Biomedical subjects
S D Gray
Publications and source records attributed to S D Gray.
Phonosurgical studies: fat-graft reconstruction of injured canine vocal cords.
Damage to the vocal cords can result in scarring and impaired vibration and can manifest clinically as hoarseness and loss of vocal power. If the vibratory characteristics could be restored in these scarred vocal cords, the vocal intensity and efficiency of phonation also should improve. In an effort to enhance the vibration of damaged vocal cords, we implanted a submucosal fat autograft within the injured vocal cord cover layer of dogs 6 weeks after unilateral mucosal excision had been performed. Three months postoperatively these animals were compared to normal dogs and those with mucosal excision but no fat-grafting. Acoustic and biomechanical measures of phonation were collected from an excised larynx preparation. We found that the fat-augmented vocal cords had lower threshold pressures for phonation, greater vocal intensity, and more efficient acoustic output than injured vocal cords without the fat-grafting. These results provide a foundation for further research on reconstructive surgery of damaged vocal cords.
Update of the Cincinnati experience in pediatric laryngotracheal reconstruction.
Surgical endeavors in the field of laryngotracheal reconstruction in children have received much interest in the past 15 years. A unique experience with laryngotracheal reconstruction in 203 children is reviewed. The majority (194) of the cases were classified as acquired; only nine were classified as congenital. Excluded from the study were those cases of stenoses managed endoscopically, all resections and end-to-end anastomoses, all anterior cricoid split procedures, and all cases of anterior glottic stenosis repaired by a laryngeal keel. The degree of stenosis was graded into four categories. Five different methods of laryngotracheal reconstruction were used depending on the pathologic lesion in the larynx and trachea. Of the 203 children, 186 (92%) were decannulated. The results support the use of laryngotracheal reconstruction in children with grades 2, 3, and 4 laryngeal stenosis.
Ontogenic development of the elastic component of the aortic wall in spontaneously hypertensive rats.
In the neonatal stage of development in spontaneously hypertensive rats (SHR), previous studies have shown that arterial pressure is already significantly increased over that of normotensive WKY controls and that other hypertensive characteristics of the cardiovascular system are also in evidence. The present study describes early development of the elastic component of the aortic wall in fetal (days 17, 19, 21-22 of gestation) and neonatal (days 1, 7, 14, 21 of age) SHR and WKY, to determine whether the early pattern of elastin accumulation differs significantly in hypertensive and normotensive animals. The data indicate that in SHR there is a greater concentration of elastin in the aortic wall, a larger cross-sectional area and an increase in the number of lamellar units, both pre- and postnatally. We conclude that the differences in arterial wall structure which are associated with genetic hypertension are established early in development.
Histochemical analysis of capillary and fiber-type distributions in skeletal muscles of spontaneously hypertensive rats.
Various studies have suggested that hypertension causes a closure and eventual loss of microvessels. In muscle tissue that purported pattern of vascular rarification has been associated with a simultaneous loss of slow twitch fibers. The present study uses histochemical techniques to examine both the capillarization and distribution of fast (FOG) and slow (SO) twitch oxidative fibers, the most vascularized of the fiber types, in five muscles of spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats: adductor magnus (AM), biceps femoris (BF), spinotrapezius (SP), medial gastrocnemius (MG), and soleus (SOL). The results show that FOG and SO tend to be slightly smaller in cross-sectional area in SHR, but that the percentage of those fibers in the total population is not decreased in any of the SHR muscles examined. Capillary/fiber (C/F) ratios for most fiber categories were not significantly different in the two strains but tended toward slightly higher values in SHR. Since capillary density (C/mm2) is related to both fiber size and C/F ratio, density values tended to be higher, rather than lower, in SHR. The data indicate that there is neither an anatomical rarification of capillaries, nor a loss of FOG or SO fibers in spontaneous hypertension.
Arterial hypertrophy in the fetal and neonatal spontaneously hypertensive rat.
Large artery dimensions in prenatal and postnatal normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were evaluated to determine whether increased medial thickness is evident during early development. Microscopic cross-sections from perfusion-fixed aortas and carotid arteries of fetal (22-day gestation) and neonatal (5-day-old) animals were examined for numbers of laminae, luminal diameter and area, and medial thickness and area. SHR had a smaller mean body weight, and luminal diameters were the same in both strains. However, medial thickness and the numbers of laminae were significantly greater in SHR at both stages. Normalized ratios of medial thickness/luminal diameter and medial area/luminal area were also greater in SHR, indicating a disproportionate size of the arterial wall relative to the luminal space. Medial area/body weight ratios were also larger for SHR, suggesting the presence of greater medial mass per unit of body weight. The data support the view that the increased mass of the hypertensive arterial system is established in SHR as early as the fetal stage.
Airway reconstruction following laryngotracheal thermal trauma.
Care of burn patients is a complex problem for the trauma team involving management of fluid and electrolyte imbalances, infections, and ultimately reconstruction. Patients with burns of the head, neck, and upper thorax present a series of unique problems because of a high incidence of associated upper and lower airway thermal trauma necessitating intubation and ventilatory support. A series of cases requiring laryngotracheal reconstruction following severe burns to the head and neck region is reported. Methods of treatment are discussed as well as modifications of standard burn therapy to decrease the incidence of severe scarring.
Decline of isometric force and fatigue resistance in skeletal muscles from spontaneously hypertensive rats.
Skeletal muscles from 6- to 7-month-old male spontaneously hypertensive rats showed a decrease in functional capacity compared with muscles from age-matched normotensive Wistar-Kyoto rats. Predominantly slow-twitch, oxidative soleus muscles developed less force (normalized to muscle wet weight) and were less resistant to fatigue. Heterogeneous, but largely fast-twitch, oxidative-glycolytic medial gastrocnemius muscles generated less force, were smaller in size (normalized to body weight), and did not demonstrate the same degree of stimulation-associated potentiation (staircase effect) as did the medial gastrocnemius of the normotensive rats. The reduced endurance of the soleus of hypertensive rats was not associated with either fiber redifferentiation or capillary "rarification," and the majority of the decline in force with time could not be attributed to impaired neuromuscular transmission. The decrease in muscle capacity in the spontaneously hypertensive rat, thus, appears to be the result of adaptive changes localized in the muscle cells themselves. The adaptive changes, regardless of site, have a pronounced negative effect on muscle function, and could significantly influence motor performance and antihypertensive therapy.
Venturi jet ventilation for microlaryngoscopy: technique, complications, pitfalls.
Our experience with Venturi jet ventilation as the method of anesthesia in 872 cases of microlaryngeal surgery is presented. Our indications and exact technique are presented, as well as a review of our complications. Possible pitfalls and their avoidance are discussed. With attention to detail and good clinical judgement on the part of anesthesiologist and surgeon, Venturi jet ventilation can be safe and efficient with minimal complications.
Salt level in weaning diet affects saline preference and fluid intake in Dahl rats.
Weanling Dahl salt-sensitive (DS) and salt-resistant (DR) rats were used to compare effects of feeding high or low NaCl diets on taste preference for, and intake of, a wide range of saline concentrations. The DS and DR were fed either 8.0 or 0.4% dietary NaCl for 4 weeks. Then, with all animals fed the 0.4% NaCl diet, their taste preferences for 0.0001 to 0.56 M saline were assessed using three 24-hour two-bottle preference tests of each solution versus distilled deionized water. Saline preference and intake were influenced by concentration and its interaction with genotype, with DS exhibiting higher preferences than DR for hypotonic saline. The DS preexposed to 8.0% dietary NaCl showed elevated consumption levels of water and total fluid (saline + water) that persisted throughout the 5-week test period, despite transfer to the 0.4% NaCl diet before the initiation of preference testing. Findings indicate that genotype, dietary NaCl levels in weaning diet, and saline concentration of preference test solutions interact to influence saline preference and saline and water intake in Dahl rats.
Morphometric analysis of skeletal muscle capillaries in early spontaneous hypertension.
Capillary narrowing, elongation, and rarification have been described in various tissues in human and animal hypertension. The present study was undertaken to assess whether they are features of the skeletal muscle vascular bed during the developmental phase of the disease in spontaneously hypertensive rats. In neonatal (19 days old) and young adult (9-10 weeks old) rats of the hypertensive (SHR) and normotensive (WKY) strains, capillary diameter, length, and density were measured in spinotrapezius muscle by histological and intravital microscopic techniques. In neonates, capillary diameters (WKY = 3.98 +/- 0.13; SHR = 4.26 +/- 0.14 micron), lengths (WKY = 327 +/- 9; SHR = 334 +/- 6 microns), and densities (WKY = 1768 +/- 106; SHR = 1779 +/- 124 capillaries/mm2) were not significantly different in WKY and SHR. In young adults, capillary diameters (WKY = 4.28 +/- 0.09; SHR = 4.61 +/- 0.09 micron), lengths (WKY = 430 +/- 13; SHR = 443 +/- 12 microns), and densities (WKY = 1263 +/- 76; SHR = 1414 +/- 37 capillaries/mm2) were also not significantly changed in hypertension. Contrary to the findings of narrowing and decreased numbers of capillaries in human hypertensives, diameters and densities were slightly increased. The data suggest that those morphological changes at the capillary level do not occur in the developmental (period of rising arterial pressure) phase of spontaneous hypertension.
Pressure profiles in neonatal spontaneously hypertensive rats.
Spontaneously hypertensive (SHR) and normotensive (WKY) rats were studied on the day of birth and from 11 days to 12 weeks of age to determine whether increases in arterial pressure are detectable in the early neonatal stage of genetic hypertension. The data show that there are significant increases in systolic, diastolic, and mean pressures in neonatal SHR. Heart rate and heart weight/body weight ratios are also increased and indicate that many parameters, which have been shown to be significantly altered in adult rats in both the early and advanced stages of the disease, are already altered at birth.
Spontaneous hypertension in the neonatal rat. A review.
'Prehypertensive stage' was originally used to designate the initial developmental stage of hypertension in spontaneously hypertensive rats (SHR). The period covered the first 6-7 weeks of age, before the systolic pressure exceeded 150 mm Hg and many investigations have used this stage as a control period with which to compare later hypertensive changes. Significant hypertensive changes occur early in this period however, and numerous studies have revealed the extent to which cardiovascular alterations have already occurred by the weanling stage. This review summarizes much of the recent literature relating to the onset of the pressure rise, arterial and ventricular hypertrophy and increased sympathetic vasomotor effects in the early postnatal stage in SHR.
Comparison of functional and total capillary densities in fast and slow muscles of the chicken.
The anterior latissimus dorsi (ALD) and posterior latissimus dorsi (PLD) of the domestic chicken were used to study the possible differences in functional capillary density of slow and fast skeletal muscle. Frozen sections of each muscle were prepared for histochemical determination of fiber homogeneity, capillary/fiber ratios, and capillary densities. The functional capillary bed (percent open capillaries) was determined by comparing the number of ink-filled capillaries, after a systemic injection of india ink (for 90-120 s), with the total number of capillaries/mm2. ALD is a slow-tonic muscle consisting of two fiber types, with an average of 1.34 +/- 0.03 capillaries/fiber, a density of 699 +/- 20 capillaries/mm2, and a functional capillary bed representing 29% (ratio of open to total number of capillaries/mm2 was 0.286 +/- 0.022) of the total bed. PLD is a fast-twitch muscle also having two fiber types, with an average of 1.08 +/- 0.04 capillaries/fiber, a density of 561 +/- 26 capillaries/mm2, and a functional bed representing 11% (ratio of open capillaries to total is 0.111 +/- 0.014) of the total. These findings of increased capillarity (24% more capillaries/fiber and 25% more capillaries/mm2) and higher functional capillary density in an avian pure slow muscle (ALD), corroborate previous findings of increased capillarity around slow fibers in mixed muscles of several mammalian species. The values given represent the means +/- SEM.
Capillarity and fiber types in the cremaster muscle of rat and hamster.
We determined muscle fiber type and capillarity in cremaster muscle samples from rats and hamsters of different ages. Histochemical estimation of oxidative capacity was made from the activity of either nicotinamide dinucleotide tetrazolium reductase (NADH-TR) or succinic dehydrogenase (SDH), and fibers were termed fast or slow from myofibrillar ATPase activity. Fibers were classified as type I (low ATPase, high NADH-TR/SDH), type IIa (high ATPase, high SDH/NADH-TR), type IIb (high ATPase, low SDH/NADH-TR), or type IIc (no acid reversal of ATPase, high NADH-TR). Type IIb fibers accounted for 60-80% of the muscle area in both species at all ages. The principal change with maturation was muscle fiber hypertrophy. Mean cross-sectional fiber area increased from 488 +/- 70 (SE) and 453 +/- 19 micron2 in young hamsters and rats, respectively, to 1,255 +/- 99 and 1,540 +/- 101 micron2 in adults. Capillary density (no. of capillaries/mm2 tissue) paralleled fiber hypertrophy; it decreased significantly with maturation from 684 +/- 60 (SE) to 228 +/- 26/mm2 in hamsters and from 341 +/- 15 to 213 +/- 15/mm2 in rats. In vitro estimates of capillary density are compared with previously obtained in vivo data (31), and sources of error are identified. We conclude that reported differences in microvascular function in the cremaster muscle in vivo during maturation or between species cannot be ascribed to changes in muscle composition.
Perfused capillary surface area in postural and locomotor skeletal muscle.
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Early changes in fiber profile and capillary density in long-term stimulated muscles.
Predominantly fast skeletal muscles of rabbits [tibialis anterior (TA), extensor digitorum longus (EDL)] were stimulated at a frequency naturally occurring in nerves to slow muscles (10 Hz continuously) for 8 h/day for 2--4 days. Such stimulation is known to convert all glycolytic fibers to oxidative and to increase capillary density. Our aim was to study early stages of conversion to investigate the factors responsible for the changes. Staining of quick-frozen sections for myosin ATPase, succinic dehydrogenase, and alkaline phosphatase was used to study the distribution of different fiber types and to measure fiber cross-sectional areas, capillaries per square millimeter, and capillary-to-fiber ratios in each fiber category. TA but not EDL showed conversion of fast glycolytic to fast oxidative fibers after 2 days, more after 4 days of stimulation. In both muscles, the largest fast glycolytic fibers were diminished in number after stimulation. There was significant increase in total capillaries per square millimeter after 4 days and some increase after 2 days of stimulation. The increase in capillaries per square millimeter exceeded the increase in the number of fibers per square millimeter, and since there was no change in mean fiber area, the increase is attributed to capillary growth. In EDL, there was an increase in the number of capillaries supplying both fast glycolytic and fast oxidative fibers, suggesting that capillary growth precedes fiber type conversion. In TA, the number of capillaries supplying fast oxidative fibers was increased but that to fast glycolytic fibers, was not. This is consistent with capillary growth simultaneous with or following fiber conversion. In both TA and EDL the number of capillaries perfused after contraction was higher in stimulated muscles, suggesting that increased capillary flow contributed to capillary growth.
Filling of microcirculation in skeletal muscles during timed India ink perfusion.
Lower leg muscles of anesthetized rabbits were perfused in situ with heparinized India ink at flows and pressures comparable to normal resting levels of 4 ml.min-1.100 g-1). Paired cross sections were counterstained with eosin to show ink-containing microvessels and reacted for alkaline phosphate to show all vessels. The fraction of microvessels filled with ink (Fi) increased progressively with perfusion time. At 3.5 s, mean Fi for the muscles studied fell between 0.12 and 0.19. At 60-90 s, the following levels were reached: medial gastrocnemius 0.74, lateral gastrocnemius 0.76, tibialis anterior 0.59, and soleus 0.80. The number of open capillaries and their distribution of flow velocities can be inferred from such data only if the perfusion rate is known or by recourse to a specified anatomic model. The time course of ink appearance shows best agreement with 60-80% of the vessels open and accessible to ink, with microvascular transit times ranging from less than 3 to greater than 30 s. If microvascular path lengths are assumed to be uniform, the range of velocities must be four times to one-fourth the mean, with 15-30% of the microvessels perfused at velocities equal to or greater than the mean. Alternatively, if microvascular velocity is assumed uniform, flow path lengths must vary from one-fourth to four times the average. Anatomic measurements of other suggest that less than one-half the variability in ink transit is attributable to differences in microvascular length. Thus both length and velocity must vary among alternate arteriovenous pathways.