Auditory verbal hallucinations and childhood trauma subtypes across the psychosis continuum: a cluster analysis

Introduction: A strong link between voice-hearing experience and childhood trauma has been established. The aim of this study was to identify whether there were unique clusters of childhood trauma subtypes in a sample across the clinical spectrum of auditory verbal hallucinations (AVH) and to examine clinical and phenomenological features across these clusters.Methods: Combining two independent international datasets (the Netherlands and Australia), childhood trauma subtypes were examined using hierarchical cluster analysis. Clinical and phenomenological characteristics were compared across emerging clusters using MANOVA and chi-squared analyses.Results: The total sample (n = 413) included 166 clinical individuals with a psychotic disorder and AVH, 122 non-clinical individuals with AVH and 125 non-clinical individuals without AVH. Three clusters emerged: (1) low trauma (n = 299); (2) emotion-focused trauma (n = 71); (3) multi-trauma (n = 43). The three clusters differed significantly on their AVH ratings of amount of negative content, with trend-level effects for loudness, degree of negative content and degree of experienced distress. Furthermore, perceptions of voices being malevolent, benevolent and resistance towards voices differed significantly.Conclusion: The data revealed different types of childhood trauma had different relationships between clinical and phenomenological features of voice-hearing experiences. Thus, implicating different mechanistic pathways and a need for tailored treatment approaches.

Comparative Pharmacokinetics and Local Tolerance of Tenofovir Alafenamide (TAF) From Subcutaneous Implant in Rabbits, Dogs, and Macaques

The administration of antiretrovirals (ARVs) for HIV pre-exposure prophylaxis (PrEP) is highly efficacious and may benefit from new long-acting (LA) drug delivery approaches. This paper describes a subcutaneous, reservoir-style implant for the LA delivery of tenofovir alafenamide (TAF) and documents the preclinical assessment of implant safety and pharmacokinetics (PK) in New Zealand White (NZW) rabbits (3 groups of n = 5), beagle dogs (2 groups of n = 6), and rhesus macaques (2 groups of n = 3). Placebo implants were placed in rabbits (n = 10) and dogs (n = 12). Implant parameters, including selection of the TAF form, choice of excipient, and PCL formulation were tuned to achieve targeted concentrations of the active anabolite of TAF, tenofovir diphosphate (TFV-DP), within peripheral blood mononuclear cells (PBMCs) and mucosal tissues relevant to HIV transmission. Sustained concentrations of TFV-DP in PBMCs over 100 fmol/10⁶ cells were achieved in all animal species indicating that the implants effectively delivered TAF for 3-6 months. Unlike placebo implants without TAF, all active implants resulted in local adverse events (AEs) proximal to the implant ranging in severity from mild to moderate and included dermal inflammation and necrosis across all species. Despite these AEs, the implant performed as designed and achieved a constant drug release profile, supporting the continued development of this drug delivery platform.

Moisturizing Lotions can Increase Transdermal Absorption of the Herbicide 2,4-Dichlorophenoxacetic Acid Across Hairless Mouse Skin

Moisturizing lotions can be an effective treatment for occupationally induced dry skin. These compounds are designed to be hygroscopic and retain water to keep the stratum corneum hydrated, while at the same time enhancing the horny layer to prevent increases in transepidermal water loss (TEWL). Skin hydration levels, however, are known to influence barrier properties. The purpose of this work was to compare skin moisture levels induced by four commercially available moisturizing lotions with their capacity as transdermal penetration enhancers using the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) as a model chemical. Further, the effect of moisturizing the skin after washing with sodium lauryl sulfate (SLS) on transdermal absorption was determined. Skin moisture levels were also measured noninvasively and were correlated to penetration enhancement. Hairless mouse skin was pretreated with commercially available moisturizing lotions either with or without SLS washing and in vitro permeability studies were performed with the herbicide 2,4-D. The data demonstrate that pretreatment with three of the four lotions tested increased the transdermal absorption of 2,4-D as evidenced by cumulative penetration or faster lag times (p < 0.05). Skin moisture levels correlated with the penetration enhancement capabilities of the lotion. Washing the skin with 5% SDS increased the transdermal absorption of 2,4-D (p < 0.05) and application of moisturizing lotions increased the absorption further. In summary moisturizing lotions may influence transdermal penetration of the skin, with the more effective moisturizers having a greater effect on 2,4-D absorption.

Potential mechanisms by which a single drink of alcohol can increase transdermal absorption of topically applied chemicals

BACKGROUND

Both chronic and acute ethanol consumption increase transdermal penetration of topically applied xenobiotics. The mechanisms by which this enhancement occurs are unknown. We hypothesized that either the vasodilatory effects of ethanol or its ability to disrupt the lipid bilayer via lipid peroxidation, may be contributing to the increased transdermal absorption observed in alcohol consuming animals.

METHODS

Male Wistar rats were gavaged with 1.5, 3, 4.3, 6 or 10 g/kg ethanol or saline control or were treated with either the vasoconstrictor epinephrine or with the vasodilator prilocaine. Dermal blood flow, transepidermal water loss (TEWL), and skin moisture were non-invasively measured. Transdermal penetration was then determined for four xenobiotics (paraquat, dimethyl formamide (DMF), 2,4-dichlorophenoxyacetic acid (2,4-D) and N,N-diethyl-m-toluamide (DEET)). Lipid peroxidation was also determined by monitoring the formation of malondialdehyde.

RESULTS

Dermal blood flow increased by approximately 27% (p<0.05), TEWL increased 1.12+/-0.2-fold while skin lipid peroxidation increased 1.4-fold (p<0.05) 2h after gavage with 10 g/kg alcohol. Transdermal penetration of paraquat was increased by prilocaine (ER=2.1+/-0.4, p<0.05), but the absorption of DEET, 2,4-D and DMF were not influenced by greater blood flow. Reducing dermal blood flow with epinephrine did not cause any significant changes in transdermal penetration.

CONCLUSIONS

Vasodilation triggered by a single episode of ethanol ingestion is not responsible for the observed increase in transdermal absorption. Ethanol induced changes in lipid peroxidation and TEWL demonstrate that drinking alcohol induces transdermal absorption of xenobiotics.

Transdermal absorption of the herbicide 2,4-dichlorophenoxyacetic acid is enhanced by both ethanol consumption and sunscreen application

Xenobiotics absorption is a health concern and skin is a major exposure site for many of these chemicals. Both alcohol consumption and topical sunscreen application act as transdermal penetration enhancers for model xenobiotics. The effect of combining these two treatments on transdermal absorption of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was therefore examined. Skin from rats ingesting low (1.5 g/kg) medium (4.3 g/kg) or high (6 g/kg) ethanol doses or saline control was treated with a commercially available sunscreen containing titanium dioxide and octyl methoxycinnimate and transdermal absorption of 2,4-D was monitored. Ethanol increased penetration by a factor of 1.9, 2.0 and 2.5 for animals treated with 1.5, 4.3 and 6 g/kg respectively, demonstrating an ethanol-induced dose response. Sunscreen application to skin from ethanol gavaged rats caused 2,4-D absorption above that induced by ethanol alone by an additional factor of 1.3, 2.1 and 2.9 for 1.5, 4.3 and 6 g/kg respectively. Comparing 2,4-D transdermal absorption after exposure to both ethanol and sunscreen with a theoretical value (sum of penetration after ethanol or sunscreen treatment) demonstrates that these two treatments enhance additively at the higher doses tested. Results of this study emphasize the importance of limiting excessive alcohol consumption in individuals with potential herbicide exposure rather than discouraging the use of sunscreens, since the consequences of UV-induced skin cancer are far more series than the risks that would be associated with observed increases in chemical exposure.

Effects of chronic alcohol consumption on dermal penetration of pesticides in rats

Topically applied ethanol is a well-known dermal penetration enhancer. The purpose of this work was to determine if ethanol consumption might also increase transdermal penetration. Male rats were fed either an ethanol containing or control diet for 6-8 wk. After the feeding regime was completed, skin was removed and placed in an in vitro diffusion system. The transdermal absorption of four very commonly used herbicides was determined. Penetration through skin from ethanol-fed rats was enhanced when compared to control by a factor of 5.3 for paraquat, 2.4 for atrazine, and 2.2 for 2,4-dichlorophenoxyacetic acid (2,4-D), and reduced by a factor 0.6 for trifluralin. Comparison of physical factors of the herbicides to the penetration enhancement revealed an inverse linear correlation with lipophilicity, as defined by log octanol/water partition coefficient (log Kow) with r2 =.98. These changes were at least partially reversible after 1 wk of abstinence from ethanol. These experiments demonstrate that regular ethanol consumption can alter the properties of the dermal barrier, leading to increased absorption of some chemicals through rat skin. If ethanol consumption has the same effect on human skin it could potentially have adverse health effects on people regularly exposed to agricultural, environmental, and industrial chemicals.

Sunscreens can increase dermal penetration of 2,4-dichlorophenoxyacetic acid

Agricultural workers are encouraged to wear sunscreen to reduce their risk of skin cancer. These workers are also exposed to herbicides during the course of their day. The skin is the major source of chemical exposure in agriculture. The purpose of this work is to determine the effect of sunscreen use on the transdermal absorption of a model herbicide, 2,4-dichlorophenoxyacetic acid. Hairless mouse skin was pretreated with one of nine commercially available sunscreens purchased at a local drug store. The herbicide 2,4-dichlorophenoxyacetic acid was placed on top of the epidermis in an in vitro diffusion chamber for 24 hours. The total penetrating through the skin in 24 hours ranged from 39.1 +/- 1.7% for the no sunscreen control to 81.0 +/- 2.8% for Neutrogena Oil Free Sunscreen. Of the nine sunscreens tested, six led to a significant enhancement of total 2,4-dichlorophenoxyacetic acid penetration as compared to the control (p < 0.01). Careful selection of sunscreen during pesticide application could reduce potential exposure.

Effects of low doses of erythromycin on the 13C Spirulina platensis gastric emptying breath test and electrogastrogram: a controlled study in healthy volunteers

OBJECTIVE

Electrogastrography and stable isotope gastric emptying breath tests (GEBTs) are relatively simple, noninvasive tests of gastric motor function that may be useful in monitoring the effects of therapeutic interventions. It was our primary objective to examine the effects of low dose i.v. erythromycin on the results of the 13C Spirulina platensis GEBT and electrogastrography. We were also interested in evaluating the reproducibility of these tests.

METHODS

In 10 healthy subjects (five female, ages 23-37 yr), we simultaneously performed the GEBT, using a prepackaged meal (340 kcal), and electrogastrography on each of four different occasions separated by at least 1 wk. After performance of baseline studies, they were repeated in random order after the infusion of 50 mg of erythromycin (Er50), 100 mg erythromycin (Er100), and a placebo (saline). Breath samples were obtained at baseline and at 75, 90, and 180 min after the meal and T1/2 and Tlag calculated. Electrogastrography recordings began 30 min before the test meal and continued for 2 h after the meal.

RESULTS

Baseline and placebo T1/2 and Tlag were similar. Er50 resulted in a modest acceleration of gastric emptying (T1/2 Er50 vs baseline vs placebo = 104.0 vs 132.7 vs 125.5 min) and reduction in lag time (Tlag Er50 vs baseline vs placebo = 47.2 vs 61.5 vs 56.2 min). A similar decrease was seen in response to Er100. The baseline and placebo fasting and fed electrogastrography parameters were similar. After infusion of Er100, the percentage of normal slow waves in the first postprandial hour decreased relative to baseline and placebo (percent normogastria Er100 vs baseline vs placebo = 64.1+/-7.5 vs 82.4+/-6.4 vs 79.7+/-5.5). This corresponded with an increase in percent tachygastria during the same period and an overall decrease in the mean dominant frequency. Similar but less striking changes were seen after administration of Er50. Replicate GEBTs showed a high degree of reproducibility both within and between individuals for T1/2 and Tlag. In contrast, replicate electrogastrograms revealed moderate to high variability for all parameters except the dominant frequency.

CONCLUSION

The stable isotope GEBT utilizing 13C S. platensis demonstrates responsiveness to the prokinetic effects of low dose i.v. erythromycin and good reproducibility.

Topical and transdermal delivery of antisense oligonucleotides

Antisense oligonucleotides have great potential as therapeutic agents. As a result, a variety of chemistries have been developed to improve the efficacy of these molecules without compromising their specificity. Because the skin is such a large organ with extensive accessibility, it is a natural target for drug delivery. It is, however, an effective barrier, so physical and chemical methods to improve drug penetration have been developed. These enhancement techniques can be combined with modified oligonucleotide chemistries to provide sufficient levels of antisense activity either within the skin or systemically. This review will describe in vitro and in vivo experiments that demonstrate the potential of antisense oligonucleotides to treat both dermal and systemic disorders.

A novel system to study the impact of epithelial barriers on cellular metabolism

Medications introduced into the systematic circulation must be transported across biological barriers such as skin, gastrointestinal, or bronchial epithelia, which can alter their kinetic and metabolic profiles. It is, therefore, important to understand diffusion kinetics across barrier membranes when choosing a dosing regime that will elicit the greatest cellular response. An in vitro system that combines membrane transport studies with a downstream cell culture chamber has been developed. The system has been tested with skin and a small intestine model (Caco-2 cell monolayers) as barriers, the peroxovanadium compound [VO(O2)2 1, 10 phenanthroline] bpV(phen), as the test chemical, Hep-G2 (liver) as the test cells, and glucose consumption as the test assay. Peroxovanadium has insulin mimetic properties and has been previously demonstrated to effectively lower blood glucose levels in diabetic rats when administered transdermally. A dose of 10 mM bpV(phen) placed on the skin epidermis with a continuous iontophoretic current of 0.5 mA/cm2 for 4.5 h led to a net 22% increase in glucose consumption by Hep-G2 cells. The same dose of bpV(phen) passively diffusing across a Caco-2 cell monolayer led to an increase in glucose consumption by Hep-G2 cells of 23%. This system is highly versatile and can be used to study many other processes, involving a variety of biological membranes, cell types, chemicals and assays, making it a valuable research tool.

Transdermal delivery of antisense oligonucleotides can induce changes in gene expression in vivo

The potential for using antisense compounds as therapeutic agents has generated great enthusiasm. Strategies for delivery of these compounds are, therefore, of great interest. Transdermal iontophoresis has been used successfully as an enhancement technique for the transdermal delivery of these compounds in vitro. The effectiveness of using percutaneous penetration as a means to deliver therapeutic levels of these compounds in vivo, however, remains to be demonstrated. The purpose of this work was to demonstrate the ability of iontophoretically delivered compounds to alter enzyme levels in the intact rat. A C5 propyne-modified phosphorothioate oligonucleotide (PS-ODN) targeted to the cytochrome p450-3A2 (CYP3A2) mRNA translational start site and the reverse sequence, used as a control, were synthesized. A patch containing either an oligonucleotide or a buffer control was placed on the animal's back, and an iontophoretic current of 0.5 mA/cm2 was applied for 3.5 hours. Twenty-four hours later, CYP3A2 levels were measured noninvasively using the midazolam-induced sleeping rat model. Liver and small intestinal microsomes were made after completion of sleep studies and assayed for CYP3A2, CYP1A1/2, CYP2B1/2, and CYP2E1. Midozolam-treated animals with antisense to CYP3A2 slept significantly longer than did the controls (p < 0.05). CYP3A2 levels were significantly lower in liver microsomes from antisense-treated animals than in either buffer control (p < 0.001) or reverse sequence animals (p < 0.05). The reverse sequence was also significantly different from the buffer control (p < 0.01), indicating a nonspecific effect of the PS background. Nontarget cytochrome levels were not altered by treatment. There were no significant differences in small intestine CYP3A2 levels between treatment groups. These data demonstrate that transdermally delivered PS-ODN can reach concentrations sufficient to induce changes in specific target enzymes in vivo. Further studies are warranted to investigate potential uses for these molecules.

A combination of iontophoresis and the chelating agent 1,10 phenanthroline act synergistically as penetration enhancers

The peroxovanadium compound VO(O2)2 1,10 phenanthroline (bpV(phen)) is capable of lowering blood glucose levels. It is not available in oral form, but it is effective when delivered transdermally. Iontophoresis can significantly reduce the lag time of this response in vivo when compared with passive penetration. To better mimic in vivo insulin release, we explored the effects of various iontophoretic current durations on dermal penetration of bpV(phen). Iontophoretic transport was not related to total applied charge, as steady-state flux was equivalent for current durations ranging from 15 minutes to 9 hours. We hypothesized that the unexpectedly large transport after just 15 minutes of current was caused by an increase in passive penetration of bpV(phen) induced by iontophoresis. Iontophoretic pretreatment with the chelating agent 1,10 phenanthroline increased passive penetration of bpV(phen), whereas neither the nonchelating isomer 1,7 phenanthroline nor the less potent chelator EDTA were effective. The use of 1,10 phenanthroline as a penetration enhancer for other chemicals was examined with the amino acids alanine and leucine. Fifteen minutes of 1,10 phenanthroline iontophoresis enhances alanine transport 11.4-fold over passive, whereas the 1,7 phenanthroline increased transport by a factor of 4.6 and the iontophoretic control of ethanol by 1.9. Surprisingly, phenanthroline did not enhance 3H leucine penetration. The reasons for this selectivity are not clear and warrant further investigation. Overall, the data suggest that chelating agents, specifically 1,10 phenanthroline, may be used as penetration enhancers for the delivery of certain compounds.

Transdermal delivery of antisense compounds

Antisense technology holds tremendous promise for therapeutic applications and the study of gene function. A broadly applicable route of administration that would provide for non-invasive, simple, and convenient delivery is highly desirable. Application of oligonucleotides to the skin may represent a solution to the delivery question for both local treatment of skin disease and for systemic delivery. The iontophoretic mode of delivery for phosphorothioate oligonucleotides across hairless mouse skin reveals the potential limitation in the delivery of sufficient oligonucleotide to provide for efficacy. A potential solution to this problem is the use of significantly more potent C-5 propyne base modifications in a phosphorothioate oligonucleotide. The combination of the iontophoretic delivery mode with potent oligonucleotides resulted in selective inhibition of the CYP3A2 gene expression in the rat liver. Alternatively, oligomers with neutral charge combined with passive modes of transdermal delivery may also be feasible and represent an even more broadly applicable technology. Future studies will focus on specific applications of local and systemic therapy of antisense oligonucleotide in animal models for the design of treatment regimens.

Transdermally delivered peroxovanadium can lower blood glucose levels in diabetic rats

The element vanadium can have insulin mimetic properties and therefore has been suggested as a possible therapeutic agent for treatment of diabetes. A series of peroxovanadium compounds that are more potent at lowering blood glucose levels than sodium metavanadate, sodium orthovanadate and vanadyl sulfate have recently been synthesized. These compounds probably will not be orally active so transdermal administration is a potential option. A patch containing either the peroxovanadium compound [VO(O2)2 1-10 phenanthroline], abbreviated bpV(phen), or placebo was placed on the back of streptozotocin induced diabetic rats and was delivered either passively (16 h) or iontophoretically (0.5 mA/cm2 for 4 h). Blood samples were analyzed for glucose and vanadium levels. Mean blood glucose levels were 83+/-1% and 109+/-1% of the starting values for animals iontophoretically treated with bpV(phen) and vehicle, respectively. The compound's insulin mimetic properties were evident within 60 min of current initiation. Blood glucose levels were reduced to 74+/-14% of the original level after 16 h of passive treatment. The compound was ineffective when fed to animals. Transdermal delivery of bpV(phen) resulted in significantly greater blood levels of vanadium than the orally delivered compound (P<0.05). Overall these experiments demonstrate that peroxovanadium delivered through the skin can lower blood glucose levels in rats. Further experiments are warranted to better characterize the nature of the response and to determine the potential for using these compounds in humans.

An experimental model for interpreting percutaneous penetration of oligonucleotides that incorporates the role of keratinocytes

Oligonucleotides have been extensively studied for their potential as therapeutic agents. Phosphorothioate oligonucleotides have been demonstrated to be particularly useful due to their stability against nucleases, their ability to be internalized by many cell types, and the ease with which they hybridize with target mRNA. These compounds have previously been delivered across the skin with the aid of iontophoresis. During transdermal delivery, the first viable cells exposed to the oligonucleotides are the keratinocytes. The purpose of this study was to determine the relationship between internalization of these compounds by keratinocytes and their transport across the skin. The in vitro uptake of 15 different fluorescently labeled phosphorothioate oligonucleotides into human keratinocytes was quantitatively measured with a fluorometer. Photomicrographs of keratinocytes indicate diffuse cytoplasmic and nuclear localization. The ability of these molecules to enter cells was linearly related to size. Cellular uptake data were inversely correlated with previously reported steady-state transport levels of oligonucleotides that had been transdermally delivered by iontophoresis across hairless mouse skin. Oligonucleotides that readily entered keratinocytes had a decreased ability to penetrate skin under iontophoretic conditions. The results indicate that oligonucleotide sequences may be designed for treating skin diseases (high uptake, low transport) or systemic disorders (low uptake, high transport).

Effects of size and sequence on the iontophoretic delivery of oligonucleotides

Adequate cellular availability of synthetic oligonucleotides is crucial to their success as therapeutic agents. These compounds, however, are not expected to be orally active. This has led to interest in a variety of alternate drug delivery methods, including iontophoretically enhanced transdermal delivery. The purpose of this work is to begin characterizing the structure-activity relationship for iontophoresis of oligonucleotides through the skin. The in vitro permeation of 16 biologically relevant phosphorothioate oligonucleotides across hairless mouse skin was studied. Oligonucleotides with less than 20 bases (n = 10) had a wide range of steady-state flux levels (2.1-26.2 pmol/ cm2 h). A lower flux differential was observed for compounds ranging from 20 to 40 bases long (1.2-2.2 pmol/cm2 h). For the smaller compounds, transport, in general, decreased with increasing size; however, there were several oligonucleotides that did not follow this pattern. These data indicate that factors other than size influence transport and that the impact is greater at shorter lengths. Differential penetration between equal sized oligonucleotides synthesized with identical bases in reversed order indicates that sequences and not simply base composition affects steady-state flux across skin. Molecular structure, therefore, is a key contributor to iontophoretically assisted transport. Further studies are necessary to develop more precise predictions about the relationship between oligonucleotide structure and transdermal delivery.

Transdermal delivery of erythromycin lactobionate--implications for the therapy of gastroparesis

BACKGROUND

The treatment of many diseases may be complicated by abnormalities in gastric emptying. Gastric motor dysfunction may lead to unpredictable food and medication delivery to the small intestine, their site of absorption. Prokinetic agents improve gastric motility, but orally administered drugs are unreliably absorbed, thereby limiting their effectiveness. A method of delivering prokinetic agents which bypasses the gastrointestinal tract could lead to more effective treatment.

METHODS

Skin samples from rat, hairless mouse and man were placed in an in vitro diffusion chamber. The epidermal side of the skin was exposed to erythromycin lactobionate and passage of the drug across the skin sample monitored and quantitated by high-performance liquid chromatography with UV detection.

RESULTS

Erythromycin passes across all skin types tested. Steady-state flux across hairless mouse skin was greater than for rat, full thickness human skin and human epidermis. In the first 3 h following introduction of erythromycin lactobionate, 1.85 mg/cm2 crossed human epidermis. Given that a dose of 50 mg may exert prokinetic effects in vivo in man, increasing the patch size to approximately equal to 28 cm2 should provide therapeutic levels of drug within 3 h.

CONCLUSIONS

Erythromycin lactobionate, when administered transdermally, can be delivered at levels sufficient to treat gastroparesis. This technique warrants in vivo investigation.

Iontophoretic delivery of a telomeric oligonucleotide

PURPOSE

To evaluate the feasibility of iontophoretically enhanced transdermal delivery of a phosphorothioate oligonucleotide across hairless mouse skin.

METHODS

The phosphorothioate sequence, 5'-d(TTAGGG)-3' (TAG-6) which mimics the repeat sequence of the telomere was used as a model compound. Iontophoresis was performed on hairless mouse skin using as in vitro flow-through diffusion system. Both 5'-FITC and uniformly 35S labeled oligonucleotide were used to monitor transdermal flux.

RESULTS

Cathodal delivery of TAG-6 resulted in substantial oligonucleotide flux. The molecular label did not alter transport properties. No flux was measured with either anodal or passive delivery. The oligonucleotide was not degraded as it crossed the skin. Molecular transport was donor condition dependent, with pH and salt concentration both having significant effects. Pre-treating the skin with ethanol reduced iontophoretic transport.

CONCLUSIONS

These data demonstrate that iontophoresis can enhance transdermal flux of an intact phosphorothioate oligonucleotide and that this penetration is donor condition dependent. Furthermore, iontophoretically enhanced transdermal delivery is a feasible approach to the administration of phosphorothioate oligonucleotides.

Convolution: a method for data analysis in perifusion systems

Considerable interest has developed in defining how imposed stimuli effect dynamic changes in cellular metabolism. We have developed a miniature perifusion system that can reveal alterations in extracellular protons within seconds after application of metabolic perturbants. This perifusion system contains two pH sensors: one before the cells records changes between medium and test solutions, and one, located just past the cells, records these alterations plus cellular modifications. Because distortion occurs as chemicals pass through perifusion systems, the shape of pH changes induced by switching from medium to test solutions is different at each electrode. This study describes and validates convolution to correct this distortion. Data from HeLa cells exposed to the metabolic uncoupler of oxidative phosphorylation carbonyl cyanide m-chlorophenyl hydrazone have been analyzed with convolution. Cellular response to oxidative phosphorylation removal is comprised of multiple components, is consistent with a rapid uncoupling, and is followed by cellular adaptation. Therefore convolutional analysis can provide an important adjunct to the analysis of data acquired by perifusion and can provide new insights into cellular responsiveness and metabolism.

Understanding the dynamics of cellular responsiveness to modifications of metabolic substrates in perifusion

A novel microperifusion system with capabilities for continuous, real-time, potentiometric monitoring of extracellular hydrogen ion concentration has been used to define the response of HeLa cells to abrupt changes in extracellular energy sources or introduction of an inhibitor of glycolysis. Glycolytic inhibition, induced by removal of glucose or introduction of iodoacetate, each led to a rapid, continuous decrease in acid release. The response to iodoacetate took longer than removal of glucose, perhaps due to the time required for binding and activation. Once inhibition began, however, the rate of change was greater than following glucose removal. Conversely, recovery time following iodoacetate inhibition was much slower than with glucose removal. Unlike the response to short-term glucose depletion, a second pulse of iodoacetate resulted in a faster response followed by an even longer recovery time. The response to switching between glucose and glutamine began almost without evident delay. The response patterns revealed that HeLa cells prefer glutamine to glucose, but, in the presence of both energy sources, some glucose continues to be used. In summary, these results indicate that continuous, real-time monitoring of the kinetics of hydrogen-ion release can be used to gain new insights into the dynamics of cellular response to perturbations of extracellular energy sources.

Continuous on-line hydrogen ion monitoring to study flow dynamics of perifusion systems and cellular metabolism

Time-dependent concentration profiles of input signals and feedback of metabolic products can strongly influence cellular responsiveness. To study these parameters, we developed a perifusion system that can deliver biological signals to cells with minimal dispersion, monitor real time responses, and remove waste products continuously. By monitoring pH with miniature hydrogen ion-selective electrodes at intervals of 1 s, effects of dispersion, flow rate, pumping system, and changes in cellular metabolism were demonstrated. Dynamic responses of a human cell line to a series of 10-min pulses of the metabolic uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) were monitored. A rapid 1-min increase in acid release occurred on exposure to CCCP, followed by a decrease in acidification and then a gradual return to a baseline slightly more acidic than before administration of CCCP. These observations demonstrate that this perifusion system can reveal small changes in pH (+/- 0.0005 units) induced by metabolic perturbations and has the potential to reveal the dynamics of cellular responsiveness to a wide range of hormonal, metabolic, and other chemical signals.

Dynamics of gonadotropin-releasing hormone release during a pulse

This study examined the nature of the GnRH signal that travels down the pituitary portal vessels and causes an LH pulse. Individual GnRH pulses were described in terms of abruptness of increase and decrease, amplitude, duration, and amount of GnRH released. Pituitary portal blood was obtained at 30-sec intervals for 2.5 or 5 h from five short-term ovariectomized ewes. Jugular blood was sampled every 10 min for LH. We examined 13 GnRH pulss; each produced an LH pulse. The contour of most GnRH pulses approximated a square wave. The rising edge of the GnRH pulse was very abrupt; GnRH secretion increased as much as 50-fold within 1 min. The mean peak amount of GnRH collected during pulses (24 pg/min, range 2-66) was 70-fold greater than the interpulse baseline (0.2-0.5 pg/min). The release period was sustained an average of 5.5 min; thereafter, GnRH fell to prepulse levels within 3 min. Overall, the larger and more prolonged pulses of GnRH were associated with higher amplitude LH pulses. To assess the distortion of the GnRH signal by the collection procedure, samples were obtained in vitro using the same technique during application of 4- and 7-min square wave GnRH pulses by means of a syringe pump. Signals were carried as square-waves through the sampling operation with minimal distoration, with the exception that amplitude decreased during the collection procedure. Our findings indicate the square-wave pulses observed in vivo are an accurate description of the dynamics of GnRH release during a pulse in short-term overiectomized ewes.