Asymmetric adaptive modeling of central tarsal bones in racing greyhounds

Fatigue fracture of the cuboidal bones of the foot, especially the navicular tarsal bone, is common in athletes and dancers. The racing greyhound is a naturally occurring animal model of this injury because both microcracking and complete fracture occur in the right central (navicular) tarsal bone (CTB). The right limb is on the outside when racing in a counter-clockwise direction on circular tracks, and is subjected to asymmetric cyclic compressive loading. We wished to study in more detail adaptive modeling in the right CTB in racing greyhounds. We hypothesized that cyclic asymmetric loading of a cuboidal bone induced by racing on a circular track would induce site-specific bone adaptation. We also hypothesized that such an adaptive response would be attenuated in greyhounds that were retired from racing and no longer subjected to cyclic asymmetric loading. Central tarsal bones from racing greyhounds (racing group, n = 6) and retired greyhounds being used for breeding (nonracing group, n = 4) were examined using quantitative computed tomography (CT). Bone mineral density (BMD) was determined in a 3-mm diameter region-of-interest (ROI) in six contiguous 1-mm-thick sagittal CT slices of each CTB. Bones were subsequently examined histomorphometrically and percentage bone area (B.Ar./T.Ar., %) was determined in 10 ROI from dorsal to plantar in a transverse plane, mid-way between the proximal and distal articular surfaces. The BMD of the right CTB was greater than the left in all greyhounds (p < 0. 001). In comparing ipsilateral limbs between groups, BMD of the racing group was greater than the nonracing group for each side (p < 0.005). In sagittal plane histologic sections, bone in the dorsal region of the right CTB had undergone adaptive modeling, through thickening and compaction of trabeculae. B.Ar./T.Ar., % in the right CTB of the racing group was greater than in the contralateral CTB (p < 0.001), and the ipsilateral CTB of the nonracing group (p < 0.001). In the nonracing group, B.Ar./T.Ar., % in the right CTB was not significantly different from left CTB (p > 0.8; power = 80% at Delta = 48%). It was concluded that greyhounds racing on circular tracks develop site-specific bone adaptation with compaction of trabecular bone and increase in BMD in the right CTB in particular, the most common site for fatigue fracture. Our data also suggested that partial reversal of this adaptive process occurred in retired, nonracing greyhounds, after cessation of asymmetric cyclic loading at racing speed. Racing greyhounds provide a model in which to study fatigue fracture and adaptation of cuboidal foot bones subjected to cyclic loading.

A java-based application for differential diagnosis of hematopoietic neoplasms using immunophenotyping by flow cytometry

We describe the implementation of a Java-based application for differential diagnosis of hematopoietic neoplasms using immunophenotyping by flow cytometry. The current version of this Java applet includes the knowledge-base for 33 hematopoietic neoplasms and 43 diagnostic immunophenotyping markers. Java, a new object-oriented computing language, helps facilitate development of this applet, a platform-independent module that can be implemented on the World Wide Web. As the Web rapidly becomes more accessible to users around the world, Web-based software may eventually form the core of decision-support systems in clinical settings. Java-based applications, such as the one described in this paper, are expected to contribute significantly in this area.

Probing the stoichiometry and oxidation states of metal centers in iron-sulfur proteins using electrospray FTICR mass spectrometry

Electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry is used to determine the stoichiometry and oxidation states of the metal centers in several iron-sulfur proteins. Samples are introduced into the ESI source under nondenaturing conditions in order to observe intact metal-containing protein ions. The stoichiometry and oxidation state of the metal or metal-sulfur cluster in the protein ion can be derived from the mass spectrum. Mononuclear metal-containing proteins and [4Fe-4S] centers are very stable and yield the molecular ion with little or no fragmentation. Proteins that contain [2Fe-2S] clusters are less stable and yield loss of one or two sulfur atoms from the molecular species, although the molecular ion is more abundant than the fragment peaks. [3Fe-4S]-containing proteins are the least stable of the species investigated, yielding abundant peaks corresponding to the loss of one to four sulfur atoms in addition to a peak representing the molecular ion. Isotope labeling experiments show that the sulfur loss originates from the [3Fe-4S] center. Negative ion mode mass spectra were obtained and found to produce much more stable [3Fe-4S]-containing ions than obtained in positive ion mode. ESI analysis of the same proteins under denaturing conditions yields mass spectra of the apo form of the proteins. Disulfide bonds are observed in the apoprotein mass spectra that are not present in the holoprotein. These result from oxidative coupling of the cysteinyl sulfur atoms that are responsible for binding the metal center. In addition, inorganic sulfide is found to incorporate itself into the apoprotein by forming sulfur bridges between cysteine residues.

A web-based teaching program for laboratory diagnosis of coagulation disorders

OBJECTIVE

To implement an interactive program for teaching coagulation disorders on the World Wide Web.

DESIGN AND RESULTS

The core materials in this program were derived from a personal computer software program previously designed by the authors. Three modules were developed in this program: (1) a coagulation profile to display typical results of coagulation screening tests for each disorder; (2) a differential diagnosis module to generate a list of diagnoses that fit the test results in a given case; and (3) a synopsis of coagulopathy and therapy to provide essential information on disorders and therapeutic options. A total of 41 coagulation disorders were included in the knowledge base.

CONCLUSIONS

Since the World Wide Web is increasingly more accessible to computer users, it has become an ideal medium for teaching purposes. Our experience with this program in teaching medical students and pathology residents at our institution has been very encouraging.

Response to genetic counseling and testing for the APC I1307K mutation

The APC I1307K gene mutation is associated with increased colorectal cancer (CRC) risk in Ashkenazi Jews. Factors predicting acceptance of this and other hereditary colon cancer mutation tests in a clinical setting are unknown. We analyzed sex, age, family history, personal history, and gene test results of patients at increased risk for cancer who sought cancer risk counseling at the Johns Hopkins (JH) CRC Risk Assessment Clinic (n = 91), and those submitting samples to the JH Pathology Molecular Diagnostic Laboratory (n = 256) for APC I1307K testing. Of patients seen at the JH Clinic, 77/91 (84.6%) elected APC I1307K testing after pretest counseling (acceptors). There were no statistically significant differences in demographic characteristics between acceptors and decliners. In comparison, only 8 of 57 (14.0%) patients offered HNPCC testing proceeded with testing (P < 0.001). Of 256 individuals tested at the JH laboratory, most were male (61.3%) and most had a personal or family history of colorectal cancer or polyps. Test positivity correlated with increasing risk of colorectal cancer. Acceptance of testing for the APC I1307K mutation is high, with more men than women pursuing counseling and testing. The reported association between the APC I1307K mutation and colon cancer risk was supported by a correlation in these data between personal or family history of CRC or polyps and a gene mutation.

Perfusion abnormalities in prodromal AD

Cerebral perfusion abnormalities in patients with established Alzheimer's disease (AD) are most commonly seen in the temporoparietal cortex. As the disease progresses, this perfusion pattern is increasingly prevalent. Recently, investigators have begun to examine the patterns of perfusion among individuals at risk for AD. To date, such studies have been conducted either in individuals who have a progressive memory difficulty but do not yet meet clinical criteria for AD, or in individuals with a genetic risk factor or family history of AD, either with or without a memory problem. These latter studies suggest that a set of brain regions show decreased perfusion during the prodromal phase of AD, and that a brain network or networks with multiple nodes is affected early in the course of AD. These perfusion abnormalities may also shed light on how AD progresses during the prodromal phase of disease and may ultimately lead to improved diagnosis or methods of monitoring response to treatment.

Human mitochondrial DNA polymerase holoenzyme: reconstitution and characterization

We have reconstituted the holoenzyme of the human mitochondrial DNA polymerase from cloned and overexpressed catalytic and accessory subunits. We have examined the polymerization activity of the catalytic subunit alone and of the holoenzyme to establish the function of the accessory subunit in this two subunit enzyme. The accessory subunit associates with the catalytic subunit with a dissociation constant of 35 +/- 16 nM as measured by the concentration dependence of its effect in stimulating maximal DNA binding and polymerization. At saturating concentrations, the accessory subunit contributes to every kinetic parameter examined to facilitate tighter binding of DNA and nucleotide and faster replication. The accessory protein makes the DNA binding 3.5-fold tighter (K(d) of 9.9 +/- 2.1 nM compared to 39 +/- 10 nM for the catalytic subunit alone) without significantly affecting the DNA dissociation rate (0.02 +/- 0.001 compared to 0.03 +/- 0.001 s(-)(1)). The ground-state nucleotide binding is improved from 4.7 +/- 2.0 to 0.78 +/- 0.065 microM, and the maximum DNA polymerization rate is increased from 8.7 +/- 1.1 to 45 +/- 1 s(-)(1) by the addition of the accessory protein. This leads to an increase in processivity from an estimated 290 +/- 46 to 2250 +/- 162. Although the accessory protein has been described as a "processivity factor" because of its effect on the ratio of rate constants defining processivity, this terminology falls short of adequately describing the profound effects of the small subunit on nucleotide-binding and incorporation catalyzed by the large subunit. By using the complete holoenzyme, we can now proceed with a comprehensive analysis of the structural and mechanistic determinants of enzyme specificity that govern toxicity of nucleoside analogues used in the treatment of viral infections such as AIDS.

A relational database for diagnosis of hematopoietic neoplasms using immunophenotyping by flow cytometry

A relational database was developed to facilitate the diagnosis of hematopoietic neoplasms using results of immunophenotyping by flow cytometry. This database runs on personal computers and uses backward-chaining search to arrive at conclusions. Results of immunologic marker studies are processed by the database to obtain a set of differential diagnoses. The current version of this database includes diagnostic immunophenotyping pattern for 33 hematopoietic neoplasms. We tested this database using 92 clinical cases from 2 tertiary care medical centers. The database ranked the actual diagnosis as 1 of the top 5 differential diagnoses in 93% of the cases tested. The user can modify the database contents to suit individual needs. This database has been posted on the World Wide Web for direct access. We propose that this user-friendly database is a potential tool for computer-assisted diagnosis of hematopoietic neoplasms.

An axonemal dynein at the Hybrid Sterility 6 locus: implications for t haplotype-specific male sterility and the evolution of species barriers

Poor sperm motility characterized by a distinct aberration in flagellar waveform known as "curlicue" is a hallmark of t haplotype (t) homozygous male sterility. Previous studies have localized "curlicue" and a flagellar developmental defect, "whipless", to the Hybrid Sterility 6 locus (Hst6), between the markers Pim1 and Crya1. More recent heterospecific breeding experiments between Mus spretus (Spretus) and Mus musculus domesticus (Domesticus) have mapped the primary source(s) of both "curlicue" and "whipless" to a small sub-locus of Hst6, Curlicue a (Ccua). Here we report the complete physical isolation of the Ccua locus and the identification of a candidate gene for expression of both "whipless" and "curlicue" at its proximal end, an axonemal dynein heavy chain gene, Dnahc8, formerly mapped by interspecific backcross analysis near Pim1. Dnahc8 mRNA expression commences in the Domesticus wild-type testis just prior to flagellar assembly and is testis-specific in the adult male. However, expression of Dnahc8 is not readily evident in the testis of either Spretus or "whipless" animals (Domesticus males homozygous for the Spretus allele of Dnahc8). Our results argue that Dnahc8 is fundamental to flagellar organization and function in Domesticus, but not Spretus, and suggest that Dnahc8 is integral to both Hst6- and t-specific male infertility.

Reliability of self-reported blood pressure measurements

BACKGROUND

Home blood pressure (BP) monitoring improves BP control, but it is unknown whether patients accurately report home BP readings to their physician. This study compared self-reported with electronically stored home BP and heart rate (HR) readings and evaluated this agreement in patients with controlled vs. uncontrolled hypertension.

METHODS

A single-blind, randomized clinical trial was conducted in an ambulatory managed care population. Subjects were identified by hypertension-related codes from the International Classification of Diseases, Ninth Revision (401.0, 401.1, and 401.9). Subjects recorded systolic BP (SBP), diastolic BP (DBP), and HR 3 times daily for 1 week by means of a digital BP monitor. Subjects were unaware that the monitor electronically stored results.

RESULTS

Thirty subjects were enrolled (29 complete data sets); their mean age (+/-SD) was 56+/-9 years, and 15 (52%) were women. Sixty-eight percent of subject-recorded SBP, DBP, and HR measurements were identical to electronically stored results. Twenty percent of recorded SBPs and 17% of recorded DBPs differed from stored SBP and DBP by more than 10 mm Hg. Erroneous reporting was evident in 9% of uncontrolled vs 4% of controlled SBPs (P<.001). Similarly, 21% of uncontrolled and 4% of controlled DBPs were erroneously reported (P<.001). In cases where the stored HR exceeded 100 beats/min, 43% of HR readings were recorded as 100 beats/min or less (P<.001).

CONCLUSIONS

Most self-reported BP and HR readings were identical to electronically stored measurements. However, erroneous reporting occurred significantly more often in cases of uncontrolled BP and HR, which may misguide physicians in the optimal treatment of their patients with hypertension.

Genetic testing and counseling for hereditary forms of colorectal cancer

The discovery of genes responsible for inherited forms of colorectal cancer have the potential to improve cancer risk assessment and counseling. Germline mutations (nonsense, frameshift) of APC are associated with familial adenomatous polyposis, an autosomal dominant syndrome, clinically characterized by young onset, hundreds of adenomatous polyps in the colon, and increased risk for extracolonic tumors. Mutations in APC are also associated with forms of attenuated familial adenomatous polyposis. Germline mutations in five mismatch repair related genes (hMSH2, hMLH1, hMSH6, hPMS1, and hPMS2) cause hereditary nonpolyposis colorectal cancer and are associated with increased risk of somatic genetic alterations and high DNA microsatellite instability. Hereditary nonpolyposis colorectal cancer is characterized by young onset colorectal cancer, proximal colon location, and increased risk of extracolonic cancers. A missense mutation in APC (I1307K) is associated with some familial colorectal cancer in Ashkenazic Jews. For persons at risk for hereditary forms of colorectal cancer, testing algorithms and gene test interpretations depend on identification of the pedigree germline gene mutation. Careful evaluation of the kindred for characteristic aggregation of tumor types among affected individuals and the availability of affected persons for testing are important issues in implementing genetic testing and follow-up management. Case reports illustrate the importance of genetic counseling as a component of cancer genetic risk assessment. The genetic counseling process includes exploration of patient risk perception, sources of anxiety related to cancer risk, patient education (specific cancer-related issues, prevention/intervention options), discussion of possible gene test options, test limitations, and consequences of various gene test outcomes.

In vivo matrix microdamage in a naturally occurring canine fatigue fracture

Greyhound central tarsal bone (CTB) from animals with (n = 11) and without CTB fatigue fracture (n = 15) was examined histologically for the presence, numerical density, and morphology of in vivo microdamage. Complete fracture of the right CTB is a common occurrence during dog racing, because this is the outside limb when running counterclockwise on a circular or oval track. The CTB consisted of both remodeled cortical bone and inner trabecular bone. Thickening and coalescence of trabeculae were observed, particularly dorsally and medially, causing reduction or elimination of the marrow void spaces. A band of tightly packed transverse osteons was also observed adjacent to the concave proximal joint surface. Typical linear microcracks were most often seen in remodeled cortical and trabecular bone and were often observed adjacent to vascular channels. In contrast, ultra-microcracking, represented by diffuse staining with basic fuchsin, was consistently observed in the plantar process around the attachment site for the plantar ligament complex. Dog status (fractured or intact) and side (left or right) both had a significant effect on microcrack density and microcrack surface density (p < 0.05). Microcrack density and microcrack surface density were increased in the right (fractured) CTB from greyhounds with CTB fracture. There was also a trend for side to have a significant effect on microcrack length, with microcrack lengths being higher in the right CTB of both intact and fractured dogs. These data support the general hypothesis that fatigue fracture occurs because of ongoing cyclic stresses after induction of reparative remodeling. Development of methods for biomechanical testing of small cuboidal bones should allow investigation of relationships between accumulation of loading cycles and bone weakening because of microdamage.

Weight gain in infants breastfed by mothers who take fluoxetine

OBJECTIVE

Despite the manufacturer's recommendation that fluoxetine not be used by women while breastfeeding, many women choose to do so. There is little information available in the literature to suggest that this practice is or is not safe. The purpose of this study was to examine weight gain in infants who are breastfed by mothers who take fluoxetine, compared with weight gain in infants who are breastfed by mothers who do not take any psychotherapeutic medication. A secondary goal was to assess the frequency of reported side effects in infants who are breastfed by mothers who take fluoxetine.

METHODOLOGY

A retrospective cohort study design was used. Subjects were identified from an ongoing pregnancy outcome study conducted through the California Teratogen Information Service and Clinical Research Program. A total of 64 women were interviewed who had taken fluoxetine during a pregnancy between the 1989 and 1997; 26 of these women breastfed their infants and continued to take the medication, and 38 breastfed their infants but did not take the medication. Postnatal weight gain was taken from pediatric records, and the frequency of side effects was measured by maternal response to the interview questionnaire.

RESULTS

Using linear regression analysis, the infants who were breastfed by mothers taking fluoxetine demonstrated a growth curve significantly below that of infants who were breastfed by mothers who did not take the drug. The average deficit in measurements taken between 2 weeks and 6 months of age was 392 g (95% confidence interval: -5, -780). Using a repeated measures analysis of covariance for those infants with more than one postnatal weight measurement available, the difference between the two groups was similar, approximately 1.2 standard deviations (P =.005). In response to interview questions regarding side effects, no mother who breastfed her infant while taking fluoxetine reported any unusual symptoms that could be attributed to the medication.

CONCLUSIONS

These data do not suggest that women who breastfeed while taking fluoxetine are likely to note unusual behavior in their infants that they consider related to use of the medication. However, although there was no excess of infants in the fluoxetine group with postnatal weight measurements >2 standard deviations below the mean, these data indicate that breastfeeding while taking fluoxetine is associated with reduced growth that may be of clinical importance in situations in which infant weight gain is already of concern.

MutS recognition of exocyclic DNA adducts that are endogenous products of lipid oxidation

The ability of the methyl-directed mismatch repair system to recognize and repair the exocyclic adducts propanodeoxyguanosine (PdG) and pyrimido[1,2-alpha]purin-10(3H)-one (M(1)G), the major adduct derived from the endogenous mutagen malondialdehyde, has been assessed both in vivo and in vitro. Both adducts were site-specifically incorporated into M13MB102 DNA, and the adducted genomes were electroporated into wild-type or mutS-deficient Escherichia coli strains. A decrease in mutations caused by both adducts was observed in mutS-deficient strains, suggesting that MutS was binding to the adducts and blocking repair by nucleotide excision repair. This hypothesis was supported by the differences in mutation frequency observed when hemimethylated genomes containing PdG on the (-)-strand were electroporated into a uvrA(-) strain. The ability of purified MutS to bind to PdG- or M(1)G-containing 31-mer duplexes in vitro was assessed using both surface plasmon resonance and gel shift assays. MutS bound to M(1)G:T-containing duplexes with similar affinity to a G:T mismatch but less strongly to M(1)G:C- and PdG-containing duplexes. Dissociation from each of the adduct-containing duplexes occurred at a faster rate than from a G:T mismatch. The present results indicate that MutS can bind to exocyclic adducts resulting from endogenous DNA damage and trigger their removal by mismatch repair or protect them from removal by nucleotide excision repair.

Nitrous acid pretreatment of tendon xenografts cross-linked with glutaraldehyde and sterilized with gamma irradiation

Collagenous xenografts made from kangaroo tail tendon cross-linked with glutaraldehyde have a potential application in the reconstruction of massive digital tendon deficits. However, a limitation to the clinical use of these xenografts has been the optimization of collagen cross-linking, and subsequent bio-incorporation and retention of mechanical properties following implantation. The purpose of this study was to evaluate the effect of nitrous acid on modulating the biologic and mechanical properties of tendon xenografts cross-linked with glutaraldehyde. Tendon xenografts were pretreated with 0.1 or 0.01 M nitrous acid solution, prior to cross-linking in 2% glutaraldehyde and sterilization by gamma irradiation. Xenografts were implanted intramuscularly in rabbits to examine biocompatability, and also used to repair ovine digital extensor tendon deficits to evaluate functional incorporation. Histologically, intramuscularly implanted nitrous acid pretreated xenografts in rabbits had a greater degree of diffuse cellular infiltration into interstitial splits in the graft than controls after 12 weeks. Xenografts implanted in an ovine extensor tendon deficit were evaluated after 26 and 52 weeks. Rate of failure of tenorrhaphies between host tendon and xenografts overall (15/21) was significantly greater (P < 0.05) than for autografts (1/21), suggesting that the holding power of sutures in xenografts was inferior to that obtained in autografts. Tensile failure stress of midsections of both nitrous acid pretreated and control xenografts was about 100 MPa prior to implantation (time zero). After 26 and 52 weeks, failure stress of both types of xenografts was significantly less than at time zero (P < 0.05). At 52 weeks, failure stress of nitrous acid pretreated xenografts (47.4 +/- 3.1 MPa) was significantly less than control xenografts (63.7 +/- 5.4 MPa); (P < 0.05). However, nitrous acid pretreated xenografts were similar to control xenografts in failure load (357 +/- 29 and 354 +/- 26 N, respectively), but they tended to have larger cross-sectional areas (7.6 +/- 0.5 versus 5.7 +/- 0.6 mm2, respectively) which were responsible for the lower calculated value for failure stress. Histologically, autografts maintained their normal tissue architecture and evoked a more limited cellular response in surrounding tissues than xenografts (P < 0.05). Both types of xenograft were surrounded by a thicker cuff of cellular response than autografts. However, compared to control xenografts, nitrous acid pretreated xenografts had more extensive fragmentation and splitting of collagen bundles, and more diffuse cellular and vascular infiltration into these interstitial splits, and these alterations were apparently contributing to the greater 'swelling' of these xenografts. It was concluded that pretreatment of tendon xenografts with nitrous acid modulated their biologic and material properties. Further studies are needed to elucidate the mechanism of these effects, and to determine if the protocol for tendon xenograft preparation could be optimized for improved clinical performance.

The catalytic mechanism of EPSP synthase revisited

Recent analysis of EPSP synthase by solid-state NMR has led to the postulation of a new enzyme reaction pathway and raised once again the question of an intermediate species covalently bound to the enzyme [Studelska, D., McDowell, L., Espe, M., Klug, C., and Schaefer, J. (1997) Biochemistry 36, 15555-15560]. Therefore, we have reexamined the mechanism of the reaction catalyzed by EPSP synthase and analyzed the reaction products formed under the conditions used in preparing samples for solid-state NMR. Single-turnover experiments were carried out using both [1-14C]- and [32P]PEP showing the formation and decay of the previously proposed tetrahedral intermediate species on a time scale comparable with the disappearance of substrate and formation of product, thus unequivocally establishing the kinetic competence. The possible presence of a covalently bound enzyme intermediate species was also investigated, using SDS-PAGE and Centricon concentration analysis of the quenched reaction samples. No covalently bound enzyme intermediates were observed during the reaction. An enzyme assay was also performed repeating the conditions used in sample preparation for the solid-state NMR studies. We show that under these conditions, total turnover of substrates to products was observed within 45 s at -30 degrees C prior to freezing and lyophilization. Following lyophilization, the samples were stored at -20 degrees C and analyzed over a period of 21 days. We observed the conversion of the product EPSP into the side product, a cyclic EPSP ketal, and the breakdown product, pyruvate. Thus, the new species reported by solid-state NMR can be accounted for by previously characterized reaction products and side products formed during sample preparation and upon incubation in the solid-state. Our conclusions are also supported by the solution and solid-state NMR studies recently reported [Jakeman et al. (1998) Biochemistry 37, 12012-12019]. These results once again highlight the importance of kinetic competence as a criterion to be used in defining enzyme intermediates and point to the errors in interpretation of results when the time dependence of formation of the proposed intermediates is not considered.

Magnetic resonance imaging of normal canine carpal ligaments

Magnetic resonance imaging was conducted on previously frozen left carpi from six normal dogs using a 1.5 Tesla magnet in combination with a transmit/receive wrist coil. Three-millimeter thick T1-weighted spin-echo images and 1-mm thick T2*-weighted gradient-recalled 3-D images were obtained in dorsal and sagittal planes. Carpi were embedded, sectioned, and stained. Anatomic structures on the histologic sections were correlated with the MR images. All of the carpal ligaments plus the radioulnar articular disc and the palmar fibrocartilage were identified on MR images. The accessorio-quartile ligament, which had not been well described previously in dogs, was also identified. It originated on the accessory carpal bone and inserted on the fourth carpal bone. The T2*-weighted gradient echo imaging technique provided better images than T1-weighted technique, largely because thinner slices were possible (1 mm vs. 3 mm), resulting in less volume averaging of thin ligaments with surrounding structures. Although MRI is currently the imaging modality of choice to identify ligamentous injury in humans, further studies are needed to determine if abnormalities can be detected in canine carpal ligaments using MRI.

Comparison of two home blood pressure monitors with a mercury sphygmomanometer in an ambulatory population

We performed a randomized, single-visit, crossover study to compare the precision of a digital monitor and an aneroid monitor relative to a desktop mercury sphygmomanometer (DMS). Three blood pressure measurements per patient, one per device, were taken over 25 minutes. Of 99 patients, 95 had complete blood pressure data. Systolic blood pressures measured with the digital monitor were significantly different from those with the DMS (p<0.01). Thirty-four percent of systolic and 48% of diastolic pressures measured with the digital monitor were within +/- 5 mm Hg of the DMS. The aneroid monitor performed significantly better than the digital monitor, with 54% of systolic (p<0.01) and 58% of diastolic blood pressures within +/- 5 mm Hg of the DMS standard. Health care providers are encouraged to supervise patients' initial use of a home blood pressure monitor and calibrate readings against a standard mercury sphygmomanometer.

Single d(GpG)/cis-diammineplatinum(II) adduct-induced inhibition of DNA polymerization

A 44 nucleotide DNA template containing a single site-specifically placed cisplatin adduct (cis-[Pt(NH3)2[d(GpG)-N7(1),-N7(2)]]) was annealed with a primer, positioning its 3'-end four bases before the adduct in the template strand. DNA polymerization in the presence of all four nucleotides revealed that both HIV-1 reverse transcriptase (RT) and T7 DNA polymerase strongly paused at one nucleotide preceding the first platinated guanine and at the positions opposite the two platinated guanines. Analysis of single nucleotide incorporation at each pause site showed that polymerization occurs with biphasic kinetics. A small percentage of DNA was bound productively, providing a small amplitude (1-3%) of a fast phase of polymerization, whereas most of the bound DNA (1-34%) was positioned at the pause site in a nonproductive manner and therefore elongated slowly (0.04-0.06 s-1). DNA substrates annealed to the cisplatin-modified template bind to HIV-1 RT with an affinity (10-20 nM) similar to that of unmodified substrates (6-9 nM). The cisplatin-DNA cross-link moderately weakened DNA binding to T7 DNA polymerase (12-115 nM) but significantly slowed the rate of incorporation of the next nucleotide (2-7 s-1 ), with larger effects closer to the cisplatin-DNA adduct. The crystal structure of the same cisplatin-DNA adduct [Takahara, P. M., Frederick, C. A., and Lippard, S. J. (1996) J. Am. Chem. Soc. 118, 12309-12321] reveals not only the bent DNA duplex but also the propeller twisted base pairs near the cisplatin-DNA adduct. The twisted base pairs may cause misalignment of the cisplatin-modified DNA at the binding cleft of T7 DNA polymerase and significantly slow the rate of the protein conformational change preceding polymerization, leading to the slight accumulation of intermediates within five base pairs of the adduct. The ground-state binding of the next correct nucleotide to the enzyme.DNA complex was weakened by the adduct with T7 DNA polymerase but unchanged with HIV-1 RT at sites other than the three strong pause sites. Nucleotide binding to both enzymes at the three strong pause sites was significantly weaker and less selective.

5-HT agonist-induced phase-advances of the circadian pacemaker are diminished by chronic antidepressant drug treatment

Serotonin (5-HT) and its agonists alter the timing of the circadian pacemaker. Previous research has shown that when they are injected 4 h before or after the onset of wheel-running, they phase-advance or delay, respectively, the timing of the pacemaker. Because serotonergic interventions alter 5-HT receptor number in the hypothalamus, we asked whether chronic treatment with an antidepressant drug (AD) that modifies serotonergic function could alter the phase-shifting effects of the 5-HT agonist 8-hydroxydipropylaminotetralin (8-OH-DPAT). Hamsters were treated chronically with the monoamine oxidase inhibitor (MAOI), clorgyline, and then injected with 8-OH-DPAT or vehicle (VEH) either 4 h before or after the onset of wheel-running. MAOI treatment decreased the magnitude of both 8-OH-DPAT- and VEH-induced phase advances, but not the magnitude of 8-OH-DPAT-induced phase-delays. The results indicate that 8-OH-DPAT-induced phase-advances and delays are functionally distinct with regard to adaptive changes during chronic AD treatment.

Interlocking nail treatment of diaphyseal long-bone fractures in dogs

OBJECTIVE

To determine results of using interlocking nails (IN) for fixation of diaphyseal long bone fractures in dogs.

DESIGN

Multi-center prospective clinical trial.

ANIMALS

134 dogs with diaphyseal fractures of the femur (n = 92), tibia (23), or humerus (19); 11 had previous unsuccessful treatments, and 103 had comminuted fractures of which 70 were classified as unstable.

PROCEDURE

All fractures were stabilized with 6- or 8-mm-diameter IN with 3.5- or 4.5-mm screws, respectively. Cerclage wires and an autogenous bone graft were used at the surgeon's discretion. Participating surgeons provided information on age, sex, weight, and breed of the dog, details of the surgery, details of any intra- or postoperative complications, fracture healing time, and limb function.

RESULTS

Eight dogs were lost to follow-up evaluation. In 105 of the remaining 126 dogs (83%), fractures healed without complications. For these 105 dogs, limb function was excellent (n = 90), good (12), fair (2), and poor (1). Complications developed for 21 dogs (17%); limb function after additional treatment was excellent (n = 10), good (2), fair (5), poor (1), or unreported (3). Interlocking nails broke in 9 dogs; breakage was attributed to fatigue failure because of use of too small an IN or because of insertion of the IN so that a screw hole was positioned at the fracture site.

CLINICAL IMPLICATIONS

The high success rate and low complication rate suggest that IN can be used to stabilize diaphyseal fractures in dogs. Good technique is necessary for optimal results.

Youth Alternative Sentencing Program: a description and evaluation of an alcohol and marijuana intervention program

An alternative program was designed for youth who were charged with an alcohol or marijuana offense in San Bernardino County, California. In place of a conviction, the youth could attend an extended educational program that emphasized their ability to change behavior and to understand the consequences of risk-taking behavior. An evaluation was completed by the participants, demonstrating that this population of youth began to experiment with alcohol and marijuana around 12 and 13 years of age. A large number of youths were identified for nontraffic offenses, which offered an opportunity to intervene before members of this population become involved in a motor vehicle crash.

State health agencies and quality improvement in perinatal care

The origin of the federal-state partnership in Maternal and Child Health (MCH) can be traced from the Children's Bureau grants of 1912, through the Sheppard-Towner Act, to the creation of Title V and other programs of today that mandate planning, accountability, and systems development. In the past decade with the transformation of the health care system and the emergence of managed care, there has been a resurgence of interest in public, professional, and governmental interest in quality measurement and accountability. Regional perinatal systems have been implemented in all states with varying levels of involvement by state health agencies and the public sector. This historical framework discusses two primary themes: the decades of evolution in the federal-state partnership, and the emergence in the last three decades of perinatal regional system policy, and suggests that the structure of the federal-state partnership has encouraged state variation. A survey of state MCH programs was undertaken to clarify their operational and perceived role in promoting quality improvement in perinatal care. Data and information from the survey, along with five illustrative state case studies, demonstrate great variation in how individual state agencies function. State efforts in quality improvement, a process to make things better, have four arenas of activity: policy development and implementation, definition and measurement of quality, data collection and analysis, and communication to affect change. Few state health agencies (through their MCH programs and perinatal staff) are taking action in all four arenas. This analysis concludes that there are improvements MCH programs could implement without significant expansion in their authority or resources and points out that there is an opportunity for states to be more proactive as they have the legal authority and responsibility for assuring MCH outcomes.