HbA1c levels and all-cause mortality in type 2 diabetic patients: epidemiological evidence of the need for personalised therapeutic targets.

BACKGROUND AND AIM: The aim of the present case-control study is to explore the effect of case mix on the relationship between glycated haemoglobin (HbA1c) and mortality in type 2 diabetic patients. METHODS AND RESULTS: A nested case-control study data set was generated from the cohort-study data set (n = 4140 type 2 diabetic outpatients) by sampling controls from the risk sets. Cases (n = 427) were compared with an equal number of controls chosen from those members of the cohort who were at risk for the same follow-up time of the case, matched for age (±3 years), sex, body mass index (BMI) (±2 kg m(-2)), duration of diabetes (±5 years), and Charlson's Comorbidity Score (CCS) (±1). The main predefined analysis was the comparison of cases and controls for proportion of patients with each HbA1c class (<6.5%, 6.5-7.4%, 7.5-8.4% and ≥8.5%). During a mean follow-up of 5.7 ± 3.5 years, 427 deaths were recorded. The lowest risk of death was observed in the HbA1c 6.5-7.4% category; a lower HbA1c was associated with a non-significant trend towards a higher risk. The risk associated with a low (<6.5%) HbA1c was significantly greater in patients who were insulin-treated than in the rest of the sample. CONCLUSIONS: The present study suggests that glycaemic targets should be individualised on the basis of the characteristics of each patient, considering age, co-morbidity and duration of diabetes. Caution should be used in prescribing insulin to reach near-normoglycaemia, particularly in older, frail patients.

Effects of antihypertensive treatments on incidence of diabetes: a case-control study.

AIMS: Aim of this case-control study is the assessment of the relationship between antihypertensive treatment and incidence of diabetes in an unselected cohort of subjects participating in a screening program for diabetes. METHODS: A case-control study nested within a cohort of nondiabetic subjects with a mean follow-up of 27.7 ± 11.3 months was performed, comparing 40 cases of incident diabetes and 160 controls matched for age, sex, body mass index, fasting plasma glucose, 2-h post-load glycemia, smoking and alcohol abuse. RESULTS: When considering antihypertensive treatment at enrolment, a lower proportion of cases was exposed to ACE-inhibitors/angiotensin receptor blockers (ACE-i/ARB) in comparison with controls. A non-significant trend toward a higher exposure to diuretics, which were mainly represented by thiazide diuretics, was observed in cases. In a multivariate analysis, including both ACE-i/ARB and diuretics, a protective effect of ACEi/ARB, and an increased risk with diuretics were observed. Similar results were obtained in alternative models, after adjusting for systolic and diastolic blood pressure at enrolment, diagnosis of hypertension, concurrent treatment with ß-blockers or calcium-channel blockers, and number of antihypertensive medications. CONCLUSIONS: Diuretics seem to be associated with a higher incidence of diabetes, whereas treatment with ACEi/ARB could have a protective effect.

Effect of metformin on cardiovascular events and mortality: a meta-analysis of randomized clinical trials.

AIM: Some studies suggested that metformin could reduce cardiovascular risk to a greater extent than that determined by glucose reduction. Aim of the present meta-analysis is to assess the effects of metformin on the incidence of cardiovascular events and mortality. METHODS: An extensive search of Medline, EMBASE and the Cochrane Library (any date up to 31 October 2009) was performed for all trials containing the word 'metformin'. Randomized trials with a duration ≥52 weeks were included. A meta-regression analysis was also performed to identify factors associated with cardiovascular morbidity and mortality in metformin-treated patients. RESULTS: A total of 35 clinical trials were selected including 7171 and 11 301 participants treated with metformin and comparator, respectively, who had 451 and 775 cardiovascular (CV) events, respectively. Overall, metformin was not associated with significant harm or benefit on cardiovascular events (MH-OR 0.94[0.82-1.07], p = 0.34). A significant benefit was observed in trials versus placebo/no therapy (MH-OR 0.79[0.64-0.98], p = 0.031), but not in active-comparator trials (MH-OR 1.03[0.72-1.77], p = 0.89). Meta-regression showed a significant correlation of the effect of metformin on cardiovascular events with trial duration and with minimum and maximum age for inclusion, meaning that the drug appeared to be more beneficial in longer trials enrolling younger patients. It is likely that metformin monotherapy is associated with improved survival (MH-OR: 0.801[0.625-1.024], p = 0.076). However, concomitant use with sulphonylureas was associated with reduced survival (MH-OR: 1.432[1.068-1.918], p = 0.016). CONCLUSION: Available evidence seems to exclude any overall harmful effect of metformin on cardiovascular risk, suggesting a possible benefit versus placebo/no treatment. The observed detrimental effect of the combination with sulphonylureas deserves further investigation.

Key role of staff competencies for patient and donor safety in a bone marrow transplantation unit: design and implementation of an accredited training and self-assessment program.

Human resources represent at the moment the most critical factor in an hospital setting characterized by a high rate of staff turnover. It is important to ensure a consistent level of expertise and knowledge of professionals who work in health care facilities to provide quality services and simultaneously support the implementation of strategies for patient safety. Unfortunately, the development of effective interventions for training newly added staff and self-evaluation of skills possessed by trained staff are closely related to understanding critical aspects of the organization. At the new Center for Bone Marrow Transplantation and Blood Transfusion Service in Meyer Hospital, during the last year, a group of professional nurses and technicians completed a specific plan to train new staff and, at the same time, a program of self-assessment of skills for experienced staff. The main purpose of this project was to promote skills development by newly added as well as experienced staff, to identify areas of weaknesses, and to correct them with training (organized by the hospital, departmental, or individual) designed to improve performance.

Glucagon-like peptide-1 response to meals and post-prandial hyperglycemia in Type 2 diabetic patients.

BACKGROUND: The impaired response of glucagonlike peptide-1 (GLP-1) to meals in diabetic patients can contribute to the pathogenesis of impaired insulin secretion and post-prandial hyperglycemia. This study is aimed at the assessment of the relationship between meal-induced GLP-1 and post-prandial hyperglycemia in Type 2 diabetic patients. METHODS: Twenty-one drug-naïve Type 2 diabetic patients were studied. Blood glucose and active GLP-1 levels were measured 0, 30, 60, 90, and 120 min after a standard test meal. A continuous glucose monitoring (CGM) system was applied for the following 3 days. Nutrient intake at each meal was calculated on the basis of patients' food records. For each patient, post-prandial 120-min glucose incremental area under the curve (iAUC) was included in linear regression model exploring its relationship with total energy and carbohydrate intake, and the angular coefficient for total energy (EAC) and carbohydrate (CAC) was calculated. RESULTS: GLP-1 levels peaked 30 min after the test meal. Logarithmically transformed 60-min GLP-1 iAUC showed a significant inverse correlation with glycated hemoglobin (HbA1c) (p<0.01). A significant inverse correlation of 60-min GLP-1 iAUC was also observed with EAC and CAC (both p<0.01), meaning that patients with a lower GLP-1 response to the test meal had a higher increment of post-prandial glucose for each additional unit of total energy or carbohydrate intake. CONCLUSIONS: In Type 2 diabetic patients, a lower GLP-1 response to meals is associated with a higher HbA1c, and with a greater degree of meal-induced hyperglycemia, both in a meal test and during CGM in "real-life" conditions.

Prevention of cardiovascular disease through glycemic control in type 2 diabetes: a meta-analysis of randomized clinical trials.

BACKGROUND AND AIMS: Randomized clinical trials (RCTs) aimed at the assessment of the efficacy of lowering blood glucose in the prevention of diabetic complications have always failed to detect a significant effect on cardiovascular events. Aim of this meta-analysis is the assessment of the effects of improvement of glycemic control on the incidence of cardiovascular diseases in patients with type 2 diabetes. METHODS: The RCTs were included in this meta-analysis if: a) the between-group difference in mean HbA1c during the trial was at least 0.5%, b) they had a planned duration of treatment of at least 3 years, c) if they had a cardiovascular endpoint. Data for analysis were extracted independently by two observers and potential contrasts were resolved by a senior investigator. RESULTS: Five studies (17,267 and 15,362 patients in the intensive and conventional therapy groups, respectively) were included. Intensive treatment, which reduced mean HbA1c by 0.9% on average, was associated with a significant reduction of incident cardiovascular events and myocardial infarction (OR 0.89 [0.83-0.95] and 0.86 [0.78-0.93], respectively), but not of stroke or cardiovascular mortality (OR 0.93 [0.81-1.07] and 0.98 [0.77-1.23], respectively). In meta-regression analysis, a higher BMI duration of diabetes, and incidence of severe hypoglycaemia were associated with greater risk for cardiovascular death in intensive treatment groups. CONCLUSION: Intensified hypoglycaemic treatment in type 2 diabetic patients leads to a significant reduction of the incidence of myocardial infarction, while it does not affect the incidence of stroke and cardiovascular mortality. Hypoglycemia induced by intensified treatment could be associated with increased cardiovascular mortality.

Continuous subcutaneous insulin infusion versus multiple daily insulin injections in type 2 diabetes: a meta-analysis.

BACKGROUND: Continuous Subcutaneous Insulin Infusion (CSII) improves HbA1c in type 1 diabetic patients unsatisfactorily controlled by Multiple Daily Injections (MDI). Few trials have explored CSII for basal-bolus therapy in type 2 diabetes. MATERIALS AND METHODS: Randomized Clinical Trials (RCTs) comparing CSII and MDI for at least 12 weeks in type 2 diabetic patients were retrieved, assessing between-group differences in HbA1c and insulin daily dose at endpoint, and incidence of hypoglycemia. RESULTS: A total of 4 RCTs was included in the analysis. CSII did not produce any significant improvement of HbA1c in comparison with MDI (Standardized difference in mean: 0.09(-0.08;0.26)%; p=0.31). No significant difference was observed in the rate of hypoglycemic episodes. CSII was associated with a nonsignificant trend toward the reduction of insulin doses used at the end of trial. CONCLUSIONS: Available data do not justify the use of CSII for basal-bolus insulin therapy in type 2 diabetes.

Pioglitazone and cardiovascular risk. A comprehensive meta-analysis of randomized clinical trials.

AIM: The aim of this meta-analysis of randomized clinical trials (RCT) was to assess whether pioglitazone is also associated with increased cardiovascular risk, as recently reported for rosiglitazone. METHODS: RCT of pioglitazone were retrieved from Medline (any date up to 31 August 2007; English language only). Unpublished RCT were identified through http://www.clinicaltrials.gov or http://www.fda.gov websites, and results on cardiovascular outcomes were retrieved from investigators and/or sponsors, whenever possible. RCT were included in meta-analysis if pioglitazone was compared with other treatments (placebo, active comparators or no treatment) for at least 4 weeks. Ninety-four trials, 10 of which were unpublished, were retrieved; those included in the analysis, which excluded PROspective PioglitAzone Clinical Trial In MacroVascular Events (PROACTIVE), enrolled 11 268 and 9912 patients in the pioglitazone and comparator groups respectively. Data for analysis, extracted independently by two observers, included all-cause and cardiovascular mortality and incidence of non-fatal coronary events and heart failure. Proportions of outcome measures across treatment groups were compared by odds ratios (ORs) and 95% confidence interval. RESULTS: Pioglitazone was associated with reduced all-cause mortality [OR 0.30 (0.14-0.63); p < 0.05], with no relevant effect on non-fatal coronary events. The observed increase in incidence of non-fatal heart failure was not statistically significant [OR 1.38 (0.90-2.12)]. CONCLUSION: The use of pioglitazone does not appear to be harmful in terms of cardiovascular events and all-cause deaths.

Treatment with insulin secretagogues and cancer-related mortality in type 2 diabetic patients a retrospective cohort study.

BACKGROUND: Recent evidence suggests that some hypoglycemic treatments could affect the incidence of malignancies. This study was aimed at the assessment of cancer-related mortality in type 2 diabetic patients treated with different hypoglycemic drugs. METHODS: A retrospective observational cohort study was performed on a consecutive series of 3002 type 2 diabetic outpatients. Cancer-related death was identified through the City Registry Office. For patients visited for the first time after January 1 (st), 2000, information on incidence of cancer was also available. RESULTS: During a mean follow-up of 4.3+/-2.5 years, 87 cases of cancer-related death were recorded, with a yearly incidence rate of 0.70%. Patients receiving secretagogues showed a significantly higher mortality than the rest of the sample (unadjusted OR [95%CI] 1.76 [1.15-2.69], p=0.009), which was maintained after adjustment for confounders (HR 2.29 [1.21-4.02], p=0.003). Conversely, no significant association of cancer-related mortality was observed with insulin sensitizers or exogenous insulin. In comparison with patients receiving no hypoglycemic treatment, those on secretagogue or insulin monotherapy showed a higher cancer-related mortality (HR 2.25 [1.10-4.78], p=0.034 and HR 2.11 [1.01-4.50], p=0.048, respectively). The effect of treatments on incidence of malignancies was similar to that observed on cancer-related death. CONCLUSIONS: Insulin secretagogues and, to a lesser extent, exogenous insulin, appear to be associated with increased mortality for cancer, even after adjustment for multiple confounders. This issue deserves further investigation through epidemiological studies on larger samples of patients.

Involvement of D-Asp in P450 aromatase activity and estrogen receptors in boar testis.

Mammalian testis contains D-aspartic acid (D-Asp), which enhances testosterone production. D-Asp, on other hand, also stimulates 17beta-estradiol synthesis in the ovary of some lower vertebrates. We studied boar testis in order to determine if D-Asp intervenes in 17beta-estradiol synthesis in the testis of those mammals which produce significant amounts of estrogens as well as testosterone. The boar testis contains D-Asp (40 +/- 3.6 nmol/g tissue) which, according to immunohistological techniques, is localized mainly in Leydig cells, and, to a lesser extent, in sustentacular (Sertoli), peritubular and some germ cells. The enzyme P450aromatase is present in Leydig cells and few germ cells. In vitro experiments showed that the addition of D-Asp to testicular tissue extracts induced a significant increase of aromatase activity, as evaluated by testosterone conversion into 17beta-estradiol. The enzyme's K(m) was not affected by D-Asp (about 25 nM in both control and D-Asp added tests). On the basis of these results we suggest that, as in the ovary, D-Asp is involved in the local control of aromatase activity of boar testis and, therefore, it intervenes in the 17beta-estradiol production. In the testis, the D-Asp targets are presumably the Leydig cells, which having also a nuclear estrogen receptor are, in turn, one of the putative targets of the 17beta-estradiol that they produce (autocrine effect).

Are sulphonylureas all the same? A cohort study on cardiovascular and cancer-related mortality.

BACKGROUND: Aim of the present study is the comparison of all-cause, cardiovascular and non-cardiovascular mortality, and cardiac morbidity, between patients treated with glibenclamide and gliclazide. METHODS: A retrospective observational cohort study was performed on a consecutive series of 568 outpatients (282 women, 286 men) with type 2 diabetes treated with either glibenclamide (n = 378) or gliclazide (n = 190). Information on all-cause mortality and on causes of death up to 31 December 2004 was obtained by the City of Florence Registry Office. Non-fatal cases requiring hospitalization were identified through the regional hospital discharge system using International Classification of Diseases. RESULTS: Mean follow-up was 5.0 +/- 1.6 and 4.4 +/- 2.0 years for death and cardiac events, respectively; during follow-up, 33 and 11 deaths were observed in the glibenclamide and gliclazide groups, with a yearly mortality rate of 4.3 and 2.2%, respectively (p < 0.05). At Cox regression, after adjustment for potential confounders, including comorbidity, glibenclamide treatment was associated with a significant increase in all-cause mortality [OR 2.1(1.2;2.7), p < 0.05], while the difference in cardiovascular mortality was not statistically significant after adjustment for age and sex. Mortality for malignancies was significantly higher in patients treated with glibenclamide after adjustment for age, sex, BMI, and insulin and metformin treatment, [OR 3.6(1.1;11.9); p < 0.05]. A higher incidence of cardiac events was associated with glibenclamide treatment only in patients with previously known ischaemic heart disease. CONCLUSIONS: Treatment with glibenclamide could be associated with higher mortality for cardiovascular diseases and malignancies, in comparison with gliclazide.

Fasting and post-prandial glycemia and their correlation with glycated hemoglobin in Type 2 diabetes.

OBJECTIVE: The relative contribution of fasting and post-prandial glucose to glycated hemoglobin (HbA1c) is controversial. In the present study, we assessed the relationship with HbA1c of fasting and post-prandial glucose measured in a more naturalistic setting, through home glucose self-monitoring or with a continuous glucose monitoring system (CGM). MATERIALS AND METHODS: A consecutive series of 300 patients with Type 2 diabetes were enrolled in the study, provided that they performed blood glucose self-monitoring. HbA1c and fasting plasma glucose (FPG) were measured at enrolment. RESULTS: Both fasting plasma and capillary glucose showed a significant correlation with HbA1c (r=0.66 and 0.61, respectively; p<0.001). When home glucose monitoring was considered, both mean fasting and post-prandial glucose showed a significant correlation with HbA1c (r=0.71 and 0.73, respectively). In patients in the lower tertile of body mass index (BMI), HbA1c showed a significant correlation at multivariate analysis with post-prandial glucose, but not with fasting glucose. In patients with HbA1c >7%, both fasting and post-prandial glucose showed a significant correlation, after adjustment for age and BMI, with HbA1c (both p<0.01); conversely, in those with HbA1c < or =7%, such a correlation could be observed for fasting (p<0.01), but not for post-prandial glucose. CONCLUSION: In conclusion, both fasting and post-prandial glucose contribute to the determination of HbA1c . Home glucose self-monitoring appears to provide a more accurate assessment of metabolic control than a single plasma glucose measurement in experimental conditions. Fasting glucose could provide a greater contribution to HbA1c in patients with lower HbA1c, while post-prandial glucose seems to play a major role in leaner Type 2 diabetic subjects.

Endogenous testicular D-aspartic acid regulates gonadal aromatase activity in boar.

D-aspartic acid (D-Asp), aromatase enzyme activity and the putative D-Asp involvement on aromatase induction have been studied in the testis of mature boars. The peroxidase-antiperoxidase and the indirect immunofluorescence methods, applied to cryostat and paraffin sections, were used to evaluate D-Asp and aromatase distributions. D-Asp level was dosed by an enzymatic method performed on boar testis extracts. Biochemical aromatase activity was determined by in vitro experiments carried out on testis extracts. D-Asp immunoreactivity was found in Leydig cells, and, to a lesser extent, in germ cells. Analogously, aromatase immunoreactivity was present in Leydig cells, but absent from seminiferous tubule elements. In vitro experiments showed that the addition of D-Asp to testicular tissue acetone powder induced a significant increase of aromatase activity, as assessed by testosterone conversion to 17beta-estradiol. Enzyme Km was not affected by D-Asp (about 25 nM in control and D-Asp added tests). These findings suggest that D-Asp could be involved in the local regulation of aromatase in boar Leydig cells and intervenes in this organ's production of estrogens.

Neurotrophin-like immunoreactivity in the gut of teleost species.

By means of immunochemistry and immunohistochemistry, we investigated in the gut of teleostean species the presence and localization of three neurotrophins: nerve growth factor (NGF), brain derived neurotrophic factor (BDNF) and neurotrophin (NT)-3. In all studied species both NGF- and NT-3-like immunoreactivity (IR) were present in the enteric nervous system, while BDNF-like IR was never detected. More in particular, both NGF and NT-3-like IR were detected in neurons of small and large intestine, while only NT3-like IR was also observed in stomach plexuses. Furthermore, Western blot analysis revealed the presence of molecules immunoreactive to NGF and NT-3, which weight were very similar to those of mammalian corresponding neurotrophins. These results extend to teleost species the presence and distribution of NGF- and NT-3-like IR in the enteric nervous system, suggesting a well-preserved presence of these substances in the gut during vertebrate phylogenesis.

NADPH-d positive neurons of the lizard Podarcis s. sicula oviduct and their relationship to 17beta-estradiol hormone.

The distribution of nicotinamide adenine dinucleotide phosphate reduced diaphorase (NADPH-d) containing neurons was examined in the oviduct of the lizard Podarcis s. sicula and the relationship between these neurons and 17beta-estradiol hormone was studied. NADPH-d-histochemistry and indirect immunofluorescence method were applied to cryostat sections. NADPH-d-nerve structures were found throughout the oviduct. Positive neurons were primarily located in the reproductive oviduct, and were more numerous in the intermuscular and circular muscle layers than in the mucosa. The vagina revealed a reactive nerve population denser than elsewhere. The NADPH-d-positive neurons densities and the 17beta-estradiol plasma levels coincided throughout the lizard sexual cycle. In addition, after 17beta-estradiol treatments, non-reproductive lizards showed an increase of NADPH-d neurons. We suppose that nitric oxide (NO) neurons play an estrogen-dependent role in the oviduct muscle motility.

TrkA and TrkC neurotrophin receptor-like proteins in the lizard gut.

The tyrosine kinase proteins (Trk), encoded by the trk family of proto-oncogenes, mediate, in mammals, the action of neurotrophins, a family of growth factors acting on the development and maintenance of the nervous system. Neurotrophins and their specific receptors, TrkA, TrkB and TrkC, seem to be phylogenetically well preserved but, in reptiles, data regarding the occurrence of Trk-like proteins are very scarce, especially in non-nervous organs. Western blot analysis demonstrated that the lizard gut contains TrkA- and TrkC-like, but not TrkB-like, proteins. Consistently, TrkA- and TrkC-like immunoreactivity were both observed in neurons of the anterior intestine, whereas endocrine cells of the stomach and anterior intestine only displayed TrkA-like immunoreactivity. These results demonstrate for the first time the occurrence of Trk-like proteins in non-neuronal tissues of reptilians and provide further evidence for the evolutionary preservation of the molecular mass and cell distribution of Trk neurotrophin receptor-like proteins in the gut of vertebrates.

The relationships of nicotinamide adenine dinucleotide phosphate-d to nitric oxide synthase, vasoactive intestinal polypeptide, galanin and pituitary adenylate activating polypeptide in pigeon gut neurons.

The distribution of nicotinamide adenine dinucleotide phosphate (NADPH)-d neurons and their relationship with nitric oxide synthase (NOS), vasoactive intestinal polypeptide (VIP), pituitary adenylate activating polypeptide (PACAP) and galanin (Gal) were examined in the gastrointestinal (GI) tract of the pigeon Columbia livia. NADPH-d-histochemistry, indirect immunofluorescence and confocal analysis were applied to cryosections. Western blot analysis was also applied on pigeon gut. NADPH-d neurons were found throughout the pigeon GI tract and they were evident in the myenteric, circular muscle and submucous plexuses. Positive varicose nerve fibres were also distributed within the longitudinal muscle layers and in the lamina propria of the mucosa. The stomach was the segment richest in positivities. The copresence VIP/Gal/NOS as well as PACAP/VIP were revealed in some NADPH-d-neurons. We suppose that the nitrergic nerve population of the pigeon GI tract belong to the muscle motility regulation as an inhibitory descending nerve pathway. Moreover the presence of VIP, Gal and PACAP in some NADPH-d-containing neurons enhances the inhibitory actions of these neurotransmitters whereas PACAP and Gal role is actually unknown.

The distribution and colocalisation of nicotinamide adenine dinucleotide phosphate reduced-diaphorase (NADPH-d)-/nitric oxide synthase (NOS)-containing neurons in the innervation of the duck ureter.

ensp;The distribution and colocalisation of nicotinamide adenine dinucleotide phosphate reduced-diaphorase (NADPH-d)-/nitric oxide synthase (NOS)-containing (nitrergic) neurons in the innervation of the duck ureter have been studied using histochemistry and immunohistochemistry. Quantitative analysis showed that nitrergic neurons made up 60% and 70% of the total intramural and adventitial neuronal populations, respectively. About 40% of intramural nitrergic neurons expressed VIP-immunoreactivity, and about 75% of nitrergic adventitial neurons expressed TH-immunoreactivity. The density of nitrergic adventitial neurons was significantly greater in the lower tract than in the upper and intermediate tracts. Nerve lesioning experiments showed that the majority of ureteral nitrergic innervation was extrinsic in origin; nitrergic adventitial neurons primarily projected caudocranially, whereas NOS-immunoreactive and NOS-/VIP-immunoreactive intramural neurons primarily projected craniocaudally. These findings suggest that, in birds, the nitrergic innervation plays a role in ureteral functions such as epithelial mucosecretion, muscular motility, and the closing and/or opening of the ureteral papilla.

Relationships between liver testosterone receptor isoforms and aromatase activity in female green frog, Rana esculenta.

Testosterone receptors (AR) are present in the liver of the female green frog, Rana esculenta, which resolve into two fractions (A and B) by ion-exchange chromatography. Fraction A is primarily located in the nuclei, fraction B predominates in the cytosols, and both fractions show a high affinity and specificity for testosterone. Liver AR fraction levels vary dramatically during the frog sexual cycle. Fraction A levels are high only when the liver is engaged in vitellogenin production and the plasma testosterone levels are high: they are maximal when aromatase activity is most intense. Fraction B levels are high when the liver is not producing vitellogenin and the plasma testosterone levels are minimal. In addition, in vivo experiments carried out on ovariectomized females treated with testosterone show that testosterone induces both fraction A and liver aromatase activity. This induction may be a step in the process that allows the liver to obtain estrogen from plasma testosterone which induces vitellogenin synthesis.

Trk-neurotrophin receptor-like immunoreactivity in the gut of teleost species.

Neurotrophins, acting through their high-affinity signal-transducing Trk receptors, are involved in the development, differentiation and maintenance of discrete neuron populations in the higher vertebrates. Furthermore, the presence of Trk receptors in some non-neuronal tissues, including the endocrine cells of the gut, could indicate an involvement of neurotrophins also in these tissues. Recently, neurotrophins and neurotrophin receptor proteins have been identified in the lower vertebrates and invertebrates, whose amino acid sequences are highly homologous with those found in mammals. The present study investigates the occurrence and distribution of Trk-like proteins in the neurons and gut endocrine cells in five species of teleost. Single and double immunolabeling was carried out on fresh and paraffin-embedded tissue using commercially available antibodies against sequences of the intracytoplasmic domain of the mammalian Trk. Western-blot analysis, carried out on samples of stomach and intestine of bass, identified proteins whose estimated molecular masses (140 kDa, 145 kDa and 143-145 kDa) were similar to those reported for full-length TrkA, TrkB and TrkC in the higher vertebrates. TrkA-like immunoreactivity was found in the enteric nervous system plexuses of three fish species. Trk-like immunoreactivity was observed in the endocrine cells as follows: sparse TrkA-like immunoreactive endocrine cells were detected only in the intestine: TrkB-like immunoreactive cells were detected only in the stomach; and TrkC-like immunoreactive cells were found both in the intestine of the carp and in the stomach of the bass, where they also showed TrkB-like immunoreactivity. These findings confirm the occurrence and distribution of Trk-like proteins in teleosts. These proteins are closely related to the Trk neurotrophin receptors of mammals. The functional significance of Trk-like proteins in both neuronal and non-neuronal cells of teleosts is still not clear.