Population Pharmacokinetics of Doxycycline in Children

Doxycycline is a tetracycline-class antimicrobial labeled by the United States (U.S.) Food and Drug Administration for children >8 years of age for many common childhood infections. Doxycycline is not labeled for children ≤8 years of age, due to the association between tetracycline class antibiotics and tooth staining, although doxycycline may be used off-label in severe conditions. Accordingly, there is a paucity of pharmacokinetic (PK) data to guide dosing in children 8 years and younger. We leveraged opportunistically-collected plasma samples after intravenous (IV) and oral doxycycline doses received per standard of care to characterize the PK of doxycycline in children of different ages, and evaluated the effect of obesity and fasting status on PK parameters.We developed a population PK model of doxycycline using data collected from 47 patients 0-18 years of age, including 14 participants ≤8 years. We developed a 1 compartment PK model and found doxycycline clearance to be 3.32 L/h/70 kg and volume to be 96.8 L/70kg for all patients; comparable to values reported in adults. We estimated a bioavailability of 89.6%, also consistent with adult data. Allometrically scaled clearance and volume of distribution did not differ between children 2 to ≤8 years of age and children >8 to ≤18 years of age, suggesting that younger children may be given the same per kg dosing. Obese and fasting status were not selected for inclusion in the final model. Additional doxycycline PK samples collected in future studies may be used to improve model performance and maximize its clinical value.

An mtDNA mutation in the initiation codon of the cytochrome C oxidase subunit II gene results in lower levels of the protein and a mitochondrial encephalomyopathy

A novel heteroplasmic 7587T-->C mutation in the mitochondrial genome which changes the initiation codon of the gene encoding cytochrome c oxidase subunit II (COX II), was found in a family with mitochondrial disease. This T-->C transition is predicted to change the initiating methionine to threonine. The mutation load was present at 67% in muscle from the index case and at 91% in muscle from the patient's clinically affected son. Muscle biopsy samples revealed isolated COX deficiency and mitochondrial proliferation. Single-muscle-fiber analysis revealed that the 7587C copy was at much higher load in COX-negative fibers than in COX-positive fibers. After microphotometric enzyme analysis, the mutation was shown to cause a decrease in COX activity when the mutant load was >55%-65%. In fibroblasts from one family member, which contained >95% mutated mtDNA, there was no detectable synthesis or any steady-state level of COX II. This new mutation constitutes a new mechanism by which mtDNA mutations can cause disease-defective initiation of translation.

Neither compatible nor self-incompatible pollinations of Brassica napus involve reorganization of the papillar cytoskeleton

Compatible pollination of Brassica napus necessitates pollen hydration, pollen germination and growth of the pollen tube through the loosened walls of stigmatic papillar cells, whereas self-incompatible (SI) pollinations fail at one of these stages. Analyses of the early stages of pollination show that at high (but not low) relative humidities, both compatible and SI pollen hydrates, but SI germination is reduced and the rare pollen tubes generally fail to penetrate the papillar walls, although there is some wall loosening. Inside the papillae, both compatible and SI interactions may induce the formation of callose, but there is no evidence for a major accumulation of cytoplasm or secretory vesicles in the vicinity of the pollen tubes and neither microtubule nor F-actin patterns re-arrange in this zone. These observations indicate that the source of the wall-loosening enzymes is probably the pollen tube or pollen coat, and that the common cellular responses of plants to attempted invasions have become suppressed in the papilla-pollen tube interaction.

SCID mice containing muscle with human mitochondrial DNA mutations. An animal model for mitochondrial DNA defects

Defects of the mitochondrial genome are important causes of disease. Despite major advances in our investigation of patients, there is no effective therapy. Progress in this area is limited by the absence of any animal models in which we can evaluate treatment. To develop such a model we have injected human myoblasts into the tibialis anterior of SCID mice after inducing necrosis. After injection of normal human myoblasts, regenerating fibers expressed human beta-spectrin, confirming they were derived from fusion of human myoblasts. The stability of the muscle fibers was inferred by demonstrating the formation of motor end plates on the regenerating fibers. In addition, we show the presence of human cytochrome c oxidase subunit II, which is encoded by the mitochondrial genome, in the regenerated fibers. After injection of human myoblasts containing either the A8344G or the T8993C heteroplasmic mitochondrial DNA mutations, human beta-spectrin positive fibers were found to contain the mutation at a similar level to the injected myoblasts. These studies highlight the potential value of this model for the study of mitochondrial DNA defects.

Treatment of mitochondrial disease

Defects of the mitochondrial genome are widely recognized as important causes of disease in man. Patients may present at any age with clinical symptoms that vary from acute episodes of lactic acidosis in infancy to severe neurodegenerative illness in adulthood. While modern molecular genetic techniques have facilitated major advances in the diagnosis and characterization of specific molecular defects, treatment for the majority of patients remains supportive in the absence of definitive biochemical therapies. As a consequence, the possibilities for mitochondrial DNA gene therapy must be considered. In this review, we will evaluate the current biochemical strategies available to clinicians for the management of patients with mitochondrial disease and examine the possible approaches to the gene therapy of mitochondrial DNA defects.

A comparison of serological tests and gross lung pathology for detecting contagious bovine pleuropneumonia in two groups of Italian cattle

Western and dot blotting techniques were compared with complement fixation tests (CFT), indirect enzyme-linked immunosorbent assays (ELISA), mycoplasma culture and gross lung pathology to detect Mycoplasma mycoides subspecies mycoides SC, the cause of contagious bovine pleuropneumonia (CBPP), in two groups of Italian cattle. None of the animals showed any clinical signs before slaughter. In group A, seven of the 20 cattle had characteristic lung lesions of acute and chronic CBPP but only six were positive by CFT. Western blotting detected antibody in eight of the animals, of which six had lesions and significant CFT titres (> 50 per cent fixation at a serum dilution of 1/10) and two had neither. In group B, seven of the 17 cattle had lesions characteristic of CBPP, and 12 were seropositive by CFT. Western blotting detected antibody in 13 of the animals including one which had a negative CFT titre. The ELISA was less sensitive than either CFT or Western blotting, detecting antibody in five animals in group A and nine animals in group B. The dot blotting test correlated well with Western blotting but gave a small number of ambiguous results. The causative organism was isolated from four of the 20 cattle in group A and six of the 17 cattle in group B.

Recurrent herpes simplex virus labialis and the use of epidural morphine in obstetric patients

A retrospective study of sequential obstetric patients delivering at University Hospital and receiving epidural anesthesia was conducted to determine if a suggested association exists between the recurrence of oral herpes simplex lesions and the use of epidural morphine. In a retrospective study of 291 patients, 13 of 134 (9.7%) receiving epidural morphine developed recurrent oral herpes lesions in contrast to 1 of 157 (0.6%) not receiving the drug (P less than 0.001). In a prospective hospital-based study of 729 consecutive obstetric patients, 146 patients received epidural opioids (morphine, fentanyl, or both) and 583 did not. Recurrent HSVL lesions occurred in 13 of 140 (9.3%) patients given epidural morphine but in only 6 of 583 (1.0%) not given epidural opioids (P less than 0.001). Three of the 13 patients with HSVL received both epidural morphine and fentanyl and 10 received only epidural morphine. Because of the small numbers of patients receiving only fentanyl, no relation between HSVL reactivation and epidural fentanyl could be established. In patients having caesarean sections, the association of recurrent HSVL and the use of epidural morphine was significant (P = 0.04), suggesting cesarean delivery was not a confounder. A hitherto undescribed triggering agent, epidural morphine, appears to be associated with reactivation of HSVL in obstetric patients in the postpartum period.

Recurrent herpes simplex virus labialis and the use of epidural morphine in obstetric patients

A retrospective study of sequential obstetric patients delivering at University Hospital and receiving epidural anesthesia was conducted to determine if a suggested association exists between the recurrence of oral herpes simplex lesions and the use of epidural morphine. In a retrospective study of 291 patients, 13 of 134 (9.7%) receiving epidural morphine developed recurrent oral herpes lesions in contrast to 1 of 157 (0.6%) not receiving the drug (P less than 0.001). In a prospective hospital-based study of 729 consecutive obstetric patients, 146 patients received epidural opioids (morphine, fentanyl, or both) and 583 did not. Recurrent HSVL lesions occurred in 13 of 140 (9.3%) patients given epidural morphine but in only 6 of 583 (1.0%) not given epidural opioids (P less than 0.001). Three of the 13 patients with HSVL received both epidural morphine and fentanyl and 10 received only epidural morphine. Because of the small numbers of patients receiving only fentanyl, no relation between HSVL reactivation and epidural fentanyl could be established. In patients having caesarean sections, the association of recurrent HSVL and the use of epidural morphine was significant (P = 0.04), suggesting cesarean delivery was not a confounder. A hitherto undescribed triggering agent, epidural morphine, appears to be associated with reactivation of HSVL in obstetric patients in the postpartum period.