Effect of variations of target location upon the peripheral responses of on-center retinal ganglion cells in the cat

Annuli of constant area but differing in distance from the receptive field center, were used to study the characteristics of the receptive field periphery of single on-center retinal ganglion cells. Two types of on-center cells were encountered. One type gave responses that reflected characteristics of both the receptive center response mechanism and the receptive field surround response mechanism. An on-off response was observed for annuli anywhere in the receptive field periphery. The strength of all components of the on-off response decreased towards the outer edge receptive field. A second group of cells gave an on-off response for targets near the receptive field center but this mixed response changed to an off response as the annulus was moved to a greater distance from the receptive field center. The off response decreased in strength as the outer edge of the receptive field was approached. The shape of the off response did not vary (within defined limits) with changes in either intensity or annulus distance. Pourétudier les caractéristiques de la périphérie des champs récepteurs de ganglionnaire rétiniennes isoléesàcentre on, on emploie des anneaux d'aire constante,àdes distances différentes du centre du champ récepteur. On trouve deux types de cellulesàcentre on. Le premier type donne des réponses qui réflètent les caractèresàla fois du mécanisme de réponseàcentre récepteur et du mécanisme de réponseàenvironnement récepteur. On observe une réponse on-off puor les anneauxàtoute position dans la périphérie du champ récepteur. L'amplitude de toutes les composantes dans la réponse on-off décroît vers le bord externe du champ récepteur. Un second groupe de cellules donne une réponse on-off pour de cibles près du centre du champ récepteur, mais cette réponse mixte se change en réponse off quand l'anneau s'écarteàplus grande distance du centre du champ récepteur. La réponse off décroît en amplitude quand on approche du bord externe du champ récepteur. La forme de la réponse off ne varie pas (entre certaines limites) quand on modifie soit l'intensitésoit la distance de l'anneau. Es wurden Ringe mit konstanter Fläche aber mit verschiedener Entfernung vom Zentrum des rezeptiven Feldes dazu benutzt, die Eigenschaften der Peripherie des rezeptiven Feldes einzelner retinaler Ganglienzellen mit On-Zentrum-Mechanismus zu untersuchen. Dabei wurden zwei Typen derartiger Zellen angetroffen. Ein Typ lieferte Antworten, die sowohl die Eigenschaften des Zentrums-Mechanismus als auch die des Umgebungs-Mechanismus des rezeptiven Feldes widerspiegelten. Eine On-Off-Antwort wurde für Ringeüberall in der Peripherie des rezeptiven Feldes beobachtet. In Richtung auf den Aussenrand des rezeptiven Feldes nahm die Stärke aller Komponenten der On-Off-Antwort ab. Eine zweite Gruppe von Zellen gab eine On-Off-Antwort für Testreize in der Nähe des Zentrums des rezeptiven Feldes; diese gemischte Antwortänderte sich jedoch in eine Off-Antwort, wenn der dargebotene Ring vom Zentrum des rezeptiven Feldes wegbewegt wurde. Die Stärke der Off-Antwort nahm ab, wenn man sich demäusseren Rand des rezeptiven Feldes näherte. Die Gestalt der Off-Antwortänderte sich (innerhalb definierter Grenzen) nicht, wenn Intensität oder Ringentfernung verändert wurden. Кoльцa, oдинaкoвыe пo плoщaди, нo pacпoлaгaющиecя нa paзлихнoм paccтoяиии oт цeнтpa peцeптивиoгo пoля, были иcпoльзoвaиы для изyхeния cвoйcтв пepифepии peцeптивиoгo пoля eдинихнyх гaнглиoзных. клeтoк ceтхaтки c “on”—цeнтpoм. Были oбнapyзeны двa типa клeтoк c “on”—цeитpoм. Oдин тип дaвaл oтвeты, кoтopыe oтpaзaли ocoбeнн ocти мeхaнизмoв peaкций кaк цeнтpa, тaк и пepнфepии peцeптивнoгo пoля. “On-of” oтвeты иaблюдaлиcь пpи любoм пoлoзeнии кoльцa нa пepифepии peцeптивнoгo пoля. Bыpaзeннocть вceх кoмпoнeнтoв “on-off” peaкции yмeньшaлacь к нapyзнoмy кpaю peцeптивнoгo пoля. Bтopaя гpyппa клeтoк дaвaлa “on-off” peaкцию для тecтoвых oбъeктoв, pacпoлoзeнных близкo к цeнтpy peцeптивнoгo пoля, нo этa cмeшaннaя peaкция измeнялacь в “off” peaкцию, кoгдa кoльцo былo cмeщeнo нa бoльщyю диcтaнцию oт цeнтpa peцeптивнoгo пoля. “off”-peaкции yмeньшaлacь кoгдa нapyзный кpaй peцeптивнoгo пoля пpиблизaлcя. Фopмa “off”-peaкцни нe измeнялacь (в oпpeдeлeнных пpeдeлaх) пpи измeнeи и либo иитeнcивнocти, либo paccтoяния дoкoльцa

Spatial summation in the receptive field periphery of two types of on-center neurons in cat retina

Peripheral annuli with the same inside diameters but variable outside diameters were used to study the peripheral summing properties of Group I and Group II cells ( Winters, Hickey and Pollack, 1973). The results showed that Group I and Group II cells could be differentiated on the basis of their responses to changes in the size of peripheral annuli. Group I cells showed spatial summation of both the on-excitation and the off-excitation of on-off responses elicted by peripheral annuli. This finding was not found to be dependent upon the location of the target in the receptive field periphery. The effect of target size on the response of Group II cells was found to be dependent upon the location of the target in the receptive field periphery. If the inside portion of the annulus was near the receptive field center, in the on-off zone, then small increases in target size produced an increase in the strength of the onexcitation whereas large changes in target size lead to a decrease in the strength of the onexcitation. Off-excitation showed spatial summation across the entire receptive field periphery. It was possible to demonstrate linear spatial summation in the receptive field periphery of Group II cells but not Group I cells. Avec des anneaux périphériques de mémes diamètres internes et de diamètres externes variables, onétude les propriétés de sommation périphérique des cellules des groupes I et II ( Winters, Hickey et Pollack, 1973). On peut différentier ces groupes par leurs réponses aux changements de taille des anneaux périphériques. Le groupe I montre une sommation spatialeàla fois pour l'excitation on et l'excitation off des réponses on-off produites par les anneaux périphériques. Ce résultat ne dépend pas de la position de la cibteàla périphérie du champ récepteur. Au contraire l'effet de la taille de la cible sur la réponse des cellules du groupe II dépend de la position de la cible dans la périphérie du champ récepteur. Si la partie interne de l'anneau est près du centre du champ récepteur, dans la zone on-off, une petite augmentation de dimension de la cible augmente l'amplitude de l'excitation on, tandis qu'une grande variation de taille de la cible fait décroître l'amplitude de l'excitation on. L'excitation off montre une sommation spatiale dans toute la périphérie du champ récepteur. On peut démontrer la linéaritéde la sommation spatíale dans la périphérie du champ récepteur pour les cellules du groupe II, mais pas pour celles du groupe I. Periphere Ringe mit gleichem Innendurchmesser aber verschiedenen Aussendurchmessern wurden dazu benutzt, die peripheren Summationseigenschaften von Zellen der Gruppe I und Gruppe II zu untersuchen, (vgl. Winters, Hickey und Pollack, 1972). Die Ergebnisse zeigten, dass die Zellen der Gruppe I und der Gruppe II aufgrund ihrer Antworten aufÄnderungen in der Grösse peripherer Ringe differenziert werden konnten. Die Zellen der Gruppe I zeigten eine räumliche Summation sowohl der On-Erregung als auch der Off-Erregung bei von peripheren Ringen hervorgerufenen On-Off-Antworten. Eine Abhängigkeit vom Ort des Testreizes in der Peripherie des rezeptiven Feldes wurde nicht gefunden. Dagegen wurde eine Abhängigkeit des Effektes der Testzeichengrösse auf die Antwort von Zellen der Gruppe II vom Ort des Testreizes in der Peripherie des rezeptiven Feldes gefunden. Befand sich die Ringinnenfläche in der Nähe des Zentrums des rezeptiven Feldes d.h. in der On-Off-Zone, so verursachten kleine Vergrösserungen der Testzeichengrösse einen Anstieg in der Stärke der On-Erregung, während grosse Veränderungen in der Testzeichengrösse zu einem Abfall in der Stärke der On-Erregung führten. Die Off-Erregung zeigte eine räumliche Summationüber die gesamte Peripherie des rezeptiven Feldes. Es war möglich, eine lineare räumliche Summation in der Peripherie des rezeptiven Feldes von Zellen der Gruppe II, aber nicht von solchen der Gruppe I zu demonstrieren. Кoльцa, pacпoлaгaeмыe нa пepнфepии peцeптнвнoгo пoля, имeвшиe oдинaкoвыe внyтpeнниe диaмeтpы, нo пepeмeнныe внeщниe диaмeтpы, были иcпoльзoвaны для изyхeния ocoбeннocтeй пpocтpaнcтвeннoй cyммaцни I и пoй гpyпц клeтoк Winters, Hickey and Pollack, 1972). Peзyльтaты пoкaзывaют, хтo клтeтки I и II гpyпп мoгyт paзлихaтьcя нa ocнoвaнии их peaкций пpи измeнeнии вeлихины кoльцa. Пepвaя гpyппa клeтoк oбнapyзивaлa пpocтpaнcтвeннyю cyммaцию кaк “on” — вoзбyздeния, тaк и “off” — вoзбyздeния “on-off” peaкций, вызывaeмых кoньцoм нa пepифepии peцeптнвнoгo пoля. Этo нe зaвиcилo oт pacпoлoзeния oбьeктa нa пepифepии peцeптивнoгo пoля. Bлияниe вeлнхины oбьeктa нa peaкцию клeтoк втopoй гpyппы зaвиcилo oт пoлoзeния oбъeктa нa пepифepии peцeптивнoгo пoля. Ecли внyтpeнняя хacть кoляцa былa блнзкo к цeнтpy peцeптнвнoгo пoля, в “on-off” зoнe, тo нeбoльщoe yвeлихeниe вeлихины oбъeктa ьызывaлo yвeлихeниecнлы “on” — вoзбyздeния”, тoгдa кaк бoльшиe измeнeния вeлихины oбъeктaвeлик yмeньшeнию cилы “on” — вoзбyздeния. “Off” — вoзбyздeниe oбнapyзивaлo пpocтpaнcтвeннyю cyммaцию в пpeдeлaх вceй пepифepии peцeптивнoгo пoля. Былo вoзмoзнo oбнapyзить линeйнyю пpocтpaнcтвeннyю cyмaцию нa цepнфepии peцeптивнoгo пoля для клeтoк IIoй гpyппы, нo нe для клeтoк Ioй гpyппы

Muscle cells become necrotic rather than apoptotic during reperfusion of ischaemic skeletal muscle

While necrosis is known as a major mechanism for the loss of viability of skeletal muscle following ischaemia and reperfusion, much less is known of the role of apoptosis. In this study rat hind limbs were subjected to 2 h of tourniquet ischaemia, then reperfused for either 0, 0.25, 0.5, 1, 3, 8, 16 or 24 h (n = 6 per group). Mean viability of muscle, assessed by tetrazolium dye reduction, after 2 h ischaemia and 24 h reperfusion was 17%. Histological examination revealed disrupted, necrotic muscle fibres from 30 min to 24 h reperfusion. Apoptotic nuclei were identified by haematoxylin staining and TUNEL, terminal deoxynucleotidyl transferase mediated dUTP nick end labelling. No TUNEL-positive cells were observed at the end of the ischaemic period, but a small number of TUNEL-positive endothelial and smooth muscle cells were found at 30 min reperfusion, with a progressive increase in their number up to 24 h reperfusion. Apoptotic neutrophils were detected after 8–24 h reperfusion. At no stage was apoptosis seen in the nuclei of skeletal muscle fibres. It appears that apoptosis plays no role in the death of muscle fibres after ischaemia-reperfusion injury to skeletal muscle

Tobacco Smoking and Risk of Second Primary Lung Cancer

Introduction: Lung cancer survivors are at high risk of developing a second primary lung cancer (SPLC). However, SPLC risk factors have not been established and the impact of tobacco smoking remains controversial. We examined the risk factors for SPLC across multiple epidemiologic cohorts and evaluated the impact of smoking cessation on reducing SPLC risk. Methods: We analyzed data from 7059 participants in the Multiethnic Cohort (MEC) diagnosed with an initial primary lung cancer (IPLC) between 1993 and 2017. Cause-specific proportional hazards models estimated SPLC risk. We conducted validation studies using the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (N = 3423 IPLC cases) and European Prospective Investigation into Cancer and Nutrition (N = 4731 IPLC cases) cohorts and pooled the SPLC risk estimates using random effects meta-analysis. Results: Overall, 163 MEC cases (2.3%) developed SPLC. Smoking pack-years (hazard ratio [HR] = 1.18 per 10 pack-years, p < 0.001) and smoking intensity (HR = 1.30 per 10 cigarettes per day, p < 0.001) were significantly associated with increased SPLC risk. Individuals who met the 2013 U.S. Preventive Services Task Force's screening criteria at IPLC diagnosis also had an increased SPLC risk (HR = 1.92; p < 0.001). Validation studies with the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial and European Prospective Investigation into Cancer and Nutrition revealed consistent results. Meta-analysis yielded pooled HRs of 1.16 per 10 pack-years (pmeta < 0.001), 1.25 per 10 cigarettes per day (pmeta < 0.001), and 1.99 (pmeta < 0.001) for meeting the U.S. Preventive Services Task Force's criteria. In MEC, smoking cessation after IPLC diagnosis was associated with an 83% reduction in SPLC risk (HR = 0.17; p < 0.001). Conclusions: Tobacco smoking is a risk factor for SPLC. Smoking cessation may reduce the risk of SPLC. Additional strategies for SPLC surveillance and screening are warranted

Tobacco Smoking and Risk of Second Primary Lung Cancer

Introduction: Lung cancer survivors are at high risk of developing a second primary lung cancer (SPLC). However, SPLC risk factors have not been established and the impact of tobacco smoking remains controversial. We examined the risk factors for SPLC across multiple epidemiologic cohorts and evaluated the impact of smoking cessation on reducing SPLC risk. Methods: We analyzed data from 7059 participants in the Multiethnic Cohort (MEC) diagnosed with an initial primary lung cancer (IPLC) between 1993 and 2017. Cause-specific proportional hazards models estimated SPLC risk. We conducted validation studies using the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (N = 3423 IPLC cases) and European Prospective Investigation into Cancer and Nutrition (N = 4731 IPLC cases) cohorts and pooled the SPLC risk estimates using random effects meta-analysis. Results: Overall, 163 MEC cases (2.3%) developed SPLC. Smoking pack-years (hazard ratio [HR] = 1.18 per 10 pack-years, p < 0.001) and smoking intensity (HR = 1.30 per 10 cigarettes per day, p < 0.001) were significantly associated with increased SPLC risk. Individuals who met the 2013 U.S. Preventive Services Task Force's screening criteria at IPLC diagnosis also had an increased SPLC risk (HR = 1.92; p < 0.001). Validation studies with the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial and European Prospective Investigation into Cancer and Nutrition revealed consistent results. Meta-analysis yielded pooled HRs of 1.16 per 10 pack-years (pmeta < 0.001), 1.25 per 10 cigarettes per day (pmeta < 0.001), and 1.99 (pmeta < 0.001) for meeting the U.S. Preventive Services Task Force's criteria. In MEC, smoking cessation after IPLC diagnosis was associated with an 83% reduction in SPLC risk (HR = 0.17; p < 0.001). Conclusions: Tobacco smoking is a risk factor for SPLC. Smoking cessation may reduce the risk of SPLC. Additional strategies for SPLC surveillance and screening are warranted