Beware Cold Agglutinins in Organ Donors! Ex Vivo Lung Perfusion From an Uncontrolled Donation After Circulatory-Determination-of-Death Donor With a Cold Agglutinin: A Case Report.

BACKGROUND: We began to recover lungs from uncontrolled donation after circulatory determination of death to assess for transplant suitability by means of ex vivo lung perfusion (EVLP) and computerized tomographic (CT) scan. Our first case had a cold agglutinin with an interesting outcome. CASE REPORT: A 60-year-old man collapsed at home and was pronounced dead by Emergency Medical Services personnel. Next-of-kin consented to lung retrieval, and the decedent was ventilated and transported. Lungs were flushed with cold Perfadex, removed, and stored cold. The lungs did not flush well. Medical history revealed a recent hemolytic anemia and a known cold agglutinin. Warm nonventilated ischemia time was 51 minutes. O2-ventilated ischemia time was 141 minutes. Total cold ischemia time was 6.5 hours. At cannulation for EVLP, established clots were retrieved from both pulmonary arteries. At initiation of EVLP with Steen solution, tiny red aggregates were observed initially. With warming, the aggregates disappeared and the perfusate became red. After 1 hour, EVLP was stopped because of florid pulmonary edema. The lungs were cooled to 20°C; tiny red aggregates formed again in the perfusate. Ex vivo CT scan showed areas of pulmonary edema and a pyramidal right middle lobe opacity. Dissection showed multiple pulmonary emboli-the likely cause of death. However, histology showed agglutinated red blood cells in the microvasculature in pre- and post-EVLP biopsies, which may have contributed to inadequate parenchymal preservation. CONCLUSIONS: Organ donors with cold agglutinins may not be suitable owing to the impact of hypothermic preservation.

Different cellular p16(INK4a) localisation may signal different survival outcomes in head and neck cancer.

BACKGROUND: Recently, the management of head and neck squamous cell carcinoma (HNSCC) has focused considerable attention on biomarkers, which may influence outcomes. Tests for human papilloma infection, including direct assessment of the virus as well as an associated tumour suppressor gene p16, are considered reproducible. Tumours from familial melanoma syndromes have suggested that nuclear localisation of p16 might have a further role in risk stratification. We hypothesised p16 staining that considered nuclear localisation might be informative for predicting outcomes in a broader set of HNSCC tumours not limited to the oropharynx, human papilloma virus (HPV) status or by smoking status. METHODS: Patients treated for HNSCC from 2002 to 2006 at UNC (University of North Carolina at Chapel Hill) hospitals that had banked tissue available were eligible for this study. Tissue microarrays (TMA) were generated in triplicate. Immunohistochemical (IHC) staining for p16 was performed and scored separately for nuclear and cytoplasmic staining. Human papilloma virus staining was also carried out using monoclonal antibody E6H4. p16 expression, HPV status and other clinical features were correlated with progression-free (PFS) and overall survival (OS). RESULTS: A total of 135 patients had sufficient sample for this analysis. Median age at diagnosis was 57 years (range 20-82), with 68.9% males, 8.9% never smokers and 32.6% never drinkers. Three-year OS rate and PFS rate was 63.0% and 54.1%, respectively. Based on the p16 staining score, patients were divided into three groups: high nuclear, high cytoplasmic staining group (HN), low nuclear, low cytoplasmic staining group (LS) and high cytoplasmic, low nuclear staining group (HC). The HN and the LS groups had significantly better OS than the HC group with hazard ratios of 0.10 and 0.37, respectively, after controlling for other factors, including HPV status. These two groups also had significantly better PFS than the HC staining group. This finding was consistent for sites outside the oropharynx and did not require adjustment for smoking status. CONCLUSION: Different p16 protein localisation suggested different survival outcomes in a manner that does not require limiting the biomarker to the oropharynx and does not require assessment of smoking status.

Primary pulmonary lymphangiectasia in infancy and childhood.

Primary pulmonary lymphangiectasia (PPL) is a rare disorder of unknown aetiology characterised by dilatation of the pulmonary lymphatics. PPL is widely reported to have a poor prognosis in the neonatal period and little is known about the clinical features of patients who survive the newborn period. The current authors report the outcome in nine patients diagnosed in infancy with PPL over a 15-yr period at a single university-based hospital clinic and followed for a median of 6 yrs. Although all of the patients initially experienced respiratory distress, respiratory symptoms improved in most patients after infancy and were notably better by the age of 6 yrs. Many patients had poor weight gain in the first years of life, which eventually improved. Radiological scans showed progressive resolution of neonatal infiltrates, but were characterised by hyperinflation and increased interstitial markings in older children. Most patients had evidence of bronchitis and grew pathogenic organisms from quantitative bronchoalveolar lavage culture. Pulmonary function tests showed predominantly obstructive disease that did not deteriorate over time. In conclusion, these results suggest that primary pulmonary lymphangiectasia does not have as dismal a prognosis as previously described and symptoms and clinical findings improve after the first year of life.

Airway surface liquid recovered by lavage with perfluorocarbon liquid in cats.

BACKGROUND: Airway surface liquid (ASL) is difficult to sample. Lavage with an immiscible perfluorocarbon (PFC) liquid to recover ASL was evaluated in cats. MATERIALS AND METHODS: Six wild-type cats underwent bronchoscopic lavage with a PFC (perfluorohexane), with the bronchoscope wedged in the feline equivalent of the right lower lobe. Two cats (control animals) were lavaged with a saline vehicle only. Four procedures were performed on each animal at 2-3-week intervals. Ionic composition of ASL was determined by flame photometry. RESULTS: Cats lavaged with PFC showed significantly more acute respiratory distress than those lavaged with saline (respiratory rate following procedure: PFC, 47 +/- 5 min-1 vs. saline, 27 +/- 2 min-1, P < 0.05; O2 saturation: PFC 80 +/- 1% vs. saline, 91 +/- 1%, P < 0.01). The PFC group also had clinical evidence of chronic respiratory compromise (mean respiratory rate before next anaesthetic; PFC, 37 +/- 2 min-1 vs. saline, 20 +/- 3 min-1, P < 0.01). The PFC-lavaged lungs demonstrated persistent radiographic changes and histological evidence of small airways obstruction with distal alveolar damage. Six PFC lavages yielded ASL samples (> 100 microL) which were sufficient for analysis. Mean (+/- SEM) ionic concentrations in these samples were Na+ 157.4 +/- 14.5 mmol L-1, Cl- 150.5 +/- 16.8 mmol L-1 and K+ 10.1 +/- 1.7 mmol L-1. CONCLUSIONS: Perfluorocarbon lavage can be used to collect unmodified ASL from the distal lung. However, repeated lavage with perfluorohexane was associated with significant pathological changes in this study.

Review: significance of, and optimal screening for, HER-2 gene amplification and protein overexpression in breast carcinoma.

Breast carcinoma is a common disease, with an estimated 183,000 new cases expected in the USA during 2000. Whereas early stage patients have high likelihood of cure, only 20-40% of patients with metastatic breast carcinoma respond to presently available chemotherapy. A need exists to identify the underlying biological subsets of morphologically similar carcinomas in order to develop customized therapies for patients who require chemotherapy. The HER-2 receptor tyrosine kinase is overexpressed in 15-30% of breast carcinomas, and is associated with a worse prognosis stage-for-stage. Humanized monoclonal antibody therapy (Herceptin; Genentech Co.) appears to benefit this subset of patients by improving their response rate and survival following anthracycline- or taxane-based chemotherapeutic regimens. Both HER-2 gene amplification and protein overexpression correlate with clinical outcomes, and screening for HER-2 gene amplification appears to be the more informative test. This article reviews data on the HER-2 gene and protein, discusses their association with clinical outcomes, and proposes a strategy for screening for HER-2 excess in formalin-fixed specimens of breast carcinoma.

Pulmonary alveolar proteinosis: a spectrum of cytologic, histochemical, and ultrastructural findings in bronchoalveolar lavage fluid.

Pulmonary alveolar proteinosis (PAP) is defined as abundant extracellular proteinaceous periodic acid-Schiff (PAS)-positive material which represents surfactant distending alveolar spaces. While this lesion is defined by histologic findings, there are characteristic radiologic features and cytologic findings in bronchoalveolar lavage (BAL) specimens that together may provide a confident diagnosis. The BAL specimens from all patients for which a diagnosis of PAP was made or suggested on either cytologic or biopsy specimens at University of North Carolina Hospitals from 1990-1999 were reviewed. There were 23 cytologic specimens from 11 patients. Patient ages ranged from 6 wk to 76 yr. All 23 specimens had slides prepared for Papanicolaou stain, 22 specimens (all patients) had Diff-Quik stains, 10 specimens (6 patients) had PAS stains, and 8 specimens (5 patients) had lipid stains. Nine patients had lung biopsies in addition to cytologic specimens. The clinical charts of all patients were reviewed. Twenty-one cytologic specimens were described as cloudy or milky, and 2 were bloody. By chart review and/or biopsy results, 8 patients were felt to have definite PAP. The initial lavage specimens from 6 of these patients showed classic cytologic findings of PAP, consisting of paucicellular specimens dominated by adundant extracellular granular to globular material which was basophilic on Diff-Quik stain, pale to focally eosinophilic on Pap stain, and PAS-positive, diastase-resistant. Five of these patients had biopsies; 3 showed PAP, and 2 were insufficient. Later BAL specimens after therapeutic lavage from these patients were often less characteristic, with scant extracellular material present. The other 2 patients with PAP clinically and by biopsy had atypical cytologic findings, with one showing numerous macrophages with scant PAS-positive material and abundant lipid mimicking lipid pneumonia, and one showing moderate eosinophils in addition to the extracellular proteinacous material. The remaining 3 patients were felt not to have PAP clinically or by biopsy (1 lymphocytic interstitial pneumonitis, 1 rheumatoid lung, and 1 hemosiderosis), and their BAL specimens predominantly contained macrophages with rare proteinaceous extracellular globules. Electron microscopy was performed in 5 patients (4 considered to have PAP, and 1 with lymphocytic interstitial pneumonitis) and in all cases showed whorled myelin figures characteristic of surfactant. The PAP cases and the non-PAP case had identical ultrastructural findings. We conclude that BAL specimens with classic cytologic features and supporting clinical and radiographic evidence may be diagnosed as PAP. Atypical specimens should be approached with caution, and may represent either PAP or other pulmonary diseases with secondary accumulation of surfactant. Cytology specimens taken subsequent to therapeutic lavage from PAP patients may also not be diagnostic.

Inflammatory myofibroblastic tumor involving the pterygopalatine fossa.

SUMMARY: Inflammatory myofibroblastic tumors (IMT) comprise a rare group of lesions characterized histologically by acute and chronic inflammatory cells with a variable degree of fibrous stroma. Occurrence in the extracranial head and neck in children is unusual, and involvement in the pterygopalatine fossa has not, to our knowledge, been reported as occurring in this age group. We present the CT findings of an IMT of the pterygopalatine fossa in a 6-year-old female patient with a 2-week history of fever and a painless swelling of the left cheek. The diagnosis of IMT should be included in the differential diagnosis of a child presenting with an aggressive mass associated with systemic features such as fever, elevated sedimentation rate, and leukocytosis.

Selective activation of NF-kappa B subunits in human breast cancer: potential roles for NF-kappa B2/p52 and for Bcl-3.

Members of the NF-kappa B/Rel transcription factor family have been shown recently to be required for cellular transformation by oncogenic Ras and by other oncoproteins and to suppress transformation-associated apoptosis. Furthermore, NF-kappa B has been shown to be activated by several oncoproteins including HER2/Neu, a receptor tyrosine kinase often expressed in human breast cancer. Human breast cancer cell lines, human breast tumors and normal adjacent tissue were analysed by gel mobility shift assay, immunoblotting of nuclear extracts and immunohistochemistry for activation of NF-kappa B. Furthermore, RNA levels for NF-kappa B-activated genes were analysed in order to determine if NF-kappa B is functionally active in human breast cancer. Our data indicate that the p65/RelA subunit of NF-kappa B is activated (i.e., nuclear) in breast cancer cell lines. However, breast tumors exhibit an absence or low level of nuclear p65/RelA but show activated c-Rel, p50 and p52 as compared to nontumorigenic adjacent tissue. Additionally, the I kappa B homolog Bcl-3, which functions to stimulate transcription with p50 or p52, was also activated in breast tumors. There was no apparent correlation between estrogen receptor status and levels of nuclear NF-kappa B complexes. Transcripts of NF-kappa B-regulated genes were found elevated in breast tumors, as compared to adjacent normal tissue, indicating functional NF-kappa B activity. These data suggest a potential role for a subset of NF-kappa B and I kappa B family proteins, particularly NF-kappa B/p52 and Bcl-3, in human breast cancer. Additionally, the activation of functional NF-kappa B in these tumors likely involves a signal transduction pathway distinct from that utilized by cytokines.

Vaginal adenosarcoma arising from endometriosis.

OBJECTIVE: Malignant transformation of endometriosis has been well documented. Endometrioid adenocarcinoma is the most common malignancy to occur in this setting, although other carcinomas and rarely stromal tumors can be seen. We present the first case in the literature of adenosarcoma, a rare mixed mullerian or mesodermal tumor, arising in extrauterine vaginal endometriosis. CASE: A 42-year-old woman underwent multiple medical therapies and surgeries for aggressive endometriosis. A pelvic exenteration was abandoned secondary to severe fibrosis, and low-dose radiotherapy was used to control bleeding from vaginal endometriosis. The pathologic diagnosis of recurrent endometriosis was confirmed multiple times over her 4-year course. Excision of a recurrent vaginal mass revealed adenosarcoma with heterologous elements. CONCLUSION: It is important to biopsy or excise recurrent endometriosis, as malignant transformation can occur, giving rise to epithelial, stromal, or mixed epithelial-mesenchymal tumors.

The relationship of chronic mucin secretion to airway disease in normal and CFTR-deficient mice.

In the cystic fibrosis (CF) patient, lung function decreases throughout life as a result of continuous cycles of infection, particularly with Pseudomonas aeruginosa and Staphylococcus aureus. The mechanism underlying the pathophysiology of the disease in humans has not been established. However, it has been suggested that abnormal, tenacious mucus, resulting perhaps from improper hydration from loss of Cl- secretion via the cystic fibrosis transmembrane conductance regulator (CFTR) protein, impairs clearance of bacteria from the CF airway and provides an environment favorable to bacterial growth. If this hypothesis is correct, it could explain the absence of respiratory disease in CFTR-deficient mice, since mice have only a single submucosal gland and display few goblet cells in their lower airways, even when exposed to bacteria. To test this hypothesis further, we induced allergic airway disease in CFTR-deficient mice. We found that induction of allergic airway disease in mice, unlike bacterial infection, results in an inflammatory response characterized by goblet cell hyperplasia, increased mucin gene expression, and increased production of mucus. However, we also found that disease progression and resolution is identical in Cftr-/- mice and control animals. Furthermore, we show that the presence of mucus in the Cftr-/- airway does not lead to chronic airway disease, even upon direct inoculation with S. aureus and P. aeruginosa. Therefore, factors in addition to the absence of high levels of mucus secretion protect the mouse from the airway disease seen in human CF patients.

Epstein-Barr virus-associated renal smooth muscle neoplasm: report of a case with review of the literature.

Epstein-Barr virus (EBV) has been associated with nasopharyngeal carcinoma, some Burkitt's-type lymphomas, and posttransplantation lymphoproliferative disorder. Recently, an association between EBV and smooth muscle tumors, both malignant and benign, in the acquired immunodeficiency syndrome and posttransplantation populations has been made. We report, to our knowledge, the first case of a renal EBV-associated smooth muscle tumor. A 33-year-old man with acquired immunodeficiency syndrome presented with a mass of the left kidney that was radiographically suspicious for malignancy. He underwent left radical nephrectomy. The tumor measured 3.0 cm in the largest dimension, was well-circumscribed, and was composed of fascicles of bland spindle cells with blunt-ended nuclei, which often intersected at right angles. Focal areas of cell crowding and nuclear pleomorphism were present. No areas of lipomatous differentiation were identified. Immunohistochemically, the tumor cells were positive for desmin and muscle-specific actin and were negative for HMB-45 and CD21 (an EBV receptor). In situ hybridization with EBV-encoded RNA-1, a probe that recognizes a non-poly(A) RNA EBV transcript expressed in latently infected cells, was diffusely positive. At 6 months postnephrectomy, the patient showed no evidence of local recurrence or metastases. The incidence of this tumor is expected to increase as both the numbers of patients undergoing solid organ transplantation and the survival time of patients with the acquired immunodeficiency syndrome increase. A better understanding of the biology and pathogenesis of this entity will be important for future management of these patients.

Preferential IgH V4-34 gene segment usage in particular subtypes of B-cell lymphoma detected by antibody 9G4.

Immunoglobulin heavy chain locus variable gene segment V4-34 (V(H)4.21) use in productive heavy chain (IgH) gene rearrangements has been described in a number of human reactive and autoimmune B cell responses, and has been shown to be frequently used in some series of cases of diffuse large cell lymphoma (DLCL). The 9G4 antibody is relatively specific for the V4-34 gene product and can be used to screen for cells that use V4-34 in their productive IgH locus rearrangements. The purposes of this study were to determine the sensitivity of the 9G4 antibody against DLCL cases known to use V4-34, then to screen a variety of human lymphoma types for 9G4 reactivity. Frozen tissue sections were cut from 118 cases of various human lymphomas. Generalized 9G4 membrane reactivity was identified in 78% of DLCL cases known to use V434. 9G4 reactivity varied by lymphoma type for the unknown cases, with diffuse large cell lymphoma (30%) and mantle cell lymphoma (28%) showing statistically significant differences (P < .001) from the expected value of 6% V4-34 positivity in peripheral blood B cells. This nonrandom increased utilization of V4-34 in productive IgH locus rearrangements supports the hypothesis that Ig binding specificity may play a role in lymphomagenesis.

DNA sequence determination by hybridization: a strategy for efficient large-scale sequencing.

The concept of sequencing by hybridization (SBH) makes use of an array of all possible n-nucleotide oligomers (n-mers) to identify n-mers present in an unknown DNA sequence. Computational approaches can then be used to assemble the complete sequence. As a validation of this concept, the sequences of three DNA fragments, 343 base pairs in length, were determined with octamer oligonucleotides. Possible applications of SBH include physical mapping (ordering) of overlapping DNA clones, sequence checking, DNA fingerprinting comparisons of normal and disease-causing genes, and the identification of DNA fragments with particular sequence motifs in complementary DNA and genomic libraries. The SBH techniques may accelerate the mapping and sequencing phases of the human genome project.

Acute illnesses necessitating urgent abdominal surgery in neutropenic cancer patients: description of 14 cases and review of the literature.

Through a review of our experience and the literature, the cases of 56 neutropenic cancer patients requiring urgent abdominal surgery have been studied. The most common underlying diagnosis of malignant disease was leukemia (70%), and the most common intra-abdominal disease discovered at surgery was neutropenic enteropathy (61%). Major postoperative complications occurred in 50% of cases. The 30-day postoperative mortality was 32%, and the determinant 6-month survival was 34%. Abdominal pain in a neutropenic cancer patient calls for a thorough evaluation of its cause and careful serial examinations. Evidence of a surgically treatable disease or failure to respond to medical therapy for a presumed medically treatable disease should prompt surgical intervention.

High-dose oral and intravenous metoclopramide in doxorubicin/cyclophosphamide-induced emesis. A randomized double-blind study.

Emesis remains a major side effect of cancer chemotherapy. High-dose intravenous metoclopramide has proved to be effective antiemetic therapy for cisplatinum induced emesis. It has not been rigorously tested in nonplatinum chemotherapy. This double-blind, noncrossover, randomized trial compared high-dose oral and intravenous metoclopramide to standard oral prochlorperazine in emesis caused by doxorubicin [70 mg/m2 body surface area (BSA)] and cyclophosphamide (700 mg/m2 BSA). Prochlorperazine (10 mg/dose), oral metoclopramide, and intravenous metoclopramide (2 mg/kg/dose each) were given 30 min before chemotherapy and then every 4 h for 24 h. Ten patients were randomized to prochlorperazine therapy, 10 to oral metoclopramide, and 9 to i.v. metoclopramide. Median number of emeses for the first chemotherapy cycle was 3, 3, and 7 for prochlorperazine, oral, and i.v. metoclopramide, respectively. Statistical analysis showed no significant advantage of any regimen (p greater than 0.4). For patients who continued the antiemetic study, frequency of emesis increased with each successive cycle of chemotherapy. Six of 19 patients treated with metoclopramide developed dystonic reactions compared with zero of 10 on prochlorperazine. High plasma metoclopramide levels were achieved with both metoclopramide regimens and did not correlate with frequency of emesis. High-dose oral and i.v. metoclopramide in an every 4 h regimen did not show any advantage over standard antiemetic therapy for doxorubicin/cyclophosphamide-induced emesis and were associated with significant toxicity.

Inhibition of DNA synthesis by a small-cell lung carcinoma-derived protein.

A tumor-derived factor that inhibits cellular DNA synthesis was identified. The factor was extractable from a small-cell lung carcinoma cell line grown in either chemically defined medium or nu/nu mice and inhibited tritiated thymidine ([3H]dThd) incorporation by tumor cell lines of autologous, allogeneic, and xenogeneic origins. The viability of nonproliferating cells from normal tissue was not affected. Tumor extract inhibitory activity was trypsin labile but was resistant to other proteases, neuraminidase, lipase, DNase, RNase, glucosidase, extremes of pH-temperature, and reducing conditions. Inhibitory activity was reversibly bound to helix pomatia lectin but not to lentil, wheat germ, or concanavalin A lectins. Purification by size-exclusion high-performance liquid chromatography yielded a bioactive unimodal 12-kilodalton (kd) peak. The bioactive 12-kd moiety could be eluted from sodium dodecyl sulfate-polyacrylamide gels. Redosing of populations of the T-lymphoblastoid cell line CEM achieved an early (24 hr) sustained depression of pulse [3H]dThd incorporation and ultimately led to decreased population density of factor-treated populations. DNA histogram analysis demonstrated no change in cell cycle phase distribution after factor treatment. 5-Bromo-2'-deoxyuridine (BrdUrd) vs. propidium iodide with the two-parameter Fluorescence-Activated Cell Sorter analysis showed relative inhibition of non-S-phase BrdUrd uptake at 24 hours. A cell-free DNA polymerase assay demonstrated significant inhibition of non-alpha-polymerase-associated DNA synthesis in factor-treated cells. These studies suggest that this tumor-derived inhibitor of DNA synthesis represents a class of cellular products involved in the autoregulation of growth by regulation of DNA synthetic activity.

Significant non-S-phase DNA synthesis visualized by flow cytometry in activated and in malignant human lymphoid cells.

The development of a monoclonal antibody to the deoxynucleoside bromodeoxyuridine (BrdU), combined with two parameter flow cytometry, has allowed us to examine large numbers of cells for non-S-phase DNA synthesis. Three human lymphoid cell populations were studied to determine the level of deoxynucleoside (dN) incorporation as a function of DNA content. In each population, non-S-phase DNA synthesis was observed. In a rapidly growing human T-lymphoblastoid cell line (CCRF-CEM), 53% of dN incorporation occurred in G0/G1 plus G2 + M. In chronic lymphocytic leukemia (CLL) cells stimulated with tetradecanoylphorbol acetate (TPA), 45% of the observed burst in thymidine incorporation was found to be localized to G0/G1 cells. Non-S-phase incorporation was not, however, limited to neoplastic cells. Normal human peripheral blood B cells treated with the Cowan strain of Staphylococcus aureus (CSA) undergo a transient burst in thymidine incorporation, but do not go on to divide in the absence of other stimuli. Flow-cytometric analysis showed that 80% of this CSA-stimulated dN incorporation was into G0/G1 cells. These data are consistent with a more dynamic state of DNA synthesis than usually envisioned. Furthermore, the data show that although thymidine incorporation levels are related to incorporation of dN into DNA, they can be unrelated to cell proliferation.

Analysis of the proliferation kinetics of Burkitt's lymphoma cells.

The in vitro proliferation kinetics of a cell line derived from a patient with American Burkitt's lymphoma were investigated at three different growth phases: lag (day 1), exponential (day 3) and plateau (day 5). The growth curve, labeling and mitotic indices, percentage labeled mitosis (PLM) curves and DNA content distributions were determined. The data obtained have been analysed by the previously developed discrete-time kinetic (DTK) model by which a time course of DNA distributions during a 10-day growth period was characterized in terms of other cell kinetic parameters. The mean cell cycle times, initially estimated from PLM curves on days 1, 3 and 5, were further analysed by the DTK model of DNA distributions and subsequently the mean cell cycle times with respect to DNA distributions during the entire growth period were determined. The doubling times were 39.6, 31.2 and 67.2 hr, respectively, at days 1, 3 and 5. The mean cell cycle time increased from 23.0 to 37.7 hr from day 3 to day 5 mainly due to an elongation of the G1 and G2 phases. A slight increase in the cell loss rate from 0.0077 to 0.0081 fraction/hr was accompanied by a decrease in the cell production rate from 0.0299 to 0.0184 fraction/hr. This calculated cell loss rate correlated significantly with the number of dead cells determined by trypan blue exclusion. Analysis of the number of dead cells in relation to the cell cycle stage revealed that a majority of cell death occurred in G1 (r + 0.908; P < 0.0001). There was a good correlation between the in vitro proliferation kinetics at plateau phase of this Burkitt's lymphoma derived cell line and the in vivo proliferation kinetics of African Burkitt's lymphoma (Iversen et al., 1974), suggesting the potential utility of information obtained by in vitro kinetic studies.