Cloning and mapping of murine superoxide dismutase copper chaperone (Ccsd) and mapping of the human ortholog

Copper does not exist in a free state within cells but is found consistently bound to metalloproteins. Specific metallochaperones escort copper to numerous targets within the cell, providing protection from the toxic effects of intracellular free copper. Many metallochaperones have been characterized in yeast, mouse, and human. To further characterize mouse metallochaperones, we cloned murine Ccsd from an adult mouse cDNA brain library, including both the coding region and the 5' and 3' UTRs. We obtained a 1,174-bp cDNA with an 825-bp open reading frame, translating a 274 amino acid protein that is 86.9% identical to human CCS. Using a mouse x hamster radiation hybrid panel, we mapped Ccsd to a proximal position on mouse chromosome 19. We mapped human CCS to 11q13 (homologous with mouse chromosome 19), utilizing a human x hamster radiation hybrid panel. The human and mouse metallochaperones are ubiquitously expressed in the major tissues of the body but seem to have different transcription products.

Effects of endurance exercise training on muscle glycogen accumulation in humans

The purpose of this investigation was to determine whether endurance exercise training increases the ability of human skeletal muscle to accumulate glycogen after exercise. Subjects (4 women and 2 men, 31 +/- 8 yr old) performed high-intensity stationary cycling 3 days/wk and continuous running 3 days/wk for 10 wk. Muscle glycogen concentration was measured after a glycogen-depleting exercise bout before and after endurance training. Muscle glycogen accumulation rate from 15 min to 6 h after exercise was twofold higher (P < 0.05) in the trained than in the untrained state: 10.5 +/- 0.2 and 4.5 +/- 1.3 mmol. kg wet wt(-1). h(-1), respectively. Muscle glycogen concentration was higher (P < 0.05) in the trained than in the untrained state at 15 min, 6 h, and 48 h after exercise. Muscle GLUT-4 content after exercise was twofold higher (P < 0.05) in the trained than in the untrained state (10.7 +/- 1.2 and 4.7 +/- 0.7 optical density units, respectively) and was correlated with muscle glycogen concentration 6 h after exercise (r = 0.64, P < 0.05). Total glycogen synthase activity and the percentage of glycogen synthase I were not significantly different before and after training at 15 min, 6 h, and 48 h after exercise. We conclude that endurance exercise training enhances the capacity of human skeletal muscle to accumulate glycogen after glycogen-depleting exercise.

Effects of growth hormone and testosterone on cortical bone formation and bone density in aged orchiectomized rats

Osteoporosis in men is a disease that is increasing in incidence, and with an increasing elderly population it poses a serious health problem. Since both testosterone (T) and growth hormone (GH) have an anabolic effect on bone and both decrease with aging, we were prompted to test whether the administration of these hormones in combination would increase bone mass in orchiectomized (orx) senile rats more than administration of either agent alone. Twenty-month-old male Wistar rats were divided into five groups with seven animals each: (a) age-matched intact control, (b) orx, (c) orx+GH (2.5 mg/kg/day), (d) orx+T [10 mg/kg, subcutaneous (s.c.), injection given twice a week], and (e) orx+GH+T. Testosterone and GH were given subcutaneously for 4 weeks. Bone histomorphometry of the tibial shaft showed that the orx group had lower cortical bone area than the intact control group. The decrease in cortical bone area was due to increased intracortical porosis as well as decreased periosteal bone formation rate (BFR). Administration of T to the orx animals prevented the development of the porosis and the decrease in periosteal BFR. The bone mineral content (BMC) and bone mineral density (BMD) of the femur as tested by dual-energy X-ray absorptiometry were significantly higher in the orx+T than in the orx group and were not significantly different from that of the intact control group. Administration of GH to the orx rats increased periosteal BFR significantly; however, the BMC and BMD measured were not increased significantly in comparison to the orx group. When GH and T were combined in treatment, the cortical bone area, periosteal BFR, and femoral BMD were all significantly higher than that of the orx and even higher than the intact control rats. Two-way analysis of variance shows that the individual effect of GH and T treatment on the periosteal BFR and cortical bone area was significant. The effect of T, but not GH, on femoral BMC and BMD was also significant; however, there is no synergistic interaction between the two treatments. Four weeks of orx with or without GH or T administration had no significant effect on tibial metaphyseal cancellous bone volume. In conclusion, this short-term study suggests that the combined intervention of GH and T in androgen-deficient aged male rats may have an independent effect in preventing osteopenia. The significant effect of GH+T may be attributed to the prevention of intracortical porosis, and an increase in periosteal bone formation and cortical bone mass.

The composition of rural hospital medical staffs: the influence of hospital neighbors

The local supply of physicians has a strong influence on the availability and the quality of services provided by rural hospitals. Nevertheless, there are no published studies that describe the composition of rural hospital medical staffs and, in particular, the availability of specialists on these staffs. This study uses 1991 and 1994 survey data from rural hospitals located in eight states to describe the specialty composition and factors that influence the presence of specialists on rural hospital medical staffs. The results show a strong, positive association between the level of medical staff specialization in rural hospitals and the level of medical specialization of their closet rural neighbors, which suggests there is competition among rural hospitals based on the composition of the hospital medical staff. Analysis by specialty type, however, indicates that the degree of competition may differ for different types of specialists.

Effect of hypophysectomy on the proliferation and differentiation of rat bone marrow stromal cells

Conditions such as estrogen deficiency, skeletal unloading, and aging have all been demonstrated to have various effects on the proliferation and differentiation of bone marrow stroma-derived osteoprogenitor cells. Here we have sought to examine the effects of pituitary hormone deficiency on the proliferation and the differentiation of these osteoprogenitor cells using the hypophysectomized (HX) rat as a model. In the present study, we use an in vitro culture system to examine the effects of HX on the osteogenic potential of rat bone marrow stroma. With the intact animal as a control, we used [3H]thymidine incorporation and cell number as indexes of proliferation. We also measured alkaline phosphatase enzyme activity, relative levels of osteocalcin expression with RT-PCR, and osteopontin and bone sialoprotein steady-state levels by Northern blot to delineate the effect on differentiation. Our results indicate that osteoprogenitor cells exposed to a pituitary hormone-deficient environment in vivo demonstrate an enhanced proliferative capacity and also exhibit an augmented expression of differentiation markers when exposed to an optimal environment in vitro.

A high fat diet impairs stimulation of glucose transport in muscle. Functional evaluation of potential mechanisms

A high fat diet causes resistance of skeletal muscle glucose transport to insulin and contractions. We tested the hypothesis that fat feeding causes a change in plasma membrane composition that interferes with functioning of glucose transporters and/or insulin receptors. Epitrochlearis muscles of rats fed a high (50% of calories) fat diet for 8 weeks showed approximately 50% decreases in insulin- and contraction-stimulated 3-O-methylglucose transport. Similar decreases in stimulated glucose transport activity occurred in muscles of wild-type mice with 4 weeks of fat feeding. In contrast, GLUT1 overexpressing muscles of transgenic mice fed a high fat diet showed no decreases in their high rates of glucose transport, providing evidence against impaired glucose transporter function. Insulin-stimulated system A amino acid transport, insulin receptor (IR) tyrosine kinase activity, and insulin-stimulated IR and IRS-1 tyrosine phosphorylation were all normal in muscles of rats fed the high fat diet for 8 weeks. However, after 30 weeks on the high fat diet, there was a significant reduction in insulin-stimulated tyrosine phosphorylation in muscle. The increases in GLUT4 at the cell surface induced by insulin or muscle contractions, measured with the 3H-labeled 2-N-4-(1-azi-2,2, 2-trifluoroethyl)-benzoyl-1,3-bis-(D-mannose-4-yloxy)-2-propyla min e photolabel, were 26-36% smaller in muscles of the 8-week high fat-fed rats as compared with control rats. Our findings provide evidence that (a) impairment of muscle glucose transport by 8 weeks of high fat feeding is not due to plasma membrane composition-related reductions in glucose transporter or insulin receptor function, (b) a defect in insulin receptor signaling is a late event, not a primary cause, of the muscle insulin resistance induced by fat feeding, and (c) impaired GLUT4 translocation to the cell surface plays a major role in the decrease in stimulated glucose transport.

Increased GLUT-4 translocation mediates enhanced insulin sensitivity of muscle glucose transport after exercise

The purpose of this study was to determine whether the increase in insulin sensitivity of skeletal muscle glucose transport induced by a single bout of exercise is mediated by enhanced translocation of the GLUT-4 glucose transporter to the cell surface. The rate of 3-O-[3H]methyl-D-glucose transport stimulated by a submaximally effective concentration of insulin (30 microU/ml) was approximately twofold greater in the muscles studied 3.5 h after exercise than in those of the sedentary controls (0.89 +/- 0.10 vs. 0.43 +/- 0.05 micromol . ml-1 . 10 min-1; means +/- SE for n = 6/group). GLUT-4 translocation was assessed by using the ATB-[2-3H]BMPA exofacial photolabeling technique. Prior exercise resulted in greater cell surface GLUT-4 labeling in response to submaximal insulin treatment (5.36 +/- 0.45 dpm x 10(3)/g in exercised vs. 3.00 +/- 0.38 dpm x 10(3)/g in sedentary group; n = 10/group) that closely mirrored the increase in glucose transport activity. The signal generated by the insulin receptor, as reflected in the extent of insulin receptor substrate-1 tyrosine phosphorylation, was unchanged after the exercise. We conclude that the increase in muscle insulin sensitivity of glucose transport after exercise is due to translocation of more GLUT-4 to the cell surface and that this effect is not due to potentiation of insulin-stimulated tyrosine phosphorylation.

Anabolic effect of prostaglandin E2 in bone is not dependent on pituitary hormones in rats

Prostaglandin E2 (PGE2) is an anabolic agent of bone in vivo but the mechanism of its action still remains unclear. The aim of this study was to determine whether the effect of PGE2 on skeleton is mediated by pituitary hormones. Forty female, Sprague-Dawley rats were divided into four groups: baseline control (basal), age-matched intact control (CON), hypophysectomy (HX), and HX + PGE2 (2 mg/kg/day) with 10 animals in each group. The basal group was sacrificed at 2 months of age, and the remaining groups after 6 weeks of treatment. Cancellous and cortical bone histomorphometry was performed on double fluorescent-labeled 40 micron-thick sections of the proximal tibia and tibial shaft. Our results show that HX resulted in a cessation of bone growth, a decrease in cancellous bone volume, and cortical bone gain compared with the age-matched, intact CON rats. Compared with the HX group, the HX + PGE2 group had a significantly greater tibial bone density (mean +/- SE, HX + PGE2:1.595 +/- 0.007 versus HX:1.545 +/- 0.013), percent cancellous bone volume (21.4 +/- 2.0 versus 8.41 +/- 1.70), percent cortical bone area (87.2 +/- 0.85 versus 81.7 +/- 0.7), and ratio of cortical area to marrow area (7.14 +/- 0.56 versus 4.52 +/- 0.21). Increased bone masses by PGE2 in the HX animals were accompanied by an increase in the trabecular and endosteal-labeled surface and bone formation rate. The trabecular number and width were increased whereas trabecular separation was decreased in the HX + PGE2 group compared with the HX group (P < 0.05). PGE2 treatment also caused a decrease in the tibial endosteal eroded surface and medullar cavity of the HX animals. In conclusion, this study clearly demonstrates that PGE2 (2 mg/kg/day) in the HX rats increases both cortical and cancellous bones and improves trabecular architecture in the tibia after 6 weeks of treatment. These skeletal alterations are due to a stimulation of bone formation and a suppression of bone resorption activity. These findings suggest that the anabolic effect of PGE2 in bone is independent of pituitary hormones.

Glycogen supercompensation masks the effect of a traininginduced increase in GLUT-4 on muscle glucose transport

Endurance exercise training induces a rapid increase in the GLUT-4 isoform of the glucose transporter in muscle. In fasted rats, insulin-stimulated muscle glucose transport is increased in proportion to the increase in GLUT-4. There is evidence that high muscle glycogen may decrease insulin-stimulated glucose transport. This study was undertaken to determine whether glycogen supercompensation interferes with the increase in glucose transport associated with an exercise-induced increase in GLUT-4. Rats were trained by means of swimming for 6 h/day for 2 days. Rats fasted overnight after the last exercise bout had an approximately twofold increase in epitrochlearis muscle GLUT-4 and an associated approximately twofold increase in maximally insulin-stimulated glucose transport activity. Epitrochlearis muscles of rats fed rodent chow after exercise were glycogen supercompensated (86.4 +/- 4.8 micromol/g wet wt) and showed no significant increase in maximally insulin-stimulated glucose transport above the sedentary control value despite an approximately twofold increase in GLUT-4. Fasting resulted in higher basal muscle glucose transport rates in both sedentary and trained rats but did not significantly increase maximally insulin-stimulated transport in the sedentary group. We conclude that carbohydrate feeding that results in muscle glycogen supercompensation prevents the increase in maximally insulin-stimulated glucose transport associated with an exercise training-induced increase in muscle GLUT-4.

GBP, an inhibitor of GSK-3, is implicated in Xenopus development and oncogenesis

Dorsal accumulation of beta-catenin in early Xenopus embryos is required for body axis formation. Recent evidence indicates that beta-catenin is dorsally stabilized by the localized inhibition of the kinase Xgsk-3, utilizing a novel Wnt ligand-independent mechanism. Using a two-hybrid screen, we identified GBP, a maternal Xgsk-3-binding protein that is homologous to a T cell protooncogene in three well-conserved domains. GBP inhibits in vivo phosphorylation by Xgsk-3, and ectopic GBP expression induces an axis by stabilizing beta-catenin within Xenopus embryos. Importantly, antisense oligonucleotide depletion of the maternal GBP mRNA demonstrates that GBP is required for the establishment of the dorsal-ventral axis in Xenopus embryos. Our results define a family of GSK-3-binding proteins with roles in development and cell proliferation.

Laser intraductal photocoagulation of bilateral parotid ducts for reducing drooling of cerebral palsied children: a preliminary report

Previous reports suggested that surgical treatment was effective to reduce abnormal, profuse drooling in children with low cognitive function, but with risk of complications. Laser photocoagulation might be an option to simplify the procedure and decrease complications. Our study considered whether laser photocoagulation could improve drooling in children with cerebral palsy (CP). CP children with drooling were recruited from the pediatric rehabilitation clinic, all of whom had persistent profuse drooling after 6 months of conservative treatment. They received neodymium:yttrium aluminum garnet (Nd:YAG) laser for intraductal photocoagulation to bilateral parotid ducts, and were followed up for 2 to 3 months. Each patient was assessed before and after the procedure by: 1) questionnaire-based semiquantitative assessment of drooling severity and frequency (Thomas-Stonell and Greensberg 1988); 2) quantitative assessment of saliva amount by collection of stimulated saliva for 2 minutes in cooperative children. Six CP children with severe drooling received laser photocoagulation, five of them had remarkable decrease of drooling 1 month later. Patients had cool liquid intake soon after the procedure, and were discharged on the second day after treatment. A period of transient face swelling ranged from 6 to 37 days. No antibiotic treatment was indicated nor were any complications noted after the procedure. As a result of these studies, it is suggested that laser intraductal photocoagulation of bilateral parotid duct could be used as a simple and effective procedure for reducing drooling in CP children, and would avoid complications from conventional surgery.

Short-term exposure to tumor necrosis factor-alpha does not affect insulin-stimulated glucose uptake in skeletal muscle

It has been hypothesized that increased production of tumor necrosis factor-alpha (TNF-alpha) plays a role in causing the insulin resistance associated with obesity. Obesity with insulin resistance is associated with increased production of TNF-alpha by fat cells. Exposure of 3T3-L1 adipocytes to TNF-alpha for 3-4 days makes them insulin resistant. TNF-alpha has also been reported to rapidly (15-60 min) cause insulin resistance, with a decrease in insulin-stimulated tyrosine phosphorylation, in a number of cultured cell lines. Because skeletal muscle is the major tissue responsible for insulin-stimulated glucose disposal, we performed the present study to determine if acute exposure to TNF-alpha causes insulin resistance in muscle. We found that exposure of soleus muscles to 6 nmol/l TNF-alpha for 45 min in vitro had no inhibitory effect on insulin-stimulated tyrosine phosphorylation of the insulin receptor or insulin receptor substrate 1 (IRS-1) or on phosphatidylinositol 3-kinase association with IRS-1. Incubation of epitrochlearis and soleus muscles with 6 nmol/l TNF-alpha for 45 min or 4 h had no effect on insulin-stimulated 2-deoxyglucose (2-DG) uptake. Treatment of epitrochlearis muscles with 2 nmol/l TNF-alpha for 8 h also had no effect on insulin-stimulated 2-DG uptake. We conclude that in contrast to Fao hepatoma cells and 3T3-L1 fibroblasts, skeletal muscle does not become insulin resistant in response to short-term exposure to TNF-alpha.

Rapid reversal of adaptive increases in muscle GLUT-4 and glucose transport capacity after training cessation

Previous studies have shown that when exercise is stopped there is a rapid reversal of the training-induced adaptive increase in muscle glucose transport capacity. Endurance exercise training brings about an increase in GLUT-4 in skeletal muscle. The primary purpose of this study was to determine whether the rapid reversal of the increase in maximally insulin-stimulated glucose transport after cessation of training can be explained by a similarly rapid decrease in GLUT-4. A second purpose was to evaluate the possibility, suggested by previous studies, that the magnitude of the adaptive increase in muscle GLUT-4 decreases when exercise training is extended beyond a few days. We found that both GLUT-4 and maximally insulin-stimulated glucose transport were increased approximately twofold in epitrochlearis muscles of rats trained by swimming for 6 h/day for 5 days or 5 wk. GLUT-4 was 90% higher, citrate synthase activity was 23% higher, and hexokinase activity was 28% higher in triceps muscle of the 5-day trained animals compared with the controls. The increases in GLUT-4 protein and in insulin-stimulated glucose transport were completely reversed within 40 h after the last exercise bout, after both 5 days and 5 wk of training. In contrast, the increases in citrate synthase and hexokinase activities were unchanged 40 h after 5 days of exercise. These results support the conclusion that the rapid reversal of the increase in the insulin responsiveness of muscle glucose transport after cessation of training is explained by the short half-life of the GLUT-4 protein.

DHEA treatment reduces fat accumulation and protects against insulin resistance in male rats

The purpose of this study was to determine whether administration of dehydroepiandrosterone (DHEA) protects male rats against the accumulation of body fat the development of insulin resistance with advancing age. We found that supplementation of the diet with 0.3% DHEA between the ages of 5 months and approximately 25 months resulted in a significantly lower final body weight (DHEA, 593 +/- 18 g vs control, 668 +/- 12 g, p < 0.02), despite no decrease in food intake. Lean body mass was unaffected by the DHEA, and the lower body weight was due to a approximately 25% reduction in body fat. The rate of glucose disposal during a euglycemic, hyperinsulinemic clamp was 30% higher in the DHEA group than in the sedentary controls due to a greater insulin responsiveness. The DHEA administration was as effective in reducing body fat content and maintaining insulin responsiveness as exercise in the form of voluntary wheel running. The DHEA had no significant effect on muscle GLUT4 content. A preliminary experiment provided evidence suggesting that muscle insulin signaling, as reflected in binding of phosphatidylinositol 3-kinase to the insulin receptor substrate-1, was enhanced in the DHEA-treated and wheel running groups as compared to controls. These results provide evidence that DHEA, like exercise, protects against excess fat accumulation and development of insulin resistance in rats.

Effects of estrogen and growth hormone on skeleton in the ovariectomized rat with hypophysectomy

To investigate whether growth hormone (GH) and 17beta-estradiol (E2) replacement can prevent osteopenia induced by pituitary and ovarian hormone deficiency [by hypophysectomy and ovariectomy (HX+OV)], we administered relatively low doses of GH (2.3 IU x kg(-1) x day(-1)) and E2 (100 microg x kg(-1) x wk(-1)) in experiment 1 and relatively high doses of GH (13.5 IU x kg(-1) x day(-1)) and E2 (3,500 microg x kg(-1) x wk(-1)) in experiment 2 to 2-mo-old HX+OV Sprague-Dawley rats for 6 wk. Our data show that the HX+OV of rats results in diminished periosteal bone formation, longitudinal bone growth, and decreased cancellous bone volume. Administration of either the low or high dose of GH to these rats increased their systemic growth, serum levels of osteocalcin, and cortical bone formation. Either low or high doses of GH or E2 alone only partially prevent cancellous bone loss. However, the combined treatment of GH plus E2 resulted in an additive increase in the cancellous bone mass. We conclude that the additive effect of GH plus E2 on cancellous bone is attributed to the suppressive effect of E2 on bone resorption and the anabolic effect of GH on bone formation.

Histologic evidence: growth hormone completely prevents reduction in cortical bone gain and partially prevents cancellous osteopenia in the tibia of hypophysectomized rats

BACKGROUND

In previous studies we found that the cause of bone loss in young hypophysectomized (HX) animals was due primarily to an inhibition in growth-dependent bone gain and a decrease in bone turnover. The aim of this study was to determine whether growth hormone, which has stimulatory effects on bone growth and turnover, can prevent HX-induced skeletal alterations in rats.

METHODS

Female Sprague-Dawley rats were divided into baseline control (BASAL), age-matched control (CON), HX, HX plus low-dose GH (1.5 mg/kg/d, subcutaneously), and HX plus high-dose GH (4.5 mg/kg/d) groups. The BASAL group was sacrificed at 2 months of age and the remaining groups were sacrificed after 6 weeks of treatment. Cancellous and cortical bone histomorphometry was performed on double-fluorescent-labeled 40 microm-thick sections of the proximal tibia and tibial shaft.

RESULTS

Both low- and high-dose GH prevented the HX-induced decrease of IGF-I serum levels. High-dose GH also significantly increased the body weight and the wet weight of the gastrocnemius muscle when compared to the CON groups. In the tibial shaft, the periosteal labeled surface, mineral apposition rate and bone formation rate were higher in both of the GH-treated groups than in the HX group (P < 0.05). The tissue area and cortical bone area of the high-dose GH-treated rats were greater than those of the HX rats, but did not differ from those of the CON rats. In the proximal tibia, both low- and high-dose GH prevented an HX-induced decrease in the longitudinal growth rate and growth plate width, and increased surface-based bone formation compared to the HX and CON. Cancellous bone volume, tissue-based bone formation rate, and eroded surface in both of the GH-treated groups were higher than those of the HX group, but lower than those of the BASAL and CON groups (P < 0.05). Bone architecture of the HX rats was also improved after GH treatment.

CONCLUSIONS

This study clearly demonstrates that GH replacement at the dosage of 4.5 mg/kg/d can completely prevent the HX-induced reduction in cortical bone gain in the tibial shaft, but can only partially prevent cancellous osteopenia in the proximal tibia after six weeks.

Effects of 17 beta-estradiol administration on cortical and cancellous bone of ovariectomized rats with and without hypophysectomy

Pituitary hormones are essential for bone growth and bone turnover. Hypophysectomy (HX) diminishes mitogenesis and abolishes the high bone turnover rate induced by ovariectomy (OV). It is not known whether the suppressive effect of estrogen on bone resorption is diminished or abolished by HX. The present study investigates the effects of 17 beta-estradiol (E2) (20 micrograms/wk) on cortical and cancellous bone mass and bone turnover as measured by histomorphometry in HX + OV (HO) rats. Sprague-Dawley rats at 2 months of age were OV or HO and the experiment was performed over a 6 week period. Hypophysectomy + OV (HO) resulted in a cessation of periosteal bone formation, and longitudinal bone growth and a decrease in cancellous bone volume. The tibial dry weight and tibial density were significantly lower in the HO than in the intact or OV groups. Administration of E2 to HO rats partially prevented cancellous bone loss, whereas the same dosage of E2 fully prevented cancellous bone loss in rats with OV alone. Nevertheless, cancellous bone volume was higher in the HO + E2 than in the HO-alone groups. Estradiol administration in HO rats did not suppress cancellous bone formation rate or the eroded surface as much as it did in the OV rats. The suppressive effect of E2 on periosteal bone formation rate and mineral apposition rate was also diminished in HO rats. However, factorial ANOVA showed that the effects of E2 on increasing cancellous bone volume and decreasing periosteal bone formation rate and mineral apposition rate were still significant in the HO rats. Tibial dry weight and tibial density did not differ between HO and HO + E2 groups. In conclusion, we have demonstrated that the estrogen-induced effects of preventing cancellous bone loss, of suppressing bone formation, and resorption as seen in OV rats was diminished but not abolished in HO rats.

Appraising the performance of medical technologists in a clinical laboratory

Medical technologists and their coworkers serve as a critical link in the delivery of health care, yet their performance typically is appraised in a traditional way, causing stress for both managers and workers. Drawing on Total Quality Management concepts, this article proposes a framework for appraising performance in a clinical laboratory context and shows how it can be used to address the problems that managers face in providing constructive appraisals to laboratory personnel.

Ovariectomy-induced high turnover in cortical bone is dependent on pituitary hormone in rats

The aim of this study is to examine the interrelationship of pituitary and ovarian hormone deficiency on the regulation of bone growth and bone formation rate. 48 female rats, at 3 months of age, were divided into age-matched intact control, hypophysectomized (HX), ovariectomized (OV), and HX + OV groups. Ten rats were killed at 3 months of age as baseline controls, and the rest of the animals were killed 5 weeks after surgery. Serum levels of osteocalcin and dynamic histomorphometry on the periosteal surface of the tibial shaft and fifth lumbar vertebrae were measured to evaluate systemic and local bone turnover. Tibial and fourth lumbar vertebral bone area, bone mineral content, and bone density were measured by dual-energy X-ray absorptiometry (DXA). Our results confirmed that OV increased and HX suppressed systemic and periosteal bone formation parameters in both bone sites, OV increased and HX suppressed the gain in bone size and bone mass. When OV rats were HX, the serum levels of osteocalcin and periosteal bone formation parameters of the tibial shaft and the fifth lumbar vertebrae were, however, depressed and did not differ from that of the HX alone. DXA results show that the effect of OV on bone size and bone mass is also abolished by HX. In conclusion, we have demonstrated that OV increases tibial and lumbar vertebral bone formation and bone growth and this effect is pituitary hormone dependent.

Bone histomorphometry of ovariectomized or orchiectomized rats fed a moderately magnesium-deficient fructose diet and treated with exogenous oestrogen or testosterone

To investigate the effects of sex hormones on bone histomorphometry, and bone density (BMD), 10 week old ovariectomized (OVX), orchiectomized (ORX), and sham-operated (SHAM) rats fed a moderately magnesium-deficient fructose diet were studied. One third of the OVX and ORX rats were injected with beta-oestradiol-3-benzoate; another third, testosterone cypionate; and the remaining SHAM rats, vehicle only. After 14 weeks, a 24 h urine sample was collected for measurements of calcium, phosphorus and cyclic AMP (cAMP). Blood was collected for determination of calcium, phosphorus, and parathyroid hormone (PTH). Femurs and tibias were removed and weighed. Femurs were used to measure bone areas, mineral contents (BMC), and BMD. Tibias were used for bone histomorphometry (that is, trabecular numbers, thicknesses, % areas and separations). Oestrogen treatment increased serum and urine calcium significantly in both OVX and ORX rats, whereas testosterone decreased serum and urine calcium significantly. Oestrogen decreased urinary cAMP and PTH in both OVX and ORX rats, whereas testosterone treatment increased them significantly. Oestrogen treatment increased BMD, trabecular numbers, thicknesses, and % areas, and decreased bone separations in both OVX and ORX rats. In contrast, testosterone did not increase these bone indices in either OVX or ORX rats; rather, it increased bone separations by decreasing bone strength. Testosterone treatment improved trabecular histomorphometry slightly in OVX rats. The results of the present study are concordant with our previous findings that exogenous oestrogen treatment can prevent osteoporosis in either OVX or ORX rats, whereas exogenous testosterone cannot.

BDNF or IGF-I potentiates free radical-mediated injury in cortical cell cultures

Free radical-mediated damage to cultured cortical neurons was induced by a 24 h exposure to Fe2+ (30 microM) or an inhibitor of gamma-glutamylcysteine synthetase, L-buthionine-[S,R]-sulfoximine (BSO, 1 mM). As expected, neuronal death was blocked by inclusion of the free radical scavenger trolox during the Fe2+ or BSO exposure. However, unexpectedly, pretreatment of the cultures with BDNF or IGF-I markedly potentiated neuronal death. This growth factor-potentiated death was still blocked by trolox, but was insensitive to glutamate antagonists. Concurrent addition of cycloheximide with the growth factors prevented injury potentiation. Present findings suggest that growth factors may increase free radical-induced neuronal death by mechanisms dependent upon protein synthesis.

Effect of ovariectomy on cancellous bone in the hypophysectomized rat

This experiment studied the effects of hypophysectomy (HX) and ovariectomy (OV) on cancellous bone in the proximal tibia and distal 5th lumbar vertebra by dynamic histomorphometry. Forty-eight female Sprague-Dawley rats, 3 months of age, were divided into age-matched control, HX, OV, and HX + OV (HO) groups. Ten rats were sacrificed at 3 months of age as baseline controls, and the rest of the animals were sacrificed 5 weeks after the surgery. While the age-matched controls, and the OV rats significantly increased in body weight compared with the baseline control rats, cancellous bone volumes in the proximal tibia and distal 5th lumbar vertebra increased in the age-matched controls and decreased in the OV rats. In the HX and HO rats, body weight equaled baseline control values, and their cancellous bone volumes were decreased with a poorer trabecular architecture in both bone sites. In all HX, OV, and HO rats, uterine weight and serum estradiol were significantly decreased. OV significantly increased longitudinal bone growth and the tissue- and surface-based bone formation and bone resorption parameters in both the proximal tibia and 5th lumbar vertebra (p < 0.05). HX alone or HO significantly decreased longitudinal bone growth and the tissue-based bone formation rate without significantly affecting surface-based bone formation and bone resorption parameters when compared with the age-matched controls. No significant differences were detected in any variables between the HX alone and HO rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Computational simulation of worker exposure using a particle trajectory method

The velocity field downstream of a worker is approximated with a discrete vortex algorithm. This information is used to calculate trajectories of massless tracer 'particles' released from a point-source of contaminant. Concentrations in the plane of this source are estimated by averaging over a number of such trajectories. Approximations include: (1) representing the worker by a two-dimensional elliptical cylinder; and (2) representing tracer gas contaminant by massless particles generated without momentum. These particles are transported by both vortex shedding and turbulent diffusion. Computer-predicted mean concentrations in the near-wake region downstream of the worker compare well with results from wind-tunnel tracer gas experiments employing a mannequin. Subsequently, the concept of a computational breathing zone is introduced, and predictions of worker exposure are made. These simulations of time-integrated breathing zone concentration also compare well with measured values.

Skeletal alterations in hypophysectomized rats: II. A histomorphometric study on tibial cortical bone

BACKGROUND

Pituitary hormones play an important role in bone growth, modeling, and remodeling. The purpose of this study is to examine the effect of hypophysectomy (HX) on tibial cortical bone with histomorphometry.

METHODS

Forty-five female Sprague-Dawley rats, at 3 months of age, were hypophysectomized or served as intact controls. They were sacrificed at 0, 2, and 5 weeks after the surgery. Cortical bone histomorphometry was performed on double-fluorescent-labeled 30-mcm-thick sections of the tibial shaft.

RESULTS

The dry weight and density of tibial diaphysis and the cortical bone area of the tibial shaft in the HX rats were significantly lower (P < 0.05) than that of the age-matched intact rats, but did not differ between the HX and basal control rats. The dynamic data show that the bone formation parameters (labeled surface, mineral apposition rate, and bone formation rate) were profoundly decreased (P < 0.01) on both the periosteal and endocortical surfaces in the HX rats as compared with the age-matched intact rats at the 2 and 5 weeks. However, the decrease in the labeled surface was much less on the endocortical envelope than on the periosteal envelope in the HX rats. Although no significant change was detected in the medullar size between the HX and age-matched intact rats, the eroded surface on the endocortical surface was greater (P < 0.05) in the HX rats than in the intact rats at either time point.

CONCLUSIONS

Hypophysectomy-suppressed, radial growth-dependent bone gain without a bone loss in the tibial shaft of the young rat. This is associated with decreased modeling-dependent bone formation. A greater eroded surface on the endosteum did not affect the marrow size at 5 weeks after hypophysectomy.

Skeletal alterations in hypophysectomized rats: I. A histomorphometric study on tibial cancellous bone

BACKGROUND

Hypophysectomy (HX) results in a cessation of bone growth and a decrease in bone metabolism. The purpose of this study is to examine the effect of HX on the static and dynamic histomorphometry of cancellous bone in the secondary spongiosa of the proximal tibial metaphysis in rats.

METHODS

Female rats, at 2 or 3 months of age, were HX and sacrificed at 0, 5 days, 2 and 5 weeks after the surgery. Age-matched intact rats served as controls. Cancellous bone histomorphometry was performed on double-fluorescent labeled, 30-microns-thick sections of the proximal tibia. Tartrate-resistant acid phosphatase histomorphometry was performed at 5 days on HX and control rats to evaluate the resorption in the metaphyseal bone.

RESULTS

Although the intact rats gained in body weight, tibial length, tibial weight, and density after 5 weeks, these changes did not occur following HX. As compared to the basal group, HX resulted in a decrease in the density and dry weight of the metaphysis. The histomorphometric data showed that the cancellous bone volume and trabecular number of the secondary spongiosa were decreased and the separation was increased in the HX rats. The dynamic results showed that HX significantly decreased longitudinal growth rate and tissue-based bone formation and resorption. However, the bone surface-based eroded surface, labeled surface, the mineral apposition rate, and the bone formation rate did not differ between the intact and the HX rats at either the 2 or 5 weeks study. Five days after HX, the bone surface and tissue-based osteoclast surfaces were significantly lower in the HX than in the intact rats.

CONCLUSIONS

Pituitary hormone deficiency results in cancellous bone loss. The bone loss is due primarily to the suppression of longitudinal growth-dependent bone gain and the inhibition of tissue-based bone turnover with a lower bone formation relative to bone resorption. The surface-based bone turnover is not affected.

Mechanical loading modifies ovariectomy-induced cancellous bone loss

The object of this study was to determine the tissue level mechanism in which mechanical loading had an influence on ovariectomy-induced cancellous bone loss. Two experiments were performed: (1) 230 g female rats were divided into basal, age-related controls and right hindlimb immobilized (RHLI) group; (2) 250 g female rats were divided into basal, age-related, ovariectomized (OVX) controls and OVX combined with RHLI. The RHLI model immobilized (IM) or underloaded (UL) the right hindlimb and loaded (L) the left hindlimb compared to the right hindlimb. Both experiments lasted 60 days. Histomorphometric data was gathered from the secondary spongiosa of double fluorescent labeled proximal tibial metaphysis (PTM). The study confirmed that IM or UL induces cancellous bone loss, by decreasing bone formation, and increasing bone resorption and OVX results in cancellous bone loss, a higher bone turnover with bone resorption exceeding bone formation in the PTM. The OVX'd and immobilized (OVX + UL) PTM showed further decreased cancellous bone mass (-48%), decreased number (-43%), and decreased tissue-level bone formation rate (-54%) from that of OVX rats. However, the OVX'd and loaded (OVX + L) PTM partially prevented the OVX-induced cancellous bone loss. The cancellous bone area (+46%), number (+29%), and ratio of node to free end (+70%) were increased and percent eroded perimeter (-44%) and bone resorption rates (-30%) were decreased from OVX rats, but cancellous bone area and number were still significantly lower than those in age-related controls. We found that IM or UL accentuated cancellous bone loss in OVX rats by inhibiting bone formation and that loading partially prevented cancellous bone loss in OVX and RHLI rats by inhibiting bone resorption.

Microvascular architecture within the pig kidney cortex

Corrosion casts of the plastic (Mercox Cl-2B) filled pig kidney cortex vasculature were sliced either parallel or perpendicular to the kidney surface. Scanning electron microscopy photographs were taken of the casts. Montages of the photographs were analyzed using a digitizing tablet and microcomputer-based software. For vessels having diameters larger than 0.05 mm, their sizes, numbers per unit area, and branching patterns were studied with respect to the kidney cortex depth. Vascular branching diameters and angles within the cortex compare favorably with those reported for other major vascular systems. The microvascular dimensions and densities were used to predict the average blood flow velocity within the kidney cortex. It is expected that the results will facilitate a better insight into the contribution of flowing blood to the heat transfer process in perfused tissues.

Effect of treadmill exercise on tibial cortical bone in aged female rats: a histomorphometry and dual energy x-ray absorptiometry study

The aim of this study was to increase our understanding of the effect of exercise on cortical bone mass and turnover in aged female rats. Female Sprague-Dawley rats, 14 months of age, were divided into four groups: 8 controls and 10 exercised for the 9-week study, and 8 controls and 9 exercised for the 16-week study. Exercise consisted of treadmill running at 17 m/min for one h/day and 5 days/week for 9 and 16 weeks. All animals received double fluorochrome labeling of bone prior to sacrifice. Histomorphometric analysis was performed on 30-microns-thick Villanueva-stained, undecalcified cross-sections of the tibial shaft. Tibial diaphyseal mineral density of each rat in the 16-week study was measured by dual energy x-ray absorptiometry in vivo at 0, 9, and 16 weeks. The diaphyseal mineral density of the exercised group was significantly greater than that of the control group (p < 0.05 by two-way ANOVA) and the individual slopes of the density vs. time was found to be higher in the exercised than in the control animals (mean +/- SE of exercised 0.56 +/- 0.13 vs. control 0.19 +/- 0.07 mg/cm2/week, p < 0.05) by the end of the experiment. The results of the histomorphometric analysis after 9 weeks of exercise showed that the periosteal labeled surface, mineral apposition rate, and bone formation rate were profoundly increased by 192% (p < 0.001), 35%, and 206% (p < 0.01), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of new technologies by rural family physicians

BACKGROUND

Although office procedures that involve special training and office equipment are often performed by a specialist in an urban setting, they are increasingly being performed by family physicians in rural settings. This study documents the prevalence of four such procedures in rural family practice: flexible sigmoidoscopy, cardiac stress testing, colposcopy, and nasopharyngoscopy. Individual and community characteristics of physicians who perform each of the procedures are compared with those of physicians who do not.

METHODS

Data were collected on office technology and the characteristics of physicians, their practices, and their communities through telephone interviews with 403 randomly selected, rural family physicians and general practitioners in eight states. Descriptive and univariate analyses were used.

RESULTS

Flexible fiberoptic sigmoidoscopy was performed by 57% of the physicians in our sample. The presence of another physician in the group or in the community who performed this procedure increased the probability of a rural physician performing it. Being male, recent licensure, board certification, and patient volume were also positively associated with the performance of this procedure.

CONCLUSIONS

This study found evidence of a collegial effect among rural physicians and of a significant number of rural physicians seeking postresidency training in new procedures.

Influence of exercise on cancellous bone of the aged female rat

Dual-energy x-ray absorptiometry and dynamic histomorphometry were used to examine the effect of treadmill exercise on the bone density and cancellous bone formation and resorption in the proximal tibia and fifth lumbar vertebra (L5) of the aged female rat. Female rats aged 14 months were divided into four groups: 8 controls and 10 exercised for a 9 week study and 8 controls and 9 exercised for a 16 week study. Exercise consisted of running on a flat-bed treadmill, 17 m/minute, 1 h/day, 5 days/week. Tibial metaphysis and L5 vertebral density of each rat were measured in the 16 week study by DXA at weeks 0, 9, and 16. Compared to the control group, a significant increase in bone density in both metaphyseal tibia and L5 vertebra was apparent at 16 weeks after exercise training (P = 0.046 and 0.025, respectively, by two-way ANOVA). Histomorphometric analysis showed that the trabecular bone eroded surface and the ratio of eroded to mineralizing surface in tibial metaphysis were significantly lower in the exercised than in the respective control group in both the 9 and 16 week studies. In L5 vertebra, these decreases by exercise were apparent only in the 16 week study. A significant increase in the bone formation rate was apparent in the cancellous bone of the tibia but not of the vertebra after 16 weeks of exercise (P < 0.05). The trabecular architecture (bone number and separation) of the L5 vertebra in the exercised rats did not differ from that of the controls in either study.(ABSTRACT TRUNCATED AT 250 WORDS)

Theoretical analysis of the large blood vessel influence on the local tissue temperature decay after pulse heating

The influence of a large blood vessel (larger than 500 microns in diameter) on the local tissue temperature decay following a point source heating pulse was determined numerically using a sink/source method. It was assumed that the vessel was large enough so that the temperature of blood flowing within it remained essentially constant and was unaffected by any local tissue temperature transients. After the insertion of a point source heating pulse, the vessel influence on the local tissue transient temperature field was estimated by representing the vessel as a set of negative fictitious instantaneous heat sources with strength just sufficient to maintain the vessel at a constant temperature. In the surrounding tissue, the Pennes' tissue heat transfer equation was used to describe the temperature field. Computations have been performed for a range of vessel sizes, probe-vessel spacings and local blood perfusion rates. It was found that the influence of a large vessel on the local tissue temperature decay is more sensitive to its size and location rather than to the local blood perfusion rate. For a heating pulse of 3s duration and 5mW of power, there is a critical probe-vessel center distance 7R (R, vessel radius) beyond which the larger vessel influence on tissue temperature at the probe can be neglected.

A clinically based service limitation option for alternative model rural hospitals

Alternative model rural hospitals are designed to address problems faced by small, isolated rural hospitals. Typically, hospital regulations are reduced in exchange for a limit on the services that alternative models may offer. The most common service limitation is a limit on length of stay (LOS), a method with little empirical or conceptual support. The purpose of this article is to present a clinically based service limitation for alternative model rural hospitals, such as the rural primary care hospital. The proposal is based on an analysis of Medicare discharges from rural hospitals most likely to convert and the judgments of a technical advisory panel of rural clinicians.

Adaptation of cancellous bone to aging and immobilization in growing rats

Two-and-half-month-old female rats were subjected to right hindlimb immobilization or served as controls for 0, 1, 2, 8, 14, and 20 weeks. The right hindlimb was immobilized by bandaging it against the abdomen, thus unloading it. Cancellous bone histomorphometry was performed on microradiographs and double-fluorescent labeled 20 microns sections of the distal femoral metaphyses. Primary spongiosa bone loss occurred rapidly by 2 weeks, and secondary spongiosa bone loss occurred rapidly by 8 weeks of immobilization, and then equilibrated at 60% less bone mass than age-related controls. The negative bone balance induced by immobilization was caused by transient increase in bone resorption, decrease in bone formation, and longitudinal bone growth. The dynamic data of secondary spongiosa cancellous bone showed that percent eroded perimeter was transiently elevated by 55 to 82% between 1 and 8 weeks, percent labeled perimeter was transiently depressed by 32% to 50% between 1 and 14 weeks, mineral apposition rate was depressed by 23% and 19% at 1 and 2 weeks, and bone formation rate-bone area referent was transiently depressed by 35% and 59% at 1 and 2 weeks. All the above parameters were at age-related control levels by 20 weeks of immobilization. However, bone formation rate-tissue area referent was depressed (-65%) throughout the study. Immobilization depressed completely longitudinal bone growth by 2 weeks and remained so. Only 0.65 mm of new metaphysis was generated in the immobilized versus 2.1 mm in controls during the study period. The immobilization induced an early cancellous bone loss which equilibrated at a new steady state with less bone and a normal (age-related control) bone turnover rate. When these findings were compared to an earlier study of 9-month-old virgin females subjected to right hindlimb immobilization up to 26 weeks, we found the adaptive responses of the cancellous bone were identical except that they occurred earlier and equilibrated sooner in younger rats.

A technique for measuring the thermal conductivity and evaluating the "apparent conductivity" concept in biomaterials

A simple technique for measuring thermal conductivity of biomaterials is described. The method is based on depositing a pulse of heat into the material of choice, and fitting the subsequent local temperature decay to that predicted by a theoretical model. This transient method is most suitable in situations where frequent measurements of the thermal conductivity are desired. The method was evaluated by calculating the thermal conductivity of several inert materials. The measured conductivities compared well with published values. The developed technique was also used to examine the applicability of the "apparent conductivity" index to combine both conductive and blood-convective thermal effects in living, blood perfused tissues. Using both simulated and experimental results, it was shown that the changes in the apparent conductivity are highly correlated with changes in blood flow. However, quantitative application of this index must be restricted to conditions that are similar to those which existed at the time the apparent conductivity was measured.

Theory on thermal probe arrays for the distinction between the convective and the perfusive modalities of heat transfer in living tissues

Recent suggestions for an improved model of heat transfer in living tissues emphasize the existence of a convective mode due to flowing blood in addition to, or even instead of, the perfusive mode, as proposed in Pennes' "classic" bioheat equation. In view of these suggestions, it might be beneficial to develop a technique that will enable one to distinguish between these two modes of bioheat transfer. To this end, a concept that utilizes a multiprobe array of thermistors in conjunction with a revised bioheat transfer equation has been derived to distinguish between, and to quantify the perfusive and convective contribution of blood to heat transfer in living tissues. The array consists of two or more temperature sensors one of which also serves to locally insert a short pulse of heat into the tissue prior to the temperature measurements. A theoretical analysis shows that such a concept is feasible. The construction of the system involves the selection of several important design parameters, i.e., the distance between the probes, the heating power, and the pulse duration. The choice of these parameters is based on computer simulations of the actual experiment.

Computer-based system for continuous on-line measurements of tissue blood perfusion

We describe a new system for an almost continuous, on-line measurement of local blood perfusion in living tissue. The technique uses a thermal method based on measurements of the tissue temperature decay after a short pulse (approximately equal to 3 s) of local heating. The instrumentation system consists of six small thermistor microprobes, a probe interface unit and a DEC LSI-11/23 microcomputer. The system is equipped with six thermistor channels, and the number can be increased with further signal conditioning modules, thereby increasing the locations at which blood perfusion can be measured. The results agree favourably with values for tissue blood flow obtained simultaneously using either the microspheres method or an electromagnetic probe. The system has been in use for three years and there is good reason to believe that it can be reliably applied in many situations where a continuous multichannel monitor of local blood perfusion is necessary.

Adaptive thermal modeling: a concept for measurement of local blood perfusion in heated tissues

A new Adaptive Thermal Modeling (ATM) method for the measurement of local tissue blood perfusion rate is introduced. The method is based on a two-phase numerical technique. The first phase includes a fast, finite difference scheme for solution of the transient temperature field. The second phase involves iterative corrections of the perfusion until the modeled temperatures coincide with those measured by the temperature sensors. The results obtained from computer generated "data", as well as from laboratory experiments demonstrate the potential capability of the ATM method to continuously measure local perfusion rates in heated tissues. Rigorous analysis of the technique is planned for the near future so that it can be applied to in vivo measurements of local tissue blood perfusions.

Thermal pulse decay method for simultaneous measurement of local thermal conductivity and blood perfusion: a theoretical analysis

Presented here is a theoretical analysis of the recently developed thermal pulse decay (TPD) method for a simultaneous measurement of local tissue conductivity and blood perfusion rate. The paper describes the theoretical model upon which the TPD method is based and details its capabilities and limitations. The theoretical aspects that affected the development of the measurement protocol are also discussed. The performance of the method is demonstrated with an experimental example which compares the measurements of local kidney blood perfusion rates made using the TPD method with the total renal blood flow obtained coincidentally using a blood flowmeter, in an anesthetized dog.

A sensitivity analysis of the Thermal Pulse Decay method for measurement of local tissue conductivity and blood perfusion

The Thermal Pulse Decay (TPD) method for the determination of local tissue thermal conductivity and blood perfusion rate is based on a comparison of measured with theoretically calculated temperatures. A sensitivity analysis of the theoretical model is performed. This analysis supports the establishment of an experimental protocol which reduces the measurement errors: An "optimal" measurement time interval for typical perfusion rates (up to 6 mL/mL/min) was found to be between 3 and 11 s after the heat pulse is turned off. Within this interval, the maximum error in determination of tissue conductivity and blood perfusion caused by experimental measurement errors is expected not to exceed 5 percent. The presently chosen pulse duration of 3 s is in agreement with the analysis as a good compromise between accuracy and excessive tissue heating.

Proposed methods for the measurement of regional renal blood flow using heat transfer analysis

The kidney, with its heterogeneous regional perfusion in the two anatomically and functionally distinct vascular beds of the renal cortex and medulla, and with its non-uniform blood vessel geometries, presents a unique challenge for measuring intrarenal blood flow distribution. Determining whole organ perfusion, on the other hand, is comparatively simple for the kidney, but it provides relatively little information about the suspected dependency of renal excretory function on local perfusion rate. Among the variety of methods proposed for gauging regional renal blood flow, some depend on measuring one or more of the tissue's thermal properties. The most straightforward, but least reliable, involve measurements either of focal tissue temperature alone, or of regional tissue thermal gradients. Simply using heat as a diffusible indicator, however, is unreliable as a measure of blood flow, for many of the same reasons that using an inert gas in a dilution technique is unreliable. Recently developed thermal analytical methods, though, hold promise for measuring local tissue blood flow with accuracy and precision. Two of them are reviewed here. One depends on measurement of the effective thermal conductivity of a small mass of tissue by evaluating the steady state ratio between regional unidirectional heat flux across it and the associated temperature gradient in one vector along a segment of it through an imposed spheroidal heat field. The other depends on analyses of tissue temperature decay subsequent to a controlled pulse of heat delivered through a small inserted thermistor bead. Both techniques use bioheat transfer equations to deduce regional blood flow by differentiating between heat dissipation due to local thermal conductivity and that attributable to the effects of regional convection. Although both methods are unavoidably invasive, neither produces debilitating damage in the tissue volume in which perfusion is measured, nor increases local temperature or metabolism enough to affect blood flow itself. Both techniques quantify local blood flow in small volumes of tissue by detailed evaluation of the many properties of tissue and blood which affect heat transfer, and both allow for a virtually unlimited number of nearly continuous sequential measurements at short (nom. 1 min) time intervals.

Cimetidine--acetaminophen interaction in humans

The effect of single-dose and multiple-dose cimetidine administration on acetaminophen pharmacokinetics was investigated in a three-phase, randomized, crossover study using four normal subjects. In each phase of the study, subjects ingested 750 mg of acetaminophen as a single dose alone (A), or in combination with 200 mg of cimetidine (A + C), or following a one-week pretreatment with daily cimetidine, 200 mg every six hours and 400 mg before retiring (A + C*). Statistical analysis using two-way analysis of variance indicated no significant difference in peak concentration and peak time of acetaminophen between treatments. Cimetidine did not significantly affect acetaminophen half-life, 2.38 hours (A), 2.65 hours (A + C), and 2.50 hours (A + C*). Acetaminophen clearance was minimally affected by cimetidine; the mean clearance of acetaminophen ranged from 4.16 (A + C*) to 5.57 mL/min/kg (A). Area under the acetaminophen plasma concentration-time curve was slightly increased by cimetidine, 35.4 (A), 41.6 (A + C), and 47.6 micrograms/mL/h (A + C*). Since cimetidine did not affect acetaminophen pharmacokinetics to any significant extent, clinical combination of both medications at therapeutic dosage presumably would not produce adverse interactions.

Absorption and disposition of ethambutol in rabbits

The absorption and disposition of ethambutol was examined in six rabbits in a three-way crossover study. Each rabbit received 45-mg/kg doses of ethambutol in three treatments: one intravenous injections and two oral solutions, ethambutol alone and ethambutol in the presence of aluminum hydroxide (40 mg/kg). Half-lives of ethambutol ranged from 2.26 to 5.20 h when administered alone and 2.18 to 4.00 h when coadministered with the antacid; the difference was not significant (p greater than 0.3). Mean clearance after the oral administrations (189.2 mL/min/kg) was significantly greater than the mean intravenous clearance (43.7 mL/min/kg) (p less than 0.01), suggesting a first-pass metabolism of ethambutol when administered nonparenterally to rabbits. The volume of distribution ranged from 5.5 to 17.8 L/kg, suggesting an extensive distribution of ethambutol outside the central compartment and, possibly, a localized deposit within the body tissues. Mean bioavailability of ethambutol was approximately 28% and was not affected by the presence of aluminum hydroxide. The rate of ethambutol absorption, however, was slightly delayed by the antacid.

Acetaminophen-aluminum hydroxide interaction in rabbits

Acetaminophen-aluminum hydroxide interaction was investigated in a crossover study using six rabbits. Blood samples were collected at various time intervals for up to 6 hr following the oral administration of acetaminophen alone or in combination with aluminum hydroxide. Aluminum hydroxide at a 40-mg/kg dose did not appear to affect the rate and extent of acetaminophen absorption. The influence of aluminum hydroxide on gastric emptying could be compromised by gastric absorption of acetaminophen, resulting in a negligible effect on the overall bioavailability of acetaminophen.

[Evaluation of the GNF computer-coding system for the identification of non-fermentative Gram-negative bacilli]

In order to evaluate the effectiveness of the GNF computer-coding system for the identification of glucose non-fermenting gram-negative bacilli, we employed 406 strains of bacteria including 367 clinical isolates and 39 standard strains for testing. These strains were inoculated into the following eleven conventional biochemical test media: Triple Sugar Iron Agar, Simmon's Citrate Agar, Christensen's Urea Agar, Sulfide-Indole-Motility Medium, Semisolid Voges-Proskauer Test Medium, Moeller's Ornithine Decarboxylase Test Medium, Pyocyanin Test Medium, Oxidation/Fermentation (O/F) Glucose, O/F Fructose, Nitrate Broth, Moeller's Arginine Dihydrolase Test Medium. The results of these tests plus those from the hanging drop motility test and the oxidase test were converted into bacterial code number and then checked with the GNF computer-coding system. It was found that the first preference of agreement was 75.6%, second 15.3%, third 5.9%, and fourth or more 3.2%. In regard to the speed of bacterial identification by using the GNF system and information from hemolysis pattern and flagella stain, it was indicated that 84.7% would be correctly identified within 36-48 hours after isolation. If more confirmational tests were employed, the accurate identification rate would reach to 98.7% after 4 days of isolation. In addition, the use of the GNF computer-coding system can standardize identification procedures, shorten the identification period, and save cost in terms of materials supply, inoculation time, media preparation and media-storing space. Therefore, we conclude that the GNF computer-coding system is an effective tool in the identification of the glucose non-fermenting gram-negative bacilli.

Pulse-decay method for measuring the thermal conductivity of living tissues

The present communication presents a single microprobe technique for measuring tissue thermal properties based on the dissipation of a measured amount of energy and the observation of the resulting temperature rise a given time later. An advantage of this method is that the effective sampling volume can be varied by varying the measurement time. Using a measurement time of a few seconds, the sampling volume was estimated to be several orders of magnitude greater than the probe volume. Hence artifacts due to probe-induced trauma or stress would be insignificant. Additional advantages of the technique are: the results were independent of the probe shape, size and properties, and hence represents absolute measurements without the need for calibration; the required electronics and computations are simple; the determination of thermal conductivity requires only a single measurement; and comparison of data at different measurement times yields a clear and unequivocal indication of nonconductive contributions of heat transfer, if present.

Maximizing health system output with political and administrative constraints using mathematical programming

Decisions about delivery programs to improve health status are characterized by indivisibilities or "lumpiness," interdependencies between case types with varying health output, high fixed costs, administrative constraints, and qualitative quity and political considerations. The nature of the constraints and the goal of health services strongly suggest a mathematical programming model to maximize a comprehensive measure of health status. In a previously unreported development, binary integer programming can be extended to consider shared fixed costs, a widespread problem in optimizing effectiveness measures such as health status. The model proposed here applies conceptually across all target populations and health programs and could be used to optimize the output of a total health system. The effects of such optimization would be appropriately reflected in the weighted life expectancy computed as a social indicator.

No-fault malparactice insurance. Proximate cause and the quality of medical care

No-fault medical malpractice insurance has been proposed as an alternative to the present tort liability approach. Statistical examination of the concept of proximate cause reveals not only that the question of acceptable care, and therefore of fault, is unavoidable in identifying patients deserving compensation, but also that specifying fault in an individual case is scientifically untenable. A simple formula for a Coefficient of Causality clarifies the question of proximate cause in existing trial practices and suggests that many of the threats associated with malpractice suits arise from the structure of the tort-insurance system rather than from professional responsibility for medical injury. The concepts could provide the basis for a revised claims and compensation procedure.