Intrauterine androgen exposure impairs gonadal adipose tissue functions of adult female rats

Prenatal androgen exposure induces fetal programming leading to alterations in offspring health and phenotypes that resemble those seen in women with Polycystic Ovary Syndrome. It has been described that prenatal androgenization affects the reproductive axis and leads to metabolic and endocrine disorders. Adipose tissue plays a crucial role in all these functions and is susceptible to programming effects. Particularly, gonadal adipose tissue is involved in reproductive functions, so dysfunctions in this tissue could be related to fertility alterations. We aimed to investigate the extent to which prenatal hyperandrogenization is able to alter the functionality of gonadal adipose tissue in female adult rats, including lipid metabolism, adipokines expression, and de novo synthesis of steroids. Pregnant rats were treated with 1 mg of testosterone from day 16 to day 19 of pregnancy, and female offspring were followed until 90 days of age, when they were euthanized. The prenatally hyperandrogenized (PH) female offspring displayed two phenotypes: irregular ovulatory (PHiov) and anovulatory (PHanov). Regarding lipid metabolism, both PH groups displayed disruptions in the main lipid pathways with altered levels of triglyceride and increased lipid peroxidation levels. In addition, we found that Peroxisome Proliferator-Activated Receptors (PPARs) alpha protein expression was decreased in both PH phenotypes (p < 0.05), but no changes were found in PPARγ protein levels. Furthermore, regarding adipokines, no changes were found in Leptin and Adiponectin protein levels, but Chemerin protein levels were decreased in the PHiov group (p < 0.05). Regarding de novo synthesis of steroids, the PHanov group showed increased protein levels of Cyp17a1 and Cyp19, while the PHiov group only showed decreased protein levels of Cyp19 (p < 0.05). These results suggest that prenatal androgen exposure affects females' gonadal adipose tissue in adulthood, disturbing different lipid pathways, Chemerin expression, and de novo synthesis of steroids.

Role of Hormones During Gestation and Early Development: Pathways Involved in Developmental Programming

Accumulating evidence suggests that an altered maternal milieu and environmental insults during the intrauterine and perinatal periods of life affect the developing organism, leading to detrimental long-term outcomes and often to adult pathologies through programming effects. Hormones, together with growth factors, play critical roles in the regulation of maternal-fetal and maternal-neonate interfaces, and alterations in any of them may lead to programming effects on the developing organism. In this chapter, we will review the role of sex steroids, thyroid hormones, and insulin-like growth factors, as crucial factors involved in physiological processes during pregnancy and lactation, and their role in developmental programming effects during fetal and early neonatal life. Also, we will consider epidemiological evidence and data from animal models of altered maternal hormonal environments and focus on the role of different tissues in the establishment of maternal and fetus/infant interaction. Finally, we will identify unresolved questions and discuss potential future research directions.

Lipid Metabolism and Relevant Disorders to Female Reproductive Health

BACKGROUND

Lipids are essential components of cells that participate in metabolic and endocrine regulation and reproductive functions. The main organs where lipid regulation takes place are the liver and adipose tissue. Besides, when each tissue specific action cannot be exerted, it could lead to several endocrine-metabolic disorders closely related to PCOS, such as non-alcoholic fatty liver disease (NAFLD) and obesity.

OBJECTIVE

This work aims to discuss the impact of lipid alterations on metabolic and reproductive health. Therefore, this review focus on the importance of carrying out an integrated study of the molecular pathways affected in PCOS for developing target therapies.

RESULTS

Lipids play a major role in PCOS pathogenesis. In this regard, failures in lipid regulation, synthesis, and/or homeostasis contribute to metabolic and reproductive abnormalities, such as those seen in PCOS. Several lipid pathways and regulators are altered in this pathology, leading to dysfunctions that worsen reproductive functions. Therefore, there are several treatments to manage dyslipidemias. Non-pharmacological therapies are considered a first line treatment being the pharmacological treatments a second line option.

CONCLUSION

The best treatment to improve the lipid profile is a lifestyle intervention, a combination of hypocaloric diet and exercise. Regarding pharmacological therapies, a combination of fibrate and statins would be the most recommended drugs. Still, in PCOS women, treatment with metformin or TZDs not only modulates the lipid metabolism, but also improves the ovulation. Also, metformin with lifestyle interventions has positive effects on the metabolic and reproductive features of PCOS patients.

Prenatal androgen exposure affects ovarian lipid metabolism and steroid biosynthesis in rats

Prenatal androgen exposure affects reproductive functions and has been proposed as an underlying cause of polycystic ovary syndrome (PCOS). In this study, we aimed to investigate the impact of prenatal androgen exposure on ovarian lipid metabolism and to deepen our understanding of steroidogenesis regulation during adulthood. Pregnant rats were hyperandrogenized with testosterone and female offspring were studied when adult. This treatment leads to two different phenotypes: irregular ovulatory and anovulatory animals. Our results showed that prenatally hyperandrogenized (PH) animals displayed altered lipid and hormonal profile together with alterations in steroidogenesis and ovarian lipid metabolism. Moreover, PH animals showed alterations in the PPARg system, impaired mRNA levels of cholesterol receptors (Ldlr and Srb1) and decreased expression of the rate-limiting enzyme of de novo cholesterol production (Hmgcr). Anovulatory PH animals presented an increase of ovarian cholesteryl esters levels and lipid peroxidation index. Together with alterations in cholesterol metabolism, we found an impairment of the steroidogenic pathway in PH animals in a phenotype-specific manner. Regarding fatty acid metabolism, our results showed, in PH animals, an altered expression of Srebp1 and Atgl, which are involved in fatty acid metabolism and triglycerides hydrolysis, respectively. In conclusion, fatty acid and cholesterol metabolism, which are key players in steroidogenesis acting as a source of energy and substrate for steroid production, were affected in animals exposed to androgens during gestation. These results suggest that prenatal androgen exposure leads to long-term effects that affect ovary lipid metabolism and ovarian steroid formation from the very first steps.

Effects of in utero androgen excess and metformin treatment on hepatic functions

This study aimed to evaluate the role of prenatal hyperandrogenization in liver functions and the extent of metformin as treatment. Pregnant rats were hyperandrogenized with subcutaneous testosterone (1mg/rat) between 16 and 19 of pregnancy. Prenatally hyperandrogenized (PH) female offspring displayed, at the adult life, two phenotypes; a PH irregular ovulatory phenotype (PHiov) and a PH anovulatory (PHanov) phenotype. From day 70 to the moment of sacrifice (90 days of age), 50% of the animals of each group received a daily oral dose of 50 mg/kg of metformin. We found that both PH phenotypes displayed a hepatic disruptions of insulin and glucose pathway and that metformin treatment reversed some of these alterations in a specific-phenotype manner. Our findings show, for the first time, that androgen excess in utero promotes hepatic dysfunctions and that metformin treatment is able to specifically reverse those hepatic alterations and sheds light on the possible mechanisms of metformin action.

Production of Recombinant Trypanosoma cruzi Antigens in Leishmania tarentolae

Trypanosomatids are unicellular organisms that colonize a wide diversity of environments and hosts. For instance, Trypanosoma cruzi is a human pathogen responsible for Chagas diseases, while Leishmania tarentolae infects amphibians and became a biotechnological tool suitable for recombinant protein expression. T. cruzi antigens are needed for the development of improved epitope-based methods for diagnosis and treatment of Chagas disease. Molecular cloning for the production of recombinant proteins offers the possibility to obtain T. cruzi antigens at high yield and purity. L. tarentolae appears as the ideal expression host to obtain recombinant T. cruzi antigens with a structure and posttranslational modifications typical of trypanosomatids. In this chapter, we present a protocol for the analytical to mid-scale production of recombinant T. cruzi antigens, using L. tarentolae as expression host (LEXSY^® inducible system).

Low levels of adherence to antiretroviral therapy in HIV-1-infected women with menstrual disorders

We evaluated the prevalence of menstrual disorders in HIV-1-infected women and explored the association between such disorders and adherence to antiretroviral therapy, sexual functioning, and depressive symptoms in a group of HIV-1-infected women aged younger than 46 years and on antiretroviral therapy. Participants were included in a cross-sectional survey between June 2005 and December 2006. Women provided information about their menstrual cycle and adherence in a single visit and responded to the Greene Climacteric Scale, the Massachusetts General Hospital Sexual Functioning Questionnaire and the Beck Depression Inventory. Women with and without menstrual disorders were compared using parametric and nonparametric tests. A multivariate stepwise logistic regression model was developed. The participants were 107 Caucasian women with a median (interquartile range [IQR]) age of 39 years (IQR, 36-42 years) and a median CD4 cell count of 483 cells/mm(3) (IQR, 332-679 cells/mm(3)). The viral load was below 50 copies per milliliter in 76.6% of the women. Sixty-four percent of the women had acquired HIV-1 infection through sexual intercourse. Menstrual disorders, observed in 32% of participants, were more frequent in women with detectable viral loads (p = 0.018). Women with menstrual disorders reported worse adherence (p = 0.005) and more sexual dysfunction (p < 0.05). Sixty-nine percent of the women who attributed their menstrual disorders to the use of antiretrovirals had inadequate adherence. Depressive symptoms were not observed. Vasomotor symptoms (p = 0.004), having a detectable viral load (p = 0.03) and adherence less than 95% (p = 0.02) were predictors of menstrual disorder. A third of the HIV-1-infected women assessed had menstrual disorders that impacted negatively on adherence to therapy and sexual function. The subjective attribution of these irregularities to antiretrovirals seems to affect medication intake, possibly favoring negative clinical consequences.

Sustained antiretroviral treatment adherence in survivors of the pre-HAART era: attitudes and beliefs

The objective of this study was to assess adherence of HIV-1-infected patients who started treatment in the pre-HAART era and to determine variables associated with better adherence, including relevant attitudes and beliefs. This is a cross-sectional study enrolling patients who had received antiretroviral therapy for >or=10 years. Adherence was evaluated through self-reporting and plasma drug concentrations. Treatment variables, attitudes and beliefs were collected during structured interviews. The results show that for 87 patients the median (interquartile range) time on therapy was 13 (10-19) years; 80 were on therapy at the time of analysis. Adherence was >or=95% in 54 patients (67.5%), 90-94% in 22 (27.5%) and <90% in 4 (5%). Drug concentrations were below the lower limit of detection in five patients. Younger age (p=0.014), female gender (p=0.005), current substance abuse (p=0.004) and hepatitis C virus co-infection (p<0.001) were related to lower adherence. Adherence did not differ in relation to different drug families or once- or twice-daily regimens. Patients with adherence <95% were more likely to have interrupted treatment without doctor's recommendation (p=0.009). Adherent patients exhibited a higher perception of risk of developing the illness and of benefits of therapy, higher self-efficacy and intention to adhere and were more influenced by events that motivate medication intake. To conclude, adherence was >90% in most patients on antiretroviral therapy for >or=10 years. Adherence was more related to beliefs about health and illness than to the characteristics of medication or level of knowledge about treatment. Care adherence interventions should include assessment of health beliefs.

Influence of the type of pegylated interferon on the onset of depressive and neuropsychiatric symptoms in HIV-HCV coinfected patients

This is a prospective observational comparative 48-week study to assess the impact of the different types of Peg-IFN on depressive and neuropsychiatric symptoms during treatment in HIV-HCV coinfected patients. Thirty-one patients treated with Peg-IFN alpha-2b 1.5 microg/kg/w plus ribavirine (RBV) (Peg-IFN alpha-2b Group) and 32 patients receiving Peg-IFN alpha-2a 180 microg/w plus RBV (Peg-IFN alpha-2a Group) were included. Depressive and neuropsychiatric symptoms, quality of life and adherence were assessed. Fifteen subjects (23%) discontinued therapy (p = 0.3, between groups). Overall, 37 patients presented mild to moderate depressive symptoms, 9 moderate to severe and 3 severe, without differences between groups. Patients in Peg-IFN alpha-2b reported higher fatigue and dizziness at weeks 12 (p < 0.05) and 24 (p < 0.05), and irritability and memory loss at week 24 (p < 0.05) with respect to Peg-IFN alpha-2a Group. At week 12, role functioning, general health perception, vitality, emotional role, mental health and the summary areas of physical health and mental health were lower in Peg-IFN alpha-2b Group (p < 0.05). The same was observed in physical functioning (p = 0.05) and role functioning, general health perception, emotional role and mental health (p < 0.001) at week 24. Three months after finishing treatment, no patient had depressive or neuropsychiatric symptoms, and quality of life improved. Antiretroviral adherence was low but adherence to anti-HCV therapy remained high in both groups. According to our data, Peg-IFN alpha-2a and Peg-IFN alpha-2b exert a similar impact on the overall rate of depressive symptoms, although patients treated with Peg-IFN alpha-2a experience less fatigue and fewer neuropsychiatric symptoms and a lower impairment in their physical and mental quality of life.

Papillary squamous cell carcinoma of the oropharynx

A case of papillary squamous cell carcinoma of the oropharynx is reported. The lesion was located in the base of the tongue and grossly presented a characteristic finger-like pattern of growth. The clinicopathological profile of the neoplasm is presented and the differential diagnosis with other exophytic squamous cell carcinomas is discussed.

Psychological impact of structured treatment interruptions in patients with prolonged undetectable HIV-1 viral loads

Structured treatment interruption strategies may help overcome problems of highly active antiretroviral therapy, but might also represent a cause of stress. We present data that indicate a psychological benefit from structured treatment interruption. Although some disturbances appear at the resumption of therapy, no definitive problems are found that preclude such therapeutic approaches from a psychological perspective. However, a close follow-up of patients during interruption periods is advisable to avoid difficulties reported at treatment resumption presenting a risk to patients' health.

Prospective randomized two-Arm controlled study to determine the efficacy of a specific intervention to improve long-term adherence to highly active antiretroviral therapy

BACKGROUND

Nearly perfect compliance seems to be indispensable to obtain the maximum benefit from highly active antiretroviral therapy (HAART). Interventions to ensure a high level of adherence during a relatively long-term period of therapy are necessary.

METHODS

This is a prospective, randomized, two-arm controlled study including patients starting their first-or second-line HAART who were randomized to receive psychoeducative intervention to implement adherence (experimental group [EG]) or a usual medical follow-up (control group [CG]). We aimed to study the efficacy of a psychoeducative intervention to ensure long-term adherence to HAART, its relation with the virologic efficacy of treatment, and to determine the variables related to long-term adherence. Visits were made at weeks 0, 4, 24, and 48 for data collection. Self-reported adherence was registered at each visit and its veracity was tested by randomized blood analyses performed without previous warning to 40% of patients. Appropriate adherence was defined as the consumption of >/=95% of medication prescribed. Statistical analyses were performed both by the as treated (AT) and the intention to treat missing = failure (ITT) methods.

RESULTS

In all, 116 patients were included. At week 48, 94% of patients in the EG versus 69% controls achieved adherence >/=95% (p =.008); 89% of patients in the EG versus 66% controls had HIV-1 RNA levels <400 copies/ml (p =.026). Overall, 85% of patients with adherence >/=95% but only 45% of those with adherence <95% had viral load (VL) <400 copies/ml (p =. 008). In multivariate analysis, variables significantly related to adherence were having received a psychoeducative intervention (odds ratio [OR], 6.58; p =.04), poor effort to take medication (OR, 5.38; p =.03), and high self-perceived capacity to follow the regimen (OR, 13.76; p =.04). Self-reported adherence and drug plasma levels coincided in 93% of cases. However, differences in adherence did not reach statistical significance in the ITT analysis although a clear tendency toward benefit was observed in EG.

CONCLUSIONS

Specific and maintained psychoeducative interventions based on excellence on clinical practice are useful to keep high levels of adherence as well as high levels of viral suppression. There is a clear relation between high adherence levels and virologic success. Assessment of certain specific variables related to adherence may be helpful to monitor patient's compliance in the clinical setting.

Intrathecal morphine for postoperative analgesia following repair of frontal encephaloceles in children: comparison with intermittent, on-demand dosing of nalbuphine

STUDY OBJECTIVE

To determine the efficacy of lumbar intrathecal (i.t.) morphine in a dose of 0.02 mg/kg in providing analgesia following repair of frontal encephaloceles.

DESIGN

Prospective, open-label investigation of i.t. morphine with secondary comparison to a retrospective cohort.

SETTING

Metropolitan hospital in the Philippines.

PATIENTS

24 ASA physical status I and II children undergoing frontal encephalocele repair.

INTERVENTIONS

Following induction of general anesthesia. I.t. morphine (Group 1) was administered via single-shot technique or through a lumbar i.t. drain placed for cerebrospinal fluid drainage during the surgical procedure. Postoperative analgesia was assessed by visual analog score in patients greater than 5 years of age or a behavioral score in patients less than 5 years of age. The retrospective cohort received postoperative analgesia with intermittent doses of intravenous nalbuphine (Group 2).

MEASUREMENTS AND MAIN RESULTS

Group 1 had decreased postoperative analgesic requirements, decreased intraoperative inhalational anesthetic requirements, and a longer time to the first request for postoperative analgesia than Group 2. The time to the first request for postoperative analgesia was 16.0 +/- 9.1 hours in Group 1 and 1.6 +/- 1.2 hours in Group 2 (p < 0.0001). Six of 12 patients in Group 1 required no analgesic drugs during the first 24 postoperative hours while all 12 patients in Group 2 (p = 0.02) did require analgesic drugs during this period. The patients in Group 1 who did not require supplemental analgesic drugs maintained pain scores of 2 or less throughout the first 24 postoperative hours.

CONCLUSION

Lumbar IT morphine provides effective analgesia following repair of frontal encephaloceles in children and adolescents.

[Mechanical ventilation-associated pneumonia and the prevention of stress ulcer. A randomized clinical trial of antacids and ranitidine versus sucralfate]

BACKGROUND

To study two groups of patients intubated with different prophylaxis of stress gastric ulcer in a prospective randomized trial. The differential effect on gastric pH, gastric colonization and the incidence of pneumonia associated to mechanical ventilation (PMV) were analyzed.

METHODS

A prospective randomized study was carried out in two groups of patients: 1) prophylaxis with antacids and H2 blockers (AA+H2) and 2) prophylaxis with sucralfate. Intubated patients without initial respiratory infection were included in the protocol. Periodically gastric aspirations were collected measuring gastric pH and performing semi-quantitative cultures. When pneumonia was suspected bronchial brushing was carried out with telescoped catheter (BBTC) and quantitative culture.

RESULTS

Fifty-one patients were studied (n = 51), distributed into 25 in the AA+H2 group and 26 in the sucralfate group. In the first group mean pH was higher (5.3 +/- 1.7) than in the sucralfate group (3.2 +/- 2.1) (p = 0.006). Nosocomial pneumonia (NP) was suspected on 25 occasions: 20 patients were positive for NP, 11 in the AA+H2 group and nine in the sucralfate group with no significant differences being observed. S. aureus, S. pneumoniae and H. influenzae (n = 14) were the etiology of predominant PMV. The global mortality of the group was of 22%.

CONCLUSIONS

The prophylaxis of stress ulcers in intubated patients treated with antacids and ranitidine provoked higher gastric pH and an increase in gastric colonization in comparison to that observed with sucralfate. No significant differences were observed in the frequency of pneumonia by PMV diagnosed by BBTC.

A lactobionate-based extracellular-type solution for donor heart preservation

The University of Wisconsin solution, which contains the impermeant lactobionate and has an intracellular-type electrolyte composition, has been shown to improve donor heart preservation. Because a deleterious effect of the intracellular-type solutions has been reported, we evaluated a new lactobionate-based extracellular-type solution, by comparing it with University of Wisconsin solution and a crystalloid cardioplegic solution in 45 rabbit hearts. Hearts were arrested by infusion of these solutions and immersed in the same solution (lactobionate-based extracellular-type solution, University of Wisconsin solution) or in the lactated Ringer's solution (crystalloid cardioplegic solution) for 6 hours at 4 degrees C. A Langendorff circuit was used for reperfusion. Left ventricular compliance was better preserved with both lactobionate-based solutions than with the crystalloid cardioplegic solution. Adenosine triphosphate was best preserved with the lactobionate-based extracellular-type solution after arrest and after reperfusion, whereas reperfusion arrhythmias were less marked with the University of Wisconsin solution. These results suggest that lactobionate plays an important role in the preservation of ventricular compliance and that the lactobionate-based extracellular-type solution is preferable for adenosine triphosphate preservation. Further study will be required to assess the factors predisposing to reperfusion arrhythmias.

Bilateral infraorbital block with 0.5% bupivacaine as post-operative analgesia following cheiloplasty in children

Various studies have shown that bupivacaine nerve blocks provide prolonged post-operative analgesia. We studied the efficacy of a 0.5% bupivacaine infraorbital nerve block as post-operative analgesia in a random, prospective, double blind manner in children undergoing cleft lip repair. Following the induction of anesthesia with ketamine 2-4 mg/kg im, 60 patients, aged 2-13 years, ASA I and II were equally divided: Group A received 1-1.5 ml bupivacaine, 0.5% with 1:200,000 epinephrine; Group B received 1-1.5 ml saline injected into the vicinity of the infraorbital foramina. In every patient, the surgeon infiltrated the lip with 4-7 ml of 1% lidocaine with 1:100,000 epinephrine for both anesthesia and hemostasis. Post-operative evaluations were completed after 4, 8, and 12 to 24 hours and were based on a visual analogue scale for pain. Similarly, the nurses and the parents also evaluated post-operative discomfort using specific criteria. All the observers were kept unaware of the solutions used for the block. The results showed that Group A was pain free for a mean duration of 19.4 +/- 5.06 (SD) hours in contrast to 11.7 +/- 6.19 hours for Group B, (p less than 0.001). Group A required no other analgesic whereas a total of 17 patients in Group B required analgesic medication starting at four hours post-operatively, (p less than 0.001). Both the nurses and the parents confirmed that those who received infraorbital block were more comfortable than those who did not. One-way analysis of variance indicates that the mean scores for both groups differs significantly at all levels of comparison, (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Enhancement of adriamycin antitumor activity by its binding with an intracellular sustained-release form, polymethacrylate nanospheres, in U-937 cells

We investigated the antitumor activity of Adriamycin on a monocytic-like cancer cell line U-937 after its binding on polymethacrylate nanospheres (diameter, 270-350 nm). Compared to free Adramycin (F-ADR), nanosphere-bound Adriamycin (B-ADR) exhibits a 3-fold enhancement of cytotoxicity, as determined by cell growth inhibition and DNA synthesis, after continuous exposure to 0.02 and 0.04 microgram/ml. The 90% growth inhibition concentration was 0.051 microgram/ml for F-ADR and was 0.018 microgram/ml for B-ADR (P less than 0.001). Furthermore, the nanosphere densities per cell play an important role since for the same drug concentration the higher the density increases, the better the activity is. Indeed, after 4 days of incubation in a medium containing 160 nanospheres at 0.5 fg/cell, the cell counts were 62.8 +/- 12.8% (SD) of the initial inoculum and they were only 16.1 +/- 0.1% after incubation in a medium containing 800 nanospheres at 0.1 fg/cell (P less than 0.001). A comparable enhancement of activity regarding the nanosphere densities was observed after a 24-h exposure to 0.02 and 0.05 microgram/ml. Short-term uptake studies showed that B-ADR accumulation was higher with B-ADR than with F-ADR. In addition, the efflux kinetics was modified. For cells exposed to F-ADR for 4 h, the efflux half-life was 23.7 +/- 7.7 h and the area to infinity under the efflux curve was 8.6 +/- 2.8 micrograms/mg protein x h-1. For cells exposed to B-ADR, the efflux half-life increased to 85.9 +/- 19.2 h and the area to infinity under the efflux curve to 29.6 +/- 6.6 micrograms/mg protein x h-1 (P less than 0.001). Electron transmission microscopy and previous findings have revealed that B-ADR was well internalized into cells. Our data support the hypothesis that B-ADR acts as an intracellular drug release complex after endocytosis. The findings regarding the number of nanospheres per cell and dose-effect relationships are consistent with mechanisms of drug actions extending to membrane domains.

[Radio-immunometric determination of the ferritin for evaluation of the iron storage pool (author's transl)]

Seventy-three patients with several haematological diseases have been studied with radio-iron-kinetic, cyto-chemical measurement of iron in the bone marrow, and radio-immunometric determination of the ferritin in the serum. This method gives results which correlate significantly with other methods which evaluate the iron storage pool, in normal or iron-deficient patients. In some cases, an excess of serum ferritin, contrasting with normal serum iron, is confirmed by cytochemical and/or Fe-kinetic studies. In myeloproliferative diseases however, secretion of ferritin by immature cells may induce an excess of serum ferritin. In such cases, the dosage of ferritinaemia cannot be considered as an index of the iron storage pool. Future development of specific dosage of isoferritins could enable to measure the true iron stores, as well as to give an index estimating the evolution of the abnormal cell population.