Sexually dimorphic mechanisms of VGLUT-mediated protection from dopaminergic neurodegeneration.

Parkinson's disease (PD) targets some dopamine (DA) neurons more than others. Sex differences offer insights, with females more protected from DA neurodegeneration. The mammalian vesicular glutamate transporter VGLUT2 and Drosophila ortholog dVGLUT have been implicated as modulators of DA neuron resilience. However, the mechanisms by which VGLUT2/dVGLUT protects DA neurons remain unknown. We discovered DA neuron dVGLUT knockdown increased mitochondrial reactive oxygen species in a sexually dimorphic manner in response to depolarization or paraquat-induced stress, males being especially affected. DA neuron dVGLUT also reduced ATP biosynthetic burden during depolarization. RNA sequencing of VGLUT+ DA neurons in mice and flies identified candidate genes that we functionally screened to further dissect VGLUT-mediated DA neuron resilience across PD models. We discovered transcription factors modulating dVGLUT-dependent DA neuroprotection and identified dj-1ß as a regulator of sex-specific DA neuron dVGLUT expression. Overall, VGLUT protects DA neurons from PD-associated degeneration by maintaining mitochondrial health.

Relevance of interactions between dopamine and glutamate neurotransmission in schizophrenia.

Dopamine (DA) and glutamate neurotransmission are strongly implicated in schizophrenia pathophysiology. While most studies focus on contributions of neurons that release only DA or glutamate, neither DA nor glutamate models alone recapitulate the full spectrum of schizophrenia pathophysiology. Similarly, therapeutic strategies limited to either system cannot effectively treat all three major symptom domains of schizophrenia: positive, negative, and cognitive symptoms. Increasing evidence suggests extensive interactions between the DA and glutamate systems and more effective treatments may therefore require the targeting of both DA and glutamate signaling. This offers the possibility that disrupting DA-glutamate circuitry between these two systems, particularly in the striatum and forebrain, culminate in schizophrenia pathophysiology. Yet, the mechanisms behind these interactions and their contributions to schizophrenia remain unclear. In addition to circuit- or system-level interactions between neurons that solely release either DA or glutamate, here we posit that functional alterations involving a subpopulation of neurons that co-release both DA and glutamate provide a novel point of integration between DA and glutamate systems, offering a key missing link in our understanding of schizophrenia pathophysiology. Better understanding of mechanisms underlying DA/glutamate co-release from these neurons may therefore shed new light on schizophrenia pathophysiology and lead to more effective therapeutics.

Roles of VGLUT2 and Dopamine/Glutamate Co-Transmission in Selective Vulnerability to Dopamine Neurodegeneration.

Growing evidence has established that a subset of dopamine (DA) neurons co-release glutamate and express vesicular glutamate transporter 2 (VGLUT2). VGLUT2 expression in DA neurons plays a key role in selective vulnerability to DA neurodegeneration in Parkinson's disease (PD). In this review, we summarize recent findings on impacts of VGLUT2 expression and glutamate co-release from DA neurons on selective DA neuron vulnerability. We present evidence that DA neuron VGLUT2 expression may be neuroprotective, boosting DA neuron resilience in the context of ongoing neurodegenerative processes in PD. We highlight genetic and pesticide models of PD that have provided mechanistic insights into selective DA neuron vulnerability. Finally, we discuss potential neuroprotective mechanisms, focusing on roles of VGLUT2 and glutamate in promoting mitochondrial health and diminishing oxidative stress and excitotoxicity. Elucidating these mechanisms may ultimately lead to more effective treatments to boost DA neuron resilience that can slow or even prevent DA neurodegeneration.

Dose-dependent toxicological effects in rats following a 90-day dietary exposure to PCB-156 include retinoid disruption.

The toxicity of PCB-156 (2,3,3',4,4',5-hexachlorobiphenyl) was investigated in rats following subchronic dietary exposure. Groups of 10 male and female Sprague-Dawley rats were administered PCB-156 in the diet at 0, 0.01, 0.1, 1 or 10 ppm for 90 days. Dose-dependent increases were detected for the liver, lung and kidney weights, as well as for the liver EROD, PROD and UDPGT enzyme activities and liver uroporphyrin concentration. Dose-dependent decreases were observed in final body weight, body weight gain, and thymus weight. Apolar retinoid concentrations were decreased in the liver and lungs and increased in the kidneys. Histopathological examination of the liver, thyroid, and thymus showed mild to moderate dose-related changes. A LOAEL of 0.01 ppm was established, based on reduced apolar liver retinoid concentration. Benchmark dose-modelling corroborated the sensitivity of liver retinoid endpoints. The lower confidence limits (BMDL) for a 5% decrease in apolar liver retinoid concentrations were 0.0009 and 0.0007 ppm, respectively, in males and females, corresponding to a daily dose of 0.06 µg PCB-156 per kg body weight. Organizing dose-response data for the individual hepatic endpoints along the PCB-156 dosing scale revealed a sequence of events compatible with a causal link between depletion of apolar retinoids and the other liver biochemistry and pathology findings. Taken together, data suggest that the retinoid endpoints should be further evaluated for a causal relationship to PCB-induced liver toxicity and that retinoid system endpoints are identified and characterized to support health risk assessment in the emerging research fields of endocrine disruption and mixture toxicology.

Hearing difficulties, uptake, and outcomes of hearing aids in people 85 years of age.

OBJECTIVE: The aim of this study was to investigate self-reported hearing difficulties, uptake, and hearing-aid outcomes and their relationships to demographic, cognitive, psychosocial, and health variables in 85 year olds. DESIGN AND STUDY SAMPLE: Three hundred and forty-six elderly adults participated in a survey that included questionnaires and home visits. Fifty-five percent of participants admitted to having hearing difficulties, and 59% of these owned hearing aids. The participants' most frequently cited reason for not acquiring hearing aids was that they did not think their hearing problem was perceived as severe enough. Participants with hearing difficulties who did not own hearing aids showed worse general and mental health. Many of the elderly participants were successful in their rehabilitation, and their hearing-aid outcomes were similar to those of a younger group, with the exception of a greater proportion of non-users among the elderly. CONCLUSION: Many older people with self-reported hearing difficulties do not acquire hearing aids, despite this study's findings that older people are likely to have success with hearing rehabilitation. It is important to make greater efforts to try to increase elderly adults' awareness of hearing loss and the benefits of hearing rehabilitation.

Xylitol concentration in saliva and dental plaque after use of various xylitol-containing products.

The study consisted of two sets of experiments, one in saliva and one in dental plaque. The xylitol concentration in saliva was determined enzymatically in 12 children (mean age 11.5 years) after a standardised use of various xylitol products: (A) chewing gums (1.3 g xylitol), (B) sucking tablets (0.8 g xylitol), (C) candy tablets (1.1 g xylitol), (D) toothpaste (0.1 g xylitol), (E) rinse (1.0 g xylitol), and (F) a non-xylitol paraffin. Unstimulated saliva was sampled 1, 3, 8, 16 and 30 min after use. The concentration in dental plaque was determined after mouthrinses with contrasting amounts of xylitol (LX = 2.0 g, HX = 6.0 g, and control) and supragingival plaque was collected and pooled after 5, 15 and 30 min. The mean xylitol concentration in saliva at baseline was approximately 0.1 mg/ml. All xylitol-containing products resulted in significantly increased levels (p < 0.05) immediately after intake and remained elevated for 8-16 min in the different groups. The highest mean value in saliva was obtained immediately after use of chewing gums (33.7 +/- 16.4 mg/ml) and the lowest was demonstrated after using toothpaste (8.2 +/- 4.9 mg/ml). No significant differences were demonstrated between chewing gums (A), sucking tablets (B), candy (C) and rinses (E). In dental plaque, the mean values were 8.6 +/- 5.4 and 5.1 +/- 4.0 mg/ml 5 min after HX and LX rinses. Concerning the higher concentration, the values remained significantly elevated (p < 0.05) during the entire 30-min follow-up. In conclusion, commonly advocated xylitol-containing products gave elevated concentrations of xylitol in unstimulated whole saliva and dental plaque for at least 8 min after intake.

Fitting hearing aids to first-time users.

Clinical experience indicates that first-time hearing aid users prefer less gain and lower maximum output levels than experienced users. This hypothesis was tested on 20 subjects being fitted with their first aids. The study was double blinded by using a programmable hearing aid, set to either the standard setting according to the manufacturer's software or to reduced gain and maximum output. Half of the subjects started with one hearing aid and half with the other, changing to the other hearing aid after 3 days trial with each setting. At the end of the study, subjects stated preference in specified situations and overall. No significant differences in APHAB, sound quality, estimated communication ability or perceived loudness scores were seen for the two settings. Nine subjects preferred the standard setting, seven the reduced setting and four were undecided. No correlation could be found between preference and audiological variables.

Whole gut transit is prolonged after Ripstein rectopexy.

OBJECTIVE: To find out if there are changes in transit time after Ripstein rectopexy and whether measurement of whole gut transit time preoperatively can predict postoperative constipation. DESIGN: Prospective open study. SETTING: Teaching hospital, Sweden. SUBJECTS: 30 patients undergoing Ripstein rectopexy for rectal prolapse (n = 17) or internal rectal intussusception (n = 13). METHODS: Whole-gut transit studies and recording of symptoms of constipation preoperatively and postoperatively. MAIN OUTCOME MEASURES: Constipation and retention of markers. RESULTS: Significantly more markers were retained in postoperative compared with preoperative transit studies (p < 0.001). Constipation mainly presented as emptying difficulties and there was no increase in the total number of patients who reported emptying difficulties postoperatively. There was a weak but significant correlation between retention of markers preoperatively and postoperative emptying difficulties (p < 0.05). CONCLUSION: Whole gut transit was prolonged after Ripstein rectopexy. Preoperative retention of markers indicated an increased risk of postoperative constipation.

Inhibition of human and duck hepatitis B virus by 2',3'-dideoxy-3'-fluoroguanosine in vitro.

The fluorinated guanosine analog 2',3'-dideoxy-3'-fluoroguanosine (FLG) has been shown to have an effect on duck hepatitis B virus (DHBV) in vivo and in vitro. In this study the inhibitory effect of FLG on DHBV and human hepatitis B virus (HBV) was evaluated in vitro. Cell lines transfected either with DHBV or HBV DNA and primary duck hepatocyte cell cultures were used. Virus production was analysed by PCR and a quantitative PCR was established for DHBV for determination of the inhibitory concentrations of the drug. 50% inhibition was achieved with an FLG concentration of 0.2 microg/ml (0.7 microM) and 90% inhibition was observed with an FLG concentration of 1.0 microg/ml (3.7 microM) using the DHBV transfected cell line. FLG showed an effect on DHBV production in primary duck hepatocyte cell cultures at concentrations down to 0.1 microg/ml (0.4 microM). However, the DHBV production returned to pre-treatment levels within a few days after cessation of treatment. HBV production in transfected cell lines was also inhibited by FLG. Both DHBV and HBV DNA-polymerases were inhibited by FLG triphosphate and 50% inhibition was observed at a concentration of 0.05 microg/ml (0.1 microM) for DHBV and 0.03 microg/ml (0.05 microM) for HBV. FLG is an efficient inhibitor of DHBV replication both in vivo and in vitro and of HBV in vitro which makes it a good candidate for treatment of HBV infections. However, it does not completely eliminate the virus since a relapse in virus production was observed when treatment was withdrawn. Therefore it would be interesting to evaluate FLG in combination with other types of anti-HBV drugs.

Clinical trial of a digital hearing aid.

A clinical trial of Oticon DigiFocus hearing aid was performed. The test aid was evaluated on 33 subjects with several years' experience as users of modern analog hearing aids. These aids were used as reference for the 1-month-long trial. The Abbreviated Profile of Hearing Aid Benefit (APHAB) showed a mean difference in benefit with superior ratings for the test aid concerning ease of communication, speech in reverberation and speech in background noise. The subjects' own aids were rated somewhat better concerning aversiveness of sounds, but this difference was not statistically significant. The Gothenburg Profile showed a statistically significant difference between the test aid and the reference aids in favour of the test aid. The difference was not most evident with regard to speech communication and the effects of hearing loss on social interactions. Sound quality ratings concerning clearness were significantly higher for the test aid. Speech recognition thresholds in noise were on average 0.7 dB better for the test aids when tested at speech levels 60 and 75 dB. The difference was statistically significant only at 75 dB. There was significant interaction between general preference and hearing aid type, indicating that overall sound quality was an important factor affecting the general preference for either the test aid or the reference aid. Twenty-three subjects generally preferred the test aid, six preferred their own aid and four stated no difference.

Hepatitis B virus X gene 1751 to 1764 mutations: implications for HBeAg status and disease.

A translational stop in the hepatitis B virus (HBV) precore codon 28 and specific changes in the core promoter region of the X gene have been suggested to influence the level of circulating HBeAg in patients. We analysed the core promoter region and precore sequences from 59 HBV strains (including 14 from the databank) of different genotypes and from patients with different HBeAg/anti-HBe patterns. The initiator and TATA elements for transcription of precore and pregenomic RNA were highly conserved. The majority of X gene deletions in the core promoter region would lead to translational frame-shifts and stops, truncating the C-terminal end of the X protein. We found significant associations between specific changes in core promoter positions 1762 to 1764, or in precore codon 28, and absence of circulating HBeAg. For the core promoter mutations alone, this association was related to the apparent degree of liver damage (as estimated by alanine aminotransferase levels) at the time of sampling. Mutations at nucleotides 1762 and/or 1764 were often accompanied by point mutations at positions 1751 to 1755. Since mutations at nucleotide positions 1762 and 1764 have recently been shown by in vitro studies to suppress HBeAg production with a concomitant enhancement of virus production, disappearance of the HBeAg-positive phenotype associated with 1762 to 1764 mutations may thus have at least as much significance for the course of infection as HBeAg absence associated with precore codon 28 stop mutations. These observations are considered against a secondary structural model for the 3' end of HBV pregenomic RNA which also predicts enhancement of virus replication after mutation at positions 1762 and 1764.

Antigenic sites on the receptor-binding domain of human adenovirus type 2 fiber.

The trimeric fiber of adenovirus type 2 (Ad2) mediates the first stage of virus-cell attachment, and the distal head region of the fiber has been implicated as the receptor-binding domain. To locate regions on the primary polypeptide sequence of the fiber which may be involved in virus-cell interaction, peptide-based epitope mapping was performed using (1) polyclonal antibodies prepared against both native Ad2 fiber and Ad2 head protein expressed in Escherichia coli and (2) 18 monoclonal antibodies prepared against trimeric Ad2 head protein expressed in baculovirus. The approach using polyclonal antibodies revealed eight domains on the primary sequence of the head which contain one or more continuous epitopes. At least two of these regions were also recognized by monoclonal antibodies reacting against both monomeric and trimeric fiber head protein. The majority of monoclonal antibodies which did not recognize Ad2 head-specific peptides in ELISA were also nonreactive against the monomeric form of protein in Western blot, suggesting that their recognition of trimer is due to the existence of as yet undefined discontinuous epitopes or to alterations in monomer configuration. Our results correspond well with the recently published X-ray crystallographic model of Ad5 fiber head (D. Xia, L.J. Henry, R.D. Gerard, and J. Deisenhofer, Structure 2, 1259-1270, 1994), since most antigenic determinants containing linear epitopes mapped to the outer loops or uppermost beta-sheets in this structure. Four of five neutralizing monoclonal antibodies recognized trimer only and none recognized linear peptides. This might suggest that the trimeric form of fiber is necessary for making contact with the receptor(s) and that discontinuous epitopes on the head domain may be involved in fiber-cell interaction.

Hepatitis B virus strains in Thailand: genomic variants in chronic carriers.

Genetic heterogeneity of the hepatitis B virus (HBV) has been shown to influence the serological pattern and clinical picture in HBV infection. Thailand has a high transmission rate of HBV, but the molecular epidemiology of HBV strains circulating in this region was hitherto unknown. In this study, the HBV strains from 34 Thai HBsAg-positive patients were investigated. In a proportion of these samples, an antigenically important region of the S gene (n = 18), and the pre-S2 and precore genes (n = 15) were sequenced after PCR amplification. Four strains had in-frame deletions of an upstream region of the pre-S2 gene, with all deletions ending at the same nucleotide. In one of three anti-HBe positive strains without a translational stop at codon 28 of the precore gene, there was a one nucleotide insertion in the precore gene. This insertion would cause a frame shift and result in a nonsense protein being expressed, thus providing one explanation for the lack of HBeAg in this patient. Several rare or unique amino acid changes in the region between residues 120 and 161 of the S protein were found. Glycine 145 was changed to alanine in one strain, and this position showed an apparent mixture of glycine and arginine in another. In total, 10 strains displayed unexpected changes that were not related to the normal variability between subtypes or genetic subgroups. It is concluded that there is considerable heterogeneity in HBV strains in Thailand and that this could have clinical and epidemiological importance in a region with high HBV transmission rates.

The hepatitis B virus X gene: analysis of functional domain variation and gene phylogeny using multiple sequences.

The hepatitis B virus (HBV) X gene shares sequences with both the polymerase and precore genes, carries several regulatory signals critical to the replicative cycle, and its product has a transactivating function. In this study, the X gene sequences of 29 HBV strains from 14 different countries were characterized and compared to all corresponding databank sequences where the origin of the strain was stated. The X gene and its product are relatively well conserved. However, several rare or unique point mutations in the predicted X protein are described which further define regions on the primary sequence which may be of structural and/or functional significance. Phylogenetic analysis of the 29 X genes and their predicted proteins in this study using unrooted trees indicates that a common ancestral sequence gave rise to two main groups of X genes, represented by HBV strains found predominantly either in the Western or Eastern Hemisphere. In turn, each of these two main groups of sequences appear to have branched into two main lineages. Introduction of 33 additional DNA sequences from the databank has further verified these inferences and confirmed the groupings as previously described subgroups A to D. Whilst the split of X gene lineages into subgroups A and D seems feasible on geographical/anthropological grounds, the corresponding split of Eastern Hemisphere lineages into B and C may require an alternative hypothesis. Additionally, there was a correlation between the HBeAg/anti-HBeAg status of our patients and nucleotide identity at two positions in the core promoter, 52 and 50 bases upstream from the precore start codon. This finding, also shown recently by others, suggests that control of HBeAg secretion may involve mutations affecting transcription and not only precore/core translation.

Human and simian adenoviruses: phylogenetic inferences from analysis of VA RNA genes.

Adenovirus VA RNA genes have primary sequence constraints due to internal promoter regions and a high degree of secondary structure in the RNA product. To determine the relationships between human and simian adenoviruses, the VA RNA genes of several primate adenoviruses were characterized and compared to those sequences already published. Human adenoviruses of subgenera A, B:2, and F have only one VA RNA gene, whereas human adenoviruses of subgenera B:1, C, D, and E have two. The genomes of 12 monkey adenoviruses were found to have only one VA RNA gene, whereas the genomes of six representative chimpanzee adenoviruses were each found to have two VA RNA genes. Phylogenetic analysis of representative VA RNA gene sequences individually, irrespective of their strain of origin or partnering VA RNA gene, gave the following inferences. (1) The single VA RNA genes of human adenovirus subgenera A and F are most closely related to those of monkey adenoviruses. (2) The VA RNAI genes of human adenoviruses in subgenera B:1, D, and E, and also the single VA RNA genes of subgenus B:2 probably diverged from a common ancestral VA RNA gene. (3) This ancestral gene most likely reduplicated to give the precursor of all VA RNAII genes, the evidence for which has been almost totally lost in subgenus B:2 adenoviruses. (4) The two VA RNA genes of human subgenus C adenoviruses are relatively distant from each other phylogenetically. Since the Ad2 and Ad5 VA RNAI genes have a higher identity to the single VA RNA gene of SAV13 (SV36) than to those of any of the other human adenoviruses, these genes may have entered the human subgenus C adenovirus genome by substitution involving recombination with a simian adenovirus. The results of this study suggest that a renewed appraisal of VA RNA function in adenoviruses other than Ad2 and Ad5 may be necessary.

Genetic conservation within subtypes in the hepatitis B virus pre-S2 region.

The antigenic determinants for the main hepatitis B virus (HBV) subtypes adw, adr, ayw and ayr lie in the S (surface) polypeptide. Two amino acid residues in particular, encoded by the S gene at codon positions 122 and 160, have been postulated to determine the different antigenic subtypes. In contrast, the 165 nucleotide pre-S2 gene encodes an immunodominant region common to all subtypes that can give rise to neutralizing antibodies. We have characterized the pre-S2 gene sequences of 29 HBV strains of the three main subtypes, adw, ayw and adr. Seven base positions showed variation that was entirely subtype-specific, with six of these variations leading to subtype-specific amino acid differences. This finding affords the possibility of using pre-S2 sequences for genetic subtyping. Two ayw strains from unrelated patients infected in the Middle East had identical pre-S2 sequences with a block of 12 nucleotides deleted. A geographical correlation with subtype observed from serological results was also apparent from phylogenetic analysis of DNA identities within the pre-S2 region. The results support the concept that the main HBV subtypes truly represent families of phylogenetically different strains.