Evaluating the Use of CT-Derived Lung Volumes in Donor-Recipient Lung Size Matching for Lung Transplantation in Patients With Interstitial Lung Disease and/or Idiopathic Pulmonary Fibrosis.

PURPOSE: This study aims to assess the efficacy of current measurement strategies for lung sizing and the feasibility of future use of computed tomography (CT)-derived lung volumes to predict a donor-recipient lung size match during bilateral lung transplants. METHODS: We reviewed the data of 62 patients who underwent bilateral lung transplantation for interstitial lung disease and/or idiopathic pulmonary fibrosis from 2018 to 2019. Data for recipients was retrieved from the department's transplant database and medical records, and the donor's data was retrieved from the DonorNet. The data included demographic data, lung heights, measured total lung capacity (TLC) from plethysmography for recipients and estimated TLC for donors, clinical data, and CT-derived lung volumes in both pre- and post-transplant recipients. The post-transplant CT-derived lung volume in recipients was used as a surrogate for donor lung CT volumes due to inadequate or poor donor CT data. Computed tomography-derived lung volumes were calculated using thresholding, region growing, and cutting techniques on Computer-Aided Design and Mimics (Materialise NV, Leuven, Belgium) programs. Preoperative CT-derived lung volumes in recipients were compared with the plethysmography TLC, Frustum Model, and donor-predicted TLC. The ratio of the recipient's pre-and postoperative CT-derived volumes, the ratio of preoperative CT-derived lung volume, and donor-estimated TLC were studied to detect a correlation with 1-year outcomes. RESULTS: The recipient preoperative CT-derived volume correlated with the recipient preoperative plethysmography TLC (Pearson correlation coefficient [PCC] of 0.688) and with the recipient Frustum model volume (PCC of 0.593). The recipient postoperative CT-derived volume correlated with the recipient's postoperative plethysmography TLC (PCC of 0.651). There was no statistically significant correlation between recipients' CT-derived pre- or postoperative volume with donor-estimated TLC. The ratio of preoperative CT-derived volume to donor-estimated TLC correlated inversely with the length of ventilation (P value = .0031). The ratio of postoperative CT-derived volume to preoperative CT-derived volume correlated inversely with delayed sternal closure (P = .0039). No statistically significant correlations were found in evaluating outcomes related to lung oversizing in the recipient (defined as a postoperative to preoperative CT-derived lung volume ratio of >1.2). CONCLUSIONS: Generating CT-derived lung volumes is a valid and convenient method for evaluating lung volumes for transplantation in patients with ILD and/or IPF. Donor-estimated TLC should be interpreted carefully. Further studies should derive donor lung volumes from CT scans for a more accurate evaluation of lung size matching.

Percutaneous in situ coronary venous arterialization: report of the first human catheter-based coronary artery bypass.

Diffuse coronary artery disease is frequently untreatable by coronary artery bypass or angioplasty. Many such "no-option" patients have been subjects for trials of angiogenesis using growth factor manipulation or laser injury. We think these novel revascularization strategies are limited by insufficient inflow to putative areas of new microvasculature and thus seek a more mechanical solution. We report the use of a catheter-based system for arterializing the adjacent anterior cardiac vein in a patient with chronic total occlusion of the left anterior descending coronary artery. A composite catheter system (phased-array ultrasound imaging system mounted on a catheter with extendable nitinol needle) was used to deliver an exchange-length intracoronary guidewire from the proximal left anterior descending coronary artery into the parallel anterior interventricular vein. Using standard angioplasty techniques, a fistula was then constructed from the proximal artery to the coronary vein using a self-expanding connector. The proximal vein was blocked with a novel self-expanding "blocker," thus precluding "steal" through the coronary sinus and forcing retroperfusion of the anterior wall. The procedure was completed without complication, and a follow-up angiogram at 3 months confirmed continued patency of the arteriovenous connection. This patient, who had severe angina before the procedure, has been asymptomatic for 12 months. Percutaneous in situ venous arterialization may be an effective therapy for diffuse, "untreatable" coronary disease by supplying a robust inflow of arterialized blood via retroperfusion to severely ischemic myocardium.

Mesenteric and portal vein thrombosis in a young patient with protein S deficiency treated with urokinase via the superior mesenteric artery.

A 32-year-old man, who was previously healthy, had acute abdominal pain without peritonitis. Diffuse mesenteric and portal vein thrombosis were shown by means of a computed tomography scan. A protein s deficiency was found by means of an extensive workup for hypercoagulable state. Successful treatment was achieved with urokinase infusion via the superior mesenteric artery without an operation. This represents an attractive alternative approach to treating patients with this disease. The previous standard of operative intervention(1) can now be reserved for complications, such as bowel infarction with peritonitis, or for those patients with absolute contraindications to thrombolytic therapy.

How accurate is helical computed tomography for clinical staging of pancreatic cancer?

BACKGROUND: Our goal was to determine if findings on an index computed tomography (CT) scan would correlate with survival in patients with pancreatic adenocarcinoma. We know that as this tumor extends out of the gland, survival decreases. Are there any CT findings that assess tumor extension sufficiently that also correlate with survival? Once identified, these CT areas would be the best factors to clinically stage patients. METHODS: Between 1993 and 1997, 160 patients with biopsy-proven adenocarcinoma of the pancreatic head were included if an index helical CT scan and clinical follow-up were available. All CT scans were reviewed by the same radiologist blinded for outcomes. CT scans were interpreted using a graded extension of tumor out of the pancreatic head in four areas: retroperitoneum (RP); anterior pancreatic capsule (S); portal/superior mesenteric veins (PV); and celiac/superior mesenteric arteries (A). Extension of tumor was graded as follows: Grade 0 (negative margin); 1 (suspicious); 2 (positive); or 3 (extensively involved). Also recorded and graded were signs of metastases: nodal enlargement > or =1.5 cm (N); and lesions consistent with hepatic metastases (H). Survival was compared between grades for each CT area using the methods of Kaplan and Meier and relative risk estimates of death (Cox regression models). RESULTS: Compared with grade 0, the following CT areas had significantly decreased survival curves: grade 1 (only S and A), grade 2 and 3 (RP, PV, S, A). N and H did not correlate with survival unless > or =1.5 cm nodes were in the liver or splenic hilum or there were multiple liver nodules. CONCLUSION: Although postoperative microscopic H or N involvement is a reliable prognostic sign, only extensive CT involvement of H or N predicts survival preoperatively. A better CT finding that predicts decreased survival preoperatively was extension out of the pancreatic head (especially S or A). Clinical methods of staging should use CT areas such as S, A, PV, and RP, and not H and N.

Antiischemic effects of nicardipine and nitroglycerin after coronary artery bypass grafting.

BACKGROUND: We assessed the efficacy of a continuous infusion of nicardipine and nitroglycerin in reducing the incidence and severity of perioperative myocardial ischemia during elective coronary artery bypass grafting procedures in a prospective, randomized, controlled study. METHODS: Patients received either nicardipine infusion (0.7 to 1.4 microg x kg(-1) x min(-1); n = 30) or nitroglycerin (0.5 to 1 microg x kg(-1) x min(-1); n = 30) or neither medication (n = 17) after aortic occlusion clamp release and for 24 hours postoperatively. Myocardial ischemic episodes (MIE) were considered to have occurred with ST-segment depressions or elevations of at least 1 mm and at least 2 mm (for both depressions or elevations), each at J + 60 ms and lasting at least 1 minute, using a two-channel Holter monitor. RESULTS: Only nicardipine significantly decreased the duration (p = 0.02) of the 1-mm or greater minutes per hour (3.2 +/- 1.2 minutes per hour) and eliminated the number (p = 0.02) of the 2-mm or greater minutes per hour (zero minutes per hour) when compared with control patients (17.2 +/- 5.6 minutes per hour and 0.17 minutes per hour, respectively) during the intraoperative postbypass period. CONCLUSIONS: Our results suggest that nicardipine lessened the severity of myocardial ischemia shortly after coronary revascularization and could be considered as an alternative to standard antiischemic therapy.

Percutaneous CT-guided catheter drainage of infected acute necrotizing pancreatitis: techniques and results.

OBJECTIVE: The objective of this paper was to assess the safety and efficacy of percutaneous catheter drainage for initial treatment of infected acute necrotizing pancreatitis. MATERIALS AND METHODS: Thirty-four patients with acute necrotizing pancreatitis shown with contrast-enhanced CT were treated for sepsis with percutaneous catheter drainage. Extent of necrosis was less than 30% in 10 cases, 30-50% in 10 cases, and greater than 50% in 14 cases. Fourteen patients had central necrosis. Eighteen patients were critically ill with multiorgan failure. RESULTS: Sixteen (47%) of the 34 patients were cured with only percutaneous catheter drainage, including four (29%) of the 14 patients with central gland necrosis and 12 (60%) of the 20 with body-tail necrosis. Sepsis was controlled (defervescence of fever and return of WBC to normal) in an additional nine patients, allowing elective pancreatic surgery for control of pancreatic duct fistula. Eight patients failed to show clinical improvement after drainage and required necrosectomy. No patient experienced catheter-related complications. Mortality was 12% (all four deaths occurred after necrosectomy because of multiorgan failure). CONCLUSION: Percutaneous catheter drainage is a safe and effective technique for treating infected acute necrotizing pancreatitis. Overall, sepsis was controlled in 74% of patients, permitting elective surgery for treatment of pancreatic fistula, and 47% of patients were cured with no surgery required. No catheter-related complications occurred.

Expression of the multidrug resistance-associated protein (MRP) and chemoresistance of human non-small-cell lung cancer cells.

Human non-small-cell lung cancer (NSCLC) is considered to be a chemotherapy-refractory malignancy. The underlying mechanisms remain rather obscure. The multidrug resistance-associated protein (MRP), mediating a multidrug resistance (MDR) phenotype, has been reported to be overexpressed in several drug-selected lung cancer cell lines. A few previous studies have described intrinsic MRP expression in both NSCLC and normal lung tissues. However, the drug-transporting activity as well as the correlation with chemoresistance is unclear. Using 15 unselected cell lines, we show that MRP (mRNA and protein as detected by reverse transcriptase polymerase chain reaction and immunoblot) is frequently expressed intrinsically, with markedly varying intensity, in NSCLC. Two cell lines expressed high MRP levels, one comparable to the drug-selected controls (GLC4/ADR, HL-60/AR) without, however, amplification of the MRP gene (Southern hybridization). Using 3H-daunomycin (3H-DM) and calcein as MRP substrates and probenecid (PRO), genistein (GEN), benzbromarone (BB), N-ethylmaleimide (NEM) and verapamil (VP) as MRP modulators, drug accumulation studies revealed a transporting activity of MRP that correlated significantly with the gene expression data. Moreover, a significant correlation between MRP expression and chemoresistance against daunomycin (DM), doxorubicin (DOX), etoposide (VP-16) and vinblastine (VBL), but not cisplatin (CDDP) and bleomycin (Bleo) (MTT-based survival assay), was detected. Correlations mainly rested on the pronounced chemoresistance of 2 highly MRP-expressing cell lines and did not reach significance when these cell lines were excluded.

Possible role of the multidrug resistance-associated protein (MRP) in chemoresistance of human melanoma cells.

Human malignant melanoma is characterised by unresponsiveness to conventional chemotherapy. Melanoma-derived cell lines are often markedly chemoresistant, suggesting that cellular mechanisms mediate the multidrug resistance (MDR) phenotype. The multidrug resistance-associated protein (MRP) is a drug transporter protein associated with resistance to a broad spectrum of lipophilic drugs. To investigate whether MRP is involved in intrinsic drug resistance of human melanoma, we analysed expression and functional activity of MRP as well as its impact on chemoresistance in 40 melanoma cell lines (35 established by us from primary and metastatic lesions and 5 obtained from international sources), as well as in one dysplastic naevus-derived cell line and in normal melanocytes. By reverse transcriptase-polymerase chain reaction various levels of MRP mRNA were detected in all melanoma cell lines, and by immunoblot the corresponding protein in a high percentage of them. Functional activity of MRP was assayed by analysing cellular accumulation of 3H-daunomycin (3H-DM) and calcein in response to MRP-modulators by beta-spectrometric and fluorescence-activated cell sorter analysis, respectively. Probenecid (PRO), N-ethylmaleimide (NEM) and benzbromarone (BB) moderately (< or = 1.43-fold) but significantly enhanced intracellular accumulation of MRP substrate probes corresponding to MRP expression. Moreover, the sensitivity of melanoma cell lines to daunomycin (DM) and doxorubicin (DOX), but not to vinblastine (VBL), etoposide (VP-16) and cisplatin (CDDP), analysed by an MTT-based survival assay, were inversely correlated with MRP-gene expression. Our results imply that MRP may be a component of the intrinsic chemoresistance phenotype characteristic of human malignant melanoma.

Transesophageal atrial pacing in anesthetized patients with coronary artery disease. Hemodynamic benefits versus risk of myocardial ischemia.

BACKGROUND: Transesophageal atrial pacing (TEAP) provides prompt and precise control of heart rate and improves hemodynamics in anesthetized patients with bradycardia and hypotension. The authors' purpose in this study was to examine the hemodynamic benefits of TEAP versus the risk of myocardial ischemia in patients about to undergo coronary artery bypass surgery. METHODS: Hemodynamics, ventricular filling pressures, mixed venous oxygen saturation, and end-diastolic, end-systolic, and fractional area change of the left ventricle, determined by transesophageal echocardiography (TEE), were measured after anesthesia induction with 30 micrograms/kg fentanyl and at incremental TEAP rates of 65, 70, 80, and 90 beats/min (bpm) in 40 adult patients. Monitoring for myocardial ischemia was accomplished with 12-lead electrocardiograms and biplane TEE assessment of left ventricular regional wall motion. Hemodynamics, electrocardiograms, and TEE measurements at each TEAP rate were compared with baseline awake measurements (except TEE) and with measurements obtained after anesthesia induction before TEAP. RESULTS: Sinus bradycardia occurred in 15 patients after anesthesia induction and was associated with a hypotensive response and a decrease in cardiac output in 10 patients. In these patients, TEAP restored diastolic blood pressure and cardiac output to baseline values at TEAP rates of 65 and 80 bpm, respectively. Stroke volume was similar to baseline measurements after anesthesia induction and at TEAP rates of 65, 70, and 80 bpm, but was significantly reduced from baseline at TEAP 90 bpm. Myocardial ischemia was detected in 7 and 5 patients at a TEAP rate of 80 and 90 bpm, respectively. CONCLUSIONS: Control of heart rate with TEAP restores intraoperative hemodynamics to baseline in patients in whom bradycardia and a hypotensive response develop before coronary artery bypass surgery. When using TEAP for patients with severe coronary artery disease, these results support using the lowest TEAP rate titrated to achieve optimal hemodynamics, while closely monitoring for myocardial ischemia, especially at TEAP rates > 80 bpm.

Successful treatment of bleeding pseudoaneurysms of chronic pancreatitis.

A ruptured pseudoaneurysm is the most rapidly fatal complication encountered in patients with chronic pancreatitis, with a reported mortality rate of 12.5% in treated patients to > 90% in those untreated. Although reportedly a rare complication of chronic pancreatitis, a pseudoaneurysm is encountered in 6-9.5% of patients with chronic pancreatitis and as many as 17% of all patients operated on for chronic pancreatitis. Timely diagnosis and treatment seems to result in markedly reduced mortality. Four patients with bleeding pseudoaneurysms associated with chronic pancreatitis and pseudocysts were encountered recently at Virginia Mason Medical Center. These patients' charts, as well as the English literature, were reviewed in detail. All of our cases occurred in alcoholic males. Pseudocysts with pancreatic ductal or pseudocyst rupture were seen in three cases. All had a history of crescendo-decrescendo pain episodes and had evidence of bleeding or were bleeding at presentation. Splenic vein occlusion was identified in 50% of the cases. A pseudoaneurysm was documented by angiography in all patients. Embolization was successfully attempted without complication in two patients. Three patients were ultimately treated with a pylorus-sparing (2) or standard (1) pancreaticoduodenectomy. These three are alive and doing well at 16, 26, and 52 months from the time of their procedure. A fourth patient was treated nonoperatively, because of severe comorbid disease and aberrant anatomy, with successful embolization of the pseudoaneurysm and biliary and pancreatic stenting. The pseudocyst resolved and he is asymptomatic 12 months after therapy. We advocate preoperative arteriography in all patients with suspected or known arterial pseudoaneurysm.(ABSTRACT TRUNCATED AT 250 WORDS)

Routine intraoperative cholangiography and its contribution to the selective cholangiographer.

Routine intraoperative cholangiography (IOC) during cholecystectomy is controversial. In order to address this debate, we asked the following questions: What intraoperative information is provided to the surgeon? What IOC criteria or standards are necessary to observe this information? Between 1990 and 1993, 624 laparoscopic cholangiography (LC) cases were performed at Virginia Mason Hospital, during which 86% (535) of the patients underwent successfully performed IOCs. Each of these cholangiograms was sought, and 420 (78%) were reviewed by a radiologist and a surgeon. Specific items involved the presence or absence of filling defects, bile duct diameter, contrast leaks, flow into the duodenum, benign or malignant stricture, contrast in a portion of the pancreatic duct, and anomalous ducts. "Relevant findings" were defined as filling defects, stricture, leaks, and the following anomalous ducts: a bile duct from the right side of the liver entering near or into the cystic duct. The entire biliary tree was visualized in 86%, and the bifurcation was seen in 95% of the cases. Considering these deficiencies, we found a 10% incidence of filling defects. Anomalies were common in the biliary tree (39%), and knowledge of the presence of some of them are important for safe dissection (at least 4%). Also, at least 68 relevant findings would have been missed in 420 LC cases without IOC. If the IOC had not visualized the biliary tree proximal to the cystic duct, 30 of 68 or 44% of these findings would not have been observed. If an IOC is performed on a routine or selective basis, the study should visualize the entire biliary tree.

Preoperative visceral angiography alters intraoperative strategy during the Whipple procedure.

To determine the importance of preoperative visceral angiography prior to pancreaticoduodenectomy, all Whipple procedures performed between 1985 and 1991 at the Virginia Mason Medical Center were retrospectively reviewed. During this period, 77 pancreaticoduodenectomies were performed for both neoplastic disease (n = 54, 70%) and chronic pancreatitis (n = 23, 30%). Sixty-four preoperative angiograms were obtained, of which 39 (61%) were abnormal findings. Thirty percent (19 of 64) of the angiograms revealed a significant vascular abnormality that required specific preoperative or intraoperative measures that might not have been performed without knowledge of these findings. Examples include celiac axis revascularization for celiac occlusion, hepatic artery preservation for replaced vessels, preoperative embolization for pseudoaneurysm or arteriovenous fistula, and splenectomy for splenic vein thrombosis. Because of the high percentage of significant findings requiring an intraoperative or preoperative technical change, we recommend the use of angiography in order to diminish morbidity in all patients preparing to undergo pancreaticoduodenectomy.

Pancreatic pseudocyst with fistula to the common bile duct: radiological diagnosis and management.

A patient was found to have fistulization of a pancreatic pseudocyst with the common bile duct. Resolution of the pseudocyst and the attendant biliary obstruction was achieved with percutaneous biliary drainage alone. The clinical and radiological features of this case are herein presented along with a brief review of the subject.

The roles of age and sex in the prognosis of chronic leukaemias. A study of 373 cases.

The roles of age and sex and their relationship to other prognostic factors were studied in 117 chronic myeloid leukaemia (CML) and in 256 chronic lymphocytic leukaemia (CLL) patients. Survival in CML was not related either to age at diagnosis or to sex. In contrast, the CLL patients classified into four age strata (less than 50, 50-59, 60-69, greater than 70 years) had an expected median survival (EMS) of 142, 101, 85 and 33 months respectively (chi 2 for heterogeneity = 35.59, P less than 0.0005; chi 2 for trend = 25.09, P less than 0.0005). Prognostic power was independent of sex, Rai stages, total tumour mass score (TTM), TTM distribution pattern, anaemia, thrombocytopenia, serum immunoglobulins and response to therapy. The relative survival rate (the ratio of patient's EMS and EMS in age- and sex-matched general population) was 0.40 in CLL patients and 0.13 in CML patients. Relative survival was more reduced in older CLL patients than in younger ones (0.37 vs 0.47, respectively), whereas relative survival was less reduced in older CML patients than in younger ones (0.18 vs 0.12, respectively). The results show that the age is a significant independent prognostic factor in CLL but not in CML. The difference in the effects of age on prognosis in CLL and CML most probably reflects the fundamental differences in their respective pathogeneses.

[Comparison of lymphangiography and computerized tomography with staging laparotomy in patients with Hodgkin's disease]. / Usporedba limfangiografije i kompjuterizirane tomografije sa "staging" laparotomijom kod bolesnika s Hodgkinovom bolescu.

The staging procedure of Hodgkin's disease is vital for planning effective management. In this paper, the diagnostic value of lymphangiography (LAG) and computed tomography (CT), as compared with the findings of staging laparotomy (SL) is determined. Sixty-five patients with Hodgkin's disease have been studied: in 44 patients CT was performed, 13 underwent LAG and in 8 patients both methods (CT and LAG) were applied. In all 65 patients SL was undertaken. The findings showed that the lymphangiography accurately detected the extent of Hodgkin's disease in 31% of the patients and CT in 61%. Thus, the computed tomography is more effective in evaluating the disease than the LAG method, and moreover, it can be repeated. On the other hand, the lymphangiography, although less reliable, presents a lymph node structure. We conclude, on the basis of the obtained results that SL is the most useful method in staging of Hodgkin's disease.

High dose ARA-C as induction therapy of acute myeloid leukaemia.

Twenty-one newly diagnosed adult AML patients were treated with high dose Ara-C (HD-ARA-C) as a single induction treatment with the dose of 2 g/m2 q 12 hours x 12. Seventy-six percent (16/21) responded with complete remission. Three patients died in induction in pancytopenia, another one died on day 44 in CR due to bleeding of pulmonary aspergilloma. This treatment seems to be highly efficient for remission induction, but requires an adequate transfusion and other supportive measures. The overall toxicity was transient and seems acceptable. However, the remission duration is unacceptably short, the consolidation with the same treatment seems to be inadequate. More aggressive treatment in postinduction period seems to be warranted.

Endoscopic studies of nabumetone in patients with rheumatoid arthritis. A comparative endoscopic and histologic evaluation.

Gastric tolerance to 1 g of nabumetone administered in a single nightly dose was assessed in two trials in patients with rheumatoid arthritis. Gastroscopy and histology of mucosal biopsy specimens were performed before and after the end of treatment in both trials. Trial 1 was an open study that compared the effects of 1 g of nabumetone at night with those of naproxen (dose, 500 mg twice daily) and indomethacin (dose, 50 mg three times daily) in 41 hospitalized patients. After three weeks of treatment, nabumetone was significantly better tolerated than naproxen or indomethacin. Trial 2 was a randomized trial with 24 patients per group that compared 1 g of nabumetone given at night with 250 mg of naproxen given in the morning and 500 mg given at night for a period of three months. This single-blind study revealed that the number of patients with microscopic or macroscopic mucosal lesions was significantly smaller following intake of nabumetone. Concerning efficacy, as judged clinically by a rheumatologist, treatment with nabumetone was superior as well.

Cytomorphological and cytochemical classification of acute myeloid leukaemia (AML).

One hundred cases of adult AML were classified cytomorphologically (FAB-classification) and cytochemically (Loeffler's classification). From this combined analysis it could be shown that some corrections have to be made in the FAB-classification; particularly groups M-1 and M-4 had to be reclassified. The authors, therefore, advocate that the final FAB-classification should be the result of cytomorphologic as well as cytochemical analysis.

Influence of splenectomy upon immunologic reactivity of patients with Hodgkin's disease.

Since most patients with Hodgkin's disease benefit from splenectomy, a study was designed to explore whether these beneficial effects could be attributed to the recovery of patients' immunologic reactivity. Using a series of ordinary skin test (PPD-tuberculine, Varidase and Candidin) determination of absolute T and B lymphocyte counts in peripheral blood and their mitogenic responsiveness, assessment of immunologic reactivity was performed in 28 Hodgkin's disease patients, prior to and 14 days after splenectomy. The results showed that overall immunologic reactivity of these patients was suppressed as judged by low absolute lymphocyte counts (1747.2 +/- 171.9), lower counts of T (592.0 +/- 92.1) and B cells (295.9 +/- 40.5) and their poor capacity to respond to phytohemagglutinin (PHA) (20342.6 +/- 3662.8 cpm), although the reactivity towards skin test antigens seemed to be well preserved. After splenectomy the reactivity improved, absolute lymphocyte counts raised to 2654.9 +/- 468.8 and were parallelled by an increase in T (936.7 +/- 138.0) and B cell counts (402.2 +/- 81.2). PHA reactivity recovered as well (26965.5 +/- 4035.6 cpm), however, its remained lower than in control cultures. Furthermore, the immunocompetence of patients' spleens was assessed. The possible influence of some suppressive mechanisms such as serum-blocking factor and prostaglandins is discussed.

Variability of mitochondrial population in Chlamydomonas reinhardii.

Several details have been published cocerning the mitochondrial number and shapes at various stages of the synchronized vegetative and generative cell cycle in Chlamydomonas reinhardii. The present study, based on ultrathin serial sections and threedimensional reconstructions, completes these data. Quantitative analysis of serial micrographs makes it possible to give specific details of mitochondrial volumes in cells at early intermediate stages of the vegetative life cycle. Our investigations clearly show that mitochondria have a relatively wide range of sizes, within certain limits, and vary like the mitochondrial shapes; in fact, they vary in various cells at various stages as well as in several cells at the same stage and even in one and the same cell. Thus, we present a plastic insight into the dynamically changing micromorphology of the mitochondrial population in Chlamydomonas reinhardii.