James A. H. Smith

CaMK activation during exercise is required for histone hyperacetylation and MEF2A binding at the MEF2 site on the Glut4 gene

The role of CaMK II in regulating GLUT4 expression in response to intermittent exercise was investigated. Wistar rats completed 5 x 17-min bouts of swimming after receiving 5 mg/kg KN93 (a CaMK II inhibitor), KN92 (an analog of KN93 that does not inhibit CaMK II), or an equivalent volume of vehicle. Triceps muscles that were harvested at 0, 6, or 18 h postexercise were assayed for 1) CaMK II phosphorylation by Western blot, 2) acetylation of histone H3 at the Glut4 MEF2 site by chromatin immunoprecipitation (ChIP) assay, 3) bound MEF2A at the Glut4 MEF2 cis-element by ChIP, and 4) GLUT4 expression by RT-PCR and Western blot. Compared with controls, exercise caused a twofold increase in CaMK II phosphorylation. Immunohistochemical stains indicated increased CaMK II phosphorylation in nuclear and perinuclear regions of the muscle fiber. Acetylation of histone H3 in the region surrounding the MEF2 binding site on the Glut4 gene and the amount of MEF2A that bind to the site increased approximately twofold postexercise. GLUT4 mRNA and protein increased approximately 2.2- and 1.8-fold, respectively, after exercise. The exercise-induced increases in CaMK II phosphorylation, histone H3 acetylation, MEF2A binding, and GLUT4 expression were attenuated or abolished when KN93 was administered to rats prior to exercise. KN92 did not affect the increases in pCaMK II and GLUT4. These data support the hypothesis that CaMK II activation by exercise increases GLUT4 expression via increased accessibility of MEF2A to its cis-element on the gene.

Caffeine induces hyperacetylation of histones at the MEF2 site on the Glut4 promoter and increases MEF2A binding to the site via a CaMK-dependent mechanism

This study was conducted to explore the mechanism by which caffeine increases GLUT4 expression in C(2)C(12) myotubes. Myoblasts were differentiated in DMEM containing 2% horse serum for 13 days and the resultant myotubes exposed to 10 mM caffeine in the presence or absence of 25 microM KN93 or 10 mM dantrolene for 2 h. After the treatment, cells were kept in serum-free medium and harvested between 0 and 6 h later, depending on the assay. Chromatin immunoprecipitation (ChIP) assays revealed that caffeine treatment caused hyperacetylation of histone H3 at the myocyte enhancer factor 2 (MEF2) site on the Glut4 promoter (P < 0.05) and increased the amount of MEF2A that was bound to this site approximately 2.2-fold (P < 0.05) 4 h posttreatment compared with controls. These increases were accompanied by an approximately 1.8-fold rise (P < 0.05 vs. control) in GLUT4 mRNA content at 6 h post-caffeine treatment. Both immunoblot and immunocytochemical analyses showed reduced nuclear content of histone deacetylase-5 in caffeine-treated myotubes compared with controls at 0-2 h posttreatment. Inclusion of 10 mM dantrolene in the medium to prevent the increase in cytosolic Ca(2+), or 25 microM KN93 to inhibit Ca(2+)/calmodulin-dependent protein kinase (CaMK II), attenuated all the above caffeine-induced changes. These data indicate that caffeine increases GLUT4 expression by acetylating the MEF2 site to increase MEF2A binding via a mechanism that involves CaMK II.

Pelvic stress fractures in long distance runners

We describe five cases of radiographically proven stress fracture of the pubic ramus in serious runners, three of whom were elite female marathoners. In a further two cases in which radiography failed to support the clinical diagnosis, there was bone scintigraphic evidence of stress fracture. Another five cases had the identical clinical presentation, but the diagnosis was not confirmed radiologically and bone scanning was not performed. Most patients experienced persistent groin discomfort during any activity for the first 4 weeks after injury, but all recovered completely after 8 to 12 weeks of rest, in particular, avoidance of running. In common with other studies, we found that the injury occurred in competitive runners, especially females, and was likely to develop during competitive races or intensive training sessions. We suggest that a diagnosis of pelvic stress fracture or stress fracture syndrome can be made with confi dence, even in the absence of radiographic evidence, if the following three features are present in a long dis tance runner presenting with groin pain: First, activity causes such severe discomfort in the groin that running is impossible. Second, the athlete develops discomfort in the groin when standing unsupported on the leg corresponding to the injured side (positive standing test). In some cases the pain is so severe that standing on one leg is impossible. Third, deep palpation reveals extreme, exquisite nauseating tenderness localized to the pubic ramus and not to the overlying soft tissues. The diagnosis can be confirmed by bone scintigraphy where such facilities exist.

The role of CaMKII in regulating GLUT4 expression in skeletal muscle

Contractile activity during physical exercise induces an increase in GLUT4 expression in skeletal muscle, helping to improve glucose transport capacity and insulin sensitivity. An important mechanism by which exercise upregulates GLUT4 is through the activation of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) in response to elevated levels of cytosolic Ca(2+) during muscle contraction. This review discusses the mechanism by which Ca(2+) activates CaMKII, explains research techniques currently used to alter CaMK activity in cells, and highlights various exercise models and pharmacological agents that have been used to provide evidence that CaMKII plays an important role in regulating GLUT4 expression. With regard to transcriptional mechanisms, the key research studies that identified myocyte enhancer factor 2 (MEF2) and GLUT4 enhancer factor as the major transcription factors regulating glut4 gene expression, together with their binding domains, are underlined. Experimental evidence showing that CaMK activation induces hyperacetylation of histones in the vicinity of the MEF2 domain and increases MEF2 binding to its cis element to influence MEF2-dependent Glut4 gene expression are also given along with data suggesting that p300 might be involved in acetylating histones on the Glut4 gene. Finally, an appraisal of the roles of other calcium- and non-calcium-dependent mechanisms, including the major HDAC kinases in GLUT4 expression, is also given.

Why Do SMEs Go Green? An Analysis of Wine Firms in South Africa

Studies on why small and medium enterprises (SMEs) engage in pro-environmental behavior suggest that managers’ environmental responsibility plays a relatively greater role than competitiveness and legitimacy-seeking. These categories of drivers are mostly considered independent of each other. Using survey data and comparative case studies of wine firms in South Africa, this study finds that managers’ environmental responsibility is indeed the key driver in a context where state regulation hardly plays any role in regulating dispersed, rural firms. However, especially proactive firms are also characterized by expectations of competitiveness gains. The authors thus emphasize the role of institutional context and potential interaction effects between these drivers in explaining the reasons why SMEs engage in pro-environmental behavior in developing countries.

Gluconeogenesis during endurance exercise in cyclists habituated to a long‐term low carbohydrate high‐fat diet

Blood glucose is an important fuel for endurance exercise. It can be derived from ingested carbohydrate, stored liver glycogen and newly synthesized glucose (gluconeogenesis). We hypothesized that athletes habitually following a low carbohydrate high fat (LCHF) diet would have higher rates of gluconeogenesis during exercise compared to those who follow a mixed macronutrient diet. We used stable isotope tracers to study glucose production kinetics during a 2 h ride in cyclists habituated to either a LCHF or mixed macronutrient diet. The LCHF cyclists had lower rates of total glucose production and hepatic glycogenolysis but similar rates of gluconeogenesis compared to those on the mixed diet. The LCHF cyclists did not compensate for reduced dietary carbohydrate availability by increasing glucose synthesis during exercise but rather adapted by altering whole body substrate utilization.

The value of cancer antigen-125 as a tumor marker in malignant germ cell tumors of the ovary

The value of cancer antigen-125 (CA-125) as a tumor marker for malignant germ cell tumors (MGCT) of the ovary was investigated and compared with the other recognized tumor markers (human chorionic gonadotrophin (hCG), alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA) and lactate dehydrogenase (LDH) isoenzymes. In the 10 months following June 1984, 4 new cases with MGCT and 1 patient with active disease on treatment were evaluated. In all cases prior to planned surgery the levels of CA-125 were significantly elevated. The serum values ranged from 154 to 617 U/ml (normal less than 20 U/ml). In 1 case (pure dysgerminoma) CA-125 was the only tumor marker. In 3 patients (2 mixed germ cell tumors and 1 immature teratoma) serum LDH (LD 1, 2, and 3) was elevated, and AFP was elevated in 1 of these. In the fifth case (mixed germ cell tumor), on treatment, serum AFP was used to monitor the disease. Four patients underwent cytoreductive surgery followed by combination chemotherapy. The changes in the serum levels of CA-125 paralleled those of the other tumor markers while on therapy. In our experience CA-125 is an invaluable indicator of the clinical status of the patient and could be a new tumor marker in patients with MGCT.

The role of cancer antigen 125 (CA 125) in the management of ovarian epithelial carcinomas

From June 1, 1984, to May 31, 1985, 98 cases of epithelial ovarian carcinomas were assessed and followed prospectively using a new murine monoclonal antibody OC 125 which detects the antigen CA 125. Serous tumors comprised 43.7% of cases, mucinous tumors 20.4%, endometrioid tumors 16%, and other epithelial tumors 19.4%. Tumors of low malignant potential and benign epithelial cystadenomas were not included. For this study the upper limit of normal for CA 125 was 20 U/ml. Thirty-six were new cases. In this group the initial CA 125 levels greater than 20 U/ml, greater than 35 U/ml, and greater than 65 U/ml were 97.2, 94.4, and 86.1%, respectively. When mucinous types were excluded the specificity rate did not change significantly. There was no significant difference in initial CA 125 levels between early stages I and II and late stages III and IV. No correlation between tumor bulk and the serum level of antigen was observed. The remaining 62 patients were being followed and in this group 50 were considered to be in remission. Six cases in the remission group had elevated CA 125 levels greater than 20 U/ml and 5 of these developed clinical recurrence. The correlation between the clinical status and concordant fluctuations in the serum levels of CA 125 in all histological types was 87.8 and 93.5% when 10 cases of mucinous tumors were excluded. The contingency coefficient was 0.746. Seven SLOs were performed. All had CA 125 levels less than 20 U/ml and the mean was 6.9 U/ml. Only 1 case was positive with microscopic disease. In our experience CA 125 was invaluable in the management and follow-up of patients with ovarian carcinoma especially for the early detection of recurrent disease and for the monitoring of patients on therapy.

Two methods of measuring food transit rates of seabirds

Abstract 1. 1. Cerium 141 and carmine red dye were used to measure rates of passage through the digestive tracts of captive Jackass Penguins (Spheniscus demersus) . 2. 2. Mean excretion times were 11.65 hr for 141 Ce and 10.15 hr forcarmine. Both markers began to appear within 2 hr of ingestion and were still being excreted after 24 hr. 3. 3. Cumulative rates of excretion were generally similar, although initial excretion of carmine was higher. 4. 4. Comparison with studies of clearance rates of food from the proventriculus and ventriculus allow comparison of residence times in different parts of the digestive tract.

Metabolic cost of running is greater on a treadmill with a stiffer running platform

ABSTRACT Exercise testing on motorised treadmills provides valuable information about running performance and metabolism; however, the impact of treadmill type on these tests has not been investigated. This study compared the energy demand of running on two laboratory treadmills: an HP Cosmos (C) and a Quinton (Q) model, with the latter having a 4.5 times stiffer running platform. Twelve experienced runners ran identical bouts on these treadmills at a range of four submaximal velocities (reported data is for the velocity that approximated 75–81% VO2max). The stiffer treadmill elicited higher oxygen consumption (C: 46.7 ± 3.8; Q: 50.1 ± 4.3 ml·kg−1 · min−1), energy expenditure (C: 16.0 ± 2.5; Q: 17.7 ± 2.9 kcal · min−1), carbohydrate oxidation (C: 9.6 ± 3.1; Q: 13.0 ± 3.9 kcal · min−1), heart rate (C: 155 ± 16; Q: 163 ± 16 beats · min−1) and rating of perceived exertion (C: 13.8 ± 1.2; Q: 14.7 ± 1.2), but lower fat oxidation (C: 6.4 ± 2.3; Q: 4.6 ± 2.5 kcal · min−1) (all analysis of variance treadmill comparisons P < 0.01). This study confirms that caution is required when comparing performance and metabolic results between different treadmills and suggests that treadmills will vary in their comparability to over-ground running depending on the running platform stiffness.