Suppression of black-hole growth by strong outflows at redshifts 5.8-6.6.

Bright quasars, powered by accretion onto billion-solar-mass black holes, already existed at the epoch of reionization, when the Universe was 0.5-1 billion years old1. How these black holes formed in such a short time is the subject of debate, particularly as they lie above the correlation between black-hole mass and galaxy dynamical mass2,3 in the local Universe. What slowed down black-hole growth, leading towards the symbiotic growth observed in the local Universe, and when this process started, has hitherto not been known, although black-hole feedback is a likely driver4. Here we report optical and near-infrared observations of a sample of quasars at redshifts 5.8 ≲ z ≲ 6.6. About half of the quasar spectra reveal broad, blueshifted absorption line troughs, tracing black-hole-driven winds with extreme outflow velocities, up to 17% of the speed of light. The fraction of quasars with such outflow winds at z ≳ 5.8 is ≈2.4 times higher than at z ≈ 2-4. We infer that outflows at z ≳ 5.8 inject large amounts of energy into the interstellar medium and suppress nuclear gas accretion, slowing down black-hole growth. The outflow phase may then mark the beginning of substantial black-hole feedback. The red optical colours of outflow quasars at z ≳ 5.8 indeed suggest that these systems are dusty and may be caught during an initial quenching phase of obscured accretion5.

Biomimetic biodegradable artificial antigen presenting cells synergize with PD-1 blockade to treat melanoma.

Biomimetic materials that target the immune system and generate an anti-tumor responses hold promise in augmenting cancer immunotherapy. These synthetic materials can be engineered and optimized for their biodegradability, physical parameters such as shape and size, and controlled release of immune-modulators. As these new platforms enter the playing field, it is imperative to understand their interaction with existing immunotherapies since single-targeted approaches have limited efficacy. Here, we investigate the synergy between a PLGA-based artificial antigen presenting cell (aAPC) and a checkpoint blockade molecule, anti-PD1 monoclonal antibody (mAb). The combination of antigen-specific aAPC-based activation and anti-PD-1 mAb checkpoint blockade induced the greatest IFN-γ secretion by CD8+ T cells in vitro. Combination treatment also acted synergistically in an in vivo murine melanoma model to result in delayed tumor growth and extended survival, while either treatment alone had no effect. This was shown mechanistically to be due to decreased PD-1 expression and increased antigen-specific proliferation of CD8+ T cells within the tumor microenvironment and spleen. Thus, biomaterial-based therapy can synergize with other immunotherapies and motivates the translation of biomimetic combinatorial treatments.

Study of equivalence: spinal bupivacaine 15 mg versus bupivacaine 12 mg with fentanyl 15 µg for cesarean delivery.

BACKGROUND: A safe and effective intrathecal dose of bupivacaine alone for cesarean delivery has not yet been established. This study tested the hypothesis that an intrathecal dose of hyperbaric bupivacaine 15 mg would produce equivalent spinal anesthesia for cesarean delivery as the combination of hyperbaric bupivacaine 12 mg and fentanyl 15 µg. METHODS: This was a single center, double-blind, randomized clinical trial of equivalence. One hundred and thirty-eight healthy parturients scheduled for elective cesarean delivery were randomized to receive either intrathecal hyperbaric bupivacaine 15 mg (Group B) or hyperbaric bupivacaine 12 mg with fentanyl 15 µg (Group BF). Parturients where asked to describe their degree of sensation during surgery using a four-point scale 20 min after spinal injection. Secondary outcomes included the incidence of maternal side effects, maternal hemodynamics and the need for supplemental analgesia. RESULTS: There was no difference in the quality of anesthesia between the two groups. Sixty-eight of 69 and 69/69 patients in Group B and Group BF, respectively had anesthesia classified as successful (RR=1.01; 95% CI 0.85, 1.22). The only two secondary outcomes that were different between the groups were the largest change in mean arterial pressure (decrease of 40 mmHg and 34 mmHg for Group B and Group BF, respectively; P=0.004) and the incidence of nausea (59% and 35% for Group B and Group BF, respectively; P=0.006). CONCLUSION: There was no difference in the degree of sensation at 20 min between Group B and Group BF. The only significant differences between the two techniques were a higher incidence of nausea and decrease in maternal blood pressure in Group B.

Bipolar spinal cord stimulation attenuates mechanical hypersensitivity at an intensity that activates a small portion of A-fiber afferents in spinal nerve-injured rats.

Spinal cord stimulation (SCS) is used clinically to treat neuropathic pain states, but the precise mechanism by which it attenuates neuropathic pain remains to be established. The profile of afferent fiber activation during SCS and how it may correlate with the efficacy of SCS-induced analgesia are unclear. After subjecting rats to an L5 spinal nerve ligation (SNL), we implanted a miniature quadripolar electrode similar to that used clinically. Our goal was to determine the population and number of afferent fibers retrogradely activated by SCS in SNL rats by recording the antidromic compound action potential (AP) at the sciatic nerve after examining the ability of bipolar epidural SCS to alleviate mechanical hypersensitivity in this model. Notably, we compared the profiles of afferent fiber activation to SCS between SNL rats that exhibited good SCS-induced analgesia (responders) and those that did not (nonresponders). Additionally, we examined how different contact configurations affect the motor threshold (MoT) and compound AP threshold. Results showed that three consecutive days of SCS treatment (50 Hz, 0.2 ms, 30 min, 80-90% of MoT), but not sham stimulation, gradually alleviated mechanical hypersensitivity in SNL rats. The MoT obtained in the animal behavioral study was significantly less than the Aα/ß-threshold of the compound AP determined during electrophysiological recording, suggesting that SCS could attenuate mechanical hypersensitivity with a stimulus intensity that recruits only a small fraction of the A-fiber population in SNL rats. Although both the MoT and compound AP threshold were similar between responders and nonresponders, the size of the compound AP waveform at higher stimulation intensities was larger in the responders, indicating a more efficient activation of the dorsal column structure in responders.

Anesthetic considerations for placenta accreta.

BACKGROUND: When diagnosed antenatally placenta accreta has often been managed by cesarean hysterectomy, but recently techniques involving uterine preservation have been developed. Uterine artery embolization has become an adjuvant treatment, although the potential for obstetric hemorrhage still exists. A multidisciplinary approach has permitted the development of anesthetic strategies for these patients. METHODS: A retrospective case note review of patients with placenta accreta between 2000 and 2008 at our institution was conducted. Anesthetic technique, estimated blood loss, requirement for blood products and disposition of patients postoperatively were recorded. RESULTS: A total of 23 cases were identified. In six, epidural anesthesia with progression to general anesthesia was planned. In 17 cases, neuraxial anesthesia was planned and in five of these (29%) excessive blood loss necessitated conversion to general anesthesia. Nine patients (39%) had intraoperative blood loss estimated at > 2L, and six required intraoperative blood transfusion. Eleven patients (48%) required hysterectomy, seven of which were performed on the day of delivery. CONCLUSION: In this case series, the expectation of major blood loss at cesarean delivery in the presence of placenta accreta and attempts at uterine conservation surgery initially prompted a conservative approach using general anesthesia. Greater experience has permitted modification of this approach and neuraxial anesthesia is now employed more frequently. When managed appropriately, most patients are able to tolerate both prolonged surgery and significant blood loss under epidural anesthesia.

The Vascular Access Questionnaire: assessing patient-reported views of vascular access.

BACKGROUND: The use of central venous catheters for vascular access in hemodialysis (HD) patients is associated with an increased risk of complications compared to arteriovenous fistulas (AVF). Despite this, catheter use remains high and patient satisfaction may be an important driver of catheter use. METHODS: We developed the Vascular Access Questionnaire (VAQ) to measure patient-reported views of their vascular access. Chronic HD patients at two centers were asked to rate how bothered they were by 17 access-related problems. VAQ symptom scores were compared between patients using catheters and those using fistulas for vascular access. RESULTS: Two hundred and twenty-two patients were eligible for the study. Symptom score was not different between patients using catheters and those using fistulas (p=0.36). However, patients using fistulas were more likely to be at least moderately bothered by pain, bleeding, bruising, swelling, and the appearance of their access than patients using catheters. Elderly patients reported lower symptom scores with catheters than fistulas. CONCLUSIONS: Patients appear to be primarily concerned with the appearance of their access and cannulation-related complications, particularly the elderly. Better education about the risk of adverse events with catheters and the implementation of measures aimed at reducing cannulation-related complications may help to increase fistula rates and improve patient satisfaction with their vascular access.

Accuracy of fetal echocardiography: a cardiac segment-specific analysis.

OBJECTIVE: In patients with congenital heart disease, comprehensive, segment-specific analysis of cardiac anatomy has become 'the standard of care', largely as a result of improvements in cardiac imaging technology. Our aim was to apply segment-specific standards to assess the accuracy of fetal echocardiography. METHODS: This was a retrospective review of all fetal echocardiograms (n = 915) performed at our center between August 1998 and June 2003. Of these, 100 studies had congenital heart disease findings and corresponding postnatal studies on the same patients for comparison. An expert independent pediatric echocardiologist, using the standards of accuracy expected of postnatal echocardiography, assessed the studies for the following cardiac segments: abdominal situs, systemic venous return (VR), pulmonary VR, atria, atrioventricular valves, ventricular septum, ventricular hypoplasia, ventricular morphology, semilunar valves, great arterial relation and aortic arch. Sensitivity, specificity, and positive and negative predictive values were calculated for each segment. RESULTS: Specificity and negative predictive value were high for all cardiac segments (range, 82-100%). Sensitivity and positive predictive value were similarly high (range, 83-100%) for most cardiac segments, but were only 50-88% for systemic VR, pulmonary VR and aortic arch segments. CONCLUSIONS: Fetal echocardiography has excellent diagnostic accuracy in describing intracardiac anatomy. However, despite both technological advances and improved physician awareness, assessment of systemic VR, pulmonary VR, and aortic arch anatomy remain challenging.

Intramuscular fat and glucose tolerance after spinal cord injury--a cross-sectional study.

STUDY DESIGN: Survey. OBJECTIVE: Determine intramuscular fat (IMF) in affected skeletal muscle after complete spinal cord injury using a novel analysis method and determine the correlation of IMF to plasma glucose or plasma insulin during an oral glucose tolerance test. SETTING: General community of Athens, GA, USA. METHODS: A total of 12 nonexercise-trained complete spinal cord injured (SCI) persons (10 males and two females 40+/-12 years old (mean+/-SD), range 26-71 years, and 8+/-5 years post SCI) and nine nonexercise-trained nondisabled (ND) controls 29+/-9 years old, range 23-51 years, matched for height, weight, and BMI, had T(1) magnetic resonance images of their thighs taken and underwent an oral glucose tolerance test (OGTT) after giving consent. RESULTS: Average skeletal muscle cross-sectional area (CSA) (mean+/-SD) was 58.6+/-21.6 cm(2) in spinal cord subjects and 94.1+/-32.5 cm(2) in ND subjects. Average IMF CSA was 14.5+/-6.0 cm(2) in spinal cord subjects and 4.7+/-2.5 cm(2) in nondisabled subjects, resulting in an almost four-fold difference in IMF percentage of 17.3+/-4.4% in spinal cord subjects and 4.6+/-2.6% in nondisabled subjects. The 60, 90 and 120 min plasma glucose or plasma insulin were higher in the SCI group. IMF (absolute and %) was related to the 90 or 120 min plasma glucose or plasma insulin (r(2)=0.71-0.40). CONCLUSIONS: IMF is a good predictor of plasma glucose during an OGTT and may be a contributing factor to the onset of impaired glucose tolerance and type II diabetes, especially in SCI. In addition, reports of skeletal muscle CSA should be corrected for IMF.

MRI evaluation of topical heat and static stretching as therapeutic modalities for the treatment of eccentric exercise-induced muscle damage.

The aim of this study was to monitor the effects of topical heat and/or static stretch treatments on the recovery of muscle damage by eccentric exercise. For this purpose, 32 untrained male subjects performed intense eccentric knee extension exercise, followed by 2 weeks of treatment (heat, stretch, heat plus stretch) or no treatment (control, n=8/group). Isometric strength testing, pain ratings, and multi-echo magnetic resonance imaging of the thigh were performed before and at 2, 3, 4, 8, and 15 days following the exercise. Increased T2 relaxation time, muscle swelling, pain ratings, and strength loss confirmed significant muscle damage during the post-exercise period. Pain ratings and muscle volume recovered to baseline by 15 days, although muscle strength remained lower [77 (4) vs. 95 (3) kg pre-exercise, mean (SE)] and T2 values higher [32.2 (0.8) vs. 28.6 (0.2) ms pre-exercise]. Our results indicate that heat and/or static stretching does not consistently reduce soreness, swelling or muscle damage. The practical implication of our findings is that clinicians should be aware that prescribing heat and/or static stretching following intense eccentric or unaccustomed exercise will not enhance the recovery of damaged muscles.

BMP regulation of the mouse connexin43 promoter in osteoblastic cells and embryos.

We examined BMP regulation of the gap junction gene Gjal (Cx43alpha1) using a series of lacZ reporter constructs containing up to 6.7 kbs of mouse Cx43alpha1 promoter sequence. Using transient transfection assays, we showed that BMP2, BMP4, and GDF5, but not BMP6 or BMP7, can modulate Cx43alpha1 promoter activity in the osteosarcoma cell line ROS17/2.8. Positive regulatory elements were found at the proximal and distal ends of the 6.7 kb promoter fragment, while negative regulatory elements were found in the intervening region. Comparison of Cx43alpha1 promoter sequences from the human vs. mouse showed five regions with significant sequence conservation, two of which contained Smad binding elements in conjunction with a BMP response element. Analysis of a transgenic mouse line containing a Cx43alpha1 promoter driven lacZ reporter construct revealed lacZ expression in the developing joints, an expression pattern similar to that previously reported for Gdf5. LacZ expression was also observed in axial regions of the skeletal anlage, which in situ hybridization analysis confirmed as sites of Gdf5 transcript expression. When the Cx43alpha1 promoter driven lacZ transgene was bred into the brachypodism mouse Gdf5(bpJ)(bp) harboring a Gdf5 loss of function mutation, lacZ expression was extinguished. This was observed in homozygous and heterozygous bp animals, suggesting that Cx43alpha1 promoter regulation by GDF5 is subject to haploinsufficiency. Overall, these observations are consistent with recent studies by others indicating a role for Cx43alpha1 in osteogenesis and osteoblastic function during mouse development.

Multimeric connexin interactions prior to the trans-Golgi network.

Cells that express multiple connexins have the capacity to form heteromeric (mixed) gap junction hemichannels. We used a dominant negative connexin construct, consisting of bacterial beta-galactosidase fused to the C terminus of connexin43 (Cx43/beta-gal), to examine connexin compatibility in NIH 3T3 cells. Cx43/beta-gal is retained in a perinuclear compartment and inhibits Cx43 transport to the cell surface. The intracellular connexin pool induced by Cx43/beta-gal colocalized with a medial Golgi apparatus marker and was readily disassembled by treatment with brefeldin A. This was unexpected, since previous studies indicated that Cx43 assembly into hexameric hemichannels occurs in the trans-Golgi network (TGN) and is sensitive to brefeldin A. Further analysis by sucrose gradient fractionation showed that Cx43 and Cx43/beta-gal were assembled into a subhexameric complex. Cx43/beta-gal also specifically interacted with Cx46, but not Cx32, consistent with the ability of Cx43/beta-gal to simultaneously inhibit multiple connexins. We confirmed that interactions between Cx43/beta-gal and Cx46 reflect the ability of Cx43 and Cx46 to form heteromeric complexes, using HeLa and alveolar epithelial cells, which express both connexins. In contrast, ROS osteoblastic cells, which differentially sort Cx43 and Cx46, did not form Cx43/Cx46 heteromers. Thus, cells have the capacity to regulate whether or not compatible connexins intermix.

Nerve harvesting procedures.

Autogenous nerve grafts currently set the standard for reconstruction of motor and sensory nerve injuries that cannot be repaired by mobilization, advancement, and approximation, and suturing without tension. Donor nerves such as the GAN and SN are easily accessible and frequently used in maxillofacial microneurosurgery. Other nerves (MACN, LCNF, LTN) may serve well in special nerve reconstruction situations. In the future, availability of biodegradable nerve conduits with neurotrophic factors may render obsolete the reconstruction of the short-span nerve gap (< 3 cm) by autogenous nerve grafts.

Gap junction assembly: PTX-sensitive G proteins regulate the distribution of connexin43 within cells.

Cells expressing connexin43 are able to upregulate gap junction (GJ) communication by enhancing the assembly of new GJs, apparently through increased connexin trafficking. Because G proteins are known to regulate different aspects of protein trafficking, we examined the effects of pertussis toxin (PTX; a specific inhibitor of certain G proteins) on GJ assembly. Dissociated Novikoff hepatoma cells were reaggregated for 60 min to form nascent junctions. PTX inhibited GJ assembly, as indicated by a reduction in dye transfer. Electron microscopy also revealed a 60% decrease in the number of GJ channels per cell interface. Importantly, PTX blocked the twofold enhancement in GJ assembly found in the presence of low-density lipoprotein. Two G(i alpha) proteins (G(i alpha 2) and G(i alpha 3)), which have been implicated in the control of membrane trafficking, reacted with PTX in ADP-ribosylation studies. PTX and/or the trafficking inhibitors, brefeldin A and monensin, inhibited GJ assembly to comparable degrees. In addition, assays for GJ hemichannels demonstrated reduced plasma membrane levels of connexin43 following PTX treatment. These results suggest that PTX-sensitive G proteins regulate connexin43 trafficking, and, as a result of inhibition with PTX, the number of plasma membrane hemichannels available for GJ assembly is reduced.

Biarticular and monoarticular muscle activation and injury in human quadriceps muscle.

We hypothesized that activation of the quadriceps femoris muscle group during eccentric exercise is related to the increase in magnitude of several markers of muscle injury that developed during the next week. Fourteen male subjects performed six to eight sets of five to ten repetitions of single-leg eccentric-only seated knee extension exercise. Magnetic resonance (MR) images were collected before and immediately after exercise and on days 2-4 and 6 after eccentric exercise. Changes in maximal voluntary contraction (MVC), perceived soreness, muscle volume and muscle transverse relaxation of water protons (T2) were determined for the quadriceps femoris muscle group each day. Changes in muscle volume and T2 were determined every day for each muscle [vastus lateralis (VL), vastus medialis (VM), vastus intermedius (VI), rectus femoris (RF)] of the quadriceps femoris group. Post-exercise T2 was greater than pre-exercise T2 (P < 0.05) for all muscles. The acute deltaT2 (Post-Pre) was similar (P>0.05) among VL, VM, VI, and RF [5.5 (0.3) ms], suggesting that the four muscles were equally activated during eccentric exercise. In the week after eccentric exercise, subjects experienced delayed-onset muscle soreness (DOMS) and all muscles demonstrated a delayed increase in T2 above pre-exercise values (P < 0.05), suggesting that muscle injury had occurred. For the quadriceps femoris muscle group, there was no correlation between acute deltaT2 and delayed (peak T2 during days 2, 3, 4, 6 minus pre-exercise T2) deltaT2 (r=0.04, P>0.05). Similar results were obtained when VL, VM, VI and RF were examined separately. Of the four muscles in quadriceps femoris, the biarticular RF experienced greater muscle injury [delayed deltaT2= 15.2 (2.0) ms] compared to the three monoarticular vasti muscles [delayed deltaT2 = 7.7 (1.3) ms; P< 0.05]. We propose that the disproportionate muscle injury to RF resulted from an ineffective transfer of torque from the knee to hip joint during seated eccentric knee extension exercise, thus causing RF to dissipate greater energy than normal. We conclude that in humans, muscle activation is not a unique determinant of muscle injury.

Effect of acrosomal defects on fertility of bulls used in artificial insemination and natural breeding.

Four bulls that produced spermatozoa with a high percentage of abnormal acrosomes were individually placed in pens with females for 21 days. Frozen semen from 2 of the bulls was used for artificial insemination. One of the bulls was placed in a competitive mating situation with normal bulls at pasture. First service pregnancy rates were determined by transrectal ultrasonography 28 days after bull removal from breeding pens, or after the last artificial insemination. The results of competitive mating at pasture were determined from breeding observations, the phenotypic characteristics of calves sired, and blood typing for parentage. The results of these studies suggest that bulls that produce a high percentage of spermatozoa with indented acrosomes may have normal fertility when used in artificial insemination or in single sire mating; however, their fertility may be low when breeding competitively with bulls with normal spermiograms.

Roles of capsaicin-insensitive nociceptors in cutaneous pain and secondary hyperalgesia.

Polymodal nociceptors respond to mechanical, thermal and chemical stimuli. Whereas sensitivities to heat and to the irritant substance capsaicin have recently been linked via the properties of the vanilloid receptor type 1 receptor ion channel, sensitivity to noxious mechanical stimuli such as the pinpricks used in clinical neurology seems to be unrelated. We investigated the peripheral neural basis of pinprick pain using quantitative psychophysical techniques combined with selective conduction block by nerve compression and selective desensitization by topical capsaicin treatment. Complete A-fibre block by compression of the superficial radial nerve (criterion: loss of first pain sensation) lowered the stimulus-response function for pinprick pain (-82 +/- 6% versus baseline). Topical pretreatment of the skin with a 10% capsaicin cream also lowered the pinprick stimulus-response function (-32 +/- 10%), whereas laser-evoked heat pain was eliminated completely (-96 +/- 2%). Under combined capsaicin desensitization and A-fibre blockade, pinprick pain was eliminated completely (-98 +/- 1%). Intradermal injection of 40 microg capsaicin into normal skin between two skin areas that had been pretreated with either capsaicin cream or vehicle produced secondary hyperalgesia with a 260% enhancement of the stimulus-response function for pinprick pain in both areas. In contrast, axon reflexive flare spread only into the vehicle-treated area. These results suggest that capsaicin-sensitive afferents, including polymodal A-fibre and C-fibre nociceptors, make a small contribution to pinprick pain and that capsaicin-insensitive C-fibres do not contribute significantly to either mechanical or heat pain. Pinprick pain is mediated primarily by capsaicin-insensitive A-fibre nociceptors, which include high-threshold mechanoreceptors and type I mechano-heat nociceptors. In addition, central sensitization to input from these A-fibre nociceptors is the primary mechanism that accounts for the enhanced pain in response to punctate mechanical stimuli in the zone of secondary hyperalgesia. These capsaicin-insensitive A-fibre nociceptors may also mediate hyperalgesia in neuropathic pain.

Abdominal fat distribution in pre- and postmenopausal women: The impact of physical activity, age, and menopausal status.

Age-related increases in total body fat have been reported, but the impact of menopause on abdominal fat distribution is still unclear. The purpose of this study was to determine the impact of menopausal status on abdominal fat distribution using magnetic resonance imaging (MRI). In addition, we investigated the influence of abdominal fat distribution on blood lipid profiles and leptin concentrations. Twenty-three premenopausal (PRE), 27 postmenopausal (POST), and 28 postmenopausal women on estrogen replacement therapy (ERT) had measurements of regional abdominal fat, blood lipids, and serum leptin concentrations. The women were matched for body mass index (BMI) and total body fat mass. Age and menopausal status were not found to be significant predictors of total abdominal fat, visceral fat, or subcutaneous fat, while physical activity was a significant predictor (P <.01) for total abdominal fat (R(2) =.16), visceral fat (R(2) =.32) and percent visceral fat (R(2) =.25). There was a trend for a greater visceral fat content in the POST women compared with the PRE women (2,495.0 +/- 228.4 v 1,770.4 +/- 240.8 cm(2), respectively, P =.06). The percent visceral abdominal fat was significantly lower (P <.05) in the premenopausal women than in either postmenopausal group (PRE, 23.2% +/- 1.7%; POST, 28.9% +/- 1.8%; ERT, 28.9% +/- 1.6%). Menopausal status and age did not influence any of the blood lipid values. Abdominal fat distribution was a significant predictor of cholesterol concentrations and the cholesterol/high-density lipoprotein-cholesterol (HDL-C) ratio, but only accounted for approximately 15% of the variability in these levels. Total body fat and physical activity accounted for 47% of the variability in leptin concentrations, while abdominal fat distribution, age, and menopausal status were not significant predictors. In conclusion, in early postmenopausal women, the level of physical activity accounts for the variability in abdominal fat distribution observed, while menopausal status and age do not play a significant role. ERT was not associated with additional benefits in abdominal fat distribution compared with postmenopausal women not on ERT or in the blood lipid profile in these women.

Delayed union of femoral fractures in older rats:decreased gene expression.

BACKGROUND: Fracture healing slows with age. While 6-week-old rats regain normal bone biomechanics at 4 weeks after fracture, one-year-old rats require more than 26 weeks. The possible role of altered mRNA gene expression in this delayed union was studied. Closed mid-shaft femoral fractures were induced followed by euthanasia at 0 time (unfractured) or at 1, 2, 4 or 6 weeks after fracture in 6-week-old and 12-15-month-old Sprague-Dawley female rats. mRNA levels were measured for osteocalcin, type I collagen alpha1, type II collagen, bone morphogenetic protein (BMP)-2, BMP-4 and the type IA BMP receptor. RESULTS: For all of the genes studied, the mRNA levels increased in both age groups to a peak at one to two weeks after fracture. All gene expression levels decreased to very low or undetectable levels at four and six weeks after fracture for both age groups. At four weeks after fracture, the younger rats were healed radiographically, but not the older rats. CONCLUSIONS: (1) All genes studied were up-regulated by fracture in both age groups. Thus, the failure of the older rats to heal promptly was not due to the lack of expression of any of the studied genes. (2) The return of the mRNA gene expression to baseline values in the older rats prior to healing may contribute to their delayed union. (3) No genes were overly up-regulated in the older rats. The slower healing response of the older rats did not stimulate a negative-feedback increase in the mRNA expression of stimulatory cytokines.

Age and ovariectomy impair both the normalization of mechanical properties and the accretion of mineral by the fracture callus in rats.

The impact of age and ovariectomy on the healing of femoral fractures was studied in three groups of female rats at 8, 32 and 50 weeks of age at fracture. In the two older groups, the rats had been subjected to ovariectomy or sham surgery at random at 26 weeks of age. At fracture, all rats received unilateral intramedullary pinning of one femur and a middiaphyseal fracture. Rigidity and breaking load of the femora were evaluated at varying times up to 24 weeks after fracture induction by three-point bending to failure. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry. In the youngest group, 8-week-old female rats regained normal femoral rigidity and breaking load by 4 weeks after fracture. They exceeded normal contralateral values by 8 weeks after fracture. In the middle group, at 32 weeks of age, fractures were induced, and the femora were harvested at 6 and 12 weeks after fracture. At 6 weeks after fracture there was partial restoration of rigidity and breaking load. At 12 weeks after fracture, only the sham-operated rats had regained normal biomechanical values in their fractured femora, while the fractured femora of the ovariectomized rats remained significantly lower in both rigidity and breaking load. In contrast, for the oldest group of rats, 50 weeks old at fracture, neither sham-operated nor ovariectomized rats regained normal rigidity or breaking load in their fractured femora within the 24 weeks in which they were studied. In all fractured bones, there was a significant increase in BMD over the contralateral intact femora due to the increased bone tissue and bone mineral in the fracture callus. Ovariectomy significantly reduced the BMD of the intact femora and also reduced the gain in BMD by the fractured femora. In conclusion, age and ovariectomy significantly impair the process of fracture healing in female rats as judged by measurements of rigidity and breaking load in three-point bending and by accretion of mineral into the fracture callus.

Capsaicin responses in heat-sensitive and heat-insensitive A-fiber nociceptors.

The recently cloned vanilloid receptor (VR1) is postulated to account for heat and capsaicin sensitivity in unmyelinated afferents. We sought to determine whether heat and capsaicin sensitivity also coexist in myelinated nociceptive afferents. Action potential (AP) activity was recorded from single A-fiber nociceptors that innervated the hairy skin in monkey. Before intradermal injection of capsaicin (10 microg/10 microl) into the receptive field, nociceptors were classified as heat-sensitive (threshold,