Bacterium genome sequence.
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Bacteriophages↗
Biomedical subjects
V Kumar
Publications and source records attributed to V Kumar.
A truncated mutant (residues 58-140) of the hepatitis B virus X protein retains transactivation function.
The hepatitis B virus X protein (HBx) sequence (154 aa) has been divided into six regions (A-F) based on its sequence homology with X proteins of other mammalian hepadnaviruses. Regions A, C, and E are more conserved and include all the four conserved cysteines (C7, C61, C69, and C137). To localize the regions of HBx important for transactivation, a panel of 10 deletion mutants (X5-X14) and 4 single point mutants (X1-X4), each corresponding to a conserved cysteine residue, was constructed by site-directed mutagenesis. A HBx-specific monoclonal antibody was developed and used to confirm the expression of mutants by Western blot. Transactivation property of the HBx mutants was studied on Rous sarcoma virus-long terminal repeat (RSV-LTR) in transient transfection assays. We observed that deletion of the most conserved region A or substitution of the N-terminal cysteine (C7) had no effect on transactivation. Deletion of the nonconserved regions B or F also had no deleterious effects. Deletions of regions C and D resulted in a significant loss of function. Substitution of both C61 and C69 present in region C, caused almost 90% loss of activity that could be partially overcome by transfecting more expression plasmid. The fully conserved 9 amino acid segment (residues 132 to 140) within region E including C137 appeared to be crucial for its activity. Finally, a truncated mutant X15 incorporating only regions C to E (amino acids 58-140) was able to stimulate the RSV-LTR quite efficiently, suggesting a crucial role played by this domain in transactivation function.
Amino Acid Sequence↗
Purification, crystallization and preliminary X-ray crystal structure analysis of copper amine oxidase from Arthrobacter globoformis.
beta-Phenylethylamine oxidase from the Gram-positive bacterium Arthrobacter globoformis has been crystallized as three crystal forms. Two belong to space group C2 and one to space group P2(1)2(1)2(1), respectively. The unit-cell volumes are consistent with one infunit of 70 644 Da per asymmetric unit for the two monoclinic forms, and with two infunits per asymmetric unit for the orthorhombic crystals. Three-dimensional intensity data have been recorded to 2.8A resolution for one of the monoclinic crystal forms and to 3A, resolution for the orthorhombic crystal form.
Journal Article↗
Significance of IgG-subclass antibody determinations in bullous pemphigoid.
The presence of circulating basement membrane zone (BMZ) antibodies is characteristic of patients with bullous pemphigoid (BP) and are routinely employed in making the diagnosis. The positive tests, however, occur in 50-70% of patients with BP, thus necessitating consideration of other tests in a significant number of patients. The purpose of this study was to examine the efficacy of indirect immunofluorescence (IF) tests specific for various IgG subclasses antibodies to BMZ in BP, especially in patients who are seronegative on routine indirect IF tests with fluorescein-conjugated antibodies to IgG. BMZ antibodies primarily are of IgG4 subclass and are present in all BMZ antibody positive BP cases. Of BP patients negative for BMZ antibodies, 72% were found positive when tested for IgG4 subclass antibodies. In conclusion, testing for IgG4 subclass BMZ antibodies enhances the sensitivity of serum tests from 68.5% to 91%. This may be due in part to the inherent increased sensitivity of the assay and for detecting subclasses of IgG and in part, due to the subclass distribution of the BP antibodies.
Antibodies↗
The photoperiodic clock is blackheaded buntings (Emberiza melanocephala) is mediated by a self-sustaining circadian system.
Three experimental protocols were employed to clarify whether the circadian system is involved in photoperiodic time-measurement in the blackheaded bunting, Emberiza melanocephala. In a single-pulse paradigm, one 8-h light pulse was delivered at different times to groups of birds across three days of constant darkness (DD). Photoperiodic induction, as measured by a rise in plasma luteinizing hormone (LH), showed clear circadian rhythmicity. The second experiment examined the LH responses in birds exposed to lighting cycles using a Nanda-Hamner type of protocol and confirmed full photostimulation under 6L:30D. The third experiment measured the time of the first photoinduced rise in LH in birds subjected to 30 h of continuous light following entrainment under short days (6L:18D). This experiment aimed to identify the position of the photoinducible phase (phi i). LH first rose at hour 18 following dawn indicating that phi i lies in the middle of the day. Plasma concentrations of melatonin were also measured under 6L:18D and 6L:30D light cycles as another physiological marker of the circadian systems in buntings. The pattern of melatonin secretion with the driving oscillator being circadian in nature. It is concluded that the circadian pacemaker driving the photoinducible rhythm in blackheaded bunting is strongly self-sustaining and free-runs under constant conditions.
Animals↗
Murine natural killer cell differentiation: past, present, and future.
Natural killer cells are bone marrow-derived lymphocytes capable of lysing a variety of target cells without prior exposure. While the biological activities and function of mature NK cells have been extensively investigated, the differentiation of NK cells from primitive hematopoietic stem cells is poorly understood. Recently, we have reported on the identification of a highly enriched bone marrow population capable of repopulating recipient mice with mature NK cells. In this review, we will summarize our findings and those of others in an attempt to clarify the current status of murine natural killer cell differentiation.
Allergy and Immunology↗
Effect of amplification or targeted disruption of the beta-lactamase gene of Nocardia lactamdurans on cephamycin biosynthesis.
The bla gene of the cephamycin cluster of Nocardia lactamdurans has been subeloned in the shuttle plasmids pULVK2 and pULVK2A and amplified in N. lactamdurans LC411. The transformants showed two- to threefold higher beta-lactamase activity. Formation of beta-lactamase preceded the onset of cephamycin biosynthesis. The beta-lactamase of N. lactamdurans inactivated penicillins and, to a lesser extent, cephalosporin C but did not hydrolyse cephamycin C. This beta-lactamase was highly sensitive to clavulanic acid (50% inhibition was observed at 0.48 microgram/ml clavulanic acid). The N. lactamdurans bla gene was disrupted in vivo by inertion of the kanamycin-resistance gene. Three bla-disrupted mutants, BD4, BD8 and BD12, were selected that lacked beta-lactamase activity. Overexpresion of the bla gene resulted in N. lactamdurans transformants that were resistant to penicillin whereas mutants in which the bla gene was disrupted were super-sensitive to this antibiotic. The three N. lactamdurans mutants with the bla gene disrupted showed a significant increase of cephamycin biosynthesis in solid medium, whereas transformants with the amplified bla gene produced reduced levels of cephamycin. The cephamycin-overproducing Merck strain N. lactamdurans MA4213 showed no detectable levels of beta-lactamase activity. The beta-lactamase plays a negative role in cephamycin biosynthesis in solid medium, but not in liquid medium.
Anti-Bacterial Agents↗
Comparison of single and trickle infections of pigs with eggs of the Asian Taenia.
Two groups of seven Belgian Landrace piglets each were either infected with a single dose of 3000 or with five consecutive doses of 600 Asian Taenia eggs at weekly intervals. Nine weeks after the first infection all pigs were autopsied and the number of metacestodes was obtained by slicing the liver. There were no significant differences between the mean number of viable or dead cysts present in both groups of animals. Only very low numbers of living metacestodes were found: 0.4% (3/779) of the total number of cysts present in the single infection group and 1.8% (13/707) in the trickle infection group. Circulating antigens could be detected in only four out of 13 animals and no differences in antibody kinetics were present between the two groups of pigs. The presence of high numbers of degenerated cysts in experimental as well as in field conditions seems to indicate that the biotic potential of the Asian Taenia is rather low.
Animals↗
Effects of wavelength and intensity of light in initiation of body fattening and gonadal growth in a migratory bunting under complete and skeleton photoperiods.
A series of experiments investigated the effects of wavelength and intensity of light in initiation of body fattening (gain in body weight) and gonadal growth in migratory blackheaded bunting under complete and skeleton photoperiods. Using fluorescent light at an intensity approximately 700 lx, the first experiment compared the inductiveness of a complete (13 h continuous light coupled with 11 h darkness; 13L:11D) and a skeleton (two light pulses of 6 and 1 h at 6 h apart; 6L:6D:1L:11D) photoperiod. Observations at the beginning and after 3, 8, 10, and 13 weeks of the treatment indicated that both photoperiods were fully inductive but that birds under 13L photoperiod fattened and lost body weight significantly earlier than birds under skeleton photoperiod. In the second experiment, bunting were subjected to 13L:11D (L = 100 lx; D = 0 lx) of white, green (528 nm), and red (654 nm) light for a period of 5 weeks. Birds gained weight and testes grew in all groups except for an inconsistent fattening response in the white light group. The third experiment tested if the inductive effects of 1-h light pulse in a skeleton photoperiod were intensity dependent. Groups of bunting were exposed to 6L:6D:1L:11D (intensity of 1-h white light pulse = 2, 10, 50, or 100 lux) and examined at the beginning and after 3 and 8 weeks of the treatment. Photoinduction occurred at a slower rate and only at 50- and 100-lx intensities. The fourth experiment was similar to the third in design but it employed 1-h light pulse of two different wavelengths (green = 528 nm, and red = 654 nm) at 50- and 100-lx intensities. Birds fattened and testes grew only under red light. The last experiment varied the wavelength and intensity of the first (6 h) light pulse of the skeleton photoperiod (6L:6D:1L:11D): 6-h entraining light pulse of white, green (528 nm), or red (654 nm) colour at 10- or 50-lx intensity was used with 1-h inducing light pulse of white light at approximately 700-lx intensity. Testes grew in all groups but significant fattening occurred only in birds entrained to 50-lx light intensity. These results indicate i) the dissociation of body weight and gonadal responses, in the sense that the timing of photostimulation and/or magnitude of photoperiod-induced body weight and testicular responses differed under various photoperiodic manipulations, and ii) the circadian processes involved in photoperiod-induced responses have differential spectral and intensity sensitivity.
Animals↗
The role of Ly49A and 5E6(Ly49C) molecules in hybrid resistance mediated by murine natural killer cells against normal T cell blasts.
We address the mechanism of hybrid resistance (HR) in vitro using NK effector cells and target lymphoblasts from H-2b, H-2d, and H-2b/d mice. The 5E6 (Ly49C)+ subset of F1 NK cells lyse BALB/c (H-2d) but not B6 (H-2b) targets unless either anti-5E6 or anti-H-2Kb MAbs are present. H-2Dd transgenic B6 (D8) targets are not susceptible to F1 Ly49A+ effectors. Furthermore, 5E6+ Ly49A+ F1 effectors lyse B6 and BALB/c targets only in the presence of anti-5E6 and anti-Ly49A MAbs, respectively. Thus, recognition of H-2Kb by 5E6 and H-2Dd by Ly49A transduce independent inhibitory signals. Moreover, anti-5E6 MAbs enable 5E6+ BALB/c NK cells to lyse (BALB/c x B6)F1 targets. These data support the "missing self" and not the "hemopoietic histocompatibility antigen" hypothesis for HR. In addition, 5E6+ NK cells from BALB/c and BALB.B, but not B6 or (BALB/c x B6)F1, mice receive negative signals from both H-2d and Kb class I antigens. Thus, allelic differences in 5E6 (C57BL versus BALB) may regulate recognition events by NK cells.
Alleles↗
Genetic vaccination: the advantages of going naked.
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Animals↗
Ventriculo-peritoneal shunt requirement in children with posterior fossa tumours: an 11-year audit.
The authors reviewed 175 paediatric patients with posterior fossa tumours treated at the Hospital for Sick Children at Great Ormond Street, London, between 1983 and 1993, in an attempt to determine the requirement for shunt procedures in these children. The age of the patient population ranged from 4 months to 14 years 6 months. The factors evaluated included age at diagnosis, tumour type, extent of surgical resection, and the presence of CSF leak and/or infection. Shunt placement was required postoperatively in 18.9% of patients. Age of the patient was felt to be a significant factor in the need for shunt placement. Tumour type and completeness of tumour excision were also felt to be significant factors affecting the need for post-operative shunt insertion.
Adolescent↗
Integrated genetic map of Anopheles gambiae: use of RAPD polymorphisms for genetic, cytogenetic and STS landmarks.
Randomly amplified polymorphic DNA (RAPD) markers have been integrated in the genetic and cytogenetic maps of the malaria vector mosquito, Anopheles gambiae. Fifteen of these markers were mapped by recombination, relative to microsatellite markers that had been mapped previously. Thirty-four gel-purified RAPD bands were cloned and sequenced, generating sequence tagged sites (STSs) that can be used as entry points to the A. gambiae genome. Thirty one of these STSs were localized on nurse cell polytene chromosomes through their unique hybridization signal in in situ hybridization experiments. Five STSs map close to the breakpoints of polymorphic inversions, which are notable features of the Anopheles genome. The usefulness and limitations of this integrated mosquito map are discussed.
Animals↗
Celiac disease and hypoparathyroidism: cross-reaction of endomysial antibodies with parathyroid tissue.
Celiac disease (CD) is a gluten-sensitive enteropathy characterized by the presence of serum antibodies to endomysial reticulin and gliadin antigens. CD has been associated with various autoimmune endocrine disorders, such as diabetes. We report a rare case of idiopathic hypoparathyroidism with coexistent CD characterized by the presence of serum autoantibodies. Studies were conducted to determine the specificities of these autoantibodies and to localize the antibody binding sites by indirect immunofluorescence and immunoelectron microscopy. Sera from a patient with idiopathic hypoparathyroidism and CD and from two patients with CD alone were tested by indirect immunofluorescence for autoantibodies to parathyroid and endomysial antigens. The specificities of the antibody reactions were determined by testing the sera before and after absorption with monkey stomach tissue. In addition, immunoelectron microscopic studies were performed to determine the localization of the endomysial antigen. Indirect-immunofluorescence studies on the patient's serum were positive with the parathyroid as well as the endomysial substrate. Similar reactions were also observed with the sera of endomysial antibody-positive patients with CD. Absorption of the sera with monkey stomach powder, which is known to have the endomysial antigen, abolished the antibody activities on both the endomysial substrate and the parathyroid tissue. Immunoelectron microscopic studies showed that endomysial antibody activity was associated with antigens localized on the myocyte plasma membrane and in the intercellular spaces. Thus, reactions of the patient's serum with the parathyroid tissue were due to endomysial antibodies and were not parathyroid specific as in patients with idiopathic hypoparathyroidism who did not have coexistent CD. In conclusion, indirect-immunofluorescence tests on parathyroid tissue detect not only tissue-specific antibodies but also cross-reactive antibodies, and this should be taken into consideration when these tests are performed.
Autoantibodies↗
Paediatricians' knowledge of cardiac arrest guidelines.
A telephone questionnaire was undertaken on middle grade trainee paediatricians to test their knowledge of European Resuscitation Council guidelines. Fifty seven responded of whom only 15 (26%) offered a correct sequence of management for asystole and eight (14%) failed to identify adrenaline in their management. For ventricular fibrillation only 18/57 (32%) identified a correct sequence and very poor specific knowledge was identified. Paediatricians will under perform in the event of cardiac arrest in children without improved training in resuscitation.
Child↗
Advances in pharmacotherapy for decline of memory and cognition in patients with Alzheimer's disease.
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Alzheimer Disease↗
Neuroticism in a family practice population in India.
This study was conducted to assess the prevalence of neuroticism and its correlation with the various sociodemographic factors and presenting complaints among patients attending a family practice outpatient clinic. One hundred and forty two consecutive patients attending the outpatient clinic were administered PGI Health Questionnaire N2. Higher incidence of neuroticism was observed in middle age group population, in females (especially housewives), unskilled workers, patients with lower educational status and those belonging to small and nuclear families. A significant number of such patients had presented with vague symptoms, were visiting the clinics frequently and had associated chronic diseases. The results suggest that patients visiting the family practice clinics frequently with multiple somatic complaints with no suggested organic basis should undergo an in-depth psychiatric evaluation.
Adult↗
A novel method for studying preadipocyte differentiation in vitro.
In vitro differentiation of rat preadipocytes has typically been induced in medium supplemented with pharmacological concentrations of hormonal mixtures. These conditions probably do not reflect the milieu within adipose tissue in vivo. We have developed a new method for inducing differentiation of preadipocytes using culture medium which has been conditioned by isolated adipocytes (ACM). In the presence of ACM, 70%-80% of test preadipocytes contained lipid inclusions compared to < 5% of control. When differentiation was assessed by assay of glycerol-3-phosphate dehydrogenase activity, ACM activity was shown to be reproducible and the consistency of response to ACM by different pools of preadipocytes was comparable to that induced by standard differentiation procedures. We have also demonstrated that the adipogenic activity of ACM may not depend on prostaglandin secretion by adipocytes. We propose that use of paracrine factors produced by components of adipose tissue provides a new approach to preadipocyte differentiation induction which may more closely reproduce the adipose tissue environment.
Adenosine↗