Reduction in the appearance of facial hyperpigmentation after use of moisturizers with a combination of topical niacinamide and N-acetyl glucosamine: results of a randomized, double-blind, vehicle-controlled trial.

BACKGROUND: Topical niacinamide and N-acetyl glucosamine (NAG) each individually inhibit epidermal pigmentation in cell culture. In small clinical studies, niacinamide-containing and NAG-containing formulations reduced the appearance of hyperpigmentation. OBJECTIVES: To assess the effect of a combination of niacinamide and NAG in a topical moisturizing formulation on irregular facial pigmentation, including specific detection of changes in colour features associated with melanin. METHODS: This was a 10-week, double-blind, vehicle-controlled, full-face, parallel-group clinical study conducted in women aged 40-60 years. After a 2-week washout period, subjects used a daily regimen of either a morning sun protection factor (SPF) 15 sunscreen moisturizing lotion and evening moisturizing cream each containing 4% niacinamide + 2% NAG (test formulation; n = 101) or the SPF 15 lotion and cream vehicles (vehicle control; n = 101). Product-induced changes in apparent pigmentation were assessed by capturing digital photographic images of the women after 0, 4, 6 and 8 weeks of product use and evaluating the images by algorithm-based computer image analysis for coloured spot area fraction, by expert visual grading, and by chromophore-specific image analysis based on noncontact SIAscopy for melanin spot area fraction and melanin chromophore evenness. RESULTS: By all four measures, the niacinamide + NAG formulation regimen was significantly (P < 0.05) more effective than the vehicle control formulation regimen in reducing the detectable area of facial spots and the appearance of pigmentation. CONCLUSIONS: A formulation containing the combination of niacinamide + NAG reduced the appearance of irregular pigmentation including hypermelaninization, providing an effect beyond that achieved with SPF 15 sunscreen.

Preclinical and phase I studies with rhizoxin to apply a pharmacokinetically guided dose-escalation scheme.

BACKGROUND: Rhizoxin is a new macrocyclic lactone isolated from the fungus Rhizopus chinensis which displays broad-spectrum antitumor activity against murine and human tumor xenografts and has activity against a number of vincristine-resistant tumors in vitro and in vivo. PURPOSE: This study describes the preclinical and clinical pharmacology of rhizoxin to apply a pharmacokinetically guided dose-escalation (PGDE) strategy during the phase I trial. METHODS: Rhizoxin was administered by a single intravenous bolus injection to female BALB/c mice over the dose range 7.5-18 mg/m2 from which we derived the dose that was lethal to 10% and 50% of the mice (i.e., LD10 and LD50, respectively). The LD10 was 11.7 +/- 0.7 mg/m2 (mean +/- SD), and the LD50 was 14.7 +/- 0.6 mg/m2. Pharmacokinetic studies were integrated with the toxicity study in female BALB/c mice at one-tenth the LD10, one-half the LD10, and the LD10 (i.e., 1.2, 6, and 12 mg/m2, respectively). From these data, a target area under the plasma drug concentration versus time curve (AUC) (i.e., 40% of the LD10 AUC) was calculated for clinical studies. Phase I studies were initiated at 0.8 mg/m2 (one-tenth the equivalent LD10 in male CD1 mice), with the intent of escalating the dose by an extended factor-of-two method until the target AUC and/or maximum tolerated dose (MTD) was reached. RESULTS: The major drug toxic effects in mice were body weight loss, sluggishness, ataxia, transient changes in hematological parameters, and hematuria. Diarrhea was universal at doses greater than 9 mg/m2, and hind limb paralysis was observed in one of 10 mice, but only at supralethal doses (18 mg/m2). Rhizoxin pharmacokinetics were best described by a two-compartment open model (half-life [t 1/2] alpha = 4.4 minutes +/- 0.9 minute [mean +/- SD], and t 1/2 beta = 84 minutes +/- 20 minutes at 12 mg/m2) and found to be nonlinear with respect to dose. At doses of 1.2, 6, and 12 mg/m2, the respective AUC values were 1.3, 22.4, and 70.6 microM x minute. From these data, a target AUC value of 28 microM x minute (40% of the LD10 AUC) was derived. Rhizoxin was not detectable in patient plasma (less than 5 ng/mL at 0.8 and 1.6 mg/m2), and doses had to be escalated by conventional methods. Myelosuppression was dose limiting in patients: Seven of eight treated at 2.6 mg/m2 experienced World Health Organization grade 3-4 neutropenia, and five of eight developed mucositis. The AUC values at the human MTD (2.6 mg/m2) were in the range of 0.41-1.01 microM x minute, considerably lower than the target AUC of 28 microM x minute. CONCLUSION AND IMPLICATIONS: Although PGDE schemes have been successfully employed for other antitumor agents, this methodology could not be applied during the phase I trial of rhizoxin. PGDE studies in the future may incorporate comparative murine versus human metabolism studies in vitro with phenotyped liver microsomes. It may also be useful to assess the comparative myelotoxicity of a new drug by performing in vitro cytotoxicity studies on mouse and human bone marrow stem cells.

Acute and chronic ultraviolet radiation induction of epidermal ornithine decarboxylase activity in hairless mice.

The effects of acute, multiple, and chronic exposure of hairless mice to ultraviolet radiation (UVR) on induction of epidermal ornithine decarboxylase (ODC) (EC 4.1.1.17) activity were investigated. Acute UVR exposure results in a biphasic time course of induction of epidermal ODC activity. Enzyme activity maxima occur at 3 and 24 h postirradiation. The biphasic time course is observed in two different strains of hairless mice (Skh:HR-1 and Jackson HRS/J) when the UVR source is either UBV fluorescent tubes or a solar simulator. The ratio of 24-h/3-h postirradiation ODC activity increases with increasing UVR dose. UVR induction of ODC activity was not significant below the mouse minimum erythemal dose (MED). The 3- and 24-h ODC activities have similar apparent Kms for ornithine (34 and 50 microM, respectively), and thermal stabilities at 52 degrees C (t1/2 = 23 and 18 min, respectively), and exhibit similar half-lives in vivo (t1/2 = 15 and 18 min, respectively). Multiple UVR exposure experiments showed 24-h ODC activity is sensitive to the preexposure history of the mouse, while 3-h ODC is not. Preexposure of hairless mice to several sub-MED levels of simulated solar radiation (SSR) specifically suppresses induction of 24-h ODC by a follow-up 2 x MED of SSR. Preexposure to a single 2 x MED of SSR specifically enhances induction of 24-h ODC induced by a second 2 x MED of SSR administered 48 h after the first. The 3-h ODC was not significantly affected by either preexposure regimen. Preexposure to a single high or low dose of UVA radiation did not affect epidermal ODC activity nor had an effect on ODC induction by UVB radiation. Several weeks of chronic exposure to UVB radiation elevated basal levels of epidermal ODC substantially (up to 350-fold). In these chronically irradiated mice, exposure to 2 x MED SSR resulted in a further 3.5-fold increase in ODC activity over the elevated basal level. These data reveal novel properties of epidermal cell expression of ODC activity in response to acute and chronic UVR insult. The results provide additional insight into the use of ODC as a marker for skin photodamage.

Phase I and pharmacokinetic study of taxotere (RP 56976) administered as a 24-hour infusion.

N-Debenzoyl-N-tert-butoxycarbonyl-10-deacytyl taxol (Taxotere, RP 56976) is a semisynthetic analogue of taxol, prepared from a noncytotoxic precursor extracted from the needles of the European yew tree (Taxus baccata L.). It has a broad spectrum of antitumor activity against a variety of transplantable tumors in mice. In vitro cytotoxicity assays suggest that it is 2-5-fold more potent than taxol. In this phase I study Taxotere was administered by 24 h i.v. infusion at 3-week intervals. Thirty patients with solid tumors refractory to conventional therapy were treated; 70 courses of Taxotere were administered at doses ranging from 10 to 90 mg/m2. Grade 4 neutropenia and grade 3 mucositis were dose limiting but reversible at 90 mg/m2. The pattern and grade of toxicity at this dose were similar in 3 heavily pretreated patients compared with 7 patients who had received a maximum of one previous chemotherapy regimen. Alopecia occurred at 55 mg/m2 and above. Other mild toxicities included phlebitis, diarrhea, emesis, and sensory peripheral neuropathy, but these were neither dose-limiting nor clearly dose-related. One patient treated at 70 mg/m2 had an anaphylactoid reaction following the second dose of Taxotere. No cardiovascular toxicity was observed. No partial or complete responses were documented. Plasma concentrations of Taxotere were determined by high-performance liquid chromatography, and end-of-fusion levels at the maximum tolerated dose exceeded drug concentrations which are cytotoxic in vitro. The maximum tolerated dose for Taxotere administered as a 24-h infusion is 90 mg/m2.

Phase I and pharmacokinetic study of rhizoxin.

Rhizoxin is a tubulin-binding cytotoxic compound, isolated from the fungus Rhizopus chinensis, with significant antineoplastic activity in several murine and human tumor models. In this Phase I study, the drug was administered by i.v. bolus injection at 3-wk intervals. Twenty-four patients with refractory solid tumors were treated; 60 courses of rhizoxin were given, at doses ranging from 0.8 to 2.6 mg/m2. Grade 3 mucositis, Grade 4 leukopenia, and Grade 3 diarrhea were dose limiting but reversible at 2.6 mg/m2, the maximum tolerated dose for both previously untreated and heavily pretreated patients. Alopecia and moderate discomfort at the injection site occurred at all doses. Other sequelae, including peripheral neuropathy, phlebitis, and nausea and vomiting, were sporadic and mild. Two heavily pretreated patients with recurrent breast cancer had minor responses to rhizoxin, one at 1.6 mg/m2 and the other at 2.6 mg/m2. Plasma concentrations of rhizoxin were measured by high-performance liquid chromatography. The drug was not detectable (less than 5 ng/ml) at doses of 0.8 mg/m2 and 1.6 mg/m2 and was not measurable 10 min after injection at 2.0 mg/m2. At 2.6 mg/m2, there was considerable intersubject variation in the plasma concentration-time profiles; the area under the curve ranged from 0.29 to 0.96 microgram/ml.min. Rhizoxin has shown some clinical activity in this Phase I study, and a dose of 2.0 mg/m2 is recommended for Phase II studies using this schedule.

Phase I clinical and pharmacokinetic study of 3'-deamino-3'-(2-methoxy-4-morpholinyl)doxorubicin (FCE 23762).

Methoxymorpholinyldoxorubicin (FCE 23762) is a novel, highly lipophilic doxorubicin analogue. It possesses potent in vitro and in vivo antitumor activity including efficacy in multidrug-resistant tumor cell lines. It is also metabolically activated in vivo resulting in an 80-fold increase in potency over the parent drug. In this phase I study the drug was administered by i.v. bolus injection at 3-week intervals. Fifty-three patients with refractory solid tumors were treated; 133 courses of FCE 23762 were administered at doses ranging from 30 to 2250 micrograms/m2. The dose limiting toxicity was reversible myelo-suppression (granulocytopenia and thrombocytopenia), demonstrating a delayed nadir and recovery in comparison to doxorubicin. Other toxicities included transient elevation of hepatic transaminases, delayed and prolonged nausea and vomiting, mucositis, anorexia, fatigue, and diarrhea. Heavily pretreated patients demonstrated more myelosuppression than previously untreated patients at 1250 micrograms/m2. No cardiotoxicity was observed. Four objective tumor responses were seen: one complete response in a patient with pelvic recurrence of cervical cancer; one partial response in a patient with cutaneous and lymph gland metastases from head and neck cancer; and two minor responses in patients with liver metastases from colorectal cancer. Plasma concentrations of FCE 23762 and its 13-dihydro metabolite, FCE 26176, were measured in 20 patients at doses > or = 675 micrograms/m2, using HPLC with fluorescence detection. The area under the plasma concentration-time curve ranged from 30 to 80 ng/h/ml; plasma data suggested linear kinetics in the range of tested doses (although there was considerable interpatient variability). The maximum tolerated dose defined in this study using this schedule is 1500 micrograms/m2. A safe phase II dose for previously untreated patients using this schedule is 1250 micrograms/m2; however, this may actually be below the optimal dose for this patient population.

Quinidine as a resistance modulator of epirubicin in advanced breast cancer: mature results of a placebo-controlled randomized trial.

PURPOSE: To evaluate the effect of quinidine, a putative modulator of P-glycoprotein-mediated drug resistance, on the response rate and toxicity profile of epirubicin in patients with advanced breast cancer. PATIENTS AND METHODS: Between 1989 and 1992, 223 eligible patients were randomized in double-blind fashion to receive epirubicin 100 mg/m2 by intravenous (i.v.) bolus and prednisolone 25 mg orally twice daily, along with either placebo or quinidine (250 mg) capsules, taken for 4 days before and 2 days after chemotherapy. Treatment was continued for a maximum of eight courses. RESULTS: Ten eligible patients did not complete the first cycle of treatment. Of the remaining patients, 106 in the placebo arm received 619 courses of treatment, and 107 in the quinidine arm received 612 courses. The median cumulative dose of epirubicin in both arms was 600 mg/m2. The median quinidine level (measured before epirubicin administration in 288 courses) was 5.5 mumol/L; at this concentration, the drug partially reverses anthracycline resistance in multidrug-resistant (MDR) breast carcinoma cells in vitro. There were no statistically significant differences in hematologic or gastrointestinal toxicity between the two arms. The response rate in the placebo arm was 44% (6% complete remission [CR], 38% partial remission [PR]), and in the quinidine arm was 43% (4% CR, 39% PR). Surviving patients have been monitored for a median time of 74 weeks, and there is no significant difference in the overall or progression-free survival between the two arms. The median survival times were 59 weeks for placebo and 47 weeks for quinidine patients. The estimated relative death rate (quinidine/placebo) was 1.2 (P = .247; 95% confidence interval [CI], 0.88 to 1.63). CONCLUSION: Quinidine at this dose does not significantly alter the toxicity profile, response rate, or survival after epirubicin chemotherapy in patients with advanced breast cancer. This may be due to ineffective modulation of P-glycoprotein by quinidine or the lack of expression of mdr-1 in a sufficient proportion of cells in these tumors, or alternative mechanisms underlying resistance to epirubicin.

A Phase I study of capecitabine in combination with oral leucovorin in patients with intractable solid tumors.

Capecitabine (Xeloda) is a novel rationally designed fluoropyrimidine carbamate. It passes through the intestinal mucosal membrane intact and is subsequently activated by a cascade of three enzymes resulting in preferential release of 5-fluorouracil (5-FU) at the tumor site. Preclinical studies indicated an enhancement of the therapeutic index when capecitabine was combined with leucovorin. This Phase I trial was designed to determine the safety profile, maximal tolerated dose, and pharmacokinetic profile of the combination of capecitabine plus a fixed dose of p.o. leucovorin (60 mg/day) during administration to patients with refractory advanced cancers. The intention was to administer both drugs continuously, but the starting dose of capecitabine was also the maximum tolerated dose (1004 mg/m2/day) in six patients treated with this regimen. A cycle of treatment was then redefined as leucovorin and capecitabine given p.o., twice daily for 2 consecutive weeks followed by a 1-week rest period. Capecitabine doses from 1004 mg/m2/day to 2510 mg/m2/day were evaluated with the intermittent schedule over approximately 80 courses in an additional 25 patients. The dose-limiting toxicities that defined the maximum tolerated dose at 2000 mg/m2/day were diarrhea, nausea, vomiting, and palmar plantar erythrodysesthesia. The recommended Phase II dose using this schedule was 1650 mg/m2/day of capecitabine plus leucovorin 60 mg/day. Plasma concentrations of capecitabine, intermediate metabolites, and 5-FU were measured in 26 patients on days 1 and 14 of therapy. The pharmacokinetics of capecitabine were characterized by rapid GI absorption, with Cmax at 1 h, followed by conversion to active drug. The coadministration of leucovorin had no effect on the pharmacokinetics of capecitabine. Two patients with colorectal cancer, both previously treated with 5-FU, had partial responses. Phase II studies have confirmed the promising antitumor activity of this drug, and capecitabine is currently in Phase III evaluation.

Pharmacokinetic and pharmacodynamic evaluation of the glycinamide ribonucleotide formyltransferase inhibitor AG2034.

Glycinamide ribonucleotide formyltransferase (GARFT) is a component of the de novo purine synthesis pathway. AG2034 is a specific inhibitor of GARFT that was designed based on the GARFT crystal structure. In conjunction with Phase I studies at four clinical centers in the United States and United Kingdom, AG2034 pharmacology was evaluated in 54 patients receiving 1-11 mg/m2 AG2034 as a 2-5 min injection. Blood samples were obtained just prior to and 5, 15, 30, and 45 min, and 1, 1.5, 2, 4, 6, 8, 12, 24, 48, 72, and 96 h after bolus injection during course 1. Limited sampling was also performed on course 3. Plasma AG2034 was measured using a sensitive and reproducible ELISA assay. AG2034 demonstrated a trimodal elimination pattern over 24 h, with median half-life (t(1/2))alpha = 8.7 min, t(1/2)beta = 72.6 min, and t(1/2)gamma = 364.2 min. AG2034 systemic clearance ranged from 9.4-144.5 ml/min/m2, and volume of distribution was 1.2-7.6 liters/m2. Course 1 AG2034 area under the concentration versus time curve (AUC) had a linear relationship with dose (r(s) = 0.86). Accumulation of AG2034 was evident, because course 3 AUC was higher than course 1 in 23 of 23 evaluable patients, but was not associated with an increase in erythrocyte AG2034. AG2034 systemic exposure had an impact on toxicity, because course 1 and course 3 AG2034 AUCs were significantly higher for patients with grade III/IV toxicity than patients with less than grade II toxicity (P < 0.001 and P = 0.001 for course 1 and course 3, respectively). This study demonstrates rapid systemic clearance of AG2034 and suggests pharmacokinetic approaches that may minimize patient toxicity and aid the development of this interesting class of anticancer agents.

Topical palmitoyl pentapeptide provides improvement in photoaged human facial skin.

The palmitoyl pentapeptide palmitoyl-lysine-threonine-threonine-lysine-serine (pal-KTTKS) is a synthetic material that was designed as a topical agent to stimulate collagen production and thus provide a skin anti-wrinkle benefit. To determine if pal-KTTKS is effective, the clinical study reported here was conducted. Caucasian female subjects (n = 93, aged 35-55) participated in a 12-week, double-blind, placebo-controlled, split-face, left-right randomized clinical study assessing two topical products: moisturizer control product vs. the same moisturizer product containing 3 ppm pal-KTTKS. Pal-KTTKS was well tolerated by the skin and provided significant improvement vs. placebo control for reduction in wrinkles/fine lines by both quantitative technical and expert grader image analysis. In self-assessments, subjects also reported significant fine line/wrinkle improvements and noted directional effects for other facial improvement parameters.

Effect of topically applied tocopherol on ultraviolet radiation-mediated free radical damage in skin.

Previously, we demonstrated by electron paramagnetic resonance (EPR) spectroscopy that ultraviolet radiation induces free-radical formation in Skh-1 hairless mouse skin. Because free-radical oxidative stress is thought to play a principal role in skin photoaging and cancer, oxidative stress and subsequent photodamage should be decreased by supplementation of skin with antioxidants. Using both the ascorbate free radical and an EPR spin-trapping system to detect short-lived radicals, we evaluated the effect of the topically applied antioxidants tocopherol sorbate, alpha-tocopherol, and tocopherol acetate on ultraviolet radiation-induced free-radical formation. We show that tocopherol sorbate significantly decreases the ultraviolet radiation-induced radical flux in skin. With our chronically exposed mouse model, tocopherol sorbate was also found to be significantly more protective against skin photoaging than alpha-tocopherol and tocopherol acetate. These results extend our previous observations of ultraviolet radiation-induced free-radical generation in skin and indicate the utility of tocopherol sorbate as an antioxidant in providing significant protection against ultraviolet radiation-induced oxidative damage.

Lysozyme binds to elastin and protects elastin from elastase-mediated degradation.

Lysozyme has been shown to be associated with damaged elastic fibers in many tissues and organs. To better characterize this interaction, binding of lysozyme to elastin was studied using solution-based binding assays. Under physiologic conditions, radio-labeled lysozyme bound specifically to elastin in a time- and concentration-dependent manner. Binding was reversible and was inhibited by unlabeled human and hen lysozyme but not by other proteins. Lysozyme had no elastolytic activity as assessed by a standard tritium-release assay, but, importantly, prevented the proteolytic degradation of elastin by human leukocyte elastase, pancreatic elastase, thermolysin, and Pseudomonas elastase. A striking feature of lysozyme's anti-elastase activity was that it did not function in the classical sense of inhibiting directly the enzymatic activity of the protease. Instead, by binding to elastin, lysozyme prevented the protease from interacting with the elastin substrate in ways that normally favor proteolysis. These results show that lysozyme binds to the elastin component of elastic fibers and that this interaction has important biological consequences for elastic fiber degradation. By preventing degradation of elastin, lysozyme can function as an important natural inhibitor that exerts a protective effect on elastic fibers at sites of tissue injury.

Methodological aspects of phase-I studies of novel anticancer agents (review).

In the last 5 years we have performed 14 phase I studies in our department. Eight of these trials involved evaluation of both the clinical and the pharmacokinetic behaviour of novel anti-cancer agents. The remainder investigated various aspects of drug delivery, targetting or resistance modification with existing anti-cancer drugs. In total these studies have involved over 200 patients. In this review article we have drawn upon our experience to suggest guidelines for future studies.

The isolation and identification of cis-diamminedichloroplatinum (ii)-DNA adducts by anion-exchange HPLC and inductively coupled plasma mass-spectrometry.

The adducts produced by the reaction of cis-diamminedichloroplatinum(II) with DNA have previously been isolated and characterised. These adducts may be measured at the cellular level by immunochemical detection but the accuracy of this assay is dependent on the number of adducts per nucleotide. We have developed a novel assay for cisplatin-DNA adducts, utilising an established method in which platinated DNA is digested to form a mixture of nucleotides and adducts; these are then separated by anion exchange HPLC. The number of cisplatin-DNA adducts is determined by measurement of the platinum content of the HPLC fractions by inductively coupled plasma mass spectrometry. The assay has been validated by cochromatography of purified drug-DNA adducts whose identity has been confirmed by NMR. We describe an application of the assay, namely the measurement of in vitro removal of cisplatin-DNA adducts from calf thymus DNA by cell free extracts derived from tumour cell lines. Adduct removal is dependent on both the amount of extract protein and the duration of the reaction. Almost 70% of adducts are removed from 5mug of DNA (drug:nucleotide ratio 0.08) by 80mug of extract. Other potential applications of the assay are discussed.

Angiosarcoma of the penis.

Sarcoma of the penis is rare. We report an angiosarcoma that was essentially an incidental finding, despite the presence of metastatic lesions, in a 46-year-old man who presented with hematemesis and melena. The diagnosis of the primary lesion was confirmed by histology, and the presence of secondary lesions by fine needle aspiration cytology. The patient was given one dose of chemotherapy, but died of a myocardial infarction before being able to receive further treatment. The literature pertaining to this very unusual lesion is discussed.

Chronic ultraviolet radiation-induced increase in skin iron and the photoprotective effect of topically applied iron chelators.

In the skin of albino hairless mice (Skh:HR-1) there is a basal level of non-heme iron. Chronic exposure of mice to sub-erythemal doses of ultraviolet (UV) B radiation results in an increased skin level of non-heme iron. The iron increase may be the result of a UVB radiation-induced increase in vascular permeability, which we measured in vivo with the dye marker Evans Blue. We also observed greater non-heme iron in sun-exposed vs non-exposed body sites of human skin, suggesting that similar events occur in man. Iron may have a role in skin photodamage by participating in formation of reactive oxygen species. These species have been implicated in skin photodamage. It is known that iron can contribute to oxygen radical production by acting catalytically in the formation of species such as hydroxyl radical. While the basal level of skin iron may be available for catalysis, the elevated iron content of UV-exposed skin increases the potential for iron-catalyzed radical production. Topical application of certain iron chelators to Skh albino hairless mice dramatically delayed the onset of UVB radiation-induced skin photodamage. Non-chelating analogs provided no significant protection.

Chronic ultraviolet B radiation-induced biochemical changes in the skin of hairless mice.

Skh:HR-1 hairless mice were irradiated chronically with sub-erythemal doses of UVB radiation, and a number of biochemical parameters in the skin were determined after 6, 12, 18, and 24 wk of exposure. The parameters measured were water, collagen, elastin, and glycosaminoglycan content; collagenase and elastase levels; and Bz-Tyr-OEt (N-benzoyl-L-tyrosine ethyl ester) and BAPNA (alpha-N-benzoyl-DL-arginine-p-nitroanilide) hydrolyzing activities. Data for UVB radiation-exposed and chronological age-matched control mice were compared with respect to unit area and to unit mass of skin. On a unit area of skin basis, UVB radiation exposure increased the level of most parameters. The particular exceptions were collagen and collagenase which remained constant. On a mass of skin basis, though, there is an apparent decrease in collagen content because of the increase in the other skin components. This suggests that there is insufficient collagen in UVB radiation-exposed skin to support the increasing mass of the tissue.

Wavelength dependence of histological, physical, and visible changes in chronically UV-irradiated hairless mouse skin.

Albino hairless mice (Skh: HR-1) exposed chronically to sub-erythemal doses of UV radiation display physical, visible and histological alterations. Using narrow bandwidth radiation covering the UV radiation spectrum from 280-380 nm, the wavelength dependence of these alterations was determined. The wavelength dependence spectra indicate that for all but one parameter measured (skin sagging), UV-B radiation is considerably more efficient than UV-A radiation in producing changes in the skin. However, in natural sunlight there is considerably more UV-A than UV-B radiation, providing the potential for UV-A to have a larger contribution to skin damage than UV-B. This argues in favor of using broad spectrum photoprotective agents to shield the skin adequately from UV-induced aging. The spectra were also used to develop potential associations among events by determining which events occur at similar wavelengths. There seems to be a correspondence between mouse visible skin wrinking (UV-B event) and two histological events: increase in glycosaminoglycans and alteration in collagen. There was no obvious correspondence among UV-A-induced events.

Preparation and characterization of a reconstituted stratum corneum film as a model membrane for skin transport.

A zwitterionic surfactant, 6-eicosyldimethyl ammoniohexanoate (C20AH), completely disaggregates stratum corneum into individual cells. The cells can be cast into a film of reconstituted stratum corneum (RSC). Such films prepared from pig and human skin mimic intact human stratum corneum in microscopic, mechanical, and barrier evaluations. The films are useful as model membranes for skin transport experiments.

Role of protein and calcium in stratum corneum cell cohesion.

The work reported here indicates that protein and calcium have roles in stratum corneum cell cohesion. A zwitterionic surfactant, 6-octadecyldimethyl ammoniohexanoate (C18AH), was found to completely disaggregate pig and human stratum corneum into intact, individual cells. This method of disaggregation provided a tool to determine the role of tissue components in cell cohesion. The C18AH disaggregation of pig and human stratum corneum was accelerated by proteolytic enzyme and ethylenediaminetetraacetate (EDTA). The C18AH disaggregation could be blocked by pretreatment of the stratum corneum with the serine-type proteolytic enzyme inhibitor phenylmethylsulfonyl fluoride (PMSF). The blockage could be overcome by addition of proteolytic enzyme or divalent metal ion chelator. These and other data indicate the importance of protein and calcium in stratum corneum cell cohesion.