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Biomedical subjects

E J Johnson

Publications and source records attributed to E J Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1993

Directed evolution of biosynthetic pathways. Recruitment of cysteine thioethers for constructing the cell wall of Escherichia coli.

We report that expansion of thioether biosynthesis in Escherichia coli generates sulfur-containing amino acids that can replace meso-diaminopimelate, the essential amino acid used for cross-linking the cell wall. This was accomplished by jointly overexpressing the metB gene coding for L-cystathionine gamma-synthase and disrupting the metC gene, whose product, L-cystathionine beta-lyase, is responsible for the destruction of L-cystathionine and other L-cysteine thioethers. As a result, meso-lanthionine and L-allo-cystathionine were produced endogenously and incorporated in the peptidoglycan, thereby enabling E. coli strains auxotrophic for diaminopimelate to grow in its absence. Thus, current techniques of metabolic engineering can be applied to evolving the chemical constitution of living cells beyond its present state.

Alanine↗
PubMed1993

Contribution of apoB-48 and apoB-100 triglyceride-rich lipoproteins (TRL) to postprandial increases in the plasma concentration of TRL triglycerides and retinyl esters.

After the ingestion of a fat-rich meal, there is a postprandial increase in the plasma concentration of both apolipoprotein B-48- and apoB-100-containing triglyceride-rich lipoproteins (apoB-48 and apoB-100 TRL). In order to determine the contribution of these lipoproteins to postprandial lipemia, the concentration of triglycerides (TG) and retinyl esters (RE) was measured in apoB-48 and apoB-100 TRL after an oral fat load. Six normolipidemic male subjects were fed heavy cream (1 g fat per kg body weight) containing vitamin A (3000 retinol equivalents). TRL were isolated by ultracentrifugation from plasma samples obtained at regular intervals after the meal, and apoB-100 TRL were separated from apoB-48 TRL by affinity chromatography using monoclonal antibodies. Postprandial increase in plasma TG concentration was due to an increase in TG in the TRL fraction, which in turn was predominantly (82 +/- 4%) due to an increase in TG in apoB-48 TRL. Contribution of apoB-100 TRL to postprandial increase in TRL TG was 3-27% in individual subjects. ApoB-100 TRL remained a significant carrier of total plasma triglyceride in the fed state, as reflected by similar apoB-100 and apoB-48 TRL TG concentrations at 2, 4, and 6 h after the fat meal. Retinyl esters were regularly detected in apoB-100 TRL. Seventy-five (+/- 9) percent of the increase in TRL-RE was due to RE in apoB-48 TRL and 25 +/- 9% was due to RE in apoB-100. These data suggest that RE in plasma are not always associated with apoB-48-containing lipoproteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Lack of an effect of multivitamins containing vitamin A on serum retinyl esters and liver function tests in healthy women.

Two hundred eighty-four female adults (aged 40-70 years) were longitudinally studied to investigate the relationship between dietary supplemental vitamin A and serum biochemical markers of vitamin A toxicity. Serum retinol, retinyl esters, and retinol-binding protein (RBP), alkaline phosphatase and aspartate aminotransferase activities and bile acids were measured at baseline, 1 and 2 years. Fasting serum retinol and retinyl ester concentrations were determined by high-performance liquid chromatography, and dietary and supplemental intake of vitamin A were assessed by 3-day food records. There was no difference in dietary vitamin A intake between supplement users and nonusers. In supplemental users, the mean +/- SEM supplemental vitamin A intake was 952 +/- 81 IU/day (range 250-5000 retinol equivalents/day). Serum retinol, retinyl esters, and RBP concentrations were not different between the two groups during the 2-year period. For each group, serum retinyl esters significantly increased over time (p < 0.03), but the magnitude of the increase was not different between the groups. Serum levels of retinol, retinyl esters, and RBP were not correlated with vitamin A intake or age in either group. Biochemical measures of liver damage (serum alkaline phosphatase and aspartate aminotransferase activities and serum bile acids) were not related to serum retinol, retinyl esters or RBP concentrations, nor were they different between nonusers and users of supplemental vitamin A. This study provides evidence that long-term supplemental vitamin A in doses commonly found in multivitamin supplements does not present a risk for hypervitaminosis A.

Adult↗
PubMed1992

Evaluation of vitamin A absorption by using oil-soluble and water-miscible vitamin A preparations in normal adults and in patients with gastrointestinal disease.

We evaluated vitamin A absorption in 50 healthy adults and 26 gastrointestinal-disease patients by measuring the postabsorptive response in plasma retinyl esters after oral doses of the vitamin. On 3 consecutive days, two physiologic-dose tests of 2000-2400 retinol equivalents (RE) and one pharmacologic-dose test (84,000 RE) were administered. The physiologic doses were given as an oil-soluble or a water-miscible preparation. In gastrointestinal-disease patients the physiologic-dose test was highly correlated with the pharmacologic-dose test for the oil-soluble preparation as determined by peak rise (r = 0.50, P less than 0.05) and area under the curve (r = 0.56, P less than 0.01), suggesting that the physiologic dose is valid for investigating vitamin A absorption. Intestinal-disease or resection patients absorbed preparations poorly. Pancreatic-disease patients absorbed the oil-soluble preparation poorly. Physiologic rather than pharmacologic doses of vitamin A can be used to study vitamin A absorption.

Absorption↗
PubMed1992

Distribution of orally administered beta-carotene among lipoproteins in healthy men.

Plasma and lipoprotein concentrations of beta-carotene (BC) were measured in men for 10 d after an oral dose of BC (120 mg) (experimental subjects, n = 11) or no BC (control subjects, n = 5). Lipoproteins were separated by sequential ultracentrifugation and BC was measured by HPLC. Plasma and lipoprotein BC concentrations in control subjects were steady. In experimental subjects, plasma BC content increased by 6 h postdosing (P less than 0.015), peaked at 24 h (P less than 0.05), and returned to baseline by 7 d. Maintenance of plasma BC concentrations suggests homeostatic control. Of the 11 experimental subjects, only 4 had a plasma response. Early increases in the BC content of chylomicrons, very-low-density lipoproteins, and intermediate-density lipoproteins. Intestinal input accounts for early rises in circulating BC concentrations whereas hepatic secretion is the source of later increases. Among all of the lipoproteins, transfer of BC may occur.

Administration, Oral↗
PubMed1992

Sex differences in postabsorptive plasma vitamin A transport.

This study examined postabsorptive plasma vitamin A after doses of retinyl palmitate in healthy men (n = 28) and women (n = 31). On consecutive days one physiologic [3000 retinol equivalents (RE)] and one pharmacologic dose (105,000 RE) were administered and blood samples collected. Plasma retinol and retinyl esters were measured by HPLC. Tolerance curves were constructed by plotting plasma retinyl ester concentration vs time. Postprandial retinyl ester response was measured as peak rise in retinyl ester concentration and area under the curve (AUC). Peak plasma retinyl ester concentration occurred earlier for females but the earlier peak was significant only for younger subjects (< or = 50 y, P < 0.02) given the low dose and older subjects (> 50 y, P < 0.02) given the high dose. Peak rise and AUC were lower in females than in males, but this difference was significant for the high dose only (P < 0.05). In the high-dose experiment, when each age group was evaluated for sex differences the peak rise was significantly greater in males than in females in the older subjects (P < 0.05). Postabsorptive plasma retinol did not change from fasting concentrations. A lower plasma response in retinyl esters in women could be due to a more efficient chylomicron-remnant clearance.

Adult↗
PubMed1990

Premature arterial disease associated with familial antithrombin III deficiency.

Antithrombin III (ATIII) deficiency is one of the few known abnormalities of the coagulation system known to predispose to venous thromboembolism but its relation to arterial disease is not established. We describe two related patients with this disorder, both of whom suffered arterial thrombotic events, at an early age. Both patients had other potential risk factors, though these would normally be considered unlikely to lead to such catastrophic events at such an age. Thrombosis due to ATIII deficiency is potentially preventable, and this diagnosis should be sought more frequently in patients with arterial thromboembolism, particularly if occurring at a young age. In addition, in patients with known ATIII deficiency, other risk factors for arterial disease should be eliminated, if possible. In particular, these patients should be counselled against smoking.

Adult↗
PubMed1990

Reduced absorption of oral ciprofloxacin after chemotherapy for haematological malignancy.

Six patients with newly diagnosed haematological malignancy were treated with ciprofloxacin 500 mg orally, as chemoprophylaxis during neutropenia. The mean serum ciprofloxacin concentrations, measured 1, 2, 3 and 4 h after dosage were reduced for up to ten days after the start of chemotherapy. The mean maximum serum concentration and AUC 0-4 h were reduced from 3.7 (95% confidence limits, 2.3-5.1) mg/l and 10.7 (6.2-15.2) mg/l.h pre-chemotherapy to 2.0 (1.4-2.6) mg/l and 5.7 (4.4-7.0) mg/l.h, 13 days after chemotherapy. Absorption of ciprofloxacin is reduced after cytotoxic chemotherapy, and this may have implications for the use of oral ciprofloxacin in this group of patients.

Administration, Oral↗
PubMed1989

The validity of verbal protocols.

The reactivity of a "think aloud" verbal protocol and the veridicality of different retrospective protocols were tested over four dissimilar tasks. Generating a concurrent protocol altered accuracy in two tasks, simple addition and a choice between two gambles, and generally prolonged response times. Such reactivity partially qualifies the dominant theory of protocol generation (Ericsson & Simon, 1984). Retrospective protocols yielded substantial forgetting or fabrication in all tasks, supporting the consensus on the nonveridicality of these methods. It is concluded that protocol validity should be based on an empirical check rather than on theory-based assurances.

Adult↗
PubMed1988

Dietary fiber intakes of nursing home residents and independent-living older adults.

Daily dietary fiber intakes were determined for two groups of older adults with significantly different bowel habits: nursing-home (NH) residents who habitually took laxatives and independent-living (IL) adults who took laxatives occasionally. Fiber intakes were calculated from neutral detergent fiber (NDF) and Southgate total dietary fiber values. IL subjects (n = 7) consumed on average 9.0 +/- 1.6 g NDF and 18.8 +/- 4.6 g total fiber daily. The NH menu provided a similar amount of NDF but more total fiber. NH residents (n = 6) consumed approximately 70-85% of the fiber served. When fiber intakes were expressed as energy, NH and IL subjects consumed similar amounts of NDF but IL subjects consumed less total fiber. Grain products were major fiber sources for both groups; IL subjects consumed more fiber from fruits. Comparisons of fiber intakes, bowel function, lifestyles, and medications suggest that dietary fiber is only part of the basis for inadequate large bowel function experienced by some elderly populations.

Activities of Daily Living↗
PubMed1987

Dynamic modifications of the popliteal arterial axis in the sagittal plane during flexion of the knee.

The authors have studied, on the basis of purely radiologic data, the modifications of the popliteal arterial axis during flexion of the knee. They note the appearance in the sagittal plane of very marked flexures of the upper part of the artery, while the lower part describes a harmonious curve. These modifications take place between two fixed points: a cranial fixed point, represented by the origin of the descending artery of the knee, and a caudal fixed point represented by the origin of the anterior tibial artery. The pathologic importance of these modifications of the course of the artery should not be underestimated when obtaining revascularization by means of an arterial prosthesis.

Humans↗
PubMed1987

Diagnostic differentiation between reactive and malignant lymphoid cells in serous effusions.

Lymphoid cell components in a total of 34 pleural and ascitic aspirates were investigated immunologically. The results indicate that reactive lymphocytes predominate in effusions from non-haemopoietic malignancies and benign conditions, while a significant proportion of fluids from patients with non-Hodgkins lymphoma show unequivocal evidence of lymphomatous involvement. Immunological typing of lymphocytes in serous effusions is a valuable adjunct to conventional methods of diagnosis particularly in those patients in whom invasive procedures are undesirable.

Ascitic Fluid↗
PubMed1987

Effect of wheat bran on bowel function and fecal calcium in older adults.

Seven healthy older volunteers participated in a 33-day study consisting of three sample collection periods, a 10-day control, and two 10-day experimental periods. Subjects consumed their usual self-selected diets throughout and a daily wheat bran supplement (30 g) during the two experimental periods. Food intake was recorded daily by subjects and accuracy and completeness checked daily by personal interview. Apparent calcium absorption decreased significantly from 22.1 +/- 5.6% (mean +/- SD) during the control to 8.6 +/- 5.2% during the second bran period. The wheat bran supplement significantly increased wet and dry stool weights but had no effect on stool moisture or defecation frequency. Gastrointestinal transit time of a dose of chromium decreased significantly, from 75 +/- 33 to 54 +/- 19 hr; of a dose of polyethylene glycol insignificantly, from 98 +/- 59 to 69 +/- 46 hr. Mean recovery of 21 doses of chromium of 98.7 +/- 5.0% verified that stool collection was complete. The results suggest that the ability of wheat bran to regulate bowel function in the apparently healthy older adult may be accompanied by increased fecal calcium losses similar to what has been reported for younger adults.

Aged↗
PubMed1986

A simple method to estimate neutral detergent fiber content of typical daily menus.

The purpose of this research was to develop a simple method to estimate daily intakes of the insoluble fraction of dietary fiber, that portion most effective in increasing stool weight and defecation frequency and decreasing gastrointestinal transit time. Neutral detergent fiber (NDF) contents of 53 foods were determined by analysis and used to calculate the NDF content of typical institutional menus; mean NDF content (n = 14 days) was 10.8 +/- 1.4 g/day. Average NDF content of one serving of fruits and vegetables was approximately 1 g, of the refined grain products, approximately 0.5 g. Estimating daily NDF content of the menus was simplified without a loss of accuracy by substituting the mean NDF content of one serving of refined grains, vegetables, and fruits for the actual values, and by eliminating foods present at less than 1/4 of a serving. Crude fiber was a poor predictor of the NDF in a menu.

Diet↗
PubMed1986

Determining compliance with a dietary fiber supplement.

The purpose of this pilot study was to evaluate possible ways to determine compliance with a dietary fiber supplement. A wheat bran supplement (30 g daily) significantly increased mean daily wet and dry stool weights (SW) in 7 adults, when compared to SW during an ad libitum low-fiber diet (paired t-test, P less than .01). Because unpaired data would be used during a clinical trial, distribution of the 7 ad libitum low-fiber mean SW observations was used to establish a reference distribution and an upper confidence limit against which the bran supplement SW could be compared. Only one of the seven bran supplement mean SW was above the confidence limit of the low-fiber period, independent of the number of days of collection (2-10) used to calculate the individual mean daily SW. Total fecal output over varying periods of time (2-10 days) suffered the same intersubject and intrasubject variability. Most (5-6) of the bran mean daily SW were above the group mean SW of the low-fiber period. However, this dose of bran was large enough to significantly decrease calcium absorption, and differences in SW produced by lower doses of wheat bran would probably not be as great. The bulk (greater than or equal to 80%) of a single dose of a fecal marker, chromium sesquioxide, which could be incorporated into a specific day's fiber supplement, was recovered in 5 days of excretion during the control period and in 4 days during the bran period. However, the blue color of the chromium before ingestion is clearly a negative feature. Another marker, polyethylene glycol, could not be recovered in excreta when transient time was 4 days or more. In a separate study, demonstration of very little overlap in the concentration of fecal neutral detergent fiber between the control and bran periods suggests that fecal fiber may be a marker of compliance with a fiber supplement.

Aged↗
PubMed1985

Composition of fecal fiber from human subjects.

This research addresses two problems of fecal fiber analysis: the nitrogen in fecal neutral detergent fiber (NDF); and the impact of sodium sulfite on NDF yield and composition. Fecal samples for analysis were collected from healthy adults during a study of the effect of a wheat bran supplement on bowel function. When sodium sulfite, originally a component of neutral detergent solution, was omitted, the yield of fecal NDF, the concentration of apparent lignin in the NDF and the amount of nitrogen recovered in both the NDF residue and the lignin increased. These data support a previous report by Van Soest that the sulfite attacks lignin. We present evidence that the effect of sodium sulfite also could be one of inhibiting the formation of Maillard products, which are detected as lignin, during the reflux step of the NDF method. Three different fractions of nitrogen were identified in fecal NDF: the fraction eliminated by sodium sulfite; a fraction removed by dilute acid; and the fraction that remained in Klason lignin. Apparent NDF digestibilities were calculated several ways by using correction factors to account for this nitrogen. Only the subtraction of Klason lignin from fecal NDF eliminated the one negative digestibility we observed.

Aged↗
PubMed1984

Preservation of platelet function in cryopreserved platelet concentrates with prostacyclin.

Prostacyclin (Epoprostenol) or a stable prostacyclin analogue (ZK 36,374) were added to platelet concentrates prior to cryopreservation. This resulted in significantly better preserved function of the thawed platelet concentrate, assessed by platelet aggregation to various concentrations of ADP, collagen and ristocetin, compared to control cryopreserved platelet concentrates. The use of prostacyclin or one of its stable analogues should be considered to reduce platelet activation and subsequent loss of function during the various manipulative procedures when preparing standard and cryopreserved platelet concentrates.

Blood Platelets↗