Influence of development on the number of calcitonin-containing cells in the mouse thyroid

Calcitonin-containing cells in serial, 6-μm sections of the thyroid glands of Swiss Webster mice, at 1 day, 2 weeks, 4 weeks and 8 weeks of age, were demonstrated by an immunoperoxidase method, using antiserum to human calcitonin. C-cell nuclei were counted in every sixth section of both left and right lobes. The average number of C-cells counted in the thyroid glands of 8-week-old animals was 18-fold, 5.5-fold and 2.5-fold greater than the number observed in 1-day, 2-week and 4-week-old animals, respectively. C-cell concentration was found to be greatest in 4-week-old mice. Mitoses of C-cells were observed in animals which were 1 day, 2 weeks and four weeks old. No mitotic figures were seen in 8-week-old animals. A few C-cells were seen in close association with neurons. The volume of the thyroid glands of 8-week-old animals was about 14-, 4- and 3-fold greater than the volume in the 1-day-old, 2-week-old and 4-week-old mice, respectively. These changes in the C-cell population during development provide a model for the study of C-cell proliferation and storage of calcitonin.     

Studies of proliferative responses by long-term-cryopreserved peripheral blood mononuclear cells to bacterial components associated with periodontitis.

Freezing techniques provide a means for repeating and extending immunological assays with frozen aliquots of an individual's peripheral blood mononuclear cell fraction. Lymphocytes which are stored frozen for a limited time retain their ability to respond to polyclonal B-cell activators, mitogens, and antigens of dental interest. Our studies extend these previous findings by determining lymphocyte functional activity following frozen storage for up to 100 weeks. In addition, the autologous immune response was measured by spontaneous lymphocyte proliferation following 0, 1, 40, and 60 weeks of frozen storage. Peak responses for all individuals occurred at day 7 of incubation. The lymphocyte proliferative response to the superantigens toxic shock syndrome toxin-1 (TSST-1) and Staphylococcus enterotoxin A (SEA) were not changed after 100 weeks of frozen storage. Maximum responses varied among the individuals but occurred at equivalent stimulator concentrations. However, slopes generated from data obtained following 0, 4, 13, 20, 30, 50, 88, and 100 weeks of frozen storage showed no significant deviation from zero (P > 0.05) for all individuals tested. After 100 weeks of storage, the total changes in proliferative activity (counts per minute per week) were -2.1% +/- 16.8% and -5.5% +/- 17.0% for TSST-1 and SEA, respectively. The lymphocyte proliferative responses to pokeweed mitogen, concanavalin A, and sonicates of two periodontal pathogens (Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans) following frozen storage were similar to those with TSST-1 and SEA. These results indicate that peripheral blood mononuclear cells stored frozen may serve as appropriate controls to monitor changes in the disease state long-term periodontal treatment.     

Characterization of Changes to the Mechanical Properties of Arteries due to Cold Storage Using Nanoindentation Tests

Understanding the effect of cold storage on arterial tissues is essential in various clinical and experimental practices. Cold storage techniques could significantly affect the post-cryosurgical or post-cryopreservation mechanical behavior of arteries. Previously, arteries were considered homogenous and elastic and the changes in material properties due to cold storage were inconclusive. In this study, using a custom-made nanoindentation device, changes to the local viscoelastic properties of porcine thoracic aorta wall due to three common storage temperatures (+4, -20, and -80 °C) within 24 h, 48 h, 1 week, and 3 weeks were characterized. The changes to both elastic and relaxation behaviors were investigated considering the multilayer, heterogeneous nature of the aortic wall. The results showed that the average instantaneous Young's modulus (E) of +4 °C storage samples decreased while their permanent average relaxation amplitude (G (∞)) increased and after 48 h these changes became significant (10 and 13% for E and G (∞), respectively). Generally, in freezer storage, E increased and G (∞) showed no significant change. In prolonged preservation (>1 week), the results of -20 °C showed significant increase in E (20% after 3 weeks) while this increase for -80 °C was not significant, making it a better choice for tissue cold storage applications.     

Changes in thymus volume in adult HIV-infected patients under HAART: correlation with the T-cell repopulation

An important thymus role has been suggested in T‐cell repopulation after HAART in adult HIV‐1 infected patients. Thymus volume increase after treatment has been described in HIV‐1 infected children but not in adult patients. The objective of this work was to evaluate the effect of HAART on the thymic volume of adult HIV‐1 infected patients and its relation with the T‐cell repopulation. Twenty‐one adult patients following 24 weeks under HAART were included in the study. All patients underwent a thoracic computed tomography (CT) evaluation for the measurement of thymic volumes at weeks 0, 12 and 24. Baseline thymus volume showed a significant correlation with the patient's age. Thymic volume significantly increased after 24 weeks of HAART. Besides, a significant correlation between changes in the thymus volume and changes in both total and naïve CD4+ cell counts was found. Only patients with increases ≥100 CD4+ cell counts after treatment significantly increased the thymic volume. These data show the first evidence of an early change in thymic volume of adult HIV‐1 infected patients under HAART. This increase was related to the rise of both total and naïve CD4+ cell counts suggesting a functional role of thymic volume increase.     

Erythropoietin treatment elevates haemoglobin concentration by increasing red cell volume and depressing plasma volume

Erythropoietin (Epo) has been suggested to affect plasma volume, and would thereby possess a mechanism apart from erythropoiesis to increase arterial oxygen content. This, and potential underlying mechanisms, were tested in eight healthy subjects receiving 5000 IU recombinant human Epo (rHuEpo) for 15 weeks at a dose frequency aimed to increase and maintain haematocrit at approximately 50%. Red blood cell volume was increased from 2933 ± 402 ml before rHuEpo treatment to 3210 ± 356 ( P < 0.01), 3117 ± 554 ( P < 0.05), and 3172 ± 561 ml ( P < 0.01) after 5, 11 and 13 weeks, respectively. This was accompanied by a decrease in plasma volume from 3645 ± 538 ml before rHuEpo treatment to 3267 ± 333 ( P < 0.01), 3119 ± 499 ( P < 0.05), and 3323 ± 521 ml ( P < 0.01) after 5, 11 and 13 weeks, respectively. Concomitantly, plasma renin activity and aldosterone concentration were reduced. This maintained blood volume relatively unchanged, with a slight transient decrease at week 11, such that blood volume was 6578 ± 839 ml before rHuEpo treatment, and 6477 ± 573 (NS), 6236 ± 908 ( P < 0.05), and 6495 ± 935 ml (NS), after 5, 11 and 13 weeks of treatment. We conclude that Epo treatment in healthy humans induces an elevation in haemoglobin concentration by two mechanisms: (i) an increase in red cell volume; and (ii) a decrease in plasma volume, which is probably mediated by a downregulation of the rennin–angiotensin–aldosterone axis. Since the relative contribution of plasma volume changes to the increments in arterial oxygen content was between 37.9 and 53.9% during the study period, this mechanism seems as important for increasing arterial oxygen content as the well-known erythropoietic effect of Epo.     

Intact and sympathectomized carotid bodies of long-term hypoxic rats: a morphometric ultrastructural study

Summary The ultrastructure of the carotid body after exposure to hypoxia (10% O₂) for one, two or three weeks was investigated morphometrically. The study was performed on rats after unilateral removal of the superior cervical ganglion. The normally occurring bimodal distribution of type I cells, representing cells with small vesicle profile diameters (SVC) and large vesicle profile diameters (LVC) respectively, changed after one week of hypoxia into a unimodal population. After one or two weeks of hypoxia the diameter range of dense-cored vesicle (DCV) profiles in type I cells was not different from that of DCV profiles in control LVC. After three weeks of hypoxia the DCV vesicle size was intermediate between those of control SVC and LVC. The volume density of DCV decreased after one week but returned to initial values after two and three weeks of hypoxia. At two or three weeks of hypoxia, however, the total cell volume was increased about 1.4 times which should reflect an increase of the total content of DCV at these times of exposure to hypoxia. An increased mean area of cell profiles indicates a hypertrophy of the type I cells, but no signs of hyperplasia could be detected. The ganglionectomy did not cause any remarkable changes compared to the intact carotid body except for a higher volume density of DCV during the early periods of hypoxia.It is inferred from the study that the increased total mass of type I cell tissue during long-term hypoxia is due to a hypertrophy of the cells. Furthermore, the type I cells can increase their storage capacity for catecholamines during hypoxia by an increase in the size and number of DCV.     

Morphometric study of cardiac muscle: the problem of tissue shrinkage

Comparison of data from morphometric studies dealing with the heart is complicated by the fact that little information dealing with cell size changes during tissue processing is available. To investigate these changes, isolated cardiac myocytes were adhered to glass cover slips of Sykes Moore chambers and photographed after each step of processing for transmission electron microscopy. Six different experiments with a minimum of 10 cells each were followed through the entire procedure after fixation with isoosmolar glutaraldehyde. Cellular dimension changes were determined by tracing individual isolated myocytes after each step of the procedure with a sonic digitizer. Significant cell volume changes occurred after osmium (16 per cent swelling), postosmium wash (10 per cent swelling), and uranyl acetate (25 per cent shrinkage). Hypertonic aldehyde solutions resulted in cellular shrinkage during fixation not found with isotonic solutions. Changes in cell cross-sectional area rather than length were largely responsible for altered cell volumes during any given phase of processing. The results indicate that, although cell volume changes occur during processing, final cell dimensions of embedded cells were not different from unfixed cells. In whole tissue blocks, inclusion of propylene oxide in the procedure resulted in tissue shrinkage which was not observed in isolated myocytes, suggesting that different tissue components react in a variable manner to propylene oxide. After each of the other steps in processing, tissue blocks reacted in a similar manner to the isolated myocytes.     

Morphological evidence for the 'implantation window' in human luminal endometrium

Endometrial tissue was taken from 21 normal fertile women (aged 18-40 years) between 4 and 13 days after the luteinizing hormone (LH) surge. Systematic random samples of luminal epithelium were taken for both light and electron microscopy and examined morphometrically. Throughout the luteal phase there were remarkably few changes in the volume fraction of nucleus, mitochondria, rough endoplasmic reticulum and 'vesicular system' to cell. Nuclear profile dimensions and cell height also did not change over time. Cell and organelle volume (estimated as volume weighted mean volume) did not change significantly, but showed numerically smallest values on day LH + 13. However the ratio of desmosomes to whole cell and both arithmetic mean thickness and harmonic mean thickness of basement membrane were minimal at the time when implantation would be most likely to occur, i.e. approximately 6 days after the LH peak. Therefore it appears that while some morphometric parameters in human luminal epithelial cells change little during the luteal phase, specific cellular changes occur to the basement membrane and desmosomes which may facilitate embryo implantation. These changes occurred around day LH+ 6 and may be a morphological representation of the 'implantation window'.     

Evaluation of bone marrow-derived mesenchymal stem cells after cryopreservation and hypothermic storage in clinically safe medium

Achievements in tissue engineering using mesenchymal stem cells (MSC) demand a clinically acceptable "off-the-shelf" cell therapy product. Efficacy of cryopreservation of human bone marrow-derived MSC in clinically safe, animal product-free medium containing 2%, 5%, and 10% dimethyl sulfoxide (DMSO) was evaluated by measuring cell recovery, viability, apoptosis, proliferation rate, expression of a broad panel of MSC markers, and osteogenic differentiation. Rate-controlled freezing in CryoStor media was performed in a programmable cell freezer. About 95% of frozen cells were recovered as live cells after freezing in CryoStor solutions with 5% and 10% DMSO followed by storage in liquid nitrogen for 1 month. Cell recovery after 5 months storage was 72% and 80% for 5% and 10% DMSO, respectively. Measurements of caspase 3 activity demonstrated that 15.5% and 12.8% of cells after 1 month and 18.3% and 12.9% of cells after 5 months storage in 5% and 10% DMSO, respectively, were apoptotic. Proliferation of MSC recovered after cryopreservation was measured during 2 weeks post-plating. Proliferation rate was not compromised and was even enhanced. Cryopreservation did not alter expression of MSC markers. Quantitative analysis of alkaline phosphatase (ALP) activity, ALP surface expression and Ca?? deposition in previously cryopreserved MSC and then differentiated for 3 weeks in osteogenic medium demonstrated the same degree of osteogenic differentiation as in unfrozen parallel cultures. Cell viability and functional parameters were analyzed in MSC after short-term storage at 4°C in HypoThermosol-FRS solution, also free of animal products. Hypothermic storage for 2 and 4 days resulted in about 100% and 85% cell recovery, respectively, less than 10% of apoptotic cells, and normal proliferation, marker expression, and osteogenic potential. Overall, our results demonstrate that human MSC could be successfully cryopreserved for banking and clinical applications and delivered to the bedside in clinically safe protective reagents.     

Persistency of larvicidal effects of plant oil extracts under different storage conditions

The persistency of larvicidal effects of 13 oils (camphor, thyme, amyris, lemon, cedarwood, frankincense, dill, myrtle, juniper, black pepper, verbena, helichrysum, and sandalwood) was examined by storage of 50-ppm solutions under different conditions (open, closed, in the light, and in the dark) for 1 month after the preparation of the solutions. The stored solutions were tested against Aedes aegypti larvae for four times during the storage period. Some oils under some conditions stayed effective until the last test, while some solutions had lost their toxicity during a short time after preparation. Thus, the mode of storage is absolutely important for the larvicidal effects. The fresh preparations were always the best.     

Forskolin inhibition of hexose transport in cardiomyocytes

The effects of insulin, forskolin, isoproterenol, and epinephrine on 3-O-methylglucose (hexose) transport and cell cyclic AMP levels were determined in adult rat cardiomyocytes. Insulin stimulated hexose transport in these cells an average of 2.5-fold. Initial hexose transport rates at 1 mM hexose were 3.75×10^–2 nmol/mg cell protein/second in the absence of insulin, and 8.25×10^–2 nmol/mg cell protein/second in the presence of 12.3 M insulin. Forskolin at 5 M nearly abolished hexose transport within 3 s of exposure, but did not increase cell cyclic AMP concentrations within 9 s. The apparentK _i for hexose transport inhibition was about 0.3 M forskolin. Epinephrine and isoproterenol at 50 M increased cell cyclic AMP 4-fold during 9 s exposure, but did not affect hexose transport. Treatment of cells with these catecholamines of forskolin for up to 99 s increased cell cyclic AMP, but only forskolin inhibited hexose transport. We coclude from these results that forskolin acts on hexose transport independent of its action on adenyl cyclase, and that cyclic AMP does not inhibit or stimulate hexose transport.Supported by NIH-HL 07094     

Ultrastructure of canine type II pneumocytes during hypothermic ischemia of the lung: a study by means of conventional and energy filtering transmission electron microscopy and stereology

Alterations in pulmonary surfactant have been reported to be associated with ischemia/reperfusion injury in experimental and clinical lung transplantation. It is unknown whether these alterations are due to damage to surfactant synthesizing type II pneumocytes during hypothermic ischemic storage. The aim of the present study was to examine the effects of hypothermic ischemic storage of the lung on canine type II pneumocytes by means of conventional (CTEM) and energy filtering TEM (EFTEM) and stereology. The lungs of 18 dogs were fixed for TEM immediately after cardiac arrest (6 double lungs) and after storage in Tutofusin at 4 degrees C for 20 min, 4 hr, 8 hr, and 12 hr (6 single lungs, respectively). Using a systematic uniform random sampling scheme, type II pneumocytes were analyzed qualitatively and stereologically. The relative phosphorus content of cell organelles, especially the surfactant containing lamellar bodies, was investigated by EFTEM. By CTEM, no major qualitative alterations could be observed in type II pneumocytes of the experimental groups. Stereologically, no significant changes in the volume densities or the volume-to-surface ratios of type II pneumocytes and their lamellar bodies were found. By EFTEM, the highest intracellular phosphorus signals were recorded over lamellar bodies in all experimental groups. No changes in the phosphorus signals were observed during ischemia. These results indicate that the ultrastructure of canine type II pneumocytes and their lamellar bodies is not affected by hypothermic ischemia of the lung up to 12 hr. Structural preservation of intracellular surfactant is possible during prolonged ischemic lung storage.     

Biosynthesis of gastric mucins. In vitro incorporation of radioactive glucose.

An in vitro model for the study of the mechanism of gastric-glycoprotein (mucin) biosynthesis is described. Gastric mucosa scrapings were incubated in Eagle's minimum medium with U-14C-glucose. Linear incorporation-kinetics were observed during 4 hours. U-14-C-glucose was incorporated into soluble and cell bound glycoproteins. In the acid hydrolysate of soluble and cell bound fractions all the amino acids separated by high voltage electrophoresis and all the carbohydrates separated by thin layer chromatography contained appreciable radioactivity showing the active conversion of the added radioactive glucose to all the amino acid and carbohydrate precursors used by the gastric cells for the biosynthesis of macromolecular glycoprotens. The carbohydrate/protein ratio of the excreted glycoproteins increases steadily during the 4h incubation period suggesting that the chemical composition of the excreted mucins changes during this period. The cell bound glycoprotein fraction retains a constant composition during the 4th incubation period. The high fucose to hexose ratio of the soluble (excreted) glycoproteins suggests that they are probably identical to the gastric mucins isolated from native gastric preparation. This model is therefore considered a valid one for the study of the regulation of the biosynthesis of gastric mucins as well as for the study of drug action.     

Early atherogenesis in the White Carneau pigeon. III. Lipid accumulation in nascent foam cells.

The role of lysosomes in aortic atherogenesis in White Carneau pigeons was examined by means of acid phosphatase cytochemistry. Foam cells were the major constituent of nascent atherosclerotic lesions in pigeons fed a 0.5% cholesterol diet for either 5 or 10 weeks. Seventy-four percent of foam cell lipid from animals at 5 weeks was in cytoplasmic droplets. The remaining lipid appeared in secondary lysosomes. After 10 weeks of cholesterol feeding, lysosomal lipid accounted for 73% of the lipid volume. The lipid accumulation correlated with increases in both size and number of lysosomes. An average of 2.4 lysosomes per 10(4) cu mu of cytoplasm was observed at 5 weeks. This value doubled by 10 weeks. The average lysosome diameter also increased between 5 and 10 weeks from 2.2 mu to 5.75 mu. Concomitantly, the complexity of lysosomes increased from simple, spherical organelles at 5 weeks to complex, multichambered organelles at 10 weeks. In contrast, lipid storage within cytoplasmic lipid droplets did not change either in size or in number. These observations suggest that by 5 weeks lipid storage within cytoplasmic droplets was maximized, and continued increases in lipid stores occurred predominantly through lysosomal loading.     

不同保存介质对脐带间充质干细胞活性的影响

背景：脐带间充质干细胞的临床应用面临移植前保存的问题,而临床保存介质对移植前细胞活性的影响直接关乎移植后疗效,目前却缺乏对临床介质保存效果的系统性研究。 目的：评价临床常用保存介质对脐带间充质干细胞活性的影响。 方法：在4 ℃与室温(25 ℃)条件下,将脐带间充质干细胞在临床常用保存液(0.9%氯化钠注射液,5%葡萄糖注射液和1%人血白蛋白溶液)中保存2,4,6 h,观察上述保存介质对脐带间充质干细胞活性、凋亡/死亡率、多向分化能力及DNA损伤的影响。 结果与结论：无论在4 ℃还是室温条件下,细胞在临床常用保存介质中的活性均在短期内呈时间依赖性下降。此外,不同保存介质引起细胞死亡而非凋亡,且死亡率呈时间依赖性增加;经不同介质保存后,细胞出现DNA损伤,但其增殖与多向分化能力未受明显影响,提示细胞核DNA损伤为细胞活性下降的关键因素。中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程全文链接：     

Osmotic responses demonstrating the extracellular character of the sarcoplasmic reticulum

1. Changes in the dimensions of the sarcoplasmic reticulum in frog sartorius muscles exposed to hypertonic and hypotonic solutions have been studied with the electron microscope.2. The volume of the sarcoplasmic reticulum has been found to be linearly related with a negative slope to the reciprocal of the osmotic pressure. Over the range 0.75 to 3.5 x normal osmotic pressure the reticulum volume has been calculated to change from 11.5 to 18.5% of normal cell volume.3. These changes in sarcoplasmic reticulum volume correspond to the calculated changes in the volume of the intra-fibre sucrose compartment, postulated by earlier workers on the basis of studies on changes in cell volume with changes in osmotic pressure in living muscles.4. To explain these and other related findings on the distribution of electrolytes in muscle, it is proposed that the sarcoplasmic reticulum of skeletal muscle is an extracellular compartment.5. The significance of this hypothesis for the mechanism of excitation-contraction coupling is discussed.     

The pathologic response of the liver and thyroid of the rat to potassium prorenoate (SC-23992)

A 3-month dose range finding study in preparation for a 2-yr carcinogenicity study of potassium prorenoate (SC-23992), a steroid with an antihypertensive profile, is reported. The drug was administered by gavage once daily at doses of 10, 30, and 100 mg/kg/day to Charles River CD rats. Treatment was terminated at 13 weeks and 10 randomly selected animals from each treatment group were killed and necropsied. The remaining 10 animals in each dose group, including controls, were maintained for an additional 4 weeks, in order to investigate reversibility of changes, and then were killed and necropsied. Dose-related increases in thyroid-stimulating hormone (TSH) levels were observed in treated animals of both sexes during the dosing period and the changes were statistically significant and correlated with an increased thyroid weight in females at 13 weeks. Dose-related morphologic changes in the thyroid, observed by light and electron microscopy, were compatible with the effects of TSH stimulation. Liver weights, which increased, were dose-related. In females the increase was statistically significant at the high dose at 2, 4, and 13 weeks. In males it was significant at the high dose at 13 weeks. Microsomal enzyme levels were increased in a time- and dose-related manner with higher values in females than in males. The pattern of enzyme induction was of the type exemplified by pregnenolone- 16-alpha-carbonitrile. Morphologic changes in the liver showed centrilobular hepatocyte enlargement with smooth endoplasmic reticulum membrane proliferation confirmed by electron microscopy. All positive findings returned to normal after the 4-week treatment-free period. The relationship between the thyroid stimulation to liver enzyme induction is of interest. Evidence is presented here that in the presence of SC-23992, TSH stimulation and liver enzyme induction occurred. The possibility that the liver metabolism stimulates the thyroid T3, T4 elimination with secondary TSH activity is a possible explanation, but on the basis of existing information, direct action by SC-23992 on the thyroid cannot be excluded.     

Statistical methods for growth allometric studies

Simple least square regression analysis, major axis regression, and reduced major axis regression have been advocated for straight line fitting to the logarithmically transformed data pairs in bivariate allometric studies. As all these techniques are based on rigid a priori assumptions on the error structure, their application may lead to considerable biases in slope estimation if these requirements are not met. A different mathematical model, the linear functional relationship, allows to remove the bias by estimating the error structure from grouped empirical data. The model is applicable to interspecific and cross-sectional growth allometric studies where natural grouping criteria are available (species, age). The technique is illustrated by growth allometry of myocardial cells and capillaries in the late postnatal period (after weaning) in 33 normal male Wistar rats (group 1: 5 weeks, group 2: 7 weeks, group 3: 13 weeks, group 4: 52 weeks). In left ventricular myocardium fixed by vascular perfusion, length and volume densities of myocardial cells and capillaries were estimated by stereological techniques at the light and electron microscopic level. Total capillary length and total myocardial cell volume were scaled to total myocardial cell length. A comparison of the scaling methods showed an underestimation of the slope and its confidence interval by all regression techniques, which would have led to the erroneous conclusion that the myocardial cell does not remain geometrically similar throughout the normal growth process. Linear functional relationship and the technique of instrumental variables led to nearly identical results and were both compatible with geometric similarity of the myocardial cell during growth. Positive allometry of total capillary length to total myocardial cell length (b = 1.674) demonstrates continuous neoformation of capillaries. The intensity of capillary proliferative activity during growth was intermediate between the reactions observed in myocardial hypertrophy due to pressure overload and that due to physical training. This agrees with the fact that both systemic arterial pressure and cardiac output increase during maturation. The study is designed as a worked example which should enable the practicing researcher to treat data from cross-sectional growth allometric studies with a simple and unbiased statistical method.     

Morphometric study of the prepubertal rabbit testis: Germ cell numbers and seminiferous tubule dimensions

Testes from rabbits aged 1–9 weeks were examined by light microscopy. Changes in seminiferous tubule dimensions, testicular volume, and volume fraction of tubules were assessed. Germ cells and Sertoli cells were counted in round tubular cross sections and total germ cell number in each testis was estimated. Mitotic, meiotic, and degenerative activities of germ cells as well as their basal or central positions within tubules were quantified. A marked, steady increase in testis volume and in tubular length and volume occurred over the prepubertal period; but diameter underwent no significant increase and in fact decreased until week 4. Overall, tubules lengthened 40-fold and testis volume increased 25-fold; the percentage volume of the testis occupied by tubules rose from one-third neonatally to three-fifths at the onset of spermatogenesis. The ratio of germ cells to total tubular (germ and Sertoli) cells was lowest at 3 weeks. However, the total number of germ cells increased little until 3 weeks, after which it rose at a sharp rate commensurate with testis volume. Percentage of germ cells in mitosis peaked sharply at 3 weeks, dropped in subsequent weeks, and then rose at 7 weeks at the initiation of spermatogenesis. Importantly, the surge in mitosis at 3 weeks was followed by a redistribution of germ cells to a predominantly basal location from 3 to 7 weeks. Meiotic activity was sparse at 7 weeks and became abundant by 9 weeks. Germ cell degeneration remained relatively constant during weeks 1 through 6, with an increase at 7 weeks.     

Volume adjustment by renal medullary cells in hypo- and hyperosmolal solutions containing permeant and impermeant solutes.

1. The changes in the volumes of cells in slices (thickness 0-3-0-4 mm) of rat renal outer and inner medulla have been investigated during aerobic incubation for 20 min at 37 degrees C in Krebs phosphate-bicarbonate Ringer modified by the addition of urea or sucrose in order to produce a range of media hypo- and hyperosmolal with respect to the calculated tissue fluid osmolalities in these regions. 2. On the assumption that under these conditions the measured inulin space approximates to the true extracellular space (ECS), it was found that osmotic swelling or shrinkage of cells was not accompanied by any significant variation in the absolute size of the ECS. 3. Calculated cell volume changes in both regions were minimal when slices were incubated in urea-containing media iso-osmolal with tissue fluids in that region. In sucrose-containing media minimal cell volume changes occurred when media were hypo-osmolal in relation to tissue fluids by a factor of approximately 0-68. 4. In all except the most hypo-osmolal media studied, calculated cell volume changes (as percentage of initial volume) were linearly related to the reciprocal of the incubation media osmolalities. The points of interception of the regression lines on the cell volume axis were dependent upon both the region studied and the composition of the incubation medium (urea or sucrose). 5. These changes were accompanied by variations in slice solute concentrations. Slice [Na] was greatest, and slice [K] least, following incubation in those media producing the greatest percentage changes in cell volume. 6. The volume of distribution [14-C]sucrose within the inner medulla was 61-7 plus or minus 2-5 mul./100 mg wet weight of tissue (mean plus or minus S.E., n equals 6) after 10 min incubation. The increase to 70-8 plus or minus 4-2 mul./100 mg (n equals 6) after 100 min was not significant (0-1 greater than P greater than 0-05). The volume of distribution within the outer medulla rose markedly during this period, from 38-1 to 58-2 mul./100 mg.