Influence of omega-3 polyunsaturated fatty acids from fish oil or meal on the structure of lipid microdomains in bovine luteal cells.

Biological membranes are composed of a lipid bilayer and proteins that form lipid microdomains. This study examined the effects of fish byproducts on lipid-protein interactions within lipid microdomains of bovine luteal cells. In Exp. 1 and 2, luteal cells were prepared from corpora lutea (CL; n = 4 to 8) collected at an abattoir. Exp. 1 was conducted to optimize ultrasonication in a detergent-free protocol for isolation of lipid microdomains. A power setting of 10 to 20% was effective in isolating lipid microdomains from bulk lipid. In Exp. 2, cells were cultured in control medium or fish oil to determine influence of fish oil on distribution of lipid microdomain markers and prostaglandin F2α (FP) receptors. Cells treated with fish oil had a smaller percentage of microdomain markers and FP receptor in microdomains (P < 0.05). In Exp. 3 and 4, cells were prepared from mid-cycle CL obtained from cows supplemented with corn gluten meal (n = 4) or fish meal (n = 4). Exp. 3 examined effects of dietary supplementation on distribution of lipid microdomain markers and FP receptor and Exp. 4 on fatty acid composition within lipid microdomains. A smaller percentage of lipid microdomain markers and FP receptor was detected in microdomains of cells collected from fish meal supplemented animals (P < 0.05). In Exp. 4, a greater percentage of omega-3 polyunsaturated fatty acids was detected in bulk lipid from fish meal supplemented cows (P < 0.05). Results show that fish byproducts influence lipid-protein interactions in lipid microdomains in bovine luteal cells.

Effect of fish meal supplementation on spatial distribution of lipid microdomains and on the lateral mobility of membrane-bound prostaglandin F2α receptors in bovine corpora lutea.

This study examined the effects of fish meal supplementation on spatial distribution of lipid microdomains and lateral mobility of prostaglandin F2α (FP) receptors on cell plasma membranes of the bovine corpus luteum (CL). Beef cows were stratified by BW and randomly assigned to receive a corn gluten meal supplement (n = 4) or fish meal supplement (n = 4) for 60 d to allow incorporation of fish meal-derived omega-3 fatty acids into luteal tissue. Ovaries bearing the CL were surgically removed between days 10 to 12 after estrus corresponding to approximately day 60 of supplementation. A 200-mg sample of luteal tissue was analyzed for fatty acid content using gas-liquid chromatography (GLC). The remaining tissue was enzymatically digested with collagenase to dissociate individual cells from the tissue. Cells were cultured to determine the effects of dietary supplementation on lipid microdomains and lateral mobility of FP receptors. Luteal tissue collected from fish meal-supplemented cows had increased omega-3 fatty acids content (P < 0.05). Lipid microdomain total fluorescent intensity was decreased in dissociated luteal cells from fish meal-supplemented cows (P < 0.05). Micro and macro diffusion coefficients of FP receptors were greater for cells obtained from fish meal-supplemented cows (P < 0.05). In addition, compartment diameter of domains was larger, whereas resident time was shorter for receptors from cells obtained from fish meal-supplemented cows (P < 0.05). Data indicate that dietary supplementation with fish meal increases omega-3 fatty acid content in luteal tissue causing disruption of lipid microdomains. This disruption leads to increased lateral mobility of the FP receptor, increased compartment sizes, and decreased resident time, which may influence prostaglandin signaling in the bovine CL.

Effect of fish oil on lateral mobility of prostaglandin F2α (FP) receptors and spatial distribution of lipid microdomains in bovine luteal cell plasma membrane in vitro.

Lipid microdomains are ordered regions on the plasma membrane of cells, rich in cholesterol and sphingolipids, ranging in size from 10 to 200 nm in diameter. These lipid-ordered domains may serve as platforms to facilitate colocalization of intracellular signaling proteins during agonist-induced signal transduction. It is hypothesized that fish oil will disrupt the lipid microdomains, increasing spatial distribution of these lipid-ordered domains and lateral mobility of the prostaglandin (PG) F2α (FP) receptors in bovine luteal cells. The objectives of this study were to examine the effects of fish oil on (1) the spatial distribution of lipid microdomains, (2) lateral mobility of FP receptors, and (3) lateral mobility of FP receptors in the presence of PGF2α on the plasma membrane of bovine luteal cells in vitro. Bovine ovaries were obtained from a local abattoir and corpora lutea were digested using collagenase. In experiment 1, lipid microdomains were labeled using cholera toxin subunit B Alexa Fluor 555. Domains were detected as distinct patches on the plasma membrane of mixed luteal cells. Fish oil treatment decreased fluorescent intensity in a dose-dependent manner (P < 0.01). In experiment 2, single particle tracking was used to examine the effects of fish oil treatment on lateral mobility of FP receptors. Fish oil treatment increased microdiffusion and macrodiffusion coefficients of FP receptors as compared to control cells (P < 0.05). In addition, compartment diameters of domains were larger, and residence times were reduced for receptors in fish oil-treated cells (P < 0.05). In experiment 3, single particle tracking was used to determine the effects of PGF2α on lateral mobility of FP receptors and influence of fish oil treatment. Lateral mobility of receptors was decreased within 5 min following the addition of ligand for control cells (P < 0.05). However, lateral mobility of receptors was unaffected by addition of ligand for fish oil-treated cells (P > 0.10). The data presented provide strong evidence that fish oil causes a disruption in lipid microdomains and affects lateral mobility of FP receptors in the absence and presence of PGF2α.

The law and ethics in relation to dentists treating HIV-positive patients: report on a recent U.S. Supreme Court case.

The U.S. Supreme Court confirms that an HIV-seropositive patient is a "handicapped" person even if totally asymptomatic. Hence, the patient is illegally discriminated against if a dentist consequently refuses to treat the person in the same manner in which he or she treats other patients. Canadian dental care providers should be aware of this decision, because it is reasonable to expect that the high-level Canadian courts and the Supreme Court of Canada would follow this U.S. Supreme Court decision. In addition, the U.S. judgment in effect supports judgments in recent Canadian lower court cases.

The right of dentists to take extra precautions when treating patients known to carry the human immunodeficiency virus.

Oral health care providers have taken various positions toward the concept of correct behavior toward and management of patients who are seropositive for human immunodeficiency virus. Several tribunal judgments and articles have discussed and analyzed this subject. This article presents a new detailed report and analysis and decision issued by a dental profession panel (tribunal) in Ontario, Canada. The concepts of universal precautions and antidiscriminatory acts are discussed.

The law and ethics in relation to dentists treating HIV-positive patients: two recent court cases.

Two recent Canadian judgements regarding the application of human rights legislation to dentistry and HIV-seropositive patients are summarized and discussed. In the Ontario case of Jerome v. DeMarco, the Ontario Human Rights tribunal found that seropositivity constitutes a "handicap" under human rights legislation. However, the tribunal dismissed the claim by a seropositive patient that he had been illegally discriminated against by a dentist who, on learning the patient was seropositive, delayed treating him until the end of the day. This decision served as a precedent in the lengthy Quebec small claims court judgment of Hamel v. Malaxos. In this case, the dentist was held to have violated Quebec human rights legislation by trying to refer an HIV-seropositive patient to a hospital treatment centre rather than performing the appropriate dental treatment himself. Court judgments regarding this problem are reported and discussed.

Laboratory diagnosis of phaeochromocytoma: which analytes should we measure?

There is a diversity of advice in the literature as to which biochemical assays are best suited to the investigation of patients with a suspected phaeochromocytoma. The challenge for the clinical laboratory is to select those assays which detect all phaeochromocytomas, whilst having the lowest incidence of false positive diagnoses. We compared the sensitivity and specificity of a wide range of assays currently used for the biochemical diagnosis of phaeochromocytoma using either specific gas chromatographic-mass spectrometric (GC/MS) or high performance liquid chromatography-electrochemical detection (HPLC/ED) techniques. Noradrenaline (NA), adrenaline (ADR), dopamine (DA), 3,4-dihydroxyphenylglycol (DHPG), hydroxymethoxymandelic acid (HMMA), normetanephrine (NMET) and metanephrine (MET) were measured in 24 h urine specimens from 20 patients with histologically proven phaeochromocytoma and a large group of patients referred for investigation but subsequently found not to have a phaeochromocytoma. Because phaeochromocytomas are a heterogeneous group of hormone secreting tumours, no single analyte could achieve 100% sensitivity; 100% sensitivity was achieved only when the combination of both NA and ADR or NMET and MET was used. DA, DHPG and HMMA all had poor sensitivities. HMMA had a sensitivity of 70% when using the upper 95% confidence level (48 mumol/24 h) of the non-tumour patients as the cut-off. By lowering the cut-off to 35 mumol/24 h the sensitivity could be increased to 100% but at the expense of the specificity which was decreased from 98 to 92%. On the basis of this study we recommend the specific measurement of either NA and ADR or NMET and MET as the most suitable analytes for the detection of phaeochromocytoma, and further that, due to its poor specificity, HMMA be abandoned as a suitable analyte.

The impact of recent advances in diagnostic technology on the clinical presentation of phaeochromocytoma.

OBJECTIVE: To examine the impact of recent advances in diagnostic technology on the spectrum of clinical and biochemical features of patients presenting with a new diagnosis of phaeochromocytoma. DESIGN: A retrospective review of the clinical and biochemical features of patients diagnosed by our laboratory as having phaeochromocytoma within a 27-month period up to December, 1990. Noradrenaline, adrenaline and dihydroxyphenylglycol were assayed in 24-hour urine specimens (19 patients) or plasma (1 anuric patient) by gas chromatography/mass spectrometry. SETTING: A tertiary level chemical pathology department. PATIENTS: Twenty patients with a new diagnosis of phaeochromocytoma. RESULTS: The classic, episodic adrenergic symptoms traditionally associated with phaeochromocytoma were absent in 9 of the 20 patients (45%). "Atypical" phaeochromocytoma presented as a mass on computed tomography imaging (6 patients, 30%), "phaeochromocytoma crisis" (4 patients, 20%) or family screening (1 patient, 5%). Excessive adrenaline production was found in 11 patients (55%) and six (30%) had predominantly adrenaline-secreting tumours. The urinary noradrenaline:dihydroxyphenylglycol ratio was raised in all nine patients with predominantly noradrenaline-secreting tumours but was not raised in nine out of ten patients with adrenaline-secreting phaeochromocytoma. Adrenaline excretion was significantly correlated with tumour size (r = 0.8; P less than 0.05). CONCLUSIONS: Advances in diagnostic technology, particularly specific adrenaline assays and computed tomography, have made possible the early diagnosis of patients with phaeochromocytoma presenting in ways previously thought to be uncommon. All patients with adrenal masses noted incidentally on CT scan should be investigated for phaeochromocytoma. Adrenaline-secreting tumours are common and both noradrenaline and adrenaline should be assayed in all patients investigated for phaeochromocytoma.