The effects of pore size and endothelial cell seeding upon the performance of small-diameter e-PTFE vascular grafts under controlled flow conditions

The purpose of this study was to determine the effects of endothelial cell seeding and graft internodal distance upon the performance of 4-mm-ID e-PTFE grafts during acute reduced blood flow conditions. PTFE grafts especially manufactured with three different mean internodal distances (28, 40, and 52 microns) were evaluated. Fifteen dogs (n = 5 for each design of PTFE graft) underwent bilateral carotid artery replacements with 6 cm lengths of 4-mm-ID PTFE grafts. In each dog one graft was seeded with enzymatically derived endothelial cells; the contralateral graft was nonseeded. All grafts were evaluated 5 weeks postoperatively. Dogs with bilaterally patent grafts were subsequently subjected to flow conditions through the graft that were maintained at 30% of the initial flow rates for 4 hr. Following controlled low flows the grafts were excised and assessed for patency, thrombus-free surface area, inner capsule thickness and prostacyclin production. Endothelial cell seeding of these small-diameter e-PTFE vascular grafts improved patency and thrombus-free surface areas in grafts of all pore sizes, with these parameters being greatest in the 40-microns grafts. Inner-capsule healing in these grafts was controlled and related to the pore size. PGI2 production was improved in endothelial cell seeded grafts of all pore sizes. However, neither endothelial cell seeding nor graft pore size affected the performance of these e-PTFE grafts under conditions of reduced blood flows.     

Neurohumoral control of esophageal epithelial electrolyte transport

The neurohumoral control of epithelial esophageal electrolyte transport was investigated by studying the effect of various hormones and neuroeffector agents on the potential difference (PD) in vivo or on the electrical parameters of electrolyte transport in vitro. The rabbit esophagus, which has no submucosal esophageal glands, demonstrated no effect of pentagastrin, cholecystokinin octapeptide, or synthetic secretin in vivo, and no effect of these hormones or of vasopressin, aldosterone, carbachol, epinephrine, or cAMP in vitro. The rabbit esophagus did respond to metabolic substrates (glucose) in vitro by increasing sodium absorption. In contrast, the opossum esophagus, which contains extensive submucosal glands, had a lower electrical resistance, PD, short-circuit current, and sodium absorption with higher chloride secretion. This esophagus responded to carbachol and epinephrine by sodium and chloride secretion. We believe that only the submucosal glands of the esophagus are under significant neurohumoral control while the sodium transporting function of the stratified squamous epithelium of this organ is important in maintaining its barrier function.     

Effects of Cigarette Smoking on Bilateral Skin Conductance

Bilateral skin conductance was recorded from 8 male and 8 female cigarette smokers and from 8 male and 8 female nonsmoker control subjects on two different days. On one day smokers smoked a cigarette prior to the recording session and on the other they remained abstinent. Subjects also engaged in tasks designed to differentially involve the cerebral hemispheres. SCR asymmetry was measured using two different indices. During both the resting and task periods smokers had larger SCRs in their right than left hands following smoking. Unlike control subjects during the first recording session, smokers did not show task related changes in SCR asymmetry. During tasks smokers showed smaller SCRs in both hands following smoking than following abstinence. Changes in SCR asymmetry associated with smoking were seen in subjects who smoked more cigarettes, reported more subjective craving, were more introverted, and indicated a preference for cognitive processes and strategies associated with the left hemisphere. Results are discussed in terms of relative involvement of the cerebral hemispheres following smoking and smoking abstinence.     

Timing of deletion of autoreactive V{beta}6+ cells and down-modulation of either CD4 or CD8 on phenotypically distinct CD4+8+ subsets of thymocytes expressing intermediate or high levels of T cell receptor

In this paper we describe a differentiation sequence amongst adult murine thymocytes which goes from CD4+8+3lo(low) to CD4+8+3int(intermediate) to CD4+8+3hi(high) and then to mature single positive CD3hi thymocytes. Phenotypic characterization of CD4+8+3int/hi cells for a number of other surface markers is consistent with them being in transition from CD4+8+3lo phenotype to mature phenotype. The same observation was made for sensitivity towards ionomycin-mediated apoptosis. In the thymus of Mls-1a mice, where autoreactive TCR-V beta 6+ cells are negatively selected, deletion of TCR-V beta 6+ cells was first detected in the CD4+8+3int subset, and was complete by the CD4+8+3hi stage, suggesting that up-regulation of the TCR/CD3 complex is required for deletion of Mls-1a autoreactive thymocytes. No sign of apoptosis was detected among any fresh thymocyte subsets suggesting that apoptotic cells are rapidly cleared from the thymus. The CD4+8+3int/CD4+8+3hi cells are therefore populations in transit from the typical cortical thymocytes to the mature T-cells.     

Giant mitochondria distinct from enlarged mitochondria in secretory and ciliated cells of gerbil trachea and bronchioles

Numerous mitochondria ranging from slightly larger than normal to several micrometers in diameter (giant) were found in about one-half the serous secretory cells in the surface epithelium of the normal gerbil trachea and proximal bronchi. Tracheal serous cells of mice also were found to contain numerous giant mitochondria. Clara cells of gerbil bronchioles contained abundant giant mitochondria in addition to normal tubular mitochondria and the second population of enlarged spherical mitochondria that have been described in Clara cells of several genera. In contrast, mouse Clara cells revealed the normal tubular and the enlarged spherical mitochondria but no giant mitochondria. A survey of a number of cell types in gerbils failed to disclose hypertrophied mitochondria outside tracheobronchial surface epithelium and bronchioles. The mitochondrial enlargement resulted from an increase of matrix but not cristae. The expansion of matrix displaced the relatively sparse cristae into small collections compressed against the outer membrane. The prevalence of giant mitochondria and of granular endoplasmic reticulum is similar among cells, and these two organelles are codistributed within cells. The megamitochondria and granular reticulum occupy a central stratum, whereas normal mitochondria occur in the apical and basal regions. The giant mitochondria are considered related to a normal biologic activity that is characteristic of respiratory tract epithelium of mice and gerbils selectively and is more prominent in secretory cells than in ciliated cells.     

Theoretic and experimental analysis of the ability of a commercially prepared system to detect mixtures of bacteria.

The validity of the biochemical identification of bacteria presumes that the inoculum consists of a pure growth of bacteria. The detection of mixtures of bacteria with the Analytab Enteric (API 20E) system was tested. Using a computer to predict the response of the API 20E system to mixed cultures, the presence of a mixture was not detected in 15% of all pairwise combinations of 324 common organisms of the Enterobacteriaceae family and in 19% of all pairwise combinations of Enterobacteriaceae with four gram-positive cocci. These theoretic predictions were confirmed experimentally for selected mixtures in which the bacteria were combined in equal concentrations. These results indicate that a purity subculture plate must be used to insure the detection of mixtures of bacteria, because the API 20E system fails to detect a large number of mixtures and may erroneously identify the organisms in such mixtures.     

Single-stage methods of hypospadias repair

Summary The repair of all hypospadias in one stage represents state of the art in virtually all instances. Implicit in the repair of hypospadias is the correction of chordee, the construction of the neourethra such that the meatus is located on the tip of the glans, and the creation of a penis which is cosmetically appropriate. Described in this paper are most of the currently employed methods utilized for the repair of hypospadias in a single stage. The techniques described herein, in skilled hands, yield good results in 85–90% of cases. Repairs of hypospadias which have been designed and which are recommended for the occasional operator have no place in today's surgical therapy.     

Conformational flexibility of the methyltetrazolethiomethyl side chain of beta-lactam antibiotics. A computer graphics study

Analysis of X-ray crystallographic data for cephalosporins and 1- oxacephalosporins shows that, although the 1-methyl-1H- tetrazol -5- ylthiomethyl side chain at position 3 of a bicyclic beta-lactam nucleus has certain conformational preferences, it also has considerable flexibility. Both the C4 = C3-C3'-S and C3-C3'-S-C5" torsional angles are frequently observed in the vicinity of +/- 90 degrees. The distance between the tetrazole ring carbon C5" and the 4-carboxyl carbon ranges from 4.07 to 5.65 A. Mean bond lengths and bond angles for the 3 and 4 side chains are tabulated.     

Exclusion criteria of DSM-III. A study of co-occurrence of hierarchy-free syndromes

The diagnostic criteria of the third edition of the DSM-III often state that one diagnosis cannot be made if it is "due to" another disorder. Using data from the National Institute of Mental Health Diagnostic Interview Schedule, with a sample of 11,519 subjects from a community population, we found that if two disorders were related to each other according to the DSM-III exclusion criteria, then the presence of a dominant disorder greatly increased the odds of having the excluded disorder. We also found that disorders, which DSM-III says are related to each other, were more strongly associated than disorders, which DSM-III says are unrelated. However, we also found there was a general tendency toward co-occurrence, so that the presence of any disorder increased the odds of having almost any other disorder, even if DSM-III does not list it as a related disorder. We concluded that empirical studies are needed to study the assumptions underlying the use of a diagnostic hierarchy.