Effects of retinoid and thyroid receptors during development of the inner ear

The sensory epithelia of the vertebrate inner ear are comprised of a complex pattern of hair cells and supporting cells. Several different families of signaling molecules have been shown to play a role in the development and maintenance of this structure. In particular, the steroid/thyroid receptor superfamily, and specifically retinoid and thyroid receptors appear to influence the determination, differentiation, maintenance, and possibly regeneration, of the sensory epithelia of the vertebrate inner ear. Clinical and experimental evidence demonstrates that changes in the relative availability of retinoic acid and thyroid hormone, the ligands for retinoid and thyroid receptors, result in perturbations in the development of hair cell sensory epithelia. Retinoic acid and retinoid receptors appear to play a role in early developmental events including cellular proliferation and determination whereas thyroid hormone and thyroid receptors appear to play a role in later events including differentiation and maintenance.     

Rapid Chromatic Detection of Bacteria by Use of a New Biomimetic Polymer Sensor

We present a new platform for visual and spectroscopic detection of bacteria. The detection scheme is based on the interaction of membrane-active compounds secreted by bacteria with agar-embedded nanoparticles comprising phospholipids and the chromatic polymer polydiacetylene (PDA). We demonstrate that PDA undergoes dramatic visible blue-to-red transformations together with an intense fluorescence emission that are induced by molecules released by multiplying bacteria. The chromatic transitions are easily identified by the naked eye and can also be recorded by conventional high-throughput screening instruments. Furthermore, the color and fluorescence changes generally occur in shorter times than the visual appearance of bacterial colonies on the agar. The chromatic technology is generic and simple, does not require identification a priori of specific bacterial recognition elements, and can be applied for detection of both gram-negative and gram-positive bacteria. We demonstrate applications of the new platform for reporting on bacterial contaminations in foods and for screening for bacterial antibiotic resistance.     

Refined mapping of the gene for thiamine-responsive megaloblastic anemia syndrome and evidence for genetic homogeneity

Thiamine-responsive megaloblastic anemia (TRMA, also known as Rogers syndrome, OMIM 249270) is a rare autosomal recessive disorder characterized by a triad of megaloblastic anemia, diabetes mellitus, and sensorineural deafness. Patients respond, to varying degrees, to treatment with megadoses of thiamine. We have recently shown genetic linkage of the TRMA gene to a 16-centimorgan (cM) region on 1q23.2–1q23.3 based on the analysis of four large, inbred families of Alaskan, Italian, and Israeli-Arab origin. Here we narrow the TRMA interval down to 4 cM based on genetic recombination, homozygosity mapping, and linkage disequilibrium (highest LOD score of 12.5 at D1S2799, at a recombination fraction of 0). We provide further evidence that the TRMA gene is located in this region and confirm the homogeneity of the disease. In this analysis, we genotyped seven additional families of diverse ethnic origin (Pakistani, Indian, Italian, Brazilian, and Japanese), and analyzed additional markers in two previously reported families showing evidence of linkage disequilibrium in a large area of their haplotypes. The multi-system manifestations of TRMA suggest that thiamine has a pivotal role in a multiplicity of physiological processes. Mapping the TRMA gene and understanding the molecular basis of the disease might, thus, shed light on the role of thiamine in common disorders such as deafness, anemia, and diabetes. Received: 16 April 1998 / Accepted: 6 July 1998     

Beta-glycosphingolipids improve glucose intolerance and hepatic steatosis of the Cohen diabetic rat

A link between altered levels of various gangliosides and the development of insulin resistance was described in transgenic mice. Naturally occurring glycosphingolipids were shown to exert immunomodulatory effects in a natural killer T (NKT) cell-dependent manner. This study examined whether glycosphingolipid-induced modulation of the immune system may reduce pancreatic and liver steatosis and stimulate insulin secretion in the Cohen diabetes-sensitive (CDS) rat, a lean model of non-insulin-resistant, nutritionally induced diabetes. Four groups of CDS rats fed a diabetogenic diet were treated with daily intraperitoneal injections of glycosphingolipids beta-glucosylceramide, beta-lactosylceramide, a combination of both (IGL), or vehicle (PBS) for up to 45 days. Immune modulation was assessed by fluorescence-activated cell sorting analysis of intrahepatic and intrasplenic lymphocytes. Steatosis was assessed by MRI imaging and histological examination of liver and pancreas, Blood glucose and plasma insulin concentrations were assessed during an oral glucose tolerance test. Administration of glycosphingolipids, particularly IGL, increased intrahepatic trapping of CD8 T and NKT lymphocytes. Pancreatic and liver histology were markedly improved and steatosis was reduced in all treated groups compared with vehicle-treated rats. Insulin secretion was restored after glycosphingolipid treatment, resulting in improved glucose tolerance. The immunomodulatory effect of beta-glycosphingolipids improved the beta-cell function of the hyperglycemic CDS rat. Thus our results suggest a role for the immune system in the pathogenesis of diabetes in this model.     

Early effects of equine FSH (eFSH) treatment on hormonal and reproductive parameters in mares intended to carry their own pregnancy

Superovulatory treatment may potentially increase the embryo recovery rate and the per-cycle pregnancy rate in normal or subfertile mares that are managed properly. However, some studies suggest a possible negative effect of superovulatory treatment on ovarian follicular maturation and embryo viability. Objectives of the present study were to investigate the early effects of eFSH treatment in reproductively normal mares in terms of: folliculogenesis, pregnancy rate, early embryonic development, reproductive tract parameters (tone and edema), and serum estradiol-17β and progesterone concentrations. Reproductively sound mares (n = 26) were evaluated daily by transrectal palpation and ultrasonography. Five days after spontaneous ovulation, mares were randomly assigned to one of two treatment groups. In the eFSH group, mares (n = 16 estrous cycles) were administered eFSH twice daily; beginning when a follicle ≥20 mm was detected, and continuing until at least one follicle reached a diameter of ≥35 mm. PGF2α was administered 2 days following initiation of eFSH therapy, and hCG was administered approximately 36 h after cessation of eFSH therapy. In the control group, mares (n = 26 estrous cycles) were administered PGF2α 7 days after spontaneous ovulation, and hCG when a follicle ≥35 mm was detected. All mares were bred with fresh semen, monitored for ovulation (Day 0), and evaluated for pregnancy on Days 11–16. Serum estradiol-17β and progesterone concentrations were analyzed using radioimmunoassay on the Day of hCG administration, and Days 8, 11 and 16. Mares treated with eFSH had more follicles ≥30 mm at the time of hCG administration (2.6 ± 0.4 compared with 1.1 ± 0.1; P < 0.01), and more ovulations (2.3 ± 0.5 compared with 1.1 ± 0.3; P < 0.01). However, pregnancy rates were not significantly different between groups (50%; 8/16 compared with 62%; 16/26). Mean overall daily growth rate of embryonic vesicles from Day 11 to 16 was not statistically different between the two groups (3.3 ± 0.3 compared with 3.7 ± 0.1 mm/day) (P = 0.2); however, was more variable (P < 0.01) in the eFSH group (95%CI: 2.6–3.8 mm/day) than in the control group (95%CI: 3.5–3.9 mm/day). Administration of eFSH modified the reproductive tract variables and serum concentrations of progesterone and estradiol-17β on the days that oocyte maturation, fertilization, and early embryonic development are expected to occur. These alterations may be related to the greater incidence of non-ovulatory follicles (25% compared with 0%), fewer embryos per ovulation rate (0.3 ± 0.1 compared with 0.6 ± 0.1), and the lesser than expected pregnancy rates in the eFSH-treated mares.     

Control of Dead end localization and activity – Implications for the function of the protein in antagonizing miRNA function

Dead end (dnd) is a vertebrate-specific component of the germ plasm and germ-cell granules that is crucial for germ-cell development in zebrafish and mouse. Dnd counteracts the inhibitory function of miRNAs, thereby facilitating the expression of proteins such as Nanos and Tdrd7 in the germ cells. Here, we show that cis-acting elements within dnd mRNA and the RNA recognition motive (RRM) of the protein are essential for targeting protein expression to the germ cells and to the perinuclear granules, respectively. We demonstrate that as it executes its function, Dnd translocates between the germ-cell nucleus and germ-cell granules. This phenomenon is not observed in proteins mutated in the RRM motif, correlating with loss of function of Dnd. Based on molecular modeling, we identify the putative RNA binding domain of Dnd as a canonical RRM and propose that this domain is important for protein subcellular localization and function.     

Peptide inhibitors of HIV-1 integrase: From mechanistic studies to improved lead compounds

The HIV-1 integrase enzyme (IN) catalyzes integration of viral DNA into the host genome. We previously developed peptides that inhibit IN in vitro and HIV-1 replication in cells. Here we present the design, synthesis and evaluation of several derivatives of one of these inhibitory peptides, the 20-mer IN1. The peptide corresponding to the N-terminal half of IN1 (IN1 1–10) was easier to synthesize and much more soluble than the 20-mer IN1. IN1 1–10 bound IN with improved affinity and inhibited IN activity as well as HIV replication and integration in infected cells. While IN1 bound the IN tetramer, its shorter derivatives bound dimeric IN. Mapping the peptide binding sites in IN provided a model that explains this difference. We conclude that IN1 1–10 is an improved lead compound for further development of IN inhibitors.     

Basal ganglia oscillations and pathophysiology of movement disorders

Low frequency rest tremor is one of the cardinal signs of Parkinson's disease and some of its animal models. Current physiological studies and models of the basal ganglia differ as to which aspects of neuronal activity are crucial to the pathophysiology of Parkinson's disease. There is evidence that neural oscillations and synchronization play a central role in the generation of the disease. However, parkinsonian tremor is not strictly correlated with the synchronous oscillations in the basal ganglia networks. Rather, abnormal basal ganglia output enforces abnormal thalamo-cortical processing leading to akinesia, the main negative symptom of Parkinson's disease. Parkinsonian tremor has probably evolved as a downstream compensatory mechanism.