Ecological correlates of paternal investment of urates in a tropical cockroach.

Females of the tropical cockroach Xestoblatta hamata feed on urates offered by the male after copulation. Females on nitrogen-deficient diets ingest and transfer to their maturing oocytes more male-derived uric acid than do females on high-protein diets. In isolated females, the greatest uptake of uric acid by the ovaries occurs during the mating stage in the reproductive cycle. Uric acid from males contributes significantly to the female's nitrogen pool and may help shorten the time between mating and oviposition. In both field and laboratory experiments males choose high-protein foods and dietary uric acid.

Vitellogenic blood protein synthesis by insect fat body.

The female fat body of a moth and a roach incorporated labeled amino acids in vitro into substances precipitable by antibodies formed in response to the sex-limited vitellogenic blood proteins of these species. The fat body of males failed to do so, as did that of females before the appearance of these proteins in the blood.

Formulating the alginate-polyornithine biocapsule for prolonged stability: evaluation of composition and manufacturing technique.

Alginate encapsulation is one of the most widely used techniques for introducing cell-based therapeutics into the body. Numerous encapsulation methodologies exist, utilizing a variety of alginates, purification technologies, and unique polycationic membrane components. The stability of a conventional alginate formulation encapsulated using a commercially available technique and apparatus has been characterized extensively. The current study employs an encapsulation protocol and ultra-pure alginate pioneered at the University of Perugia. The enhanced microcapsules were produced, characterized, and implanted into the brain, peritoneal cavity, and subcutaneous space of Long-Evans rats. After 14, 28, 60, 90, 120, and 180 or 215 days, capsules were explanted and the surface was analyzed using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Image analysis was carried out to measure changes in diameter and wall thickness. FTIR peak analysis and surface morphology from SEM indicated that the enhanced encapsulation technique and formulation produced a stable biocapsule capable of survival in all sites, including the harsh peritoneal environment, for at least 215 days. Preimplant analysis showed a marked increase in the structural integrity of the enhanced formulation with improved elasticity and burst strength compared with the baseline formulation, which remained stable for less than 60 days. The enhanced microcapsule composition showed advantages in physical strength and longevity, indicating that small changes in encapsulation methodologies and materials selection can dramatically impact the stability and longevity of alginate microcapsules and their contents.

Vitellogenin: its structure, synthesis and processing in the cockroach Periplaneta americana.

The vitellogenin in the oocyte of the American cockroach contains three different polypeptides with approximate molecular weights of 123 000, 118 000 and 57 000. These are present in a molar ratio of 2 : 2 : 2; all three contain carbohydrate. The same subunit structure is observed in vitellogenin isolated from hemolymph and in that secreted by fat body in organ culture. The only protein found within fat body by precipitation with female-specific antiserum is a large polypeptide, with a molecular weight of approx. 250 000. No mature vitellogenin subunits are found in fat body, even after pulsing with labeled amino acids and chasing with unlabeled substrates for up to 4 h. These data suggest that vitellogenin is synthesized in the fat body as a large precursor, which is processed to smaller polypeptides upon secretion into the hemolymph.

Cell-mediated immune-type response of the American cockroach.

Cell-mediated immunity in the American cockroach, Periplaneta americana, was measured by counting nuclei in a transect through the mass of host hemocytes reacting against transplanted xenograft or autograft integument. Responses to xenografts (Leucophaea maderae) were significantly higher than control responses to autograft integument. Responses to Leucophaea xenografts increased with longer durations of xenograft exposure to hosts for up to eight days, then decreased by day sixteen. Responses to cockroach species from a phylogenetically graded series of donors were stronger and correlated with increasing phylogenetic distance between various donors and hosts (Periplaneta americana).

Transport characterization of membranes for immunoisolation.

This study relates to the diffusive transport characterization of hollow fibre membranes used in implantable bio-hybrid organs and other immunoisolatory devices. Techniques were developed to accurately determine the mass transfer coefficients for diffusing species in the 10(2)-10(5) MW range, validated and then used to study one membrane type known to effectively immunoisolate both allografts and xenografts in vivo. Low-molecular-weight diffusing markers included glucose, vitamin B12 and cytochrome C; higher-molecular-weight molecules were bovine serum albumin, immunoglobulin G, apoferritin and a range of fluorescein-tagged dextrans. Overall and fractional mass transfer coefficients through the hollow fibres were determined using a resistance-in-series model for transport. A flowing dialysis-type apparatus was used for the small-molecular-weight diffusants, whereas a static diffusion chamber was used for large-molecular-weight markers. For diffusion measurements of small-molecular-weight solutes, convective artefacts were minimized and the effect of boundary layers on both sides of the membrane were accounted for in the model. In measuring diffusion coefficients of large-molecular-weight species, boundary layer effects were shown to be negligible. Results showed that for small-molecular-weight species (< 13,000 MW) the diffusion coefficient in the membrane was reduced relative to diffusion in water by two to four times. The diffusion rate of large-molecular-weight species was hindered by several thousand-fold over their rate of diffusion in water.

Intraventricular encapsulated calf adrenal chromaffin cells: viable for at least 500 days in vivo without detectable adverse effects on behavioral/cognitive function or host immune sensitization in rats.

Numerous studies have reported that adrenal chromaffin cell transplants, including encapsulated xenogeneic adrenal chromaffin cells, have analgesic effects. However, in addition to efficacy, the clinical utility of encapsulated xenogeneic adrenal chromaffin cells for treatment of chronic pain is dependent on the duration of cell viability in vivo, and their relative safety. The objectives of the present study in rats were to: (1) examine encapsulated calf adrenal chromaffin (CAC) cells for evidence of viable cells and continued release of analgesic agents after an extended period in vivo; (2) determine if intraventricular encapsulated CAC cells produce detectable adverse effects on behavioral/cognitive function; and (3) test for evidence of host immune sensitization after an extended period of exposure to encapsulated xenogeneic adrenal chromaffin cells. Results of the present study suggest that some encapsulated CAC cells remain viable for nearly 1.5 years in vivo and continue to produce catecholamines and met-enkephalin. Post-explant device norepinephrine output was equivalent to amounts previously shown to produce analgesic effects with intrathecal implants. Encapsulated adrenal chromaffin cells also appeared relatively safe, even when implanted in the cerebral ventricals, with a lower side-effect profile than systemic morphine (4 mg/kg). There was no evidence that encapsulated CAC-cells implanted in the ventricles affected body weight, spontaneous activity levels, or performance in the delayed matching to position operant task which is sensitive to deficits in learning, memory, attention, motivation, and motor function. Finally, encapsulated CAC cells produced no detectable evidence of host immune sensitization after 16.7 months in vivo, although unencapsulated CAC cells produced a robust immune response even in aged rats. The results of the present study suggest that adrenal chromaffin cells remain viable in vivo for long periods of time, and that long-term exposure to encapsulated xenogeneic adrenal chromaffin cell implants appears relatively safe.

Two PC12 pheochromocytoma lines sealed in hollow fiber-based capsules tonically release L-dopa in vitro.

Two PC12 cell-derived lines have been studied following encapsulation into polymer-based hollow fibers with respect to secreted catecholamines and their metabolites. Cellular encapsulation provides a chronic microperfusion environment within which basally secreted PC12 products can be readily measured. Encapsulated PC12 cells grown and held under the conditions specified in this report basally release amounts exceeding their total cellular stores of the dopamine precursor L-DOPA and the electrochemically active dopamine metabolites DOPAC and HVA during 45-min static incubations. Under these same conditions, these cells release less than 0.1% of their total cellular store of dopamine. Depolarizing incubations enhance dopamine secretion eightyfold and enhance secretion of L-DOPA, HVA, and DOPAC about twofold. The relative composition of products basally secreted differs between PC12-derived cell lines, and an inverse relationship exists between basal release of L-DOPA and total cellular store of dopamine. These results further indicate that selected PC12 cell lines are potentially a source of both dopamine and L-DOPA in therapeutic cellular replacement applications.

A simple video position-digitizer for studying animal movement patterns.

A simple video position-digitizer has been developed for studying the movement patterns of small animals. This report provides a complete procedure for constructing the circuit, which when used in conjunction with a conventional video camera and an IBM PC compatible computer, automatically digitizes and records the path of a dark animal against a light colored background for relatively long periods of time.

Defining stops in search pathways.

The alternation of stationary periods and periods of movement may be an important feature of an animal's search tactic. Unambiguously differentiating stops and moves may be difficult, especially from highly resolved digitized pathways, but their identification may be essential for understanding an animal's searching behavior. In this paper, we describe a method for defining stops in search pathways. A computer program that identifies the stop-and-go movement patterns from digitized pathway data is available upon request from the authors.

Measuring and developing suturing technique with a virtual reality surgical simulator.

BACKGROUND: We have developed an interactive virtual reality (VR) surgical simulator for the training and assessment of suturing technique. The surgical simulator is comprised of surgical tools with force feedback, a 3-dimensional graphics visual display of the simulated surgical field, physics-based computer simulations of the tissues and tools, and software to measure and evaluate the trainee's performance. STUDY DESIGN: This study uses the simulator to measure and compare the skills of 8 experienced vascular surgeons versus 12 medical students when performing a virtual reality suturing task. Eight parameters of the suturing task were measured: total tissue damage, accuracy of needle puncture, peak tissue tearing force, time to complete the task, damage to the surface of the tissue, angular error in needle technique, total distance traveled by the tool tip, and a measure of overall error. Three test conditions (dominant hand, nondominant hand, and 3-dimensional needle guide) were tested. Statistical significance was defined as a univariate two-sided p value < or = 0.05. RESULTS: The surgeons' average performance was significantly better than the students' average performance for three of the measured parameters (total tissue damage, time to complete the task, and total distance traveled by the tool tip) for each of the test conditions. For the test condition most similar to surgery (using the dominant hand to suture) one additional parameter was also significantly different (the measure of overall error). The medical students showed improvements for 6 of the 7 parameters for which the users received feedback during the training process. The surgeons also had significant improvement for 4 of the 7 parameters. The students had a larger improvement than the surgeons for 6 of the parameters, but these differences were not statistically significant. CONCLUSIONS: Data indicate differences between surgeon and nonsurgeon performance and in improvement in performance with training. One possible explanation for the superior performance of the surgeons is that their suturing skills applied well to the simulated suturing task. Additional research is required to confirm or deny the similarity between actual and simulated surgical tasks and the relevance of virtual reality surgical simulation to surgical skill assessment and training.

Radon-222 in the gastrointestinal tract: a proposed modification of the ICRP Publication 30 model.

The New England states have a long involved history of radon in individual well water supplies. As a result of these previous findings on the abundance of radon, coupled with its potential health impact, the New England Radiological Health Committee (NERHC) formulated a technical working group in 1980 which was charged with evaluating the possibility of developing uniform concentration guidelines for radon in individual domestic water supplies. This working group determined that the current ICRP Publication 30 metabolic model for the gastrointestinal (GI) tract was inadequate to address the empirically observed rates of 222Rn removal from the body. A modification to the ICRP Publication 30 GI tract model is proposed which attempts to resolve these differences. Calculations are presented, using both the original and modified ICRP Publication 30 models, which indicate that individual potable water supplies containing 222Rn concentrations as high as 400,000 pCi/l. do not significantly increase the probability of stomach or intestinal cancer, as defined by the BEIR III risk estimates. Since this paper deals exclusively with the GI tract, no attempt is made to address the lung burden imposed by the contribution of radon released into the household air by aeration at the tap or other fixtures. Only when the contribution of the radon water source term to both the respiratory and ingestion pathways is evaluated as a whole can any meaningful standard for 222Rn in individual domestic water supplies be established.