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Biomedical subjects

A S Chang

Publications and source records attributed to A S Chang.

At least 19 recordsLinked to original sources
PubMed2001

Measurement of thoracic and lumbar fracture kyphosis: evaluation of intraobserver, interobserver, and technique variability.

STUDY DESIGN: Statistical analysis of various measurement techniques for thoracolumbar burst fracture kyphosis on lateral radiograph. OBJECTIVE: To determine the most reliable measurement technique. SUMMARY OF BACKGROUND DATA: The treatment of thoracic and lumbar burst fractures involves many factors, including the degree of resultant kyphosis. Although various methods have been described, no study has directly compared these methods for reliability and reproducibility. METHODS: Fifty lateral radiographs of thoracic and lumbar burst fractures were randomly selected and measured on two separate occasions by three spine surgeons using five different measurement techniques. Radiograph quality, fracture type, and the center beam location were determined. Statistical analysis included analysis of variance for repeated measures and analysis of variance using a generalized linear model. RESULTS: Intraclass correlation coefficients were most consistent for Method 1 (rho = 0.83-0.94) followed by Method 4 (rho = 0.65-0.89) and Method 5 (rho = 0.73-0. 85). Intraobserver agreement (% of repeated measures within 5 degrees of the original measurement) ranged between 72% and 98% for all techniques for all three observers, with Method 1 showing the best agreement (84%-98%). Paired comparisons between observers varied considerably with interobserver reliability correlation coefficients ranging from 0.52 to 0.93. Method 1 showed the highest interobserver reliability coefficient (0.81, range 0.71-0.93) followed by Method 5 (0.71, range 0.68-0.75). Method 1 also had the highest percentage of agreement within categories (90% within 5 degrees ). CONCLUSIONS: Method 1 (measuring from the superior endplate of the vertebral body one level above the injured vertebral body to the inferior endplate of the vertebral body one level below) showed the best intraobserver and interobserver reliability overall.

Analysis of Variance↗
PubMed2001

Human chorionic gonadotropin levels after blastocyst transfer are highly predictive of pregnancy outcome.

OBJECTIVE: To determine the predictive value(s) of beta-hCG serum levels for pregnancy outcome following blastocyst transfer. DESIGN: Retrospective review. SETTING: University-based assisted reproductive technology (ART) program. PATIENTS: All ART patients enrolled from January 1998 to December 1999. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Beta-hCG serum levels and pregnancy outcomes. RESULT(S): Of the 836 ART cycles initiated, 608 embryo transfers met study criteria and were assigned to one of two groups: 248 day 5 blastocyst transfers or 360 day 3 embryo transfers. In the day 5 blastocyst group, 147 pregnancies occurred (59.2%), and day 3 transfers resulted in 165 pregnancies (45.8%). For day 3 and day 5 transfers, mean values of beta-hCG on day 16 post-retrieval of spontaneous abortions were lower than ongoing pregnancies (P< .05). A beta-hCG value on day 16 of >300 mIU/mL predicted an ongoing pregnancy for day 5 transfer group in 97% of pregnancies compared with 92% for day 3 embryo transfers. A multiple gestation was observed in 70% of pregnancies with a beta-hCG level >400 mIU/mL in the day 5 group compared with 63% for the day 3 group. The incidence of higher-order multiple gestations was significantly lower in the day 5 blastocyst group (P< .05). CONCLUSION(S): Beta-hCG serum levels on day 16 post-retrieval were highly predictive of pregnancy outcome after a blastocyst transfer.

Adult↗
PubMed2001

Brain excitatory amino acid concentrations are lower in the neonatal pig: a buffer against excitotoxicity?

Hypoglycemic brain damage has been associated with high levels of the excitatory amino acids (EAA) aspartate and glutamate in the newborn and adult. We hypothesized that newborn piglet EAA would be different from those of older pigs when stressed with severe insulin-induced hypoglycemia (<30 mg/dl). Brain EAA were measured in piglets and adolescent pigs via microdialysis. Eleven of 12 newborn normoglycemic piglets had no detectable baseline levels (<0.5 microM) of EAA, while pigs had aspartate and glutamate concentrations of 1.78 +/- 0.44 and 3.43 +/- 1.14 microM (mean +/- SEM), respectively. Piglet aspartate and glutamate concentrations reached but did not significantly exceed normoglycemic pig levels after 2 h with plasma glucose values < or =20 mg/ml. Elevations in EAA were only detected in piglets whose EEG activity ceased. Aspartate and glutamate concentrations did not increase in insulin-treated pigs nor in control animals. We speculate that newborns with blood glucose less than clinically acceptable values (35 mg/dl) may be protected from EAA-associated neuronal damage during acute hypoglycemia. Lower normoglycemic and hypoglycemic levels of EAA in newborns when compared to older pigs provide this protection.

Animals↗
PubMed2000

Gestational changes in uterine L-type calcium channel function and expression in guinea pig.

Pregnancy can influence both the resting membrane potential and the ion channel composition of the uterine myometrium. Calcium flux is essential for excitation-contraction coupling in pregnant uterus. The uterine L-type calcium channel is an important component in mediating calcium flux and is purported to play a role in parturition. This study was undertaken to characterize gestational changes in 1) the uterine contractile response to the L-type calcium channel agonist, Bay K 8644; 2) the mRNA expression of channel subunits by semiquantitative reverse transcriptase-polymerase chain reaction; and 3) estimate channel protein levels by measuring (3)H-isradipine binding at the dihydropyridine binding site of the alpha(1c) subunit utilizing saturation binding methods. Sensitivity to Bay K 8644 increases beginning at 0.8 of gestation and persists through term. The change in sensitivity is coincident with an increased mRNA expression of the alpha(1c) and beta(2) subunits but with the least detectable amounts of isradipine binding. The expressed alpha(1c) transcript represents a novel structural variant with a 118-amino acid deletion in the III-IV linker and repeats IVS1-S3 of the protein sequence. The guinea pig uterine L-type calcium channel activity is highly regulated through gestation, but the regulation of mRNA expression may be different from regulation of protein levels, estimated by isradipine binding. The up-regulation of function, alpha(1c) subunit mRNA expression, and isradipine binding at term gestation are consistent with a role for this ion channel in parturition.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1999

Nongenomic steroidal modulation of high-affinity serotonin transport.

The ability of steroids to modulate high-affinity 5-HT transport was investigated using cell-based models which stably manifest all known properties of this transport system. beta-Estradiol (E2) exhibited noncompetitive, and possibly allosteric, inhibition of both radiolabeled serotonin ([3H]5-HT) transport by, and radiolabeled cocaine congener ([3H]CFT) binding to, this system. Such inhibitory effects were observed within short time courses and unlikely to result from genomic effects normally ascribed to estrogen action. Rather, such nongenomic effects on 5-HT uptake were more akin to modulatory effects of select steroid metabolites on other plasma membrane systems such as neurotransmitter receptors and ionic channels. Beyond E2, preliminary examination of other steroid metabolites and synthetic steroid receptor agonists/antagonists revealed that inhibition of 5-HT transport is additionally attributable only to estriol (E3, an E2 metabolite) and tamoxifen (a nonsteroidal, E2 receptor antagonist). These findings indicate that the present form of transport modulation is only rendered by select compounds and not a general property of steroidal and related agents. Assessments of covalent conjugates of E2 suggested that E2 interacts with the transporter protein at allosteric site(s) inaccessible from the extracellular domain. These findings collectively suggest that steroid-mediated regulation of 5-HT transport may be a physiologically relevant mechanism, and that antidepressant as well as psychostimulant effects in vivo may contain a steroidal component.

Animals↗
PubMed1999

Chemical analysis of adnexal cyst fluid.

OBJECTIVE: The purpose of the study was to determine if adnexal cyst fluid glucose, protein, and lactate dehydrogenase (LDH) levels can discriminate between cancerous and noncancerous adnexal masses. METHODS: Intracystic fluid was aspirated from adnexal masses immediately after operative excision. Patient age and menopausal status, mass size, and cyst fluid specific gravity were recorded. Cyst fluid and intraoperative serum glucose, protein, and LDH levels were measured. Masses were grouped by histopathologic diagnosis. Cyst fluid chemical levels and cyst fluid/serum ratios were compared among and between the groups. RESULTS: Fifty-eight adnexal masses were analyzed: 15 nonneoplastic (group 1), 23 benign neoplastic (group 2), and 20 malignant (group 3). There were no significant differences among the groups with regard to patient age, menopausal status, or cyst fluid specific gravity. Cyst size (cm2) was significantly different among the three groups (P < 0.01), with the largest mean size found in the cancer group. No significant differences in cyst chemistries or cyst fluid/serum ratios were found between groups 1 and 2. Comparing groups 1 and 3, all values were significantly different (P < 0.05), with the greatest level of significance attained by comparison of cyst fluid LDH levels (P < 0.001). Groups 2 and 3 statistically differed in cyst fluid levels and cyst fluid/serum ratios of both protein and LDH, with the highest levels of significance achieved by comparisons of cyst fluid levels and ratios of LDH (P = 0.001 and P < 0.001, respectively). The cyst fluid LDH level was found to be the best single chemistry for distinguishing noncancerous (groups 1 and 2) from cancerous (group 3) adnexal masses. A cyst fluid LDH level of >/=451 U/L imparted a 90% sensitivity and 71% specificity for detecting malignancy. CONCLUSIONS: Evaluation of adnexal cyst fluid LDH may help to distinguish benign from malignant adnexal masses. More cases are needed to adequately assess the predictive value and clinical utility of this approach.

Adnexal Diseases↗
PubMed1999

The effect of oral decontamination with clindamycin palmitate on the incidence of bacteremia after esophageal dilation: a prospective trial.

BACKGROUND: Antibiotic prophylaxis to prevent bacterial endocarditis is recommended in high-risk patients undergoing esophageal dilation, a high-risk procedure. Some studies suggest that the oropharynx is the source of bacteremia. A topical antibiotic mouthwash, which reduces bacterial colonization of the oral flora, might decrease bacteremia rates and would be an attractive alternative to systemic administration of antibiotics. METHODS: Adults undergoing outpatient bougienage for a benign or malignant esophageal stricture were randomized in a clinician-blinded fashion to either pre-procedure clindamycin mouthwash or no treatment. Subjects were stratified by type of dilator used. Blood cultures were obtained immediately after the first esophageal dilation and 5 minutes after the last dilation. RESULTS: Fifty-nine patients were enrolled: 30 in the treatment arm and 29 in the no-treatment arm. There were 7 positive blood cultures: 5 in the treatment arm and 2 in the no-treatment arm. The identified organisms were Streptococcus viridans (2), Staphylococcus mucilaginous (2), Lactobacillus (2), and Actinomyces odontolyticus (1). Patients with bacteremia reported greater subjective difficulty with dysphagia (p = 0.01) irrespective of stricture diameter, procurement of biopsies, or dilator type. CONCLUSIONS: The percentage of cases with bacteremia for all dilations performed in this manner was 12% (95% CI [5.3, 23.6]), much lower than previously cited. All organisms in this study were oral commensals. There appears to be no effect of a clindamycin mouthwash on reducing bacteremia after esophageal dilation.

Aged↗
PubMed1999

Near-site monitoring of the antiplatelet drug abciximab using the Hemodyne analyzer and modified thrombelastograph.

OBJECTIVE: This investigation examines the hypothesis that the antiplatelet effect of abciximab and its reversal can be monitored using the Hemodyne (Hemodyne, Inc, Midlothian, VA) analyzer and modified Thrombelastograph (Haemoscope, Skokie, IL). DESIGN: In vitro dose-response and reversal study. SETTING: Anesthesia Research (Dallas, TX) and Special Studies Coagulation Laboratories (Washington, DC). PARTICIPANTS: Nine healthy volunteers. INTERVENTIONS: The addition of increasing concentrations of abciximab, 0 to 10 microg/mL, and purified fibrinogen, 50 to 400 mg/dL. The reversal of abciximab, 4 microg/mL, with the addition of fresh platelet-rich plasma (PRP) sufficient to increase the platelet concentration by approximately 10%. MEASUREMENTS AND MAIN RESULTS: Platelet aggregation and platelet contractile force using the Hemodyne analyzer were used as platelet-specific measurements. The Thrombelastograph maximum amplitude (MA) for platelets (MA(PLT)) was calculated by subtracting the MA from a platelet-poor plasma (PPP) sample (MA(ppp)) determined in one thromboelastography well from that of whole-blood MA (MA(WB)) run simultaneously in the second thromboelastography well. The addition of abciximab, 0 to 10 microg/mL, resulted in significant concentration-dependent reductions in platelet aggregation (p < 0.001), platelet contractile force (p < 0.001), and MA(PLT) (p < 0.001). Platelet contractile force (p < 0.03) and MA(PLT) (p < 0.05) were significantly more responsive than MA(WB) to the effect of abciximab, 4 microg/mL, and its reversal with the addition of fresh PRP. Purified fibrinogen concentration directly correlated with thromboelastography MA (r(s) = 0.97; p < 0.001), yet had no effect on platelet contractile force. The addition of abciximab had no measurable influence on the MA(ppp). CONCLUSION: This in vitro study suggests that the Hemodyne analyzer and modified Thrombelastograph might be clinically useful methods to monitor the platelet inhibitory effects of agents such as abciximab.

Abciximab↗
PubMed1998

Possible existence of quaternary structure in the high-affinity serotonin transport complex.

Deletion-mutants of the cloned mouse serotonin transporter (SERT) rendered dominant negative-mutant effects upon wild-type transporter activities in heterologous expression studies; such effects were transporter-selective and did not influence the activities of co-expressed neuronal GABA transporter. Heterologous expression of linear concatenates (up to four copies) of SERT further revealed discernable uptake activities for both transporter-dimer and -tetramer, but not for the trimer. Kinetic and pharmacological analyses revealed that the monomer, dimer, and tetramer manifested comparable transport Km and potencies for known serotonin uptake inhibitors; the tetramer was distinct from the others only in manifesting notably reduced transport Vmax. Surprisingly, equivalent cocaine congener-binding activities were observed for all concatenates, including the functionally inactive trimer. These findings collectively support the existence of quaternary structure in the active 5-HT transport complex; such structure is likely to be a critical determinant of ligand transport activities, but apparently not of transporter-inhibitor interactions.

Animals↗
PubMed1998

Mechanistic analyses of ion dependences in a high-affinity human serotonin transport system in transfected murine fibroblast cells.

1. A clonal cell line, L-S1, has been identified from transfection of human genomic DNA into cultured mouse L-M fibroblasts. Because this transfectant cell line stably expresses a high-affinity serotonin (5-HT) transport mechanism with kinetic and pharmacological properties comparable to those of other serotonin uptake systems, it was used to investigate the mechanistic involvement of Na+ and Cl- ions in the ligand binding and kinetic uptake processes of this system. 2. Intact transfectant cells, when incubated at low temperature (4 C), enabled quantitative assessment of imipramine-displaceable 5-[3H]HT binding to the 5-HT transport system. This binding activity is insensitive to the presence of various ligands specific for 5-HT receptor subtypes. 3. Imipramine-displaceable 5-[3H]HT binding to intact L-S1 cells was shown to be a Cl--dependent but Na+-independent process. Chloride ions lack binding co-operativity in facilitating ligand binding. Changes in external Cl- concentration altered the Kd but not the Bmax of binding. 4. The overall transport activity was observed to be highly dependent on both external Na+ and Cl- concentrations, characterized by a 5-HT:Na+:Cl- coupling ratio of 1:1:1 per transport cycle. Alterations in the external concentrations of both Na+ and Cl- ions altered only the Km and not the Vmax of transport. 5. Both binding and kinetic results are consistent with kinetic modelling predictions of the Cl- ion in facilitating 5-HT binding to the transport system, and of the Na+ ion in enabling translocation of bound 5-HT across the plasma membrane. Thus, Na+ and Cl- ions facilitate mechanistically distinct and discernible functions in the transport cycle.

Animals↗
PubMed1998

Determination of 60% or greater carotid stenosis: a prospective comparison of magnetic resonance angiography and duplex ultrasound with conventional angiography.

The morbidity and cost of conventional angiography (CA) have focused recent efforts in cerebrovascular imaging upon the exclusive use of noninvasive techniques. Our purpose was to prospectively evaluate carotid magnetic resonance angiography (MRA) and to compare its accuracy with color-flow duplex (CFD). Fifty patients were prospectively evaluated with CA and MRA after clinical and CFD findings indicated the need for carotid angiography. CFD measurements of peak systolic velocity (PSV) and end-diastolic velocity (EDV) were made. MRA results were categorized as 0%-39%, 40%-59%, 60%-79%, or 80%-99% stenosis or occluded. Determination of percent carotid stenosis by CA was made as in the North American Symptomatic Carotid Endarterectomy Trial (NASCET). Using receiver operating characteristic (ROC) curves, the probability of correctly predicting a > or =60% stenosis using various CFD thresholds and MRA was assessed. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) in determining > or =60% stenosis were estimated. For MRA the sensitivity was 85% (95% Confidence Interval [CI] = 69%-94%), specificity 70% (CI = 56%-81 %), PPV 68% (CI = 53%-80%), and NPV 86% (CI = 72%-94%). For CFD the sensitivity was 89% (CI = 74%-96%), specificity 93% (CI = 82%-98%), PPV 89% (CI = 74%-96%), and NPV 93% (CI = 82%-98%). When MRA and CFD results were concordant (n = 64), the sensitivity was 100% (CI = 89%-100%), specificity 95% (CI = 81%-99%), PPV 94% (CI = 77%-99%), and the NPV was 100% (CI = 92%-100%). The area under the ROC curve for CFD was 95%, compared to 83% for MRA (p = 0.0005). We conclude that the low specificity of MRA precludes its use as the definitive imaging modality for carotid stenosis. The 93% specificity of CFD alone warrants its consideration as a definitive carotid imaging study. By ROC curve analysis, CFD offers superior accuracy to MRA. Our data support noninvasive preoperative carotid imaging for detecting a threshold stenosis of > or =60% whether CFD is used alone, or in combination with the selective use of MRA.

Aged↗
PubMed1998

The incidence of heparin-induced antibodies in patients undergoing vascular surgery: a prospective study.

PURPOSE: This study prospectively assessed the incidence of heparin-induced antibodies in patients undergoing peripheral vascular surgery and determined whether the incidence is influenced by previous heparin exposure. METHODS: Fifty-four hospitalized patients (36 men and 18 women) undergoing peripheral vascular surgery and receiving intraoperative heparin anticoagulation were studied. Unfractionated porcine heparin was given for intraoperative anticoagulation and was not continued postoperatively. Carotid endarterectomy was performed in 36 patients, aortic reconstruction in 11 patients, and infrainguinal bypass in 7 patients. Plasma was tested before and after (14 +/- 7.5 [SD] days) surgery for IgG antibodies to the complex of heparin/platelet factor 4, using a standardized, validated enzyme-linked immunosorbent assay (ELISA). Results are expressed as an optical density ratio (ODR) of patient plasma to normal plasma, with the threshold for a positive result of > or = 1.8. Platelet counts and clinical outcomes were also assessed. RESULTS: The mean patient age was 67.2 +/- 9.7 years. A prior exposure to heparin was documented in 41% of patients. The mean intraoperative heparin dose was 9089 +/- 3607 units. Only 1 patient converted from a negative antibody status to a positive status (1.9%, 95% CI = 0.10%-11.18%). The change in the ELISA ODR after surgery was not significantly different for patients with (+0.042 +/- 0.272) and without (-0.022 +/- 0.299, P = 0.57) prior heparin exposure. Postoperatively, the platelet counts dropped from 227,620 +/- 78,308 microL, to 185,706 +/- 80,842 microL (P < .001). The decrease in platelet count was the same in patients with prior heparin exposure (-23.0 +/- 18.0%) and without (-18.0 +/- 14.0%, P = .46). One thrombotic complication occurred, a femorotibial bypass graft occlusion in a patient who tested negative for antibodies. CONCLUSION: Heparin-induced antibodies occur infrequently after peripheral vascular surgery. The commonly observed, mild degree of postoperative thrombocytopenia does not appear to be caused by heparin-induced antibodies. These results indicate that a standard dose of heparin for intraoperative anticoagulation during vascular surgery is not associated with a significant risk of heparin-induced thrombocytopenia and thrombosis.

Aged↗
PubMed1998

Dual agency, dual relationships, boundary crossings, and associated boundary violations: a survey of military and civilian psychiatrists.

We hypothesized that psychiatrists with high dual-agency potential (military and health maintenance organization [HMO] psychiatrists) were more likely than non-HMO civilian psychiatrists to engage in dual relationships, report pressures to do so, participate in other general boundary-crossing activities, and report associated counter-therapeutic outcomes (boundary violations). Ninety military and 191 demographically matched civilian psychiatrists reported the number of boundary-crossing activities (including dual relationships) and associated counter-therapeutic outcomes in the preceding year with adult patients. Military and HMO psychiatrists reported greater external pressures than non-HMO civilian psychiatrists to engage in dual relationships; however, all three groups were similar in their reported numbers of dual relationships. The reported boundary-crossing activities and dual relationships studied here are not necessarily associated with reported boundary violations. The relative risk of a particular boundary crossing associating with harm to a patient likely depends on the therapeutic context and should be determined on a case-by-case basis.

Adult↗
PubMed1997

Concomitant and hormonally regulated expression of trp genes in bovine aortic endothelial cells.

Recent findings have suggested that the vertebrate trp family of channel proteins is the structural basis for Ca2+ influx through the capacitative calcium entry (CCE) pathway. We have discerned, in bovine aortic endothelial cells, the concomitant expression of four such vertebrate genes: trp-1 (two splice variants), trp-3, trp-4 and trp-5. Exogenous hormones rendered dynamic effects on the transcript levels of these genes. Most notably, beta-estradiol significantly down-regulated trp-4 while trans-retinoic acid dramatically up-regulated trp-5; yet these hormones rendered little change in CCE. These findings suggest that the extent of a given trp channel's participation in CCE is not reflected in alterations of its transcript level.

Amino Acid Sequence↗
PubMed1997

A modified thromboelastographic method for monitoring c7E3 Fab in heparinized patients.

The monoclonal antibody, c7E3 Fab, binds to the platelet surface fibrinogen receptor (GPIIb/IIIa), inhibiting platelet aggregation and clot retraction. We performed an in vitro study to assess the ability of a modification of the thromboelastograph (MTEG) to detect inhibition of clot strength by c7E3 Fab and its reversal with platelet-rich plasma (PRP). In the modified assay (MTEG), thrombin was added to whole blood (WB) and platelet-poor plasma (PPP) and the resultant maximum amplitude (MA) was measured, MAWB and MAPPP, respectively. Anticoagulated blood samples from 17 patients scheduled for cardiac surgery were collected for a dose response (Part I; n = 5) and c7E3 Fab reversal (Part II; n = 12) study. Clot strength was reduced in a dose-dependent manner by c7E3 Fab. Ecteola cellulose effectively reversed the effect of heparin on the thrombin time and the addition of PRP significantly increased the MAWB (P < 0.0001) and MAWP-PPP (P < 0.0001). Subtracting the MAPPP from MAWB significantly magnified the response of MA to the addition of c7E3 Fab (P = 0.002) and its reversal with PRP (P = 0.005). This in vitro study indicates that the MTEG is a responsive assay demonstrating that inhibition by the antiplatelet c7E3 Fab is reversible with PRP.

Abciximab↗
PubMed1997

Gestational changes in the uterine expression of an inwardly rectifying K+ channel, ROMK.

We have examined the repertoire and relative expression levels of voltage-gated K+ channels in timed-pregnant rat uteri. These studies have revealed the gestation-specific and abundant expression of mRNA encoding an inwardly rectifying K+ channel, ROMK (originally identified in renal outer medulla), within the gravid uterus. Steady-state levels of ROMK transcripts undergo dynamic gestational changes: they are undetectable in virgin uteri, reach a maximum level by Day 12 of gestation, decline thereafter until, by term, they are again undetectable. Kidney cells also express ROMK transcripts at high levels but do not undergo apparent changes during gestation. Molecular analyses (by "rapid amplification of cDNA ends", or "5'-RACE") of the ROMK mRNAs revealed the presence of two alternative-splicing variants which are likely to arise from distinct transcription-start sites within the same gene. Polymerase chain reaction-based assessments of gravid uteri from other species revealed the expression of ROMK transcripts in the myometrium as well. Uterine expression of ROMK therefore represents a generalized phenomenon, characterized by both gestation- and tissue-specific regulation, and the transcription-regulatory mechanisms of this channel protein are potentially complex. From the biophysical properties of this channel in vitro and the observed gestational profile, we hypothesize that this channel modulates both the resting membrane potential and cellular excitability of myometrial cells, and in turn contributes to the observed contractile quiescence of the gravid uterus.

Amino Acid Sequence↗
PubMed1996

Cloning and expression of the mouse serotonin transporter.

A mouse brain cDNA encoding the high-affinity serotonin transporter (SERT) has been identified and characterized. The mouse transporter sequence (mSERT) encodes a protein of 630 amino acids which contains twelve potential transmembrane domains (TMDs), N-linked glycosylation and kinase-mediated phosphorylation sites, and high levels of homology with rat and human SERTs. Heterologous expression of mSERT in COS-I cells resulted in a [3H]serotonin transport activity characterized by kinetic saturability (Km = 403 +/- 42 nM. Vmax = 1.02 +/- 0.10 pmol/mg/min), Na1 and Cl- dependences (5HT:Na+:Cl- coupling ratio of 1:1:1), and sensitivity to known inhibitors of serotonin transport (including antidepressant and psychostimulant agents). Northern analysis using mSERT cDNA as probe revealed a single 3.4 kb mRNA species expressed in mouse lung, midbrain and brainstem regions, and absent from heart and liver. In situ hybridization studies further established the specific localization of mSERT gene expression to the raphe nuclei of the mouse midbrain. The identified mSERT cDNA sequence provides a new tool for the evaluation of serotonin transport pharmacology in heterologous expression systems and provides an opportunity for the evaluation of mSERT gene expression in a well-characterized model of mammalian development.

Animals↗