A case of acute aconitine poisoning caused by chuanwu and caowu

A case of aconitine poisoning following the ingestion of 'chuanwu', the main root of Aconitum carmichaeli, and 'caowu', the root of Aconitum kusnezoffii is described. A 35-year-old man became unwell about 90 minutes after ingesting these herbs and his symptoms lasted for about two days. In addition to the typical gastrointestinal (nausea and vomiting) and neurological (generalized weakness, numbness and paraesthesia) features of aconitine poisoning, there was evidence of cardiotoxicity (hypotension and ventricular ectopics). Management of such patients should include measures to enhance elimination and close monitoring for cardiotoxicity. Legislation controlling the use of such herbs should be considered.

A novel non-peptidyl growth hormone secretagogue

Direct screening of preselected compounds in a rat primary pituitary cell culture assay, followed by chemical modification of selected pharmacophores led to the identification of a novel non-peptidyl class of GH secretagogues (substituted benzolactams). The prototype compound of this class, L-692,429, stimulated GH release from rat primary pituitary cells in a time- and dose-dependent manner with an EC50 value of 60 nM. Under the same conditions, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (GH-releasing peptide, GHRP-6) and GH-releasing factor (GRF) had EC50 values of 10(-8) and 5 x 10(-10) M, respectively. L-692,428, the S-enantiomer, of L-692,429, was inactive at a concentration as high as 2 microM. GH release induced by L-692,429 was inhibited by somatostatin as well as by GHRP-6 and substance P antagonists but not by GRF or opiate antagonists. L-692,400, which is structurally related to L-692,429 but biologically inactive, inhibited GH response not only to L-692,429 but also GHRP-6. Like GHRP-6, L-692,429 alone had no effect on intracellular cAMP levels; however, it synergized with GRF to further increase both the accumulation of cAMP and the release of GH. Maximal effects of L-692,429 and GHRP-6 on GH release were comparable. Interestingly, when presented together in maximal concentrations, L-692,429 and GHRP-6 did not cause an additional GH release when compared with either secretagogue alone. L-692,429 had a small effect on prolactin release but not adrenocorticotropin.(ABSTRACT TRUNCATED AT 250 WORDS)

PMA-sensitive protein kinase C is not necessary in TRH-stimulated prolactin release from female rat primary pituitary cells

In GH3 cells and other clonal rat pituitary tumor cells, TRH has been shown to mediate its effects on prolactin release via a rise of cytosolic Ca2+ and activation of protein kinase C. In this study, we examined the role of protein kinase C in TRH-stimulated prolactin release from female rat primary pituitary cell culture. Both TRH and PMA stimulated prolactin release in a dose-dependent manner. When present together at maximal concentrations, TRH and PMA produced an effect which was slightly less than additive. Pretreatment of rat pituitary cells with 10(-6) M PMA for 24 hrs completely down-regulated protein kinase C, since such PMA-pretreated cells did not release prolactin in response to a second dose of PMA. Interestingly, protein kinase C down-regulation had no effect on TRH-induced prolactin release from rat pituitary cells. In contrast, PMA-pretreated GH3 cells did not respond to a subsequent stimulation by either PMA or TRH. Pretreatment of rat pituitary cells with TRH (10(-7) M, 24 hrs) inhibited the subsequent response to TRH, but not PMA. Forskolin, an adenylate cyclase activator, stimulated prolactin release by itself and in a synergistic manner when incubated together with TRH or PMA. The synergistic effects of forskolin on prolactin release was greater in the presence of PMA than TRH. Down-regulation of protein kinase C by PMA pretreatment abolished the synergistic effect produced by PMA and forskolin but had no effect on those generated by TRH and forskolin. sn-1,2-Dioctanylglycerol (DOG) pretreatment attenuated the subsequent response to DOG and PMA but not TRH. The effect of TRH, but not PMA, on prolactin release required the presence of extracellular Ca2+. In conclusion, the mechanism by which TRH causes prolactin release from rat primary pituitary cells is different from that of GH3 cells; the former is a protein kinase C-independent process whereas the latter is at least partially dependent upon the activation of protein kinase C.

Evidence for a role of protein kinase-C in His-D-Trp-Ala-Trp-D-Phe-Lys-NH2-induced growth hormone release from rat primary pituitary cells

We have recently reported that His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (GHRP-6) synergizes with GH-releasing factor (GRF) to increase GH release and cAMP accumulation in rat pituitary cells in vitro. This study was undertaken to further investigate the mechanism of action of GHRP-6 on GH release, particularly the involvement of protein kinase-C. Forskolin (10(-5) M), A23187 (10(-6) M), and phorbol 12-myristate 13-acetate (PMA; 10(-7) M) all stimulated GH release. However, only PMA can mimic the synergistic effects of GHRP-6 on GRF-stimulated GH release and intracellular cAMP accumulation. 4 alpha-Phorbol 12,13-didecanoate, an inactive phorbol ester, was unable to stimulate GH release or potentiate the effect of GRF. Extracellularly added phospholipase-C not only stimulated GH release in a dose-dependent manner, but also potentiated GRF-induced GH release. Phloretin, a protein kinase-C inhibitor, in a concentration range of 10-250 microM had very little or no effect on basal and GRF-stimulated GH release, but markedly inhibited the stimulatory effects induced by either PMA or GHRP-6. Incubation of rat pituitary cells with 10(-6) M PMA for 24 h completely down-regulated protein kinase-C, since such PMA-pretreated cells did not release GH in response to a second dose of PMA. The protein kinase-C-depleted cells had an attenuated GHRP-6 response, but they responded normally to GRF. Moreover, the synergistic effects of GHRP-6 and GRF on GH release and cAMP accumulation were also greatly inhibited by protein kinase-C down-regulation. These data suggest that the effects of GHRP-6 on GH release, either alone or together with GRF, are at least partially mediated via the activation of protein kinase-C.

Postirradiation angiosarcoma of the vaginal vault

We describe a unique case of an angiosarcoma arising in the vaginal vault 21 years after hysterectomy and radiotherapy for stage I carcinoma of the cervix. We also review the literature regarding angiosarcomas arising after previous radiation therapy for gynecologic malignancies.

Phosphorus-containing inhibitors of aspartate transcarbamoylase from Escherichia coli

A tetrahedral intermediate is the prominent feature of the generally accepted mechanism for aspartate transcarbamoylase. We have synthesized N-pyrophosphoryl-L-aspartate as a charged analogue of the postulated intermediate. Surprisingly, its affinity for the enzyme from Escherichia coli was substantially lower than that of the previously known inhibitor phosphonoacetyl-L-aspartate which contained a trigonal carbonyl group. Similar results were obtained with the corresponding mercaptosuccinate derivatives. We also tested a number of new pyrophosphate analogues as inhibitors. Our results cast doubt on some aspects of the current model for the mechanism of this enzyme.

Effects of L-deprenyl and amantadine in an MPTP-model of parkinsonism

Mongolian gerbils of both sexes received a single daily dose of 40 mg/kg of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) over 4 consecutive days. On the fifth day the animals were treated with 15 mg/kg i.p. of L-deprenyl or amantadine or the combination of both drugs. At different time intervals (1, 2, 5 hours) the animals were sacrificed. In the caudate nuclei dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) were measured by an HPLC technique. MPTP affected the dopaminergic (HVA -25%) as well as the serotoninergic system (5-HT -54%, 5-HIAA -31%). L-deprenyl and amantadine accumulated DA and 5-HT in the MPTP affected caudates. Synergistic effects of the drug combination could be proven.

Improved prognosis since 1969 of myocardial infarction treated in a coronary care unit: lack of relation with changes in severity

OBJECTIVE

To study changes from 1969 to 1983 in the prognosis of patients with acute myocardial infarction treated in a coronary care unit.

DESIGN

Mortality follow up of all patients with definite acute myocardial infarction.

SETTING

The coronary care unit of the Royal Melbourne Hospital, a tertiary referral centre.

SUBJECTS

4253 Patients (3366 men, 887 women) admitted from 1969 to 1983.

MAIN OUTCOME MEASURE

Mortality recorded at discharge from hospital and 12 months after admission.

RESULTS

Details of clinical findings, history, electrocardiograms, arrhythmias, and radiological findings were recorded on admission. Mean ages were 63 for women and 57 for men, and women had haemodynamically more severe infarcts than men. In the later years patients were older and had less severe infarcts. Overall, hospital mortality in men was 16.7% in 1969-73 and 8.5% in 1979-83 and declined in all grades of the Norris and Killip infarct severity indices compared with a constant 19.2% in women. Even after adjustment for age and severity by logistic regression, hospital mortality fell in men by an average of 8% (95% confidence interval 4% to 11%) a year but remained constant in women. By 1983 male mortality was 60% that of women of similar age and comparable severity of infarction. Mortality of hospital survivors at 12 months declined by 7% (4% to 9%) a year in both sexes, even after adjustment for age and severity, with a male to female mortality ratio of about 0.8. New indices were derived to predict mortality in hospital and at 12 months.

CONCLUSION

The observed declines in mortality cannot be explained by changes in severity of infarction or in prognostic characteristics of patients.

The synergistic effects of His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 on growth hormone (GH)-releasing factor-stimulated GH release and intracellular adenosine 3',5'-monophosphate accumulation in rat primary pituitary cell culture

His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (GHRP-6) stimulated GH release from rat primary pituitary cells in a time- and dose-dependent manner. Stimulation was observed after a 15-min, but not a 4-h, incubation. The concentrations of GHRP-6 required for half-maximal and maximal stimulation were 7 x 10(-9) and 10(-7) M, respectively. GH release induced by GHRP-6 was not affected by the addition of either naloxone or the GRF antagonist [N-Ac-Tyr1,D-Arg2]GRF-(1-29)-NH2. The latter inhibited GRF-stimulated GH release by shifting the dose-response curve to the right. His-D-Trp-D-Lys-Trp-D-Phe-Lys-NH2, an analog of GHRP-6, inhibited GH release stimulated by GHRP-6 without affecting that induced by GRF. When present together at maximal concentrations, GHRP-6 and GRF produced a synergistic effect on GH release. GHRP-6 had no effect on intracellular cAMP levels, whereas GRF increased intracellular cAMP concentrations by 3-fold. Combined treatment of pituitary cells with GRF and GHRP-6 resulted in a potentiation of the GRF-induced increase in cAMP levels. Basal GH release was reduced by 30% after pretreatment with GHRP-6 (10(-7) M) for 1 h. Pretreatment with GHRP-6 also decreased the subsequent response to GHRP-6, but not GRF. In contrast, pretreatment with GRF for 1 h had no effect on the subsequent action of GHRP-6 or GRF on GH release. The desensitization induced by GHRP-6 was completely reversed within 1 h after removal of the peptide. Results from this study indicate that GHRP-6 and GRF stimulated GH release from somatotrophs via different receptors and through discrete mechanisms.

Oral treatment of peritonitis in CAPD patients with two dosage regimens of ofloxacin

Two open studies of oral treatment of peritonitis in CAPD patients with ofloxacin are described. The first study included 10 episodes of peritonitis treated with ofloxacin 400 mg followed by 200 mg daily for a total of seven days. In the second study of 18 peritonitis episodes, the treatment was ofloxacin 400 mg followed by 300 mg daily for a total of ten days. The cure rate was 50% in the first study and 83% in the second. There was significant accumulation of ofloxacin in the serum but the mean serum trough level with the second treatment regimen plateaued at 6 mg/l on day 10. Peritoneal effluent ofloxacin levels correlated well with the prevailing serum concentrations of the antibiotic and, except on day 1, the mean peritoneal effluent ofloxacin levels all exceeded 3 mg/l with the second dosing scheme. Side effects were mainly nausea and dizziness.

Multiple sites and synergism in the binding of inhibitors to microsomal aminopeptidase

The active site of microsomal aminopeptidase has been probed by studying the inhibition of the enzyme in the simultaneous presence of two ligands. The results have been analyzed with the Yonetani-Theorell plot to quantitate the degree of interaction between the two inhibitors. As expected, the enzyme contains a strong binding site for the alpha-amino group and the hydrophobic side chain of specific substrates. In addition, however, the enzyme can interact with another amine and a second hydrophobic group. Evidence suggests that this extra amine may bind to the zinc in an unprotonated form and that one of the hydrophobic sites is located in the vicinity. Another unexpected finding in this work is a strong synergism between the binding of ammonia and that of zinc ligands such as hydroxamates. This synergism may reflect an induced-fit mechanism that brings the catalytically important zinc atom into the optimal state only in the presence of specific substrates.

Synergistic binding of ligands to angiotensin-converting enzyme

We have investigated the interaction of ligands in the active site of the angiotensin-converting enzyme from rabbit lung by monitoring the concurrent effects of two inhibitors on enzyme activity. A strong synergism is found in the binding of N-acetyl-L-proline (an analog of the COOH-terminal dipeptide portion of preferred substrates) and acetohydroxamate (a zinc ligand). Analysis of the inhibition data with the Yone-tani-Theorell plot yields an unusually low value of 0.0063 for the interaction constant (alpha). This result indicates that each of the above ligands stimulates the binding of the other by about 150-fold. Similar but often less pronounced synergism is observed for other zinc ligands and with some other N-acyl amino acids. These specific structural requirements suggest that the above effect is associated with an induced-fit mechanism which brings the important zinc atom into a catalytically optimal state only in the presence of certain preferred substrates.

Control of preweaning diarrhea in piglets by acupuncture and Chinese medicine

Preweaning diarrhea in piglets is a very common disease. Even thought vaccination and antibiotics are used widely for controlling the disease nowadays, it is still a serious production problem. Therefore, the search for a new medication that is both cheaper and more effective is of major importance. During the last year, acupuncture and Chinese medicine have been evaluated for this purpose. The results are summarized as follows: 1) Oral administration of 0.5 g of Ko-ken-huang-lien-huang-chin-tang (pueraria, coptis, scute and licorice combination) to piglets at 1 day old was effective in reducing incidence of infection (P less than 0.1) and increasing the body weight gain (P less than 0.05) during the first 10 days of life. Gentamycin or aqua-acupuncture at day 1 of life had no prophylactic value. 2) Piglets with preweaning diarrhea were treated by aqua-acupuncture at Chang-Chiang point (VG 1, or so called Chiao-Chao in traditional pig charts) with 0.2 ml of 3% saline, or by oral administration of 0.5 g of Ko-ken-huang-lien-huang-chin-tang or by injection of gentamycin (10 mg/piglet) twice a day for 1-3 days. These treatments significantly reduced the duration of illness (P less than 0.01) when compared with the control groups which received 0.5 g lactose orally. These results indicate that both acupuncture treatment and Chinese medicine have a high clinical value for controlling piglet diarrhea.

Effects of electroacupuncture and gonadotropin-releasing hormone treatments on hormonal changes in anoestrous sows

The therapeutic effects of acupuncture in treating reproductive disturbances of man and animals have been proven in the past and is used clinically already. However, the mechanism of such therapy is not known yet. In this study, anoestrous sows were used to investigate the mechanism. Anoestrous sows with luteal ovaries were allocated to three groups. Four sows received electroacupuncture treatment at Pai-Hui and Wei-Ken (acupuncture treated group; group 1). Three sows received electroacupuncture treatment at Chiang-Feng and Chou-Shu (acupuncture control group; group 2). Four received 50 micrograms of gonadotropin-releasing hormone (GnRH) intravenously (drug control group; group 3). The concentrations of luteinizing hormone, progesterone, oestradiol and cortisol in serum were measured by radioimmunoassay. Oestrus return was monitored during 14 days after treatment. At the end of this observation period, the number of animals returned to oestrus were 3, 1 and 1 in groups 1, 2 and 3, respectively. It suggests that only treatment with acupuncture at Pai-Hui and Wei-Ken had therapeutic effects in inducing oestrus. This finding is further supported by the changes of serum sex hormone concentrations. Serum LH concentrations decreased for about 2 hours after electro-acupuncture treatment both in groups 1 and 2, whereas those in group 3 increased sharply at 10 minutes, reached to a peak at 20 minutes and returned gradually to basal level between 4 and 6 hours after GnRH injection. Serum progesterone concentrations rose between 4 to 6 hours after treatment in groups 1 and 3 but not in group 2. Five sows become oestrus, showed a decreased progesterone level 2 days after treatments whereas the other six anoestrous sows did not. Oestradiol levels did not have meaningful changes during the blood sampling period of 5 to 7 days in these 3 groups. Cortisol levels elevated in 15 minutes after the electroacupuncture in groups 1 and 2. However, the increment of cortisol induced by the electroacupuncture was less than that induced by the first bleeding, indicating that the adrenal stimulation may not be the main reason of the therapeutic action. The results indicated that the electroacupuncture treatment and GnRH injection could alter the release of LH from the pituitary in different ways but only electroacupuncture at Pai-Hui and Wei-Ken has a specific action on ovary and a significant therapeutic effect. Therapeutic effects of electroacupuncture on reproductive disturbance may involve a synergism of somatic-ovary and uterus reflex and central nervous-endocrine system (the hypothalamo-pituitary-ovary axis).

Ofloxacin pharmacokinetics in patients on continuous ambulatory peritoneal dialysis

Pharmacokinetics of ofloxacin (OFX) was studied in patients on continuous ambulatory peritoneal dialysis (CAPD) carrying out three exchanges per day. In 11 patients given 300 mg of OFX orally, serum OFX concentration peaked at 2.44 mg/l 3.7 hours after administration and the mean elimination half-life of OFX was 25 hours. OFX concentrations in peritoneal fluid underwent cyclical changes with each change of solutions, reaching beyond 0.5 mg/l after 2 hours of equilibration. There was a highly significant correlation between corresponding serum and peritoneal fluid concentrations of OFX after an 8 h equilibration (r = 0.85, p less than 0.001). In 5 patients given a 400 mg loading dose followed by 200 mg of OFX per day for 7 days, trough serum OFX concentrations ranged from 1.35 to 7.00 mg/l and no adverse effects were noticed. CAPD per exchange removed less than 2% of the total dose of OFX given.

Ligand interactions at the active site of aspartate transcarbamoylase from Escherichia coli

The active site of aspartate transcarbamoylase from Escherichia coli was probed by studying the inhibitory effects of substrate analogues on the catalytic subunit of the enzyme. The inhibitors were chosen to satisfy the structural requirements for binding to either the phosphate or the dicarboxylate region. In addition, they also contained a side chain that would extend into the normal position occupied by the carbamoyl group. All the compounds tested showed competitive inhibition against carbamoyl phosphate. The ionic character of the side chain was found to be highly important in determining the affinity of the inhibitor. On the other hand, very little effect on binding was produced by changing the geometry of the functional group from trigonal to tetrahedral. Our findings suggest that the electrostatic stabilization of the negative charge that develops in the transition state may be a major factor in promoting catalysis. From the available X-ray diffraction data, we propose His-134 as the residue most likely to participate in this interaction. These results have significant implications on the design of reversible and irreversible inhibitors to this enzyme.

Structural requirements for specific inhibition of microsomal aminopeptidase by mercaptoamines

L-Leucinthiol, a synthetic derivative of mercaptoethylamine with a hydrophobic side chain, was recently reported to be a potent inhibitor of microsomal aminopeptidase. The structural features necessary for interaction of mercaptoamines with this enzyme have now been explored more systematically. Optimal binding requires a primary amine linked to the mercapto group via two carbon atoms. Only a substituent with L-configuration at the 1 position increased the affinity toward the enzyme. The high degree of specificity and other evidence suggest that the mode of binding of these inhibitors is similar to that of substrates. Comparison of leucinthiol with other amino compounds suggest that the mercapto group makes a much greater contribution to the binding than the hydrophobic side chain. L-Leucinthiol is fairly specific for aminopeptidase although some inhibition of thermolysin and carboxypeptidase A is observed.

Conformations of bound nucleoside triphosphate effectors in aspartate transcarbamylase. Evidence for the London-Schmidt model by transferred nuclear Overhauser effects

Transferred nuclear Overhauser effects were used to determine the conformations of ATP, CTP, and ITP bound to the regulatory site of aspartate transcarbamylase. The results are in accord with the predictions of the London-Schmidt model [London, R. E., & Schmidt, P. G. (1972) Biochemistry 11, 3136] and show that ATP and CTP bind in the anti conformation while ITP binds in the syn conformation.

An assay for ribonucleotide reductase based on ion-exchange chromatography of the reaction product

A rapid and convenient assay for ribonucleotide reductase has been developed in which the reaction product, deoxycytidine diphosphate (dCDP), is isolated without further conversion. The enzymatic reaction is terminated by the addition of ethanol and the sample is chromatographed on a single, small, and disposable column of polyethylenimine cellulose. A two-step elution is conducted with buffers containing 25% ethanol. First, contaminants and byproducts such as cytidine and its monophosphate are removed at low ionic strength while the diphosphates are retained. Then dCDP is selectively eluted as a sharp peak with a strong borate buffer. Under these conditions, the excess substrate, cytidine diphosphate, remains on the column, presumably as the borate complex. The assay is linear with time for 15 min at 25 degrees C and linear with the amount of enzyme even at very low concentrations. With slight modifications, the assay seems applicable to the use of UDP or ADP as substrates. The method is not suitable for samples which contain nucleotide kinase or other interfering enzymes which convert a significant amount of dCDP into byproducts. However, another chromatographic system based on similar principles has been found which could be used to measure any dCTP produced in this way.

Activation of brain calcineurin towards proteins containing Thr(P) and Ser(P) by Ca2+, calmodulin, Mg2+ and transition metal ions

Using Thr(P)-inhibitor-1 and Ser(P)-casein as substrates, studies on the activation of calcineurin purified from bovine brain have been carried out. The phosphatase requires the synergistic action of Ca2+, calmodulin and another divalent cation (Mg2+, Mn2+, Co2+ or Ni2+, but not Zn2+) for full expression of its activity. Ca2+ and Ca2+ X calmodulin act as allosteric activators to transform the phosphatase to a relaxed conformation, while Mg2+ acts solely as a cofactor for the catalytic action of the enzyme. In addition to their function as cofactors for catalysis, transition metal ions can also substitute for Ca2+ as allosteric activators. Ca2+ and calmodulin exert their activating effects mainly by increasing the Vm of the phosphatase reaction with little effect on the Km values for the substrates or on the KA values for the divalent cation cofactors. The predominant factor in dictating the catalytic properties of calcineurin is the divalent cation cofactor. For example, with Mg2+ as a cofactor, the phosphatase exhibits an optimum around pH 8.0-8.5; while with a transition metal ion as a cofactor, the optimum is around pH 7.0-7.5, regardless of whether Thr(P)-inhibitor-1 or Ser(P)-casein serves as a substrate, in the absence or the presence of Ca2+ X calmodulin.

Some properties of aminopeptidase associated with rat brain cortical synaptosomes

To understand the breakdown of peptides in the brain, we studied the aminopeptidase associated with synaptosome particles. A continuous spectrophotometric assay in stirred cuvettes was used to follow the kinetics of inactivation by EDTA and by diethyl pyrocarbonate. The sensitivity of the enzyme towards puromycin and leucine hydroxamate was also determined. The results are consistent with the presence of a single species of aminopeptidase in freshly prepared synaptosome. This enzyme is capable of degrading Met-enkephalin in vitro and is distinct from microsomal leucine aminopeptidase. Storage of synaptosomes by freezing and subsequent thawing changed some properties of the enzyme and partially solubilized the enzyme. These studies suggest that there are advantages in studying the enzyme in its native particle-bound state.

L-leucinthiol - a potent inhibitor of leucine aminopeptidase

L-leucinthiol (2-amino-4-methyl-1-pentanethiol) was designed as an inhibitor of leucine aminopeptidase by analogy with sulfhydryl inhibitors of other zinc-containing peptidases. It was synthesized from L-leucinol and shown to be a potent competitive inhibitor of the microsomal aminopeptidase from porcine kidney (Ki = 2.2 X 10(-8) M). The results suggest that the mechanism of aminopeptidase may be similar to that of other metalloproteases.

Topography of preemptying ventricular segments in patients with Wolff-Parkinson-White syndrome using scintigraphic phase mapping and esophageal pacing

We analyzed the sequence of ventricular emptying using the phase image in 10 patients with accessory pathways and in 15 normal subjects. In normal subjects, the earliest emptying occurred in ventricular septal, apical and left basal segments. Eight patients had manifest preexcitation; the earliest emptying occurred ectopically in the right ventricle in one of these patients and in the left ventricle in five. The remaining two patients had normal phase maps. Two patients had concealed left-sided pathways. Their phase maps showed earliest emptying in left basal segments. Six of the 10 patients underwent electrophysiologic mapping. There was complete agreement between phase and electrophysiologic maps. Transesophageal atrial pacing increased preexcitation in one patient, normalized the ECG in another and precipitated narrow QRS tachycardia in four patients. Phase maps then showed enlargement, reduction and loss of the ectopic earliest emptying segments, respectively. We conclude that this technique in conjunction with pacing is successful in lateralizing accessory pathways.