Accounting for Evil and Cruelty: Is to Explain to Condone?

Analysts of evil and violence express the concern that to explain harmdoing may result in a condoning attitude toward perpetrators. An examination of research relevant to this hypothesis suggests that there are a variety of cognitive and affective processes that may produce a relatively condoning attitude toward perpetrators as a result of explaining their actions. Evidence from 3 exploratory studies supported the exonerating effects of explanations. Participants generating explicit explanations of harmdoing displayed a more condoning attitude toward perpetrators than did those forming impressions of perpetrators without first explaining the acts. Participants reading social-psychological explanations of harmdoing also judged the researcher to be more condoning of perpetrators than those reading dispositional explanations of the same behavior. Implications of these findings are discussed.

Anterolateral Drawer Versus Anterior Drawer Test for Ankle Instability: A Biomechanical Model

BACKGROUND

The addition of unconstrained internal rotation to the physical examination could allow for detection of more subtle degrees of ankle instability. We hypothesized that a simulated anterolateral drawer test allowing unconstrained internal rotation of the ankle would provoke greater displacement of the lateral talus in the mortise versus the anterior drawer test.

METHODS

Ten cadaveric lower extremities were tested in a custom apparatus designed to reproduce the anterior drawer test and the anterolateral drawer test, in which the ankle was allowed to internally rotate about the intact deep deltoid ligament while being subluxed anteriorly. Specimens were tested intact and with anterior tibiofibular ligament sectioned. A differential variable reluctance transducer was used to measure lateral talar displacement with anterior forces of 25 and 50 N.

RESULTS

No significant differences in talar displacement or ankle rotation were noted in intact specimens between the groups. Among sectioned specimens, significantly more talar displacement (25 N [6.5 ± 1.7 mm vs 3.8 ± 2.4 mm] and 50 N [8.7 ± 0.9 mm vs 4.5 ± 2.5 mm], P < .001) and ankle rotation (25 N [13.9 ± 8.0 degrees vs 0.0 ± 0.0 degrees] and 50 N [23.7 ± 5.8 degrees vs 0.0 ± 0.0 degrees], P < .001) were found in the anterolateral drawer versus anterior drawer group.

CONCLUSION

In an ankle instability model, the anterolateral drawer test provoked almost twice the lateral talus displacement found with the anterior drawer test.

CLINICAL RELEVANCE

Allowing internal rotation of the ankle while testing for ankle instability may allow the examiner to detect more subtle degrees of ankle instability.

Distal femoral fracture during primary total knee arthroplasty

PURPOSE

To review 6 cases of periprosthetic distal femoral fracture during total knee arthroplasty (TKA).

METHODS

Of 778 women and 691 men who underwent primary TKAs using posterior-stabilised (n=1240), cruciate-retaining (n=165), or semiconstrained (n=64) implant, 5 women and one man with a mean age of 73.3 years and a mean body mass index of 31.6 kg/m(2) sustained an intra-operative periprosthetic distal femoral fracture and were followed up for a mean of 12.8 (range, 2-39) months.

RESULTS

Respectively in patients with a posterior-stabilised, cruciate-retaining, or semi-constrained implant, the intra-operative fracture rates were 0.32%, 0%, and 3.13%. For women, the respective rates were 0.46%, 0%, and 5.10%. Intra-operative fracture was 9.69 times (p=0.03) more likely to occur in patients with a semi-constrained implant than those with a posterior-stabilised implant, and was 4.44 times (p=0.22) more likely to occur in women than in men. Half of the fractures occurred during the trial phase when the tibia was reduced onto the femur, and half during final prosthesis implantation.

CONCLUSION

Distal femoral fracture during primary TKA is rare and associated with the use of a semiconstrained implant. Preserving as much bone in the distal femur is advised.

Near-anatomic allograft tenodesis of chronic lateral ankle instability

BACKGROUND

Current operative treatment options for chronic lateral ankle instability include anatomic repairs utilizing existing local tissue and nonanatomic reconstructions sacrificing the peroneus brevis tendon to mechanically stabilize the ankle. Recent studies have modified these techniques to create an anatomic reconstruction utilizing allograft tendons. The purpose of this study was to retrospectively examine the clinical outcomes of a near-anatomic ligament reconstruction utilizing an allograft tendon for recurrent or complex lateral ankle instability.

METHODS

Twenty-eight patients underwent a near-anatomic allograft lateral ankle ligament reconstruction with a semitendinosis allograft for severe or recurrent lateral ankle ligamentous instability, and all of them were available for follow-up at an average 32 months. Twelve patients had previously undergone lateral ankle ligament stabilizing surgery, 4 had Ehlers Danlos syndrome with poor local tissue, 5 had greater than 30 degrees of varus angulation of talar tilt, while 12 had associated hindfoot varus requiring concomitant reconstruction. Patients were assessed pre- and postoperatively for Visual Analog Scores (VAS) for pain, Foot and Ankle Ability Measures (FAAM), patient satisfaction, radiographic correction, and complications.

RESULTS

Median VAS of pain decreased from 8 before surgery to 1 after surgery (P < .001). Median FAAM score increased from 41.7 to 95.2 after surgery (P < .001). Radiographic comparison demonstrated correction of preoperative varus malalignment in all but 1 patient. No patients developed subsequent subtalar arthritis or pain. Three patients had mild persistent instability, all of which was managed nonoperatively. One of the patients with persistent instability also developed chronic regional pain syndrome following surgery. At final follow-up, 25 of 28 patients rated their satisfaction as good or excellent and 3 as fair. No patients required revision surgery.

CONCLUSION

Lateral ligament reconstruction utilizing a near-anatomically placed and tensioned allograft tendon was a viable option in treating recurrent and complex lateral instability. Not sacrificing the peroneal tendons avoided loss of eversion strength. Near-anatomic placement of the allograft provided good ankle stability without sacrificing subtalar motion or predisposition to subtalar arthritis in short-term follow-up.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Conversion arthrodesis for failed first metatarsophalangeal joint hemiarthroplasty

BACKGROUND

Arthrodesis is currently the most commonly performed surgical procedure for the treatment of arthritis of the first metatarsophalangeal (MTP) joint. Hemiarthroplasty of the first MTP joint has been shown to have inferior clinical results and higher revision rates. The objective of this study was to assess the clinical outcome of the salvage of failed hallux phalangeal hemiarthroplasty with conversion to arthrodesis.

METHODS

A retrospective review of patients who underwent salvage of the first MTP joint hemiarthroplasty with conversion to arthrodesis was performed. Preoperative assessment included the visual analog pain (VAP) scale and AOFAS Hallux Metatarsophalangeal Interphalangeal scoring system (AOFAS-HMI). Postoperative outcomes were graded via AOFAS-HMI, VAP, and Foot and Ankle Ability Measure (FAAM).

RESULTS

Twenty-one hemiarthroplasties were converted to arthrodesis in 21 patients, with 18 available for follow-up included in the study. There were 13 women and 5 men. Local autologous bone graft was used in 12 cases, while 6 patients required tricortical iliac crest bone graft for the treatment of extensive bone loss. At final follow-up, at a mean of 4.3 years, the average VAS pain score had diminished to 0.75 from 7.8 preoperatively out of 10, while the mean AOFAS-HMI improved from 36.2 out of 100 preoperatively to 85.3 out of 90 (modified to exclude first MTP motion). The mean FAAM ADL/sports were 97.3/91.3, respectively. All patients achieved fusion although at a longer interval than primary fusions.

CONCLUSIONS

Conversion from a failed hallux phalangeal hemiarthroplasty to arthrodesis showed similar success to primary arthrodesis which was achieved in the majority of cases with the use of regional bone graft for small defects. However, the time to fusion was longer than that of primary arthrodesis, and it sometimes required structural bone graft for augmentation.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Spinal anesthesia: should everyone receive a urinary catheter?: a randomized, prospective study of patients undergoing total hip arthroplasty

BACKGROUND

The objective of this randomized prospective study was to determine whether a urinary catheter is necessary for all patients undergoing total hip arthroplasty under spinal anesthesia.

METHODS

Consecutive patients undergoing total hip arthroplasty under spinal anesthesia were randomized to treatment with or without insertion of an indwelling urinary catheter. All patients received spinal anesthesia with 15 to 30 mg of 0.5% bupivacaine. The catheter group was subjected to a standard postoperative protocol, with removal of the indwelling catheter within forty-eight hours postoperatively. The experimental group was monitored for urinary retention and, if necessary, had straight catheterization up to two times prior to the placement of an indwelling catheter.

RESULTS

Two hundred patients were included in the study. There was no significant difference between the two groups in terms of the prevalence of urinary retention, the prevalence of urinary tract infection, or the length of stay. Nine patients in the no-catheter group and three patients in the catheter group (following removal of the catheter) required straight catheterization because of urinary retention. Three patients in the catheter group and no patient in the no-catheter group had development of urinary tract infection.

CONCLUSIONS

Patients undergoing total hip arthroplasty under spinal anesthesia appear to be at low risk for urinary retention. Thus, a routine indwelling catheter is not required for such patients.

Near-anatomic allograft tenodesis of chronic lateral ankle instability

BACKGROUND

Current operative treatment options for chronic lateral ankle instability include anatomic repairs utilizing existing local tissue and nonanatomic reconstructions sacrificing the peroneus brevis tendon to mechanically stabilize the ankle. Recent studies have modified these techniques to create an anatomic reconstruction utilizing allograft tendons. The purpose of this study was to retrospectively examine the clinical outcomes of a near-anatomic ligament reconstruction utilizing an allograft tendon for recurrent or complex lateral ankle instability.

METHODS

Twenty-eight patients underwent a near-anatomic allograft lateral ankle ligament reconstruction with a semitendinosis allograft for severe or recurrent lateral ankle ligamentous instability, and all of them were available for follow-up at an average 32 months. Twelve patients had previously undergone lateral ankle ligament stabilizing surgery, 4 had Ehlers Danlos syndrome with poor local tissue, 5 had greater than 30 degrees of varus angulation of talar tilt, while 12 had associated hindfoot varus requiring concomitant reconstruction. Patients were assessed pre- and postoperatively for Visual Analog Scores (VAS) for pain, Foot and Ankle Ability Measures (FAAM), patient satisfaction, radiographic correction, and complications.

RESULTS

Median VAS of pain decreased from 8 before surgery to 1 after surgery (P < .001). Median FAAM score increased from 41.7 to 95.2 after surgery (P < .001). Radiographic comparison demonstrated correction of preoperative varus malalignment in all but 1 patient. No patients developed subsequent subtalar arthritis or pain. Three patients had mild persistent instability, all of which was managed nonoperatively. One of the patients with persistent instability also developed chronic regional pain syndrome following surgery. At final follow-up, 25 of 28 patients rated their satisfaction as good or excellent and 3 as fair. No patients required revision surgery.

CONCLUSION

Lateral ligament reconstruction utilizing a near-anatomically placed and tensioned allograft tendon was a viable option in treating recurrent and complex lateral instability. Not sacrificing the peroneal tendons avoided loss of eversion strength. Near-anatomic placement of the allograft provided good ankle stability without sacrificing subtalar motion or predisposition to subtalar arthritis in short-term follow-up.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Risk factors for wound complications after ankle fracture surgery

BACKGROUND

The overall rate of complications after ankle fracture fixation varies between 5% and 40% depending on the population investigated, and wound complications have been reported to occur in 1.4% to 18.8% of patients. Large studies have focused on complications in terms of readmission, but few studies have examined risk factors for wound-related issues in the outpatient setting in a large number of patients. A review was performed to identify risk factors for wound complications tracked in the hospital and outpatient setting.

METHODS

Four hundred and seventy-eight patients underwent open reduction and internal fixation of an ankle fracture between 2003 and 2010 by a single surgeon at a single institution. Demographic characteristics, time to surgery, comorbidities, and postoperative care were tracked. Wound complications were defined as those requiring dressing care and oral antibiotics or requiring further surgical treatment.

RESULTS

Of the 478 patients who were followed, six (1.25%) had wounds requiring surgical debridement. Fourteen patients (2.9%) required further dressing care or a course of oral antibiotics. There were significant associations between wound complications and a history of diabetes (p < 0.001), peripheral neuropathy (p = 0.003), wound-compromising medications (p = 0.011), open fractures (p = 0.05), and postoperative noncompliance (p = 0.027). There was a significant difference in age between patients with and without wound complications (p = 0.045). We did not identify a relationship between time to surgery and complications.

CONCLUSIONS

These results highlight the difficulty of treating medically complex and noncompliant patient populations. With careful preoperative monitoring of swelling, time to surgery does not affect wound outcome. The failure of the patient to adhere to postoperative instructions should be a concern to the treating surgeon.

Effect of work-hour restrictions and resident turnover in orthopedic trauma

The resident 80-hour workweek and the July phenomenon have raised concern regarding the continuity of care of orthopedic patients in teaching institutions and its effect on postoperative complications and mortality. This study examined the effect of resident work-hour restrictions and the July phenomenon on patient outcomes after hip fracture at a large academic institution. Seven hundred twenty-two patients (mean age, 76.7 years) sustaining 319 femoral neck fractures and 403 intertrochanteric fractures between 2000 and 2010 were identified. Analysis was performed before and after July 1, 2003, as well as for the month of treatment. No difference existed in the postoperative outcome measures of delay of surgery (P=.061), complications (P=.904), and mortality (P=.981) between patients treated before and after July 1, 2003. Patients treated after July 1, 2003, had a significantly higher median number of preoperative comorbidities (4 vs 3, respectively; P<.0005). Turnover months, July and August, showed no difference in the outcome measures of delay of surgery (P=.171), complications (P=.776), and mortality (P=.524) compared with other months. This study suggests that 80-hour workweek restrictions or resident turnover months have no effect on patient care with respect to in-hospital time to surgery, complications, and mortality. This success can be attributed to ancillary staff support, physician extenders, and well-designed patient care protocols.

Outcome of modified Kidner procedure with subtalar arthroereisis for painful accessory navicular associated with planovalgus deformity

BACKGROUND

Type II accessory naviculars are frequently associated with planovalgus deformity. Operative treatment for patients recalcitrant to nonoperative treatment involves resection, with or without takedown, and reattachment of the tibialis posterior tendon as described by Kidner. This does not address the planovalgus deformity. The authors hypothesized that adding a subtalar arthroereisis to the Kidner procedure would lead to improvement of pain and function and correction of the deformity.

METHODS

Institutional Review Board-approved, prospectively collected data were reviewed for 20 patients (23 feet), who underwent a combined modified Kidner and subtalar arthroereisis for painful type II accessory navicular with planovalgus deformity recalcitrant to nonoperative treatment. The average age at the time of surgery was 18 years. Patients were evaluated preoperatively and at final follow-up clinically, radiographically, and via the visual analog pain scale (VAPS), the American Orthopaedic Foot and Ankle Society (AOFAS) ankle hindfoot score, and a satisfaction rating. Mean follow-up was 53.9 months.

RESULTS

The mean AOFAS scores improved from 53 preoperatively to 95 at final follow-up and the mean VAPS score decreased from 7.4 preoperatively to 1.7 at final follow-up. Radiographically, the average Meary's angle improved from 18.5° apex plantar preoperatively to 3° apex plantar on weight-bearing lateral radiographs, and the average talar head uncoverage percentage on weight-bearing anteroposterior radiographs improved from 24% preoperatively to 3%. Nineteen of 20 patients reported good or excellent results. Three patients required implant removal because of pain; no recurrence of planovalgus deformity occurred after implant removal. No patients developed subtalar arthritis.

CONCLUSION

The modified Kidner procedure combined with a subtalar arthroereisis resulted in significant pain and functional improvement. The deformity correction obtained at surgery was maintained even if the arthroereisis plug was removed. The extra-articular plug did not lead to subtalar arthritis.

Accuracy of digital templating in total knee arthroplasty

Preoperative planning is an important aspect of total joint arthroplasty. Although significant attention has been given to how total hip arthroplasty templates are magnified, total knee arthroplasty (TKA) digital templating magnification methods have not been compared. In this study, 50 patients undergoing TKA by the same surgeon were digitally templated using 2 common digital magnification methods to determine if there is any difference in accuracy or precision. Radiographs were randomly chosen to include a 25-mm magnification marker (MM) at the level of the joint or no magnification marker with uniform 115% magnification (NM). There was no statistical difference between templated and actual component sizes. Preoperative templating determined the exact component size in 64% of femurs and 60% of tibias using the NM technique. Femurs were slightly oversized (mean, 0.2 femur size), whereas tibias had no such trend. In MM templating, 52% of femurs and 48% of tibias were exact. Various methods of digital templating-the new standard of preoperative templating-provide no clear advantage over one another. The benefit of templating in TKA appears to be 2-fold: the surgeon can reliably predict a range of implant sizes needed and can ascertain a reliable starting point in determining implant size and position.

Total knee arthroplasty component templating: a predictive model

Preoperative planning is essential to total knee arthroplasty (TKA); however, TKA templating is historically inaccurate. To improve on templating accuracy and streamline preoperative planning, we set out to predict component sizes based on patient characteristics without radiographs. A total of 123 consecutive patients undergoing unilateral TKA were identified and included in the model study. Input variables consisted of age, gender (as a binary number), height, weight, and body mass index. A linear regression model was created. The models predicted component size exactly in 74% of femurs and 85% of tibias. All model predictions were within a ±1 size of the actual components implanted. Our models were more accurate than any previous model for TKA reported.

Conversion total hip arthroplasty: a reason not to use cephalomedullary nails

Previous studies have yet to compare outcomes of conversion to hip arthroplasty from screw and side plate vs cephalomedullary nail. Seventy-six patients at our institution underwent hip conversion after fixation failure. We performed a retrospective chart review to compare perioperative outcomes in these 2 groups. Both operative time (P = .020) and blood loss (P = .041) were significantly greater in patients converted from cephalomedullary nail. Greater length of stay in this group trended to significance (P = .101). Perioperative complications were similar. Recent practice patterns reveal a dramatic increase in the use of cephalomedullary nails despite lack of evidence suggesting their clinical superiority in certain fracture patterns. Our results suggest that conversion to total hip arthroplasty after internal fixation with cephalomedullary nail is a more complex procedure than is conversion from screw and side plate. The surgeon should consider possible later hip conversion and these results when choosing the appropriate fixation implant.

Terrible triad of the shoulder in a competitive athlete

The terrible triad injury to a shoulder consists of shoulder dislocation, rotator cuff tear, and brachial plexus palsy. We present a case of a high velocity shoulder dislocation in an athlete with concomitant massive rotator cuff tear and incomplete infraclavicular brachial plexus injury. In this injury, most neurologic symptoms resolve, prompt surgical intervention is warranted, and comprehensive physical therapy is integral to recovery.

Aliskiren reduces vascular pathology in diabetic retinopathy and oxygen-induced retinopathy in the transgenic (mRen-2)27 rat

AIM/HYPOTHESIS

We examined whether the renin inhibitor, aliskiren, provides similar or greater protection than ACE inhibition from non-proliferative diabetic retinopathy and from the proliferative neoangiogenesis of oxygen-induced retinopathy.

METHODS

Transgenic (mRen-2)27 rats, which overexpress mouse renin and angiotensin in extra-renal tissues, were studied. For diabetic studies, non-diabetic, diabetic (streptozotocin, 55 mg/kg), diabetic + aliskiren (10 mg kg(-1) day(-1), pump), or diabetic + lisinopril (10 mg kg(-1) day(-1), drinking water) rats were evaluated over 16 weeks. For oxygen-induced retinopathy studies, rats were exposed to 80% oxygen (22 h/day) from postnatal days 0 to 11, and then room air from postnatal days 12 to 18. Aliskiren (10 or 30 mg kg(-1) day(-1), pump) or lisinopril (10 mg kg(-1) day(-1), drinking water) was administered during retinopathy development between postnatal days 12 and 18.

RESULTS

Systolic BP in diabetic (mRen-2)27 rats was reduced with 10 mg kg(-1) day(-1) aliskiren, but only lisinopril normalised systolic blood pressure. In diabetic (mRen-2)27 rats, 10 mg kg(-1) day(-1) aliskiren and lisinopril reduced retinal acellular capillaries and leucostasis to non-diabetic levels. In oxygen-induced retinopathy, neoangiogenesis and retinal inflammation (leucostasis, ED-1 immunolabelling) were partially reduced by 10 mg kg(-1) day(-1) aliskiren and normalised by 30 mg kg(-1) day(-1) aliskiren, whereas lisinopril normalised neoangiogenesis and reduced leucostasis and ED-1 immunolabelling. Aliskiren and lisinopril normalised retinal vascular endothelial growth factor expression; however, only aliskiren reduced intercellular adhesion molecule-1 to control levels.

CONCLUSIONS/INTERPRETATION

Aliskiren provided similar or greater retinal protection than ACE inhibition and may be a potential treatment for diabetic retinopathy.

Multimodal pain management after total joint arthroplasty

Adequate postoperative pain control in patients who have undergone total joint arthroplasty allows faster rehabilitation and reduces the rate of postoperative complications. Multimodal pain management involves the introduction of adjunctive pain control methods in an attempt to control pain with less reliance on opioids and fewer side effects. Current research suggests that traditional nonsteroidal anti-inflammatory drugs (NSAIDs) and the associated cyclooxygenase type-2 (COX-2) inhibitors improve pain control in most cases. Nearly all multimodal pain management modalities have a safe side-effect profile when they are added to existing methods. The exception is the administration of DepoDur (extended-release epidural morphine) to elderly or respiratory-compromised patients because of a potential for hypoxia and cardiopulmonary events.

Corticosteroid-binding globulin regulates cortisol pharmacokinetics

OBJECTIVE

Corticosteroid-binding globulin (CBG) is the principal carrier for cortisol in the circulation. Variations in CBG-binding capacity are predicted to alter total serum cortisol disposition, but free serum cortisol is believed to be unaffected. Unbound cortisol pharmacokinetics (PK) have not been studied in the context of CBG changes. We aimed to assess the regulation of cortisol PK by CBG.

DESIGN AND SUBJECTS

Women on oestrogens [oral contraceptive pill, (OCP)], patients homozygous for a nonfunctioning CBG variant (CBG null) and healthy controls (HV) were studied before and after IV and oral administration of hydrocortisone 20 mg.

MEASUREMENTS

PK parameters were studied for total serum cortisol (SerF), free serum cortisol (FreeF) and cortisone (FreeE), and salivary cortisol (SalF) and cortisone (SalE): area under the curve (AUC), clearance (CL), half-life and volume of distribution (V(d)).

RESULTS

Following IV hydrocortisone, AUC and half-life of SerF were significantly higher in the OCP group and lower in the CBG null. SerF CL and V(d) were significantly lower in the OCP group and increased in the CBG null, compared to HV. PK parameters for FreeF and the salivary biomarkers were not different between the CBG null and HV, although OCP patients still had higher AUC compared to HV and prolonged half-life. These findings were confirmed following oral hydrocortisone, but concentration-time profiles were highly heterogeneous and SalF interpretation was problematic because of oral contamination.

CONCLUSIONS

We have demonstrated that CBG has a distinct effect on cortisol PK. When CBG binding is disrupted, FreeF retains normal PK characteristics, although CBG null patients lack a CBG-bound pool of readily releasable cortisol. Women on oestrogens may have altered free serum cortisol kinetics and thus may be potentially overexposed to glucocorticoids.

Dermabond efficacy in total joint arthroplasty wounds

The goals of wound closure are a low infection rate and timely healing. Total joint arthroplasty (TJA) requires mobile recovery, and, therefore, a high-tension wound care environment. We conducted a study to compare the efficacy of high-viscosity Dermabond (Ethicon, Somerville, New Jersey) and the efficacy of surgical staples in healing high-tension, mobile surgical sites of TJA. Of 236 total knee arthroplasties and 223 total hip arthroplasties (459 surgeries total), 250 were performed with Dermabond and 209 with staples. According to χ2 analysis, case and control infection rates were equivalent. Signs of acute inflammation (redness, drainage, dehiscence) also were statistically equivalent. Absence of staples accounted for a significant decrease in tape blisters and skin abscesses. Dermabond is superior to staples in high-tension wound care.

Anemia is associated with decreased survival time in dogs with lymphoma

BACKGROUND

Anemia is a common complication in human patients with neoplasia and has been associated with decreased survival time and a poorer quality of life.

HYPOTHESIS

The presence of anemia at diagnosis is negatively associated with survival and remission times in dogs with lymphoma, but not in dogs with osteosarcoma.

ANIMALS

Eighty-four dogs with lymphoma and 91 dogs with osteosarcoma that presented for treatment at the Animal Cancer Center, Colorado State University.

METHODS

Retrospective, case-control study. Medical records were reviewed to determine the presence or absence of anemia (PCV < 40) at initial presentation. Median survival and remission times were identified by the Kaplan-Meier product limit method and the association between anemia and survival was determined by a multivariable Cox proportional hazard regression analysis.

RESULTS

Cancer-related anemia is more frequent in dogs with lymphoma than in control dogs or dogs with osteosarcoma. Dogs with lymphoma and anemia had a significantly decreased survival time compared with dogs without anemia. There was no effect of anemia on remission time in dogs with lymphoma. Anemic dogs with osteosarcoma did not have decreased survival or remission time compared with nonanemic dogs with osteosarcoma.

CONCLUSIONS AND CLINICAL IMPORTANCE

Shortened survival time in dogs with lymphoma and anemia at initial presentation has important prognostic significance. Understanding cancer-related anemia in dogs might offer new opportunities to improve quality of life and survival times in these patients.

Protein cross-linking in food

The aims of this paper are (1) to probe the relationship between molecular structure and protein cross-linking ability for a range of small molecules; (2) to establish whether this relationship holds within a food matrix; and (3) to test the impact of Maillard cross-linking on food functionality, particularly texture, in wheat- and soy-based food systems. A variety of molecules were obtained, either commercially or via organic synthesis. Cross-linking ability was tested using our standard model system, employing ribonuclease A and analyzing the results by SDS-PAGE. Molecules of varying reactivity were tested in wheat- and soy-based products, and the changes in functionality were correlated with changes in protein cross-linking. No simple relationship was found between molecular structure and ability to cross-link ribonuclease. Only the most reactive reagents were able to cross-link within the food matrix. Nevertheless, a low degree of cross-linking was shown to have significant consequences on the properties of wheat- and soy-based foods, suggesting that the Maillard reaction may represent a means to control food texture.

Heterogeneity in the rate of benzo[a]pyrene metabolism in single cells: quantitation using flow cytometry

We describe a method for quantitating heterogeneity in the rate of benzo[a]pyrene metabolism in single cells by using flow cytometry. We have used the technique to study the response of Hepa-1c1c7 mouse hepatoma cells to the microsomal enzyme inducer 2,3,7,8-tetrachlorodibenzo-p-dioxin. Cells responded in a relatively homogeneous fashion at different times of induction with a maximally inducing concentration of the inducer. However, the induction response could be heterogeneous at a submaximal inducer concentration. We found even higher heterogeneity of enzyme activity among low-activity variants derived from the Hepa-1c1c7 cell line. When cells of either high or low activity were isolated from such a clonal population, propagated, and reanalyzed, they displayed average enzyme activity and heterogeneity identical to the parental cells; therefore, the heterogeneity represents transient, nonheritable differences between cells within the population.

The photoreduction of H(2)O(2) by Synechococcus sp. PCC 7942 and UTEX 625

It has been claimed that the sole H(2)O(2)-scavenging system in the cyanobacterium Synechococcus sp. PCC 7942 is a cytosolic catalase-peroxidase. We have measured in vivo activity of a light-dependent peroxidase in Synechococcus sp. PCC 7942 and UTEX 625. The addition of small amounts of H(2)O(2) (2.5 microM) to illuminated cells caused photochemical quenching (qP) of chlorophyll fluorescence that was relieved as the H(2)O(2) was consumed. The qP was maximal at about 50 microM H(2)O(2) with a Michaelis constant of about 7 microM. The H(2)O(2)-dependent qP strongly indicates that photoreduction can be involved in H(2)O(2) decomposition. Catalase-peroxidase activity was found to be almost completely inhibited by 10 microM NH(2)OH with no inhibition of the H(2)O(2)-dependent qP, which actually increased, presumably due to the light-dependent reaction now being the only route for H(2)O(2)-decomposition. When (18)O-labeled H(2)O(2) was presented to cells in the light there was an evolution of (16)O(2), indicative of H(2)(16)O oxidation by PS 2 and formation of photoreductant. In the dark (18)O(2) was evolved from added H(2)(18)O(2) as expected for decomposition by the catalase-peroxidase. This evolution was completely blocked by NH(2)OH, whereas the light-dependent evolution of (16)O(2) during H(2)(18)O(2) decomposition was unaffected.

Career pathways in dentistry

During the next decade we are likely to see the greatest changes in the way in which dentistry is delivered than at any point since the introduction of the National Health Service in 1948. The move in the primary-care sector from a mainly NHS service to a mixed economy, the emergence of more practices operated by bodies corporate and the possibility of high-street specialists will all impact on every aspect of professional life. For those trying to plan a career or looking to change pathways it can be difficult to identify which pathway to follow. The purpose of this article is to explore the possible routes for career development.

Characterization of the non-photochemical quenching of chlorophyll fluorescence that occurs during the active accumulation of inorganic carbon in the cyanobacterium Synechococcus PCC 7942

Previous work has shown that the maximum fluorescence yield from PS 2 of Synechococcus PCC 7942 occurs when the cells are at the CO2 compensation point. The addition of inorganic carbon (Ci), as CO2 or HCO3 (-), causes a lowering of the fluorescence yield due to both photochemical (qp) and non-photochemical (qN) quenching. In this paper, we characterize the qN that is induced by Ci addition to cells grown at high light intensities (500 μmol photons m(-2) s(-1)). The Ci-induced qN was considerably greater in these cells than in cells grown at low light intensities (50 μmol photons m(-2) s(-1)), when assayed at a white light (WL) intensity of 250 μmol photons m(-2) s(-1). In high-light grown cells we measured qN values as high as 70%, while in low-light grown cells the qN was about 16%. The qN was relieved when cells regained the CO2 compensation point, when cells were illuminated by supplemental far-red light (FRL) absorbed mainly by PS 1, or when cells were illuminated with increased WL intensities. These characteristics indicate that the qN was not a form of energy quenching (qE). Supplemental FRL illumination caused significant enhancement of photosynthetic O2 evolution that could be correlated with the changes in qp and qN. The increases in qp induced by Ci addition represent increases in the effective quantum yield of PS 2 due to increased levels of oxidized QA. The increase in qN induced by Ci represents a decrease in PS 2 activity related to decreases in the potential quantum yield. The lack of diagnostic changes in the 77 K fluorescence emission spectrum argue against qN being related to classical state transitions, in which the decrease in potential quantum yield of PS 2 is due either to a decrease in absorption cross-section or by increased 'spill-over' of excitation energy to PS 1. Both the Ci-induced qp (t 0.5<0.5 s) and qN (t 0.5≃1.6 s) were rapidly relieved by the addition of DCMU. The two time constants give further support for two separate quenching mechanisms. We have thus characterized a novel form of qN in cyanobacteria, not related to state transitions or energy quenching, which is induced by the addition of Ci to cells at the CO2-compensation point.

Placental weight, birth measurements, and blood pressure at age 8 years

OBJECTIVE

To examine relationships between blood pressure during childhood and both placental weight and body size at birth, in an Australian population.

DESIGN

A follow up study of a birth cohort, undertaken when cohort members were aged 8 years.

SETTING

Adelaide, South Australia.

SUBJECTS

830 children born in the Queen Victoria Hospital in Adelaide, South Australia, during 1975-6.

MAIN OUTCOME MEASURES

Systolic and diastolic blood pressure measured when the children were aged 8 years.

RESULTS

Blood pressure at 8 years was positively related to placental weight and inversely related to birth weight, after adjusting for the child's current weight. For diastolic pressure there was a decrease of 1.0 mm Hg for each 1 kg increase in birth weight (95% confidence interval (CI) = -0.4 to 2.4) and an increase of 0.7 mm Hg for each 100 g increase in placental weight (95% CI = 0.1 to 1.3). Diastolic pressure was also inversely related to chest circumference at birth, independently of placental weight, with a decrease of 0.3 mm Hg for each 1 cm increase in chest circumference (95% CI = 0.2 to 0.5).

CONCLUSIONS

These findings are further evidence that birth characteristics, indicative of fetal growth patterns, are related to blood pressure in later life.

Conversion of a delayed rectifier K+ channel to a voltage-gated inward rectifier K+ channel by three amino acid substitutions

Single, double, and triple mutations progressively shift Shaker activation to more hyperpolarized potentials, resulting in an increase in the fraction of inactivated channels at negative resting voltages. The most negatively shifted mutation, the triple mutant, behaves like an inward rectifier. What is usually considered activation of an inward rectifier is, for the triple mutant, recovery from inactivation, and what is usually considered deactivation is inactivation. This conversion from outward rectifier to inward rectifier does not rely on a difference in sign or direction of charge movement of the voltage sensor, since activation of the Shaker outward rectifier is due to a different gate than activation of the triple mutant inward rectifier. Other voltage-dependent inward rectifiers in the Shaker family may work by a similar mechanism.

Junctional permeability measurements in the embryonic chick lens

The purpose of this paper is two-fold: to measure junctional permeability of different types of dissociated lens cells and to compare the junctional permeability of dissociated lens cells to that of cells in the intact lens. Dissociated embryonic chick lens cells and intact embryonic chick lenses were loaded with the fluorescent dye 5,6 carboxyfluorescein diacetate. The return of fluorescence after bleaching an individual cell was used to estimate cell-to-cell permeability. Use of the confocal microscope facilitated quantitation of the return of fluorescence as well as optical sectioning needed to measure cell-to-cell permeability in an intact lens. Two types of dissociated cells were studied: spherical and short elongated cells. The average rate constant for 5,6 carboxyfluorescein transfer between these cells was 7.9 x 10(-3) sec-1 and 8.1 x 10(-3) sec-1, respectively. The junctional permeability for both types of cells was reduced by lowering internal pH to 6.0 by bathing the cells in a sodium acetate solution. Permeability measurements of the central epithelial cells of an isolated whole lens gave an average rate constant of 2.6 x 10(-3) sec-1, comparable to the rates measured in the dissociated cells. These results establish that the photobleach method can be used in intact lens to quantitatively assess junctional permeability and that dissociated epithelial cells have very nearly the same junctional permeabilities as cells in the intact lens.

A typology of mother-daughter relationship patterns for young adult women and their mothers

Qualitative and quantitative methods were used in this study of developmental themes in the context of the mother-daughter relationship. Semistructured interviews were conducted with 60 women, aged 23-42 years. A rating guide for individuation was developed for content analysis of interview material. The dimensions of the rating guide included (1) psychological autonomy from family of origin, (2) empathy, (3) tolerance of ambiguity, and (4) maintenance of self-esteem. Cluster analysis was employed to assign women with similar individuation profiles into five groups. A typology was constructed that represents styles of mother-daughter interaction. The study findings suggest that typological differences based on individuation themes can be used to describe overall patterns of the mother-daughter relationship over time. These patterns provide a useful context in which to study mother-daughter interactions through the life span.

Family nurse practitioner clinical competencies in alcohol and substance use

The prevalence of substance use among patients presenting to primary health care settings mandates clinical competency in the area for nurse practitioners (NPs). An educational intervention with an evaluation component is described. The effect of incorporating substance use content into a Family Nurse Practitioner (FNP) curriculum was tested with a convenience sample of 16 FNP students and 8 practicing NPs. Students' knowledge increased significantly; however, differences in students' and practicing NPs' knowledge did not reach significance. Students' clinical competency increased significantly, as demonstrated by standardized patient clinical evaluations, and was significantly better than the practicing NPs in the skill domains of evaluation and record keeping. Educational intervention can improve NP identification of substance-abusing patients in primary health care settings.

Diurnal urinary volume and uranium output in uranium workers and unexposed controls

Volume and uranium content were determined in individual urine voids over a 76-h (3.25-d) period from six unexposed normal male subjects and three male uranium workers. Uranium analyses were accomplished by a newly developed high-precision kinetic phosphorescence analysis technique with a lower level of detection of 0.007 ng mL-1. Urinary uranium concentrations in individual voids varied by a factor of 2 or less for any one unexposed subject, although there was an order of magnitude variation among the group of unexposed men. The fractional urinary volume excreted in the "standard" so-called simulated 24-h sample was the same for both the unexposed and exposed groups and averaged 0.42 +/- 0.13 of the total daily urine volume. The fraction of uranium in the simulated 24-h samples was 0.43 +/- 0.15 in the unexposed group but only 0.31 +/- 0.13 in the uranium worker group, suggesting that the use of the simulated 24-h urine sample would underestimate the total daily urinary uranium output by approximately a factor of 2 in the uranium workers. Daily urinary excretion relative to intake from drinking water (essentially equal to the gastrointestinal uptake fraction) among the unexposed group ranged from 0.002-0.028, averaging 0.011 +/- 0.008, with an indication that the gastrointestinal uptake factor was inversely proportional to total intake via drinking water.

Single-membrane and cell-to-cell permeability properties of dissociated embryonic chick lens cells

Ion channels are believed to play an important role in the maintenance of lens transparency. In order to ascribe junctional and nonjunctional permeability properties to specific lens cell types, embryonic chick lenses were enzymatically dissociated into cell clusters, cell pairs and single cells, and both cell-to-cell and single-membrane permeability properties were characterized with the patch-clamp technique. Double patch-clamp experiments and single patch-clamp experiments with Lucifer yellow in the pipette demonstrated that the cells in the dissociated preparation were well coupled, the average conductance between pairs being 42 +/- 27 nS. Double patch-clamp experiments also revealed single cell-to-cell channel events with a predominant unitary conductance of 286 +/- 38 pS. Whole-cell measurements of surface membrane conductance indicate heterogeneity within the population of dissociated embryonic chick lens cells: 63% of the cells have a voltage-independent leak current, 14% of the cells have a potassium-selective inward-rectifier current, and 23% of the cells have a current which turns off with positive voltage on a time scale on the order of seconds. The time constant for this turnoff is voltage dependent.

High Affinity Transport of CO(2) in the Cyanobacterium Synechococcus UTEX 625

The active transport of CO(2) in Synechococcus UTEX 625 was measured by mass spectrometry under conditions that preclude HCO(3) (-) transport. The substrate concentration required to give one half the maximum rate for whole cell CO(2) transport was determined to be 0.4 +/- 0.2 micromolar (mean +/- standard deviation; n = 7) with a range between 0.2 and 0.66 micromolar. The maximum rates of CO(2) transport ranged between 400 and 735 micromoles per milligram of chlorophyll per hour with an average rate of 522 for seven experiments. This rate of transport was about three times greater than the dissolved inorganic carbon saturated rate of photosynthetic O(2) evolution observed under these conditions. The initial rate of chlorophyll a fluorescence quenching was highly correlated with the initial rate of CO(2) transport (correlation coefficient = 0.98) and could be used as an indirect method to detect CO(2) transport and calculate the substrate concentration required to give one half the maximum rate of transport. Little, if any, inhibition of CO(2) transport was caused by HCO(3) (-) or by Na(+)-dependent HCO(3) (-) transport. However, (12)CO(2) readily interfered with (13)CO(2) transport. CO(2) transport and Na(+)-dependent HCO(3) (-) transport are separate, independent processes and the high affinity CO(2) transporter is not only responsible for the initial transport of CO(2) into the cell but also for scavenging any CO(2) that may leak from the cell during ongoing photosynthesis.

Glycolaldehyde Inhibits CO(2) Fixation in the Cyanobacterium Synechococcus UTEX 625 without Inhibiting the Accumulation of Inorganic Carbon or the Associated Quenching of Chlorophyll a Fluorescence

When studying active CO(2) and HCO(3) (-) transport by cyanobacteria, it is often useful to be able to inhibit concomitant CO(2) fixation. We have found that glycolaldehyde was an efficient inhibitor of photosynthetic CO(2) fixation in Synechococcus UTEX 625. Glycolaldehyde did not inhibit inorganic carbon accumulation due to either active CO(2) or HCO(3) (-) transport. When glycolaldehyde (10 millimolar) was added to rapidly photosynthesizing cells, CO(2) fixation was stopped within 15 seconds. The quenching of chlorophyll a fluorescence remained high (</= 82% control) when CO(2) fixation was completely blocked by glycolaldehyde. This quenching was relieved upon the addition of a glucose oxidase oxygentrap. This is consistent with our previous finding that q-quenching in the absence of CO(2) fixation was due to O(2) photoreduction. Photosynthetic CO(2) fixation was also inhibited by d,l,-glyceraldehyde but a sixfold higher concentration was required. Glycolaldehyde acted much more rapidly than iodoacetamide (15 seconds versus 300 seconds) and did not cause the onset of net O(2) evolution often observed with iodoacetamide. Glycolaldehyde will be a useful inhibitor when it is required to study CO(2) and HCO(3) (-) transport without the complication of concomitant CO(2) fixation.

Selective and Reversible Inhibition of Active CO(2) Transport by Hydrogen Sulfide in a Cyanobacterium

The active transport of CO(2) in the cyanobacterium Synechococcus UTEX 625 was inhibited by H(2)S. Treatment of the cells with up to 150 micromolar H(2)S + HS(-) at pH 8.0 had little effect on Na(+)-dependent HCO(3) (-) transport or photosynthetic O(2) evolution, but CO(2) transport was inhibited by more than 90%. CO(2) transport was restored when H(2)S was removed by flushing with N(2). At constant total H(2)S + HS(-) concentrations, inhibition of CO(2) transport increased as the ratio of H(2)S to HS(-) increased, suggesting a direct role for H(2)S in the inhibitory process. Hydrogen sulfide does not appear to serve as a substrate for transport. In the presence of H(2)S and Na(+) -dependent HCO(3) (-) transport, the extracellular CO(2) concentration rose considerably above its equilibrium level, but was maintained far below its equilibrium level in the absence of H(2)S. The inhibition of CO(2) transport, therefore, revealed an ongoing leakage from the cells of CO(2) which was derived from the intracellular dehydration of HCO(3) (-) which itself had been recently transported into the cells. Normally, leaked CO(2) is efficiently transported back into the cell by the CO(2) transport system, thus maintaining the extracellular CO(2) concentration near zero. It is suggested that CO(2) transport not only serves as a primary means of inorganic carbon acquisition for photosynthesis but also serves as a means of recovering CO(2) lost from the cell. A schematic model describing the relationship between the CO(2) and HCO(3) (-) transport systems is presented.

Use of Carbon Oxysulfide, a Structural Analog of CO(2), to Study Active CO(2) Transport in the Cyanobacterium Synechococcus UTEX 625

Carbon oxysulfide (carbonyl sulfide, COS) is a close structural analog of CO(2). Although hydrolysis of COS (to CO(2) and H(2)S) does occur at alkaline pH (>9), at pH 8.0 the rate of hydrolysis is slow enough to allow investigation of COS as a possible substrate and inhibitor of the active CO(2) transport system of Synechococcus UTEX 625. A light-dependent uptake of COS was observed that was inhibited by CO(2) and the ATPase inhibitor diethylstilbestrol. The COS taken up by the cells could not be recovered when the lights were turned off or when acid was added. It was concluded that most of the COS taken up was hydrolyzed by intracellular carbonic anhydrase. The production of H(2)S was observed and COS removal from the medium was inhibited by ethoxyzolamide. Bovine erythrocyte carbonic anhydrase catalysed the stoichiometric hydrolysis of COS to H(2)S. The active transport of CO(2) was inhibited by COS in an apparently competitive manner. When Na(+)-dependent HCO(3) (-) transport was allowed in the presence of COS, the extracellular [CO(2)] rose considerably above the equilibrium level. This CO(2) appearing in the medium was derived from the dehydration of transported HCO(3) (-) and was leaked from the cells. In the presence of COS the return to the cells of this leaked CO(2) was inhibited. These results showed that the Na(+)-dependent HCO(3) (-) transport was not inhibited by COS, whereas active CO(2) transport was inhibited. When COS was removed by gassing with N(2), a normal pattern of CO(2) uptake was observed. The silicone fluid centrifugation method showed that COS (100 micromolar) had little effect upon the initial rate of HCO(3) (-) transport or CO(2) fixation. The steady state rate of CO(2) fixation was, however, inhibited about 50% in the presence of COS. This inhibition can be at least partially explained by the significant leakage of CO(2) from the cells that occurred when CO(2) uptake was inhibited by COS. Neither CS(2) nor N(2)O acted like COS. It is concluded that COS is an effective and selective inhibitor of active CO(2) transport.

Placenta praevia--a review with emphasis on the role of ultrasound

Considerable confusion exists in the literature as a result of the wide range of classification systems for placenta praevia (PP) and low-lying placenta. The discrepancy between frequency of low-lying placentas in the second trimester and PP at term reflects to a certain extent the lack of understanding of the anatomy and physiology of the pregnant uterus. It seems that 'placental conversion' is a real phenomenon and is probably due to the differential growth rates of the placenta and uterus. Maternal bladder overdistension and myometrial contractions account for only a small part of the discrepancy. Diagnostic ultrasound obviously has an important role in placental localization. The role of Magnetic Resonance Imaging remains to be determined. The management of patients with low-lying placenta diagnosed in the second trimester, and the frequency of repeat scans is determined largely by the management protocol of the attending obstetrician.

Active CO(2) Transport by the Green Alga Chlamydomonas reinhardtii

Mass spectrometric measurements of dissolved free (13)CO(2) were used to monitor CO(2) uptake by air grown (low CO(2)) cells and protoplasts from the green alga Chlamydomonas reinhardtii. In the presence of 50 micromolar dissolved inorganic carbon and light, protoplasts which had been washed free of external carbonic anhydrase reduced the (13)CO(2) concentration in the medium to close to zero. Similar results were obtained with low CO(2) cells treated with 50 micromolar acetazolamide. Addition of carbonic anhydrase to protoplasts after the period of rapid CO(2) uptake revealed that the removal of CO(2) from the medium in the light was due to selective and active CO(2) transport rather than uptake of total dissolved inorganic carbon. In the light, low CO(2) cells and protoplasts incubated with carbonic anhydrase took up CO(2) at an apparently low rate which reflected the uptake of total dissolved inorganic carbon. No net CO(2) uptake occurred in the dark. Measurement of chlorophyll a fluorescence yield with low CO(2) cells and washed protoplasts showed that variable fluorescence was mainly influenced by energy quenching which was reciprocally related to photosynthetic activity with its highest value at the CO(2) compensation point. During the linear uptake of CO(2), low CO(2) cells and protoplasts incubated with carbonic anhydrase showed similar rates of net O(2) evolution (102 and 108 micromoles per milligram of chlorophyll per hour, respectively). The rate of net O(2) evolution (83 micromoles per milligram of chlorophyll per hour) with washed protoplasts was 20 to 30% lower during the period of rapid CO(2) uptake and decreased to a still lower value of 46 micromoles per milligram of chlorophyll per hour when most of the free CO(2) had been removed from the medium. The addition of carbonic anhydrase at this point resulted in more than a doubling of the rate of O(2) evolution. These results show low CO(2) cells of Chlamydomonas are able to transport both CO(2) and HCO(3) (-) but CO(2) is preferentially removed from the medium. The external carbonic anhydrase is important in the supply to the cells of free CO(2) from the dehydration of HCO(3) (-).

Characterization of the na-requirement in cyanobacterial photosynthesis

The Na(+) requirement for photosynthesis and its relationship to dissolved inorganic carbon (DIC) concentration and Li(+) concentration was examined in air-grown cells of the cyanobacterium Synechococcus leopoliensis UTEX 625 at pH 8. Analysis of the rate of photosynthesis (O(2) evolution) as a function of Na(+) concentration, at fixed DIC concentration, revealed two distinct regions to the response curve, for which half-saturation values for Na(+) (K((1/2))[Na(+)]) were calculated. The value of both the low and the high K((1/2))(Na(+)) was dependent upon extracellular DIC concentration. The low K((1/2))(Na(+)) decreased from 1000 micromolar at 5 micromolar DIC to 200 micromolar at 140 micromolar DIC whereas over the same DIC concentration range the high K((1/2))(Na(+)) decreased from 10 millimolar to 1 millimolar. The most significant increases in photosynthesis occurred in the 1 to 20 millimolar range. A fraction of total photosynthesis, however, was independent of added Na(+) and this fraction increased with increased DIC concentration. A number of factors were identified as contributing to the complexity of interaction between Na(+) and DIC concentration in the photosynthesis of Synechococcus. First, as revealed by transport studies and mass spectrometry, both CO(2) and HCO(3) (-) transport contributed to the intracellular supply of DIC and hence to photosynthesis. Second, both the CO(2) and HCO(3) (-) transport systems required Na(+), directly or indirectly, for full activity. However, micromolar levels of Na(+) were required for CO(2) transport while millimolar levels were required for HCO(3) (-) transport. These levels corresponded to those found for the low and high K((1/2))(Na(+)) for photosynthesis. Third, the contribution of each transport system to intracellular DIC was dependent on extracellular DIC concentration, where the contribution from CO(2) transport increased with increased DIC concentration relative to HCO(3) (-) transport. This change was reflected in a decrease in the Na(+) concentration required for maximum photosynthesis, in accord with the lower Na(+)-requirement for CO(2) transport. Lithium competitively inhibited Na(+)-stimulated photosynthesis by blocking the cells' ability to form an intracellular DIC pool through Na(+)-dependent HCO(3) (-) transport. Lithium had little effect on CO(2) transport and only a small effect on the size of the pool it generated. Thus, CO(2) transport did not require a functional HCO(3) (-) transport system for full activity. Based on these observations and the differential requirement for Na(+) in the CO(2) and HCO(3) (-) transport system, it was proposed that CO(2) and HCO(3) (-) were transported across the membrane by different transport systems.

Active Transport of Inorganic Carbon Increases the Rate of O(2) Photoreduction by the Cyanobacterium Synechococcus UTEX 625

Chlorophyll a fluorescence of Synechococcus UTEX 625 was quenched during the transport of inorganic carbon, even when CO(2) fixation was inhibited by iodoacetamide. Measurements with a pulse modulation fluorometer showed that at least 75% of the quenching was due to oxidation of Q(a), the primary acceptor of photosystem II. Mass spectrometry revealed that transport of inorganic carbon increased the rate of O(2) photoreduction. Hence, O(2) could serve as an electron acceptor to allow oxidation of Q(a) even in the absence of CO(2) fixation.

Simultaneous Transport of CO(2) and HCO(3) by the Cyanobacterium Synechococcus UTEX 625

A mass spectrometer was used to simultaneously follow the time course of photosynthetic O(2) evolution and CO(2) depletion of the medium by cells of the cyanobacterium Synechococcus leopoliensis UTEX 625. Analysis of the data indicated that both CO(2) and HCO(3) (-) were simultaneously and continuously transported by the cells as a source of substrate for photosynthesis. Initiation of HCO(3) (-) transport by Na(+) addition had no effect on ongoing CO(2) transport. This result is interpreted to indicate that the CO(2) and HCO(3) (-) transport systems are separate and distinctly different transport systems. Measurement of CO(2)-dependent photosynthesis indicated that CO(2) uptake involved active transport and that diffusion played only a minor role in CO(2) acquisition in cyanobacteria.

Chlorophyll a Fluorescence Yield as a Monitor of Both Active CO(2) and HCO(3) Transport by the Cyanobacterium Synechococcus UTEX 625

Simultaneous measurements have been made of inorganic carbon accumulation (by mass spectrometry) and chlorophyll a fluorescence yield of the cyanobacterium Synechococcus UTEX 625. The accumulation of inorganic carbon by the cells was accompanied by a substantial quenching of chlorophyll a fluorescence. The quenching occurred even when CO(2) fixation was inhibited by iodoacetamide and whether the accumulation of inorganic carbon resulted from either active CO(2) or HCO(3) (-) transport. Measurement of chlorophyll a fluorescence yield of cyanobacteria may prove to be a rapid and convenient means of screening for mutants of inorganic carbon accumulation.

Active Transport of CO(2) by the Cyanobacterium Synechococcus UTEX 625 : Measurement by Mass Spectrometry

Mass spectrometry has been used to confirm the presence of an active transport system for CO(2) in Synechococcus UTEX 625. Cells were incubated at pH 8.0 in 100 micromolar KHCO(3) in the absence of Na(+) (to prevent HCO(3) (-) transport). Upon illumination the cells rapidly removed almost all the free CO(2) from the medium. Addition of carbonic anhydrase revealed that the CO(2) depletion resulted from a selective uptake of CO(2), rather than a total uptake of all inorganic carbon species. CO(2) transport stopped rapidly (<3 seconds) when the light was turned off. Iodoacetamide (3.3 millimolar) completely inhibited CO(2) fixation but had little effect on CO(2) transport. In iodoacetamide poisoned cells, transport of CO(2) occurred against a concentration gradient of about 18,000 to 1. Transport of CO(2) was completely inhibited by 10 micromolar diethylstilbestrol, a membrane-bound ATPase inhibitor. Studies with DCMU and PSI light indicated that CO(2) transport was driven by ATP produced by cyclic or pseudocyclic photophosphorylation. Low concentrations of Na(+) (<100 microequivalents per liter), but not of K(+), stimulated CO(2) transport as much as 2.4-fold. Unlike Na(+)-dependent HCO(3) (-) transport, the transport of CO(2) was not inhibited by high concentrations (30 milliequivalents per liter) of Li(+). During illumination, the CO(2) concentration in the medium remained far below its equilibrium value for periods up to 15 minutes. This could only happen if CO(2) transport was continuously occurring at a rapid rate, since the continuing dehydration of HCO(3) (-) to CO(2) would rapidly raise the CO(2) concentration to its equilibrium value if transport ceased. Measurement of the rate of dissolved inorganic carbon accumulation under these conditions indicated that at least part of the continuing CO(2) transport was balanced by HCO(3) (-) efflux.