A secretagogin locus of the mammalian hypothalamus controls stress hormone release

A hierarchical hormonal cascade along the hypothalamic-pituitary-adrenal axis orchestrates bodily responses to stress. Although corticotropin-releasing hormone (CRH), produced by parvocellular neurons of the hypothalamic paraventricular nucleus (PVN) and released into the portal circulation at the median eminence, is known to prime downstream hormone release, the molecular mechanism regulating phasic CRH release remains poorly understood. Here, we find a cohort of parvocellular cells interspersed with magnocellular PVN neurons expressing secretagogin. Single-cell transcriptome analysis combined with protein interactome profiling identifies secretagogin neurons as a distinct CRH-releasing neuron population reliant on secretagogin's Ca(2+) sensor properties and protein interactions with the vesicular traffic and exocytosis release machineries to liberate this key hypothalamic releasing hormone. Pharmacological tools combined with RNA interference demonstrate that secretagogin's loss of function occludes adrenocorticotropic hormone release from the pituitary and lowers peripheral corticosterone levels in response to acute stress. Cumulatively, these data define a novel secretagogin neuronal locus and molecular axis underpinning stress responsiveness.

Secretagogin is a Ca2+-binding protein identifying prospective extended amygdala neurons in the developing mammalian telencephalon

The Ca(2+)-binding proteins (CBPs) calbindin D28k, calretinin and parvalbumin are phenotypic markers of functionally diverse subclasses of neurons in the adult brain. The developmental dynamics of CBP expression are precisely timed: calbindin and calretinin are present in prospective cortical interneurons from mid-gestation, while parvalbumin only becomes expressed during the early postnatal period in rodents. Secretagogin (scgn) is a CBP cloned from pancreatic beta and neuroendocrine cells. We hypothesized that scgn may be expressed by particular neuronal contingents during prenatal development of the mammalian telencephalon. We find that scgn is expressed in neurons transiting in the subpallial differentiation zone by embryonic day (E)11 in mouse. From E12, scgn(+) cells commute towards the extended amygdala and colonize the bed nucleus of stria terminalis, the interstitial nucleus of the posterior limb of the anterior commissure, the dorsal substantia innominata (SI) and the central and medial amygdaloid nuclei. Scgn(+) neurons can acquire a cholinergic phenotype in the SI or differentiate into GABA cells in the central amygdala. We also uncover phylogenetic differences in scgn expression as this CBP defines not only neurons destined to the extended amygdala but also cholinergic projection cells and cortical pyramidal cells in the fetal nonhuman primate and human brains, respectively. Overall, our findings emphasize the developmentally shared origins of neurons populating the extended amygdala, and suggest that secretagogin can be relevant to the generation of functional modalities in specific neuronal circuitries.

Trends in bicycling-related head injuries in children after implementation of a community-based bike helmet campaign

BACKGROUND/PURPOSE

The aim of this study was to determine the effect of a community-based bike helmet promotion campaign on bike helmet use and related head injuries in children (0 to 14 years of age) in a large North American city.

METHODS

The authors established a multifaceted, multidisciplined, community-based campaign to promote bike helmet use by children in 1989. The goals were to increase helmet use by 100% per year, to reduce fatal bike-related head injuries by 50% overall, and to explore the feasibility of legislation mandating helmet use. Helmet use was measured by standardized field observations repeated annually in a single borough within the metropolitan area. To estimate head injury incidence, the number of admissions to hospital for the treatment of bike-related head injuries in a regional trauma registry, which included all residents in the target population was used. The authors were unable to control for changes in exposure to bicycling or in the criteria for admissions to hospital for the treatment of head injuries during the study period.

RESULTS

The bike helmet use rate rose from 4% in 1990 to 67% in 1996. The number of head injury admissions fell from 46 in 1990 to 24 in 1996. Legislation requiring helmet use by all children went into effect in October 1995.

CONCLUSIONS

Bike helmet use increased significantly during the first 4 years of the campaign and again after the helmet law was implemented. The total number of bike-related head injury admissions declined by more than 50%. The campaign achieved all of its goals except for a 50% reduction in fatal head injuries, which were too infrequent for analysis.

MRI of pediatric growth plate injury: correlation with plain film radiographs and clinical outcome

PURPOSE

To evaluate pediatric growth plate injuries with conventional radiographs and magnetic resonance imaging (MRI). To review potential clinical impact of MRI on subsequent patient management and outcome.

METHODS

Fourteen patients with known or suspected growth plate injury were studied. Each patient underwent imaging by conventional radiography and MRI within 2 weeks of injury. Findings on conventional radiographs and on MR images were compared and then correlated with subsequent management and outcome at a mean of 12 months.

RESULTS

Direct visualization of cartilage afforded by MRI improved evaluation of growth plate injury in each case. MRI changed Salter Harris classification or staging in 2 of 9 patients with fractures visualized on conventional radiographs, allowed the detection of radiographically occult fractures in 5 of 14 cases, and resulted in a physical change in management in 5 of the 14 patients studied.

CONCLUSION

MRI has an important role in the evaluation of acute pediatric growth plate injury, particularly when diagnostic uncertainty persists following the evaluation of conventional radiographs. MRI allows detection of occult fractures, may alter Salter Harris staging, and in the reported study it frequently resulted in a change in patient management.

Safety of MR imaging in patients who have retained metallic materials after cardiac surgery

OBJECTIVE

Epicardial pacing wires retained in patients who undergo cardiac surgery are thought to be a relative contraindication to MR imaging. However, to our knowledge no published evidence supports this belief. Because other metallic materials retained after cardiac surgery might represent a hazard to patients who undergo MR imaging, we sought to determine the safety of such imaging.

SUBJECTS AND METHODS

We examined 200 patients who underwent MR imaging at 1 or 1.5 T after cardiac surgery. Eighty-one were examined with ECG monitoring. The presence of temporary epicardial pacing wires, prosthetic valves, and other metal materials was confirmed by chest radiography.

RESULTS

Of the 200 patients reviewed, all had postoperative metallic material visible on chest radiographs. Temporary epicardial pacing wire, cut short at the skin, was seen in 51 patients. Of the 81 patients examined with ECG monitoring, we found that MR imaging produced no changes from baseline ECG rhythms. None of the 200 patients reported symptoms suggesting arrhythmia or other cardiac dysfunction during MR imaging.

CONCLUSION

MR imaging can be performed safely in patients who have undergone cardiac surgery and have retained metallic material, including valve replacements and temporary epicardial pacing wires cut short at the skin. MR imaging of patients with pacemakers was not evaluated, and we recommend that pacemakers remain a contraindication to MR imaging.

Monoclonal antibody characterization of Jamestown Canyon (California serogroup) virus topotypes isolated in Canada

Jamestown Canyon (JC) virus of the California (CAL) serogroup has been isolated in 12 American states and 6 Canadian provinces. A study was undertaken to produce monoclonal antibodies (MAbs) to JC virus and to use these MAbs to assay for possible heterogeneity among naturally occurring JC topotypes in Canada. MAbs were produced to the prototype strain of JC virus using BALB/c mice. Twenty-seven secreting MAbs were obtained and three of these MAbs were propagated and studied. All three MAbs, M1 (IgG1), M2 (IgG2b), and M3 (IgG2a), were reactive by immunofluorescent antibody assay against JC-infected vero cells and by ELISA against JC antigen. MAb M2 reacted with all members of the Melao complex, MAb M1 reacted only with Keystone virus, while MAb M3 exhibited no reactivity with other CAL serogroup viruses. Only MAb M3 possessed neutralization and hemagglutination inhibition activities against JC virus. The MAbs were also tested by ELISA and for neutralizing activity against 13 JC topotypes isolated in 5 provinces from Newfoundland to Saskatchewan. ELISA confirmed closer identity of the Canadian topotypes to JC as opposed to the closely related South River virus. The MAbs verified all Canadian topotypes to be JC virus but revealed different patterns of reactivity between these topotypes and prototype JC virus.

Imported arbovirus infections in Canada 1974-89

From 1974 to 1989, sera from symptomatic patients with histories of recent travel outside Canada were tested for antibodies to several arboviruses, principally of the alphavirus and flavivirus families. Diagnostic seroconversions were documented in 84 individuals from six provinces, including one alphavirus (Chikungunya) and 83 flavivirus seroconvertors. Dengue 1 virus was isolated from the blood of one patient. Most flavivirus seroconvertors were likely infected with dengue virus, but infections with tick-borne encephalitis, St Louis encephalitis and Powassan viruses were also recognized. Patients had histories of recent travel to the Caribbean, South America, Asia, Africa, North America (outside Canada), Tahiti, Fiji and Europe. Possible imported infections due to Japanese encephalitis, Ross River, western equine encephalitis and Colorado tick fever viruses were also encountered.

Diagnosis and incidence of cardiac injury in children with blunt thoracic trauma

Over a 20-month period, we prospectively studied 41 children with blunt thoracic trauma (BTT) to determine the incidence and morbidity of cardiac injury in this population. Four patients died, and the data were incomplete in 10, leaving 27 for analysis. Serial electrocardiograms (ECG) were abnormal in 36% of the patients studied, serial creatine phosphokinase isoenzyme (CK-MB) ratios were elevated in 31%, echocardiogram showed septal dysfunction in 14%, and pyrophosphate scan showed grade 1 uptake in 14%. There was poor correlation among tests, since only four patients had more than one abnormal test. There was no significant difference in Injury Severity Score or Thoracic Abbreviated Injury Scale between patients with and without abnormal investigations. No patient in the study developed arrhythmias or cardiac failure. In 13 trauma-related deaths undergoing autopsy over the same period, including the four with thoracic trauma, none had evidence of cardiac injury. These results indicate a striking lack of consistency in the diagnosis of posttraumatic cardiac injury in children using standard investigations. The absence of adverse cardiac events in surviving patients and the lack of autopsy evidence of cardiac injury in the trauma deaths suggest that the actual incidence and clinical significance of these lesions in children is lower than generally reported. Children with BTT should be followed clinically, and reliance on screening tests should be avoided.

Development of urease conjugated enzyme-linked immunosorbent assays (ELISA) for the detection of IgM and IgG antibodies against Mycoplasma pneumoniae in human sera

Urease conjugated enzyme linked immunosorbent assays (ELISA) were developed for the detection of human IgM and IgG antibodies against Mycoplasma pneumoniae. Results obtained by ELISA were compared with complement fixation test (CFT); which showed that of the 214 serum specimens tested, 80 were found to have antibody against M. pneumoniae. ELISA revealed that 70 of these specimens were IgG antibody, and 27 of them also contain IgM antibody. CFT failed to detect the presence of antibody against M. pneumoniae in five serum specimens tested. However, by using ELISA, three of them were found to have IgG and IgM antibodies. and the other two sera have IgG antibody only. Four out of the five specimens tested were the first serum specimens collected from patients with clinical and serological evidence of M. pneumoniae infection. In addition, 28 serum specimens, including 10 sera containing IgM rheumatoid factors and sera known to contain IgM antibody to other infectious organisms, were also tested for IgM antibody against M. pneumoniae by ELISA. None of these specimens showed a nonspecific reaction. ELISA had a sensitivity of 87.5% and a specificity of 96.3% when compared with CFT. Thus, ELISA developed in our laboratory is a specific test, and the results indicated that IgM ELISA might be used as a rapid diagnosis for M. pneumoniae infection.

Amplified ELISA for the detection of western equine encephalitis virus from mosquitoes in Manitoba, Canada

Current monitoring systems to detect western equine encephalitis (WEE) virus in mosquitoes involve isolation in suckling mice or cell culture followed by serological identification of the isolates obtained. Studies were undertaken to develop an amplified ELISA for the rapid detection of WEE virus from mosquitoes. Virus was inoculated onto primary chick embryo cells in 96 well plates, incubated at 37 degrees C for various time periods, monolayers were fixed, and an ELISA performed. By this procedure, 10 plaque-forming units or greater of WEE virus were detected by 24 h postinfection. This amplified ELISA procedure was successfully applied in parallel with standard isolation methods to monitor mosquitoes collected in Manitoba, Canada, in 1985 for WEE virus.

Arbovirus infections in several Ontario mammals, 1975-1980

Serological studies for arboviruses were conducted on 725 animal sera collected in 22 Ontario townships between 1975 and 1980 including 44 coyote (Canis latrans), 277 red fox (Vulpes vulpes), 192 raccoon (Procyon lotor) and 212 striped skunk (Mephitis mephitis). Hemagglutination inhibition antibodies to two flaviviruses, namely St. Louis encephalitis and Powassan were found in 50% of coyote, 47% of skunk, 26% of fox and 10% of raccoon sera. Similarly, hemagglutination inhibition antibodies to a California serogroup virus, snowshoe hare, were found in 12% of fox, 7% of skunk, 7% of raccoon and 5% of coyote sera. No antibodies were detected to two alphavirus, namely eastern equine encephalitis and western equine encephalitis, antigens. This study affirms the endemic presence of Powassan and snowshoe hare virus and further delineates the scope of St. Louis encephalitis activity in Ontario.

Observations on the use of oral poliovirus vaccines in the Caribbean and Canada

Investigations on the use of poliovirus vaccines in the Caribbean and Canada are reviewed. Studies in Trinidad and Tobago in 1963 showed that children who were given two doses of oral poliovirus vaccine responded satisfactorily to the type 2 and type 3 components but poorly to the type 1 component. Studies on poliovirus vaccines in Canada have indicated that both killed and live vaccines are capable of controlling poliomyelitis. Results of studies undertaken in Ontario suggested that the response to a killed vaccine was not entirely satisfactory. The need for continued surveillance for poliomyelitis is emphasized. Action should be taken to review immunization procedures when a single case occurs. Consideration should be given to the use of monovalent vaccines in tropical countries.

Serological evidence of infection with California serogroup viruses (family Bunyaviridae) in residents of Long Hua, suburb of Shanghai, People's Republic of China

Sera from 126 residents of Long Hua, a suburb of Shanghai, in the People's Republic of China, were studied. Sera were tested for haemagglutination inhibiting antibodies to alphavirus (eastern equine encephalitis, western equine encephalitis), flavivirus (St. Louis encephalitis, Powassan, dengue) and California serogroup (snowshoe hare) antigens. Flavivirus antibodies were found in 14 (11.1%) and California serogroup antibodies in 5 (3.9%) individuals. Neutralizing antibodies with highest titres to snowshoe hare virus were demonstrated in 3 of the 5 California serogroup reactors. We believe this to be the first report of California serogroup virus antibodies in Chinese residents and the first evidence to suggest that California serogroup viruses may be circulating in the Orient.

Avian pox in birds from Trinidad

Over a 7-year period in Trinidad, 9,514 birds were examined for avian pox and four species were found infected: the golden-headed manakin, Pipra erythrocephala (7% infected), the white-bearded manakin, Manacus manacus (5%), the violaceous euphonia Euphonia violacea (1%), and the bare-eyed thrush, Turdus nudigenis (less than 1%). The elaborate courtship displays of manakins may have a bearing on a "common source" type of infection. The apparently abrupt appearance of the disease at three localities in Trinidad in 1964 perhaps indicates introduction of the virus by migratory birds.

The relative importance of rotavirus and other pathogens in the etiology of gastroenteritis in Trinidadian children

Over a 2-year period, 300 infants less than 3 years old with gastroenteritis admitted to hospitals in Trinidad were investigated for the presence of certain microorganisms in the feces, along with an equal number of age- and sex-matched controls. Rotavirus was detected in 23% of cases and 1% of controls; Salmonella in 7% of cases and in 1% of controls; Shigella in 4% of cases and in no controls and two serotypes of enteropathogenic E. coli in 7% of cases and in 2% of controls. Campylobacter fetus subspecies jejuni was cultured from 7 out of 60 cases and from 1 of 60 controls. Enterotoxigenic E. coli, most strains of enteropathogenic E. coli, cytopathic enteroviruses and adenoviruses and fecal parasites were not significantly associated with diarrhea. Rotaviruses were detected throughout the year but were more prevalent in the dry than in the rainy season. They were found less often in children younger than 6 months than in those aged 6 to 35 months and were present in 6 of the 20 children who died.

Antibodies to the California group of arboviruses in the moose (Alces alces americana Clinton) population of Nova Scotia

Moose (Alces alces americana Clinton) blood collected by hunters during the 1977 and 1978 hunting seasons was tested for California group antibodies. Hemagglutination inhibition (HI) tests using snowshoe hare virus (SSH) as antigen yielded 37.02% HI-positive sera. Neutralization tests showed reactors reactors (67.5% positive) to SSH and classified six reactors as Jamestown Canyon virus (JC). This study reports the first finding of JC in a moose population; it also provides the first evidence of JC in Atlantic Canada and supports previous findings of SSH in Nova Scotia.

Aseptic meningitis in Ontario

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Antibodies to snowshoe hare virus of the California group in the horse population in Nova Scotia

A large number of North American equine samples were tested for the California group of arboviruses (CAL). Of 861 equine sera tested by hemagglutination inhibition using the snowshoe hare virus as an antigen, 106 (12.3%) were positive. Neutralization tests confirmed antibodies to this virus in 72 of the positive sera. This study provides evidence of CAL activity in the domestic animal population of Nova Scotia.

Virus isolations from mosquitoes in southern Ontario, 1976 and 1977

Following the 1975 epidemic of St. Louis encephalitis (SLE) in Ontario, programs were instituted to monitor virus activity in mosquito populations during 1976 and 1977. Mosquitoes were trapped with CDC light traps and CO2 cone traps, pooled by species, and tested for virus by intracerebral inoculation of suckling mice. In 1976, 51 175 mosquitoes were tested. SLE virus was isolated from two mixed pools of Culex pipiens--C. restuans mosquitoes. Five isolations of California serogroup viruses were made. Three of these were trivittatus virus, which has not been demonstrated previously in Canada, and the other two were snowshoe have virus. Other viruses isolated in 1976 were a virus antigenically identical to the virus of infectious bursal disease of chickens and 34 Flanders viruses. In 1977, 34 428 mosquitoes were tested. Flanders virus was isolated most frequently, from pools of mixed C. pipiens--C. restuans mosquitoes. The only other isolate was a Bunyamwera group virus, Cache Valley virus. This virus has not been reported previously in Ontario.

Quantitative determination of cytomegalovirus IgG antibody by enzyme-linked immunosorbent assay (ELISA)

Quantitative determination of cytomegalovirus (CMV) human IgG antibody by ELISA performed in polystyrene trays was carried out and compared with results obtained by the routine complement fixation (CF) test. The antibody titres of all the sera determined by ELISA were higher than those detected by the CF test. Of the 27 sera negative (less than 1:8) by the CF test, 22 of them were also negative (less than 1:50) by ELISA. The other five CF negative sera were found to have low levels of antibody by ELISA. ELISA is a sensitive and specific assay for CMV antibody. The CMV antigen adsorbed readily to the microtitre plates and the test was simple to perform. The results of ELISA could be obtained in 5 to 6h. A description of the test procedure is given including the method of CMV antigen attachment to the plates. The possibility of using paired sera at a single dilution in the ELISA test to detect seroconversion is discussed.

Use of antisera against bovine (NCDV) and simian (SA11) rotaviruses in ELISA to detect different types of human rotavirus

Two ELISA systems for the detection of human rotaviruses were developed. In the first system antibodies to Nebraska calf diarrhea virus (NCDV) were used for coating the solid matrix and for the preparation of the enzyme conjugate. In the second system antibodies to human rotavirus and antibodies to simian rotavirus (SA11) were used for coating the solid matrix and for the preparation of the enzyme conjugate respectively. The second ELISA system proved to have a broader spectrum for the detection of human rotaviruses. By using the two ELISA systems, the different types of human rotavirus could be distinguished. The ELISA tests developed were 8 to 64 times as sensitive as electron microscopy (EM) and (or) counterimmunoelectrophoresis (CIEP). The antigen detected by ELISA was shown to be different from that detected by the hemagglutination test.

A prospective study of respiratory infection in adult asthmatics and their normal spouses

A prospective study of respiratory infections was performed in nineteen married asthmatics and their normal spouses who were examined at monthly intervals during a 1-year period. The colds described were associated with nasal symptoms, sore throat and usually malaise, fever, cough and hoarseness. The asthamtics reported a larger number of these symptomatic episodes than the non-asthmatics but significantly fewer of the episodes in the asthmatics were objectively confirmed by viral isolation or rise in serum titre of viral antibody. The frequency of respiratory infections was not influenced by the long term use of inhaled beclomethasone dipropionate and oral corticosteroid drugs. Less than 10% of the exacerbations of asthma were associated with respiratory infection. The disability resulting from respiratory infections in the asthmatics did not significantly exceed that in the non-asthmatics.

California encephalitis virus activity in mosquitoes and horses in southern Ontario, 1975

A study was undertaken in 1975 to determine California encephalitis virus activity in southern Ontario. Three thousand and sixty-one mosquitoes, primarily Aedes species, were divided into 104 pools and inoculated into suckling mice. Isolates of snowshoe hare virus were obtained from one pool each of Aedes fitchii and A. triseriatus mosquitoes collected in the Guelph area. Serological testing of horse sera revealed extensive virus activity in southern Ontario and indicated that horses may serve as excellent monitors for California encephalitis virus.

Antibodies to snowshoe hare virus of the California group in the snowshoe hare (Lepus americanus) population of Nova Scotia

Serological study showed the presence of antibodies to snowshoe hare virus in 6--14% of snowshoe hares (Lepus americanus) samples in Nova Scotia. This report extends the known range of this virus in North America.

Comparison of rotavirus strains by hemagglutination inhibition

Rotaviruses have been shown to be of importance as aetiologic agents of gastroenteritis in infants and in domestic animals of several species. Hemagglutinins were prepared from two Canadian isolates of bovine rotavirus and from one isolate of a simian rotavirus. A United Kingdon isolate of bovine rotavirus was shown not to possess hemagglutinating activity, indicating a strain difference between a Canadian and United Kingdom bovine rotavirus. In hemagglutination-inhibition (HAI) tests a rabbit hyperimmune (two injections) serum, prepared to one of the bovine rotaviruses, was not helpful in distinguishing the two bovine viruses because of cross-reactions between the viruses. However, it was possible to distinguish the bovine viruses from the simian virus with this serum. When guinea pig immune sera were prepared to the four rotavirus strains and tested with the three hemagglutinins in the HAI test, antigenic differences between the four strains of rotavirus were demonstrated. Hyperimmune guinea pig serum prepared to a strain of human rotavirus did not inhibit any of three hemagglutinins indicating that the human strain is different from the three rotavirus strains which gave hemagglutinins.

Immune adherence hemagglutination test applied to the study of herpes simplex and varicella-zoster virus infections

The immune adherence hemagglutination (IAHA) test has been used successfully to detect antibody to herpes simplex (HS) virus and varicella-zoster (V-Z) virus. Comparative studies between the complement-fixation (CF) test and the IAHA test revealed that, in most cases, the IAHA test was more sensitive than the CF test. Furthermore, diagnosis on the basis of a fourfold change in antibody titer was made more rapidly by the IAHA test. The IAHA test was found to be a very simple and practical technique requiring only a few hours for completion compared with the conventional CF test which required up to 24 h. In addition, both sera and cerebrospinal fluids could be tested in very low dilutions in the IAHA test, so that very low levels of antibody could be detected. Also, the IAHA test detected antibody to V-Z virus more frequently than did the CF test in adults with a history of varicella occurring 9 to 30 years prior to sampling. The level of cross-reaction between HS and V-Z viruses was examined by both the CF test and the IAHA test, and no major differences between the two techniques were found.

Hemagglutination and hemagglutination-inhibition studies with a strain of Nebraska calf diarrhea virus (bovine rotavirus)

A hemagglutinin has been prepared from Nebraska calf diarrhea virus (NCDV) propagated in BS-C-1 cell line. After cesium chloride centrifugation, the hemagglutinin of the bovine rotavirus was found to be associated with intact virions (density 1.355 g/ml) but not with virions lacking an outer capsid layer (density 1.375 g/ml). In hemagglutination-inhibition (HAI) tests, the hemagglutinin reacted specifically with NCDV serum, and HAI seroconversions were detected in some sera tested. Cross-reactions were observed in complement fixation tests between the human and bovine rotaviruses but were not demonstrated by HAI, suggesting that the hemagglutinin detects a specific rather than a group antibody response.

A simple method for the inactivation of St. Louis encephalitis virus preparations for immunofluorescent microscopy

A study was made of different treatments for the inactivation of St. Louis encephalitis virus in smears prepared for immunofluorescence microscopy. Treatment of infected cells with 0.3% betapropiolactone at 56 degrees C for 40 min resulted in an inactivated virus suitable for immunofluorescence studies.

Rotavirus isolation and cultivation in the presence of trypsin

Rotaviruses are generally difficult to isolate and culture in vitro; therefore, virus isolation has not been used as a method of diagnosing this group of agents. The present report describes a simple procedure for isolating bovine rotaviruses directly from feces after pretreatment of fecal samples with trypsin. This procedure resulted in virus isolation from five of five samples that contained virus particles, as demonstrated by electron microscopy, and four of seven samples where virus particles could not be observed but were considered positive by the presence of immunofluorescent-staining cells in feces. Virus could not be isolated from "normal" feces. If the virus was not passaged in the presence of trypsin, the infectivity was gradually lost, but infectivity could be restored again if trypsin was added, resulting in increased virus spread and concomitant increase in virus yield. The application of this technique as a diagnostic tool for bovine and other rotaviruses is briefly discussed.

Immune electron microscopy of arboviruses

Representative members of four arbovirus taxons were studied by immune electron microscopy (IEM) in an attempt to determine whether the technique can be applied to the specific identification of arboviruses. Alphavirus, flavivirus, bunyavirus, and rhabdovirus antigens were prepared by propagation in tissue culture. The viruses were used to titrate homologous antibody and test heterologous antibody in the IEM test. Specific clumping together with visualization of antibody attachment was observed for all homologous systems studied. For the alphaviruses, titers of antibody, as determined by IEM, were comparable with the titers obtained by hemagglutination inhibition. Alphavirus cross-reactions were observed at low antibody dilutions by IEM. However, further dilution of antibody resulted in specific clumping only of homologous virus, allowing specific identification of alphavirus unknowns. For all viruses studied, positive IEM reactions were obtained with homologous grouping ascitic fluids but not with heterologous grouping fluids.

Comparison of Counterimmunoelectrophoresis and electron microscopy for laboratory diagnosis of human reovirus-like agent-associated infantile gastroenteritis

Counterimmunoelectrophoresis was compared with electron microscopy for detection of human reovirus-like agent in fecal specimens. Both tests gave very similar results.

St. Louis encephalitis in southern Ontario: laboratory studies for arboviruses

The first reported outbreak of St. Louis encephalitis in Canada occurred in the summer of 1975 in southern Ontario -- in the Windsor-Sarnia-Chatham area, the Niagara region and the city of Toronto. Hemmagglutination inhibition and complement fixation testing of serum samples collected during the outbreak confirmed that St. Louis encephalitis virus was the etiologic agent. Furthermore, this virus was isolated from brain tissue of a patient who died. This outbreak was probably an extension of the outbreak that occurred in the United States that summer. It was the first outbreak of arbovirus encephalitis in the province of Ontario.

Frequency of hepatitis B surface antibody (anti-HBs) in various Canadian populations as measured by modified solid-phase radioimmunoassay

A short incubation solid-phase radioimmunoassay test was developed and used for the detection of hepatitis B surface antibody (anti-HBs) in the sera collected from patients recovering from hepatitis B infection, health care personnel, staff and residents of an institution for the mentally retarded and in pregnant and non-pregnant women in Ontario. The test was slightly more sensitive than the passive haemagglutination method (PHA) and less sensitive than the Ausab Radioimmunoassay technique (RIA).The prevalence of anti-HBs in different populations tested ranged from 0 to 44.3%. They were classified according to the statistical analysis into three main categories: low, intermediate, and high risk. Students and administrative staff were in the low-risk category, Microbiology, histology, pathology technologists, renal dialysis staff, and the health care personnel responsible for the care of the institutionalized mentally retarded were in the intermediate-risk category. Pathologists, haematologists, and biochemists were in the high-risk category. The results showed that health care personnel who were exposed to blood or blood products had a higher frequency of anti-HBs than those who were not exposed.

Detection of core antibody in hepatitis B infection

Hepatitis B core antigen (HBcAg) is found on the decoated Dane particle and on a morphologically similar particle detected mainly in the nucleus of hepatocytes of patients with hepatitis B. HBcAg prepared from the liver of a chimpanzee infected with hepatitis B virus was used to test human serum for core antibody (anti-HBc) by complement fixation. Anti-HBc was found in serum collected from patients with hepatitis B in both the acute and convalescent stages, from carriers of hepatitis B surface antigen (HBsAg) and from patients with chronic liver or renal disease who were carriers of HBsAg. It was not found in patients with hepatitis A or infectious mononucleosis, or in healthy persons who were not carriers of HBsAg.

Letter: Test for reovirus-like agent

Cranial sonography is an established procedure for the detection of neonatal intracranial hemorrhage. A 3 year experience in imaging such infants is reviewed. Representative examples are presented to comprehensively illustrate the spectrum of sonographic appearances of intracranial hemorrhage and its complications from the initial hemorrhage to resolution. Diagnostic problems in the initial staging of the grade of hemorrhage and in evaluating subsequent ventricular changes are addressed.