Are biomarkers associated with sensitivity to physical activity?

BACKGROUND: Activity-based treatments play an integral role in managing musculoskeletal conditions including low back pain. However, while therapeutic exercise has been shown to reduce pain in such conditions, certain individuals experience a paradoxical pain increase in response to exercise. The physiological processes underlying this sensitivity to physical activity (SPA) are not fully understood, however stress and inflammation have been shown to contribute to SPA. The present cross-sectional study investigated whether physiological indicators of stress (cortisol) and inflammation (IL-6) help explain SPA. METHODS: Twenty-seven patients with chronic low back pain and 21 healthy controls completed a 1-h exercise session of standardized physical tasks. SPA was calculated from the difference between post- and pre-exercise pain levels. Participant's saliva was collected at several timepoints for cortisol and IL-6 levels quantification. Their waking cortisol response was calculated to reflect their cortisol regulation. Reactivity of IL-6 and cortisol was calculated to reflect changes in these measures during exercise. RESULTS: IL-6 reactivity was significantly and positively correlated with SPA among participants with low back pain. In contrast, neither cortisol waking response nor cortisol reactivity was significantly correlated within the low back pain group. No significant differences in IL-6 reactivity, cortisol reactivity or cortisol waking response were observed. CONCLUSION: These findings are the first to link SPA to an objective biomarker among people with low back pain. These findings help describe the physiological mechanisms of SPA and can support new clinical research that targets the inflammatory response of patients with chronic low-back pain and elevated SPA. SIGNIFICANCE: This study reveals a correlation between SPA and an objective salivary biomarker of IL-6 in people with low back pain, improving our understanding of this clinically relevant subjective experience.

[Feminizing genitoplasty for prepubertal children and teenagers female]. / Génitoplastie féminisante dans les anomalies du développement sexuel de l'enfant pré-pubère et de l'adolescente au Cameroun. À propos de 9 cas.

OBJECTIVE: The aim of this study was to report our experience after 10 years of practice of feminizing genitoplasty in prepubertal and adolescent patients with disorders of sex development (DSD) assigned females as females in a developing country. METHODOLOGY: This was a cross-sectional, descriptive and retrospective study over a period of 9 years. All pre-pubertal (8-12 years) and adolescent patients female sex assigned with DSD who had willfully consented to the surgery with their guardians and underwent feminizing genital surgery were enrolled in the study. Data collection included: age at presentation, precise diagnosis, surgical procedures, complications, cosmetic result and duration of follow-up. Each patient had a precise diagnosis and the surgery was planned after discussion with the multidisciplinary team. Cosmetic results were assessed based on: appearance of the clitoris and separation of the vaginal and urethral openings. RESULTS: Nine patients raised as females with a median age of 8 years (IR: 10.75) were recorded. Surgery was performed at a median age of 11 years (IR: 9.5). In this series, 6 had a 46, XY karyotype with varying diagnoses: partial androgen insensitivity syndrome (n=2); 5-alphareductase insufficiency (n=2); 17-ketoreductase insufficiency (n=2); gonadal dysgenesis with a mutation in the NR5A1 gene (n=2), 2 had ovostesticular DSD, (karyotypes 46, XX), and 1 had mixed gonadal dysgenesis (karyotype 45, X/46, XY). Partial or total gonad(s) removal in accordance with assigned gender was the most common associated procedure. It was bilateral in 7 cases and unilateral in 2 cases. Follow-up ranged from 3 months to 4.5 years (median: 26 months, IR:18.25). One patient had acute urinary retention in the early follow-up. No other complication such as incision bleeding was recorded. The cosmetic appearance of the external genitalia was satisfactory in all patients. CONCLUSION: Feminizing genital surgery in Cameroon remains a major challenge and should seldom be realized without a precise diagnosis. Late age at presentation is peculiar to our setting; however, it gives room for the patients' participation and input to decisions that will have a life-long personal impact on their lives in terms of psychosocial development and fertility. LEVEL OF EVIDENCE: 3.

[Outcomes of cumulative transfers of fresh and frozen embryos in in vitro fertilization in women infected by hepatitis B virus]. / Issues des transferts cumulés d'embryons frais et congelés en fécondation in vitro chez les femmes infectées par le virus de l'hépatite B.

OBJECTIVE: To assess the impact of hepatitis B virus (HBV) infection in women on in vitro fertilization (IVF) outcomes. METHODS: An observational monocentric case-control cohort study conducted between 2012 and 2019 compared the outcomes of the first cycle of IVF between 64 woman infected with HBV and 128 seronegative controls. Frozen embryos transfers made within 18 months of the puncture were included. The exclusion criteria were severe infections, viral co-infection in women, any viral infection in their spouse, or lack of fresh embryo transfer. The matching was performed according to age, primary infertility or secondary, conventional or intracytoplasmic injection IVF technique and date of attempt. The main analysis focused on cumulative live births rates (LBR). RESULTS: The clinical and ovarian stimulation characteristics were comparable except for a longer period of infertility in the HBV group. The LBR in the HBV group, when compared to controls, was not different after transfer of fresh (14.06 vs. 25.00% P=0.08) or frozen embryos (4.17 vs. 18.92% P=0.08), but significantly decreased in cumulative analysis (15.63 vs. 35.94% P=0.003). HBV infection was negatively associated with LBR in multivariate analysis OR=0.38 (95% CI 0.14-0.92) P<0.05. The implantation rate was lower in the HBV group versus controls, in fresh (14.89 vs. 27.72% P=0.02) and frozen (3.03 vs. 21.65% P=0.01) embryo transfers. CONCLUSION: This study suggests a negative impact of HBV infection in women on the cumulative LBR after IVF.

Follicular fluid concentrations of lipids and their metabolites are associated with intraovarian gonadotropin-stimulated androgen production in women undergoing in vitro fertilization.

CONTEXT: Although growing evidence points toward a role of lipotoxicity in the development of hyperandrogenesis, the main feature of polycystic ovary syndrome, few studies directly assessed this association in vivo in humans, and none targeted the ovarian milieu. OBJECTIVE: The main objective of this study was to correlate follicular fluid (FF) T levels with lipids, lipid metabolites, and inflammation markers. DESIGN: This was a cross-sectional study. SETTING: Recruitment was performed in two fertility clinics at one private and one academic center. PARTICIPANTS: Eighty women requiring in vitro fertilization were recruited during one of their scheduled visit at the fertility clinic. All women aged between 18 and 40 years with a body mass index between 18 and 40 kg/m(2) were invited to participate. INTERVENTION(S): There were no interventions. MAIN OUTCOME MEASURE(S): At the time of oocyte aspiration, FF was collected and analyzed for total T, lipids [nonesterified fatty acids (NEFAs) plus triglycerides], NEFA metabolites (acylcarnitines; markers of ineffective NEFAs ß-oxidation), and inflammatory marker composition. The hypothesis being tested was formulated before the data collection. RESULTS: FF T levels were significantly correlated with FF levels of lipids (r = 0.381, P = .001; independently of IL-6), acylcarnitines (r ≥ 0.255, all P = .008; not independently of lipids), and IL-6 (r = 0.300, P = .009, independently of lipids). Additionally, FF lipid levels were significantly and strongly correlated with acylcarnitines (r ≥ 0.594; all P < .001). CONCLUSIONS: These results suggest that ovarian androgen production is related to intraovarian exposure to lipids, independently of inflammation and mainly through ineffective NEFA ß-oxidation (as shown by higher acylcarnitine levels). Inflammation is also associated with intraovarian androgenesis, independently of lipids.

The effect of smoking cessation counselling in pregnant women: a meta-analysis of randomised controlled trials.

BACKGROUND: Pregnant smokers are often prescribed counselling as part of multicomponent cessation interventions. However, the isolated effect of counselling in this population remains unclear, and individual randomised controlled trials (RCTs) are inconclusive. OBJECTIVE: To conduct a meta-analysis of RCTs examining counselling in pregnant smokers. SEARCH STRATEGY: We searched the CDC Tobacco Information and Prevention, Cochrane Library, EMBASE, Medline and PsycINFO databases for RCTs evaluating smoking cessation counselling. SELECTION CRITERIA: We included RCTs conducted in pregnant women in which the effect of counselling could be isolated and those that reported biochemically validated abstinence at 6 or 12 months after the target quit date. DATA COLLECTION AND ANALYSIS: Overall estimates were derived using random effects meta-analysis models. MAIN RESULTS: Our search identified eight RCTs (n = 3290 women), all of which examined abstinence at 6 months. The proportion of women that remained abstinent at the end of follow up was modest, ranging from 4 to 24% among those randomised to counselling and from 2 to 21% among control women. The absolute difference in abstinence reached a maximum of only 4%. Summary estimates are inconclusive because of wide confidence intervals, albeit with little evidence to suggest that counselling is efficacious at promoting abstinence (odds ratio 1.08, 95% confidence interval 0.84-1.40). There was no evidence to suggest that efficacy differed by counselling type. CONCLUSIONS: Available data from RCTs examining the isolated effect of smoking cessation counselling in pregnant women are limited but sufficient to rule out large treatment effects. Future RCTs should examine pharmacological therapies in this population.

Distinguishing risk factors for the onset of cravings, withdrawal symptoms and tolerance in novice adolescent smokers.

AIM: While many studies report determinants of adolescent cigarette smoking, few identify risk factors for nicotine dependence (ND). This study distinguished between risk factors for three hallmarks of ND including cravings, withdrawal symptoms and tolerance. METHODS: A total of 319 novice smokers were followed every 3 months from first puff on a cigarette until the end of secondary school. Outcomes included time to first report of cravings, withdrawal symptoms and tolerance. RESULTS: Female sex, inhalation, smoking a whole cigarette, weekly smoking, daily smoking and alcohol use each independently increased the incidence of the onset of cravings. Inhalation, weekly smoking, daily smoking and alcohol use predicted the onset of withdrawal symptoms. Withdrawal symptoms, smoking a whole cigarette, monthly smoking, daily smoking and friends and siblings smoking increased the incidence of the onset of tolerance. None of parental education, impulsivity, novelty seeking, self-esteem, depression, stress, parental smoking, physical activity, or participation in sports teams was associated with the outcomes. CONCLUSION: The hallmarks of early ND are related to intensity and frequency of cigarette use. Avoidance of daily smoking may be particularly important in preventing the onset of ND symptoms and sustained smoking.

Effects of CD40 binding on ovarian carcinoma cell growth and cytokine production in vitro.

The poor prognosis associated with ovarian carcinoma (OVCA) is linked to the high incidence of local recurrence. There is a pressing need to identify factors that can play a role in OVCA growth and spread. Here, we focused on CD40, a member of the tumour necrosis factor (TNF) receptor superfamily with important functions in immune response. The expression of CD40 has been reported on various types of carcinoma cells, but its biological role is still poorly understood. The aim of the present study was to investigate the expression and function of the CD40 in OVCA cell lines. Detectable CD40 levels ranging from low to very high were found on the cell surface of several OVCA cell lines by flow cytometry analysis. Co-culture with a murine cell line transfected with CD40 ligand (CD40L) inhibited cell growth and up-regulated the secretion of proinflammatory cytokines interleukin (IL)-6, IL-8 and TNF-alpha in high-level CD40-expressing OVCA cell lines. Similarly, an increase of IL-6 and IL-8 release could be obtained by adding a soluble form of CD40L to the OVCA cultures. These results suggest that CD40-CD40L interaction is an important pathway affecting growth regulation and cytokine production in OVCA.

Conversion of a CHO cell culture process from perfusion to fed-batch technology without altering product quality.

During the development of a new drug product, it is a common strategy to develop a first-generation process with the aim to rapidly produce material for pre-clinical and early stage clinical trials. At a later stage of the development, a second-generation process is then introduced with the aim to supply late-stage clinical trials as well as market needs. This work was aimed at comparing the performance of two different CHO cell culture processes (perfusion and fed-batch) used for the production of a therapeutically active recombinant glycoprotein at industrial pilot-scale. The first-generation process was based on the Fibra-Cel packed-bed perfusion technology. It appeared during the development of the candidate drug that high therapeutic doses were required (>100mg per dose), and that future market demand would exceed 100 kg per year. This exceeded by far the production capacity of the first-generation process, and triggered a change of technology from a packed-bed perfusion process with limited scale-up capabilities to a fed-batch process with scale-up potential to typical bioreactor sizes of 15m(3) or more. The productivity per bioreactor unit volume (in product m(-3)year(-1)) of the fed-batch process was about 70% of the level reached with the first-generation perfusion process. However, since the packed-bed perfusion system was limited in scale (0.6m(3) maximum) compared to the volumes reached in suspension cultures (15m(3)), the fed-batch was selected as second-generation process. In fact, the overall process performance (in product year(-1)) was about 18-fold higher for the fed-batch compared to the perfusion mode. Data from perfusion and fed-batch harvests samples indicated that comparable product quality (relative abundance of monomers dimers and aggregates; N-glycan sialylation level; isoforms distribution) was obtained in both processes. To further confirm this observation, purification to homogeneity of the harvest material from both processes, followed by a complementary set of studies (e.g. full physico-chemical characterization, assessment of in vitro and in vivo bioactivity, comparative pharmacokinetics and pharmacodynamics studies in relevant species, etc.) would be required. Finally, this illustrates the need to fix the production process early during the development of a new drug product in order to minimize process conversion efforts and to shorten product development time lines.

Acute hepatitis C infection in HIV positive men who have sex with men in Paris, France, 2001-2004.

In mid-2004, three Parisian hospital wards informed the Institut de veille sanitaire of recent acute hepatitis C in HIV-infected (HIV+) men who had sex with men (MSM). These cases for whom none of the usual bloodborne routes for hepatitis C (HCV) transmission was found, reported having had unprotected sex. In October 2004, we conducted a retrospective investigation in Parisian hospital wards to explore HCV modes of transmission in recent acute hepatitis C in HIV+ MSM. Patient demographics, clinical and biological status of HIV infection, reasons for HCV testing, sexual behaviour and risk factors for HCV transmission within the 6 months before hepatitis onset were collected from medical records. An anonymous self-administered questionnaire on sexual behaviour within the six months before hepatitis onset was also offered to all cases. We identified 29 cases of acute hepatitis C in HIV+ MSM with onset from April 2001 to October 2004. HIV infection was asymptomatic for 76%. Median age at hepatitis C onset was 40 (28-54) years. In all records, were noted unprotected anal sex, fisting in 21% and a concomitant sexually transmitted infection (STI) in 41%. Median time between HIV diagnosis and HCV infection was 6.5 years (0-22). From the 11 self-administered questionnaires completed, 10 reported an STI, 8 'hard' sexual practices, 6 bleeding during sex and 5 fisting. HCV transmission probably occurred through bleeding during unprotected traumatic anal sex among HIV+ MSM and may be facilitated by STI mucosal lesions. This report stresses the continuous need to strongly advocate safer sex to MSM.

Failure of valacyclovir for herpes zoster in a moderately immunocompromised HIV-infected patient.

Whereas valacyclovir is widely used and is recommended by some authors in moderately immunocompromised HIV-infected patients, its use has not been validated by clinical studies. We report a case of herpes zoster in an HIV-infected patient for whom neurologic complication was not avoided despite valacyclovir therapy. Clinical outcome was favorable after intravenous acyclovir. This case suggests careful monitoring of valacyclovir in HIV-infected patients is necessary.

Smoking cessation counseling practices of general practitioners in Montreal.

BACKGROUND: Despite the cost-effectiveness of physician smoking cessation counseling, many physicians do not adhere to current clinical practice guidelines. METHODS: A cross-sectional mail survey was conducted in a random sample of general practitioners in Montreal to document cessation-counseling practices and identify correlates of these activities. RESULTS: Of 440 eligible general practitioners, 337 (77%) completed the questionnaire. Despite favorable beliefs/attitudes about cessation counseling, only 10.5% of general practitioners provided "thorough" counseling. While high proportions of general practitioners ascertained smoking status and encouraged patients to quit, relatively few offered adjunct support (i.e., for patients preparing to quit, 49.8% offered follow-up visits; 42.5% offered educational material; 20% referred patients to community resources). Correlates of counseling completeness included high self-efficacy to provide counseling (odds ratio (OR) = 2.0, 95% confidence interval (1.1-3.6)) and favorable beliefs/attitudes about counseling (OR = 3.6 (2.0-6.4)). Correlates of ascertaining smoking status included female gender (OR = 2.3 (1.5-3.5)), high self-efficacy (OR = 3.5 (2.0-5.9)), and favorable beliefs/attitudes (OR = 2.7 (1.6-4.5)). Correlates of offering adjunct support included female gender (OR = 1.9 (1.1-3.2)), awareness of stages of change (OR = 2.4 (1.3-4.4)), and knowledge of community resources to help patients quit (OR = 2.3 (1.3-3.9)). CONCLUSION: Support, training, and intervention programs to overcome lack of awareness and knowledge, unfavorable beliefs/attitudes, and low self-efficacy could increase and enhance cessation counseling practices among general practitioners.

Prospective study on anti-hepatitis C virus-positive patients with persistently normal serum alanine transaminase with or without detectable serum hepatitis C virus RNA.

A significant proportion of patients with detectable antibodies to hepatitis C virus have normal serum alanine transaminase levels. Our aim was to study the outcome of this group. Between 1992 and 1999, 135 consecutive anti-HCV-positive patients with persistently normal ALT were followed for 3.6 +/- 2.3 years (0.5 to 8.5 years), 108 had a liver biopsy at inclusion, and 24 had a second liver biopsy 3.5 +/- 1.0 years later. Serum HCV RNA was detectable with PCR in 94 patients (69%) and not detectable in 41 patients (31%). Patients with and without detectable serum HCV RNA had similar epidemiological characteristics. Serum ALT levels and anti-HCV ratio were lower (P =.001), and histological lesions had lower grade and stage in patients without detectable serum HCV RNA (P =.001). Liver HCV RNA was not detectable with PCR in the 12-serum HCV RNA-negative patients tested. During follow-up, all patients without detectable serum HCV RNA remained HCV RNA-negative and kept normal serum ALT; all patients with detectable serum HCV RNA remained HCV RNA-positive, 20 (21%) had a slight fluctuation of serum ALT above the upper limit of normal. No significant changes were observed in the liver lesions of the 24 patients who underwent a second liver biopsy. In anti-HCV-positive patients with persistently normal serum ALT, histological lesions are significantly lower in HCV RNA-negative than in HCV RNA-positive patients. During follow-up, the HCV RNA status of patients remained unchanged; 21% of the patients with detectable serum HCV RNA had slight increase in serum ALT levels, but histological lesions remained stable.

Quantitation of hepatic hepatitis C virus RNA in patients with chronic hepatitis C. Relationship with severity of disease, viral genotype and response to treatment.

BACKGROUND/AIMS: To determine the correlation between hepatic hepatitis C virus (HCV) RNA and histological lesions, viral genotype or response to alpha interferon therapy. METHODS: Forty-three patients with chronic hepatitis C (14 sustained responders (SR) and 29 non-sustained responders (NSR)) were studied. A liver tissue sample was obtained before and 1 year after treatment. Quantitation of hepatic HCV-RNA was performed by competitive PCR. RESULTS: Before treatment, HCV-RNA was detectable in all liver samples. There was no association between hepatic HCV-RNA and the severity of liver lesions. There was a significant association between old age and hepatic HCV-RNA (P = 0.03). There was an association, at the limit of significance, between genotype 1 and high hepatic HCV-RNA amounts (15 x 106 and 4.1 x 10(6) copies/g, P = 0.05). Pre-treatment hepatic HCV-RNA amounts were lower in SRs than in others (0.65 x 10(6) and 13.2 x 10(6) copies/g, P = 0.0002). After treatment, no liver HCV-RNA was detectable in the SRs while in the NSRs, the HCV-RNA amounts were unchanged. CONCLUSIONS: The amount of hepatic HCV-RNA is correlated to genotype and response to interferon therapy but not to histologic lesions. Hepatic HCV-RNA clearance is observed in SRs, suggesting viral eradication.

Physicians Taking Action Against Smoking: an intervention program to optimize smoking cessation counselling by Montreal general practitioners.

In 1997 the Direction de la santé publique de Montréal-Centre initiated "Physicians Taking Action Against Smoking," a 5-year intervention program to improve the smoking cessation counselling practices of general practitioners (GPs) in Montreal. Program development was guided by the precede-proceed model. This model advocates identifying factors influencing the outcome, in this case counselling practices. These factors are then used to determine the program objectives, to develop and tailor program activities and to design the evaluation. Program activities during the first 3 years included cessation counselling workshops and conferences for GPs, publication of articles in professional interest journals, publication of clinical guidelines for smoking cessation counselling and dissemination of educational material for both GPs and smokers. The program also supported activities encouraging smokers to ask their GPs to help them stop smoking. Results from 2 cross-sectional surveys, conducted in 1998 and 2000, of random samples of approximately 300 GPs suggest some improvements over time in several counselling practices, including offering counselling to more patients and discussing setting a quit date. More improvements were observed among female than male GPs in both psychosocial factors related to counselling and specific counselling practices. For example, improvements were noted among female GPs in self-perceived ability to provide effective counselling and in the belief that it is important to schedule specific appointments to help patients quit; in addition, the perceived importance of several barriers to counselling decreased among female GPs. A greater proportion of the female respondents to the 2000 survey offered written educational material than was the case in 1998, and a greater proportion of the male GPs devoted more time to counselling in 2000 than in 1998; however, among male GPs the proportion who discussed the pros and cons of smoking with patients in the pre-contemplation stage declined between 1998 and 2000, as did the proportion who referred patients in the preparation stage to community resources. Our experience suggests that an integrated, theory-based program to improve physicians' counselling practices could be a key component of a comprehensive strategy to reduce tobacco use.

Tolerability of treatments for viral hepatitis.

Interferon-alpha is the most widely used antiviral drug in chronic hepatitis B and C. Tolerability is usually good and serious adverse effects are rare. Most of the adverse effects are mild or transient and do not necessitate drug withdrawal. More than 90% of patients who are given interferon-alpha achieve 6 months to 1 year of treatment without serious adverse effects. The serious adverse effects usually occur in predisposed patients with pre-existing organ dysfunction. Nevertheless, careful selection of patients for therapy and observation during therapy are recommended. Nucleoside analogues are promising drugs in the treatment of chronic hepatitis B through inhibition of viral DNA polymerase. Lamivudine has been licensed for use in this indication. Its tolerability is excellent even when used for periods of 1 year or more. The main concern is the relatively high incidence of viral resistance resulting in breakthrough during or relapse after therapy. In the treatment of chronic hepatitis C, ribavirin, in combination with interferon-alpha is currently the reference therapy. The main adverse effect is haemolytic anaemia, which necessitates careful monitoring and adjustment of dosage in many cases. Recently, large trials showed the better efficacy of pegylated interferons as compared with standard interferon. The combination of pegylated interferon with ribavirin is under evaluation.

Hepatitis after intravenous buprenorphine misuse in heroin addicts.

BACKGROUND: Sublingual buprenorphine is used as a substitution drug in heroin addicts. Although buprenorphine inhibits mitochondrial function at high concentrations in experimental animals, these effects should not occur after therapeutic sublingual doses, which give very low plasma concentrations. CASE REPORTS: We report four cases of former heroin addicts infected with hepatitis C virus and placed on substitution therapy with buprenorphine. These patients exhibited a marked increase in serum alanine amino transferase (30-, 37-, 13- and 50-times the upper limit of normal, respectively) after injecting buprenorphine intravenously and three of them also became jaundiced. Interruption of buprenorphine injections was associated with prompt recovery, even though two of these patients continued buprenorphine by the sublingual route. A fifth patient carrying the hepatitis C and human immunodeficiency viruses, developed jaundice and asterixis with panlobular liver necrosis and microvesicular steatosis after using sublingual buprenorphine and small doses of paracetamol and aspirin. CONCLUSIONS: Although buprenorphine hepatitis is most uncommon even after intravenous misuse, addicts placed on buprenorphine substitution should be repeatedly warned not to use it intravenously. Higher drug concentrations could trigger hepatitis in a few intravenous users, possibly those whose mitochondrial function is already impaired by viral infections and other factors.

Regulation of microglial development: a novel role for thyroid hormone.

The postnatal development of rat microglia is marked by an important increase in the number of microglial cells and the growth of their ramified processes. We studied the role of thyroid hormone in microglial development. The distribution and morphology of microglial cells stained with isolectin B4 or monoclonal antibody ED1 were analyzed in cortical and subcortical forebrain regions of developing rats rendered hypothyroid by prenatal and postnatal treatment with methyl-thiouracil. Microglial processes were markedly less abundant in hypothyroid pups than in age-matched normal animals, from postnatal day 4 up to the end of the third postnatal week of life. A delay in process extension and a decrease in the density of microglial cell bodies, as shown by cell counts in the developing cingulate cortex of normal and hypothyroid animals, were responsible for these differences. Conversely, neonatal rat hyperthyroidism, induced by daily injections of 3,5,3'-triiodothyronine (T3), accelerated the extension of microglial processes and increased the density of cortical microglial cell bodies above physiological levels during the first postnatal week of life. Reverse transcription-PCR and immunological analyses indicated that cultured cortical ameboid microglial cells expressed the alpha1 and beta1 isoforms of nuclear thyroid hormone receptors. Consistent with the trophic and morphogenetic effects of thyroid hormone observed in situ, T3 favored the survival of cultured purified microglial cells and the growth of their processes. These results demonstrate that thyroid hormone promotes the growth and morphological differentiation of microglia during development.