Ventilação oscilatória de alta freqüência em pediatria e neonatologia

Este trabalho teve por objetivo rever a literatura e descrever a utilização da ventilação oscilatória de alta freqüência em crianças e recém-nascidos. Revisão bibliográfica e seleção de publicações mais relevantes sobre ventilação de alta freqüência utilizando as bases de dados MedLine e SciElo publicadas nos últimos 15 anos. As seguintes palavras-chave foram utilizadas: ventilação oscilatória de alta freqüência, ventilação mecânica, síndrome do desconforto respiratório agudo, crianças e recém-nascidos. Descreveu-se o emprego da ventilação oscilatória de alta freqüência em crianças com síndrome do desconforto respiratório agudo, síndrome de escape de ar e doença pulmonar obstrutiva. Avaliou em recém-nascidos, síndrome do desconforto respiratório, displasia broncopulmonar, hemorragia peri-intraventricular, leucoencefalomalácia e extravasamento de ar. Também, abordou a transição da ventilação mecânica convencional para a ventilação de alta freqüência e o manuseio específico da ventilação de alta freqüência quanto à oxigenação, eliminação de gás carbônico, realização de exame radiológico, realização de sucção traqueal e utilização de sedação e bloqueio neuromuscular. Foram abordados o desmame deste modo ventilatório e as complicações. Em crianças maiores a ventilação oscilatória de alta freqüência é uma opção terapêutica, principalmente na síndrome do desconforto respiratório agudo, devendo ser empregada precocemente. Também pode ser útil em casos de síndrome de escape de ar e doença pulmonar obstrutiva. Em recém-nascidos, não há evidências que demonstram superioridade da ventilação oscilatória de alta freqüência em relação à ventilação convencional, sendo a síndrome de escape de ar a única situação clínica em que há evidência de melhores resultados com este modo ventilatório.

Análise de um ciclone semi-estacionário na costa sul do Brasil associado a bloqueio atmosférico

Na primeira semana de maio de 2008, durante quatro dias, um ciclone em superfície permaneceu semi-estacionário na costa da região sul do Brasil. Este sistema foi responsável por chuvas e ventos fortes no Rio Grande do Sul e Santa Catarina, os quais causaram muitos danos (queda de árvores, enchentes e desabamentos). O objetivo deste trabalho é avaliar o processo de formação e entender os mecanismos responsáveis pelo lento deslocamento do ciclone, já que a maioria dos ciclones nesta região possui deslocamento mais rápido. A equação de desenvolvimento de Sutcliffe mostrou que a advecção de vorticidade absoluta ciclônica na média troposfera e a advecção de ar quente na camada entre 1000-500 hPa foram mecanismos importantes para a ciclogênese. Neste período, o intenso aquecimento diabático também contribuiu para a ciclogênese, à medida que se contrapôs ao intenso resfriamento adiabático devido aos movimentos verticais ascendentes. A advecção de vorticidade absoluta ciclônica que favoreceu a ciclogênese esteve associada a um Vórtice Ciclônico em Altos Níveis (VCAN), que se formou numa região de anomalia de vorticidade potencial. O VCAN se manteve semi-estacionário e compôs o setor norte de um bloqueio do tipo dipolo. Tal bloqueio intensificou um anticiclone em superfície, situado a sul/leste do ciclone, o que contribuiu para o ciclone se manter semi-estacionário. O movimento atípico e lento do ciclone para sul, e em alguns períodos para sudoeste, esteve associado com advecções de vorticidade absoluta ciclônica na média troposfera e de ar quente no seu setor sul. Somente quando o bloqueio em níveis médios e a anomalia de vorticidade potencial em níveis médios/altos se enfraqueceram, o ciclone em superfície se afastou da costa sul do Brasil.

Association between neuromuscular tests and kumite performance on the Brazilian Karate National Team

The aim of this study was to verify the relationship of strength and power with performance on an international level karate team during official kumite simulations. Fourteen male black belt karate athletes were submitted to anthropometric data collection and then performed the following tests on two different days: vertical jump test, bench press and squat maximum dynamic strength (1RM) tests. We also tested power production for both exercises at 30 and 60% 1RM and performed a kumite match simulation. Blood samples were obtained at rest and immediately after the kumite matches to measure blood lactate concentration. Karate players were separated by performance (winners vs. defeated) on the kumite matches. We found no significant differences between winners and defeated for strength, vertical jump height, anthropometric data and blood lactate concentration. Interestingly, winners were more powerful in the bench press and squat exercises at 30% 1RM. Maximum strength was correlated with absolute (30% 1RM r = 0.92; 60% 1RM r = 0.63) and relative power (30% 1RM r = 0.74; 60% 1RM r = 0.11, p > 0.05) for the bench press exercise. We concluded that international level karate players' kumite match performance are influenced by higher levels of upper and lower limbs power production.

Neuromuscular activity during bench press exercise performed with and without the preexhaustion method

Brennecke, A, Guimaraees, TM, Leone, R, Cadarci, M, Mochizuki, L, Simao, R, Amadio, AC, and Serrao, J. Neuromuscular activity during bench press exercise performed with and without the preexhaustion method. J Strength Cond Res 23(7): 1933-1940, 2009-The purpose of the present study was to investigate the effects of exercise order on the tonic and phasic characteristics of upper-body muscle activity during bench press exercise in trained subjects. The preexhaustion method involves working a muscle or a muscle group combining a single-joint exercise immediately followed by a multi-joint exercise (e. g., flying exercise followed by bench press exercise). Twelve subjects performed 1 set of bench press exercises with and without the preexhaustion method following 2 protocols (P1-flying before bench press; P2-bench press). Both exercises were performed at a load of 10 repetition maximum (10RM). Electromyography (EMG) sampled at 1 kHz was recorded from the pectoralis major (PM), anterior deltoid (DA), and triceps brachii (TB). Kinematic data (60 Hz) were synchronized to define upward and downward phases of exercise. No significant (p > 0.05) changes were seen in tonic control of PM and DA muscles between P1 and P2. However, TB tonic aspect of neurophysiologic behavior of motor units was significantly higher (p < 0.05) during P1. Moreover, phasic control of PM, DA, and TB muscles were not affected (p > 0.05). The kinematic pattern of movement changed as a result of muscular weakness in P1. Angular velocity of the right shoulder performed during the upward phase of the bench press exercise was significantly slower (p < 0.05) during P1. Our results suggest that the strategies set by the central nervous system to provide the performance required by the exercise are held constant throughout the exercise, but the tonic aspects of the central drive are increased so as to adapt to the progressive occurrence of the neuromuscular fatigue. Changes in tonic control as a result of the muscular weakness and fatigue can cause changes in movement techniques. These changes may be related to limited ability to control mechanical loads and mechanical energy transmission to joints and passive structures.

Sagittal spinal alignment in paraplegics: a new paradigm for the rehabilitation under neuromuscular electrical stimulation

Study design: Radiographic analysis of sagittal spinal alignment of paraplegics in a standing position under surface neuromuscular electrical stimulation (NMES). Objectives: Describing the radiographic parameters of the sagittal spinal alignment of paraplegics going through a rehabilitation program with NMES. Setting: The University Hospital`s Ambulatory (UNICAMP), Campinas, Sao Paulo, Brazil. Methods: Panoramic X-ray images in profile were taken for 10 paraplegics. All patients participated in the rehabilitation program and were able to perform gait through NMES of the femoral quadriceps muscles. The radiographic parameters used for the analysis were the same as those described in the literature for healthy people. The results were didactically organized into three groups: anatomical shape of the spine, morphology and kinetics of the pelvis and spinopelvic alignment. Results: The physiological curvature of the spine in paraplegics showed average values similar to those described in the literature for healthy patients. The inversion of the pelvic tilt and the increase in the sacral slope were defined by the anterior backward rotation of the pelvis. The existing theoretical mathematical formulas that define lumbar lordosis, pelvic incidence and pelvic tilt showed normal values, despite the anterior intense sagittal imbalance. Conclusions: The adaptive posture of the spine in paraplegics standing through the stimulation of the femoral quadriceps does not allow for a neutral sagittal alignment. This novel radiographic detailed description of the various segments of the spine can be of assistance toward the understanding of the global postural control for such subjects. Spinal Cord (2010) 48, 251-256; doi: 10.1038/sc.2009.123; published online 29 September 2009

Neuromuscular activity of BaTX, a presynaptic basic PLA(2) isolated from Bothrops alternatus snake venom

We have previously isolated a Lys49 phospholipase A(2) homolog (BaTX) from Bothrops alternatus snake venom using a combination of molecular exclusion chromatography and reverse phase HPLC and shown its ability to cause neuromuscular blockade. In this work, we describe a one-step procedure for the purification of this toxin and provide further details of its neuromuscular activity. The toxin was purified by reverse phase HPLC and its purity and molecular mass were confirmed by SIDS-PAGE, MALDI-TOF mass spectrometry, amino acid analysis and N-terminal sequencing. BaTX (0.007-1.4 mu M) produced time-dependent, irreversible neuromuscular blockade in isolated mouse phrenic nerve-diaphragm and chick biventer cervicis preparations (time to 50% blockade with 0.35 mu M toxin: 58 +/- 4 and 24 +/- 1 min, respectively; n = 3-8; mean +/- S.E.) without significantly affecting the response to direct muscle stimulation. In chick preparations, contractures to exogenous acetylcholine (55 and 110 mu M) or KCl (13.4 mM) were unaltered after complete blockade by all toxin concentrations. These results, which strongly suggested a presynaptic mechanism of action for this toxin, were reinforced by (1) the inability of BaTX to interfere with the carbachol-induced depolarization of the resting membrane, (2) a significant decrease in the frequency and amplitude of miniature end-plate potentials, and (3) a significant reduction (59 +/- 4%, n=12) in the quantal content of the end-plate potentials after a 60 min incubation with the toxin (1.4 mu M). In addition, a decrease in the organ bath temperature from 37 degrees C to 24 degrees C and/or the replacement of calcium with strontium prevented the neuromuscular blockade, indicating a temperature-dependent effect possibly mediated by enzymatic activity. (C) 2009 Elsevier Inc. All rights reserved.

Electromyographic Evaluation of Neuromuscular Coordination of Subject After Orthodontic Intervention

The aim of this work was to investigate the neuromuscular changes associated with the orthodontic post-treatment using surface electromyography. One hundred (100) young, healthy adults without signs and symptoms of temporomandibular dysfunction (TMD) were divided into two groups: 60 subjects who were undergoing orthodontic intervention (Ortho Group) and 40 subjects who had no orthodontic intervention (Control Group), aged 18-25 years. EMG activity of masseter and temporalis anterior muscle was recorded during two different tests: 1. maximum voluntary clench (MVC) with cotton rolls; and 2. MVC in intercuspal position. In all subjects, both tests were performed with symmetric muscular patterns (more than 85%) and with insignificant latero-deviating of the mandible (lower than 10%). There are no statistically significant differences between the subjects of both groups evaluated. Both groups showed medium index values calculated according to the normal standards established previously.

Animal models for genetic neuromuscular diseases

The neuromuscular disorders are a heterogeneous group of genetic diseases, caused by mutations in genes coding sarcolemmal, sarcomeric, and citosolic muscle proteins. Deficiencies or loss of function of these proteins leads to variable degree of progressive loss of motor ability. Several animal models, manifesting phenotypes observed in neuromuscular diseases, have been identified in nature or generated in laboratory. These models generally present physiological alterations observed in human patients and can be used as important tools for genetic, clinic, and histopathological studies. The mdx mouse is the most widely used animal model for Duchenne muscular dystrophy (DMD). Although it is a good genetic and biochemical model, presenting total deficiency of the protein dystrophin in the muscle, this mouse is not useful for clinical trials because of its very mild phenotype. The canine golden retriever MD model represents a more clinically similar model of DMD due to its larger size and significant muscle weakness. Autosomal recessive limb-girdle MD forms models include the SJL/J mice, which develop a spontaneous myopathy resulting from a mutation in the Dysferlin gene, being a model for LGMD2B. For the human sarcoglycanopahties (SG), the BIO14.6 hamster is the spontaneous animal model for delta-SG deficiency, whereas some canine models with deficiency of SG proteins have also been identified. More recently, using the homologous recombination technique in embryonic stem cell, several mouse models have been developed with null mutations in each one of the four SG genes. All sarcoglycan-null animals display a progressive muscular dystrophy of variable severity and share the property of a significant secondary reduction in the expression of the other members of the sarcoglycan subcomplex and other components of the Dystrophin-glycoprotein complex. Mouse models for congenital MD include the dy/dy (dystrophia-muscularis) mouse and the allelic mutant dy(2J)/dy(2J) mouse, both presenting significant reduction of alpha 2-laminin in the muscle and a severe phenotype. The myodystrophy mouse (Large(myd)) harbors a mutation in the glycosyltransferase Large, which leads to altered glycosylation of alpha-DG, and also a severe phenotype. Other informative models for muscle proteins include the knockout mouse for myostatin, which demonstrated that this protein is a negative regulator of muscle growth. Additionally, the stress syndrome in pigs, caused by mutations in the porcine RYR1 gene, helped to localize the gene causing malignant hypertermia and Central Core myopathy in humans. The study of animal models for genetic diseases, in spite of the existence of differences in some phenotypes, can provide important clues to the understanding of the pathogenesis of these disorders and are also very valuable for testing strategies for therapeutic approaches.

Neuromuscular electrical stimulation improves GLUT-4 and morphological characteristics of skeletal muscle in rats with heart failure

Aim: Changes in skeletal muscle morphology and metabolism are associated with limited functional capacity in heart failure, which can be attenuated by neuromuscular electrical stimulation (ES). The purpose of the present study was to analyse the effects of ES upon GLUT-4 protein content, fibre structure and vessel density of the skeletal muscle in a rat model of HF subsequent to myocardial infarction. Methods: Forty-four male Wistar rats were assigned to one of four groups: sham (S), sham submitted to ES (S+ES), heart failure (HF) and heart failure submitted to ES (HF+ES). The rats in the ES groups were submitted to ES of the left leg during 20 days (2.5 kHz, once a day, 30 min, duty cycle 50%- 15 s contraction/15 s rest). After this period, the left tibialis anterior muscle was collected from all the rats for analysis. Results: HF+ES rats showed lower values of lung congestion when compared with HF rats (P = 0.0001). Although muscle weight was lower in HF rats than in the S group, thus indicating hypotrophy, 20 days of ES led to their recovery (P < 0.0001). In both groups submitted to ES, there was an increase in muscle vessel density (P < 0.04). Additionally, heart failure determined a 49% reduction in GLUT-4 protein content (P < 0.03), which was recovered by ES (P < 0.01). Conclusion: In heart failure, ES improves morphological changes and raises GLUT-4 content in skeletal muscle.

Relative contribution of pre- and post-synaptic effects to the neostigmine-induced recovery of neuromuscular transmission blocked by vecuronium

The relative contribution of the pre- and post-synaptic effects to the neostigmine-induced recovery of neuromuscular transmission blocked by vecuronium was studied. A conjunction of myographical and electrophysiological techniques was employed. The preparation was the sciatic nerve-extensor digitorum longus muscle of the rat, in vitro. The physiological variables recorded were nerve-evoked twitches (generated at 0.1 Hz), tetanic contractions (generated at 50 Hz) and end-plate potentials (epps), generated in trains of 50 Hz. The epps were analyzed in: amplitude of first epp in the train; mean amplitude of the 30th to the 59th epp in the train (epps-plateau); half-decay time of the epp; early tetanic rundown of epps in the train; plateau tetanic rundown of epps in the train; quantal content of the epps and quantal size. In myographical experiments, a concentration of vecuronium was found (0.8 mu m) that affected both twitches and tetanic contractions and a concentration of neostigmine was found (0.048 mu m) that completely restored the twitch affected by vecuronium. The cellular effects of vecuronium and neostigmine, studied alone or in association, in the above-mentioned concentrations, were scrutinized by means of electrophysiological techniques. These showed that vecuronium alone decreased the peak amplitude, the quantal content of epps and the quantal size and reinforced the tetanic rundown of epps. Neostigmine alone increased the peak amplitude, the quantal content and the half-decay time of the epps. When employed in the presence of vecuronium, neostigmine increased both the quantal content of the epps (via a presynaptic effect) and the half-decay time of the epps (via a postsynaptic effect). Seeing the pre- and the post-synaptic effects of neostigmine were of similar magnitude, they permit to conclude that both these effects contributed significantly to the restoration by neostigmine of the neuromuscular transmission blocked by vecuronium.

Differential effects of neuromuscular blockers on twitches and tetani in the isolated rat muscle: a multiple comparison study using simultaneous confidence intervals

In the present work a comparative quantitative evaluation of the differential effects of neuromuscular blockers on twitches and tetani was performed, encompassing: atracurium, cisatracurium, mivacurium, pancuronium, rocuronium and vecuronium. The sciatic nerve-extensor digitorum longus muscle of the rat was used, in vitro. Twitches were evoked at 0.1 Hz and tetani at 50 Hz. The differential effects of the studied compounds on twitches and tetani were statistically compared using simultaneous confidence intervals for the ratios between mean IC(50) for the block of twitches and mean IC(50) for the block of tetani. The results of ratios of mean IC(50) together with their corresponding 95% simultaneous confidence intervals were: vecuronium: 2.5 (1.8-3.5); mivacurium: 3.8 (3.0-4.9); pancuronium: 3.9 (2.0-7.6); rocuronium: 6.1 (3.8-9.9); atracurium: 9.0 (6.4-12.6); cisatracurium: 13.1 (6.0-28.4). Using the criteria that neuromuscular blockers displaying disjunct confidence intervals for the ratios of mean IC(50) differ statistically with regard to differential effects on twitches and tetani, significant differences in ratios of IC(50) were detected in the following cases: vecuronium vs. rocuronium, vs. atracurium and vs. cisatracurium and mivacurium vs: cisatracurium and vs. atracurium. The results show that the magnitude of the differential effects of neuromuscular blockers on twitches and tetani, as evaluated in the present work in the form of ratios of mean IC(50), does not depend on the chemical structure (comparing steroidal and isoquinolinic compounds), but seems to depend on differential pre- and post-synaptic effects of the compounds. It is also suggested that the greater the ability of a compound to block twitches and tetani in a differential manner, the safer is the compound from the clinical anesthesiology viewpoint.

Effect of neuromuscular electrical stimulation and isotonic exercises in flexor and extensor muscles of knee of hemiplegic patients

Aim. To verify the muscular force and resistance to the movement of the flexor and extensor muscles of the knee of patients with spasticity after treatment with neuromuscular electrical stimulation (NMES) and isotonic exercises. Patients and methods. The patients this study were divided into group I (NMES) and group 2 (isotonic exercises). Their muscular torque and resistance to the movement of the flexor and extensor knee muscles were measured by the isokinetic dynamometer and the degree of spasticity by the modified Ashworth scale before and after ten sessions. Results. Alterations in the scores of the modified Ashworth scale were not observed. An increase in the flexor torque in group 1 (p = 0.041) and in group 2 (p = 0.001) was verified. In the passive mode, group 1 presented a reduction of resistance to the flexion movement (p = 0.026), while in group 2, a reduction of resistance to both the flexion (p = 0,029) and extension movements (p = 0.019) was verified. Conclusions. The two therapeutical resources had their efficiency proven only for the increase of the force of the flexor muscles. The resistance to movement, the isotonic exercises were more effective because they promoted a reduction in the resistance of the flexor and extensor knee muscles.

Efeitos cardiorrespiratórios e analgésicos da cetamina por via epidural, por infusão intravenosa contínua ou pela associação de ambas, em cães submetidos à osteossíntese de fêmur

A cetamina tem demonstrado efeito analgésico em doses subanestésicas, além da manutenção da estabilidade dos parâmetros fisiológicos. O estudo objetivou avaliar os efeitos cardiorrespiratórios e a analgesia pós-operatória da cetamina administrada por via epidural, por infusão intravenosa contínua ou pela associação de ambas, em cães submetidos à osteossíntese de fêmur. Foram utilizadas 25 cadelas, hígidas, distribuídas aleatoriamente em quatro grupos: CEP (2mg kg-1 de cetamina associada à lidocaína 2% via epidural), CIV (lidocaína 2% via epidural e 1mg kg-1 de cetamina IV seguido de infusão contínua IV com 100µg kg min-1 da mesma), CIVEP (2mg kg-1 de cetamina associada à lidocaína 2% via epidural e 1mg kg-1 de cetamina IV, seguido de infusão contínua IV com 100µg kg min-1) e CON (anestesia epidural com lidocaína 2%). Avaliaram-se FC, f, PAS, PAM, PAD, T°C, tempo de bloqueio motor e analgesia pós-operatória por meio de escala analógica visual. Houve elevação da FC no CIV e diminuição desse parâmetro no CEP. As pressões arteriais mantiveram-se dentro dos valores fisiológicos e não foram observadas diferenças na f e T°C. O tempo de duração do bloqueio anestésico foi potencializado nos grupos que receberam cetamina epidural, diferindo significativamente em relação ao controle. O tempo para a analgesia resgate não diferiu entre os grupos. Conclui-se que a administração de cetamina pela via epidural, por infusão contínua intravenosa ou pela associação de ambas promoveu estabilidade cardiorrespiratória no período transcirúrgico, porém não foi capaz de prolongar a duração da analgesia pós-operatória em cães submetidos à osteossíntese de fêmur.

Estudo de caso de uma situação atmosférica entre 12 e 19 de setembro de 2008, com algumas características semelhantes ao evento Catarina

Este trabalho apresenta uma análise das condições sinótica e dinâmica associadas ao desenvolvimento do ciclone ocorrido entre 12 e 19 de setembro de 2008, com o objetivo de destacar diferenças e semelhanças com o ambiente em que se inseriu o evento Catarina em março de 2004. As principais semelhanças foram encontradas no padrão sinótico geral: a ocorrência de um padrão típico de bloqueio do tipo dipolo associado à anomalia de vorticidade potencial em altos níveis; cavado em níveis médios com inclinação para oeste; a presença de uma coluna de vorticidade ciclônica desde a superfície até a baixa estratosfera; e, em superfície, o padrão de uma alta ao sul de uma baixa pressão. Apesar das semelhanças no padrão geral, diferenças ocorreram entre os dois eventos que influenciaram na intensidade dos sistemas: o Catarina ocorreu em latitudes mais baixas em relação ao caso de setembro de 2008; o padrão típico de bloqueio associado ao caso de setembro de 2008 durou um dia e meio, enquanto no evento Catarina foi de três dias; a configuração da advecção de temperatura na camada entre 1000-500 hPa favoreceu o deslocamento do evento de setembro de 2008 para leste/sudeste, ao contrário do Catarina, a advecção de ar quente a leste do ciclone foi praticamente suprimida e a tendência de altura geopotencial passou a ser positiva, padrões que impedem o deslocamento do sistema para leste; no caso de setembro de 2008 o padrão da inversão do gradiente meridional de temperatura potencial na superfície de -2,0 unidade de vorticidade potencial (UVP) foi caracterizado pela incursão de uma região alongada de ar quente vinda do equador em direção ao sul e ar frio vinda do sul em direção ao equador, enquanto no caso Catarina a inversão ocorre pelo isolamento de uma bolha de ar frio ao norte e uma bolha de ar quente ao sul, o que pode ter contribuído para maior duração do padrão de bloqueio, pois a dissipação neste caso é dificultada. Sistemas como o Catarina podem ser raros no Atlântico Sul, mas isso não ocorre em relação ao ambiente sinótico em que se formou o Catarina. Para melhor entender o processo atmosférico que levou à formação do Catarina, é necessário realizar experimentos numéricos de sensibilidade para o caso de setembro de 2008 com o objetivo de verificar a possibilidade do ciclone extratropical se tornar um ciclone tropical.

Mechanisms of pigmentation loss in subterranean fishes

Troglobitic (exclusively subterranean) organisms usually present, among their apomorphies related to the subterranean life (troglomorphisms), the regression of eyes and melanic pigmentation. The degree of regression varies among species, from a slight reduction to the complete loss of eyes and dark pigmentation, without a taxonomic correlation. While mechanisms of eye reduction have been intensively investigated in some troglobites such as the Mexican blind tetra characins, genus Astyanax, and the European salamander, Proteus anguinus, few studies have focused on pigmentation. The Brazilian subterranean ichthyofauna distinguishes not only by the species richness (23 troglobitic fishes so far known) but also by the variation in the degree of reduction of eyes and pigmentation. This study focused on Brazilian fishes completely devoid of melanic pigmentation: the characiform Stygichthys typhlops (Characidae) and the siluriforms Ancistrus formoso (Loricariidae), Rhamdiopsis sp.1 (Heptapteridae; from caves in the Chapada Diamantina, Bahia) and Rhamdiopsis sp. 2 (cave in Campo Formoso, Bahia). In order to investigate if such depigmentation is the result of blockage in some step in the melanogenesis, in vitro tests of administration of L-DOPA were done, using caudal-fin fragments extracted from living fish. Except for Rhamdiopsis sp. 2, all the studied species were DOPA(+), i.e., melanin was synthesized after L-DOPA administration. This indicates these fish do have melanophores but they are unable to convert L-tyrosine to L-DOPA. On the other hand, Rhamdiopsis sp. 2, like the albino specimens of Trichomycterus itacarambiensis previously studied (which correspond to one third of the population), are DOPA(-), either because the block of melanin synthesis occurs downstream in melanogenesis, which is probably the case with T. itacarambiensis (monogenic system in view of the phenotypic discontinuity), or because the so-called albinos do no possess melanophores. The physiological loss in the ability to synthesize melanin, apparently caused by different genetic processes in DOPA(+) and in DOPA(-) fishes, may co-exist in subterranean populations with a decrease in the density of melanophores, as observed in the pigmented two thirds of T. itacarambiensis population, a morphological reduction apparently controlled by polygenic systems producing a continuous phenotypic variation.