ultimately, in more concentrated products. The so-called "Triangle-method" by Storti et al. [AIChE J., 39 (1993) 471] to obtain the region of complete separation, is extended for this novel SMB method. Theoretical evaluation of the proposed methodology supports the anticipated solvent reduction relative to fixed-bed RP-HPLC for the cases of the purification of the polyketide antibiotic nystatin and the separation of bovine insulin from porcine insulin.

Library of sequence-specific radioimmunoassays for human chromogranin A

BACKGROUND

Human chromogranin A (CgA) is an acidic protein widely expressed in neuroendocrine tissue and tumors. The extensive tissue- and tumor-specific cleavages of CgA at basic cleavage sites produce multiple peptides.

METHODS

We have developed a library of RIAs specific for different epitopes, including the NH2 and COOH termini and three sequences adjacent to dibasic sites in the remaining part of CgA.

RESULTS

The antisera raised against CgA(210-222) and CgA(340-348) required a free NH2 terminus for binding. All antisera displayed high titers, high indexes of heterogeneity ( approximately 1.0), and high binding affinities (Keff0 approximately 0.1 x 10(12) to 1.0 x 10(12) L/mol), implying that the RIAs were monospecific and sensitive. The concentration of CgA in different tissues varied with the assay used. Hence, in a carcinoid tumor the concentration varied from 0.5 to 34.0 nmol/g tissue depending on the specificity of the CgA assay. The lowest concentration in all tumors was measured with the assay specific for the NH2 terminus of CgA. This is consistent with the relatively low concentrations measured in plasma from carcinoid tumor patients by the N-terminal assay, whereas the assays using antisera raised against CgA(210-222) and CgA(340-348) measured increased concentrations.

CONCLUSION

Only some CgA assays appear useful for diagnosis of neuroendocrine tumors, but the entire library is valuable for studies of the expression and processing of human CgA.

Role of physiological HCO3-buffer on intracellular pH and histamine release in rat peritoneal mast cells

The purpose of this study was to examine how intracellular pH (pHi) regulation and histamine release are affected by HCO3- in rat peritoneal mast cells. The pHi was measured using the pH-sensitive dye 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). We observed a pHi of 6.88+/-0.012 (n=24) in resting mast cells exposed to a HEPES buffer (pH 7.4), but a sustained drop of 0.21 pH units to 6.67+/-0.015 (n=23) when we exposed the mast cells to a HEPES/HCO3- buffer equilibrated at all time with 5% CO2 (pH 7.4). This fall in pHi is inhibited by the carbonic anhydrase inhibitor dichlorphenamide and is Na+-independent, indicating the involvement of Na+-independent Cl-/HCO3- exchange activity. Furthermore removal of external Cl- in the presence but not in the absence of HCO3- reversed the Cl-/HCO3- exchange and induced an alkaline load. The recovery from this alkaline load was dependent on external Cl- but independent of Na+. Both the alkalinization and the recovery were inhibited by the anion transport inhibitor 4, 4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS). In addition, 36Cl- uptake measurements confirm the presence of a Cl-/HCO3- exchanger. Histamine release stimulated by antigen and compound 48/80 was substantially reduced in the presence of HEPES/ HCO3- buffer (pHo 7.4, pHi 6.66). Histamine release was increased, however, when pHi was clamped to 6.66 in HCO3--free media (pHo 6.9). We conclude that: (1) Na+-independent Cl-/HCO3- exchange determines steady-state pHi in rat peritoneal mast cells; and (2) the reduction in histamine release observed in the presence of HCO3- is not due to its effect on pHi per se, but rather on other changes in ion transport.

Development of an assay for histamine using automated high-performance liquid chromatography with electrochemical detection

Previous studies have measured histamine by derivatization with o-phthaldialdehyde (OPA) and mercaptoethanol (ME), followed by reversed-phase HPLC separation and electrochemical detection. The derivatization product, however, was very unstable. In the present study, inclusion of less polar solvents (e.g., acetonitrile or tetrahydrofuran) in the OPA/ME derivatization reaction produced an OPA/ME-histamine product that was stable for many hours. Changes of the HPLC mobile phase (increasing its ionic strength and pH and including triethylamine) dramatically improved the chromatography and reduced the histamine detection limit to < 0.1 pmol. The modified assay was suitable for batchwise manual derivatization of histamine samples followed by their automated analysis by HPLC with an automatic injector.

Immunocytochemical localisation of pancreastatin and chromogranin A in porcine neuroendocrine tissues

Pancreastatin is a 49 amino acid peptide with a C-terminal glycine amide originally isolated from porcine pancreas. In the present study the cellular localisation of pancreastatin in porcine neuroendocrine tissue was examined immunocytochemically using an antiserum raised against porcine pancreastatin (33-49) that does not cross-react with porcine chromogranin A. In order to study the possible precursor-product relationship between chromogranin A and pancreastatin the cellular localisation of both peptides was examined in peripheral tissues using simultaneous double immunostaining. The pancreastatin antiserum immunostained cells and nerve fibers throughout the neuroendocrine system. In most of the examined tissues we found colocalisation of pancreastatin and chromogranin A immunostaining. These results support the precursor-product concept for chromogranin A and pancreastatin. However, in the gastrointestinal tract and the adenohypophysis a minor population of the endocrine cells exhibited immunostaining with only one of the two antibodies. This discrepancy between immunostaining with pancreastatin antiserum and monoclonal chromogranin A antibody could be due to absence of, or extensive, processing of chromogranin A in certain cell populations.

Students' perception of stress in a baccalaureate-MD degree program

The quality of student life in combined baccalaureate-M.D. degree programs has rarely been investigated although these programs address widely recognized problems in medical education. Through the use of an environmental stress inventory, 183 students' perceptions of the learning environment of a combined-degree program were examined. Students in that program rated few situations in their environment as stressful. Yet, they were significantly concerned about information overload and attendant time problems, just as their peers in 4-yr. schools were. Unlike their 4-yr. counterparts, however, they did not see relations with other students and faculty as problematic. Their scores on the inventory were best predicted at each year level by a combination of personal characteristics, notably living arrangements, sex, and to a lesser extent, introversion.

Distribution of membrane thickness determined by lineal analysis

The expected statistical distributions of intercept length are derived in terms of geometrical probability density functions pertaining to plates with known thickness penetrated by lines with random orientation. These expressions provide arithmetic and graphical solutions for obtaining distributions of membrane thickness and reciprocal membrane thickness from empirical distributions of intercept lengths. Furthermore, general relationships between probability density functions of distributions of intercept length and membrane thickness are derived as well as those between their moments. Examples of the application of the method to biological samples are given, and estimated distributions of glomerular basement membrane thickness are compared to those obtained by an independent, direct method. Various sources of bias, which in practice may occur due to departures from the sample model, are discussed and the influence of some of them is estimated. The knowledge of the probability density function of reciprocal intercepts makes it possible to perform a correction of the distribution of measured intercept length, which to some extent eliminates bias.