Effect of mutation of potassium-efflux system, KefA, on mechanosensitive channels in the cytoplasmic membrane of Escherichia coli

The effect of a kefA mutation on the mechanosensitive channels in the cytoplasmic membrane of Escherichia coli was established by introducing a mutation of the kefA gene into wild-type E. coli by P1 transduction. The mutation of the kefA gene not only made the cells sensitive to K+ in the medium but also changed the mechanosensitive channel activity. The kefA mutation did not change the conductances of the two mechanosensitive channels in the cytoplasmic membrane of E. coli, but it prolonged the channel open time. Also, the kefA mutation made the cells more sensitive to pressure in comparison to wild-type cells. The high sensitivity to pressure of the kefA mutant was not modulated by betaine or by the potassium gradient across the membrane. The effect of the kefA mutation on mechanosensitive channels was not due to a membrane fluidity change. KefA might be a regulator for mechanosensitive channels.

Peripherin assembles into homopolymers in SW13 cells

The properties of full-length and mutant peripherins were studied in intermediate filament-less SW13 cells to define regions of peripherin that are essential for initiation of filament assembly. A full-length rat peripherin gene transfected into SW13 cells resulted in filament formation, consistent with the close structural relationship of peripherin to other type III intermediate filament proteins that readily form homopolymers. Translation of full-length rat peripherin is initiated predominantly at the second of two inframe AUGs. Deletions within the amino terminus of wild-type peripherin abolished its ability to form filaments in SW13 cells. In contrast, deletion of the entire carboxyl-terminal tail of peripherin did not affect its ability to form filamentous arrays in transfected SW13 cells. These results indicate that, of the intermediate filament proteins that are expressed in mature neurons, only peripherin and alpha-internexin are capable of making homopolymer intermediate filaments. In addition, mutations of the carboxyl tail of peripherin generally do not interfere with filament network formation.

Characterization of mechanosensitive channels in Escherichia coli cytoplasmic membrane by whole-cell patch clamp recording

Whole-cell patch clamp recordings were done on giant protoplasts of Escherichia coli. The pressure sensitivity of the protoplasts was studied. Two different unit conductance mechanosensitive channels, 1100 +/- 25 pS and 350 +/- 14 pS in 400 mM symmetric KCl solution, were observed upon either applying positive pressure to the interior of the cells or down shocking the cells osmotically. The 1100 pS conductance channel discriminated poorly among the monovalent ions tested and it was permeable to Ca2+ and glutamate-. Both of the two channels were sensitive to the osmotic gradient across the membrane; the unit conductances of the channels remained constant while the mean current of the cell was increased by increasing the osmotic gradient. Both of the channels were voltage sensitive. Voltage-ramp results showed that the pressure sensitivity of protoplasts was voltage dependent: there were more channels active upon depolarization than hyperpolarization. The mechanosensitive channels were reversibly blocked by gadolinium ion. Also they could reversibly be inhibited by protons. Mutations in two of the potassium efflux systems, KefB and KefC, did not affect the channel activity, while a null mutation in the gene for KefA changed the channel activity significantly. This indicates a potential modulation of these channels by KefA.

[The application of thin subdermal vascular network flap with a pedicle by a named vessel for repair of hand defects]

Thin subdermal vascular network flaps of the hypogastric region were created close to inguinal, superficial epigastric or superficial circumflex vessels. They were used to repair the defects of the hand in 12 patients. The pedicle was divided about one week after the flap transfer. All the flaps survived with satisfactory results.

[Antidepressant active constituents in the roots of Morinda officinalis How]

Five compounds having antidepressant activities have been isolated from the roots of Morinda officinalis, a Chinese traditional Yang-tonic drug. These compounds were identified as succinic acid (1), nystose (2), 1F-fructofuranosylnystose (3), inulin-type hexasaccharide (4) and heptasaccharide (5) by chemical and spectroscopic methods. All of the compounds are isolated from the species of genus Morinda for the first time.

Interaction of the protein kinase Raf-1 with 14-3-3 proteins

Members of a family of highly conserved proteins, termed 14-3-3 proteins, were found by several experimental approaches to associate with Raf-1, a central component of a key signal transduction pathway. Optimal complex formation required the amino-terminal regulatory domain of Raf-1. The association of 14-3-3 proteins and Raf-1 was not substantially affected by the activation state of Raf.

Reporter genes in transgenic mice

Although in vivo models utilizing endogenous reporter genes have been exploited for many years, the use of reporter transgenes to dissect biological issues in transgenic animals has been a relatively recent development. These transgenes are often, but not always, of prokaryotic origin and encode products not normally associated with eukaryotic cells and tissues. Some encode enzymes whose activities are detected in cell and tissue homogenates, whereas others encode products that can be detected in situ at the single cell level. Reporter genes have been used to identify regulatory elements that are important for tissue-specific gene expression or for development; they have been used to produce in vivo models of cancer; they have been employed for the study of in vivo mutagenesis; and they have been used as a tool in lineage analysis and for marking cells in transplantation experiments. The most commonly used in situ reporter gene is lacZ, which encodes a bacterial beta-galactosidase, a sensitive histochemical marker. Although it has been used with striking success in cultured cells and in transgenic mouse embryos, its postnatal in vivo expression has been unreliable and disappointing. Nevertheless, the ability to express reporter genes in transgenic mice has been an invaluable resource, providing insights into in vivo biological mechanisms. The development of new in vivo models, such as those in which expression of transgenes can be activated or repressed, should produce transgenic animal systems that extend our capacity to address heretofore unresolved biological questions.

Clinical applicability of bioelectric impedance to measure body composition in health and disease

The applicability of bioelectric impedance analysis (BIA) as a measure of body composition in children and young adults in both health and disease was studied in 155 subjects (5 mo to 54 yr of age) who were healthy (n = 21), had cystic fibrosis (n = 16), or had end-stage liver disease with variable clinical ascites or edema (n = 62). BIA and phase angle measured at a frequency of 50 kHz between the wrist and contralateral ankle by use of a tetrapolar measuring technique was compared with fat-free mass (FFM) estimated from skin-fold (SK) thickness measurements (n = 57), and body cell mass (grams potassium) measured by total-body potassium (TBK) counting. In a subgroup of subjects with end-stage liver disease, BIA was compared with total-body water measured by deuterium dilution (n = 21). High levels of correlation were found in healthy subjects, cystic fibrosis patients, and patients with end-stage liver disease when impedance (height2/resistance) was used to predict TBK (r = 0.96, 0.96, 0.98, respectively), and SK was used to predict FFMs (r = 0.96, 0.99, 0.90, respectively), by linear regression analysis. However, less satisfactory relationships were found when the methods were more appropriately analyzed with an estimated limits of agreement procedure (1 SD = 8.5, 5.0, 27.7% [TBK] and 9.4, 6.7, 23.0% [FFMs], respectively). A poor level of technique agreement (1 SD = 14%) was found when this method was compared with total-body water measured by isotope dilution in patients with liver disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of a single missense mutation in the adenine phosphoribosyltransferase (APRT) gene from five Icelandic patients and a British patient

We have completely sequenced the adenine phosphoribosyltransferase (APRT) gene from each of six patients--five (I-V) from Iceland and one (VI) from Britain. Cases I and II shared a common ancestor six and seven generations ago, and cases I and V shared a common ancestor seven generations ago, but cases III and IV were unrelated to the above or to each other, over seven generations. Genomic DNA was amplified by PCR, subcloned into M13mp18, and sequenced. Genomic and PCR-amplified DNAs were also analyzed by restriction-enzyme digestion and Southern blotting. The same missense mutation was identified in all six patients. This mutation leads to the replacement of asp (GAC) by val (GTC), at amino acid position 65. The gene sequences from all patients were otherwise identical to our wild-type sequence. The homozygous nature of the mutation was confirmed by sequencing the PCR product directly. All six patients were homozygous for the 1.25-kb TaqI RFLP. The Icelandic patients were also homozygous for the 8-kb SphI RFLP, but the British patient was heterozygous at this site. These studies suggest that a founder effect is likely to be responsible for APRT deficiency in the Icelandic population. The finding of the same mutation in a patient from Britain suggests that this mutation may have originated in mainland Europe.

[Clinical types of trifascicular block and a follow-up study of pacemaker application]

Thirty five patients (pts) with trifascicular block (TFB) were followed up for 5 years, and indication of pacemaker and clinical types of TFB were discussed. All of the 35 pts were diagnosed with clinical, ECG monitoring and His bundle electrogram (HBE) and classified into 4 groups: (1) acute transient TFB (3 cases) characterized by RBBB + LAHB + I or II AVB, caused by acute myocarditis or AMI, recovered with medicinal treatment; (2) 4 cases of acute advanced TFB characterized by RBBB + LAHB or LAPB + III AVB with severe symptoms such as syncope and Adams-Stokes syndrome; (3) 12 cases of chronic TFB characterized by RBBB + LAHB or LPHB + I, II or III AVB, with 40 beats/min lower heart rate and severe symptoms; (4) 18 cases of chronic advanced TFB characterized by RBBB + LAHB or LPHB + 1, 11 or III AVB, with severe symptoms. The 32 pts in groups 2, 3, and 4 were treated with implanted pacemakers and recovered very well. 29 pts are still well with pacemakers, and 5 cases with cardiomyopathy died due to chronic heart failure during the follow-up period of 5 years.

CONCLUSION

all of the pts with TFB and severe symptoms treated with pacemakers were appropriate, and are living well except those with chronic heart failure.