Medullary Volume Research Articles

Immune system of the spontaneously hypertensive rat: II. Morphology and function

The spontaneously hypertensive rat (SHR) is a stress-sensitive animal which exhibits moderate immune dysfunction that has been implicated in the onset of hypertension. In this study, we examined the morphology of SHR thymus and spleen and further characterized the immune deficiency using Wistar-Kyoto (WKY) and Fisher 344 (F-344) rats for comparison. The adult SHR thymus does not display the increase in medullary volume typically noted with aging and the volume density of the marginal zone is decreased in the spleen. In vivo tritiated-thymidine incorporation is also decreased in the spleen of unstimulated SHR. In mixed lymphocyte reactions (MLR), the proliferative response of SHR splenocytes is significantly decreased relative to controls, WKY and F-344. Addition of interleukin-1 (IL-1), interleukin-2 (IL-2), or indomethacin to the MLR cultures does not increase proliferation. The proliferative response to T cell receptor monoclonal antibody (mAb-TCR) or interleukin-2 (IL-2) are similarly impaired in the SHR. The depressed proliferative T cell response is reversed by prolactin. It is suggested that the SHR is a valuable model for the study of immune deficiency.

Effects of perches on trabecular bone volume in laying hens

Trabecular bone remodelling is known to be affected by loading or exercise, and thus exercise may effect the trabecular bone loss associated with osteopenia in laying hens. Sixteen ISA Brown hens were housed from 18 to 72 weeks old in cages with perches and 16 in similar cages without perches to examine the effects of the exercise afforded by perch provision on trabecular bone volume. At 72 weeks, mean trabecular bone volume in the proximal tarsometatarsus of birds with access to perches was significantly greater than in control birds, while medullary bone volume was not significantly different in the two groups. However, all the birds were considered osteoporotic, though to varying degrees, and the beneficial effects of perches were relatively minor. It was concluded that while trabecular bone loss may be reduced by perch provision, other factors are probably more influential in the development of the osteoporosis typical of laying hens.

Endurance Exercise Training Causes Adrenal Medullary Hypertrophy in Young and Old Fischer 344 Rats

The purpose of the present investigation was to determine the effects of endurance exercise training on adrenal medullary volume and epinephrine content in young (5 month) and old (23 month) female Fischer 344 rats. Animals from each group underwent 10 weeks of treadmill running (60 minutes per day, 5 days per week). 72 hours following the last training session animals were killed and the adrenal glands removed for subsequent analysis. Plantaris muscle citrate synthase activity increased with training in both young and old animals (39.8% young; 36.4% old). Trained animals had larger adrenal medullary volumes (48% increase in young, and 18% in old) than untrained controls. Trained animals also had higher total adrenal medullary epinephrine content (36% increase in young, and 24% in old). There were no differences in adrenal medullary epinephrine or norepinephrine concentration (micrograms/microliters medulla). It was concluded that the training-induced increase in adrenal epinephrine content is due to an increase in the size of the medulla, and not to a greater medullary epinephrine concentration. Furthermore, similar responses to training occur in both old and young animals.

The Effect of a Low-Osmolar Radiographic Contrast Medium on In Vivo and Postmortem Renal Size

High osmolar radiographic contrast media (CM) are known to cause an increase in renal size. To examine the effect of low-osmolar CM on renal size, 14 anesthetized dogs received 12 intravenous bolus injections of 0.5 mL/kg iohexol (541 mOsm/L). The postmortem renal, cortical, and medullary volumes were determined by fluid displacement. Renal volumes of 18 control dogs were determined similarly. The mean (+/- SEM) postmortem renal volumes were 66.1 +/- 2.2 mL for the CM group and 52.3 +/- 3.3 mL for the control group (P = 0.003), whereas the cortical and medullary volumes were similar. Six dogs were also scanned by fast computerized tomography before and after iohexol administration. The in vivo whole renal and medullary volumes enlarged from 67.4 +/- 3.0 to 77.1 +/- 2.8 mL (P = 0.006), and from 28.5 +/- 2.0 to 35.1 +/- 1.1 mL (P = 0.026), respectively, while the cortical volume remained unaltered. These results suggest that even low osmolar CM may significantly increase renal volume, probably by causing tubular expansion.

Effects of vitamin or mineral deficiency on the morphology of medullary bone in laying hens

Adult laying hens were fed diets deficient in phosphorus, calcium, calcium and phosphorus, and vitamin D 3 to determine their effects on bone histology and parathyroid gland size. The phosphorus deficient diet caused an insignificant decrease in parathyroid size while the other diets caused significant increases. A considerable amount of individual variation in medullary bone volume and osteoid seam width was observed in all groups but, despite this, the calcium, calcium and phosphorus and vitamin D 3 deficient diets clearly resulted in increased osteoid. Birds receiving diets deficient in calcium and phosphorus, and in vitamin D 3 for longer periods were observed to have partially or completely resorbed medullary bone. Osteodystrophia fibrosa was noted in vitamin D 3 deficient birds which had no follicular activity.

Magnetic resonance imaging (MRI) and pathophysiology of the rat kidney in streptozotocin-induced diabetes

Proton magnetic resonance imaging was performed on rats before induction of diabetes with streptozotocin (STZ) and at 2 and 12 days postinduction. Images revealed an increase in maximal longitudinal and axial dimensions of the kidneys at 2 days and a further increase at 12 days. Similarly, an increase in the size of the remaining kidney was seen in a rat which underwent uninephrectomy as a positive control. Two major differences were observed between the kidney undergoing compensatory hypertrophy and those developing diabetic nephropathy: (i) Expansion of the renal vasculature was seen only in images of the diabetic rat; (ii) A loss in conspicuity of the normal corticomedullary junction was seen in the T 2-weighted images of the diabetic rat but not in the uninephrectomized rat. Histologic examination revealed that the medulla increased to a size greater than the cortex during diabetic nephropathy whereas the medullary volume was less than that of the cortex during compensatory hypertrophy. In vitro T 1 relaxation times in cortex, outer medulla and inner medulla of kidneys from control rats were measured and compared with the same respective regions in diabetic rats. When these values were correlated with tissue water content, a linear increase in relaxation rate versus percent water content from cortex to inner medulla was found in the control kidneys, but this correlation was absent in diabetic nephropathy. These studies demonstrate that MRI is an effective noninvasive tool for studying the course of renal hypertrophy and hydration changes in the development of renal disease in STZ-induced diabetes in the rat.

Quantitation of the In Vivo Kidney Volume with Cine Computed Tomography

The authors examined the utility of cine computerized tomography (CT) for noninvasive determination of whole kidney, cortical, and medullary volumes. The right kidneys of 14 anesthetized dogs were scanned after an intravenous bolus injection of iohexol, and their volumes determined after boundary identification. After the scans, the kidneys were excised at postmortem examination and their volumes determined by fluid displacement. The mean (+/- standard error of the mean [SEM]) postmortem and in vivo renal volumes were 66.1 +/- 2.2 cc and 78.2 +/- 2.4 cc, respectively (r = 0.86; P less than 0.001). The difference was consistent with the blood, filtrate, and urine contents of the in vivo kidney. The in vivo cortical and medullary volumes correlated poorly with their postmortem volumes because of difficulties in boundary definition. These results demonstrate the feasibility for fast and reliable in vivo whole kidney volume quantitation by cine CT.

Morphology of medullary bone during the egg formation cycle

The medullary bone of birds is known to function as a calcium store for egg shell production, but it is not known if the stage of shell formation within the egg formation cycle is reflected by the thickness of osteoid seams on the medullary bone. Adult laying hens were killed at two points in the formation cycle to determine the effects of shell formation on medullary bone using histological techniques. No differences in medullary bone volume or osteoid thickness were apparent at either of the two points. Fluorochrome bone labelling techniques demonstrated, however, that less medullary bone mineralisation occurred during the active period of shell formation.

Involution of thymic epithelium and low serum thymulin bioactivity in weanling mice subjected to severe food intake restriction or severe protein deficiency

The volume of epithelium in the cortex and in the medulla of the thymus was compared in four goups of weanling male and female CBA J mice. Well-nourished controls (C), food intake restricted (R), and animals given a low-protein diet ad libitum (LP) were fed from 23 to 37 days of age. Baseline controls (B) were studied at 23 days of age. Epithelial volume fraction was estimated for each group by point-counting morphometry on electron micrographs. Other mice were used to obtain group mean estimates of thymic index (mg/g live weight) and volume fraction of cortex and medulla (light microscope-level point-counting morphometry). Cortical and medullary epithelial volumes were calculated for each animal examined by electron microscopy by obtaining the live weight and applying, in sequence, the group mean thymic index, an assumed thymic density of 1.0 mm 3/mg, the group mean cortical or medullary volume fraction, and the measured cortical or medullary volume fraction for that animal. Serum thymulin bioactivity was also measured in C, R, and LP mice. The results reveal thymic epithelial involution in the two most common rodent models of malnutrition, and suggest that this may contribute to the low serum thymulin levels found in malnourished experimental animals and humans.

Iliac crest trabecular bone mass and structure in patients with non-steroid treated rheumatoid arthritis.

Iliac crest trabecular bone volume and structure have been studied in bone biopsy specimens from 48 patients with classical or definite rheumatoid arthritis, none of whom had received steroids. Results were compared with those obtained from healthy controls matched for age and sex. The mean trabecular bone volume in female patients aged 34-50 years was significantly lower than in controls (p less than 0.01); in male patients aged 34-50 years values were also lower than those in controls (mean (SD) 17.8 (3.2) v 22.4 (5.6)% total medullary volume), though this difference was not statistically significant. Values in older patients were similar to those of controls. The mean trabecular plate thickness was significantly lower in female patients in all three age groups when compared with the controls (p less than 0.005, 0.05, and 0.005). Similar but non-significant changes were seen in male patients. The mean trabecular plate density, an index of trabecular number, and the mean trabecular plate separation showed no age related change in either male or female patients, in contrast with the female control group, in whom the mean trabecular plate density decreased and separation increased with age. These results suggest that non-steroid treated rheumatoid arthritis is associated with premature bone loss, the structural basis of which is trabecular thinning.

A quantitative analysis of rat adrenal chromaffin tissue: Morphometric analysis at tissue and cellular level correlated with catecholamine content

A morphometric analysis of normal Wistar rat adrenal medulla following perfusion fixation and Araldite embedding, was correlated with catecholamine levels on fresh tissue, measured by high-performance liquid chromatography. The mean volume of whole adrenal is 13.2 mm 3 and the mean medullary volume 1.3mm 3. Volume density estimates showed that the medulla is composed of 63% chromaffin tissue with an adrenaline to noradrenaline storing cell ratio of 4.4:1. The vasculature occupies 20%, neuronal tissue 5% and interstitial tissues 12% of the medulla. A comparison was made of cell volumes, cell numbers and volume and surface density estimates of cytoplasmic organdies in adrenaline and noradrenaline storing cells. The mean cell volume of adrenaline storing cells at 1300 μm 3 is larger than that of noradrenaline storing cells at 980 μm 3. A single adrenal medulla contains4.4−5.7 × 10 5 adrenaline cells and1.5−1.9 × 10 5 noradrenaline cells. Chromaffin granules account for approximately 30% of the volume of the cytoplasm; the numerical density of granules at different sites in the cell was calculated for adrenaline cells. The volume density of mitochondria (4%) and the surface density of mitochondrial membranes (the ratio of outer to inner membrane being approximately 1:2.3) were similar in both cell types. Rough endoplasmic reticulum was the only organelle to show a significant difference in volume and surface density between the two cell types. Adrenaline storing cells have stacks of rough endoplasmic reticulum which have two to three times the surface and volume densities of that found diffusely scattered throughout noradrenaline cells. The adrenaline content of an adrenaline storing cell is0.14 × 10 −6 μM and that of a granule 3.0 × 10 −12 or3.8 × 10 −12 μ moles depending on the method of calculation. The noradrenaline content of noradrenaline storing cells can only be calculated on the assumption that all noradrenaline is stored in this cell type though it is likely that some is contained within adrenaline cells. Based on this assumption the noradrenaline content is0.17 × 10 −6μ moles per cell and5 × 10 −12 μ moles per granule. The present study provides baseline morphometric data on the rat adrenal medulla at tissue and cellular level correlated with amine levels in adrenaline and noradrenaline storing cells and granules.

Medullary bone matrix formation, mineralization, and remodeling related to the daily egg-laying cycle of Japanese quail: A histological and radiological study

A model is presented concerning the remodeling of medullary bone during the egg-laying cycle of hens. This model is partly based on earlier results that showed that the active period of medullary bone resorption that produces part of the calcium needed for the eggshell coincides with the period of medullary bone matrix formation. It was hypothesized that mineralization of this matrix takes place during the subsequent inactive period. The present study examines this model. The medullary bone matrix volume, regardless of the degree of mineralization, is quantified in quail hens at four time points during the egg-laying cycle. No significant changes in the medullary bone volume (i.e., matrix and bone) during the egg-laying cycle were found, implying that matrix formation and bone resorption are kept in balance within a time interval of only a few hours. In the radiological part of this study the whole body retention (WBR) of 99mTc(Sn)MDP is used as a measure of the amount of low calcium medullary bone matrix formed during the egg-laying cycle. This use of 99mTc(Sn)MDP is justified by an autoradiographic experiment that showed that 99mTc(Sn)MDP actually labels newly formed medullary bone. Localization of the radioactive label showed a high positive correlation with the localization of fluorescent tetracycline labels in the medullary bone. From 4 to 22 hours after ovulation, the amount of medullary bone matrix increases linearly in quail hens. From 22 to 4 hours, during the inactive period of the egg cycle, the WBR of 99mTc(Sn)MDP decreases to the basal level, indicating that during this period the medullary bone matrix becomes calcified. From these findings we conclude that our model is valid and that matrix formation and mineralization in the medullary bone are separately regulated processes.

PGE2 stimulates both resorption and formation of bone in vitro: differential responses of the periosteum and the endosteum in fetal rat long bone cultures.

The ability of PGE2 to stimulate bone resorption in vitro and in vivo is well established but the effects of this compound on bone formation are still controversial. Recent clinical reports have suggested that long-term infusion of PGE in infants with cyanotic heart diseases led to a stimulation of periosteal bone formation and to hyperostosis. In the present report, we describe the effects of PGE2 (10(-5) M) in bone organ cultures on bone resorption, measured by the release of 45Calcium and the number of osteoclasts in sections of cultured bones, and bone volume, by measuring separately medullary and cortical areas. PGE2 induced a marked increase in 45Ca release and in cortical and medullary osteoclast numbers over 4 days in vitro; despite this increase in bone resorption, cortical bone volume remained constant, indicating a parallel increase in bone resorption and formation at this site. Morphological and quantitative data demonstrated a higher extent of osteoblastic surface along the periosteum of PGE2-treated bones when compared with control cultures. Medullary bone volume, on the other hand, decreased sharply during the culture period, demonstrating a lack of parallel increase in bone formation at this site. It is concluded that, under these experimental conditions, prostaglandin E2 stimulated both resorption and formation along the periosteum and only bone resorption along the endosteum of the cultured bones. The overall effect of PGE2 on bone as a whole, however, was net bone loss.

Morphometric analysis of thymic medullary non-lymphoid cell changes during postnatal development

Thymic non-lymphoid cells have been shown to influence the differentiation of T-lymphocytes. Large numbers of non-lymphoid cells are concentrated in the thymic medullary zone. A morphometric analysis of these cells in the medulla identified little change in their absolute number and volume density during thymic development in the rat. Expansion of thymic medullary volume with age was documented by planimetry. Several subtypes of medullary non-lymphoid cell were identified by electron microscopy, including both squamous and cystic epithelial cells, interdigitating cells and macrophages. Changes in their relative proportion during development were determined with the percentage of squamous epithelial cells declining, interdigitating cells increasing and the other cell types exhibiting little change. Subcellular evidence of secretory activity was sought by analysis of changes in the volume density of organelles in each of the non-lymphoid classes. Cystic enlargement in epithelial cells and a decrease in the volume density of macrophage inclusion bodies were noted but no clear morphometric trend could be correlated with increased secretory activity expected in the developing endocrine thymus.

Changes in activity of chicken medullary bone cell populations in relation to the egg-laying cycle

Osteoblastic and osteoclastic activity was studied in avian medullary bone in vivo. During the active period of eggshell calcification, medullary bone active resorption surface increased ninefold. This correlated with a sevenfold increase in the percentage of active osteoclasts. Osteoblast activity is also increased during the active period, as demonstrated by a twofold increase in the active osteoblastic surface. These findings and our observation that the medullary bone volume remains the same (± 13%) whether the eggshell is being formed (active period) or not (inactive period) led to the conclusion that the activities of osteoblasts and osteoclasts rapidly return to balance.

Weight and shape of the human adrenal medulla in various age groups.

The weight and shape of the adrenal medulla were studied in 118 adrenal glands obtained at autopsies of 62 patients (38 males and 24 females) between 0 and 52 years of age. In adolescents 15 years and older and adults cases of sudden death only were entered in this study. The weight was calculated using morphometric measurements done on serial sections of the glands. In the new-born, the medulla accounts for less than 1% of the total volume of the adrenal gland. Though there is a rapid growth of the adrenal medulla after birth, the percentage of adrenal medullary volume at all age levels during childhood and adolescence is lower than in adults where it constitutes 9% of the total adrenal volume on the average. This corresponds to an average medullary weight of 0.43 g. In the new-born, the medulla consists of a thin plate made up of immature medulloblasts. Within a few months these are transformed into mature medullary cells; the shape of the medulla soon approaches that of the adult gland: an increase in thickness around the central vein and flat processes into the alae. With increasing age the cortico-medullary border becomes irregular and ragged. Especially in the vicinity of the central vein an intermingling of medullary and cortical cell complexes is found. An unequivocal diagnosis of genuine adrenal medullary hyperplasia can be established only by weighing the dissected medulla or by applying morphometric methods.

Studies on the relationship between rat renal medullary cell volume and external anion concentration in hyperosmolal media.

1. The volumes of cells in slices of rat renal outer medulla have been examined following incubation or 25 min in hyperosmolal media (650 and 950 m-osmole/kg H2O) containing independently variable concentrations of Cl (70-325 mM) and HCO3 (10-60 mM) (gas phase 95% O2/5% CO2). 2. For any given level of external Cl concentration cell volumes were reduced by increasing the external HCO3 concentration. These reductions were accompanied by net loss of cellular K and Cl. In confirmation of earlier findings, cell volumes were also reduced by increasing external Cl concentration. 3. Experiments in which the HCO3 concentration and pH of the incubation media were independently varied by the use of N-2-hydroxyethylpiperazine-N'-2-ethanesulphonic acid (HEPES)/100% O2 showed that it is the HCO3 anion per se which influences cell volume. 4. The anion exchange inhibitor 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonic acid (SITS, disodium salt, 1 mM) abolished the dependence of cell volume upon HCO3 but not upon Cl. 5. Acetazolamide (1 mM) influenced (reduced) cell volumes only in the presence of low (10 mM) HCO3. 6. CNS (25 mM) also markedly reduced cell volumes in media containing 10mM-HCO3 and, to a lesser extent, 25 mM-HCO3. It was without effect on cell volume when external HCO3 was 60 mM. 7. The presence of CNS was associated with the significant cellular net accumulation of Cl in media in which either Cl or HCO3 concentration (or both) was low (70 or 130 mM and 19 mM respectively). 8. The outer medullary [35S]CNS space at 25 min, determined for slices incubated in a representative selection of the various media employed in this study, exceeded the [14C]inulin space by 1.77 microliters/10 mg wet weight.

Vasopressin-Induced Increase in Renal Lymph Flow and Natriuresis in Dogs

1. Renal lymph flow and composition as well as renal haemodynamics and electrolyte excretion were studied in dogs during three experimental periods: control [endogenous antidiuretic hormone (ADH)], water diuresis (low ADH) and during exogenous ADH administration. 2. During water diuresis CPAH and CCr were significantly increased although lymph flow and urinary sodium excretion were unchanged. 3. Infusion of ADH significantly increased renal lymph flow and sodium excretion. However, when compared with values obtained during water diuresis, ADH infusion did not significantly change clearance for p-aminohippurate (CPAH), creatinine (Ccr) and osmolal clearance (Cosm), filtration fraction or net capillary colloid osmotic pressure in dogs forming concentrated urine. 4. It is suggested that a shift of blood flow from vasa recta to outer medullary capillaries, with increased capillary protein leakage and medullary interstitial volume, is responsible for the changes observed in lymph flow and sodium excretion.

The effect of orchiectomy and androgen supplement on the adrenal cortex and medulla of rats.

Orchiectomy in rats resulted in retarded body growth, and an increase in thymus and adrenal weights. With concomitant increase in adrenal cholesterol and corticosterone contents, adrenal norepinephrine, a minor component of medullary hormones, and the total catecholamine contents were also increassed by the operation. These changes were prevented or to be recovered by 2mg of testosterone propionate supplement (1mg per rat per week for 2 weeks). A conventional estimation of the cortical and the medullary volumes revealed that orchiectomy caused a marked increase in the whole adrenal and cortical volumes and also an increase in the medullary volume, although it was not statistically significant. The data suggest that androgen in male rat affects not only the adrenal cortex but also the medulla.

EFFECT OF ADRENALINE AND ACETYLCHOLINE ON THE HISTOCHEMISTRY AND VOLUME OF ADRENAL MEDULLA OF RAT

ABSTRACT By means of a modified chromaffin reaction, the adrenal glands of albino rats were studied microscopically and their medullary volumes determined planimetrically and graphically following the administration of adrenaline or acetylcholine. The animals receiving single or consecutive adrenaline injections showed an increase in the intensity of the chromaffin reaction and higher values of medullary volume. These findings could be due to a decrease in catccholamine secretion as a result of their increased level in the circulation. The animals receiving acetylcholine, presented, after 12 hours, a decrease in the intensity of the chromaffin reaction and vacuolization of the cytoplasm as well as lower values of the medullary volume. These findings are probably due to a decrease in the catecholamine content of the gland, or to a decrease in the blood flow resulting from the direct vasoconstricting action of the released medullary catecholamines. Three days later, the intensity of the chromaffin reaction was increased while the cytoplasmic vacuolization was less conspicuous. Six days after the injection, the intensity of the chromaffin reaction had returned to normal.