Impact of boredom on perceived inequity and discretionary behaviors: a latent growth curve approach

Purpose

This study seeks to examine the effect of work-related boredom and a perceived lack of external stimulation on benevolent and entitled employees' perceived inequity and discretionary workplace behaviors.

Design/methodology/approach

A total of 668 useable three-wave panel data were obtained via Amazon Mechanical Turk during a three-month period. The hypothesized model was tested using a latent growth curve modeling via EQS 6.4 for Windows.

Findings

This study finds the following results. First, benevolent employees who experience higher initial work-related boredom report positive inequity. Second, entitled employees who experience higher initial work-related boredom and a perceived lack of external stimulation report negative inequity. Third, increases in work-related boredom and a perceived lack of external stimulation result in a faster increase in entitled employees' perceived negative inequity. Fourth, entitled employees who perceive higher negative inequity at the initial measurement period report higher interpersonal deviance. Finally, increases in entitled employees' perceived negative inequity result in a faster increase in interpersonal deviance.

Originality/value

This study highlights how employees may assess their effort and rewards when experiencing boredom. This study also offers some practical recommendations that help human resource managers manage boredom in the organization effectively.

Impact of basic psychological needs on organizational justice and helping behavior: a self-determination perspective

Purpose

Integrating the social exchange perspective of helping behavior with self-determination theory (SDT), this study seeks to examine the impact of employees' psychological needs on perceived organizational justice and the impact of perceived organizational justice on employees' helping behavior.

Design/methodology/approach

Cross-sectional and cross-organizational data were obtained from 177 full-time employees employed in 12 small- and medium-sized oil and gas service companies. A partial least squares approach using SmartPLS was employed to test the hypotheses.

Findings

Results illustrate that the psychological need for competence and need for autonomy are positively related to perceived distributive and procedural justice, respectively. Moreover, perceived distributive and procedural justice are related to helping behavior. Furthermore, perceived distributive justice fully mediates the relationship between the psychological need for competence and helping behavior, whereas perceived procedural justice partially mediates the relationship between the psychological need for autonomy and helping behavior.

Originality/value

From a theoretical standpoint, this study offers some theoretical explanations for how the basic psychological needs identified by SDT activate employees' perceived organizational justice. Practically, this study offers several managerial recommendations that help managers manage helping behavior in the organization effectively.

Millennials as organizational citizens: Conceptualization and measurement development

Despite existing scholarly progress in organizational citizenship behavior (OCB), prior research has predominantly investigated OCB using Baby Boomers and Generation Xers. As Millennials who possess different sets of workplace values and beliefs are entering the workforce, there is a need for conceptualizing OCB and developing an OCB scale suitable for Millennials. In this study, we conceptualize OCB in Millennials as voluntary behaviors that promote the prosperity of oneself, coworkers, the organization, and the community. Additionally, we employ exploratory factor analysis and identify a four-factor model of OCB, including empathetic responsiveness, role modeling, professional development, and social responsibility. We then conduct confirmatory factor analysis and construct a 13-item measurement scale for Millennial OCB. Finally, we assess and find evidence for the construct validity of the 13-item measurement scale. We conclude this study with an overview of theoretical and managerial implications.

Helping coworkers only when I have more? Integrating social comparison, attribution and conservation of resources theories

Purpose

Drawing upon conservation of resources (COR) and attribution theories, prior research in helping behavior has mainly focused on an independent view of the helper’s personal resources. This perspective, however, falls short of capturing the comparative nature of personal resources and attributions in a helping context. The purpose of this paper is, therefore, to develop a theoretical model that helps predict employees’ decisions to help or not to help.

Design/methodology/approach

A theoretical model was developed by integrating social comparison, COR and attribution theories.

Findings

The theoretical model proposes the following. First, when employees perceive that they have fewer personal resources than a coworker who needs help, they are less likely to help. Second, when employees perceive that they have more personal resources than a coworker who needs help, they make causal attributions as to why the coworker failed to deploy personal resources. Finally, when employees have more personal resources than a coworker who needs help, they are more likely to help if they make situational, unstable and uncontrollable attributions to the coworker’s failure to deploy personal resources.

Originality/value

This paper extends the literature by offering a theoretical model that emphasizes comparisons and attributions of personal resources in a helping context. Additionally, this paper offers several managerial implications that help managers manage helping behavior effectively.

Feeling Capable and Worthy? Impact of Employee Silence on Self-Concept: Mediating Role of Organizational Citizenship Behaviors

While existing research findings have highlighted the consequences of employee silence at the interpersonal and organizational levels, little is known about how employee silence influences an employee's inferences of self. Drawing on a cross-organizational sample of 142 employees, we test the impact of employee silence, in the forms of acquiescent, quiescent, prosocial, and opportunistic silence, on employees' job self-efficacy and organization-based self-esteem. In addition, we examine how organizational citizenship behavior toward the organization and toward individuals mediates the direct effects. Results indicate that quiescent silence negatively affects organization-based self-esteem, and that opportunistic silence has a negative impact on job self-efficacy. In addition, organizational citizenship behavior toward the organization and organizational citizenship behavior toward individuals fully mediate the relationship between opportunistic silence and organization-based self-esteem, whereas organizational citizenship behavior toward individuals and organizational citizenship behavior toward the organization partially mediate the relationship between opportunistic silence and job self-efficacy. Implications for theory and practice are discussed.

A multilevel model of organizational learning

Purpose

Organizational learning has long been recognized as an important determinant of organizational performance and sustainability. Existing research, however, has commonly viewed organizational learning as a single-level, top-down and organized organizational event initiated by the leader. This particular perspective may fall short of explaining the effect of employee spontaneous workplace behaviors on organizational learning. Thus, the purpose of this paper is to develop a multilevel theoretical model exploring how an employee’s upward helping and voice behavior foster organizational learning through developing leadership capital.

Design/methodology/approach

A conceptual analysis was conducted by incorporating relevant research.

Findings

This paper proposes the following. First, an employee’s upward helping increases a leader’s human capital and social capital. Second, the leader’s human capital and social capital enhance the employee’s psychological empowerment and knowledge leadership. Third, the employee’s psychological empowerment leads to employee voice behavior. Fourth, employee voice behavior strengthens knowledge leadership. Finally, knowledge leadership promotes organizational learning.

Originality/value

This paper provides a theoretical framework for future research attempting to understand organizational learning from a multilevel, bottom-up perspective. Practically, this paper offers several implications that help promote organizational learning through encouraging employee upward helping and voice behavior.

A theoretical analysis of immigrant employees’ organizational citizenship behaviors in organizations

Purpose

The purpose of this paper is to develop a theoretical model describing how immigrant employees’ organizational citizenship behaviors (OCBs) are influenced by their immigrant status. Additionally, this study attempts to explore the mediating role of perceived job mobility as well as the moderating role of organizational tenure in the relationship between immigrant status and OCBs.

Design/methodology/approach

A conceptual analysis was performed.

Findings

Drawing upon social identity, self-categorization, and impression management theories, this study proposes the following. First, an immigrant employee’s perceived different categorization of employment and organizational status will have a negative impact on his or her challenge-oriented OCB. Second, an immigrant employee’s perceived categorization of employment and organizational status will have a positive impact on his or her affiliation-oriented OCB. Third, perceived job mobility mediates the relationship between the perceived different categorization of employment and organizational status and challenge- and affiliation-oriented OCBs of an immigrant employee. Finally, an immigrant employee’s organizational tenure weakens (or strengthens) the negative (or positive) impact of immigrant status on challenge-oriented (or affiliation-oriented) OCB.

Originality/value

From a theoretical standpoint, this study provides a novel theoretical base that guides future research on immigrant employees’ OCBs in organizations. More importantly, this study offers recommendations that help maximize the effectiveness of immigrant employee’s OCBs.

The costs of being rejected

Purpose

This paper aims to develop a theoretical model describing how newcomers’ team-member exchange (TMX), team identification and workplace loneliness may be affected by existing team members’ rejections to the newcomers’ interpersonal helping behavior (IHB).

Design/methodology/approach

A theoretical analysis was performed.

Findings

The authors propose the following propositions. First, higher levels of IHB rejections result in lower levels of TMX and team identification and higher levels of workplace loneliness experienced by a newcomer. Second, a newcomer’s TMX mediates the relationship between IHB rejections and the newcomer’s workplace loneliness and team identification. Finally, a newcomer’s team identification mediates the relationship between IHB rejections and the newcomer’s workplace loneliness.

Practical implications

This theoretical study provides the following managerial implications. First, managers need to proactively implement tactics that help satisfy newcomers’ affiliation needs through the development of strong formal work relationships with existing members. Second, managers are advised to consider the use of tactics that facilitate the development of effective informal relationships between newcomers and existing team members upon the entry of the team. Third, managers need to implement informal social events where newcomers have the opportunity to exhibit their helpful behaviors. Fourth, managers should periodically inform existing team members of some common anxieties and fears of newcomers that are triggered by entering new interpersonal environments. Finally, managers may utilize mentoring programs that help facilitate newcomers’ accurate interpretations of phenomena occurring around them.

Originality/value

This theoretical study is the first study that examines consequences of IHB rejections in organizations.

What happens when “younger” helpers meet “older” recipients? A theoretical analysis of interpersonal helping behaviour in Chinese organizations

Purpose

– The purpose of this paper is to develop a theoretical model describing psychological states and behavioral outcomes experienced and exhibited by older generation interpersonal helping behavior (IHB) recipients in Chinese organizations.

Design/methodology/approach

– The paper draws upon relevant literature and develops a theoretical model.

Findings

– The analysis suggests that the extent of IHB that older generation Chinese employees receive from younger generation employees will lead to loss of mianzi, which will then result in reduced perceived generational guanxi, increased intended social isolation, and reduced intention to share task-related knowledge with the younger generation employees. The paper also proposes that perceived generational guanxi and intended social isolation will mediate the relationship between loss of mianzi and intention to share task-related knowledge with younger generation employees.

Practical implications

– Because mianzi is an important cultural feature in Chinese societies, this paper provides four implications. First, younger generation employees could preserve and/or enhance older generation employees’ mianzi using less powerful messages. Second, younger generation employees should initiate task behaviors involving seeking opinions and expertise from older generation employees before exhibiting IHB. Third, mangers could reduce the negative impact of generational differences by establishing generational mentoring relationships between younger and older generation employees. Finally, younger generation employees could preserve and/or enhance older generation employees’ mianzi by playing the role of an informal subordinate rather than a problem solver when exhibiting IHB.

Originality/value

– This paper is the first study exploring consequences of IHB from the perceptive of older generation IHB recipients in the Chinese context.

Millennials in the Workplace: A Conceptual Analysis of Millennials’ Leadership and Followership Styles

The Millennial Generation in the workplace has received increasing attention as it has been shown that Millennials demonstrate different attitudes, values, beliefs, and aspirations in the workplace compared to the previous generations. Although a number of studies have devoted to the investigation of Millennials, the leadership and followership styles exhibited by Millennials at work has been largely neglected. Thus, the major purpose of this article is to develop a conceptual framework that explores Millennials’ leadership and followership styles in the workplace. By examining Millennials in the context of leadership and followership, this article provides important theoretical and practical implications.

Coherent electron transport in a Si quantum dot dimer

We show that the coherence of charge transfer through a weakly coupled double-dot dimer can be determined by analyzing the statistics of the conductance pattern, and does not require a large phase coherence length in the host material. We present an experimental study of the charge transport through a small Si nanostructure, which contains two quantum dots. The transport through the dimer is shown to be coherent. At the same time, one of the dots is strongly coupled to the leads, and the overall transport is dominated by inelastic cotunneling processes.

17Beta-estradiol inhibits oxidized low density lipoprotein-induced generation of reactive oxygen species in endothelial cells

Increase of intracellular reactive oxygen species (ROS) has been proposed to cause endothelial injury, and oxidized LDL (oxLDL) actions are associated with an early increase of ROS. Estrogen protects vascular cells partly via its antioxidant effects and by preventing lipid peroxidation. However, whether it can inhibit oxLDL-induced stimulation of ROS generation in endothelial cells is unknown. We utilized the fluorescent dye (DCFH-DA) to measure ROS generation and compared the stimulant effect of tert-butylhydroperoxide (TBH) and oxLDL in human umbilical vein endothelial cells (HUVECs). We found that TBH, H2O2, and oxLDL rapidly stimulated ROS generation, and in a dose-dependent manner with TBH. A concentration of estrogen effective in preventing lipid peroxidation was employed either by pretreatment of cells 18 h prior to or by direct co-incubation (30 min) with HUVEC and oxLDL. Estrogen (54 microM) pretreatment significantly suppressed both TBH- and oxLDL- induced stimulation of ROS generation. Both 1 and 54 microM concentration of estrogen could directly inhibit oxLDL-induced ROS production in HUVECs. Thus, either 18 h pretreatment or 30 min co-incubation with estrogen reduced stimulated ROS generation, suggesting that both cellular and direct actions of estrogen may be involved.

Sacral parasite conjoined twin

BACKGROUND

A variant of conjoined twins is one in which one twin is incomplete.

CASE

A female infant was born vaginally at 40 weeks' gestation to a healthy primipara. No important abnormalities were noted during prenatal examinations. The infant was fully developed in all external aspects except for a parasitic body conjoined with her sacrococcygeal region. Separated by operation 2 weeks after birth, the parasite contained lower limbs, adipose tissue, muscles, and a bowel sac. Over 4 years of observation, no abnormalities have been found since the operation.

CONCLUSION

Obstetricians should be aware of the existence of a parasite twin during prenatal examinations and of the importance of the differential diagnosis of parasite and teratoma, a neoplasm with malignant potential.

Magnetically induced reconstruction of the ground state in a few-electron Si quantum dot

We report unexpected fluctuations in the positions of Coulomb blockade peaks at high magnetic fields in a small Si quantum dot. The fluctuations have a distinctive sawtooth pattern: as a function of magnetic field, linear shifts of peak positions are compensated by abrupt jumps in the opposite direction. The linear shifts have large slopes, suggesting formation of the ground state with a nonzero angular momentum. The value of the momentum is found to be well defined, despite the absence of the rotational symmetry in the dot.

Regional expression of inducible nitric oxide synthase in the kidney in dogs with unilateral ureteral obstruction

PURPOSE

In the early stage of unilateral ureteral obstruction total renal blood flow increases but medullary blood flow decreases, exacerbating medullary tissue hypoxia. We examined the expression of inducible nitric oxide synthase, a product of a hypoxia sensitive gene, in the cortex and medulla in dogs with unilateral ureteral obstruction for 21 hours.

MATERIALS AND METHODS

Hemodynamic and clearance experiments were performed after release of ureteral obstruction in 6 dogs with unilateral ureteral obstruction, followed by Western blot analysis of nitric oxide synthase and immunohistochemistry.

RESULTS

Ureteral obstruction raised mean ureteral pressure plus or minus standard error to 35.0 +/- 7.2 mm. Hg. In dogs with unilateral ureteral obstruction mean renal blood flow was 116 +/- 10 ml. per minute, lower than the 213 +/- 22 ml. per minute in sham operated dogs (p <0.01). After unilateral ureteral obstruction release the mean glomerular filtration rate was 9.5 +/- 2.1 ml. per minute, lower than the 27.3 +/- 1.8 ml. per minute in the contralateral unobstructed kidney (p <0.01). Western blot analysis showed that mean nitric oxide synthase/beta-actin in the cortex of the obstructed kidney was 0.04 +/- 0.01 densitometry units, lower than 0.11 +/- 0.02 densitometry units in the unobstructed contralateral kidney (p <0.05). In contrast, mean nitric oxide synthase/beta-actin in the medulla of the obstructed kidney was 1.29 +/- 0.33 densitometry units, greater than the 0.34 +/- 0.03 densitometry units in the unobstructed kidney (p <0.05). Immunohistochemistry revealed that the increased expression of nitric oxide synthase protein was localized to the endothelium of the vasa recta.

CONCLUSIONS

Unilateral ureteral obstruction enhances nitric oxide synthase expression in the medulla but not in the cortex. This increased expression in the medulla may be the result of increased medullary hypoxia in unilateral ureteral obstruction, possibly contributing to medullary hyperemia after unilateral ureteral obstruction release.

Hospital ownership and cost and quality of care: is there a dime's worth of difference?

Nonprofit organizations may predominate when output quality is difficult to monitor. Hospital care has this characteristic. This study compared program cost and quality of care for Medicare patients hospitalized following onset of four common conditions by hospital ownership. Payments on behalf of Medicare patients admitted to for-profit hospitals during the first 6 months following a health shock were higher than for those admitted to other hospitals. With quality measured in terms of survival, changes in functional and cognitive status, and living arrangements, we found no differences in outcomes by hospital ownership.

Contaminated site remedial investigation and feasibility removal of chlorinated volatile organic compounds from groundwater by activated carbon fiber adsorption

Groundwater contaminated by dense, non-aqueous phase liquids (DNAPLs) such as chlorinated solvents has become a serious problem in some regions of Taiwan. The sources of these contaminants are due to industrial discharges. These chlorinated volatile organic compounds (VOCs) have been proven to be carcinogenic to humans. The groundwater is used for domestic drinking water supply in some cities of Taiwan and the severely contaminated groundwater has to be treated in order to meet the requirement of drinking water standards. This study covers two areas of work. In the first part, polluted groundwater samples were collected from the contaminated site and analytical results indicated measurable concentrations of 12 representative chlorinated VOCs in water samples. The primary VOCs detected included trichloroethene (TCE), tetrachloroethene (PCE), 1,1,2-trichloroethane (1,1,2-TCA), and 1,1-dichloroethene (1,1-DCE). Second, to remove VOCs groundwater was treated using adsorption on activated carbon fiber (ACF). This involved pumping groundwater through vessels containing ACF. Most VOCs, including TCE, PCE, 1,1,2-TCA, and DCE, were readily adsorbed onto ACF and are removed from the water stream. Our study showed that the technology was able to significantly reduce chlorinated VOCs concentrations in groundwater.

The price elasticity of opium in Taiwan, 1914-1942

Between 1895 and 1945, the Japanese colonial government virtually eliminated opium use in Taiwan by licensing and treating existing users, prohibiting sales to others, and raising the price. We evaluate these policies using a two-part model to describe the fraction of the population using opium and consumption among users, and the rational addiction model by Becker et al. (1991). We confirm that opium is addictive and find no evidence supporting the rational addiction hypothesis. Demand is price-elastic with estimated short- and long-run demand elasticities of -0.48 and -1.38. These results have implications for control of other addictive substances.

Neuro-ophthalmic complications of raised intracranial pressure, hydrocephalus, and shunt malfunction

1. Ophthalmic signs are important for the diagnosis and management of elevated intracranial pressure. 2. Visual loss, visual field loss, dorsal midbrain syndrome, and acute papilledema may occur well in advance of ventricular dilation. 3. For younger patients with hydrocephalus, amblyopia should be checked for, and the absence of papilledema does not ensure normal intracranial pressure. 4. Treatment should be delivered to control intracranial pressure and preserve vision in a timely fashion.

Renal actions of endothelin-1 under endothelin receptor blockade by BE-18257B

PURPOSE

Endothelin-1 (ET-1), a peptide produced by the vascular endothelium, causes profound renal vasoconstriction by binding to ET-A receptors. The present study examined the renal actions of ET-1 after ET-A receptors were blocked by BE-18257B to unmask the functions of ET-B receptors.

MATERIALS AND METHODS

Renal hemodynamics and clearance measurements were obtained in anesthetized dogs after intrarenal infusion of BE-18257B at 100 ng./kg./min. (Group 1), after intrarenal infusion of ET-1 at 2 ng./kg./min. (Group 2), or after intrarenal infusion of ET-1 superimposed on BE-18257B (Group 3).

RESULTS

In Group 1, BE-18257B infusion did not alter arterial pressure, renal blood flow (RBF), GFR or tubular function. In Group 2, ET-1 infusion led to a significant decrease in RBF and GFR (37 and 40%, respectively) without altering arterial pressure. Urinary volume and sodium excretion were not changed but osmolality decreased significantly. In Group 3, BE-18257B infusion significantly attenuated the decrease in RBF caused by ET-1 and increased GFR by 40% without altering arterial pressure, associated with significant diuresis and natriuresis.

CONCLUSION

Renal vasoconstriction caused by ET-1 is attenuated by ET-A receptor blockade with BE-18257B, which unmasks the hemodynamic and tubular actions of ET-B receptors. As a result, it limits the ET-1 induced decrease in RBF and raises GFR, and leads to a diuresis and natriuresis.

Activation of endothelium-derived relaxing factor system in acute unilateral ureteral obstruction

PURPOSE

To investigate the effects of 1-arginine, a substrate for nitric oxide (NO) synthase, on renal hemodynamics in acute ureteral obstruction (UUO).

MATERIALS AND METHODS

Renal blood flow (RBF) and ureteral pressure (UP) were measured in anesthetized dogs with or without UUO.

RESULTS

In 9 dogs (Group 1), RBF was 212 +/- 13 ml./min. before UUO, and significantly increased to 302 +/- 18 and 268 +/- 9 ml./min. at 90 and 140 min. post-UUO, respectively, associated with a marked increase in UP from 3 +/_ 1 mm. Hg to 73 +/- 5 and 83 +/-2 mm. Hg at 90 and 140 min. post-UUO, respectively. In 6 dogs (Group 2) prostaglandin synthesis was inhibited with meclofenamate (5 mg./kg., i.v.). After UUO, RBF did not change significantly and the increase in UP was markedly attenuated when compared with Group 1, as UP rose only to 27 +/-3 and 34 +/- 4 mm. Hg at 90 and 140 min. post-UUO, respectively. In 6 dogs pre-treated with meclofenamate, L-arginine was infused into the renal artery at 5 mg./kg./min. at 90 min. after UUO (Group 3). Prostaglandin synthesis inhibition prevented renal vasodilation after UUO and significantly attenuated the increase in UP. Upon infusion of L-arginine, RBF and UP rose sharply from 202 +/- 16 ml./min. and 24 +/- 6 mm. Hg to 264 +/- 22 ml./min. and 70 +/- 4 mm. Hg, respectively, at 140 min. post-UUO (p <0.001), values approaching those in Group 1. In sham-operated dogs, L-arginine infusion did not alter RBF in dogs with or without pretreatment with meclofenamate.

CONCLUSION

In UUO the L-arginine-NO pathway is activated, contributing to renal vasodilation and a marked increase in UP.

Contribution of endothelin-1 to renal vasoconstriction in unilateral ureteral obstruction: reversal by verapamil

PURPOSE

In unilateral ureteral obstruction (UUO) vasoconstriction occurs both during and after release of UUO. ET-1, an endogenous peptide, causes marked vasoconstriction mediated by an increase in cytosolic calcium. We measured renal output of endothelin-1 (ET-1) in dogs with UUO and examined if the renal vasoconstriction that persisted after release of UUO could be reversed by a calcium antagonist, verapamil.

MATERIALS AND METHODS

Hemodynamic and clearance experiments were performed in anesthetized mongrel dogs in three groups. Group I consisted of 9 dogs with sham-operation. Group 2 consisted of 7 dogs in whom ureteral obstruction was released 1.9 hours after UUO. Group 3 consisted of 5 dogs in whom verapamil was infused into the renal artery at two doses (5 and 10 microg./min., respectively) after release of UUO of 19-hour duration. ET-1 concentrations (measured by radioimmunoassay) were determined for renal venous and arterial plasma.

RESULTS

In Group 1 renal venous plasma ET-1 level was 16.7 +/- 2.2, significantly lowered than 22.8 +/- 3.2 pg./ml. in arterial plasma, indicating a net clearance of ET-1. In Group 2 and 3, renal venous plasma ET-1 levels (28.2 +/- 5.2 and 27.2 +/- 2.4 pg./ml., respectively) were significantly greater than those in arterial plasma (24.2 +/- 5.7 and 17.4 +/- 0.8 pg./ml., respectively), indicating a net output of ET-1 in the kidney, In addition, renal vasoconstriction occurred in Groups 2 and 3 as indicated by significantly lower renal blood flow and GFR than those in Group 1. In Group 3, intrarenal infusion of verapamil at two doses did not change arterial pressure but caused an ipsilateral, significant increase in RBF (from 132 +/- 4 17 to 1.84 +/- 19 and 180 +/- 16 ml./min., respectively) and dose-dependent increases in GFR (from 12 +/- 2 to 25 +/- 3 and 38 +/- 7 ml./min., respectively), associated with a profound dose-dependent ipsilateral diuresis and natriuresis.

CONCLUSION

Profound renal vasoconstriction in UUO was associated with an increase in renal production of ET-1, possibly contributing to renal vasoconstriction, and was reversed by intrarenal infusion of verapamil.

Molecular cloning and analysis of a HSP (heat shock protein)-like 42 kDa antigen gene of Mycoplasma hyopneumoniae

The recombinant clone expressing the 42 kDa protein (P42) of Mycoplasma hyopneumoniae in Escherichia coli was analyzed. The 4.4 kb HindIII-Xmal DNA fragment expressing the p42 gene product encodes three ORFs: p42 and p16 in the forwarding strand, p24 in the reverse strand. Sequence comparisons revealed that p42 could be part of a p65 gene, and has 62% identities with Mycoplasma genitalium HSP70 gene and 56% identities with Bacillus subtilis dnaK gene; p16 and p24 genes share 73% and 47% identities with Erysipelothrix rhusiopathiae dnaJ gene and Pseudomonas fluorescens uvrC gene, respectively. Further analysis demonstrated that P42 is indeed a heat shock protein and the monospecific antibodies against P42 can block the growth of Mycoplasma hyopneumoniae.

A Silicon Single-Electron Transistor Memory Operating at Room Temperature

A single-electron memory, in which a bit of information is stored by one electron, is demonstrated at room temperature. The memory is a floating gate metal-oxide-semiconductor transistor in silicon with a channel width ( approximately 10 nanometers) smaller than the Debye screening length of a single electron and a nanoscale polysilicon dot ( approximately 7 nanometers by 7 nanometers) as the floating gate embedded between the channel and the control gate. Storing one electron on the floating gate screens the entire channel from the potential on the control gate and leads to (i) a discrete shift in the threshold voltage, (ii) a staircase relation between the charging voltage and the shift, and (iii) a self-limiting charging process. The structure and fabrication of the memory should be compatible with future ultralarge-scale integrated circuits.

Reversal of trimethoprim-induced antikaliuresis

High-dose trimethoprim-sulfamethoxazole (TMP-SMX) causes hyperkalemia, thought to result from TMP-induced blockade of amiloride-sensitive Na(+)-channels in the distal nephron. The present study was performed in anesthetized dogs to determine if increasing distal sodium delivery affects this antikaliuretic effect. In Group 1, intrarenal infusion of vehicle did not alter renal function. In Group 2, i.v. infusion of amiloride led to diuresis, natriuresis and antikaliuresis associated with a reduction of the transtubular potassium gradient (TTKG) in both kidneys. Intrarenal infusion of TMP (0.2 mg/kg/min) into the left kidney did not further alter these parameters. In groups 3 and 4, intrarenal infusion of TMP caused an ipsilateral diuresis, natriuresis, antikaliuresis and a reduction in (TTKG) without affecting the contralateral kidney. The TMP infusion was followed by furosemide (20 mg i.v.) in group 3 and acute saline loading in group 4. Despite continuous TMP infusion, both furosemide and saline loading reversed the antikaliuretic effect of TMP in the ipsilateral kidney and was associated with a similar kaliuresis, diuresis, natriuresis and decrease in urine osmolality in both kidneys. The TTKG following furosemide or saline loading increased in the ipsilateral kidney and decreased in the contralateral kidney. In all groups the systemic and renal hemodynamics remained unchanged. These results suggest that acute administration of TMP inhibits the amiloride-sensitive Na(+)-channel and K+ secretion in the distal nephron. Maneuvers that increase distal Na+ delivery can abrogate TMP's antikaliuretic effect due, in part, to an increase of the low TTKG observed with TMP.

Tissue-specific regulation by vitamin D status of nuclear and mitochondrial gene expression in kidney and intestine

Vitamin D is responsible, through the actions of its metabolite, 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25-(OH)2D3], for the generation of a wide array of biological responses, particularly in the intestine, kidney, and bone. 1 alpha,25-(OH)2D3 is known to interact with its nuclear receptor to mediate the regulation of gene transcription. Although many genes and gene products have been shown to be regulated by 1 alpha,25-(OH)2D3 (e.g. calbindin-D28K in the intestine and kidney; collagen, osteocalcin,and osteopontin in bone), their recognition has been largely the result of empirical testing. In this report we have used subtractive hybridization analysis of complementary DNA libraries prepared from messenger RNA (mRNA) isolated from the intestine and kidney of vitamin D-replete or vitamin D-deficient chicks to identify genes for novel proteins whose steady state mRNA levels are regulated by dietary vitamin D status. In the kidney we observed the down-regulated expression of at least seven mitochondrially encoded transcripts and the up-regulated expression of five nuclear encoded genes, two of which are metallothionein and the beta-subunit of aldolase. In the intestine, six mitochondrially encoded transcripts are up-regulated, and seven nuclear encoded transcripts were either up- or down-regulated. Thus, in addition to identifying new nuclear encoded genes whose mRNAs are regulated by vitamin D status, our approach has demonstrated the tissue-specific regulation of mitochondrial gene expression in the intestine and kidney.

Pulmonary metastasis of hepatocellular carcinoma associated with transarterial chemoembolization

Recent advances in both diagnosis and treatment of hepatocellular carcinoma have improved the prognosis and changed the clinical significance of the subsequently increasing distant metastases. Pulmonary metastasis of hepatocellular carcinoma associated with transcatheter arterial chemoembolization has rarely been reported.

METHODS

To evaluate whether transcatheter arterial chemoembolization increases the risk of pulmonary metastasis of hepatocellular carcinoma, 230 patients were studied. Among them, 156 received transcatheter arterial chemoembolization with an interval of 12-16 weeks, the remaining 74 cases refused transcatheter arterial chemoembolization and received only conservative treatment. All patients were followed up with chest x-ray films taken before transcatheter arterial chemoembolization, during admission or in the out-patient department. The mean follow-up interval was 3.37 +/- 1.51 months.

RESULTS

Pulmonary metastasis was found in 25.6% (40/156) and 8.1% (6/74) of the patients with and without transcatheter arterial chemoembolization (p = 0.002). The median interval between initial diagnosis and pulmonary metastasis was 3.39 +/- 0.08 and 11.72 +/- 2.91 months among patients with and without transcatheter arterial chemoembolization (p = 0.001). The mean age, sex, existence of cirrhosis, severity of cirrhosis, presence of collateral arterial circulation, amount of lipiodol and agent of anti-cancer drugs were not associated with the development of lung metastasis. However, factors predisposing to lung metastasis included: solitary tumor with tumor size > 10 cm, multiple tumors with main tumor > 5 cm or diffuse hepatocellular carcinoma, intrahepatic portal vein thrombosis, arterioportal or arteriovenous shunt, and the presence of incomplete tumor necrosis after transcatheter arterial chemoembolization (especially combined with necrotic area > 50% main tumor size).

CONCLUSIONS

Pulmonary metastasis associated with transcatheter arterial chemoembolization has a strong adverse impact on patient survival.

Prevalence of antibodies to hepatitis C virus in patients with nonalcoholic fatty liver

BACKGROUND

Nonalcoholic fatty liver can be caused by obesity, diabetes mellitus, hyperlipidemia or nonalcoholic steatohepatitis. Hepatitis C viral infection can also cause macrovesicular steatosis and such inflammation of the liver as nonalcoholic steatohepatitis. To determine whether the prevalence of anti-HCV is higher in patients with nonalcoholic fatty liver, this clinical study was undertaken; we also tried to detect which factors predict the presence of anti-HCV in these patients.

METHODS

The study included 205 nonalcoholic fatty liver patients (122 males and 83 females) with a mean age of 46.5 years, diagnosed by ultrasonic examination, on whom anti-HCV antibody tests were then done.

RESULTS

Eleven cases (5.4%) were anti-HCV positive with a higher mean age of 56.4 +/- 11.1 years (p < 0.05). Anti-HCV positive patients had higher serum AST and ALT levels than negative patients (95 +/- 59 U/L, 166 +/- 116 U/L vs. 34 +/- 26 U/L, 51 +/- 43 U/L; p < 0.05), while anti-HCV negative patients had higher mean body weight (124 +/- 15% vs. 114 +/- 11% of IBW) and serum cholesterol levels (202 +/- 41 mg/dl vs. 159 +/- 45 mg/dl). There was no statistical difference between anti-HCV positive and negative groups in clinical parameters including gender, presence of HBsAg, history of DM, operation, blood transfusion, oral contraceptive usage, and cancer with or without chemotherapy. The prevalence of anti-HCV increased with age from 1.8% in the fourth and fifth decades to 25% in the eighth decade. The prevalence of anti-HCV was 1.4% (1 case) in 72 fatty liver with normal biochemical tests and 7.5% (10 cases) in 133 cases with abnormal biochemical tests, a difference which was statistically marginally significant (p = 0.055). Those with ALT levels greater than three-fold the normal limit had a significantly higher anti-HCV prevalence rate (25.9%) than those with normal (1.4%) or mildly (2.8%) elevated ALT levels (p < 0.001). Logistic regression analysis revealed that only age and serum ALT levels were independent predictive factors for the presence of HCV infection.

CONCLUSIONS

Results revealed that the prevalence of anti-HCV in patients with nonalcoholic fatty liver was 5.4%, slightly higher than in the general population. Age and serum ALT level were the predictive factors for the presence of HCV infection.

Renal actions of endothelin-1 and endothelin-3: interactions with the prostaglandin system and nitric oxide

Endothelins (ET) possess both vasodilatory and vasoconstrictive properties. The renal actions of ET-1 and ET-3, as well as in vivo interactions of these two isopeptides with the prostaglandin and endothelium-derived relaxation factor/nitric oxide systems were studied in anesthetized dogs. The ETs were infused intrarenally at doses not affecting systemic hemodynamics. Both ET-1 and ET-3 induced an early transient renal vasodilation, followed by a prolonged vasoconstriction. Inhibition of nitric oxide synthase with NG-monomethyl-L-arginine completely abolished the renal vasodilation induced by either ET-1 or ET-3 and enhanced the vasoconstriction. Endothelin-1 was associated with an increase in the renal release of prostacyclin, while urinary thromboxane A2 was increased after ET-3 administration. Inhibition of cyclooxygenase (with indomethacin) augmented the renal vasoconstriction induced by ET-1, but inhibition of cyclooxygenase (with meclofenamate) abolished the ET-3-evoked vasoconstriction. Endothelin-1 showed little effects on urinary water and sodium excretion; however, ET-3 displayed significant diuretic and natriuretic effects, which were inhibited by nitric oxide synthase inhibition. These findings suggest that these two isopeptides activate the endothelial endothelium-derived relaxation factor/nitric oxide system, which elicits early renal vasodilation, whereas direct effects on the vascular smooth muscle leads to vasoconstriction. Endothelin-3 causes diuresis and natriuresis, possibly by inducing release of nitric oxide in medullary collecting duct cells.

Renal hemodynamics in acute unilateral ureteral obstruction: contribution of endothelium-derived relaxing factor

The increase in ureteral pressure after acute unilateral ureteral obstruction (UUO) is associated with an initial increase in renal blood flow (RBF). The present study examines the role of nitric oxide, a major endothelium-derived relaxing factor (EDRF), in UUO-induced renal hyperemia in anesthetized dogs. In Group 1, vehicle solution was infused into the left renal artery. In Group 2, nitric oxide formation from L-arginine was competitively inhibited by intrarenal infusion of N omega-monomethyl-L-arginine (L-NMMA) (50 micrograms/kg./min.) before UUO. In Group 3, L-arginine (2 mg./kg./min.) was infused together with L-NMMA (50 micrograms/kg./min.) into the renal artery. After UUO, ureteral pressure increased in all groups, averaging 69 mm.Hg. In Group 1, RBF at 10 and 20 minutes after UUO increased 7.9 +/- 1.6% and 16.5 +/- 5.2%, respectively, significantly greater than in Group 2 (1.2 +/- 1.6% and 2.4 +/- 1.5%). After L-NMMA was discontinued in Group 2, RBF increased 17%, reaching a level similar to that in Group 1. In Group 3, L-arginine infusion abolished the effects of L-NMMA, and RBF was similar to that in Group 1 at all postobstructive intervals. Our data indicate that release of nitric oxide in the kidney is augmented by UUO and mediates the early renal hyperemia induced by UUO.

Spontaneous rupture of the liver associated with pregnancy: a report of two cases

Spontaneous rupture of the liver associated with pregnancy is a rare and grave complication, usually occurring in preeclampsia or eclampsia. Two cases of ruptured subcapsular hematoma of the right liver during pregnancy are reported. The first case was a 19-year-old woman who had suffered from epigastralgia and absent fetal heart beat in the 32nd week of gestation. The second case was a 31-year-old female who complained of nausea and right upper quadrant pain in the 35th week of pregnancy. Both had preeclampsia, and developed shock with disseminated intravascular coagulation soon after admission. Both received surgery and were found to have ruptured hematoma over the right liver. Finally, the first patient died of renal failure, but the second survived because preoperative diagnosis had been exact. Greater suspicion, then awareness of diagnosis can lead to better timing of surgery and an improved prognosis for mother and child.

Occupational hand dermatoses of hairdressers in Tainan City

OBJECTIVES

To determine the prevalence, clinical features, and patterns of hand dermatosis in hairdressers in Tainan, Taiwan, and to examine the associations between patterns of dermatosis and risk factors such as job description, work exposure, and sensitisation to common allergens.

METHODS

Interviews, examinations, and patch tests of the hairdressers from nine hairdressing stores randomly selected from Tainan City. Patch test agents included 41 substances with common allergens, shampoo preservatives, hair dyes, permanent waving and bleaching agents.

RESULTS

98 hairdressers finished the examination, 83% of them had occupational dermatosis and 32% had scissor induced scars or wounds. Most of the dermatoses belonged to either dry metacarpophalangeal dermatitis or eczema of the fingers. 44% of the hairdressers showed positive skin reaction to one or more patch test agents. The patch test results were different from previous reports in that the most common allergens were nickel, thimerosal, Captan, Kathon CG, and fragrance mix, and that the sensitivity to hair dye and permanent wave ingredients were low. The dry metacarpophalangeal dermatitis was associated with exposure to shampoo, and the eczema of the fingers with skin sensitivity to patch test agents.

CONCLUSION

Hairdressers in Tainan City had a high prevalence of dermatoses including traumatic wounds, and allergic and irritant contact dermatitis. The rates of sensitivity to some of the common sensitising agents were different from previous reports.

Evidence that inactive p42 mitogen-activated protein kinase and inactive Rsk exist as a heterodimer in vivo

Mitogen-activated protein kinases (MAP kinases) are active only when phosphorylated. Here we examine whether the activation of Xenopus p42 MAP kinase might involve changes in its association with other proteins as well as changes in its phosphorylation state. We find that when p42 MAP kinase is phosphorylated and active, it is monomeric, and that when p42 MAP kinase is nonphosphorylated and inactive, about half of it is monomeric and half is a component of a 110-kDa complex. We identify Rsk, an 82-kDa protein kinase that can be phosphorylated and partially activated by p42 MAP kinase, as being specifically associated with inactive p42 MAP kinase. It is possible that the complex of inactive p42 MAP kinase and inactive Rsk acts as a single signal reception particle and that the activation of the two kinases may be better described as a fork in a bifurcating signal transduction pathway than as successive levels in a kinase cascade.

Inflammatory fibroid polyp of the jejunum causing intussusception: a case report

Inflammatory fibroid polyp is a rare benign lesion of the gastrointestinal tract. This report concerns a 56-year-old female who presented with intermittent abdominal pain, vomiting and diarrhea; she had had partial intestinal obstruction over a period of two months. Plain abdomen showed dilatation of the small bowels. Abdominal echo revealed intussusception of the small intestine. During exploratory laparotomy a polypoid dumb-bell shaped polyp was noted as the leading point of the jejunojejunal intussusception, segmental resection of the jejunum was performed. Histological features of the polyp met the diagnosis of inflammatory fibroid polyp.

Hyperkalemia with high-dose trimethoprim-sulfamethoxazole therapy

In a patient with the acquired immunodeficiency syndrome, a progressive increase in the serum potassium concentration occurred with high-dose trimethoprim-sulfamethoxazole (TMP-SMX) therapy for Pneumocystis carinii pneumonia. In this patient, factors known to alter transcellular potassium shifts to induce hyperkalemia were not present. There was no evidence of glucocorticoid or mineralocorticoid insufficiency at the time of hyperkalemia, while the transtubular potassium gradient decreased. The hyperkalemia resolved spontaneously on discontinuation of TMP-SMX therapy, suggesting that this electrolyte abnormality is related to altered renal tubular secretion of potassium as a consequence of the high-dose TMP-SMX therapy.

Trimethoprim-sulfamethoxazole induces reversible hyperkalemia

OBJECTIVE

To determine the effect of trimethoprimsulfamethoxazole (Tmp-Smx) on serum potassium concentration.

DESIGN

Retrospective cohort study.

SETTING

An urban teaching hospital.

PATIENTS

Fifty-one persons hospitalized for symptomatic infection with human immunodeficiency virus (HIV). Twenty-five patients who were taking high-dose Tmp-Smx (trimethoprim 20 mg/kg per day; sulfamethoxazole, 100 mg/kg per day) for Pneumocystis carinii pneumonia were the study group. Twenty-six patients who had not received the drug were the control group. Patients who received potassium supplements, those taking medications known to alter potassium homeostasis or renal function, or those with a serum creatinine level more than 186 mumol/L were excluded.

MEASUREMENTS AND MAIN RESULTS

Serum potassium concentration in the study group was 4.1 +/- 0.1 mmol/L (mean +/- SE) and increased by 1.1 mmol/L (Cl, 0.8 to 1.5 mmol/L) (P < 0.0001) 9.8 +/- 0.5 days after starting Tmp-Smx therapy. Patients followed longitudinally showed a progressive increase in serum potassium levels during therapy and a progressive decline after discontinuing Tmp-Smx. Blood urea nitrogen and serum creatinine levels increased mildly from 4.3 +/- 0.5 mmol/L and 85 +/- 6 mumol/L to 6.4 +/- 0.7 mmol/L and 113 +/- 8 mumol/L, respectively. The serum potassium level in the control group was 4.3 +/- 0.1 mmol/L and remained unchanged during hospitalization.

CONCLUSIONS

High-dose Tmp-Smx therapy used for the treatment of P. carinii pneumonia in HIV-infected patients leads to an increase in the serum potassium concentration and may result in life-threatening hyperkalemia. Patients receiving high doses of Tmp-Smx require close monitoring of their serum potassium concentration, particularly 7 to 10 days after the start of therapy.

The stimulatory effect of insulin on diacylglycerol generation in adipocyte membranes from ob/ob mice is impaired by growth hormone

Physiologically, the action of insulin on carbohydrate and lipid metabolism is opposed by several hormones, including glucocorticoids, glucagon, catecholamines, and pituitary GH. Perhaps least is known about the mechanism(s) involved in the antiinsulin action of GH. Since the generation of diacylglycerol (DAG) appears to be an early event in the insulin-signaling cascade, it was of interest to determine whether GH would interfere with this effect of insulin. Experiments were conducted to determine whether insulin would stimulate the generation of DAG in adipocytes of the obese (ob/ob) mouse, and whether this response could be blocked by the diabetogenic GH derivative S-carboxymethylated human GH (RCM-hGH). Isolated adipocytes of the ob/ob mouse were used for these studies, because unlike normal rodents, the ob/ob mouse responds predictably to the antiinsulin action of GH. Insulin produced a rapid biphasic increase in the amount of DAG in a crude membrane fraction of the adipocytes. The first peak in DAG mass occurred within 5 min of exposure of the cells to insulin, and the second peak occurred after 30 min. The first peak in DAG mass did not occur in adipocytes that had been incubated with pertussis toxin before exposure to insulin. Also, adipocytes isolated from ob/ob mice that had been treated with RCM-hGH failed to respond to insulin with an increase in DAG mass. RCM-hGH blocked both the first and second insulin-induced peaks in DAG mass within 6 h of its administration. This is the time at which ob/ob mouse adipocytes exhibit increased insulin resistance in response to RCM-hGH. Neither exposure to insulin nor treatment with RCM-hGH had any appreciable effect on the fatty acid composition of the DAG present in the adipocyte membranes. These findings are compatible with the idea that GH produces some defect in the insulin-signaling cascade that is proximal to the events that result in the generation of DAG in the adipocyte.

The renal hemodynamic response to endothelin in chronic cyclosporine-treated dogs

Use of the immunosuppressive agent cyclosporine A (CyA) is limited by its associated nephrotoxicity, characterized by an increase in renal vascular resistance (RVR) and reductions in renal blood flow (RBF) and glomerular filtration rate (GFR). The vascular endothelium produces vasoactive substances including endothelium derived relaxation factor (EDRF) and endothelin (ET), which modulate vascular tone. Since CyA has been shown to damage the endothelium, we examined the renal hemodynamic response to intrarenal ET infusion (4 micrograms./kg./minute) in chronic cyclosporine-treated dogs. Prior to ET infusion, CyA-treated dogs had a lower RBF and a greater RVR than normal dogs. In normal dogs, after ET infusion RVR increased from 30.24 +/- 0.64 to 44.60 +/- 1.66 mmHg./ml./minute (p < 0.001), RBF decreased from 4.26 +/- 0.28 to 2.90 +/- 0.30 ml./min./g. (p < 0.001) and GFR decreased from 50.20 +/- 5.90 to 36.50 +/- 7.90 ml. per minute (p < 0.001). In contrast, there was no change in RBF, GFR and RVR after intrarenal ET infusion in CyA-treated dogs. Prior to ET infusion, arterial plasma ET concentration was 5.0 +/- 1.1 pg./ml. in CyA-treated dogs, similar to 7.5 +/- 1.4 pg./ml. in normal dogs, and was not significantly altered in either group after intrarenal ET infusion. We conclude that ET may not contribute to the increased RVR in chronic cyclosporine nephrotoxicity, and suggest a vascular toxicity of CyA, rendering renal vessels unresponsive to the vasoconstrictive effect of ET.

Inhibition of c-Jun DNA binding by mitogen-activated protein kinase

Here we demonstrate that partially purified Xenopus p42 mitogen-activated protein (MAP) kinase phosphorylates bacterially expressed human c-Jun at a single site, serine 243. Several lines of evidence argue that this phosphorylation is due to p42 MAP kinase itself rather than some contaminating species. Phosphorylation of serine 243 markedly decreases the binding of c-Jun to oligonucleotides containing the 12-O-tetradecanoylphorbol-13-acetate response element. These findings suggest that MAP kinase may play a role in the down-regulation of c-Jun or in the cycle of transcriptional initiation and elongation.

Failure of atrial natriuretic peptide to induce natriuresis in aortocaval fistula dogs

Creation of an aortocaval fistula (ACF) in dogs induces salt and water retention, activation of the renin-angiotensin and adrenergic nervous systems and renal papillary ischemia associated with high levels of circulating atrial natriuretic peptide (ANP). The effects of intrarenal ANP (1.2 micrograms/min) infusion on systemic and renal hemodynamics, renal excretory function, renal output of renin and norepinephrine (NE) and papillary plasma flow (PPF) were studied in both normal and ACF dogs. ANP did not alter systemic hemodynamics in either group, but led to a significant increase in renal blood flow (RBF), glomerular filtration rate (GFR), urine flow rate (V), sodium excretion (UNaV) and fractional excretion of sodium (FENa), and a significant decrease in renal vascular resistance (RVR) and urine osmolality (UOsm) in normal dogs. GFR, RBF, RVR, V, UNaV, FENa and UOsm remained unchanged, however, in ACF dogs. In ACF dogs, both renal renin and NE output were significantly greater during baseline and remained significantly greater following ANP infusion, associated with a significantly lower PPF compared with normal dogs. These data suggest that ACF dogs are resistant to the renal effects of ANP, which can neither mitigate the hormonal mediators of sodium retention nor reverse the papillary ischemia observed in this model.

Reversal of Na+ retention in chronic caval dogs by verapamil: contribution of medullary circulation

The effects of verapamil on papillary plasma flow (PPF) and Na+ excretion were studied in anesthetized chronic caval dogs with low cardiac output and Na+ retention. Infusion of verapamil into the left renal artery (5 and 10 micrograms.kg-1.min-1) caused a dose-dependent ipsilateral increase in renal blood flow and Na+ excretion (from 10 +/- 2 to 171 +/- 32 and 225 +/- 35 mu eq/min, respectively). PPF in the left kidney was 26.6 +/- 4.4 and was significantly greater than that measured in the contralateral kidney (13.3 +/- 2.4 ml.min-1.100 g-1) (P < 0.01). The natriuresis occurred independent of changes in cardiac output and peripheral vascular resistance. In a separate group of caval dogs in which stimulation of the renin-angiotensin and adrenergic systems was intensified with a tighter caval constriction, verapamil failed to induce renal vasodilation or natriuresis and PPF was not altered. Despite the disparate hemodynamic responses, verapamil stimulated renal production of both renin and prostaglandin E2 in both groups of caval dogs. We conclude that the ability of verapamil to induce papillary vasodilation may contribute to the natriuresis seen in the caval dog, in which the site of Na+ retention includes the loop of Henle.

The cellular and molecular regulation of 1,25(OH)2D3 production

The synthesis of 1,25(OH)2D3 is a critical control point in the regulation of calcium metabolism, and possibly in the growth and differentiation of a number of cell types. This paper reviews our current understanding of the regulation of this process at the cellular and molecular levels, with the emphasis on the mechanisms of feedback control 1,25(OH)2D3 itself, control of parathyroid hormone, the roles of cyclic AMP dependent protein kinase and protein kinase C, and the interaction between the various intracellular regulators of 1,25(OH)2D3 production.

Growth hormone inhibits activation of phosphatidylinositol phospholipase C in adipose plasma membranes: evidence for a growth hormone-induced change in G protein function

Pituitary growth hormone (GH) functions physiologically to oppose the actions of insulin on carbohydrate and lipid metabolism by interfering with metabolic events that occur after insulin binds to its receptor. Which postreceptor effects are involved is presently unknown. Recently, we found that insulin rapidly stimulates a phosphatidylinositol phospholipase C (PI-PLC) in adipose tissue of obese (ob/ob) mice and that this effect of insulin is blocked by treatment of the animals with S-carboxymethylated human GH (RCM-hGH), a derivative having mainly anti-insulin activity. The activation of this PI-PLC by insulin is also inhibited by pertussis toxin. Thus, this study was performed to examine whether the inhibitory effect of GH on the activation of this PI-PLC is exerted at the level of signal transmission by guanine nucleotide binding proteins (G proteins). We found that the nonhydrolyzable GTP analogue, guanosine 5'-[gamma-thio]triphosphate, stimulated basal PI-PLC activity in plasma membranes of adipose tissue of saline-treated ob/ob mice, but it did not stimulate the enzyme in adipose membranes from RCM-hGH-treated mice. Also, RCM-hGH treatment markedly inhibited pertussis toxin-catalyzed ADP ribosylation of G protein alpha subunits in the membranes, suggesting some modification of the G proteins by GH. Immunoblot analysis of adipose membranes from saline- and RCM-hGH-treated mice using antiserum AS/7 (anti-Gi1 alpha and anti-Gi2 alpha) or antiserum EC/2 (anti-Gi3 alpha) showed no difference in the amount of Gi alpha-like protein between the groups. These findings suggest that GH interferes with the ability of a putative Gi-like protein to mediate the activation of PI-PLC in adipose membranes without altering the expression of the G protein.

Renal actions of endothelin: interaction with prostacyclin

The renal actions of endothelin were examined by infusing it intrarenally in anesthetized dogs at 4 ng.min-1.kg-1 without affecting arterial blood pressure or cardiac output. Endothelin infusion caused a transient and significant increase in renal blood flow (RBF) by 13 +/- 2%, followed by large decreases in RBF and glomerular filtration rate (GFR; by 26 +/- 2 and 23 +/- 7%, respectively) but did not alter urine flow rate or absolute sodium excretion. After endothelin infusion, renal venous and arterial plasma 6-ketoprostaglandin F1 alpha increased from 250 +/- 58 and 117 +/- 31 to 1,044 +/- 249 and 617 +/- 211 pg/ml, respectively, and its renal output increased from 339 +/- 99 to 963 +/- 202 pg.min-1.g-1 (P less than 0.01 for all). The renal prostacyclin synthesis was augmented by endothelin without stimulating the renal renin release or norepinephrine output. Inhibition of prostaglandin synthesis with indomethacin partially prevented the early renal vasodilation induced by endothelin, which then caused a more pronounced decline in RBF and GFR (by 65 +/- 7 and 54 +/- 8%, respectively). With suppression of prostacyclin synthesis, inhibition of renin release by endothelin was observed. Thus the vasoconstrictive effects of endothelin on renal hemodynamics are significantly modified by its ability to enhance production of vasodilators, including prostacyclin.