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Biomedical subjects

E Jiménez

Publications and source records attributed to E Jiménez.

At least 19 recordsLinked to original sources
PubMed2006

Lactobacillus salivarius CECT 5713, a potential probiotic strain isolated from infant feces and breast milk of a mother-child pair.

In this study, Lactobacillus salivarius CECT 5713 was originally isolated from feces of a one-month-old breast-fed infant. Since it has been suggested that the gut microbiota of breast-fed infants reflects that of the maternal breast milk, we investigated if this specific strain was present in breast milk of the respective mother. RAPD and PFGE analysis revealed the presence of the strain L. salivarius CECT 5713 in this biological fluid. To our knowledge, this is the first report of a L. salivarius strain isolated from breast milk. L. salivarius CECT 5713 produced l-lactate, acetate and hydrogen peroxide, which may be responsible for its antimicrobial activity against most of the indicator organisms used in this study; in addition, this strain showed a high survival rate after exposition to conditions simulating those found in the gastrointestinal tract. Finally, it was strongly adhesive to Caco-2 and HT-29 cells did not produce biogenic amines and were unable to degrade gastric mucin in vitro.

Acetic Acid↗
PubMed2005

[Torsion of paraovarian cyst in pediatrics].

The paraovarian cyst ploughs to little frequency in pediatric population. We report a case of twist proved at surgery, and the difficulty of preoperatory diagnosis. It is very important to consider the possibility of twist to be a complication of a paraovarian cyst to try to prevent salpinguectomy.

Adolescent↗
PubMed2005

[Cardiac failure and diastolic disfunction in hemodialysis patients: associated factors].

UNLABELLED: Heart failure (CHF) and diastolic dysfuction (DD) relationship has received poor attention in hemodialysis patients (HD). OBJECTIVE: To analyse the incidence of CHF in our HD patients, the relationship with DD and impact on mortality. METHODS: We studied 79 patients: 48 +/- 15 years old, mean time on HD 83 +/- 63 months. Vascular calcification (PVC) was evaluated by radiologic series (55.7%). We analyzed the presence of clinical and analytical cardiovascular factors. All patients underwent M-mode, two-dimensional, Doppler echocardiography. Patients were followed for two years. Clinical information collected: incidence of ischemic heart disease (IHD), CHF, and mortality due to cardiovascular events. RESULTS: Most frequent finding was Left Ventricular Hypertrophy (LVH) (93%), followed by DD (63.5% had anormal LV relaxation) (ALVR). Incidence of CHF was 38.3%; and was significantly associated with higher: time on HD (130/72 months), Ca x P (74/65), PTH (677/376), bone alkaline phosphatase (27/16), and systolic BP (145 vs 130 mmHg); IHD, PVC, valvular calcification (VC), LVH and ALVR (p < 0.01). Systolic function was normal in both groups (with/without CHF). Logistic regression identified as risk factors for CHF: ALVR (OR: 9.5), IHD (OR: 15) and systolic BP (OR: 2.2). ALVR was associated with greater age (55/37), longer time on HD (76/60), PVC and VC (p < 0.001). Predictor factors identified were age (OR: 2.13) and PVC (OR: 3.9). CONCLUSIONS: HD patients showed a high incidence of CHF. IHD, systolic BP and DD (ALVR) have behave as risk factors for CHF. Vascular calcifications were intimately related to these findings and, therefore, they contribute to the greater mortality of these patients.

Cross-Sectional Studies↗
PubMed2003

Gemcitabine/vinorelbine in metastatic breast cancer patients previously treated with anthracyclines: results of a phase II trial.

This phase II study was designed to evaluate the response rate (RR) and toxicity of gemcitabine/vinorelbine in patients with metastatic breast cancer. All patients had previously received anthracyclines. Treatment consisted of gemcitabine 1200 mg/m2 and vinorelbine 30 mg/m2 on days 1 and 8, every 3 weeks. Twenty-five patients were enrolled. Median age was 59 years (range, 33-73 years). Ten patients had received only adjuvant therapy with anthracyclines. The remaining 15 patients had received chemotherapy for metastatic disease, including taxanes in 11 cases. Four patients could not be evaluated for response. By intent-to-treat analysis, the overall RR was 44% (95% CI, 24.4%-65%). Median duration of response and median time to treatment failure were 21 and 17 weeks, respectively. The main toxicity was hematologic, with grade 3/4 neutropenia occurring in 13 patients and 1 patient developing febrile neutropenia. Two deaths from pneumonia occurred. These results reveal an encouraging activity with a reasonable toxicity profile in a patient population with an unfavorable prognosis. Our group is conducting a randomized study to compare this combination with vinorelbine alone in patients with metastatic breast cancer after failure to respond to anthracyclines and taxanes

Adult↗
PubMed2002

Muscarinic acetylcholine receptor activation induces Ca2+ mobilization and Na+/K+-ATPase activity inhibition in eel enterocytes.

The effect of carbachol (Cch) on intracellular calcium concentration ([Ca2+]i) in eel enterocytes was examined using the fluorescent Ca2+ indicator fura-2. Cch caused a biphasic increase in [Ca2+]i, with an initial spike followed by a progressively decreasing level (over 6 min) to the initial, pre-stimulated, level. The effect of Cch was dose-dependent with a 7.5-fold increase in [Ca2+]i over basal level induced by the maximal dose of Cch (100 microM). In Ca2+-free/EGTA buffer the effect of Cch was less pronounced and the [Ca2+]i returned rapidly to basal levels. The increment of [Ca2+]i was dose-dependently attenuated in cells pre-treated with U73122, a specific inhibitor of phospholipase C, suggesting that the Cch-stimulated increment of [Ca2+]i required inositol triphosphate formation. In the presence of extracellular Ca2+, thapsigargin (TG), a specific microsomal Ca2+-ATPase inhibitor, caused a sustained rise in [Ca2+]i whereas in Ca2+-free medium the increase in [Ca2+]i was transient; in both cases, subsequent addition of Cch was without effect. When 2 mM CaCl2 were added to the cells stimulated with TG or with Cch in Ca2+-free medium, a rapid increase in [Ca2+]i was detected, corresponding to the capacitative Ca2+ entry. Thus, both TG and Cch depleted intracellular Ca2+ stores and stimulated influx of extracellular Ca2+ consistent with capacitative Ca2+ entry. K+ depolarization obtained with increasing concentrations of KCl in the extracellular medium induced a dose-related increase in [Ca2+]i which was blocked by 2 microM nifedipine, a non-specific L-type Ca2+ channel blocker. Nifedipine also changed significantly the height of the Ca2+ transient, and the rate of decrement to the pre-stimulated [Ca2+]i level, indicating that Ca2+ entry into enterocytes also occurs through an L-type voltage-dependent calcium channel pathway. We also show that isolated enterocytes stimulated with increasing Cch concentrations (0.1-1000 microM) showed a dose-dependent inhibition of the Na+/K+-ATPase activity. The threshold decrease was at 1 microM Cch; it reached a maximum at 100 microM (50.5% inhibition) and did not decrease further with the use of higher dose. The effect of Cch on Na+/K+-ATPase activity was dependent on both protein kinase C (PKC) and protein phosphatase calcineurin activation since the PKC inhibitor calphostin C abolished Cch effects, while the calcineurin inhibitor FK506 augmented Cch effect. Collectively, these data establish a functional pathway by which Cch can modulate the activity of the Na+/K+-ATPase through a PKC-dependent (calphostin C-sensitive) pathway and a calcineurin-dependent (FK506-sensitive) pathway.

Analysis of Variance↗
PubMed2001

Distinct mechanisms contribute to generate and change the CD4:CD8 cell ratio during thymus development: a role for the Notch ligand, Jagged1.

In adult life, the high CD4:CD8 cell ratio observed in peripheral lymphoid organs originates in the thymus. Our results show that the low peripheral CD4:CD8 cell ratio seen during fetal life also has an intrathymic origin. This distinct production of CD4(+)CD8(-) and CD4(-)CD8(+) thymocytes is regulated by the developmental age of the thymic stroma. The differential expression of Notch receptors and their ligands, especially Jagged1, throughout thymus development plays a key role in the generation of the different CD4:CD8 cell ratios. We also show that the intrathymic CD4:CD8 cell ratio sharply changes from fetal to adult values around birth. Differences in the proliferation and emigration rates of the mature thymocyte subsets contribute to this change.

Animals↗
PubMed2001

Muscarinic receptor subtypes and calcium signaling in Fischer rat thyroid cells.

A specific and saturable binding site for [3H]N-methyl-scopolamine ([3H]NMS) was observed in plasma membrane of Fischer rat thyroid (FRT) cells with an equilibrium dissociation constant (K(d)) of 0.11 +/- 0.02 nM and a concentration of receptor sites (B(max)) of 14.1 +/- 3.9 fmol/mg protein. Pharmacological characterization of this binding site using pirenzepine, himbacine, (11(2-diethyl-amino)methyl)-1-piperidinylacetyl-5-11-dihydro-6H-pyrido(14) benzodiazepine (AF-DX 116), dicyclomine, 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP), and hexahydro-sila-difenidol (HHSD) showed clear differences, in terms of affinities, between these muscarinic receptor antagonists. The order of potency for inhibiting [3H]NMS binding was HHSD = dicyclomine > 4-DAMP > pirenzepine = himbacine > AF-DX 116. These findings suggest that the muscarinic receptors found in FRT cells belong to the M3 subtype. Stimulation of FRT cells with carbachol produced a biphasic and dose-dependent increase in the intracellular calcium concentration ([Ca2+]i), which was blocked in pretreated cells with atropine and almost abolished by a low concentration of 4-DAMP and HHSD. Removal of extracellular Ca2+ from the incubation medium reduced the initial transient peak and completely abolished the plateau phase, while the transient phase was markedly reduced by the phospholipase C inhibitor U73122. These data indicate that [Ca2+]i results from both Ca2+ influx across Ca2+ channels and mobilization of Ca2+ from intracellular Ca2+ stores. The present data showed the presence of the M3 muscarinic acetylcholine receptor subtype in plasma membrane of FRT cells, which may influence cellular function via modulation of [Ca2+]i.

Animals↗
PubMed2001

Nitrergic relaxation in urethral smooth muscle: involvement of potassium channels and alternative redox forms of NO.

We examined the contribution of K+ channels to the relaxation responses induced by different redox forms of nitric oxide (NO., NO- and NO+) in comparison with those evoked by electrical field stimulation (EFS) of nitrergic nerves in the sheep urethra. K+ channel blockers with different selectivity profile were used. Sodium nitroprusside (SNP) and different S-nitrosothiols were used as NO+ donors, Angeli's salt as an NO- donor and nitroglycerin (GTN) was chosen as a representative compound known to require metabolic activation in the target tissue. Pure NO gas was used to prepare NO. solutions. Relaxation evoked by EFS of nitrergic nerves or by exogenous NO was not inhibited by any of the K+ channel blockers, but was enhanced by 4-aminopyridine [inhibitor of voltage-dependent K+ (KV) channels]. This suggests that, whereas K+ channel activation and hyperpolarization of the postsynaptic membrane do not contribute to relaxation, prejunctional modulation of the nitrergic neurotransmission by Kv channels may be relevant. Relaxation induced by NO+ or NO- donors was not affected by K+ channel blockade with the following exceptions: glybenclamide, a blocker of ATP-sensitive K+ channels (KATP), enhanced responses to SNP and Angeli's salt, 4-aminopyridine inhibited relaxation evoked by Angeli's salt and GTN, and charybdotoxin, a blocker of large-conductance, Ca2+-activated K+ channels (BKCa) inhibited those induced by the S-nitrosothiol S-nitrosoglutathione. These results do not suggest the existence of a general mechanism of action on K+ channels for compounds releasing either NO+ or NO- in the sheep urethra. None of the K+ channel blockers affected relaxation induced by the membrane-permeable analogue of cGMP, 8-bromo-cGMP. However, the fact that the addition of the phosphodiesterase inhibitor zaprinast (0.1 mM) enhanced the relaxation to Angeli's salt, while preventing the inhibition induced by 4-aminopyridine, suggests that involvement of guanylate cyclase activation in the action of NO donors on K+ channels can not be excluded. Accordingly, the guanylate cyclase inhibitors 1H-[1,2,4]-oxadiazole-[4,3-a]-quinoxalin-1-one (ODQ, 10 microM) and 4H-8-bromo-1,2,4-oxadiazolo(3,4-d)benz(b)(1,4)oxazin-1-one (NS 2028, 10 microM) almost abolished relaxations to EFS and Angeli's salt. In contrast, ODQ only moderately inhibited relaxations to NO.. In addition, the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl imidazoline-1-oxyl 3-oxide (carboxy-PTIO) effectively inhibited responses to NO. whilst not affecting those to EFS or NO-, suggesting a close similarity between the nitrergic transmitter and nitroxyl ion. We conclude that nitrergic relaxation induced either by the endogenous transmitter or by exogenous NO donors in the ovine urethra is not mediated by postsynaptic alterations in the K+ conductance; only a prejunctional modulation through Kv channels seems to be significant. In addition, the production and/or release of alternative redox forms of NO, such as NO-, may be involved in neurotransmission processes in the urethra.

Animals↗
PubMed2001

Activation of muscarinic acetylcholine receptors induces Ca(2+) mobilization in FRT cells.

The effect of the muscarinic receptors agonist carbachol (Cch) on intracellular calcium concentration ([Ca(2+)](i)) and cAMP level was studied in polarized Fischer rat thyroid (FRT) epithelial cells. Cch provoked a transient increase in [Ca(2+)](i), followed by a lower sustained phase. Thapsigargin, a specific microsomal Ca(2+)-ATPase inhibitor, caused a rapid rise in [Ca(2+)](i) and subsequent addition of Cch was without effect. Removal of extracellular Ca(2+) reduced the initial transient response and completely abolished the plateau phase. Ryanodine, an agent that depletes intracellular Ca(2+) stores through stimulation of ryanodine receptors (RyRs), had no effect on [Ca(2+)](i). However, the transitory activation of [Ca(2+)](i) was dose-dependently attenuated in cells pretreated with U73122, a specific inhibitor of phospholipase C (PLC). These data suggest that the Cch-stimulated increment of [Ca(2+)](i) required IP(3) formation and binding to its specific receptors in Ca(2+) stores. Further studies were performed to investigate whether the effect of Cch on Ca(2+) entry into FRT cells was via L-type voltage-dependent Ca(2+) channels (L-VDCCs). Nicardipine, a nonspecific L-type Ca(2+) channel blocker, decreased Cch-induced increase on [Ca(2+)](i), while Bay K-8644, an L-type Ca(2+) channel agonist, slightly increased [Ca(2+)](i) in FRT cells. These data indicate that Ca(2+) entry into these nondifferentiated thyroid cells occurs through an L-VDCC, and probably through another mechanism such as a capacitative pathway. Cch did not affect the intracellular cAMP levels, but its effects on [Ca(2+)](i) were significantly reduced when cells were pretreated with forskolin, suggesting the existence of an intracellular cross-talk between PLC and cAMP mechanisms in the regulation of intracellular Ca(2+) mobilization in neoplastic FRT cells.

Animals↗
PubMed2001

Impact of surgeon organization and specialization in rectal cancer outcome.

PURPOSE: The present study was designed to assess the differences in the outcome of patients with rectal cancer treated by a group of surgeons before and after being organized as a Coloproctology Unit at the same University Department of Surgery. METHODS: Comparison of two periods of rectal cancer surgery: I (1986-91) and II (1992-95). Period I: 94 patients were operated on by 14 general surgeons. Period II: 108 patients were operated on by only 4 surgeons of the same group organized as a Colorectal Surgery Unit after visiting referral centres abroad, adopting techniques such as total mesorectal excision (TME) for middle and low rectal cancer and washout of rectal stump. Mean follow-up during periods I and II was 69.1 and 42.0 months, respectively. A prospective data base analysis was used. Survival and local recurrence rates were calculated by the actuarial method. For comparison between groups the log rank method was used. RESULTS: The two groups were comparable with respect to mean age, gender, TNM and rectal tumour location. A significant increase in radical resectability and a decrease of the Abdominoperineal resection (APR)/Low anterior resection (LAR) ratio were observed in the second period. The overall pelvic recurrence rate was 25% in the first period and 11 in the second (P < 0.01). Significant differences were also found when the patients with LAR were compared between both periods, 30% vs 9% (P < 0.01) and specially when the 10 cm anal verge distance was considered to divide the LAR groups. No differences were found regarding the APR procedures in both periods. There was improved cancer-specific survival for the LAR group in the second period (P=0.03). CONCLUSION: Specialization and centralization influence the quality of rectal cancer surgery, mainly local recurrence rates and survival after low anterior resection.

Journal Article↗
PubMed2000

Analysis of the human neonatal thymus: evidence for a transient thymic involution.

The neonatal period is marked by the impairment of the major components of both innate and adaptive immunity. We report a severe depletion of cortical CD4+CD8+ double-positive thymocytes in the human neonatal thymus. This drastic reduction in immature double-positive cells, largely provoked by an increased rate of cell death, could be observed as early as 1 day after birth, delaying the recovery of the normal proportion of this thymocyte subset until the end of the first month of postnatal life. Serum cortisol levels were not increased in newborn donors, indicating that the neonatal thymic involution is a physiological rather than a stress-associated pathological event occurring in the perinatal period. Newborn thymuses also showed increased proportions of both primitive CD34+CD1- precursor cells and mature TCRalphabetahighCD69-CD1-CD45RO+/RAdull and CD45ROdull/RA+ cells, which presumably correspond to recirculating T lymphocytes into the thymus. A notable reinforcement of the subcapsular epithelial cell layer as well as an increase in the intralobular extracellular matrix network accompanied modifications in the thymocyte population. Additionally neonatal thymic dendritic cells were found to be more effective than dendritic cells isolated from children's thymuses at stimulating proliferative responses in allogeneic T cells. All these findings can account for several alterations affecting the peripheral pool of T lymphocytes in the perinatal period.

CD4-CD8 Ratio↗
PubMed2000

Spontaneous photo-relaxation of urethral smooth muscle from sheep, pig and rat and its relationship with nitrergic neurotransmission.

1. In the present work we have characterized the relaxant response induced by light stimulation (LS) in the lower urinary tract from sheep, pig and rat, establishing its relationship with nitrergic neurotransmission. 2. Urethral, but not detrusor, preparations showed pronounced photo-relaxation (PR) which declined progressively following repetitive LS. Sheep urethral PR was again restored either spontaneously or (to a greater extent) by exogenous nitric oxide (NO) addition and by electrical field stimulation (EFS) of intrinsic nitrergic nerves. 3. Greater NO generation was detected from sheep urethral than from detrusor homogenates following illumination. 4. Sheep urethral PR was inhibited by oxyhaemoglobin, but not by methaemoglobin, carboxy-PTIO, extracellular superoxide anion generators or superoxide dismutase. Guanylyl cyclase but not adenylyl cyclase activation mediates urethral relaxation to LS. 5. Urethral PR was more resistant to inhibition by L-thiocitrulline than EFS-induced responses, although this agent prevented PR restoration by high-frequency EFS. 6. Urethral PR was TTX insensitive and partially modified in high-K+ solutions. Cold storage for 24 h greatly impaired urethral PR, although it was restored by high-frequency EFS. 7. Repetitive exposure to LS, EFS or exogenous NO induced changes in the shape of the EFS-induced nitrergic relaxation, possibly by pre-synaptic mechanisms. 8. In conclusion, we suggest the presence of an endogenous, photo-labile, nitro-compound store in the urethra, which seems to be replenished by neural nitric oxide synthase activity, indicating a close functional relationship with the nitrergic neurotransmitter.

Adenine↗
PubMed2000

Opposite transitions of chick brain catalytically active cytosolic creatine kinase isoenzymes during development.

Postnatally the rat brain synthesizes catalytic forms of muscle type (MM) and heart type (MB) creatine kinase (CK), besides the supposedly sole type vertebrate brain-specific (BB) CK. We intended to demonstrate that in Rhode Island chicken brain, cytosolic (c) CK isoenzymatic transitions. (for example BB-CK is followed by the appearance of MB-CK and MM-CK during muscle differentiation), can also occur during development and aging. Cytosolic post 125000 x g, mitochondrial CK-free, brain samples were obtained for zone electrophoresis separation and identification of catalytically active cCK isoforms. BB-CK was never found during chicken brain ontogeny. Against the accepted view, an opposite isoenzyme transition pattern from MM through BB-CK was found in the chicken embryonic brain from the very early stages of development up to day 2 post-hatching. At very early stages of chicken brain ontogeny constitutive MM- and MB-CK isoenzymes were present before the advent of creatine. It seems to be that typical and atypical brain MM- and MB-CK could be working as ATPases in the absence of creatine before embryonic stage 28 (day 5.5) and/or such CK isoforms may begin to form part of the slow component b in developing early neurons and later in the nuclei of glial cells to be used by the CK/phosphocreatine (PC) system as the neural tissues mature. The post-hatching transition pattern showed simultaneous expression of more than one CK isoenzyme within the same neural sample as in post-natal rat brain, presumably due to regional differential transphosphorylation requirements. Strain-dependent enzymatic specific activities have been reported in several species. Since equivalent values of brain CK specific activity were obtained previously from the embryonic plateau phase of CK activity during White Leghorn development, and those from Rhode Island brain neurons cultured 11 days, we compared if, in vivo, a similar brain CK specific activity pattern was physiologically equivalent during Rhode Island and White Leghorn chicken ontogeny. We found quantitatively different strain-specific CK specific activity patterns during this period. Rhode Island brain CK activity values were approximately 4.5-fold those of White Leghorn ones. This indicates that production of energy from anaerobic metabolism and transphosphorylation by the CK/PC system to synthesize ATP more efficiently is strain-specific. In Rhode Islands, there was an age-dependent increase of CK specific activity, mostly in older animals (440% above the value found during the embryonic plateau), when the Krebs cycle and glycolysis lose capacity. During adult life and aging, under physiological conditions, the three CK isoenzymes may participate in diverse functions of the different cell compartments of brain glia and neurons with regard to their high and fluctuating energy demands that are not completely covered by anaerobic and aerobic glycolisis.

Animals↗
PubMed2000

nm23-H1 expression defines a high-risk subpopulation of patients with early-stage epithelial ovarian carcinoma.

The role of the nm23 gene in human ovarian cancer is still controversial. We studied the expression of the nm23-H1 gene in 247 human epithelial ovarian carcinomas. The patients were followed-up until their death, or for a minimum of 5 years if they survived. The expression of the gene was studied by means of immunohistochemistry and a semiquantitative scoring system considering the staining intensity and the number of reactive tumour cells. Patients carrying tumours with higher expression scores (4-6 on a scale from 0 to 6) had a significantly lower survival (P = 0.01) than the rest. Further stratified statistical analysis revealed that this effect was mainly attributable to the subgroup of patients with early-stage (I and II), well- and moderately differentiated tumours. In fact, a multivariate analysis carried out for this subset of patients showed nm23-overexpression to be the only significant independent predictor of an ominous prognosis. The association of nm23-overexpression with a worse prognosis was most probably not due to mutation of the nm23 gene, since mutational analysis in 60 tumours by means of single-strand conformational polymorphism and direct sequencing disclosed only one mutation, which was located outside the open reading frame. Our results seem to indicate that nm23 expression is associated with a significantly worse prognosis in early-stage, well-differentiated epithelial ovarian carcinoma, a finding with important clinical implications, considering that many patients with ovarian cancers showing these features do not undergo any further treatment beyond surgical staging. If confirmed, they could help in tailoring the treatment of these patients in the future.

Aged↗
PubMed2000

Role of glucocorticoids in early T-cell differentiation.

The results of the T-cell differentiation in the progeny of adrenalectomized pregnant rats (Adx fetuses), an experimental model that ensures the absence of glucocorticoids (GCs) during the first stages of development, are summarized. In Adx thymuses there is an accelerated maturation of thymocytes that is reversed by in vivo GC replacement. In addition, Adx thymuses show decreased cell content, which correlates with both the increased numbers of apoptotic cells and an early migration of DP (CD4+CD8+) and SP (both CD4+CD8- and CD4-CD8+) thymocytes to the spleen. As shown by in vitro recolonization assays, accelerated T-cell differentiation is a consequence of changes in the biology of lymphoid precursors occurring in the fetal liver of Adx fetuses. They arrive at the thymic primordium earlier and mature faster than the fetal liver lymphoid progenitors from Sham control fetuses. After the establishment of a fetal hypothalamus-pituitary-gland-adrenal-gland (HPA) axis, there is a gradual normalization of the T-cell development Adx fetuses.

Animals↗
PubMed1999

Early maturation of T-cell progenitors in the absence of glucocorticoids.

In the present work, we demonstrated that both fetal liver and thymic T-cell precursors express glucocorticoid receptors (GRs) indirectly suggesting a role for glucocorticoids (GCs) in the earliest events of T-cell differentiation. To evaluate this issue, we analyzed the thymic ontogeny in the progeny of adrenalectomized pregnant rats (Adx fetuses), an in vivo experimental model, which ensures the absence of circulating GCs until the establishment of the fetal hypothalamus-pituitary-adrenal (HPA) axis. In the absence of maternal GCs, T-cell development was significantly accelerated, the process being reversed by in vivo GC replacement. Mature single positive thymocytes (both CD4 and CD8) appeared in 16-day old fetal Adx thymus when in the control fetuses, most thymocytes still remained in the double-negative (DN) CD4(-)CD8(-) cell compartment. In addition, emigration of T-cell receptor (TcR)alphabeta positive cells to the spleen also occurred earlier in Adx fetuses than in control ones. In vitro recolonization of cultured deoxiguanosine-treated mouse fetal thymus lobes with 13-day-old fetal liver cell suspensions from both Adx and control fetuses demonstrated changes in the developmental capabilities of fetal liver T-cell precursors from embryos grown in the absence of GCs. Furthermore, a precocious lymphoid colonization of the thymic primordium from Adx fetuses was evidenced by ultrastructural analysis of both Adx and Sham early thymus. Both findings accounted for the accelerated T-cell differentiation observed in Adx fetuses. Together, these results support a role for GCs not only in the thymic cell death, but also in the early steps of T-cell differentiation.

Adrenalectomy↗
PubMed1999

Angiotensin II receptor internalization and signaling in isolated rat hepatocytes.

Since angiotensin II (Ang II)-induced receptor internalization is required to maintain the production of certain intracellular signals in some target cells, we investigated the relationships between Ang II receptor endocytosis and the generation of second messengers in rat hepatocytes. The results of the present study demonstrate that in response to exposure of hepatocytes to Ang II, a decrease in surface Ang II receptors occurred, consistent with a rapid endocytosis of the receptor-bound hormone complex. Pretreatment of cells with okadaic acid (OA) did not have any effect on receptor-mediated internalization. In contrast, a marked reduction of the Ang II receptor endocytosis process occurred after treatment of hepatocytes with phenylarsine oxide (PAO), indicating that cysteine residues could be involved in receptor-mediated endocytosis. Stimulation of cells with Ang II blocked the generation of cyclic adenosine monophosphate (cAMP), which follows the stimulation of hepatocytes with forskolin. Moreover, Ang II increased both inositol 4,5-bisphosphate (IP2) and inositol 1,4,5-trisphosphate (IP3) generation, and enhanced intracellular calcium concentration ([Ca2+]i). Exposure of cells to PAO did not alter the effect of Ang II on the accumulation of cAMP after forskolin stimulation, indicating that endocytosis of the agonist-receptor complex is not involved in adenylate cyclase inhibition. Conversely, PAO and OA markedly reduced IP2 and IP3 synthesis, and the plateau phase of Ang II-induced Ca2+ mobilization. The relationship between Ang II-induced endocytosis and the generation of phosphoinositols and increment in [Ca2+]i indicates that sequestration of the Ang II receptor is necessary to maintain the production of these intracellular signals in rat hepatocytes.

Angiotensin II↗