The Treatment of Missing Values in Logistic Regression

The efficiencies of the estimators in the linear logistic regression model are examined using simulations under six missing value treatments. These treatments use either the maximum likelihood or the discriminant function approach in the estimation of the regression coefficients. Missing values are assumed to occur at random. The cases of multivariate normal and dichotomous independent variables are both considered. We found that in general, there is no uniformly best method. However, mean substitution and discriminant function estimation using existing pairs of values for correlations turn out to be favourable for the cases considered.     

Distribution of sugar residues in the bovine testis during postnatal ontogenesis demonstrated with lectin-horseradish peroxidase conjugates

Summary In the present study the distribution of various sugar residues in the cells of the male gonad during postnatal organogenesis was examined employing eight lectin-horseradish peroxidase conjugates (BS-I, ConA, DBA, PNA, RCA-I, SBA, UEA-I, WGA) on paraffin-embedded testicular tissue. The tissue was obtained from bull calves and young bulls of recorded age (4, 8, 16, 20, 25, 30, 40 and 52 weeks) and two adult bulls. During the whole observation period, lectin affinity in the developing testicular tubules was restricted to the germ cell line, while the Sertoli cells and their precursors remained completely unstained. DBA, a lectin with specific affinity to -d-GalNAc, served as a selective marker for prespermatogonia (PSG), the only precursors of bovine spermatogonia until the onset of spermatogenesis at week 30. -d-GalNAc, detected in the PSG Golgi zone and its vicinity, seems to play an important role during PSG proliferation and migration in the prepuberal testis. Concomitant with the differentiation of PSG into spermatogonia, the binding intensity of DBA to the Golgi zone of these cells decreased. After the gradual onset of spermatogenesis, the lectins revealed staining of Golgi complexes of most germ cell stages. Glycosylation of the cell components takes place in the Golgi complex, which explains the strong affinity of the lectins to this cell compartment. Inner and outer membrane of the acrosomal complex of spermatids, especially during Golgi and cap phase of spermiogenesis, were intensely stained with PNA, RCA-I and SBA. This staining disappeared in the maturation phase at the latest and indicates a role of terminal d-Gal-(13)-d-GalNAc, d-Gal and d-GalNAc during the formation of the sperm head and intraepithelial orientation of the spermatid. Other parts of the spermatid, such as the anulus and the cytoplasmic droplet, exhibited d-Gal, d-GlcNAc or sialic acid and d-GalNAc. In the intertubular tissue BS-I, RCA-I and UEA-I bound to vascular endothelia. Components of the intertubular extracellular matrix were stained with ConA (-d-Man), RCA-I (d-Gal), UEA-I (-l-Fuc) and WGA (d-GlcNAc or sialic acid).     

Histochemical localization and quantification of glucose-6-phosphate dehydrogenase in bovine leydig cells

Some of the critical steps in the qualitative histochemical localization of glucose-6-phosphate dehydrogenase (freezing procedures, incubation techniques and the influence of intermediate electron carriers, respiratory chain inhibitors and different tetrazolium salts) were evaluated in sections of bovine testis as a prerequisite for the microdensitometric estimation of the activity of the enzyme in bovine Leydig cells in situ. A modification of the gel incubation method of Rieder et al. (1978) gave the best results and was used for the quantitative investigations. Quantitative data for the dehydrogenase activity gained from microdensitometry of the formazan final reaction products in Leydig cells in situ were compared with the results of assays of the activity in homogenates of testis. The following apparent kinetic properties of glucose-6-phosphate dehydrogenase were obtained for the enzyme in Leydig cells in situ: Vmax = 0.11 absorbance units/min, Km = 0.37 mM. The quantitative characterization of glucose-6-phosphate activity in Leydig cells in situ appears to be suitable for combined morphological and functional diagnoses of small tissue samples such as testicular biopsies. This would give valuable information of the functional status of Leydig cells in normal and diseased testicular tissue.     

Morphologische Untersuchungen an der Glandula bulbourethralis der Katze

Zusammenfassung Das Parenchym der Glandula bulbourethralis der Katze besteht aus weitlumigen, gebuchteten intraglandulären Gängen, in welche kurze, englumige, zumeist unverzweigte Tubuli einmünden. Der Drüse fehlt eine äußere Organkapsel, so daß ihre peripheren Tubuli stellenweise direkt zwischen den Fasern des quergestreiften M. bulboglandularis liegen. Die Drüsentubuli und die Buchten der intraglandulären Gänge sind mit einem einschichtigen Zylinderepithel ausgekleidet, auf den Gangfalten ist das Epithel abschnittsweise mehrreihig, Die sezernierende Epitheloberfläche ist durch die Ausbildung von interzellulären Sekretkapillaren vergrößert. Breite Zwischenzellspalten (Durchmesser etwa 1,5), in welche schlanke interdigitierende Cytoplasmafortsätze hineinragen, erstrecken sich von der Basalmembran bis kurz unter das Tubulusbzw. Ganglumen. Die lumenseitigen Zellgrenzen tragen einige stummelförmige Mikrovilli und besitzen zerklüftete Außenkonturen, die durch glykogenreiche Cytoplasmaprojektionen bedingt sind. Alle Epithelzellen sind reich an Mitochondrien. Die supranuklearen Abschnitte der meisten Gang- und Tubuluszellen enthalten Sekretgranula, welche im Elektronenmikroskop unterschiedliche optische Dichten aufweisen können. Die Granula enthalten ein PAS-positives, neuraminsäurehaltiges epitheliales Muzin, das in einzelnen Sekretkörnchen auch eine histochemische Reaktion auf Sulfatgruppen gibt. Alle Epithelzellen reagieren sehr stark auf unspezifische Esterase und stark auf -D-Glucuronidase, -D-Glactosidase sowie die Enzyme des Citronensäurezyklus, der Glykolyse und der Atmungskette (NAD-ICDH, SDH, ALD, LDH, ADH, GDH, NADH-T-Red, Cyt-Ox).

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Morphological studies on the bulbourethral gland of the male cat

Summary The bulbourethral glands of sexually mature male cats are studied with the light and electron microscope. The parenchyma consists of spacious, sinus-like intraglandular ducts and short, narrow, mostly unbranched tubular endpieces. The gland has no complete connective tissue capsule, consequently some of the peripheral tubules are situated directly in between the fibers of the surrounding bulboglandularis muscle. The endpieces and the sinus of the intraglandular ducts are lined by a simple columnar epithelium, whereas the folds of the ducts are generally covered by a low pseudostratified epithelium. The secretory surface of the cells is increased by intercellular canaliculi which communicate with the gland lumen. These canaliculi are identified on the light microscopic level by their strong 5-nucleotidase activity. Furthermore widened intercellular spaces (approximately 1,5 in diameter) filled with slender, interdigitating cytoplasmic processes extend from the basal lamina to the apical junctional complexes. The luminal cell pole exhibits some short microvilli and forms irregularly shaped, glycogen containing protrusions. Within the cytoplasm of the gland cells numerous spherical mitochondria, some dense bodies, a typical Golgi apparatus, free ribosomes and a poorly developed endoplasmic reticulum are to be observed. Secretory granules which can be grouped into three types on the basis of their electron density occur in the supranuclear regions of most of the cells. According to histochemical tests all granules contain a periodate reactive sialomucin and some of them also sulfate groups. The glandular parenchyma is site of an exceptionally strong unspecific esterase activity and is rich in -D-glucuronidase, -D-glactosidase, aldolase, -glycerophosphate dehydrogenase, lactate dehydrogenase, alcohol dehydrogenase, NAD-dependent isocitrate dehydrogenase, succinate dehydrogenase and cytochrome oxydase.

Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Zur Morphologie der braunen Inguinaldrüse des Kaninchens

Zusammenfassung Die braune Inguinaldrüse des Kaninchens ist eine einfach gebaute tubulöse Drüse. Das Epithel der Drüsenschläuche ist einschichtig kubisch bis hochzylindrisch und wird von spindelförmigen Myoepithelzellen unterlagert. Die Drüsenzellen besitzen nahezu organellenfreie, fein granulierte Cytoplasmaprotrusionen, die weit in das Lumen hineinragen; in der Lichtung werden häufig isolierte Cytoplasmabereiche gefunden. Der Sekretionsmodus ist somit deutlich apokrin (decapitation secretion).Das endoplasmatische Retikulum ist überall in der Zelle zu erheblich zerklüfteten Cisternen erweitert; Golgi-Apparate sind spärlich. Große, matrixreiche Mitochondrien zeichnen sich durch Armut an Cristae aus. Elektronendichte Sekretpfützen liegen vornehmlich supranukleär; Sekretvakuolen kommen nicht vor.

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On the morphology of the brown inguinal gland of the rabbit

Summary The tubular brown inguinal glands of the rabbit have been studied by light and electron microscopy. The apocrine secretory cells are columnar elements with prominent apical cytoplasmic caps and protrusions extending into the glandular lumen. These protrusions contain neutral mucopolysaccharides demonstrable by light microscopy. The secretory cells are characterized by the presence of large mitochondria with scant cristae and an electron dense matrix. Electron dense plaques, presumably secretory masses, are present in the supranuclear cytoplasm. The cytoplasm contains cisternae of a granular endoplasmic reticulum. Myoepithelial cells are situated between the secretory cells and the basal lamina.

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Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Die Histotopik einiger Oxydoreduktasen im Hoden von Hund und Katze

Zusammenfassung Im Hoden von Hund und Katze werden folgende Enzyme histochemisch nachgewiesen: NADH-Tetrazoliumreduktase (NADH-T-Red), NADPH-Tetrazoliumreduktase (NADPH-T-Red), Cytochromoxydase (Cyt-Ox), Lactat-Dehydrogenase (LDH), Aldolase (ALD), Alkohol-Dehydrogenase (ADH), Glycerin-1-phosphat-Dehydrogenase (GDH), Glucose-6-phosphat-Dehydrogenase (G-6-PDH), Succinat-Dehydrogenase (SDH), NAD-spezifische Isocitrat-Dehydrogenase (NAD-ICDH). Die starke Fermentaktivität der G-6-PDH und der LDH in den Leydig-Zellen beider Spezies, der relativ hohe Gehalt an histochemisch nachweisbarer ADH in den Zwischenzellen der Katze sowie eine deutliche Reaktion auf GDH in den Sertoli-Zellen der Katze werden diskutiert.

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Summary In the testes of dog and cat the distribution pattern of NADH-tetrazolium reductase, NADPH-tetrazolium reductase, cytochrome oxydase, lactate dehydrogenase, aldolase, alcohol dehydrogenase, -glycerophosphate dehydrogenase, glucose-6-phosphate dehydrogenase, succinate dehydrogenase and NAD specific isocitrate dehydrogenase was studied by histochemical means. The strong reaction of G-6-PDH and LDH in the Leydig cells of both species, the relatively high amount of ADH in the interstitial cells of the cat testis and the principal site of -GPDH in the Sertoli cells of the cat are discussed.

     

The bovine tubouterine junction: general organization and surface morphology

The bovine tubouterine junction is composed of three parts (terminal tubal segment, transition region proper, uterine apex) and follows a sigmoidal course displaying a tubal and an uterine curvature. In the terminal tubal segment, 4–8 primary longitudinal folds and a system of lower secondary folds, ridges and chords project into the centrally located lumen. The transition region proper possesses a slit-like lumen because of the existence of a thick mucosal pad containing the first uterine glands. The longitudinal primary folds of the tube broaden, flatten and start to diverge when they reach the transition region proper. The mucosal pad and broadened folds are heavily vascularized. A system of lateral outpocketings with blind ends pointing in an ampullary direction develops between the primary and secondary folds, the ridges and chords of the terminal tubal segment and transition region proper. From the bottom of these outpocketings, short tubulo-alveolar crypts originate. The mucosa of the uterine apex forms low transversal ridges. The musculature of the bovine tubouterine junction is divided into a continuous circular or spiral intermediate layer, flanked by inner and outer longitudinal layers. The outer longitudinal layer is incomplete in the terminal tubal segment but increases in thickness to form a continuous stratum in the uterine apex. An inner longitudinal layer occurs only in the terminal tubal segment where it is best developed in the bases of the primary longitudinal folds. The simple columnar surface epithelium of the tubouterine junction contains ciliated and non-ciliated cells. The former undergo cyclical changes, and increase during estrus and postestrus. During proestrus, groups of non-ciliated cells display bulbous apical protrusions. During proestrus and estrus, circumscribed epithelial lesions expose the underlying basal lamina.     

Pattern-based clustering of daily weigh-in trajectories using dynamic time warping

“Smart”-scales are a new tool for frequent monitoring of weight change as well as weigh-in behavior. These scales give researchers the opportunity to discover patterns in the frequency that individuals weigh themselves over time, and how these patterns are associated with overall weight loss. Our motivating data come from an 18-month behavioral weight loss study of 55 adults classified as overweight or obese who were instructed to weigh themselves daily. Adherence to daily weigh-in routines produces a binary times series for each subject, indicating whether a participant weighed in on a given day. To characterize weigh-in by time-invariant patterns rather than overall adherence, we propose using hierarchical clustering with dynamic time warping (DTW). We perform an extensive simulation study to evaluate the performance of DTW compared to Euclidean and Jaccard distances to recover underlying patterns in adherence time series. In addition, we compare cluster performance using cluster validation indices (CVIs) under the single, average, complete, and Ward linkages and evaluate how internal and external CVIs compare for clustering binary time series. We apply conclusions from the simulation to cluster our real data and summarize observed weigh-in patterns. Our analysis finds that the adherence trajectory pattern is significantly associated with weight loss.     

Vascular morphology of the bovine spermatic cord and testis

Summary The highly coiled testicular artery within the bovine spermatic cord has a constant luminal diameter but a continuously decreasing mural thickness. The pampini form plexus is composed of three interconnected venous networks differing in mesh sizes and calibres. The large veins of the first network display pouches and permanent constrictions, which may serve as throttle devices. The constitutents of the third network are venules or venous capillaries with diameters between 10 and 20 m; they favor a periarterial position or even occupy the media-adventitia border of the testicular artery. All plexus veins are devoid of valves. The existence of true arteriovenous anastomoses between smaller branches of the testicular artery and plexus veins was established by serial sections. The vascular morphology of the spermatic cord is discussed with special attention to a postulated venous-arterial steroid transfer in this region.Supported by the Deutsche Forschungsgemeinschaft and the Stiftung zur Förderung der wissenschaftlichen Forschung an der Universität Bern     

Intertubular topography in the bovine testis

Summary The intertubular stroma of the bovine testis is composed of narrow strands between two adjacent tubules and larger tri- and quadrangular interstices between three to four tubules. The latter contain the majority of Leydig cells, larger blood vessels and testicular lymph vessels. Ley dig cells occur in groups or cords, not every cell being in close contact to a capillary, lymph vessel or venule. Between adjacent Leydig cells intercellular canaliculi and gap junctions are frequently encountered. Bovine Leydig cells are further characterized by an abundance of ribosome-associated endoplasmic reticulum, by mitochondria often containing crystalloid structures and displaying both tubular and lamelliform cristae, as well as by a relative paucity of lipid droplets and lysosomes. Independent of the size of intertubular lymph vessels their walls consist only of an endothelium of varying thickness, no typical basal lamina or associated musculature being present. The interstitial surface of the endothelium sends anchoring cytoplasmic pedicles into the subjacent ground substance and collagen fibrils. Among occasional plasma cells, mast cells and mononuclear leucocytes, a regular constituent of the intertubular region studied is a population of electron-lucid, irregularly shaped cells (light intercalated cells = LIC) with slender, pleomorphic processes. These cells are believed to be involved in testicular androgen storage and distribution.Supported by a grant from the Deutsche Forschungsgemeinschaft