Biosynthesis and secretion of pituitary hormones: dynamics and regulation

Production and secretion of hormones by the pituitary involve highly orchestrated intracellular transport and sorting steps. Hormone precursors are routed through a series of compartments before being packaged in secretory granules. These highly dynamic carriers play crucial roles in both prohormone processing and peptide exocytosis. We have employed the ACTH-secreting AtT-20 cell line to study the membrane sorting events that confer functionality (prohormone activation and regulated exocytosis) to these secretory carriers. The unique ability of granules to promote prohormone processing is attributed to their acidic interior. Using a novel avidin-targeted fluorescence ratio imaging technique, we have found that the trans-Golgi of live AtT-20 cells maintains a mildly acidic (approximately pH 6.2) interior. Budding of secretory granules causes the lumen to acidify to <pH 6.0, which is both necessary and sufficient to trigger SPC3-mediated proteolytic conversion of proopiomelanocortin to ACTH. Investigation of the pH regulatory mechanism indicates that the trans-Golgi and secretory granules maintain different pH values by distinct sorting of key membrane transporters. Mathematical modeling of our data suggests that the decreasing pH values of organelles of the regulated secretory pathway is established by gradually increasing the density of active H+ pumps from the ER to Golgi while concomitantly decreasing the H+ permeability from ER to Golgi to secretory granules. An in vitro assay was developed to study the formation of processing-competent secretory granules from their processing-incompetent precursor trans-Golgi compartment. Our data suggest that ARF1-mediated sorting of proton pumps and leaks during early stages of granule formation confers processing competency to the resulting organelle. Once formed, these young granules continue to undergo membrane remodeling which results in dynamic changes in their exocytotic behavior. Two SNAREs, VAMP4 and synaptotagmin IV, enter newly formed granules but are removed from the maturing granule membrane by vesicle budding. Sorting of these proteins is correlated with the acquisition of Ca2+-triggered exocytosis and a decrease in unregulated exocytotic rate. Thus, biosynthesis and secretion of pituitary hormones are dynamically regulated by intracellular sorting events that govern the functions of their secretory carriers.

Proton leak and CFTR in regulation of Golgi pH in respiratory epithelial cells

Work addressing whether cystic fibrosis transmembrane conductance regulator (CFTR) plays a role in regulating organelle pH has remained inconclusive. We engineered a pH-sensitive excitation ratiometric green fluorescent protein (pHERP) and targeted it to the Golgi with sialyltransferase (ST). As determined by ratiometric imaging of cells expressing ST-pHERP, Golgi pH (pH(G)) of HeLa cells was 6.4, while pH(G) of mutant (DeltaF508) and wild-type CFTR-expressing (WT-CFTR) respiratory epithelia were 6.7-7.0. Comparison of genetically matched DeltaF508 and WT-CFTR cells showed that the absence of CFTR statistically increased Golgi acidity by 0.2 pH units, though this small difference was unlikely to be physiologically important. Golgi pH was maintained by a H(+) vacuolar (V)-ATPase countered by a H(+) leak, which was unaffected by CFTR. To estimate Golgi proton permeability (P(H(+))), we modeled transient changes in pH(G) induced by inhibiting the V-ATPase and by acidifying the cytosol. This analysis required knowing Golgi buffer capacity, which was pH dependent. Our in vivo estimate is that Golgi P(H(+)) = 7.5 x 10(-4) cm/s when pH(G) = 6.5, and surprisingly, P(H(+)) decreased as pH(G) decreased.

Mechanisms of pH regulation in the regulated secretory pathway

A precise pH gradient between organelles of the regulated secretory pathway is required for sorting and processing of prohormones. We studied pH regulation in live endocrine cells by targeting biotin-based pH indicators to cellular organelles expressing avidin-chimera proteins. In AtT-20 cells, we found that steady-state pH decreased from the endoplasmic reticulum (ER) (pH(ER) = 7.4 +/- 0.2, mean +/- S.D.) to Golgi (pH(G) = 6.2 +/- 0.4) to mature secretory granules (MSGs) (pH(MSG) = 5.5 +/- 0.4). Golgi and MSGs required active H(+) v-ATPases for acidification. ER, Golgi, and MSG steady-state pH values were also dependent upon the different H(+) leak rates across each membrane. However, neither steady-state pH(MSG) nor rates of passive H(+) leak were affected by Cl(-)-free solutions or valinomycin, indicating that MSG membrane potential was small and not a determinant of pH(MSG). Therefore, our data do not support earlier suggestions that organelle acidification is primarily regulated by Cl(-) conductances. Measurements of H(+) leak rates, buffer capacities, and estimates of surface areas and volumes of these organelles were applied to a mathematical model to determine the H(+) permeability (P(H+)) of each organelle membrane. We found that P(H+) decreased progressively from ER to Golgi to MSGs, and proper acidification of Golgi and MSGs required gradual decreases in P(H+) and successive increases in the active H(+) pump density.

Cystic fibrosis transmembrane conductance regulator and H+ permeability in regulation of Golgi pH

This paper reviews experiments from this lab that have tested the hypothesis that pH of the Golgi (pH(G)) of cystic fibrosis (CF) airway epithelial cells is alkaline compared to normal, that this altered pH affects sialyltransferase and other Golgi enzymes controlling biochemical composition of the plasma membrane and that altered surface biochemistry increases bacterial binding. We generated a plasmid encoding a modified green fluorescence protein-sialyltransferase (GFP-ST) chimera protein that was pH-sensitive and localized to the Golgi when transfected into HeLa cells and also CF and normal or cystic fibrosis transmembrane conductance regulator- (CFTR)-corrected airway epithelial cells. Digital imaging microscopy of these Golgi-localized probes showed that there was no correlation between pH(G) (6.4-7.0) and the presence of CFTR, whether cells were in HCO(3)(-)/CO(2)-containing or in HCO(3)(-)/CO(2)-free solutions. Activation of CFTR by raising cell [cAMP] had no effect on pH(G). Thus, CFTR seemed not to be involved in controlling pH(G). Experiments on HeLa cells using an avidin-sialyltransferase chimera in combination with a pH-sensitive fluorescent biotin indicated that even in cells that do not express CFTR, Cl(-) and K(+) conductances of the Golgi and other organelle membranes were large and that pH(G) was controlled solely by the H(+) v-ATPase countered by a H(+) leak. A mathematical model was applied to these and other published data to calculate passive H(+) permeability (P(H+)) of the Golgi, endoplasmic reticulum, trans-Golgi network, recycling endosomes and secrety granules from a variety of cells. An organelle's acidity was inversely correlated to its calculated P(H+). We conclude that the CFTR plays a minor role in organelle pH regulation because other (Cl(-) and K(+)) channels are present in sufficient numbers to shunt voltages generated during H(+) pumping. Acidity of the Golgi (and perhaps other organelles) appears to be determined by the activity of H(+) pumps countered by H(+) leaks.

Perioperative antibiotic prophylaxis in urology

This report reviews recent studies on infectious complications and antibiotic prophylaxis in common urological instrumentation. As a result of variations in the definitions of infectious complications and inconsistencies in study design and risk factor analysis there is presently limited clear-cut evidence for giving definite standards regarding antibiotic prophylaxis for most urological interventions. The consequences are that patients may be exposed to unnecessary hazards and the healthcare system to additional costs. Nonetheless, most authors agree that patients should have sterile urine at urological instrumentation and that any other detected risk factor should be controlled. When antibiotic prophylaxis is considered, it should be timed properly before the intervention, which varies with the type of intervention and the choice of antibiotic, and should last for a limited period of time. In most common urological manipulations, correctly administered oral prophylaxis has been shown to be as effective as intravenous prophylaxis. A series of guidelines aimed at keeping the rates of healthcare-associated infections and the level of bacterial resistance as low as possible should, in combination with the rational use of antibiotics, be one of several marks of quality of a urological centre. To achieve this goal, new well-designed studies considering different regimens, risk factor analysis and economical analysis should be encouraged.

The mechanochemistry of V-ATPase proton pumps

The vacuolar H(+)-ATPases (V-ATPases) are a universal class of proton pumps that are structurally similar to the F-ATPases. Both protein families are characterized by a membrane-bound segment (V(o), F(o)) responsible for the translocation of protons, and a soluble portion, (V(1), F(1)), which supplies the energy for translocation by hydrolyzing ATP. Here we present a mechanochemical model for the functioning of the V(o) ion pump that is consistent with the known structural features and biochemistry. The model reproduces a variety of experimental measurements of performance and provides a unified view of the many mechanisms of intracellular pH regulation.

How Fo-ATPase generates rotary torque

The F-ATPases synthesize ATP using a transmembrane ionmotive force (IMF) established by the electron transport chain. This transduction involves first converting the IMF to a rotary torque in the transmembrane Fo portion. This torque is communicated from Fo to the F1 portion where the energy is used to release the newly synthesized ATP from the catalytic sites according to Boyer's binding change mechanism. Here we explain the principle by which an IMF generates this rotary torque in the Fo ion engine.

Energy transduction in the sodium F-ATPase of Propionigenium modestum

The F-ATPase of the bacterium Propionigenium modestum is driven by an electrochemical sodium gradient between the cell interior and its environment. Here we present a mechanochemical model for the transduction of transmembrane sodium-motive force into rotary torque. The same mechanism is likely to operate in other F-ATPases, including the proton-driven F-ATPases of Escherichia coli.

The use of a water extract from the bark of Choerospondias axillaris in the treatment of second degree burns

Burns are common in Vietnam, and because of economic constraints and limited resources for the import of appropriate treatments, the health authorities are obliged to rely on traditional herbal remedies. It is therefore essential to evaluate current drugs, one of which is the water extract of the bark of the tree Choerospondias axillaris. It has been used for many years in the Vietnam-Sweden hospital at Uong Bi in northern Vietnam. We assessed the efficacy of the remedy in an open, randomised controlled clinical trial, in which 20 patients with second degree burns were treated with the extract of the Choerospondias axillaris and 19 with saline gauze. The mean healing time was significantly shorter for patients treated with Choerospondias axillaris (11 days) compared with patients treated with saline gauze (17 days) (p < 0.01), and the number of wound infections was significantly lower in the Choerospondias axillaris group (7/20 compared with 16/19, p = 0.003). The bark extract was easy to apply and additional wound care was not usually necessary, while the treatment with saline gauze was laborious for both patients and staff and was much more expensive. The extract from Choerospondias axillaris is a convenient treatment for second degree burns in both children and adults.

Survey on immunization, diarrhoeal disease and mortality in Quang Ninh Province, Vietnam

A survey on EPI, CDD, child morbidity, and mortality was conducted in 1988 in one province of northeastern Vietnam. Thirty out of 114 communes were randomly selected for the survey and the interviews were made by 60 students from the provincial nursing school, supervised by 10 teachers. It was found that 23 per cent of the children (n = 211) were fully vaccinated, while 54 per cent had partial coverage. Lack of information or ignorance were the main causes of vaccination failure. The adjusted yearly diarrhoeal rate was 1.6 per child under 5 years of age (n = 9.691). Infant mortality and under-five mortality rates were found to be 28 per thousand live births (95 per cent confidence interval: 21-35; n = 2.321) and 44 (36-52), respectively. High literacy among mothers, good breast-feeding practices, low mortality due to diarrhoea, malaria, and measles, and a well-functioning rural health care system were considered to be the main contributing factors to the low infant mortality. The results also point out the weaknesses in the existing reporting system and indicates the need for follow-up studies.

Long term survival after transurethral resection of the prostate. Influence of preoperative bacteriuria and indwelling catheter treatment on late mortality

In this report we have analysed the long term survival after transurethral resection of the prostate in patients with cancer and benign hyperplasia, with special reference to the effect of bacteriuria. One hundred and eighty-nine men were followed for seven years after operation. Life tables according to the Kaplan-Meier method indicated a decreased survival rate for patients with preoperative catheter treatment and/or bacteriuria (p = 0.004 and p = 0.013, respectively). In order to evaluate the influence on the long-term survival of each of these factors alone as well as of other factors like diagnosis, age at operation and perioperative antibiotic treatment, a multivariate analysis, according to Cox proportional hazards method was made. This displayed a two-fold increase of mortality in the patients attributed to the catheter treatment per se, whereas bacteriuria alone was not associated with an increased risk of earlier death.

Significance of group B streptococci in urine cultures from males and non-pregnant females

Over a 2-year period, 1% of 24,000 urine cultures with possible relevant bacteria from males and non-pregnant females greater than or equal to 15 years of age were found to harbour group B streptococci (GBS) in quantities greater than or equal to 10(5) colony forming units (cfu)/ml; a further 0.9% harboured GBS in quantities greater than or equal to 10(4) but less than 10(5) cfu/ml. Patients with GBS in urine were evenly distributed by age. Those with greater than or equal to 10(5) cfu GBS/ml in voided urine more frequently had true bacteriuria (i.e. bacteria in the urine bladder) than did patients with less amounts (p = 0.01) as determined by suprapubic aspiration of 23 patients. One third (3/9) of the aspirated patients with greater than or equal to 10(5) cfu GBS/ml in simultaneously voided urine, had contaminated urine only and no true bacteriuria. The acute symptoms and clinical conditions of 128 patients with greater than or equal to 10(5) cfu GBS/ml urine were studied by matching 128 patients with negative urine cultures (less than 10(2) cfu/ml) and 128 patients with comparable quantity of Escherichia coli. The incidence of acute lower urinary tract symptoms in patients with GBS was greater than that in patients with negative urine cultures (p less than 0.01), and the same as that in patients with E. coli. The incidence of fever was lower in patients with GBS than in those with E. coli (p less than 0.01). The incidence of urinary tract abnormalities was greatest in patients with GBS in urine. No GBS serotype seems to have particular affinity to the urinary tract.

Controlled trial of a short and a prolonged course with ciprofloxacin in patients undergoing transurethral prostatic surgery

The efficacy of a short (Group I) and a prolonged (Group II) course with ciprofloxacin was assessed in patients undergoing transurethral prostatic resection for benign hyperplasia or cancer of the prostate and compared with that of controls without antibiotic (Group III). Both regiments significantly reduced the frequency of postoperative bacteriuria (p less than 0.01) and of severe infectious complications (p = 0.004) as compared to the controls. Both regimens were equally effective in preventing perioperative and postoperative acquisition of bacteriuria in patients without bacteriuria at surgery. In patients with bacteriuria before surgery, bacteriuria was found postoperatively in 35% in Group I and 10% in Group II (p = 0.012), but in 82% of the patients in Group III. Ciprofloxacin inhibited all but 7 of 176 bacterial strains at an MIC of less than or equal to 1 microgram/ml. Given orally ciprofloxacin is a valuable alternative antimicrobial for use in conjunction with transurethral prostatic resection. A short course is sufficient for prophylaxis, and adequate therapy is achieved with a prolonged regimen.

Retrograde trypsin instillation into the renal pelvis for the dissolution of obstructive blood clots

A case of heavy hematuria after renal biopsy causing retention of blood clots and obstruction of the renal pelvis is reported. The blood clots were successfully lysed by retrograde ureteral instillation of crystalline trypsin (Trypure) without any signs of harmful effects on the renal parenchyma.

The effectiveness of a short perioperative course with pivampicillin/pivmecillinam in transurethral prostatic resection: clinical results

In a randomized control study comprising 261 patients undergoing transurethral prostatic resection (TUR), the effect of a short perioperative course with the oral combination of pivampicillin/pivmecillinam (PAPM) was analysed in 129 patients. The study was divided in 2 parts: the first 60 patients received 450 mg and the following 69 patients, 900 mg every 12 h until removal of catheter but not longer than for 1 week. 132 controls received parenterally 1 g of cefotaxime (CFT) daily throughout the study. During the first part of the study the frequency of bacteriuria in the PAPM group was 43% preoperatively and 30% 10 days postoperatively, during the second part 47% and 12%, respectively (p less than 0.025). In the CFT group the frequency of bacteriuria was reduced from 52% preoperatively to 28% postoperatively. The prophylactic effect (i.e. the protection against acquired bacteriuria) was 96% and 92% in the PAPM and the CFT groups, respectively. Preoperative bacteriuria was eliminated in 40% of the patients during first part and 69% during second part in the PAPM group, while corresponding figures were 48% and 46% in the cefotaxime group. There were 2 cases of septicemia and 5 of upper urinary tract infections throughout the study evenly distributed between the two groups. Oral pivampicillin/pivmecillinam 900 mg every 12 h was found to be a good alternative for perioperative antibiotic prophylaxis at TUR.

The effectiveness of a short perioperative course with pivampicillin/pivmecillinam in transurethral prostatic resection: bacteriological results

We analysed the bacteriological findings in 261 patients undergoing transurethral prostatic resection (TUR) and receiving either an oral course of pivampicillin/pivmecillinam (PAPM) or parenteral cefotaxime (CFT) in a randomized clinical trial. 123/261 patients had bacteriuria before TUR; 80% of the bacteria were gram-negative strains and 20% gram-positive. 88% of the strains were sensitive to PAPM and 93% to CFT but only 58% to ampicillin. The sensitivity of recurring bacteria was not influenced by the short course of PAPM or CFT. The faecal flora was influenced by the treatment with PAPM in terms of growth of Pseudomonas aeruginosa and fungi in some patients, but no resistant strains of Enterobacteriaceae were observed. The peak serum concentrations of ampicillin and mecillinam were obtained 2 hours after intake of the drug and were 4.5 micrograms/ml and 1.7 micrograms/ml respectively. The prostate tissue concentration of ampicillin and mecillinam (AM) was low.

Long-term follow-up after transurethral prostatic resection with or without a short peri-operative antibiotic course

This study was undertaken to analyse the results in 192 patients who 3 to 4 years earlier had undergone transurethral resection (TUR) in a controlled clinical trial on the value of a short peri-operative course of antibiotics. The survival rate was comparable in both groups. Most deaths were due to cardiovascular disease and/or cancer of the prostate and the gastrointestinal tract. Infectious events predominated in the control group and more antibiotics were prescribed for these patients during follow-up than for the patients in the peri-operative antibiotic group. Bacteriuria was found in 24% of patients, evenly distributed between the groups. Eighty-three per cent were satisfied with the results of prostatectomy but 38% complained of symptoms from the lower urinary tract. The maximum urinary flow rate was not influenced by the presence of bacteriuria and/or symptoms. There was no difference between the groups regarding mortality or morbidity except for the frequency of post-operative urethral stricture formation, which was significantly higher in the controls. It was concluded that prospective long-term follow-up is indicated to assess the effect of short peri-operative antibiotic courses.

Impact of short perioperative courses of cefotaxime on aerobic bacterial flora in patients undergoing transurethral prostatic resection

The influence of short-term prophylactic courses of cefotaxime on the microbial environment was studied. The distribution of bacterial species and their antibiotic resistance was recorded in isolates collected over a six-year period, during which time cefotaxime was used for perioperative prophylaxis in patients undergoing transurethral prostatic resection. In three consecutive studies covering the six-year observation period, the species distribution and antibiotic resistance patterns remained essentially unchanged for both cefotaxime and ampicillin. Examination of the faecal coliform flora in 23 patients given cefotaxime revealed no marked qualitative or quantitative change in the flora. It is concluded that short-term prophylactic courses of cefotaxime do not promote the emergence of resistance in the aerobic bacterial flora.

Species distribution and antibiotic sensitivity of bacteria isolated pre- and postoperatively from patients undergoing transurethral prostatic resection

The identity and antibiotic sensitivity of the isolated bacteria from 179 patients undergoing transurethral resection of the prostate were analysed. The patients were randomized into a group receiving a short course of cefotaxime in conjunction with the operation and a control group given no antibiotics. Preoperatively 70 patients had bacteriuria (greater than or equal to 10(7) CFU/l) with a predominance of Gram-negative bacteria (57 isolates, mainly Escherichia coli, Enterobacter, Klebsiella ssp, Proteus ssp), although Gram-positive species (24 isolates, mainly enterococci and Staphylococcus epidermidis) were also frequently encountered. Preoperatively isolated pathogens were evenly distributed in both groups and the sensitivity pattern was comparable. In the cefotaxime group postoperative recurrence of the preoperatively identified bacteria occurred in a lower frequency (11/43) than persistence in the control group (24/38). Only Gram-negative pathogens were isolated from patients with postoperative septicemia and upper urinary tract infections indicating that it is most important to direct prophylaxis against Gram-negative bacteria. A high degree of sensitivity against cefotaxime, gentamicin, trimethoprim, co-trimazine and a combination of ampicillin and mecillinam was recorded among both pre- and postoperatively isolated bacteria.

The effect of a short antibiotic course in transurethral prostatic resection

In a prospective randomized study of 192 patients, the effect of a short course of cefotaxime in connection with transurethral prostatic resection was analyzed. The antibiotic was given to 98 patients, while 94 were assigned to a control group without antibiotic. The frequency of bacteriuria in the cefotaxime group was 43% preoperatively and 18% six weeks postoperatively. In the control group the corresponding figures were 40 and 42% (p less than 0.01). Complicated postoperative infection did not occur in the cefotaxime group, but in the control group there was one case of septicemia and seven patients had upper urinary tract infections (p less than 0.01). In the cefotaxime group, patients with preoperatively negative urine culture were prevented from acquiring bacteriuria, and 67% of preoperatively present infections were eliminated at six weeks after the operation, as compared with 30% in the control group. There were essentially no side effects of cefotaxime. Renal function was not influenced by the combination of cefotaxime and furosemide.

A short antibiotic course given in conjunction with and after catheter removal consecutive to transurethral prostatic resection

In a prospective randomized study of 96 patients, the effect of a short antibiotic course given after transurethral prostatic resection was analysed. Cefotaxime (1 g. i.m. every 12 hours to a total of 3 g) was given to 47 patients with the first doses when the postoperative catheter was removed while 49 were assigned to a control group without antibiotic. The frequency of bacteriuria was 48% preoperatively in the cefotaxime group and 33% six weeks postoperatively. In the control group the corresponding figures were 63% and 50% (p greater than 0.1). There were two cases of septicemia in each group immediately post-operatively whereas upper urinary tract infection developed in five patients in the control group and one patient in the cefotaxime group (p greater than 0.1). The total number of infectious and non-infectious complications was significantly greater in the control group (22) compared to the cefotaxime group (12) (p less than 0.05). The patients receiving the antibiotic remained a shorter time in hospital as compared to the controls. Bacteriological analysis showed a good in vitro effect of cefotaxime on isolated bacteria.