Noradrenergic mediation of the memory-enhancing effect of corticotropin-releasing factor in the locus coeruleus of rats

A role for the locus coeruleus (LC) in attention and behavioral arousal has been suggested. The present study examined the effect of corticotropin-releasing factor (CRF) in the LC on memory retention of a passive-avoidance task in rats. Our results indicate that intra-LC CRF injection significantly improved retention performance. Decreases of norepinephrine (NE) levels in the hippocampus and the amygdala occurred in these animals. Intra-hippocampal 6-hydroxydopamine pretreatment did not affect memory alone, while it antagonized the memory-enhancing effect of CRF in the LC. This finding suggests that the dorsal NE pathway is involved in the memory consolidation process. Similar to the effect of CRF, application of the alpha 2-adrenergic antagonist yohimbine to the LC also dose-dependently enhanced memory, suggesting that CRF improved memory through activation of NE neurons in the LC. Finally, the anxiolytic chlordiazepoxide, at a concentration that did not alter memory by itself, prevented the memory-facilitating effect of CRF in the LC. Our findings suggest that the LC is an important structure in modulating learning and memory processes of passive avoidance learning in rats. CRF may enhance memory through activation of NE neurons in the LC and, at least in part, through the dorsal NE pathway. Furthermore, the LC is probably an anatomical substrate for anxiety and intra-LC CRF may enhance memory through its anxiogenic actions.

Solid-state low-loss intracavity saturable absorber for Nd:YLF lasers: an antiresonant semiconductor Fabry-Perot saturable absorber

We introduce a new low-loss fast intracavity semiconductor Fabry-Perot saturable absorber operated at anti-resonance both to start and sustain stable mode locking of a cw-pumped Nd:YLF laser. We achieved a 3.3-ps pulse duration at a 220-MHz repetition rate. The average output power was 700 mW with 2 W of cw pump power from a Ti:sapphire laser. At pump powers of less than 1.6 W the laser self-Q switches and produces 4-ps pulses within a 1.4-micros Q-switched pulse at an approximately 150-kHz repetition rate determined by the relaxation oscillation of the Nd:YLF laser. Both modes of operation are stable. In terms of coupled-cavity mode locking, the intra-cavity antiresonant Fabry-Perot saturable absorber corresponds to monolithic resonant passive mode locking.

[The relationship between weights of fetuses with autosomal trisomies and low maternal serum alpha-fetoprotein]

An association between low maternal serum alpha-fetoprotein (MSAFP) and fetal trisomy has now been thoroughly documented. The mechanisms resulting in low MSAFP are still unclear. In order to determine whether the low values of MSAFP in autosomal trisomies are associated with smaller fetal weights, we compared 11 fetuses with Down syndrome (trisomy 21), 4 with trisomy 18, with 45 normal fetuses. All of them are aborted in the second trimester of pregnancy. No significant difference in the weight distribution between fetuses with Down syndrome and control fetuses was found. In contrast, as compared with the control fetuses, fetuses with trisomy 18 had a significant lower weight distribution. The mean value of MSAFP was 0.72 +/- 0.26 MoM for those with Down syndrome and 0.51 +/- 0.33 MoM for fetuses with trisomy 18; both results being significantly lower than that of normal control (1.01 +/- 0.28). The mean value of amniotic fluid AFP was 0.63 +/- 0.23 MoM for fetuses with Down syndrome. This value was significantly lower than those of the fetuses with trisomy 18 and normal controls (1.02 +/- 0.09 and 1.02 +/- 0.30). A linear relationship between MSAFP and fetal weight was found in normal fetuses at a given gestational age but was not found in trisomy pregnancy. Fetal weight cannot be used to explain the reason for low MSAFP in Down syndrome pregnancy but may partially account for the lower levels noted in fetuses with trisomy 18.

CRF increases protein phosphorylation and enhances retention performance in rats

This study examines the roles of PKC and protein phosphorylation in the retention performance of a passive avoidance learning (PAL) task in rats. Results revealed that H7 injected into the dentate gyrus (DG) of the hippocampus impaired retention in a dose-dependent manner. Corticotropin-releasing factor (CRF) injected into the DG improved retention and this facilitation was antagonized by H7 pretreatment. CRF increased phosphorylation of five proteins, whereas H7 decreased phosphorylation in three of these proteins in both the cytosol and the membrane fractions of hippocampus. These effects were shown not to be associated with stress. These results demonstrate that CRF increased protein phosphorylation associated with enhanced retention of PAL task in rats.

Differential tolerance to the antipentylenetetrazol activity of benzodiazepines in flurazepam-treated rats

Rats were treated for one week with flurazepam (FZP). After an additional two days with no treatment, each rat was injected with one of seven benzodiazepines (BZs). Several different doses of each BZ were evaluated. Ten min later, 100 mg/kg pentylenetetrazol (PTZ) was injected, IP, and convulsive activity was recorded. Rats treated for a week with FZP were tolerant to ataxia induced by each of the seven BZs tested. There was a dose-dependent anti-PTZ effect for each BZ. Whether or not tolerance to the anti-PTZ effect was found depended on the particular BZ used. Tolerance was found for four of the drugs: diazepam, clobazam, flurazepam and desalkylflurazepam. However, no tolerance was found to the anti-PTZ actions of midazolam, triazolam or clonazepam. Brain BZ levels were measured by the ability of brain extracts to displace specifically bound [3H]flunitrazepam in vitro. There was no significant effect of one week of flurazepam treatment. It was proposed that differences among BZs in their interactions with receptors allowed some to circumvent the mechanism responsible for tolerance to the anti-PTZ effect.

Changing trends of forceps delivery in Chang Gung Memorial Hospital

Two hundred and fifty-five patients underwent forceps deliveries in Chang Gung Memorial Hospital from January 1, 1985 to June 30, 1990. There was neither maternal nor perinatal mortality related to this procedure during this period; and the perinatal outcome was good without sequela. In the past three years, cesarean section took the place of forceps delivery in some cases with acute fetal distress and malposition. As a result, maternal problems became the most common indication for forceps delivery during that period. Fourth degree laceration of the perineum was the major maternal complication, occurring in 22.4% of total forceps deliveries. Postpartum voiding problems continued to be another complication after forceps delivery, accounting for 7.0%. Either fourth degree laceration of the perineum or postpartum voiding difficulty could be prevented to a certain extent if the forceps were handled delicately in an experienced hand and there was early diagnosis with prompt management of voiding dysfunction.

Analysis of birth weight and gestational age in Taiwan

Appropriate interpretation of monitored fetal growth throughout pregnancy in individual patients and populations is dependent upon the availability of adequate standards. Previously published standards either were based on small samples, data decades old or were characteristic of foreign subpopulations. We have reviewed the data on a series of 46,575 singleton live births at Chang Gung Memorial Hospital from 1979 to 1989. The ratio of males to females was 1.08. The fetal growth pattern in the third trimester of pregnancy approximates a sigmoid curve. Fetal growth was most rapid from the 32nd to the 37th week of gestation with an average increase of 240 g per week. The birth weight declined beyond 42 weeks' gestation. There were significantly greater weight gains amongst male fetuses as compared to female fetuses from the 34th to the 42nd week of gestation. The mean birth weight recorded at 40 weeks' gestation in male and female newborns was 3,381 g and 3,262 g, respectively. Comparing the birth weight of term pregnancies using our data, with those of a previous, two-decade old report (1945-1967) by Chen, we found that birth weight were slightly higher in this study. The derived fetal growth curves are useful for clinical, public health, and investigational purposes.

The value of cordocentesis in management of patients with severe preeclampsia

Severe preeclampsia affects placental function and causes fetal compromise. It is necessary to deliver the fetus at an appropriate time in order to minimize fetal mortality and morbidity. Cordocentesis was performed in 9 patients with severe preeclampsia (group 1) and 10 patients with other pregnancy complications (group 2). Intrauterine growth retardation occurred in 5 patients in group 1 and in only one patient in group 2. Blood gas parameters including pH, pO2 and O2 saturation were significantly lower for group 1, while pCO2 was significantly higher, as compared to group 2. For patients in group 1, non-invasive fetal surveillance successfully identified 5 patients with fetal compromise, who required immediate termination of pregnancy. All 5 of these patients had abnormal fetal blood gas analyses by cordocentesis. Fetal blood gas analysis was abnormal in 2 additional fetuses among the remaining 4 patients who exhibited normal findings by non-invasive methods of fetal surveillance. These results suggest that cordocentesis is useful in identifying fetal compromise (fetal hypoxia/acidosis) prior to the onset of labor in high-risk patients, such as preeclampsia associated with intrauterine growth retardation.

Regional GABA-stimulated chloride uptake in amygdala kindled rats

gamma-Aminobutyric acid (GABA)-stimulated 36chloride (Cl-) influx into membrane vesicles derived from cerebral cortex, hippocampus, cerebellum and midbrain/brainstem was evaluated in naive rats and amygdala or sham kindled rats. GABA-stimulated 36Cl- uptake was greatest in cortex and hippocampus of naive rats. One week after amygdala kindling, 10 microM GABA-stimulated 36Cl- influx was significantly reduced in each brain region, except midbrain/brainstem, indicating a regional variation in impaired GABAergic function. Midazolam potentiation of GABA-mediated Cl- flux showed a regional variation. The effect of midazolam in kindled rats indicated either an increase in efficiency of GABA/benzodiazepine coupling in areas of reduced GABA function or its ability to restore Cl- channel function to the pre-kindled state.

Pregnancy outcome in patients undergoing long-term hemodialysis

Three uremic patients receiving hemodialysis for more than 5 years became pregnant and proceeded to the third trimester. A variety of complications were noted, including threatened abortion, vanished twin, preterm premature rupture of membranes, polyhydramnios, intra-uterine fetal death, intra-uterine growth retardation, premature labor and hypertension. Two of these 3 mothers gave birth to healthy babies under the management of the high-risk pregnancy team.

Electrophysiological effects of dermorphin on locus coeruleus neurons of rat

Intracellular recording was used to study the effects of dermorphin on neurons of the locus coeruleus in the rat, in a totally submerged brain slice preparation. Dermorphin caused the inhibition of spontaneous firing of all neurons of the locus coeruleus tested, with an IC50 of 7 nM. Based on the inhibition of spontaneous firing rate, dermorphin was 16.5 times more potent than morphine. Larger concentrations of dermorphin (30-100 nM) further hyperpolarized the neurons of the locus coeruleus and simultaneously caused a reduction in input resistance. These effects were antagonized by naloxone, with a dissociation equilibrium constant of 0.8 nM. The hyperpolarization of neurons of the locus coeruleus, caused by dermorphin, was reversed at a membrane potential of -112 mV in this preparation. Furthermore, this hyperpolarization was blocked by cesium chloride and barium chloride. Thus, these data suggest that dermorphin binds to mu-opioid receptors on the cell membrane of neurons of the locus coeruleus. This leads to opening of the inward-going rectification potassium channels, resulting in the observed hyperpolarization of the membrane.

Modulation of GABA-stimulated Cl- flux by a benzodiazepine agonist and an 'inverse agonist' after chronic flurazepam treatment

Rats treated one week with flurazepam were killed while still on the drug or 48 h after termination of drug treatment. The brain 'microsac' preparation derived from the cerebral cortices was used for studying the GABA-stimulated chloride influx. There was no significant change in the basal or GABA-stimulated influx between control and treated groups. However, the effect of flunitrazepam to enhance 10 microM GABA-stimulated influx was significantly reduced, indicating tolerance. Methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3- carboxylate (DMCM), an 'inverse agonist' at benzodiazepine receptors, dose dependently inhibited 50 microM GABA-stimulated influx; chronic treatment did not alter the effect of DMCM. This study demonstrates that one week treatment with flurazepam produces tolerance to benzodiazepines without any change in the effect of GABA or DMCM. This indicates that GABA and benzodiazepine sites are differently modulated after chronic treatment with benzodiazepines. However, since both benzodiazepine and DMCM act on the same receptors it appears that the different 'domains' on the benzodiazepine receptor are differently altered during chronic treatment.

Tolerance to diazepam and methyl-beta-carboline-3-carboxylate measured in substantia nigra of benzodiazepine tolerant rats

The spontaneous activity of neurons in the pars reticulata of substantia nigra (SNpr) was studied in chloral hydrate anesthetized rats. As a function of dose, intravenous diazepam decreased, and methyl-beta-carboline-3-carboxylate (beta CCM) increased discharge frequency. Two days after terminating a one week treatment with flurazepam (FZP), both diazepam and beta CCM showed decreased ability to alter SNpr neuronal activity. Neither residual FZP nor down-regulation of benzodiazepine receptors can account for these results. In contrast, behavioral testing revealed no change in the ability of i.v. beta CCM to cause convulsions, suggesting that sites other than the SNpr are of prime importance in expressing the convulsant actions of systemically injected beta CCM.

Selective continuation in quadruplets pregnancy following treatment of GIFT plus IVF and ET

In this report, we present the selective reduction of quadruplets to triplets by transabdominal ultrasound guided cardiac puncture and injection of 1% xylocaine and air. This treatment resulted in the successful continuation of pregnancy until premature labor developed at the 33th week. Alive births of a normal male and a normal female infant, and a dead female infant were delivered.

Perinatal outcome of chorionic villus sampling versus amniocentesis

This study assesses the relative risks of first trimester transcervical chorionic villus sampling (CVS) versus midtrimester amniocentesis performed between April 1986 and March 1988. The most common indication for prenatal diagnosis was advanced maternal age. We discovered 5.1% chromosomal aberrations in CVS compared to 1.0% in amniocentesis. Bleeding was the most frequent early complication, and only 1 case had major hemorrhage with subsequent spontaneous abortion. The fetal loss rate (gestational age less than 28 weeks) was 4.5% in CVS versus 1.2% in amniocentesis, which was not significantly different from the background fetal loss rate reported in normal pregnancies after an 8-week gestational age. Three cases of fetal loss after CVS were probably procedure-related; 1 case had spontaneous abortion and 2 cases had chorioamnionitis. Therefore, we considered that the causal relationship between CVS and the infection was highly probable. The clinical pregnancy outcome indicated that there were no differences in overall perinatal mortality, Apgar score, body weight, body length, gestational age at delivery, intrauterine growth retardation, placenta weight and placental disorders between the CVS group and the amniocentesis group. The pregnancies did not reveal any specific effects of the prenatal diagnostic procedure, but a long-term pediatric follow-up is needed.

Regional GABA/benzodiazepine receptor/chloride channel coupling after acute and chronic benzodiazepine treatment

GABA/benzodiazepine coupling was evaluated in 8 regions of rat brain by the ability of GABA to stimulate 0.5 nM [3H]flunitrazepam binding. Rats were treated acutely with diazepam (p.o) or chronically with flurazepam, offered in the drinking water for 4 weeks, and compared to a pair-handled vehicle-treated control group. Regional variations in GABA/benzodiazepine coupling were found in control membranes. GABA increased benzodiazepine binding maximally (40%) in cerebellum and medulla, and least (25%) in olfactory bulb. A significant decrease in the effect of GABA was found in cortex of chronically treated rats immediately after, but not 2 days following treatment. The Emax for GABA stimulation of [3H]flunitrazepam binding was significantly increased in medulla after acute treatment but was not altered after acute or chronic treatment in other brain areas evaluated. Treatment had no effect on the ability of bicuculline to inhibit [3H]flunitrazepam binding in cortex. Benzodiazepine/Cl- coupling in cortex or hippocampus of acutely and chronically treated rats, evaluated by the ability of Cl- to stimulate specific [3H]flunitrazepam binding, was not changed. The results support the hypothesis that a functional uncoupling of the benzodiazepine recognition site from the GABA receptor in cortex, but not from the anion recognition site, may play a role in tolerance development.

Tolerance to anticonvulsant effects of diazepam, clonazepam, and clobazam in amygdala-kindled rats

Benzodiazepines are effective anticonvulsants, but long-term clinical usefulness is limited by development of tolerance. Tolerance to the actions of three prototype anticonvulsant benzodiazepines (BZDs)--diazepam (DZP), clonazepam (CZP), and clobazam (CLB)--was studied in amygdala-kindled rats. Fully kindled rats were dosed three times daily for 2 or 4 weeks. Amygdala stimulation was given 30 min after drug administration on days 1, 2, 3, 5, and 7 of chronic treatment and then three times weekly. During treatment, tolerance was observed as a loss of drug effect to suppress behavioral and EEG manifestations of seizure activity. Seizure activity remained stable in rats treated with vehicle. Tolerance to the anticonvulsant effects developed most rapidly during CLB treatment and most slowly during CZP treatment. Tolerance to the motor impairment caused by the drugs developed more rapidly. Assay of the amount of drug in brain extracts, using a BZD receptor assay, showed that tolerance was functional, not metabolic. Doubling the dose did not readily restore full anticonvulsant activity. The response to amygdala stimulation 24 h after treatment was stopped showed no residual BZD effect, but there was a rebound in duration of some seizure measures in rats that had been treated with CLB or DZP. Retesting 48 h after treatment was stopped showed that rats were still tolerant. The amygdala-kindled rat is a reliable and sensitive model for studying long-term actions of anticonvulsant BZDs.

[Incidental myomectomy in cesarean section]

In the retrospective study, from January 1984 to December 1987, incidental myomectomy was performed on 47 patients who received cesarean section. The control group consisted of 80 random samples who received cesarean section during the same period. The general information in both groups was similar. Postoperative infection rate was similar in both groups. Myomectomy added 11 minutes to the operation time, 112 milliliter to the operation blood loss and extended the hospital stay about one and a half day. Recovery of gastrointestinal tract function was one hour later in myomectomy group. There were no wound infection or serious morbidity in both groups. In order to estimate the value of incidental myomectomy in cesarean section, a further study of long term change of the myoma should be considered.

A comparison of the anticonvulsant effects of 1,4- and 1,5-benzodiazepines in the amygdala-kindled rat and their effects on motor function

Studies suggest that the 1,5-benzodiazepine clobazam possesses a favorable anticonvulsant profile due to its minimal neurotoxicity. The anticonvulsant and motor impairment effects of clobazam and 2 1,4-benzodiazepine, diazepam and clonazepam, were compared by dose-response analysis in amygdala-kindled rats and on 3 tests of motor function: gross motor impairment, a vertical screen test, and muscle tone. All drugs produced a significant, dose-dependent decrease in the duration of both behavioral and electrographic kindled seizure measures. Forelimb clonus suppression was the most sensitive measure of anticonvulsant drug effect. The order of potency for all effects was clonazepam greater than diazepam greater than clobazam. ED50s for the benzodiazepines' effects on motor impairment were compared to their ability to protect rats from forelimb clonus. Different spectrums of action for the various benzodiazepines were found depending on the comparison measure. Clonazepam had the most favorable ratio of potency for anticonvulsant vs. motor impairment activity when ataxia rating was the comparison measure. Diazepam had the most advantageous profile when the more sensitive screen test was used for comparison. Clobazam was not found to have a superior spectrum of action when compared across these measures. The results emphasize the importance of dose-response analyses and the consideration of behavioral measures used to assess beneficial and adverse effects of anticonvulsants.

Photoaffinity labeling of [3H]flunitrazepam- and [3H]Ro15-4513-bound pellets in rat cerebral cortex and cerebellum

Irreversible incorporation of [3H]flunitrazepam and [3H]Ro15-4513 into GABA/benzodiazepine receptor subunits was studied by UV irradiation using ligand-bound membrane pellets from rat cerebral cortical and cerebellar synaptic membranes. Specific incorporation for [3H]flunitrazepam was greater in the pellet than in the suspension. The incorporation was identical for [3H]Ro15-4513 in both pellet and suspension. With the ligand-bound pellets, 50% of the available binding sites were photolabeled by both ligands in cortex and cerebellum. SDS polyacrylamide gel electrophoresis and fluorography of [3H]flunitrazepam photo-labeled receptor revealed the same number of major sites in both brain regions. In contrast, [3H]Ro15-4513 appears to label fewer sites in cortex and cerebellum. Photoaffinity labeling with [3H]flunitrazepam in ligand-bound membrane pellet provides a more selective and reliable method for studying the subunit structure of GABA/benzodiazepine receptor complex.

Biosyntheses of galactosyl lipids and polysaccharide in Streptococcus mutans

The syntheses of galactosylphospholipids and a galactose-containing polymer were observed when radio-labeled UDP-galactose was incubated with the membrane enzymes prepared from a strain of Streptococcus mutans, FA-1. The lipids were resolved into two components, lipids-1 and -2, by thin-layer and DEAE-cellulose column chromatographies. In the latter chromatography, lipid-1 was eluted by 0.0075 M and lipid-2 by 0.18 M ammonium acetate. The syntheses of lipids-1 and -2 were strongly inhibited by UDP and UMP, respectively. Both lipids-1 and -2 were degraded by mild acid, but were stable to mild alkaline hydrolysis. These results, together with their mobilities on thin-layer chromatography, suggest that lipid-1 is a galactosylphosphorylundecaprenol, and lipid-2 is a galactosylpyrophosphorylundecaprenol. When UDP-galactose was incubated with radiolabeled undecaprenol and ATP in the presence of membrane enzymes, lipids with thin-layer chromatographic mobilities of lipid-1 and lipid-2 were observed. The phosphate-to-galactose ratios in lipid-1 and lipid-2 were determined to be 1:1 and 2:1, respectively. These results indicated that lipid-1 and lipid-2 formed are galactosylmonophosphorylundecaprenol and galactosylpyrophosphorylundecaprenol, respectively. The polymer formed was eluted from the DEAE-cellulose column with a low concentration of salts (less than 0.1 M), suggesting that it is probably a polysaccharide, but not a lipoteichoic acid or teichoic acid-type polymer. In order to identify the sugars present in the polymer synthesized, the polymer purified by Sephadex G-50 and DEAE-cellulose column chromatographies was subjected to acid hydrolysis followed by NaB3H4 reduction and paper chromatographic analysis. [3H]Galactitol and a small amount of [3H]galactosaminitol were detected. This result suggests that the polymer is a nascent polysaccharide containing mainly galactose and a small amount of galactosamine, which probably derived from N-acetylgalactosamine during acid hydrolysis of the polymer.

Modulation of GABA-gated chloride ion flux in rat brain by acute and chronic benzodiazepine administration

gamma-Aminobutyric acid (GABA)-gated Cl- influx was studied in rat brain "microsacs." Midazolam caused a shift to the left of the GABA log dose-response curve. Pentobarbital produced a similar shift plus an increase in maximum response. Diazepam, flurazepam and desalkylflurazepam also enhanced GABA-gated Cl- flux. Their effects were blocked by Ro15-1788, a benzodiazepine antagonist. Acute diazepam pretreatment caused a shift to the left of the GABA dose-response curve but had no effect on the ability of benzodiazepines or pentobarbital to increase GABA-gated Cl- influx. In rats made tolerant by 4 weeks of flurazepam treatment, there was no decrease in the ability of GABA to mediate Cl- flux. GABA was more potent in microsacs from nonwithdrawn rats. In rats withdrawn for 12 but not 48 hr, the maximum GABA response was increased. The ability of benzodiazepines and of pentobarbital to enhance GABA-gated Cl- influx was reduced, showing tolerance. However, 2 days after withdrawal from chronic treatment, this was no longer statistically significant. The results show that benzodiazepine tolerance involves reduced functional coupling between the benzodiazepine recognition site and the GABA recognition site-Cl- channel. Furthermore, reduced effectiveness of GABAA agonists in benzodiazepine-tolerant animals might result from alterations in neuronal activity that occur subsequently to activation of the GABA receptor-gated anion channel.

Effects of chronic flurazepam treatment on firing rate of rat substantia nigra pars reticulata neurons

The effect of a benzodiazepine, flurazepam, on the spontaneous activity of neurons in the pars reticulata of the substantia nigra was studied in chloral hydrate anesthetized rats. Flurazepam produced a dose-related suppression of neuronal activity. In rats that were chronically treated with flurazepam, tolerance to flurazepam was present after 7 and 28 days, but not after only 3 days of treatment. Tolerance persisted at least 2, but not 7 days after 4 weeks of chronic treatment.

A comparison of the effects of midazolam and pentobarbital on the dose-response of GABA-gated Cl- influx in rat brain microsacs

gamma-Aminobutyric acid (GABA)-gated Cl- influx was studied in a rat brain 'microsac' preparation. Midazolam (a benzodiazepine), at 0.1-10 microM, increased GABA potency (maximum 2-fold) without affecting its efficacy or exerting GABA-mimetic effect. Pentobarbital (10-500 microM) increased GABA potency (maximum 12-fold) and efficacy (maximum 40%). Pentobarbital exhibited GABA-mimetic effect at concentrations above 200 microM. The differential effects of midazolam and pentobarbital in modulating GABA-mediated responses may account for some of the differences between these two classes of drugs.

Experience with fully bioresorbable aortic grafts in the dog

Reorganization of the arterial wall through natural processes on the resorption of a totally bioresorbable graft was investigated in dogs with Vicryl prostheses coated with two different blends of bioresorbable polyesters capable of slowing down considerably the disintegration of a Vicryl fabric in vivo. The prostheses (8 to 9 mm in internal diameter, 8 to 10 cm long) were implanted in the infrarenal aortic position for up to 24 weeks. All 18 animals implanted with coated prostheses survived, whereas one animal implanted with an uncoated Vicryl prosthesis died because of early rupture of the graft. Patent tubular conduits were present in 14 animals at the time of retrieval. On resorption of the synthetic polymers, the tissue layers that formed on both sides of the prosthetic material either fused or remained separated, depending on the polymer used as a retardant coating. We conclude that polymer composition influences the repair process and that a fully resorbable vascular graft can function effectively in a canine model, provided that tissue organization is sufficiently advanced by the time the prosthesis has lost its mechanical integrity. Further studies are needed to document the performance of the newly formed blood conduit over extended periods, in hypertensive subjects, and when presented with a bacterial challenge.