The proposed Stark II regulations. What physicians should know

Although the proposed regulations do not yet have the force and effect of law and HCFA is still seeking input in a variety of substantive areas, the regulations as proposed reflect HCFA's current view of enforcement of Stark II. Although simply complying with the statutory language and the Stark I regulations may be enough to avoid scrutiny until the proposed regulations are promulgated in final form, this approach may set physicians and physician groups up for significant disruption in their relationships in the future, particularly when proposed regulations have called certain practices into question. Clearly, every relationship between a physician (and his or her physician group) and any entity that provides DHS should be reexamined in light of the proposed regulations. In addition, arrangements under negotiation should be structured with the proposed new requirements in mind.     

Acquisition of CD24 expression by Lin-CD43+B220(low)ckit(hi) cells coincides with commitment to the B cell lineage

The present study describes three subsets of bone marrow-derived Lin CD43+B220(low) (B220(low)) progenitor cells which represent distinct stages in hematopoietic development. These populations differ in their expression of CD24 and ckit and the occurrence of IgH gene rearrangement. B220(low) CD24-ckit(hi) progenitors have their IgH loci in germ-line configuration and are multipotent since they can give rise to B cells, T cells and myeloid cells. B220lowckit(hi) cells which have acquired CD24 expression have retained IgH loci in germ-line configuration and the ability to generate B cells, however, they have lost the ability to generate T cells and myeloid cells. Thus acquisition of CD24 by B220(low) cells occurs concurrently with the transition from a multipotent to a lineage-restricted progenitor population. B220(low)CD24+ cells expressing low levels of ckit are also lineage restricted, giving rise to only B cells and have begun D-J(H) rearrangement, implying that initiation of IgH rearrangement coincides with the down-regulation of ckit expression.     

Cyclin-dependent kinase inhibitor p57KIP2 in soft tissue sarcomas and Wilms'tumors

Mammalian cyclin-dependent kinase inhibitors fall into two families, the INK4 and the CIP/KIP. The CIP/KIP family comprises three structurally related members, including p21CiP1/WAF1, p27KIP1, and p57KIP2. These proteins are all capable of inhibiting the progression of the cell cycle by binding and inhibiting G(1) cyclin/cyclin-dependent kinase complexes. In humans, p57KIP2 is expressed specifically in skeletal muscle, heart, brain, kidney, and lung. Human KIP2 resides in 11p15.5, a chromosomal region that is a common site for loss of heterozygosity in certain sarcomas, Wilms' tumors, and tumors associated with the Beckwith-Wiedemann syndrome. Because of the function, selective expression, and chromosomal location of p57KIP2, we undertook the present study to search for potential mutations of KIP2 in a cohort of 126 tumors composed of 75 soft tissue sarcomas and 51 Wilms' tumors. The KIP2 gene was characterized by Southern blot, comparative multiplex PCR, PCR -single-strand conformational polymorphism, and DNA sequencing assays in these neoplasms. Deletions of the KIP2 gene or point mutations at the region encoding the cyclin-dependent kinase inhibitory domain were not found in the tumors analyzed. The absence of KIP2 mutations might indicate that these tumors arise due to defects at a closely linked but separate locus. Alternatively, similarly to the mouse homologue, inactivation of KIP2 could occur via genomic imprinting.     

Recombinant expression and characterization of the major beta-lactamase of Mycobacterium tuberculosis

New antibiotic regimens are needed for the treatment of multidrug-resistant tuberculosis. Mycobacterium tuberculosis has a thick peptidoglycan layer, and the penicillin-binding proteins involved in its biosynthesis are inhibited by clinically relevant concentrations of beta-lactam antibiotics. beta-Lactamase production appears to be the major mechanism by which M. tuberculosis expresses beta-lactam resistance. beta-Lactamases from the broth supernatant of 3- to 4-week-old cultures of M. tuberculosis H37Ra were partially purified by sequential gel filtration chromatography and chromatofocusing. Three peaks of beta-lactamase activity with pI values of 5.1, 4.9, and 4.5, respectively, and which accounted for 10, 78, and 12% of the total postchromatofocusing beta-lactamase activity, respectively, were identified. The beta-lactamases with pI values of 5.1 and 4.9 were kinetically indistinguishable and exhibited predominant penicillinase activity. In contrast, the beta-lactamase with a pI value of 4.5 showed relatively greater cephalosporinase activity. An open reading frame in cosmid Y49 of the DNA library of M. tuberculosis H37Rv with homology to known class A beta-lactamases was amplified from chromosomal DNA of M. tuberculosis H37Ra by PCR and was overexpressed in Escherichia coli. The recombinant enzyme was kinetically similar to the pI 5.1 and 4.9 enzymes purified directly from M. tuberculosis. It exhibited predominant penicillinase activity and was especially active against azlocillin. It was inhibited by clavulanic acid and m-aminophenylboronic acid but not by EDTA. We conclude that the major beta-lactamase of M. tuberculosis is a class A beta-lactamase with predominant penicillinase activity. A second, minor beta-lactamase with relatively greater cephalosporinase activity is also present.     

Circulating plasma prekallikrein and tissue kallikrein in normotensive and hypertensive humans: effects of angiotensin II infusion

Kinins lower blood pressure but the stimuli leading to kinin generation and their origin are less well known. We administered angiotensin II in graded infusion doses to patients with primary hypertension and normotensive controls to study the effects of on circulating kallikreins. Angiotensin II infusion did not significantly alter plasma prekallikrein or tissue kallikrein levels and the plasma levels and their changes did not correlate with blood pressure levels or changes. In the normotensive group prekallikrein levels and renin activity correlated negatively with urinary sodium and chloride excretion during basal conditions and partially during the infusion. U-tissue kallikrein concentration increased in the normotensive group. Thus, acute elevation of blood pressure induced by angiotensin II does not activate the circulating kallikrein-kinin systems. Data rather indicate that the circulating kallikrein-kinin systems may be related to alterations in volume and sodium balance and that these mechanisms may be altered in primary hypertension.     

Effects of acute and chronic morphine on rotational behavior in nigral-lesioned rats

Stimulation of mu-opioid receptors located on dopaminergic neurons in the striatum and the nucleus accumbens increases dopamine release, which may account for some of the behavioral effects of morphine. In this study, we examined the effects of acute and chronic morphine treatment on rotational behavior in rats with unilateral 6-hydroxydopamine dopamine (6-OHDA)-induced lesions of the nigrostriatal pathway. Rats receiving morphine acutely (0.3-10 mg/kg) did not show a significant bias toward contralateral or ipsilateral turning. Mini osmotic pumps dispensing morphine continuously (20-24 mg/kg/day) were implanted s.c. in these animals. This treatment induced tolerance to the behavioral depression produced by the highest dose of morphine (10 mg/kg) when it was given acutely. A slight but significant increase in ipsilateral turning occurred over the range of morphine doses examined. The effects of morphine on rotational behavior are slight, and do not correlate well with the reported increase in locomotor activity or extraneural dopamine in the striatum that are produced by doses of morphine similar to the ones tested in this study.     

Circulatory disturbances following transient soft tissue compression trauma

Circulatory changes following standardized compression trauma to the hind leg in dogs were evaluated using an electromagnetic flow meter and repeated angiography. A transient increase of flow to the injured limb and within the traumatized region was observed. Good agreement was found between the electromagnetic flow recordings and estimates of relative changes in flow by the angiographic method.     

A case-control study of menopausal estrogen therapy and breast cancer

The association between estrogen replacement therapy and female breast cancer was studied in two Los Angeles area retirement communities. The 138 study cases of breast cancer occurring in residents younger than 75 years were compared with age- and race-matched community control subjects. The risk ratio for a total cumulative dose in excess of 1,500 mg was estimated to be 2.5 in women with intact ovaries. This increase was present using various independent sources of drug usage information but was inconsistent at low dose and undetectable in oophorectomized women. No important sources of confounding could be identified, and no risk modifiers could be identified except for a history of surgically confirmed benign breast disease. In such women with intact ovaries, the risk ratio for a high cumulative dose rose to 5.7 relative to nonusers with normal breasts.     

Effects of albumin and/or furosemide therapy on pulmonary edema induced by hydrochloric acid aspiration in rabbits

Aspiration of hydrochloric acid in rabbits resulted in an increased P(A-a)O2 together with increases in both lung water volume and lung extravascular albumin. This finding suggests lung damage following acid aspiration is related to changes in capillary permeability, with pulmonary edema resulting from the movement of albumin and water into the interstitial space. Therapy with albumin and furosemide together reduced the lung water and albumin accumulation and decreased P(A-a)O2. Treatment with albumin or furosemide alone was ineffective. Caution should be exercised in administering albumin alone for therapy of pulmonary edema when plasma protein is not clearly decreased, or when increased pulmonary capillary permeability is suspected.