The effects of hypoxia on growth cones in the ovine fetal brain.

OBJECTIVE: This study was designed to investigate the effects of hypoxia on neural process proliferation by studying its effects on growth cone tubulin and insulin-like growth factor (IGF)-I receptor content. METHODS: Six fetal lambs were catheterized in the brachial artery and vein. Maternal oxygenation was reduced in steps from a fractional inspired oxygen concentration (FiO2) of 20% to 6% by addition of nitrogen to the inhaled gas mixture for a period of 4 h of reduced oxygen intake. Fetal arterial blood was sampled after the maternal FiO2 and oxygen were stable for >5 min at maternal FiO2 of 20% to 6%. Controls were obtained from normoxic fetuses whose ewes had similar surgery and were kept at an FiO2 of 20% throughout the experiment. Growth cones were isolated from the fetal cerebrum and cerebellum. alpha-tubulin and IGF-I receptors were quantified by immunoblotting. Tubulin and IGF-I receptor mRNA expressions were quantified by real-time polymerase chain reaction. RESULTS: Maternal nitrogen breathing reduced fetal arterial pH from 7.32+/-0.06 to 6.99+/-0.02 (p<0.001). Hypoxia increased IGF-I receptors from 143+/-10 to 327+/-14 (p<0.001) and from 272+/-26 to 396+/-34 (p<0.001) fluorescence units/microg protein in the cerebrum and cerebellum, respectively. It also increased alpha-tubulin from 713+/-30 to 1873+/-126 (p<0.001) and from 780+/-34 to 2362+/-79 (p<0.001) fluorescence units/microg protein in the cerebrum and cerebellum, respectively. Expression of IGF-I receptor mRNA increased significantly in the hypoxic animals both in the cerebrum and the cerebellum, but there was no change in expression of alpha-tubulin mRNA. CONCLUSIONS: This increase in IGF-I receptor expression and growth cone content may be an adaptive response to hypoxia to maintain neurite growth by facilitating binding of IGF-I. Hypoxia also increased the growth cone level of alpha-tubulin but did not increase its mRNA expression, which may indicate an inability to polymerize tubulin and build microtubules.

Correlation between fetal scalp blood samples and intravascular blood pH, pO2 and oxygen saturation measurements.

OBJECTIVE: This study was designed to compare the values of blood gases in local scalp blood, obtained by scalp blood sampling, with direct measurements of fetal preductal arterial blood in fetal sheep. METHODS: Six fetal lambs were catheterized in the brachial artery and vein. Maternal oxygenation was reduced in steps from a fractional inspired oxygen concentration (FiO2) of 20 to 5% by addition of nitrogen to the inhaled gas mixture. Fetal scalp and arterial blood were sampled simultaneously at maternal FiO2 step intervals after maternal FiO2 and oxygen were stable for > 5 min. Blood pH, pO2 and oxygen saturation were measured and linear regression was performed to determine the correlation between these values. RESULTS: Scalp pH correlated well with arterial pH, whereas scalp pO2, pCO2 and oxygen saturation did not. However, when a secondary analysis was performed taking into account the effects of aerobic contamination, scalp pCO2, pO2 and oxygen saturation became highly correlated with arterial values. CONCLUSIONS: Local scalp blood oxygen saturation correlates highly with fetal preductal arterial values, when physiological artifacts are eliminated. The technique of scalp blood sampling introduces error into oxygenation saturation measurements, owing to difficulties in anaerobic sample collection. These results suggest that continuous measurement of fetal scalp oxygenation by noninvasive oximetry may be superior to direct sampling of scalp blood.

Provider resource planning. A study of methods in multispecialty groups and systems.

This article profiles the state of the art in provider resource planning based on a sample of large multispeciality group practices. Senior administrative representatives from a geographically dispersed sample of 12 practices, each employing over 100 physicians, participated in telephone interviews to discuss their respective organization's provider resource planning practices. There was significant variation with regard to the structural and process components and evaluation criteria used to plan provider resources. Variability was most pronounced by the lack of consensus and experience within and across organizations regarding the number and type of criteria deemed useful in evaluating new position requests. This research suggests that there is an opportunity to develop more objective provider resource planning methods that recognize differences across organizations and their respective markets. The authors recommend a series of research steps to develop methods that would identify needs prospectively, minimize the complexities of provider resource planning and maximize the alignment of strategic plans and operations.

Intrachromosomal triplication of 2q11.2-q21 in a severely malformed infant: case report and review of triplications and their possible mechanism.

A female fetus with brain malformations, multicystic kidneys, absence of the right thumb, and a posterior cleft of palate was delivered at 32 weeks of gestation. Cytogenetic studies including FISH showed a novel intrachromosomal triplication of the proximal long arm of chromosome 2 (q11.2-q21), resulting in tetrasomy for this segment. The middle repeat was inverted. At least 11 patients with intrachromosomal triplications have been reported, mostly involving chromosome 15q. The mechanism involved in formation of these rearrangements is compatible with U-type exchange events among three chromatids.

Effects of hypothyroidism on the DNA, carbohydrate, soluble protein and sialic acid contents of rat submandibular glands.

Submandibular glands are a target organ of thyroid hormones. This study examined the effects of hypothyroidism on the biochemical characteristics of these glands in the rat. There were no effects on the neutral sugar and DNA contents. However, soluble protein concentrations (micrograms/mg wet weight) were significantly decreased and sialic acid concentrations micrograms/mg soluble protein) were significantly elevated.

Nutritional needs of the female adolescent.

This paper emphasizes the need for adequate nutrition in order to sustain normal growth in adolescence. The special needs of the adolescent athlete and the pregnant teenager are also reviewed. Adolescent athletes require added nutrient intake for optimal performance. And, if pregnancy occurs, it imposes severe nutritional demands on the adolescent which must be met to prevent low birthweight infants. Although many teenagers consume a good deal of their food outside of the home, there seems to be little evidence of widespread nutritional deficiencies except with respect to iron. However, there is a high incidence of obesity and anorexia among female adolescents and these disorders are discussed.

The effect of alterations in ketone body availability on the utilization of beta-hydroxybutyrate by developing rat brain.

The effect of alterations in ketone body availability during the early postnatal period on the in vitro and in vivo utilization of beta-hydroxybutyrate (beta OHB) by developing rat brain was determined. Ketone body availability was prolonged by feeding a high fat diet during pregnancy and lactation and to pups after weaning. Availability was decreased by early weaning pups at 16 days to a low fat liquid diet. In the in vitro studies, oxidation of [14C]beta OHB to CO2 and incorporation into brain lipid was determined at 7, 14, 21, and 35 days of age. In the in vivo studies incorporation of [14C]beta OHB and [3H]glucose into brain lipid was measured. The results indicate that it is possible to alter the brain's utilization of beta OHB for lipid synthesis and energy metabolism during the developmental period. This was particularly evident in the in vivo studies. The in vivo results also suggest a relationship between beta OHB availability in the blood and incorporation into brain lipid. When availability was decreased by early weaning pups to the low fat diet, incorporation of beta OHB into lipid was also decreased. Likewise, when availability was increased, such as was seen in the high fat feeding study, incorporation was increased.

Brain beta-hydroxybutyrate utilization in neonatal hypothyroidism in rats.

The in vitro and in vivo utilization of 14C-beta-hydroxybutyrate (BOHB) by the brain in neonatal hypothyroidism was studied in rat pups made hypothyroid by feeding dams a diet containing 0.02% propylthiouracil during pregnancy and lactation. In the in vitro studies, the oxidation of BOHB to CO2 was lower at 14 and 21 days of age in hypothyroid pups than in pair-fed controls but higher at 35 days. The incorporation of BOHB into brain lipid was significantly higher in hypothyroid pups at 14, 21 and 35 days. In contrast, in the in vivo studies, incorporation of BOHB into lipid was significantly lower in hypothyroid pups at 14 and 21 days. These results suggest that hypothyroid pups may have a normal or increased capability to use BOHB for lipid synthesis, but were unable to achieve normal rates of utilization in vivo, possibly due to a decreased substrate availability. These findings may have implications for the decreased brain lipid content characteristic of neonatal hypothyroidism.

The effect of early postnatal undernutrition on the growth and development of the rat brain.

1. Rat pups were undernourished during the period of the brain growth-spurt by feeding their mothers a low-protein diet from the third day post partum. 2. The pups were killed on days 5, 6, 9, 12, 16, 20 and 24 post partum, and their brains were analysed for protein, DNA, glycosides and glycoproteins. The activities of four enzymes involved in neurotransmission, and in the synthesis of glycolipids and myelin were also measured. Results of the analyses were compared with those obtained for pups that were suckled by well-nourished dams. 3. The brains of the undernourished pups contained substantially less protein and DNA; gangliosides and glycoproteins were also reduced. 4. All four enzymes showed lower peak activities in the nutritionally deprived animals, and the attainment of peak activity was retarded by several days. 5. These results suggest that undernutrition imposed during the brain growth-spurt leads to a deficit in the glial cell population and thus in the capacity to form myelin, and reduced development of cellular processes.

A useful correlation between blood and brain N-acetylneuraminic acid contents.

A study was conducted to determine if serum N-acetylneuraminic acid (NeuAc) levels correlate with brain NeuAc levels. Sprague-Dawley rats were given either a diet containing 100 g casein/kg or one with 200 g casein/kg throughout pregnancy and lactation. At 12, 16 and 21 days' postpartum, litters of pups from each of the groups were killed. Their serum was assayed for NeuAc and their brains for total ganglioside and glycoprotein NeuAc. It was found that brain wet weight, ganglioside and glycoprotein NeuAc contents all correlate with serum NeuAc levels. It is suggested that serum NeuAc levels might represent a new method of measuring functional development of the brain.

Effects of essential fatty acid deficiency during late gestation on brain N-acetylneuraminic acid metabolism and behaviour in the progeny.

1. Rat dams given a diet containing 100 g maize oil/kg for approximately two weeks before mating and during the first 14 d of gestation, were given the same diet or one containing 100 g hydrogenated coconut oil/kg (essential fatty acid (EFA)-deficient) in place of maize oil until parturition. After parturition the dams were given the same diets and all progeny were weaned to the maize oil diet at 21 d of age. Brain N-acetylneuraminic acid (NeuNAc) content as well as neuraminidase (sialidase; (EC 3.2.1.18), and cytidine monophosphate N-acetylneuraminic acid synthetase (CMP-NeuNAc synthetase) activities were measured at days, 7, 14, 21 and 168 in the progeny. Y-maze learning was measured at 168 d. 2. Brain weight was independent of dietary fat at all ages. 3. Lack of EFA in the maternal diet during gestation and lactation depressed ganglioside and glycoprotein NeuNAc levels and the activities of sialidase and CMP-NeuNAc synthetase. 4. Maternal dietary deprivation of EFA irreversibly impaired learning behaviour of the progeny. A relationship exists between early exposure to EFA deficiency and learning potential of the progeny.

The subcellular localization of administered N-acetylneuraminic acid in the brains of well-fed and protein restricted rats.

1. This study investigated the subcellular localization of injected N-acetylneuraminic acid (NeuNAc) in brain. Forty pregnant rats were distributed into four groups. Two groups were given a 200 g casein/kg diet and the other two groups a 100 g casein/kg diet throughout gestation. One group from each of the low- and high-protein groups were given their respective diets for the first 11 d of lactation. On day 12 of lactation, 2.5 microCi [14]NeuNAc/kg body-weight were injected intraperitoneally into their pups. After 1 h the pups were killed, their brains removed and subjected to subcellular fractionation. On day 16 of lactation the other two groups were similarly treated. 2. In all groups of animals 80% of the [14C]NeuNAc incorporated into the brains was found in the synaptosomal fraction and the remainder distributed among the other subcellular fractions in proportion to their total NeuNAc content. 3. These results suggest that NeuNAc exerts its effects on behaviour via the synaptic membrane.

Value of dietary protein for hyperplastic growth at restricted energy intakes.

The study describes three experiments of similar design relating dietary protein to growth over a period of 16 days in rats prematurely weaned at 19 days of age. In experiment 1, group 1 was fed ad libitum a 10% caseindiet. Group 2 was pair-fed an isoenergetic 40% casein diet. Groups 3 and 4 received 3 g of the 10% casein and 40% casein diets, respectively. The experiment demonstrated that protein may be used to sustain growth when energy intake is restricted. In experiment 2, all rats were given 3 g of diet per day. Group 1 was given the 10% casein diet, group 2 the 40% casein diet, group 3 a diet with 10% casein plus 30% of a mixture of dispensable amino acids and group 4 the 10% casein diet plus an energy supplement. Results showed that amino nitrogen seems to be a requisite for organ protein synthesis. In experiment 3, group 1 ate the 10% casein diet, group 2 the amino acid-supplemented diet and group 3 the latter minus glycine. Group 3 showed increased liver and kidney growth. The inclusion of glycine in group 2 caused a further increment in organ protein content.

Effects of administration of N-acetylneuraminic acid (NANA) on brain NANA content and behavior.

Rat pups were malnourished during the first 3 weeks after birth. Experimental rats were injected intraperitoneally with 1 mg N-acetylneuraminic acid (NANA) per 50 g body weight daily from 14 to 21 days postnatally. Control animals were similarly injected with 1 mg glucose per 50 g body weight. At 21 days of age, the rats were tested in an open field and their brains analyzed for protein, DNA, ganglioside NANA and glycoprotein NANA. The administration of NANA was associated with an increase in cerebral and cerebellar ganglioside and glycoprotein NANA concentrations. However, it had no effects on brain weight, cell size and number. There was also a reduction in the expected behavioral abnormalities secondary to malnutrition. At 21 days of age, similarly treated littermates of the experimental animals were weaned to a stock diet and tested in a Y maze at 6 months of age. Rats treated with NANA learned the maze quicker than controls and the previously noted changes in brain biochemistry were found to have persisted. Intraperitoneal injection of [14C]NANA into malnourished rats during the same period showed that it was readily incorporated into brain glycoproteins and gangliosides. The possibility that the brain concentration of NANA has an effect on behavior is discussed.

Effects of environmental stimulation on brain N-acetylneuraminic acid content and behavior.

A study was conducted in which the nutritional and early stimulation conditions of rat pups were manipulated during the first 3 weeks of life. Early stimulation reduced the change in open-field behavior caused by malnutrition at 21 days postnatally. The cerebrum and cerebellum were analyzed for ganglioside and glycoprotein N-acetylneuraminic acid (NANA), DNA and protein content. The improved behavioral performance was associated with a significantly higher ganglioside and glycoprotein NANA content in both brain areas analyzed. The remaining rats from each litter were weaned onto a standard laboratory stock diet at 21 days of age and housed individually until age 6 months. At this time, their performance in a Y maze was tested. Once again early stimulation was associated with an improved ability to learn the maze. The biochemical changes persisted into adulthood in the stimulated groups with the exception that the difference in cerebellar ganglioside content had disappeared by this time. The results are discussed with respect to the possible role of NANA in behavior.

The effects of folic acid supplementation during pregnancy in the rat.

1. Twenty-four Sprague-Dawley female rats were randomly assigned to three groups (groups A, B, C). Group A was given a folic acid-free diet and groups B and C received 0.0018 g folic acid/kg diet. Rats in group C were also given a supplement of 1 mg folic acid/d by intraperitoneal injection. 2. After 14 d of feeding the rats were mated. The diets were continued throughout gestation. On day 21, of gestation the dams were killed and their livers and products of conception assayed for RNA, DNA, protein and tetrahydrofolate dehydrogenase (5,6,7,8-tetrahydrofolate dehydrogenase; EC 1.5.1.3) activity. 3. The foetuses, placentas and livers from supplemented rats (group C) were significantly larger than those from groups A and B and had a higher content of RNA, DNA and protein. Those tissues from group A dams were smaller than those from the other groups and had a correspondingly reduced nucleic acid and protein content. 4. The activity of tetrahydrofolate dehydrogenase, the first and rate-limiting enzyme in the metabolism of folate, was increased in the folate supplemented rats (group C) and reduced in the rats given a folic acid-free diet (group A). These changes in enzyme activity could explain the differences in nucleic acid biosynthesis and growth shown by the different groups.