[Long-term results of the Blalock-Taussig shunts]

One-hundred and thirty-six patients received the classical Blalock-Taussig shunts between 1980 and 1990. Their age range at operation was 4 days to 12.8 years and their median age was 13 months. The operative mortality rate was 0.7% (1/136). The survivors were followed up from 1 month to 11.5 years, 5.4 years in average. Twenty-five patients required another shunt and the mean interval to that procedure was 2.4 years (modified Blalock-Taussig 23, classical Blalock-Taussig 2, Glenn 1, internal mammary artery-pulmonary artery shunt 1). Forty-five patients received corrective operations, there were four operative deaths (Fontan 2, Rastelli 2). There were 15 late deaths of which three deaths were not cardiogenic. One year after operation, 91.0% of patients remained in well-palliated condition. At three years after operation, 76.4% of patients continued to be in well-palliated condition. There were twelve neonates in this series. Their age range was 4 to 26 days and their median age was 13 days. There was no operative death. Five patients required second shunt. There were two late deaths. At present, six patients continue to be in well-palliated condition 8 months to 9 years after first operation. Angiographic findings showed the stenotic change of the vascular anastomoses in 49.3% (35/71) of patients. This study suggests that polydioxanone suture (PDS) will be useful for the growth of the anastomoses in Blalock-Taussig operation.

[Measurement of intracellular pH]

Since various cellular processes depend on changes in pH, the regulation of intracellular pH (pHi) is important both for the individual cell and for the organism. The mechanisms of the regulation of pHi can be investigated by monitoring pHi. In this report, we discuss the four major techniques available for measuring pHi, which are 1) Distribution of weak acids and bases, 2) pH-sensitive microelectrodes, 3) pH-sensitive dyes, and 4) Nuclear magnetic resonance. Among four techniques, the advantage of the microelectrode approach is that it can monitor membrane potential at the same time and be applied to a single cell. The dye technique is a relative new developing technique, which has lots of advantages. It is easy to use, and is capable of monitoring rapid pHi changes, and being applied to a smaller cell, or a single cell.

Simulation of the profile of water, NaCl, and urea transport in the countercurrent multiplication system between thin ascending limb and inner medullary collecting duct

We simulated the profiles of water, NaCl, and urea transport in the countercurrent multiplication system between thin ascending limb (TAL) and inner medullary collecting duct (IMCD) by a mathematical model consisting of three compartments (TAL, IMCD, and CNW [capillary network]), using phenomenological coefficients for hamsters. They are separated by two membranes with distinct permeability properties. The primary driving force which generates "single effect" has a lower reflection coefficient for urea than for NaCl in IMCD. The difference in urea and NaCl concentrations between CNW and IMCD provides an effective osmotic driving force which is favorable for water absorption from IMCD without physicochemical osmotic gradient. The entry of water in the CNW reduces the concentration in CNW and generates the concentration gradients which are favorable for these solutes to diffuse out of TAL. Thus, the fluid in IMCD is concentrated and that in TAL is diluted. The results of simulation showed that the concentration gradients were generated along the medullary axis, resulting in excretion of hypertonic urine. In addition, we examined effects of changes in phenomenological coefficients of IMCD on this concentrating system. Decreases in permeability and in reflection coefficient for urea and increase in hydraulic conductivity increased the osmotic gradients along each compartment.

[A clinical course and autopsy results of an 8-year-old severely handicapped girl with marked periventricular leukomalacia]

We reported a clinical course and autopsy results of an 8-year-old severely handicapped girl with marked periventricular leukomalacia. She was well until 3 days prior to first admission in local hospital. Two days prior to admission, she began to vomit. Twelve hours later, she was noted to be lethargic and developed malaise with frequent vomiting. At physical examination on admission, she had frequent fits and her posture was decerebrate rigidity. Consciousness disturbance continued for two weeks. Thereafter, she became severely handicapped with spastic quadriplegia, mental retardation and intractable epilepsy. She was transferred to our hospital one month later. We cared her totally and carefully with our rehabilitation staff, but during her course several rare happening occurred; she suffered from subdural hemorrhage due to hypocupremia and received an operation for the release of contracture of her hips. She died of acute cardio-respiratory failure at 8 years and 5 months of age. Her autopsy findings were characteristic of the damage to an immature brain during development; cactus formation of cerebellar cortex and periventricular leukomalacia.

The interferon-alpha 2b gene in Japanese patients with chronic viral hepatitis who developed antibodies after treatment with recombinant interferon-alpha 2a

DNA was extracted from leucocytes of 23 Japanese patients with chronic viral hepatitis who received treatment with recombinant interferon-alpha 2a (IFN-alpha 2a) and nine healthy controls, as well as eight human cell lines of Caucasian or African origin. A part of the gene encoding IFN-alpha 2 was amplified by polymerase chain reaction and the sequence of nucleotides 1-231 was determined. Interferon-alpha 2a, -alpha 2b and -alpha 2c genes were tested for in five clones each from a patient or control, or a cell line, based on adenine or guanine at nucleotide positions 68 and 101. The IFN-alpha 2b gene was detected in all 160 clones from 23 Japanese patients and nine controls, but the IFN-alpha 2a or -alpha 2c gene was not found in any. Of five cell lines derived from Caucasians, four exhibited only the IFN-alpha 2b gene, while the remaining one exhibited both IFN-alpha 2a and -alpha 2b genes. Of three cell lines derived from Africans, one each showed only the IFN-alpha 2b or -alpha 2c gene, and the remaining one both IFN-alpha 2b and -alpha 2c genes. The 23 patients with the IFN-alpha 2b gene and chronic viral hepatitis included 10 who developed antibodies against IFN after treatment with recombinant IFN-alpha 2a. These results indicated a distinct geographical distribution of the three IFN-alpha 2 genes, and suggested the use of a recombinant IFN-alpha 2 preparation in agreement with the IFN-alpha 2 gene possessed by the recipient to avoid antibody responses.

[Valve injury: a new complication of internal jugular vein cannulation]

Although internal jugular vein cannulation is performed commonly, most physicians are not aware of existence of the internal jugular venous valve. This is the only valve between the right atrium of the heart and the brain, and it has an important role of preventing retrograde blood flow and increased back pressure to the brain. In this study, anatomic appearance of human internal jugular valves is described, and the competence of these valves is assessed. We examined also a safe approach to percutaneous cannulation of the internal jugular vein to avoid this complication. In the cadaveric subjects, the internal jugular vein with its valve was removed at the time of autopsy. In the living subjects, to examine the movement of this valve, endoscopic visualization utilizing the superfine fiberscope, and ultrasound techniques were applied. Next, to detect the competence of the jugular venous valve, transvalvular pressure gradients were measured. Nineteen internal jugular valves were obtained from 20 cadaveric subjects. These valves were situated directly above the termination of the internal jugular vein into the inferior bulb. The opening and closing of the valve were easily visualized with both superfine fiberscope and real-time ultrasound technique. Patients with competent valves showed transvalvular pressure gradients of 50-100 mmHg during cough-induced high intrathoracic pressure. Internal jugular venous valve is located 0.5-2.0 cm above the union of the subclavian and internal jugular veins, and the central approach performed at the summit of the cervical triangle has been shown to have a risk of injuring the internal jugular venous valve.(ABSTRACT TRUNCATED AT 250 WORDS)

Histological and histochemical investigations on Japanese lizard esophagus

The authors previously investigated the bottle-shaped glands distributed in the lamina propria mucosae of the Japanese lizard and gecko. We made two sets of sections of the Japanese lizard at that time. The numerical values of the physical dimensions of the two individuals were as given table 1, showing that No. 2 was slightly smaller. Moreover we found very unusual tissue in the lower portion of the esophagus of No. 2. Therefore we excluded this individual from the preceding investigations. However, we made various observations, and the results of these investigations are as follows. 1. The lumen of the upper portion of the esophagus has no fold. However, the middle and lower portions formed very complicated folds. Therefore, the lumen was remarkably narrow. 2. The epithelium of the esophageal mucous membrane consisted of simple columnar cells and throughout each part, reacted strongly to PAS and moderately to AB (pH 2.5 and 0.5). It presented a dark blue (R18-B13 of Blue-Purple-Red) color in response to PAS-AB (pH 2.5) and contained no pepsinogen granules. The esophageal upper portion of small individuals only exhibited the PAS reaction in this investigation. 3. A number of bottle-shaped glands were distributed in the lamina propria mucosae of the lower portion of the esophagus of each material. The glandular cells in the basal portion were most differentiated and contained a great number of pepsinogen granules. 4. The above-mentioned glands were extremely simple and glands of this type could not be found in textbooks and theses. Accordingly, we previously described them with the tentative name of shimple branched tubular glands, but subsequently found this to be erroneous. We assume that these glands are esophageal gastric glands. 5. Compound tubular glands are formed in the lamina propria mucosae of the human esophagus, but do not exist in the Japanese macaque, crab-eating monkey, horse, cow, swine, dog, cat, rabbit, mouse and rat. Dellmann-Brown also described the absence of such glands in the esophagus of the horse, swine, cow, goat, sheep, dog and cat. 6. We subsequently found compound tubular glands distributed in the lamina propria mucosae of the fowl, goose and wild duck esophagus. They similarly secreted pepsinogen granules. 7. We assume that these glands of the Japanese lizard and gecko have a phylogenic relation with the glands in the bird. The pepsinogen-granule-secreting cells in the snake do not extend into the lamina propria mucosae.(ABSTRACT TRUNCATED AT 400 WORDS)

Replenishment of brain adenosine triphosphate content by morphinan-type N-methyl-D-asparatate receptor antagonists, dextrorphan and dextromethorphan through the activation of adenylate kinase

The in vitro effects of four N-methyl-D-aspartate (NMDA) receptor antagonists, dextrorphan, (DX, CAS 125-73-5), dextromethorphan, (DM, CAS 125-71-3), dizocilpine (CAS 77086-21-6) and (+/-) 2-amino-7-phosphonoheptanoate (AP-7, CAS 85797-13-3) on rat brain adenylate kinase (AK) have been studied. DM was the most active of the four compounds in increasing rat brain AK activity. DX was slightly less active than DM, while the most potent NMDA antagonist, dizocilpine was somewhat weaker than the above two morphinan analogs (DX and DM). For AP-7, the AK activity was unchanged. The results may indicate that a causal relation cannot be made between the activation of the AK by these compounds and their ability to act as NMDA antagonists. When DX was added, the Km and Vmax values of the enzyme for ADP as a substrate decreased and increased, respectively, possibly reflecting an affinity change for the enzyme-substrate interaction by DX. The observed increase in the AK activity by the morphinan-type NMDA antagonists in vitro might result in their preserving effects on cerebral neuron integrity under the conditions where cerebral energy metabolism is disturbed. This assumption was at least partly confirmed in in vivo tests in which DX, unlike dizocilpine, increased ATP content of the brain in mice under the influence of hypoxia exerted by i.v. injection of KCN.

Effect of dietary sodium restriction on mRNA for aldosterone synthase cytochrome P-450 in rat adrenals

Changes in the level of mRNA for aldosterone synthase cytochrome P-450 (cytochrome P-450aldo) in rats on dietary sodium restriction were studied by means of Northern and slot blot hybridization using an oligonucleotide probe that allowed differentiation of the message for this enzyme from that for cytochrome P-450(11)beta. These two enzymes have been shown to be highly homologous with each other, exhibiting 88% homology in their nucleotide sequences in the coding region. Upon sodium restriction for 2 weeks, cytochrome P-450aldo mRNA in rat adrenals increased 7-fold, whereas the cytochrome P-450(11) beta mRNA level in the same adrenals did not change significantly. The increase in cytochrome P-450aldo mRNA paralleled that in cytochrome P-450aldo protein, as analyzed by immunoblot technique. These results, together with our previous finding that angiotensin II induced cytochrome P-450aldo in rat adrenocortex [Shibata, H., Ogishima, T., Mitani, F., Suzuki, H., Murakami, M., Saruta, T., & Ishimura, Y. (1991) Endocrinology 128, 2534-2539], suggest that the production of cytochrome P-450aldo is regulated by angiotensin II at the pretranslational level, most likely at the transcriptional level.

[A case of sarcoidosis with primary acute pulmonary cavitation]

A 23-year-old man was admitted to our hospital on June 24, 1991, because of worsening chest X-ray findings of sarcoidosis. In August 1990, he was referred to our outpatient office, because of BHL and nodular lesions on chest X-ray film performed at his company 4 months earlier. At that time, serum ACE was elevated to 34.0 IU/l, and Ga scintigraphy showed abnormal uptake in bilateral lacrimal and salivary glands, mediastinal and hilar lymph nodes, and in the lung fields. TBLB specimen showed noncaseating epithelioid granuloma with giant cells and negative stains for acid-fast bacilli. Although it was planned to follow this patient without medication, he did not return to our outpatient department. In June 1991, because of worsening of lesions in the lung at annual checkup at his company, he was referred and admitted for steroid therapy. Chest X-ray film on admission showed BHL, multiple nodular lesions in both lung fields, and bullous change in the left upper lobe. Chest CT on admission showed three cavitating lesions within preexisting nodules. PPD skin test was negative, and sputum smears and cultures were repeatedly negative for pyogenic bacteria and acid-fast bacilli. Therapy was initiated with prednisolone 30 mg daily. Four months later, there was marked resolution of BHL and nodular lesions, and the cavitating lesions were no longer visible on chest X-ray film. From the clinical and radiological observations, it is concluded that the cavitating lesions in the present case were primary acute pulmonary cavitation in sarcoidosis, distinct from infection, bullae, or cystic bronchiectasis which are seen in the chronic and fibrotic stages of sarcoidosis.

[Control of blood pressure by a calcium antagonist during cataract surgery]

The authors evaluated the systemic and ocular hypotensive effects of nicardipine hydrochloride (Perdipine:NH) in 31 cases with acute hypertension (over 160/95 mmHg) during cataract surgery. All cases received an intravenous bolus injection of NH 30 micrograms/kg. Blood pressure and intraocular pressure were compared with level at rest, a preoperatively and 5 minutes after the administration of NH. Blood pressure significantly elevated from 136.9 +/- 10.6/73.4 +/- 10.2 mmHg at rest to 187 +/- 11.5/98 +/- 13.1 mmHg preoperatively (p less than 0.001), but it significantly reduced to 125.6 +/- 13.1/67.1 +/- 8.3 mmHg 5 minutes after the administration of NH (p less than 0.001). On the other hand, in the same way an blood pressure changed, intraocular pressure significantly elevated from 13.3 +/- 2.8 mmHg at rest to 19.8 +/- 2.9 mmHg preoperatively (p less than 0.001), but significantly reduced 17.1 +/- 3.0 mmHg 5 minutes after administration of NH (p less than 0.001). The hypotensive effect of NH continued for over 90 minutes. There were no side effects apart from mild tachycardia in all cases. NH is safe, easy to administer and useful for control of acute hypertension during limited-period surgery such as cataract surgery.

[Direct observation of the epidural space by the superfine fiberscope]

The anatomy of the epidural space was examined in 82 patients 3 to 90 years old who had indications of epidural anesthesia. The superfine fiberscope with an outer diameter of 0.8 mm was utilized for this study. It was advanced through 18 gauge Tuohy needle inserted into the epidural space. All findings were documented by videography. The epidural space was located at the thoracic intervertebral space (52 patients), at the lumbar interspace (27 patients) and at the caudal space (3 patients), using an 18-gauge Tuohy needle with either median or paramedian approach. The epidural space was identified by either hanging drop or loss of resistance method. 65 of 82 cases gave a clear view of epidural space. The epidural space presented as either a space that opened widely or a space that was occupied with large masses of fat. Vessels were encountered on the dura and the flaval ligaments, as well as in the connective tissue. Large amounts of connective tissue were present in all cases. No complications, such as accidental dural puncture, epidural hematoma, infection, nerve injury attributed to this technique were observed.

Family of a patient with serum cholinesterase deficiency

A-39-year-old man was admitted to our hospital because of a markedly decreased level of serum cholinesterase found incidentally by a blood test. Detailed examination did not reveal severe liver disease, malignant tumor, infection or organophosphate compound poisoning. Investigation of three generations of his family revealed two homozygous and five heterozygous family members with the cholinesterase deficiency gene E1s indicating familial serum cholinesterase deficiency.

Transcription in vivo within the replication origin of the Escherichia coli chromosome: a mechanism for activating initiation of replication

Within the replication origin, oriC, of the Escherichia coli chromosome, novel in vivo transcripts were detected which proceeded rightward and whose production was activated by DnaA protein. In contrast, DnaA protein repressed the previously described ori-L leftward transcription. The former should introduce negative supercoiling, and the latter positive supercoiling, into the 13-mers. The effects of transcription on the initiation of replication were also investigated by making constructs with promoters placed near oriC. Transcription was found to enhance the origin activity only when it was oriented in such a way as to introduce negative supercoiling into the 13-mers. From these results, we propose that transcription within oriC regulates replication initiation by altering the topology of the 13-mer region.

Cardiac fibroma. Long-term fate after excision

Between 1980 and July 1983 three infants and children with cardiac fibromas underwent surgical resection at Kobe Children's Hospital. Two of them survived and have an excellent clinical result 6 years and 7 years postoperatively. The results of late follow-up with the use of 24-hour dynamic electrocardiography, two-dimensional echocardiography, thallium-201 myocardial scintillation scan, and technetium 99m sodium pertechnetate-gated blood pool imaging have proved that the patients are free of arrhythmic episodes, free of recurrence of tumor, have no significant myocardial perfusion defect, and have normal left ventricular function.

Glands distributed in the lamina propria mucosae of the esophagus in the gecko and Japanese lizard

In an earlier study, we found compound tubular glands distributed in the lamina propria mucosae of human and fowl esophagus. Subsequently, we discovered bottle-shaped glands in the Japanese lizard and gecko esophagus in the same lamina as that of the human and fowl. Moreover those glands produced equivalent pepsinogen granules. We provide below, a detailed description on the results. 1. Bottle-shaped glands were distributed in the lamina propria mucosae of the Japanese lizard and gecko esophagus. 2. A large number of those glands were distributed in the lower region of the esophagus, but did not exist in the upper and middle regions of the esophagus. 3. The esophageal mucous membrane of the gecko and Japanese lizard were covered with a simple columnar ciliated epithelium, and the same epithelium reacted strongly to PAS and AB (pH 2.5), moderately to AB (pH 0.5) or negatively. 4. PAS-AB (pH 2.5) stain presented a dark blue color or a deep red color or a deep red and dark blue mixed color in one section. 5. The above-mentioned glands contained pepsinogen granules. 6. Those glands do not possess parietal cells.

Tissue distribution of mouse mammary tumor virus (MMTV) antigens and new endogenous MMTV loci in Japanese laboratory mouse strains

The distribution of mouse mammary tumor virus (MMTV) antigens was studied by the immunoperoxidase method in the II-TES and I-TES mouse strains as well as their progenitors, CS and DBA/2 strains. In the II-TES, I-TES and CS strains, and BALB/c mice foster-nursed with these strains, MMTV antigens were found not only in epithelial cells of the mammary glands but also in those of other tissues including the seminal vesicle, vas deferens, epididymis, prostate, parotid, submandibular, lacrimal, sebaceous, and urethral glands. In DBA/2 and BALB/cfDBA/2 mice, however, the MMTV antigens were found only in the mammary glands. Electron microscopic examination showed MMTV particles in these organs. When we examined the presence of Mtv-1 and 2 proviruses, which are known to be responsible for MMTV expression, in the genomes of the II-TES, I-TES, CS and DBA/2 strains by Southern blotting, Mtv-2 was not found in any of the mice and Mtv-1 was found in the II-TES and DBA/2 mice but not in the I-TES and CS mice. Instead, four new endogenous MMTV loci, which have never previously been reported in laboratory mouse strains, were detected in the genomes of the II-TES, I-TES and CS strains. One (designated Mtv-42) was common in the three strains and the other three (designated Mtv-43, 44 and 45) were common in the II-TEX and I-TES strains or the II-TES and CS strains. These results thus suggest that new endogenous MMTV loci may be responsible for MMTV expression in a variety of tissues of these three strains.

Structural differences in 5'-flanking regions of rat cytochrome P-450aldo and P-450(11) beta genes

Two rat genomic clones, one for cytochrome P-450aldo and the other for P-450(11) beta, were isolated and characterized. The two genes, encoding structurally homologous proteins, were closely similar in their intron-exon organizations. Their 5'-flanking regions, however, contained only a few homologous regions. A putative cyclic AMP responsive element, TGACGTGA, was found in the P-450aldo gene, but this sequence was altered at two positions in the P-450(11) beta gene. S1 nuclease protection assay revealed a single transcription initiation site for the P-450aldo gene, while multiple sites were found for the P-450(11) beta gene. These results suggest that transcriptional regulation of the rat P-450aldo and P-450(11) beta genes is due to differences in the sequences of their 5'-flanking regions.

[Results of open heart surgery in neonates--comparison between profound hypothermia with circulatory arrest and deep hypothermic bypass]

To investigate factors affecting surgical outcome of open heart surgery in neonates, a retrospective review was carried out on 38 patients operated in the 9 years period from May 1981 to August 1990, in our institution (TAPVR19, TGA7, HLHS7, and others 5). In the former 3 years and 9 month period, 12 patients were operated with the use of profound hypothermia and circulatory arrest (Group I) and in the latest 5 year and 5 month period, continuous deep hypothermic bypass was used in all but for 7 patients with HLHS (Group II). In the group of neonates with TAPVR, operative mortality improved to 7% (1 of 14) in Group II compared to that of 60% (3 of 5) in Group I. CVP and LAP measured immediately after cessation of cardiopulmonary bypass (CPB) were lower in Group II and the value of CPK-MB was significantly lower in Group II. There was a significant negative correlation (r = -0.695, p less than 0.05) between CPB time and urine volume for 72 hours after operation. A significant negative correlation (r = -0.899, p less than 0.01) was also obtained between CPB time and urine volume in the group of 7 neonates with TGA. There was no significant difference in urine volume between patients with TAPVR and TGA despite of significantly longer CPB time in patients with TGA. It is concluded that, 1) improved protection of cardiac and renal function was obtained in neonates operated with the use of continuous deep hypothermic bypass, 2) surgical outcome was influenced by the method of CPB, CPB time and differences in cardiac function ascribed to primary lesions.

Pepsinogen granules in the esophageal epithelium of the rock snake

We demonstrated a large number of pepsinogen granules in the esophageal pseudostratified ciliated epithelium of the rock snake. 1. The snake esophagus is covered with a pseudostratified ciliated epithelium. 2. This epithelium develop mostly in the upper portion of the esophagus. 3. Long supranuclear portions of the same cells are strongly PAS-positive and contain pepsinogen granules. Those cells possess cilia. 4. The strongly PAS-positive cells and pepsinogen granules decrease or are lost in the middle and lower portions of the esophagus. 5. Glands are distributed in the lamina propria mucosae of the esophagus of the Japanese lizard and gecko. Those in humans and the bird are compound tubular glands and those of the Japanese lizard and gecko are bottle-shaped. The pepsinogen granules of these glands are secreted into the excretory ducts and then discharged into the esophageal lumen. 6. However, the same granules of the snake are contained in the supranuclear portion of the epithelium and are secreted directly into the esophageal lumen. 7. The mode of pepsinogen granule secretion of the esophagus is most simple in the snake.

Effect of protamine on ion conductance of ascending thin limb of Henle's loop from hamsters

To evaluate the contribution of paracellular shunt pathway in ascending thin limb (ATL) of hamsters, we examined the effect of protamine, a selective blocker of paracellular conductance, on salt-diffusion voltage (dVT) and transmural resistance (RT) during in vitro microperfusion. Lumen-negative dVT generated on reduction of lumen NaCl concentration was increased further from -7.3 +/- 0.5 to -10.3 +/- 0.7 mV when 300 micrograms/ml protamine was added to the lumen, and calculated Na+/Cl- permeability ratio was decreased from 0.46 +/- 0.03 to 0.31 +/- 0.03. Although the effect of protamine persisted after removal of the agent from the lumen, addition of 30 U/ml heparin returned the dVT toward the control level. The effect of protamine was dose dependent from 30 to 300 micrograms/ml. Protamine also exerted its effect from the bath, and the effect was inhibited by heparin either from the lumen or from the bath. The inhibitory effect was almost the same when the orientation of imposed NaCl gradient was reversed. Inhibition of transcellular Cl- transport with 0.1 mM 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB) in the bath caused lumen-positive dVT. This voltage was decreased significantly by protamine. Protamine markedly decreased the apparent transference number for Na+ but slightly increased the value for Cl-. Transmural cable analysis showed that 300 micrograms/ml protamine added to the lumen increased RT from 0.59 +/- 0.10 to 1.20 +/- 0.20 omega.cm2, with the effect being reversed by 30 U/ml heparin.(ABSTRACT TRUNCATED AT 250 WORDS)