Radiomics for differentiation of gliomas from primary central nervous system lymphomas: a systematic review and meta-analysis

Background and objective

Numerous radiomics-based models have been proposed to discriminate between central nervous system (CNS) gliomas and primary central nervous system lymphomas (PCNSLs). Given the heterogeneity of the existing models, we aimed to define their overall performance and identify the most critical variables to pilot future algorithms.

Methods

A systematic review of the literature and a meta-analysis were conducted, encompassing 12 studies and a total of 1779 patients, focusing on radiomics to differentiate gliomas from PCNSLs. A comprehensive literature search was performed through PubMed, Ovid MEDLINE, Ovid EMBASE, Web of Science, and Scopus databases. Overall sensitivity (SEN) and specificity (SPE) were estimated. Event rates were pooled using a random-effects meta-analysis, and the heterogeneity was assessed using the χ2 test.

Results

The overall SEN and SPE for differentiation between CNS gliomas and PCNSLs were 88% (95% CI = 0.83 - 0.91) and 87% (95% CI = 0.83 - 0.91), respectively. The best-performing features were the ones extracted from the Gray Level Run Length Matrix (GLRLM; ACC 97%), followed by those obtained from the Neighboring Gray Tone Difference Matrix (NGTDM; ACC 93%), and shape-based features (ACC 91%). The 18F-FDG-PET/CT was the best-performing imaging modality (ACC 97%), followed by the MRI CE-T1W (ACC 87% - 95%). Most studies applied a cross-validation analysis (92%).

Conclusion

The current SEN and SPE of radiomics to discriminate CNS gliomas from PCNSLs are high, making radiomics a helpful method to differentiate these tumor types. The best-performing features are the GLRLM, NGTDM, and shape-based features. The 18F-FDG-PET/CT imaging modality is the best-performing, while the MRI CE-T1W is the most used.

Radiomics for Differentiation of Pediatric Posterior Fossa Tumors: A Meta-Analysis and Systematic Review of the Literature

PURPOSE

To better define the overall performance of the current radiomics-based models for the discrimination of pediatric posterior fossa tumors.

METHODS

A comprehensive literature search of the databases PubMed, Ovid MEDLINE, Ovid EMBASE, Web of Science, and Scopus was designed and conducted by an experienced librarian. We estimated overall sensitivity (SEN) and specificity (SPE). Event rates were pooled across studies using a random-effects meta-analysis, and the χ2 test was performed to assess the heterogeneity.

RESULTS

Overall SEN and SPE for differentiation between MB, PA, and EP were found to be promising, with SEN values of 93% (95% CI = 0.88-0.96), 83% (95% CI = 0.66-0.93), and 85% (95% CI = 0.71-0.93), and corresponding SPE values of 87% (95% CI = 0.82-0.90), 95% (95% CI = 0.90-0.98) and 90% (95% CI = 0.84-0.94), respectively. For MB, there is a better trend for LR classifiers, while textural features are the most used and the best performing (ACC 96%). As for PA and EP, a synergistic employment of LR and NN classifiers, accompanied by geometrical or morphological features, demonstrated superior performance (ACC 94% and 96%, respectively).

CONCLUSIONS

The diagnostic performance is high, making radiomics a helpful method to discriminate these tumor types. In the forthcoming years, we expect even more precise models.

Cigarette Smoking and Intracranial Aneurysms: A Pilot Analysis of SNPs in the CYP2A6 Gene in the Italian Population

BACKGROUND

Cigarette smoking is a modifiable risk factor associated with formation and rupture of intracranial aneurysms (IAs). Cytochrome P450 2A6 (CYP2A6) is the main enzyme implied in catabolism of nicotine and xenobiotics, giving rise to oxidative stress products. Our study investigated the associations between specific single-nucleotide polymorphisms (SNPs) in the CYP2A6 gene and the presence of sporadic IAs in a cluster of Italian patients, as well as their rupture regarding cigarette smoking habit.

METHODS

Three hundred and thirty-one Italian patients with sporadic IAs were recruited in a single institution. We recorded data on clinical onset with subarachnoid hemorrhage (SAH) and smoking habit. Genetic analysis was performed with a standard procedure on peripheral blood samples: CYP2A6 ∗1B2, CYP2A6 ∗2, and CYP2A6 ∗14 SNPs were analyzed in the study group along with 150 healthy control subjects. Statistical analysis was conducted according to genetic association study guidelines.

RESULTS

In the patient cohort, the frequency of aSAH was significantly higher in current smokers (P < 0.001; OR=17.45), regardless of the pattern of CYP2A6 SNPs. There was a correlation between IA rupture and cigarette smoking in patients with the heterozygous CYP2A6 ∗1B2 allele (P < 0.001; OR=15.47). All patients carrying the heterozygous CYP2A6 ∗14 allele had an aSAH event (100%), regardless of smoking habit, although this correlation was not statistically significant (P = 1).

CONCLUSIONS

According to our findings, a cigarette smoker carrying a fully active CYP2A6 enzyme (heterozygous ∗1B2 allele) may have an increased risk of IA rupture compared to those with functionally less active variants: further investigation on a larger sample is needed to verify this result. The role of the heterozygous CYP2A6 ∗14 allele in aSAH is yet to be clarified.

Improving CNNs classification with pathologist-based expertise: the renal cell carcinoma case study

The prognosis of renal cell carcinoma (RCC) malignant neoplasms deeply relies on an accurate determination of the histological subtype, which currently involves the light microscopy visual analysis of histological slides, considering notably tumor architecture and cytology. RCC subtyping is therefore a time-consuming and tedious process, sometimes requiring expert review, with great impact on diagnosis, prognosis and treatment of RCC neoplasms. In this study, we investigate the automatic RCC subtyping classification of 91 patients, diagnosed with clear cell RCC, papillary RCC, chromophobe RCC, or renal oncocytoma, through deep learning based methodologies. We show how the classification performance of several state-of-the-art Convolutional Neural Networks (CNNs) are perfectible among the different RCC subtypes. Thus, we introduce a new classification model leveraging a combination of supervised deep learning models (specifically CNNs) and pathologist's expertise, giving birth to a hybrid approach that we termed ExpertDeepTree (ExpertDT). Our findings prove ExpertDT's superior capability in the RCC subtyping task, with respect to traditional CNNs, and suggest that introducing some expert-based knowledge into deep learning models may be a valuable solution for complex classification cases.

Exploiting generative self-supervised learning for the assessment of biological images with lack of annotations

Motivation

Computer-aided analysis of biological images typically requires extensive training on large-scale annotated datasets, which is not viable in many situations. In this paper, we present Generative Adversarial Network Discriminator Learner (GAN-DL), a novel self-supervised learning paradigm based on the StyleGAN2 architecture, which we employ for self-supervised image representation learning in the case of fluorescent biological images.

Results

We show that Wasserstein Generative Adversarial Networks enable high-throughput compound screening based on raw images. We demonstrate this by classifying active and inactive compounds tested for the inhibition of SARS-CoV-2 infection in two different cell models: the primary human renal cortical epithelial cells (HRCE) and the African green monkey kidney epithelial cells (VERO). In contrast to previous methods, our deep learning-based approach does not require any annotation, and can also be used to solve subtle tasks it was not specifically trained on, in a self-supervised manner. For example, it can effectively derive a dose-response curve for the tested treatments.

Availability and implementation

Our code and embeddings are available at https://gitlab.com/AlesioRFM/gan-dl StyleGAN2 is available at https://github.com/NVlabs/stylegan2.

[Harvesting vascular segments]

The authors report the importance of the use of vascular homografts in treatment of prosthetic infections. To have good results is very important to obtain vascular segments prelevated and preserved in the best conditions. The importance of the explant is fundamental. The authors report the right sequence of organs' explant and the technique to obtain good vascular segments; for this purpose is important the coordination of the surgical equips taking part in the explant.

Mid-term results of endovascular repair for abdominal aortic aneurysm, with loco-regional anesthesia, in high-risk patients

BACKGROUND

Aim of this study was to evaluate the results of endovascular repair of abdominal aortic aneurysm (AAA) in patients considered not suitable for traditional open surgical repair because of the high anesthesiological risk.

METHODS

We have retrospectively evaluated the result of the endovascular treatment of 11 patients with AAA of more than 6 cm diameter and high surgical risk due to cardiac hypokinesia and/or respiratory insufficiency. Patients were selected by a team composed of vascular surgeons and vascular radiologists who decided to implant the graft according to anatomical features of the AAA and of the iliac arteries. The treatment was performed in loco-regional anesthesia. The main end-points were: implantation success, mortality, morbidity, the absence of endoleak during the follow up that lasted two years.

RESULTS

All the grafts were successfully implanted. There were no complications caused by anesthesiological manouvres. We had a minor intra-operative vascular complication and we performed three adjunctive endovascular procedures. A patient died of acute myocardial infarction, in the post operative period. Mean stay was six days. Pre-discharge scan showed 3 endoleaks (type I), two of these healed spontaneously and one sealed by percutaneous endovascular treatment. During follow-up (3-24 months) no patient died. One endoleak (type II) still persists. CONCLUSIONS The use of loco-regional anaesthesia allows us to treat high risk patients. Following strictly the criteria of patient selection, the surgical high risk seems not to influence significantly the mid term results that are almost equal to the ones obtained in low-risk patients.

Donor and recipient postoperative complications in living related kidney transplantation. A multicentric study

BACKGROUND

Living related kidney transplantation is considered a gold standard of renal transplantation in order to overcome end-stage renal disease within the same family members. Living donation, albeit decreasing cadaveric donor shortage, exposes donors to the risk of surgical complications.

METHODS

In order to assess the postoperative complication rate in donors and recipients, we reviewed retrospectively 90 consecutive living related kidney transplants in a multicentric study. All nephrectomies were performed extraperitoneally through a left flank incision.

RESULTS

Major perioperative complications (first 3 weeks after surgery) occurred in 12 subjects: these included bleeding (2.2%), symptomatic pneumothorax (1.1%), iliac thrombophlebitis (3.3%), iliac artery dissection (1.1%), laparotomic dehiscence (2.2%), perirenal hematoma (1.1%), renal artery stenosis (1.1%), urinary fistula (1.1%). Minor perioperative complications took place in 8 cases. One recipient died. Donor postoperative major complications occurred in 2 subjects.

CONCLUSIONS

On the basis of these results we conclude that living related kidney transplantation is an important treatment of end stage renal disease, due to the associated low major complication rate and the high feasibility of this methodology.

Reactogenicity and immunogenicity of a new combined measles-mumps-rubella vaccine: results of a multicentre trial. The Cooperative Group for the Study of MMR vaccines

A large single blind, multi-centre study involving 1779 children was performed in Italy. Infants, aged between 12 and 27 months were divided between two groups: group A received a single dose of a new MMR vaccine, 'Priorix'(3), while group B received a widely used MMR vaccine, Triviraten(4). Solicited local and general symptoms were recorded using diary cards and antibody levels were measured, prior to and 60 days post-vaccination, using ELISA assays. The incidence of solicited symptoms (evaluated in 1754 subjects) was comparable between groups, with the exception of fever which was significantly lower in group B. Immunogenicity was evaluated in 686 subjects. Of note, was the significantly higher anti-mumps seroconversion rate (p<0.001) observed in group A (97.0%) compared to group B (35.4%). However the anti-measles and anti-rubella seroconversion rates were equivalent between groups. Significantly higher (p<0.001) post-vaccination GMTs were in group A vs group B for anti-measles (2830 vs 784 IU/ml) and anti-mumps (1640 vs 469 U/ml), however the anti-rubella GMTs were significantly higher (p<0.001) in group B (117.6 IU/ml) compared to group A (92.6 IU/ml). The persistence of antibodies in 35 subjects was assessed 1 year after vaccination and the results showed no appreciable decline in titres with either vaccine. The trial demonstrates 'Priorix' is well tolerated and highly immunogenic.

Prospects of prostanoid therapy. Preliminary results

BACKGROUND

To evaluate the efficacy of treatment with prostaglandins (Iloprost and Alprostadil) in patients with peripheral arterial disease in whom a surgical act or a redo operation is not proposable and to set the role of these drugs in the therapy of arterial diseases.

METHODS

We analyzed the results of 96 treatments in patients with peripheral arterial diseases of different etiology, treated in the Day Hospital in the Division of Vascular Surgery from the 1/1/1993 to the 30/6/1998. The efficacy of the treatment has been evaluated on the basis of the clinical picture (healing or reduction of ulcers, reduction of rest-pain, improvement of the ability to walk).

RESULTS

We had positive results in 60% of the patients who completed the treatment, a good outcome for patients with particularly severe arterial disease. Interruptions induced by the occurrence of uncontrolled side-effects are a few (6.25%). Better results have been found in a special category of disease (arterial diseases not associated with diabetes, not very advanced clinical picture, female gender). Iloprost proved to be superior to Alprostadil.

CONCLUSIONS

Prostaglandins today represent an effective therapeutic solution to be considered. Further studies need to be done to find a category of patients who can have the best benefit from this kind of drug.

Experience with the Stentor endograft at four Italian centers

PURPOSE

To report the outcome of an Italian multicenter trial of endovascular abdominal aortic aneurysm (AAA) exclusion using the Stentor device.

METHODS

Between April 1995 and July 1996, 66 patients (63 men; average age 69 years, range 53 to 84) with infrarenal AAAs meeting the inclusion criteria were enrolled. The average diameter of the aneurysm was 4.6 cm (range 4.2 to 7). Three (4.5%) of the 66 AAAs were anastomotic aneurysms.

RESULTS

Sixteen (25%) tubular and 50 (76%) bifurcated endograft procedures were attempted; 4 (6.1%) were converted and 1 terminated owing to technical faults with the bifurcated graft's second limb. One tube graft was too short and failed to exclude an anastomotic aneurysm. Sixty (91%) endograft procedures were completed successfully. Six (9.1%) vascular complications occurred, three in one patient who subsequently died of pulmonary embolism 72 hours postoperatively (1.5% mortality). There were four (6.1%) proximal endoleaks; two sealed spontaneously in < 1 month, and a third was converted (7.6% conversion rate). The fourth is being observed. Clinical success (aneurysm exclusion with no death or endoleak) at 30 days was 86.3% (57/66). In the 23-month follow-up of 57 eligible patients, 2 patients died of unrelated causes and 1 graft limb thrombosed, requiring a crossover femoral bypass. One patient was converted to surgical repair at 5 months postoperatively when increasing aneurysm size signaled an undisclosed endoleak (1.8% late conversion rate). Five other secondary endoleaks were treated with endovascular techniques.

CONCLUSIONS

The Stentor was technically feasible in 10% to 40% of AAA candidates in this study, although deployment of the second limb was problematic in the bifurcated device. Introduction of the second-generation Vanguard endograft brought this study to an end.

[Post-traumatic pseudoaneurysm of the common carotid artery]

The authors report their experience of one single case of carotid pseudo-aneurysm consequent on cervical trauma. The treatment required the substitution of the interested carotid segment by PTFE no. 6. This case is a rare event but the surgeon must always keep it in mind in the presence of cervical trauma.

[Carotid-subclavian bypass. Our experience with locoregional anesthesia]

Carotid-subclavian bypass has been adopted since 1956. The commonest indication is to abolish arterial occlusion or stenosis in patients with subclavian steal syndrome. Ten patients were submitted to carotid-subclavian bypass under regional anaesthesia: block of anterior rami of spinal nerves C3-C4 and block of cervico-brachial plexus by injection into the continuous perineural connective tissue space at the level of C6. The surgical procedure required carotid occlusion and cerebral function monitoring. The advantages of regional anaesthesia are the ability to monitor the patient's cerebral perfusion and function, to detect intraoperative ischaemia and embolisation and minimal interference with the cardiovascular and respiratory function.

Oxiracetam prevents the hippocampal cholinergic hypofunction induced by the NMDA receptor blocker AP7

The intracerebroventricular injection of the N-methyl-D-aspartate (NMDA) receptor antagonist D,L-2-amino-7-phosphonoheptanoic acid (AP7) induces an increase of the hippocampal levels of acetylcholine (ACh) which is dose-dependent in the range 1.5-10 micrograms. Similar doses of AP7 failed to affect the ACh content of the striatum. The effect of the i.c.v. administration of 3.5 micrograms AP7 on hippocampal ACh levels was prevented by pretreatment with oxiracetam 100 mg/kg i.p. In the passive avoidance test the i.c.v. administration of 3.5 micrograms of AP7 caused severe amnesia which was antagonized in a dose-dependent manner by the pretreatment with oxiracetam. These results show that oxiracetam prevents the imbalance of cholinergic activity and the amnesia caused by blockade of NMDA receptors. The present study suggests that the hippocampal cholinergic activity is modulated by glutamatergic neuronal pathways and that the functional integrity of both systems is essential for learning and memory processes.

[Loco-regional anesthesia vs general anesthesia in carotid endarterectomy. Response to the surgical stress]

The advantages of performing carotid endarterectomy in the awake patient, perioperative analgesia, circulatory parameters, plasma cortisol and PRL response to surgery have been evaluated. Ten patients were submitted to general anaesthesia and ten patients to superficial and deep cervical block. The Authors conclude that, although the number of patients studied is limited, there are no significant differences between the two groups for intraoperative analgesia, hemodynamic imbalance and plasma cortisol and PRL. This result support the belief that carotid endarterectomy in awake patients can be safely performed on patients with chronic obstructive pulmonary disease.

[Endocrine-metabolic response to 2 different techniques in surgery of the abdominal aorta]

Plasma cortisol and PRL were measured in two groups of patients undergoing reconstructive aortic surgery under either general anaesthesia and continuous epidural analgesia with supplemental general anaesthesia. The results confirmed that epidural analgesia with light general anaesthesia is much able than general anaesthesia to suppress the metabolic response associated with aortic surgery procedures.

[Atherosclerotic vascular nephropathy. Description of 2 clinical cases and review of the literature]

Atheromatous nephropathy, due to a reduction of arterial blood flow caused by stenosis or thrombosis of renal arteries, is now recognized as an important cause of chronic renal failure in the elderly. It has been shown that renal revascularization may allow a recovery of renal function up to the withdrawal of dialytic treatment. Digital arteriography is the preferred diagnostic method, but doppler scan and renal scintigraphy after administration of captopril may also prove useful, specially in the follow-up of the patients. Therapeutic means include percutaneous transluminal angioplasty and surgical revascularization; both treatments may improve or stabilize renal function. Surgery may allow better results in the long term, but is loaded by a significant morbidity. Our experience confirms the possibility to obtain a significant long term improvement of renal function after bilateral surgical revascularization.

[Neurovascular syndrome of the arm caused by acquired luxation of the sternoclavicular articulation]

The Authors report on a case of neurovascular syndrome of the upper extremity caused by acquired luxation of the sternoclavicular articulation. The patient was treated by simple scalenotomy with a favourable long-term result.

[15 cases of femoro-popliteal bypass with PTFE graft]

The authors report their clinical experience of 15 cases of femoro-popliteal by-pass with PTFE; all patients underwent postoperative anti-platelet therapy, in 8 cases with ASA and dipyridamole, in 7 with indobufene in accordance with a double blind randomized work. The Authors report the results of a one year follow-up. They deal with patency duration results and tolerance of pharmacological treatment.

[Use of slowly resorbing mesh in the repair of kidney rupture due to rejection]

Personal experience about the use of Vicryl mesh in a case of kidney rupture following rejection is presented. The stopping of bleeding and recovery of diuresis were obtained almost immediately after intervention.

In-vivo radiolabelled oxiracetam binding to rat brain

The in-vivo binding of [3H]oxiracetam has been studied in brain areas of rats examined 30 min after i.c.v. injection. Soluble radioactivity accounted for more than 90% of total radioactivity in all the structures considered and was not affected by co-injection with a 1000-fold excess of unlabelled oxiracetam. Both total and bound radioactivity showed a marked regional distribution, with highest concentrations in the septum, followed by the hippocampus; the cerebral cortex, striatum and cerebellum had the lower concentrations of radioactivity. Computer-assisted quantitative autoradiography with [14C]oxiracetam confirms these findings. Analysis of [3H]oxiracetam bound to membranes indicated that, after co-injection with a 1000-fold excess of unlabelled oxiracetam, there was a significant reduction of binding only in the septum, hippocampus and cerebral cortex. These results suggest that in those cerebral structures oxiracetam binds to saturable sites.

Brain entry and direct central pharmacological effects of the nootropic drug oxiracetam. Oxiracetam: brain entry and pharmacological effects

Oxiracetam administered systemically to rats as a 14C radiolabelled drug (200 mg/kg p.o. or 100 mg/kg intra-artery) enters the brain and is found unmetabolized above all in some of the brain areas functionally involved in the modulation of cognitive processes. Among the brain areas examined, the largest amount of compound was recovered in septum, followed by hippocampus; a smaller amount was found in cerebral cortex and striatum. 14C oxiracetam administered directly into the lateral ventricles of the brain presented a similar pattern of distribution, indicating that the tropism of the drug for the above brain areas does not depend on its route of administration. The amounts of oxiracetam that could reach the brain after systemically administered pharmacologically active doses were also estimated. These amounts (1.9 to 19 nmols/rat) were delivered through a permanently implanted cannula, into the lateral ventricles of the brains of conscious, freely moving rats. In this experimental condition oxiracetam dose-dependently antagonized the amnesia induced by scopolamine (0.66 mg/kg s.c.). The above findings clearly indicate that oxiracetam enters the brain and directly exerts its pharmacological activity there.

Differential response to immobilization stress of striatal dopaminergic and hippocampal noradrenergic systems in aged rats

The effect of restraint stress on synthesis of central norepinephrine (NE) and dopamine (DA) was studied in adult and old rats. The rate of in vivo synthesis of the two catecholamines was determined in hippocampus (a prevalently noradrenergic area) and in striatum (a prevalently dopaminergic area) by measuring the accumulation of DOPA for 60 min after decarboxylase inhibition. NE synthesis was stimulated by stress in the first 30 min, after which the accumulation of DOPA declined. The stimulation was much greater in old rats. In striatum, endogenous DOPA concentration was significantly lower in old rats. Stress significantly enhanced DOPA accumulation in the first 30 min in both age groups but after this interval accumulation continued linearly only in young rats. These results indicate that in aged rats the response to stress of some noradrenergic and dopaminergic systems may be altered in opposite directions.

[A case of giant lumbar neurinoma]

A rare case of a giant extradural neurinoma of the IV lumbar root with an anterior development and a soft neurological picture is reported. The Authors stress the important role of CT both in the neurinoma diagnosis and in the correct preoperative evaluation of its extension and its relationship with contiguous organs.

Behavioural and biochemical studies on 6-methylamino-4,5,6,7-tetrahydrobenzothiazole (14.839JL), a new potent dopaminergic agonist

6-Methylamino-4,5,6,7-tetrahydrobenzothiazole monochlorhydrate (14.839JL) is a new, potent dopaminergic agonist. The stereotypy induced by this drug was greater than that induced by an equivalent dose of apomorphine, was antagonized by pretreatment with sulpiride and counteracted the hypomotility induced by reserpine. Striatal levels of the dopamine metabolites homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC) and 3-methoxytyramine (3-MT) were significantly lowered for up to 4-6 h by doses from 0.05 to 1 mg/kg. The drug was also very effective in lowering prolactine secretion. 14.839JL displaced [3H]N-n-propylnorapomorphine [3H]NPA from striatal binding sites with an IC50 similar to dopamine (DA). Conversely, the ability of 14.839JL to displace 3H spiperone from its binding sites was 100 and 10 times lower than that of haloperidol and sulpiride, and similar to that of SCH 23390. Differently from the latter, however, 14.839JL did not modify adenylate cyclase activity. All these data suggest that 14.839JL is a new, potent, long-lasting direct DA agonist, probably acting on D2 receptors.

Age-related changes in metabolic responses to chronic monoamine depletion in central dopaminergic and serotonergic systems of rats treated with reserpine

Groups of 5, 15, and 27-month-old rats were treated with reserpine (5 mg/kg IP) and killed after 1, 7, 14, and 21 days. Reserpine's effects on dopamine (DA) and serotonin (5HT) metabolism were studied in the striata and limbic areas, on the basis of changes in metabolite concentrations and a calculated index [delta(C/M)] expressing changes in the molar ratio between metabolite and parent monoamine. Twenty-four hours after drug treatment, when the two monoamines reached a new steady-state, about 10% of the normal concentration, there was evident enhancement in the metabolism of striatal DA, indicated by HVA levels and delta(C/M) changes. This increase was significantly lower in the senescent rats. In contrast with HVA, the levels of DOPAC were lowered in reserpinized rats. This effect, present in all three age groups, lasted up to 21 days in young and 14 days in adult and old rats. However, for this metabolite too, the delta(C/M) indicated an increase in its formation which was lower in 27-month-old rats. Similar effects were observed in limbic areas, but here the age-related differences were less evident. Serotonin metabolism was also increased by reserpine as indicated by the delta(C/M). This parameter was lower in young than in adult and old rats, at least in limbic area. Similarly, 5HIAA increased only in the senescent rats. These age-related differences were not evident in striata. In this rat population, aging apparently modified the compensatory metabolic responses of some dopaminergic and serotonergic systems. The direction of these changes, however, depends on the system and the brain region considered.

Differences in the effect of the antidepressant amineptine on striatal and limbic DOPAC measured by HPLC-ECD and in vivo voltammetry

The acute effect of the antidepressant amineptine was studied in two dopaminergic areas, the striatum and the limbic system, by in vivo voltammetry. This electrochemical technique uses carbon fibre electrodes implanted in brain areas of non-anaesthetized freely moving rats to measure DOPAC diffusing from the neurons. In vivo voltammetry recordings showed that amineptine induced a slight and transient decrease in DOPAC levels in the caudate nucleus but a persistent, clear-cut decrease in the nucleus accumbens. These results were confirmed by classical biochemical determination in tissue samples. The findings indicate the possible importance of the limbic area in the mechanism of action of amineptine.

Amineptine: its effect on the dopaminergic system of rats

3-Methoxytyramine formation was enhanced by amineptine (40 mg kg-1 i.p.) in the striatum and limbic area, indicating an increase in the concentration of dopamine in the extraneuronal space. Since dopamine turnover, determined as the rate of L-dopa accumulation, is reduced by the drug at short (10 min) times, the enhanced extraneuronal dopamine concentration seems mainly related to amineptine-induced inhibition of its uptake.

Neurochemical effects of buspirone in rat hippocampus: evidence for selective activation of 5HT neurons

The effect of buspirone on neurotransmitter systems in rat hippocampus has been evaluated in vitro and in vivo. In vitro buspirone does not affect the specific binding of 3H-flunitrazepam, 3H-GABA, 3H-dexetimide, but displaces 3H-5HT binding with nanomolar affinity. Oral administration of buspirone does not modify the hippocampal concentrations of GABA, acetylcholine, choline and of 3H-flunitrazepam specifically bound in vivo, but results in a dose-dependent reduction of 5HIAA and noradrenaline concentrations. While the effect on noradrenaline is also obtained in striatum of buspirone-treated animals, the effect on 5HIAA shows a regional specificity. The in vitro and in vivo data suggest that buspirone specifically activates 5HT neurons in hippocampus, and are compared with those obtained with diazepam.

Application of the dual-cell coulometric detector: a method for assaying monoamines and their metabolites

A new HPLC assay technique for monoamines and their metabolites, using a controlled potential coulometric detector equipped with a dual working electrode cell of fully porous graphite through which the samples flow, is described in comparison with a classical amperometric detector equipped with a glassy carbon electrode. Different potentials can be applied at each cell of the coulometric detector to improve sample resolution and detection sensitivity. The signal-to-noise ratio (s/n) calculated in similar conditions was 10 times lower for the coulometric detector than for the amperometric one. The dual-coulometric detector does not undergo daily decay or variation, and needs no particular care or preparation. It is therefore possible to achieve stable routine sensitivity in a range of 10 fmol. This new technique has been applied for assaying monoamines and their precursors and metabolites by direct injection of clear supernatant after centrifugation and for determination of catecholamine turnover in rat pineal gland and neuro- and adenohypophysis in samples purified by Al2O3 adsorption.

Central side effects of pentamethylmelamine: biochemical and behavioural studies

The central side effects of pentamethylmelamine (PMM), an antitumoral agent, were studied on brain neurotransmitters from the biochemical and behavioural points of view. PMM causes a dose-related reduction in the body temperature and motility of mice. 100 mg/kg of PMM lowers the levels of noradrenaline (NA) and raises 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) in the telencephalon. A similar dose increased striatal levels of dopamine (DA) metabolites, homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC), at earlier times (30 min), reducing their levels at 2 hr. These effects disappear at longer times (4 hr). No changes were observed in the levels of 3-methoxytyramine (3-MT), the extraneuronal metabolite of DA. The serotonin metabolite 5-hydroxyindolacetic acid (5HIAA) was almost not affected. PMM and its metabolites do not displace [3H]-spiroperidol from mouse striatal binding sites. These data show that some of the neurological effects induced by PMM are associated with changes in the metabolism and/or release of brain catecholamines but are not mediated by direct action on DA receptors.

Depletion and recovery of neuronal monoamine storage in rats of different ages treated with reserpine

The effect of reserpine on dopamine, noradrenaline, adrenaline and serotonin concentrations in different brain regions, and the recovery of normal levels of these monoamines after such treatment were studied in rats aged 5, 15 and 27 months. In a preliminary experiment we found that distribution of the drug was not altered in the aged rats. Then we observed that a single dose of reserpine (5 mg/kg IP) had a similar depleting effect on all the brain monoamines, in all the brain regions considered in all three age groups. The curves expressing recovery of monoamine storage in all the nerve terminals, several days after treatment, were superimposable. These results suggest that in the rat, age does not influence the effect of reserpine on the storage mechanism of brain monoamines. Moreover, as restoration of this mechanism depends on the synthesis of new vesicles, the similarity in the rates of recovery in adult, old and very old rats indicated indirectly that synthesis of these neuronal organelles is not affected by aging.

In vivo and in vitro evidence of dopaminergic system down regulation induced by chronic L-DOPA

The biochemical modifications which occur in the dopaminergic system after chronic administration of L-DOPA are investigated. Levels of DA and of its metabolite 3-methoxytyramine (3-MT), an expression of the amount of DA released, were raised to the same extent in controls given a single dose of 1-DOPA and in chronically treated rats given 100 mg/kg of 1-DOPA plus 25 mg/kg of benserazide twice a day for 24 days. However, the reduction in neuronal function expressed by the decrease in 3-MT which follows treatment with DA agonists such as piribedil and apomorphine was less pronounced in the chronically L-DOPA treated rats. This suggests that such treatment causes a down regulation of DA receptors. These in vivo results were confirmed by in vitro analysis of DA receptor activity after chronic L-DOPA. Under these conditions there was a significant reduction in the number of [3H]-spiperone and [3H]-ADTN binding sites with no changes in their affinity. The in vivo and in vitro findings both suggest the involvement of a subsensitive compensatory mechanism or down regulation of dopaminergic neurons after chronic treatment with L-DOPA.

Does acute L-DOPA increase active release of dopamine from dopaminergic neurons?

L-DOPA is believed to be decarboxylated by the residual striatal dopaminergic presynaptic terminals with formation of the putative neurotransmitter dopamine (DA) and with increased availability of DA at post-synaptic receptors. However there is no direct evidence that the DA formed is released into the synaptic cleft. We therefore investigated the biochemical modifications occurring in the dopaminergic system after acute administration of L-DOPA. After acute L-DOPA (100 mg/kg plus 25 mg/kg of benserazide p.o.) the levels of 3-methoxytyramine (3-MT), a metabolite reflecting release of the neurotransmitter DA, were significantly raised, following the same pattern as DA levels, indicating that DA release from DA nerve terminals is increased after L-DOPA administration. The increased DA release and 3-MT formation were not reduced by pretreatment with direct DA agonists such as apomorphine (5 mg/kg i.p.) or piribedil (120 mg/kg p.o.). Thus in this case DA release is not under the control of the compensatory mechanisms induced by post-synaptic receptor hyperstimulation.

Simultaneous determination of DA, NA, 5HT and their metabolites in several rat brain areas by HPLC with electrochemical detection

A simple and rapid method is presented for the determination of serotonin, dopamine, noradrenaline and their metabolites. The method is based on separation of the different compounds by absorption onto A1(2)O3 or organic solvent separation. The compounds extracted are further separated by HPLC and detected electrochemically. Amounts of 5HT, DA, NA and DA metabolites in several brain regions are reported. An account of the relationships between different neuronal systems, the possibility of simultaneously assaying serotonin (5HT) dopamine (DA) and noradrenaline (NA) and their metabolites dihydroxy-phenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxy-indolacetic acid (5HIAA) in the same brain area is sometime important for understanding the drugs' effects of mechanisms of action on monoaminergic systems (Ponzio et al., 1981; Holmes and Rutledge, 1976). Therefore we modified our liquid chromatography with electrochemical detection (LCEC) methods for assaying 5HT (Ponzio and Jonsson, 1979), NA and DA (Keller et al., 1976), DOPAC, HVA and 5HIAA (Ponzio and Jonsson, 1978) in order to determine their levels in the same sample.

Dopaminergic effects of buspirone, a novel anxiolytic agent

The novel anxiolytic drug buspirone raised striatal levels of the dopamine metabolites homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC) 1 hr after oral administration. This effect was dose-dependent with a peak at 60 min. No changes were observed in the levels of 3-methoxytyramine (3MT), the extraneuronal metabolite of dopamine. Noradrenaline, serotonin and its metabolite 5-hydroxyindoleacetic acid (5HIAA) were not affected. Buspirone displaced [3H]spiroperidol from striatal binding sites, with an IC50 (1.8 x 10(-7) M), comparable to that of clozapine (IC50 = 1.4 x 10(-7) M) but considerably lower than that of haloperidol (4.7 x 10(-9) M). Buspirone was only a weak inhibitor of dopamine-stimulated adenyl cyclase. Buspirone was not active on the binding of trifluoperazine to calmodulin and did not modify calmodulin-induced activation of phosphodiesterase (PDE). Repeated administration of buspirone did not increase the number of DA receptors. These data show that, although buspirone has antidopaminergic activity, it can hardly be classified as a classic neuroleptic agent.