Some clinical implications of recombinant DNA technology with emphasis on prenatal diagnosis of hemoglobinopathies

Recombinant DNA technology has made possible remarkable advances in understanding the molecular genetics of human and other eucaryotic cells. This technology also has clinical applications, some of which may soon involve clinical laboratories. Restriction endonucleases and cloned DNA probes permit the direct analysis of cellular DNA to detect sequence abnormalities associated with particular genetic disorders. Use of this approach in the antenatal diagnosis of hemoglobinopathies is now possible on a routine basis. The principles behind the methods are quite general and may be applied to other hereditary diseases once suitable DNA probes become available. The same approach may be used to detect carriers of recessive gene defects and so improve genetic counselling. Other clinically related applications of recombinant DNA technology include the production of antigens for vaccine preparation and of specific human proteins (e.g. interferon and human growth hormone) for therapeutic use, as well as the use of nucleic acid hybridization for identification of microbial pathogens. It seems likely that recombinant DNA technology will, in the future, play an increasingly important role in the diagnosis, prevention and treatment of human disease.

Eggs, serum lipids, emotional stress, and blood pressure in medical students

Emotional stress that occurred as a result of anticipation and participation in final exams did not change mean serum total cholesterol or high density lipoprotein cholesterol significantly in 26 male students who had eaten two eggs daily while maintaining a controlled diet for 12 wk. These same men continued to maintain a controlled diet but abstained from eating eggs for 12 wk which resulted in a statistically significant lower total cholesterol level at the end of 6 wk and on the day of final exams at the end of 12 wk. Mean values for high-density lipoprotein cholesterol in abstainers were significantly reduced at the end of 6 wk, but did not change further by 12 wk. Mean serum triglycerides values were variable. Blood pressures were not changed significantly.

Segmental homologies in the coding and 3' non-coding sequences of rat liver cytochrome P-450e and P-450b cDNAs and cytochrome P-450e-like genes

The nucleotide sequence of a cloned cDNA insert carried by pHDQ14 was determined and found to code for the 107 C-terminal amino acids of rat liver cytochrome P-450e. Comparison of the pHQ14 cDNA sequence with those of cloned cDNAs for cytochrome P-450b and of 2 P-450e-like genes revealed segmental homologies that may have resulted from gene conversion. These results suggest that gene conversion may generate sequence variants of genes for rat liver cytochrome P-450s.

A simplified hot-wire cutting aid for PVC trays used in radioimmunoassay

Images

Rapid suppression of alpha 1-fetoprotein gene transcription by dexamethasone in developing rat liver

The administration of glucocorticosteroid hormones to newborn rats interrupts selectively (and reversibly, if the hormone is withdrawn) the hepatic production of alpha 1-fetoprotein (AFP). This results from a decreased concentration of AFP mRNA in the liver [Bélanger, L., Frain, M., Baril, P., Gingras, M.C., Bartkowiak, J., & Sala-Trepat, J.M. (1981) Biochemistry 20, 6665]. We have delineated further the mechanism and time course of this hormonal action in 4-day-old rats treated with dexamethasone (DEX). DNA from a recombinant plasmid containing a 578-bp insert of rat AFP cDNA was used to develop a cell-free nuclear run-off system and directly assess AFP gene transcription activity. Five minutes after DEX injection, AFP gene transcription activity is unchanged, but after 30 min, it drops to 25% that of the control; this correlates with the time required for translocation of DEX receptors to the nucleus. Dose-response curves also show that the degree of AFP gene suppression is closely correlated with the amount of DEX receptor translocated to the nucleus. The nuclear concentration of AFP mRNA, monitored by dot-blot hybridization, decreases to undetectable levels within 48 h, whereas that of albumin mRNA increases slightly, which indicates the selectivity of DEX action. These results show that DEX suppresses AFP gene expression at the transcriptional level and suggest a direct negative action of DEX-receptor complexes on the AFP chromatin transcription unit.

Curing and induction of the Fels 1 and Fels 2 prophages in the Ames mutagen tester strains of Salmonella typhimurium

A method is described for curing the Ames Salmonella mutagen tester strains of their Fels 1 and Fels 2 prophages with the aid of the antitumor drug daunorubicin. Non-lysogenic derivatives corresponding to TA100 and TA1535 were isolated and designated TAQ100 and TAQ1535 respectively. In addition, the Fels 1 monolysogens TAQ100F1 and TAQ1535F1, as well as the Fels 2 monolysogens TAQ100F2 and TAQ1535F2, were obtained. Finally, strains corresponding to TA98 and TA1538 cured of Fels 2, but retaining a cryptic Fels 1 (F1d) prophage were isolated and designated TAQ98F1d and TAQ1538F1d respectively. The various cured derivatives were identified by colony hybridization with 32P-labeled probes of Fels 1 and Fels 2 DNA. Southern blot hybridizations confirmed that phage-specific Fels DNA sequences were missing from the cured strains. The Fels 2-cured strains were resistant to Fels 2, but Fels 1 grew, albeit poorly, on the Fels 1-cured strains. Strains TAQ100F1, TAQ1535F1, TAQ100F2 and TAQ1535F2 were used in prophage induction assays, in the presence of rat-liver extract where necessary. Daunorubicin, bleomycin, mitomycin C, aflatoxin B1, 2-amino-dipyrido[1,2-a:3',2'-d]imidazole (Glu-P-2) were found to induce Fels 1 and/or Fels 2 in at least one of these strains. The induction of the Fels prophages in the TAQ monolysogens may provide a useful complement to the Ames test for the detection of DNA-damaging agents and potential carcinogens.

The effect of ketanserin in essential hypertension

Ketanserin, a 5HT2-receptor blocking drug was given to 17 patients with essential hypertension. Satisfactory control was achieved in 13 patients. Control was not as satisfactory when given once daily. There was no rebound effect when the drug was ceased. Side-effects were few. Ketanserin was a satisfactory drug to reduce blood pressure in patients with moderate hypertension.

Mutagenic response of Ames strains cured of their inducible Fels 1 and Fels 2 prophages

Ames strain TA100 was cured of its Fels 1 and Fels 2 prophages to yield the corresponding nonlysogenic derivative designated TAQ100. The two monolysogenic strains corresponding to TA100 lysogenic for Fels 1 (TAQ100F1) and for Fels 2 (TAQ100F2) were also isolated. In addition, the equivalent strains lacking pKM101 and designated TAQ1535, TAQ1535F1, and TAQ1535F2 were obtained. Ames strains TA98 and TA1538 are lysogenic for Fels 2 and were observed by colony hybridization to contain cryptic Fels 1 DNA sequences. Strains corresponding to TA98 and TA1538 cured of Fels 2 were isolated and designated TAQ98F1d and TAQ1538F1d, respectively. Fels 1 grew poorly on Fels 1-cured strains, and Fels 2 grew not at all on Fels 2-cured strains. The cured strains had therefore to be identified as such by their failure to react in colony hybridization with 32P-labeled probes of Fels 1 and/or Fels 2 DNA. The specificity of the labeled probes was confirmed with the aid of the nonlysogenic Salmonella typhimurium strain Q1 and its two monolysogenic derivatives Q1 (Fels 1) and Q1 (Fels 2). The cured strains were found to respond in the same manner as did the standard Ames strains to a variety of well-known mutagens, including aflatoxin B1, 7, 12-dimethylbenz(a)anthracene, daunorubicin, 2-amino-dipyrido[1,2-a:3',2'-d]imidazole, and beta-naphthylamine. Also, mitomycin C, bleomycin, and diethylstilbestrol were nonmutagenic to TAQ100 and TAQ98F1d as they are to TA100 and TA98. Since the Fels prophages are inducible by aflatoxin B1, by daunorubicin, and by other agents, it seems that mutagenesis and Fels prophage induction occur in separate subpopulations of cells; this situation had previously been reported to occur for mutagenesis and prophage lambda induction in Escherichia coli. In any case, the Fels prophages appear to have no major influence on the mutagenic response of the Ames strains.

Oncodevelopmental and hormonal regulation of alpha 1-fetoprotein gene expression

The main features of the oncodevelopmental biology of alpha 1-fetoprotein (AFP) are reviewed. Progress made in the molecular biology of AFP gene regulation is discussed and we present our recent data on the mechanisms of AFP suppression by glucocorticoid hormones. The relationship between AFP gene transcription and cell replication is examined, and it is suggested that the degree of methylation of the AFP gene (or of co-methylated regulatory DNA sequences) conditions its response to hormones.

Transplantation of islets and bone marrow cells to animals with immune insulitis

The results of islet transplantation in an animal model of spontaneous immune insulitis were studied to see whether this disease process might damage transplanted tissue. Since the insulitis occurs only in "BB" rats (which are not genetically uniform) syngeneic grafts could not be used, therefore allograft rejection was avoided by rendering "BB" rats tolerant of WF transplantation antigens by inoculating them neonatally with WF bone marrow cells. Despite the resultant tolerant state, which permitted successful engraftment of WF skin and islets transplanted to artificially diabetic "BB" rats, tolerant "BB" rats with spontaneous diabetes accepted transplanted WF islets only briefly before they were destroyed by immune insulitis. "BB" rats were found to have abnormalities in immune response (delayed skin graft rejection and decreased alloreactivity in mixed lymphocyte response). "BB" rats that were treated neonatally with WF bone marrow. Moreover, "BB" rats inoculated with WF bone marrow neonatally were found less likely to become diabetic than untreated "BB" controls. It is suggested that the chimeric state (persistence of WF bone marrow cells) may be responsible for the improved immune response and perhaps for the decreased susceptibility to diabetes.

Radioimmunoassay of thyroxine and 3,3',5'-triiodothyronine (reverse T3) in human amniotic fluid

Measurement of amniotic fluid iodothyronine concentrations may enable antenatal detection of fetal thyroid abnormalities; however, the delineation of normal ranges is complicated by methodological problems associated with strong and highly variable protein-binding, and specificity of antisera. Improved radioimmunoassays of thyroxine (T4) and 3,3',5-triiodothyronine (reverse T3, rT3) have been developed to overcome these problems. In normal pregnancy, mean rT3 concentrations at less than 17 weeks, 17-22 weeks and 35-42 weeks gestation were 3.6 nmol/l (n = 21), 6.1 nmol/1 (n = 14) and 0.66 nmol/1 (n = 39) respectively; corresponding mean T4 concentrations were 2.4 nmol/1, 6.5 nmol/1 and 3.6 nmol/1. rT3 concentrations showed a strong positive correlation with T4 concentration in each age range; however, the molar ratio of rT3:T4 decreased progressively with gestational age, from 1.69 at less than 17 weeks to 0.19 at 35-42 weeks. In both mid- and late gestation, rT3 and T4 concentrations were strongly correlated with total amniotic fluid protein concentrations.

Pharmacokinetics of the H2- receptor antagonist ranitidine in man

1 Ranitidine pharmacokinetics were studied in six healthy volunteers. Following an overnight fast, doses of 20 mg intravenously 20, 40 and 100 mg orally and 100 mg orally with a standard meal, were administered to each subject on separate occasions. 2 Following intravenous administration there was a bioexponential decline in plasma levels from 576 +/- 56 ng/ml at 4 min to 10 +/- 2 ng/ml at 8 h. The distribution half-life (T 1/2 alpha) was 6.1 +/- 0.9 min, elimination half-life (T 1/2 beta) was 1.9 +/- 0.1 h, the volume of distribution (Vd beta) was 115 +/- 7 l and systemic plasma clearance (Cltp) was 709 +/- 62 ml/min. 3 Following 20 mg oral doses, peak levels were reached at 1.6 +/- 0.2 h and the systemic availability was 88 +/- 10%. Elimination half-life (T 1/2 beta) was unaffected by dose and the area under the curve increased linearly with dose and was unaffected by food. 4 Renal excretion (24 h) of unmetabolized ranitidine accounted for 50-70% of the dose with a further 1-3% appearing as desmethyl ranitidine.

Analysis of the anti-coccidial drug, halofuginone, in chicken tissue and chicken feed using high-performance liquid chromatography

Methods are described for the analysis of the anti-coccidial drug, halofuginone, in chicken tissue at concentrations as low as 1 ppb (0.001 ppm) and in chicken feed at a concentration of 3 ppm, using high-performance liquid chromatography. The tissue analysis involves: enzymatic release of the halofuginone followed by ethyl acetate extraction under basic conditions, partition into ammonium acetate buffer, concentration using Sep-pakTM C18 cartridge. The feed analysis involves: ethyl acetate extraction under basic conditions, partition into hydrochloric acid, concentration using XAD-2 column chromatography. Both methods use high-performance liquid chromatography with ultraviolet detection for the final analysis. Precision and accuracy data for both methods are given.

High-performance liquid chromatographic analysis of captopril in plasma

A sensitive assay is described for quantitating plasma captopril levels. Captopril is an orally active inhibitor of angiotensin-converting enzyme. Blood from patients taking this drug was collected into tubes containing edetate and ascorbic acid, and the plasma was separated by centrifugation. After addition of an internal standard, the plasma was deproteinized and the supernate was adjusted to pH 6.5 N-(1-Pyrene)-maleimide was added to derivatize captopril and an internal standard to fluorescent adducts. These derivatives then were extracted into ethyl acetate-benzene (1:1) and separated from other derivatized thiols by high-performance liquid chromatography. The sensitivity of the assay was 150 pmoles/ml. Preliminary pharmacokinetics were obtained in patients taking captopril chronically for essential hypertension. After administration of 100 mg of captopril for patients who had fasted overnight, the plasma levels rose rapidly; peak levels were obtained at approximately 37 min. Thereafter, the plasma levels declined rapidly, and the terminal half-life was approximately 40 min. In these patients, the time course of the plasma levels did not reflect changes in blood pressure, so there appeared to be no direct relationship between plasma levels of the parent compound and blood pressure changes.

Pharmacokinetic and gastric secretory studies of ranitidine in man

A sensitive and specific high pressure liquid chromatographic procedure for ranitidine estimation is described and pharmacokinetic studies in six healthy volunteers reported. Each subjects received 20 mg of ranitidine i.v.; 20 mg, 40 mg and 100 mg orally having fasted overnight and 100 mg with a standard meal. Following the i.v. dose, ranitidine plasma concentrations fell biexponentially with a distribution half-life of 6.1 +/- 0.9 min and a terminal elimination half-life of 1.9 +/- 0.1 h. The volume of distribution was 115 +/- 7 1 and the systemic plasma clearance 709 +/- 62 ml/min. After 20 mg oral doses the systemic availability was high (88 +/- 10%). Bioavailability was unaffected by food and AUC increased linearly with dose to 100 mg. Renal excretion of unchanged ranitidine was between 50 and 70% and a further 1-3% was excreted as desmethylranitidine. In separate studies, the inhibitory action of cimetidine and ranitidine on pentagastrin stimulated gastric acid output was compared in seven duodenal ulcer patients. Results so far indicate that ranitidine 150 mg i.v. produces a more pronounced and more prolonged suppression of pentagastrin stimulated gastric acid output than cimetidine 200 mg i.v. (p less than 0.001). Ranitidine produced a sustained near total (greater than 90%) suppression in acid output in the period 60 to 120 min after drug administration, whereas acid output with cimetidine was less and fell from 82 to 54% in the same period.

Types of paradoxical intervention and indications/contraindications for use in clinical practice

A review of theoretical mechanisms underlying paradoxical interventions is undertaken in an effort to classify them into three broad types: redefinition, symptom escalation and crisis induction, and redirection. A list of individual and family patient characteristics and problems particularly applicable to each type of paradoxical intervention is presented along with contraindications for use. Last, implications for training and cautions as to their use are presented.