Biomedical subjects

H M Brown-Borg

Publications and source records attributed to H M Brown-Borg.

22 records · Page 2Linked to original sources

PubMed1986

Influence of stimulus polarity on far-field auditory-evoked electrical responses in the chick.

The effects of inverting click phase on far-field peripheral and brainstem auditory-evoked responses (PBARs) were examined in 8 White Leghorn chicks of age 3 wks. Significant latency differences occurred in all major positive peaks (Pla, P2a peripheral; P3a central) in response to rarefaction vs condensation clicks of equal intensity, with condensation clicks producing the shortest latencies (latency differences: Pla = 0.374, P2a = 0.372 and P3a = 0.352 msec, p less than .001). The mean latency shift corresponds to an equivalent sine wave frequency of approximately 1360 c/s, a value close to the spectral peak energy of the click. No differences in interpeak latency values were found nor any significant amplitude effects.

Acoustic Stimulation↗

PubMedDate not supplied

Glutathione metabolism in long-living Ames dwarf mice.

Ames dwarf mice live significantly longer than their wild type siblings and exhibit elevated antioxidative defenses and reduced oxidative damage. This study was conducted to determine the levels of components of glutathione (GSH) synthesis, degradation and utilization in dwarf and wild type mice. Glutamate-cysteine ligase protein levels were significantly elevated in dwarf liver at 3 and 24 months of age and muscle tissue at all ages examined. In kidney, activity of gamma-glutamyltranspeptidase (GGT) was decreased 42, 30 and 33% in 3, 12 and 24-month-old dwarf mice compared to wild type mice (P<0.0001). In contrast, GSH-S-transferase (GST) activity was markedly elevated (85, 113 and 53%) in kidneys of 3, 12 and 24-month-old dwarf mice (P<0.0001). GGT activity was higher in hearts of young dwarf and wild type mice while GST activity tended to be greater in dwarf mice. Similar to liver and kidney, brain GGT activity was also lower in dwarf mice (P<0.0001). Results of these experiments coupled with previous data provide a mechanism to partially explain the enhanced resistance to oxidative insult and conceivably, the extended longevity of dwarf mice.

Aging↗

PubMedDate not supplied

Does growth hormone prevent or accelerate aging?

It is very well documented that plasma growth hormone (GH) levels decline with age in the human and in experimental animals, and there is considerable evidence that age-related changes in body composition may be caused by reduced function of the GH-IGF-I system. However, excessive GH levels are associated with reduced life expectancy in acromegalic patients and with symptoms of accelerated aging in GH transgenic mice. Hereditary dwarf mice deficient in GH, prolactin, and TSH live much longer than their normal siblings. Possible mechanisms of delayed aging in dwarf mice include lower core body temperature and reduced oxidative processes. It is suggested that the controversies concerning the apparent potential of GH to both prevent and accelerate aging may be reconciled by interpreting the results in light of the negative relationship between body size and life span within a species.

Aging↗

PubMedDate not supplied

Effect of fasting on plasma thyroid and adrenal hormone levels in turkey poults infected with Bordetella avium.

Plasma triiodothyronine (T3), thyroxine (T4), and corticosterone (CS) were measured in fasted and nonfasted control and Bordetella avium-infected poults. The stress of B. avium infection increased plasma CS, and fasting for 24 hours caused a further significant increase in CS levels. Plasma T3 was not affected by the infection, but fasting caused a significant reduction in both control and infected poults. Plasma T4 of fasted poults was increased in both control and infected groups, but infection attenuated the plasma T4 response. Total iodothyronines were increased in the control-fasted poults more than in infected-fasted poults, indicating a reduced responsiveness to stress by the thyroids of infected poults. Changes in plasma thyroid hormones and CS partially explain the decreased body weight gain and decreased body temperature after exposure to B. avium.

Animals↗