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Biomedical subjects

M Schimmel

Publications and source records attributed to M Schimmel.

At least 19 recordsLinked to original sources
PubMed2001

Establishment of the urogenital junction in the male bovine embryo: an ultrastructural study.

The ultrastructure of the developing extratesticular rete testis, the efferent ductules and the establishment of the urogenital junction were studied in bovine embryos and fetuses of 41 through 95 days post conceptionem. The efferent ductules originate as a new set of secondary mesonephric tubules from the dorsal aspect of the nephric giant corpuscle and grow in the direction of the Wolffian duct. Cytological differentiation of the efferent ductules proceeds in a proximo--distal direction. At about 50-60 days, the simple columnar epithelium of the proximal portions of the efferent ductules already consists of the two typical cell types, i.e. reabsorptive principal cells with an endocytotic apparatus and a brush-border and ciliated cells. The lumen of the proximal portion is temporarily filled with intraductular blood vessels and perivascular tissue which may represent vestigial rudiments of glomeruli associated with the efferent ductules. At 50 to 60 days, the extratesticular rete still has a blastema--like appearance and consists of irregular cells with abundant glycogen. Extensions of the extratesticular rete come into contact with the efferent ductules and create the first end-to-side anastomoses with the latter. Somewhat later, the separating basal laminas vanish and invading rete cells intermingle with the epithelium of the efferent ductules, thus establishing the urogenital junction.

Animals↗
PubMed2001

Emphasizing difficulties in the detection of rhythms with Lomb-Scargle periodograms.

The Lomb-Scargle periodogram was introduced in astrophysics to detect sinusoidal signals in noisy unevenly sampled time series. It proved to be a powerful tool in time series analysis and has recently been adapted in biomedical sciences. Its use is motivated by handling non-uniform data which is a common characteristic due to the restricted and irregular observations of, for instance, free-living animals. However, the observational data often contain fractions of non-Gaussian noise or may consist of periodic signals with non-sinusoidal shapes. These properties can make more difficult the interpretation of Lomb-Scargle periodograms and can lead to misleading estimates. In this letter we illustrate these difficulties for noise-free bimodal rhythms and sinusoidal signals with outliers. The examples are aimed to emphasize limitations and to complement the recent discussion on Lomb-Scargle periodograms.

Circadian Rhythm↗
PubMed2001

The issue of significant features in random noise.

With respect to the first example in Schimmel (2001), Van Dongen et al. (2001) conclude from their Lomb-Scargle analysis that the noise I used 'contains new periodicities that are added to the signal (these periodicities by themselves resemble a harmonic series of a 38-hour rhythm).' They infer that 'the variance of the added noise is about five times as large as the variance of the signal' causing the detection of the new significant periodicities in the noise prior to the 24-h bimodal rhythm. Moreover the 'example reflects a combination of an extremely non-sinusoidal signal with noise that is not independent, which results in a time series that is difficult to analyze with virtually any know method.' In the following, I briefly examine these concerns to avoid misunderstandings and to alert that with an adequate use of the statistical significance test, misleading conclusions can be obtained. Although this paper further emphasizes difficulties in the detection with Lomb-Scargle periodograms, this should not be used as de-motivation. As stated in Schimmel (2001) Lomb-Scargle is a powerful technique but such as any other method one should be aware about its limitations, and use additional tools to constrain the true data characteristics.

Circadian Rhythm↗
PubMed2001

Selective apoptosis induction in transformed fibroblasts by B cell lines: involvement of reactive oxygen and nitrogen species.

B cell lines induce apoptosis selectively in transformed fibroblasts. Apoptosis induction is independent of direct cell contact. It seems to be based on superoxide anion production by transformed cells, subsequent spontaneous dismutation to hydrogen peroxide and utilization of the hydrogen peroxide by a peroxidase released by effector cells. The peroxidase then generates hypochlorous acid which may interact with target cell derived superoxide anions, yielding apoptosis-inducing hydroxyl radicals. In parallel, NO released by effector cells may interact with target cell derived superoxide anions and generate the apoptosis inducer peroxynitrite. Therefore, in parallel to their specific functions in humoral immunity, B cells seem to have the potential to contribute to those signalling pathways directed against transformed cells that have been recently shown to be established by TGF-beta treated fibroblasts. This intercellular signalling system seems to represent an evolutionary ancient system for the control of cells that potentially endanger the survival of multicellular organisms.

Acetylcysteine↗
PubMed2000

A comparative study of 2 fluoride-based mouthrinses.

OBJECTIVE: The purpose of this study was to compare the effectiveness of 2 mouthrinses (conventional Meridol and alcohol-free Meridol). METHOD AND MATERIALS: A controlled, single-blind clinical study of 3 weeks' duration was conducted on 80 adult subjects in good general health and without severe periodontitis (probing depths no deeper than 4 mm). The mouthrinses supplemented regular measures of oral hygiene for the reduction of plaque and gingivitis. In preliminary examinations to determine general conditions of oral health, especially the level of plaque, gingivitis, and periodontal findings, the approximal plaque index, sulcular bleeding index, and gingival index were established for each subject. Afterward the subjects were provided with a professional toothcleaning, as required. Each subject was randomly provided with 1 of the 2 mouthrinses, to be used 3 times daily in addition to routine oral health measures. The 3 indexes were reevaluated after 3 weeks; in addition, an optional stain index was employed. RESULTS: In both subject groups, a statistically significant reduction in plaque accumulation, as well as a reduction in inflammation and the tendency to bleeding, was observed. Reversible staining of the teeth and tongue was observed in fewer than one third of the subjects in both groups. CONCLUSION: Comparison of the 2 Meridol mouthrinses revealed no difference in effectiveness related to the alcohol content.

Adult↗
PubMed1997

Understanding donors' motivations: a study of unrelated bone marrow donors.

Medical advances in bone marrow transplantation techniques and immunosuppressive medications have dramatically increased the number of such transplants performed each year, and consequently, the demand for bone marrow from unrelated donors. Although physiological aspects of bone marrow donation have been thoroughly investigated, very few studies have examined psychosocial factors that may impact individuals' donation decisions and outcomes. To examine one particular set of donor psychosocial issues, this study investigated motives for bone marrow donation among 343 unrelated bone marrow donors who donated through the National Marrow Donor Program. Six distinct types of donor motives were identified from open-ended questionnaire responses. Donors most frequently reported motives reflecting some awareness of both the costs (to themselves) and potential benefits (to themselves and the recipient) of donation. A desire to act in accordance with social or religious precepts, expected positive feelings about donating, empathy for the recipient, and the simple desire to help another person were also commonly cited reasons for donating. Among a series of donor background characteristics, donors' gender was the variable most strongly associated with motive type; women were most likely to cite expected positive feelings, empathy, and the desire to help someone. Central study findings indicated that donor motives predicted donors reactions to donation even after the effects of donor background characteristics (including gender) were controlled. Donors who reported exchange motives (weighing costs and benefits) and donors who reported simple (or idealized) helping motives experienced the donation as less positive in terms of higher predonation ambivalence and negative postdonation psychological reactions than did remaining donors. Donors who reported positive feeling and empathy motives had the most positive donation reactions in terms of lower ambivalence, and feeling like better persons postdonation. These finding add substantially to the body of work concerning medical volunteerism generally, and also have important practical implications for the recruitment and education of potential bone marrow donors.

Adult↗
PubMed1996

Immunohistochemical demonstration of nerve growth factor receptor in bovine testis.

Nerve growth factor receptor (low-affinity form) was demonstrated immunohistochemically in bovine testis by using a monoclonal mouse anti-human antibody. In the 7-month-old fetus and in the early postnatal testis, the peritubular and intertubular fibroblast-like mesenchymal cells showed a strong reaction. Following differentiation of these cells into Leydig and myoid peritubular cells, the nerve growth factor receptor was no longer expressed. However, peritubular and intertubular testicular fibroblasts/fibrocytes, which are also derived from mesenchymal precursors, remained positive. Additionally, the nerve growth factor receptor was demonstrated in postnatal prespermatogonia, A-spermatogonia, I-spermatogonia and members of the spermatogonia precursor cell line; B-spermatogonia remained negative. In A-spermatogonia and I-spermatogonia, the expression of the nerve growth factor receptor was cell-cycle-dependent and was mostly observed during G1-phase. Pre-embedding ultrahistochemistry with gold-conjugated antibody followed by silver-enhancement revealed that the nerve growth factor receptor was localized at the outer cell surface. The metal granules showed a regular distribution in positive spermatogonia. In testicular fibroblasts/fibrocytes the long narrow processes were preferentially decorated.

Animals↗
PubMed1995

Configuration and distribution of bovine spermatogonia.

The configuration and distribution of bovine spermatogonia, preleptotene primary spermatocytes and Sertoli cells in the basal seminiferous tubular compartment have been studied by means of whole-mount preparations, immunohistochemistry and quantitative morphology. Three types of spermatogonia (Sg) can be identified. Large A-spermatogonia are irregularly distributed in the tubular periphery. Following the period of propagation of the A-spermatogonia, an interconnected meshwork of medium-sized spermatogonia with different cytogenetic potency is observed. Although the majority of the medium-sized spermatogonia are kinetically of the I type and divide to produce small B-spermatogonia, some members of the medium-sized population are seen in a growth phase and differentiate into large A-spermatogonia. These mark the beginning of a new round of spermatocytogenesis. Only one generation of B-spermatogonia divides into preleptotene primary spermatocytes. The architectural arrangement of multiplying spermatogonia in circles or rows is primarily the result of the distribution of the Sertoli cells. Spermatogonial multiplication is not strictly coordinated with the stages of the seminiferous epithelial cycle. Spermatogonial degeneration amounts on average to 3.6% and has therefore no decisive impact on the yield of primary spermatocytes.

Animals↗
PubMed1995

Evolution and ultrastructure of the bovine spermatogonia precursor cell line.

The spermatogonial stem cell line in prepubertal and adult bovine testis was studied by electron microscopy and protein gene product 9.5 immunohistochemistry. Three successive spermatogonia precursor cell configurations were observed. Small basal stem cells were found to possess a spherical shape and nuclei with two to three nucleoli. They were observed in prepubertal testes (25 and 30 weeks) and in low numbers during all the stages of the seminiferous epithelial cycle in the adult. Aggregated spermatogonia precursor cells are the dominating germ cell type in the 25-week-old and 30-week-old calf. In the adult seminiferous epithelium, they cause expansion of the basal tubular compartment as they form dense groups containing up to 15 cells. These groups are observed concomitantly with cycling A-spermatogonia and preleptotenes at the beginning of spermatocytogenesis. At the end of A-spermatogonia propagation, the aggregated spermatogonia precursor cells separate and intermingle with cycling A-spermatogonia. The spermatogonia precursor cells can later be found together with I-spermatogonia as members of an interconnected cellular network of medium-sized cells. When the I-spermatogonia divide to form the smaller B-spermatogonia, the precursor cells, which stay connected with the cycling spermatogonial population, pass through a growth phase. They can now be considered as committed spermatogonia precursor cells and are continuously being transformed into A1-spermatogonia to start a new round of spermatocytogenesis. Ultrastructurally, all members of the precursor cell line are similar. However, a number of features have been found to show a quantitative increase (endoplasmic reticulum, mitochondria) or to exhibit a rising degree of complexity (nucleolus) during the progression from basal stem cells to committed spermatogonia precursor cells.

Animals↗
PubMed1995

Quantitative morphology of the ovine seminiferous epithelium.

Ultrastructural features and morphometric values of ovine Sertoli and spermatogenic cells are reported with special reference to the 6 stages of the seminiferous epithelial cycle. Seminiferous tubules occupy about 83% of the testicular parenchyma. Average tubular diameter (about 275 microns) and epithelial height (about 95 microns) do not vary significantly during the cycle. From preleptotene to late diplotene the cellular volume of primary spermatocytes increases nearly five-fold; the nuclear volume increases three-fold in the same period. Secondary spermatocytes are observed exclusively during stage 4 of the seminiferous epithelial cycle. Due to partial cell necrosis and autolytic events, ovine spermatids lose a considerable amount of their cytoplasm during acrosome and maturation phases prior to spermiation. Sertoli cells occupy between 27.6% (stage 3) and 36.6% (stage 1) of the tubular epithelium. The average volume of a Sertoli cell varies between 6380 microns 3 (stage 2) and 7195 microns 3 (stage 4), the absolute surface area between 10550 microns 2 and 12305 microns 2. The irregularly contoured Sertoli cell nucleus contains a vesicular nucleolus and occupies about 7.5% of the cell. Mitochondria (about 5%) and smooth endoplasmic reticulum are other prominent organelles, but three-quarters of the Sertoli cell are taken up by cytoplasmic matrix with a well-developed cytoskeleton. Ovine Sertoli cells contain large basal lipid droplets, but no typical lipid cycle can be observed.

Animals↗
PubMed1994

Immunocytochemical demonstration of cytoskeletal proteins in seminiferous tubules of adult rams and bulls.

The immunohistochemical localization of actin, vimentin and tubulin in adult ovine and bovine seminiferous tubules was studied at both the light and electron microscopical levels, using an improved methodical protocol. alpha-smooth muscle actin and structural F-actin were found to be present in myoid peritubular cells. Structural F-actin also occurs in Sertoli cells at three localizations; 1) As part of the Sertoli-Sertoli-junctions in a stage-dependent manner; 2) where Sertoli cells are in contact with spermatocytes; 3) in ectoplasmic specializations lining the recesses that support elongating spermatid heads. Vimentin is localized in peritubular myoid and fibroblastic cells and in Sertoli cells. In the latter, vimentin is concentrated in a perinuclear position. alpha-tubulin is observed in the cytoplasm of spermatogonia, in axonema and manchette of spermatids and in Sertoli cells with their abundant microtubules. Since the alpha-tubulin reaction decorates even the narrowest lateral and apical cell processes, it is an excellent marker to study changes in Sertoli cell shape and size during the seminiferous epithelial cycle in rams and bulls.

Actins↗
PubMed1993

Psychosocial effects of unrelated bone marrow donation: experiences of the National Marrow Donor Program.

In this study, we investigated the psychosocial effects of unrelated marrow donation. Survey questionnaires were administered pre-donation, shortly post-donation, and 1 year post-donation to all donors through the National Marrow Donor Program over a 3-year period. Univariate, bivariate, and multivariate analyses were then performed. Donors were generally quite positive about the donation 1 year post-donation: 87% felt it was "very worthwhile" and 91% would be willing to donate again in the future. Marrow donors were more likely than kidney donors to feel better about themselves as a result of the donation (P < .001). Donors with longer collection times, in general, had less positive psychosocial outcomes from the donation. Donors who experienced lower back pain or difficulty walking as a result of the donation were more likely to experience the donation as more stressful and painful than expected, but no more likely to experience it as less positive emotionally than donors who did not experience these side effects.

Anesthesia↗
PubMed1993

Fetal mild idiopathic lateral ventriculomegaly: is there a correlation with fetal trisomy?

Mild idiopathic lateral ventriculomegaly in the mid-trimester fetus can be accurately detected using modern prenatal ultrasonography. Since an abnormal karyotype has been reported in some of these cases, the present prospective study was designed to evaluate, first, the prevalence of mild idiopathic lateral ventriculomegaly in the general obstetric population and, second, to determine the incidence of abnormal fetal karyotype associated with mild idiopathic lateral ventriculomegaly. Eight cases of mild idiopathic lateral ventriculomegaly (0.15%) were detected among 5400 routine prenatal sonographic examinations, between 16 and 22 weeks' gestation. Three newborn infants were found to be normal; in one baby, spontaneous resolution of the lesion occurred in utero, and, among the other five cases, two had an abnormal karyotype: one had Down's syndrome, and one trisomy 18. A review of the English literature revealed that 12% of fetuses with mild idiopathic lateral ventriculomegaly have an abnormal karyotype. Since 3% of the fetuses with Down's syndrome can be visualized in utero with mild idiopathic lateral ventriculomegaly, the calculated risk for Down's syndrome when such lesions appear is about 3%. We, therefore, conclude that karyotypic study is warranted in the mid-trimester fetus with incidental findings of mild idiopathic lateral ventriculomegaly.

Journal Article↗
PubMed1993

Fetal intracranial haemorrhage: clinical significance of in utero ultrasonographic diagnosis.

OBJECTIVE: To review in utero detection of fetal intracranial haemorrhage. DESIGN: Retrospective survey of pregnant women presenting to the ultrasonographic unit in whom the diagnosis of fetal intracranial haemorrhage was reached. SETTING: The Chaim Sheba Medical Center in Ramat Gan, and Shaare Zedek Medical Center in Jerusalem; two large district general hospitals, each with 6000 maternity patients per year. SUBJECTS: Five fetuses with gestational ages ranging from 26 to 36 weeks. MAIN OUTCOME MEASURES: Maternal complications, fetal monitoring, prenatal Doppler ultrasound studies, postnatal imaging studies, neonatal morbidity and mortality. RESULTS: Transabdominal sonography showed hyperechoic lesions in the brain parenchyma, and the lateral ventricle in three of five fetuses. In the remaining two fetuses, transvaginal sonography enhanced the visualisation of ventriculomegaly with intraventricular haemorrhage in one and periventricular leukomalacia was identified in the second. Three fetuses were appropriate for gestational age, and two were severely growth retarded. In one woman severe pre-eclamptic toxaemia may explain intracranial haemorrhage. Abnormal nonstress test and abnormal flow velocity waveforms in the umbilical and cerebral arteries were present in the two growth retarded fetuses, and in one who was appropriate for gestational age. The two growth retarded fetuses died shortly after birth. Of the three surviving infants, two had normal long term development, and one developed hydrocephalus with subsequent severe neurodevelopmental retardation, dying at the age of seven months. CONCLUSIONS: This small series shows that intracranial haemorrhage has a broad spectrum of manifestations with diverse prognosis. Following an antenatal diagnosis of intracranial haemorrhage, the obstetrician must give special consideration to electronic fetal heart monitoring and Doppler velocity waveforms. The prenatal diagnosis of intracranial haemorrhage has medico-legal implications suggesting that neurological outcome may not necessarily be due solely to intrapartum events and management.

Adult↗
PubMed1993

The self-image of unrelated bone marrow donors.

This study investigated the self-image of individuals who donate bone marrow to strangers as part of the National Marrow Donor Program. Quantitative surveys were administered to donors before donating (N = 849), shortly after donating (N = 754), and a year after donating (N = 370). In addition, 52 donors were interviewed in-depth by telephone at the same three points in time. Many of these donors felt that by donating bone marrow they were actualizing a central trait in their identity. Thus, many donors believed that they were distinct from others in the centrality of the traits of helpfulness and generosity to their identities. This belief often stemmed from a strong emphasis on helping in their families of origin. Other qualities activated by donation included religious identity, being a helping professional, and desire to be a role model. Self-evaluation appeared to have been enhanced for some donors due to the donation.

Altruism↗
PubMed1989

Morphology of the bovine Sertoli cell during the spermatogenetic cycle.

The morphology of the bovine Sertoli cell was studied during 6 different phases of the spermatogenetic cycle. Tubular dimensions do not vary significantly during the phases. Sertoli cells occupy 27.0% (phase 4) to 38.4% (phase 8) of the tubular epithelium. Sertoli cells of phase 1 are approximately 20% larger than during the other phases. 30-35% of Sertoli cell volume consists of organelles. Mitochondrial (about 5.0%) and nuclear (about 5.7%) volume densities remain remarkably stable during the cycle, irrespective of changes in Sertoli cell size. Phagocytic capacity of bovine Sertoli cells is only moderate. Elimination of excess spermatid cytoplasm occurs to a large extent prior to spermiation. The majority of spermatid residual bodies undergoes autolytic decay while attached to the Sertoli cell apical surface. Aggregates of densely packed cisternae of the smooth endoplasmic reticulum (ER) located in a basal position and associated with the acrosome-phase and maturation-phase spermatids contribute between 14 and 17% to Sertoli cell volume. During phase 3 the ER pinches off a large number of small, smooth-walled vesicles filled with flocculent content. The contact area between Sertoli cells and other tubular constituents changes considerably during the different phases. It is concluded that the blood-testis barrier is particularly impassible during phases 1 and 8. A lipid cycle does not exist in the bovine testicular tubular epithelium.

Animals↗
PubMed1988

Postnatal development of the tubular lamina propria and the intertubular tissue in the bovine testis.

The postnatal development of intertubular cells and vessels and of the tubular lamina propria was studied in three locations of perfusion-fixed bovine testes from 31 animals ranging from 4 to 78 weeks. The postnatal morphological differentiation of the testis is not uniform, regional differences have to be considered. The intertubular cell population is composed of mesenchyme-like cells, fibrocytes, Leydig cells, peritubular cells and mononuclear cells. In 4- and 8-week-old testes mesenchyme-like cells are the dominating element. These pluripotent cells proliferate by frequent mitoses and are the precursors of Leydig cells, contractile peritubular cells and fibrocytes. Morphologically differentiated Leydig cells are encountered throughout the entire period of postnatal development. In 4-week-old testes degenerating fetal and newly formed postnatal Leydig cells are seen in juxtaposition to each other. From the 8th week on, only postnatal Leydig cells are present. Between 16 and 30 weeks large-scale degeneration of prepuberal Leydig cells is observed. The Leydig cells that survive this degenerative phase constitute the long-lasting adult population. 20-30% (numerically) of all intertubular cells at all ages are free mononuclear cells. These are found as lymphocytes, plasma cells, monocytes, macrophages and light intercalated cells (LIC). The latter are monocyte-derived, Leydig cell-associated typical cells of the bovine testis. The differentiation of the two main components of the tubular lamina propria, (i) basal lamina and (ii) peritubular cell sheath, seems to be effected rather independent from each other and also from hormonal signals important for the development of the germinal cells. The laminated basal lamina reaches nearly 3 micron at 16 weeks and is later on continuously reduced. At 25 weeks the peritubular cells have transformed into contractile myofibroblasts. At this period the germinal epithelium is still in a prepuberal state.

Aging↗