Number Of Connective Tissue Cells Research Articles

Morphological features of histogenic differon cells in connective tissue of guinea pigs’ lungs after sensitization with ovalbumin

An urgent issue of modern morphology is establishing a number of patterns of morphological changes and reactivity of connective tissue components of lungs in case of experimental sensitization with allergens. The aim is to estimate morphological features of histogenic differon cells in connective tissue of guinea pigs’ lungs after sensitization with ovalbumin. Materials and methods. Using morphometric and histological method, we have estimated the lung connective tissue of 48 male guinea pigs with experimental ovalbumin-induced allergic inflammation, simulated by subcutaneous sensitization and aeroallergization with ovalbumin. The number of fibrocytes, fibroblasts per 5000 μm2 and their ratio – fibroblast/fibrocyte coefficient were determined. Results. We have established the regularity of morphological changes dynamics in the cellular elements of pulmonary connective tissue. Experimental sensitization and inhalated allergization with ovalbumin leads to a statistically significant increase in the average number of fibroblasts and fibrocytes throughout the observation period in all experimental groups. It has been proved that the dynamics of cells has a multidirectional character, demonstrated by indicators of the fibroblast/fibrocyte coefficient, which shows the disproportion in the fibroblast/fibrocyte ratio and proves the tendency to the development of fibrosis in guinea pigs’ pulmonary connective tissue in case of experimental sensitization with ovalbumin. Conclusions. A gradual increase in the number of fibrocytes, against the background of a decrease in the number of fibroblasts is observed from the 23rd day to the completion of experimental sensitization with ovalbumin in the lungs of guinea pigs, compared with control group. A decrease of fibroblast/fibrocyte coefficient from 1.37 ± 0.03 in the early period to 0.82 ± 0.03 in the late period of the allergic inflammation demonstrates multidirectional nature of the dynamics in the number of connective tissue cells and indicates a tendency towards the development of fibrosis in pulmonary connective tissue.

Effects of microcurrent therapy on excisional elastic cartilage defects in young rats.

The effects of microcurrent application on the elastic cartilage defects in the outer ear of young animals were analyzed. Sixty male Wistar rats were divided into a control (CG) and a treated group (TG). An excisional lesion was created in the right outer ear of each animal. Daily treatment was started after 24h and consisted of the application of a low-intensity (20μA) continuous electrical current to the site of injury for 5min. The animals were euthanized after 7, 14 and 28 days of injury and the samples were submitted to analyses. In CG, areas of newly formed cartilage and intense basophilia were seen at 28 days, while in TG the same observations were made already at 14 days. The percentage of birefringent collagen fibers was higher in CG at 28 days. The number of connective tissue cells and granulocytes was significantly higher in TG. Ultrastructural analysis revealed the presence of chondrocytes in TG at 14 days, while these cells were observed in CG only at 28 days. Cuprolinic blue staining and the amount of glycosaminoglycans were significantly higher in TG at 14 days and 28 days. The amount of hydroxyproline was significantly higher in TG at all time points studied. The active isoform of MMP-2 was higher activity in TG at 14 days. Immunoblotting for type II collagen and decorin was positive in both groups and at all time points. The treatment stimulated the proliferation and differentiation of connective tissue cells, the deposition of glycosaminoglycans and collagen, and the structural reorganization of these elements during elastic cartilage repair.

Effects of allergic rhinitis and desloratadine on the submandibular gland in a rat allergy model.

Allergic rhinitis (AR) and antihistamine usage can cause xerostomia. The study aims to examine if AR, antihistamines, and the use of antihistamines in AR have histopathological effects on the submandibular gland. The study also investigates the effect of oxidant and antioxidant plasma parameters. Thirty-two adult Sprague-Dawley rats were used in the study. The rats were divided into the 4 following groups: the control group (C group); the AR group; an antihistamine-treated group (AH group); and an AR plus antihistamine-treated group (AR+AH group). The AR and AR+AH groups were sensitized using ovalbumin. The AR+AH and AH groups received desloratadine. The histopathological effects of AR and desloratadine treatment on the submandibular glands (SMGs) and the values of the oxidative and antioxidative serum parameters were evaluated. Histopathological examination of sections of the SMGs from the AR and AH groups revealed that vacuolization was present in the mucous acinar and ductal cells and that the number of connective-tissue cells was greater than that of the control group. The appearances of the AR+AH-group sections were similar to those of the control group. The superoxide dismutase activity level and the glutathione level were relatively decreased in these groups compared with those of the control group. The malondialdehyde level in the AR group was increased compared with that of the control group. The AR-induced pathological changes were diminished by desloratadine treatment. Thus, the new-generation antihistamine desloratadine may be used to treatment of AR patients who have xerostomia.

Effects of maturation and aging on the pressure‐bearing region of the plantaris longus tendon of the bullfrog (Lithobates catesbeianus)

The plantaris longus tendon (PLT) in bullfrog develops a fibrocartilage-like tissue in the area that is functionally subject to compressive forces. The aim of this study was to analyze the modifications of the pressure-bearing region in bullfrog PLT with different ages (7, 180, and 1,080 days after the end of metamorphosis) using histomorphometric, ultrastructural and biochemical methods. Weak basophilia and cells with a fibroblastic phenotype were observed in the compression region at 7 days of age. On the other hand, a large area of intense tissue basophilia associated with a chondroblast-like cell population was noted at the other ages. Collagen fibers exhibited a three-dimensional network-like arrangement at all ages. The number of connective tissue cells increased between 7 and 180 days of age and was reduced in older animals. The 180-day-old animals presented a well-developed pericellular matrix rich in proteoglycans. The mean diameter of collagen fibrils increased from 7 to 180 days and was the same at 1,080 days. Glycosaminoglycan content was higher in 7-day-old animals. A higher amount of hydroxyproline was observed at 180 and 1,080 days. The swelling test showed a significant increase of wet weight in 7-day-old animals. In conclusion, the alterations that occur in the pressure-bearing of bullfrog PLT are the result of physiological alterations of the animal with the maturation and aging.

Growth Factors, Their Receptors, Neuropeptide-Containing Innervation, and Matrix Metalloproteinases in the Proximal and Distal Ends of the Esophagus in Children With Esophageal Atresia

The pathogenesis of esophageal atresia (EA) remains unknown despite a relatively high incidence of this anomaly in population affecting 1 newborn per 3000 live births. The aim of this study was to examine the relative occurrence of growth factors, their receptors, neuropeptide-containing innervation, and tissue-degradating enzymes--matrix metalloproteinases--in the proximal and distal parts of the esophagus with EA. A histopathological study was conducted on 15 patients with EA. Tissues were processed for NGFRp75, PGP 9.5, TGF-β, FGFR, VEGF, EGFR and MMP-2 by means of biotin-streptavidin immunohistochemistry. In the control and EA-affected distal esophageal specimens, numerous and abundant NGFR-containing structures were detected, while in the proximal part of the esophagus, a decrease in their number was observed in patients. PGP 9.5 also marked neuronal structures similarly. TGF-β was found only in occasional cells in the EA-affected esophageal specimens, while control material demonstrated moderate to numerous TGF-β-containing structures. Abundance of FGFR and only occasional appearance of VEGF-positive cells were found in both the control and EA-affected material. A moderate number of connective tissue cells in controls contained EGFR. Compared with controls, the number of MMP-2 expressing cells in the EA-affected tissues was decreased in the proximal esophagus. A decrease in PGP 9.5-containing neuronal structures in the proximal esophagus supports insufficient innervation of this part of the organ in EA. A decrease in MMP-2 positive cells in the esophageal atresia-affected proximal esophagus indicates also a possible decrease of tissue adaptive and regenerative reactions. Low expression of TGF-β and almost the absence of EGFR in the EA-affected specimens may result in disturbances of cell growth, proliferation, and differentiation, indicating a significant role of these substances in morphopathogenesis of EA. FGFR and VEGF seem not to characterize EA pathogenesis.

Periodontal treatment of two siblings with juvenile hyaline fibromatosis

Juvenile hyaline fibromatosis (JHF) is an autosomal recessive disease that presents with multiple subcutaneous nodular tumours, gingival fibromatosis, flexion contractures of the joint and hyaline material accumulation in extracellular area. Recently, the causative gene for JHF, capillary morphogenesis protein 2 (CMG2) was identified. In this case report, periodontal status, treatment and follow-up together with histopathologic evaluation of gingival tissue specimens and mutation screening of two JHF cases are presented. A 10-year-old female (case 1) and her 3-year-old brother (case 2) were first examined in our department with a complaint of gingival hyperplasia in 1991. Symptoms of the disease were detected in two of four siblings in the family. Several gingivectomy operations were carried out over 11 years with hygiene motivation and initial phase therapy. After the last gingivectomy operation in 2002, the patients were reviewed frequently. Although there was linear marginal gingival inflammation, no remarkable enlargement was noted at last appointment. Histopathological findings showed increased amounts of subepithelial nodular connective tissue, thinned epithelial mucosa, separated inter-cellular bridges and decreased numbers of connective tissue cells in gingival tissue samples. Electron microscopic examinations supported the histopathological findings. Mutation screening of CMG2 demonstrated that the siblings were homozygous for a pathogenic missense mutation, V386F. Our clinical findings demonstrate that gingivectomy is useful and frequent periodontal visits are important for maintaining oral hygiene and decreasing growth rate of gingiva in JHF.

Delayed appearance of decorin in healing burn scars.

We have previously shown that hypertrophic scar tissue from burn patients contains abnormally high amounts of the proteoglycans versican and biglycan and reduced amounts of decorin, in comparison with normal dermis or mature scar. The lack of decorin may account for the poor organization of collagen fibrils in the nodular areas of these scars. Decorin has also been reported to neutralize the fibrogenic growth factor TGF-beta1. This study was conducted to monitor the time-course of expression of decorin in healing burn wounds by in-situ hybridization to determine whether its absence from hypertrophic scars could result from reduced synthesis. Scar tissue from 19 patients and normal dermis from six patients, was fixed in paraformaldehyde, embedded in paraffin and sectioned. Digoxigenin-labelled cRNA probes were prepared from a plasmid containing a 622-bp insert of human decorin cDNA and used for in-situ hybridization. Total numbers of connective tissue cells and cells positive for decorin mRNA were counted in 10 random fields in the upper (papillary), middle and lower (reticular) one-thirds of the dermis. In all regions the number and percentages of cells with decorin mRNA were low during the first 12 months after injury (eight samples), much higher between 12 and 36 months (seven samples) and low and similar to those in normal skin after 36 months (five samples). The differences between intermediate and early or late stage samples were statistically significant (one-way ANOVA). Immunohistochemistry showed little staining for decorin in early stage samples and much stronger staining in mid-stage. Late stage tissue showed intense staining for decorin, almost comparable to that in normal dermis. Expression of decorin in burn wounds is suppressed for about 12 months and then increases at a time when resolution of hypertrophic scarring is generally considered to occur.

Electrochemical and histomorphometric evaluation of the TiNiCu shape memory alloy

By means of electrochemical and quantitative histomorphometric methods, the corrosion resistance and tissue biocompatibility of Ti50Ni50 and Ti50Ni50-xCux (x = 1, 2, 4, 6, 8) were investigated. It is discovered that the repassivation potential of Ti50Ni50-xCux (x = 2, 4, 6, 8) alloys is about 200 mV higher than that of Ti50Ni50 alloy. Namely, the addition of Cu raises the repassivation potential of TiNi shape memory alloys and improves their corrosion resistance. Pitting potentials of Ti50Ni50 and Ti50Ni50-xCux (x = 1, 2, 4, 6, 8) alloys increase with solution pH value, but the repassivation potentials keep constant. The adding of Cu has no obvious influence on pitting potential (Epit) of TiNi alloys, meanwhile, the corrosion potential and corrosion rate of Ti50Ni50-xCux (x = 1, 2, 4, 6, 8) alloys are irrelevant to its Cu content and the values are almost the same as those of TiNi alloys. The connective tissue layer covering the plates is statistically significantly thicker for Ti50Ni42Cu8 plates (p < 0.05) than that of Ti50Ni50, Ti50Ni48Cu2, Ti50Ni44Cu6 plates after one month. The numbers of connective tissue cells, polynucleated cells, macrophages and round cells are higher for Ti50Ni42Cu8 plates than those of the other three types of plates, but no statistically significant differences are detected. There are no significant differences on tissue reaction parameters after two and three months among four alloys. After one, two and three months implantation, no corrosion is observed on the plates surfaces. A preliminary conclusion can be drawn that Ti50Ni50-xCux (x = 2, 6, 8) shape memory alloys have good biocompatibility.

Development of the Hair in the Rat: In vivo and in Transplanted Tissue

Differentiation of the hair was examined in the head skin of rat embryos aged from days 12.5 to 18.5 of gestation. In 12.5-day-old embryos, the skin consisted of single layered epidermis and underlying loose connective tissue. On day 17.5 of gestation, the epidermis appeared to have a two or three layered epithelium, and the subepidermal connective tissue gave rise to an overlying dense tissue, into which blood capillaries arose from the deeper layer. The epidermis showed partial thickenings, where basal cells were arranged perpendicular to the surface of the epidermis. Beneath the epidermal thickenings, a number of connective tissue cells appeared to have accumulated and occasionally were accompanied by blood capillaries. In sequential development of the skin, the thickenings protruded as cords to the underlying dermal tissue and formed hair follicles covered with a connective tissue sheath. Skin obtained from 12.5-day-old embryos was transplanted singly or with cerebral cortex into the third ventricle of adult male rats. Thirty days after the transplantation, hairs and sebaceous glands had developed from the grafted skin. Hair growth tended to be more prominent in the cotransplanted skin grafts. However, no nerve fibers immunoreactive for substance P or calcitonin gene-related peptide (CGRP) were found in the grafted skin, although these fibers appeared in the dermis at the end of gestation in vivo. These results showed that the skin of 12.5-day-old embryos was able to induce hair growth in the third ventricle without accompanying peripheral neuronal fibers or blood capillaries, although the effects of connective tissue cells could not be ruled out.

Myocardial changes in pressure overload-induced left ventricular hypertrophy

Morphological changes in human myocardium associated with pressure overload-induced left ventricular hypertrophy were studied in 22 normal and 21 hypertrophic hearts obtained at autopsy. Samples were obtained from the left lateral ventricular wall, half way between the apex and the base. Myocyte dimensions, polyploidization, multinucleation and relative volume fractions were studied. Regression analysis in relation to indexed heart weight yielded statistically significant correlation coefficients for myocyte volume: r = 0.69 (P less than 0.001), for degree of polyploidization: r = 0.77 (P less than 0.001), for number of nuclei per myocyte: r = 0.47 (P less than 0.01) and for volume fraction of myocytes: r = 0.32 (P less than 0.05). Approximate numbers of myocytes and connective tissue cells per left ventricle were calculated. Correlation coefficients related to indexed heart weight were r = 0.34 (P less than 0.05) for the number of myocytes and r = 0.76 (P less than 0.001) for the number of connective tissue cells. Based on regression analysis in relation to indexed heart weight, we calculated that a doubling of indexed heart weight was associated with an increase in mean myocyte volume by 65%, degree of polyploidization by 24%, multinucleation by 7%, number of myocytes by 20% and number of connective tissue cells by 141%. The volume percentage of myocytes decreased by 6% in favour of the connective tissue fraction. These changes in myocardial composition indicate that the term 'hypertrophy' inadequately describes the actual myocardial changes in response to pressure overload.

Immunolocalization of Fibronectin and Laminin in the Amphibian Intestine During Spontaneous and Triiodothyronine-Induced Metamorphosis: (laminin/fibronectin/extraepithelial matrix/intestine/amphibian).

Fibronectin and laminin were detected by indirect immunofluorescence in the intestine of Alytes obstetricans (anuran amphibian) during triiodothyronine (T3)-induced metamorphosis and spontaneous post-embryonic development. Fibronectin was first detected between a small number of connective tissue cells. As T3-treatment and spontaneous development progressed, fibronectin became detectable as a fine network extending throughout the whole thickness of the connective tissue and particularly in the core of the developing epithelial folds. During the first week of T3-treatment and throughout the spontaneous larval period, laminin was present as a linear band within the basement membrane. Between day 6 and 12 of hormonal treatment, an increase in the laminin fluorescent staining was noted. After hormonal treatment for two weeks and at the end of spontaneous metamorphosis, laminin staining was localized within the basement membrane of the folded epithelium and around muscle fibers. These observations indicate that variations in the density and distribution of extracellular matrix molecules are closely related spatiotemporarily to the structural changes occurring in the connective and muscle tissues of the intestine during metamorphosis.

Myocardial DNA content, ploidy level and cell number in geriatric hearts: Post-mortem examinations of human myocardium in old age

A reduced adaptation rate of the myocardium must, in many cases, be made responsible for heart insufficiency of old patients. The present investigations are aimed towards the question whether heart in old age is accompanied by a loss of myocardial cells and whether a polyploidisation of heart muscle cells takes place thus indicating an adaptive process. A total of 40 human hearts obtained from autopsy material were studied, among them 30 geriatric hearts. Following preparation of the hearts, the myocardium was weighed and the total amount of DNA was determined biochemically. By means of Feulgen cytophotometry the ploidy levels of the heart muscle nuclei were detected. We have used a special method for estimating the total number of heart muscle cells and connective tissue cells in the individual hearts. It could be shown that the total amount of DNA in the myocardium is correlated with the myocardial weight and not with the age of the individual. Instead, DNA synthesis occurs in the heart muscle cells of all age groups depending on the functional activity of the heart. The degree of polyploidisation is closely correlated with myocardial hypertrophy without any influence of age. In hypertrophic hearts the number of connective tissue cells increases from normally 4 to 5 X 10(9) to 12 X 10(9) (in hearts weighing more than 700 g); in hearts with interstitial fibrosis these values are even higher. In normal hearts 1.8 to 2.1 X 10(9) heart muscle cells can be estimated; in hearts weighing more than 500 g numerical hyperplasia of the heart muscle cells is produced, reaching a maximum number of 4.8 X 10(9) muscle cells in excessively hypertrophied hearts weighing more than 800 g. No correlation between age and myocardial cell number (i.e. heart muscle cells or connective tissue cells) could be observed. This means that no agespecific changes occur in the myocardium with regard to the DNA content and cell number. The structural changes found in the hearts of old individuals are produced by extracardial influences (i.e. arteriosclerosis, hypertension, etc.) leading to myocardial hypertrophy. Polyploidisation and augmentation of heart muscle cells in cardiac hypertrophy or decrease in the number of heart muscle cells in heart atrophy may occur at any time of life and are not age-specific.

Alterations of substances (DNA, myoglobin, myosin, protein) in experimentally induced cardiac hypertrophy and under the influence of drugs (isoproterenol, cytostatics, strophanthin).

In growing human hearts the biochemically estimated total amount of DNA increases from 20 mg to 50–100 mg, and in hypertrophied hearts the increase may be threefold compared with normal hearts. Whereas most animal hearts have nearly only diploid muscle cells, in human hearts most muscle cell nuclei are polyploid. According to the grade of hypertrophy a pronounced polyploidisation of heart muscle cells occurs. The quantitative ratio of noncondensed chromatin/condensed chromatin remains constant 4:1 in all grades of hypertrophy. The amount of myoglobin in hearts above 500 g weight is more than 100% compared with normal hearts and is correlated with the width of the heart muscle fibres. In hypertrophied hearts an irregular and higher double refraction of myosin can be seen indicating an early stage of necrosis. In concentric cardiac hypertrophy the dry weight of the muscle fibres is more increased than in eccentric hypertrophy. The protein concentration within the muscle fibres increases with rising heart weight. Some cytostatics cause a decrease of the myocardial DNA content, a reduction of the ploidy level and a diminishing of the number of connective tissue cells. Isoproterenol effects, within the first 3 weeks after administration, a severe reduction of the cell number; after 2 months a pronounced polyploidisation of the heart muscle cells occurs and the cell number increases again above the normal level indicating the regeneration capabilities of the myocardium.

Histological aspects of cervical ripening.

There is a close relationship between the rate of the uterine cervix opening during parturition and the presence or absence of a completely ripened cervix. In order to learn the basic pattern of the ripening of cervix, histological and histochemical studies were performed on the human uterine cervix during pregnancy. It was noted that the collagen bundles disintegrated into fine fibers and also underwent quantitative changes during the ripening process of the cervix. During pregnancy, the number of connective tissue cells was increased, but that of mast cells was decreased. Acid mucopolysaccharides in the cervical ground substance were found to increase in late pregnancy.

Zum Verhalten von Fettzell- und Bindegewebszellzahlen im weißen Fettgewebe nach chronischem Hunger und Wiederauffütterung I. Untersuchungen an experimentell erzeugt fettsüchtigen Mäusen (Aurothioglukose)

Introduction Former investigations ( Rakow et al., 1970, 1971 b) on epididymal fat pads of lean NMRI-Albino-mice during starvation and refeeding have shown that the number of fat cells (adipocytes) remained unchanged while the number of cells of connective tissue decreased during starvation and increased during the refeeding period. In the present paper the problem has been investigated whether these variations could be demonstrated also in NMRI-Albino-mice obesified by administration of aurothioglucose. Material and Methods The investigations were performed with male NMRI-Albinomice rendered obese by administration of aurothioglucose (800 mg per kg body weight). These animals were fed 2.5 g Altromin® 1115 R daily for six weeks. After this they were fed Altromin® 1115 R and additional oat flakes ad libitum for three (exp. groups HW 3) and seven (exp. groups HW 7) days respectively. After this time the animals were sacrificed. The epididymal fat pads were removed and weighed. One of both pads of each animal was used for chemical investigations. After PCA-treatment (0.5 n, 90°C. 15 min.) the DNA ( Burton, 1956) and RNA ( Ceriotti, 1955) was determined in the supernatant. After NaOH-treatment (0.5 n, 37°C, 24 hrs.) the noncollagen protein content ( Lowry et al., 1951) of the sediment was estimated. After HCl-treatment (25%, 110°C, 20 hrs.) the collagen content ( Stegemann, 1958; modified by Rauskolb, 1967) was determined. The remaining fat pad was used for calculations of cell numbers in the fat cell and conneective tissue cell compartment. For this reason fat cells were isolated according to Rodbell (1964). The fat cell diameters were determined microscopically and the average masses of the fat cells were estimated. From the wet weight of the fat pads and the average fat cell mass the number of fat cells was calculated. The remaining suspension of fat cells and cells of connective tissue was utilized for cell smears. These smears were stained with Schiffs reagent ( Feulgen et al., 1924; Graumann, 1952). With an integrating microdensitometer ( Deeley, 1955) the average relative DNA-content of single cell nuclei were measured and the ploidy patterns were estimated. From the whole DNA-content of the fat pads and the DNA-content of the fat cell population the number of cells of the connective tissue was calculated. Also the collagen content due to the connective tissue cells was calculated. Results and Discussion Our investigations have shown that after chronic starvation and during subsequent refeeding the number of fat cells of the epididymal fat pads of obese NMRI-mice remained unchanged. The DNA-content of the fat pads and therefore the number of connective tissue cells decreased during starvation and remained at this level during the refeeding phase although the RNA and noncollagen protein content of the fat pads increased. But the chemically determined collagen content remained also unchanged. These results are different from those obtained with lean NMRI-Albino-mice ( Rakow et al., 1970). The lean mice have shown an increase in connective tissue cell number and collagen content during the refeeding phase. Possible explanations for this different behavior are discussed.

Myocardial ultrastructure of young and senescent rats

Myocardial ultrastructure was compared in specimens from rats aged 3–6 months (young) and 27–28 months (senescent). Retrograde aortic aldehyde perfusion produced uniform preservation. Characteristic effects were observed with variations in buffer systems, fixative concentration, and osmolality. Myocardial cells of senescent rats are characterized by increased lipofuscin pigment containing material of varying density; the granules are often associated with smaller lysosomelike structures. Golgi structures are numerous. Foci of small densely accumulated mitochondria, and dilated vesicles in the intercalated disc region are frequent. Irregular myofibers, numerous surface vesicles, and increased numbers of connective tissue cells are common. These findings suggest that aging of the myocardium includes structural alterations which are not altogether consistent with various pathological conditions.

Untersuchungen über die Zellvermehrung im weissen Fettgewebe der Maus bei durch Aurothioglukose experimentell erzeugter Adipositas

Epididymal fat pads (white adipose tissue) of adult male albino mice of the NMRI strain rendered obese by the administration of aurothioglucose were investigated. Cytophotometric measurements (DNA content of single cells), chemical determination of DNA content of fat pads, determination of average fat cell diameter (as a mean of calculating the number of fat cells), and, to determine cell proliferation, radioautography, were employed to demonstrate changes in the number of fat cells and of cells of connective tissue. It was found that the number of fat cells did not change during the development of obesity, indicating that increased amounts of fat to be stored failed to constitute a stimulus for cell proliferation. In contrast, connective tissue and blood vessels revealed striking increases in cellular proliferation. The number of connective tissue cells was found to be correlated to the amount of fat stored in fat cells. Increased storage of fat thus increases the requirement of connective tissue and of blood supply.

Ultrastructural studies on fetal and early postnatal mouse ovaries. I. Histogenesis and organogenesis.

AbstractOvaries of fetal mice obtained during the twelfth to eighteenth day of gestation and from the first to third postnatal day have been studied by electron microscopy. The interrelationships of follicle cells to oögonia and to connective tissue cells have received special attention. On day 12, when the female gonad can first be distinguished, relatively few large oögonia are visible. These are loosely aggregated and are accompanied by only a few follicle cells.On days 13 and 14 loose groups of oögonia become better demonstrated, and now are always surrounded peripherally by follicle cells. Beginning on day 14 very thin cytoplasmic processes of the follicle cells are interposed between adjacent oögonia. Subsequently, by following this process the follicle cells are drawn into the groups of oögonia or oöcytes. Increasing numbers of connective tissue cells and capillaries are growing into the cortex from the medulla and hilar regions. By day 18 and postnatal day 1 this ingrowth has separated the groups of oöcytes and follicle cells further. By postnatal days 2 and 3 most oöcytes have become enclosed by a follicular epithelium of either flattened, cuboidal or columnar cells. Many stages of zona pellucida formation can be recognized. It is postulated that the manner of fetal and early postnatal differentiation of the ovary explains a number of follicular configurations which deviate from the normal. At no time have cords of cells been observed to originate from germinal epithelium. By contrast the underlying tunica albuginea is derived by ingrowth of cells from the medulla.