bluuebunny/crossref_metadata_2025 huggingface dataset:
Complications and Costs of Treatment of Refractory Generalized Convulsive Status Epilepticus in Children
Authors: Gilbert Donald L. , Glauser Tracy A.
Published: January 2008

Multiple case series in the literature suggest that benzodiazepines and barbiturates are highly efficacious at stopping seizures. Apparent differences in mortality might not be due solely to drug effect. In this systematic review of the medical literature, we assessed the complications and costs of treatment of refractory status epilepticus in 111 children who met strict inclusion criteria, as part of an effort to provide an evidenced-based recommendation for optimal therapy. All children treated with barbiturates required mechanical ventilation, versus 13% of patients treated with benzodiazepines. Benzodiazepine treatment was associated with pressor use in 3.5% of cases, versus 35% with barbiturate treatment. Midazolam treatment was for the shortest duration and allowed the most rapid return to consciousness. Differences in mean 24-hour drug costs were small compared to savings produced by shorter length of treatment and return to consciousness. Benzodiazepines appear to have higher drug costs but lower complications and overall costs than barbiturates. (J Child Neurol 1999;14:597-601).
A Novel Mutation in the Mitochondrial DNA Transfer Ribonucleic AcidAsp Gene in a Child With Myoclonic Epilepsy and Psychomotor Regression
Authors: Shtilbans Alexander , El-Schahawi Magda , Malkin Elfrida , Shanske Sara , Musumeci Olimpia , DiMauro Salvatore
Published: January 2008

A novel A7543G mutation was found in the mitochondrial DNA transfer ribonucleic acidAsp gene in an 11-year-old girl with myoclonic seizures, developmental delay, and severe behavioral problems. Muscle histochemistry failed to show any ragged red fibers or cytochrome c oxidase-negative fibers, and muscle biochemistry showed partial cytochrome c oxidase deficiency. The mutation was heteroplasmic in muscle, fibroblasts, and blood from the patient and in blood from other affected family members, and the proportion of mutant mitochondrial DNA correlated with the severity of symptoms. (J Child Neurol 1999;14:610-613).
Neonatal Suck Reflex Pattern Does Not Predict Apnea
Authors: Richards Steven D. , Ritchie Susan , Hobbs Gerald R. , Mandich Marybeth , Sheth Raj D.
Published: January 2008

Respiration and suck are gestational age-dependent reflexes modulated in the brain stem. To determine if the suck reflex pattern could be used to predict apnea, the relationship between the two was examined in 28 neonates. The suck reflex was quantified with respect to burst-pause rhythm, amplitude of negative suck pressure, and synchrony of the negative-positive pressure. Apneas were counted 5 days prior to and following measurement of the suck reflex pattern. Increasing gestational age correlated with a lower frequency of apnea (P < .01) and higher suck scores (P < .01). A mature suck reflex pattern, however, failed to predict the occurrence of apnea. ( J Child Neurol 1999;14:614-616).
Parental Burden, Coping, and Family Functioning in Primary Caregivers of Children With Joubert Syndrome
Authors: Luescher Jennifer L. , Dede Duane E. , Gitten Jill C. , Fennell Eileen , Maria Bernard L.
Published: January 2008

Children with Joubert syndrome have physical and intellectual disabilities. The purpose of this study was to assess the impact of Joubert syndrome on parental burden, coping, and family functioning. Forty-nine primary caregivers were surveyed. Forty-three primary caregivers were mothers and six were fathers; their mean age was 34 years. The following measures were used: Beck Depression Inventory, Child Development Inventory, Caregiver Strain Index, Family Assessment Device, and Ways of Coping Checklist-Revised. The data show that caregiver burden is not related to the severity of the child's illness, but that caregivers report significant burden. Higher burden was associated with the use of palliative coping methods, and family functioning was problematic. The results of this study suggest that for parents of children with Joubert syndrome, degree of parental burden depends more on the parents' coping skills and the level of family functioning rather than on the degree of the child's impairment. These findings highlight the importance of assessing caregiver burden, as well as decreased family functioning or coping abilities, since these problems often can be managed with psychologic intervention. ( J Child Neurol 1999;14:642-648).
Neuropathology of Joubert Syndrome
Authors: Yachnis Anthony T. , Rorke Lucy B.
Published: January 2008

Very little documentation of the neuropathologic changes in Joubert syndrome exists. This paper presents a detailed postmortem neuropathologic study of a clinically and radiographically well-documented case of Joubert syndrome. In addition to aplasia of the cerebellar vermis and fragmentation of the dentate nuclei, there was marked dysplasia of structures at the pontomesencephalic junction and caudal medulla. There was abnormal decussation of the superior cerebellar peduncles and an enlarged iter (rostral 4th ventricle) with elongated tegmental nuclei (including the locus coeruleus). Neurons of the basis pontis and reticular formation appeared reduced. Extensive malformations of the medulla included hypoplasia of the inferior olivary nuclei, solitary nuclei and tracts, and the nucleus and spinal tracts of trigeminal nerve (cranial nerve V). Even more striking was dysplasia of the caudal medulla at the cervicomedullary junction, which was characterized by the absence of a posterior median sulcus, neuronal swelling and axonal spheroids in the region of malformed nuclei gracilis and cuneatus, and absence of pyramidal decussation. This study suggests that, in addition to vermal agenesis, Joubert syndrome is characterized by malformation of multiple brainstem structures. The latter could explain certain clinical features of the syndrome, including episodic hyperpnea and oculomotor apraxia. (J Child Neurol 1999;14:655-659).
Clinical Nosologic and Genetic Aspects of Joubert and Related Syndromes
Authors: Chance Phillip F. , Cavalier Laurent , Satran Daniel , Pellegrino Joan E. , Koenig Michel , Dobyns William B.
Published: January 2008

Joubert syndrome is an autosomal-recessive disorder characterized by cerebellar hypoplasia, hypotonia, developmental delay, abnormal respiratory patterns, and abnormal eye movements. The biochemical and genetic basis of Joubert syndrome is unknown and a specific chromosomal locus for this disorder has not been identified. Review of this disorder and related syndromes suggests that (1) hypoplasia of the cerebellar vermis in Joubert syndrome is frequently associated with a complex brain stem malformation represented as the "molar tooth sign" on magnetic resonance imaging, (2) the "molar tooth sign" could be present in association with the Dandy-Walker malformation and occipital encephalocele, (3) cerebellar hypoplasia is present in conditions related to Joubert syndrome such as Arima syndrome; Senior-Loken syndrome; cerebellar vermian hypoplasia, oligophrenia, congenital ataxia, coloboma, and hepatic fibrosis syndrome; and juvenile nephronophthisis due to NPH1 mutations, and (4) the brainstem-vermis malformation spectrum is probably caused by at least two and probably several genetic loci. We have ascertained previously a cohort of 50 patients with a putative diagnosis of Joubert syndrome in order to evaluate the presence of associated malformations, and to initiate studies leading to the identification of genes causing Joubert and related syndromes. Among the associated malformations found in patients ascertained as having Joubert syndrome, 8% of patients had polydactyly, 4% had ocular colobomas, 2% had renal cysts, and 2% had soft-tissue tumors of the tongue. The WNT1 gene has been tested as a candidate gene for Joubert syndrome based on its expression in the developing cerebellum and an associated mutation in the swaying mouse. A search for mutations in WNT1 in a series of patients with Joubert syndrome did not detect mutations at this locus. This analysis suggested that mutations in WNT1 might not have a significant role in Joubert syndrome, and other functional candidate genes related to development of the cerebellum need to be examined. A genome-wide linkage analysis carried out in 10 Joubert syndrome pedigrees did not identify a specific chromosomal locus for this disorder. This observation, along with those from clinical studies, provides further evidence that Joubert and related syndromes are genetically heterogeneous. ( J Child Neurol 1999;14:660-666).
Positron Emission Tomography Using [18F] Fluorodeoxyglucose and [ 11C] L-Methionine to Metabolically Characterize Dysembryoplastic Neuroepithelial Tumors
Authors: Kaplan Allen M. , Lawson Michael A. , Spataro Joseph , Bandy Daniel J. , Bonstelle Charles T. , Moss S. David , Manwaring Kim H. , Reiman Eric M.
Published: January 2008

Dysembryoplastic neuroepithelial tumors are unique and benign congenital tumors occurring frequently in children and adolescents. Differentiation from other low-grade tumors is important for management. Five patients with confirmed dysembryoplastic neuroepithelial tumors were studied with positron emission tomography using glucose and protein metabolic uptake in an attempt to categorize these tumors metabolically. Functional brain mapping also was obtained to aid in operative management. Results of the study conclude that dysembryoplastic neuroepithelial tumors, although having similar neuroimgaing characteristics to other low-grade tumors, are distinguished by a unique metabolic profile. They are inactive tumors with no significant glucose or protein metabolic activity. The combination of preoperative positron emission tomographic metabolic studies with functional brain mapping allowed for prediction of tumor type, defined eloquent areas of cortical function, and improved approach and resection of the tumors with minimal risk of neurologic impairment. ( J Child Neurol 1999;14:673-677).
Pyridoxine-Dependent Seizures in an Older Child
Authors: Yoshikawa Hideto , Abe Tokinari , Oda Yoshihiko
Published: January 2008

The case of a 12-year-old girl with pyridoxine-dependent seizures is reported. She developed status epilepticus just after birth and ordinary antiepileptic drugs were administered without effect. Her seizures ceased only on the administration of pyridoxine. Status epilepticus associated with the withdrawal of pyridoxine occurred three times, and ceased only after the renewed administration of pyridoxine. She now has mental retardation and mild spastic diplegia. The reported cases of pyridoxine-dependent seizures usually have been neonates and infants. Older patients were not fully investigated, and so we have reviewed these cases of pyridoxine-dependent seizures. As known previously, pediatricians should not forget that pyridoxine should be continued for life. ( J Child Neurol 1999;14:687-690).
Topical Review: Progressive Spinal Muscular Atrophies
Authors: Strober Jonathan B. , Tennekoon Gihan I.
Published: January 2008

Spinal muscular atrophy is the most common autosomal-recessive genetic disorder lethal to infants. It was first described in the 1890s. Since then our understanding of the disorder has progressed significantly. Progression of the disease is due to loss of anterior horn cells, thought to be caused by apoptosis. Diagnosis is based on the course of the illness, as well as certain changes seen on nerve and muscle biopsy and electrodiagnostic studies. More recently, our understanding of the genetics of this disorder has provided a noninvasive approach to diagnosis. This method of testing has its downside, but the quest for a more sensitive analysis is still underway. Even though our knowledge of this disease has come a long way since its first recognition, the therapies available to these children are still only supportive. Again, researchers eagerly look for new therapeutic interventions to allow for improved quality of life and an extended life span. (J Child Neurol 1999;14:691-695).
Treatment of Acquired Epileptic Aphasia With the Ketogenic Diet
Authors: Christina Bergqvist A.G. , Chee Claire M. , Lutchka Lisa M. , Brooks-Kayal Amy R.
Published: January 2008

Acquired epileptic aphasia remains a poorly understood entity, which is frequently difficult to treat. Previously described treatment modalities have included antiepileptic drugs, corticosteroids, intravenous immunoglobulin, and multiple subpial transections. We describe three patients with acquired epileptic aphasia refractory to traditional treatments who were successfully treated with the ketogenic diet. All three patients had lasting improvement of their language, behavior, and seizures for 26, 24, and 12 months, respectively. This is the first reported series of patients with acquired epileptic aphasia successfully treated with the ketogenic diet, and suggests a new therapeutic alternative for patients with this often difficult-to-treat disorder. ( J Child Neurol 1999;14:696-701).
Cranial Magnetic Resonance Imaging Examination of Normal Term Neonates: A Pilot Study
Authors: Holden Kenton R. , Titus M. Olivia , Van Tassel Pamela
Published: January 2008

This pilot study's aim was to determine, using magnetic resonance imaging (MRI), if and to what extent asymptomatic intracranial hemorrhage occurs in normal term neonates after uncomplicated vaginal deliveries. Eight normal, term, vaginally delivered infants and three cesarean-section deliveries used as controls underwent cranial MRI. No sedation was administered. Small subdural hematomas of the falx cerebri or tentorium cerebelli were found in half of those with an uneventful vaginal delivery. Pediatric follow-up, on average 3.9 years after the MRI study was performed, demonstrated normal growth and development. It appears that more data is needed to confirm the observation that the intracranial hemorrhages described should not be considered the etiology for neurologic abnormalities present in symptomatic neonates. ( J Child Neurol 1999;14:708-710).
Interstitial Deletion of 14q, 46, XY, del (14) (q24.3q32.1) Associated With Status Nonepileptic Myoclonia and Delayed Myelination
Authors: Ono Jiro , Kurahashi Hiroki , Okinaga Takeshi , Mano Toshiyuki , Imai Katsumi , Inui Koji , Okada Shintaro
Published: January 2008

A Japanese boy with interstitial deletion of the long arm of chromosome 14, including band 14q31, is described. The characteristic dysmorphic facial features, such as dolichocephaly, bushy eyebrows, horizontal narrow palpebral fissures, long philtrum, etc, and mental and motor developmental delay were observed. Other characteristic clinical manifestations were anuresis and status nonepileptic myoclonia. The finding of delayed myelination of the cerebral white matter was observed on magnetic resonance examination, suggesting that an unknown factor related to myelination in the central nervous system might be localized in band 14q31. ( J Child Neurol 1999;14:756-758).
SYSTEMS: School-Years Screening Test for the Evaluation of Mental Status
Authors: Ouvrier Robert , Hendy Julie , Bornholt Laurel , Black Fiona H.
Published: January 2008

This paper introduces the School-Years Screening Test for Evaluation of Mental Status (SYSTEMS). It was designed to be used by neurologists, pediatricians, and other health professionals assessing children with suspected cognitive problems or changes. SYSTEMS was initially based on the adult Mini-Mental State Examination developed by Folstein, Folstein, and McHugh in 1975. SYSTEMS is a 7- to 12-minute, one-on-one interview test containing 46 items for use in children between 5 and 12 years of age. Although a full diagnosis cannot be made, the results do provide an indication of whether to send a child for further detailed cognitive assessment. The development of SYSTEMS comprised seven studies with a total of 1207 children involved from Sydney primary schools and neurology clinics of the New Children's Hospital, Westmead, New South Wales, Australia. All children were administered the SYSTEMS. Some of the children also were administered the Stanford-Binet Intelligence Test, 4th edition, or the Differential Ability Scales. Results showed that the SYSTEMS was internally consistent, unbiased by sex, socioeconomic indicators, or language groups; discriminated well by age; and strongly correlated (r = 0.88) with mental age. No significant differences in results obtained by two trained administrators were evident and no indication of apparent practice effect was found. The SYSTEMS was found to have desirable levels of sensitivity (83% and 92%), specificity (76% and 95%), and likelihood ratio for cognitive impairment (3.63 and 17.5) when compared with neurologic judgments and the Differential Ability Scales, respectively. (J Child Neurol 1999; 14:772-780).
Treatment of Childhood Myoclonus With Botulinum Toxin Type A
Authors: Awaad Yasser , Tayem Hassan , Elgamal Ahmad , Coyne Martha F.
Published: January 2008

Because of inadequate response to or intolerable side effects of oral medication, nine patients with segmental, generalized, and focal myoclonus were treated with intramuscular botulinum toxin type A. All patients were evaluated with neuroimaging, routine and limb-monitored electroencephalography, electromyography, evoked potentials and appropriate biochemical studies. Patients were aged 2 to 22 years, with duration of myoclonus from 1 month to 10 years. Multiple medication trials included antiepileptic drugs, benzodiazepines, tryptophan, L-dopa/carbidopa, baclofen, and dantrolene. Patients were injected with botulinum toxin in their affected area with electromyographic guidance to affected muscles with different doses (8 to 20 units/kg), except two patients who were injected with 32 and 45 units/kg, respectively, at 4- to 8-month intervals. One patient did not complete botulinum toxin treatment because of subjective weakness, although there were virtually no side effects reported in patients completing therapy. Patients reported a dramatic reduction in painful myoclonus. In addition, patients exhibited improved functional skills, as demonstrated by markedly improved use of affected extremities and improvements in ambulation. One patient, who was nonambulatory prior to treatment, was able to walk afterward. Long-term benefits could be related to higher dosage used or negative feedback effect. (J Child Neurol 1999;14:781-786).
Differential Patterns of Executive Function in Children With Attention-Deficit Hyperactivity Disorder According to Gender and Subtype
Authors: Houghton Stephen , Douglas Graham , West John , Whiting Ken , Wall Melvyn , Langsford Shane , Powell Lesley , Carroll Annemaree
Published: January 2008

The present investigation examined differential patterns in executive functions of children with attention-deficit hyperactivity disorder (ADHD; no diagnosed comorbid disorders) according to subtype and gender, and identified instrumentation sensitive to executive function in children aged 6 to 12 years with ADHD. Data were obtained from 94 children diagnosed with ADHD (predominantly inattentive, n = 32, ADHD combined, n = 62), and from 28 controls. Participants with ADHD, who were unmedicated at the time of testing, were administered five tests of executive function (the Wisconsin Card Sorting Test, the Stroop Color-Word Test, the Matching Familiar Figures Test, the Trail Making Test, and the Tower of London). A two-way multivariate analysis of covariance with age as the covariate and subtype and gender as the independent variables was conducted on all of the tests administered. While children with ADHD predominantly inattentive and those with ADHD combined differed from controls, it was only the latter subtype that differed significantly in perseveration and response inhibition. The absence of diagnosed comorbidity in the children with ADHD at the time of test administration demonstrates that the impairments in executive function are clearly located in ADHD, particularly in the ADHD combined subtype, thus providing support for Barkley's proposed unifying theory of ADHD. (J Child Neurol 1999;14:801-805).
Molecular Approaches to the Rett Syndrome Gene
Authors: Schanen N. Carolyn
Published: January 2008

Rett syndrome is a neurodevelopmental disorder affecting 1 in 10,000 to 15,000 females worldwide. Apparently normal at birth, girls with Rett syndrome undergo developmental regression and acquire a neurologic and behavioral profile that has been used to define diagnostic criteria for the disorder. Neurochemical and anatomic alterations indicate that Rett syndrome appears to result from an arrest of normal neuronal maturation. Although Rett syndrome generally occurs sporadically, rare familial recurrences indicate a genetic basis for the disorder. Data from familial recurrences are consistent with an X-linked dominant locus causing the classic phenotype in female patients and a distinct, more severe phenotype in hemizygous male patients. Exclusion mapping data from rare kindreds with recurrent Rett syndrome localize the gene to the distal long arm of the X chromosome (Xq27.3-Xqter). (J Child Neurol 1999; 14:806-814).
Postictal Psychosis in a Child
Authors: Nissenkom Andreea , Moldavsky Maria , Lorberboym Mordechai , Raucher Alona , Bujanover Yoram , Lerman-Sagie Tally
Published: January 2008

Postictal psychoses are brief psychotic episodes that usually occur after poorly controlled partial complex seizure clusters. The psychosis commonly appears following a lucid interval, ranging from a few hours to days after seizure termination. An underlying structural brain abnormality is common and usually involves the temporal lobe. Postictal psychosis, while well known in adults, has not been described previously in children. We describe a 9-year-old boy with right hemiparesis due to a neonatal stroke, who developed a postictal schizophrenia-like psychosis following status epilepticus. Electroencephalography showed left-sided slowing. A brain computed tomographic scan and magnetic resonance imaging revealed left hemisphere hypoplasia. A 99mTc-ECD single photon emission computed tomographic scan of the brain revealed decreased left-hemisphere perfusion, most pronounced to the medial temporal lobe. The psychosis resolved gradually over 7 days without antipsychotic therapy. To the best of our knowledge, this is the first description of postictal psychosis in a child. ( J Child Neurol 1999; 14:818-819).
Phenobarbital Still Has a Role in Epilepsy Treatment
Authors: Lerman-Sagie Tally , Lerman Pinchas
Published: January 2008

Phenobarbital, the oldest of the currently available antiepileptic drugs, has lost its popularity in this era of multiple new drugs and is seldom used after infancy in developed countries. We report a group of patients with generalized epilepsy in whom phenobarbital proved to be the drug of choice. Phenobarbital monotherapy was given to 20 patients with idiopathic generalized epilepsy beginning in childhood but persisting into adulthood. All the patients have normal intelligence and neurologic status. The electroencephalogram has either been normal or showed generalized spike-wave discharges. All patients' seizures are fully controlled on once-a-day low-dose phenobarbital with no side effects. Attempts to discontinue the medication have led to recurrence of seizures. We believe that in patients with mild generalized tonic-clonic seizures phenobarbital could still be the drug of choice since it is cheap, safe, convenient, and effective. ( J Child Neurol 1999;14:820-821).
Restoring Cardiac Function: An Emerging Spectrum of Therapeutic Options
Authors: Kantrowitz Adrian
Published: January 2008

A spectrum of techniques for restoring cardiac function is emerging. Among patients with global congestive heart failure (CHF), cardiac transplantation may help a small minority for whom allografts are available; the total artificial heart may eventually benefit a larger number.

For patients with left-sided CHF, parallel-assist techniques maximally augment cardiac output. In-series techniques can help others without major arrhythmias and some residual cardiac output.

As compared with parallel assist, in-series methods offer lesser hemodynamic augmentation but greater intrinsic reliability and the possibility of deactivation of support for hours or days without increased risk. Additional advantages include simplicity of management and documented long-term clinical efficacy.
Thermedics' Approach to Ventricular Support Systems
Authors: Szycher M. , Clay W. , Gernes D. , Sherman C.
Published: January 2008

Temporary and permanent ventricular assist systems, developed by Thermedics, Inc., are described, including rationale, design, operation and surgical applications.

Clinical data are presented for pneumatically driven temporary left ventricular assist devices (LVAD). Usefulness of this device rests on the assumption that tissue of a weakened heart can recover if relieved for a time by an LVAD. The surgical implantation of an LVAD is reported in a case where the patient later received a heart transplant.

The concept and technology of the subsystems of a permanent ventricular assist system (VAS), now ready for preclinical trials, are discussed. Design of a low-speed, torque-motor driven blood pump is described. Details are presented on transcutaneous energy transmission by means of a transformer, one of whose coils is embedded under the skin. Though less efficient than percutaneous transmission, the method eliminates infection risk. Special types of polyurethanes are analyzed in respect to their biocompatibility. It is concluded that flocking of the polyurethane surface allows the growth of a biological lining which is highly antithrombogenic. Sintered metal powders are found to be most efficient for fabrication of rigid pump components. A lenticular pump design is proposed to solve the problem of pressure differentials in the sealed device.

Cardiac endocrine functions are cited in support of using assist devices that leave the heart in place.
Societal and Ethical Considerations of Artificial Hearts
Authors: Paquin Michael
Published: January 2008

The present state of artificial heart research and development is analyzed in light of public perceptions affected by accounts of the experiences of those who received the Jarvik-7.

On the assumption that research will continue, it is argued that the therapeutic goals of the artificial heart can be realized, and funding be obtained, only in an atmosphere of positive publicity. To this end, formation of an association of companies involved in artificial heart R & D is recommended. Such a group would articulate voluntary standards and produce reports of advances in the field. Artificial hearts, it is noted in conclusion, have been effective as temporary assist devices in patients destined to receive heart transplants.
Biocompatible Resins in Dentistry
Authors: Hammesfahr Paul D.
Published: January 2008

The evolution of treatment for dental disease has been keyed to developments in technology. Once the diseased tooth structure was removed, various materials were then utilized to restore health and function to the tooth. A major consideration must be the biocompatibility of the restorative materials—both to the vital process of the tooth, as well as the oral cavity. It has been generally accepted that calcium hydroxide containing products are the materials of choice to be placed in direct contact with the pulp, prior to placement of these restorative materials. As the demands on restorative materials became more defined, the requirements of the base materials also became greater. Due to the numerous desirable features of polymeric resins, the search for a biocompatible resin base system incorporating calcium hydroxide was initiated. PRISMA® VLC DYCAL® represents the first dental use of biocompatible resin in direct contact with vital tissue.
Biomaterials for the Dental Market
Authors: Cornell John
Published: January 2008

There are a number of products and improvements in existing products desired by the dental industries. However, it is important to realize that the dental marketing system is changing and uses different criteria than those which influenced the marketing in the last decade. More integrated systems are being marketed to the dentists, and the consumers are more interested in products which will help them maintain their teeth and gums. Fluoridation and other changes have helped in retaining the teeth, usually for the whole lifetime. This progress will change the way dentists practice, and will change the materials and equipment they need.
Softening of Thermoplastic Polyurethanes: A Structure/Property Study
Authors: Zdrahala Richard J. , Spielvogel David E. , Strand Marc A.
Published: January 2008

Softening of thermoplastic polyurethanes (TPU) in a simulated body environment (37°C n-saline) was studied as a function of composition, structure and resultant morphology of these ( AB) n type block copolymers. The structural variations were attempted by changing chemical composition and molecular weight of both hard A and soft B segments and their weight ratio in the polymer. In addition, the influence of bulk and/or surface modifiers, such as "reacted-in" polysiloxanes and fluorinated polyalkylether glycols, was also investigated.

The degree of softening, expressed as a percentage decrease of the elastic modulus (5% tensile modulus) upon two hours exposure to the testing environment, is significant, reversible and depends on the ratio of hard to soft segment and the extent of microphase separation. Since these parameters can be selected during the polymer synthesis and processing into desirable shapes, the degree of softening can thus be controlled. This softening at body temperature represents one of the most notable performance advantages of these biomaterials.
Advanced Biomaterials Development from "Natural Products"
Authors: Baier R.E.
Published: January 2008

Natural substances and structures can serve increasingly well as biomedical products, given recent advances in understanding of requirements for biocompatibility and of methods for their preservation and surface tailoring. A successful example is the derivation of limb salvaging vessels, used in arterial reconstructive surgery, from human umbilical cords. There are numerous opportunities for additional product development from the umbilical cords' main ingredient, Wharton's gel, ranging from biolubricants to wound-healing aids. Major problems yet to be overcome with natural starting materials are their propensity for calcification and eventual biodeterioration. Surface modification of biomaterials to exhibit desired degrees of interaction with contacting viable tissues promises the greatest beneficial results. General principles of bioadhesion have broad applicability, predicting material behavior in environments as diverse as blood, saliva, and seawater.
An Evaluation of Retrieved UHMWPE Hip Joint Cups
Authors: Kurth M. , Eyerer P. , Ascherl R. , Dittel K. , Holz U.
Published: January 2008

In this study it is demonstrated that the combined chemical and mechanical influences of the implant situation cause property changes of ultra-high-molecular-weight polyethylene (UHMWPE) hip joint cups. Nearly 250 loosened hip cups, retrieved 3 weeks to 14 years after implantation, were investigated. The clinical long-term behavior of various shaped polyethylene hip sockets are statistically analyzed. The main damage features were defined and described. Density measurements show a density increase with implantation time and a dependence of these changes from implant position and loading conditions. The rate of extractable constituents also increases with course of time. An increased in vivo conditioned oxidation of the UHMWPE can be demonstrated by infrared (IR) spectrometry. The density increase can be explained by post-crystallization, which is the result of oxidative chain scission. This leads to a reduction of the average molecular weight of the PE and to an increased extractability of constituents. Since these changes have been recognized as the reasons for aging and failing of UHMWPE, the methods of material characterization used in this study for retrieved implants will help to develop suitable in vitro testing and simulating methods. Characteristic damage features of hip cups allow direct relationships with construction characteristics and their improvement.
In vitro Release Characteristics of Hard Shell Capsule Products Coated with Aqueous- and Organic-Based Enteric Polymers
Authors: Murthy K.S. , Kubert Daniel A. , Fawzi Mahdi B.
Published: January 2008

In this article, an overview of the rationale for the use of enteric coated (EC) dosage forms is presented. The benefits and disadvantages inherent in the use of aqueous dispersions and organic solutions of the various polymers to generate these products are discussed. The comparative dissolution stability of a hard shell capsule product coated with enteric polymers applied as either aqueous dispersions, or as organic solutions, were assessed under accelerated conditions of storage. Polymethacrylic acid methacrylate copolymer, cellulose acetate phthalate (CAP) and polyvinyl acetate phthalate (PVAP), along with the corresponding commercially available aqueous dispersions, Eudragit® L30D, Aquateric®, and Coateric™, were employed in these studies as enteric polymers. Diethyl phthalate (DEP) was used as the plasticizer and procainamide HCl 250 mg capsules served as the substrate. Storage of the coated capsules at 37°C/80% RH and at 45°C for 2 months revealed that, while the stability of Eudragit® L30D coatings are comparable or superior to the corresponding organic-based coatings, Coateric™ films are markedly unstable when compared with PVAP coatings applied through the use of organic vehicles. After storage at 37°C/80% RH, Aquateric®-based capsules demonstrated stability comparable to CAP organic-based coatings only when a protective seal coat was present. The performance failures of the capsules that occur upon storage primarily result in a loss of gastric resistance. Scanning Electron Microscopy (SEM) and thermomechanical analysis (TMA) of the different coatings revealed differences in the film-forming properties of the polymer films and provide an explanation for the changes that occur during storage of the coated capsules.
Aliphatic Polyesters and Cellulose-Based Polymers for Controlled Release Applications
Authors: Chang Rong-Kun , Price James C.
Published: January 2008

The general technologies for fabricating drug delivery systems are briefly discussed in the present review. Furthermore, two types of commonly used polymers, biodegradable aliphatic polyesters for parenteral administration and cellulose-based polymers for oral uses, are presented by means of selected examples of their properties and applications to control drug release.
The Use of Silicone/Polyurethane Graft Polymers as a Means of Eliminating Surface Cracking of Polyurethane Prostheses
Authors: Pinchuk L. , Martin J.B. , Esquivel M.C. , Macgregor D.C.
Published: January 2008

The long-term biodegradation of various polyurethanes with and without surface modifications was evaluated by implanting small porous filamentous patches of these materials subcutaneously in the backs of dogs for one month. Data were compared to those obtained with spun polyurethane vascular grafts of similar materials implanted in the aorto-iliac position in dogs. The extremely high surface area of approximately 7 m2/cm3 of these porous filamentous patches provided numerous sites for surface cracking and the very fine filaments (10 microns in diameter) provided an easily identifiable structure to study the cracking phenomenon. Results from numerous one month implants clearly demonstrated that the subcutaneous implant model effectively reproduced the biodegradation behavior observed in vascular graft implants. The degradation was most pronounced in the softer Shore 80A polyurethanes and less pronounced in the harder 55D and 75D polyurethanes. The degradation could not simply be stopped by stress annealing the polyurethane and the degradation did not require the presence of metallic ions. Antioxidants, surface adsorbed albumin, poly(2-hydroxyethyl-methacrylate) grafting, silicone copolymerization, tetrafluoroethylene plasma discharge and the addition of urea linkages to the polymer were also shown to be ineffective in stopping the biodegradation process. In contrast, covalent bonding or grafting of silicone polymer to the surface of the urethane successfully inhibited the biodegradation process.
Permeability of PEUU Membranes: Their Modification Towards Blood Compatibility
Authors: Jayasree G. , Sharma Chandra P.
Published: January 2008

An attempt was made to develop haemodialysis membranes using polyether urethane urea synthesised in our laboratory. It was observed that the processing parameters such as precipitation medium, precipitation temperature etc. can influence the porosity of the membrane and subsequently the permeability property. It was also noted that the permeability of the dried membrane was negligible even though it was kept in distilled water overnight before use. The effect of pH on permeability through the membrane was studied by dialysis experiment using mixtures of various components such as urea, creatinine, uric acid, inulin, albumin, NaCl and KCI at various pH. Standard cellulose acetate (CA) membrane was used for comparison.

Membranes were also prepared using biomer solution by precipitating in distilled water at room temperature and the monomer, 2-hydroxy ethyl methacrylate (HEMA) was grafted onto it by glow discharge technique. It was found that the permeability was increased by HEMA grafting with some loss of tensile strength and strain.

A comparative study of fibrinogen adsorption during dialysis and adsorption by direct exposure of samples to a mixture containing urea, uric acid, creatinine, dextran, fibrinogen and electrolytes like sodium and potassium ions was also done with 125I labelled fibrinogen. Platelet adhesion studies indicated that the number of adhered platelets was less on the HEMA grafted samples which may enhance blood compatibility.

Finally, the membranes were subjected to different sterilization processes possible under wet conditions such as glutaraldehyde treatment and autoclaving. The contact angle, permeability, mechanical property and platelet adhesion studies indicated that the sterilization method can affect the performance of the membrane.
An Arterial Prosthesis from Argentina: The Barone Microvelour® Arterial Graft
Authors: Torcht Dominique , Guidoin Robert , Boyer Denis , Marceau Daniel , Marois Yves , Debille Elisabeth , Lacombe Jean , King Martin
Published: January 2008

The manufacture of a polyester vascular prosthesis in the southern hemisphere is a new development in the global dissemination of this maturing technology. Hence the recent introduction of the Barone Microvelour® arterial graft from Argentina has highlighted the need for a comparative in vitro and in vivo study to compare its structure and performance with that of existing commercial products. Following a series of laboratory tests and implantations as a thoracoabdominal bypass in dogs, the Barone Microvelour® has been identified as a strong graft constructed after the style of early weft-knitted designs. It provides an equivalent sequence and rate of healing to that of other polyester knitted grafts.
Mechanical Assistance in Cardiogenic Shock
Authors: Moulopoulos Spyridon D.
Published: January 2008

Cardiogenic shock following myocardial infarction or surgical interventions with extracorporeal circulation, not responding to conventional treatment, is an "intractable" condition, unless mechanical assistance is applied.

In today's practice mechanical assistance consists in counterpulsating an intraaortic balloon or, if this does not improve the condition, in using a left ventricle bypassing pump. In spite of the complexity of the procedures and the com. plications, a number of patients can recover with or without a subsequent corrective intervention or heart transplantation.

The need for developing systems for chronic assistance to non-correctable hearts and the difficulties of the endeavour are pointed out.
Antimicrobial Activity of Polymers Coated with Iodine-Complexed Polyvinylpyrrolidone
Authors: Kristinsson K.G. , Jansen B. , Treitz U. , Schumacher-Perdreau F. , Peters G. , Pulverer G.
Published: January 2008

Polymer-associated infection is a problem of increasing importance in modern medicine. In a new approach to prevent such infections we have modified polyvinylfluoride (TEDLAR) films by graft copolymerization with N-vinylpyrrolidone to which iodine can be complexed. Grafting reaction was performed by the preirradiation technique using an electron accelerator. Grafted films were then treated in Lugol's solution for at least 24 h. Release of free iodine from the films was determined either by titration or using the agar disc diffusion test, showing an iodine release for up to 4-5 days. The antimicrobial activity of the films was tested in bacterial adhesion measurements. Bacterial and fungal cells in the range of 103 to 106 cfu/cm2 polymer were found on control samples without iodine, whereas on iodine-complexed films no viable cells could be detected at least for 5 days or even longer. Thus, microbial adhesion and growth can be inhibited by iodine-containing polymers.
Factors Influencing Bacterial Adherence to Biomaterials
Authors: Merritt K. , Chang C.C.
Published: January 2008

The adherence of bacteria to implanted medical devices is believed to be important in the development of implant associated infections. Measures which reduce bacterial adherence should reduce the incidence of these infections. However, in order to assess the importance of adherence, the effectiveness of methods to reduce adherence, and compare data from different laboratories, the conditions of the in vitro studies on adherence need to be specified. There are currently no correct and incorrect methods, however, methods used need to be carefully described. The studies reported here indicate that the definition of adherence needs to be established, with the use of polystyrene as the reference material recommended. Since the adherent organisms lose adherence traits with culture, cultures must be selected for adherence regularly. It is important to control the number of organisms/ml but the volume used is not important. The medium used to grow the organisms and the use of stationary, rocking or flow conditions will alter adherence and need to be specified and be consistent within a set of experiments. Culture conditions, methods of rinsing the material, methods of elution and counting, or direct counting of organisms on the material need to be specified. Finally, as much information as possible on the bulk and surface properties of the material should be provided. The handling of the material for the experiments should be careful and defined. Fingerprints, contact with protein, wet surfaces vs dry surfaces, etc., will all affect the subsequent adherence. The materials should not be re-used since the removal of the adherent proteins or the biofilm is very difficult. Progress can be made in this important area if the details of procedures are specified.
Surface Properties and Platelet Reactivity of Segmented Poly(etherurethanes) and Poly(etherurethaneureas)
Authors: Kajiyama Tisato , Takahara Atsushi
Published: January 2008

Segmented poly(etherurethanes) (SPUs) and segmented poly-(etherurethaneureas) (SPUUs) with various hard and soft segment components were prepared. The surface characterization of SPUs and SPUUs in the air-equilibrated state and in the hydrated-state was carried out by means of X-ray photoelectron spectroscopic (XPS) and dynamic contact angle measurements. XPS revealed that in the air-equilibrated state, lower surface free energy components were enriched at the air-solid interface, whereas in the hydrated-state higher surface free energy components were enriched at the water-solid interface. The change in environment from air to water induced the surface reorganization in order to minimize interfacial free energy. The large contact angle hysteresis was observed for SPUs and SPUUs. This hysteresis can be mainly ascribed to the surface reorganization process. Platelet adhesion tests on SPU and SPUU surfaces indicated that the existence of surface microphase separated structure played an important role in the attainment of blood compatibility.
Titanium-Protein Interaction: Changes with Oxide Layer Thickness
Authors: Sunny M.C. , Sharma Chandra P.
Published: January 2008

Since titanium is being used for various biomedical applications requiring enhanced blood compatibility, which may be partly due to its extremely stable oxide layer, an attempt is made here to understand the effect of oxide layer thickness on protein adsorption. Different thickness of oxide layers have been coated on titanium foil using anodizing method and thickness of oxide layers deposited have been measured by an ellipsometer. Studies of competitive adsorption of proteins, using I125 labelled protein from a mixture of 25 mg% albumin, 15 mg% γ-globulin and 7.5 mg% fibrinogen indicate an increased adsorption of proteins onto the oxide layer coated surfaces compared to the bare surface.
In vivo Testing of a Biostable Polyurethane
Authors: Szycher Michael , Reed Andrew M. , Siciliano Arthur A.
Published: January 2008

At present all the commercially available "medical grade" urethane elastomers exhibit a phenomenon known as environmental stress cracking (ESC). This phenomenon is characterized by surface microcracking when the elastomer is elongated while in vivo. The degree of strain that is required to initiate microcracking varies from composition to composition. It has been found that harder compounds generally tend to have a higher strain threshold than corresponding softer ones.

We theorized that this degradation occurs when certain enzymes (present only in vivo) attack and break down the ether linkages that link the polymer molecules together. Those elastomers that contain more ether linkages (such as the softer compositions) appear to microcrack more easily than elastomers with fewer ether linkages (such as the harder ones).

The molecular composition of ChronoFlex™ urethane has been chosen so that the finished elastomer will be free of ether linkages; thus, it is expected to be immune from environmental stress cracking.
Testing Intelligent Wound Dressings
Authors: Palamand Shashi , Reed Andrew M. , Weimann Ludwig J.
Published: January 2008

While occlusive wound dressings help provide patients with moist wound healing to reduce pain and increase reepithelialization rate, the moisture vapor transmission rate (MVTR) of these dressings remains constant even though wound exudate levels may vary with time and from wound to wound. The clinician is therefore faced with exudate buildup in heavily exuding wounds and desiccation in lightly exuding wounds-a situation requiring frequent patient monitoring and dressing changes.

Am "intelligent" wound dressing would have the ability to automatically respond to a wound's exudate level by self-adjusting its MVTR to maintain a constant moist wound environment. Such a dressing could help ensure that exudate buildup or wound desiccation is reduced or avoided.

Three commercial wound dressings (hydrocolloid, thin film, and membrane laminate) were studied for their ability to alter their MVTR in response to varying moisture level. An efficient test methodology and experimental design was developed, which involved direct and indirect fluid contact with the dressings using two temperatures and two test methods.

One dressing, a membrane laminate, was found to exhibit intelligent MVTR behavior. Data is presented which shows this dressing's ability to adjust its MVTR nearly eight-fold as a function of hydration level. Information regarding the mechanism of action of this intelligent dressing is also presented.