Tetrameric assembly of CHIP28 water channels in liposomes and cell membranes: a freeze-fracture study

Channel forming integral protein of 28 kD (CHIP28) functions as a water channel in erythrocytes, kidney proximal tubule and thin descending limb of Henle. CHIP28 morphology was examined by freeze-fracture EM in proteoliposomes reconstituted with purified CHIP28, CHO cells stably transfected with CHIP28k cDNA, and rat kidney tubules. Liposomes reconstituted with HPLC-purified CHIP28 from human erythrocytes had a high osmotic water permeability (Pf0.04 cm/s) that was inhibited by HgCl2. Freeze-fracture replicas showed a fairly uniform set of intramembrane particles (IMPs); no IMPs were observed in liposomes without incorporated protein. By rotary shadowing, the IMPs had a diameter of 8.5 +/- 1.3 nm (mean +/- SD); many IMPs consisted of a distinct arrangement of four smaller subunits surrounding a central depression. IMPs of similar size and appearance were seen on the P-face of plasma membranes from CHIP28k-transfected (but not mock-transfected) CHO cells, rat thin descending limb (TDL) of Henle, and S3 segment of proximal straight tubules. A distinctive network of complementary IMP imprints was observed on the E-face of CHIP28-containing plasma membranes. The densities of IMPs in the size range of CHIP28 IMPs, determined by non-linear regression, were (in IMPs/microns 2): 2,494 in CHO cells, 5,785 in TDL, and 1,928 in proximal straight tubules; predicted Pf, based on the CHIP28 single channel water permeability of 3.6 x 10(-14) cm3/S (10 degrees C), was in good agreement with measured Pf of 0.027 cm/S, 0.075 cm/S, and 0.031 cm/S, respectively, in these cell types. Assuming that each CHIP28 monomer is a right cylindrical pore of length 5 nm and density 1.3 g/cm3, the monomer diameter would be 3.2 nm; a symmetrical arrangement of four cylinders would have a greatest diameter of 7.2 nm, which after correction for the thickness of platinum deposit, is similar to the measured IMP diameter of approximately 8.5 nm. These results provide a morphological signature for CHIP28 water channels and evidence for a tetrameric assembly of CHIP28 monomers in reconstituted proteoliposomes and cell membranes.

Localization and functional analysis of CHIP28k water channels in stably transfected Chinese hamster ovary cells

CHIP28 is a major water transporting protein in erythrocytes and plasma membranes in kidney proximal tubule and thin descending limb of Henle. Chinese hamster ovary cells were stably transfected with the coding sequence of cloned rat kidney CHIP28k using expression vectors containing cytomegalovirus or Rous sarcoma virus promoters. Clonal cell populations expressed a 1.3-kilobase mRNA on Northern blot probed by CHIP28k cDNA and a 28-kDa protein on immunoblot probed by a polyclonal CHIP28 antibody. The clone with greatest expression produced approximately 8 x 10(6) copies of CHIP28k protein/cell. Plasma membrane osmotic water permeability (Pf), measured by stopped-flow light scattering, was 0.004 cm/s in control (vector-transfected) cells (10 degrees C) and 0.014 cm/s in the CHIP28k-transfected cells. Pf in CHIP28k-transfected cells had an activation energy of 4.9 kcal/mol and was reversibly inhibited by HgCl2. CHIP28k expression did not affect the transport of protons and the small polar non-electrolytes urea and formamide. CHIP28k immunoreactivity and function was then determined in subcellular fractions. Pf in 6-carboxyfluorescein-labeled endocytic vesicles, measured by a stopped-flow fluorescence quenching assay, was 0.002 cm/s (control cells) and 0.011 cm/s (CHIP28k-transfected cells); Pf in transfected cells was inhibited by HgCl2. Immunoblotting of fractionated endoplasmic reticulum, Golgi, and plasma membranes revealed high densities of CHIP28k (approximately 5000 monomers/microns 2 in plasma membrane) with different glycosylation patterns; functional water transport activity was present only in Golgi and plasma membrane vesicles. Antibody detection of CHIP28k by confocal fluorescence microscopy and immunogold electron microscopy revealed localization to plasma membrane and intracellular vesicles. These studies establish a stably transfected somatic cell line that strongly expresses functional CHIP28k water channels. As in the original proximal tubule cells, the expressed CHIP28k protein is a selective water channel that is functional in endocytic vesicles and the cell plasma membrane.

Fatigue life of preceramic soldered and postceramic soldered joints

This research investigated the fatigue life (ie, the number of cycles of a given stress that can be sustained by a sample prior to catastrophic failure) of metal ceramic soldering. One metal ceramic alloy was joined using four postceramic solders and one preceramic solder. All specimens received appropriate heat treatment simulating ceramic application although no porcelain was applied. Five specimens were fabricated for each solder type, and a 35,000 psi (241.4 MPa) fatigue stress was applied to each solder joint during specimen testing. The test variable was the number of stress cycles required to fail each specimen. The postceramic solders exhibited significantly higher fatigue lives than did the preceramic solder. Scanning electron microscope analysis showed that the preceramic solder not only exhibited a larger grain size, but also showed micropores between these grains.

Magnetic resonance imaging of brain and the neuromotor disorder in endemic cretinism

Neurological endemic cretinism, resulting from severe iodine deficiency, is characterized by mental deficiency, deafmutism, and a spastic-rigid motor disorder. Its neuropathology and pathophysiology have been investigated very little. We report the clinical and magnetic resonance imaging brain scan findings of 3 adult Chinese cretins. All show an apparent magnetic resonance imaging abnormality in the globus pallidus and substantia nigra, with hyperintensity on T1-weighted images and hypointensity on T2-weighted images. The motor abnormality, characterized by truncal and proximal limb-girdle rigidity and spasticity, with relative sparing of the hands and feet, is analogous to other extrapyramidal disorders. Endemic cretinism is a unique form of cerebral palsy of potential interest for students of human neuromotor development.

The epidemiology of iodine-deficiency diseases in China

Iodine-deficiency diseases (IDDs) are wide-spread in China, distributed mainly in the inland and mountainous regions. About one-third of the total Chinese population lives in IDD-endemic areas. The severity of IDD is related to the severity of iodine deficiency. All the selenium-deficient areas of China are also IDD-endemic areas; however, IDD can be very severe in areas where selenium status is thought to be adequate. The distribution of myxedematous cretinism in China is not related to selenium deficiency. In the Tarim Basin, the selenium status of the population is normal and myxedematous cretinism is prevalent. In the northeastern regions of China, selenium deficiency is common and neurological cretinism is very rare.

A technique for fabrication of interim midfacial prostheses

The interim midfacial prosthesis uses a rigid backing support with flexible margins and can be made with most types of commercially available medical grade silicone elastomers. The technique may be modified for fabrication of definitive midfacial prostheses. The disadvantage of the technique is that an extra step is required to make a duplicate master cast, and a vacuum adaptor is needed.

Glucocorticoid regulation of c-myc promoter utilization in P1798 T-lymphoma cells

Glucocorticoids rapidly inhibit the expression of c-myc mRNA in P1798 lymphoma cells. Statistically significant decreases can be observed within 5-10 min after the addition of glucocorticoids. Although transcription of c-myc decreases within a few hours after dexamethasone is added to P1798 cell cultures, nuclear run-on transcription cannot be used to demonstrate that the very early changes in mRNA abundance reflect corresponding changes in transcriptional activity. An RNase protection assay has been used to measure the abundance and rates of turnover of the two major c-myc transcripts arising from the P1 and P2 initiation sites. The relative rates of synthesis of the c-myc mRNAs (i.e. transcription) can be calculated from such data. The abundance of the P2 transcript exceeds that of P1 mRNA by 3- to 4-fold in midlog phase cells. The turnover rates of the two c-myc mRNAs are essentially identical (0.02 min-1), indicating that the P2 promoter is 3-4 times stronger than P1. This was confirmed by measuring the relative transcriptional activities of templates containing the individual c-myc promoters in P1798 extracts in vitro. The expression of P1 and P2 mRNAs decreases at different rates in glucocorticoid-treated cells. A 50% decrease in the abundance of P1 mRNA occurs within 1 h after the addition of dexamethasone. Expression of P2 mRNA is reduced by 50% within 4 h. However, the turnover rates of the major c-myc transcripts do not change in glucocorticoid-treated cells. The t1/2 values of P1 and P2 mRNAs are about 25-30 min and not different from the turnover rates measured in control cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Blocking type immunoglobulins in patients with nongoitrous primary hypothyroidism in area of iodine deficiency

We have evaluated the role of circulating serum immunoglobulins (IgG) which inhibit the growth of thyroid in the etiology of thyroid atrophy in endemic cretinism. Twenty nongoitrous cretins (13 women and 7 men, age range: 9-33) were classified on the basis of clinical criteria for cretinism in China. They were born and living in an iodine deficient area, Xinjiang, northwest China. Antimicrosomal antibody titers were negative in all serum. Nine patients (seven women and two men; age range: 11-23) were biologically primary hypothyroid. Seven subjects were of a myxedematous form and two subjects were of a mixed form. We have studied thyroid-growth inhibiting immunoglobulin (TGII) activity that was measured as an inhibitory effect of 4 mg/ml IgG on TSH-induced [3H]-thymidine incorporation into the DNA of a rat thyroid follicular cell line, FRTL5 cells. Six (five women and one man) out of the nine patients with primary hypothyroidism (66.7 percent) had TGII. We also measured other growth-blocking IgG that inhibited [3H]-thymidine incorporation into DNA stimulated by insulin-like growth factor-I (IGF-I), a growth factor working through a cAMP-independent pathway. Five (three women and two men) out of nine patients (55.6 percent) with nongoitrous primary hypothyroidism had IGF-I-blocking IgG. These results indicate that TGII plays an important role in atrophy of the thyroid in spite of increased serum TSH concentrations, and IgG which inhibits thyroid growth stimulated by IGF-I also might play a role in thyroid atrophy in some endemic cretins.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of taurine and ketamine on bovine retinal membrane lipid peroxidation

Lipid peroxidation disrupts membrane integrity and causes structural and functional alterations in ischemic tissues. Taurine and ketamine are putative ischemic protectants that affect Ca2+ influx. Here we report the influence of these compounds on lipid peroxidation in subcellular fractions, isolated cells and intact tissue from bovine retinas. P2 membrane fractions and isolated cells were exposed to the lipid peroxidation inducers cadmium chloride (200 microM) or L-ascorbic acid (1 mM) in the presence of 0-50 mM taurine, 0-10 mM ketamine, 1 mM kynurenic acid or 1 mM dextromethorphan. The latter compounds are N-methyl-D-aspartate receptor antagonists. Lipid peroxidation in isolated eyes reperfused after 1 h of ischemia either with or without protectants was determined by thiobarbituric acid assay. Glutathione was measured in isolated retinas subjected in vitro to simulated ischemia (no glucose or oxygenation) for 60 min either alone or in the presence of taurine or ketamine. Ketamine inhibited chemical- or ischemia-induced lipid peroxidation as well as ischemic glutathione depletion. Under the same conditions, taurine failed to affect lipid peroxidation or glutathione. The data show a direct effect of ketamine on lipid peroxidation and point to separate mechanisms of action for ketamine and taurine.

A boxing technique for making moulages of facial defects

A technique using irreversible hydrocolloid in conjunction with conventional boxing method is described for making impressions of facial defects. The technique improves control of impression material without causing distortion of soft tissue adjacent to facial defects.

Regulation of polyethylene glycol 400 intestinal permeability by endogenous and exogenous prostanoids. Influence of non-steroidal anti-inflammatory drugs

Polyethylene glycol 400 (PEG 400) is a clinically useful intestinal permeability probe whose rate of intestinal permeation is influenced in part by solvent drag. As mucosal prostanoids are increased in inflammatory bowel disease and affect water transport we examined the possible relationship between prostaglandin E2 (PGE2) and the inhibitors of endogenous prostaglandins--the non-steroidal anti-inflammatory drugs (NSAIDS)--on PEG 400 absorption in vivo using segmental perfusion of rat small intestine. We found that the addition of exogenous PGE2 in concentrations of 0.5, 1.0, and 1.5 micrograms/ml significantly (p less than 0.01) decreased PEG 400 and water absorption. Addition of 5 mmol/l of the cyclooxygenase inhibitors acetylsalicylic acid (ASA) or indomethacin in concentrations 2.5 or 5.0 mmol/l to the perfusate significantly (p less than 0.01) increased PEG 400 and water absorption. The simultaneous addition of 1.0 micrograms/ml of exogenous PGE2 to the perfusate with 5 mmol/l of ASA or with 2.5 mmol/l of indomethacin reversed the increase of PEG 400 and water transport (p less than 0.01). There were no differences in PEG 400 and water absorption when PGE2 was given alone or in combination with ASA or indomethacin. This study suggests that endogenous or exogenous prostanoids play an important role in the regulation of PEG 400 permeation. PGE2 and NSAIDS modify PEG 400 permeation in parallel with changes in water transport indicating that their effect on permeability is through changes in solvent drag. These findings provide a mechanism which might explain the increase in PEG 400 intestinal permeability in Crohn's disease patients and the increase in intestinal permeability found in patients receiving NSAIDS.

A technique for fabrication of a custom tracheostomy prosthesis

A technique is described for using an endotracheal tube to make an impression of the intratracheal anatomy for fabrication of a custom-fitted tracheostomy prosthesis.

Polyethylene glycol 900 permeability of rat intestinal and colonic segments in vivo and brush border membrane vesicles in vitro

Increased intestinal absorption of medium-sized aqueous probes has been found in patients with a variety of disorders. We studied the physiologic control mechanisms, intestinal regions, and effects of lumenal factors on the intestinal absorption of polyethylene glycol (PEG) 900 in the rat in vivo and in rabbit brush border membrane vesicles (BBMVs). The kinetics of PEG 900 intestinal absorption were compatible with simple passive diffusion. Because transport across BBMVs was minimal, we concluded that transport of PEG 900 is mostly through the paracellular tight junctions. Absorption was highest in the midcolon (104.3 +/- 9.5 mumol/100 mg protein per hour vs 9.1 +/- 1.2 mumol/100 mg protein per hour in the jejunum). Absorption was decreased by higher lumenal osmolarity (greater than 400 mOsm/L) after the additions of 2.5 to 5.0 mmol/L chenodeoxycholate or 2.5 mmol/L lysolecithin, or at higher lumenal flow rates (greater than 1 ml/minute), higher lumenal pressure (7.5 cm H2O),or higher lumenal pH (8.0). Lipid solubility of PEG 900 was less than 0.00079%. Under all experimental conditions, PEG net absorption followed changes in water transport. When water transport changed from absorption to secretion, PEG absorption decreased. When water absorption increased, PEG 900 absorption increased in parallel. We conclude that PEG 900 is absorbed by passive diffusion that is modulated by solvent drag and is maximal in the midcolon. Transport directly across cell membranes is mimimal, but overall PEG 900 permeability is closely linked to water absorption by solvent drag and takes place primarily through the paracellular junctions. We propose that these features and mechanisms of PEG 900 transport make PEG 900 a suitable probe molecule for studying intestinal permeability changes.

Chairside color verification for facial prostheses

The coloring technique may be used for facial prosthetic materials that can be processed in gypsum molds. With different surface textures and varying thicknesses built into the technique, it is a reliable method for color verification of facial prosthesis before final processing.

The effects of high iodine on the brain development of mice

C57 mice were divided into two groups: (A): experiment group (H group). Each female mouse was injected with 20 microliter iodized oil; (B): control group (N group). Both groups were mated 8 days after iodized oil injection. Urine iodine contents/24 h of H group was 20 times higher than that in N group 7 days after injection and 18 times higher two months later. Serum T4 values were determined. Brain protein, DNA, body weight, motility and learning ability were measured in the progeny. The results indicate that there was no statistically significant difference between the groups in any of the parameters mentioned above. This strongly suggests that a high iodine dose, given as iodized oil, does not have obvious damaging effects on brain development, at least in mice.

The color accuracy of the Kubelka-Munk theory for various colorants in maxillofacial prosthetic material

The reflectance model developed by Kubelka and Munk was evaluated for agreement in color prediction of thick pigmented samples and for linearity of optical absorption and scattering coefficients with concentration of colorant in maxillofacial elastomer. The colorants tested were generic opacifiers, dry mineral earth pigments, and fibrous colorants. Significant linear relationships were commonly found between the optical coefficients and the concentration of the colorants. These relationships indicated occasional optical interaction between the colorants and the elastomer. Color differences between theoretical and observed colors of the thick samples averaged 2.96, 3.47, and 1.60 for the opacifiers, mineral earth pigments, and fibrous colorants, respectively, when measured using the CIELAB uniform-color space. The agreement between theoretical and observed colors was significantly closer for the fibrous colorants than for the dry mineral earth pigments of the same labeled color.

Nonenzymatic separation of myocardial cell nuclei from whole heart tissue

A simple and rapid nonenzymatic method has been developed to isolate myocardial cell nuclei from whole heart tissue. This method consists of a controlled disruption of cells followed by isopycnic gradient centrifugation. We have reviewed and compared our method to others more lengthy and laborious. By using a number of criteria, such as morphometric measurements, chemical composition, functional studies, specific nuclear protein markers, and mathematical analysis, we show that the nonenzymatic digestion method provides a most useful technique for the study of the biochemistry of the myocardial cell nucleus.

A comparison of cognitive impairment due to benzodiazepines and to narcotics

In an attempt to determine the source of cognitive impairment in 106 consecutively admitted patients at the Johns Hopkins Chronic Pain Treatment Center, EEG, the Wechsler Adult Intelligence Scale, Memory Quotient, and Bender Gestalt tests were administered. Patients receiving benzodiazepines alone demonstrated alterations in cognitive functioning and EEG evidence of a sedative effect. Patients receiving narcotics alone and a group of patients not receiving medication did not show signs of cognitive impairment. The effects of benzodiazepines on sleep and perception of chronic pain, in combination with the cortical changes that they produce, imply that these drugs should not be used in most patients with chronic pain.