Deletion of the Nuclear Localization Sequences and C-Terminus of PTHrP Impairs Embryonic Mammary Development but also Inhibits PTHrP Production

Parathyroid hormone-related protein (PTHrP) can be secreted from cells and interact with its receptor, the Type 1 PTH/PTHrP Receptor (PTHR1) in an autocrine, paracrine or endocrine fashion. PTHrP can also remain inside cells and be transported into the nucleus, where its functions are unclear, although recent experiments suggest that it may broadly regulate cell survival and senescence. Disruption of either the PTHrP or PTHR1 gene results in many abnormalities including a failure of embryonic mammary gland development in mice and in humans. In order to examine the potential functions of nuclear PTHrP in the breast, we examined mammary gland development in PTHrP (1–84) knock-in mice, which express a mutant form of PTHrP that lacks the C-terminus and nuclear localization signals and which can be secreted but cannot enter the nucleus. Interestingly, we found that PTHrP (1–84) knock-in mice had defects in mammary mesenchyme differentiation and mammary duct outgrowth that were nearly identical to those previously described in PTHrP^−/− and PTHR1^−/− mice. However, the mammary buds in PTHrP (1–84) knock-in mice had severe reductions in mutant PTHrP mRNA levels, suggesting that the developmental defects were due to insufficient production of PTHrP by mammary epithelial cells and not loss of PTHrP nuclear function. Examination of the effects of nuclear PTHrP in the mammary gland in vivo will require the development of alternative animal models.     

Transitory hematologic effects of moderate exercise are not influenced by iron supplementation

A young women's exercise/fitness class tested the idea that administration of supplemental iron would prevent "sports anemia" that may develop during exercise and training and improve iron status of exercising females of menstrual age. Fifteen women (aged 18-37) were selected for each of three treatment groups: (1) no supplemental iron; (2) 9 mg X d-1 of Fe; and (3) 18 mg X d-1 of Fe (1 US Recommended Daily Allowance). Women exercised at approximately 85% of maximal heartrate for progressively increasing lengths of time in a jogging program and worked up to 45 min of exercise 4 d X week-1 for 8 weeks. Hematologic analysis was performed in weeks 1, 5, and 8. A significant decline in hemoglobin (Hb) concentration and hematocrit (Hct) was observed at week 5 when all data were examined without regard for iron intake; these red cell indices returned to pre-exercise levels by week 8. Reduction of mean cell hemoglobin concentration (MCHC) indicated that the midpoint decline was not caused by simple hemodilution during exercise. Serum ferritin (SF) concentration changed in parallel with Hb and Hct. Although the midpoint decline in SF was not statistically significant, it ruled out the possibility that turnover of red cell iron was directed to storage. Lowered MCHC and SF suggested lower availability of iron during the synthesis of a new generation of red cells. Few iron treatment effects of magnitude were observed. Iron did not prevent the midpoint decline in Hb concentration. Iron intake did not affect SF, serum iron, transferrin saturation, or final Hb, and Hct.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dihydrofolate reductase: low-resolution mass-spectrometric analysis of an elastase digest as a sequencing tool (Short Communication)

An elastase digest of a protein of unknown structure, dihydrofolate reductase, was studied by mass spectrometry. This soluble digest contained a large number of small peptides in different yields, within the ideal molecular-weight range (200-1200) for mixture-analysis mass spectrometry. Sequences of the major component peptides in the digest are reported.     

Kinetics and mechanism of action of muscle pyruvate kinase

1. The mechanism of rabbit muscle pyruvate kinase was investigated by measurements of fluxes, isotope trapping, steady-state velocity and binding of the substrates. All measurements were made at pH8.5 in Tris/HCl buffer and at 5mm-free Mg(2+). 2. Methods of preparing [(32)P]phosphoenolpyruvate from [(32)P]P(i) in high yield and determining [(32)P]-phosphoenolpyruvate and [8-(14)C]ADP are described. 3. The ratio Flux of ATP to ADP/Flux of ATP to phosphoenolpyruvate (measured at equilibrium) increased hyperbolically with ADP concentration from unity to about 2.1 at 2mm-ADP, but was unaffected by phosphoenolpyruvate concentration. Since the ratio is greater than unity, one pathway for the addition of substrates must involve phosphoenolpyruvate adding first to the enzyme in a rate-limiting step. However, the substrates must also add in the alternative order, because of the non-linear increase in the ratio with ADP concentration and because the rate of increase is very much less than that predicted from the steady-state velocity data for an ordered addition. The lack of influence of phosphoenolpyruvate on the ratio is consistent with the rapid addition of ADP in the alternative pathway. At low ADP concentrations the alternative pathway contributes less than 33% to the total reaction. 4. Isotope trapping was observed with [(32)P]phosphoenolpyruvate, confirming that when phosphoenolpyruvate adds first to the enzyme it is in a rate-limiting step. The release of phosphoenolpyruvate from the ternary complex must also be a slow step. Trapping was not observed with [8-(14)C]ADP, hence the addition of ADP to the free enzyme must be rapid unless its dissociation constant is very large (>20mm). 5. Binding studies showed that 4mol of [(32)P]phosphoenolpyruvate binds to 1mol of the enzyme, probably unligated to Mg(2+), with a dissociation constant appropriate to the mechanism indicated above. Binding of [8-(14)C]ADP could not be detected, and hence the binding of ADP occurs by a low-affinity step. The latter is also demanded by the steady-state velocity data. 6. The ratio Flux of phosphoenolpyruvate to ATP/Flux of phosphoenolpyruvate to pyruvate (determined from the incorporation of label into phosphoenolpyruvate from [3-(14)C]-pyruvate or [gamma-(32)P]ATP during the forward reaction) did not differ significantly from unity. Steady-state velocity data predicted grossly different flux ratios for ordered dissociations of the products, and the results indicate that the dissociation must be rapid and random. The data also exclude a Ping-Pong mechanism. 7. Permissible rate constants for the above mechanism are calculated. The results indicate a high degree of cooperativity in binding, whatever the order of addition of substrate.     

Mechanism of "L"-type pyruvate kinase from rabbit liver. Evidence against phosphoenzyme formation.

The "L"-type pyruvate kinase from rabbit liver does not catalyse exchange between phosphoenol[1-14C]pyruvate and pyruvate at either pH 8.5 or 6.2. Spectrophotometric experiments at pH 8.5 and 6;2 and gel-filtration experiments with [32P]phosphoenolpyruvate at pH 8,5 also fail to demonstrate phosphoenzyme formation. It is concluded that it is very unlikely that the enzyme has a phosphoenzyme mechanism.     

Correction to: Transmission of a novel predatory behaviour is not restricted to kin

Biological Invasions - A correction to this paper has been published: https://doi.org/10.1007/s10530-021-02548-x     

Risk factors of peripheral arterial disease: a case control study in Sri Lanka

Background

Peripheral artery disease (PAD) is an important global health problem and contributes to notable proportion of morbidity and mortality. This particular manifestation of systemic atherosclerosis is largely under diagnosed and undertreated. For sustainable preventive strategies in a country, it is mandatory to identify country-specific risk factors. We intended to assess the risk factors of PAD among adults aged 40–74 years.

Methods

This case control study was conducted in 2012–2013 in Sri Lanka. Seventy-nine cases and 158 controls in the age group of 40–74 years were selected for the study in order to have case to control ratio 1:2. The criterion for selecting cases and control was based on Ankle brachial pressure index (ABPI). Cases were selected from those who had ABPI 0.85 or less (ABPI ≤0.85) in either lower limb. Controls were selected from those ABPI score between 1.18 and 1.28 in both lower limbs. Only newly identified individuals with PAD were selected as cases. Controls were selected from the same geographical location and within the 5 year age group as cases.

Results

The history of diabetes mellitus more than 10 years (OR 5.8, 95% CI 2.2–14.2), history of dyslipidemia for more than 10 years (OR 4.9, 95% CI 2.1–16.2), history of hypertension for more than 10 years (OR 3.8, 95% CI 1.8–12.7) and smoking (OR 2.9, 95% CI 1.2–6.9), elevated HsCRP (OR 3.7, 95% CI 1.2–12.0) and hyperhomocysteinemia (OR 3.0, 95% CI 1.1–8.1) were revealed as country specific significant risk factor of PAD.

Conclusions

Diabetes mellitus, hypertension, dyslipidemia, smoking as well as elevated homocysteine and HsCRP found as risk factors of PAD. Longer the duration or higher level exposure to these risk factors has increased the risk of PAD. These findings emphasis the need for routine screening of PAD among patients with the identified risk factors.

     

The role of fish-poultry integration on fish growth performance,yields and economic benefits among smallholder farmers in sub-Saharan Africa,Tanzania

Aquaculture practices from sub-Saharan Africa are characterised by low production, owing to improper technology. Production can be increased through integrating fish farming with other existing on-farm activities, particularly livestock husbandry. We assessed the role of fish-poultry integration on all male Nile tilapia, Oreochromis niloticus growth performance, yields and economic benefits among smallholder farmers in sub-Saharan Africa, Tanzania. The study also compared phytoplankton species composition, abundance and biomass between the fish-poultry integration and non-integrated system. After 180 days of the experiment, all male O. niloticus cultured under fish-poultry integration exhibited significantly higher growth rates than those in the non-integrated system (p < 0.05). Gross fish yield (GFY), net fish yield (NFY) and net annual yields (NAY) obtained from fish-poultry integration were significantly higher than those from non-integrated system (p < 0.05). Partial enterprise budget analysis revealed that fish-poultry integration was more profitable than the non-integrated system. Moreover, fish-poultry integrated system produced significantly higher phytoplankton abundance and biomass than those from the non-integrated system. Results demonstrate that rural smallholder farmers can achieve higher growth rate, farm net yields and income by integrating all male O. niloticus with other on-farm activities than practising a stand-alone fish culture system.