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The aim of this study was to examine the righting reflex from a supine to a prone position in the albino guinea pig fetus. Ultrasound examinations of one-fetus gestations were performed in the period from the 31st to the 66th day of gestation. The experimental and control group each encompassed 6 fetuses. Fetuses were brought into supine positions relative to the gravity vector by manipulating the pregnant females into the appropriate positions. The control group received 15 mg/kg of diazepam intraperitoneally before the examination to show whether changes in fetal position occurred as the result of passive rotation. In the experimental group, each fetus was examined every other day (summary results: absent 69 times, prone position 10 times, lateral position 29 times). In the control group, each fetus was examined every five days (summary results: absent 42 times). The absence of the righting reflex in the control group was statistically significant (chi(2) = 18.66, df = 1, p = 0.000, p < 0.05). The experimental group fetuses assumed a prone position more frequently in the period from the 51st to the 66th day of gestation than in the period from the 31st to the 50th day of gestation (chi(2) = 4.17, df = 1, p = 0.0412, p < 0.05), suggesting maturation of the righting reflex.

Polyhydramnios is a condition related to an excessive accumulation of amniotic fluid in the third trimester of pregnancy and it can be acute and chronic depending on the duration. Published data suggest that during muscle development, in the stage of late histochemical differentiation decreased mechanical loading cause decreased expression of myosin heavy chain (MHC) type 1 leading to slow-to-fast transition. In the case of chronic polyhydramnios, histochemical muscle differentiation could be affected as a consequence of permanent decreased physical loading. Most affected would be muscles which are the most active i.e., spine extensor muscles and muscles of legs. Long-lasting decreased mechanical loading on muscle should cause decreased expression of MHC type 1 leading to slow-to-fast transition, decreased number of muscle fiber type I especially in extensor muscles of spine and legs. Additionally, because MHC type 1 is present in all skeletal muscles it could lead to various degrees of hypotrophy depending on constituting a percentage of MHC type 1 in affected muscles. These changes in the case of preexisting muscle disorders have the potential to deteriorate the muscle condition additionally. Given these facts, idiopathic chronic polyhydramnios is a rare opportunity to study the influence of reduced physical loading on muscle development in the human fetus. Also, it could be a medical entity to examine the influence of micro- and hypogravity conditions on the development of the fetal muscular system during the last trimester of gestation. [ABSTRACT FROM AUTHOR]

The most sensitive period in brain development is during prenatal life. The use of antibiotics in pregnancy is still controversial. Recent studies revealed the high neurotoxic potential of the antibiotic and antiprotozoal medication, metronidazole. However, there are insufficient data from animal studies about prenatal treatment effects. We investigated the effect of prenatal treatment with metronidazole on cerebellar development in guinea pigs. Treatment with metronidazole was performed from the 42nd to the 49th day of gestation. On the 50th day of pregnancy, all dams were killed, and the cerebella of the fetuses were analyzed. Gross cerebellar changes characterized by malposition of the folia with partial atrophy were found in 12 of 19 fetuses in the experimental group, but in none of 20 control fetuses that received saline. The most affected were folia VII with depletion of the areal fraction of the external granular layer, molecular layer and the internal granular layer. Purkinje cells displayed cell distortion with loss of normal dendritic polarity. The investigation revealed cell depletion, with a disturbance of the cytoarchitectonic of the cerebellar cortex and folia alteration. [ABSTRACT FROM AUTHOR]

Existing data related to the probability of breech presentation suggest that the breech presentation is a consequence of mere filling of the intrauterine space, with the same probability of breech and cephalic presentation. As a consequence, group of cephalic presenting fetuses is heterogenous. Some fetuses randomly assume the cephalic presentation while others assume cephalic presentation ‘intentionally’ for a reason. Before comparing breech and cephalic presenting fetuses/newborns, bias should be eliminated by subtracting from the cephalic-presenting group the number of fetuses/newborns that is identical with the number of breech-presenting fetuses/newborns with identical characteristics. The subtracted group should be added to the breech-presenting group before comparison with the remaining cephalic-presenting fetuses/newborns. The comparison should be corrected for the gestational age and according to data that are not influenced by delivery. Data suggest that the physiological process that accounts for 92% of cephalic-presenting human fetuses at delivery should be sought from the 25th gestational week onwards. [ABSTRACT FROM AUTHOR]

Ultrasonography has not previously been used for studying fetal movements in precocial rodents. The objective of this study was to ultrasonographically determine the sequence of the appearance of basic movements in a guinea pig fetus. The research included eight guinea pig females carrying one fetus each. Fetal movements were observed for 10 minutes each day, from the 25th to 38th day of gestation. The time and sequence of the appearance of movements was observed as follows: whole body flexion (mean 27.6 SD ± 1.68), whole body extension (mean 28.1 SD ± 1.12), head flexion (mean 28.1 SD ± 1.80), head extension (mean 30.5 SD ± 2.67) forelimbs flexion (mean 30.5 SD ± 2.32), forelimbs extension (mean 30.7 SD ± 1.84), trunk rotation (mean 31.9 SD ± 2.23), forelimbs alternating flexion and extension (mean 32.1 SD ± 2.1), hind limbs extension (mean 32.2 SD ± 3.2), hind limbs flexion (mean 32.4 SD ± 3.16), and hind limbs alternating flexion and extension (mean 33.5 SD ± 2.39). The identical sequences of basic movement appearances in guinea pigs, sheep, and rats suggest that the rostrocaudal gradient of basic movement appearance could be a general developmental pattern in mammalian species. [ABSTRACT FROM AUTHOR]