Suggestive linkage to chromosome 6q in families with bilateral vestibulopathy

BACKGROUND

Of the more than 40 genetically defined dominantly inherited hearing loss syndromes, only a few are associated with bilateral vestibulopathy. No genetic mutations have been identified in families with bilateral vestibulopathy and normal hearing.

OBJECTIVE

To perform a genome-wide scan for linkage in four families with dominantly inherited bilateral vestibulopathy.

METHODS

Patients in four families reported brief episodes of vertigo followed by imbalance and oscillopsia. Bilateral vestibulopathy was documented with quantitative rotational testing. Most patients with bilateral vestibulopathy also had migraine. A 10 cM genome-wide screen was conducted using 423 microsatellite markers to identify linkage with vestibulopathy.

RESULTS

The authors identified a 24 cM region on chromosome 6q suggestive of linkage to vestibulopathy in these four families (maximum lod score of 2.9 at marker D6S1556). A small fifth family with a different phenotype was not linked to this region on chromosome 6q.

CONCLUSIONS

This is the first report of linkage in families with dominantly inherited vestibulopathy and normal hearing. Genetic heterogeneity is likely with inherited vestibulopathy.

Placental endothelial nitric oxide synthase localization and expression in normal human pregnancy and pre-eclampsia

1. The aim of the present study was to investigate whether pre-eclampisa, a state of placental hypoxia, is associated with placental abnormalities in the amount, distribution and expression of endothelial nitric oxide synthase (eNOS). 2. Localization and intensity of eNOS was determined by immunohistochemistry using an antibody specific for eNOS. The amount of eNOS mRNA expression was determined by reverse transcription-polymerase chain reaction (RT-PCR) and the densitometry of gel bands was expressed as a ratio of the band density of the housekeeping gene beta2-microglobulin. 3. Endothelial NOS staining was localized to syncytiotrophoblast cells within the villi and decidual trophoblast cells. It was not present in the endothelium of terminal villous vessels. There was no significant difference in eNOS villous or decidual staining intensity between normal pregnancy (NP; n = 12), pre-eclampsia (n = 14), or gestational hypertension (GH; n = 4). Staining for eNOS was not significantly different in the decidua compared with the villi in NP, GH or pre-eclampsia. Within the decidua, the depth of eNOS staining was similar in NP, pre-eclampisa and GH. 4. There was no significant difference in eNOS mRNA expression between NP (0.70 +/- 0.11), pre-eclampsia (0.5 +/- 0.07) or GH (0.69 +/- 0.26). 5. These findings suggest that the amount of eNOS in the placenta is not deficient in pre-eclampsia, excluding a possible pathogenic role for eNOS in this disease. Furthermore, placental hypoxia, which is associated with pre-eclampsia, did not induce an upregulation of eNOS

Rates of pediatric and adolescent injuries by year of age

OBJECTIVE

The purpose of this study was to analyze causes of injury hospitalization/death by individual year of age and by specific causes of injury and to examine how well aggregate age groups represented individual year-of-age rates.

METHODS

Hospital discharge data and death certificate data for California residents age 0 to 19 years with a principal external cause of injury code (E-code) of E800 to E869, E880 to E929, or E950 to E999, calendar year 1997, were analyzed. Annual rates of injury hospitalization/death by year of age were calculated using combined hospital discharges and deaths as the numerator for major causes and important subcategories. For comparison, rates of injury hospitalization/death were calculated for conventional vital statistics age groups: <1 year, 1 to 4 years; 5 to 9 years, 10 to 14 years, and 15 to 19 years.

RESULTS

In 1997 in California, 35 277 children and adolescents 0 to 19 years were hospitalized and 1934 died as a result of injury, a ratio of 17 hospitalizations to 1 death. The distribution was bimodal with rates highest among 18-year-olds (732/100 000) and 1-year-olds (495/100 000). Except for children who were 5 to 9 years of age, the group rates for all injuries were not reflective of the individual year-of-age rates. In specific categories of injuries, variation in rates by year of age were masked by age group rates for unintentional poisoning among 1- to 4-year-olds, self-inflicted poisoning for 10- to 19-year-olds, falls from playground equipment among 5- to 9-year-olds, falls from furniture among 1- to 4-year-olds, and motor vehicle occupant injury rates among 10- to 19-year-olds. The peak rate of falls from playground equipment among 6-year-olds (34/100 000) was more than twice the rate for 9-year-olds (15/1000,000). Motor vehicle occupant injury rates doubled between 10 and 14 years of age and quadrupled between 14 and 18 years of age.

CONCLUSIONS

Analyses using conventional age groups did not identify the age of highest risk for many causes of childhood injury. Changes in the rates often transected the traditional age groups and were not apparent with conventional age group analysis. These data can inform on the age at which to begin a specific injury intervention and on how to allocate resources. These data allow pediatricians and other health professionals to be anticipatory in providing injury prevention counseling. The greatest impact can be achieved by making the counseling topic most age appropriate in anticipation of the high-risk period.

Diagnosing disease through DNA. An exciting new frontier

BACKGROUND

The family physician is at the forefront of the modern genetics (DNA) revolution. Advances in genetics will continue to escalate as the human genome project reaches its conclusion. The result will be a vast compendium of newly discovered genes and demand from both patients and doctors for more information about them.

OBJECTIVE

To describe the role of DNA testing in diagnosing and predicting disease.

DISCUSSION

DNA is an ideal medium to search for gene mutations. The DNA content of our cells does not age, thereby expanding the scope for DNA testing. The general practitioner will often be the first contact for those with a genetic disorder. Following DNA diagnosis, ongoing support may be required. To do this effectively will require a new approach to continuing education, as well as active participation in the 'molecular medicine' team. Sourcing reliable and accurate information may be a problem with many turning to the Internet for this.

Impact of resuscitation and thrombolysis on mortality rate from acute myocardial infarction

Our objective was to estimate the saving of life by thrombolysis and resuscitation in acute myocardial infarction (AMI) before and after hospital admission. We studied all 1516 patients admitted to a Scottish teaching hospital in 1990 and 1992 who had a final diagnosis of AMI, and 311 patients enrolled in the Grampian region early anistreplase trial (GREAT). Cardiac arrest occurred in 250/1516 (16%) hospital patients. Of these, 77 (31%) were discharged alive--a saving of 51 lives per thousand cases. 797 (53%) patients received thrombolysis, of whom 114 (14%) died. Assuming the same relative reduction in mortality as in the second international study of infarct survival (ISIS-2; 23%), 34 lives were saved by thrombolytic therapy, representing 22 lives per thousand cases. Of 311 patients in GREAT, 15 (5%) had prehospital cardiac arrest, with 7 patients surviving to discharge (48%)--a saving of 23 lives per thousand cases. Those patients given domiciliary thrombolysis had a one month mortality of 6.7% (11/163) compared with 12.2% (18/148) for those receiving hospital thrombolysis--a saving of 55 lives per thousand cases for prehospital thrombolysis. This is additional to 28 lives per thousand estimated for thrombolytic therapy in hospital, totalling 83 lives saved per thousand cases of AMI receiving thrombolytic therapy prehospital. In hospital, more lives were saved by resuscitation than by thrombolytic therapy, but this ratio was reversed in the period before hospital admission. These results emphasise the paramount importance of resuscitation in hospital, and the enhanced efficacy of thrombolysis when given at the earliest opportunity.

Electrocardiographic evidence of reperfusion occurring before hospital admission. A Grampian Region Early Anistreplase Trial (GREAT) sub-study

The benefits of thrombolysis are believed to be related to the speed of reperfusion of the infarct-related artery. In this sub-study, evidence for the occurrence of reperfusion before admission to hospital has been sought. In a randomized double-blind controlled trial, 311 patients with suspected acute myocardial infarction were given anistreplase 30 units i.v., either at home at a median 101 min (early group, n = 163), or in hospital at a median 240 min after symptom onset (large group, n = 148). Paired electrocardiograms recorded at home and on admission to hospital were available for study in 143 and 137 patients in early and late groups. Reduction in ST elevation between home and hospital electrocardiograms of > 25% in a single lead was taken as evidence of reperfusion. Patients with significant ST elevation in either electrocardiogram comprised the sub-study groups, and numbered 63/143 (44%) and 68/137 (50%) in early and late groups respectively. A reduction of > 25% in the single lead demonstrating greatest ST elevation on the presenting electrocardiogram was observed in 37/63 (59%) and 23/68 (34%) patients in the early and late sub-study groups (difference 25%, 95% confidence interval 8% to 42%, P = 0.003). It was found that domiciliary thrombolysis was associated with electrocardiographic evidence of an increased rate of reperfusion occurring before admission to hospital. Evidence of reperfusion occurring pre-hospital, whether spontaneous or following thrombolytic therapy, was associated with a better outcome.

Role of the mandibular first molar in the development of the supraorbital region in apes and humans

Our previous studies in apes and humans have demonstrated that the development of the supraorbital ridge is a direct consequence of masticatory forces. The smaller the power arm/load arm ratio of the mandible, the greater the force exerted by the temporalis muscle and the larger the supraorbital ridge. The purpose of the present study is to further elucidate the role of the masticatory apparatus, in particular the role of the first mandibular molar. Measurements of the size of the supraorbital ridges in ape skulls and in human skulls from Tuscany, Italy and St. Lawrence Island, Alaska, were determined using parasagittal CAT scans as in our previous studies. For the purpose of this study, the mesio-distal and buccolingual dimensions of the first molar were measured from the actual tooth in all cases. Statistical analysis shows a positive correlation between the mesio-distal dimension of the mandibular first molar and the size of the ridge in humans (r = 0.61, p < 0.005) and in apes (r = 0.79, p < 0.01), which explains much of the variation in the size of the supraorbital ridge, 37% (0.61(2)) in humans and 62% (0.79(2)) in apes. The role of the mandibular first molar differs in humans versus apes because of differences in masticatory mechanics.

Earliest electrocardiographic evidence of myocardial infarction: implications for thrombolytic treatment. The GREAT Group

OBJECTIVES

To determine the incidence of the earliest electrocardiographic changes in patients with suspected myocardial infarction and their sensitivity and specificity for predicting the final diagnosis of acute myocardial infarction.

DESIGN

Retrospective study of paired electrocardiograms recorded at home and on admission to hospital.

SETTING

29 rural practices in Grampian and teaching hospitals in Aberdeen.

PATIENTS

137 patients participating in the early anistreplase trial in the Grampian region, who received placebo at home and for whom paired electrocardiograms were available.

MAIN OUTCOME MEASURES

Classified electrocardiographic abnormalities and diagnosis at discharge.

RESULTS

Electrocardiograms were recorded immediately before injection of placebo at home and anistreplase in hospital at median times of 110 and 240 minutes after the onset of symptoms. Definite or probable myocardial infarction was later confirmed in 93 (68%) patients. Of these, 66 (71%) had the same findings on both electrocardiograms of either ST elevation, bundle branch block, or a non-specific abnormality, while 27 (29%) showed a major change of classification between home and hospital recordings; 21 (23%) had ST elevation or bundle branch block on only one of the paired recordings. Although ST elevation was the commonest abnormality in the 93 patients with myocardial infarction, in only 51 was it recorded at home (sensitivity 55%) and in 49 on admission (sensitivity 53%). Of 57 patients with ST elevation at home, six did not have infarction (specificity 86%), while of 51 with ST elevation on admission, two did not have infarction (specificity 95%).

CONCLUSIONS

Elevation of the ST segment is a transient electrocardiographic abnormality that has high specificity but low sensitivity for predicting the diagnosis of acute myocardial infarction; it is an unsatisfactory precondition for giving thrombolytic treatment to patients with suspected acute myocardial infarction.

Hagfish humoral defense protein exhibits structural and functional homology with mammalian complement components

A genomic clone and cDNA fragment encoding a portion of a humoral recognition molecule from the hagfish were isolated and sequenced. The serum protein has previously been described as having structural features that are immunoglobulin-like. Amino acid sequence obtained from the 77-kDa H1 heavy chain facilitated the isolation of a genomic clone containing at least two coding regions. Through use of primers derived from the genomic sequences, a 231-base-pair cDNA fragment was obtained by PCR from liver RNA. Comparison of the deduced 120-amino acid sequence from the N terminus of H1 with known protein sequences revealed substantial sequence similarity with the beta chain of the murine fourth complement component C4 and with the related third and fifth complement molecules C5 and C3 and the major histocompatibility complex-encoded sex-limited protein. Observation of structural and functional similarities associated with the sequence similarity indicate that these molecules share an evolutionary relationship: the polypeptide chain structure of hagfish complement-like protein (CLP) resembles that of C4; CLP contains a hidden thioester group on the 70-kDa chain; CLP binds to streptococcal cells and enhances the phagocytosis of yeast by hagfish leukocytes. These data suggest that CLP forms part of a non-clonally-derived complement-related humoral defense system in the hagfish.

Alterations in T gamma cells in patients with chronic idiopathic thrombocytopenic purpura

The number and percentage of T cells bearing Fc gamma receptors (T gamma) was quantitated in peripheral blood of patients with the autoimmune disease chronic ITP. In over half the patients, low initial percentages were obtained, the great majority of which returned to within the normal range after incubation under capping conditions. The phenomenon could be reproduced by pretreating normal T cells with immune complex containing sera or aggregated HGG. Furthermore, a reversible reduction in T gamma cells was observed in control patients with nonimmune thrombocytopenia and in pregnancy. In each case an association was observed between the reduced T gamma cell levels and the presence of circulating immune complexes, which suggested that the results could be explained by masking of Fc gamma receptors with preformed IgG-containing complexes. By contrast, patients with other autoimmune diseases such as scleroderma and rheumatoid arthritis had high or normal numbers of T gamma cells, respectively. Taken together, the findings do not support the existence of a gross deficiency of suppressor cells in patients with autoimmune disease and emphasize the need for caution in selection of markers for identification of T cell subsets.

Alterations in T gamma cells in patients with chronic idiopathic thrombocytopenic purpura

The number and percentage of T cells bearing Fc gamma receptors (T gamma) was quantitated in peripheral blood of patients with the autoimmune disease chronic ITP. In over half the patients, low initial percentages were obtained, the great majority of which returned to within the normal range after incubation under capping conditions. The phenomenon could be reproduced by pretreating normal T cells with immune complex containing sera or aggregated HGG. Furthermore, a reversible reduction in T gamma cells was observed in control patients with nonimmune thrombocytopenia and in pregnancy. In each case an association was observed between the reduced T gamma cell levels and the presence of circulating immune complexes, which suggested that the results could be explained by masking of Fc gamma receptors with preformed IgG-containing complexes. By contrast, patients with other autoimmune diseases such as scleroderma and rheumatoid arthritis had high or normal numbers of T gamma cells, respectively. Taken together, the findings do not support the existence of a gross deficiency of suppressor cells in patients with autoimmune disease and emphasize the need for caution in selection of markers for identification of T cell subsets.

A modified C1q deviation radioimmunoassay for use in a routine clinical laboratory

Current clinical interest in circulating immune complexes defines a need to develop immune complex assays suitable for use in routine clinical immunology laboratories. We describe one such assay based on the principle of immune complexes binding to radiolabelled C1q, using commercially available IgG-coated latex particles for competitive binding. The assay is simple, rapid, cheap, reproducible and sensitive (5 micrograms/ml). Specificity for both antibody and antigen was demonstrated and clinical value was proven with defined clinical groups.

Autosensitization and immune complexes in chronic idiopathic thrombocytopenic purpura

Argument exists as to whether platelet damage in chronic idiopathic thrombocytopenic purpura (ITP) is mediated by an autoimmune response to platelet antigen or by immune complexes. We have studied thirty-nine patients with ITP for evidence of (i) sensitization to platelet antigen, using a macrophage migration inhibition factor (MIF) assay, (ii) circulating immune complexes, using a Clq deviation technique, and (iii) serum-induced platelet 'immunoinjury', using a 3H-serotonin release assay. Eighty-one per cent of the patient group had a migration index of less than 0.8 (normal range 0.8-1.3), while 91% of those tested had a serum factor (presumably immune complexes) which bound to labelled Clq. The serotonin release assay was abnormal in 32% of twenty-two patients, and the results of this test bore no clear relationship to either those of the Clq deviation test or the MIF results. We conclude that most patients with ITP are sensitized to platelet-associated antigen, and have circulating immune complexes. The contribution of these factors to platelet destruction and the nature of the antigen in the complexes remain to be demonstrated. The serotonin release assay is less sensitive, non-specific, and has limited value in the diagnosis of ITP.