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Biomedical subjects

J Parker

Publications and source records attributed to J Parker.

At least 199 records · Page 11Linked to original sources
PubMed1990

The equine fundus. II: Normal anatomical variants and colobomata.

A wide range of fundic variants are encountered during routine ophthalmoscopic examination of visually normal horses, often causing the examiner difficulty in assessing their clinical significance. Many of these are anatomical variants having no significant effect on visual function, and lie within the limits of normality in the horse. This paper illustrates this range of variants and discusses their anatomical basis and physiological consequences. Colobomata are non-progressive discontinuities in the structure of the anatomic fundus, occasionally noted as incidental findings during ophthalmoscopy. This paper illustrates typical and atypical colobomata of the equine fundus, the latter occurring outside the embryonic optic fissure. The anatomical basis of these colobomata and their possible consequence on vision is discussed.

Animals↗
PubMed1990

The equine fundus. III: Pathological variants.

A wide range of ophthalmoscopic variants are encountered during routine examination of the horse. Some result from minor anatomical anomalies, cause no significant effect on vision and may be considered to lie within the limits of 'biological normality'. Others are a consequence of pathological disruption of the anatomical integrity of the fundus, and may directly or indirectly affect the neurosensory retina and produce some degree of visual deficit. This paper illustrates the ophthalmoscopic appearance of a number of pathological variants of the anatomic fundus, and discusses their possible effect upon vision. Among the abnormalities discussed is peripapillary chorioretinitis, which commonly presents as the so-called peripapillary 'butterfly lesion'. It is concluded that, although this lesion may occur in conjunction with signs of more generalised posterior segment disease, eg posterior capsular cataract, in the absence of concurrent signs of anterior uveitis there is no reason to associate the lesion with equine recurrent uveitis (periodic ophthalmia).

Animals↗
PubMed1990

DNA sequence of the purC gene encoding 5'-phosphoribosyl-5-aminoimidazole-4-N-succinocarboxamide synthetase and organization of the dapA-purC region of Escherichia coli K-12.

5'-Phosphoribosyl-5-aminoimidazole-4-N-succinocarboxamide synthetase (EC 6.3.2.6), encoded by the purC gene of Escherichia coli K-12, catalyzes the synthesis of 5'-phosphoribosyl-5-aminoimidazole-4-N-succinocarboxamide from 5'-phosphoribosyl-5-aminoimidazole-4-carboxylic acid. The mature protein, as deduced from the purC structural gene sequence, contains 237 amino acids and has a calculated Mr of 26,998. The control region of the purC gene was identified by primer extension mapping of the 5' end of the purC mRNA. The purC control region contains a binding site for and is regulated by the purine repressor, the product of the purR gene. An unusual feature of the 5' untranslated region of the purC mRNA is the presence of a repetitive extragenic palindrome sequence normally found in intercistronic or 3' untranslated regions. The DNA sequence was extended 1.281 kilobases upstream of the purC structural gene and overlapped with the previously determined dapA sequence. Termination of transcription from the dapA-purC intercistronic region may occur within the -35 region of the purC control region. The purC gene has been positioned on the E. coli restriction map and is transcribed in a counterclockwise direction.

Amino Acid Sequence↗
PubMed1990

Professional nursing education in the university context.

This paper examines the notion of the character of the nurse, how it was moulded with the development of modern professional nursing in the patriarchal society of the time and how it has changed in the context of the rise of modern medicine. Emphasis is given to the importance of ensuring the humanising development of the nursing student in the university context through an appropriate balance of theory and practice and access to study of the liberal arts.

Australia↗
PubMed1990

Phase I study of combination recombinant interleukin-2 and interferon gamma in patients with advanced malignancies.

A phase I trial of interleukin-2 and interferon gamma combination treatment in patients with advanced malignancies was performed based on preclinical in vitro and in vivo data which demonstrated synergistic antitumor effect. The toxicities, immune parameters, and tumor responses are described. The clinical and biologic maximal tolerated doses were extrapolated from these data.

Adolescent↗
PubMed1990

Reduction in ESRD reimbursement rate: identifying research priorities and quality indicators.

In October 1972, Public Law 92-603 extended Medicare benefits to patients suffering with chronic renal failure, and the End Stage Renal Disease (ESRD) Program was established. The availability of registered nurses to care for the ESRD patient has been directly related to the financial reimbursement obtained by providers from Medicare. This article identifies legislation passed to establish and maintain the ESRD Program and summarizes the ESRD regulations. A review of the literature to examine research on the impact of quality of care following the reduction in reimbursement rates and the implications for nephrology nursing research are explored.

Humans↗
PubMed1989

Cloning and sequence analysis of the fermentative alcohol-dehydrogenase-encoding gene of Escherichia coli.

A 6-kb fragment of DNA, which complemented defects in the alcohol dehydrogenase (ADH)-encoding gene (adhE) of Escherichia coli, was cloned into a multicopy vector. Both ADH and coenzyme-A-linked acetaldehyde dehydrogenase (ACDH) activities were encoded by the plasmid, pHIL8. The adhE gene was identified as an open reading frame of 891 codons encoding an Mr 96,008 protein (minus the initiating methionine). Codon usage analysis indicates that adhE should be highly expressed. This gene shows no significant homology to any previously sequenced ADH-encoding gene.

Alcohol Dehydrogenase↗
PubMed1989

Modulation of platelet function by extracellular adenosine triphosphate.

A potential physiologic role of extracellular adenosine triphosphate (ATP) on platelet function is proposed in this report. It is widely accepted that ATP competitively inhibits adenosine diphosphate (ADP)-induced platelet aggregation. Our observations of platelet aggregation with the agonists, collagen, epinephrine, and ADP in the presence of 180 mumol/L ATP could support this competitive nature of ATP. However, the disaggregation of maximally aggregated platelets induced by ATP, theophylline, or ATP plus theophylline indicates that additional mechanisms of ATP action may be present. Extracellular gamma-32P-ATP (7 pmol) labels surface-membrane proteins in intact platelets as demonstrated by several criteria. The reaction is Ca++-dependent. Stimulation by calcium occurs in the physiologic range of 1 to 5 mmol/L. Significant levels of phosphorylation occur within one minute with near maximal levels reached by five minutes. Platelet cyclic AMP (cAMP) levels were elevated in a dose-dependent fashion in cells incubated for four minutes with increasing amounts of extracellular ATP (18 to 540 nmol). The addition of ATP plus theophylline resulted in a synergistic stimulation of cAMP levels. ATP was not being hydrolyzed to adenosine by plasma nucleotidases, as demonstrated by the lack of effect of ten U of adenosine deaminase. The phosphorylation of surface proteins by extracellular ATP released from activated platelets may modulate platelet responsiveness to agonists at distances removed from the site of vascular injury. Phosphorylation may also play a role in signal transduction to regulate the levels of intracellular cAMP, which further inhibits platelet activation.

Adenosine Triphosphate↗
PubMed1989

Context specific misreading of phenylalanine codons.

It has previously been shown that the phenylalanine codon UUC encoding residue 8 of the Escherichia coli argI gene product, ornithine transcarbamylase, is misread as leucine at a high frequency during phenylalanine starvation. However, no misreading of the UUU encoding residue 3 was observed under these conditions. Using oligonucleotide-directed, site-specific mutagenesis, we have constructed mutants where these codons have been changed. Using these mutant argI genes we see a high level of mistranslation at position 8 during phenylalanine starvation whether the codon is UUU or UUC. With either codon at position 3 we see no leucine substitution. We also constructed a gene with a leucine codon at position 3. The product of this latter mutated gene is stable and active, indicating that preferential turnover of mistranslated protein is not obscuring an otherwise high rate of misreading. This would seem to indicate that it is the context rather than the particular phenylalanine codon which is important in determining these misreading levels.

Amino Acid Sequence↗
PubMed1989

Effect of chronic lithium on sensitivity to light in male and female bipolar patients.

1. Sensitivity to white light was quantified in euthymic bipolar male and female patients maintained on long term lithium therapy and age and sex matched unmedicated controls. 2. The Dark Adaptation Threshold procedure was used to assess sensitivity of both the cone and rod photoreceptors to short pulses of light. 3. Male and female controls did not differ in sensitivity to light. 4. Male patients in comparison to both controls and female patients evidenced reduced sensitivity to light during the cone and rod portion of the dark adaptation procedure. 5. Female patients did not differ from controls on sensitivity to light. 6. Using these and other published data the results were interpreted as suggesting that lithium reduces sensitivity to light during adaptation to dark.

Adaptation, Ocular↗
PubMed1989

Continuous oxygen insufflation in addition to IPPV causes air trapping in a mechanical lung model.

It has previously been reported that continuous insufflation of either supracarinal or subcarinal oxygen in addition to intermittent positive-pressure ventilation (IPPV) in patients under general anesthesia, and in critically ill patients in the intensive care unit, causes increased proximal airway pressure, decreased systemic blood pressure, and decreased cardiac output. The investigators hypothesized that these deleterious hemodynamic effects were due to intrapulmonary air trapping, resulting in an increased distal intrapulmonary pressure and volume. The purpose of this study was to test this hypothesis in an appropriate mechanical lung model. The study determined end-inspiratory and end-expiratory lung pressures and volumes during eight experimental sequences: (1) IPPV alone; (2) insufflation of oxygen alone at 2.5, 5.0, and 10.0 L/min (O2-2.5, 5.0, 10.0); (3, 4, and 5) IPPV plus insufflation of oxygen (IPPV + O2-0.0, 2.5, 5.0, 10.0) through a supracarinal catheter (sequence 3), subcarinal catheters (sequence 4), and through a CO2 sampling port of an endotrachael tube (sequence 5); (6 and 7) IPPV + O2-5.0 with increased expiratory time caused by an increased inspiratory flow rate (sequence 6) and a decreased respiratory rate (sequence 7); (8) IPPV + O2-5.0 with increased airway diameter. Experimental sequences 1 and 2 resulted in no increases or minimal ones in lung pressure and volume, respectively. With each insufflation catheter system (sequences 3, 4, and 5), each incremental increase in insufflation flow rate resulted in significant increases in lung pressure and volume. Increasing expiratory times (sequences 6 and 7 compared with 3, 4, and 5) decreased lung pressure and volume. Increasing the airway diameter (sequence 8) had only slight effect on lung pressure and volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Obstruction↗
PubMed1989

Solubilization and characterization of sigma-receptors from guinea pig brain membranes.

The sigma-receptor, a distinct binding site in brain tissue that may mediate some of the psychotomimetic properties of benzomorphan opiates and phencyclidine, has been solubilized using the ionic detergent sodium cholate. Binding assays were performed with the solubilized receptor using vacuum filtration over polyethyleneimine-treated glass fiber filters. The pharmacological specificity of the solubilized binding site for sigma-receptor ligands is nearly identical to the membrane-bound form of the receptor, with the order of potencies for displacement of the selective sigma-ligand [3H]di-o-tolylguanidine ([3H]DTG) closely correlated. The stereoselectivity for (+)-benzomorphan opiate enantiomers was retained by the solubilized receptor. The soluble receptor retained high affinity for binding of [3H]DTG (KD = 28 +/- 0.5 nM) and (+)-[3H]3-(3-hydroxyphenyl)-N-(1-propyl)piperidine [(+)-[3H]3-PPP] (KD = 36 +/- 2 nM). Photoaffinity labeling of the solubilized receptor by [3H]p-azido-DTG, a sigma-selective photoaffinity label, resulted in labeling of a 29-kilodalton polypeptide identical in size to that labeled in intact membranes. Estimation of the Stokes radius of the [3H]DTG binding site was obtained by Sepharose CL-6B chromatography in the presence of 20 mM cholate and calculated to be 8.7 nm. This value was identical to the molecular size found for the binding sites of the sigma-selective ligands (+)-[3H]3-PPP and (+)-[3H]SKF-10,047, supporting the hypothesis that all three ligands bind to the same macromolecular complex.

Affinity Labels↗