Polyamines modulate the binding of GABAA-benzodiazepine receptor ligands in membranes from the rat forebrain.

The effects of spermine, spermidine and putrescine on the binding of the GABAA-benzodiazepine receptor complex were examined in the hippocampus and frontal cortex membranes of the rat. The results demonstrated modulatory effects of polyamines on the binding of diazepam and flunitrazepam but not on that of GABA, muscimol and Ro 15-1788. When membranes were prepared without detergent, the polyamines enhanced the binding of diazepam. However, while the binding capacity increased after homogenization in the presence of the non-ionic detergent Triton X-100, the polyamines did not enhance the binding but inhibited the binding of diazepam and flunitrazepam at greater concentrations. Considered together with other studies, the present findings indicate that polyamines can modulate the binding characteristics of several different neurotransmitter receptor-ionophore complexes.     

Assessment of 5α-reductase activity in hirsute women: comparison of serum androstanediol glucuronide with urinary androsterone and aetiocholanolone excretion

OBJECTIVE Recent evidence suggests that androstanediol glucuronide (AG), a metabolite of dihydrotestosterone (DHT) formed in skin, is frequently elevated in hirsute women, presumably reflecting enhanced 5a-reductase activity. An alternative method of demonstrating 5a-reductase activity is the androsterone (A)/aetiocholano-lone (E) ratio in urine. A and E are the 5α- and 5β- reduced metabolites, respectively, of androstenedione, which is the principal metabolite of dehydroepiandrosterone (D). Although serum AG and the urinary A/E ratio have both been considered valid methods for assessing 5α-reductase activity, the two have not been previously compared in hirsute women. The present study was undertaken to assess 5a-reductase activity in hirsute patients as determined by these two different methods. PATIENTS AND MEASUREMENTS We surveyed 47 untreated women (ages 17–33) with various degrees of hirsutism. Serum testosterone, bioavailable testosterone, dehydroepiandrosterone sulphate, and AG were determined. Additionally, A, E and D were measured in 24-hour collections of urine. RESULTS For the 47 women, 37 had elevated blood levels of AG (17.4 ± 2.2, mean±SEM; normal <8 nmol/l), but only 18 of these had an increased urinary A/E ratio (> 1.5). All but one of the remainder had elevated urinary and/or serum androgen levels. Overall, no significant correlation between AG and A/E was observed. There was a highly significant correlation between AG in serum and A in urine (r= 0.82, P<0 001). AG was also positively related to dehydroepiandrosterone sulphate (r= 0.64; P< 0.005), bioavailable testosterone (r= 0.6; P<0001), aetiocholanolone (r= 0.58; P<0 001) and total testosterone (r= 0.52; P& 0.01). In contrast, A/E was not significantly related to androgen production. CONCLUSIONS There is a poor correlation between AG and the A/E ratio in hirsute women. Although AG may be raised by increased 5α-reductase activity, it is probably also affected by the presence of elevated androgens regardless of 5α-reductase activity.     

Spontaneous ovarian hyperstimulation mimicking an ovarian tumour

Ovarian hyperstimulation syndrome in a spontaneous singletonpregnancy is exceedingly rare. We report a case of ovarian hyperstimulationpresenting as bilateral ovarian masses in association with spontaneouspregnancy, occurring in a woman with disturbed liver function.A possible mechanism is discussed.     

Increased yield of full GBA sequencing in Ashkenazi Jews with Parkinson's disease

Background

Variants in GBA are the most common genetic risk factor for Parkinson's disease (PD), and are especially prevalent in the Ashkenazi Jewish (AJ) population. However, most studies on GBA in AJ genotype only seven selected Gaucher-associated pathogenic variants rather than sequencing the whole gene, which may leave carriers of PD-associated GBA variants undiscovered.

Predominance of null mutations in ataxia-telangiectasia

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder involving cerebellar degeneration, immunodeficiency, chromosomal instability, radiosensitivity and cancer predisposition. The responsible gene, ATM, was recently identified by positional cloning and found to encode a putative 350 kDa protein with a Pl 3-kinase-like domain, presumably involved in mediating cell cycle arrest in response to radiation-induced DNA damage. The nature and location of A-T mutations should provide insight into the function of the ATM protein and the molecular basis of this pleiotropic disease. Of 44 A-T mutations identified by us to date, 39 (89%) are expected to inactivate the ATM protein by truncating it, by abolishing correct initiation or termination of translation, or by deleting large segments. Additional mutations are four smaller in-frame deletions and insertions, and one substitution of a highly conserved amino acid at the Pl 3-kinase domain. The emerging profile of mutations causing A-T is thus dominated by those expected to completely inactivate the ATM protein. ATM mutations with milder effects may result in phenotypes related, but not identical, to A-T.      

Childhood Cancer and the Risk of ESKD

BackgroundIncreasing cancer incidence among children alongside improved treatments has resulted in a growing number of pediatric cancer survivors. Despite childhood cancer survivors’ exposure to various factors that compromise kidney function, few studies have investigated the association between childhood cancer and future kidney disease.MethodsTo assess the risk of ESKD among childhood cancer survivors, we conducted a nationwide, population-based, retrospective cohort study that encompassed all Israeli adolescents evaluated for mandatory military service from 1967 to 1997. After obtaining detailed histories, we divided the cohort into three groups: participants without a history of tumors, those with a history of a benign tumor (nonmalignant tumor with functional impairment), and those with a history of malignancy (excluding kidney cancer). This database was linked to the Israeli ESKD registry to identify incident ESKD cases. We used Cox proportional hazards models to estimate the hazard ratio (HR) of ESKD.ResultsOf the 1,468,600 participants in the cohort, 1,444,345 had no history of tumors, 23,282 had a history of a benign tumor, and 973 had a history of malignancy. During a mean follow-up of 30.3 years, 2416 (0.2%) participants without a history of tumors developed ESKD. Although a history of benign tumors was not associated with an increased ESKD risk, participants with a history of malignancy exhibited a substantially elevated risk for ESKD compared with participants lacking a history of tumors, after controlling for age, sex, enrollment period, and paternal origin (adjusted HR, 3.2; 95% confidence interval, 1.3 to 7.7).ConclusionsChildhood cancer is associated with an increased risk for ESKD, suggesting the need for tighter and longer nephrological follow-up.     

Accumulation of exogenous polyamines in gerbil brain after ischemia

Regionally selective delayed neuronal degeneration is a characteristic sequel of cerebral ischemia. Recent evidence indicates that changes in brain polyamine metabolism may be critical for nerve cell survival after ischemia. Within hours after ischemia, intracellular putrescine levels are greatly increased and remain elevated for days, whereas only minor changes are noted in the levels of the polyamines spermine and spermidine. In contrast, the extracellular levels of all polyamines are low after ischemia. Injections of polyamines following ischemia, however, can protect neurons in the gerbil brain from delayed cell death, with spermine being the most potent of the polyamines. In the present study, therefore, we sought to determine if increased polyamine uptake occurs in the brain after ischemia. In the hippocampal slice preparation, temperature-dependent uptake was unique for spermine, but not for spermidine or putrescine. Uptake of [¹⁴C]spermine was transiently increased after ischemia, peaking at 150% of control by 12–13 h and subsiding by 24 h. Intravenous injections of [³H]spermidine resulted in a postischemic accumulation of this polyamine throughout the forebrain parenchyma. We conclude that:

1. Active cellular uptake of spermine is transiently increased early after ischemia;
2. A nonspecific accumulation of exogenous polyamines occurs early after ischemia probably owing to a compromised blood-brain barrier, and
3. The findings indicate that exogenous polyamines can exert their effect directly in the brain after ischemia.

     

Phosphorylation of Ribosomal Protein S6 Mediates Mammalian Target of Rapamycin Complex 1–Induced Parathyroid Cell Proliferation in Secondary Hyperparathyroidism

Secondary hyperparathyroidism is characterized by increased serum parathyroid hormone (PTH) level and parathyroid cell proliferation. However, the molecular pathways mediating the increased parathyroid cell proliferation remain undefined. Here, we found that the mTOR pathway was activated in the parathyroid of rats with secondary hyperparathyroidism induced by either chronic hypocalcemia or uremia, which was measured by increased phosphorylation of ribosomal protein S6 (rpS6), a downstream target of the mTOR pathway. This activation correlated with increased parathyroid cell proliferation. Inhibition of mTOR complex 1 by rapamycin decreased or prevented parathyroid cell proliferation in secondary hyperparathyroidism rats and in vitro in uremic rat parathyroid glands in organ culture. Knockin rpS6^p−/− mice, in which rpS6 cannot be phosphorylated because of substitution of all five phosphorylatable serines with alanines, had impaired PTH secretion after experimental uremia- or folic acid–induced AKI. Uremic rpS6^p−/− mice had no increase in parathyroid cell proliferation compared with a marked increase in uremic wild–type mice. These results underscore the importance of mTOR activation and rpS6 phosphorylation for the pathogenesis of secondary hyperparathyroidism and indicate that mTORC1 is a significant regulator of parathyroid cell proliferation through rpS6.