Eicosapentaenoic acid modulates cyclin expression and arrests cell cycle progression in human leukemic K-562 cells

Eicosapentaenoic acid (EPA) is a polyunsaturated fatty acid (20:5omega3) found primarily in aquatic organisms. We have shown previously that EPA inhibits the growth but is not toxic to human leukemic K-562 cells. In this study, the anti-proliferative effect of EPA on the leukemic cells was further determined and its impacts on cell cycle progression and cyclin expression were investigated. EPA inhibited proliferation of K-562 cells, which was associated with accumulation of G0/G1 cells and down-regulation of cyclin E expression. Cyclin B1-expressing cells were also reduced showing that down-regulation of cyclin expression might be important in the anti-proliferation of EPA.

Induction of apoptosis by a ribosome-inactivating protein from Agrostemma githago is associated with down-regulation of anti-apoptotic bcl-2 protein expression

Agrostin is a type 1 ribosome-inactivating protein (RIP) isolated from the seeds of Agrostemma githago. 3[H]-thymidine incorporation in human leukemic HL-60 cells was significantly reduced after incubation with agrostin showing that the RIP was inhibitory on the cell proliferation. Results from flow cytometric studies illustrated that apoptosis was induced by agrostin, which was associated with activation of endonucleases and DNA fragmentation of the leukemic cells. Anti-apoptotic bcl-2 protein level was also reduced by agrostin showing that the associated apoptotic pathway might involve down-regulation of the intracellular bcl-2 protein level.

Induction of apoptosis by dietary polyunsaturated fatty acids in human leukemic cells is not associated with DNA fragmentation

Apoptosis is important in anticancer strategy. In this study, bivariate annexin V/PI flow cytometry showed that dietary polyunsaturated fatty acids, arachidonic acid (AA) and eicosapentaenoic acid (EPA), induced apoptosis in human leukemic HL-60 but not K-562 cells. Results from DNA-PI flow cytometry and TUNEL flow cytometry illustrated that neither AA nor EPA induced DNA fragmentation in the leukemic cells. These findings suggested that the AA- and EPA-induced apoptosis might not associate with endonucleases activation, and DNA fragmentation could not be used as a sole criterion to identify apoptotic cells.

The binding characteristics and intracellular localization of temoporfin (mTHPC) in myeloid leukemia cells: phototoxicity and mitochondrial damage

The state of aggregation of the photosensitizer meso-tetrahydroxyphenylchlorin (mTHPC) in both cell free and intracellular environment was elucidated by comparing its absorption and excitation spectra. In methanol, mTHPC existed as monomers and strongly fluoresced. In aqueous solutions such as phosphate-buffered saline (PBS), mTHPC formed nonfluorescent aggregates. Some portion of mTHPC monomerized in the presence of 10% fetal calf serum PBS. In murine myeloid leukemia M1 and WEHI-3B (JCS) cells, cytoplasmic mTHPC were monomeric. By using organelle-specific fluorescent probes, it was found that mTHPC localized preferentially at the mitochondria and the perinuclear region. Photodynamic treatment of mTHPC-sensitized leukemia cells caused rapid appearance of the apoptogenic protein cytochrome c in the cytosol. Results from flow cytometric analysis showed that the release of cytochrome c was especially pronounced in JCS cells, and well correlated with the extent of apoptotic cell death as reported earlier. Electron microscopy revealed the loss of integrity of the mitochondrial membrane and the appearance of chromatin condensation as early as 1 h after light irradiation. We conclude that rapid release of cytochrome c from photodamaged mitochondria is responsible for the mTHPC-induced apoptosis in the myeloid leukemia JCS and M1 cells.

Induction of apoptosis in HL-60 cells by eicosapentaenoic acid (EPA) is associated with downregulation of bcl-2 expression

Dietary polyunsaturated fatty acids (PUFAs) have been reported as a potential group of natural products which modulate tumor cell growth. In present study, eicosapentaenoic acid (EPA) was found to inhibit proliferation of human leukemic HL-60 and K-562 cells in vitro. EPA arrested cell cycle progression at G0/G1 phase, and induced necrosis in both HL-60 and K-562 cells. However, EPA induced apoptosis only in HL-60 but not K-562 cells. Also, bcl-2 protein expression was downregulated in much greater extent than that of bax showing that depression of bcl-2 might be an important step during the EPA-induced apoptosis in HL-60 cells.

Biliary ascariasis: CT, MR cholangiopancreatography, and navigator endoscopic appearance--report of a case of acute biliary obstruction

A case of acute common bile duct obstruction caused by a roundworm in a 6-year-old girl is reported. Computed tomography (CT) and magnetic resonance imaging (MRI) showed "bull's-eye" and "eye-glass" appearances of the ascaris in the common bile duct. On reformation of the transverse CT and coronal MR images, the tubular Ascaris was better depicted. MRI and navigator endoscopic demonstrations of the common bile duct ascaris have not been described previously in the literature. These CT and MRI findings may be helpful in the diagnosis of Ascaris.

Magnetic resonance angiography in the diagnosis of thoracic venous obstruction

The aims of this study were to evaluate the diagnostic value of orthogonal magnetic resonance angiography (MRA) and to compare the results of MRA with those of digital subtraction venography (DSV) in thoracic venous diseases. Ten normal volunteers were evaluated using two-dimensional time-of-flight MRA in three orthogonal planes to determine the image quality of each venous segment. Twelve consecutive patients suspected of having thoracic venous disease were studied with both MRA and DSV. In the normal subjects, the plane perpendicular to the target vein provided the most consistent visualization. Using three orthogonal MRA images, a diagnostic-quality image was obtained in 175 (83%) of 210 venous segments in normal volunteers. In patients with thoracic venous obstructive disease, MRA was more effective than DSV in detecting total (84 vs 54), patent (56 vs 36), stenotic (13 vs 10), and obstructive (15 vs 8) venous segments, poststenotic or postobstructive veins (15 vs 10), thrombosis of the internal jugular vein (7 vs 2), intraluminal thrombus (5 vs 3), and azygos veins (12 vs 2). Using venous segments visible on DVS (n = 54) as the standard, the sensitivity and specificity of MRA were 94% and 100%, respectively, in detecting venous patency, and 100% and 98% in detecting complete venous obstruction. In the shoulder region, the sensitivity and specificity of MRA were 93% and 100%, respectively, in detecting venous patency, and 100% and 97% in detecting venous obstruction. We conclude that MRA with three orthogonal planes can provide relatively complete and reliable venous mapping, without the need for contrast medium.

2-D time-of-flight (TOF) MRA of thrombophlebitis of upper extremity and subclavian veins. A case report

In this report, the authors present a case of segmental thrombosis of left subclavian vein that was inaccessible to conventional venography and inconclusive in magnetic resonance techniques (spin echo, gradient echo) but was clearly demonstrated by two-dimensional time-of-flight magnetic resonance angiography (2D TOF MRA). This technique is very sensitive to detect slow flow or partial occlusion of the vessels and is of great help in solving the problem of axillary-subclavian venous obstruction or thrombophlebitis.

Effect of polysaccharide peptide (PSP) on in vivo sulphation and glucuronidation of paracetamol in the rat

The effect of polysaccharide peptide (PSP), an immunomodulator isolated from Coriolus versicolor COV-1, on the disposition of paracetamol was investigated in the rat. PSP (100 and 200 mg/kg, i.v.) was administered 30 min before a moderate dose (100 mg/kg, i.v.) of paracetamol was given. Plasma and bile concentrations of paracetamol, paracetamol glucuronide and paracetamol sulphate were measured by high performance liquid chromatography. The pharmacokinetics of paracetamol (100 mg/kg) alone was consistent with those reported previously, using a one-compartment model. PSP (200 mg/kg) significantly (P < 0.05) increased the clearance (controls, 19.06 +/- 2.74 ml/min/kg: PSP treated, 26.22 +/- 0.84 ml/min/kg) and volume of distribution (controls, 1.35 +/- 0.11 l/kg: PSP treated, 1.61 +/- 0.04 l/kg) of paracetamol by 37% and 21%, respectively. These changes were associated with concomitant increases in the glucuronide and sulphate metabolites in plasma, with significant increases in the Cmax and Tmax for both metabolites. The biliary excretion rate of paracetamol glucuronide and paracetamol sulphate were also measured. The Cmax values of paracetamol sulphate were significantly (P < 0.01) increased by 2.4-fold from 907.8 +/- 157.7 micrograms/ml (controls) to 3061 +/- 331 micrograms/ml after PSP treatment. The lower dose of PSP (100 mg/kg) had no significant effect on the disposition of paracetamol in this study, which agreed with previous reports that a low dose of PSP (100-200 mg/kg, i.p.) was less effective in the protection against paracetamol-induced hepatotoxicity. The time course of the increase in paracetamol sulphate in plasma and bile in this study coincided with the transient perturbation of glutathione (GSH) turnover by a similar dose range of PSP previously described, such that more cysteine was available for oxidation to inorganic sulphate. This increase in sulphate conjugation by PSP would, in part, contribute to the increase in disposition of paracetamol and may be related to the ability of PSP to decrease the covalent binding of paracetamol to microsomal proteins previously reported. Further studies are necessary to understand the mechanism(s) involved in the PSP-induced increases in paracetamol glucuronide and paracetamol sulphate formation and biliary excretion.

Effect of polysaccharide peptide (PSP) on glutathione and protection against paracetamol-induced hepatotoxicity in the rat

The protective effects of polysaccharide peptide (PSP), isolated from Coriolus versicolor COV-1, on paracetamol-induced hepatotoxicity was investigated in this study. The effect of PSP on hepatic glutathione status was also studied. PSP (300 mg/kg, i.p.) caused a 40% depletion of hepatic reduced glutathione (GSH) with a concomitant 50% increase in oxidized glutathione (GSSG), thus producing a 3-fold increase in the GSSG/GSH ratio. The PSP-induced GSH depletion itself had no hepatotoxic effects. PSP protected against paracetamol-induced hepatotoxicity by decreasing the paracetamol-induced elevation of serum glutamic-pyruvic transaminase (SGPT) activity from 511 +/- 71 U/ml to 187 +/- 58 U/ml (controls without paracetamol 105 +/- 4 U/ml) and serum glutamic-oxaloacetic transaminase (SGOT) activity from 462 +/- 63 to 152 +/- 48 U/ml (controls without paracetamol 54 +/- 6 U/ml). PSP did not reverse the depletion of total glutathione (GSH+GSSG) by the toxic dose of paracetamol. The GSSG/GSH ratio, which is a measure of oxidative stress, was significantly (p < 0.05) decreased when PSP was coadministered with paracetamol. PSP dose-dependently decreased the covalent binding of [14C]-paracetamol to microsomal proteins in vitro. When PSP was given to rats subchronically for 7 days (300 mg/kg/day, i.p.), the subsequent microsomes obtained also showed a 25% decrease in covalent binding to [14C]-paracetamol, suggesting that PSP interacted with the microsomal proteins rather than the chemically reactive metabolite of paracetamol. The changes in the binding affinity and capacity of the microsomal proteins by PSP may be related to its ability to alter the redox potential as indicated by the effects of PSP on the GSSG/GSH status.

Evaluation of hip disorders by radiography, radionuclide scanning and magnetic resonance imaging

Thirty-six hips were studied because of significant hip pain. Radiography of the hip and bone scintigraphy showed subtle changes. Magnetic resonance imaging (MRI) was performed using a 1.5 Tesla superconductive unit. All MRI findings were confirmed by surgical or pathologic results. Twenty-nine hips had a single lesion, including: infection (one), fracture (eight), avascular necrosis of the femur(two), or contralateral hip (four), transient osteoporosis (six), osteoporosis (one), post-irradiation myositis (one), metastasis (four), and synovitis (two). Twenty-six lesions (89.6%) appeared normal on the radiographs of the hip, while three lesions (10.4%) showed only osteoporotic change. Another seven hips had more than one lesion, including: avascular necrosis and fracture (four), fracture foci (two), and metastasis and fracture (two). Radiography of the hip showed either a negative finding or detected only a single lesion, missing other important pathologic foci. MRI is extremely sensitive to alterations in the bone marrow that may represent pathology occult to plain radiography and bone scintigraphy of the hips. For diagnosis and treatment planning, MRI of the hips should be performed early in patients with persistent pain and negative radiography findings.

MR patterns of rotator cuff and labral lesions: comparison between low-field and high-field images

Eighteen people (10 men, 8 women) were examined on a 0.3-T (low-field) imager with T1-weighted axial and coronal images and either axial or coronal T2-weighted images. Thirty-two people (22 men, 10 women) were examined on a 1.5-T (high-field) imager with axial T1-weighted images and coronal, sagittal dual-echo images. Rotator cuff lesions were diagnosed by the following findings: abnormal signal in the tendon, irregularity or discontinuity at the musculo-tendinous junction, or muscle abnormality. Glenoid labrum tears were considered if one or more of the following criteria were present: labral deformity of unusual size, focal defect, amputation or displacement with fluid, or capsular stripping. Comparison between the high-field and low-field MR images in the evaluation of rotator cuff lesions suggests that the high-field imager is better than the low-field imager in the differentiation of tendinitis from tears, in the confirmation of bursitis and in detection of subscapularis lesions. A higher contrast-to-noise ratio (CNR), less time consumption, and more section planes (especially, sagittal sections) appear to be the main reasons for this. As far as labral lesions are concerned, the performances of the high-field imagers and low-field imagers were almost equal. The artifact of greater chemical shift with a high-field imager would more or less, we assume, degrade the better CNR achievable in the diagnosis of labral lesions.

Multiplanar gradient recalled images of the knee: comparison of different flip angles and echo times

To determine the most appropriate combination of echo time (TE) and flip angle in gradient echo images of the knee, the authors used different TEs (10, 20 and 30 msec) and flip angles (10, 30, 50, 70, 90, 120 and 150 degrees) to perform a systematic study of MRI on 10 volunteer knees. Contrast-to-noise ratios of cartilage-fat, fluid-cartilage, fluid-fat and fluid-ligament were calculated and compared. Images with a 30-degree flip angle combined with 20 msec of TE were found to have the best contrast-to-noise ratios in both objective data analysis and subjective observation. Hyaline cartilage of the knee was hyperintense and was well delineated on this pulse sequence, appearing distinct in contrast to the intra-articular fluid. It is concluded that this T2-weighted gradient echo pulse sequence is an alternative to conventional spin echo T2-weighted imaging of the knee.

Effect of field strength on susceptibility artifacts in magnetic resonance imaging

In magnetic resonance imaging susceptibility artifacts occur at the interface of substances with large magnetic susceptibility differences, resulting in geometric distortions of the image at those boundaries. The susceptibility artifacts are often subtle on clinical images and if not carefully examined they may lead to misdiagnosis. Magnetic susceptibility artifacts are prevalent on the boundary of air-containing paranasal sinuses, as well as bone-soft tissue interfaces in the spinal canal. The appearance of these artifacts on images from three different magnetic field strength instruments, 0.3, 0.5, and 1.5 Tesla were studied. T1- and T2-weighted spin echo and gradient recalled echo pulse sequences were selected to image a water phantom containing substances of varying susceptibilities. The effects were also studied in MR images of the head in a normal human volunteer. At any given field strength the artifacts were more prominent in the gradient echo imaging than in the corresponding spin echo pulse sequence. As expected, the distortions were also greater at higher field strengths. The results in human subjects paralleled the findings in the phantom study.

Nuclear magnetic resonance study of obsessive-compulsive disorder

Magnetic resonance imaging (MRI) of the brains of 32 patients who met the DSM-III criteria for obsessive-compulsive disorder and of 14 normal subjects frequently revealed abnormalities, but none was specific to obsessive-compulsive disorder. Spin-lattice relaxation time (T1) for right frontal white matter was prolonged in the patients compared to the control subjects, and the patients had greater right-minus-left T1 differences for frontal white matter. Right-minus-left T1 differences in the orbital frontal cortex were strongly correlated with symptom severity in the unmedicated patients and in the patients with family histories of obsessive-compulsive disorder.

A magnetic resonance imaging study of autism: normal fourth ventricle size and absence of pathology

Magnetic resonance imaging did not diagnose neuropathology in 15 autistic patients. Measurements of the midsagittal area and volume of the fourth ventricle did not differ between these patients and matched control subjects.

Perirenal hemangioendothelioma in a newborn: sonograph and MR findings

This is a case report of perirenal hemangioendothelioma in a newborn and discussion of lesions in the perirenal space in newborns. The findings in this case, high echogenicity on sonographic images and high signal intensity on T2-weighted spin echo magnetic resonance images, mimic those described for hemangiomas in other locations.

Pott's disease. A resurgent challenge to the thoracic surgeon

Nineteen patients were treated at the Los Angeles County Harbor/UCLA Medical Center between 1971 and 1986 for tuberculosis of the spine. Fourteen were immigrants, a high-risk group. A high index of suspicion is required for Pott's disease, which occurs in fewer than 1 percent of patients with tuberculosis, often presents with nonspecific symptoms, and may result in permanent deformity or neurologic impairment. CT scan, the most useful diagnostic test, showed abnormal results in 11 of 11 patients. MRI, a newer modality, may provide even more information. Eight patients required operation in addition to antimicrobial therapy. Four had lesions between T3 and T10, where the spinal canal is narrow, of whom three (75 percent had neurologic involvement. All four underwent anterior approach (thoracotomy) for decompression, debridement, and spinal fusion. Fifteen had lesions between T11 and S2. Three (20 percent) had neurologic involvement but responded to medical treatment alone. Four underwent drainage of abscess or spinal fusion for deformity. Combined surgical and medical treatment gave excellent results in this series.

MRI of the upper abdomen using motion artifact suppression technique (MAST)

Magnetic resonance imaging of the upper abdomen has been hampered by motion artifacts that cause suboptimal image quality. A promising software solution to this problem, motion artifact suppression technique (MAST), is described. Using mathematically determined refocussing gradients, it has improved image clarity significantly. Unlike alternate techniques such as respiratory gating, there is no increase in scan time, and patient throughput is expedited.

Motion artifact suppression technique (MAST) for MR imaging

A technique has been developed that significantly improves the image resolution and reduces motion artifacts in conventional two-dimensional Fourier transform and three-dimensional Fourier transform magnetic resonance imaging sequences. Modifications on the gradient waveforms completely refocus the transverse magnetization at the echo time, regardless of the motion occurring between the time of the 90 degrees radiofrequency excitation and the echo time (within-view). This accomplishes suppression of motion artifacts and regains the signal from flowing blood and CSF. Images of the head, abdomen, chest, and spine are reproduced which show the increase in signal and anatomical detail that would otherwise be degraded and lost in artifact noise. This technique has reduced the practical difficulty of obtaining clinically diagnostic T2-weighted abdominal images. It also has allowed diagnostic quality T1- and T2-weighted images to be obtained with one acquisition per view, thus reducing the total scan time.

Superior vena cava obstruction: a venographic classification

Analysis of venacavograms in 27 patients with superior vena caval obstruction revealed the following four patterns of venous collateral return: type I, partial obstruction (up to 90% stenosis) of the superior vena cava with patency of the azygos vein; type II, near-complete to complete obstruction (90-100%) of the superior vena cava with patency and antegrade flow through the azygos vein and into the right atrium; type III, near-complete to complete obstruction (90-100%) of the superior vena cava with reversal of azygos blood flow; type IV, complete obstruction of the superior vena cava and one or more of the major caval tributaries, including the azygos system. These patterns correlate well with the patients' clinical courses and can be used to identify patients who are at risk of developing cerebral and airway compromise and therefore would benefit from superior vena cava bypass surgery.

Contiguous computed tomography angiography (CTA) of the chest

Contiguous computed tomography angiography (CTA) of the chest is a useful diagnostic adjunct to the overall process of mediastinal imaging. The authors' method, termed Chiu-Dynamic, which includes multiple bolus injection of contrast material and advanced software programming for rapid scanning, produces excellent opacification of mediastinal vasculature and allows easier assessment of vascular anomalies and pathological soft tissue lesions.

Visceral CT findings associated with Thorotrast

Plain radiography and CT of the abdomen were reviewed in four patients who had undergone angiography with thorium dioxide (Thorotrast). In three patients CT showed irregularly scattered focal punctate collections of Thorotrast in the liver parenchyma, predominantly in the subcapsular zone, associated with areas of low or nonhomogeneous attenuation. These areas of low attenuation were identified on microscopic studies as sites of hepatic fibrosis or neoplasia. Computed tomography identified intrahepatic Thorotrast deposits more definitively than plain radiography.

Sporadic Legionnaires' disease: clinical observations on 87 nosocomial and community-acquired cases

To add information about sporadic Legionnaires' disease, 87 cases of L. pneumophila pneumonia were reviewed. Twenty cases were nosocomial infections and 67 cases were community-acquired. Most cases (64%) occurred between July and October. The mean age of patients was 51.4 years and males outnumbered females 2.5:1.0. Thirty-one percent of patients were receiving corticosteroid, immunosuppressive, or antineoplastic chemotherapy when illness began. Immunosuppression at onset of illness was more common in nosocomial infections (90%) than in community-acquired infections (14%). Seventy percent of patients had underlying diseases. Malignancies, renal failure, and transplantation were the most common conditions underlying nosocomial infections. Chronic lung disease and malignancies were the most common diseases underlying community-acquired infections. The case-fatality rate in nosocomial infection (70%) was greater than that in community-acquired disease (22%). Clinical, laboratory, and radiologic features of the cases were examined. Illness ranged from mild to severe. Extrapulmonary findings of encephalopathy and renal failure were more common in fatal than in non-fatal cases. Indirect immunofluorescent and microagglutination antibody responses plateaued by the fourth week of illness. Twenty-nine patients died. The case-fatality rate of patients receiving erythromycin (6%) was less than that of patients receiving penicillin (36%), ampicillin (28%), cephalosporin (32%), or aminoglycosides (41%). Despite erythromycin therapy, the case fatality rate for nosocomial L. pneumophilia pneumonia was unacceptably high (25%).

Gastrointestinal bleeding and mycotic superior mesenteric aneurysm

This is a case report of management of a delayed mycotic superior mesenteric artery aneurysm occurring in a patient 2 years after aortic valve replacement for endocarditis. A chronic ulcer history, anticoagulation therapy, episodic gastrointestinal bleeding associated with negative gastrointestinal series, and gastritis seen at endoscopy delayed the ultimate diagnosis. An episode of massive hemorrhage precipitated angiography with subsequent surgical confirmation of the diagnosis. Management included debridement and extirpation of the major part of the aneurysm, Doppler assessment of the inadequacy of collateral mesenteric arterial blood flow, and restoration of flow with a bypassing saphenous vein graft segment. Although this technique of reconstruction has been suggested, we can find no other report of such a similar case among the few reported surgical successes with superior mesenteric artery mycotic aneurysm.

Legionnaires' disease among pneumonias in Iowa (FY 1972-1978) II. Epidemiologic and clinical features of 30 sporadic cases of L. pneumophila infection

We reviewed retrospectively the clinical records of 30 cases of sporadic Legionella pneumophila infection that occurred in Iowa between FY 1972 and 1978. Cases occurred throughout the year, most between May and December. Twenty-one male patients and 9 female patients ranging in age from 5-80 years were infected. Half the patients smoked or had an underlying illness; five were receiving corticosteroids or immunosuppressive therapy. Occupations and exposures related to hospitals, construction and travel were common; four patients had been exposed to birds. In addition to L. pneumophila infection, six patients had evidence of infection with a viral, mycoplasmal, bacterial, mycobacterial or fungal pathogen; three had had preceding dental infections. Twenty-seven cases were pneumonias visible on radiographs. Fever, cough, chills, myalgia and rales occurred inover half the cases. Headache, gastrointestinal symptoms and encephalopathy also were seen. Upper respiratory symptoms were uncommon. Urinalysis and blood studies often suggested renal and hepatic involvement, but other routine laboratory diagnostic tests were not helpful. All but two patients were hospitalized; seven required intensive care. The median duration of hospitalization was 12 days. Two patients who did not receive erythromycin or tetracycline therapy died.

Comparison of radionuclide and computed tomography scanning in non-neoplastic intracranial disease

In this comparison of computed tomography (CT) and radionuclide scanning (RN) in non-neoplastic disease, the CT and RN patterns in vascular occlusive disease, vascular anomalies, cerebral hemorrhage, cerebral infections, and trauma are described in detail. A retrospective evaluation of CT and RN findings in 514 patients provides a basis for determining which modality is more sensitive in a given disease entity. Illustrative cases demonstrate pertinent findings in both CT and RN scanning in the aforementioned disease categories.

Computed tomography of the pelvis

The computed tomography scan has revealed the location and size of abnormal pelvic masses as an adjunct to other diagnostic studies. We have extended its usefulness by air distension of the bladder, which accommodates to adjacent structures and, therby, highlights abnormalities in its own wall and in other organs. The patients are prepared according to a simple routine. As we attempt further economy and efficiency the cost of each study becomes justified by the information gained.