22nd Day Of Gestation Research Articles

Congenital anomalies of lens shape.

The crystalline lens is an important structure in the eye that starts to develop as early as the 22nd day of gestation, with further differentiation that continues after the induction. Congenital anomalies of the lens may involve the size, shape, and position of the lens. They may sometimes be associated with anterior segment dysgenesis or persistence of the tunica vasculosa lentis and hyperplastic vitreous and hyaloid system. Manifestations of anomalies of the lens shape are usually seen in early or late childhood however may sometimes be delayed into adulthood based on the level of visual impairment or the presence or absence of any syndromic associations. While lens coloboma has more often been reported in isolation, the more commonly implicated genes include the PAX6 gene, lenticonus in particular anterior is often part of Alport syndrome with extra-ocular manifestations in the kidneys and hearing abnormalities due to mutations in the alpha 5 chain of the Type IV collagen gene. Recognition of these manifestations and obtaining a genetic diagnosis is an important step in the management. The level of visual impairment and amblyopia dictates the outcomes in patients managed either conservatively with optical correction as well as surgically where deemed necessary. This review discusses the various anomalies of the lens shape with its related genetics and the management involved in these conditions.

Selective Fetal Hypophysectomy in utero: Microsurgical Technique and Comparisons with Hypophysectomy by Decapitation

A detailed description is given of a surgical technique for selectively removing the pituitary anlage from the intrauterine fetal rat as an alternative to the more generally applied fetal hypophysectomy by decapitation. Fetuses on the 17th day of gestation were approached through a narrow opening in the uterine wall and fetal membranes. The pituitary gland was sucked out with a fine glass tube introduced from the side of the head into the space between the pons and the ventral hypothalamus, where the gland is situated. The female rat was sacrificed on the 22nd day of gestation (the day before delivery) and the surviving fetuses were preserved. On average, 20% of the operated fetuses survived until that day, 20% of which were completely hypophysectomized (microscopical examination). Operated fetuses with intact pituitaries served as surgical controls for the evaluation of selected effects of the total hypophysectomy. Initial comparisons were made with published results based on hypophysectomy by decapitation, evaluated without access to surgical controls. The two methods of fetal pituitary removal provide consistent results as regards the weight increase of adrenal and thyroid glands (retardation), thymus gland (stimulation) and testicles (no effect). On the other hand, body weight increase was not affected by selective hypophysectomy but instead slowed down after decapitation, whereas the growth in length of the humerus bone was stimulated and retarded, respectively.

Music for the unborn child

Our modern culture with its emphasis on the tactile and visual senses is endangering the loss of aural capabilities. Research over the last 50 years shows that the aural sense is most important for the acculturation of the human species. The ear begins its development as early as the 22nd day of gestation and the unborn child has the capability of storing information ‘heard’ as early as in the first trimester of pregnancy. Music can play an important role in bonding, and the preference for a particular type of music can be instilled in the unborn child. Programmes for parents-to-be such as Dr Lorna Zemke's Lovenotes at Silver Lake College in Manitowoc, Wisconsin, can prove to be important not only for the development of a contented child and its curiosity for the world around it but also for the future of classical music.

Low-density lipoprotein catabolism does not respond to estrogen in the fetal and newborn rat.

The elimination of native and methylated low-density lipoprotein (LDL) from serum and the effect of estradiol on the serum LDL-apoB pool, the uptake of homologous [125I]-LDL into liver and adrenals, and the fractional catabolic rate (FCR) of [125I]-LDL was studied in fetal (22nd day of gestation), newborn (15th day postpartum), and adult rats. In fetal rats the receptor-mediated LDL decay accounted only for 47%, whereas in adults it was calculated to 65%. In the latter, estrogen caused (1) a diminution of the serum LDL-apoB pool by 85%; (2) an enhancement of the LDL uptake into the liver and the adrenals by 5- and 10-fold, respectively, and (3) an acceleration of the [125I]-LDL decay in the serum with a rise of the FCR by 3-fold. In contrast, neither the LDL pool and uptake nor the LDL elimination (FCR) did respond to estrogen in fetal and newborn rats. In summary, the LDL catabolism of the rat is insensitive towards estrogen in the late gestational period and during the first 2 weeks of postnatal life [3].

Serum growth hormone levels in hypothyroid and GH-treated thyroidectomized rats and their progenies.

Growth hormone (GH) was measured in the sera of control, hypothyroid (thyroidectomized [Tx]) and GH-treated Tx rats and their fetuses on Days 19, 20, 21, and 22 of gestation and in their progenies on postnatal Days 1, 5, 30, and 75. Maternal endogenous serum GH increased dramatically between the 19th and 20th days of gestation and remained elevated through the 22nd day in control rats, but was depressed significantly in Tx and GH-treated Tx rats during this period. GH was not always detected in the sera of 19-day-old fetuses. On Day 20, GH was depressed in fetuses of Tx mothers as compared with those form controls or GH-treated Tx mothers. GH was elevated in sera of fetuses from GH-treated Tx rats over fetuses of control and Tx only rats on the 22nd day of gestation. In postnatal rats, those from GH-treated mothers continued to show elevated serum GH on Day 1 as compared with those from Tx only mothers. On postnatal Days 5 and 30, progenies of Tx mothers had significantly elevated GH as compared with progenies of control mothers. At 75 days of age, the GH levels of these progenies had normalized. We have shown previously that the hormonal secretions of the pituitary-thyroid axis are badly disrupted in the progenies of Tx and GH-treated Tx mothers and that even as adults these animals have tissue (brain and liver) deficits of active thyroid hormones. Although the onset of GH secretion is mildly delayed in fetuses of Tx but not GH-treated Tx mothers, the serum GH levels of both groups of progenies are elevated during most of the neonatal period through the time of puberty. It is, therefore, concluded that GH in the absence of adequate levels of thyroid hormones is ineffective in preventing many of the learning and memory deficits induced in the progenies of Tx mothers.

Increased Peripheral Resistance During Reduced Uterine Perfusion Pressure Hypertension in Pregnant Rabbits

The role of an increase in total peripheral resistance (TPR) and the contribution of angiotensin II (ANG II) to the hypertension induced by reduced uterine perfusion pressure (RUPP) was explored in pregnant rabbits. On the 22nd day of gestation, a catheter and a microthermocouple were placed in the aorta to measure mean arterial pressure (MAP) and cardiac output (CO), respectively. Three days later, RUPP was induced by a clip on the aorta proximal to the ovarian and distal to the renal arteries. Mean arterial pressure distal to the clip (uterine perfusion pressure) was reduced to 56 +/- 8% (mean +/- SD) of the initial level. Twenty-four hours later, MAP rose from 65 +/- 3 to 84 +/- 11 mm Hg; CO index decreased from 207 +/- 18 to 169 +/- 27 ml/min/kg; and TPR index increased from 0.32 +/- 0.03 to 0.51 +/- 0.08 mm Hg kg/ml/min, respectively (n = 7, all p less than 0.01). Sham-operated pregnant rabbits (n = 7) and non-P rabbits (n = 5) with a comparable distal aortic pressure reduction experienced no change in MAP or CO. Infusion of a receptor antagonist of angiotensin II (Sar1,Ile8-Ang II, 1 microgram/kg/min for 20 min) decreased MAP in sham-operated pregnant rabbits from 64 +/- 6 to 54 +/- 6 mm Hg (p less than 0.01) but did not change MAP in RUPP hypertensive rabbits (86 +/- 9 mm Hg before and 87 +/- 8 at the end of infusion, n = 6). These data indicate that RUPP in pregnant rabbits leads to a high resistance form of hypertension in which the formation of Ang II is not increased.

Regulation of fetal Na +/K +-ATPase in rat kidney by corticosteroids

The enzymatic differentiation of various tissues is under hormonal control in the perinatal period. Since the regulation of Na +/K +-ATPase has not been explored prenatally, the aim of this study was to determine the corticosteroid sensitivity of sodium pump maturation in the fetal period. Na +/K +-ATPase activity was both measured in kidney homogenates of fetal rats and localized by in-situ histochemistry. Sodium pump activity was first quantifiable on day 18 of fetal development as 1.4 ± 0.17 μ mol P i/h per mg protein, and was increased 3.4-times by day 22 of gestation. While the Na +/K +-ATPase activity was the most intense in cortical tubules at an earlier fetal age (18th and 19th day), the reaction product in the medullary tubules increased with fetal age, becoming highly intense on the 21st and 22nd day of gestation. From the 18th to 21st day of fetal development homogenate Na +/K +-ATPase activity increased as a function of chronologic age. While mineralocorticoids were without any effect on Na +/K +-ATPase activity, on the last day of the fetal development, the glucocorticoid dexamethasone proved to be successful in stimulating enzyme activity in corticosteroid-suppressed animals. According to our results, glucocorticoid hormones seem to be operating as an endogenous driving force for sodium pump maturation at the end of fetal development.

Changes in the mechanical properties of the longitudinal and circular muscle tissues of the rat myometrium during gestation

Changes in the mechanical properties of the longitudinal and circular muscle tissues of the rat myometrium during gestation were investigated. In isolated longitudinal and circular muscles of the rat myometrium, spontaneous contractions and contractions per unit cross-sectional area induced by 128 mM K+ and 1 X 10(-5) M acetylcholine (ACh) increased with the progress of gestation. These increases appeared in longitudinal muscles to a greater extent than in circular muscles. ACh induced the largest contraction for both intact muscle tissues, at all stages of gestation. In both muscle layers, the ACh-induced contraction reached the same amplitude as the 1 X 10(-5) M Ca-induced contraction of skinned muscles, except for the longitudinal muscle at the 22nd day of gestation. In Ca-free solution containing 2 mM EGTA, ACh produced contraction in both intact muscle tissues at all stages and the amplitude was increased during the progress of gestation, whereas the K-induced and spontaneous contractions ceased. In saponin-treated skinned muscles of both layers, the free Ca concentration required to produce contraction was lowered, the maximum amplitudes of the contraction were increased and the pCa-tension relationships shifted to the left during the progress of gestation. The results indicate that during the progress of gestation, Ca sensitivity of of the contractile proteins and mechanical responses to agonists increased and that the properties of the intracellular Ca store site were also altered in both muscle layers.

Studies of the Teratogenic Potential of Exposure of Rats to 6000-MHz Microwave Radiation: I. Morphologic Analysis at Term

Thirty-six pregnant Wistar strain albino rats were exposed throughout pregnancy to 6000-MHz microwave radiation at a power density level of 35 mW/cm2 or were used as controls. The irradiation did not cause a significant increase in maternal body temperature as measured by a rectal thermocouple. The rats were randomly assigned to one of four groups: home cage control (5), anechoic chamber control (10), sham-irradiated concurrent control (10), and irradiated (11). All animals were killed on the 22nd day of gestation, and maternal tissues were removed and weighed and maternal blood samples were taken. The 384 resultant fetuses and their placentas were individually weighed, fixed, and dissected to determine normality. Teratologic evaluation included the following parameters: maternal weight and weight gain; mean litter size; maternal organ weight and organ weight/body weight ratios; body weight ratios of brain, liver, kidneys, and ovaries; maternal peripheral blood parameters including hematocrit, hemoglobin, and white cell counts; number of resorptions and resorption rate; number of abnormalities and abnormality rate; mean term fetal weight. The irradiated fetuses exhibited slight but statistically significant growth retardation at term. Term maternal monocyte count was also significantly depressed. No other parameters differed between the control groups and the irradiated group.

The effects of hyperphenylalaninemia on fetal development: a new animal model of maternal phenylketonuria.

A new model has been developed for the study of maternal phenylketonuria. Beginning on the 12th day of gestation the diet of pregnant rats was supplemented with 0.5% alpha-methylphenylalanine and 3% phenylalanine. This resulted in an 83% reduction of hepatic phenylalanine hydroxylase activity. The maternal plasma phenylalanine was elevated 10-20-fold for two-thirds of the day, but the degree and persistence of the fetal hyperphenylalaninemia may have been even greater. The brain phenylalanine concentrations in the fetus were raised up to 2900 nmole/g brain, whereas the highest level observed in the dam was 382 nmole/g. Experimentally-treated fetuses showed small reductions in both body and brain weight when compared to age-matched controls; however, no differences were seen in crown to rump length, litter size, DNA and protein concentrations per g, or in postnatal survival. Initiation of the diet at conception rather than on the 12th day caused a significantly greater inhibition of fetal growth, and 21% mortality. The fetal cerebral concentrations of methionine and the branched chain amino acids (valine, leucine and isoleucine) were decreased by hyperphenylalaninemia. From the 16th day on, the concentration of the inhibitor neurotransmitter glycine was elevated. Cerebral serotonin showed a 20-30% deficit and its primary metabolite 5-hydroxyindoleacetic acid a 71-77% deficit. Of twelve enzymes quantified in the brains of hyperphenylalaninemic fetuses only phosphoserine phosphatase showed any change. From the 20th to the 22nd day of gestation its activity was 46-67% higher in experimental than in normal fetuses. Measurement on the 22nd day of gestation showed that the increases in phosphoserine phosphatase activity and glycine content were present in brain stem, cerebellum, and forebrain.

Alterations of serum thyroxine, triiodothyronine, and thyrotropin in the progeny of hypothyroid rats.

Thyroid function in the progeny of hypothyroid rats was studied from 19 days of gestation until adulthood. Total T4, T3, and TSH were measured by RIA in the sera of control, surgically thyroidectomized (Tx), and GH-treated Tx pregnant rats and their progeny from the late fetal period through adulthood. By the 22nd day of gestation, the fetuses of Tx mothers had T4 and TSH levels significantly above those of their controls. This condition, whereby fetal serum T4 and TSH levels were elevated, was aggravated by GH treatment of the Tx mothers. The progeny of Tx- and Tx and GH-treated mothers also showed alterations in serum T4, T3, and TSH. While the T4 levels of the progeny of Tx mothers were significantly below those of th control progeny only at 30 days of age, T3 levels were significantly depressed at 1, 5, and 30 days of age. These same animals had lower serum TSH levels than the control progeny at 1 and 5 days of age and higher TSH levels at 30 and 75 days of age. Prenatal GH treatment of the mother did not consistently correct thyroid function of the progeny. As adults the progeny of the Tx mothers had normal serum concentrations of T4 and T3 but TSH was high. High serum TSH values were not seen in the progeny of Tx plus GH-treated mothers. These results suggest that maternal hypothyroidism during pregnancy may result in permanent alterations in the thyroidal response to TSH in their progeny.

Development of innervation to the ventricular myocardium of the rabbit

Catecholamine histochemistry and electron microscopy were used to study the development of innervation to the ventricular myocardium of rabbits from the 22nd day of gestation to 35 days postnatally. Special attention was directed to the first morphologic appearance of nerve fibers and terminals and the closeness of juxtaposition of terminals with myocardial cells. In animals treated with α-methylnorepinephrine fluorescent adrenergic fibers were first evident in the ventricles on the 24th day of gestation. Ultrastructurally adrenergic and cholinergic terminals were also evident on the 24th day of gestation and such terminals had close relationships with cardiac muscle cells. During the next few weeks the density of innervation increased and reached the adult pattern by 35 days postpartum. In many instances adrenergic and cholinergic fibers were evident in the same nerve bundle and were closely apposed without any intervening Schwann cell cytoplasm. Such a relationship could allow peripheral interaction between these fibers in the myocardium.

Identification and ontogeny of β-adrenergic receptors in fetal rabbit lung

High affinity (Kd=0.2 nM), low capacity (48 fmoles per mg protein), stereospecific binding sites, with properties characteristic of the β 1-subtype of β-adrenergic receptors, have been detected in fetal rabbit lung membranes as early as the 22nd day of gestation. The concentration of the receptor did not change significantly between the 22nd and 26th day of gestation, but increased 3-fold between the 26th and 29th day, reaching a level of 198 fmoles per mg protein. A further increase (from 198 to 315 fmoles per mg protein) in receptor concentration was observed in adult female rabbits. The increase in the levels of pulmonary β-adrenergic receptors between the 26th and 29th day of gestation is temporally related to the increase in surfactant release into the alveolar spaces of the fetal lung. Thus β-adrenergic agonists may act directly on the fetal lung to regulate surfactant secretion.

Postnatal development of rat liver mitochondria: State 3 respiration, adenine nucleotide translocase activity, and the net accumulation of adenine nucleotides

The postnatal maturation of respiratory activity was studied in mitochondria isolated from livers of newborn rats that had been Caeserean delivered on the 22nd day of gestation. At birth, the State 3 respiratory rate with glutamate + malate (68.1 ± 8.4 ng atoms O/min/ mg protein) was much lower than the 2,4-dinitrophenol-uncoupled rate (112.7 ± 13.3 ng atoms O/min/mg protein). During the first hour of postnatal life, the State 3 rate increased to nearly equal the uncoupled rate, which did not change significantly. The State 4 rate and ADP O ratio did not change. After 1 h postnatal, when State 3 respiration had increased 1.6-fold, the total adenine nucleotide content (ATP + ADP + AMP) had increased 1.8-fold, and adenine nucleotide translocase activity had increased 1.5-fold. However, the total adenine nucleotide content and translocase activity continued to increase between 1 and 4.5 h postnatal in parallel with each other, but long after State 3 respiration had developed maximally. The ability of newborn liver mitochondria to accumulate adenine nucleotides in relation to the maturation of State 3 respiration was studied in vitro. Mitochondria incubated with 1 m m ATP at 30 °C for 10 min doubled their total adenine nucleotide content, and this was correlated with a doubling of the State 3 respiratory rate. The net accumulation of adenine nucleotides was inhibited 76 ± 1.8% by 100 μ m N-ethylmaleimide and to a lesser extent (57 ± 0.5%) by 50 μ m atractyloside. It was concluded that the accumulation of intramitochondrial adenine nucleotides, via the net uptake of ATP or ADP, probably accounted for the postnatal maturation of adenine nucleotide translocase activity and State 3 respiration. The data suggested that the translocase rate varied as a function of a much greater range of intramitochondrial adenine nucleotide contents than did the overall State 3 rate. The low rate of ADP-stimulated respiration at birth may have been limited by the rate of translocase-mediated exchange of newly synthesized ATP for external ADP, and/or by the absolute size of the exchangeable internal adenine nucleotide pool, which may have been submaximal for the F 1-ATPase.

Failure of zinc acetate to reduce ethylenethiourea-induced fetal anomalies in rats

Ethylenebisdithiocarbamate of manganese (maneb) and zinc (zineb) and their degradation and metabolic product, ethylenethiourea (ETU), have produced similar teratogenic anomalies in rats. The mode of teratogenicity of maneb, deduced from the protective effects of zinc acetate following their simultaneous administration, has been attributed to its ability to chelate zinc. Whether ETU has a similar mode of action was investigated. Mated females from five control groups were fed a standard diet for the entire period of pregnancy. Dams in five other groups were fed the standard diet to which 0.0444% zinc (as zinc acetate) was added during the period from the 11th to the 14th day of pregnancy. On the 13th day of pregnancy, control dams and those given supplemental zinc were not treated, treated with distilled water, or with 80, 120, or 160 mg/kg ETU sc. A necropsy was performed on some dams 3 hr postinjection and concentrations of zinc were measured in the conceptus and maternal serum. The remaining dams were sacrificed and a necropsy performed on the 22nd day of gestation and their fetuses were examined for external, visceral, or skeletal anomalies. Zinc acetate was ineffective in reducing ETU-induced malformations, and concentrations of zinc in the conceptus and maternal serum were not affected by feeding zinc acetate or injecting ETU.

Teratologic assessment of maleic hydrazide and daminozide, and formulations of ethoxyquin, thiabendazole and naled in rats.

Teratogenicity studies were conducted in rats treated orally from days 6-15 of gestation with single daily doses of 400-1600 mg/kg of maleic hydrazide, 300-1000 mg/kg daminozide, 125-500 mg/kg ethoxyquin or thiabendazole, or 25-100 mg/kg naled. Dams were killed on the 22nd day of gestation, and fetuses were evaluated by routine teratologic methods. No adverse effect was related to any treatment other than an increased incidence of anomalous fetuses at the highest dose (500 mg/kg) of thiabendazole.

Teratogenicity studies on linuron, malathion, and methoxychlor in rats

Technical grades of linuron, Malathion, and methoxychlor, and formulations of linuron and methoxychlor, were given to bred rats by gastric intubation on Days 6 to 15 of gestation. Dams were killed on the 22nd day of gestation, and fetuses were evaluated by routine teratologic methods. Technical grades of linuron at doses as high as 100 mg/kg, technical grades of Malathion at doses as high as 300 mg/kg and formulations of linuron, from one supplier, at doses as high as 200 mg/kg were not teratogenic. Formulations of linuron from another supplier were teratogenic at 200 mg/kg, but not at 100 mg/kg. Treatment with methoxychlor (technical grade or formulation) was associated with reduced maternal body weight gain during gestation at all test doses ranging from 50 to 400 mg/kg. Both methoxychlor samples were fetotoxic at 200 and 400 mg/kg, and both produced a dose-related increase in the incidence of wavy ribs at 100, 200, and 400 mg/kg/day.

194 THE EFFECT OF INTRAUTERINE GROWTH RETARDATION (IUGR) ON SMALL INTESTINAL ENZYMES

Fetal malnutrition and growth retardation can be related, in part, to poor placental blood supply. Experimental IUGR was induced on the 18th day of gestation in pregnant rats by ligating the uterine horn, while leaving the opposite horn intact as a control. On the 22nd day of gestation, the weight of the fetal, small intestine parallels the decrease of body weight. The weight loss is related to a significant reduction in DNA content and in cell number, and to a lesser extent, to a decrease in cell size. In contrast to maltase (M), alkaline phosphatase (AP), and enterokinase (EK), only lactase (L) activity is significantly decreased in fetuses paired from same mothers. These results suggest, that in addition to the decreases in small intestinal cell number and enzyme content in IUGR, there is a proportionally greater decrease in L activity. This can be explained by either a selective effect of IUGR on a critical developmental period for lactase, or that lactase is more vulnerable to insult. (*Units ± S.D. = μmole/gm protein/min.)

Fetal rat adrenal steroidogenesis and steroid transfer to adrenalectomized mother.

On the 22nd day of gestation in rats, fetuses of acutely adrenalectomized mothers were injected subcutaneously with 0.43 muCi 4-14C-progesterone in 0.05 ml saline. Ten and 20 min after injection to fetuses, samples were taken to determine the 14C-progesterone metabolites in the plasma and adrenal glands. After extraction of the samples taken, the metabolites were separated by two-dimensional thin-layer chromatography and identified by autoradiography. 11-deoxycorticosterone, 18-hydroxy-11-deoxycorticosterone, corticosterone and 11beta-hydroxyprogesterone were identified in the plasma of injected fetuses, and, in far smaller amounts, in the plasma of their mothers. The plasma of noninjected fetuses also contained very small amounts of these corticoids. The fetal adrenal glands contained far smaller amounts of radioactive steroids than the fetal plasma did. The results obtained show that steroids of fetal origin can cross the placenta in and out, constituting evidence that the fetal adrenal glands are the only source of the plasma corticoids of their adrenalectomized mothers.

ORIGIN OF MACROPHAGE IN THE TELENCEPHALIC WALL OF THE RAT FETUS ‐ AN OBSERVATION BASED ON METHYLAZOXYMETHANOL AND RADIATION INDUCED LESIONS

Pregnant rats in the 15th day of gestation received an injection of methylazoxymethanol 20 mg/kg and were exposed to 200 r. of Co60. Fetuses were examined at various time intervals up to the 22nd day of gestation. Widespread necrosis throughout the dorso‐lateral wall of the telencephalon appeared early. At a subsequent stage frequently observed in the ventricular zone was necrotic cell debris in the ventricular columnar cells and macrophages. The macrophages migrated outwards and eventually digested their content to lipid droplets and transformation to an elongated cell with branching processes was traced. Vacuolated amoeboid cells first described electron microscopically by Caley and Maxwell in the neonatal rat cerebrum, appeared in later fetal life in untreated control animals and increased in treated animals. Additional to pinocytosis their phagocytic activity was enhanced and ultimate digestion of their content to lipid droplets was observed. Although the fate of the macrophage was not ascertained, their ectodermal origin was discussed.