PubMed Health⌕ Search

Biomedical subjects

P Kirkpatrick

Publications and source records attributed to P Kirkpatrick.

34 records · Page 2Linked to original sources
PubMed1995

Can cerebrovascular reactivity be measured with near-infrared spectroscopy?

BACKGROUND AND PURPOSE: We used near-infrared spectroscopy (NIRS) to monitor the cerebral oxygenation changes during CO2 reactivity tests. METHODS: Fifty healthy volunteers were examined (age range, 19 to 68 years). The monitored parameters were as follows: transcranial Doppler (TCD) time-averaged middle cerebral artery flow velocity end-tidal CO2 (EtCO2); change in concentration of cerebral oxyhemoglobin (HbO2), deoxyhemoglobin (Hb), and total hemoglobin; mean arterial blood pressure; peripheral arterial oxygen saturation (SaO2); and extracranial tissue perfusion with the use of cutaneous laser-Doppler flowmetry. The examination protocol included both hypercapnia and hypocapnia. The cerebrovascular reactivity indexes were calculated as follows: TCD, relative change in flow velocity per 1 kPa increase in EtCO2; NIRS, absolute change in HbO2, Hb, and total hemoglobin concentration (micromoles per liter) per 1 kPa increase in EtCO2. RESULTS: Mean middle cerebral artery flow velocity was found to be 58 cm/s at a mean baseline EtCO2 of 4.7 kPa. Mean cerebrovascular reactivities were as follows: TCD, 24%/kPa (SEM, 1.1); HbO2, 2.06 mumol/L per kilopascal (SEM, 0.08); Hb, -0.63 mumol/L per kilopascal (SEM, 0.09); and total hemoglobin concentration, 1.44 mumol/L per kilopascal (SEM, 0.1). Statistical analysis revealed significant correlation between reactivities calculated with the use of NIRS and TCD (P < .001). Although some fluctuations were observed in SaO2 and laser-Doppler flux, they were not correlated with either EtCO2 or NIRS. CONCLUSIONS: NIRS signal changes in HbO2, Hb, and total hemoglobin concentration are very sensitive to alterations in EtCO2, which are largely independent of extracranial tissue perfusion. NIRS may be developed as an alternative method for testing cerebrovascular reactivity and may be of particular clinical importance when the ultrasound window is poor.

Adult↗
PubMed1994

Testing of cerebral autoregulation in head injury by waveform analysis of blood flow velocity and cerebral perfusion pressure.

Thirty five head injured patients were subjected to day-by-day monitoring of intracranial pressure (ICP), arterial blood pressure (ABP) and blood flow velocity (FV) in middle cerebral artery. Parameters describing cerebral autoregulation: flow velocity time average, systolic, diastolic values, pulsatility index (PI), estimate of cerebrovascular resistance (CVR = CPP/FV) etc. were analyzed as functions of CPP (ABP-ICP). The results show that for CPP below 55 mmHg the evidence of exhausted autoregulation can be observed in FV, CVR, PI. The method is helpful in assessment ot the optimal level of CPP in order to reduce the probability of ischaemic brain insults.

Blood Flow Velocity↗
PubMed1994

Computer supported multimodal bed-side monitoring for neuro intensive care.

Multimodal monitoring in neuro-intensive care requires computer supported data analysis and archiving. This paper describes a computer system that is able to integrate the results of analysis of intracranial pressure, cerebral perfusion pressure, transcranial Doppler blood flow velocity, jugular bulb oxygen saturation, laser Doppler blood flow, near infrared spectroscopy. A research-oriented software installed in a standard IBM PC equipped with a low-cost analog-to-digital converter allows a broad spectrum of waveform analyses, from calculation of simple mean values to a selective waveform detection and cross-correlation analysis. The architecture for the signal processing algorithm, the principles of system interfacing and data presentation are discussed briefly. Results from two years of multimodal monitoring in neuro-intensive care show that, apart from simple recording of time trends of monitored variables, certain calculated parameters are particularly useful in the continuous assessment of cerebral haemodynamic and compensatory reserves. Such parameters include: transcranial Doppler pulsatility indices, the dependence between blood flow velocity or laser Doppler flux and cerebral perfusion pressure and the correlation coefficient between pulse amplitude and mean intracranial pressure.

Adolescent↗
PubMed1994

Assessment of cerebral autoregulation with ultrasound and laser Doppler wave forms--an experimental study in anesthetized rabbits.

The aim of the study was to correlate changes in transcranial Doppler blood flow velocity wave form in the basilar artery with cortical red blood cell flux measured with a laser Doppler flowmeter during hemorrhage-induced hypotension in anesthetized and ventilated New Zealand rabbits. Although systolic flow velocity and flux exhibited an autoregulatory threshold at 45 mm Hg, diastolic flow velocity started to fall when mean arterial blood pressure fell below 65 mm Hg. The difference between the mean arterial blood pressure at which diastolic blood flow velocity decreases and the pressure at which mean flux decreases is the difference between systolic and diastolic blood pressure. The increasing divergence between systolic and diastolic flow velocities was reflected in an increase in the amplitude of blood flow velocity pulsations and pulsatility indices. An increase in flux pulsatile wave form was noted as cerebral resistive vessels dilated with hypotension.

Animals↗
PubMed1987

Immunohistological detection of Legionella pneumophila in lung sections.

Immunohistology was used for the detection of Legionella pneumophila serogroup I in necropsy tissue. Study of pneumonic lung from the recent Stafford outbreak has shown that this technique has a high sensitivity. A retrospective postmortem examination showed that L pneumophila serogroup 1 was an unusual cause of pneumonia in Oxfordshire during the study period. L pneumophila serogroup 1 can be successfully subgrouped, using a panel of monoclonal antibodies on formalin fixed paraffin embedded sections. Immunohistological methods have a potentially useful role in the diagnosis of Legionellosis at postmortem examination and in the epidemiological investigation of individual cases and outbreaks.

Antibodies, Monoclonal↗
PubMed1986

Laminin and fibronectin in adenoid cystic carcinoma.

The distribution of fibronectin and laminin was examined by immunohistochemistry in 11 adenoid cystic breast carcinomas, six adenoid cystic carcinomas of mouth and salivary gland, and six cribriform ductal breast carcinomas. Both proteins were present lining cystic lumina and around tumour islands in all the adenoid cystic breast carcinomas and in five of six salivary gland tumours. Abundant laminin and fibronectin were dispersed among adenoid cystic tumour cells arranged in sheets. One adenoid cystic carcinoma from buccal mucosa showed a transition from a cribriform tumour positive for both fibronectin and laminin to a cribriform tumour negative for fibronectin and laminin to undifferentiated carcinoma. Fibronectin and laminin seemed to disappear simultaneously from tumour cell surfaces. Another adenoid cystic carcinoma from buccal mucosa was negative for fibronectin and laminin from the time of initial biopsy. This was the only tumour that gave rise to disseminated metastases, resulting in the death of the patient within two years of surgery. In cribriform invasive ductal breast carcinomas the linings of cystic lumina were always negative for fibronectin and laminin. Varying quantities were present at the tumour boundaries. We suggest that staining for fibronectin and laminin may be a valuable aid to the diagnosis of adenoid cystic carcinomas and that the absence of these proteins may have important prognostic implications.

Aged↗
PubMed1984

Primary Kaposi's sarcoma of the lung in an immunocompetent 32-year-old heterosexual white man.

Primary visceral involvement by Kaposi's sarcoma in the immunocompetent adult American population is extremely rare. Six cases of primary Kaposi's sarcoma of the lung have been previously reported; all four patients in whom immune function was evaluated had abnormalities. A case of primary Kaposi's sarcoma of the lung in a young adult heterosexual man with normal immunologic function is described. The patient had no response to either weekly vinblastine or doxorubicin (Adriamycin). A subsequent solitary right occipital metastasis responded to 3500 rad of radiotherapy. The patient died 3 months after diagnosis; postmortem examination revealed only two small nodules of extrathoracic Kaposi's sarcoma, one in the liver and the other in the right posterior occipital lobe of the brain. Bacterial, mycobacterial, fungal, and viral cultures were negative.

Adult↗
PubMed1984

Effects of fixation and enzymatic digestion on the immunohistochemical demonstration of laminin and fibronectin in paraffin embedded tissue.

The effects of different fixatives and enzymatic digestion procedures on the immunohistochemical demonstration of fibronectin and laminin in paraffin embedded tissues have been compared. None of the fixatives tested enabled staining of these proteins without enzymatic digestion. No intracytoplasmic laminin was found either in fixed or in fresh frozen tissue. Fixation in formol acetic acid was unsatisfactory for demonstration of fibronectin; prolonged fixation in formol sublimate was unsatisfactory for demonstration of laminin. Optimal results were achieved after fixation in routine 10% formol saline. Trypsin was completely ineffective for unmasking laminin antigens except after fixation in ethanol acetic acid; it was only partially effective for showing fibronectin antigens. The best results were obtained with protease digestion, but pepsin was an adequate, although slightly less reliable, alternative. These enzymes may be used at lower concentrations than usually recommended.

Acetates↗
PubMed1984

Distribution of laminin, fibronectin, and interstitial collagen type III in soft tissue tumours.

The distributions of laminin, fibronectin, and interstitial collagen type III have been investigated in a series of 60 soft tissue tumours by immunochemistry. Positive laminin staining was seen in sites predicted by the distribution of ultrastructurally visible basal lamina. Pericellular laminin was present in all benign tumours of Schwann cell and smooth muscle origin examined, in the two malignant Schwannomas examined, and in six of 13 leiomyosarcomas. It was also evident around nests of cells in an alveolar soft part sarcoma and around malignant endothelial cells in an angiosarcoma. In fibroblastic and fibrohistiocytic tumours it was found only in blood vessel walls. The results of laminin staining led to revision of the original histopathological diagnosis in seven of the 60 cases studied. Fibronectin was abundant in the stroma of most neoplasms, both benign and malignant. It was also found in a distribution parallel to that of laminin. In some tumours this was clearly distinguishable from the distribution of interstitial collagen. Intracellular fibronectin was shown consistently only in mast cell granules. Its demonstration in synovial cells, fibroblasts, and histiocytes was more variable. Interstitial collagen type II had the most irregular distribution of the three proteins. It was as plentiful in tumours of smooth muscle origin as in tumours of fibroblastic origin, but was scanty in fibrous histiocytomas. Its distribution appeared similar to that of laminin and fibronectin in leiomyomas, but differed from these two proteins in Schwann cell tumours and other neoplasms. In one leiomyosarcoma fibronectin, laminin, and type III collagen appeared to be lost concomitantly from tumour cell peripheries.

Collagen↗
PubMed1983

Comparative distribution of fibronectin and type III collagen in normal human tissues.

The distribution of fibronectin (FN) and type III collagen (IIIC) in normal adult human tissues have been directly compared using immunofluorescence and immunoperoxidase techniques on fresh frozen and formalin-fixed paraffin embedded material. Although in many tissues localisation of these two proteins appeared similar, two major differences were identified: (1) Where the ratio of extracellular matrix to cells is high (e.g. in breast, intestinal submucosa), FN was scanty and present predominantly in association with cells, whether of epithelial, endothelial or mesenchymal origin. IIIC was present diffusely throughout interstitial connective tissue. (2) In the highly specialised vascular beds of spleen and renal glomeruli, FN was abundant and accompanied by little or no IIIC. It is postulated that these differences reflect a generalised more intimate association of FN with cell surfaces and basal laminae which is not always discernible by light microscopy. Proximity of FN and IIIC may nevertheless be important for cell-matrix interactions. It was also noted that "reticulin" fibres as defined by silver impregnation do not all have an identical composition.

Adult↗
PubMed1982

Use of orcein in detecting hepatitis B antigen in paraffin sections of liver.

This study has shown that different supplies/batches of orcein perform differently and may fail. The "natural" forms generally performed better although the most informative results were obtained with a "synthetic" product. Orcein dye solutions can be used soon after preparation and for up to 7 days without the need for differentiation. After 10 days or so the staining properties become much less selective. Non-specific staining severely reduces contrast and upon differentiation overall contrast is reduced and the staining of elastin is reduced. Copper-associated protein positivity gradually fails and after 14 days is lost. For demonstrating HBsAg in paraffin sections of liver, it is best to use orcein dye preparations that are no older than 7 days and to test each batch or orcein against a known positive control.

Coloring Agents↗