Capillary Volume Density Research Articles

The volume density of cells and capillaries of the normal stria vascularis.

The purpose of this study was to provide morphometric (i.e. quantitative anatomical) data on the normal chinchilla stria vascularis. Five normal chinchillas were used in the present investigation and four regions of the cochlea were examined in each animal. The width, radial area and number of marginal cells across the stria's width increased from the cochlear apex toward the base. The increase in strial width and area appeared to be due to hyperplasia of the marginal cells. The mean total endolymphatic surface area of the stria vascularis was estimated to be 7.4 mm2 (S.E. = 1.23). The mean total volume of the stria vascularis was estimated to be 0.15 microliter (S.E. = 0.01). In addition, using a stereological method we found that the volume density of the cells and capillaries of the stria vascularis was constant along the length of the scala media. The mean (+/- S.E.) volume density of the stria cells and capillaries was estimated to be: marginal cells = 0.528 (0.013), intermediate cells = 0.212 (0.026), basal cells = 0.163 (0.009) and capillaries = 0.097 (0.009).

Dipyridamole-induced capillary endothelial cell proliferation in the rat heart--a morphometric investigation.

20 male Wistar rats were randomly divided into two equal groups. Each experimental rat was injected with 4 mg . kg-1 dipyridamole ip twice daily for 4 weeks, the control rats received sham injections of an equal volume of saline. The rats were fixed by retrograde vascular perfusion. Left ventricular papillary muscles were sampled for light and electron microscopic morphometry. By means of a combination of serial section reconstruction and morphometry we could demonstrate that the number of capillary endothelial cell nuclei per tissue volume had increased by 37% (P less than 0.01), whereas the average nuclear volume remained constant. All other morphometric parameters (volume densities of myocardial cells, capillaries, cellular and non-cellular interstitial tissue, and myocardial cell nuclei; surface area, diameter, and density of capillaries; volume densities of myofibrils, mitochondria, and sarcoplasmic matrix; surface areas of the inner and outer mitochondrial membranes; dimensions of average mitochondrial section profiles) were unchanged. We conclude that chronic dipyridamole application induces proliferation of capillary endothelial cells in the rat myocardium, possibly by an increase of myocardial blood flow.

Morphometrics of rapidly frozen goose lungs

To understand the structural basis of avian gas exchange better, we made a morphometric study of domestic and Canada goose lungs. The volume of glutaraldehyde-fixed domestic goose lungs (30 cm 3/kg body weight) was similar to that determined from silicone casts of Canada goose lungs by Duncker (33 cm 3/kg). To examine finer structures, we rapidly froze goose lungs under physiologic conditions, fixed tissue samples by a freeze substitution procedure and analyszed samples with stereological methods. From light micrographs we determined that about 55% of the lung is parabronchi in both species. Volume densities of air capillaries, blood capillaries and tissue and surface : volume ratios of these same structures were determined from electron micrographs. Our measurements agree with those from glutaraldehyde-fixed Canada goose lungs from other laboratories. Gas exchange surface area was largest in the good flier (Canada goose) but both birds had larger surface areas than comparably sized mammals. The harmonic mean blood-gas barrier thickness is smaller in both species of birds (0.3 μm) than in mammals. Thus, membrane diffusing capacities for gases should be larger in birds than in mammals. Pulmonary blood capillary transit time, as calculated from blood capillary volume and normal levels of cardiac output, are longer in birds than in mammals and should allow more time for blood-gas equilibrium. Pleats and folds were frequently observed in air and blood capillaries, suggesting that the avian lung may not be as rigid as was previously thought and that capillary volumes and surface areas may change under physiologic conditions.

Plasmalemmal vesicles in pulmonary capillary endothelium of developing fetal lamb lungs

In adult mammalian lungs pinocytotic vesicles (PV) play a role in macromolecular transport across endothelium. The time course of their development in fetal lungs was examined. Morphometric techniques were used to measure the relative capillary volume as percentage of lung volume. Mean diameter ( D ), numerical density ( N v), and endothelial fractional volume ( V v) represented by PV were determined in randomly selected capillaries, measuring 5.3–8.4 μm in diameter, from right upper (RUL) and left lower (LLL) lobes of lungs from fetal lambs ranging in gestational ages from 39 to 144 days. Three newborn lambs, 1 hr after birth, were also examined. There was a 20-fold increase in the volume density of capillaries during the period studied. The vesicular D ± SD was 739.6 ± 4.1 and 735.1 ± 2.8 Å in RUL and LLL, respectively, and remained unchanged throughout gestation. By contrast, following a gradual increase in N v from 24.7 to 65.1/μm 3 in the glandular stage (39–85 days), there was a rapid rise in N v during both canalicular (95–121 days) and alveolar (130–144 days) stages of development, reaching a final N v of 254.8/μm 3. In newborn lambs, 1 hr after birth, there was no significant change in N v. There was a significant correlation between N v and fetal age, but there was no difference in N v between RUL and LLL at any time. Thus, a more than 10-fold increase in N v of PV occurs in ovine pulmonary capillary endothelium during gestation, the biochemical and/or physiological basis of which remains to be determined. By contrast, observations made on coated vesicles indicate that N v of these structures does not change with gestation.

Morphometry of right ventricular hypertrophy induced by strenuous exercise in rat.

Effects on the myocardium, particularly those structural properties of the capillary network relevant to tissue oxygenation, were studied morphometrically in rats subjected to a severe running program. Physical conditioning produced a 31% increase in right ventricular weight and only a 12% increase in the weight of the left ventricle. Quantitative analysis of right ventricular myocardium demonstrated relative decreases in capillary luminal volume density (-27%) and capillary luminal surface density (-20%) and an increase in the average maximum distance from the capillary wall to the mitochondria of myocytes (14%). In contrast, the contractile mass expanded in proportion to the growth of the ventricle through augmentation of the cross-sectional area (17%) and length (19%) of the average myocyte. Evaluation of the subcellular constituents of myocytes showed no change in the mitochondria-to-myofibril volume ratio. In conclusion, the capillary bed controlling oxygen availability, diffusion, and transport suggests that excessive physical activity may be detrimental to the myocardium.

Adaptation of the growing lung to increased oxygen consumption. II. Morphometric analysis.

This paper is the second part of a study investigating the effect of increased O2 consumption on the lungs of growing animals. By means of injections of the drug IDPN (imino-betabeta'-dipropionitrile) hyperkinesia was permanently induced in white mice aged 3 weeks, thus increasing their Vo2 per gram body weight (= specific VO2) by 50%. 3 1/2 months later the lungs of these animals were fixed by standardized procedure, analysed by morphometric techniques and the results compared with those of control mice originating from the same litters. Whereas the specific weights (= weights per gram body weight) of various organs did not differ significantly in the two groups, the specific volume of the lungs fixed with standardized techniques was up by 23% in IDPN mice. The relative composotion of lung parenchyma was also altered: air space volume density was slightly but significantly reduced, whereas tissue and capillary volume densities were both increased by 15%. An analogous increase was detected in alveolar and capillary surface densities. These changes led to significantly higher specific capillary and tissue volumes, as well as higher specific gas exchange surface areas in DIPN mice. Therefore the morphometrically determined specific pulmonary diffusion capacity was increased by more than 40% in the IDPN-treated animals. The findings are compared with those hitherto reported, where a structural adaptation of the gas exchange apparatus to exercise or altered PO2 had been found. In view of our present knowledge of the postnatal lung growth the quantitative structural alterations found in this experiment indicate that the higher O2 requirements in IDPN mice induced an alteration in the septal morphology. This consisted in an augmentation of septal volume possibly due to a lengthening and corrugation of the intralveolar septa. This change is reflected by the increased alveolar surface area in IDPN mice and by the increase of the ratio Sa/Va estimating the air space surface complexity.

Stria vascularis as source of endocochlear potential.

Stria vascularis as source of endocochlear potential.