Glucagon-like peptide-1 does not mediate amylase release from AR42J cells.

In this study, AR42J pancreatic acinar cells were used to investigate if glucagon-like peptide-1 (GLP-1) or glucagon might influence amylase release and acinar cell function. We first confirmed the presence of GLP-1 receptors on AR42J cells by reverse trasncriptase-polymerase chain reaction (RT-PCR), Western blotting, and partial sequencing analysis. While cholecystokinin (CCK) increased amylase release from AR42J cells, GLP-1, alone or in the presence of CCK, had no effect on amylase release but both CCK and GLP-1 increased intracellular calcium. Similar to GLP-1, glucagon increased both cyclic adenosine monophosphate (cAMP) and intracellular calcium in AR42J cells but it actually decreased CCK-mediated amylase release (n = 20, P < 0.01). CCK stimulation resulted in an increase in tyrosine phosphorylation of several cellular proteins, unlike GLP-1 treatment, where no such increased phosphorylation was seen. Instead, GLP-1 decreased such protein phosphorylations. Genestein blocked CCK-induced phosphorylation events and amylase secretion while vanadate increased amylase secretion. These results provide evidence that tyrosine phosphorylation is necessary for amylase release and that signaling through GLP-1 receptors does not mediate amylase release in AR42J cells. J. Cell. Physiol. 181:470-478, 1999. Published 1999 Wiley-Liss, Inc.     

Fructosamine in human and bovine semen.

We detected the presence of fructosamine in human and bovine semen. In seminal plasma of healthy normozoospermic men (N = 17) fructosamine was found in 53% of the cases (fru+). In fru+ semen samples the concentration of fructosamine was (mean +/- S.E.M., N = 9) 0.45 +/- 0.09 mmol/L and varied from 0.15 to 0.75 mmol/L. It was 3-12 times lower than in blood serum of healthy men. In semen of infertile men (N = 57) fructosamine was present only in 21% of the cases and its concentration was lower than in fertile men i.e. (mean +/- S.E.M., N = 12) 0.27 +/- 0.007 mmol/L. In bulls (N = 98) fructosamine was found in semen of 82% of animals. In fru+ semen samples the concentration of fructosamine was (mean +/- S.E.M., N = 80) 0.77 +/- 0.12 mmol/L and varied from 0.30 to 1.15 mmol/L. We did not find any correlation between the concentration of fructosamine on one hand, and that of fructose and glucose on the other hand, in either human or bull semen. The difference in the frequency of fructosamine appearance in semen of fertile and infertile men suggests that fructosamine may be in some way involved in the process of fertilisation.     

Development of biological value of sperm in delayed puberty]

Changes in the biological value of sperm depending on the time of the first ejaculation are presented. A control group included 194 boys with normal puberty in whom a biologic value of sperm was evaluated in dependence of the first ejaculation. In all time points a biological value of sperm was significantly worse in the delayed puberty than that in the control group. Twenty four months following the first ejaculation sperm was not normal in any case whereas in the control group normospermia prevailed in this period of time.     

Atrial contractile dysfunction, fibrosis, and arrhythmias in a mouse model of cardiomyopathy secondary to cardiac-specific overexpression of tumor necrosis factor-{alpha}

Transgenic mice overexpressing the inflammatory cytokine TNF-alpha in the heart develop a progressive heart failure syndrome characterized by biventricular dilatation, decreased ejection fraction, decreased survival compared with non-transgenic littermates, and earlier pathology in males. TNF-alpha mice (TNF1.6) develop atrial arrhythmias on ambulatory telemetry monitoring that worsen with age and are more severe in males. We performed in vivo electrophysiological testing in transgenic and control mice, ex vivo optical mapping of voltage in the atria of isolated perfused TNF1.6 hearts, and in vitro studies on isolated atrial muscle and cells to study the mechanisms that lead to the spontaneous arrhythmias. Programmed stimulation induces atrial arrhythmias (n = 8/32) in TNF1.6 but not in control mice (n = 0/37), with a higher inducibility in males. In the isolated perfused hearts, programmed stimulation with single extra beats elicits reentrant atrial arrhythmias (n = 6/6) in TNF1.6 but not control hearts due to slow heterogeneous conduction of the premature beats. Lowering extracellular Ca(2+) normalizes conduction and prevents the arrhythmias. Atrial muscle and cells from TNF1.6 compared with control mice exhibit increased collagen deposition, decreased contractile function, and abnormal systolic and diastolic Ca(2+) handling. Thus abnormalities in action potential propagation and Ca(2+) handling contribute to the initiation of atrial arrhythmias in this mouse model of heart failure.     

Voltage-independent changes in L-type Ca(2+) current uncoupled from SR Ca(2+) release in cardiac myocytes

To determine the effect of voltage-independent alterations of L-type Ca(2+) current (I(Ca)) on the sarcoplasmic reticular (SR) Ca(2+) release in cardiac myocytes, we measured I(Ca) and cytosolic Ca(2+) transients (Ca(i)(2+); intracellular Ca(2+) concentration) in voltage-clamped rat ventricular myocytes during 1) an abrupt increase of extracellular [Ca(2+)] (Ca(o)(2+)) or 2) application of 1 microM FPL-64176, a Ca(2+) channel agonist, to selectively alter I(Ca) in the absence of changes in SR Ca(2+) loading. On the first depolarization in higher Ca(o)(2+), peak I(Ca) was increased by 46 +/- 6% (P < 0.001), but the increases in the maximal rate of rise of Ca(i)(2+) (dCa(i)(2+)/dt(max), where t is time; an index of SR Ca(2+) release flux) and the Ca(i)(2+) transient amplitude were not significant. Rapid exposure to FPL-64176 greatly slowed inactivation of I(Ca), increasing its time integral by 117 +/- 8% (P < 0.001) without significantly increasing peak I(Ca), dCa(i)(2+)/dt(max), or amplitude of the corresponding Ca(i)(2+) transient. Prolongation of exposure to higher Ca(o)(2+) or FPL-64176 did not further increase peak I(Ca) but greatly increased dCa(i)(2+)/dt(max), Ca(i)(2+) transient amplitude, and the gain of Ca(2+) release (dCa(i)(2+)/dt(max)/I(Ca)), evidently due to augmentation of the SR Ca(2+) loading. Also, the time to peak dCa(i)(2+)/dt(max) was significantly increased in the continuous presence of higher Ca(o)(2+) (by 37 +/- 5%, P < 0.001) or FPL-64176 (by 63 +/- 5%, P < 0.002). Our experiments provide the first evidence of a marked disparity between an increased peak I(Ca) and the corresponding SR Ca(2+) release. We attribute this to saturation of the SR Ca(2+) release flux as predicted by local control theory. Prolongation of the SR Ca(2+) release flux, caused by combined actions of a larger I(Ca) and maximally augmented SR Ca(2+) loading, might reflect additional Ca(2+) release from corbular SR.