A noncyclical analog of salmon calcitonin (N alpha-propionyl Di-Ala1,7,des-Leu19 sCT) retains full potency without inducing anorexia in rats

A new analog of salmon calcitonin (N alpha-propionyl Di-Ala1,7,des-Leu19 sCT; RG-12851; here termed CTR), which lacks the ring structure of native calcitonin, was tested for biological activity in several in vitro and in vivo assay systems. The analog (CTR) and salmon calcitonin (sCT) stimulated kidney cell adenylate cyclase activity and inhibited bone resorption in organ cultures of fetal rat long bones with similar potencies and efficacies. Furthermore, CTR and sCT, at similar doses, induced comparable hypocalcemic responses in mice following sc injection or infusions. However, unlike sCT, CTR did not induce anorexia and weight loss in rats following sc injection. These data suggest that the ring structure of sCT may be important for the anorexigenic effect but is not required for effect on bone resorption or calcium homeostasis. Clinical studies appear warranted as, potentially, CTR might induce fewer side effects than does sCT.     

Dynamic Postural-Stability Deficits After Cryotherapy to the Ankle Joint

Context

 Decreased postural stability is a primary risk factor for lower limb musculoskeletal injuries. During athletic competitions, cryotherapy may be applied during short breaks in play or during half-time; however, its effects on postural stability remain unclear.

Objective

 To investigate the acute effects of a 15-minute ankle-joint cryotherapy application on dynamic postural stability.

Design

 Controlled laboratory study.

Setting

 University biomechanics laboratory.

Patients or Other Participants

 A total of 29 elite-level collegiate male field-sport athletes (age = 20.8 ± 1.12 years, height = 1.80 ± 0.06 m, mass = 81.89 ± 8.59 kg) participated.

Intervention(s)

 Participants were tested on the anterior (ANT), posterolateral (PL), and posteromedial (PM) reach directions of the Star Excursion Balance Test before and after a 15-minute ankle-joint cryotherapy application.

Main Outcome Measure(s)

 Normalized reach distances; sagittal-plane kinematics of the hip, knee, and ankle joints; and associated mean velocity of the center-of-pressure path during performance of the ANT, PL, and PM reach directions of the Star Excursion Balance Test.

Results

 We observed a decrease in reach-distance scores for the ANT, PL, and PM reach directions from precryotherapy to postcryotherapy (P < .05). No differences were observed in hip-, knee-, or ankle-joint sagittal-plane kinematics (P > .05). We noted a decrease in mean velocity of the center-of-pressure path from precryotherapy to postcryotherapy (P < .05) in all reach directions.

Conclusions

 Dynamic postural stability was adversely affected immediately after cryotherapy to the ankle joint.Key Words: postural balance, lower limb, kinetics

Key Points

• A 15-minute cryotherapy application to the ankle joint decreased cutaneous temperature recorded over the anterior talofibular ligament and deltoid ligament.
• Reach distances in the anterior, posterolateral, and posteromedial directions of the Star Excursion Balance Test and center-of-pressure mean velocity decreased after cryotherapy.
• A 15-minute cryotherapy application negatively influenced dynamic postural-stability performance.
• Elite-level field-based athletes should undergo a rewarming period before returning to participation after cryotherapy to the ankle joint to ensure they are not predisposed to injury due to decreased dynamic postural stability.

Cryotherapy is a treatment modality that clinicians commonly use to promote quicker recovery from soft tissue injury in athletes to expedite return to participation. It has been described as the application of cold therapy to living tissues that results in a lower tissue temperature^1,2 and often is used as an immediate treatment method to relieve the acute pain of soft tissue injuries.¹The proposed physiologic benefits of cryotherapy for injury have been widely reported. Cryotherapy facilitates edema reduction, produces analgesia,^2,3–6 reduces muscle temperature,⁷ and reduces injury-induced inflammation.^8,9 If an athlete incurs a mild sprain or contusion to the ankle joint in a game, the accepted practice during a break in participation (eg, during a half-time period) is to apply cryotherapy to the affected area.In contrast to the aforementioned positive physiologic effects, Bleakley et al¹⁰ reported in a recent literature review that cryotherapy application negatively affected at least 1 of the following outcomes: vertical-jump height, sprint time, or agility performance. These tasks are integral components of field-based sports, and any decrement in performance could predispose individuals to injury during participation. Pritchard and Saliba¹¹ suggested that athletic performance may be adversely affected when athletes return to participation immediately after cryotherapy. Furthermore, Costello and Donnelly¹² reported that cryotherapy negatively affects knee-joint positional sense. Uchio et al¹³ observed that a 15-minute cryotherapy application increased knee-joint stiffness and decreased knee-joint position sense acuity. Stal et al¹⁴ reported that ankle-joint sensorimotor control as quantified by static postural stability was negatively affected by a 20-minute cooling procedure known as hypothermic anesthesia, which is similar to a cryotherapy application.Postural stability refers to the ability to control the center of mass in relation to the base of support to prevent falls¹⁵ and is considered a fundamental component required for performing movement skills.¹⁶ Dynamic postural stability can be defined and measured as an assessment of an individual''s ability to maintain balance while transitioning from a dynamic to a static state.¹⁷ It is an essential part of an athlete''s physical attributes, especially for field sports, given their dynamic nature.¹⁸ Both static and dynamic postural stability result from the complex coordination of central processing from visual, vestibular, and somatosensory pathways, as well as the resultant efferent response.¹⁹Static-standing balance ability decreases after cryotherapy application. Cross et al²⁰ reported that after cryotherapy to the lower extremity, study participants had difficulty maintaining their balance on the treated extremity. More recently, Kernozek et al²¹ reported a deficit in mediolateral (ML) ground reaction force variability on the test leg immediately after a 20-minute cryotherapy application to the ankle joint, with a mean difference of 0.48 N relative to precryotherapy measures (P < .001; d = 1.20). At the 10-minute and 20-minute measurements postcryotherapy, participants continued to exhibit deficits in static-standing balance. However, traditional laboratory measures of postural stability, including static single-legged stance on instrumented force plates, may not be sensitive enough to detect postural-stability deficits associated with lower limb injury.²² Furthermore, Hrysomallis et al²³ indicated that postural-stability performance in static positions cannot be extrapolated to dynamic postural-stability performance, concluding that it is not advisable to infer the latter based on the former. Douglas et al²⁴ reaffirmed this conclusion, postulating that measures of dynamic standing balance may better represent the demands of the lower extremity during functional tasks and, therefore, may be a more appropriate assessment than static standing balance. In addition, Hrysomallis²⁵ showed that Australian Rules football players with an increased ML center-of-pressure (COP) excursion incurred at least twice as many ankle-ligament injuries as players with average or good postural stability. Kernozek et al²¹ and Douglas et al²⁴ observed that cryotherapy debilitated dynamic postural stability, potentially increasing the risk of lower limb injury.Considering the potential shortcomings of static postural-stability testing, our contention was that further investigations of the effects of cryotherapy application to the ankle joint on dynamic postural-stability performance are warranted. One potential method to investigate the influence of ankle-joint cryotherapy application on dynamic postural-stability performance is to use the Star Excursion Balance Test (SEBT) as a primary assessment, supplemented by lower limb sagittal-plane motion analysis and force-plate–derived kinetic assessment. Therefore, the purpose of our study was to evaluate the acute influence of a 15-minute cryotherapy application to the ankle joint on dynamic postural stability as quantified by performance on selected reach directions of the SEBT, associated lower limb sagittal-plane kinematic profiles, and kinetic measures of postural stability. We hypothesized that a 15-minute cryotherapy application to the ankle joint would result in decreased reach distances on the selected directions of the SEBT and altered sagittal-plane ankle-joint kinematics and kinetic measures of postural stability.     

Validation of 64Cu-ATSM damaging DNA via high-LET Auger electron emission

Radioactive copper (II) (diacetyl-bis N4-methylthiosemicarbazone) (Cu-ATSM) isotopes were originally developed for the imaging of hypoxia in tumors. Because the decay of a ⁶⁴Cu atom is emitting not only positrons but also Auger electrons, this radionuclide has great potential as a theranostic agent. However, the success of ⁶⁴Cu-ATSM internal radiation therapy would depend on the contribution of Auger electrons to tumor cell killing. Therefore, we designed a cell culture system to define the contributions to cell death from Auger electrons to support or refute our hypothesis that the majority of cell death from ⁶⁴Cu-ATSM is a result of high-LET Auger electrons and not positrons or other low-LET radiation. Chinese hamster ovary (CHO) wild type and DNA repair–deficient xrs5 cells were exposed to ⁶⁴Cu-ATSM during hypoxic conditions. Surviving fractions were compared with those surviving gamma-radiation, low-LET hadron radiation, and high-LET heavy ion exposure. The ratio of the D₁₀ values (doses required to achieve 10% cell survival) between CHO wild type and xrs5 cells suggested that ⁶⁴Cu-ATSM toxicity is similar to that of high-LET Carbon ion radiation (70 keV/μm). γH2AX foci assays confirmed DNA double-strand breaks and cluster damage by high-LET Auger electrons from ⁶⁴Cu decay, and complex types of chromosomal aberrations typical of high-LET radiation were observed after ⁶⁴Cu-ATSM exposure. The majority of cell death was caused by high-LET radiation. This work provides strong evidence that ⁶⁴Cu-ATSM damages DNA via high-LET Auger electrons, supporting further study and consideration of ⁶⁴Cu-ATSM as a cancer treatment modality for hypoxic tumors.     

Colonoscope length and procedure efficiency

OBJECTIVE: We set out to compare the success of colonoscopy using long and intermediate length standard adult instruments. METHODS: An intermediate length (133 cm working length) and long (168 cm) videocolonoscope were used on an alternate patient basis during routine endoscopy lists. Completion rates, times, and the need for external abdominal pressure were documented, as were causes of failed cecal intubation. RESULTS: Among patients with no history of colon resection and with satisfactory bowel preparation, 173 procedures were performed with the intermediate and 167 with the long colonoscope. There was no significant difference in completion rates (96% for both, excluding patients with strictures), completion times (intermediate mean = 7.73 min, long = 8.11 min; p = 0.44), or need for external abdominal pressure. Similarly, no difference was observed for male and female patients analyzed separately. Though there was no significant difference in completion rates for males and females overall (99% vs 95% excluding patients with strictures, p = 0.08), the latter had significantly longer completion times (mean = 8.75 vs 6.76 min, p < 0.001) and were more likely to require external abdominal pressure. Intermediate colonoscope length was responsible for failure to reach the cecum in one patient only (0.6%). CONCLUSIONS: Although the length of the intermediate instrument rarely compromises colonoscopy, it offers no significant advantage over the long scope for routine procedures.     

Blockade of autocrine stimulation in simian sarcoma virus-transformed cells reverses down-regulation of platelet-derived growth factor receptors.

The viral (v)-sis oncogene encodes a protein (p28sis) that is structurally homologous to platelet-derived growth factor (PDGF). We have shown that simian sarcoma virus (SSV)-transformed cells containing the v-sis oncogene release a Mr 20,000 substance that is recognized by antisera to synthetic peptide sequences contained in p28sis. Medium conditioned by SSV-transformed cells competes with 125I-labeled PDGF for specific PDGF receptor sites, initiates DNA synthesis, and stimulates tyrosine phosphorylation of the PDGF receptor when added to normal cells. When normal cells are co-cultured with SSV-transformed cells, the PDGF receptors of the normal cells are down-regulated by factors released from the transformed cells. Thus, SSV-transformed cells release material that is functionally similar to PDGF. We have used anti-phosphotyrosine antibodies to purify PDGF receptors and to detect PDGF-stimulated receptors in normal cells. SSV-transformed cells have no PDGF receptors detectable by these antibodies or by 125I-labeled PDGF binding studies. However, when SSV-transformed cells are exposed to suramin, a compound that blocks binding of PDGF to its receptors, the receptors reappear on the cell surface and within 8 hr are present at the same levels as in control cells. These "new" receptor sites can be phosphorylated in response to PDGF. Thus, the absence of PDGF receptors in SSV-transformed cells is due to down-regulation of the receptors by an autocrine mechanism that can be blocked by suramin.     

Undetectable viral load is associated with sexual risk taking in HIV serodiscordant gay couples in Sydney

OBJECTIVE: To determine whether reporting that the HIV-positive partner's viral load is undetectable rather than detectable is associated with unprotected anal intercourse (UAI) in HIV serodiscordant gay couples. METHOD: A cross-sectional study nested within two cohort studies, the Health in Men (HIM) cohort of HIV-negative men, from July 2001 to December 2003 and the Positive Health (PH) cohort of HIV-positive men, from February 2002 to August 2003. The study participants were 119 men in an HIV serodiscordant regular relationship of at least 6 months duration (45 HIV-negative men from HIM, 74 HIV-positive men from PH). The main outcome measure was the occurrence of UAI within the relationship in the previous 6 months. RESULTS: Eighty-two men reported no UAI and 37 reported some UAI. Of couples in which the HIV-positive partner's viral load was reported to be undetectable, 39.4% reported UAI compared with 20.8% of those where viral load was reported to be detectable (P = 0.04). In multivariate analysis, significant predictors of UAI were younger age [odds ratio (OR), 0.94; 95% confidence interval (CI), 0.87-1.00; P = 0.05], greater HIV optimism (OR, 4.98; 95% CI, 1.25-19.8; P = 0.02) and reported undetectable viral load (OR, 2.88; 95% CI, 1.13-7.37; P = 0.03). CONCLUSIONS: Most serodiscordant gay couples do not engage in any UAI. UAI within such relationships is significantly more likely to occur where the HIV-positive partner is reported to have undetectable viral load. UAI in HIV serodiscordant relationships is problematic even if viral load is undetectable because of unknown risk parameters, viral load variability and the possibility of drug-resistant strains of HIV.     

The Effects of a Valgus Collapse Knee Position on In Vivo ACL Elongation

There are conflicting data regarding what motions increase ACL injury risk. More specifically, the mechanical role of valgus collapse positions during ACL injury remains controversial. Our objective was to evaluate ACL elongation in a model that mimics knee movements thought to occur during ACL injury. Eight healthy male subjects were imaged using MR and biplanar fluoroscopy to measure the in vivo elongation of the ACL and its functional bundles during three static knee positions: full extension, 30° of flexion, and a position intended to mimic a valgus collapse position described in the literature. For this study, the valgus collapse position consisted of 30° of knee flexion, internal rotation of the hip, and 10° of external tibial rotation. ACL length decreased significantly from full extension (30.2?±?2.6?mm) to 30° of flexion (27.1?±?2.2?mm). ACL length further decreased in the valgus collapse position (25.6?±?2.4?mm). Both functional bundles of the ACL followed similar trends with regards to decreases in length in each of the three positions. Since strain would follow patterns of ACL length, landing on an extended knee may be a more relevant risk factor for ACL injuries than the valgus collapse position in males. Future studies should evaluate the effects of dynamic motion patterns on in vivo ACL strains.