Constraints faced by sex workers in use of female and male condoms for safer sex in urban zimbabwe

We investigated whether female condoms are acceptable to sex workers in Harare and whether improved access to male and female condoms increases the proportion of protected sex episodes with clients and boyfriends. Sex workers were randomly placed in groups to receive either male and female condoms (group A, n = 99) or male condoms only (group B, n = 50) and were followed prospectively for about 3 months each. We found a considerable burden of human immunodeficiency virus (HIV) and sexually transmitted infections (STIs) in our cohort at enrollment (86% tested HIV positive and 34% had at least one STI). Consistent male condom use with clients increased from 0% to 52% in group A and from 0% to 82% in group B between enrollment and first follow-up 2 weeks later and remained high throughout the study. Few women in group A reported using female condoms with clients consistently (3%-9%), and use of either condom was less common with boyfriends than with clients throughout the study (8%-39% for different study groups, visits, and types of condom). Unprotected sex still took place, as evidenced by an STI incidence of 16 episodes per 100 woman-months of follow-up. Our questionnaire data indicated high self-reported acceptability of female condoms, but focus group discussions revealed that a main obstacle to female condom use was client distrust of unfamiliar methods. This study shows that a simple intervention of improving access to condoms can lead to more protected sex episodes between sex workers and clients. However, more work is needed to help sex workers achieve safer sex in noncommercial relationships.

Role of alphavbeta3 integrin receptors in breast tumor

The intriguing problem of tumor metastasis involves adhesion of the metastatic cells via the integrin group of cell surface receptors to the ECM proteins of the basement membrane. Modulation of integrin family of cell surface receptors is believed to be associated with stages of tumor metastasis. In this present study, results obtained indicate that alphavbeta3 vitronectin receptors may play an important role in the malignant behaviour of human breast tumor. Alphavbeta3 integrin receptors can modulate the activity of collagenase enzyme and thereby the invasive property of breast tumor cells.

Identification of a critical lysine residue at the active site in glyceraldehyde-3-phosphate dehydrogenase of Ehrlich ascites carcinoma cell. Comparison with the rabbit muscle enzyme

The involvement of the lysine residue present at the active site of Ehrlich ascites carcinoma (EAC) cell glyceraldehyde-3-phosphate dehydrogenase (Gra3PDH) was investigated by using the lysine specific reagents trinitrobenzenesulfonic acid (TNBS) and pyridoxal phosphate (PP). Both TNBS and PP inactivated EAC cell Gra3PDH with pseudo-first-order kinetics with the rate dependent on modifier concentration. Kinetic analysis, including a Tsou plot, indicated that both TNBS and PP apparently react with one lysine residue per enzyme molecule. Two of the substrates, d-glyceraldehyde-3-phosphate and NAD, and also NADH, the product and competitive inhibitor, almost completely protected the enzyme from inactivation by TNBS. A comparative study of Gra3PDH of EAC cell and rabbit muscle indicates that the nature of active site of the enzyme is significantly different in these two cells. A double inhibition study using 5,5'-dithiobis(2-nitrobenzoic acid) and TNBS and subsequent reactivation of only the rabbit muscle enzyme by dithiothreitol suggested that a cysteine residue of this enzyme possibly reacts with TNBS. These studies on the other hand, confirm that an essential lysine residue is involved in the catalytic activity of the EAC cell enzyme. This difference in the nature of the active site of EAC cell Gra3PDH that may be related to the high glycolysis of malignant cells has been discussed.

Action of an algicide from a cyanobacterium, Oscillatoria laetevirens, on photosystem II

Oscillatoria laetevirens produces an algicide, named oscillatorin (OS), which inhibits growth of higher plants. Effect of purified oscillatorin and some 'urea-triazine type' herbicides was studied on photosystem II activity and composition of pigment protein complex in spinach thylakoid membrane. For oscillatorin the I50 at 10 microg chlorophyll concentration, inhibitor constant (Ki), specific binding sites and Hill coefficient were calculated to be 1.45, 0.15, 2.3 and 0.2 microM respectively. Metribuzin and oscillatorin affected towards the donor side and brought about identical changes in polypeptide composition of PSII complex. Further, metribuzin and atrazine exerted antagonistic and synergistic responses on oscillatorin action. Some of these parameters were also studied on weed plants to assess upon the weedicidal potential of oscillatorin.

8-Cl-adenosine induces growth arrest without differentiation of primary mouse epidermal keratinocytes

In some cell systems, the antiproliferative effects of 8-Cl-cAMP, a site-selective cAMP analog specific for the type I cAMP-dependent protein kinase, are mediated by its metabolite, 8-Cl-adenosine. These effects were once thought to be specific to transformed cells. We investigated the ability of 8-Cl-adenosine to regulate growth and differentiation in primary cultures of mouse epidermal keratinocytes. A 24 h exposure of keratinocytes to 8-Cl-adenosine inhibited [3H]thymidine incorporation in a dose-dependent manner with an apparent IC(50) of 7.5 microM, and these effects were completely reversible. To determine the ability of 8-Cl-adenosine to induce differentiation of primary keratinocytes, we measured keratin-1 expression and transglutaminase activity, markers of early and later stages of keratinocyte differentiation, respectively. Interestingly, exposure of keratinocytes to 25 microM 8-Cl-adenosine for 24 h had no effect on keratin-1 expression or transglutaminase activity. The 8-Cl-adenosine-induced growth arrest of keratinocytes required uptake of the compound and was accompanied by an increase in protein expression of the cyclin-dependent protein kinase inhibitor p21(WAF1/Cip1). These results demonstrate that 8-Cl-adenosine inhibits growth in a non-transformed/non-immortalized cell system, possibly through an elevation in p21(WAF1/Cip1) protein levels, without inducing differentiation.

A mutation in the human MPDU1 gene causes congenital disorder of glycosylation type If (CDG-If)

We describe a new congenital disorder of glycosylation, CDG-If. The patient has severe psychomotor retardation, seizures, failure to thrive, dry skin and scaling with erythroderma, and impaired vision. CDG-If is caused by a defect in the gene MPDU1, the human homologue of hamster Lec35, and is the first disorder to affect the use, rather than the biosynthesis, of donor substrates for lipid-linked oligosaccharides. This leads to the synthesis of incomplete and poorly transferred precursor oligosaccharides lacking both mannose and glucose residues. The patient has a homozygous point mutation (221T-->C, L74S) in a semiconserved amino acid of MPDU1. Chinese hamster ovary Lec35 cells lack a functional Lec35 gene and synthesize truncated lipid-linked oligosaccharides similar to the patient's. They lack glucose and mannose residues donated by Glc-P-Dol and Man-P-Dol. Transfection with the normal human MPDU1 allele nearly completely restores normal glycosylation, whereas transfection with the patient's MPDU1 allele only weakly restores normal glycosylation. This work provides a new clinical picture for another CDG that may involve synthesis of multiple types of glycoconjugates.

Elevated K(+) induces myristoylated alanine-rich C-kinase substrate phosphorylation and phospholipase D activation in glomerulosa cells

Elevated extracellular potassium concentrations ([K(+)](e)) are known to stimulate aldosterone secretion from adrenal glomerulosa cells in vivo and in vitro. The mechanism is thought to involve depolarization-elicited activation of voltage-dependent calcium channels and an increase in calcium influx. Until now protein kinase C (PKC) was thought not to play a role in the steroidogenic response to elevated [K(+)](e). In this report, we provide evidence in bovine adrenal glomerulosa cells to suggest that elevated [K(+)](e) increases PKC activity, as shown by an enhancement in the phosphorylation of myristoylated alanine-rich C-kinase substrate (MARCKS). Elevated [K(+)](e)-induced MARCKS phosphorylation was delayed and transient and was not the result of a local production of angiotensin II (AngII). MARCKS phosphorylation in response to elevated [K(+)](e) was not accompanied by phosphoinositide hydrolysis but was inhibited by a selective PKC inhibitor. Elevated [K(+)](e) also activated phospholipase D (PLD) in a delayed but sustained manner. We propose that the observed PLD activation mediates the elevated [K(+)](e)-induced MARCKS phosphorylation via PKC, although other factors may modulate this phosphorylation event.

Does extubation result in haemodynamic instability in patients following coronary artery bypass grafts?

Coronary heart disease and its management continue to be at the centre of Government health policy. The present political climate demands clinical effectiveness and best practice should be established, while maintaining the philosophy of cost-effectiveness and resource management. These directives have led practitioners to question the care of patients following coronary artery bypass surgery, in particular the role of mechanical ventilation and the subsequent act of extubation. A retrospective study of 89 patients who had coronary artery bypass grafts (emergency and elective) was undertaken, to establish if extubation had a significant effect on the haemodynamic status of patients with variable degrees of left ventricular function (19% with poor left ventricular function). The study found that extubation was achieved within a mean time of 4.97 hours following return from surgery. Extubation resulted in a significant increase in heart rate (P = 0.001), as well as a respiratory acidosis (pCO2: P = 0.000; pH: P = 0.000). However, the stability of the patient was not compromised, with neither mean arterial blood pressure (P = 0.825) nor oxygenation levels (P = 0.267) being significantly altered by extubation. On multivariate analysis, the act of extubation had no significant effect on any of the dependent variables. These results suggest that it is not extubation alone that has an impact on the haemodynamic stability of patients following coronary artery bypass grafts, but that this is indeed multifactorial. Therefore extubation is 'safe' practice for patients with varying degrees of left ventricular function following coronary artery bypass grafts. Limitations of the study are acknowledged.

Electronic and magnetic structures of Sr(2)FeMoO(6)

We have investigated the electronic and magnetic structures of Sr(2)FeMoO(6) employing site-specific direct probes, namely x-ray absorption spectroscopy with linearly and circularly polarized photons. In contrast to some previous suggestions, the results clearly establish that Fe is in the formal trivalent state in this compound. With the help of circularly polarized light, it is unambiguously shown that the moment at the Mo sites is below the limit of detection (<0.25 mu(B)), resolving a previous controversy. We also show that the decrease of the observed moment in magnetization measurements from the theoretically expected value is driven by the presence of mis-site disorder between Fe and Mo sites.

A new strategy for modulating chemotherapy-induced alopecia, using PTH/PTHrP receptor agonist and antagonist

Parathyroid hormone (PTH) related peptide (PTHrP) and the PTH/PTHrP receptor (PTH/PTHrP-R) show prominent cutaneous expression, where this signaling system may exert important paracrine and/or autocrine functions, such as in hair growth control. Chemotherapy-induced alopecia - one of the fundamental unsolved problems of clinical oncology - is driven in part by defined abnormalities in hair follicle cycling. We have therefore explored the therapeutic potential of a PTH/PTHrP-R agonist and two PTH/PTHrP-R antagonists in a mouse model of cyclophosphamide-induced alopecia. Intraperitoneal administration of the agonist PTH(1-34) or the antagonists PTH(7-34) and PTHrP(7-34) significantly altered the follicular response to cyclophosphamide in vivo. PTH(7-34) and PTHrP(7-34) shifted it towards a mild form of "dystrophic anagen", associated with a significant reduction in apoptotic (TUNEL+) hair bulb cells, thus mitigating the degree of follicle damage and retarding the onset of cyclophosphamide-induced alopecia. PTH(1-34), in contrast, forced hair follicles into "dystrophic catagen", associated with enhanced intrafollicular apoptosis. We had previously shown that an induced shift in the follicular damage-response towards "dystrophic catagen" mitigates cyclophosphamide-induced alopecia, whereas a shift towards "dystrophic catagen" initially enhanced the hair loss, yet subsequently promoted accelerated hair follicle recovery. Therefore, this study in an established animal model of chemotherapy-induced alopecia, which closely mimics human chemotherapy-induced alopecia, strongly encourages the exploration of PTH/PTHrP-R agonists and antagonists as novel therapeutic agents in chemotherapy-induced alopecia.

Topical triiodothyronine stimulates epidermal proliferation, dermal thickening, and hair growth in mice and rats

The skin is a classic target tissue for thyroid hormone action. Although the histology of skin in hypothyroid states is well documented, the literature contains little assessment of skin in thyrotoxic states. In light of the paucity of information on skin under the influence of excess thyroid hormone, we investigated the direct effect of thyroid hormone on skin. Triiodothyronine (T3) was applied topically daily in liposomes to SKH-1 hairless mice for 7 days and to CD rats for 2 weeks. There was a dose-dependent increase in epidermal proliferation, dermal thickening, and hair growth in T3-treated animals. Mice that received 3.8 microg of T3 had 42% more hairs per millimeter than controls (p < 0.01), hair length that was 1,180% longer (p < 0.001), 49% greater epidermal 3H-thymidine incorporation (p < 0.01), and 80% more 5-bromo-2'-deoxyuridine (BrdU) stained cells (p < 0.05). Rats receiving 12.8 microg T3 had 48% greater dermal thickness than controls (p < 0.001), 26% greater epidermal thickness (p < 0.001), 85% more hairs per millimeter (p < 0.005), and 130% greater 3H-thymidine incorporation into the epidermis (p < 0.01). Thus, topically applied thyroid hormone has dramatic effects on both skin and hair growth. These observations offer a new strategy for developing thyroid hormone and its analogues for treating disorders of skin and hair growth.

Production of withaferin A in shoot cultures of Withania somnifera

Multiple shoot cultures of Withania somnifera were established from single shoot tip explants and their potential for the production of two principle withanolides, withaferin A and withanolide D was investigated. Shoot tips grown on MS medium supplemented with BA (1 mg l(-1)) induced 10.0 +/- 1.15 microshoots per explants and shoot cultures accumulated both withanolides (withaferin A = 0.04%, withanolide D = 0.06%). Supplementation of MSSM (solid) agar medium with 4% sucrose enhanced accumulation of both withaferin A (0.16%) and withanolide D (0.08%). Reduction of the agar concentration to 0.16% increased the number of microshoots induced per explant to 25.5. MSSM liquid medium containing 10% coconut milk favoured a maximum increase in biomass (27 fold); number of microshoots induced (37.6 +/- 1.45) as well as accumulation of withaferin A (0.14%).

Do any preoperative variables affect extubation time after coronary artery bypass graft surgery?

OBJECTIVE

The purpose of this study was to determine whether any preoperative variable had a significant effect on extubation time after coronary artery bypass graft surgery.

DESIGN

The study design was retrospective.

SETTING

The study was conducted in a cardiac center in the United Kingdom where 1700 cardiac surgical operations are performed per year.

SUBJECTS

The study sample was composed of 89 patients who had coronary artery bypass graft surgery performed by the designated consultant cardiac surgeon in the first 6 months of 1998.

OUTCOME MEASURES

The measures included preoperative variables (age, gender, body mass index, cardiac status, pulmonary status) and extubation time.

RESULTS

Mean extubation time was found to be 4.97 hours. Left ventricular function was found to be statistically significant (P =.05) to extubation time.

CONCLUSIONS

We found that cardiac status had an effect on extubation time and that this warranted further investigation. No other preoperative variable had a significant effect on extubation time, raising questions concerning the need for strict preoperative exclusion criteria.

Binding of a denatured heme protein and ATP to erythroid spectrin

Spectrin is a large, worm-like cytoskeletal protein that is abundant in all cell types. The denatured heme enzyme, horseradish peroxidase showed significant decrease in the reactivation yield, after 30 min of refolding, in presence of increasing concentrations of spectrin from that in the absence. This indicated that spectrin could bind denatured HRP and inhibit their refolding. In presence of 1 mM ATP and 10 mM MgCl(2) the spectrin binding of denatured HRP is abolished. This activity of decreasing the reactivation yield was found to be ATP-dependent and the denatured enzyme after 30 min refolding in the presence of spectrin, pretreated with Mg/ATP, showed about 40% increase in the reactivation yield compared to the same in absence of spectrin. Fluorescence spectroscopic studies indicated binding of ATP to native spectrin showing concentration-dependent quenching of tryptophan fluorescence by ATP. The apparent dissociation constant of binding of ATP to spectrin was estimated to be 1.1 mM. A high affinity binding of spectrin with denatured HRP has been characterized (K(d) = 16 nM). Since these properties are similar to those of established molecular chaperone proteins, these data indicate that spectrin might have a chaperone-like function in erythrocytes.

Effectiveness of training on infant feeding practices among community influencers in a rural area of west Bengal

Total 34 Influencers were trained in a subcentre area of South 24-parganas district of West Bengal. Knowledge was imparted to community influencers on infant feeding practices through lecture, group discussion, question-answer session and hand-on-training by trained health workers. Pre-assessment was done before initiation of training. Repeat training was conducted at frequent intervals within a period of 3 months. Mean score of knowledge of influencers during pre-training assessment was 13.3 and improved thereafter-following training to 20.8 (1st assessment), 20.6 (2nd assessment), 23.7 (3rd assessment) and 25.2 (final-assessment). Repeat training had also desired impact.

Neuroretinitis

Despite the growing list of agents that can present as neuroretinitis, nearly one-half remain idiopathic. However, many of the candidate etiologies are treatable conditions, and accurate diagnosis can result in visual rehabilitation. A complete workup in patients presenting with acute neuroretinitis should include a thorough history and general medical evaluation. Exposure history should be thoroughly explored, including recent travel, unpasteurized and uncooked foods, sexual experience, and animal contacts. A detailed physical examination should be performed to note hidden rashes and inoculation sites and should include routine measurements of blood pressure and heart rate. Laboratory tests should be tailored to the history and may include complete blood count; erythrocyte sedimentation rate; bacterial, fungal, and viral blood cultures; antinuclear antibody test; angiotensin-converting enzyme; anti-double-stranded DNA; and C3. Serological evaluation should look for syphilis, Lyme disease, histoplasmosis, brucellosis, chlamydia, HIV, toxoplasmosis, Epstein-Barr virus, viral hepatitis B and C, and tuberculin skin test. Neuroretinitis is a clinical entity in which there is inflammation of the retinal architecture and optic nerve. There are numerous entities that can cause a picture of neuroretinitis ranging from vascular to infectious to autoimmune. With regards to the infectious etiologies, it is interesting to note that many of these organisms are obligate intracellular pathogens. The microorganisms B. henselae, T. gondii, R. typhi, T. pallidum, Mycobacterium tuberculosis, Histoplasma capsulatum, and various viruses, such as HIV, mumps, and HSV, are known intracellular agents. Other major infectious agents, such as B. burgdorferi and Leptospirosis spp. are known to remain sequestered within the circulatory system. It is possible that in this way these agents are able to breach the delicate blood-brain barrier. The implication of such findings on the treatment and management of neuroretinitis remains to be explored. Interestingly, the vast majority of infected patients do not develop neuroretinitis or demonstrate CNS involvement. Detailed examination of this variability may provide further insight into the pathogenic properties of these infectious agents, host tissue susceptibility, and mechanisms of blood-retina barrier integrity. A detailed retinal examination can provide an unobstructed view of the CNS. Careful inspection of this delicate interface may reveal subtle findings critical for accurate and rapid diagnosis of underlying systemic pathology. The varied visual and neurological symptoms of neuroretinitis attest to the fact that this is a disease of both the retina and contiguous neuronal elements. Such involvement significantly elevates the risk to the patient and emphasizes the need for early detection and prompt treatment.

The Florida "truth" anti-tobacco media evaluation: design, first year results, and implications for planning future state media evaluations

OBJECTIVES

To outline the design and present selected findings from the evaluation of a state counter-advertising, anti-tobacco media campaign. The appropriateness of the design for states developing media evaluations is discussed.

DESIGN

Four cross sectional, telephone surveys of the 12--17 year old population were used to track and monitor advertising and campaign awareness, confirmed awareness, and receptivity. The Florida baseline and one year surveys were used with two parallel national surveys in a quasi-experimental design to assess attitude and smoking related behaviour change attributable to the campaign.

MEASURES

Awareness was measured by self report, confirmed awareness by unaided description, and receptivity by self reports of how well advertisements were liked, talked to friends about, and made one think about whether or not to smoke. Eleven attitude and three smoking behaviour items for Florida (treatment) and a national (control) population were compared at baseline and after 12 months.

RESULTS

Significant increases in ad specific awareness, confirmed, receptivity, and campaign awareness, and confirmed awareness were reached by the sixth week. They continued to rise through the first year. No attitude and only minor behaviour differences were noted between the treatment and comparison populations at baseline. By the end of the first year, Florida youth had stronger anti-tobacco attitudes and better behaviour patterns than the comparison population.

CONCLUSIONS

The industry manipulation strategy used in the Florida campaign resulted in high rates of recall, significant changes in attitudes/beliefs, and reduced rates of smoking behaviour among youth.

Acute and long-term safety evaluation of a novel IH636 grape seed proanthocyanidin extract

Grape seed proanthocyanidins are known to possess a broad spectrum of pharmacological, medicinal and therapeutic properties. Previous studies in our laboratories have demonstrated the various protective abilities of a novel IH636 grape seed proanthocyanidin extract (GSPE) against various pathologic conditions. However no extensive safety studies have been conducted on grape seed proanthocyanidins to date. This study demonstrates the acute and chronic safety studies on GSPE. Acute oral toxicity, dermal toxicity, dermal irritation and eye irritation studies have been conducted. The LD50 of GSPE was found to be greater than 5000 mg/kg when administered once orally via gastric intubation to fasted male and female albino rats. The LD50 of GSPE was found to be greater than 2000 mg/kg when administered once for 24 hr to the clipped, intact skin of male and female albino rats. In addition, 2000 mg/kg was found to be the no-observed-effect level (NOEL) for systemic toxicity under the conditions of the study. In a dermal irritation study, GSPE received a descriptive rating classification of moderately irritating. Extensive chronic studies were also conducted. We have assessed the effects of chronic administration of 100 mg GSPE/kg/day for twelve months and its effect on seven vital target organs, namely, brain, heart, intestine, kidney, liver, lung and spleen, and on serum chemistry changes in male B6C3F1 mice. Furthermore, the dose-dependent chronic effects of GSPE in female B6C3F1 mice were evaluated. Mice were fed 0, 100, 250 or 500 mg GSPE/kg/day for six months and the effects of GSPE exposure were examined on brain, duodenum, heart, kidney, liver, lung, pancreas and spleen, and on serum chemistry changes in female mice. These acute studies demonstrated that GSPE is safe and did not cause any detrimental effects in vivo under the conditions investigated in this study.

Nutrients and pH regulate algicide accumulation in cultures of the cyanobacterium Oscillatoria laetevirens

• The change in algicide synthesis in response to nutrients and pH in axenic cultures of the planktonic cyanobacterium, Oscillatoria laetevirens is reported. • Analytical and bioassay techniques were used to determine the effects of nitrogen (N), sulpher (S), phosphorus (P), magnesium (Mg²⁺ ), calcium (Ca²⁺ ) and hydrogen (H⁺ ) on Oscillatoria laetevirens growth, secondary metabolite accumulation and minimum inhibitory concentration in culture filtrates. • Growth and secondary metabolite production were affected by nutrient addition. High algicide production, which was not dependent on optimal growth, correlated with deficiences of magnesium and phosphate, and high pH. Algicidal activity in the culture medium was not detected following organic nitrogen addition while optimal growth was sustained; however, ammonia reduced biomass yield but did not affect algicide formation. The differential algicide concentration inside the cells and in the culture medium indicated secretion by an efflux mechanism rather than leakage from aging cells. • Algicide production by Oscillatoria laetevirens was negatively regulated by both phosphate and magnesium, and by pH. The interactive influence of nutrients and allelopathy is discussed in species succession and dominance in the maintenance of freshwater blooms.

Influence of a counteradvertising media campaign on initiation of smoking: the Florida "truth" campaign

OBJECTIVES

The purpose of this study was to assess the short-term effects of television advertisements from the Florida "truth" campaign on rates of smoking initiation.

METHODS

A follow-up survey of young people aged 12 to 17 years (n = 1820) interviewed during the first 6 months of the advertising campaign was conducted. Logistic regression analyses were used to estimate the independent effects of the campaign on smoking initiation while other factors were controlled for.

RESULTS

Youths scoring at intermediate and high levels on a media effect index were less likely to initiate smoking than youths who could not confirm awareness of television advertisements. Adjusted odds ratios between the media index and measures of initiation were similar within categories of age, sex, susceptibility, and whether a parent smoked.

CONCLUSIONS

Exposure to the "truth" media campaign lowered the risk of youth smoking initiation. However, the analysis did not demonstrate that all such media programs will be effective.

Structural perturbation of proteins in low denaturant concentrations

The presence of very low concentrations of the widely used chemical denaturants, guanidinium chloride and urea, induce changes in the tertiary structure of proteins. We have presented results on such changes in four structurally unrelated proteins to show that such structural perturbations are common irrespective of their origin. Data representative of such structural changes are shown for the monomeric globular proteins such as horseradish peroxidase (HRP) from a plant, human serum albumin (HSA) and prothrombin from ovine blood serum, and for the membrane-associated, worm-like elongated protein, spectrin, from ovine erythrocytes. Structural alterations in these proteins were reflected in quenching studies of tryptophan fluorescence using the widely used quencher acrylamide. Stern-Volmer quenching constants measured in presence of the denaturants, even at concentrations below 100 mM, were higher than those measured in absence of the denaturants. Both steady-state and time-resolved fluorescence emission properties of tryptophan and of the extrinsic probe PRODAN were used for monitoring conformational changes in the proteins in presence of different low concentrations of the denaturants. These results are consistent with earlier studies from our laboratory indicating structural perturbations in proteins at the tertiary level, keeping their native-like secondary structure and their biological activity more or less intact.

Requirement of the Lec35 gene for all known classes of monosaccharide-P-dolichol-dependent glycosyltransferase reactions in mammals

The Lec35 gene product (Lec35p) is required for utilization of the mannose donor mannose-P-dolichol (MPD) in synthesis of both lipid-linked oligosaccharides (LLOs) and glycosylphosphatidylinositols, which are important for functions such as protein folding and membrane anchoring, respectively. The hamster Lec35 gene is shown to encode the previously identified cDNA SL15, which corrects the Lec35 mutant phenotype and predicts a novel endoplasmic reticulum membrane protein. The mutant hamster alleles Lec35.1 and Lec35.2 are characterized, and the human Lec35 gene (mannose-P-dolichol utilization defect 1) was mapped to 17p12-13. To determine whether Lec35p was required only for MPD-dependent mannosylation of LLO and glycosylphosphatidylinositol intermediates, two additional lipid-mediated reactions were investigated: MPD-dependent C-mannosylation of tryptophanyl residues, and glucose-P-dolichol (GPD)-dependent glucosylation of LLO. Both were found to require Lec35p. In addition, the SL15-encoded protein was selective for MPD compared with GPD, suggesting that an additional GPD-selective Lec35 gene product remains to be identified. The predicted amino acid sequence of Lec35p does not suggest an obvious function or mechanism. By testing the water-soluble MPD analog mannose-beta-1-P-citronellol in an in vitro system in which the MPD utilization defect was preserved by permeabilization with streptolysin-O, it was determined that Lec35p is not directly required for the enzymatic transfer of mannose from the donor to the acceptor substrate. These results show that Lec35p has an essential role for all known classes of monosaccharide-P-dolichol-dependent reactions in mammals. The in vitro data suggest that Lec35p controls an aspect of MPD orientation in the endoplasmic reticulum membrane that is crucial for its activity as a donor substrate.