Functional analysis of the serpin domain of C1 inhibitor

To analyze the role of the heavily glycosylated amino-terminal domain of C1 inhibitor in protease inhibitory activity, two truncated C1 inhibitor molecules were constructed. The abilities of the recombinant truncated inhibitors to complex with target proteases were compared with that of the wild-type recombinant protein. One recombinant truncated molecule consisted of amino acid residues 76 to 478 (C-serp(76)) and the other of residues 98 to 478 (C-serp(98)). The recombinant proteins were each expressed in similar quantities. The thermal denaturation profiles of the two truncated proteins were similar to that of the wild-type protein. Identical binding of C1s, C1r, kallikrein, and beta factor XIIa was observed with the three molecules. Furthermore, the truncated molecules also effectively inhibited C1 activity in hemolytic assays. These studies therefore clearly demonstrate that the amino-terminal domain of C1 inhibitor does not influence complex formation with target proteases.

A cluster of mutations within a short triplet repeat in the C1 inhibitor gene

Mutations in the C1 inhibitor gene that result in low functional levels of C1 inhibitor protein cause hereditary angioneurotic edema. This disease is characterized by episodic edema leading to considerable morbidity and death. Among 60 unreported kindred with the disease, four patients were discovered to have mutations clustered within a 12-bp segment of exon 5 from nucleotide 8449 to nucleotide 8460. This short segment of DNA contains three direct repeats of the triplet CAA and is immediately preceded by a similar adenosine-rich sequence (CAAGAACAC). These triplet repeats make this region susceptible to mutation by a slipped mispairing mechanism. There are two other short triplet repeat elements in the coding region for this gene, but they have not become mutated in any kindred examined. This suggests that the apparent enhanced mutation rate in this region of exon 5 may be influenced by DNA structural characteristics.

Aspirin reduces the incidence of colonic carcinoma in the dimethylhydrazine rat animal model

BACKGROUND

Epidemiological studies in humans suggest that regular use of non-steroidal anti-inflammatory drugs (NSAIDS) especially aspirin significantly decreases the risk of developing colorectal cancer.

AIMS

The purpose of this study was to investigate the effect of aspirin on colonic carcinogenesis using the dimethylhydrazine (DMH) colonic cancer model in rats.

METHODS

Groups of animals were given daily doses of aspirin either 0, 5, 30 or 60 mg/kg for 18 weeks. Half of each group also received 18 x 30 mg/kg/wk injections of DMH.

RESULTS

Aspirin at doses of 5, 30 or 60 mg/kg/dy had a progressive effect on the reduction of tumour numbers and the percentage of tumours greater or equal to 5 mm in diameter. Aspirin at doses of 30 and 60 mg/kg/dy significantly reduced tumour incidence.

CONCLUSION

These findings support the epidemiological studies in humans. The rat DMH model would appear to be suitable for investigating the mechanism of action of aspirin in reducing colonic tumour formation.

Acquired C1 inhibitor deficiency as a result of an autoantibody to the reactive center region of C1 inhibitor

An autoantibody that we hypothesize to react with the reactive center of the plasma serine proteinase inhibitor, C1 inhibitor (C1INH), has been found in a patient with acquired C1INH deficiency. The Ab blocks the ability of C1INH to inhibit the hydrolysis of N-carbobenzyloxy-L-lysine thiobenzylester by purified C1s. A cryoprecipitate from the patient's plasma as well as the Ig fraction were able to block C1INH inhibition of C1s. The immunoaffinity purified Ab to C1INH from the patient's plasma Ig fraction neutralizes the inhibitory activity of C1INH in a dose-dependent manner and blocks the ability of normal C1INH to form a complex with C1s. The neutralizing activity of the purified Ab is reversed by a synthetic peptide that corresponds to the amino acid sequence in the P1 to P15 positions of the reactive center of C1INH but not by a 34-amino-acid trypsin peptide or 37-amino-acid elastase peptide derived from the C-terminus of C1INH. Western blot analysis indicated that the Ab is an oligoclonal Ig with kappa light chains.

Acquired C1 inhibitor deficiency as a result of an autoantibody to the reactive center region of C1 inhibitor

An autoantibody that we hypothesize to react with the reactive center of the plasma serine proteinase inhibitor, C1 inhibitor (C1INH), has been found in a patient with acquired C1INH deficiency. The Ab blocks the ability of C1INH to inhibit the hydrolysis of N-carbobenzyloxy-L-lysine thiobenzylester by purified C1s. A cryoprecipitate from the patient's plasma as well as the Ig fraction were able to block C1INH inhibition of C1s. The immunoaffinity purified Ab to C1INH from the patient's plasma Ig fraction neutralizes the inhibitory activity of C1INH in a dose-dependent manner and blocks the ability of normal C1INH to form a complex with C1s. The neutralizing activity of the purified Ab is reversed by a synthetic peptide that corresponds to the amino acid sequence in the P1 to P15 positions of the reactive center of C1INH but not by a 34-amino-acid trypsin peptide or 37-amino-acid elastase peptide derived from the C-terminus of C1INH. Western blot analysis indicated that the Ab is an oligoclonal Ig with kappa light chains.

Transcriptional regulation of the C1 inhibitor gene by gamma-interferon

Treatment of the hepatoma cell line, Hep3B, with gamma-interferon (IFN) enhanced expression of C1 inhibitor (C1INH) mRNA, primarily due to an enhanced transcription rate. Hep3B cells transfected with reporter constructs containing various regions of the C1INH gene between positions -1182 and +587, and stimulated with gamma-IFN, expressed increased levels of chloramphenicol acetyltransferase in the presence of the first intron and as few as 12 bases of the 5'-flanking region. However, a 66% reduction in the inducibility of the constructs was observed when the upstream region between -582 and -252 was eliminated. Successive deletions mapped the first intron IFN-responsive elements to a region between +368 and +410. The data indicate that both the upstream and the first intron sequences can independently enhance induction of C1INH gene expression. Examination of the immediate upstream sequence of the C1INH gene reveals the absence of a TATA box. The promoter of the C1INH gene was mapped to a region within 81 bases of the upstream sequence and the first exon. Further examination indicated two regions that were potentially important for promoter activity as follows: 1) a G-C-rich region from -81 to -49, and 2) an initiator element at -3 to +5. The results indicate that the upstream sequences including -81 to -49 and the H-DNA region between -48 and -17 are not necessary for promotor activity. The initiator element from -3 to +5 is sufficient and necessary for promoter function.

Contiguous deletion and duplication mutations resulting in type 1 hereditary angioneurotic edema

Mutations that cause low antigenic and functional levels of C1 inhibitor protein result in type 1 hereditary angioneurotic edema. This disease is characterized by episodic edema leading to considerable morbidity and sometimes death. We present here two novel mutations in the reactive center coding region. One mutation is a deletion of an imperfect palindrome encompassing nucleotides 1395-1428 and the other is a direct duplication of nucleotides 1414-1433. These mutations do not depend on improper pairing of direct repeats, but may form as a consequence of a peculiar consensus sequence or an alternative secondary structure.

Hereditary angioneurotic oedema: characterization of plasma kinin and vascular permeability-enhancing activities

The mediator(s) responsible for localized enhanced vascular permeability that characterizes an exacerbation of hereditary angioneurotic oedema (HAE) is thought to be a product of either contact or complement system activation. In contrast to normal individuals, plasma from these patients generates both kinin and vascular permeability-enhancing activity following incubation at 37 degrees C. Depletion of C1 inhibitor in both normal and C2-deficient plasma, but not in contact factor-deficient plasmas, resulted in generation of these activities. The kinin activity from incubated HAE plasma was susceptible to kininase inactivation and was blocked by a Bk2 receptor antagonist. Furthermore, this activity was isolated from HAE plasma; amino acid sequence analysis proved it to be bradykinin. Similarly, the vasopermeability-enhancing activity from ethanol-fractionated or boiled HAE plasma, collected during either attack or remission, co-eluted with bradykinin on reverse-phase high performance liquid chromatography (HPLC). These studies conclusively demonstrate that bradykinin is the major kinin and mediator of enhanced vascular permeability generated during incubation of HAE plasma. The role of other bioactive products, such as the C2 kinin, at local sites of oedema formation remains to be further defined.

Mutations in the C1 inhibitor gene that result in hereditary angioneurotic edema

Mutations in one C1 INH allele result in the autosomal dominant disease, hereditary angioedema. The plasma antigenic level of C1 INH in this disease may be low, normal, or high, while the functional level is uniformly depressed. Investigation of the mutations in the C1 INH gene reveal several key features about the DNA itself as well as protein structure-function relationships. The largest single group of mutations with a defined mechanism are recombinations associated with Alu repetitive DNA elements. Current data suggest that there may be an increased number of mutations within the region encoding the reactive center which, like some other serpins, contains both primary and secondary structure DNA polymerase pause sites. These sites may enhance the rates of mutation and evolution in the reactive center region. Some of the dysfunctional C1 INH proteins that result from hinge region mutations support models for reactive center loop interaction with beta sheet A during complex formation. The analysis of the dysfunctional mutants, therefore, suggest regions of the molecule that are important for inhibitor function.

Structure and regulation of the C1 inhibitor gene

C1 esterase inhibitor is a M(r) approximately 105,000 glycoprotein and the sole regulation of the activities of C1r and C1s. As such, it plays an extremely important role in the regulation of the classical complement pathway. Hereditary angioedema (HAE) is the clinical manifestation of C1INH deficiency. Two types of HAE have been described. Type I HAE is characterized by low antigenic and functional levels of C1INH, while Type II HAE is characterized by normal or increased antigenic levels of C1INH with low levels of functionally active protein. C1INH is encoded by a single gene on chromosome 11. The C1INH gene consists of 8 exons and 7 introns and is approximately 1.7 x 10(4) base pairs in length. Expression of C1INH in vivo is enhanced by androgens. In vitro studies indicate that C1INH mRNA and protein levels are increased by up to 20 fold after stimulation with interferon-gamma (gamma-IFN) and to a lesser extent in response to alpha-interferon (alpha-IFN), tumor necrosis factor-alpha (TNF-alpha), Interleukin 6 (IL-6) and monocyte colony stimulating factor (M-CSF). In this chapter, we will discuss the structure of the C1INH gene and mechanisms of its regulation as well as some of the elements which may contribute to its transcriptional regulation.

Immune escape by human immunodeficiency virus type 1 from neutralizing antibodies: evidence for multiple pathways

Sera from many HIV-1-infected individuals contain broadly reactive, specific neutralizing antibodies. Despite their broad reactivity, variant viruses, resistant to neutralization, can be selected in vitro in the presence of such antisera. We have previously shown that neutralization resistance of an escape mutant with an amino acid substitution in the transmembrane protein (A582T) occurs because of alteration of a conformational epitope that is recognized by neutralizing antibodies directed against the CD4 binding site. In this report we demonstrate that immune escape via a single-amino-acid substitution (A281V) within a conserved region of the envelope glycoprotein gp120 confers neutralization resistance against a broadly reactive neutralizing antiserum from a seropositive individual. We show this alteration affects V3 and additional regions unrelated to V3 or the CD4 binding site. Together with previous studies on escape mutants selected in vitro, our findings suggest that immune-selective pressure can arise by multiple pathways.

A rapid method for site-specific mutagenesis using larger plasmids as templates

To facilitate the introduction of specific point mutations in plasmids that are too large to be amplified efficiently by a single PCR, we have developed a method for site-directed mutagenesis by generating partial plasmid fragments, which introduces changes as simply as conventional techniques. Plasmids containing a fragment of the human immunodeficiency virus type-1 (HIV-1) envelope gene were subjected to PCR with four pairs of PCR primers for each desired point mutation. One primer in each of two of these four pairs contained the desired mutation. The four pairs of primers were designed so that four overlapping fragments were amplified from the plasmid template, two of which contained the mutation. These fragments were then reannealed and electroporated directly into Escherichia coli. The desired mutation was typically found in 66% to 83% of the resulting colonies. The technique is almost as simple as previous techniques, shows similar efficiency and is applicable to plasmids that would normally be too large for efficient site-specific mutagenesis. The entire procedure, from PCR amplification to transfection into E. coli, can be completed in one day.

A hinge region mutation in C1-inhibitor (Ala436-->Thr) results in nonsubstrate-like behavior and in polymerization of the molecule

C1-inhibitor(Mo), a dysfunctional C1-inhibitor molecule produced in two kindred with type II hereditary angioedema, has a mutation at the P10 position (Ala436 to Thr). Like most serpins with hinge region mutations (P14, P12, P10), C1-inhibitor(Mo) loses its inhibitory activity. However, unlike the other hinge region mutations, this mutant is not converted to a substrate. As shown by nondenaturing gel electrophoresis, gel filtration, sucrose density gradient ultracentrifugation, and electron microscopy, C1-inhibitor(Mo) exists in both monomeric and multimeric forms. Polymerization probably results from reactive center loop insertion into the A sheet of an adjacent molecule. Native C1-inhibitor(Mo) was shown to have a thermal stability profile intermediate to those of intact and of cleaved normal C1-inhibitor. Native C1-inhibitor(Mo) did not bind to monoclonal antibody KII, which binds only to reactive center-cleaved normal C1-inhibitor. It did, however, react with monoclonal antibody KOK12, which recognizes complexed or cleaved C1-inhibitor but not intact normal C1-inhibitor. Native C1-inhibitor(Mo), therefore, exists in a conformation similar to the complexed form of normal C1-inhibitor.

Chymotrypsin inhibitory activity of normal C1-inhibitor and a P1 Arg to His mutant: evidence for the presence of overlapping reactive centers

C1-inhibitor is a serine proteinase inhibitor that is active against C1s, C1r, kallikrein, and factor XII. Recently, it has been shown that it also has inhibitory activity against chymotrypsin. We have investigated this activity of normal human C1-inhibitor, normal rabbit C1-inhibitor, and P1 Arg to His mutant human C1-inhibitors and find that all are able to inhibit chymotrypsin and form stable sodium dodecyl sulfate-resistant complexes. The Kass values show that the P1 His mutant is a slightly better inhibitor of chymotrypsin than normal human C1-inhibitor (3.4 x 10(4) compared with 7.3 x 10(3)). The carboxy-terminal peptide of normal human C1-inhibitor, derived from the dissociated protease-inhibitor complex, shows cleavage between the P2 and P1 residues. Therefore, as with alpha 2-antiplasmin, C1-inhibitor possesses two overlapping P1 residues, one for chymotrypsin and the other for Arg-specific proteinases. In contrast, with the P1 His mutant, the peptide generated from the dissociation of its complex with chymotrypsin demonstrated cleavage between the P1 and P'1 residues. Therefore, unlike alpha 2-antiplasmin, chymotrypsin utilizes the P2 residue as its reactive site in normal C1-inhibitor but utilizes the P1 residue as its reactive site in the P1 His mutant protein. This suggests that the reactive center loop allows a degree of induced fit and therefore must be relatively flexible.

The effect of therapeutic drugs used in inflammatory bowel disease on the incidence and growth of colonic cancer in the dimethylhydrazine rat model

An increased incidence of colonic cancer is associated with chronic inflammatory bowel disease. Sulphasalazine, metronidazole and more recently, modified forms of 5-aminosalicylic acid are used for maintenance therapy of inflammatory bowel disease. In a series of experiments, we used the 1,2-dimethylhydrazine animal model of colonic cancer in conjunction with these drugs, to study the effect on the development of colon cancer. Inbred male Wistar rats were divided into groups receiving orally: metronidazole 18 mg Kg-1 dy-1; sulphasalazine 60 mg Kg-1 dy-1; 5-aminosalicylic acid 30 and 60 mg Kg-1 dy-1 and olsalazine 60 mg Kg-1 dy-1 administered daily. Half of each group also received weekly injections of DMH 40 mg Kg-1. Metronidazole, sulphasalazine and 30 mg Kg-1 dy-1 5-aminosalicylic acid were co-carcinogenic, increasing either the number of cancers or tumour size. In contrast 60 mg Kg-1 dy-1 5-aminosalicylic acid inhibited tumour size and olsalazine had no effect. These results may have a bearing on long term maintenance therapy in inflammatory bowel disease.

C5 deficiency in A/J mice is not associated with resistance to the development of secondary amyloidosis

The aim of the study was to determine whether C5 deficiency in the mouse is associated with resistance to the development of secondary amyloidosis. Chronic inflammation was induced in the F2 progeny, derived from matings between amyloid-susceptible and amyloid-resistance mice, by daily injections of azocasein for thirty days. Using a restriction fragment length polymorphism generated by digestion of genomic DNA with the restriction enzyme HindIII, C5 sufficient and deficient DNA can be clearly differentiated. Eight mice were found to be C5 sufficient, 32 were heterozygotes and 14 were found to be C5 deficient. Grading of the splenic amyloid load from negative to 4+ was performed after staining tissue squashes with Congo red and viewing them under a polarizing microscope. Seventeen mice were noted to have negative to trace, 18 had moderate (1+ - 2+) and 19 had heavy (3+ - 4+) amyloid deposition. There was no correlation between splenic amyloid load and C5 deficiency. Based on these results it is clear that C5 deficiency and resistance to secondary amyloidosis are not associated.

C1 inhibitor hinge region mutations produce dysfunction by different mechanisms

Heterozygosity for a mutant dysfunctional C1 inhibitor protein, a member of the serine proteinase inhibitor (serpin) superfamily, results in type II hereditary angioneurotic oedema. We identified a "hinge" region mutation in C1 inhibitor with a Val to Glu replacement at P14 Val-432. Recombinant C1 inhibitors P10 Ala-->Thr and P14Val-->Glu did not form stable complexes with fluid phase C1s or kallikrein. The P14 Val-->Glu mutant, however, was cleaved to a 96K form by C1s, while the P10 Ala-->Thr mutant was not. The recombinant P10 mutant also did not complex with C1s, kallikrein or beta-factor Xlla-Sepharose. The two mutations, therefore, result in dysfunction by different mechanisms: in one (P14 Val-->Glu), the inhibitor is converted to a substrate, while in the other (P10 Ala-->Thr), interaction with target protease is blocked.

A dysfunctional C1 inhibitor protein with a new reactive center mutation (Arg-444-->Leu)

A P1 mutation (Arg-444-->Leu) was identified in a dysfunctional C1 inhibitor from a patient with type 2 hereditary angioneurotic edema. The mutation was defined at the level of the protein (by sequence analysis of the Pseudomonas aeruginosa elastase-derived reactive center peptide), and the mRNA (CGC-->CTC) (by sequence analysis of PCR-amplified DNA).

Enhancing Quality Critical Care Education: Establishing a Consortium

The demand for expanded knowledge and accountability in critical care nursing has increased the need for qualified critical care nurses and is tempered by requirements that their preparation be cost-effective. The Emory University School of Nursing (EUSN) has pioneered in meeting this challenge. Since June 1988, a Critical Care Consortium consisting of the EUSN and Emory-affiliated hospitals has been operational, providing uniform critical care education to multiple hospital nursing staffs. Instructional resources are being economically utilized, eliminating duplication of efforts. This collaboration between academic and service settings enhances productivity, quality patient care, professional growth, and promotes significantly greater interinstitutional cohesiveness.

Localization of the human complement component C3 binding site on the IgG heavy chain

The location of the covalent binding site of the third component of complement (C3) on the IgG heavy chain was determined by sequence analysis of peptides generated by cyanogen bromide digestion of C3-IgG adducts. Activation of the alternative pathway by incubation of heat-aggregated human IgG1 with fresh normal human plasma formed covalent adducts of C3b-IgG. CNBr peptides of these adducts were transferred to a polyvinylidene difluoride membrane, and amino-terminal sequences were determined. A 40-kDa dipeptide containing the covalent bond was identified by labeling the free thiol group (generated during activation of the internal thioester of C3b) with iodo[1-14C]acetamide and analyzed by amino acid sequencing. The resulting double sequence suggested an adduct with NH2 termini at residue 938 (pro-C3 numbering) of C3 (75 residues NH2-terminal to the thioester) and residue 84 in the variable region of the IgG heavy chain. These results combined with results from hydroxylamine treatment (splits ester linkage between C3b and IgG) imply that this adduct peptide consists of a 22-kDa C3 fragment and an 18-kDa IgG fragment. Therefore, C3 binds covalently within the region extending from the last 20 residues of the variable region through the first 20 residues of CH2.

Nonsense mutations affect C1 inhibitor messenger RNA levels in patients with type I hereditary angioneurotic edema

Members of two unrelated families with type I hereditary angioneurotic edema (HANE) were found to have elevated levels of C1 inhibitor (C1INH) mRNA. DNA sequence analysis of PCR-amplified monocyte C1INH mRNA revealed normal and mutant transcripts, as expected in this disorder that occurs in heterozygous individuals. Single base mutations near the 3' end of the coding sequence were identified in affected members of each family. One mutation consisted of insertion of an adenosine at position 1304 which created a premature termination codon (TAA), whereas the second consisted of deletion of the thymidine at position 1298 which created a premature termination codon (TGA) 23 nucleotides downstream. These mutations are approximately 250 nucleotides upstream of the natural termination codon. Nuclear run-off experiments in one kindred revealed no difference in transcription rates of the C1INH gene between the patients and normals. C1INH mRNA half-life experiments were not technically feasible because of the prolonged half-life of the normal transcript. Dideoxynucleotide primer extension experiments allowed the differentiation of the normal and mutant transcripts. These studies showed that the mutant transcript was not decreased relative to the normal, and this therefore was at least partially responsible for the C1INH mRNA elevation. This elevation may be due to the decreased catabolism of the mutant transcript.

Synthesis of C1 inhibitor in fibroblasts from patients with type I and type II hereditary angioneurotic edema

Patients with hereditary angioneurotic edema (HANE) have serum levels of functionally active inhibitor of the first component of complement (C1 INH) between 5 and 30% of normal, instead of the 50% expected from the single normal allele. Increases in rates of catabolism have been documented in patients with HANE and certainly account for some of decrease in C1 INH level. A possible role for a decrease in synthesis of C1 INH in producing serum levels of C1 INH below the expected 50% of normal has not been well studied. We studied the synthesis of C1 INH in skin fibroblast lines, which produce easily detectable amounts of C1 INH. In type I HANE cells, C1 INH synthesis was 19.6 +/- 4.0% (mean +/- SD) of normal, much less than the 50% predicted. In type II HANE cells, the total amount of C1 INH synthesis (functional and dysfunctional) was 98.9 +/- 17% of normal; the functional protein comprised 43% of the total. Thus, type II HANE cells synthesized functional C1 INH at a much greater rate than for the type I cells. In both type I and II HANE cells, amounts of steady-state C1 INH mRNA levels paralleled rates of C1 INH synthesis, indicating that control of C1 INH synthesis occurred at pretranslational levels. Both type I and type II fibroblasts synthesized normal amounts of C1r and C1s. These data suggest that the lower than expected amounts of functionally active C1 INH in type I HANE may be due, in part, to a decrease in rate of synthesis of the protein, and that the expressions of the normal C1 INH allele in HANE is influenced by the type of abnormal allele present.

Paramyosin is the Schistosoma mansoni (Trematoda) homologue of antigen B from Taenia solium (Cestoda)

Antigen B, a major antigen of the cestode parasite Taenia solium, has been purified and a portion of amino acid sequence obtained. Paramyosin of the trematode parasite Schistosoma mansoni, an immunogenic protein that has shown promise as a vaccine candidate, has several biochemical and immunological properties in common with antigen B. A full-length cDNA clone of S. mansoni paramyosin has been obtained and the predicted translation product contains a sequence that is highly homologous to the sequence obtained for antigen B. The predicted amino acid composition and isolectric point of paramyosin are nearly identical to those established for antigen B. Recombinant S. mansoni paramyosin, expressed in Escherichia coli as a fusion protein with beta-galactosidase, was recognized by antisera against T. solium antigen B. We conclude from these results that S. mansoni paramyosin and T. solium antigen B are homologous proteins. Since S. mansoni paramyosin is thought to be a muscle protein and T. solium antigen B a secreted glycoprotein with anti-complement activity, this conclusion raises some interesting questions regarding the role of this class of proteins in the host-parasite relationship.

Recombinations between Alu repeat sequences that result in partial deletions within the C1 inhibitor gene

Genomic DNA sequence analysis was used to define the extent of deletions within the C1 inhibitor gene in two families with type I hereditary angioneurotic edema. Southern blot analysis initially indicated the presence of the partial deletions. One deletion was approximately 2 kb and included exon VII, whereas the other was approximately 8.5 kb and included exons IV-VI. Genomic libraries from an affected member of each family were constructed and clones containing the deletions were analyzed. Sequence analysis of the deletion joints of the mutants and corresponding regions of the normal gene in the two families demonstrated that both deletion joints resulted from recombination of two Alu repetitive DNA elements. Alu repeat sequences from introns VI and VII combined to make a novel Alu in family A, and Alu sequences in introns III and VI were spliced to make a new Alu in family B. The splice sites in the Alu sequences of both mutants were located in the left arm of the Alu element, and both recombination joints overlapped one of the RNA polymerase III promoter sequences. Because the involved Alu sequences, in both instances, were oriented in the same direction, unequal crossingover is the most likely mechanism to account for these mutations.

Chemodectoma of the larynx

Chemodectomas of the larynx are rare tumors. Only 35 cases were reported in the literature prior to the publication of this paper. We report a further case and discuss the problems associated with hemorrhage during surgery.

Dysfunctional C1 inhibitor Ta: deletion of Lys-251 results in acquisition of an N-glycosylation site

Hereditary angioneurotic edema is inherited as an autosomal dominant disorder and is characterized by potentially life-threatening episodic angioedema. In type II hereditary angioneurotic edema, a dysfunctional C1 inhibitor molecule is present together with low levels of normal C1 inhibitor. About 70% of these dysfunctional proteins result from reactive center (Arg-444) mutations. We describe the deletion of nucleotides encoding Lys-251 (AAG) in C1 inhibitor Ta, the dysfunctional C1 inhibitor from a family with type II hereditary angioneurotic edema. DNA sequence analysis was derived from clones obtained through polymerase chain reaction amplification of blood monocyte C1 inhibitor mRNA. As expected, clones with both normal and abnormal sequence were isolated. The deletion was verified by protein sequence analysis. These data, together with biochemical analysis of the protein and cell-free translation studies, suggest that this deletion, by altering the normal amino acid sequence from Asn-Lys-Ile-Ser to Asn-Ile-Ser, creates a new glycosylation site. The additional carbohydrate accounts for the larger size on SDS/PAGE and very likely interferes with protein function.

Computer multitasking with Desqview 386 in a family practice

Computers are now widely used in medical practice for accounting and secretarial tasks. However, it has been much more difficult to use computers in more physician-related activities of daily practice. I investigated the Desqview multitasking system on a 386 computer as a solution to this problem. Physician-directed tasks of management of patient charts, retrieval of reference information, word processing, appointment scheduling and office organization were each managed by separate programs. Desqview allowed instantaneous switching back and forth between the various programs. I compared the time and cost savings and the need for physician input between Desqview 386, a 386 computer alone and an older, XT computer. Desqview significantly simplified the use of computer programs for medical information management and minimized the necessity for physician intervention. The time saved was 15 minutes per day; the costs saved were estimated to be $5000 annually.

386 computer: a solution to 'computer lag' in medical practice

Physicians have been quick to utilize computers in the business aspects of medical practice. The movement of computers into clinical medicine, however, especially in office practice, has been much slower. The main reason for this "computer lag" is suggested to be the inability of most computer systems to handle the numerous tasks often occurring concurrently in a medical practice. The 386 computer, with multitasking capabilities, can manage this type of information flow and could allow the entry of computers into daily office medical practice.

Type II hereditary angioneurotic edema that may result from a single nucleotide change in the codon for alanine-436 in the C1 inhibitor gene

Identical single-base changes in the C1 inhibitor gene that may result in dysfunctional inhibitor proteins are described in two different families with type II hereditary angioneurotic edema. Initially, a restriction fragment length polymorphism was defined that resulted from loss of a Pst I site within exon VIII, which encodes the region containing the reactive center. Exon VIII from the normal and abnormal allelles was amplified by the polymerase chain reaction. Amplified DNA product was cloned into plasmid pUC18; clones representing normal and mutant allelles were distinguished by the presence and absence, respectively, of the Pst I restriction site. DNA sequence analysis revealed a G----A mutation in the codon for alanine-436, which would result in replacement with a threonine residue. This position is nine amino acid residues amino-terminal to the reactive-center arginylthreonine peptide bond. In contrast, previously defined mutations in type II hereditary angioneurotic edema result in replacement of the reactive-center arginine.

Insulin stimulates dephosphorylation of phosphorylase in rat epitrochlearis muscles

We have investigated the effects of insulin on the phosphorylation of glycogen phosphorylase in skeletal muscle. Rat epitrochlearis muscles were incubated in vitro with 32Pi to label cellular phosphoproteins, before being treated with hormones. Phosphorylase, phosphorylase kinase, and glycogen synthase were immunoprecipitated under conditions that prevented changes in their phosphorylation states. Based on measurements of the activity ratio (-AMP/+AMP) and the 32P content of phosphorylase, 4-8% of the phosphorylase in untreated muscles appeared to be phosphorylated. Epinephrine promoted increases of approximately 4-fold in the 32P content and activity ratio. Neither these effects nor the epinephrine-stimulated increases in phosphorylation of glycogen synthase and phosphorylase kinase were attenuated by insulin. However, insulin at physiological concentrations rapidly decreased the 32P content of phosphorylase in muscles incubated without epinephrine. Results from peptide mapping experiments indicate that phosphorylase was phosphorylated at a single site in both control and insulin on phosphorylase represented a decrease in 32P of approximately 50%. By comparison, the 32P content of glycogen synthase and the beta subunit of phosphorylase kinase were decreased by only 20 and 16%, respectively; the 32P content of the kinase alpha subunit was not affected by insulin. The results provide direct evidence that insulin decreases the amount of phosphate in phosphorylase and phosphorylase kinase. These findings have important implications with respect to both the regulation of glycogen metabolism in skeletal muscle and the mechanism of insulin action.

Type I C1 inhibitor deficiency with a small messenger RNA resulting from deletion of one exon

The molecular genetic basis of C1 inhibitor (C1 INH) deficiency in a patient with type I hereditary angioneurotic edema was studied. This patient was found to have an abnormally short C1 INH mRNA together with a normal message. Restriction fragment length polymorphism of the C1 INH gene was detected by Southern blot analysis of the patient's DNA after digestion with Pst I or Sac I, and hybridization with a full-length C1 INH cDNA. Hybridization of the same blot with three different fragments of the full-length cDNA suggested that exon VII and portions of both flanking introns were deleted in the C1 INH gene. Northern blot analysis of RNA from cultured monocytes, using a probe corresponding to exon VII, also indicated that the abnormal C1 INH mRNA had a deletion of these nucleotides. To confirm the hypothesis that the short C1 INH mRNA contained a deletion, the involved segment of the patient's C1 INH mRNA was amplified using the polymerase chain reaction (PCR). PCR amplification yielded two C1 INH DNA fragments of different lengths (380 and 160 bp). Southern blot and sequence analysis of both DNA fragments clearly revealed that the smaller 160-bp DNA was derived from the abnormal message and had a deletion of nucleotides corresponding to exon VII.

Molecular characterization of sialophorin (CD43), the lymphocyte surface sialoglycoprotein defective in Wiskott-Aldrich syndrome

Sialophorin (CD43) of leukocytes and platelets is a surface sialoglycoprotein that is phenotypically defective on lymphocytes of patients with the X chromosome-linked immunodeficiency Wiskott-Aldrich syndrome. Previous studies with monoclonal antibodies indicate that sialophorin is a component of a T-lymphocyte activation pathway. Here we describe the cDNA cloning and derived amino acid sequence of human sialophorin. The sequence predicts an integral membrane polypeptide with an N-terminal hydrophobic signal region followed by a mucin-like 235-residue extracellular region with a uniform distribution of 46 serine, 47 threonine, and 24 proline residues. This is followed by a 23-residue transmembrane region and a 123-residue C-terminal intracellular region. These latter regions have been highly conserved during evolution; the intracellular region contains a number of potential phosphorylation sites that might mediate transduction of activation signals. The chromosomal location of the sialophorin gene was determined and the implications of this assignment for the pathogenesis of the Wiskott-Aldrich syndrome are discussed.

Structural and functional division into two domains of the large (100- to 115-kDa) chains of the clathrin-associated protein complex AP-2

The clathrin-associated protein complex 2 (AP-2 complex) is a group of proteins associated with clathrin-coated vesicles and believed to interact with cytoplasmic domains of receptors found in the plasma membrane. AP-2 was purified as an assembly of several polypeptide chains (alpha, beta, AP50, and AP17), of which only the alpha and beta chains (100-115 kDa) show significant heterogeneity. We have obtained cDNA clones for two distinct rat brain beta chains. We have also studied the domain organization of bovine brain AP-2 complexes by selective proteolysis. Results of these studies show that the alpha and beta chains have a similar two-domain organization. Their amino-terminal domains are relatively invariant whereas their carboxyl-terminal domains are variable in both sequence and length. We propose that the variable domains select receptors for inclusion in coated vesicles.

Biologic activity of a C2-derived peptide. Demonstration of a specific interaction with guinea pig lung tissues

A synthetic peptide derived from the carboxy terminus of C2b has been investigated for its ability to induce the contraction of guinea pig lung parenchymal strips. This peptide is known to enhance vascular permeability in guinea pig and human skin, and to induce contraction of estrous rat uterus. This C2 peptide (C2 207-223) is active from 5 x 10(-5) M to 5 x 10(-4) M and is not tachyphylactic to itself. No cross-activity between C2 207-223 and C5a or C3a could be demonstrated. C2 207-223 is not inhibited by antihistamines or cyclooxygenase inhibitors. These data indicate that the peptide exerts its action via a mechanism distinct from those of the C3a and C5a anaphylatoxins.

Biologic activity of a C2-derived peptide. Demonstration of a specific interaction with guinea pig lung tissues

A synthetic peptide derived from the carboxy terminus of C2b has been investigated for its ability to induce the contraction of guinea pig lung parenchymal strips. This peptide is known to enhance vascular permeability in guinea pig and human skin, and to induce contraction of estrous rat uterus. This C2 peptide (C2 207-223) is active from 5 x 10(-5) M to 5 x 10(-4) M and is not tachyphylactic to itself. No cross-activity between C2 207-223 and C5a or C3a could be demonstrated. C2 207-223 is not inhibited by antihistamines or cyclooxygenase inhibitors. These data indicate that the peptide exerts its action via a mechanism distinct from those of the C3a and C5a anaphylatoxins.

Human rectosigmoid electromyography: a new approach and some pitfalls

A method has been developed to record directly myoelectrical activity from the smooth muscle of the colon of intact subjects using pairs of intramuscular wires. Discrete bursts of myoelectrical activity occurred at 4-20 per min. A small interelectrode distance in this method allows contamination of colonic myoelectrical activity by the electromyogram of skeletal muscle to be excluded. This artefact has not been considered in previous recordings of 'colonic' activity.

Transpalatal approach to the petrous apex

A case is described in which a transpalatal, transpharyngeal approach was used for access to a cyst of the petrous apex. Although its indications are limited, in selected patients this conservative procedure has advantages over the more invasive lateral routes.

An ultrastructural study of the mucosal surface of the human inferior concha. I. Normal appearances

A study is presented of normal human nasal mucosa. Tissue was taken from a defined site on the inferior concha to minimise individual variation and was studied using scanning and transmission electron microscopy. Three cell types were found at the epithelial surface; ciliated and non-ciliated columnar cells and goblet cells. The distribution of cell types varied greatly between specimens, perhaps owing to environmental factors. All cells bore microvilli which showed minor structural differences between the cell types. Two important features were common to all microvilli. Cytoplasmic filaments were seen running parallel to the long axis of the structure; these may be involved in microvillar motility. Also found was a prominent surface glycocalyx. This may help maintain the volume and viscosity of periciliary fluid; it may also prevent adhesion and tangling of microvilli and cilia. A notable feature of the cilia seen on transmission electron microscopy was the presence of occasional ciliary crowns; these claw-like projections from the cilial tips may be involved in the propulsion of mucus. The goblet cells showed apocrine secretory droplets which were extruded intact into the nasal lumen. This may help to preserve the integrity of the mucous and periciliary fluid layers. We conclude that the mechanism of mucus secretion and transport in the nose may involve several surface structures including ciliary crowns and microvilli. Their function is not yet clear and further study is indicated.

Angioedema induced by a peptide derived from complement component C2

Synthetic peptides that correspond to the COOH-terminal portion of C2b enhance vascular permeability in human and guinea pig skin. In human studies, 1 nmol of the most active peptide of 25-amino acid residues produced substantial local edema. A pentapeptide and a heptapeptide corresponding to the COOH-terminal sequence of C2b each induced contraction of estrous rat uterus in the micromole range; a peptide of 25 amino acids from this region induced a like contraction of rat uterus at a concentration 20-fold lower than the smaller peptides. The vascular permeability of guinea pig skin was enhanced by doses of these synthetic peptides in a similar fashion as that observed for the concentration of rat uterus. The induction of localized edema by intradermal injection in both the guinea pig and the human proceeds in the presence of antihistaminic drugs, suggesting that there is a histamine-independent component to the observed increase in vascular permeability. Cleavage of C2 with the enzymic subcomponent of C1, C1s, yields only C2a and C2b, and no small peptides, whereas cleavage of C2 with C1s and plasmin yields a set of small peptides. These plasmin-cleaved peptides are derived from the COOH terminus of C2b, and they induce the contraction of estrous rat uterus.

Herpes simplex and duodenal ulcer pathology

An association between Herpes simplex Virus 1 (HSV-1) and duodenal ulcer disease has been suggested. Duodenal ulcers, like HSV-1 lesions, exhibit periodicity in recurrence. Several of the presently available anti-ulcer agents may have an antiviral action. Antibody titres in some studies have shown selective increases to HSV-1 in duodenal ulcer patients. The aim of this study was to determine whether a real association exists between HSV-1 and endoscopically proven duodenal ulcer or duodenal erosive disease. In a prospective study, 27 patients with either duodenal ulcer (16) or duodenal erosions (11) were studied in order to attempt isolation of HSV-1. Acute and convalescent sera were also taken and examined by an enzyme linked-immunoabsorbent assay system for antibody titres to HSV-1. Duodenal biopsies from a further 26 patients with duodenal ulcer or erosive disease were also examined retrospectively for HSV-1 by the immunoperoxidase technique. In no case of either duodenal ulcer or duodenal erosive disease was HSV-1 isolated by any of the above methods, nor was a relationship demonstrated by acute or convalescent HSV-1 antibody titres. Hence, this study does not support an association between HSV-1 and duodenal ulcer or erosive disease.

Homograft materials in otolaryngology: the risk of transmitting human immunodeficiency virus

Homograft materials are extensively used in various surgical procedures in otolaryngology, but with the increasing prevalence of human immunodeficiency virus (HIV) in the population this practice must be reviewed. Careful donor selection and antibody testing reduce but do not fully eliminate the risk of an HIV positive donor, and current preservation techniques may not inactivate all viruses. The use of homograft tissues should therefore be reconsidered as autograft or prosthetic material provides a satisfactory alternative in many cases.

Structure of C3f, a small peptide specifically released during inactivation of the third component of complement

C3f, a peptide presumed to be generated by the combined actions of factors I and H on fluid-phase C3b, has been isolated and sequenced. The peptide is 17 residues long and has a molecular weight of 1,847 daltons. The amino-terminal sequence is, with the exception of a single residue, identical to that deduced for the 46-kilodalton polypeptide seen transiently in the generation of iC3b from C3b, and is in full agreement with the sequence deduced from cDNA analysis. In addition, high-pressure liquid chromatography of the digestion of C3b by factor I has shown that C3f is the sole peptide released during iC3b generation.

Restriction fragment length polymorphism of the C1 inhibitor gene in hereditary angioneurotic edema

Hereditary angioneurotic edema (HANE) results from the deficiency of the inhibitor of the first component of human complement (C1-INH). It is inherited as an autosomal dominant trait. Heterogeneity of this defect has been shown at the protein and mRNA level. Southern blot analysis of genomic DNA was performed after digestion with six different restriction endonucleases in 24 families affected with type 1 HANE (low antigenic and functional C1-INH levels) and five with type 2 (low functional C1-INH levels and normal or elevated levels of dysmorphic C1-INH). Blots were hybridized with a C1-INH cDNA probe of 1,227 bp. With one enzyme (Pst I), two different patterns of restriction fragment length polymorphism (RFLP) were detected. One was present in one kindred with type 1 HANE and the other appeared the same in one type 1 and in one type 2 family, thus indicating that each RFLP resulted from a different mutation. Analysis of a total of 34 members of these three families suggested that the polymorphisms are tightly linked to the mutation responsible for the disease. Using a 170-bp probe we showed that the three different mutations leading to these polymorphisms are located in the same region of the C1-INH gene. These data suggest that different mutations in the same region of the C1-INH gene are responsible for C1-INH deficiency in these families. Most of these mutations are probably point mutations or other "minor" defects and do not appear to be due to major deletions or rearrangements.