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Various authors have associated increased susceptibility to infectious diseases in certain patients to inhibitors of neutrophil chemotaxis demonstrable in serum or diluted plasma of these patients. The present experiments showed, however, that serum and diluted plasma but not undiluted plasma from normal human donors consistently inhibited chemotactic migration of autologous human neutrophil granulocytes. Therefore, the presence of such inhibitors in the circulating blood can only be assessed by the evaluation of undiluted plasma. The findings suggest that the experimental conditions which have been used in the past to demonstrate such inhibitors in the circulating blood of patients with increased susceptibility to infections are inadequate, and results need reexamination. The inhibitors affect random locomotion and chemotaxis of neutrophil granulocytes but not phagocytosis or the metabolic burst resulting in nitroblue—tetrazolium reduction. On the other hand, phagocytosis of Staphylococcus albus rendered neutrophils chemotactically unresponsive. The significance of so-called cellular defects of neutrophil chemotaxis in such patients is also considered.

A suspension of thymocytes labeled with 125IUdR or 3HTdR was injected into the jejunum of mice. The bulk of the radioactivity disappeared within few hours from the intestine and was recovered principally in the urine. This indicated a very rapid breakdown of labeled thymic cells, reabsorption and subsequent elimination of the tracer in the kidney. In mice injected with cells labeled with 3HTdR, the initial rapid loss of radioactivity was of shorter duration, and slower during the second phase, presumably due to more extensive reutilization and/or prolonged persistence of acid-soluble radioactivity. Pretreatment of the recipients with antibiotics did not significantly reduce the rate of radioactivity loss.

The thymic cortex was locally labeled with 125Iododeoxyuridine (125IUdR) in young adult mice in an attempt to provide a simple quantitative assessment of the fate of cortical thymocytes. Similarly operated and nonoperated mice given 125IUdR intravenously were used for comparison. Analogous experiments were performed in adrenalectomized animals. More than 90% of thymic activity present 1 day after labeling had been lost by day 8. That proportion of radioactivity contributed to a given organ by accumulation of labeled thymic migrants was estimated by comparison of values obtained after local labeling with those acquired after systemic labeling. Thymic cell accumulation was apparent in the intestine, spleen, mesenteric lymph node, and femurs of locally labeled mice; however, only a few per cent of the total activity lost from the thymus was accounted for in these lymphoid organs. The pattern of fecal and urinary elimination of 125I did not markedly differ in the various experimental groups, the bulk of the activity being recovered in the urine. The intestine could not be ruled out as a major site of thymocyte loss. Since significant radiation or pharmacologic toxicity was unlikely with the doses of 125IUdR used, the data indicated that the vast majority of newly formed thymocytes dies after a short life and only a small fraction of thymic migrants is longer lived.

A newly developed material, which we call biocement, consisting of bisphenol-a-glycidyl methacry-later`('epoxide methacrylate') as organic matrix and Bio-ceramic Battelle, Bioglass Hench and/or pentacalcium hydroxide triphosphate ('tri-calcium phosphate') powder as filling particles is presented. In an extension of previous experiments, various types of this biocement, containing different admixtures of paniculate matter, were employed to test their usefulness in head surgery, in particular maxillo-facial reconstruction, on dogs and a rhesus monkey. Encouraging results were obtained with regard to (a) fixing a titanium alloimplant under some degree of mechanical stress; (b) covering a defect in the skull cap, including the closure of an artificially induced meningeal fistula with liquorrhea; and (c) reconstruction of defects in the anterior wall of frontal sinuses. Spescial emphasis is placed on direct contact between biocement and bone, interdigitations between these two, reactions of meningeal tissue, and regeneration of ciliated epithelium underneath fixed reimplants over the frontal sinus.

The thymic cortex was locally labeled with 125Iododeoxyuridine (125IUdR) in young adult mice in an attempt to provide a simple quantitative assessment of the fate of cortical thymocytes. Similarly operated and nonoperated mice given 125IUdR intravenously were used for comparison. Analogous experiments were performed in adrenalectomized animals. More than 90% of thymic activity present 1 day after labeling had been lost by day 8. That proportion of radioactivity contributed to a given organ by accumulation of labeled thymic migrants was estimated by comparison of values obtained after local labeling with those acquired after systemic labeling. Thymic cell accumulation was apparent in the intestine, spleen, mesenteric lymph node, and femurs of locally labeled mice; however, only a few per cent of the total activity lost from the thymus was accounted for in these lymphoid organs. The pattern of fecal and urinary elimination of 125I did not markedly differ in the various experimental groups, the bulk of the activity being recovered in the urine. The intestine could not be ruled out as a major site of thymocyte loss. Since significant radiation or pharmacologic toxicity was unlikely with the doses of 125IUdR used, the data indicated that the vast majority of newly formed thymocytes dies after a short life and only a small fraction of thymic migrants is longer lived.

Coarse granularity of nuclear chromatin texture is a prominent feature of most malignant cell lines. We have chosen the abrupt transition from eu to heterochromatic foci (high contrast gradient [CG]) as a novel parameter for coarseness. This feature was quantified using automated image analysis of single nuclei in smears stained by the MayGrünwaldGiemsa technique. The principle of this approach consists of eliminating, with the help of substraction between two image lowpass filters, the small grey level differences among pixels, so that only high CG values are retained on the digitized image. The sum of these distinctive microareas is then taken as a fraction of the area of the peripherally eroded nucleus, and this ratio is designated as contrast gradient index (CGI) per nucleus. This method was tested on fine needle aspirates from 11 patients with benign breast disease (BBD) and 14 with mammary carcinoma (CA). For each specimen, 60 nuclei were analyzed, with a measuring time per nucleus of about 1 min. A highly significant distinction between epithelial cell populations in BBD and CA, respectively, was obtained by variance analysis of all CGIs per nucleus (p = 2 × 10−18). The median and the mean values of CGI per specimen were the next best discriminators, followed by the modes and the standard deviation of CGI per specimen. The percentage of nuclei per specimen with CGI values of >12 was also significantly greater in CA than in BBD.

We analysed the chemokinetic actions of fMet-Leu-Phe (FMLP) and human serum albumin (HSA) on preparations of human neutrophils. Our work focused on the extent to which these agents, individually or in combination, affected locomotion by inducing changes in motile activity and/or the degree of cellular adhesion to the substratum. Because polymorphonuclear leucocyte (PMN) preparations derived from different individuals were found to exhibit broad variations in their basal motility and level of adhesiveness to glass substrata, it became of major interest to clarify mechanisms responsible for the reported variations in neutrophil responses to FMLP. We performed detailed studies on three separate PMN preparations, which differed in terms of their basal motility and adhesiveness. The unequivocal findings that emerged from this study were as follows : (1) HSA did not stimulate or modify motility of cells in suspension. Its orthokinetic effect was exclusively due to its capacity to decrease adhesion to the substratum. It prevented immobilization of motile cells that made contact with the substratum. (2) The orthokinetic effect of FMLP was primarily due to its effects on motility, but there were also secondary effects on spreading and adhesion. The peak chemokinetic activity of FMLP occurred at 10−8M, when measured by the two-filter count method and this was correlated with the percentage of polarized neutrophils in suspension. (3) The response to HSA and/or FMLP depended on the basal activity of the cells. If the cells were non-motile and spherical, HSA had no chemokinetic effect. Such an effect was only observed with cells that were initially motile. In contrast, the stimulatory effect of FMLP on motility and locomotion was marked in cases where basal motile activity of the neutrophils was low. If the basal motile activity was high, motility and locomotion could not be stimulated further. Therefore, the chemokinetic effects of HSA and FMLP can be predicted when one knows the basal motile activity of the neutrophils. The variable effect of FMLP on adhesion may also contribute to the regulation of locomotion. These findings help to explain earlier conflicting reports on the chemokinetic effect of FMLP. (4) FMLP can elicit simultaneous changes in motility and adhesiveness, which may have synergistic or antagonistic effects on locomotion. (5) The average speed of the whole neutrophil population is essentially regulated by changes in the proportion of locomoting cells and not, or to a lesser extent, by changes in the speed of the locomoting subset. The proportion of locomoting cells in PMN preparations can be predicted accurately after measuring their content of motile polarized cells in suspension and spread cells that are immobilized on glass. (6) HSA and FMLP elicited orthokinetic responses, but no significant klinokinetic responses. The present studies show that the effects of FMLP, and presumably of other agents as well, become predictable when motility and adhesiveness of a cell population is known. Analysis of chemokinesis requires independent assessment of motility and adhesion.

DNA-synthetizing lymphocytes were identified in the lymph nodes regional and more distal to the site of developing P-815 tumours by incorporation of [3H]-thymidine followed by autoradiography of lymph node sections. It appeared that not only T but also B cell areas of draining and to a lesser extent of distal lymph nodes were stimulated by the growing tumour. This result was unexpected since neither humoral nor tumour cell-bound antibody could be identified so far as a functional correlate of B cell stimulation. In general the proliferative response of lymphocytes followed a biphasic pattern with an early peak of reactivity on days 2-3 and a second peak around day 12-15 after tumour cell inoculation. In the draining (axillary) lymph node the second peak of reactivity was suppressed, possibly as a consequence of metastatic tumour cells in this node when tumour cells were inoculated in the flank. The pattern of lymphocyte stimulation revealed larger individual variations after tumour cell inoculation in the flank than the foot pad. These results were associated with a slower and less regular drainage of carbon particles from the flank to the axillary and exceptionally the brachial lymph node than from the foot pad to the popliteal node after injection of India ink.

An economic and sensitive test system for measuring random and directional migration of human neutrophils is described. The technique, based on a modified Boyden chamber equipped with a two-filter system, permits a substantial reduction of both incubation time and sample volume. The influence of various technical factors such as the neutrophil concentration in the cell suspension, the incubation time of the chambers, the test concentration of activated plasma or serum, the presence of heparin, and the procedure for separating neutrophils from human peripheral blood, was investigated. Standardized procedures for measuring and reporting neutrophil chemotaxis are proposed.

“Alveolitis”, as opposed to “pneumonia”sensu striction, is a term used to denote diffuse inflammatory changes of the pulmonary parenchyma, excluding those that result from local bacterial, fungal or other extracellular microbial growth. The various types of alveolitis are classified according to their histological characteristics and range from “luminal phagocytic” or “mural lymphoplasmacellular” and “exudative” to “fibrosing” alveolitis. In this overview, various exogenous and endogenous causes of different types of alveolitis, and the cellular events in their pathogenesis are briefly discussed to illustrate the complex mechanisms involved. Particular emphasis is placed on the possible transition from diffuse exudative to fibrosing alveolitis. It appears that pulmonary fibrosis, which is usually patchy rather than truly diffuse, does not have a uniform pathogenesis. Besides the possibility of a certain degree of a diffuse fibrosis three major pathways are evident: (1) granulation tissue budding into alveolar lumina (luminal fibrosis) (2) exudate incorporation into alveolar walls (mural fibrosis) and — at least equally important-(3) so-called collapse (atelectatic) induration (obliterative-interseptal fibrosis), a process that has largely been neglected so far.

Summary Large lung sections of humans of advanced adult age revealed a markedly nonuniform retention pattern of dense anthracotic particle aggregates, with an impressive accumulation of this material along pulmonary lymphatics, i.e. the deep (peribronchial), septal (perivenous) and superficial (pleural) networks. Conversely, the alveolar parenchyme contained only occasional, small aggregates of macrophages heavily loaded with carbon, representing little more than 2% of this material in lung tissue. Although translocation kinetics of anthracotic particles cannot readily be compared to those of highly toxic a-emitting, poorly soluble radionuclides such as239PuO2, lymphatic drainage of the latter over the years may also be expected to lead to a concentration of radioactive material along lymph vessels. Since human data on the effects of inhaled239PuO2 are virtually lacking, the above distribution pattern is apt to help in identifying cells and other tissue components most heavily at risk. Findings are also relevant to the problem of “hot spot” formation in vivo and its possible sequelae. The latter are briefly discussed with regard to both stochastic and non-stochastic effects.

Various authors have associated increased susceptibility to infectious diseases in certain patients to inhibitors of neutrophil chemotaxis demonstrable in serum or diluted plasma of these patients. The present experiments showed, however, that serum and diluted plasma but not undiluted plasma from normal human donors consistently inhibited chemotactic migration of autologous human neutrophil granulocytes. Therefore, the presence of such inhibitors in the circulating blood can only be assessed by the evaluation of undiluted plasma. The findings suggest that the experimental conditions which have been used in the past to demonstrate such inhibitors in the circulating blood of patients with increased susceptibility to infections are inadequate, and results need reexamination. The inhibitors affect random locomotion and chemotaxis of neutrophil granulocytes but not phagocytosis or the metabolic burst resulting in nitroblue-tetrazolium reduction. On the other hand, phagocytosis of Staphylococcus albusrendered neutrophils chemotactically unresponsive. The significance of so-called cellular defects of neutrophil chemotaxis in such patients is also considered.

The terminal involution pattern of the human thymus was studied based on autopsy cases (both sexes, age range 63-91 years). Large sections through the entire thymic fat body were examined with the help of both conventional histological and immunohistochemical techniques. The findings demonstrate that thymic atrophy in old humans (a) goes far beyond the degree of involution observed in small rodents; (b) results in a system of thin, branching, in part interrupted, non-keratinizing epithelial plates containing no typical Hassall bodies; (c) concerns all components of the thymus except fat tissue which progressively replaces original thymic structures; and (d) involves various types of disorganization of individual lobules with T and B lymphocytes often located outside rather than within epithelial remnants. Effects of low-level radiation on this final regression of the human thymus are unknown.

The origin and fate of small lymphoid cells in the dog bone marrow were studied autoradiographically by observing the effect of clamping of the femoral artery during in vivo availability of H3-thymidine. Heavily labeled small lymphoid cells appeared in the bone marrow of the clamped leg 3 hours after injection of the tracer and increased in number up to 6 days. The labeling indices of these cells, however, were significantly lower than those of control marrow. A possible interpretation is that dog bone marrow contains two populations of small lymphoid cells, one migrating into the marrow via the blood stream, the other originating from local precursor cells within the marrow. There was no evidence for a transformation of migrated small lymphoid cells into erythroblasts during the first 48 hours after injection of H3-thymidine.

1. Extracorporeal x-irradiation of the circulating blood of the calf severely depletes the population of small lymphocytes within the body. 2. The number of circulating blood lymphocytes drops to a low constant level after 12 hours of extracorporeal irradiation that is maintained up to 48 hours of extracorporeal irradiation. On the other hand the lymphoreticular tissues continue to lose lymphocytes between the twelfth and forty-eighth hour of extracorporeal irradiation. Therefore, the apparent steady-state lymphocyte level in the peripheral blood is maintained by a non-steady-state process in the lymphoreticular organs where the new production of lymphocytes is far insufficient to replace the cells leaving these tissues. 3. The cellular debris caused by extracorporeal irradiation of the circulating blood is found within the spleen, lung, liver, lymph nodes and elsewhere, in this order of relative concentration. 4. A unique pathologic phenomenon is produced within two days of extracorporeal irradiation of the circulating blood, e.g., a combination of intact or even actively proliferating germinal centers with a marked diminution in the concentration of small lymphocytes. This technic of depletion of small lymphocytes, leaving germinal centers intact, should permit studies for evaluation of the relative importance of germinal centers vs. small lymphocytes in primary and secondary immune responses. 5. The above findings are discussed in relation to lymphocyte production rate, stores, mobilization and recirculation.

Thymic lymphopoiesis in 2 day old Swiss albino mice (Hale-Stoner strain) was studied autoradiographically based on the variation of mitotic labeling indices and intensities after a single intraabdominal injection of 3H-thymidine. Best estimates for the duration of various phases of the generative cell cycle are as follows: G2 for the majority of cells: 86-94 minutes, shortest possible duration for a small fraction of cells: 35-48 minutes; mitosis: 27-44 minutes; DNA synthesis: 7 hours; generation time: 9¼ hours. G1 could not be determined directly by the methods used but probably is short. The present data do not indicate different generation times for proliferating thymic lymphoid cells of unequal size although the very largest elements must be excluded from this statement because of rare occurrence. The results obtained in this study together with data on changes of thymic weight and proliferative activity in the neonatal period indicate that during the third day after birth, a fraction corresponding to one third of all lymphoid cells present in the organ at the end of this period is lost. In view of the extremely low pyknotic index in the thymus at this age, the present data provide support in favor of an extensive emigration of lymphoid cells being the major cause of this cell loss.

Two calves received 48 hours of extracorporeal irradiation of the circulating blood (ECIB) immediately prior to cannulation of the thoracic duct and administration of a single intravenous injection of 3H-thymidine. Lymph samples were then removed at short time intervals during 24 hours and smears from sedimented cells were processed for autoradiography. For different groups of mitotic figures classified according to size, cytoplasmic-nuclear ratio and degree of cytoplasmic basophilia, the variation of the mitotic labeling index (MLI) and of the mean grain count per labeled mitotic figure (MGC/LMF), as a function of time after a single injection of 3H-thymidine, was analyzed. Based on the pooled data obtained from the two animals, it was found that tinctorial properties of the cytoplasm permit differentiation into at least two populations of lymphoid cells in the thoracic duct of the calf: one of more basophilic cells with a mean DNA synthesis time of 4 hours and a mean generation time of 5½ to 6 hours and one or more populations of less basophilic cells with longer DNA synthesis and generation times.

Ultrastructural differences between small lymphocytes of the thymic cortex and those located in the cortical zone of lymph nodes of mice were examined by electron microscopy and cytometric methods. The particle size analyzer TGZ 3 (Zeiss) was used to measure the size-frequency distribution of nucleolar cross-section diameters, and the resulting data were computed mathematically and statistically to determine the corresponding mean volumina. It could be shown that thymic, as compared to lymph node cortical small lymphocytes, (1) have a smaller mean nucleolar volume (0.11µ3 versus 0.46µ3); (2) represent a more uniform population with regard to the frequency distribution of the nucleolar cross section diameters; and (3) are of smaller size due to less cytoplasm, while the mean nuclear volume does not differ significantly from that of small lymphocytes located in the cortex of lymph nodes. These findings are discussed in relation to qualitative ultrastructural peculiarities and probable differences in the magnitude of RNA turnover as estimated by the use of tritiated cytidine. The possible significance of cytometrically defined populations of small lymphocytes with regard to sensitized and nonsensitized cells is considered.

The kinetics of the mega-caryocytic cell line of the rat bone marrow were studied using tritiated thymidine as a cell label. The changes in the percentage of labeled cells as a function of time after injection of the tracer were registered separately for arbitrarily chosen successive recognizable stages of megacaryocytic differentiation. Emphasis is put on the development of initially labeled cells into a stage of maturation corresponding to initially non-labeling cell forms. The following results were obtained: 1. The transit time for the most immature recognizablestage of megacaryocytic development to megacaryocytic disintegration is approximately 40 hours. 2. Evidence was obtained that the recognizable megacaryocytic elements originate from unrecognized precursors which continuously synthesize DNA for a period of at least 1 to 3 days prior to maturation into recognizable megacaryocytic precursors. 3. The immature megacaryocytic cells able to synthesize DNA take up more H3thymidine than the rest of the bone marrow cells. This is consistent with polyploidy. 4. The process of nuclear lobulation is not accomplished by the end of DNA synthesis, thus being comparable to nuclear segmentation in neutrophilic granulocytes. This latest phase of maturation is relatively long (approximately 25–30 hours) as compared to the phase during which recognizable megacaryocytic precursors are able to synthesize DNA (less than 15 hours).

Dogs were bled 40% of their blood volume (32 ml/kg). Thereafter, at intervals to 52 hours, the in vitrouptake of tritiated thymidine by erythrocytic precursors of the marrow did not differ from the controls as measured by percent labeling and grain counts in morphologically differentiated cells. Also, no alterations from control values were found with regard to morphological distribution, relative numbers of the marrow normoblasts, and mitotic index. The data suggest that the acute blood loss did not influence detectably the chosen parameters for the time intervals studied.

Young adult female Sprague-Dawley rats were given intramuscular injections of thymidine-3H at 8-hour intervals for a period of 30 days in order to follow the labeling indices and labeling intensities of small lymphocytes and of large lymphoid cells in the circulating blood and lymph nodes. Assuming that radiotoxic, pharmacological and/or hormonal effects were negligible, the following conclusions seem to be justified:1.During the first day of the injection period the labeling index of small lymphocytes in the peripheral blood rose from zero to an average of 18% (maximum: 29%). Labeling indices of this cell type in the circulating blood, as a function of time after onset of the labeling procedure, followed a curve which reached 50% around day 8 and 79% at the 30 day terminal interval.2.Results can best be explained by the hypothesis that the frequency distribution of the values for G0 time or residence (recirculation) time of small lymphocytes in the circulating blood is a continuous one and shows a marked peak from one to a few days.3.Large lymphoid cells in the peripheral blood were replaced much more rapidly than small lymphocytes.4.The labeling index of small lymphocytes in lymph node smears at the end of the injection period corresponded to that of small blood lymphocytes. Autoradiographs of histological sections revealed that the outer zones of the lymph node cortex which contains preferentially the more sessile pool of lymphocytes, contained as high a percentage of unlabeled small lymphocytes as did the circulating blood.5.Blood monocytes were labeled to 100% 4 days after beginning repeated injections of thymidine-3H and maintained this labeling index throughout the labeling period.

EXTRACORPOREAL x-irradiation of the circulating blood has been shown to be practical in animals1–4and in man.5

MAMMALIAN BONE MARROW contains a considerable number of small lymphoid cells (small lymphocytes and small lymphocyte-like cells). The total number of these cells (50,000 to 500,000 per cu. mm) depends on species, age and other factors.1–6The origin, function and fate of these cells remain obscure in many respects.7–14In particular, definitive evidence is lacking on whether small lymphoid cells enter the bone marrow from the blood, whether their origin lies entirely within the bone marrow, or whether they arise by both processes. In addition, it has not been clearly shown whether or not these cells may function as multipotential hemopoietic stem cells. Results obtained from experiments with irradiated parabiotic animals15,16and animals given regional fractionated doses of X-irradiation,17and transplantation of leukocytes from peripheral blood into lethally irradiated recipients18afford indirect evidence that peripheral blood of mice and rats may contain stem cells capable of DNA synthesis and division.

Neonatal mice were given a subcapsular, intrathymic injection of thymidine-3H using a modified microneedle technique, and the migration of labeled cells to spleen, lymph nodes, Peyer's patches, and bone marrow was followed radioautographically with time. Assuming that nonlabeled lymphocytes migrated in the same manner as labeled lymphocytes, it can be concluded that the majority of lymphocytes present within mesenteric lymph nodes (74%) and Peyer's patches (61%), and a large proportion of those located in popliteal lymph nodes (40%) and the spleen (26%), were of thymic origin. Evidence is presented indicating that these are minimum values. The difference in the magnitude of thymic cell migration to gut-associated lymphoid tissue on the one hand and to the spleen and popliteal lymph node on the other hand was tentatively attributed to antigenic stimulation from the intestinal flora which develops during the first days of life. Thymus-derived lymphocytes were scattered throughout the lymph node cortex and splenic follicles. No noticeable thymic cell migration to the bone marrow was found. Labeling indices in the peripheral lymphoid organs paralleled those of cortical thymic lymphocytes suggesting the thymic cortex as the major source of migrants. By 2 days postinjection, the mean grain counts of labeled lymphocytes in all peripheral lymphoid tissues were higher than the mean grain counts of labeled lymphocytes in the thymus. At 7 days postinjection heavily labeled cells constituted 11–16% of the labeled population in peripheral tissues while they were absent from the thymic cortex. These results indicate that a fraction of thymus-derived cells, upon settling in the periphery, remained in, or reentered, a nonproliferative phase for at least 7 days. Conversely, many thymus-derived lymphocytes underwent division in the periphery and/or penetrated the intestinal epithelium. Since the relative number of thymus-derived cells found in the mesenteric lymph nodes of 1- and 2-day old mice was considerably higher than the percentage of cells at this site having the theta (θ) alloantigen, as reported by other authors, the possibility exists that θ-antigen on thymus-derived lymphocytes may, at least in a fraction of these cells, no longer be detectable as they reach the peripheral organs.

The effect of chemotactic peptides which lack chemokinetic activity has been investigated. The neutrophil response is proportional to the logarithm of the stimulus intensity, or alternatively a power function with an exponent of 0.3. Equal responses are obtained for equal ratios between the peptide concentration in the lower compartment and the threshold concentration. The significance of Weber-Fechner's law in leucocyte chemotaxis is discussed.

ALTHOUGH renewed efforts have been made towards an understanding of the function(s) of the thymus, the exact mechanisms involved remain unclear. It is not known whether the thymus serves primarily as a source of immunologically competent cells, or whether it produces a substance or substances and/or contact factors which may control proliferation and immunological maturation of peripheral lymphoid cells. Combinations of such suggestions have been made repeatedly1,2. A meaningful evaluation of the existence and magnitude of thymic cell migration during the perinatal period of life requires more information on at least the following thymic growth characteristics as a function of age before and after birth: (a) the rate of thymic growth; (b) proliferative activity of thyrnic lymphoid cells; (c) the generation time of thymic lymphoid cells; and (d) a quantitative estimate of intrathymic cell death. We report here an investigation of growth and proliferative activity of the thymus of mice ranging in age from 3 days before to 6 days after birth.

Es wird ein typisches Oligodendrogliom bei einer 495 Tage alten, weiblichen unbehandelten Albinomaus beschrieben, eine Geschwulstform, die bisher bei dieser Species nicht bekannt war.

Experiments performed by means of time lapse cinematography or the filter technique show that human serum albumin has marked chemokinetic effects on neutrophil cultured in Gey's solution. The average speed of the cells, as well as the proportion of neutrophils showing locomotion, is increased. Enhanced locomotion correlates with decreased attachment to the substratum as determined by morphological and functional criteria.