Biomedical subjects
Publications and source records attributed to Michael A Skinner.
Although diseases of the thyroid and parathyroid glands are relatively uncommon in children, the implications of missed diagnoses can be severe. This review describes the embryology, anatomy, and physiology of the thyroid and parathyroid glands, and focuses on significant benign and malignant pathologies of these glands.
PURPOSE OF REVIEW: We provide a summary of the literature published in the past year addressing the surgical approach to multiple endocrine neoplasia type 2 in the pediatric population. RECENT FINDINGS: The review focuses first on medullary thyroid carcinoma and performing prophylactic thyroidectomy for the prevention or cure of this disease. The timing and extent of surgery as well as additional surgical intervention for persistent or recurrent disease is discussed. Then the surgical management of hereditary pheochromocytoma is reviewed. SUMMARY: Surgery is often the only treatment that can prevent or cure the endocrinopathies associated with multiple endocrine neoplasia type 2. Determining the proper timing and extent of surgical intervention in children affected with multiple endocrine neoplasia type 2 will lead to better outcomes and survival.
Avipoxvirus infections have been observed in an extensive range of wild, captive and domesticated avian hosts, yet little is known about the genome diversity and host-range specificity of the causative agent(s). Genome-sequence data are largely restricted to Fowlpox virus (FWPV) and Canarypox virus (CNPV), which have been sequenced completely, showing considerable divergence between them. It is therefore proving difficult, by empirical approaches, to identify pan-genus, avipoxvirus-specific oligonucleotide probes for PCR and sequencing to support phylogenetic studies. A previous preliminary study used the fpv167 locus, which encodes orthologues of vaccinia virus core protein P4b (A3). PCR per se did not discriminate between viruses, but restriction-enzyme or sequence analysis indicated that the avipoxviruses clustered either with FWPV or with CNPV. Here, further study of the P4b locus demonstrated a third cluster, from psittacine birds. A newly identified locus, flanking fpv140 (orthologue of vaccinia virus H3L), confirms the taxonomic structure. This locus is particularly useful in that viruses from the fowlpox-like and canarypox-like clusters can be discriminated by PCR on the basis of fragment size, whilst sequence comparison allows discrimination for the first time between Pigeonpox virus and Turkeypox virus. Except within the psittacines, virus and avian host taxonomies do not show tight correlation, with viruses from the same species located in very different clades. Nor are all the existing recognized avipoxvirus species, defined primarily by avian host species (such as CNPV and Sparrowpox virus), resolved within the present structure.
The emergence of variant fowlpox viruses (FWPVs) and increasing field use of recombinants against avian influenza H5N1 emphasize the need to monitor vaccines and to distinguish them from field strains. Five commercial vaccines, two laboratory viruses and two European field isolates were characterized by PCR and sequencing at 18 loci differing between attenuated FP9 and its pathogenic progenitor. PCR failed to discriminate between the viruses and sequence determination revealed no significant differences at any locus, except for a polymorphic locus encompassed by deletion 24 (9.3 kbp) in FP9. Surprisingly, 'novel' previously unreported sequence (spanning 1.2 kbp) was found in both European field isolates and three of the vaccines. It was absent from the other two vaccines, removed by a 1.2 kbp deletion identical to that surprisingly also observed in the completely sequenced genome of FPV USDA. This locus (H9) adds a potentially useful tool for discriminating between FWPV field isolates and vaccines.
The FP9 strain of F has been described as a more immunogenic recombinant vaccine vector than the Webster FPV-M (FPW) strain (R. J. Anderson et al., J. Immunol. 172:3094-3100, 2004). This study expands the comparison to include two separate recombinant antigens and multiple, rather than single, independent viral clones derived from the two strains. Dual-poxvirus heterologous prime-boost vaccination regimens using individual clones of recombinant FP9 or FPW in combination with recombinant modified V Ankara expressing the same antigen were evaluated for their ability to elicit T-cell responses against recombinant antigens from Plasmodium berghei (circumsporozoite protein) or human immunodeficiency virus type 1 (a Gag-Pol-Nef fusion protein). Gamma interferon enzyme-linked immunospot assay and fluorescence-activated cell sorting assays of the responses to specific epitopes confirmed the approximately twofold-greater cellular immunogenicity of FP9 compared to FPW, when given as the priming or boosting immunization. Equality of transgene expression in mouse cells infected with the two strains in vitro was verified by Western blotting. Directed partial sequence analysis and PCR analysis of FPW and comparison to available whole-genome sequences revealed that many loci that are mutated in the highly attenuated and culture-adapted FP9 strain are wild type in FPW, including the seven multikilobase deletions. These "passage-specific" alterations are hypothesized to be involved in determining the immunogenicity of fowlpox virus as a recombinant vaccine vector.
BACKGROUND: Medullary thyroid carcinoma is the most common cause of death in patients with multiple endocrine neoplasia (MEN) type 2A (MEN-2A) or type 2B or familial medullary thyroid carcinoma. We sought to determine whether total thyroidectomy in asymptomatic young members of kindreds with MEN-2A who had a mutated allele of the RET proto-oncogene could prevent or cure medullary thyroid carcinoma. METHODS: A total of 50 patients 19 years of age or younger who were consecutively identified through a genetic screening program as carriers of a RET mutation characteristic of MEN-2A underwent total thyroidectomy. Five to 10 years after the surgery, each patient was evaluated by physical examination and by determination of plasma calcitonin levels after stimulation with provocative agents. RESULTS: In 44 of the 50 patients, basal and stimulated plasma calcitonin levels were at or below the limits of detection of the assay (proportion, 0.88; 95 percent confidence interval, 0.76 to 0.95). Two patients had basal and stimulated plasma calcitonin levels above the normal range. Stimulated plasma calcitonin levels had increased but remained within the normal range in four patients. The data suggest that there was a lower incidence of persistent or recurrent disease in children who underwent total thyroidectomy before eight years of age and in children in whom there were no metastases to cervical lymph nodes. CONCLUSIONS: In this study, young patients identified by direct DNA analysis as carriers of a RET mutation characteristic of MEN-2A had no evidence of persistent or recurrent medullary thyroid carcinoma five or more years after total thyroidectomy. A longer period of evaluation will be necessary to confirm that they are cured.
Malaria is a major global health problem for which an effective vaccine is required urgently. Prime-boost vaccination regimes involving plasmid DNA and recombinant modified vaccinia virus Ankara-encoding liver-stage malaria antigens have been shown to be powerfully immunogenic for T cells and capable of inducing partial protection against experimental malaria challenge in humans, manifested as a delay in time to patent parasitemia. Here, we report that substitution of plasmid DNA as the priming vector with a specific attenuated recombinant fowlpox virus, FP9, vaccine in such prime-boost regimes can elicit complete sterile protection that can last for 20 months. Protection at 20 months was associated with persisting memory but not effector T cell responses. The protective efficacy of various immunization regimes correlated with the magnitude of induced immune responses, supporting the strategy of maximizing durable T cell immunogenicity to develop more effective liver-stage vaccines against Plasmodium falciparum malaria.
UNLABELLED: Hematopoietic stem cell (HSC) engraftment is delayed in children with hypersplenism, and splenectomy may improve HSC engraftment. However, the use of total splenectomy in children is limited because of concerns for postsplenectomy sepsis. In this study, the authors sought to assess the role of partial splenectomy for children with hypersplenism undergoing HSC transplantation. METHODS: Five children with a variety of conditions and associated hypersplenism underwent partial splenectomy before an HSC transplantation at the authors' institution between 2000 and 2003. Primary outcome measures were rates of neutrophil and platelet engraftment. Secondary outcome measures included perioperative complications, splenic regrowth, graft-versus-host disease, and infection rate. All outcomes were compared with recipients of an HSC transplant from both age-matched nonsplenectomized children (n = 497) and hypersplenic children who underwent total splenectomy (n = 10). Outcomes were compared using Wilcoxon's rank sum test. RESULTS: The rate of both neutrophil and platelet engraftment was faster in children who underwent either partial or total splenectomy as compared with nonsplenectomized children (mean rates of neutrophil engraftment were 26, 19, and 19 days for the nonsplenectomy, total splenectomy, and partial splenectomy groups, respectively; mean rates of platelet engraftment were 97, 37, and 45 days for the nonsplenectomy, total splenectomy, and partial splenectomy groups, respectively). Graft-versus-host disease rates were similar between the 3 groups. The mean percentage of splenic regrowth after partial splenectomy was 39%. There were no perioperative complications. CONCLUSIONS: Partial splenectomy may be safely performed before HSC transplantation and, similar to total splenectomy, may improve the rate of HSC engraftment. Although this series has a limited number of patients, the use of partial splenectomy appears to be safe and may allow for splenic salvage to minimize the risk of postsplenectomy sepsis.
PURPOSE: The aim of this study was to examine the association between E-cadherin expression and markers of Wilms' tumor aggression, including metastasis and recurrence. METHODS: Forty Wilms' tumor samples from the National Wilms' Tumor Study Group underwent immunohistochemical staining for E-cadherin. Tumor stage at diagnosis, recurrence, and loss of heterozygosity at 16q status was known for each of the tumor samples. E-Cadherin cell staining was defined as high (>33%) or low (<33%), and values were assigned by a pathologist blinded to the tumor characteristics. Five stage IV tumors were ineligible for assay because of lack of a tubular component. To identify a mechanism of downregulation, we screened tumor DNA for genetic mutations in exons 1-16 using a combination of WAVE and sequence analysis. To assess the functional significance of the identified mutations, the authors compared amino acid homology across multiple species. Finally, they performed reverse transcriptase-polymerase chain reaction for those tumors with intronic single nucleotide polymorphisms (SNPs) to evaluate for mRNA splice variants. RESULTS: Wilms' tumors presenting with metastatic (stage IV) disease demonstrated decreased levels of E-cadherin expression compared with localized tumors (stage I) (Fisher's Exact test, P < .01). In a search for the mechanism of the downregulation of E-cadherin, we identified 5 different mutations in 7 high stage tumors (7/15) and 1 mutation in a low stage tumor (1/20). The mutations occurred in amino acids that were conserved across multiple species. Additionally, 11 of 15 high stage tumors contained an intronic SNP located within 6 bp of the 5 intronic splice junction immediately downstream of exon 1. However, examination of 5 of these tumors using reverse transcriptase-polymerase chain reaction showed that this intronic SNP does not appear to disrupt the assembly of full-length E-cadherin transcripts. Lastly, no correlation was identified between E-cadherin expression and recurrence of disease. CONCLUSIONS: In this study, the authors have found an association between decreased E-cadherin expression and metastatic Wilms' tumor. Mutations identified may help identify a mechanism for downregulation. The functional significance of these mutations is supported by the conserved nature of the amino acids across multiple species. The authors believe these findings support the involvement of E-cadherin in the evolution of Wilms' tumor.
AIM: The availability of large clinical databases allows for careful evaluation of surgical practices, indicators of quality improvement, and cost. We used a large clinical database to compare the effect of surgeon and hospital volume for the care of children with hypertrophic pyloric stenosis (HPS). METHODS: Patients with International Classification of Diseases-9 codes for HPS and pyloromyotomy were selected from the 1994 to 2000 National Inpatient Samples database. Multiple and logistic regression models were used to evaluate the risk-adjusted association between provider volume and outcomes. RESULTS: Postoperative complications occurred in 2.71% of patients. Patients operated on by low- and intermediate-volume surgeons were more likely to have complications compared with those operated on by high-volume surgeons (95% confidence interval [CI], 1.25-3.78 and 95% CI, 1.25-2.69, respectively). Patients operated at low-volume hospitals were 1.6 times more likely to have complications compared with those operated at intermediate- or high-volume hospitals (95% CI, 1.19-2.20). Procedures performed at high-volume hospitals were less expensive than those at intermediate-volume hospitals by a margin of 910 dollars (95% CI, 443-1377 dollars). CONCLUSIONS: These data represent the largest study to date on the epidemiology, complication rate, and cost for care for HPS. Patients treated by both high-volume surgeons and at high-volume hospitals have improved outcomes at less cost.
BACKGROUND: The functional results of cryopreserved heterotopic parathyroid autotransplantation (CHPA) are not well defined. The authors evaluated the outcomes of delayed CHPA for the treatment of surgically induced hypoparathyroidism. METHODS: Since November 1991, 448 parathyroid samples from 436 patients were cryopreserved at our institution. Of these, 29 patients underwent 34 CHPA procedures, with placement of 20 to 25 pieces of parathyroid tissue (approximately 50 to 75 mg) into the forearm. Outcomes were determined based on peripheral parathyroid hormone (PTH) levels and, where available, PTH gradients between grafted and nongrafted arms. Graft function results were defined as completely functional (patients with normal PTH and calcium levels off all calcium/vitamin D supplementation), partially functional (normal PTH levels and mild hypocalcemia on calcium supplementation), or nonfunctional (low PTH levels and dependent on calcium/vitamin D supplementation). RESULTS: Of the 29 patients with CHPA, prospective data were available for 26 patients undergoing 30 CHPA procedures (9 patients with MEN 1, 4 with MEN 2A, 1 with MEN 2B, and 12 with sporadic hyperparathyroidism). The mean follow-up interval was 2 years. Twelve of 26 patients (46%) had completely functional grafts, 6 patients (23%) had partially functional grafts, and the remaining 8 patients (31%) had nonfunctional grafts. No patient with CHPA had graft-dependent recurrent hyperparathyroidism. Of the 14 patients (15 autografts) with MEN, 7 patients (50%) had fully functional grafts, and 2 patients (14%) had partially functional grafts. The mean cryopreservation period was 7.9 months (range, 1 week to 22 months) for functional autografts and 15.3 months (range, 2 weeks to 106 months) for nonfunctional autografts (P < .01). CONCLUSIONS: Based on these data and those in previous studies, approximately 60% of delayed, cryopreserved parathyroid autografts are functional. In this study 40% autografts (46% of patients) achieved full competency off supplements. Some patients have evidence of graft function with normal PTH levels but are not normocalcemic. Results were similar for patients with MEN and nonhereditary hyperparathyroidism. The duration of cryopreservation was a significant indicator of graft failure, and no functional autograft was observed beyond 22 months of preservation. CHPA is a useful treatment modality for patients with postoperative hypocalcemia after thyroid or parathyroid surgery, who do not respond to immediate parathyroid autotransplantation.
We generated a line of transgenic mice using a yeast artificial chromosome containing the Ret mutation responsible for the multiple endocrine neoplasia type 2B syndrome (MEN 2B). The resulting animals did not develop any of the expected neoplasms associated with MEN 2B. Transgenic animals were then bred with animals lacking murine Ret (Ret(M)) to further evaluate the function of human mutated Ret (Ret(H)(2B)) in the murine context. Whereas mice lacking Ret(M) exhibit intestinal aganglionosis and the absence of kidneys with other genitourinary anomalies, expression of the Ret(H)(2B) transgene in Ret(M)-deficient mice allowed significant renal development with a partial rescue of the enteric nervous system. These Ret(H)(2B)-positive/Ret(M)-deficient mice exhibit normal Ret expression and survive longer than Ret(M)-deficient mice, but still die at 3 to 5 days of age with evidence of enterocolitis. We conclude that the normal expression of a human Ret proto-oncogene with the MEN 2B mutation does not cause any features of MEN 2B in mice. Although the gene is normally expressed in the appropriate target tissues, there is incomplete phenotypic rescue in mice lacking murine Ret. These results suggest important interspecies differences between humans and mice in the function of the Ret oncogene.
OBJECTIVE: Purposes of this study were: 1) to compare mortality and postoperative morbidities (intra-abdominal abscess, wound dehiscence, and intestinal stricture) in extremely low birth weight (ELBW) infants who underwent initial laparotomy or drainage for necrotizing enterocolitis (NEC) or isolated intestinal perforation (IP); 2) to determine the ability to distinguish NEC from IP preoperatively and the importance of this distinction on outcome measures; and 3) to evaluate the association between extent of intestinal disease determined at operation and outcome measures. BACKGROUND: ELBW infants who undergo operation for NEC or IP have a postoperative, in-hospital mortality rate of approximately 50%. Whether to perform laparotomy or drainage initially is controversial. Also unknown is the importance of distinguishing NEC from IP and the current ability to make this distinction based on objective data available prior to operation. METHODS: A prospective, multicenter cohort study of 156 ELBW infants at 16 neonatal intensive care units (NICU) within the NICHD Neonatal Research Network. RESULTS: Among the 156 enrolled infants, 80 underwent initial peritoneal drainage and 76 initial laparotomy. Mortality rate was 49% (76 of 156). Ninety-six patients had a preoperative diagnosis of NEC and 60 had presumed IP. There was a high level of agreement between the presumed preoperative diagnosis and intraoperative diagnosis in patients undergoing initial laparotomy (kappa = 0.85). The relative risk for death with a preoperative diagnosis of NEC (versus IP) was 1.4 (95% confidence interval, 0.99-2.1, P = 0.052). The overall incidence of postoperative intestinal stricture was 10.3%, wound dehiscence 4.4%, and intra-abdominal abscess 5.8%, and did not significantly differ between groups undergoing initial laparotomy versus initial drainage. CONCLUSIONS: Survival to hospital discharge after operation for NEC or IP in ELBW neonates remains poor (51%). Patients with a preoperative diagnosis of NEC have a relative risk for death of 1.4 compared with those with a preoperative diagnosis of IP. A distinction can be made preoperatively between NEC and IP based on abdominal radiographic findings and the patient's age at operation. Future randomized trials that compare laparotomy versus drainage would likely benefit from stratification of treatment assignment based on preoperative diagnosis.
Live vaccines against fowlpox virus, which causes moderate pathology in poultry and is the type species of the Avipoxvirus genus, were developed in the 1920s. Development of recombinant fowlpox virus vector vaccines began in the 1980s, for use not only in poultry, but also in mammals including humans. In common with other avipoxviruses, such as canarypox virus, fowlpox virus enters mammalian cells and expresses proteins, but replicates abortively. The use of fowlpox virus as a safe vehicle for expression of foreign antigens and host immunomodulators, is being evaluated in numerous clinical trials of vaccines against cancer, malaria, tuberculosis and AIDS, notably in heterologous prime-boost regimens. In this article, technical approaches to, and issues surrounding, the use of fowlpox virus as a recombinant vaccine vector in poultry and mammals are reviewed.
Successful vaccination against intracellular pathogens, including liver-stage Plasmodium falciparum, will require induction of strong antigen-specific T lymphocyte responses. The multiple epitope (ME)-thrombospondin-related adhesion protein (TRAP) construct includes CD8(+) and CD4(+) T cell epitopes from pre-erythrocytic P. falciparum antigens fused in-frame to the entire pre-erythrocytic antigen TRAP. Three carriers for this construct--plasmid DNA and 2 recombinant nonreplicating poxviruses (modified vaccinia virus Ankara [MVA] and fowlpox strain 9 [FP9])--were administered at 3-week intervals in a heterologous prime-boost combination to 29 Gambian men aged 18-45 years. Doses of DNA ME-TRAP, MVA ME-TRAP, and FP9 ME-TRAP were 2 mg and 1.5x10(8) and 1x10(8) plaque-forming units, respectively. DNA ME-TRAP was injected intramuscularly; MVA ME-TRAP and FP9 ME-TRAP were injected intradermally. There were no clinically relevant laboratory abnormalities and no severe or serious adverse events related to vaccination. DNA/MVA and FP9/MVA regimens were the most potent inducers of circulating effector T cells seen to date in sub-Saharan Africa. Twelve months after the final vaccination, a single booster vaccination expanded the effector T cell pool to a similar or higher magnitude than that after the primary vaccinations. These results highlight optimized combination regimens with general relevance to the development of vaccines targeting intracellular pathogens.
Complete DiGeorge syndrome is a fatal congenital disorder characterized by athymia, hypoparathyroidism, and heart defects. Less than half of patients are 22q11 hemizygous. The goal of this study was to assess if immune suppression followed by postnatal thymus transplantation would lead to T-cell function in 6 infant patients who had host T cells at the time of transplantation. All infants had fewer than 50 recent thymic emigrants (CD3(+)CD45RA(+)CD62L(+)) per cubic millimeter (mm(3)) and all had some proliferative response to the mitogen phytohemagglutinin. Four infants had rash, lymphadenopathy, and oligoclonal populations of T cells in the periphery. Five of 6 patients are alive at the follow-up interval of 15 months to 30 months. The 5 surviving patients developed a mean of 983 host CD3(+) T cells/mm(3) (range, 536/mm(3)-1574/mm(3)), a mean of 437 recent thymic emigrants/mm(3) (range, 196/mm(3)-785/mm(3)), and normal proliferative responses to phytohemaglutinin (follow-up from day 376 to day 873). The TCR repertoire became polyclonal in patients who presented with oligoclonal T cells. All patients had thymopoiesis on allograft biopsy. Postnatal thymus transplantation after treatment with Thymoglobulin shows promise as therapy for infants with complete DiGeorge syndrome who have significant proliferative responses to mitogens or who develop rash, lymphadenopathy, and oligoclonal T cells.
Sterile immunity can be provided against the pre-erythrocytic stages of malaria by IFN-gamma-secreting CD8(+) T cells that recognize parasite-infected hepatocytes. In this study, we have investigated the use of attenuated fowlpox virus (FPV) strains as recombinant vaccine vectors for eliciting CD8(+) T cells against Plasmodium berghei. The gene encoding the P. berghei circumsporozoite (PbCS) protein was inserted into an FPV vaccine strain licensed for use in chickens, Webster's FPV, and the novel FPV vaccine strain FP9 by homologous recombination. The novel FP9 strain proved more potent as a vaccine for eliciting CD8(+) T cell responses against the PbCS Ag. Sequential immunization with rFP9 and recombinant modified vaccinia virus Anakara (MVA) encoding the PbCS protein, administered by clinically acceptable routes, elicited potent CD8(+) T cell responses against the PbCS protein. This immunization regimen elicited substantial protection against a stringent liver-stage challenge with P. berghei and was more immunogenic and protective than DNA/MVA prime/boost immunization. However, further improvement was not achieved by sequential (triple) immunization with a DNA vaccine, FP9, and MVA.
BACKGROUND: Five patients with DiGeorge syndrome presented with infections, skin rashes, and lymphadenopathy after the newborn period. T-cell counts and function varied greatly in each patient. Initial laboratory testing did not suggest athymia in these patients. OBJECTIVE: The purpose of this study was to determine whether the patients had significant immunodeficiency. METHODS: Research testing of peripheral blood included immunoscope evaluation of T-cell receptor beta variable gene segment repertoire diversity, quantification of T-cell receptor rearrangement excision circles, and detection of naive T cells (expressing CD45RA and CD62L). RESULTS: The patients were classified as having DiGeorge syndrome on the basis of syndromic associations and heart, parathyroid, and immune abnormalities. Immunoscope evaluation revealed that the T-cell repertoires were strikingly oligoclonal in all patients. There were few recent thymic emigrants, as indicated by the very low numbers of naive T cells (<50/mm(3)) and the absence of T-cell receptor rearrangement excision circles. These studies showed that all 5 patients were athymic. Two patients died, one from infection. No thymus was found during the complete autopsy performed on one patient. CONCLUSION: Patients with DiGeorge syndrome, skin rash, and lymphadenopathy should undergo analysis of naive T-cell numbers and of T-cell receptor beta variability segment repertoire to determine whether they are athymic, even if they have T cells with mitogen responsiveness. It is important for physicians to realize that patients with complete DiGeorge syndrome remain profoundly immunodeficient after development of these atypical features (rash, lymphadenopathy, and oligoclonal T cells). Prompt diagnosis is necessary for appropriate management.