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Biomedical subjects

T Baker

Publications and source records attributed to T Baker.

At least 19 recordsLinked to original sources
PubMed1992

The effects of smoking on postoperative recovery.

Two recent studies have implicated smoking as a principal risk factor for increasing the time patients spend in the postanesthesia care unit (PACU) following a wide range of surgical procedures. Hospitals are performing an increasing number of surgical procedures, with growing pressure to do more on an outpatient basis. With more internal and external pressures to streamline the rising costs of medical care, increased focus is being placed on the length of stay in the PACU. More than 300 patients were examined in each study. PACU time varied from 15 minutes to 5 hours, with a median of 75 minutes. Anesthesia duration correlated most closely with the length of stay in the PACU. All other variables were found to be unrelated to the length of time in the PACU or secondary to anesthesia time. The only independent factor was a history of smoking. While there were comparable ratios of smokers in all tested groups, there was a marked difference between smokers and nonsmokers in length of PACU stay. Of the nonsmokers, 38% were found to have PACU stays of less than 1 hour, compared with 23% of the smokers. Only 7% of the nonsmokers required longer PACU stays, compared with 19% of the smokers. Among the various smoking groups, however, there were no significant differences. While previous studies have suggested that smokers may have higher rates of various perioperative complications, these two studies are significant in that they have identified a population previously overlooked. These people who stay longer in the PACU would not otherwise be identified as having complications, and their eventual outcome was good. But it suggests that even these patients, who may view themselves as "healthy smokers," are significantly different from their nonsmoking counterparts. Further, varying the degree of smoking from heavy to light does not negate the increased PACU time. Therefore, any degree of smoking must now be viewed as having serious consequences in the immediate postoperative period and must be discouraged.

Anesthesia Recovery Period↗
PubMed1992

Locating essential Escherichia coli genes by using mini-Tn10 transposons: the pdxJ operon.

The mini-Tn10 transposon (delta 16 delta 17Tn10) confers tetracycline resistance. When inserted between a gene and its promoter, it blocks transcription and prevents expression of that gene. Tetracycline in the medium induces divergent transcription of the tetA and tetR genes within the transposon, and this transcription extends beyond the transposon in both directions into the bacterial genes. If the mini-Tn10 inserts between an essential bacterial gene and its promoter, the insertion mutation can cause conditional growth which is dependent on the presence of tetracycline. Two essential genes in adjacent operons of Escherichia coli have been detected by screening for tetracycline dependence among tetracycline-resistant insertion mutants. These essential genes are the era gene in the rnc operon and the dpj gene in the adjacent pdxJ operon. The pdxJ operon has not been described previously. It consists of two genes, pdxJ and dpj. Whereas the dpj gene is essential for E. coli growth in all media tested, pdxJ is not essential. The pdxJ gene encodes a protein required in the biosynthesis of pyridoxine (vitamin B6).

Amino Acid Sequence↗
PubMed1991

Supportive and unsupportive responses of others to rape victims: effects on concurrent victim adjustment.

Evaluated the impact that actions of significant others have on adjustment following rape. Significant other behavior is conceptualized as having two dimensions--supportive behavior and unsupportive behavior--and each dimension was measured using multiple items. Unsupportive behavior, but not supportive behavior, was found to bear a significant association to victim adjustment. Implications for those who work with victims are discussed.

Adaptation, Psychological↗
PubMed1991

Smoking prevention: towards a process approach.

Current studies of smoking prevention treat the adolescent as a target of influence, they emphasize the acquisition of skills for resisting peer pressure and give too little attention to motivation for resistance. Studies consistent with this social learning framework show moderate reductions in the incidence of smoking for the short term; recent, long-term follow-ups show no reduction in experimental over control conditions. We propose a re-examination of the influence framework and suggest that adolescents use smoking and dress, to project an image of self that will increase the likelihood of success in the formation of relationships in which participants share feelings and attitudes toward each other and the adult world. We also suggest that adults focus upon external, perceptible, and remote threats, e.g. smoking is seen as evil, a response to peer pressure, and a long term threat to health, and ignore discourse about proximal, subjective feelings respecting the changing sexual urges and feelings of social anxiety that accompany adolescence. The socialization of these affects is left to the peer group. It is suggested that future programs intensify their focus on motivation for resisting smoking based upon a revised view of the adolescents objectives in self definition, and combine this with the best of the current skills approaches.

Adolescent↗
PubMed1991

Effects of oral phosphocysteamine and rectal cysteamine in cystinosis.

Diurnal variation in leucocyte cystine and the effects of equimolar single doses of oral phosphocysteamine and rectal cysteamine were studied in eight patients with cystinosis, aged 1.8-16.5 years. No significant diurnal variation in leucocyte cystine was found. Absorption of cysteamine was reduced after rectal administration compared with the oral dose: mean (SD) peak concentration 17.2 (6.3) mumol/l v 36.4 (5.5) mumol/l at 40 min and mean (SD) area under the curve 22.3 (14.3) v 59.4 (33.1) mumol/h/l. Oral phosphocysteamine significantly reduced the mean (SD) leucocyte cystine from 8.09 (0.47) to 3.26 (1.48) nmol 1/2 cystine/mg protein at three hours. At 12 hours the mean leucocyte cystine was significantly lower than the pretreatment concentration. Rectal cysteamine did not significantly reduce the mean leucocyte cystine concentration. In conclusion, phosphocysteamine suspension may be administered every 12 hours. Rectal cysteamine administration is feasible but higher doses are required before efficacy can be judged.

Administration, Oral↗
PubMed1990

Postpartum cardiovascular complications after bromocriptine and cocaine use.

A case is presented of a postpartum woman in whom hypertension and pulmonary edema developed after administration of bromocriptine mesylate. Caution is advised when there is additional recent use of cocaine because of a suggested potentiating action of cocaine on the development of adverse cardiovascular and cerebral sequelae in postpartum patients who take bromocriptine.

Adult↗
PubMed1988

Activity-dependent differences between rat fast and slow neuromuscular systems.

Activity-dependent pharmacologic differences between the fast tibialis anterior and slow soleus neuromuscular systems of the rat were studied. The tibialis anterior was more sensitive than the soleus to d-tubocurarine tetanic fade (50 Hz), as determined from recordings of compound muscle action potentials. Pre-treatment with physostigmine prevented curare-induced tetanic fade in the tibialis anterior, but not the soleus. Additionally, when contractile tension was 80% blocked by d-tubocurarine, the tibialis anterior was more responsive than the soleus to the decurarizing action of tetanic stimulation (25, 50 and 100 Hz). These results disclose that activity-dependent pharmacologic differences exist between neuromuscular systems. Further, they indicate that the tibialis anterior and the soleus differ in their processes of transmitter release. It is speculated that differences in nerve terminal Ca2+ account for the observed pharmacologic differences between the tibialis anterior and soleus.

Action Potentials↗
PubMed1988

Comparison of technetium-99m MAG3 with iodine-131 hippuran by a simultaneous dual channel technique.

Technetium-99m MAG3, a technetium-labeled analog of hippuran, was compared with [131I] hippuran using a simultaneous dual isotope study in 20 patients. The plasma clearance for MAG3 was lower than that of hippuran, but its plasma concentration was higher, resulting in similar rates of excretion and similar renal time-activity curves. Apart from better statistics with the technetium-labeled agent, there were no clinically significant differences in this group of patients.

Adult↗
PubMed1988

Response of delta (0-3 Hz) EEG and eye movement density to a night with 100 minutes of sleep.

In one of a series of experiments aimed at gathering the empirical data required to formulate mathematically our recovery model of sleep, we recently (1) measured the increase in delta electroencephalogram (EEG) following one night of total sleep deprivation (TSD). We found that the delta rebound was confined to the first non-rapid eye movement period (NREM-P1) of recovery sleep; this unexpected result was documented with direct computer measurement of 0-3 Hz EEG, as well as with visual scoring of stages 3 and 4. We also found a robust decrease in eye movement density during the second and third REM periods, which we hypothesized to be due to the increased depth of recovery sleep. In the present experiment, we awakened young adult subjects after 100 min of sleep, a duration that includes the first cycle for this age group, and analyzed visual and computer measures of delta and eye movement density during recovery sleep. We again found eye movement density to be significantly reduced in REM-P2 and P3, but to a lesser degree than after total sleep deprivation, a condition that may be presumed to produce a greater increase in sleep depth. Delta increases were again limited to the first cycle, although all subjects completed this cycle on the 100-min night. The major difference between recovery sleep patterns following the total deprivation and the 100-min sleep conditions was that 0-3-Hz wave amplitude increased significantly after the former, but not after the latter. In both studies, recovery sleep showed increased 0-3-Hz wave density. The neurophysiological implications of a response of EEG amplitude as opposed to wave density are briefly considered; separate measurement of these variables is more readily accomplished with period-amplitude than with spectral analysis. Our results further illustrate the importance of measuring sleep by physiological units, such as the successive NREMPs and REMPs. They also support other data that indicate that NREM-P1 plays a special role in human sleep: it responds selectively to sleep deprivation, shows the greatest ontogenetic variation across the human lifespan, and is the component of sleep that is most frequently abnormal in psychiatric patients. As we have long argued, it is inappropriate to conceptualize this high priority component of NREM sleep as "REM latency" and as a measure of REM "pressure" exclusively.

Adult↗
PubMed1987

Drug actions at mammalian motor nerve endings: the suppression of neostigmine-induced fasciculations by vecuronium and isoflurane.

The occurrence of fasciculations following administration of agents is a well-known pharmacologic phenomenon. Using the cat soleus nerve-muscle preparation, intravenous neostigmine doses between 20-200 micrograms/kg evoked fasciculations in a dose-related manner. The data demonstrate that the fasciculations were the result of the direct effect of neostigmine acting at the motor nerve endings. Vecuronium in a dose-related manner (3 and 5 micrograms/kg iv) suppressed this prejunctional activity of neostigmine. The prejunctional effect of vecuronium explains its effectiveness in preventing succinylcholine-induced fasciculations. In the presence of isoflurane (end-tidal concentration 0.20-0.25%), the suppressant effect of vecuronium on motor nerve endings was enhanced. The prejunctional action of isoflurane may be a major contribution to the additive effects of non-depolarizing muscle relaxants and potent inhalation agents.

Animals↗
PubMed1987

A note on shelf-life extension of British fresh sausage by vacuum packing.

Vacuum packing of British fresh sausage in a low oxygen permeability film (Diolon) extended the product shelf-life at 6 degrees C to more than 20 d compared with 9-14 d in conventional packs. After 10 d storage, counts of key spoilage organisms such as yeasts and Brochothrix thermosphacta were generally 2 log cycles lower in vacuum packs. Vacuum-packed sausages also displayed a slower rate of loss of free sulphite. Variations in pack permeability to SO2 were not responsible for this. Losses of free SO2 in stored sausages are largely due to the production of sulphite-binding agents by yeasts. Selective enumeration of these yeasts showed them to be inhibited by conditions of vacuum packing. The extension of shelf-life observed is ascribed to the reduction in growth rate of the spoilage flora in vacuum packs coupled with the consequent maintenance of inhibitory levels of sulphite for a longer period.

Animals↗
PubMed1986

Selection and optimisation of monoclonal antibodies for a two-site immunoradiometric assay for ACTH.

Four monoclonal antibodies with predominant specificities towards different sequences within the ACTH molecule were investigated in a 2-site immunoradiometric assay (IRMA) for human ACTH. Antibody 3H9 recognises the extreme N-terminal sequence, antibodies 1A12 and 1D1 are specific for the mid N-terminal sequence but differ in that the former cross-reacts with alpha MSH whereas the latter does not, and antibody 2A3 recognises the C-terminal sequence. Combinations of iodinated antibodies with antibodies covalently linked to Sephacryl S300 were tested for their compatibility and potential for a sensitive assay. Two antibody combinations (1D1 plus 3H9 or 1A12) gave no dose-response curve indicating severe steric inhibition, whereas other combinations yielded assays with widely different detection limits (2-2400 ng ACTH/l). The combination of labelled 1D1 and solid-phase 2A3 gave the most sensitive assay and when optimised for antibody concentrations and incubation times the working range was 10-5 X 10(4) ng/l (CV less than 20%). The optimised sequential 2-step IRMA involves incubation of standard or test sample with labelled 1D1 for 18 h at 4 degrees C followed by incubation with solid-phase 2A3 for 2 h at room temperature, after which the labelled complex is separated by the sucrose layering technique. The detection limit of this IRMA was several 100-fold lower than by RIA using the same antibodies. The IRMA detected large molecular weight precursors containing the full ACTH sequence (22 000, 31 000 and 34 000) but not ACTH fragments (1-18, 1-24, 18-39). It is concluded that selected monoclonal antibodies provide a sensitive and rapid 2-site IRMA for intact ACTH and its precursors.

Adrenocorticotropic Hormone↗