Expanding the Natural History of SNORD118-Related Ribosomopathy: Hints from an Early-Diagnosed Patient with Leukoencephalopathy with Calcifications and Cysts and Overview of the Literature

Leukoencephalopathy with calcifications and cysts (LCC) is a rare autosomal recessive disorder showing a pediatric or adult onset. First described in 1996 by Labrune and colleagues, it was only in 2016 that bi-allelic variants in a non-protein coding gene, SNORD118, were found as the cause for LCC, differentiating this syndrome from coats plus (CP). SNORD118 transcribes for a small nucleolar RNA, which is necessary for correct ribosome biogenesis, hence the classification of LCC among ribosomopathies. The syndrome is characterized by a combination of white matter hyperintensities, calcifications, and cysts on brain MRI with varying neurological signs. Corticosteroids, surgery, and recently bevacizumab, have been tried with unclear results since the natural history of the disease remains elusive. To date, 67 patients with a pediatric onset of disease have been described in the literature, with a clinical-radiological follow-up carried out in only eleven of them. We described the clinical-radiological follow-up from birth to almost five years of age of a late-preterm patient diagnosed with LCC and carried out a thorough overview of pediatric patients described in the literature. It is important to gather serial clinical-radiological data from other patients to depict the natural history of this disease, aiming to deeply depict genotype-phenotype correlations and make the role of new therapeutics clearer.

Adult onset familiar dystonia-plus syndrome: A novel presentation of IRF2BPL-associated neurodegeneration

Pathogenic variants of the IRF2BPL gene have been mostly associated with early onset epileptic encephalopathy. Movement disorders such as dystonia and ataxia were also reported, with symptoms mainly developing between childhood and adolescence. Here we describe a family with several members affected by a late onset dystonic and ataxic progressive syndrome, caused by a novel heterozygous pathogenic variant in the IRF2BPL gene.

Clinical variability at the mild end of BRAT1-related spectrum: Evidence from two families with genotype-phenotype discordance

Biallelic mutations in the BRAT1 gene, encoding BRCA1-associated ATM activator 1, result in variable phenotypes, from rigidity and multifocal seizure syndrome, lethal neonatal to neurodevelopmental disorder, and cerebellar atrophy with or without seizures, without obvious genotype-phenotype associations. We describe two families at the mildest end of the spectrum, differing in clinical presentation despite a common genotype at the BRAT1 locus. Two siblings displayed nonprogressive congenital ataxia and shrunken cerebellum on magnetic resonance imaging. A third unrelated patient showed normal neurodevelopment, adolescence-onset seizures, and ataxia, shrunken cerebellum, and ultrastructural abnormalities on skin biopsy, representing the mildest form of NEDCAS hitherto described. Exome sequencing identified the c.638dup and the novel c.1395G>A BRAT1 variants, the latter causing exon 10 skippings. The p53-MCL test revealed normal ATM kinase activity. Our findings broaden the allelic and clinical spectrum of BRAT1-related disease, which should be suspected in presence of nonprogressive cerebellar signs, even without a neurodevelopmental disorder.

ARF1 haploinsufficiency causes periventricular nodular heterotopia with variable clinical expressivity

The primary anatomical defect leading to periventricular nodular heterotopia occurs within the neural progenitors along the neuroepithelial lining of the lateral ventricles and results from a defect in the initiation of neuronal migration, following disruption of the neuroependyma and impaired neuronal motility. Growing evidence indicates that the FLNA-dependent actin dynamics and regulation of vesicle formation and trafficking by activation of ADP-ribosylation factors (ARFs) can play an important role in this cortical malformation. We report the first inherited variant of ARF1 in a girl with intellectual disability and periventricular nodular heterotopia who inherited the variant from the father with previously undiagnosed single nodular heterotopia and mild clinical expression. Additionally, both patients presented some features suggestive of hypohidrotic ectodermal dysplasia. These clinical features showed similarities to those of three previously reported cases with ARF1 missense variants, confirming that haploinsufficiency of this gene causes a recognisable neurological disorder with abnormal neuronal migration and variable clinical expressivity.

Refining the mutational spectrum and gene-phenotype correlates in pontocerebellar hypoplasia: results of a multicentric study

BACKGROUND

Pontocerebellar hypoplasias (PCH) comprise a group of genetically heterogeneous disorders characterised by concurrent hypoplasia of the pons and the cerebellum and variable clinical and imaging features. The current classification includes 13 subtypes, with ~20 known causative genes. Attempts have been made to delineate the phenotypic spectrum associated to specific PCH genes, yet clinical and neuroradiological features are not consistent across studies, making it difficult to define gene-specific outcomes.

METHODS

We performed deep clinical and imaging phenotyping in 56 probands with a neuroradiological diagnosis of PCH, who underwent NGS-based panel sequencing of PCH genes and MLPA for CASK rearrangements. Next, we conducted a phenotype-based unsupervised hierarchical cluster analysis to investigate associations between genes and specific phenotypic clusters.

RESULTS

A genetic diagnosis was obtained in 43 probands (77%). The most common causative gene was CASK, which accounted for nearly half cases (45%) and was mutated in females and occasionally in males. The European founder mutation p.Ala307Ser in TSEN54 and pathogenic variants in EXOSC3 accounted for 18% and 9% of cases, respectively. VLDLR, TOE1 and RARS2 were mutated in single patients. We were able to confirm only few previously reported associations, including jitteriness and clonus with TSEN54 and lower motor neuron signs with EXOSC3. When considering multiple features simultaneously, a clear association with a phenotypic cluster only emerged for EXOSC3.

CONCLUSION

CASK represents the major PCH causative gene in Italy. Phenotypic variability associated with the most common genetic causes of PCH is wider than previously thought, with marked overlap between CASK and TSEN54-associated disorders.

Novel unconventional variants expand the allelic spectrum of OPHN1 gene

Mutations in the OPHN1 gene cause a rare X-linked recessive neurodevelopmental disorder characterized by intellectual disability, variably associated with cerebellar hypoplasia and distinctive facial appearance. In most of cases so far reported, the identified genomic variants involve the region encoding the central RhoGAP domain of the oligophrenin-1 protein, and are predicted to result in a complete loss of function. By using a NGS-based diagnostic approach, we identified three male and a female patients from two unrelated families carrying novel non-disruptive OPHN1 variants (the in-frame c.116_127 deletion and the missense c.2129C>T change, respectively), affecting either the BAR domain or the C-terminus proline-rich domain of the protein. Clinical and neuroimaging findings in the patients recapitulated the main features of OPHN1-related syndrome, including developmental delay, intellectual disability, behavioral disorder, dysmorphic features, seizures, cerebellar hypoplasia, and ventriculomegaly. Yet, we observed a wide variability even among affected siblings, confirming the lack of clear genotype-phenotype correlation. Our results expand the allelic spectrum of OPHN1 and illustrate the challenges for clinical interpretation of non-disruptive variants affecting X-linked genes.

Age and sex prevalence estimate of Joubert syndrome in Italy

Objective

To estimate the prevalence of Joubert syndrome (JS) in Italy applying standards of descriptive epidemiology and to provide a molecular characterization of the described patient cohort.

Methods

We enrolled all patients with a neuroradiologically confirmed diagnosis of JS who resided in Italy in 2018 and calculated age and sex prevalence, assuming a Poisson distribution. We also investigated the correlation between proband chronological age and age at diagnosis and performed next-generation sequencing (NGS) analysis on probands' DNA when available.

Results

We identified 284 patients with JS: the overall, female- and male-specific population-based prevalence rates were 0.47 (95% confidence interval [CI] 0.41–0.53), 0.41 (95% CI 0.32–0.49), and 0.53 (95% CI 0.45–0.61) per 100,000 population, respectively. When we considered only patients in the age range from 0 to 19 years, the corresponding population-based prevalence rates rose to 1.7 (95% CI 1.49–1.97), 1.62 (95% CI 1.31–1.99), and 1.80 (95% CI 1.49–2.18) per 100,000 population. NGS analysis allowed identifying the genetic cause in 131 of 219 screened probands. Age at diagnosis was available for 223 probands, with a mean of 6.67 ± 8.10 years, and showed a statistically significant linear relationship with chronological age (r² = 0.79; p < 0.001).

Conclusions

We estimated for the first time the age and sex prevalence of JS in Italy and investigated the patients’ genetic profile. The obtained population-based prevalence rate was ≈10 times higher than that available in literature for children population.

Agenesis of the putamen and globus pallidus caused by recessive mutations in the homeobox gene GSX2

Basal ganglia are subcortical grey nuclei that play essential roles in controlling voluntary movements, cognition and emotion. While basal ganglia dysfunction is observed in many neurodegenerative or metabolic disorders, congenital malformations are rare. In particular, dysplastic basal ganglia are part of the malformative spectrum of tubulinopathies and X-linked lissencephaly with abnormal genitalia, but neurodevelopmental syndromes characterized by basal ganglia agenesis are not known to date. We ascertained two unrelated children (both female) presenting with spastic tetraparesis, severe generalized dystonia and intellectual impairment, sharing a unique brain malformation characterized by agenesis of putamina and globi pallidi, dysgenesis of the caudate nuclei, olfactory bulbs hypoplasia, and anomaly of the diencephalic-mesencephalic junction with abnormal corticospinal tract course. Whole-exome sequencing identified two novel homozygous variants, c.26C>A; p.(S9*) and c.752A>G; p.(Q251R) in the GSX2 gene, a member of the family of homeobox transcription factors, which are key regulators of embryonic development. GSX2 is highly expressed in neural progenitors of the lateral and median ganglionic eminences, two protrusions of the ventral telencephalon from which the basal ganglia and olfactory tubercles originate, where it promotes neurogenesis while negatively regulating oligodendrogenesis. The truncating variant resulted in complete loss of protein expression, while the missense variant affected a highly conserved residue of the homeobox domain, was consistently predicted as pathogenic by bioinformatic tools, resulted in reduced protein expression and caused impaired structural stability of the homeobox domain and weaker interaction with DNA according to molecular dynamic simulations. Moreover, the nuclear localization of the mutant protein in transfected cells was significantly reduced compared to the wild-type protein. Expression studies on both patients' fibroblasts demonstrated reduced expression of GSX2 itself, likely due to altered transcriptional self-regulation, as well as significant expression changes of related genes such as ASCL1 and PAX6. Whole transcriptome analysis revealed a global deregulation in genes implicated in apoptosis and immunity, two broad pathways known to be involved in brain development. This is the first report of the clinical phenotype and molecular basis associated to basal ganglia agenesis in humans.

Hypomorphic Recessive Variants in SUFU Impair the Sonic Hedgehog Pathway and Cause Joubert Syndrome with Cranio-facial and Skeletal Defects

The Sonic Hedgehog (SHH) pathway is a key signaling pathway orchestrating embryonic development, mainly of the CNS and limbs. In vertebrates, SHH signaling is mediated by the primary cilium, and genetic defects affecting either SHH pathway members or ciliary proteins cause a spectrum of developmental disorders. SUFU is the main negative regulator of the SHH pathway and is essential during development. Indeed, Sufu knock-out is lethal in mice, and recessive pathogenic variants of this gene have never been reported in humans. Through whole-exome sequencing in subjects with Joubert syndrome, we identified four children from two unrelated families carrying homozygous missense variants in SUFU. The children presented congenital ataxia and cerebellar vermis hypoplasia with elongated superior cerebellar peduncles (mild "molar tooth sign"), typical cranio-facial dysmorphisms (hypertelorism, depressed nasal bridge, frontal bossing), and postaxial polydactyly. Two siblings also showed polymicrogyria. Molecular dynamics simulation predicted random movements of the mutated residues, with loss of the native enveloping movement of the binding site around its ligand GLI3. Functional studies on cellular models and fibroblasts showed that both variants significantly reduced SUFU stability and its capacity to bind GLI3 and promote its cleavage into the repressor form GLI3R. In turn, this impaired SUFU-mediated repression of the SHH pathway, as shown by altered expression levels of several target genes. We demonstrate that germline hypomorphic variants of SUFU cause deregulation of SHH signaling, resulting in recessive developmental defects of the CNS and limbs which share features with both SHH-related disorders and ciliopathies.

ALS5/SPG11/KIAA1840 mutations cause autosomal recessive axonal Charcot-Marie-Tooth disease

Charcot-Marie-Tooth disease is a group of hereditary peripheral neuropathies that share clinical characteristics of progressive distal muscle weakness and atrophy, foot deformities, distal sensory loss, as well as diminished tendon reflexes. Hundreds of causative DNA changes have been found, but much of the genetic basis of the disease is still unexplained. Mutations in the ALS5/SPG11/KIAA1840 gene are a frequent cause of autosomal recessive hereditary spastic paraplegia with thin corpus callosum and peripheral axonal neuropathy, and account for ∼ 40% of autosomal recessive juvenile amyotrophic lateral sclerosis. The overlap of axonal Charcot-Marie-Tooth disease with both diseases, as well as the common autosomal recessive inheritance pattern of thin corpus callosum and axonal Charcot-Marie-Tooth disease in three related patients, prompted us to analyse the ALS5/SPG11/KIAA1840 gene in affected individuals with autosomal recessive axonal Charcot-Marie-Tooth disease. We investigated 28 unrelated families with autosomal recessive axonal Charcot-Marie-Tooth disease defined by clinical, electrophysiological, as well as pathological evaluation. Besides, we screened for all the known genes related to axonal autosomal recessive Charcot-Marie-Tooth disease (CMT2A2/HMSN2A2/MFN2, CMT2B1/LMNA, CMT2B2/MED25, CMT2B5/NEFL, ARCMT2F/dHMN2B/HSPB1, CMT2K/GDAP1, CMT2P/LRSAM1, CMT2R/TRIM2, CMT2S/IGHMBP2, CMT2T/HSJ1, CMTRID/COX6A1, ARAN-NM/HINT and GAN/GAN), for the genes related to autosomal recessive hereditary spastic paraplegia with thin corpus callosum and axonal peripheral neuropathy (SPG7/PGN, SPG15/ZFYVE26, SPG21/ACP33, SPG35/FA2H, SPG46/GBA2, SPG55/C12orf65 and SPG56/CYP2U1), as well as for the causative gene of peripheral neuropathy with or without agenesis of the corpus callosum (SLC12A6). Mitochondrial disorders related to Charcot-Marie-Tooth disease type 2 were also excluded by sequencing POLG and TYMP genes. An additional locus for autosomal recessive Charcot-Marie-Tooth disease type 2H on chromosome 8q13-21.1 was excluded by linkage analysis. Pedigrees originated in Italy, Brazil, Canada, England, Iran, and Japan. Interestingly, we identified 15 ALS5/SPG11/KIAA1840 mutations in 12 families (two sequence variants were never reported before, p.Gln198* and p.Pro2212fs*5). No large deletions/duplications were detected in these patients. The novel mutations seemed to be pathogenic since they co-segregated with the disease in all pedigrees and were absent in 300 unrelated controls. Furthermore, in silico analysis predicted their pathogenic effect. Our results indicate that ALS5/SPG11/KIAA1840 is the causative gene of a wide spectrum of clinical features, including autosomal recessive axonal Charcot-Marie-Tooth disease.

Complications associated with arthroscopic rotator cuff repair: a literature review

The aim of this literature review was to report complications associated with arthroscopic rotator cuff repair (RCR). A computerized search of articles published between 200 and 2009 was performed using MEDLINE and PubMed. We included clinical studies (Level 1-4): (a) investigating patients with rotator cuff tears, managed by a completely arthroscopic RCR technique; (b) reported data about complications. Data about arthroscopic-assisted techniques were excluded. Articles that meet criteria inclusion were analytically examined. Complications were classified into general complications and specific complications related to arthroscopic RCR. We found 414 complications in 2,890 patients; most of them were specific complications related to arthroscopic RCR. Re-rupture was the most frequently encountered complication: re-tear rate ranged between 11.4 and 94%. Stiffness and hardware-related complications were observed in 74 and 12 patients, respectively. Eleven less common complications were also reported: 5 neurovascular, 3 septic, 2 thromboembolic events, and 1 anesthesiological complication. This review stated that arthroscopic RCR is a low-risk surgical procedure. Anatomical failure of the repair is the most common complication encountered in the literature.

Use of sibutramine, an inhibitor of the reuptake of serotonin and noradrenaline, in the treatment of binge eating disorder: a placebo-controlled study

Binge-eating disorder, which is characterized by repeated episodes of uncontrolled eating, is common in obese patients and is often accompanied by comorbid psychiatric disorders, especially depression. In previous studies, selective serotonin reuptake inhibitors have demonstrated efficacy in reducing the frequency of binge eating and addressing comorbid psychiatric disorders, but they have not shown the ability to promote weight loss. Sibutramine, a new serotonin and norepinephrine reuptake inhibitor, has been shown in short- and long-term studies to be effective in promoting and maintaining weight loss in obese patients who have binge-eating disorder. In this randomized, double-blind, placebo-controlled study, the efficacy, safety, and tolerability of sibutramine were evaluated in the treatment of binge-eating disorder in obese patients. Twenty patients were randomly assigned in equal numbers to receive either sibutramine 10 mg/day or placebo for 12 weeks. Assessments were made at baseline and every 2 weeks throughout the study. Binge frequency, defined as the number of days during the previous week that included binge-eating episodes, was the primary outcome measure. By the end of the study, the binge frequency among patients given sibutramine was significantly lower than that among those given placebo. The main adverse events in the sibutramine group were dry mouth and constipation. The findings suggest sibutramine is an effective medication in the treatment of binge-eating disorders and is well tolerated. In addition, it addresses the 3 main goals in the treatment of binge-eating disorder: reducing the frequency of binge eating, promoting and maintaining weight loss, and treating the comorbid psychiatric conditions.

Cryptococcus neoformans infection in a cohort of Italian AIDS patients: natural history, early prognostic parameters, and autopsy findings

This observational cohort study of 4,160 AIDS patients hospitalised in a single institution in northern Italy between January 1985 and December 1999 was carried out in order to assess the natural history of cryptococcosis, the epidemiological trend of this opportunistic infection, the risk factors predictive of death at 10 weeks, the response to therapy, and autopsy findings. Cryptococcosis was diagnosed in 177 (4.2%) patients and was the AIDS-defining disease in 2.8% of cases. Its prevalence decreased significantly over time (from 6.4% in the period 1985-1989 to 5.7% in 1990-1993, 3.1% in 1994-1996, and 1.9% in 1997-1999, P <0.0001). Although neurologic disease was the most frequent clinical picture, a significant proportion of the patients (24.2%) presented with extraneural cryptococcosis. In a Cox multivariate analysis, high titres of cerebrospinal fluid antigen (>5000) and drug addiction were predictive of death at 10 weeks. A complete clinical and mycological response was achieved in 60.8% of the treated patients, with the highest response rate being observed in those treated with amphotericin plus flucytosine (66.6%). Cryptococcosis relapsed in 12.8% of patients on secondary prophylaxis. Autopsy findings demonstrated that cryptococcosis is a disseminated disease, but long-term antifungal treatment may be able to eradicate it in a subgroup of patients.

Papillary carcinoma of the base of the tongue. Case clinic

Ectopic lingual thyroid tissue is an uncommon developmental anomaly. Tumours of identical pathological characteristics as those arising in the eutropic thyroid tissue, may be present in ectopic locations. There are very few cases of malignant tumours reported in the literature. Here we report a review of this pathology and we describe a case of a papillary carcinoma of the base of the tongue, located in ectopic lingual thyroid tissue, in a 66 year-old white man, complaining of dysphagia and oral bleeding. Surgical treatment was carried out, consisting of radical resection of the right hemineck, tumour resection, right hemiglossectomy and total thyroidectomy. Postoperative treatment with 131I and substitutive thyroid hormonal therapy was prescribed.

Diffuse acute cellulitis with severe neurological sequelae. A clinical case

The incidence of head and neck odontogenic infections considerably diminished in the last decades due to appropriate antibiotic therapy. Herein we describe a case of acute diffuse facial cellulitis following tooth extraction in a patient with no apparent risk factor. During the acute process, injury was caused to the hypoglossal, vagal, glossopharyngeal and recurrent nerves of both sides. For this reason the patient currently has a nasogastric line for enteral feedings and a tracheotomy tube, which significantly affects his quality of life.

[Oncologic post-resection reconstruction of mandibular defects]

BACKGROUND AND AIM

If not reconstructed, mandibular defects resulting from oncological surgery can leave major functional and cosmetic sequelae which may impede these patients from returning to professional and family life. Reconstruction may be immediate or deferred, but the authors clearly recommend immediate reconstruction.

METHODS

An analysis is made of the different techniques used for the reconstruction of mandibular defects, specifying those which are currently used and the situations in which they are applied. The advantages and disadvantages of microsurgical flaps and pedicled flaps are emphasised. The immediate use of endosseous implants is also discussed.

RESULTS

The results of the various types of reconstruction are compared from a cosmetic and functional point of view. The latter includes a study of the quality of speech, deglutition, mastication and labial competence. Mastication is studied in two types of patients: those with osteointegrated implants with neomandibular reconstruction and those in whom osteointegrated implants were not used. All these patients survived 5 years after surgery.

CONCLUSIONS

The authors recommend the immediate reconstruction of mandibular defects. Microsurgical flaps and pedicled flaps can be used for this purpose. Bone flaps may be used for endosseous titanium implants, whereas osseous flaps which do not provide a sufficient guarantee of rehabilitation should not be used. Implants should be inserted during oncological surgery, since postoperative radiotherapy may alter osteointegration of titanium implants are then used. The overall survival of these patients depends on the margins of local resection which are much wider using these techniques.

[A statistical contribution to fractures of the maxillofacial area]

Twenty years experience (from 1975 to 1994), on 483 patients with injury of the maxillo-facial area observed at the Department of Maxillo-Facial Surgery of the University of Naples "Federico II" is reported. The analysis of the data, according to the literature, shows that the sex most involved is male (76%) with a prevalence of the second decade of life (38%); street injury is the most frequent cause of maxillo-facial fracture (48.5%), while in 1.6% the cause is not reported. Mandibular fractures (57%), particularly those of the left condyle, are more frequent. The type of treatment is discussed in relation to the site of fracture, in particular the therapy of the condylar ones. In fact, in the treatment of those fractures the authors use sequential functional plates, the first of whose presents a monolateral byte, homolateral to the injury, while the second a contralateral guide in closure. The use of such plates, even if it doesn't often obtain a perfect anatomical realignment of the fracture, allows an optimal functional rehabilitation due to the potential of remodelling of the condyle, avoiding complications related to surgical intervention.

The role of allopurinol in preventing oxygen free radical injury to skeletal muscle and endothelial cells after ischemia-reperfusion

One of the most important mechanisms in the production of ischemic damage after replantation surgery is the rise of oxygen free radicals during revascularization of ischemic tissues. Free radicals produce damage in the cell membranes (lipoperoxydation). This occurs not only in muscle tissue, but also in endothelial cells, with a consequent increase of local edema and the risk of compartment syndrome. This study attempted to interrupt the ischemic-reperfusion injury process in ischemic rat hindlimbs. Complete ischemia was induced for different numbers of hours (3, 6, 9, 12 hr) in four groups of rats (24 animals in each group). Allopurinol, an oxygen free radical scavenger, was tested in solution, 12.5 mg/kg b.w., in half the studied animals (n = 12). Collected data showed an increase (mean value: 0.60 nM/mg 3 hri 0.90 nM/mg at 6 hr; 0.80 nM/mg at 9 hr; 0.89 nM/mg at 12 hr; mean value in nonischemic muscle = 0.526 nM/mg) in lipoperoxides (NS between treated/untreated groups, p > 0.05) and high tissue pressure values in the posterior compartment of the ischemic rat hindlimbs. Allopurinol reduced the pressure values (p < 0.05 in Groups 1-3; p < 0.1 in Group 4), but was not effective in reducing lipoperoxides in skeletal muscle.

[The correlation between sonoarthrographic and arthroscopic data. Its verification in a clinical case]

Surgical arthroscopy is an important option in the treatment of TMJ pain and disfunction. Also sonography of the TMJ is a technique that with recent improvements graphically displays and analyzes joint sounds. A comparison was performed between presurgical data obtained by sonography, clinical findings obtained by surgical arthroscopy, and post surgical control performed by sonography. Precise correlation between these data was found in the case reported.

Influence of cigarette smoking on pituitary and sex hormone balance in healthy premenopausal women

Plasma gonadotropin FSH and LH, PRL, sex steroids (17-beta E2, E1, and P), SBP binding capacity, and urine estrogens (E1, E2, and E3) were measured in 485 premenopausal healthy women, subdivided according to smoking habits. The aim of the study was to verify if cigarette smoking influences sex hormone balance. Baseline PRL levels were significantly lower (P less than 0.002) in smoker (n = 174) than in nonsmoker (n = 311) women. No difference was found in the other parameters of the two groups, particularly in plasma and urine estrogenic pattern. Our data suggest that smoking directly affects PRL levels by involving the hypothalamic mechanism that regulates PRL secretion.

Synthesis, spectral properties and enzymatic hydrolysis of fluorescent derivatives of cerebroside sulfate containing long-wavelength-emission probes

Fluorescent derivatives of cerebroside sulfate (sulfogalactosyl ceramide, sulfatide) containing long-wavelength-emission fluorophores were synthesized. For this purpose a procedure was developed for preparing a cerebroside 3-sulfate derivative with an amino group on the terminal carbon atom of its fatty acyl residue. The latter compound has been used to prepare cerebroside 3-sulfate, coupled to lissamine-rhodamine, fluoresceine, eosine and NBD. The spectroscopic properties of these compounds, in different solvent systems and when incorporated into micelles of a non-ionic detergent or liposomes of a phospholipid, are reported. Incubation of these respective sulfatides with a human leukocyte preparation, resulted in the formation of the corresponding fluorescent cerebrosides.

Rapid preparation of a distinct lysosomal population from myelinating mouse brain using Percoll gradients

To study the vesicular lysosome-associated transport and the metabolism of some brain macromolecules (in particular, sialoglycoconjugates), we developed a rapid procedure to obtain a distinct lysosomal population starting from myelinating mouse brain. This procedure is based on an initial differential centrifugation step producing a 1,000-17,500-g fraction (P2), followed by isopycnic centrifugation of fraction P2 on a self-generated colloidal silica gel (Percoll) gradient. The heaviest subfraction thus obtained is very rich in acid hydrolase activities like beta-galactosidase, arylsulfatase A, and acid phosphatase. The enrichment of these enzymes is approximately 100-fold as compared with the starting homogenate, whereas the markers of other subcellular organelles, such as mitochondria, plasma membranes, or the Golgi apparatus, are virtually absent. The lysosomal preparation contains approximately 12-14% of the total acid hydrolase activities, with a protein yield of approximately 0.12%. Electron microscopy shows that the lysosomal fraction is composed of an approximately 90% pure population of lysosomes. Therefore, the procedure described here is suitable for obtaining a highly purified lysosome preparation from myelinating mouse brain.

Rat liver L-threonine deaminase: properties and purification

A new method of purification of rat liver L-threonine deaminase has been developed, and the results obtained are compared with values obtained by other authors. Some properties of this enzyme (pH optimum, temperature optimum, thermal stability, specificity, etc.) have been examined and we found that the enzyme is inhibited by carbonate ions, that L-cysteine (a competitive inhibitor) is also an inactivator of the enzyme and that it is bound to the enzyme in a ratio of 0.25 mole of cysteine per mole of enzyme, supporting the hypothesis that the enzyme consists of 4 subunits.

Specificity of the reaction of rat liver L-serine dehydratase with aminothiols

The degree, the mechanism, and the specificity of the inhibition of purified rat-liver L-serine dehydratase (EC 4.2.1.13) by L-cysteine and aminothiols have been investigated. All the aminothiols tested react with free pyridoxal-5'-phosphate (PLP); only L-cysteine reacts with PLP bound to the enzyme giving an absorption spectrum similar to that of the thiazolidinic ring formed in the chemical reaction. The reaction between L-cysteine and PLP bound to the enzyme has a particular behaviour, different from all the other aminothiols. A stereospecific interaction between L-cysteine and PLP bound to the enzyme, forming one of the two possible diastereoisomers, is postulated.

[The influence of fasting, of a hyperprotein diet and of nicotinamide on hepatic L-threonine deaminase]

The induction of L-threonine deaminase, following nicotinamide injection has been studied: the effect of fasting and of hyperproteic diet have been also taken in consideration. Maximal induction is observed after 5 days hyperproteic diet, and is additional only with nicotinamide treatment. Results are interpreted assuming a different hepatic content and behavior of multiple forms of the enzyme.