The importance of controlled passive mobilization on flexor tendon healing. A biomechanical study

The effects of controlled passive motion on primary tendon repair were studied using the canine forepaw flexor apparatus as experimental model. The animals were divided into seven groups based on duration(3 to 12 weeks post repair) and mode of immobilization and partial mobilization. The repaired tendons were subjected to biomechanical evaluation of their gliding function and tensile strength characteristics. The results showed positive effects of controlled passive motion on tendon repair. The rate of tendon repair was significantly improved over those animals that were continuously immobilized. At 12 weeks, the repaired flexors from the motion group had regained over one-third of the ultimate tensile load as compared to their contralateral intact controls. Of equal importance is that these repaired tendons maintained good gliding function within the sheath during the repair process. The gliding function of these tendons was also significantly better than those subjected to continuous immobilization.

Mosaic structure and mRNA precursors of uteroglobin, a hormone-regulated mammalian gene

The synthesis of uteroglobin in the rabbit uterus is induced by progesterone and is repressed by estrogen which has an over-riding effect over the inducer. The dual hormonal control system offers an excellent model for studying hormonal regulation of mammalian gene expression. Using a full-length uteroglobin cDNA clone as a specific hybridization probe, recombinant lambda phages containing the entire chromosomal uteroglobin gene have been isolated from a rabbit genomic DNA library. Electronmicroscopic analysis of hybrid molecules formed between the chromosomal uteroglobin gene and uteroglobin mRNA indicated the presence of 2 intervening sequences within this gene. The mosaic structure of the uteroglobin gene has been substantiated by detailed restriction mapping and Southern hybridization. The gene is 3.0 kilobases in length to code for a mature mRNA of 465 nucleotides. Northern hybridization of poly(A)-containing RNA from 4-day-pregnant rabbit uterus with the full-length cDNA clone revealed the presence of uteroglobin mRNA precursors. The size of the largest precursor RNA species detected by the cDNA clone is the same as the entire chromosomal uteroglobin gene. The fidelity of the precursor RNAs was established by their ability to hybridize with specific intervening sequence probes. Thus the entire uteroglobin gene is expressed into primary RNA transcripts, which are subsequently processed into mature mRNA molecules by splicing.

The time and history-dependent viscoelastic properties of the canine medical collateral ligament

The viscoelastic properties of the canine medial collateral ligament (MCL) were investigated. Stress-strain relationships at different strain rates, long-term stress relaxation and cyclic stress-strain curves of the MCL were obtained experimentally using a bone-MCL-bone preparation. The experimental data were used in conjunction with the quasi-linear viscoelastic theory as proposed by Fung [15] to characterize the reduced relaxation function, G(t) and elastic response sigma e (epsilon) of this tissue. It was found that the quasi-linear viscoelastic theory can adequately describe the time and history-dependent rheological properties of the canine medial collateral ligament.

Cloning and sequence of cDNA coding for alpha 1-antitrypsin

Recombinant plasmids containing human and baboon cDNA have been screened for alpha 1-antitrypsin, a major serine protease inhibitor present in blood. One plasmid, designated pBa alpha 1a2, was found to contain a cDNA insert of 1352 base pairs coding for the baboon inhibitor. It included 45 nucleotides that code for 15 amino acids present in the amino-terminal signal sequence of the protein, 1182 nucleotides that code for 394 amino acids in the mature protein, a stop codon, and a noncoding region of 76 nucleotides. Comparison of the amino acid sequences of baboon alpha 1-antitrypsin, human antithrombin III, and chicken ovalbumin indicated that these three proteins are about 230% homologous. A second plasmid, designated pH alpha 1a1, was found to contain a human cDNA insert of 306 base pairs. This plasmid coded for 69 amino acids present in the carboxyl-terminal region of human alpha 1-antitrypsin. The human and baboon cDNAs and their amino acid sequences are greater than 96% homologous.

Complete nucleotide sequence of the chicken chromosomal ovalbumin gene and its biological significance

The nucleotide sequence of the entire chicken chromosomal ovalbumin gene has been determined. The gene is 7564 nucleotides in length to code for a mature messenger RNA of 1872 nucleotides. Comparison of the sequence at the 5'-terminal region of the gene with that reported by others has revealed multiple polymorphic nucleotides in the structural, intervening, and flanking DNA sequences. Some of the polymorphic sites occur at positions very close to splice junctions or the eucaryotic promoter sequence, yet apparently have little or no effect on the expression of this gene. The heptanucleotide promoter sequence TATATAT present in the 5'-flanking region of the ovalbumin gene does not occur within the confines of the gene. Nevertheless, multiple Hogness box sequences similar to those found in other eucaryotic genes were delineated within the boundaries of the gene. These internal Hogness box sequences are not used for transcription initiation. Similarly, the hexanucleotide sequence AATAAA common to all eucaryotic messenger RNAs at the 3'-untranslated region occurs seven additional times within the ovalbumin gene. These sites are not used for transcription termination or polyadenylation. Thus, although these sequences may play important roles in the initiation or termination of gene transcripts as well as polyadenylation of the transcripts, the specificity for such biological functions must not reside within these sequences alone. Furthermore, sequences complementary to the highly conserved rat U1 small nuclear RNA have been found throughout the gene. Many of these regions of complementarity occur in the structural sequences. If the small nuclear RNA does play a role in splicing, the specificity must be provided also by other as yet undefined components.

Identification and sequence analysis of the 5' domain of the X and Y pseudo-ovalbumin genes

The expression of the X and Y pseudo-ovalbumin genes is stimulated by estrogen to a much lesser extent than the expression of the authentic ovalbumin gene in the chicken oviduct. Since it is possible that the primary structures of the 5' flanking regions of these genes are responsible for their differential hormonal responses, we have identified the 5' transcription domains of the X and Y pseudo-ovalbumin genes and determined their nucleotide sequences. Similar to many other eukaryotic genes, the X, Y, and ovalbumin genes each contain an (A + T)-rich heptamer located about 30 nucleotides upstream from the cap site. This sequence is TATATAT for the X and ovalbumin genes, but GATATAT for the Y gene. The 5' flanking sequences of all three genes are about 70% homologous when allowances are made for deletions and insertions. There is no obvious feature of the 5' flanking sequences of the pseudo-ovalbumin genes which can be related to differential hormonal responsiveness. Nevertheless, these 5' flanking regions appear to have been conserved relative to the intervening sequences of the pseudogenes, and thus may be important to gene function.

Role of fascia in maintenance of muscle tension and pressure

The effect of fasciotomy on muscle tension (measured by a force transducer attached to the tendon) and interstitial fluid pressure (measured by Wick catheters in the muscle belly) was studied in the anterolateral compartments of 13 dog hindlimbs. Muscle tension and pressure were monitored in the tibialis cranialis muscle after low- and high-frequency stimulation of the peroneal nerve to produce twitch- and tetanic-type contractions. Fasciotomy decreased muscle force during the low-frequency stimulation by 16% (35.3 +/- 4.9 to 28.4 +/- 3.9 N) and during the high-frequency stimulation by 10% (60.8 %/- 4.9 to 54.8 +/- 3.9 N). Muscle pressure decreased 50% after fasciotomy under both conditions, 15 +/- 2 to 6 +/- 1 mmHg and 84 +/- 17 to 41 +/- 8 mmHg), respectively. Repeated functional evaluations during the testing procedure indicated that muscle fatigue was not a major factor in these results. It was concluded that fascia is important in the development of muscle tension and changes in interstitial pressure. Furthermore, the results raised questions concerning the merits of performing a fasciotomy for athletes with a compartment syndrome.

The effect of prolonged physical training on the properties of long bone: a study of Wolff's Law

Five one-year-old immature swine were subjected to twelve months of exercise training. Four matched swine with no training served as controls. After they were killed, four-millimeter-wide strips of bone taken from the anterior, medial, posterior, and lateral quadrants of the central femoral diaphysis were subjected to four-point bending tests to failure. It was found that although exercise did not change the mechanical properties of the cortical bone, it resulted in significant increases in the averaged femoral cross-sectional properties: 17 per cent in cortical thickness, 23 per cent in cortical cross-sectional area, and 21 per cent and 27 per cent in maximum and minimum area moments of inertia, respectively. These changes were due primarily to reduction in the diameter of the medullary canal. The analyses of bone composition showed that the bone density and biochemical contents of the control and exercised animals were similar, but the total volume and the dry, ash, and calcium weights of the exercised bone were significantly higher. These combined results suggest that prolonged exercise has a significant effect on the quantity of the bone, but not on its quality.

CLINICAL RELEVANCE

It has long been recognized that stress deprivation from immobilization in plaster casts results in profound bone atrophy, and it is generally accepted that a minimum level of activity is necessary for homeostasis of bone. These results show that exercise at a level comparable to that prescribed in running fitness programs for humans (65 to 80 per cent of maximum heart rate) can not only maintain homeostasis, but produce actual hypertrophy of bone. This work further suggests the importance of graduated, prolonged, supervised rehabilitation programs in overcoming osteoporotic states.

A cloned calmodulin structural gene probe is complementary to DNA sequences from diverse species

Calmodulin mRNA has been partially purified from a total nucleic acid extract of the electroplax of Electrophorus electricus by oligo(dT)-cellulose chromatography and sucrose gradient centrifugation. A 9- to 10S fraction was determined to contain 39% calmodulin mRNA by translation in a reticulocyte lysate followed by immunoprecipitation with antibodies to calmodulin. Double-stranded cDNA was synthesized from the RNA fraction by using reverse transcriptase from avian myeloblastosis virus. The double-stranded cDNA was joined to pBR322 linearized by restriction endonuclease Pst I and used to transform Escherichia coli RRI. DNAs from 60 tetracycline-resistant cloned hybridized to [32P]cDNA synthesized from the partially purified calmodulin mRNA fraction. By direct DNA sequence analysis, one of these clones, pCM109, was shown to contain calmodulin-specific sequences corresponding to amino acid residues 93--148 of calmodulin or approximately 38% of the peptide-coding region of the calmodulin structural gene sequence. pCM109 was hybridized to DNA isolated from three vertebrate and one plant species by the procedure of Southern. Positive hybridization bands were noted regardless of the DNA source. These data suggest thaat calmodulin gene sequences are evolutionarily conserved, as has been shown to be the case for the primary amino acid sequence.

The effects of exercise on the biomechanical and biochemical properties of swine digital flexor tendons

The digital flexor tendons of the miniature swine were studied after 12 mo of running exercise. Using a newly developed methodology whereby the properties of tendon substance and tendon-bone composite are measured simultaneously, it was found that training augments the strength of the tendon insertion site, but has minimal effect on the tendon substance. Biochemical analyses also showed that the collagen concentration in the tendon substance remains unchanged following exercise. There was also moderate, but not significant, tendon hypertrophy. The present results on flexor tendon differ from those previously obtained for the swine digital extensors [6]. Such difference in response to functional stress may be attributed to the biochemical composition and mechanical properties of these tissues.

Evaluation of reconstituted collagen tape as a model for chemically modified soft tissues

In the last decade a number of chemically fixed, soft tissue based bioprostheses have become commercially available. Chemical fixation of these materials changes a number of their physical and chemical properties. Quantitation of these effects has been difficult because of: anisotropy of the biopolymers, variable composition of the materials, and sample size and configuration limitations. Collagen tape, made from reconstituted collagen, has been chosen as a model material because it alleviates many of the aforementioned problems. Its constituent fibers are homogeneous and unidirectional. The cross-sectional area is constant. Thus, the resultant uniaxial tensile stress-strain relationship is reproducible to allow for systematic parametric studies. Results are presented for the change in tensile properties of the collagen tape as a function of exposure time to glutaraldehyde fixative. These properties are described by the equation: sigma = A (eB epsilon-1) The tensile properties of fresh and fixed pericardial tissue were also tested and corroborative results were found.

Hormonally regulated mammalian gene expression: steady-state level and nucleotide sequence of rabbit uteroglobin mRNA

Uteroglobin is a protein that is synthesized in large quantities by the rabbit uterine endometrial cells and secreted into the uterine lumen around the time of implantation of the developing blastocysts. The protein is also synthesized constitutively at a low level in the lung. In the uterus, synthesis of the protein is induced by progesterone but repressed by estradiol; whereas in the lung, it is not hormonally responsive. Using a full-length cDNA clone, we have established the nucleotide sequence of uteroglobin mRNA and have determined its levels in uterus and lung during early pregnancy. The clone, pUG617, contains all but 24 nucleotides at the 5' untranslated region of the structural gene. To establish the full mRNA sequence, we isolated a 5' end-labeled DNA fragment from pUG617 and extended its length using reverse transcriptase after hybridization with uterine poly(A)-containing RNA. The 5'-terminal sequence of uteroglobin mRNA was established by sequencing the extended DNA fragment. The nucleotide sequence of the peptide-coding portion of the gene has resolved some previously reported discrepancies in the amino acid sequence of the mature protein and those in the signal peptide. By comparison of sequences with a partial uteroglobin cDNA clone isolated by another laboratory, a polymorphic nucleotide at position 246 of the gene has been identified, where a G-A transition has caused an amino acid substitution from aspartic acid to asparagine at residue 46 of the mature protein. Analysis of steady-state RNA levels in the uterus has shown that the induction and repression of uteroglobin synthesis during early pregnancy is the result of accumulation and depletion of its mRNA, respectively. During the same period in the lung, no consistent changes in uteroglobin mRNA level were evident, reflecting the constitutive levels of the protein in this tissue.

Differential hormonal responsiveness of the ovalbumin gene and its pseudogenes in the chick oviduct

We describe the isolation of recombinant phages from a chicken gene library which contain two genes designated X and Y. These two genes are linked to the ovalbumin gene (OV) in the order 5'-X-Y-ovalbumin-3' [Royal, A., Garapin, A., Cami, B., Perrin, F., Mandel, J. L., LeMeur, M., Bregegegre, F., Gannon, F, LePennec, J. P., Chambon, P., & Kourilsky, P. (1979) Nature (London) 279, 125-132]. Both genes contain multiple intervening sequences and share limited sequence homology with the authentic ovalbumin gene but are expressed in oviduct cells at different levels. X and Y hybridization probes were prepared in order to study the expression and the relative hormonal responsiveness of these three genes in chicken oviduct. The sequence specificity of the probes was demonstrated by Southern hybridization assays. Northern hybridization studies using the X and Y gene probes indicated the presence of putative precursor molecules in stimulated oviduct ribonucleic acid preparations, which differ in size from those observed for ovalbumin. R0t analysis has demonstrated that, similar to the ovalbumin gene, the level of X and Y gene transcripts is increased by the steroid hormone estrogen, but to varying degrees. The extent of hormonal responsiveness of the three closely related genes is in the order (normalized) relative to ovalbumin of OV:Y:X congruent to 100:10:1. Pulse-labeling studies of these three closely linked genes suggest that in estrogen-stimulated oviduct, the markedly different steady-state levels of the X, Y, and ovalbumin gene transcripts reflect their differential transcription rates.

Cloning and analysis of a cDNA coding for bovine prothrombin

Poly(A)-RNA enriched for prothrombin was isolated by specific immunoprecipitation of bovine liver polysomes. Prothrombin consisted of about 8% of the cell-free translation products of this RNA. A double-stranded cDNA was synthesized by using reverse transcriptase (RNA-dependent DNA nucleotidyltransferase) and made blunt-ended with nuclease S1. After tailing with dCTP and terminal transferase, the double-stranded cDNA was annealed to pBR322 DNA that had been cleaved previously at the single Pst I site and similarly tailed with dGTP. The resulting plasmids were used to transform Escherichia coli strain RR1 under P3-EK1 conditions. Sixty-three tetracycline-resistant clones were obtained that hybridized to 32P-labeled cDNA synthesized from prothrombin-enriched mRNA. Recombinants containing cDNA to prothrombin mRNA sequences were screened by a solution hybridization assay with a [3H]cDNA synthesized from mRNA. This enriched mRNA was 50% prothrombin mRNA, as determined by a reticulocyte lysate translation assay. Three positive clones were identified by this assay; they contained bovine DNA inserts of 700, 500, and 400 base pairs. The DNA sequence of the 700-base-pair insert was then determined. This recombinant plasmid contained DNA coding for the carboxyl-terminal 160 residues of bovine prothrombin followed by a noncoding region of 119 base pairs and a poly(A) tail of 60 base pairs.

Internal fixation plates after fifty-six years of implantation: report of a case

Lane plates removed and examined after 56 years in the femur of a 77-year-old man were markedly corroded. There was no loss of tensile strength, but other structural properties were altered and inflammation may have been locally induced by leaching of metal ions from the steel alloy.

Principles of less rigid internal fixation with plates

The paradox of internal fixation for treating fractures is that fixation is required to achieve union, while flexibility is necessary to restore normal mechanical properties of bone after union. Three series of experiments were performed to investigate the role of plate rigidity on fracture repair and changes in bone mass. Using plates with tenfold differences in axial and bending rigidities, the authors were able to show some advantages in fracture healing and bone remodelling with less rigid plates.

Quasi-linear viscoelastic properties of normal articular cartilage

A combined experimental and analytical approach was used to determine the history-dependent viscoelastic properties of normal articular cartilage in tension. Specimens along the surface split line direction, taken from the middle zone of articular cartilage were subjected to relaxation and cyclic tests. A quasi-linear viscoelastic theory proposed by Fung was used in combination with the experimental results to determine the nonlinear viscoelastic properties and the elastic stress-strain relationship of normal articular cartilage.

The biomechanical and biochemical properties of swine tendons--long term effects of exercise on the digital extensors

Positive effects on the tensile characteristics of swine digital extensors were found following twelve months of exercise training. Compared to sedentary controls, the tendons from the exercised animals became stronger as a material and exhibited hypertrophy. These biomechanical results were supported by biochemical analyses of tendon composition. Exercise increased the concentration of collagen as well as the total weights of the tendons. For determining stress and strain in tendon material, we used specially designed instruments to measure the tendon cross-sectional area, and a video dimensional analyzer system to measure accurately its "non-contact" tensile strain. With these newly developed apparatus, the mechanical properties of the tendons were accurately determined so that the effects of exercise training could be compared.

Ovalbumin is synthesized in mouse cells transformed with the natural chicken ovalbumin gene

The entire chicken ovalbumin gene, accompanied by genomic DNA sequences flanking both termini of the gene and three copies of the herpes simplex virus thymidine kinase gene, has been cloned in plasmid pBR322. This recombinant plasmid was linearized and used to transform thymidine kinase-deficient mouse cells. Thymidine kinase-positive transformants were selected by their ability to grow in the hypoxanthin/aminopterin/thymidine (HAT) medium. The entire ovalbumin gene integrated into high molecular weight DNA within all the transformants and retained its original sequence organization. In all of the transformants examined, a protein identified as chicken ovalbumin by immunoreactivity was detected within the cells. It is estimated that between 1000 and 100,000 molecules of chicken ovalbumin were produced per mouse cell in each of these transformants. Our results demonstrate that the mouse cellular machinery can be utilized to accurately express genetic information encoded in a cloned gene from a different eukaryotic organism into its specific protein product.

Molecular structure and flanking nucleotide sequences of the natural chicken ovomucoid gene

Five independent clones containing the natural chicken ovomucoid gene have been isolated from a chicken gene library. One of these clones, CL21, contains the complete ovomucoid gene and includes more than 3 kb of DNA sequences flanking both termini of the gene. Restriction endonuclease mapping, electron microscopy and direct DNA sequencing analyses of this clone have revealed that the ovomucoid gene is 5.6 kb long and codes for a messenger RNA of 821 nucleotides. The structural gene sequence coding Ifor the mature messenger RNA is split into at least eight segments by a minimum of seven intervening sequences of various sizes. The shortest structural gene segment is only 20 nucleotides long. All seven intervening sequences are located within the peptide coding region of the gene, and the sequences at the 5' and 3' untranslated regions of the mRNA are not interrupted by intervening sequences. The DNA sequences of the regions flanking the 5' and 3' termini of the gene have been determined. Thirty nucleotides before the start of the messenger RNA coding sequence is the heptanucleotide TATATAT, which is also present in a similar location relative to the chicken ovalbumin gene and other unique sequence eucaryotic genes. This sequence resembles that of the Pribnow box in procaryotic genes where a promoter function has been implicated. Seven nucleotides past the 3' end of the gene is the tetranucleotide TTGT, a sequence found to be present at identical locations as either TTTT or TTGT in other eucaryotic genes that have been sequenced. These conserved DNA sequences flanking eucaryotic genes may serve some regulator function in the expression of these genes.

The ovalbumin gene: cloning and molecular organization of the entire natural gene

We report the analyses of recently cloned restriction fragments of the natural ovalbumin gene that overlap in part with previously cloned DNA fragments but extend further into the flanking sequences of the gene. These clones now permit us to identify the DNA sequence that codes for the 5' end of ovalbumin mRNA. Based on these and previous results, the molecular organization of the entire ovalbumin gene was established. The entire gene is composed of eight structural DNA sequences separated by seven intervening sequences that are not present in the mature mRNA. In addition, an ovalbumin gene clone has been obtained from a chicken gene library. Analysis of DNA isolated from this particular clone by molecular hybridization and electron microscopic mapping revealed that it contains the entire ovalbumin gene a single segment of DNA and its structure was consistent with that predicted from our physical map constructed from individually cloned fragments of the gene.

The chick ovomucoid gene contains at least six intervening sequences

A 15-kilobase pair EcoRI chick DNA fragment, containing both the termination codon UGA and the 5'-portion of the structural ovomucoid gene, has been cloned in lambda phage Charon 4A by in vitro packaging. Restriction mapping and electron microscopic analyses of this cloned DNA have revealed that the structural ovomucoid gene sequences are separated by at least six intervening sequences.

The ovalbumin gene: alleles created by mutations in the intervening sequences of the natural gene

Two allelic forms of the natural chicken ovalbumin gene have been independently cloned. These alleles differ from each other by an Eco RI restriction cleavage site in one of the seven intervening sequences within the natural ovalbumin gene. Restriction endonuclease mapping and sequence analyses of these cloned genotypic alleles have shown identical sequence organization and molecular structures of the interspersed structural and intervening sequences except for the particular Eco RI cleavage site. Sequencing data of the cloned DNA suggest that this Eco RI site may be created or eliminated by a single base mutation in the intervening sequence of the ovalbumin gene. The occurrence of apparent homozygous and heterozygous allelic forms of the ovalbumin gene in individual hens and roosters within the same breed has been observed. 10 and 40% of the chickens examined are homozygous for the ovalbumin gene with and without the extra Eco RI site, respectively, while 50% of them are heterozygous. Further analysis of individual chicken DNA cleaved by restriction endonuclease Hae III has revealed that there may be a series of such mutational variations within the ovalbumin gene. We have identified two Hae III cleavage sites that do not occur in all of the chickens, thus giving rise to several additional allelic variations of the ovalbumin gene. At least one of these Hae III sites is situated in the intervening sequence of the ovalbumin gene, and its lcoation has been mapped. Such allelic variations must be taken into consideration when determining eucaryotic gene structure by restriction mapping of the genomic DNA. Furthermore, this type of mutation within the intervening sequences of an eucaryotic gene has no known phenotypic manifestation. It represents an extrastructural silent mutation that must be taken account of in studies to estimate the rates of eucaryotic gene sequence divergence during evolution.

Nascent chicken ovalbumin contains the functional equivalent of a signal sequence

Highly purified mRNA for chicken ovalbumin has been translated in a cell-free protein synthesizing system from rabbit reticulocytes in the presence or absence of EDTA-stripped microsomal membranes from dog pancreas. Nascent--but not completed--ovalbumin was transferred across the microsomal membrane, as demonstrated by cotranslational core glycosylation of ovalbumin nascent chains, by resistance to posttranslational proteolysis of only the glycosylated ovalbumin chains, and by cosedimentation with the membrane of exclusively the glycosylated form. Furthermore, nascent chains of bovine prolactin were observed to compete with nascent ovalbumin for transfer across the microsomal membrane. However, no competition for membrane sites was observed between nascent chains of rabbit globin and either nascent ovalbumin or prolactin. We interpret these results to suggest that nascent ovalbumin contains the functional equivalent of a signal sequence for transfer across membranes, and that membrane components involved in the segregation of secretory proteins with cleaved signal sequences also function in the segregation of ovalbumin.

The ovalbumin gene: cloning of the natural gene

The structural ovalbumin DNA sequences are not contiguous and are separated by multiple "intervening regions" in native chicken DNA. EcoRI, a restriction endonuclease that does not cleave the structural ovalbumin DNA sequences, digests the natural ovalbumin gene into three distinct fragments of 2.4, 1.8, and 9.5 kilobase pairs in length by cleaving within these "intervening regions." The 2.4-kilobase pair fragment contains only about 450 nucleotide pairs of coding sequence, with the rest being intervening sequences. This DNA fragment was cloned in bacteria by using the certified EK2 vector lambdagtWES.lambdaB after enrichment from total EcoRI-digested chicken DNA by a combination of RPC-5 column chromatography and preparative agarose gel electrophoresis. Five out of approximately 20,000 recombinant phage plaques were capable of hybridizing with a (32)P-labeled Hha I fragment of a recombinant plasmid pOV230 containing the entire structural ovalbumin gene. DNA amplified in these recombinant phages, lambdagtWES.OV2.4, was shown to contain the same restriction endonuclease cleavage sites as in the 2.4-kilobase pair EcoRI fragment previously determined by restriction mapping of total genomic chicken DNA. The intervening sequences were allowed to hybridize with excess total chicken DNA and oviduct nuclear RNA after nick-translation. They were found to be unique chicken DNA sequences, and appeared to be transcribed in their entireties during gene expression. Like the structural gene sequences, the expression of the intervening sequences is also inducible by steroid hormones.

The natural ovalbumin gene contains seven intervening sequences

EcoRI fragments of the natural ovalbumin gene were cloned and studied by hybridisation with mature ovalbumin mRNA, electron microscopy, restriction enzyme mapping and limited sequence analysis. The structural gene sequences coding for ovalbumin were found to be separated into eight sequentially orientated pieces by seven intervening sequences of various lengths.

The ovalbumin gene: structural sequences in native chicken DNA are not contiguous

The sequence organization of the structural ovalbumin gene and flanking sequences in native chicken DNA was studied by restriction mapping and filter hybridization using a nick-translated probe generated from pOV230, a recombinant plasmid that contains a full-length ovalbumin DNA synthesized from ovalbumin mRNA. The structural sequences of the ovalbumin gene in native chicken DNA were found to be noncontiguous because at least two restriction endonucleases that do not cut the structural sequence do cleave the natural gene into multiple fragments by cleaving within nonstructural sequences interspersed between the structural sequences. The observation that all ovalbumin DNA-containing sequences were contained within a single DNA fragment generated by BamHI digestion of total chicken DNA has allowed us to construct an inclusive restriction map of the natural ovalbumin gene which contains at least two "insert regions." These regions may be further subdivided into alternating structural and insert sequences. Both insert regions were located within the peptide-coding regions of the gene and the sizes of these insert regions were estimated to be approximately 1.0 and 1.5 kilobase pairs, respectively.

Biomechanics and biochemistry of the intervertebral disks: the need for correlation studies

The literature on the biomechanics of the intervertebral disk is reviewed with emphasis on biomechanical--biochemical--morphological correlative studies. The deficiency of definitive correlative studies is apparent and an appeal is made to interested investigators to fill in the voids in this extremely important area of study. A comprehensive theory of intervertebral disk failure awaits application of existing biomechanical, biochemical and morphological techniques in a detailed and methodical manner to the normal and early degenerative human intervertebral disks.

The ovalbumin gene. Insertion of ovalbumin gene sequences in chimeric bacterial plasmids

Double-stranded ovalbumin DNA was amplified and purified by the cloning of bacterial transformants. The double-stranded DNA was synthesized from a complete complementary DNA transcript of ovalbumin mRNA using Escherichia coli DNA polymerase I and the self-priming ability of the initial transcript. After S. nuclease treatment, poly(dA) was added to the 3' termini with terminal deoxynucleotidyltransferase and the ovalbumin gene was hybridized to a linear plasmid DNA, pMB9, containing 3'-poly(dT) termini. This hybrid molecule was used to transform the E. coli strain X1849. The cloned transformants contained from 30 to 53% of the complete ovalbumin DNA as determined by hybridization with full length cDNA. The length of the inserts was confirmed by treatment of the isolated plasmids with the restriction enzyme Hha I. Separation of the fragments by agarose gel electrophoresis showed that the amount of inserted DNA in clones tested varied from 680 to 1090 base pairs.

Collagen cross-linking alterations in joint contractures: changes in the reducible cross-links in periarticular connective tissue collagen after nine weeks of immobilization

A significant increase in the NaBH4 reducible intermolecular cross-links in the 9 week immobilized rabbit periarticular connective tissue was found. Dihydroxylysinonorleucine, hydroxylysinonorleucine, and histidinohydroxymerodesmosine were the major cross-links which increased during the period of immobilization. No change in the hydroxlysine/lysine ratio between the immobilized and control periarticular connective tissue collagen was detected during the 9 weeks of enforced immobilization of the rabbit knee. Since the collagen mass in the immobilized periarticular connective tissue does not change, or at most is reduced 10%, we suggest that there is an increase in collagen cross-links expressed both in per unit weight of collagen and on the basis of collagen mass per knee due to the lack of physical stress and motion.

Rapid recovery from contracture in rabbit hindlimb. A correlative biomechanical and biochemical study

Between 3 to 6 weeks after release of immobilized rabbits' knees, joint stiffness as determined by measurement of torque and area of hysteresis was overcome. The total hexosamine and water content of periarticular tissues had increased to within the range of control rabbits' joints and showed strong correlation with the biomechanical measurements.