Radiofrequency ablation alters the microstructural organization of healthy and enzymatically digested porcine mitral valves.

BACKGROUND: Myxomatous mitral valve degeneration is a common cause of mitral regurgitation and is often associated with mitral valve prolapse. With no known targets to pharmacologically treat mitral valve prolapse, surgery is often the only treatment option. Recently, radiofrequency ablation has been proposed as a percutaneous alternative to surgical resection for the reduction of mitral valve leaflet area. OBJECTIVE: Using an in vitro model of porcine mitral valve anterior leaflet enlargement following enzymatic digestion, we sought to investigate mechanisms by which radiofrequency ablation alters the geometry, microstructural organization, and mechanical properties of healthy and digested leaflets. METHODS: Paired measurements before and after ablation revealed the impact of radiofrequency ablation on leaflet properties. Multiphoton imaging was used to characterize changes in the structure and organization of the valvular extracellular matrix; planar biaxial mechanical testing and constitutive modeling were used to estimate mechanical properties of healthy and digested leaflets. RESULTS: Enzymatic digestion increased leaflet area and thickness to a similar extent as clinical mitral valve disease. Radiofrequency ablation altered extracellular matrix alignment and reduced the area of digested leaflets to that of control. Additionally, enzymatic digestion resulted in fiber alignment and reorientation toward the radial direction, causing increased forces during ablation and a structural stiffening which was improved by radiofrequency ablation. CONCLUSION: Radiofrequency ablation induces radial extracellular matrix alignment and effectively reduces the area of enlarged mitral valve leaflets. Hence, this technique may be a therapeutic approach for myxomatous mitral valve disease and is thus an avenue for future study.

Isolation and characterization of low density structures from orotic acid-induced fatty livers.

Centrifugation of a sucrose homogenate of the livers of female albino rats fed a 1.5% orotic acid diet for 3 wk yielded a pellicle containing low density structures. In morphology and biochemical properties these structures resembled those portions of endoplasmic reticulum which accumulated lipid. Electron microscopy indicated large droplets of lipid bounded by a membrane with attached ribosome-like particles. The presence of ribosomes in these structures was established by treatment with deoxycholate and centrifugation. The proportion of 18S and 29S RNA was the same as that found in the ribosomes from normal liver; however, the distribution of radioactivity between the 18S and the 29S RNA after injection of 8-(14)C-adenine was distinctly different. The RNA isolated from these structures contained a higher guanylic acid to cytidylic acid ratio than that found in the microsomes of the normal liver. It is proposed that these low density structures may be those portions of the endoplasmic reticulum in which there exists a defect responsible for the block in the assembly or secretion of plasma lipoprotein.

Transformation of Maize Cells and Regeneration of Fertile Transgenic Plants.

A reproducible system for the generation of fertile, transgenic maize plants has been developed. Cells from embryogenic maize suspension cultures were transformed with the bacterial gene bar using microprojectile bombardment. Transformed calli were selected from the suspension cultures using the herbicide bialaphos. Integration of bar and activity of the enzyme phosphinothricin acetyltransferase (PAT) encoded by bar were confirmed in all bialaphos-resistant callus lines. Fertile transformed maize plants (R0) were regenerated, and of 53 progeny (R1) tested, 29 had PAT activity. All PAT-positive progeny analyzed contained bar. Localized application of herbicide to leaves of bar-transformed R0 and R1 plants resulted in no necrosis, confirming functional activity of PAT in the transgenic plants. Cotransformation experiments were performed using a mixture of two plasmids, one encoding PAT and one containing the nonselected gene encoding [beta]-glucuronidase. R0 plants regenerated from co-transformed callus expressed both genes. These results describe and confirm the development of a system for introduction of DNA into maize.

Yolk sac tumor of the anterior mediastinum. Case report with light- and electron-microscopic examination and immunohistochemical study of alpha-fetoprotein.

A case of yolk sac tumor of the anterior mediastinum was studied by light and electron microscopy and found to have characteristic patterns which were similar to a neoplasm of gonadal origin. These findings, in addition to the immunohistochemical identification of alpha-fetoprotein in the tumor, indicated that the neoplasm was germ cell in origin. A brief review of previously reported cases is included. Prognosis of the patients with yolk sac tumor of the anterior mediastinum was generally dismal; however, those patients with tumors incidentally found but completely excised survived without evidence of reucrrence.

Scalenectomy versus first rib resection for treatment of the thoracic outlet syndrome.

Five years ago a follow-up study of first rib resections disclosed a recurrence rate of over 15%. Many patients were reexplored supraclavicularly, and in every case the anterior scalene muslce was found to be reattached to the bed of the first rib. Scalenectomy invariably was successful, which led to this study of scalenctomy as the first operation for all cases of persistent thoracic outlet syndrome (TOS). The study revealed that most patients with TOS gave a history of neck trauma and had symptoms not only of paraesthesias of the hands and weakness of the arms, but also of neck pains and headaches. The common physical findings were tenderness over the scalene muscles and duplication of symptoms with the arms raised. A scalene muslce block with a local anesthetic was the most useful diagnostic test. The good-to-excellent long-term results following 239 scalenctomies and 214 first rib resections were almost identical, 68% and 70%, respectively, with fair results in 20% and 13%, respectively. In patients with a history of neck trauma followed by headache, neck pain, arm weakness, and parasthesias in the hand, anterior and middle scalenectomy should be considered. On the other hand, first rib resection is recommended for patients with no history of neck trauma and symptoms limited to the arm and hand, particularly those patients with signs of arterial or venous insufficiency.

Pilot-scale harvest of recombinant yeast employing microfiltration: a case study.

In order to develop a cost-effective recovery process for an intracellular product, crossflow microfiltration was studied for the harvest of a recombinant yeast under severe time constraint. It was required to process yeast broth in a short period of time to minimize the risk for product degradation. Preliminary microfiltration studies employing flat sheet membranes showed high throughout with initial fluxes on the order of water fluxes (> 1000 LMH, regime I, < 2 min), followed by a rapid decay towards a low pseudo-steady state flux (20 LMH, regime II, > 2 min). Exploitation of these high fluxes and control of their eventual decline were crucial in establishing a rapid crossflow filtration process. The effect of several parameters, such as initial cell concentration, shear rate, transmembrane pressure, membrane pore size and medium composition on filtration performance were investigated to better understand the flux decline mechanisms. We found that the major contributor to flux decay was reversible fouling by the cake formation on the membrane surface. Within the operating boundaries of our microfiltration system, large-pore membrane (0.65 micron) was much more desirable for harvesting our yeast (10 microns size) without cell leakage than smaller pore ones (0.22 micron and 0.45 micron). Among adjustable operating parameters, feed flow rate (i.e., shear rate) exerted significant impact on average flux, whereas manipulation of transmembrane pressure afforded little improvement. Although initial cell concentration affected adversely the permeation rates, growth medium components, especially soy-peptone, was deemed pivotal in determining the characteristics of cell cake, thus controlling yeast microfiltration.

Role of adenosine A1 and A2A receptors in the alcohol withdrawal syndrome.

The role of adenosine receptor-mediated signaling was examined in the alcohol withdrawal syndrome. CD-1 mice received a liquid diet containing ethanol (6.7%, v/v) or a control liquid diet that were abruptly discontinued after 14 days of treatment. Mice consuming ethanol showed a progressive increase in signs of intoxication throughout the drinking period. Following abrupt discontinuation of ethanol diet, mice demonstrated reversible signs of handling-induced hyperexcitability that were maximal between 5-8 h. Withdrawing mice received treatment with adenosine receptor agonists at the onset of peak withdrawal (5.5 h) and withdrawal signs were blindly rated (during withdrawal hours 6 and 7). Adenosine A1-receptor agonist R-N6(phenylisopropyl)adenosine (0.15 and 0.3 mg/ kg) reduced withdrawal signs 0.5 and 1.5 h after drug administration in a dose-dependent fashion. Adenosine A2A-selective agonist 2-p-(2-carboxyethyl)phenylethyl-amino-5'-N-ethylcarboxamidoadenosine (0.3 mg/kg) reduced withdrawal signs at both time points. In ethanol-withdrawing mice, there were significant decreases in adenosine transporter sites in striatum without changes in cortex or cerebellum. In ethanol-withdrawing mice, there were no changes in adenosine A1 and A2A receptor concentrations in cortex, striatum, or cerebellum. There appears to be a role for adenosine A1 and A2A receptors in the treatment of the ethanol withdrawal syndrome. Published by Elsevier Science Inc.

Radiotelemetric measurement of body temperature in feedlot steers during winter.

Little is known concerning body temperature regulation in cattle under conditions of low ambient temperature. To investigate the influence of cold on body temperature regulation, core body temperatures of feedlot steers (crossbred Bos taurus) were monitored for two winters in Nebraska, from late December to mid-March in yr 1 and from late December through June in yr 2. In yr 1, radiotransmitters to monitor temperature were implanted in the peritoneum of five steers (360 kg); in yr 2, four steers (320 kg) were used. Body temperatures and ambient temperatures were recorded at 3-min intervals and were mathematically filtered to produce 120 readings/d. For yr 1 and 2, daily maximum (40.09 and 39.66 degrees C), minimum (38.78 and 38.64 degrees C), and average (39.29 and 39.06 degrees C) body temperatures were not affected by ambient temperatures. Body temperatures exhibited circadian rhythms with the minima at approximately 0800 and the maxima at approximately 1900. For both years, sharp peaks in body temperature were often seen in the evening and, for yr 2, to a lesser extent in the morning. The occurrence of peaks was normally congruent, within a 1.5-h window, across steers. Congruent peaks in the evening with peak heights of 1.05 and .77 degrees C occurred on 65 and 56% of the days in yr 1 and 2, respectively. Occurrence of congruent peaks was correlated with dusk; peaks followed dusk by 30 to 60 min. Ambient temperature also influenced the occurrence of peaks; few peaks were observed when average daily ambient temperatures were below -7.5 degrees C. The dynamic changes in body temperature throughout the day, including the peaks in body temperature after dusk, strongly suggest that thermoregulatory systems in steers respond not only to current ambient conditions, but also to more integrative measures such as day length and daily heat load.

Radiotelemetry measurement of body temperatures of feedlot steers during summer.

Heat stress is a common problem for cattle. General consequences of heat stress include increased body temperatures and reduced feed intakes. As a measure of heat stress, core body temperatures of unshaded feedlot steers (crossbred Bos taurus) were monitored from mid-June to early November in Nebraska using transmitters implanted in the peritoneum of 10 steers (initially 10 mo of age). Steers were fed at 0630 and 1430 using a finishing diet of 1.52 NEg Mcal/kg with 13% protein and 4% roughage per day and housed in two open lots with stocking densities of 15.2 or 19.3 m2/steer. Core body temperatures, ambient temperature, relative humidity, and wind speed were measured at 3-min intervals and mathematically filtered to produce 120 readings/ d. For 94 usable daily records, body temperature means (39.04 +/- .12 degrees C), maxima (39.89 +/- .21 degrees C at 1836 +/- .73 h), minima (38.33 +/- .29 degrees C at 0823 +/- .38 h), and patterns were similar among steers. As daily maximum ambient temperatures increased, minimum body temperatures decreased slightly (.04 degree C per 5 degrees C; P < .01). After daily maximum ambient temperatures reached a threshold of 25.6 degrees C, daily maximum body temperatures increased linearly with maximum ambient temperatures (.42 degree C per 5 degrees C; P < .01). Sharp peaks in body temperature were often seen in the late evening (approximately 2200) after ambient temperature had decreased to well below maximum values. These evening peaks occurred on an average of 25% of the days, had amplitudes ranging from .7 to 3.5 degrees C relative to mean daily temperatures and lasted for 1.5 h. From a practical standpoint, we suggest that producers monitor meteorological forecast of peak ambient temperatures and make special efforts, such as spraying animals, when exceptionally hot weather is predicted.

Tryptophan deficiency and alcohol consumption in rats as a model for disadvantaged human populations: a preliminary study.

Choice of diet is a combination of socioeconomic, psychological, and biological factors. This article reports on a preliminary study using an animal model and approximating the dietary conditions found on some Native American reservations. The results suggest that alcohol consumption in these disadvantaged populations may be a result of tryptophan deficiency. Tryptophan-deficient rats consumed more alcohol under ad-libitum conditions, perhaps to compensate for the lack of this essential amino acid. Tryptophan is the biological precursor of serotonin, a central neurotransmitter that has been implicated in mood elevations and declines. Alcohol has been found to mimic the effects of tryptophan or serotonin. We suggest that alcohol consumption may act to compensate for the dietary deficiency of this amino acid. The model attributing alcohol consumption to tryptophan deficiency thus connects socioeconomic, psychological, and biological factors.

Why the health care industry should fight union organization and the high cost the industry will pay if its fight is unsuccessful.

The health care industry is being hit hard with an aggressive effort by outside unions to organize health care employees. The interest of health care workers in union organization and their receptiveness to the unions' messages has grown substantially over the last five years--with negative effects on health care workers and the health care industry as a whole. This article addresses union trends in health care, discusses specific cases and their outcomes, and makes recommendations on what the health care industry can, and should, do to preserve a union-free work environment.

Use of postoperative steroids to reduce pain and inflammation.

Postoperative injection of a steroid is used by many podiatric surgeons to reduce pain and inflammation after foot surgery. The authors present a review of the literature on postoperative steroid use from many medical specialties as well as a review of wound and bone healing. The literature indicates that using a steroid is a safe and effective means to reduce postoperative pain and edema. Studies have shown steroids to delay healing, inhibit collagen synthesis, and increase the risk of postoperative infection. No author reported a delay in wound or bone healing or increased infection rate in patients in which a steroid was used. Although there is literature to support this practice, many questions remain and further investigation is needed.

Prediction of liver vitamin A in rats by an oral isotope dilution technique.

Male Sprague-Dawley rats (n = 41) that had liver vitamin A levels ranging from 5 nmol to 22 mumol (0.48 to 1629 nmol/g) were intubated with [3H]retinol in oil (167 kBq/rat). Plasma samples collected at 3, 4, 4.4, 5, 5.4 and 6 d were analyzed for radioactivity, and liver vitamin A mass was determined at 8 d. Nonlinear regression analysis was used to develop a biexponential equation describing the relationship at each sampling time between fraction of the dose remaining in plasma (FDp) and liver vitamin A. The best equation, developed with 3-d data, was liver vitamin A (nmol) = 58,577 x exp(-2715 x FDp) + 1810 x exp(-127 x FDp); Spearman's rank correlation coefficient = 0.982. This equation showed good predictive ability as evidenced by the ratio of the calculated to the observed liver vitamin A (1.23 +/- 0.65) and by its ability to distinguish animals with deficient, marginal, adequate or high vitamin A status. We conclude that this sensitive, noninvasive procedure can be used to predict rat liver vitamin A over a wide range.

Differential effects of ethylene on pith peroxidase of intact tobacco plants and excised tissue.

Ethylene increases the pith peroxidase activity of intact tobacco plants (Nicotiana tabacum) but not of excised pith, either at atmospheric or reduced pressures. In the intact plant, the increased activity involves augmentation of the two constitutive anodic isoperoxidases. In the excised pith, ethylene strongly represses one injury-induced isoperoxidase, while not markedly affecting other isozymes known to be repressed by auxin. Thus, the previously described auxin-induced repression of peroxidase is not due mainly to auxin-induced ethylene formation.

Location of ferritin-labeled concanavalin A binding to influenza virus and tumor cell surfaces.

Concanavalin A (Con-A) was linked to ferritin with glutaraldehyde and chromatographed on Sepharose 6B to separate unconjugated Con-A and ferritin from covalently cross-linked molecules. Ehrlich ascites tumor cells were infected with WSA influenza virus, stained at intervals with the ferritin-labeled Con-A and examined by electron microscopy. The surfaces of most mature viruses were specifically stained, providing direct evidence that influenza viruses maturing in this cell type have exposed Con-A receptor sites. The ferritin cores of the staining reagent were found at an average distance of 21.3 nm from the virus membrane and 10.8 nm from the uninfected cell membrane. This finding was interpreted to mean that the population of Con-A receptor sites on influenza virus particles is located at an average distance from the virus membrane twice that of the population of Con-A receptor sites found on uninfected cells. The structural elements of viral membranes can provide a reliable means for evaluating electron microscopy staining reagents, thereby enhancing their usefulness as probes for the study of membrane relationships.