Algae in mosquito breeding sites and the effectiveness of the mosquito larvicide Bacillus thuringiensis H-14

The presence of cyanobacteria generally decreased the effectiveness of Bacillus thuringiensis H-14 (BTI) as a mosquito larvicide. The effect was more pronounced when the mosquito larvae were exposed to BTI in the presence of several cyanobacterial strains. No synergistic or antagonistic effect between the -endotoxin from BTI and the hepatotoxin from cyanobacteria was seen. Neurotoxic cyanobacterial strains caused very fast paralysis in mosquito larvae; the decreases in the effectiveness of BTI when tested in combination with a neurotoxic strain might be due to the effect of this paralytic action on the feeding rate of the mosquito larvae.     

A free-running endogenous rhythm of the resting heart rate in man

A sine-wave oscillating rhythm of the heart rate is reported in 24 out of 31 resting healthy subjects. Identification of these free-running cycles was by spectral analysis of minute-by-minute recordings of electrocardiograms, and in a few cases by inspection of cardiotachometer records. The periodicity of this rhythm was circa 10 min and was intermediate in frequency between the rapid fluctuations with frequencies of 15, 30, and 60 s and those of a frequency recurrent every 90 min already described in the literature. Our cycles were independent of age and sex.     

Preliminary application of a mosquito densovirus-mediated artificial intron in vitro and in vive of mosquito

An artificial intron consisting of the 5'-donor site (from the first intron of the human beta-globin gene) and the 3'-acceptor site (from the intron of an immunoglobulin gene heavy chain variable region) was obtained with a splice overlap extension PCR and was then inserted in frame into the coding sequence of nostructural protein NS1 gene fused to GFP gene in a recombinant mosquito densovirus plasmid p7NS1-GFP. The constructed plasmid was named as p7NS1-Intron-GFP. The plasmid p7NS1-Intron-GFP was co transfected with the helper plasmid pUCA into C6/36 cells, then the packaged recombinant and wild type viruses were purified and recovered. The second-instars of Aedes albopictus larvae were exposed to recombinant and wild type virus mixed stock. The high level GFP expression in C6/36 cells and larvae was observed under fluorescence microscope, indicating that the inserted artificial intron exerted its normal function in self-splicing both in vitro and in vivo. This study laid a foundation for application of an artificial intron in insect cells and development of new strategy for genetic engineering technology of mosqtuito and its pathogens.     

Impacts of reduced sulfur components on active and resting ammonia oxidizers

While there has been significant research on the nature and extent of the impact of inhibitory reduced sulfur with respect to anaerobic (e.g., methanogenic and sulfidogenic) microbial systems, only limited study has yet been conducted on the comparable effects of soluble sulfides which might occur within aerobic wastewater treatment systems. Admittedly, aerobic reactors would not normally be considered conducive to the presence of reduced sulfur constituents, but there do appear to be a number of processing scenarios under which related impacts could develop, particularly for sensitive reactions like nitrification. Indeed, the following scenarios might well involve elevated levels of reduced sulfur within an aerobic reactor environment: (1) mixed liquor recycle back through sulfide-generating anaerobic zones (e.g., in conjunction with biological nutrient removal processes, etc.), (2) high-level side-stream sulfide recycle via sludge digestion, etc., back to aerobic reactors, and (3) high-level influent sulfide inputs to wastewater treatment facilities via specific industrial, septage, etc., streams. The objective of this study was, therefore, to determine the subsequent metabolic impact of soluble sulfide under aerated and unaerated conditions, focusing in particular on ammonia-oxidizing bacteria due to their critical first-step role with nitrification. The obtained results indicated that, under catabolically active conditions, cultures of ammonia oxidizers were extremely sensitive to the presence of sulfide. At total soluble sulfide concentrations of 0.25 mg l^–1 S, active ammonia oxidation was completely inhibited. However, immediately following the removal of this soluble sulfide presence, ammonia oxidation started to recover; and it continued to improve over the next 24 h. Similar sulfide impact tests conducted with inactive ammonia oxidizers exposed during anaerobic conditions, albeit at higher dosage levels, also revealed that their subsequent aerobic activity would correspondingly be retarded. These results indicated that, after sulfide exposure under unaerated conditions, subsequent aerobic oxidative activity rates rapidly decreased as the soluble sulfide exposure was increased from 0.5 gm l^–1 S to 5 mg l^–1 S and that further reductions in this activity progressively developed as the concentration was increased to 200 mg l^–1 S. The recovery following unaerated exposure to sulfide was significantly higher at pH 7, as compared with pH 8, and although the specific nature of this variation was not established, a hypothetical explanation appeared warranted.     

A technique for repeated sampling of the blood of individual resting fish.

A dorsal cannulation technique is described. It has been employed for repeated blood sampling in unanaesthetized rainbow trout (Salmo gairdneri) kept singly in special receptacles described in the paper. The level of the studied haematological parameters (Haematocrit, Hb, glucose, lactate, K+, Na+, Ca2+) differed between fish kept in receptacles for 1 week and free-swimming fish, most probably owing to differences in the motility of the fish. The receptacle seems to minimize visual and handling disturbances, and permits both the standardization of experimental conditions and quick and easy sampling via the dorsal aorta cannula. The general variation in the blood parameter values was very small compared with the previously reported variation in such values for rainbow trout.     

Comparison of carbon dioxide-baited trapping systems for sampling outdoor mosquito populations in Tanzania

For collecting mosquitoes (Diptera: Culicidae) the outdoor catching efficiency of four types of trapping devices baited with carbon dioxide (CO2, 300 ml/ min) was evaluated and compared in two areas of Tanzania. The types of traps employed were: the CDC miniature trap with the incandescent light bulb switched on or off; electric nets (ENT) and a Counterflow Geometry (CFG) trap. In Njage, southeast Tanzania, Anopheles gambiae Giles sensu stricto was the most abundant of the seven mosquito species obtained, comprising of 74.3% of the total number caught (n=2,171). In Muheza, north-east Tanzania, Culex quinquefasciatus Say was the predominant species (90.9%) among 1,080 caught. At both localities the CFG trap was superior to the CDC trap with light-on or light-off for sampling both An. gambiae and Cx. quinquefasciatus. Efficiency of the CFG trap and ENT were similar for sampling these species of mosquitoes (P > 0.05). However, ENT was superior to the CDC trap with light-off for collecting both species. Significantly more (P < 0.05) Cx. quinquefasciatus were obtained by the CDC trap with light-off than with light-on, especially outdoors. It is concluded that both ENT and the CFG are effective tools for sampling populations of An. gambiae and Cx. quinquefasciatus outdoors.     

Effects of high-frequency artificial respiration on the rhythm of heart contraction in cats

High-frequency artificial hyperventilation of cat lung with a rate above the initial rhythm of the heart reconstructs the rhythm so that each breathing cycle coincides with one systole of the heart. Synchronization of breathing movements and heart systoles is easily removed by atropine, and cold blockade of vagus nerves by open artificial pneumothorax.     

The value of georeferenced collection records for predicting patterns of mosquito species richness and endemism in the Neotropics

Abstract.  1. Determining large-scale distribution patterns for mosquitoes could advance knowledge of global mosquito biogeography and inform decisions about where mosquito inventory needs are greatest.
2. Over 43 000 georeferenced records are presented of identified and vouchered mosquitoes from collections undertaken between 1899 and 1982, from 1853 locations in 42 countries throughout the Neotropics. Of 492 species in the data set, 23% were only recorded from one location, and Anopheles albimanus Wiedemann is the most common species.
3. A linear log–log species–area relationship was found for mosquito species number and country area. Chile had the lowest relative density of species and Trinidad-Tobago the highest, followed by Panama and French Guiana.
4. The potential distribution of species was predicted using an Ecological Niche Modelling (ENM) approach. Anopheles species had the largest predicted species ranges, whereas species of Deinocerites and Wyeomyia had the smallest.
5. Species richness was estimated for 1° grids and by summing predicted presence of species from ENM. These methods both showed areas of high species richness in French Guiana, Panama, Trinidad-Tobago, and Colombia. Potential hotspots in endemicity included unsampled areas in Panama, French Guiana, Colombia, Belize, Venezuela, and Brazil.
6. Argentina, The Bahamas, Bermuda, Bolivia, Cuba, and Peru were the most under-represented countries in the database compared with known country species occurrence data. Analysis of species accumulation curves suggested patchiness in the distribution of data points, which may affect estimates of species richness.
7. The data set is a first step towards the development of a global-scale repository of georeferenced mosquito collection records.     

An evaluation of artificial substrates for sampling macrobenthos in reservoirs

Artificial substrates were compared with a Ponar grab for sampling benthic macroinvertebrates in Lake Anna, Louisa Co., Virginia. The objective was t0 find which technique was best for assessment 0f thermal effluent effects using the following criteria: 1) provide reliable data on density and composition 0f the macrobenthos with a reasonable number 0f replicates; 2) collect the most taxa; and, 3) require the least amount 0f time. Leaves, 3M Corporation's #200 conservation web, and limestone rocks were compared. Each material was tested separately in chicken wire baskets placed 0n the bottom at several depths. Three replicates of each type were retrieved monthly from each depth using SCUBA and cloth flour sacks and compared with grab samples taken from the same depths. Lesser amounts of these materials were tested separately in smaller plastic containers. All large artificial substrate samplers collected significantly more individuals (P = 0.05) and taxa than the Ponar grab. Small web and leaf samplers best met all three 0f the established criteria. The SCUBA system developed in the study is a fast and reliable sampling method.     

Semen collection,cryopreservation and artificial insemination in the dromedary camel

Collection of semen with a bovine artificial vagina (AV) was attempted with each of 14 camels over a period of 2 years. Semen samples were evaluated, extended and cryopreserved. Frozen thawed semen, diluted cooled semen or whole semen was used to inseminate some female camels which were induced to ovulate with hCG. Males ejaculated semen into the AV in 74.6% collection attempts. The male copulated for at least 200s in 62.9% attempts. The remaining copulations were of shorter duration. Similarly, 49.3% ejaculates were at least 3ml of semen. Libido and donation of semen improved from December onwards and reached a peak after mid January with peak performance persisting until April. It declined during May. The majority of camels had lost libido and refuse to donate semen by the end of May. Camel semen is in gel form. While 35.9% of 203 semen samples exhibited no individual sperm motility, 28.5% exhibited low to fair grade individual sperm motility and only 35.4% exhibited >50% sperm motility. Differences existed between animals (P<0.01) and months (P<0.05) of collection, while effect of copulation time was not significant. Mass motility was not observed in camel semen. Individual sperm motility develops after liquefaction of semen. Addition of caffeine but not chymotrypsin improved the individual motility. The mean live percent sperm count and normal acrosome were 73.3+/-1.0 and 92.0+/-0.5, respectively. Only 51.1% of 45 semen samples with pre-freeze motility of >50% and 25% of 16 semen samples from low pre-freeze motility group with an overall success of 44.2% of 61 semen samples were successfully preserved. Wide variation was observed in the freezability of semen from different males. Attempts to impregnate female camels with liquid semen, frozen thawed semen and whole semen after hCG induced ovulation resulted in 0/10, 1/13 and 4/10 pregnancies.     

The effect of nocturnal sampling on semen quality and the efficiency of collection in bovine species

This study evaluated night and day semen collection regimes in Holstein and Brahman bulls (four bulls of each breed) that were collected weekly, each during a morning and a night collection. Ejaculates (n=64) were obtained via artificial vagina over 4 weeks. The first collection of each week alternated between night and day. Two collection teams were employed. Bull behavior parameters included reaction time to first mount, time to ejaculation, a refractory period test, and a thrust intensity test. The numbers of interruptions were counted as a managerial parameter. Pre-freeze semen parameters included total volume, initial motility and concentration. Post-freeze semen parameters measured were: 0- and 3-h post-thaw motility; percent intact acrosomes; and percent sperm abnormalities. Data were analyzed by least squares methods. The bull within breed effect differed (P<0.05) for behavior parameters. The bull within breed effect for total motile sperm harvested was not significant. The bull within breed response was mixed for post-freeze semen viability parameters. Bull within breed was not significant for sperm abnormalities. The night versus day treatment was significant for the managerial parameter (P=0.002). Although a different collection schedule for Bos indicus cattle was not warranted, the efficiency of the collection process was affected by extraneous environmental conditions.     

Effectiveness of an artificial substrate for sampling macroinvertebrates in small streams

SUMMARY. Factors affecting invertebrate colonization of samplers consisting of twenty-five 5-cm diameter porcelain balls were studied in small northern California streams. Peaks in diversity, in number of individuals and in taxa, occurred after 2—4 weeks in each of four 10-week colonization runs. Most variation in number of organisms was correlated with increases in organic detritus. Time was the second most important variable.
The average coefficient of variation in total numbers collected from the artificial sampler was 0.40, slightly less than the average 0.56 for the Surber sampler. Published coefficients of variation for artificial substrates range from 0.109 to 0.849, which are similar to values reported from work with the Surber sampler. We had several practical difficulties with the artificial substrates. Samplers were lost, became clogged or buried, supported vertebrate predators and were costly. The samplers also collected some organisms in greater proportion than their occurrences in the natural substrate. In sampling small streams these disadvantages (compared to a Surber sampler) outweigh the slight reduction in sampling variability.     

A circadian rhythm in spontaneous locomotor activity in the larvae and pupae of the mosquito, Culiseta incidens

ABSTRACT. The spontaneous locomotor activity of the larvae of Culiseta incidens was monitored with acoustic actographs. Individuals, in water resting on the cones of the speakers, displayed an activity rhythm in LD 12:12 with peak activity in the light phase. A similar rhythm occurred in DD following rearing in either LD 12:12 or LL, with free-running periods of 23.5–24 h. No evidence was found of any consistent differences between the periods of the larvae and pupae. The amplitude of the pupal rhythm gradually increased as metamorphosis progressed. It is suggested that rhythmicity might also be found in those behavioural responses of mosquito larvae and pupae which have been the subject of previous studies.     

Ecdysteroid titer and oocyte growth in the northern house mosquito, Culex pipiens L

In an anautogenous strain of the northern house mosquito, Culex pipiens, the ovaries reached the resting stage (follicle length = 90 microns) three days after adult emergence. Follicle length increased from 90 to 550 microns between 0 and 60 hr after a blood meal. Total ecdysteroids reached a peak at 400 fmol/insect at 36 hr after a blood meal then declined rapidly. The ratio of 20-hydroxyecdysone to ecdysone increased in conjunction with the total ecdysteroid level. Oocyte growth beyond the resting stage and initiation of vitellogenesis was dependent on a head factor which was released within 4-8 min of the start of the blood meal.     

Impacts of nutrient enrichment and sediment on phytoplankton community structure in the northern Baltic Sea

A three-week mesocosm experiment was conducted in order to study the effects of bottom sediment and nutrient enrichment on phytoplankton and zooplankton community structure in the Archipelago Sea, northern Baltic Sea. The transparent polyethylene enclosures included the whole water column and varied in volume from 30 to 40 m³. There were two types of enclosures: some with natural sediment as a bottom and others with a plastic bottom. The experiment was a 2 × 2 factorial design with presence of sediment and nutrient enrichment as treatment factors. Both the sediment presence and nutrient enrichment significantly increased water nutrient concentrations and the rate of primary production. However, external nutrient enrichment and the presence of sediment stimulated the growth of different phytoplankton groups, indicating that the effect of sediment was not related to nutrient fluxes alone, but involved more complex interactions. External nutrient enrichment was primarily channelled to picoplanktonic cyanobacteria, the biomass of which increased four- to fivefold due to enrichment. The presence of sediment increased the biomass of cryptophytes, chrysophytes and prasinophytes, but decreased the biomass of N₂-fixing cyanobacteria. Zooplankton biomass increased during the experiment, but was not affected by the treatments. The study shows that sediment plays a significant role in phytoplankton dynamics, underlining the importance of including sediment in shallow-water mesocosm experiments. Handling editor: J. Padisak     

Prevalence and distribution of Clostridium difficile PCR ribotypes in cats and dogs from animal shelters in Thuringia,Germany

Clostridium difficile is an important cause of nosocomial diarrhoea in humans. Pet animals and livestock are discussed as potential natural reservoirs and sources of infection. In this study faecal samples from dogs and cats were collected at 10 animal shelters in Thuringia, Germany. C. difficile was isolated from 9 out of 165 (5.5%) canine and 5 out of 135 (3.7%) feline samples. Five PCR ribotypes (010, 014/020, 039, 045, SLO 066) were identified. PCR ribotypes 010 and 014/020 were detected in more than one shelter and PCR ribotypes 014/020 and 045 were isolated from dogs and cats. MLVA profiles of strains of a PCR ribotype from one shelter were identical or closely related, while strains of the same PCR ribotype from different shelters showed significant differences. This study shows that dogs and cats kept in animal shelters are a reservoir of C. difficile PCR ribotypes which can infect also humans.     

Comparative analysis of core collection sampling methods for mandarin germplasm based on molecular and phenotypic data

Gene banks have been established to conserve the genetic diversity of crop species. Large germplasm collections lead to management problems (space, maintenance costs, etc.), especially in collections involving species with recalcitrant seeds that must be maintained as growing plants. Core collections (CCs) are thus developed to reduce the size of large germplasm collections while keeping the maximum variability. This also facilitates fine phenotypic evaluation. In this study, several software packages (DARwin, PowerMarker and MSTRAT) and methods (Max length subtree, M strategy, simulated annealing and MinSD) were compared to define a mandarin (Citrus reticulata) CC. One hundred and sixty‐seven accessions were sampled from two germplasm collections, which were genotyped with 50 SSR, 24 InDel and 68 single nucleotide polymorphism markers. All the CC obtained were tested for the maintenance of the genetic variability parameters (Ho and He) of the initial collection, the level of linkage disequilibrium (LD) and the phenotypic diversity retention. The Max length subtree function from DARWin seemed to be the most appropriate method for establishing a CC in C. reticulata. It maintained 96.82% of the allelic richness and 17.96% of the size of the initial collection with only 30 accessions. Besides it did not increase the LD (r² value) of the initial collection and retained the vast majority of the phenotypic variability. However, a CC with 70 accessions would be more helpful for genetic association studies.     

Seasonal effects of semen collection and artificial insemination on dairy cow conception

The effects of four seasons of semen collection and of artificial insemination on conception in dairy cows were studied. The solstices and equinoxes (December, March, June and September) defined the beginning and/or end of each season. Semen was collected from 973 progeny-test bulls over 8 years at the two Norwegian AI stations at 60.8 degrees N and 63.4 degrees N where artificial light was used to provide a minimum photoperiod of 10 h/day. The effect of using semen of elite bulls during progeny testing and after selection as elite sires also was investigated. Norwegian Red (NRF) cows were inseminated over a 7-year period using progeny test semen and over the last 4 years of the same period using the semen of the elite sires. The probability of conception to only first inseminations for cows up to, and including, the fifth lactation was assessed by 56-day non-return rate (56d NRR) and calving rate. Two data sets were analysed which excluded cows culled within 270 days of AI or included such cows as non-calving. The reasons for culling were categorised as those for fertility problems or all other reasons. Semen was used for AI irrespective of the season in which it had been collected. Season of semen collection did not affect 56d NRR but calving rate was significantly higher (by 0.5-0.8%, approximately; P < 0.01) for semen collected in the December-March period, when photoperiod was increasing, than at other times of the year. The season in which AI was performed showed a peak of 56d NRR in spring for heifers (P < 0.01) and in summer for parous animals (P < 0.01). For calving rate, however, no seasonal peak was found in heifers, whereas pluriparous cows had much higher calving rates in summer and autumn/early winter than late winter and spring (P < 0.01). Semen of elite sires resulted in higher calving rates by 0.5 (NS) to 1.9% (P < 0.01) when used after selection than when used during progeny testing. The difference between the calving rate achieved when the semen from elite sires was used during progeny testing and after selection indicates that farmers select different classes of cows for submission to AI by progeny test bulls and sires. The 56d NRR was not as good as calving rate for assessing seasonal and other effects on conception rates.     

A comparative evaluation of the effectiveness of methods for serological sampling examinations]

Blood serum samples of 3,448 schoolchildren of grades 1-10 in 35 schools of Dushanbe were examined in the passive hemagglutination test in 1988 and 1989. The proportion of persons unprotected against diphtheria and tetanus was estimated by common methods in different kinds of selective serologic survey: mass screening (43.4-83.0%), testing in selected groups reduced 2, 3 and 5 times, cluster sampling. The reduction of the groups to be examined (from 3,033 to 250 persons) was not accompanied by essential changes (t < 2) in the characteristics of mass immunity against diphtheria and tetanus. The cluster method was shown to be highly reliable also in the study of population immunity.