Time-Driven Activity-based Costing and Outcomes of Same-Day Discharge vs Inpatient Robotic Partial and Radical Nephrectomy

OBJECTIVE

To assess the outcomes, total healthcare utilization, and cost savings for same-day discharge (SDD) vs inpatient robotic-assisted partial nephrectomy (RAPN) and robotic-assisted radical nephrectomy (RARN).

METHODS

We compared 146 RAPNs and 65 RARNs consecutively performed as SDD (RAPN=21, RARN=9) vs inpatient (RAPN=125, RARN=56) from April 2015 to May 2023 at two academic medical centers. We collected baseline demographics, perioperative characteristics, and 30-day complications. We applied the Time-Driven Activity-Based Costing analysis to compare total costs of RAPN and PARN throughout the cycle of care, including inpatient vs SDD.

RESULTS

Baseline demographics and comorbidities were similar between patients undergoing inpatient vs SDD RAPN and RARN. One Clavien-Dindo grade II complication (3.3%) requiring readmission due to wound infection for antibiotics occurred after SDD RAPN; no complications occurred after SDD RARN. Two unscheduled office or emergency department visits (6.7%) occurred after SDD RAPN for surgical-site infection and urinary retention. SDD vs inpatient RAPN and RARN demonstrated a $3091 (18%) and $4003 (25%) overall cost reduction, respectively.

CONCLUSION

SDD RAPN and RARN result in cost savings of 18%-25% without a difference in complications, and thereby improves value-based care for appropriately selected patients.

Changes in Semen Analysis over Time: A Temporal Trend Analysis of 20 Years of Subfertile Non-Azoospermic Men

PURPOSE

To examine trends of population-level semen quality over a 20-year period.

MATERIALS AND METHODS

We performed a retrospective review of data from the andrology lab of a high volume tertiary hospital. All men with semen samples between 2000 and 2019 were included and men with azoospermia were excluded. Semen parameters were reported using the World Health Organization (WHO) 4th edition. The primary outcome of interest was changes in semen parameters over time. Generalized least squares (GLS) with restricted cubic splines were used to estimate average-monthly measurements, adjusting for age and abstinence period. Contrasts of the estimated averages based on GLS between the first and last months of collection were calculated.

RESULTS

A total of 8,990 semen samples from subfertile non-azoospermic men were included in our study. Semen volume decreased over time and estimate average at the beginning and end were statistically different (p<0.001). Similarly sperm morphology decreased over time, with a statistically significant difference between estimated averages from start to finish (p<0.001). Semen pH appeared to be increasing over time, but this difference was not significant over time (p=0.060). Sperm concentration and count displayed an increase around 2003 to 2005, but otherwise remained fairly constant over time (p=0.100 and p=0.054, respectively). Sperm motility appeared to decrease over time (p<0.001).

CONCLUSIONS

In a large sample of patients presenting to a single institution for fertility assessment, some aspects of semen quality declined across more than two decades. An understanding of the etiologies and driving forces of changing semen parameters over time is warranted.

Development of an improved and specific inhibitor of NADPH oxidase 2 to treat traumatic brain injury

NADPH oxidases (NOX's), and the reactive oxygen species (ROS) they produce, play an important role in host defense, thyroid hormone synthesis, apoptosis, gene regulation, angiogenesis and other processes. However, overproduction of ROS by these enzymes is associated with cardiovascular disease, fibrosis, traumatic brain injury (TBI) and other diseases. Structural similarities between NOX's have complicated development of specific inhibitors. Here, we report development of NCATS-SM7270, a small molecule optimized from GSK2795039, that inhibited NOX2 in primary human and mouse granulocytes. NCATS-SM7270 specifically inhibited NOX2 and had reduced inhibitory activity against xanthine oxidase in vitro. We also studied the role of several NOX isoforms during mild TBI (mTBI) and demonstrated that NOX2 and, to a lesser extent, NOX1 deficient mice are protected from mTBI pathology, whereas injury is exacerbated in NOX4 knockouts. Given the pathogenic role played by NOX2 in mTBI, we treated mice transcranially with NCATS-SM7270 after injury and revealed a dose-dependent reduction in mTBI induced cortical cell death. This inhibitor also partially reversed cortical damage observed in NOX4 deficient mice following mTBI. These data demonstrate that NCATS-SM7270 is an improved and specific inhibitor of NOX2 capable of protecting mice from NOX2-dependent cell death associated with mTBI.

Impact of testicular delivery and vasal vein ligation on clinical outcomes in men undergoing microsurgical varicocelectomy

PURPOSE

To assess the impact of microsurgical varicocelectomy technique on clinical outcomes.

METHODS

Men diagnosed with varicocele between 2017 and 2020 were reviewed. We included men who underwent microsurgical varicocelectomy by two high-volume surgeons who differed in surgical technique: Method (1) testicular delivery with gubernacular vein ligation, and ligation of vasal veins > 2.5 mm; Method (2) no delivery and ligation of dilated vasal veins in cases of recurrence. Post-operative changes for semen parameters, DNA fragmentation, and serum testosterone were evaluated for each technique and compared.

RESULTS

313 patients were included; 162 with Method 1 and 151 with Method 2. The cohorts were of similar age (median 35 years, interquartile range (IQR) 28-43; 34, IQR 28-39, respectively), and BMI (25 kg/m², IQR 23-27; 25, IQR 23-28, respectively). For Method 1, 84 (51.9%) had bilateral surgery, and 78 (48.1%) had unilateral surgery. For Method 2, 63 (41.7%) had bilateral surgery, and 88 (58.3%) unilateral surgery. In patients with sperm concentration > 5 M/mL, both techniques resulted in an improvement (p < 0.01), but there was no difference between the methods (p = 0.18). Both methods were associated with an improvement in total motile count (p < 0.05) and the amount of DNA fragmentation (p < 0.05), although no differences were apparent between the techniques (p = 0.09, p = 0.81, respectively). Finally, testosterone levels improved with Method 1, but the post-operative difference was not different than Method 2 (p = 0.06).

CONCLUSION

Delivery of the testis and ligation of dilated vasal veins compared to not performing those steps do not impact semen parameters, but are associated with improvement in testosterone levels.

Sex-Related Differences in Clinical Presentation and Risk Factors for Mortality in Patients Hospitalized With Coronavirus Disease 2019 in New York City

We evaluated sex-related differences in symptoms and risk factors for mortality in 4798 patients hospitalized with coronavirus disease 2019 in New York City. When adjusted for age and comorbidities, being male was an independent predictor of death with mortality significantly higher than females, even with low severe acute respiratory syndrome coronavirus 2 viral load at admission.

The Effect of Topical Tacrolimus on Pedicled Flap Survival: A Histological Analysis

PURPOSE

Our previous rodent study demonstrated significantly decreased full-thickness necrosis in pedicled dorsal skin flaps with topical tacrolimus as compared with petroleum jelly. The pathophysiology of tissue necrosis involves lymphatic congestion, followed by venous congestion and ultimately arterial insufficiency. Topical tacrolimus has been shown to increase growth of lymphatic collateral vessels and decrease lymphedema, potentially obviating one contributor to necrosis. The purpose of this study was to investigate the vascular and histological differences between these 2 groups to identify the etiology of our research findings.

METHODS

A 3 × 10-cm cranially based dorsal skin flap was raised and reinset on 22 Sprague Dawley rats. They were randomized to receive 0.2 g of either topical petroleum jelly or topical 0.1% tacrolimus ointment daily to the flaps. The rats were killed 7 days postoperatively. Two blinded reviewers marked the total flap area as well as areas of viable tissue, reversible ischemia, and necrotic tissue. Full-thickness biopsies of each area were taken from 2 randomly chosen animals in each group. Paraffin-embedded tissue was sectioned to generate hematoxylin and eosin-stained slides. Representative images of each area of the flap were taken less than 40× magnification using light microscopy. Arteries, veins, and lymphatics in the dermal layer were quantified under blinded conditions by a trained pathologist and calculated per cross-sectional area using Fiji software.

RESULTS

The average area of the dorsal flaps in the control and tacrolimus groups was 22.5 and 23.9 cm2, respectively. Total necrotic area was significantly lower in rats receiving topical tacrolimus as compared with controls (P = 0.015). In the control cohort, average total number of vessels was 12.5, 6, and 0, in the areas of viable tissue, reversible ischemia, and necrosis, respectively. In the tacrolimus cohort, average total number of vessels increased was 20, 11.5, and 5.4, in the areas of viable tissue, reversible ischemia, and necrosis, respectively.

CONCLUSIONS

On a histological level, topical tacrolimus is correlated with increased vascular growth in areas most susceptible for ischemic damage as compared with topical control. Future work is needed to investigate vascular biomarkers and increase the power of our study.

Optimal timing for repeat semen analysis during male infertility evaluation

Objective

To assess whether the 4-week time period between semen analyses during the workup of male infertility is optimal and whether two samples are needed.

Design

Retrospective study.

Setting

Tertiary hospital.

Patient(s)

Men whose semen samples were obtained within 90 days of each other, without known fertility intervention, treatment, and/or azoospermia.

Intervention(s)

Semen analysis.

Main Outcome Measure(s)

Correlation between semen parameters and agreement among consecutive semen analyses.

Result(s)

A total of 2,150 semen samples from 1,075 men were included in the analysis. The optimal correlation for volume occurred at weeks 2, 8, and 12 (r = 0.803, r = 0.802, and r = 0.821, respectively). For concentration, the correlation was maximized at weeks 1, 4, and 5 (r = 0.950, r = 0.841, and r = 0.795, respectively). Total sperm count correlated at weeks 1, 2, and 4 (r = 0.929, r = 0.727, and r = 0.808, respectively). Motility was maximally correlated at weeks 1, 10, and 13 (r = 0.711, r = 0.760, and r = 0.708, respectively). Morphology was optimally correlated at weeks 1, 2, and 9 (r = 0.935, r = 0.815, and r = 0.839, respectively). Semen volume was correlated in 55% of men, sperm concentration in 64% of men, sperm motility in 52% of men and sperm morphology 64% of men.

Conclusion(s)

Our data suggest that four weeks may not be the optimal time for repeat semen analysis and that one sample is insufficient to assess any abnormalities in the result of semen analysis. The optimal time between repeat semen analyses should be individualized depending on the results of the initial analysis and additional factors, suggesting the need for future large-scale studies to investigate this trend.

Predictors of varicocele-associated pain and its impact on semen parameters following microsurgical repair

Our study aimed to assess for predictors of varicocele-associated pain and whether it predicts semen parameters after microsurgical varicocelectomy. We assessed all men diagnosed with a varicocele by two surgeons from 2017 to 2020, excluding those who did not undergo surgical treatment. Patients were stratified based on the presence of pain at clinical assessment, and these groups were compared. Logistic regression models were utilised to assess for predictors of pain. A total of 313 men were included, with relatively similar proportions completed by both surgeons (48.2% and 51.8%). A total of 98 (31.3%) had typical varicocele-associated pain at the time of assessment. The pain group was younger than the no pain group (30.5 versus. 35.0, respectively, p < .01), and those with pain had greater varicocele grades (p = .008). Although not statistically different, there was a greater portion of left-sided only varicoceles in the pain group (p = .09). No significant differences were demonstrated between sperm concentration, motility, volume or morphology pre-operatively, or post-operatively between groups. Younger age and varicocele grade were predictive of varicocele-associated pain. In conclusion, almost 1/3 of men presented with varicocele-associated pain. Pain does not predict response to varicocelectomy, but these men tend to be younger, and have higher grade varicoceles.

Assessing the clinical value of the Kruger strict morphology criteria over the World Health Organization fourth edition criteria

Objective

To assess if the newer Kruger strict morphology (WHO5; normal ≥4%) adds any clinical value beyond the criteria of the World Health Organization fourth edition (WHO4; normal ≥14%).

Design

Retrospective study.

Setting

Tertiary hospital.

Patients

Men without known azoospermia who had semen analysis (SA) collected over a 10-year period of time.

Interventions

Morphology classification under Kruger WHO5 strict criteria and WHO4 criteria.

Main Outcome Measures

Correlation between the WHO5 and WHO4 morphological classifications.

Results

A total of 4,510 SAs were identified during the study period. Of these, both Kruger WHO5 and WHO4 morphologies were included in 932 SAs (20.7%) from a total of 691 men. The median age of the men was 37 years (interquartile range, 32.0-43.8 years). The mean (±SD) semen volume, sperm concentration, and motility were 2.6 ± 1.4 mL, 50.0 ± 35.6 × 10⁶/mL, and 53.1% ± 18.6%, respectively. The correlation between the WHO4 and WHO5 morphology assessments was high (Spearman correlation coefficient = 0.94). Only 545 (58.5%) of 932 SAs had abnormal Kruger WHO5 morphology, of which 543 (99.6%) of 545 also had abnormal morphology by the WHO4 criteria.

Conclusions

The Kruger WHO5 and WHO4 morphologic criteria correlate closely. Only two men (0.4%) with an abnormal Kruger morphology had normal WHO4 morphology. Given the limited predictive value of sperm morphology, the additional cost and effort of Kruger criteria may not be warranted in lieu of, or in addition to, the WHO4 classification.

Low Plasma Gelsolin Concentrations in Chronic Granulomatous Disease

Plasma gelsolin (pGSN) is the secreted isoform of an intracellular actin remodeling protein found in high concentrations in human plasma. Clinical studies demonstrate reduced pGSN concentrations in several disease states, including severe trauma, burns, and sepsis. Markedly decreased pGSN concentrations in these conditions precede and predict adverse clinical outcomes. In this study, we measured pGSN in patients with chronic granulomatous disease (CGD), a primary immunodeficiency characterized by recurrent infections and dysregulated inflammation. pGSN was quantified using a sandwich ELISA in plasma from healthy volunteers, clinically stable CGD patients, and X-linked CGD carriers and in sera from 12 CGD patients undergoing bone marrow transplantation. pGSN was also quantified in healthy volunteers challenged with intravenous endotoxin. pGSN concentrations were lower in CGD patients without active infection or systemic inflammation compared with healthy control subjects. In CGD patients undergoing bone marrow transplantation, pGSN concentrations increased significantly following successful transplant. X-linked carriers of CGD had normal pGSN. Despite reduction of pGSN in CGD patients, we did not detect significant changes in pGSN over 24 h following challenge of healthy volunteers with intravenous endotoxin (4 ng/kg) that elicited a febrile response. We describe, for the first time, significantly lower pGSN in clinically stable patients with CGD compared with age- and sex-matched healthy volunteers. Low pGSN levels in CGD patients significantly increased following bone marrow transplantation. X-linked carriers of CGD had normal pGSN. In healthy volunteers challenged with intravenous endotoxin, pGSN is not an acute phase reactant.

Obesity diminishes response to PD-1-based immunotherapies in renal cancer

BACKGROUND

Obesity is a major risk factor for renal cancer, yet our understanding of its effects on antitumor immunity and immunotherapy outcomes remains incomplete. Deciphering these associations is critical, given the growing clinical use of immune checkpoint inhibitors for metastatic disease and mounting evidence for an obesity paradox in the context of cancer immunotherapies, wherein obese patients with cancer have improved outcomes.

METHODS

We investigated associations between host obesity and anti-programmed cell death (PD-1)-based outcomes in both renal cell carcinoma (RCC) subjects and orthotopic murine renal tumors. Overall survival (OS) and progression-free survival (PFS) were determined for advanced RCC subjects receiving standard of care anti-PD-1 who had ≥6 months of follow-up from treatment initiation (n=73). Renal tumor tissues were collected from treatment-naive subjects categorized as obese (body mass index, 'BMI' ≥30 kg/m2) or non-obese (BMI <30 kg/m2) undergoing partial or full nephrectomy (n=19) then used to evaluate the frequency and phenotype of intratumoral CD8+ T cells, including PD-1 status, by flow cytometry. In mice, antitumor immunity and excised renal tumor weights were evaluated ±administration of a combinatorial anti-PD-1 therapy. For a subset of murine renal tumors, immunophenotyping was performed by flow cytometry and immunogenetic profiles were evaluated via nanoString.

RESULTS

With obesity, RCC patients receiving anti-PD-1 administration exhibited shorter PFS (p=0.0448) and OS (p=0.0288). Treatment-naive renal cancer subjects had decreased frequencies of tumor-infiltrating PD-1highCD8+ T cells, a finding recapitulated in our murine model. Following anti-PD-1-based immunotherapy, both lean and obese mice possessed distinct populations of treatment responders versus non-responders; however, obesity reduced the frequency of treatment responders (73% lean vs 44% obese). Tumors from lean and obese treatment responders displayed similar immunogenetic profiles, robust infiltration by PD-1int interferon (IFN)γ+CD8+ T cells and reduced myeloid-derived suppressor cells (MDSC), yielding favorable CD44+CD8+ T cell to MDSC ratios. Neutralizing interleukin (IL)-1β in obese mice improved treatment response rates to 58% and reduced MDSC accumulation in tumors.

CONCLUSIONS

We find that obesity is associated with diminished efficacy of anti-PD-1-based therapies in renal cancer, due in part to increased inflammatory IL-1β levels, highlighting the need for continued study of this critical issue.

Obesity induces limited changes to systemic and local immune profiles in treatment-naive human clear cell renal cell carcinoma

Understanding the effects of obesity on the immune profile of renal cell carcinoma (RCC) patients is critical, given the rising use of immunotherapies to treat advanced disease and recent reports of differential cancer immunotherapy outcomes with obesity. Here, we evaluated multiple immune parameters at the genetic, soluble protein, and cellular levels in peripheral blood and renal tumors from treatment-naive clear cell RCC (ccRCC) subjects (n = 69), to better understand the effects of host obesity (Body Mass Index "BMI" ≥ 30 kg/m2) in the absence of immunotherapy. Tumor-free donors (n = 38) with or without obesity were used as controls. In our ccRCC cohort, increasing BMI was associated with decreased percentages of circulating activated PD-1+CD8+ T cells, CD14+CD16neg classical monocytes, and Foxp3+ regulatory T cells (Tregs). Only CD14+CD16neg classical monocytes and Tregs were reduced when obesity was examined as a categorical variable. Obesity did not alter the percentages of circulating IFNγ+ CD8 T cells or IFNγ+, IL-4+, or IL-17A+ CD4 T cells in ccRCC subjects. Of 38 plasma proteins analyzed, six (CCL3, IL-1β, IL-1RA, IL-10, IL-17, and TNFα) were upregulated specifically in ccRCC subjects with obesity versus tumor-free controls with obesity. IGFBP-1 was uniquely decreased in ccRCC subjects with obesity versus non-obese ccRCC subjects. Immunogenetic profiling of ccRCC tumors revealed that 93% of examined genes were equivalently expressed and no changes in cell type scores were found in stage-matched tumors from obesity category II/III versus normal weight (BMI ≥ 35 kg/m2 versus 18.5-24.9 kg/m2, respectively) subjects. Intratumoral PLGF and VEGF-A proteins were elevated in ccRCC subjects with obesity. Thus, in ccRCC patients with localized disease, obesity is not associated with widespread detrimental alterations in systemic or intratumoral immune profiles. The effects of combined obesity and immunotherapy administration on immune parameters remains to be determined.

Obesity-induced changes to the immune landscape in human renal cell carcinoma subjects

Immunotherapy for advanced renal cell carcinoma (RCC) has shown tremendous promise. However, clinical responses remain &lt;30% and the reasons are unclear. Obesity affects ~35% of U.S. adults and is a major risk factor for RCC. We reported previously that obesity impairs immunotherapeutic efficacy in a murine renal cancer model, due to increased myeloid suppressor cells and weakened effector CD8 T cell responses. Based on these results, we hypothesized that obesity would also induce detrimental shifts in the immune landscape in treatment-naive subjects with confirmed RCC. In an IRB-approved study, we consented 86 RCC subjects with obesity (mean BMI = 38.4) and 77 normal to over-weight RCC subjects (mean BMI = 25.0), plus tumor-free controls, into a prospective study to examine intra-tumoral and systemic leukocytes by multi-parameter flow cytometry, plasma proteins via multiplex, and tumor gene expression by Nanostring. Numerous systemic cell populations (ex: CD45RO+ PD1+ CD4 or CD8 T cells, and HLA-DR- CD14− CD11b+MDSC, all p&gt;0.05) were unaltered by obesity in RCC subjects. Peripheral CD14+ inflammatory monocytes and Foxp3+ Tregs were decreased in RCC subjects with obesity (both p&lt; 0.05). However, obesity altered plasma proteins to favor RCC progression, with increased angiopoietin, VEGF-A and –C, and IL-8 (all p&lt; 0.05). Within renal tumors, obesity did not alter CD4 or CD8 T cell percentages or phenotypes (CD45RO, PD1, CD56). Nanostring analysis of renal tumors revealed multiple obesity-related changes in pro-tumorigenic genes. Thus, obesity in RCC subjects had surprisingly few effects on cellular immunity, but multiple effects on protein mediators that may shift the overall immune landscape toward one that favors tumor progression.

Obesity triggers enhanced MDSC accumulation in murine renal tumors via elevated local production of CCL2

Obesity is one of the leading risk factors for developing renal cell carcinoma, an immunogenic tumor that is treated clinically with immunostimulatory therapies. Currently, however, the mechanisms linking obesity with renal cancer incidence are unclear. Using a model of diet-induced obesity, we found that obese BALB/c mice with orthotopic renal tumors had increased total frequencies of myeloid-derived suppressor cells (MDSC) in renal tumors and spleens by d14 post-tumor challenge, relative to lean counterparts. Renal tumors from obese mice had elevated concentrations of the known myeloid cell chemoattractant CCL2, which was produced locally by increased percentages of dendritic cells, macrophages, B cells, and CD45^- cells in tumors. MDSC expression of the CCL2 receptor, CCR2, was unaltered by obesity but greater percentages of CCR2⁺ MDSCs were present in renal tumors from obese mice. Of note, the intracellular arginase levels and per-cell suppressive capacities of tumor-infiltrating and splenic MDSCs were unchanged in obese mice relative to lean controls. Thus, our findings suggest that obesity promotes renal tumor progression via development of a robust immunosuppressive environment that is characterized by heightened local and systemic MDSC prevalence. Targeted intervention of the CCL2/CCR2 pathway may facilitate immune-mediated renal tumor clearance in the obese.

ON THE DISTRIBUTION OF VITAMINS A(1) AND A(2)

The distribution of vitamins A(1) and A(2) has been determined in the eye tissues and livers of a number of fishes. The vitamins were differentiated by means of the antimony chloride reaction, which yields with A(1) a band at 615-620 mmicro and with A(2) a band at about 696 mmicro. In the retina the presence of vitamin A(1) is diagnostic of the operation of a rhodopsin, and vitamin A(2) of a porphyropsin cycle. The eye tissues of all permanently marine fishes examined, except the tautog, contain vitamin A(1) alone. Those of all permanently freshwater fishes possess only vitamin A(2). Those of all euryhaline (potentially migratory) fishes, except possibly the alewife, contain mixtures of both vitamins A, and always predominantly that one which ordinarily is associated with the environment in which the fish is spawned. These correlations extend in part to the liver oils, but most livers contain mixtures of both vitamins A, and occasionally in proportions the reverse of those in the eye tissues. The vitamin A configuration does not depend upon environmental circumstances, but is determined genetically. The transfer from vitamin A(1) to A(2) metabolism appears associated phylogenetically with migration of marine teleosts into fresh water.

PIGMENTS OF THE RETINA : I. THE BULL FROG

1. The interrelations of visual purple, retinene, and vitamin A in the bull frog retina are analyzed in simple experiments, the results of which are presented in a series of automatically recorded spectra. 2. Observations are reported upon the distributions, properties, and concentrations of xanthophyll, vitamin A, and flavine in the pigmented tissues of the eye.

AREA AND VISUAL THRESHOLD

1. The variation of threshold with field area was measured in fields homogeneous in rod-cone composition. At 15° above the fovea, an increase in field diameter from 1° to 5° reduces the threshold sevenfold, at 25° above the fovea tenfold. 2. These changes are shown to follow qualitatively from simple statistical properties of the retinal mosaic. Analytic treatment leads to the expression, (A – n_t)^k I = C, in which A = area, n_t = constant threshold number of elements, I = threshold intensity, and k and C are constants. This equation describes the available data accurately, and is the general form of previous empirical area-threshold formulae.

VITAMIN A IN EYE TISSUES

1. Vitamin A has been found in the retinas and the combined pigment epithelia and choroid layers of frogs, pigs, sheep, and cattle. The vitamin was identified by (a) its specific absorption at 328 mµ; (b) the blue color yielded with antimony trichloride, associated with an absorption band at about 620 mµ; (c) anti-xerophthalmic and growth-promoting activity; and (d) quantitative relationships among the results of these three types of observation. 2. The mammalian retinas contain about 22γ, the frog retinas about 400γ, and the frog pigmented layers almost 2 mg. of vitamin A per gram of dry tissue. 3. With the possible exception of hepaxanthin, no other carotenoids were found in the mammalian tissues.

THE PORPHYROPSIN VISUAL SYSTEM

1. In the rods of fresh-water and some anadromous fishes, rhodopsin is replaced by the purple photolabile pigment porphyropsin. This participates in a retinal cycle identical in form with that of rhodopsin, but in which new carotenoids replace retinene and vitamin A. 2. Porphyropsin possesses a broad absorption maximum at 522 +/- 2 mmicro, and perhaps a minimum at about 430 mmicro. The vitamin A-analogue, vitamin A(2), possesses a maximum in chloroform at 355 mmicro and yields with antimony trichloride a deep blue color due to a band at 696 mmicro. The retinene-analogue, retinene(2), absorbs maximally in chloroform at 405 mmicro and possesses an antimony chloride maximum at 706 mmicro. 3. Its non-diffusibility through a semi-permeable membrane, salting-out properties, and sensitivity to chemical denaturants and to heat, characterize porphyropsin as a conjugated carotenoid-protein. 4. The porphyropsin cycle may be formulated: porphyropsin See PDF for Structure. retinene(2)-protein ((2)) (-->) vitamin A(2)-protein ((3)) (-->) porphyropsin. Isolation of the retina cuts this cycle at (3); denaturation procedures or extraction of porphyropsin into aqueous solution eliminate in addition (1) and (2). 5. The primary difference between the rhodopsin and porphyropsin systems appears to be the possession by the latter of an added ethylenic group in the polyene chain.

THE VISUAL SYSTEM AND VITAMINS A OF THE SEA LAMPREY

The porphyropsin-vitamin A(2) cycle has been found heretofore only in the retinas of bony fishes capable of existence in fresh water. Cyclostomes, due to their primitive and isolated phylogenetic position, might be expected to possess the rhodopsin-vitamin A(1) cycle common to marine elasmobranchs, almost all marine teleosts, and all terrestrial vertebrates so far examined. Yet the anadromous sea lamprey, Petromyzon marinus, possesses primarily the porphyropsin system, like an anadromous teleost. This observation greatly extends the phylogenetic association of vitamin A(2) with the capacity for freshwater existence. Compared with freshwater and anadromous teleosts, the lamprey retina contains the porphyropsin system in extremely low concentration. The remaining eye tissues, like the retina, contain both vitamins A(1) and A(2), the latter greatly predominant. The livers of larval and adult lampreys, however, appear to contain vitamin A(1) alone. This situation also is not without teleost precedent, since the carp and certain anadromous salmonids display similar reversals of vitamin A pattern in the liver and eye tissues.

THE VISUAL ACUITY AND INTENSITY DISCRIMINATION OF DROSOPHILA

Drosophila possesses an inherited reflex response to a moving visual pattern which can be used to measure its capacity for intensity discrimination and its visual acuity at different illuminations. It is found that these two properties of vision run approximately parallel courses as functions of the prevailing intensity. Visual acuity varies with the logarithm of the intensity in much the same sigmoid way as in man, the bee, and the fiddler crab. The resolving power is very poor at low illuminations and increases at high illuminations. The maximum visual acuity is 0.0018, which is 1/1000 of the maximum of the human eye and 1/10 that of the bee. The intensity discrimination of Drosophila is also extremely poor, even at its best. At low illuminations for two intensities to be recognized as different, the higher must be nearly 100 times the lower. This ratio decreases as the intensity increases, and reaches a minimum of 2.5 which is maintained at the highest intensities. The minimum value of ΔI/I for Drosophila is 1.5, which is to be compared with 0.25 for the bee and 0.006 for man. An explanation of the variation of visual acuity with illumination is given in terms of the variation in number of elements functional in the retinal mosaic at different intensities, this being dependent on the general statistical distribution of thresholds in the ommatidial population. Visual acuity is thus determined by the integral form of this distribution and corresponds to the total number of elements functional. The idea that intensity discrimination is determined by the differential form of this distribution—that is, that it depends on the rate of entrance of functional elements with intensity—is shown to be untenable in the light of the correspondence of the two visual functions. It is suggested that, like visual acuity, intensity discrimination may also have to be considered as a function of the total number of elements active at a given intensity.

ON RHODOPSIN IN SOLUTION

1. The properties of rhodopsin in solution have been examined in preparations from marine fishes, frogs, and mammals. 2. The bleaching of neutral rhodopsin in solution includes a photic and at least three thermal ("dark") processes. Thermal reactions account for approximately half the total fall in extinction at 500 mµ. 3. Bleaching has been investigated at various pH's from 3.9 to about 11. With increase in pH the velocity of the thermal components increases rapidly. Though the spectrum of rhodopsin itself is scarcely affected by change in pH, the spectra of all product-mixtures following irradiation are highly pH-labile. 4. The spectrum of pure rhodopsin—or of the rhodopsin chromophore—is fixed within narrow limits. The extinction at 400 mµ lies between 0.20 to 0.32 of that at the maximum. 5. Within the limitations of available data, the spectrum of pure rhodopsin corresponds in form and position with the spectral sensitivity of human rod vision, computed at the retinal surface. 6. The nature of bleaching of rhodopsin in solution, its kinetics, and its significance in the retinal cycle are discussed.

RESPIRATORY EFFECTS UPON THE VISUAL THRESHOLD

Measurements are reported of the effects of respiratory stresses upon the absolute threshold of peripheral (rod) vision. Since subjects were kept wholly dark adapted and the photochemical system of the rods therefore stationary, the changes recorded may be assumed to have originated more centrally. To this degree the measurements provide a quantitative index of central nervous imbalance. Breathing room air or 32 to 36 per cent oxygen at about double the normal rate causes the visual threshold to fall to approximately half the normal value within 5 to 10 minutes. This change is due primarily to alkalosis induced by the hyperventilation, and can be abolished or reversed by adding carbon dioxide to the inspired mixtures. Normal or rapid breathing of 2 per cent carbon dioxide causes no change in threshold; with 5 per cent carbon dioxide the threshold is approximately doubled. Breathing 10 per cent oxygen at the normal rate also approximately doubles the threshold. This effect is compensated in part by rapid breathing. When 10 per cent oxygen is breathed at twice the normal rate the threshold usually falls at first, then slowly rises to supernormal levels. Due primarily to variations in their breathing patterns subjects yield characteristically different responses on sudden exposure to low oxygen tensions with breathing uncontrolled. The threshold may either rise or fall; and on release from anoxia it may rise, or fall to normal or subnormal levels. The threshold adjusts to anoxia rapidly; exposures lasting 5 to 6 hours do not produce greater or more persistent changes than those of much shorter duration.

PIGMENTS OF THE RETINA : II. SEA ROBIN, SEA BASS, AND SCUP

1. Visual purple from the sea robin, sea bass, and scup is almost identical spectroscopically with that from frogs. The interrelations of this pigment with vitamin A and retinene are also the same as in the frog. 2. In strong acids or at pH > 11, the visual yellow of sea robin retinas is converted irreversibly into a pH indicator, yellow in acid and almost colorless in alkaline solution. Unlike neutral visual yellow, the indicator is not removed to form either vitamin A or visual purple. In the ammoniacal retina the reversion of visual yellow itself to purple is accelerated. 3. The combined pigment epithelium and choroid layer in these fishes contain vitamin A, flavine, and an unidentified xanthophyll.

THE DARK ADAPTATION OF RETINAL FIELDS OF DIFFERENT SIZE AND LOCATION

The decrease in threshold shown by the eye during dark adaptation proceeds in two steps. The first is rapid, short in duration, and small in extent. The second is slow, prolonged, and large. The first is probably due to cone function; the second to rod function. In centrally located fields the two parts of adaptation change differently with area. With small, foveal fields the first part dominates and only traces of the second part appear. As the area increases the first part changes a little, while the second part covers an increasing range of intensities and appears sooner in time. Measurements with an annulus field covering only the circumference of a 20° circle show most of the characteristics of a 20° whole field centrally located. Similarly a 2° field located at different distances from the center shows dark adaptation characteristics essentially like those of large centrally located fields whose edges correspond to the position of the central field. Evidently the behavior in dark adaptation of centrally located fields of different size is determined in the main not by area as area, but by the fact that the retina gradually changes in sensitivity from center to periphery, and therefore the larger the field the farther it reaches into peripheral regions of permanently greater sensibility.

CAROTENOIDS AND THE VISUAL CYCLE

1. Carotenoids have been identified and their quantities measured in the eyes of several frog species. The combined pigment epithelium and choroid layer of an R. pipiens or esculenta eye contain about 1γ of xanthophyll and about 4γ of vitamin A. During light adaptation the xanthophyll content falls 10 to 20 per cent. 2. Light adapted retinas contain about 0.2–0.3 γ of vitamin A alone. 3. Dark adapted retinas contain only a trace of vitamin A. The destruction of their visual purple with chloroform liberates a hitherto undescribed carotenoid, retinene. The bleaching of visual purple to visual yellow by light also liberates retinene. Free retinene is removed from the isolated retina by two thermal processes: reversion to visual purple and decomposition to colorless products, including vitamin A. This is the source of the vitamin A of the light adapted retina. 4. Isolated retinas which have been bleached and allowed to fade completely contain several times as much vitamin A as retinas from light adapted animals. The visual purple system therefore expends vitamin A and is dependent upon the diet for its replacement. 5. Visual purple behaves as a conjugated protein in which retinene is the prosthetic group. 6. Vitamin A is the precursor of visual purple as well as the product of its decomposition. The visual processes therefore constitute a cycle.

VISUAL ADAPTATION AND CHEMISTRY OF THE RODS

1. The reality of a chemical cycle proposed to describe the rhodopsin system is tested with dark adaptation measurements. 2. The first few minutes of rod dark adaptation are rapid following short, slower following long irradiation. As dark adaptation proceeds, the slow process grows more prominent, and occupies completely the final stages of adaptation. 3. Light adaptation displays similar duality. As the exposure to light of constant intensity lengthens, the visual threshold rises, and independently the speed of dark adaptation decreases. 4. These results conform with predictions from the chemical equations.

THE VISUAL SYSTEMS OF EURYHALINE FISHES

1. The retinas of all marine fishes so far examined except the Labridae, and of all terrestrial vertebrates contain the rhodopsin system alone; those of fresh water fishes the porphyropsin system alone. In the present paper the visual systems of a number of euryhaline fishes are examined—fishes capable of existence in a wide range of salinities, though usually restricted in spawning either to the sea (catadromous) or to fresh water (anadromous). 2. The retinas of the anadromous salmonids (brook trout, rainbow trout, and chinook salmon) contain mixtures of the rhodopsin and porphyropsin systems, predominantly the latter. The retinas of the catadromous eel and the killifish also contain mixtures of both systems, but in reverse proportions. The retinas of the anadromous white perch and alewife contain the porphyropsin system alone. 3. There is therefore an extensive parallelism between the salinity relations of these animals and the composition of their visual systems. All of them possess predominantly or exclusively the visual system commonly associated with the environment in which the fish spawns. 4. These patterns are fixed genetically, and are to a first approximation independent of the history of the individual. They may represent transitional stages in the evolutionary migration of fishes to and from the sea. The presence of both types of visual system in the retinas of some euryhaline fishes incidentally satisfies one formal requirement of two-component color vision.