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Biomedical subjects

K Cunningham

Publications and source records attributed to K Cunningham.

At least 19 recordsLinked to original sources
PubMed1995

Precision and accuracy of clinical and radiological signs in premature infants at risk of patent ductus arteriosus.

OBJECTIVE: To determine the precision (interobserver agreement) and accuracy (agreement with criterion standard) of clinical and radiological signs in premature infants at risk of patent ductus arteriosus (PDA) with left-to-right shunting. DESIGN: Masked comparison of clinical and radiological examination with Doppler flow echocardiography (criterion standard). SETTING: Neonatal intensive care unit. PATIENTS: One hundred infants with birth weights less than 1750 g were studied once between days 3 and 7 of life. A third of the cohort was intubated at the time of study. INTERVENTION: Five independent observers noted the presence or absence of an increased pulse volume, an active precordium, a heart murmur, a cardiothoracic ratio greater than 60%, increased pulmonary vascular markings on a concurrent chest x-ray film, and a relative increase of the cardiothoracic ratio compared with that from the previous chest x-ray film. Pulsed and color flow Doppler echocardiography was performed within 4 hours. All 100 tapes were reviewed by a second pediatric cardiologist. RESULTS: Twenty-three infants had a PDA with left-to-right shunting. The precision of clinical signs was modest, with average kappa values of 0.15 for pulse volume, 0.32 for precordium, and 0.41 for murmur. Pulse quality (43%) and murmur (42%) had the highest mean sensitivities. Corresponding specificities were 74% for pulse volume and 87% for murmur. The combination of a cardiac murmur with an abnormal pulse volume had the highest positive predictive value (77%). The radiological examination did not improve the observers' ability to distinguish between patients with and without PDA. CONCLUSIONS: The precision and accuracy of clinical and radiological signs of a PDA with left-to-right shunting are unsatisfactory. Therefore, Doppler flow echocardiography is required to diagnose PDA confidently in preterm infants between days 3 and 7 of life.

Ductus Arteriosus, Patent↗
PubMed1992

Cytochromes c1 and b2 are sorted to the intermembrane space of yeast mitochondria by a stop-transfer mechanism.

The pathway by which cytochromes c1 and b2 reach the mitochondrial intermembrane space has been controversial. According to the "conservative sorting" hypothesis, these proteins are first imported across both outer and inner membranes into the matrix, and then are retranslocated across the inner membrane. Our data argue against this model: import intermediates of cytochromes c1 and b2 were found only outside the inner membrane; maturation of these proteins was independent of the matrix-localized hsp60 chaperone; and dihydrofolate reductase linked to the presequence of either cytochrome was imported to the intermembrane space in the absence of ATP. We conclude that cytochromes c1 and b2 are sorted by a mechanism in which translocation through the inner membrane is arrested by a "stop-transfer" signal in the presequence. The arrested intermediates may be associated with a proteinaceous channel in the inner membrane.

Adenosine Triphosphate↗
PubMed1992

Obsessive-compulsive disorder in Huntington's disease.

Two patients with Huntington's disease (HD) and obsessive-compulsive disorder (OCD) are reported. The OCD was manifested by repetitive, stereotyped, complex, egodystonic behaviors that were disabling. These cases and other neurological syndromes with OCD (Gilles de la Tourette syndrome, neuroacanthocytosis, postencephalitic parkinsonism, caudate infarction, carbon monoxide poisoning, manganese intoxication, anoxia, progressive supranuclear palsy, Sydenham's chorea, and frontal lobe lesions) indicate that the frontal lobe, caudate nucleus, and globus pallidus are members of a complex circuit that plays a key role in mediating the symptoms of OCD. Evidence of excitatory subcortical output to cortex is shared by many neurological disorders manifesting OCD.

Basal Ganglia↗
PubMed1992

Cefuroxime and cefuroxime axetil versus amoxicillin plus clavulanic acid in the treatment of lower respiratory tract infections.

In a large multinational study, the clinical and bacteriological efficacy of intravenous cefuroxime 750 mg t.i.d. followed by oral cefuroxime axetil 500 mg b.i.d. was compared to that of amoxicillin plus clavulanic acid (CA) administered as 1.2 g intravenously t.i.d. followed by 625 mg orally t.i.d. in the treatment of lower respiratory tract infections in hospitalised patients. A total of 512 patients were entered (256 in each treatment group). All were suffering from pneumonia or acute exacerbations of chronic bronchitis or bronchiectasis and required initial parenteral antibiotic therapy. Parenteral therapy lasted 48 to 72 h and was followed by five days of oral therapy. The clinical responses in the two treatment groups were very similar: 223 of 256 (87.1%) patients were cured or improved with cefuroxime/cefuroxime axetil compared to 220 of 256 (85.9%) with amoxicillin/CA. Positive pre-treatment sputum samples were obtained from 44% of the patients. Clearance rates obtained were again similar: 72.8% with cefuroxime/cefuroxime axetil and 70% with amoxicillin/CA. Ten percent of the isolates were beta-lactamase producers, similar numbers of which were cleared in both groups. Both regimens were generally well tolerated, with only 5% of patients treated with the cefuroxime regimen and 4.3% of patients treated with amoxicillin/CA experiencing drug-related adverse events. Cefuroxime/cefuroxime axetil "follow-on" therapy produces clinical and bacteriological efficacy equivalent to that of amoxicillin/CA, with the advantage of twice daily oral administration.

Administration, Oral↗
PubMed1991

TGF beta elicits opposite responses in clonal subpopulations of NRK-49F cells.

Clonal subpopulations of NRK-49F cells were isolated and characterized for their responses to transforming growth factor beta (TGF beta). Two fibroblastic clones, N1 and N4, were found to have opposite TGF beta responses. TGF beta inhibits EGF-induced proliferation in growth-arrested, subconfluent monolayer cultures of N1 but not N4 cells. In contrast, TGF beta stimulates DNA synthesis and an increase in cell number in N4 but not N1 cells. The inhibitory effect of TGF beta on DNA synthesis in N1 cells is due not to modulation of the EGF receptor or other early G1 events. EGF-induced myc mRNA accumulation is not inhibited, and the action point for TGF beta inhibition of the entry into S of N1 cells is at the G1-S boundary.

Animals↗
PubMed1991

Antibacterial activity and inhibition of protein synthesis in Escherichia coli by antisense DNA analogs.

Protein synthesis, which takes place within ribosomes, is essential for the survival of any living organism. Ribosomes are composed of both proteins and RNA. Specific interaction between the 3' end CCUCC sequence of prokaryotic 16S rRNA and a partially complementary sequence preceding the initiating codon of mRNA is believed to be a prerequisite for initiation of protein synthesis. Here we report the use of short (three to six nucleotides) synthetic DNA analogs complementary to this sequence to block protein synthesis in vitro and in vivo in Escherichia coli. In the DNA analogs the normal phosphodiester bond in the antisense DNA was replaced by methylcarbamate internucleoside linkages to enhance transport across plasma membranes. Of the analogs tested, those with the sequence AGG and GGA inhibit protein synthesis and colony formation by E. coli strains lacking an outer cell wall. Polyethylene glycol 1000 (PEG 1000) was attached to the 5' end of some of the test methylcarbamate DNAs to enhance solubility. Analogs of AGG and GGAG with PEG 1000 attached inhibited colony formation in normal E. coli. These analogs may be useful food additives to control bacterial spoilage and biomedically as antibiotics.

3T3 Cells↗
PubMed1990

Nutrient intakes in long-stay mentally handicapped persons.

A study of the dietary intake of 115 male and 217 female mentally handicapped persons aged 15-64 years in five long-stay institutions was carried out using a semi-weighed technique over 4 d. Nineteen per cent of males and 5% of females were classified as being underweight and 15% of males and 27% of females were classified as being obese. The average daily intakes of nutrients were: energy 8.8 MJ, protein 92 g, carbohydrate 218 g, fat 101 g, dietary fibre 18 g, calcium 1024 mg, iron 12.5 mg, vitamin B6 1.4 mg, vitamin B12 10.8 micrograms, ascorbic acid 68 mg. The distribution of energy between protein, carbohydrate and fat was 18, 39 and 43% respectively. Energy intakes were not related to ambulatory status, degree of mental handicap, the level of drug usage or body mass index. Energy intakes varied significantly between hospitals and between the sexes.

Adolescent↗
PubMed1990

Subcutaneous fat necrosis with hypercalcemia.

We report the case of an infant with diffuse subcutaneous fat necrosis following birth asphyxia who had hypercalcemia and the rare complication of venous calcification. The clinical and radiologic findings resolved over 5 months. The disease is characterized by the presence of painless subcutaneous nodules, mainly over bony prominences, possibly associated with hypercalcemia and calcification. Early identification of hypercalcemia will avert its serious sequelae.

Calcinosis↗
PubMed1989

SecA protein, a peripheral protein of the Escherichia coli plasma membrane, is essential for the functional binding and translocation of proOmpA.

We have reconstituted protein translocation across plasma membrane vesicles of Escherichia coli using purified proOmpA and trigger factor, a 63 kd soluble protein. Treatment of membrane vesicles with urea inactivates them for translocation unless a factor present in cytoplasmic extracts is added during the translocation reaction. Sedimentation analysis showed that the stimulatory activity is of distinctly higher mol. wt than trigger factor. Cytoplasmic extracts from a strain that greatly overproduces the SecA protein are highly enriched in the stimulatory activity for untreated membranes and restore translocation to urea-treated membranes, suggesting that this protein is the stimulatory factor. This assay was used to monitor the isolation of SecA protein from the overproducing strain. The purified protein is soluble, yet binds peripherally to membranes with high affinity and supports translocation. Using pure proOmpA, SecA protein, trigger factor and urea-treated membranes, the protein export process was resolved into binding and translocation steps. We find that proOmpA binds to membrane vesicles with or without SecA protein, but that translocation only occurs when SecA was bound prior to proOmpA.

Amino Acid Isomerases↗
PubMed1989

SecA protein hydrolyzes ATP and is an essential component of the protein translocation ATPase of Escherichia coli.

Bacterial protein export requires two forms of energy input, ATP and the membrane electrochemical potential. Using an in vitro reaction reconstituted with purified soluble and peripheral membrane components, we can now directly measure the translocation-coupled hydrolysis of ATP. This translocation ATPase requires inner membrane vesicles, SecA protein and translocation-competent proOmpA. The stimulatory activity of membrane vesicles can be blocked by either antibody to the SecY protein or by preparing the membranes from a secY-thermosensitive strain which had been incubated at the non-permissive temperature in vivo. The SecA protein itself has more than one ATP binding site. 8-azido-ATP inactivates SecA for proOmpA translocation and for translocation ATPase, yet does not inhibit a low level of ATP hydrolysis inherent in the isolated SecA protein. These data show that the SecA protein has a central role in coupling the hydrolysis of ATP to the transfer of pre-secretory proteins across the membrane.

Adenosine Triphosphatases↗
PubMed1989

Specific recognition of the leader region of precursor proteins is required for the activation of translocation ATPase of Escherichia coli.

The ATP-hydrolytic activity of SecA protein is stimulated up to 100-fold by the translocation-competent precursor to outer membrane protein A (pro-OmpA) in conjunction with inner-membrane vesicles bearing active SecY [Lill, R., Cunningham, K., Brundage, L., Ito, K., Oliver, D. & Wickner, W. (1989) EMBO J. 8, 961-966]. This reaction is saturable, with Michaelis-Menten kinetics for an enzyme with two substrates, ATP and pro-OmpA, and is defined as translocation ATPase. Another precursor protein, pre-PhoE, is also a substrate for this translocation ATPase. Neither OmpA nor its synthetic leader peptide are effective substrates for translocation ATPase, suggesting that both domains of the complete precursor are necessary for the reaction. The leader peptide is a potent inhibitor and apparently competes with pro-OmpA for necessary binding sites on translocation ATPase. After a brief preincubation, the activity of translocation ATPase becomes resistant to inhibition by leader peptide, suggesting that the leader peptide is recognized at an early step in the protein translocation pathway. Our enzymological studies show that translocation ATPase recognizes and functionally binds the leader region of precursor proteins.

Amino Acid Sequence↗
PubMed1989

Detergent disruption of bacterial inner membranes and recovery of protein translocation activity.

Isolation of the integral membrane components of protein translocation requires methods for fractionation and functional reconstitution. We treated inner-membrane vesicles of Escherichia coli with mixtures of octyl beta-D-glucoside, phospholipids, and an integral membrane carrier protein under conditions that extract most of the membrane proteins into micellar solution. Upon dialysis, proteoliposomes were reconstituted that supported translocation of radiochemically pure [35S]pro-OmpA (the precursor of outer membrane protein A). Translocation into these proteoliposomes required ATP hydrolysis and membrane proteins, indicating that the reaction is that of the inner membrane. The suspension of membranes in detergent was separated into supernatant and pellet fractions by ultracentrifugation. After reconstitution, translocation activity was observed in both fractions, but processing by leader peptidase of translocated pro-OmpA to OmpA was not detectable in the reconstituted pellet fraction. Processing activity was restored by addition of pure leader peptidase as long as this enzyme was added before detergent removal, indicating that the translocation activity is not associated with detergent-resistant membrane vesicles. These results show that protein translocation activity can be recovered from detergent-disrupted membrane vesicles, providing a first step towards the goal of isolating the solubilized components.

Bacterial Outer Membrane Proteins↗