Ocular and regional cerebral blood flow in aging Fischer-344 rats.

Vascular remodeling and changes in vascular responsiveness occur in the rat cerebrum with old age. This includes reductions in cerebral arteriolar numerical density, cross-sectional area, distensibility, the relative proportion of distensible elements in the cerebral arteriolar wall, and reduced endothelium-dependent relaxation. The purpose of this study was to test the hypothesis that old age results in an increase in vascular resistance and, correspondingly, a decrease in blood flow to ocular, regional cerebral, and spinal tissue in the rat. Blood flow was measured in the eye, olfactory bulb, left and right cerebrum, pituitary gland, midbrain, pons, cerebellum, medulla, and spinal cord of juvenile (2-mo-old, n = 6), adult (6-mo-old, n = 7), and aged (24-mo-old, n = 7) male Fischer-344 rats. Arterial pressure and blood flow were used to calculate vascular resistance. Vascular resistance in the eye of aged rats (6.03 +/- 1.08 mmHg . ml-1 . min . 100 g) was higher than that in juvenile (3.83 +/- 0.38 mmHg . ml-1 . min . 100 g) and adult rats (3.12 +/- 0.24 mmHg . ml-1 . min . 100 g). Similarly, resistance in the pons of older rats (2.24 +/- 0.55 mmHg . ml-1 . min . 100 g) was greater than in juvenile (0.66 +/- 0.06 mmHg .ml-1 . min . 100 g) and adult rats (0.80 +/- 0.11 mmHg . ml-1 . min . 100 g). In contrast, vascular resistance in the pituitary gland was lower in the aged rats (juvenile, 3.09 +/- 0.22; adult, 2.79 +/- 0.42; aged, 1.73 +/- 0.32 mmHg . ml-1 . min . 100 g, respectively). Vascular resistance was not different in other cerebral tissues or in the spinal cord in the aged rats. These data suggest that regional cerebral and spinal blood flow and vascular resistance remain largely unchanged in conscious aged rats at rest but that elevations in ocular vascular resistance and, correspondingly, decreases in ocular perfusion with advanced age could have serious adverse effects on visual function.

A comparative study of the mannose-resistant and mannose-sensitive haemagglutinins of Escherichia coli isolated from urinary tract infections.

The distribution of mannose-resistant (MRHA) and mannose-sensitive (MSHA) fimbrial haemagglutinins was examined in 482 strains of Escherichia coli isolated from 390 adult women and 45 pregnant mothers with a variety of urinary tract infections (UTI), and from 47 healthy controls. The proportion of MRHA strains was significantly higher in patients with symptomatic UTI (75%) than in women with non-significant bacteriuria (30%, p less than 0.001), pregnant women with asymptomatic UTI (34%, p less than 0.0001) and healthy controls (0%). The proportion of MSHA strains was significantly lower in patients with symptomatic UTI (22%) than in women with non-significant bacteriuria (46%, p less than 0.001) and pregnant women with asymptomatic UTI (52%, p less than 0.01). Only 17% of the strains from healthy controls had MSHA activity. In pregnant women with UTI, whether this was symptomatic or asymptomatic, there was a significant association between infection with MRHA strains of E. coli and a past history of UTI. Thus, in a pregnant woman with an infection and a past history of UTI there is a seven-fold greater chance that this infection is due to an MRHA-bearing organism than in pregnant women without such a history. There was also a significant association between MRHA organisms and symptomatic infection. The risk of symptomatic patients having an infection with an MRHA strain is six times greater than that for a patient with a covert infection.