The use of complementary and alternative therapies for chronic pain following spinal cord injury: a pilot survey

OBJECTIVE

The purpose of this study was to determine the patterns and reasons for the use of complementary and alternative medicine (CAM) as a treatment for chronic pain among individuals with spinal cord injuries (SCI).

METHODS

Telephone surveys were conducted in a sample of 77 people with SCI and chronic pain.

RESULTS

Of those surveyed, 40.3% had used at least one CAM technique to manage chronic pain. The most common reason was dissatisfaction with conventional medicine. Acupuncture was the most frequently used modality, followed by massage, chiropractic manipulation, and herbal medicine. Acupuncture was rated lowest for satisfaction with pain relief, and massage was rated highest. Individuals not using conventional pain medication or who desired greater control over their health care practices tended to use more CAM techniques than others. Income, insurance coverage, and duration of pain were related to use of CAM. In general, CAM methods were effective for some and totally ineffective for others, indicating selective utility in this population.

CONCLUSIONS

Despite this small opportunistic sample, the prevalence of CAM among individuals with SCI appears similar to that in the general population. A placebo-controlled trial is needed to evaluate the efficacy of various therapies in the SCI population. The fact that the most effective therapy, massage, was not frequently used suggests the need for more awareness of and research into this technique.

The Phe-X-Glu DNA binding motif of MutS. The role of hydrogen bonding in mismatch recognition

The crystal structures of MutS protein from Thermus aquaticus and Escherichia coli in a complex with a mismatch-containing DNA duplex reveal that the Glu residue in a conserved Phe-X-Glu motif participates in a hydrogen-bonded contact with either an unpaired thymidine or the thymidine of a G-T base-base mismatch. Here, the role of hydrogen bonding in mismatch recognition by MutS is assessed. The relative affinities of MutS for DNA duplexes containing nonpolar shape mimics of A and T, 4-methylbenzimidazole (Z), and difluorotoluene (F), respectively, that lack hydrogen bonding donors and acceptors, are determined in gel mobility shift assays. The results provide support for an induced fit mode of mismatch binding in which duplexes destabilized by mismatches are preferred substrates for kinking by MutS. Hydrogen bonding between the O epsilon 2 group of Glu and the mismatched base contributes only marginally to mismatch recognition and is significantly less important than the aromatic ring stack with the conserved Phe residue. A MutS protein in which Ala is substituted for Glu(38) is shown to be defective for mismatch repair in vivo. DNA binding studies reveal a novel role for the conserved Glu residue in the establishment of mismatch discrimination by MutS.

The concept of hospice in theory and practice

Initially the word 'hospice' was used to convey the friendly and warm feeling between the guest and the host. Later the place where this feeling was experienced represented the meaning of the word. Hospice is a union between the tough and rigid principles of curative clinical science and more flexible 'compassion' of human behaviour. The aim should be more on to relieve distressing symptoms of advanced cancer and other terminal diseases by control of symptoms and good nursing. In India one in 10 deaths is related to cancer and a sizeable section of this huge population die in unrelieved pain and suffering. AIDS cases are rising in the developing countries, which cannot afford expensive treatment. So the provision of good palliative care will remain for many years to come. But with the advent of antibiotics, doctors changed their goal from palliative care to absolute cure. The incurable cases were gradually made to feel unwelcome. The best option between the two is compassion of the old days and the modern scientific advances. Principles of ethics in clinical practice rotate around autonomy, beneficence, non-maleficence and justice. Euthansia poses a big question. Lack of awareness among patients, doctors and paramedical personnel causes unrelieved pain in cancer and other terminal diseases. Gastro-intestinal symptoms, respiratory symptoms, lymphoedema and complications of cancer and other diseases can be looked carefully to give proper benefit to the patients. Complementary and alternative medicine plays a key role in palliative care and improves the quality of life.

Is acupuncture effective in treating chronic pain after spinal cord injury?

OBJECTIVES

To evaluate the efficacy of acupuncture as a treatment for chronic pain and secondary symptoms after spinal cord injury (SCI) and to identify disease-specific variables associated with response to treatment.

DESIGN

A within-subjects design consisting of a 7(1/2)-week no-acupuncture baseline period followed by a 7(1/2)-week treatment period and a follow-up assessment 3 months posttreatment.

SETTING

Medical rehabilitation research center.

PARTICIPANTS

Twenty-two people with SCI who experienced moderate to severe pain of at least 6 months' duration.

INTERVENTION

A course of 15 acupuncture treatments was administered over a 7(1/2)-week period.

MAIN OUTCOME MEASURES

Numeric Rating Scale of pain intensity; ratings of interference with activity, individualized symptom rating, Center for Epidemiologic Studies-Depression Scale; Speilberger State Trait Anxiety Inventory, and General Well-Being Schedule.

RESULTS

Ten patients (46%) showed improvement in pain intensity and pain sequelae after treatment. However, 6 patients (27%) reported an increase in pain that was still present 3 months after treatment.

CONCLUSIONS

About 50% of the study sample reported substantial pain relief after acupuncture treatment, suggesting that acupuncture may provide pain relief for at least a subgroup of individuals with SCI. Future research is needed to determine what part of this effect is because of acupuncture versus nonspecific effects such as placebo effects and regression to the mean.

Autosomal dominant neurohypophyseal diabetes insipidus in a Swiss family, caused by a novel mutation (C59Delta/A60W) in the neurophysin moiety of prepro-vasopressin-neurophysin II (AVP-NP II)

OBJECTIVE

To study clinical, morphological and molecular characteristics in a Swiss family with autosomal dominant familial neurohypophyseal diabetes insipidus (adFNDI).

PARTICIPANTS AND METHODS

A 15-month-old girl presenting with symptoms of polydipsia and polyuria was investigated by water deprivation test. Evaluation of the family revealed three further family members with symptomatic vasopressin-deficient diabetes insipidus. T1-weighted magnetic resonance images of the posterior pituitary were taken in two affected adult family members and molecular genetic analysis was performed in all affected individuals.

RESULTS

The water deprivation test in the 15-month-old child confirmed the diagnosis of vasopressin-deficient diabetes insipidus and the pedigree was consistent with autosomal dominant inheritance. The characteristic bright spot of the normal vasopressin-containing neurophypophysis was absent in both adults with adFNDI. Direct sequence analysis revealed a new deletion (177-179DeltaCGC) in exon 2 of the AVP-NP II gene in all affected individuals. At the amino acid level, this deletion eliminates cysteine 59 (C59Delta) and substitutes alanine 60 by tryptophan (A60W) in the AVP-NP II precursor; interestingly, the remainder of the reading frame remains unchanged. According to the three-dimensional structure of neurophysin, C59 is involved in a disulphide bond with C65.

CONCLUSIONS

Deletion of C59 and substitution of A60W in the AVP-NP II precursor is predicted to disrupt one of the seven disulphide bridges required for correct folding of the neurophysin moiety and thus disturb the function of neurophysin as the vasopressin transport protein. These data are in line with the clinical and morphological findings in the reported family with adFNDI.

Spinal subarachnoid hemorrhage complicating oral anticoagulant therapy

Spinal subarachnoid hemorrhage (SAH) is rare clinical entity possible owing to the diluting and fibrinolytic effects of cerebrospinal fluid (CSF). When it occurs, it is most commonly encountered in the thoracic segment of the subarachnoid space. We present a case of a 50-year-old man who sustained spinal SAH in the cervical and thoracic segments related to anticoagulant therapy. He progressed to significant neurological deficit since he was inoperable, an observation that supports the need for decompression surgery. We should be aware of potential hematomyelia should a patient on anticoagulant therapy develop neurological symptoms localized to the spinal cord. When available, magnetic resonance (MR) imaging is the modality of choice to diagnose and follow-up spinal SAH.

Interaction of Escherichia coli MutS and MutL at a DNA Mismatch

MutS and MutL are both required to activate downstream events in DNA mismatch repair. We examined the rate of dissociation of MutS from a mismatch using linear heteroduplex DNAs or heteroduplexes blocked at one or both ends by four-way DNA junctions in the presence and absence of MutL. In the presence of ATP, dissociation of MutS from linear heteroduplexes or heteroduplexes blocked at only one end occurs within 15 s. When both duplex ends are blocked, MutS remains associated with the DNA in complexes with half-lives of 30 min. DNase I footprinting of MutS complexes is consistent with migration of MutS throughout the DNA duplex region. When MutL is present, it associates with MutS and prevents ATP-dependent migration away from the mismatch in a manner that is dependent on the length of the heteroduplex. The rate and extent of mismatch-provoked cleavage at hemimethylated GATC sites by MutH in the presence of MutS, MutL, and ATP are the same whether the mismatch and GATC sites are in cis or in trans. These results suggest that a MutS-MutL complex in the vicinity of a mismatch is involved in activating MutH.

Segmental anatomy of the temporal bone

More of us suffer from hearing loss than from visual impairment, coronary artery disease, and cancer combined. Auditory dysfunction is detected in less than one third of newborns afflicted and is underdiagnosed in the elderly. Despite biomedical and technological advances, our understanding of vestibular dysfunction has grown little. Forming part of the lateral and inferior surfaces of the skull, the temporal bone contains the organs of hearing and balance. Diagnosis of diseases in these important regions requires adequate clinical information and a thorough knowledge of normal temporal bone anatomy to recognize abnormal findings when present. This article dissects the temporal bone into segments, describes the relevant radiologic anatomy of each, and discusses the imaging appropriate to specific concerns.

ADP-dependent DNA strand exchange by the mutant [P67G/E68A] RecA protein

We have prepared a mutant RecA protein in which proline 67 and glutamic acid 68 in the NTP binding site were replaced by a glycine and alanine residue, respectively. The [P67G/E68A]RecA protein catalyzes the single-stranded DNA-dependent hydrolysis of ATP and is able to promote the standard ATP-dependent three-strand exchange reaction between a circular bacteriophage phiX174 (phiX) single-stranded DNA molecule and a homologous linear phiX double-stranded (ds) DNA molecule (5.4 kilobase pairs). The strand exchange activity differs from that of the wild type RecA protein, however, in that it is (i) completely inhibited by an ATP regeneration system, and (ii) strongly stimulated by the addition of high concentrations of ADP to the reaction solution. These results indicate that the strand exchange activity of the [P67G/E68A]RecA protein is dependent on the presence of both ATP and ADP. The ADP dependence of the reaction is reduced or eliminated when (i) a shorter linear phiX dsDNA fragment (1.1 kilobase pairs) is substituted for the full-length linear phiX dsDNA substrate, or (ii) the Mg(2+) concentration is reduced to a level just sufficient to complex the ATP present in the reaction solution. These results indicate that it is the branch migration phase (and not the initial pairing step) of the [P67G/E68A]RecA protein-promoted strand exchange reaction that is dependent on ADP. It is likely that the [P67G/E68A]RecA mutation has revealed a requirement for ADP that also exists (but is not as readily apparent) in the strand exchange reaction of the wild type RecA protein.

Quantification and validation of enzyme immunoassay for urinary aflatoxin B1-N7-guanine adduct for biological monitoring of aflatoxins

The aflatoxin B1-N7-guanine (AFB1-N7-guanine) adduct has been established as one of the relevant biomarkers of dietary aflatoxin (AFB1) exposure. Measurement of this adduct is potentially a useful dosimeter in molecular epidemiological studies. This paper reports the application and evaluation of a sensitive indirect competitive enzyme-linked immunosorbent assay (ELISA) for the detection and quantification of urinary AFB1-N7-guanine adduct in high risk populations exposed to dietary aflatoxin. Earlier, we had reported a simple and rapid indirect ELISA method for AFB1-N7-guanine adduct in the urine and liver tissues using polyclonal antibodies specific to AFB1-N7-guanine adduct. The method was evaluated using a rodent model (Fischer 344), exposed to 1 mg kg-1 body mass of AFB1 and human urine samples obtained from a maize eating population, environmentally exposed to AFB1 through their diet. The levels of AFB1-N7-guanine adduct in rat and human urine ranged from 6.42 to 20.16 micrograms mg-1 creatinine and from 9.30 to 13.43 ng mg-1 creatinine, respectively. The level of AFB1 in the diet as estimated by ELISA ranged from 1000 to 3600 ng d-1. The interesting observation in these studies is that the females (in both rodents and human subjects) are more efficient than males at excreting the adduct. Total adduct (DNA bound adduct and guanine adduct excreted in urine) was found to be similar in male and female rats. However, 63% of the total adduct was accounted for in urine of female rats, whereas male rats excreted 47% of the total adduct in their urine. The present method may find wide application as a biochemical tool in molecular epidemiological studies with respect to human exposure to dietary aflatoxins.

Reduced levels of rat lens antioxidant vitamins upon in vitro UVB irradiation

Ultraviolet (UV) radiation is one of the major risk factors of cataractogenesis. UV radiation induced damage to the eye lens is believed to be mediated through reactive oxygen species. Antioxidant defense systems, enzymatic and non-enzymatic, resist this damage. In the present study, the levels of rat lens endogenous antioxidants, L-ascorbic acid, alpha-tocopherol and beta-carotene, have been determined by HPLC upon in vitro UVB irradiation. UVB irradiation for 24 h (300 nm; 100 µW/cm(2)) of three months old rat lens suspended in RPMI medium, leads to 69-89% decrease in endogenous levels of these antioxidants. The addition of ascorbic acid (2 mM), alpha-tocopherol (2.5 µM) or beta-carotene (10 µM), separately to the medium during irradiation significantly prevented the decrease in their endogenous levels, thereby suggesting a protective role for these antioxidant micronutrients against photodamage to the eye lens.

Ocular oscillations induced by shifts of the direction and depth of visual fixation

Shifts of the point of fixation between two targets aligned on one eye that are located near and far (Müller paradigm) stimulates a combined saccadic-vergence movement. In normal subjects, this test paradigm often induces saccadic oscillations of about 0.3 degrees at 20 to 30 Hz. We measured eye movements using the magnetic search coil technique in 2 patients recovering from viral opsoclonus-myoclonus syndrome, comparing saccadic-vergence responses to the Müller paradigm with conjugate saccades between distant targets. Both patients exhibited intermittent conjugate ocular oscillations of about 4 to 5 degrees amplitude at about 10 Hz. Combined saccadic-vergence movements induced these oscillations twice as often as did conjugate saccades. One patient also exhibited disjunctive ocular oscillations at 10 Hz while sustaining fixation on the near target. The Müller paradigm provides a useful clinical and experimental technique for inducing saccadic oscillations. The probable mechanism is that pontine omnipause neurons, which normally gate saccades, are inhibited during the sustained vergence movement that follows the saccadic component of the response to the Müller paradigm.

FOG-2, a novel F-box containing protein, associates with the GLD-1 RNA binding protein and directs male sex determination in the C. elegans hermaphrodite germline

Male sex determination in the Caenorhabditis elegans hermaphrodite germline requires translational repression of tra-2 mRNA by the GLD-1 RNA binding protein. We cloned fog-2 by finding that its gene product physically interacts with GLD-1, forming a FOG-2/GLD-1/tra-2 3′untranslated region ternary complex. FOG-2 has an N-terminal F-box and a novel C-terminal domain called FTH. Canonical F-box proteins act as bridging components of the SCF ubiquitin ligase complex; the N-terminal F-box binds a Skp1 homolog, recruiting ubiquination machinery, while a C-terminal protein-protein interaction domain binds a specific substrate for degradation. However, since both fog-2 and gld-1 are necessary for spermatogenesis, FOG-2 cannot target GLD-1 for ubiquitin-mediated degradation. We propose that FOG-2 also acts as a bridge, bringing GLD-1 bound to tra-2 mRNA into a multiprotein translational repression complex, thus representing a novel function for an F-box protein. fog-2 is a member of a large, apparently rapidly evolving, C. elegans gene family that has expanded, in part, by local duplications; fog-2 related genes have not been found outside nematodes. fog-2 may have arisen during evolution of self-fertile hermaphroditism from an ancestral female/male species.

A simple technique to improve recovery and morphology of cells exfoliated into fluids

OBJECTIVE

To devise a simple, inexpensive and effective method for the cytologic study of fluids and to compare the results of the method with the conventional centrifuge smear (CS) method.

STUDY DESIGN

We examined 200 fluid samples from various body sites using CS and thick and thin (TT) smears. Cellular yield, cytomorphology and background of the smears were studied and scored. The scores were compared and analyzed with the chi 2 test.

RESULTS

TT smears gave a higher cellular yield, better morphologic details and cleaner background. The values of all three features were statistically significant (P < .001). In 38 cases a definitive diagnosis could be made on TT smears and not on CS smears.

CONCLUSION

TT smears give significantly better results than CS smears. Simple to prepare and requiring no additional investment in terms of cost, technical skill and sophisticated instruments, this method is ideally suited to small laboratories, especially in developing countries.

Reduced GLP-1 and insulin responses and glucose intolerance after gastric glucose in GRP receptor-deleted mice

By applying a newly developed ELISA technique for determining biologically active intact glucagon-like peptide [GLP-1, GLP-1-(7-36)amide] in mouse, plasma baseline GLP-1 in normal NMRI mice was found to be normally distributed (4.5 +/- 0.3 pmol/l; n = 72). In anesthetized mice, gastric glucose (50 or 150 mg) increased plasma GLP-1 levels two- to threefold (P < 0.01). The simultaneous increase in plasma insulin correlated to the 10-min GLP-1 levels (r = 0.36, P < 0.001; n = 12). C57BL/6J mice deleted of the gastrin-releasing peptide (GRP) receptor by genetic targeting had impaired glucose tolerance (P = 0.030) and reduced early (10 min) insulin response (P = 0.044) to gastric glucose compared with wild-type controls. Also, the GLP-1 response to gastric glucose was significantly lower in the GRP receptor-deleted mice than in the controls (P = 0.045). In conclusion, this study has shown that 1) plasma levels of intact GLP-1 increase dose dependently on gastric glucose challenge in correlation with increased insulin levels in mice, and 2) intact GRP receptors are required for normal GLP-1 and insulin responses and glucose tolerance after gastric glucose in mice.

Blood pressure response to acupuncture in a population at risk for autonomic dysreflexia

OBJECTIVE

To determine whether acupuncture can lead to autonomic dysreflexia (AD) when used to treat chronic pain in individuals with spinal cord injury (SCI).

DESIGN

Acupuncture analgesia study.

SETTING

Medical rehabilitation research center.

PARTICIPANTS

Fifteen participants with post-SCI chronic pain who were at risk for AD (ie, SCI at or above T8).

INTERVENTIONS

Half-hour acupuncture treatment sessions twice a week for 7.5 weeks, for a total of 15 treatments. Acupuncture needles were inserted both above and below the patient's spinal lesion level. Blood pressure (BP) was measured before and after acupuncture treatments.

MAIN OUTCOME MEASURES

Systolic BP (SBP) and diastolic BP (DBP). Participants monitored for signs and symptoms of AD.

RESULTS

On average, SBP and DBP remained stable across all 15 treatment sessions. None of the participants experienced any symptoms of AD. However, examination of individuals' BP readings indicated acute elevations (20 mmHg or higher) in SBP for 3 of the 15 participants.

CONCLUSIONS

Although none of the 15 participants who were at risk for developing AD developed symptoms consistent with this diagnosis, 3 displayed an acute elevation in SBP, suggesting a pattern of imminent AD. Comorbid hypertension appeared to contribute to the elevation in 1 patient. Therefore, careful monitoring of patients with SCI or hypertension during acupuncture treatments is advisable.

Molecular cloning and sequence analysis of the cDNA encoding beta-lactoglobulin in Bubalus bubalis

The cDNA for bubaline beta-lactoglobulin (beta lg) has been cloned through RT-PCR approach and sequenced. Sequence data showed a single open reading frame coding for a protein of 180 amino acids with a signal sequence of 18 amino acid residues. Comparison with other ruminant beta lg sequences revealed a high homology indicating the protein to be conserved through evolution. The degree of homology, at amino acid level, is 96.1%, 95.6%, 93.9% and 63.7% with goat, sheep, cow and pig, respectively.

Rnf4, a RING protein expressed in the developing nervous and reproductive systems, interacts with Gscl, a gene within the DiGeorge critical region

A yeast 2-hybrid screen was performed to identify possible transcriptional modulators interactive with goosecoid-like (gscl), a transcription factor with suppressive activity, expressed during early brain and gonad development. The screen resulted in the identification of a RING protein known as rnf4 or snrf. Gscl/rnf4 interactions were confirmed by affinity chromatography and by immunoprecipitation. Northern analysis confirmed earlier reports of ubiquitous rnf4 expression in adult tissues. Immunohistochemical analysis of mouse embryos revealed expression primarily in the developing nervous system, with strong expression in the dorsal root ganglia and developing gonads. In contrast to previous reports, both cytoplasmic and nuclear expression of rnf4 was documented. The results reported here confirm and extend earlier reports of rnf4 expression. They suggest for the first time, that in addition to acting as a modulator of transcriptional activity, rnf4 may function, as do other RING proteins, to promote the formation of intracytoplasmic complexes involved in shuttling information between the cytoplasm and the nucleus.

Cytology of sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease)

Sinus histiocytosis with massive lymphadenopathy (SHML) is a benign, self-limiting condition of unknown etiology, which generally presents as massive bilateral cervical lymphadenopathy. It is important to distinguish SHML from other causes of histiocytosis because of the different treatment modalities. This study was carried out to assess the utility of fine-needle aspiration cytology (FNAC) findings in SHML and to distinguish if from other reactive lymphadenopathies. The lymph nodes in 4 patients (3 male and 1 female) presenting with massive bilateral cervical lymphadenopathy were aspirated. All presented with persistent bilateral cervical lymphadenopathy, polymorphnuclear leukocytosis, and raised erythrocyte sedimentation rate (ESR). Smears showed a reactive lymphoid population consisting of mature lymphocytes, plasma cells, a few polymorphs, and many histiocytes showing emperipolesis. Based on the cytologic and clinical findings, a diagnosis of SHML was made. Histopathology confirmed the diagnosis in all cases. A conclusive diagnosis of SHML can be based on cytology, provided that the cytologic findings are interpreted in the appropriate clinical context. Biopsy can be avoided in these patients. Diagn. Cytopathol. 2000;22:181-185.

The origin of anti-nuclear antibodies in bcl-2 transgenic mice

bcl-2 transgenic mice develop anti-double-stranded (ds) DNA antibodies similar to those present in systemic lupus erythematosus. To begin to understand where a breakdown in the regulation of autoreactive lymphocytes is occurring, we have used a bcl-2 transgene (Tg) in conjunction with an Ig Tg that allows us to identify and track anti-dsDNA B cells. Previously, we have shown that anti-dsDNA B cells are actively tolerized in BALB/c mice as manifested by their developmental arrest, follicular exclusion, increased in vivo turnover rate and lack of their antibody in the serum. The bcl-2 Tg mice increased the lifespan of anti-dsDNA B cells, but did not alter the other features of tolerance, indicating that the anergy of the anti-dsDNA B cells is independent of their reduced lifespan. Furthermore, these data suggest that the serum anti-dsDNA antibodies in bcl-2 transgenic mice are not due to a breakdown in the induction or maintenance of B cell anergy; rather they may originate from B cells that have transited through a germinal center.

Radiologic anatomy of the paranasal air sinuses

Over the last decade, significant strides have been made in the imaging-guided management of sinonasal inflammation. We are now able to achieve an enhanced level of understanding of the complex functional and surgical anatomy of this region. This facilitates meaningful communication with the surgeons who consult with us. Sectional imaging using both CT and MR is applied well to sinonasal imaging, but anatomic CT landmarks are emphasized in this article with its connection to minimally invasive sinus surgery. Our ongoing research efforts target dynamic functional anatomy with advanced postprocessing techniques.

Magnetic resonance anatomy of spaces in the neck

Owing to its complex anatomy, the neck harbors multiple pathologic processes. A comprehensive knowledge of regional anatomy and recognition of the patterns of disease presentation are vital to arriving at a meaningful differential diagnosis. This review of basic neck anatomy has utilized magnetic resonance imaging in showcasing the well-accepted spatial approach that emphasizes anatomic imaging, surgical landmarks, and imaging principles. To permit early recognition of neck pathology, detailed anatomic correlation is mandatory. Current imaging with high-resolution helical computed tomography, high speed magnetic resonance, and multiplanar reformations permit a detailed analysis of the complex anatomy in this region and is the key to understanding many of its disorders. Through such understanding we can recognize the issues involved in conservative neck surgery, neck nodal texture and functional assessment, brachial plexopathy, and the treated neck, appreciate the relevant surgical anatomy of the spaces in the neck, and relate better with our ENT colleagues.

Differential rates of NTP hydrolysis by the mutant [S69G]RecA protein. Evidence for a coupling of NTP turnover to DNA strand exchange

The x-ray crystal structure of the Escherichia coli RecA protein indicates that the phosphate groups of the nucleotide cofactor are bound by a loop whose amino acid sequence ((66)GPESSGKT(73)) corresponds to a consensus phosphate binding loop sequence (GXXXXGK[T/S]) found in many NTP-binding proteins. As part of an investigation of the role of the P-loop in ATP hydrolysis, we prepared a mutant RecA protein in which serine 69 was replaced by a glycine residue. We have found that the [S69G]RecA mutation has a differential effect on the hydrolysis of various nucleoside triphosphates. The [S69G]RecA protein catalyzes the single-stranded DNA-dependent hydrolysis of rATP, ddATP, and dATP with turnover numbers of 10, 20, and 36 min(-1), respectively. The wild type RecA protein, in contrast, hydrolyzes each of these nucleoside triphosphates with similar turnover numbers of 20-24 min(-1). Significantly, the [S69G]RecA protein promotes strand exchange with all three nucleoside triphosphates, and the rate of strand exchange is directly proportional to the rate of hydrolysis of each of the nucleotide cofactors. These findings with the [S69G]RecA protein provide support for the existence of a mechanistic coupling between NTP hydrolysis and DNA strand exchange.