Combined replacement of the ascending aorta and the aortic valve in 42 consecutive patients: A comparison of composite graft techniques and conventional techniques over one year

During 1978, 42 consecutive patients underwent simultaneous aortic valve and ascending aorta replacement in our institution. Seventy-one percent were at low risk despite a high incidence of dissection. Twenty-nine percent were high-risk patients requiring repeat or concomitant cardiac procedures, mostly on an emergency basis. Depending upon the extent of the disease at the aortic root, either of two surgical approaches was used: (1) conventional aortic valve and supracoronary ascending aorta replacement, with or without right coronary artery ostium reimplantation, or (2) insertion of a composite graft containing an aortic valve prosthesis, with reconstruction of both coronary arteries. Preservation of coronary ostia was possible in 85% of the patients, and composite grafts were used in 15%. The conventional method was associated with a higher percentage of survivors. This technique was found to be satisfactory unless severe dilatation or complete destruction of the aortic annulus made composite grafting necessary. The latter technique was associated with fewer re-explorations for postoperative hemorrhage. Both procedures were equally effective, resulting in an operative mortality of 10% in uncomplicated situations. Surgery appeared to offer the only chance of survival for the high-risk group, and half of these patients were salvaged.     

Disturbances in cardiac rhythm caused by the removal of temporary pacemaker wires

The effects of temporary pacemaker wire removal on cardiac rhythm were studied in 22 open-heart surgery patients who had temporary pacemaker wires implanted at the time of chest wall closure. During wire removal, 16 patients developed premature ventricular contractions (PVCs), most commonly occurring as single PVCs, and less often as ventricular couplets. The authors recommend that external pacemaker wire removal be accompanied by electrocardiographic monitoring or at least by a short period of careful clinical observation.     

Phenotypic and Genotypic Characterization of Avian Escherichia coli O86:K61 Isolates Possessing a Gamma-Like Intimin

Escherichia coli O86:K61 has long been associated with outbreaks of infantile diarrhea in humans and with diarrheal disease in many animal species. Studies in the late 1990s identified E. coli O86:K61 as the cause of mortality in a variety of wild birds, and in this study, 34 E. coli O86:K61 isolates were examined. All of the isolates were nonmotile, but most elaborated at least two morphologically distinct surface appendages that were confirmed to be type 1 and curli fimbriae. Thirty-three isolates were positive for the eaeA gene encoding a gamma type of intimin. No phenotypic or genotypic evidence was obtained for elaboration of Shiga-like toxins, but most isolates possessed the gene coding for the cytolethal distending toxin. Five isolates were selected for adherence assays performed with tissue explants and HEp-2 cells, and four of these strains produced attaching and effacing lesions on HEp-2 cells and invaded the cells, as determined by transmission electron microscopy. Two of the five isolates were inoculated orally into 1-day-old specific-pathogen-free chicks, and both of these isolates colonized, invaded, and persisted well in this model. Neither isolate produced attaching and effacing lesions in chicks, although some pathology was evident in the alimentary tract. No deaths were recorded in inoculated chicks. These findings are discussed in light of the possibility that wild birds are potential zoonotic reservoirs of attaching and effacing E. coli.     

Differential responses to endurance training in subsarcolemmal and intermyofibrillar mitochondria

To examinethe effect of endurance training (6 wk of treadmill running) onregional mitochondrial adaptations within skeletal muscle,subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria wereisolated from trained and control rat hindlimb muscles.Mitochondrial oxygen consumption(O₂) was measuredpolarographically by using the following substrates: 1 mM pyruvate + 1 mM malate (P+M), 10 mM 2-oxoglutarate, 45 µMpalmitoyl-DL-carnitine + 1 mMmalate, and 10 mM glutamate. Spectrophotometric assays ofcytochrome-c reductase andNAD-specific isocitrate dehydrogenase (IDH) activity were alsoperformed. Maximal (state III) and resting (state IV) O₂ were lower in SS than inIMF mitochondria in both trained and control groups. In SSmitochondria, training elicited significant 36 and 20% increases instate III O₂ with P+M andglutamate, respectively. In IMF mitochondria, training resulted in asmaller (20%), yet significant, increase in state IIIO₂ with P+M as a substrate,whereas state IIIO₂ increased 33 and 27% with 2-oxoglutarate andpalmitoyl-DL-carnitine + malate,respectively. Within groups,cytochrome-c reductase and IDHactivities were lower in SS when compared with IMF mitochondria.Training increased succinate-cytochrome-c reductase inboth SS (30%) and IMF mitochondria (28%). IDH activity increased 32%in the trained IMF but remained unchanged in SS mitochondria. Weconclude that endurance training promotes substantial changes inprotein stoichiometry and composition of both SS and IMF mitochondria.

     

Transmission dynamics of a zoonotic pathogen within and between wildlife host species

The transmission dynamics of the cowpox virus infection have been quantified in two mixed populations of bank voles (Clethrionomys glareolus) and wood mice (Apodemus sylvaticus), through analyses of detailed time-series of the numbers of susceptible, infectious and newly infected individuals. The cowpox virus is a zoonosis which circulates in these rodent hosts and has been shown to have an adverse effect on reproductive output. The transmission dynamics within species is best described as frequency dependent rather than density dependent, contrary to the 'mass action' assumption of most previous studies, both theoretical and empirical. Estimation of a transmission coefficient for each species in each population also allows annual and seasonal variations in transmission dynamics to be investigated through an analysis of regression residuals. Transmission between host species is found to be negligible despite their close cohabitation. The consequences of this for the combining ability of hosts as zoonotic reservoirs, and for apparent competition between hosts, are discussed.     

Measurements of multiply scattered light for on-line monitoring of changes in size distribution of cell debris suspension

Dual wavelength frequency-domain measurements of photon migration (FDPM) are conducted on filtrate samples obtained from an industrial centrifugation process designed to separate Escherichia coli cell debris from the inclusion bodies. FDPM measurements consist of detecting phase delay of intensity-modulated light at 670 and 820 (or 830) nm. Optical properties of isotropic scattering and absorption are obtained from the regression of phase delay data to the optical diffusion equation. We show that the corresponding intensity-based measurements alone cannot provide accurate and independent estimates for these optical properties. However, FDPM-derived scattering coefficients of filtrate solutions (primarily consisting of 0.1-0.2 micrometer E. coli cell debris) are sensitive to approximately 1 vol % of added inclusion bodies (of 1-2 micrometer size). The technique, theory, and future adaptation of FDPM as an on-line monitor to detect the loss of inclusion bodies in centrifugation following homogenization are presented and contrasted to conventional, intensity-based measurements.     

Vacuolar H+-ATPase Is Expressed in Response to Gibberellin during Tomato Seed Germination

Completion of germination (radicle emergence) by gibberellin (GA)-deficient (gib-1) mutant tomato (Lycopersicon esculentum Mill.) seeds is dependent upon exogenous GA, because weakening of the endosperm tissue enclosing the radicle tip requires GA. To investigate genes that may be involved in endosperm weakening or embryo growth, differential cDNA display was used to identify mRNAs differentially expressed in gib-1 seeds imbibed in the presence or absence of GA₄₊₇. Among these was a GA-responsive mRNA encoding the 16-kD hydrophobic subunit c of the V₀ membrane sector of vacuolar H⁺-translocating ATPases (V-ATPase), which we termed LVA-P1. LVA-P1 mRNA expression in gib-1 seeds was dependent on GA and was particularly abundant in the micropylar region prior to radicle emergence. Both GA dependence and tissue localization of LVA-P1 mRNA expression were confirmed directly in individual gib-1 seeds using tissue printing. LVA-P1 mRNA was also expressed in wild-type seeds during development and germination, independent of exogenous GA. Specific antisera detected protein subunits A and B of the cytoplasmic V₁ sector of the V-ATPase holoenzyme complex in gib-1 seeds only in the presence of GA, and expression was localized to the micropylar region. The results suggest that V-ATPase plays a role in GA-regulated germination of tomato seeds.     

Estimation of the extent of the cutoff region from the spatial distribution of labelling and mitotic indices of intestinal crypts of a fixed length

Current understanding of the pattern of proliferation within intestinal crypts involves the notion of a cutoff region introduced by Cairnieet al. (Exp. Cell. Res. 39, 539–553, 1965b). (Cells produced above the cutoff are non-cycling, whereas cells produced below the cutoff are cycling.) They contrasted the predicted distribution of proliferation in the extreme cases of a cutoff of width 0 (a sharp cutoff) with one eight cells wide (a slow cutoff) and concluded that the data were better explained by the latter. We have shown that crypt size variation artificially broadens the apparent distribution of proliferating cells in the crypt (Totafurnoet al., Biophys. J. 54, 845–858, 1988). Here we show that the measurement and analysis of crypts of a specified height reduces this artifact. This work introduces the use of distance from the crypt base (in microns) to specify the location of cells within the crypt as an improvement over the cell position ordering traditionally used in the determination of the distribution of proliferating cells. We also show how to explicitly correct for several artifacts in the measurement of the labelling index. We conclude that cell proliferation within the crypt is more localized than previously realized; in fact, a cutoff as slow as eight cells wide is rejected.     

Legionella quinlivanii sp. nov. isolated from water

SixLegionella-like organisms were isolated from the evaporative air conditioning system of a bus in South Australia. All six isolates were presumptively identified as legionellae by their growth requirement forl-cysteine and their cellular branched-chain fatty acids. They were serologically distinct from other legionellae in the slide agglutination test. DNA hybridization studies showed that the six isolates belong to a new species ofLegionella, Legionella quinlivanii (ATCC 43830).Use of trade names is for identification only and does not imply endorsement by the Public Health Service or by the U.S. Department of Health and Human Services.