An evaluation of head movement in backboard-immobilized helmeted football, lacrosse, and ice hockey players

OBJECTIVE

Improper handling of an unstable neck injury in the prehospital setting may result in iatrogenically induced neurologic injury. Due to helmet design, stabilization of the cervical spine in American football does not require routine removal of the helmet and shoulder pads prior to transport. Adequate data is not available evaluating hockey and lacrosse helmets. This study compares the amount of head movement in American football, lacrosse, and ice hockey helmets during head and neck stabilization procedures.

STUDY DESIGN

Prospective.

PARTICIPANTS

12 ice hockey, 9 football, and 9 lacrosse athletes from an National Collegiate Athletic Association Division 1 program.

SETTING

On-campus biomechanical laboratory with three HiRes cameras, routinely tested for accuracy.

METHODS

Athletes were immobilized on backboards as per protocol. Three motion analysis HiRes cameras follow retroreflective markers placed on the helmet and bite mouthplate to measure relative head and helmet motion.

MAIN OUTCOME MEASURES

Helical angles determine the relative range of motion of the head inside the helmets.

RESULTS

The mean range of head motion for football players was 4.88 degrees (n = 9, SD 2.07), lacrosse players 6.56 degrees (n = 9, SD 1.61), and ice hockey players 5.54 degrees (n = 12, SD 1.19). These results were not significantly different (p > 0.05).

CONCLUSIONS

The rotational head motion seen inside standard immobilized lacrosse and ice hockey helmets is similar to that seen in football helmets. This supports the safety of prehospital stabilization of the potential cervical spine-injured ice hockey and lacrosse athletes with in-line stabilization and helmet in place. Extrapolation of data may not be applicable to other helmet designs, and future studies are needed to determine the safety of emergency procedures in all helmet designs.

The role of leptin resistance in the lipid abnormalities of aging

Leptin resistance has been implicated in the pathogenesis of obesity-related complications involving abnormalities of lipid metabolism that resemble those of old age. To determine whether development of leptin resistance in advancing age might account for such abnormalities, we compared the effects of hyperleptinemia (>40 ng/ml) induced in 2-month-old and 18-month-old lean wild-type (+/+) Zucker diabetic fatty rats by adenovirus gene transfer. The decline in food intake, body weight, and body fat in old rats was only 25%, 50%, and 16%, respectively, of the young rats. Whereas in young rats plasma free fatty acids fell 44% and triacylglycerol (TG) 94%, neither changed in the rats. In hyperleptinemic young rats, adipocyte expression of preadipocyte factor 1 increased dramatically and leptin mRNA virtually disappeared; there was increased expression of acyl CoA oxidase, carnitine palmitoyl transferase 1, and their transcription factor peroxisome proliferator-activated receptor alpha, accounting for the reduction in body fat. These hyperleptinemia-induced changes were profoundly reduced in the old rats. On a high-fat diet, old rats consumed 28% more calories than the young and gained 1.5x as much fat, despite greater endogenous hyperleptinemia. Expression of a candidate leptin resistance factor, suppressor of cytokine signaling 3 (SOCS-3), was compared in the hypothalamus and white adipocytes of young and old rats before and after induction of hyperleptinemia; hypothalamic SOCS-3 mRNA was approximately 3x higher in old rats before, whereas it was 3x higher in WAT after, hyperleptinemia. We conclude that the anorexic and antilipopenic actions of leptin decline with age, possibly through increased SOCS-3 expression, and that this could account for the associated abnormalities in lipid metabolism of the elderly.

Corticosteroid injections for trigger digits: is intrasheath injection necessary?

Ninety-five patients with 107 trigger digits were divided into 2 groups and studied prospectively to evaluate steroid injection placement and efficacy. In 1 group, an attempt was made to deliver 1 injection into the tendon sheath at the A1 pulley. In the other group, 1 injection infiltrated the subcutaneous tissues overlying the A1 pulley. Radiopaque dye provided contrast to the injection medium, and postinjection x-rays identified the true delivery site of the steroid solution. Of the 52 digits into which intrasheath injection was attempted, 19 digits (37%) received all the injection within the sheath, 24 (46%) received medication into both the sheath and the subcutaneous tissues, and 9 (17%) received no medication within the tendon sheath. The results were analyzed to determine whether injection placement influences the efficacy of steroid injection. The confirmed all-sheath injection group exhibited a 47% good response, the mixed sheath and subcutaneous group had a 50% good response, and the all-subcutaneous group had a 70% good response. The results of this study suggest that true intrasheath injection offers no apparent advantage over subcutaneous injection in the treatment of trigger digits.

Thyrotropin-releasing hormone action on the prolactin promoter is mediated by the POU protein pit-1

TRH is known to regulate transcription of the PRL gene in pituitary cells, but little is known about the mechanism involved. We have characterized TRH response elements (TRHREs) in the promoter region of the rat PRL gene and the gene-proximal protein that transmits the TRH signal to these elements. Exposure of GH3 rat pituitary cells to TRH yielded a large specific stimulation of transient expression of a PRL-chloramphenicol acetyltransferase (PRL-CAT) construct containing the PRL promoter region [(-204)PRL-CAT]. Analysis of 5' deletions of this construct implied that regions -174/-113 and -75/+38 each contain a TRHRE. GH3 cell nuclear extracts are known to footprint four sites, termed, respectively, 1P-4P, on the PRL promoter region. The TRHRE between positions -75/+38 was identified as element 1P, residing at -63/-39, since two copies of a 1P oligodeoxynucleotide transferred a TRH response to either (-39)PRL-CAT or mouse metallothionein-CAT construct (-39)mMT-CAT. Similarly, the more proximal TRHRE may be element 3P, residing at -167/-144, since two copies of this element also transferred a TRH response to (-39)PRL-CAT. Binding of pit-1 to site 1P is known to be capable of activating pituitary cell-specific PRL gene expression. To investigate whether pit-1 can also transduce a TRH signal to this site, oligodeoxynucleotides were prepared corresponding to mutations in either or both of two consensus sequences in site 1P.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of a growth hormone gene promoter repressor element and its cognate double- and single-stranded DNA-binding proteins

In previous investigations, cell fusion was found to silence either the endogenous rat growth hormone (GH) gene or a transfected rat GH gene promoter, implying that repression plays a role in regulation of this gene. To search the rat GH gene promoter for repressor sequences, a series of 5'-deleted GH-CAT constructs was analyzed by transient expression in GH3 rat pituitary cells. Deletion of either a distal region between positions -307/-244 or a proximal sequence between -169/-152 increased CAT enzymatic activity by 3-4-fold. Since the action of the proximal repressor element (PRE) at -169/-152 was serum-independent, and the element is located between two strong positive elements, the PRE and its cognate binding proteins were further analyzed. A 5-base pair sequence centered at -163 is critical for PRE repressor activity, since mutation of this sequence in GH-CAT constructs yielded 6-11-fold increases in expression in GH3 cells. Although the PRE is adjacent to the GH thyroid hormone (T3) response region, they are distinct elements, since the PRE mutation has little effect on the T3 response of GH-CAT constructs. Nuclear extracts of 10 cell lines were searched by DNA mobility shift for protein(s) binding specifically to a double-stranded PRE probe. No such protein was detected in any of four rodent pituitary cell lines or three human cell lines. However, three different rodent non-pituitary cell lines yielded a common shifted band, corresponding to a DNA sequence-specific PRE-binding protein (PREB). Similar analysis with the coding strand of the PRE detected no shifted band in any of these cell lines. However, the PRE noncoding strand yielded a common shifted band in all of the cell lines, corresponding to a ubiquitous, strand-specific, single-stranded PRE-binding protein (ssPREB). Mutation of the PRE permitted ssPREB binding to the coding strand, implying that the wild-type coding strand somehow excludes ssPREB binding. That PREB and ssPREB are distinct proteins was confirmed by the inability of their DNA binding sites to cross-compete binding of the proteins.

Proximal rat prolactin promoter sequences direct optimal, pituitary cell-specific transcription

Previous studies have shown that transferred hybrid constructs containing the PRL promoter are expressed specifically in rat pituitary (GH) cell lines. However, it is not yet clear which DNA region(s) is primarily responsible for expression directed by this promoter in pituitary cells. In the present studies we have examined the DNA sequences required for cell type-specific transcription of the rat PRL (rPRL) promoter either during transient expression in intact cells or in nuclear chromatin extracts. RNase protection and nuclear run-on transcription assays showed directly that a PRL-chloramphenicol acetyltransferase (CAT) construct containing about two kilobase-pairs of the rPRL promoter region (pPRL-CAT) is transcribed specifically in pituitary (GH3) cells. Analysis by transient expression in GH3 cells of pPRL-CAT and its 5' deletions showed that 1) deletion of sequences between positions -1957 and -958 did not significantly affect CAT activity; 2) the first 187 basepairs (bp) of the rPRL promoter directs full CAT activity; and 3) 98% of this activity is accounted for by rPRL DNA sequences between positions -187 and -113, containing two GH3 chromatin footprinting sites. Analysis in GH3 cell nuclear extracts showed that transcription of PRL-CAT constructs is unaffected by successive 5' deletions from position -1957 to -187, and that further deletion to -75 yielded only a moderate (approximately 2-fold) decrease in transcription.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of the mutation rates of animal viruses: influenza A virus and poliovirus type 1

Epidemiologic and genetic evidence suggests that influenza A viruses evolve more rapidly than other viruses in humans. Although the high mutation rate of the virus is often cited as the cause of the extensive variation, direct measurement of this parameter has not been obtained in vivo. In this study, the rate of mutation in tissue culture for the nonstructural (NS) gene of influenza A virus and for the VP1 gene in poliovirus type 1 was assayed by direct sequence analysis. Each gene was repeatedly sequenced in over 100 viral clones which were descended from a single virion in one plaque generation. A total of 108 NS genes of influenza virus were sequenced, and in the 91,708 nucleotides analyzed, seven point changes were observed. A total of 105 VP1 genes of poliovirus were sequenced, and in the 95,688 nucleotides analyzed, no mutations were observed. We then calculated mutation rates of 1.5 X 10(-5) and less than 2.1 X 10(-6) mutations per nucleotide per infectious cycle for influenza virus and poliovirus, respectively. We suggest that the higher mutation rate of influenza A virus may promote the rapid evolution of this virus in nature.