Search PubMed⌕ Search

Biomedical subjects

M Clarke

Publications and source records attributed to M Clarke.

At least 253 records · Page 14Linked to original sources
PubMed1987

Crucial role of the connecting region joining the two functional domains of yeast tryptophan synthetase.

We constructed a hybrid plasmid expressing yeast tryptophan synthetase in Escherichia coli. Several deletion variants lacking the A or B domains of this polypeptide (recognized by their homology to the alpha and beta subunits of prokaryotic tryptophan synthetase) showed no enzymatic activity and failed to substitute for the corresponding E. coli subunits. To examine the role of a presumed interdomain connecting region in the yeast enzyme, we constructed a variant lacking 18 amino acids in that region. The variant polypeptide was completely inactive. Replacing 14 of the 18 missing amino acids with a segment having a different sequence partially restored activity. A spontaneous revertant was characterized and shown to have a duplication of 16 amino acid residues in this region; the activity of the duplication polypeptide was better than that of the 14-residue replacement. If confirmed by additional studies, our finding that the length of the connecting region is more critical than its sequence has implications for understanding the origin of gene fusions during evolution as well as for designing artificial fusions.

Amino Acid Sequence↗
PubMed1987

Myosin filaments in cytoskeletons of Dictyostelium amoebae.

Cytoskeletons were prepared from vegetative amoebae of Dictyostelium discoideum by extraction with Triton X-100. The cytoskeletons were suspended in buffers known to induce the assembly or disassembly of myosin filaments. The samples were fixed, and thin sections were examined by transmission electron microscopy. In both types of buffers, myosin-containing cytoskeletons exhibited a ring of densely staining proteinaceous material within the cortical filament matrix; this ring was not observed in myosin-free cytoskeletons. When myosin-containing cytoskeletons were placed in buffers that induced myosin polymerization, the ring appeared as an array of rodlike filaments approximately 13 nm wide and up to 0.5 micron in length--dimensions appropriate for myosin thick filaments. If ATP was added to cytoskeletons containing such filaments, the cytoskeletons contracted and the ring of filaments disappeared. ATP-induced contraction of cytoskeletons was also visualized by indirect immunofluorescence by using monoclonal antibodies to Dictyostelium myosin. All data were consistent with the identification of the protein ring seen by electron microscopy as cortical myosin. Its location and organization were appropriate for the production of cortical contraction through a sliding filament mechanism.

Adenosine Triphosphate↗
PubMed1987

Sequential calcium and phosphorus balance studies in preterm infants.

Forty-six infant boys less than 1500 g at birth and less than 32 weeks gestation were fed enterally from birth until day 47. Cohorts were given milk formula varying in calcium and phosphorus content: group A, calcium 45 mg/dL, phosphorus 33 mg/dL; group B, calcium 85 mg/dL, phosphorus 33 mg/dL; group C, calcium 125 mg/dL, phosphorus 33 mg/dL; group D, calcium 125 mg/dL, phosphorus 50 mg/dL; and group E, calcium 125 mg/dL, phosphorus 64 mg/dL. Three-day balance studies were begun at days 10, 20, 30, and 40. Calcium net absorption and retention were influenced by postnatal age and calcium intake. Calcium retention best approached intrauterine accretion rates in group C. Phosphorus was well absorbed irrespective of the calcium content of the milk. Phosphorus retention increased with increments in the calcium content of the milk. Increasing the phosphorus content of the milk (groups D and E) resulted in no overall change in calcium absorption and retention but some increments in phosphorus retention.

Birth Weight↗
PubMed1987

The axenic mutations and endocytosis in Dictyostelium.

The axenic mutations of Dictyostelium offer a unique opportunity to explore the relationship between phagocytosis and pinocytosis and to examine the mechanism by which a cell shifts from one mode of feeding to the other. The axenic mutations also provide a means of exploring the relationships between endocytosis and other forms of cell motility. This chapter has described the known mutations that affect axenic growth, methods for culturing wild-type and axenic cells and measuring their growth, and methods for monitoring the effects of the axenic mutations on endocytosis and cell movement. The importance has been emphasized of distinguishing effects of the axenic genotype that are expressed constitutively (i.e., during growth on either bacteria or liquid medium) from those that are a function of axenic growth conditions. The methods described in this chapter, applied to wild-type cells and to cells carrying a full complement of the axenic mutations, have shown that the axenic mutations have constitutive effects on cell-substratum interactions, and inducible effects on cell locomotion and pinocytosis.

Cell Movement↗
PubMed1987

A profile of disordered micturition in the elderly at home.

A prevalence survey of disturbed micturition in the elderly identified 7% with important degrees of disorder, 1% with lesser disorder and 1% who were catheterized. Incontinence, urgency, frequency and nocturia were the symptoms most commonly reported. Fifty-three per cent of people describing incontinence used preventive aids but one third of these continued to experience wetting of external clothing. Crude categorization of dysfunction on the basis of symptoms suggested that a component of unstable bladder was present in approximately 4% of the elderly population.

Aged↗
PubMed1987

Density-dependent induction of discoidin-I synthesis in exponentially growing cells of Dictyostelium discoideum.

The synthesis of the lectin, discoidin I, by vegetative cells of Dictyostelium discoideum (strain NC4) was monitored using immunoblot analysis and indirect immunofluorescence. Suspension cultures were used, so that the D. discoideum cell density and the concentration of bacteria could be controlled. Discoidin-I production was found to be a function of the relative densities of D. discoideum cells and food bacteria. Synthesis was initiated in exponentially growing D. discoideum cells approximately three generations before depletion of the food supply. In the growth medium of cells producing discoidin I, a soluble activity was detected that caused low-density cells to begin discoidin-I synthesis. This activity was not dialyzable and was destroyed by heat. A similar activity was produced by AX3 cells during axenic growth. Density-dependent induction of other 'early developmental' proteins was also detected in wild-type cells. These findings suggest that the expression of several 'early developmental' genes is regulated by a mechanism that measures cell density relative to food supply, not by starvation per se.

Cell Differentiation↗
PubMed1987

Early infantile epileptic encephalopathy with suppression burst: Ohtahara syndrome.

Eleven infants with neonatal onset of intractable epilepsy are described, who showed the clinical and electroencephalographic features of Ohtahara syndrome. With time, transition to West and Lennox-Gastaut syndromes occurred. No cause could be found in eight cases. All nine survivors are severely mentally and physically handicapped and continue to have seizures. Early infantile epileptic encephalopathy represents the earliest of the age-dependent epileptic encephalopathies.

Age Factors↗
PubMed1987

Temporary sequential atrioventricular pacing in myocardial infarction.

The loss of atrial contraction can seriously impair cardiac output when complete heart block follows myocardial infarction. We describe two cases in which temporary sequential atrioventricular pacing was lifesaving. The pacemaker used was a previously explanted internal pacemaker. By avoiding the need for an expensive dedicated temporary pacemaker this technique may be more widely applied.

Cardiac Pacing, Artificial↗
PubMed1987

The latency of the visual evoked potential as an index of myelin disturbance in children treated for acute lymphoblastic leukemia.

The phase of central nervous system prophylaxis using cranial irradiation and intrathecal chemotherapy during the treatment of childhood leukemia, may disturb myelination. It has been suggested that this disturbance may be permanent in some children. In this study we report the visual evoked potentials from flash and pattern stimuli in 29 children who were in long-term hematological remission following treatment for acute lymphoblastic leukemia, and who were attending normal schools. We compared these to 29 control children who were matched for age, sex and social class. No difference was detected in the latencies of the response, and we conclude that we could demonstrate no permanent disturbance of myelination by this technique in these long-term survivors.

Acute Disease↗
PubMed1987

Sex and health promotion: the need for a new primary care initiative.

The adverse consequences of sexual behaviour are increasingly important. Half a million new cases of sexually transmitted diseases were reported in England in 1984 and at present there is one legal abortion for every five births. The services provided for the sexually active population are disparate and uncoordinated and it is time for a radical reappraisal of the care and advice they receive. The case is made for a new member of the primary care team, a ;sex education and health promotion nurse', who would ensure that all sexually active men and women are identified and are receiving the sex education and contraceptive services they need, provide pre-conception and fertility advice, run cervical and breast screening programmes, and counsel patients who have AIDS or who have had an abortion.

Counseling↗
PubMed1986

Antibody response and clinical reactions in children given measles vaccine with immunoglobulin.

Antibody responses and clinical reactions to three measles vaccines (Attenuvax, Mevilin, and Rimevax) injected into the opposite arm to immunoglobulin were assessed in 45 children with brain disorders making them susceptible to fits if given measles vaccine alone. In this small study no unacceptable reactions occurred and in only three cases was the antibody response minimal or absent. More children in this special category should be considered for vaccination against measles in this way.

Antibody Formation↗
PubMed1986

Cognitive impairment in the elderly--a community survey.

Previous studies have suggested that up to a fifth of people over the age of 80 years may suffer severe dementia-like illnesses. This total population survey of over a thousand people over the age of 75 suggests that the prevalence of marked cognitive impairment is much less than expected. However, differences in the age structure, representativeness, response rates and size of the samples surveyed, together with differences in methods of measurement, make comparison between studies difficult.

Age Factors↗
PubMed1986

Action and reflection: practice and theory in nursing.

There are three issues related to theory and practice in nursing which are continually problematic. These are: the separation of theory from practice; reality vs the ideal; and nursing adherence to a scientific paradigm versus nursing adherence to an arts paradigm. It is suggested that Shotter's 'theory of personal action' (1974, 1975) may form the basis for a resolution of these three issues. Applying Shotter's work, a nursing action may be defined as an action which is deliberately thought out and which has as its goal the benefit of the patient and client. The 'deliberate thought and goal' of the action which is an integral component of it then forms the basis of nursing theory which is concerned with reasons for and reflections on action. This immediately unites theory and practice as two components of nursing action. The use which could be made of the theory of personal action in nursing practice, research and theory building and nurse education is explored.

Education, Nursing↗
PubMed1986

Identification of the single gene for calmodulin in Dictyostelium discoideum.

We report the isolation and sequence determination of a cDNA containing most of the coding sequence for Dictyostelium discoideum calmodulin. The cloned cDNA was used as a probe to examine the complexity of D. discoideum genomic DNA. These studies indicated that D. discoideum cells possess a single calmodulin gene.

Amino Acid Sequence↗
PubMed1986

Metabolic activity of erosions in rheumatoid arthritis.

The hands of 10 patients with rheumatoid arthritis were investigated with diphosphonate scanning and radiology. Increased uptake of isotope can be associated with some erosions but not all and also reflects other processes more linked to acute inflammatory areas unassociated with the development of erosions. If the latter are the hallmark of active rheumatoid arthritis then bone scans are not.

Adult↗
PubMed1986

Is acute glaucoma a symptom of diabetes?

Forty-three patients who had suffered an episode of angle closure glaucoma had an assessment of glucose tolerance. Two patients were known diabetics and one new diabetic was found as a result of the study. The prevalence of diabetes in this series did not differ significantly from the normal in view of the age distribution of the patients.

Adult↗
PubMed1986

Provision of services for incontinent elderly people at home.

Results of a survey of elderly people living at home suggest that 8% suffer from important degrees of urinary dysfunction and are accessible to community based services. Supply of NHS incontinence aids was inadequate, and improvements in provision are recommended. Attendance at a continence clinic established for the survey period suggests a need for additional specialist services to be made available close to home. Correspondence between actual and predicted cystometric diagnosis provides encouragement to develop simple, valid assessment procedures as an aid to patient management. For the average District Health Authority serving a population of 250 000, two continence nurse advisers and 50 continence clinic sessions per annum are recommended for people aged 75 and over.

Aged↗