Audit of newborn screening programme for congenital hypothyroidism.

Newborn screening for congenital hypothyroidism (CH) was implemented in Hospital UKM in December 2004 using cord blood sample. From the audit over a period of 25 months, a total of 13,875 newborn babies were screened with a coverage of 98.8%. From this cohort, the mean recall rate was 0.32%; unfortunately the mean percentage of recalled babies that came for retesting was only 79.5%. In addition, the mean sample rejection rate was high, i.e. 2.2%. Two babies were diagnosed to have CH. These findings implied that whilst the coverage of screening was good, there is a need for regular surveillance of performance of both clinical and laboratory personnel. In addition, a more concerted effort should be carried out to promote community awareness of such a programme.

N,N',N''-triethylenethiophosphoramide (thio-TEPA) oxygenation by constitutive hepatic P450 enzymes and modulation of drug metabolism and clearance in vivo by P450-inducing agents.

The cancer chemotherapeutic drug N,N',N''-triethylenephosphoramide (thio-TEPA) is oxidatively desulfurated to yield the active metabolite N,N',N''-triethylenephosphoramide (TEPA) in a reaction catalyzed by the phenobarbital-inducible rat liver P450 enzyme IIB1. In the current study, the role of constitutively expressed P450 enzymes in thio-TEPA metabolism was studied using purified P450s, isolated liver microsomes, and intact rats. Metabolism of thio-TEPA (100 microM) to TEPA by uninduced adult female and male rat liver microsomes proceeded at initial rates of 0.10 and 0.28 nmol TEPA formed/min/mg microsomal protein, respectively. Although these rates are low compared to those catalyzed by phenobarbital-induced liver microsomes (3.5 nmol TEPA/min/mg), they are sufficient to contribute to the systemic metabolism of this drug. Thio-TEPA metabolism catalyzed by uninduced female liver microsomes was approximately 70% inhibitable by antibodies selectively reactive with P450 IIC6. For the uninduced male liver microsomes, which exhibit a severalfold higher rate of thio-TEPA metabolism, enzyme activity was only 15-20% inhibitable by these antibodies but was 80-85% inhibited by an anti-P450 IIC6 monoclonal antibody cross-reactive with P450 IIC11, which is expressed only in the males. Consistent with these observations, purified P450s IIC11 and IIC6 both oxidized thio-TEPA in reconstituted systems (turnover, 1.1 and 0.3 min-1 P450-1, respectively, at 100 microM substrate), while several other constitutive hepatic P450s exhibited significantly lower or undetectable activities (turnover, less than or equal to 0.15 min-1 P450-1). Metabolism of thio-TEPA by purified P450 IIC11 was associated with a time-dependent inactivation of the cytochrome analogous to that previously shown to accompany thio-TEPA metabolism catalyzed by P450 IIB1. Depletion of hepatic P450 IIC11 by cisplatin treatment of adult male rats led to a 70% reduction of TEPA formation catalyzed by the isolated liver microsomes, suggesting that cisplatin may influence thio-TEPA pharmacokinetics when these two drugs are given in combination. The extent to which hepatic P450s contribute to thio-TEPA metabolism and clearance in vivo was assessed by monitoring thio-TEPA and TEPA pharmacokinetics in rats that exhibit widely differing rates of microsomal thio-TEPA metabolism, i.e., uninduced female and male rats, and male rats treated with the P450 IIB1 inducers clofibrate and phenobarbital. In accord with the microsomal activities, conversion of thio-TEPA to TEPA was less extensive and thio-TEPA elimination slower in female than in male rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Biotransformation of N,N',N''-triethylenethiophosphoramide: oxidative desulfuration to yield N,N',N''-triethylenephosphoramide associated with suicide inactivation of a phenobarbital-inducible hepatic P-450 monooxygenase.

Oxidative metabolism of the polyfunctional alkylating agent N,N',N''-triethylenethiophosphoramide (thio-TEPA) was studied in isolated rat liver microsomes and purified, reconstituted cytochrome P-450 (P-450) enzyme systems in order to elucidate the pathways of drug oxidation and to identify the possible contributions of individual P-450 enzymes to the bioactivation of this chemotherapeutic agent. Rat liver microsomes were found to catalyze conversion of thio-TEPA to its oxo metabolite, N,N',N''-triethylenephosphoramide (TEPA), in a P-450-dependent reaction that was markedly stimulated by prior in vivo treatment with drug inducers of hepatic P-450 subfamily IIB (phenobarbital), but not by pretreatment with inducers of P-450 subfamilies IA (beta-naphthoflavone) or IIE (isoniazid). Thio-TEPA depletion and TEPA formation catalyzed by phenobarbital-induced liver microsomes were both inhibited by greater than 90% by antibodies selectively reactive with P-450 PB-4 (gene product IIB1), the major phenobarbital-inducible rat liver microsomal P-450 form, but not by antibodies inhibitory toward 7 other rat hepatic P-450s. Oxidation of thio-TEPA to TEPA was also catalyzed by purified P-450 PB-4 (Km (app) 19 microM; Vmax (app) = 11 mol thio-TEPA metabolized/min/mol P-450 PB-4) following reconstitution of the cytochrome with NADPH P-450 reductase in a lipid environment. Metabolism of thio-TEPA by P-450 PB-4 was associated with a suicide inactivation of the cytochrome characterized by kinactivation = 0.096 min-1, KI = 24 microM, and a partition ratio of 136 +/- 28 (SD) mol thio-TEPA metabolized/mol P-450 inactivated. The thio-TEPA metabolite TEPA, however, did not inactivate the cytochrome, nor was it subject to further detectable metabolism. In microsomal incubations, metabolism of thio-TEPA led to the inactivation of P-450 PB-4 (steroid 16 beta-hydroxylase) as well as P-450 IIIA-related enzymes (steroid 6 beta-hydroxylase) and the P-450-independent enzyme steroid 17 beta-hydroxysteroid:NADP+ 17-oxidoreductase, as demonstrated by use of the P-450 form-selective steroidal substrate androst-4-ene-3,17-dione. In contrast, little or no inactivation of microsomal P-450 IIA-related enzymes (steroid 7 alpha-hydroxylase) or microsomal NADPH P-450 reductase was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

A case-control study of risk factors associated with rectal colonization of extended-spectrum beta-lactamase producing Klebsiella sp. in newborn infants.

To determine the risk factors for rectal colonization by extended-spectrum beta-lactamase (ESBL) Klebsiella sp. in 368 newborns admitted consecutively to a neonatal intensive care unit over six months, rectal swabs were cultured on admission and weekly until discharge. Eighty infants (21.7%) had ESBL Klebsiella sp. cultured from their rectal swabs. Eighty controls were selected at random from infants with negative cultures admitted within the 14-day period prior to the detection of ESBL Klebsiella sp. in the cases. Cases had significantly lower birth weight, gestational age, earlier age of admission, longer hospital stay, and higher proportions of congenital malformations, early-onset pneumonia and respiratory distress syndrome compared with controls. Significantly more cases received mechanical ventilation, nasal continuous positive airway pressure support, total parenteral nutrition, umbilical vascular catheterization, arterial line insertion, urinary bladder catheterization, and prior treatment with antibiotics. However, stepwise logistic regression analysis showed that only two independent risk factors were significantly associated with ESBL rectal colonization: duration of hospital stay [adjusted odds ratio (OR): 1.3; 95% confidence intervals (CI): 1.2, 1.4; P<0.0001) and early-onset pneumonia (adjusted OR: 8.3; 95% CI: 1.6, 43.4; P=0.01).

Effect of biosynthetic human growth hormone on insulin action in individual tissues of the rat in vivo.

Excessive endogenous production or exogenous administration of human growth hormone (hGH) causes insulin resistance at both the hepatic and extrahepatic levels. However, which extrahepatic tissues are involved have not been defined. We have examined the diabetogenic action of authentic biosynthetic hGH on whole body glucose disposal, hepatic glucose output, and glucose metabolism in individual peripheral tissues. The use of a highly purified preparation of the hormone allowed us to examine the isolated effects of 22K hGH. The euglycemic hyperinsulinemic (approximately 100 mU/L) clamp plus 3H-2-deoxyglucose technique was used to quantitate the effects of hGH on insulin action in vivo. Administration of biosynthetic hGH at a dose of 10 IU/kg/24 h for 48 hours in male Wistar rats (approximately 340 g) produced a highly significant decrease in the steady state clamp glucose infusion rate (GIR) when compared with controls (8.1 +/- 0.6 v 18.7 +/- 0.7 mg/kg/min, P less than .001), reduced insulin-mediated suppression of hepatic glucose output (Ra) (3.9 +/- 0.6 v 0.7 +/- 0.3 mg/kg/min, P less than .05) and a decreased clamp glucose disposal rate (Rd) (12.0 +/- 0.4 v 18.10 +/- 1.1 mg/kg/min, P less than .001). There was a significant decrease in insulin-mediated glucose uptake as indicated by tissue accumulation of [3H]-2-deoxyglucose phosphorylation in diaphragm and hindlimb muscles. Insulin action was more substantially reduced in muscles (approximately 50%) than in adipose tissues (approximately 20%). These studies confirm that the diabetogenic action of hGH in the rat is due to a combination of inhibition of insulin suppression of hepatic glucose output and inhibition of the uptake and subsequent utilization of glucose in skeletal muscles.

Somatic function of the micronucleus of Stylonychia mytilus during asexual propagation.

The somatic function of the micronucleus during vegetative propagation of the hypotrichous ciliate Stylonychia mytilus was investigated, by generating amicronucleate cell lines with microinjection or amputation. The amicronucleate cell lines exhibited reduction in fission rate and ingestion shortly after the loss of the micronucleus. There was partial recovery of growth rate in the following months of propagation. Amicronucleate cultures carried both normal-looking and abnormal cells. The normal-looking ones underwent binary fission, and also physiological reorganization, in the usual manner. After binary fission, normal-looking amicronucleates gave rise to normal-looking post-dividers, which might then undergo abnormal transformation in the interfission period by developing a bulge on the posterior-right side of the cell (Type A), or on the dorsal surface (Type B). Type A cells could enter binary fission directly, eventually recovering normal cell shape. The hump-back Type B cells went through atypical cortical reorganization(s) to generate spherical cells, which then recover to normal shape by normalizing reorganization(s). The emergence of these two types of abnormalities was correlated with the failure of macronuclear division during binary fission. These observations indicate that the micronucleus possesses morphogenetic function, and that this function is division-related. The micronucleus probably affects cytoskeletal/membranellar development during binary fission, and in its absence the cortical abnormalities exhibited represent a delayed expression of the infirmities incurred during binary fission. In view of the persistence of such abnormalities in amicronucleate cultures for up to a year of culture, the morphogenetic function of the micronucleus appeared not to be replaced; this resembles the situation in the hypotrich Pseudourostyla cristata, but differs from Paramecium where recovery to near-normal is the rule. Chromatin bodies resembling pseudomicronuclei were present in low frequency in the culture, and these appeared to arise in connection with macronuclear development in Type B cells.

Discrimination of cytoskeletal elements of Paramecium by heterologous antisera: A preliminary investigation on the presence of intermediate filament-related protein.

The present study of the cytoskeleton of Paramecium employed a number of heterologous monoclonal antisera raised against intermediate filament proteins of higher organisms, and also an antiserum against a 49 K protein from Tetrahymena. Anti-49 K, and also monoclonal anti-bovine cytokeratin K 8.13 which has a broad cross-reaction spectrum for epithelial intermediate filaments, differentiated the microtubular systems of Paramecium into two categories. Those closely associated with surface membranes, such as basal bodies, contractile vacuole pores and the cytospindle, and the gullet also, were labeled by these antibodies. Others internal to the epiplasm are not labeled, such as transverse and postciliary microtubular bands associating with basal bodies, contractile vacuole canals, cytopharyngeal ribbons and postoral fibers. None of the heterologous anti-tubulins tested in this and previous studies generated such a pattern of discrimination of the microtubular systems of Paramecium, indicating that the discrimination by anti-49 K and by anti-cytokeratin K 8.13 was not based on the molecular composition (α- or ß-tubulin) of the microtubular systems, their state of tyrosination, or acetylation. These two antibodies thus reveal a determinant that is associated exclusively with certain membrane-bound microtubular systems of Paramecium. This determinant appears to participate in the development of nascent structures like the cytospindle and the oral apparatus, since it co-distributed with these structures in their different stages of development. In addition, two monoclonal antibodies were superimposable specifically on certain cytoskeletal elements also residing close to surface membranes: anti-pig vimentin V 9 labeled the epiplasm underlying the inner alveolar membrane, while anti-human cytokeratin K 4.62 labeled the outer lattice lining the cortical ridges. On the other hand, anti-49 K labeled the micronucleus and its derivatives in all stages of sexual nuclear reorganization in Paramecium, unlike the specific labeling of postmeiotic and zygotic nuclei in Tetrahymena. The presence of intermediate filament-related protein in Paramecium is discussed.

Stomatogenesis in Paramecium tetraurelia: The roles of the micronucleus and the pre-existing oral apparatus.

Removal of the micronuclei from Paramecium generated amicronucleate cell lines which produced oral apparatuses of much reduced length and abnormal oral membranellar pattern during an initial depression period. They subsequently recovered, but only partially. Reimplantation of the amicronucleates with micronuclei generally allowed a greater oral length to be reached in renucleated cell lines, and more normal membranellar pattern in some, but full recovery was frequently not attained even in these. However, the length of the oral apparatuses produced by the renucleated cells during autogamy, when the pre-existing oral apparatus degenerates, were mostly comparable to those of micronucleate controls. These relationships are discussed in terms of the control of development of the oral apparatus by the micronucleus and the preexisting oral apparatus.

The nature of control of oral development by the micronucleus in sexual reproduction of Paramecium tetraurelia.

Twelve laser-irradiated cell lines and eight cis. platin-treated cultures possessing defective micronuclei exhibited micronuclear and oral abnormalities during autogamy. Micronuclear abnormalities were characterized by the failure of some of the cells to complete the micronuclear cycle resulting in the absence of either micronuclei or macronuclear anlagen, or both. Oral abnormalities included reduction in the length of the buccal cavity and oral membranelles, abnormal oral membranellar patterns and arrest of oral development at early and late stages. The present study demonstrated a close relationship between micronuclear and stomatogenic abnormalities during sexual reproduction. It is concluded that the micronucleus plays an important role in the specification of a normal oral pattern during sexual reproduction. The participation of postzygotic micronuclear activities in the control of sexual stomatogenesis is discussed. In contrast to the situation in sexual reproduction, the development of the oral apparatus was normal during asexual propagation of the cell lines possessing defective micronuclei. This paradoxical situation forms the basis of speculations on the nature of micronuclear control of oral development in sexual reproduction. It is probable that micronuclear genes are involved.

Nuclear control of cortical reorganization during sexual reproduction of Stylonychia mytilus: A study with amicronucleates.

During conjugation, Stylonychia mytilus undergoes repetitive somatic development by reorganizing the cortical ciliature consecutively for three times. The control of these reorganizations by the nucleus was investigated employing amicronucleates generated by microsurgery. When amicronucleates conjugate, they underwent only the first round of cortical reorganization; the exconjugants perished before the second cortical reorganization commenced. This shows that the micronucleus is dispensable for the first cortical reorganization, but that the micronucleus, or its divisional derivatives in sexual nucleogenesis, are essential for immediate postconjugational survival. Conjugation of amicronucleates with micronucleates in most cases resulted in the arrest of macronuclear anlage development at the post-polyteny DNA-poor stage; the second cortical reorganization could not be initiated in such cells. In others where the macronuclear anlage developed beyond the post-polyteny DNA-poor stage, the cell underwent the second, and then the third round of cortical reorganization. This correlation between macronuclear anlage development and the second cortical reorganization argues for a causal relationship between the two. Very likely, the macronuclear anlage up to the post-polyteny DNA-poor stage provides the crucial morphogenetic signal(s) for the second cortical reorganization. The nature of the first and second rounds of cortical reorganization are thus fundamentally different from each other, as their nuclear controls are radically dissimilar.

Programming of the macronucleus of Paramecium during asexual and sexual reproduction: A further study with cytidine analogues, dimethylsulfoxide, L-ethionine and N-butyric acid.

The control of the function of the macronucleus of Paramecium is studied, in connection with its role in the compensation for the asexual somatic function of the micronucleus. Following removal of the micronuclei, amicronucleate cell lines as a rule suffer a transient period of growth and developmental depression in the initial phase of asexual propagation. But they gradually recover to near-normal. Previous studies of treatment of amicronucleate cells with cytidine analogues have implicated the macronucleus in compensating for the somatic function of the micronucleus following the loss of the micronucleus, and the activation of this macronuclear function probably involves DNA-demethylation. The present study further tests this notion, by treating micronucleate cells with agents known to promote demethylation of 5-methylcytosine. After treatment, the cells were vegetatively propagated, and then enucleated to give rise to amicronucleate cell lines. Treatments with dimethylsulfoxide, L-ethionine, and 5-aza-2'-deoxycytidine promoted recovery in amicronucleate cell lines thus derived. Cells treated with 6-azacytidine did not produce such an effect. Hence, the compensatory mechanism, presumably residing in a repressed state in the macronucleus, can be activated or primed to activate by demethylating agents even before the loss of the micronucleus, and once established the new macronuclear programme perpetuates in succeeding asexual cell generations. This shows that during asexual propagation the macronuclear programme can be altered to 'pre-adapt' the cells for amicronuclearity. Treatment of micronucleate conjugants with 5-azacytidine, when the macronuclear anlagen develop, produced clones that had become similarly pre-adapted. There were also some indication of persistence of such effects of the analogue into the next clonal cycle following autogamy. The notion of macronuclear DNA-demethylation as a basis for the activation and maintenance of the compensatory mechanism is discussed.

Repressive function of the micronucleus during asexual reproduction in Paramecium tetraurelia: Experimental analysis with defective-micronucleates generated by laser microbeam irradiation.

The present paper reports on the experimental analysis of a novel regulatory function of the micronucleus of Paramecium tetraurelia. Previous studies have made clear that amicronucleate cell lines shortly after their generation generally suffer depression, in exhibiting low viability, slow growth and abnormal oral development in binary fission, but they eventually recover to near-normal. A compensatory mechanism is thus activated in the absence of the micronucleus, to allow recovery of the amicronucleate cell line. Implicit in this conclusion is the role of the micronucleus in repression of the compensatory mechanism. The present study tested this notion by perturbing the micronucleus with laser microbeam irradiation. This operation generated cell lines possessing defective micronuclei; during their asexual propagation, some cells lost the micronucleus and gave rise to amicronucleates. The viability of amicronucleate cell lines derived in this manner was found to be higher, compared to others generated by a different operation involving instantaneous removal of normal micronuclei from the cell with a microinjection needle. Some evidence also suggested that their oral development was less abnormal during the initial depression period. Hence, damage of the micronucleus has apparently facilitated the activation of the compensatory function, and the latter might have occurred even before the loss of the defective micronucleus. The present findings provide support for a regulatory role of the micronucleus during asexual propagation. Previous studies have indicated that the physical basis of the compensatory mechanism resides with the macronucleus. The micronuclear repressive function may be directed against this compensatory mechanism of the macronucleus.

Purification of the surface membrane-cytoskeleton complex (Cortex) of Paramecium and identification of several of its protein constituents.

In ciliates, the major morphogenetic events take place in the cortex, a complex of membranes and closely associated filamentous networks. To analyze the problems of assembly and morphogenesis at the molecular level in Paramecium, we have developed a method of purification of cortex fragments which retain their in situ organization and display a highly reproducible electrophoretic profile. The method used either a four-step sucrose gradient yielding a cortex + oral apparatus fraction or a six-step gradient which allowed the cortex fragments to be freed from the oral apparatuses (which were recovered separately). By comparative electrophoresis and immunological probing of these and other cell fractions or purified organelles, we could identify several of the major polypeptides resolved by SDS PAGE as components of specific cortical or oral structures. The purification method was successfully applied to morphological mutants, and the first case of a mutational modification of a cortical polypeptide was observed.

Infantile isolated sulphite oxidase deficiency in a Chinese family: a rare neurodegenerative disorder.

We report the clinical, biochemical, neuroradiological, and neurophysiological findings of a 4-year-old Chinese girl with infantile isolated sulphite oxidase deficiency. This is the first reported case in our locality. She presented at the age of 5 months with refractory seizures and developmental regression, and progressed rapidly to profound psychomotor retardation, spasticity, dystonia, microcephaly, and blindness. At the age of 3.5 years, she was admitted to the intensive care unit with septic shock. Ophthalmologic examination at this time revealed bilateral dislocation of the lens. Diagnosis of this very rare disorder was made on the basis of increased levels of urinary sulphite, thiosulphate, and sulphocysteine; normal urine xanthine and hypoxanthine; normal plasma uric acid; and low plasma cystine levels. The diagnosis was confirmed by the absence of sulphite oxidase activities in skin fibroblasts. Isolated sulphite oxidase deficiency is a rare inborn error of sulphur metabolism that is difficult to diagnose on clinical features and routine metabolic tests. The presence of ectopia lentis, seizures, and progressive neurological abnormalities should alert clinicians to the diagnosis.

A rare case of ambiguous genitalia.

Genes on the Y chromosome are essential for normal sex determination and sex differentiation of male genitalia. However, genes on the X chromosome and other autosomes have been shown to be anti-testes and have a detrimental effect on this process. Addition of X chromosomes to the 46,XY karyotype results in seminiferous tubules dysgenesis, hypogonadism and malformed genitalia. We report a term male newborn with 49,XXXXY syndrome presenting with ambiguous genitalia, multiple extra-gonadal anomalies, facial dysmorphism, and radioulnar synostosis.

Identifying HIV/AIDS primary care development needs.

AIM: This paper reports a study aimed at identifying the primary health care experiences of people living with human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) in Malaysia. The rationale behind the study was to enable informed action for developing more responsive and effective primary care. BACKGROUND: Reports such as from the World Health Organisation forecast sharp escalations in the incidence of HIV/AIDS in Malaysia and the Asia-Pacific region within the next few years. With sparse information on the course of infection on the local population and an understanding of health care needs of those afflicted, health services would be ill-prepared for projected increases. METHOD: Semi-structured interviews were conducted with a convenience sample of 99 patients attending two major HIV/AIDS clinics in Malaysia. FINDINGS: Several gaps in care provision were highlighted, such as with treatment/consultation facilities and availability and accessibility of information. What is also evident is that there are a number of good support services available but not well publicized to those in need of them. That includes health professionals who could be making appropriate referrals. The lack of communications and inter-professional working appears to be part of the problem. CONCLUSION: The findings provide baseline data and preliminary insights to government and other service providers towards advancing, optimizing and refining existing policies and infrastructure. Although the availability of a number of primary care facilities have been identified, the study indicates the need for more effective co-ordinated efforts with clear leadership to pull together scarce resources towards the aim of some degree of seamless primary care provision. It is suggested that nurses would be well placed for such a role in view of the nature of their education and training that helps prepare them for the multi-faceted role.

Unidirectional regeneration is an intrinsic property of longitudinal microtubules in Tetrahymena--an in vivo study.

The cortex of Tetrahymena contains a regular array of longitudinal microtubular bands (lms) next to basal body rows running from pole to pole. The lm exhibits a predominant unidirectionality in assembly. The direction of regeneration following breakage of the microtubules is from posterior to anterior of the cell. When the lm and the accompanying basal body row are rotated 180 degrees (inverted), so that their polarity is opposite to that of the cell, the predominant direction of regeneration exhibited by the inverted lm is from anterior to posterior. This shows that the lm has an inherent direction of regeneration independent of cellular polarity. This implies that the microtubules constituting the lm have an intrinsic property which controls the direction of assembly. This finding is in accord with the in vitro demonstration using Chlamydomonas flagellar fragments. On the basis of this finding and also the possible pattern of arrangement of the microtubules constituting the lm, it is suggested that growth of the lm involves both elongation of pre-existing microtubules constituting the lm and also laying down of new ones.

Analysis of contractile vacuole pore morphogenesis in Tetrahymena pyriformis by 180 degree rotation of ciliary meridians.

The contractile vacuole pores (CVPs) in Tetrahymena pyriformis are usually found to the left of ciliary meridians (CVP meridians). When the CVP meridians are experimentally rotated 180 degrees ('inverted'), the CVPs are now found to the right of the rotated CVP meridians. In other words, the CVP is almost invariably found on the same side with respect to the CVP meridian. Thus, the 2 sides of the CVP meridian have different morphogenetic properties and such differences are determinative in the asymmetrical fine-positioning of the CVP. The number of CVPs per animal and their general placement on the animal (i.e. with which ciliary meridians the CVPs are associated) are known to be a function of the total number of ciliary meridians possessed by the animal. Rotation of the CVP meridians affects both the number of CVPs per animal and their general placement. The specificity of such effects appears to depend on whether both, or one, or which one, of the CVP meridians is rotated. Rotation of ciliary meridians may be used as a tool in analysing the mechanism determining the number of CVPs per animal and their general placement.

Extra cytoproct mutant in Paramecium tetraurelia: morphogenetical analysis of proters and opisthes.

To account for the differences between proters and opisthes with regard to extra cytoproct morphogenesis in Paramecium tetraurelia, two hypotheses have been proposed and tested. (i) The differences may be a result of different actions of proter-macronucleus and opisthe-macronucleus. This hypothesis has been tested by cytoplasmically connecting the proter with the opisthe in the form of chains, some of which have only one macronucleus per chain. However, the connected proters and opisthes remain different in extra cytoproct morphogenesis, thus arguing against the hypothesis. (ii) The differences may be a result of differences between the proter and the opisthe with regard to the development of their posterior-ventral cortex: proters have a newly-developed posterior-ventral cortex whereas opisthes receive the posterior-ventral cortex from the pre-fission mother animal. This hypothesis has been tested by surgically producing an opisthe with a newly-regenerated posterior cortex. Such opisthes, however, remain different from proters in extra cytoproct morphogenesis. Thus no direct support for the second hypothesis is obtained. Also, proter-opisthe difference in morphogenesis may be understood in terms of Wolpert's positional information hypothesis, by assuming that the anterior and posterior ends of a dividing animal serve as reference points for establishing a gradient and that positional information before separation of the two daughter animals leads to differences in extra cytoproct morphogenesis between them after separation.