Gene duplication and subsequent diversification strongly affect phenotypic evolvability and robustness.

We study the effects of non-determinism and gene duplication on the structure of genotype-phenotype (GP) maps by introducing a non-deterministic version of the Polyomino self-assembly model. This model has previously been used in a variety of contexts to model the assembly and evolution of protein quaternary structure. Firstly, we show the limit of the current deterministic paradigm which leads to built-in anti-correlation between evolvability and robustness at the genotypic level. We develop a set of metrics to measure structural properties of GP maps in a non-deterministic setting and use them to evaluate the effects of gene duplication and subsequent diversification. Our generalized versions of evolvability and robustness exhibit positive correlation for a subset of genotypes. This positive correlation is only possible because non-deterministic phenotypes can contribute to both robustness and evolvability. Secondly, we show that duplication increases robustness and reduces evolvability initially, but that the subsequent diversification that duplication enables has a stronger, inverse effect, greatly increasing evolvability and reducing robustness relative to their original values.

A neonicotinoid pesticide impairs foraging, but not learning, in free-flying bumblebees.

Neonicotinoids are widely-used pesticides implicated in the decline of bees, known to have sub-lethal effects on bees' foraging and colony performance. One proposed mechanism for these negative effects is impairment to bees' ability to learn floral associations. However, the effects of neonicotinoids on learning performance have largely been addressed using a single protocol, where immobilized bees learn an association based on a single sensory modality. We thus have an incomplete understanding of how these pesticides affect bee learning in more naturalistic foraging scenarios. We carried out the first free-foraging study into the effects of acute exposure of a neonicotinoid (imidacloprid) on bumblebees' (Bombus impatiens) ability to learn associations with visual stimuli. We uncovered dose-dependent detrimental effects on motivation to initiate foraging, amount of nectar collected, and initiation of subsequent foraging bouts. However, we did not find any impairment to bees' ability to learn visual associations. While not precluding the possibility that other forms of learning are impaired, our findings suggest that some of the major effects of acute neonicotinoid exposure on foraging performance may be due to motivational and/or sensory impairments. In light of these findings, we discuss more broadly how pesticide effects on pollinator cognition might be studied.

Determinism and boundedness of self-assembling structures.

Self-assembly processes are widespread in nature and lie at the heart of many biological and physical phenomena. The characteristics of self-assembly building blocks determine the structures that they form. Two crucial properties are the determinism and boundedness of the self-assembly. The former tells us whether the same set of building blocks always generates the same structure, and the latter whether it grows indefinitely. These properties are highly relevant in the context of protein structures, as the difference between deterministic protein self-assembly and nondeterministic protein aggregation is central to a number of diseases. Here we introduce a graph theoretical approach that can determine the determinism and boundedness for several geometries and dimensionalities of self-assembly more accurately and quickly than conventional methods. We apply this methodology to a previously studied lattice self-assembly model and discuss generalizations to a wide range of other self-assembling systems.

Scaling of the surface vasculature on the human placenta.

The networks of veins and arteries on the chorionic plate of the human placenta are analyzed in terms of Voronoi cells derived from these networks. Two groups of placentas from the United States are studied: a population cohort with no prescreening, and a cohort from newborns with an elevated risk of developing autistic spectrum disorder. Scaled distributions of the Voronoi cell areas in the two cohorts collapse onto a single distribution, indicating common mechanisms for the formation of the complete vasculatures, but which have different levels of activity in the two cohorts.

Increased local antitumor effects of interleukin 2 liposomes in mice with MCA-106 sarcoma pulmonary metastases.

The effects of liposome formulations of interleukin 2 (IL-2) and local route were studied in C57BL/6 mice with MCA-106 sarcoma pulmonary metastases. IL-2 liposomes made by hydration of powdered dimyristoyl-phosphatidylcholine with aqueous recombinant IL-2 had 95% of the IL-2 associated with the lipid fraction. When mice with pulmonary micrometastases were treated once daily with free cytokine on days 5, 6, and 7 after tumor inoculation, the intrathoracic route was superior to the i.p. or s.c. routes. When IL-2 liposomes were administered by the local intrathoracic route, significantly better antitumor effects (P less than 0.01) were seen compared to empty liposomes or free IL-2 as determined by (a) increased survival and (b) reduced numbers of pulmonary metastases. Minimal toxicity was observed. Results indicate that local route and incorporation of IL-2 in liposomes may enhance therapeutic efficacy and facilitate more practical daily dosing regimens.

Antitumor effects of interleukin 2 liposomes and anti-CD3-stimulated T-cells against murine MCA-38 hepatic metastasis.

The stimulation of murine splenocytes with the monoclonal antibody anti-CD3 and interleukin 2 (IL-2) results in the propagation of large numbers of cells (T-activated killer; T-AK) which demonstrate high therapeutic efficacy when infused with IL-2 into mice bearing pulmonary metastases. Interleukin 2 infusions are required to maintain the function of the adoptively transferred cells. Recent data demonstrate that the therapeutic efficacy can be enhanced by encapsulating IL-2 in liposomes. The present work tested the combination of T-AK cells with IL-2 liposomes in an immunotherapy model utilizing the MCA-38 murine colon adenocarcinoma. Expansion of murine splenocytes was achieved with anti-CD3 monoclonal antibody plus IL-2 and was consistently greater than 50-fold during a 9-day culture period. Cytolytic activity of the murine T-AK cells was mediated primarily by Lyt-2+ cells. In vivo results demonstrate synergistic therapeutic efficacy of the combination of IL-2 liposomes and T-AK cells. Evaluation of the in vivo distribution of these T-AK cells utilizing congenic mice demonstrates that Lyt-2+ cells from these in vitro cultures infiltrate hepatic metastases in vivo. The activation of lymphocytes with anti-CD3 monoclonal antibody and IL-2 appears to be a reproducible and convenient method of producing cells capable of producing antitumor effects in models of adoptive immunotherapy.

Light and electron microscopic features of the liver in mucopolysaccharidosis.

The mucopolysaccharidosis (MPS) diseases lead to the accumulation of glycosaminoglycan in many tissues. In this study 19 MPS I, one MPS II, five MPS III, and two MPS VI patients underwent liver biopsy for light and electron microscopic examination. Electron microscopy was performed for all 27 specimens. Twenty-six specimens were studied by light microscopy, and the slides were stained with colloidal iron and alcian blue in 26 and six biopsy specimens, respectively. By hematoxylin-eosin stain 20 of 26 cases showed hepatocellular dilatation with rarefaction of the cytoplasm; the Kupffer cells were unremarkable. Twenty-four and 25 of the 26 biopsy specimens showed substantial colloidal iron staining of hepatocytes and Kupffer cells, respectively. The six biopsy specimens prepared with alcian blue stain showed no reactivity of any cell type. Electron microscopy revealed characteristic membrane-bound inclusions within the hepatocytes and Kupffer cells of all 27 biopsy specimens. Of 19 cases in which Ito cells were identified, 18 included cells containing similar inclusions. Twenty of 27 biopsy specimens also demonstrated the hepatocellular accumulation of lipid droplets. Although there were no absolute distinguishing features among the various MPS diseases, the two MPS VI cases showed glycosaminoglycan inclusions that were fewer in number, smaller, and contained more abundant lipofusion than those associated with the other MPS types.

Cuff-occluded rate of rise of peripheral venous pressure: a new, highly sensitive technique for monitoring blood volume status during hemorrhage and resuscitation.

We investigated the cuff-occluded rate of rise of peripheral venous pressure (CORRP)--a new, nearly noninvasive peripheral hemodynamic monitoring parameter--in dogs subjected to hemorrhage and resuscitation. Twelve adult mongrel dogs under general anesthesia were subjected to hemorrhage of 30% of their estimated total blood volume (TBV) for 30 minutes; after this time the extracted blood was reinfused. Arterial pressure (AP), central venous pressure (CVP), pulmonary arterial pressure (PAP), cardiac output (CO), pulmonary venous pressure (PWP), heart rate, and CORRP were continuously monitored. A "clinically significant change" (CSC) in CORRP and CO was defined as a change that exceeded two standard deviations from the mean of five baseline measurements made before the onset of hemorrhage, whereas a CSC in PWP or CVP was conservatively defined as a change that exceeded 2 mm Hg from the average of five baseline measurements, and a CSC in PAP and AP was defined as a change that exceeded 3 mm Hg and 5 mm Hg, respectively from the average of the baseline measurements. There was no consistent change in heart rate during hemorrhage. Thus defined, a CSC in CORRP occurred after an average extraction of 9.2% +/- 4.7% TBV, whereas a CSC was not seen until an average loss of 16.5% +/- 8.1% TBV for AP, 21% +/- 13% TBV for PWP, 15.5% +/- 7% TBV for PAP, and 35% +/- 3% TBV for CVP. These average blood losses are all significantly different from the average blood loss required to effect a CSC in CORRP. The blood loss required to effect a CSC in CO averaged 9.7% +/- 6%. We conclude that in these anesthetized dogs, CORRP detected blood loss earlier than other commonly used hemodynamic parameters, including several invasive parameters such as CVP, PAP, and PWP; CORRP and CO were equivalent in their ability to detect early stages of blood loss.

Peripheral postcapillary venous pressure--a new hemodynamic monitoring parameter.

Peripheral postcapillary venous pressure (PCVP) appears to be an indicator of peripheral perfusion (cutaneous blood flow) in the experimental animal. Eighteen male mongrel dogs under balanced anesthesia were subjected to either slow, continuous hemorrhage 0.65 ml/kg/min) or plasma expansion with dextran 40 (0.80 ml/kg/min) over a period of 1 hour. Peripheral PCVP, cental venous pressure arterial pressure, cardiac output (CO), mixed venous oxygen saturation, pulmonary arterial pressure, and pulmonary wedge pressure were monitored on a continuous basis. The only parameter that consistently gave a predictable measure of the degree of induced volume change without requiring pulmonary arterial catheterization was PCVP. PCVP showed a close correlation with CO (r = 0.96).

Complications and risks of central venous catheter placement in children.

BACKGROUND: Since Aubaniac's first description in 1952, the use of central venous catheters has increased dramatically; they are now considered commonplace. Placement of these catheters, however, has an associated risk of morbidity and mortality. In most cases, this risk is outweighted by the benefit gained, especially when long-term access to the central venous system is needed for multiple transfusions, chemotherapy, antibiotics, or parenteral nutrition. A large number of central venous catheters are placed in children at our institution, usually by interns and residents. METHODS: To identify associated risks and complications, we reviewed the records of 1435 consecutive catheterizations in children over a 10-year period. Data collected included age, sex, site of catheterization, type of catheter, primary disease, prior catheterizations, indication for placement, failed attempts, number of attempts, catheter misplacement, level of physician training, new needle punctures, and complications. We then used logistic regression analysis to identify independent risk factors for complications. RESULTS: We noted 39 (3.1%) perioperative complications, including 19 (1.5%) arterial punctures, 10 (0.8%) pneumothoraces, 6 (0.5%) hemothoraces, 2 (0.2%) cases of superior vena cava syndrome, 1 (0.1%) episode of ventricular fibrillation that required cardioversion, and 1 episode of bleeding that required a cutaneous suture. Univariate analysis revealed that catheters placed in a subclavian vein (vs all other sites combined, P < .01) were less likely to have an associated complication. In addition, multiple attempts (vs success on first attempt, P < .0001), failed attempt (vs success at initial site, P < .0001), catheter misplacement (vs proper initial position, P < .01), and prior catheterizations (vs no prior catheterization, P < .0005) were associated with complications. Logistic regression revealed multiple attempts (vs success on first attempt, odds ratio (OR) = 5.4), failed attempt (vs success at initial site, OR = 5.2), and catheter misplacement (vs proper initial position, OR = 6.9) to be independent risk factors for complications. Age, sex, type of catheter, primary disease, indication for placement, and level of physician training (intern or resident vs staff) were not associated with complications. CONCLUSIONS: Central venous catheterization in children is relatively safe, with only a 3.2% complication rate and no mortality in our series.

Surgical management of islet-cell adenoma in infancy.

Persistent neonatal hypoglycemia is a potentially serious condition which should be recognized promptly, investigated thoroughly, and treated expeditiously. Islet-cell adenoma causing hypoglycemia in infancy is very unusual. Only 23 cases have been reported in the literature. This report documents eight cases of our own and summarizes diagnostic methods, proper medical preparation, and fundamental surgical management. Prompt surgical intervention is emphasized, as this will relieve hypoglycemia and may be important in preventing irreversible central nervous system damage. We are of the opinion that any infant with unremitting hypoglycemia, a high corrected insulin/glucose ratio, and failure to respond to maximum diazoxide therapy will require partial pancreatectomy. Identification of the adenoma at the time of operation is unlikely, and blind pancreatectomy and/or reoperation is not unusual.

Peripheral postcapillary venous pressure: a new, more sensitive monitor of effective blood volume during hemorrhagic shock and resuscitation.

Peripheral postcapillary venous pressure (PCVP) and mixed venous oxygen saturation (SvO2 or PASO2) have been shown to be sensitive indicators of volume status and appear to reflect the adequacy of peripheral perfusion during controlled bleeding. This study demonstrates that in an open-chest dog model with controlled venous return, PCVP is closely and linearly (r2 = 0.6) correlated with cardiac output (CO). Furthermore, oxygen saturation as measured in the central venous system (CVSO2) and peripheral vein PVSO2) were found to be closely and linearly related to PASO2 (r = 0.72 to 0.99 and 0.91 to 0.98, respectively). Thus PCVP, CVSO2, and PVSO2 represent easily and safely obtainable parameters that closely reflect major physiologic variables. During resuscitation after controlled hemorrhage, the PCVP and PVSO2 accurately reflected the restoration of blood volume and were as good as CO and central saturations. Central venous and pulmonary wedge pressures both poorly reflected the return to full volume repletion (P less than 0.01). Thus, PCVP and PVSO2 seem to be reliable indices of volume status and perfusion and do not require invasive, central monitoring.

A new approach to massive blood transfusion during pediatric liver resection.

Morbidity and death during liver resection in children are due to hemorrhage and the consequences of massive transfusion. To overcome these problems, a new rapid method of blood transfusion was used in four children (8 to 35 months, 8.6 to 13 kg) undergoing extensive hepatic resection for tumor (tumor weight, 440 to 1625 gm). The rapid infusion device consisted of a roller pump and a bubble oxygenator-warmer circuit primed with washed packed red cells resuspended in fresh-frozen plasma and calcium-free balanced salt solution (Plasmalyte). The infusate was warmed, oxygenated, and buffered before it was administered. An average of 5130 ml per patient of this reconstituted blood was infused at an average rate of 122 +/- 45 ml/min, with peak infusion rates sometimes as great as 1 L/min. Cardiac output, pulmonary artery wedge pressure, body temperature, urine output, blood gases, blood chemistries, and coagulation factors remained unchanged during and after these massive transfusions. Blood transfusion at rapid rates required during pediatric liver resection can be accomplished safely if the storage lesion of the bank blood is previously corrected.

Congenital supratentorial and infratentorial peripheral neurogenic tumor: a clinical, ultrastructural, and immunohistochemical study.

Congenital neoplasms of the central nervous system are extremely rare, although they have been well documented since the earliest reports from the mid-19th century. Medulloblastoma, other primitive neuroectodermal tumors, and various types of gliomas have comprised the majority of cases. This report describes a highly unusual infratentorial and supratentorial tumor presenting as a scalp mass in a neonate who experienced in utero distress. The supratentorial mass extended through a defect in the skull to the parietooccipital lobe, and the infratentorial aspect involved the 9th and 10th cranial nerves in the region of the cerebellopontine angle. A complex spindle cell neoplasm incorporating peripheral nerve sheath and vascular characteristics was further characterized by electron microscopy and immunohistochemistry. Based upon these studies, the tumor was interpreted as a congenital schwannoma with divergent vascular differentiation. The child has been tumor-free for approximately 2 years after the initial operative procedure.

Knotted bowel: small-bowel obstruction from coiled peritoneal shunt catheters. Report of two cases.

Knotting of a peritoneal catheter around a loop of bowel is a rare occurrence, which may lead to bowel obstruction. The incomplete removal of two ventriculoperitoneal shunts resulted in two cases of iatrogenically knotted peritoneal catheters. One patient underwent a laparotomy for relief of obstruction and the other was successfully treated by uncoiling the catheter by means of a wire passed into its lumen. A plan for management of a knotted peritoneal catheter is outlined.

Operative therapy of gallbladder disease in patients with cystic fibrosis.

We retrospectively studied 20 patients with cystic fibrosis who underwent surgery for gallbladder disease from 1973 to 1986. A long delay between the onset of symptoms and the diagnosis was noted (mean 7.4 months). This delay was attributed to masking of the symptoms of biliary disease by the malabsorption and pulmonary symptoms seen in this patient population. There was a notable lack of common bile duct disease in our patients as well as in those reported in the literature. This may have been due to a combination of factors: the increased viscosity of the mucus, the small caliber of the gallbladder and ductal system, and the hypotonicity of the gallbladder. We do not recommend routine intraoperative cholangiography in patients with cystic fibrosis and gallbladder disease. Cystic fibrosis is a disease with progressive pulmonary deterioration. Cholecystectomy can be performed in these patients with relative safety if careful preoperative and postoperative care is provided. We recommend early operative intervention in the patient with gallbladder disease and cystic fibrosis.

Aggressive metastasectomy for pulmonic sarcomatous metastases: a follow-up study.

Pulmonary metastases are the primary cause of death due to bone and soft tissue sarcomas. We have previously shown that an aggressive approach and a new technique of multiple pulmonary metastasectomies have resulted in improved survival for patients with pulmonary metastases. In this follow-up study, an expanded database of patients was retrospectively analyzed to determine survivability as well as to evaluate potential prognostic indicators. Forty-nine patients, 26 of whom had osteogenic sarcoma (OGS), were evaluated. A number of patients had been referred from other institutions where their disease had been considered inoperable because it was extensive or recurrent. Using lateral thoracotomies exclusively, employment of a laser technique, and excision of minimal pulmonary parenchymal tissue, we performed aggressive metastasectomy. A mean of 3.0 thoracotomies was performed, in which an average of 10.2 nodules per thoracotomy were excised. Operative morbidity and mortality were minimal. The disease-free interval, the number of nodules resected, the number of thoracotomies performed, and the size of the nodules were evaluated as potential prognostic indicators. Statistically significant correlation could be established only for the size of the nodules resected. The 5-year survival rate for all patients was 39%; it was 24% for patients with OGS and 71% for those without OGS. Aggressive surgical resection of pulmonary metastases from bone and soft tissue sarcoma should be considered when there is control of local disease, no evidence of extrapulmonary metastasis, and adequate post-resection pulmonary reserve. The presence of bilateral, extensive, or recurrent disease is not a contraindication to thoracotomy. Aggressive resection of multiple nodules and improved chemotherapy appear to prolong survival of these patients when compared with survival rates of historical control subjects.

Rapid long tube intubation of the jejunum by a new endoscopic device.

Despite the advantages of aseptic nonoperative intubation of the small intestine for decompression of obstructed loops, 48% of the attempts lead to failure to pass the tube through the pylorus. The difficulty and inconvenience of passage beyond the stomach have been overcome by the development of a special tube attachment adapted to a fiberoptic duodenoscope (Olympus Model GIF-K). Under direct endoscopic vision the tube can be carried into the second and third portion of the duodenum, released from the scope, and then further prodded into the jejunum. The entire procedure takes less than 15 minutes. Rapid intubation has now been easily carried out in five patients. Three patients had mechanical bowel obstruction. Rapid and effective decompression allowed adequate time for stabilization of concomitant serious problems such as (1) marked cardiopulmonary dysfunction secondary to a near fatal pulmonary embolus, (2) severe peritonitis post appendectomy, and (3) acidosis and dehydration. Surgical correction of the obstructing lesions was safely deferred for up to one week until the concomitant problems improved. The fourth patient, who was a renal transplant recipient, had chronic gastric ileus secondary to duodenal ulcer. Rapid passage of the long tube into the jejunum allowed restoration of nutrition and avoidance of gastrostomy. The fifth patient, with an ileus secondary to an infected abdominal aortic graft, underwent successful decompression but died of sepsis. He represents the only mortality. We propose that jejunal intubation using our technic is not only rapid but relatively easy and should encourage the wider acceptance of aseptic long tube intestinal decompression.

Surgery of the immunodeficient child.

A great deal has been learned about the surgery of immunodeficient patients. If one assesses the problem and follows the surgical principles described, in most instances one can solve the problem and be a great help to the oncologist and immunotherapist. A team approach is most important.

Role of the surgeon in the treatment of children's cancer.

The management of children's tumors has changed significantly in the past several years. New techniques and combined surgical, chemotherapeutic, and radiation approaches are responsible for improved survival in most instances. Cooperation of the surgeon with the specialists in separate disciplines is imperative to continued advancements in neoplastic disease of childhood.