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PubMed1990

[Prosthetic possibilities with the Denar "Steri-Oss" implant].

Implantology, very frequently presented under only the surgical angle, must in fact be approached from a biological and functional point of view. The analysis of the future prosthetic situation will allow an overall treatment scheme to be established, in which periodontics, surgery, prosthodontics and occlusal equilibration will follow each other in order to achieve the functional rehabilitation. In the first part of this article, the various steps which make up the treatment scheme are briefly and quickly described. It is imperative to approach them according to this chronological order when there is any treatment involving implants. While implantology involved only one surgical session a few years ago, it now involves two: the first, consisting of placing the implant in the living tissues, and the second, at some months interval from the first, allowing the endo-osseous portion to be attached to the future prosthesis. These two surgical acts are inter-dependent. Given the wide array of systems proposed and the quantity of "Implant-Prosthesis" connections produced in each system, the practitioner does not always know which kind of connection to choose or how to use it. The second part of the article is devoted to the study of the various connection possibilities between the Steri-oss implants and the prosthesis. The methods for lining up the cores in relation to the others are studied in detail, as are the different possibilities for stabilising removable prosthesis. Some of the methods described can be used with other implant systems.

Dental Implantation, Endosseous↗
PubMed2026

A Practical Workflow for Spatial Transcriptomics Data Analysis: From Data Acquisition to Advanced Analyses.

Spatial transcriptomics (ST) profiles genome-wide gene expression while preserving the two-dimensional spatial context of mRNA molecules within tissue sections, enabling studies of tissue architecture and microenvironment-associated biology. However, ST analysis remains challenging because data import, quality control, integration, deconvolution, spatial statistics, and visualization often require multiple software environments and reproducible parameter choices. This protocol presents a practical computational workflow for public ST datasets in R, beginning with data acquisition and software setup and proceeding through Seurat-based data loading, quality control, normalization, multi-sample integration, clustering, and spatially variable gene analysis. The workflow then applies complementary deconvolution strategies, including reference-guided SPOTlight analysis and unsupervised STdeconvolve topic modeling, followed by Giotto-based spatial cell-cell communication analysis and interactive region-of-interest (ROI) selection using a custom Python Dash application. By emphasizing script-based execution, explicit parameter rationales, expected outputs, and troubleshooting checkpoints, the protocol provides an adaptable framework for standard array-based ST datasets and related platforms after dataset- and platform-specific parameter evaluation.

Spatial Transcriptomics↗
PubMed1992

Human in situ dosimetry: differential insertion loss during passage through abdominal wall and myometrium.

We constructed a specialized in vivo exposimetry system and determined selected ultrasonic field quantities. We examined two groups of non-pregnant women (nulliparas = 14, multiparas = 9) under conditions of full and empty bladder. A calibrated 7-element linear array hydrophone was placed in the anterior fornix of the vagina in each subject. In the full bladder condition, the sound beam traversed the anterior abdominal wall and full bladder, whereas after voiding, the sound beam traversed the abdominal wall and anteverted uterine fundus. Each study was conducted using a 3.5 MHz mechanical sector transducer. Calibration data were recorded after completion of each in vivo experiment. Data from both groups were pooled for analysis. Assuming (1) the sound path through the full bladder is loss less, the insertion loss (ILFULL) should represent the insertion loss for the abdominal wall (ILABD WALL) 8.2 +/- 5.6 dB; whereas (2) for the empty bladder condition, (ILEMPTY) represents (ILABD WALL+ILUTERUS). Subtracting ILFULL from ILEMPTY yields ILUTERUS = 5.8 +/- 6.8 dB. Therefore, knowing the respective path lengths and normalizing for frequency, the mean tissue attenuation coefficients (A) are estimated to be AABD WALL = 1.39 dB/cm-MHz and AUTERUS = 0.14 dB/cm-MHz. These attenuation data suggest that the abdominal wall is the principal source of ultrasonic energy loss.

Abdominal Muscles↗
PubMed2025

Altered DNA Methylation Pattern Contributes to Differential Epigenetic Immune Signaling in the Upper Respiratory Airway of Unvaccinated COVID-19 Patients.

SARS-CoV-2 infection remains a global health concern, with its impact on host immune responses not fully understood. In a case-control study, we examined how COVID-19 affects DNA methylation patterns in the upper respiratory airway of hospitalized individuals. DNA methylation arrays were performed on nasopharyngeal samples at inclusion/hospitalization and 6 weeks post-inclusion. We found a distinct DNA methylation pattern in COVID-19 patients compared to healthy controls, identifying 510,099 differentially methylated CpGs. Within the transcription start sites (TSSs) and gene body, COVID-19 patients displayed a higher number of genes/CpGs with elevated methylation levels. Enrichment analysis of TSS-methylated genes revealed effects of SARS-CoV-2 on genes associated with type I interferons, anti-viral and inflammatory responses, and immune functions. Some CpG methylations were transient, and normalized at group level by 6 weeks post-inclusion. Several IFN-regulated genes, including OAS1, OAS3, IFIT3, and MX1, were identified. Among the top regulators were IL17A and ERK1/2, both involved in inflammatory processes. Networks nodes included IGF1 and EGF, associated with processes including tissue repair and activation of immune responses. Overall, our data suggests that COVID-19 can impact the upper airway by modifying gene methylation patterns. This could have implications for conditioning of the airways, how individuals respond to future airway infections, and therapeutic interventions.

Humans↗
PubMed1986

Design and fabrication of a capillary cell culture chamber for the study of convective flow.

The use of capillary culture chambers as artificial pancreas and artificial liver devices would be aided by an improved ability to control the movement of molecules through the capillary walls. The modeling and analysis of the flow and mass transfer in capillary cell culture chambers in which cultured mammalian cells are grown to form masses with tissue density in the extra-capillary spaces is desirable as a basis for scaleup and optimization of the particular microenvironment. The relative roles of diffusion and ultrafiltration with convection in enhancing mass transfer across the capillary membranes are poorly understood in real cell cultures and the effects on culture viability of flow conditions chosen to promote convective flow across the capillary membranes and through the cultured cell masses are also of interest. In this report, experience with materials and techniques for fabricating capillary culture chambers with a more readily analyzed fully defined regular geometric relationship between 90 to 100 capillaries in a parallel bundle is described. High and low pressure capillaries were interspersed in a regular array. Evidence is presented for retention of cell viability during flow conditions which were chosen to induce convective flow through the cultured cells in such a chamber.

Artificial Organs↗
PubMed1991

Isocratic high-performance liquid chromatography-photodiode-array detection method for determination of lysine- and arginine-vasopressins and oxytocin in biological samples.

A simple, isocratic, sensitive (1 ng), and specific high-performance liquid chromatographic (HPLC) method based on photodiode-array detection (PAD) is described for simultaneous quantitation of the bioactive peptides, lysine vasopressin (LVP), arginine vasopressin (AVP) and oxytocin (OXY). Acidified pig plasma and left ventricular (LV) tissue samples were first extracted with Sep-Pak C18 columns, and the bioactive peptides were eluted with methanol, then dried at 37 degrees C and reconstituted with HPLC mobile phase. The bioactive peptides were separated by HPLC on a Dynamax 3009-A C8 column with a mobile phase of 0.1% trichloroacetic acid-50 mM heptanesulfonic acid-30mM triethylamine-20% acetonitrile in water, pH 2.5 and identified with a Waters 990-PAD system (spectrum index plots in the range 200-400 nm). Standards of LVP, AVP and OXY and their mixtures showed a linear increase in the range 5 to 100 ng and were eluted at 6.1, 6.9 and 4.6 min, respectively. Spectrum analysis showed a distinct absorption peak at 280 nm, corresponding to peptide bonds. The reproducibility of the method coefficient of variation for standards is 6.9, 5.8 and 4.7% for LVP, AVP and OXY, respectively. In plasma and tissue it is much higher: 12.9% (LV tissue) and 18.6% (plasma) for LVP. Pig plasma contains negligible amounts of AVP and OXY; LVP is much higher (0.28 +/- 0.19 ng/ml). In pig tissue, LVP predominates (6.95 ng/g wet weight) compared to AVP (1.45) and OXY (1.50). Spectral analysis is necessary to identify the bioactive peptide peaks among interfering substances and to increase the sensitivity four-fold. The method described here is useful for the simultaneous determination of LVP, AVP and OXY in the nanogram range and can be extended to picogram levels by employing PAD spectral analysis techniques.

Animals↗
PubMed1984

Electron microscopic evidence for RNA polymerase loading at repeated sequences in non-transcribed spacers of D. virilis.

The organization of transcribed and non-transcribed sequences in transcriptionally active ribosomal DNA (rDNA) chromatin from Drosophila virilis nurse cells (excluding follicle cells) was examined by electron microscopy. Nuclear spread preparations revealed that the actively transcribing rRNA genes (rTUs) exhibited a single uniform length distribution (7 +/- 0.5 kb). Non-transcribed 'spacer' regions separating active rTUs were, on the other hand, quite heterogeneous in length with a mean of 1.95 +/- 1.4 kilobase pairs (kb). Within each 'spacer' segment of chromatin two morphologically distinct regions were discernable: (1) A fiber-free region adjacent to the 3' termination site of the preceding rTU which accounted for the majority of each non-transcribed 'spacer'. This region was highly heterogeneous in length, and was termed the 'Non-repetitive Spacer' (NRS). (2) A short region, largely uniform in length, which was located immediately 5' to each rTU. This region was covered by a linear array of RNA polymerase molecules with a few very short fibers. The arrangement of polymerase in these arrays and their proximity to rRNA coding sequences appeared to be morphologically indicative of multiple initiation sites which are thought to be present in this region of the non-transcribed spacer as evidenced by direct sequence analysis (Coen, E S & Dover, G A, Nucl acid res 10 (1982) 1017 and Miller, J R et al., Nucl acid res 11 (1983) 11) [6, 18]. The data suggest that the repeated sequences in the non-transcribed spacer region serve as multiple in vivo loading and/or initiation sites for RNA polymerase I. Our results further indicate that, although an estimated 75% of the ribosomal RNA genes in Drosophila virilis are interrupted by an intron in the 28Sb gene sequence (Barnett, T & Rae, P M M, Cell 16 (1979) 763) [1], none of those genes appear to be transcribed to any appreciable extent in the tissues examined. It is also reasonable to infer that the actively transcribing uninterrupted genes (and therefore the intron-containing genes as well) are clustered and not randomly interspersed.

Animals↗
PubMed1987

Circus movement in the canine atrium around the tricuspid ring during experimental atrial flutter and during reentry in vitro.

A Y-shaped lesion in the right atrium allows induction of atrial flutter in dogs. We recorded the activation sequence during this tachycardia from 96 endocardial bipolar electrodes using intracavitary electrode arrays during 12 separate episodes in three isolated perfused hearts. In each case a reentrant impulse circulated around the tricuspid valve orifice in either a clockwise or counter-clockwise direction. Cutting the pathway terminated the rhythm and prevented its reinduction. There was no discrete segment of markedly slow conduction in the reentrant circuit. The tachycardia cycle length was decreased by methacholine and increased by lidocaine. Reentry was also induced in atrial tissue around the tricuspid orifice when this structure was isolated and superfused in vitro. Tachycardia cycle lengths varied from 205 to 399 msec, depending on the circumference of the ring and temperature. Induction of tachycardia by premature stimulation depended on differences in the duration of the effective refractory period among parts of the ring. Conduction velocity was relatively uniform and was slower during tachycardias than during pacing at long cycle lengths. Analysis of the response to premature stimuli that reset the tachycardia provided evidence for incomplete recovery of excitability between depolarizations during the tachycardia. Fast-response action potentials were recorded throughout the pathway and up to six to eight cell layers deep. Histologic studies showed the supravalvular lamina, a circumferential band of fibers several cell layers below the endocardial surface, to be continuous around the tricuspid orifice. Propagation through this layer best explains the conduction velocities observed in the intact heart during flutter in this preparation.

Action Potentials↗
PubMed1988

In vitro estimation and imaging of attenuation coefficients and instantaneous frequency for breast tissue characterization.

For breast tissue characterization, three acoustic parameters, integrated attenuation coefficient(IAC), frequency-dependent attenuation coefficient(FDAC) and instantaneous frequency(IF), were estimated in vitro and processed to make images of these parameters for resected human breast specimens. Experimental system with a 5 MHz center frequency was used and the same estimating and imaging system was connected with a clinical diagnostic device with a 7.5 MHz annular array probe (Aloca SSD 270) for in vivo type studies. To estimate these parameters, fast Fourier transform and spectral difference method were adopted for IAC and FDAC and the Hilbert transform for IF. Large statistical variances were found in the estimated values of these parameters. These dispersions of data may be due to insufficient size and tissue heterogeneity of the breast specimens. Additional miscellaneous problems may be involved. However, all of these can be, in part, overcome by averaging procedures. The significance of estimating and imaging these parameters for breast tissue characterization was discussed.

Acoustics↗
PubMed1992

Identification of a 58-kilodalton cell surface fibrinogen-binding mannoprotein from Candida albicans.

Treatment of both yeast (blastoconidia) and hyphal (blastoconidia with germ tubes) cells of Candida albicans with beta-mercaptoethanol (beta ME) releases a complex array of cell wall-bound proteins and glycoproteins. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western immunoblotting with fibrinogen-anti-fibrinogen antibody allowed the identification of a 58-kDa mannoprotein (mp58) in both extracts which specifically interacts with human fibrinogen. Treatment of intact cells with low concentrations of beta-glucanase (Zymolyase 20T) for short periods or with beta ME abolished or significantly reduced binding of fibrinogen. A rabbit polyclonal antiserum was raised against the purified mp58 species released by beta ME from germinated blastoconidia (PAb anti-mp58). By Western blotting, the antiserum cross-reacted with the homologous 58-kDa fibrinogen-binding mannoprotein present in beta ME extracts from blastoconidia, and by indirect immunofluorescence, the antiserum labelled both yeast cells and hyphae, yet reactivity was found primarily on the cell surface of filamentous forms. Immunostaining of human infected tissue sections with PAb anti-mp58 showed that the mp58 species is also expressed in vivo; in this case, the species is in the forms of both yeast and hyphal elements similarly labelled by the antiserum. Purified immunoglobulin G fraction from the antiserum did not alter the binding of fibrinogen as determined by a modified enzyme-linked immunosorbent assay and Western blotting. The N- and O-glycosidically linked carbohydrates represent 18 to 20% and 3 to 4%, respectively, of the molecular mass of the mp58. O-linked sugar residues may be involved in the interaction of the molecule with fibrinogen.

Animals↗
PubMed1985

A comparison of deep regional hyperthermia from an annular array and a concentric coil in the same patients.

Twenty-two patients with advanced pelvic or abdominal malignancy (or both) were treated on successive occasions with hyperthermia produced by an annular array (AA) (60-80 MHz, 500-1800 W forward power) and a concentric coil (CC) (13.56 MHz, 350-1000 W forward power). Both devices were compared with respect to acute toxicity and power limitations. There was no power limiting factor in pelvic heating in 7/14 patients treated with the AA, however 13/14 experienced power limiting sacrococcygeal pain with the CC. The 9 patients who underwent abdominal heating had a variety of power limitations with both devices. Thermal mapping was performed in 23 treatments with the AA and in 19 with the CC. Composite thermal maps of patients with similar thermometry sites show that heating patterns produced by the CC were predictable from theory and static phantom measurements. The AA achieved broader regional heating, particularly at depth, but heating patterns were less predictable. Spatial thermal dose (TD) analysis revealed higher minimum tumor TDs and more favorable mean tumor/normal tissue TD ratios with the AA than with the CC. We conclude that the AA is superior to the CC for pelvic treatment and that both devices have limitations in abdominal treatment.

Abdominal Neoplasms↗
PubMed1986

Regional hyperthermia for clinically advanced deep-seated pelvic malignancy.

Forty-three patients with deep-seated pelvic malignancy have been treated at the University of Utah on a pilot protocol involving regional hyperthermia (HT) produced by the BSD-1000 HT system and the annular phased array applicator (AA) usually driven at 60 MHz. Acute toxicity consisted primarily of pain within the AA aperture (74%), pain outside the aperture (33%), and bladder spasm (26%) or systemic stress (25%). Systemic stress only infrequently was power limiting. The most common power-limiting factors were pain (33%) and excessive heating of normal tissues (23%). In 9 patients (21%), there was no power-limiting factor. Treatment-related complications were uncommon and consisted of superficial second degree burns (3 patients), small bowel obstruction (1 patient), and rectal fistula (1 patient), all of which resolved with supportive nonsurgical therapy. Detailed thermal mapping and thermal dosimetry were performed on 36 patients. Thermal dosimetry parameters were all rather disappointing; however, the protocol prioritized the prevention of complications, and patients with acute toxicity or other power-limiting factors were not pushed to achieve high thermal doses. A logistic regression analysis was performed to determine if any factors were correlated with response (PR + CR). "Concurrent radiation dose" and "number of satisfactory heat treatments" were highly and independently correlated with response (p = 0.002). Responders (median survival = 10 months) survived significantly longer (p = 0.0014) than nonresponders (median survival = 4 months). Four of the responders are alive and currently without evidence of disease.

Humans↗
PubMed1988

Distribution of a 69-kD laminin-binding protein in aortic and microvascular endothelial cells: modulation during cell attachment, spreading, and migration.

Affinity chromatography and immunolocalization techniques were used to investigate the mechanism(s) by which endothelial cells interact with the basement membrane component laminin. Bovine aortic endothelial cells (BAEC) membranes were solubilized and incubated with a laminin-Sepharose affinity column. SDS-PAGE analysis of the eluted proteins identified a 69-kD band as the major binding protein, along with minor components migrating at 125, 110, 92, 85, 75, 55, and 30 kD. Polyclonal antibodies directed against a peptide sequence of the 69-kD laminin-binding protein isolated from human tumor cells identified this protein in BAEC lysates. In frozen sections, these polyclonal antibodies and monoclonal antibodies raised against human tumor 69-kD stained the endothelium of bovine aorta and the medial smooth muscle cells, but not surrounding connective tissue or elastin fibers. When nonpermeabilized BAEC were stained in an in vitro migration assay, there appeared to be apical patches of 69 kD staining in stationary cells. However, when released from contact inhibition, 69 kD was localized to ruffling membranes on cells at the migrating front. Permeabilized BAEC stained for 69 kD diffusely, with a granular perinuclear distribution and in linear arrays throughout the cell. During migration a redistribution from diffuse to predominanately linear arrays that co-distributed with actin microfilaments was noted in double-label experiments. The 69-kD laminin-binding protein colocalized with actin filaments in permeabilized cultured microvascular endothelial cells in a continuous staining pattern at 6 h postplating which redistributed to punctate patches along the length of the filaments at confluence (96 h). In addition, 69 kD co-distribution with laminin could also be demonstrated in cultured subconfluent cells actively synthesizing matrix. Endothelial cells express a 69-kD laminin-binding protein that is membrane associated and appears to colocalize with actin microfilaments. The topological distribution of 69 kD and its cytoskeletal associations can be modulated by the cell during cell migration and growth suggesting that 69 kD may be a candidate for a membrane protein involved in signal transduction from extracellular matrix to cell via cytoskeletal connections.

Actin Cytoskeleton↗
PubMed1991

Three-dimensional characterization of human ventricular myofiber architecture by ultrasonic backscatter.

Normal human left ventricular architecture comprises a highly aligned array of cardiac myofibers whose orientation depends on transmural location. This study was designed to determine whether measurement of integrated backscatter could be used detect the progressive transmural shift of myofiber alignment that occurs from epicardium to endocardium in human ventricular wall segments. Integrated backscatter was measured at 32 transmural levels in seven cylindrical biopsy specimens (1.4 cm diam) sampled from normal regions of six explanted fixed human hearts by insonification of samples at 180 independent angles in 2 degrees steps around their entire circumference with a 5-MHz broadband piezoelectric transducer. Histologic analysis was performed to determine fiber orientation. Integrated backscatter varied approximately as a sinusoidal function of the angle of insonification at each transmural level. Greater integrated backscatter was observed for insonification perpendicular as compared with parallel to fibers (difference = 14.5 +/- 0.6 dB). Ultrasonic analysis revealed a progressive transmural shift in fiber orientation of approximately 9.2 +/- 0.7 degrees/mm of tissue. Histologic analysis revealed a concordant shift in fiber orientation of 7.9 +/- 0.8 degrees/mm of tissue. Thus, human myocardium manifests anisotropy of ultrasonic scattering that may be useful for characterization of the intramural fiber alignment and overall three-dimensional organization of cardiac myofibers.

Heart Diseases↗
PubMed1989

Distribution of gap junctions and square array junctions in the mammalian lens.

The morphology of membrane specializations of the cortex and nucleus of bovine lenses has been analyzed for both isolated membrane fractions and intact tissue fragments. Fractions of fiber cell membranes isolated from the outer cortex and the inner nucleus of lenses have been compared using x-ray diffraction, electron microscopy, SDS polyacrylamide gels and Western blots. Each fraction has distinctive structural characteristics. In x-ray experiments, the cortical fraction gives no sharp equatorial reflections (from the plane of the membrane), whereas the nuclear fraction gives sharp equatorial reflections which index on a square lattice of 6.6 nm. In thin-section electron micrographs, the cortical fraction is composed primarily of closed vesicles and flat membrane sheets, some of which contain pentalamellar structures similar in appearance to the 16-18 nm thick gap junctions found in other tissues. The nuclear fraction contains mostly undulating membrane pairs which often show 11-14 nm pentalamellar profiles and occasionally thicker junctions. In freeze-fracture images the cortical membranes display irregular clusters of intramembrane particles which resemble gap junctions, whereas the nuclear membranes contain numerous large square arrays with a 6.6 nm repeat and few irregular clusters or individual intramembrane particles. Images of fragments of intact lenses used in the membrane isolations give similar results; in the cortex the area covered by gap junctions is over 50 times the area covered by square lattices, whereas nuclear fiber cell membranes contain large square arrays. Thus, cortical and nuclear fiber cell membranes have quite different morphologies. In particular, the size of the square arrays of protein increases as the fiber cells mature. SDS polyacrylamide gels from cortical and nuclear fractions are similar in that they both contain MP26 as the major band. However, Western blot analysis shows increasing quantities of lower molecular weight, 25 kD and 22 kD, cleavage products as one progresses from the cortex to the nucleus. These data indicate that MP26 and/or its cleavage products form square crystalline arrays in nuclear fibers. The morphology of these arrays suggests a role for MP26 in cell-to-cell adhesion.

Animals↗
PubMed1982

Preservation of mesangium and immunohistochemically defined antigens in glomerular basement membrane isolated by detergent extraction.

To define the characteristics of isolated glomerular basement membrane (GBM), immunohistochemical and morphometric analyses have been carried out on rat and human tissues. Site-specific arrays of antigens were identified in detergent-isolated GBM in a distribution similar to that observed in intact kidney. In the human, fibronectin, procollagen IV, and collagen V were observed along the internal aspect of GBM continuous with antigenic sites in the mesangium. Another array of antigens was identified in the GBM but not within the mesangium--Goodpasture's antigen, bovine lens capsule type IV collagen, and amyloid P component. In addition, sites reactive with rabbit antiserum to laminin were present on both sides of the lamina densa as well as within the mesangial region. Actomyosin, a presumed mesangial cell antigen persisted in the mesangium of isolated GBM. Mesangial matrix was identified in detergent-isolated GBM in an amount equivalent to that present in intact glomeruli. Sonicated GBM contained the same antigens but it was not possible to quantitate the amount of mesangial material by immunofluorescence or morphometric analysis. The thickness of the lamina densa was greater in sonicated and detergent-treated rat GBM preparations than in native rat kidney. These studies demonstrated that isolated GBM is heterogeneous with respect to its antigenic constituents and in addition contains mesangial matrix, which is morphologically and immunohistochemically distinct from peripheral GBM.

Actomyosin↗
PubMed1983

Quantitative autoradiography with radiopharmaceuticals, Part 1: Digital film-analysis system by videodensitometry: concise communication.

A simple low-cost digital film-analysis system using videodensitometry was developed to quantitate autoradiograms. It is based on a TV-film analysis system coupled to a minicomputer. Digital sampling of transmitted light intensities through the autoradiogram is performed with 8-bit gray levels according to the selected array size (128 X 128 to 1024 X 1024). The performance characteristics of the system provide sufficient stability, uniformity, linearity, and intensity response for use in quantitative analysis. Digital images of the autoradiograms are converted to radioactivity content, pixel by pixel, using step-wedge standards. This type of low-cost system can be installed on conventional mini-computers commonly used in modern nuclear medical facilities. Quantitative digital autoradiography can play an important role, with applications stretching from dosimetry calculations of radiopharmaceuticals to metabolic studies in conjunction with positron-emission tomography.

Animals↗
PubMed1989

Capillary growth in the mesentery of normal young rats. Intravital video and electron microscope analyses.

Capillary sprouting was studied by a combination of intravital video recording and subsequent electron microscopy in the mesentery of young female rats without previous experimental manipulation. Selected segments of the mesenteric microvascular bed with capillary sprouts were carefully surveyed and mapped at a monitor magnification of 255 times and submitted to detailed in vivo analysis concerning flow pattern and cells at 2000 times magnification. The mesentery was preserved for light and electron microscopy by a superfusion of glutaraldehyde while observed and recorded on video, confirming earlier investigations that this type of fixation does preserve exceptionally well vascular topography and diameters of the mesenteric microvascular bed. Capillary sprouts originated as endothelial spurs from arteriolar-venular arcades and continued to grow in size through a bipolar rearrangement of endothelial cells, forming a solid sprout tip which progressively lengthened by alternately rapid and slow growth phases. The extended leading tip of the migrating endothelial cells displayed microspikes and pseudopodia denuded of basal lamina. The cytoplasm of the leading tip contained an array of microtubules, 75 A filaments and many small vesicles. In similarity with the situation in nerve growth cones, all these organelles probably participate in cytoplasmic streaming and cell migration. The sprout lumen arose between endothelial cells of the solid sprout. Mesenteric connective tissue fibroblasts approached and settled down on the sprouts, being converted to pericytes as the fibroblasts became enveloped by a basal lamina. The pericytes reinforced the wall of the delicate and fragile capillary sprouts, and trapped plasma, platelets and red blood cells which had leaked out temporarily, in the process assuming an umbrella shape. The arteriolar feeder of the arcades was surrounded by cells which were classified as intermediate between pericytes and true smooth muscle cells. Sprouts that presumably were on the verge of merging with other capillaries were analyzed for indications of how anastomoses are formed.

Animals↗