A survey of image-guided radiation therapy use in the United States

BACKGROUND

Image-guided radiation therapy (IGRT) is a novel array of in-room imaging modalities that are used for tumor localization and patient setup in radiation oncology. The prevalence of IGRT use among US radiation oncologists is unknown.

METHODS

A random sample of 1600 radiation oncologists was surveyed by Internet, e-mail and fax regarding the frequency of IGRT use, clinical applications, and future plans for use. The definition of IGRT included imaging technologies that are used for setup verification or tumor localization during treatment.

RESULTS

Of 1089 evaluable respondents, 393 responses (36.1%) were received. The proportion of radiation oncologists using IGRT was 93.5%. When the use of megavoltage (MV) portal imaging was excluded from the definition of IGRT, the proportion using IGRT was 82.3%. The majority used IGRT rarely (in <25% of their patients; 28.9%) or infrequently (in 25%-50% of their patients; 33.1%). The percentages using ultrasound, video, MV-planar, kilovoltage (kV)-planar, and volumetric technologies were 22.3%, 3.2%, 62.7%, 57.7%, and 58.8%, respectively. Among IGRT users, the most common disease sites treated were genitourinary (91.1%), head and neck (74.2%), central nervous system (71.9%), and lung (66.9%). Overall, 59.1% of IGRT users planned to increase use, and 71.4% of nonusers planned to adopt IGRT in the future.

CONCLUSIONS

IGRT is widely used among radiation oncologists. On the basis of prospective plans of responders, its use is expected to increase. Further research will be required to determine the safety, cost efficacy, and optimal applications of these technologies.

Single-isocenter frameless intensity-modulated stereotactic radiosurgery for simultaneous treatment of multiple brain metastases: clinical experience

PURPOSE

To describe our clinical experience using a unique single-isocenter technique for frameless intensity-modulated stereotactic radiosurgery (IM-SRS) to treat multiple brain metastases.

METHODS AND MATERIALS

Twenty-six patients with a median of 5 metastases (range, 2-13) underwent optically guided frameless IM-SRS using a single, centrally located isocenter. Median prescription dose was 18 Gy (range, 14-25). Follow-up magnetic resonance imaging (MRI) and clinical examination occurred every 2-4 months.

RESULTS

Median follow-up for all patients was 3.3 months (range, 0.2-21.3), with 20 of 26 patients (77%) followed up until their death. For the remaining 6 patients alive at the time of analysis, median follow-up was 14.6 months (range, 9.3-18.0). Total treatment time ranged from 9.0 to 38.9 minutes (median, 21.0). Actuarial 6- and 12-month overall survivals were 50% (95% confidence interval [C.I.], 31-70%) and 38% (95% C.I., 19-56%), respectively. Actuarial 6- and 12-month local control (LC) rates were 97% (95% C.I., 93-100%) and 83% (95% C.I., 71-96%), respectively. Tumors <or=1.5 cm had a better 6-month LC than those >1.5 cm (98% vs. 90%, p = 0.008). New intracranial metastatic disease occurring outside of the treatment volume was observed in 7 patients. Grade >or=3 toxicity occurred in 2 patients (8%).

CONCLUSION

Frameless IM-SRS using a single-isocenter approach for treating multiple intracranial metastases can produce clinical outcomes that compare favorably with those of conventional SRS in a much shorter treatment time (<40 minutes). Given its faster treatment time, this technique is appealing to both patients and personnel in busy clinics.

Utilization of advanced imaging technologies for target delineation in radiation oncology

PURPOSE

The aim of this study was to evaluate the utilization of advanced imaging technologies for target delineation among radiation oncologists in the United States.

METHODS

A random sample of 1,600 radiation oncologists was contacted by Internet, e-mail, and fax and questioned regarding the use of advanced imaging technologies, clinical applications, and future plans for use. Advanced imaging technologies were defined as any of the following that were directly incorporated into radiation therapy planning: MRI, PET, single-photon emission CT, 4-D CT, functional MRI, and MR spectroscopy.

RESULTS

Of 1,089 contactable physicians, 394 (36%) responded. Of respondents, 65% were in private practice and 35% were in academic practice. The proportion using any advanced imaging technology for target delineation was 95%. However, the majority reported only rare (in <25% of their patients; 46.6%) or infrequent (in 25%-50% of their patients; 26.0%) utilization. The most commonly used technologies were 2-[(18)F]fluoro-2-deoxyglucose PET (76%), MRI (72%), and 4-D CT (44%). The most common cancers treated using image-guided target delineation were those of the lung (83%), central nervous system (79%), and head and neck (79%). Among users of advanced imaging technologies, 66% planned to increase use; 30% of nonusers planned to adopt these technologies in the future.

CONCLUSIONS

Advanced imaging technologies are widely used by US radiation oncologists for target delineation. Although the majority of respondents used them in <50% of their patients, the frequency of utilization is expected to increase. Studies determining the optimal application of these technologies in radiation therapy planning are needed.

Toxicity analysis of postoperative image-guided intensity-modulated radiotherapy for prostate cancer

PURPOSE

To report on the acute and late gastrointestinal (GI) and genitourinary (GU) toxicity associated with a unique technique of image-guided radiotherapy (IGRT) in patients undergoing postprostatectomy irradiation.

METHODS AND MATERIALS

Fifty patients were treated with intensity-modulated radiation therapy (IMRT) after radical prostatectomy. Daily image guidance was performed to localize the prostate bed using kilovoltage imaging or cone-beam computed tomography. The median prescription dose was 68 Gy (range, 62-68 Gy). Toxicity was graded every 3 to 6 months according to the Common Terminology Criteria for Adverse Events version 3.0.

RESULTS

The median follow-up was 24 months (range, 13-38 months). Grade 2 acute GI and GU events occurred in 4 patients (8%) and 7 patients (14%), respectively. No Grade 3 or higher acute GI or GU toxicities were observed. Late Grade 2 GI and GU events occurred in 1 patient (2%) and 8 patients (16%), respectively. Only a single (2%) Grade 3 or higher late toxicity was observed.

CONCLUSIONS

Image-guided IMRT in the postprostatectomy setting is associated with a low frequency of acute and late GI/GU toxicity. These results compare more favorably to radiotherapy techniques that do not use in-room image-guidance, suggesting that daily prostate bed localization may reduce the incidence of adverse events in patients undergoing postprostatectomy irradiation.

Optically-guided frameless linac-based radiosurgery for brain metastases: clinical experience

The purpose of this study was to describe our clinical experience using optically-guided linear accelerator (linac)-based frameless stereotactic radiosurgery (SRS) for the treatment of brain metastases. Sixty-five patients (204 lesions) were treated between 2005 and 2008 with frameless SRS using an optically-guided bite-block system. Patients had a median of 2 lesions (range, 1-13). Prescription dose ranged from 14 to 22 Gy (median, 18 Gy) and was given in a single fraction. Clinical and radiographic evaluation occurred every 2-4 months following treatment. At a median follow-up of 6.2 months, actuarial survival at 12 months was 40% [95% confidence interval (CI), 28-52). Of 135 lesions that were evaluable for local control (LC), 119 lesions (88%) did not show evidence of progression. Actuarial 12 month LC was 76% (95% CI, 66-86). Tumors <or=2 cm in size had a better 12 month LC rate (81% vs. 36%, P = 0.017) than those >2 cm. Adverse events occurred in three patients (5%). Optically-guided linac-based frameless SRS can produce clinical outcomes that compare favorably to frame-based techniques. As this technique is convenient to use and allows for the uncomplicated delivery of hypofractionated radiotherapy, frameless SRS will likely have an increasingly important role in the management of brain metastases.

In situ biosurfactant production by Bacillus strains injected into a limestone petroleum reservoir

Biosurfactant-mediated oil recovery may be an economic approach for recovery of significant amounts of oil entrapped in reservoirs, but evidence that biosurfactants can be produced in situ at concentrations needed to mobilize oil is lacking. We tested whether two Bacillus strains that produce lipopeptide biosurfactants can metabolize and produce their biosurfactants in an oil reservoir. Five wells that produce from the same Viola limestone formation were used. Two wells received an inoculum (a mixture of Bacillus strain RS-1 and Bacillus subtilis subsp. spizizenii NRRL B-23049) and nutrients (glucose, sodium nitrate, and trace metals), two wells received just nutrients, and one well received only formation water. Results showed in situ metabolism and biosurfactant production. The average concentration of lipopeptide biosurfactant in the produced fluids of the inoculated wells was about 90 mg/liter. This concentration is approximately nine times the minimum concentration required to mobilize entrapped oil from sandstone cores. Carbon dioxide, acetate, lactate, ethanol, and 2,3-butanediol were detected in the produced fluids of the inoculated wells. Only CO(2) and ethanol were detected in the produced fluids of the nutrient-only-treated wells. Microbiological and molecular data showed that the microorganisms injected into the formation were retrieved in the produced fluids of the inoculated wells. We provide essential data for modeling microbial oil recovery processes in situ, including growth rates (0.06 +/- 0.01 h(-1)), carbon balances (107% +/- 34%), biosurfactant production rates (0.02 +/- 0.001 h(-1)), and biosurfactant yields (0.015 +/- 0.001 mol biosurfactant/mol glucose). The data demonstrate the technical feasibility of microbial processes for oil recovery.

Nerve growth factor promotes survival of new neurons in the adult hippocampus

Exogenously provided NGF enhances cognitive performance in impaired rodents and humans and is currently a promising compound for the treatment of dementia. To investigate whether NGF-dependent cognitive improvement may be due in part to increased hippocampal neurogenesis, adult and aged male rats were treated with NGF or vehicle intracerebroventricularly for 6 or 20 days followed by evaluation of cholinergic parameters and hippocampal neurogenesis. We show that NGF increases hippocampal cholinergic activity as rapidly as 3 days after initiation of treatment. NGF treatment for 6 days did not affect proliferation of progenitor cells in the dentate gyrus granule cell layer (GCL). However, continuous NGF infusion enhanced survival of new neurons in the GCL of young adult, but not aged rats. Taken together, these findings suggest that NGF, likely mediated through increased cholinergic tone, promotes neurogenesis in the adult hippocampus, which may relate to the nootropic action of NGF.

The relationship of inflammation in the papanicolaou smear to Chlamydia trachomatis infection in a high-risk population

Chlamydia trachomatis is a significant etiologic agent responsible for pelvic inflammatory disease leading to tubal infertility. A screening test aimed at identifying women at risk for Chlamydia trachomatis would be of great utility. The Papanicolaou smear is the most widely used screening test in the world. The association of inflammatory cells in the Papanicolaou smear to Chlamydia infection is controversial. We retrospectively examined the Papanicolaou smears of 80 Chlamydia-negative patients with 80 age-matched Chlamydia-positive patients in a high-risk population to see if a significant difference in inflammation was noted between the two groups. We found a statistically significant difference in inflammation scores between the Chlamydia-positive and Chlamydia-negative groups, evidenced by a sensitivity of 83% and a positive predictive value of 65% when using inflammation on Papanicolaou smears as a marker for Chlamydia infection. Grading of inflammation in the Papanicolaou smear can be of potential use in defining patients at highest risk for Chlamydia in a group considered to be at high risk based on sexual history.

High incidence of extramedullary relapse of AML after busulfan/cyclophosphamide conditioning and allogeneic stem cell transplantation

While allogeneic stem cell transplantation (SCT) is curative for a significant number of patients with AML, relapse of disease within the bone marrow and/or extramedullary (EM) sites following high-dose therapy continues to limit the success of this treatment. Between October 1985 and December 1996, 81 adults underwent allogeneic SCT for de novo AML at our centre. Forty-two patients remain alive and free of leukaemia with a median follow-up of 50 months. The 5-year actuarial event-free survivals (EFS) for all patients and for those undergoing SCT in CR1 or with advanced disease were 46% (95% confidence interval (CI) 34-58%), 63% (CI 46-76%), and 19% (CI 7-36%), respectively. Twenty-two patients relapsed at a median of 8 (range 1.6-54.5) months with the actuarial risk of relapse for all, CR1 and advanced disease patients being 38%, (CI 27-52%), 23% (CI 13-40%) and 68% (CI 46-88%), respectively. Ten patients relapsed at EM sites; six of these (27% of relapses) had an isolated EM relapse at a median of 31 (range 8.5-54) months. Three of the patients with isolated EM relapse survived > or =24 months following relapse and two patients remain disease-free at 29+ and 33+ months. BuCy conditioning followed by allogeneic SCT in AML results in satisfactory EFS although there is a significant risk of late isolated EM relapse.

Successful treatment of veno-occlusive disease with recombinant tissue plasminogen activator in a patient requiring peritoneal dialysis

There have been encouraging reports of the use of recombinant tissue plasminogen activator (tPA) in established veno-occlusive disease (VOD). Haemodialysis has been considered a contraindication to this therapy in view of the potential haemostatic complications. We report a case of a woman who developed moderately severe VOD complicated by anuria following an allogeneic bone marrow transplant for relapsed acute myeloid leukaemia. Following initiation of peritoneal dialysis she received tPA at a dose of 10 mg/day for 5 days. There was rapid improvement in her urine output and liver function with no bleeding complications. This case suggests that the requirement of dialysis may not preclude the use of tPA in established VOD and therefore warrants further study.

Time of nitrogen application and yield of Bengal lychee on a sandy loam soil in subtropical Queensland

Nitrogen (N) was applied over 4 years to 6-year-old lychee trees (Litchi chinensis Sonn. cv. Bengal) growing in subtropical Queensland (lat. 27�S.) on a sandy loam soil (0-15 cm) with 2.8 mg nitrate-N/kg, to determine the effect of time of N application on leaf N concentration, vegetative growth, flowering, and yield. Applications of N (equivalent to 750 kg N/ha in year 4) were made after panicle emergence in July, after harvest in January, or split between the 2 periods. Control trees received no N. Leaf N concentrations in April-June were, on average, about 0.1% lower after a single N application in winter than application in summer or split applications. Leaf N concentrations in November-February were about 0.1% higher after winter or split N applications than after summer applications. Timing of fertiliser application had no affect on yield. It took 4 years without N fertiliser to show significant reductions in yield compared with fertilised trees. In year 4, yield increased from 20 to 60 kg/tree on individual pairs of trees as leaf N in August increased from 0.95 to 1.56%. Lower yields in control trees in year 4 were associated with poor leaf growth in the previous 2 years, and with lower concentrations of N in the panicles, leaves, twigs, and small branches, as well as lower chlorophyll concentrations and net CO2 assimilation after fruit set, compared with trees receiving N.

Effect of paclobutrazol on growth and flowering of lychee (Litchi chinensis)

The effects of either foliar (1.00-4.00 g/L) or soil applications (0.25-1.00 g/m2 tree ground cover) of paclobutrazol, during autumn, on vegetative flushing and flowering of 3 lychee (Litchi chiriensis) cultivars (Bengal, Kwai May Pink and Tai So) were investigated over 3 years at 8 sites in subtropical southern Queensland. Cultivars at these sites varied in the level of vegetative flushing prior to panicle emergence in May-August and flowering in spring. Paclobutrazol reduced flushing and increased flowering in 5 out of 8 orchards, maintained dormancy and reduced flowering in 1 orchard, and had variable effects in 2 orchards, depending on the method of application. The maximum level of flowering in paclobutrazol treated trees occurred when the control trees bloomed moderately (40-60% of terminal branches). The responses were sometimes weak when the trees were very vigorous (<30% bloom). Paclobutrazol had no significant effect or reduced flowering of heavily blooming (70-100% bloom) trees. Paclobutrazol had only a small effect on panicle development, fruit set and fruit quality at most sites. Yield reflected the flowering response to paclobutrazol, except when yields were lowered by excessive male flowering or bird damage to the fruit.

Effect of cincturing on growth and flowering of lychee over several seasons in subtropical Queensland

The effects of autumn cincturing on vegetative flushing and incidence of flowering of 2 lychee (Litchi chinensis) cultivars (Bengal and Tai So) were investigated over 1-3 years at 8 sites in subtropical southern Queensland. Cultivars at these sites varied in the level of natural vegetative dormancy in winter (3-100% of terminal branches) and flowering in spring (0- 100% of terminal branches). There was a strong correlation between percentage flowering (y) and the level of dormancy (x) in the 1-2 months prior to floral initiation (y= 8.8 + 0.83~; r=0.89, P<.001). Cincturing increased flowering by 40-800% in trees that would have flowered poorly in spring (< 70�/o), but had no significant effect (P> 0.05) on flowering in trees that would have bloomed profusely (70-100%), provided trees were adequately fertilised and actively flushing after harvest. This was shown by the relationship, y= 899 - 23.0x+ 0.14x2; r= -0.96, P<0.001), where y is the percentage change in flowering after cincturing and x is the percentage flowering in control trees. Cincturing reduced or delayed flowering if nutrition was not maintained. It is concluded that trees to be cinctured should be adequately fertilised and complete a significant vegetative flush after harvest.

Architectural design and fiber-type distribution of the major elbow flexors and extensors of the monkey (cynomolgus)

Because the architectural and biochemical properties of skeletal muscle dictate its force, velocity, and displacement properties, the major extensors (triceps brachii) and flexors (biceps brachii, brachialis, and brachioradialis) of the elbow in a primate (cynomolgus, monkey) were studied. Functional cross-sectional areas (CSA) were calculated from muscle mass, mean fiber length (normalized to a 2.20 microns sarcomere length), and angle of fiber pinnation measurements from each muscle. Fiber-type distributions were determined and used as a gross index of the biochemical capacities of the muscle. The extensor group had a shorter mean fiber length (31 vs. 47 mm), a larger CSA (13 vs. 8 cm2), and a higher overall percentage of slow-twitch fibers (47 vs. 26%). Consequently, the elbow extensors had a relatively greater potential for force production and force maintenance than the flexors. In contrast, the flexors were designed to optimize their length-velocity potentials; i.e., they had relatively long fibers and a higher fast-twitch fiber composition than the extensors. These morphologic differences between antagonistic muscle groups should be considered when evaluating the motor control mechanisms regulating reciprocal movements about the elbow.

Architectural and histochemical analysis of the semitendinosus muscle in mice, rats, guinea pigs, and rabbits

The architectural and histochemical properties of the anatomically distinct compartments of the semitendinosus muscle (ST) of mice, rats, guinea pigs, and rabbits show that the ST is composed of two separate compartments aligned in series--a distal compartment (STd) and a proximal one (STp). The STp is further subdivided into a ventral head (STpv) and a dorsal head (STpd). The muscle fibers were arranged in parallel to the line of muscle pull within each compartment. The STd has the longest and the STpv the shortest fibers in all species. The physiological cross-sectional area and the estimated tetanic tension was greatest in the STd. Based on the staining pattern for myosin ATPase (alkaline preincubation) and an oxidative indicator (NADH or SDH), the STpv has the highest percentage of slow-oxidative (SO) or SO plus fast-oxidative-glycolytic (FOG) fibers of any portion of the muscle. The differences in fiber-type distributions and architectural designs of the separate compartments suggest a specialization of function of the individual compartments.

Characteristics of blood gas in response to iron treatment and exercise in iron-deficient and anemic subjects

The effects of iron deficiency anemia and iron treatment on blood gas and acid-base balance at rest and during exercise were studied. Eight Sri Lankan males and 13 females were randomly divided into an iron treatment or placebo group. Their initial hemoglobin (Hb) levels were 6.2 +/- 0.5 and 5.5 +/- 0.7 g/100 ml (mean +/- SEM) with serum iron levels of 41 +/- 8 and 30 +/- 6 micrograms/100 ml, respectively. Hemoglobin concentration was increased significantly within 7 days after iron treatment to 7.2 +/- 0.4 g/100 ml. Resting lactate was higher than normal, while base excess, buffer base, and actual bicarbonate were lower, maintaining a normal pH. Heart rates during exercise at a given work load and lactate production following exercise decreased after the elevation of Hb. Venous blood PCO2 rose as Hb concentration increased, preceding a significant increase in resting O2 content, 16 days after iron treatment. With anemia, O2 delivery is potentially maintained by a shift of the O2-dissociation curve to the right due, in part, to 2,3-diphosphoglycerate. There was no significant change in PO2 or Hb-O2% saturation following exercise or iron treatment. These data suggest that severe iron deficiency anemia results in lactate accumulation in blood even at rest but pH is maintained within normal limits. It was also suggested that severe anemia may impair CO2 transport capacity of blood which could limit continuation of muscle metabolism.

External scintigraphy in monitoring the behavior of pharmaceutical formulations in vivo I: technique for acquiring high-resolution images of tablets

A new method for monitoring tablet disintegration in vivo was developed. In this method, the tablets were labeled with a short-lived radionuclide, technetium 99m, and monitored by a gamma camera. Several innovations were introduced with this method. First, computer reconstruction algorithms were used to enhance the scintigraphic images of the disintegrating tablet in vivo. Second, the use of a four-pinhole collimator to acquire multiple views of the tablet resulted in high count rates and reduced acquisition times of the scintigraphic images. Third, the magnification of the scintigraphic images achieved by pinhole collimation led to significant improvement in resolution. Fourth, the radioinuclide was incorporated into the granulation so that the whole mass of the tablet was uniformly labeled with high levels of activity. This technique allowed the continuous monitoring of the disintegration process of tablets in vivo in experimental animals. Multiple pinhole collimation and the labeling process permitted the acquisition of quality scintigraphic images of the labeled tablet every 30 sec. The resolution of the method was tested in vitro and in vivo.

Glucocorticoid-induced atrophy in different fibre types of selected rat jaw and hind-limb muscles

Six weeks of glucocorticoid treatment (triamcinolone-acetonide-21-phosphate, 1 mg/kg of body weight daily) resulted in a similar pattern of fibre type atrophy in jaw and hind-limb muscles. Fast-twitch glycolytic fibres were significantly atrophied in all muscles investigated. Fast-twitch oxidative glycolytic fibres were affected only in the fast (white) regions of the mixed muscles, while slow-twitch oxidative fibres were unaffected. The results from pair-fed controls (food intake matched to the glucocorticoid-treated animals) showed that the glucocorticoid produced an atrophic response in addition to that produced by the decreased food intake in the experimental animals. These results suggest that the jaw musculature shares the wasting effects induced by elevated circulating glucocorticoid levels often found in stress situations.

Changes in work tolerance associated with metabolic and physiological adjustment to moderate and severe iron deficiency anemia

The time course of metabolic and physiological adjustment to moderate iron deficiency anemia (MIDA, 8 g Hb/dl) and to severe iron deficiency anemia (SIDA, 4 g Hb/dl) was studied in adult, male Sprague-Dawley rats at 3, 7, 14, 30, 60, 90, 150, and 360 days, respectively. Our previous studies using the same rats used in the present study indicated that bone marrow iron was absent and plasma iron was significantly lower (p less than 0.001) in MIDA and SIDA relative to control. The following results with MIDA and SIDA rats are all expressed relative to control values. Red cell 2,3-diphosphoglycerate ranged from 45 to 146% greater in MIDA over the 360-day period and was 130% greater in SIDA at 30 days. Exhaustive run time consistently averaged 64 +/- 3% (SEM) less in MIDA over the time course and was further lowered to 18% in SIDA at 30 days. Heart rates of MIDA were elevated (p less than 0.05) at 180 days but lower (p less than 0.001) at 360 days in response to exercise. Resting heart rates of MIDA were the same at 180 and 360 days. Heart rates of SIDA were elevated (p less than 0.05) at rest and during exercise at 30 days. Organ weight/body weight changes indicated cardiomegaly in MIDA from 90 to 150 days which reverted to normal at 360 days; splenomegaly in MIDA from 90 to 360 days; and kidney atrophy in MIDA at 60 and 90 days which reverted to normal thereafter; in SIDA cardiomegaly and splenomegaly were present at 30 days. These results indicate that the onset and magnitude of physiological and metabolic adjustments occur in proportion to the severity of the anemia, and despite compensatory adjustments in parameters related to work performance, a new stable, lowered level of work tolerance is reached.

Evidence for a direct action of thyroid hormone in specifying muscle properties

Thyroidal trophic effects on slow-twitch skeletal muscle properties were compared in normally innervated and denervated soleus of rats maintained at different thyroid states. Hypothyroidism caused fast to slow changes in fiber type composition (99% decrease in proportion of type II fibers), ATPase activities (down 20-30%), myosin light chain pattern (54% less fast light chains), calcium uptake by SR (down 60%), LDH activity (down 11%), and isozyme pattern (9% decrease in M-subunits). Changes of similar magnitude but opposite in direction were induced by thyrotoxicosis. Denervations reversed, to varying degrees, the fast to slow transformations observed in hypothyroidism. However the slow to fast changes found in hyperthyroidism were facilitated rather than inhibited by denervation. These latter results clearly show that the hormone effect can be elicited in the absence of motor innervation. Furthermore, denervation alone caused slow to fast changes in euthyroid muscles. From these results, it is proposed that denervation and dysthyreosis alter muscle properties by independent mechanisms. Our data favor a direct action of thyroid hormone over a neurally mediated mechanism.

The ratio of 3-hydroxyacyl-CoA dehydrogenase to lipoamide dehydrogenase activity in individual muscle fibers: mitochondrial specialization for source of energy

3-Hydroxyacyl-CoA dehydrogenase (HAD) has been widely used to assess the capacity for fatty acid oxidation by different muscle fiber types, with various Krebs cycle enzymes as a base for comparison. We have measured this enzyme in individual lyophilized fibers of the guinea pig soleus and the white and red portions of the vastus lateralis, and compared its activity in each fiber with that of lipoamide dehydrogenase (LAD), which as a part of the pyruvate dehydrogenase complex fulfills a function similar to HAD in forming acetyl-CoA, but from pyruvate and, thus, mainly from a carbohydrate source. The mean HAD/LAD ratio was 17.2 +/- 3 in the red vastus, 24.9 +/- 3 in the white vastus, and 43.7 +/- 10 in the soleus, all differences being highly significant. The two types of fast fibers were not distinguished from one another by the enzyme ratio within either the white or the red portion of the vastus lateralis. Data from all of the fast fibers taken together indicate a close correlation (0.93) between the two enzymes, whereas values from the soleus indicate a specialization of the mitochondria of the slow muscle fibers for the oxidation of fatty acids.

Responses of leukocytes and other hematologic parameters to thermal dehydration

Effects of thermal dehydration without exercise on leukocyte differentials, serum protein fractions, and other hematologic characteristics were studied in six healthy subjects. Both leukocyte and serum total protein levels increased beyond that predicted by hemoconcentration alone. Eosinophil counts decreased significantly, although other leukocyte counts tended to increase. Serum globulin concentrations tended to increase, but the albumin level did not change. Serum K+ concentration was elevated, but Na+ and Cl- were unaffected. It is suggested that thermal dehydration affects blood leukocyte composition and protein metabolism in many of the same ways as physical exercise.

Effects of a mild weight-lifting program on the progress of glucocorticoid-induced atrophy in rat hindlimb muscles

The effect of a mild weight-lifting program on the progress of glucocorticoid-induced atrophy was investigated. Groups of rats were either injected daily for 6 weeks with triamcinolone acetonide, 1 mg/kg (group S), subjected to a weight-lifting program 4 times per week (group T), or subjected to the injection and weight-lifting programs concurrently (group ST). The training program, besides decreasing the normal body weight gain of control (group C) rats, had no effects on gastrocnemius and soleus muscles. In group ST, the extent of gastrocnemius atrophy was less severe than in group S, and the mean areas of all fiber types were greater in similar proportion. Gastrocnemius muscles were also tetanically stronger (g, g/g body weight) in group ST than group S. The soleus muscles of groups ST and S were similar in all indices of size and strength, except for a significantly decreased fast-twitsch-oxidative-glycolytic (FOG) mean fiber area in the ST seleus muscles. The extent of fast-twitsch muscle atrophy resulting from chronic glucocorticoid treatment can be lessened by mild weight-lifting exercise. Differences in fiber area responses between soleus and gastrocnemius may reflect recruitment and/or metabolic differences of similar fiber types in the two muscles.