In vivo molecular imaging of somatostatin receptors in pancreatic islet cells and neuroendocrine tumors by miniaturized confocal laser-scanning fluorescence microscopy.

The aim of the study was to evaluate real time in vivo molecular imaging of somatostatin receptors (sstrs) using a handheld miniaturized confocal laser scan microscope (CLM) in conjunction with fluorescein-labeled octreotate (OcF) in healthy mice and murine models of neuroendocrine tumors. For CLM a small rigid probe (diameter 7 mm) with an integrated single line laser (488 nm) was used (optical slice thickness 7 mum; lateral resolution 0.7 mum). OcF was synthesized via Fmoc solid-phase peptide synthesis and purified by HPLC showing high-affinity binding to the sstr2 (IC(50) 6.2 nmol). For in vitro evaluation, rat and human pancreatic cancer cells were used and characterized with respect to its sstr subtype expression and functional properties. For in vivo confocal imaging, healthy mouse pancreatic islet and renal tubular cells as well as immunoincompetent nude mice harboring sstr-expressing tumors were evaluated. Incubation of sstr-positive cells with OcF showed a specific time- and dose-dependent staining of sstr-positive cells. CLM showed rapid internalization and homogenous cytoplasmatic distribution. After systemic application to mice (n = 8), specific time-dependent internalization and cytoplasmatic distribution into pancreatic islet cells and tubular cells of the renal cortex was recorded. After injection in tumor-harboring nude mice (n = 8), sstr-positive cells selectively displayed a cell surface and cytoplasmatic staining. CLM-targeted biopsies detected sstr-positive tumor cells with a sensitivity of 87.5% and a specificity of 100% as correlated with ex vivo immunohistochemistry. CLM with OcF permits real-time molecular, functional, and morphological imaging of sstr-expressing cell structures, allowing the specific visualization of pancreatic islet cells and neuroendocrine tumors in vivo.

General model, based on two mixed weibull distributions of bacterial resistance, for describing various shapes of inactivation curves.

Cells of Listeria monocytogenes or Salmonella enterica serovar Typhimurium taken from six characteristic stages of growth were subjected to an acidic stress (pH 3.3). As expected, the bacterial resistance increased from the end of the exponential phase to the late stationary phase. Moreover, the shapes of the survival curves gradually evolved as the physiological states of the cells changed. A new primary model, based on two mixed Weibull distributions of cell resistance, is proposed to describe the survival curves and the change in the pattern with the modifications of resistance of two assumed subpopulations. This model resulted from simplification of the first model proposed. These models were compared to the Whiting's model. The parameters of the proposed model were stable and showed consistent evolution according to the initial physiological state of the bacterial population. Compared to the Whiting's model, the proposed model allowed a better fit and more accurate estimation of the parameters. Finally, the parameters of the simplified model had biological significance, which facilitated their interpretation.

Variations over time of microbial load and physicochemical properties of floor materials after cleaning in food industry premises.

Changes over time of microbial load, surface free energy, and roughness of a variety of floor materials were investigated after hygiene operations in meat, pastry, and milk processing environments. Measurements were made in the laboratory on test plates which had been inserted in floors of food premises and subjected to the habitual fouling-cleaning cycles for up to 16 weeks. Microbial contamination of floor materials, assessed after sonication, appeared to be controlled in the milk site, which was generally dry. In both pastry and meat sites a specific microbial population developed and could stabilize to levels up to 10(4) and 10(6) CFU cm(-2), respectively. In the meat site bacterial contamination could be as high as 10(7) CFU cm(-2) on one rough floor material. After introduction in the premises, all flooring materials tended to have similar surface free energy values that could be simulated in the laboratory either perfectly by conditioning the surface with the treated food (in the case of the milk premises) or approximately by conditioning the surface with the hygiene agents used (in the case of the meat and pastry premises).

125I-8-L-arginine vasopressin binding to human mononuclear phagocytes.

The binding of vasopressin to human circulating blood cells was examined. Direct binding studies with preparations of single cell types indicated that the mononuclear phagocyte system is almost entirely responsible for binding of the hormone. Binding of 125I-8-L-arginine vasopressin (AVP) (40 pM) in the presence of excess unlabeled hormone was saturable (2.8 +/- 0.4 fmol/2 x 10(6) cells per ml), was linear with cell number, was dependent upon the concentration of the radioligand used, and was reversible. Binding equilibrium was achieved in 30--40 min at 22 degrees C. Scatchard analysis of binding at this time showed an apparent dissociation constant of 25 +/- 0.21 pM, providing an estimate of 640 +/- 80 sites/cell. Pretreatment of the cells with cytochalasin B, an agent that can block phagocytosis, did not modify radioligand binding, which indicates that 125I-AVP uptake by the cells is due to binding and not to endocytosis. Specificity of vasopressin-sensitive sites on mononuclear phagocytes was demonstrated with a series of vasopressin analogues with various degrees of antidiuretic potency, and with peptide hormones that bind to specific receptors on circulating blood cells but that lack antidiuretic activity. AVP (40 pM) elevated the intracellular level of cyclic AMP from 137 +/- 8.6 to 350 +/- 20.5 pmol/mg cell protein. The binding affinities of the various analogues were correlated with their ability to stimulate intracellular cyclic AMP synthesis (Lys8-vasopressin less than deamino(8-D-Arg)-vasopressin less than oxytocin).

Regional myocardial blood flow and cardiac function in a naturally occurring congestive cardiomyopathy of turkeys.

Round heart disease, a presumed viral myocarditis of turkeys, provides a unique opportunity for the study of congestive cardiomyopathy. Regional myocardial blood flow and cardiac output measurements were made in nine, 19 to 34 day old anaesthetised birds using 141Ce labelled microspheres (15 micron diameter). Atrial, right ventricular and weighted-average left ventricular myocardial blood flow values were similar in control (n = 5) and round heart disease (n = 4) turkeys. The left ventricular subendocardial/subepicardial blood flow ratio of 0.89 +/- 0.02 (mean +/- SE) in round heart disease birds was, however, reduced compared with the value of 1.19 +/- 0.09 in the control birds (P < 0.05). Round heart disease turkeys also had lower systemic pressures and lower cardiac outputs when compared with control birds. M-mode echocardiograms were obtained in 42 unanaesthetised 17 to 37 day old turkeys, 34 control and eight with round heart disease. Echocardiographic evidence of left ventricular dysfunction characterised by left atrial and left ventricular dilation and a markedly reduced left ventricular shortening fraction was found in round heart disease turkeys. Paradoxical motion of the interventricular septum was present in two of eight round heart disease turkeys but in none of the control turkeys. The interventricular septum/left ventricular posterior wall ratio in control and round heart turkeys were similar. Although the body weight of control and round heart disease turkeys were similar, and the diastolic thickness of the left ventricular wall were not substantially different, the ventricular weight/body weight ratio in round heart disease turkeys was increased approximately 52%. The increased ventricular weight was not due to myocardial oedema, as myocardial water content was similar in control and round heart disease turkeys. The features which characterise round heart disease in turkeys: left atrial and left ventricular dilatation, reduced left ventricular shortening fraction, systemic hypotension, low cardiac output, relative subendocardial underperfusion, and an increase in ventricular mass, make it a useful model for congestive cardiomyopathy.

A new cardiac prosthesis: the St. Jude Medical cardiac valve: in vivo results.

The St. Jude Medical cardiac valve prosthesis is a low profile, lightweight, bi-leaflet, central-flow device constructed entirely of pyrolytic carbon. In vivo testing was performed in 24 cows in which the tricuspid valve (n = 14) or mitral valve (n = 10) was replaced by a St. Jude Medical prosthesis with a 26 mm tissue annulus diameter. Eight animals died in the operative period. The 16 surviving animals were sacrificed at 4, 8, 12, or 18 weeks. There were no valve-related deaths nor mechanical valve failures. Anticoagulation was not used in the postoperative period during which time monthly laboratory parameters were obtained including hemoglobin, hematocrit, white cell count, red cell count and indices, lactic acid dehydrogenase, serum haptoglobin, and, additionally at sacrifice, platelet and red cell morphology. Values indicated this prosthesis did not cause hemolysis. At sacrifice the pulmonary arterial tree and peripheral organs showed no evidence of thromboemboli. There was smooth endocardial ingrowth on all valve sewing rings. One valve had thrombus formation on the valve sewing ring. Nine animals were anesthetized prior to sacrifice and underwent open cardiac catheterization. Ventriculography (n = 6) showed minimal transvalvar reflux, and atriograms (n = 6) demonstrated central flow. Transvalvar gradients were 0 to 22 mm Hg (n = 9). One valve of an 18-week tricuspid implant was examined for wear; valve life was calculated to be greater than 2500 years. These data in conjunction with in vitro test results justify clinical trial of the St. Jude Medical prosthesis.