Thyrotropin (TSH)-releasing hormone regulation of TSH subunit biosynthesis and glycosylation in normal and hypothyroid rat pituitaries

The regulation of TSH apoprotein and carbohydrate biosynthesis by TRH was studied by incubating pituitaries from normal and hypothyroid (3 weeks postthyroidectomy) rats in medium containing varying doses of TRH, [14C] alanine or [35S]methionine, and [3H]glucosamine. Samples were sequentially treated with anti-TSH beta to precipitate TSH and free TSH beta, anti-LH beta to remove LH and free LH beta, and anti-LH alpha to precipitate free alpha-subunits. Total proteins were acid precipitated. All precipitates were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In hypothyroid samples, acute TRH (6 h) stimulated [3H] glucosamine incorporation into secreted combined alpha-subunit to 204% and secreted combined beta-subunit to 227% of control values (P less than 0.01), and stimulated [14C]alanine incorporation into secreted combined alpha-subunit to 201% and secreted combined beta-subunit to 258% of control values (P less than 0.01); pituitary content was not altered by TRH. In hypothyroid incubates, the half-maximal response was 8 X 10(-10) M TRH for both labeled precursors. In contrast, in normal samples, acute TRH (6 H) did not stimulate TSH subunit carbohydrate and apoprotein synthesis, but after 24 h, TRH stimulated [3H]glucosamine incorporation into both subunits of TSH to 270% of control values (P less than 0.02), with no change in [14C]alanine incorporation. Free alpha-subunit synthesis was not altered by TRH in normal or hypothyroid incubates. The glucosamine to alanine ratio of total newly synthesized TSH, reflecting its relative glycosylation, was increased by TRH in both combined subunits in hypothyroid samples as early as 6 h (P less than 0.05) and in normal samples only at 24 h (P less than 0.01). In summary, 1) TRH in hypothyroid incubates stimulated apoprotein and carbohydrate synthesis in combined alpha- and beta-subunits, but not free alpha-subunits, at 6 and 24 h. 2) In normal pituitary incubates, TRH stimulated TSH subunit carbohydrate, but not apoprotein, synthesis only at 24 h. 3) TRH increased the relative glycosylation of TSH in hypothyroid and normal rat pituitary incubates. Such alterations in TSH glycosylation may be due to structural changes in the carbohydrate moiety and may be important for hormone release, biological activity, or clearance.

Bioequivalence of a sustained-release isosorbide dinitrate formulation at steady-state

Isosorbide 2,5-dinitrate and its pharmacologically active metabolites, isosorbide 2-nitrate and isosorbide 5-nitrate, in plasma accumulated to the predicted steady-state after five consecutive oral doses of sustained-release tablets containing 40 mg isosorbide dinitrate at 12-h intervals and after five consecutive oral doses of reference standard-release tablets containing 20 mg at 6-h intervals to 12 subjects in a crossover study. The comparative bioavailability of isosorbide dinitrate, isosorbide 2-nitrate and isosorbide 5-nitrate from the sustained-release tablet was 110 per cent (p greater than 0.05), 89 per cent (p greater than 0.05), and 89 per cent (p less than 0.05), respectively, of that from the reference standard-release tablet. The isosorbide dinitrate plasma level data were the more variable, as expected for a drug of low systemic availability subject to extensive first-pass elimination. The posterior probability that the true bioavailability of isosorbide dinitrate was included within the usually accepted limits of 80-120 per cent was 0.74, a value which is probably insufficient to justify claims of bioequivalence with the reference formulation in respect of extent of availability. In contrast, the posterior probability that the bioavailability of the metabolites isosorbide 2- and 5-nitrate was included within these limits was 0.90 and 0.98, respectively. On the basis of the mononitrate data, these two formulations may be judged bioequivalent in respect of extent of availability despite a formal statistically significant formulation-related effect in the analysis of variance of the isosorbide 5-nitrate bioavailability data. Claims of bioequivalence of isosorbide dinitrate sustained-release formulations may be more economically justified by analysis of the mononitrate plasma concentrations, although concentrations of the formulated parent dinitrate should also be known.

Differential regulation of thyrotropin subunit apoprotein and carbohydrate biosynthesis by thyroid hormone

The regulation of TSH apoprotein and carbohydrate biosynthesis by thyroid hormone was studied by incubating pituitaries from normal and hypothyroid (3 weeks post-thyroidectomy) rats in medium containing [14C]alanine and [3H] glucosamine. After 6 h, samples were sequentially treated with anti-TSH beta to precipitate TSH and free TSH beta, anti-LH beta to clear the sample of LH and free LH beta, then anti-LH alpha to precipitate free alpha-subunit. Total proteins were acid precipitated. All precipitates were subjected to electrophoresis on sodium dodecyl sulfate-polyacrylamide gels, which were then sliced and assayed by scintillation spectrometry. In hypothyroid pituitaries plus medium, [14C]alanine incorporation in combined and free beta-subunits was 26 times normal (P less than 0.001) and considerably greater than the 3.4-fold increase seen in total protein (P less than 0.05); combined and free alpha-subunits showed no specific increase in apoprotein synthesis. [3H]Glucosamine incorporation in combined alpha- and beta-subunits in hypothyroid samples was 13 and 21 times normal, respectively, and was greater than the 1.9-fold increase in total protein (P less than 0.05); free alpha-subunit showed no specific increase in carbohydrate synthesis. The glucosamine to alanine ratio, reflecting relative glycosylation of newly synthesized molecules, was increased in hypothyroidism for combined alpha-subunits (P less than 0.001), but not for combined beta-subunits, free alpha-subunits, or total proteins. In summary, short term hypothyroidism selectively stimulated TSH beta apoprotein synthesis and carbohydrate synthesis of combined alpha- and beta-subunits. Hypothyroidism also increased the relative glycosylation of combined alpha-subunit. Thus, thyroid hormone deficiency appears to alter the rate-limiting step in TSH assembly (i.e. beta-subunit synthesis) as well as the carbohydrate structure of TSH, which may play important roles in its biological function.

beta-Endorphin stimulates plasma renin and aldosterone release in normal human subjects

To determine the effect of beta-endorphin on the renin-angiotensin-aldosterone system, human synthetic beta-endorphin (0.3, 1.0, and 3.0 micrograms/kg X min) was infused iv in normal subjects. Each dose was administered for 30 min, and a control infusion of 5% dextrose and water was given on another day. Ten subjects were studied recumbent and in balance while ingesting a 10-meq Na+ diet. Plasma renin activity (PRA), plasma aldosterone (PA), and plasma cortisol (F) were measured basally and every 30 min for 210 min. The increments in PRA and PA above basal significantly (P less than 0.05) increased (3.1 +/- 1.2 ng/ml X h and 12.2 +/- 5.3 ng/dl, respectively; P less than 0.05) at the end of the beta-endorphin infusion. beta-Endorphin also significantly (P less than 0.01) suppressed F levels. Since in the low salt study, beta-endorphin suppressed F release while stimulating renin secretion, an additional five subjects were pretreated with dexamethasone (0.5 mg every 6 h) and were studied in balance while ingesting a 200-meq Na+ diet to suppress the renin-angiotensin system. Significant (P less than 0.025) increments in PRA (2.1 +/- 0.7 ng/ml X h) and PA (4.1 +/- 1.7 ng/dl) levels above basal were again found during the sequential dose infusion of beta-endorphin (0.3, 1.0, and 3.0 micrograms/kg X min). However, PA elevations were sustained for at least 120 min after the beta-endorphin infusion was stopped despite a drop in PRA 90 min earlier. In additional studies, an attempt was made to define the minimal effective dose of beta-endorphin by 60-min infusions (0.03, 0.1, and 0.3 micrograms/kg X min) in subjects on a 200-meq Na+ diet who were dexamethasone pretreated. The PRA and PA levels rose significantly (P less than 0.05) above basal at the 0.3 micrograms/kg X min dose, but not at the 0.03 or 0.1 micrograms/kg X min dosage levels. There were no changes in blood pressure or potassium during either the 10 or 200-meq Na+ studies. Thus, beta-endorphin stimulates aldosterone release in vivo. However, the underlying mechanisms are complex, since renin levels also increased. The data suggest that the early aldosterone rise may be secondary to an increase in renin release, but renin cannot account for the sustained postinfusion elevations of aldosterone.

Effects of spinal fusion on the proteoglycans of the canine intervertebral disc

Posterior lumbar two-level spinal fusion was undertaken in 10 mature beagles. The animals were sacrificed 6 and 12 months later. Two months before sacrifice control and experimental animals received intravenously Na2(35)SO4 (1 mCi/kg). Discs encompassed by the fusion and those adjacent to it were dissected into the nucleus pulposus and annulus fibrosus (AF), which were analysed separately. Proteoglycans (PGs) were extracted with 4.0 M guanidine HCl and purified by CsCl density gradient ultracentrifugation. The hydrodynamic size and ability of the PG subunits to aggregate in the presence of hyaluronic acid were investigated by Sepharose CL-2B chromatography. The PG subunits were analysed for their galactosamine (galN), glucosamine (glcN), hexuronic acid, and protein content or were subjected to digestion with papain or chondroitin-ABC-lyase to establish the size of the chondroitin (CS) and keratan (KS) sulphate chains and the KS-PG core protein complex. Decreased ability to aggregate of PGs isolated from discs 6 and 12 months after surgery was demonstrated. While their hydrodynamic size after 6 months was generally the same or smaller than those in control tissues, the PG population present after 12 months was larger, particularly in the AF. Analysis of PG subunits from fusion discs afforded galN/glcN, galN/protein, and hexuronic acid/protein ratios that were compatible with the presence in these tissues of PGs in which the proportion of CS attached to core protein was greater than in control tissues. These studies provide the first experimental evidence that a metabolic response of discs in a fused segment may be accompanied by the biosynthesis of a new PG population whose structure is similar to that present in immature tissues.

The influence of food and repeated dosing on the bioavailability of indomethacin from a multiple-units controlled-release formulation

A concomitant meal did not affect the extent of bioavailability of indomethacin from a multiple-units controlled-release capsule formulation containing enteric-coated pellets, but the presence of food delayed absorption. When a capsule containing 75 mg indomethacin was administered after a 12 h fast, the mean peak drug concentrations in plasma of 2.7 micrograms/ml +/- 0.8 SD occurred at a mean time of 4.2 h (range 2-6 h). When this dose was administered with a substantial breakfast, the mean of the peak plasma concentration of 2.2 micrograms/ml +/- 1.0 SD occurred at 6.4 h (range 5-12 h). Secondary peak plasma drug concentrations, occurring at approximately 14 h after dosing, were more prominent and the times to reach the second peak more variable when the capsules were administered with food. Drug bioavailability after co-administration with food was 91% of that following administration after fasting. When the controlled-release capsule was administered during 3 days in a b.i.d. dosage regimen, drug bioavailability was 103% of that from a standard capsule administered q.i.d. The mean peak level after administration of the last dose of 50 mg as controlled-release capsules was 2.5 micrograms/ml +/- 1.1 SD and the means of peak levels after the penultimate and last doses of 25 mg as standard capsules were 2.0 micrograms/ml +/- 0.3 SD and 2.1 micrograms/ml +/- 0.7 SD, respectively. The controlled-release capsule formulation was a reliable and reproducible source of indomethacin when administered as repeated doses or with food.

Coexistence of muscle anomalies and rheumatoid arthritis in patients with carpal tunnel syndrome

During a five-year period, surgical release of the carpal tunnel was performed on 150 patients with median nerve compression. Seventeen (11%) had rheumatoid arthritis. Among this subgroup, six patients had anomalous muscles in the wrist and proximal palm. An additional patient with psoriatic arthritis demonstrated a comparable abnormality. No other patients in this series had similar findings. This statistically highly significant occurrence is probably related to additive effects of the two disorders in producing median nerve compression.

Fetal weight/placental weight ratio and perinatal outcome

The relationship of placental size to perinatal outcome was investigated in a population of low-risk infants. A trimmed and drained placenta was weighed for each of 417 low-risk infants, and for 108 infants whose intrapartum course was complicated only by compression of the umbilical cord. Tracings from intrapartum electronic fetal heart rate monitoring were analyzed by an investigator who was unaware of the fetal weight/placental weight ratio. The incidence of perinatal problems was increased in those infants whose fetal weight/placental weight ratio was greater than 11: intrapartum fetal distress, 20% (p = 0.0046); meconium-stained amniotic fluid, 28.9% (p = 0.0017); Apgar score less than 7, 11.1% (p = 0.04); and hyperbilirubinemia, 24.4% (p = 0.0008). On the basis of these data, the conclusion drawn was that there is a population of presumably low-risk infants who are at increased risk because they have outgrown their placentas.

Duration of action and short-term hormonal responses to enalapril (MK 421) in normal subjects

Enalapril is a converting enzyme inhibitor with a prolonged duration of action. We investigated the arterial pressure and hormonal responses to angiotensin I infusion(s) in eight normotensive human volunteers at various intervals after administration of 10 mg enalapril to assess more precisely its duration of action, particularly in relationship to angiotensin II's influence on aldosterone secretion and renal vasoconstriction. In normotensive sodium-restricted subjects, there was significant attenuation (p less than 0.025) of diastolic blood pressure response to angiotensin I infusion even as long as 28 h after administration of enalapril. This was accompanied by a significant (p less than 0.02) accumulation of angiotensin I and reduction of the angiotensin II increment in response to angiotensin I infusion. In contrast to the persistent efficacy of enalapril, as assessed by angiotensin I infusion, basal levels of angiotension II had returned to control levels by 22-24 h postdrug. Yet there was a persistent reduction of diastolic blood pressure even as long as 28 h postdrug. The persistent hypotension could not be explained on the basis of changes in other potential vasoactive factors (epinephrine, norepinephrine, bradykinin, or prostaglandin), as none of these was significantly modified by enalapril administration. In summary, enalapril in a dose of 10 mg p.o. produced a significant reduction in blood pressure in this study for up to 28 h. Unlike captopril, enalapril does not modify circulating prostaglandins and kinins. Although the level of activation of the renin-angiotensin system had returned to control values 24 h after enalapril administration, there was evidence from the angiotensin I infusions of continued blockade of the angiotensin-converting enzyme for as long as 28 h.

Isosorbide 5-mononitrate kinetics

The kinetics of isosorbide 5-mononitrate (5-ISMN) were studied in 12 healthy subjects after intravenous infusion and oral doses of 20 mg. Kinetic parameters calculated by model-independent methods or by assumption of a one-compartment open model were in good agreement. Mean (+/- SD) systemic clearance of 5-ISMN was 127 +/- 21 ml/min, volume of distribution was 48.5 +/- 6.1 l, t 1/2 was 4.4 +/- 0.5 hr, and mean residence time was 6.2 +/- 0.7 hr. At the end of intravenous infusion of 5-ISMN at a rate of 8 mg/hr for 2.5 hr, mean plasma drug concentrations reached 356 +/- 39 ng/ml. Oral doses of 5-ISMN were essentially completely absorbed (93% +/- 13% systemic availability), and mean peak plasma drug concentrations of 388 +/- 70 ng/ml occurred at 0.83 +/- 0.46 hr. Mean absorption t 1/2 was 19 +/- 12 min. Unlike other vasodilator organic nitrates in clinical use, 5-ISMN is notable for its relatively long t 1/2, essentially complete oral absorption, lack of active metabolites, and low intersubject variability in kinetics.

Isosorbide dinitrate plasma concentrations and bioavailability in human subjects after administration of standard oral and sublingual formulations

The bioavailability of isosorbide dinitrate from formulations containing 5, 10, and 20 mg in tablets and 10 mg in solution for oral use and 5 mg in tablets for sublingual use, has been compared. When adjusted for dose, the peak mean plasma drug concentrations after oral administration were similar (e.g., 9.2 ng/mL after a 10-mg tablet) and about one-half that obtained after sublingual administration. Drug concentrations declined monoexponentially with mean half-lives ranging from 25-36 min. The relative bioavailability of isosorbide dinitrate from the oral formulations was not significantly different (p greater than 0.05) over the dose range studied, whereas the relative bioavailability after sublingual administration was about twice as great (p less than 0.01) as that after oral administration. The plasma drug concentration-time profile after administering the 5-mg sublingual tablet was similar to that obtained after administering orally a solution containing 10 mg, indicating that the latter should be as clinically effective as the former.

Human platelet angiotensin II receptors: regulation by the circulating angiotensin level

Human platelets possess angiotensin II (AII) receptors which increase in number in response to sodium loading, a response similar to that reported for animal smooth muscle and renal AII receptors. In these studies, we studied platelet AII binding (by Scatchard analysis of competitive binding curves) in normal subjects as they changed their dietary sodium intake from 200 to 10 to 200 meq/day. Binding capacity fell significantly after 24 h of sodium restriction and furosemide diuresis, declining to a nadir of 40% of the binding capacity found during sodium loading (from 23 to 10 fmol AII/10(9) platelets). Binding increased again after 24 h of sodium loading. There were no significant changes in receptor affinity during either low or high salt intake. The binding changes were significantly inversely correlated with the changes in plasma AII levels (r = -0.87), suggesting that AII itself is the regulator of the platelet AII receptor. Short term increases in AII level (by furosemide administration or AII infusion) did not alter platelet AII binding, indicating that the changes in platelet binding were not due simply to receptor occupancy changes. These results show that platelets have the capacity for dynamic rapid up- and down-regulated of their AII receptors and that these receptor changes are regulated by the plasma AII level.

Saliva concentrations of isosorbide dinitrate, isosorbide 2-mononitrate and isosorbide 5-mononitrate

Correlations between saliva and plasma concentrations of isosorbide dinitrate (ISDN), and its active metabolites, isosorbide 2-mononitrate (2-ISMN) and isosorbide 5-mononitrate (5-ISMN) were examined. In the case of 5-ISMN (r = 0.98, P less than 0.01), saliva concentrations are probably reliable indices of the plasma concentrations of this drug and their measurement should provide a useful non-invasive procedure to assess compliance during the clinical use of products containing either ISDN or 5-ISMN: it may also be helpful in assessing the clinical pharmacokinetics of 5-ISMN. Less satisfactory correlations were obtained for ISDN (r = 0.84) and 2-ISMN (r = 0.83).

[Bioavailability of isosorbide-5-mononitrate from delayed-action formulations]

The relative bioavailability of isosorbide-5-mononitrate (IS-5-MN) has been determined after a 3-day period of dosing with 20 mg in standard-release reference tablets and sustained-release capsules at 12-h intervals, 40 mg in sustained-release capsules (Olicard 40 retard) at 24-h intervals and after single oral dose of 60 mg sustained-release capsules (Olicard 60 retard), in a cross-over study with 12 human subjects. Accumulation factors of 1.1-fold or 1.2-fold occurred during administration of 20 mg in standard- or sustained-release tablets and capsules respectively at 12-h intervals, and negligible accumulation of drug occurred after administration of 40 mg in sustained-release capsules at 24-h intervals or was calculated by the superposition principle to occur after doses of 60 mg in sustained-release capsules at 24-h intervals. The mean extent of bioavailability of IS-5-MN from the 20 mg, 40 mg and 60 mg sustained-release capsules was 79%, 67% and 70% respectively, of that from the standard-release reference tablets. The posterior probability that the bioavailability of IS-5-MN was included within the limits 60%-90% of the reference tablets was 97%, 86% and 95% for the 20 mg, 40 mg and 60 mg sustained-release capsules respectively. Means of peak plasma levels of IS-5-MN after administration of the sustained-released capsules were linearly related to the doses administered.(ABSTRACT TRUNCATED AT 250 WORDS)

Converting-enzyme inhibition corrects the altered adrenal response to angiotensin II in essential hypertension

Of patients with essential hypertension, 30% to 50% do not modulate adrenal and renovascular responsiveness to angiotensin II (AII) with changes in sodium intake. To define the role of AII in mediating these altered responses, the adrenal and renal vascular responses to AII infusion (0.3, 1.0, 3.0 ng/kg/min) were assessed on a sodium-restricted intake in 31 patients with essential hypertension and 13 normotensive controls before and after 72 hours of converting-enzyme inhibition. Forty percent of the hypertensive patients had a subnormal adrenal response to AII. There were no differences between the normal and abnormal responding hypertensive patients in a number of clinical and biochemical factors except that the "abnormal responders" had a significantly (p less than 0.03) greater control AII level (37 +/- 3 vs 29 +/- 3 pg/ml) and lower control plasma aldosterone level (14 +/- 2 vs 22 +/- 3 ng/dl) than the "normal responders." When a converting-enzyme inhibitor was administered, no change in adrenal responsiveness to AII occurred in the normotensive controls or the hypertensive normal responders. In the hypertensive abnormal responders, both the threshold sensitivity and the entire dose response curve was significantly (p less than 0.01) enhanced following short-term converting-enzyme inhibition. This increased sensitivity could not be explained by differences in AII increment with AII infusions, in basal aldosterone levels, or in blood pressure or basal AII response to converting-enzyme inhibition. Since they occurred whether captopril or enalapril (MK 421) were used, this phenomenon is likely to be a specific effect of converting-enzyme inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Who is the patient? A family case study of a recurrent dilemma in family practice

This article presents a family case study of a recurrent dilemma in family medicine. The ethical dilemma involves what role the physician should play in mediating a conflict in a family when the health needs and wishes of the individual patient do not parallel those of the other family members. Who is the patient, the individual or the family? It is the authors' conviction that in meeting the needs of the presenting patient, the family context is of great importance. To this end, the authors delineate a framework for analyzing ethical conflicts of this nature, utilizing key ethical principles in combination with a systems perspective to aid in the clarification of such choices. The principles examined include autonomy, nonmaleficence, and justice. Also taken into account are the relevant facts, values, and the biases of the physician. Exploration of these factors allows the physician a comprehensive and logical approach for resolving such conflicts. Such a framework, however, can only provide guidance; it does not guarantee easy or uniformly acceptable alternatives to difficult issues.

Symptomatic hypotension following the clonidine suppression test for pheochromocytoma

A 42-year-old man with generalized atherosclerosis underwent surgery of the left carotid artery with eventual placement of a Dacron graft bypassing the left carotid sinus. Subsequently, symptoms suggestive of pheochromocytoma developed, and 24-hour urine catecholamine levels were elevated. Clonidine testing resulted in suppression of plasma norepinephrine levels but was complicated by severe hypotension and a transient ischemic attack. Baroreceptor dysfunction may have been involved. Caution is advised and recommendations are offered for future usage of the clonidine suppression test.

Bioavailability of isosorbide dinitrate and its two mononitrate metabolites from sustained-release formulations

Plasma concentrations and bioavailability of isosorbide dinitrate (ISDN) and its active metabolites isosorbide 2-mononitrate (2-ISMN) and isosorbide 5-mononitrate (5-ISMN) from two sustained-release formulations and one standard-release formulation of isosorbide dinitrate were compared. Means of peak drug concentrations of ISDN, 2-ISMN, and 5-ISMN after administration of the 20-mg sustained-release formulation were 5.5, 24.4, and 129.1 ng/ml, respectively, at 3.1, 4.2, and 4.5 h; after the 40-mg sustained-release formulation, they were 10.9, 44.0, and 214.5 ng/ml, respectively, at 4.2, 6.3, and 6.7 h; and after the 20-mg standard formulation, they were 19.1, 34.7, and 159.2 ng/ml, respectively, at 0.5, 1.0, and 1.5 h. As might be expected, peak concentrations and their times of occurrence were statistically significantly different when results from the sustained-release formulation were compared to those from the standard formulation. Plasma drug concentrations were detectable for longer after administration of the sustained-release formulations. The extent of bioavailability of ISDN, 2-ISMN, and 5-ISMN from the three formulations as estimated from the areas under the plasma drug concentration - time curves were not statistically significantly different (p greater than 0.05). The ratios for relative drug bioavailability from the respective formulations were similar whether ISDN, 2-ISMN, or 5-ISMN data were used for calculation. Reasons are discussed for the biphasic decline of plasma ISDN concentrations (half-lives 26 min and 5.1 h) obtained after administration of the standard-release formulation.

beta-endorphin suppresses adrenocorticotropin and cortisol levels in normal human subjects

To determine the effect of beta-endorphin on the pituitary-adrenal axis, human synthetic beta-endorphin was infused iv in 10 normal human subjects. Either beta-endorphin (0.3, 1.0, and 3.0 micrograms/kg . min, each dose for 30 min) or a control (sham) infusion of 5% dextrose water was administered in a blind fashion in the same subjects on 2 successive days. Plasma ACTH and cortisol and serum human GH and PRL levels were measured 30 min before and then every 30 min for 210 min during and after both the beta-endorphin and control infusions. In all subjects, cortisol levels decreased below the basal level in response to the infusion of beta-endorphin. The threshold dose was 1.0 micrograms/kg . min, with the mean control cortisol level (12 +/- 2 micrograms/dl) declining significantly to 7 +/- 1 micrograms/dl (1.0 micrograms/kg . min) and 6 +/- 1 micrograms/dl (3.0 micrograms/kg . min; P less than 0.01). ACTH levels also were significantly lower than the control value (48 +/- 6 pg/ml) at the 1.0 microgram/kg . min dose (32 +/- 4 pg/ml; P less than 0.05). The decline in ACTH and cortisol levels was also significantly different from levels obtained during the control infusions (P = 0.001 and P = 0.01, respectively). The results are consistent with short feedback loop inhibition of pituitary ACTH release or suppression of hypothalamic corticotropin-releasing factor release by beta-endorphin.

Pancreatic structure and function in the immature reserpinized rat

Immature rats were reserpinized to determine whether the model used for adults may be suitable for the study of pancreatic exocrine insufficiency seen in infants with cystic fibrosis. Rats were reserpinized by injections either into pregnant dams or into newborn rats. The dose of reserpine used by others was lethal to immature rats, so lower doses were used. Pancreas from 1-day-old fetal-treated pups was hypoplastic, but concentration of chymotrypsinogen was elevated. At age 7 days hyperplasia was seen. When rats were reserpinized as neonates, hypoplasia and decrease in all parameters measured was observed at age 7 days. Progressive recovery occurred during the following 2 weeks in both groups. Electron microscopic study of the fetal-treated 24-hr-old pancreas revealed evidence of acinar cell degeneration with the presence of abnormal zymogen granules. At age 7 days the pancreas from neonatal-treated rat pups appeared to have a reduced number of granules. At ages 14 and 21 days the pancreas was similar to that seen at age 7 days except that the granules were larger and some acinar lumina were filled with a finely granular, homogeneously dense material. It is concluded that prenatal and neonatal reserpinization of rats induces changes in pancreas similar to those found in cystic fibrosis.

The metabolic fate of the anti-androgenic agent, oxendolone, in man

After intramuscular administration of 16 beta-ethyl-17 beta-hydroxy-4-4-[4-14C]estren-3-one (14C-oxendolone; 300 mg) to 3 human subjects, excretion of 14C was very slow and incomplete despite a 20-day sample collection period. During this time, means of 37% and 21% of the administered 14C were recovered in urine and faeces, respectively, and if excretion continued at the same rate, approximately 90% of the administered 14C would have been excreted during 5-12 weeks. Peak plasma 14C concentrations were reached at 3-6 days after dosing, when they represented 0.2-1.1 micrograms equiv./ml, and declined very slowly thereafter with a half-life of 5.0-6.6 days. Concentrations of unconjugated drug-related steroids circulating in plasma never exceeded about 0.1 microgram/ml. Mass spectroscopic analysis of isolated urinary and faecal metabolites indicated that the principal routes of biotransformation of oxendolone in man are similar to those of the endogenous androgens-namely, reduction of the 4,5-double bond, further reduction of the saturated 3-ketone to the 3 alpha-hydroxysteroid, and oxidation of the 17 beta-alcohol to the corresponding ketone, followed by conjugation, mainly with glucuronic acid, and excretion in the urine and bile.

The Winnecott "set situation". A useful tool for the pediatrician

D.W. Winnecott devised a short, simple test which he used to evaluate normal infants. In this study, we compared 9-month-old infants' behaviors elicited during the Winnecott Test (WSS), both with historical data and with their behavior during a structured separation from their mothers. We found significant correlations between the WSS, the structured separation, and historical data. This simple test can provide the practitioner with invaluable information regarding the infant, his temperamental style, and his relationship with others.

The percutaneous absorption and excretion of promestriene (3-propoxy-17 beta-methoxy-1,3,5(10)-estratriene) in rats and humans

The percutaneous absorption of 3H-promestriene (an antiseborrhoeic agent; 3-propoxy-17 beta-methoxy-1,3,5(10)-estratriene) was studied in rats and human subjects. Extensive and continual absorption of the tritium label (about 50% dose in 3 days) occurred in rats when the treated area of skin (ca. 30 micrograms/cm2) was occluded; when unabsorbed material was washed off after 6 h, a substantial proportion of the applied 3H (about 25% dose) had been absorbed to be excreted later. In contrast, less than 1% of the 3H applied to the skin of human volunteers (0.1-0.5 mg/cm2) was absorbed within 6 h and subsequently excreted. In rats, tissue concentrations of 3H were greatest in the liver, adrenals and ovaries.

Bioavailability of bemetizide and triamterene from a combination formulation

The bioavailability of the thiazide diuretic bemetizide from a tablet containing 25 mg of this drug and 50 mg of the chemically unrelated diuretic triamterene was lower than, and significantly different (p less than 0.01) from that from a tablet containing 25 mg bemetizide alone. The mean peak plasma level of bemetizide after administration of the combination tablet (68.3 ng ml-1) was lower than that after administration of bemetizide alone (87.9 ng ml-1), although the times of occurrence of the peak levels were similar. The bioavailability of triamterene from the combination tablet was greater than, but not significantly different from that after administration of a capsule containing 50 mg triamterene alone. The mean peak plasma level of triamterene after administration of the combination tablet (44.6 ng ml-1) was higher than and significantly different (p less than 0.001) from that after administration of triamterene alone (15.7 ng ml-1). Although bemetizide is unstable in urine, measurement of the apparent excretion of unchanged drug in the 24 h post-dose urine (less than 4 per cent of the dose) agreed with the estimate of drug bioavailability from the plasma level data. Less than 2 per cent of the dose of triamterene was excreted unchanged in the 24 h post-dose urine, but the urinary excretion data also agreed with the bioavailability estimates from the plasma level data. The results of this study and those reported in the literature suggest that because of their physicochemical properties, the bioavailability of some thiazides and triamterene needs to be evaluated when new formulations of these drugs are produced. However, with respect to the combination formulation reported in this paper, the difference in bioavailability of the thiazide component did not detectably effect the diuretic activity of the formulation.

Sulfhydryl groups of native myosin and of the myosin heavy chains from Physarum polycephalum compared to vertebrate skeletal, smooth, and non-muscle myosins

Although a previously reported analysis of Physarum myosin detected no cysteine residues in the molecule, the myosin ATPase activity was inhibited by p-chloromercuribenzoate. We have re-examined this apparently contradictory finding. We found highly purified plasmodial myosin to be very sensitive to N-ethylmaleimide inhibition of the K+, Ca2+ -activated ATPase. An estimate of the number of reactive sulfhydryls of the native myosin using Ellman's reagent showed only 1.5 mol 11 min-reactive sulfhydryl/mol as compared to 4.5 for chicken breast myosin in 5 min. 3H- and 14C-labelled N-ethylmaleimide was used to estimate the total sulfhydryls of the SDS-denatured heavy chains. Plasmodial myosin heavy chains bound 10-13% of the N-ethylmaleimide bound by chicken breast myosin heavy chains. Smooth muscle myosin heavy chains as well as heavy chains of embryonic chicken presumptive myoblasts had 65-70% of the reactive groups of chicken myotube myosin heavy chains. Amino acid analyses of purified Physarum myosin showed that some preparations contained cysteic acid residues even before performic oxidation. After the performic oxidation a mean value of 3 mol cysteic acid per 10(5) g Physarum myosin was found, or less than half that reported for striated muscle myosin. Our results show that in the sulfhydryl-poor plasmodial myosin each heavy chain contains at least two sulfhydryls, and probably more, but that there is variable oxidation of the total sulfhydryls. It has been reported that plasmodial myosin lacks rapidly reacting sulfhydryls groups when tested with an ATP analogue which reacts with light chains of vertebrate muscle myosins. Therefore, the 1-2 sulfhydryls of plasmodial myosin which react rapidly with Ellman's reagent appear to be on the heavy chain. Our results also suggest that during development of myotubes changes occur in the myosin heavy chains.

Bioavailability of indomethacin from two multiple-units controlled-release formulations

Two multiple-units controlled-release indomethacin capsule formulations containing enteric-coated pellets were bioequivalent to a standard capsule formulation (taken as the reference) in respect of extent of bioavailability in a crossover study with normal human subjects. However, drug absorption from the enteric-coated pellet formulations was slower, when compared to that from the standard reference capsule. The standard reference capsule released 85% of its drug content in vitro during 10 min at pH 6.5 and 98% during 1 h at pH 7.5. On enteric-coated pellet capsule formulation (I) released 77% during 1 h at pH 6.5 and the other (II) released 10% during 1 h at pH 6.5. Release of drug from each capsule of enteric-coated pellets was complete during 1 h at pH 7.5. Although differences in areas under the plasma indomethacin concentration-time curves were not significantly different, the peak plasma levels and the times of their occurrence indicated that the absorption rates of indomethacin decreased in the order, reference formulation greater than pellet formulation I greater than pellet formulation II, which was the same rank order as that of their dissolution rates in vitro. The data indicated that multiple units controlled-release formulations represent a reliable and reproducible source of indomethacin, which by avoiding extremes of local or systemic drug concentrations also should be better tolerated by individuals susceptible to unwanted gastrointestinal and centrally-mediate side-effects.

Metabolic fate of the beta-blocker 14C-bupranolol in humans, dogs, and rhesus monkeys

An oral dose of 14C-bupranolol hydrochloride was well absorbed by humans (100 mg), dogs (1 mg/kg), and rhesus monkeys (1 mg/kg). These species excreted 87.8 and 3.5%, 81.1 and 13.6%, and 92.9 ad 5.0% of the 14C-dose in urine and feces, respectively, mainly in 12 or 24 hr. Mean plasma levels of 14C, which appeared to be almost entirely associated with a single metabolite, peaked at 1 hr in humans (1.6 micrograms-equiv./ml) and dogs (1.6 micrograms-/ml) and at 2 hr in monkeys (0.8 micrograms-equiv./ml). Concentrations initially declined with similar half-lives (about 1.5 hr) in all three species. Biliary excretion of 14C occurred in the animal species in which also peak plasma 14C levels exceeded those in most tissues. Unchanged bupranolol was not detected in plasma; the peak plasma and urinary 14C was mainly associated (greater than 90% in humans) with a metabolite produced by oxidation of the aromatic ring methyl group of bupranolol to a carboxyl group.

Clinical and secretory differences in pancreatic cancer and chronic pancreatitis

The differential diagnosis between chronic pancreatitis and pancreatic cancer can be very difficult. In 60 patients with either of these conditions, who had satisfactory ERCP study, clinical features were correctly matched with the final diagnosis by discriminant analysis in 44 (73%). The sensitivity of ERCP radiographic findings in pancreatic cancer was 80% and sensitivity of cytology was 54%. To see if exocrine function was specific for cancer, fresh pancreatic secretions were aspirated in 27 patients at the time of ERCP. By isoelectric focusing, a pattern of extreme zymogen depletion was observed in chronic alcoholic pancreatitis (Group 1), pancreatic cancer (Group 2), and chronic nonalcoholic pancreatitis (Group 3). The three groups were not distinguishable. By contrast, significant changes in albumin, IgG and IgA concentrations were seen in Group 2. The albumin level was over ten-fold greater than in Groups 1 and 3 (p less than 0.02 and less than 0.05). The IgG was seven-fold and two-fold greater (p less than 0.01 and greater than 0.2) and the IgA was 15-fold and six-fold greater (p less than 0.002 and less than 0.05) than in Groups 1 and 3, respectively. The two groups of pancreatitis had similar concentrations of albumin and IgA. The ratio of albumin to IgG was also different in Group 2 from the other groups, suggesting different mechanisms for the appearance of proteins in pancreatic secretions. Nonzymogen protein levels can distinguish chronic pancreatitis from pancreatic cancer, and further study of them may identify useful tumor-specific markers.

Isosorbide 5-mononitrate pharmacokinetics in humans

When isosorbide 5-mononitrate was intravenously infused at a rate of 4 mg h-1 for 2.5 h to five human subjects, its concentrations in plasma increased slowly to 185 ng ml-1 +/- 5 per cent C.V. at 2.5 h and a steady-state plasma level was not reached during the infusion. When the infusion was discontinued, plasma drug concentrations declined with an elimination half-life of 4.2 h +/- 6 per cent C.V. The systemic clearance after the infusion doses was 132 ml min-1 +/- 18 per cent C.V. and the volume of distribution was 48.4 +/- 16 per cent C.V. After equal oral doses of 10 mg, the peak plasma isosorbide 5-mononitrate concentration of 191 ng ml-1 +/- 16 per cent C.V. was reached at 1.1 h +/- 30 per cent C.V., and plasma levels declined with a terminal half-life of 4.9 h. The complete systemic availability of isosorbide 5-mononitrate indicated that pre-systemic elimination after the oral doses was negligible. A one-compartment open model appeared adequate to describe the plasma level data after intravenous infusion and oral dose. After single oral doses of 10 mg isosorbide dinitrate, the peak plasma concentration of the 5-mononitrate metabolite of 72 ng ml-1 +/- 27 per cent C. V. occurred at 1.7 h +/- 41 per cent C.V. Approximately 50 per cent (range 22--68 per cent) of the oral dose of isosorbide dinitrate circulated in plasma as the 5-mononitrate metabolite. The pharmacokinetics of isosorbide mononitrates are markedly different to those of the parent dinitrate and these differences follow from the greater systemic availability and volume of distribution of the mononitrates.

Plasma concentrations and bioavailability of isosorbide dinitrate and pindolol from a combination formulation

The plasma concentrations and bioavailability of sustained-release isosorbide dinitrate and standard-release pindolol have been compared after administration of these drugs in combination and alone. Bioavailability parameters of isosorbide dinitrate and pindolol obtained after administration of the drugs in combination were not significantly different (P greater than 0.05) to those obtained after administration of either drug alone. Two peaks of mean concentrations of isosorbide dinitrate occurred in plasma after administration of 30 mg of this drug in combination with 7.5 mg pindolol (4.4 ng ml-1 at 1 h and 4.5 ng ml-1 at 5 h), or alone (5.9 ng ml-1 at 2 h and 5.7 ng ml-1 at 5 h). In each case, plasma concentrations of isosorbide dinitrate were maintained during at least 8 h, whereas the drug was not detected in plasma at 2.5 h after administration of a standard-release formulation. The peaks of mean concentrations of pindolol were 39.7 ng ml-1 at 1.5 h after administration of 7.5 mg drug in combination with isosorbide dinitrate and 38.0 ng ml-1 at 1 h administration of the drug alone. Concentrations of pindolol in plasma declined with a half-life of 3 h.

Concentrations of N-descyclopropylmethylprazepam in whole-blood, plasma, and milk after administration of prazepam to humans

After oral doses of 30 mg of prazepam to humans, N-descyclopropylmethylprazepam (desalkylprazepam, N-desmethyldiazepam) is the only major drug-related compound in plasma. Neither the parent drug, nor its major urinary metabolites were detected in plasma. The overall concentration-time profile of desalkylprazepam in the plasma of females was lower than, and significantly different (p less than 0.001) from that in the plasma of males. However, the mean peak desalkylprazepam concentrations in the plasma of females (265 ng ml-1 +/- 60 S.D.) were not significantly different (p greater than 0.05) from those in males (342 ng ml-1 +/- 60 S.D.). Concentrations declined in the plasma of either sex with similar half-lives (mean 60 h, range 37-93 h). Apparent plasma desalkylprazepam clearances were also similar (mean 60 h, range 37-93 h). Apparent plasma desalkylprazepam clearances were also similar (mean 1.09 l h-1), range 0.74-1.84 l h-1). At 12 h after the last of multiple doses of prazepam (60 mg d-1 for 3 days) to lactating women, mean plasma concentrations of desalkylprazepam were 823 ng ml-1 +/- 200 S.D. and declined with a mean half-life of about 60 h over the time-course studied. There was only slight uptake of desalkylprazepam into blood cells; plasma; whole blood concentration ratios were constant at about 1.6. Concentrations of desalkylprazepam in milk were low at about 10 per cent of the corresponding plasma levels (e.g. 86 ng ml-1 +/- 37 S.D. at 12 h). The data suggest that, expressed on a mg kg-1 basis, exposed neonates could receive about 4 per cent of the maternal dose of prazepam as desalkylprazepam.

Plasma concentration and disposition of buprenorphine after intravenous and intramuscular doses to baboons

Buprenorphine is a newly-developed strong analgesic. A selected ion monitoring method has been developed to measure its plasma levels over the concentration range 20-3000ng ml-1. Six baboons each received intravenous and intramuscular doses of buprenorphine hydrochloride at a level of 5mg/kg in a cross-over study. The mean peak plasma concentrations (+/-standard deviation) were 2290 +/- 357ng ml-1 and 805 +/- 416ng ml-1 respectively and the corresponding times to the peak levels were 4.0 +/- 1.5 minutes and 30.3 +/- 24.6 minutes suggesting the rapid release of the drug from intramuscular sites. Comparison of areas under the plasma concentration versus time curves to 24 hours after dosing showed the mean bioavailability of buprenorphine from the intramuscular doses was 70% of that from the reference intravenous doses.

Measurement of plasma concentrations of isosorbide dinitrate

Concentrations of the vasodilator isosorbide dinitrate (ISDN) in human plasma can be measured with good sensitivity (about 0.2--0.5 ng ml-1) using electron-capture gas chromatography after a one-stage extraction. The mean recovery of ISDN from plasma was 83 per cent +/- 9 standard deviation (S.D.). The precision of the method for the measurement of ISDN in plasma ranged from +/- 14 per cent at 1 ng ml-1 to +/- 7 per cent at 5 ng ml-1 to +/- 4 per cent at 50 ng ml-1. The 95 per cent confidence limits of the least-squares regression calibration line forced through the origin were +/- 100 percent at 1 ng ml-1, +/- 11 per cent at 10 ng ml-1, and +/- 8 per cent at 30 ng ml-1. The method has been used to assay many samples withdrawn after doses of drug at therapeutic levels to normal subjects.

Pharmacokinetics of isosorbide dinitrate after intravenous infusion in human subjects

Plasma concentrations of isosorbide dinitrate have been measured after intravenous infusion of drug at a rate of 5.0 mg h-1 for 150 min and after single equal oral doses of 12.5 mg of drug in solution to two normal human subjects. During the infusion, uneven plateau concentrations were approached after 30 min. The calculated average steady-state plasma levels were 258 ng ml-1 and 514 ng ml-1 in the two subjects respectively. The half-life of elimination of isosorbide dinitrate after termination of the infusion was 9--10 min. After oral doses, peak plasma levels of 26.6 ng ml-1 and 12.7 ng ml-1 occurred at 10 min and 20 min in the two subjects respectively. The terminal half-life of drug after the oral doses was much longer than the elimination half-life (about 10 min), and was associated with the absorption phase. Fairly good agreement was obtained between the observed concentrations and those predicted by a one-compartment open model. The systemic availability of isosorbide dinitrate after the oral doses was up to only 3 per cent of the equal doses infused, indicating that presystemic elimination processes accounted for very large proportions of the oral doses. The systemic clearances of drug after infusion of 0.32 l min-1 and 0.16 l min-1 were unexpectedly low for a drug of reported high liver extraction ratio.

Plasma concentrations and pharmacokinetics of dihydralazine after single oral doses to human subjects

After single oral doses of 20 mg of a suspension of dihydralazine sulphate to human subjects, the peak of mean plasma concentrations of dihydralazine of 47.0 ng ml-1 +/- 11.0 standard deviation (S.D.) (n = 7) was reached at 1 h. Mean concentrations declined biphasically with apparent half-lives of 0.57 and 4.96 h respectively. Dihydralazine was partly converted to hydralazine. The peak of mean plasma concentrations of the latter drug of 3.9 ng ml-1 +/- 1.7 S.D. (n = 7) occurred at 1-2 h after dosing with dihydralazine sulphate and declined to 1.5 ng ml-1 +/- 1.5 S.D. at 6 h. Of the seven subjects studied, three were classified as fast and four as slow acetylators. Mean clearances appeared to be slightly more rapid in fast acetylators (1.63 l min-1 +/- 0.32 S.D.) when compared to slow acetylators (1.31 l min-1 +/- 0.31 S.D.) but this difference and differences in plasma concentrations and in areas under the plasma drug concentration-time curves were not significant (p > 0.1).

Plasma concentrations of isosorbide dinitrate after cutaneous and sublingual doses to human subjects

After application of 100 mg (nominal dose) isosorbide dinitrate as an ointment to the skin of human subjects, mean drug concentrations were 1 to 2 ng/ml for 1.5 hour and reached a peak of 6.2 ng/ml at 6 hours. Thereafter, mean concentrations declined slowly to 2.9 ng/ml at 12 hours and 1.2 ng/ml at 24 hours. After a sublingual dose of 5 mg isosorbide dinitrate, mean drug concentrations reached a peak of 15.9 ng/ml at 0.5 hour and declined with a half-life of about 50 minutes. The mean bioavailability of isosorbide dinitrate from the ointment was estimated as 30 per cent of that from the sublingual tablet when corrected for differences in dose/body weight ratio. The results demonstrate that concentrations of isosorbide dinitrate in plasma can be maintained for relatively long periods when the drug is applied to the skin.

High-performance liquid chromatographic determination of benzodiazepines in human plasma

A simple and sensitive method for determination of benzodiazepines in plasma has been developed using high-performance liquid chromatography in a reverse-phase mode. The method is illustrated by application to plasma samples containing diazepam and N-desmethyldiazepam at concentrations which would be encountered during therapy, with limits of detection of 10 ng/ml and 2 ng/ml for diazepam and N-desmethyldiazepam, respectively.

Plasma concentrations and bioavailability of clofibric acid from its calcium salt in humans

The bioavailability of clofibric acid from formulations containing calcium clofibrate along and mixed with calcium carbonate (1:1 w/w) was compared to that from a standard clofibrate formulation in a crossover study in 12 human subjects. The 95% confidence intervals of bioavailability differences were such that they were unlikely to be detected in clinical practice; all three formulations may be considered bioequivalent, although the bioavailability rate was probably greater from the formulation containing calcium clofibrate alone. Peaks of mean concentrations of 80 +/- 13,67 +/- 16, and 64 +/- 18 microgram/ml +/- SD occurred after administration of 853 mg of clofibric acid calcium salt alone, 809 mg of clofibric acid calcium salt mixed with calcium carbonate, and 885 mg of clofibrate, respectively; mean concentrations declined from peak levels with half-lives of 15-17 hr.