Characterization of a phosphodiesterase-immunoreactive polypeptide from rod photoreceptors of developing rd mouse retinas

In the inherited retinal degeneration of rd mice, cyclic GMP accumulates in affected rod photoreceptors prior to their degeneration. A deficiency in the activity of the visual cell phosphodiesterase apparently results in the accumulation of cyclic GMP. The cyclic GMP phosphodiesterase (PDE) of normal mouse photoreceptors is a heteromeric protein complex of about 170 kDa, consisting of the alpha beta catalytic unit and the gamma inhibitory unit. The isolated complex has low enzyme activity but it can be activated by incubation with histone. Affinity-purified polyclonal antibodies against the PDE complex of bovine rod outer segments were prepared and used to identify in retinas of both normal and rd mice PDE-immunoreactive polypeptides which comigrated on SDS-polyacrylamide gels with the large subunits (88 kDa) of the normal PDE complex. During development of normal retinas, the 88 kDa immunoreactive component of the PDE complex were detected by day 7, with immunoreactivity increasing throughout the second postnatal week. In rd retinas, the 88 kDa immunoreactivity increased after 9 postnatal days, decreased during rod photoreceptor degeneration, and was undetectable in mature rd retinas. Under nondenaturing conditions, the PDE-immunoreactive polypeptide of rd retinas sedimented on sucrose gradients with a sedimentation coefficient of 5.6S and an apparent molecular mass of about 105 kDa; no associated histone-activated PDE activity was detected. These findings show that PDE-immunoreactive polypeptides are synthesized in immature rd photoreceptors and that the PDE-immunoreactive polypeptides fail to form a PDE complex which is comparable to that of normal photoreceptors.

The photoreceptor-specific 33 kDa phosphoprotein of mammalian retina: generation of monospecific antibodies and localization by immunocytochemistry

The distribution in mouse retina of a 33,000 Da phosphoprotein (33 kDa) that complexes with the beta/gamma subunits of transducin (T beta gamma) and undergoes light-induced dephosphorylation was determined by immunocytochemistry. An antiserum containing antibodies for the 33 kDa protein and beta-transducin of mouse and bovine retinas was generated against the purified 33 kDa-T beta gamma complex from bovine retina. The antiserum reacts with beta-transducin derived from either 33 kDa-T beta gamma complex or transducin complex (T alpha beta gamma), but not with the alpha- or gamma-transducin. It also reacts with both the phosphorylated and unphosphorylated form of the 33 kDa-T beta gamma complex. Antibodies, monospecific for the 33 kDa and beta-transducin subunits respectively, were purified from the antiserum by immunoadsorption and used in immunocytochemical analysis of the respective antigens. The 33 kDa protein was found to be associated exclusively with the photoreceptor cells of the retinas, with the most intense staining in the inner and outer segments' layers and lighter staining in the synaptic terminal layers. beta-Transducin also is found in the photoreceptors, but some T beta immunoreactivity exists within the inner plexiform layer. The specific localization of the 33 kDa protein together with its light-modulated phosphorylation suggest that the 33 kDa-T beta gamma complex is involved in light-regulated activities of the rod photoreceptor cells.

A novel complex from bovine visual cells of a 33,000-dalton phosphoprotein with beta- and gamma-transducin: purification and subunit structure

Photoreceptors of mammalian retinas contain a 33-kDa (33K) protein that is phosphorylated, in vitro, by cyclic nucleotide dependent protein kinases. The 33K protein is phosphorylated in the dark, in situ, and dephosphorylated upon illumination. The soluble 33K protein from bovine retinas has been purified to near homogeneity by extraction at pH 5.7 and chromatography on ion-exchange, gel filtration, and hydroxylapatite columns. In the native conformation, the 33K protein is associated with a 37-kDa (37K) and a 10-kDa (10K) protein, forming a trimeric complex with a sedimentation coefficient of 4.9 S and an apparent molecular mass of 77 kDa. The 33K protein can be dissociated from the 37K/10K complex by centrifugation in the presence of high pH and high salt; the subunits reassociate to form the trimeric complex upon recentrifugation in an isotonic buffer with neutral pH. The 33K protein is phosphorylated rapidly by exogenous kinase, in vitro, whereas the 37K and 10K subunits remain unphosphorylated. The 37K and 10K subunits cross-react with antibodies prepared against the beta- and gamma-subunits, respectively, of bovine transducin, indicating that the 37K and 10K subunits are immunologically identical with beta- and gamma-transducin, respectively. No immuno-cross-reactivity was observed between the 33K protein and an antibody against the alpha-subunit of bovine transducin. The 33K-beta-/gamma-transducin complex exhibits striking similarity to transducin in its subunit structure and mode of subunit interaction, suggesting it may play an important role in the metabolism and function of rod photoreceptor cells.

Seizures and transient cognitive deterioration as sequelae of acute lithium intoxication

Acute lithium toxicity has been reported to produce transient convulsions and permanent cognitive deficits. We report a case of a permanent seizure disorder and transient cognitive deficit as sequelae of acute severe lithium toxicity.

Residency positions offered in three specialties

Many believe that the changing economic environment might have dramatic effects on the quality or quantity of graduate medical training, yet the evidence is scant. This article assesses the impact of economic factors on the number of residency positions offered by teaching hospitals in surgery, in medicine, in pathology, and in the hospital as a whole. It first outlines in a nontechnical way the policy and empirical implications of an economic approach to residency training. The empirical analysis then compares results from three separate data sets, using both hospitalwide and department-specific information. The article closes by using the estimates to attempt an assessment of the likely impact of cost control and increased competition on training opportunities.

Immunological determination of transducin content in retinas exhibiting inherited degeneration

The inherited disorders of rd mice and affected Irish setter dogs are characterized by the accumulation of cyclic GMP (cGMP). Since the cGMP level in normal retinal rods is regulated by a light-activated enzyme cascade involving rhodopsin, transducin, and phosphodiesterase, an abnormality associated with any of these three proteins would cause cGMP accumulation. In order to determine the relationship between different forms of retinal degeneration and the transducin content in the affected retinas, affinity-purified antibodies directed against the individual subunits of bovine transducin were prepared. These antibodies, which recognized transducin in many vertebrate species, were used to compare the retinal content of this protein at various stages of inherited photoreceptor degeneration. In each of the disorders studied (rd and rds mice, RCS rat, and affected Irish setter dog), retinas at early stages of degeneration displayed two characteristics similar to those of normal control retinas. First, all three subunits of transducin were detected and found to have normal electrophoretic mobility, suggesting that these disorders are unlikely to be due to changes in the composition of transducin subunits. Second, the amount of cross-reactive T beta always exceeded those of T alpha and T gamma. This disproportionately higher amount of T beta-like protein became more pronounced as the visual cells degenerated. In retinas which had undergone complete photoreceptor degeneration, cross-reactive T alpha and T gamma were undetectable. In contrast, anti-T beta gamma antibodies detected an amount of T beta-like polypeptide corresponding to 10-25% of the control. Since our anti-T beta gamma antibodies recognize the beta subunit of the GTP-binding N proteins of the adenylate cyclase system, this finding suggests that this residual T beta-like protein, which is not part of transducin, may be associated with other GTP-binding regulatory proteins.

A 7 year experience with low anterior sigmoid resections using the EEA stapler

The EEA stapler was used in 205 patients over a 7 year period with 19 complications (9 percent) and 1 death (0.5 percent). Meticulous attention to technique and familiarization with the EEA stapler are necessary to achieve such results. The use of mechanical and oral antibiotic bowel preparation, perioperative systemic antibiotics, povidone-iodine irrigation of the rectal ampulla, and meticulous surgical technique have combined to lower the complication rate of this procedure to a minimum. The EEA stapler has greatly improved the safety and ease of anterior sigmoid resections and now provides a frequent alternative to abdominoperineal resection in many patients with midrectal and even low rectal lesions.

Rod photoreceptor cells dissociated from mature mice retinas

Intact rod photoreceptors were dissociated from pronase-treated whole retinas of adult mice by repeated passage through a plastic pipette tip. Hemocytometer counts of the cell suspensions indicate that, during a series of ten dissociation steps, a total of about 1-2 million intact photoreceptor cells are dissociated from one adult mouse retina, with less than 5% contamination from Müller cells and neurons of the inner retina. Visual cells with rod outer segments (ROS) and synaptic terminals are released in each step, but they occur in the greatest number during the sixth to ninth steps; detached ROS are released most frequently in the early steps, and neurons of the inner retinal layers appear in the later steps of dissociation. Nuclei are found in each step. Cell intactness was estimated by Trypan blue and Erythrosin B exclusion and by microscopic analysis using differential interference optics or scanning electron microscopy. The cells bind lectins (concanavalin A, Ricinis communis, and wheat germ agglutinin but not peanut agglutinin), displaying surface topography like that observed in situ. The metabolic capacity of dissociated cells was assessed by measuring the utilization of 32P inorganic phosphate for the synthesis of phospholipids and for the light-dependent phosphorylation of rhodopsin. Mature photoreceptor cells were estimated to contain, on average, 6.4 X 10(-12) g DNA, 2.3 X 10(-12) g RNA and 42-64 X 10(-12) g protein. The dissociation procedure provides a population of photoreceptor cells that appears suitable for microscopic, electrophysiological, and biochemical analysis.

The diffusion of innovations in hospitals. Some econometric considerations

Empirical studies of the diffusion of innovations have not addressed adequately econometric problems that are characteristic of such analyses. Reanalysis of data for five innovations using an estimator with desirable statistical properties results in a considerably revised estimate of the impact of prospective reimbursement on diffusion.

The demand for residents

This paper develops an empirical model of the demand for medical residents. Not-for-profit teaching hospitals are viewed as firms facing shadow prices that differ from market prices, and the impacts of variations in stipends in the quality of training, in the cost of teaching, and in hospitals' objectives on the shadow cost of hiring residents are made explicit. Empirical results from three data sets are shown to be consistent with a simple derived demand model, and the indirect effects of increased competition and cost control initiatives on the demand for residents are assessed.

Phosphodiesterase-probes show distinct defects in rd mice and Irish setter dog disorders

The phosphodiesterase from the visual cells of rd mice and affected Irish setter dogs has been analyzed, using biochemical, biophysical, and immunological techniques. The authors' findings demonstrate that the mechanisms that cause a deficiency in phosphodiesterase activity in rd mice and Irish setter dogs are distinctly different. Apparently, the phosphodiesterase complex is normal in affected Irish setter dogs but is abnormal in rd mice. The criteria used for determining the normalcy of the phosphodiesterase complex were sedimentation characteristics, immuno-cross-reactivity, and histone-activation, which is shown to be a unique characteristic of the visual cell enzyme. According to these criteria, the phosphodiesterase complex in the visual cells of rd mice is either absent or abnormal from the onset of visual cell differentiation until degeneration, because it exhibits no cross-reactivity with antibody to phosphodiesterase; it is not activated by histone; and if present, it exhibits abnormal sedimentation characteristics and perhaps subunit structure. On the other hand, phosphodiesterase from the visual cells of affected Irish setter dogs is normal by the same criteria, because it cross-reacts with antibody against phosphodiesterase; it is activated by histone; and it exhibits normal sedimentation and electrophoretic patterns. It is proposed that depressed levels of phosphodiesterase activity in affected setter photoreceptors are due, perhaps, to a defect in the light-initiated cascade which activates the enzyme normally, in situ.

Hydrophobicity of amino acid residues in globular proteins

During biosynthesis, a globular protein folds into a tight particle with an interior core that is shielded from the surrounding solvent. The hydrophobic effect is thought to play a key role in mediating this process: nonpolar residues expelled from water engender a molecular interior where they can be buried. Paradoxically, results of earlier quantitative analyses have suggested that the tendency for nonpolar residues to be buried within proteins is weak. However, such analyses merely classify residues as either "exposed" or "buried." In the experiment reported in this article proteins of known structure were used to measure the average area that each residue buries upon folding. This characteristic quantity, the average area buried, is correlated with residue hydrophobicity.

Impact of adjuvant chemotherapy on cosmesis and complications in stages I and II carcinoma of the breast treated by biopsy and radiation therapy

Cosmesis and complication rates were examined in patients with early stage carcinoma of the breast treated by biopsy and radiation therapy with and without adjuvant chemotherapy in an attempt to determine the effect of chemotherapy upon these parameters. Between April 1, 1975 and June 1, 1980, 51 patients were treated with radiation therapy and adjuvant chemotherapy (XRT + ACT) and 83 patients with radiotherapy alone (XRT). Chemotherapy usually consisted of cytoxan, methotrexate and 5-fluorouracil for 6 or 12 cycles. Minimum follow-up was 36 months. Cosmetic results deteriorated with time in both groups but to a greater extent in the XRT + ACT group. At 36 months, excellent cosmetic results were obtained in 73 of the 83 patients (88%) in the XRT group compared to 37 of 51 patients (73%) in the XRT + ACT group (p = less than .05). Comparison of the two treatment groups revealed that complication rates were significantly increased in the XRT + ACT group. Of the 51 patients in the XRT + ACT group, 21 patients (41%) suffered complications compared to 8 (10%) of the 83 patients in the XRT group (p = less than .001). This difference in complication rates resulted primarily from an increased incidence in the XRT + ACT group of wet desquamation in the electron beam portal used to treat the internal mammary lymph nodes and a trend towards a higher incidence of spontaneous nonpathologic rib fractures, myositis and arm edema. An increased incidence of nonbreast primary cancers was not seen. Our preliminary conclusions are that adjuvant chemotherapy has a negative impact upon cosmesis and complication rates in patients being treated with definitive radiotherapy. However, cosmetic results remain satisfactory and complication rates are maintained at an acceptable level. Continued close follow-up will be required before definitive conclusions can be reached as to the overall incidence and severity of the changes noted.

Outpatient adult inguinal hernia repair

Repair of adult inguinal hernia has been done on an outpatient basis at our surgical facility for the past six years. In 616 consecutive repairs, complications have been remarkably few: one patient was electively admitted to hospital, two hernias have recurred and one patient needed to be catheterized. Patient acceptance has been enthusiastic.

Light-induced dephosphorylation of a 33K protein in rod outer segments of rat retina

Phosphorylated proteins may play an important role in regulating the metabolism or function of rod photoreceptors. In mammalian retinas, a photoreceptor protein of 33 000 (33K) molecular weight is phosphorylated in a cyclic nucleotide dependent manner in vitro. Since light initiates the activation of a photoreceptor-specific phosphodiesterase and a rapid reduction in guanosine cyclic 3',5'-phosphate concentration, phosphorylation of the 33K protein may be modulated by light in situ. In order to test this possibility, dark-adapted rat retinas were incubated for 30 min in the dark in phosphate-free Kreb's buffer containing [32P]orthophosphate. Following incubation, rod outer segments were detached by shaking, and the 32P-labeled rod outer segment proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, detected by autoradiography, and quantitated by densitometric scanning. The incorporation of radioactivity (32P) into the 33K protein was higher than into any other rod outer segment protein, and the amount of 32P-labeled 33K protein in the detached rod outer segments remained unchanged during 10 additional min of darkness. The addition of isobutylmethylxanthine to the incubation medium enhanced the incorporation of 32P into 33K protein to about 400% of the original level. Exposure of freshly detached rod outer segments to room light for 90 s decreased the amount of labeled 33K protein to 45% of its original level. The dephosphorylation of labeled 33K protein continued, reaching 12% of the original dark value 10 min after the previously illuminated sample was returned to darkness. Light initiated the phosphorylation of rhodopsin, and rhodopsin phosphorylation continued during the postillumination period of darkness.

Prospective reimbursement and the diffusion of new technologies in hospitals

This paper presents new evidence on the effects of prospective hospital reimbursement on the diffusion of new medical technologies in American hospitals. The probability, speed, and extent of adoption of five specific new technologies in six states, three with prospective reimbursement and three without, are examined using the results of a hospital survey conducted by the American Hospital Association for this study in 1980. The analysis demonstrates the influence of prospective reimbursement on the diffusion of new technologies. It is clear as well that these effects depend upon the specific attributes of the prospective reimbursement program and the characteristics of the technologies themselves.

Subsidizing the affluent: the case of medical education

State and federal funds are important sources of revenue for medical schools, and a strong case can be made for public support for these institutions. Although the federal role is more widely known, the states in fact provide the bulk of direct support for medical training. The nature of aid from the two sources differs in significant ways. Most federal aid supports research or patient care, but much of state aid goes to support unconditional tuition subsidies. The primary beneficiaries of these subsidies are relatively affluent nonminority students who are beginning lucrative careers in the medical field--careers that would be lucrative even if no subsidies were provided. Nor does it appear that general subsidies are needed to attract poor and minority applicants. While targeted loans and scholarships to individuals may be justified, general tuition subsidies are not.

An internally referenced test strip immunoassay for morphine

We describe an internally referenced immunochemical test-strip for use in the rapid detection of morphine. The method is based on the "enzyme-channelling" immunoassay technique, and a glucose oxidase-horseradish peroxidase enzyme pair is used to immunospecifically generate an insoluble, colored reaction product on the test-strip surface. Test strips are composed of two active surfaces, each of which contain co-immobilized glucose oxidase and antibody. The indicator pad contains antibody directed against the drug, and the color that develops on its surface is inhibited by the presence of drug in the sample. The reference pad contains anti-peroxidase and is used to set the assay detection limit and normalize for variations in temperature, timing, and sample interference. The 10-min assay protocol involves incubating the strip in sample, then incubating it in a developer solution containing glucose, a peroxidase chromogenic substrate, and a peroxidase conjugate of the analyte. The ratio of the color formed on the indicator pad to that formed on the reference pad is used to score the test as positive or negative for drug at a predetermined concentration.