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Biomedical subjects

R Jones

Publications and source records attributed to R Jones.

At least 793 records · Page 44Linked to original sources
PubMed1987

Retrolabyrinthine or retrosigmoid vestibular neurectomy: indications.

Selective vestibular nerve section is indicated for the treatment of vertigo in unilateral Meniere's disease or other inner ear disorders, in patients with salvageable hearing. Since 1978, the retrolabyrinthine approach to the vestibular nerve in the cerebellopontine angle has been used extensively with good success and minimal morbidity. In an attempt to obtain more complete section of the vestibular nerve, the retrosigmoid-internal auditory canal approach was developed in 1985 and has been employed in 13 patients, all of whom obtained complete control of vertigo. The surgical techniques are presented with emphasis on the advantages and disadvantages of each approach. Relative indications and contraindications are suggested.

Ear, Inner↗
PubMed1987

Effects of atropine and 2-PAM chloride on vision and performance in humans.

These experiments assessed the time course and severity of effects of atropine and 2-PAM chloride on selected visual functions, physiological measures, and a tracking performance task. Atropine up to 4 mg X 70 kg-1 body weight and 2-PAM Cl in doses up to 1200 mg X 70 kg-1 body weight were administered intramuscularly in a double-blind Latin square design. A long lasting and dose-related increase in pupillary diameter and decrease in accommodative amplitude with accompanying loss of near visual acuity was found following atropine administration. These functions returned to baseline 2 d after injection. Distance acuity, contrast sensitivity, color vision, and intraocular pressure showed no changes after atropine. Tracking performance was significantly decreased by 4 mg of atropine. The changes in vision function cannot readily explain the tracking performance loss, since the tracking involved a distant visual target while the atropine produced degradation of near vision. Most of the physiological tests, tracking performance and all visual functions were unaffected by 2-PAM Cl.

Accommodation, Ocular↗
PubMed1986

Requirement of gene transcription and protein synthesis for cold- and norepinephrine-induced stimulation of thyroxine deiodinase in rat brown adipose tissue.

The increase in propylthiouracil-insensitive 'type II' thyroxine 5'-deiodinase activity of brown adipose tissue was investigated in rats exposed to acute cold stress or single-dose norepinephrine injection. The 20-fold cold-induced increase in enzyme activity showed a 2-h lag phase and reached a maximum after only 8 h; reacclimation occurred with a 2-h time lag and a half-life of 2.2 h. 4 h after a single norepinephrine injection, the deiodinase activity was almost identical to that after a 4-h cold stress; norepinephrine could not potentiate the effect of the cold stress. Treatment with the protein synthesis inhibitor cycloheximide before exposure to cold or before norepinephrine injection totally blocked the increase in deiodinase activity, suggesting that the increase is due to de novo protein synthesis. The half-life of the enzyme in vivo was estimated to be 0.7 h. Treatment with the RNA synthesis inhibitor actinomycin D totally abolished the cold- and norepinephrine-induced increases, indicating that the increase requires mRNA synthesis. It was concluded that the dramatic cold-induced increase in thyroxine deiodinase activity in brown adipose tissue was not due to activation of preexisting enzyme but was fully due to a norepinephrine-induced increase in expression of the gene and subsequent synthesis of the protein.

Adipose Tissue, Brown↗
PubMed1986

Second gene (nifH*) coding for a nitrogenase iron protein in Azotobacter chroococcum is adjacent to a gene coding for a ferredoxin-like protein.

Azotobacter chroococcum MCD1 contains a cluster of nitrogen fixation (nif) genes coding for the structural polypeptides for nitrogenase (nifH for the Fe-protein and nifD and nifK for the MoFe protein) and a second sequence in the genome homologous to nifH. DNA fragments bearing this second nifH-like sequence were cloned and the DNA sequence around the homologous region determined. Two open reading frames were identified in this region. One codes for a protein of 289 amino acid residues and is highly homologous to other Fe-proteins but is different from the gene adjacent to the nifDK genes in A. chroococcum. This putative gene we call nifH*. The following open reading frame codes for a protein of 63 amino acids, nine of which are cysteine residues. The protein is homologous to the small low-potential ferredoxins found in anaerobic bacteria, and in particular those from Chlorobium limicola. Linkage between a structural gene for nitrogenase and a small ferredoxin has not previously been observed. Sequence analysis suggests that the two genes form an operon. Transcription of the ferredoxin gene on a 1320-bp transcript was only detectable under conditions in which A. chroococcum MCD1155, which carries a chromosomal deletion of 6.3 kb removing the entire nifHDK cluster, is capable of fixing N2, i.e. in media containing no added molybdenum or high levels of NH3. The size of the observed transcript agrees well with the predicted size for a transcript encoding nifH* and the ferredoxin genes. Expression of the nifH* promoter was not significantly activated in Escherichia coli even when nifA, the positive activator of nif genes in Klebsiella pneumoniae, was supplied in multiple copies. The results are discussed in relation to an alternative pathway for N2 fixation in A. chroococcum.

Amino Acid Sequence↗
PubMed1986

High pass digital filtering applied to quantitative UV spectrometry.

High pass digital filtering is a novel method of data treatment for quantitative UV spectrometry in the presence of broad interfering bands. The test and standard spectra are digitally filtered using the binomial filter to remove low frequency components and a least squares fit of the standard to the test is then carried out. This paper reports a preliminary evaluation of the method, including a theoretical comparison with derivative spectrometry and the successful application to a typical problem in pharmaceutical analysis, the assay of the decongestant pseudoephedrine hydrochloride in the presence of the antihistamine triprolidine hydrochloride. The procedure should also be suitable for enhancing the specificity of other spectroscopic techniques.

Journal Article↗
PubMed1986

A comprehensive clinical validation of the nuclear stethoscope.

Five studies were conducted to examine the degree of variability to be expected during the use of the non-imaging nuclear probe (BIOS Inc.) under a variety of clinical conditions. Comparison of the ejection fraction (EF) readings between the nuclear probe and a gamma camera showed good agreement, with the nuclear probe tending to underestimate lower, and overestimate higher camera EF values [mean (S.D.) difference, 0.84% (6.06)]. A comparison of two nuclear probes showed a small mean (S.D.) difference of EF readings of 0.063% (2.26). EF readings obtained in normal subjects 6 weeks apart were reproducible and differed by a mean (S.D.) of 0.23% (4.42). The administration of placebo to 10 normal subjects followed by sequential measurements for 4 h produced EF changes large enough to mimic a clinical effect, the largest hourly change observed being 5.4%, indicating the need for strict placebo control in interventional experiments. Data on four patients with heart failure showed small non-significant EF changes in the 1 h after placebo administration but a wide intra-subject range of ejection time and time to peak filling measurements. This highlights the problem of accurate, reproducible cursor placement in such patients. The nuclear probe is a portable, low cost instrument which produces accurate EF measurements when compared with the gamma camera.

Adolescent↗
PubMed1986

Bacteremia during bronchoalveolar lavage.

We prospectively evaluated the incidence of bacteremia during fiberoptic bronchoalveolar lavage (BAL) and its relationship to postlavage symptoms in 12 volunteers. Qualitative and quantitative blood cultures were obtained before and during BAL. Three persons had qualitative blood cultures positive for organisms typical of normal skin flora. Quantitative blood cultures done simultaneously were negative. Approximately 42% of our subjects had postlavage symptoms, but no correlation was found between bacteremia and the occurrence of postlavage symptoms. Our results confirm the relative safety of BAL and the low incidence of BAL-associated bacteremia.

Adult↗
PubMed1986

Reducing adolescent smoking: a comparison of peer-led, teacher-led, and expert interventions.

To test the effectiveness of a psychosocial strategy of smoking deterence on seventh grade students, the School Health Education Development project implemented peer-led, teacher-led, and expert-led interventions in six Vermont schools. Four additional schools served as control groups. The teacher-led approach reduced the rate of smoking onset and the intention to smoke in the future among highly vulnerable females but not among males. The peer-led approach reduced the behavioral intention to smoke for both sexes but did not affect current smoking behavior. The expert-led approach did not produce favorable effects. Both the peer-led and teacher-led interventions had positive, though not significant, effects on student perception of locus of control. In the control schools, females experienced higher levels of smoking onset than males. Generally, the study points toward further development of a teacher-led approach to smoking deterence based on the theory of adolescent psychosocial development and the principle of continuous reinforcement.

Adolescent↗
PubMed1986

Cultivation and characterization of three strains of murine rotavirus.

Three distinct strains of murine rotavirus were adapted to growth in cell culture. These strains are genetically related but not identical; they are serotypically heterogeneous. The cultivatable strains were substantially more infectious (approximately 10(6)-fold) for suckling mice than heterologous simian rotaviruses were. Homologous murine rotavirus strains spread from inoculated to uninoculated litter mates and caused diarrhea, while heterologous rotaviruses did not spread and cause illness.

Animals↗
PubMed1986

External high frequency oscillation in cats. Experience in the normal lung and after saline lung lavage.

In an effort to develop a method of assisted ventilation that would avoid endotracheal intubation, 11 anesthetized, paralyzed, nonintubated adult mongrel cats with normal lungs were externally oscillated by means of a thoracoabdominal chamber connected to a vacuum source and a high frequency oscillator. Chamber pressure was adjusted to the desired negative pressure using the vacuum source, and the animal was then oscillated above and below this pressure. The lowest PaCO2 and AaPO2 were observed at 3 Hz. Tidal volume (VT) fell (p less than 0.001) with increases in frequency, and lung volume (VL) rose with increased negative chamber pressure (p less than 0.001). In 11 additional tracheostomized cats, a stiff lung was created by repeated saline lung lavage. External high frequency oscillation (EHFO), using pressures comparable to those used for conventional mechanical ventilation (CMV), was associated with a significant increase in PaO2 (p less than 0.001), and a significant fall in AaPO2 (p less than 0.01) compared with that during CMV. Lung volume was significantly higher during EHFO (p less than 0.001) and, as in the normal lung, VT fell with increasing frequencies to 15 Hz (p less than 0.001). There were no significant frequency-dependent variations in gas exchange or VL. An increasingly negative mean chamber pressure was associated with a significant increase in PaO2 (p less than 0.05) and VL(p less than 0.005) and a significant decrease in PaCO2 (p less than 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Cocaine increases natural killer cell activity.

The administration of epinephrine to humans increases natural killer (NK) cell activity and numbers. If endogenous catecholamines regulate NK cells, then their activity should be increased by cocaine, an agent that potentiates endogenous catecholamines. We investigated the in vivo effect of cocaine on NK cell activity and on the distribution of lymphocyte subsets, including NK cells. Intravenous cocaine (0.6 mg/kg) produced a three- to fourfold increase in NK cell activity in peripheral blood. The increase was accompanied by a marked and selective increase in circulating NK cells, as identified by the Fc receptor (Leu-11). Normal saline and benzoylecgonine, a major metabolite of cocaine, had little effect on NK cell activity or on levels of Leu-11+ cells. Other lymphocyte subpopulations were not increased by cocaine. The time course of the alterations in NK cell numbers and activity paralleled plasma levels of cocaine. In vitro cocaine did not increase NK cell activity. Our results indicate that cocaine selectively alters the activity and distribution of the NK lymphocyte subset. Because cocaine increases the activity of endogenous catecholamines, these findings suggest that human NK cells are selectively regulated by the sympathetic nervous system.

Adult↗
PubMed1986

Alcohol-related expectancies: have they a role in the understanding and treatment of problem drinking?

This paper reviews the theoretical and empirical literature on the role of alcohol-related expectancies in problem drinking. It is shown that alcohol-related expectancies are involved in the initiation, maintenance and treatment of problem drinking. Given that alcohol-related expectancies can influence the consumption of alcohol, it is argued that any future theoretical model and applied treatment programme for problem drinkers must include the interplay among pharmacological, environmental and cognitive, in particular alcohol-related expectancies variables.

Adolescent↗