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PubMed1983

[Absorbable polydioxanone monofilament in the surgery of the anterior segment of the eye].

PDS (Polydioxanone suture), a new synthetic absorbable suture, was used in experimental and clinical trials. The experiment was performed on 14 rabbits anesthetized with intravenous sodium pentobarbital. Five months were needed for complete absorption of a piece of PDS left in a tunnelled corneal stroma. As late as the end of the second month no histological absorption was detected. This was twice as long as that persistence of polyglactin sutures studied under the same experimental conditions. In another series of 12 animals, the PDS suture was placed in the central cornea and tied with a buried knot. The PDS suture broke four to six weeks postoperatively in the superficial part of the cornea. The histologic tissue reaction in both these studies was minimal, resembling that obtained with black 10/0 monofilament nylon. In the clinical study, PDS sutures were used (size 0.2 metric and 0.3 metric) in 38 cases of cataract extraction. The material was easy to handle, especially when dyed violet. No side-effects attributable to the suture material were observed. PDS retained its tensible strength longer than other absorbable sutures, but can be used only for closing limbal incisions with conjunctival flaps in order to prevent tear hydrolysis of the suture.

Absorption↗
PubMed1980

Inhibition of growth of human breast cancer cell line MCF-7 by serum derived from calcium chloride-clotted plasma.

The growth of MCF-7 cells, established from a metastatic mammary carcinoma, and of HBL-100 cells, derived from a primary culture of human milk, was examined in medium supplemented with whole blood serum (WBS), defibrinogenated plasma, and plasma-derived serum (PDS). PDS obtained from platelet-poor plasma collected with the anticoagulant citrate phosphate dextrose and clotted by the addition of calcium chloride did not promote the growth of MCF-7 cells as well as did WBS or platelet-poor defibrinogenated plasma alone. Growth-inhibitory activity was observed when final cell densities in the presence of PDS combined with fetal bovine serum (FBS) were compared with those in control cultures maintained in FBS alone. The level of this activity in PDS varied among donors. Inhibition was not observed with HBL-100 cells. Calcium chloride did not induce inhibitory activity when added to WBS or defibrinogenated plasma, and platelet components did not alter the level of inhibition in PDS. However, platelet extracts did affect the expression of inhibition when added to plasma before clotting. Activity was diminished following dialysis of PDS, which suggested that inhibition stemmed from a small-molecular-weight factor for which expression depended on the mechanism of plasma coagulation.

Adenocarcinoma↗
PubMed1994

Polydioxanone absorbable sutures in vascular anastomoses: experimental and preliminary clinical studies.

To assess the safety and efficacy of polydioxanone suture (PDS) for vascular anastomoses, bilateral carotid end-to-end anastomoses using PDSs on the left and Dacron sutures on the right in 18 dogs were performed. The anastomoses were assessed at 4, 6 and 8 weeks after surgery. A breaking-strength test (300 mmHg) did not show a significant difference between PDS and Dacron anastomoses, but partial absorption was grossly evident in the PDS group. Some 35 venous and 21 arterial reconstructive procedures were also carried out using PDS in 53 patients. At follow-up of 3-5 (mean 3.5) years, none of the patients had experienced any suture-related complications. The results indicate that PDS maintains an adequate tensile strength in anastomoses until suture-line healing occurs, suggesting that this material may be safely used in venous or small arterial anastomoses. In addition, because it is absorbable, resulting in decreased foreign-body reactions, PDS may have the potential to improve the long-term patency of venous or small arterial reconstructions.

Adolescent↗
PubMedDate not supplied

Demographic, educational, and experiential factors associated with dentists' decisions to report hypothetical cases of child maltreatment.

The purpose of this study was to examine demographic factors associated with dentists' decisions to report hypothetical cases suggestive of child maltreatment. Surveys were mailed to 500 general dentists (GDs) in Georgia and all 200 pediatric dentists (PDs) in Georgia and Florida. The general dentists were chosen from a pool of 1500 by a stratified randomization scheme. Each survey contained two brief vignettes suggestive of, but not conclusive for, child neglect and abuse. Respondents were asked about their likelihood of reporting each vignette. General demographic questions were asked about the population served by the dentist, the year of dental degree and speciality certificate acquisition, and gender of the respondent. Further questions were asked about the individual's exposure to continuing education in child maltreatment, knowledge of legal requirements to report and the agency to which reports should be directed, and experience with suspected and filed cases. Responses were received from 185 GDs (37%) and 103 PDs (51.5%), a total of 288 (41.4%). PDs had more practitioners in larger communities and had more female respondents. PDs were more likely to answer yes to the questions about education/experience with child maltreatment. Factors associated with likely reporting of neglect were: 1) serving communities with populations < or = 100,000; 2) PDs acquiring specialty certificates after 1980; 3) being female; 4) exposure to continuing education; 5) having suspected cases in practice; and 6) having filed a maltreatment report. Factors associated with likely reporting of abuse were: 1) PDs acquiring specialty certification after 1980 and 2) self-reported recognition of the legal obligation to report.

Attitude of Health Personnel↗
PubMed2000

Clinical and histological results of septoplasty with a resorbable implant.

BACKGROUND: The use of a resorbable implant connected with septal cartilage would facilitate external septoplasty, offering mechanical stability until the cartilage fragments heal. OBJECTIVE: To study the histological and clinical results of septoplasty with a resorbable implant (polydioxanone [PDS; Ethicon, Norderstedt, Germany]) in conjunction with cartilage. DESIGN: To provide histological information in 5 rabbits, PDS foil was implanted into the outer ear in conjunction with an artificial cartilage defect. Observations were made at 2, 5, 10, 15, and 25 weeks. Resorption of the implant was investigated, including the time to complete elimination. In addition, septoplasty with PDS foil was performed on 71 patients with severe septal deformities. Surgery consisted of excision of the quadrilateral cartilage and division into straight fragments, which were sutured to the PDS foil and replaced as a free graft. SETTING: Ear, nose, and throat department of the General District Hospital Steyr, Steyr, Austria. RESULTS: Histological examination showed that the foil remained unchanged for at least 10 weeks and was completely resorbed after 25 weeks with minimal remaining scar tissue. Newly formed cartilage developed bordering the cartilage defect. In the clinical study, all patients experienced varying degrees of improvement in nasal blockage. No immediate or long-term complications occurred. CONCLUSIONS: The use of PDS foil in connection with cartilage facilitates surgical correction of severe septal deformities, additionally providing support for the nasal dorsum. The histological examination showed that no inflammatory or foreign body reaction occurred. Cartilage regeneration was even found. The foil was completely resorbed within 25 weeks, avoiding the long-term complications that occur with other artificial implants.

Absorbable Implants↗
PubMed1986

Biosynthesis and processing of proteodermatan sulphate.

The biosynthesis and processing of the small iduronic acid-rich proteodermatan sulphate (PDS) was studied in cultured human skin fibroblasts and arterial smooth muscle cells (SMC) with the aid of core-directed antibodies and various inhibitors of protein synthesis, intracellular transport, and glycosylation. Components of the linkage region became attached to the core protein most likely in a pre-Golgi compartment. Phosphorylation of PDS precursors also occurred in the endoplasmic reticulum with a minor contribution by the Golgi complex. Serine residues and the linkage region were identified as phosphorylated species in secreted PDS. Blockade of transport by monensin did not affect 6-sulphation but affected uronic acid epimerization and 4-sulphation. On relief from the monensin block, additional sulphation along the glycosaminoglycan chain was possible, whereas chain elongation was as in the continuous presence of the drug. Asparagine-bound oligosaccharides or glycosaminoglycan chains were not required for secretion of PDS or core protein. PDS from fibroblast and SMC secretions differed markedly in the composition of the glycosaminoglycan chains. No significant difference, however, was found on isoelectric focusing of core protein and after limited proteolysis of chondroitin ABC lyase-treated core protein. Tryptic and chymotryptic peptide maps of iodinated core proteins were similar.

Arteries↗
PubMed2003

The natural course of bulimia nervosa and eating disorder not otherwise specified is not influenced by personality disorders.

OBJECTIVE: To examine prospectively the natural course of bulimia nervosa (BN) and eating disorder not otherwise specified (EDNOS) and to test the effects of personality disorder (PD) comorbidity on the outcomes. METHOD: Ninety-two female patients with current BN (N=23) or EDNOS (N=69) were evaluated at baseline enrollment in the Collaborative Longitudinal Personality Disorders Study (CLPS). Eating disorders (EDs) were assessed with the Structured Clinical Interview for DSM-IV Axis I Disorders. Personality disorders (PDs) were assessed with the Diagnostic Interview for DSM-IV PD (DIPD-IV). The course of BN and EDNOS was assessed with the Longitudinal Interval Follow-up Evaluation and the course of PDs was evaluated with the Follow-Along version of the DIPD-IV at 6, 12, and 24 months. RESULTS: Probability of remission at 24 months was 40% for BN and 59% for EDNOS. To test the effects of PD comorbidity on course, ED patients were divided into groups with no, one, and two or more PDs. Cox proportional regression analyses revealed that BN had a longer time to remission than EDNOS (p<.05). The number of PDs was not a significant predictor of time to remission, nor was the presence of Axis I psychiatric comorbidity or Global Assessment of Functioning scores. Analyses using proportional hazards regression with time-varying covariates revealed that PD instability was unrelated to changes in ED. CONCLUSIONS: BN has a worse 24-month course (longer time to remission) than EDNOS. The natural course of BN and EDNOS is not influenced significantly by the presence, severity, or time-varying changes of co-occurring PDs, co-occurring Axis I disorders, or by global functioning.

Adolescent↗
PubMed2001

Pendred syndrome, DFNB4, and PDS/SLC26A4 identification of eight novel mutations and possible genotype-phenotype correlations.

Mutations in PDS (SLC26A4) cause both Pendred syndrome and DFNB4, two autosomal recessive disorders that share hearing loss as a common feature. The hearing loss is associated with temporal bone abnormalities, ranging from isolated enlargement of the vestibular aqueduct (dilated vestibular aqueduct, DVA) to Mondini dysplasia, a complex malformation in which the normal cochlear spiral of 2(1/2) turns is replaced by a hypoplastic coil of 1(1/2) turns. In Pendred syndrome, thyromegaly also develops, although affected persons usually remain euthyroid. We identified PDS mutations in the proband of 14 of 47 simplex families (30%) and nine of 11 multiplex families (82%) (P=0.0023). In all cases, mutations segregated with the disease state in multiplex families. Included in the 15 different PDS allele variants we found were eight novel mutations. The two most common mutations, T416P and IVS8+1G>A, were present in 22% and 30% of families, respectively. The finding of PDS mutations in five of six multiplex families with DVA (83%) and four of five multiplex families with Mondini dysplasia (80%) implies that mutations in this gene are the major genetic cause of these temporal anomalies. Comparative analysis of phenotypic and genotypic data supports the hypothesis that the type of temporal bone anomaly may depend on the specific PDS allele variant present.

Abnormalities, Multiple↗
PubMed1993

Hydrolytic degradation and morphologic study of poly-p-dioxanone.

The in vitro hydrolytic degradation of 2-0 size PDS monofilament suture was studied for the purpose of revealing its morphologic structure and degradation mechanism. The sutures were immersed in phosphate buffer of pH 7.44 for up to 120 days at 37 degrees C. These hydrolyzed sutures were examined by the changes in tensile properties, weight, thermal properties, x-ray diffraction structure, surface morphology, and dye diffusion phenomena. It was found that hydrolysis had significant effects on the change of PDS fiber morphology and properties. Hydrolysis, however, had no significant effect on overall molecular orientation of the fiber until the very late stage. PDS suture fibers retained their skeleton throughout the earlier periods of hydrolysis concurrent with mass and tensile strength losses. PDS sutures exhibited an absorption delay of 120 days. Both heat of fusion and melting point exhibited a maximum function of hydrolysis time. Hydrolysis of PDS suture fibers proceeded through two stages: random scission of chain segments located in the amorphous regions of microfibrils and intermicrofibrillar space, followed by stepwise scission of chain segments located in the crystalline regions of microfibrils. Dye diffusion data showed that the passage along the longitudinal direction of the fiber was relatively easier than the lateral direction as evident in the diffusion coefficient, activation energy, and flexibility of chain segments. Swiss-cheese model of fiber structure appears to describe the observed dye diffusion phenomena and their dependence on hydrolysis time and dying temperature.

Adsorption↗
PubMed1981

Regulation of human amnion cell growth and morphology by sera, plasma, and growth factors.

The requirements of human epithelial cells derived from the amnion membrane for serum factors were investigated. The growth promoting effects of human whole blood serum (WBS), platelet-poor defibrinogenated plasma, and plasma-derived serum (PDS) were examined in primary cultures of these ectodermal cells. The numbers of population doublings recorded after 10 days in the presence of 10% WBS, defibrinogenated plasma, or PDS were 2.3, 2.0 or 1.5, respectively. Although dialysis of sera or plasma had little effect on growth promotion, it markedly decreased the capacity of plasma to maintain cells in culture beyond 10 days. The differences in growth activities could not be attributed to the presence of anticoagulant in plasma and PDS or to the presence of excess calcium in PDS. Platelet lysates and purified platelet-derived growth factor had no effect on growth. Amnion cell growth was enhanced by epidermal growth factor (EGF) or hydrocortisone, but the glucocorticoid did not condition cells to respond to growth factors. Insulin and fibroblast growth factor singly or in combination had no effect on cell replication. Giant cell formation accompanied maintenance in hydrocortisone with defibrinogenated plasma and PDS. Discrete regions of dense population appeared in the presence of hydrocortisone, EGF, and undialyzed supplements.

Amnion↗
PubMed1987

Control of spontaneous epileptiform discharges by extracellular potassium: an "in vitro" study in the CA1 subfield of the hippocampal slice.

1. The effects evoked by changing [K+]o upon the synchronous epileptiform discharges (SEDs) generated in the presence of GABA antagonists were studied in the "in vitro" hippocampal slice with extra- and intracellular recordings. [K+] in the artificial cerebrospinal fluid (ACSF) was varied in steps of 1 or 2 mM between 3.25 and 10.25 mM. 2. Spontaneous SEDs occurred rarely at [K+]o lower than 5.25 mM. Augmenting [K+]o from 5.25 to 10.25 mM caused a four to five fold increase in the frequency of occurrence of SEDs while the duration of each SED was inversely related to the rate of occurrence. 3. Similar findings were observed when the CA1 subfield had been surgically disconnected from the CA2-CA3 subfields. In these experiments SEDs occurred independently in the two regions, but at any given [K+]o SEDs in the CA3 subfield displayed a frequency two to three times higher than that of SEDs generated in the CA1 area. 4. The intracellular correlate of the SEDs in the CA1 subfield either intact or isolated from the CA2-CA3 ones was a large amplitude depolarization (duration 100-600 ms) associated with a burst of action potentials. This intracellular event, which was similar to the paroxysmal depolarizing shift (PDS) recorded in focal models of epilepsy "in vivo", behaved largely like a synaptic phenomenon when the resting membrane potential (Vm) was changed with intracellularly injected current. A long lasting (half-width: 0.3-2 s in 6.25 mM [K+]o) hyperpolarizing potential usually followed the PDS and could be inverted by hyperpolarizing the Vm by 15-25 mV. When [K+] in the ACSF was raised from 7.25 to 10.25 mM, pyramidal cells depolarized in a dose related fashion. At the same time the post-PDS hyperpolarization decreased in duration and peaked earlier, thus curtailing the depolarizing envelope of the PDS. Consequently, the effect of increasing [K+]o was that of evoking more frequent, but shorter PDSs. 6. These findings demonstrate that the appearance of spontaneous SEDs in the presence of GABA antagonists is dependent upon [K+]o. The effects of evoked by increasing [K+]o are presumably mediated through: (i) a decreased strength of K+ repolarizing conductances; (ii) an increased efficacy of synaptic potentials; (iii) a steady depolarization of the neuronal membrane. The modulation of the frequency of occurrence of SEDs appears to be related to a decreased duration of the hyperpolarization which follows the PDS, a potential which is largely mediated by a K+ conductance.

Animals↗
PubMed1998

[Comparison of internal fixation methods for the symphysis in multi-directional dynamic gait simulation].

For the stabilization of the ruptured pubic symphysis, rigid forms of fixation such as plate osteosynthesis and flexible fixations such as wire loops or PDS banding have been recommended. All methods have only been tested by static unidirectional loading until failure of the system. By this experimental arrangement Ecke and Hofmann found comparable results for flexible and rigid methods of internal stabilization of the pubic symphysis. They preferred flexible methods to maintain mobility of the symphysis and to prevent symphyseal fusion. We tested dynamic compression plate osteosynthesis, reconstruction plate osteosynthesis, wire loops and PDS banding for internal fixation of injured pubic symphysis in a dynamic multidirectional experimental arrangement simulating gait conditions. The specimens were loaded with 85 N in vertical (y-) direction and 34 N in sagittal (z-) direction, which represent 50% of the forces acting at the pubic symphysis during walking and with a frequency of 1.5 Hz over 55,500 loads simulating the conditions over a 6-week mobilization period. Loading with 100% of the acting forces (corresponding to full weight bearing mobilization) led to early failure of the system. Our experimental analysis showed that neither wire loops nor PDS banding is able to stabilize the ruptured pubic symphysis, even immediately after fixation before loading. During the tests instability increased until failure of the system due to cutting of the bone or breaking of the wires or PDS banding. Success of plate osteosynthesis was dependent on the initial stability of the fixation. Overwinding of the screws, as in osteoporotic bone, lead to increasing loosening during repeated loading, whereas primary stable fixation of the screws was almost completely maintained during the test. In consequence, neither wire loops nor PDS banding should be used for stabilization of injured pubic symphysis if early mobilization with partial weight bearing is desired. Plate osteosynthesis (DC or reconstruction plate) tolerates early half weight bearing in patients with "open-book" injury only if safe screw fixation is guaranteed.

Biomechanical Phenomena↗
PubMed2004

Personality disorders in the community: results from the Australian National Survey of Mental Health and Well-being Part III. Relationships between specific type of personality disorder, Axis 1 mental disorders and physical conditions with disability and health consultations.

BACKGROUND: The aim of the present study was to examine in a national survey sample the risks of having a specific personality disorder (PD) and associations with gender, of having one or more physical conditions, of having one or more Axis 1 conditions, and of the severity (or degree) of disability. We also examined the association of specific PDs with having sought a consultation for health or mental health problems with a general practitioner (GP), a psychologist, or psychiatrist over the past 12 months. METHOD: Data were derived from the Australian National Mental Health and Well-Being Survey, conducted between May and August 1997. A stratified random sample of households was generated, from which all persons aged 18 or over were considered potential interviewees. There were 10,641 survey respondents, this representing a response rate of 78%. Each interviewee was asked 59 questions indexing specific ICD-10 PD criteria. RESULTS: Logistic regressions identified that some specific PDs, especially borderline PD, were more strongly associated with having one or more Axis I conditions, greater mental disability and lost days of total and partial role functioning than having No PD, and that others, notably anankastic PD, were less likely to be associated with the same variables. Some specific PDs, again most notably borderline PD, were more associated than others, again most notably anankastic PD, with having sought mental health consultations from GPs, psychiatrists, and psychologists. By contrast, PD associations with gender, physical conditions, physical disability and health consultations with the three professional groups were weaker as reflected in the comparatively smaller odds ratios and were also less consistent than the pattern with the previously mentioned variables. CONCLUSION: The study reports findings from a nationwide survey and, as such, the data are less influenced by the selection and setting bias found in most other studies investigating these variables. The findings of the study do point to some specific PDs, such as borderline PD, being associated with greater Axis 1 psychopathology, disability and mental health consultations than others, such as anankastic PD. It appears that although anankastic PD in itself is associated with more disability than having No PD, it becomes significantly more disabling when it is associated with other comorbid PDs.

Adult↗
PubMed2003

Impact of postpartum depressive symptoms on mother and her 18-month-old infant.

BACKGROUND: Postpartum depression (PPD) is known to have important negative effects on mother, infant and mother-child relationship. METHODS: We present a case-control study of 35 mothers and their 18-month-old infants. These mothers suffered from postpartum depressive symptoms (PDS) when the infants were three months old, as rated with the Edinburgh Postnatal Depression Scale (EPDS, Cox 1987). A control group of 35 mothers without postpartum depressive symptoms (NPDS) with their 18-month-old infants was also evaluated. The infants were assessed using the Infant Behavior Record of the Bayley Scales of Infant Development, the Strange Situation and an object concept task. RESULTS: 15 months later, the PDS mothers were less affectionate and more anxious than the NPDS mothers. The PDS dyads demonstrated less verbal interaction and less playing interaction. 18-month-old infants of PDS mothers performed less well on object concept tasks, and were more often insecurely attached to their mothers. Only some results were linked to the mothers' depressive state (D-mothers) diagnosed at 18 months (e. g. responsiveness to persons). CONCLUSIONS: The important negative effects observed at 18 months on mother and infant of maternal PDS at 3 months confirm the need for early identification and therapeutic or preventive interventions.

Adult↗
PubMed2004

Contrast-enhanced power Doppler sonography of knee synovitis in rheumatoid arthritis: assessment of therapeutic response.

The aim of this study was to evaluate the ability of power Doppler sonography (PDS) with ultrasound contrast agent to assess the synovial perfusion changes induced by intra-articular steroid injection therapy in the knee joints of patients with rheumatoid arthritis (RA). Eighteen RA patients (16 women, 2 men) with a history and signs of active knee synovitis were studied. Tenderness was evaluated using Thompson's modified index of synovitis activity. All patients underwent joint aspiration followed by intra-articular injection of 40 mg of triamcinolone hexacetonide. Gray-scale ultrasonography and PDS with an intravenous ultrasound contrast agent (Levovist) examinations were carried out before and 3 weeks after the intra-articular steroid injection. The calculation of the time--intensity curves provided a quantitative estimation of the synovial perfusion. The median values of the index of synovitis activity decreased significantly from 7.0 (95% confidence interval (CI) 6.0-8.0) to 3.0 (95% CI 2.0-4.0) ( p<0.01) 3 weeks after the intra-articular steroid injection. All patients showed a reduction of PDS signal after intra-articular steroid therapy and the baseline and follow up median values of the area underlying time-intensity curves were 7.48 (95% CI 5.79-8.73) and 2.45 (95% CI 1.92-3.61), respectively. The comparison between baseline and follow-up median values of the area under the curves showed a statistically significant reduction of PDS findings ( p<0.01). At follow-up examinations the changes in the index score of the synovitis activity were significantly correlated to the changes in the values of the area underlying time-intensity curves ( r=0.785; p<0.01). A significant correlation was also observed between baseline values of the area underlying time-intensity curves and C-reactive protein (CRP) ( r=0.548; p=0.023). In conclusion, PDS with an intravenous ultrasound contrast agent has been shown to be able to detect changes in synovial perfusion after intra-articular steroid injection and may be an additional useful method in the evaluation of synovial inflammation and in the assessment of the therapeutic response.

Adult↗
PubMed2004

Comparison of the posttraumatic stress disorder scale versus the clinician-administered posttraumatic stress disorder scale in domestic violence survivors.

The posttraumatic diagnostic scale (PDS) is a self-report instrument for PTSD that is simple to administer and has demonstrated good psychometric properties. We compared the PDS with the gold standard clinician administered PTSD scale (CAPS) diagnostic interview for PTSD. We assessed 138 women who were victims of domestic violence using both the PDS and the CAPS. Findings confirmed that PTSD develops at a high base rate in this sample. The PDS generally performed well in relation to the CAPS although with a tendency to overdiagnose PTSD. The findings lend further support to the use of the PDS as a diagnostic tool for PTSD but indicate that it is better at identifying survivors with PTSD than those without the disorder.

Adolescent↗
PubMed1996

The assessment of personality disorders: implications for cognitive and behavior therapy.

This article reviews the comorbidity of personality disorders (PDs) and Axis I disorders and discusses implications for assessment and treatment. Pros and cons of various assessment methods are discussed. The co-occurrence of PDs with Axis I disorders is considerable; roughly half of patients with anxiety disorders, depressive disorders or eating disorders received a PD diagnosis. Comorbidity models are discussed and implications for assessment and treatment are provided. Regarding the impact of PDs on cognitive-behavioral treatment outcome for Axis I disorders, conflicting results are found due to differences in assessment methods, treatment strategies, and patient samples. It is argued that additional Axis I pathology should be taken into account when studying the impact of PDs on treatment outcome for the target Axis I disorders. Finally, it is argued that the interpersonal behavior of the PD patient and the therapeutic relationship deserve more attention in the assessment and treatment of patients with PDs.

Comorbidity↗
PubMed1988

Enhancement of cyclic AMP-dependent sodium current by the convulsant drug pentylenetetrazol.

The convulsant drug pentylenetetrazol (PTZ) causes paroxysmal depolarizing shifts (PDS) and bursting in molluscan neurons. PDS has been found to be accompanied by increased levels of cyclic AMP (cAMP) and supported by persistent Na+ current. In neurons of the snail Lymnaea stagnalis the blocker of cAMP degradation isobutylmethylxanthine (IBMX) mimicks PTZ action. Na+ dependence of PTZ-induced inward shift in holding current in voltage-clamped cells supports the potential Na+ current origin of PDS. Intracellular cAMP injection elicits a transient Na+ current whose amplitude and duration are enhanced by both PTZ and IBMX. PTZ may cause PDS partly through slowing cAMP degradation, thus enhancing the cAMP-dependent Na+ current. PDS-generated bursts cause partial inactivation of the Na+ current, which may contribute towards burst termination.

1-Methyl-3-isobutylxanthine↗