Apoptosis of polymorphonuclear leukocytes of the juvenile bovine mammary gland during induced influx

Free access article

Issue		Vet. Res. Volume 31, Number 6, November-December 2000


Page(s)		553 - 563
DOI		10.1051/vetres:2000139
How to cite this article		Vet. Res. (2000) 553-563

DOI: 10.1051/vetres:2000139

Vet. Res. 31 (2000) 553-563

Apoptosis of polymorphonuclear leukocytes of the juvenile bovine mammary gland during induced influx

Zbysek Sládek^a - Dusan Rysánek^b

^aDepartment of Morphology, Physiology and Veterinary Sciences, Mendel University of Agriculture and Forestry, Zemedelská 1, 613 00 Brno, Czech Republic
^bVeterinary Research Institute, Hudcova 70, 621 32 Brno, Czech Republic

(Received 2 March 2000; accepted 28 June 2000)

Abstract:

The dynamics of apoptosis of polymorphonuclear leukocytes (PMN) during induced influx of PMN into the cavity system of the juvenile bovine mammary gland in order to investigate the role of apoptosis of PMN in the resolution of mastitis was studied. The instillation of a synthetic analogue of muramyl dipeptide into teat sinus of the sixteen mammary glands was followed by a massive influx of PMN culminating after 24 h and resolving after 96 h. Every 24 h following the influx, apoptotic PMN were microscopically detected, based on morphological characteristics. Twenty four hours after the stimulation, apoptotic PMN were already observed, and peak counts of apoptotic PMN were reached 48 h after the stimulation. The lowest differential count of apoptotic PMN, corresponding to the pre-stimulation value, was found 96 h after the stimulation. The presence of macrophages (MAC) containing phagocytized apoptotic PMN was observed by histochemical staining for myeloperoxidase (MPO) and electron microscopy. The percentage of MPO-positive macrophages increased during the resolution phase to reach peak values 48 h after the stimulation. Apoptosis of PMN and phagocytosis by macrophages may represent a removal mechanism that is important in the resolution of the induced influx of PMN in the cavity system of juvenile bovine mammary gland.

Keywords: polymorphonuclear leukocyte / macrophage / apoptosis / juvenile bovine mammary gland

Résumé:

Apoptose des leucocytes polymorphonucléaires de la glande mammaire juvénile des bovins durant l'influx induit. Afin de déterminer le rôle de l'apoptose dans la résolution des mammites, la dynamique de l'apoptose des leucocytes polymorphonucléaires (PMN) durant l'influx induit dans le système des cavités de la glande mammaire juvénile des bovins a été étudiée. L'application du dérivé synthétique du muramyl dipeptide dans le sinus du trayon de la glande mammaire a été suivi de l'influx massif de PMN avec un pic à 24 h et une résolution 96 heures après la stimulation. Au cours des 24, 48, 72 et 96 h après la stimulation, les suspensions cellulaires ont été examinées en microscopie optique pour détecter l'apoptose des PMN. L'identification des PMN apoptotiques a été réalisée a partir des caractéristiques morphologiques. Les PMN apoptotiques ont été observés dès 24 h après la stimulation et ont atteint un pic à 48 h. La proportion la plus faible de PMN apoptotiques a été observée au bout de 96 h après la stimulation, ce qui correspondait aux valeurs obtenues avant stimulation. La présence des macrophages contenant des PMN phagocytés apoptotiques a été révélée par coloration histochimique à la myélopéroxydase (MPO) et par microscopie électronique. Durant la phase de résolution les macrophages MPO positifs ont atteint un pic 48 h après la stimulation. L'apoptose des PMN et la phagocytose par les macrophages semble représenter un mécanisme de déblaiement important dans la résolution de l'influx induit des PMN dans le système des cavités de la glande mammaire juvénile.

Mots clé : leucocyte polymorphonucléaire / macrophage / apoptose / glande mammaire juvénile des bovins

Correspondence and reprints: Zbysek Sládek
Tel.: (42) 0 5 4513 3151; fax: (42) 0 5 4521128; e-mail: sladekz@seznam.cz

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