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Biomedical subjects

G F Johnson

Publications and source records attributed to G F Johnson.

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

Determination of choline in erythrocytes using high-resolution proton nuclear magnetic resonance spectroscopy: comparison with a choline oxidase method.

Detailed operating conditions are reported for the determination of choline in human erythrocytes using proton nuclear magnetic resonance spectroscopy in conjunction with the inversion-recovery spin-echo pulse sequence. The results of the NMR method were in excellent agreement with those obtained using an enzymatic (choline oxidase) assay; however, they were approximately three times higher than those reported using gas chromatography/mass spectrometry techniques. The differences may be partly due to the method of preparing or sampling cells since there is a distribution of choline in cells of different ages. However, choline levels were not affected by the methods used in the present study for storing or preparing cells.

Alcohol Oxidoreductases↗
PubMed1984

Lithium, red blood cell choline and clinical state. A prospective study in manic-depressive patients.

Red blood cell (RBC) choline and ergothioneine levels were measured after repeated sampling of bipolar manic-depressive patients over 11 months of lithium maintenance. In addition, blood levels were measured in healthy volunteers, newly hospitalised lithium-free patients and from patients prior to, and after, initiating lithium. RBC choline levels did not differ between normal volunteers and newly admitted lithium-free patients with either mania or depression. After 4 weeks of lithium treatment RBC choline levels increased 6-fold, whereas the levels of the closely related compound ergothioneine did not change. Significant changes in mood during lithium maintenance were not accompanied by changes in RBC choline levels. These data indicate that lithium produced a specific accumulation of choline in erythrocytes. However the increased levels appear to be unrelated to clinical state and do not distinguish lithium responders from non-responders

Adult↗
PubMed1984

Dexamethasone suppression test (DST) and plasma dexamethasone levels in depressed patients.

The dexamethasone suppression test (DST) was evaluated in newly hospitalized patients with a DSM-III diagnosis of major depression. Patients with other psychiatric disorders and a normal control group were also studied. Plasma dexamethasone levels were obtained in all patients, and the relationship between plasma cortisol and plasma dexamethasone was examined. Rates of non-suppression in patients with major depression (39%) were not significantly different from those in patients with minor depression (25%), mania (38%), or other psychiatric illnesses (17%). The ranges of dexamethasone levels at 8 a.m. and 4 p.m. were similar between patient groups and controls. However, there was a significant difference in dexamethasone levels between suppressors and nonsuppressors, irrespective of diagnosis, which could not be explained by differences in weight or plasma dexamethasone half-life. Inappropriately high dexamethasone levels were found in some patients with a 1 mg test, a problem that critically affects the sensitivity of the test procedure.

Adolescent↗
PubMed1984

Pharmacokinetics of lithium preparations in patients.

Equivalent oral dosages (800 mg, 21.6 mmol) of standard ( Lithicarb ) and sustained-release ( Priadel ) lithium carbonate preparations were administered using a randomised cross-over design to six patients receiving long-term lithium maintenance and eight healthy student volunteers. In both patients and students there were no significant differences between the two lithium preparations for plasma lithium level curves, bioavailability or total urinary excretion rates. There were no differences in peak lithium concentrations (C max) between the two preparations in both patients and students, although the times to maximal levels (T max) were delayed after Priadel in patients and volunteers. These data indicate that Priadel is a delayed-release rather than a true sustained-release preparation.

Administration, Oral↗
PubMed1984

Renal function and lithium treatment: initial and follow-up tests in manic-depressive patients.

Assessment of renal function was carried out in an unselected sample of patients with bipolar manic-depressive disorder receiving lithium for an average period of 4.5 years. Overall, glomerular filtration rate (GFR) fell within the established normal range based on sex and age, whereas measures of urinary concentrating ability were generally impaired. There was no relationship between duration of lithium treatment and either GFR or impairment of urinary concentrating ability. Moreover, there was no evidence of a progressive impairment of glomerular or tubular function in patients re-tested after 2 years. The results of this study confirm the safety of lithium administration in the majority of patients and emphasize the importance of careful clinical monitoring to avoid lithium intoxication.

Adult↗
PubMed1984

Model for theophylline overdose treatment with oral activated charcoal.

The effect of repeated oral doses of activated charcoal on theophylline kinetics was studied in six subjects with hepatic cirrhosis and five patients with moderate theophylline poisoning to determine whether an activated charcoal regimen would be a useful strategy in patients with theophylline poisoning who did not require hemoperfusion. Six subjects with cirrhosis were injected IV with 6 mg/kg aminophylline followed by either water or water with activated charcoal (140 gm) in divided doses over 12 hr. In these subjects, treatment with activated charcoal decreased the mean (+/- SE) serum theophylline t1/2 from 12.7 +/- 4.0 hr to 4.0 +/- 0.7 hr. Subjects with the longest control t1/2s demonstrated the greatest charcoal effect. We developed a mathematical model that predicts that treatment with repeated oral doses of activated charcoal would result in an average serum theophylline t1/2 of 7.1 hr or less even if the subject's endogenous theophylline t1/2 is very long. In a pilot study of five patients with moderate theophylline poisoning, treatment with repeated oral doses of activated charcoal was well tolerated and led to a mean (+/- SE) t1/2 that was shorter than expected (4.9 +/- 0.8 hr, range 3.1 to 7.1 hr). We conclude that repeated oral doses of activated charcoal are relatively more effective in decreasing the serum theophylline t1/2 in persons with long endogenous t1/2s and that this may be useful for certain patients with mild or moderate theophylline poisoning.

Adult↗
PubMed1984

Proton nuclear magnetic resonance spectroscopy of rabbit brain homogenate.

Proton nuclear magnetic resonance (1H NMR) spectroscopy in conjunction with the inversion-recovery spin-echo pulse sequence was used to obtain spectra from rabbit brain homogenate. The instrumental parameters required for the acquisition of spectra together with the assignment of major peaks are given. The rationale and prospectus for the use of this technique for the study of neurochemistry is outlined.

Animals↗
PubMed1984

Studies of rat brain metabolism using proton nuclear magnetic resonance: spectral assignments and monitoring of prolidase, acetylcholinesterase, and glutaminase.

The first application of inversion-recovery spin-echo proton nuclear magnetic resonance spectroscopy to the monitoring of reactions in rat brain preparations is presented. The initial report of the assignment of proton spin-echo nuclear magnetic resonance spectra from rabbit brain homogenates (C. R. Middlehurst et al., J. Neurochem. 42, 878-879, 1984) was used to assist in the assignment of spectra acquired from rat brain homogenates that were obtained from animals killed by cervical fracture or focussed microwave irradiation. Microwave-irradiated brains were divided into four major anatomical regions. Differences in metabolite levels were detected when spectra from fresh tissue and from various regions were compared. The in situ steady-state kinetics of prolidase in whole brain homogenate was determined. The procedure relies on the spectral differences between enzyme substrates and reaction products. The concentration dependence of the rate of hydrolysis of glycyl-L-proline was discribable by the Michaelis-Menten expression with a Michaelis constant of 1.90 mmol L-1 and a maximal velocity of 9.30 mumol min-1 mg-1 protein. The reactions catalysed by glutaminase and acetylcholinesterase in the brain were also monitored.

Acetylcholine↗
PubMed1984

Cytochemical detection of inherited copper toxicosis of Bedlington terriers.

Sections of paraffin-embedded specimens of liver obtained from Bedlington terriers were stained with rhodanine for copper and examined and graded by two pathologists. Their results correlated well with each other, as well as with the results of quantitative determinations of hepatic copper content. Copper toxicosis was established by cytochemistry in 20 of 21 specimens, indicating a sensitivity of 95%. The method is highly specific--none of the 19 specimens obtained from unaffected dogs displayed copper-containing granules suggestive of copper toxicosis. Copper cytochemistry appears to be a satisfactory substitute for chemical analysis of hepatic copper content.

Age Factors↗
PubMed1983

Feline hyperthyroidism: pretreatment clinical and laboratory evaluation of 131 cases.

Hyperthyroidism was diagnosed in 131 cats during a 3 1/2-year period. The cats ranged in age from 6 to 20 years; there was no breed or sex predilection. The most frequent clinical signs included weight loss, polyphagia, increased activity, polydipsia, polyuria, and vomiting. Common serum biochemical abnormalities included high values for alkaline phosphatase activity (75%), lactate dehydrogenase activity (66%), aspartate transaminase activity (66%), and alanine transaminase activity (54%). Electrocardiographic changes included tachycardia (greater than or equal to 240 beats/min) and increased R-wave amplitude in lead II (greater than or equal to 0.9 mV) in 66% and 29% of the 131 cats, respectively. Thoracic radiography in 82 cats revealed cardiomegaly in 40 (49%) of these cats; 16 cats with congestive heart failure also had pulmonary edema or pleural effusion. In 5 cats with markedly increased fecal volume, mean 48-hour fecal fat content was significantly greater than normal, with daily fat excretion 2 to 15 times the upper limit of normal. Base-line serum thyroxine concentrations were increased above normal range in all cats, whereas triiodothyronine concentrations were increased in 127 (97%) of the 131 cats. In 11 cats tested, mean thyroxine concentration did not increase significantly after thyroid-stimulating hormone administration. Mean 24-hour percentage of thyroid radioiodine uptake in 32 hyperthyroid cats was significantly higher (39.1%) than normal (9.2%). Thyroid scans, performed on 126 cats, showed enlargement and increased radionuclide accumulation in 1 thyroid lobe in 36 (29%) and both lobes in 90 (71%) of the cats.

Adenocarcinoma↗
PubMed1983

Skeletal lesions following meningococcemia and disseminated intravascular coagulation. A recognizable skeletal dystrophy.

Partial destruction of the right humeral and right femoral head were discovered in a 30-month-old girl, two years after her recovery from meningococcal septicemia and disseminated intravascular coagulation (DIC). Additional findings were symmetrical epiphyseal-metaphyseal lesions of the lower femora and upper and lower tibiae. The combined skeletal lesions seem to be characteristic sequelae of infantile meningococcemia complicated by DIC. Since this condition is no longer uniformly fatal, the characteristic skeletal dystrophy will be encountered more frequently and should be recognized by radiologists, pediatricians, and orthopedists. The features shared by our patient and the seven previously published cases are presented.

Bone Diseases↗
PubMed1983

Effects of size and frequency of oral doses of charcoal on theophylline clearance.

The effect of size and frequency of oral doses of activated charcoal on theophylline kinetics was studied. Six fasting, healthy men received intravenous infusions of aminophylline (6 mg/kg) over 1 hr, followed by either no activated charcoal as a control, 5 gm activated charcoal every 2 hr for 6 doses, 10 gm every 2 hr for 6 doses, 10 gm every hr for 12 doses, 20 gm every 2 hr for 6 doses, or 40 gm every 4 hr for 3 doses. Five grams every 2 hr decreased serum theophylline t 1/2 from the control of 9.1 +/- 0.7 to 5.6 +/- 0.4 (SE) hr and decreased the AUC from the control of 123 +/- 11 to 79 +/- 6 mg X hr/l. The regimen of 20 gm every 2 hr further decreased theophylline t 1/2 to 4.3 +/- 0.4 hr and decreased AUC to 62 +/- 6 mg X hr/l. When a 120-gm dose of activated charcoal was given as a regimen of 40 gm every 4 hr or as a regimen of 10 gm every hr, there were small differences in serum theophylline t 1/2 (5.4 +/- 0.3 and 4.3 +/- 0.2 hr) and in AUC (73 +/- 5 and 60 +/- 4 mg X hr/l). Repeated small doses of oral activated charcoal enhanced the total body clearance of theophylline, and larger doses induced a relatively small further increase. There was little difference between the effects of the same total dose every 4 hr vs every hour.

Adult↗
PubMed1983

Enhancement of theophylline clearance by oral activated charcoal.

A randomized crossover trial of the effect of oral activated charcoal on the kinetics of intravenous theophylline was carried out in six normal male subjects. After intravenous aminophylline (6 mg/kg), subjects received water or water with activated charcoal (140 gm) in divided doses over 12 hr. Serum theophylline concentrations were measured from 0 to 24 hr after the aminophylline infusion. Treatment with activated charcoal decreased the serum t 1/2 from 6.4 +/- 1.2 to 3.3 +/- 0.4 (SEM) hr and the serum AUC from 78 +/- 14 to 42 +/- 4 mg . hr/l. Percent decrease in AUC after treatment with charcoal correlated positively with the endogenous theophylline serum t 1/2 (r = 0.94). These results suggest that oral activated charcoal (1) enhanced the total body clearance of theophylline and (2) may be efficacious in the treatment of theophylline poisoning, especially in patients with prolonged serum t 1/2s of theophylline.

Adult↗