Stages Of Embryological Development Research Articles

Differentiation of Sclera in Chick Embryo at Various Stages of its Development- A Histological Study

Background: The sclera is the outer strong opaque covering of the eye that functions as protective layer and provides site for attachment of extra ocular muscles. Aim: To study the microscopic anatomy of sclera in chick at various stages of embryological development keeping in mind the practical application of this information in understanding human development and disease processes. Methodology: It was an experimental study. The study was carried out at department of Anatomy, CPSP Regional Centre, Islamabad. Eyeballs were collected from group A, B and C (n=30 each) on day 10, 12 and 15 of incubation respectively. Dissected out tissues were processed and stained with Hematoxylin & Eosin and Alizarin red. The prepared specimens for group A and C were analysed under light microscope while the specimens from group B were observed via stereomicroscope. Data was evaluated by using SPSS version 23. Independent t-test was applied with p-value of less than 0.05 was considered significant. Results: As the chondrocytes in cartilaginous layer of sclera became mature, they change their shape from flattened to more rounded cells. The proteoglycan content in the cartilaginous matrix increased. The mean number of chondrocytes increased from 17.4 ±1.4/unit area on day 10 to 10.0 ±0.8/unit area on day 15. The mean thickness of cartilaginous layer increased from 44 ±2.4µm on day 10 to 77 ±8.3 µm on day 15 of development. Calcification of scleral ossicles became obvious at about 12 days of incubation when seen under stereomicroscope. Practical Implication: This study highlighted that understanding for the development of scleral elements (understudied tissue of the eye) can be critical in research involving autoimmune diseases and neural crest defects. Considering similar developmental stages among humans as in chick embryo. Conclusion: It was concluded that growth of sclera in eye of chick has been indicated by increase in thickness of its layers and increase in the number of chondrocytes/unit area and progressing calcification of ossicles in its bony part. Keywords: Chick Embryo, Chondrocytes, Hyaline Cartilage and Ossicular Ring.

An observational study on Awareness of Teratogenic drugs among Undergraduate Medical Students from two medical institutes of Central India

Background: Teratogenicity caused by drugs can be avoided to major extent just by creating more awareness about rational use of drugs among treating doctors. Deleterious effects of a drug upon developing foetus are directly related with the stage of embryological development at the time of exposure. Attainment of right knowledge at right time about teratogenicity of a particular drug is very crucial which requires more awareness among general doctors in a country like India where most of the pregnant females are manged by these doctors only in peripheral regions. Present study was an observational study to assess basic knowledge of undergraduate medical students regarding teratogenicity in order to make necessary changes in existing mode of training of this particular topic.Methods: Present study was a questionnaire based cross sectional observational study to assess basic knowledge of undergraduate medical students regarding different aspects of teratogenicity. It included 250 students of two medical colleges of central India.Results: Out of 250 students 146 students reported on time. Maximum students (71%) were aware about the teratogenicity property of certain harmful drugs. Although 90% of students knew that early first trimester is the most susceptible time, only 21% could state the importance of doing counselling regarding use of drugs even before pregnancy.Conclusions: Based on the findings of present study it is obvious that more emphasis should be put on improving knowledge about teratogenic drugs during early years of medical training in order to bring about necessary changes in existing practices of treating doctors.

Induced Miscarriage in Early Mālikī and Hanafī Fiqh

AbstractThis article traces the manner in which Mālikī and Hanafī jurists in the first six centuries AH arrived at their respective legal assessments of induced miscarriage. Each madhhab developed its own interpretation of embryogenesis, based on Q. 5:95 and Q. 65:4, and, therefore, its own distinctive position on induced miscarriage: The Mālikīs hold for legal relevance from the moment of conception, while the Hanafīs hold for legal relevance at a later stage of embryological development. This difference was also caused by different opinions on ways to legally establish that a miscarriage was induced. Finally, the question of ensoulment, which became widespread in Islamic legal reasoning on induced miscarriage only after the 2nd/8th century, was linked to the Hanafī position that induced miscarriage is not punishable until the 120th day following conception.

Microcephaly with plate-like cortical calcification

Congenital malformations of the central nervous system have varied presentations depending on the stage of embryological development when the insult occurred. We report a neonate with microcephaly associated with plate-like cortical calcification, probably secondary to an unidentified insult at around 11–12 weeks post-conceptional age causing an arrest of the proliferative phase. The associated vasculopathy probably caused diffuse cortical calcification.

Congenital Clubfoot

The medical records of 330 children who were born with uncomplicated congenital clubfoot were reviewed retrospectively. To determine their months of conception, the duration of gestation was extrapolated and those which were less than 40 weeks were noted. The years of conception for the studied children were from 1956 to 1994. Months of the year were ascribed angle values and the distribution of conceptions per month were grouped in radial manner. Using a circular analysis for variance a lack of uniform circular distribution was found for the grouped months of conception. There is a significant seasonal variation in the data. The mean month of conception was June. This finding is at variance with the peak months of conception for the population of the United States for the years 1989 through 1993. The theory that congenital clubfoot is caused by an intrauterine Enterovirus may be supported by this data. The summer and fall peak of Enterovirus infections in temperate climates coincide with the stage of embryologic development (>8 weeks) which would allow an anterior horn cell lesion to lead to a deformity such as congenital club foot.

Congenital clubfoot. Month of conception.

The medical records of 330 children who were born with uncomplicated congenital clubfoot were reviewed retrospectively. To determine their months of conception, the duration of gestation was extrapolated and those which were less than 40 weeks were noted. The years of conception for the studied children were from 1956 to 1994. Months of the year were ascribed angle values and the distribution of conceptions per month were grouped in radial manner. Using a circular analysis for variance a lack of uniform circular distribution was found for the grouped months of conception. There is a significant seasonal variation in the data. The mean month of conception was June. This finding is at variance with the peak months of conception for the population of the United States for the years 1989 through 1993. The theory that congenital clubfoot is caused by an intrauterine Enterovirus may be supported by this data. The summer and fall peak of Enterovirus infections in temperate climates coincide with the stage of embryologic development (> 8 weeks) which would allow an anterior horn cell lesion to lead to a deformity such as congenital club foot.

Differences in embryological development in two closely related species: Ihlea racovitzai and Ihlea magalhanica (Tunicata, Thaliacea)

Differences in the early stages of embryological development confirm the validity of the closely related salp species Ihlea racovitzai and Ihlea magalhanica. In the latter 8–12 oocytes and thus 8–12 follicles and uterine sacs are observed in the ovary; however most of them undergo a progressive degradation and only two embryos complete their development. In Ihlea racovitzai two embryos also develop but from the very beginning only the two successful follicles are found.

Hatching and viability of copepod eggs at two stages of embryological development: anoxic/hypoxic effect

The effects of low oxygen concentrations on the hatching and viability of copepod eggs at two stages of embryological development were investigated. Fully developed eggs from Acartia tonsa (Dana) and Labidocera aestiva (Wheeler) collected between July and September 1991 at Turkey Point, Florida, USA, hatched at lower oxygen concentrations than newly spawned eggs given the same incubation periods. Since many of the newly spawned eggs subsequently hatched when exposed to normoxic conditions, it is likely that the exposure to low oxygen delayed embryonic development. At oxygen concentrations where no initial hatching occurred, the subsequent hatching success of fully developed eggs of A. tonsa was higher than that of newly spawned eggs, indicating that newly spawned eggs were more sensitive to low oxygen concentrations. No such difference was observed for the eggs of L. aestiva.

Effects of prenatal x-irradiation on development and postnatal viability of inbred and hybrid mice.

1. Developmental malformations and effects on postnatal viability were measured in inbred and hybrid mice that had been irradiated at different stages of embryological development. Three genetically differentiated inbred strains of mice, BALB, K, and S, and their six possible types of hybrids, including reciprocals. were used. The design for these studies was factorial. There were five levels of irradiation: 0, 20, 80, 160, and 320r; five embryological stages: untreated, 6½, 10½ 14½, and 17½ days of gestation; two sexes; and mice of nine different inheritance types. Pregnant females were exposed to single whole-body 250 pkv x-rays on a specified day of gestation as timed from the appearance of a vaginal plug. Malformations were scored at birth and postnatal mortality was followed through 75 days of age. 2. Morphological anomalies observable at birth were found only after irradiation at 10½ days gestation. Anomalies were observed after doses of 80r or more. Neonatal mortality also was highest following irradiation at 10½ days. The LD50 at birth was found to be between 80 and 160r, with a dose of 320r causing all progeny to be stillborn. 3. A differential response both in the induction of malformations and in the incidence of neonatal deaths was found between inbred and hybrid genotypes. Following treatment with 160r at 10½ days there was 64 per cent abnormal and 100 per cent stillborn progeny among the inbreds compared to 29 per cent abnormal and 64 per cent stillborn among the hybrids. 4. Effects of prenatal irradiation on postnatal survival to 60 days were at a minimum after treatment at 6½ days gestation, reached a maximum following irradiation at 10½ days, and then declined at 14½ or 17½ days. No consistent patterns of survival differences between males and females and level of irradiation and embryological stage at the time of treatment was observed. 5. Among the control or non-irradiated mice, inbred progeny suffered a higher mortality than the hybrids especially during the first few days after birth. In those treatments which produced a significant increase in postnatal mortality, inbred genotypes responded to a greater degree than did hybrid genotypes.

Fusion capability of rat embryonic extra-oral tissue in vitro

Epithelial mesenchymal interaction in the fusion process was studied by the means of fusing different extremities of a 15 day 16 hr rat foetus. The extremities used were the hands, feet, and tails, which at this stage of embryologic development appear to have a similar type of epithelial covering but differ markedly in the degree of specialization of the underlying mesenchyme. Two hands from one embryo were placed in palm to palm contact and grown under organ culture conditions for 72 hr with ten pairs of hands making up the experimental group. Ten pairs of feet made up the second experimental group with two feet from the same embryo being placed in sole to sole contact and grown under organ culture conditions. The third experimental group consisted of ten pairs of tails from littermate embryo's and were placed side by side and cultured for 72 hr. In all three experimental groups, fusion with epithelial breakdown occurred though to different extents. It was noted that the degree of mesenchymal penetration across the interrupted epithelial barrier was related to the extent of specialization of the mesenchymal tissue. The greater the degree of specialization of the mesenchyme the less was the intermingling with the mesenchyme of the opposite member. The most specialized extremity the hand, also showed the lowest incidence of the fusion process progressing as far as the epithelial breakdown stage.

Lifetime reproductive performance of mice exposed as embryos to x-irradiation.

1. Lifetime reproductive performance was observed in mice that had been irradiated at different stages of embryological development. Three genetically differentiated inbred strains of mice, BALB, K, and S, and all their possible hybrids, including reciprocals, were used. Pregnant females were exposed to single whole-body 250 pkv x-ray dosages from 20 r to 320 r on 6½, l0½, l4½ and l7½ days gestation, as timed from the appearance of a vaginal plug. Efforts were made to obtain two mice of each sex and inheritance type for each of the irradiation dose-embryological age treatment combinations. No progeny or not sufficient progeny were obtained following irradiation with 160 r or 320 r at embryological ages of 6½, 10½, and 14½ days of age. At 75 days of age treated mice were outcrossed to mice of the Z strain, and matings were maintained for the lifetime of the treated mice.2. Adult reproductive performance was found to be related both to the age of the embryo at the time of irradiation and the level of irradiation. The embryological ages in order of increasing sensitivity were 6½, 17½, 14½, and l0½ days. The incidence of sterile matings was pronounced only following 160 r or 320 r at 17½ days. Significant effects on reproduction due to genotype and sex were observed at all ages. Survivors of irradiation at 6½ days had normal fertility and fecundity. A dose of 80 r at 10½ days reduced reproductivity to 76% of control values. Significant effects due to levels of irradiation were observed at both l4½ and 17½ days. Mice irradiated with 160 r at 14½ days produced only 72% as many progeny as controls. Following irradiation with 160 r at l7½ days, irradiated mice produced 83% as many progeny as controls. With a dose of 320 r at 17½ days the incidence of sterility was 67% and progeny production fell to 21%3. Genetic differences in the response of the fetal reproductive system were most evident following irradiation on day 17½. Inbred progeny appeared to be more radiosensitive than hybrid progeny. The incidence of sterility after 320 r was 100% in inbreds compared to 50% for hybrids. Fecundity following 160 r was reduced in inbreds, but remained near normal in hybrids.

EFFECTS OF X-IRRADIATION OF MICE EXPOSED IN UTERO DURING DIFFERENT STAGES OF EMBRYOLOGICAL DEVELOPMENT ON DURATION OF MATURE LIFE

1. Mature lifespans, 75 days of age to death, when the mice were exposed to irradiations at different stages of uterine development, showed reductions in mean longevity which were dependent on both x-ray dose and period of embryological cycle. The design for this study was factorial. There were five irradiation treatments, 0, 20, 80, 160 and 320 r, six embryological stages: untreated, 6½, 10½, 14½, 17½ and newborn (19½) days of uterine development, two sexes and nine mouse strains. Three of the inheritance groups were inbred strains and six were the reciprocal crosses of these strains. Efforts were made to obtain two mice for each cell of the design. However, some treatments were so severe that this was impossible. X-ray dosages of 160 and 320 r at embryological ages 6½, 10½ and 14½ days were too lethal to obtain the requisite number of progeny in these groups.2. Six hundred and forty-seven completed mouse lives were collected. Mature lifespan ranged downward from 1194 days for the males and 921 days for the females. Both of these long-lived individuals had been irradiated, the male with 160 r at 14½ days embryological development and the female with 80 r at 10½ days embryological development. The frequency distributions of lifespan were of several types for the different groups, depending on the treatments, strains or sexes of the individuals.3. In terms of changes in mature lifespan, sex differences in the mice resulted in marked differences in the mean days they survived. Considering the in utero treated mice, the average unirradiated females survived for only 69% of the mean male lifespan. This male-to-female difference cannot be attributed to irradiation effects but rather to the hazards which differentially affect the physiological processes which separate the lives of the sexes, chiefly those associated with reproduction. Adjusting for these effects shows that the average female life under irradiation still exhibits greater sensitivities to irradiation in utero. Considering the available data for the dosages taken separately, the 20 r females had 85% of the mean lifespan observed for the untreated females, the males 96.7% that of the untreated males. Like comparisons for the 80 r were 82 vs. 93; for the 160 r, 73 vs. 89 and for the 320 r, 30 vs. 43.4. Intrauterine irradiations, when limited to 20 to 80 r, reduced the female durations of life at all stages of embryological development more than they did those of the males.5. Variance analyses emphasized the importance of sex as a controlling element in adult survival when the mice are under pressure of reproduction.6. Genotypic differences, as measured by strain and as separate from sex, have little effect on subsequent mature lifespans when the irradiation is small in amount, 20 including 80 r, or when given at 6½ or 10½ days of embryological development. The amount of radiant energy absorbed becomes more important to mature life's duration when the dosages of radiation are larger, 160 including 320 r, or when the exposures occur in the latter half of pregnancy. The variance analyses support the significance of the differences on which the above conclusions were based.7. Genotype also interacts with both stage of embryological development when irradiation occurred and with the dosage of x-rays absorbed.8. Individually the embryological stages when the irradiations took place have but small percentage effects on mature lifespan, although they do have pronounced effects on survival in the juvenile stage. All changes in lifespan come as direct irradiation effect to the soma of the embryos, as caused by acute irradiation. Lifespan lowering comes largely in the 320 r treated embryos in the form of a threshold effect which then carries through to the adult as cryptic damage to appear later in life.

ABSENCE OR HYPOPLASIA OF A PULMONARY ARTERY WITH ANOMALOUS SYSTEMIC ARTERIES TO THE LUNG

The pulmonary vascular plexus at one stage of embryologic development has important dorsal branches from the aorta which normally disappear. These vascular communications with the aorta or its branches may persist when there is faulty development of the pulmonary artery. Although most recently reported cases of anomalous systemic arteries to the lungs have been discovered because of the associated presence of bronehiogenic cysts, bronchiectasis or sequestration of lung tissue, anomalous arteries from the aorta or its branches may enter grossly normal pulmonary tissue. Anomalies of the bronchial branching and lobar development may also be present. The clinical features and the radiologic findings in cases of absence of the pulmonary artery to one lung are presented with illustrative examples. Two cases with a hypoplastic lung receiving a considerable blood flow through systemic arteries are discussed. The effect of ligation of these systemic arteries is reported. The clinical and physiologic questions which anomalous vascular communications to the lungs present are briefly considered.

THE NEUROCUTANEOUS SYNDROME

The often bizarre neurologic symptoms and signs occurring in conjunction with nevoid changes in the skin are perhaps more familiar to the neurologist than to the dermatologist. In most cases, however, the recognition of the nature of the cutaneous changes gives the key to the diagnosis. Since the skin and the nervous system have a common embryonic origin, namely, the ectoderm, aberrations in the genesis of this embryonal layer often result in congenital malformations affecting both structures selectively. To this varied group of neurologic signs and symptoms, following no true pattern and occurring in association with cutaneous nevi, the term neurocutaneous syndrome has been applied. The wide variety of neural and cutaneous pictures included in this syndrome is to be expected, inasmuch as the nature and degree of aberration from the normal will depend on the stage of embryologic development and differentiation reached by the embryonic ectodermal layer when the