Is the gut microbiota dysbiotic in patients with classical homocystinuria?

Classical homocystinuria (HCU) is characterized by increased plasma levels of total homocysteine (tHcy) and methionine (Met). Treatment may involve supplementation of B vitamins and essential amino acids, as well as restricted Met intake. Dysbiosis has been described in some inborn errors of metabolism, but has not been investigated in HCU. The aim of this study was to investigate the gut microbiota of HCU patients on treatment. Six unrelated HCU patients (males = 5, median age = 25.5 years) and six age-and-sex-matched healthy controls (males = 5, median age = 24.5 years) had their fecal microbiota characterized through partial 16S rRNA gene sequencing. Fecal pH, a 3-day dietary record, medical history, and current medications were recorded for both groups. All patients were nonresponsive to pyridoxine and were on a Met-restricted diet and presented with high tHcy. Oral supplementation of folate (n = 6) and pyridoxine (n = 5), oral intake of betaine (n = 4), and IM vitamin B12 supplementation (n = 4), were reported only in the HCU group. Patients had decreased daily intake of fat, cholesterol, vitamin D, and selenium compared to controls (p < 0.05). There was no difference in alpha and beta diversity between the groups. HCU patients had overrepresentation of the Eubacterium coprostanoligenes group and underrepresentation of the Alistipes, Family XIII UCG-001, and Parabacteroidetes genera. HCU patients and controls had similar gut microbiota diversity, despite differential abundance of some bacterial genera. Diet, betaine, vitamin B supplementation, and host genetics may contribute to these differences in microbial ecology.

Effects of medical food leucine content in the management of methylmalonic and propionic acidemias

PURPOSE OF REVIEW

The current review highlights the varied effects of medical foods high in leucine (Leu) and devoid of valine (Val) and isoleucine (Ile) in the management of methylmalonic acidemia (MMA) and propionic acidemia and cobalamin C (cblC) deficiency, aiming to advance dietary practices.

RECENT FINDINGS

Leu is a key metabolic regulator with a multitude of effects on different organ systems. Recent observational studies have demonstrated that these effects can have unintended consequences in patients with MMA as a result of liberal use of medical foods. The combination of protein restriction and medical food use in MMA and propionic acidemia results in an imbalanced branched-chain amino acid (BCAA) dietary content with a high Leu-to-Val and/or Ile ratio. This leads to decreased plasma levels of Val and Ile and predicts impaired brain uptake of multiple essential amino acids. Decreased transport of methionine (Met) across the blood-brain barrier due to high circulating Leu levels is of particular concern in cblC deficiency in which endogenous Met synthesis is impaired.

SUMMARY

Investigations into the optimal composition of medical foods for MMA and propionic acidemia, and potential scenarios in which Leu supplementation may be beneficial are needed. Until then, MMA/propionic acidemia medical foods should be used judiciously in the dietary management of these patients and avoided altogether in cblC deficiency.

Guidelines for the diagnosis and management of cystathionine beta-synthase deficiency

Cystathionine beta-synthase (CBS) deficiency is a rare inherited disorder in the methionine catabolic pathway, in which the impaired synthesis of cystathionine leads to accumulation of homocysteine. Patients can present to many different specialists and diagnosis is often delayed. Severely affected patients usually present in childhood with ectopia lentis, learning difficulties and skeletal abnormalities. These patients generally require treatment with a low-methionine diet and/or betaine. In contrast, mildly affected patients are likely to present as adults with thromboembolism and to respond to treatment with pyridoxine. In this article, we present recommendations for the diagnosis and management of CBS deficiency, based on a systematic review of the literature. Unfortunately, the quality of the evidence is poor, as it often is for rare diseases. We strongly recommend measuring the plasma total homocysteine concentrations in any patient whose clinical features suggest the diagnosis. Our recommendations may help to standardise testing for pyridoxine responsiveness. Current evidence suggests that patients are unlikely to develop complications if the plasma total homocysteine concentration is maintained below 120 μmol/L. Nevertheless, we recommend keeping the concentration below 100 μmol/L because levels fluctuate and the complications associated with high levels are so serious.

Dietary practices in pyridoxine non-responsive homocystinuria: a European survey

BACKGROUND

Within Europe, the management of pyridoxine (B6) non-responsive homocystinuria (HCU) may vary but there is limited knowledge about treatment practice.

AIM

A comparison of dietetic management practices of patients with B6 non-responsive HCU in European centres.

METHODS

A cross-sectional audit by questionnaire was completed by 29 inherited metabolic disorder (IMD) centres: (14 UK, 5 Germany, 3 Netherlands, 2 Switzerland, 2 Portugal, 1 France, 1 Norway, 1 Belgium).

RESULTS

181 patients (73% >16 years of age) with HCU were identified. The majority (66%; n=119) were on dietary treatment (1-10 years, 90%; 11-16 years, 82%; and >16 years, 58%) with or without betaine and 34% (n=62) were on betaine alone. The median natural protein intake (g/day) on diet only was, by age: 1-10 years, 12 g; 11-16 years, 11 g; and >16 years, 45 g. With diet and betaine, median natural protein intake (g/day) by age was: 1-10 years, 13 g; 11-16 years, 20 g; and >16 years, 38 g. Fifty-two percent (n=15) of centres allocated natural protein by calculating methionine rather than a protein exchange system. A methionine-free l-amino acid supplement was prescribed for 86% of diet treated patients. Fifty-two percent of centres recommended cystine supplements for low plasma concentrations. Target treatment concentrations for homocystine/homocysteine (free/total) and frequency of biochemical monitoring varied.

CONCLUSION

In B6 non-responsive HCU the prescription of dietary restriction by IMD centres declined with age, potentially associated with poor adherence in older patients. Inconsistencies in biochemical monitoring and treatment indicate the need for international consensus guidelines.

Neurologic and neurodevelopmental phenotypes in young children with early-treated combined methylmalonic acidemia and homocystinuria, cobalamin C type

Abnormal neurodevelopment has been widely reported in combined methylmalonic aciduria (MMA) and homocystinuria, cblC type (cblC disease), but neurodevelopmental phenotypes in cblC have not previously been systematically studied. We sought to further characterize developmental neurology in children with molecularly-confirmed cblC. Thirteen children at our center with cblC, born since implementation of expanded newborn screening in New York State, undertook standard-of-care evaluations with a pediatric neurologist and pediatric ophthalmologist. At most recent follow-up (mean age 50 months, range 9-84 months), of twelve children with early-onset cblC, three (25%) had a history of clinical seizures and two (17%) meet criteria for microcephaly. A majority of children had hypotonia and nystagmus. Twelve out of thirteen (92%) underwent neurodevelopmental evaluation (mean age 41 months; range 9-76 months), each child tested with standardized parental interviews and, where possible, age- and disability-appropriate neuropsychological batteries. All patients showed evidence of developmental delay with the exception of one patient with a genotype predictive of attenuated disease and near-normal biochemical parameters. Neurodevelopmental deficits were noted most prominently in motor skills, with relative preservation of socialization and communication skills. Nine children with early-onset cblC underwent magnetic resonance imaging and spectroscopy (MRI/MRS) at mean age of 47 months (range 6-81 months); common abnormalities included callosal thinning, craniocaudally short pons, and increased T2 FLAIR signal in periventricular and periatrial white matter. Our study further characterizes variable neurodevelopmental phenotypes in treated cblC, and provides insights into the etiopathogenesis of disordered neurodevelopment frequently encountered in cblC. Plasma homocysteine and MMA, routinely measured at clinical follow-up, may be poor predictors for neurodevelopmental outcomes. Additional data from large, prospective, multi-center natural history studies are required to more accurately define the role of these metabolites and others, as well as that of other genetic and environmental factors in the etiopathogenesis of the neurologic components of this disorder.

[Clinical management of homocystinuria: case report and review of the literature]

Homocystinuria is a congenital disorder of methyonine metabolism that leads to increased plasmatic, urinary and tissue deposits of methyonine and its main metabolite: homocysteine. Homocysteine deposits are toxic for the skeletal system (osteoporosis), the eyes (lens dislocation), central nervous system (seizures, psychiatric disorders) and also induce vascular damage (stroke and other cardiovascular events). This article reports two patients with homocystinuria in two siblings, followed by a concise review on the therapeutic strategies available for this disorder.

Altered expression of apoA-I, apoA-IV and PON-1 activity in CBS deficient homocystinuria in the presence and absence of treatment: possible implications for cardiovascular outcomes

Classical homocystinuria (HCU) is caused by mutations in cystathionine beta-synthase (CBS) which, if untreated, typically results in cognitive impairment, thromboembolic complications and connective tissue disturbances. Paraoxonase-1 (PON1) and apolipoprotein apoA-I are both synthesized in the liver and contribute to much of the cardioprotective effects of high density lipoprotein. Additionally, apoA-I exerts significant neuro-protective effects that act to preserve cognition. Previous work in a Cbs null mouse model that incurs significant liver injury, reported that HCU dramatically decreases PON1 expression. Conflicting reports exist in the literature concerning the relative influence of homocysteine and cysteine upon apoA-I expression. We investigated expression of PON1 and apoA-I in the presence and absence of homocysteine lowering therapy, in both the HO mouse model of HCU and human subjects with this disorder. We observed no significant change in plasma PON1 paraoxonase activity in either mice or humans with HCU indicating that this enzyme is unlikely to contribute to the cardiovascular sequelae of HCU. Plasma levels of apoA-I were unchanged in mice with mildly elevated homocysteine due to CBS deficiency but were significantly diminished in both mice and humans with HCU. Subsequent experiments revealed that HCU acts to dramatically decrease apoA-I levels in the brain. Cysteine supplementation in HO mice had no discernible effect on plasma levels of apoA-I while treatment to lower homocysteine normalized plasma levels of this lipoprotein in both HO mice and humans with HCU. Our results indicate that plasma apoA-I levels in HCU are inversely related to homocysteine and are consistent with a plausible role for decreased expression of apoA-I as a contributory factor for both cardiovascular disease and cognitive impairment in HCU.

Homocystinuria and oral health. A report of 14 cases

The aim of this study was to explore the oral health in Swedish individuals with the diagnosis of homozygote cystathionine beta synthase-deficient homocystinuria (HC), a rare disorder of amino acid metabolism affecting connective tissue, in which the phenotypic abnormalities include dislocation of the optic lens, skeletal abnormalities, thromboembolic events, and sometimes mental retardation. Further aims were to evaluate the oral findings against previous oral observations in a medical case report, such as high narrow palate, mandibular prognathia, crowding and early eruption of teeth. Every hospital in Sweden was contacted, with the inquiry of patients with diagnosis of HC,which resulted in 14 individuals participating in oral clinical examination. The oral findings evaluated against previous medical case reports showed to be partly in accordance with previous observations. Dental health showed to be compromised in a majority of cases. Together with the fact that methionine restriction (low-protein diet) is involved in the treatment of the condition and might result in a diet high in sugars, this points out the role of regular dental checkups and preventive oral care for individuals suffering from HC. In addition, short dental roots were a finding not previously reported in the literature. All the studied cases had central maxillary incisors with short roots, when compared to reference values used.

Two successful pregnancies in pyridoxine-nonresponsive homocystinuria

Two successful pregnancies are reported in a pyridoxine-nonresponsive woman who was also homozygous for the MTHFR 677C>T polymorphism. Two healthy children were delivered, although there had also been an early miscarriage of an apparently normal fetus in another pregnancy. Management of the patient's homocystine and methionine levels was maintained throughout pregnancy and, in view of the increased thromboembolic risk, anticoagulation therapy was also included in management.

Dietary management of inborn errors of metabolism

Inborn errors of metabolism are individually rare but are an important cause of mortality and morbidity in infants and children. Dietary therapy is the mainstay of treatment in phenylketonuria, maple syrup urine disease, homocystinuria, galactosemia and glycogen storage disease (Type I/III). Some disorders like urea cycle disorders and organic acidurias require dietary modification in addition to other modalities. Certain basic principles of dietary management should be clearly understood for proper management of these disorders. Commercially available diets are very expensive and modification in routine Indian diet may be tried based on content of different nutrients but the desirable fine control is not achieved.

Progressive cerebral edema associated with high methionine levels and betaine therapy in a patient with cystathionine beta-synthase (CBS) deficiency

Cystathionine beta-synthase (CBS) deficiency, the most common form of homocystinuria, is an autosomal recessive inborn error of homocysteine metabolism. Treatment of B6-nonresponsive patients centers on lowering homocysteine and its disulfide derivatives (tHcy) by adherence to a methionine-restricted diet. However, lifelong dietary control is difficult. Betaine supplementation is used extensively in CBS-deficient patients to lower plasma tHcy. With betaine therapy, methionine levels increase over baseline, but usually remain below 1,500 micromol/L, and these levels have not been associated with adverse affects. We report a child with B6-nonresponsive CBS deficiency and dietary noncompliance whose methionine levels reached 3,000 micromol/L on betaine, and who subsequently developed massive cerebral edema without evidence of thrombosis. We investigated the etiology by determining methionine and betaine metabolites in our patient, and several possible mechanisms for her unusual response to betaine are discussed. We conclude that the cerebral edema was most likely precipitated by the betaine therapy, although the exact mechanism is uncertain. This case cautions physicians to monitor methionine levels in CBS-deficient patients on betaine and to consider betaine as an adjunct, not an alternative, to dietary control.

Betaine and homocysteine concentrations in infant formulae and breast milk

BACKGROUND

Early diagnosis and treatment of homocystinuria with methionine-free or low methionine formulae significantly improve prognosis in children found by newborn screening and treated soon after birth. Betaine (Bet) supplementation is also an effective strategy for dietary treatment of homocystinuria. However, previous reports on diet therapy have only examined methionine and cysteine concentrations but not those of Bet and homocysteine (Hcy) in infant diets.

METHODS

We measured Bet and Hcy concentrations in three methionine-free formulae, five infant starter formulae, and 33 samples of human breast milk from 10 mothers.

RESULTS

In methionine-free formulae, Hcy but not Bet was isolated. However, in human breast milk and infant starter formulae, both Bet and Hcy were detected. However, the Bet concentration was not sufficient for the treatment.

CONCLUSIONS

Our study suggests that methionine-free formulae should have Hcy eliminated and be fortified with Bet to the concentration of 150 mg/dL for the treatment of homocystinuria.

Strategies for the treatment of cystathionine beta-synthase deficiency: the experience of the Willink Biochemical Genetics Unit over the past 30 years

Strategies for the treatment of cystathionine beta-synthase (CBS) deficiency include (1) increasing residual enzyme activity by giving pyridoxine in those patients with vitamin responsive variants, (2) reducing the load on the affected pathway with a low methionine diet and supplementing the diet with cysteine; and (3) giving betaine in order to utilise alternative pathways to remove homocyst(e)ine. In our experience of over 30 years in the diagnosis and management of patients with CBS deficiency, a normal outcome can only be achieved in patients diagnosed and treated from infancy. Pyridoxine combined with folic acid prevents further deterioration in pyridoxine responsive patients. Dietary treatment of patients with non-pyridoxine responsive CBS deficiency becomes more difficult outside childhood but since late complications are not uncommon must be continued for life. Betaine can be effective in this group but compliance is often poor.

Nutritional therapy for pregnant women with a metabolic disorder

Nutritional therapy is essential for a normal reproductive outcome in phenylketonuric women. In homocystinuria, fetal outcome is good in women whose disorder is responsive to vitamin B6 therapy and is poor in women whose disorder is unresponsive to therapy. Pregnancy in galactosemia is rare because of the almost universal ovarian dysfunction present in female patients with this disorder. Transplantation of the fertilized ovum is a promising possibility for these women. In women with MSUD, there has been only one case of pregnancy reported to date.

Patients with homocystinuria: high metal concentrations in hair, blood and urine

Patients with homocystinuria excrete a large amount of metal in their urine. Homocysteine similar to penicillamine, administration to methylmercury treated rats resulted in a large amount of urinary methylmercury excretion. These results suggested that the total metal amounts in the whole body of patients with homocystinuria might be decreased. However, actually metal concentrations in hair and plasma of these patients were higher than those of normal controls. High plasma and hair metal levels are not accounted for in patients with homocystinuria. The physiological metal excretory mechanism in which small amounts of metals bind to the small, plasma molecular substances filter through the kidney and emerge in the urine is necessary for reconfirmation. Strongly perturbed metal metabolism exists in the patients with homocystinuria.

Functional and morphological deficits in late-treated patients with homocystinuria: a clinical, electrophysiologic and MRI study

Seven late-treated patients between the ages of 10-30 years suffering from homocystinuria were examined clinically and electrophysiologically; four had MRI. The clinical examination showed extrapyramidal features and slight impairment of proprioception. Electrophysiological evaluation revealed normal results in the acoustic and central motor system; a minor, possibly vitamin B6 related, sensory neuropathy was detected by peripheral conduction studies. MR imaging showed small focal areas of gliosis in the white matter, generalized cortical atrophy in two patients, but only one small cortical infarct. No changes in the basal ganglia were detected. These results support the view that neurological signs and symptoms in patients suffering from homocystinuria are related to morphological findings, as well as pharmacological effects.

[Homocystinuria. A type with vascular thrombosis and factor VII deficiency]

In homocystinuria, thrombosis is frequent (50% of the cases). The authors report a case of cystathionine-synthetase deficiency-induced homocystinuria associated with thrombosis of a common iliac vein. This patient presented with a blood coagulation disorder which was related to severe factor VII deficiency and which was corrected by treatment. Homocystinuria was pyridoxine independent as witnessed by the fact that Brand's reaction remained positive with vitamin B6 therapy and cystathionine. Cystathionine-synthetase activity measured in cultured fibroblasts increased only slightly with pyridoxine therapy. Treatment (Betaine, folic acid, vitamin B 12) induced the disappearance of plasma methionine. Clinically, the patient whose treatment came late in the course of her disease, was only slightly improved. Hypotheses about etiopathogenic mechanisms of this disease are discussed. Difficulties of treatment and diet are reviewed. The relative inefficacy of therapy, even in case with early treatment, makes antenatal diagnosis preferable to neonatal diagnosis.

The dietary management of inborn errors of metabolism

Many inborn errors have now been described that can be treated by alterations in diet. Such treatment requires an understanding of both the biochemistry of the defect and of normal nutritional requirements. The principal strategies are cofactor therapy, steps to prevent accumulation of toxic metabolites and the replacement of essential nutrients that are deficient as a result of the metabolic block. It is essential to make sure that any diet used for more than a brief period is complete and capable of sustaining normal growth and development. The treatment of disorders of carbohydrate and amino acid metabolism including organic acidaemias and disorders of the urea cycle and of fat oxidation are discussed.

Nutrition support of inborn errors of amino acid metabolism

Programs for nutrition support of patients with phenylketonuria, maternal phenylketonuria, branched chain ketoaciduria and vitamin B-6 non-responsive homocystinuria were written in BASIC. These programs plan diets to fill diet prescriptions using natural foods, available amino acid-free or restricted elemental products, milk or infant proprietary formulae and protein-free fat and carbohydrate sources. Emphasis is placed on satisfying the amino acid and protein prescriptions simultaneously. The final semisynthetic formula is evaluated for vitamins, minerals, renal solute load and renal net acid excretion. Fluid requirement is estimated. The paper describes how the conventional protocols are enhanced by computerization and details the requisite calculations.

The natural history of homocystinuria due to cystathionine beta-synthase deficiency

An international questionnaire survey has been conducted to define better the natural history of homocystinuria due to cystathionine beta-synthase deficiency and permit evaluation of treatment. Data were compiled for 629 patients. Among patients not discovered by newborn screening, B6-responsive individuals on the average have significantly better mental capabilities (mean IQ, 79) than do B6-nonresponsive individuals (mean IQ, 57). Time-to-event curves are presented for the other major clinical abnormalities produced by this disease. Each occurred at significantly lower rates in untreated B6-responsive than in untreated B6-nonresponsive patients, as shown by the following examples: (1) dislocation of optic lenses (at age 10, chances of dislocation: 55% and 82%, respectively); (2) initial clinically detected thromboembolic events (at age 15, chances of having had such an event: 12% and 27%, respectively); (3) radiologic detection of spinal osteoporosis (at age 15, chances of such osteoporosis having been detected: 36% and 64%, respectively); and (4) mortality (at age 30, chances of not surviving: 4% and 23%, respectively). Methionine restriction initiated neonatally prevented mental retardation, retarded the rate of lens dislocation, and may have reduced the incidence of seizures. Pyridoxine treatment of late-detected B6-responsive patients retarded the rate of occurrence of initial thromboembolic events. Following 586 surgical procedures, 25 postoperative thromboembolic complications occurred, six of which were fatal. Reproductive histories were reported predominantly for B6-responsive patients. Living offspring of either men or women patients had few abnormalities. The evidence is inconclusive whether untreated maternal cystathionine beta-synthase deficiency leads to excessive fetal loss. Only 13% of patients detected in screening programs of newborns and classified as to B6-responsiveness were B6-responsive, compared to 47% among late-detected patients. Current screening programs that identify neonatal hypermethioninemia may be preferentially failing to detect B6-responsive patients.

[Diet therapy and coenzyme therapy in hereditary metabolic diseases]

A greater number of inherited metabolic disorders can now be treated with special diets or cofactors. Recent progress is illustrated by the example of various hyperphenylalaninaemias (HPHE), of maple syrup urine disease (MSUD) and of various homocystinurias (HCY). Of special importance for the future is a severe embryopathy in infants of mothers with HPHE and its possible prevention by reintroducing a phenylalanine - restricted diet for the mother before conception. Of considerable scientific interest and therapeutic impact is also the treatment of patients with HPHE due to tetrahydrobiopterin deficiency. This consists in substituting the patients' metabolism with this cofactor of phenylalanine hydroxylase as well as with neurotransmitters. Cofactor deficiencies have also been described in MSUD and HCY, and substitution with high doses of thiamine and pyridoxin has been successful. The management of the acute metabolic derangement of neonatal MSUD is a great therapeutic challenge even to experienced metabolic centres. Rational therapy for homocystinurias due to remethylation defects is still being explored. In siblings with methylenetetrahydrofolate reductase deficiency we used leucovorin for the first time and with success.

Homocystinuria (cystathionine synthase deficiency). Results of treatment in late-diagnosed patients

The clinical outcome in 12 late-diagnosed patients with homocystinuria is reported. Three children died: all were mentally damaged and were never treated effectively. Eight children have been treated with pyridoxine--or with a low-methionine diet with supplemental L-cystine--for 2 to 9 years. Follow-up of these patients shows a striking improvement in behaviour and intellectual development in close correlation to the biochemical normalisation. No thromboembolic episodes occurred in adequately treated patients. However, in one child thrombosis of the retinal artery developed during dietary failure. In another patient the characteristic symptoms of an endangiitis obliterans completely disappeared. Both the reversibility and the improvement of some of the main sequelae in homocystinuria emphasize the need to treat all patients, regardless of their age at diagnosis.

Homocystinuria: pathogenetic mechanisms

Homocystinuria with elevated plasma homocysteine and methionine levels is the result of deficient activity of cystathionine synthetase, the enzyme catalyzing conversion of homocysteine to cystathionine. It is inherited as an autosomal recessive trait with a worldwide distribution. The major clinical manifestations result from the elevated plasma homocysteine level. The excitotoxic effect of homocysteic acid accounts for mental retardation and seizures. Interference with collagen cross-linking by sulfhydryl groups of homocysteine causes ectopia lentis and skeletal deformities. Sulfation factor-like effects contribute to disruption of vascular endothelium, which is followed by platelet thrombosis and widespread arterial and venous occlusions. Low methionine homocystinuria, with deficient remethylation of homocysteine, results from deranged vitamin B(12) metabolism and from deficient 5,10-methylene-tetrahydrofolate reductase. Administration of azaribine produces homocystinuria by mechanism not yet elucidated.

American Academy of Pediatrics. Committee on Nutrition: special diets for infants with inborn errors of amino acid metabolism

A sufficient variety of semisynthetic dietary products is now available to permit control of amino acid imbalance in several inborn errors of metabolism. However, they must be used carefully, and their effects monitored closely. Continuing development of products for this type of special diet--to provide a wider variety--is necessary. Regionalization of treatment programs for patients with inborn errors of metabolism is recommended. Metabolic centers which are accumulating experience and have good laboratory support may be the most efficient way of providing adequate treatment for patients with inborn errors of metabolism.

Enhancement of acquistion and performance of level-pressing behavior in rats by an experimental diet

Rats given diets containing jack bean had superior performance during learning and testing of level pressing compared with rats given control diets. To evaluate the factors which might have contributed to the differences in their performance, the testing conditions, testing schedules, and the reinforcement were varied. The results strongly suggested that the rate of learning depended largely on factors inherent within the individual animals. The rats preferred the reinforcement, Noyes pellets, to diets containing jack bean. Therefore the superior performance of rats given diets containing jack bean could be, to a certain extent, due to their motivation to lever press for Noyes pellets. However, there was also evidence suggesting that other factors in jack bean enhanced the behavioral performance of rats when water droplets were used as the reinforcement.

Cystine deficiency during dietotherapy of homocystinemia

Cystine deficiency was inadvertently produced in a boy receiving specific dietary therapy for homocystinuria. This was manifested as a loss in weight, the reappearance of significant amounts of homocystine in the plasma and urine, and the elevation of the plasma methionine level. In addition, there was a significant reduction in the level of cystine in the plasma. This reduction in plasma cystine level differentiates cystine deficiency from loss of biochemical control due to failure to keep the prescribed diet. The addition of cystine to the regime of this child, without any other dietary modification, resulted in a complete remission.