Biomedical subjects

D L Walker

Publications and source records attributed to D L Walker.

At least 37 records · Page 2Linked to original sources

PubMed1997

Influence of estradiol and progesterone withdrawal on the secretion of and the temporal correlation between pulses of oxytocin and prostaglandin F2(alpha) in ewes.

The primary objective was to examine the effects of estradiol and the progesterone receptor antagonist onapristone on the pulsatile secretion of prostaglandin F(2alpha) (PGF(2alpha)) and ovarian and pituitary oxytocin. A 2 x 2 factorial arrangement of estradiol and onapristone treatments was administered to groups of 5 ewes after destruction of ovarian follicles on Day 8 of the cycle. Estradiol treatments consisted of the administration of a silicone elastomer implant, either containing or not containing estradiol, on Day 8 plus 50 microg of estradiol or corn oil on Days 11 and 12. Onapristone (2 mg/kg) or its vehicle were administered on Day 13, immediately preceding the simultaneous collection of blood samples from the carotid artery, jugular vein, and vena cava at 7.5-min intervals for 7 h. Ewes were immediately killed for measurements of uterine oxytocin receptor concentrations and phosphatidylinositide turnover. More oxytocin pulses were detected in the jugular vein than in the carotid artery (p < 0.01), suggesting that the pituitary is a source of oxytocin. A similar number (p > 0.1) of PGF(2alpha) pulses were correlated with oxytocin pulses as were not. The linked PGF(2alpha) pulses were longer in duration (p = 0.01) with a tendency toward a higher amplitude (p = 0.08). The corresponding vena caval oxytocin pulses had a longer duration (p = 0.02) than those not linked to PGF(2alpha). Estradiol increased oxytocin receptor concentrations and the turnover of phosphatidylinositides (p = 0.02) without affecting PGF(2alpha) pulse characteristics. Onapristone increased (p = 0.03) PGF(2alpha) pulse amplitude. Although a lower than expected temporal correlation between oxytocin and PGF(2alpha) pulses was observed, the distinguishing characteristics of linked pulses may be indicative of their physiological significance.

Animals↗

PubMed1996

Preclinical pharmacology of ecteinascidin 729, a marine natural product with potent antitumor activity.

Ecteinascidins are marine natural products with potent antiproliferative activity under evaluation as chemotherapeutic agents by the National Cancer Institute. Ecteinascidins bind the minor groove of DNA and may form covalent adducts with DNA by binding the N-2 of guanine in a fashion similar to saframycin antibiotics. The most potent ecteinascidin is ET-729 with antitumor activity observed following administration of 3.8 and 10 micrograms/kg to mice bearing P388 leukemia and B16 melanoma, respectively. A reverse-phase high-performance liquid chromatography (HPLC) assay and an L1210 cell bioassay were developed for ET-729 and utilized for stability and murine pharmacokinetic studies. HPLC analysis showed that ET-729 was stable in organic solvents, mobile phase and acidic buffer (t1/2 > 100 h). Stability was diminished under neutral and basic conditions (t1/2 < 14 h). Following a 48-h incubation with L1210 cells in growth medium in the absence and presence of 2.5% murine plasma, the 50% growth inhibitory concentrations (IC50) of ET-729 were 37 and 72 pM, respectively. Following intravenous administration of ET-729 to male CD2F1 mice, the disappearance of antiproliferative activity determined by the bioassay was described by a two-compartment open model. The mean values of the elimination half-life and plasma clearance were 28 min and 39.7 ml/min per kg, respectively. Following intraperitoneal administration, peak plasma concentrations of antiproliferative activity were observed 6-15 min after injection and antiproliferative concentrations remained above 1 nM for longer than 1 h. Intraperitoneal bioavailability varied over a wide range (20-91%). Antiproliferative activity was detected in every urine sample following intravenous and intraperitoneal administration, but the total 48-h urinary recovery was less than 0.1%.

Animals↗

PubMed1995

Transactivation of LAP/NF-IL6 is mediated by an acidic domain in the N-terminal part of the protein.

LAP/NF-IL6 is a member of the C/EBP family of transcriptional activators and has been shown to be involved in the regulation of the acute-phase response. We have previously shown that phosphorylation of the liver-enriched transcriptional activator protein (LAP) Ser-105 enhances the activation of LAP-dependent genes. To identify the region which is important for gene activation, a series of LAP mutants were constructed, and domain swapping experiments with the DNA-binding domain of GAL4 were performed. These experiments point to an acidic region located between amino acids 21 and 105 of LAP/NF-IL6 which activates genes independent of the DNA-binding domain and the leucine zipper of LAP/NF-IL6. Computer-assisted predictions reveal two regions, a helical and a hydrophobic region in the transactivation domain, which could be important in mediating the direct interaction with the basal machinery. Site-directed mutagenesis of acidic residues in both regions demonstrates that the hydrophobic region located between amino acids 85 and 95 is the likely motif for the interaction with the basal machinery. Our results demonstrate that a hydrophobic region in the acidic transactivation domain of LAP/NF-IL6 seems to be relevant in mediating gene activation of LAP-dependent genes.

Base Sequence↗

PubMed1995

Development and experience of a university-based, freestanding birthing center.

OBJECTIVE: To describe our experience with a freestanding birthing center established in conjunction with a university medical center, and to determine the safety and effectiveness of such a program. METHODS: The University of California Irvine Medical Center opened a freestanding birthing center 2 miles from the hospital. The unit provides prenatal, labor, delivery, postpartum and well-baby care 24 hours/day. All direct patient care is provided by certified nurse-midwives. Data were collected prospectively to provide a descriptive account and to evaluate maternal and perinatal morbidity and mortality to determine the safety and efficacy of this approach. RESULTS: During the first 20 months of operation, the University of California Irvine Birthing Center cared for 1830 patients. Approximately 90% were indigent, 85% were Hispanic, and 35% were nulliparas. Of the total patients, 12% were transferred antenatally for high-risk conditions and 19% were transferred intrapartum. The cesarean rate for all patients was 10% (6.5% for those whose intrapartum care began at the birthing center). The perinatal mortality rate was six per 1000. Neonatal morbidity rates, neonatal intensive care unit admissions, and maternal complications were not greater than expected. CONCLUSION: The first 20 months of experience with a university-based, freestanding birthing center suggests that this alternative is safe for delivering obstetric and newborn care to low-risk patients.

Adolescent↗

PubMed1994

Intra-amygdala kinase inhibitors disrupt retention of a learned avoidance response in rats.

To assess the involvement of intra-amygdala kinase activity in aversively motivated learning, rats received intracranial injections of polymixin B sulfate (PMXB)--a protein kinase C (PKC) and calcium/calmodulin-dependent kinase II inhibitor--immediately after inhibitory avoidance training. When tested 48 h later, retention was significantly impaired relative to vehicle-injected controls. Delayed injections (2 h posttraining) and injections made dorsal to the amygdala were ineffective. Immediate posttraining injections of the more selective PKC inhibitor, NPC 15437, also impaired retention. These results suggest that intra-amygdala protein phosphorylation must occur soon after training for learned avoidance responses to be successfully retained.

Amygdala↗

PubMed1994

Preclinical pharmacology of bizelesin, a potent bifunctional analog of the DNA-binding antibiotic CC-1065.

Bizelesin (NSC-615291), a potent, bifunctional analog of the cyclopropylpyrroloindole antitumor antibiotics CC-1065 and adozelesin, has been selected by the National Cancer Institute for evaluation as a potential chemotherapeutic agent. All three compounds bind to and alkylate DNA at the N-3 position of adenine in a sequence-selective manner. Bizelesin is unique among the analogs with bifunctional alkylating capability due to two chloromethyl moieties that are converted to the cyclopropyl alkylating species that interact with DNA. A reverse-phase high-performance liquid chromatography (HPLC) assay and an L1210 cell bioassay were developed for bizelesin and subsequently applied to stability and murine pharmacokinetics studies. Following 48 h of incubation with L1210 cells the 50% growth-inhibitory concentrations (IC50) of bizelesin, adozelesin, and CC-1065 were 2.3, 3.4, and 88.1 pM, respectively. Bizelesin was stable in organic solvents but was less stable in aqueous solutions, with the half-life values obtained in buffers at pH 4, 7, and 10 being 9.6, 2.1, and < 1 h, respectively. By HPLC analysis, bizelesin degradation was associated with the appearance of two peaks, the mono- and dicyclopropyl derivatives formed by base-catalyzed intramolecular alkylation of the chloromethyl groups. Bizelesin and the dicyclopropyl derivative were equipotent in the L1210 cell bioassay. Following i.v. administration of bizelesin (15 micrograms/kg) to male CD2F1 mice, the plasma elimination of cytotoxic activity determined with the bioassay was described by a two compartment open model; the alpha-phase (t1/2 alpha) and beta-phase (t1/2 beta) half-lives, steady-state volume of distribution (VSS), and total body clearance (ClTB) were 3.5 min, 7.3 h, 7,641 ml/kg, and 16.3 ml min-1 kg-1, respectively. The systemic drug exposure following i.p. administration was at least 10 times lower than that resulting from i.v. infusion. Following i.v. or i.p. administration the recovery of material in urine was < 0.1% of the delivered dose.

Alkylating Agents↗

PubMed1994

Intrahippocampal administration of both the D- and the L-isomers of AP5 disrupt spontaneous alternation behavior and evoked potentials.

We previously reported that systemically administered N-methyl-D-aspartate (NMDA) antagonists significantly impair spontaneous alternation behavior. Others have reported that the restricted blockade of hippocampal NMDA receptors disrupts performance on different tests of spatial learning and have suggested that the resulting impairments are attributable to a disruption of endogenous NMDA-dependent long-term potentiation (LTP). In the present study, we determined whether spontaneous alternation performance was disrupted by circumscribed blockade of hippocampal NMDA receptors as well as by a second class of compounds which disrupt LTP, protein kinase inhibitors. The effect of hippocampal NMDA blockade on inhibitory avoidance was also examined insofar as this behavior too is disrupted by systemically administered NMDA antagonists. When injected into the hippocampus 15 min prior to spontaneous alternation testing, the NMDA antagonists CPP and D,L-AP5 each decreased alternation rates. The specific protein kinase C (PKC) inhibitor, NPC 15437, also disrupted spontaneous alternation, whereas the more general kinase inhibitor, PMXB, did not. When injected 15 min prior to inhibitory avoidance training, CPP also impaired inhibitory avoidance learning as assessed during a subsequent test session, 48 h later. Interpretation of these data was complicated by the additional findings that intrahippocampal infusion of L-AP5 (which is inactive with respect to NMDA receptors) also disrupted alternation performance, and that both the D- and the L-isomers of AP5 as well as each kinase inhibitor dramatically disrupted evoked responses (i.e., population spike amplitude, spike latency, and EPSP slope), as recorded in the dentate gyrus and evoked by perforant path stimulation. These data indicate that behaviorally effective doses of AP5 may have effects which extend beyond NMDA blockade. Moreover, the effects of these compounds on hippocampal transmission, in general, suggest that attribution of the amnestic consequences of their administration to impaired LTP may be unwarranted.

2-Amino-5-phosphonovalerate↗

PubMed1993

Maturational asynchrony between oocyte cumulus-coronal morphology and nuclear maturity in gonadotropin-releasing hormone agonist stimulations.

OBJECTIVE: To determine oocyte meiotic maturity and asynchrony between cumulus-coronal morphology and nuclear maturity after gonadotropin-releasing hormone agonist (GnRH-a) and norethindrone-programmed stimulations. DESIGN: Oocyte meiotic maturity was evaluated at follicular aspiration in 4,961 oocytes after GnRH-a/follicle-stimulating hormone (FSH)/human menopausal gonadotropin stimulations (hMG) for in vitro fertilization patients and 299 oocytes after norethindrone-programmed clomiphene citrate (CC)/hMG in oocyte donors. Maturational asynchrony between the oocyte's cumulus-coronal morphology and nuclear maturity was evaluated in 2,336 oocytes. SETTING: In vitro fertilization program at the University of Iowa Hospitals and Clinics; academic tertiary care center. INTERVENTIONS: After evaluating oocyte cumulus-coronal maturity, cumulus masses were spread to determine oocyte nuclear maturity. RESULTS: Fourteen percent, 17%, 50%, 17%, and 2% of oocytes were prophase I, metaphase I, metaphase II, postmature metaphase II, and atretic, respectively. Asynchrony was noted in 28% of prophase I, 71% of metaphase I, 11% of metaphase II, 45% of postmature metaphase II, 32% of atretic, and 28% of all oocytes. Significant differences were not found between GnRH-a and norethindrone-programmed stimulations in asynchrony between cumulus-coronal morphology and nuclear maturity or percentage of prophase I, metaphase I, metaphase II, postmature metaphase II, or atretic oocytes. Sixty-seven percent of oocytes possessed a polar body at retrieval. The rate of fertilization was significantly higher for metaphase II oocytes than postmature metaphase II and metaphase I oocytes > prophase I oocytes. Parthenogenetic activation tended to be highest for postmature metaphase II oocytes. Embryo cleavage was significantly higher for postmature metaphase II, metaphase II, and metaphase I oocytes than for prophase I oocytes. CONCLUSIONS: This is the first report of asynchrony between cumulus-coronal morphology and nuclear maturity at follicular aspiration in GnRH-a and norethindrone-programmed stimulations. Asynchrony was observed in 28% of oocytes. A higher percentage of oocytes possessed a polar body at egg retrieval with these stimulation regimens compared with rates reported previously for FSH, FSH/hMG, and CC/hMG stimulations.

Cell Cycle↗

PubMed1993

Conditions of oocyte storage and use of noninseminated as compared with inseminated, nonfertilized oocytes for the hemizona assay.

OBJECTIVES: To examine differences in sperm binding to the zona and recovery of oocytes from the storage vessel after oocyte preservation for the hemizona assay (HZA) by the method currently in predominant use, salt storage at 4 degrees C, as compared with a new method that should allow for indefinite preservation of zona receptors, dimethylsulphoxide (DMSO)/sucrose in liquid nitrogen (-196 degrees C). A second objective was to compare sperm binding to noninseminated zona as opposed to zona from inseminated, nonfertilized oocytes and to examine whether differences in binding potential were related to the patient's fertilization rate from the cycle in which the oocytes for the HZA originated. DESIGN: Binding and recovery were evaluated after 1, 2, 3, 6, 9, 12, and 17 to 25 months of storage. SETTING: In vitro fertilization and andrology laboratories at the University of Iowa Hospitals and Clinics; academic tertiary care center. RESULTS: Binding of sperm was significantly lower for nonfertilized oocytes stored > 12 months in salt at 4 degrees C than for those stored in liquid nitrogen. Binding was similar after storage for 1, 2, 3, 6, 9, and 12 months. Oocyte recovery was significantly lower after storage in salt for > 12 months as compared with storage in liquid nitrogen. Greater variability in sperm binding was observed between matching zona halves of nonfertilized as compared with noninseminated oocytes. Nonfertilized oocytes also bound fewer total sperm than noninseminated oocytes. The number of sperm bound to noninseminated oocytes was not related to the patient's fertilization rate from the cycle in which the oocytes originated. However, significantly fewer sperm bound to the zona of nonfertilized oocytes when the oocyte originated from a cycle in which the patient's fertilization rate was > 50%. CONCLUSIONS: These results indicate that storage of oocytes in DMSO/sucrose in liquid nitrogen results in superior long-term (> 12 months) preservation of zona receptors for sperm binding and improves oocyte recovery as compared with salt storage at 4 degrees C. Although noninseminated oocytes appear to be optimal for use in the HZA, nonfertilized oocytes can be used successfully if the oocytes originate from an IVF cycle in which the fertilization rate is < or = 50%.

Adult↗

PubMed1992

Prediction of nuclear maturity from cumulus-coronal morphology: influence of embryologist experience.

PURPOSE: A majority of in vitro fertilization (IVF) programs continues to evaluate oocyte maturity on the basis of cumulus-coronal morphology (CCM) even though marked asynchrony has been reported between CCM and nuclear maturity. This study was designed to examine changes in embryologists' ability to correctly predict nuclear maturity from CCM as a function of increasing experience. Nuclear maturity was assessed by inverted microscopy with a modified spreading technique at follicular aspiration. A second objective was to determine the percentage of oocytes which displayed asynchrony between CCM and nuclear maturity as assessed by embryologists with extensive experience in oocyte maturity evaluation. RESULTS: The three participating embryologists had directly evaluated 1304, 75, and 0 oocytes for nuclear maturity and CCM at study initiation and correctly predicted nuclear maturity from CCM in 74, 64, and 47% of oocytes, respectively. Embryologist 1 did not significantly change in predictive ability during the 17-month study period. Embryologist 2 significantly improved in predictive ability during the first 9 months of the study (841 oocytes evaluated) and plateaued thereafter, at a similar percentage of correct predictions as embryologist 1. Embryologist 3 continued to improve in predictive ability throughout the study period, reaching 61% correct predictions at the close of the study after evaluating 223 oocytes. Once embryologists had plateaued in their predictive ability, 72% of oocytes evaluated received the correct nuclear maturity classification based on CCM. Significantly fewer oocytes (54%; 375/690) evaluated by embryologists who had not plateaued in their predictive ability received the correct nuclear maturity classification based on CCM. CONCLUSIONS: These results indicate that embryologists' ability to predict oocyte nuclear maturity correctly from CCM continues to change over several months even when pretraining video recordings are used before beginning direct evaluations. After embryologists plateaued in their predictive ability, nuclear maturity still could not be correctly predicted from CCM in 28% of oocytes due to asynchrony between nuclear and CCM maturity. Based upon this, circumstances in which the spreading technique should be used for direct assessment of nuclear maturity as opposed to assessment of CCM only are discussed.

Cell Differentiation↗

PubMed1992

Sleep deficits in rats after NMDA receptor blockade.

N-Methyl-D-aspartate (NMDA) receptor blockade disrupts a variety of functions associated with neural plasticity, including acquisition of learned responses and long-term potentiation. Deficits in memory are significantly correlated with deficits in measures of paradoxical sleep in several amnesic populations. The present experiment therefore assessed whether NPC 12626, a competitive NMDA receptor antagonist, also disrupts sleep. NPC 12626 (1, 10, 50, and 100 mg/kg) or saline was administered to Sprague-Dawley rats 30 min prior to 3-h daytime recording periods. Paradoxical sleep was selectively impaired at all but the highest dose, which prevented all sleep during the recording period. Some deficits in nonparadoxical sleep first appeared at the 10 mg/kg dose but did not became prominent until the 50 mg/kg dose. The results thus show that NPC 12626 impairs sleep states in rats and demonstrate that paradoxical sleep is particularly susceptible to the effects of NMDA receptor blockade. These findings, along with previous evidence that NMDA antagonists impair waking measures of arousal, provide evidence that all sleep-wake states are impaired by NMDA receptor blockade. More generally, the results suggest that some brain mechanisms underlying sleep and memory may share common elements.

Amino Acids↗

PubMed1992

Impairment of spontaneous alternation performance by an NMDA antagonist: attenuation with non-NMDA treatments.

N-Methyl-D-aspartate (NMDA) receptor antagonists disrupt learning on a variety of tasks. Previous findings indicate that glucose, naloxone, and physostigmine ameliorate learning deficits produced by several treatments. The present experiment examines whether these agents also reverse the amnestic effects of NMDA receptor blockade. Mice were tested for spontaneous alternation performance in a Y-maze. The animals received either saline or the NMDA antagonist, NPC 12626 (35 mg/kg, IP), 50 min prior to testing and received an additional injection of saline, glucose, naloxone, or physostigmine 30 min prior to testing. NPC 12626 significantly decreased alternation scores. Glucose (250 mg/kg), physostigmine (0.01 mg/kg), and naloxone (1 mg/kg) reversed the effects of NPC 12626. Thus, impairments of learning after NMDA receptor blockade share with other amnestic conditions the susceptibility to attenuation by glucose, naloxone, and physostigmine.

Amino Acids↗

PubMed1991

Effects of the novel NMDA antagonist, NPC 12626, on long-term potentiation, learning and memory.

NPC 12626 (2-amino-4,5-(1,2-cyclohexyl)-7-phosphonoheptanoic acid), a newly developed drug which crosses the blood-brain barrier, is a competitive antagonist of N-methyl-D-aspartate receptors. In Experiment I, the effects of NPC 12626 on perforant path - dentate gyrus LTP were tested. NPC 12626 (100 mg/kg, i.p.), injected 150 min prior to tetanization, prevented potentiation of the EPSP slope and population spike amplitude. EPSP-spike potentiation was also prevented. Post-tetanus administration was ineffective. In Experiment II, mice were injected with NPC 12626 (35 mg/kg, i.p.) or saline 35 min prior to spontaneous alternation testing. NPC 12626 significantly decreased alternation rates, but did not affect turn bias or the mean delay between arm entries. This pattern of results may reflect impaired learning or memory. In Experiment III, mice were tested on an inhibitory avoidance task. NPC 12626 (35 mg/kg, i.p.), administered before but not after training, significantly impaired performance. When the drug was administered before training as well as before testing, performance was similarly impaired, indicating that the observed deficits were not attributable to state-dependent learning. Pre-test injections were ineffective. Overall, these results support the hypothesis that some forms of learning require the participation of NMDA receptors and that this participation is largely limited to acquisition processes. In addition, these results point to the utility of peripherally administered NPC 12626 as a tool with which to examine the involvement of NMDA receptors in LTP and learning.

Amino Acids↗

PubMed1991

Treatment of severe male-factor infertility with high concentrations of motile sperm by microinsemination in embryo cryopreservation straws.

A microinsemination technique was evaluated for treating our program's most severe cases of male-factor infertility. Oocytes were inseminated with high concentrations of motile sperm (1 to 9 x 10(6)/ml) in 10 to 150 microliters within embryo cryopreservation straws. Fertilization was obtained in 20 of 29 (69%) couples treated by this technique. In the 15 patients in which only embryos generated from the straw technique were transferred, 7 clinical pregnancies resulted (46.7% per transfer). The implantation rate for couples receiving embryos from the straw technique only (12/58; 20.7%) compared favorably to that observed for other cases treated during this same time period with regular insemination techniques (111/766; 14.5%). Clinical pregnancy rates per transfer for IVF-ET, TET, and PROST were 33.0% (1/3), 0% (0/2), and 60.0% (6/10), respectively. The percentage of polyploidic embryos was significantly lower (P less than 0.0001) for male-factor patients treated by the straw technique with high sperm concentrations than for non-male-factor patients treated during this same time period with standard sperm concentrations. Normal births have resulted from straw inseminations with 3.4 x 10(6) and ongoing pregnancies with 5.0 x 10(6) motile sperm/ml. The results of this study suggest that some cases of male-factor infertility can be successfully treated by insemination with high concentrations of motile sperm in embryo cryopreservation straws. A technique of centrifuging sperm in straws was also developed to concentrate the entire fraction of washed sperm into 10 microliters. Further development of this technique may allow treatment of more severe cases of oligo/asthenospermia by microinsemination with high concentrations of motile sperm than is presently possible with standard washing techniques.

Adult↗

PubMed1991

Naloxone modulates the behavioral effects of cholinergic agonists and antagonists.

Peripheral glucose administration enhances memory in rodents and humans. Recent findings suggest that glucose may affect behavior, in part, by augmenting central cholinergic functions and by attenuating central opiate functions. The present experiments examined interactions between an opiate antagonist, naloxone, and cholinergic agents to determine whether the effects would parallel those found with glucose. Three behavioral measures were assessed: tremors, hyperactivity, and spontaneous alternation. Naloxone (1 mg/kg) significantly augmented tremors elicited by physostigmine (0.3 mg/kg). Naloxone (1 mg/kg) also attenuated increases in locomotor activity and impairments in spontaneous alternation performance elicited by scopolamine (1 and 3 mg/kg for activity and alternation measures, respectively). Thus, across three diverse measures, naloxone produced effects similar to those previously reported for glucose. These findings are consistent with the hypothesis that release of cholinergic activity from opiate inhibition may contribute to glucose effects on behavior.

Animals↗

PubMed1991

Comparison of the effects of scopolamine administered before and after acquisition in a test of visual recognition memory in monkeys.

The effect of scopolamine on visual recognition memory in rhesus monkeys was assessed with a delayed nonmatching-to-sample task employing trial-unique stimuli. During the acquisition phase, 40 sample stimuli were presented sequentially. During the test phase, these same stimuli were presented in the reverse order, each paired with a novel stimulus. The animal was rewarded for choosing the novel stimulus in each pair. Two versions of this design were used. In Task 1, scopolamine (10.0 or 17.8 micrograms/kg) was administered 20 min prior to acquisition, which was followed immediately by the test phase. In Task 2, the drug was administered immediately after acquisition, which was followed 20 min later by the test phase. Performance was impaired in a dose-related manner in Task 1, but not at all in Task 2, indicating that the effects of scopolamine on performance cannot be attributed to an impairment either in the retrieval of stored information or in the attentive or perceptual discriminative processes needed for such retrieval, or, by implication, for storage. In addition, the forgetting curves for scopolamine in Task 1 were parallel to those of the control sessions; i.e., the curves did not diverge with increasing delay intervals, indicating that scopolamine did not increase the rate of forgetting. Taken together, the results suggest that scopolamine interferes selectively with the initial storage of the information to be remembered.

Animals↗

PubMed1990

Cloning and expression of three rabbit kidney cDNAs encoding lauric acid omega-hydroxylases.

cDNAs encoding three cytochrome P-450 enzymes were cloned from a rabbit kidney cDNA library. These three cDNAs exhibit greater than 90% nucleotide sequence identity across the coding region. This degree of sequence identity is also seen with P450IVA4, an enzyme that catalyzes the omega-hydroxylation of prostaglandins and that is elevated during pregnancy and induced by progesterone in rabbit lung. The 3' untranslated regions of the three cDNAs display very little sequence identity, suggesting that they are the products of distinct genes. The predicted amino acid sequences derived from each cDNA and for P450IVA4 exhibit about 85% identity. Each cDNA was inserted into an expression vector for transient transfection of COS-1 cells. The transfected cells each expressed a protein recognized by antibodies to P450IVA4. Microsomes isolated from the cells transfected with each cDNA efficiently catalyzed the omega-hydroxylation of lauric acid with rates that greatly exceed that catalyzed by microsomes isolated from the host cell line. One of the cDNAs encodes an enzyme that omega-hydroxylates prostaglandin A1; however, the specific activity was 2 orders of magnitude lower than that for lauric acid. Our results indicate that the substrate selectivity of the kidney P-450s encoded by these cDNAs is distinct from that of the lung P450IVA4 and that multiple enzymes comprise P-450 class IVA in the rabbit.

Amino Acid Sequence↗

PubMed1990

Antigenic and transforming properties of the DB strain of the human polyomavirus BK virus.

The analysis of the antigenic and transforming properties of the DB strain of the human polyomavirus BK Virus [BKV(DB)] is presented. Two genomes were molecularly cloned from a single virus preparation and were shown to represent viable virus; one clone [pBKV(DB)dl82] contained an 82 nucleotide deletion in the regulatory region relative to the second clone [pBKV(DB)]; pBKV(DB)dl82 demonstrated enhanced lytic and transforming activities relative to pBKV(DB). BKV(DB) is antigenically distinct from the prototype Gardner strain of BK Virus, and 50 to 60% of the population display serological evidence of BKV(DB) infection. Implications of the existence of antigenic variants on estimation of BK virus prevalence in the population are discussed.

Animals↗