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Biomedical subjects

T C King

Publications and source records attributed to T C King.

At least 55 records · Page 3Linked to original sources
PubMed1984

Complete transection of the intrathoracic trachea due to blunt trauma.

A 24-year-old man was transferred to Columbia-Presbyterian Medical Center from a local hospital 24 hours after a car crash. Bronchoscopy at the local hospital revealed transection with discontinuity of the trachea just above the carina. At Columbia-Presbyterian Medical Center, following cautious intubation without positive airway pressure, a right posterolateral thoracotomy was performed, and the bronchi were intubated with sterile endotracheal tubes for initial airway control. A 6-cm tracheal disruption was repaired. Early care was complicated by chest wall instability and pulmonary contusions, but the patient was discharged breathing comfortably on the tenth postoperative day. Subsequent to discharge, flow-volume loops revealed the development of a tracheal stricture. Three months after the initial procedure, tracheal resection for stenosis was completed. To date, the patient is asymptomatic.

Accidents, Traffic↗
PubMed1984

The role of brain stimulation priming effects in self-deprivation.

Choice of brain stimulation reward (BSR) over biologically necessary substances in some self-stimulating animals is referred to as self-deprivation. In several recent papers, it has been argued that this phenomenon is produced by the rewarding aspects of the brain stimulation. This conclusion is partially based on data showing that self-deprivation and brain stimulation reward increase and decrease in a similar manner in response to changes in the brain stimulation parameters. However, the priming aspects of the brain stimulation also fluctuate with changes in stimulation parameters. Therefore, changes in the priming rather than the rewarding aspects of the brain stimulation could be responsible for self-deprivation. To determine whether the priming effects of brain stimulation play an important role in self-deprivation, rats with bipolar stimulating electrodes were given the choice between BSR and food. Time-outs were enforced within each BSR/food competition session. Since priming effects decay over time, increasing time-out length should have decreased self-deprivation due to decay of priming. It was found that time-out length did not affect the degree of self-deprivation. It was concluded that self-deprivation is not mediated by the priming aspects of brain stimulation.

Animals↗
PubMed1984

RNase III cleavage is obligate for maturation but not for function of Escherichia coli pre-23S rRNA.

RNase III makes the initial cleavages that excise Escherichia coli precursor 16S and 23S rRNA from a single large primary transcript. In mutants deficient in RNase III, no species cleaved by RNase III are detected and the processing of 23S rRNA precursors to form mature 23S rRNA fails entirely. Instead, 50S ribosomes are formed with rRNAs up to several hundred nucleotides longer than mature 23S rRNA. Unexpectedly, these aberrant subunits function well enough to participate in protein synthesis and permit cell growth. Consistent with the inference that RNase III cleavages are absolutely required for 23S rRNA maturation, when 50S ribosomes from a strain deficient in RNase III were incubated with a ribosome-free extract from a RNase III+ strain, rRNA species processed by RNase III and species with normal mature 23S rRNA termini were produced.

Base Sequence↗
PubMed1983

S1 nuclease mapping analysis of ribosomal RNA processing in wild type and processing deficient Escherichia coli.

S1 nuclease mapping was used to assess rRNA processing in Escherichia coli. Single-stranded DNA probes complementary to the sequences bordering each terminus of 16 S and 23 S rRNA were end-labeled, hybridized to total E. coli RNA, and treated with S1 nuclease. The resultant DNA fragments were then displayed on denaturing polyacrylamide gels. Measurements of steady state levels of precursor rRNA species and measurements of the rates of decay of precursors after transcription arrest by rifampicin gave consistent results. 1) The rRNA precursor species identified in wild type cells corresponded to those previously identified by other means. 2) In RNase III-deficient strains, mature 16 S rRNA termini form at the same rate as in wild type cells; but the normal mature termini of 23 S rRNA are never generated. 3) RNase III cleavage at the 5' end of 23 S rRNA can occur before the 3' end of the same molecule is synthesized. 4) The cleavages that generate the mature termini of 16 S rRNA are interdependent; in the BUMMER strain, slow processing at the 5' end is accompanied by slow processing at the 3' end. Thus, the kinetically observed order of processing reactions is obligate for some cleavages but not for others, and the assumption that complete rRNA processing is required for function fails for 23 S rRNA.

Base Sequence↗
PubMed1983

Structure of partially denatured Escherichia coli 23 S ribosomal RNA determined by electron microscopy.

The secondary structure of 23 S ribosomal RNA was analyzed by electron microscopy after partial denaturation. A reproducible pattern of loops was seen when molecules were spread for electron microscopy in 50% formamide solutions containing various concentrations of Mg2+ and Na+. Some loops were stabilized more than others by Na+ or by Mg2+; but in general, small amounts of Mg2+ (0.5 to 1.0 mM) markedly stabilized all the major loops, as did much greater amounts of Na+ (100 mM). However, at all levels of Mg2+ examined, increasing levels of Na+ destabilized loop structures. These data are consistent with the known salt dependence of double-stranded DNA and transfer RNA structure. The four most frequently observed loops correspond, within the limits of measurement error, to the major loops in the secondary structure models of Noller et al. (1981) and Glotz et al. (1981). These four loops are, in length and position of their midpoints along the 23 S rRNA molecule: 490 +/- 50 at 250 +/- 40; 350 +/- 50 at 1860 +/- 80; 400 +/- 70 at 2330 +/- 150; and 570 +/- 100 at 2350 +/- 100. Three of the four have base-paired stems with delta G0 values among the lowest of all the loops in the two indirect models. At least two are also among the most stable loops found in computer searches of the 23 S rRNA sequence for dyad symmetry. These results demonstrate that partial denaturation mapping can both identify prominent features of secondary structure in rRNA and estimate their relative stability.

Escherichia coli↗
PubMed1983

Spectrophotometric assessment of dose-response curves for single antimicrobial agents and antimicrobial combinations.

The activity of single antimicrobial agents and antimicrobial combinations was examined by measuring their effects on the growth rate constant of a test strain of Escherichia coli. This spectrophotometric method provides a kinetic view of antimicrobial action and is sufficiently precise to define dose-response curves, in contrast to standard methods such as broth or agar dilution testing, which are static and measure only all-or-none responses. The results demonstrate that dose-response curves for single antimicrobial agents are logarithmic (rather than linear) and that the effects of antimicrobial combinations may be exquisitely concentration dependent. Although the results for some antimicrobial combinations were similar with the spectrophotometric and checkerboard methods, other combinations produced different results in the two systems. Additional studies will be necessary to determine whether one or the other of these methods more accurately predicts clinical outcome.

Anti-Bacterial Agents↗
PubMed1982

Postoperative deterioration in muscular function.

To clarify the postoperative fatigue state, we analyzed some components of muscular function before and after surgical procedures. Eleven subjects undergoing elective surgery were studied for test periods of up to 35 days. Significant impairment of muscular functioning, particularly muscle endurance, developed postoperatively. Maximum deterioration was noted on postoperative days 8 and 9. Isometric strength was affected more than isokinetic strength. Changes in muscular functioning in two young volunteers undergoing bed rest were surprisingly similar to those observed in postoperative patients.

Adult↗
PubMed1981

Postoperative deterioration in psychomotor function.

To help understand the postoperative fatigue state, psychomotor performance before and after surgical procedures or bed rest has been analyzed. Forty subjects in three groups were studied during test periods ranging from five to 21 days. Patients undergoing routine elective operations as well as subjects at bed rest alone experienced substantial impairment in several measures of psychomotor performance. Maximum deterioration was noted on postoperative days 4 and 5.

Bed Rest↗
PubMed1981

Escherichia coli ribosome unfolding in low Mg2+ solutions observed by laser Raman spectroscopy and electron microscopy.

Ribosomes unfolded by the removal of Mg2+ at 25 degrees C were studied by Raman spectroscopy and electron microscopy. Raman spectra showed a reduction in the 813 cm-1 phosphodiester signal of 30S and 50S ribosomes compared to intact ribosomes, suggesting that a fraction of the ribose moieties had shifted from the 3' endo (ordered) to the 3' exo (disordered) conformation. The maximum diameters of unfolded 30S and 50S ribosomes, judged by electron microscopy, were 1.8 and 2.5-fold greater, respectively, than those of intact ribosomes. Most unfolded 30S ribosomes had three distinct structural domains and appeared "Y-shaped"; whereas most unfolded 50S ribosomes had four distinct domains and appeared "X-shaped". When ribosomes were partially unfolded (by brief exposure to 0.04 mM Mg2+ or EDTA), several possible intermediates in the unfolding process were observed. Both the shapes of particles and their Raman spectra reached the same final state in 0.04 mM Mg2+, where more than 50% of the rRNA phosphates are discharged by Mg2+, as in 10 mM EDTA, where less than 1% are discharged.

Escherichia coli↗
PubMed1981

Effect of cimetidine on serum calcium levels in an elderly patient.

A 92-year-old woman with a normal serum calcium level received cimetidine postoperatively. She became severely hypocalcemic and exhibited tetany, seizures, and impaired mental status. Her condition responded to intravenous diazepam, phenytoin sodium, and gluconate calcium. Normal serum calcium levels were maintained by calcium infusions until the cimetidine treatment was stopped. Cimetidine may have been responsible for the observed complications due to its effect on serum parathyroid hormone level.

Aged↗
PubMed1980

Monoclonal antibodies to Escherichia coli 50S ribosomes.

Hybridoma cell lines that produce monoclonal antibodies directed against 50S Ribosomal proteins have been isolated. Spleen cells (from BALB/c mice immunized with 50S ribosomal subunits extracted from Escherichia coli) were fused to mouse myeloma cell line SP2/O-Ag 14. The initial screening for antibody producing hybridomas was carried out by a double antibody sandwich method; hybridomas were subsequently cloned in soft agar. Antibodies were characterized by their specific binding to individual 50S ribsomal proteins separated on phosphocellulose columns and in two-dimensional polyacrylamide gels. The assignments were confirmed with purified single ribosomal proteins. Of four clones analyzed thus far, two are identical with specificity for r-protein L5. The other clones produce two different antibodies directed against r-protein L20. Each monoclonal antibody formed ribosome dimers visualizable in the electron microscope. Dimers could be reacted with a different second antibody to form chains containing 8 or more ribosomes, which may be useful for structural studies.

Animals↗