The formation of the insulo-acinar portal system in the pancreas of human fetuses]

In human fetuses 12-20-week-old peculiarities in creation and development of the pancreatic hemo-microcirculatory bed have been studied in connection of its incretory part formation. The vascular glomerulus begins to form on the 12th-14th week as transformation of capillaries of the exocrinic parenchyma into the glomerular capillaries, which, on their getting out of the glomeruli, turn into vessels. The latter participate in formation of the insulo-acinar portal system. Certain structures have been revealed for adaptation of an elevated volume of the blood stream in the glomeruli place, where the glomerular microvessels pass into the acinar anastomoses. The latter perform shunting of the glomerular capillaries with the arteriole, which brings blood, enriched in insular hormones, to distantly situating acinar cells.     

The sclerocorneal trabecula of the primates

In this work, after having studied the chamber angle of 14 types of primates, we describe the sclerocorneal trabecula. They are a formation dependent on the tendinous insertion fibres of the longitudinal portion of the ciliary muscle. These trabecula consist of a reticulate area and another spongy area with some interstices that we think get bigger or smaller in size according to the degree of contraction of the ciliary muscle, thus either easing or impeding the flow of aqueous humour to Schlemm's canal.     

Brain hemorrhages in cocaine-exposed human fetuses

Autopsies of 4 fetuses exposed to maternal cocaine are reported. Brain examination revealed hemorrhages in 3 of the fetuses involving the germinal matrix. The hemorrhages resembled subependymal germinal matrix hemorrhages seen as postnatal complications in premature infants with idiopathic respiratory distress syndrome. One of the placentas had sonographic evidence of abruption which could not be confirmed pathologically. The findings are discussed in light of reports of neurobehavioral deficits and other congenital anomalies in children and animals exposed to cocaine in utero. Speculations about the pathophysiologic events leading to these findings are made.     

Urea biosynthesis in normal human fetuses

Normal human fetuses at different gestation periods were collected on ice after hysterotomy and the enzymes of the urea cycle were measured in the liver. The activity of all enzymes increased with increasing gestational age towards the adult value, however, in no case did the values reach the normal adult level. The bladder fluid of these fetuses contained urea and ammonia nitrogen at concentrations which were akin to the concentrations found in fetal blood. The ornithine transcarbamylase activity was the lowest when compared to the adult values and appeared to be the rate-limiting enzyme in the cycle, along with argininosuccinic acid synthetase activity, which was also very low. The activity of arginase was found to be the highest in the cycle. The very low ornithine transcarbamylase and argininosuccinic acid synthetase activities and the comparatively higher arginase activity migh lead to the channeling of ornithine into alternate metabolic pathways.     

Distribution of argyrophilic cells in the lungs of human fetuses

Lungs of the human fetuses have been investigated at the age of 11, 18, 22 and 25 weeks. General histological staining methods and silver nitrate impregnation of the sections after Grimelius have been applied. Single argyrophile endocrinic cells (apudocytes) are revealed in the fetal lungs during all the time investigated. Groups of the argyrophilic cells--neuroepithelial bodies (NEB)--appear later and in small quantity. The quantity of the apudocytes and NEB gradually increases, especially noticeably in the distal parts of the bronchial tree. The number of the apudocytes increases during the canalicular stage of the pulmonary development. The endocrinic apparatus of the human lungs is forming in connection with development of the airy pathways, respiratory part and intraorganic vascular system.     

Structure of the neuromuscular spindles in the tongue of human fetuses

The dynamics in development of some components--of the neuromuscular spindles in the human fetus and newborn tongues have been studied by means of certain general and neurohistological methods with elements of morphometry. During the whole prenatal period of the human life, there is a certain synchronism in the development of the lingual proper muscles and the neuro-muscular spindles. Certain integration in the development of the neuro-muscular spindles is observed in 4-6-month-old fetuses; in 8-9-month-old fetuses and in newborns it is substituted for heterochronicity. By the time of birth, the muscle spindle contractile elements are supplied with a more differentiated efferent innervation. The latter actively effects the morphological state of the intrafusal muscle fibers and forms a base for functional activity of the tongue.     

Early development of visual cortex in human fetuses

Prenatal development of visual cortex (area 17) was studied in human fetuses of 8-9, 13-15 and 16-18 weeks of gestation, with a view to analyse the early critical events. Under light microscope, five zones of development were seen in all the age groups. The total thickness of cortex of area 17 as well as that of its cortical plate was measured with the help of camera lucida. It was observed that the total thickness of the cortex increased with increase in age. Diversity in the shape, size, staining intensity and arrangement of neurons was noted in the different zones. Most of the cells were found to have a thin rim of cytoplasm and a prominent nucleus with multiple nucleoli. The cells in subventricular zone and cortical plate were regularly arranged in vertical rows while in other zones, they were irregularly scattered. Several mitotic figures were seen in the ventricular zone at 8-9 weeks but later they were also noticed in subventricular and intermediate zones. In the later ages the mitotic figures were observed to be fewer in the ventricular zone. No mitosis was seen in cortical plate at any age period.     

Topographical distribution of trabecular bone strength in the human os calcanei

Mechanical properties of twenty human os calcanei were determined by uniaxial compression testing of bone specimens from facies articularis talaris posterior, facies articularis cuboidea, and tuber calcanei. Specimens were taken oriented perpendicular to the planes of the facies articularis, and in tuber along the presumed loading axis throughout the gait cycle. Young's modulus and strength at facies articularis cuboidea and facies articularis talaris posterior were about three times those at the tuber calcanei. The variation of the relationship between Young's modulus and apparent density indicated differences in the orientation of the trabecula, in relation to the direction of evaluation between these locations. A more detailed analysis of the topographical variation of strength within each location was made using penetration testing of a further nineteen specimens. The results of both types of measurements indicated that the major part of the load during walking is carried by facies articularis talaris posterior and facies articularis cuboidea.     

Multi-axial mechanical properties of human trabecular bone

In the context of osteoporosis, evaluation of bone fracture risk and improved design of epiphyseal bone implants rely on accurate knowledge of the mechanical properties of trabecular bone. A multi-axial loading chamber was designed, built and applied to explore the compressive multi-axial yield and strength properties of human trabecular bone from different anatomical locations. A thorough experimental protocol was elaborated for extraction of cylindrical bone samples, assessment of their morphology by micro-computed tomography and application of different mechanical tests: torsion, uni-axial traction, uni-axial compression and multi-axial compression. A total of 128 bone samples were processed through the protocol and subjected to one of the mechanical tests up to yield and failure. The elastic data were analyzed using a tensorial fabric–elasticity relationship, while the yield and strength data were analyzed with fabric-based, conewise generalized Hill criteria. For each loading mode and more importantly for the combined results, strong relationships were demonstrated between volume fraction, fabric and the elastic, yield and strength properties of human trabecular bone. Despite the reviewed limitations, the obtained results will help improve the simulation of the damage behavior of human bones and bone-implant systems using the finite element method.