Intralobular lymphatic vessels and their relationship to blood vessels in the mouse thymus

Summary The spatial distribution and fine structure of the lymphatic vessels within the thymic lobules of normal and hydrocortisone-injected mice were studied by light- and electron microscopy. The lymphatic vessels of the cortex and medulla of normal thymus are irregularly shaped spaces closely associated with branches of the intralobular artery and vein. The overall distribution of these vessels in the greatly involuted thymus of hydrocortisone-treated mice is essentially the same as in the normal thymus. The wall of the lymphatic vessels consists of only a layer of endothelial cells supported by underlying reticular cells. The luminal surface of the endothelial cell is smooth, but trabecular processes are often seen. There are three morphological types of intercellular contacts between contiguous cells, namely, end-to-end, overlapping and interdigitating. The lymphatic vessel has anchoring filaments and collagen fibrils, but a basal lamina is either absent, or if present, is discontinuous. This is in contrast to the continuous basal lamina of the venule. The perivascular space surrounding the postcapillary venule opens into a terminal lymphatic vessel at the cortico-medullary junction and in the medulla. Lymphocytes are seen penetrating the lymphatic endothelium, particularly in acutely involuted thymuses. These findings suggest that the intralobular lymphatic vessels may originate from the vacuities that surround the postcapillary venules, and the lymphatic system may function as a pathway for the migration of lymphocytes into or out of the lymphatic circulation.     

Optical measurement of age-related calcification in human blood vessels

Vascular calcification is commonly associated with aging. Quantification of calcium accumulation in vessel walls is important in understanding the mechanisms of vascular calcification. To elucidate age-related change of calcification, site dependence of calcification, and the effect of hemodynamic stress on calcification, we measured calcium contents in various blood vessels with atomic emission spectrometry and simulated blood flow in the vessels by computational fluid dynamics. The content of calcium in the arteries increased progressively with aging while there is no change in the veins. The higher accumulation of calcium occurred in the arteries of the lower limb in comparison to the arteries of the upper limb. In the arterial bifurcation, there was the correlation at hemodynamic stress distribution and calcium content. The results of this study quantitatively support clinical findings of nonuniform calcification, and suggest that hemodynamic stress affects vascular calcification.     

Individual differences in behaviour and their statistical consequences

Some elementary points concerning the statistical consequences of individual differences in behaviour are discussed. Various ways are suggested of taking individual differences into account when designing experiments. True individual differences are represented by the within-group variability that remains after the effects of measurement error have been excluded. Thus, mere variability in data does not necessarily demonstrate that true individual differences are present. Individual differences have two important effects. First, statistical power is reduced, which means that true effects are more difficult to detect. Second, statements about groups may be untrue for all individuals in the group and, conversely, group characteristics may be difficult to infer from measurements of individuals. Some simple tactics for coping with individual differences in experimental data are outlined: (1) obtaining repeated outcome scores for each subject; (2) obtaining a baseline score for each subject prior to the experimental treatment; (3) a combination of 1 and 2; and (4) using a longitudinal design, i.e. obtaining a series of scores across time for each subject. Each of these tactics also has the merit of providing additional information about the nature of the response to the treatment. A fifth tactic is to increase the sample size. Finally, some possible disadvantages of a sixth tactic, that of matching experimental and control subjects, are pointed out.     

Applied aspects of anatomy of the lumbar lymph nodes and their vessels

Using anatomical and roentgenoanatomical methods in 132 corpses of persons (from newborns up to 83 years of age) the anatomy of the lumbar lymph nodes and their vessels has been studied. Their topography, skeletotopy , amount, dimensions and form have been determined. Afferent and deferent lymphatic vessels in various groups of the lumbar lymph nodes, collateral pathways of lymph outflow to by-pass the lumbar lymph nodes are described. Certain data on the types of the thoracic duct formation are presented.     

Distributing and delivering vessels of the human heart

The branching characteristics of the right coronary artery, acute marginal, posterior descending, left anterior descending, circumflex, and obtuse marginal arteries are compared with those of diagonal branches, left and right ventricular branches, septal, and higher-order branches, to test a newly proposed functional classification of the coronary arteries in which the first group rank as distributing vessels and the second as delivering vessels. According to this classification, the function of the first type is merely to convey blood to the borders of myocardial zones, while the function of the second is to implement the actual delivery of blood into these zones. This functional difference is important in the hemodynamic analysis of coronary heart disease, as it provides an assessment of the role of a vessel within the coronary network and hence an assessment of the functional importance of that vessel in a particular heart. Measurements from casts of human coronary arteries are used to examine the relevant characteristics of these vessels and hence to test the basis of this classification.     

Individual and age-related characteristics of the mitotic condensation of human Y chromosome

Three types of contraction (steady, speeding and slowing) of fluorescent (f) and nonfluorescent (nf) parts of the human Y chromosome were revealed in the spiralization interval limited by reper chromosome 3 length from 16.6 to 2.9 mkm. On the basis of regression analysis it was shown that in the initial phase of the spiralization interval studied the f-block was condensed more rapidly than the nf-region; then the speed of contraction of the latter exceeded that of the former. A decline of the Y chromosome condensation in relation to ageing was revealed. A possible chromosome segregation disturbance in gametogenesis due to senescent changes of heterochromatic regions is discussed.     

Individual quantitative differences in the structure of the human hippocampus

The volume of the hippocampal grey substance (Corpus Ammoni--CA) and that of the denticulated plate (Fasciculus dentatus--FD) have been studied in mature persons of various sex and age (17 subjects, 22 cerebral hemispheres) under cytoarchitectonic control defining the borders of the cerebral formations mentioned. Certain quantitative and spatial differences of CA and FD have been revealed in some subjects. Especially great differences are noted between more seldom occurring extreme individual variants, their difference being as great as three times. The differences revealed are demonstrated to be independent on the brain mass of the human beings studied. The observation performed causes to revise the competency of the principle concerning a constant proportional dependence between the reference points on the cerebral surface and the internal cerebral structures. These data are used in neurosurgery when surgical interventions are performed on brains with different dimensions. A suggestion is made that the individual volumetric differences revealed in the hippocamp of various persons are defined by its functional specificity.