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Biomedical subjects

J Porter

Publications and source records attributed to J Porter.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1996

Porcine islets for xenotransplantation.

Long-term function of isolated porcine islets was investigated in diabetic nude mice. Seven of eight mice that received transplants of porcine islets remained normoglycemic for 1 year with progressive weight gain. Circulating porcine C-peptide was detected throughout the study period. Intravenous glucose tolerance tests showed a rapid glucose clearance rate. Together with our recent finding that porcine islets contained within an immunoexclusion device achieved glycemic control in a totally pancreatectomized dog, these results clearly demonstrate that isolated porcine islets are capable of functioning for prolonged periods in xenogeneic hosts and are suitable for long-term use in an immunoexclusion device in a discordant host.

Animals↗
PubMed1996

Effect of acute stimulation on Fos expression in spinal neurons in the presence of persisting C-fiber activity.

Expression of the inducible transcription factor c-Fos has been examined in the lumbar spinal cord following noxious chemical stimulation (injection of 2% formalin) of the ankles or the ventral skin of the hindpaws of either normal rats, or monoarthritic rats during the chronic phase of the disease. In normal animals the basal expression of c-Fos was low. One day after induction of monoarthritis by an intra-articular injection of killed Mycobacterium butyricum (in complete Freund's adjuvant) there were numerous c-Fos labelled cells in the ipsilateral dorsal horn, and bilaterally in lamina VIII and in other areas of the ventral horn. Four weeks after induction of the arthritis, although marked inflammation of the ankle was still present, all the expression of c-Fos had returned to the basal levels. One hour after formalin stimulation of the ankle or hindpaw skin of normal rats expression of c-Fos was observed throughout the ipsilateral, but not contralateral dorsal horn. Formalin stimulation of the inflamed ankle in four-week arthritic rats induced a 3-to-6 fold increase in c-Fos expression in the ipsilateral dorsal horn compared to formalin stimulation of the ankle in normal rats. In addition, c-Fos expression was induced in the contralateral deep, but not superficial laminae, at a density similar to that produced ipsilaterally by formalin stimulation of the ankle of normal rats. Formalin stimulation of the contralateral ankle in monoarthritic rats (i.e. the non-inflamed ankle) induced an ipsilateral expression of c-Fos which was similar to that observed after stimulation of the arthritic ankle. This stimulation of the normal ankle also resulted in an expression of c-Fos in the contralateral deep, but not superficial laminae, that was similar to that induced ipsilaterally by stimulation of the arthritic ankle. Finally, formalin stimulation of the hindpaw skin (which was not inflamed) of the arthritic limb induced the same number of c-Fos labelled cells in the superficial laminae as did formalin stimulation of the skin of normal rats; but in the deep laminae there was a 1.6-fold increase in the number of labelled cells. These different observations show that the down-regulation of c-Fos expression observed in chronic monoarthritis is in fact associated with a sensitization and an extension of the field of its expression in response to an acute nociceptive stimulation.

Animals↗
PubMed1996

Betidamino acids: versatile and constrained scaffolds for drug discovery.

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. Betidamino acids are most conveniently generated on solid supports used for the synthesis of peptides by selective acylation of one of the two amino functions of orthogonally protected aminoglycine(s) to generate the side chain either prior to or after the elongation of the main chain. We have used unresolved Nalpha-tert-butyloxycarbonyl-N'alpha-fluorenylmethoxycarbonyl++ + aminoglycine, and Nalpha-(Nalpha-methyl)-tert-butyloxycarbonyl-N'alpha-fluo renylmethoxycarbonyl aminoglycine as the templates for the introduction of betidamino acids in Acyline [Ac-D2Nal-D4Cpa-D3Pal-Ser-4Aph(Ac)-D4Aph(A c)-Leu-Ilys-Pro-DAla-NH2, where 2Nal is 2-naphthylalanine, 4Cpa is 4-chlorophenylalanine, 3Pal is 3-pyridylalanine, Aph is 4-aminophenylalanine, and Ilys is Nepsilon-isopropyllysine], a potent gonadotropin-releasing hormone antagonist, in order to test biocompatibility of these derivatives. Diasteremneric peptides could be separated in most cases by reverse-phase HPLC. Biological results indicated small differences in relative potencies (<5-fold) between the D and L nonalkylated betidamino acid-containing Acyline derivatives. Importantly, most betide diastereomers were equipotent with Acyline. In an attempt to correlate structure and observed potency, Ramachandran-type plots were calculated for a series of betidamino acids and their methylated homologs. According to these calculations, betidamino acids have access to a more limited and distinct number of conformational states (including those associated with alpha-helices, beta-sheets, or turn structures), with deeper minima than those observed for natural amino acids.

Amino Acid Sequence↗
PubMed1996

Fluorescent probes and flow cytometry: new insights into environmental bacteriology.

Recent trends in flow cytometry have established new techniques in bacteriology. Advances in fluorescent dye technology complement these improvements, offering probes for a variety of cellular functions. Bacterial ecology requires the application of new techniques to help answer questions unanswerable by traditional methods alone. Here we review some aspects of how coupling the two technologies has enabled researchers to directly study individual bacterial cells, and revealed the complexity and heterogeneity present in both laboratory cultures and in environmental samples. Results are discussed with respect to viability analysis, stress induced changes, specific cell detection and cell sorting.

Bacteriological Techniques↗
PubMed1996

Dose relationship between GnRH antagonists and pituitary suppression.

While the clinical significance of gonadotrophin-releasing hormone (GnRH) agonists is well recognized, the potential use of GnRH antagonists in humans awaits the availability of potent analogues with no untoward side-effects. We have designed, synthesized and tested several hundred linear and cyclic analogues (agonists and antagonists) of GnRH in different rat models; some have high histamine releasing activity and others have poor solubility in aqueous buffers with a pH > 6.0. Furthermore, we have identified analogues exhibiting short (< 12 h), intermediate (12-72 h) and long (> 72 h) duration of action in the rat (50 micrograms s.c. dose/rat). We have concluded that the basis for such resistance to degradation and elimination must be specific. In order to gain further information on the optimal nature and sterical requirements of side-chains, preliminary experiments were carried out using betidamino acids. Finally, mono- and dicyclic analogues of GnRH with potencies comparable with that of the most potent linear analogues were also obtained. Our approach to the development of such analogues included the use of nuclear magnetic resonance and computational techniques as well as that of state-of-the-art synthetic approaches. We intend to use the information derived from these structure/activity relationship studies to design conformationally-similar peptido-mimetics.

Amino Acid Sequence↗