Nuclear size of live and dead bovine spermatozoa

Effect of processing and measuring procedures on estimated sizes of bull sperm heads

Reported estimates of sperm head size within a species vary considerably, partly due to procedural effects. A simple India ink method was developed that provided good contrast without inducing artifacts. Semen from five fertile bulls was smeared on replicate slides and left unfixed or fixed in Carnoys solution, with ink added for background. Other slides were fixed, and sperm were stained by the Feulgen procedure. Sperm head area was measured four ways. These were linear measurements made with the aid of an ocular micrometer and an oil immersion objective, plus three methods of measuring sperm heads projected at magnification 5,000 x. The areas of unfixed and fixed sperm heads did not differ (41.5 microm(2) versus 41.6 microm(2), respectively, P>0.05). The Feulgen-stained head area was smaller (26.2 microm(2), P<0.05). Sperm head areas calculated from ocular micrometer measurements were slightly smaller (P<0.05) than areas measured using projection. Identical results obtained by two technicians were treated as duplicates and approximately half of the variation was biological, due to source of semen. There was an interaction (P<0.05) between the sample source and fixation procedures. Thus, preparative techniques must be carefully controlled, and experiments designed to partition possible interactions between the biological material sampled and procedures used.

Multiplication of measles virus in cell cultures

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PLAQUE DIFFERENTIATION AND REPLICATION OF VIRULENT AND ATTENUATED STRAINS OF MEASLES VIRUS

Rapp, Fred (Baylor University College of Medicine, Houston, Tex.). Plaque differentiation and replication of virulent and attenuated strains of measles virus. J. Bacteriol. 88:1448-1458. 1964.-Plaque formation by strains of measles virus in a stable line of African green monkey kidney cells (BSC-1) is characterized by development of large plaques (>1 mm) within 4 days after inoculation of the cultures with the virulent Edmonston strain or by small plaques (<1 mm) after inoculation with the attenuated Edmonston strain of virus. Plaque formation by measles virus is not influenced by iododeoxyuridine, cytosine arabinoside, isatinthiosemicarbazone, streptonigrin, actinomycin D, or mitomycin C. The predominant cytopathic effect observed with both strains is the formation of large, multinucleated giant cells. Development of the giant cells is correlated with development of virus antigen and synthesis of infectious virus. Synthesis of virus is similar at 34 and at 37 C. Appearance of intracellular virus precedes release, and is later in the attenuated virus-infected cells than in cells infected with the virulent strain. With the virulent strain, equal concentrations of intra- and extracellular virus are found but, with attenuated virus, only a small fraction reaches the extracellular fluids, and more than 95% of the newly synthesized virus remains cell-associated.