Paradoxical arterial embolism involving both upper extremities in a patient with pulmonary embolism and a patent foramen ovale

Paradoxical embolization is an uncommon but devastating complication of pulmonary embolism (PE). Awareness of this complication with prompt recognition and treatment could serve to preclude significant disability and death. Described is a case of PE associated with paradoxical embolism to the arteries of both upper extremities. While patent foramen ovale (PFO) is common, paradoxical embolism is infrequent but can involve almost any artery of the body. Discussed are the risk factors, clinical presentations, and diagnostic and treatment options for paradoxical embolism. Awareness of the potential for paradoxical embolization in patients with PE is essential to its prompt recognition and treatment.

Model-based Drug Development

The low productivity and escalating costs of drug development have been well documented over the past several years. Less than 10% of new compounds that enter clinical trials ultimately make it to the market, and many more fail in the preclinical stages of development. These challenges in the "critical path" of drug development are discussed in a 2004 publication by the US Food and Drug Administration. The document emphasizes new tools and various opportunities to improve drug development. One of the opportunities recommended is the application of "model-based drug development (MBDD)." This paper discusses what constitutes the key elements of MBDD and how these elements should fit together to inform drug development strategy and decision-making.

Pharmacokinetics of sildenafil after single oral doses in healthy male subjects: absolute bioavailability, food effects and dose proportionality

AIMS

To determine the absolute bioavailability, dose proportionality and the effects of food on the pharmacokinetics of single oral doses of sildenafil citrate.

METHODS

Three open-label, randomized crossover studies were conducted in healthy male subjects. Absolute bioavailability was determined by comparing pharmacokinetic data after administration of single oral and intravenous 50-mg doses of sildenafil (n=12 subjects). Food effects were examined by comparing pharmacokinetic data for sildenafil and its primary circulating metabolite, UK-103,320, after administration of a single oral 100-mg dose in the fasted and fed states (n=34 subjects). Dose proportionality was assessed from pharmacokinetic data obtained after administration of four single oral doses of sildenafil (25, 50, 100 and 200 mg) to 32 subjects. The safety and tolerability of sildenafil were also assessed in all of these studies.

RESULTS

The calculated absolute oral bioavailability of sildenafil was 41% (90% CI: 36--47). Food slowed the rate of absorption, delaying mean tmax by approximately 1 h and reducing Cmax by 29% (90% CI: 19--38). Systemic exposure, as assessed by the mean area under the plasma concentration--time curve (AUC), was reduced by 11% (90% CI: 6--16). These food effects were not considered to be of clinical significance. There was statistical evidence of nonproportionality in Cmax and AUC over the dose range 25--200 mg. However the degree of nonproportionality was small, with predicted increases in Cmax and AUC of 2.2- and 2.1-fold, respectively, for a doubling in dose, and was thought to be clinically nonsignificant. Sildenafil was well tolerated in the three studies; the majority of adverse events were mild and transient.

CONCLUSIONS

Sildenafil had a mean absolute bioavailability of 41%. Food caused small reductions in the rate and extent of systemic exposure; these reductions are unlikely to be of clinical significance. Across the dose range of 25--200 mg, systemic exposure increased in a slightly greater than dose-proportional manner.

Pharmacodynamic effect of continuous vs intermittent dosing of dofetilide on QT interval

AIMS

To investigate the pharmacokinetics and pharmacodynamics of dofetilide 1 mg twice daily continuously for 24 days compared with intermittent single dose treatments.

METHODS

A randomized, single-blinded, placebo-controlled, parallel-group, multiple-dose study design was utilized. Healthy male volunteer subjects were randomized into three groups. Group 1 received dofetilide 1.0 mg twice daily for 23 days and once on day 24. Group 2 received matching placebo capsules under the same regimen as group 1. Group 3 received a single dose of dofetilide 1.0 mg on days 1, 5, 10, 17, and 24 with identical placebo capsules administered at all other times to match the dosing pattern of the other groups.

RESULTS

Continuous administration of dofetilide resulted in the achievement of steady-state concentrations by day 5. Pharmacokinetic parameters following intermittent treatment showed no accumulation. Maximum daily QTc interval (mean +/- s.e. mean) increased in response to continuous twice-daily dofetilide from baseline (373 +/- 5) to day 2 (453 +/- 9) but thereafter decreased slightly, but not beyond day 5, by which time the mean maximum QTc was 440 +/- 7 ms. In contrast, single doses of dofetilide in the intermittently treated group led to reproducible increases in QTc. Thus mean (+/- s.e. mean) maximum QTc increased from a baseline of 387 +/- 7-467 +/- 14, 467 +/- 18, 469 +/- 14 and 458 +/- 10 ms on days 5, 10, 17 and 24, respectively. In view of the pharmacokinetic accumulation on continuous dosing, the attenuation of responsiveness is best represented by the slope of the QTc vs plasma concentration relationship. In the continuously treated group, an initial decrease in the value of the mean slope between day 1 (14.2 +/- 1.7 ms/ng ml(-1)) and day 5 (9.1 +/- 0.8 ms/ng ml(-1)) did not progress beyond day 5. The mean difference in slopes (95% CI) between the intermittent and continuously treated groups were 4.4 (1.3, 7.4) on day 5, 4.9 (1.6, 8.2) on day 10, 5.2 (1.1, 9.2) on day 17 and 4.4 (0.4, 8.4) on day 24.

CONCLUSIONS

With continuous twice-daily administration the QT interval responsiveness to dofetilide is greater after the first dose than it is at steady state. After day 5 the relationship between dofetilide plasma concentration and its QT interval effect is predictable and stable over time.

Evaluation of the Intelisite capsule to deliver theophylline and frusemide tablets to the small intestine and colon

The objective of the research was to establish the capability of the Intelisite capsule to deliver the probe drugs, theophylline and frusemide, in the form of split immediate release (IR) tablets, to the small intestine and colon. The two probe drugs were administered together in an open, random, three-way crossover study in eight healthy volunteers, comparing absorption following Intelisite delivery in the small bowel and colon to conventional IR dosing. Gamma scintigraphy was employed to monitor the gastrointestinal transit and activation of the Intelisite capsule. Standard pharmacokinetic parameters, and the percentage remaining in the capsules post defecation were determined. The Intelisite capsule was well tolerated in human volunteers and successfully activated on 15/16 occasions. Pharmacoscintigraphy showed internal marker release from the Intelisite capsule to be approximately 10-fold faster in the small intestine than in the colon. Theophylline and frusemide were both well absorbed following Intelisite activation in the small intestine, whereas complete colonic absorption was only observed in 1/7 subjects for theophylline, and 0/7 subjects for frusemide. The probe drugs were successfully delivered in particulate form from the Intelisite capsule in the small intestine and produced expected pharmacokinetic profiles. However drug release in the colon was incomplete and variable possibly due to: low water content, poor mixing, and a high loading dose.

Effect of dofetilide on the pharmacokinetics of digoxin

The effect of dofetilide on the steady-state pharmacokinetics of digoxin was evaluated in a randomized, double-blind study. Five days of dofetilide treatment did not significantly affect steady-state pharmacokinetic variables of digoxin compared with placebo; therefore, the use of dofetilide does not necessitate an adjustment in digoxin dose to maintain therapeutic digoxin levels.

The pharmacokinetics and pharmacodynamics of oral dofetilide after twice daily and three times daily dosing

AIMS

The pharmacokinetics and pharmacodynamics of oral dofetilide, a novel, class III antiarrhythmic drug, were assessed during administration either twice or three times daily.

METHODS

Dofetilide was administered orally to three groups of healthy subjects in daily doses of 1000 microg (n = 8), 1500 microg (n = 8), or 2500 microg (n = 9) as twice daily and three times daily treatment regimens, with the two regimens assigned randomly as a two-way crossover for each subject and separated by at least a 6 day washout period.

RESULTS

Pharmacokinetic analysis indicated a rise in plasma dofetilide concentrations until steady state was attained on day 3. Ctrough had a linear dependence on dose for both the twice daily and three times daily dosing regimens. The maximum concentration attained (Cmax) and the area under the concentration vs time curve (AUC(0,tau) increased linearly with dose for each dosing regimen on both days 1 and 5 of dosing. Cmax occurred at 2 h. Pharmacodynamic measurements showed that the QTc interval increased in a dose-dependent manner and that the time to maximum QTc was 2 h after dosing. A linear relationship was determined between plasma dofetilide concentration and the prolongation of the QTc interval. The slope of this line was significantly greater on day 1 (ranging from 12.9 to 14.2 ms/ng ml-1) than on day 5 (ranging from 9.9 to 12. 8 ms/ng ml(-1).

CONCLUSIONS

The pharmacokinetics and pharmacodynamics of dofetilide are predictable and based on a linear relationship for both twice daily and three times daily dosing regimens. The QT responsiveness to dofetilide is greater on day 1 than on day 5.

Involvement of conserved aspartate and glutamate residues in the catalysis and substrate binding of maize starch synthase

Chemical modification of maize starch synthase IIb-2 (SSIIb-2) using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDAC), which modifies acidic amino acid residues, resulted in a time- and concentration-dependent inactivation of SSIIb-2. ADPGlc was found to completely protect SSIIb-2 from inactivation by EDAC. These results suggest that glutamate or aspartate is important for SS activity. On the basis of the sequence identity of SS, conserved acidic amino acids were mutagenized to identify the specific amino acid residues important for SS activity. Three amino acids (D21, D139, and E391) were found to be important for SS activity. D21N showed 4% of the wild-type enzyme activity and a 10-fold decrease in the affinity for ADPGlc, while the conservative change from D21 to E resulted in a decrease in V(max) and no change in affinity for ADPGlc, suggesting that the negative charge is important for ADPGlc binding. When sites D139 and E391 were changed to their respective amide form, no SS activity was detected. With the conservative change, D139E showed a decrease in V(max) and no changes in apparent K(m) for substrates. E391D showed a 9-fold increase in K(m) for ADPGlc, a 12-fold increase in apparent K(m) for glycogen, and a 4-fold increase in apparent K(m) for amylopectin. The circular dichroism analysis indicates that these kinetic changes may not be due to a major conformation change in the protein. These results provide the first evidence that the conserved aspartate and glutamate residues could be involved in the catalysis or substrate binding of SS.

Effect of cimetidine and ranitidine on pharmacokinetics and pharmacodynamics of a single dose of dofetilide

AIMS

The aim of this open-label, placebo-controlled, randomized, four-period crossover study was to determine the effects of cimetidine and ranitidine on the pharmacokinetics and pharmacodynamics of a single dose of dofetilide.

METHODS

Twenty healthy male subjects received 100 or 400 mg twice daily of cimetidine, 150 mg twice daily of ranitidine, or placebo for 4 days. On the second day, a single oral 500 microg dose of dofetilide was administered immediately after the morning doses of cimetidine, ranitidine, or placebo. Treatment periods were separated by 1-2 weeks. Pharmacokinetic parameters were determined from plasma and urinary dofetilide concentrations; prolongation of the QTc interval was determined from three-lead electrocardiograms.

RESULTS

Ranitidine did not significantly affect the pharmacokinetics or pharmacodynamics of dofetilide; however, a dose-dependent increase in exposure to dofetilide was observed with cimetidine. When dofetilide was administered with 100 and 400 mg of cimetidine, the area under the plasma concentration-time curve of dofetilide increased by 11% and 48% and the maximum plasma dofetilide concentration increased by 11% and 29%, respectively. The respective cimetidine doses reduced renal clearance of dofetilide by 13% and 33% and nonrenal clearance by 5% and 21%. Dofetilide-induced prolongation of the QTc interval was enhanced by cimetidine; the mean maximum change in QTc interval from baseline was increased by 22% and 33% with 100 and 400 mg of cimetidine, respectively. However, the relationship between the prolongation of the QTc interval and plasma dofetilide concentrations was unaffected by cimetidine or ranitidine; a 1 ng ml-1 increase in plasma dofetilide concentration produced a 17-19 ms prolongation of the QTc interval. Dofetilide was well tolerated, with no treatment-related adverse events or laboratory abnormalities.

CONCLUSIONS

These results suggest that cimetidine increased dofetilide exposure by inhibiting renal tubular dofetilide secretion, whereas ranitidine did not. This effect is not an H2-receptor antagonist class effect but is specific to cimetidine. If therapy with an H2-receptor antagonist is required, it is recommended that cimetidine at all doses be avoided; since ranitidine has no effect on dofetilide pharmacokinetics or prolongation of the QTc interval, it can be seen as a suitable alternative.

Analysis of purified maize starch synthases IIa and IIb: SS isoforms can be distinguished based on their kinetic properties

Since starch synthases IIa (SSIIa) and SSIIb have not been purified from plant tissue, their structure-function relationships have not been well characterized. Therefore, we have expressed these SS genes in Escherichia coli, purified them to apparent homogeneity, and studied their kinetic properties. In addition, the N-terminally truncated forms of these enzymes were studied in an attempt to understand the function of the diverse N-terminal sequences in SS. Our results show that, like SSI, the N-terminal extensions of SSIIa and SSIIb are not essential for catalytic activity and no extensive changes in their kinetic properties are observed upon their N-terminal truncation. Each isoform of SS can be distinguished based on its kinetic properties. Maize SSI and maize SSIIb exhibit higher Vmax with glycogen as a primer, while the converse is true for SSIIa. However, the specific activity of SSIIb is at least two- to threefold higher than that for either SSI or SSIIa. Although SSIIb exhibits the highest maximal velocity of the isoforms compared, its apparent affinity for primer is twofold lower than the affinity of SSI and SSIIa for primer. Perhaps these differences in primer affinity, primer preference, and maximal velocities all contribute in some way to the different structure(s) of starch during its synthesis. Expression and purification of maize SS has now provided us a useful tool to address the role(s) of SS in starch synthesis and starch structure.

Case study of institution-building by nurse Bertha Wright and colleagues

PURPOSE

To illuminate the history of nurses' participation in institution-building in the early 1900s, using the Baby Hospital in Oakland, California (now called Children's Hospital Oakland) as a case.

DESIGN

Historical research using a framework of women's history theory focused on the women who founded Oakland's Baby Hospital, 1910-1930.

METHOD

Data collection included studying original sources, archival material, and interviews. Data evaluation included external criticism for authenticity and genuineness, and internal criticism for accuracy and bias.

FINDINGS

In 1912, nurse Bertha Wright and social worker Mabel Weed, with a circle of community women, including Jessica Peixotto and Jean Howard McDuffie, established the Baby Hospital. Their activism included home visits, education, research, publications, political lobbying, and state policy and program development. At the center of this activity, was the lifelong commitment of Wright and Weed, who created new definitions of family. With social changes in the late 1920s, the male Board of Directors seized control of the hospital, and relegated women to auxiliary roles.

CONCLUSIONS

Health and social issues of the United States at the turn of the century are still problematic as a new century approaches and pertain to maternal-child health, foster care, and immigration. Feminists, including nurses, have played a central role in creating solutions. Knowledge of some of their incredible effort has been lost, particularly nursing's history in the western United States.

Pharmacokinetics and metabolism of darifenacin in the mouse, rat, dog and man

1. Following intravenous administration to animals at 2.5 mg/kg, darifenacin exhibited terminal plasma half-lifes < 2 h due to high plasma clearance (with respect to blood flow) and volumes of distribution greater than total body water. 2. Following oral administration to animals at doses > 4 mg/kg there was evidence of saturation of clearance since oral AUCs exceeded those expected from the high plasma clearances. In addition, terminal plasma half-lifes were greater than those estimated from intravenous administration. 3. In man, oral clearance was high with respect to liver blood flow. 4. Following oral administration of the radiolabelled drug to animals and man, unchanged darifenacin was only a minor component of the faecal radioactivity indicating that darifenacin was well absorbed from the gut. 5. Darifenacin was metabolized by three main routes in all species: monohydroxylation, oxidative dihydrobenzfuran ring opening and N-dealkylation. There were no marked species differences in the metabolism of darifenacin.

Influence of dofetilide on QT-interval duration and dispersion at various heart rates during exercise in humans

BACKGROUND

The objective of this study was to assess the influence of heart rate on QT-interval duration and dispersion during administration of the new selective potassium-channel blocker dofetilide in normal subjects.

METHODS AND RESULTS

Dofetilide 0.25 and 0.75 mg was administered for 4 days to 12 subjects in a randomized-sequence, double-blind, three-period, placebo-controlled, crossover study. QT-RR pairs were measured on study day 4 over a wide range of RR intervals obtained at rest and during an exercise test. QT-interval durations were calculated at seven predetermined RR intervals ranging from 400 ms (150 bpm) to 1000 ms (60 bpm) by use of monoexponential nonlinear curve fitting. QTmax and QTmin were calculated similarly, and QT-interval dispersion was measured as QTmax-QTmin at each predetermined RR interval. Minimal effects were found with 0.25 mg dofetilide. Two hours after administration of 0.75 mg dofetilide, QT interval was prolonged by 16.7 +/- 8.7% at a heart rate of 60 bpm (P < .01) and by 7.4 +/- 8.2% at a heart rate of 150 bpm (P < .05). QT prolongation at a heart rate of 150 bpm was less pronounced than at lower heart rates. Neither placebo nor dofetilide at either dose significantly increased QT-interval dispersion at any heart rate.

CONCLUSIONS

Dofetilide increases QT-interval duration but does not increase QT-interval dispersion in healthy subjects. QT-interval prolongation remains significant at high heart rates, although some degree of reverse rate dependence is observed at high concentrations.

Prevalence of exercise-induced asthma in schoolchildren in Kingston, St. Andrew and St. Catherine, Jamaica

A cross-sectional study was done, focusing on the prevalence of exercise-induced asthma in Jamaica and variables that may account for this rate. No previous study of this nature had been undertaken, and the investigators contend that there is a need to identify children who suffer from this condition but are unaware of it. A sample of 214 students from primary and secondary schools in the Corporate Area were chosen and given questionnaires to complete. Eighty-four of the children reported a history consistent with that of exercise-induced asthma and were further subjected to stress testing for a definitive diagnosis of this condition. A prevalence of 20.8% [C.I. +/- 5.35] was identified which reflected a rate comparable to that recorded in North America. There was a significantly higher prevalence in children of primary school ages, but all other variables considered for significance testing to determine associations between these and the prevalence of EIA proved not significant. A recommendation has been made for opportunity screening by medical practitioners.

Perceptions and practices relating to condom use among urban men in Haiti

This report is based on a survey conducted in 1986-87 of sexually active adult male residents in a low-income community of Port-au-Prince, Haiti. The objectives were to investigate knowledge of and attitudes toward condoms; to evaluate the effectiveness of the existing condom distribution program; and to obtain information that can be used in the design of strategies to increase condom acceptance and use among men throughout Haiti. A final sample of 706 sexually active adult male residents in stable unions, including a specially drawn sample of male partners of condom acceptors, were interviewed in their homes. Although condoms are almost universally known, they are rarely used. The majority felt that the responsibility for family planning should be borne by the woman. Whereas condoms may be of limited popularity for family planning purposes in Haiti, it should be determined whether they might be more acceptable as an effective means of controlling the spread of AIDS and other STDs.

Pharmacokinetics of trospectomycin sulphate in healthy subjects after single intravenous and intramuscular doses

The pharmacokinetics of trospectomycin (75-1000 mg free base equivalents) were studied in 128 healthy males (eight per dose group), after a 20 min intravenous (i.v.) infusion and intramuscular (i.m.) injection of trospectomycin sulphate. The concentrations of trospectomycin in serum were described by bi- or tri-exponential disposition functions indicating an initial half-life of 1.1-1.4 h for the i.v. dose and 1.6-2.1 h for the i.m. dose and terminal half-lives of over 15 h. Most of the drug was eliminated rapidly (mean residence time 5-12 h). The distribution volume was 59-112% of body weight and clearance was 112-152 ml min-1. The absorption into blood after i.m. dosing was rapid. The area under the concentration-time curve and maximum concentration values were linearly related to dose. Serum drug concentrations fell below the minimum inhibitory concentration values for a variety of organisms by 8-12 h, which indicates that two or three times daily dosing would be appropriate. However, the long terminal half-life suggests that significant accumulation is likely in some tissues with an 8 h dose interval and this may prolong the action of trospectomycin.

Pharmacokinetics and fate of 3H-trospectomycin sulphate, a novel aminocyclitol antibiotic, in male and female rats

1. The pharmacokinetics and fate of 3H-trospectomycin sulphate, a novel aminocyclitol antibiotic, were examined in male and female rats after intramuscular (i.m.), intravenous (i.v.) and subcutaneous (s.c.) dosing. 2. Total radioactivity levels in plasma were associated with unchanged trospectomycin. Two radioactive components were found in urine, one was indistinguishable from trospectomycin and the other was probably a degradation product formed after excretion or during storage rather than a metabolite. 3. The disappearance of drug from plasma followed a biphasic pattern with half lives of 0.3-0.4 h and 45-80 h and a large distribution volume, which indicated some retention of drug by tissues. Clearance rates were within the normal range for glomerular filtration rate, which indicated that the primary process of elimination is filtration of unchanged drug. 4. Excretion was initially rapid (greater than 40% by 4 h) and mainly into urine (faecal excretion greater than 20%). Urinary excretion was significantly larger in males than females but faecal excretion was significantly smaller, so that there was no significant difference in total excretion. 5. The bioavailability following s.c. dosing was only approximately 75% but there were few other biologically significant differences between the routes of administration. Absorption following i.m. and s.c. dosing was rapid. 6. Clearance rate and volume of distribution were higher in males than females. Over the dose range 50-200 mg/kg the pharmacokinetics appeared to be mostly linear.

Pharmacokinetics and fate of [3H]trospectomycin sulfate, a novel aminocyclitol antibiotic, in male and female dogs and rabbits. Allometric scaling with human

The pharmacokinetics and fate of [3H]trospectomycin sulfate, a novel aminocyclitol antibiotic, were examined in male and female dogs and rabbits. Total radioactivity levels in plasma were associated with unchanged trospectomycin in both dog and rabbit. No unchanged drug was found in rabbit urine. Two radioactive components were found in dog urine; one was indistinguishable from trospectomycin and the other was probably a degradation product. The disappearance of drug from plasma followed a biphasic pattern and was well described by a bi-exponential function with half-lives of 0.4-0.8 and 30-70 hr in the dog and 0.4 and 90-120 hr in the rabbit. There was a large distribution volume (Vss), which indicated some retention of drug by tissues. The clearance (CL) for both animals was within the normal range for glomerular filtration rate. CL and Vss were not different between the sexes in the dog or rabbit. Excretion in both animals was initially rapid (greater than 40% by 4 hr) and mainly by the urinary route (fecal excretion less than 10%). Urinary excretion was not significantly different between the sexes. Over the dose range of 25-100 mg/kg, the plasma pharmacokinetics in the dog were linear. However, the recovery of radioactivity in the urine was significantly reduced at the highest dose. Trospectomycin CL in rat, human (obtained from previous studies), dog, and rabbit was described by the allometric equation, CL (ml/hr) = 132 x M0.91 where M is the body mass in kg.

Efflux of potassium ions in angiotensin II-stimulated bovine adrenocortical cells

Angiotensin II (AII) stimulation of steroidogenesis is known to be associated with depolarization of the adrenocortical cell membrane. In these cells, membrane permeability to potassium ions governs electrical potential. The effects of AII on the rate of efflux of K+ in relation to the control of aldosterone synthesis has been investigated in bovine adrenocortical cells preloaded with 43K. In static incubations, the pattern of 43K efflux fitted a model with two exponential components with t1/2 values of 47.7 +/- 1.7 and 14.2 +/- 0.6 (S.E.M.) min. AII increased the efflux rate of the slow-exchange component (t1/2 37.1 +/- 0.6 min) and retarded efflux from the fast-exchange component. With ouabain present to prevent reuptake of the isotope, the rate of efflux for both components was increased in unstimulated cells (t1/2 28.4 +/- 1.1 and 12.0 +/- 0.7 min). AII again increased the rate of efflux from the slow component (t1/2 = 24.2 +/- 1.7 min, P less than 0.01) and retarded efflux from the fast component. These biphasic effects were apparent in cells treated with a range of AII concentrations (0.1 nmol/l-1 mumol/l) but the point in time at which increased efflux from the slower component predominated over retardation of the slow component was earlier for cells treated with 1 mumol AII/l than for cells treated with lower concentrations. We suggest that decreases and increases in K+ efflux caused by AII are associated with depolarization and repolarization respectively. Changes in intracellular concentrations of Ca2+ may link these events.

Multiple-dose, double-blind, placebo controlled intravenous tolerance and pharmacokinetic study of trospectomycin sulfate (U-63, 366F) in healthy male volunteers

Trospectomycin sulfate is a novel aminocyclitol antibiotic. This study evaluated the tolerance and the pharmacokinetics of multiple, intravenous doses of trospectomycin (TRO) in healthy male volunteers. Three groups of 10 volunteers were studied. Eight volunteers in each group were studied in a parallel design to receive trospectomycin (Group 1 = 250 mg, Group 2 = 500 mg, Group 3 = 750 mg) while 2 volunteers received placebo (normal saline). Drug doses were administered in 30 ml volumes over 30 min every 8 h for 7 days (i.e. 21 total doses). Evaluations of vital signs, side effects, and safety laboratory tests were made at regular intervals during the study. The most frequent medical events observed in the volunteers receiving trospectomycin were perioral/facial paresthesias (54%), pain at the i.v. infusion site (46%), dizziness/lightheadedness (58%), and GI symptoms (38%). A statistically significant dose response relationship was observed for the incidence of perioral/facial paresthesias and pain at the i.v. infusion site (i.e., increased incidence with increased dose). All the medical events were mild or moderate in severity and reversible following drug discontinuation. In the 500 and 750 mg trospectomycin groups, standing systolic blood pressure decreased significantly with the first dose of study drug. Elevated levels of SGPT were observed in 9 volunteers (1 in placebo, 3 in 250 mg, 1 in 500 mg, and 4 in 750 mg dose groups). This study demonstrates that multiple intravenous trospectomycin doses up to 750 mg are reasonably well tolerated in healthy male volunteers. The concentration of trospectomycin in serum, measured with a sensitive HPLC assay, was less than 3 mcg/ml at 8 h postinfusion for all dose levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Fluid volumes in rainbow trout, Salmo gairdneri: application of compartmental analysis

1. The measurement of fluid volumes by the indicator dilution technique and compartmental analysis was re-evaluated in free-swimming, undisturbed rainbow trout. 2. Plasma (33.5 ml/kg body wt) and blood (41.3 ml/kg body wt) volumes estimated by compartmental analysis from blood samples taken early (less than 5 min) after dye injection were 40% lower than volumes calculated by sampling late (greater than or equal to 80 min). 3. The rate of exchange of dye between plasma and interstitial fluid was high (48%/hr) compared to mammals (5%/hr) which supports the hypothesis that teleost capillaries have high protein permeability. 4. Total extracellular volume estimated using a single pool model (210.5 ml/kg body wt) of inulin kinetics was 20% higher than that calculated by a three pool model (172.8 ml/kg body wt).

A demonstration of pharmacokinetics and physiological modelling using a microcomputer for data capture and analysis

We describe a simple and inexpensive demonstration of mass transport and exchange using dye clearance from a hydrodynamic model. A microcomputer was used for data acquisition and storage, non-linear least squares curve fitting, compartmental analysis and parameter estimation. The system is useful for demonstrating the indicator-dilution technique for fluid volume measurement and compartmental analysis in pharmacokinetics.

Palynological and Iridium Anomalies at Cretaceous-Tertiary Boundary, South-Central Saskatchewan

The Cretaceous-Tertiary boundary in south-central Saskatchewan is marked by coincident anomalies in abundance of iridium and fern spores at the extinction level of a suite of Cretaceous pollen taxa. Evidence of disruption of the terrestrial flora includes the fern-spore abundance anomaly and local extinction of as much as 30 percent of angiosperm species. The reorganized earliest Tertiary flora is made up largely of surviving species that assumed new roles of dominance. Persistence of climatically sensitive taxa across the boundary indicates that if paleoclimate was altered by the terminal Cretaceous event, it returned quickly to the pre-event condition.

Cortisol kinetics and fluid distribution in brook trout (Salvelinus fontinalis)

Cortisol kinetics were examined in brook trout (Salvelinus fontinalis) to assess possible relationships with body fluid distribution during acclimation to sea water (SW). The disappearance curve of [3H]cortisol in plasma, after a bolus injection, was analysed by compartmental analysis using a three-pool mammillary model. The results indicated that only approximately 10% of the total exchangeable cortisol was located in the plasma pool. Over 75% of the total cortisol was associated with a large slowly exchanging pool and the remaining cortisol was located in a second extravascular tissue pool which was in rapid exchange with the plasma pool. Two days after transfer of trout from fresh water to SW, when plasma chloride concentration was at a new steady state, body weight, intracellular fluid volume, haematocrit and inulin clearance rate were lowered but plasma, blood and extracellular volumes were unaltered. Cortisol plasma clearance rate was unaltered but plasma cortisol concentration, cortisol secretion rate, total cortisol pool size and interpool transport rates were increased. These results are consistent with an acute role for cortisol in SW adaptation of brook trout. The fraction of the total cortisol cleared was smaller and the average time that cortisol spent in the tissue pools was slightly longer in trout after transfer to SW, possibly reflecting altered fluid dynamics. The fractional disappearance rate was larger at higher plasma cortisol concentrations in the SW trout. This relationship is compatible with the hypothesis that cortisol protein binding protects cortisol from metabolism.

Cortisol dynamics during seawater adaptation of Atlantic salmon Salmo salar

We examined plasma cortisol concentration (PCC), cortisol metabolism, and cortisol protein binding (CPB) in chronically cannulated Atlantic salmon (Salmo salar) during seawater (SW) adaptation. PCC rose significantly 2 h after freshwater (FW) to SW changeover but tended to be lower for 6 days thereafter. Plasma chloride concentrations began to stabilize 24-48 h after entry to SW. Cortisol metabolic clearance rate (MCR) was significantly higher 24 h after SW transfer than in FW; CPB and plasma protein concentration were significantly lower, but cortisol production rate was unchanged. The change in plasma chloride after 24 h in SW was negatively correlated with the change in plasma protein (r = -0.915, n = 9, P less than 0.001). The changes in CPB and plasma protein were correlated with the change in MCR (r = -0.643, n = 14, P less than 0.02; r = -0.850, n = 9, P less than 0.005). We hypothesize that these changes in protein concentration reflect an ion-induced expansion of extracellular volume and lead to increased MCR.

Plasma cortisol concentrations in Atlantic salmon, Salmo salar: episodic variations, diurnal change, and short term response to adrenocorticotrophic hormone

Short term episodic peaks 1-2 hr in duration in plasma cortisol levels were observed in adult Atlantic salmon. These results support the concept that episodic secretion of corticosteroids may be a characteristic feature of the vertebrate adrenal/interrenal regulatory system and provide an explanation for the variability frequently observed in plasma cortisol concentrations in salmonids. Plasma cortisol levels also varied throughout the light-dark cycle and mean concentrations were higher during the night. High frequency variations in plasma cortisol levels (with a time scale of minutes rather than hours) were not observed. Porcine adrenocorticotrophic hormone (ACTH) and ACTH1-24 but not alpha-melanocyte-stimulating hormone (alpha-MSH) increased plasma cortisol levels 10 min after injection. The change in plasma cortisol levels after injection of 1 mU/kg porcine ACTH was of similar magnitude and duration as endogenous episodic variations. Plasma cortisol levels during episodic peaks, circadian changes, or after ACTH injection were less than the binding capacity of the "high" affinity protein binding system for cortisol. Hence, the unbound cortisol concentration is a linear function of the total cortisol concentration. Whereas episodic release of cortisol is indicated here, the physiological importance of this mode of hormone secretion is unclear. Plasma glucose levels were unaffected up to 2 hr after injection of ACTH and did not show close temporal correlation with endogenous episodic peaks in plasma cortisol.

Child survivorship and pregnancy spacing in Iran

Using data collected over a 12-month period (1977–78) from more than 15,000 hospital deliveries at a single maternity hospital in Tehran, Iran, we have examined the effects of previous pregnancy outcomes, breast-feeding and contraceptive use on birth spacing. The outcomes of previous pregnancies, particularly the most recent, significantly affect the length of the pregnancy interval, and so does breast-feeding. Pregnancy outcomes influence both breast-feeding and subsequent contraceptive behaviour, and breast-feeding adds to the degree of protection against pregnancy afforded by conventional contraception. Improved survivorship increases the length of pregnancy intervals most when it results in increased use of contraception and when breast-feeding is commonly practised for extended periods.

Abortion and contraception in the Korean fertility transition

Abstract In this paper the relationship between the use of abortion and contraception among married women in a society experiencing uronid decline in fertility is analysed using data from the Korean National Fertility Survey of 1974. The level and pattern of abortion before and after modern contraceptives became widely available are described, and the implications of the changing patterns of abortion and contraception are discussed.

Adrenocortical responses and changes during the oestrous cycle in mice: effects of male presence, male urine and housing conditions

Male urine applied daily to their bedding raised the basal levels of plasma corticosterone in individually housed, virgin female mice, when compared with females (grouped or individually housed) living with male mice or with group-housed females exposed daily to male urine. Values were not affected during ether-induced stress. A single application of male urine raised plasma levels 30 min later regardless of housing conditions; but after 4 and 24 h levels had fallen to normal. The results are discussed in terms of sensitization of the pituitary-adrenal system and of stress and reproductive pheromones. Male urine was less effective than male presence at inducing 4-day oestrous cycles. Length and type of cycle varied continuously under the influence of a spectrum of environmental signals.