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Biomedical subjects

K Smith

Publications and source records attributed to K Smith.

At least 433 records · Page 24Linked to original sources
PubMed1988

Inhibition of protein breakdown by glutamine in perfused rat skeletal muscle.

We have assessed the effects of glutamine (Gln) availability on protein breakdown in perfused rat hindlimb by measuring net phenylalanine (Phe) production (an index of protein balance), the dilution of [15N]Phe labelling (an index of mixed protein breakdown) and rate of production of 3-methylhistidine (3-MeH) (an index of myofibrillar breakdown). 15 mM Gln significantly inhibited net protein loss and protein breakdown compared to rates obtained in its absence (net protein loss, 200 +/- 230 vs 2080 +/- 200 nmol Phe/hindlimb per h; protein breakdown, 4566 +/- 480 vs 1614 +/- 180 nmol Phe/hindlimb per h; both p less than 0.01). Insulin (100 microU/ml) inhibited protein breakdown but less than Gln. The effects on protein breakdown of Gln and insulin together were not additive, suggesting a common mode of action. Production of 3-MeH (mean 20.3 +/- 2.8 nmol/hindlimb per h) was unaffected by Gln or insulin. Gln appears to inhibit protein breakdown of soluble rather than myofibrillar protein in muscle.

Animals↗
PubMed1988

Stability and immunological cross-reactivity of malate dehydrogenases from mesophilic and thermophilic sources.

The thermostability in vitro of dimeric and tetrameric malate dehydrogenases [S)-malate:NAD+ oxidoreductase, EC 1.1.1.37) from mesophilic and thermophilic bacteria shows a good correlation to the growth temperature of the source organism but no consistent relationship to enzyme subunit structure. The thermophile malate dehydrogenases are, in general, more resistant to the surfactants, sodium dodecyl sulphate (SDS) and hexadecyltrimethylammonium bromide, and to the denaturants, guanidinium chloride and urea, than their mesophilic counterparts, with the dimer in each thermal class being more resistant to the chemical perturbants than the tetramer. Sedimentation analysis suggests that denaturation of the malate dehydrogenases by acid-periodate or SDS produces discrete subunits, whereas denaturation by guanidinium chloride followed by carboxymethylation yields ill-defined protein species. SDS and acid-periodate were therefore preferred to generate denatured malate dehydrogenases for use as immunogens and antigens. The native malate dehydrogenases exhibit immunological cross-reactivity only when they are in the same oligomeric form and derived from closely related species, which may, however, be from different thermal classes. Taking immunological cross-reactivity as an indicator of structural similarity, this supports the idea that the thermophilic trait evolved independently within each phyletic line. With denatured malate dehydrogenases as immunogens and antigens, cross-reactivity is manifested between all the malate dehydrogenases examined. This suggests that appreciable primary structural homology exists between the malate dehydrogenases, whether dimeric or tetrameric, from thermophiles and mesophiles and from various taxa.

Bacillus↗
PubMed1988

Automated measurement of 13C enrichment in carbon dioxide derived from submicromole quantities of L-(1-13C)-leucine.

The 13C enrichment of the carboxyl carbon of leucine was measured by isotope ratio mass spectrometry after conversion to CO2 by reaction with ninhydrin in a Vacutainer and cryogenic purification using the Finnigan MAT Breath Gas Analysis System designed for processing 13C breath test samples. The sources of error which arise with submicromole samples are examined and corrections provided for suboptimal mass spectrometer signals and contamination of the evolved CO2 with CO2 from the reaction medium. The main limitations to the accuracy and precision of the method are not instrumental but arise from the contamination with residual CO2 in the reaction medium, and this sets a lower limit of around 0.25 mumol leucine on the practical sample size. This is an improvement of about five-fold on the previous manual method of CO2 isolation.

Autoanalysis↗
PubMed1988

Ultrastructure of the attachment of Cryptosporidium sporozoites to tissue culture cells.

The attachment of Cryptosporidium sporozoites to Madin-Darby canine kidney (MDCK) cells was examined using transmission electron microscopy. As the anterior end of the sporozoite came into close proximity to the MDCK cell, the host cell membrane evaginated around the sporozoite, forming a parasitophorous vacuole. A dense band formed below the host cell membrane at the site nearest to the conoid. Variably electron-dense material was apparently released from the conoid and a large membrane-bound vacuole was formed in the anterior end of the sporozoite, displacing the typical anterior electron-dense organelles (rhoptries and micronemes). The outer membrane of the sporozoite pellicle then fused with the host cell membrane immediately adjacent to the conoid. The membrane surrounding the anterior vacuole was also fused with the common host-parasite membrane, forming Y-shaped membrane junctions where each limb was a unit membrane. A direct link was thereby established between the anterior vacuole of the sporozoite and the host cell cytoplasm. The anterior vacuole membrane separating the sporozoite and the host cell cytoplasm was the precursor of the feeder organelle.

Animals↗
PubMed1988

Minor infection, minor life events and the four day desirability dip.

Sixty-five subjects volunteered to take part in an intensive prospective investigation into the role of minor life events in precipitating episodes of minor infectious illness of the upper respiratory tract, notably 'colds'. Subjects provided daily records of desirable and undesirable events, as well as information concerning their physical health. Information was collected using standardized methods which have proven useful in recent research. Among those subjects who both provided adequate data and experienced a suitable illness episode, it was found that, relative to carefully matched control days, illness episodes were characterized by a statistically significant decrease in desirable events during the 4 days prior to symptom onset. Undesirable events were unrelated to illness episodes. This replicates and extends the most recent findings in this area, is consistent with psychoimmunological hypotheses regarding aetiological mechanisms and illustrates the promise of the new life events research based on a consideration of minor daily events.

Adaptation, Psychological↗
PubMed1988

Objective analysis of stallion sperm motility.

An image-analysis system utilizing a microcomputer and CellSoft computer-assisted semen analysis software package was evaluated to assess stallion sperm motility characteristics. Analyses were performed at 37 degrees C on a 6 microl drop of diluted semen placed on a glass slide and covered with an 18 mm(2) coverslip. Four groups of 25 cells each per slide, four slides per ejaculate and four ejaculates from each of three stallions were analyzed in a nested model. The percentage of motile sperm cells, mean velocity (microm/sec), mean linearity, and mean angular head displacement (microm) were measured. Statistical analysis of variance components showed that within ejaculates, more variation was accounted for in the differences among groups of 25 cells than among slides. Predicted standard deviations calculated for combinations of slides and groups of cells showed that a combination of two slides from which a total of 400 cells were analyzed resulted in a mean intra-assay coefficient of variation (CV) of 5.7% for the four measured variables. The following are individual coefficients of variation: percentage of motile cells (7.8%), mean velocity (6.4%), mean linearity (1.9%) and mean angular head displacement (6.6%). When ejaculate differences were included in the model and predicted standard deviations were calculated for a single ejaculate, the mean inter-assay CV was 9.2%. Mean velocity (6.4%) and mean linearity (4.7%) were more repeatable among ejaculates than either the percentage of motile sperm (14.4%) or angular head displacement (11.2%). It was concluded that this system is precise enough to determine differences in motility characteristics of stallion semen samples.

Journal Article↗
PubMed1988

Immunoregulation and prostaglandin production by mechanically-derived and enzyme-derived murine decidual cells.

Uterine cells from pregnant mice release soluble mediators which suppress in vitro immune responses non-specifically. Two methodologic approaches have been employed to obtain regulatory cells, and, although all cell populations derived by both methods were immunosuppressive, different factors and possibly different mechanisms of suppression appear to have been involved. The current study was designed to determine how suppression by mechanically and enzymatically derived cells might differ. Both enzymatically and mechanically derived cell populations suppressed mixed lymphocyte reactions non-specifically, mediated their effects through release of soluble factors, were immunosuppressive whether added at initiation or near the end of culture, suppressed generation of both IL-1 and IL-2, and suppression was not reversible with IL-1, IL-2, gamma interferon or combinations of the above. Immunosuppression by enzymatically derived, but not mechanically derived cells, was reversible with indomethacin. Enzymatically derived cells, but not mechanically derived cells, produced considerable amounts of PGE2. Morphological and immunohistochemical analysis revealed significant numbers of macrophages in both populations. Enzymatic treatment of mechanically derived cells did not increase the output of PGE2 when cells were cultured in vitro. The results suggest that, despite several similarities, enzymatically and mechanically derived cell populations are distinct and produce a distinct profile of soluble suppressive molecules.

Animals↗
PubMed1988

Nucleolar organiser regions in fibrous proliferations of childhood and infantile fibrosarcoma.

A silver colloid technique to identify nucleolar organiser region associated protein (AgNOR) was applied to 16 fibrous proliferations of childhood and six low grade fibrosarcomas. The fibrous proliferations comprised five cases of infantile digital fibromatosis, seven of infantile desmoid type fibromatosis, and four of infantile myofibromatosis. The AgNORs were visualised as dots within the nuclei of the cells, and on the basis of their relative mean numbers of AgNORs fibrous proliferations of childhood could be easily differentiated from low grade infantile fibrosarcoma. The differences observed were significant (0.01 greater than p greater than 0.001). This technique, previously the province of the cytogeneticist, may be of use to the pathologist in differentiating infantile fibrous proliferations.

Child↗
PubMed1988

Patient data system for monitoring shunts.

Rapidly locating accurate data on a patient's shunt system is often extremely difficult. We have developed a simple system to fill a perceived need for recording current data on a patients shunt. This system employs an easily updated record in the patient's hospital or clinic chart as well as a wallet-sized data card for the patient or his family to carry. The data in the chart include the configuration of the patient's current shunt system and a graphic record of previous shunt problems. The small patient data card describes the age of the shunt system and its current configuration. We have found that this system provides assistance in the routine follow-up of patients with shunts and plays an extremely necessary role in the emergency evaluation of these patients, particularly when an emergency evaluation is undertaken in facilities distant from the location of regular treatment.

Adolescent↗
PubMed1988

LY146032 in a hamster model of Staphylococcus aureus pneumonia--effect on in vivo clearance and mortality and in vitro opsonophagocytic killing.

The effect of the new peptolide LY146032 (LY) was studied in a hamster model of methicillin-resistant Staphylococcus aureus (MRSA) pneumonia. In vivo, after infection with one of two well-encapsulated strains of MRSA, A83 and A116 (type 8 and type 5), LY was protective only in A116 pneumonia. An in vitro assay of the effect of subinhibitory concentrations of LY on opsonophagocytic killing by pulmonary phagocytes demonstrated marked enhancement of killing of A116 (92.6 and 63.8% kill with 1/10 MIC and 1/50 MIC LY; no kill in the absence of LY). This effect was dependent on the presence of fresh serum. LY in subinhibitory concentrations produces a surface effect that may allow complement binding and activation and subsequent phagocytosis and killing to take place. The opsonizing effect of subinhibitory concentrations of LY was not demonstrable for the A83 strain. Differences in capsular types may be determinants of response to therapy of MRSA infections.

Animals↗
PubMed1988

Psychosocial problems in cancer survivors.

Cancer is a disease with both physical and psychosocial sequelae. While much is being learned about the physical late effects of cancer and its treatment, less is known about its psychosocial morbidity. Research shows that cancer survivors typically function quite adequately in their daily lives but may experience distress related to their past illness. The cancer survivor's self-image is crucial to the way he or she reenters and adapts to family and social life, school, or work, and this reentry and adaptation in turn influences self-image. The physician plays as important a role in the survivor's psychosocial healing as he did in the patient's physical treatment.

Adult↗
PubMed1988

Mucosal immune response to cholera toxin in ageing rats. I. Antibody and antibody-containing cell response.

Although ageing is accompanied by systemic immunodeficiencies, the status of the mucosal immune system in the elderly remains unresolved. The gastrointestinal mucosal immune response was evaluated in young, mature and old male rats subjected to intra-intestinal immunization with cholera toxin (CTx). Five days following secondary immunization, the alpha-CTx-IgA titre in the bile of immunized rats was markedly reduced, i.e. the values measured in young rats were approximately five-fold higher than those of old animals. alpha-CTx-IgA levels in non-immunized rats were negligible and age-related shifts in other antibody titres (alpha-CTx IgG and IgM) were not significant. The antibody response to CTx was not reflected in the total IgA content of the samples. The number of alpha-CTx antibody-containing cells (ACCs) in the small intestinal lamina propria was significantly reduced in old immunized rats in comparison with the young or mature animals. These data suggest that ageing compromises both non-immune cell (antibody transport by hepatocytes) and immune cell (number of ACCs in the gut wall) functions in response to cholera toxin immunization in this animal model.

Aging↗
PubMed1988

New autoperfusion preparation for long-term organ preservation.

The problems in long-term organ preservation are ischemia and toxicity from metabolic waste. A simple self-perfusing self-cleaning system has been developed that kept the heart, lungs, and kidney functioning for a mean time of 24 hours. Nine adult dogs were anesthetized and artifically ventilated. The heart and lungs were removed en bloc while being perfused by the heart. One kidney was connected to the descending aorta and inferior vena cava. No anticoagulant was used. Another group of six dogs without functioning kidneys was used as the control group. In the experimental group, urine output ranged from 26 to 48 ml/hr, aortic systolic pressures were 80-107 mm Hg, heart rate was 85-100 beats/min, serum potassium content was 3.25-4.40 mmol/l, and serum sodium content was 155-163 mmol/l. In the experimental group, blood creatinine levels decreased from 0.95 to 0.47 mg/dl during preservation; in the control group, blood creatinine levels decreased from 0.96 to 0.79 mg/dl. Lung biopsies in the preparation with the longest survival showed good preservation for as long as 24 hours, and no thrombi were present. This preparation has the advantage of no ischemic time, no foreign material in the circulation, and the ability to automatically maintain acid-base balance and blood electrolytes. The simplicity of this autoperfusion preparation may allow greater transport distance in organ procurement for subsequent transplantation.

Animals↗