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Biomedical subjects

V Kumar

Publications and source records attributed to V Kumar.

At least 271 records · Page 15Linked to original sources
PubMed1993

Use of newborn liver cells as a murine model for cord blood cell transplantation.

There is current interest in using umbilical cord blood cells as a substitute for bone marrow cells (BMC) in human transplantation. However, T cell-depleted BMC are more susceptible to rejection. Because CBC lack mature T cells, mouse newborn liver cells (NLC) were used as a model to investigate the role of T cells in engraftment. BALB/c BMC, C.B-17 scid/scid (SCID) BMC, and BALB/c NLC were transplanted into lethally irradiated BALB/c and (B6 x DBA/2) F1 (B6D2F1) hosts. Splenic 125IUdR incorporation 5 days later assessed engraftment. BALB/c BMC, NLC, and SCID BMC grew well in BALB/c hosts, but only BALB/c BMC grew in B6D2F1 hosts. This suggests that T cells are necessary for engraftment of H-2d stem cells in the B6D2F1 host. Addition of BALB/c thymocytes to SCID BMC or NLC allowed engraftment in the F1 hosts. It appears that NK cells mediated the resistance because their depletion by mAb increased engraftment of SCID BMC or NLC. Anti-NK1.1 mAb and -asialo GM1 serum eliminate all NK cells, although anti-5E6 mAb eliminate a subpopulation of NK cells that responds to Hh-1d (determinant 2+) stem cells. Treatment of F1 hosts with any of these mAb prevented rejection of SCID BMC or BALB/c NLC. Also, activation of NK cells by poly I:C caused rejection of donor cells in the F1 that could not be overcome by the presence of thymocytes. This effect of the poly I:C could also be reversed by mAb depletion of host NK cells. Thus, engraftment of stem cells is influenced by the presence of donor T cells and the activation level of host NK cells.

Animals↗
PubMed1993

A detailed genetic map for the X chromosome of the malaria vector, Anopheles gambiae.

Anopheles gambiae, the primary vector of human malaria in Africa, is responsible for approximately a million deaths per year, mostly of children. Despite its significance in disease transmission, this mosquito has not been studied extensively by genetic or molecular techniques. To facilitate studies on this vector, a genetic map has been developed that covers the X chromosome at an average resolution of 2 centimorgans. This map has been integrated with the chromosome banding pattern and used to localize a recessive, sex-linked mutation (white eye) to within 1 centimorgan of flanking markers.

Alleles↗
PubMed1993

A novel function-associated molecule related to non-MHC-restricted cytotoxicity mediated by activated natural killer cells and T cells.

NK cells and IL-2-propagated splenic T cells mediate non-MHC-restricted cytotoxicity. The molecules involved in this process are not well defined. We describe a novel 66-kDa cell surface molecule called 2B4 that is expressed on cells that mediate non-MHC-restricted cytotoxicity. All resting and rIL-2 cultured NK cells and a significant number of T cells cultured in high doses of rIL-2 are 2B4+. In fresh as well as cultured spleen cells, all non-MHC-restricted cytotoxicity is contained within the 2B4+ population. In addition to defining cells capable of non-MHC-restricted killing, the 2B4 molecule is also involved in modulation of their function. In the presence of anti-2B4, the lytic activity of cultured NK cells and non-MHC-restricted T cells against a wide variety of FcR- and FcR+ targets is greatly augmented. Anti-2B4 is also able to transduce other signals in IL-2-activated NK cells such as IFN-gamma secretion and granule exocytosis. In addition, 2B4+ T cells can specifically lyse the 2B4 hybridoma cells. Unlike many other activation and adhesion molecules (such as murine CD2, LFA-1, and CD16), 2B4 expression is restricted to cells that mediate NK-like killing. Conversely, highly activated T cells that do not express 2B4 do not mediate non-MHC-restricted killing. Together these data suggest that the 2B4 molecule is likely to be a part of a receptor complex or a component of signal-transducing complex on cells that mediate non-MHC-restricted killing.

Animals↗
PubMed1993

Mapping of neutralizing epitopes and the receptor binding site of human interleukin 1 beta.

Antibodies to synthetic peptides of human interleukin 1 beta (IL-1 beta) and to recombinant human IL-1 beta were used to identify epitopes of IL-1 beta associated with the neutralization of its biological activity. Analysis of antisera raised to 17 synthetic peptides derived from the mature IL-1 beta sequence showed that five regions (residues 6-15, 49-80, 58-80, 92-101, and 120-133) were both immunoprecipitating and neutralizing. Using a hexamer epitope mapping method, comparison of the regions recognized by four neutralizing rabbit antisera with those recognized by a rabbit antiserum raised to denatured IL-1 beta suggested two further neutralizing epitopes, residues 39-48 and 83-95. Finally, a neutralizing monoclonal antibody was shown to bind to the peptides 6-11 and 87-95 by peptide binding and mutagenesis. All of these regions appear predominantly on one face of IL-1 beta. The effect of mutations in residues 4-11 and 88-97, which lie within this face, on receptor binding and biological activity was determined. Most of the mutations tested affected both receptor binding and activity, whereas mutations in another face of IL-1 beta (residues 74-80) had no effect. Purification of two of the mutants with reduced bioactivity and receptor binding and analysis by two-dimensional NMR indicated no gross changes in tertiary structure. A third mutant had reduced bioactivity in two different bioassays but no change in receptor binding. Although two-dimensional NMR revealed no gross changes in conformation, small changes did occur at a site distal from that mutated. The data are consistent with other epitope mapping and receptor binding mutagenesis data and suggest that the neutralizing antibodies and receptor recognize different but overlapping regions of IL-1 beta.

Amino Acid Sequence↗
PubMed1993

Linkage of pemphigus vulgaris antibody to the major histocompatibility complex in healthy relatives of patients.

Pemphigus vulgaris (PV) is an autoimmune disease caused by high concentrations of antibody to an epidermal cadherin. The disease is associated with two kinds of HLA-DR4, DQ8 haplotypes dominantly distributed among Jewish patients, and these plus DR6, DQ5 haplotypes in non-Jewish patients. Low levels of the PV antibody were found in 48% of a total of 120 asymptomatic parents, children, and siblings of 31 patients, thus exhibiting dominant inheritance. The inheritance of these low levels of antibody in asymptomatic relatives was linked to the major histocompatibility complex with a highly significant logarithm of the odds score of 9.07, almost always to a DR4 or DR6 haplotype of the patient. Disease appears to occur in susceptible individuals with low levels of antibody when a second factor, either environmental or genetic, induces high levels, sufficient to produce blisters.

Autoantibodies↗
PubMed1993

Photoperiodic control of annual reproductive cycle in subtropical brahminy myna, Sturnus pagodarum.

The aims of this investigation were to: (i) study the effect of the length of photoperiod on the timing of onset of gonadal recrudescence and postreproductive decline in photoresponsivity, and (ii) identify the mechanism(s) involved in the initiation of gonadal recrudescence in the subtropical brahminy myna (Sturnus pagodarum). Two series of experiments were performed using adult birds: (1) Groups of birds were subjected to 12L:12D, 14L:10D, and 16L:8D in January and to 12L:12D and 14L:10D in March. Those exposed to 12L and 14L in March were transferred to longer daylengths (16L:8D, 20L:4D) after 180 days. In the January birds, 14L and 16L induced testicular growth and regression earlier than 12L; also, 16L caused gonadal recrudescence earlier than 14L. The 14L photoperiod, however, induced gonadal development in March birds within 30 days, similar to that found in January birds under 16L:8D. The response of March birds to 12L:12D was, however, similar to those of January birds, except that the time of maximum testicular response and subsequent regression was advanced in the former group. It is concluded that the refractoriness to long day photostimulation is fully dissipated in March but not in January. (2) Groups of unstimulated and stimulated birds were exposed to "resonance" and "interrupted-night" light: dark cycles for 5 weeks. Resonance LD cycles of 12 (8L:4D)- and 36 (8L:28D)-hour induced day responses, while groups under 24 (8L:16D)- and 48 (8L:40D)-hr cycles behaved as if exposed to short days. In night-interruption experiments, a 1 hr light pulse given 12 and 16 hr, but not 20 hr, after dawn induced the long day response. These results suggest that in brahminy myna the time to the onset of gonadal recrudescence and subsequent regression (photorefractoriness) is dependent on the length of photophase as well as time of the year when exposed to stimulatory photoperiods, and that a light-sensitive rhythm with a period of about 24 hr is involved in the photoperiodic induction of gonadal recrudescence.

Animals↗
PubMed1993

Sequence complexity of the S receptor kinase gene family in Brassica.

A genomic library from an S29/S29 self-incompatible genotype of Brassica oleracea was screened with a probe carrying part of the catalytic domain of a Brassica S-receptor kinase (SRK)-like gene. Six positive phage clones with varying hybridisation intensities (K1 to K6) were purified and characterised. A 650-700 bp region corresponding to the probe was excised from each clone and sequenced. DNA and predicted protein sequence comparisons based on a multiple alignment identified K5 as a pseudogene, whereas the others could encode functional proteins. K3 was found to have lost an intron from its genomic sequence. The six genes display different degrees of sequence similarity and form two distinct clusters in a dendrogram. The 98% similarity between K4 and K6, which extends across intron sequences, suggests that these might be very recently diverged alleles or daughters of a duplication. In addition, K2 showed a comparably high similarity to the probe. Clones K1, K3 and K5 cross-hybridised with an SLG29 cDNA probe, indicating the presence of upstream receptor domains homologous to the Brassica SLG gene. This suggests that the previously reported S sequence complexity may be ascribed to a large receptor kinase gene family.

Base Sequence↗
PubMed1993

Incidence of celiac disease identified by the presence of serum endomysial antibodies in children with chronic diarrhea, short stature, or insulin-dependent diabetes mellitus.

We determined the incidence of celiac disease in the western New York area to be 1.29 per 10,000 live births. Celiac disease occurred in 29 children with gastrointestinal symptoms. Two children (1.7%) of 117 with short stature and 10 (4.0%) of 211 with diabetes mellitus had serum anti-endomysial antibodies. We conclude that the incidence of childhood celiac disease in our area is much less than that reported in Europe.

Adolescent↗
PubMed1993

Observations on the morphology of adults and larval stages of Oesophagostomum sp. isolated from man in northern Togo and Ghana.

Infection with Oesophagostomum sp. appears to be extremely common in man in northern Togo and Ghana. Adult specimens were recovered from the intestinal lumen by treatment with pyrantel pamoate and the morphological characteristics of oesophagostomes of man could for the first time be compared with information available on the morphology of oesophagostomes of monkeys. The observations and measurements demonstrated that the species involved is Oesophagostomum bifurcum and that the eggs of this species cannot be differentiated from those of Necator americanus. Both infections occur simultaneously in the population involved. The L1 larvae, too, cannot be differentiated from hookworm L1 larvae. The L3 larvae, however, are characteristic. Diagnoses of human Oesophagostomum infections is based on the detection of these larvae in coprocultures. In the present paper, the eggs, the L1 and L3 larval stages and the adults, are carefully described and photos are given.

Animals↗
PubMed1993

Plasma levels of luteinizing hormone in intact and castrated photosensitive blackheaded buntings (Emberiza melanocephala) exposed to stimulatory and nonstimulatory photoperiods.

Experiments were performed to investigate the effects of castration and/or photostimulation on plasma luteinizing hormone (LH) in photosensitive blackhead buntings. Castration evoked a significant rise in plasma LH in birds held under 8 h light: 16 h darkness (8L:16D). On exposure to 18L:6D for 24 d, both the intact birds and the castrates exhibited a significant rise in plasma LH, although the change in LH levels in the castrates was approximately 8 times greater than in the intact birds. When control birds under 8L:16D which showed no change in plasma LH up to d 13 were transferred to a 36-h resonance cycle (8L:28D), plasma LH rose significantly within 4 cycles of the treatment. Furthermore, the intact buntings showed rapid increase and decrease in the plasma LH levels during a 16-wk exposure to long (16L:8D) but not to short (8L:16D) photoperiods. These results suggest that: i) the photoperiodic drive on LH secretion is inhibited by the testes; ii) the blackheaded bunting has a strong photoresponsive system; and iii) a circadian rhythm of photosensitivity is involved in the photoperiodic time measurement in this species.

Animals↗
PubMed1993

Childhood lichen planus (LP).

In adults, lichen planus (LP) is relatively more common than in children. Among 222 cases of LP, there were 25 (11.2%) children in our study. The majority of the cases were females in the age group of 8-14; the youngest child was 3 years old. Papular and linear types of LP were common in children. There was no familial history of LP in any of the cases. The patients with classic LP lesions responded well to dapsone therapy. This study supports the suggestion of Ramsay and Hurley that childhood LP is more common in the tropics.

Adolescent↗
PubMed1993

Effects of excitatory amino acid receptor agonists and antagonists on the secretion of melatonin, luteinizing hormone and prolactin in the ram.

To assess the role of excitatory amino acids (EAA) as neurotransmitters in the transmission of light information from the retina to the pineal gland, we have determined whether the systemic injection of EAA agonists in Soay rams will mimic the suppressive effect of light on the secretion of melatonin, and whether pretreatment of rams with EAA antagonists will block this effect. In addition, the efficacy of the drugs in affecting neuroendocrine systems was investigated by measuring the changes in the secretion of luteinizing hormone (LH) and prolactin. Injections fo the EAA receptor agonist, NMDA (N-methyl-D,L-aspartate: 4.0 mg/kg iv), and the non-NMDA type EAA receptor agonist, AMPA (DL-alpha-amino-3-hydroxy-5-methylisoxazole-propionic acid: 0.2 mg/kg iv) given at night to rams exposed to long days (16 h light: 8 h darkness), caused no change in the blood plasma concentrations of melatonin. The treatments induced an acute increase in the concentrations of LH, and NMDA, but not AMPA, caused a sustained increase in the concentrations of prolactin. Injections of the specific NMDA-type receptor antagonist, CGP (CGP 37849: 1.0 mg/kg iv) and the non-NMDA-type receptor antagonist, DNQX (6,7 Dinitroquinoxaline-2,3-dione: 0.5 mg/kg iv), given prior to a 1-h light period at night, in rams under long days, caused no change in the light-induced decrease in blood plasma concentrations of melatonin. The drug treatments had no effect on the plasma concentrations of LH, but CGP, and not DNQX, stimulated an acute increase in the plasma concentrations of prolactin. These results provide support for the hypothesis that EAA mechanisms operate in the hypothalamus to regulate the release of peptides and catecholamines which control the secretion of LH and prolactin from the pituitary gland; different sub-types of EAA receptors are involved in the control of the two pituitary hormones. The failure of the treatments to affect the secretion of melatonin may indicate that EAA receptor activation is not involved in the photic relay to the pineal gland, or may merely reflect the inability of the drugs to penetrate into the retina/SCN/pineal neural circuits to produce a response.

2-Amino-5-phosphonovalerate↗
PubMed1993

The circadian nature of melatonin secretion in Japanese quail (Coturnix coturnix japonica).

Plasma melatonin concentrations were measured in Japanese quail held under different photoperiods and constant darkness (< 1 lux). When subjected to LD6:18 (6 hr light: 18 hr darkness), levels rose approximately 2 hr after lights-off, attained a peak level 8 hr after lights off, and subsequently declined to low daytime levels before the next lights-on signal. This generated a distinct daily rhythm in melatonin secretion with a duration of approximately 13 h. On exposing quail to a range of photoperiods, containing 6, 9, 11, 12, 13, 15, 18, or 20 hr of light per day, the onset of melatonin secretion remained essentially similar with the rise occurring soon after lights-off. However, the offset of melatonin secretion was suppressed by the light of the next day and thus a much truncated rhythm was produced under long (> 12 hr) photoperiods. Importantly, between night lengths of 4 to 18 hr (i.e., LD 20:4 to LD 6:18) a linear relationship existed between the duration of night-length and secretion of melatonin with the duration increasing by about 0.8 hr for each additional hour of darkness. If quail were released into darkness following a short (LD 6:18) or long (LD 20:4) day schedule, the rhythm persisted for at least two cycles with peaks occurring at about 24 hr intervals. In those quail coming into darkness from long days (LD 20:4), the rhythm of melatonin secretion decompressed rapidly on both sides of the peak, indicating that both the onset and offset of melatonin secretion were suppressed under long days.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Synovial schistosomiasis of the hip.

Schistosomiasis is a common parasitic infestation in Egypt. We describe the case of a 24-year-old Egyptian man who presented with the signs of acute septic arthritis of the hip and in whom biopsy subsequently revealed schistosome ova in the synovium.

Adult↗