The relationship between nitro group reduction and the intestinal microflora.

The capacity of rats to reduce a 25-mg dose of p-nitrobenzoic acid (PNBA) was measured by quantifying the amount of this compound recovered in the urine as p-aminobenzoic acid (PABA) and its conjugates. It was found that germfree rats converted approximately 1% of PNBA to PABA; in conventional rats the conversion was approximately 25%. Various bacteria isolated from the rat cecum were selectively associated with germfree rats and it was demonstrated that these bacteria colonized their gastrointestinal tracts.

Age, sex, and experience as related to the neural basis of cognitive development.

Studies of rhesus monkeys raised from infancy without portions of the central nervous systems provide evidence regarding the timing of functional maturity of specific regions. Some findings have been presented which show that deficits following lesions of specific cortical areas emerge at that age when abilities dependent upon the cortical area in question take on adult form in unoperated monkeys. However, age is but a convenient abstraction for conditions that vary over time.

Sex-dependent behavioral effects of cerebral cortical lesions in the developing rhesus monkey.

Male rhesus monkeys with orbital prefrontal lesions were imtpaired on behavioral tests at 2(1/2) months of age whereas similar deficits were not detected in females with comparable lesions until 15 to 18 months of age. The results suggest that the maturation of a cortical region in the primate brain proceeds at different tempos in males and females.

Delayed recovery of function following orbital prefrontal lesions in infant monkeys.

Monkeys given orbital prefrontal lesions at 1, 4, or 8 weeks of age exhibited a severe learning disability when they were tested at 1 year of age, but showed substantial recovery by the time they were 2 years old. These results suggest that the protracted maturation of intact cortical regions is important in recovery of function after early brain injury.

Role of intestinal microflora in the metabolism of guanidinosuccinic acid.

Among a variety of bacteria isolated from the gastrointestinal tracts of rats and humans, only streptococci of group N are capable of degrading guanidinosuccinic acid added to their culture medium. The urinary excretion of guanidinosuccinic acid by germfree rats is greater than that of conventional rats. The excretion of this compound by gnotobiotic rats correlates with the capacity of their intestinal microflora to degrade guanidinosuccinic acid in culture.

Caffeic acid metabolism by gnotobiotic rats and their intestinal bacteria.

Most metabolites of caffeic acid that are found in the urine of man and experimental animals arise as the result of reactions of the intestinal microflora of the host. This conclusion is now confirmed by the observation that O-methylation, which can be attributed to mammalian enzymes, is the only reaction sustained by caffeic acid in germfree rats. When the germfree rats are selectively infected by one or more bacteria characteristic of the gastrointestinal tract of rodents, the feeding of caffeic acid leads to the appearance in the urine of additional metabolites of caffeic acid.