Allosteric characteristics of GTP cyclohydrolase I from Escherichia coli

The kinetic and regulatory properties of GTP cyclohydrolase I were investigated using an improved enzyme assay and direct determination of the product, dihydroneopterin triphosphate. The enzyme was purified from Escherichia coli to absolute homogeneity as demonstrated by N-terminal sequencing of up to 50 amino acid residues. A 30-residue internal fragment showed 42% similarity with rat liver GTP cyclohydrolase I. The enzyme did not obey Michaelis-Menten kinetics or show a sigmoid reaction curve. The substrate saturation kinetics were found to be slow with low response to minor changes in GTP concentrations. GTP cyclohydrolase I has a relatively high apparent Km. The values are slightly different for enzyme purified by GTP-agarose (100 microM) and UTP-agarose (110 microM). Low turnover numbers of 12/min and 19/min were calculated for the respective enzyme preparations. GTP-cyclohydrolase-I activity was modulated in Vmax by K+, divalent cations, UTP and tetrahydrobiopterin. Divalent cations, such as Mg2+, had an activating effect with an optimum at 8 mM Mg2+. A different catalytic function and formation of a new, unidentified product by GTP cyclohydrolase I was observed in the presence of Ca2+. In the presence of 1 mM EDTA and Mg2+, GTP-cyclohydrolase-I activity was strongly inhibited by chelate complexes. UTP proved not to be a competitive inhibitor, but a positive modulator. The inhibition by chelate complexes was totally abolished by UTP. Tetrahydrobiopterin showed an inhibitory effect, with 50% inhibition at 100 microM tetrahydrobiopterin. UTP was able to reduce the inhibition by tetrahydrobiopterin. Using monoclonal antibody 1F11 (related to the GTP-binding site), and monoclonal antibody NS7 (mimicking tetrahydrobiopterin), different binding sites were demonstrated for GTP and tetrahydrobiopterin on each enzyme subunit. Western-blot competition analysis revealed a UTP-binding site different from the binding sites of GTP and tetrahydrobiopterin. Based on the kinetic behaviour and the kind of modulations observed we defined GTP cyclohydrolase I as an M-class allosteric enzyme.

A mother's work: two levels of feminist analysis of family-centered care

The following case describes 5 years of a mother's care for her child with multiple chronic conditions, in the neonatal intensive care unit and at home. Because caregiving is primarily a female activity, a feminist approach is used. This mother's efforts on behalf of her son show how work within the domains of direct medical care, normal mothering care, coordination of equipment and supplies and professionals, and synthesis of meaning emanated from her definition of motherhood. The case suggests interventions in family-centered care, offers an examination of two levels of feminist analysis for their usefulness to occupational therapy, and provides an opportunity to examine the topic of motherhood within feminism.

Opening feminist histories of occupational therapy

This paper frames the history of occupational therapy in feminist terms. It focuses on gender segregation in occupational therapy, the influence of class and race in shaping opportunities for occupational therapists, and the place of feminism in the goals and achievements of the occupational therapy profession. Such issues have been addressed by feminist scholars in histories of women in medicine, nursing, and other helping professions. These sources help place the achievements of occupational therapy within the context of women's historic entry and advancement in the American work force.

The response of African Americans to the Rorschach: a review of the research

Studies exploring the performance of African Americans on the Rorschach were reviewed. The review revealed the limited number of studies done in this area of study, as well as the fact that the research paradigm for all of this research has been limited to comparing the Rorschach performance of African Americans to that of Whites. However, no one has offered a rationale for such a research paradigm. Without a scientific reason to expect personality to be a function of race, another research design was recommended, one that explores the effect of a variety of aspects of living conditions on the development of the personality of African Americans.

PCR amplification products are of limited use for the study of DNA/protein interaction

Conventional methods for labeling double-stranded DNA lead to high specific activity. Yet they often alter the target DNA sequence to such an extent as to prevent a meaningful protein/DNA interaction analysis. Therefore we tried to establish a polymerase chain reaction (PCR)-based method which allows radiolabeling to high specific activity and should maintain the protein binding capability of small double stranded DNA fragments. By using PCR it is possible to label double stranded DNA to high specificity, but the protein binding capability of such DNA is drastically reduced.

Role of mapping-guided surgery in patients with recurrent ventricular tachycardia

To assess the value of ventricular tachycardia (VT) surgery 108 patients with recurrent episodes of VT were studied. There were 97 patients with coronary artery disease (group I) and 11 patients without coronary artery disease (group II). All patients in group I underwent subendocardial resection; 12 patients also underwent cryoablation. Cryoablation alone was performed in all patients in group II. During a mean follow-up period of 40 +/- 27 months, 29 patients (30%) in group I and two patients (18%) in group II died (p = 0.33). There were nine patients (9%) in group I and six patients (55%) in group II who had nonfatal recurrences of VT after surgery (p less than 0.01). In group I, there was a higher mortality rate among patients who had VT of posterolateral origin (14 of 31 patients; 45%) compared with 3 of 11 patients (28%) who had VT of anterolateral origin, 1 of 8 patients (12%) who had VT of inferoseptal, and 11 of 39 (29%) patients who had VT of anteroseptal origin. None of the eight patients with two distinct origins of VT died.

Primary intrasellar germinoma: case report

Intracranial germinomas arising primarily within the sella turcica are extremely rare. Preoperative diagnosis is difficult to establish even with sophisticated procedures. Diabetes insipidus is the main clinical manifestation. The authors report a case of an apparently primary intrasellar germinoma causing subclinical pituitary apoplexy in a 12-year-old boy. The transsphenoidal approach and appropriate radiotherapeutic management were employed with a good outcome.

The primary structure of the antenna polypeptides of Ectothiorhodospira halochloris and Ectothiorhodospira halophila. Four core-type antenna polypeptides in E. halochloris and E. halophila

Antenna polypeptides from two species of the family Ectothiorhodospiraceae have been investigated. By means of gel filtration and subsequent high-performance liquid chromatography, at least five polypeptides were isolated from each of Ectothiorhodospira halochloris and Ectothiorhodospira halophila. The majority of their primary structures was identified by Edman degradation. Comparison of these polypeptide sequences with the known primary structures of antenna polypeptides from various purple non-sulfur bacteria revealed interesting new aspects with regard to the structure of the core-peripheral antenna system. E. halochloris and E. halophila contain two pairs of alpha- and beta-polypeptides each with typical primary structure elements of core complexes, indicating a modified antenna complex organization.

Meningeal sarcoma with rhabdomyoblastic differentiation: case report

A case of primary neoplasm of the meninges with unusual histological and clinical features, which occurred in a 61-year-old man is described. Although conventional light microscopy revealed an undifferentiated tumor consisting of small- to medium-sized elements, it did not allow any definitive histogenetic interpretation. Immunohistochemistry showed that the neoplastic cells were positive for actin, desmin, myoglobin, and vimentin, thus leading to the diagnosis of meningeal sarcoma with rhabdomyoblastic differentiation. This interpretation was also supported by electron microscopy, in dewaxed tissue samples, which revealed the presence of abortive Z-lines. It is noteworthy that retrospective microscopic examination of all the slides obtained both at initial presentation and at relapses demonstrated in some fields that the undifferentiated population was associated with typical meningiomatous features, as was also shown by the staining for the epithelial membrane antigen. Clinically, the tumor was characterized by an exceedingly long course (10 years). The histogenesis of the tumor and the diagnostic relevance of immunohistochemical techniques are discussed.

Phycobilisome structure in the cyanobacteria Mastigocladus laminosus and Anabaena sp. PCC 7120

Phycobilisomes of the cyanobacteria Mastigocladus laminosus and Anabaena sp. PCC7120 differ from typical tricylindrical, hemidiscoidal phycobilisomes in three respects. Firstly, size comparisons of the core-membrane linker phycobiliproteins (LCM) in different cyanobacteria by SDS/PAGE reveal an apparent molecular mass of 120 kDa for the LCM of M. laminosus and Anabaena sp. PCC7120. This observation suggests that the polypeptides of these species have four linker-repeat domains. Secondly, phycobilisomes of M. laminosus are shown to contain at least three, but most probably four, different rod-core linker polypeptides (LRC). These LRC, which attach the peripheral rods to the core and thereby make phycocyanin/allophycocyanin contacts, have been identified and characterized by N-terminal amino acid sequence analysis. Additionally, electron microscopy of phycobilisomes isolated from M. laminosus and Anabaena sp. PCC7120 reveals similar structures which differ from those of Calothrix sp. PCC7601 with their typical six, peripheral rods. Based upon protein-analytical results and a reinterpretation of the data of [Isono, T. & Katoh, T. (1987) Arch. Biochem. Biophys. 256, 317-324], we discuss structural implications of recent findings on the established hemidiscoidal model for the phycobilisomes of M. laminosus and Anabaena sp. PCC7120. Up to eight peripheral rods are suggested to radiate from a modified core substructure which contains two additional peripheral allophycocyanin hexamer equivalents that serve as the core-proximal discs for two peripheral rods.

Secretion of mammalian ribonucleases from Escherichia coli using the signal sequence of murine spleen ribonuclease

A nucleotide sequence identical with that of the recently identified murine pancreatic ribonuclease (RNAase) was isolated from a murine spleen cDNA library. Active RNAase was expressed and secreted from Escherichia coli lon-htpr- transformed with a plasmid containing the E. coli trp promoter followed by the murine RNAase gene sequence, including the original eukaryotic 26-amino-acid signal sequence. Approx. 1 mg of properly matured RNAase protein/litre was secreted into the medium of a fermentor culture after the promotor was induced by tryptophan starvation. When the signal sequence was deleted from the plasmid, intracellular RNAase activity was very low and there was no significant supernatant RNAase activity. Even higher RNAase yields were obtained with a synthetic gene for bovine pancreatic ribonuclease cloned after the signal sequence of the murine gene. About 2 mg of correctly processed RNAase A/litre was isolated from the growth medium, and a further 8-10 mg of correctly processed RNAase/litre could be isolated from the soluble fraction of the cells. Thus this eukaryotic signal sequence is both recognized by the E. coli transport and processing apparatus and gives efficient secretion, as well as export, of active, mature mammalian RNAases.

Surgical therapy for drug-refractory ventricular tachycardia: role of additional aneurysmectomy or bypass grafting

To assess whether additional aneurysmectomy and/or bypass grafting influence prognosis we studied 97 patients with recurrent sustained monomorphic ventricular tachycardia after an old myocardial infarction. All patients underwent subendocardial resection due to drug-refractory ventricular tachycardia. There were 41 patients who had resection alone, 27 patients had resection and aneurysmectomy, 13 patients had resection and bypass grafting and the remaining 16 patients had resection with both, aneurysmectomy and bypass grafting. During the mean follow-up of 40 +/- 27 months 29 patients died (30%) (total mortality), 7 patients suddenly (7%) and 20 patients from cardiac causes (20%). There were no significant differences in total mortality between patients with resection alone (32%), patients with resection and aneurysmectomy (22%), patients with resection and bypass grafting (31%) and patients who had resection, aneurysmectomy and bypass grafting (38%). In addition, no significant differences were observed in the incidence of sudden death and nonfatal recurrences between patients with resection alone: sudden death 12%, recurrences 7%; patients with resection and aneurysmectomy: sudden death 0%, recurrences 19%; patients with resection and bypass grafting: sudden death 0%, recurrences 8%; and patients with resection, aneurysmectomy and bypass grafting: sudden death 13%, recurrences 0%. Postoperatively, left ventricular function improved in 56% of patients who had resection and aneurysmectomy compared to 17% of patients with resection alone, 31% of patients with resection and bypass grafting and 19% of patients who had resection, aneurysmectomy and bypass grafting. There is a low risk of sudden death and nonfatal recurrences after subendocardial resection. An influence of additional surgical approaches (aneurysmectomy or bypass grafting) on prognosis is not visible.

Three C-phycoerythrin-associated linker polypeptides in the phycobilisome of green-light-grown Calothrix sp. PCC 7601 (cyanobacteria)

Microanalyses by SDS-PAGE and microsequencing demonstrate that, under green-light conditions, 3 C-phycoerythrin associated rod-linker polypeptides with different N-terminal amino acid sequences are present in phycobilisomes (PBS) from Calothrix sp. 7601 cells. Two of these polypeptides, corresponding to SDS-PAGE bands at 36 and 37 kDa, could be assigned, respectively, to the cpeC and cpcD genes found on a separate cpeCD-operon in Calothrix sp. 7601 (Federspiel, N.A. and Grossman, A.R. (1990) J. Bacteriol, 172, 4072-4081). The third C-PE rod-linker polypeptide, LR,2PE,33, requires, therefore, a third gene with the suggested locus designation 'cpeE'. A C-PE (alpha beta)6-LR,2PE,33 complex containing this third rod-linker polypeptide could be isolated from phycobilisomes and characterized. PBS from both green- and red-light cells of Calothrix contain a single, unique LRC28 rod-core linker polypeptide which is not altered during chromatic adaptation.

Advantages and disadvantages of using the hydrogen clearance technique to measure pancreatic blood flow

This study was undertaken to identify the advantages and disadvantages of using the hydrogen clearance technique (HCT) to measure pancreatic blood flow (PBF) in the opossum over short and long periods. An open study was performed on 8 opossums. A total of 72 platinum electrodes were implanted into the pancreas. On the fifth day 41 additional electrodes were implanted. All implantation sites were examined histologically after five days. Measurements of pancreatic blood flow were taken every other day for five days. Three measurements were taken from each electrode and the mean of the three was used for analysis. In the anaesthetized animal mean PBF (SD) was 63.5 (12.8) ml min-1 100 g-1 immediately after electrode implantation and 34.3 (11.4) ml min-1 100 g-1 on the 5th postoperative day. Of the implanted electrodes, 35% failed during the experimental course, mainly as the result of proliferation of scar tissue around the electrodes. Mild to moderate fibroproliferation had taken place around the platinum tips of the remaining 65%. Primary electrode implantation caused no or negligible trauma to the pancreas. We recommend the HCT only for short-term measurements of PBF. Implantation of electrodes for any length of time leads to inflammatory changes around the platinum tips that cause proliferation of scar tissue and lead to failure of the electrodes, misleadingly low PBF recordings, and fewer monoexponential clearance curves.

A small multigene family encodes the rod-core linker polypeptides of Anabaena sp. PCC7120 phycobilisomes

The cpc operon of Anabaena sp. PCC7120 is shown to encode ten genes: 5'-cpcB-cpcA-cpcC-cpcD-cpcE-cpcF- cpcG1-cpcG2-cpcG3-cpcG4-3'. The 3' portion of this operon includes four tandemly repeated genes encoding phycocyanin (PC)-associated, rod-core linker polypeptides of the phycobilisomes (PBS). The products of these four genes are most similar at their N termini, and overall are 50-61% identical and 68-76% similar to one another. The four CpcG proteins of Anabaena sp. PCC7120 are 41-47% identical and 62-65% similar to the single CpcG rod-core linker protein in Synechococcus sp. PCC7002. The N-terminal domains of the polypeptides are also more distantly related to the conserved domains of other types of rod-linker polypeptides associated with PC, phycoerythrin, and allophycocyanin (AP). Three of these rod-core linker proteins (CpcG1, CpcG2, and CpcG4) were demonstrated to occur in isolated PBS by N-terminal amino acid sequence analyses. These results indicate that previously proposed models for the PBS of Anabaena sp. are incorrect. It is suggested that the PBS of Anabaena sp. have eight peripheral rods, each of which interacts with the AP of the core via a specific rod-core linker (CpcG) polypeptide.

Polypeptide composition of the Photosystem I complex and the Photosystem I core protein from Synechococcus sp. PCC 6301

The polypeptide composition of the Photosystem I complex from Synechococcus sp. PCC 6301 was determined by sodium-dodecyl sulfate polyacrylamide gel electrophoresis and N-terminal amino acid sequencing. The PsaA, PsaB, PsaC, PsaD, PsaE, PsaF, PsaK and PsaL proteins, as well as three polypeptides with apparent masses less than 8 kDa and small amounts of the 12.6 kDa GlnB (PII) protein, wee present in the Photosystem I complex. No proteins homologous to the PsaG and PsaH subunits of eukaryotic Photosystem I complexes were detected. When the Photosystem I complex was treated with 6.8 M urea and ultrafiltered using a 100 kDa cutoff membrane, the resulting Photosystem I core protein was found to be depleted of the PsaC, PsaD and PsaE proteins. The filtrate contained the missing proteins, along with five proteolytically-cleaved polypeptides with apparent masses of less than 16 kDa and with N-termini identical to that of the PsaD protein. The PsaF and PsaL proteins, along with the three less than 8 kDa polypeptides, were not released from the Photosystem I complex to any significant extent, but low-abundance polypeptides with N-termini identical to those of PsaF and PsaL were found in the filtrate with apparent masses slightly smaller than those found in the native Photosystem I complex. When the filtrate was incubated with FeCl3, Na2S and beta-mercaptoethanol in the presence of the isolated Photosystem I core protein, the PsaC, PsaD and PsaE proteins were rebound to reconstitute a Photosystem I complex functional in light-induced electron flow from P700 to FA/FB. In the absence of the iron-sulfur reconstitution agents, there was little rebinding of the PsaC, psaD or PsaE proteins to the Photosystem I core protein. No binding of the truncated PsaD polypeptides occurred, either in the presence or absence of the iron-sulfur reagents. The reconstitution of the FA/FB iron-sulfur clusters thus appears to be a necessary precondition for rebinding of the PsaC, psaD and psaE proteins to the Photosystem I core protein.

Infected intravenous port device causing tricuspid valve regurgitation

Sepsis and tricuspid valve regurgitation developed in a 29-year-old man with Crohn's disease after implantation of an intravenous port device for parenteral nutrition. A thrombus, caused by Staphylococcus epidermidis, had grown along the catheter and prolapsed through the valve without affecting it. Complete removal in an open heart procedure led to quick recovery.

Occupational science: academic innovation in the service of occupational therapy's future

Occupational science is a new scientific discipline that is defined as the systematic study of the human as an occupational being. A doctoral program in occupational science has been established at the University of Southern California, Los Angeles. With its emphasis on the provision of a multidimensional description of the substrates, form, function, meaning, and sociocultural and historical contexts of occupation, occupational science emphasizes the ability of humans throughout the life span to actively pursue and orchestrate occupations. In this paper, occupational science is described, defined, and distinguished from other social sciences. A general systems model is presented as a heuristic to explain occupation and organize knowledge in occupational science. The development of occupational science offers several key benefits to the profession of occupational therapy, including (a) fulfillment of the demand for doctoral-level faculty members in colleges and universities; (b) the generation of needed basic science research; and (c) the justification for and potential enhancement of practice.

The able self: adaptive patterns and choices in independent living for a person with cerebral palsy

An ethnographic approach was used to study adaptation to independent living of a 53-year-old woman with cerebral palsy in a West Coast Canadian city. The subject's adaptation through her use of technology (including augmentative communication systems and a powered wheelchair), activity routines, and social supports was documented with the life history method. Short-term accommodations to disruption or breakdown of stable adaptations were observed through participant observation. The criterion of function alone was found insufficient to account for the subject's choice of adaptive techniques, routines, and social supports. Adaptive choices appeared to depend on the subject's desire to be perceived as able, especially as mentally competent, to the greatest extent possible. The way field experiences may be used to challenge professionals' assumptions, in this case, concerning disability and treatment, is modeled for future ethnographic research in occupational therapy.

Assessment and treatment of a pediatric patient in chronic care: ethnographic methods applied to occupational therapy practice

Ethnographic methods were used to examine how an experienced occupational therapist assesses and treats a pediatric patient within a relatively long-term clinical relationship. Treatment goals for this preverbal child with Hirschsprung disease, who began occupational therapy at 22 months of age, included (a) introduction of oral feeding to reduce dependence on total parenteral nutrition through intravenous feeding and (b) facilitation of exploratory play, which had been developmentally delayed during extensive periods of immobilization during medical care. This article shows how the meaning of therapeutic activities changes for the patient over time, as the occupational therapist builds trust through affect attunement, validates his or her empathic interpretations, and develops common understandings with the patient's family and others within the social and cultural contexts of chronic care.

Research on the clinical usefulness of the Rorschach: 2. The assessment of cerebral dysfunction

A review of research on the use of the Rorschach in the assessment of cerebral dysfunction indicated that the Rorschachs of patients with cerebral dysfunction do not manifest any characteristic response in terms of percentages, ratios, or any unique response to any one of the stimulus determinants of the blots (color, shading, the stimulus for movement). The patient with cerebral dysfunction does manifest a unique style of thinking; responses tend to be concrete, perseverative, and stereotypic. This finding is similar to that found with schizophrenics where research, summarized by Frank in 1990, also indicated no uniquely 'objective' response style but reflected a unique cognitive style. These two reviews taken together suggest that the better way to use Rorschach data in clinical work is as an opportunity to assess patients' thinking as opposed to the Rorschach being used as a psychometric device, yielding 'numbers.'