Polyhedral inclusion body

The virions of subgroups A and B are occluded in a protein matrix, whereas virions of subgroups C and D have no inclusion bodies (Figure 1). Because the inclusions of subgroup A frequently have a polyhedral shape, they are called polyhedral inclusion bodies (PIB) or, simply, polyhedra the disease caused by these viruses is known as nuclear polyhedrosis or nucleopolyhedrosis. The virions occluded in polyhedra can be unicapsid (one nucleocapsid per envelope) or multicapsid (more than one nucleocapsid per envelope, usually from two to seven, rarely more). 

Until recently, the polyhedral inclusion body has been used conveniently as the "unit of potency of NPV preparations. Thus, in the United States, the potency of preparations of NPV of Heliothis spp. was expressed in "viral units" (1 VU 109 pib), in "larval equivalents" (lLE 6VU 6x 10 PIB), or simply in billions (10 ) PIB per unit weight or volume of the preparation. The reproducibility of PIB counts, however, is... 

Pieris brassicae Granulovirus Polyhedral inclusion bodies Pieris rapae Granulovirus Tri-(n-butyl)-phosphate Trichoplusia ni Granulovirus Trichoplusia ni Nuclear Polyhedrosis Vims Vaccinia virus Variola virus... 

To investigate how the loss of PSII polypeptides affected the ultra-structure of the thylakoids we looked at thin section electron micrographs of wildtype and mutant cells (Fig. 2). Two differences are worth pointing out 1) The thylakoid content in mutant cells is less than in wildtype cells. 2) The thylakoid regions in mutant cells are less dense than in wildtype cells. Apart from the differences in thylakoid abundance and morphology there are several other differences between wildtype and mutant cells 3) The fourth cellwall layer in mutant cells is thicker than in wildtype cells. 4) The polyhedral bodies (the carboxisomes) in mutant cells are denser than in wildtype cells. 5) Mutant cells contain inclusion bodies of unknown nature (possibly polyphosphate bodies). Some or all of these latter differences may be attributed to the different growth modes for the two cell types. 

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