Novel fold and assembly of the repetitive B region of the Staphylococcus aureus collagen-binding surface protein.

BACKGROUND: [corrected] The Staphylococcus aureus collagen-binding protein Cna mediates bacterial adherence to collagen. The primary sequence of Cna has a non-repetitive collagen-binding A region, followed by the repetitive B region. The B region has one to four 23 kDa repeat units (B(1)-B(4)), depending on the strain of origin. The affinity of the A region for collagen is independent of the B region. However, the B repeat units have been suggested to serve as a 'stalk' that projects the A region from the bacterial surface and thus facilitate bacterial adherence to collagen. To understand the biological role of these B-region repeats we determined their three-dimensional structure. RESULTS: B(1) has two domains (D(1) and D(2)) placed side-by-side. D(1) and D(2) have similar secondary structure and exhibit a unique fold that resembles but is the inverse of the immunoglobulin-like (IgG-like) domains. Comparison with similar immunoglobulin superfamily (IgSF) structures shows novel packing arrangements between the D(1) and D(2) domains. In the B(1)B(2) crystal structure, an omission of a single glycine residue in the D(2)-D(3) linker loop, compared to the D(1)-D(2) and D(3)-D(4) linker loops, resulted in projection of the D(3) and D(4) in a spatially new orientation. We also present a model for B(1)B(2)B(3)B(4). CONCLUSIONS: The B region of the Cna collagen adhesin has a novel fold that is reminiscent of but is inverse in nature to the IgG fold. This B region assembly could effectively provide the needed flexibility and stability for presenting the ligand binding A region away from the bacterial cell surface.

Quantitative and neurogenic analysis of the total population and subpopulations of neurons defined by axon projection in the superficial dorsal horn of the rat lumbar spinal cord.

The total neuron population of the superficial dorsal horn (SDH), i.e., laminae I and II, was quantitated in Nissl preparations of spinal segment L1 in the rat. Subpopulations of the SDH, defined by axon projection, were quantitated following strategic intraspinal injections of dual retrograde tracers (Fluoro-Gold and true blue). These methods were used in conjunction with [3H]thymidine (delivered in utero) autoradiography for neurogenic pattern analysis. Following stereological correction, each dorsal horn in spinal segment L1 contained 11 neurons in lamina I and 42.6 neurons in lamina II per 10-microm transverse section. Neurons with long projections, i.e., neurons with projections rostral to spinal segment T5, were only slightly more numerous in lamina I than in lamina II. These neurons made up 34% of the total neuron population in lamina I and 7.0% in lamina II. Most of these neurons did not demonstrate descending connections, and many (presumed supraspinal projection neurons) did not demonstrate short, ascending, intersegmental connections. Neurons with short propriospinal projections, i.e., neurons with connections caudal to spinal segment T5, made up approximately half of the total neuron population in both lamina I and lamina II: 55% and 52%, respectively. Of these, 79% had both short ascending and descending projections; the remaining 21% had only descending projections. Neurons that were not labeled with retrograde tracers (presumed local circuit cells) represented 11% of the neurons in lamina I and 41% in lamina II. Neurogenesis in the SDH proceeded along an axon-length gradient, whereby neurons with the longest axons completed neurogenesis first, and those with the shortest completed neurogenesis last. The generation of both propriospinal and supraspinal projection neurons began on embryonic day 13 (E13). Nearly equal numbers of neurons in this group were generated in laminae I and II through E14. On E15, neuron production slowed in lamina I and accelerated in lamina II as local circuit neurons and the remaining propriospinal neurons were generated. Neuron production ceased simultaneously in both lamina I and lamina II on E16.

Quantitative and neurogenic analysis of neurons with supraspinal projections in the superficial dorsal horn of the rat lumbar spinal cord.

Dual retrograde axonal tracers, Fluoro-Gold (FG) and true blue (TB), were used in conjunction with [3H]thymidine autoradiography to determine the number and neurogenic pattern of neurons with supraspinal projections in the superficial dorsal horn (SDH), i.e., laminae I and II, in spinal segment L1 of the rat. FG was injected into rostral brain centers (dorsal thalamus and midbrain), and TB was injected into the caudal brainstem (medulla) in young adult rats previously administered [3H]thymidine in utero. Following stereological correction, each dorsal horn had an average of 1.22 neurons in lamina I and 0.24 neurons in lamina II that had supraspinal projections per 10-microm transverse section. In the SDH, 52% of the neurons with supraspinal projections were found to project to rostral brain centers alone, 3.0% only to the caudal brainstem, and 45% to both areas. There was no significant difference in the percentage distribution of each of the three groups of neurons between lamina I and lamina II. Cell counts in the present study, in conjunction with previous observations in the literature, suggest that the majority of supraspinal projection neurons in the SDH fall into two groups: 1) spinomesencephalic neurons with collaterals to the medulla and 2) spinothalamic neurons with collaterals to the midbrain. The neurogenesis of supraspinal projection neurons in the SDH proceeded along an axon-length gradient, whereby neurons with the longest axons, those with projections to rostral brain centers, completed neurogenesis prior to neurons with shorter axons, those with projections only to the caudal brainstem. The generation of all SDH neurons with supraspinal projections was completed on embryonic day 14 (E14), 2 days prior to the completion of neurogenesis for SDH neurons with intraspinal projections.

The stability of cognitive and behavioral parameters in autism: a twelve-year prospective study.

Sixty-two autistic patients enrolled in a prospective study an average of 12 years ago. Current retesting results are now available on 53 of the original 62 patients (85.5%). Results indicate that 36 (67.9%) achieved scores within their original IQ group. Twelve (22.6%) moved up IQ groups and five (9.4%) moved down. Of particular clinical importance is the observation that Vineland Adaptive Behavior Scores were consistently lower than cognitive scores, and maladaptive behaviors occurred with equal frequency in the high, medium, and low IQ groups. The implications of this new data for understanding the natural history of autism, educational and vocational planning, and future research are discussed.

Neurogenesis of spinothalamic and spinocerebellar tract neurons in the lumbar spinal cord of the rat.

The temporal and spatial neurogenic patterns of spinothalamic and spinocerebellar neurons were determined in spinal cord segment L1 of the rat. Neurogenic patterns were demonstrated with [3H]thymidine administered to fetal rats during the period when neurons with supraspinal projections are known to be generated, i.e. on one of embryonic (E) days E13, E14, or E15. The animals were allowed to survive 50 to 100 days postpartum, then neurons with spinothalamic and spinocerebellar projections were retrogradely filled with fluorescent axonal tracers, Fluoro-Gold or True blue, which were pressure injected into the dorsal thalamus and cerebellum in various combinations in the same and in separate animals. Neurons labeled with each retrograde tracer and [3H]thymidine and neurons labeled with retrograde tracers alone were counted in spinal cord segment L1 in each of the animals. Spinothalamic and spinocerebellar neurons were found to be separate and distinct populations. Statistical analysis of the data showed that spinothalamic and spinocerebellar neurons also have distinctly different patterns of neurogenesis which suggest early determination in each cell line. The temporal neurogenic pattern followed a projection-distance gradient, such that spinothalamic neurons, which have longer axons than spinocerebellar neurons, completed neurogenesis prior to spinocerebellar neurons in each region of the spinal gray.

The influence of urinary incontinence on publicly financed home care services to low-income elderly people.

Urinary incontinence (UI) has been shown to be prevalent and a risk factor for permanent institutionalization; yet it is not routinely measured in research of home care utilization. A retrospective cohort design is used to directly estimate the effect of UI on the public costs of home care services to elderly individuals. Multivariate analyses controlling for other individual, household, and supply characteristics demonstrate that those with UI generate significantly greater public costs for home care services. Patterns of service use suggest palliative rather than rehabilitative service, raising questions regarding the effective use of resources.

Comments on health indicators: methodological perspectives.

This paper discusses several basic conceptual and methodological problems in the development and use of health indicators. We observe that two tendencies of the health indicators movement may deter progress toward producing informations of health status indexes and the tendency to conceptualize "health" in terms of expansive definitions should measure variables specified by a social system model and should be scaled according to units that are relevant to decision-making criteria.

Health care: an international comparison of perceived morbidity, health services resources, and use.

Selected summary findings from the World Health Organization/International Collaborative Study of Medical Care Utilization are presented, based on data collected during a twelve-month period in 1968-1969 in twelve study areas in seven countries in the Americas and Europe. A household interview survey of almost 48,000 persons, representing a total population of about 15 million, elicited information on demographic characteristics, on perceptions of illness, its severity and character, and on attitudes toward and use of major components of health services. Information was also collected on the prevailing health care systems and resources available to the study population, as well as on socioeconomic characteristics of the study areas. Standardized rates for those defined as "healthy" and "functionally healthy" are quite similar across the twelve study areas, as are the rates for persons who reported being sick within two weeks. Rates for the volume of sick days within two weeks vary widely, and levels of chronicity with disability are much higher in the four continental European study areas. Rates for volume of physician contacts within two weeks vary considerably across study areas, but rates for persons with contacts are more stable, although for persons with perceived morbidity of high severity, the corresponding rates are lower in the four continental European study areas. By contrast, the rates for persons with an administrative reason for their most recent physical examination within twelve months are substantially higher in the latter. Where unmet need for a physician contact is greatest, the volume of hospital nights used is also greatest; a direct relationship between these two measures is evident without regard to the ratio of hospital beds available to the population. Wide differences are observed between the extremes of the measures of need, resources, and use employed in the study, raising questions about the ways in which resources are organized to provide services and about the effectiveness and efficiency of these services.

Social science and health services research: contributions to public policy.

Public skepticism of the promised links between research and practical ends, and of the role of natural scientists as the ultimate judges of progress, is not new. After the unprecedented new social legislation and related research of the 1960s, social scientists today are being questioned about their contribution to improved public policy. Government interventions in the health services industry created new needs for information and knowledge, and at the same time altered the institutions and mechanisms through which relevant research is conducted and used. Social scientists and public officials will have to act in concert in response to new policy and research environments.

Risk vulnerability and enrollment in a prepaid group practice.

An hypothesis that specifies conditions under which risk vulnerability factors are associated with enrollment in prepaid practices is presented and tested. We assert that such factors as illness histories and previous use of medical services are linearly and positively associated with enrollment when the prepaid option offers significantly lower marginal out-of-pocket costs. The hypothesis is supported by observations from a prostpective study of a lowincome population.

The impact of certificate-of need controls on hospital investment.

Certificate-of-Need (CON) controls over hospital investment have been enacted by a number of states in recent years and the National Health Planning and Resources Development Act of 1974 provides strong incentives for adoption of CON in additional states. In this study, we review the questions that have been raised about the effectiveness of CON controls and then we develop quantitative estimates of the impact of CON on investment. These estimates show that CON did not reduce the total dollar volume of investment but altered its composition, retarding expansion in bed supplies but increasing investment in new services and equipment. We suggest that this finding may be due to (1) the emphasis in CON laws and programs on controlling bed supplies and (2) a substitution of new services and equipment for additional beds in response to financial factors and organizational pressures for expansion. Finally, we caution against the conslusion that CON controls should be broadened and tightened, though our results might be so interpreted, because of the practical difficulties involved in reviewing and certifying large numbers of small investment projects.

Relaxation, reduction in angry articulated thoughts, and improvements in borderline hypertension and heart rate.

An intensive 7-week relaxation therapy was evaluated in a sample of unmedicated borderline hypertensive men. All subjects were provided state-of-the-art medical information regarding changes known to affect hypertension favorably, e.g., lower salt intake and regular exercise. In addition, relaxation subjects were trained in muscle relaxation that entailed audiotaped home practice. As predicted, relaxation combined with hygiene lowered blood pressure more than did hygiene alone. Neither treatment favorably affected a paper-and-pencil measure of anger but relaxation did lower anger-hostility on a new cognitive assessment procedure, Articulated Thoughts in Simulated Situations (ATSS). Moreover, ATSS anger-hostility reduction was correlated with blood pressure or heart rate reductions, for all subjects and especially for those in the Relaxation condition. This represents the first clinically demonstrated link between change in a cognitive variable and change in cardiovascular activity. Finally, results were especially strong in subjects high in norepinephrine, suggesting its importance in essential hypertension.

Crystallization and preliminary crystallographic investigation of porcine quinolinate phosphoribosyltransferase.

Quinolinate phosphoribosyltransferase (QPRT), purified from hog liver, has been crystallized using PEG 8000 as the precipitant. The crystals form long hexagonal rods in the space group P6322 with cell dimensions a = b = 121.7, c = 94.5 A. Based on the unit-cell dimensions and the calculated molecular mass of 33 500 Da, the Matthews coefficient suggests one molecule per asymmetric unit (Vm = 3.45 A3 Da-1; 64% solvent). Three native data sets were collected to a resolution of 2.5 A and merged to provide a set that is 94.7% complete, with an Rsym value of 9.6%.

Crystallization of ClfA and ClfB fragments: the fibrinogen-binding surface proteins of Staphylococcus aureus.

Recombinant constructs encoding the fibrinogen-binding domains of ClfA and ClfB from Staphylococcus aureus have been crystallized. ClfA was crystallized in the orthorhombic space group P212121 with unit-cell parameters a = 39.58, b = 81.39 and c = 112.65 A. A complete data set was recorded to 2.1 A resolution and had a Vm of 2. 3 A3 Da-1 with 46.5% solvent, suggesting one molecule per asymmetric unit. Co-crystals of ClfA with the 17 amino-acid C-terminal peptide of fibrinogen gamma-chain diffracted to 2.1 A resolution and had unit-cell parameters a = 39.11, b = 81.39 and c = 109.51 A in the space group P212121. ClfB was crystallized in the tetragonal space group P41212 or P43212 with unit-cell parameters a = 96.31, b = 96. 31 and c = 84.13 A and diffracted to 2.45 A resolution. The estimated Vm of 2.6 A3 Da-1 with 53% solvent indicated one molecule in the asymmetric unit.