Energy-dependent accumulation of fluoroquinolones in quinolone-resistant Klebsiella pneumoniae strains

The intracellular accumulation of norfloxacin and pefloxacin in Klebsiella pneumoniae was evaluated. The roles of lipopolysaccharide, capsule, and outer membrane proteins were not important for the intrabacterial accumulation of fluoroquinolones in isogenic strains with known outer membrane alterations. In fluoroquinolone-resistant clinical isolates also expressing GyrA alterations, an active efflux leading to decreased accumulation of the drugs enhanced their resistance to these agents.     

Isolation of fecal coliform bacteria from the diamondback terrapin (Malaclemys terrapin centrata)

Total and fecal coliform bacteria were isolated from the cloaca and feces of the estuarine diamondback terrapin. The majority of samples contained fecal coliforms. Escherichia coli was the predominant fecal coliform species isolated, and members of the genus Salmonella were isolated from 2 of 39 terrapins. Fecal coliform numbers are used to regulate shellfish harvests, and diamondback terrapins inhabit the brackish-water habitats where oyster beds are found; therefore, these findings have implications for the efficacy of current regulatory parameters in shellfishing waters.     

Warfarin anticoagulation in the perioperative period: is it safe?

A useful correlation between maximum thyroid uptake and radioiodine urine levels at different times after exposure was developed in order to determine when the intervention with an adequate blocking agent might still be effective. In an animal model (dog), six different doses were administered in the range of 100-600 kBq. The best correlation was found between the 125I uptake after 48 h (T-48) and urine radioactivity 4-6 h (U-4, U-5, U-6) after exposure. For the case of U-4, the equation Y(T-48) = 0.790 X(U-4) + 2.973 (r = 0.974 with a level of significance of p < 0.001) was obtained. An analogous study, carried out in humans (n = 20) to whom 1311 was administered, showed a similar correlation and level of significance: Y(T-24) = 1.162 X(U-4)+3.263 (r = 0.926; p < 0.001). The validity of this correlation was confirmed in four volunteers who received small doses of 125I(25-100 kBq), with good agreement between measured and extrapolated thyroid uptake and a mean difference of less than 10% (CV = 16.2%). Three different blocking agents were then tested in the same dog: potassium iodide, potassium perchlorate, and a thionamide (Tapazole). The blocking action of the first two compounds was about 90%, as opposed to only 48% for the third compound. Potassium iodide was chosen for its limited side effects and more universal utilization. The final study, carried out with four different doses, indicated that 25 mg of KI is the ideal amount to be administered to the dog. This corresponds to approximately 100 mg for a 70 kg human being (i.e., 1.4 mg kg(-1)). This dose, when administered to a volunteer 4 h after exposure, provided a thyroid blocking of 68%.     

Enzyme activity of macrophage migration inhibitory factor toward oxidized catecholamines

Macrophage migration inhibitory factor (MIF) is a relatively small, 12.5-kDa protein that is structurally related to some isomerases and for which multiple immune and catalytic roles have been proposed. MIF is widely expressed in tissues with particularly high levels in neural tissues. Here we show that MIF is able to catalyze the conversion of 3,4-dihydroxyphenylaminechrome and norepinephrinechrome, toxic quinone products of the neurotransmitter catecholamines 3,4-dihydroxyphenylamine and norepinephrine, to indoledihydroxy derivatives that may serve as precursors to neuromelanin. This raises the possibility that MIF participates in a detoxification pathway for catecholamine products and could therefore have a protective role in neural tissues, which as in Parkinson's disease, may be subject to catecholamine-related cell death.     

Abnormalities in the p34cdc2-related PITSLRE protein kinase gene complex (CDC2L) on chromosome band 1p36 in melanoma

Recently, several clusters of hepatitis A have been observed among hemophiliacs linked to factor VIII concentrates treated for virus inactivation solely with the solvent/detergent (S/D) method, a procedure that does not affect nonenveloped viruses such as the hepatitis A virus (HAV). A new outbreak of hepatitis A in six hemophiliacs treated with the same lot of a factor VIII preparation occurred recently in Germany. The objective of the study was to clarify whether these diseases were caused by the administration of the S/D-treated plasma product, rather than a community-acquired infection. Polymerase chain reactions designed to detect HAV nucleic acid have been carried out in the implicated factor VIII lots, in the corresponding plasma pools, and in serum samples of four out of six infected individuals. The nucleic acid sequences were determined in samples that resulted in positive amplification products. HAV sequences were found in one of the two plasma pools used for manufacture of the incriminated product, in the incriminated lot itself, and in all recipient sera tested so far, although the latter were collected up to 7 weeks after the onset of jaundice. The sequences obtained were completely identical, revealing a unique HAV strain of genotype IA. This study provides conclusive evidence that hepatitis A can be transmitted by factor VIII concentrates treated solely by the S/D procedure for virus inactivation. This inactivation method is not effective against nonenveloped viruses. Since a number of hepatitis A transmission episodes have been described with such preparations during the past 10 years, their continued use seems to be questionable unless additional virus removal or inactivation steps are introduced to prevent the transmission of nonenveloped viruses. Molecular approaches again proved to be reliable tools for elucidating the chain of virus transmission.     

Perioperative predictors of colonic ischemia after ruptured abdominal aortic aneurysm

PURPOSE: Colonic ischemia and colonic resection occur frequently after ruptured abdominal aortic aneurysm (rAAA). The purpose of this study was to identify the perioperative risk factors that might help to determine earlier in the postoperative period which patients are at risk for colonic ischemia and colonic resection. METHODS: The medical records of the 43 patients who underwent repair of rAAA from January 1989 to November 1997 were reviewed. The data were reviewed for the following factors: acidosis, pressor agents, lactate levels, guaiac status, cardiac index, coagulopathy, early postoperative bowel movement, the lowest intraoperative pH level, the temperature at the conclusion of the case, the location and duration of aortic cross clamping, the amount of fluid boluses administered after surgery, the amount of packed red blood cells administered during the case, and the average systolic blood pressure at admission and during surgery. Univariate analysis was performed with Fisher exact test, chi2 test, and Student t test. Multivariate analyses also were performed with the variables that were found to be significant on the univariate analysis. RESULTS: Thirteen of the 43 patients (30. 2%) had colonic ischemia, and seven of the 13 underwent colonic resection (53.8%). The overall mortality rate was 51.2% (22/43) five of the deaths were intraoperative and excluded from the study. In a comparison of the patients who had colonic ischemia with those who did not, statistically significant differences were found in the following variables: average systolic blood pressure at admission 90 mm Hg or less, hypotension of more than 30 minutes' duration, temperature less than 35 degreesC, pH less than 7.3, fluid boluses administered after surgery 5 L or more, and packed red blood cells 6 units or more. Multivariate analysis indicated that the number of these variables present correlated significantly with the positive predicted probability of colonic ischemia occurring. No patient with two factors or fewer had an ischemic bowel, and the positive predictive probability of colonic ischemia for those patients with six factors was 80%. CONCLUSION: The results of this study show that: (1) colonic ischemia after rAAA may be predicted with the presence of two or more specific perioperative factors, (2) the lack of a guaiac-positive bowel movement may be misleading for the early diagnosis of colonic ischemia, and (3) more than 50% of the patients with colonic ischemia will require a colonic resection. We recommend that any patient with rAAA with more than two perioperative factors undergo sigmoidoscopy every 12 hours after surgery for 48 hours to rule out colonic ischemia without waiting for early or guaiac-positive bowel movement.     

Neural control of left ventricular contractility in the dog heart: synaptic interactions of negative inotropic vagal preganglionic neurons in the nucleus ambiguus with tyrosine hydroxylase immunoreactive terminals

Recent physiological evidence indicates that vagal postganglionic control of left ventricular contractility is mediated by neurons found in a ventricular epicardial fat pad ganglion. In the dog this region has been referred to as the cranial medial ventricular (CMV) ganglion [J.L. Ardell, Structure and function of mammalian intrinsic cardiac neurons, in: J.A. Armour, J.L. Ardell (Eds.). Neurocardiology, Oxford Univ. Press, New York, 1994, pp. 95-114; B.X. Yuan, J.L. Ardell, D.A. Hopkins, A.M. Losier, J.A. Armour, Gross and microscopic anatomy of the canine intrinsic cardiac nervous system, Anat. Rec., 239 (1994) 75-87]. Since activation of the vagal neuronal input to the CMV ganglion reduces left ventricular contractility without influencing cardiac rate or AV conduction, this ganglion contains a functionally selective pool of negative inotropic parasympathetic postganglionic neurons. In the present report we have defined the light microscopic distribution of preganglionic negative inotropic neurons in the CNS which are retrogradely labeled from the CMV ganglion. Some tissues were also processed for the simultaneous immunocytochemical visualization of tyrosine hydroxylase (TH: a marker for catecholaminergic neurons) and examined with both light microscopic and electron microscopic methods. Histochemically visualized neurons were observed in a long slender column in the ventrolateral nucleus ambiguus (NA-VL). The greatest number of retrogradely labeled neurons were observed just rostral to the level of the area postrema. TH perikarya and dendrites were commonly observed interspersed with vagal motoneurons in the NA-VL. TH nerve terminals formed axo-dendritic synapses upon negative inotropic vagal motoneurons, however the origin of these terminals remains to be determined. We conclude that synaptic interactions exist which would permit the parasympathetic preganglionic vagal control of left ventricular contractility to be modulated monosynaptically by catecholaminergic afferents to the NA-VL.     

A new mouse model of experimental melanoma for vaccine and lymphokine therapy

The annual incidence of malignant melanoma is estimated at 10-12 per 100,000 inhabitants in countries of central Europe and the United States, and alarmingly there has been a dramatic upward trend in that estimate. The B16 murine melanoma is a rapidly growing metastatic tumor of spontaneous origin, as are human malignant melanomas. Melanoma cells produce specific antigens which are uniquely different from normal cellular antigens, and the expression of such antigens is the cornerstone for preparation of anti-melanoma vaccines. One major problem in evaluating the effectiveness of vaccination and other biologic therapies is the variability of experimental tumor models. A new metastatic model of experimental melanoma which was developed in our laboratory imitates the major clinical stages of malignant metastatic melanoma: stage I, primary (local) tumor growth and bone marrow invasion; stage II, regional lymph node involvement; and stage III, metastasis to distant organs, such as the lungs. This model has been used successfully for screening vaccines constructed in our laboratory. Immunization with formalinized vaccines (of extracellular antigens, intact melanoma cells, or B700 antigen) or irradiated vaccines (of intact melanoma cells) partially inhibit primary melanoma tumor growth, reduce metastasis to regional lymph nodes and lungs, and significantly increase mean survival time. These anti-tumor effects were improved when polyvalent and monovalent vaccines were combined with IL-2 therapy. We also compared the immunogenic activity of vaccines made from B16 melanoma cells transfected with genes encoding murine IL-2 or GM-CSF, and effects on tumor bearing mice were compared with or without therapy using the corresponding lymphokines. In sum, comparison of antibody production, growth of primary melanoma tumors, number of surviving mice, mean survival time, and percent of mice with lung metastases, showed that the best course of immunotherapy involves vaccination of mice with irradiated B16 melanoma cells transfected to secrete GM-CSF, coupled with GM-CSF therapy.     

Melanin biosynthesis patterns following hormonal stimulation

The effect of melanocyte-stimulating hormone (MSH) on the differentiation of mammalian melanocytes has been widely studied since the early 1950s. There have been many reports about the stimulatory effect of MSH on melanin production and specifically on the activity of tyrosinase, the critical enzyme in the melanogenic pathway. However, few and variable results have been obtained concerning the effect of this hormone on the regulation of DOPAchrome tautomerase (TRP2), another melanogenic enzyme which functions later in the melanogenic pathway, or on other melanogenic activities, such as TRP1. In this study, we show that the MSH-induced stimulation of tyrosinase is accompanied by no significant change in the synthesis or catalytic activities of other melanogenic enzymes such as TRP1 or TRP2. This in turn elicits a dramatic increase in melanin production accompanied by a significant decrease in the incorporation of carboxylated precursors into that melanin biopolymer, although the biological implication of that is still unclear.