Laminar analysis of the number of neurons, astrocytes, oligodendrocytes and microglia in the visual cortex (area 17) of 6- and 12-month-old rhesus monkeys fed a human infant soy-protein formula with or without taurine supplementation from birth.

The effect of taurine supplementation of a commercial (taurine-free) soy protein formula on the development of the visual cortex has been examined in 6- and 12-month-old rhesus monkeys. The thickness, numerical density and total number of neurons, oligodendrocytes, astrocytes and microglia have been measured in the different laminae. There was no difference in brain weight at either age. The thickness of layers I and VI were greater in the taurine-deprived (-T) monkeys at 12 months than in the taurine-supplemented (+T) monkeys. There was no difference in any measure of neurons at 6 or 12 months between the +T and -T groups, but there were several differences in the measures of glial cells. Somewhat surprisingly, monkeys fed the taurine-free formula for 6 months followed by the taurine-supplemented formula for 6 months (reversal group, -T/+T) had a number of differences from the other 12-month groups in measures of both neurons and glial cells. These results add to our previous data indicating that there are significant disadvantages to primates fed a taurine-fed formula during development.

Laminar analysis of the number of neurons, astrocytes, oligodendrocytes and microglia in the visual cortex (area 17) of 3-month-old rhesus monkeys fed a human infant soy-protein formula with or without taurine supplementation from birth.

The effect of taurine addition to a commercial (taurine-free) soy-protein formula on the development of the visual cortex has been examined in 3-month-old rhesus monkeys. The thickness, number of neurons, astrocytes, oligodendrocytes and microglia have been measured in the different laminae. There were no significant differences in cortical thickness, total number of neurons, astrocytes, oligodendrocytes, or microglia between the groups, but there were some significant differences in some laminae as well as some qualitative differences. The numerical density of neurons in layers IV-C alpha and V-2 was significantly greater in the taurine-supplemented monkeys than in those fed the taurine-free formula; the numerical density of astrocytes in layer IV-A was significantly greater and in layer IV-C alpha was significantly smaller in the taurine-supplemented monkeys than in those fed the taurine-free formula. A number of other measurements in the two groups approached significance. These differences indicate that there are developmental disadvantages in the visual cortex of rhesus monkeys raised on a taurine-free human infant formula in addition to those previously reported.

Severe myocardial dysfunction induced by ventricular remodeling in aging rat hearts.

To determine if aging engenders alterations in the functional properties of the myocardium and ventricular remodeling, the hemodynamic performance and structural characteristics of the left ventricle of male Fischer 344 rats at 4, 12, 20, and 29 mo of age were studied by quantitative physiology and morphology. In vivo assessment of cardiac pump function showed no change up to 20 mo, whereas left ventricular end-diastolic pressure was increased at 29 mo. Moreover, peak rates of pressure rise and decay, stroke volume, ejection fraction, and cardiac output were depressed at the later age interval, demonstrating the presence of ventricular failure at this time. The measurements of chamber size and wall thickness showed that ventricular end-diastolic and end-systolic volumes progressively increased with age with the greatest change occurring at 20-29 mo. Aging was also accompanied by a marked augmentation in the volume fraction of fibrotic areas in the ventricular myocardium that was due to an increase in their number and cross-sectional area with time. These architectural rearrangements, in combination with the abnormalities in ventricular function, resulted in an elevation in the volume of wall stress throughout the cardiac cycle. Wall stress increased by 64, 44, and 50% from 4 to 12, 12 to 20, and 20 to 29 mo of age. In conclusion, aging leads to a continuous rise in wall stress that is not normalized by ventricular remodeling. These two independent processes appear to be responsible for the onset of heart failure in the senescent rat.

Myocyte cell loss and myocyte cellular hyperplasia in the hypertrophied aging rat heart.

To determine the effects of age on the myocardium, the functional and structural characteristics of the heart were studied in rats at 4, 12, 20, and 29 months of age. Mean arterial pressure, left ventricular pressure and its first derivative (dP/dt), and heart rate were comparable in rat groups up to 20 months. During the interval from 20 to 29 months, elevated left ventricular end-diastolic pressure and decreased dP/dt indicated that a significant impairment of ventricular function occurred with senescence. In the period between 4 and 12 months, a reduction of nearly 19% in the total number of myocytes was measured in both ventricles. In the subsequent ages, similar decreases in myocyte cell number were found in the left ventricle, whereas in the right ventricle, the initial loss was fully reversed by 20 months. Moreover, from 20 to 29 months, a 59% increase in the aggregate number of myocytes occurred in the right ventricular myocardium. In the left ventricle, a 3% increment was also seen, but this small change was not statistically significant. These estimations of myocyte cellular hyperplasia, however, were complicated by the fact that cell loss continued to take place with age. The volume fraction of collagen in the tissue, in fact, progressively increased from 8% and 7% at 4 months to 16% and 22% at 29 months in the left and right ventricles, respectively. In conclusion, myocyte cellular hyperplasia tends to regenerate the ventricular mass being lost with age in the adult mammalian rat heart.

Left ventricular failure induced by long-term hypertension in rats.

To determine whether the duration of hypertension is an essential component in the evolution of myocardial dysfunction, renal artery constriction was performed in male Fischer 344 rats at 4 months of age, and in vivo global cardiac performance of sham-operated and experimental animals was evaluated 8 months later. Systemic arterial blood pressure increased to 173 +/- 5 mm Hg 2 weeks after the arteries were clipped and remained elevated for the following 5 months. Blood pressure decreased over the remaining 3 months to a value not significantly different from control rats that were killed, 132 +/- 4 mm Hg. After 8 months of renovascular hypertension, we observed that the elevated level of systolic arterial pressure was accompanied by a distinct absence of left ventricular hypertrophy when measured at the ventricular weight level. Moreover, left ventricular end-diastolic pressure increased in hypertensive animals from 6.0 to 24.0 mm Hg while peak left ventricular pressure was identical to controls. In addition, peak +dP/dt and -dP/dt were depressed in hypertensive animals. Although stroke volume was unaltered, cardiac output in renal artery clipped animals was depressed by 34% while total peripheral resistance was elevated by 50%. Ventricular chamber remodeling in the hearts of hypertensive animals was evidenced as a 19% increase in the transverse and a 16% increase in the longitudinal axes of the left ventricle with a 27% diminution of wall thickness. Myocardial damage, in the form of myocyte loss and replacement fibrosis, increased in the hearts of hypertensive animals resulting in a ninefold augmentation in the volume fraction of collagen within the ventricular wall. These alterations in the architectural properties of chamber geometry coupled with the abnormalities in contractile performance resulted in a severe reduction in ejection fraction from 82% to 47% and a marked elevation in transmural diastolic and systolic stress in hypertensive animals. The gradient in stress across the ventricular wall, from epicardium to endocardium, revealed a direct correlation with the regional distribution of myocardial damage. In conclusion, the loading state of the myocardium, tissue injury, and myocardial fibrosis all appear to be critical determinants in the genesis of left ventricular failure in long-term pressure overload.

Hypertensive cardiomyopathy. Myocyte nuclei hyperplasia in the mammalian rat heart.

To determine whether long-term hypertension leads to hyperplasia of myocyte nuclei in the heart, a phenomenon suspected to occur in humans, renal hypertension was produced in rats and the animals were killed 8 mo later. Arterial blood pressure remained elevated for approximately 5 mo, but decreased progressively in the last 3 mo so that at 8 mo this parameter was practically identical to that found in controls. Moreover, left ventricular end diastolic pressure was markedly increased in experimental animals in association with a substantial decrease in left ventricular dP/dt. The alteration of these physiological measurements was indicative of severe ventricular dysfunction. Quantitative analysis of the transmural distribution of myocyte nuclei in the left ventricle showed 36 and 23% increases in myocyte nuclei concentration in the epimyocardium and endomyocardium, respectively. These changes in nuclei were accompanied by 25 and 16% reductions in myocyte cell volume per nucleus in the outer and inner layers of the wall. In conclusion, long-term hypertension leads to impairment of ventricular function and proliferation of nuclei in myocytes.

Ventricular remodeling induced by acute nonocclusive constriction of coronary artery in rats.

To determine the consequence of acute nonocclusive constriction of the epicardial coronary artery on the adaptation of the left ventricle and its impact as a function of age, the left main coronary artery was narrowed in rats 4 and 12 mo of age, and the animals were killed 45 min later. Similar reductions in the luminal diameter, averaging 4%, were obtained in both groups of animals, and this change resulted in an increase in left ventricular end-diastolic pressure and a decrease in positive and negative change in pressure overtime (dP/dt) and in peak-developed ventricular pressure. Left ventricular volume increased by 66% and 56% at 4 and 12 mo because of increases in both the longitudinal and transverse chamber diameters. In contrast, wall thickness decreased by 27% and 35%, whereas sarcomere length increased only by 8.0% and 6.0%, respectively. These changes implied the occurrence of side-to-side slippage of myocytes within the wall to accommodate the larger chamber volume. The alterations in myocardial performance combined with the variations in ventricular size and wall thickness produced a marked elevation in diastolic and systolic wall stress. Moreover, myocyte cell damage in the form of contraction bands and disorganization of the intercalated disc region was seen. No consistent difference was found in any of the parameters measured as a function of age. Measurements of resting coronary blood flow across the left ventricular wall before coronary artery narrowing were comparable with those obtained 45 min after constriction. In conclusion, acute nonocclusive coronary artery stenosis has profound detrimental effects on the function and structure of the myocardium in the absence of an impairment of resting coronary blood flow.

In vitro holding and PLD-repair: II. A flow cytometric and electron microscopic analysis of some mammalian cell lines.

The repair of potentially lethal damage (PLDR) in mammalian cells is expected to be better in quiescent cultures since PLD is supposedly fixed during cycle progression. Plateau phase cultures, therefore, serve as models because of assumed mitotic quiescence. Four established cell lines (V79, CHO, L5178Y and HELA) and one euploid cell strain IMR-90 have been analysed by flow cytometry and electron microscopy to address questions on quiescence in the plateau phase and the effect of holding (induction of quiescence by nutrient privation). In contrast to commonly held views, our results indicate that the quiescent fraction in cultures from transformed cells is exceedingly low (1% or less). Plateau phase cultures of transformed cells are constantly turning over. Euploid cells like the IMR-90 show true quiescence in the plateau phase. Holding causes typical cytopathological changes. These changes have been ultrastructurally++ characterised. Resistant sub-populations of cells can be selected out under holding-conditions. Such selected cells show completely different radiobiological characteristics, which raise questions on the interpretation of data on PLDR.

Abnormal visual cortex development in the kitten associated with maternal dietary taurine deprivation.

We have examined the visual cortex of newborn and 8-week-old kittens born to mothers consuming a taurine-supplemented or taurine-free diet using the rapid Golgi technique. Kittens from taurine-supplemented mothers exhibited normal development of the visual cortex. Kittens from taurine-depleted mothers showed striking differences. In newborn kittens, neuroblasts are aggregated both at the ventricular and pial zones, having failed to migrate and differentiate normally. Eight weeks after birth, only few pyramidal and nonpyramidal neurons are found. Those present have heavily spined dendritic processes indicative of poor arborization. Protoplasmic astrocytes are represented by undifferentiated cellular masses. The taurine concentration in the cortex of such kittens is four- to fivefold smaller than in kittens from taurine-supplemented mothers. These results suggest that normal concentrations of taurine in visual cortex, as well as cerebellum, are required for normal ontogeny of neurons. Once such deficits are established in the prenatal and immediate postnatal period, they result in permanent abnormalities. These findings have clear implications for vegetarian women who intend to have children, since virtually no taurine is present in plants and vegetables.