Expression of functional melanocortin-4 receptor in the hypothalamic GT1-1 cell line.

Mutations in the melanocortin-4 receptor (MC4-R) cause obesity in both mice and humans, and the receptor is presumed to have an important role in the regulation of energy homeostasis. The MC4-R is expressed in discrete sets of neurons in the central nervous system, and thus it has been technically difficult to study the regulation of expression and the signaling mechanisms of this receptor. We report here a neuronal cell line that exhibits endogenous functional expression for the MC4-R. Initially, RT-PCR analysis showed the presence of MC4-R RNA in the hypothalamic GT1-1 and GT1-7 cells. In addition, GT1-7 cells expressed melanocortin-3 receptor while the GT1-1 subclone specifically expressed predominantly the MC4-R RNA. High-affinity binding sites were demonstrated in the GT1-1 and GT1-7 cells for NDP-alpha melanocyte-stimulating hormone (MSH; K(i) = 1.1 x 10(-10) and 1.8 x 10(-10) M) and agouti-related protein (AGRP; K(i) = 1.548 x 10(-9) and 1.663(-9) M). alpha-MSH-stimulated cAMP production in GT1-1 cells with an EC(50) of 2.2 x 10(-8) M, and cAMP production was inhibited in the presence of AGRP, an endogenous antagonist of the MC4-R. Stimulation of gonadotropin-releasing hormone (GnRH) secretion was achieved with 1 nM to 1 microM concentrations of NDP-alpha-MSH while no GnRH secretion was observed when the GT1-1 cells were treated with AGRP. The data presented here show that GT1-1 cells specifically express a functional MC4-R that couples to GnRH release.

Cervical cord injury in an elderly man with a fused spine--a case report.

We report a case of an elderly man presenting with co-existing diffuse idiopathic skeletal hyperostosis (DISH) and ossified posterior longitudinal ligament (OPLL) resulting in central cord syndrome. Only three such cases have been reported co-existing with DISH. The patient recovered most of his neurological deficit through conservative management. A discussion on the radiological features of DISH co-existing with OPLL and how these differ from ankylosing spondylitis (AS) follows.

A case of Mycobacterium scrofulaceum osteomyelitis of the right wrist.

INTRODUCTION: The objective of the case report is to highlight the possibility of osteomyelitis caused by atypical mycobacteria. Such an infection may simulate tuberculous bone infection and yet fail to respond to standard anti-tuberculous drug therapy. CLINICAL PICTURE: A 66-year-old man who suffered from diabetes mellitus presented with osteomyelitis of the right wrist, with extensive synovial swellings of the flexor tendon sheaths. The clinical features, radiological appearances and histology suggested a tuberculous infection, but subsequent culture grew an atypical mycobacterium, Mycobacterium scrofulaceum. TREATMENT AND OUTCOME: There was good clinical improvement and control of the infection with a regime of kanamycin, ethambutol and ethionamide to which the organism was sensitive. CONCLUSION: This case illustrates the need to be aware of the possibility of infection with atypical mycobacteria in cases of suspected tuberculosis of the skeletal system which fail to respond to standard treatment.

A unique metabolic syndrome causes obesity in the melanocortin-3 receptor-deficient mouse.

The central melanocortin system is critical for the long term regulation of energy homeostasis. Null mutations of the melanocortin-4 receptor (MC4-R) are associated with hyperphagia, obesity, and accelerated longitudinal growth in mice and humans. However, little is known about the function of another central melanocortin receptor, the MC3-R. To assess the role of the MC3-R in energy homeostasis, the majority of the mc3r coding sequence was deleted from the mouse genome. In contrast to the MC4-R knockout, which exhibits increased food intake, increased somatic growth, and defects in metabolism, mc3r-/- mice exhibit an exclusively metabolic syndrome. Homozygous null mc3r mice, while not significantly overweight, exhibit an approximately 50% to 60% increase in adipose mass. Mc3r-/- mice also exhibit an unusual increase in respiratory quotient when transferred onto high fat chow, suggesting a reduced ratio of fat/carbohydrate oxidation. Furthermore, male mc3r-/- mice also exhibit an approximately 50% reduction in locomotory behavior on the running wheel, suggesting reduced energy expenditure.

Compounds that activate the mouse melanocortin-1 receptor identified by screening a small molecule library based upon the beta-turn.

A library of 951 compounds based upon the beta-turn motif were examined for their ability to stimulate the melanocortin-1 receptor. From this screening process, we have identified two compounds possessing low micromolar agonist activity at the mMC1R. The compound EL1 with racemic Nal(2') in the i + 1 position, DPro in the i + 2 position, and Trp in the i + 3 position possesses an EC(50) of 42.5 +/- 6.9 microM. Compound EL2 with Trp in the i + 1 position, DLys in the i + 2 position, and Phe in the i + 3 position possesses an EC(50) value of 63.4 +/- 26.9 microM. The results of the library screening process are consistent with a hypothesis dating back to the 1980s proposing that a beta-turn conformation involving the melanocortin "Phe-Arg-Trp" core amino acids provides the key recognition element. Additionally, these compounds represent the first nonpeptidic heterocyclic molecules reported to date that are able to activate the MC1R, a melanocyte receptor involved in skin pigmentation and animal coat coloration.

A study of joint mobility in a normal population.

Joint hypermobility is a clinical entity that has been little studied in Southeast Asia in contrast to the many studies that have been conducted in the West. A pioneer study was conducted in Singapore involving 306 subjects from the three major races i.e. Chinese, Malays and Indians. Their ages ranged from 15 to 39 years. The objective was to ascertain the joint mobility profile in a study sample representative of the Singapore population and the prevalence of joint hypermobility amongst normal individuals. Joint mobility was assessed using criteria according to Carter and Wilkinson modified by Beighton et al. The distribution of the three major races in the study sample was based on the 1990 census of the Singapore population. The prevalence of joint hypermobility was found to be 17%. The results showed that joint mobility decreases with age and that females had consistently higher degree of joint mobility compared to males throughout the age group. Among the racial groups, Malays had the highest degree of joint mobility followed by Indians and Chinese.

The effect of storage at -70 degrees C and -150 degrees C on the torsion properties of the canine femur.

This study investigates the effect of storage at -150 degrees C in the vapour phase of liquid nitrogen on the torsion properties of whole intact femurs to be used as allografts. Twenty-five adult dog femurs, stripped of all soft tissue, were used. It has been established that storage at -70 degrees C does not significantly affect the torsion properties of bone. In this study we found no significant difference in structural properties in torsion between the allografts stored at -150 degrees C and -70 degrees C. However, cortical hairline cracks, which were not present before storage, after the bones were stored for 3 months and thawed at 1 degree C/min rate were observed. These cracks fractured longitudinally, and not spirally, when tested to failure and were noted to originate from the vessel foramen. The mean torsion strength of these "damaged" bones was reduced by 48%. We also determined that these hairline cracks occurred during the thawing process at about -42 degrees C. This may suggest an effect of recrystallisation of fluids or water crystals within the "closed" medullary cavity and the foramen, thus increasing the pressure and paying for hairline cracks to propagate from stress risers. No incidence of cortical hairline cracks were observed if the medullary canal was decompressed and the medullary canals washed-out. In tissue banking whole intact bones as allografts, caution should be taken when selecting the freezing and thawing rates for storage as cortical hairline cracks could result and eventually weaken the strength of the allograft.

Predilection for supracondylar fractures in children with cubital recurvatum.

It has been a common observation that children with supracondylar fracture of the humerus tend to demonstrate hyperextensibility of their elbow joints. In this study, we measured and compared the degree of hyperextension of the uninjured elbow of children less than sixteen years old who sustained either a supracondylar or a distal radial fracture. We concluded that children with higher degree of hyperextension in the elbow are more likely to sustain a supracondylar fracture than a distal radius fracture during a fall on the outstretched hand.

Radiation dosage from use of the image intensifier in orthopaedic surgery.

The image intensifier is now commonly used in orthopaedic surgery for intraoperative assessment of fracture reduction and implant placement, especially with the increasing trend toward use of closed nailing devices. We conducted a study using lithium fluoride chips to measure the radiation dosage to the surgeon and the operating theatre personnel. Over a 6-month period we measured the cumulative radiation dosage over the eyes (0.83mSv), thyroid (with shield 0.51mSv, without 0.79mSv), waist (with apron 0.48mSv, without 0.86mSv), hands (right 0.7mSv, left 0.14mSv) and feet (0.62 mSv). These values were well within the ICRP safety guidelines. The use of protective lead shielding was effective in reducing radiation dosage to operators. A survey of the operating theatre area using a radiation counter showed that radiation scatter to OT personnel was low. This study hopes to allay the fears that use of the image intensifier is hazardous to OT personnel.

Torsional performance of canine femoral osteotomy union.

This study allows the establishment of a protocol for standardizing the technical methodology of canine surgery for mechanical testing. Twenty mongrels were divided into 4 groups of 5 dogs each. All dogs had one femur selected as the test bone and the contralateral as paired control. The test femur was osteotomized and plated. The dogs were sacrificed at 7, 10, 13 and 16 weeks according to their group designation to determine healing of the osteotomy. Both test and control femora were tested to fracture in torsion using a computerized torsion machine. Various mechanical parameters were studied with the age of osteotomy union. The study found that all bones sustained spiral fractures through the osteotomy site. The maximum torque capacity and stiffness increased with age of union. There is an apparent biphasic pattern in the remodelling process. Up till the 13th week there was a decline in the polar moment of inertia and a rise in the torsional stress with an increase in strength. We postulate that this was due to a reduction of the outer diameter of the external bridging callus. After the 13th week, there was a reversal in the process and the outer diameter of the callus increased. The findings provide a baseline reference for future studies involving osteotomy healing as is necessary in bone allograft reconstruction and bone transport.