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Biomedical subjects

B Sarkar

Publications and source records attributed to B Sarkar.

At least 37 records · Page 2Linked to original sources
PubMed1997

Detection of cross-reactive antigens shared by Fusarium oxysporum and Glycine max by indirect ELISA and their cellular location in root tissues.

Pathogenicity test of Fusarium oxysporum on ten cultivars of soybean revealed Soymax and Punjab-1 to be most resistant while JS-2 and UPSM-19 were most susceptible. Antigens were prepared from the roots of all the ten varieties of soybean and the mycelium of F. oxysporum. Polyclonal antisera were raised against the mycelial suspension of F. oxysporum and the root antigen of the susceptible cultivar UPSM-19. Cross reactive antigens shared by the host and the pathogen were detected first by immunodiffusion. The immunoglobulin fraction of the antiserum was purified by ammonium sulfate precipitation and DEAE-Sephadex column chromatography. The immunoglobulin fractions were used for detection of cross-reactive antigens by enzyme-linked immunosorbent assay. In enzyme-linked immunosorbent assay, antigens of susceptible cultivars showed higher absorbance values when tested against the purified anti-F. oxysporum antiserum. Antiserum produced against UPSM-19 showed cross-reactivity with the antigens of other cultivars. Indirect staining of antibodies using fluorescein isothiocyanate indicated that in cross-sections of roots of susceptible cultivar (UPSM-19) cross-reactive antigens were concentrated around xylem elements, endodermis and epidermal cells, while in the resistant variety, fluorescence was concentrated mainly around epidermal cells and distributed in the cortical tissues. CRAs were also present in microconidia, macroconidia and chlamydospores of the fungus.

Antigens↗
PubMed1997

Identification of two poly(A) polymerases in Bacillus subtilis.

Two poly(A) polymerase activities were identified in extracts of a strain of Bacillus subtilis in which the gene for polynucleotide phosphorylase was disrupted. Gel filtration studies showed a large difference in the molecular size of the two poly(A) polymerases. On the other hand, the two enzymes resembled the two major poly(A) polymerases of Escherichia coli both with respect to size and in many of their catalytic properties. The observation that both B. subtilis and E. coli have two poly(A) polymerases with many common properties suggest interesting parallels in the processing of the 3'-ends of mRNA in gram-positive and gram-negative bacteria.

Bacillus subtilis↗
PubMed1997

NMR structure of neuromedin C, a neurotransmitter with an amino terminal CuII-, NiII-binding (ATCUN) motif.

The structure of neuromedin C, a 10-residue bombesin-like neuropeptide with the sequence Gly-Asn-His-Trp-Ala-Val-Gly-His-Leu-Met-NH2, has been investigated. Like human serum albumin, neuromedin C contains the amino-terminal CuII-, NiII-binding (ATCUN) motif which has high affinity for CuII and NiII. The solution structure of the NiII-peptide complex has been calculated based on 2D ROESY data obtained at 25 degrees C, using a hybrid distance geometry-simulated annealing approach. Comparison of 1H, 13C and 15N chemical shifts and ROESY data in the presence and absence of NiII demonstrates that the metal binds at the N-terminus of the peptide, leading to a conformational change. The metal complex adopts a conformation comprising two connected turns including residues 1Gly to 3His and 5Ala to 8His. The first turn corresponds to the NiII coordination ligands in a square planar conformation, and the second reflects the interaction between 4Trp and 8His. The results may have important physiological implications in the phenomenon of neurotransmission.

Amino Acid Sequence↗
PubMed1997

Studies on the aerobic photooxidation of cysteine using riboflavin as a sensitizer: evidence for the photogeneration of a superoxide anion and hydrogen peroxide.

The riboflavin sensitized oxidation of cysteine under an aerobic condition was investigated. The effects of various scavengers, such as superoxide dismutase, catalase, mannitol, sodium azide and potassium ferrocyanide (an electron donor), on the photooxidation were determined. A reaction mechanism involving the superoxide anion is proposed for the photooxidation of cysteine to cysteic acid.

Cysteine↗
PubMed1996

Reversible zinc exchange between metallothionein and the estrogen receptor zinc finger.

We report here the first demonstration that reversible metal exchange occurs between metallothionein (MT) and full-length estrogen receptor (ER). Specific binding of ER to estrogen response element is inhibited in the presence of 40 microM thionein and restored by 120 microM zinc. Moreover, ER in metal-depleted nuclear extracts exhibits reduced DNA binding which can be restored by 140 microM native MT. Hence, thionein inhibits DNA binding by abstracting zinc from functional ER while native MT is capable of restoring binding to metal-depleted extracts by donating metal to ER. This indicates MT may be an important physiological regulator of intracellular zinc and/or other metals.

Base Sequence↗
PubMed1996

The designed protein M(II)-Gly-Lys-His-Fos(138-211) specifically cleaves the AP-1 binding site containing DNA.

A new specific DNA cleavage protein, Gly-Lys-His-Fos(138-211), was designed, expressed, and characterized. The DNA-binding component of the design uses the basic and leucine zipper regions of the leucine zipper Fos, which are represented by Fos(138-211). The DNA cleavage moiety was provided by the design of the amino-terminal Cu(II)-, Ni(II)-binding site GKH at the amino terminus of Fos(138-211). Binding of Cu(II) or Ni(II) by the protein activates its cleavage ability. The GKH motif was predicted to form a specific amino-terminal Cu(II)-, Ni(II)-binding motif as previously defined [Predki, P. F., Harford, C., Brar, P., & Sarkar, B. (1992) Biochem. J. 287, 211 -215]. This prediction was verified as the tripeptide, GKH, and the expressed protein, GKH-Fos(138-211), were both shown to be capable of binding Cu(II) and Ni(II). The designed protein upon heterodimerization with Jun(248-334) was shown to bind to and cleave several forms of DNA which contained an AP-1 binding site. The cleavage was shown to be specific. This design demonstrates the versatility of the amino-terminal Cu(II)-, Ni(II)-binding motif and the variety of motifs which can be generated. The site of cleavage by GKH-Fos(138-211) on DNA provides further information regarding the bending of DNA upon binding to Fos-Jun heterodimers.

Amino Acid Sequence↗
PubMed1996

In vivo and in vitro iron-replaced zinc finger generates free radicals and causes DNA damage.

The estrogen receptor (ER) is a ligand-activated transcription factor whose DNA-binding domain (ERDBD) has eight cysteines, which coordinate two zinc atoms, forming two zinc finger-like structures. We demonstrate the capability of iron to replace zinc in zinc finger (hereby referred to as iron finger) both in vivo (using Escherichia coli BL21 (DE3)) and in vitro. Iron has the ability to substitute for zinc in the ERDBD as demonstrated by mobility shift and methylation interference assays of iron finger, which show specific recognition of the estrogen response element. The DNA binding constants for both in vivo and in vitro iron-replaced zinc fingers were similar to that of the native finger. Atomic absorption analysis revealed a ratio of 2:1 iron atoms/mol of ERDBD protein, as found for zinc in the crystal structure of native ERDBD. More importantly, we demonstrate that iron finger in the presence of H2O2 and ascorbate generates highly reactive free radicals, causing a reproducible cleavage pattern to the proximate DNA, the estrogen response element. The deoxyribose method, used to detect free radical species generated, and the resultant cleaved DNA ends, caused by iron finger, suggest that the free radicals generated are hydroxyl radicals. Due to the close proximity of the zinc finger to DNA, we postulate that iron-substituted zinc finger may generate free radicals while bound to genetic regulatory response elements, leading to adverse consequences such as iron-induced toxicity and/or carcinogenesis.

Base Sequence↗
PubMed1996

Hypokalaemia following nebulized salbutamol in children with acute attack of bronchial asthma.

OBJECTIVE: To determine whether use of nebulized salbutamol therapy for treatment of an acute attack of asthma in children is associated with hypokalaemia and if so what is its frequency, severity and effect on recovery. METHODOLOGY: Forty-six children, aged 10 months to 12 years (mean 7.9 +/- 1.5 years) with acute attack of bronchial asthma, treated initially with three doses of nebulized salbutamol 0.15-0.3 mg/kg, every 30 min participated in the study. Blood for serum potassium was obtained at the beginning and after three doses of nebulized salbutamol therapy, before administering other drugs. RESULTS: The mean +/- SD serum potassium level decreased marginally from 3.9 +/- 0.5 mEq/L to 3.7 +/- 0.5 mEq/L (P < 0.05). A decrease in serum potassium concentration was noted in 26 (56.5%) and hypokalaemia (serum potassium < 3.5 mg/L) in 17 (39%) patients. It was more frequent in patients who had received oral salbutamol for the preceding 7 days. The average time taken for recovery was longer in patients who had hypokalaemia than those who had normal serum potassium concentration (8.6 +/- 2.7 h vs 6.5 +/- 2.7 h; P < 0.005). CONCLUSIONS: Hypokalaemia may occur in about one-third of patients treated with three doses of nebulized salbutamol therapy, especially those on prior oral salbutamol therapy. The monitoring of serum potassium concentration may be warranted in such patients.

Acute Disease↗
PubMed1996

Polyarteritis nodosa--a few unusual findings.

OBJECTIVE: To report the clinical spectrum of polyarteritis nodosa (PAN) from North India and highlight some unusual findings. DESIGN: Retrospective study. SETTING: Hospital based. SUBJECTS: Eight children with PAN. INTERVENTION: Treatment with prednisolone and cyclophosphamide. RESULTS: One child had spontaneous remission while another started deteriorating rapidly in spite of treatment and died within 2 weeks. Six children went into remission-of these one died, two were lost to follow-up and the remaining three are on regular follow-up for periods ranging from 3-5 years. CONCLUSIONS: Prednisolone and cyclophosphamide can significantly improve the outcome in childhood PAN.

Child↗
PubMed1995

Neuromedin C binds Cu(II) and Ni(II) via the ATCUN motif: implications for the CNS and cancer growth.

Neuromedin C is a bombesin-like neuropeptide of the sequence Gly-Asn-His-Trp-Ala-Val-Gly-His-Leu-Met-NH2. Characterization of the amino terminal Cu(II), Ni(II) binding motif in albumins led us to predict that any other peptides or proteins with the same motif would also bind Cu(II) and Ni(II) specifically (1). The primary sequence of neuromedin C contains the motif in the form Gly-Asn-His. Neuromedin C was therefore predicted to bind Cu(II) and Ni(II) specifically. The studies presented here confirm that prediction. These findings may have implications for the transport of Cu(II) within the central nervous system as well as both Menkes disease and Wilson disease. Both are genetic copper metabolism disorders which are characterized by severe neurological symptoms. In addition, Cu(II) may interfere with the neurotransmission or growth factor effects of neuromedin C.

Amino Acid Sequence↗
PubMed1995

Cooperative interaction of oestrogen receptor 'zinc finger' domain polypeptides on DNA binding.

The consensus oestrogen response element (ERE) contains two inverted copies of an AGGTCA consensus hexameric half-site, spaced by three base pairs. It differs from many other hormone response elements, such as consensus thyroid (TREp) and retinoic acid (DR-5 RARE) response elements, only in the relative spacing and orientation of these sequences. In the present study we report values for cooperativity (omega) of an oestrogen receptor DNA-binding domain polypeptide upon binding to these sequences. The polypeptide binds with negative cooperativity, or without cooperativity to retinoic acid and thyroid response elements respectively, but with high cooperativity to the ERE. We have also examined cooperativity upon binding of the polypeptide to an ERE variant. Since naturally occurring EREs commonly contain one hexamer which is considerably more degenerate than the other, we designed a hybrid response element in which one hexamer is a consensus ERE, while specific mutations were introduced into the other. We chose to mutate the second half-site to a glucocorticoid response element (GRE) half-site sequence (AGAACA), since normally no binding of the DNA-binding domain polypeptide to a GRE hexamer alone can be detected. In the hybrid response element, however, the GRE half-site is recognized with relatively high affinity, although binding to this sequence is dependent on the previous binding of a polypeptide to the ERE hexamer. Thus, cooperative interactions are capable of mediating the recognition of ERE sequence degeneracy. The ability of protein-protein interactions to mediate recognition of DNA sequence degeneracy may also have implications for transcription factors in general.

Base Sequence↗
PubMed1995

Benign cutaneous polyarteritis nodosa in children below 10 years of age--a clinical experience.

OBJECTIVE: To report 10 children younger than 10 years of age with benign cutaneous polyarteritis nodosa (BCPAN). METHODS: Ten children aged 1.25-10 years (mean 4.7 years; M:F = 7:3) were admitted with an unusual vasculitis. The clinical features, laboratory investigations, treatment and follow up data were analysed. RESULTS: Clinical features of these patients included: fever (10), peripheral gangrene (eight), livido reticularis (four), ulceration, nodules and vesiculobullous lesions alone or in combination (10), black necrotic patches over limbs and trunk (three), and arthralgia or swelling of large joints (seven). Cryoglobulinaemia was transient in three children, lasting for eight months in one of them. Histopathology of the skin lesions revealed vasculitis of small and occasionally medium sized blood vessels in nine of the 10 children. Possible association of BCPAN was noted with diphtheria-pertussistetanus immunisation (one), drugs (two), streptococcal infection (two), wasp sting (one), and falciparum malaria (one). The clinical course was interspersed with remissions and exacerbations. Response to corticosteroids alone occurred in seven patients, while three children needed cytotoxic drugs in addition. In a follow up of 5.6 years (mean) no evidence of systemic involvement was noted. CONCLUSIONS: A rare form of vasculitis, BCPAN, is reported in children. The features that distinguished our patients from those reported earlier were onset in the first decade of life and higher incidence of peripheral gangrene.

Child↗
PubMed1995

Alteration in alkaline phosphatase activity of duodenal tissue following vestibulo-cerebellar modulation.

Effect of electrolytic lesion in vestibulo-cerebellar area of male Wistar rats was investigated on duodenal alkaline phosphatase (AP) activity. Histomorphological observations of brain indicated, that extensive lesion restricted to the wide area of nodule including ventral uvula, resulted in significant fall of AP activity at the mucosal brush border within 20 days. A comparative behavioural study in experimental and control groups by openfield test indicated that, sympathoexcitation resulting from vestibulo-cerebellar lesion may contribute to significant alteration of AP activity in duodenum of rats.

Alkaline Phosphatase↗