Sonic hedgehog regulates growth and morphogenesis of the tooth

During mammalian tooth development, the oral ectoderm and mesenchyme coordinate their growth and differentiation to give rise to organs with precise shapes, sizes and functions. The initial ingrowth of the dental epithelium and its associated dental mesenchyme gives rise to the tooth bud. Next, the epithelial component folds to give the tooth its shape. Coincident with this process, adjacent epithelial and mesenchymal cells differentiate into enamel-secreting ameloblasts and dentin-secreting odontoblasts, respectively. Growth, morphogenesis and differentiation of the epithelium and mesenchyme are coordinated by secreted signaling proteins. Sonic hedgehog (Shh) encodes a signaling peptide which is present in the oral epithelium prior to invagination and in the tooth epithelium throughout its development. We have addressed the role of Shh in the developing tooth in mouse by using a conditional allele to remove Shh activity shortly after ingrowth of the dental epithelium. Reduction and then loss of Shh function results in a cap stage tooth rudiment in which the morphology is severely disrupted. The overall size of the tooth is reduced and both the lingual epithelial invagination and the dental cord are absent. However, the enamel knot, a putative organizer of crown formation, is present and expresses Fgf4, Wnt10b, Bmp2 and Lef1, as in the wild type. At birth, the size and the shape of the teeth are severely affected and the polarity and organization of the ameloblast and odontoblast layers is disrupted. However, both dentin- and enamel-specific markers are expressed and a large amount of tooth-specific extracellular matrix is produced. This observation was confirmed by grafting studies in which tooth rudiments were cultured for several days under kidney capsules. Under these conditions, both enamel and dentin were deposited even though the enamel and dentin layers remained disorganized. These studies demonstrate that Shh regulates growth and determines the shape of the tooth. However, Shh signaling is not essential for differentiation of ameloblasts or odontoblasts.

When is reduced-compression bandaging safe and effective?

During a one-year period 44 patients were treated with reduced-compression bandaging in the vascular unit at a district general hospital. Twenty patients with venous ulcers were referred from community leg ulcer clinics because they could not tolerate standard compression bandaging (group 1). A further 24 patients had mixed aetiology leg ulcers (group 2), and high-compression bandaging was not attempted because of significant peripheral vascular disease (ankle brachial pressure index < 0.8). Forty-two patients tolerated reduced-compression bandaging without discomfort or skin pressure changes. Healing was achieved in 32 patients (13 in group 1 and 19 in group 2). All non-healed ulcers were considered smaller at the time of final follow-up, and had less exudate. Reduced-compression bandaging has been shown to be effective and well tolerated by patients with venous ulcers who cannot comply with high-compression bandaging. With close supervision, it is safe to use in patients with significant peripheral vascular disease.

Variant Alzheimer's disease with spastic paraparesis and cotton wool plaques is caused by PS-1 mutations that lead to exceptionally high amyloid-beta concentrations

We describe 3 new families affected by Alzheimer's disease with spastic paraparesis. In affected individuals, including the earliest known patient with this clinical syndrome, neuropathological examination revealed large "cotton wool" plaques similar to those we have previously described in a Finnish family. In the families in which DNA was available, presenilin-1 mutations were observed. Transfection of cells with these mutant genes caused exceptionally large increases in secreted Abeta42 levels. Furthermore, brain tissue from individuals with this syndrome had very high amyloid-beta concentrations. These findings define the molecular pathogenesis of an important subgroup of Alzheimer's disease and have implications for the pathogenesis of the disease in general.

Outcomes of weight-based heparin dosing based on literature guidelines and institution individualization

STUDY OBJECTIVE

To determine whether unfractionated heparin is optimally dosed using published weight-based guidelines.

DESIGN

Six-month, prospective study.

SETTING

University hospital.

PATIENTS

Ninety-six patients in the weight-based unfractionated heparin-dosing group 1 (WBHD1; 37 men; mean age 66.9 +/- 15.1 years; mean weight 80.1 +/- 20.6 kg) and 68 patients in the WBHD2 (25 men; mean age 68.2 +/- 15.6 years; mean weight 82.0 +/- 19.6 kg).

INTERVENTIONS

The WBHD1 received a 100-U/kg intravenous bolus followed by an 18-U/kg/hour continuous intravenous infusion. After 3 months, the protocol was modified, and the WBHD2 received a 90-U/kg bolus followed by a 16-U/kg/hour continuous infusion for 3 months.

MEASUREMENTS AND MAIN RESULTS

Activated partial thromboplastin times (aPTTs), frequency of bleeding episodes that required blood transfusions, and the number of recurrent thromboembolic events were collected from both groups after 3 months on the study. In the WBHD1, 24 hours after starting heparin, 38.5% of patients had therapeutic aPTTs, and at 48 hours, 54.3% were therapeutic. In the WBHD2, 42.6% and 51.4% of patients had therapeutic aPTTs at 24 and 48 hours, respectively. There was no statistical difference between the WBHD1 and WBHD2 in the percentage of patients with therapeutic aPTTs.

CONCLUSIONS

Weight-based heparin dosing resulted in low percentages of patients with therapeutic aPTTs. The use of weight alone to dose heparin may not be adequate to optimize therapy.

Prospective long-term study of vagus nerve stimulation for the treatment of refractory seizures

PURPOSE

To determine the long-term efficacy of vagus nerve stimulation (VNS) for refractory seizures. VNS is a new treatment for refractory epilepsy. Two short-term double-blind trials have demonstrated its safety and efficacy, and one long-term study in 114 patients has demonstrated a cumulative improvement in efficacy at 1 year. We report the largest prospective long-term study of VNS to date.

METHODS

Patients with six or more complex partial or generalized tonic-clonic seizures enrolled in the pivotal EO5 study were prospectively evaluated for 12 months. The primary outcome variable was the percentage reduction in total seizure frequency at 3 and 12 months after completion of the acute EO5 trial, compared with the preimplantation baseline. Subjects originally randomized to low stimulation (active-control group) were crossed over to therapeutic stimulation settings for the first time. Subjects initially randomized to high settings were maintained on high settings throughout the 12-month study.

RESULTS

The median reduction at 12 months after completion of the initial double-blind study was 45%. At 12 months, 35% of 195 subjects had a >50% reduction in seizures, and 20% of 195 had a >75% reduction in seizures.

CONCLUSIONS

The efficacy of VNS improves during 12 months, and many subjects sustain >75% reductions in seizures.

The impact of race on freedom from prostate-specific antigen failure in prostate cancer patients treated with definitive radiation therapy

Many studies have reported that African-American men have the highest incidence and mortality rates for prostate cancer in the United States. A retrospective analysis of 607 patients treated with definitive radiation therapy was performed at the University of California San Francisco and its affiliated hospitals between 1987 and 1995. The patient population analyzed included African-American, Caucasian, and Asian men with AJCC T1-T3 disease. Race, Gleason score, pretreatment prostate-specific antigen levels, stage, and treatment delivery were all evaluated. The percent free from PSA failure at 48 months for African-American, Caucasian, and Asian men were 53%, 59%, and 53%, respectively. There was no difference among the three races or for any of the pairwise comparisons. Gleason score and stage of disease were each independent predictors of outcome, but race was not associated with remaining free from PSA failure. These results are similar to those recently reported in the literature from centers of excellence across the United States.

Rabies virus entry at the neuromuscular junction in nerve-muscle cocultures

Early events in rabies virus entry into neurons were investigated in chick spinal cord-muscle cocultures. Rabies virus (CVS strain) was adsorbed to the surface of cells in the cold. At times up to 10 min of warming to 37 degrees C, virus was most intensely localized to dense swellings on the myotube surface. Texas Red-labeled alpha-bungarotoxin, which binds to nicotinic acetylcholine receptors, colocalized precisely with virus at the densities identifying these regions as neuromuscular junctions. Rabies virus also colocalized in the junctions with synapsin I, a marker for synaptic vesicles. The endosome tracers Lucifer Yellow, Texan Red-dextran, and rhodamine-wheat germ agglutinin were added to the cultures at the end of the virus adsorption period and the cultures were warmed. At 10 min, rabies virus and tracers colocalized at neuromuscular junctions and nerve terminals. At 30 min, rabies virus and tracers showed more intense fluorescence over nerve fibers and nerve cell bodies. At 60 min, nerve terminals, nerve fibers, and nerve cell bodies showed intense fluorescence and colocalization for rabies virus and tracers. LysoTracker Red, a marker for acidic compartments, colocalized with rabies virus at nerve-muscle contacts. These findings show that in nerve-muscle cocultures, the neuromuscular junction is the major site of entry into neurons. Colocalization of virus and endosome tracers within nerve terminals indicates that virus resides in an early endosome compartment, some of which are acidified. The progressive increase of virus and tracers in nerve fibers and nerve cell bodies over time is consistent with retrograde transport of endocytosed virus from the motor nerve terminal.

Scintigraphy in the foot and ankle

Nuclear medicine provides a number of sensitive, although unfortunately not always specific techniques, for the evaluation of foot pain and suspected infection. In most patients the 3 phase bone scan is the initial means of evaluation, with a labeled white cell scan included when osteomyelitis is suspected. Nuclear medicine studies must be interpreted with knowledge of the patient's history and symptoms and with close correlation to plain film findings. Attention to detail when acquiring images, possibly with the addition of SPECT or pinhole images in difficult patients, results in excellent anatomic localization in most patients.

Job satisfaction in a rural differentiated-practice setting

This article reports the findings of a 3-year study that assessed the job satisfaction of nursing personnel in a rural nursing center that uses a differentiated practice model. Job satisfaction was measured using the Brayfield Job Satisfaction Questionnaire, the McCloskey/Mueller Satisfaction Survey, and the Job Descriptive Index. A high level of job satisfaction was found across all 3 years. Factors associated with job satisfaction are also described. The findings of this study add to the growing body of literature on the importance of differentiated practice in creating satisfying work environments.

A suicide prevention advisory group at an academic medical center

During a 15-month period, there were seven suicides among patients who were in active treatment or who had been seen recently by providers in the Department of Psychiatry of Tripler Army Medical Center, Honolulu, Hawaii. As a result, a Suicide Prevention Advisory Group was formed to identify possible causes and make recommendations aimed at improving the identification and treatment of suicidal patients. The group made 11 specific recommendations. No known suicides occurred during the 22 months after the implementation of the Suicide Prevention Advisory Group's recommendations.

Molecular characterization and pathogenesis of transmissible gastroenteritis coronavirus (TGEV) and porcine respiratory coronavirus (PRCV) field isolates co-circulating in a swine herd

TGEV replicates in intestinal enterocytes and causes diarrhea in young pigs. PRCV, a spike (S) gene deletion mutant of TGEV with an altered respiratory tissue tropism, causes mild or subclinical respiratory infections. Comparisons of TGEV and PRCV strains suggest that tropism and pathogenicity are influenced by the S gene and ORF3, respectively. Recently, outbreaks of TGE of reduced virulence were reported in the field. We investigated a similar suspect TGEV outbreak of reduced virulence in nursery pigs from a swine herd in the Midwest. A TGEV strain (BW021898B) was isolated in swine testicular cells from gut contents of a diarrheic pig and three PRCV strains (BW126, BW154, BW155) were isolated from nasal swabs from normal TGEV-seronegative sentinel pigs in contact with the diarrheic pigs. Sequence analysis of the TGEV isolate in the partial S gene and ORF3/3a and ORF3-1/3b revealed high homology with enteropathogenic TGEV strains. Gnotobiotic pig inoculation and histopathological results revealed that this TGEV isolate retained virulence even though in the field outbreak the diarrheal disease was of reduced severity. Sequence analysis of the S gene deletion region of the three PRCV isolates revealed identical deletions between nt 105-752, which differ from deletions previously reported among PRCV strains. The three PRCV isolates had variable sequence changes in ORF 3/3a and ORF 3-1/3b, affecting the ORF size and amino acid sequence. Thus, sequence analysis and pathogenicity studies indicate that this TGEV isolate resembles other enteropathogenic TGEV strains. Therefore, the reduced severity of TGE observed in this herd may be due to the ongoing PRCV infections, which induce antibodies cross-reactive with TGEV and result in decreased disease severity. The results outlined in this study highlight the need to monitor the molecular epidemiology of TGEV/PRCV strains with sensitive differential diagnostic assays, followed by sequence analysis of the critical regions to identify changes and pathogenicity studies to confirm the disease potential of the TGEV isolates.

Loss of chromosome 10 is an independent prognostic factor in high-grade gliomas

Loss of heterozygosity (LOH) for chromosome 10 is the most frequent genetic abnormality observed in high-grade gliomas. We have used fluorescent microsatellite markers to examine a series of 83 patients, 34 with anaplastic astrocytoma (grade 3) and 49 with glioblastoma multiforme (grade 4), for LOH of chromosome 10. Genotype analysis revealed LOH for all informative chromosome 10 markers in 12 (35%) of patients with grade 3 and 29 (59%) grade 4 tumours respectively, while partial LOH was found in a further eight (24%) grade 3 and ten (20%) grade 4 tumours. Partial LOH, was confined to the long arm (10q) in six and the short arm (10p) in three cases, while alleles from both arms were lost in four cases. Five tumours (one grade 3 and four grade 4) showed heterogeneity with respect to loss at different loci. There was a correlation between any chromosome 10 loss and poorer performance status at presentation (chi2 P = 0.005) and with increasing age at diagnosis (Mann-Whitney U-test P = 0.034) but not with tumour grade (chi2 p= 0.051). A Cox multivariate model for survival duration identified age (proportional hazards (PH), P= 0.004), grade (PH, P= 0.012) and any loss of chromosome 10 (PH, P= 0.009) as the only independent prognostic variables. Specifically, LOH for chromosome 10 was able to identify a subgroup of patients with grade 3 tumours who had a significantly shorter survival time. We conclude that LOH for chromosome 10 is an independent, adverse prognostic variable in high-grade glioma.

Dealing with drug-seeking patients: the Tripler Army Medical Center experience

Patients who exhibit drug-seeking behavior are a chronic problem in most health care delivery settings. In June 1996, Tripler Army Medical Center, a tertiary care hospital serving approximately 300,000 beneficiaries, implemented a sole provider program to identify and help such patients. A multidisciplinary sole provider team assigns a sole provider to identified drug seekers. Twice a year, the team scans a printout of all prescriptions for controlled substances to identify suspicious drug usage patterns. The team also accepts referrals from health care providers. This article describes the program and reports on results, problems encountered, and steps taken to improve its efficacy.

The retroperitoneal approach to unusual abdominal aortic aneurysms

A retroperitoneal approach was used to repair an infrarenal abdominal aortic aneurysm in three patients. The technique was used because of unusual pathology obscuring the aneurysm neck. We discuss the technique of retroperitoneal exposure and suggest advantages over conventional transperitoneal repair in patients with uncomplicated infrarenal abdominal aortic aneurysm.