PubMed Health⌕ Search

Biomedical subjects

L Otten

Publications and source records attributed to L Otten.

At least 37 records · Page 2Linked to original sources
PubMed1992

Organization and functional analysis of three T-DNAs from the vitopine Ti plasmid pTiS4.

The vitopine Ti plasmid pTiS4 of Agrobacterium vitis has an unusual T-DNA organization. The pTiS4 oncogenes, localized by screening selected pTiS4 clones for growth-inducing activity, are localized on three T-DNAs, whereas in all other characterized Ti plasmids one or two T-DNAs are found. The nucleotide sequences and predicted amino acid sequences of the pTiS4 oncogenes set them apart from the corresponding genes from other Ti or Ri plasmids. The oncogenes induce the same type of reaction on various test plants as the well-known pTiAch5 oncogenes but the pTiS4 ipt gene induces considerably more shoots than its Ach5 homologue. We have also identified the gene coding for vitopine synthase as well as a vitopine synthase pseudogene. Both sequences show homology to the octopine synthase gene. In terms of both nucleotide sequence and overall organization, the pTiS4 T-DNAs appear to be only distantly related to previously characterized T-DNAs.

Amino Acid Sequence↗
PubMed1992

Physical map of the vitopine Ti plasmid pTiS4.

Within the Agrobacterium vitis group the vitopine strains represent a special subclass. Vitopine bacteria carry Ti plasmids with little or no homology with the well-characterized T-DNAs of Agrobacterium tumefaciens or Agrobacterium rhizogenes. The 262-kb Ti plasmid of the vitopine strain S4 was cloned and mapped. Homology studies with the octopine Ti plasmid pTiAch5, the nopaline Ti plasmid pTiC58, and the agropine/mannopine Ri plasmid pRiHRI identified several regions of homology. The origin of replication was localized to within 2.5 kb.

Drug Resistance, Microbial↗
PubMed1992

Identification of closely related Agrobacterium vitis isolates by chromosomal DNA probes.

Crown gall formation on grapevine by Agrobacterium vitis is an important plant disease in many regions of the world. On grapevine, octopine/cucumopine (o/c) strains are widely distributed. Here we describe two chromosomal sequences of o/c strains of 15 and 20 kb, which reveal a high degree of polymorphism in different o/c isolates. Part of the polymorphism is due to the presence or absence of a 2.2-kb-long repeated sequence, a homolog of which is also found on the octopine Ti plasmid of Ach5, immediately to the left of the left TL-region border. The occurrence and distribution of this repeat in different o/c isolates make it possible to reconstruct the evolution of these strains. The chromosomal DNA sequences outside the repeats also differ in various isolates. The two probes described here can be used to identify strains from a collection, classify new isolates, or trace a given isolate under experimental release conditions.

Base Sequence↗
PubMed1991

35S-beta-glucuronidase gene blocks biological effects of cotransferred iaa genes.

The iaaM and iaaH genes of Agrobacterium tumefaciens and Agrobacterium rhizogenes play an important role in crown gall and hairy root disease. The iaaM gene codes for tryptophan monooxygenase which converts tryptophan into indole-3-acetamide (IAM). IAM is converted into the auxin indole-3-acetic acid (IAA) by indoleacetamide hydrolase, encoded by the iaaH gene. In functional studies on the activity of the iaa genes of the TB region of the A. tumefaciens biotype III strain Tm4, the frequently used 35S-beta-glucuronidase (35S-UidA or GUS) marker gene was found to inhibit IAA synthesis and root induction encoded by the TB iaa genes. To exert this inhibition, the 35S-UidA gene must be cotransferred with the iaaH gene. The 35S promoter alone is sufficient to cause the inhibitory effect.

Amidohydrolases↗
PubMed1991

Sequence of the iaa and ipt region of different Agrobacterium tumefaciens biotype III octopine strains: reconstruction of octopine Ti plasmid evolution.

The TA regions of biotype III octopine/cucumopine (OC) Ti plasmids are closely related to the TL region of the biotype I octopine Ti plasmids pTiAch5 and pTi15955. Sequence analysis shows that the limited and wide host range biotype III OC TA regions are derived from a common ancestor structure which lacked the 6a gene found in the biotype I octopine TL region. The TA region of the wide host range OC Ti plasmids has conserved most of the original TL-like structure. In most wide host range OC isolates the TA-iaaH gene is inactivated by the insertion of an IS866 element. However, the TA region of the wide host range isolate Hm1 carries an intact TA-iaaH gene. This gene encodes a biologically active product, as shown by root induction tests and indole-3-acetic acid measurements. The limited host range OC Ti plasmids pTiAB3 and pTiAg57 have shorter TA regions which are derived from a wide host range TA region. The AB3 type arose by an IS868-mediated, internal TA region deletion which removed the iaa genes and part of the ipt gene and left a copy of IS868 at the position of the deleted fragment. The pTiAB3 iaa/ipt deletion was followed by insertion of a second IS element, IS869, immediately 3' of the ipt gene. pTiAg57 underwent the same iaa-ipt deletion as pTiAB3, but lacks the IS868 and IS869 elements. Analysis of the various TA region structures provides a detailed insight into the evolution of the biotype III OC strains.

Amino Acid Sequence↗
PubMed1991

Exposure of fertile chicken eggs to microwave radiation (2.45 GHz, CW) during incubation: technique and evaluation.

A multi-mode cavity constructed of 22-gauge perforated galvanized steel with a horn irradiator was used to expose chicken embryos to microwave (MW) radiation during incubation. The MW exposure system was placed within an environmental chamber. Mean +/- standard error of mean (SEM) power level was 3.6 +/- 0.02 mW/cm2 and mean egg specific absorption rate was 0.8 mW/g per mW/cm2. Mean temperature of the MW-exposed eggs was 37.5 +/- 0.9 degrees C as monitored by a Luxtron fluoroptic thermometer. Non-irradiated eggs were incubated at 37.5 +/- 0.1 degrees C and 55% relative humidity. There was no significant different in percent fertile eggs hatched between eggs exposed to MW radiation during incubation or eggs incubated conventionally (82.9% and 87.7%, respectively).

Animals↗
PubMed1991

Age-related differences in the metabolism of proteoglycans in bovine articular cartilage explants maintained in the presence of insulin-like growth factor I.

Articular cartilage explants from bovine calf and steer were cultured for up to 19 days in medium with or without 20% fetal bovine serum (FBS) or insulin-like growth factor I (IGF-I). Lower concentrations of IGF-I were required for maximal stimulation of PG synthesis in calf than in steer. In calf, but not in steer, IGF-I was as effective as 20% FBS in stimulating PG synthesis. The stimulation by IGF-I or FBS was not accompanied at either age by alterations in the composition of the aggregating PGs nor by changes in the proportions of CS-rich and CS-poor PG subpopulations. In calf, IGF-I and FBS did not markedly alter the rate of turnover of either the 35S-PGs synthesized in vitro or the unlabeled PGs. In steer, explants cultured in the absence of IGF-I or FBS exhibited very fast rates of turnover and depletion of matrix PG with time; IGF-I and FBS were both effective in reducing the turnover rate of 35S-PGs and unlabeled PGs and in preventing PG depletion.

Aging↗
PubMed1991

Effect of exposure to operant-controlled microwaves on certain blood and immunological parameters in the young chick.

Twenty-two 1-wk-old broiler chicks (Gallus domesticus) were housed at 16 C and operantly conditioned to activate either a 250-W infrared bulb (control) or a microwave generator delivering 13 mW/cm2 (treated). Plasma corticosterone concentration did not differ between groups (P greater than .05) at 4 wk of age. At that time the birds were killed, and post-mortem examination revealed no treatment differences in gross morphology of the chicks or in weights of spleen and bursa of Fabricius (P greater than .05). Histological study of comparable segments of spleen, bursa, adrenal, and thyroid tissue did not show differences in any of the chosen parameters (P greater than .05). Heterophil:lymphocyte ratios, packed cell volume, and total plasma protein content were similar between groups (P greater than .05). These results suggest that operant exposure to low density microwave radiation did not result in stress or immunological disturbances.

Adrenal Glands↗
PubMed1991

Circulating keratan sulfate: a marker of cartilage proteoglycan catabolism in osteoarthritis.

The serum level of a highly sulfated epitope present on long keratan sulfate chains provides a direct measure of the rate of catabolism of cartilage proteoglycans. Levels of the keratan sulfate epitope are elevated in patients with generalized osteoarthritis (OA), indicating these individuals have elevated rates of cartilage proteoglycan catabolism. In the Pond-Nuki model of canine OA, the serum level of the keratan sulfate epitope rises rapidly after the transection of the anterior cruciate ligament, long before OA lesions can be detected, and remains high for at least 13 weeks.

Animals↗
PubMed1990

Functional analysis of a complex oncogene arrangement in biotype III Agrobacterium tumefaciens strains.

The ubiquitous grapevine-associated octopine/cucumopine Ti plasmids of biotype III Agrobacterium tumefaciens strains carry two T regions, TA and TB, with a complex oncogene arrangement. Within the octopine/cucumopine group, two main strain types were identified: 'large TA' strains with a TA region resembling the TL region of the biotype I octopine strain Ach5 and 'small TA' strains with a similar T region organization as the 'large TA' strains but with a large internal TA deletion. Structural and functional studies of the representative 'large TA' strain Tm4 revealed six oncogenes. Each oncogene was inserted in a disarmed vector and tested for biological activity using the corresponding oncogenes of Ach5 as standards. Five Tm4 oncogenes, TA-iaaM, T-ipt, T-6b, TB-iaaH and TB-iaaM, were shown to be active, the IS-interrupted TA-iaaH gene was inactive. To study the role of each gene in the pTiTm4 context, several single and multiple pTiTm4 mutations were constructed. It was shown that whereas TA-iaaM and TB-iaaH are essential for tumour formation on grapevine, T-ipt, T-6b and TB-iaaM are not. The avirulence of the TA-iaaM- mutant was shown to be due to an inhibitory effect of the T-ipt gene, since a TA-iaaM-/T-ipt- double mutant was fully virulent. We conclude that the TA-iaaM gene of 'large TA' strains is specifically required to counteract the tumour growth inhibiting activity of the T-ipt gene. Both TA-iaaM and T-ipt are absent from the 'small TA' strains. A model on the roles and interactions of the different oncogenes in 'large TA' and 'small TA' strains is presented.

Chromosome Deletion↗
PubMed1990

IAA synthesis and root induction with iaa genes under heat shock promoter control.

We have devised a heat shock-inducible indole-3-acetic acid (IAA) synthesis system for plant cells, which is based on the iaa genes of the Agrobacterium tumefaciens T-DNA and the heat shock promoter hsp70 of Drosophila melanogaster. Two DNA constructs were tested: one contains the iaaM gene linked to the hsp70 promoter (hsp70-iaaM) and encodes the production of indoleacetamide (IAM), the other contains hsp70-iaaM and the wild-type iaaH gene which codes for the conversion of IAM into IAA (hsp70-iaaM/iaaH). Heat shock-controlled IAM and IAA synthesis was tested on two levels: biochemically by measuring IAM and IAA levels in Kalanchoe stem segments infected with the two constructs, and morphologically by IAA-dependent root formation on Kalanchoe plants, on carrot discs and on tobacco leaf fragments. At both levels the responses were found to be controlled by the heat shock promoter. IAM levels of segments infected with hsp70-iaaM increased 6-fold upon heat shock induction to 240 pmol IAM per stem segment. The accumulation of IAA in segments infected with hsp70-iaaM/iaaH and heat-shocked was found to be more variable, possibly due to IAA transport and metabolism. Heat shock treatment of Kalanchoe plants and tobacco leaf fragments infected with hsp70-iaaM/iaaH led to a strong increase in root formation. On carrot discs, heat shock-specific root induction was also demonstrated, but the responses differed between individual carrots.

Amidohydrolases↗
PubMed1990

Agrobacterium tumefaciens T-DNA gene 6b stimulates rol-induced root formation, permits growth at high auxin concentrations and increases root size.

All Agrobacterium tumefaciens strains studied up to now transfer an active 6b gene to plant cells. However, the role of this gene in natural tumour induction is unknown. Various effects of 6b on plant cell growth have been described, but the precise mechanism by which 6b causes these effects has not been elucidated. Earlier experiments indicated that the 6b gene might increase auxin sensitivity as do the A. rhizogenes rol genes. The 6b gene from Tm4 (T-6b) was therefore compared with the rolB and rolABC genes. Although T-6b was unable to induce root formation, it strongly interfered with root induction and root elongation. In rolABC/T-6b coinfection experiments on carrots, T-6b-transformed cells stimulated root outgrowth of rolABC-transformed cells, indicating that the biologically active T-6b product is diffusible. Carrot rolABC roots containing the T-6b gene rapidly developed into unorganized calli. Nicotiana rustica roots with rolABC and T-6b continued their development, but became very large. Fragments of such roots formed callus at alpha-naphthaleneacetic acid concentrations which inhibited growth of rolABC and normal root fragments, suggesting that the role of 6b genes in natural tumour induction may be to reduce the inhibitory effects of high auxin levels and to keep cells in an undifferentiated state.

Cloning, Molecular↗
PubMed1990

Identification of different agrobacterium strains isolated from the same forest nursery.

Several Agrobacterium strains isolated from the same forest nursery from 1982 to 1988 were compared by serological, biochemical, and DNA-DNA hybridization methods. Similarities among strains belonging to biovar 2 were observed by indirect immunofluorescence, whereas biovar 1 strains showed serological heterogeneity. Electrophoretic analysis of bacterial envelope-associated proteins showed that few bands appeared in the strains belonging to biovar 1, whereas many proteins appeared in the case of biovar 2 strains. Chromosomal DNA was analyzed with six random C58 chromosomal fragments. None of the six probes hybridized to the DNA of the two biovar 2 strains. One of the probes gave the same hybridization pattern with all biovar 1 strains, whereas the other probes yielded different patterns. The vir regions were closely related in the different pathogenic strains. The T-DNA and replication regions were less conserved and showed some variations among the strains.

Journal Article↗
PubMed1989

Nucleotide sequence, evolutionary origin and biological role of a rearranged cytokinin gene isolated from a wide host range biotype III Agrobacterium strain.

A DNA fragment with homology to the cytokinin (ipt) gene from biotype I Agrobacterium tumefaciens strain Ach5 was cloned from the Ti plasmid of the wide host range biotype III Agrobacterium strain Tm-4 and sequenced. The fragment contains an intact ipt coding sequence. However, the 3' non-coding region of this ipt gene is rearranged due to a 0.9 kb deletion fusing it to the 3' coding region of the neighbouring gene 6a, most of which was found to be deleted. The Tm-4 ipt gene is strongly related to the partially deleted ipt gene of the limited host range biotype III strain Ag162. To test its biological activity, the Tm-4 ipt gene was inserted into a specially constructed, disarmed Ti vector lacking tzs and tested on tobacco, where the rearranged ipt gene induced shoot formation. The cloned Tm-4 ipt gene was mutated with Tn5 and the intact gene on the wild-type Tm-4 Ti plasmid was replaced by the mutated gene. The resulting strain was avirulent on tobacco but normally virulent on the natural host of the wild-type strain Tm-4, grapevine. As the biotype I 6b gene diminishes the effect of a corresponding ipt gene, a larger Tm-4 fragment carrying both the ipt gene and an adjacent 6b-like gene was also tested on tobacco and compared with the Tm-4 ipt fragment alone and with an ipt and 6b/ipt fragment derived from Ach5. The Tm-4 6b gene diminishes the effect of the Tm-4 ipt gene, showing the Tm-4 6b gene to be active as well. The Tm-4 6b/ipt combination is less effective than the Ach5 combination. These results provide further insight into the molecular basis of the host range differences between limited host range and wide host range biotype III Agrobacterium strains and show that the WHR cytokinin gene, although active, does not significantly contribute to tumour formation on the natural host of the WHR biotype III strains, grapevine.

Base Sequence↗
PubMed1989

Sequence and distribution of IS866, a novel T region-associated insertion sequence from Agrobacterium tumefaciens.

We have identified a new insertion sequence, IS866, located in the auxin synthesis gene TA iaaH of Tm4, a wide host range biotype III octopine/cucumopine type Agrobacterium tumefaciens strain with two T regions on its tumor-inducing (Ti) plasmid, TA, and TB. IS866 is 2716 bp long, has inverted repeats of 27 bp with three mismatches, and generates 8-bp direct repeats upon integration. In addition to IS866, pTiTm4 carries two copies of a related element, IS867, associated with TA and TB, respectively. A systematic study of 92 virulent Agrobacterium strains has shown that among the three biotypes all octopine/cucumopine and vitopine biotype III isolates contain IS866-like elements. The various octopine/cucumopine Ti plasmids always carry IS866 and IS867 at the same position as in pTiTm4. The chromosomes of the bacteria which contain these Ti plasmids also carry IS866 and IS867 copies but in varying numbers and locations.

Bacterial Typing Techniques↗
PubMed1987

Performance of male broiler chicks exposed to heat from infrared or microwave sources.

In eight trials, 240 male broiler birds, initially 7 days old, were randomly allocated to three treatments. Treatments were: continuous infrared (CI), intermittent infrared (II; 4 min on, 2 min off, 10 cycles/h), and intermittent microwaves (IM; 2 min on, 4 min off, 10 cycles/h). At the conclusion of the 14-day experimental period the 21-day-old birds were killed. Although there were significant differences (P less than or equal to .05) in mean gain over the 2-wk treatment period between trials, no differences (P greater than .05) were attributed to treatments. There were, however, significant differences in feed:gain ratios between trials and between treatments. Feed:gain ratios of birds kept under CI and II treatments did not differ significantly (P greater than .05). However, feed:gain ratios, 1.61 +/- .04 and 1.57 +/- .04 for CI and II, respectively, differed significantly (P less than or equal to .05) from that of the IM treatment (1.76 +/- .04). The protein content of chicks under II was significantly (P less than or equal to .05) lower than that of birds under IM. There were no differences (P greater than .05) in fat, ash, calcium, and phosphorus content of chicks among treatments.

Animals↗
PubMed1986

Behavioral observations and operant procedures using microwaves as a heat source for young chicks.

Four trials, using operant conditioning procedures, were conducted to study the response of chicks, housed at 16 C, to microwave or infrared heat. Microwave power density was 26 mW/cm2 in Trial 1, 13 mW/cm2 in Trial 2, and 10 mW/cm2 in Trials 3 and 4. Chicks voluntarily demanded between 28 and 63% as much heat (min heat/hr) from microwave source as from infrared source at all power densities. There was no correlation, however, between the ratio of heat demanded and the power density used. There were no significant differences in growth between infrared- or microwave-heated chicks. It is evident from these studies that 8-day-old broiler chicks are capable of associating the performance of a task with a thermal reward provided by the microwaves. They are also able to utilize these microwaves through operant conditioning without any visible detrimental effect to their health or behavior.

Animals↗