Overcoming the Limitations of Organocatalyzed Glycolysis of Poly(ethylene terephthalate) to Facilitate the Recycling of Complex Waste Under Mild Conditions.

Although multiple methods have been reported in the literature for the chemical recycling of poly(ethylene terephthalate) (PET), large-scale depolymerization is not yet widely employed. The main reasons for the limited adoption of chemical recycling of PET are the harsh conditions required and the lack of selectivity. In this study, the organocatalytic glycolysis of PET mediated by organic bases at low temperatures is studied, and routes to avoid the deactivation of the catalyst are explored. It is shown that the formation of terephthalic acid by uncontrolled hydrolysis leads to issues which can be resolved using potassium tert-butoxide as a cocatalyst. Finally, complex PET waste obtained from a mechanical recycling plant was depolymerized under optimized conditions, obtaining bis(2-hydroxyethyl) terephthalate yields >90% in less than 15 min at only 100 °C. These results open the way to efficient recycling of PET-enriched waste streams under milder conditions.

Co-localization of TSC1 and TSC2 gene products in tubers of patients with tuberous sclerosis.

Two genes, mutations in which result in the phenotype of tuberous sclerosis (TSC), have recently been cloned. TSC2 on chromosome 16p13.3 encodes the protein tuberin, which appears to have growth regulating properties. TSC1 on chromosome 9q34 encodes hamartin which, as yet, has no specified cellular functions. Polyclonal antibodies were raised to synthetic peptides representing portions of tuberin and hamartin and used in immunoblots and immunohistochemical studies to localize the proteins in surgically resected neocortical tubers from four TSC patients. On Western blots of autopsy brain specimens, K-562 cell, and NT2 lysates, each antibody labelled a single band at the expected molecular weight. In immunohistochemical protocols on paraffin embedded tissue, antibodies to both tuberin and hamartin prominently labelled atypical and dysmorphic neuroglial cells that are a defining feature of TSC tubers. Some abnormal cells within cortical tuber sections were labelled with both tuberin and hamartin antisera. Our results suggest that tuberin and hamartin are both robustly expressed in similar populations of neuroglial cells of TSC tubers, even in the presence of TSC1 or TSC2 germline mutations. The roles of these gene products in normal and abnormal cortical development, tuber pathogenesis and the generation of seizures remain to be defined.

Congenital olivopontocerebellar atrophy: report of two siblings with paleo- and neocerebellar atrophy.

We report two sisters with congenital olivopontocerebellar atrophy, including immunohistochemical studies of autopsy brain tissue. Both cases showed microcephaly with disproportionately marked hypoplasia of the posterior fossa structures including pons, inferior olivary nuclei, and cerebellum. Microscopically, the pons was atrophic with near total loss of pontine nuclei and transverse pontocerebellar tracts (inferior and middle cerebellar peduncles). The medulla showed absent inferior olivary and arcuate nuclei. The cerebellum showed hypoplasia with rudimentary dentate nuclei, profound loss of Purkinje cells and external granule cell layer, a sparse internal granule cell layer of the entire dorsal vermis and the dorsal portions of the lateral folia, as well as markedly reduced underlying axon fibers in the white matter with marked astrogliosis. These features were highlighted by immunohistochemical study using antibodies against Purkinje cell epitopes, synaptophysin, neurofilament, glial fibrillary acidic protein, and tuberin. The cerebral hemispheres were unremarkable. Our cases are characterized by a pattern of diffuse posterior cerebellar involvement that has rarely been described in previous reports. An autosomal recessive pattern of inheritance is suggested. The abnormalities may result from antenatal degeneration or atrophy of neurons in the involved sites rather than hypoplasia or developmental arrest starting in the second and third month of late embryonic life.

Tuberous sclerosis-related gene expression in normal and dysplastic brain.

Cortical dysplasia (CD) broadly defines a complex cerebral malformative lesion associated clinically with intractable, pharmacoresistant epilepsy (including infantile spasms), especially in infants and children. In CD, the spectrum of structural brain abnormalities includes (at a minimum) neuronal dyslamination and (in severe cases) neuronal cytomegaly with cytoskeletal alterations and the presence of gemistocyte-like 'balloon cells'. In some CD variants, the neuropathological features are essentially indistinguishable from those of a tuber of tuberous sclerosis (TSC). Two genes associated with the autosomal dominant, multi-system disorder TSC have recently been cloned: TSC2 (on chromosome 16p13.3) encodes the protein tuberin and TSC1 (on 9q34) encodes hamartin. Tuberin has been immunolocalized to neurons and possibly astrocytes in normal brain and CD/TSC tubers, and is widely expressed in normal viscera; loss of heterozygosity and tissue culture studies suggest it functions as a growth suppressor. The TSC1 gene has been cloned within the last year and hamartin as yet has no well-defined cellular function, though its protein product may also function as a growth suppressor. This article focuses on the cellular pathogenesis of CD and TSC brain lesions and how the two may be biologically related. Studies of how TSC1 and TSC2 function in normal and dysplastic cerebral neocortex may provide a paradigm for understanding the neurobiology of other genes that determine epilepsy-associated cerebral malformations (e.g. lissencephaly, double cortex).

Micronodular pneumocyte hyperplasia.

Tuberous sclerosis complex (TSC) is an autosomal-dominant disorder characterized by mental retardation, seizures, and central nervous system and visceral hamartomas. Pulmonary involvement manifesting as lymphangioleiomyomatosis (LAM) occurs in 1% of patients (all women) with TSC. Micronodular pneumocyte hyperplasia also has been described as a rare pulmonary manifestation of TSC. We report 14 patients with micronodular pneumocyte hyperplasia (MNPH). The patients ranged in age from 23 to 57 years (mean 37.5). There were 12 women and 2 men. Nine of the patients (one man and eight women) had documented clinical manifestations of TSC: seven with LAM, two without LAM (including one man). Of the five patients who did not have TSC, three had LAM and two did not (including one man). Histologically, all 14 cases demonstrated multiple well-demarcated nodules usually measuring up to 8 mm in size, but most were 1-3 mm. The nodules were produced by a proliferation of enlarged cytologically benign type II pneumocytes, with an associated increase in alveolar macrophages and interstitial reticulin. Immunoperoxidase studies showed the type II pneumocytes within lesions to be reactive with antibodies to cytokeratin (four of four), epithelial membrane antigen (EMA) (five of five), and surfactant apoprotein B (8 of 10). HMB-45 was negative in the MNPH lesions in all nine cases studied. Follow-up was available in 9 of 10 living patients and ranged from 1 to 14 years (mean 6 years). Nine patients are alive; six are clinically stable and three have repeated pneumothoraces related to LAM. Four patients have died. None of the deaths were attributable to MNPH. MNPH appears to be a hamartomatous proliferation occurring most frequently in patients with tuberous sclerosis, is separable from and not a manifestation of LAM, has been observed to occur in men, and, like other hamartomas of tuberous sclerosis, does not appear to possess malignant potential.

Tissue and cell-type specific expression of the tuberous sclerosis gene, TSC2, in human tissues.

TSC2 is a gene on chromosome 16p13.3 associated with the autosomal dominant neurocutaneous disorder, tuberous sclerosis complex (TSC). By using a partial nucleotide sequence from the cloned TSC2 and polymerase chain reaction methodology, we constructed a digoxigenin-labeled complementary DNA probe to examine TSC2 gene expression in autopsy- or biopsy-derived human tissues by in situ hybridization. TSC2 messenger RNA was widely expressed in various cell types throughout the body, including epithelia, lymphocytes, and cells with endocrine functions, e.g., adrenal cortex and anterior pituitary. It was prominently and selectively (within the central nervous system) expressed in pyramidal cells of the cerebral cortex and other motor neurons, e.g., in spinal cord and brainstem nuclei. Visceral TSC2 expression was comparable in autopsy tissues from patients with and without TSC; TSC2 messenger RNA expression was most prominent in cells with a rapid mitotic rate and turnover, e.g., epithelia and lymphocytes, with central nervous system pyramidal cells and other neurons being an obvious exception, and/or in cells with important secretory/transport functions. This widespread expression of the TSC2 gene supports the view that it encodes a protein vital to cell growth and metabolism or one that functions as a tumor/growth suppressor.

Localization of tuberous sclerosis 2 mRNA and its protein product tuberin in normal human brain and in cerebral lesions of patients with tuberous sclerosis.

Tuberous sclerosis (TSC), an autosomal dominant disorder, is characterized by malformations, hamartomas and tumors in various organs including the brain. TSC is genetically linked to two loci: TSC1 on chromosome 9q34 and TSC2 on 16p13.3. TSC2 has been cloned, sequenced and encodes a protein (tuberin) which functions as a tumor suppressor. We have analyzed the distribution of TSC2 mRNA and tuberin in the brains of TSC patients and non-affected individuals using both autopsy and biopsy material. High levels of transcript and protein expression were observed in choroid plexus epithelium, ependymal cells, most brainstem and spinal cord motor neurons, Purkinje cells and the external granule cell layer of the cerebellum in both TSC and control cases. Individual balloon cells from TSC patients showed very faint expression while other glia showed no expression of either transcript or tuberin. Neocortical and hippocampal neurons expressed high levels of TSC2 transcript, but only modest levels of tuberin. The internal granule cell layer of the cerebellum expressed abundant transcript but low levels of tuberin. These observations suggest either that tuberin expression is controlled at the level of both transcription and translation or the antibody and in-situ hybridization recognize different splice variants of the TSC2 gene. In TSC patients, dysmorphic cytomegalic neurons expressed high levels of tuberin and transcript, particularly when in an 'ectopic' location. Individual cells within subependymal giant cell astrocytomas (SEGAs) and hamartomas from TSC patients expressed moderate to high levels of TSC2 transcript and tuberin. While the TSC2 transcript is widely expressed primarily within neurons, tuberin is demonstrable primarily within dysplastic/cytomegalic cells of the cortex and subependymal hamartomas/SEGAs. CNS expression of tuberin is unique in that primarily non-dividing cells express it in this location, whereas extra-CNS expression of tuberin is mainly found in actively proliferating cell types such as epithelium.