The association of lipophilic phospholipids with native bovine casein micelles in skim milk: Effect of lactation stage and casein micelle size

A known biological role of casein micelles is to transport calcium from mother to young and provide amino acids for growth and development. Previous reports demonstrated that modified casein micelles can be used to transport and deliver hydrophobic probes. In this study, the distribution of lipid-soluble phospholipids, including sphingomyelins (SM) and phosphatidylcholines (PC), was quantified in whole raw milk, skim raw milk, and casein micelles of various sizes during early, mid, and late lactation stages. Low-pressure size exclusion chromatography was used to separate casein micelles by size, followed by hydrophobic extraction and liquid chromatography-mass spectrometry for the quantification of PC and SM. Results showed that the SM d18:1/23:0, d18:1/22:0, d18:1/16:0, d16:1/22:0, d16:1/23:0, and d18:1/24:0 and the PC 16:0/18:1, 18:0/18:2, and 16:0/16:0 were dominating candidates appearing in maximum concentration in whole raw milk obtained from late lactation, with 21 to 50% of total SM and 16 to 35% of total PC appearing in skim milk. Of the total SM and PC found in skim milk, 35 to 46% of SM and 22 to 29% of PC were associated with the casein micelle fraction. The highest concentrations of SM d18:1/22:0 (341 ± 17 µg/g of casein protein) and PC 16:0/18:1 (180 ± 20 µg/g of casein protein) were found to be associated with the largest casein micelles (diameter = 149 nm) isolated in milk from late lactation, followed by a decrease in concentration as the casein micelle size decreased.

The binding of orally dosed hydrophobic active pharmaceutical ingredients to casein micelles in milk

Casein proteins (α_S1-, α_S2-, β- and κ-casein) account for 80% of the total protein content in bovine milk and form casein micelles (average diameter = 130 nm, approximately 10¹⁵ micelles/mL). The affinity of native casein micelles with the 3 hydrophobic active pharmaceutical ingredients (API), meloxicam [351.4 g/mol; log P = 3.43; acid dissociation constant (pK_a) = 4.08], flunixin (296.2 g/mol; log P = 4.1; pK_a = 5.82), and thiabendazole (201.2 g/mol; log P = 2.92; pK_a = 4.64), was evaluated in bovine milk collected from dosed Holstein cows. Native casein micelles were separated from raw bovine milk by mild techniques such as ultracentrifugation, diafiltration, isoelectric point precipitation (pH 4.6), and size exclusion chromatography. Acetonitrile extraction of hydrophobic API was then done, followed by quantification using HPLC-UV. For the API or metabolites meloxicam, 5-hyroxy flunixin and 5-hydroxy thiabendazole, 31 ± 3.90, 31 ± 1.3, and 28 ± 0.5% of the content in milk was associated with casein micelles, respectively. Less than ∼5.0% of the recovered hydrophobic API were found in the milk fat fraction, and the remaining ∼65% were associated with the whey/serum fraction. A separate in vitro study showed that 66 ± 6.4% of meloxicam, 29 ± 0.58% of flunixin, 34 ± 0.21% of the metabolite 5-hyroxy flunixin, 50 ± 4.5% of thiabendazole, and 33 ± 3.8% of metabolite 5-hydroxy thiabendazole was found partitioned into casein micelles. Our study supports the hypothesis that casein micelles are native carriers for hydrophobic compounds in bovine milk.

The association of low-molecular-weight hydrophobic compounds with native casein micelles in bovine milk

The agreed biological function of the casein micelles in milk is to carry minerals (calcium, magnesium, and phosphorus) from mother to young along with amino acids for growth and development. Recently, native and modified casein micelles were used as encapsulating and delivery agents for various hydrophobic low-molecular-weight probes. The ability of modified casein micelles to bind certain probes may derive from the binding affinity of native casein micelles. Hence, a study with milk from single cows was conducted to further elucidate the association of hydrophobic molecules into native casein micelles and further understand their biological function. Hydrophobic and hydrophilic extraction followed by ultraperformance liquid chromatography-high resolution mass spectrometry analysis were performed over protein fractions obtained from size exclusion fractionation of raw skim milk. Hydrophobic compounds, including phosphatidylcholine, lyso-phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin, showed strong association exclusively to casein micelles as compared with whey proteins, whereas hydrophilic compounds did not display any preference for their association among milk proteins. Further analysis using liquid chromatography-tandem mass spectrometry detected 42 compounds associated solely with the casein-micelles fraction. Mass fragments in tandem mass spectrometry identified 4 of these compounds as phosphatidylcholine with fatty acid composition of 16:0/18:1, 14:0/16:0, 16:0/16:0, and 18:1/18:0. These results support that transporting low-molecular-weight hydrophobic molecules is also a biological function of the casein micelles in milk.

Second messengers in platelet aggregation evoked by serotonin and A23187, a calcium ionophore

We investigated the combined effect of 5-hydroxytryptamine (5-HT, serotonin) and calcium ionophore (A23187) on human platelet aggregation. Aggregation, monitored at 37 degrees C using a Dual-channel Lumi-aggregometer, was recorded for 5 min after challenge by a change in light transmission as a function of time. 5-HT (2-200 microM) alone did not cause platelet aggregation, but markedly potentiated A23187 (low dose) induced aggregation. Inhibitory concentration (IC50) values for a number of compounds were calculated as means +/- SEM from dose-response determinations. Synergism between 5-HT (2-5 microM) and A23187 (0.5-2 microM) was inhibited by 5-HT receptor blockers, methysergide (IC50 = 18 microM) and cyproheptadine (IC50 = 20 microM), and calcium channel blockers (verapamil and diltiazem, IC50 = 20 microM and 40 microM respectively). Interpretation of the effects of these blockers is complicated by their lack of specificity. Similarly, U73122, an inhibitor of phospholipase C (PLC), blocked the synergistic effect at an IC50 value of 9.2 microM. Wortmannin, a phosphatidylinositide 3-kinase (PI 3-K) inhibitor, also blocked the response (IC50 = 2.6 microM). However, neither genistein, a tyrosine-specific protein kinase inhibitor, nor chelerythrine, a protein kinase C inhibitor, affected aggregation at concentrations up to 10 microM. We conclude that the synergistic interaction between 5-HT and ionophore may be mediated by activation of PLC/Ca2+ and PI 3-kinase signalling pathways, but definitive proof will require other enzyme inhibitors with greater specificity.

Pattern of thyroid lesions and role of fine needle aspiration cytology (FNA) in the management of thyroid enlargement: a retrospective study from a teaching hospital in Riyadh

The study aims to determine the cytological pattern of thyroid lesions, in addition to the utility and accuracy of fine needle aspiration (FNA) cytology as an initial diagnostic method in the investigation of these lesions among Saudi patients. Four hundred and seventy-nine (479) FNAs were performed on patients presenting with diffuse or nodular thyroid enlargement to the endocrinology clinic at King Khalid University Hospital in Riyadh during the period September 1993 to September 1996. The results of the FNA and the 125 histological diagnoses obtained from the subsequent partial and subtotal thyroidectomies were retrospectively and independently reviewed and compared by two cytopathologists. The results of the FNA cytological diagnosis showed that 372 patients (77.7%) had benign lesions, 24 (5%)) had lesions which were suspected of malignancy, 25 (5.2%) had malignant neoplasms, and 58 (12.1%) had FNAs which were inadequate for cytological assessment. Colloid and adenomatous nodules were the most common benign lesions reported (47.8%). Papillary carcinoma was the most common malignant neoplasm (4.2%). Despite the relatively limited number of patients who underwent surgery, cytohistopathology combined with statistical analysis of the results showed that our FNA accuracy rate is in the region of 94.4% with a sensitivity of 78% and a specificity of 100%. In addition, the negative predictive value (NPV) and the positive predictive value (PPV) of FNA thyroid cytology were 93% and 100% respectively. Our findings indicate that FNA cytology can be used effectively in the evaluation of both nodular and diffuse thyroid lesions whilst cytopathologist should be aware of the potential diagnostic pitfalls and the limitations of the procedure in the diagnosis of follicular, cystic, and small neoplasms, the positive identification of thyroiditis and most cases of neoplasia by itself provides justification for FNA.

The value of immediate cytologic evaluation for needle aspiration lung biopsy

RATIONALE AND OBJECTIVES

The authors evaluate the role of immediate cytologic evaluation (ICE) with fine-needle aspiration biopsy (FNAB) for lung lesions at highest risk for pneumothorax.

METHODS

A prospective randomized study was conducted of 80 patients with lung lesions surrounded by aerated parenchyma undergoing FNAB with and without ICE (47 and 33 patients, respectively). An analysis of needle passes, procedure time, complications, specimen adequacy, diagnostic yield, and accuracy of procedure was made.

RESULTS

There was an increased number of needle passes with ICE (> or = three passes: 23% [11 biopsies] versus 3% [1 biopsy]; P = 0.01). Fluoroscopic procedures took longer with ICE (median time: 15 versus 9 minutes; P = 0.002) with no difference in complication rates. Specimen adequacy was similar (74% and 64%) and the procedure was diagnostic in 79% (37 biopsies) with ICE and in 70% (33 biopsies) without ICE. There were no significant differences in the sensitivity, specificity, or accuracy of the biopsy.

CONCLUSIONS

Immediate cytologic evaluation improved results marginally with increased procedure time and needle passes. Immediate cytologic evaluation may be most useful for lesions at lowest risk of complications to assure that a second procedure is not required.

Ethanol-induced aspartate and taurine release from primary astrocyte cultures

Exposure of primary astrocyte cultures to isosmotic ethanol from 10-100 mM led to both swelling of the cells and release of [3H]taurine and D-[3H]aspartate. Exposure to hyperosmotic ethanol, in the same concentration range, caused neither swelling nor release. Release was inhibited by the anion transport blocker L-644,711, already shown to inhibit amino acid release evoked by hypoosmotic or high-potassium medium, conditions that also cause astrocytic swelling. Ethanol-induced release generally showed a decline in response to successive exposures to ethanol, and release was not dependent on extracellular calcium. Thus, the characteristics of swelling-induced release of amino acids by isosmotic ethanol seem to correspond to those of swelling-induced release from astrocytes due to exposure to hypotonic or high-K+ media. We discuss whether such effects may contribute to CNS damage after head injury and stroke.

Effects of conjugated estrogen on the calcitriol response to parathyroid hormone in postmenopausal women

We evaluated the effects of estrogen on the calcitriol response to the active peptide, human PTH(1-34), in postmenopausal women. Fifteen women were studied before and again after at least 1 month of treatment with conjugated equine estrogens, 1.25 mg/day. Six women received two series of four graded peptide infusions, each with the sequence 200, 400, 800, and 1600 USP U hPTH(1-34). Nine women received only one dose of peptide, either 200 or 800 U, before and while taking estrogen. Baseline values and the incremental and percent changes in circulating calcitriol 24 h after the 20-min infusions were evaluated. Estrogen treatment resulted in significant reductions in blood levels of calcium (2.26 +/- 0.03 mmol/L vs. 2.16 +/- 0.02, P less than 0.05) and phosphorus (1.23 +/- .05 mmol/L vs. 1.14 +/- 0.03, P less than 0.005), a rise in serum calcitriol concentrations (42.2 +/- 3.9 pg/mL vs. 28.6 +/- 3.1, P less than 0.005), and no change in circulating PTH. The rise in calcitriol after 200 U hPTH(1-34) was significantly greater on estrogen (17.6 +/- 2.0 pg/mL vs. 9.5 +/- 1.8, P less than 0.01), but estrogen did not alter incremental responses to larger doses. When results were normalized for differences in baseline values, the estrogen-related change in response to 200 U was no longer significant. hPTH(1-34) acutely increased urinary clearance of cAMP and phosphorus, but estrogen did not affect this response. We conclude that exogenous estrogen does not increase renal sensitivity to PTH in postmenopausal women.

Effects of aluminum hydroxide on the parathyroid-vitamin D axis of postmenopausal women

In previous studies we proposed that estrogen increases circulating calcitriol in postmenopausal women by reducing plasma phosphorus concentrations. For this model to be plausible, a reduction in plasma phosphorus must be itself be sufficient to increase circulating calcitriol in elderly women. To assess this question we studied the effects of Al(OH)3 on daylong circulating levels of phosphorus, calcium, PTH, and calcitriol in 14 postmenopausal women. Subjects were studied on two 7-day periods of dietary control, in which calculated intakes for phosphorus, calcium, and sodium were 950, 800, and 3000 mg/day, respectively. During one randomly assigned period, subjects were given Al(OH)3 with each meal. Al(OH)3 significantly lowered daylong plasma phosphorus concentrations by 17% (0.95 +/- 0.02 mmol/L vs. 1.15 +/- 0.02, P less than 0.0005) (2.94 +/- 0.06 mg/dL vs. 3.57 +/- 0.07), and this was associated with a 38% rise in circulating calcitriol from 61.8 +/- 10.3 pmol/L to 85.2 +/- 10.1 pmol/L (25.7 +/- 4.3 pg/ml to 35.5 +/- 4.2 pg/ml) (P less than 0.0001). The rise in calcitriol correlated significantly with the reduction in phosphorus (r = 0.51, P = 0.03). Al(OH)3 did not significantly alter average daily circulating total calcium (2.32 +/- 0.008 vs. 2.32 +/- 0.005 mmol/L) (9.31 +/- 0.03 vs. 9.29 +/- 0.02 mg/dL), ionized calcium (1.19 +/- 0.003 vs. 1.19 +/- .004 mmol/L), or intact PTH (24.6 +/- 0.6 vs. 24.2 +/- 0.8 ng/L). Moreover, neither the renal phosphorus reabsorption maximum (TmP/GFR), baseline excretion of cAMP, nor the phosphaturic, cAMP, or calcitriol responses to infused hPTH(1-34) were altered by Al(OH)3. We conclude that Al(OH)3 treatment of older women lowers plasma phosphorus concentrations by restricting intestinal phosphorus absorption, and that older women retain the capacity to increase calcitriol levels in response to phosphorus restriction.

Lipid vehicles for intestinal lymphatic drug absorption

The lipoprotein fractions in mesenteric lymph were monitored following intraduodenal administration of arachis oil and oleic, linoleic and linolenic fatty acids to rats. An increase in the chylomicron fraction, but not the VLDL or LDL fraction, was observed with each lipid. The greater the degree of unsaturation of the fatty acid, the more rapid the onset of chylomicron synthesis. The administration of linoleic acid and arachis oil produced the highest concentration of chylomicrons in the lymph. These results reflect differences in the rate of absorption and biochemical metabolism of the lipids and have implications for the selection of vehicles for the delivery of drugs by the lymphatic route.