Biomedical subjects

M B Singh

Publications and source records attributed to M B Singh.

At least 19 recordsLinked to original sources

PubMed2006

Dengue fever with papilledema: a case of dengue-3 virus infection in central nervous system.

BACKGROUND AND OBJECTIVES: Neurological manifestations of dengue fever are rarely reported during acute illness and clinical presentation commonly observed is of acute encephalitis or one of the post-infectious immune mediated manifestations. We describe a case of dengue fever having mild encephalopathy and papilledema at presentation. CASE REPORT: Twenty-year-old female presented with fever, headache and vomiting. On examination she did not have classical signs of dengue fever and was found to have bilateral papilledema on fundus examination. Detailed work-up did not reveal any other cause of papilledema. Diagnosis of dengue fever was established by blood IgM antibody test on day 7 of illness. Retrospective analysis of CSF (drawn on day 5 of illness) by RT-PCR assay showed a characteristic band of dengue-3 virus. Papilledema was transient and subsided following symptomatic treatment. The patient recovered from acute illness and follow-up was unremarkable. CONCLUSION: Especially in dengue endemic areas, in the patients having acute febrile illness with subtle signs and symptoms suggestive of CNS involvement, dengue virus infection should also be ruled out early in the clinical course.

Adult↗

PubMed2003

A study of nonepileptic seizures in an Indian population.

OBJECTIVE: The goal of this study was to evaluate the background and the clinical profile of nonepileptic seizures (NESs) confirmed by short-term video encephalography (ST-VEEG) recording in an Indian population. METHODS: Seventy-one patients with NESs were enrolled. A complete history was taken and the recorded event was reviewed to define the ictal events. Patients were divided into two groups, Group 1 with a paucity of movements and Group 2 with an excess of movement, and results were analyzed. RESULTS: The mean age was 22.9 (9.6); there were 15 males (21.1%) and 56 females (78.9%). Twenty-four patients (33.8%) were receiving antiepileptic drugs. The majority of the patients (42, 59.1%) were students. All patients were amnesic for the event and were unresponsive during the event. The other characteristics were similar events in 98.6%, hyperventilation in 58 (81.7%). Forty-two patients (59.2%) were in Group 1 and 29 patients (40.8%) were in Group 2. CONCLUSION: NES is a disease of the young and can affect the student or professional. A wrong diagnosis can result in inappropriate treatment. Awareness of this entity is critical to ensuring prompt diagnosis and early intervention.

Adult↗

PubMed2002

Landau Kleffner syndrome: electroclinical and etiopathogenic heterogeneity.

Landau - Kleffner syndrome is a rare, functional, age-related epilepsy with aphasia and epileptiform discharges on EEG. The heterogenity of clinical presentations, course, long-term outcome and response to treatment suggests multiple underlying etiologies. Normal children abruptly develop deterioration of language functions along with spike and wave discharges on EEG. Clinical seizures may or may not be present. The aphasia responds poorly to most drugs. Valproic acid and benzodiazepines are most effective. Steroids and intravenous immunoglobulins have shown a variable response. Long-term outcome of aphasia is variable, many patients persist with residual impairment. Important questions regarding etiopathogenesis are unanswered.

Anticonvulsants↗

PubMed2001

Biphasic illness pattern due to early relapse in Japanese-B virus encephalitis.

Japanese-B virus encephalitis (JE) is considered a uniphasic illness with a variable outcome. Biphasic illness patterns have never been reported previously. From an endemic zone in India we observed six patients of JE (from 62 patients treated in 7 years) who had an early relapse resulting in the biphasic clinical course. Five had poor socio-economic status and three had laboratory evidence of nutritional deficiency. Two patients were adults and the other four were children. Fever, rigors, headaches, body aches, altered consciousness, rigidity and tremors predominated the first phase of illness. During the second phase, behavioural changes, dystonia, pen-oral dyskinesia, drooling, mutism and muscle wasting due to anterior horn cell involvement were the important features. Though the serial antibody titres against the JE virus showed a four-fold rise in the initial or late convalescent phases, there was no increase during the second phase of the illness as compared to the first phase. On MRI, fresh lesions appeared during the second phase at the sites known for their involvement in JE, suggesting recrudescence of the virus. One patient survived with major sequelae, two with minor sequelae and the other three had complete recovery. We conclude that some patients with JE may have an early relapse after partial recovery, giving rise to the biphasic illness pattern. A locally prevalent genetic variant of the virus or host factors may be responsible for the altered clinical course of the disease. Biphasic illness does not necessarily mean a bad prognosis.

Adolescent↗

PubMed2001

Identification of pronp1, a tobacco profilin gene activated in tip-growing cells.

In plant cells, several cellular processes depend on rapid reorganization of a dynamic network of actin cytoskeletal elements in response to internal and environmental stimuli. Profilins, ubiqitous eukaryotic actin monomer-binding proteins with highly conserved three-dimensional structures, regulate the actin cytoskeleton and are considered to link the microfilament system with signal transduction pathways. Plant profilins have been grouped into two distinct classes, gametophytic (pollen-specific) and sporophytic. Here we report the isolation of a profilin gene that seems to be activated during tip growth of specialized cells of gametophytic as well as sporophytic origin. Identification of a genomic DNA clone containing a tobacco profilin gene, pronp1, and analysis of the pronp1 promoter-uidA fusion gene in transgenic Nicotiana tabacum plants revealed a prominent expression of pronp1 in mature pollen and elongating pollen tubes and significant activity in root hairs of developing seedlings. This expression pattern was distinct from that of any other profilin gene isolated so far. Pronp1 thus represents a unique profilin gene that is activated at the transcriptional level in two kinds of tip-growing cells, pollen tubes and root hairs, both of which require rapid organization of the actin cytoskeleton. The isolation of such a gene has fundamental importance for our understanding of modulation of the actin cytoskeleton at the molecular level.

Contractile Proteins↗

PubMed2001

Molecular mechanisms of DNA damage and repair: progress in plants.

Despite stable genomes of all living organisms, they are subject to damage by chemical and physical agents in the environment (e.g., UV and ionizing. radiations, chemical mutagens, fungal and bacterial toxins, etc.) and by free radicals or alkylating agents endogenously generated in metabolism. DNA is also damaged because of errors during its replication. The DNA lesions produced by these damaging agents could be altered base, missing base, mismatch base, deletion or insertion, linked pyrimidines, strand breaks, intra- and inter-strand cross-links. These DNA lesions could be genotoxic or cytotoxic to the cell. Plants are most affected by the UV-B radiation of sunlight, which penetrates and damages their genome by inducing oxidative damage (pyrimidine hydrates) and cross-links (both DNA protein and DNA-DNA) that are responsible for retarding the growth and development. The DNA lesions can be removed by repair, replaced by recombination, or retained, leading to genome instability or mutations or carcinogenesis or cell death. Mostly organisms respond to genome damage by activating a DNA damage response pathway that regulates cell-cycle arrest, apoptosis, and DNA repair pathways. To prevent the harmful effect of DNA damage and maintain the genome integrity, all organisms have developed various strategies to either reverse, excise, or tolerate the persistence of DNA damage products by generating a network of DNA repair mechanisms. A variety of different DNA repair pathways have been reported that include direct reversal, base excision repair, nucleotide excision repair, photoreactivation, bypass, double-strand break repair pathway, and mismatch repair pathway. The direct reversal and photoreactivation require single protein, all the rest of the repair mechanisms utilize multiple proteins to remove or repair the lesions. The base excision repair pathway eliminates single damaged base, while nucleotide excision repair excises a patch of 25- to 32-nucleotide-long oligomer, including the damage. The double-strand break repair utilizes either homologous recombination or nonhomologous endjoining. In plant the latter pathway is more error prone than in other eukaryotes, which could be an important driving force in plant genome evolution. The Arabidopsis genome data indicated that the DNA repair is highly conserved between plants and mammals than within the animal kingdom, perhaps reflecting common factors such as DNA methylation. This review describes all the possible mechanisms of DNA damage and repair in general and an up to date progress in plants. In addition, various types of DNA damage products, free radical production, lipid peroxidation, role of ozone, dessication damage of plant seed, DNA integrity in pollen, and the role of DNA helicases in damage and repair and the repair genes in Arabidopsis genome are also covered in this review.

Animals↗

PubMed2000

RAPD analysis of seed purity in a commercial hybrid cabbage (Brassica oleracea var. capitata) cultivar.

The use of random amplified polymorphic DNA (RAPD) markers for evaluating seed purity in a commercial F1-hybrid cabbage (Brassica oleracea var. capitata) cultivar is demonstrated. Genomic DNA isolated from single ungerminated seed was found to be suitable for RAPD analysis. DNA from F1-hybrid and its parental lines was subjected to RAPD screening with 36 random decamer arbitrary primers. A total of 241 scorable products were observed with 54 (22%) being polymorphic. The RAPD data showed that the parental lines of this commercial cabbage cultivar were not very closely related. Two primers were chosen for purity testing of the F1-hybrid seeds. The sib (inbred seed; seed from self-pollination of parental lines) contamination results obtained by RAPD analysis were comparable to the commonly used grow-out trial and isozyme analysis, hence showing that RAPD analysis can be used for seed purity testing of commercial hybrid cabbage seeds.

Brassica↗

PubMed1999

Antisense-mediated silencing of a gene encoding a major ryegrass pollen allergen.

Type 1 allergic reactions, such as hay fever and allergic asthma, triggered by grass pollen allergens are a global health problem that affects approximately 20% of the population in cool, temperate climates. Ryegrass is the dominant source of allergens because of its prodigious production of airborne pollen. Lol p 5 is the major allergenic protein of ryegrass pollen, judging from the fact that almost all of the individuals allergic to grass pollen show presence of serum IgE antibodies against this protein. Moreover, nearly two-thirds of the IgE reactivity of ryegrass pollen has been attributed to this protein. Therefore, it can be expected that down-regulation of Lol p 5 production can significantly reduce the allergic potential of ryegrass pollen. Here, we report down-regulation of Lol p 5 with an antisense construct targeted to the Lol p 5 gene in ryegrass. The expression of antisense RNA was regulated by a pollen-specific promoter. Immunoblot analysis of proteins with allergen-specific antibodies did not detect Lol p 5 in the transgenic pollen. The transgenic pollen showed remarkably reduced allergenicity as reflected by low IgE-binding capacity of pollen extract as compared with that of control pollen. The transgenic ryegrass plants in which Lol p 5 gene expression is perturbed showed normal fertile pollen development, indicating that genetic engineering of hypoallergenic grass plants is possible.

Allergens↗

PubMed1999

Male gametic cell-specific gene expression in flowering plants.

The role of the male gamete-the sperm cell-in the process of fertilization is to recognize, adhere to, and fuse with the female gamete. These highly specialized functions are expected to be controlled by activation of a unique set of genes. However, male gametic cells traditionally have been regarded as transcriptionally quiescent because of highly condensed chromatin and a very reduced amount of cytoplasm. Here, we provide evidence for male gamete-specific gene expression in flowering plants. We identified and characterized a gene, LGC1, which was shown to be expressed exclusively in the male gametic cells. The gene product of LGC1 was localized at the surface of male gametic cells, suggesting a possible role in sperm-egg interactions. These findings represent an important step toward defining the molecular mechanisms of male gamete development and the cellular processes involved in fertilization of flowering plants.

Chromatin↗

PubMed1999

Male gametic cell-specific expression of H2A and H3 histone genes.

Formation of the generative cell in flowering plants initiates the male spermatogenesis pathway which eventually culminates in the process of double fertilization. Little is known about the molecular mechanisms operative in the generative cell. Here, we report the isolation and characterization of cDNA clones encoding generative cell-specific histones, gcH2A and gcH3. In situ hybridization analysis revealed that both genes are activated after formation of the generative cell and accumulation of transcripts increases progressively during generative cell maturation. These results suggest that gcH2A and gcH3 mRNAs are products of transcriptional activation of the generative cell nucleus and thus provide the first evidence for male germ line cell-specific gene expression in flowering plants.

Amino Acid Sequence↗

PubMed1999

Genetically engineered plant allergens with reduced anaphylactic activity.

Allergy immunotherapy is based on the administration of increasing amounts of the disease-eliciting allergens in order to yield allergen-specific non-responsiveness. Success of this therapy is associated with modulation of the immune response to allergenic molecules at the level of T-helper cells and the induction of blocking antibodies. The extracts used for immunotherapy are highly heterogenous preparations from natural sources and contain additional components, mostly proteins which are not well defined. Recombinant DNA technology offers novel tools for production of pure and well-characterised allergens for specific immunotherapy. However, high IgE reactivity of pure recombinant allergens is associated with an increased risk of potentially life-threatening anaphylactic reactions. A major improvement in allergen-specific immunotherapy may be achieved by using genetically engineered recombinant allergens with reduced anaphylactic activity. Recently the site- directed mutagenesis technique has been applied successfully to produce variants of major grass, birch and oilseed rape allergens with reduced IgE reactivity but retained T-cell reactivity. These modified allergens with reduced anaphylactic potential are novel candidates for safer and more effective allergen-specific immunotherapy.

Allergens↗

PubMed1998

Engineering of hypoallergenic mutants of the Brassica pollen allergen, Bra r 1, for immunotherapy.

The Brassica pollen allergen Bra r 1 belongs to a new family of Ca2+-binding proteins, characterized by the presence of two potential EF-hand calcium-binding domains. Disruption of these EF-hand motifs by amino acid substitutions demonstrated that both domains of Bra r 1 constitute functional Ca2+-binding sites. Calcium-binding deficient mutants displayed significantly reduced IgE-binding activity. Injection of these mutated Bra r 1 variants into a murine model system showed that mouse IgG raised against the mutants recognized native Bra r 1 in Brassica pollen extracts suggesting the potential use of the engineered allergens for effective immunotherapy.

Allergens↗

PubMed1998

Genetic control of male fertility in Arabidopsis thaliana: structural analyses of postmeiotic developmental mutants.

Seven new male-sterile mutants (ms7-ms13) of Arabidopsis thaliana (L.) Heynh. (ecotype columbia) are described that show a postmeiotic defect of microspore development. In ms9 mutants, microspores recently released from the tetrad appear irregular in shape and are often without exines. The earliest evidence of abnormality in ms12 mutants is degeneration of microspores that lack normal exine sculpturing, suggesting that the MS12 product is important in the formation of pollen exine. Teratomes (abnormally enlarged microsporocytes) are also occasionally present and each has a poorly developed exine. In ms7 mutant plants, the tapetal cytoplasm disintegrates at the late vacuolate microspore stage, apparently causing the degeneration of microspores and pollen grains. With ms8 mutants, the exine of the microspores appears similar to that of the wild type. However, intine development appears impaired and pollen grains rupture prior to maturity. In ms11 mutants, the first detectable abnormality appears at the mid to late vacuolate stage. The absence of fluorescence in the microspores and tapetal cells after staining with 4',6-diamidino-2-phenylindole (DAPI) and the occasional presence of teratomes indicate degradation of DNA. Viable pollen from ms10 mutant plants is dehisced from anthers but appears to have surface abnormalities affecting interaction with the stigma. Pollen only germinates in high-humidity conditions or during in-vitro germination experiments. Mutant plants also have bright-green stems, suggesting that ms10 belongs to the eceriferum (cer) class of mutants. However, ms10 and cer6 are non-allelic. The ms13 mutant has a similar phenotype to ms10, suggesting is also an eceriferum mutation. Each of these seven mutants had a greater number of flowers than congenic male-fertile plants. The non-allelic nature of these mutants and their different developmental end-points indicate that seven different genes important for the later stages of pollen development have been identified.

Arabidopsis↗

PubMed1998

Molecular basis of IgE-recognition of Lol p 5, a major allergen of rye-grass pollen.

Grass pollen, especially of rye-grass (Lolium perenne). represents an important cause of type I allergy. Identification of IgE-binding (allergenic) epitopes of major grass pollen allergens is essential for understanding the molecular basis of interaction between allergens and human IgE antibodies and therefore facilitates the devising of safer and more effective diagnostic and immunotherapy reagents. The aim of this study was to identify the allergenic epitopes of Lol p 5, a major allergen of rye-grass pollen, immunodissect these epitopes further so that the amino acid residues critical for antibody binding can be determined and investigate the conservation and nature of these epitopes within the context of the natural grass pollen allergens. Peptides, 12-13 amino acid residues long and overlapping each other by 4 amino acid residues, based on the entire deduced amino acid sequence of the coding region of Lol p 5, were synthesised and assayed for IgE-binding. Two strong IgE-binding epitopes (Lol p 5 (49-60) and (265-276), referred to as peptides 7 and 34, respectively) were identified. These epitopes were further resolved by truncated peptides and amino acid replacement studies and the amino acid residues critical for IgE-binding determined (Lol p 5 (49-60) residue Lys57 and (265-276) residue Lys275). Sequences of these epitopes were conserved in related allergens and may form the conserved allergenic domains responsible for the cross-reactivity observed between pollen allergens of taxonomically related grasses. Furthermore, due to its strong IgE-reactivity, synthetic peptide Lol p 5 (265-276) was used to affinity-purify specific IgE antibodies which recognised proteins of other clinically important grass pollens. further indicating presence of allergenic cross-reactivity at the level of allergenic epitope. Moreover, Lol p 5 (265 276) demonstrated a strong capacity to inhibit IgE-binding to natural rye-grass pollen proteins highlighting the antibody accessibility to these sequences within the context of the natural allergens. Strong IgE-binding epitopes of Lol p 5 have been identified down to single critical amino acid residues and are shown to occur as linear or continuous domains in the natural conformation of natural Lol p 5 and other group 5 grass pollen allergens. The fact that such an allergenic synthetic epitope has the capacity to strongly inhibit IgE-binding to natural allergens highlight its potential for use as a candidate in future therapeutics to treat pollen-associated allergies.

Allergens↗

PubMed1998

Isolation and collection of two populations of viable sperm cells from the pollen of Plumbago zeylanica.

A protocol is described for individually collecting two populations of sperm cells, Svn and Sua, from pollen of Plumbago zeylanica. Pollen grains were burst in 10 mM MOPS buffer containing 0.8 M mannitol (pH 4.6). Paired sperm cells released from pollen were separated using a microinjector. Svn and Sua were then collected individually with a microinjector, based upon known size differences. Collected sperm cells were washed with isolation medium and transferred to liquid nitrogen until use. Fluorochromatic reaction (FCR) test of isolated sperm cells showed a positive reaction, indicating that the isolated sperm cells are viable; most of the sperm cells retain viability for at least 2 h.

Cell Separation↗

PubMed1998

Plant homologue of human excision repair gene ERCC1 points to conservation of DNA repair mechanisms.

Nucleotide excision repair (NER), a highly versatile DNA repair mechanism, is capable of removing various types of DNA damage including those induced by UV radiation and chemical mutagens. NER has been well characterized in yeast and mammalian systems but its presence in plants has not been reported. Here it is reported that a plant gene isolated from male germline cells of lily (Lilium longiflorum) shows a striking amino acid sequence similarity to the DNA excision repair proteins human ERCC1 and yeast RAD10. Homologous genes are also shown to be present in a number of taxonomically diverse plant genera tested, suggesting that this gene may have a conserved function in plants. The protein encoded by this gene is able to correct significantly the sensitivity to the cross-linking agent mitomycin C in ERCC1-deficient Chinese hamster ovary (CHO) cells. These findings suggest that the NER mechanism is conserved in yeast, animals and higher plants.

Amino Acid Sequence↗

PubMed1998

A comparison of a community mental health centre-based psychiatric service with one based in an outpatient department at the same hospital.

Referrals and response to referrals of two psychiatric services with similar catchment areas of the same hospital, one with a Community Mental Health Care (CMHC) centre and the other based at an outpatient department, were compared over a five-month period. While the service with a CMHC had an increased number of referrals, which may reflect the aims of the CMHC of making mental health services more accessible and less stigmatised, most referrals were from general practitioners and therefore likely to be appropriate. In spite of its increased workload, the time from referral to assessment for the CMHC-based service was significantly shorter than for the outpatient-based service.

Adolescent↗

PubMed1997

Effect of three hours of hypoxia on atrial natriuretic factor gene expression in the ovine fetal heart.

OBJECTIVES: The current study investigated the effects of 3 hours of hypoxia on atrial natriuretic factor gene expression and peptide content in each of the four cardiac chambers of the near-term ovine fetus. STUDY DESIGN: Twenty-three chronically catheterized ovine fetuses at 125 to 129 days' gestation (term 145 days) were used for this study. Fetal hypoxia was induced for 3 hours in 12 fetuses by infusion of nitrogen into the maternal trachea. The remaining fetuses were used as controls. Fetal arterial PO2 and plasma atrial natriuretic factor concentrations were measured during hypoxia. At the end of the hypoxic period atrial natriuretic factor peptide contents and messenger ribonucleic acid levels in each cardiac chamber were determined by radioimmunoassay and Northern blot analysis, respectively. RESULTS: With infusion of nitrogen into the maternal trachea, fetal arterial PO2 was reduced within 30 minutes by an average of 8.0 +/- 0.3 (SEM) mm Hg (p < 0.0001) and remained reduced at this level throughout the entire hypoxic period. Plasma atrial natriuretic factor concentrations increased by 1152 +/- 212 pg/ml (p < 0.003) and the increase was sustained for the duration of hypoxia. Atrial natriuretic factor peptide and messenger ribonucleic acid levels were much higher in the atria than in the ventricles. Hypoxia did not result in alterations of atrial natriuretic factor peptide content or messenger ribonucleic acid abundance in each cardiac chamber. CONCLUSIONS: In the near-term ovine fetus, 3 hours of hypoxia resulted in greatly elevated plasma atrial natriuretic factor concentrations; this response was sustained for the duration of hypoxia. However, the increase was not associated with a detectable change in atrial natriuretic factor peptide content or an induction of atrial natriuretic factor gene expression in the atria and ventricles.

Animals↗