Effects of doxycycline on heartworm embryogenesis, transmission, circulating microfilaria, and adult worms in microfilaremic dogs

Tetracycline treatment of animals or humans infected with filariae that harbor Wolbachia endosymbionts blocks further embryogenesis, and existing microfilariae gradually die. This treatment also kills developing larvae and has a slow-kill effect on adult filariae, all presumably due to elimination of the Wolbachia. Also, Dirofilaria immitis microfilariae in blood collected from dogs up to 25 days after the last dose of doxycycline developed to infective L3 that were normal in appearance and motility in mosquitoes but did not continue to develop or migrate normally after subcutaneous (SC) injection into dogs. The present study was designed to determine whether heartworm microfilariae collected at later times after treatment would regain the ability to continue normal development in a dog. The study also was expected to yield valuable data on the effects of treatment on microfilariae and antigen levels and adult worms. The study was conducted in 16 dogs as two separate replicates at different times. A total of five dogs (two in Replicate A and three in Replicate B) infected either by SC injection of L3 or intravenous transplantation of adult heartworms were given doxycycline orally at 10mg/kg twice daily for 30 days, with three untreated controls. Microfilarial counts in the five treated dogs gradually declined during the 12-13 months after treatment initiation. Two dogs were amicrofilaremic before necropsy and three had 13 or fewer microfilariae/ml. Only one treated dog was negative for heartworm antigen before necropsy. Overall, treated dogs generally had fewer live adult heartworms than controls, and most of their live worms were moribund. All three control dogs remained positive for microfilariae and antigen and had many live worms. L3 from mosquitoes fed on blood collected 73-77 or 161-164 days after initiation of doxycycline treatments were injected SC into five dogs. None of the dogs injected with L3 from mosquitoes fed on blood from doxycycline-treated dogs were ever positive for microfilariae or antigen, and none had worms at necropsy; three control dogs were positive for microfilariae and antigen and had many live worms. These data indicate that doxycycline treatment of microfilaremic dogs gradually reduces numbers of microfilariae and blocks further transmission of heartworms. This latter effect should be highly effective in reducing the rate of selection of heartworms with genes that confer resistance to macrocyclic lactone preventives and microfilaricides. The data also suggest that doxycycline has a slow-kill effect on adult heartworms.

Oregon subduction zone: venting, fauna, and carbonates

Transects of the submersible Alvin across rock outcrops in the Oregon subduction zone have furnished information on the structural and stratigraphic framework of this accretionary complex. Communities of clams and tube worms, and authigenic carbonate mineral precipitates, are associated with venting sites of cool fluids located on a fault-bend anticline at a water depth of 2036 meters. The distribution of animals and carbonates suggests up-dip migration of fluids from both shallow and deep sources along permeable strata or fault zones within these clastic deposits. Methane is enriched in the water column over one vent site, and carbonate minerals and animal tissues are highly enriched in carbon-12. The animals use methane as an energy and food source in symbiosis with microorganisms. Oxidized methane is also the carbon source for the authigenic carbonates that cement the sediments of the accretionary complex. The animal communities and carbonates observed in the Oregon subduction zone occur in strata as old as 2.0 million years and provide criteria for identifying other localities where modern and ancient accreted deposits have vented methane, hydrocarbons, and other nutrient-bearing fluids.

Heartworm and Wolbachia: therapeutic implications

A safer, more effective adulticidal treatment and a safe method for reducing microfilaremia and breaking transmission of heartworm disease early in the treatment are needed. The present study evaluated efficacy of ivermectin (IVM) and doxycycline (DOXY) alone or together (with or without melarsomine [MEL]) in dogs with induced adult heartworm infection and assessed the ability of microfilariae from DOXY-treated dogs to develop to L3 in Aedes aegypti mosquitoes and subsequently to become reproductive adults in dogs. Thirty beagles were each infected with 16 adult heartworms by intravenous transplantation. Six weeks later, dogs were ranked by microfilarial count and randomly allocated to 6 groups of 5 dogs each. Beginning on Day 0, Group 1 received IVM (6 mcg/kg) weekly for 36 weeks. Group 2 received DOXY (10 mcg/(kgday)) orally Weeks 1-6, 10-11, 16-17, 22-25, and 28-33. Groups 3 and 5 received IVM and DOXY according to doses and schedules used for Groups 1 and 2. At Week 24, Groups 3 and 4 received an intramuscular injection of MEL (2.5 mg/kg), followed 1 month later by two injections 24h apart. Group 6 was not treated. Blood samples were collected for periodic microfilaria counts and antigen (Ag) testing (and later immunologic evaluation and molecular biology procedures). Radiographic and physical examinations, hematology/clinical chemistry testing, and urinalysis were done before infection, before Day 0, and periodically during the treatment period. At 36 weeks, the dogs were euthanized and necropsied for worm recovery, collection of lung, liver, kidney, and spleen samples for examination by immunohistochemistry and conventional histological methods. All dogs treated with IVM + DOXY (with or without MEL) were amicrofilaremic after Week 9. Microfilarial counts gradually decreased in dogs treated with IVM or DOXY, but most had a few microfilariae at necropsy. Microfilarial counts for dogs treated only with MEL were similar to those for controls. Antigen test scores gradually decreased with IVM + DOXY (with or without MEL) and after MEL. Antigen scores for IVM or DOXY alone were similar to controls throughout the study. Reduction of adult worms was 20.3% for IVM, 8.7% for DOXY, 92.8% for IVM + DOXY + MEL, 100% for MEL, and 78.3% for IVM + DOXY. Mosquitoes that fed on blood from DOXY-treated dogs had L3 normal in appearance but were not infective for dogs. Preliminary observations suggest that administration of DOXY+IVM for several months prior to (or without) MEL will eliminate adult HW with less potential for severe thromboembolism than MEL alone.

Goal setting & Network 9/10 efforts to improve care

TRN, through its Medical Review Board, has developed, endorsed, and articulated goals for two aspects of dialysis treatment. These goals promote the use of continuous quality improvement by encouraging dialysis programs to perform internal examinations of their own data in the context of regional and national data. TRN believes that this combination of data feedback, CQI, and goal setting will impact positively on patient outcomes for all dialysis patients within The Renal Network.

Language recovery after left hemispherectomy in children with late-onset seizures

We investigated the language capabilities of the isolated right hemisphere in 6 children (age, 7-14 years) after left hemidecorticectomy for treatment of Rasmussen's syndrome. Patients were right-handed before surgery and had at least 5 years of normal language development before the onset of seizures. Language testing included speech sound (phoneme) discrimination, single word and phrasal comprehension, repetition, and naming. Within 4 to 16 days after surgery, patients showed improved phoneme discrimination compared with their performance shortly before surgery. Other language functions remained severely impaired until at least 6 months after surgery. By 1 year after surgery, receptive functions were comparable with, or surpassed, patient presurgery performance. Although word repetition was intact by 1 year after surgery, naming remained impaired, and patient speech was limited largely to production of single words. These results suggest that the right hemisphere is innately capable of supporting multiple aspects of phoneme processing. Recovery of higher level receptive and, to a lesser extent, expressive language functions is attributed to plasticity of the right hemisphere, which appears to persist beyond the proposed critical period for language acquisition and lateralization.

The injured drunk driver in central Texas: incidence, demographics, and legal ramifications

INTRODUCTION

This study was designed to define 1 trauma center's drunk driver patient population, determine the incidence of alcohol intoxication in motorists admitted to the hospital following a collision, and ascertain the frequency of the Driving Under the Influence (DUI) charges filed against this population.

METHODS

Hospitalized motorists were divided into 2 groups--those who did and did not have blood alcohol levels measured--then further classified into 3 subsets based on serum ethanol values. A 2-year retrospective trauma registry review established patient demographics, outcomes, hospital costs, blood alcohol levels, and concomitant drug use. Local police records were accessed to determine the number of patients cited for DUI.

RESULTS

Eighty percent of those intoxicated were men. On the average, drunk drivers were 1.7 years younger than were sober patients. Minimally to moderately intoxicated motorists had the highest overall injury severity scores and hospital costs and were the most likely to concomitantly abuse illegal drugs. Patients who did not have ethanol levels measured had the highest mortality rate.

DISCUSSION

Overall, 60% of admitted injured drivers who were tested had positive results for 1 or more substances known to impair driving ability, yet only 16% of those with a blood alcohol level of > or = 100 mg/dL were charged with DUI. This finding supports previously published data suggesting that injury and transport to a hospital protect the alcohol-impaired driver from legal consequences.

Two-year retention and caries rates of UltraSeal XT and FluoroShield light-cured pit and fissure sealants

The purpose of this study was to evaluate the long-term retention and effect on caries rates of pit and fissure sealants containing fluoride (UltraSeal XT and FluoroShield). These sealants were placed in vivo on opposite sides of the arch in adolescent patients in a private practice. A total of 470 sealants were placed on permanent molars and premolars. After two years, 74.3 percent of the sample was available for recall. The total retention rate (Category A) was 96.3 percent for UltraSeal XT and 91.4 percent for FluoroShield. There were no new pit and fissure carious lesions over the two years of the study. The results for the UltraSeal XT is the highest retention rate yet documented.

Chromosome abnormalities in meningeal neoplasms: do they correlate with histology?

Thirty-three meningeal neoplasms were karyotyped, and the results were compared with histologic features. Thirteen neoplasms had no discernible abnormality or sex chromosome loss only; nine had monosomy or structural abnormality involving only chromosome 22; and 11 had other chromosome abnormalities with or without chromosome 22 involvement. Histologic evidence of invasion was not associated with an abnormal karyotype in the three angioblastic tumors examined. All seven fibroblastic meningiomas had abnormal karyotypes, with monosomy 22 the most common change. Abnormal karyotypes were detected in 76% of syncytial and 55% of transitional meningiomas. When these results were combined with those from 259 meningeal tumors reported since 1987, abnormal karyotypes were detected in at least half of all histologic types. Chromosome changes secondary to those involving chromosome 22 may indicate additional areas of the genome that play a role in tumor progression. In the combined series, chromosome losses were most frequently observed in meningiomatous and transitional histologies; chromosomes 1, 6, 14, 18, and Y each were lost in 10 or more meningiomas, whereas only chromosome 20 was gained at the same frequency. Structural abnormalities most frequently involved chromosome 1. These changes are distinctly different from those observed in other common intracranial neoplasms, specifically astrocytic neoplasms.

A 2-year clinical evaluation of two pit and fissure sealants placed with and without the use of a bonding agent

The purpose of the study was to evaluate whether the clinical effectiveness of pit and fissure sealant was increased (as demonstrated by an increased retention rate) when a bonding agent was used prior to the placement of the sealant. Two pit and fissure sealants, Concise Light Cured White Sealant and Prisma Shield Light Cured Sealant, were placed in vivo with and without the use of the bonding agents, Scotchbond 2 and Prisma Universal Bond. After 2 years, 55% of the sample was available for recall. The retention rates for the sealants were 77% for Concise with Scotchbond 2, 84% for Concise with no bonding agent, 77% for Prisma Shield with Universal Bond, and 77% for Prisma Shield with no bonding agent. Results of this study indicated that the use of a bonding agent prior to the application of a pit and fissure sealant does not increase the retention rate.

Craniocervical decompression for cervicomedullary compression in pediatric patients with achondroplasia

The congenital osseous abnormalities associated with achondroplasia include stenosis of the foramen magnum and the upper cervical spinal canal. In the pediatric achondroplastic patient, such stenosis may lead to cervicomedullary compression with serious sequelae, including paresis, hypertonia, delayed motor mile-stones, and respiratory compromise. Using a standardized protocol the authors have treated 15 young achondroplastic patients with documented cervicomedullary compression by craniocervical decompression and duroplasty. Following this procedure, significant improvement in presenting neurological or respiratory complaints was noted in all patients. The mortality rate in this series was zero. The major cause of morbidity associated with this procedure was perioperative cerebrospinal fluid (CSF) leakage from the surgical wound, presumably related to coexisting abnormalities of CSF dynamics. This problem was successfully managed by temporary or, when necessary, permanent CSF diversion procedures. It is concluded that craniocervical decompression is an effective and safe treatment for young achondroplastic patients with cervicomedullary compression.

Ventriculoamniotic shunt for treatment of hydrocephalus in one of twins: medical, ethical and legal considerations

One of a pair of preterm twin fetuses was identified as having progressive hydrocephalus. After an extensive evaluation of the parents and both fetuses, a ventriculoamniotic shunt was placed. The affected twin, despite multiple additional neonatal procedures, has done well as matched against her normal twin sister. Both children are well 4 years after the surgery. The case presented a remarkable complexity of medical, ethical and legal issues which are presented.

Foramen magnum decompression in an infant with homozygous achondroplasia. Case report

Homozygous achondroplasia is a rare yet distinct clinical entity. Most infants succumb to an early death as a result of respiratory compromise due to upper airway obstruction, thoracic cage deformity, and/or cervicomedullary compression. The successful cervicomedullary decompression of a 16-week-old infant with homozygous achondroplasia is described. This report suggests that homozygous achondroplasia is not universally fatal and that these infants are potentially viable if managed by aggressive respiratory and surgical measures.

The pericranial flap for reconstruction of anterior skull base defects

In 1981, the senior author first reported the use of the pericranial flap for support of the brain following resection of the anterior skull base. Since the initial report, considerable experience has been gained with this flap. It is currently deployed via a bifrontal craniotomy and is placed primarily as a support beneath the frontal lobes. The pericranial flap may also be used to repair dural laceration and defects. The sinonasal surface is routinely grafted with split-thickness skin or dermis. This technique provides an excellent barrier between the sinonasal cavity and the cerebrospinal fluid, establishing a tough, fibrous platform. Herniation of intracranial contents has not occurred. One major complication has been reported in which radiation necrosis occurred during postoperative therapy, leading to progressive devitalization of the pericranial flap. Ultimately, dural repair and closure with a latissimus dorsi free flap was required. The pericranial flap repair of anterior skull base defects has a 90% complication-free and 95% overall success rate. It is simple and extremely effective. Bone grafting has not been necessary in our experience.