Electron tomography of large, multicomponent biological structures

Genome-wide scans for linkage of chromosome regions to type 1 diabetes in affected sib pair families have revealed that the major susceptibility locus resides within the major histocompatibility complex (MHC) on chromosome 6p21 (lambda s = 2.5). It is recognised that the MHC contains multiple susceptibility loci (referred to collectively as IDDM1), including the class II antigen receptor genes, which control the major pathological feature of the disease: T lymphocyte-mediated autoimmune destruction of the insulin-producing pancreatic beta cells. However, the MHC genes, and a second locus, the insulin gene minisatellite on chromosome 11p15 (IDDM2; lambda s = 1.25), cannot account for all of the observed clustering of disease in families (lambda s = 15), and the scans suggested the presence of other susceptibility loci scattered throughout the genome. There are four additional loci for which there is currently sufficient evidence from linkage and association studies to justify fine mapping experiments: IDDM4 (FGF3/11q13), IDDM5 (ESR/6q22), IDDM8 (D6S281/6q27) and IDDM12 (CTLA-4/2q33), IDDM4, 5 and 8 were detected by genome scanning, and IDDM12 by a candidate gene strategy. The results suggest that the clustering of type 1 diabetes in families is due to the sharing of alleles at multiple loci, and that the as yet unidentified environmental factors are not causing clustering, but instead appear to influence the overall penetrance of genetically programmed susceptibility. The data are consistent with a polygenic threshold model for the inheritance of type 1 diabetes.     

A monoclonal antibody to the ligand-binding domain of the neurokinin 1 receptor (NK1-R) for the neuropeptide substance P

For PCR-based genotyping using polymorphic microsatellite markers, DNA from decomposed postmortem human tissues was fractionated into six groups according to molecular size. The minimum required amounts of this degraded DNA, for detecting alleles at five microsatellite loci (ACTBP2, CMAG, HUMTH01, CYP19, and LPL) and one minisatellite locus (MCT118) were investigated respectively. The allele patterns were detected by electrophoresis of the PCR products on a 6%-denaturing polyacrylamide gel following silver staining. The detection of alleles for the loci with large allele size required more template DNA with higher molecular size than for that with small allele size. Amounts from 0.3 ng to 5 ng were needed for allele detection on genomic DNA from fresh blood. When the decomposed DNA mixture was used as the template, approximately ten times the amount of genomic DNA was required to detect alleles at the three loci of LPL, CYP19 and HUMTH01, while 24 to 67 times was required for the loci, CMAG, ACTBP2 and MCT118. It was demonstrated that a minimum molecular, size and amount of template DNA was needed for amplifying alleles of the six loci, and degraded DNA less than minimum size in the samples would prevent the detection of the loci which have large allele size.     

Pharmacological and biochemical evidence for the regulation of osteocalcin secretion by potassium channels in human osteoblast-like MG-63 cells

Previous reports have suggested the involvement of voltage-activated calcium (Ca2+) channels in bone metabolism and in particular on the secretion of osteocalcin by osteoblast-like cells. We now report that potassium (K+) channels can also modulate the secretion of osteocalcin by MG-63 cells, a human osteosarcoma cell line. When 1,25-dihydroxyvitamin D3(1,25(OH)2D3)-treated MG-63 cells were depolarized by step increases of the extracellular K+ concentration ([K+]out) from 5-30 mM, osteocalcin (OC) secretion increased from a control value of 218 +/- 13 to 369 +/- 18 ng/mg of protein/48 h (p < 0.005 by analysis of variance). In contrast, in the absence of 1,25(OH)2D3, there is no osteocalcin secretion nor any effect of cell depolarization on this activity. The depolarization-induced increase in 1,25(OH)2D3-dependent osteocalcin secretion was totally inhibited in the presence of 10 microM Nitrendipine (a Ca2+ channel blocker, p < 0.005) without affecting cellular alkaline phosphatase nor cell growth. Charybdotoxin, a selective blocker of Ca2+-dependent K+ channels (maxi-K) present in MG-63 cells, stimulated 1,25(OH)2D3-induced osteocalcin synthesis about 2-fold (p < 0.005) after either 30, 60, or 120 minutes of treatment. However, Charybdotoxin was without effect on basal release of osteocalcin in the absence of 1,25(OH)2D3 pretreatment. Using patch clamp technique, we occasionally observed the presence of a small conductance K+ channel, compatible with an ATP-dependent K+ channel (GK[ATP]) in nonstimulated cells, whereas multiple channel openings were observed when cells were treated with Diazoxide, a sulfonamide derivative which opens GK(ATP). Western blot analysis revealed the presence of the N-terminal peptide of GK(ATP) in MG-63 cells, and its expression was regulated with the proliferation rate of these cells, maximal detection by Western blots being observed during the logarithmic phase of the cycle. Glipizide and Glybenclamide, selective sulfonylureas which can block GK(ATP), dose-dependently enhanced 1,25(OH)2D3-induced OC secretion (p < 0.005). Reducing the extracellular calcium concentration with EGTA (microM range) totally inhibited the effect of Glipizide and Glybenclamide on osteocalcin secretion (p < 0.005), which remained at the same levels as controls. Diazoxide totally prevented the effect of these sulfonylureas. These results suggest that voltage-activated Ca2+ channels triggered via cell depolarization can enhance 1,25(OH)2D3-induced OC release by MG-63 cells. In addition, OC secretion is increased by blocking two types of K+ channels: maxi-K channels, which normally hyperpolarize cells and close Ca2+ channels, and GK(ATP) channels. The role of these channels is closely linked to the extracellular Ca2+ concentration.     

Absence of modulating effects of cytokines on antioxidant enzymes in peritoneal mesothelial cells

Erectile dysfunction is a common (affecting 10-20 million men in the USA) and multifactorial disease due to organic and/or psychological factors that strongly impairs the quality of life in man. During the past decade many advances in the understanding of the pathophysiology of erectile dysfunction have been made and new therapeutic strategies have become available. It has been established that an insufficient production of nitric oxide by penile nerve terminals and/or vascular endothelium may result in an impaired erection or complete impotence. Nowadays, intracavernous injection of vasoactive drugs represents a standardized approach for the diagnosis, and the treatment of choice, for erectile dysfunction, but is not widely accepted by the patients. The possibility of treating erectile dysfunction with intraurethral administration of prostaglandin-E1 has recently become available in the USA, and is a therapy more acceptable to the patients. Other noninvasive medical therapies are undergoing evaluation.     

Immunologic phenotype of hosts orally immunized with corneal alloantigens

PURPOSE: To evaluate the immunologic phenotype of hosts tolerized by oral administration of corneal alloantigens. METHODS: CB6F1 mice were tolerized by oral administration of allogeneic C3H/Hej corneal epithelial and endothelial cells before receiving heterotopic C3H/Hej corneal allografts. C3H-specific cytotoxic T-lymphocyte (CTL), delayed-type hypersensitivity (DTH), and mixed-lymphocyte responses were evaluated in orally tolerized and control mice. Cytokine profiles of Peyer's patch cells from orally tolerized mice were determined by enzyme-linked immunosorbent assay and mink lung cell culture bioassay. RESULTS: Oral administration of corneal cells produced a profound inhibition of allospecific CTL, DTH, and mixed-lymphocyte responses. Conjugation with the B subunit of cholera toxin markedly increased the tolerizing activity of corneal endothelial cells, so that a single dose of cholera toxin-conjugated corneal cells inhibited alloimmune responses to the same degree as 10 doses of corneal cells unconjugated with cholera toxin. Peyer's patch cells from orally tolerized mice produced reduced quantities of interferon-gamma and interleukin-2 but produced increased amounts of transforming growth factor-beta and interleukin-10 compared with concentrations in normal control animals. CONCLUSIONS: Oral administration of cholera toxin-conjugated corneal cells produces a dose-dependent inhibition of allospecific CTL, DTH, and mixed-lymphocyte responses. Orally induced inhibition of cell-mediated immune responses to corneal alloantigens is correlated with a sharp increase in the secretion of transforming growth factor-beta and interleukin-10 and a concomitant suppression of interleukin-2 and interferon-gamma. The well-recognized immunosuppressive characteristics of transforming growth factor-beta and interleukin-10 are suggestive that orally induced tolerance to corneal alloantigens is mediated by these cytokines.     

Clear cell papulosis of the skin

Clear cell papulosis is a new entity first described in 1987. To date, six patients have been reported: all were young Taiwanese children. The disease is characterized clinically by multiple small, whitish maculopapules distributed along the milk line and by the presence of large, benign pagetoid cells in the epidermis resembling the clear cell of the nipple. The significance of this entity lies in its potential histogenetic link with Paget's disease of the skin. We report four new Taiwanese patients, three girls and one boy, aged between 21 months and 4 years. Two were sisters. Small hypopigmented macules first appeared on the pubis. They were eventually distributed bilaterally along the milk line but were most numerous in the public area. The disease may easily be overlooked when the macules are tiny or few in number and thus display no clear milk-line distribution, or when they occur in white-skinned individuals. Histologically, solitary large clear cells with large, round pale nuclei were detected in the basal layer of the hypomelaninized epidermis. The numbers of clear cells varied on haematoxylin and eosin staining and were only small in two patients. The cytoplasm of the clear cells was decorated by antikeratin AE1 and anticarcinoembryonic antigen antibodies. AE1 was the best marker of the clear cell. Some of the AE1-positive cells were tadpole-like in shape and were situated well above the basal layer. Ultrastructurally, large clumps of disintegrated or vacuolated mucin granules were present in the cytoplasm of the clear cells. The melanocytes appeared normal; the suprabasal keratinocytes were essentially devoid of melanosomes. The pathological findings in the present study support the hypothesis that these clear cells are an aberrant derivative of sweat gland cells in the epidermis and are potentially the precursor cells giving rise to mammary and extramammary Paget's disease. The differential diagnosis includes chicken pox scars, idiopathic guttate hypomelanosis, hypomelanotic tinea versicolor, anetoderma and early, hypopigmented lesions of Paget's disease.     

The blood contribution to early myocardial reperfusion injury is amplified in diabetes

Cardiovascular disease is excessive in diabetes, and blood cell function is altered. It is not clear, however, if alterations in the blood contribute to the excessive cardiovascular complications of this disease. In this study, we compared the contribution of nondiabetic and diabetic blood to myocardial reperfusion injury. The recovery of cardiac contractile function following no-flow ischemia was studied in isolated diabetic and nondiabetic rat hearts perfused with diabetic or nondiabetic diluted whole blood. Hearts were isolated from 10- to 12-week-old diabetic (streptozotocin, 65 mg/kg, i.v.) and nondiabetic rats and perfused with a Krebs-albumin-red cell solution (K2RBC, Hct 20%). After a 30-min pre-ischemic control period, during which cardiac pump function was evaluated, diabetic and nondiabetic hearts were perfused for 5 min with diluted whole blood (DWB; Hct 20%) collected from either diabetic or nondiabetic donor animals. Coronary flow was then stopped and the hearts subjected to 30 min of no-flow ischemia. Following ischemia, the hearts were reperfused with the K2RBC perfusate. Cardiac contractile function was evaluated throughout the 60-min reperfusion period. Six groups were studied: diabetic and nondiabetic hearts perfused before ischemia with either K2RBC, nondiabetic DWB (NDDWB), or diabetic DWB (DDWB). Perfusion with DWB prior to ischemia impaired the recovery of contractile function in all cases. The impairment to recovery was greater with DDWB than with NDDWB. Although diabetic hearts perfused with K2RBC throughout recovered quite well, the effect of DDWB perfusion in the diabetic hearts was dramatic. In an effort to determine why diabetic blood impaired functional recovery, measures of blood filterability and the generation of reactive oxygen species (ROS) were made. We found that diabetic blood was less filterable than nondiabetic blood; that is, the diabetic blood cells tended to plug the 5-microm filter pores more readily than the nondiabetic blood cells. Also, we found that the diabetic blood was capable of generating significantly greater ROS (oxygen free radicals) than nondiabetic blood (P < 0.05). These findings suggest that the blood contribution to myocardial reperfusion injury is amplified in diabetes. A tendency for diabetic blood cells to plug capillary-sized pores and show enhanced oxygen free radical production may account for the excessive contribution of diabetic blood to reperfusion injury in the heart.