Is sugar consumption detrimental to health? A review of the evidence 1995-2006

Many countries set quantitative targets for added sugars, justifying this by expressing concern about the likely impact of sugar on weight control, dental health, diet quality, or metabolic syndrome. This review considers whether current intakes of sugar are harmful to health, and analyses recent literature using a systematic approach to collate, rank, and evaluate published studies from 1995-2006. Results from high quality obesity studies did not suggest a positive association between body mass index and sugar intake. Some studies, specifically on sweetened beverages, highlighted a potential concern in relation to obesity risk, although these were limited by important methodological issues. Diet adequacy appeared to be achieved across sugar intakes of 6 to 20% energy, depending on subject age. Studies on metabolic syndrome reported no adverse effects of sugar in the long-term, even at intakes of 40-50% energy. The evidence for colorectal cancer suggested an association with sugar, but this appeared to have been confounded by energy intake and glycemic load. There was no credible evidence linking sugar with attention-deficit, dementia, or depression. Regarding dental caries, combinations of sugar amount/frequency, fluoride exposure, and food adhesiveness were more reliable predictors of caries risk than the amount of sugar alone. Overall, the available evidence did not support a single quantitative sugar guideline covering all health issues.

Black tea--helpful or harmful? A review of the evidence

OBJECTIVE

To consider whether consumption of black tea has a positive or negative impact on health.

DESIGN

Databases were searched for relevant epidemiological and clinical studies published between 1990 and 2004.

RESULTS

Clear evidence was found for coronary heart disease (CHD), where an intake of > or = 3 cups per day related to risk reduction. The mechanism could involve the antioxidant action of tea polyphenols. While experimental models have suggested that flavonoids attenuated cancer risk, epidemiological studies failed to demonstrate a clear effect for tea, although there is moderate evidence for a slightly positive or no effect of black tea consumption on colorectal cancer. Studies on cancer were limited by sample sizes and insufficient control of confounders. There is moderate evidence suggestive of a positive effect of black tea consumption on bone mineral density although studies were few. There is little evidence to support the effect of tea on dental plaque inhibition but evidence to support the contribution of tea to fluoride intakes and thus theoretical protection against caries. There was no credible evidence that black tea (in amounts typically consumed) was harmful. Normal hydration was consistent with tea consumption when the caffeine content was < 250 mg per cup. A moderate caffeine intake from tea appeared to improve mental performance, although sample sizes were small. There was no evidence that iron status could be harmed by tea drinking unless populations were already at risk from anaemia.

CONCLUSIONS

There was sufficient evidence to show risk reduction for CHD at intakes of > or = 3 cups per day and for improved antioxidant status at intakes of one to six cups per day. A maximum intake of eight cups per day would minimise any risk relating to excess caffeine consumption. Black tea generally had a positive effect on health.

Direct assay for O6-methylguanine-DNA methyltransferase and comparison of detection methods for the methylated enzyme in polyacrylamide gels and electroblots

We describe in detail a direct assay for the substrate-inactivated DNA-repair enzyme, O6-methylguanine-DNA methyltransferase (O6-MT), which measures the transfer of radiolabelled methyl groups from a prepared O6-methylguanine-DNA substrate to the protein fraction of an enzyme-containing cell/tissue extract. This assay, a modification of a previously suggested method for monitoring O6-ethylguanine-DNA repair [Renard, Verly, Mehta & Ludlum (1983) Eur. J. Biochem. 136, 461-467], is sensitive, highly reproducible, accurate and is, as described here and relative to previously published methods, well suited for use with a large number of test samples. We identified two problems with the O6-[Me-3H]methylguanine-DNA substrate used in the present work and in other reported assay: firstly, that of progressively higher assay backgrounds with increasing age of substrate, which was nullified by once-only purification of the double-stranded substrate by hydroxyapatite chromatography; secondly, a substrate of high specific radioactivity (30 Ci/mmol), made with freshly prepared tritiated methylnitrosourea, behaved as a substrate of 5 Ci/mmol when referenced against radiolabelled O6-methylguanine-DNA made with either [3H]- or [14C]-methylnitrosourea at the lower specific radioactivities of 1 Ci/mmol and 61 mCi/mmol respectively. This apparently stemmed from the known instability of high-specific-radioactivity [3H]methylnitrosourea and indicated that an expected increase in sensitivity of the assay does not necessarily result from increasing the specific radioactivity of substrates above approx. 1 Ci/mmol. Although O6-MT was stable to preincubation at 25 degrees C, marked losses of activity were observed at 37 degrees C, and more so at 45 degrees C. Enzyme lability at the higher temperatures was not, however, seen during preincubation in the presence of its substrate. O6-[Me-3H]methylguanine-DNA, which apparently protected O6-MT against thermal inactivation. As previously seen with other human cells and tissues, extracts of human spleen in the present study showed wide interindividual differences in O6-MT specific activity (18-fold), which spanned the range 50-900 fmol/mg of protein. Cultured human lymphoblastoid Jurkat cells contained approx. 57,000 enzyme molecules/cell. Substrate-inactivated [Me-3H]methylated O6-MT was analysed by SDS/PAGE and electroblotting. The different but similarly sized forms of this enzyme that we previously detected in human spleen [Major, Gardner, Carne & Lawley (1990) Nucleic Acids Res. 18, 1351-1359] were clearly resolved by fluorography of electroblots, but only at considerable expense of time. As expected, scintillation counting of the protein extracted from gel slices and linear-wire scanning of enzyme-associated radioactivity on electroblots were quicker methods for detecting the [Me-3H]methylated inactivated O6-MT.

Purification to homogeneity and partial amino acid sequence of a fragment which includes the methyl acceptor site of the human DNA repair protein for O6-methylguanine

DNA repair by O6-methylguanine-DNA methyltransferase (O6-MT) is accomplished by removal by the enzyme of the methyl group from premutagenic O6-methylguanine-DNA, thereby restoring native guanine in DNA. The methyl group is transferred to an acceptor site cysteine thiol group in the enzyme, which causes the irreversible inactivation of O6-MT. We detected a variety of different forms of the methylated, inactivated enzyme in crude extracts of human spleen of molecular weights higher and lower than the usually observed 21-24kDa for the human O6-MT. Several apparent fragments of the methylated form of the protein were purified to homogeneity following reaction of partially-purified extract enzyme with O6-[3H-CH3]methylguanine-DNA substrate. One of these fragments yielded amino acid sequence information spanning fifteen residues, which was identified as probably belonging to human methyltransferase by virtue of both its significant sequence homology to three procaryote forms of O6-MT encoded by the ada, ogt (both from E. coli) and dat (B. subtilis) genes, and sequence position of the radiolabelled methyl group which matched the position of the conserved procaryote methyl acceptor site cysteine residue. Statistical prediction of secondary structure indicated good homologies between the human fragment and corresponding regions of the constitutive form of O6-MT in procaryotes (ogt and dat gene products), but not with the inducible ada protein, indicating the possibility that we had obtained partial amino acid sequence for a non-inducible form of the human enzyme. The identity of the fragment sequence as belonging to human methyltransferase was more recently confirmed by comparison with cDNA-derived amino acid sequence from the cloned human O6-MT gene from HeLa cells (1). The two sequences compared well, with only three out of fifteen amino acids being different (and two of them by only one nucleotide in each codon).

DNA polymorphism analysis of hereditary multiple exostoses in horses

Genomic DNA polymorphisms obtained by restriction fragment-length polymorphism from healthy horses and horses with hereditary multiple exostoses were analyzed. These DNA were digested by 12 restriction enzymes and were hybridized against 6 isotopically labeled oncogene probes. Hybridization was not detected with the viral oncogene, v-ras, which indicated this oncogene was absent in the equine genome. Oncogenes (c-raf-1, c-fes, c-myb, c-myc, and c-sis) were present and had similar hybridization patterns and signal intensities in DNA from healthy horses and horses with hereditary multiple exostoses. Unique and distinct restriction fragment-length polymorphisms were detected with the c-raf-1 probe only in BamHI- and PstI-digested equine DNA.

Segregation and linkage analysis of nine Utah breast cancer pedigrees

The analysis of nine Utah families that were ascertained for clusters of breast cancer cases is reported. Segregation analysis of an inherited susceptibility to breast cancer shows two distinct maximum likelihood solutions that have almost equal likelihood. One model indicates that most females had zero risk for breast cancer, but 10% of the female population had risks much greater than the Utah age-specific incidence rates. The other model indicates that most females have a risk defined by the Utah rates for breast cancer, but a rare dominant gene is segregating for increased susceptibility to breast cancer. Our analysis shows that linkage results under the two models are consistent in sign but not in magnitude. No evidence for linkage was found with the 14 marker loci examined. In addition to demonstrating distortion of linkage results from ignoring sporadic cases, this analysis shows the inherent difficulty of obtaining parameter estimates for segregation analysis when families are ascertained from a cluster of cases.

Hereditary multiple exostosis. A comparative human-equine-epidemiologic study

Hereditary multiple exostosis (HME), a bone tumor first described by Virchow, has been studied over a period of 15 years on a comparative basis. The horse, an excellent biomedical model for this physically deforming multiple bone tumor in man, has been utilized in this study. The etiology, hereditary pattern, potential for malignancy and other aspects of this strange affliction need additional clarification. This in-depth study of 261 individuals from 144 families was compared with that of 55 horses bearing the HME trait, selectively bred and studied over the same period. Important information has been collected and evaluated about this condition that is suspect of being frequently missed diagnostically, with a higher incidence in humans that recognized. Continuing development studies of offspring of the original study participants; sarcomatous transformation monitoring; and recently developed genetic techniques should add to our understanding of this puzzling hereditary condition.

Prevalence and importance of pigmented ocular fundus lesions in Gardner's syndrome

We examined 134 members of 16 families with Gardner's syndrome for pigmented ocular fundus lesions. Of 41 patients with documented Gardner's syndrome, 37 (90.2 percent) had such lesions. The lesions were bilateral in 32 of the patients (78.1 percent) and in 2 of 42 controls (4.8 percent). Twenty (46.5 percent) of 43 first-degree relatives at 50 percent risk for Gardner's syndrome had bilateral pigmented fundus lesions, indicating that they had probably inherited the abnormal gene. The presence of bilateral lesions, multiple lesions (more than four), or both appeared to be a specific (specificity, 0.952) and sensitive (sensitivity, 0.780) clinical marker for Gardner's syndrome. The lesions are probably congenital; they were observed in a three-month-old baby at risk. The multiplicity of the pigmented fundus lesions and their association with diffuse disturbances of the retinal pigment epithelium in the same eye suggest a widespread expression of the abnormal gene in the retinal pigment epithelial cells.

Villous adenoma of the duodenal papilla presenting as necrotizing pancreatitis in a patient with Gardner's syndrome

The majority of patients with Gardner's syndrome and familial polyposis coli develop duodenal adenomatous polyps. Duodenal cancer sometimes arises in this setting, but nonmalignant problems from duodenal polyps have not been described. This report presents a patient with Gardner's syndrome who developed hemorrhagic pancreatitis and was found to have a villous adenoma encasing the pancreatic duct at the duodenal papilla. The case is important because it suggests that patients with polyposis coli may be at risk for significant nonmalignant problems from duodenal polyps, particularly if polyps exhibit villous histology and occur at the duodenal papilla.

Deficient immune function of peripheral blood mononuclear cells from patients with Gardner syndrome

Genetic susceptibility to certain cancers is recognized as a contributor to malignancy in man and experimental animals. Colorectal adenocarcinoma associated with Gardner syndrome is considered to be a hereditary form of cancer in which family members are at increased risk because they inherit an autosomal dominant gene for adenomas of the colorectum. The adenomas, if untreated, transform into adenocarcinoma. The purpose of the current study was to characterize immune function in patients with Gardner syndrome since reports exist of immune defects in patients with other forms of hereditary cancer. An analysis of the ability of lymphocytes from the patients to be stimulated by the T cell mitogens, phytohaemmaglutinin and concanavalin A, revealed severely depressed responses by peripheral blood mononuclear cells (PBMC) from all of the patients studied. A depressed response by patient PBMC to the B cell mitogen, pokeweed mitogen, also was observed but the extent of depression was not statistically significant. Natural killer (NK) cell activity of the patients was studied to determine if a possible genetic defect in this function is associated with Gardner syndrome. PBMC from half of the patients had marginally depressed NK cell function. An enumeration of patient cells revealed a significantly lower ratio of T4 (helper) to T8 (suppressor) T cells, but normal percentages of rosette forming, 7.2 (Ia) positive and Leu 11 positive (NK) cells.

Evaluation of chromosomal diagnosis for hereditary adenomatosis of the colorectum

Hereditary adenomatosis, particularly familial polyposis coli (FPC) and Gardner's syndrome (GS), has been investigated from family pedigrees and chromosomal markers for precancer and cancer. FPC and GS are much alike in phenotypes. Studies are in progress to determine if the two adenomatous diseases are controlled by the same DNA sequence. Chromosome numerical and structural instability is a good diagnostic criterion for hereditary adenomatous diseases where risk factors are already determined to the level of 0.5 probability from pedigree analysis. This has been applied successfully at the pediatric age level to identify family members who carry the gene but have no adenomas in the colorectum. Sister chromatid exchange (SCE) did not distinguish plasma samples from FPC, GS, or solitary adenoma patients form each other or from controls with no adenomas. SCE did distinguish invasive from recurrent and noninvasive cancer. The chromosome #2 polymorphism observed at 2q-21.3 has not been confirmed as a deletion, but is under investigation with more refined methods.

Classification and risk assessment of individuals with familial polyposis, Gardner's syndrome, and familial non-polyposis colon cancer from [3H]thymidine labeling patterns in colonic epithelial cells

A probabilistic analysis has been developed to assist the binary classification and risk assessment of members of familial colon cancer kindreds. The analysis is based on the microautoradiographic observation of [3H]thymidine-labeled epithelial cells in colonic mucosa of the kindred members. From biopsies of colonic mucosa which are labeled with [3H]thymidine in vitro, the degree of similarity of each subject's cell-labeling pattern measured over entire crypts was automatically compared to the labeling patterns of high-risk and low-risk reference populations. Each individual was then presumptively classified and assigned to one of the reference populations, and a degree of risk for the classification was provided. In carrying out the analysis, a linear score was calculated for each individual relative to each of the reference populations, and the classification was based on the polarity of the score difference; the degree of risk was then quantitated from the magnitude of the score difference. When the method was applied to kindreds having either familial polyposis or familial non-polyposis colon cancer, it effectively segregated individuals affected with disease from others at low risk, with sensitivity and specificity ranging from 71 to 92%. Further application of the method to asymptomatic family members believed to be at 50% risk on the basis of pedigree evaluation revealed a biomodal distribution to nearly zero or full risk. The accuracy and simplicity of this approach and its capability of revealing early stages of abnormal colonic epithelial cell development indicate potential for preclinical screening of subjects at risk in cancer-prone kindreds and for assisting the analysis of modes of inheritance.

Upper gastrointestinal polyps in Gardner's syndrome

Upper gastrointestinal polyps have been considered an uncommon finding in patients with Gardner's syndrome and familial polyposis coli. Investigators from Japan, however, have recently reported finding gastric and duodenal polyps in a high percentage of Japanese patients with these conditions. We endoscopically examined 11 affected members of the originally described Gardner's syndrome kindred to determine if upper gastrointestinal polyps also occurred in patients with Gardner's syndrome living in the United States. Six of the patients were found to have numerous small polyps of the gastric fundus and body. Polyp histology in 5 of the 6 patients was consistent with fundic gland hyperplasia. Biopsy specimens from the remaining patient demonstrated normal mucosa only. Another patient with no fundic polyps had a single antral polyp that was an adenoma. Eight patients exhibited small polyps of the duodenum. Biopsy specimens were obtained in 7 of the 8. All polyps biopsied were adenomas. The terminal ileum was examined by endoscopy in 9 of the 11 study patients. All 9 had ileal polyps, but the polyps were adenomas in 6 patients and lymphoid aggregates in 3 patients. The results indicate that upper gastrointestinal polyps are a common pleiotropic manifestation of the genetic defect responsible for Gardner's syndrome.

Failure to demonstrate a chromosome 2 deletion in adenomatous colorectal polyposis patients

A group of researchers recently reported a specific chromosome abnormality consisting of a deletion in the long arm (q) of chromosome 2 in patients with adenomatous colorectal polyposis. Using a high resolution chromosome banding technique and a blind study design, the authors karyotyped two patients with Gardner syndrome, two patients with familial polyposis, and four normal controls. No deletion was found in chromosome 2.

Inherited susceptibility to retrovirus-induced transformation of Gardner syndrome cells

Skin fibroblasts from patients with Gardner syndrome (GS), those with familial polyposis coli (FPC), and spouse or unrelated controls were karyotyped and tested for various growth properties including susceptibility to transformation by viral or chemical agents. Our results indicated that based on the higher susceptibility to retrovirus-induced transformation and chromosomal aneuploidy, the GS and FPC cells could be distinguished from those of the general population with more than 70% accuracy. However, much work is in order before any biological assay can be used for clinical diagnosis of GS or FPC patients.

The use of a tumor promoter for the detection of individuals with the Gardner syndrome

The effects of the tumor promoter 12-O-tetradecnoyl phorbol-13-acetate (TPA) on the proliferation out of cultured skin fibroblasts (SF) obtained from 21 individuals representing a single pedigree of the Gardner variant of hereditary adenomatosis of the colon and rectum (ACR) were analyzed. SF from both gene-carriers and normal individuals displayed an unusual biphasic dose-response (concaved upward), but the latter were considerably more sensitive to the toxic effects of this probe at all concentrations tested. Based on the differential sensitivity to TPA (range, 0-100 ng/ml), a good correlation has been found in this study between the results, the pedigree analysis, and the clinical findings. Of 21 individuals examined, two were apparently false-negatives. Two other individuals who are currently listed as clinically asymptomatic and, who through pedigree analysis might presumably be disease-free, appeared strongly positive by the criteria. The results extend the previous observations that the measurement of cloning efficiency in the presence of a TPA probe provides a reliable assay to distinguish SF of colorectal cancer-prone persons from those of normal subjects within a single pedigree of the Gardner syndrome.

Numerical and structural chromosome aberrations in cultured lymphocytes and cutaneous fibroblasts of patients with multiple adenomas of the colorectum

Excessive random loss and gain of simple chromosomes at the diploid and tetraploid levels, and numerous chromosomal aberrations, have been observed in lymphocytes and fibroblasts, cultured from Gardner syndrome and familial polyposis coli patients and children at risk for multiple adenomas. This increase in numerical and structural aberrations seems to represent a general instability of chromosomes in the lymphocyte and fibroblast nuclei of patients with multiple adenomas in the colorectum. A consistent heteromorphism of chromosome No. 2 homologous tentatively identified as a deletion was observed in all 17 patients with multiple adenomas in the colorectum, and two younger people of 13 and six years of age who are at risk for Gardner syndrome but do not have colorectal polyps. The chromosome No. 2 aberration was not observed in two symptomatic patients with occasional discrete colorectal adenomas.Eighteen controls who did not have Gardner syndrome nor familial polyposis coli did not show the structural aberration in chromosome No. 2 nor chromosome instability.

Hereditary multiple exostoses. Hereditary multiple exostoses in horses

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Adrenal adenomas in a patient with Gardner's syndrome

Gardner's syndrome is an autosomal dominant condition characterized by multiple colorectal polyposis, associated with various soft- and hard-tissue tumors. The occurrence of adrenal adenomas in patients with the syndrome has not been fully appreciated. The following is a report of a member of the original Utah kindred #109, first described in the early 1950's who was found at autopsy to have bilateral adrenal adenomas. A review of the literature resulted in the identification of six cases with adrenal adenomas and one with a primary adrenal carcinoma. The association with the syndrome of these adrenal tumors, as well as other endocrine tumors, especially thyroid tumors, is discussed.

Spontaneous mesenteric fibromatosis in Gardner's syndrome

Mesenteric fibromatosis has been reported in frequent association with familial polyposis and with Gardner's syndrome. This vague "benign" process has been characterized as a postsurgical phenomenon with low morbidity. Two cases of spontaneous mesenteric fibromatosis, noted at the time of original laparotomy for colectomy in Gardner's syndrome patients, are reported. No history of abdominal trauma was present, and both have well-documented Gardner's findings. A 32% incidence of desmoid reaction is reported among affected members of the original Gardner's syndrome Kindred 109; five or 55% of these patients had the mesenteric form of the process. The potential fatal course of the mesenteric disease is emphasized.

Gastrointestinal Polyposis: Syndromes and Genetic Mechanisms

Adenomas and hamartomas, two genetically transmitted histologic types of gastrointestinal polyposis, are associated in syndromes with extragastrointestinal manifestations. Adenomas that predispose to adenocarcinoma are basic to familial polyposis coli, the Gardner syndrome and the Turcot syndrome. Gastrointestinal polyps and extragastrointestinal lesions serve as a warning, providing time for diagnosis and treatment of adenomas to prevent their malignant transformation in patients and their relatives. Hamartomas with no malignancy potential, but having a tendency toward bleeding and bowel obstruction, are associated with the Peutz-Jeghers syndrome, juvenile polyposis, multiple hamartoma syndrome, basal-cell nevus syndrome and the Cronkhite-Canada syndrome. Most of these lesions and syndromes follow the inheritance pattern of a single autosomal dominant gene.

Desmoid tumors and mesenteric fibromatosis in Gardner's syndrome: report of kindred 109

Kindred 109, from which Gardner's syndrome was first described, now has 224 members, 28 of whom have inherited the syndrome. Among the group of 28, desmoid tumors or mesenteric fibromatosis or both have developed in eight (29%). In four patients, the fibrous dysplasia appeared to originate in postsurgical abdominal incisional scars; in two of these cases, the mesenteric involvement resulted in death. In one patient, the process was present in the mesentery at the original operation. In three patients, the fibrous dysplastic lesions were extraincisional, with no known trauma associated with their occurrence.

Hereditary multiple exostoses: clinicopathologic features of a comparative study in horses and man

Investigation of hereditary multiple exostoses in horses under controlled research conditions for 10 years and epidemiologic studies that have spanned up to five generations of human families contain notable similarities. The present study demonstrated that a single dominant autosomal gene is responsible for hereditary multiple exostoses in horses and man. Affected individuals transmit this trait to approximately 50% of their progeny, whereas nonaffected individuals do not transmit the condition to their offspring. The tumors in affected horses are most often present at birth. They tend to be bilaterally symmetrical and vary in size, shape, and texture. Those on the legs generally do not appear to enlarge as the animal matures, but others, notably those on the ribs and scapulae, enlarge until skeletal maturity, Histologically, the tumors appear as typical ostosteochondromas in both horse and man. Sarcomatous transformations have not yet been detected after 10 years in horses, although such changes are occasionally reported in the similar disease condition in man. The remarkable similarities of hereditary multiple exostoses in the horse to that in man provide an opportunity for comparative biomedical study.

The Gardner syndrome: a cell culture study on kindred 109

In vitro studies on skin cultures established from 49 members from Kindred 109, in whom the Gardner syndrome was first delineated, showed that increased in vitro tetraploidy occurred only in those cultures derived from branches with the full expression of the Gardner gene (colorectal polyps with multiple extracolorectal benign tumours) and not in those derived from branches showing only extracolorectal lesions. Increased in vitro tetraploidy appeared to identify only those family members at risk who had, or would ultimately be expected to show, full expression of the Gardner gene including colorectal polyps which become malignant.

Nature of the vitamin K-dependent CO2 fixation in microsomal membranes

Vitamin K is a component of a membrane-bound enzyme complex which catalyzes the posttranslational carboxylation of peptide-bound glutamate to form the gamma-carboxyglutamate (Gla) residues of prothrombin. The reaction requires reduced vitamin K, bicarbonate, oxygen, and a carboxylase, and does not require ATP. In a Triton X-100 solubilized carboxylase system, it was found that the naphthoquinone ring structure is essential for activity, as is the 2-methyl group. Menaquinone homologs from MK-1 to MK-4 all had carboxylase activity, whereas menadione was inactive. However, dithiothreitol and other thiols form thioethers with menadione, which restores considerable carboxylation activity to the provitamin. Hydrogenation of the beta-gamma double bond in phylloquinone reduced its activity only slightly. The active species of "CO2" utilized in this carboxylation is CO2 and not bicarbonate. Ribosomes contain Gla residues and are labeled with CO2 when whole microsomes are incubated with CO2 in the presence of NADH and vitamin K. About 25% of the activity is releasable with puromycin, suggesting that Gla residues are formed on both the nascent chains and the structural proteins of ribosomes. The deoxycholate-solubilized carboxylase system can be dialyzed to yield membranous vesicles with enhanced carboxylase activity. The warfarin-binding protein from normal rats, but not that from warfarin-resistant rats, further enhances the carboxylase activity of these reformed vesicles.

Vitamin K-dependent carboxylation of peptide-bound glutamate. The active species of "CO2" utilized by the membrane-bound preprothrombin carboxylase

Vitamin K participates in the post-translational carboxylation of peptide-bound glutamate to form the gamma-carboxy-glutamate residues of prothrombin. The reaction requires reduced vitamin K, bicarbonate, oxygen, and a membrane-bound carboxylase. The active species of "CO2," i.e. CO2 or HCO3-, utilized in this carboxylation was determined by the low temperature method of Filmer and Cooper ((1970) J. Theor. Biol. 29, 131-145), taking advantage of the fact that menaquinone-2, in contrast to phylloquinone, is very active at 10 degrees. Microsomes from livers of vitamin K-deficient rats, were incubated in the presence of cycloheximide, avidin, NADH, menaquinone-2, 1 mM acetazolamide (to inhibit carbonic anhydrase), and either 14CO2 or H14CO3-. At 1-min intervals aliquots were removed from the reaction mixture. gamma-Carboxyglutamate was isolated from these samples by ion exchange chromatography after alkaline hydrolysis. After 1 min the incorporation of 14CO2 into gamma-carboxyglutamate was 8 to 10 times as great as that found with H14CO3-. When the carbonic anhydrase inhibitor was omited (with or without addition of exogenous carbonic anhydrase) the two incorporation curves approximated each other at a rate near that exhibited by bicarbonate alone. Similar results were obtained in a microsomal carboxylase system solubilized with Triton X-100. It is concluded that CO2 is the active species of "CO2" initially participating in the vitamin K-dependent carboxylation of preprothrombin and that neither ATP nor biotin is required for the reaction.

Penetrance and expressivity of the gene responsible for the Gardner syndrome

The Gardner syndrome is an autosomal dominant condition characterized by multiple polyposis of the colon, associated with various soft- and hard-tissue tumors. Our original kindred, first reported in the early 1950's has been updated and serves as the basis for a discussion of the penetrance and expressivity of the gene responsible for the syndrome. The family consists of 188 members spread over six generations, with 28 individuals clearly documented as having the syndrome. Using two different methods of calculating penetrance, the responsible gene was found to be fully penetrant. This observation was confirmed by an analysis of 160 additional sibships from the literature. This estimation of penetrance is considerably higher than has been previously reported. The expressivity of the gene, however, is quite variable, and this is illustrated using examples from both our kindred and the literature.

Hereditary multiple exostosis. A comparative genetic evaluation in man and horses

Comparative studies are being conducted on hereditary multiple exostosis in man and the horse. In both, there is an unquestionable inheritance pattern of a typical single, dominant, autosomal gene. Those who carry the gene have a one-half chance of transmitting it to each offspring, whereas, those who do not carry the gene do not transmit this abnormality to their progeny. The lesions are clinically and histologically similar; no persistent chromosomal irregularities have been associated with the abnormality in either man or the horse and no single evidence of malignancy in either man or animal has been detected in this study to date.

The compound eye in the opaque-eye phenotype of Drosophilia melanogaster

The compound eye of the opaque-eye mutant of Drosophila melanogaster was investigated by means of electron microscopy to determine the morphological and physical properties of ommatidial elements. These elements in the mutant were found to differ from those of the wild-type flies in the following ways: (1) The cuticular lens was thinner than that of the control and lacked the typical lamellar construction. (2) The Semper cells were irregular in shape and contained many membranous inclusions similar to those found in degenerating cells; also their nuclei contained virus-like particles. (3) The primary pigment cells contained an abundance of drosopterin-containing granules which were lacking in those of wild-type flies. (4) The superior and inferior central photoreceptor cells were misplaced and their rhabdomeres evidenced some degeneration. (5) The secondary pigment cells had only one type of pigment granules instead of the three types found in the control. These morphological changes in ommatidial elements induced physical abnormalities such as the apparent opaqueness of the eye, the lack of a pseudopupil, the probable disability of the photoreceptor cells to respond to light and the inability of the dioptric system to produce utilizable geometric images.