Paracrine interactions among parathyroid cells: effect of cell density on cell secretion

Cell-cell interactions are important in the regulation of endocrine cell secretion. To investigate the possibility that cell communication may alter the regulation of parathyroid cell secretion, we utilized the reverse hemolytic plaque assay (RHPA) to measure parathyroid hormone (PTH) release from individual cells. Bovine parathyroid cells were dispersed and plated with protein A-conjugated erythrocytes at cell densities ranging from 0.9 to 36 x 10(2) cells/cm2 in 0.2 mM calcium. Cell populations were greater than 98% homogenous as determined by immunocytochemistry and in situ hybridization for PTH mRNA. Plaques were developed and data analyzed for the amount of PTH per cell released (plaque area in microns 2 x 10(4)) and the determination of cell recruitment (% plaques formed). A positive correlation existed between parathyroid cell density and the amount of PTH released. As the distance between cells increased, the plaque area (amount of PTH released per cell) decreased (ranging from 1.0 x 10(4) microns 2 at 0.9 x 10(2) cells/cm2 versus 1.6 x 10(4) microns 2 at 36 x 10(2) cells/cm2). The percentage of cells releasing PTH (recruitment) also decreased (16% at 0.9 x 10(2) cells/cm2 versus 47% at 36 x 10(2) cells/cm2). These data suggest that parathyroid cells in close proximity are stimulated to secrete more hormone than those at lesser densities. In addition, parathyroid cells are recruited to secrete PTH when plated at high density. Factor(s) released by the parathyroid cell may increase cell responsiveness and stimulate secretion in a paracrine fashion.

Nonradioactive screening of glucokinase mutations in maturity onset diabetes of the young

DNA mutations were previously identified in the glucokinase gene in 56% of French families affected with maturity onset diabetes of the young (MODY), an early onset autosomal dominant form of non-insulin-dependent diabetes mellitus (NIDDM). Mutations were found on almost all exons using the common radioactive single-strand conformation polymorphism (SSCP) technique. In this paper, we describe a non-isotopic SSCP method using the Pharmacia Biotech PhastSystem for the routine screening of new mutations in diabetic patients or in offsprings of diabetic patients. The use of the PhastSystem allowed us to easily and reproducibly optimize the electrophoretic conditions for each exon. We demonstrate the efficiency of this technique by identifying 8 mutations, 7 of which have never previously been detected, in patients referred to us for diagnostic purposes. It appears to be a sensible, easy and reliable method to improve the routine diagnosis of MODY in diabetic subjects or relatives and should be applicable to other genetic diseases.

Six mutations in the glucokinase gene identified in MODY by using a nonradioactive sensitive screening technique

We have reported that 56% of French families with maturity-onset diabetes of the young (MODY) carry a mutation in the glucokinase gene (GCK). Therefore, we have established a quick and sensitive nonradioactive technique (with the PhastSystem based on single-strand conformation polymorphism [SSCP] analysis) to routinely screen the 12 exons of GCK for mutations. We have studied GCK in 12 young hyperglycemic patients with a strong family history of type II diabetes. SSCP variants were observed in 6 of those 12 patients (50%), which cosegregated with diabetes in five families where DNA from additional members was available. Direct sequencing identified a 10-bp (base pair) deletion in exon 3; a 33-bp deletion at the exon 5/intron 5 junction, including the two consensus bases (GT) of the donor splice site; a nonsense mutation in exon 5 (Arg186-->Stop) in a Black-African family, which has been identified previously in a Caucasian family; and three missense mutations: Thr209-->Met209 in exon 6, Gly261-->Glu261 in exon 7, and Arg36-->Trp36 in exon 2. The missense mutation in exon 2 was found only in the second and third generation of the tested family but not in the first. To our knowledge, this is the first time that a de novo mutation of GCK is reported within a family. All six families carrying a mutation in GCK were typical MODY and most of their affected members had a mild form of diabetes. This nonradioactive SSCP technique may be useful to routinely diagnose glucokinase deficiency, which is an important cause of hyperglycemia among young type II diabetic patients.

Search for a third susceptibility gene for maturity-onset diabetes of the young. Studies with eleven candidate genes

Maturity-onset diabetes of the young (MODY) is a model for genetic studies of non-insulin-dependent diabetes mellitus. We have identified 15 MODY families in which diabetes is not the result of mutations in the glucokinase gene. This cohort of families will be useful for identifying other diabetes-susceptibility genes. Nine other candidate genes potentially implicated in insulin secretion or insulin action have been tested for linkage with MODY in these families, including glucokinase regulatory protein, hexokinase II, insulin receptor substrate 1, fatty acid-binding protein 2, glucagon-like peptide-1 receptor, apolipoprotein C-II, glycogen synthase, adenosine deaminase (a marker for the MODY gene on chromosome 20), and phosphoenolpyruvate carboxykinase. None of these loci showed evidence for linkage with MODY, implying that mutations in these genes do not make a major genetic contribution to the development of MODY. In addition to these linkage analyses, one or two affected subjects from each family were screened for the presence of the A to G mutation at nucleotide 3,243 of the mitochondrial tRNA(Leu(UUR)) gene. This mutation was not found in any of these subjects. Finally, we report the localization of the gene encoding the regulatory protein of glucokinase to chromosome 2, band p22.3 and the identification of a restriction fragment length polymorphism at this locus.

On the structures of crambescins B and C1

Revised structures have been assigned to the cyclic guanidine-containing crambescins B [3] and C1 [5], from the Mediterranean sponge Crambe crambe. The revisions were based on the fabms/cid/ms spectra of the [M+H]+ ions from crambescins B and C1 and hrfabms measurements on key fragment ions in the ms/ms spectra, which identify losses of C9H19 and C8H18N3O side-chains.

A new synthesis of in situ cyclopropanones and the observation of a thermal cyclopropanone–dienol rearrangement

A new in situ low-temperature synthesis of cyclopropanones from α,α′-dibromo ketones is described. The synthetic procedure is particularly well suited to NMR tube-scale experiments, which then easily allows one to spectroscopically characterize low-temperature solutions of these unstable molecules. Nine systems were studied, seven of which give high yields of the cyclopropanones at −78 °C or, in one case, −93 °C. The major rearrangement pathway of these cyclopropanones leads to an α,β-unsaturated ketone. The mechanism of this reaction has been studied in some detail, including deuterium isotope studies, and the direct observation of enols, silyl enol ethers, and dimers. The rearrangement reaction is postulated to involve the intermediacy of an oxyallyl, the transfer of a hydrogen from the anti-alkyl substituent of this oxyallyl to the oxyallyl oxygen atom, which leads to an enol, and then finally tautomerization of the enol to the ketone. The thermal stability of the cyclopropanones is directly related to the ease of this rearrangement and, in two cases studied here, the rearrangement takes place rapidly even at −95 °C and the cyclopropanones could not be observed. There is a remarkably strong correlation between cyclopropanone structure and reactivity, with the main structural factor being the external angles of the cyclopropanone substituents.

Deletion of the donor splice site of intron 4 in the glucokinase gene causes maturity-onset diabetes of the young

Missense and nonsense mutations in the glucokinase gene have recently been shown to result in maturity-onset diabetes of the young (MODY), a subtype of non-insulin-dependent diabetes mellitus with early age of onset. Glucokinase catalyzes the formation of glucose-6-phosphate and is involved in the regulation of insulin secretion and integration of hepatic intermediary metabolism. Nucleotide sequence analysis of exon 4 and its flanking intronic regions of the glucokinase gene, in four hyperglycemic individuals of a MODY family, revealed a deletion of 15 base pairs, which removed the t of the gt in the donor splice site of intron 4, and the following 14 base pairs. This deletion resulted in two aberrant transcripts, which were analyzed by reverse transcription of RNA from lymphoblastoid cells obtained from a diabetic patient. In one of the abnormal transcripts, exon 5 is missing, while in the other, the activation of a cryptic splice site leads to the removal of the last eight codons of exon 4. This intronic deletion in a donor splice site seems to cause a more severe form of glucose intolerance, compared with point mutations described in glucokinase. This might be due to a more pronounced effect on insulin secretion.

Effect of acupuncture on weight loss evaluated by adrenal function

In order to understand the relationship between patients' adrenal function and simple obesity and effect of acupuncture on it, the obesity indices, lipid indices, fasting blood-glucose, noradrenaline, dopamine, adrenalin and cortisol were observed. The results indicated that patients with simple obesity had hypofunction of the sympathetic-adrenal system and the hypothalamus-pituitary-adrenal system. Acupuncture treatment not only affected weight loss but also enhanced functioning of the two systems, suggesting that the effect of acupuncture on weight loss may be produced by enhancing the functions of both the sympathetic-adrenal system and the hypothalamus-pituitary-adrenal system.

Linkage analysis and molecular scanning of glucokinase gene in NIDDM families

Mutations in the glucokinase gene are a major cause of maturity-onset diabetes of the young. To evaluate the contribution of this gene to the development of late-onset NIDDM, linkage analyses between DNA polymorphisms at the glucokinase locus and NIDDM were performed in 79 multigenerational French families. In addition, all exons and the islet promoter region of glucokinase gene from 1 affected member from each family as well as from 17 unrelated women with previous gestational diabetes were amplified by polymerase chain reaction and screened for mutations by single-strand conformational polymorphism and DNA sequencing. Linkage of glucokinase and NIDDM was significantly rejected under all models tested. However, in 1 family, the lod score was 2.30, and we found a nucleotide substitution at the position -30 in the islet promoter region that cosegregated with diabetes. The proband of this family was a gestational diabetic individual. No other mutation in glucokinase was found in the 79 NIDDM families. We identified a missense mutation (TGG257-->CGG257) in exon 7 of glucokinase gene from 1 of 17 women with gestational diabetes, which was present in all diabetic members of her family. This family is likely to be a cryptic maturity-onset diabetes of the young, as 4 younger members, carrying this mutation, were subsequently found to be hyperglycemic. In conclusion, no evidence was obtained to incriminate glucokinase as a major gene for late age of onset NIDDM. Diabetic families with mutations in glucokinase must be carefully investigated, to differentiate cryptic maturity-onset diabetes of the young from late-onset NIDDM. Furthermore, pregnancy reveals diabetes in women carrying a glucokinase defect.

Mycoplasma corogypsi sp. nov., a new species from the footpad abscess of a black vulture, Coragyps atratus

Strain BV1 was isolated from the exudate of the footpad abscess of a black vulture (Coragyps atratus). The colonies had a "fried-egg" appearance consistent with that of mycoplasmal species. Electron microscopic examination of the cells revealed irregular elongated or elliptical forms and smaller circular budding processes. Profuse growth was observed in Frey medium supplemented with 20% swine serum at 37 degrees C in a humidified atmosphere of 10% CO2 and air. Typical of mycoplasma, strain BV1 required sterol for growth and catabolized glucose but did not hydrolyze arginine or urea. The guanine-plus-cytosine content of the DNA was 28 mol%. The organism demonstrated the ability to hemolyze, absorb onto, and agglutinate the erythrocytes from several animal species. Strain BV1 was serologically unrelated by the growth inhibition test to previously established Mycoplasma, Acholeplasma, Entomoplasma, and Mesoplasma species, as well as to strains belonging to these genera but not identified to species level. Moreover, BV1 had a 16S rRNA gene with a nucleotide sequence distinct from reported sequences of other mycoplasmas. This organism represents a new species for which the name Mycoplasma corogypsi is proposed. Strain BV1 (ATCC 51148T) is the type strain of Mycoplasma corogypsi sp. nov.

Familial hyperglycemia due to mutations in glucokinase. Definition of a subtype of diabetes mellitus

BACKGROUND AND METHODS

Non-insulin-dependent diabetes mellitus (NIDDM) is a genetically heterogeneous disorder. Maturity-onset diabetes of the young, a form of NIDDM with an early age of onset and autosomal dominant inheritance, can result from mutations in glucokinase, a key enzyme of glucose metabolism in beta cells and the liver. We studied 32 French families with maturity-onset diabetes of the young as well as 21 families with late-onset NIDDM to determine the frequency and clinical features of mutations of glucokinase. Fasting plasma glucose concentrations and oral glucose-tolerance tests were used to determine metabolic status. DNA was isolated from lymphocytes, and DNA polymorphisms in the glucokinase gene were tested for linkage with diabetes. Individual exons of the glucokinase gene from one affected member in each family were amplified by the polymerase chain reaction and screened for mutations by analysis of the conformation-dependent polymorphisms of single-stranded DNA and by DNA sequencing.

RESULTS

We found substantial evidence of linkage between the glucokinase locus and maturity-onset diabetes of the young but not between this locus and late-onset NIDDM: Sixteen mutations were identified in 18 of the 32 families with maturity-onset diabetes of the young, but none were found in families with late-onset NIDDM: They included 10 mutations that resulted in an amino acid substitution, 3 that resulted in the synthesis of a truncated protein, and 3 that affected RNA processing. The affected subjects with glucokinase mutations usually had mild hyperglycemia that began during childhood, whereas in subjects with maturity-onset diabetes of the young not due to glucokinase mutations, hyperglycemia usually appeared after puberty.

CONCLUSIONS

Mutations in glucokinase are the primary cause of hyperglycemia in a substantial fraction of French patients with maturity-onset diabetes of the young and result in a relatively mild form of NIDDM that can be diagnosed in childhood.

Isolation of <Glu-Asn-Phe-His-Leu-Arg-Pro-NH2 (Antho-RPamide II), a novel, biologically active neuropeptide from sea anemones

Using a radioimmunoassay against the C-terminal sequence Arg-Pro-NH2 (RPamide) we have isolated the neuropeptide <Glu-Asn-Phe-His-Leu-Arg-Pro-NH2 (Antho-RPamide II) from extracts of the sea anemone Anthopleura elegantissima. Addition of low concentrations of Antho-RPamide II to a tentacle preparation of sea anemones inhibited the spontaneous, rhythmic contractions, suggesting that the peptide is a neurotransmitter or neuromodulator.

Chemical characterization and toxicity of dihydro derivatives of nodularin and microcystin-LR, potent cyanobacterial cyclic peptide hepatotoxins

Dihydro derivatives of nodularin (1) and microcystin-LR (4), potent cyclic peptide hepatotoxins isolated from Nodularia spumigena and Microcystis aeruginosa, respectively, were prepared by sodium borohydride reduction of the dehydroamino acid residues. The two stereoisomers of both dihydronodularin (2 and 3) and dihydromicrocystin-LR (5 and 6), isolated by reversed-phase HPLC, showed similar toxicity to each other [ip in mice, LD50 = 150 (2), 150 (3), 85 (5), and 100 (6) micrograms/kg]. The stereochemistries of the reduced amino acids obtained by acid hydrolysis of dihydronodularin and dihydromicrocystin-LR [respectively, alpha-(methylamino)butyric acid and N-methylalanine] were determined by GC on a permethylated beta-cyclodextrin capillary column as their trifluoroacetyl methyl ester derivatives. Authentic L- and DL-N-methylamino acids were prepared to compare directly with the natural amino acids. Deuterated derivatives were also prepared using sodium borodeuteride (98 atom % D), and the location (beta) and percentage (78-84%) of the deuterium incorporation were determined.

Glucokinase mutations associated with non-insulin-dependent (type 2) diabetes mellitus have decreased enzymatic activity: implications for structure/function relationships

The glycolytic enzyme glucokinase plays an important role in the regulation of insulin secretion and recent studies have shown that mutations in the human glucokinase gene are a common cause of an autosomal dominant form of non-insulin-dependent (type 2) diabetes mellitus (NIDDM) that has an onset often during childhood. The majority of the mutations that have been identified are missense mutations that result in the synthesis of a glucokinase molecule with an altered amino acid sequence. To characterize the effect of these mutations on the catalytic properties of human beta-cell glucokinase, we have expressed native and mutant forms of this protein in Escherichia coli. All of the missense mutations show changes in enzyme activity including a decrease in Vmax and/or increase in Km for glucose. Using a model for the three-dimensional structure of human glucokinase based on the crystal structure of the related enzyme yeast hexokinase B, the mutations map primarily to two regions of the protein. One group of mutations is located in the active site cleft separating the two domains of the enzyme as well as in surface loops leading into this cleft. These mutations usually result in large reductions in enzyme activity. The second group of mutations is located far from the active site in a region that is predicted to undergo a substrate-induced conformational change that results in closure of the active site cleft. These mutations show a small approximately 2-fold reduction in Vmax and a 5- to 10-fold increase in Km for glucose. The characterization of mutations in glucokinase that are associated with a distinct and readily recognizable form of NIDDM has led to the identification of key amino acids involved in glucokinase catalysis and localized functionally important regions of the glucokinase molecule.

Heterogeneous response to calcium by individual parathyroid cells

Classical stimulus-secretion theory suggests that each individual cell responds to a given stimulus. We tested this theory by determining the response of single bovine parathyroid cells to calcium with the reverse hemolytic plaque assay (RHPA), an assay that measures hormone release from individual cells. As calcium concentrations decreased, the amount of parathyroid hormone (PTH) released per cell increased, and cells were recruited to release PTH. To confirm that adequate stores of PTH were present, immunocytochemistry and in situ hybridization were performed. To test if cells that did not release PTH were capable of secretion, we performed a sequential RHPA; 47.8% of cells did not release PTH after the first stimulus. After the second exposure to low concentrations of calcium, 26.5% of these "nonsecretory" cells were able to release PTH. We conclude that parathyroid cells are homogeneous for PTH content and synthetic capability. Parathyroid cells respond to changes in extracellular calcium heterogeneously in that more PTH per cell is released, and individual parathyroid cells are "recruited" to release PTH at low calcium concentrations. In addition, parathyroid cells can be induced to secrete suggesting that cells are viable but in a depressed secretory state. Parathyroid cells may exist in an "on" or "off" secretory state.

Organometallic products from the reaction of the isoelectronic Mn(CO)5− and Cr(CO)4NO− metallate anions with bis-α-bromocyclopropyl ketone

Mn(CO)5− and Cr(CO)4NO− react with the title ketone to give organometallic products. In the chromium case, a single metallofuran product is produced. In the manganese reaction, one can isolate a series of four complexes, two of which have a structure closely related to the chromium complex. The other two complexes are assigned an acyl manganese structure. The structures of the chromium complex and one of the acyl manganese complexes have been determined by X-ray methods. One finds a distorted octahedral bonding about the metal atom in each case. The chromium complex has bond lengths very similar to those reported for a closely related manganese structure, implying a delocalization of electrons within a metallofuran ring. As expected for this mixed carbonyl nitrosyl complex, the nitrosyl group is positioned trans to the oxide bond, representing the weakest and strongest "trans-effect" substituents. The acyl manganese structures contain an Mn(CO)4 unit in contrast to the usual Mn(CO)5 acyl complexes, with the 18e− count being provided by an internal chelation with the n-electrons of the dicyclopropyl ketone group. The reaction mechanism for the formation of the complexes is postulated to involve initial bromine abstraction (two-electron reduction) by the metallate anion, with the Cr(CO)4NO− reaction being much faster compared to Mn(CO)5−. The resulting organic enolate then "back-reacts" with a carbonyl group of the just-formed metal carbonyl bromide to form a transient anionic Fischer carbene complex. Ultimately this intermediate loses the metal bromide ion with the formation of the neutral complexes.

Isolation and structures of microcystins from a cyanobacterial water bloom (Finland)

A hepatotoxic cyanobacterial (blue-green algal) water bloom was collected from a constructed water reservoir in Finland. The water bloom contained two cyanobacterial species, Microcystis aeruginosa and Aphanizomenon flos-aquae. Two hepatotoxins, 1 and 2, were isolated from extracts of lyophilized cells. The structures of 1 and 2 were assigned based upon their amino acid analyses on a Waters Pico Tag HPLC system and a chiral GC capillary column (Chirasil Val III), fast atom bombardment mass spectrometry (FABMS), high resolution FABMS, and tandem FABMS data. Toxin 1 was identical to a previously reported compound, [D-Asp3]microcystin-RR. Toxin 2 was new and was assigned the structure [D-Asp3]microcystin-YR.

Two new L-serine variants of microcystins-LR and -RR from Anabaena sp. strains 202 A1 and 202 A2

Two new microcystins, [L-Ser7]microcystin-LR (1) and [L-Ser7]microcystin-RR (2), were isolated from a filamentous fresh water cyanobacterium (blue-green alga), Anabaena sp. strain 202 A1, along with the two major toxins, [Dha7]microcystin-LR (3) and [Dha7]microcystin-RR (4) and their minor components the D-Asp variants [D-Asp3,Dha7]microcystin-LR (5) and [D-Asp3,Dha7]microcystin-RR (6). Anabaena sp. strain 202 A1 also produced another new toxin, whose structure is tentatively proposed as [D-Asp3,L-Ser7]microcystin-XR (7), where X is a leucine homologue. Anabaena sp. strain 202 A2 produced one new microcystin, 1, and three known microcystins, 3, 4, and 5. The structures of the toxins were assigned based on their amino acid analyses, and fast atom bombardment mass spectrometry data.

[A new virus of rabbit. III. Study on morphological superstructure and antigenicity of rabbit hemorrhagic disease virus (RHDV)]

In the spring 1986, an acute infectious disease occurred in Wuhan Second Producing Medical Manufactory, and the rabbit almost died. We tested the mortal symptom and confirmed rabbit Hemorrhagic Disease (RHD) as same as Huang Yinyao report. Hubei Traditional Chinese Medicine Institute appear this RHD also. After we purified virus of above two source by low speed, high speed and sucrose density gradient centrifugation, they can react with antiserum of RHDV from Nanjing Agricultural University in agar gel immunodiffusion tests. These results proved that they belong to the same serotype. Data indicate RHDV have difference morphological superstructure, viral polypeptides and especially RHDV can't react with antiserum of standard Parvovirus of rabbit and so on, so we suggest RHDV is a new virus.

Isolation and characterization of a variety of microcystins from seven strains of the cyanobacterial genus Anabaena

Hepatotoxins (microcystins) from seven freshwater Anabaena strains originating from three different Finnish lakes and one lake in Norway were isolated by high-performance liquid chromatography and characterized by amino acid analysis and fast atom bombardment mass spectrometry. All strains produced three to seven different microcystins. A total of 17 different compounds were isolated, of which 8 were known microcystins. The known compounds identified from six strains were MCYST (microcystin)-LR, [D-Asp3]MCYST-LR, [Dha7]MCYST-LR, [D-Asp3,Dha7]MCYST-LR, MCYST-RR, [D-Asp3]MCYST-RR, [Dha7]MCYST-RR, and [D-Asp3,Dha7]MCYST-RR. With the exception of MCYST-LR and [D-Asp3]MCYST-LR, this is the first time that isolation of these toxins from Anabaena strains has been reported. Three of the strains produced one to three toxins as minor components which could not be identified. Anabaena sp. strain 66 produced four unidentified toxins. The other Anabaena strains always contained both MCYST-LR and MCYST-RR and/or their demethyl variants. Quantitative differences between toxins within and between strains were detected; at times MCYST-LR and at other times MCYST-RR or demethyl derivatives thereof were the most abundant toxins found in a strain.

[A new virus of rabbit. II. Study on morphological structure and some physicochemical properties of a strain of rabbit hemorrhagic disease virus]

In this paper a strain of Rabbit Hemorrhagic Disease Virus (RHDV) was isolated and purified from the diseased rabbit livers with a method of using chloroform, two-phase of polyethylene-glycol-dextran sulfate sodium and sucrose density gradient centrifugation. Purified virus was nonenveloped, icosahedeal symmetry with a triangulation number of 3, and 33-37 nm in diameter. The capsid was composed of 32 capsomeres with central holes in an outer diameter of about 9nm. Two types of viral particles having different sedimentation coefficient, 130s and 166s could be identified after sucrose density gradient centrifugation. Probably no less than four virion proteins with molecular weight of 66.4, 65.0, 63.5, 41.0 x 10(3) dalton were detected by SDS-polyacrylamide gel electrophoresis. Viral nucleic acid was extracted from purified virus by using SDS-proteinase K-phenol. Tests with diphenylamine, formaldehyde, and staining with acridine orange as well as the curves of thermal denaturation showed that this kind of virus had a single-stranded DNA. The molecular weight of the ssDNA was approx 2.1 x 10(6) dalton as determined by electron microscopy. Data indicate that the RHDV may like the parvovirus of the family Parvoviridae.

Degenerate oligonucleotide primers for enzymatic amplification of recA sequences from gram-positive bacteria and mycoplasmas

RecA protein in gram-negative bacteria, especially in Escherichia coli, has been extensively studied, but little is known about this key enzyme in other procaryotes. Described here are degenerate oligonucleotide primers that have been used to amplify by the polymerase chain reaction (PCR) recA sequences from several gram-positive bacteria and mycoplasmas. The DNA sequences of recA PCR products from Streptococcus pyogenes, Streptococcus mutans, Enterococcus faecalis, and Mycoplasma pulmonis were determined and compared. These data indicate that the M. pulmonis recA gene has diverged significantly from recA genes of other eubacteria. It should be possible to use cloned recA PCR products to construct recA mutants, thereby providing the means of elucidating homologous genetic recombination and DNA repair activities in these organisms.