Differential requirements for alpha4 integrins during fetal and adult hematopoiesis

Mice chimeric for the expression of alpha4 integrins were used to dissect the roles of these receptors in development and traffic of lymphoid and myeloid cells. During fetal life, T cell development is alpha4 independent, but after birth further production of T cells becomes alpha4 dependent. Precursors for both T and B cells require alpha4 integrins for normal development within the bone marrow. In contrast, monocytes and natural killer cells can develop normally without alpha4 integrins. Thus, there are lymphocyte-specific, developmentally regulated requirements for alpha4 integrins in hematopoiesis in the bone marrow. We also show that alpha4 integrins are essential for T cell homing to Peyer's patches, but not to other secondary lymphoid organs, including spleen, lymph nodes, and intestinal epithelium.

Prediction of protein secondary structure from amino acid sequence

The conformational parameters Pk for each amino acid species (j = 1-20) of sequential peptides in proteins are presented as the product of P(i,k), where i is the number of the sequential residues in the kth conformational state (k = alpha-helix, beta-sheet, beta-turn, or unordered structure). Since the average parameter for an n-residue segment is related to the average probability of finding the segment in the kth state, it becomes a geometric mean of (Pk)av = II (P(i,k))1/n with amino acid residue i increasing from 1 to n. We then used ln(Pk)av to convert a multiplicative process to a summation, i.e., ln(Pk)av = (1/n)sigma P(i,k) (i = 1 to n) for ease of operation. However, this is unlike the popular Chou-Fasman algorithm, which has the flaw of using the arithmetic mean for relative probabilities. The Chou-Fasman algorithm happens to be close to our calculations in many cases mainly because the difference between their Pk and our ln Pk is nearly constant for about one-half of the 20 amino acids. When stronger conformation formers and breakers exist, the difference become larger and the prediction at the N- and C-terminal alpha-helix or beta-sheet could differ. If the average conformational parameters of the overlapping segments of any two states are too close for a unique solution, our calculations could lead to a different prediction.

Density of muscarinic receptors in rat myocardium during early sepsis

The muscarinic receptor changes in two subcellular fractions of rat myocardium during sepsis, the sarcolemma (SL) and light vesicles (LV), were studied. [3H]-quinuclidinyl benzilate ([3H]-QNB) was used as a radioligand. Sepsis was induced by cecal ligation and puncture (CLP). The septic rats had higher pulse rates and slightly higher blood glucose levels than control rats. The marker enzyme assays revealed that the SL fraction was enriched with 5'-nucleotidase and the Na(+)-K(+)-ATPase activity increased over 20-fold, while the LV fraction showed very little enrichment when compared with the homogenate. [3H]-QNB binding studies showed that Bmax increased by 58.8% in SL with no changes in LV during early sepsis (9 h post-CLP), but there was no significant change in the Kd value. These data indicate that muscarinic cholinergic receptors in rat heart SL increase during early sepsis. Since the muscarinic cholinergic receptors mediate parasympathetic modulation of myocardial contractility, changes in the number of muscarinic receptors in the cardiac SL may have a pathophysiologic significance in the development of hemodynamic changes during sepsis.

The HPV 16 genome induces carcinomas and T-cell lymphomas in transgenic mice

Human papillomavirus type 16 is highly associated with cervical carcinoma. Here we report families of transgenic mice produced by the microinjection of a dimer repeat sequence of the human papillomavirus type 16 genome. Thirty-two transgenic animals in four families developed multiple organ malignancies that appeared in middle age without other intervention. The tumor phenotype of poorly differentiated carcinomas or malignant lymphomas and the transgene cosegregate in these lineages. The tumors arise in the subcutaneous compartment, thoracic cavity, or abdomen; are widely metastatic; and grow rapidly in nude mice. No cervical lesions were identified in six females examined. No rearrangements in transgene E6/E7, E2, and E1 regions were found in tumor tissues, and the truncated E2 region, which was thought to play an important role in human cervical carcinogenesis, was not needed for tumorigenesis in these animals. The transgenic mice produce RNA from the E6/E7 open reading frames, which has been identified in both the carcinomas and the lymphomas, but RNA from the E2 open reading frame is present only in malignant T-cell lymphomas and not in carcinomas, hyperplastic lymphoid tissue, or normal lymphoid tissue.

Cell adhesion events mediated by alpha 4 integrins are essential in placental and cardiac development

alpha 4 integrins are cell surface receptors that mediate cell-extracellular matrix (ECM) and cell-cell adhesions by interacting with fibronectin (FN) and vascular cell adhesion molecule 1 (VCAM-1), respectively. We have generated a null mutation in the gene for the alpha 4 integrin subunit. Homozygous null embryos express no alpha 4 integrins and show two unexpected defects, both of which lead to embryonic lethality. The first defect is failure of fusion of the allantois with the chorion during placentation. The second is in the development of the epicardium and coronary vessels leading to cardiac hemorrhage. Both processes clearly involve alpha 4 integrin interactions that were previously unsuspected. alpha 4 integrin and VCAM-1 are expressed at the sites of these interactions. These results raise the possibility of abortifacients targeting alpha 4 integrins, and raise serious questions about potential side effects of drugs currently being designed to block alpha 4 integrin functions in inflammation.

Conformation of bilirubin oxidase in native and denatured states

The conformation of bilirubin oxidase (EC 1.3.3.5) from Myrothecium verrucaria was studied by circular dichroism (CD). The far-UV CD spectrum showed a single minimum at 215 nm and a maximum near 198 nm, suggesting the dominance of beta-sheets. There was another negative band at 187 nm that is absent from the spectra of model alpha-helix or beta-sheet. CD analysis by the method of Chang et al. agreed well with the estimates based on the Chou and Fasman sequence-predictive method, but the Provencher-Glöckner method of CD analysis agreed well with the sequence-predictive method of Garnier et al. At pH 12 the 215- and 187-nm bands completely disappeared and the protein was denatured. This denaturation was accompanied by the appearance of a large positive band at 250 nm, probably due to ionization of tyrosine residues. In 20 mM sodium dodecyl sulfate the magnitude of the 215-nm band increased, but the spectrum transformed to that of partial helices after heating at 100 degrees C. In 6 M guanidine hydrochloride the far-UV CD spectrum was monotonic and became more negative at the lower wavelength limit (near 212 nm), suggesting that the secondary structure of the protein was disrupted. However, the near-UV CD spectrum retained residual aromatic bands even after heating at 100 degrees C. Thus, our denaturation studies suggest that bilirubin oxidase has a rigid tertiary structure.

Arterialized tendocutaneous venous flap for dorsal finger reconstruction

We describe three cases of combined loss of skin and tendon on the dorsum of the finger that were reconstructed with venous flaps. The technique is feasible and offers a good treatment modality for the small but complex defect on the dorsum of the finger by a one-stage operation.

Eosinophilic granuloma of the skull--report of four cases

Eosinophilic granuloma is a benign form of the three clinical variants of histiocytosis-X. It is an uncommon, localized granulomatous process, forming solitary or multiple lytic skeletal lesions, and primarily involving male children and young adults. We studied 4 cases, three boys and one girl, aged 4, 8, 27 and 12 years, in Chang Gung Memorial Hospital from 1981 to 1990. Their common presentation was the rapidly growing, painful, and protruding scalp masses without neurological deficits. En bloc excisions of these lesions were performed. Then radiotherapy was given postoperatively in two cases, chemotherapy in one, and no adjuvant treatment in one. During their follow-up period of 2 to 10 years, all 4 patients were well, without evidence of recurrence.

Embryonic mesodermal defects in alpha 5 integrin-deficient mice

A loss of function mutation of the murine alpha 5 integrin gene generated by gene targeting in embryonic stem cells is a recessive embryonic lethal. The mutant embryos start to show observable defects by day 9 of gestation and die around day 10–11. The alpha 5-null embryos have pronounced defects in posterior trunk and yolk sac mesodermal structures, suggesting a role for alpha 5 beta 1 integrin in mesoderm formation, movement or function. However, the embryos progress significantly further than embryos null for fibronectin, for which alpha 5 beta 1 integrin is a receptor, suggesting the involvement of other fibronectin receptors. In vitro studies on cells derived from the alpha 5-null embryos confirm that the alpha 5 beta 1 integrin is not expressed on mutant cells and show that the mutant cells are able to assemble fibronectin matrix, form focal contacts, and migrate on fibronectin despite the complete absence of the alpha 5 beta 1 fibronectin receptor integrin. All these functions have previously been thought to involve or require alpha 5 beta 1. The results presented show that these cellular functions involving fibronectin can proceed using other receptors.

Circular dichroic analysis of denatured proteins: inclusion of denatured proteins in the reference set

We hypothesize that inclusion of denatured proteins in the set of reference native proteins may better represent the unordered form in the current circular dichroism (CD) analyses of proteins involving unfolding ones. Adding three denatured-protein spectra and one oligopeptide spectrum to 16 reference protein spectra markedly improved the correlation coefficients (r) between CD calculations and X-ray determinations for the unordered form and, to a lesser extent, for beta-turn, but the r-values for alpha-helix and beta-sheet decreased slightly. With 20 reference proteins the estimates of the unordered form of denatured proteins were significantly improved. Thus, we suggest that as a compromise the new set of reference proteins be used for estimating the changes in conformation for unfolding proteins. However, the current use of 16 reference native proteins appears to be adequate for CD analysis of native proteins and the expansion to 20 reference proteins including denatured ones may not enhance the analysis of native proteins.

Conformation of the abortifacient protein pinellin: a circular dichroic study

The conformation of pinellin was studied by circular dichroism, which showed a minimum at 223 nm and a double maximum at 198-200 nm. The protein was rich in beta-sheet (about 40%) with little alpha-helix, based on current CD analyses. It was stable between pH4 and 10 beyond which it unfolded reversibly, but in alkaline solution, prolongly stored at, say, pH 12, it became irreversibly denatured. Thermal denaturation indicated a transition between 55 degrees and 68 degrees C; the solution at 80 degrees C was partially renatured upon air-cooling back to room temperature. Addition of sodium dodecyl sulfate caused a sharp increase in alpha-helix, which leveled off at 0.25 mM surfactant.

Conformation and activity of Phaseolus coccineus var. rubronanus lectin

The conformation of native and denatured Phaseolus coccineus var. rubronanus lectin was studied by circular dichroism (CD) and correlated to the hemagglutinating activity. The far-UV CD spectrum at 25 degrees C showed a broad, negative band around 223 nm and a positive one at 196 nm. CD data analysis of the lectin indicated a beta-sheet-rich protein. At high temperatures, the spectrum was blue-shifted with increasing magnitude; these changes correlated well with the loss of the activity. The conformation of lectin between pH 2 and 10 remained essentially unchanged. At pH 13 the CD spectrum resembled that of unordered form with a negative band near 200 nm and the activity was completely lost. The denatured lectin in 6 M guanidine hydrochloride would be renatured upon diluting the denaturant to 0.75 M; the changes in CD spectrum again correlated well with the loss of the activity. The effect of sodium dodecyl sulfate on the lectin was drastic; it sharply increased the alpha-helix at the expense of the beta-sheet and reduced the activity; the changes reached a plateau above 20 mM surfactant.

Conformation and activity of mannose- and N-acetylgalactosamine-specific lectins from Vicia villosa seeds

The conformation of two Vicia villosa lectins specific for mannose and N-acetylgalactosamine, respectively, was studied by circular dichroism. Both showed a broad negative CD band around 220 nm and a positive one above 190 nm. CD data analysis indicated that they were rich in beta-sheet. However, they differed in conformational stability against extreme pH, at elevated temperature, and in guanidine hydrochloride and sodium dodecyl sulfate solutions. The unusual feature was that the conformation of N-acetylgalactosamine-specific lectin was virtually unaltered in 6 M guanidine hydrochloride and 7.5 mM surfactant.

Conformational stability of porcine serum transferrin

The conformation of porcine serum ferric transferrin (Tf) and its stability against denaturation were studied by circular dichroism. Tf was estimated to have 19-24% alpha-helix and 50-55% beta-sheet based on the methods of Chang et al. (Chang, C.T., Wu, C.-S.C., & Yang, J.T., 1978, Anal. Biochem. 91, 13-31) and Provencher and Glöckner (Provencher, S.W. & Glöckner, J., 1981, Biochemistry 20, 33-37). Removal of the bound ferric ions (apo-Tf) did not alter the overall conformation, but there were subtle changes in local conformation based on its near-UV CD spectrum. The Tfs were stable between pH 3.5 and 11. Denaturation by guanidine hydrochloride (Gu-HCl) showed two transitions at 1.6 and 3.4 M denaturant. The process of denaturation by acid and base was reversible, whereas that by Gu-HCl was partially reversible. The irreversible thermal unfolding of Tfs began at temperatures above 60 degrees C and was not complete even at 80 degrees C. The bound irons (based on absorbance at 460 nm) were completely released at pH < 4 or in Gu-HCl solution above 1.7 M, when the protein began to unfold, but they remained intact in neutral solution even at 85 degrees C. The NH2- and COOH-terminal halves of the Tf molecule obtained by limited trypsin digestion had CD spectra similar to the spectrum of native Tf, and the COOH-terminal fragment had more stable secondary structure than the NH2-terminal fragment.

Metabolism of [14C]azelastine in guinea pigs

A specific HPLC separation method was used to generate 14C metabolite profiles in lung, muscle, and liver tissue and in bile, urine, and feces obtained from male guinea pigs that received a single oral dose of 1 mg/kg [14C]azelastine. Profiles were also generated in urine and feces of animals that received a single iv dose of labeled drug. In lung and muscle tissue, azelastine (AZ) and desmethylazelastine (DAZ) were the major components of 14C radioactivity. The amount of the amino acid metabolites (2- and 7-ACID), formed by oxidation and azepinyl ring opening, was relatively small. In the liver significant amounts of the 7-ACID were observed in addition to AZ and DAZ. The major metabolite in bile, urine, and feces was the 7-ACID, with much less AZ and DAZ present. The balance of 14C in the form of AZ and three metabolites in excreta (percentage of dose) was: AZ, 9.7-10.5%; DAZ, 8.7-9.6%; 2-ACID, 2.9-3.0%; and 7-ACID, 43.0-54.6%. No large differences in the quantitative profile between the two dosing routes were observed.

Tissue distribution and lung localization of [14C]azelastine in guinea pigs

Tissue distribution was performed in male guinea pigs that received a single oral dose of 1 mg/kg [14C]azelastine. Determination of 14C concentrations by liquid scintillation counting in 16 tissues and by whole-body autoradiography showed preferential uptake of the radioactivity by the lung. The liver had a higher and all other tissues had lower concentrations of 14C than the lung. The lowest 14C concentrations were in the eyes and brain. Light microscopy autoradiography of lung and trachea sections indicated localization of 14C, possibly in alveolar macrophages. The radioactivity cleared completely from lung tissue, as well as from other tissues within 48 hr.

Conformation of concanavalin A and its fragments in aqueous solution and organic solvent-water mixtures

The conformations of concanavalin A (con A), an all-beta protein, and its three CNBr-cleaved fragments were studied by CD. Con A in buffer showed a 197 nm maximum and a 223 nm minimum, which were red-shifted by 6-7 nm from those of regular all-beta proteins and beta-sheet of (Lys)n. Fragment 1 (residue 1-42) resembled an unordered form with a CD maximum at 200 nm, but fragments 2 (residues 43-129) and 3 (residues 130-237) showed a regular CD spectrum with two extrema at 192-193 nm (+) and 214-216 nm (-). Equimolar mixture of the three fragments showed some degree of interaction, but did not reconstitute the conformation of native con A, probably because of the loss of bound Ca2+ and Mn2+ ions in the fragments. In ethanol-, methanol-, and dioxane-water mixed solvents, con A and its fragments remained as beta-sheet. In contrast, addition of trifluoroethanol and sodium dodecyl sulfate induced alpha-helix at the expense of beta-sheet for con A and its fragments in aqueous solution. In 80% trifluoroethanol, the induced helicities exceeded their sequence-predicted helix-potentials, but in 10 mM sodium dodecyl sulfate the helicities agreed well with corresponding predictions.

Beta-II conformation of all-beta proteins can be distinguished from unordered form by circular dichroism

The CD spectrum of certain all-beta globular proteins resembles that of unfolded proteins with a characteristic negative band around 200 nm. The conformation of this class is tentatively termed beta-II, which had two features that were absent for unfolded proteins. First, beta-II proteins usually had CD bands due to aromatic side groups in the near-ultraviolet region. Second, the CD intensities both in the far- and in the near-uv region of these compact and rigid proteins usually showed a sharp transition upon thermal denaturation, whereas those of an unordered form changed linearly with rising temperature.

Felbamate metabolism in pediatric and adult beagle dogs

In a metabolism study, three male and three female pediatric dogs and three male and three female adult beagle dogs received a single oral dose of 60 mg/kg [14C]felbamate. Urine and feces were collected up to 72 hr. Excreta samples were extracted with ethyl acetate and 14C metabolite profiles were generated by HPLC analysis of the extracts. The total 14C dose recoveries were 88.2% for the pediatric and 85.9% for the adult groups; recovery in urine accounted for 61.7 and 69.7%, respectively. The 14C metabolite profiles in urine and feces were similar, with three major peaks corresponding to unchanged felbamate and two hydroxylated metabolites. There was no significant sex difference in profiles within each age group. However, the sum amount of all metabolites in the urine was higher, and the amount of unchanged drug was lower in pediatric dogs. For the 0-24 hr samples, the metabolites/drug ratio in urine was 2.0-2.1 for pediatric dogs and 1.0-1.2 for adult dogs. This indicated a higher metabolic rate in the pediatric dogs.

Felbamate pharmacokinetics in the rat, rabbit, and dog

Rats, rabbits, and dogs were given single iv or single and multiple oral doses of felbamate ranging from 1.6-1000 mg/kg. Absorption of oral drug was complete in all species. The mean Cmax increased with dose from 13.9 to 185.9 micrograms/ml in rats, from 19.1 to 161.9 micrograms/ml in rabbits, and from 12.6 to 168.4 micrograms/ml in dogs. The tmax also increased with dose from 1-8 hr in rats, 8-24 hr in rabbits, and 3-7 hr in dogs. The plasma elimination half-life for the drug increased with dose from 2-16.7 hr in rats, 7.2-17.8 hr in rabbits, and 4.1-4.5 hr in dogs. A proportional increase in Cmax with dose was observed in all species up to 300-400 mg/kg doses. A biexponential equation fitted the drug plasma concentration vs. time data well. For multiple oral doses of 50 mg/kg or less, projected and observed steady-state concentrations agreed well. Animals dosed with [14C]felbamate eliminated most of the radioactivity in urine (58-87.7%), less in feces (7-23.7%), with considerable amounts in the bile. In rats, radioactivity was readily distributed into tissues and crossed the placenta and blood-brain barrier, but no accumulation in any tissue was observed. The volume of distribution was 131, 54, and 72% of body weight for rats, rabbits, and dogs, respectively. Binding of drug to rat, rabbit, and dog plasma proteins ranged from 22.4-35.9%. The overall plasma clearance of the drug for rats, rabbits, and dogs was 327, 52, and 108 ml.h-1.kg-1, respectively. Renal clearance of unchanged drug accounted for an estimated 20-35% and hepatic clearance due to metabolism for 65-80% of the overall clearance.

Felbamate metabolism in the rat, rabbit, and dog

Two major and one minor metabolite of felbamate (FBM) as well as unchanged drug were isolated and identified by electron impact and chemical ionization mass spectrometry from rat and dog urine after dosing with [14C]FBM. The metabolites were 2-(4-hydroxyphenyl)-1,3-propanediol dicarbamate (p-OHF), 2-hydroxy-2-phenyl-1,3-propanediol dicarbamate, and 2-phenyl-1,3-propanediol monocarbamate. The metabolites and FBM were excreted mainly in urine, where their sum accounted to 81-94% of the radioactivity in hydrolyzed rat urine samples, 71-82% in rabbit urine samples, and 69-83% in dog urine samples. The amount of metabolites in the conjugated form was estimated to be 20-35% in rat, 20-30% in rabbit, and 10-20% in dog urine. The major biliary metabolite in all three species was p-OHF, whereas the amount of FBM was small. Metabolites found in dog feces were the same as those in the urine.

Some problems of CD analyses of protein conformation

The circular dichroic (CD) spectra of 16 reference proteins were analyzed by the Provencher-Glöckner method (Biochemistry 20, 31, 1981) with the lower-wavelength limit raised from 190 to 235 nm at 5-nm intervals. Fifty-one data points at 1-nm intervals were taken between 190 and 240 nm. Variations of the correlation coefficients (r) and root-mean-square (RMS) deviations between X-ray diffraction results and CD analyses showed no definite trend with shorter wavelength ranges. The CD spectra (190-240 nm) were also analyzed by assigning the secondary structure of X-ray results according to the Levitt-Greer method (J. Mol. Biol. 114, 181, 1977) and the Kabsch-Sander method (Biopolymers 22, 2577, 1983). The r and RMS values based on the Levitt-Greer assignment were good and comparable to those based on the secondary structure given by crystallographers, but the Kabsch-Sander assignment seemed to give unsatisfactory results. The choice of reference proteins remains one of the uncertainties in the CD analysis. The five most significant orthogonal spectra (190-240 nm) calculated from the 16 reference proteins and those based on another 16 proteins used by Hennessey and Johnson (Biochemistry 20, 1085, 1981) were similar to each other, but different in intensities. These methods still cannot recognize a failed analysis of unknown proteins without X-ray results to check their reliability.