Assessing the heat tolerance of 17 beef cattle genotypes.

Cattle production plays a significant role in terms of world food production. Nearly 82% of the world's 1.2 billion cattle can be found in developing countries. An increasing demand for meat in developing countries has seen an increase in intensification of animal industries, and a move to cross-bred animals. Heat tolerance is considered to be one of the most important adaptive aspects for cattle, and the lack of thermally-tolerant breeds is a major constraint on cattle production in many countries. There is a need to not only identify heat tolerant breeds, but also heat tolerant animals within a non-tolerant breed. Identification of heat tolerant animals is not easy under field conditions. In this study, panting score (0 to 4.5 scale where 0 = no stress and 4.5 = extreme stress) and the heat load index (HLI) [HLI(BG<25°C) = 10.66 + 0.28 × rh + 1.30 × BG - WS; and, HLI (BG> 25°C) = 8.62 + 0.38 × rh + 1.55 × BG - 0.5 × WS + e((2.4 - WS)), where BG = black globe temperature ((o)C), rh = relative humidity (decimal form), WS = wind speed (m/s) and e is the base of the natural logarithm] were used to assess the heat tolerance of 17 genotypes (12,757 steers) within 13 Australian feedlots over three summers. The cattle were assessed under natural climatic conditions in which HLI ranged from thermonuetral (HLI < 70) to extreme (HLI > 96; black globe temperature = 40.2°C, relative humidity = 64%, wind speed = 1.58 m/s). When HLI > 96 a greater number (P < 0.001) of pure bred Bos taurus and crosses of Bos taurus cattle had a panting score ≥ 2 compared to Brahman cattle, and Brahman-cross cattle. The heat tolerance of the assessed breeds was verified using panting scores and the HLI. Heat tolerance of cattle can be assessed under field conditions by using panting score and HLI.

A new heat load index for feedlot cattle.

The ability to predict the effects of extreme climatic variables on livestock is important in terms of welfare and performance. An index combining temperature and humidity (THI) has been used for more than 4 decades to assess heat stress in cattle. However, the THI does not include important climatic variables such as solar load and wind speed (WS, m/s). Likewise, it does not include management factors (the effect of shade) or animal factors (genotype differences). Over 8 summers, a total of 11,669 Bos taurus steers, 2,344 B. taurus crossbred steers, 2,142 B. taurus x Bos indicus steers, and 1,595 B. indicus steers were used to develop and test a heat load index (HLI) for feedlot cattle. A new HLI incorporating black globe (BG) temperature ( degrees C), relative humidity (RH, decimal form), and WS was initially developed by using the panting score (PS) of 2,490 Angus steers. The HLI consists of 2 parts based on a BG temperature threshold of 25 degrees C: HLI(BG>25) = 8.62 + (0.38 x RH) + (1.55 x BG) - (0.5 x WS) + e((2.4-WS)), and HLI(BG<25) = 10.66 + (0.28 x RH) + (1.3 x BG) - WS, where e is the base of the natural logarithm. A threshold HLI above which cattle of different genotypes gain body heat was developed for 7 genotypes. The threshold for unshaded black B. taurus steers was 86, and for unshaded B. indicus (100%) the threshold was 96. Threshold adjustments were developed for factors such as coat color, health status, access to shade, drinking water temperature, and manure management. Upward and downward adjustments are possible; upward adjustments occur when cattle have access to shade (+3 to +7) and downward adjustments occur when cattle are showing clinical signs of disease (-5). A related measure, the accumulated heat load (AHL) model, also was developed after the development of the HLI. The AHL is a measure of the animal's heat load balance and is determined by the duration of exposure above the threshold HLI. The THI and THI-hours (hours above a THI threshold) were compared with the HLI and AHL. The relationships between tympanic temperature and the average HLI and THI for the previous 24 h were R(2) = 0.67, P < 0.001, and R(2) = 0.26, P < 0.001, respectively. The R(2) for the relationships between HLI or AHL and PS were positive (0.93 and 0.92 for HLI and AHL, respectively, P < 0.001). The R(2) for the relationship between THI and PS was 0.61 (P < 0.001), and for THI-hours was 0.37 (P < 0.001). The HLI and the AHL were successful in predicting PS responses of different cattle genotypes during periods of high heat load.

Influence of alternansucrase-derived oligosaccharides and other carbohydrates on alpha-galactosidase and alpha-glucosidase activity in Bifidobacterium adolescentis.

AIMS: To determine the influence of alternansucrase-derived oligosaccharides (AOS) and other carbohydrates on alpha-galactosidase and alpha-glucosidase activity in Bifidobacterium adolescentis. METHODS AND RESULTS: Activities for alpha-galactosidase and alpha-glucosidase were determined from cell extracts of B. adolescentis grown on 18 test carbohydrates including AOS. alpha-galactosidase activity was enhanced on a variety of alpha-linked or beta-linked carbohydrates regardless of a galactoside or glucoside. alpha-glucosidase, however, was enhanced only on alpha-linked carbohydrates. AOS significantly enhanced enzyme activity compared with most of the carbohydrates tested. Most of the AOS showed significant increases in activity for both enzymes over that displayed by their corresponding acceptor carbohydrates. CONCLUSIONS: alpha-galactosidase may serve as a biomarker for microbial metabolic activity within the large intestine for potential prebiotics composed of alpha-linked or beta-linked oligosaccharides whereas alpha-glucosidase activity may be restricted to assessing the influence of only alpha-linked carbohydrates. The AOS synthesis process provided a value-added component to carbohydrates by increasing metabolic activity (via alpha-galactosidase and alpha-glucosidase) over certain acceptor carbohydrates. SIGNIFICANCE AND IMPACT OF THE STUDY: Fundamental knowledge of enzyme activity in Bifidobacterium may aid in the design of more effective prebiotics and may also help identify enzyme indicators of metabolic activity when assessing influence within the intestine.

Growth of various intestinal bacteria on alternansucrase-derived oligosaccharides.

AIMS: To determine whether alternansucrase (ASR)-derived oligosaccharides can support the in vitro growth of various intestinal bacteria. METHODS AND RESULTS: Growth was assessed from each culture after incubation in a medium containing ASR-derived oligosaccharide as sole carbohydrate source. Most of the Bifidobacterium spp. tested showed growth on all five of the oligosaccharides tested while the Lactobacillus spp., Bacteroides thetaiotaomicron, coliforms and pathogenic bacteria displayed no or little growth. CONCLUSIONS: The ASR-derived oligosaccharides were selectively utilized by many of the Bifidobacterium spp. tested but did not support significant growth of the Lactobacillus spp., Bact. thetaiotaomicron, coliforms and pathogenic bacteria tested. SIGNIFICANCE AND IMPACT OF THE STUDY: Alternansucrase-derived oligosaccharides are a potential source of new prebiotics.

Strategies to reduce feedlot cattle heat stress: effects on tympanic temperature.

Three experiments were conducted to evaluate the effect of different management strategies on body temperature of feedlot steers finished in the summer months. In Exp. 1, 24 crossbred steers were chosen to assess the effect of altered feed intake and feeding time on tympanic temperature (TT) response. Managed feeding (MF) treatments were applied for 22 d only and provided 1) ad libitum access to feed at 0800 (ADLIB), 2) feed at 1600 with amount adjusted so that no feed was available at 0800 (BKMGT), 3) feed at 1600 at 85% of predicted ad libitum levels (LIMFD). During heat stress conditions on d 20 to 22 of MF, LIMFD and BKMGT had lower (P < 0.05) TT than ADLIB from 2100 through 2400. A carryover effect of limit-feeding was evident during a severe heat episode (d 36 to 38) with LIMFD steers having lower (P < 0.05) TT than ADLIB. In Exp. 2, TT were obtained from 24 crossbred steers assigned to three treatments, consisting of no water application (CON), water applied to feedlot mound surfaces from 1000 to 1200 (AM) or 1400 to 1600 (PM). From 2200 to 0900 and 1200 to 1400, steers assigned to morning sprinkling treatment had lower (P < 0.05) TT than steers assigned to afternoon sprinkling treatment. In Exp. 3, 24 steers were utilized in a 2 x 2 factorial arrangement of treatments with factors of feeding time [0800 (AMF) and 1400 (PMF)] and sprinkling (WET and DRY). Tympanic temperatures were monitored under hot environmental conditions on d 30 to 32 and 61 to 62. A feeding time x sprinkling interaction (P < 0.001) was evident on d 30 to 32, although AMF/DRY steers had the highest (P < 0.05) TT. On d 61 to 62, TT of PMF steers was higher (P < 0.05) than AMF between 1500 to 1800. Use of sprinklers can effectively reduce TT of feedlot cattle, whereas shifting to an afternoon vs morning feeding time was most beneficial when bunks were empty several hours prior to feeding.

Feeding strategies for managing heat load in feedlot cattle.

Eighty-four Bos taurus crossbred steers were used to investigate effects of level and duration of limit-feeding feedlot cattle in a hot environment. Pens (four/treatment) of steers (seven/pen) were fed feedlot finishing diets and randomly assigned to the following treatments: 1) restricted to approximately 75% of feed consumed when offered ad libitum for 21-d duration (RES21); 2) restricted to approximately 75% of ad libitum for 42-d duration (RES42); and 3) feed offered ad libitum (ADLIB). Tympanic temperatures (TT) were measured via thermistors placed in the ear canal and attached to data loggers. Restricting feed intake for both 21- and 42-d reduced tympanic temperature when compared with ADLIB treatment groups under hot environmental conditions. Temperature reductions exceeded 0.5 degrees C (P < 0.05) depending on time of day. The reduced tympanic temperature is likely due to a reduction in metabolic heat load and/or a concurrent reduction in metabolic rate. Within respective periods, no differences (P > 0.05) were found among treatments for panting or bunching score. However, different proportions of cattle were found to be bunching and panting with ADLIB cattle displaying a greater number of bunched steers that were panting when compared with the other groups. When averaged across diet treatments, dark-colored cattle had the greatest percentage of cattle showing moderate to excessive panting, while light-colored cattle displayed the least panting under thermoneutral climatic conditions. Under hot (mean daily temperature-humidity index >74) conditions, dark-colored cattle tended to bunch more (P = 0.073) and pant more (P < 0.01) than light-colored cattle. Mean TT were 0.2 to 0.6 degrees C (P < 0.05) greater for dark- vs light-colored cattle under hot conditions. Limit-feeding feedlot cattle during early summer is a successful tool for enhancing animal comfort by alleviating the combined effects of high climatic and metabolic heat load.

Characterization of dextran-producing Leuconostoc strains.

Leuconostoc strains were characterized according to their antibiotic susceptibilities, carbohydrate fermentation profiles, sucrase activity patterns and plasmid content. All the strains tested were resistant to the antibiotics sulphathiazole, trimethoprim and vancomycin, and could be separated into two groups based on whether or not they could ferment melibiose and raffinose. Six Leuconostoc strains possessed plasmids and many produced unique sucrase activity patterns in polyacrylamide gels. These data will aid in distinguishing among physiologically similar dextran-producing leuconostocs, frequently used in research and industry.

Frequency of postoperative carotid duplex surveillance and type of closure: results from a randomized trial.

BACKGROUND/PURPOSE: In several nonrandomized studies investigators have reported on the value of postoperative carotid duplex surveillance (PCDS) with mixed results; however the type of closure was not analyzed in these studies. In this study we analyze the frequency and timing of postoperative carotid duplex ultrasound scanning according to the type of closure from a randomized carotid endarterectomy (CEA) trial comparing primary closure (PC) versus patching. PATIENT POPULATION AND METHODS: We randomized 399 CEAs into 135 PCs, 134 polytetrafluoroethylene (PTFE) patch closures, and 130 vein patch closures (VPCs) with a mean follow-up of 47 months. PCDS was done at 1, 6, and 12 months and every year thereafter (a mean of 4.0 studies per artery). Kaplan-Meier analysis was used to estimate the rate of > or = 80% restenosis over time and the time frame of progression from < 50%, to 50%-79% and > or = 80% stenosis. RESULTS: Restenoses of > or =80% developed in 24 (21%) arteries with PC and nine (4%) with patching. Kaplan-Meier estimate of freedom of > or = 80% restenosis at 1, 2, 3, 4, and 5 years was 92%, 83%, 80%, 76%, and 68% for PC, respectively, and 100%, 99%, 98%, 98%, and 91% for patching, respectively, (P <.01). Of 56 arteries with 20% to 50% restenosis, two of 28 patch closures and 10 of 28 PCs progressed to 50% to < 80% restenosis (P =.02); none of the patch closures and six of 28 PCs progressed to > or =80% (P =.03). In PCs, the median time to progression from <50% to 50%-79%, < 50% to > or =80%, and 50%-79% to > or = 80% was 42, 46, and 7 months, respectively. Of the 24 arteries with > or =80% restenosis in PC, 10 were symptomatic. Thus, assuming th symptomatic restenosis would have undergone duplex scan examinations regardless, there were 14 asymptomatic arteries (12%) that could have been detected only with PCDS (estimated cost, $139, 200), and those patients would have been candidates for redo CEA. Of the 9 arteries (3 PTFE closures and 6 VPCs) with > or =80% restenosis with patch closures, 6 asymptomatic (4 VPCs and 2 PTFE closures) arteries (3%) could have been detected with PCDS. In patients with normal duplex scan findings at the first 6 months, only four (2%) of 222 patched arteries (two asymptomatic) developed > or = 80% restenosis versus five (38%) of 13 in patients with abnormal duplex scan examination findings (P<.001). CONCLUSIONS: PCDS is beneficial in patients with PC, but is less beneficial in patients with patch closure. PCDS examinations at 6 months and at 1- to 2-year intervals for several years after PC are adequate. For patients with patching, a 6-month postoperative duplex scan examination with normal results is adequate.

Perioperative and late stroke rates of carotid endarterectomy contralateral to carotid artery occlusion : results from a randomized trial.

BACKGROUND AND PURPOSE: Several previous studies have reported the benefits of carotid endarterectomy (CEA) contralateral to carotid occlusion with mixed results, but none of these were randomized except for the North American Symptomatic Carotid Endarterectomy Trial. The purpose of this study was to analyze the results of surgery in patients with contralateral carotid artery occlusion in a randomized trial in which randomization was done according to the method of closure. METHODS: In 399 CEAs (357 patients) that were randomized into primary closure versus patching, 49 had contralateral occlusion. Strokes were designated as ipsilateral if they arose from the same CEA side and contralateral if they arose from the occluded side. A Kaplan-Meier analysis was used to estimate perioperative strokes and stroke-free survival in patients with contralateral occlusion (group A) versus those without contralateral occlusion (group B). RESULTS: Demographic characteristics and mean follow-up for both groups were similar (group A, 40 months; group B, 33 months). Group A had a higher incidence of contralateral transient ischemic attacks (TIAs) (12.2% versus 0.9%; P<0.0001), contralateral strokes (2% versus 0%; P=0.025), and combined contralateral TIAs/strokes (14.3% versus 0.9%; P<0.0001). The rates for perioperative and all strokes (operative and late) were 2% and 4. 1% (2% ipsilateral and 2% contralateral strokes) for group A and 2. 9% and 3.4% (all ipsilateral) for group B (P=0.60 and 0.85, respectively). The rates for perioperative and all TIAs were 0% and 14.3% for group A versus 2.6% and 6.3% for group B (P=0.918 and P=0. 08, respectively). The rates for perioperative and all neurological events (TIA and stroke) were 2% and 18.4% for group A and 5.4% and 9. 7% for group B (P=0.27 and 0.113, respectively). The cumulative stroke-free survival rates at 5 years were 84% for group A and 77% for group B (P>0.1). The cumulative stroke-free survival rates at 5 years for symptomatic and asymptomatic patients in group A and group B were also similar. The perioperative and late deaths were similar for both groups (group A, 8%; group B, 14%). CONCLUSIONS: Group A had a higher incidence of contralateral TIAs and strokes than group B; however, the perioperative and all late stroke rates and survival rates of CEA were comparable in patients with and without contralateral occlusion.

Prospective controlled study of polytetrafluoroethylene versus saphenous vein in claudicant patients with bilateral above knee femoropopliteal bypasses.

BACKGROUND: Although several studies have compared the patency rates of polytetrafluoroethylene (PTFE) and saphenous vein grafts (SVG) for the above knee location, none have compared the 2 grafts when implanted in the same patient with claudication who needs bilateral above knee femoropopliteal bypasses. METHODS: Forty-three patients (86 limbs) with bilateral disabling claudication who had superficial femoral artery occlusion and above knee reconstitution with 2- to 3-vessel runoff were analyzed. Patients were treated on one side with PTFE and on the other side with SVG. They were sequentially assigned to PTFE-SVG alternating with SVG-PTFE. All patients were followed using duplex ultrasound and ankle/brachial indexes at 1 month and every 6 months thereafer. RESULTS: The perioperative complication rates were 5% for PTFE and 12% for SVG. There was no operative death or perioperative amputation for either procedure. The Kaplan-Meier estimate of primary, assisted primary, and secondary patency rates at 72 months were 68%, 68%, and 77% for PTFE and 76%, 83%, and 85% for SVG. There were no statistically significant differences between primary and secondary patency rates for both grafts; however; the assisted primary patency rates were higher for SVG (P < .05). The crude limb salvage rate at 72 months was 98% for PTFE and 98% for SVG. There were no risk factors identified that had an impact on graft patency. CONCLUSIONS: PTFE and SVG for above knee bypasses have comparable patency and limb salvage rates in claudicant patients with bilateral superficial femoral artery occlusion and 2- to 3-vessel runoff This may justify the use of PTFE for above knee locations in these selected patients.

Heat tolerance of Boran and Tuli crossbred steers.

Experiments were conducted to evaluate the heat tolerance of the following breeds: Hereford (H), Brahman (B), H x B, H x Boran (H x Bo), and H x Tuli (H x T). Heat tolerance was evaluated in a climatically controlled room (Exp. 1) and under summer environmental conditions (Exp. 2) by comparing rectal temperatures (RT), respiration rates (RR), and sweating rates (SW). In Exp. 1, under extremely hot conditions (mean temperature-humidity index [THI] > 90), purebred B had significantly (P < .05) lower RT and RR than other genotypes, which may be indicative of greater surface area per mass to dissipate heat and a lower metabolic rate than other genotypes. Boran and Tuli crosses had RT (39.5 degrees C) that were intermediate to those of B (39.0 degrees C) and H x B (40.0 degrees C). The H genotype had the greatest RT at 40.3 degrees C. Among the breeds, trends in RR were similar to RR observed at THI < 77; B had the lowest RR, and H x B were intermediate. However, in these extreme conditions, RR did not differ among the purebred H and the Boran and Tuli crossbred steers, but H x B steers had lower RR than the other H crossbred steers. Sweating rates were significantly greater for the Bos indicus x Bos taurus crosses (H x B and H x Bo) than for the purebred genotypes (H and B) and the Bos taurus cross (H x T). In Exp. 2, mean RT for B, H x B, H x Bo, and H x T were very similar to those recorded under the moderate heat stress conditions found in Exp. 1. There were no differences in RT among B, H x Bo, and H x T genotypes. The RR increased over time for H only, and RR for other genotypes tended to be elevated only slightly over time. Among genotypes, SW was significantly greater for the H x Bo steers. The ability of the Bos indicus crosses to dissipate heat through enhanced SW and associated evaporative cooling was evident. However, the heat-tolerant nature of the Bos taurus cross (H x T) was not evident through enhanced RR or SW in either experiment. Compared with other genotypes, the lower RR of B steers was clearly evident and is assumed to be due to greater surface area and other skin characteristics that allow them to dissipate heat to maintain lower RT. These data suggest that the H x Bo and H x T are similar to H x B and intermediate to H and B genotypes in maintaining homeostasis when exposed to a high heat load.

The role of carotid duplex ultrasound in evaluating plaque morphology: potential use in selecting patients for carotid stenting.

PURPOSE: To study the role of duplex ultrasonography in evaluating plaque morphology and its correlation to neurological symptoms and cerebral infarctions on computed tomographic scans. METHODS: The hospital records of 181 patients (107 males; average age 66 years, range 41 to 89) with > 50% carotid stenosis (29 bilateral lesions) who had undergone duplex ultrasonography, carotid arteriography, and cerebral computed tomography were studied retrospectively. Of 210 duplex examinations, 139 were appropriate for morphological analysis of surface characteristics and echogenicity. RESULTS: Over half of the plaques examined had irregular surfaces (81, 58%) and displayed mixed (i.e., heterogeneous) echogenic patterns (74, 53%). Irregular (68 of 81, 84%) and heterogeneous (65 of 74, 88%) plaques were associated with ipsilateral neurological symptoms (p < 0.0001). Similarly, 44 (54%) of 81 irregular plaques and 42 (57%) of 74 heterogeneous plaques were found in patients with cerebral infarctions in the carotid territory (p < 0.0001). CONCLUSIONS: Heterogeneous and/or irregular plaques were more often associated with both neurological symptoms and infarctions than smooth or homogeneous plaques. These findings may have implications in patient selection for endoluminal therapy.

Heterologous expression of endo-beta-1,4-D-glucanase from Clostridium cellulovorans in Clostridium acetobutylicum ATCC 824 following transformation of the engB gene.

Heterologous expression of the Clostridium cellulovorans engB gene by Clostridium acetobutylicum BKW-1 was detected as zones of hydrolysis on carboxymethyl cellulose (CMC) Trypticase glucose yeast plates stained with Congo red. The extracellular cellulase preparation from C. acetobutylicum BKW-1 has a specific activity towards CMC which is more than fourfold that present in C. acetobutylicum ATCC 824. Western blot (immunoblot) analysis using the C. cellulovorans anti-EngB primary antibody demonstrated that an additional 44-kDa protein band was present in the supernatant derived from C. acetobutylicum BKW-1 but was not present in ATCC 824 or ATCC 824(pMTL500E).

Localization of the properdin structural locus to Xp11.23-Xp21.1.

Properdin is a serum protein belonging to the alternative pathway of complement activation whose absence is often associated with fatal bacterial infections. Properdin deficiency segregates with an X-linked recessive pattern and its position has been recently refined by genetic linkage analysis to the proximal part of the X-chromosome short arm near the OTC and DXS7 loci. We have hybridized an 0.8-kb genomic clone encoding part of the human properdin gene to a panel of somatic cell hybrids retaining different portions of the human X chromosome and thereby localized the probe to Xcen-Xp21.1. Furthermore, in situ hybridization of the same probe to replication banded metaphase chromosomes refined this localization to the region Xp11.23-Xp21.1 (with a peak grain distribution in the region equivalent to Xp11.4). As OTC and DXS7 map to Xp21.1 and Xp11.3, respectively, the data presented here strongly suggest that the X-linked deficiency syndrome is due to a defect in the locus encoding the structural properdin gene or in a physically close regulatory locus.

Enzyme-capture assay for rapid detection of Escherichia coli in oysters.

Enzyme-capture assays (ECAs) for Escherichia coli beta-D-glucuronidase (GUD) were performed directly from 24-h gas-positive lauryl tryptose broth (LTB) fermentation tubes that had been inoculated with oyster homogenate seeded with E. coli. The LTB-ECA method yielded results in 1 day that were equivalent to those obtained in 2 days by an LTB and EC-4-methylumbelliferyl-beta-D-glucuronide (EC-MUG) method. Overall, 62 of 64 (97%) positive EC-MUG broths from which E. coli was isolated were correctly identified by ECA. Of 61 LTB tubes identified as GUD negative by ECA, 59 were confirmed to be free of E. coli by using EC-MUG; thus, the false-negative rate was approximately 3%. Polyclonal antibodies prepared against E. coli GUD reacted only with GUDs of E. coli, Escherichia vulneris, and Shigella sonnei. The antibodies did not react with GUDs from Flavobacterium spp., Staphylococcus spp., Yersinia enterocolitica, shellfish, or bovine liver. The GUD ECA test, when used in conjunction with the most-probable-number technique, was a rapid method for E. coli enumeration in oysters.

Enhancement of UV survival, UV- and MMS-mutability, precise excision of Tn10 and complementation of umuC by plasmids of different incompatibility groups.

29 conjugative resistance and colicin plasmids from 19 different incompatibility (Inc) groups were examined for their ability to enhance post-ultraviolet (UV) survival and UV- and methyl methanesulfonate(MMS)-induced mutability in Salmonella typhimurium LT2 strains. 14 Muc+ plasmids enhanced each of the survival and mutation-related properties tested, while 14 Muc- plasmids showed no enhancing effects in any tests. One Muc+ plasmid, pRG1251 (IncH1), enhanced post-UV survival and each of the mutation-related properties tested, except MMS-induced mutagenesis. Two further noteworthy plasmids, R391 (IncJ) and R394 (IncT), produced apparent strain-dependent effects in S. typhimurium which differed from those reported to have been found in Escherichia coli. Plasmid R391 enhanced post-UV survival in S. typhimurium, in contrast to its UV-sensitizing effects in E. coli. In both hosts plasmid R391 enhanced UV- and MMS-induced mutagenesis. Plasmid R394 had no enhancing effects on UV survival or UV- and MMS-induced mutagenesis in S. typhimurium, in contrast to its reported enhancement of MMS-induced mutagenesis in E. coli. Conjugal transfer of R394 to E. coli strain AB1157 and assays of mutagenesis-related traits supported results observed in S. typhimurium. Muc+ plasmids were found to enhance the frequency of precise excision of the transposon Tn10 when inserted within hisG or trpA in S. typhimurium strains. Precise excision could be further enhanced in S. typhimurium by UV-irradiation. Analysis of Tn10 mutants with altered IS10 ends indicated that intact inverted repeats at the ends of Tn10 were required for efficient enhancement of precise excision.

A hospital-based community paediatric unit.

Children with multiple handicaps often require the services of a team of professionals to ensure that they receive a comprehensive assessment. It is essential that the information derived from this assessment is conveyed accurately to the child's parents in language that they understand. It is also important that a member of the assessment team is made responsible for seeing that the recommendations made for the child's future are actually carried out. On hundred and twenty-nine children referred for assessment of developmental delay were found to have multiple intellectual, physical and social problems needing a team approach to their assessment, and the mobilization of a variety of community resources to provide their ongoing care.