The dilemma of negative analysis of variance estimators of intraclass correlation

At least two common practices exist when a negative variance component estimate is obtained, either setting it to zero or not reporting the estimate. The consequences of these practices are investigated in the context of the intraclass correlation estimation in terms of bias, variance and mean squared error (MSE). For the one-way analysis of variance random effects model and its extension to the common correlation model, we compare five estimators: analysis of variance (ANOVA), concentrated ANOVA, truncated ANOVA and two maximum likelihood-like (ML) estimators. For the balanced case, the exact bias and MSE are calculated via numerical integration of the exact sample distributions, while a Monte Carlo simulation study is conducted for the unbalanced case. The results indicate that the ANOVA estimator performs well except for designs with family size n = 2. The two ML estimators are generally poor, and the concentrated and truncated ANOVA estimators have some advantages over the ANOVA in terms of MSE. However, the large biases may make the concentrated and truncated ANOVA estimators objectionable when intraclass correlation (ϱ) is small. Bias should be a concern when a pooled estimate is obtained from the literature since ϱ<0.05 in many genetic studies.

Adipogenesis in a myeloid supporting bone marrow stromal cell line

The bone marrow stroma contains pre-adipocyte cells which are part of the hemopoietic microenvironment. Cloned stromal cell lines differ both in their ability to support myeloid and lymphoid development and in their ability to undergo adipocyte differentiation in vitro. These processes have been examined in the +/+2.4 murine stromal cell line and compared to other stromal and pre-adipocyte cell lines. In long-term cultures, the +/+2.4 stromal cells support myeloid cell growth, consistent with their expression of macrophage-colony stimulating factor mRNA. However, despite the presence of mRNA for the lymphoid supportive cytokines interleukins 6 and 7, +/+2.4 cells failed to support stromal cell dependent B lineage lymphoid cells in vitro, suggesting that these stromal cells exhibit only a myelopoietic support function. The +/+2.4 cells differentiate into adipocytes spontaneously when cultured in 10% fetal bovine serum. The process of adipogenesis can be accelerated by a number of agonists based on morphologic and gene marker criteria. Following induction with hydrocortisone, methylisobutylxanthine, indomethacin, and insulin in combination, a time dependent increase in the steady state mRNA and enzyme activity levels of the following adipocyte specific genes was observed: adipocyte P2, adipsin, CAAT/enhancer binding protein, and lipoprotein lipase. In contrast, adipogenesis was accompanied by a slight decrease in the signal intensity of the macrophage-colony stimulating factor mRNA level, similar to that which has been reported in other bone marrow stromal cell lines. These data demonstrate that although the lympho-hematopoietic support function of pre-adipocyte bone marrow stromal cell lines is heterogeneous, they share a common mechanism of adipogenesis.

Immunological Characterization of a Tapetal Protein in Developing Anthers of Lilium longiflorum

Antiserum was raised in rabbits against a lily (Lilium longiflorum) anther-specific protein (LLA-15). Monospecific anti-LLA-15 antibodies were prepared to investigate the distribution of LLA-15 during anther development in a variety of flowering plants. Immunoblot analyses of total protein from floral and vegetative organs confirmed that LLA-15 or LLA-15-like proteins accumulated to detectable levels only in a discrete stage of anther development. In situ localization using anti-rabbit immunoglobulin G conjugated with gold particles confirmed that LLA-15 was specifically localized in the tapetal tissue of lily anthers. The maximal level of LLA-15 was strictly coincident with the peak of tapetal secretory functions. Immunoblots of two-dimensional polyacrylamide gels of lily anther proteins indicated that the seven LLA-15 isoforms ranged from isoelectric point 5.6 to 6.1. In vitro translation of lily anther mRNAs showed that four of these isoforms were primary products, the additional three being a result of posttranslational processing of the primary translation products.

Inhibition of lipoprotein lipase activity by synthetic peptides of apolipoprotein C-III

In this study we have examined effects of synthetic polypeptide fragments of apoC-III on the kinetic properties of lipoprotein lipase (LPL) activity. Based on the loss of 79% of LPL-inhibitory activity after CNBr cleavage at the N-terminal portion of apoC-III and a systematic search for synthetic peptides with LPL-inhibitory activity spanning the apoC-III sequence, we concluded that the N-terminal domain is the most important in the modulation of LPL activity. In addition, there are multiple attachment sites in apoC-III for its interaction with LPL and these sites reside in the hydrophilic sequences of apoC-III. Probably for this reason the intact apo-CIII exhibited higher inhibitory potential than its peptide components. Based on the deduced inhibition constants derived for the synthetic apoC-III1-79 we concluded that apoC-III is likely to exhibit a physiological role in regulating LPL activity since the derived dissociation constants for the LPL-apoC-III interaction are within the physiological concentration range of plasma apoC-III. In addition, as the synthetic apoC-III1-79 lacks the carbohydrate moiety, we also concluded that the presence of the oligosaccharide in native apoC-III is not essential for its inhibitory activity on LPL. The fact that the I50 (concentration for inhibition of LPL at 50% activity) decreases for apoC-III-1 when assayed in the presence of apoC-II indicated that the activator actually caused an increased affinity between LPL and apoC-III and demonstrated that apoC-III does not compete for the activator site of apoC-II.

A prospective study of the effect of cholecystectomy on duodenogastric reflux in humans using 24 hour gastric hydrogen monitoring

Duodenogastric reflux (DRG) was quantified with continuous 24 hour monitoring of gastric pH in 30 patients, 12 of whom underwent operation for repair of an inguinal or femoral hernia used as a control group. The remaining 18 patients with noncomplicated gallstone disease underwent a simple cholecystectomy. Eight weeks after the operation, the tests were repeated. We found that patients with cholelithiasis were accompanied with DGR or alkaline shift more often than the patients in the control group and cholecystectomy decreased the percentage of time that gastric pH was less than two and increased the time at four and six. Although cholecystectomy itself does cause DGR, most patients with DGR may be asymptomatic.

Investigation on the effect of selenium on T lymphocyte proliferation and its mechanisms

The effects of selenium on T lymphocyte proliferation and its mechanisms have been investigated. The results showed that selenium is able to enhance lectin-stimulated T lymphocyte proliferation, to increase the production of interleukin 2 (IL-2) by lymphocytes and interleukin 1 (IL-1) by macrophages in the presence of lectin and to augment the response of T lymphoblasts to IL-2 and that of thymocytes to IL-1. The data presented suggest that selenium may be an important modulator for immune response. Selenium might enhance IL-2 production and response through the augmentation of IL-1 production and response, thereby promoting the enhancement of the proliferation and action of T lymphocytes and other immunocompetent cells. Based on these results, we may consider using selenium as an immunological enhancement agent to enhance or recover immune functions of the organism.

Localization of obscure gastrointestinal bleeding by technetium 99m-labeled red blood cell scintigraphy

When a bleeding source from the gastrointestinal (GI) tract cannot be identified with conventional diagnostic studies, it is known as GI bleeding of an obscure origin. In the past three years, in vivo Technetium 99m-labeled red blood cell scintigraphy (RBC scan) has been added to our armamentarium for the diagnosis of obscure GI bleeding. Out of a total of 26 cases, the bleeders could be detected in 12 or 46.2% by RBC scan. The time required ranged from 15 minutes to 24 hours (median, one hour). In 14 patients with active bleeding during the scan period, 11 had positive scans (sensitivity, 78.6%). In 12 patients with inactive bleeding, 11 had negative scans (specificity, 91.7%). Angiography was conducted in nine cases, with all showing negative findings; however, six of them had a positive focus by RBC scan. Laparotomy was performed in seven scan-positive patients, and in three scan-negative patients because of a positive Meckel's scan (two cases) or recurrent bleeding (one case). Of the 12 scan-positive patients, incorrect localization was noted in two patients due to rapid transit of the labeled RBC in the small bowel. False localization could be prevented by shortening the sequential imaging interval. It is concluded that an RBC scan is a very sensitive and safe tool for detection of GI bleeding of an intermittent nature, because the bleeder can be monitored for 24 hours after a single injection. It can be used as a preangiographic screening test and to guide the surgeon in surgical planning or decision-making.(ABSTRACT TRUNCATED AT 250 WORDS)

Secretory state of gastric mucosa does not protect against acute gastric mucosal injury induced by hemorrhagic shock in rats

The protective effect of the secretory state of gastric mucosa against acute gastric mucosal injury due to hemorrhagic shock was investigated in rats with tetragastrin infusion. A total of 26 male Spraque-Dawley rats were divided into 3 groups (n = 6, 8, and 12, respectively). Tetragastrin (8 micrograms/Kg/h) was added into the normal saline infusion (5 ml/h) in group 3, but not in the other 2 groups. The mucosal surface was instilled with 0.1 N HCl (pH = 1) in group 2, with normal saline (pH = 7) in group 1, and with nothing in group 3. Hemorrhagic shock at 40 mmHg of arterial pressure was induced by withdrawing blood from the femoral artery, and was maintained at this level for 20 minutes; later, the shed blood was re-infused. During hemorrhagic shock, scattered areas of white circumscribed white lesions appeared on the mucosal folds of the glandular region in all of group 2 and in 8 (with gastric pH less than 3) of group 3, yet did not appear in group 1 or in the remaining 4 (with gastric pH greater than 3) of group 3. After reinfusion, varying degrees of mucosal hemorrhage from the whitened areas occurred in all of group 2 and in 8 (with pH less than 3) of group 3, but in only one of group 1. The severity of acute gastric mucosal injury in group 2 and group 3 (n = 8, with gastric pH less than 3) was significantly greater than group 1. However, it was not significantly different between groups 2 and 3.(ABSTRACT TRUNCATED AT 250 WORDS)

Acyl-chain specificity of human milk bile-salt-activated lipase

In order to probe the active-site structure of human milk bile-salt-activated lipase (BAL), the kinetics of the BAL-catalysed reaction were studied using monoesters as substrates. Among the fatty acyl chains, ranging from C8 to C16 of monoacylglycerols in a single equimolar assay mixture, there was a consistent trend of increased reactivity with decreased fatty-acyl-chain length for both the basal and taurocholate-stimulated activities of BAL. In addition, the detection of hydrolysis of long-chain monoacylglycerols in the absence of bile salt indicates that it is possible for the long-chain fatty acid monoester to form an enzyme-substrate complex with the basal form of BAL. I further examined the reaction kinetics of BAL with water-soluble short-chain esters of p-nitrophenol. The results indicated that there is a consistent trend towards a decreased Michaelis-Menten constant with increased acyl-chain length. Therefore it was concluded that the decreased reactivity with increased acyl-chain length of acylglycerols is probably not a consequence of the lowered affinity of the substrate for the enzyme. The fact that butyrate ester has the optimum acyl chain to be a substrate of BAL can be attributed to its acyl-chain length being long enough for interaction with the active centre of BAL and short enough to provide adequate positioning of the ester bond for transition state complex formation. The calculated free energy of BAL catalysis based on the derived kinetic parameters provides additional insight into the effect on the enzyme-substrate interaction of increasing the number of methylene groups in the acyl chain of substrates.

Influence of age on results of resection of hepatocellular carcinoma

One hundred and fifty-eight elective hepatectomies carried out between 1976 and 1989 for hepatocellular carcinoma were classified into three groups according to age: group I (n = 20) under 30 years of age; group II (n = 102) 30 to 60; and group III (n = 36) over 60. The number of operations carried out on patients in group III has increased since 1983, and the types of hepatic resection in the three different age groups were slightly but not significantly different. The incidence of small tumours (diameter less than 5 cm) and associated cirrhosis were relatively low in the younger patients. Postoperative complications developed in 4 patients (20%) in group I, 18 (18%) in group II and 8 (22%) in group III, the main ones being hepatic failure and intraabdominal sepsis. Operative mortality was 4%; one patient (5%) died in group I, 4 (4%) in group II, and 2 (6%) in group III, and the principal causes were hepatic failure and massive haemorrhage. Hepatic resection for hepatocellular carcinoma in most patients over 60 years old was associated with slightly higher operative morbidity and mortality, but the risks were such that we recommend that operation should not be denied to selected patients in this age group.

Bias of maximum likelihood estimator of intraclass correlation

A bias correction was derived for the maximum likelihood estimator (MLE) of the intraclass correlation. The bias consisted of two parts: a correction from MLE to the analysis of variance estimator (ANOVA) and the bias of ANOVA. The total possible bias was always negative and depended upon both the degree of correlation and the design size and balance. The first part of the bias was an exact algebraic expression from MLE to ANOVA, and the corrected estimator by this part was ANOVA. It was also shown that the first correction term was equivalent to Fisher's reciprocal bias correction on hisZ scores. The total possible bias of MLE was large for small and moderate samples. Relative biases were larger for small parametric values and vice versa. To ensure a relative bias less than 10% assuming an intraclass correlation of 0.025, which is not unusual in most of the animal genetic studies, the total number of observations (N) should be not less than 500. From a design point of view, minimum bias occurred atn = 2, the minimum family size possible, underN fixed.

[Efficiency of patient-controlled analgesia versus conventional analgesia in patients after thoracotomy]

The patients received thoracotomy usually suffered from significant severe pain postoperatively, which accompanied with impaired pulmonary function or increased incidences of atelectasis and pneumonia. So adequate analgesia for those patients is indicated. The purpose of this study is to investigate the efficiency of patient-controlled analgesia (PCA) and determine whether it is better than conventional analgesia or not. Twenty-six patients, ASA physical status class I and II, were randomized into two groups: PCA and intramuscular (IM). The effect on pain relief was assessed by a visual analogue pain scale (VAPS) q 4 h postoperatively for two days. Forced vital capacity (FVC) and the questionnaire of nocturnal sleep disturbance by pain were evaluated preoperatively, the first, second postoperative mornings. As result of this study, the patients of PCA group get less pain than IM group after the first and second days of surgery. VAPS values are 3.7 +/- 1.1, 2.8 +/- 0.8 and 6.1 +/- 0.9, 5.3 +/- 1.1 respectively pertaining to PCA and IM groups (p less than 0.05). The patients of IM group get more disturbance of nocturnal sleep than PCA group at initial two nights of postoperation as well (p less than 0.05). It is manifest to look out the significant difference between these two groups in accordance with FVC ratio records of post-surgery vs presurgery at initial two days after surgery on the subject of respiratory function recovery. PCA group are 46.46 +/- 7.29%, 52.25 +/- 8.32% in a condition of more progress on lung function recovery than IM group of 38.13 +/- 10.25%, 42.15 +/- 7.82% (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Change of gastric liquid emptying after highly selective vagotomy and pyloric dilatation for patients with obstructing duodenal ulcer

Gastric liquid emptying was studied in duodenal ulcer patients with and without stenosis before highly selective vagotomy (HSV) and 1 week, 3 months, and 1 year after. The test meal consisted of 1 mCi of 99m Technetium-diethylene penta-acetic acid (DTPA) in 500 ml of isotonic saline. The patients were divided into 2 groups: group 1 (16 cases) without clinical stenosis, who underwent HSV alone, served as control; group 2 (14 cases) with mild to moderate stenosis, who underwent HSV and transgastric dilatation to 20 mm in diameter. Before HSV, the stenotic group showed a significantly slower liquid emptying than the nonstenotic. Most of the stenotic group could resume a normal diet quickly after operation, but they still had prolonged liquid emptying. At 3 months, the emptying curve of the stenotic patients had approached that of the preoperative controls without a significant difference, while the nonstenotic patients showed an accelerated initial emptying. Although there was a significant improvement with the appearance of accelerated initial emptying at 1 year, the stenotic group still demonstrated slightly slower emptying than the nonstenotic group. A temporary state of preexistent gastric atony due to chronic outlet obstruction may explain the delayed emptying in the early postoperative period; however, minor residual resistance in the fibrotic, scarred tissue was postulated to be persistent despite dilatation, and responsible for the slower emptying of the stenotic than the nonstenotic group at 1 year.

Structure of human milk bile salt activated lipase

The structure and some functional sites of human milk bile salt activated lipase (BAL) were studied by cDNA cloning and chemical analysis of the enzyme. Eighteen cDNA clones of human BAL were identified from lactating human breast cDNA libraries in lambda gt11 and lambda gt10 with antibody and synthetic oligonucleotides as probes. The sequence of four clones was sufficient to construct a 3018-bp BAL cDNA structure. This sequence codes for an open reading frame of 742 amino acid residues. There is a putative signal sequence of 20 residues which is followed by the amino-terminal sequence of BAL, and the mature BAL contains 722 amino acid residues. The cDNA sequence also contains a 678-base 5'-untranslated sequence, a 97-base 3'-untranslated region, and a 14-base poly(A) tail. The sequence of a 1.8-kbp insert of clone G10-4A differs from that of the other cDNA in that it contains a deletion of 198 bases (1966-2163) corresponding to 66 amino acid residues. By use of BAL cDNA as probe, it was found that the major molecular species of BAL mRNA in human mammary gland HBL-100 cells had a size of 2.9 kb and two minor species had sizes of 3.8 and 5.1 kb by Northern blot analyses. The deduced BAL protein structure contains in the carboxyl-terminal region 16 repeating units of 11 amino acids each. The repeating units have the basic structure Pro-Val-Pro-Pro-Thr-Gly-Asp-Ser-Gly-Ala-Pro with only minor substitutions. The amino acid sequence of human BAL is related to that of pancreatic lysophospholipase, cholesterol esterase, cholinesterase, acetylcholinesterase, and thyroglobulin. Ten of the 14 cyanogen bromide fragments of diisopropyl fluorophosphate inhibited human milk BAL were isolated, determined for N-terminal sequences, analyzed for amino sugars, and tested for some functional properties. These chemical studies established that the active site of human milk BAL is located at serine-194, the N-glycosylation site is present at asparagine-187, the O-glycosylation region is in the 16 repeating units near the C-terminus, and the heparin binding domain is in the N-terminal region. We have also determined the location of disulfide bridges as Cys64-Cys80 and Cys246-Cys257. The cyanogen bromide cleavage and the partial sequencing of CNBr peptides also confirmed the location of methionines in the polypeptide chain as well as the deduced cDNA sequence of BAL.

Isolation and characterization of an apoA-II-containing lipoprotein (LP-A-II:B complex) from plasma very low density lipoproteins of patients with Tangier disease and type V hyperlipoproteinemia

Previous studies have shown that very low density lipoproteins (VLDL) from patients with Tangier disease are less effective as a substrate for human milk lipoprotein lipase (LPL) than VLDL from normal controls as assessed by measuring the first order rate constant (k1) of triglyceride hydrolysis. Tangier VLDL also has a higher content of apolipoprotein (apo) A-II than normal VLDL. To explore the possible relationship between the relatively high concentration of apoA-II in VLDL and low k1 values, Tangier VLDL were fractionated on an anti-apoA-II immunosorber. The retained fraction contained a newly identified triglyceride-rich lipoprotein characterized by the presence of apolipoproteins A-II, B, C-I, C-II, C-III, D, and E (LP-A-II:B:C:D:E or LP-A-II:B complex), whereas the unretained fraction consisted of previously identified triglyceride-rich apoB-containing lipoproteins free of apoA-II. In VLDL from patients with Tangier disease or type V hyperlipoproteinemia, the LP-A-II:B complex accounted for 70-90% and 25-70% of the total apoB content, respectively. The LP-A-II:B complexes had similar lipid and apolipoprotein composition; they were poor substrates for LPL as indicated by their low k1 values (0.014-0.016 min-1). In contrast, the apoA-II-free lipoproteins present in unretained fractions were effective substrates for LPL with k1 values equal to or greater than 0.0313 min-1. These results indicate that triglyceride-rich lipoproteins consist of several apoB-containing lipoproteins, including the LP-A-II:B complex, and that lipoprotein particles of similar size and density but distinct apolipoprotein composition also possess distinct metabolic properties.