All giant neurons of the medial basal forebrain stained for choline acetyltransferase (ChAT). Cell numbers declined from 400,000 to 475,000 in young controls to approximately 140,000 in elderly controls. Five senile dementia cases had counts ranging from 45,000 to 100,000 cells. ChAT levels in control frontal cortex decreased from 1.2 mumol/hr/100 mg protein at age 40 to 0.5 at age 95. Five senile dementia cases had levels ranging from 0.04 to 0.30. When the cholinergic cell count in the basal forebrain drops below about 100,000 cells, the level of cortical ChAT may be so low that clinical dementia appears.

Inherited bacteria which kill males during early development are widely distributed throughout the insects, but have been little studied outside of a single family of beetles, the Coccinellidae. We have investigated a male‐killing bacterium discovered in the butterfly Acraea encedana. This bacterium belongs to the genus Wolbachia and is identical in wsp gene sequence to a male‐killer in the closely related butterfly A. encedon, suggesting that it has either recently moved between host species or was inherited from a common ancestor of the butterflies. The prevalence of Wolbachia is remarkably high, 95% of females are infected and only 6% of wild caught butterflies are male. Measurements of the vertical transmission efficiency were used to calculate that this high prevalence is the result of infected females producing at least 1.79 times the number of surviving daughters as uninfected females (lower confidence limit is 1.25).

No abstract

No abstract

Temperate bacteriophages of diverse morphology were demonstrated by electron microscopy in toxigenic cultures of Clostridium botulinum. The 41 strains examined included 23 type E and multiple representatives of all other types. Cultures induced with mitomycin-C generally gave better yields, but phages were also demonstrable in untreated cultures.A provisional grouping of toxigenic types into four categories is suggested, based mainly upon associated phage patterns. Group 1 comprises types A, B, and F (all proteolytic), many of whose cultures showed an icosahedral contractile phage; others contained a "bullrushy" phage with elongated head and long flexible tail; some strains yielded both. Group 2, types B and F (non-proteolytic), were associated with icosahedral contractile phages; the latter also had an octahedral flexible phage. Group 3, types C and D, yielded conspicuously large phages with octahedral heads and very long sheathed tails. One type C strain produced a long-tailed icosahedral phage. Type E phages constituted group 4. These were icosahedral with tails generally contracted but sometimes flexible, often accompanied by superfluous sheathed tail-like structures resembling certain bacteriocins. Although non-toxigenic "OS" mutants of types A, B, E, and F were phageless, two non-toxic type E strains yielded phages. The possible role of lysogeny in the toxigenicity of certain types of this species is likely to prove difficult to elucidate.