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Biomedical subjects

J Porter

Publications and source records attributed to J Porter.

At least 73 records · Page 4Linked to original sources
PubMed1998

The understanding of counting in children with severe learning difficulties and nursery children.

BACKGROUND: Little is known about the development of counting in children with severe learning difficulties (SLD) although early research has stressed the rote nature of children's understanding. AIMS: We investigated the attainments of children with SLD both with regard to their skills and understanding of counting and compared performance with typically developing preschoolers. SAMPLES: Twenty-five children with SLD (aged 7-14 years) matched to one group of preschoolers on the basis of their receptive language scores and to a second group using a broader measure, performance on a non-verbal intelligence test. METHODS: Children were presented with a simple counting task and an error detection task. RESULTS: There were no differences between the SLD and preschool groups in the mean scores on either task. In each group more children were able to count than detect errors. However, analysis of their counting performance suggested a difference in the acquisition of counting skills. Furthermore, the SLD group included three transitional children-able to count competently but not able to detect errors. This pattern was not evident in the preschool groups: if the children were competent counters they were able to detect errors. CONCLUSION: The acquisition of procedures for counting is an important first step in developing an understanding of counting. There is some evidence to suggest that children with SLD may have difficulty learning the number words and producing them whilst pointing to count items. We cannot assume that children with SLD will move smoothly towards an understanding of counting. These aspects warrant further investigation and raise the important question of what experiences best promote the acquisition of procedures and understanding in children with SLD.

Adolescent↗
PubMed1998

Can accident and emergency nurse practitioners interpret radiographs? A multicentre study.

OBJECTIVE: To assess the ability of nurse practitioners in accident and emergency (A&E) to interpret distal limb radiographs, by comparison with senior house officers. DESIGN: Nurse practitioners and senior house officers in 13 A&E departments or minor injury units were shown 20 radiographs of distal limbs, with brief history and examination findings, and asked to record their interpretation. OUTCOME MEASURE: A total score for each subject was calculated by comparing answers against agreed correct responses. RESULTS: Nurse practitioners in general compared favourably with senior house officers. Those nurse practitioners who interpret radiographs as part of their role in minor injury units performed as well as the experienced senior house officer group. CONCLUSIONS: Nurse practitioners in A&E are able to interpret radiographs to a standard equal to senior house officers with three to five months' experience. Those nurse practitioners actively interpreting radiographs as part of their role in minor injury units are able to interpret radiographs to the same standard as senior house officers with more than five months' experience.

Analysis of Variance↗
PubMed1998

Tuberculosis control in refugee populations: a challenge to both relief agencies and national programs.

Today's worldwide tuberculosis epidemic and the movement of a growing number of refugees overlap geographically and have made tuberculosis control in refugee populations an issue of increasing importance. However, in developing countries, where both of these problems are concentrated, tuberculosis control in refugee populations remains a largely unmet need. Experience shows that despite difficult field conditions, tuberculosis control programs can be managed successfully in this setting. The range of outcome results reported for treatment completion and defaulting is, however, wide. Analyzing possible determinants for observed variation in treatment outcome results, this paper outlines prerequisites for establishing a tuberculosis control program in a refugee setting. An attempt is made to formulate a general strategy for the main policies which, if applied consistently, will reduce morbidity, mortality and transmission of tuberculosis among refugee populations living in camps. Criteria for the evaluation and monitoring of such a program are discussed.

Communicable Disease Control↗
PubMed1997

Betidamino acid scan of the GnRH antagonist acyline.

Strong clinical evidence suggests that GnRH antagonists will replace GnRH agonists in a number of indications because of their ability to inhibit gonadotropin secretion as long as an adequate concentration of the analogue is present in the circulation whereas superagonists will take approximately 2 weeks to desensitize the gonadotrophs. Until recently, antagonists were either too weak and/or would release histamine. Azaline B {[Ac-D2Nal1,D4Cpa2,D3Pal3, 4Aph5(atz),D4Aph6(atz),ILys8,DAla10] GnRH} and long-acting members of the azaline family {Ac-D2Nal-D4Cpa-D3Pal-Ser-4Aph(X)-D4Aph(Y) -Leu-ILys-Pro-DAla-NH2}, however, appear to be promising drug candidates. Because these antagonists tend to form gels (due to the formation of beta-sheet structures) and, as a result, are not readily amenable to formulation for long-term delivery, we have investigated ways of increasing hydrophilicity while retaining high potency and lack of histamine releasing activity. Betidamino acids (a contraction of "beta" position and "amide") are N'-monoacylated (optionally, N'-monoacylated and N-mono- or N,N'-dialkylated) aminoglycine derivatives in which each N'-acyl/alkyl group may mimic naturally occurring amino acid side chains or introduce novel functionalities. We have used unresolved N alpha-Boc,N'alpha-Fmoc-aminoglycine, and N alpha-Boc,N'alpha-(CH3)Fmoc-aminoglycine as templates for the introduction of betidamino acids in acyline (Ac-D2Nal-D4Cpa-D3Pal-Ser-4Aph(Ac)-D4Aph(A c)-Leu-Ilys-Pro-DAla-NH2), a long acting member of the azaline B family, to test biocompatibility of these betide derivatives. Diastereomeric peptides could be separated using RP-HPLC in most cases. Biological results obtained in vitro (binding affinity to rat pituitary gland membranes) and in vivo (rat antiovulatory assay, AOA) indicate in most cases small differences in relative potencies (< 5-fold) between the D- and L-nonalkylated betidamino acid-containing acylines. Importantly, most betide diastereomers have high affinity for the GnRH receptor and were equipotent with acyline in the AOA. Greater differences in affinity and potency between diastereomers were observed after introduction of a methyl group on the side chain nitrogen ("beta" position) of the same analogues, with one of the diastereomer having an affinity and a potency in the AOA equivalent to that of acyline. These results suggest that chirality at the alpha-carbon coupled to side chain orientation is important for receptor recognition. The duration of action of some of the most potent analogues was also determined in the castrated male rat in order to measure the extent (efficacy and duration of action) of inhibition of luteinizing hormone release. Data suggest that introduction of a betidamino acid results in reduction of duration of action. Also, introduction of betidamino acids results in peptides with increased hydrophilicity (as determined by elution times on C18 silicas at pH 7.3) compared to that of the parent compound. N'-Methyl substitution results in parallel increase in retention times on C18 silicas as expected.

Amides↗
PubMed1997

A novel post-translational modification involving bromination of tryptophan. Identification of the residue, L-6-bromotryptophan, in peptides from Conus imperialis and Conus radiatus venom.

We report a novel post-translational modification involving halogenation of tryptophan in peptides recovered from the venom of carnivorous marine cone snails (Conus). The residue, L-6-bromotryptophan, was identified in the sequence of a heptapeptide, isolated from Conus imperialis, a worm-hunting cone. This peptide does not elicit gross behavioral symptoms when injected centrally or peripherally in mice. L-6-Bromotryptophan was also identified in a 33-amino acid peptide from Conus radiatus; this peptide has been shown to induce a sleep-like state in mice of all ages and is referred to as bromosleeper peptide. The sequences of the two peptides and were determined using a combination of mass spectrometry, amino acid, and chemical sequence analyses, where Pca = pyroglutamic acid, Hyp = hydroxyproline, Gla = gamma-carboxyglutamate, and Trp* = L-6-bromotryptophan. The precise structure and stereochemistry of the modified residue were determined as L-6-bromotryptophan by synthesis, co-elution, and enzymatic hydrolysis experiments. To our knowledge this is the first documentation of tryptophan residues in peptides/proteins being modified in a eukaryotic system and the first report of halogenation of tryptophan in vivo.

Amino Acid Sequence↗
PubMed1997

Glucose-stimulated sodium transport by the human intestine during experimental cholera.

BACKGROUND & AIMS: Net sodium absorption from oral rehydration solution is increased by both glucose-sodium cotransport and solvent drag. The aim of this study was to measure the relative importance of glucose-sodium cotransport and solvent drag in the stimulation of net sodium absorption by oral rehydration solution. METHODS: Total intestinal perfusion was used in normal subjects with and without intrajejunal cholera toxin using three test solutions containing 100 mmol/L sodium and either 100 mmol/L mannitol (control), 100 mmol/L glucose, or no additional solute (hypotonic solution). The increase in sodium absorption greater than control with hypotonic solution represented sodium absorption stimulated by solvent drag; the further increase in sodium absorption induced by glucose, greater than that noted with the hypotonic solution, represented sodium absorption stimulated by cotransport. RESULTS: Without cholera toxin, solvent drag and cotransport promoted sodium absorption at rates of 62 and 33 mmol/h, respectively. With cholera toxin, solvent drag and cotransport promoted sodium absorption at rates of 44 and 71 mmol/h, respectively. CONCLUSIONS: Net sodium absorption caused by cotransport increased more than twofold after exposure of the intestine to cholera toxin (P < 0.003). This could be mediated by increased cotransport, a change in the stoichiometry of cotransport, or an increase in chloride permeability.

Adult↗
PubMed1997

The effect of dehydroepiandrosterone (DHEA) on Zucker rat food selection and hypothalamic neurotransmitters.

The effect of dehydroepiandrosterone (DHEA) administered as an acute intraperitoneal (IP) injection on food selection and levels of hypothalamic neurotransmitters of obese Zucker rats was investigated. Animals consumed a 'macronutrient selection' diet which consisted of three separate foodstuffs; they were nearly pure selections of fat, protein or carbohydrate. On the day before DHEA treatment, food bowls were removed at 1700 h and the animals fasted. The next morning some were treated with IP DHEA (100-200 mg/kg) while the controls received vehicle. Two hours later, their food intakes over 4 h were quantitated or, in other experiments, the animals were decapitated and hypothalamic neurotransmitter levels determined. Results showed that the administration of DHEA clearly diminished the amount of fat the animals consumed while their intakes of carbohydrate and protein were unchanged. Levels of neurotransmitters in the paraventricular nuclear region were altered. It is concluded that DHEA diminishes the fat food consumption of obese Zucker rats by altering the levels of neurotransmitters in select regions of the hypothalamus.

Animals↗
PubMed1997

Validation of polyethylene glycol 3350 as a poorly absorbable marker for intestinal perfusion studies.

Polyethylene glycol (PEG) has been used as a poorly absorbable marker in intestinal perfusion studies, but there is controversy about the absorbability of PEG, particularly when glucose-sodium cotransport is occurring. Total intestinal perfusion studies were done in five normal humans using three solutions containing 1 g/liter PEG 3350 and designed to produce low rates of water absorption, high rates of water absorption, or high rates of glucose-sodium cotransport. Water absorption rates were calculated by traditional nonabsorbable marker equations and by a novel balance technique in which absorption was taken as the difference between the volumes of solution infused and recovered during steady-state conditions. Effluent PEG recovery was 99 +/- 4%, 109 +/- 2%, and 104 +/- 6% of the amount infused with each solution. Water absorption rates measured by use of PEG concentrations were similar to those calculated by the balance technique (r = 0.99). The complete recovery of PEG confirms the poor absorbability of PEG 3350, and the excellent agreement between techniques validates PEG as a poorly absorbed marker, even when glucose-sodium cotransport is occurring.

Adult↗
PubMed1997

Detection, distribution and probable fate of Escherichia coli O157 from asymptomatic cattle on a dairy farm.

The use of commercial anti-Escherichia coli O157-labelled magnetic beads was investigated to improve detection of E. coli O157 by immunomagnetic separation (IMS) from a range of environments on a dairy farm. Immunomagnetic separation proved effective for separation of target cells from laboratory mixtures and during stress in sterile and non-sterile pond water. The IMS procedure was possible with a range of samples (water, faeces, slurry, grass and soil). Non-specific binding of non-target bacterial cells proved problematic in a number of sample types. However, indigenous E. coli O157 cells were detected from samples with a high faecal load, and only with use of IMS. Data on the probable survival and spread of the organism around the farm environment are also discussed.

Animals↗
PubMed1997

Efficiency of the polymerase chain reaction amplification of the uid gene for detection of Escherichia coli in contaminated water.

Direct detection of Escherichia coli from polluted river water was achieved using polymerase chain reaction (PCR) amplification of the uid gene. Amplification using DNA from environmental samples resulted in non-specific DNA fragments. Specific amplification was achieved through use of the touch-down PCR procedure. Targeting the uidA structural region of the gene gave reproducibly better amplification than targeting the uidR regulatory region. The data demonstrate conditions for optimal specific detection.

Bacteriological Techniques↗
PubMed1997

Modelling the economic benefits of tuberculosis preventive therapy for people with HIV: the example of Zambia.

OBJECTIVE: To assess the economic benefits and costs of providing isoniazid preventive therapy for tuberculosis (TB) in HIV-infected persons in Zambia. DESIGN: A spreadsheet model incorporating variables drawn from published studies and unpublished data. SUBJECTS: Data drawn from a number of different studies and published literature involving a range of subjects. SETTING: Zambia. RESULTS: Using data primarily from Zambia we have modelled the costs and benefits of a TB preventive therapy programme using daily isoniazid for 6 months. The basecase scenario assumes recruitment at a voluntary testing and counselling site where HIV seroprevalence is 30%; persons with HIV have a 25% probability of developing active TB during their lifetime; two additional cases of TB would be prevented per person completing a course of preventive therapy; compliance would be 63%, and the efficacy of the isoniazid in preventing active TB of 60%. The costs under this scenario would exceed the benefits by a factor of 1.16 [benefit: cost ratio (BCR) of 0.86]. However, if preventing one case of TB prevented an additional five cases, the benefits would exceed the costs by a significant margin (BCR of 1.71). Other scenarios indicate that the targeted preventive therapy of persons with HIV whose occupation or living situation places them in contact with a large number of others (teachers and students, health personnel, military and police, miners, prisoners, etc.) would yield significant net benefit. The operational challenge for TB preventive therapy is thus to identify and target large numbers of such persons.

AIDS-Related Opportunistic Infections↗
PubMed1997

Which patients with ankylosing spondylitis derive most benefit from an inpatient management program?

OBJECTIVE: To evaluate the benefit achieved from an inpatient management program by testing the hypothesis that more mobile, younger patients on their first course show the most improvement. METHODS: We assessed 236 patients over an 18 month period. Patients were assessed at the beginning and end of the course by 4 indices, 3 of which were self-administered (disease activity, functional ability, and global well being) and one administered by a trained physiotherapist (metrology). Paired t tests and ordinary least squares regression analysis were used to compare pre and postcourse results for each index. RESULTS: The wide range of disease duration (0-53 years) and disease severity [0.69-9.39 (on a 0-10 scale)] reveal that patients are from a wide spectrum of disease. Results revealed a mean improvement of 18-27% over baseline in the 4 indices. Significant predictors of greater improvement over the 2 week course were found for each index. CONCLUSION: Our results confirm the benefit of an intensive regime of inpatient physiotherapy. Although the original hypothesis cannot be accepted or rejected as the results were different for the 4 indices, the following general conclusions may be drawn: (1) there is a trend for females to improve more than males; (2) patients who have attended fewer courses tend to achieve more improvement; (3) younger patients do better than older patients; and (4) age of disease onset has little effect.

Adult↗
PubMed1997

A comparative microscopic analysis of the capsule of the nerve to the inferior oblique muscle.

PURPOSE: To delineate the nature of the nerve capsule to the inferior oblique muscle at birth and adulthood, and to compare it to the nerve capsules of other extraocular muscles. METHODS: Fresh autopsy specimens were obtained from a newborn and a 26 year-old male. The length of the inferior oblique nerve was analyzed with high magnification photomicroscopy and electron microscopy and compared to the nerve capsules of the adult medial, lateral, inferior and superior rectus muscles. These were also compared to the intracranial portion of the third cranial nerve of the adult specimen. RESULTS: The collagen layer of the nerve to the inferior oblique was present throughout its course. It is well developed in the newborn and comparable to the adult specimen. The nerves to the medial, inferior, lateral and superior rectus muscles are also surrounded by a similar capsule containing collagen fibers that are aligned parallel to the axon of the nerve. The intracranial portion of the third cranial nerve only has a thin fibrous capsule. CONCLUSION: The nerve capsule of the inferior oblique comprises a surrounding collagen layer, presumably to protect the nerve from stretching. This layer is well developed along the entire course of the nerve and is present from birth. The nerves to the other extraocular muscles have a similar capsule that likely serves a similar function. These findings expand current understanding of the nerves to the extraocular muscles and may be useful for improving treatments.

Adult↗