Metal Ion Dependence of the Matrix Metalloproteinase-1 Mechanism

Matrix metalloproteinase-1 (MMP-1) plays crucial roles in disease-related physiologies and pathological processes in the human body. We report here solution studies of MMP-1, including characterization of a series of mutants designed to bind metal in either the catalytic site or the structural site (but not both). Circular dichroism and fluorescence spectroscopy of the mutants demonstrate the importance of the structural Zn(II) in maintaining both secondary and tertiary structure, while UV-visible, nuclear magnetic resonance, electron paramagnetic resonance, and extended X-ray absorption fine structure show its presence influences the catalytic metal ion's coordination number. The mutants allow us to demonstrate convincingly the preparation of a mixed-metal analogue, Co(C)Zn(S)-MMP-1, with Zn(II) in the structural site and Co(II) in the catalytic site. Stopped-flow fluorescence of the native form, Zn(C)Zn(S)-MMP-1, and the mixed-metal Co(C)Zn(S)-MMP-1 analogue shows that the internal fluorescence of a nearby Trp residue is modulated with catalysis and can be used to monitor reactivity under a number of conditions, opening the door to substrate profiling.

Scorpion envenoming in two regions of Colombia: clinical, epidemiological and therapeutic aspects

To determine clinical and epidemiological features of scorpion stings in two departments of Colombia, a descriptive study was performed in the hospitals of 10 towns from Antioquia (2 256 071 inhabitants) and five from Tolima (630 424 inhabitants). One hundred and twenty-nine cases were admitted during one year, 51 in Antioquia, 78 in Tolima and 41 were children less than 15 years old. Most stings (70.5%) occurred inside the house; 27.9% were on the hands and 26.4% on the feet. The scorpion species involved were Tityus pachyurus (51), Centruroides gracilis (31), T. fuehrmanni (29), T. asthenes (7) and Chactas spp. (1). In 10 cases the scorpion involved was not identified. Systemic envenoming signs (e.g. vomiting, tachypnea) were significantly more frequent in children than in adults (P < 0.05). Four children had hypertension, but none developed pulmonary oedema. One 3-year-old girl, stung by T. asthenes, had acute oedematous pancreatitis. Ninety-eight patients had mild envenoming. Moderate (27 patients) and severe (four patients) envenoming was significantly more frequent in children than in adults (P = 0.003; relative risk = 2.97). A pepsin-digested anti-Centruroides spp. antivenom was administered to 19 of 31 patients presenting systemic envenoming signs. No adverse reactions to antivenom were observed.

The sensitivity, specificity, and clinical relevance of gel versus tube DATs in the clinical immunology laboratory

The DAT is a test used to demonstrate in vivo antibody and/or complement coating of RBCs. Typically, the DAT is performed in test tubes; however, recently a number of commercially available tests using gel-filled microtubes have become available. Few data comparing the sensitivity of these test media are available. To compare the rate of detection of a positive DAT performed in test tubes versus in gel-filled microtubes and to assess the clinical significance of the results in patients undergoing evaluation of anemia, we tested 310 consecutive EDTA-anticoagulated blood samples from adult patients. The samples were analyzed using both the conventional tube technique and a gel-based assay (DiaMed; Cressier sur Morat, Switzerland). Test results were expressed as either positive or negative. When a positive result by either technique was encountered, the treating physician was interviewed to determine whether the result warranted further patient investigation or treatment. In 268 out of 310 cases the DAT was negative by both methods. Of the 42 patients with a positive DAT, the test was positive by both methods in 18 patients. In the remaining 24 cases the DAT was positive by the gel test only. In all cases positive by both techniques the test result affected patient management. Of the 24 cases that were positive only by gel test, 3 were judged to be clinically significant. In this study, the gel test was more sensitive than the tube technique for performance of the DAT. However, the clinical significance of a DAT positive only by a gel test is doubtful. We believe that use of the gel-based DAT should be more extensively evaluated before it is adopted as a standard technique in general clinical laboratory practice.

Extended HLA haplotypes in a Carib Amerindian population: the Yucpa of the Perija Range

Eleven MHC loci haplotypes have been defined among a Carib speaking Amerindian population; the Yucpa, inhabiting the northern section of the Perija Range, on the limits between Colombia and Venezuela. This tribe has been known with the name of "Motilones mansos" and is located close to the Chibcha-Paeze speaking Bari or "Motilones bravos." Seventy-three full blooded Yucpa living at the villages of Aroy, Marewa, and Peraya, were selected using a genealogy previously collected by an anthropologist and tested for Bf-C4AB complement allotypes and by serology, high resolution PCR-SSO and SBT typing for HLA class 1 and class 2 alleles. Combinations of 6 HLA-A, 6 HLA-B, 5 HLA-C, 1 Bf, 3 C4AB, 3 DQA1, 3DQB1 and 2 DPA1 and 2 DPB1 alleles present in this population originate 17 different haplotypes, 3 of which represent 63% of the haplotypic constitution of the tribe. The presence of 13 individuals homozygous for 11-loci haplotypes corroborates the existence of the following allelic combinations: DRB1*0411 DQA1*03011 DQB1*0302 DPA1*01 DPB1*0402 with HLA-A*6801 C*0702 B*3909 BfS C4 32 (f = 0.3372) or with A*0204 C*0702 B*3905 (f = 0.1977) and a third haplotype which differs only in DRB1*0403 and A*2402 (f = 0.0930). The results demonstrate the isolation of the tribe and the existence of high frequencies of a reduced number of "Amerindian" ancestral and novel class 1 and class 2 alleles (B*1522, DRB1*0807) with significant linkage disequilibria. These results will be useful to test the hypothesis that differentiation of Amerindian tribal groups will have to rely on haplotypes and micropolymorphism rather than allelic lineage frequencies due to the uniformity shown thus far by the putative descendants of the original Paleo-Indians.

Molecular modeling, affinity labeling, and site-directed mutagenesis define the key points of interaction between the ligand-binding domain of the vitamin D nuclear receptor and 1 alpha,25-dihydroxyvitamin D3

We have combined molecular modeling and classical structure-function techniques to define the interactions between the ligand-binding domain (LBD) of the vitamin D nuclear receptor (VDR) and its natural ligand, 1alpha,25-dihydroxyvitamin D(3) [1alpha,25-(OH)(2)D(3)]. The affinity analogue 1alpha,25-(OH)(2)D(3)-3-bromoacetate exclusively labeled Cys-288 in the VDR-LBD. Mutation of C288 to glycine abolished this affinity labeling, whereas the VDR-LBD mutants C337G and C369G (other conserved cysteines in the VDR-LBD) were labeled similarly to the wild-type protein. These results revealed that the A-ring 3-OH group docks next to C288 in the binding pocket. We further mutated M284 and W286 (separately creating M284A, M284S, W286A, and W286F) and caused severe loss of ligand binding, indicating the crucial role played by the contiguous segment between M284 and C288. Alignment of the VDR-LBD sequence with the sequences of nuclear receptor LBDs of known 3-D structure positioned M284 and W286 in the presumed beta-hairpin of the molecule, thereby identifying it as the region contacting the A-ring of 1alpha, 25-(OH)(2)D(3). From the multiple sequence alignment, we developed a homologous extension model of the VDR-LBD. The model has a canonical nuclear receptor fold with helices H1-H12 and a single beta hairpin but lacks the long insert (residues 161-221) between H2 and H3. We docked the alpha-conformation of the A-ring into the binding pocket first so as to incorporate the above-noted interacting residues. The model predicts hydrogen bonding contacts between ligand and protein at S237 and D299 as well as at the site of the natural mutation R274L. Mutation of S237 or D299 to alanine largely abolished ligand binding, whereas changing K302, a nonligand-contacting residue, to alanine left binding unaffected. In the "activation" helix 12, the model places V418 closest to the ligand, and, consistent with this prediction, the mutation V418S abolished ligand binding. The studies together have enabled us to identify 1alpha,25-(OH)(2)D(3)-binding motifs in the ligand-binding pocket of VDR.

Synthesis and estrogen receptor binding affinity of a porphyrin-estradiol conjugate for targeted photodynamic therapy of cancer

A tetraphenylporphyrin-C11-beta-estradiol conjugate has been synthesized. Competitive binding assay of the conjugate with estrogen receptor (ER)-ligand-binding domain showed that the conjugate binds specifically to the protein with high affinity. Potential use of this conjugate to selectively deliver cytotoxic porphyrins to ER-positive cells in various carcinomas is discussed.

Interpretation of nonstress tests by an artificial neural network

OBJECTIVE

Our purpose was to evaluate an artificial neural network in the interpretation of nonstress tests.

STUDY DESIGN

A nonlinear artificial neural network trained by backpropagation was taught to interpret records of nonstress tests by two learning sets. The first set contained nonstress tests that were similarly interpreted by three human experts; the second set contained a subset of nonstress tests that led to interobserver disagreement. Both "raw" fetal heart rate and uterine contraction data and 17 quantified variables obtained by automated computer analysis were introduced to the input layer. After training, the network was tested by presenting it with input patterns to which it had not been exposed. The performance of the system was examined in relation to the human expert.

RESULTS

After training the neural network with the first set, a sensitivity of 88.9% and a false-positive rate of 4.3% were obtained at testing. When the learning and test set contained records that led to interobserver disagreement, a sensitivity of 86.7% and a false-positive rate of 19.7% were obtained. Sixty percent of fetal heart rate records interpreted as abnormal by the neural network were interpreted likewise by the human experts.

CONCLUSIONS

The results obtained are encouraging in that the neural network could discriminate between normal and abnormal nonstress tests. Further evaluation of this new technique is mandatory to evaluate its efficacy and reliability in interpreting fetal heart rate records.

Banana Ripening: Implications of Changes in Internal Ethylene and CO(2) Concentrations, Pulp Fructose 2,6-Bisphosphate Concentration, and Activity of Some Glycolytic Enzymes

In ripening banana (Musa acuminata L. [AAA group, Cavandish subgroup] cv. Valery) fruit, the steady state concentration of the glycolytic regulator fructose 2,6-bisphosphate (Fru 2,6-P(2)) underwent a transient increase 2 to 3 hours before the respiratory rise, but coincident with the increase in ethylene synthesis. Fru 2,6-P(2) concentration subsequently decreased, but increased again approximately one day after initiation of the respiratory climacteric. This second rise in Fru 2,6-P(2) continued as ripening proceeded, reaching approximately five times preclimacteric concentration. Pyrophosphate-dependent phosphofructokinase glycolytic activity exhibited a transitory rise during the early stages of the respiratory climacteric, then declined slightly with further ripening. Cytosolic fructose 1,6-bisphosphatase activity did not change appreciably during ripening. The activity of ATP-dependent phosphofructokinase increased approximately 1.6-fold concurrent with the respiratory rise. A balance in the simultaneous glycolytic and gluconeogenic carbon flow in ripening banana fruit appears to be maintained through changes in substrate levels, relative activities of glycolytic enzymes and steady state levels of Fru 2,6-P(2).

Rapid oscillations in fructose 2,6-bisphosphate levels in plant tissues

The fructose 2,6-bisphosphate (Fru 2,6-P(2)) content of pea, Pisum sativum, roots and leaves were measured following flooding with water and found to change in times of minutes and to exhibit oscillatory-type changes. Each organ changes its Fru 2,6-P(2) content in a unique pattern in response to environmental disturbances such as flooding or light. For example, when roots of intact illuminated pea plants are flooded, roots decrease their Fru 2,6-P(2) content while simultaneously leaves increase their Fru 2,6-P(2) content; but both organs exhibit oscillatory-type patterns within flooding time of about 30 minutes. Half-change times can be as rapid as 2 to 3 minutes. The endogenous extractable activity of the root pyrophosphate-dependent phosphofructokinase also exhibits an oscillatory pattern upon root immersion slightly after Fru 2,6-P(2) changes occur. We postulate from these results that Fru 2,6-P(2) is a primary signal molecule which enables plants to regulate their metabolism to cope with changing environments.