Occult injuries to the diaphragm: prospective evaluation of laparoscopy in penetrating injuries to the left lower chest

BACKGROUND

To evaluate the incidence of occult diaphragmatic injuries and investigate the role of laparoscopy in patients with penetrating trauma to the left lower chest who lack indications for exploratory celiotomy other than the potential for a diaphragm injury.

STUDY DESIGN

Patients with penetrating injuries to the left lower chest who were hemodynamically stable and without indications for a celiotomy were prospectively evaluated with diagnostic laparoscopy to determine the presence of an injury to the left hemidiaphragm. Diagnostic laparoscopy was performed in the operating room under general anesthesia.

RESULTS

One-hundred-ten patients (94 stab wounds, 16 gunshot wounds) were evaluated with laparoscopy. Twenty-six (24%) diaphragmatic injuries were identified (26% for stab wounds and 13% for gunshot wounds). Comparison of patients with diaphragmatic injuries with those without diaphragmatic injuries demonstrated a slightly greater incidence of hemo/pneumothoraces (35% versus 24%, NS). The incidence of diaphragmatic injuries in patients with a normal chest x-ray was 21% versus 31% for patients with a hemo/pneumothorax. An elevated left hemidiaphragm was associated with a diaphragmatic injuries in only 1 of 7 patients (14%). The incidence of diaphragmatic injuries was similar for anterior, lateral, and posterior injuries (22%, 27%, and 22% respectively).

CONCLUSIONS

The incidence of occult diaphragmatic injuries in penetrating trauma to the left lower chest is high, 24%. These injuries are associated with a lack of clinical and radiographic findings, and would have been missed had laparoscopy not been performed. Patients with penetrating trauma to the left lower chest who do not have any other indication for a celiotomy should undergo videoscopic evaluation of the left hemidiaphragm to exclude an occult injury.

Inability of an aggressive policy of thromboprophylaxis to prevent deep venous thrombosis (DVT) in critically injured patients: are current methods of DVT prophylaxis insufficient?

BACKGROUND

Deep venous thrombosis (DVT) in severely injured patients is a life-threatening complication. Effective and safe thromboprophylaxis is highly desirable to prevent DVT. Low-dose heparin (LDH) and sequential compression device (SCDs) are the most frequently used methods. Inappropriate use of these methods because of the nature or site of critical injuries (eg, brain lesion, solid visceral or retroperitoneal hematoma, extremity fractures) may lead to failure of DVT prophylaxis.

STUDY DESIGN

A prospective study was performed to evaluate the efficacy of a policy of aggressive use of LDH and SCDs in patients who are at very high risk for DVT. From January 1996 to August 1997, 200 critically injured patients were followed by weekly Doppler examinations to detect DVT at the proximal lower extremities. Only 3 patients did not receive any thromboprophylaxis. SCDs were applied in 97.5% and LDH was administered to 46% of the patients; 45% had both.

RESULTS

DVT was found in 26 patients (13%). The majority (58%) developed DVT within the first 2 weeks, but new cases were found as late as 12 weeks after admission. The incidence of DVT was the same among patients who had SCDs only or a combination of LDH and SCDs. Mechanism of injury, type and number of operations, site of injury, Injury Severity Score, and the incidence of femoral lines were not different between patients with and without DVT. Differences were found in the severity of injury to the chest and the extremities and the need for high-level respiratory support. Patients with DVT had prolonged ICU and hospital stays (on average, 34 and 49 days, respectively) and a high mortality rate (31%).

CONCLUSIONS

The incidence of DVT remains high among severely injured patients despite aggressive thromboprophylaxis. A combination of LDH and an SCD showed no advantage over SCD alone in decreasing DVT rates. Risk factors in this group of patients who are already at very high risk are hard to detect; Doppler examinations are justified for surveillance in all critically injured patients. Current methods of thromboprophylaxis seem to offer limited efficacy, and the search for more effective methods should continue.

Timing of fracture fixation in blunt trauma patients with severe head injuries

BACKGROUND

Early fracture fixation in blunt trauma patients is suggested to decrease postoperative morbidity by allowing early mobilization and reducing the release of harmful inflammatory mediators. Some studies have challenged this concept in the presence of severe associated injuries, and especially head trauma.

METHODS

The records of 47 consecutive blunt trauma patients with severe head injuries, as defined by a Glasgow Coma Score (GCS) < or =8 and a head Abbreviated Injury Score (AIS) > or =3, and long bone fractures requiring surgical fixation were reviewed. The study population was divided into the early fixation (EF) group, consisting of 22 patients who underwent fracture fixation within 24 hours of admission (mean time 17 +/- 8.5 hours); and the late fixation (LF) group, consisting of 25 patients, who had orthopedic repair at a later time (mean 143 +/- 178 hours).

RESULTS

The two groups were similar in terms of overall injury severity, neurologic injuries, hemodynamic and neurologic status on admission, and operations received. Patients in the EF group had a higher injury severity of extremity fractures (extremity AIS: 2.9 +/- 0.2 versus 2.4 +/- 0.5, P = 0.0002) and a higher incidence of open fractures (72% versus 36%, P = 0.02). There was no difference in intraoperative and postoperative hypoxic and hypotensive episodes. Neurologic, orthopedic, and general complications were the same between the two groups. The mean GCS on discharge was 12 +/- 3 for both groups with equal distribution among patients. Although there was a trend toward longer hospital stay (25 +/- 17 versus 17 +/- 10 days, P = 0.057) among LF patients, mechanical ventilation days, length of stay, and mortality were not different.

CONCLUSIONS

Timing of fracture fixation in this group of blunt trauma patients with severe head injuries did not influence morbidity, mortality, or neurologic outcome.

Lethal abdominal gunshot wounds at a level I trauma center: analysis of TRISS (Revised Trauma Score and Injury Severity Score) fallouts

BACKGROUND

The TRISS methodology (composite index of the Revised Trauma Score and the Injury Severity Score) has become widely used by trauma centers to assess quality of care. The American College of Surgeons recommends including negative TRISS fallouts (fatally injured patients predicted to survive by the TRISS methodology) as a filter to select patients for peer review. The purpose of this study was to analyze the TRISS fallouts among patients with lethal abdominal gunshot wounds admitted to a level I trauma center.

STUDY DESIGN

All patients categorized as TRISS fallouts admitted from January 1995 through December 1996 were analyzed.

RESULTS

During the study period, 848 patients with abdominal gunshot wounds were admitted. Of the 108 patients with any sign of life on admission who subsequently died, 39 (36%) were TRISS fallouts. The patients were largely young (mean age, 29 years) and male (87%), received rapid transport (mean scene time, 11 minutes), and had an attending-led trauma-team response (<5 minutes, 87%). Major vascular (80%) and multiple intraabdominal injuries (90%) predominated. The mean Penetrating Abdominal Trauma Index was 40.3. The mean TRISS probability of survival was 89%. The peer-review process deemed the deaths to be nonpreventable in 38 patients (97%) and potentially preventable in one patient (3%).

CONCLUSIONS

"TRISS fallouts" were predominantly patients who died despite receiving rapid prehospital transport, rapid senior-level trauma-team response, and surgical intervention for a serious complex of injuries. We conclude that without regional adjustment of coefficients used to predict the probability of survival, the TRISS methodology is of limited use in patients with abdominal gunshot wounds.

The fate of colonic suture lines in high-risk trauma patients: a prospective analysis

BACKGROUND

Some authors have stated that virtually all patients with penetrating colon injuries can be safely managed with primary repair. The purpose of this study is to test the applicability of this statement to all trauma patients by evaluating a protocol of liberal primary repair applied to a group of patients at high risk of septic complications.

STUDY DESIGN

We performed a prospective analysis of a liberal policy of primary repair applied to patients at high risk of developing postoperative septic complications admitted to a Level I urban trauma center. Inclusion criteria were full-thickness colon injury and at least one of three additional risk factors: 1) Penetrating Abdominal Trauma Index (PATI) of 25 or more; 2) 6 U or more of blood transfused; and 3) 6 hours or longer elapsed between injury and surgery.

RESULTS

Of 56 patients studied (55 male, 1 female, average age 28.8 years, mean PATI 35.3), the vast majority had gunshot wounds as the mechanism of injury (89%), PATI 25 or more (95%), multiple blood transfusions (77%), an Injury Severity Score greater than 15 (66%), and a need for postoperative ventilatory support in the surgical intensive care unit (61%). Of 56 patients, 49 (88%) had at least one colonic suture line, and 25 patients (45%) had destructive colon injuries requiring resection. Intraabdominal infections occurred in 15 (27%) of 56 patients and colon suture line disruption occurred in 3 (6%) of 49. Two of these patients developed multisystem organ failure, and death was directly related to breakdown of their colonic anastomosis.

CONCLUSIONS

On the basis of these data and the relative infrequency of patients in prospective randomized trials with destructive colon injuries, we believe there is still room for consideration of fecal diversion in patients in high-risk categories with destructive colon injuries requiring resection.

Localisation and interaction of the protein components of the yeast 2 mu circle plasmid partitioning system suggest a mechanism for plasmid inheritance

Replicating plasmids are highly unstable in yeast, because they are retained in mother cells. The 2 mu circle plasmid overcomes this maternal inheritance bias by using a partitioning system that involves the plasmid encoded proteins Rep1p and Rep2p, and the cis-acting locus STB. It is thus widely exploited as a cloning vehicle in yeast. However, little is known about the cellular or molecular mechanisms by which effective partitioning is achieved, and models of both free diffusion and plasmid localisation have been proposed. Here we show that Rep1p and Rep2p proteins interact to form homo- and hetero-complexes in vitro. In vivo, Rep1p and Rep2p are shown to be nuclear proteins, exhibiting sub-nuclear concentration in distinct foci. The number of foci appears constant regardless of plasmid copy number and cell ploidy level. Before cell division, the number of foci increases, and we observe approximately equal allocation of foci to mother and daughter cell nuclei. We show that whereas Rep2p expressed alone is found exclusively in the nucleus, Rep1p requires the presence of Rep2p for effective nuclear localisation. High levels of 2 mu plasmid induce a multiple-budded elongated cell phenotype, which we show can be phenocopied by overexpression of both REP1 and REP2 together but not alone. Taken together, these results suggest that Rep1p and Rep2p interact in vivo, and occupy defined nuclear sites that are allocated to both mother and daughter nuclei during division. We propose a model for 2 mum plasmid partitioning based on these results, involving the association of plasmid DNA with specific, segregated subnuclear sites.

Multiple genes encoding the conserved CCAAT-box transcription factor complex are expressed in Arabidopsis

The CCAAT motif is found in the promoters of many eukaryotic genes. In yeast a single complex of three proteins, termed HAP2, HAP3, and HAP5, binds to this sequence, and in mammals the three components of the equivalent complex (called variously NF-Y, CBF, or CP1) are also represented by single genes. Here we report the presence of multiple genes for each of the components of the CCAAT-binding complex, HAP2, 3,5, from Arabidopsis. Three independent Arabidopsis HAP subunit 2 (AtHAP2) cDNAs were cloned by functional complementation of a yeast hap2 mutant, and two independent forms each of AtHAP3 and AtHAP5 cDNAs were detected in the expressed sequence tag database. Additional homologs (two of AtHAP3 and one of AtHAP5) have been identified from available Arabidopsis genomic sequences. Northern-blot analysis indicated ubiquitous expression for each AtHAP2 and AtHAP5 cDNA in a range of tissues, whereas expression of each AtHAP3 cDNA was under developmental and/or environmental regulation. The unexpected presence of multiple forms of each HAP homolog in Arabidopsis, compared with the single genes in yeast and vertebrates, suggests that the HAP2,3,5 complex may play diverse roles in gene transcription in higher plants.

Postbulbar duodenal ulceration and stenosis associated with celiac disease

The case histories of five patients with celiac disease and postbulbar duodenal ulceration and stenosis are presented. Celiac disease was unexpected in three of the five patients until endoscopic biopsy revealed villous atrophy. Our findings suggest that duodenal ulceration and stenosis may be a more common complication of celiac disease than previously thought and may precede the clinical diagnosis of celiac disease or occur when there are minimal symptoms and nonspecific radiographic findings for the disease.

The maize retinoblastoma protein homologue ZmRb-1 is regulated during leaf development and displays conserved interactions with G1/S regulators and plant cyclin D (CycD) proteins

Recent discoveries of plant retinoblastoma (Rb) protein homologues and D-type cyclins suggest that control of the onset of cell division in plants may have stronger parallels with mammalian G1/S controls than with yeasts. In mammals, the Rb protein interacts specifically with D-type cyclins and regulates cell proliferation by binding and inhibiting E2F transcription factors. However, the developmental role of Rb in plants and its potential interaction with cell cycle regulators is unknown. We show that the maize Rb homologue ZmRb-1 is temporally and spatially regulated during maize leaf development. ZmRb-1 is highly expressed in differentiating cells, but almost undetectable in proliferating cells. In vitro, both ZmRb-1 and human Rb bind all classes of plant D-type cyclins with the involvement of a conserved N-terminal Leu-x-Cys-x-Glu (LxCxE) Rb-interaction motif. This binding is strongly reduced by mutation of the conserved Cys-470 of ZmRb-1. ZmRb-1 binds human and Drosophila E2F, and inhibits transcriptional activation of human E2F. We also show that ZmRb-1 is a good in vitro substrate for all human G1/S protein kinases. The functional conservation of proteins that control the G1/S transition in mammals and plants points to the existence of plant E2F homologues. We conclude that evolution of Rb and cyclin D proteins occurred after separation of the fungi from the higher eukaryotic lineage, but preceded the divergence of plant and animal kingdoms.

Percutaneous techniques for the diagnosis and treatment of localized Langerhans-cell histiocytosis (eosinophilic granuloma of bone)

We retrospectively studied the outcome of percutaneous needle biopsy and intralesional injection of a corticosteroid (methylprednisolone) in thirty-nine patients who had localized Langerhans-cell histiocytosis (eosinophilic granuloma of bone). All thirty-nine patients had a solitary symptomatic lesion at presentation; a second lesion developed in two patients, two and four months after the first lesion was diagnosed. Therefore, there were forty-one lesions in thirty-nine patients. Fine-needle aspiration with or without core-needle biopsy was performed for all forty-one lesions, and the diagnosis of Langerhans-cell histiocytosis was established for thirty-seven (90 per cent). A corticosteroid was injected into thirty-five lesions. Twenty-nine received the injection at the time of the fine-needle aspiration on the basis of the cytological findings in the aspirate. Six patients who had a solitary lesion had a two-stage procedure because the injection was delayed until the diagnosis was confirmed with histological evaluation of specimens obtained by core-needle biopsy. Thirty-four (97 per cent) of the thirty-five lesions healed. The clinical symptoms associated with thirty-one lesions resolved within two weeks after a single injection of the corticosteroid. There were no complications associated with either the biopsy or the injection. At a median of ninety months (range, twenty-four to 199 months), no patient had recurrence of symptoms or of radiographic evidence of the lesion. All patients who had been managed with an intralesional injection of the corticosteroid had full range of motion of the affected extremity and had resumed unlimited activities. Although the mechanism of action of intralesional injection of a corticosteroid has not been defined, use of percutaneous needle biopsy to diagnose localized Langerhans-cell histiocytosis and treatment with intralesional administration of methylprednisolone relieved pain expeditiously, enabled the patient to avoid an operative procedure, and resulted in osseous healing. The specific role of corticosteroid therapy remains to be determined by prospective, randomized studies.

Penetrating thoracoabdominal trauma

Penetrating injuries to the thoracoabdominal region represent a complex and diverse population of injuries. The clinician managing such cases must be able to consider all potential injuries, rapidly recognize life-threatening sequelae, and precisely diagnose and quickly manage these patients. The diverse nature of some of the potential presentations of patients with penetrating thoracoabdominal trauma is discussed. The most recent advances and controversies involving the evaluation and management of patients with penetrating thoracoabdominal trauma are also discussed.

Effect of hydroxyl radical (OH.) on sphincter of Oddi motility

Antioxidant enzymes are present in sphincter of Oddi nerves and regulate sphincter of Oddi motor function mediated by NO-releasing nerves. Oxygen free radicals (O2-.) produce hydrogen peroxide (H2O2) by the action of superoxide dismutase (SOD). Hydroxyl radical (OH.) has been shown to play an important role as a mediator of H2O2 toxicity. The aims of our study were to determine the effects of H2O2 on sphincter of Oddi motility and if these effects are mediated by OH.. Adult opossums were sacrificed and the sphincter of Oddi removed and placed in a tissue bath containing oxygenated Krebs solution. Force transducers recorded tension in a transverse orientation at two sites along the sphincter of Oddi specimen. H2O2 was added into the tissue bath at concentrations from 0.01 to 0.5%. O2-. radicals were inhibited by the addition of SOD, while OH. was scavenged by the addition of alcohol (ETOH) or dimethyl sulfoxide (DMSO). H2O2 produced a dose-dependent increase in baseline amplitude, frequency, and peak amplitude of contractions. The effect of 0.01% H2O2 on sphincter of Oddi contractile frequency was inhibited by 0.2% ETOH and DMSO, but not by SOD. We conclude that H2O2 has profound effects on sphincter of Oddi motility and that the actions of H2O2 are probably mediated through OH..

Penetrating left thoracoabdominal trauma: the incidence and clinical presentation of diaphragm injuries

OBJECTIVE

The objective of this study was to (1) determine the incidence of diaphragmatic injuries in penetrating left thoracoabdominal trauma and (2) evaluate the role of laparoscopy in detecting clinically occult diaphragmatic injuries.

PATIENTS AND METHODS

One hundred nineteen consecutive patients with penetrating injuries to the left thoracoabdominal region presenting to Los Angeles County-University of Southern California Medical Center were prospectively evaluated during an 8-month period. Either celiotomy (with hemodynamic instability or peritonitis) or laparoscopy was performed. Results of the clinical examination and roentgenographic findings were recorded preoperatively.

RESULTS

One hundred seven patients were fully evaluated. Fifty patients required emergent celiotomy. Fifty-seven patients underwent laparoscopy. The overall incidence of diaphragmatic injuries was 42% (59% for gunshot wounds, 32% for stab wounds). Among the 45 patients with diaphragmatic injuries, 31% had no abdominal tenderness, 40% had a normal chest roentgenogram, and 49% had an associated hemopneumothorax. Fifteen of the patients undergoing laparoscopy (26%) had occult diaphragm injuries.

CONCLUSION

(1) The incidence of diaphragmatic injuries in association with penetrating left thoracoabdominal trauma is high. (2) The clinical and roentgenographic findings are unreliable at detecting occult diaphragmatic injuries. (3) Laparoscopy is a vital tool for detecting occult diaphragmatic injuries among patients who have no other indications for formal celiotomy.

Serodiagnosis of celiac disease

The detection rate of celiac disease greatly underestimates its prevalence. This is the result of lack of awareness of the many manifestations of the condition and the requirement for at least one small intestinal biopsy for diagnosis. The advent of effective serologic tests for the condition heralds a new era of non-invasive testing. The clinical utility and acceptance of these tests is limited by a lack of standardization of both the techniques used and variability of reference ranges quoted.

Effects of calcitonin gene-related peptide on opossum esophageal smooth muscle

BACKGROUND & AIMS

Peristaltic contraction of the esophagus and relaxation of the lower esophageal sphincter (LES) are mediated by nitric oxide (NO.)-producing myenteric nerves. NO synthase immunoreactivity and calcitonin gene-related peptide (CGRP) immunoreactivity colocalize in these nerves. CGRP relaxes the LES and decreases the amplitude of esophageal peristalsis. The aim of this study was to test the hypothesis that CGRP plays a role in nerve-induced responses of the esophagus.

METHODS

Smooth muscle strips from the LES and the body of the esophagus were stimulated by an electrical field to evoke nerve-mediated responses.

RESULTS

CGRP decreased the amplitude and lengthened the latency of the off-response, and it relaxed the LES. Tetrodotoxin did not block the CGRP-induced LES relaxation. The CGRP antagonist CGRP 8-37 inhibited the effects of exogenous CGRP. It increased the amplitude and shortened the latency of the off-response, and it increased the resting tone of the LES. CGRP 8-37 did not inhibit LES relaxation or esophageal contraction. N omega-nitro-L-arginine abolished nerve-induced relaxation of the LES muscle and the esophageal off-response but not the relaxation produced by CGRP.

CONCLUSIONS

These data support the hypothesis that CGRP may decrease the LES basal tone and modulate the timing and amplitude of the esophageal off-responses.

Celiac disease in an adult population with insulin-dependent diabetes mellitus: use of endomysial antibody testing

OBJECTIVE

Studies from Europe and North Africa suggest an association between type 1 diabetes mellitus (IDDM) and celiac disease (CD). Although IDDM is as common in the United States as it is in Europe, CD is diagnosed much less often in this country than in Europe. The purpose of our study was to determine the frequency with which CD occurs in patients with IDDM in the United States.

METHODS

Several serological tests are used for CD screening. The most specific and sensitive of these, the antiendomysial antibody, is the indirect immunofluorescence test which uses monkey esophagus smooth muscle as substrate. This test, which correlates closely with actual enteropathy, was used to screen 185 unselected patients with IDDM who attended the Diabetic Clinic or were housed on the Diabetic Unit of the University of Iowa Hospitals and Clinics.

RESULTS

Nine of 185 patients had positive IgA antiendomysial antibody tests. Antibody positivity did not correlate with the presence of diabetic complications, age, sex, or duration of IDDM. Five of nine antibody-positive patients underwent subsequent small intestinal biopsy. Enteropathy was confirmed in four of these patients.

CONCLUSIONS

These data suggest that CD is more common in American patients with IDDM than was previously suspected.

The role of antioxidant enzymes in the control of opossum sphincter of Oddi motility

Superoxide rapidly oxidizes nitric oxide (NO) to form peroxynitrite, thus terminating the biological activity of NO. The aims of our study were to determine if superoxide alters the motor function of the sphincter of Oddi and to localize the antioxidant enzymes in the sphincter of Oddi. Immunostaining was performed and enzyme activities were measured in the sphincter of Oddi. In physiological experiments, force-displacement transducers recorded tension in the spontaneously contracting sphincter of Oddi and after electrical field stimulation (EFS) of precontracted sphincter of Oddi. Superoxide was generated by the addition of xanthine with xanthine oxidase, superoxide radicals were scavenged by the addition of superoxide dismutase (SOD), and catalase or SOD was inhibited by diethyldithiocarbamic acid. Immunostaining demonstrated SOD and catalase immunoreactivity in ganglia situated at the serosal surface of the circular muscle. Total SOD activity was 202 +/- 12 U/mg. Generation of superoxide or inhibition of SOD increased the contractile frequency and decreased relaxation after EFS. We conclude that superoxide alters sphincter of Oddi motor function, and the presence of superoxide scavenging enzymes in enteric plexuses suggests that they may regulate sphincter of Oddi neuromuscular function by clearing endogenous superoxide.

Effects of oxygen radicals and radical scavenging on opossum lower esophageal sphincter

Nitric oxide mediates esophageal peristalsis and lower esophageal sphincter (LES) relaxation. Superoxide produced with inflammation inactivates nitric oxide. Superoxide is cleared in biological systems by superoxide dismutase. We tested the hypothesis that superoxide and the superoxide scavenging system modulate LES function. Transverse strips of muscle from the opossum LES relaxed when stimulated by an electrical field. Diethyldithiocarbamite was used to inhibit copper/zinc superoxide dismutase. Xanthine and xanthine oxidase were used to generate superoxide. Xanthine with xanthine oxidase or diethyldithiocarbamite alone had no effect on the LES. However, xanthine/xanthine oxidase and diethyldithiocarbamite reduced LES relaxation 34.1% and increased its resting tone 71.2%. Superoxide dismutase did not affect LES function, but protected the tissue from the effects of diethyldithiocarbamite and xanthine/xanthine oxidase. These studies are consistent with the hypothesis that superoxide acts by inactivating nitric oxide and suggest that these antioxidant enzyme systems may play a role in the maintenance of LES function.

Hyperparathyroidism in pregnancy: diagnostic dilemma?

Primary hyperparathyroidism is rarely encountered in pregnancy. Because the symptoms may be variable in nature, the diagnosis may be delayed with an increase in maternal and perinatal morbidity or mortality. Several of the symptoms and clinical findings in hyperparathyroidism may also be present with preeclampsia, thus causing difficulty in distinguishing one from the other. Our case report describes a pregnant patient in the third trimester with HELLP syndrome and primary hyperparathyroidism.

The effect of ethanol on sphincter of Oddi motility in vitro

Antioxidant enzymes are present in nerves supplying the sphincter of Oddi and regulate its motor function. Oxygen free radicals (O2.-) produce hydrogen peroxide (H2O2) by the action of superoxide dismutase (SOD). Hydroxyl radical (OH.), an important mediator of H2O2 toxicity, oxidizes ETOH. Thus, the aim of our study was determine the effects of ETOH on sphincter of Oddi motility. The sphincter of Oddi was removed from opossums and force transducers recorded tension in its transverse axis. Alcohol (ETOH) was added to the tissue bath in concentrations from 0.1 to 0.4%. OH. was generated by the addition of 0.01% H2O2. Nitric oxide production was inhibited by the addition of 0.3 mM N omega-nitro-L-arginine (L-NNA). H2O2 increased the frequency of sphincter of Oddi contractions. Concentrations of ETOH > 0.3% decreased contractile frequency; however, 0.2% ETOH alone had no affect on the basal frequency of contraction but inhibited the increase in contractile frequency caused by H2O2. L-NNA also increased the contractile frequency; however, this effect was not inhibited by ETOH. We conclude that ETOH attenuates the effect of H2O2 on sphincter of Oddi motility.

Plant cyclins: a unified nomenclature for plant A-, B- and D-type cyclins based on sequence organization

The comparative analysis of a large number of plant cyclins of the A/B family has recently revealed that plants possess two distinct B-type groups and three distinct A-type groups of cyclins. Despite earlier uncertainties, this large-scale comparative analysis has allowed an unequivocal definition of plant cyclins into either A or B classes. We present here the most important results obtained in this study, and extend them to the case of plant D-type cyclins, in which three groups are identified. For each of the plant cyclin groups, consensus sequences have been established and a new, rational, plant-wide naming system is proposed in accordance with the guidelines of the Commission on Plant Gene Nomenclature. This nomenclature is based on the animal system indicating cyclin classes by an upper-case roman letter, and distinct groups within these classes by an arabic numeral suffix. The naming of plant cyclin classes is chosen to indicate homology to their closest animal class. The revised nomenclature of all described plant cyclins is presented, with their classification into groups CycA1, CycA2, CycA3, CycB1, CycB2, CycD1, CycD2 and CycD3.

Uvulopalatopharyngoplasty may compromise nasal CPAP therapy in sleep apnea syndrome

Uvulopalatopharyngoplasty (U3P) has been advocated for treatment of snoring and sleep apnea/hypopnea syndrome (SAHS), but often it does not effect a cure, so that other therapy (CPAP) is often required. We hypothesized that patients with U3P will have increased mouth air leak during CPAP because of loss of the soft palatal seal. This may result in decreased tolerance and compliance if CPAP therapy is required after U3P. We have therefore compared CPAP tolerance in 13 awake normal male subjects, 13 male patients with SAHS and 13 male patients treated with U3P, all naive to CPAP and matched for age and body mass index. All normal subjects and patients with SAHS were able to tolerate pressures of at least 20 cm H2O without mouth air leak or appreciable discomfort. In contrast male U3P patients started to leak air via the mouth at a mean CPAP pressure of 6.8 (SD, 2.4) cm H2O and were able to tolerate a mean maximal pressure of only 14.5 (SD, 2.6) cm H2O, which was significantly less than that in the other two groups (p < 0.001). We also examined nasal CPAP compliance (machine run time) in eight patients with SAHS who had previous U3P compared with 16 patients with SAHS without U3P. Both groups were matched for age, body mass index, and apnea/hypopnea index. Patients with U3P had significantly lower compliance (mean, 3.5 h/night) compared with patients without U3P (mean, 5.7 h/night), p = 0.01. We conclude that U3P may compromise nasal CPAP therapy by increasing mouth air leak and reducing the maximal level of pressure that can be tolerated.

One for tea, not two

This case report illustrates a potentially common cause for the inhibition of iron absorption that can be overlooked at the initial consultation and may lead to extensive investigation of a patient with iron deficiency. The case shows that early questioning of the patient regarding their beverage intake can lead to a positive outcome and avoid unnecessary investigation or treatment.

An Escherichia coli system for assay of F1p site-specific recombination on substrate plasmids

We have developed an Escherichia coli system for testing the behaviour of plasmids carrying target sites for the F1p site-specific recombinase. The E. coli strain BL-FLP is described, which carries a chromosomally integrated bacteriophage T7 RNA polymerase gene expressed from a lac promoter, and harbours the plasmid pMS40.pMS40 has the features: (i) it carries the FLP recombinase gene under the control of a bacteriophage T7 promoter, (ii) it confers kanamycin resistance, and (iii) it uses an R6K origin of replication; these two latter features make it compatible with most conventional cloning vectors. Substrate plasmids carrying F1p-recognition targets (FRT) are transformed into BL-FLP, and the consequences of F1p-mediated recombination can be analysed after subsequent extraction of plasmid DNA. We show that this system is capable of base-perfect F1p-mediated recombination on plasmid substrates. We also present a corrected sequence of the commonly used F1p substrate plasmid, pNEO beta GAL (O'Gorman et al. (1991) Science 251, 1351-1355).

Conventional and dedifferentiated parosteal osteosarcoma. Diagnosis, treatment, and outcome

BACKGROUND

Dedifferentiated parosteal osteosarcoma (dd-POS) designates high grade transformation, of conventional low grade parosteal osteosarcoma (c-POS). The paradigm of preoperative diagnosis, neoadjuvant chemotherapy, and wide local excision has not been adequately evaluated for dd-POS, as it has been for conventional high grade intramedullary osteosarcoma.

METHODS

A retrospective review was conducted of 28 patients treated at the authors' institution between January 1980 and December 1992 for an osteosarcoma arising on the surface of the bone diagnosed as either c-POS or dd-POS. The clinicopathologic features, diagnosis, treatment, and patient outcome were analyzed.

RESULTS

A dedifferentiated component was identified in 12 of 28 tumors (43%). Neither the presence of radiolucencies (77% in c-POS and 100% in dd-POS, P = 0.06) nor medullary invasion (42% in c-POS and 50% in dd-POS, P = 0.28) distinguished dd-POS from c-POS. However, all patients who presented with focal hypervascularity on an arteriogram defined the high grade component of dd-POS that was confirmed by selective needle biopsy. This differed significantly (P = 0.00003) from c-POS. None of the patients with c-POS died of the disease (median survival duration, 77 months; range, 16-152 months). Six patients (35%) developed a local recurrence, but five were treated successfully with further surgery. In the dd-POS group, 7 of the 12 patients died of the disease. Ten patients with dd-POS received preoperative chemotherapy (IA cis-diamminedichloroplatinum, IV doxorubicin), and a good response (> 90% necrosis of high grade component) was observed in four. Among patients whose disease was localized, continuous disease free survival was prolonged significantly (P = 0.03) in patients with a good response (median, 75 months) compared with those who responded poorly (median, 13 months). Five patients remained continuously disease free (median, 66 months, range, 29-95 months).

CONCLUSIONS

Wide surgical excision alone is adequate treatment for patients with c-POS. Recognition of dedifferentiated areas with angiography and percutaneous biopsy of hypervascular areas should prompt the administration of chemotherapy and wide local excision to optimize patient outcome.

Modulation of cyclin transcript levels in cultured cells of Arabidopsis thaliana

Previous studies on the cell cycle of Arabidopsis thaliana have been hindered by the lack of synchronous cell culture systems. We have used liquid callus cultures and a cycloheximide-synchronized suspension culture of Arabidopsis to investigate changes in cyclin transcript levels in response to exogenous auxin, cytokinin, and nutrients, and during the cell cycle. CYCD1 (delta 1) transcript was virtually undetectable in liquid-cultured callus or suspension-culture cells. CYCD2 (delta 2) transcript levels were largely unaffected by the readdition of phytohormones or nitrate to the growth medium, and remained constant throughout the cell cycle in suspension-culture cells. CYCD3 (delta 3) transcript levels were strongly dependent on nitrate, and were induced at the G1/S transition following phytohormone readdition. In synchronized suspension-culture cells, CYCD3 transcript accumulated during the S phase, and remained constant thereafter. These results support the hypothesis that D cyclins function as part of the cellular machinery that integrates diverse signals impinging upon commitment to cell division. In synchronized cells transcripts of the mitotic cyclins CYC1, CYC2, and CYC3 reached a maximum with peak mitotic index, but CYC3 transcript levels increased earlier than those of CYC1 or CYC2. The kinetics of accumulation of CYC transcript levels support their classification as A-type (CYC3) and B-type (CYC1 and CYC2) cyclins, respectively.

Early physiologic patterns in acute illness and accidents: toward a concept of circulatory dysfunction and shock based on invasive and noninvasive hemodynamic monitoring

The aim of the present study was to explore methods, concepts, and techniques that provide recognition of circulatory deficiencies at the earliest possible time in the patient's illness. We used both the standard invasive pulmonary artery thermodilution catheter and noninvasive hemodynamic monitoring systems consisting of a new bioimpedance cardiac output device, pulse oximetry, transcutaneous oxygen (PtCO2) and carbon dioxide tensions as well as the transcutaneous oxygen tension/fraction of inspired oxygen ratio (PtCO2/FIO2). These three noninvasive systems were used to evaluate cardiac function, pulmonary function, and tissue perfusion, respectively. This approach to early noninvasive monitoring is based on recent evidence suggesting that poor tissue perfusion and oxygenation initiate circulatory dysfunction that leads to shock and organ failure. We studied 303 acute episodes of circulatory dysfunction and shock in 261 patients in a university-run county hospital; 75 were acute traumatic injuries and 109 acute nontrauma medical emergencies on admission to the emergency department, and 77 ICU patients with an acute illness or exacerbation of their current illness. The study was a prospective, descriptive study to identify early abnormal circulatory patterns reflecting the cardiac, pulmonary, and perfusion functions associated with death and with survival. We described noninvasively monitored patterns in individual illustrative cases, in common etiologic groups, and in physiologic categories representing various abnormal functional patterns. We found that hypotensive shock usually was preceded by episodes of high flow followed by low flow and inadequate tissue perfusion indicated by reduced PtCO2; this frequent pattern was modified by associated co-morbid conditions, especially hypovolemia, limited cardiac reserve capacity, age, hypertensive states, and increased body metabolism from infection, trauma, stress, exercise, temperature, and endocrine disorders. Reduced pulmonary function occurred in 18% of emergency patients; these were usually patients with thoracic trauma, severe hypovolemia, head injuries, chronic obstructive pulmonary disease, asthma, drug overdose, and central nervous system failure (massive stroke and coma). We concluded that noninvasive measurements identify early circulatory problems reliably and provide objective criteria for physiologic analysis as well as for definition of therapeutic goals and titration of therapy.

Improved thermostability of the North American firefly luciferase: saturation mutagenesis at position 354

We have used random chemical mutagenesis and a simple genetic screen to generate and isolate a thermostable mutant of luciferase from the North American firefly (Photinus pyralis). A single G-to-A transition mutation, resulting in the substitution of a glutamate for a lysine residue at position 354 in the protein sequence, was shown to be responsible for this enhanced thermostability. Replacement of Glu-354 with all possible amino acid residues was achieved using directed mutagenesis, and produced mutant enzymes with a range of thermostabilities. The mutations E354K and E354R conferred the largest increases in thermostability, suggesting that side-chain size and hydrophobicity, as well as charge, may also be important contributors to the overall thermostability of the polypeptide chain at this position. Unusually for such mutations, biochemical studies suggest that this position is on the surface of the protein and exposed to solvent.

Day case tonsillectomy in adults: how many are suitable?

Day case surgery is increasing to improve health care cost efficiency. The economic benefits of day surgery depend on how many patients are suitable. Adult tonsillectomy is a common operation. This study aims to define what proportion of adults undergoing tonsillectomy are suitable for day case surgery. One hundred consecutive adults undergoing elective in-patient tonsillectomy were studied prospectively. Patients were questioned, examined and investigated for any general medical or social contra-indications to day surgery as specified by the Royal College of Surgeons of England. They were also questioned about specific contra-indications to day case tonsillectomy, including NSAID contra-indications and tonsillectomy indicated for biopsy, quinsy or with another procedure. Seventy-six per cent patients satisfied the requirements. The most common reasons for failure were social. A high proportion of adults are suitable for day case tonsillectomy and therefore significant economic benefits are possible. However, prior to such surgery further work on operation suitability is required.

Chondrosarcoma of the pelvis. Prognostic factors for 67 patients treated with definitive surgery

BACKGROUND

Chondrosarcoma (CS) most commonly involves the pelvis. Local and systemic failures often result in poor outcome. Prognostic factors that determine patient outcome remain ill-defined.

METHODS

We retrospectively analyzed 67 patients with CS of the pelvis treated by definitive surgery from January 1970 to December 1992. All patients had localized disease including Grade 1 (19 patients), Grade 2 (18 patients), Grade 3 (17 patients), and dedifferentiated (13 patients) tumors. Thirty-two patients underwent a limb-sparing surgical resection and 35 patients underwent hemipelvectomy. Follow-up was available for all patients. The median duration of follow-up for the survivors was 115 months (range, 24-288 months).

RESULTS

At last follow-up, 52% of the patients were disease free, 8% were alive with disease, 36% died of disease, and 4% died of other causes. Nineteen patients (28%) had developed a local recurrence (LR). The median time to LR was 23 months (range, 1-111 months). Independent variables in a multivariate analysis associated with increased risk of LR included inadequate surgical margin, tumor epicenter in the pubis, and high grade histology. LR did not influence overall patient survival. Twenty-three patients (36%) developed distant metastases at a median time of 9 months (range, 1-111 months) postoperatively. Metastases developed in 0% of the patients with Grade 1, 20% of the patients with Grade 2 60% of the patients with Grade 3 and 75% of patients with dedifferentiated CS. On multivariate analysis, histologic high grade was the only significant predictive variable for distant relapse (P = 0.005).

CONCLUSIONS

The critical issue for a favorable outcome in low grade CS of the pelvis is adequate surgical excision (i.e., negative surgical margin). The high rate of systemic failure in high grade and dedifferentiated CS, despite adequate surgery, emphasizes the need for more effective systemic therapy.

The benevolent overreaction: nursing assessment and intervention in families coping with seizure disorder

Boone and Hartman identified the phenomenon of benevolent overreaction to describe the enmeshment seen in parents and their chronically ill children. The cylce of the benevolent overreaction begins with the child's diagnosis with a chronic illness and the subsequent natural protective behaviors of the parents. However, overprotection may become pathologic if these protective behaviors persist and delay or prevent the child's achieving developmental goals. This ego boundary deficit is one of the most frequently seen phenomena in families with chronically ill children. On the Comprehensive Epilepsy Unit this phenomenon was repeatedly observed. The purpose of this investigation was to ascertain the frequency of benevolent overreaction seen on the unit, and to identify the nursing interventions used to address this issue. A chart review was used to identify the frequency of the phenomenon during the past year, the discipline first identifying the phenomenon and nursing interventions applied to the phenomenon. Nursing staff interviews were then conducted, using unit census records of the past year, to identify staff recall of the phenomenon. Nursing staff frequently identified the components of benevolent overreaction in the inpatient population, however, consistent intervention for the phenomenon was less frequently seen. Autonomy, empowerment and self-advocacy for families are goals of the Comprehensive Epilepsy Unit. Consistent application of the nursing process to this phenomenon is vital to providing quality patient care.

Abrupt cessation of immunosuppression in a patient with persistent acute lymphoblastic leukaemia following allogeneic transplantation

A 20-year-old man with acute lymphoblastic leukaemia (ALL) in second complete remission underwent sibling donor transplant. Post-transplant there was haematological and immunophenotypic evidence of persisting disease. Cyclosporine was abruptly discontinued and following this the leukaemic clone disappeared. Discontinuation of immunosuppression may be of benefit in leukaemia which persists following transplant.

Treatment of facial synkinesis and facial asymmetry with botulinum toxin type A following facial nerve palsy

Facial synkinesis and asymmetry commonly impair the outcome of facial nerve palsy. Botulinum toxin type A is a neurotoxin which prevents acetylcholine release at the neuromuscular endplate, paralysing skeletal muscle. This paper examines its use in 24 patients with synkinesis and asymmetry affecting the eye and mouth. Sixty-eight of 72 treatments produced improved cosmesis. Dose-related complications occurred in 26 treatments but were generally mild and transient. The total dosages of toxin used were analysed. The higher dose group compared with the lower dose group had no significant advantage in overall cosmetic improvement but the complication rate was significantly higher in the higher dose group (20/39) compared with the lower dose group (6/33) (chi 2 6.675, P > 0.05).

Function of identified nerves in orientation to water flow in Tritonia diomedea

We determined which sensory and motor nerves mediate orientation to flow in the marine slug Tritonia diomedea, and tested the hypothesis that the slug orients to water flow by comparing the intensities of water flow stimulation on each side of its body. Lesion experiments revealed which nerves carried information necessary for flow orientation. The lateral branches of Cerebral Nerve #2 were the only cerebral nerves necessary for flow orientation. Cutting all cerebral nerves except the lateral branches of Cerebral Nerve #2 did not eliminate flow orientation. Thus, the lateral branches of Cerebral Nerve #2 were both necessary and sufficient (among the cerebral nerves) for flow orientation. Denervation of one side of the head by cutting Cerebral Nerves #1-4 on one side did not eliminate normal flow orientation. We have revised our model of how Tritonia diomedea orients to flow to allow for this unilateral determination of flow direction. Unilaterally cutting Pedal Nerve #3, which contains many pedal motor axons, reduced turning toward that side, but did not affect final orientation to flow. The ability to detect flow direction was not compromised by the inability to initially turn towards flow.

Antioxidant enzymes in intramural nerves of the opossum esophagus

Superoxide radical (O2-.) combines with nitric oxide (NO) to form peroxynitrite, thereby nullifying the biological activity of NO. Superoxide dismutase (SOD) prevents this reaction by converting O2-. to H2O2. We tested the hypotheses that the antioxidant enzymes catalase (CAT), Mn SOD, and Cu/Zn SOD are present in enteric neurons of the opossum esophagus, and that O2-. alters esophageal motor function. Immunostaining demonstrated CAT, Mn SOD, and Cu/Zn SOD immunoreactivity in interganglionic nerve bundles and ganglia of the myenteric and submucosal plexuses. Western blot analysis confirmed the presence of these enzymes in homogenates of esophageal muscularis propria, and enzyme assays demonstrated Cu/Zn SOD and Mn SOD activities of 262 and 73 U/mg protein, respectively. Both diethyldithiocarbamic acid, an inhibitor of Cu/Zn SOD, and xanthine (X) with xanthine oxidase (XO), which generate O2-., shortened the latency of the nerve-mediated contraction of circular esophageal muscle, the off response, by 20.2 and 23.4%, respectively. SOD alone did not affect the latency, but it inhibited the effect of X with XO on the latency. Antioxidant enzymes found in intramural esophageal nerves may play a role in regulating NO-mediated neuromuscular communication in the esophagus.

Multiple cloning sites carrying loxP and FRT recognition sites for the Cre and Flp site-specific recombinases

Plasmids were constructed carrying the loxP and FRT recognition sites for the Cre and Flp site-specific recombinases, respectively, within multiple cloning sites. Vectors carrying single and tandemly repeated targets are available with various flanking restriction enzyme sites. In addition, a series of plasmids carrying both loxP and FRT sites is available. These vectors facilitate construction of target molecules for these site-specific recombinases which are becoming increasingly important tools for the in vivo manipulation of DNA.

Would day-case adult tonsillectomy be safe?

Day-case surgery is increasing to improve health care efficiency. Adult tonsillectomy is performed on an inpatient basis in the UK because of safety concerns regarding primary haemorrhage. This study aims to investigate the likely safety of day-case tonsillectomy in adults, by defining the incidence and timing of primary haemorrhage and therefore to establish a safe time period for same-day discharge. Prospectively recorded data on 2,157 adult tonsillectomies over a five-year period were reviewed. Serious primary haemorrhage was uncommon (0.8 per cent). The 95 per cent reference range of time to primary haemorrhage was within 0 to 6.8 hours of surgery and the 95 per cent confidence interval (C.I.) of its upper limit was 5.2 to 8.4 hours. The results compare favourably with the UK inpatient and US adult day-case literature. We conclude that day-case tonsillectomy would probably be safe in adults if the patients are discharged after 8.4 hours.

Effect of nitroblue tetrazolium on NO synthase and motor function of opossum esophagus

Nitric oxide mediates neuromuscular events in the opossum esophagus. The NADPH diaphorase stain is used to localize nitric oxide synthase-containing enteric neurons. Cells stain by the NADPH diaphorase technique because they reduce nitroblue tetrazolium to the visible formazan. The effects of nitroblue tetrazolium on neuromuscular function and nitric oxide synthase of esophageal muscle were studied. The NADPH diaphorase stain was performed. Nitroblue tetrazolium inhibited lower esophageal sphincter relaxation, abolished the latency gradient of the off response, and inhibited nitric oxide synthase. The NADPH diaphorase technique stained myenteric plexus nerve cell bodies and nerve processes. Nitroblue tetrazolium is not a nonspecific muscle or nerve toxin, as nerve-mediated cholinergic responses, responses to exogenous nitric oxide, and responses to myogenic stimulation were maintained after nitroblue tetrazolium abolished the off response and lower esophageal sphincter relaxation. Nitroblue tetrazolium inhibits nitric oxide-mediated events and nitric oxide synthase. It stains neurons in the esophageal myenteric plexus.

The effects of recombinant human hemoglobin on esophageal motor functions in humans

BACKGROUND & AIMS

Nitric oxide controls lower esophageal sphincter (LES) relaxation and esophageal peristalsis in opossums, but its role in the control of esophageal motility in humans is not defined. Hemoglobin inactivates NO by binding it. Recombinant human hemoglobin (rHb1.1) was used to test the hypothesis that NO mediates esophageal motor functions in humans.

METHODS

rHb1.1 or human serum albumin was administered intravenously to fasting male volunteers. Esophageal manometric studies were performed before, during, and up to 6 hours after the infusion.

RESULTS

rHb1.1 increased the velocities of peristaltic contractions to produce simultaneous contractions in 6 of 9 subjects. It increased the amplitude and duration of contractile waves in the esophagus. There was no consistent effect on the resting tone of the LES, but LES relaxation was inhibited. Spontaneous, simultaneous high-pressure contractions occurred in 8 of 9 subjects. Lower retrosternal chest pain during swallowing was observed in 4 subjects.

CONCLUSIONS

rHb1.1 interfered with esophageal peristalsis and LES relaxation. It precipitated esophageal spasm in some subjects. These data support the hypothesis that the timing of smooth muscle esophageal peristalsis and LES relaxation are mediated by NO. They suggest that some disorders of esophageal motor function may result from defects in NO neuromuscular communication.

Nitric oxide modulates a calcium-activated potassium current in muscle cells from opossum esophagus

Nitric oxide mediates nerve-induced hyperpolarization of circular smooth muscle of the esophagus. Two mechanisms are proposed to explain this hyperpolarization: an increase in K+ current or a decrease in Cl- current. These studies test the hypothesis that nitric oxide increases a K+ current in esophageal smooth muscle. Three outward K+ currents are present in circular smooth muscle cells from the opossum esophagus. One current is a Ca(2+)-activated K+ current (IKCa2+). This current is inhibited by charybdotoxin. Whole cell currents were recorded from isolated opossum esophageal smooth muscle cells using the whole cell patch-clamp technique. These studies showed that IKCa2+ is activated at potentials more positive than -30 mV. Bath application of S-nitroso-L-cysteine increased IKCa2+ by 50% above control levels throughout the entire activation range of potentials. The enhanced current was reversible on washout. Either charybdotoxin, an inhibitor of IKCa2+, or (R)-p-8-(4-chloropenylthio)-guanosine 3',5'-cyclic monophosphorothioate, an inhibitor of protein kinase G, antagonized the increase in outward current induced by S-nitroso-L-cysteine. These data suggest that nitric oxide activates IKCa2+ via the guanosine 3',5'-cyclic monophosphate-protein kinase G signal transduction pathway.

Re-innervation of facial nerve territory using a composite hypoglossal nerve--muscle autograft--facial nerve bridge. An experimental model in sheep

The hypoglossal nerve has been used both entirely and in part to repair the facial nerve. Using the partial technique it may be difficult to obtain sufficient length and a free interposed graft is then required to extend the hypoglossal element. In six sheep the facial nerve was excised between its emergence from the stylomastoid foramen and its bifurcation in the parotid gland. The hypoglossal nerve was exposed and split longitudinally producing a limb which was reflected towards the distal stump of the facial nerve. This left a gap of 4-5 cm which was bridged with a freeze-thawed coaxially aligned skeletal muscle autograft. The sheep were examined at 8 months. Laser doppler blood-flow studies showed the blood-flow distal to the graft to be about 25% of that at an equivalent site on the normal side. Peak nerve conduction velocities were also reduced on the repaired side but stimulation of the proximal hypoglossal nerve was nevertheless capable of causing adequate contraction of both facial and tongue muscles. Histological comparison of the repaired facial nerves with equivalent sites on the normal side showed a reduction in mean axon and fibre diameters with normal myelin sheath thickness for the regenerated axon sizes. All of these features are to be expected in a regenerated nerve and are consistent with a good level of recovery of function.

A family of cyclin D homologs from plants differentially controlled by growth regulators and containing the conserved retinoblastoma protein interaction motif

A new family of three related cyclins has been identified in Arabidopsis by complementation of a yeast strain deficient in G1 cyclins. Individual members show tissue-specific expression and are conserved in other plant species. They form a distinctive group of plant cyclins, which we named delta-type cyclins to indicate their similarities with mammalian D-type cyclins. The sequence relationships between delta and D cyclins include the N-terminal sequence LXCXE. This motif was originally identified in certain viral oncoproteins and is strongly implicated in binding to the retinoblastoma protein pRb. By analogy to mammalian cyclin D, these plant homologs may mediate growth and phytohormonal signals into the plant cell cycle. In support of this hypothesis, we show that, on restimulation of suspension-cultured cells, cyclin delta 3 is rapidly induced by the plant growth regulator cytokinin and cyclin delta 2 is induced by carbon source.