PubMed Health⌕ Search

Biomedical subjects

Keith Morris

Publications and source records attributed to Keith Morris.

8 recordsLinked to original sources
PubMed2006

Infant feeding with soy formula milk: effects on puberty progression, reproductive function and testicular cell numbers in marmoset monkeys in adulthood.

BACKGROUND: This marmoset study addresses concerns about feeding human male infants with soy formula milk (SFM). METHODS: From age 4 to 5 days, seven male co-twin sets were fed standard formula milk (SMA) or SFM for 5-6 weeks; blood samples were subsequently collected at 10-week intervals. Testes from co-twins killed at 120-138 weeks were fixed for cell counts. RESULTS: SFM- and SMA-fed twins showed normal weight gain; puberty started and progressed normally, based on blood testosterone measurements. Body weight, organ weights (prostate, seminal vesicles, pituitary, thymus and spleen) and penis length were comparable in co-twins. All SMA- and 6/7 SFM-fed males were fertile. Unexpectedly, testis weight (P = 0.041), Sertoli (P = 0.025) and Leydig cell (P = 0.026) numbers per testis were consistently increased in SFM-fed co-twins; the increase in Leydig cell numbers was most marked in males with consistently low-normal testosterone levels. Seminiferous epithelium volume per tubule showed a less consistent, non-significant increase in SFM-fed males; raised germ cell numbers per testis, probably due to increased Sertoli cells, conceivably resulted in larger testes. Average lumen size, although greater in SFM-fed group, was inconsistent between co-twins and the difference was not significant. CONCLUSIONS: Infant feeding with SFM has no gross adverse reproductive effects in male marmosets, though it alters testis size and cell composition, and there is consistent, if indirect, evidence for possible 'compensated Leydig cell failure'. Similar and perhaps larger changes likely occur in adult men who were fed SFM as infants.

Animals↗
PubMed2005

Platelet nitrate responsiveness in fasting and postprandial type 2 diabetes.

Vascular responsiveness to exogenous nitrates in type 2 diabetes (T2DM) is attenuated in brachial and coronary vessels. We determined platelet responsiveness to nitric oxide (NO) in T2DM and control subjects. We examined whether the postprandial (PP) state affected platelet sensitivity to NO donors in T2DM patients and the extent of correlation between this and measures of oxidative stress, compared to changes in endothelial function. Twelve T2DM subjects were studied fasting and four hours after a test meal and compared with 15 healthy controls. We assessed the inhibitory effects of NO donors on adenosine 5'-diphosphate (ADP)-induced platelet aggregation. Oxidative stress was assessed by lipid-derived free radicals, ex vivo by electron paramagnetic resonance spectroscopy and markers of lipid peroxidation. Endothelial function was assessed by flow-mediated vasodilatation (FMD) of the brachial artery. Results are expressed as (mean +/- SEM). Fasting platelet aggregation was increased in diabetics versus controls (14.86 +/- 1.1 Ohms vs. 10.76 +/- 1.1 Ohms, p < 0.05). Sodium nitroprusside (SNP) and glyceryl trinitrate (GTN) inhibited ADP-induced aggregation by 73.1 +/- 5.9% and 50.3 +/- 7.7% in healthy controls compared to 15.4 +/- 7% and 19.5 +/- 8.2% in T2DM (p < 0.05). Fasting and postprandial inhibition of platelet aggregation with NO donors in T2DM was similar. T2DM patients had higher levels of oxidative stress in the fasting state and postprandially. There were no PP correlations with platelet NO resistance. In conclusion, there is platelet hyporesponsiveness to NO donors (SNP/GTN) in T2DM compared to controls, with increased ADP-induced platelet aggregation. Platelet abnormalities were associated with increased oxidative stress.

Adenosine Diphosphate↗
PubMed2003

Training common marmosets (Callithrix jacchus) to cooperate during routine laboratory procedures: ease of training and time investment.

The first author trained 12 laboratory-housed common marmosets (Callithrix jacchus) in pairs to assess the practicality of positive reinforcement training as a technique in the management of these nonhuman animals. Behaviors taught were (a) target training to allow in homecage weighing and (b) providing urine samples. Between 2 to 13, 10-minute training sessions established desired behaviors. Training aggressive animals only after they had been fed eliminated aggression during training. Trained animals proved extremely reliable, and data collection using trained animals was considerably faster than collection using current laboratory techniques. The results suggest that positive reinforcement training is a practical option in the management of laboratory-housed marmosets.

Animal Husbandry↗
PubMed2002

Infant feeding with soy formula milk: effects on the testis and on blood testosterone levels in marmoset monkeys during the period of neonatal testicular activity.

BACKGROUND: This study has addressed concerns about possible effects of feeding human infants soy formula milk (SFM). METHODS: This is a feeding study in marmosets, using a mainly co-twin design. From 4-5 until 35-45 days of age, co-twin males were fed by hand with either standard (cow) formula milk (SMA = controls) or with SFM for approximately 8 h each day (2 h at weekends) and intake related to bodyweight. Blood samples were collected at 18-20 and at 35-45 days of age in 13 sets of co-twins plus two non-twin males per group and, at the later age, seven sets of co-twins were killed and the testes and pituitary gland fixed for cell counts. RESULTS: Weight gain and formula intake were similar in both feeding groups. SMA-fed males had mean testosterone levels of 2.8-3.1 ng/ml, typical of the "neonatal testosterone rise", whereas SFM-fed males exhibited consistently lower mean levels (1.2-2.6 ng/ml); paired comparison in SMA-and SFM-fed co-twins at day 35-45 revealed 53-70% lower levels in 11 of 13 co-twins fed with SFM (P = 0.004). Further evidence for suppression of testosterone levels in SFM-fed males came from comparison of the frequency of low testosterone levels (<0.5 ng/ml). In historical controls aged 35-45 days, two out of 22 values were <0.5 ng/ml, a similar frequency as found in control SMA-fed males (one out of 15 values <0.5 ng/ml). In contrast, 12 out of 15 values for SFM-fed males were <0.5 ng/ml (P < 0.001). There was no consistent relationship between SFM intake/g and testosterone levels. Paradoxically, the mean number of Leydig cells per testis was increased by 74% (P < 0.001) in co-twins fed SFM, when compared with their SMA-fed brothers, whereas no significant changes were found in numbers of Sertoli and germ cells. Because of the lack of gonadotrophin assays, the number of immunopositive LHbeta and FSHbeta cells in the pituitary gland, and their ratio, were determined but no consistent difference was found between SMA- and SFM-fed twins. CONCLUSIONS: Based on the average isoflavone content of the SFM brand used, intake of isoflavones was estimated at 1.6-3.5 mg/kg/day in the SFM-fed marmosets which is 40-87% of that reported in 4 month human infants fed on a 100% SFM diet. It is therefore considered likely that similar, or larger, effects to those shown here in marmosets may occur in human male infants fed with SFM. Whether the changes described result in longer-term effects is under investigation.

Animal Feed↗
PubMed2002

Cage use and feeding height preferences of captive common marmosets (Callithrix j. jacchus) in two-tier cages.

Determining appropriate feeding regimes has important welfare implications for cap-tive primates. This study examined the preference of food bowl heights in 6 pairs of common marmosets (Callithrix jacchus) housed in a 2-tier cage system. Given that marmosets are arboreal and spend most of their time in the upper half of their cages, we predicted that the marmosets would prefer a food bowl positioned at the top of the cage over one positioned at the bottom. We further predicted that this would be more apparent for the marmosets housed in lower tier than upper tier cages. Given a choice regarding where to feed, marmosets did prefer the top bowl to the bottom bowl; how-ever, when only 1 food bowl was presented, its position had no significant effect on the marmosets' feeding behavior. In addition, contrary to the prediction, there were few differences in the marmosets' feeding behavior in the upper and lower tier cages. Feeding the marmosets in a bowl at the bottom of their cage did not result in greater cage use. On the basis of this study, we recommend positioning captive marmosets' food bowls high in the cage.

Animal Welfare↗
PubMed2002

The effects of caretaker-primate relationships on primates in the laboratory.

As contact with caretakers is likely to make up the majority of human-primate interactions in laboratories, caretakers represent an important influence in the lives of captive primates. The aim of this study was to determine how caretaker-primate relationships affected the behavior of primates in the laboratory. We examined whether stump-tailed macaques (Macaca arctoides) who were evaluated by caretakers as being either friendly or unfriendly differed in the quality and quantity of interactions with their caretakers during husbandry procedures and in their behavior at times of high and low levels of caretaker activity. Results revealed that animals who had friendly relationships with caretakers were less disturbed by routine husbandry procedures, approached caretakers more often, and were willing to accept food offered by caretakers compared with animals considered unfriendly toward their caretakers. The study concluded that the quality of the primate-caretaker relationship may have an important impact on behavior and may have implications for the well-being of animals and caretakers, as both can benefit from positive feedback from one another.

Animal Welfare↗