Manganese-dependent Dopa/tyrosine sulfation in HepG2 human hepatoma cells: novel Dopa/tyrosine sulfotransferase activities associated with the human monoamine-form phenol sulfotransferase

Human monoamine (M)-form phenol sulfotransferase (PST) was PCR-cloned and transiently expressed in COS-7 cells. The recombinant enzyme was demonstrated to display not only the previously reported sulfotransferase activity toward dopamine, but also novel manganese-dependent Dopa/tyrosine sulfotransferase activities. These results imply a new functional role of the human M-form PST in the homeostatic regulation of Dopa and tyrosine.

Mechanical white blood cell damage in rotary blood pumps

Mechanical trauma of white blood cells (WBC) due to the operation of a rotary blood pump was examined, using a simple method of trypan blue dye exclusion test for a cell viability measurement. The degree of WBC trauma was investigated using a roller pump (RP) and 3 commercially available centrifugal pumps (Bio-Medicus [BP], Capiox [CP], Nikkiso [NK]), and compared with the red blood cell (RBC) trauma. Each pump was operated 3 times at a flow rate of 5 L/min against the total pressure head of 350 mm Hg for 6 h in a mock circuit with 400 ml of fresh bovine blood. Blood was sampled at 2 h intervals measuring plasma free hemoglobin concentration and the percentage of damaged WBC in the trypan blue dye exclusion test. Each pump demonstrated a linear increase in the degree of WBC trauma, and there were differences among the tested pumps (RP > BP > CP > NK). These findings were similar to those of the free hemoglobin measurements. To compare the degree of RBC and WBC trauma, the probability (gamma, omega) of RBC and WBC to be damaged was calculated, respectively. gamma = delta DRBC/delta N, omega = delta DWBC/delta N where DRBC and DWBC are the ratios of the damaged RBC and WBC, respectively, and N is the passing number defined as Qt/V (Q, flow rate; t, time; V, circulating volume). The data of this study demonstrated that the omega value was approximately 20 times or more greater than the gamma equally in all the tested pumps. This suggests that a WBC is more vulnerable to mechanical damage by a rotary blood pump than a RBC.

Material of the double pivot bearing system in the Gyro C1E3 centrifugal pump

A double pivot bearing system is adopted for the Gyro C1E3 centrifugal blood pump to achieve a completely sealless structure that prevents blood leakage and thrombus formation around the shaft. The double pivot bearing system is also a critical factor for blood trauma and durability of the C1E3 pump. This study focuses on the double pivot bearing material. The pump with the male ceramic and female polyethylene pivots (PE) was compared with the pump with the male ceramic and female ceramic pivots (CRM), pertaining to stability of the impeller spinning motion, hemolysis, and durability. At first, the wear rate of the pivots was recorded after operating the pumps in various rotational speeds. As for hemolysis, in vitro tests were carried out using fresh bovine blood in 2 conditions (5 L/min, 350 mm Hg and 5 L/min, 100 mm Hg). Then, stability of the spinning motion was investigated by evaluating the vibration of the pump. The two pumps with different female pivots were operated identically at 2,700 rpm, and the vibration signals were measured using an accelerometer that was mounted on the top of the pump housing. The following findings were obtained in this study. The wear sites were different between the PE and CRM. Most of the wear occurred at the top female polyethylene pivot in the PE. In contrast, most of the wear occurred at the top male ceramic pivot in the CRM. In addition, the amount of the initial wear was less and the wear rate was lower in the PE than in the CRM. The hemolysis caused by the PE was less than the hemolysis caused by the CRM. The vibration signals of the PE had less amplitude and a narrower range of frequency than the vibration signals of the CRM. In conclusion, the combination of materials male ceramic-female polyethylene are superior to the male ceramic-female ceramic for the double pivot bearing system of the Gyro C1E3 centrifugal pump because of less vibration, less hemolysis, and less wear.

An approximately half set of histone genes is enough for cell proliferation and a lack of several histone variants causes protein pattern changes in the DT40 chicken B cell line

Of the 44 chicken histone genes, 39 are located in a major histone gene cluster of 110 kb, the others residing in four separate regions. The 42 sequenced genes encode six H1 variants, three H2A variants, four H2B variants, two H3 variants, and one histone H4. To clarify the influence on cell functions of simultaneous deletion of an approximately half set of the genes and some of the variants, we generated homozygous chicken DT40 mutants by disruption of two allelic segments of 57 kb, containing the 21 genes, using gene targeting techniques. Analyses with antisense RNA probes common or specific for gene families H1, H2A, H2B, H3 and H4 indicated that the remaining members of each of the gene families were expressed more in the mutants than in DT40 cells, resulting in maintenance of constant steady-state levels of mRNAs. Two-dimensional polyacrylamide gel electrophoresis showed that in the mutants several cellular proteins newly appeared or increased, and some other proteins disappeared or decreased quantitatively. These results demonstrate that all the histone gene families have the inherent ability to compensate for the disruption of a fair number of their own constituents. Furthermore, some of the histone variants are involved in regulation of the expression of putative genes that encode the proteins that varied in mutant DT40 cells, this participation is not compensated for by any residual variant of the same histone subtype(s).

Flow characteristics and required control algorithm of an implantable centrifugal left ventricular assist device

As the clinical application of LVADs has increased, attempts have been made to develop smaller, less expensive, more durable and efficient implantable devices using rotary blood pumps. Since chronic circulatory support with implantable continuous-flow LVADs will be established in the near future, we need to determine the flow characteristics through an implantable continuous-flow LVAD. This study describes the flow characteristics through an implantable centrifugal blood pump as a left ventricular assist device (LVAD) to obtain a simple non-invasive algorithm to control its assist flow rate adequately. A prototype of the completely seal-less and pivot bearing-supported centrifugal blood pump was implanted into two calves, bypassing from the left ventricle to the descending aorta. Device motor speed, voltage, current, flow rate, and aortic blood pressure were monitored continuously. The flow patterns revealed forward flow in ventricular systole and backward flow in diastole. As the pump speed increased, an end-diastolic notch became evident in the flow profile. Although the flow rate (Q [l/min]) and rotational speed (R [rpm]) had a linear correlation (Q = 0.0042R - 5.159; r = 0.96), this linearity was altered after the end-diastolic notch was evident. The end-diastolic notch is considered to be a sign of the sucking phenomenon of the centrifugal pump. Also, although the consumed current (I [A]) and flow rate had a linear correlation (I = 0.212Q + 0.29; r = 0.97), this linearity also changed after the end-diastolic notch was evident. Based upon the above findings, we propose a simple algorithm to maintain submaximal flow without inducing sucking. To maintain the submaximal flow rate without measuring flow rate, the sucking point is determined by monitoring consumed current according to gradual increases in voltage.

Hydraulic assessment of the floating impeller phenomena in a centrifugal pump

A compact eccentric inlet port centrifugal blood pump (C1E3) has been perfected for a long-term centrifugal ventricular assist device as well as a cardiopulmonary bypass pump. The C1E3 pump incorporates a sealless design and a blood stagnation free structure. The pump's impeller is magnetically coupled to the driver magnet in a sealless manner. The latest hemolysis study reveals that hemolysis is affected by the magnetic coupling distance between the driver and impeller magnet. Furthermore, a floating phenomenon can be observed in a pivot bearing supported pump. Attention was focused on the relationship between the floating phenomenon's characteristics and the magnetic coupling design in the C1E3 pump. Studies were conducted to evaluate the hydromechanical performance in the floating phenomenon. In this study, the relationship between the magnetic coupling design and the floating phenomenon was verified with a smooth spinning condition. The optimized magnetic coupling distance for the floating mode was estimated to be 12 mm for left ventricular assist device and 9 mm for cardiopulmonary bypass pump. Obtaining an optimal spinning condition is required for regulating the magnetic coupling force. To develop a double pivot bearing pump, it is necessary to establish an optimal spinning and/or floating condition and to determine the proper magnetic coupling and magnetic force between the impeller and driver.

Effect of surface roughness on hemolysis in a pivot bearing supported Gyro centrifugal pump (C1E3)

The blood contacting surface quality is an important pump parameter for blood compatibility and cell damage. This study investigates the surface roughness and the effect it has on hemolysis in a centrifugal blood pump. In vitro hemolysis tests were performed with a pivot bearing supported Gyro centrifugal pump (C1E3) simulating cardiopulmonary bypass (CPB; 5 L/min, 350 mm Hg) and left ventricular assist device (LVAD; 5 L/min, 100 mm Hg) conditions. To produce 4 different grades of surface roughness, the impellers and housings were subjected to vapor polishing, sand papering, fine sand blasting, or coarse sand blasting. Seven pumps were assembled with different impeller and housing surfaces. These surfaces were then examined by a surface profile instrument and a scanning electron microscope. The results of this study are as follows. First, the effect of surface roughness on hemolysis was significantly greater in the CPB condition than in the LVAD condition. Second, surface roughness, regardless of whether it is the impeller or pump housing, had little effect on hemolysis in the LVAD condition. Third, in the CPB condition, the surface roughness of the pump housing has a greater effect on hemolysis than does that of the impeller. From a hemolytic point of view, an extremely smooth pump housing is required for use of an impeller type centrifugal pump as a CPB device. In contrast, it is conceivable that a smooth surface is not always essential for an impeller type centrifugal pump that is used as an LVAD.

Effect of surface roughness on hemolysis in a centrifugal blood pump

Surface roughness of a blood pump is an important factor for blood cell damage. This study investigated the effect of surface roughness pertaining to hemolysis in a centrifugal pump. In vitro hemolysis tests were performed under cardiopulmonary bypass (CPB; 5 L/min, 350 mmHg) and left ventricular assist device (LVAD; 5 L/min, 100 mmHg) conditions using the pivot bearing supported Gyro centrifugal pump (C1E3). Seven types of pumps with impellers and housings with different surface roughness were prepared as follows: vapor polish (VP) housing and VP impeller; VP housing and sandpaper (SP) impeller; VP housing and fine sandblasting (FSB) impeller; VP housing and coarse sandblasting (CSB) impeller; SP housing and VP impeller; FSB housing and VP impeller; and CSB housing and VP impeller. The results revealed that 1) the effect of surface roughness on hemolysis was significantly larger with CPB than LVAD; 2) surface roughness, regardless of the impeller or housing, had little effect on hemolysis with LVAD; and 3) during CPB, the surface roughness of the pump housing had a larger effect on hemolysis than did that of the impeller. In conclusion, from a hemolytic point of view, it is likely that an extremely smooth pump housing is required for an impeller centrifugal pump for CPB. However, it is likely that a smooth surface is not as essential for this impeller centrifugal pump as for an LVAD.

Hemolytic characteristics of a pivot bearing supported Gyro centrifugal pump (C1E3) simulating various clinical applications

Centrifugal blood pumps are playing a key role in circulatory mechanical assist systems including cardiopulmonary bypass (CPB), right and left ventricular assist devices (RVAD and LVAD), percutaneous cardiopulmonary support (PCPS), and extracorporeal membrane oxygenation (ECMO). Each of these circulatory assist systems requires specific flow and pressure conditions. In vitro hemolysis tests were performed using five compact mock loops with flow and pressure set equivalent to clinical conditions. These studies determined the hemolytic characteristics and clinical applicability of the pivot bearing-supported Gyro centrifugal pump with an eccentric port (C1E3) compared with the Bio-Medicus pump (BP-80). Normalized index of hemolysis (NIH) values of the C1E3 were less than those of the BP-80 under all conditions; in particular, they were significantly less in the CPB, LVAD, and RVAD conditions. In addition, linear correlation was observed between NIH values, rotational pump speed (RPM), total pressure head (delta P), and flow rate (Q) with both the C1E3 and BP-80: NIH = a(RPM/Q) + b, NIH = c(delta P/Q) + d. However, the slopes (a and c) of these equations were smaller with the C1E3 than those with the BP-80, which suggests that the C1E3 has decreased hemolytic characteristics when increasing the RPM and delta P. In other words, the increase of RPM and delta P results in less shear stress with the C1E3 than with the BP-80. One cause of these decreased hemolytic characteristics of the C1E3 is thought to be less pump power loss against an increase of RPM and delta P than with the BP-80. Furthermore, the average exposure time is shorter with the C1E3 than with the BP-80 because the priming volume of the C1E3 (30 ml) is smaller than that of the BP-80 (80 ml). From the point of both shear stress and exposure time, the C1E3 has less hemolytic features than the BP-80.

Safety margin of magnetic coupling distance in decoupling of a pivot bearing-supported Gyro centrifugal pump (C1E3)

The pivot bearing-supported Gyro C1E3 centrifugal pump is driven by magnetic coupling. The magnetic coupling distance (MCD) between the impeller magnet and the driver magnet affects both hydraulic performance and hemolysis. Although a greater MCD causes less hemolysis, it increases the risk of decoupling of the impeller magnet. Therefore, it is important to consider the effect of the MCD on both hemolysis and decoupling when the C1E3 pump is applied in various circulatory assist conditions. This study investigates the effect of the MCD on decoupling in a C1E3 pump that is driven by the Nd-Fe-B composite ring-shaped magnets. The results will determine which MCD is the most practical in all assist device conditions. The MCD of the C1E3 pump was varied from 9.5 to 14.5 mm by inserting spacers between the bottom pump housing and the driver magnet. At a rotational speed just before the decoupling occurred, the flow rate and total pressure head were measured. The results revealed that a MCD between 9.5 and 14.5 mm was enough to produce a flow rate of more than 10 L/min without decoupling, and a MCD of less than 11.5 mm was required when the total pressure head was more than 500 mm Hg. Thus, the limiting factor for the MCD of the C1E3 pump is the total pressure head rather than the flow rate. An MCD of less than 11.5 mm is required to prevent decoupling of the impeller of the C1E3 pump with the specific Nd-Fe-B magnets in the full range of clinical circulatory assist conditions.

Pump power loss and heat generation in a pivot bearing-supported Gyro centrifugal pump (C1E3)

Pump power loss is defined as input power that is not used for the output work of the pump. Less pump power loss means a higher pump efficiency. A common opinion is that the pump power loss is closely related to heat generation of the pump, which may affect not only the endurance of pump materials, but also blood damage in a blood pump. In this study, the relationship between pump power loss and heat generation in centrifugal blood pumps was investigated using the pivot-bearing supported Gyro C1E3 pump (C1E3) and Bio-Medicus pump (BP-80) under four different total pressure heat/flow conditions. A single special torque measuring driver motor was used for operating both the C1E3 and BP-80 in the four conditions. The pump power loss was calculated from the measured motor torque and hydraulic power. The changes in blood temperature were measured while the pump was operated at room temperature (25 degrees C) to obtain the following findings: First, the C1E3 caused less pump power loss and less temperature increase in blood than the BP-80 in all clinical simulated conditions that were tested; and second, the pump power loss and heat generation had a linear correlation with temperature rise from 22 to 25 degrees C in both the C1E3 and BP-80. During this period, approximately 30% of the pump power loss was transformed to heat, independent of the centrifugal blood pump type, provided that heat conduction through the pump housing and tubing was negligible during this particular period.

Development of a pivot bearing supported sealless centrifugal pump for ventricular assist

Since 1991, in our laboratory, a pivot bearing-supported, sealless, centrifugal pump has been developed as an implantable ventricular assist device (VAD). For this application, the configuration of the total pump system should be relatively small. The C1E3 pump developed for this purpose was anatomically compatible with the small-sized patient population. To evaluate antithrombogenicity, ex vivo 2-week screening studies were conducted instead of studies involving an intracorporeally implanted VADs using calves. Five paracorporeal LVAD studies were performed using calves for longer than 2 weeks. The activated clotting time (ACT) was maintained at approximately 250 s using heparin. All of the devices demonstrated trouble-free performances over 2 weeks. Among these 5 studies, 3 implantations were subjected to 1-month system validation studies. There were no device-induced thrombus formations inside the pump housing, and plasma-free hemoglobin levels in calves were within the normal range throughout the experiment (35, 34, and 31 days). There were no incidents of system malfunction. Subsequently, the mass production model was fabricated and yielded a normalized index of hemolysis of 0.0014, which was comparable to that of clinically available pumps. The wear life of the impeller bearings was estimated at longer than 8 years. In the next series of in vivo studies, an implantable model of the C1E3 pump will be fabricated for longer term implantation. The pump-actuator will be implanted inside the body; thus the design calls for substituting plastic for metallic parts.

Evaluation of the wear of the pivot bearing in the Gyro C1E3 pump

To estimate the lifetime of the pivot bearing system of the sealless centrifugal Gyro C1E3 pump, pivot bearing wear phenomena of the C1E3 were studied. The pivot bearing system consisted of a male and female pivot made of ceramics and ultrahigh molecular weight polyethylene (UHMWPE), respectively. First, many pumping tests were performed with the C1E3 under various pumping conditions, and the effects of impeller position and fluid on wear were analyzed. Through these preliminary tests, it was found that the wear progress of the pivot bearing consisted of initial wear and stationary wear. Most of this initial wear is caused by the plastic deformation of the polyethylene female pivot. It also was observed that bovine blood was almost comparable to water in its effect on the stationary wear rate at the same rotational speed. Based on these results, a long-term pumping test was performed with the C1E3, and initial and stationary wear rates were determined. At the same time, the maximal loosening distance (LDmax) (permissible total wear) of the C1E3 was determined experimentally from hemolytic and hydraulic performance perspectives. By using experimentally determined parameters the lifetime of the pivot bearing system of the C1E3 was typically 10 years for right ventricular assist, 8 years for left ventricular assist, and 5 years for cardiopulmonary bypass.

Dispase/detergent treated dermal matrix as a dermal substitute

A method for preparing acellular allogeneic dermal matrix (ADM) and its effectiveness as a dermal substitute are described. Treatment of rat skin with Dispase followed by Triton X-100 completely removed cellular components from the dermis. Subcutaneously implanted ADM evoked no immunological reaction and 20 weeks after implantation, the size of the implanted ADM was reduced to about 60 per cent of its original area. ADM became completely vascularized within 2 weeks after implantation into full thickness skin defects in the rat and inhibited extensive wound contracture. A second layer of ADM placed onto the implanted ADM served as an excellent dressing, providing mechanical protection and permitting vascularization of the underlying implant. Onlay skin autografts placed onto vascularized allogeneic ADM showed good survival when the skin was grafted more than 1 week after ADM implantation. Dispase/detergent treated ADM derived from animal or human skin may be useful in full thickness skin defects providing a vascularized bed for subsequent epidermal coverage.

Organization of the chicken histone genes in a major gene cluster and generation of an almost complete set of the core histone protein sequences

We present a detailed picture of the disposition of the histone genes in the chicken genome and an almost complete set of the core histone protein sequences. Thirty-nine histone genes, six H1, nine H2A, eight H2B, eight H3 and eight H4, were located within a histone gene cluster of 110 kb, which was covered by five cosmid clones and two lambda clones. Results of our sequence analyses, together with those reported previously, generated a set of the core histone amino acid sequences as follows: three H2A variants, four H2B variants, two H3 variants and an H4 protein.

The effect of the impeller-driver magnetic coupling distance on hemolysis in a compact centrifugal pump

Blood trauma is one of the important performance parameters of centrifugal pumps. To investigate the blood trauma induced by these pumps, in vitro hemolysis tests have become an important procedure and are increasingly used for pump development and comparisons. The Baylor compact eccentric inlet port (CIE) centrifugal blood pump was developed as a long-term centrifugal ventricular assist device (VAD) as well as a cardiopulmonary bypass pump (CPB). The Baylor CIE pump incorporates a seal-less design with a blood stagnation-free structure. This pump can provide flows of 5 L/min against 350 mm Hg of total pressure head at 2,600 revolutions per minute. The pump impeller is magnetically coupled to the driver magnet in a seal-less manner. The latest hemolysis study revealed that hemolysis may be affected by the gap distance between the driver and the impeller magnet. The purpose of this study was to verify the effect of the magnetic coupling distance on the normalized index of hemolysis (NIH) with the CIE model and to obtain an optimal gap distance. The NIH value was clearly decreased by alteration of the magnetic coupling distance from 7.7 to 9.7 mm in CPB and left ventricular assist device (LVAD) conditions. The NIH, when using the pump as an LVAD condition, was reduced to a level of 0.0056 from 0.095 when the magnetic coupling distance was extended. The same results were also obtained when the pumps were used in a CPB condition. The magnetic coupling distance is an important factor for the CIE model in terms of hemolysis. Different coupling forces effect the bearings and impeller stability. These results suggest that an optimal driving condition with a proper magnetic coupling and an optimal force between the impeller and driver is necessary to develop an atraumatic centrifugal pump.

Modification of a pivot bearing system on a compact centrifugal pump

The pivot bearing centrifugal blood pump was developed as a long-term centrifugal ventricular assist device (VAD) as well as a cardiopulmonary bypass pump. This pivot bearing supported centrifugal pump with an eccentric port (CIE) incorporates a seal-less design with a blood stagnation-free structure. This pump can provide flows of 12 L/min against 650 mm Hg total pressure head at 3,600 rpm, and in a CPB condition 5 L/min against 350 mm Hg total pressure head at 2,600 rpm. Very recently, the pivot bearing system was modified to obtain a stable and smooth spinning movement. The material of the female pivot was changed from ceramic to polyethylene. Three kinds of bearings were tested simultaneously with bovine blood in two types of in vitro circuits to determine the blood damage from the bearings. Pressure differences across the pump (total head pressure, delta P) of 140 mm Hg (n = 12) and 330 mm Hg (n = 12) were examined. The normalized index of hemolysis (NIH) was slightly higher in a ball bearing (BB) pump than in a polyethylene bearing (PB) pump and statistically higher than the BioMedicus Pump (BP-80) on delta P of 140 mm Hg. When the delta P was at 330 mm Hg, a comparison between the three types of pumps revealed no difference in NIH. In addition, the primary vane of the impeller was redesigned to obtain an atraumatic structure. In the second study (n = 14), there was no difference in the NIH between BP-80 and the current model when the delta P was 300 mm Hg (0.019 +/- 0.002 vs. 0.027 +/- 0.006, p = 0.3) and/or when the delta P was 100 mm Hg (0.0008 +/- 0.0001 vs. 0.0014 +/- 0.0002, p = 0.07). The modified pivot bearing had an improved spinning condition and no change in hemolysis. A proper selection of pivot bearing materials is important to develop an atraumatic centrifugal pump. The modification of the bearing system and redesign of the vane enabled a compact centrifugal pump to become a reality.

[Coronary artery bypass grafting for ischemic heart disease associated with acromegaly: a case report]

Coronary artery bypass grafting (CABG) for ischemic heart disease associated with acromegaly has never been reported in Japan, though coronary artery sclerosis is known as complicating factor in acromegaly. A 44-year-old man with ischemic heart disease was admitted to our hospital and emergency percutaneous transluminal coronary recanalization was performed. After admission, he was diagnosed as acromegaly from endocrinological studies and operated on CABG. The peri- and post-operative course was uneventful in spite of our fear for complications due to acromegalic heart muscle disease.

Purification, characterization, and molecular cloning of a novel rat liver Dopa/tyrosine sulfotransferase

A novel sulfotransferase was purified from the rat liver cytosol to electrophoretic homogeneity via five column chromatography steps (hydroxylapatite I, DEAE Bio-Gel, ATP-agarose I, hydroxylapatite II, and ATP-agarose II). The minimum molecular weight of the purified enzyme was determined by sodium dodecyl sulfatepolyacrylamide gel electrophoresis to be approximately 33,000. Gel filtration chromatography revealed a native molecular weight of approximately 34,000, indicating the enzyme being present in the monomeric form. The purified sulfotransferase displayed enzymatic activities, with a pH optimum of 9.25, toward various tyrosine and 3,4-dihydroxyphenylalanine (Dopa) isomers, except DL-ortho-tyrosine. Thyroid hormones, as well as dopamine and p-nitrophenol, could also be used as substrates. The apparent Km value of the enzyme (designated the Dopa/tyrosine sulfotransferase) for L-Dopa, determined at a constant 14 microM of 3'-phosphoadenosine 5'-phosphosulfate, was 0.76 mM. The intact enzyme was found to be N-blocked when subjected to N-terminal sequencing. Three internal partial amino acid sequences, obtained by analyzing its proteolytic fragments, were found to be distinct from the homologous sequences of other known rat liver sulfotransferases. The deduced amino acid sequence of a full-length cDNA isolated from a rat liver cDNA library confirmed the identity of the Dopa/tyrosine sulfotransferase as a new type of aryl sulfotransferase. Upon transfection of COS-7 cells with an expression vector (pMSG-CMV) harboring the full-length cDNA, a 33-kDa protein displaying enzymatic and immunological properties similar to those of the purified Dopa/tyrosine sulfotransferase was expressed.

Targeted disruption of H2B-V encoding a particular H2B histone variant causes changes in protein patterns on two-dimensional polyacrylamide gel electrophoresis in the DT40 chicken B cell line

The chicken H2B gene family comprises eight members (H2B-I to H2B-VIII), which are all located in two major histone gene clusters. All of them have been shown to encode four different protein variants (classes I to IV). In the DT40 chicken B cell line, the H2B-V gene, encoding the class III H2B variant, constituted about 10% of the total intracellular mRNA from all the H2B genes. To study the nature of this particular variant in vivo, we generated heterozygous (H2B-V, +/-) and homozygous (H2B-V, -/-) DT40 mutants by targeted integration. The remaining H2B genes were shown to be expressed more in these mutants than in the wild-type cell lines. The growth rate of DT40 cells was unchanged in the absence of the H2B-V gene. Two-dimensional polyacrylamide gel electrophoresis showed that the protein patterns were, on the whole, similar between the wild-type and homozygous cell lines. However, within this constant background, some cellular proteins disappeared or decreased quantitatively in the homozygous mutants, and several other proteins increased or newly appeared. These results suggest that the class III H2B variant participates negatively or positively in regulation of the expression of particular genes that encode the proteins that vary in DT40 cells. This type of regulation is possibly mediated through alterations in nucleosome structure over the restricted regions involving the putative genes of the DT40 genome.

Targeted disruption of 01H1 encoding a particular H1 histone variant causes changes in protein patterns in the DT40 chicken B cell line

Six members of the chicken H1 gene family, all of which are located in two major histone gene clusters, have been shown to encode six different protein variants. The intracellular mRNA level from one of them, 01H1, encoding the 01H1 variant composed of 218 amino acid residues, constitutes 9.9% of the total H1 mRNA in the DT40 chicken B cell line. To study the specific role of this particular H1 variant, besides its well-known functions as a linker in chromatin maintenance and as a general repressor of transcription, we used targeted integration to construct heterozygous and homozygous DT40 mutants with disruption of one and two 01H1 alleles, respectively. Analyses of the stable transfectants showed that the growth rate of DT40 was unchanged in the absence of two 01H1 alleles. Moreover, the remaining H1 genes were shown to be expressed more in these mutants than in the wild-type cell lines. Two-dimensional polyacrylamide gel electrophoresis showed that within an almost constant background in the homozygous mutants several cellular proteins newly appeared or increased, while some other proteins disappeared or decreased quantitatively. These variable proteins all differed from those that varied in DT40 mutants deprived of one of the eight chicken H2B genes, H2B-V, encoding a particular H2B variant. These results suggest that the 01H1 variant is involved in the regulation of expression of genes that encode the proteins that vary in 01H1-deleted mutants of DT40 cells.

Possible involvement of a ubiquitous and several distinct elements in the transcription regulation of the chicken H3 histone gene family

We have studied possible modes of transcription regulation of four members (H3-II, H3-III, H3-IV and H3-V) of the twelve chicken H3 genes. Results of transient CAT assays using 5'-truncated mutants of H3-IV, together with those reported previously for H3-II and H3-III, indicated that all these four H3 genes possessed a ubiquitous element, the CCAAT sequence, in addition to several distinct elements. Transient CAT assays using the 5'-extended mutants of these four H3 genes showed that the promoter activities decreased with increasing lengths of the 5'-extended fragments, and that the effects were strong for H3-IV and H3-V, but only moderate for H3-II and H3-III.

Disappearance of Langerhans cells and melanocytes after cryopreservation of skin

Cryopreserved skin allografts have been extensively reported to remain viable for longer periods after grafting, both in the laboratory and in the clinic, than skin stored by other methods. We investigated the immunocytochemical and electron microscopic properties of samples of cryopreserved human skin (-196 degrees C) for comparison with fresh samples. In an immunocytochemical study of fresh skin, reagents S-100 and CDIa indicated numerous mesenchymal origin cells in the squamous cell layer, basal layer and dermis; 2B7 identified these cells in the basal layer and PC-10 identified them in the basal and squamous cell layers. In cryopreserved skin, however, few cells reacted to these reagents. An electron microscopic study of the cryopreserved skin showed Langerhans cells (LC); however, these had suffered degeneration, with partial defects of the cell membrane and vacuolation in the cytoplasm. We speculate these effects are responsible for the virtually complete abolition of LC membrane and cytoplasm markers. In summary, we detected few mesenchymal origin cells, melanocytes, Langerhans cells, or S-phase cells, in cryopreserved skin by immunocytochemical methods. Langerhans cells existed but had degenerated. These results indicate that cryopreservation at -196 degrees C causes degeneration of Langerhans cells, and that is the reason for the prolonged viability of cryopreserved allograft.

Targeted disruption of an H3-IV/H3-V gene pair causes increased expression of the remaining H3 genes in the chicken DT40 cell line

The chicken H3 gene family contains 12 members (H3-I to H3-XII). Nine of them belong to two major histone gene clusters, but the genomic locations of the others are unknown. In the DT40 chicken B cell line, H3-IV and H3-V, which are located in inverted orientation and share a 3'-untranslated region of 531 bp, produce about 24% of the steady-state level of total mRNAs from all the H3 genes. To study the nature of these two genes, we carried out targeted integration into DT40 cells of constructs of the H3-IV/H3-V locus. Analysis of the stable transfectants showed that the growth rate of DT40 cells was unchanged in the absence of two copies of the H3-IV/H3-V locus. Furthermore, the remaining H3 genes were shown to be expressed more in the mutants lacking one or two H3-IV/H3-V alleles than DT40 cells, and the steady-state level of total H3 mRNAs remained constant in all the mutant cell lines tested. The levels of mRNAs from the H2B and H1 genes, which are located close to the H3 genes, were unchanged. These results demonstrate that the chicken H3 gene family has the ability to compensate for disruption of H3-IV/H3-V, which are normally responsible for about 24% of total H3 mRNAs.