knobbed acrosomes in bull semen · knobbed acrosomes in bull semen may occur in several different...
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Knobbed acrosomes in bull semen
Peter Chenoweth BVSc (Hon), PhD, MANCVSc (Reproduction), DACT
ChenoVet Animal Andrology Pty Ltd
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Normal Bull SpermDIC 1000X
Post nuclear region
Equatorial region
Acrosome
Apical ridge
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Knobbed acrosomes in bull semen may occur in several different ways.
1. Secondary to a spermatogenic stressor – e.g. heat.re they normally appear in numbers at approximately 3 weeks post insult, in association with numbers of other typical sperm defects
following such stress.
2. As a genetic fault. These are uncommon and so far have been identified in certain lines of Friesian, Angus and Wagyu bulls.
Some rules for categorising these are shown below.
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KA Criteria
To qualify as a “problem”:• In 20% plus of sperm population
• Consistent over time
• Lack of other indications of major spermatogenic dysfunction
• Infertility? Generally suspected if not apparent.
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Bull NE 1000X
Most commonly picked up first as a flattened, thickened top edgeof the acrosome (erroneously termed a flat acrosome)
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Bull NE 1000X
Folded, version – quite common
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Bull Phase 1000X
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Bull Phase 1000X
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Bull DIC 1000X
Knob form, from which the name derives
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Transmission Electron Micrograph Showing normal apical ridges.Note, all solid appearance.
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Transmission EM of both knobbed and normal apical ridges
Knob
Normal
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TEM classic knob – note cyst-like spacecontaining loose material
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Phase 1000xClassic knob (whichIs relatively less common Than other forms.
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NE 1000X Classic knobs
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DIC 1000xFolded knob, plusPNC loss and midpiece defect
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Modified phase 1000XClassic folded, thickenedKnob.