Management of Children Admitted to Hospitals across Bangladesh with Suspected or Confirmed COVID-19 and the Implications for the Future: A Nationwide Cross-Sectional Study

There is an increasing focus on researching children admitted to hospital with new variants of COVID-19, combined with concerns with hyperinflammatory syndromes and the overuse of antimicrobials. Paediatric guidelines have been produced in Bangladesh to improve their care. Consequently, the objective is to document the management of children with COVID-19 among 24 hospitals in Bangladesh. Key outcome measures included the percentage prescribed different antimicrobials, adherence to paediatric guidelines and mortality rates using purposely developed report forms. The majority of 146 admitted children were aged 5 years or under (62.3%) and were boys (58.9%). Reasons for admission included fever, respiratory distress and coughing; 86.3% were prescribed antibiotics, typically parenterally, on the WHO ‘Watch’ list, and empirically (98.4%). There were no differences in antibiotic use whether hospitals followed paediatric guidance or not. There was no prescribing of antimalarials and limited prescribing of antivirals (5.5% of children) and antiparasitic medicines (0.7%). The majority of children (92.5%) made a full recovery. It was encouraging to see the low hospitalisation rates and limited use of antimalarials, antivirals and antiparasitic medicines. However, the high empiric use of antibiotics, alongside limited switching to oral formulations, is a concern that can be addressed by instigating the appropriate programmes.

Digital library services to support online learning amid COVID-19: a study of a private university library in Bangladesh

Purpose

The purpose of this paper is to discuss the East West University Library’s (EWUL’s) response to COVID-19 situation through their transformation to digital services. The paper tries to explain how these digital library services support the user community of East West University (EWU) in online teaching and access to information resources.

Design/methodology/approach

This paper describes the EWUL’s several digital services that are used to meet the needs of its user community during the COVID-19 pandemic. The reflective practice approach has been undertaken for this study on the basis of the authors’ personal experiences working at an academic library. The authors used the reflective practice approach to assess the library’s practice during crisis situation, make the use of technological interventions in service providing and also to re-innovate the digital services for future.

Findings

During the pandemic, the library shifted all the possible physical or on-site services to digital services, i.e. online resource facilities and remote access to these, federated searching, Web online public access catalog, engaging users through social media, specialized knowledge space, online document delivery, article on request, information literacy training, virtual reference service, etc. The user engagement in all these services is also notable.

Research limitations/implications

The nature of this study is limited to the COVID-19 pandemic and within a particular geographic location.

Practical implications

This paper has implications and possible applications for other university libraries in developing countries, which intends to transform their services into digital for ensuring better service quality for their respective user community.

Originality/value

This paper makes a valuable contribution to the literature on how a private university library of a developing country is responding to pandemics such as COVID-19.

Pilot Study on the Current Management of Children with COVID-19 In Hospitals in Bangladesh; Findings and Implications

Objective: The focus on COVID-19 in children in low- and middle-income countries including Bangladesh has been on addressing key issues including poor vaccination rates as well as mental health issues, domestic violence and child labour. However, the focus on optimally managing children in hospitals is changing with new variants and concerns with the development of hyperinflammatory syndromes. There are also concerns with the overuse of antimicrobials to treat patients with COVID-19 in hospitals enhancing resistance rates. The Bangladesh Paediatric Association have developed guidelines to improve patient care building on national guidance. Consequently, there is a need to document the current management of children with COVID-19 in Bangladesh and use the findings for future guidance. Methods: Rapid analysis of the management of children with COVID-19 among eight private and public hospitals in Bangladesh with varying numbers of in-patient beds using purposely developed case report forms (CRFs). The CRFs were piloted before full roll-out. Results: Overall low numbers of children in hospital with COVID-19 (4.3% of in-patient beds). The majority were male (59.6%) and aged 5 years or under (63.5%). Reasons for admission included respiratory distress/ breathing difficulties with 94.2% of COVID-19 cases confirmed. All children were prescribed antibiotics empirically, typically those on the Watch list of antibiotics and administered parenterally, with only a small minority switched to oral therapy before discharge. There was appreciable prescribing of Vitamins (C and D) and zinc and encouragingly limited prescribing of other antimicrobials (antivirals, antimalarials and antiparasitic medicines). Length of stay was typically 5 to 10 days. Conclusion: Encouraging to see low hospitalisation rates and limited use of antimicrobials apart from antibiotics. Concerns with high empiric use of antibiotics and limited switching to oral formulations can be addressed by instigating antimicrobial stewardship programmes. We will be monitoring this. Bangladesh Journal of Medical Science Vol.20(5) 2021 p.188-198

Public libraries’ responses to a global pandemic: Bangladesh perspectives

The whole world is experiencing a new reality – the global outbreak of COVID-19, which has forced every institution into lockdown. This study aims to explore the responses of the government public libraries of Bangladesh. An online questionnaire was used to gather primary data from all of the 71 public libraries, which was followed by semi-structured interviews with eight librarians. The analysis suggests that more than 50% of the libraries had a low level of preparedness to face any crisis, and none of the libraries were fully prepared to manage this pandemic. All of the libraries were open for administrative functions without physical access to users. The study found that 52% of the libraries created public awareness through social media, while 46% supported local government organizations and 40% provided counselling services. Considering the existing challenges, the study recommends some measures for the public libraries of Bangladesh to cope with this situation.

Effect of Elevated Temperature on Immediate Neurodevelopmental Outcome in Term Neonates with Hypoxic-Ischemic Encephalopathy

Background: Among term infants, hypoxic-ischemic encephalopathy due to acute perinatal asphyxia remains an important cause of neurodevelopmental deficits in childhood. Treatment is currently limited to supportive intensive care, without any specific brain-oriented therapy. Objective: To determine whether the risk of death or moderate/severe neurodevelopmental impairment in term infants with hypoxic-ischemic encephalopathy increases with relatively high skin or rectal temperature between 12 and 72 hours of birth. Materials and Methods: This was a prospective observational study. Asphyxiated newborns who came within 12 hours of birth were enrolled in this study. Both axillary and rectal temperature were recorded 6 hourly for 72 hours and each infant`s temperature for each site were rank ordered. Then mean of all axillary and rectal temperatures of each neonate was calculated. Outcomes were related to temperatures in logistic regression analyses for the elevated/relatively high temperatures and normal/low temperatures group, with adjustment of the level of encephalopathy and gender. Results: The mean axillary temperature was 36.07 ± 6.10C and in 25.71%, 11.92% and 6.32% cases axillary temperatures were >370C, >37.50C and >380C respectively. The mean rectal temperature was 36.8 ± 60C, and in 43.53%, 30.02% and 19.97% cases rectal temperatures were >370C, >37.50C and >380C respectively. Mean ambient temperature was 26.170C. There was significant correlation between axillary and rectal temperatures (r=0.889). For elevated temperature, the odds of death or moderate to severe impairment increased 8.9-fold (CI 0.906–88.18) and the odds of death alone increased 4.6-fold (CI 0.373–56.83). The odds of impairment increased 1.84-fold (CI 0.45– 7.50). Conclusion: Relatively high temperature during usual care after hypoxic-ischemia in term neonates was associated with adverse neurodevelopmental outcomes. J Enam Med Col 2019; 9(3): 160-165

Validation of a rapid neurodevelopmental assessment tool for 10- to 16-year-old young adolescents in Bangladesh

OBJECTIVE

To validate a Rapid Neurodevelopmental Assessment (RNDA) tool for use by child health professionals to determine neurodevelopmental impairments (NDIs) in young adolescents aged 10-16 years in Bangladesh.

STUDY DESIGN

In a convenience sample of community children (n = 47), inter-rater reliability was determined between four testers, and concurrent validity was determined by simultaneous administration of an intelligence quotient (IQ) test (Wechsler Intelligence Scale for Children, Revised) by a child psychologist.

RESULTS

Inter-rater reliability was excellent between the testers on the 47 children administered the RNDA (kappa = 1.00). Significantly lower IQ scores were obtained in those identified with 'any (>1) NDI' (n = 34) compared with those with no NDI (n = 13) on Verbal IQ (P-value < 0.0001), Performance IQ (P-value < 0.0001) and Full-scale IQ (P-value < 0.0001) scores on the Wechsler Intelligence Scale for Children, Revised.

CONCLUSION

The RNDA shows promise as a tool for use by child health professionals for identifying NDIs in young adolescents aged 10-16 years. A larger study sample is needed to determine its usefulness for identification of some impairments not found in the study population, i.e. gross motor, fine motor, hearing and seizures.

Temperature Effect on the Surface Properties of ZnO(am)

The point of zero charge and surface acidity constants of zinc oxide were determined over the temperature range 293–323 K. Both the point of zero charge (pzc) and the surface acidity constants (pKa1 and pKa2) were found to decrease with increasing temperature. The values of the dissociation constants (pKa1 and pKa2) determined from the Henderson-Hasselbach equation agreed very well with those determined using the Gaines-Thomas equation. The thermodynamic parameters ΔH0 and ΔS0 for the processes were also evaluated.

Correlation of hyperinsulinemia with hyperandrogenemia in primary infertile women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy among women of the reproductive age and is the most common form of anovulatory infertility. Hyperinsulinemia and hyperandrogenemia are the characteristic features of PCOS, but the association between hyperinsulinemia and hyperandrogenemia is not well established. To find out any causal association between Hyperinsulinemia and hyperandrogenemia, a retrospective study was done on primary infertile women suffering from PCOS in the department of Biochemistry, Bangabandhu Sheikh Mujib Medical University. A total of 80 subjects were selected, among them 60 were cases and 20 were controls. Depending on their body mass index, the cases were divide into two groups, obese (n=30) and non-obese (n=30). Age and BMI matched controls were taken for both age groups. Observations derived from the study suggested that hyperinsulinemia and hyperandrogenemia are characteristic features of PCOS but significant correlation was not found between hyperinsulinemia and hyperandrogenemia. However, we cannot negate any possible association between the two and thereby we recommend further study to be done with a larger sample size.

Validation of a home-based neurodevelopmental screening tool for under 2-year-old children in Bangladesh

BACKGROUND

Home-based screening to identify young children at risk for neurodevelopmental impairments (NDIs) is needed to guide the targeting of child neurodevelopmental intervention services in Bangladesh. This study aimed to validate such a tool for children under age 2 years.

METHODS

A Developmental Screening Questionnaire was administered to mothers of children aged 0-<2 years in an urban community. Inter-rater reliability among the interviewers, who were high school graduates, was determined. All children who were screen positive and a proportion of screen negatives were subsequently assessed for NDIs by professionals. Sensitivity and specificity were calculated by comparing screening with assessment results.

RESULTS

Mean kappa coefficient of agreement among interviewers was 0.95. A total of 197 children were screened, of whom 17% screened positive. Fifty-one children, including 24 screen negatives, were assessed for NDIs. Screen-positivity was significantly different between income groups (P = 0.019), and higher in stunted children (odds ratio = 5.76, 95% confidence interval = 1.72-19.28), indicating good discriminant validity Specificity was excellent (84-100%) for all developmental domains. Sensitivity was 100% for vision and hearing; 70% for speech; and 63%, 53%, 48%, and 45% for gross motor, behaviour, fine motor and cognitive impairments, respectively.

CONCLUSION

A tool for screening <2-year-old children at risk for NDIs showed high specificity; and was able to identify all children at risk for vision and hearing impairments, nearly three-fourths with speech impairments, two-thirds with gross motor impairments, and about half with behavioural, cognitive and fine motor impairments. The Developmental Screening Questionnaire tool has potential for use by frontline workers to screen large populations and to link to definitive assessment as well as intervention services.

Validation of rapid neurodevelopmental assessment for 2- to 5-year-old children in Bangladesh

OBJECTIVE

Validate a tool to determine neurodevelopmental impairments (NDIs) in >2- to 5-year-old children in a country with limited child development expertise.

METHODS

Rapid Neurodevelopmental Assessment (RNDA) is a tool designed to detect functional status and NDIs across multiple neurodevelopmental domains. Validity was determined in 77 children enrolled by door-to-door sampling in Dhaka and who were administered the RNDA by 1 of 6 testers (4 developmental therapists, 2 special education teachers) and simultaneously administered a test of adaptive behavior (AB; Independent Behavior Assessment Scale) and intelligence quotient (IQ) tests (Bayley Scales of Infant Development II, Stanford Binet Intelligence Scale, Wechsler Preschool and Primary Scales of Intelligence) by psychologists.

RESULTS

Interrater reliability ranged from good to excellent. There were significant differences in AB in mean percentile scores on the Independent Behavior Assessment Scale for motor (P = .0001), socialization (P = .001), communication (P = .001), and full-scale (P = .001) scores in children with ≥1 NDI ("any NDI") versus no NDI. Significant differences in those with versus those without "any NDI" were found on IQ scores. Sensitivity and specificity for "significant difficulties" (defined as AB z-scores < -2 SDs and/or IQ <70) and "mild difficulties included" (AB z-scores < -1SD and/or IQ <85) were 90% and 60% and 80% and 76%, respectively.

CONCLUSIONS

The RNDA validity results are promising for use by child care professionals in field and clinical settings, but the tool needs further replication and refinement for assessment of specific impairments of vision, hearing, and seizures.

Child Psychiatric Disorders Presenting to a Tertiary Multidisciplinary Child Development Service in Bangladesh

Background: Shishu Bikash Kendra (SBK or Child Development Center) of the Dhaka Shishu (Children’s) Hospital (DSH) has been using a multidisciplinary approach for assessment and management of children with various neurodevelopmental disorders since its establishment in 1991. In the past decade, a major proportion have presented with a range of emotional and behavioural problems. This paper aims to describe the types of child psychiatric disorders and the multidisciplinary team approach used in this centre for diagnosis and management of these children.Patients and Methods: Clinical records of 300 children who were assessed by the Child Mental Health Clinic of SBK during April 2004 to December 2006 were analyzed. These children were among the 1648 children who were referred for behavioural problems after having a General Developmental assessment (GDA). Children received services by a team comprising of child health physicians, child neurologists, child psychologists, developmental therapists and psychosocial counselors and a social worker. Psychiatric conditions were diagnosed using the multi-axial diagnostic guidelines of the Diagnostic and Statistical Manual (DSM-IV) and the International Classification of Diseases (ICD-10). The role of various clinics of the SBK to address specific aspects of a child’s mental health condition is described.Results: Of the 300 children seen 55% were of primary school age (ie, between 5-10 years), boys comprising 71%. The majority (94%) could be categorized into a psychiatric condition. Sixty three percent had a developmental problem. In addition, with 44% children having some intellectual deficit. Sixty one percent had an associated neurological or general medical condition. It was important to note also that 54% had some form of psychosocial adversity which needed immediate help. Commonest psychiatric diagnosis was Hyperkinetic Disorders (33%) followed by Autism Spectrum Disorders (ASD) and other Pervasive Developmental Disorders (PDD) (27%).Conclusion: Psychiatric morbidity is a common presentation among children who come to the child development and neurodisability service. If Child Mental Health professionals work with a multidisciplinary team within a child development service such as SBK, it may best utilize the multiaxial diagnosis system.DOI: http://dx.doi.org/10.3329/bjch.v35i3.10385  Bangladesh J Child Health 2011; Vol 35 (3): 84-89

Validation of rapid neurodevelopmental assessment instrument for under-two-year-old children in Bangladesh

OBJECTIVE

The objective of this study was to determine the reliability and validity of a comprehensive assessment procedure for ascertaining neurodevelopmental status of children aged 0 to 24 months for use by multidisciplinary professionals in a developing country.

METHODS

We developed the Rapid Neurodevelopmental Assessment (RNDA) to determine functional status in the following domains: primitive reflexes, gross motor, fine motor, vision, hearing, speech, cognition, behavior, and seizures. Reliability was determined for 50 children who were aged <3 months and 30 children who were aged > or =3 to 24 months and were administered the RNDA by 8 different professionals (3 physicians, 4 therapists, and 1 special teacher). Validity was determined on 34 children aged <3 months in hospital and 81 children aged > or =3 to 24 months in urban (n = 47) and rural (n = 34) community-based populations by any 1 of the 8 professionals, with simultaneous administration of the adapted Bayley Scales of Infant Development II by a psychologist as the gold standard.

RESULTS

Mean kappa coefficients of agreement among professionals in overall and individual domains in the 2 age groups ranged from good to excellent. For both younger and older children, there was good concurrent validity (ie, significantly lower mean Mental Development Index and Psychomotor Development Index scores) for children with > or =1 neurodevelopmental impairment and for children with impairments in most functional domains, compared with children with no impairments. Significantly more impairments were found in children from disadvantaged compared with socioeconomically more advantaged communities, indicating good discriminant validity.

CONCLUSIONS

The RNDA can be used by professionals from a range of backgrounds with high reliability and validity for determining functional status of children who are younger than 2 years. The study findings have important practical implications for early identification and intervention to mitigate neurodevelopmental impairments in large populations that live in developing countries where professional expertise is sparse.

Accelerated induction of mycobacterial antigen-specific CD8+ T cells in the Mycobacterium tuberculosis-infected lung by subcutaneous vaccination with Mycobacterium bovis bacille Calmette-Guérin

Both CD4(+) and CD8(+) T cells are important in protection against Mycobacterium tuberculosis infection. To evaluate the effect of vaccination with Mycobacterium bovis bacille Calmette-Guérin (BCG) on the CD8(+) T-cell response to pulmonary M. tuberculosis infection, we analyzed the kinetics of CD8(+) T cells specific to the mycobacterial Mtb32a(309-318) epitope, which is shared by M. tuberculosis and M. bovis BCG, in the lung of mice infected with M. tuberculosis. The CD8(+) T cells were detected by staining lymphocytes with pentameric major histocompatibility complex (MHC) class I H-2D(b-)Mtb32a(209-318) peptide complex and were analysed by flow cytometry. Mtb32a-specific CD8(+) T cells became detectable on day 14, and reached a plateau on day 21, in the lung of M. tuberculosis-infected unvaccinated mice. Subcutaneous vaccination with M. bovis BCG in the footpads induced Mtb32a-specific CD8(+) T cells in the draining lymph nodes (LNs) on day 7 and their numbers further increased on day 14. When M. bovis BCG-vaccinated mice were exposed to pulmonaryinfection with M. tuberculosis 4 weeks after vaccination, the Mtb32a-specific CD8(+) T cells in the infected lung became detectable on day 7 and reached a plateau on day 14, which was 1 week earlier than in the unvaccinated mice. The pulmonary CD8(+) T cells from the BCG-vaccinated M. tuberculosis-infected mice produced interferon-gamma in response to Mtb32a(209-318) peptide on day 7 of the infection, whereas those of unvaccinated mice did not. The results demonstrate that induction of mycobacterial antigen-specific protective CD8(+) T cells in the M. tuberculosis-infected lung is accelerated by subcutaneous vaccination with M. bovis BCG.

Diploid/polyploid syntenic shuttle mapping and haplotype-specific chromosome walking toward a rust resistance gene (Bru1) in highly polyploid sugarcane (2n approximately 12x approximately 115)

The genome of modern sugarcane cultivars is highly polyploid (approximately 12x), aneuploid, of interspecific origin, and contains 10 Gb of DNA. Its size and complexity represent a major challenge for the isolation of agronomically important genes. Here we report on the first attempt to isolate a gene from sugarcane by map-based cloning, targeting a durable major rust resistance gene (Bru1). We describe the genomic strategies that we have developed to overcome constraints associated with high polyploidy in the successive steps of map-based cloning approaches, including diploid/polyploid syntenic shuttle mapping with two model diploid species (sorghum and rice) and haplotype-specific chromosome walking. Their applications allowed us (i) to develop a high-resolution map including markers at 0.28 and 0.14 cM on both sides and 13 markers cosegregating with Bru1 and (ii) to develop a physical map of the target haplotype that still includes two gaps at this stage due to the discovery of an insertion specific to this haplotype. These approaches will pave the way for the development of future map-based cloning approaches for sugarcane and other complex polyploid species.

Stress in mothers of preterm infants in Bangladesh: associations with family, child and maternal factors and children's neuro-development

BACKGROUND

The aim of this paper was to ascertain stress experienced by mothers of prospectively followed up preterm infants, and associations with family, child and maternal factors and children's neuro-development.

METHODS

Within a follow-up study of preterm infants<33 weeks gestational age at a Child Development Center in Dhaka Shishu Hospital, mothers were interviewed with the Self-Report Questionnaire (SRQ) at each visit. Association between SRQ scores and child, family and maternal variables at first and final visit and children's neuro-developmental outcomes was determined.

RESULTS

Low income mothers were more compliant (54%) compared with the defaulters (31%) (P=0.0001) among the 159 mothers enrolled. Of the 88 mothers who were followed up until a mean age of 22 months of their child, 29.3% were at high risk for psychiatric morbidity at first visit compared with 23.9% on their last visit. Use of abortifacients (P=0.026) and higher maternal age (P=0.040) were significantly associated with maternal stress at first visit; while at last follow-up, total number of visits had the most significant association (P=0.041). Twenty-five per cent and 19% of mothers were at risk for psychiatric morbidity in children developing normally and those with neuro-developmental impairments respectively.

CONCLUSIONS

Mothers at risk for psychiatric morbidity can be helped through follow-up support within public hospitals close to their homes, which is most availed by low income families. Neuro-developmental monitoring of high-risk infants closer to homes may be more feasible in resource poor countries than reliance on hospital visits, which increase stress. Biological markers of stress and coping strategies need further research.

Physical mapping, BAC-end sequence analysis, and marker tagging of the soilborne nematicidal bacterium, Pseudomonas synxantha BG33R

A bacterial artificial chromosome (BAC) library was constructed for the genome of the rhizosphere-inhabiting fluorescent pseudomonad Pseudomonas synxantha BG33R. Three thousand BAC clones with an average insert size of 140 kbp and representing a 70-fold genomic coverage were generated and arrayed onto nylon membranes. EcoRI fingerprint analysis of 986 BAC clones generated 23 contigs and 75 singletons. Hybridization analysis allowed us to order the 23 contigs and condense them into a single contig, yielding an estimated genome size of 5.1 Mb for P. synxantha BG33R. A minimum-tile path of 47 BACs was generated and end-sequenced. The genetic loci involved in ring nematode egg-kill factor production in BG33R Tn5 mutants, 246 (vgrG homolog), 1122 (sensor kinase homolog), 1233 (UDP-galactose epimerase homolog), 1397 (ferrisiderophore receptor homolog), and 1917 (ribosomal subunit protein homolog), have been mapped onto the minimum-tile BAC library. Two of the genetic regions that flank Tn5 insertions in BG33R egg-kill-negative mutants 1233 and 1397 are separated by a single BAC clone. Fragments isolated by ligation-mediated PCR of the Tn5 mutagenized regions of 29 randomly selected, non-egg-kill-related, insertion mutants have been anchored onto the ordered physical map of P. synxantha.

Sequence and analysis of the tomato JOINTLESS locus

A 119-kb bacterial artificial chromosome from the JOINTLESS locus on the tomato (Lycopersicon esculentum) chromosome 11 contained 15 putative genes. Repetitive sequences in this region include one copia-like LTR retrotransposon, 13 simple sequence repeats, three copies of a novel type III foldback transposon, and four putative short DNA repeats. Database searches showed that the foldback transposon and the short DNA repeats seemed to be associated preferably with genes. The predicted tomato genes were compared with the complete Arabidopsis genome. Eleven out of 15 tomato open reading frames were found to be colinear with segments on five Arabidopsis bacterial artificial chromosome/P1-derived artificial chromosome clones. The synteny patterns, however, did not reveal duplicated segments in Arabidopsis, where over half of the genome is duplicated. Our analysis indicated that the microsynteny between the tomato and Arabidopsis genomes was still conserved at a very small scale but was complicated by the large number of gene families in the Arabidopsis genome.

JOINTLESS is a MADS-box gene controlling tomato flower abscission zone development

Abscission is a universal and dynamic process in plants whereby organs such as leaves, flowers and fruit are shed, both during normal development, and in response to tissue damage and stress. Shedding occurs by separation of cells in anatomically distinct regions of the plant, called abscission zones (AZs). During abscission, the plant hormone ethylene stimulates cells to produce enzymes that degrade the middle lamella between cells in the AZ. The physiology and regulation of abscission at fully developed AZs is well known, but the molecular biology underlying their development is not. Here we report the first isolation of a gene directly involved in the development of a functional plant AZ. Tomato plants with the jointless mutation fail to develop AZs on their pedicels and so abscission of flowers or fruit does not occur normally. We identify JOINTLESS as a new MADS-box gene in a distinct phylogenetic clade separate from those functioning in floral organs. We propose that a deletion in JOINTLESS accounts for the failure of activation of pedicel AZ development in jointless tomato plants.

A new approach for the identification and cloning of genes: the pBACwich system using Cre/lox site-specific recombination

With current plant transformation methods ( Agrobacterium, biolistics and protoplast fusion), insertion of DNA into the genome occurs randomly and in many instances at multiple sites. Associated position effects, copy number differences and multigene interactions can make gene expression experiments difficult to interpret and plant phenotypes less predictable. An alternative approach to random integration of large DNA fragments into plants is to utilize one of several site-specific recombination (SSR) systems, such as Cre/ lox. Cre has been shown in numerous instances to mediate lox site-specific recombination in animal and plant cells. By incorporating the Cre/ lox SSR system into a bacterial artificial chromosome (BAC) vector, a more precise evaluation of large DNA inserts for genetic complementation should be possible. Site-specific insertion of DNA into predefined sites in the genome may eliminate unwanted 'position effects' caused by the random integration of exogenously introduced DNA. In an effort to make the Cre/ lox system an effective tool for site-directed integration of large DNAs, we constructed and tested a new vector potentially capable of integrating large DNA inserts into plant and fungal genomes. In this study, we present the construction of a new BAC vector, pBACwich, for the system and the use of this vector to demonstrate SSR of large DNA inserts (up to 230 kb) into plant and fungal genomes.

Analysis of kafirin promoter activity in transgenic tobacco seeds

Sequences corresponding to 855 bp of 5' promoter region and the transit peptide from lambdaGK.1,a genomic clone encoding a 22 kDa alpha-kafirin seed protein from sorghum, were translationally fused to a cloned beta-glucuronidase (GUS) coding sequence from uidA and transferred to tobacco via Agrobacterium tumefaciens-mediated transformation. No GUS expression was detectable at any stage of growth in stems or leaves of these plants. However, GUS expression was detected in both embryo and endosperm tissues of resulting tobacco seeds 10-15 days after flowering. Dissected tissues indicate endosperm expression was localized within the bulk endosperm and not within the parenchyma cell layer underlying the integument. These studies also demonstrate that within dissected tobacco embryos, expression from the kafirin promoter was restricted to the mesocotyl region.

Direct detection of Shiga-like toxin-producing Escherichia coli in ground beef using the polymerase chain reaction

We recently reported the development and assessment of a technique for the detection of Shiga-like toxin-producing Escherichia coli (SLTEC) using the polymerase chain reaction (PCR) and a digoxigenin-11-dUTP-labelled DNA probe. This technique has now been adapted for the direct identification of SLTEC in ground beef. Ground beef homogenates were diluted 1000-fold to reduce the concentration of components which inhibit the thermostable polymerase. Assessment of four different ground beef samples using the PCR detection technique revealed that fat content was a major inhibitory component. As few as 30 SLTEC ml-1 of a ground beef homogenate were detected using the PCR technique, although it was necessary to enrich six of the samples for positive detection. These findings indicate that the PCR detection technique is suitable for the identification of SLTEC directly from contaminated ground beef without isolation of the bacterium or purification of its DNA.

Analysis of Shiga toxin subunit association by using hybrid A polypeptides and site-specific mutagenesis

Shiga toxin (STX), a bacterial toxin produced by Shigella dysenteriae type 1, is a hexamer composed of five receptor-binding B subunits which encircle an alpha-helix at the carboxyl terminus of the enzymatic A polypeptide. Hybrid toxins constructed by fusing the A polypeptide sequences of STX and Shiga-like toxin type II were used to confirm that the carboxyl terminus of the A subunits governs association with the B pentamers. The alpha-helix of the 293-amino-acid STX A subunit contains nine residues (serine 279 to methionine 287) which penetrate the nonpolar pore of the B-subunit pentamer. Site-directed mutagenesis was used to establish the involvement of two residues bordering this alpha-helix, aspartic acid 278 and arginine 288, in coupling the C terminus of StxA to the B pentamer. Amino acid substitutions at StxB residues arginine 33 and tryptophan 34, which are on the membrane-contacting surface of the pentamer, reduced cytotoxicity without affecting holotoxin formation. Although these B-subunit mutations did not involve receptor-binding residues, they may have induced an electrostatic repulsion between the holotoxin and the mammalian cell membrane or disrupted cytoplasmic translocation.

Evaluation of a technique for identification of Shiga-like toxin-producing Escherichia coli by using polymerase chain reaction and digoxigenin-labeled probes

A polymerase chain reaction (PCR) technique for the identification of Shiga-like toxin (SLT)-producing Escherichia coli was assessed by using 95 strains of SLT-producing E. coli and 5 Shigella dysenteriae type 1 strains. PCR was used for the amplification of slt gene sequences from whole bacterial colonies. A digoxigenin-labeled DNA probe was used for identification of the PCR products in a spot blot hybridization assay. Modifications were made to adapt this technique for the proper identification of 10 SLT-producing isolates which were refractory to the heat lysis step that was used to liberate whole-cell DNA for PCR and 6 isolates which gave nonspecific amplification products. The sensitivity and specificity of this assay were each 99% when compared with toxin neutralization results by using SLT-specific monoclonal antibodies. These values indicate that this detection technique could be suitable for use in a clinical laboratory.

Positive and negative cis-acting DNA domains are required for spatial and temporal regulation of gene expression by a seed storage protein promoter

Mutations affecting spatial and temporal regulation of a beta-phaseolin gene encoding the major storage protein of bean (Phaseolus vulgaris) were analyzed by stable and transient transformation approaches. The results substantiate the value of transient assays for rapid determination of the functionality of cis-acting sequences and the importance of stable transformation to identify tissue-specific determinants. Spatial information is specified primarily by two upstream activating sequences (UAS). UAS1 (-295 to -109) was sufficient for seed-specific expression from both homologous and heterologous (CaMV 35S) promoters. In situ localization of GUS expression in tobacco embryos demonstrated that UAS1 activity was restricted to the cotyledons and shoot meristem. A second positive domain, UAS2 (-468 to -391), extended gene activity to the hypocotyl. Temporal control of GUS expression was found to involve two negative regulatory sequences, NRS1 (-391 to -295) and NRS2 (-518 to -418), as well as the positive domain UAS1. The deletion of either negative element caused premature onset of GUS expression. These findings indicate combinatorial interactions between multiple sequence motifs specifying spatial information, and provide the first example of the involvement of negative elements in the temporal control of gene expression in higher plants.

Regulation of beta-glucuronidase expression in transgenic tobacco plants by an A/T-rich, cis-acting sequence found upstream of a French bean beta-phaseolin gene

A 0.8-kilobase fragment from the 5'-flanking region of a French bean beta-phaseolin gene yielded strong, temporally regulated, and embryo-specific expression of beta-glucuronidase (GUS) in transgenic tobacco plants, paralleling that found for the seed protein phaseolin [Sengupta-Gopalan, C., Reichert, N.A., Barker, R.F., Hall. T.C., and Kemp, J.D. (1985) Proc. Natl. Acad. Sci. USA 82, 3320-3324]. Gel retardation and footprinting assays using nuclear extracts from immature bean cotyledons revealed strong binding of nuclear proteins to an upstream region (-628 to -682) that contains two inverted A/T-rich motifs. Fusion of a 103-base pair fragment or a 55-base pair synthetic oligonucleotide containing these motifs to a minimal 35S promoter/GUS cassette yielded strong GUS expression in several tissues. A different pattern of GUS expression was obtained in immature embryos and germinating seedlings from the nominally constitutive, full-length, 35S promoter. Whereas GUS expression under the control of the 0.8-kilobase beta-phaseolin regulatory region is limited to immature embryos, expression from constructs containing the A/T-rich motifs is strongest in roots. These data, combined with S1 mapping, provide direct evidence that a plant upstream A/T-rich sequence that binds nuclear proteins can activate transcription in vivo. They also indicate that additional regulatory elements in the beta-phaseolin 5'-flanking region are required for embryo-specific gene expression.

Regulation of beta-glucuronidase expression in transgenic tobacco plants by an A/T-rich, cis-acting sequence found upstream of a French bean beta-phaseolin gene

A 0.8-kilobase fragment from the 5'-flanking region of a French bean beta-phaseolin gene yielded strong, temporally regulated, and embryo-specific expression of beta-glucuronidase (GUS) in transgenic tobacco plants, paralleling that found for the seed protein phaseolin [Sengupta-Gopalan, C., Reichert, N.A., Barker, R.F., Hall. T.C., and Kemp, J.D. (1985) Proc. Natl. Acad. Sci. USA 82, 3320-3324]. Gel retardation and footprinting assays using nuclear extracts from immature bean cotyledons revealed strong binding of nuclear proteins to an upstream region (-628 to -682) that contains two inverted A/T-rich motifs. Fusion of a 103-base pair fragment or a 55-base pair synthetic oligonucleotide containing these motifs to a minimal 35S promoter/GUS cassette yielded strong GUS expression in several tissues. A different pattern of GUS expression was obtained in immature embryos and germinating seedlings from the nominally constitutive, full-length, 35S promoter. Whereas GUS expression under the control of the 0.8-kilobase beta-phaseolin regulatory region is limited to immature embryos, expression from constructs containing the A/T-rich motifs is strongest in roots. These data, combined with S1 mapping, provide direct evidence that a plant upstream A/T-rich sequence that binds nuclear proteins can activate transcription in vivo. They also indicate that additional regulatory elements in the beta-phaseolin 5'-flanking region are required for embryo-specific gene expression.

Role of Intravenous Immunoglobulin (IVIG) as an Adjuvant in the Treatment of Neonatal Sepsis in Preterm Babies

(J Bangladesh Coll Phys Surg 2006; 24 : 97-104)