Search PubMed⌕ Search

Biomedical subjects

S J Roberts

Publications and source records attributed to S J Roberts.

At least 19 recordsLinked to original sources
PubMed1999

Temporal and spatial complexity measures for electroencephalogram based brain-computer interfacing.

There has been much interest recently in the concept of using information from the motor cortex region of the brain, recorded using non-invasive scalp electrodes, to construct a crude interface with a computer. It is known that movements of the limbs, for example, are accompanied by desynchronisations and synchronisations within the scalp-recorded electroencephalogram (EEG). These event-related desynchronisations and synchronisations (ERD and ERS), however, appear to be present when volition to move a limb occurs, even when actual movement of the limb does not in fact take place. The determination and classification of the ERD/S offers many exciting possibilities for the control of peripheral devices via computer analysis. To date most effort has concentrated on the analysis of the changes in absolute frequency content of signals recorded from the motor cortex. The authors present results which tackle the issues of both the interpretation of changes in signals with time and across channels with simple methods which monitor the temporal and spatial 'complexity' of the data. Results are shown on synthetic and real data sets.

Computer User Training↗
PubMed1999

Health related behaviors and cancer screening of lesbians: results from the Boston Lesbian Health Project.

The purpose of this article is to present data on lesbian health-related and cancer screening behavior. This is an area in which not a great deal of data exist and which is particularly interesting in view of previous data suggesting that lesbians do not seek routine services because of a fear of homophobia. This paper discusses a portion of a larger survey completed by a national community-based lesbian sample. The results show that the lesbians in this sample have healthy behaviors in general and utilize routine health screening. There is some indication that alcohol use is heavier in this sample than among women in general, an area that warrants further investigation.

Adolescent↗
PubMed1998

A comparison of fast Fourier transform (FFT) and autoregressive (AR) spectral estimation techniques for the analysis of tremor data.

This review outlines the theory of spectral estimation techniques based on the fast Fourier transform (FFT) and autoregressive (AR) model and their application to the analysis of human tremor data. Two FFT-based spectral estimation techniques are presented, the Blackman-Tukey and periodogram methods. Factors that influence the quality of spectral estimates are discussed including the choice of windowing function. The theory of parametric modelling is introduced and AR modelling identified as the technique best suited to the analysis of tremor data. The processes of parameter estimation and model order selection are described. The theory of AR spectral estimation is outlined and differences between the AR and FFT-based spectral estimates are summarised. A brief guide to the implementation of FFT-based and AR spectral estimation techniques is given concentrating on data analysis packages that require little or no programming expertise. This review concludes that the AR modelling approach can produce tremor spectra that are superior to those from FFT-based methods for short data sequences. Although the spectral estimates are improved, the benefits of AR modelling for providing information about the physiological mechanisms of tremor generation are not yet clear.

Algorithms↗
PubMed1998

Cyclic AMP accumulation in rat soleus muscle: stimulation by beta2- but not beta3-adrenoceptors.

The beta-adrenoceptor subtypes involved in cyclic AMP accumulation in rat soleus muscle were studied using beta1- beta2- and beta3-adrenoceptor agonists and antagonists. Responses to (-)-isoprenaline were antagonised by (-)-propranolol (p KB = 8.32 at 0.1 microM) and by erythro-DL-1(7-methylindian-4-yloxy)-3-isopropylaminobuta n-2-ol (+/-)-ICI 118551) (pKB = 9.38 at 10 nM and 9.65 at 100 nM) but not by 2-hydroxy-5(2-((2-hydroxy-3-(4-((1-methyl-4-trifluoromethyl)1H-imidazole -2-yl)-phenoxy)propyl)amino)ethoxy)-benzamide monomethane sulfonate ((+/-)-CGP 20712A at 10 nM or 100 nM). The beta3-adrenoceptor agonist sodium-4-[-2[-2-hydroxy-2-(-3-chlorophenyl)ethylamino]propyl]phenoxya cetate (BRL 37344 at 10 pM or 10 microM) caused no significant change in basal cyclic AMP levels and had no effect on the level of cyclic AMP accumulation stimulated by (-)-isoprenaline, zinterol or forskolin. (-)-Isoprenaline pretreatment (400 microg kg(-1) h(-1), 14 days) abolished responses to (-)-isoprenaline (10 microM) and zinterol (1 microM) while BRL 37344 had no effect in either isoprenaline or vehicle-treated groups. These results show that beta3-adrenoceptor agonists do not stimulate cyclic AMP accumulation in rat soleus muscle and that (-)-isoprenaline induced increases in cyclic AMP levels are mediated predominantly by beta2-adrenoceptors. This suggests that the previously reported increase in glucose uptake by beta3-adrenoceptor agonists in skeletal muscle does not involve direct stimulation of adenylate cyclase.

Adrenergic beta-2 Receptor Agonists↗
PubMed1998

Role of individual N-linked glycosylation sites in the function and intracellular transport of the human alpha folate receptor.

Glycosylation is a structural feature of all three isoforms of the human folate receptor. We have used site-directed mutagenesis to study the role of individual glycosylation sites in the assembly and function of the a isoform of the human folate receptor (alpha(h)FR). Three potential N-linked glycosylation sites in the alpha(h)FR sequence were disrupted by conservative mutation of the S or T residues in the consensus sequence (N-X-S/T) to A or V, respectively. Constructs with the single mutations S(71)-->A (alpha(h)FR(-1)), T(163)-->V (alpha(h)FR(-2)), and S(203)-->A (alpha(h)FR(-3)); the double mutation S(71)--> A/S(203)-->A (alpha(h)FR(-1-3)); and the triple mutation S(71)--> A/S(203)--> A/T(163)--> V (alpha(h)FR(-1-2-3)) were stably transfected into Chinese hamster ovary (CHO) cells. The proteins produced in CHO cells by the mutated cDNAs have apparent molecular weights that are reduced relative to the wild type and are consistent with the loss of carbohydrate residues. The triple mutant, which lacks all three consensus glycosylation sites, yields protein that comigrates with the enzymatically deglycosylated native protein. Determinations of the K(D) for folic acid by Scatchard analyses of the glycosylation mutants indicate that folic acid binding affinity is not significantly affected in the single mutants alpha(h)FR(-1) and alpha(h)FR(-2). However, in the single mutant, alpha(h)FR(-3), and the double mutant, alpha(h)FR(-1-3), folic acid binding affinity is respectively 2.7- and 3.5-fold lower than that in wild type. Deglycosylation by mutation of all three consensus sites (alpha(h)FR(-1-2-3) eliminates both folic acid binding and cell surface expression. In contrast, enzymatic deglycosylation of purified wild-type alpha(h)FR with endoglycosidase F does not significantly affect folate binding affinity. Thus, while carbohydrate residues are not essential for the folate binding activity of the mature folate receptor, at least one of the three core glycosylated residues is necessary for the synthesis of alpha(h)FR in its active conformation.

Animals↗
PubMed1998

Prescribing of anti-epileptic drugs in the northern and Yorkshire region: 1992-1995.

Epilepsy is a condition for which regular drug treatment is normally prescribed. We have examined the primary care prescribing rates for anti-epileptic drugs (AEDs) in a region of northern England with a population of 6.8 million. Over the 4-year period 1992-1995 the number of AED prescription items issued rose by 15%. A third of this rise is accounted for by increased prescribing of the new anticonvulsants, vigabatrin, lamotrigine and gabapentin, which are primarily indicated for adjunct use. Prescribing of phenytoin and barbiturates fell over the same period, but this reduction was more than compensated for by increased prescribing of carbamazepine and sodium valproate. There were notable differences in both the overall volume and the choice of AEDs used in different health authority areas and these are probably attributable to the influence of the local secondary-care sector on the therapeutic regimens adopted by general practitioners in the area.

Anticonvulsants↗
PubMed1998

Isolation of isoproturon-degrading bacteria from treated soil via three different routes.

Three different isolation routes (flask enrichment/flask degradation assay, flask enrichment/microplate degradation assay, MPN assay/microplate degradation assay) were used to obtain pure cultures of bacteria which degraded isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea) as sole carbon and nitrogen source in a mineral salts medium from a field soil treated with isoproturon in the laboratory. All three isolation routes were successful, but the microplate assay of degradation was more successful than the flask assay. Characterization of 36 isolates indicated that they formed 16 distinct phenotypes (10 Gram-positive phenotypes, six Gram-negative phenotypes) which are likely to represent distinct species. Low concentrations of the degradation product 3-(4- isopropylphenyl)-1-methylurea (IPPMU) were occasionally found in the culture solutions. When provided as the sole source of carbon and nitrogen, the monomethyl degradation product was itself rapidly degraded by several of the isolates. Some isolates were also able to use the demethylated degradation product 3-(4-isopropylphenyl)-urea (IPPU) as sole source of carbon and nitrogen, although there was occasionally an extended lag-phase before rapid degradation commenced. One isolate was particularly active and degraded isoproturon, the monomethyl and demethylated degradation products of isoproturon, and demethylated the related phenylureas diuron and linuron.

Bacteria↗
PubMed1998

Stochastic complexity measures for physiological signal analysis.

Traditional feature extraction methods describe signals in terms of amplitude and frequency. This paper takes a paradigm shift and investigates four stochastic-complexity features. Their advantages are demonstrated on synthetic and physiological signals; the latter recorded during periods of Cheyne-Stokes respiration, anesthesia, sleep, and motor-cortex investigation.

Anesthesia↗
PubMed1997

Tissue-specific promoters of the alpha human folate receptor gene yield transcripts with divergent 5' leader sequences and different translational efficiencies.

The alpha human folate receptor (alphahFR), or KB cell folate receptor, gene contains two major promoters that produce transcripts, KB1 and KB4, varying only in the length and sequence of their 5' untranslated regions (UTRs). Using RNase protection assays specific for each isoform, we show that the level of expression of these two transcripts is tissue-specific, indicating that promoter usage is regulated, not constitutive. RNA stabilities and translational efficiencies of the KB1 and KB4 transcripts were compared to determine the functional significance of the different 5' UTRs. Analyses of RNA turnover in vivo with actinomycin D to block new transcription and in vitro with a cytoplasmic extract indicate no discernible differences in the stabilities of the two transcripts. However, the KB4 transcript is 2-3-fold more efficiently translated in wheat germ extracts in vitro and transfected CHO cells in vivo. Also, high ionic strength, which favours the formation of RNA secondary structure, differentially affects the translational efficiencies of the two transcripts. Translation of the longer KB1 mRNA is 2-5-fold more inhibited by hypertonic conditions than translation of the KB4 mRNA. Because the 5' UTR of KB1 is approximately four times longer than the 5' UTR of KB4, 149 bp (75%) of the KB1 5' UTR were deleted to determine whether the long leader sequence inhibited translation. The resulting derivative, dKB1, has a 5' UTR similar in length, but not sequence, to the 5' UTR of KB4. dKB1 is translated at a level approaching that of KB4 in wheat germ extracts, indicating that the upstream portion of the 5' leader sequence contributes to the relative translational inefficiency of KB1. Hence, one consequence of tissue-specific promoter usage is the production of alphahFR transcripts with different 5' non-coding regions that affect translational efficiency.

Animals↗
PubMed1997

Synthetically modified cellulose: an alternative to synthetic membranes for use in haemodialysis?

Renal replacement therapy relies predominantly on the use of cellulose-based membranes. Such membranes have a biocompatibility profile which is inferior to membranes manufactured from synthetic polymers. Synthetically modified cellulose (SMC) is a new, low-flux haemodialysis membrane in which hydroxyl groups have been replaced with benzyl groups. The biocompatibility profile characterized by changes in white cell and platelet counts and the activation of complement components (C3a, C5a and C5b-9) have been studied in vivo and compared with those of cellulose acetate, unmodified cellulose (Cuprophan ) and low-flux polysulphone (Fresenius Polysulfone) in the same group of patients. For SMC, the white cell count at 15 min declined to 65.6% of pretreatment level, compared with 63.8% for the cellulose acetate, 79.6% for low-flux polysulphone and 28.1% for Cuprophan, thereafter returning to pretreatment levels. Both modified cellulose membranes were superior to unmodified cellulose (P = 0.001); the differences between the modified cellulose membranes were not significant statistically. The changes induced by all three cellulose-based membranes exceeded those for low-flux polysulphone (P = 0.001). Associated with the neutropenia was a reduction in platelet count, but this was independent of membrane type. The mean time-averaged concentrations of C3a(des Arg) over 150 min were 1168 ng ml(-1) (SMC), 1030 ng ml(-1) (cellulose acetate), 1297 ng ml(-1) (Cuprophan) and 790 ng ml(-1) (low-flux polysulphone). Equivalent values for C5a(des Arg) were 6.12 (SMC), 2.98 (cellulose acetate), 11.03 (Cuprophan) and 1.33 ng ml(-1) (low-flux polysulphone). C5b-9 values were 385 (SMC), 386 (cellulose acetate), 177 (Cuprophan) and 185 ng ml(-1) (low-flux polysulphone). For each of the complement components the differences between the membranes were significant [P = 0.0009 (C3a(des Arg)), P = 0.0001 (c5a(des Arg) and C5b-9)]. The levels of C5b-9 generated during dialysis also showed a significant positive correlation compared to C5a for all membranes considered as a single group (Pearson's correlation coefficient = 0.870, P = 0.0001). It is concluded that the modification of the cellobiosic unit is a promising approach to improve the biocompatibility profile of cellulose-based membranes. The two different methods of modification lead to similar improvements in biocompatibility compared with unmodified cellulose, but as yet do not match that of low-flux polysulphone.

Biocompatible Materials↗
PubMed1997

Functional and molecular evidence for beta 1-, beta 2- and beta 3- adrenoceptors in human colon.

1. Relaxation of carbachol pre-contracted human colonic muscle to (-)-isoprenaline was examined in circular, longitudinal and taenia coli preparations to determine the beta-adrenoceptor subtypes involved. beta 1-, beta 2- and beta 3-Adrenoceptor mRNAs were also measured in colonic muscle and mucosa. 2. (-)-isoprenaline caused relaxation of longitudinal smooth muscle preparations with pEC50-7.39 +/- 0.12, and this response was inhibited by both propranolol (0.1 microM, pKB 8.55 +/- 0.12) and the selective beta 1-antagonist, CGP 20712A (0.1 microM, pKB 8.80 +/- 0.20), while the selective beta 2-antagonist, ICI 118551 (0.1 microM) failed to inhibit isoprenaline relaxation consistently. 3. (-)-Isoprenaline caused relaxation of taenia coli with a pEC50 of 6.70 +/- 0.17. Propranolol (0.1 microM). CGP 20712A (0.1 microM) and ICI 118551 (0.1 microM) inhibited the isoprenaline response with similar low affinities (pKB values 7.93, 7.71 and 7.54, respectively). Carbachol pre-contracted circular smooth muscle preparations failed to relax consistently to isoprenaline and these responses were not characterized. 4. beta 1- and beta 2-Adrenoceptor mRNAs were present in circular longitudinal muscle samples and taenia coli samples, and lower levels were detected in mucosa. beta 3-mRNA was also present in both muscle preparations but was not detected in human colonic mucosa. 5. In summary, beta 1-adrenoceptors are the predominant subtype mediating isoprenaline-induced relaxation of the thin longitudinal smooth muscle of human colon, while beta 1-receptors do not appear to be involved in these responses. However, beta 3-adrenoceptors may play a role in relaxation of the taenia coli as conventional antagonist affinities are low. beta 3-Adrenoceptor mRNA was present in taenia coli and circular/longitudinal smooth muscle but absent from human colonic mucosa.

Adrenergic beta-Agonists↗
PubMed1997

Nurse executives in the 1990s: empowered or oppressed?

Nursing executives are at the center of change. They are involved in the reenginnering of the workplace and often implement new procedures, in addition to downsizing staff. This article explores oppressed group behavior and its implications for nursing executives at this time of change in the health care system. The purpose of this exploration is to encourage a dialogue about its relevance in order to enhance empowerment and to break the cycle of oppression.

Behavior↗
PubMed1997

Lesbian uses of and satisfaction with mental health services: results from Boston Lesbian Health Project.

In response to the dearth of specific information about lesbians' health status and practices in the health literature, a national study utilizing a self-administered questionnaire was conducted in 1987 by four associates of the Fenway Community Health Center in Boston to access data in these areas. The questionnaire solicited information about demographics, health practices, stress in personal and work lives, mental and physical health problems, sexual practices, family history of health related problems, and genetic attributes hypothesized to be related to "gayness." Questionnaires from 1,633 lesbian women provided the database for the study. This paper discusses the portion of the survey that dealt with mental health services and life experiences. Past studies that investigated mental health needs of lesbians focused on the quality of treatment by mental health providers, rates of suicide attempts, and alcoholism. This paper compares these past findings with the responses of the lesbians in this national, community-based study. Findings indicate that although a significant number of the lesbian women in this sample had been in therapy, they sought out therapy as a coping strategy to deal with similar issues as other women, i.e., depression and relationships. Suicide attempts decreased considerably after adolescence and "coming out." Rates of alcohol use and abuse, although difficult to compare with other studies, were higher than other women but similar to other studies investigating a community sample of lesbians. Even with a high family history of alcoholism, less than 5 percent reported having sought out therapy to deal with any issues of alcohol or drug use.

Adolescent↗
PubMed1997

Bacterial endosymbionts in the gills of the deep-sea wood-boring bivalves Xylophaga atlantica and Xylophaga washingtona.

Bacterial endosymbionts found in gill tissues in several bivalve families convert otherwise unavailable energy sources (sulfide, methane, or cellulose) to forms readily metabolized by their hosts. We investigated the existence of such a symbiosis in two species of Xylophaga (family Pholadidae). The genus Xylophaga includes opportunistic species that are the predominant colonizers of wood at depths greater than 150 m. It has been hypothesized that, like their shallow-water counterparts the shipworms (family Teredinidae), species of Xylophaga utilize wood for nutrition. Results from transmission and scanning electron microscopy of X. atlantica and X. washingtona clearly demonstrate the presence of endosymbionts that resemble the shipworm endosymbionts both morphologically and in their anatomical location within the gills. Xylophaga and the teredinids both have a caecum packed with wood chips but lack the dense populations of microorganisms associated with cellulose digestion in termites or ruminants. These observations suggest that Xylophaga has evolved a symbiotic solution to wood digestion similar to that seen in shipworms. Hence, the Xylophaga symbiosis suggests a mechanism for the conversion of terrestrially derived cellulosic carbon from wood into animal biomass in the deep sea.

Animals↗
PubMed1997

Epigenesis of the nurse practitioner role revisited.

In the mid-1970s, an article discussed the identity crises of nurse practitioner (NP) students which occurred during their educational experience. This article noted that NP students progress from dependence to interdependence and demonstrate regression, anxiety and conflict. Twenty years later we have also observed these changes in our own graduate students. This article describes our observations, analyzes them with respect to well-known developmental theory, and offers suggestions for teaching methodologies which enhance successful transitions through the crises.

Adaptation, Psychological↗