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H J Peter

Publications and source records attributed to H J Peter.

At least 37 records · Page 2Linked to original sources
PubMed1990

Generation of intercellular heterogeneity of growth and function in cloned rat thyroid cells (FRTL-5).

The most characteristic hallmarks of human nodular goiters are nodular growth and heterogeneity of structure and function between different areas of the same goiter. In search of the earliest detectable stage of thyroid heterogeneity we have observed doubling times, TSH dependency, and thyroglobulin production in colonies formed from individual FRTL-5 cells growing as monolayers in slide flasks. Single cells and the colonies derived thereof were followed on photographs taken daily until confluence. We observed that each cell had its individual stable multiplication rate throughout the observation period. This was true for all TSH doses tested (0.625-10 mU/ml). A wide range of doubling times (20 h to almost infinite) in the individual cells was observed. The mean growth velocity of subcloned cell lines was highly reproducible in consecutive passages, although a minority of cells escaped this rule. Cells with either high or low thyroglobulin content occurred in clusters, indicating again that specific traits tend to remain stable in the offspring. We conclude that a highly individual growth program, unrelated to mutation, appears to be switched on at the very moment a cell is generated and that this program is passed on to the majority of the offspring, with a minority of cells acquiring qualities differing from those of their sister cell. Therefore, goiter heterogeneity may be the in vivo amplification of a natural phenomenon occurring in all growing cells. Monoclonal adenomas in vivo and nontransformed immortal cell lines in vitro may represent the far end of the large spectrum of individual growth potency among normal thyrocytes.

Animals↗
PubMed1990

Intercellular propagation of individually programmed growth bursts in FRTL-5 cells. Implications for interpreting growth factor actions.

Five methods are commonly used to quantify FRTL-5 cells' and other thyrocytes' growth in vitro and the impact of growth inhibiting or stimulating maneuvers: Total cell count, mitotic index, DNA measurement, total [3H]thymidine incorporation, and the fraction of [3H]thymidine labeled cells. All of them assess cell growth as though all cells were homogeneous with an identical response to growth factors. We demonstrate here that this assumption is not valid. Rather, some intrinsically growth-prone cells appear to pass a growth signal to neighboring cells so that variably sized colonies of synchronized cells within each cluster growing from monodispersed cells are formed. This is true for FRTL-5 cells growing in vitro in monolayers and in three-dimensional, collagen embedded spheroids. The pattern is the same when cell suspensions or collagen-embedded spheroids are implanted onto nude mice. Patches with alternating high and low growth become particularly prominent in the large tumor-like organoids grown from monodispersed cells in nude mice. The pattern much reminds of similar observations in growing intact thyroids. Since there is no significant correlation between the fraction of [3H]thymidine labeled cells and the size of two- or three-dimensional clusters in any experiment, growth of signal-spreading cells is assumed to occur in leaps and bounds. Growth velocity in each subclone of a cell population depends on the mean interval between bursts of replications and on the number of cells synchronized by cell-to-cell diffusion of the growth signal emanating from one dividing cell. Thus, growth-promoting and growth-inhibiting factors may not only act on the mean interval between successive growth bursts, but they may also change cell-to-cell spreading of growth signals.

Animals↗
PubMed1990

Cold follicles in a multinodular human goiter arise partly from a failing iodide pump and partly from deficient iodine organification.

To investigate whether the common cold follicles in human multinodular goiters are the consequence of a functional defect of the apical membrane peroxidase, a failure of the iodide transport system, or both deficiencies, we studied iodide accumulation and iodine organification in 30 fragments of a large multinodular goiter transplanted to nude mice and labeled with 125I. Transplants were frozen to -80 C immediately after removal to avoid diffusion of inorganic iodide. Autoradiographic assessment of over 1000 cryosections (exposed either at -20 C or after thawing and washing out unbound iodide) showed two types of cold follicles, namely those that failed to accumulate iodide and, therefore, did not organify iodine, and those that readily accumulated iodide but failed to bind it, suggesting a failure of apical membrane peroxidase. The two types of pathogenetically different cold follicles coexisted in an apparently randomly intermingled fashion throughout the whole goiter.

Aged↗
PubMed1988

Autonomous growth, but not autonomous function, in embryonic human thyroids: a clue to understanding autonomous goiter growth?

Thyroid glands from six 8- to 10-week-old fetuses obtained at the time of legal abortion were cryopreserved in liquid nitrogen and transplanted into nude nu/nu mice. Histological and autoradiographic studies of the grafts labeled with [3H]thymidine and [125I]iodine showed proliferation and functional differentiation of the fetal thyroid tissue. Despite T4-mediated suppression of host TSH secretion, up to 36% of the follicular cell nuclei incorporated the thymidine label, reflecting autonomous proliferation, while iodine organification was almost entirely obliterated. Methimazole-induced TSH hypersecretion readily stimulated both growth and function of the transplanted tissue. Thus, during early development, the human thyroid largely depends on TSH for function, but not for growth. Similar findings were obtained in newborn mice, in whom 58% of the thyroid follicular cells proliferated autonomously, i.e. in the absence of TSH. The number of autonomously proliferating cells gradually declined with increasing age to about 1% in 60-day-old animals and, as reported previously, in xenotransplanted normal human thyroid tissue, whereas the number of autonomously proliferating cells was previously found to be several times higher in xenotransplanted human multinodular goiters. We, therefore, hypothesize that the rapidly and autonomously replicating cells that initiate nodule formation in human multinodular goiters reflect the persistence in the adult gland of cells with fetal growth potential.

Age Factors↗
PubMed1988

[Histopathogenesis of goiters].

The basic mechanisms acting in the transformation of a normal thyroid gland into a toxic or nontoxic goiter are summarized: 1) Any goiter arises from multiplication of follicular epithelial cells forming new follicles. 2) In the follicular epithelium there are cell families with much higher than average growth potential. 3) Cells of an individual follicle are not identical but heterogeneous. 4) Each follicular cell has a certain level of autonomy of growth and of function.

Cell Division↗
PubMed1988

Pathogenesis of nodular goiter and its implications for surgical management.

Despite sufficient iodine supply, goiter continues to be of considerable surgical significance in formerly endemic countries. It now appears that iodine deficiency and increased thyrotropin stimulation are not the only causes of goiter. Xenotransplantation of human thyroid tissue onto nude mice allowed study of the regulation of growth and function in human goiter tissue. Grafts of human thyroid tissue growing in nude mice could be shown to react to endogenous mouse thyrotropic stimulation and suppression. 131I autoradiographs of xenotransplanted goiter tissue showed as marked a heterogeneity as did the original goitrous tissue prior to transplantation. There was no firm correlation between the morphologic appearance of a follicle and its iodine metabolism. Scintigraphically "cold" and "hot" goiter tissue differed from each other quantitatively but not qualitatively; i.e., both "hot" and "cold" tissue were composed of metabolically active and nonactive follicles. Iodine organification was not completely suppressible by thyroxine treatment; this indicates autonomous functional activity. The distribution of proliferating tissue labeled by 3-H-thymidine did not parallel the distribution of functionally active tissue labelled by 131I. Thyroxine treatment did not completely inhibit 3-H-thymidine incorporation, indicating autonomous growth. Thus, our pathogenetic concept of goiter formation is based on three mainstays: (1) goiter heterogeneity, (2) autonomy of growth and function, and (3) dissociation of growth and function in human goiter tissue. Thus, the surgeon dealing with goiter ought to remove all pathologically altered tissue, i.e., nodular tissue, irrespective of its appearance on scintiscans.

Animals↗
PubMed1987

[Current TSH-sensitive assays simplify thyroid diagnosis].

The methodology and clinical application of sensitive TSH assays are discussed. The new immunometric assays not only distinguish between normal and elevated, but also between normal and suppressed TSH values. Therefore, after clinical examination of the patient, serum TSH measurement by a sensitive assay may be used as a first line test whenever hypo- or hyperthyroidism is suspected. Normal TSH indicates euthyroidism and obviates the need for further thyroid function testing. In patients with elevated or suppressed TSH values, free T4 and (if TSH is suppressed and free T4 normal) free T3 are measured to discriminate between overt and subclinical hypo- or hyperthyroidism. Testing with TRH continues to be useful in some more complex cases, when the above-mentioned tests are not conclusive.

Diagnosis, Differential↗
PubMed1987

Naturally occurring clones of cells with high intrinsic proliferation potential within the follicular epithelium of mouse thyroids.

The proliferation pattern of some scattered clones of naturally occurring follicular cells with an exceedingly high intrinsic growth potential was investigated in the mouse thyroid gland. In particular, evidence was sought to demonstrate that the high propensity to replicate is a stable trait transmitted from the progenitor cells to their offspring. We hypothesize that these cell clones are at the origin of the multiple adenomas that invariably arise in chronically stimulated thyroid. Growth stimulation was induced either by hemithyroidectomy or by methimazole feeding. In a first series of experiments, involving hemithyroidectomized animals, [3H]thymidine was administered continuously for 3 weeks by means of osmotic minipumps, so that all cells entering the mitotic cycle during that time were labeled. Hemithyroidectomy led to a 3-fold increase of the fraction of labeled cells in the remaining lobe. The increase was prevented by thyroxine treatment in thyroid-stimulating hormone-suppressing doses. Autoradiographs of contiguous serial sections across whole follicles showed that roughly 75% of the labeled cells were clustered in groups of 3 or more, rather than being randomly distributed. In a second set of experiments, glands stimulated by methimazole-induced thyroid-stimulating hormone hypersecretion were pulse-labeled by a single i.p. injection of [3H]thymidine. Animals were sacrificed either 2 h or 3 weeks after the administration of the label. The thyroids were excised and the fate of labeled thyroid cells was analyzed autoradiographically. In the 2-h exposure, about 95% of all labeled follicular cells were single and the remaining 5% were in pairs. In contrast, about 50% of all labeled cells were clustered in groups of 3 to 12 cells 3 weeks after the pulse labeling. The number of silver grains per nucleus was compared to that of the identically exposed controls. The intensity of label per cell appeared to be decreased in proportion to the size of the labeled clusters, indicating that clusters had generated several subsequent generations of cells. The results support previously produced evidence that highly growth-prone cells naturally occur within the normal thyroid and demonstrate, in addition, that their high intrinsic growth rate is a stable, inheritable trait. Cells which replicate at a rate faster than that of the average epithelial cell have a tendency to overgrow during goitrogenesis. They may be at the very origin of the nodules and adenomas commonly found in experimentally produced and naturally occurring goiters.

Animals↗
PubMed1987

Autonomy of growth and of iodine metabolism in hyperthyroid feline goiters transplanted onto nude mice.

Hyperthyroidism caused by nodular goiters is a common disease of aging cats. Growth and iodine metabolism were studied by autoradiography in normal and hyperfunctioning thyroid tissue obtained from cats injected with 125I before surgery, and in xenografts, grown in nude mice, after double-labeling with 131I and [3H]thymidine. Hyperthyroid cat goiters contain single or multiple hyperplastic nodules, consisting of highly cellular tissue with an iodine metabolism exceeding that of the surrounding normal tissue. Xenografts of hyperplastic hot tissue in thyroxine-treated nude mice retain their original histologic pattern and continue to accumulate radioiodine intensely. Autoradiographs assessed for [3H]thymidine incorporation reveal autonomously proliferating follicular cells within the hyperplastic foci but not within the normal tissue. Administration of sera from donor cats into host mice fails to stimulate the xenografts. Neither hyperfunction nor growth of toxic cat goiters depends on extrathyroidal stimulators. The basic lesion appears to be an excessive intrinsic growth capacity of some thyroid cells.

Animals↗
PubMed1987

Progressive recruitment of follicular cells with graded secretory responsiveness during stimulation of the thyroid gland by thyrotropin.

One of the earliest responses of the thyroid cells to TSH is macropinocytosis with formation of intracellular colloid droplets. We demonstrate here that increasing stimulation with TSH not only elicits a highly individual macropinocytotic response among different follicular cells but that the fraction of TSH-responsive cells is also a function of the TSH dose. After pretreatment with T4, mice and rats were injected ip with bovine TSH and killed 2 h later. The macropinocytotic response to TSH was evaluated on periodic acid-Schiff-stained 3-microns sections of the thyroids in terms of droplet number per 25 follicles and, in addition, by assessing recruitment, i.e. percentage of droplet-containing cells. Both variables increased with increasing TSH stimulation until they reached a plateau at about 9 mU TSH in mice and at about 300 mU TSH in rats: the percentage of droplet-containing cells gradually increased in mice from 2% (no TSH) to 67% (9 mU TSH) and in rats from 11% (no TSH) to 54% (300 mU TSH). Overall pinocytotic response as well as thyrocyte recruitment could be modified by extra- and intrathyroidal factors: for example, pretreatment of the mice with an iodine-deficient diet increased the maximal percentage of droplet containing cells to nearly 90%. Obviously, two separate components of the macropinocytotic response of the thyroid gland to TSH can be distinguished: the first is the gradually increasing fraction of droplet-containing cells, the second is the well known increase of the number of colloid droplets in each TSH-responsive cell with progressive TSH stimulation. Recruitment of thyrocytes with a gradually increasing natural threshold to a hormonal stimulus appears to be a fundamental mechanism in the thyroid gland and possibly in other organs.

Animals↗
PubMed1987

Age-related failure of endocytosis may be the pathogenetic mechanism responsible for "cold" follicle formation in the aging mouse thyroid.

With advancing age, 60-80% of the follicles of the mouse thyroid gland turn "cold", i.e. they lose their normal capacity to iodinate thyroglobulin (Tgb). Cold follicles are morphologically characterized by their large size, by deeply periodic acid-Schiff-stained colloid and by flat epithelial cells. We investigated the hypothesis that a progressive, age-related failure of endocytosis, leading to a gradually increasing mismatch between production of new Tgb and resorption of stored Tgb, could lead to overfilling of colloid stores with consecutive impediment of diffusion. To this purpose, labeling of the thyroids was started when mice were 3 months old, and 125I was continuously administered thereafter for 2-6 months. After this time, all follicles were homogeneously labeled in autoradiographs. Tracer application was then discontinued. Autoradiographs obtained at intervals during the washout of the tracer yielded a mirror image of that observed after acute labeling. The large follicles which were cold after acute labeling in old animals now still retained labeled iodoproteins even after 7 weeks of washout, i.e. at a time when morphologically normal follicles had long lost their labeled Tgb stores. Thus, the cold follicles of the old thyroid must have been functioning normally during equilibration of young thyroids, but have then gradually lost their capacity to iodinate and to remove stored Tgb from the colloid. The observation supports the thesis that aging primarily affects the cytoskeleton and, thus, the cell's endocytotic machinery. This effect of aging on the thyroid can be prevented by life-long stimulation of the gland by TSH.

Aging↗
PubMed1986

Cryopreservation of human fetal organs.

The effects of low temperature preservation on morphology, viability and differentiation capacity of different human fetal organs were studied using transmission (TEM) and scanning (SEM) electron microscopy, in vitro cultivation as well as xenogeneic transplantation. For this purpose fragments of lung, kidney, small intestine, thyroid, brain, liver and spleen from 10 human fetuses (aged 9 to 14 weeks of gestation) were frozen by a three step cooling procedure. After 3 to 12 months the specimens were thawed rapidly and processed for TEM and/or in vitro cultivation and/or transplantation into nude mice. TEM studies on frozen lung, kidney and intestine revealed generally a well preserved ultrastructure whereas liver and spleen fragments appeared highly necrotic. From three fetuses, frozen intestine and lung specimens were used for the establishment of monolayer cultures. Following trypsinization, both epithelial and mesenchymal cells formed a continuous layer on the bottom of plastic bottles. During further subpassages the number of epithelial cells decreased resulting in the formation of pure fibroblast cultures. Frozen brain tissue from one fetus was also successfully cultivated forming cell clusters and fiber bundles of variable size at the surface of glass cover slips. Following subcutaneous implantation into nude mice, the vast majority of fragments from lung, kidney, intestine and thyroid was found to grow in the recipients. The growth of xenografts was accompanied by persistence (kidney, intestine) or even increase (lung, thyroid) in cellular differentiation studied by TEM or autoradiography. Transplanted liver and spleen fragments, however, regularly regressed forming solid scars in the subcutaneous tissue of nude mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Diffusion of thyroglobulin in the follicular colloid. (Minireview).

Methods used for estimating in vivo diffusion velocity of thyroglobulin (Tgb), the factors affecting hydrodynamic properties of thyroidal colloid and the effects of changing diffusion properties on follicular function are briefly reviewed. The principal methods, besides pure in vitro techniques, are autoradiography of thyroid sections after in vivo labelling of Tgb and freezing autoradiography for examining colloidal diffusion of ions or other small molecules. The main factors known to affect diffusion of Tgb in the colloid space are concentration and actual physico-chemical properties of the Tgb molecule itself, the latter parameter depending on several factors such as sugar content, iodination degree, etc. Additional factors are thyrotropin which speeds up and drugs such as pentobarbital or verapamil which slow down the velocity of Tgb diffusion. High iodine supply has a retarding effect on Tgb diffusion in the colloid of mice thyroids. Any change of Tgb diffusion in the colloid may have a striking effect on follicular function. The hydrodynamic properties of the colloid components are increasingly recognized as a potentially important factor in regulating kinetics of hormone synthesis.

Animals↗
PubMed1985

Toxic nodular goitre.

Toxic nodular goitre is the late result of a slow growth process generating new daughter follicles from the mother follicles of a normal thyroid gland. Since the normal follicular shell is not built up by monoclonal epithelial cells, but rather by cells with widely variable functional equipment, daughter follicles generated by the preferential replication of particular mother follicular cells endowed with a high growth potential, may be different from mother follicles. For instance, the progeny of follicles may have a higher or lower iodine metabolism than their progenitor follicles. Some of the newly generated follicles have a high autonomous, i.e. TSH-independent, iodine turnover, while some others have a high autonomous growth potential. The degree of autonomous function is entirely independent of that of growth. In the process of goitrogenesis, newly generated follicles may, in addition, acquire new forms of expressing genetic functions. Such new traits, e.g. a particular growth pattern, may become inheritable and are then passed on from mother to daughter cells. The result is the most characteristic of all hallmarks of nodular goitres, which is the heterogeneity of structure and function between two diseased glands and even between closely adjacent follicles of the same gland. Greatly uneven intrinsic replication rates between different follicular cells and equally varying independency on growth stimuli account for regional differences in goitre growth. This, together with a network of fibrous scars interfering with unimpeded expansion of the growing follicle population, invariably produces a nodular growth pattern of the goitre. TSH certainly does not account for the growth of this type of goitre. Instead, a number of thyroid growth factors, including growth-stimulating immunoglobulins akin to those found in Graves' disease, have been discovered in recent years. Once the number of follicular cells with high intrinsic growth potential has become large enough under the impact of extrathyroidal growth stimuli, goitre growth may become autonomous and self-perpetuating. Whether or not a nodular goitre will produce thyrotoxicosis is a function of the number of follicles with high intrinsic iodine turnover which happen to be generated in the course of goitrogenesis. In contrast to thyrotoxicosis in Graves' disease, hyperthyroidism in nodular goitre is a very slowly progressing, insidiously evolving complication.

Autoradiography↗
PubMed1985

Pathogenesis of heterogeneity in human multinodular goiter. A study on growth and function of thyroid tissue transplanted onto nude mice.

Functional and morphologic heterogeneity of human multinodular goiters was investigated in 300 samples from "cold" and "hot" regions of 20 goiters transplanted onto nude mice. Transplants were labeled with [3H]thymidine and radioiodine, while the host's thyroid-stimulating hormone (TSH) secretion was either stimulated or suppressed. Proliferation and function of follicular cells were assessed in whole follicles reconstructed from autoradiographs of serial sections. Hot transplants had a higher autonomous iodine uptake than those of cold tissue in TSH-suppressed hosts. Functional autonomy widely varied among the follicles, but even more so among individual cells. Hot grafts differed from cold ones only by a comparatively larger fraction of autonomous cells. Intercellular differences of iodinating activity were not abolished by TSH. Grafts faithfully reproduced the individual growth pattern of the original tissue. Between 0.5% and 7% of all follicular cells replicated despite suppression of TSH. Up to 70% of these cells were clustered, forming scattered foci of autonomously growing tissue. Other cells only started replicating after long-term TSH stimulation. Thus, goiters contained subsets of cells with high and others with low growth response. Progenies of replicating cells remained clustered, sometimes budding outwards to form new follicles. Autonomy of growth and autonomy of function are independent traits of epithelial cells. Epithelial cells have their individual growth pattern, replication rate, and functional capacity. These traits are passed on from a mother cell to its progeny during follicle neogenesis. To this main mechanism accounting for the morphologic and functional heterogeneity of human goiters, inheritable modifications of gene expression must probably be added.

Animals↗