Human immunodeficiency virus type 1 IgA antibody in breast milk and serum

Breast-feeding plays a potentially significant role in mother to child transmission of human immunodeficiency virus type 1 (HIV-1). The additional transmission risk attributable to breast-feeding and the factors that enhance or inhibit transmission are presently unknown. One mechanism by which breast milk might inhibit HIV-1 transmission is the presence of specific antibodies directed against HIV-1 in breast milk of seropositive mothers. In this study serum and breast milk samples from women in Nairobi, Kenya, were tested to determine the prevalence of HIV-1 IgA antibodies. A Western blot test developed in our laboratory was used to detect anti-HIV-1 immunoglobulin A in serum and anti-HIV-1 secretory IgA (sIgA) in breast milk. Ninety-four percent of 63 HIV-1 seropositive women had anti-HIV-1 IgA in serum and 59% had anti-HIV-1 sIgA in their breast milk. No significant associations with maternal characteristics or serum anti-HIV-1 IgA or IgG banding patterns and the presence of anti-HIV-1 sIgA in breast milk were found. No protective effect of anti-HIV-1 sIgA was seen regarding mother to child transmission; however, further studies are necessary to determine the effect of these antibodies in maternal sera or in breast milk on the efficacy of HIV-1 transmission.

Ophthalmia neonatorum in a trachoma endemic area

BACKGROUND AND OBJECTIVES

Chlamydia trachomatis can be directly transmitted by sexual or perinatal contact and indirectly transmitted by flies or fomites. Whether distinct epidemiologic forces among human populations or biologic characteristics of the organism are responsible for the different routes of transmission is uncertain.

STUDY DESIGN

To determine if ophthalmia neonatorum and trachoma are linked epidemiologically, 38 infants with ophthalmia and 277 children with trachoma were studied for evidence of C. trachomatis infection using culture, antigen and DNA detection tests. The study was performed in a trachoma endemic area of central Kenya.

RESULTS

Of infants with ophthalmia neonatorum, 8% to 9% had microbiologic evidence of ocular C. trachomatis infection. Of the children with trachoma, 31% had evidence of chlamydial infection. Ninety-two percent of the 59 identified strains causing trachoma belonged to the classic trachoma serovars (A, B, Ba and C). Neither of the two chlamydial strains recovered from infants with ophthalmia was a trachoma serovar. Mothers rarely (3%) had cervical C. trachomatis infection.

CONCLUSION

This study does not support a major role for perinatally transmitted C. trachomatis infection in trachoma epidemiology.

TdcA, a transcriptional activator of the tdcABC operon of Escherichia coli, is a member of the LysR family of proteins

The tdcB and tdcC genes of the tdcABC operon of Escherichia coli encode threonine dehydratase and a threonine-serine permease, respectively. These proteins are involved in transport and metabolism of threonine and serine during anaerobic growth. In this study, we functionally characterized tdcA, which encodes a 35 kDa polypeptide consisting of 312 amino acid residues. Non-polar and partially polar mutations introduced into tdcA drastically reduced the expression of the genes down-stream from tdcA. Complementation studies using single-copy chromosomal integrants of a tdcB-lacZ fusion harboring an in-frame deletion of tdcA with chromosomal or plasmid-borne tdcA+ in trans showed complete restoration of tdc operon expression in vivo. The amino acid sequence at the amino-terminal end of TdcA revealed a significant homology to the helix-turn-helix motifs of typical DNA binding proteins. Sequence alignment of TdcA with LysR also showed considerable sequence similarity throughout their entire lengths. Our results suggest that TdcA is related to the LysR family of proteins by common ancestry and, based on its functional role in tdc expression, belongs to the LysR family of transcriptional activators.

Catabolite gene activator protein and integration host factor act in concert to regulate tdc operon expression in Escherichia coli

Anaerobic expression of the tdcABC operon of Escherichia coli requires cyclic AMP and the catabolite gene activator protein (CAP). Purified CAP binds to a 30-bp sequence in the tdc promoter between positions -55 and -26, and a mutant CAP site with base substitutions at positions -48, -47, and -45 failed to bind CAP and also drastically reduced the beta-galactosidase expression from a tdcB'-'lacZ fusion plasmid. Recently, we showed that efficient expression of the tdc operon also requires a functional integration host factor (IHF) and an IHF-binding site in the tdc promoter between positions -118 and -88. The levels of beta-galactosidase activity from the tdcB'-'lacZ fusion plasmids were also reduced in an IHF-deficient strain with the wild-type or mutant plasmid CAP sequence. In vitro footprinting experiments revealed that CAP and IHF occupy their specific binding sites on tdc DNA when they are present separately or together. These regulatory proteins also induced significant bending of the tdc promoter DNA. Our results suggest that CAP and IHF act in concert as positive transcription factors for tdc operon expression in vivo.

Increased risk of early measles in infants of human immunodeficiency virus type 1-seropositive mothers

An increase in illness due to measles is one of the potential consequences of the human immunodeficiency virus (HIV) epidemic in Africa. During a study of perinatal HIV transmission conducted in Kenya, the risk of acquiring measles before vaccination (9 months of age) was found to be 3.8 times higher in infants born to HIV-seropositive mothers than in control infants (10 [9%] of 109 vs. 5 [3%] of 194 infants; P = .02; odds ratio, 3.8; 95% confidence interval, 1.2-13.2). The majority of infants who developed measles in this study had significant sequelae related to their measles infection. The increased risk of measles appeared to be related to relatively lower anti-measles antibody titers detected in cord blood samples of affected infants born to HIV-seropositive mothers. However, 94% of all infants were susceptible to measles on the basis of ELISA testing at age 6 months regardless of maternal HIV serology. These observations highlight the need for improved measles vaccination strategies in Africa and for studies to delineate the effects of HIV infection on the incidence, presentation, and sequelae of childhood infectious illnesses.

Integration host factor is required for positive regulation of the tdc operon of Escherichia coli

A 14-bp segment in the promoter region of the tdcABC operon of Escherichia coli shows sequence identity with the consensus binding site for the E. coli integration host factor (IHF). In an himA (IHF-deficient) strain, expression of beta-galactosidase from a tdcB'-'lacZ protein fusion plasmid was about 10% of that seen with an isogenic himA+ strain. Threonine dehydratase activity from the chromosomal tdcB gene in the himA mutant was also about 10% of the wild-type enzyme level. Two different mutations introduced into the putative IHF-binding site in the fusion plasmid greatly reduced the plasmid-coded beta-galactosidase activity in cells containing IHF. In vitro gel retardation and DNase I footprinting analyses showed binding of purified IHF to the wild-type but not to the mutant promoter. IHF protected a 31-bp region between -118 and -88 encompassing the conserved IHF consensus sequence. These results suggest that efficient expression of the tdc operon in vivo requires a functional IHF and an IHF-binding site in the tdc promoter.

Physical linkage and transcriptional orientation of the tdc operon on the Escherichia coli chromosome

The physical and genetic structure of 37 kilobases of DNA encompassing the tdc region at 68.3 min of the Escherichia coli chromosome was determined by DNA sequence analysis and restriction mapping. Re-examination of new data concerning the direction of transcription of the tdc operon revealed that in strain W3110 the tdc region is located on a transposable segment of DNA.

Adjuvant activity of non-ionic block copolymers. V. Modulation of antibody isotype by lipopolysaccharides, lipid A and precursors

Non-ionic block copolymers and lipopolysaccharides are both effective immunological adjuvants which are thought to act via distinct mechanisms. We hypothesized that they might produce synergistic effects when used together. We prepared a series of lipopolysaccharide (LPS) preparations ranging from the smallest precursor, lipid X through complete LPS with O-polysaccharide chains. Three preparations with reduced toxicity, monophosphoryl lipid A, partially hydrolysed Ra-LPS and LPS of Rhodopseudomonas sphaeroides were also utilized. All LPS preparations except the smallest were effective adjuvants for inducing early antibody responses to trinitrophenyl-conjugated hen egg albumin (TNP-HEA) when injected in squalane-in-water emulsions with copolymer L141. Only the larger LPS preparations induced sustained antibody responses. By itself, emulsions of copolymer L141 induced a predominant IgG1 antibody isotype response with lesser amounts of IgG2a and IgG2b. Surprisingly, all of the LPS preparations tested increased the proportion of IgG2 isotypes even though some had little effect on overall titres. The detoxified Ra-LPS (Ra-detox) was the most effective preparation for both increasing antibody titres and inducing the desirable IgG2a and IgG2b isotypes. These results demonstrate that the combination of LPS and block polymer adjuvants can produce synergistic effects without unacceptable toxicities.

Impact of maternal HIV infection on obstetrical and early neonatal outcome

In a case-control study of 177 HIV-seropositive and 326 seronegative women and their newborns in Nairobi, Kenya, maternal HIV infection at term was independently associated with travel to other African countries [odds ratio (OR) 4.9, P less than 0.0001], history of a blood transfusion since 1980 (OR 3.5, P = 0.01), history of more than one sexual partner in the previous 5 years (OR 1.8, P = 0.02) and unmarried status (OR 1.8, P = 0.02). Neonates of HIV-positive and HIV-negative women differed little with respect to occurrence of congenital malformations, stillbirths, in-hospital mortality, sex, APGAR score, or gestational age. However, the mean birth weight of singleton neonates of HIV-positive women was significantly lower than that of controls (3090 versus 3220 g, P = 0.005), and birth weight was less than 2500 g in 9% of cases and 3% of controls (OR 3.0, P = 0.007). Among neonates of HIV-seropositive women, birth weight was less than 2500 g in 17% if mothers were symptomatic and 6% if mothers were asymptomatic (OR 3.4, P = 0.08).

A novel membrane-associated threonine permease encoded by the tdcC gene of Escherichia coli

A novel L-threonine transport system is induced in Escherichia coli cells when incubated in amino acid-rich medium under anaerobic conditions. Genetic and biochemical analyses with plasmids harboring mutations in the anaerobically expressed tdcABC operon indicated that the tdcC gene product was responsible for L-threonine uptake. Competition experiments revealed that the L-threonine transport system is also involved in L-serine uptake and is partially shared for L-leucine transport; L-alanine, L-valine, and L-isoleucine did not affect L-threonine uptake. Transport of L-threonine was inhibited by the respiratory chain inhibitors KCN and carbonyl cyanide m-chlorophenylhydrazone and was Na+ independent. These results identify for the first time an E. coli gene encoding a permease specific for L-threonine-L-serine transport that is distinct from the previously described threonine-serine transport systems. A two-dimensional topological model predicted from the amino acid composition and hydropathy plot showed that the TdcC polypeptide appears to be an integral membrane protein with several membrane-spanning domains exhibiting a striking similarity with other bacterial permeases.

Outbreak of dysentery due to nalidixic acid resistant S. dysenteriae 1 at Agartala, Tripura: a hospital based study

During the epidemic of bacillary dysentery at Agartala, Tripura, a total of 62 hospitalized patients suffering from diarrhoeal diseases were studied during the later part (11-16 June, 1988) of the epidemic. Principal features of Shigellosis cases were discussed. Of these 62 cases investigated, 19(30.6%) cases had the mucoid diarrhoea. From them S.dysenteriae type 1 and S.flexneri had been recovered from 31.6% and 10.5% cases, respectively. All the strains of S.dysenteriae type 1 isolated during the period of investigation were resistant to nalidixic acid.

Effect of protein rich diet during acute phase of dysentery

Ninety six children upto the age of five years suffering from uncomplicated acute dysentery of less than 3 days' duration were studied to find out the impact of feeding of extra-protein rich diet during their acute phase of illness. These children were randomly allocated to either control group (receiving only hospital diet) and study group (receiving hospital diet and extra milk which constituted 30% of ideal total calorie requirement of patients. Patients in the two groups were comparable on admission. Forty percent reduced food intake was observed among the children of both the groups due to severe anorexia which was reflected by no significant differences in clinical outcome, anthropometrical measurements and haematological parameters between the two groups on day 7 of hospitalisation and on day 15 after discharge.

Increased expression of biodegradative threonine dehydratase of Escherichia coli by DNA gyrase inhibitors

The synthesis of inducible biodegradative threonine dehydratase of Escherichia coli increased several-fold in the presence of the DNA gyrase inhibitors, nalidixic acid and coumermycin. Temperature-sensitive gyrB mutants expressed higher levels of dehydratase as compared to an isogenic gyrB+ strain. Immunoblotting experiments showed increased synthesis of the dehydratase protein in the presence of gyrase inhibitors; addition of rifampicin and chloramphenicol to cells actively synthesizing enzyme preventing new enzyme production. Increased expression of dehydratase by gyrase inhibitors was accompanied by relaxation of supercoiled DNA.

Isolation and characterization of a cDNA clone encoding the lima bean lectin

The complete amino acid sequence of the lima bean (Phaseolus lunatus) lectin was deduced from the nucleotide sequence of a cDNA clone. The lectin appears to be synthesized as a prepeptide consisting of a signal sequence of 21 residues and a mature protein of 241 amino acids. Comparison of the lima bean lectin sequence to the sequences of other leguminous seed lectins indicates regions of extensive homology. Northern blot analysis showed absence of lectin mRNA in the leaves, roots, or stems of 16-day-old lima bean plants.

Lack of correlation of maternal human immunodeficiency virus infection with neonatal malformations

A malformation syndrome has been proposed in infants with acquired immunodeficiency syndrome or acquired immunodeficiency syndrome-related complex secondary to congenital infection with human immunodeficiency virus (HIV) in the United States and Europe. To determine whether embryopathy is detectable in HIV-exposed African infants, 85 infants of HIV-seropositive mothers and 98 infants of HIV-seronegative mothers in Nairobi, Kenya, were examined for minor and major anomalous features shortly after birth. No mother used intravenous drugs. With the exception of growth failure no anomalous feature was associated with in utero HIV exposure. No increase in the number of anomalous features per infant was correlated with HIV, nor did any infant have the reported malformation syndrome. Thus in this population of African infants examination for anomalous features during the neonatal period failed to identify those infants with fetal exposure to HIV.

Identification and DNA sequence of tdcR, a positive regulatory gene of the tdc operon of Escherichia coli

Efficient in vivo expression of the biodegradative threonine dehydratase (tdc) operon of Escherichia coli is dependent on a regulatory gene, tdcR. The tdcR gene is located 198 base pairs upstream of the tdc operon and is transcribed divergently from this operon. The nucleotide sequence of tdcR and two unrelated reading frames has been determined. The deduced amino acid sequence of TdcR indicates that it is a polypeptide of Mr 12,000 with 99 amino acid residues and contains a potential helix-turn-helix DNA binding motif. Deletion analysis and minicell expression of the tdcR gene suggest that TdcR may serve as a trans-acting positive activator for the tdc operon.

Cloning and sequence analysis of the Escherichia coli metH gene encoding cobalamin-dependent methionine synthase and isolation of a tryptic fragment containing the cobalamin-binding domain

A gene encoding cobalamin-dependent methionine synthase (EC 2.1.1.13) has been isolated from a plasmid library of Escherichia coli K-12 DNA by complementation to methionine prototrophy in an E. coli strain lacking both cobalamin-dependent and -independent methionine synthase activities (RK4536:metE, metHH). Maxicell expression of a series of plasmids containing deletions in the metH structural gene was employed to map the position and orientation of the gene on the cloned DNA fragment. A 6.3-kilobase EcoRI-SalI fragment containing the gene was cloned into the sequencing vector pGEM3B for double-stranded DNA sequencing; the MetH coding region consists of 3372 nucleotides. The enzyme was purified from an overproducing strain of E. coli harboring the recombinant plasmid, in which the level of methionine synthase was elevated 30- to 40-fold over wild-type E. coli. Recombinant enzyme is a protein of 123,640 molecular weight and has a turnover number of 1,450 min-1 in the standard assay. These values are to be compared with previously reported values of 133,000 for the molecular weight and 1,240-1,560 min-1 for the turnover number of the homogenous enzyme purified from a wild-type strain of E. coli B (Frasca, V., Banerjee, R. V., Dunham, W. R., Sands, R. H., and Matthews, R. G. (1988) Biochemistry 27, 8458-8465). Limited proteolysis of the native enzyme with trypsin resulted in loss of enzyme activity but retention of bound cobalamin on a peptide fragment of 28,000 molecular weight. This fragment has been shown to extend from residue 643 to residue 900 of the 1124-residue deduced amino acid sequence.

Amino acid sequence of the regulatory-site glyoxylate peptide of biodegradative threonine dehydratase of Escherichia coli

Incubation of purified Escherichia coli biodegradative threonine dehydratase with glyoxylate resulted in covalent binding of 1 mol of glyoxylate per mol of protein with concomitant loss of enzyme activity. The glyoxylate-binding site was identified as a heptapeptide representing amino acid residues Ser-33-Asn-Tyr-Phe-Ser-Glu-Arg-39 in the protein primary structure. Addition of glyoxylate to a culture of E. coli cells led to time-dependent enzyme inactivation. Immunoprecipitation with anti-dehydratase antibody of extract from [14C]glyoxylate-treated cells revealed labeled dehydratase polypeptide. These results are interpreted to mean that enzyme inactivation by glyoxylate in E. coli cells is associated with covalent protein modification.

Photoaffinity labeling of the allosteric AMP site of biodegradative threonine dehydratase of Escherichia coli with 8-azido-AMP

The photoreactive AMP analog, 8-azido-AMP, stimulated the activity of biodegradative threonine dehydratase of Escherichia coli in a reversible manner and, like AMP, decreased the Km for threonine. The concentrations required for half-maximal stimulation by AMP and 8-azido-AMP were 40 microM and 1.5 microM, respectively, and the maximum stimulation by 8-azido-AMP was 25% of that seen with AMP. Gel-filtration experiments revealed that 8-azido-AMP stabilized a dimeric form of the enzyme, whereas AMP promoted a tetrameric species. When present together, AMP and 8-azido-AMP showed mutual competition in influencing catalytic activity as well as the conformational state of the protein. Photolabeling of AMP-free dehydratase with 8-azido-[2-3H]AMP resulted in a time and concentration-dependent enzyme inactivation and concomitant incorporation of 8-azido-AMP into protein. At low 8-azido-AMP concentrations, incorporation of about 1 mol 8-azido-AMP/mol dehydratase tetramer was correlated with almost complete inactivation of the enzyme. The presence of AMP in the photolabeling reaction greatly reduced the extent of enzyme inactivation and 8-azido-AMP binding. Ultraviolet irradiation with 20 microM 3H-labeled 8-azido-AMP revealed one tryptic peptide, Thr230-Thr-Gly-Thr-Leu-Ala-Asp-Gly-Cys-Asp-Val-Ser-Arg242, with bound radioactivity. This peptide, labeled at low concentration of 8-azido-AMP, most likely represents the AMP-binding region on the dehydratase molecule.

Molecular characterization of the tdc operon of Escherichia coli K-12

The nucleotide sequence of a 2-kilobase DNA fragment of the tdc region of Escherichia coli K-12, previously cloned in this laboratory, revealed two open reading frames, tdcC and ORFX, downstream from the tdcB gene (formerly designated tdc) encoding biodegradative threonine dehydratase. A 24-base-pair sequence separated tdcC from the dehydratase coding region, and an untranslated region of 60 nucleotides, which contains a recognizable -10 consensus sequence, was found between tdcC and ORFX. The deduced amino acid sequence of tdcC showed it to be a large hydrophobic polypeptide of 431 amino acid residues, whereas ORFX coded for a small 135-residue polypeptide lacking glutamine and tryptophan. A computer-assisted sequence analysis revealed no similarity among the tdcB, tdcC, and ORFX polypeptides, and a search of the GenBank database failed to detect similarity with any other known proteins. The tdc genes and ORFX showed similar codon usage and, in analogy with other bacterial genes, showed codon usage typical for genes expressed at an intermediate level. Transcriptional analysis with S1 nuclease indicated two distinct transcription start sites upstream of the tdcB gene in regions previously identified as promoterlike elements P1 and P2. Interestingly, expression of tdcB and tdcC, but not ORFX, was contingent upon the presence of P1. These results taken together tend to suggest that the biodegradative threonine dehydratase is the second gene in a polycistronic transcription unit constituting a novel operon (tdcABC) in E. coli implicated in anaerobic threonine metabolism.

Genetic analysis of the tdcABC operon of Escherichia coli K-12

The biodegradative threonine dehydratase (tdc) operon was mapped at 68 min on the Escherichia coli K-12 chromosome. The order of markers in the clockwise direction was dnaG uxaA tdc argG. A tdc deletion was isolated and mapped to this region of the chromosome. By using a tdcB-lacZ fusion the clockwise direction of transcription of tdc was determined.

Infection and disease after perinatal exposure to Chlamydia trachomatis in Nairobi, Kenya

A cohort of 49 infants exposed to maternal chlamydial infection and 40 nonexposed infants was studied after birth for a mean of 3.3 +/- 1.5 and 3 +/- 1.7 mo, respectively. Eighteen (37%) exposed infants had at least one positive culture for Chlamydia trachomatis, whereas C. trachomatis was not isolated from any of the nonexposed infants. Eighteen (37%) exposed infants developed ophthalmia neonatorum (n = 12) or infant conjunctivitis (n = 7), compared with six (15%) of the nonexposed infants (P = .04). Six (12%) exposed infants developed pneumonia, compared with none of the 40 nonexposed infants (P = .05). One infant in the exposed group died during follow-up. These results suggest that appreciable infant morbidity in Kenya may be associated with the high prevalence of maternal chlamydial infection.

Prophylaxis of gonococcal and chlamydial ophthalmia neonatorum. A comparison of silver nitrate and tetracycline

We evaluated the use of silver nitrate drops and tetracycline ointment for the prophylaxis of ophthalmia neonatorum in a controlled trial involving 2732 newborns in Nairobi, Kenya. The overall rates of prevalence of intrapartum maternal gonococcal and chlamydial infection were 6.4 and 8.9 percent, respectively. After prophylaxis with silver nitrate, the incidence rates of gonococcal, chlamydial, and nongonococcal, nonchlamydial ophthalmia neonatorum were 0.4, 0.7, and 6.2 percent, respectively, whereas after prophylaxis with tetracycline, the rates were 0.1, 0.5, and 4.5 percent. The attack rates of gonococcal ophthalmia neonatorum in newborns exposed to Neisseria gonorrhoeae at birth were 7.0 percent in those receiving silver nitrate and 3.0 percent in those receiving tetracycline (95 percent confidence interval for the difference in rates, -3.4 to 11.4 percent). As compared with historical controls, the incidence of gonococcal ophthalmia neonatorum decreased 83 percent among infants treated with silver nitrate and 93 percent among those treated with tetracycline. Failure of prophylaxis was associated with postpartum maternal endometritis (P = 0.05). Among newborns exposed to maternal infection with Chlamydia trachomatis, chlamydial conjunctivitis developed in 10.1 percent given silver nitrate and in 7.2 percent given tetracycline (95 percent confidence interval for the difference in rates, -4.7 to 10.5 percent), yielding reductions in the incidence of chlamydial ophthalmia of 68 and 77 percent, respectively, as compared with the historical controls. We conclude that tetracycline is as effective as silver nitrate in preventing gonococcal ophthalmia neonatorum.

Covalent structure of biodegradative threonine dehydratase of Escherichia coli: homology with other dehydratases

The 987-base-pair coding region of the tdc gene of Escherichia coli K-12 encoding biodegradative threonine dehydratase [Tdc; L-threonine hydro-lyase (deaminating), EC 4.2.1.16], previously cloned in this laboratory, was sequenced. The deduced polypeptide consists of 329 amino acid residues with a calculated Mr of 35,238. Although the purified enzyme was shown to contain tryptophan, no tryptophan codon was found in the tdc reading frame. Incubation of purified Tdc with [14C]tryptophan revealed apparent "covalent" binding of tryptophan, indicating posttranslational modification of the enzyme. A heptapeptide, 54Thr-55Gly-56Ser-57Phe-58Lys-59Ile- 60Arg, was found to contain Lys-58, which binds pyridoxal phosphate coenzyme. A comparison of amino acid sequences between the Tdc polypeptide and the biosynthetic threonine dehydratases of yeast (encoded by ILV1) and E. coli (encoded by ilvA) and the E. coli D-serine dehydratase (DsdA, encoded by dsdA) revealed various extents of homology: five domains of the Tdc polypeptide were 63-93% homologous with the yeast enzyme, and three of these same regions were 80% homologous with the biosynthetic E. coli dehydratase; two different domains showed 67% and 83% homology with DsdA. In addition, two other sequences were highly conserved in all four proteins, one of which was shown to contain the conserved lysine residue that binds pyridoxal phosphate in the Tdc and DsdA polypeptides. These observations suggest that, despite their diverse origin and metabolic significance, these enzymes may have evolved from a common ancestral protein.

Interference by IgG paraproteins in the Jaffe method for creatinine determination

A large (60-100%) negative interference in serum creatinine value of some (3 of 18 myeloma patients, all with monoclonal gammopathy of IgG type, was observed on several instruments that determine creatinine by the Jaffe reaction. No interference was observed in an enzymatic method. Serum electrophoresis showed a monoclonal band in all three samples. The interferent could be removed by acid precipitation or dithiothreitol preincubation, and partially isolated in the high molecular weight dialyzate from the serum. It was demonstrated that the interferent is not albumin or normal gammaglobulin. Kinetic analysis of the Jaffe reaction showed large initial decreases in absorbance, in agreement with the corresponding creatinine results. It is suggested that some monoclonal IgGs may react with the Jaffe picrate reagent, resulting in a false lowering of serum creatinine values.

Rectal histology in acute bacillary dysentery

A recent epidemic of acute Shigella dysentery in West Bengal (India) provided us with an opportunity to examine the rectal mucosal abnormalities seen in this condition. One hundred two patients were investigated using sigmoidoscopy, rectal biopsy, and rectal swab for culture. Pure culture of Shigella was obtained in 37 cases, and the rectal biopsy specimens from these patients were assessed in detail. The mean (+/- SD) duration of illness was 47.8 +/- 27.4 h (range 8-120 h), and most patients (31 of 37, 84%) had diarrhea with blood and mucus in the stools. Significant findings at histology were as follows. (a) Cellular infiltrate was predominantly round cell or mixed round cell and neutrophilic in the majority of patients (27, 73%). (b) Disorganization of crypts was seen in as many as 31 patients (84%); in most subjects the distorted architecture was mild, but in a few the defect was severe with crypt branching and dilatation. (c) In the majority of patients the inflammatory process extended to the muscularis mucosae and submucosa; edema with or without increased cellular infiltrate was seen in the muscularis mucosae in 92% and in the submucosa in 80%. (d) There was no difference in the rectal histology of patients with a short history of disease (less than 48 h) compared with those with a longer history, except for goblet cell depletion which was more in those with diarrhea for more than 48 h. (e) The mucosal abnormalities in patients with watery diarrhea were, in general, milder than in those with dysentery, although the difference was statistically not significant; 2 of 6 patients with watery diarrhea had severe colitis. (f) The mucosal abnormalities were more severe in patients with Shigella dysenteriae infection compared with Shigella flexneri.

Quality control for a 14- to 18-megohm-cm deionized water supply

We studied the quality control for a 14- to 18-megohm-cm deionized water system with multiple outlets. The quality of water was determined by measuring specific resistance, performing a total colony count, trace metal analysis, and high-performance liquid chromatographic analysis. The specific resistivity of water was at the level of 17 to 18 megohms-cm at the recirculation loop and greater than 10 megohms-cm at the individual faucets. The microbial content was consistently less than 100 colony-forming units/mL. Periodic trace-metal analysis indicated less than 1 microgram/L of copper, bismuth, zinc, cadmium, mercury, thallium, and lead. High-performance liquid chromatographic analysis, as determined by the absorbance of the highest peak by ultraviolet and fluorescence spectroscopy, indicated less than or equal to 0.001 absorbance unit. Our experience suggests that maintaining laboratory water at 14 to 18 megohms using a plastic system with plastic faucets eliminates the likelihood of bacterial organic and trace-metal contamination of the water.

Molecular cloning and expression of the biodegradative threonine dehydratase gene (tdc) of Escherichia coli K12

The biodegradative threonine dehydratase gene (tdc) of Escherichia coli was cloned by isolating a dehydratase negative mutant after Tn5 mutagenesis, cloning the tdc::Tn5 DNA into pBR322 and then replacing the Tn5 element on the plasmid in vivo. Subcloning and nucleotide sequence data revealed two distinct procaryotic promoter-like elements each containing a potential CAP-binding site and AT-rich regions, and a Shine-Dalgarno sequence. One of these putative promoters, P2, was located immediately upstream from the tdc coding region, and a second, P1, was approximately 1 kilobase upstream from P2. Deletion of the potential CAP-binding site from P1 prevented tdc gene expression. However, removal of P2 and a large segment of the upstream DNA had no discernible effect on dehydratase synthesis. A 936-base pair open reading frame was found between P1 and the tdc coding region, which produced a polypeptide of about 32 kilodaltons. The data suggest that P1, and not P2, is necessary for tdc gene expression, and that the DNA sequences coding for the 32 KD polypeptide and threonine dehydratase are part of a single transcriptional unit.