SPACR, a novel interphotoreceptor matrix glycoprotein in human retina that interacts with hyaluronan

SPACR (sialoprotein associated with cones and rods), is the major 147-150-kDa glycoprotein present in the insoluble interphotoreceptor matrix of the human retina. Immunocytochemistry localizes SPACR to the matrix surrounding rods and cones (Acharya, S., Rayborn, M. E., and Hollyfield, J. G. (1998) Glycobiology 8, 997-1006). From affinity-purified SPACR, we obtained seven peptide sequences showing 100% identity to the deduced sequence of IMPG1, a purported chondroitin 6-sulfate proteoglycan core protein, which binds peanut agglutinin and is localized to the interphotoreceptor matrix. We show here that SPACR is the most prominent 147-150-kDa band present in the interphotoreceptor matrix and is the gene product of IMPG1. SPACR is not a chondroitin sulfate proteoglycan, since it is not a product of chondroitinase ABC digestion and does not react to a specific antibody for chondroitin 6-sulfate proteoglycan. Moreover, the deduced amino acid sequence reveals no established glycosaminoglycan attachment site. One hyaluronan binding motif is present in the predicted sequence of SPACR. We present evidence that SPACR has a functional hyaluronan binding domain, suggesting that interactions between SPACR and hyaluronan may serve to form the basic macromolecular scaffold, which comprises the insoluble interphotoreceptor matrix.

The role of pharmacists in HIV/STD prevention: evaluation of an STD syndromic management intervention in Nepal

OBJECTIVE

To evaluate the effects of a pilot sexually transmitted disease (STD) syndromic case management training for pharmacists in Nepal on STD drug dispensing behavior, HIV/STD prevention communication, and condom promotion and sales.

METHODS

Pre- and post-intervention interviews with samples of 160 pharmacists were conducted utilizing the simulated client method to collect data on pharmacists' response to men reporting urethral discharge. In order to assess the long-term effects, a sub-sample of 38 pharmacists trained 7-9 months before the follow-up survey was analysed separately.

RESULTS

There were no significant differences in the percentages of pharmacists who suggested taking medications, dispensed medications, or referred clients to a physician. The proportion of pharmacists who recommended an injection declined from 27% to 14%. Prior to the intervention, only one pharmacist (0.8%) dispensed the correct drugs and regimen for the syndromic treatment of urethritis. This increased to 45% immediately following the training. In a sub-sample of pharmacists who were interviewed 7-9 months after the training, the correct drugs and regimen were dispensed by 26%. The proportion of pharmacists who recommended to clients to have their sex partners treated increased from 5% to 21%. Although the proportion of pharmacists who suggested condom use increased from 14% to 24%, the proportion of pharmacists actually selling a condom or giving advice on HIV testing remained low and unchanged pre- and post-intervention. Over one-third of pharmacists mentioned HIV or AIDS in their interactions with clients, compared to 9% prior to the intervention.

CONCLUSIONS

The findings suggest that STD services provided by pharmacists can be significantly improved through a short-term training intervention, although the improvements are modest and probably time-limited. Interventions must be more intensive and combined with regular follow-ups if they are to meet their desired goals of improving STD treatment in a pharmacy setting.

Characterization of SPACR, a sialoprotein associated with cones and rods present in the interphotoreceptor matrix of the human retina: immunological and lectin binding analysis

Rod and cone photoreceptors project from the outer retinal surface into a carbohydrate-rich interphotoreceptor matrix (IPM). Unique IPM glycoconjugates are distributed around rods and cones. Wheat germ agglutinin (WGA) strongly decorates the rod matrix domains and weakly decorates the cone matrix domains. This study characterizes the major WGA-binding glycoprotein in the human IPM, which we refer to as SPACR (sialoprotein associated with cones and rods). SPACR, which has a molecular weight of 147 kDa, was isolated and purified from the IPM by lectin affinity chromatography. A polyclonal antibody to SPACR was prepared that colocalizes in tissue preparations with WGA-binding domains in the IPM. Sequential digestion of SPACR with N- and O-glycosidases results in a systematic increase in electrophorectic mobility, indicating the presence of both N- and O-linked glycoconjugates. Complete deglycosylation results in a reduction in the relative molecular mass of SPACR by about 30%. Analysis of lectin binding allowed us to identify some of the structural characteristics of SPACR glycoconjugates. Treatment with neuraminidase exposes Galbeta1-3GalNAc disaccharide as indicated by positive peanut agglutinin (PNA) staining, accompanied by the loss of WGA staining. Maackia amurensis agglutinins (MAA-1 and MAA-2), specific for sialic acid in alpha2-3 linkage to Gal, bind SPACR, while Sambucus nigra agglutinin (SNA), specific for alpha2-6 linked sialic acid, does not, indicating that the dominant glycoconjugate determinant on SPACR is the O-linked carbohydrate, NeuAcalpha2-3Galbeta1-3GalNAc. The abundance of sialic acid in SPACR suggests that this glycoprotein may contribute substantially to the polyanionic nature of the IPM. The carbohydrate chains present on SPACR could also provide sites for extensive crosslinking and participate in the formation of the ordered IPM lattice that surrounds the elongate photoreceptors projecting from the outer retinal surface.

Multicentric reticulohistiocytosis

A 54-year old male presented with multiple, itchy, reddish-brown coloured papules on the face, arms and trunk of 8 months duration. Histopathological study of the skin biopsy specimen revealed features typical of multicentric reticulohistiocytosis.

User fees, self-selection and the poor in Bangladesh

The widespread uncontrolled introduction of user fees in any developing country is likely to have a disastrous impact on poorer patients. Furthermore, traditional targeting schemes aimed at their exemption are often expensive, difficult to administer and ineffective at reaching those in greatest need. This research study examines how user fees can raise revenue and target poorer patients, under the right market conditions, without resorting to costly targeting schemes. The authors draw their findings from case studies of cost recovery in the health and population sectors in Bangladesh. The mechanism suggested in the paper is to use self-selection. It is argued that under certain market conditions poorer patients will choose the health-care option that is appropriate to their means. They will thus identify themselves as poor without having to be selected or tested by an independent authority. This self-selection allows the relevant authorities to cross-subsidize their market choice by over-charging the non-poor in other segments of the market.

The human mismatch recognition complex hMSH2-hMSH6 functions as a novel molecular switch

The mechanism of DNA mismatch repair has been modeled upon biochemical studies of the E. coli DNA adenine methylation-instructed pathway where the initial recognition of mismatched nucleotides is performed by the MutS protein. MutS homologs (MSH) have been identified based on a highly conserved region containing a Walker-A adenine nucleotide binding motif. Here we show that adenine nucleotide binding and hydrolysis by the human mismatch recognition complex hMSH2-hMSH6 functions as a novel molecular switch. The hMSH2-hMSH6 complex is ON (binds mismatched nucleotides) in the ADP-bound form and OFF in the ATP-bound form. These results suggest a new model for the function of MutS proteins during mismatch repair in which the switch determines the timing of downstream events.

A histopathological study of liver and kidney in male Wistar rats treated with subtoxic doses of t-butyl alcohol and trichloroacetic acid

Tertiary butyl alcohol and trichloroacetic acid are known to be contaminants in drinking water. In order to evaluate the interactive toxicity of t-butyl alcohol with trichloroacetic acid, young male Wistar rats were dosed through water at a dose level of t-butyl alcohol (TBA)-0.5% (v/v), trichloroacetic acid (TCA)-25 ppm and a combined dose of TBA + TCA (0.5% v/v TBA-25 ppm TCA) for a period of 10 weeks ad libitum and were maintained on normal diet. The control animals received plain water and normal diet. The liver and kidney histology was undertaken to see whether subtoxic administration of TBA and TCA individually as well as combined administration for a period of 10 weeks would bring about any histological alterations. It was observed that TBA, TCA and TBA + TCA caused histological alterations in the liver such as centrilobular necrosis, vacuolation in hepatocytes and loss of hepatic architecture. TBA and TBA + TCA caused periportal proliferation and lymphocytic infiltration. Hypertrophy of hepatocytes in the periportal area was a characteristic feature in the liver of TCA treated rats. Moreover, in the histology of the kidney, in the three treated groups, degeneration of renal tubules, with syncitial arrangements of the nucleus of renal tubular epithelial cells was evident. In addition to this, degeneration of the basement membrane of the Bowmans capsule, diffused glomeruli and vacuolation of glomeruli was also evident in the three treated rat kidneys. Renal tubular proliferation in certain areas was also evident in certain areas of the kidney in TCA treated rats. The results indicate that, TBA and TCA do bring about alterations in histology of liver and kidney, but on combined administration, do not show enhanced toxicity in the form of increased hepatic and renal injury.

In vivo lipid peroxidation responses of tissues in lead-treated Swiss mice

A single intraperitoneal injection of lead acetate (200 mg/kg body weight) increased the lipid peroxidation potential (LPP) measured as thiobarbituric acid-reactive substance (TBA-RS) in different tissues of Swiss mice. All the tissues taken for experimentation, generated significantly higher amount of TBA-RS in lead-treated mice when compared with the respective control value. However, none of the tissues could correspond to the control value after the lapse of four weeks post-treatment. Possibilities of differential responsiveness of tissues to generate lipid peroxides in lead-treated mice have been discussed.

Prenatally diagnosed neuroblastoma

BACKGROUND

Prenatally diagnosed neuroblastomas have been reported in increasing numbers over the past several years, and there are now a few reviews based on up to 21 cases. The purpose of this article is to review the clinical and biologic features of prenatally diagnosed neuroblastoma based on a review of 55 cases.

METHODS

A review was conducted of 3 cases seen at the study institution and 52 other cases reported thus far in the literature.

RESULTS

Prenatal diagnosis was made usually after 32 weeks of gestation. Approximately 93% of the tumors were adrenal in origin, and 44% of these were cystic. Thirty-seven patients (67%) had Stage I disease, 12 (22%) had Stage IV-S disease, and only 3 (5%) had Stage IV disease. The DNA index was favorable (> 1) in 14 of 16 patients studied. None of these 16 patients studied had amplification of the N-myc oncogene. Catecholamines were elevated in only 33% of the patients. The liver was the most common site of dissemination, which was observed in 25% of patients; bone involvement was not observed in any patient. Ultrasonography failed to detect existing hepatic metastasis in three patients. Primary surgical resection was performed in 47 patients (85%). Chemotherapy was given to five patients and radiotherapy to three. Of the 50 patients for whom follow-up information was available, 45 (90%) were alive at a range of 2-120 months from diagnosis.

CONCLUSIONS

Prenatally diagnosed neuroblastomas are predominantly adrenal in origin and frequently cystic. The liver is the most common site of dissemination and bone involvement is notably absent. The vast majority of these infants have a favorable stage of disease (I, II, and IV-S) and favorable biologic features, and consequently have an excellent prognosis. Although surgery alone is curative for most patients, a period of observation may avoid surgery in some individuals who may achieve spontaneous regression.

Human MSH2 binds to trinucleotide repeat DNA structures associated with neurodegenerative diseases

The expansion of trinucleotide repeat sequences is associated with several neurodegenerative diseases. The mechanism of this expansion is unknown but may involve slipped-strand structures where adjacent rather than perfect complementary sequences of a trinucleotide repeat become paired. Here, we have studied the interaction of the human mismatch repair protein MSH2 with slipped-strand structures formed from a triplet repeat sequence in order to address the possible role of MSH2 in trinucleotide expansion. Genomic clones of the myotonic dystrophy locus containing disease-relevant lengths of (CTG)n x (CAG)n triplet repeats were examined. We have constructed two types of slipped-strand structures by annealing complementary strands of DNA containing: (i) equal numbers of trinucleotide repeats (homoduplex slipped structures or S-DNA) or (ii) different numbers of repeats (heteroduplex slipped intermediates or SI-DNA). SI-DNAs having an excess of either CTG or CAG repeats were structurally distinct and could be separated electrophoretically and studied individually. Using a band-shift assay, the MSH2 was shown to bind to both S-DNA and SI-DNA in a structure-specific manner. The affinity of MSH2 increased with the length of the repeat sequence. Furthermore, MSH2 bound preferentially to looped-out CAG repeat sequences, implicating a strand asymmetry in MSH2 recognition. Our results are consistent with the idea that MSH2 may participate in trinucleotide repeat expansion via its role in repair and/or recombination.

Factors affecting the pharmacokinetics of parenteral chloramphenicol in enteric fever

Chloramphenicol pharmacokinetics were studied in 29 Nepalese adults diagnosed with uncomplicated enteric fever and randomized to receive succinate ester 30 mg/kg i.v. or i.m. Serial plasma concentrations of chloramphenicol, and iothalamate (to estimate glomerular filtration rate), antipyrine (hepatocellular function) and Indocyanine Green (liver blood flow) were measured by HPLC and kinetic parameters estimated by non-compartmental analysis. In culture-positive patients (n = 16), mean residence times (MRTs) and steady-state volumes of distribution (V(d)ss) for i.v. chloramphenicol (mean +/- S.D.; 4.9 +/- 0.9 h and 1.9 +/- 0.8 L/kg; n = 7) were less than after i.m. chloramphenicol (12.3 +/- 7.3 h and 3.7 +/- 2.5 L/kg; n = 9; P < 0.05), with a higher peak plasma concentration after i.v. (16.2 +/- 9.1 versus 7.8 +/- 3.6 mg/L; P < 0.05); plasma clearance (Cl(p)) was similar in the two groups (368 +/- 172 and 310 +/- 224 mL/kg/min after i.v. and i.m. respectively). In 17 patients examined during convalescence, MRT and Vdss were less than in acute illness regardless of route chloramphenicol administration. There were similar changes in chloramphenicol kinetic parameters in culture-negative patients. Antipyrine Cl(p) and liver blood flow correlated weakly with chloramphenicol Cl(p) in culture-positive patients (P < 0.1) and were higher in convalescence; no such associations were seen for iothalamate Cl(p). These data indicate that i.v. chloramphenicol produces peak plasma concentrations which are on average twice those after i.m. injection of the same dose, due principally to a smaller V(d)ss. Cl(p) is uninfluenced by route of administration and is determined more by hepatic metabolism than renal excretion. Intramuscular treatment may result in sub-therapeutic chloramphenicol concentrations initially, but continued regular i.v. dosing is more likely to produce levels at which bone marrow toxicity occurs.

Transducin-alpha C-terminal peptide binding site consists of C-D and E-F loops of rhodopsin

The binding of heterotrimeric GTP-binding proteins (G-proteins) to serpentine receptors involves several independent contacts. We have deduced the points of interaction between mutant bovine rhodopsins and alphat-(340-350), a peptide corresponding to the C terminus of the alpha subunit (alphat) of bovine retinal G-protein, transducin. Direct binding of alphat-(340-350) to rhodopsin stabilizes the activated metarhodopsin II state (M II), consequently uncoupling the rhodopsin-transducin interaction. This peptide action requires two segments on the cytoplasmic domain of rhodopsin: the Tyr136-Val137-Val138-Val139 sequence on the C-D loop and the Glu247-Lys248-Glu249-Val250-Thr251 sequence on the E-F loop. We propose that a tertiary interaction of these two loop regions forms a pocket for binding the alphat C terminus of the transducin during light transduction in vivo. In most G-proteins, the C termini of alpha subunits are important for interaction with receptors, and, in several serpentine receptors, regions similar to those in rhodopsin are essential for G-protein activation, indicating that the interaction described here may be a generally applicable mode of G-protein binding in signal transduction.

Role of proofreading and mismatch repair in maintaining the stability of nucleotide repeats in DNA

The role of the proofreading exonuclease in maintaining the stability of multiply repeated units in DNA was studied in Escherichia coli. Reversion of plasmids in which the beta-galactosidase alpha complementing sequence was moved +2 out of frame by inserts containing (CA)14, (CA)5, (CA)2 or (TA)6 or +1 by creating a run of 8 C was compared in mutS and mutSdnaQ strains. Proofreading corrects at least half of the frameshift errors for all the plasmids and at least 99% of the errors in the (CA)2 plasmid. The (CA)2 plasmid reverts mostly by +1 frameshifts in the restriction sites flanking the insert. With the (CA)14, (TA)6, (CA)5 and 8C plasmids, reversion is mainly by loss of a repeat unit. The data support the hypothesis that the dnaQgene product recognizes frameshifts close to the DNA growing point. Frameshifts distal to the growing point are mainly corrected by mismatch repair. We speculate that mismatches in mononucleotide repeats are susceptible to proofreading because they can either migrate to a point where they are recognized by the exonuclease or, alternatively, because single nucleotide distortions are more readily detected than dinucleotides.

Cell cycle regulation of the human DNA mismatch repair genes hMSH2, hMLH1, and hPMS2

Hereditary nonpolyposis colorectal cancer is a cancer susceptibility syndrome that has been found to be caused by mutations in any of several genes involved in DNA mismatch repair, including hMSH2, hMLH1, or hPMS2. Recent reports have suggested that hMSH2 and hMLH1 have a role in the regulation of the cell cycle. To determine if these genes are cell cycle regulated, we examined their mRNA and protein levels throughout the cell cycle in IMR-90 normal human lung fibroblasts. We demonstrate that the levels of hMSH2 mRNA and protein do not change appreciably throughout the cell cycle. Although hMLH1 mRNA levels remained constant, there was a modest (approximately 50%) increase in its protein levels during late G1 and S phase. The levels of hPMS2 mRNA fluctuated (decreasing 50% in G1 and increasing 50% in S phase), whereas hPMS2 protein levels increased 50% in late G1 and S phase. Our data indicate that, at least in normal cells, the machinery responsible for the detection and repair of mismatched DNA bases is present throughout the cell cycle.

hMSH2 forms specific mispair-binding complexes with hMSH3 and hMSH6

The genetic and biochemical properties of three human MutS homologues, hMSH2, hMSH3, and hMSH6, have been examined. The full-length hMSH6 cDNA and genomic locus were isolated and characterized, and it was demonstrated that the hMSH6 gene consisted of 10 exons and mapped to chromosome 2p15-16. The hMSH3 cDNA was in some cases found to contain a 27-bp deletion resulting in a loss of nine amino acids, depending on the individual from which the cDNA was isolated. hMSH2, hMSH3, and hMSH6 all showed similar tissue-specific expression patterns. hMSH2 protein formed a complex with both hMSH3 and hMSH6 proteins, similar to protein complexes demonstrated by studies of the Saccharomyces cerevisiae MSH2, MSH3, and MSH6. hMSH2 was also found to form a homomultimer complex, but neither hMSH3 nor hMSH6 appear to interact with themselves or each other. Analysis of the mismatched nucleotide-binding specificity of the hMSH2-hMSH3 and hMSH2-hMSH6 protein complexes showed that they have overlapping but not identical binding specificity. These results help to explain the distribution of mutations in different mismatch-repair genes seen in hereditary nonpolyposis colon cancer.

Characterisation of a DNA pairing activity copurifying with DNA ligase in a partially purified extract from rat testis

Rat testicular nuclear extracts were fractionated sequentially on phosphocellulose, heparin-agarose and ssDNA-cellulose columns, in order to isolate and characterise a strand-transfer activity from a mammalian meiotic tissue. A partially purified fraction, eluting at 0.6 M KCl from ssDNA-cellulose column, catalyzed the formation of two classes of products migrating slowly on an agarose gel. The formation of one of these classes of products-the aggregates-was dependent on the presence of both the substrates (M13mp19 RF III and M13mp19 ssDNA) and on homology. The presence of ATP was essential for the formation of aggregates, though its hydrolysis was not required. EM analysis of the products indicated the presence of structures which resembled paired DNA molecules: duplex-duplex paired (Y-shaped and ds-ds paired structures) and ss-ds paired (duplex DNA paired with the single-stranded DNA) structures, indicating the presence of a pairing protein in the fraction. However, alpha- and sigma-structures were not observed. The other class of products, seen as discrete bands, were identified biochemically and by electron microscopy as ligated products. A DNA ligase-adenylate adduct of molecular weight 100 kDa was formed by the fraction. Both 5' to 3' and 3' to 5' exonucleases were absent and hence did not contribute to the formation of the products.

Bilateral fractures of the capitulum. A case report

We report a case of isolated displaced fracture of the capitulum in both elbows. Treatment was by closed manipulation and immobilisation for 3 weeks which achieved a satisfactory result, both elbows regaining 100 degrees of flexion.

Modulation of GDP release from transducin by the conserved Glu134-Arg135 sequence in rhodopsin

A superfamily of seven-transmembrane helix receptors catalyzes GDP release from heterotrimeric guanine nucleotide-binding proteins (G proteins) to initiate the intracellular signaling cascade. The photoreceptor rhodopsin is a prototypical member of the superfamily that activates the retinal G protein transducin (Gt). The cytoplasmic domain of rhodopsin binds and activates Gt, but residues that stimulate GDP release from Gt have not been identified until now. We show here that the abnormal signal transduction phenotypes of several different mutations affecting the highly conserved Glu134-Arg135 charge pair result from alteration of the GDP release step in the Gt activation cascade. We propose that Glu134 and Arg135 constitute the site that directly provides the signal from rhodopsin to activate GDP release from Gt. Because the Glu/Asp-Arg sequence occurs at a topologically identical location in most of the seven-transmembrane helix receptors, we propose that these residues constitute a switch for signal transfer.

The mismatch-repair protein hMSH2 binds selectively to DNA adducts of the anticancer drug cisplatin

BACKGROUND

The antitumor drug cis-diamminedichloroplatinum(II) (cis-DDP or cisplatin) exerts its cytotoxic effects through the formation of covalent DNA adducts. A family of proteins possessing a common HMG box motif that binds specifically to cisplatin DNA adducts has been previously suggested to be important in the clinical efficacy of the drug.

RESULTS

We have shown that the human mismatch-repair protein, hMSH2, also binds specifically to DNA containing cisplatin adducts and displays selectivity for the DNA adducts of therapeutically active platinum complexes. Moreover, hMSH2 is overexpressed in testicular and ovarian tissue; tumors in these tissues are most effectively treated by cisplatin.

CONCLUSIONS

Our results suggest a role for hMSH2 in mediating cisplatin toxicity. Supporting this view, previous studies in Escherichia coli dam- strains demonstrate that mutations in mismatch-repair proteins confer resistance to cisplatin toxicity. Mismatch-repair deficiency is also correlated with tolerance to O6-methylguanine, a cytotoxic DNA lesion formed by methylating agents. A current model ascribes O6-methylguanine toxicity to unsuccessful attempts at repair of this lesion by mismatch-repair proteins, resulting in a futile cycle of incision and synthesis, leading ultimately to lethal DNA-strand breaks. We propose that mismatch repair may contribute to cisplatin toxicity by a similar mechanism. Alternatively, hMSH2 may shield cisplatin adducts from repair, allowing adducts to persist, thus enhancing lethality.

Efficacy of dexamethasone pulse therapy in progressive systemic sclerosis

BACKGROUND

Systemic sclerosis is a disease of unknown etiology for which no specific treatment is effective. Pulse therapy with corticosteroids has been tried for various autoimmune disorders with minimal side effects. We undertook this study to determine the efficacy of dexamethasone pulse therapy in progressive systemic sclerosis (PSS).

METHODS

Five women with PSS between the ages 30 and 60 years, received 100 mg dexamethasone in 500 mL of 5% dextrose by slow intravenous infusion over 3 hours for 3 consecutive days, once a month.

RESULTS

All patients had symptomatic and clinical improvement. The vital capacity improved in three and posttreatment histopathologic regression was seen in two patients.

CONCLUSIONS

Dexamethasone pulse therapy may provide an additional option for treating systemic sclerosis.

Administration of subtoxic doses of t-butyl alcohol and trichloroacetic acid to male Wistar rats to study the interactive toxicity

Tertiary butyl alcohol and trichloroacetic acid (TCA) are known to be contaminants in drinking water. In order to evaluate the interactive toxicity of t-butyl alcohol (TBA) with TCA, young male Wistar rats were dosed through water at a dose level of TBA (0.5% v/v), 25 ppm TCA and a combined dose of TBA+TCA (0.5% v/v TBA, 25 ppm TCA) for a period of 10 weeks ad libitum and were maintained on normal diet. The control animals received plain water and normal diet. There was remarkable loss of body weight and significantly decreased liver triglycerides in the treatment groups in the order of TBA+TCA, TCA, TBA and increased liver weights were observed. Serum succinate dehydrogenase (SDH) levels were significantly increased in TCA- and TBA+TCA-treated groups. There was no significant change in serum alanine (GPT), aspartate (GOT) aminotransferase, serum alkaline (ALP) and acid (ACP) phosphatase levels as well as liver glutathione (GSH) and liver and serum cholesterol levels in the treated groups. But serum triglycerides, liver glycogen, serum glucose (only in TBA- and TCA-treated animals) were significantly high in the treated groups. Lipid peroxidation measured by diene conjugation was significant in TBA+TCA-treated group and kidney GSH levels were significantly low in the treated groups. These results show that interaction of TBA+TCA does bring about alteration in biochemical parameters which may play a pivotal role in toxic responses on long-term exposure.

Production of UV-induced frameshift mutations in vitro by DNA polymerases deficient in 3'-->5' exonuclease activity

In order to study the conversion of UV lesions into frameshift and base substitution mutations, M13mp2 phage DNA was altered by the addition of extra pyrimidines, or by construction of a nonsense codon preceded by a run of pyrimidines within the beta-galactosidase complementing region. The normal sequence 5' GTC GTT TTA CAA 3' was changed to GTC GTT T TTA CAA (MIDT) or GTC GTT C TTA CAA (MIDC) to study frameshifts and to GTC GTT CTT TAA (OCHRE) to study reversion of the ochre (TAA) codon. Escherichia coli pol I Kf and T7 DNA polymerase mutant enzymes devoid of 3'-->5' exonuclease activity produced UV-induced revertants at higher frequency than did their exonuclease proficient counterparts. Removal of cyclobutane dimers with photolyase before in vitro synthesis did not greatly affect mutant frequency although such treatment led to significantly increased DNA synthesis by the wild-type T7 DNA polymerase on UV-irradiated substrate. Reversions of the in frame ochre sequence GTT CTT TAA produced by the delta 28 T7 DNA polymerase were mainly by base substitution in the TAA codon. About half of the E. coli Kf exo- enzyme ochre revertants had a TTA deletion. Five mutant T7 DNA polymerases with varying exonuclease activity gave revertant frequencies that correlated better with published values of enzyme velocity than with exonuclease activity or with measured bypass synthesis. Our data indicate that loss of proofreading activity increases the frequency of UV-induced frameshifts, but lack of such activity is not sufficient for their production. We suggest that frameshifts occur more frequently when nucleotide addition opposite the lesion is slow. The same lesion can give rise to a different spectrum of mutations depending on the polymerase.

Tumoral calcinosis of the fingers. A report of two cases

Tumoral calcinosis is an uncommon condition which usually appears in the region of large joints. It is rare in the hand. We present two cases affecting the fingers. No causative abnormality was found.

Footwear dermatitis

We conducted a study to determine the prevalence and clinical patterns of footwear dermatitis, patch testing 50 patients with suspected footwear dermatitis and 30 controls with 22 allergens of a shoe series (Chemotechnique Diagnostics AB, Malmö, Sweden). The overall prevalence among contact dermatitis cases was 11.7%. The dorsa of the feet and toes were the commonest sites involved. 70% of patients showed sensitivity to footwear allergen(s), as opposed to 6.67% of controls. Potassium dichromate and colophony were the commonest sensitizers. Other sensitizers were the rubber accelerators 2-mercaptobenzothiazole (MBT) and diphenylguanidine (DPG) and a dye p-aminoazobenzene. Of the 23 patients patch tested with pieces or scrapings of footwear, only 3 showed positive reactions. We recommend that there should be primary and secondary footwear screening series to detect the responsible allergens, with the ultimate objective of providing correct nonallergenic footwear for our patients, with the help of manufacturers and research institutes.

GSTM1 null polymorphism at the glutathione S-transferase M1 locus: phenotype and genotype studies in patients with primary biliary cirrhosis

Studies were carried out to test the hypothesis that the GSTM1 null phenotype at the mu (mu) class glutathione S-transferase 1 locus is associated with an increased predisposition to primary biliary cirrhosis. Starch gel electrophoresis was used to compare the prevalence of GSTM1 null phenotype 0 in patients with end stage primary biliary cirrhosis and a group of controls without evidence of liver disease. The prevalence of GSTM1 null phenotype in the primary biliary cirrhosis and control groups was similar; 39% and 45% respectively. In the primary biliary cirrhosis group all subjects were of the common GSTM1 0, GSTM1 A, GSTM1 B or GSTM1 A, B phenotypes while in the controls, one subject showed an isoform with an anodal mobility compatible with it being a product of the putative GSTM1*3 allele. As the GSTM1 phenotype might be changed by the disease process, the polymerase chain reaction was used to amplify the exon 4-exon 5 region of GSTM1 and show that in 13 control subjects and 11 patients with primary biliary cirrhosis, GSTM1 positive and negative genotypes were associated with corresponding GSTM1 expressing and non-expressing phenotypes respectively. The control subject with GSTM1 3 phenotype showed a positive genotype.

Exercise-induced cholesterol depletion and Na+,K(+)-ATPase activities in human red cell membrane

Red cell membranes were isolated from blood samples obtained from athletes during exhaustive exercise on a bicycle ergometer and during the subsequent recovery period of 60 min. Plasma lactate levels were also determined. During exercise, cell membranes were progressively depleted of cholesterol and, at exhaustion, membrane cholesterol was less than 80% of the initial level. A parallel decline in Na+,K(+)-ATPase was also noted, while phospholipid reduction was around 5%. During recovery, the erythrocyte membrane cholesterol and Na+,K(+)-ATPase increased, but at a slow rate and were inversely proportional to plasma lactate content.

In vivo sister chromatid differentiation and baseline sister chromatid exchanges in a mouse ascites tumour model

Induction of differentially stained sister chromatids at G2/M and determination of baseline sister chromatid exchanges (SCEs) in ascites form of mouse sarcoma 180 cell line have been done by in vivo incorporation of 5-bromodeoxyuridine (BrdU) for two consecutive DNA replication cycles. The baseline SCE frequency is 6.24 at log phase of tumour growth.

Influences of norepinephrine, and adrenergic agonists and antagonists on gonadotropin secretion from dispersed pituitary cells of goldfish, Carassius auratus

Static incubations of dispersed goldfish pituitary cells with 1-100 nM norepinephrine (NE) stimulated gonadotropin (GTH) release. Additions of the alpha-agonist phenylephrine, and the alpha 1-agonist 6-fluoronorepinephrine, but not the alpha 2-agonist clonidine, nor the beta-agonist isoproterenol, also enhanced GTH secretion. The GTH responses to 1 nM NE was significantly inhibited by coincubations with 1 microM of the alpha-antagonist phentolamine, the alpha 1-antagonists prazosine and benoxathian, but not the alpha 2-antagonist yohimbine nor the beta-antagonist propranolol. The GTH responses to NE and phenylephrine were also additive to salmon GTH-releasing hormone (sGnRH)-induced GTH release. These results suggests that NE directly stimulates GTH secretion independent of sGnRH receptors via alpha 1-like adrenergic receptors.

Osteosarcoma following a fractured shaft of femur. A case report

A boy, aged 14 years, sustained a fracture of the midshaft of the femur. This was treated conservatively and healed in 13 weeks. One year later an osteosarcoma developed at the site of the healed fracture.

Thermodynamic analysis of ligand binding to winged bean (Psophocarpus tetragonolobus) acidic agglutinin reveals its specificity for terminally monofucosylated H-reactive sugars

The sugar-specific binding of N-dansylgalactosamine to WBA II (n = 2; Ka = 5.6 x 10(3) M-1; delta H = -21 kJ.mol-1; delta S = -21.3 J.mol-1.K-1) was utilized in substitution titrations for evaluating the association constants for the interaction of sugars with the lectin. An axial hydroxyl at C-4 and equatorial hydroxyls at C-3 and C-6 as in D-galacto configuration are crucial for binding. Both axial and equatorial hydroxyls are tolerated at C-2. Conformationally akin disaccharides such as lactose, N-acetyllactosamine, Gal beta 1-3GlcNAc, and Gal beta 1-3GalNAc show similar affinities. 2'-Fucosyllactose and H-disaccharide display 146 and 13 times stronger affinity over lactose and galactose, yet fucose by itself is devoid of activity. An interesting feature, noted for the first time, in protein-sugar interactions is the positive entropy change for the binding of 2'-fucosyllactose, suggesting that nonpolar interactions play an important role in stabilization of the lectin-sugar complex. 3-Fucosyllactose, lactodifucotetraose, lacto-N-fucopentaose II and III are inactive, whereas lacto-N-fucopentaose I has 14-fold lower affinity as compared with 2'-fucosyllactose. Conformational analysis indicates that the substitution at subterminal glucose or GlcNAc by L-fucose in either alpha 1-3 or alpha 1-4 linkage leads to its projection so as to sterically hinder the access of 3'-fucosyllactose, lactodifucotetraose, and lacto-N-fucopentaose II and III to the binding site of winged bean agglutinin II. Similarly the projection of alpha 1-3 linked Gal/GalNAc also leads to steric hindrance and hence prevents the binding of blood group A and B reactive sugars. Considering its unique specificity winged bean agglutinin II should be useful in the isolation and characterization of terminally monofucosylated H-reactive oligosaccharides from those that are difucosylated or internally fucosylated.

Molecular cloning, sequencing, and mapping of EGR2, a human early growth response gene encoding a protein with "zinc-binding finger" structure

Early growth response gene-1 (Egr-1) is a mouse gene displaying fos-like induction kinetics in diverse cell types following mitogenic stimulation. Egr-1 encodes a protein with "zinc-binding finger" structure. Zinc fingers are a protein structural motif that serve as DNA-binding domains in several transcriptional regulatory proteins. Using low-stringency hybridization with an Egr-1 cDNA probe, we identified a distinct human cDNA (designated EGR2 for early growth response gene-2), which is coregulated with EGR1 by fibroblast and lymphocyte mitogens; however, several stimuli that induce Egr-1 mRNA in PC12 (rat pheochromocytoma) cells do not induce Egr-2 mRNA. The cDNA sequence predicts a protein of 406 amino acids, including three tandem zinc fingers of the Cys2-His2 class. Strikingly, the deduced amino acid sequences of human EGR2 and mouse Egr-1 are 92% identical in the zinc finger region but show no similarity elsewhere. EGR2 maps to human chromosome 10 at bands q21-22. Structure-function analysis of EGR2 and EGR1 proteins should provide insight into the mechanisms linking signal transduction and transcriptional regulation of gene expression.

Copper, iron, zinc, and selenium dietary intake and status of Nepalese lactating women and their breast-fed infants

The dietary intake of copper, iron, zinc, and selenium of 26 Nepalese lactating mothers was estimated from chemical analysis of 24-h food and beverage composites. Fasting blood and milk samples were obtained from the mothers and blood samples were obtained from the infants. The Nepalese mothers consumed significantly more Cu, significantly less Fe and Se, and similar amounts of Zn as compared with American lactating women. Blood Fe status indices and plasma concentrations of Cu, Zn, and Se were lower in the Nepalese mothers than in the American mothers. These lower values may in part be related to the high neutral detergent fiber and phytate content of the Nepalese diet, which could make these minerals less available for absorption. The high exposure to infections in Nepal may also depress Fe status indices and plasma Zn concentrations. The lower dietary Se intake of the Nepalese mothers was reflected in lower milk concentrations.