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Biomedical subjects

N Banchero

Publications and source records attributed to N Banchero.

At least 19 recordsLinked to original sources
PubMed1990

Scalene muscle abnormalities in traumatic thoracic outlet syndrome.

Thoracic outlet syndrome (TOS) is not a single disorder but a collection of abnormalities in the same anatomic area that elicit similar symptoms. The many causes of TOS are best classified into one of three groups: osseous, traumatic, and nontraumatic. Although patients with traumatic TOS constituted 86% of our last 600 patients with TOS who underwent surgical treatment, the precise mechanism underlying the condition remains obscure. To determine if there was microscopic abnormalities, 45 anterior and middle scalene muscles from patients with traumatic TOS were studied by means of histochemical stains applied after freezing of the muscles. The results revealed a consistent abnormal histologic pattern in patients with traumatic TOS: type II fibers were atrophied; there was an increase in the average number of type I fibers (78% versus 53% in muscles from control patients); and there was a significant increase (mean: 36%) in connective tissue (muscles from control patients averaged less than 15%). Although type II fiber atrophy and type I fiber predominance are seen in a variety of other conditions, their association with fibrosis is rare. Following neck injuries, the changes in the anterior and middle scalene muscles are compatible with trauma, suggesting that fibrotic scalene muscles are an important cause of symptoms in traumatic TOS.

Adult↗
PubMed1987

Volume density and distribution of mitochondria in myocardial growth and hypertrophy.

The volume density and distribution of mitochondria relative to capillaries have been measured using the technique of point counting in concentric rings, on normal and hypertrophied guinea pig myocardium. Right ventricular hypertrophy was produced by hypobaric hypoxia. In control guinea pigs right ventricular weight increased linearly with body weight. In control and hypoxic guinea pigs fiber cross sectional area (FCSA) and ventricular weight were related by a single straight line. Capillary density decreased hyperbolically with FCSA in both control and hypoxic animals. Capillary density was significantly higher (P less than 0.001) in the right ventricles of the hypoxic animals than in controls when the fibers were small but this difference disappeared as the fibers hypertrophied beyond FCSA values of 260 microns2. Volume density of mitochondria reached a peak (29-35%) close to the capillary but then decreased significantly in the spaces farthest from the capillary (mean 25.2%). There was no significant difference in peak mitochondrial volume density in controls versus hypoxic animals. There was thus an increase in the total volume of mitochondria in these myofibers that was in direct proportion to the increases in FCSA and heart volume. The highest volume density of mitochondria was found at a distance that is approximately 15% of the total distance over which O2 must diffuse in myocardial tissue and the peak volume density of mitochondria was thus a function of capillary density. The speculation is presented that the distribution of mitochondria may be related both to oxygen supply to the mitochondria and to the movement of high energy phosphate compounds out of mitochondria for use by myofibrils.

Animals↗
PubMed1987

Pulmonary development in growing guinea pigs exposed to chronic hypercapnia.

The role of lung stretch in causing pulmonary hyperplasia was studied in weanling male guinea pigs breathing air or 5% CO2 (in 22% O2, 73% N2) for 4 weeks. By the end of the exposure, oxygen consumptions were similar for both groups, but tidal volume and minute ventilation doubled in the hypercapnic group compared to controls. Arterial and venous blood gases reflected compensatory increases in plasma bicarbonate in animals breathing 5% CO2. The two groups did not differ in growth rate, lung volume or weight, alveolar surface area, anatomically estimated pulmonary diffusing capacity, or lung cellularity and protein content. Despite a chronic doubling of tidal volume during a peak growth period, hyperventilation did not stimulate pulmonary development, at least in normoxia and when oxygen consumption remained constant.

Animals↗
PubMed1987

Fiber composition and capillarity in growing guinea pigs acclimated to cold and cold plus hypoxia.

The central portion of the medial head of the gastrocnemius of control (normoxic and normothermic), hypoxia-, cold-, and cold plus hypoxia-acclimated guinea pigs was analyzed for capillary supply and fiber composition to elucidate changes in capillarity induced by environmental stresses. The muscle was cut at midbelly, frozen, sectioned, and stained for myosin ATPase. Fiber cross-sectional areas; percentages of slow-twitch oxidative (SO), fast-twitch oxidative-glycolytic (FOG), and fast-twitch glycolytic (FG) fibers; and numbers of capillaries around each fiber type were measured. Growth rates of all four guinea pig groups were similar. Capillarity was not affected by acclimation to hypoxia. Cold and cold plus hypoxia acclimation led to increased numbers of capillaries around the fiber in all three fiber types. In addition, significant increases in the percentage of FOG fibers and concomitant decreases in the percentage of FG fibers compared to controls were found in cold and in cold plus hypoxia indicating that a transformation of fiber type from FG to FOG had occurred. The increase in FOGs at the expense of the FGs did not occur in the guinea pigs grown in a hypoxic environment. The increased total capillarity in those muscles studied was the result of more capillaries around all fiber types and was not due to simple transformation of fibers.

Acclimatization↗
PubMed1987

Ventricular weights in guinea pigs acclimated to cold plus hypoxia.

Weanling male guinea pigs (Cavia porcellus), 2-3 weeks of age, with initial body weights of 207-271 g were exposed for 2-16 weeks to constant cold (6 degrees C) and hypoxia (PO2 = 85 Torr) equivalent to 4800 m above sea level. Their growth rates and body weights did not differ from those of control animals of the same age maintained under normoxic conditions (22 degrees C, PO2 = 133 Torr). After 2, 3, 4, 6, 10, or 16 weeks exposure the animals were sacrificed, the hearts were removed, the ventricles were separated and weighed, and myoglobin concentrations were determined. Total heart weight as well as both right and left ventricular weights increased linearly with age. By the second week of exposure of the guinea pigs to cold plus hypoxia the total heart and right ventricular weights were 25 and 50% greater than those of the normoxic control animals. Both weights increased at greater rates than those of the controls until Week 6 and then remained at 30 and 80% throughout the 16th week. The weights of the left ventricles in these animals were only slightly greater than those of the controls. In spite of the severe right ventricular hypertrophy these animals showed no clinical signs of right heart failure. Myoglobin concentrations were significantly greater in both ventricles for the cold-plus-hypoxic animals than for the controls.

Acclimatization↗
PubMed1985

Myocardial capillarity in acclimation to hypoxia.

Capillarity, O2 diffusion distances and fiber cross-sectional growth were measured in the hearts of guinea pigs exposed early during growth to hypobaric hypoxia (PB = 430 torr, PO2 = 90 torr). Twelve 5-week old males were maintained in a hypobaric chamber for 4-14 weeks. Their hearts were perfusion-fixed via the aorta with a 2.5% glutaraldehyde, 1% formaldehyde buffered solution; blocks were cut from left (LV) and right (RV) ventricles, post-fixed in OsO4, dehydrated and embedded in Spurr medium. Blocks were cut transversely to fiber orientation, 0.5 micron thick, stained with Toluidine Blue, and photographed at 400 X. Number and location of capillaries and fiber cross-sectional areas (FCSA) were scored from these photographs and from those of normoxic controls. Growth rates were similar for control and hypoxic guinea pigs. As animals grew, LV and RV weights increased linearly with body weight. Hypoxic guinea pigs had LV weights similar to controls but the RV showed varying degrees of hypertrophy. Control and hypoxic guinea pigs showed similar linear increases in FCSA with ventricular weight, suggesting that hypertrophy was due to increased FCSA. Capillary density (CD) decreased and capillary-to-fiber ratio (C:F) increased with FCSA, and O2 diffusion distances lengthened in LV and RV of animals in both groups. CD and C:F were higher and O2 diffusion distances were shorter in most hypoxic animals compared to controls. When RV hypertrophy was large (RV greater than 0.7 g) and failure imminent, CD, C:F and O2 diffusion distances were similar to controls suggesting that in these hearts oxygenation was impaired.

Acclimatization↗
PubMed1985

Sequential perfusion of skeletal muscle capillaries.

Rats were injected intraarterially with a fluorescent dye that binds to capillary endothelium, thereby labeling any capillary through which it has passed. After 10, 15, or 30 sec of circulation of the dye blood flow was interrupted, the gastrocnemius was frozen, and the density and distribution of labeled capillaries were measured in transverse sections of the central portion of the medial head. These tissue sections were then counterstained by the myosin ATPase method for capillaries to mark all capillaries. After 10 sec, 45% of all capillaries were labeled and after 15 sec, 59% of all capillaries were labeled. Thirty seconds after injection, all capillaries were labeled with the fluorescent dye. In all three time intervals, the distributions of labeled capillaries were ordered, suggesting that there is a tissue-level control mechanism for regulating capillary perfusion to maintain relatively short maximal oxygen diffusion distances.

Adenosine Triphosphatases↗
PubMed1985

Volume overload hypertrophy elicited by cold and its effects on myocardial capillarity.

Capillarity and fiber cross-sectional areas were measured in the hearts of guinea pigs exposed to cold early during growth. Twelve male guinea pigs were kept at 5 +/- 1 degrees C for 4-18 weeks. Hearts were perfusion fixed via the aorta with a 2.5% glutaraldehyde, 1% formaldehyde-buffered solution, blocks were cut from left (LV) and right (RV) ventricles, post-fixed in OsO4, dehydrated and embedded in Spurr medium. Blocks were cut transversely to fiber orientation, 0.5 micron thick, stained with Toluidine Blue and photographed at 400 x. Heart weights, number and location of capillaries and fiber cross-sectional areas (FCSA) were measured in cold-acclimated animals and in normothermic controls. Growth rates for all guinea pigs were similar. Acclimation to cold caused modest LV and RV hypertrophy. The greater LV weight seemed due to longer fibers of normal FCSA, whereas the greater RV weight was due to larger FCSA. Capillary density, capillary-to-fiber ratio and number of capillaries around the fibers were similar in the two groups of animals. Mean and maximal diffusion distances in cold-acclimated animals were not different from controls. Thus the myocardial hypertrophy induced by chronic volume overload was fully compensated for by increases in capillarity commensurate with increases in fiber girth.

Acclimatization↗
PubMed1985

Ventilation and oxygen consumption in the guinea pig.

Respiratory values were determined in guinea pigs studied under normal laboratory conditions in Denver. The effects of anesthesia and acute hypercapnia were also assessed. In normal laboratory conditions, VO2 and VE were proportional to body weight (BW). Specific VO2 and VE for small guinea pigs (mean BW: 269 g) were 1.14 +/- 0.04 (SEM) and 57.5 +/- 3.9 ml/g X h, respectively, compared to 0.82 +/- 0.03 (P less than 0.001) and 29.9 +/- 0.8 ml/g X h (P less than 0.001), respectively, for large animals (mean BW: 817 g). Tidal volume (VT) was related to BW by the following equation: VT (ml) = 3.97 X 10(-3) BW (g) + 2.05 (r = 0.82; P less than 0.001). During anesthesia VO2 decreased 25-63% and VE was reduced by 45% in those animals having the largest change in VO2. In hypercapnia, VE was more than twice that in normocapnia primarily due to a 75-95% elevation in VT.

Anesthesia↗
PubMed1985

Effects of cold and hypoxia on ventilation and oxygen consumption in awake guinea pigs.

Ventilation and oxygen consumption were measured in awake, unrestrained and unintubated guinea pigs during chronic and acute exposure to cold or hypoxia. Specific VE and VO2 in acute and chronic exposure to cold were more than twice that of animals in normal environmental temperatures. Increased ventilation was mainly due to a 70% greater VT in cold. Cold-acclimated guinea pigs returned acutely to normal temperatures, maintained higher VE and VO2 than that of control animals. Acclimation to cold did not result in respiratory advantages over that of control animals acutely exposed to cold. In hypoxia-acclimated guinea pigs, specific VE was 30% higher than that of control animals due to an elevation in VT; however, VO2 was similar in both groups of animals. In contrast, acute hypoxia did not increase VE in control animals. This lack of ventilatory response to acute hypoxia apparently causes the marked erythropoiesis and the severe increase in hematocrit observed throughout chronic exposure to hypoxia. The high blood viscosity resulting from the increased hematocrit contributes to the right ventricular hypertrophy and cardiac failure in guinea pigs chronically exposed to hypoxia.

Adaptation, Physiological↗
PubMed1985

Increased capillarity in skeletal muscle of growing guinea pigs acclimated to cold and hypoxia.

Capillarity was evaluated on transverse sections of frozen gastrocnemius and soleus muscles of young, growing guinea pigs exposed to the combined stresses of cold (6 degrees C) (C) and hypoxia (ambient PO2 = 85 Torr) (H) for up to 16 weeks and these data were compared to those obtained in a control group of guinea pigs kept in Denver (22 degrees C, ambient PO2 = 133 Torr). Capillarity was assessed from measurements of capillary density and capillarity density to fiber density ratios. Mean (R) and maximal (R95) diffusion distances were measured by the closest individual method. The body growth rate of guinea pigs exposed to C + H was the same as that in the control condition. The gastrocnemius muscle grew at the same rate as in the control guinea pigs. Exposure to C + H produced a significant (P less than 0.001) increase in the capillary density and the C/F of the gastrocnemius, reducing the mean and the maximal diffusion distances. However, the soleus muscles of the guinea pigs in C + H did not grow at the same rate and relative to body size the soleus muscles of these guinea pigs in C + H were smaller due to their smaller fiber cross-section area; consequently, there was a relatively larger capillarity in these muscles. It is hypothesized that the increased muscle capillarity in animals exposed to C + H results from a marked lowering of the tissue PO2 which may result from a leftward shift of the Hb-O2 dissociation curve.

Acclimatization↗
PubMed1983

Distribution of capillaries and diffusion distances in guinea pig myocardium.

A frequency distribution of distances from random points to the nearest capillary was generated from high-magnification photomicrographs of thin sections of the myocardium of seven guinea pigs. Individual mean capillary densities taken from regions viewed in transverse section ranged from approximately 1800 to 2500 capillaries/mm2. Mean (R) and maximal (R95) diffusion distances measured by the closest individual method ranged from R = 6.6 to 8.7 microns and R95 = 11 to 18 microns. Further mathematical analysis of the frequency distributions of diffusion distances indicated that the capillaries of the myocardium are distributed in an ordered array.

Animals↗
PubMed1982

Advanced pulmonary development in newborn guinea pigs (Cavia porcellus).

Morphological and morphometric evidence is presented to support the hypothesis that lung growth is advanced in mammals born at a relatively mature stage. The lungs from fetal and postnatal guinea pigs ranging in age from gestational age 56 days (normal gestation is 68 days in this species) through 16 days postpartum were fixed in situ by intratracheal glutaraldehyde. Morphometry included measurements of lung volume (VL), tissue and air-space volumes, fraction of respiratory parenchyma, alveolar (SA) and capillary (SC) surface areas, and the arithmetic mean thickness of the tissue barrier (tau t). VL, SA, and SC all increased monoexponentially versus body weight (W) from birth to adulthood; the lungs appeared to be in the equilibrated growth phase, with no postnatal period of pronounced tissue proliferation as reported in the newborn rat and mouse. The prepartum value of tau t was 1.96 micrometers; this value decreased by parturition of 1.27 micrometers and did not change significantly with additional age. At the light-microscopical level, respiratory bronchioles could be visualized giving rise to alveolar ducts by a gestational age of 58 days (10 days preterm) with well-developed alveolar septal partitioning evident. Structures resembling the primitive pre-alveolar saccules of newborn rats were never seen in even the youngest fetal animals. Elastin fibers were also evident at this age, both in bronchiolar and duct walls, as well as in alveolar septa. Using electron microscopy, the air-blood barrier appeared mature by a gestational age of 61 days and thereafter, double capillary layers were only rarely seen in septal walls.

Animals↗
PubMed1982

The distribution of diffusion distances in the gastrocnemius muscle of various mammals during maturation.

Large changes in fiber size, capillary density and capillary/fiber architecture occur during maturation of mammalian skeletal muscle. To examine the effect of these changes on oxygen diffusion distance, the mean (R) and maximal (R95) distances from the capillary to the tissue were measured in the gastrocnemius of maturing guinea pigs, rats and dogs. Hyperbolic relationships between capillary density and R and between capillary density and R95 were found for the combined data from these three species. The R and R95 increased with decreasing CD in growing guinea pigs and rats, but they remained constant in dogs. Statistical analyses showed that the capillaries in this muscle in all three species tended to be distributed in ordered arrays. These anatomical measurements are discussed in relation to their potential physiological impact on oxygen delivery to tissues.

Animals↗