Cytokeratin fragment 19 (CYFRA 21-1) as a tumor marker in non-small cell lung cancer

To evaluate the diagnostic value of the serum cytokeratin 19 fragment (CYFRA 21-1) in bronchogenic carcinoma, we investigated the sera of 138 patients (58 with benign pulmonary disease and 80 with non-small cell lung cancer (NSCLC)) using immunoradiometric assay. The mean (SD) value of serum CYFRA 21-1 in NSCLC (13.26 (16.54)) was significantly higher than in benign lung diseases (1.74 (1.55)) (p < 0.0001). Sensitivity for CYFRA 21-1 (using 3.5 ng/ml, a cut-off value corresponding to a 95% specificity for benign pulmonary disease) in NSCL was 62%. Positive CYFRA 21-1 levels were significantly higher in 75% of patients with squamous cell carcinoma (n = 36) than in 53% with other NSCLC (n = 44) (p < 0.05). CYFRA 21-1 levels were significantly different between squamous cell carcinoma (17.28 (19.94)) and the other NSCLC (9.96 (12.44)) (P < 0.05). Elevated CYFRA 21-1 levels in patients with stage III and IV disease (n = 64, 18.19 (26.51)) were significantly higher than in stage I and II (n = 16, 4.41 (5.76)) (p < 0.02). The positive rate of CYFRA 21-1 in tumor stage I and II was only 37%. Our results indicate that CYFRA 21-1 may be a useful tumor marker in NSCLC, especially in squamous cell carcinoma. However, CYFRA 21-1 cannot be used for the diagnosis of early stage disease of NSCLC. CYFRA 21-1 may also contribute to the monitoring of NSCLC.

Urinary PCO2 for hemodynamically unstable patients

BACKGROUND

Gastric intramural pH (pHi) derived from gastric PCO2 has been successfully used to assess splanchnic ischemia for patients with unstable hemodynamics, but with some limitations. Urinary bladder, also an easily accessible hollow viscus, should provide as a useful route for the same purpose. However, no study has used urinary PCO2 to evaluate the adequacy of perfusion in critically ill patients.

METHODS

Fifty patients admitted to intensive care unit were included and divided into hemodynamically stable and unstable groups. Several parameters such as arterial pressure, dopamine dosage, heart rate, serum lactate, arterial blood gas, urinary PCO2, and concentrations of Na, K and Cl in urine were measured. Patients with some other renal or pre-renal conditions that might affect urinary PCO2 were excluded.

RESULTS

Urinary PCO2 was markedly higher (78.6 +/- 9.9 vs. 43.1 +/- 1.7 mmHg, p < 0.0001) in unstable group. Serum anion gap level, dopamine dosage and heart rate were significantly higher and PaO2/FiO2 ratio as well as mean arterial pressure was lower in unstable group. Serum lactate, arterial pH and other parameters failed to distinguish between groups. Dopamine dosage significantly correlated with urinary PCO2 (r = 0.5357, p = 0.0149) in unstable group.

CONCLUSIONS

With careful selection of patients, urinary PCO2 can effectively differentiate hemodynamically unstable patients from stable ones. It also correlates significantly with dopamine dosage in patients with unstable hemodynamics.

Asynchronous DNA replication between 15q11.2q12 homologs: cytogenetic evidence for maternal imprinting and delayed replication

DNA replication kinetics of Prader-Willi/Angelman syndrome region of 15q11.2q12 was studied without synchronization in five human amniotic cell and five skin fibroblast strains with a marker 15 chromosome, i.e., 15p+ or der(15), as cytological marker to distinguish between the two homologs. BrdU-33258 Hoechst-Giemsa techniques were used to analyze and compare the late replication patterns in the 15q11.2q12 region between the homologs. Asynchronous replication between the homologs was observed in both amniocytes and fibroblasts. From cells of a marker 15 of known parental origin, the paternal 15q11.2q12 replicated earlier than that of the maternal 15 in 92%-95% of asynchronous metaphases. The remaining 5%-8% of asynchronous metaphases displayed maternal early/paternal late replication. This mosaic pattern of replication in the 15q11.2q12 region may be due to methylation mosaicism of genomic imprinting or a relative lack of self-control of replication. These results provide cytogenetic evidence of maternal imprinting and delayed replication in the 15q11.2q12 region.

Allergic bronchopulmonary aspergillosis: a case report

Aspergillus-associated pulmonary diseases are aspergilloma, invasive aspergillosis, and allergic bronchopulmonary aspergillosis. Allergic bronchopulmonary aspergillosis is caused by a complex of immunologic reactions to the presence of the Aspergillus species colonizing the bronchial trees. The disease is not common in Taiwan. The major diagnostic criteria for allergic bronchopulmonary aspergillosis are 1) bronchial asthma, 2) pulmonary infiltration, 3) peripheral eosinophilia, 4) positive skin test to Aspergillus fumigatus, 5) serum precipitin to Aspergillus fumigatus, 6) elevated serum Ig E, and 7) central bronchiectasis. We report a case who has had a chronic asthmatic-like cough for 5 years. He worked in a silo for two years before he was troubled by the disease. He was admitted to hospitals four times in the past, and received five bronchoscopic examinations and one open lung biopsy without definite diagnosis. Sputum eosinophilia directed our attention to the differentiation of eosinophilic lung diseases. A bronchogram which revealed central brochiectasis helped us to make the diagnosis of allergic bronchopulmonary aspergillosis, despite negative sputum culture for Aspergillus fumigatus and negative serum precipitin to Aspergillus fumigatus.

Prescribing patterns in primary health care in Taiwan

To identify the prescribing patterns in public group practice centers (GPCs), 84,453 prescription sheets written by primary care physicians in 168 GPCs during the period from December 7-12, 1992, were collected and analyzed. The average number of drugs per script was 4.3 and the ratio of drug to total medical expense was 44%. The 5 most common diagnoses were, in a descending order, upper respiratory tract infection, skeletomuscular and joint disease, hypertension, functional gastrointestinal disorder (including peptic ulcer) and diabetes mellitus. The top 5 most commonly dispensed drug categories were antacids and anti-ulcer drugs, anti-cough and anti-cold preparations, vitamins, simple analgesics and non-steroidal anti-inflammatory drugs, accounting for 48.8% of total prescriptions. In view of the frequency of relevant diagnoses, the overuse of antacids, vitamins, intravenous nutrient and electrolyte solutions, anti-cold preparations and antibiotics was apparent, as was that of drugs of questionable pharmacological value. These data indicate that polypharmacy is a widespread phenomenon and confirms our long-term concern over irrational drug use in GPCs in Taiwan. Both administrative and educational intervention should be implemented to improve prescribing quality at the primary health care level.

Expansion of mycobacterium-reactive gamma delta T cells by a subset of memory helper T cells

Human gamma delta T cells expressing the V gamma 9/V delta 2 T-cell receptor have been previously found to proliferate in response to certain microorganisms and to expand throughout life, presumably because of extrathymic activation by foreign antigens. In vitro expansion of V gamma 9/V delta 2 cells by mycobacteria has been previously shown to be dependent on accessory cells. In order to gain an insight into the mechanisms involved in the expansion of these cells, we have undertaken to identify the peripheral blood subset of cells on which proliferation of V gamma 9/V delta 2 cells in response to mycobacteria is dependent. Contrary to their role in antigen presentation to alpha beta T cells, professional antigen-presenting cells, such as monocytes, B cells, and dendritic cells, were unable to provide the cellular support for the expansion of V gamma 9/V delta 2 cells. Selective depletion of T-cell subsets, as well as the use of highly purified T-cell populations, indicated that the only subset of peripheral blood cells that could expand V gamma 9/V delta 2 cells were CD4+ CD45RO+ CD7- alpha beta T cells. These cells underwent distinct intracellular signaling events after stimulation with the mycobacterial antigen. Expansion of V gamma 9/V delta 2 cells by alpha beta T cells was dependent on cell-cell contact. This is the first evidence that a small subset of the memory helper T-cell population is exclusively responsible for the peripheral expansion of V gamma 9/V delta 2 cells. These data illustrate a unique aspect of antigen recognition by gamma delta T cells and provide new means to study their immune defense role.

Use of esmolol to prevent hemodynamic changes during intubation in general anesthesia

To assess the minimal effective dosage of esmolol to prevent hypertension and tachycardia during laryngoscopy and endotracheal intubation in fentanyl-pretreated anesthesia, a double-blinded, randomized study was conducted. Two hundred patients undergoing elective, noncardiac surgeries were randomly allocated into four groups: group A received saline, group B esmolol 20 mg, group C esmolol 40 mg and group D esmolol 60 mg intravenously. General anesthesia was induced with 0.1 mg/kg vecuronium, 5 micrograms/kg fentanyl and 0.3 mg/kg etomidate. Heart rates (HR), systolic blood pressures (SBP), mean arterial pressures (MAP) and diastolic blood pressures (DBP) were recorded before induction, after induction, before intubation, 30 seconds, 1 minute, 2 minutes, 4 minutes, 6 minutes, and 10 minutes after intubation. After intubation HR and SBP increased significantly in group A (86.7 beats/min, 166.6 mmHg) in comparison with groups C (77.6 beats/min, 153.9 mmHg) and D (73.4 beats/min, 153.4 mmHg) (p < 0.05). Tachycardia (HR > 100) was found in 13 of 50(26%) patients in group A, 10 of 50(20%) patients in group B, 7 of 50(14%) patients in group C and 2 of 50(4%) patients in group D. Hypertension (SBP > 180) was found in 18(36%) patients in group A, 19(38%) patients in group B, 9(18%) patients in group C, and 6(12%) patients in group D. When compared with group A, only group D had significantly lower incidence of these adverse events (p < 0.05). In conclusion, fentanyl 5 micrograms/kg could not completely prevent the hemodynamic changes associated with endotracheal intubation, and 60 mg esmolol was observed to have positive effect in helping to control these changes.

Nucleolar organizer regions in small cell carcinoma of lung

Agyrophilic staining of nucleolar organizer regions (NOR) has been used to differentiate between cells of small cell carcinoma and lymphocytes in tissue specimens. We used cytologic smears which were previously Papanicolaou-destained to study the one-step agyrophilic staining technique for nucleolar organizer regions (AgNOR) in cell of small cell carcinoma and lymphocyte. The purposes of this study were to assess the feasibility and usefulness of AgNOR staining in diagnostic cytology and to try to set up a procedure that could be used on prestained smears for retrospective study. While the NOR of each lymphocyte appeared to be one round dot after AgNOR staining, the NOR of cell of small cell carcinoma showed dots, slightly variable in size and shape. The mean number of NOR was significantly higher (p < 0.01) in cells of small cell carcinoma (4.7 +/- 0.7) than in lymphocytes (1.4 +/- 0.4). In conclusion, AgNOR staining was demonstrated to be a useful method to differentiate between cells of small cell carcinoma and lymphocyte in Papanicolaou-destained smears.

Finite element analysis of cerebral contusion

Finite element analysis was carried out to study the mechanism of cerebral contusion. Clinical findings indicate that most cerebral contusions in the absence of skull fracture occur at the frontal and temporal lobes. To explain these observations, cavitation and shear strain theories have long been advocated. Plane strain finite element models of a parasagittal section of the human head were developed in the present study. The model was first validated against a set of experimental results from the literature. Frontal and occipital impacts were then simulated, and pressure and shear stress distributions in the brain were compared. While comparable negative pressures always developed in the contrecoup regions, shear stress distributions remained nearly identical regardless of the impact direction, consistent with the clinically observed pattern for contusion. Therefore, shear strain theory appears to account better for the clinical findings in cerebral contusion.

Nucleolar organizer regions in smears of pleural effusion

Agyrophil staining was applied to nucleolar organizer regions (NOR) to differentiate cells of adenocarcinoma and histiomesotheliosis in pleural effusion. The smears were either nuclearly unstained, but cytoplasmically counterstained by Papanicolaou method or Papanicolaou-destained before agyrophil staining of nucleolar organizer regions (AgNOR). The purposes of this study were to assess the feasibility and usefulness of AgNOR staining in diagnostic cytology and to try to set up a procedure that could be used on prestained smears for retrospective study. All smears showed good background and cellular outline. The distribution of NOR was either intranuclearly or in the nucleoplasm diffusely. In previously nuclearly unstained smears, NOR showed granular to powder-like appearance. The mean number of NOR in adenocarcinoma (38.4 +/- 12.5) was significantly higher than that in histiomesotheliosis (15.6 +/- 2.9). In Papanicolaou-destained smears, the NOR showed confluent dots. The mean number of NOR was much lower as compared to that of previously nuclearly unstained smears. Furthermore, the mean number of NOR in adenocarcinoma (3.6 +/- 1.4) showed no significant difference with that of histiomesotheliosis (2.7 +/- 0.8). In conclusion, AgNOR staining is one of the methods to differentiate benign from malignant cells, but not in Papanicolaou-destained smears.

A rare 6q11+ heteromorphism: cytogenetic analysis and in situ hybridization

A rare variant of 6q11+ heteromorphism was found in a fetus and the mother during amniocentesis. The G- and Q-banding and DA/DAPI stain were negative. The C-banding was positive and the C-banded segment was 3-fold longer in the variant than in its homologue. Neither of the C-banded regions of chromosomes 6 decondensed when exposed to distamycin A or 5-azacytidine. A DNA replication study indicated that the C-banded variant was late replicating. The lateral asymmetry observed in the 6q11 variant after one replication cycle in 5-bromodeoxyuridine may result from an unequal interstrand distribution of thymidine in the repetitive DNA. Fluorescent in situ hybridization using a chromosome-6-specific alpha-satellite probe (D6Z1) demonstrated hybridization signals on the centromere of chromosome 6. The 6q11 variant showed a signal which was 3-fold larger than its homologue. These results indicate that the 6q11 variant is an amplification of a chromosome-6-specific alpha repeat, and the size of the hybridization signal correlates with the size of the laterally asymmetric and C-banded region.

Nonfatal systemic allergic reactions induced by skin testing and immunotherapy

Skin testing and immunotherapy with allergens can induce systemic allergic reactions. In order to identify factors associated with systemic allergic reactions, a prospective study was conducted from 1976-1989 with more than 10,000 patients being tested and a total of 513,368 injections being recorded. Our study showed that the probability of inducing systemic allergic reactions by skin testing was less than 0.02% and the probability of systemic allergic reactions caused by immunotherapy was 2.9%. The female to male ratio was 3 to 2. The highest incidence of systemic allergic reactions was in patients between the ages of 16 to 39 years of age. The majority of systemic allergic reactions occurred when patients were on increasing doses rather than maintenance doses. More than 95% of systemic allergic reactions were associated with pollens and most of them happened between the concentration of 100 and 1000 PNU/mL. There was no increased incidence during grass or ragweed pollination seasons in those patients who received grass or ragweed injections during the respective seasons. Only 50% of systemic allergic reactions developed within 30 minutes after injections. The three most important factors determining the incidence of systemic allergic reactions are the type of allergens, the "rate" of increase of allergen concentrations, and sensitivity of the patients to allergens. The prick test at initial allergy assessment can be used to "rule out," with a high degree of certainty, the likelihood of systemic allergic reactions. The prick test is easy to perform and it is cost-effective. Prick tests and RAST together are helpful in identifying the patients and the allergens at higher risk of systemic allergic reactions.

B cell differentiation. II. Isotype potential of a single B cell

Clonal, functionally responsive B cells are important tools for analyzing B cell activation and differentiation. Previously, we developed a method to immortalize murine B lymphoblast cells using an oncogene-carrying retroviral vector. The immortalized B cells express a cell surface phenotype similar to that of normal splenic B cells. These cells were shown to respond to B cell polyclonal mitogens and IL-4. More significantly, these cells could form conjugates with TH2 cells in the presence of a T cell superantigen. The T-B interaction promoted by the T cell superantigen resulted in B cell differentiation as demonstrated by IgM secretion and switching to IgG1 production. In this report, we analyze Ig isotype potential using two retrovirus-immortalized B cell clones. The clonality of both B cell clones was confirmed by Southern blot analysis using JH probes. It was found that anti-CD3-activated TH1 and TH2 cells promoted clonal B cells to differentiate into IgM-secreting cells. More significantly, activated TH1 cells promoted clonal B cells to switch to IgG2a production, whereas activated TH2 cells promoted clonal B cells to switch to IgG1 production. Thus, depending on which type of T helper cell a given B cell interacts with, a single B cell has the potential to switch to more than one Ig isotype. Addition of rIL-4 and anti-IFN-gamma to cultures containing TH1 and B cells resulted in IgG1 production (in addition to IgG2a production). Similarly, addition of IFN-gamma and anti-IL-4 to cultures containing TH2 and B cells resulted in IgG2a production (in addition to IgG1 production). Therefore, interaction of B cells with a given type of T helper cells could commit the B cells to a given Ig isotype. However, the presence of exogenous cytokines could divert B cells to switch to other Ig isotypes.

99mTc-sestamibi can improve the inferior attenuation of TL-201 myocardial spect imaging

Tl-201 myocardial scintigraphy (Tl study) tends to be attenuated by soft tissues (such as the diaphragm) due to its low energy emission. 99mTc-sestamibi (2-methoxy isobutyl isonitrile) is a relatively new agent with a higher energy emission and this characteristic accounts for the higher quality of 99mTc-sestamibi images. The purpose of this study is to evaluate the ability of 99mTc-sestamibi in alleviating the inferior attenuation of Tl studies. 99mTc-sestamibi SPECT myocardial scintigraphy was performed on 13 patients with inferior wall perfusion defects as determined by Tl study (but with normal coronary artery as evidenced by cardiac catheterization). All patients underwent Tl SPECT study using a standard procedure. Same-day protocol (rest-stress sequence) was used for 99mTc-sestamibi SPECT imaging. All images were analyzed by two independent observers. The results of our study reveal that 99mTc-sestamibi produced better images. The inferior wall perfusion defects in the T1 study were noted in one case only (1/13) in the 99mTc-sestamibi study. Our study suggests that 99mTc-sestamibi can remarkably reduce the inferior attenuation of Tl study.

Clinical study of Mycoplasma pneumoniae pneumonia

From 1982 to 1991, we experienced 76 patients with Mycoplasma pneumoniae pneumonia which were confirmed by serologic tests. There were 32 (42%) male and 44 (58%) female patients. One patient had underlying disease of diabetes mellitus while the other patients were in good health. The age ranged from 9 months old to 72 years old. All the patients complained of fever and coughing; 63% had dry cough and 37% had sputum production. Upper respiratory tract complaints such as rhinorrhea, sore throat, or earache were noted in 57% of the patients. Fifty-five percent of the patients had GI symptoms of anorexia, nausea, vomiting, or diarrhea. Other complaints included myalgia/arthralgia (29%), headache (30%), and general malaise (32%). Dyspnea (17%) and chest pain (20%) were occasional complaints. Seventy-one percent of the patients had WBC counts < 10000/cu mm and 29% > 10000/cu mm. The mean value of C-reactive protein (CRP) was 53.1 micrograms/ml, while 16% of the patients had a CRP value above 100 micrograms/ml. Thirty-one percent of the patients were noted to have a transient elevation of serum transaminase. Four different patterns of infiltration were seen in chest radiographic manifestation: 1) peribronchial and perivascular interstitial infiltrates (18.4%), 2) nonhomogeneous patchy consolidations (22.4%), 3) homogeneous acinar consolidations (27.6%), and 4) mixed interstitial and alveolar infiltrates (27.6%). Interstitial infiltration was more commonly seen in pediatric than adult patients (46% vs 20%). Other features of the radiologic manifestation were as follows: unilateral lesions in 80% of patients, single lobe lesions in 77%, lower lobe predominant in 69%, pleural effusion in 7%, and radiographic deterioration in 10%. Mycoplasmal pneumonia should be considered in the differential diagnosis of community-acquired pneumonias.

Effects of 5-hydroxymethyl-2'-deoxyuridine and 3-aminobenzamide on chromosome aberrations in cultured human lymphocytes

Effects of 5-hydroxymethyl-2'-deoxyuridine (HmdUrd, a thymidine analog) and 3-aminobenzamide (3AB) on chromosome aberrations in cultured human lymphocytes were studied. The results show that HmdUrd is an effective clastogen in human peripheral lymphocytes. When cells were treated with HmdUrd and 3AB, a synergistic effect on chromatid gaps, breaks and exchanges was found. These findings support the hypotheses that 5-hydroxymethyluracil (HmUra) residues in DNA are formed and then removed by the action of 5-HmUra-DNA glycosylase (Teeber et al., 1984) and that 3AB interferes with the completion of DNA repair following HmUra excision.

Effects of epidural morphine and intramuscular diclofenac combination in postcesarean analgesia: a dose-range study

To assess the efficacy of combinations of epidural morphine and intramuscular diclofenac in postcesarean analgesia, a double-blind, randomized study was conducted. Epidural anesthesia was administered to 120 parturients who were randomly allocated into six treatment groups; these groups, A, B, C, D, and E, received 0.5, 1, 2, 3, and 4 mg of epidural morphine in 10 mL of normal saline solution, respectively, and 75 mg (3 mL) of diclofenac intramuscularly (IM). Group F received 4 mg of epidural morphine in 10 mL of normal saline solution and 3 mL of normal saline solution IM. Epidural injections were given after delivery of the placenta and IM injections were given on arrival in the recovery room. Verbal analogue pain score and pruritus score were recorded at 2, 4, 8, 12, 18, and 24 h after epidural injection. Subjective scores of overall pain relief also were recorded at 24 h. Results showed that group A had the highest pain scores and required more supplemental meperidine than groups C, D, E, and F. None of the patients in groups D and E requested supplemental analgesia. There were no differences in wound pain score among groups B, C, D, E, and F. Compared with group F, groups D and E experienced a superior analgesic effect in relieving uterine contraction pain from 4 to 12 h (P < 0.05). There were no differences in overall pain relief among the six groups. The incidence of nausea or vomiting or both, pruritus, and bleeding was similar. There was no evident relationship between severity of pruritus and morphine doses. No bradyspnea was observed during the study period.(ABSTRACT TRUNCATED AT 250 WORDS)

A survey on drug-related hospitalization in a community teaching hospital

We retrospectively studied 2,695 patients admitted to the Department of Medicine over a 10-month period in 1990 to determine the incidence of drug-related hospitalization. A drug-related problem was identified as the primary cause of hospitalization in 109 (4.0%) admissions. The incidence was significantly greater in the elderly group as compared with the non-elderly group (5.2% vs 3.2%). Non-steroidal anti-inflammatory drugs, hypoglycemic agents, herbal medicine, adrenocorticosteroids and antihypertensive drugs were most often involved. The five most common adverse events were upper gastrointestinal tract bleeding, skin rashes, hypoglycemia, hypercorticism and hepatitis. Iatrogenic disease was fatal in 2 cases. Patients used drugs without medical supervision in 45 cases. In view of the increasing complexity of modern pharmacotherapy and the popularity of self-medication in our society, educational efforts should be enhanced for medical professionals and the general population to reduce the risk of drug-related hospitalization.

Flow cytometric DNA analysis of pleural effusions

A total of 71 cases of pleural effusion in patients with and without cancer were analyzed by conventional cytology and flow cytometry (FCM) in order to detect cells with an abnormal DNA content (aneuploidy). For cytologic examination, the samples were prepared using standard techniques. Sample for FCM analysis were centrifuged and exposed to hypotonic solution containing detergent and propidium iodide. Thirty-eight patients had pleural effusion due to benign disease, whilst 33 patients had primary lung cancer. All 38 patients with benign pleural effusions showed FCM diploidy. There were 17 aneuploidy (52%) and 16 diploidy (48%) in the 33 patients with lung cancer by FCM analysis. Four of these 33 effusions were cytologically negative, however, FCM showed aneuploidy in 2 of these 4 patients. Based on these results, FCM analysis combined with conventional cytopathology yielded 100% specificity, 94% sensitivity and 100% predictive value of positive result. There were no false-positive results but 2 false-negative results. These findings suggest that FCM is a rapid and useful technique in the analysis of pleural effusion and can be a very useful adjunct to conventional cytopathology.

B cell differentiation: I. Development and functional analysis of murine B cells immortalized by a recombinant retrovirus

B lymphoblast cells were immortalized by infection with a v-myc and v-raf/mil containing recombinant retrovirus. The immortalized B cells do not require exogenous growth factors or mitogens for growth. These cells express characteristic mature B cell phenotypic markers including IgM and IgD. Northern blot analysis detected mu and delta mRNA, and Southern blot analysis revealed rearrangements of Ig genes but not TCR genes in these cells. The immortalized B cells were found to respond to B cell mitogens by proliferation and IgM secretion, and to respond to IL-4 by an increase in la expression. Furthermore, they were found to differentiate to secrete IgM and to switch to IgG1 production following interaction with Staphylococcal enterotoxin B- activated Th2 cells. These cell lines are thus valuable tools for analyzing the molecular events involved in B lymphocyte growth and differentiation.