Density determinations of human parathyroid glands by density gradients.

The densities of human parathyroid glands were measured in density gradient columns of various media. Percoll (an aqueous colloidal solution of polyvinylpyrrolidone-coated silica), equilibrated to 300 mOsm with sodium chloride, was found to be the ideal gradient medium for density measurements of tissues with a density greater than 1.0 g/ml. which includes most parathyroid glands. The densities of the glands varied between 0.96 and 1.06 g/ml. Density measurements in gradients of Percoll were simple and reproducible and were made with an accuracy of approximately 0.001 g/ml. In other gradient media (aqueous solutions of sucrose and Ficoll, and organic solvents) there was a drift in density caused by osmotic or lipid-solving effects of the media. For measurements of densities less than 1.0 g/ml no ideal gradient medium was found, but a silicon oil or carbon tetrachloride/kerosone gradient could be used with somewhat reduced accuracy. It is concluded that the density gradient technique with the use of Percoll is potentially useful as a complement to routine histopathological parathyroid diagnosis, as glandular density is a good indicator of the relative proportions of parenchymal and fat tissue.     

Estimation of parenchymal cell content of human parathyroid glands using the image analyzing computer technique.

By means of the image analyzing computer technique, a complete determination of the parenchymal tissue distribution in serially sectioned parathyroid glands were accomplished. The technique had good reproducibility. Taking into account the shrinkage of the different tissue components during histotechnical procedures and the tissue densities, it was possible to calculate the parenchymal cell mass of unfixed glands. The cell distribution varied considerably, and in most glands as many as 10 sections at different levels had to be examined to get a reliable ratio between the parenchymal and fat cell tissue. The results seriously question the validity of histopathologic examination of one or a few sections of parathyroid glands in evaluation of the parenchymal cell mass, as well as diagnoses based on examination of partial glandular biopsy specimens.     

Nuclear DNA density of parathyroid lesions.

Nuclear DNA density analysis was carried out on six normal control human parathyroid glands and forty-six pathological lesions of human parathyroid tissue. The pathological glands had originally been classified as twenty hyperplasias, twenty-one adenomas, and five carcinomas in accordance with clinical-pathological information. Specimens had been obtained through the Surgical Pathology Department of the University Hospital, London, in the form of either imprints from the cut surface of a lesion, or as cell separation samples from a paraffin block. Nuclear DNA ploidy analysis of the normal glands showed, as expected, a diploid cell population. Sixty-one percent of nuclei of the carcinomas were above 2C, extending to 7C. There was a significant difference in nuclear DNA content between normal and benign tissue versus tissue classified as carcinoma. No significant difference in nuclear DNA ploidy could be established between the benign adenoma and hyperplasia tissue; however, marked significant DNA ploidy differences were found between tissue from the latter two and carcinoma. DNA ploidy from cell image analysis using Feulgen's reaction can be useful in establishing a differential diagnosis between carcinoma and benign lesions.     

Cellular alignment by grafted adhesion peptide surface density gradients

The extracellular matrix and extracellular matrix-associated proteins play a major role in growth and differentiation of tissues and organs. To date, few methods have been developed that allow researchers to examine the affect of surface density gradients of adhesion molecules in a controlled manner. Fibroblasts cultured on surfaces with a surface density gradient of RGD peptide aligned parallel to the gradient while fibroblasts on constant density RGD surfaces spread but did not align as has been shown in numerous earlier studies. Not only did fibroblasts align on the gradient surfaces, but they also showed significantly greater elongation than on constant density peptide surfaces or on control surfaces. This type of method is easy to replicate and can be used by laboratories interested in investigating alignment of various cell types without mechanical force or other stimulation, and without cell-cell interaction or for investigation of affects of surface density gradients of molecules on cellular biochemistry and biophysics. This method also has potential applications for developing scaffolds for tissue engineering applications where cellular alignment is necessary.     

Ultrastructure of the water-clear cell in the rabbit parathyroid gland.

The ultrastructure of water-clear cells has been described in human hyperplastic parathyroid glands. However, previous studies have failed to demonstrate this type of cell in normal human or other vertebrate parathyroid glands. Upon recently recognizing water-clear cells in the parathyroid glands of the golden hamster, we intended to examine the occurrence of these cells in other animals. In the present study the parathyroid glands of about one-year-old rabbits were observed by electron microscopy. Water-clear cells containing numerous vacuoles were demonstrated dispersed among the chief cells. The cells were generally situated close to the basal lamina of perivascular space which lay against the capillary vessel and were attached by desmosomes to the chief cells. Irregularly shaped vacuoles in the water-clear cells resembled dilated cisternae of the granular endoplasmic reticulum in the chief cells. Several ribosomes could be seen attached to the membrane of some of the irregularly shaped vacuoles. It is conceivable that the water-clear cells are transformed from the chief cells.     

Estimation of mass apparent density and Young’s modulus of femoral neck-head region

Abstract

The purpose of this study is to estimate mass apparent density and Young’s modulus to investigate biomechanical properties of the proximal femur bone. In this study eleven specimens of sheep femur bone having age between 1–1.25?years and human femur bone having age between 14 and 81years are used. In the present study, the first technique attempts to estimate the density from the image-based Hounsfield unit which is obtained directly from a computed tomography image. The modulus of elasticity is estimated from density-elasticity relation which is available in the literature. Another technique is used to develop a correlation between computed apparent density and greyscale based coefficient obtained by material mapping method using commercial Simpleware ScanIP software. Estimated mean deviation in apparent mass density and Young’s modulus is 4.34% and 4.69% in sheep bone and 4.35% and 4.94% in human bone respectively. It is found that apparent density and Young's modulus obtained shows close agreement with values reported in the literature. Moreover, the study attempts to build up a new material model between human and sheep for orthopaedics clinical trials and research in Indian context. In addition, it is also observed that bone mass density of sheep is 1.60 times human. This method can also be useful to study and analyse biomechanical properties of the human femur bone.     

Studies on the liver of Xenopus laevis. I. The ultrastructure of the parenchymal cell.

The liver of Xenopus laevis was examined with electron microscopy. Its structure was found to be markedly different from that of mammals, particularly regarding the morphology of the hepatocytes to be classified as typical. It was established that the main function of such a cell is the storage of glycogen, and further that it possesses only scant organelles and other inclusions. Since this type of cell was found most frequently in the liver of untreated animals, it was designated as normal cell. The fact appears noteworthy that in the normal liver of Xenopus laevis an abundance of cell types occur which are otherwise found to be proliferated under experimental conditions, e.g. cells with pronouncedly augmented RER, enlarged Golgi complexes, increased lipid inclusions etc. This high number of divergent hepatocytes and the fact that all intermediate stages between the individual extremes are present and not to be accounted for by the position of the cell within the liver was interpreted as being the expression of a cyclic passage of the various stages of activity. It is of special interest that augmented degradation of glycogen in the liver cell takes place only during vitellogenesis. Acute and chronic hunger, as well as adaptation to cold, hardly affect the morphology of the normal cell, especially as far as the glycogen is concerned. The possible causes for this are discussed.     

Separation of different cell populations of rat liver by density gradient centrifugation in a vertical rotor with self-generated Percoll gradients

A procedure is described which, with good resolution, separates viable rat liver parenchymal cells from other cell populations present in crude suspensions of liver cells. Fractionation is carried out by vertical rotor centrifugation in a self-generated Percoll gradient. Kupffer cells can be separated from other sinusoidal cells, resulting in a separate peak of peroxidase negative non-parenchymal cells, composed mainly of endothelial cells.     

Langerhans cell histiocytosis involving the thyroid and parathyroid glands.

Langerhans cell histiocytosis (LCH) is a rare illness, and the disease afflicting the thyroid gland is very uncommon, even in the presence of multisystem involvement. In this report, we document histologically, for the first time, concurrent involvement of the thyroid and parathyroid glands by LCH. A young Chinese woman with a history of diabetes insipidus and hypogonadism underwent a total thyroidectomy for enlarged thyroid gland secondary to LCH causing airway obstruction. Microscopic examination of the excised specimen disclosed CD1a- and S-100-positive LCH cells involving the thyroid and parathyroid glands. In a patient with LCH affecting the thyroid gland, parathyroid gland disease should be suspected when the serum calcium levels are depressed in association with an inappropriate serum parathyroid hormone level, such as a normal parathyroid hormone level in this case.     

Separation of human monocytes on density gradients of percoll

Monocytes from human blood have been isolated by centrifugation in Percoll®. A one-step procedure has been designed to isolate the cells from 7 ml of blood. When 5% of the white blood cells are assumed to be monocytes, an estimated average yield of 100% and a purity of 20% is achieved. The contaminating cells are almost exclusively lymphocytes. By a two-step procedure the monocytes can be obtained 90% pure with an approximate yield of 35%. The cells can be used for tissue culture without washing and they display the usual properties of mononuclear phagocytes in vitro.     

Modulation of bacterial association to HeLa cell cultures by cell density and by chlamydial infection.

The effect of cell density on the rate of association of Escherichia coli and Staphylococcus aureus by monolayer cultures of HeLa 229 cells was investigated. Radioactively labeled bacteria were incubated with sparsely and densely plated cells. The rate of bacterial uptake was 10- to 20-fold higher in sparse cultures. Kinetic analysis of data with different multiplicities of input bacteria showed that the Km of the reaction was unaltered, whereas the Vmax was inversely related to cell density. Pretreatment of HeLa cultures with dibutyryl adenosine 3',5'-phosphate had little effect on the rate of bacterial association. The simultaneous presence of an obligately parasitic bacterium, Chlamydia trachomatis LGV434, enhanced the Vmax of association of E. coli and S. aureus. This effect was more pronounced in dense HeLa cell cultures. Heat-inactivated chlamydiae were unable to modify the association. Enhanced association persisted for at least 3 h after infection with chlamydiae.     

Homogeneity of antibody-producing cells as analysed by their buoyant density in gradients of Ficoll

Ficoll, a polymer of sucrose, has several advantages over proteins for preparation of density gradients used to study mammalian cells. In addition to its ease of preparation, Ficoll as a result of being an uncharged molecule, does not bind ions from solution and, therefore, does not affect the osmolality of the medium in which it is dissolved.

In studies on antibody-producing cells we found that the measurement of buoyant density in Ficoll at pH 7.2 gives an accurate measurement of cell density. In such gradients antibody-producing cells band in a single peak at a density of 1.070 g/cm³. Two factors have a profound influence on the density profile of antibody-producing cells. Lowering the pH to 5.5 lowers their buoyant density to 1.062 g/cm³. Creation of an inverse osmotic gradient varying from 294 m-osmolal at the top of the gradient to 286 m-osmolal at the bottom splits the single peak of antibody-producing cells into three distinct peaks. This effect of osmotic gradients could account for the multiple peaks observed when cells are separated on protein gradients.

     

Control of Langerhans' cell density by a skin tumour-derived cytokine.

Langerhans' cells (LC) are bone marrow-derived dendritic antigen-presenting cells (APC) found in the epidermis of mammals. It is not known why they accumulate in the epidermis. Human and murine skin tumours are infiltrated with large numbers of LC, however previous experiments have shown that this does not seem to be associated with immune responses against the tumours. Here we show that a squamous-derived tumour cell line (T7) produces a cytokine which increases the number of LC in normal epidermis. T7 supernatant increased the density of LC in both mice syngeneic to the T7 cells (Skh:HR-1) as well as in BALB/c mice, indicating that the cytokine is not genetically restricted. The cytokine is a protein, not a prostaglandin, with a MW of > 12,000 as its production was inhibited by cycloheximide but not indomethacin and it could not be removed by dialysis against a 12,000 MW cut-off membrane. The increased numbers of LC found in tumour supernatant-treated epidermis expressed Ia as well as the molecule defined by the J11d monoclonal antibody, which is expressed by LC but not macrophages, confirming that these cells are LC. Another squamous-derived skin tumour, T79, which is not infiltrated with large numbers of LC when inoculated into syngeneic mice, did not produce a factor capable of increasing the density of LC. Hence these studies demonstrate either the activity of a novel cytokine or a new biological activity of a previously described cytokine. It is most likely that this cytokine increased the number of LC by attracting precursors into the epidermis. As the cytokine was produced by transformed squamous cells it is also possible that this cytokine is responsible for attracting LC into normal epidermis.