PubMed Health⌕ Search

Biomedical subjects

M E Johnston

Publications and source records attributed to M E Johnston.

At least 19 recordsLinked to original sources
PubMed2006

The dietary valine requirement for prolific lactating sows does not exceed the National Research Council estimate.

Two studies were conducted to determine the effect of increasing the valine:lysine (V:L) ratio in diets of lactating sows above the minimum proposed by the NRC (1998). The first experiment involved 189 PIC, Camborough product sows (parity 1 to 4) that were allotted to 1 of 3 dietary treatments. Diets were formulated to achieve total dietary V:L ratios of 0.90, 1.05, or 1.25:1, respectively, and were corn and soybean meal-based. The second experiment involved 279 PIC, Camborough sows (parity 1 to 5) that were allotted to 1 of 4 treatments. Diets 1 and 3 were formulated using corn and a fixed inclusion of soybean meal (16.7%), with 0.27% L-lysine HCl. The V:L ratios in diets 1 and 3 were 0.73 and 1.25:1, respectively. Diets 2 and 4 were typical corn-soybean meal diets containing 0.05% L-lysine HCl, with a fixed inclusion of soybean meal (22.7%). The V:L ratios in diets 2 and 4 were 0.86 and 1.25:1, respectively. In both experiments, each litter was standardized to a minimum of 10 pigs, which achieved litter growth rates of 2.22 and 2.56 kg/d in Exp. 1 and 2, respectively. In Exp. 1, increasing the dietary V:L ratio beyond 0.90:1 did not improve (P > 0.10) the number of pigs weaned, survival rate, or piglet growth rate, even though sows were nursing more than 10 pigs per litter for 19 d. In Exp. 2, total lysine intake was similar among treatments and ranged from 52.1 to 55.3 g/d. Valine intake increased as the diet valine concentration increased (diet 1 vs. 3 and diet 2 vs. 4, P < 0.001), ranging from 40.0 to 66.1 g/d. Litter gain tended to improve (P = 0.14) when the 0.27% L-lysine HCl control (0.73 V:L) was supplemented with valine to achieve a 1.25:1 V:L ratio. In contrast, no aspect of sow or litter response was improved when the practical control diet containing 0.05% L-lysine HCl (0.86 V:L) was supplemented with valine to achieve a 1.25:1 V:L ratio. Collectively, this research shows that a V:L ratio in excess of 0.86 does not conserve maternal tissue loss or improve piglet growth rate, but a V:L ratio of 0.73 may compromise litter growth rate.

Animal Feed↗
PubMed2004

Phosphorus requirements of growing-finishing pigs reared in a commercial environment.

The objective of this study was to identify available phosphorus (aP) requirements of pigs reared in commercial facilities. In a preliminary study, 600 gilts (PIC) were allotted randomly to low (0.30%) or high (0.37%) dietary aP from 43 to 48 kg BW, and later to 0.19 or 0.27% aP from 111 to 121 kg BW. No differences were observed (P = 0.42 to 0.88) in ADG, but G:F from 43 to 48 kg tended to improve (P = 0.07) for pigs fed low aP. Results suggested that the aP requirement was at or below 0.30 and 0.19%. These concentrations were used to titrate aP requirements in Exp. 1 and 2. In Exp. 1, 1,260 gilts (initially 33.8 kg) were allotted randomly to one of five dietary treatments containing 0.18, 0.22, 0.25, 0.29, or 0.32% aP, corresponding to 0.5, 0.6, 0.7, 0.8, or 0.9 g of aP/Mcal of ME. There were 28 pigs per pen and nine pens per treatment. From d 0 to 14, increasing aP increased ADG (linear, P = 0.03) and G:F (quadratic, P = 0.07), with the greatest response observed as aP increased from 0.18 to 0.22% (G:F breakpoint = 0.22%). However, from d 0 to 26, no differences (P = 0.12 to 0.81) were observed for any growth traits. Pooled bending moment of the femur, sixth rib, and third and fourth metatarsals increased (linear, P = 0.007) with increasing aP. In Exp. 2, 1,239 gilts (initially 88.5 kg BW) were randomly allotted to one of five dietary treatments containing 0.05, 0.10, 0.14, 0.19, or 0.23% aP, equivalent to 0.14, 0.28, 0.39, 0.53, or 0.64 g of aP/Mcal of ME. The diet with 0.05% aP contained no added inorganic P. From d 0 to 14, increasing aP increased (linear, P = 0.008 to 0.02) ADG and G:F; however, from d 0 to 28, increasing aP had no effect (P = 0.17 to 0.74) on growth performance. Increasing aP increased (linear, P < 0.001 to 0.04) metacarpal bone ash percent and bending moment. Results suggest that 33- to 55-kg pigs require approximately 0.22% aP, which corresponds to 0.60 g of aP/Mcal of ME or 3.30 g of aP/d to maximize ADG and G:F compared with NRC (1998) estimates of 0.23%, 0.70 g of aP/Mcal of ME, and 4.27 g of aP/d for 20- to 50-kg pigs. Finishing pigs (88 to 109 kg) require at least 0.19% aP, corresponding to 0.53 g of aP/Mcal of ME or 4.07 g aP/d compared with NRC (1998) estimates of 0.15%, 0.46 g of aP/Mcal of ME and 4.61 g of aP/d for 80- to 120-kg pigs. However, the percentage of bone ash and bending moment continued to increase with increasing aP. These data also suggest that complete removal of supplemental P in diets for finishing pigs (>88 kg) will decrease ADG and G:F.

Animal Feed↗
PubMed2002

Chemotherapy for recurrent epithelial ovarian cancer previously treated with platinum--a systematic review of the evidence from randomized trials.

PURPOSE: To evaluate the chemotherapeutic options for women with recurrent epithelial ovarian cancer who have received platinum-based chemotherapy. METHODS: A systematic search of the Medline, CancerLit and Cochrane Library databases was performed for the period from 1984 to June 2001 to find randomized trials comparing second- or higher-line chemotherapy regimens in patients with recurrent platinum-pretreated epithelial ovarian cancer. RESULTS: Seven randomized trials have failed to demonstrate the clear superiority of any one chemotherapy regimen in terms of improvements in long-term survival, quality of life or response rate. One trial detected a statistically significant difference between treatments in progression-free survival, which was longer with cyclophosphamide/doxorubicin/cisplatin than with paclitaxel in women with platinum-sensitive ovarian cancer. Another trial did not show a difference between liposomal doxorubicin and topotecan overall in women with recurrent ovarian cancer but a subgroup analysis detected a significant survival advantage for liposomal doxorubicin over topotecan in women with platinum-sensitive disease. CONCLUSION: The evidence available does not support firm conclusions about the preferred chemotherapy regimen for recurrent ovarian cancer. Randomized trials that compare new drugs with current standard treatments are needed.

Antineoplastic Agents↗
PubMed1994

Effects of computer-based clinical decision support systems on clinician performance and patient outcome. A critical appraisal of research.

OBJECTIVE: To review the evidence from controlled trials of the effects of computer-based clinical decision support systems (CDSSs) on clinician performance and patient outcomes. DATA SOURCES: The literature in the MEDLARS, EMBASE, SCISEARCH, and INSPEC databases was searched from 1974 to the present. Conference proceedings and reference lists of relevant articles were reviewed. Evaluators of CDSSs were asked to identify additional studies. STUDY SELECTION: 793 citations were examined, and 28 controlled trials that met predefined criteria were reviewed in detail. DATA EXTRACTION: Study quality was assessed, and data on setting, clinicians and patients, method of allocation, computer system, and outcomes were abstracted and verified using a structured form. Separate summaries were prepared for physician and patient outcomes. Within each of these categories, studies were classified further according to the primary purpose of the CDSS: drug dose determination, diagnosis, or quality assurance. RESULTS: Three of 4 studies of computer-assisted dosing, 1 of 5 studies of computer-aided diagnosis, 4 of 6 studies of preventive care reminder systems, and 7 of 9 studies of computer-aided quality assurance for active medical care that assessed clinician performance showed improvements in clinician performance using a CDSS. Three of 10 studies that assessed patient outcomes reported significant improvements. CONCLUSIONS: Strong evidence suggests that some CDSSs can improve physician performance. Additional well-designed studies are needed to assess their effects and cost-effectiveness, especially on patient outcomes.

Clinical Competence↗
PubMed1993

A program to enhance clinical use of MEDLINE. A randomized controlled trial.

OBJECTIVE: To determine if a preceptor and individualized feedback improves the performance of physicians in searching MEDLINE in clinical settings. DESIGN: Randomized controlled trial with 2 to 10 months follow-up. SETTING: A 300-bed teaching hospital. PARTICIPANTS: All 392 physicians and physicians-in-training from 6 major clinical departments were invited to participate if they made patient-care decisions during the study period; 79.4% agreed. INTERVENTIONS: All participants were given 2 hours of basic training, then randomized to a control group (no further intervention) or an intervention group in which each person chose a clinical preceptor experienced in MEDLINE searching and received individualized feedback from a study librarian on each of their 1st 10 searches. MAIN OUTCOME MEASURES: The number and proportion of relevant and irrelevant references retrieved for 1st, 4th, and 8th searches of participants were compared with independent librarian searches on the same topics. RESULTS: Intervention group members did not search more often than controls (5.9 searches per month versus 4.7, respectively; P = 0.26) and there were no significant differences in the quality of searches. Rather, search performance for both groups improved, with the average number of relevant references retrieved per search increasing from 4.5 to 7.4 (P < 0.01). The librarian retrieved more relevant citations than participants for the 1st search (P = 0.001) but not for the 4th (P = 0.60) or 8th (P = 0.76) searches. CONCLUSIONS: A program of assigning preceptors and providing feedback on individual searches did not enhance the quantity or quality of searches. Soon after a basic introduction to searching, however, clinicians in both groups improved their search performance.

Clinical Medicine↗
PubMed1993

Effect of problem-based, self-directed undergraduate education on life-long learning.

OBJECTIVE: To compare how well graduates of a self-directed, problem-based undergraduate curriculum (at McMaster University [MU], Hamilton, Ont.) and those of a traditional curriculum (at the University of Toronto [UT]) who go on to primary care careers keep up to date with current clinical practice guidelines. DESIGN: Analytic survey. Management of hypertension was chosen as an appropriate topic to assess guideline adherence. An updated version of a previously validated questionnaire was mailed to the participants for self-completion. SETTING: Private primary care practices in southern Ontario. PARTICIPANTS: A random sample of 48 MU graduates and 48 UT graduates, stratified for year of graduation (1974 to 1985) and sex, who were in family or general practice in Ontario; 87% of the eligible subjects in each group responded. MAIN OUTCOME MEASURES: Overall and component-specific scores; analysis was blind to study group. RESULTS: The overall mean scores were 56 (68%) of a possible 82 for the MU graduates and 51 (62%) for the UT graduates (difference between the means 5, 95% confidence interval 1.9 to 8.2; p < 0.01). Multivariate linear regression analysis of seven factors that might affect questionnaire scores revealed that only the medical school was statistically significant (p < 0.01). The MU graduates had significantly higher mean scores than the UT graduates for two components of the questionnaire: knowledge of recommended blood pressures for treatment (p < 0.05) and successful approaches to enhance compliance (p < 0.005). The trends were similar for the other components but but were not significant. CONCLUSIONS: The graduates of a problem-based, self-directed undergraduate curriculum are more up to date in knowledge of the management of hypertension than graduates of a traditional curriculum.

Curriculum↗
PubMed1993

The effects of porcine somatotropin and dietary lysine on growth performance and carcass characteristics of finishing swine fed to 105 or 127 kilograms.

One hundred twenty barrows (initially 59 kg) were used to determine the effects of dietary lysine and porcine somatotropin (pST) on growth performance and carcass characteristics of finishing pigs fed to heavy market weights (127 kg). Pigs were injected daily with either 4 mg of pST or a placebo and fed diets containing either .8, 1.0, 1.2, or 1.4% lysine in a 2 x 4 factorial arrangement. Performance data were collected and evaluated for the weight ranges: 59 to 105, 105 to 127, and 59 to 127 kg. In addition, daily accretion rates of protein (DPA), lipid (DLA), moisture, and ash were determined by slaughtering six randomly selected pigs at the start of the experiment, then one pig per pen when pigs reached mean weights of 105 and 127 kg. Pigs injected with pST had greater (P < .05) ADG than control pigs at all weight ranges. Increased dietary lysine had no effect (P > .20) on ADG during the entire trial (59 to 127 kg). Although control pigs showed no increase in ADG with increasing lysine, ADG of pST-treated pigs tended to increase. This resulted in a pST x lysine interaction (P < .07) for ADG from 59 to 127 kg. Feed consumption decreased (P < .05) in pigs from 59 to 105 kg and 59 to 127 kg with pST treatment and with increasing dietary lysine. Feed conversion (G/F) was improved (P < .01) by pST administration and a tendency for a pST x lysine interaction (P < .12) was observed. At 105 kg, average backfat thickness, kidney fat, longissimus muscle area, and DPA were unaffected by dietary lysine but were improved by pST treatment (P < .01). At a slaughter weight of 127 kg, average backfat thickness decreased and DPA increased (linear, P < .05) with increasing dietary lysine and pST treatment (P < .01). Longissimus muscle area was increased and DLA was decreased (P < .01) by injections of pST but both were unchanged by dietary lysine. These data indicate that growth performance and carcass characteristics at 105 and 127 kg were improved by daily administration of 4 mg of pST. At both slaughter weights, increasing dietary lysine resulted in increased carcass leanness (increased carcass protein and decreased carcass lipid). Although increasing lysine did not improve overall (59 to 127 kg) ADG and feed efficiency, pST-treated pigs showed a greater response to increasing dietary lysine. The data indicate that pST-treated pigs (4 mg/d) require approximately 28 g/d of lysine.

Adipose Tissue↗
PubMed1992

Depression, problem-solving ability, and problem-solving appraisals.

Behavioral analytic methods were used to create a college student version of the Means Ends Problem Solving Procedure (MEPS). This instrument then was administered with measures of perceived problem-solving ability to depressed and nondepressed students to determine whether differences exist in both problem-solving ability and problem-solving appraisal. Analyses revealed that depressed subjects had more negative expectations and lower appraisals of their problem-solving ability. However, the groups did not differ in terms of the actual quality of their behavioral solutions to interpersonal, intrapersonal, and emotional problem situations. The results are interpreted as support for the role of cognitive factors in depression and problem-solving across a range of problem-solving situations.

Adaptation, Psychological↗
PubMed1992

Performance appraisal of online MEDLINE access routes.

OBJECTIVE: To compare the performance and cost of 11 online MEDLINE systems with MEDLINE at Elhill. DESIGN: Comparative study. SYSTEMS: Eleven online daytime systems commercially available in North America offering the MEDLINE database. MEASURES: Number of relevant citations, number of irrelevant citations, proportion of searches producing no relevant citations and cost per relevant citation were analyzed for each system. Relevance and cost for each system were compared with direct searching of MEDLINE through NLM for librarian and clinician search strategies for 18 clinical questions. The citations retrieved by both strategies were pooled and rated for relevance on a 7-point scale. RESULTS: Numbers of relevant and irrelevant citations and cost per relevant citation were higher for clinician searches than librarian searches, reflecting the higher total number of citations retrieved by the clinician approaches. A lower proportion of clinician searches produced no relevant citations than librarian searches. CONCLUSIONS: Eleven daytime MEDLINE systems performed similarly in terms of retrieval and cost within similar searching groups. Clinicians, however, tended to capture larger overall retrievals resulting in higher numbers of relevant and irrelevant citations than librarians.

CD-ROM↗
PubMed1992

Increases in knowledge and use of information technology by entering medical students at McMaster University in successive annual surveys.

OBJECTIVE: To determine self-reported microcomputer and information technology competency, access, and usage by entering medical students and their perceptions of the need for training in additional applications. DESIGN: Cross-sectional surveys of successive classes. SETTING: McMaster University Faculty of Health Sciences Medical Undergraduate Program, which has a 33-month, problem-based, self-directed learning curriculum and a high applicant-to-student ratio. PARTICIPANTS: Medical school classes entering in 1987, 1988, and 1989. Response rates were 80%, 90%, and 86% respectively. MEASURES: A self-report questionnaire was sent to each student, with up to two follow-up letters to prompt a response. RESULTS: There was a progressive rise in reported information technology access and use for the three years. For the classes starting in 1987, '88, and '89 respectively, computer access was 29%, 49%, and 49% (P < 0.002 for linear trend), and, among those with computer access, modem access was 17%, 29% and 50% (P = 0.012). Self-service MEDLINE use on CD-ROM at the Health Sciences Library was 65%, 75%, and 89% respectively (P < 0.001) for all respondents within the first few months of starting medical school. Over 50% of each class stated they would take courses, if available, on clinical applications software, office management, online searching, filing, and CD-ROM searching. CONCLUSIONS: Half of the most recent entering students already had access to a personal computer and most wished to learn computer applications that would assist them with patient management, and with information access and organization. Medical schools need to address which applications they will teach or make available and how to bring all students to acceptable competency in their use.

Computer Literacy↗
PubMed1992

A critical appraisal of the literature on the effects of computer-based clinical decision support systems on clinician performance and patient outcomes.

OBJECTIVE: To review the evaluations of computer-based clinical decision support systems (CDSS's). DATA SOURCES: The literature collected in the MEDLARS, EMBASE, SCISEARCH and INSPEC databases was searched from 1974 to the present. The reference lists of relevant articles were reviewed as were conference proceedings. STUDY SELECTION: Prospective, controlled studies were included. Studies were rated for methodological quality. DATA EXTRACTION: Study quality was assessed and data on study setting, subjects, method of allocation, and computer system were collected and verified using a structured form. CONCLUSIONS: There is considerable heterogeneity in both systems evaluated and design features of those systems. Future evaluations of CDSS's should focus on methodological issues in order to enhance overall quality of evaluations.

Clinical Medicine↗
PubMed1991

A study to enhance clinical end-user MEDLINE search skills: design and baseline findings.

OBJECTIVE: To determine if a preceptor and timely, individualized feedback improves the performance of physicians in searching MEDLINE using GRATEFUL MED in clinical settings. DESIGN: Randomized controlled trial. SETTING: A 300 bed primary to tertiary care teaching hospital. Computers were installed in wards and clinics of 6 major clinical services, and the emergency room, intensive care and neonatal intensive care units. SUBJECTS: All physicians and physicians-in-training from the departments of Medicine, Family Medicine, Surgery, Psychiatry, Pediatrics, and Obstetrics and Gynecology were included if they made patient care decisions for at least 8 weeks during the study period. INTERVENTION: All participants were given a 1-hour training class and 1 hour of individualized searching with 1 of the 2 study librarians. After training, participants were randomized to a control group who received no further intervention or to an intervention group in which each person chose a clinical preceptor experienced in MEDLINE searching and received individualized feedback by a study librarian on their first 10 searches, indicating search quality and providing suggestions for improvement. Feedback was mailed the first week day after the search was done. MAIN MEASURES: Baseline characteristics by study group, department and level of training, study participation rates, and searching rates. MAIN RESULTS: 308 of 392 eligible physicians joined the study. Participation was almost 80% with some variation by department and level of training. Excellent balance in the baseline characteristics was achieved for the 2 groups, as well as for the number who did first searches. Intervention group participants searched MEDLINE more often than did controls (3.5 searches per month vs 2.5 per month for controls, P = 0.046). The recall and precision for first searches for both groups was significantly less than that of librarians. The analysis of study data will be completed by September 1991. CONCLUSIONS: Clinicians are willing to do self-service searching of MEDLINE in clinical settings but their precision and recall are less than a trained librarian at baseline. Search skills enhancements are needed and the effect of feedback and preceptors is being tested. SOURCE OF FUNDING: U.S. National Library of Medicine and Ontario Ministry of Health.

Computer User Training↗
PubMed1990

Adenosine transport systems on dissociated brain cells from mouse, guinea-pig, and rat.

The kinetics and sodium dependence of adenosine transport were determined using an inhibitor-stop method on dissociated cell body preparations obtained from mouse, guinea-pig and rat brain. Transport affinity (KT) values for the high affinity adenosine transport systems (KT(H] were significantly different between these three species; mean +/- SEM values were 0.34 +/- 0.1 in mouse, 0.9 +/- 0.2 in rat, and 1.5 +/- 0.5 microM in guinea-pig. The KT values for the low affinity transport system (KT(L) were not different between the three species. Brain cells from rat displayed a significantly greater maximal capacity to accumulate [3H]adenosine (Vmax) than did mouse or guinea-pig for the high affinity system, or than did mouse for the low affinity system. When sodium chloride was replaced in the transport medium with choline chloride, the KT(H) values for guinea-pig and rat were both increased by approximately 100%; only in rat did the change reach statistical significance. The sodium-dependence of adenosine transport in mouse brain was clearly absent. The differences between KT(H) values in mouse and those in guinea-pig or rat were accentuated in the absence of sodium. The differences in kinetic values, ionic requirements, and pharmacological characteristics between adenosine transporters in CNS tissues of mouse, guinea-pig and rat may help account for some of the variability noted among species in terms of their physiological responses to adenosine.

Adenosine↗
PubMed1990

Effect of select menhaden fish meal in starter diets for pigs.

Two trials were conducted to evaluate a select menhaden fish meal (SMFM) as a protein source in starter diets for 390, 3-wk-old weaned pigs. Initial weights averaged 4.8 and 5.5 kg in Trials 1 and 2, and trials were conducted for 5 and 4 wk, respectively. Diets in Trial 1 were formulated by substituting levels of 0, 4, 8, 12, 16 or 20% SMFM for soybean meal plus corn on a protein basis. The 20% fish meal diet contained no soybean meal; all diets contained between 19.8 and 20.2% CP, between 1.34 and 1.40% lysine and 25% dried whey. Replacement of soy protein with fish meal elicited a quadratic improvement (P = .01) in cumulative ADG and average daily feed intake (ADFI) by the end of wk 5. The diet containing 8% SMFM resulted in the maximum observed ADG; however, the maximum ADFI occurred in pigs fed the diet containing 12% SMFM. Breakpoint analysis indicated that 4.5 and 9.3% SMFM maximized ADG and ADFI, respectively. Addition of SMFM did not affect efficiency of feed utilization (F/G). In Trial 2, a 2 X 3 factorial with two levels of dried whey (10 or 20%) and three levels of SMFM (0, 4 or 8%), a SMFM X dried whey interaction (P less than .05) was observed for cumulative ADG and F/G by the of wk 4 with greater benefit from SMFM with 10% than with 20% dried whey.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1989

HLA class I-related impairment in IL-2 production and lymphocyte response to microbial antigens in reactive arthritis.

The contribution of certain Gram-negative bacteria and host HLA class I Ag to the development of reactive arthritis (ReA)3 has strong epidemiologic support but the pathogenesis of the arthritis is unknown. An outbreak of Salmonella typhimurium afforded the opportunity to compare the immune response to the organism between those who developed ReA (ReA+, n = 11) with those who did not (ReA-, n = 12). Of the 11 ReA+ patients, 4 were B27-positive and 6 were B7-positive; of the ReA- patients none was B27- or B7-positive. The causative pathogen S. typhimurium phage 22 was used to examine PBL proliferation by [3H]thymidine incorporation. Impairment in lymphocyte response to S. typhimurium in ReA+ compared with ReA- was demonstrated by: i) lower stimulation index (1.9 +/- 0.3 for ReA+, 5.7 +/- 0.6 for ReA-, p less than 0.01); ii) lower in vitro Ig production; and iii) lower Ag-induced IL-2 production. Mixing experiments did not demonstrate a soluble suppressor factor in ReA+ supernatants. Thus, after infection with S. typhimurium there is an impairment in cellular immunity that has correlates in immunogenetic and clinical features of the infected population.

Antibodies, Bacterial↗
PubMed1989

Sodium-dependent uptake of nucleosides by dissociated brain cells from the rat.

Sodium-dependent 3H-labeled nucleoside transport was studied using a mixed population of dissociated brain cells from adult rats. The accumulation of [3H]adenosine during brief (15-s) incubation periods was significantly greater in the presence of 110 mM Na+ than in its absence. This occurred at substrate concentrations that ranged from 0.25 to 100 microM. Similar findings were observed for the rapid accumulation of [3H]uridine. Kinetically, the rapid accumulation of [3H]adenosine in both the absence and the presence of Na+ was best described by a two-component system. In the presence of Na+, the KT and Vmax values for the high-affinity affinity component were 0.9 microM and 8.9 pmol/mg of protein/15 s, and those for the low-affinity component were 313 microM and 3,428 pmol/mg of protein/15 s, respectively. In the absence of Na+, the KT value for the high-affinity component was significantly higher (1.8 microM). [3H]Uridine accumulation was best described kinetically by a one-component system that in the presence of Na+ had KT and Vmax values of 1.0 mM and 2.6 nmol/mg of protein/15 s, respectively. As was found for [3H]adenosine, in the absence of Na+, the KT value was significantly higher (1.8 mM). The sodium-dependent transport of [3H]adenosine was inhibitable by ouabain and 2,4-dinitrophenol. Of the three nucleoside transport inhibitors tested, only nitrobenzylthioninosine demonstrated high affinity and selectivity in blocking the sodium component. Thus, high-affinity sodium-dependent nucleoside transport systems, in addition to facilitated diffusion systems, exist on brain cells from adult rats.

Adenosine↗