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Ultrastructure of the human skeletal muscle sarcocyst
1Department of Pathology, Faculty of Medicine, University of Malaya, Kuala Lumpur.
Abstract:
The ultrastructure of the human skeletal muscle sarcocyst found in Malaysia is reported. Sarcocyst-positive, formalin-fixed tongue tissues were postfixed in osmium tetroxide. The primary cyst wall consisted of a thin membrane supported by osmiophilic material that was interrupted regularly by vesicle-like invaginations. Although there were no cytophaneres, stubby protrusions of the primary wall were observed. These protrusions were accentuated by dense, curvilinear material externally. The primary wall was wavy over about half the cross section of the cyst. The granular ground substance underlying the primary wall occasionally contained hitherto undescribed coiled microtubular structures. Branching septa extended from the ground substance into the cyst, separating mature merozoites into compartments. A few peripheral metrocytes and many laminated myelin figure-like structures, probably degenerating merozoites, were found. Although the human muscular sarcocyst has the same basic ultrastructure as those found in other animals, the stubby protrusions and coiled microtubular structures in the ground substance have not been described previously in nonhuman animals.
Insights
This study details the ultrastructure of human skeletal muscle sarcocysts from Malaysia. Unique stubby protrusions and coiled microtubular structures were observed in the cyst wall and ground substance.
Area of Science:
- Parasitology
- Ultrastructural Biology
- Human Pathology
Background:
- Sarcocystis species are protozoan parasites that infect various animals and humans.
- Human infections with Sarcocystis are typically acquired through ingestion of undercooked meat containing sarcocysts.
- Understanding the ultrastructural characteristics of human Sarcocystis is crucial for diagnosis and pathogenesis research.
Purpose of the Study:
- To describe the ultrastructure of a human skeletal muscle sarcocyst identified in Malaysian isolates.
- To compare the observed ultrastructure with known Sarcocystis species in other animals.
- To identify any novel structural features in human Sarcocystis.
Main Methods:
- Human tongue tissues confirmed positive for Sarcocystis were utilized.
- Tissues were fixed in formalin and postfixed with osmium tetroxide for electron microscopy.
- Ultrastructural examination was performed using transmission electron microscopy.
Main Results:
- The primary cyst wall exhibited a thin membrane with osmiophilic material, vesicle-like invaginations, and unique stubby protrusions.
- The ground substance contained previously undescribed coiled microtubular structures.
- Branching septa compartmentalized mature merozoites; degenerating merozoites appeared as myelin figure-like structures.
Conclusions:
- Human muscular sarcocysts share basic ultrastructure with those in animals.
- Stubby protrusions and coiled microtubular structures in the ground substance are novel findings in human Sarcocystis.
- These unique ultrastructural features may aid in differentiating human Sarcocystis species.