Delayed gastric emptying in neurologically impaired children with gastroesophageal reflux: the role of pyloroplasty

The presence of delayed gastric emptying in neurologically impaired children with gastroesophageal reflux has led to controversy regarding appropriate surgical management. The authors reviewed the charts of neurologically impaired children requiring fundoplication to answer two questions: (1) is pyloroplasty needed in addition to fundoplication for delayed gastric emptying? and (2) Does delayed gastric emptying influence the morbidity associated with fundoplication? To answer the first question, 40 neurologically impaired children with delayed gastric emptying undergoing fundoplication were divided into two groups: Nissen and pyloroplasty (n = 21) and Nissen only (n = 19). The Nissen and pyloroplasty group had significantly more postoperative complications (23.8% v 5.0%) and took longer to reach full feeding (14.6 v 3.9) days. There were no differences in the incidence of recurrent symptoms, readmissions, or reoperations. To answer the second question, 58 neurologically impaired children undergoing fundoplication were grouped based on gastric emptying scan results: normal gastric emptying (> 32% in 1 hour) (n = 29) and delayed gastric emptying (n = 29). There were no differences in postoperative feeding tolerance, postoperative complications, recurrent symptoms, readmissions, or reoperations between the two groups. Delayed gastric emptying in neurologically impaired children with gastroesophageal reflux did not increase postoperative morbidity after fundoplication, and the addition of a pyloroplasty to fundoplication provided no additional benefit. The authors conclude that the procedure of choice for neurologically impaired children with gastroesophageal reflux is a fundoplication without pyloroplasty, regardless of the degree of delay in gastric emptying.

Translation of encephalomyocarditis virus RNA: parameters influencing the selection of the internal initiation site

The initiation of encephalomyocarditis virus RNA translation is by internal ribosome entry almost exclusively at the 11th AUG codon from the 5'-end, which is the central of the three AUG codons in the sequence..[sequence: see text].., and is located some 25 nt downstream from an oligopyrimidine tract conserved amongst related viruses. As the sequences between the oligopyrimidine tract and AUG-10/11 are poorly conserved and thus possibly serve only as a spacer, the influence of this spacer length on initiation frequency at the three AUG codons was examined in vitro and in vivo. Deletion of 11 residues resulted in initiation almost exclusively at AUG-12 but at significantly reduced overall efficiency. Insertion of eight residues caused a 15-fold increase in initiation frequency at AUG-10 and a decrease at AUG-11. Longer insertions reduced overall efficiency without changing the initiation site preferences. With the wild-type spacing, complete substitution of the oligopyrimidine tract by purines caused a 30-35% decrease in initiation efficiency, and partial substitution only a 10-15% decrease. Thus the internal initiation mechanism selects the initiation site partly on the basis of its distance from upstream elements, of which the oligopyrimidine tract is not the most critical, but for reasons not yet understood a preference for AUG-11 is superimposed on this selection.

Dose-response assessment of airborne methyl isothiocyanate (MITC) following a metam sodium spill

A tank car derailment in northern California in 1991 spilled metam sodium into the Sacramento River, and released its breakdown product, methyl isothiocyanate (MITC), into the air. This paper describes the risk evaluation process used. Over 240 individuals reported symptoms such as eye and throat irritation, dizziness, and shortness of breath. Reference exposure levels (RELs) for 1 hr were developed for MITC and compared to exposure concentrations. Ocular irritation in cats was the most sensitive endpoint reported. The no observed adverse effect level (NOAEL), divided by an uncertainty factor (UF) of 100, produced an REL of 0.5 ppb of MITC in air to prevent discomfort. An REL to prevent disability was estimated to be 40 ppb. An REL to prevent life-threatening injury was estimated to be 150 ppb. Measured MITC levels ranged from 0.2-37 ppb and estimated peak levels ranged from 140-1600 ppb. The usefulness of RELs for emergency planning is discussed.

Regulation of translation by specific protein/mRNA interactions

This review will focus on cases of specific translational control by protein/RNA interactions in the 5'- or 3'-UTR of eukaryote mRNA where either the cis-acting RNA determinant or the trans-acting protein (or preferably both) have been identified with fair certainty. Examples of messages that are regulated by 5' motifs, which are proposed to occlude ribosome binding when bound by their specific factors, include ferritin and ribosomal protein mRNAs and the autoregulated thymidylate synthase and poly(A)-binding mRNAs. However, it has become increasingly evident recently that 3' UTR determinants and their specific binding proteins also regulate translation efficiency either directly, or indirectly via an influence on the polyadenylation status of the mRNA. It is still unclear how events at the 3' end of mRNA influence ribosome binding. Most, if not all, of the mRNAs known to be regulated by 3' UTR motifs are subject to regulation during early development or during differentiation such as several spermatocyte and oocyte mRNAs and erythroid lipoxygenase mRNA. To date, in all cases where translation is controlled directly by specific protein/mRNA interactions, the protein seems to act as a negative regulator, a translational repressor, whose binding to the specific site on the mRNA results in inhibition of initiation. The only cases of translational activation known so far concern internal initiation of translation of picornaviral RNAs, but this topic is beyond the scope of this review.

The common mucosal immune system: from basic principles to enteric vaccines with relevance for the female reproductive tract

The realization that induction of immune responses at mucosal surfaces may prevent colonization, invasion or dissemination of pathogenic microorganisms has spurred intensive efforts to develop vaccines which elicit effective mucosal immunity. In this paper, recent results are discussed for mice given cholera toxin as both an immunogen and as an adjuvant for inducing both humoral and gastrointestinal mucosal immune responses. Oral administration of cholera toxin alone or with a co-administered protein vaccine tetanus toxoid induces a strong T helper type 2 (TH2) cell response in both Peyer's patches and spleen. Both serum IgG and secretory IgA antibodies specific for cholera toxin or for the co-administered protein tetanus toxoid were induced. When administered parentally, however, no mucosal antibody responses were evident and a mixed TH1- and TH2-type CD4+ T cell response was noted in the spleen. Various vectors are being employed in an effort not only to induce mucosal immune responses but also to direct the response to a TH1-type response, thought to promote strong cell-mediated immune responses, or to a TH2-type response for maximum B cell antibody responses. The ability to manipulate the TH cell responses may provide a more rational approach for the design of vaccines. Although lymphoid tissues of the female reproductive tract differ from that of the gut, many of the strategies and evolving principles may be directly applicable to the development of vaccines designed to prevent sexually transmitted diseases.

Virus-vectored immunocontraception for control of wild rabbits: identification of target antigens and construction of recombinant viruses

The need to control animal populations arises in many situations in the world from a variety of motives. Present control strategies are almost universally based on lethal procedures. Increasingly, there is dissatisfaction with such approaches from many different perspectives. In response to these concerns, the concept of controlling populations of pest species through control of their fertility has been mooted. Successful examples of this approach exist in cases of small, discrete pest populations but application of this to a widely distributed species over a broad geographical area has not yet been achieved. In this article, we report on a new approach to fertility control, virus-vectored immunocontraception, and discuss its applicability to control of wild rabbit populations. Particular emphasis is placed on the strategy for selection of a target molecule capable of inducing an immunocontraceptive response and on how the gene encoding such a molecule might be engineered into the myxoma virus for distribution into the population. The fact that the procedures for antigen identification and the viral engineering methods used are, to varying extents, generic means that the broad principles of this approach are applicable in other species.

The influence of viral coding sequences on the efficiency of internal initiation of translation of cardiovirus RNAs

Since internal initiation of translation of cardiovirus RNAs requires the approximately 450-nt segment of the viral genome immediately upstream of the authentic initiation codon for viral polyprotein synthesis, the question arises as to whether the immediately adjacent sequences, the start of the polyprotein coding region, also influence the efficiency of internal initiation. Therefore, a variety of constructs derived from encephalomyocarditis virus and Theiler's murine encephalomyelitis virus retaining various lengths of viral coding sequence were translated in rabbit reticulocyte lysates. Efficient internal initiation showed no requirement specifically for viral coding sequences, but on the other hand certain motifs, notably G-rich sequences, located immediately downstream of the initiation codon were highly inhibitory. These results suggest a possible explanation for the evolution of cardiovirus polyproteins lacking N-terminal myristylation signals and are also pertinent to the design of constructs in which the cardiovirus internal ribosome entry signal is used to drive the expression of a reporter cistron.

Optimizing oral vaccines: induction of systemic and mucosal B-cell and antibody responses to tetanus toxoid by use of cholera toxin as an adjuvant

Cholera toxin (CT) is an effective mucosal antigen and acts as an adjuvant when given orally with various antigens; however, few studies have compared the levels of antibody responses to CT and coadministered protein in systemic and mucosal tissues. In this study, we used tetanus toxoid (TT) for assessment of immune responses. Time course and dose-response studies established that 250 micrograms of TT given orally with 10 micrograms of CT three times at weekly intervals induced high serum and gastrointestinal tract anti-TT and anti-CT antibody responses. Oral immunization with TT alone induced no detectable mucosal immunoglobulin A (IgA) antibodies in fecal extracts and only weak serum IgG anti-TT responses. The coadministration of CT and TT induced peak serum IgG anti-TT responses following two oral doses that remained constant after the third oral immunization, while optimal mucosal IgA responses were seen after the third oral immunization. The serum anti-TT response obtained with CT and TT proved protective against TT challenge (100 minimum lethal doses), whereas mice orally given CT or TT alone died. Antigen-specific B-cell responses were assessed with an isotype-specific Elispot assay of isolated lymphoid cells from the spleen, Peyer's patches, and the small intestinal lamina propria. Interestingly, approximately fourfold-higher numbers of IgA anti-CT than of anti-TT antibody-producing (spot-forming) cells occurred in lymphocytes from the lamina propria of mice orally immunized with both TT and CT. The adjuvant CT did not induce polyclonal B-cell responses in mice given CT by the oral route, since no significant differences in total numbers of B cells producing IgA, IgG, or IgM were found compared with the numbers in mice given TT alone. The results clearly indicate that serum and mucosal antibody responses develop with different kinetics and that protective TT-specific antibody responses are generated in the systemic compartment when TT is administered with CT via the oral route.

New perspectives in mucosal immunity with emphasis on vaccine development

In this review, we have purposely focused on five areas that are currently receiving extensive research attention and will be of major importance for development of mucosal and systemic immunity to oral vaccines. These five areas include the following: (1) helper T-cell (Th) subsets and cytokines for mucosal IgA responses; (2) Th1- and Th2-type subsets in regulation of mucosal IgA responses; (3) antigen uptake and presentation in the mucosal immune system; (4) the importance of memory in mucosal immunity to vaccines; and (5) the determination of whether oral immunization alone induces immunity in all mucosal effector tissues. It is now established that the mucosal immune system can be divided into discrete mucosal inductive sites where vaccines/antigens are encountered and taken up, processed, and presented to B and T cells, and separate areas where immune cells actually function (mucosal effector tissues). Further, through the help provided by Th cells and cytokines, the B cells respond to antigen and undergo expansion including memory cell formation. Following the migration of memory B cells to mucosal effector tissues, the cells rapidly develop into IgA plasma cells, and the prevalence of the latter cell type represents a major characteristic of mucosal effector tissues. It also appears that antigen-specific Th cells and perhaps even CD8+ cytotoxic T lymphocytes can make this circular journey (along with memory/activated B cells) from inductive to mucosal effector sites, and this is termed the common mucosal immune system (CMIS). The major implications of the CMIS for development of vaccines would include each of the five components that are discussed.

Helper T cell subsets for immunoglobulin A responses: oral immunization with tetanus toxoid and cholera toxin as adjuvant selectively induces Th2 cells in mucosa associated tissues

Antigen-specific B cell responses to mucosally delivered proteins are dependent upon CD4-positive T helper (Th) cells, and the frequency of Th1 and Th2 cell responses after oral immunization may determine the level and isotype of mucosal antibody responses. We have used a protein-based vaccine, tetanus toxoid (TT), together with the mucosal adjuvant cholera toxin (CT), for oral immunization of mice to study the nature of antigen-specific Th cell subsets induced in Peyer's patches (PP) of the gastrointestinal (GI) tract and in the spleen (SP) during peak antibody responses. Mice orally immunized with TT and CT responded with antigen-specific secretory immunoglobulin A (S-IgA) antibodies in the GI tract, and with both IgG and IgA antibody responses in serum. PP and SP CD4+ T cells from mice orally immunized with TT plus CT were cultured with antigen-coated latex microspheres for induction of proliferative responses and for enumeration of cytokine producing CD4+ T cells. Interestingly, both PP and SP CD4+ T cell cultures showed increased numbers of IL-4- and IL-5 (Th2-type)-producing, spot-forming cells (SFCs) after 21 d of immunization, while essentially no interferon-gamma (IFN-gamma) or IL-2 (Th1-type) SFCs were noted. Cytokine-specific Northern blots and RT-PCR also revealed that significant IL-4 and IL-5 mRNA levels, but not IFN-gamma or IL-2 mRNA, were present in CD4+ T cells isolated from antigen-stimulated cultures. However, systemic immunization with TT and CT induced antigen-specific IgG and IgM but not IgA antibodies in serum. Further, both IL-2 and IFN-gamma-producing Th1-type cells as well as IL-4- and IL-5-secreting Th2-type cells were generated in SP. Our results show that oral immunization with TT and the mucosal adjuvant CT selectively induced antigen-specific Th2-type responses which may represent the major helper cell phenotype involved in mucosal IgA responses in the GI tract.

Environmental equity and pesticide exposure

Although people of color and low-income groups bear a disproportionate share of the health risks from exposure to pesticides, research attention has been meager, and data on acute and chronic health effects related to their toxic exposures are generally lacking. Increased resources are needed both to study this issue and to mitigate problems already identified. People of color should be a major research focus, with priority on long-term effects, particularly cancer, neurodevelopmental and neurobehavioral effects, long-term neurological dysfunction, and reproductive outcome. Suitable populations at high risk that have not been studied include noncertified pesticide applicators and seasonal and migrant farm workers, including children.

The involvement of a spliceosome component in internal initiation of human rhinovirus RNA translation

Human rhinoviruses (HRVs) and encephalomyocarditis virus (EMCV) belong to different genera of the picornavirus family, but the translation of the RNAs of both viruses is by the same mechanism, that is, internal ribosome entry. In rabbit reticulocyte lysates this translation initiation is efficient for mRNAs bearing the EMCV 5' untranslated region (5' UTR), but very inefficient for mRNAs bearing the HRV 5' UTR, unless factors from HeLa cells are added. The copurification of the HeLa cell translation stimulatory activity with proteins which can be specifically cross-linked to the HRV 5' UTR by u.v. irradiation has been examined. Both the EMCV and HRV 5' UTRs can be cross-linked to a 58/60K protein doublet present in HeLa cell extracts in higher amounts than in reticulocyte lysates, which is shown to be very similar, if not identical to the polypyrimidine tract binding protein (PTB) previously identified as a component of a multi-subunit complex necessary for pre-mRNA splicing. However, the activity in HeLa cell extracts that specifically stimulates translation initiation on mRNAs with the HRV 5' UTR does not copurify with the majority of the 58/60K protein present in these extracts, but copurifies with a minor fraction of these proteins and with a 97K protein which can be cross-linked to the HRV 5' UTR but not to the EMCV 5' UTR, and which is absent from reticulocyte lysates. It is proposed that the specific translation initiation stimulatory activity found in HeLa cells is due to a high M(r) complex containing the 97K polypeptide and PTB.

Selective decontamination in pediatric liver transplants. A randomized prospective study

Although it has been suggested that selective decontamination of the digestive tract (SDD) decreases postoperative aerobic Gram-negative and fungal infections in orthotopic liver transplantation (OLT), no controlled trials exist in pediatric patients. This prospective, randomized controlled study of 36 pediatric OLT patients examines the effect of short-term SDD on postoperative infection and digestive tract flora. Patients were randomized into two groups. The control group received perioperative parenteral antibiotics only. The SDD group received in addition polymyxin E, tobramycin, and amphotericin B enterally and by oropharyngeal swab postoperatively until oral intake was tolerated (6 +/- 4 days). Indications for operation, preoperative status, age, and intensive care unit and hospital length of stay were no different in SDD (n = 18) and control (n = 18) groups. A total of 14 Gram-negative infections (intraabdominal abscess 7, septicemia 5, pneumonia 1, urinary tract 1) developed in the 36 patients studied. Mortality was not significantly different in the two groups. However, there were significantly fewer patients with Gram-negative infections in the SDD group: 3/18 patients (11%) vs. 11/18 patients (50%) in the control group, P < 0.001. There was also significant reduction in aerobic Gram-negative flora in the stool and pharynx in patients receiving SDD. Gram-positive and anaerobic organisms were unaffected. We conclude that short-term postoperative SDD significantly reduces Gram-negative infections in pediatric OLT patients.

Substitution mutations at the putative catalytic triad of the poliovirus 3C protease have differential effects on cleavage at different sites

Picornavirus 3C proteases are substrate-specific cysteine proteases, proposed to be homologous to the trypsin/chymotrypsin-like serine proteases on the basis of structural predictions. Substitutions at the putative active-site residues (Glu71 and Cys147) of the poliovirus 3C protease did not completely abolish proteolytic processing in vitro. The activity of mutated 3C proteases was in the following hierarchy: Glu71-Cys147 (wild type) > Asp71-Cys147 > Glu71-Ser147 > Gln71-Cys147 > Asp71-Ser147 > Gln71-Ser147 (inactive at all sites). Such mutations had differential effects on cleavage at different sites of the poliovirus polyprotein. Cleavage within the P1 region of the polyprotein was the most defective, at the 1ABC/VP1 junction and particularly at the VP0/VP3 junction. Cleavage at the 3AB/3CD and 2B/2C junctions was less affected by the mutations, and the P2/P3 and 2A/2BC junctions were cleaved efficiently by all mutants except Gln71-Ser147. All the 3C mutants gave negative results in infectivity and replication assays after transfection, indicating that mutation of Glu71 or Cys147 virtually abolishes viral replication, irrespective of the efficiency of processing of the nonstructural part of the polyprotein.

Successful repair of major retrohepatic vascular injuries without the use of shunt or sternotomy

Injury to the retrohepatic veins and vena cava secondary to blunt abdominal trauma is often fatal. The purpose of this report is to describe the successful isolation and repair of retrohepatic vascular injuries without the use of median sternotomy or vena caval shunt. Two children with both hepatic vein and retrohepatic caval injuries from blunt trauma were treated by the following surgical approach: (1) bilateral subcostal incision with vertical midline extension; (2) packing of the liver and volume resuscitation with the Rapid Infusion System prior to vascular isolation; (3) isolation of the intrapericardial vena cava through a transdiaphragmatic pericardial window; (4) control of the suprarenal vena cava and porta hepatis; and (5) repair of vein lacerations with vascular occlusion and continuous saline irrigation for improved visualization despite continued venous bleeding. This approach was tolerated and allowed successful repair without shunting in these patients despite an average weight of 14 kg and the loss of 3 L and 23 L of blood, respectively. We attribute the success of this technique to rapid control of hemorrhage and volume resuscitation. This success suggests that the routine use of shunt or sternotomy is not necessary in these devastating injuries.

A myxoma virus intergenic transient dominant selection vector

The purpose of this study was to construct an intergenic transfer vector which can be used for the generation of recombinant myxoma viruses (MVs) expressing a foreign gene insert. Recombinant MVs expressing the Escherichia coli lacZ gene were constructed in vitro by transfection of MV-infected rabbit cells with a transfer expression vector, and isolated under growth conditions selecting for transient expression of the E. coli gpt gene. The effect of inserting foreign DNA sequences between the viral thymidine kinase gene and open reading frame MF8a upon the transcription of these genes was investigated.

Seizures after eating a snack food contaminated with the pesticide endrin. The tale of the toxic taquitos

In September 1988 we investigated reports of seizures in persons who had eaten taquitos, a commercially prepared snack food. We identified and interviewed 5 persons with new-onset seizures within 12 hours of eating taquitos, all purchased during a 1-week period from a single store. Leftover taquitos were found to contain endrin, a highly toxic chlorinated hydrocarbon pesticide. Although tissue confirmation of exposure to endrin was not possible and the level of contamination in the tested taquitos was below that previously thought to be capable of inducing seizures, the pattern of symptoms and the common time and place of purchase strongly suggested that the seizures were due to endrin-contaminated taquitos. The source of endrin contamination could not be determined. This episode is the first report of illness associated with endrin-contaminated food products in the United States.

Plasmid cDNA-directed protein synthesis in a coupled eukaryotic in vitro transcription-translation system

A system is described in which transcription of cDNA clones by bacteriophage T7 RNA polymerase is coupled to translation in the micrococcal nuclease treated rabbit reticulocyte lysate in a single reaction of coupled transcription-translation. The monovalent and divalent cation requirements for translation are dominant for optimum expression in this coupled system, so that transcription is relatively inefficient. Nevertheless, the use of appropriate DNA concentrations leads to the synthesis of sufficient RNA to saturate the protein synthesis capacity of the system. The fidelity and efficiency of expression in this coupled system are high, and the degree of purification of the plasmid DNA is relatively uncritical. The system therefore offers very considerable advantages for rapid screening of 'mini-preparations' of cDNA plasmid constructs for retention of the correct reading frame and expression of the desired protein product.

Assessment of acute health effects from the Medfly Eradication Project in Santa Clara County, California

Surveys were performed to assess the acute health effects of aerial application of malathion bait over a large urban area. Three indirect attempts to assess utilization of health care services were made: (1) surveillance of a major hospital emergency department was undertaken, (2) ambulance dispatches were reviewed, and (3) emergency treatments for asthma at a university hospital were reviewed. These assessments were negative but insensitive. Prevalence of self-reported symptoms was assessed with two surveys that were subject to severe time constraints. Personal interviews of the same individuals, before and after the spraying, were conducted: one was conducted by telephone and the other by residential visit. Results indicated no detectable increase in acute morbidity. Also, after the spraying, there was a decrease in anxiety-related symptoms.

Initiation of translation of human rhinovirus RNA: mapping the internal ribosome entry site

In order to map the 3' boundary of the segments needed for translation initiation at the correct site on human rhinovirus 2, deletions were made from the 3' end of the viral 5'-untranslated region. These truncated viral segments were placed immediately upstream of a reporter gene, a derivative of the influenza virus NS cDNA, either as monocistronic constructs or as dicistronic constructs in which the upstream cistron was the Xenopus laevis cyclin B2 cDNA. In vitro transcripts of these clones were translated in the rabbit reticulocyte lysate system, with or without supplementation with crude HeLa cell initiation factors, or in a HeLa cell-free system. When the full-length viral 5'-untranslated region was present, the HeLa cell factors strongly stimulated the synthesis of the NS-related polypeptides, especially in the case of the dicistronic mRNAs. Deletions from the 3' end extending up to nt 562 had little effect on translation efficiency or the response to HeLa cell factors, but more extensive deletions resulted in the complete loss of response to these factors, an almost total inhibition of NS synthesis from dicistronic mRNAs, and a partial inhibition in the case of the monocistronic mRNAs. In the case of a deletion extending to nt 554, insertion of a 15 nucleotide residue linker failed to restore efficient translation initiation. We conclude that the essential sequences for internal initiation extend to a point located between nt 554 and 562, and that the ribosome entry site, defined as the most 5'-proximal point where the ribosome can bind in an initiation-competent manner, must lie within 6 residues on either side of nt 562, and certainly not further downstream than nt 568.

The myxoma virus thymidine kinase gene: sequence and transcriptional mapping

The myxoma virus thymidine kinase (TK) gene is encoded on a 1.6 kb SacI-SalI restriction fragment located between 57.7 and 59.3 kb on the 163 kb genomic map. The nucleotide sequence of this fragment as well as 228 bp from the adjacent SalI-AA2 fragment was determined and found to encode four major open reading frames (ORFs). Three of these ORFs are similar in nucleotide sequence to ORFs L5R and J1R, and the TK gene of vaccinia virus (VV). The fourth ORF, MF8a, shows similarity to the ORFs found in the same position relative to the TK genes of Shope fibroma virus, Kenya sheep-1 virus and swine-pox virus. A search of the complete VV nucleotide sequence for regions of similarity to MF8a identified the host specificity gene C7L. Northern blot analysis of early viral RNA identified transcripts of approximately 700 nucleotides for both the TK gene and ORF MF8a. The 5' ends of the TK gene and ORF MF8a early mRNAs were mapped by primer extension to initiation sites 13 nucleotides downstream of sequences with similarity to the VV early promoter consensus. The sizes of the TK and MF8a mRNAs are consistent with transcription termination and polyadenylation occurring downstream of the sequence TTTTTNT, which is identical to the consensus sequence for the VV transcription termination signal.