A cellular lineage analysis of the chick limb bud.

The chick limb bud has been used as a model system for studying pattern formation and tissue development for more than 50 years. However, the lineal relationships among the different cell types and the migrational boundaries of individual cells within the limb mesenchyme have not been explored. We have used a retroviral lineage analysis system to track the fate of single limb bud mesenchymal cells at different times in early limb development. We find that progenitor cells labeled at stage 19-22 can give rise to multiple cell types including clones containing cells of all five of the major lateral plate mesoderm-derived tissues (cartilage, perichondrium, tendon, muscle connective tissue, and dermis). There is a bias, however, such that clones are more likely to contain the cell types of spatially adjacent tissues such as cartilage/perichondrium and tendon/muscle connective tissue. It has been recently proposed that distinct proximodistal segments are established early in limb development; however our analysis suggests that there is not a strict barrier to cellular migration along the proximodistal axis in the early stage 19-22 limb buds. Finally, our data indicate the presence of a dorsal/ventral boundary established by stage 16 that is inhibitory to cellular mixing. This boundary is demarcated by the expression of the LIM-homeodomain factor lmx1b.

Genetic mapping of a 17q chromosomal region linked to obesity phenotypes in the IRAS family study.

OBJECTIVE: Obesity is widely accepted to be influenced by both environmental and genetic factors. Several recent studies have used the positional cloning approach in an attempt to discover genes contributing to obesity. In the IRAS Family Study a genomewide scan was performed on 1425 individuals of Hispanic descent (90 extended pedigree families) to identify regions of the genome linked to obesity phenotypes. METHODS: Nonparametric QTL linkage analysis was performed using a variance components approach. The genome scan was performed in two phases: an initial genome scan in 45 families and a replication scan in 45 families. Fine mapping and candidate gene analyses were also performed. General estimating equations (GEE1) and quantitative pedigree disequilibrium tests (QPDT) were used for association analysis of single SNP and haplotype data. RESULTS: Evidence for linkage to obesity traits was observed in each scan on the long arm of chromosome 17. When data from both scans was combined, a region on chromosome 17q was identified with evidence of linkage to visceral adipose tissue (VAT; LOD 3.11), waist circumference (WAIST) (LOD 2.5) and body mass index (BMI) (LOD 2.81). Nine additional microsatellite markers were identified and genotyped on all Hispanic individuals, with a mean marker density of approximately 1 marker/3 cM. Evidence of linkage remained significant with LOD 3.05 for VAT, LOD 2.44 for BMI and LOD 1.92 for WAIST. Fine mapping analyses suggest the possibility of two different obesity loci. In addition, the LOD - 1 interval of the major VAT peak decreased from 83-108 to 95-111 cM. Three positional candidate genes under the peak: somatostatin receptor 2 (SSTR2), galanin receptor 2 (GALR2), and growth hormone bound protein receptor 2 (GRB2) were chosen for detailed evaluation. Multiple polymorphisms within each candidate were genotyped and tested for association with the obesity phenotypes. Little evidence of association was detected between polymorphisms and obesity traits. CONCLUSION: In conclusion, replication of linkage and fine mapping suggest that a region on chromosome 17q contains a gene (or genes) that contributes to the genetic etiology of obesity with the strongest evidence for linkage to VAT. Candidate genes in the region do not appear to account for the evidence of linkage. Additional studies are necessary to identify the obesity-related polymorphisms.

A thorn in the side.

This case demonstrates the importance of a thorough secondary survey in the management of ballistic injury. It also illustrates the need for systematic use of radiology, and the early management of life threatening conditions--regardless of whether their cause is known.

Optimum trephine length in the assessment of bone marrow involvement in patients with diffuse large cell lymphoma.

BACKGROUND: The National Cancer Institute has recommended a bone marrow biopsy length of >/=20 mm for the staging and surveillance of patients with non-Hodgkin's lymphoma. However, there are few published data to support this recommendation, particularly the role of examining multiple levels. PATIENTS AND METHODS: Bone marrow biopsies from 172 patients with newly diagnosed diffuse large cell lymphoma (DLCL) entered in two consecutive trials of the Australasian Leukaemia and Lymphoma Group were analysed. The original haematoxylin and eosin-stained trephine biopsy and two or more deeper sections cut at 0.1-0.2 mm intervals were assessed with respect to the morphology, extent and pattern of lymphomatous involvement. The rate of positive diagnosis was correlated with the length of the biopsy specimen and the number of sections examined. RESULTS: Forty-seven biopsies (27%) demonstrated marrow involvement on examination of a mean of four trephine biopsy sections. The rate of positivity increased with the examination of multiple levels and correlated with increasing trephine length but was not dependent on the number of sites sampled. Twenty per cent of biopsies <20 mm in length were positive for lymphoma; this increased to 35% for biopsies >/=20 mm (P = 0.023). CONCLUSIONS: Morphological bone marrow involvement in DLCL is optimally demonstrated by a 20-mm long trephine biopsy from a single site which is examined at multiple levels (four or more). This obviates the need for bilateral sampling, thereby reducing patient morbidity from the procedure. This study provides evidence to support the National Cancer Institute recommendations regarding trephine biopsy in the staging of DLCL, providing multiple levels are examined.

Diffuse large cell lymphoma and t(8;22) (q24;q11) in a patient with idiopathic CD4+ T-lymphopenia.

We describe a unique case of a patient with a three-year history of idiopathic CD4(+) T cell lymphopenia (HIV negative) who presented with stage IV diffuse large cell non Hodgkin's lymphoma with t(8;22). Despite the severe lymphopenia, the patient tolerated intensive chemotherapy well and at 18 months, remains in complete remission.

Correlation between psychometric test scores and learning tying of surgical reef knots.

We have investigated the correlation between the scores attained on a computerised psychometric test, measuring psychomotor aptitude and learning tying of a surgical reef knot. Fifteen surgical trainees performed a test of psychomotor aptitude (ADTRACK 2) from the MICROPAT testing system. They then performed a simple test of their ability to tie a surgical reef knot and were assessed by a panel of experts prior to embarking on a standardised course of instruction and practice session. The knot-tying test was repeated at the end of the day and the differences in average scores recorded. There was a significant correlation between the means of the differences in knot tying scores and ADTRACK 2 scores (r = -0.533, P < 0.05). Psychomotor abilities appear to be determinants of trainees' initial proficiency in learning to tie a surgical reef knot.

Developmental toxicity of lead-contaminated sediment to mallard ducklings.

Sediment ingestion has been identified as an important exposure route for toxicants in waterfowl. The toxicity of lead-contaminated sediment from the Coeur d'Alene River Basin (CDARB) in Idaho was examined on posthatching development of mallard (Anas platyrhynchos) ducklings for 6 weeks. Day-old ducklings received either untreated control diet, clean sediment (24%) supplemented control diet, CDARB sediment (3,449 microg/g lead) supplemented diets at 12% or 24%, or a positive control diet containing lead acetate equivalent to that found in 24% CDARB. The 12% CDARB diet resulted in a geometric mean blood lead concentration of 1.41 ppm (WW) with over 90% depression of red blood cell ALAD activity and over threefold elevation of free erythrocyte protoporphyrin concentration. The 24% CDARB diet resulted in blood lead of 2.56 ppm with over sixfold elevation of protoporphyrin and lower brain weight. In this group the liver lead concentration was 7.92 ppm (WW), and there was a 40% increase in hepatic reduced glutathione concentration. The kidney lead concentration in this group was 7.97 ppm, and acid-fast inclusion bodies were present in the kidneys of four of nine ducklings. The lead acetate positive control group was more adversely affected in most respects than the 24% CDARB group. With a less optimal diet (mixture of two thirds corn and one third standard diet), CDARB sediment was more toxic; blood lead levels were higher, body growth and liver biochemistry (TBARS) were more affected, and prevalence of acid-fast inclusion bodies increased. Lead from CDARB sediment accumulated more readily in duckling blood and liver than reported in goslings, but at given concentrations was generally less toxic to ducklings. Many of these effects are similar to ones reported in wild mallards and geese within the CDARB.

Developmental toxicity of lead-contaminated sediment in Canada geese (Branta canadensis).

Sediment ingestion has recently been identified as an important exposure route for toxicants in waterfowl. The effects of lead-contaminated sediment from the Coeur d'Alene River Basin (CDARB) in Idaho on posthatching development of Canada geese (Branta canadensis) were examined for 6 wk. Day-old goslings received either untreated control diet, clean sediment (48%) supplemented control diet, or CDARB sediment (3449 microg/g lead) supplemented diets at 12%, 24%, or 48%. The 12% CDARB diet resulted in a geometric mean blood lead concentration of 0.68 ppm (ww), with over 90% depression of red blood cell ALAD activity and over fourfold elevation of free erythrocyte protoporphyrin concentration. The 24% CDARB diet resulted in blood lead of 1.61 ppm with decreased hematocrit, hemoglobin, and plasma protein in addition to the effects just described. The 48% CDARB diet resulted in blood lead of 2.52 ppm with 22% mortality, decreased growth, and elevated plasma lactate dehydrogenase-L (LDH-L) activity. In this group the liver lead concentration was 6.57 ppm (ww), with twofold increases in hepatic lipid peroxidation (thiobarbituric acid-reactive substances, TBARS) and in reduced glutathione concentration; associated effects included elevated glutathione reductase activity but lower protein-bound thiols concentration and glucose-6-phosphate dehydrogenase (G-6-PDH) activity. The kidney lead concentration in this group was 14.93 ppm with subacute renal tubular nephrosis in one of the surviving goslings. Three other geese in this treatment group exhibited calcified areas of marrow, and one of these displayed severe chronic fibrosing pancreatitis. Lead from CDARB sediment accumulated less readily in gosling blood and tissues than reported in ducklings but at given concentrations was generally more toxic to goslings. Many of these effects were similar to those reported in wild geese and mallards within the Coeur d'Alene River Basin.

Teleteaching--a practical and economical method of delivering surgical education.

The Plymouth Regional MRCS Course was initiated in 1997 to support the College STEP learning course and supplement the BST clinical training programmes. The course is a comprehensive fortnightly day-release scheme, covering, over one year in 21 full days of teaching, the entire MRCS syllabus in a structured programme of learning.

Propofol anesthesia for invasive procedures in ambulatory and hospitalized children: experience in the pediatric intensive care unit.

OBJECTIVES: To describe our experience with propofol anesthesia to facilitate invasive procedures for ambulatory and hospitalized children in the pediatric intensive care unit (PICU) setting. METHODS: We retrospectively reviewed the hospital records of 115 children who underwent 251 invasive procedures with propofol anesthesia in our multidisciplinary, university-affiliated PICU during a 20-month period. All patients underwent a medical evaluation and were required to fast before anesthesia. Continuous monitoring of the patient's cardiorespiratory and neurologic status was performed by a pediatric intensivist, who also administered propofol in intermittent boluses to obtain the desired level of anesthesia, and by a PICU nurse, who provided written documentation. Data on patient demographics, procedures performed, doses of propofol used, the occurrence of side effects, induction time, recovery time, and length of stay in the PICU were obtained. RESULTS: Propofol anesthesia was performed successfully in all children (mean age, 6.4 years; range, 10 days to 20.8 years) who had a variety of underlying medical conditions, including oncologic, infectious, neurologic, cardiac, and gastrointestinal disorders. Procedures performed included lumbar puncture with intrathecal chemotherapy administration, bone marrow aspiration and biopsy, central venous catheter placement, endoscopy, and transesophageal echocardiogram. The mean dose of propofol used for induction of anesthesia was 1.8 mg/kg, and the total mean dose of propofol used was 8.8 mg/kg. In 13% of cases, midazolam also was administered but did not affect the doses of propofol used. The mean anesthesia induction time was 3.9 minutes, and the mean recovery time from anesthesia was 28.8 minutes for all patients. The mean PICU stay for ambulatory and ward patients was 140 minutes. Hypotension occurred in 50% of cases, with a mean decrease in systolic blood pressure of 25%. The development of hypotension was not associated with propofol doses, the concomitant use of midazolam, or the duration of anesthesia, but was associated with older patient age. Hypotension was transient and not associated with altered perfusion. Intravenous fluid was administered in 61% of the cases in which hypotension was present. Respiratory depression requiring transient bag-valve-mask ventilation occurred in 6% of cases and was not associated with patient age, propofol doses, concomitant use of midazolam, or the duration of anesthesia. Transient myoclonus was observed in 3.6% of cases. Ninety-eight percent of procedures were completed successfully, and no procedure failures were considered secondary to the anesthesia. Patients, parents, and health care providers were satisfied with the results of propofol anesthesia. CONCLUSIONS: Propofol anesthesia can safely facilitate a variety of invasive procedures in ambulatory and hospitalized children when performed in the PICU and is associated with short induction and recovery times and PICU length of stay. Hypotension, although usually transient, is common, and respiratory depression necessitating assisted ventilation may occur. Therefore, appropriate monitoring and cardiorespiratory support capabilities are essential. Propofol anesthesia in the PICU setting is a reasonable therapeutic option available to pediatric intensivists to help facilitate invasive procedures in ambulatory and hospitalized children.

The hypnic ("alarm clock") headache syndrome.

Hypnic headache syndrome is a rare, sleep-related, benign headache disorder. We report 19 new cases (84% females) with follow-up data. The mean age at headache onset was 60.5 +/- 9 years (range 40-73 years). Headache awakened the patients from the night's sleep at a consistent time, usually between 1.00 and 3.00 a.m. (63%); three patients (16%) reported that identical headaches could occur also during daytime naps. Headache frequency was high, occurring more than 4 nights/week in 68% of the patients. Headache resolution occurred within 2 h in 68% of patients. Neurologic examination, laboratory studies, and brain imaging were unrevealing at the time of diagnosis. Headache severity largely remains unchanged or attenuates over time, but frequency may vary in either direction. Only one patient had spontaneous relief from headache. Four patients (24%) achieved permanent suppression of headache with medication, and two were able to abort individual headache attacks. Caffeine in a tablet or beverage was helpful in four patients. Lithium carbonate therapy caused side effects requiring cessation of treatment in four patients.

A family practice residency cervical screening project: perceived screening barriers.

BACKGROUND AND OBJECTIVES: A community-based family practice residency program initiated a cervical screening project to provide free Pap smears to women who had not had one in 3 years. The research identified reasons why patients had not been screened within the past 3 years. METHODS: A total of 214 consecutive participants in the free Pap smear clinic completed questionnaires. The questionnaire asked about reasons why screening had not occurred over the last 3 years. RESULTS: Altogether, 65.4% of the study group reported cost-related factors as barriers to participation; 37.9% cited either scheduling concerns, fear, or embarrassment; and 36% cited misinformation issues about either screening recommendations, effectiveness of treatment, or disease presentation. CONCLUSIONS: Strategies to increase participation in Pap smear screening clinics may include increasing availability of free or low-cost screening examinations, increasing time efficiency and scheduling flexibility of examinations, and making efforts to mitigate the fear and embarrassment associated with the exam.

Activation of the 43 kDa inositol polyphosphate 5-phosphatase by 14-3-3zeta.

The 43 kDa inositol polyphosphate 5-phosphatase (5-phosphatase) hydrolyzes and thereby inactivates the second messenger molecules inositol 1,4,5-trisphosphate -Ins(1,4,5)P3- and inositol 1,3,4,5-tetrakisphosphate in a signal terminating reaction. Recent studies have shown that the platelet protein pleckstrin forms a complex with the 43 kDa 5-phosphatase and activates Ins(1,4,5)P3 hydrolysis 2-fold [Auethavekiat, V., Abrams, C. S., & Majerus, P. W. (1997) J. Biol. Chem. 272, 1786-1790]. We now show that another platelet protein, 14-3-3zeta, forms a complex with the 43 kDa 5-phosphatase and thereby activates the hydrolysis of Ins(1,4,5)P3. Both pleckstrin and 14-3-3zeta contain one or more pleckstrin-homology domains, both are present in platelet cytosol, and both dimerize and form complexes with other signalling proteins. Purified platelet pleckstrin and 14-3-3zeta enhanced the rate of the hydrolysis of Ins(1,4,5)P3 by the 43 kDa 5-phosphatase 1.9- and 3.8-fold, respectively, but did not activate the 75 kDa 5-phosphatase. We have demonstrated that the mechanism of 5-phosphatase activation by 14-3-3zeta results from specific complex formation between the 43 kDa 5-phosphatase and 14-3-3zeta. Recombinant 43 kDa 5-phosphatase bound to recombinant glutathione S-transferase (GST)/14-3-3zeta fusion protein, but not GST alone, immobilized on glutathione-Sepharose. A potential 14-3-3 binding motif was located in the 43 kDa, but not the 75 kDa, 5-phosphatase. The motif "363RSESEE" is present in close proximity to the proposed catalytic domain of the 43 kDa 5-phosphatase. A synthetic peptide corresponding to the putative 14-3-3 binding motif demonstrated specific, saturable binding to purified 125I-14-3-3, with a Kd of 92 nM. In addition, platelet cytosolic 5-phosphatase bound to recombinant 14-3-3zeta immobilized on glutathione-Sepharose. Thus, 14-3-3zeta serves in human platelets to activate the 43 kDa 5-phosphatase and may thereby function to prevent generation of Ins(1,4,5)P3 -mediated calcium release in unstimulated platelets.

Regulation of second messengers by the inositol polyphosphate 5-phosphatases.

The inositol polyphosphate 5-phosphatases are an enlarging family of enzymes that terminate the signals generated by the phosphoinositide kinases and phospholipase C. Given the diverse signalling functions of both the polyphosphoinositides and Ins(1,4,5)P3, it is predicted that the 5-phosphatases will play a critical role in regulating many cellular events, in particular membrane trafficking and cell growth.

An overview of the diagnosis and pharmacologic treatment of migraine.

Migraine, an episodic headache disorder, is one of the most common complaints encountered by primary-care physicians and neurologists. Nevertheless, it remains underdiagnosed and undertreated. Rational migraine treatment necessitates an accurate diagnosis, identification and removal of potential triggering factors, and, frequently, pharmacologic intervention. Effective management also includes establishing realistic expectations, patient reassurance, and education. The choice of medication (abortive, symptomatic) for an acute attack depends on such factors as the severity of the attack, presence or absence of vomiting, time of onset to peak pain, rate of bioavailability of the drug, comorbid medical conditions, and side-effect profile. Effective agents for acute attacks include simple or combination analgesics, nonsteroidal anti-inflammatory drugs, ergot derivatives, selective serotonin agonists, and antiemetics. Opioid analgesics are unnecessary for most patients. The choice of preventive (prophylactic, interval) medication depends primarily on comorbid medical conditions and side-effect profile. Useful preventive agents include beta-adrenergic blockers, calcium channel blockers, tricyclic antidepressants, anticonvulsant medications, and serotonin antagonists.