The visual pigment and visual cycle of the lobster,Homarus

Summary The visual pigment of the American lobster,Homarus americanus, has been studied in individual isolated rhabdoms by microspectrophotometry. Lobster rhodopsin has _max at 515 nm and is converted by light to a stable metarhodopsin with _max at 490 nm. These figures are in good agreement with corresponding values obtained by Wald and Hubbard (1957) in digitonin extracts. Photoregeneration of rhodopsin to metarhodopsin is also observed. The absorbance spectrum of lobster metarhodopsin is invariant with pH in the range 5.4–9, indicating that even after isomerization of the chromophore fromcis totrans, the binding site of the chromophore remains sequestered from the solvent environment. Total axial density of the lobster rhabdom to unpolarized light is about 0.7.As described for several other Crustacea, aldehyde fixation renders the metarhodopsin susceptible to photobleaching, a process that is faster at alkaline than at neutral or acid pH. Small amounts of a photoproduct with _max at 370 nm are occasionally seen. A slower dark bleaching of lobster rhabdoms (_1/2–2 h) also occurs, frequently through intermediates with absorption similar to metarhodopsin.The molar extinction coefficient of metarhodopsin is about 1.2 times greater than that of rhodopsin, each measured at their respective _max. Isomerization of the chromophore fromcis totrans is accompanied by a change in the orientation of the absorption vector of about 3°. The absorption vector of metarhodopsin is either tilted more steeply into the membrane or is less tightly oriented with respect to the microvillar axes.When living lobsters are kept at room temperature, light adaptation does not result in an accumulation of metarhodopsin. At 4 °C, however, the same adapting lights cause a reduction of rhodopsin and an increase in metarhodopsin. There is thus a temperature-sensitive regeneration mechanism that supplements photoregeneration. Following 1 ms, 0.1 joule xenon flashes that convert about 70% of the rhodopsin to metarhodopsin in vivo, dark regeneration occurs in the living eye with half-times of about 25 and 55 min at 22 °C and 15 °C respectively.This work was supported by USPHS research grant EY 00222 to Yale University. S.N.B. was aided by NIH Postdoctoral Fellowship EY 52378.     

Dark adaptation,sensitivity, and rhodopsin level in the eye of the lobster,Homarus

Summary Dark adaptation of living lobsters was measured by recording the ERG at several temperatures in the range 5–20 °C following adapting flashes that convert about 70% of the rhodopsin to metarhodopsin. Recovery of log threshold is rapid, and at 10–20° is nearly complete in 10 min. Only at 5 °C is dark adaptation significantly slowed. Comparison of dark adaptation with data on regeneration of pigment (Bruno et al., 1977) is consistent with the hypothesis that as rhodopsin concentration rises and falls, its only effect on sensitivity is to alter the probability of quantum catch. This interpretation is further bolstered by observations on winter lobsters that have a 70% deficiency of rhodopsin without the concomitant increase in metarhodopsin that accompanies light adaptation. No effect of metarhodopsin on sensitivity was detected. These experiments support the growing body of evidence indicating that the relationship between rhodopsin concentration and log threshold is fundamentally different in the rhabdomeric photoreceptors of invertebrates and the rods and cones of vertebrates.This work was supported by USPHS research grant EY 00222 to Yale University. S.N.B. was aided by NIH Postdoctoral Fellowship EY 52378, by funds made available through the Unidel Foundation, and by a grant from the University of Delaware Research Foundation.     

Studies on the H-Y antigen in rats

The H-Y antigen has been studied under a variety of experimental conditions in BN and Lewis rats. The results indicate that 1. graft size is crucially important in determining the fate of male skin isografts on females; 2. H-Y incompatible ear skin grafts survive significantly better than those of trunk origin; 3. prior exposure of females to male lymphoid cells greatly increases their capacity to reject male skin isografts; 4. neonatal castration has no influence on the expression of H-Y; 5. multiparity can induce unresponsiveness to H-Y; and 6. although BN females respond better than do Lewis females to H-Y, the antigen is stronger in Lewis males. These findings are compared with the results of similar experiments conducted with mice.Submitted in memory of Dr. Joy Palm, member of the Wistar Institute, who pioneered the genetic analysis of histocompatibility in rats.     

Anatomy of Bovine Mammillitis DNA I. Restriction Endonuclease Maps of Four Populations of Molecules That Differ in the Relative Orientation of Their Long and Short Components

In this paper, we report that the DNA of bovine mammillitis virus (BMV) consists of two covalently linked components that are 71.5 x 10(6) and 15.7 x 10(6) in molecular weight and designated L and S, respectively. We further report that the BMV DNA consists of four equimolar populations differing only in the orientation of the L and S components relative to each other. This conclusion is based on the following: (i) The sum molecular weight of fragments generated by digestion of BMV DNA with Hsu I, Hpa I, Bgl II, or Xba I significantly exceeds the established molecular weight of the intact DNA. (ii) In each digest, the fragments form three groups differing in molar concentration. In reference to the molar concentration of intact DNA, each enzyme digest contained a set of four fragments 0.25 M in concentration, a set of four fragments 0.5 M in concentration, and a variable size set, unique for each enzyme digest, 1.0 M in concentration. (iii) Experiments involving digestion of intact DNA by lambda exonuclease followed by restriction endonuclease digestion established that each of four 0.5 M fragments were positioned at the termini of the BMV DNA. (iv) Complete maps for the fragments generated by each enzyme established that the 0.25 M fragments arise by fusion of the sequences of the terminal fragments when these are juxtaposed as a consequence of the inversion of L and S components. The maps also established the dimensions of the L and S components. We conclude that the structure of BMV DNA is similar to that of HSV DNA previously shown to consist of two unequal size components that invert relative to each other.     

Preparative size-exclusion chromatography of human serum apolipoproteins using an analytical liquid chromatograph

Apolipoproteins, extracted from human serum high-density lipoproteins, can be resolved and recovered with high yield from a preparative MicroPak TSK Type 3000SW size-exclusion column using Tris-buffered 6 m urea or 6 m guanidinium chloride mobile phases. Adequate resolution of some apolipoprotein pairs is only achieved at low flow velocities and low sample loads, necessitating repetitive injections of small amounts of material for preparative isolation. An analytical high-performance liquid chromatograph equipped with a simplified sample introduction scheme and low-pressure switching valves for fraction collection was used to isolate milligram quantities of HDL apolipoproteins.     

Blood volume pulse biofeedback treatment of chronic cluster headache

Behavioral interventions shown to be clinically effective in the treatment of migraine headache have generally not been employed for cluster headache. Herein, we report on the treatment of a severe case of chronic cluster headache with a common method of migraine treatment, temporal blood volume pulse (BVP) biofeedback. The patient was a 61-year-old male, medically diagnosed as suffering from chronic cluster headaches for over 20 years. Following an 18-day baseline, 14 BVP biofeedback sessions were conducted over a 7-week period. By the last 2 weeks of treatment, there was a 70% reduction in daily headache frequency and a 45% decrease in headache severity. Improvement was maintained at 1, 3, 6, 12, and 21 months follow-up. Large decreases in the consumption of migraine abortives, narcotic analgesics, and antiemetics were also observed. These encouraging results call for further evaluation of the efficacy of BVP biofeedback treatment of chronic cluster headache.This research was supported in part by the Psychological Services Center, Memphis State University. Portions of this article were presented at the meeting of the Society of Behavioral Medicine, Chicago, March 1982.     

Studies on the subcellular localization and role of glutathione-insulin transhydrogenase in rat liver

₁₂₅I-insulin was shown to be internalized in vivo to a discrete population of low-density membranes (ligandosomes), distinct from the Golgi, endoplasmic reticulum, plasma membrane, and lysosomes. However, analytical subcellular fractionation shows that glutathione-insulin transhydrogenase is localized to the endoplasmic reticulum. Measurement of the specific enzyme activity of glutathione-insulin transhydrogenase showed no differences between normal, diabetic, and hyperinsulinaemic rats. These results suggest that glutathione-insulin transhydrogenase is not directly involved in the subceltular processing of receptor-bound internalized insulin.     

1,25-Dihydroxyvitamin D3 receptor in bovine thymus gland

1,25-Dihydroxyvitamin D₃ [1,25-(OH)₂D₃] receptor was characterized after partial purification of thymus cytosol by ammonium sulfate fractionation. The 1,25-(OH)₂D₃ receptor sediments at 3.7S in 5–20% sucrose gradients. The binding of 1,25-(OH)₂D₃ in thymic cytosol was a saturable process with high affinity (Kd = 0.12?0.48 nM) at 4°C. Competition for 1,25-(OH)₂[³H]D₃ receptor by nonradioactive analogs demonstrated the affinities of these analogs to be in order; 1,25-(OH)₂D₃ = 1,24R,25-(OH)₃D₃ = 1,25S,26-(OH)₃D₃ = 1,25R,26-(OH)₃D₃ > 1,25-(OH)₂D₃-26,23 lactone > 25-OHD₃ > 23R,25-(OH)₂D₃ > 24R,25-(OH)₂D₃ > 23S,25-(OH)₂D₃ ? 25-OHD₃-26,23 lactone. The receptor bound to DNA cellulose columns in low salt buffer and eluted as a single peak at 0.21 M KCl. These findings provide evidence that the thymus possesses a 1,25-(OH)₂D₃ receptor with properties indistinguishable from 1,25-(OH)₂D₃ receptors in other tissues.     

Control of cell migration in atrioventricular pads during chick early heart development: Analysis of cushion tissue migration in vitro

The formation of the valvular and septal primordia of the embryonic heart depends upon the migration of endocardial cushion tissue mesenchyme (CT) to populate the cardiac jelly (CJ) in specific heart regions (e.g., atrioventricular (AV) pads). It has been proposed that the migration of CT may be directed by macromolecules of the CJ. In this study, [³H]thymidine-labeled endocardial (EC) and CT cells were transplanted onto intact pre- and postmigratory AV pads in vitro to test whether the compositional or structural changes known to occur in the cardiac jelly during development influence the migration of cushion tissue cells. After transplantation of labeled donor cells, host AV pads were fixed, embedded, and sectioned, and autoradiography was performed to determine the distribution of labeled donor cells within the host CJ. The experiments indicate that transplanted mural EC cells remain primarily at the AV pad surface, while grafted CT cells of all developmental ages rapidly invade both developmentally young and older AV pads. Furthermore, CT cells readily migrate in a direction opposite to that of cells in vivo when transplanted to inverted AV pads from which the myocardium has been removed. It is concluded that the CJ matrix, which is clearly a suitable framework for CT cell migration, provides no direct cues to determining the polarity or extent of migration.     

Anomalous carbonylation of [Pd(dppm)(O2CCF3)]2 to give an asymmetric μ-CO complex

The reactive palladium dimer, [Pd(dppm)(O₂CCF₃)]₂, is carbonylated to [Pd(dppm)(O₂CCF₃)]₂(μ-CO) in a reversible reaction with K = c. 7.2(2)x10⁴ atm⁻¹ (P_1/2 = c. 2.4 Torr). This is significantly larger than is expected based on the λ_max = 280 nm in the electronic spectrum. The product can be isolated in analytically pure form by crystallization under a CO atmosphere. It forms crystals in the monoclinic space group Cc with a = 18.584(5), b = 28.65(1), c = 11.164(3) Å and β = 95.16(2)°. The structure is significantly distorted. The bonding about the two palladium atoms is quite asymmetric. While one is close to a square planar geometry with a Pd---C(O) distance of 1.90(2) Å, the other is significantly pyramidalized and has a longer (2.00(2) Å) bond to the bridging CO. The Pd---Pd distance is only 2.896(2) Å, much shorter than that usually observed for formally non-bonded Pd atoms.