Double-blind randomised trial of a very-low-dose warfarin for prevention of thromboembolism in stage IV breast cancer

Patients receiving chemotherapy for metastatic breast cancer are at high risk of thromboembolic disease. Long-term oral anticoagulant therapy is needed but increases the risk of haemorrhagic complications. We have assessed the safety and efficacy of warfarin in very low doses as prophylaxis. Women receiving chemotherapy for metastatic breast cancer were randomly assigned either very-low-dose warfarin (152 patients) or placebo (159). The warfarin dose was 1 mg daily for 6 weeks and was then adjusted to maintain the prothrombin time at an international normalised ratio (INR) of 1.3 to 1.9. Study treatment continued until 1 week after the end of chemotherapy. The average daily dose from initiation of titration was 2.6 (SD 1.2) mg for the warfarin group and the mean INR was 1.52. The mean time at risk of thrombosis was 199 (126) days for warfarin-treated patients and 188 (137) days for placebo recipients (p = 0.45). There were 7 thromboembolic events (6 deep-vein thrombosis, 1 pulmonary embolism) in the placebo group and 1 (pulmonary embolism) in the warfarin group, a relative risk reduction of about 85% (p = 0.031). Major bleeding occurred in 2 placebo recipients and 1 warfarin-treated patient. There was no detectable difference in survival between the treatment groups. Very-low-dose warfarin is a safe and effective method for prevention of thromboembolism in patients with metastatic breast cancer who are receiving chemotherapy.

Related target enhancers for dorsal and NF-kappa B signaling pathways

Drosophila dorsoventral (DV) patterning and mammalian hematopoiesis are regulated by related signaling pathways (Toll, interleukin-1) and transcription factors (dorsal, nuclear factor-kappa B). These factors interact with related enhancers, such as the rhomboid NEE and kappa light chain enhancer, that contain similar arrangements of activator and repressor binding sites. It is shown that the kappa enhancer can generate lateral stripes of gene expression in transgenic Drosophila embryos in a pattern similar to that directed by the rhomboid NEE. Drosophila DV determinants direct these stripes through the corresponding mammalian cis regulatory elements in the kappa enhancer, including the kappa B site and kappa E boxes. These results suggest that enhancers can couple conserved signaling pathways to divergent gene functions.

Summary of the round table discussion on strategies for cancer prevention: diet, food, additives, supplements, and drugs

A Round Table Discussion was held at the Fourth International Conference on Anticarcinogenesis and Radiation Protection. Scientists from government and academia were brought together to discuss the evidence for the preventive effect of foods, specific nutrients and drugs against cancer, and the most appropriate methods of initiating nutritional cancer prevention activities to improve the health of the public. The panel reviewed the epidemiological evidence of the role of diet and specific micronutrients for the prevention of cancer, the doses of specific micronutrients required for preventive effects and their safety, the evidence for aspirin as a chemopreventive agent, the issue of foods versus specific micronutrients in the prevention of cancer, food safety, and approaches to prevention such as food fortification or dietary supplements. The remarks of the panel members are summarized.

A novel latency-active promoter is contained within the herpes simplex virus type 1 UL flanking repeats

Herpes simplex virus type 1 (HSV-1) expresses a unique series of RNA molecules, the latency-associated transcripts or LATs, during latent infection of neuronal tissues. Previous studies by others have described a TATA box-containing latency-active promoter, referred to here as LAP1, located approximately 700 bp upstream of the 5' end of the major 2.0-kb LAT. In this report, transient gene expression assays were employed to identify a second, novel latency-active promoter (LAP2) present within a region downstream of LAP1 and 5' proximal to the major 2.0-kb LAT. In contrast to LAP1, this promoter lacks a TATA box but possesses cis-acting regulatory elements and other features frequently observed within eukaryotic housekeeping gene promoters. Unlike most other HSV promoters, LAP2 was down-regulated by the viral transcriptional activators ICP4 and ICP0. The majority of LAP2-positive regulatory elements were located within sequences from -257 to -58 relative to the 5' end of the 2.0-kb LAT, and the basal promoter mapped within sequences from -14 to +28. RNase protection experiments demonstrated that chimeric LAT-chloramphenicol acetyltransferase transcripts produced in the transient assays initiated at or near the 5' end of the major 2-kb LAT. Tn5 insertional mutagenesis of the ICP4 regulatory gene determined that down-regulation of LAP2 required the ICP4 transactivating domain and targeted the minimal promoter region as the site of action by ICP4. Replicating recombinant viruses containing a LAP2-lacZ reporter gene cassette in an ectopic site (glycoprotein C locus) were shown to be active in mouse trigeminal ganglia. Taken together, these experiments suggest that the LAT region of the HSV-1 genome contains at least two latency-active promoters which may play different roles in expressing the various LATs. Alternatively, these promoters may comprise a larger promoter-regulatory complex which may influence transcription during latency.

Competitive quantitative PCR analysis of herpes simplex virus type 1 DNA and latency-associated transcript RNA in latently infected cells of the rat brain

Competitive quantitative PCRs were used to examine the consequences of stereotactically injecting a highly attenuated herpes simplex virus type 1 mutant into rat brains. This mutant virus, designated RR1CAT/RR2lacZ, was engineered so that coding sequences of the genes UL39 and UL40 specifying the subunits of the viral ribonucleotide reductase were replaced by the chloramphenicol acetyltransferase (CAT) and the lacZ gene coding sequences, respectively. Stereotactic injection of this virus into the hippocampal region of the rat brain resulted in a localized infection. Viral gene products were visualized by immunochemical, cytochemical, or in situ hybridization techniques in the injected hippocampal region at 2 days postinjection. Viral genomes, represented by glycoprotein B (gB), latency-associated transcript (LAT), and lacZ sequences could be amplified by PCR from templates obtained by scraping hippocampal tissue off single 10-microns frozen sections. Both gB message and LAT could be detected by reverse transcriptase (RT)-PCR. At day 7 postinjection, neither CAT message, gB message, nor beta-galactosidase activity could be visualized by the same techniques, although viral DNA was detected by PCR and LAT could be detected by RT-PCR. A similar pattern was seen at 8 weeks, suggesting that latency was established by the mutant virus in cells of the injected hippocampus. By competitive quantitative PCR, hippocampal sections were determined to contain 2.6 x 10(5) genome equivalents (represented by the gB gene) on day 2, 6.2 x 10(4) on day 7, and 8.3 x 10(4) at 8 weeks. By competitive quantitative RT-PCR, the numbers of LAT molecules at the same time points were 3.2 x 10(6), 1.3 x 10(6), and 1.2 x 10(6), respectively. The numbers of LAT molecules per genome equivalent were 12.5, 20.3, and 14.5, respectively, being approximately the same for each of the three time points. The data permit the conclusion that the RR mutant virus establishes latency in the rat brain with the persistence of the viral genome and the production of LAT molecules. Once latency is established, the numbers of viral genomes and LAT RNA molecules remain constant. Thus the competitive quantitative PCR and RT-PCR techniques provide very sensitive and reliable methods to quantitate viral DNA and RNA present in infected tissue.

Ascorbic acid and insulin secretion in pancreatic islets

The effect of ascorbic acid on glucose-induced insulin release from single pancreatic islets was measured using a new, ultra-sensitive enzyme-linked immunosorbent insulin assay. Within 20 s ascorbic acid inhibited insulin secretion; inhibition was dose dependent and completely reversible. There was a 50% inhibition of the secretory response with 200 microM ascorbic acid and 90% inhibition with 400 microM ascorbic acid. The decrease in insulin secretion was recorded as a reduction of the amplitudes of the fast insulin transients, which give rise to the oscillatory nature of insulin secretion. The inhibition of glucose-induced insulin release by ascorbic acid was associated with hyperpolarization of the pancreatic beta-cell. Suppression of glucose-induced membrane depolarization was evident after 20 s, was dose dependent, and was completely reversible. The data here may provide the first explanation of why plasma ascorbate concentrations are tightly controlled.

Role of Mg-ATP in norepinephrine biosynthesis in intact chromaffin granules

Dopamine beta-monooxygenase converts dopamine to norepinephrine in intact chromaffin granules using intragranular ascorbic acid as a cosubstrate. Mg-ATP with external ascorbic acid is required for maximal norepinephrine biosynthesis. Mechanisms to explain these requirements were investigated specifically using intact granules. The effect of Mg-ATP was independent of membrane potential (delta psi) because norepinephrine biosynthesis was unchanged whether delta psi was positive or collapsed. Furthermore, the effect of Mg-ATP was independent of absolute intragranular and extragranular pH as well as the pH difference across the chromaffin granule membrane (delta pH). Nevertheless, norepinephrine biosynthesis was inhibited by N-ethylmaleimide, 4-chloro-7-nitrobenzofurazane, and N,N-dicyclohexylcarbodiimide, specific inhibitors of the secretory vesicle ATPase that may directly affect proton pumping. Biosynthesis occurred normally with other ATPase inhibitors that do not inhibit the ATPase in secretory vesicles. The data indicate that the effect of Mg-ATP with ascorbic acid is mediated by the granule membrane ATPase but independent of maintaining delta psi and delta pH. An explanation of these findings is that Mg-ATP, via the granule ATPase, may change the rate at which protons or dopamine are made available to dopamine beta-monooxygenase.

Neurogenic expression of snail is controlled by separable CNS and PNS promoter elements

The Drosophila snail (sna) gene is first expressed in cells giving rise to mesoderm and is required for mesoderm formation. sna is subsequently expressed in the developing nervous system. sna expression during neurogenesis evolves from segmentally repeated neuroectodermal domains to a pan-neural pattern. We have identified a 2.8 kb regulatory region of the sna promoter that drives LacZ expression in a faithful neuronal pattern. Deletion analysis of this region indicates that the pan-neural element is composed of separable CNS and PNS components. This finding is unexpected since all known genes controlling early neurogenesis, including the proneural genes (i.e. da and AS-C), are expressed in both the CNS and PNS. We also show that expression of sna during neurogenesis is largely independent of the proneural genes da and AS-C. The separate control of CNS and PNS sna expression and independence of proneural gene regulation add to a growing body of evidence that current genetic models of neurogenesis are substantially incomplete.

Dif, a dorsal-related gene that mediates an immune response in Drosophila

There are striking parallels between the regulation of gene expression along the dorsoventral (DV) axis of Drosophila embryos and lymphoid-restricted expression in the mammalian immune system. Both depend on regulatory factors containing rel domains (dorsal and NF-kappa B) that are controlled at the level of nuclear transport. A novel Rel-containing gene in Drosophila, Dif (dorsal-related immunity factor), provides a potential link between these seemingly disparate processes. Although Dif maps close to dorsal, it does not appear to participate in DV patterning, but instead mediates an immune response in Drosophila larvae. Dif is normally localized in the cytoplasm of the larval fat body, but quickly accumulates in the nucleus upon bacterial infection or injury. Evidence is presented that once in the nucleus, Dif binds to kappa B-like sequence motifs present in promoter regions of immunity genes. These results suggest that mammalian and insect immunity share a common evolutionary origin.

Spacing ensures autonomous expression of different stripe enhancers in the even-skipped promoter

The even-skipped (eve) promoter contains a series of enhancers that control the expression of different segmentation stripes in the Drosophila embryo. The stripe 3 enhancer is located 1.7 kb upstream of the stripe 2 enhancer. Here we demonstrate that these enhancers must be physically separated by a minimum distance for proper stripe expression. When they are directly coupled in either orientation, the enhancers generate abnormal patterns of expression in the early embryo. For example, the levels of stripe 2 expression are augmented and there is a posterior expansion of the pattern when the stripe 3 enhancer is positioned immediately upstream of the stripe 2 enhancer. Despite this spacing requirement, the order of the enhancers within the eve promoter can be reversed without affecting the normal expression pattern. These results suggest that spacing maintains the autonomous activities of the stripe enhancers and that interactions between enhancers can generate novel patterns of gene expression.

Spacing ensures autonomous expression of different stripe enhancers in the even-skipped promoter

The even-skipped (eve) promoter contains a series of enhancers that control the expression of different segmentation stripes in the Drosophila embryo. The stripe 3 enhancer is located 1.7 kb upstream of the stripe 2 enhancer. Here we demonstrate that these enhancers must be physically separated by a minimum distance for proper stripe expression. When they are directly coupled in either orientation, the enhancers generate abnormal patterns of expression in the early embryo. For example, the levels of stripe 2 expression are augmented and there is a posterior expansion of the pattern when the stripe 3 enhancer is positioned immediately upstream of the stripe 2 enhancer. Despite this spacing requirement, the order of the enhancers within the eve promoter can be reversed without affecting the normal expression pattern. These results suggest that spacing maintains the autonomous activities of the stripe enhancers and that interactions between enhancers can generate novel patterns of gene expression.

Cellular functions of ascorbic acid: a means to determine vitamin C requirements

Optimal ascorbic acid (vitamin C) requirements in humans are unknown. In situ kinetics is a biochemical approach to determine requirements for vitamin C and other vitamins. In situ kinetics requires that cellular functions of ascorbic acid are characterized. Vitamin-C-dependent cellular reactions are directly related to vitamin C concentrations inside and outside cells. By coupling intracellular and extracellular functions of ascorbic acid to vitamin concentration, in situ kinetics provides a novel approach to determining vitamin C requirements.

Adjuvant radiotherapy for early breast cancer: patterns of practice in Ontario

OBJECTIVE

To determine the number of different radiation schedules used in Ontario to treat women with node-negative breast cancer after lumpectomy and axillary dissection.

DESIGN

Retrospective survey.

SETTING

Princess Margaret Hospital, Toronto, and regional centres of the Ontario Cancer Treatment and Research Foundation (in Hamilton, London, Ottawa, Windsor and Thunder Bay).

PATIENTS

A total of 551 of 1624 consecutive patients with node-negative breast cancer having undergone lumpectomy and axillary dissection who were eligible but did not participate in the Ontario Clinical Oncology Group randomized clinical trial and who received adjuvant breast irradiation between April 1984 and February 1989.

OUTCOME MEASURES

Schedules of radiotherapy received.

RESULTS

Forty-eight different radiotherapy schedules were identified. Total doses ranged from 4000 to 6600 cGy and the number of fractions from 15 to 30. Several different schedules were preferred: 322 patients (58.5%) received 4000 cGy in 15 or 16 fractions to the whole breast over 3 weeks plus a local boost of 1250 cGy to the primary site in 5 fractions over 1 week; 66 patients (12.0%) received 4000 cGy in 15 or 16 fractions over 3 weeks to the whole breast plus a local boost of 1000 cGy to the primary site in 4 or 5 fractions over 1 week; and 63 patients (11.5%) received 5000 cGy in 25 fractions to the whole breast in 5 weeks, without a boost.

CONCLUSIONS

The practice of adjuvant radiotherapy for early breast cancer in Ontario varies. The optimal radiation regimen for patients after lumpectomy should be determined through randomized clinical trials.

Meaningful interpretation of risk reduction from clinical drug trials

OBJECTIVE

To illustrate the concepts of relative and absolute risk reduction, and by example, present and discuss the results of prevention trials that have evaluated the impact of drug therapy on cardiovascular disease. Additional approaches to evaluating the results of prevention trials are also presented.

DATA SOURCES

Data were gathered from eight frequently quoted major cardiovascular intervention trials.

CONCLUSIONS

Reference to large reductions in relative risk in review papers, newspapers, and at professional meetings can lead to false expectations among clinicians and patients regarding the potential impact of the treatment in individual patients. When making decisions about preventive drug therapy, clinicians are encouraged to examine measures other than relative risk reduction and to include the patient in the decision process. Educators should emphasize these other measures of outcome and not rely solely on relative risk reduction in discussing particular areas of therapeutics.

The RR1 gene of herpes simplex virus type 1 is uniquely trans activated by ICP0 during infection

As has been demonstrated for herpes simplex virus type 2, we show in this report that the herpes simplex virus type 1 ribonucleotide reductase large subunit (RR1) gene is trans activated in transient transfection assays by VP16 and ICP0 but not by ICP4. Deletion analysis demonstrated that responsiveness to induction to VP16 resides in an octamer/TAATGARAT sequence of the RR1 promoter and that the TATA box alone is sufficient to provide induction by ICP0. The induction of the RR1 gene by ICP0 but not by ICP4 suggested that it might be possible to identify the cis-acting element(s) responsive to ICP4 in an ICP4-inducible promoter. To this end, a series of chimeric promoters containing various portions of the regulatory sequences of the RR1 promoter and thymidine kinase (TK) promoter were constructed. The TK promoter is trans activated by both ICP0 and ICP4 in transient transfection assays and by ICP4 in infection. The data show that replacing the RR1 TATA region with the TK TATA region permits ICP4 inducibility even if the rest of the RR1 promoter elements remain intact. To test whether the RR1 gene is induced by ICP0 during infection, four mutant viruses were constructed. (i) TAATGARAT+ has the wild-type RR1 promoter driving chloramphenicol acetyltransferase (CAT) and the RR2 promoter driving the lacZ gene. The RR2 gene codes for the small subunit of the ribonucleotide reductase and is expressed as a beta gene. (ii) TAATGARAT- has a triple-base change in the octamer/TAATGARAT element which renders it unresponsive to VP16 trans activation, eliminating that portion of the activation of the RR1 gene. (iii) TAATGARAT- delta alpha 0 has a deletion of the alpha 0 gene. (iv) TAATGARAT- delta alpha 4 has a deletion of the alpha 4 gene. Infections were carried out in Vero cells at a multiplicity of infection of 10 per cell; cells were assayed for CAT and beta-galactosidase (beta-Gal) activities and for virus yields. The first two infections gave strong CAT and beta-Gal activities and high yields of progeny virus. Infection with the third virus showed no CAT activity but did produce high levels of beta-Gal activity and virus progeny. The fourth infection resulted in strong CAT activity but no beta-Gal activity or progeny virus. The data demonstrated that the RR1 promoter was activated in the absence of ICP4 but not in the absence of ICP0 in these infections.(ABSTRACT TRUNCATED AT 400 WORDS)

Interactions between dorsal and helix-loop-helix proteins initiate the differentiation of the embryonic mesoderm and neuroectoderm in Drosophila

The dorsal (dl) morphogen has been implicated in the establishment of the embryonic mesoderm, neuroectoderm, and dorsal ectoderm in Drosophila. Here we show that the simultaneous reduction in the levels of dl and any one of several helix-loop-helix (HLH) proteins results in severe disruptions in the formation of mesoderm and neuroectoderm. Certain triple heterozygous combinations essentially lack mesoderm as a result of a block in ventral furrow formation during gastrulation. HLH proteins that have been implicated previously in sex determination and neurogenesis (daughterless, achaete, and scute) are shown to be required for the formation of these embryonic tissues. Evidence is also presented that dl-HLH interactions involve the direct physical association of these proteins in solution mediated by the rel and HLH domains. We discuss the striking parallels in mesoderm formation and sex determination.

A comparison of regularly dosed oral morphine and on-demand intramuscular morphine in the treatment of postsurgical pain

A randomized, placebo-controlled, double-blind clinical trial was conducted to compare the use of regularly dosed po morphine and on-demand in morphine in 47 patients undergoing total hip arthroplasty. Patients were randomized to receive either 20 mg (initial dose) of regularly dosed morphine (every four hours po) plus breakthrough pain medication on-demand consisting of both 10 mg morphine po and placebo im, or an equivalent regularly dosed oral placebo (every four hours) with breakthrough pain medication consisting of oral placebo and 5-10 mg morphine im. Subsequent to each request for breakthrough pain medication, the next regularly dosed oral solution was increased by 5 mg (or equivalent volume of placebo) to a maximum of 40 mg po Q4H. Time-averaged pain scores were lower on both postoperative day 1 and 2 in the group receiving regularly dosed morphine po (P < 0.05). Fewer patients requested breakthrough pain medication on both days in the oral morphine group. The incidence of nausea and vomiting, and of decreased respiratory rates were similar in both groups. Regularly dosed oral morphine is inexpensive and should be compared to other methods of opioid delivery.

Ascorbic acid accumulation and transport in human fibroblasts

As the initial step in the use of fibroblasts as a model system for 'in situ kinetics', ascorbic acid (vitamin C) accumulation in normal human fibroblasts was investigated for the first time. Ascorbic acid was transported into fibroblasts and accumulated against a concentration gradient up to 20-fold, as measured by h.p.l.c. with coulometric electrochemical detection. Ascorbic acid accumulation was mediated by two concentration-dependent transport activities. The first was a high-affinity activity with an apparent Km of 6 microM and an apparent Vmax. of 203 microM/h, and the second was a low-affinity activity with an apparent Km of 5 mM and an apparent Vmax. of 1.8 mM/h. Both activities were inhibited by metabolic inhibitors and inhibitors of ascorbic acid transport in human neutrophils. The low-affinity transporter could not be accounted for by diffusion. Although the high-affinity transport activity was comparable with that described for human neutrophils, the low-affinity transporter was different. These data provide the first evidence that two-component ascorbic acid transport may be a generalized mechanism for accumulation of this vitamin in humans.

Conversion of a dorsal-dependent silencer into an enhancer: evidence for dorsal corepressors

In Drosophila, the dorsal (dl) morphogen gradient initiates the differentiation of the embryonic mesoderm and neuroectoderm by activating the expression of regulatory genes (e.g. twist and snail) in a concentration-dependent manner. dl also functions as a repressor that establishes the dorsal epidermis and amnioserosa by restricting regulatory genes such as dpp and zen to dorsal regions of the embryo. The ability of dl to function as both an activator and repressor distinguishes it from the bicoid morphogen, which appears to function solely as an activator. In an effort to determine how dl functions as a repressor we have performed a detailed characterization of a zen silencer element, called the VRE, which mediates ventral repression in response to the dl gradient. A minimal 110 bp VRE sequence is identified, which is able to silence the ventral expression of a heterologous promoter. This sequence contains two dl binding sites as well as binding sites for additional nuclear factors present in early embryos. Mutations in the latter binding sites convert the minimal VRE into an enhancer, which mediates transcriptional activation in ventral regions in response to dl. These results suggest that dl is intrinsically an activator, but is converted into a potent silencer when it interacts with neighboring corepressors.

Haemophilus influenzae type b polysaccharide-tetanus protein conjugate vaccine does not depress serologic responses to diphtheria, tetanus or pertussis antigens when coadministered in the same syringe with diphtheria-tetanus-pertussis vaccine at two, four and six months of age

The safety and immunogenicity of a vaccine against Haemophilus influenzae type b consisting of purified polyribosylribitol phosphate conjugated to tetanus toxoid (PRP-T) were evaluated in 277 Chilean infants who were randomly assigned to one of three treatment groups: Group A, PRP-T mixed with diphtheria-tetanus-pertussis (DTP) vaccine in a single syringe and given as a single inoculation in one arm and placebo in the other arm; Group B, PRP-T given in one arm and DTP in the other arm; Group C, DTP given in one arm and placebo in the other. Infants were immunized at 2, 4 and 6 months of age and examined daily for 4 days after each immunization. Serum PRP antibodies; tetanus, diphtheria and pertussis antitoxin; pertussis agglutinins; and antibodies to Bordetella pertussis filamentous hemagglutinin were measured at baseline and 2 months after each dose. PRP-T was well-tolerated. After three doses of PRP-T vaccine 100% of infants attained PRP antibody concentrations > or = 0.15 micrograms/ml and 96 to 99% achieved high anti-PRP concentrations (> or = 1.0 micrograms/ml). The post-third dose anti-PRP geometric mean titer was high (6.94 micrograms/ml) in infants who were given PRP-T combined with DTP, although it was somewhat lower than the geometric mean titer of the group who received PRP-T in a separate arm (9.93 micrograms/ml) (P not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Polyvinylchloride containers do not influence the hemodynamic response to intravenous nitroglycerin

In-vitro evidence of sorption of nitroglycerin (NTG) to polyvinylchloride (PVC) containers suggests that these containers may deliver less nitroglycerin to the patient than glass containers. Sorption of NTG to the PVC container may result in hemodynamic changes in the patient when a fresh solution of NTG is prepared and administered from a PVC container. This study was designed as a prospective, randomized trial to measure the hemodynamic response in patients receiving NTG in glass or PVC containers, during the first hour after a container exchange. Patients admitted to the coronary care unit in a University hospital with chest pain considered to be due to unstable angina or acute myocardial infarction were eligible. Patients who received other vasoactive drugs within one hour of container exchanges were excluded. Systolic and diastolic blood pressures, and heart rate were measured at baseline and at intervals for one hour following a container exchange. Twenty patients completed the study. There were no significant changes with time in either group (ANOVA, p > 0.05) with respect to systolic, diastolic, or mean arterial blood pressure or heart rate. No chest pain occurred during the 60 minutes following the container exchange in either group. We conclude that NTG can be administered safely and effectively in PVC containers to patients with unstable angina or acute myocardial infarction. However, it remains possible that changes in hemodynamic status could occur in patients on NTG if a change in container type (i.e., from PVC to glass or vice versa) is made during the course of therapy.

Ascorbic acid recycling in human neutrophils

Ascorbic acid (vitamin C) accumulation in activated human neutrophils is increased as much as 10-fold above the mM concentrations present in normal neutrophils. Internal concentrations as high as 14 mM are achieved when external vitamin is at physiologic concentration. The mechanism is by oxidation of external vitamin to dehydroascorbic acid, preferential transmembrane translocation of dehydroascorbic acid, and intracellular reduction to ascorbic acid within minutes. These data indicate that vitamin C accumulation is enhanced in activated human neutrophils and that human neutrophils utilize and recycle oxidized external vitamin C under physiologic conditions.