Activation of phosphodiesterase by rhodopsin and its analogues

Activation of guanosine 3,5-cyclic monophosphate (cGMP) phosphodiesterase (EC 3.1.4.35.) in frog rod outer segment membrane by rhodopsin and its analogues was investigated. The Schiff-base linkage between opsin and retinal in rhodopsin was not always necessary for the phosphodiesterase activation. The binding of -ionone ring of retinal to a hydrophobic region of opsin was not enough to induce the enzyme activation. A striking photo-activation of the enzyme was induced by photo-isomerization of rhodopsin analogues from cis to trans form. It seems probable that an expanded conformation of opsin around the retinylidene chromophore induced by the cis to trans isomerization may be the trigger for the activation of phosphodiesterase. On the other hand, the phosphodiesterase in frog rod outer segment was activated by warming of bathorhodopsin to –12 C and then incubating it at the same temperature. Thus, metarhodopsin II or an earlier intermediate than metarhodopsin II should be a direct intermediate for the enzyme activation.Based on material presented at the Fifth International Congress of Eye Research, Eindhoven, October 1982     

Principal absorption axes of rhodopsin and prelumirhodopsin

The experimental data on the absorption of plane polarized light by a solution of cattle rhodopsin at –196 C have been theoretically analysed to model the directional absorption properties of rhodopsin and prelumirhodopsin. It has been found that rhodopsin and prelumirhodopsin are planar absorbers having ratios of about 1007 and 1004, respectively, between the extinction coefficients along the long axis and perpendicular to it. These results support that the chromophore in prelumirhodopsin is more linear than the chromophore in rhodopsin.Work partially supported by Department of Science and Technology (India)Associated with the Biochemistry Cell     

Growth temperature acclimation byAmoeba proteus: Effects on cytoplasmic organelle morphology

Summary The effects on subcellular morphology of maintaining amoebae at temperatures other than 20 C (the routine culture temperature) were assessed. Estimations of cycling potential at each temperature confirmed that acclimation had affected gross cell functioning. Generation times ranged from no division at 6 C, to an optimal minimum of 2 days at 22 C.Organelle morphology changes were studied after 5 days of growth at the new temperatures; alterations were most evident at the extremes of 6 and 28 C. The main mitochondrial alteration resulted in changes to the ratio of Type I: Type II organelles; with a decrease in Type I forms away from the optimal range of 20–22 C. Extended culturing at 6 C generated mitochondrial matrical inclusions. Ribosomal attachment to the endoplasmic reticulum, a common feature of 20 C-grown cells, decreased at the temperature extremes, where an increase in free ribosomes occurred. Upon extended culture at 6 C helical structures, usually observed in groups only within the nucleus, were also present in the cytoplasm. Golgi complexes were less common in cells maintained at extreme temperatures and often showed differences in shape. These changes were all reversible on a return to culturing at 20 C.The possible functional significance of these findings is discussed.     

Estimation of sweat rate and thermal tolerance of pure Creole and of Limousin × Creole crossbred growing bulls in Guadeloupe (French West Indies)

Four out of 8 Limousin × Creole (Li × Cr) and 4 out of 8 Creole growing bulls were exposed to full sunshine in Guadeloupe (French West Indies), the others being kept under shade. Sweating rate (measured on the back with capsules filled with a dessicator), rectal temperature and respiratory rhythm were measured between 11 a.m. and 3 p.m., as well as climatic environmental data. Rectal temperature of Creole bulls (overall mean: 38.8C) remains unaffected by black globe temperature (TG), while, for Li × Cr bulls, it is well related to TG, reaching 39.5C when TG=39C; at this moment, Li × Cr respiratory rhythm reaches 100 breaths/min, compared with only 70 for Creole animals. The shade mean levels of these two parameters for each genotype are consistently the same (38.7C and 39 breaths/min). Under full sunshine, mean sweat rate is almost the same for the 2 genotypes; under shelter, the crossbred bulls sweat more than the Creole bulls, both shade means being significantly lower than means in the sun. Probably, when shaded, the Li × Cr animals must sweat more to balance a greater heat production, but their maximum sweat ability is not very different than the one of Creole bulls.     

Variations in mental performance under moderate cold stress

Effects of moderate cold stress on reasoning ability, associative learning and critical flicker frequncy of Indian subjects were studied by exposing them to 25C,. 20C, 15C and 10C for three hours. A second set of experiments was also conducted to confirm the conclusions of the first by using the same temperatures and duration of exposure. However, not only the sample used in the second case was larger and different but also the mental functions tested were numerical ability, running memory and mental alertness. It has been concluded that there is a significant impairment of simple cognitive functions at 15C which is 10C lower than their most comfortable temperature of 25C.     

Flash photolysis of rhodopsin in rabbit

Flash photolysis of rhodopsin in rabbit's retina has been analysed theoretically, and the results are found to be in good agreement with the experimental results of Hagins (1957). We have also obtained the variation of relative concentrations of rhodopsin, lumirhodopsin, isorhodopsin and metarhodopsin I during the period of the flash corresponding to two different intensities of the flash. It has been found that the quantum efficiencies of conversion of lumirhodopsin into rhodopsin and isorhodopsin will lie in the range 0.24–0.45 and 0.20–0.44 respectively; quantum efficiencies of conversion of metarhodopsin I into rhodopsin and isorhodopsin are found to have values greater than 0.52 and 0.45 respectively and the quantum efficiency of conversion of isorhodopsin into lumirhodopsin has been found to be approximately 0.865. Also the maximum value of the rate constant of the reaction metarhodopsin Imetarhodopsin II at 37 C has been determined in decerebrated eye and it has been found that it is of the same order as found by Pugh (1975) in the case of human eye.Work partially supported by Department of Science and Technology     

Effects of hyperthermia on enzymes and electrolytes in blood and cerebrospinal fluid in dogs

The effects of exposure to various degrees of heat stress on serum glutamate—oxaloacetate transaminase (SGOT), serum glutamate-pyruvate transaminase (SGPT), alkaline phosphatase (ALK-P-ase), calcium and chlorides have been studied on 75 dogs. Rectal temperature (T_re) was recorded before and after exposure to heat stress. These dogs were divided into 5 groups, according to the T_re level attained after exposure to heat stress. Rectal temperature was raised from normal to 39.45±0.47C in the first group, to 40.93±0.17C in the second group, to 41.87±0.22C in the third group, to 42.90 ± 0.21C in the fourth group and to 43.93±0.19C in the fifth group. The concentration of enzymes SGOT, SGPT and ALK-P-ase in blood and cerebrospinal fluid (CSF) increased significantly with hyperthermia. Calcium and chlorides concentrations in blood and in CSF tended to increase in hyperthermia. The integrity of the blood brain barrier for these enzymes and calcium is maintained under mild hyperthermia but it breaks down partially under influence of more severe hyperthermia. Core temperature above 41C results in damage to tissues and consequential rise of plasma enzymes. This degree of hyperthermia also seems to mark the beginning of injury to blood brain barrier. Critical core temperature tolerated by 50% of animals was 44C.     

Body temperature responses of Savanna Brown goat to the harmattan and hot-dry season

Rectal and vaginal temperature responses of the Savanna Brown goat indigenous to the Nigerian guinea savanna were determined during the harmattan and the hot-dry season. Measurements were made at 06:00h and at 14:00h after 8h exposure to field conditions. At the 06:00h measurements during the harmattan, all animals were observed to shiver. A significant (P<0.01) positive correlation was found between rectal (T_re) and vaginal temperatures. During the harmattan, mean T_re was 38.2C at 06:00h and 39.7C at 14:00h; the mean difference, T_re was 1.5C. During the hot-dry season, T_re at 06:00h was 38.1C, and at 14:00h, 38.7; T_re was 0.6C. It is concluded that the harmattan is thermally more stressful than the hot-dry season and that passive thermolability may not be an important mechanism in the Savanna Brown goat in adaptation to thermal stress.     

Novel prebiotic systems: Nucleotide oligomerization in surfactant entrapped water pools

Summary Oligomerization of 5-TMP in water pools entrapped by dodecyl-ammonium chloride surfactant aggregates in benzene: hexane in the presence of dicyanodiimide at temperatures ranging from 21°–72° resulted in the formation of linear and cyclic oligonucleotides containing up to pentamers. Effects of temperature, time and surfactants have been examined. Rate constants for the formation of oligomers have been determined at five different temperatures. These data afforded values of H = 11.8 ± 1.9 Kcal mole^–1, S=–53 6 e.u. and G = 27.4 4.0 Kcal mole^–1. Prebiotic significance of these results are discussed.     

Effects of fasting on maximum thermogenesis in temperature-acclimated rats

To further investigate the limiting effect of substrates on maximum thermogenesis in acute cold exposure, the present study examined the prevalence of this effect at different thermogenic capabilities consequent to cold- or warm-acclimation. Male Sprague-Dawley rats (n=11) were acclimated to 6, 16 and 26C, in succession, their thermogenic capabilities after each acclimation temperature were measured under helium-oxygen (21% oxygen, balance helium) at –10C after overnight fasting or feeding. Regardless of feeding conditions, both maximum and total heat production were significantly greater in 6>16>26C-acclimated conditions. In the fed state, the total heat production was significantly greater than that in the fasted state at all acclimating temperatures but the maximum thermogenesis was significant greater only in the 6 and 16C-acclimated states. The results indicate that the limiting effect of substrates on maximum and total thermogenesis is independent of the magnitude of thermogenic capability, suggesting a substrate-dependent component in restricting the effective expression of existing aerobic metabolic capability even under severe stress.     

Frostbite and the significance of a temperature-sensation scale in field and laboratory conditions

The literature indicates that rapid thawing in water between 42 and 45C provides the best prognosis for frostbitten limbs.A temperature:sensation scale for the normal hand was derived and tested in laboratory and field conditions. The scale permitted the preparation of water suitable for frostbite treatment by the majority of subjects without access to a thermometer. The maximum observed inaccuracy was 1.2C outside the preferred range but was well withing the safe range for treatment.

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Zusammenfassung Die beste Prognose zur Behandlung von Erfrierungen bietet nach den Erfahrungen in der Literatur das schnelle Auftauen von erfrorenen Gliedern bei Wassertemperaturen von 42–45C. Für die gesunde Hand wurde eine Temperatur-Wahrnehmungsskala aufgestellt und unter verschiedenen Bedingungen im Laboratorium und im Freien geprüft. Ohne Zugang zu einem Thermometer gestattete die Skala in der Mehrzahl der FÄlle die ErwÄrmung von Wasser auf Temperaturen, die für die Behandlung von Erfrierungen geeignet sind. Die grösste Ungenauigkeit zwischen SchÄtzwert und Thermometerwert war 1.2C ausserhalb des gewünschten aber noch innerhalb des für die Behandlung zulÄssigen Bereiches.

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Résumé D'après les indications de plusieurs auteurs, le meilleur traitement de membres gelés consiste à les dégeler dans de l'eau à une temperature entre 42 et 45C. Une échelle température-sensation pour la main normale a été mise au point et vérifiée au laboratoire ainsi qu'en plain air.Cette méthode a permis la préparation d'eau en vue d'un traitement de gelures sans faire usage d'un thermomètre dans la plupart des cas. L'erreur maximum observée était de 1,2 C sans que les limites de l'intervalle propice à un traitement ne soient jamais dépassées.

     

Interaction of cytochrome c L with methanol dehydrogenase from Methylophaga marina 42:

The reaction of methanol dehydrogenase with cytochrome c _L from Methylophaga marina and the reactions of the non-physiological substrates, Wurster's blue and ascorbic acid, with both proteins were studied as a function of temperature (4–32 °C), pressure (1–2000 bar) and ionic strength using the optical high pressure stopped-flow method. The thermodynamic parameters H, S and V were determined for all reactions where electron transfers are involved. These data allowed the determination of the Maxwell relationships which proved the internal thermodynamic consistency of the system under study. A conformational change on the cytochrome c _L level was deduced from both breaks in the Arrhenius plots and the variation of the V with temperature.Abbreviations MOPS 4-morpholinepropanesulfonic acid - CHES 2-(cyclohexylamino)ethanesulfonic acid - MDH methanol dehydrogenase - EDTA ethylenedinitrilotetraacetic acid disodium salt - BTB bromothymol blue (3,3-dibromothymolsulfoneph-thalein) - PQQ 2,7,9-tricarboxy-lH-pyrrolo-[2,3f]quinoline-4,5-dione - cytochrome c _HH mammalian horse heart cytochrome c     

Temperature dependent structural changes of intraphage T7 DNA

The phenomena connected with the first phase transition step of the native T7 phage at 40C–65 C have been studied using various methods. In this temperature range a) the optical melting curve shows an absorption decrease, b) the maximum of the small-angle X-ray scattering characteristic for DNA packing disappears, c) there is a drop of biological activity and d) there are changes in the structure of the difference absorption spectra of native phages versus isolated DNA. All data are interpreted assuming a structural change of the DNA due to the release of its protein coat towards the end of the first phase transition step (at 60–65 C in the case of M9 buffer). Above this temperature the intraphage DNA packing appears to be destroyed and the DNA structure seems to be similar to that in DNA solution.     

On the rise time of the R1-component of the “Early receptor potential...: Evidence for a fast light-induced charge separation in rhodopsin

The rising phase of the R₁-component of the early receptor potential from isolated cattle retinas was measured with high time resolution. When the measuring capacitance was 133 pF, a latency of about 200 ns was observed. A rise time of about 0.8 s at 0 C and 1.6 s at 37 C (extrapolated to ideal measuring conditions) was found. The negative temperature dependence indicates that the rise is not directly related to the production and decay of photolysis products of rhodopsin since the latter have positive temperature coefficients. An increase of the external measuring capacitance caused a slower rise time. The analysis of this effect allowed the determination of the source impedance of the R₁-component. The experimental results can be described with a model in which it is assumed that a fast charge separation (ns or ps) takes place in the outer segment of a photoreceptor cell, and spreads passively to the inner segment via the resistance of the interconnecting cilium. The inner relaxation could be circumvented by using isolated rod outer segments which lack the passive inner segments, i.e., a rise time of 90 ns could be measured when isolated rod outer segments were attached to Millipore filters. The results suggest that the molecular event leading to the R₁-component is an early charge separation which may be as fast as the cis-trans isomerization of the retinal chromophore.     

The relative influence of urban climates on outdoor human energy budgets and skin temperature II. Man in an urban environment

Four typical urban neighborhoods or street canyon settings (including street parks) were simulated. These urban morphologies were exposed to typical summer and winter climatic scenarios for latitudes 10, 34, and 50N. The changes induced in the components of the human energy budget were examined. Resultant skin temperatures were compared with non-urban, unobstructed environments.     

Thermoregulation and thermal perception in the cold and heat before and after intermittent heat adaptation

Students wearing swim suits were exposed for 30 min to neutral room temperature (T_R=28C). During the following 60 min they were subjected to gradual decreases or increases of room temperature reaching 12C or 45C, respectively. Static thermal stimuli were applied to the palms of the right (38C) and left (25C) hands. Hands and feet of all subjects were thermally isolated at 22C ambient temperature. General thermal comfort (GTC), local thermal comfort (LTC), skin blood flow (which is proportional to heat transport index ) several body temperatures, oxygen-consumption , and sweat rate (S), were measured. After moderate intermittent heat exposures (7 times for 1h at T_R=42.5C) the experiments started again. From GTC, LTC, or as functions of T_R, no new knowledge about thermoregulatory or adaptive mechanisms was available. The high in the cold stimulated left hand, however, and the oscillatory thresholds (_OSC) for rhythmic vasomotion indicated the peripheral influence of skin temperature, as well as local, mean skin temperature (¯T_s) and core temperature. When exposed to moderate temperature decreases or increases the body seems to react only with increasing thermal resistance by vasoconstriction or an increase of sweat rate, respectively. Moderate heat adaptation is only able to raise sweat rate, but not the thresholds and gain of the S-function. We assume that functional studies of adaptive modifications in humans must be conducted at temperatures greatly beyond those used in these experiments.     

Phorbol ester stimulation of phosphatidylcholine synthesis in four cultured neural cell lines: Correlations with expression of protein kinase C isoforms

Phosphatidylcholine (PtdCho) can provide lipid second messengers involved in signal transduction pathways. As a measure of phospholipid turnover in response to extracellular stimulation, we investigated differential enhancement of [³H]choline incorporation into PtdCho by phorbol esters. In C6 rat glioma and SK-N-SH human neuroblastoma cells, [³H]PtdCho synthesis was 2–4 fold stimulated by -12-O-tetradecanoylphorbol-13-acetate (-TPA) when [³H]choline was incubated simultaneously with, or 15 min prior to, -TPA treatment. By contrast, in N1E-115 mouse and SK-N-MC human neuroblastoma cells, phorbol esters had no appreciable effect on [³H]choline incorporation; however, in all cells, 200 M oleic acid enhanced PtdCho synthesis, indicating a stimulable process. Alterations by thymeleatoxin (TMT), an activator of conventional PKC isoforms (, and ), were similar to -TPA. We investigated whether expression of specific PKC isoforms might correlate with these effects of phorbol esters on PtdCho synthesis. All cell lines bound phorbol esters, had PKC activity that was translocated by phorbol esters and differentially expressed isoforms of PKC. Northern and western blot analyses, using specific cDNA and antibodies for PKC-,-,-,-,-, and-, revealed that expression of -isoform predominated in C6 and SK-N-SH cells. In contrast, TPA-responsive -isoform predominated in SK-N-MC cells. -PKC was not detected in any cells and only in C6 cells was PKC- present and translocated by -TPA treatment. PKC- was not detected in SK-N-MC cell lines but translocated with TPA treatment in the other three cell lines. PKC- was present in all cells but was unaltered by TPA treatment. Accordingly, stimulation of PtdCho turnover by phorbol esters correlated only with expression of PKC-; presence of PKC- alone was insufficient for a TPA response.Abbreviations DAG diacylglycerol - DMEM Dulbecco's modified Eagle's medium - dPPA 12-deoxyphorbol-13-phenylacetate-20-acetate - PKC protein kinase C - cPKC conventional PKC - PtdCho phosphatidylcholine - TPA 12-O-tetradecanoylphorbol-13-acetate - TMT thymeleatoxin     

Detrimental effects of high ambient temperature on fertility and early embryo survival in sheep

Percent of ova fertilized was significantly (P<0.01)lower in ewes exposed to 32C temperature on the twelfth day of the cycle before breeding (40.7.% vs 94.2% for controls). The average rectal temperature of the ewes was increased 1.7C within 24 hr after exposure to the elevated temperature. Morphologically abnormal ova were increased from 3.8% in control ewes to 55.6% in treated ewes. In ewes exposed to the 32C one day after breeding all ova were cleaved,but 30.8% were morphologically abnormal. In control ewes 87.5% lambed,but none of the ewes exposed to 32C before or at time of breeding lambed. In ewes exposed to 32C at 1, 3,5 or 8 days after breeding, 20%, 35%, 40% and 70%, respectively, lambed.Embryo mortality was significantly (P<0.01) higher for all treated ewes except those in the 8-day group.The sheep zygote is most sensitive to the harmful effects of high ambient temperature during the initial stages of cleavage before it enters the uterus.

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Zusammenfassung Die Zahl befruchteter Eier von Schafen, die vor dem Decken am 12. Tage des Zyklus einer Temperatur von 32C exponiert wurden, war signifikant niedriger(40,7%)als bei Kontrolltieren (94,2%) 24 Stunden nach übergang in die höhere Temperatur war die Rektaltemperatur 1,7C höher als vorher.Der Anteil morphologisch abnormaler Eier bei den Kontrollen betrug 3,8%, bei den exponierten Tieren 55,6%. Bei Tieren,die einen Tag nach dem Decken 32C exponiert wurden, zeigten alle Eier Teilung,doch davon waren 30,8% morphologisch abnormal. Von den exponierten Tieren lammte keines, von den Kontrolltieren 87,5%. Von Schafen, die 1, 3, 5 oder 8 Tage nach dem Decken 32C exponiert wurden, trugen 20, 35, 40 und 70% aus. In allen exponierten Gruppen war die MortalitÄt signifikant höher (P<0,01) — ausser in der 8-Tage Gruppe — als bei Kontrollen. Die Zygote des Schafes ist Äusserst empfindlich gegen hohe Temperatur wÄhrend der Initialstadien der Teilung, ehe sie in den Uterus gelangt.

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Resume La proportion d'ovules fécondés a été trouvée significativement moindre (P<0,01) chez des brebis exposées à une température de 32C lors du 12ème jour du cycle précédant l'insémination que chez des animaux-témoins (40,7% contre 94,2%).Pendant les 24 heures consécutives à l'exposition à la chaleur, la température rectale des brebis dépassait de 1,7C sa valeur au cours de la période précédente.La proportion d'ovules morphologiquement anormaux était de 3,8% chez les animaux-témoins contre 55,6% chez les animaux exposés à la chaleur. Chez des animaux qui avaient été exposés à une température de 32C le lendemain de l'insémination, tous les oeufs étaient segmentés, pourtant 30,8% d'entre eux présentaient des anomalies morphologiques.Desbrebis ainsi exposées, aucune n'a conduit sa gestation à terme alors que 87,5% des animaux-témoins ont agnelé. Des brebis exposées à la chaleur 1, 3, 5 ou 8 jours après l'insémination, respectivement 20, 35, 40 et 70% ont mené leur gestation à terme. Dans tous les groupes exposés, la mortalité embryonnaire a été significativement plus élevée (P<0,01) que chez les témoins, à l'exception toutefois du groupe exposé 8 jours après l'insémination. Dans l'espèce ovine, le produit de la fécondation est très sensible à 1'hyperthermie pendant les premiers stades de la segmentation qui précèdent son entrée dans l'utérus.

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The investigation reported in this paper is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.     

Variations cardio-respiratoires et metaboliques à l'effort sous-maximal (P=40% Pmax) et maximal (Vita Max) en conditions thermiques froide (0‡C) et neutre (20‡C)

Resume Cette étude a pour but d'étudier les variations physiologiques et métaboliques tant au repos, qu'au cours d'efforts physiques de longue durée (2h) à 40% de la puissance maximale et d'efforts exhaustifs dans des conditions d'hypothermie ambiante (0C) en comparaison de valeurs recueillies en conditions thermiques neutres (20C). L'ensemble des épreuves furent exécutées en chambre climatique par: d'une part 11 sujets mâles pour l'effort exhaustif et d'autre part 8 sujets mâles pour l'exercice sous-maximal. Nous avons observé une légère bradycardie à 0C pour nos deux groupes à la fin de l'effort. La VO₂ et la ventilation pulmonaire sont plus élevées à 0C lors de l'effort maximal, nous observons toutefois le phénomène inverse lors de l'exercice sousmaximal. Les concentrations plasmatiques en acide lactique sons moins élevées et les bicarbonates plus élevés en ambiance thermique froide pour les deux conditions expérimentales. Le pH et la température rectale demeurent stables. Le RQ ne présente pas de différences significatives à la fin de chacun des deux efforts à 20C et 0C.

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The purpose of this study is to investigate the responses on cardiorespiratory and metabolic level measured at rest, during a long-term (2 h) submaximal exercise (P=40% Pmax) and during an exhaustive exercise (Vita Max) and recovery time in normal (20C) and in hypothermic (0C) conditions. The ergometric exercises were performed by 11 male subjects (Vita Max) and 8 male subjects (submaximal exercise) in a climatic room. We have observed a slight but mostly not significant (P<.05) bradycardia for both groups at the end of the exercise. VO₂ and pulmonary ventilation are higher at the end of the maximal exercise performed at 0C, this phenomenon is reversed for the submaximal exercise. The lactate concentrations are lower at 0C. For the same temperature the bicarbonates are higher. pH and T rect are not different in both experimental conditions and RQ is not significantly affected by temperature variations.

     

Interaction of bovine rhodopsin with calcium ions

The formation of metarhodopsin II in various bovine rhodopsin preparations (rod outer segment (ROS) suspensions and rhodopsin-detergent solutions) was measured by means of flash spectrophotometry. The half-lifetime and formation of metarhodopsin II in ROS did not depend on the calcium concentration in the range of less than 10^–9 M (using EGTA or EDTA) to 15×10^–3 M calcium at pH values of 5.0, 7.1, and 9.0 (Table 1).The regeneration of rhodopsin from opsin by adding 11-cis retinal to ROS-suspensions and rhodopsin digitonin solutions was measured spectrophotometrically. It was not substantially different in either saline, one containing less than 10^–7 M calcium (by adding EGTA), the other containing 10^–3 M calcium (Table 2).Abbreviations A absorption - A absorption change - CTAB N-Cetyl-N,N,N-trimethylammoniumbromide - E₇₀₀ extinction at =700 nm - EDTA ethylenediamine-NNNN-tetraacetic acid - EGTA 2,2-ethylenedioxybis [ethyliminodi (acetic acid)] - MI metarhodopsin I - MII metarhodopsin II - Rh rhodopsin - ROS rod outer segment This work is based upon a Ph. D. dissertation (Nöll, 1974) and was presented in part at the Jahrestagung der Deutschen Gesellschaft für Biophysik, Freiburg, Germany, October 1974