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Biomedical subjects

C Clark

Publications and source records attributed to C Clark.

At least 127 records · Page 7Linked to original sources
PubMed1994

Cloning, characterization, and expression of the murine cytomegalovirus homologue of the human cytomegalovirus 28-kDa matrix phosphoprotein (UL99).

We have identified, characterized, and expressed in bacteria and recombinant vaccinia viruses a protein which likely represents the murine cytomegalovirus (MCMV) homologue of the human cytomegalovirus (HCMV) 28-kDa matrix phosphoprotein, the product of the HCMV UL99 open reading frame (ORF). This protein, referred to as the MCMV UL99, is encoded by a 336-nucleotide ORF within the HindIII G fragment of MCMV strain Smith (K181). Using a DNA probe that corresponded to the amino terminus of the ORF, we detected a transcript of 4.8 kb at 8 hr and additional transcripts of 0.88, 2.4, and 5.7 kb at 24-48 hr postinfection (p.i.) of NIH 3T3 cells with MCMV. The smallest transcript is unspliced, initiates 235 nucleotides upstream from the start of the ORF, and utilizes a polyadenylation site located 62 nucleotides downstream from the end of the ORF. The ORF encodes a protein of 112 amino acids, with a predicted mass of 11.8 kDa. Comparison of the derived amino acid sequence with that of the HCMV UL99 gene product reveals 34.8% identity in an overlap of 66 amino acids. Within the amino acid sequence are at least two potential protein kinase C and one potential casein kinase II target motifs for phosphorylation. The ORF was cloned into the pGEX-KG prokaryotic expression vector and bacterially expressed protein was used to generate a specific rabbit antiserum against the protein. Western blotting of MCMV-infected NIH 3T3 cells showed that the ORF was expressed as a doublet of 16.3 and 15.2 kDa at 48 hr p.i. only in the absence of phosphonoacetic acid, thus demonstrating that this protein is a member of the true late gene class. The immunoreactive protein in MCMV-infected cells comigrated with that produced in cells infected with recombinant vaccinia virus containing the ORF. The protein appears to be part of the MCMV virion, is phosphorylated in vivo, and generates a strong humoral immune response following MCMV infection of BALB/c mice.

3T3 Cells↗
PubMed1994

Experimental investigation of the motions of the pumping diaphragm within a sac-type pneumatically driven ventricular assist device.

The motions of the pumping diaphragm within a sac-type pneumatically driven ventricular assist device (VAD) were monitored non-intrusively using a laser Doppler anemometer (LDA) working in the back-scattering mode. The interaction between the diaphragm and the flow, and the causative factors of the motions were investigated. The motions of a number of points on the diaphragm were determined by analysing the timing of interruption of the Doppler signals due to intrusion of the diaphragm on the LDA sampling volume. The position-time relationships for the identified diaphragm points were then interpolated into two-dimensional surfaces to reconstruct the moving patterns of the diaphragm at selected instants. The motion is strongly affected by the orientation of the device with respect to gravity due to hydrostatic pressure gradients on the liquid side, which are generally large compared with those associated with the fluid accelerations. Hence, during ejection, the part of the diaphragm experiencing the lowest hydrostatic pressure is always set in motion first, while during filling, the part with the highest hydrostatic pressure moves first. Consequences of these non-symmetrical motions on local flow behaviour are discussed, and methods of controlling diaphragm shape during pumping are outlined.

Acceleration↗
PubMed1994

Pressure development within a sac-type pneumatically driven ventricular assist device.

Intrinsic features of the pumping process of a pneumatically driven ventricular assist device (VAD) and the effects of different types of pneumatic drivers upon its performance were investigated in vitro by analysing the pressure distributions within the device and the motions of the prosthetic valves. It was found that the stretching of the flexible, elastic diaphragm in both late systole and diastole initiates a pressure oscillation which directly affects the timing of the pumping process. The timing was also found to be dependent on the length and stiffness of the cannulae which link the VAD to the model circulation system. During the stretch-induced oscillation in late systole, the VAD housing experiences partial collapse due to fluid momentum effects, which tends to increase the effective stroke volume of the device, and reduce the amplitude of the pressure oscillation. Reducing the rising (falling) rate of driving pressures (dpd/dt) may not necessarily reduce the maximum rate of change of the blood chamber pressure (dpch/dtmax) but may upset the stability of the pumping process. This is because a minimum dpch/dtmax exists, which is determined by the stretch-induced oscillation. In order to minimize dpch/dtmax and to provide the device with a stable working condition, dpd/dt should match the dpch/dtmax.

Algorithms↗
PubMed1994

Intelligence quotient profile in myotonic dystrophy, intergenerational deficit, and correlation with CTG amplification.

An abbreviated Wechsler Adult Intelligence Scale Revised (WAIS-R) was used to assess verbal and arithmetical cognitive performance in 55 subjects with myotonic dystrophy (DM), covering all grades of disease severity, and 31 controls at 50% risk of inheriting DM. Scaled scores from the assessment were converted into an intelligence quotient (IQ) estimation on each person. Significant IQ differences were found between: (1) all 55 DM subjects (mean 90.2, SD 16.1) and 31 controls (102.6, SD 9.4), with no sex differences in either group; (2) 15 affected parents (99.3, SD 12.2) and their affected children (88.1, SD 17.2), where significance was dependent on parental sex being female; and (3) 15 pairs of affected sibs (89.6, SD 13.2) and their normal sibs (100.2, SD 7.6). IQ steadily declined as (1) the age of onset of signs and symptoms decreased, and (2) the CTG expansion size increased. The correlation appeared to be more linear with age of onset. The correlation of IQ difference and CTG expansion difference in both the DM parent-child pairs and normal sib-affected sib pairs was poor, indicating that CTG expansion is not a reliable predictor of IQ either in individual persons or families. Further analysis of cognitive function in DM is required to clarify specific deficits characteristic of this patient group.

Adolescent↗
PubMed1994

Effect of dobutamine on oxygen consumption and gastric mucosal pH in septic patients.

Decreases in gastric mucosal pH (pHi) are associated with splanchnic hypoxia in animals and with increased mortality in patients. In the present study we measured changes in gastric pHi with a tonometer in septic patients after a short-term infusion of dobutamine. These changes were compared with concurrent alterations in systemic O2 consumption (VO2) and arterial lactate. Twenty-one patients admitted sequentially to a medical intensive care unit with sepsis and gastric pHi < 7.32 were prospectively separated into a normal lactate group (< or = 2.2 mM; n = 10) and an elevated lactate group (> 2.2 mM; n = 11). Dobutamine HCl was infused intravenously at 5 micrograms/kg/min for approximately 3 h and then increased to 10 micrograms/kg/min. Measurements were obtained after each increase in the dose of dobutamine. Dobutamine infused at 10 micrograms/kg/min produced increases in O2 transport in both groups (p < 0.05) whereas systemic O2 consumption remained unchanged. These changes were accompanied by decreases in the arterial lactate concentration of the elevated lactate group (p < 0.01). Arterial lactate remained constant in the normal lactate group. Gastric pHi increased in both groups when dobutamine was infused at 5 micrograms/kg/min (p < 0.01), and then again at 10 micrograms/kg/min (p < 0.05). These results imply that regional tissue hypoxia, as characterized by a low gastric pHi, may be present in septic patients with normal arterial lactate concentration. Moreover, a rise in gastric pHi in response to increases in systemic O2 transport may be a better indicator of regional hypoxia in septic patients than related increases in systemic VO2.

Adult↗
PubMed1994

Assessment of the magnitude of anxiety in adults undergoing first oxygen treatment in a hyperbaric chamber.

The purpose of this study was to determine the magnitude and specific foci of anxiety experienced by patients receiving their initial hyperbaric treatment. The Spielberger State-Trait Inventory questionnaire and a personal interview were administered to 24 patients to determine anxiety levels. Upon arrival at the hyperbaric clinic and prior to any type of health teaching, the State and Trait questionnaire was administered to the patients. One hour prior to the treatment, the State questionnaire was repeated to determine any significant changes in anxiety levels. No significance was found in anxiety levels between pre-health and pre-treatment. The Trait questionnaire revealed that this specific group of patients, regardless of the circumstances, felt they were not very anxious individuals. Post-treatment, the State questionnaire was administered again and these anxiety levels did differ significantly from the pre-health and pre-treatment levels. The findings indicate the need to continue to validate clients' perceived needs during hyperbaric treatment, which will help direct future nursing practice.

Adolescent↗
PubMed1994

The information highway--where will it take physicians?

While the Iowa Legislature struggles with political issues such as who will own the state's fiber optics network and who will be allowed into it, physicians are envisioning its possible uses in health care. Some say telemedicine could revolutionize the practice of medicine, especially in rural Iowa.

Computer Communication Networks↗
PubMed1993

Technical influences on immunophenotyping by flow cytometry. The effect of time and temperature of storage on the viability of lymphocyte subsets.

The typing of lymphocyte subsets may be influenced by a variety of technical influences including the duration and temperature of sample storage and the method used for staining samples. We have extended a previous study examining the effect of storage conditions on the baseline values of a number of lymphocyte subsets. EDTA-anticoagulated samples from 13 HIV-1-positive and 15 healthy laboratory controls were analyzed for a number of lymphocyte subsets (CD3+, CD4+/CD3+, and CD8+/CD3+ T cells and CD19+ B cells) (whole blood lysis method, Becton-Dickinson FACScan flow cytometer and reagents) at 0, 24, 48, 72, and 96 h after storage at 4 degrees C, 17 degrees C or 21 degrees C. During storage at both 4 degrees C and 21 degrees C, there were significant changes in baseline values of the majority of lymphocyte subsets and some of these were related to the HIV status of the donor. The optimum temperature for storage in our system appeared to be around 17 degrees C in both our study groups. We have also used propidium iodide in order to discriminate between viable and non-viable cells during flow cytometry of lymphocytes from eight HIV-1-positive and five control subjects. The results show that for both HIV-positive and control samples stored at 4 degrees C, and for control subjects at 21 degrees C, the changes in baseline values of lymphocyte subsets observed were not due to selective loss of particular subsets arising from cell death during storage. However, there was substantial loss of cells from all three subsets in HIV-positive subjects during storage at 21 degrees C, with loss of CD8+ and CD3+ T cells being more significant than loss of CD4+ T cells.

Blood Preservation↗
PubMed1993

Accessible, acceptable, appropriate.

In the final article in the homelessness series, Carolyn Clark and Catherine George describe the development of a healthcare purchasing strategy.

Contract Services↗
PubMed1993

Double-staining artefact observed in certain individuals during dual-colour immunophenotyping of lymphocytes by flow cytometry.

An unusual double-staining artefact has been repeatedly observed in certain individuals (both HIV-positive and healthy laboratory controls) during 2-colour immunophenotyping of lymphocytes by flow cytometry after red cell lysis. This artefact can falsely suggest co-expression of CD4 and CD8, as well as some of the other monoclonal antibody pairs commonly used in the typing of lymphocytes. It is caused by a serum factor associated with the ammonium-sulphate-precipitated and gamma-globulin fractions. It appears to be fairly common in the population (being found in 6 out of 105 of our healthy laboratory controls and in 42 out of 247 of our HIV-1 seropositive subjects); it may be genetically determined, but may be acquired in some. It is a potential source of error in lymphocyte immunophenotyping, which can be avoided by simple adjustments to the recommended techniques.

Antibodies, Monoclonal↗
PubMed1993

Experimental investigation of unsteady flow behaviour within a sac-type ventricular assist device (VAD).

The flow behaviour of human blood in a pneumatically driven sac-type ventricular assist device (VAD) has been simulated by a non-Newtonian polymer (Separan) solution, and investigated by both a one-component laser Doppler anemometer (LDA) in back-scattering mode and flow visualisation. The device was driven by a pneumatic driver with a squarewave output pressure, and was operated at a pumping rate of 70 bpm, and a systolic duration of 35% of the pumping cycle. The preload and the average afterload to the device were set at 10 mmHg and 100 mmHg, respectively. The output flowrate was 4.05 l min-1. The wall of the peripheral and the central parts of the blood chamber of the VAD were well 'washed' by a main vortex developed during filling and the flow components perpendicular to the base of the VAD produced by the diaphragm motions, respectively. Flow recirculation regions were found at several locations. Around the junction between the tube sections and the blood chamber, the recirculation with an associated fluid particle deposition indicates an underlying risk of thrombus formation. This risk will be reduced by modifying the device design. The maximum turbulent shear stress estimated from the maximum turbulent normal stress (74 N m-2), is unlikely to cause significant damage to blood for the exposure times found. The maximum particle residence time was found to be closely related to the heart rate and the degree of completion of ejection/filling. At a given flow rate, the operating conditions which produce the highest stroke volume give the shortest residence times.

Adult↗
PubMed1993

Use of ambiguous visual stimuli to demonstrate the value of acoustic cues in speech perception.

The purpose of this study was to evaluate a set of English phrases and sentences in a minimal-pairs syllable-test format for assessing use of acoustic cues in the audiovisual perception of speech; in particular, by persons with severe or profound hearing loss. Test items that were not rejected were categorized as "acceptable" or "ideal." An acceptable item was visually confusable but auditorally distinct compared to its foil (analogous to /p/vs/m/). An ideal item was, in addition, tactilely distinct. Forty-eight items, spoken by a male and a female talker, were presented in a videotaped two-alternative force-choice format under three conditions to three young-adult subject groups. In a lipreading-without-sound condition, 39 items were visually confusable; of these, 16 items were reliably identifiable when sound was added (the "acceptable" items). Seven of the 16 acceptable items were also identifiable in a tactile-pattern-alone condition (the "ideal" items). Performance on the 16 acceptable items was analyzed for an additional 27 young adults with moderate, severe, or profound hearing loss. Results obtained with the new protocol were consistent with conventional assessment results (CID Everyday Sentences, with and without sound) in all but 4 cases. Communication characteristics of the exceptions were examined to explain lack of agreement.

Acoustic Stimulation↗
PubMed1993

Olfactory deficits in neuroleptic naive patients with schizophrenia.

Because previous studies have shown deficits in olfactory identification for male patients with schizophrenia, either withdrawn from or receiving neuroleptic medication, the purpose of the current study was to determine if such deficits occurred in male patients who had never received neuroleptics. A sample of male (n = 30) and female (n = 10) patients as well as age appropriate controls (males, n = 28, females, n = 30) was assessed in terms of olfactory acuity and identification ability. No differences were found in olfactory acuity, but an olfactory identification deficit was present in 31% of the male patients with schizophrenia. As the olfactory pathways project through the limbic system and to the orbitofrontal cortex, odour identification may be a measure of the functional integrity of these structures. Therefore, these results suggest that for a sub-sample of male patients, the functional integrity of these structures is compromised.

Adult↗