Fractionated mid-infrared resurfacing

Fractional resurfacing devices thermally alter microscopic treatment columns in the skin, leaving intervening areas between the columns untouched. Because only a fraction of the skin is being modified, untreated areas are able to rapidly repopulate the treatment columns to greatly reduce recovery time and adverse events. Mid-infrared fractional systems have shown improvement in treating photoaging, scars, rhytides, dyschromia, and textural disorders. An additional advantage is that they are safe and effective for the treatment of nonfacial areas such as the neck, chest, and extremities.

Evaluation of the 1,540-nm Erbium:Glass Laser in the Treatment of Inflammatory Facial Acne

BACKGROUND

The erbium:glass laser is approved to treat inflammatory acne on the back.

OBJECTIVE

This aim of this study was to evaluate the use of the 1,540-nm erbium:glass laser in the treatment of moderate to severe inflammatory acne on the face.

METHODS AND MATERIALS

An erbium:glass laser (Aramis, Quantel Medical, Clermont-Ferrand, France) was used to treat 15 patients with moderate to severe acne four times at 2-week intervals. Active lesions were first treated with six pulses at 10 J/cm(2). The entire face was then treated with a single pass using bursts of four pulses at 10 J/cm(2). Sebum measurements were performed. Six patients continued in a double-arm study to determine whether an additional treatment at 6 months would prolong the lesion-free period. Final evaluation was at 9 months. RESULTS At 6-month follow-up, patients rated improvement as 68%, and the mean investigator improvement assessment was 78%. Sebum measurements did not change. No patients required anesthesia, and no side effects were observed. A single retreatment session 6 months after the initial course held clearance at 80% at 9-month follow-up, whereas patients without retreatment had 72% clearance.

CONCLUSION

Treatment of inflammatory facial acne with the 1,540-nm erbium:glass laser is effective and relatively painless. Papules, pustules, and nodules all respond well to therapy. Additional treatment sessions may prolong the lesion-free period, and maintenance therapy should be included as a part of the treatment course.

Plasma skin regeneration technology

Plasma skin regeneration is a novel type of skin rejuvenation technology developed over the last 3 years. Plasma is the fourth state of matter in which electrons are stripped from atoms to form an ionized gas. Although high temperature plasmas have been used in surgery for over a decade, plasma had previously been used as a conduction medium for electric current. Unlike lasers which rely on the principle of selective photothermolysis to deliver heat to specific targets in the skin, plasma technology delivers heat energy directly to tissue upon contact without reliance on skin chromophores. The plasma itself produces controlled thermal damage to the skin surface to elicit changes such as new collagen formation and improvement in photodamaged skin. The technology can be used at varying energies for different depths of effect, from superficial epidermal effects to deeper dermal heating.

Evaluation of the multiple pass, low fluence algorithm for radiofrequency tightening of the lower face

BACKGROUND AND OBJECTIVE

Non-ablative monopolar radiofrequency technology delivers heat to the deep dermis and subdermal layers of the skin to improve facial laxity. The purpose of this study is to evaluate the multiple pass, low fluence treatment algorithm for lower face laxity.

STUDY DESIGN/MATERIALS AND METHODS

Sixty-six subjects with moderate facial laxity were treated with a maximum of 5 passes over the lower face and neck. Treated areas were evaluated using the Leal Laxity Classification System and by independent photographic assessment. Measurements of skin stiffness and energy absorption were taken with the BTC2000 device.

RESULTS

The average treatment level was 62.0 (83 J/cm(2)) with 556 pulses per treatment. At the 6 month follow-up visit, 92% of patients had a measurable improvement in overall appearance. Independent photographic review revealed improvement in 84% of subjects at 6 months. Objective measures utilizing the BTC2000 device demonstrated improvement that diminished with time.

CONCLUSION

The low-fluence, multiple pass technique is an effective algorithm for radiofrequency skin tightening.

Comparison of Stacked Pulses versus Double-Pass Treatments of Facial Acne with a 1,450-nm Laser

BACKGROUND

Although effective as a monotherapy for the treatment of inflammatory acne, the 1,450-nm diode laser is associated with considerable pain at higher fluences.

MATERIALS AND METHODS

Eleven subjects were treated with a 1,450-nm diode laser in a split-face bilateral paired acne study. One-half of the face received a single-pass consisting of stacked double pulses. The other side received a double-pass treatment of single pulses. Settings were 11 J/cm(2) or lower as tolerated with appropriate dynamic cooling device (range 25-35).

RESULTS

The mean pain rating was 5.33 on a 0 to 10 scale on the stacked-pulse treatment side and 5.12 on the double-pass side. Blinded reduction in mean acne lesion counts were 57.6% and 49.8% reduction, respectively. An overall acne scar improvement was seen in 83% of subjects with acne scarring. Transient hyperpigmentation occurred in two patients on the stacked pulse side and completely resolved without sequelae.

CONCLUSIONS

The pulsed 1,450-nm diode laser can be used at lower fluences that elicit less discomfort yet effectively improve inflammatory acne. Stacking pulses appears to render a slightly higher efficacy than the multipass technique. Single-pulse, multiple-pass treatments may have a lower risk of cryogen-induced transient hyperpigmentation compared to standard high fluence techniques.

A Split-Face Comparison Study of Pulsed 532-nm KTP Laser and 595-nm Pulsed Dye Laser in the Treatment of Facial Telangiectasias and Diffuse Telangiectatic Facial Erythema

BACKGROUND AND OBJECTIVES

Pulsed 595 nm and 532 nm lasers can effectively diminish or eliminate facial telangiectasia. We performed a split-face, single-blind, controlled, comparison study in an effort to determine their individual and comparative efficacy.

STUDY DESIGN/MATERIALS AND METHODS

Fifteen patients were treated using a 595-nm PDL on one side of the face and a pulsed 532-nm potassium-titanyl-phosphate (KTP) laser on the other. Each subject was evaluated at 3 weeks after three treatments.

RESULTS

Both devices improved telangiectasia. The 532-nm device, however, was at least as effective or more effective than the 595-nm laser in all subjects. On average, the KTP laser achieved 62% clearing after the first treatment and 85% clearing 3 weeks after the third treatment, compared to 49% and 75% for the PDL, respectively. Seventy-nine percent of KTP laser-treated patients continued to have swelling for greater than 1 day versus 71% of PDL-treated patients. Of those patients who noted persistent erythema for at least 1 day after treatment, 58% noted more erythema on the KTP laser-treated side compared to 8% on the PDL-treated side.

CONCLUSIONS

Both the 595-nm and the 532-nm pulsed lasers are highly effective in the treatment of facial telangiectasia and redness. The 532-nm KTP laser appears to be more effective but causes more swelling and erythema.

Evaluation of Plasma Skin Regeneration Technology in Low-Energy Full-Facial Rejuvenation

OBJECTIVE

To evaluate the use of multiple, low-energy, full-face plasma skin regeneration treatments.

DESIGN

Plasma skin regeneration delivers energy to the skin through plasma pulses induced by passing radiofrequency into nitrogen gas. Single-treatment, high-energy, 1-pass treatments have been demonstrated to achieve good results with an excellent safety profile. Eight volunteers underwent full-face treatments every 3 weeks, for a total of 3 treatments, using energy settings of 1.2 to 1.8 J. Before each subsequent treatment, the quality of regenerated epidermis, the degree of downtime, and erythema were recorded. Full-thickness skin biopsy specimens were obtained from 6 patients before treatment and 90 days following the last treatment. Patients were seen for follow-up 4 days after each treatment and 30 and 90 days after the third treatment.

RESULTS

Three months after treatment, investigators found a 37% reduction in facial rhytids and study participants noted a 68% improvement in overall facial appearance. Reepithelialization was complete in 4 days. Patients assessed erythema to persist an average of 6 days after treatment. Epidermal regeneration from the first treatment was longer than from the following treatments (9 vs 4 and 5 days, respectively). One patient developed localized hyperpigmentation after the first treatment, which resolved by follow-up at day 30. No scarring or hypopigmentation occurred. A histologic evaluation 3 months after treatment revealed a band of new collagen at the dermoepidermal junction with less dense elastin in the upper dermis. The mean depth of new collagen was 72.3 mum.

CONCLUSIONS

Plasma skin regeneration using the multiple low-energy treatment technique allows significant successful treatment of photodamaged facial skin with minimal downtime. Results are comparable to a single high-energy treatment, but with less healing time.

Plasma skin regeneration technology

Plasma skin regeneration (PSR) technology uses energy delivered from plasma rather than light or radiofrequency. Plasma is the fourth state of matter in which electrons are stripped from atoms to form an ionized gas. The plasma is emitted in a millisecond pulse to deliver energy to target tissue upon contact without reliance on skin chromophores. The technology can be used at varying energies for different depths of effect, from superficial epidermal sloughing to deeper dermal heating. With the Portrait PSR device (Rhytec, Inc.) there are three treatment guidelines termed PSR1, PSR2, and PSR3. The PSR1 protocol uses a series of low-energy treatments (1.0,1.2 Joules) spaced 3 weeks apart. The PSR2 protocol uses one high-energy pass (3.0, 4.0 Joules) performed in a single treatment, and the PSR3 protocol uses two high-energy passes (3.0 4.0 Joules) performed in a single treatment. All protocols improve fine lines, textural irregularities, and dyspigmentation; however, skin tightening is probably more pronounced with the high-energy treatments.

Cutaneous fungal infections in the oncology patient: recognition and management

There are two main types of fungal infections in the oncology patient: primary cutaneous fungal infections and cutaneous manifestations of fungemia. The main risk factor for all types of fungal infections in the oncology patient is prolonged and severe neutropenia; this is especially true for disseminated fungal infections. Severe neutropenia occurs most often in leukemia and lymphoma patients exposed to high-dose chemotherapy. Fungal infections in cancer patients can be further divided into five groups: (i) superficial dermatophyte infections with little potential for dissemination; (ii) superficial candidiasis; (iii) opportunistic fungal skin infections with distinct potential for dissemination; (iv) fungal sinusitis with cutaneous extension; and (v) cutaneous manifestations of disseminated fungal infections. In the oncology population, dermatophyte infections (i) and superficial candidiasis (ii) have similar presentations to those seen in the immunocompetent host. Primary cutaneous mold infections (iii) are especially caused by Aspergillus, Fusarium, Mucor, and Rhizopus spp. These infections may invade deeper tissues and cause disseminated fungal infections in the neutropenic host. Primary cutaneous mold infections are treated with systemic antifungal therapy and sometimes with debridement. The role of debridement in the severely neutropenic patient is unclear. In some patients with an invasive fungal sinusitis (iv) there may be direct extension to the overlying skin, causing a fungal cellulitis of the face. Aspergillus, Rhizopus, and Mucor spp. are the most common causes. We also describe the cutaneous manifestations of disseminated fungal infections (v). These infections usually occur in the setting of prolonged neutropenia. The most common causes are Candida, Aspergillus, and Fusarium spp. Therapy is with systemic antifungal therapy. The relative efficacies of amphotericin B, fluconazole, itraconazole, voriconazole, and caspofungin are discussed. Recovery from disseminated fungal infections is unlikely, however, unless the patient's neutropenia resolves.

Primary cutaneous B-cell lymphoma

Primary cutaneous B-cell lymphomas include extranodal marginal zone B-cell lymphoma, follicular lymphoma, large B-cell lymphoma, and, rarely, mantle cell lymphoma. Our purpose in conducting this review was to determine the clinical and behavioral characteristics of primary cutaneous B-cell lymphomas, their relationship to infectious triggers, and therapeutic response. We conducted a retrospective chart review of 23 adult patients presenting to the dermatology clinic at M. D. Anderson Cancer Center with primary cutaneous B-cell lymphoma between January 1999 and May 2003. Primary cutaneous B-cell lymphomas generally present on the head and neck, with the trunk and extremities afflicted to a lesser extent. Patients were found to have serologic evidence of prior infection with Borrelia burgdorferi (n = 10), Helicobacter pylori (n = 5), and Epstein-Barr virus (n = 6). Overall, treatment of primary cutaneous B-cell lymphoma should involve multiple modalities; however, specific treatment aimed at concurrent or suspected infection, particularly B burgdorferi, is a helpful adjunct and may achieve complete remission in a small subset of patients.

Primary cutaneous opportunistic mold infections in a pediatric population

OBJECTIVE

We sought to describe the features of cutaneous opportunistic mold infections in a general pediatric population.

METHODS

Computerized pathology records from Texas Children's Hospital in Houston during the years 1991 to 2000 were used to identify any biopsy specimens of skin diagnosed as having fungus or mold. The corresponding medical records were reviewed to identify cases of cutaneous opportunistic mold infections. Cases were limited to those with histologic confirmation of hyphae within the dermis or extending to the dermis.

RESULTS

A total of 11 cases in neonates and 22 cases in children and adolescents were identified. Prematurity and low birth weight were the major risk factors in the neonatal population. The nonneonatal cases mainly occurred in those with malignancies or undergoing transplantation. Mortality in neonates was 64%, but decreased to 18% in the nonneonatal population.

CONCLUSION

Our overview of cutaneous infection by opportunistic molds in a pediatric population highlights the risk factors, causative organisms, and outcome of this group of infections. Even in the presence of severe compromise of the immune system, children with primary cutaneous mold infections had a favorable outcome with appropriate diagnosis and therapy.

Severe Radiation Dermatitis is Related to Staphylococcus Aureus

Acute radiation dermatitis commonly occurs following local radiation therapy for various cancers and, when severe, may necessitate disruption of treatment. Intense inflammatory reaction may result in a breakdown of the skin's barrier function and accompanying bacterial colonization. Bacterial superantigens may exacerbate inflammation through activation of T-cells and subsequent cytokine release. We report six cases of severe radiation dermatitis in cancer patients. Four of the six grew pathogenic bacteria, and three had psoriasiform or eczematous reactions at distant sites. Both the radiation dermatitis and the distant cutaneous reactions resolved rapidly on a combination of topical steroids and oral plus topical antibiotic therapy. We suggest that staphylococcal superinfection of acute radiodermatitis intensifies the inflammatory process and hinders repair of the epidermal barrier. Patients with acute radiation dermatitis should be investigated for secondary infection. We emphasize the importance of including topical and oral antibiotic therapy in conjunction with topical corticosteroids to eradicate infection as well as hasten repair of the skin's barrier function. These cases are presented to call attention to the role of Staphylococcus aureus in the pathogenesis of severe radiation dermatitis and the need to include appropriate antibiotic therapy based on culture in the management of acute radiation dermatitis.

Trichofolliculoma with Incidental Focal Acantholytic Dyskeratosis

Incidental focal acantholytic dyskeratosis has been described in a variety of cutaneous lesions, including benign and malignant epithelial lesions, fibrohistiocytic lesions, inflammatory lesions, and melanocytic lesions. It has also been observed in follicular lesions such as comedones and ruptured follicles. We report the case of a 47-year-old man with a firm, flesh-colored 2-mm pruritic papule in the sun-exposed area above the left eyebrow. An excisional biopsy was performed, the tissue was processed, and the hematoxylin and eosin slides were evaluated. Microscopic examination showed a dilated cystic cavity filled with keratinous debris and scattered fragments of hair. Smaller secondary follicular structures branched from the primary cyst's walls into the adjacent dermis. Hyperkeratosis, acantholysis, dyskeratosis, and suprabasilar clefts were also focally present. Correlation of the lesion's clinical morphology and microscopic features established a diagnosis of trichofolliculoma with incidental focal acantholytic dyskeratosis. Hence, trichofolliculoma can be added to the list of follicular lesions in which focal acantholytic dyskeratosis may be observed as an incidental microscopic change.

Use of a dental roll coated with flavored viscous lidocaine for nasal mucosal surgery

BACKGROUND

Nasal mucosal surgery may be unpleasant for patients for a variety of reasons. Injection of local anesthetic into this region may be exquisitely tender, and patients may complain of the taste or passage of anesthetic or other secretions down the nasopharynx. In addition the odor of electrocautery may also be disturbing to some patients.

OBJECTIVE

The objective was to decrease patient discomfort during extensive nasal surgery.

METHODS

A dental roll coated with flavored viscous lidocaine may be placed in the nasal cavity 5 min before injecting local anesthetic and left in place during extensive nasal surgery. Flavored lidocaine may also be simply applied to the mucosal surface and will help anesthetize the area as well as mask the odor of electocautery.

RESULTS

We propose that use of a lidocaine-coated dental roll during extensive nasal surgery will reduce the pain of subsequent local anesthetic injections, disguise the taste of anesthetic and other secretions that may drain down the nasopharynx, and help mask the odor of electrocautery.

CONCLUSION

The use of a dental roll coated with flavored viscous lidocaine appears to be a simple way to improve patient comfort during extensive nasal surgery. This form of lidocaine may also be used to improve patient comfort during steel and laser surgery on the oral and nasal mucosas as well as placement of intraoral nerve blocks. Viscous lidocaine can be compounded with flavor at a pharmacy or in the office.

Mohs micrographic surgery for the eradication of phaeohyphomycosis of the hand

BACKGROUND

Phaeohyphomycosis is a rare mycotic infection that is caused by dematiaceous fungi requiring surgical excision or long-term use of oral antifungal agents for treatment.

OBJECTIVE

To report a case of phaeohyphomycosis of the dorsal hand successfully cleared with Mohs micrographic surgery.

METHODS

We performed Mohs micrographic surgery on phaeohyphomycosis of the dorsal hand. The fungus was cleared in three stages of surgery. Permanent processing and special stains of the final stage confirmed eradication of the infection.

RESULTS

The patient remained free of the phaeohyphomycosis, without complications, at the 6-month follow-up.

CONCLUSION

Mohs micrographic surgery is an effective, tissue-sparing technique for the eradication of phaeohyphomycosis, potentially eliminating the need for costly long-term antifungal therapy.

Intravenous immunoglobulin prophylaxis for recurrent Stevens-Johnson syndrome

Human intravenous immunoglobulin has been described as a treatment for patients with Stevens-Johnson syndrome and toxic epidermal necrolysis. We describe the prophylactic use of intravenous immunoglobulin to prevent Stevens-Johnson syndrome in a woman undergoing cardiac catheterization with a previous history of four episodes of Stevens-Johnson after receiving intravenous contrast dye.

In situ bioreduction of technetium and uranium in a nitrate-contaminated aquifer

The potential to stimulate an indigenous microbial community to reduce a mixture of U(VI) and Tc(VII) in the presence of high (120 mM) initial NO3- co-contamination was evaluated in a shallow unconfined aquifer using a series of single-well, push-pull tests. In the absence of added electron donor, NO3-, Tc(VII), and U(VI) reduction was not detectable. However, in the presence of added ethanol, glucose, or acetate to serve as electron donor, rapid NO3- utilization was observed. The accumulation of NO2-, the absence of detectable NH4+ accumulation, and the production of N2O during in situ acetylene-block experiments suggest that NO3- was being consumed via denitrification. Tc(VII) reduction occurred concurrently with NO3- reduction, but U(VI) reduction was not observed until two or more donor additions resulted in iron-reducing conditions, as detected by the production of Fe(II). Reoxidation/remobilization of U(IV) was also observed in tests conducted with high (approximately 120 mM) but not low (approximately 1 mM) initial NO3- concentrations and not during acetylene-block experiments conducted with high initial NO3-. These results suggest that NO3(-)-dependent microbial U(IV) oxidation may inhibit or reverse U(VI) reduction and decrease the stability of U(IV) in this environment. Changes in viable biomass, community composition, metabolic status, and respiratory state of organisms harvested from down-well microbial samplers deployed during these tests were consistent with the conclusions that electron donor additions resulted in microbial growth, the creation of anaerobic conditions, and an increase in activity of metal-reducing organisms (e.g., Geobacter). The results demonstrate that it is possible to stimulate the simultaneous bioreduction of U(VI) and Tc(VII) mixtures commonly found with NO3- co-contamination at radioactive waste sites.

Multicentric reticulohistiocytosis with pulmonary involvement

Multicentric reticulohistiocytosis (MRH) is a rare and possibly devastating systemic disorder characterized by tissue infiltration by histiocytes and multinucleated giant cells. The disease commonly involves the skin, joints, and mucous membranes, with the rare involvement of other organ systems. We describe a patient with MRH presenting with papules and nodules on both hands and a rapidly progressive arthritis who may have had pulmonary involvement of the disease.

Primary hyperoxaluria in a 27-year-old woman

Primary hyperoxaluria is a rare autosomal recessive disorder resulting in precipitation of insoluble oxalate crystals in the joints, kidneys, heart, eyes, and skin. Two thirds of patients have calcium oxalate nephrolithiasis by age 5 years and 80% die of renal failure by age 20 years. Rarely, the disease will present in adulthood, with the onset of symptoms occurring as late as the sixth decade. We present a 27-year-old woman with end-stage renal disease who presented to the dermatology department for the evaluation of a reticular rash shortly after beginning peritoneal dialysis. Associated symptoms included arthralgias and episodic acral cyanosis. Previous kidney and skin biopsy specimens revealed crystalline deposition, however, the diagnosis of primary hyperoxaluria was not entertained until an atrial mass was found to have the same crystalline material. This report reviews primary hyperoxaluria and underscores the importance of recognizing the disease as a cause of renal failure in a patient with livedo reticularis and skin lesions resembling calciphylaxis. Early recognition of the disease is important because combined liver-kidney transplantation may achieve long-term survival.

Morbilliform drug reaction with histologic features of pustular dermatosis associated with bryostatin-1

Bryostatin-1 is a new chemotherapeutic agent that inhibits protein kinase C. The most common side effect and the dose limiting toxicity is myalgia. The cutaneous side effects reported during the phase I and II trials were alopecia, mucositis, nonspecific "rash," "bronzing," and hyperpigmentation in sun exposed areas. No specific acute drug eruptions have been reported. We present the first reported case of a morbilliform drug eruption with histologic features of intraepidermal and subcorneal spongiotic pustules containing eosinophils secondary to bryostatin-1.

Acrokeratoelastoidosis

Acrokeratoelastoidosis is a genodermatosis characterized by firm papules or plaques on the sides of the hands and feet. Although poorly understood, the lesions may result from an abnormality in the secretion or excretion of elastic material by fibroblasts in the dermis. In this report, we will present a patient with this rare condition and review the clinical and histopathologic features, cause, and differential diagnosis.

Perineural invasion of cutaneous malignancies

BACKGROUND

Perineural invasion is an important mode of tumor spread and is associated with increased aggressiveness and a propensity for recurrence among cutaneous malignancies.

OBJECTIVE

To review the pathogenesis, diagnosis, and treatment of cutaneous tumors exhibiting perineural invasion.

METHODS

This article is based on a review of the medical literature concerning tumors with perineural involvement.

RESULTS

This article describes the clinical signs and histologic features of cutaneous malignancies exhibiting perineural involvement.

CONCLUSION

Appropriate patient care mandates consideration of perineural invasion in the evaluation of cutaneous tumors. As the majority of patients present without symptoms of neural involvement, physicians must be vigilant in the search for this type of tumor spread.

Spread monomolecular films of monohydroxy bile acids and their salts: influence of hydroxyl position, bulk pH, and association with phosphatidylcholine

Undissociated dihydroxy bile acids, alone or with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), lie with their long axes parallel to aqueous-lipid interfaces [Fahey, D. A., Carey, M. C., and Donovan, J. M. (1995) Biochemistry 34, 10886-10897]. To test the generality of this orientation, we used an automated Langmuir-Pockels surface balance to examine pressure-molecular area isotherms and dipole moments of insoluble monohydroxy bile acids and their salts, which are sparingly soluble because of their presumed high Krafft points. We studied lithocholic acid (LCA) (the natural 3alpha-OH isomer), glycolithocholic acid (GLCA) (its glycine conjugate), and the semisynthetic isomers, 7alpha-OH- and 12alpha-OH-cholanoic acids with and without POPC, at pH values ranging from 2 to 12. Monolayer collapse pressures increased sigmoidally with ionization, giving apparent pK values of 7.0-8.5 and implying a stronger affinity of the bile salt anions for the interface. At monolayer collapse, the molecular area of LCA was approximately 85 A(2) independent of pH, consistent with the steroid nucleus lying flat. In contrast, the interfacial area of 7-OH-cholanoic acid decreased from approximately 80 A(2) at pH 2 to approximately 40 A(2) above pH 9, consistent with a more vertical orientation and approximating 12-OH-cholanoic acid, which exhibited a molecular area of approximately 45 A(2) at all pH values. All monohydroxy bile acids condensed POPC monolayers more effectively at low than at high (ionized) pH. We conclude that the 3-OH group is crucial for anchoring bile acids and their salts to the aqueous interface, with all monohydroxy species condensing phospholipid membranes regardless of ionization state.

Form of mercury in stream fish exposed to high concentrations of dissolved inorganic mercury

The form of mercury predominating in mercury-contaminated fish from both pristine and industrialized waters in North America and Europe has almost universally been methylmercury. Sunfish (Lepomis auritus) living in a stream contaminated with 0.5-1 micrograms/L dissolved inorganic mercury accumulated greater concentrations of total mercury at headwater sites, where the dissolved mercury concentrations were greatest, than they did at downstream sites. However, despite evidence from laboratory studies that dissolved inorganic mercury is rapidly accumulated by fish without transformation to methylmercury, methylmercury constituted 85% or more of the total mercury concentration in fish at all sites.

Bacterial Communities in Acidic and Circumneutral Streams

The relationship between pH and the abundance and activity of bacteria in streams was examined as part of a study of the effect of acidification on stream communities. Of the bacterial communities examined, the epilithic community appeared to be the most significantly affected by acidification. Microbial biomass, as quantified by measuring the ATP level, on rock surfaces was significantly correlated with pH. Also, bacterial production by the epilithic bacteria, indicated by incorporation of tritiated thymidine into DNA, was always higher at high-pH sites than at low-pH sites of the same stream order and elevation. Bacterioplankton concentrations varied between 0.53 × 10 5 and 9.42 × 10 5 cells · ml −1 in the first- to fourth-order streams examined. The bacterioplankton concentration in one sample from a spring was 0.17 × 10 5 cells · ml −1 . Bacterioplankton concentrations were not correlated with pH but were significantly correlated with seston concentrations. The correlation with seston is a result of increases in particle-associated bacteria at high seston concentrations. The proportion of bacterioplankton attached to particles varied from 0 to 70%. Bacterial numbers and production in the sediments were significantly correlated with the organic content of the sediment rather than with the pH of the overlying water. Thus, reduced abundance and activity of bacteria as a result of acidification could be detected only for the relatively active community on rock surfaces; this community was exposed to the low pH because of the unbuffered nature of its environment.