Phenotypic flexibility of digestive system in Atlantic cod (Gadus morhua).

This study examined the restoration of the digestive capacity of Atlantic cod (Gadus morhua Linnaeus) following a long period of food deprivation. Fifty cod (48 cm, 1 kg) were food-deprived for 68 days and then fed in excess with capelin (Mallotus villosus Müller) on alternate days. Ten fish were sampled after 0, 2, 6, 14 and 28 days and the mass of the pyloric caeca, intestine and carcass determined. Two metabolic enzymes (cytochrome c oxidase and citrate synthase) were assayed in white muscle, pyloric caeca and intestine, and trypsin activity was measured in the pyloric caeca. A delay of 14 days was required before body mass started to increase markedly, whereas most of the increase in mass of both the pyloric caeca and intestine relative to fish length occurred earlier in the experiment. By day 14, the activities of trypsin and citrate synthase in the pyloric caeca as well as citrate synthase in the intestine had reached maxima. The growth of the digestive tissues and restoration of their metabolic capacities thus occur early upon refeeding and are likely required for recovery growth to take place. The phenotypic flexibility of the cod digestive system is therefore remarkable: increases in trypsin activity and size of pyloric caeca resulted in a combined 29-fold increase in digestive capacity of the fish during the refeeding period. Our study suggests that Atlantic cod are able to cope with marked fluctuations in food availability in their environment by making a rapid adjustment of their digestive capacity as soon as food availability increases.

Characterization of a multifunctional methyltransferase from the orchid Vanilla planifolia.

The final enzymatic step in the synthesis of the flavor compound vanillin (4-hydroxy-3-methoxybenzaldehyde) is believed to be methylation of 3,4-dihydroxybenzaldehyde. We have isolated and functionally characterized a cDNA that encodes a multifunctional methyltransferase from Vanilla planifolia tissue cultures that can catalyze the conversion of 3,4-dihydroxybenzaldehyde to vanillin, although 3,4-dihydroxybenzaldehyde is not the preferred substrate. The higher catalytic efficiency of the purified recombinant enzyme with the substrates caffeoyl aldehyde and 5-OH-coniferaldehyde, and its tissue distribution, suggest this methyltransferase may primarily function in lignin biosynthesis. However, since the enzyme characterized here does have 3,4-dihydroxybenzaldehyde-O-methyltransferase activity, it may be useful in engineering strategies for the synthesis of natural vanillin from alternate sources.

Using empirical data to model transgene dispersal.

One element of the current public debate about genetically modified crops is that gene flow from transgenic cultivars into surrounding weed populations will lead to more problematic weeds, particularly for traits such as herbicide resistance. Evolutionary biologists can inform this debate by providing accurate estimates of gene flow potential and subsequent ecological performance of resulting hybrids. We develop a model for gene flow incorporating exponential distance and directional effects to be applied to windpollinated species. This model is applied to previously published data on gene flow in experimental plots of Agrostis stolonifera L. (creeping bentgrass), which assessed gene flow from transgenic plants resistant to the herbicide glufosinate to surrounding non-transgenic plants. Our results show that although pollen dispersal can be limited in some sites, it may be extensive in others, depending on local conditions such as exposure to wind. Thus, hybridization under field conditions is likely to occur. Given the nature of the herbicide resistance trait, we regard this trait as unlikely to persist in the absence of herbicide, and suggest that the ecological consequences of such gene flow are likely to be minimal.

Expression of pokeweed antiviral proteins in creeping bentgrass.

Fungal diseases of creeping bentgrass, an important amenity grass used extensively on golf courses, are a serious problem in golf course management. Transgenic approaches to improving disease resistance to fungal diseases are being explored in many species, and in some cases ribosome-inactivating proteins have been found to be effective. We have generated transgenic creeping bentgrass plants expressing three forms of ribosome-inactivating proteins from pokeweed, which are termed pokeweed antiviral proteins (PAP). PAP-Y and PAP-C are nontoxic mutants of PAP; PAPII is the native form of another ribosome-inactivating protein from pokeweed. In creeping bentgrass, PAP-C transformants did not accumulate the protein, suggesting that it is unstable, and in a field test these plants were not protected from infection by the fungal pathogen Sclerotinia homoeocarpa, the causal agent of dollar spot disease. PAPII transformants could accumulate stable levels of the protein but had symptoms of toxicity; one low-expressing line exhibited good disease resistance. PAP-Y transformants accumulated stable levels of protein, and under greenhouse conditions they appeared to be phenotypically normal.

Timely detection of meningococcal meningitis epidemics in Africa.

BACKGROUND: Epidemics of meningococcal disease in Africa are commonly detected too late to prevent many cases. We assessed weekly meningitis incidence as a tool to detect epidemics in time to implement mass vaccination. METHODS: Meningitis incidence for 41 subdistricts in Mali was determined from cases recorded in health centres (1989-98) and from surveillance data (1996-98). For incidence thresholds of 5 to 20 cases per 100000 inhabitants per week, we calculated sensitivity and specificity for detecting epidemics, and determined the time lapse between threshold and epidemic peak. FINDINGS: We recorded 9084 meningitis cases. Clinic-based weekly incidence of 5 and 10 cases per 100000 inhabitants detected all meningitis epidemics (sensitivity 100%, 95% CI 93-100), with median threshold-to-peak time of 5 and 3 weeks. Under-reporting reduced sensitivity: only surveillance thresholds of 5 or 7 cases per 100000 inhabitants per week detected all epidemics. Crossing the lower threshold before the 10th calendar week doubled epidemic risk relative to crossing it later (relative risk 2.1, 95% CI 1.4-3.2). At 10 cases per 100000 inhabitants per week, specificity for outbreak prediction was 88%, 95% CI 83-91). For populations under 30000, 3 to 5 cases in one or two weeks predicted epidemics with 85% to 97% specificity. INTERPRETATION: Low meningitis thresholds improve timely detection of epidemics. Ten cases per 100000 inhabitants per week in one area confirm epidemic activity in a region, with few false alarms. An alert threshold of 5 cases per 100000 inhabitants per week allows time to investigate, prepare for an epidemic, and initiate mass vaccination where appropriate. For populations under 30000, the alert threshold is two cases in a week. High quality surveillance is essential.

Rapid assessment of population size by area sampling in disaster situations.

In the initial phase of a complex emergency, an immediate population size assessment method, based on area sampling, is vital to provide relief workers with a rapid population estimate in refugee camps. In the past decade, the method has been progressively improved; six examples are presented in this paper and questions raised about its statistical validity as well as important issues for further research. There are two stages. The first is to map the camp by registering all of its co-ordinates. In the second stage, the total camp population is estimated by counting the population living in a limited number of square blocks of known surface area, and by extrapolating average population calculated per block to the total camp surface. In six camps selected in Asia and Africa, between 1992 and 1994, population figures were estimated within one to two days. After measuring all external limits, surfaces were calculated and ranged between 121,300 and 2,770,000 square metres. In five camps, the mean average population per square was obtained using blocks 25 by 25 meters (625 m2), and for another camp with blocks 100 by 100 m2. In three camps, different population density zones were defined. Total camp populations obtained were 16,800 to 113,600. Although this method is a valuable public health tool in emergency situations, it has several limitations. Issues related to population density and number and size of blocks to be selected require further research for the method to be better validated.

Doctor shopping before and after a visit to a paediatric emergency department.

BACKGROUND: Use of multiple care providers is known to be associated with poor continuity of care. OBJECTIVES: To estimate the prevalence of and identify risk factors for doctor shopping by parents of children with common acute illnesses seen in the emergency department (ED) of a children's hospital. SETTING: ED at the Montreal Children's Hospital (MCH), Montreal, Quebec. METHODS: Doctor shopping was defined as visiting three or more different care sites (the MCH ED, other EDs, outpatient clinics or private offices) for a single illness episode, including all visits occurring within successive 72 h periods up to a maximum of 15 days before and after an ED visit from April 1995 to March 1996. Logistic regression was used to compare characteristics of illness episodes with doctor shopping versus those without. RESULTS: Of the total 40,150 visits during the study period, doctor shopping was observed in 18% of the visits. The risk of doctor shopping was positively associated with an initial visit at other EDs (odds ratio [OR] 9.08, 95% CI 7.16 to 11.52), outpatient clinics (OR 4.47, 95% CI 3.71 to 5.37) or private offices (OR 1.71, 95% CI 1.48 to 1.96) versus those who visited the MCH ED first. The risk did not differ according to whether a paediatrician versus a general practitioner saw the child during the initial visit (OR 0.99, 95% CI 0.86 to 1.15). Some diagnoses (the reference category was upper respiratory infection), including urinary tract infection (OR 3.31, 95% CI 2.58 to 4.23) and gastroenteritis (OR 1.59, 95% CI 1.35 to 1.88), were associated with an increased risk of doctor shopping, while asthma was associated with a reduced risk (OR 0.71, 95% CI 0.60 to 0.86). CONCLUSION: Doctor shopping is common among parents of children with acute illnesses. Parents of children who were seen in the MCH ED first were less likely to doctor shop, perhaps because the parents were more confident about the advice and treatment received. Further research should investigate the underlying reasons for doctor shopping, eg, services other than an ED were not available and parents' perceptions of the quality of health services.

Effectiveness of incidence thresholds for detection and control of meningococcal meningitis epidemics in northern Togo.

BACKGROUND: Early outbreak detection is necessary for control of meningococcal meningitis epidemics. A weekly incidence of 15 cases per 100 000 inhabitants averaged over 2 consecutive weeks is recommended by the World Health Organization (WHO) for detection of meningitis epidemics in Africa. This and other thresholds are tested for ability to predict outbreaks and timeliness for control measures. METHODS: Meningitis cases recorded for 1990-1997 in health centres of northern Togo were reviewed. Weekly and annual incidences were determined for each district. Ability of different weekly incidence thresholds to detect outbreaks was assessed according to sensitivity, specificity, and positive and negative predictive values. The number of cases potentially prevented by reactive vaccination in 1997 was calculated for each threshold. RESULTS: Outbreaks occurred in 1995-1996 and in 1996-1997. The WHO-recommended threshold had good specificity but low sensitivity. Thresholds of 10 and 7 cases per 100,000 inhabitants in one week had sensitivity and specificity of 100% and increased the time available for intervention by more than one or two weeks, respectively. A maximum of 65% of cases could have been prevented during the 1997 epidemic, with up to 8% fewer cases prevented for each week of delay in achieving vaccine coverage. CONCLUSIONS: In northern Togo, thresholds of 7 or 10 cases per 100,000 inhabitants per week were excellent predictors of meningitis epidemics and allowed more time for a reactive vaccination strategy than current recommendations.

Variation in utilization of computed tomography scanning for the investigation of minor head trauma in children: a Canadian experience.

OBJECTIVES: To compare the utilization rates of CT scans in investigating minor head trauma in children in Canada, to identify the injuries determined by these scans, and to identify clinical findings that are highly associated with its diagnosis and the injury itself. METHODS: A retrospective cohort study involving nine pediatric hospitals in Canada was conducted. A structured data collection method was used. Inclusion criteria included age 16 years or less, history of blunt head trauma, and a Glasgow Coma Scale score (GCS) greater than or equal to 13. Data collected included demographic information, type of injury, relevant clinical information, computed tomography (CT) scan data, and clinical outcome. Clinical findings associated with CT scan and positive CT scan were identified using logistic regression. RESULTS: One thousand one hundred sixty-four children were included in the study. One hundred seventy-one (15%) had a CT scan, of which 60 (35%) were abnormal. There was a significant difference in the rate of ordering of CT scans among the participating hospitals, but no significant difference in the rate of abnormal CT scans. Mechanism of injury, GCS, and loss of consciousness were significantly related to the presence of an abnormal CT scan. CONCLUSIONS: Although there is a significant difference in the utilization of CT scans to investigate minor head trauma in children across Canada, there is no significant difference in the frequency of head injuries in these patients. This suggests that it may be possible to determine clinical criteria that are predictive of a head injury in these patients.

Fungal proteinase expression in the interaction of the plant pathogen Magnaporthe poae with its host.

Infection by pathogenic fungi involves breaching the outer layer of the host by either mechanical or enzymatic means. Subtilisin-like proteinases are considered to be important in the infection process of entomopathogenic, nematophagous, and mycoparasitic fungi. Little is known regarding the expression of such proteinases by plant pathogenic fungi. Magnaporthe poae, a fungal pathogen of Kentucky bluegrass, expressed a subtilisin-like proteinase, proteinase Mp1, in the infected roots. Antibody was produced against the purified enzyme. From immunoblot analysis, expression of the proteinase in infected roots correlated with increasing severity of disease symptoms. Sequence analysis of a genomic clone indicated proteinase Mp1 was homologous to other fungal subtilisin-like proteinases. DNA gel blot analysis indicated proteinase Mp1 was encoded by a small gene family.

Incidence and risk factors of toxoplasmosis in a cohort of human immunodeficiency virus-infected patients: 1988-1995. HEMOCO and SEROCO Study Groups.

The incidence of cerebral and extracerebral toxoplasmosis among 1,699 HIV-infected patients followed in the SEROCO and HEMOCO cohorts (1988-1995) was studied. It increased from 0.7 per 100 person-years in 1988 to 2.1 per 100 person-years in 1992, as a result of the increasing prevalence of patients with CD4 cell counts below 200/microL. It decreased thereafter to 0.2 per 100 person-years in 1995, while the proportion of patients receiving specific prophylaxis was increasing. A Toxoplasma antibody titer of >150 IU/mL was an important predictor of toxoplasmosis (adjusted relative risk [aRR], 3.6 [95% confidence interval, 2.1-6.0]), independent of a CD4+ cell count of <200/microL (aRR, 20.8) and specific prophylaxis (aRR, 0.2 [0.1-0.3]). The median CD4+ cell count was 389/microL at the time the antibody titer was first noted to be >150 IU/mL, while the median CD4 cell count at onset of toxoplasmosis was 58/microL. Thus, disease was diagnosed 10 days to 74 months after the rise in Toxoplasma antibody titers. While the risk factors for development of toxoplasmosis remain incompletely defined, the importance of specific prophylaxis for patients with low CD4 cell counts and high Toxoplasma antibody titers is supported by these findings.

Cholelithiasis and dietary risk factors: an epidemiologic investigation in Vidauban, Southeast France. General Practitioner's Group of Vidauban.

Dietary risk factors have been implicated in the development of cholelithiasis. The aim of this study was to determine in a homogeneous French population whether a particular type of diet may be lithogenic. Seventy-six subjects over 30 years of age (26 men, 50 women) with cholelithiasis detected by ultrasound were selected from a population sample of 830 subjects by drawing lots using the polling list. These were matched by 76 control subjects without cholelithiasis randomly selected from the same population. Univariate analysis was significant for a high calorie diet >2500 kcal/day (OR = 3.62, P = 0.0065), a diet rich in carbohydrates with a consumption > or = 55 g/day (OR = 2.98, P = 0.0067), and a diet rich in total lipids (OR = 4.97, P = 0.023) or saturated fatty acids (OR = 3.06, P = 0.0146). An alcohol consumption equivalent to 20-40 g/day was protective (P = 0.018). Multivariate analysis confirmed these results. Our study suggests that a change in dietary habits by limiting excess calories, saturated fats and carbohydrates could reduce the incidence of cholelithiasis.

Inducible overexpression of a toxic protein by an adenovirus vector with a tetracycline-regulatable expression cassette.

We have constructed two new adenovirus expression cassettes that expand both the range of genes which can be expressed with adenovirus vectors (AdV) and the range of cells in which high-level expression can be attained. By inclusion of a tetracycline-regulated promoter in the transfer vector pAdTR5, it is now possible to generate recombinant adenoviruses expressing proteins that are either cytotoxic or that interfere with adenovirus replication. We have used this strategy to generate a recombinant adenovirus encoding a deletion in the R1 subunit [R1(delta2-357)] of the herpes simplex virus type 2 ribonucleotide reductase. Cell lines expressing the tetracycline-regulated transactivator (tTA) from an integrated vector or following infection with an AdV expressing tTA are able to produce deltaR1 protein at a level approaching 10% total cell protein (TCP) when infected with Ad5TR5 deltaR1 before they subsequently die. To our knowledge, this is the first report of the overexpression of a toxic gene product with AdV. We have also constructed a new constitutive adenovirus expression cassette based on an optimized cytomegalovirus immediate-early promoter-enhancer that allows the expression of recombinant proteins at a level greater than 20% TCP in nonpermissive cell lines. Together, these new expression cassettes significantly improve the utility of the adenovirus system for high-level expression of recombinant proteins in animal cells and will undoubtedly find useful applications in gene therapy.

Heat shock inhibits release of the signal recognition particle from the endoplasmic reticulum in barley aleurone layers.

When barley (Hordeum vulgare) aleurone layers are subjected to heat shock there is a selective degradation of the normally stable mRNAs encoding secreted proteins. Messages for nonsecreted proteins are not degraded. The synthesis of heat shock proteins is not required for this selective message degradation. Our hypothesis explaining this phenomenon is that a component of the early steps in the synthesis of secreted proteins is damaged by heat shock, resulting in a selective halt in translation on secretory mRNAs, which may in turn lead to degradation of those messages. The first committed step in the synthesis of secreted proteins is the binding of the nascent signal sequence to the signal recognition particle. We have obtained cDNA clones and antibodies for the barley 54-kDa subunit of the signal recognition particle. In cell fractionation experiments, more signal recognition particle was bound to the endoplasmic reticulum membranes and less was in the free particle fraction following a heat shock. The results suggest that heat shock inhibits the release of the signal recognition particle from the endoplasmic reticulum. This would, in turn, inhibit the resumption of translation and may be the underlying cause of the secretory message degradation.

Influence of age at infection on human immunodeficiency virus disease progression to different clinical endpoints: the SEROCO cohort (1988-1994). The Seroco Study Group.

METHOD: The influence of age at infection on progression of human immunodeficiency virus (HIV) disease to different clinical endpoints was studied among 393 HIV-seropositive adults selected from the French SEROCO cohort; follow-up lasted from January 1988 to November 1994. Selected patients had a known date of infection and were enrolled shortly after seroconversion. Age-associated risk ratios (RR) were estimated using the Cox model (age fitted as a continuous variable and RR expressed for each 10-year increment after adjustment for symptomatic primary infection and sexual preference). RESULTS: Age had a weak influence on progression from the date of infection to the first category B event (crude RR = 1.15; adjusted RR = 1.09; 95% confidence interval [CI]: 0.89-1.36) but a marked influence on progression from the first category B to the first category C event (crude RR = 1.95; adjusted RR = 1.97; 95% CI: 1.37-2.79). Similar results were obtained after adjustment for the CD4+ cell count at enrollment. A qualitative CD4+ cell defect could explain the influence of age, but this remains to be confirmed. CONCLUSION: Age at infection should be included in the definition of CD4+ cell count thresholds for clinical management and treatment initiation. Risk factors for progression should be assessed according to the different clinical endpoints.

Mutualistic fungal endophytes express a proteinase that is homologous to proteases suspected to be important in fungal pathogenicity.

Many cultivated and wild grass species are hosts to mutualistic fungal endophytes. These associations are ecologically and agronomically significant, yet little is known regarding the physiological aspects of the interaction. In the Poa ampla/Acremonium typhinum interaction, a fungal serine proteinase, At1, is surprisingly abundant and may constitute 1 to 2% of the total leaf-sheath protein. Sequence analysis of cDNA and genomic clones indicates that proteinase At1 is a member of the eukaryotic subtilisin-like protease family. It is homologous to proteases suspected to be virulence factors in fungal pathogens of insects, nematodes, and other fungi. Gel blot analysis of RNA extracted from infected leaf-sheath tissue indicates that the proteinase At1 transcript level is extremely high. RNA gel blots and immunoblots of purified enzymes indicate that similar proteinases are produced by Epichloë festucae and Acremonium lolii, the fungal endophytes infecting Festuca rubra subsp. rubra and Lolium perenne, respectively. Fungal expression of proteinase At1-like enzymes may be a general feature of endophyte infection.

Evidence for the thiamine biosynthetic pathway in higher-plant plastids and its developmental regulation.

Thiamine or vitamin B-1, is an essential constituent of all cells since it is a cofactor for two enzyme complexes involved in the citric acid cycle, pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase. Thiamine is synthesized by plants, but it is a dietary requirement for humans and other animals. The biosynthetic pathway for thiamine in plants has not been well characterized and none of the enzymes involved have been isolated. Here we report the cloning and characterization of two cDNAs representing members of the maize thi1 gene family encoding an enzyme of the thiamine biosynthetic pathway. This assignment was made based on sequence homology to a yeast thiamine biosynthetic gene and by functional complementation of a yeast strain in which the endogenous gene was inactivated. Using immunoblot analysis, the thi1 gene product was found to be located in a plastid membrane fraction. RNA gel blot analysis of various tissues and developmental stages indicated thi1 expression was differentially regulated in a manner consistent with what is known about thiamine synthesis in plants. This is the first report of cDNAs encoding proteins involved in thiamine biosynthesis for any plant species.

Arabidopsis thaliana expresses three divergent Srp54 genes.

The Arabidopsis thaliana Srp54 gene family was determined to consist of three genes, all of which were cloned and sequenced. In addition, cDNAs corresponding to two of the genes were obtained. To our knowledge this is the first description of multiple Srp54 genes within an organism. In contrast to the situation in mammals, where there are only three amino acid differences between the mouse and canine sequences, there was significant amino acid sequence diversity among the genes, particularly in the methionine-rich region of the protein, which is the region responsible for binding to the 7S RNA of the signal recognition particle and to the signal sequence of newly synthesized proteins. The amino acid sequences of the GTP-binding domains of the three clones were 86% identical, whereas the methionine-rich domains were only 65% identical. RNA gel blots of various tissues and developmental stages hybridized with gene-specific probes revealed that all three genes were expressed in all the tissues investigated. There were, however, quantitative differences in expression levels.

[Multicenter French cohort of adults with HIV infection. Description and course after 4 years of follow-up. SEROCO]. / Cohorte francaise multicentrique d'adultes infectés par le VIH. Description et évolution après 4 ans de suivi. SEROCO.

OBJECTIVES: A prospective multicentric epidemiological study (SEROCO) of subjects with a diagnosis of human immunodeficiency virus (HIV) infection was started on January 1, 1988 in order to better understand the natural history of HIV infection and factors related to outcome. Observations after 4 years of follow-up are reported here. METHODS: After authorization by the French national ethics committee and the national commission for personal freedom, 18 French centres included non-haemophiliac volunteers who were asymptomatic, had had non anti-HIV treatment and whose HIV positivity had been known less than 1 year at inclusion. These last three criteria were not required for patients whose precise date of contamination was known within a range of +/- 3 months. RESULTS: On July 15, 1992, there were 1453 infected subjects in the cohort (1063 males, 417 females; age range at inclusion 18-75 years; mean age 31.3 +/- 9.4). Globally, 2.7% of the subjects were symptomatic at inclusion. Mean CD4 lymphocyte count at inclusion was 508/mm3. Clinically, 51.5% of the patients had a history of sexually transmitted disease at inclusion. After 4 years (on July 15, 1992) mean follow-up was 28 +/- 12.9 months for a total of 3428 patient-years. Disease progression to stage IV was observed in 439 patients including 202 who developed the acquired immuno-deficiency syndrome (AIDS). Among these 202 patients, 113 had died at the end-point of this report. The first manifestation of AIDS was Kaposi sarcoma in 44, pulmonary pneumocystosis in 38 and cerebral toxoplasmosis in 27. The probability of developing AIDS was calculated at 13.9% at 5 years, 27.7% at 7 years and 33.7% at 10 years. The probability of a CD4 count below 200/mm3 was 32.7, 55.6 and 67% at 5, 7 and 10 years respectively. For patients with a CD4 count below 200, the probability of developing AIDS was 18% at 1 year, 39% at 2 years and 51% at 3 years. CONCLUSIONS: SEROCO has been a most useful prospective epidemiological tool due to the diversity of the subjects included. The observed natural history of HIV infection will lead to specific research projects aimed at better understanding the disease process.