Characterization of gonadotrophin-releasing hormone precursor cDNA in the Old World mole-rat Cryptomys hottentotus pretoriae: high degree of identity with the New World guinea pig sequence

Regulation of pituitary gonadotrophins by the decapeptide gonadotrophin-releasing hormone 1 (GnRH1) is crucial for the development and maintenance of reproductive functions. A common amino acid sequence for this decapeptide, designated as 'mammalian' GnRH, has been identified in all mammals thus far investigated with the exception of the guinea pig, in which there are two amino acid substitutions. Among hystricognath rodents, the members of the family Bathyergidae regulate reproduction in response to diverse cues. Thus, highveld mole-rats (Cryptomys hottentotus pretoriae) are social bathyergids in which breeding is restricted to a particular season in the dominant female, but continuously suppressed in subordinate colony members. Elucidation of reproductive control in these animals will be facilitated by characterization of their GnRH1 gene. A partial sequence of GnRH1 precursor cDNA was isolated and characterized. Comparative analysis revealed the highest degree of identity (86%) to guinea pig GnRH1 precursor mRNA. Nevertheless, the deduced amino acid sequence of the mole-rat decapeptide is identical to the 'mammalian' sequence rather than that of guinea pigs. Successful detection of GnRH1-synthesizing neurones using either a guinea pig GnRH1 riboprobe or an antibody against the 'mammalian' decapeptide is consistent with the guinea pig-like sequence for the precursor and the classic 'mammalian' form for the decapeptide. The high degree of identity in the GnRH1 precursor sequence between this Old World mole-rat and the New World guinea pig is consistent with the theory that caviomorphs and phiomorphs originated from a common ancestral line in the Palaeocene to mid Eocene, some 63-45 million years ago.

ERKs regulate cyclic AMP-induced steroid synthesis through transcription of the steroidogenic acute regulatory (StAR) gene

Cyclic AMP-dependent expression of the steroidogenic acute regulatory (StAR) protein is thought to be the controlling step for steroid production, but the mechanisms through which external signals are translated into increased transcription of the StAR gene are unknown. We demonstrate that cyclic AMP-induced steroid synthesis is dependent upon the phosphorylation and activation of ERKs and that ERK activation results in enhanced phosphorylation of SF-1 and increased steroid production through increased transcription of the StAR gene. Adenylate cyclase activation with forskolin (FSK) caused a time-dependent increase in ERK activity and translocation from cytoplasm to nucleus, which correlated with an increase in StAR mRNA levels, StAR protein accumulation, and steroidogenesis. Similarly, ERK inhibition led to a reduction in the levels of FSK-stimulated StAR mRNA, StAR protein, and steroid secretion. These effects were attributed to the finding that ERK activity is required for SF-1 phosphorylation, a transcription factor required for the regulation of StAR gene transcription. This conclusion was supported by our demonstration of an ERK-dependent increase in the binding of SF-1 from FSK-treated Y1 nuclei to three consensus double-stranded DNA sequences from the StAR promoter region. These observations suggest that the activation of ERK2/1 by increasing cAMP is an obligatory and regulated stage in the stimulation of steroid synthesis by cyclic AMP-generating stimuli.

Crystal structure of bis(4-methylimidazole)tetraphenylporphyrinatoiron(III) chloride and related compounds. Correlation of ground state with Fe-N bond lengths

The crystal structure of the title compound is presented and shown to be one of a class of low-spin iron porphyrin complexes having a ground-state electronic configuration of (dxy)2(dxz)2(dyz)1. If their Fe-N bond lengths (average N-porphyrin plotted against average N-axial) are considered, this class of low-spin iron(III) porphyrins of general formula [Fe(III)Por(L)2]+X- and of 2B ground state is shown to be distinctly different crystallographically from a similar class of compounds with the same general formula but with a 2E or a (dxy)2(dxz,dyz)3 ground state. A third group of compounds with the same general formula have a (dxz,dyz)4(d)1 ground state and again are in a different region of the plot. Compounds showing intermediate properties can be forecast from the simple relationship presented in this work. The electron paramagenetic resonance data are shown to be dependent on the ground state, and those of configuration (dxy)2(dxz,dyz)3 and the 2B ground state obey a correlation previously suggested in the literature.

Dysfunction in smooth pursuit eye movements and history of childhood trauma

Several commentators recently have advocated the view that a deficit in the performance of a smooth pursuit eye-movement task is a biological marker of the genetic predisposition to schizophrenia. This study considered the possibility that such an impairment is due in part to experiential or acquired characteristics, and specifically, to a history of childhood trauma. A sample of 100 Australian adults performed a visual tracking task and completed a self-report measure of childhood trauma. Although the effect size was small, a relationship was found between eye-tracking performance and a childhood history of physical and emotional abuse. This finding suggests that eye-tracking performance may not be governed entirely by genetic factors, a possibility that has implications for the use of indices of smooth pursuit eye movement as a purely genetic marker of proneness to schizophrenia. Further investigation is needed to clarify the basis of the association between these deficits and childhood abuse.

Comparison of IgE and IgG antibody-dependent cytotoxicity in vitro and in a SCID mouse xenograft model of ovarian carcinoma

Allergic reactions are mediated by IgE antibodies bound to high-affinity receptors on mast cells in peripheral tissues and are characterized by their immediacy and hypersensitivity. These properties could also be advantageous in immunotherapy against cancer growth in peripheral tissues. We have constructed chimeric IgE and IgG1 antibodies with murine V regions and human C regions corresponding to the MOv18 monoclonal antibody against the human ovarian tumor-associated antigen, folate binding protein. The antibodies exhibited the expected binding affinities for antigen and Fc receptors, and effector activities with human basophils and platelets in vitro. The protective activities of MOv18-IgE and MOv18-IgG1 were compared in a SCID mouse xenograft model of ovarian carcinoma. The beneficial effects of MOv18-IgE were greater and of longer duration than those of MOv18-IgG1. Our results suggest that the allergic reaction could be harnessed for the suppression of ovarian tumors.

The periodontopathogen Porphyromonas gingivalis binds iron protoporphyrin IX in the mu-oxo dimeric form: an oxidative buffer and possible pathogenic mechanism

Mössbauer spectroscopy was used to re-evaluate iron protoporphyrin IX, FePPIX, binding and the chemical nature of the black iron porphyrin pigment of Porphyromonas gingivalis. We demonstrate that FePPIX is bound to the cell in the mu-oxo dimeric form, [Fe(III)PPIX]2O, and that the iron porphyrin pigment is also composed of this material. P. gingivalis also assimilated monomeric Fe(II)- and Fe(III)PPIX into mu-oxo dimers in vitro. Scatchard analysis revealed a greater binding maximum of cells for mu-oxo dimers than for monomeric Fe(III)-or Fe(II)PPIX, although the relative affinity constant for the dimers was lower. Formation of [Fe(III)PPIX]2O via reactions of Fe(II)PPIX with oxygen, and its toxic derivatives, would serve as an oxidative buffer and permit P. gingivalis and other black-pigmenting anaerobes to engender and maintain a local anaerobic environment. Tying up of free oxygen species with iron protoporphyrin IX would also reduce and limit Fe(II)PPIX-mediated oxygen-radical cell damage. More importantly, formation of a cell-surface mu-oxo dimer layer may function as a protective barrier against assault by reactive oxidants generated by neutrophils. Selective interference with these mechanisms would offer the possibility of attenuating the pathogenicity of P. gingivalis and other iron protoporphyrin IX-binding pathogens whose virulence is regulated by this reactive molecule.

Integrated health systems: building the perfect IT beast

The evolution of managed care, from strictly paying for to actually providing care, has shifted the focus of information technology in this industry as well. Today, the perfect managed care information system requires functionality beyond claims processing and back-end HMO operations. The IT goal for integrated health system (IHS) executives should be a hybrid of both payor- and provider-based functionalities.

Keeping an eye on the IHS pendulum

Managed care is pushing the pendulum of integration in healthcare, and it is likely to continue gaining momentum. As a result, integrated health systems (IHSs) are approaching integration from two perspectives--payor and provider--and approaching a middle ground where healthcare financing and delivery are well-balanced and equal in emphasis. Still, IHS officials would like to monitor all members on a continual basis that is the only way to improve the health of their population and, ultimately, reduce the economic burden of healthcare.

The chemical mechanism of beta-haematin formation studied by Mössbauer spectroscopy

Spontaneous formation of beta-haematin (malaria pigment) from haematin in acetate solution follows pseudo-zero-order and not autocatalytic kinetics. Acetate appears to facilitate the reaction by solubilizing the haematin and acting as a phase-transfer catalyst, a role which, in vivo, could be fulfilled by carboxylic acids or amino acids.

The iron environment in heme and heme-antimalarial complexes of pharmacological interest

Mössbauer spectroscopy has been utilized to probe the electronic environment of iron in a number of Ferriprotoporphyrin IX complexes of relevance to malaria. The markedly different iron environments found for the complexes of hemin with quinine, chloroquine, and the Chinese herbal antimalarial artesunate suggest that these compounds act by protecting the heme from polymerization to insoluble hemozoin, and by facilitating the transport of the protected heme to the food vacuole membrane where it is able to exercise its cytotoxic redox catalytic activity. Mössbauer parameters determined here for purified malaria pigment and synthetic beta-hematin confirm the chemical identical-ness of these species. The Mössbauer spectra of the complexes are discussed in light of the proposed structures of the complexes.

Ecthyma gangrenosum occurring at sites of iatrogenic trauma in pediatric oncology patients

We report two cases of ecthyma gangrenosum which occurred at sites of iatrogenic trauma. The first case developed due to metastatic seeding with Pseudomonas aeruginosa during an episode of septicaemia and the second case occurred as a primary skin lesion. Both required prolonged courses of antibiotics and one patient died. The different pathogenic mechanisms and outcomes associated with this condition are discussed.

Anterior chamber aspirate cultures in small incision cataract surgery

BACKGROUND

Anterior chamber aspirates on completion of extracapsular cataract surgery contain significant numbers of organisms, particularly coagulase negative staphylococci, an important cause of endophthalmitis.

METHODS

Culture rates were compared in 50 patients after phacoemulsification surgery, which allows the possible benefits of a small, self sealing wound and maintenance of positive intraocular pressure, with a similar number of extracapsular cases.

RESULTS

A culture positive rate of 20% and 24% respectively was found, an insignificant difference.

CONCLUSION

Small incision surgery has no proved advantage over extracapsular surgery in terms of reducing the intraoperative bacterial inoculum. The significance of this result in terms of causation of endophthalmitis is discussed.

Definition of local recurrence after surgery for rectal carcinoma

Local recurrence rates of rectal carcinoma have been analysed among 284 patients in a prospective randomized multicentre trial of adjuvant preoperative radiotherapy for locally advanced rectal carcinoma. Wide variations in local recurrence rates are demonstrated depending on the definition of local recurrence employed and the subgroup studied. Thus after surgical operation alone, rates as high as 43.3 per cent or as low as 12.7 per cent can be calculated. After both adjuvant preoperative radiotherapy and operation the overall local recurrence rate is 12.8 per cent, although the local recurrence rate inside the radiotherapy field (true recurrence) may be as low as 2.3 per cent. It is recommended that local recurrence after operation for rectal carcinoma be defined as any detectable local disease at follow-up, occurring either alone or in conjunction with generalized recurrence, in patients who have undergone resection. A rate should be given both for all patients and for those operated on for cure, but not for the latter group alone as this could introduce bias.

Adjuvant preoperative radiotherapy for locally advanced rectal carcinoma. Results of a prospective, randomized trial

PURPOSE

A prospective, randomized clinical trial was conducted by the Northwest Rectal Cancer Group to study the effects of preoperative radiotherapy given one week before surgery in locally advanced (tethered or fixed) rectal carcinoma.

METHODS

A total of 284 patients were entered into the trial between 1982 and 1986; 141 were allocated to receive surgical treatment alone, and 143 were allocated to receive preoperative radiotherapy. A 10 x 10 x 10 cm volume in the posterior pelvis, centered on the tumor, was irradiated at a dose of 20 Gy, divided into four daily fractions of 5 Gy each.

RESULTS

No differences were observed in any of the clinicopathologic variables in the two arms of the trial; there were no striking down-staging effects in the irradiated tumors. After a minimum follow-up period of 96 months, the overall and cancer-related mortality rates were similar in both arms of the study (P = 0.21 and P = 0.09, respectively). There was a highly significant reduction in local recurrences in the irradiated group (12.8 percent x-ray therapy vs. 36.5 percent surgery; P = 0.0001). The majority of local recurrences after preoperative radiotherapy occurred inside the radiotherapy field (10 cases; 7 percent), with only six cases (5 percent) outside the field. No significant difference was observed in the rates of distant metastasis between the two treatment groups (P = 0.73).

CONCLUSIONS

Although there is no statistically significant survival benefit in the whole series, there is a survival benefit for the subset of patients considered by the surgeon to have undergone a curative operation. We recommend that this form of adjuvant therapy should be offered to all patients with locally advanced rectal cancer who are to undergo radical surgery.

Enterococcal bacteraemia: a prospective study of 125 episodes

One hundred and twenty-five episodes of enterococcal bacteraemia occurring over a 50-month period were studied prospectively. Enterococcus faecium was the commonest species, accounting for 76 (59.8%) of the 127 isolates. Overall, 33.1% of isolates were resistant to ampicillin and one isolate (0.8%) to vancomycin; high-level gentamicin resistance was detected in 4.3% of 93 isolates tested. The percentage of nosocomial episodes was 70.4, and 95.2% of the patients had significant underlying illness. Central venous catheters (CVCs) were the commonest source of infection. Eighty-four per cent of episodes were ultimately treated with appropriate antibiotics. The overall mortality rate was 17.6%, and that directly attributable to infection was 8.0%. An increased mortality rate was observed in intensive care and neonatal unit patients, and in patients who had received antimicrobial therapy in the 2 weeks prior to enterococcemia. CVC-related infections were associated with a reduced mortality. No other clinical or microbiological factors were found to influence outcome.

Prognostic significance of 5T4 oncofetal antigen expression in colorectal carcinoma

The 5T4 oncofetal antigen is a 72 kDa glycoprotein defined by a monoclonal antibody raised against human placental trophoblast and is expressed in many different carcinomas but detected only at low levels in some normal epithelia. Immunohistochemical analysis of the patterns of expression in colorectal carcinomas has indicated a significant association between the presence of the antigen in tumour cells and metastatic spread. The 5T4 antigen phenotype of 72 colorectal cancers has been compared with the clinical outcome of the patients in order to assess its relationship with prognosis. Forty per cent of tumours were 5T4 positive; the remainder were either unlabelled or exhibited stroma-associated labelling only. There was a significant correlation between 5T4 expression in the malignant cells and unfavourable course of disease (P < 0.001). The 5 year survival with 5T4-positive tumours was 22% compared with 75% for patients with 5T4-negative tumours; median survival was 24 versus > 90 months respectively. Stratified analysis showed that 5T4 antigen tumour positivity was acting independently of each of stage, site of tumour, age or sex. There were significant differences in survival for patients with Dukes' B and C stage carcinomas (P = 0.001 and P = 0.034). The results suggest that in colorectal cancer immunohistochemical assessment of 5T4 expression may be useful in identifying patients at high risk for tumour recurrence and for whom additional treatment strategies might be most appropriate.

conformation and phasing of dystrophin structural repeats

The presumptive rod domain of dystrophin contains a series of degenerate repeating sequences with homology to those of spectrin. To determine the relation of the implied structural repeating units to the sequence repeat (the phasing), recombinant fragments of the domain of dystrophin were prepared by expression in Escherichia coli. The phasing was established by identifying the minimum sequence element that would form a stable fold of high (approx. 75%) alpha-helicity: by contrast, incorrectly phased fragments had labile structure with an average alpha-helicity of about 40%. The isolated folded structural repeat showed high stability towards proteolysis and a urea-denaturation profile with a plateau at low denaturant concentration, indicative of a unique folded conformation. The phasing is consistent with a structure inferred from analysis of the amino acid sequence and also found in spectrin, in which each structural repeat comprises a three-stranded coiled-coil, made up of one short helix (approx. 30 residues) and the N and C-terminal halves of two separate long helices, such that each long helix participates in the formation of two contiguous structural units.

p53 overexpression as a marker of malignancy in gastric biopsies

Inactivation of the p53 tumour-suppressor gene is the commonest genetic abnormality in human cancers. This results in a conformational change in the p53 protein, and a consequent prolongation in its half-life; thereby permitting the identification of p53 immunoreactivity in malignant cells. Such reactivity is observed in up to 57% of gastric carcinomas, and is a proven indicator of poor prognosis. We have investigated the use of p53 immunohistochemistry in the diagnosis of malignancy in pre-operative gastric biopsy specimens. Using a three-stage immunoperoxidase technique, p53 expression was examined in 117 gastric biopsies obtained during flexible upper gastrointestinal endoscopy: 80 of these biopsies were from known gastric carcinomas, 20 from benign gastric disorders and 17 from normal gastric mucosa. Of the gastric cancers 40% (n = 32) exhibited overexpression of p53. No reactivity was observed in any of the biopsies of gastric ulcers, polyps or normal mucosa. The expression of p53 by gastric carcinomas improved the diagnostic accuracy of conventional histopathology from 86% to 92.5%; with 5% of biopsies incorrectly diagnosed and 2.5% of an equivocal appearance. These results demonstrate that the detection of p53 is a highly specific marker of gastric malignancy, and that such a technique can easily be performed on biopsies obtained at endoscopy.

Immunological properties and cDNA sequence analysis of an intermediate-filament-like protein from squid neuronal tissue

A cDNA library has been constructed in the expression vector lambda gt11 from mRNA isolated from squid (Loligo forbesi) optic lobes. The library was screened with antibodies generated against purified squid neurofilaments. A positive clone was isolated, which harboured a lambda gt11 recombinant having an insert size of 3.5 kb. Hybridization analysis by Southern and northern blotting showed that the corresponding protein is encoded by a single gene that gives rise to a transcript of 2.6 kb. Translation of the full nucleotide sequence of the gene revealed an open reading frame covering 557 amino acids. This squid-neurofilament-like protein, SNLK, bears the characteristic N-terminal head, rod and C-terminal tail domains present in all intermediate filament (IF) proteins. The rod has the classical heptad repeats indicating coiled-coil-forming ability, and the predicted lengths of the coils are similar to coils 1a, 1b and 2 of intermediate filaments. At the C-terminal end of the rod there is a strongly conserved IF epitope, and a fusion protein containing SNLK is recognised by the pan-specific intermediate filament antibody, IFA. A polyclonal antibody raised against SNLK has been used to show that the protein is present only in neuronal tissues and that it is immunologically related to neurofilaments from Myxicola but not from mammals.

Rapid cytochemical demonstration of cytochrome oxidase activity in pathogenic bacteria

AIMS

To develop and assess a cytochemical technique for the light microscopical detection of oxidase activity in pathogenic bacteria.

METHODS

Live bacterial cells were deposited on to aminopropylsilane treated glass coverslips by centrifugation, dried, then reacted with either 1% (w:v) n,n,n',n'-tetramethyl-p-phenylene diamine (TPD) or 5 mM diaminobenzidine (DAB) at 37 degrees C. The preparations were mounted in 50% glycerol and assessed by brightfield microscopy. An optimised DAB procedure (5 minutes of drying at 37 degrees C and 10 minutes of reaction time) was applied to 44 strains of organisms commonly associated with infections in man and to two fresh positive blood culture containing Gram negative bacilli.

RESULTS

TPD gave no discernible localised reaction product and was not investigated further. With DAB, oxidase positive cells (brown) were clearly differentiated from oxidase negative cells (colourless) even in mixed preparations. The DAB technique correctly assigned 18 oxidase positive isolates (seven genera), 26 oxidase negative isolates (eight genera), and the organisms present in the two freshly positive blood cultures to their appropriate oxidase reactivity as defined by the standard macroscopic TPD technique.

CONCLUSIONS

The cytochemical reaction seems to be a reliable indicator of the macroscopic oxidase test. It permits determination of oxidase reactivity at an early stage in the assessment of clinical material when infecting organisms can be demonstrated by microscopy. Further development of this and related cytochemical techniques could permit the provision of microbiological information that would be relevant to patient management, well in advance of conventional techniques.

A simplified method for in vivo footprinting using DMS

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A monoclonal anti-IgE antibody against an epitope (amino acids 367-376) in the CH3 domain inhibits IgE binding to the low affinity IgE receptor (CD23)

We have produced three different mAb specific for human IgE-Fc. Their binding pattern to either heat-denatured IgE or a family of overlapping IgE-derived recombinant peptides and their ability to affect interaction of IgE with its low affinity receptor Fc epsilon R2/CD23 demonstrate that they recognize distinct epitopes on the IgE molecule. All three mAb were able to induce basophil degranulation as measured by the induction of histamine release. mAb 173 recognizes a thermolabile epitope in the CH4 domain. It does not affect the binding of IgE to Fc epsilon R2/CD23. mAb 272 recognizes a thermostable epitope that maps to a sequence of 36 amino acids (AA) spanning part of the CH2 and CH3 domain and it does not affect the binding of IgE to Fc epsilon R2/CD23. mAb 27 recognizes a thermolabile epitope located on a 10 AA stretch (AA 367-376) in the CH3 domain. This area contains one N-linked oligosaccharide (Asn-371), but the antibody is not directed against carbohydrate because it binds to Escherichia coli-derived IgE peptides. mAb 27 inhibits the binding of IgE to Fc epsilon R2/CD23 but is still capable of reacting with IgE already bound to Fc epsilon R2/CD23. These data suggest that upon binding to Fc epsilon R2/CD23, the IgE molecule engages one of two equivalent-binding sites close to the glycosylated area of the CH3 domain.

A monoclonal anti-IgE antibody against an epitope (amino acids 367-376) in the CH3 domain inhibits IgE binding to the low affinity IgE receptor (CD23)

We have produced three different mAb specific for human IgE-Fc. Their binding pattern to either heat-denatured IgE or a family of overlapping IgE-derived recombinant peptides and their ability to affect interaction of IgE with its low affinity receptor Fc epsilon R2/CD23 demonstrate that they recognize distinct epitopes on the IgE molecule. All three mAb were able to induce basophil degranulation as measured by the induction of histamine release. mAb 173 recognizes a thermolabile epitope in the CH4 domain. It does not affect the binding of IgE to Fc epsilon R2/CD23. mAb 272 recognizes a thermostable epitope that maps to a sequence of 36 amino acids (AA) spanning part of the CH2 and CH3 domain and it does not affect the binding of IgE to Fc epsilon R2/CD23. mAb 27 recognizes a thermolabile epitope located on a 10 AA stretch (AA 367-376) in the CH3 domain. This area contains one N-linked oligosaccharide (Asn-371), but the antibody is not directed against carbohydrate because it binds to Escherichia coli-derived IgE peptides. mAb 27 inhibits the binding of IgE to Fc epsilon R2/CD23 but is still capable of reacting with IgE already bound to Fc epsilon R2/CD23. These data suggest that upon binding to Fc epsilon R2/CD23, the IgE molecule engages one of two equivalent-binding sites close to the glycosylated area of the CH3 domain.

Recombinant human IgE

The gene for a human epsilon chain Fc fragment has been cloned and expressed at a high level in Escherichia coli, and its biological activity in binding to the high-affinity receptors on mast cells and basophils and mediating histamine release has been examined in a variety of assays, including the inhibition of passive cutaneous anaphylaxis in human skin, which was induced by ragweed immunoglobulin IgE antibody and antigen. The positive results obtained in these assays encouraged us to try to analyse the binding site on IgE by site-directed mutagenesis. We describe deletion mutants here that narrow down the binding site on IgE for the mast cell receptor to a stretch of 76 amino acids (residues 301-376 on the ND epsilon chain) spanning the CH2 and CH3 domains. This peptide displays activity in the human skin test indistinguishable from that of a myeloma IgE.