In Vitro Assessment of Cardiac Fibroblast Activation at Physiologic Stiffness

Cardiac fibroblasts (CF) are an essential cell type in cardiac physiology, playing diverse roles in maintaining structural integrity, extracellular matrix (ECM) synthesis, and tissue repair. Under normal conditions, these cells reside in the interstitium in a quiescent state poised to sense and respond to injury by synthesizing and secreting collagen, vimentin, hyaluronan, and other ECM components. In response to mechanical and chemical stimuli, these "resident" fibroblasts can undergo a transformation through a continuum of activation states into what is commonly known as a "myofibroblast," in a process critical for injury response. Despite progress in understanding the contribution of fibroblasts to cardiac health and disease, much remains unknown about the signaling mediating this activation, in part owing to technical challenges in evaluating CF function and activation status in vitro. Given their role in monitoring the ECM, CFs are acutely sensitive to stiffness and pressure. High basal activation of isolated CFs is common due to the super-physiologic stiffness of traditional cell culture substrates, making assays dependent on quiescent cells challenging. To overcome this problem, cell culture parameters must be tightly controlled, and the use of dishes coated with biocompatible reduced-stiffness substrates, such as 8-kPa polydimethylsiloxane (PDMS), has shown promise in reducing basal activation of fibroblasts. Here, we describe cell culture protocol for maintaining CF quiescence in vitro to enable a dynamic range for the assessment of activation status in response to fibrogenic stimuli using PDMS-coated coverslips. Our protocol provides a cost-effective tool to study fibroblast signaling and activity, allowing researchers to better understand the underlying mechanisms involved in cardiac fibrosis. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Generation of 8-kPa polydimethylsiloxane (PDMS)/gelatin-coated coverslips for cardiac fibroblast cell culture Basic Protocol 2: Isolation of adult cardiac fibroblasts and plating onto PDMS coverslips Basic Protocol 3: Assessment of cardiac fibroblast activation by α smooth muscle actin (αSMA) immunocytochemistry.

SCI peer health coach influence on self-management with peers: a qualitative analysis

STUDY DESIGN

A process evaluation of a clinical trial.

OBJECTIVES

To describe the roles fulfilled by peer health coaches (PHCs) with spinal cord injury (SCI) during a randomized controlled trial research study called 'My Care My Call', a novel telephone-based, peer-led self-management intervention for adults with chronic SCI 1+ years after injury.

SETTING

Connecticut and Greater Boston Area, MA, USA.

METHODS

Directed content analysis was used to qualitatively examine information from 504 tele-coaching calls, conducted with 42 participants with SCI, by two trained SCI PHCs. Self-management was the focus of each 6-month PHC-peer relationship. PHCs documented how and when they used the communication tools (CTs) and information delivery strategies (IDSs) they developed for the intervention. Interaction data were coded and analyzed to determine PHC roles in relation to CT and IDS utilization and application.

RESULTS

PHCs performed three principal roles: Role Model, Supporter, and Advisor. Role Model interactions included CTs and IDSs that allowed PHCs to share personal experiences of managing and living with an SCI, including sharing their opinions and advice when appropriate. As Supporters, PHCs used CTs and IDSs to build credible relationships based on dependability and reassuring encouragement. PHCs fulfilled the unique role of Advisor using CTs and IDSs to teach and strategize with peers about SCI self-management.

CONCLUSION

The SCI PHC performs a powerful, flexible role in promoting SCI self-management among peers. Analysis of PHC roles can inform the design of peer-led interventions and highlights the importance for the provision of peer mentor training.

Recovery from neuromuscular blockade after either bolus and prolonged infusions of cisatracurium or rocuronium using either isoflurane or propofol-based anesthetics

We examined the recovery characteristics of cisatracurium or rocuronium after bolus or prolonged infusion under either isoflurane or propofol anesthesia. Sixty patients undergoing neurosurgical procedures of at least 5 h were randomized to receive either isoflurane with fentanyl (Groups 1 and 2) or propofol and fentanyl (Groups 3 and 4) as their anesthetic. Groups 1 and 3 received cisatracurium 0.2 mg/kg IV bolus, spontaneously recovered, after which time an infusion was begun. Groups 2 and 4 received rocuronium 0.6 mg/kg IV, spontaneously recovered, and an infusion was begun. Before the end of surgery, the infusion was stopped and recovery of first twitch (T(1)), recovery index, clinical duration, and train-of-four (TOF) recovery was recorded and compared among groups by using appropriate statistical methods. Clinical duration was shorter for rocuronium compared with cisatracurium using either anesthetic. Cisatracurium T(1) 75% recovery after the infusion was shorter with propofol compared with isoflurane. Cisatracurium TOF 75% recovery was similar after either bolus or infusion, but rocuronium TOF 75% recovery after the infusion was delayed. Infusion rates decreased for cisatracurium but remained relatively constant for rocuronium regardless of the anesthetic used. Isoflurane enhances the effect of both muscle relaxants but prolonged cisatracurium recovery more than rocuronium. Of the two muscle relaxants studied, rocuronium's recovery was most affected by length of the infusion. Cisatracurium may be a more desired muscle relaxant for prolonged procedures because recovery was least affected by prolonged infusion.

IMPLICATIONS

This study describes the effect of different anesthetic techniques on the recovery of two different muscle relaxants, cisatracurium and rocuronium, when administered as either a single bolus or prolonged infusion during neurosurgery. This study demonstrates the feasibility of using these relaxants for these prolonged procedures.

Recovery from neuromuscular blockade after either bolus and prolonged infusions of cisatracurium or rocuronium using either isoflurane or propofol-based anesthetics

We examined the recovery characteristics of cisatracurium or rocuronium after bolus or prolonged infusion under either isoflurane or propofol anesthesia. Sixty patients undergoing neurosurgical procedures of at least 5 h were randomized to receive either isoflurane with fentanyl (Groups 1 and 2) or propofol and fentanyl (Groups 3 and 4) as their anesthetic. Groups 1 and 3 received cisatracurium 0.2 mg/kg IV bolus, spontaneously recovered, after which time an infusion was begun. Groups 2 and 4 received rocuronium 0.6 mg/kg IV, spontaneously recovered, and an infusion was begun. Before the end of surgery, the infusion was stopped and recovery of first twitch (T(1)), recovery index, clinical duration, and train-of-four (TOF) recovery was recorded and compared among groups by using appropriate statistical methods. Clinical duration was shorter for rocuronium compared with cisatracurium using either anesthetic. Cisatracurium T(1) 75% recovery after the infusion was shorter with propofol compared with isoflurane. Cisatracurium TOF 75% recovery was similar after either bolus or infusion, but rocuronium TOF 75% recovery after the infusion was delayed. Infusion rates decreased for cisatracurium but remained relatively constant for rocuronium regardless of the anesthetic used. Isoflurane enhances the effect of both muscle relaxants but prolonged cisatracurium recovery more than rocuronium. Of the two muscle relaxants studied, rocuronium's recovery was most affected by length of the infusion. Cisatracurium may be a more desired muscle relaxant for prolonged procedures because recovery was least affected by prolonged infusion.

IMPLICATIONS

This study describes the effect of different anesthetic techniques on the recovery of two different muscle relaxants, cisatracurium and rocuronium, when administered as either a single bolus or prolonged infusion during neurosurgery. This study demonstrates the feasibility of using these relaxants for these prolonged procedures.

Evolution of abstracts presented at the annual scientific meetings of academic emergency medicine

There has been a general trend in medicine towards greater sophistication in research design. In order to assess this trend in emergency medicine we compared the characteristics of abstracts presented at the 1974, 1983, 1989, and 1997 annual scientific meetings of academic emergency medicine. All 870 abstracts were reviewed by 1 of 3 investigators who determined research design attributes using a standardized classification scheme that has good interrater reliability. Over the last 25 years the following trends were noted: more surveys (0% v1% v3% v8%, P = 0.002), more randomized studies (0% v10% v12% v15%, P = 0.05), and more blinded studies (0% v7% v5% v11%, P = 0.01). Tests of statistical significance were reported with increasing frequency (8% v26% v59% v69%, P < 0.001) as were power calculations (0% v0% v1% v3%, P = 0.02). During the study period there were also increases in the median number of authors, proportion of foreign lead authors, and the proportion of studies involving human subjects. These results reflect considerable improvement in the degree of research design sophistication reported in selected abstracts of academic emergency medicine over the study period. Further strategies to assure continued enhancement of emergency medicine research should be explored.

Evolution of abstracts presented at the annual scientific meetings of academic emergency medicine

There has been a general trend in medicine toward greater sophistication in research design. To assess this trend in emergency medicine, we compared the characteristics of abstracts presented at the 1974, 1983, 1989, and 1997 annual scientific meetings of Academic Emergency Medicine. All 870 abstracts were reviewed by 1 of 3 investigators who determined research design attributes using a standardized classification scheme that has good interrater reliability. Over the last 25 years, the following trends were noted: more surveys (0% v1% v3% v8%, P=.002), more randomized studies (0% v10% v12% v15%, P=.05), and more blinded studies (0% v7% v5% v11%, P=.01). Tests of statistical significance were reported with increasing frequency (8% v26% v59% v 69%, P < .001), as were power calculations (0% v0% v1% v3%, P=.02). During the study period, there were also increases in the median number of authors, proportion of foreign lead authors, and the proportion of studies involving human subjects. These results reflect considerable improvement in the degree of research design sophistication reported in selected abstracts of academic emergency medicine over the study period. Further strategies to assure continued enhancement of emergency medicine research should be explored.

Comparison of personal history with patch test results in metal allergy

In order to compare the validity of patient personal history of contact sensitivity to metal alloys with patch test results, 160 patients with hand eczema were patch tested with a standard series according to the ICDRG after a special questionnaire. In 65%, history and patch test results were identical. Seventy-eight (48.8%) patients thought they would be allergic to metal ions, whereas the patch test revealed a positive result in only 21.3% cases. Positive history but negative test was more frequent in women; in the male group, negative history and positive patch test was the most common finding. Although 82 patients had a negative history, the patch test was positive for contact sensitivity to metal allergens in 12 of them. Both false positive patch tests and false negative histories are possible. Since many factors influence a positive patch test, not only the patient's history but also a synopsis of the anamnesis and patch testing will help to achieve the correct diagnosis of metal contact hypersensitivity.

Expression of the genes encoding the rat renal insulin-like growth factor-I system

Insulin-like growth factor-I (IGF-I) modulates renal function, growth, and repair. IGF-I produced in the kidney is one component of the intrarenal IGF-I system comprising the IGF-I receptor (IGF-IR) and six IGF-binding proteins (IGFBP). Because of the physiologic importance of IGF-I and its potential therapeutic properties, the renal sites of mRNA synthesis for IGF-I, IGF-IR, and IGFBP-I through IGFBP-5 were characterized in rat kidney by in situ hybridization. Anatomical heterogeneity was prominent. IGF-I mRNA was present in the thick ascending limb of Henle in the outer medulla, whereas IGF-IR mRNA was diffusely present at low levels throughout the kidney. IGFBP-I mRNA was localized to cells within the distal convoluted tubules as well as the thick ascending limb of Henle. IGFBP-2 mRNA was expressed in glomeruli, medullary ray collecting ducts, pelvic smooth muscle and uroepithelium, and the papilla tip; IGFBP-3 mRNA was localized to the cortical interstitium, whereas IGFBP-4 mRNA was expressed in proximal tubules, medullary ray collecting ducts, and glomeruli. IGFBP-5 was strongly positive throughout the medulla with lesser expression in the distal convoluted tubules and glomeruli. This study highlights the complexity of the intrarenal IGF-I system. The striking heterogeneity of IGFBP gene expression suggests that the various IGFBP may have diverse modulatory effects on the action of IGF-I or discrete effects of their own.

[Successful treatment of panarteritis nodosa with low-dose methotrexate therapy]

We report on a 45-year-old male patient who presented a classic polyarteritis nodosa (PAN). The clinical course extended over 7 years. In spite of 2 years immunosuppressive therapy with azathioprine and methylprednisolone the course was progressive. Low-dose methotrexate therapy was the only treatment that controlled the disease, leading to rapid clinical and histopathological remission. In low concentrations methotrexate acts as an IL-1 inhibitor, and it obviously suppresses the pathogenetic mechanism of PAN.

Validation of a new instrument for determining migraine prevalence: the UCSD Migraine Questionnaire

To provide a reliable instrument for use in large population surveys, we developed a short questionnaire based on existing International Headache Society diagnostic criteria and administered the questionnaire to 50 consecutive patients seeking evaluation at a university-based headache clinic. A single neurologist subsequently examined all patients. Based only on the questionnaires, reviewers scored each patient as having migraine with aura, migraine without aura, or nonmigrainous headache. High predictive validity and low interobserver variability between the examining neurologist and the independent reviewers suggest that the questionnaire may be quite useful as a survey instrument.

Mechanism of action of methotrexate: experimental evidence that methotrexate blocks the binding of interleukin 1 beta to the interleukin 1 receptor on target cells

Interleukin 1, a multifunctional cytokine, plays a central role in inflammatory processes and induction of the immune response. Target cells possess 200-5000 (or more) interleukin 1 receptors per cell, but they exhibit a full biological response when only 1-2% of these receptors are occupied by interleukin 1 alpha or 1 beta. Methotrexate has been reported to be beneficial in several inflammatory and autoimmune diseases. On the other hand, many of these diseases are known to share an overproduction of interleukin 1. It has been demonstrated that methotrexate has no influence on the interleukin 1 synthesis, so we focused our attention on the ability of methotrexate to interfere with the binding of interleukin 1 beta to the interleukin 1 receptor. The experiments were performed on monocytes, lymphocytes and granulocytes using a recombinant human cytokine probe. Methotrexate led to an astonishing decrease in the binding of interleukin 1 beta to the interleukin 1 receptor of peripheral blood cells, whereas methylprednisolone and indomethacin were not inhibitory. The inhibitory effect of methotrexate was dose dependent. An excess of interleukin 1 beta abolished the inhibition of cytokine binding by methotrexate. We also demonstrated that methotrexate does not affect the integrity of the interleukin 1 receptor or of the target cells. Our results demonstrate that methotrexate blocks the interleukin 1 beta-interleukin 1 receptor pathway. Methotrexate is therefore another interleukin 1 inhibitor and a clinically efficient anticytokine.

[Cold agglutinin syndrome after rubella infection]

Cold agglutinins are antibodies against erytrocyte membrane antigens, and are produced primarily or secondarily. We report on the case of a 5 year old girl who developed cold agglutinin disease 3 days after an attack of German measles. Following exposure to cold, appeared blue-red cutaneous manifestations of the fingers, hands cheeks and nose. The clinical manifestations cleared up without any specific therapy. The occurrence of cold agglutinins after German measles is rare. The case report is discussed within the context of reports in the literature.

Characterization of the relation between sodium channels and electrical activity in cultured rat skeletal myotubes: regulatory aspects

The relation among sodium channel density, frequency of electrical activity and maximal rate of rise of the action potential was studied in developing and mature rat skeletal myotubes in culture. The number of tetrodotoxin (TTX)-sensitive Na-channels was determined by measurements of the amount of [3H]saxitoxin (STX) bound to the cultures, and electrical properties were recorded with intracellular microelectrodes. The EC50 for TTX-induced decreases in maximal STX-binding, frequency and rate of rise of action potentials was in the range 8-20 nM. The 3 variables increased in parallel with age in culture to reach peak values at age 7-8 days, and then decreased in parallel until 10-12 days in culture. The age-related increase in Na-channel density was decreased, but not abolished, by prevention of myoblast fusion. Treatment with the Ca2+ ionophore, A23187, down-regulated, and blockade of Ca-channels with verapamil up-regulated the number of Na-channels. Na-channel density was also increased by chronic treatment with TTX and elevated external [K+], which eliminated spontaneous electrical and contractile activity. Parallel effects were observed on frequency and rate of rise of action potentials. Up-regulation of Na-channels was prevented by simultaneous treatment of myotubes with inhibitors of protein synthesis. We conclude that electrical and mechanical activity of cultured myotubes regulate de novo synthesis of Na-channels through alterations in the level of cytosolic Ca2+.

Discharge planning for the mentally disabled

Hepatitis C virus (HCV) is a major cause of chronic liver diseases including steatosis, cirrhosis and hepatocellular carcinoma. Currently, there is no vaccine available for prevention of HCV infection due to high degree of strain variation. The current treatment of care, Pegylated interferon α in combination with ribavirin is costly, has significant side effects and fails to cure about half of all infections. The development of in-vitro models such as HCV infection system, HCV sub-genomic replicon, HCV producing pseudoparticles (HCVpp) and infectious HCV virion provide an important tool to develop new antiviral drugs of different targets against HCV. These models also play an important role to study virus lifecycle such as virus entry, endocytosis, replication, release and HCV induced pathogenesis. This review summarizes the most important in-vitro models currently used to study future HCV research as well as drug design.

Discharge planning for the mentally disabled

Discharge planning is an idiosyncratic process that depends on each patient's needs and situation. Consequently, each mental health professional plays various roles as the process evolves. The most fundamental and pervasive issue in planning for the discharge and placement of the mentally ill patient is balancing the client's need for stability and security against the need for independence and unrestricted functioning. Although the needs and resources relevant to each individual situation must be analyzed, everyone requires some degree of continuity in his or her relationships and in such fundamental aspects of his or her life such as living arrangements and financial security, in order to function well. Stability and consistency are vital for the mentally disabled person, whose very illness is often characterized by severe difficulties with trusting, forming lasting relationships, and an inability to cope with frustrations and problems. Conversely, stability and consistency can translate into overdependence on others or a restricted view of the world that may contribute to overdependence. The discharge planner must maintain a reasonable degree of stability and consistency without totally extinguishing the spark that encourages the degree of risk taking necessary for a normal existence. The discharge planner will also be forced to deal with other issues such as public reactions to the mentally ill and fiscal constraints. The mentally ill have no real constituency to advocate for them; therefore, the services provided for them are often easy targets of a budget crunch. In addition, residences for the mentally ill are difficult to establish because of public attitudes and fears; often communities resist having one developed in their midst. Consequently, many residences are located in impoverished areas where clients are subjected to innumerable obstacles in attempting to live normal, productive lives. The discharge planner also may struggle with the discouragement of repeatedly placing the same patients. Many patients can manage community life for a limited time only before they decompensate and require read-mission, which starts the discharge planning process all over again. Other patients may learn to manipulate the system by getting readmitted when they want respite from the responsibilities of everyday life in the community. Community placement philosophy dictates that, assuming some measure of psychiatric stability, any time spent in the community as opposed to the hospital is advantageous to the patient. Thus readmission rates are not accurate indicators of success or failure in community placement.(ABSTRACT TRUNCATED AT 400 WORDS)

In vitro release of immunoreactive substance P from putative afferent nerve endings in bovine pia arachnoid

The release of substance P-like immunoreactivity was examined using bovine pia arachnoid and its attendant blood vessels in vitro. At concentrations of 20,51, and 100 mM, potassium ions evoked the release of substance P-like immunoreactivity in a dose-dependent manner. The drug capsaicin released substance P at concentrations greater than 10(-8) M. Both potassium- and capsaicin-induced release were abolished by omitting calcium ions from the superfusion buffer. When subjected to separation by reverse phase high performance liquid chromatography, the superfusate from capsaicin perfused tissues contained a peak of immunoreactivity which migrated at the retention time corresponding to substance P. During basal and stimulated states, the percent endogenous substance P released ranged between 0.4-6.5 X 10(-2) and 1.3-11.6 X 10(-2) per minute, rates comparable to those previously reported by others using slices of dorsal horn or spinal cord segments. The immunoreactivity measurable in the conditioned buffer probably reflected release from afferent nerve endings in as much as most of the substance P immunoreactivity in pia arachnoid arises from trigeminal ganglia. Release of substance P, a cerebrovasodilating peptide from perivascular nerve endings in pia arachnoid suggests a possible role for substance P in the pathophysiology of disorders associated with pain of cerebrovascular origin.

Sympathetic nerves protect against stroke in stroke-prone hypertensive rats. A preliminary report

Studies were performed to determine whether sympathetic nerves protect against stroke in hypertensive rats. The superior cervical ganglion was removed on one side in 28 stroke-prone spontaneously hypertensive rats (SHRSP) when the rats were 4 weeks old. The rats were fed Japanese rat chow and 1% saline drinking water. When the rats were 19 weeks old, systolic pressure was 206 +/- 4 mm Hg (mean +/- SE). All rats died between 19 and 23 weeks of age. Microscopic and histological examination demonstrated cerebral hemorrhage in seven rats. All the hemorrhages occurred in the denervated hemispheres. Ischemic cerebral infarctions were found in 13 rats; in 10 rats, the infarcts were only in the denervated hemisphere. Pathological changes of cerebral arteries (hyalinosis, fibrinoid changes, and thrombus formation) were observed primarily in denervated hemispheres. Wall-to-lumen ratio was less in arteries of the denervated hemisphere than in arteries of the innervated hemisphere. These preliminary observations suggest that denervation of cerebral vessels increases susceptibility to stroke and inhibits development of cerebral vascular hypertrophy in SHRSP.

Screening for congenital hypothyroidism in the Republic of Ireland

A national pilot study for detecting congenital hypothyroidism by radioimmunoassay of thyroid-stimulating hormone concentrations in dried blood was incorporated into the newborn screening programme in Ireland on 1 August 1979. The programme has been monitored by a steering committee and follows the guidelines set by the European Society of Paediatric Endocrinologists. During the first 12 months 76 224 infants were screened and 19 cases confirmed, giving an incidence of 1:4012. Fifty infants (0.07%) were recalled for a serum sample, though most of the recalls (31; 0.04%) occurred during the first three months, before the methodology had become established. No case was detected clinically. At recall only three of the 19 affected infants had obvious features, and nine inconspicuous features. Organisation was directed at early diagnosis and treatment, the mean age at beginning treatment being 15 days. These results confirm the efficacy of screening for congenital hypothyroidism and suggest that capital and running costs will be offset by savings in maintenance treatment of untreated patients. Screening does not, however, remove the need for continued vigilance, and clinicians should request thyroid-function tests in any suspected case.

Cerebrospinal fluid immunoglobulins in children

Cerebrospinal fluid (CSF) immunoglobulins were measured in 62 normal children, in 9 children with purulent meningitis, and in 10 children with presumptive viral meningitis. The mean values in normal children were IgA 0, IgM 0, and IgG 0.84 +/- 1.4 mg/100 ml (+/- SD). The mean levels of all CSF immunoglobulins were raised in acute bacterial meningitis and were significantly greater than the levels found in viral meningitis. CSF IgM was 0.16 +/- 0.5 mg/100 ml in viral meningitis compared with 2.64 +/- 2.06 mg/100 ml in bacterial meningitis (P less than 0.01). However, these values overlapped to a considerable extent and, generally, measurement of CSF immunoglobulins did not enhance diagnostic accuracy in this group of children.

Direct and indirect mechanisms of deaggregation by fatty acids in chlorophyll-countaining systems

The ability of an exogenous long-chain unsaturated fatty acid (linolenic acid) to induce changes in the circular dichroism (C.D.) spectra of chlorophyllous systems of various levels of organization is demonstrated and attributed to its deaggregating influence. In the case of chlorophyll in solution (CCl(4) or CCl(4)-hexane), deaggregation is by direct action on the chromophore. Evidence is also given for an indirect mechanism when chlorophyll is attached to protein (e.g., in HP-700 complexes); in this case, deaggregation results from a conformational change in the protein. Interpretations are given for the differences in C.D. spectra of nonmembranous and membranous chlorophyll-containing systems. (The latter include "digitonin-isolated" system I particles, subchloroplast particles obtained by means of sonication, and specially prepared intact chloroplasts.)

The influence of two naturally occurring factors, from the leaves of Ricinus communis, on the fluorescence induction of higher plant chloroplasts and intact algae

Changes in fluorescence induction, brought about by incubation of chloroplasts (Zea mays) in an aqueous extract of Ricinus leaf, have been divided, on the basis of speed of manifestation, into two categories: "fast" changes and "slow" changes (i.e. those observed after 5 min and 1(1/2) hr of incubation, respectively). The former, which include a large increase in the magnitude of the fast component of variable fluorescence and a retardation of decay from maximum to minimum levels of fluorescence, have been ascribed to inhibition of electron transport at a site beyond that of 3-(p-chlorophenyl)-1,1-dimethylurea (CMU)-i.e., towards system I; these changes result from the action of a fraction of the extract consisting of molecules of small size. The latter changes, which include a marked attenuation of the variable part of fluorescence induction, have been associated with system II and may arise from inhibition of electron flow between water and Q or from decrease in number of functional reaction centers; these changes result from the activity of a proteinaceous fraction of the extract, that simultaneously converts the low temperature steady-state emission spectrum of the chloroplasts into a one-banded one, with maximum at 698 nm.

Effects of linolenic acid on system II and system I-associated light induced changes in absorption of chloroplasts

The addition of linolenic acid to chloroplasts and sub-chloroplast particles has pronounced effect on light induced absorption changes. At a concentration of 10-4 M linolenic acid or [LINO] /[CHL] ≈ 2 (on a mole to mole basis) spectral changes associated with System II are diminished to 50 percent. In this same range there is also a small increase in the spectral change ascribed to System I; this increase may reflect the action of linolenic acid in uncoupling phosphorylation. While at [LINO] / [CHL] ≈ 4, light induced absorption changes of System II are completely blocked, there seems to be no inhibition of System I. The effects of linolenic acid on the 515 nm spectral change are interpreted as an increase in the permeability of the thylakoid membrane.